An integrative computational model for intestinal tissue renewal.

OBJECTIVES: The luminal surface of the gut is lined with a monolayer of epithelial cells that acts as a nutrient absorptive engine and protective barrier. To maintain its integrity and functionality, the epithelium is renewed every few days. Theoretical models are powerful tools that can be used to test hypotheses concerning the regulation of this renewal process, to investigate how its dysfunction can lead to loss of homeostasis and neoplasia, and to identify potential therapeutic interventions. Here we propose a new multiscale model for crypt dynamics that links phenomena occurring at the subcellular, cellular and tissue levels of organisation. METHODS: At the subcellular level, deterministic models characterise molecular networks, such as cell-cycle control and Wnt signalling. The output of these models determines the behaviour of each epithelial cell in response to intra-, inter- and extracellular cues. The modular nature of the model enables us to easily modify individual assumptions and analyse their effects on the system as a whole. RESULTS: We perform virtual microdissection and labelling-index experiments, evaluate the impact of various model extensions, obtain new insight into clonal expansion in the crypt, and compare our predictions with recent mitochondrial DNA mutation data. CONCLUSIONS: We demonstrate that relaxing the assumption that stem-cell positions are fixed enables clonal expansion and niche succession to occur. We also predict that the presence of extracellular factors near the base of the crypt alone suffices to explain the observed spatial variation in nuclear beta-catenin levels along the crypt axis.

The parturient with coronary heart disease.

Cardiac disease is one of the leading indirect causes of maternal mortality in the UK, exceeding numbers of direct deaths from thromboembolism and hypertension combined. Over one year in our unit we managed six women with coronary heart disease. In this series five women had stable coronary heart disease. Three delivered electively by caesarean section under combined spinal-epidural anaesthesia, a further two women had spontaneous vaginal deliveries, one planned under epidural analgesia, the second unplanned after a rapid labour. The sixth woman had unstable angina requiring percutaneous coronary intervention in the 28th week of pregnancy and went on to deliver by caesarean section under general anaesthesia. Regional anaesthesia was avoided in this case because of antiplatelet and anticoagulant medication. There is a lack of level-one evidence to direct the management of these women. Clinical decisions were directed by guidelines for the perioperative management of patients with cardiac disease in non-cardiac surgery and the management of all cardiac disease in the obstetric population. A multi-disciplinary approach was taken, with a collaborative plan made for each pregnancy and delivery. A thorough clinical history and examination together with transthoracic echocardiography allows risk stratification of women with coronary heart disease at risk of peripartum cardiac events. Further investigation specific to each woman's management can then be undertaken.

Erratum: ZnO-based MIS photodetectors.

[This corrects the article DOI: 10.1016/j.sna.2007.06.006.].

Do resuscitation attempts in children who die, cause injury?

OBJECTIVE: To determine the incidence, type, and pattern of injury related to resuscitation attempts in children who die. DESIGN: Retrospective review of ambulance, hospital, and necropsy case records. METHOD: All children who died aged 0-14 years between 1994 and 1996, and underwent a full necropsy at the Victorian Institute of Forensic Medicine (Melbourne, Australia) were identified. Children who were subject to recognised trauma before resuscitation or died because of a congenital abnormality were excluded. The records of all remaining children were reviewed. Children were grouped according to whether resuscitation was attempted or not. RESULTS: From a total of 346 children who died, 204 (58.6%) were identified as meeting the inclusion criteria. Resuscitation was performed in 153 (75%) children and was started before ambulance arrival in 123 (60.3%) children. Injuries were detected at necropsy in 65 (42.5%) of children who had resuscitation compared with six (11.7%) of children who had no resuscitation (p<0.0001) chi(2) test. All but two of these injuries were of a minor nature consisting principally of bruises or abrasions. Two significant injuries were identified both occurring as a result of readily identifiable resuscitation procedures. The likelihood of injury increased with the length of resuscitation. In children resuscitated for less than 60 minutes the incidence of injury was 27% compared with 62% for children resuscitated for longer ( p<0.0001). CONCLUSION: This study has shown that cardiopulmonary resuscitation commonly causes minor injuries such as superficial bruises and abrasions and the likelihood of such injury increases with the duration of the cardiopulmonary resuscitation. This information should reassure parents and caregivers that basic life support may be instituted without fear of causing significant injury or adversely affecting outcome in the child with cardiorespiratory arrest. Caution must be exercised when attributing significant injuries to resuscitation attempts and alternative causes must be fully investigated.

The non-specific inhibition of enzymes by environmental pollutants: a study of a model system towards the development of electrochemical biosensor arrays.

Previous research has shown that lactate dehydrogenase (LDH) was competitively inhibited by pentachlorophenol (PCP) and a modified assay produced a detection limit of 1 microM (270 microg l(-1)). This work used spectrophotometric rate-determination but in order to move towards biosensor development the selected detection method was electrochemical. The linkage of LDH to lactate oxidase (LOD) provided the electroactive species, hydrogen peroxide. This could be monitored using a screen-printed carbon electrode (SPCE) incorporating the mediator, cobalt phthalocyanine, at a potential of +300 mV (vs. Ag/AgCl). A linked LDH/LOD system was optimised with respect to inhibition by PCP. It was found that the SPCE support material, PVC, acted to reduce inhibition, possibly by combining with PCP. A cellulose acetate membrane removed this effect. Inhibition of the system was greatest at enzyme activities of 5 U ml(-1) LDH and 0.8 U ml(-1) LOD in reactions containing 246 microM pyruvate and 7.5 microM NADPH. PCP detection limits were an EC(10) of 800 nM (213 microg l(-1)) and a minimum inhibition detectable (MID) limit of 650 nM (173 microg l(-1)). The inclusion of a third enzyme, glucose dehydrogenase (GDH), provided cofactor recycling to enable low concentrations of NADPH to be incorporated within the assay. NADPH was reduced from 7.5 to 2 microM. PCP detection limits were obtained for an assay containing 5 U ml(-1) LDH, 0.8 U ml(-1) LOD and 0.1 U ml(-1) GDH with 246 microM pyruvate, 400 mM glucose and 2 microM NADPH. The EC(10) limit was 150 nM (39.9 microg l(-1)) and the MID was 100 nM (26.6 microg l(-1)). The design of the inhibition assays discussed has significance as a model for other enzymes and moves forward the possibility of an electrochemical biosensor array for pollution monitoring.

Striatal cells containing aromatic L-amino acid decarboxylase: an immunohistochemical comparison with other classes of striatal neurons.

In a previous study, we described a population of striatal cells in the rat brain containing aromatic L-amino acid decarboxylase, the enzyme involved in the conversion of L-DOPA into dopamine. We have also presented evidence that these cells produce dopamine in the presence of exogenous L-DOPA. In this paper, we further characterize these striatal aromatic L-amino acid decarboxylase-containing cells in order to determine whether they form a subclass of one of the known categories of striatal neurons or if they represent a novel cell type. Using immunohistochemical methods, we compared the morphology and distribution of the aromatic L-amino acid decarboxylase-immunolabeled cells with those of other classes of striatal neurons. Our results show that both the morphology and distribution of aromatic L-amino acid decarboxylase-immunolabeled cells are very distinctive and do not resemble those of cells labeled for other striatal neuronal markers. Double-labeling procedures revealed that aromatic L-amino acid decarboxylase cells do not co-localize somatostatin or parvalbumin, and only a very small percentage of them co-localize calretinin. However, the population of aromatic L-amino acid decarboxylase cells label intensely for GABA.Overall, our results suggest that these aromatic L-amino acid decarboxylase-containing cells represent a class of striatal GABAergic neurons not described previously.

International telemicroscopy with a 3 MV ultrahigh voltage electron microscope.

The ability for remote microscope operation via a network connection was added recently to the ultrahigh voltage electron microscope (UHVEM) in Osaka University, and used successfully for the observation of thick biological samples across the Pacific Ocean by researchers at the National Center for Microscopy and Imaging Research (NCMIR) at the University of California San Diego. High-quality images at video rate were transferred by a satellite link and control signals were transmitted by an ISDN connecting the workstations at both sites. Most microscope functions operated from the console of the UHVEM were replicated on the graphical user interface of the remote workstation. By clicking on icons or in boxes in the display window with a mouse, the researcher could operate the UHVEM from the remote-site. The total delay time for sending images and returning control signals was about 0.7 s, which did not interfere significantly with the smooth operation of the instrument. Researchers at the remote site were able to record images on film in the microscope which were later sent to San Diego.

Inhalant abuse and the abuse of other drugs.

AIMS: To examine the relationship between inhalant abuse and other substances of abuse. DESIGN: Survey using a structured interview administered by a single trained interviewer. SETTING: A juvenile detention facility. PARTICIPANTS: 209 children incarcerated at the facility over a 3-month period. SELECTION PROCEDURE: Consecutive sample. INTERVENTIONS: None. MEASUREMENTS/FINDINGS: The structured interview was adapted from the American Drug and Alcohol Survey, which has been extensively used to obtain substance abuse epidemiologic data. We collected information on inhalants, alcohol, marijuana, downers, pep pills, lysergic acid diethylamide (LSD), cocaine, designer drugs, phencyclidine (PCP), Talwin and Ritalin, speed, and narcotics. The chi-square or Fisher exact test were used when appropriate. Mean ages of initial experimentation were as follows: inhalants, 9.7 years; marijuana, 11.9 years; alcohol (inebriated), 12.0 years; cigarettes, 11.2 years; for the remaining substances of abuse, the mean age was 13.2-14.7 years. Thirty subjects had used inhalants. Significant relationships were found between inhalants and cocaine (p = .004), Talwin and Ritalin (p = .001), downers (p = .01), and narcotics (p = .003). CONCLUSIONS: For children incarcerated in a juvenile detention facility in our community, inhalant abuse is associated with the later use of other substances of abuse. If this finding is replicated in other populations, it underscores the need for effective preventive strategies.

Web-based telemicroscopy.

By taking advantage of network-based computing and the recent developments in Web interfaces, centralized research facilities housing specialized and unique imaging instruments along with associated high-performance computing can be made available to researchers for use from their own laboratories. In addition to increasing access and utilization of these facilities, operation over the Internet is expected to enhance research by facilitating collaboration between researchers. We describe the implementation of a platform-independent Web-based system written in Java that supplements automated functions with video-guided interactive, collaborative remote control and data acquisition from an intermediate-high-voltage electron microscope.

Modification of postsynaptic densities after transient cerebral ischemia: a quantitative and three-dimensional ultrastructural study.

Abnormal synaptic transmission has been hypothesized to be a cause of neuronal death resulting from transient ischemia, although the mechanisms are not fully understood. Here, we present evidence that synapses are markedly modified in the hippocampus after transient cerebral ischemia. Using both conventional and high-voltage electron microscopy, we performed two- and three-dimensional analyses of synapses selectively stained with ethanolic phosphotungstic acid in the hippocampus of rats subjected to 15 min of ischemia followed by various periods of reperfusion. Postsynaptic densities (PSDs) from both area CA1 and the dentate gyrus were thicker and fluffier in postischemic hippocampus than in controls. Three-dimensional reconstructions of selectively stained PSDs created using electron tomography indicated that postsynaptic densities became more irregular and loosely configured in postischemic brains compared with those in controls. A quantitative study based on thin sections of the time course of PSD modification indicated that the increase in thickness was both greater and more long-lived in area CA1 than in dentate gyrus. Whereas the magnitude of morphological change in dentate gyrus peaked at 4 hr of reperfusion (140% of control values) and declined thereafter, changes in area CA1 persisted and increased at 24 hr of reperfusion (191% of control values). We hypothesize that the degenerative ultrastructural alteration of PSDs may produce a toxic signal such as a greater calcium influx, which is integrated from the thousands of excitatory synapses onto dendrites, and is propagated to the neuronal somata where it causes or contributes to neuronal damage during the postischemic phase.

Altered long-term potentiation in the hippocampus of apolipoprotein E-deficient mice.

Recent studies suggest that apolipoprotein E (apoE) plays a neurotrophic role in the central nervous system and that an aberrant function of this molecule might result in neurodegeneration. Supporting this notion, apoE-deficient mice show neurodegenerative and cognitive alterations. To characterize physiological changes associated with synaptic damage and cognitive impairment in apoE-deficient mice, we investigated synaptic plasticity in the hippocampus of urethane anesthetized mice. Electrical stimulation was delivered to the perforant pathway and the resulting evoked field excitatory postsynaptic potential (EPSP) and population spike were recorded in the hilus. Long-term potentiation, as measured in the population spike, was reduced by 50% in apoE-deficient mice when compared to wild-type controls. In contrast, there were no significant differences in the evoked field EPSP between wild-type and apoE-deficient mice following high-frequency stimulation. These results support the notion that cognitive impairment and synaptic loss in the hippocampus of apoE-deficient mice might be associated with impaired long-term potentiation.

Intravenous tenoxicam for analgesia following laparoscopic cholecystectomy.

In a double-blind, placebo-controlled clinical trial (power of 80% to detect a 30% reduction in morphine consumption, P < 0.05) we have determined that intraoperative intravenous administration of tenoxicam 40 mg during laparoscopic cholecystectomy, when compared with placebo, was associated with a significant reduction in consumption of morphine at 6 hours and 12 hours (P < 0.05) but not at 24 hours, when assessed by patient-controlled analgesia. Furthermore there was a significantly greater requirement for "rescue" analgesia with intramuscular morphine in the placebo group during the period of the study. There was no difference between the groups in pain scores, either at rest or on movement, nor in the incidence of nausea and vomiting. No patient in either group suffered a respiratory rate less than 8/min or oversedation at any time, and there were no other adverse effects.

The health of a group of young Australians in a New South Wales juvenile justice detention centre: a pilot study.

OBJECTIVE: To consider the health profile of a sample of young, largely male Australians as assessed on their admission to a New South Wales Juvenile Justice Detention Centre. METHOD: A retrospective analysis of primary care nurse health records for 100 sequential admissions. RESULTS: Of the 97 males and three females (mean age = 15.9 years), 30 were Aboriginal and 39 did not live with either parent at the time of admission. Respiratory illness, such as bronchitis and asthma were common. These diagnoses were overshadowed by histories of significant physical injury. The sample was at high risk of sexually transmitted disease. Forty-six per cent had prior contact with a mental health professional, 26% reported they had thought of suicide and 9% reported having attempted suicide. There was a high prevalence of substance abuse. CONCLUSION: The health of these young Australians is at risk from every perspective. Improving the quality of their health assessments is an important issue for the clinicians who attend them as individuals and for policy makers who aim to reduce the considerable social and economic cost of juvenile crime. The discussion of these results from one centre has revealed opportunities to make such improvements. There is a need for a gathering of expertise to address the issue, preferably on a national basis.

Fine structure of the murine leptin receptor gene: splice site suppression is required to form two alternatively spliced transcripts.

The fine structure of the murine leptin receptor gene (Lepr) is described. Duplicated ligand binding domains (conserved among cytokine receptors) are found in eight exons (coding exons 3 to 6 and 8 to 11). Thus, it is possible that a single leptin receptor molecule could have two functional ligand binding domains. The transmembrane region of Lepr is in coding exon 16 while the juxtamembrane JAK docking site is in coding exon 17. For all membrane-bound forms, the transcript must include 17 invariant exons and 1 alternatively spliced 3' terminal exon. The transcript encoding the soluble receptor (Re) includes 14 coding exons and an alternatively spliced 3' terminal exon. We have identified two splice variants (Rc and Re) for which there are no intervening sequences between the two final exons. This unusual juxtaposition of exons requires that splice donor sites at the 5' end of the respective terminal exons be ignored in the production of these splice variants. We suggest that splice site suppression is responsible for the formation of two of the alternatively spliced forms of the mouse Lepr gene. The juxtaposition of two coding exons separated by a consensus splice donor sequence is the structural substrate for this mode of alternative splicing. We present evidence that the Rc form is expressed in human tissues while the Re form, the soluble receptor, is not expressed.

Lesions in the dentate hilum and CA2/CA3 regions of the rat hippocampus produce cognitive deficits that correlate with site-specific glial activation.

Thirty male rats pressed a lever three times (FR3) when a stimulus light (sD) was off to obtain sucrose pellets. They were then evenly divided into sham Controls versus groups lesioned bilaterally in the hippocampus by stercotaxic injection of ibotenic acid into the dentate hilum (HIL) or the CA2/CA3 region (CA2/3). On measures of recall of the FR3-sD task taken during the initial 30 min of a postlesion test session, the CA2/3 and especially the HIL groups showed significant (p < .05) impairments relative to the Controls. During an ensuing 30-min period, rats were reshaped to criterion, beginning at FR1, and no appreciable intergroup differences were noted on this schedule or at FR1-sD. At FR2-sD, the HIL but not the CA2/3 group showed some impairment relative to Controls. At FR3-sD, both the CA2/3 and HIL groups had impaired task performance. An immunocytochemical index of glial activation showed higher reactivity in CA2/3 or the dentate hilum among CA2/3 or HIL animals, respectively, that was associated with the degree to which they showed an FR3-sD performance deficit.