Emerging dominance of summer rainfall driving High Arctic terrestrial-aquatic connectivity.

Hydrological transformations induced by climate warming are causing Arctic annual fluvial energy to shift from skewed (snowmelt-dominated) to multimodal (snowmelt- and rainfall-dominated) distributions. We integrated decade-long hydrometeorological and biogeochemical data from the High Arctic to show that shifts in the timing and magnitude of annual discharge patterns and stream power budgets are causing Arctic material transfer regimes to undergo fundamental changes. Increased late summer rainfall enhanced terrestrial-aquatic connectivity for dissolved and particulate material fluxes. Permafrost disturbances (<3% of the watersheds' areal extent) reduced watershed-scale dissolved organic carbon export, offsetting concurrent increased export in undisturbed watersheds. To overcome the watersheds' buffering capacity for transferring particulate material (30 ± 9 Watt), rainfall events had to increase by an order of magnitude, indicating the landscape is primed for accelerated geomorphological change when future rainfall magnitudes and consequent pluvial responses exceed the current buffering capacity of the terrestrial-aquatic continuum.

Century-scale time since permafrost thaw affects temperature sensitivity of net methane production in thermokarst-lake and talik sediments.

Permafrost thaw subjects previously frozen soil organic carbon (SOC) to microbial degradation to the greenhouse gases carbon dioxide (CO2) and methane (CH4). Emission of these gases constitutes a positive feedback to climate warming. Among numerous uncertainties in estimating the strength of this permafrost carbon feedback (PCF), two are: (i) how mineralization of permafrost SOC thawed in saturated anaerobic conditions responds to changes in temperature and (ii) how microbial communities and temperature sensitivities change over time since thaw. To address these uncertainties, we utilized a thermokarst-lake sediment core as a natural chronosequence where SOC thawed and incubated in situ under saturated anaerobic conditions for up to 400 years following permafrost thaw. Initial microbial communities were characterized, and sediments were anaerobically incubated in the lab at four temperatures (0 °C, 3 °C, 10 °C, and 25 °C) bracketing those observed in the lake's talik. Net CH4 production in freshly-thawed sediments near the downward-expanding thaw boundary at the base of the talik were most sensitive to warming at the lower incubation temperatures (0 °C to 3 °C), while the overlying sediments which had been thawed for centuries had initial low abundant methanogenic communities (< 0.02%) and did not experience statistically significant increases in net CH4 production potentials until higher incubation temperatures (10 °C to 25 °C). We propose these observed differences in temperature sensitivities are due to differences in SOM quality and functional microbial community composition that evolve over time; however further research is necessary to better constrain the roles of these factors in determining temperature controls on anaerobic C mineralization.

Human pluripotent stem cells for modeling toxicity.

The development of xenobiotics, driven by the demand for therapeutic, domestic and industrial uses continues to grow. However, along with this increasing demand is the risk of xenobiotic-induced toxicity. Currently, safety screening of xenobiotics uses a plethora of animal and in vitro model systems which have over the decades proven useful during compound development and for application in mechanistic studies of xenobiotic-induced toxicity. However, these assessments have proven to be animal-intensive and costly. More importantly, the prevalence of xenobiotic-induced toxicity is still significantly high, causing patient morbidity and mortality, and a costly impediment during drug development. This suggests that the current models for drug safety screening are not reliable in toxicity prediction, and the results not easily translatable to the clinic due to insensitive assays that do not recapitulate fully the complex phenotype of a functional cell type in vivo. Recent advances in the field of stem cell research have potentially allowed for a readily available source of metabolically competent cells for toxicity studies, derived using human pluripotent stem cells harnessed from embryos or reprogrammed from mature somatic cells. Pluripotent stem cell-derived cell types also allow for potential disease modeling in vitro for the purposes of drug toxicology and safety pharmacology, making this model possibly more predictive of drug toxicity compared with existing models. This article will review the advances and challenges of using human pluripotent stem cells for modeling metabolism and toxicity, and offer some perspectives as to where its future may lie.

Renal effects of hypotensive anaesthesia in combination with acute normovolaemic haemodilution with hydroxyethyl starch 130/0.4 or isotonic saline.

BACKGROUND: Hypotensive anaesthesia (HA) and acute normovolaemic haemodilution (ANH) are used separately to decrease per-operative blood loss. Reducing blood viscosity by adding ANH to HA may appear profitable in a situation with lowered perfusion pressure and concern about organ ischemia. The aim of this study was to clarify the influence of HA in combination with ANH using crystalloid or colloid as replacement fluid on renal function. METHODS: Hypotensive anaesthesia was induced in 11 patients referred to major spine surgery using sevoflurane in combination with fentanyl/remifentanil. Acute normovolaemic haemodilution was carried out by drawing venous blood into standard blood bags and replacing it by isotonic saline 0.9% (Group S) or HES 130/0.4 (Group V). Renal function was evaluated before, during and up to 8 h after hypotension as the glomerular filtration rate (GFR) and effective renal plasma flow (ERPF) by means of 51Cr-EDTA and 125I-Hippuran clearances. RESULTS: Lowering mean arterial blood pressure decreased GFR and ERPF in both groups. During hypotension ERPF was lower in Group S (n = 5) than Group V (n = 6). Renal function was normalized postoperatively. We found a positive but non-significant correlation between the relative GFR change and the duration of hypotension. CONCLUSION: In conclusion, our study demonstrated that renal function, assessed by GFR and ERPF, is transiently reduced during the combination of hypotensive anaesthesia and acute normovolaemic haemodilution. A colloid-based fluid regime (HES 130/0.4) used for haemodilution may preserve renal function to a greater extent than a crystalloid-based regime (0.9% saline).

Thrombelastographic whole blood clot formation after ex vivo addition of plasma substitutes: improvements of the induced coagulopathy with fibrinogen concentrate.

BACKGROUND: Plasma substitutes such as hydroxyethyl starch (HES) and various dextrans may compromise the haemostatic system, thereby causing potentially dangerous bleeding. Whilst several mechanisms have been advanced to explain the nature of the coagulopathy induced by this colloid, there has been comparably little interest in devising ways to optimize haemostasis after a relative colloid overdose. METHODS: Real-time whole blood (WB) clot formation profiles were recorded using a thrombelastographic method employing activation with tissue factor. The coagulation tracings were transformed into dynamic velocity profiles of WB clot formation. WB from healthy individuals (n=20) was exposed to haemodilution of approximately 55% with isotonic saline, HES 200/0.5, HES 130/0.4, and dextran 70, respectively. Possible modalities for improvement of the induced coagulopathy were explored, in particular ex vivo addition of a fibrinogen concentrate. RESULTS: WB coagulation profiles changed significantly with decreased clot strength, and a compromised propagation phase of clot formation. The duration of the initiation phase of WB coagulation was unchanged. No statistical differences were detected amongst the HES solutions and dextran 70. However, dextran 70 returned a more suppressed clot development and strength compared with the HES solutions. Ex vivo haemostatic addition of washed platelets (75 x 10(9) litre(-1)) and factor VIII (0.6 IU ml(-1)) produced insignificant changes in clot initiation, propagation, and in the clot strength. In contrast, ex vivo addition of a fibrinogen concentrate (1 g litre(-1)) improved the coagulopathy induced by all of the three individual plasma expanders tested. CONCLUSION: Coagulopathy induced by haemodilution with either HES 200/0.5, HES 130/0.4, and dextran 70 may be improved by fibrinogen supplementation.

The health and welfare needs of female and transgender street sex workers in New South Wales.

OBJECTIVES: To determine the health and welfare status of female and transgender street sex workers and their work-related experiences. Also to estimate population numbers, determine work locations, and identify the most appropriate education, health and welfare services for this group. METHODS: Forty-eight street sex workers completed a questionnaire, mainly at their place of work. Demographic and sexual health profiles of sex workers attending the Sydney Sexual Health Centre and the Kirketon Road Centre in 1997 were compared with the street sample. RESULTS: Up to 120 female and transgender sex workers worked on the streets in Sydney, Newcastle, Wollongong and surrounding areas in any one night: more than 80% of these were female. Of those sampled, fewer street workers than brothel sex workers (6% vs. 41%; p<0.001) were from non-English speaking backgrounds, and more (77% vs. 7%; p<0.0001) were currently injecting drugs. The street workers reported lower rates of condom use at work than local brothel workers (91.7% vs. 98.8%; p<0.016) and high rates of hepatitis B and C infection. Seventy-five per cent had experienced violence at work. Child care, lack of supportive relationships, community intolerance and low self-esteem were important problems for the street workers. While the police were frequently required by the community to move the street workers on, there were no reports of corrupt behaviour by police. CONCLUSIONS: Health services need to specifically target this group with particular attention to the prevention of blood-borne virus infections, contraception, drug dependency and transgender issues. Consideration should be given to developing a network of safe houses to reduce community pressure and violence.

Protection of cattle from bovine tuberculosis by vaccination with BCG by the respiratory or subcutaneous route, but not by vaccination with killed Mycobacterium vaccae.

Groups of cattle were vaccinated either with BCG Pasteur by the intratracheal or subcutaneous route or with killed Mycobacterium vaccae by the intradermal route and challenged intratracheally 54 days later with Mycobacterium bovis. Vaccination with BCG resulted in fewer animals developing tuberculous lesions and in a reduction in the number of lesions in the diseased animals compared with the unvaccinated group and the group vaccinated with M vaccae. None of the nine animals vaccinated intratracheally with BCG developed any tuberculous lung lesions after challenge with M bovis, but two of the nine animals from each of the groups dosed subcutaneously with low and medium doses of BCG developed lung lesions. There was little difference in protection against the M bovis challenge between the animals receiving the low dose (10(3) colony forming units, cfu) or medium dose (10(5) cfu) of subcutaneous BCG, but the medium dose of BCG produced stronger cell-mediated immune responses to bovine purified protein derivative (PPD) after vaccination. Vaccination intradermally with 10(9) heat-killed M vaccae did not protect cattle against an experimental challenge with M bovis and induced only weak cell-mediated immune responses to bovine PPD.

Evaluation of three serological assays for the diagnosis of Mycobacterium bovis infection in brushtail possums.

Three serological tests for the diagnosis of Mycobacterium bovis infection were evaluated on 29 possums (Trichosurus vulpecula) with tuberculosis and on 100 possums from a tuberculosis-free area. An indirect ELISA using M. bovis culture filtrate as the antigen had a sensitivity of 45% and a specificity of 96%, while an indirect ELISA using a M. bovis specific antigen (MPB70) had a sensitivity of 21% and a specificity of 98%. A blocking ELISA which utilised a monoclonal antibody against MPB70 had a sensitivity of 28% and a specificity of 99%. Combination of the test results of the three ELISAs resulted in an increase in sensitivity to 51% and a decrease in specificity to 93%. A previous study has shown that possums experimentally infected with M. bovis produced cellular responses to M. bovis antigens relatively early in the infection, but these responses decreased in the terminal stages of the disease. In contrast, analysis of serological responses in the current study from sequentially collected sera of possums experimentally and naturally infected with M. bovis showed that antibody was first detected late in the disease.

Effectiveness of BCG vaccination in protecting possums against bovine tuberculosis.

Three groups of eight possums were vaccinated with BCG Pasteur by the subcutaneous, intratracheal or intragastric routes, with a fourth group serving as unvaccinated controls. Forty-two days after the start of vaccination, five possums from each group were challenged intratracheally with virulent Mycobacterium bovis. The vaccination by the subcutaneous or intratracheal routes resulted in a marked reduction in the severity of disease compared with the unvaccinated animals or the animals vaccinated intragastrically. The severity of the disease was assessed by changes in bodyweight, pathological changes in the lungs and bronchial nodes and the number of acid-fast bacilli in the lesions. Before the challenge, lymphocyte blastogenic responses to bovine PPD were observed in the eight animals vaccinated subcutaneously and in two of the animals vaccinated intratracheally.

Peritoneal fine structure of inguinal hernia: a transmission electron microscope study.

Fine structure of normal human parietal peritoneum served as control data for recording changes in the fine structure of the peritoneum of hernial sacs. In these sacs, mesothelial cells retracted, rounded up and some of them eventually separated altogether to give rise to wide open intercellular spaces thus creating unhindered passageways (stomata) between the subserosal connective tissue and the cavity of the sacs. There was a considerable collagen build-up in the subserosal fibrous tissue of hernial sacs. Occurrence of this fibrosis is at variance with an accepted surgical concept which suggests a defect in collagen synthesis as the cause of herniation. In some sacs mesothelial nodules and/or peritoneal adhesions were present. Certain cytological changes in the mesothelial cells of hernial sacs showed features in common with cells of malignant tumours in general, and features mimicking malignant mesotheliomas in particular. This is in spite of the fact that thorough gross and light microscopic examination of operative specimens and cytological evaluation of peritoneal effusion failed to reveal any evidence of malignancy. Pathologists should be aware of the consummate ability of mesothelial cells to mimic carcinomas in order to avoid possible diagnostic errors. In this report, an electron micrograph of peritoneal adhesion is being published for the first time in the literature. A syncytium-like firm bond between adjoining mesothelial cells constituted the adhesion which is obviously an irreversible process.

Beneficial response to megoestrol acetate in AIDS-related cachexia and a possible megoestrol withdrawal-associated syndrome?

A man with AIDS is described in whom a profound weight loss was converted into a weight gain by treatment with megoestrol acetate, a synthetic progesterone. His appetite improved and was accompanied by a feeling of improved well-being. Following abrupt discontinuation of the drug, there was a significant but transient depression of mood and appetite associated with loss of energy; it is suggested that this complex of symptoms might represent a megoestrol acetate withdrawal-associated syndrome.

Piles and rectoceles.

Symptomatic rectocele is known to contribute to the formation of piles in female patients. This paper describes a subset of women pile sufferers who have occult rectoceles which are asymptomatic, and which are not obvious on routine visual examination, even with the use of the speculum. These patients are multiparous and have sustained perineal damage either from episiotomy or from laceration. They present with symptoms of piles. If treated by conventional pile surgery the postoperative course is bedevilled with difficult defaecation, the patient often needing to insert a finger into the vagina to gain satisfactory evacuation. An accurate case history will show all these patients to have a preoperative story of straining at stool. Anterior rectal wall pressure on rectal examination shows a definite occult rectocele (spinnaker deformity) coupled with a deficient scarred perineum. This paper describes 15 such patients who have been seen over the past 4 years. Treatment has been by either pile surgery and later colpoperineorrhaphy (four cases), by combined colpoperineorrhaphy and pile surgery (eight cases), or by surgical correction of the rectocele alone (three cases).

Subsecond and second changes in inositol polyphosphates in GH4C1 cells induced by thyrotropin-releasing hormone.

It has been demonstrated previously that thyrotropin-releasing hormone (TRH) induces changes in inositol polyphosphates in the GH3 and GH4C1 strains of rat pituitary cells within 2.5-5.0 s. TRH also causes a rapid rise in cytosolic free calcium concentration ([Ca2+]i) in these cells which is due largely to redistribution of cellular calcium stores. Therefore, it has been concluded that TRH acts to release sequestered calcium in these cells via enhanced generation of inositol 1,4,5-trisphosphate [Ins(1,4,5)P3]. If this conclusion were correct, TRH-enhanced accumulation of Ins(1,4,5)P3 should occur at least as rapidly as the increase in [Ca2+]i. We have shown previously that the rise in [Ca2+]i induced by TRH occurs within about 400 ms; thus, it was important to investigate the subsecond time-course of changes in inositol phosphates caused by TRH. Using a rapid mixing device, we have measured changes in inositol polyphosphates on a subsecond time scale in GH4C1 cells prelabelled with myo-[2-3H]inositol. Although TRH did alter inositol polyphosphate metabolism within 500 ms, the changes observed did not reveal a statistically significant increase in Ins(1,4,5)P3 within time intervals of less than 1000 ms. Thus, we have been unable to demonstrate that a TRH-induced rise in Ins(1,4,5)P3 precedes or occurs concomitantly with the rise in [Ca2+]i in GH4C1 cells. Although these results do not disprove the current view that Ins(1,4,5)P3 mediates the action of TRH on intracellular calcium redistribution, we conclude that caution should be exercised in this, and possibly other cell systems, in accepting the dogma that all of the rapid, agonist-induced redistributions of intracellular calcium are mediated by Ins(1,4,5)P3.

Inositol(3,4)bisphosphate and inositol(1,3)bisphosphate in GH4 cells--evidence for complex breakdown of inositol(1,3,4)trisphosphate.

Analysis of inositol bisphosphates in GH4 cells labelled with [3H]myo-inositol shows that these cells contain three detectable inositol bisphosphates: inositol(1,4)bisphosphate, and two novel inositol bisphosphates. These latter inositol bisphosphates were degraded by periodate oxidation, borohydride reduction and alkaline phosphatase dephosphorylation; each yielded single non-cyclic alditols, ribitol and threitol, indicating that they must be respectively inositol(1,3)bisphosphate and inositol(3,4) bisphosphate. These two inositol bisphosphates are putative breakdown products of inositol(1,3,4)trisphosphate, and their occurrence suggests a complex route of hydrolysis of inositol(1,3,4)trisphosphate in intact cells.

Effects of bombesin and insulin on inositol (1,4,5)trisphosphate and inositol (1,3,4)trisphosphate formation in Swiss 3T3 cells.

The effects of bombesin and insulin, separately and in combination, have been studied in Swiss mouse 3T3 cells. Bombesin caused a rapid transfer of 3H from the lipid inositol pool of prelabeled cells into inositol phosphates. Label in inositol tetrakisphosphate (InsP4) and in Ins1,4,5P3 and Ins1,3,4P3 rose within 10 sec of stimulation and that in Ins1,4P2, another InsP2 and InsP1, more slowly. Insulin, which had little effect on its own, increased the turnover of inositol lipids due to acute bombesin stimulation and also enhanced the DNA synthesis evoked by prolonged bombesin treatment. The results suggest that bombesin acting as a growth factor, uses inositol lipids as part of its transduction mechanism and that insulin acts synergistically to enhance both inositol phosphate formation and DNA synthesis.

The inositol tris/tetrakisphosphate pathway--demonstration of Ins(1,4,5)P3 3-kinase activity in animal tissues.

Recent advances in our understanding of the role of inositides in cell signalling have led to the central hypothesis that a receptor-stimulated phosphodiesteratic hydrolysis of phosphatidylinositol 4,5-bisphosphate (PtdIns(4,5)P2) results in the formation of two second messengers, diacylglycerol and inositol 1,4,5-trisphosphate (Ins(1,4,5)P3). The existence of another pathway of inositide metabolism was first suggested by the discovery that a novel inositol trisphosphate, Ins(1,3,4)P3, is formed in stimulated tissues; the metabolic kinetics of Ins(1,3,4)P3 are entirely different from those of Ins(1,4,5)P3 (refs 6, 7). The probable route of formation of Ins(1,3,4)P3 was recently shown to be via a 5-dephosphorylation of inositol 1,3,4,5-tetrakisphosphate (Ins(1,3,4,5)P4), a compound which is rapidly formed on muscarinic stimulation of brain slices, and which can be readily converted to Ins(1,3,4)P3 by a 5-phosphatase in red blood cell membranes. However, the source of Ins(1,3,4,5)P4 is unclear, and an attempt to detect a possible parent lipid, phosphatidylinositol 3,4,5-trisphosphate (PtdIns(3,4,5)P3), was unsuccessful. The recent discovery that the higher phosphorylated forms of inositol (InsP5 and InsP6) also exist in animal cells suggested that inositol phosphate kinases might not be confined to plant and avian tissues, and here we show that a variety of animal tissues contain an active and specific Ins(1,4,5)P3 3-kinase. We therefore suggest that an inositol tris/tetrakisphosphate pathway exists as an alternative route to the dephosphorylation of Ins(1,4,5)P3. The function of this novel pathway is unknown.