A millisecond pulsar in a stellar triple system.

Gravitationally bound three-body systems have been studied for hundreds of years and are common in our Galaxy. They show complex orbital interactions, which can constrain the compositions, masses and interior structures of the bodies and test theories of gravity, if sufficiently precise measurements are available. A triple system containing a radio pulsar could provide such measurements, but the only previously known such system, PSR B1620-26 (refs 7, 8; with a millisecond pulsar, a white dwarf, and a planetary-mass object in an orbit of several decades), shows only weak interactions. Here we report precision timing and multiwavelength observations of PSR J0337+1715, a millisecond pulsar in a hierarchical triple system with two other stars. Strong gravitational interactions are apparent and provide the masses of the pulsar M[Symbol: see text](1.4378(13), where M[Symbol: see text]is the solar mass and the parentheses contain the uncertainty in the final decimal places) and the two white dwarf companions (0.19751(15)M[Symbol: see text] and 0.4101(3))M[Symbol: see text], as well as the inclinations of the orbits (both about 39.2°). The unexpectedly coplanar and nearly circular orbits indicate a complex and exotic evolutionary past that differs from those of known stellar systems. The gravitational field of the outer white dwarf strongly accelerates the inner binary containing the neutron star, and the system will thus provide an ideal laboratory in which to test the strong equivalence principle of general relativity.

Body Temperature Frequency Distributions: A Tool for Assessing Thermal Performance in Endotherms?

There is increasing recognition that rather than being fully homeothermic, most endotherms display some degree of flexibility in body temperature. However, the degree to which this occurs varies widely from the relatively strict homeothermy in species, such as humans to the dramatic seasonal hibernation seen in Holarctic ground squirrels, to many points in between. To date, attempts to analyse this variability within the framework generated by the study of thermal performance curves have been lacking. We tested if frequency distribution histograms of continuous body temperature measurements could provide a useful analogue to a thermal performance curve in endotherms. We provide examples from mammals displaying a range of thermoregulatory phenotypes, break down continuous core body temperature traces into various components (active and rest phase modes, spreads and skew) and compare these components to hypothetical performance curves. We did not find analogous patterns to ectotherm thermal performance curves, in either full datasets or by breaking body temperature values into more biologically relevant components. Most species had either bimodal or right-skewed (or both) distributions for both active and rest phase body temperatures, indicating a greater capacity for mammals to tolerate body temperatures elevated above the optimal temperatures than commonly assumed. We suggest that while core body temperature distributions may prove useful in generating optimal body temperatures for thermal performance studies and in various ecological applications, they may not be a good means of assessing the shape and breath of thermal performance in endotherms. We also urge researchers to move beyond only using mean body temperatures and to embrace the full variability in both active and resting temperatures in endotherms.

Changing patterns of plasma membrane-associated filaments during the initial phases of polymorphonuclear leukocyte adherence.

By utilizing a combination of several ultrastructural techniques, we have been able to demonstrate differences in filament organization on the adherent plasma membranes of spreading and mobile PMN as well as within the extending lamellipodia. To follow the subplasmalemmal filaments of this small amoeboid cell during these kinetic events, we sheared off the upper portions of cells onto glass and carbon surfaces for 30 s--5 min. The exposed adherent membranes were immediately fixed and processed for high-resolution SEM or TEM. Whole cells were also examined by phase contrast microscopy, SEM, and oriented thin sections. Observed by SEM, the inner surface of nonadherent PMN membranes is free of filaments, but within 30 s of attachment to the substrate a three-dimensional, interlocking network of globular projections and radiating microfilaments--i.e., a subplasmalemmal filament complex--is consistently demonstrable (with or without postfixation in OsO4). Seen by TEM, extending lamellipodia contain a felt of filamentous and finely granular material, distinct from the golbule/filament complex of the adjacent adherent membrane. In the spread cell, this golbule-filament complex covers the entire lower membrane and increases in filament-density over the next 2--3 min. By 3--5 min after plating, as the PMN rounds up before the initiation of amoeboid movements, another pattern emerges--circumferential bands of anastomosing filament bundles in which thick, short filaments resembling myosin are found. This work provides structural evidence on the organization of polymerized contractile elements associated with the plasma membrane during cellular adherence.

Organization of the cytoskeleton in resting, discoid platelets: preservation of actin filaments by a modified fixation that prevents osmium damage.

This study evaluates the structural organization of the cytoskeleton within unactivated, discoid platelets. Previously, such studies have been difficult to interpret because of the ease with which platelets are stimulated, the sensitivity of actin filaments to cell extraction buffers, and the general problem of preserving actin filaments with conventional fixatives, compounded by the density of the cytoplasm in the platelet. In this study we have employed a new fixative containing lysine, which protects actin filaments against damage during fixation and thin-section processing. We used thick (0.25-micron) sections and conventional thin sections of extracted cells (fixed and lysed simultaneously by the addition of 1% Triton X-100 to the initial fixative) as well as thin sections of whole cells to examine three preparations of human platelets: discoid platelets washed by sedimentation; discoid platelets isolated by gel filtration; and circulating platelets collected by dripping blood directly from a vein into fixative. In all of these preparations, long, interwoven actin filaments were observed within the platelet and were particularly concentrated beneath the plasma membrane. These filaments appeared to be linked at irregular intervals to the membrane and to each other via short, approximately 20- to 50-nm-long cross-links of variable width. Although most filaments were outside the circumferential band of microtubules and the cisternae of the open canalicular system, individual filaments dipped down into the cytoplasm and were found between the microtubules and in association with other membranes. The ease with which single actin filaments can be seen in the dense cytoplasm of the human platelet after lysine/aldehyde fixation suggests the great potential of this new fixative for other cells.

Uptake of chemically modified low density lipoproteins in vivo is mediated by specific endothelial cells.

Acetoacetylated (AcAc) and acetylated (Ac) low density lipoproteins (LDL) are rapidly cleared from the plasma (t1/2 approximately equal to 1 min). Because macrophages, Kupffer cells, and to a lesser extent, endothelial cells metabolize these modified lipoproteins in vitro, it was of interest to determine whether endothelial cells or macrophages could be responsible for the in vivo uptake of these lipoproteins. As previously reported, the liver is the predominant site of the uptake of AcAc LDL; however, we have found that the spleen, bone marrow, adrenal, and ovary also participate in this rapid clearance. A histological examination of tissue sections, undertaken after the administration of AcAc LDL or Ac LDL (labeled with either 125I or a fluorescent probe) to rats, dogs, or guinea pigs, was used to identify the specific cells binding and internalizing these lipoproteins in vivo. With both techniques, the sinusoidal endothelial cells of the liver, spleen, bone marrow, and adrenal were labeled. Less labeling was noted in the ovarian endothelia. Uptake of AcAc LDL by endothelial cells of the liver, spleen, and bone marrow was confirmed by transmission electron microscopy. These data suggest uptake through coated pits. Uptake of AcAc LDL was not observed in the endothelia of arteries (including the coronaries and aorta), veins, or capillaries of the heart, testes, kidney, brain, adipose tissue, and duodenum. Kupffer cells accounted for a maximum of 14% of the 125I-labeled AcAc LDL taken up by the liver. Isolated sinusoidal endothelial cells from the rat liver displayed saturable, high affinity binding of AcAc LDL (Kd = 2.5 X 10(-9) M at 4 degrees C), and were shown to degrade AcAc LDL 10 times more effectively than aortic endothelial cells. These data indicate that specific sinusoidal endothelial cells, not the macrophages of the reticuloendothelial system, are primarily responsible for the removal of these modified lipoproteins from the circulation in vivo.

Actin filament content and organization in unstimulated platelets.

The extent of actin polymerization in unstimulated, discoid platelets was measured by DNase I inhibition assay in Triton X-100 lysates of platelets washed at 37 degrees C by gel filtration, or in Triton X-100 lysates of platelets washed at ambient temperatures by centrifugation in the presence of prostacyclin. About 40% of the actin in the discoid platelets obtained by either method existed as filaments. These filaments could be visualized by electron microscopy of thin sections. Similar results were obtained when the actin filament content of discoid platelets was measured by sedimentation of filaments from Triton X-100 lysates at high g forces (145,000 g for 45 min). However, few of these filaments sedimented at the lower g forces often used to isolate networks of actin filaments from cell extracts. These results indicate that actin filaments in discoid cells are not highly crosslinked. Platelets isolated by centrifugation in the absence of prostacyclin were not discoid, but were instead irregular with one or more pseudopodia. These platelets also contained approximately 40-50% of their actin in a filamentous form; many of these filaments sedimented at low g forces, however, indicating that they were organized into networks. The discoid shape of these centrifuged platelets could be restored by incubating them for 1-3 h at 37 degrees C, which resulted in the reversal of filament organization. High g forces were then required for the sedimentation of the actin. Approximately 80-90% of the actin in platelets washed at 4 degrees C was filamentous; this high actin filament content could be attributed to actin polymerization during the preparation of the platelets at low temperatures. These studies show that platelet activation involves mechanisms for the structural reorganization of existing filaments, in addition to those previously described for mediating actin polymerization.

Evidence that activation of platelet calpain is induced as a consequence of binding of adhesive ligand to the integrin, glycoprotein IIb-IIIa.

Calpain (a Ca(2+)-dependent protease) is present in many cell types. Because it is present in the cytosol, the potential exists that it may regulate critical intracellular events by inducing crucial proteolytic cleavages. However, the concentrations of Ca2+ required to activate calpain are higher than those attained in the cytoplasm of most cells. Thus, the physiological importance of calpain and the mechanisms involved in its activation have remained elusive. In this study, we show that calpain rapidly moved to a peripheral location upon the addition of an agonist to suspensions of platelets, but it remained unactivated. We provide three lines of evidence that calpain was subsequently activated by a mechanism that required the binding of an adhesive ligand to the major platelet integrin, glycoprotein (GP) IIb-IIIa: calpain activation was prevented by RGDS, a tetrapeptide that inhibits the binding of adhesive ligand to GP IIb-IIIa; it was also prevented by monoclonal antibodies that inhibit adhesive ligand binding to GP IIb-IIIa; and its activation was markedly reduced in platelets from patients whose platelets have greatly reduced levels of functional GP IIb-IIIa. Thus, in platelets, binding of the extracellular domain of GP IIb-IIIa to its adhesive ligand can initiate a transmembrane signal that activates intracellular calpain. Because calpain is present in focal contacts of adherent cells, the interaction of integrins with adhesive ligands in the extracellular matrix may regulate activation of calpain in other cell types as well.

Role of the membrane skeleton in preventing the shedding of procoagulant-rich microvesicles from the platelet plasma membrane.

The platelet plasma membrane is lined by a membrane skeleton that appears to contain short actin filaments cross-linked by actin-binding protein. Actin-binding protein is in turn associated with specific plasma membrane glycoproteins. The aim of this study was to determine whether the membrane skeleton regulates properties of the plasma membrane. Platelets were incubated with agents that disrupted the association of the membrane skeleton with membrane glycoproteins. The consequences of this change on plasma membrane properties were examined. The agents that were used were ionophore A23187 and dibucaine. Both agents activated calpain (the Ca2(+)-dependent protease), resulting in the hydrolysis of actin-binding protein and decreased association of actin with membrane glycoproteins. Disruption of actin-membrane interactions was accompanied by the shedding of procoagulant-rich microvesicles from the plasma membrane. The shedding of microvesicles correlated with the hydrolysis of actin-binding protein and the disruption of actin-membrane interactions. When the calpain-induced disruption of actin-membrane interactions was inhibited, the shedding of microvesicles was inhibited. These data are consistent with the hypothesis that association of the membrane skeleton with the plasma membrane maintains the integrity of the plasma membrane, preventing the shedding of procoagulant-rich microvesicles from the membrane of unstimulated platelets. They raise the possibility that the procoagulant-rich microvesicles that are released under a variety of physiological and pathological conditions may result from the dissociation of the platelet membrane skeleton from its membrane attachment sites.

Identification of a membrane skeleton in platelets.

Platelets have previously been shown to contain actin filaments that are linked, through actin-binding protein, to the glycoprotein (GP) Ib-IX complex, GP Ia, GP IIa, and an unidentified GP of Mr 250,000 on the plasma membrane. The objective of the present study was to use a morphological approach to examine the distribution of these membrane-bound filaments within platelets. Preliminary experiments showed that the Triton X-100 lysis buffers used previously to solubilize platelets completely disrupt the three-dimensional organization of the cytoskeletons. Conditions were established that minimized these postlysis changes. The cytoskeletons remained as platelet-shaped structures. These structures consisted of a network of long actin filaments and a more amorphous layer that outlined the periphery. When Ca2+ was present, the long actin filaments were lost but the amorphous layer at the periphery remained; conditions were established in which this amorphous layer retained the outline of the platelet from which it originated. Immunocytochemical experiments showed that the GP Ib-IX complex and actin-binding protein were associated with the amorphous layer. Analysis of the amorphous material on SDS-polyacrylamide gels showed that it contained actin, actin-binding protein, and all actin-bound GP Ib-IX. Although actin filaments could not be visualized in thin section, the actin presumably was in a filamentous form because it was solubilized by DNase I and bound phalloidin. These studies show that platelets contain a membrane skeleton and suggest that it is distinct from the network of cytoplasmic actin filaments. This membrane skeleton exists as a submembranous lining that, by analogy to the erythrocyte membrane skeleton, may stabilize the plasma membrane and contribute to determining its shape.

The influence of particle size and multiple apoprotein E-receptor interactions on the endocytic targeting of beta-VLDL in mouse peritoneal macrophages.

Low density lipoprotein (LDL) and beta-very low density lipoprotein (beta-VLDL) are internalized by the same receptor in mouse peritoneal macrophages and yet their endocytic patterns differ; beta-VLDL is targeted to both widely distributed and perinuclear vesicles, whereas LDL is targeted almost entirely to perinuclear lysosomes. This endocytic divergence may have important metabolic consequences since beta-VLDL is catabolized slower than LDL and is a more potent stimulator of acyl-CoA/cholesterol acyl transferase (ACAT) than LDL. The goal of this study was to explore the determinants of beta-VLDL responsible for its pattern of endocytic targeting. Fluorescence microscopy experiments revealed that large, intestinally derived, apoprotein (Apo) E-rich beta-VLDL was targeted mostly to widely distributed vesicles, whereas small, hepatically derived beta-VLDL was targeted more centrally (like LDL). Furthermore, the large beta-VLDL had a higher ACAT-stimulatory potential than the smaller beta-VLDL. The basis for these differences was not due to fundamental differences in the means of uptake; both large and small beta-VLDL were internalized by receptor-mediated endocytosis (i.e., not phagocytosis) involving the interaction of Apo E of the beta-VLDL with the macrophage LDL receptor. However, large beta-VLDL was much more resistant to acid-mediated release from LDL receptors than small beta-VLDL. Furthermore, partial neutralization of the multiple Apo Es on these particles by immunotitration resulted in a more perinuclear endocytic pattern, a lower ACAT-stimulatory potential, and an increased sensitivity to acid-mediated receptor release. These data are consistent with the hypothesis that the interaction of the multivalent Apo Es of large beta-VLDL with multiple macrophage LDL receptors leads to a diminished or retarded release of the beta-VLDL from its receptor in the acidic sorting endosome which, in turn, may lead to the widely distributed endocytic pattern of large beta-VLDL. These findings may represent a physiologically relevant example of a previously described laboratory phenomenon whereby receptor cross-linking by multivalent ligands leads to a change in receptor targeting.

Nonsteroidal anti-inflammatory agents and musculoskeletal injuries in Thoroughbred racehorses in Kentucky.

Injuries sustained by horses during racing have been considered as an unavoidable part of horse racing. Many factors may be associated with the musculoskeletal injuries of Thoroughbred race horses. This study surveyed the amounts of nonsteroidal anti-inflammatory agents (NSAIDs) in injured horse's biological system (plasma) at Kentucky racetracks from January 1, 1995 through December 31, 1996. During that period, there were 84 catastrophic cases (euthanized horses) and 126 noncatastrophic cases. Plasma concentrations of NSAIDs were determined by High Performance Liquid Chromatography in injured and control horses. The possible role of anti-inflammatory agents in musculoskeletal injuries of Thoroughbred race horses was investigated by comparing the apparent concentrations of NSAIDs in injured horses to concentrations in control horses. The plasma concentrations of phenylbutazone and flunixin were higher in injured horses than in control horses. Most injured and control horses did not have a detectable level of naproxen in their plasma samples. Further studies must be carried out to determine whether horses with higher plasma concentrations of NSAIDs have an altered risk of musculoskeletal injuries compared with other horses.

Apolipoprotein E associated with astrocytic glia of the central nervous system and with nonmyelinating glia of the peripheral nervous system.

The plasma protein apolipoprotein (apo) E is an important determinant of lipid transport and metabolism in mammals. In the present study, immunocytochemistry has been used to identify apo E in specific cells of the central and peripheral nervous systems of the rat. Light microscopic examination revealed that all astrocytes, including specialized astrocytic cells (Bergmann glia of the cerebellum, tanycytes of the third ventricle, pituicytes of the neurohypophysis, and Müller cells of the retina), possessed significant concentrations of apo E. In all of the major subdivisions of the central nervous system, the perinuclear region of astrocytic cells, as well as their cell processes that end on basement membranes at either the pial surface or along blood vessels, were found to be rich in apo E. Extracellular apo E was present along many of these same surfaces. The impression that apo E is secreted by astrocytic cells was confirmed by electron microscopic immunocytochemical studies, which demonstrated the presence of apo E in the Golgi apparatus. Apo E was not present in neurons, oligodendroglia, microglia, ependymal cells, and choroidal cells. In the peripheral nervous system, apo E was present within the glia surrounding sensory and motor neurons; satellite cells of the dorsal root ganglia and superior cervical sympathetic ganglion as well as the enteric glia of the intestinal ganglia were reactive. Apo E was also present within the non-myelinating Schwann cells but not within the myelinating Schwann cells of peripheral nerves. These results suggest that apo E has an important, previously unsuspected role in the physiology of nervous tissue.

Phenotypes of apolipoprotein B and apolipoprotein E after liver transplantation.

Apolipoprotein (apo) E and the two B apolipoproteins, apoB48 and apoB100, are important proteins in human lipoprotein metabolism. Commonly occurring polymorphisms in the genes for apoE and apoB result in amino acid substitutions that produce readily detectable phenotypic differences in these proteins. We studied changes in apoE and apoB phenotypes before and after liver transplantation to gain new insights into apolipoprotein physiology. In all 29 patients that we studied, the postoperative serum apoE phenotype of the recipient, as assessed by isoelectric focusing, converted virtually completely to that of the donor, providing evidence that greater than 90% of the apoE in the plasma is synthesized by the liver. In contrast, the cerebrospinal fluid apoE phenotype did not change to the donor's phenotype after liver transplantation, indicating that most of the apoE in CSF cannot be derived from the plasma pool and therefore must be synthesized locally. The apoB100 phenotype (assessed with immunoassays using monoclonal antibody MB19, an antibody that detects a two-allele polymorphism in apoB) invariably converted to the phenotype of the donor. In four normolipidemic patients, we determined the MB19 phenotype of both the apoB100 and apoB48 in the "chylomicron fraction" isolated from plasma 3 h after a fat-rich meal. Interestingly, the apoB100 in the chylomicron fraction invariably had the phenotype of the donor, indicating that the vast majority of the large, triglyceride-rich apoB100-containing lipoproteins that appear in the plasma after a fat-rich meal are actually VLDL of hepatic origin. The MB19 phenotype of the apoB48 in the plasma chylomicron fraction did not change after liver transplantation, indicating that almost all of the apoB48 in plasma chylomicrons is derived from the intestine. These results were consistent with our immunocytochemical studies on intestinal biopsy specimens of organ donors; using apoB-specific monoclonal antibodies, we found evidence for apoB48, but not apoB100, in donor intestinal biopsy specimens.

A role for apolipoprotein E, apolipoprotein A-I, and low density lipoprotein receptors in cholesterol transport during regeneration and remyelination of the rat sciatic nerve.

Recent work has demonstrated that apo E secretion and accumulation increase in the regenerating peripheral nerve. The fact that apoE, in conjunction with apoA-I and LDL receptors, participates in a well-established lipid transfer system raised the possibility that apoE is also involved in lipid transport in the injured nerve. In the present study of the crushed rat sciatic nerve, a combination of techniques was used to trace the cellular associations of apoE, apoA-I, and the LDL receptor during nerve repair and to determine the distribution of lipid at each stage. After a crush injury, as axons died and Schwann cells reabsorbed myelin, resident and monocyte-derived macrophages produced large quantities of apoE distal to the injury site. As axons regenerated in the first week, their tips contained a high concentration of LDL receptors. After axon regeneration, apoE and apoA-I began to accumulate distal to the injury site and macrophages became increasingly cholesterol-loaded. As remyelination began in the second and third weeks after injury, Schwann cells exhausted their cholesterol stores, then displayed increased LDL receptors. Depletion of macrophage cholesterol stores followed over the next several weeks. During this stage of regeneration, apoE and apoA-I were present in the extracellular matrix as components of cholesterol-rich lipoproteins. Our results demonstrate that the regenerating peripheral nerve possesses the components of a cholesterol transfer mechanism, and the sequence of events suggests that this mechanism supplies the cholesterol required for rapid membrane biogenesis during axon regeneration and remyelination.

The dental caries experience of 5-year-old children in Great Britain (2005/6). Surveys co-ordinated by the British Association for the study of community dentistry.

OBJECTIVE: This paper reports the results of standardized clinical caries examinations of 5-year-old children from across England, Wales and Scotland in 2005/6. These co-ordinated surveys are the latest in a series which seek to monitor the dental health of children and to assess the delivery of dental services. METHOD: The criteria and conventions of the British Association for the Study of Community Dentistry were used. Representative samples were drawn from participating strategic health authorities (SHAs), primary care trusts (PCTs) and health boards (HBs). Caries was diagnosed at the caries into dentine threshold using a visual method without radiography or fibre-optic transillumination. RESULTS: 239,389 five and six year-old children from across England, Wales, Scotland and the Isle of Man were examined in 2005/2006. The results again demonstrated a wide variation in disease prevalence and care strategies across Great Britain. Mean d3mft across England was 1.47 (d3t = 1.10, mt = 0.20, ft = 0.16), across Wales the corresponding values were 2.38 (d3t = 1.70, mt = 0.43, ft = 0.25) and in Scotland 2.16 (d3t = 1.45, mt = 0.51, ft = 0.20). Overall, 39.4% of children in Great Britain had evidence of caries experience in dentine (d3mft > 0, including visual dentine caries). The distribution of caries was highly skewed. Thus the mean caries experience for those with dentinal decay was 3.99, as opposed to the overall mean of 1.57. Trends over time demonstrate a small change in mean d3mft since 2003/4 when the mean was 1.62, although the mean value for those with dentine decay experience remained constant (4.00 vs 3.99). The care index has also fallen marginally from 12% to 11%. The BASCD co-ordinated NHS Epidemiology Programme will evolve in coming years as differing priorities in the frequency of inspecting particular age groups is being seen as well as a desire to measure other aspects of oral health in addition. CONCLUSION: Overall, there has been only a small overall improvement in the dental health of 5-year-old children over the last 2 years and no diminution of the level of disease in those affected for some time, although in Scotland a pattern of continuing steady progress from previously high levels is seen. While many children enjoy good oral health, sizable groups remain within the population of 5-year-old children who have a clinically significant burden of preventable dental disease.

Does student debt affect dental students' and dentists' stress levels?

Introduction Many studies have shown financial worries and debt to induce stress in individuals, this combined with the existing stress of being a dentist raises the question of how student debt affects students' and dentists' stress levels.Objectives Determine whether student debt has had any noticeable effect on student stress levels; investigate whether student debt has any effect on dentists' career choice; investigate whether the increase in tuition fees has influenced the number of applicants to study dentistry at the University of Birmingham.Method Anonymous questionnaires were completed by 70 4th year and 38 5th year BDS and 22 Dental Core Trainees (DCTs). Participants circled the response which best fitted their situation regarding statements on their level of stress and future career path. Ethical approval granted. Application figures to study dentistry obtained from head of admissions.Results Forty-two percent of males and 63% of females strongly agreed with the statement that having no debt would reduce their stress levels. Of those with debt >£40,000, 11% strongly agreed and 42% agreed that their total amount of student debt causes them stress. Whereas, those whose debt is <£40,000 only 2% strongly agreed and 28% agreed that their total amount of student debt causes them stress. Seventy-seven percent of participants who had parental or family financial support reported this reduced their stress levels. Student debt was found to deter females from undertaking further study more than it deters males (P <0.001). Students with a higher level of debt were more likely to worry about their total student loan(s) (P <0.001). Moreover, students with a higher level of debt were more likely to be stressed about their total student loan(s) (P <0.001). Parental/family contribution to student expenses reduces student stress (P <0.001). Applications to study dentistry since the rise in tuition fees have decreased by 42%.Conclusion Student debt has had an impact on student stress; students reporting a higher level of debt also report more stress and concern about paying off their student debt. Having no student debt would reduce stress levels, although to what extent is undetermined. Applications to study dentistry have fallen since the increase in tuition fees.

The dental caries experience of 11-year-old children in Great Britain. Surveys coordinated by the British Association for the Study of Community Dentistry in 2004 / 2005.

OBJECTIVE: This paper reports the results of standardized clinical caries examinations of 11-year-old children from across England and Wales, Scotland, Isle of Man, and Jersey in 2004/5. These co-ordinated surveys are the latest in a series which seek to monitor the dental health of children and to assess the delivery of dental services. METHOD: The criteria and conventions of the British Association for the Study of Community Dentistry were used. Representative samples were drawn from participating strategic health authorities (SHAs), primary care trusts (PCTs), health boards (HBs), and local health boards (LHBs). Caries was diagnosed at the caries into dentine threshold using a visual method without radiography or fibre-optic transillumination. RESULTS: The results again demonstrated a wide variation in disease prevalence and care strategies across Great Britain. Mean values for D3MFT within the current English strategic health authorities ranged from 0.19 in Harlow to 1.32 in North Manchester and in Salford; in Wales mean values ranged from 0.69 in Vale of Glamorgan to 2.09 in Blaenau Gwent; while in Scotland they ranged from 0.59 in Orkney to 1.77 in Western Isles. Mean D3MFT across England was 0.64 (D3T = 0.32, MT = 0.06, FT = 0.25), across Wales it was 1.09 (D3T = 0.48, MT 0.11, FT = 0.50), and across Scotland values were 1.29 (D3T = 0.52, MT = 0.17, FT = 0.60). Overall, 31.3% of children in England & Wales and 47.1% of children inspected in Scotland had evidence of caries experience in dentine (D3MFT > 0, including visual dentine caries). As in previous surveys, the distribution of caries was highly skewed. Thus the mean caries experience for those with dentinal decay in England and Wales was 2.12, as opposed to the overall mean of 0.66; in Scotland the corresponding values were 2.74 and 1.29. Trends over time demonstrate an improvement in overall mean D3MFT for England and Wales since the 2000/2001 of 12-year-olds, although part of this difference is accountable to the younger age, at examination, in this survey. The mean value for those with dentine decay experience was also marginally less at 2.12 compared with 2.35 in the previous survey. (Figures for Scotland were not included in the 2000/2001 survey.) The care index was also found to be marginally lower than previously at 41% compared with 48% but again the younger age of the children would influence this value. CONCLUSION: Dental health of 11-year-old children has been surveyed in Great Britain, Jersey, and the Isle of Man: being a slightly younger mean age than in previous BASCD surveys. Geographic variation in oral health is marked at both the local and national levels. Overall, the provision of operative care for those with dentinal decay is around 42%. While many children enjoy good oral health, sizable groups remain within the population of 11-year-old children who have a clinically significant burden of preventable dental disease.

Astrocytes synthesize apolipoprotein E and metabolize apolipoprotein E-containing lipoproteins.

We have previously demonstrated that astrocytes synthesize and secrete apolipoprotein E in situ. In the present work, primary cultures of rat brain astrocytes were used to study apolipoprotein E synthesis, secretion, and metabolism in vitro. The astrocytes in culture contained immunoreactive apolipoprotein E in the area of the Golgi apparatus. Incubation of the astrocytes with [35S]methionine resulted in the secretion of labeled immunoprecipitable apolipoprotein E, which constituted 1-3% of the total secreted proteins. The apolipoprotein E secreted in culture and the apolipoprotein E in rat brain extracts differed from serum apolipoprotein E in two respects: both had a slightly higher apparent molecular weight (approx. 36,000) and more acidic isoforms than serum apolipoprotein E. Sialylation of the newly secreted apolipoprotein accounted for the difference in both the apparent molecular weight and isoelectric focusing pattern of newly secreted apolipoprotein E and plasma apolipoprotein E. The astrocytes possessed apolipoprotein B,E(LDL) receptors capable of binding and internalizing apolipoprotein E-containing lipoproteins. The uptake of lipoproteins by the cells led to a reduction in the number of cell surface receptors and to the intracellular accumulation of cholesteryl esters. Since apolipoprotein E is present within the brain, and since brain cells can express apolipoprotein B,E(LDL) receptors, apolipoprotein E-containing lipoproteins may function to redistribute lipid and regulate cholesterol homeostasis within the brain.

The dental caries experience of 5-year-old children in England and Wales (2003/4) and in Scotland (2002/3). Surveys co-ordinated by the British Association for the Study of Community Dentistry.

OBJECTIVE: This paper reports the results of standardized clinical caries examinations of 5 year old children from across England and Wales in 2003/4 and Scotland in 2002/3. These co-ordinated surveys are the latest in a series which seek to monitor the dental health of children and to assess the delivery of dental services. METHOD: The criteria and conventions of the British Association for the Study of Community Dentistry were used. Representative samples were drawn from participating strategic health authorities (SHAs), primary care trusts (PCTs) and health boards (HBs). Caries was diagnosed at the caries into dentine threshold using a visual method without radiography or fibre-optic transillumination. Data for Jersey and the Isle of Man are also included. RESULTS: The results again demonstrated a wide variation in disease prevalence and care strategies across Great Britain. Mean values for d3mft within the current English Strategic Health Authorities ranged from 0.47 in Maidstone Weald (South) to 3.69 in North Kirklees (North); in Wales mean values ranged from 1.48 in Flintshire (NW) to 3.73 in Merthyr (SE); while in Scotland they ranged from 1.29 in Borders to 3.67 in Argyll & Clyde. Mean d3mft across England was 1.49 (d3t = 1.12, mt = 0.19, ft = 0.18), across Wales it was 2.42 (d3t = 1.70, mt = 0.43, ft = 0.29) and across Scotland values were 2.76 (d3t = 1.87, mt = 0.65, ft = 0.24). Overall, 39.6% of children in England & Wales and 55.4% of children inspected in Scotland had evidence of caries experience in dentine (d3mft > 0, including visual dentine caries). The distribution of caries was highly skewed. Thus the mean caries experience for those with dentinal decay in England and Wales was 3.90, as opposed to the overall mean of 1.55; in Scotland the corresponding values were 4.98 and 2.76. Trends over time demonstrate virtually no change in the overall mean d3mft for England and Wales since 2001/2, although the mean value for those with dentine decay experience increased marginally from 3.83 to 3.90. In Scotland there had been deterioration in the overall mean (2.76 as compared to the 2.55 reported in 1999). The care index has also fallen (for example in England & Wales to 12% from 13.2% in 2001/2002 and 14.3% in 1999/2000). CONCLUSION: There has been no overall improvement in the dental health of 5 year old children over the last 2 years. Geographic variation in oral health is marked at both the local and national levels. Overall, the provision of operative care for those with dentinal decay has again decreased slightly. While many children enjoy good oral health, sizable groups remain within the population of 5 year old children who have a clinically significant burden of preventable dental disease.

A new fixative for the preservation of actin filaments: fixation of pure actin filament pellets.

Conventional fixation for thin-section microscopy is insufficient to preserve many elements of cells and tissues. Actin filaments, for example, are destroyed during post-fixation in OsO4. In our search for a better fixative, we chose pellets of pure actin filaments as a very sensitive model system. In the present study, the potential of amines for improving aldehyde fixation was explored, and the results were compared to those obtained with the use of tannic acid. Aldehyde and amine were used together as an initial fixative, followed by aldehyde alone with postfixation in 1% OsO4 in buffer at 4 degrees C for 15 min, uranyl acetate en bloc stain, acetone dehydration, and embedding in Epox 812. Some primary monoamines improved the preservation of filaments; filaments were not broken beyond recognition by OsO4, as occurs when glutaraldehyde alone is used. Excellent preservation was seen when certain primary diamines were used. The quality of this fixation was superior to that obtained with tannic acid and was without the large increase in filament diameter that is seen with concentrations of tannic acid sufficient to protect filaments against osmium damage. The effects on filaments of the amines lysine, putrescine, ammonium, and arginine have been documented in detail, as we systematically varied all the major parameters normally considered in formulating fixation protocols.