Shelf-ocean exchange and hydrography west of the Antarctic Peninsula: a review

The West Antarctic Peninsula (WAP) is a highly productive marine ecosystem where extended periods of change have been observed in the form of glacier retreat, reduction of sea-ice cover and shifts in marine populations, among others. The physical environment on the shelf is known to be strongly influenced by the Antarctic Circumpolar Current flowing along the shelf slope and carrying warm, nutrient-rich water, by cold waters flooding into the northern Bransfield Strait from the Weddell Sea, by an extensive network of glaciers and ice shelves, and by strong seasonal to inter-annual variability in sea-ice formation and air-sea interactions, with significant modulation by climate modes like El Niño-Southern Oscillation and the Southern Annular Mode. However, significant gaps have remained in understanding the exchange processes between the open ocean and the shelf, the pathways and fate of oceanic water intrusions, the shelf heat and salt budgets, and the long-term evolution of the shelf properties and circulation. Here, we review how recent advances in long-term monitoring programmes, process studies and newly developed numerical models have helped bridge these gaps and set future research challenges for the WAP system.This article is part of the theme issue 'The marine system of the West Antarctic Peninsula: status and strategy for progress in a region of rapid change'.

Chemosensory cues affect amygdaloid neurogenesis and alter behaviors in the socially monogamous prairie vole

The current study examined the effects of pheromonal exposure on adult neurogenesis and revealed the role of the olfactory pathways on adult neurogenesis and behavior in the socially monogamous prairie vole (Microtus ochrogaster). Subjects were injected with a cell proliferation marker [5-bromo-2'-deoxyuridine (BrdU)] and then exposed to their own soiled bedding or bedding soiled by a same- or opposite-sex conspecific. Exposure to opposite-sex bedding increased BrdU labeling in the amygdala (AMY), but not the dentate gyrus (DG), of female, but not male, voles, indicating a sex-, stimulus-, and brain region-specific effect. The removal of the main olfactory bulbs or lesioning of the vomeronasal organ (VNOX) in females reduced BrdU labeling in the AMY and DG, and inhibited the male bedding-induced BrdU labeling in the AMY, revealing the importance of an intact olfactory pathway for amygdaloid neurogenesis. VNOX increased anxiety-like behavior and altered social preference, but it did not affect social recognition memory in female voles. VNOX also reduced the percentage of BrdU-labeled cells that co-expressed the neuronal marker TuJ1 in the AMY, but not the DG. Together, our data indicate the importance of the olfactory pathway in mediating brain plasticity in the limbic system as well as its role in behavior.

The tensor distribution function

Diffusion weighted magnetic resonance imaging is a powerful tool that can be employed to study white matter microstructure by examining the 3D displacement profile of water molecules in brain tissue. By applying diffusion-sensitized gradients along a minimum of six directions, second-order tensors (represented by three-by-three positive definite matrices) can be computed to model dominant diffusion processes. However, conventional DTI is not sufficient to resolve more complicated white matter configurations, e.g., crossing fiber tracts. Recently, a number of high-angular resolution schemes with more than six gradient directions have been employed to address this issue. In this article, we introduce the tensor distribution function (TDF), a probability function defined on the space of symmetric positive definite matrices. Using the calculus of variations, we solve the TDF that optimally describes the observed data. Here, fiber crossing is modeled as an ensemble of Gaussian diffusion processes with weights specified by the TDF. Once this optimal TDF is determined, the orientation distribution function (ODF) can easily be computed by analytic integration of the resulting displacement probability function. Moreover, a tensor orientation distribution function (TOD) may also be derived from the TDF, allowing for the estimation of principal fiber directions and their corresponding eigenvalues.

Variations in behavior and condition of a Southern Ocean top predator in relation to in situ oceanographic conditions

Responses by marine top predators to environmental variability have previously been almost impossible to observe directly. By using animal-mounted instruments simultaneously recording movements, diving behavior, and in situ oceanographic properties, we studied the behavioral and physiological responses of southern elephant seals to spatial environmental variability throughout their circumpolar range. Improved body condition of seals in the Atlantic sector was associated with Circumpolar Deep Water upwelling regions within the Antarctic Circumpolar Current, whereas High-Salinity Shelf Waters or temperature/salinity gradients under winter pack ice were important in the Indian and Pacific sectors. Energetic consequences of these variations could help explain recently observed population trends, showing the usefulness of this approach in examining the sensitivity of top predators to global and regional-scale climate variability.

The South African stroke risk in general practice study

BACKGROUND

Incidence of stroke is increasing in sub-Saharan Africa and stroke prevention is an essential component of successful stroke management. General practitioners (GPs) are well placed to manage stroke risk factors. To design appropriate strategies for risk factor reduction we need to know the risk factor prevalence in each of the population groups attending GPs. The aim of this study was to establish the prevalence of stroke risk factors in the South African general practice population.

METHOD

We conducted a multicentre, observational study of patients attending general practice in South Africa. Two hundred general practices were randomly selected from lists provided by pharmaceutical representatives. Each GP approached 50 consecutive patients aged 30 years and older. Patients completed an information sheet and the GP documented the patient's risk factors. The resulting sample is relevant if not necessarily representative in a statistical sense.

RESULTS

A total of 9 731 questionnaires were returned out of a possible 10,000. The mean age of particpants was 50.7 years. Seventy-six per cent had 1 or more risk factors and 40% had 2 or more risk factors. Hypertension was the commonest risk factor in all population groups (55%) but was highest in black patients (59%). Dyslipidaemia was commonest in whites (37%) and least common in blacks (5%). Diabetes was commonest in Asians (24%) but least common in whites (8%). Risk factors other than smoking increased with age.

CONCLUSION

This study provides unique data on the prevalence of stroke risk factors in a South African general practice population. Risk factors are common in all population groups, but differ in distribution among the groups. There is considerable opportunity to reduce the burden of stroke in South Africa through GP screening for and treatment of risk factors.

Vomeronasal organ: electrical stimulation activates Fos in mating pathways and in GnRH neurons

Electrical stimulation of the vomeronasal organ in male hamsters activated Fos expression in neurons of the chemosensory pathways, as in experiments where animals were stimulated with female chemical stimuli. Fos was also activated in gonadotropin hormone releasing hormone (GnRH, or LHRH) neurons in the rostral medial preoptic region of the brain, a possible substrate for GnRH influence on chemosensory-dependent reproductive behavior.

Risk factors for frequent and severe hypoglycemia in type 1 diabetes

OBJECTIVE

To determine the risk of frequent and severe hypoglycemia and the associated demographic and clinical risk factors.

RESEARCH DESIGN AND METHODS

Demographic and diabetes self-management factors were measured in 415 subjects followed prospectively for 4-6.5 years of type 1 diabetes duration as participants in a population-based incident cohort. Blood samples were collected up to three times yearly to test glycosylated hemoglobin (GHb) levels. Reports of frequent (2-4 times/week) and severe (lost consciousness) hypoglycemia as well as other diabetes self-management data were collected by questionnaires.

RESULTS

Frequent hypoglycemia was common (33 and 35% of participants reported this on the 4- and 6.5-year questionnaires, respectively), whereas severe hypoglycemia occurred much less often. Better glycemic control (odds ratio [OR] 1.3 per 2% decrease in GHb, 95% CI 1.1-1.5) and more frequent self-monitored blood glucose (1.5 per blood glucose check, 1.3-1.7) were independently related to frequent hypoglycemia. The association of frequent hypoglycemia with intensive insulin therapy increased with age. Better glycemic control (1.5 per 2% decrease in GHb, 1.2-2.0) and older age were related to severe hypoglycemic reactions. No sociodemographic factors other than age increased the risk of hypoglycemia.

CONCLUSIONS

Frequent hypoglycemia was common in a population representing the full range of glycemic control in the community. Intensive insulin management and blood glucose monitoring independently predicted frequent but not severe hypoglycemia. This information may be useful for updating patients such that minor changes in diabetes management might decrease the daily burden of this condition while maintaining intensive insulin therapy.

Human vomeronasal organ function: a critical review of best and worst cases

The human vomeronasal organ (VNO) has been the subject of some interest in the scientific literature and of considerable speculation in the popular science literature. A function for the human VNO has been both dismissed with ridicule and averred with conviction. This question of VNO function has been needlessly tied to the separate question of whether there is any place for pheromone communication among humans, a topic that is itself bogged down in conflicting definitions. This review is an attempt to weigh the evidence for and against human VNO function, to deconvolve that question from the question of pheromone communication and finally to provide a working definition of 'pheromone'. Further experimental work is required to resolve the conflicting evidence for and against human VNO function but chemical communication does appear to occur among humans. However, several examples reported in the literature do not meet the proposed definition for communication by pheromones: 'chemical substances released by one member of a species as communication with another member, to their mutual benefit'.

The ferret's vomeronasal organ and accessory olfactory bulb: effect of hormone manipulation in adult males and females

The male ferret, a carnivore, was recently shown to possess a vomeronasal organ (VNO). We compared the morphology of the VNO and its associated accessory olfactory bulb (AOB) in male and female ferrets that were killed in adulthood. The volume and surface area of the VNO neuroepithelium were similar in adult gonadectomized male and female ferrets regardless of whether they were treated with testosterone propionate (TP) or oil vehicle. An AOB was localized bilaterally in the medial caudal part of the olfactory bulbs of adult ferrets using soybean agglutin binding and immunostaining for luteinizing hormone-releasing hormone and tyrosine hydroxylase as well as Nissl staining of coronal, horizontal, and sagittal brain sections. There was no effect of sex or TP treatment on AOB cell layer volume in adult gonadectomized animals. We found the ferret's AOB to be more medially located and much smaller than previously reported in this species, thus highlighting the importance of using several histochemical markers to characterize this structure in any previously unexamined species. Adult male and female ferrets both have a VNO and an associated AOB. More research is needed to determine what role, if any, this accessory olfactory system plays in mediating behavioral and neuroendocrine responses to pheromones in ferrets of either sex.

A defect late in stimulus-secretion coupling impairs insulin secretion in Goto-Kakizaki diabetic rats

A widely accepted genetically determined rodent model for human type 2 diabetes is the Goto-Kakizaki (GK) rat; however, the lesion(s) in the pancreatic islets of these rats has not been identified. Herein, intact islets from GK rats (aged 8-14 weeks) were studied, both immediately after isolation and after 18 h in tissue culture. Despite intact contents of insulin and protein, GK islets had markedly deficient insulin release in response to glucose, as well as to pure mitochondrial fuels or a non-nutrient membrane-depolarizing stimulus (40 mmol/l K+). In contrast, mastoparan (which activates GTP-binding proteins [GBPs]) completely circumvented any secretory defect. Basal and stimulated levels of adenine and guanine nucleotides, the activation of phospholipase C by Ca2+ or glucose, the secretory response to pertussis toxin, and the activation of selected low-molecular weight GBPs were not impaired. Defects were found, however, in the autophosphorylation and catalytic activity of cytosolic nucleoside diphosphokinase (NDPK), which may provide compartmentalized GTP pools to activate G-proteins; a deficient content of phosphoinositides was also detected. These studies identify novel, heretofore unappreciated, defects late in signal transduction in the islets of our colony of GK rats, possibly occurring at the site of activation by NDPK of a mastoparan-sensitive G-protein-dependent step in exocytosis.

The ability of herpes simplex virus type 1 immediate-early protein Vmw110 to bind to a ubiquitin-specific protease contributes to its roles in the activation of gene expression and stimulation of virus replication

Herpes simplex virus type 1 immediate-early protein Vmw110 stimulates the onset of virus infection and is required for efficient reactivation from latency. In transfection assays, Vmw110 is a potent activator of gene expression, but its mode of action has yet to be determined. Previous work has shown that Vmw110 localizes to specific intranuclear structures known as ND10, PML bodies, or PODs and causes the disruption of these domains. The ability of Vmw110 to disrupt ND10 correlates with its biological activities in infected and transfected cells. It has also been found that Vmw110 binds strongly and specifically to a ubiquitin-specific protease known as HAUSP, itself a component of a subset of ND10. In this study we have investigated the role of HAUSP in Vmw110 activity; single amino acid residues of Vmw110 required for the interaction were identified, and the effects of mutation of these residues in infected and transfected cells were then assayed. The results indicate that the ability to bind to HAUSP contributes to the functional activities of Vmw110.

Vomeronasal, olfactory, hormonal convergence in the brain. Cooperation or coincidence?

This paper briefly reviews three topics: (a) Convergent vomeronasal and olfactory chemosensory input into a common circuit considered important for mating in male golden hamsters; (b) Apparent activation of this circuit by intracerebral luteinizing hormone-releasing hormone (LHRH) and (c) Interaction of the LHRH and the two chemosensory inputs. Mapping of c-fos protein in male hamsters mating with females or exposed to female pheromones indicates intense activation in the central vomeronasal pathways, induced by both olfactory and vomeronasal input. This input appears to activate the medial preoptic area, where chemosensory activation is greater in experienced than in inexperienced animals. Intracerebral injection of LHRH facilitates mating behavior and increases Fos expression in the medial preoptic area of mating males. Despite evidence that the release of LHRH in response to female chemosignals is dependent on vomeronasal input, no activation of LHRH neurons has been demonstrated in males exposed to such chemosignals. Electrical stimulation of the vomeronasal organ can induce Fos expression in chemosensory pathways and in medial preoptic LHRH neurons.

Increase in gonadotropin-releasing hormone (GnRH) levels in CSF after stimulation of the nervus terminalis in Atlantic stingray, Dasyatis sabina

The nervus terminalis (NT) contains many cells immunoreactive to gonadotropin-releasing hormone (GnRH). The potential of the NT to release GnRH in vivo was investigated by stimulating the peripheral nerve trunk of Atlantic stingrays and collecting cerebrospinal fluid (CSF). The CSF samples from stimulated animals averaged about twice the levels of mGnRH-like peptide as those of unstimulated animals. These results demonstrate that nervus terminalis activity can effect in vivo GnRH levels in the brain.

Vomeronasal function

This contribution briefly explores some unanswered questions about vomeronasal organ function, and introduces other contributions from the symposium 'Vomeronasal Function', presented at the XVII Meeting of the Association for Chemoreception Sciences (1996). Key publications appearing since the symposium are also listed.

Olfactory contribution to Fos expression during mating in inexperienced male hamsters

Male hamsters are very dependent on chemosensory cues for normal mating behavior. We have previously reported that central, vomeronasal pathways are intensely and selectively activated during mating or pheromonal stimulation. The contribution of main olfactory sensory input to the patterns of c-fos activation was investigated in this study. Sexually inexperienced male hamsters were either made anosmic by intranasal infusion of zinc sulfate or remained intact. Fos protein immunoreactivity was analyzed in main olfactory and vomeronasal pathways of the zinc sulfate-treated, anosmic animals after mating with receptive females for 45 min, and compared with Fos patterns seen in intact mating animals, some of which have been described in a previous publication. The zinc sulfate-treated anosmic males described here all mated when given access to receptive females. Whether mated or unstimulated, anosmic males had little or no Fos expression in main olfactory pathways; significantly less even than in unstimulated intact animals. Mating did not increase Fos expression in main olfactory pathways of intact animals over that of unstimulated intact controls. However, Fos expression in central vomeronasal pathways was significantly higher in mating anosmic males, as in intact males, compared with appropriate non-mating controls. Fos expression was significantly different between intact and zinc sulfate-treated anosmic mating males in only one area studied. The rostral anterior medial amygdala, known to receive a small olfactory terminal field, had significantly lower Fos expression in zinc sulfate-treated anosmic males that mated when compared with intact-mating animals. Thus, functional main olfactory input to the rostral vomeronasal amygdala can be demonstrated but does not appear to be critical for mating behavior in previously inexperienced male hamsters with intact vomeronasal organs. Other main olfactory input appears to have a negligible contribution to Fos-patterns in such animals.

Therapy for type 2 diabetes mellitus

Type 2 diabetes mellitus is a common, chronic disease affecting nearly 6% of the adult US population. It remains a leading cause of morbidity and mortality in Wisconsin as well as the country. Multiple lines of evidence show that controlling blood glucose in patients with type 2 diabetes can significantly decrease the development of and/or progression of microvascular complications as well as the macrovascular complications of diabetes. There are now four different classes of oral medications which are available to treat diabetes-sulfonylureas, biguanides, thiazolidinediones, and alpha-glucosidase inhibitors. Each class works differently to treat the underlying defects of diabetes which include impaired insulin secretion, insulin resistance and exaggerated postprandial hyperglycemia. This article will compare and contrast the different agents available, including appropriate use of each agent as monotherapy and in combination therapy. It will also discuss use of insulin in the patient who has failed oral therapy. Rational use of these tools, tailored for the individuals metabolic abnormalities, should allow for good glycemic control in the majority of patients with type 2 diabetes mellitus. Relaxation, massage, opium, and moderate exercise were among the recommended options for treatment of diabetes mellitus nearly 100 years ago. In the late nineteenth century, diabetes was a poorly characterized disorder, which was increasing in prevalence even at that time. Today, the underlying defects contributing to the development of type 2 diabetes are better understood, and include peripheral insulin resistance, relative pancreatic beta-cell insufficiency, increased hepatic glucose output, and an exaggerated postprandial glucose excursion. However, despite our better understanding of the disease, the prevalence of type 2 diabetes continues to increase in the US, now afflicting over 6% of the population. As our population ages and the proportion of obese people increases, we can expect to see a marked increase in the prevalence of diabetes in the future. Fortunately, our treatment options for type 2 diabetes have expanded remarkably within the last few years. Along with these new treatment options comes the exciting, although likely expensive, possibility of prevention of type 2 diabetes in at risk individuals.

Use of In-111 pentetreotide scintigraphy in the diagnosis of a midgut carcinoid causing Cushing's syndrome

A 57-year-old man presented with clinical features of hypercortisolism and was diagnosed with ACTH-dependent Cushing's syndrome. Biochemical testing showed partial suppression of urinary free cortisol with high dose dexamethasone. Initial computed tomography (CT) of the chest and abdomen, and magnetic resonance imaging of the pituitary were negative. In-111 pentetreotide scintigraphy with single photon emission computerized tomography revealed two 'hot' lesions in the abdomen which were then confirmed by subsequent directed thin-slice abdominal CT and small bowel barium study. At surgery, two segments of ileum, adjoining mesentery and lymph nodes were resected. Histopathology was consistent with a malignant carcinoid tumor of the ileum which stained intensely for ACTH. Plasma ACTH, and serum and urinary cortisol normalized postoperatively. To our knowledge, this is the first reported case of ileal carcinoid tumor causing Cushing's syndrome with premortem diagnosis. Another unique feature of this case is that In-111 pentetreotide scan provided the decisive clue to localization of the tumor.

Inhibition of calcium-induced insulin secretion from intact HIT-T15 or INS-1 beta cells by GTP depletion

Using intact rat islets, we previously observed that GTP depletion (achieved through the use of mycophenolic acid or other synthesis inhibitors) impedes nutrient- but not K+-induced insulin secretion. It was concluded that a proximal nutrient-dependent step in stimulus-secretion coupling (but not the process of Ca2+-induced exocytosis itself) is modulated by ambient GTP levels. To examine Ca2+-dependent steps further in intact beta cells, INS-1 cells (which synthesize GTP and ATP similarly to rat islets) and HIT-T15 cells (whose synthesis of purine nucleotides is different) were studied following cell culture for 1-18 hr in various concentrations of mycophenolic acid (MPA) or mizoribine (MZ). Both agents profoundly reduced GTP content (mean: -78%) and lowered the GTP/GDP ratio by an average of -73%; concomitantly, MPA or MZ reduced insulin secretion induced by 10 mM glucose, 30 or 40 mM KCl, or 100 microM tolbutamide, independent of any changes in cell viability, insulin content, ATP content, the ATP/ADP ratio, or cytosolic free Ca2+ concentrations. In INS-1 cells (which appear to have normal nucleobase transport and "salvage" pathway activities), guanine (but not adenine) restored GTP content, the GTP/GDP ratio, and Ca2+-induced secretion. In HIT cells, the phosphoribosylation of exogenous guanine or hypoxanthine is defective; however, provision of 500 microM guanosine (but not adenosine) reversed the effects of MPA. We conclude that, at least in certain situations, a requisite role for GTP in the distal step(s) of exocytosis can be demonstrated.

A novel ubiquitin-specific protease is dynamically associated with the PML nuclear domain and binds to a herpesvirus regulatory protein

Herpes simplex virus type 1 immediate-early protein Vmw110 is a non-specific activator of gene expression and is required for efficient initiation of the viral lytic cycle. Since Vmw110-deficient viruses reactivate inefficiently in mouse latency models it has been suggested that Vmw110 plays a role in the balance between the latent and lytic states of the virus. The mechanisms by which Vmw110 achieves these functions are poorly understood. Vmw110 migrates to discrete nuclear structures (ND10) which contain the cellular PML protein, and in consequence PML and other constituent proteins are dispersed. In addition, Vmw110 binds to a cellular protein of approximately 135 kDa, and its interactions with the 135 kDa protein and ND10 contribute to its ability to stimulate gene expression and viral lytic growth. In this report we identify the 135 kDa protein as a novel member of the ubiquitin-specific protease family. The protease is distributed in the nucleus in a micropunctate pattern with a limited number of larger discrete foci, some of which co-localize with PML in ND10. At early times of virus infection, the presence of Vmw110 increases the proportion of ND10 which contain the ubiquitin-specific protease. These results identify a novel, transitory component of ND10 and implicate a previously uncharacterized ubiquitin-dependent pathway in the control of viral gene expression.

A novel ubiquitin-specific protease is dynamically associated with the PML nuclear domain and binds to a herpesvirus regulatory protein

Herpes simplex virus type 1 immediate-early protein Vmw110 is a non-specific activator of gene expression and is required for efficient initiation of the viral lytic cycle. Since Vmw110-deficient viruses reactivate inefficiently in mouse latency models it has been suggested that Vmw110 plays a role in the balance between the latent and lytic states of the virus. The mechanisms by which Vmw110 achieves these functions are poorly understood. Vmw110 migrates to discrete nuclear structures (ND10) which contain the cellular PML protein, and in consequence PML and other constituent proteins are dispersed. In addition, Vmw110 binds to a cellular protein of approximately 135 kDa, and its interactions with the 135 kDa protein and ND10 contribute to its ability to stimulate gene expression and viral lytic growth. In this report we identify the 135 kDa protein as a novel member of the ubiquitin-specific protease family. The protease is distributed in the nucleus in a micropunctate pattern with a limited number of larger discrete foci, some of which co-localize with PML in ND10. At early times of virus infection, the presence of Vmw110 increases the proportion of ND10 which contain the ubiquitin-specific protease. These results identify a novel, transitory component of ND10 and implicate a previously uncharacterized ubiquitin-dependent pathway in the control of viral gene expression.

Dual functional effects of interleukin-1beta on purine nucleotides and insulin secretion in rat islets and INS-1 cells

Interleukin-1beta (IL-1beta) has been shown to inhibit glucose-induced insulin secretion from rat islets and purified beta-cells, primarily through the generation of nitric oxide (NO). However, the mechanisms by which NO exerts its effects remain unclear. To examine the role of purine nucleotides, we cultured intact rat islets or INS-1 (glucose-responsive transformed rat) beta-cells for 18 h in the presence or absence of IL-1beta. In islets, the exposure to IL-1beta (100 pmol/l) inhibited subsequent glucose-induced insulin secretion by 91% with no significant effect on insulin content or basal insulin release. IL-1beta also diminished insulin secretion induced by pure mitochondrial fuels, 40 mmol/l K+, or a phorbol ester. Concomitantly, IL-1beta significantly decreased islet ATP (-45%), GTP (-33%), ATP/ADP (-54%), and GTP/GDP (-46%). These effects were totally reversed by provision of N(omega)-nitro-L-arginine methyl ester (NAME) in arginine-free media that inhibited NO production. In contrast, in INS-1 cells, IL-1beta (10 or 100 pmol/l) reduced both basal and glucose-induced insulin secretion by 50%, but insulin content was also reduced by 35%. Therefore, the INS-1 cells were still able to respond to glucose stimulation with a 1.8-2.0-fold increase in insulin release in either the presence or absence of IL-1beta. Concomitantly, in INS-1 cells, IL-1beta had no effect on ATP/ADP or GTP/GDP ratios, although it modestly decreased ATP (-25%) and GTP (-22%). As in islets, all effects of IL-1beta in INS-1 cells were prevented by NAME. Thus, in rat islets, IL-1beta (via the generation of NO) abolishes insulin exocytosis in association with large decreases in the ATP/ADP (and GTP/GDP) ratio, implying the impairment of mitochondrial function. Furthermore, IL-1beta inhibits cytosolic synthesis of new purine nucleotides (via the salvage pathway), as assessed by a decrease in their specific activity after labeling with [3H]hypoxanthine. In contrast, in INS-1 cells, IL-1beta appears to impair cytosolic synthesis of purine nucleotides and insulin biosynthesis selectively (both possibly reflecting decreased glycolysis) with little direct effect on insulin exocytosis itself.

Assignment of the human gene (GLCLR) that encodes the regulatory subunit of gamma-glutamylcysteine synthetase to chromosome 1p21

We recently assigned the human gene (GLCLC) that encodes the catalytic subunit of gamma-glutamylcysteine synthetase (glutamate-cysteine ligase, E.C. 6.3.2.2) to human chromosome 6p12. Here we specify the chromosomal sublocalization of the human gene (GLCLR) that encodes the regulatory subunit of E.C. 6.3.2.2 to chromosome 1p21.

The issue of substance abuse in the health care industry. A preliminary survey of managerial thinking

Substance abuse in the workplace has been a growing concern in recent years and ways to detect employees and applicants who use drugs has been the subject of much debate. In this article, the results of a survey on the attitudes of medical practice human resource managers on drug testing of both employees and applicants are given. For this study, 273 human resource managers were sent questionnaires detailing various attitude statements and were asked for their level of agreement. Categories of questions included the administrators' general philosophy of drug testing, their attitudes toward the organizational impact of drug testing, their attitudes toward the implementation of drug testing and their attitudes toward specific issues pertinent to drug testing in medical groups.

Evidence of a role for GTP in the potentiation of Ca(2+)-induced insulin secretion by glucose in intact rat islets

Glucose initiates insulin secretion by closing K(+)-ATP channels, leading to Ca2+ influx (E1); it also potentiates Ca(2+)-induced secretion (E2) when the K(+)-ATP channel is kept open using diazoxide and depolarizing concentrations of K+ are provided. To examine the roles of purine nucleotides in E2, we compared the effects of glucose to those of the mitochondrial fuel monomethylsuccinate. Either agonist could induce E2 accompanied by significant increases in ATP, ATP/ADP ratio, and GTP/GDP ratio; GTP increased significantly only with glucose. Mycophenolic acid (MPA), an inhibitor of cytosolic GTP synthesis, markedly inhibited glucose-induced E2 (either in perifusions or in static incubations) and decreased GTP and the GTP/GDP ratio, but did not alter the ATP/ADP ratio. Provision of guanine (but not adenine) reversed these changes pari passu. In contrast, MPA had no effect on succinate-induced E2, despite generally similar changes in nucleotides. A similar lack of effect of MPA on E2 was seen with a second mitochondrial fuel, alpha-ketoisocaproic acid (KIC). However, in the absence of diazoxide and K+, MPA blunted the secretory effects of either glucose, succinate, or KIC. These studies suggest that GTP plays a role in both glucose and succinate or KIC-induced insulin secretion at a step dependent on mitochondrial metabolism and the K(+)-ATP channel. In addition to mitochondrial effects, glucose appears to have extramitochondrial effects important to its potentiation of Ca(2+)-induced insulin secretion that are also dependent on GTP.

Separation of sequence requirements for HSV-1 Vmw110 multimerisation and interaction with a 135-kDa cellular protein

Herpes simplex virus type 1 immediate-early polypeptide Vmw110 (ICP0) is a general transactivator of gene expression in transfection assays and is required for the fully efficient onset of viral lytic replication. It has also been implicated in the process of viral reactivation from latency. Its mechanism of action is unknown, but any involvement in latency requires interactions between viral and host factors. We have previously shown that Vmw110 binds to a 135-kDa cellular protein. In this paper we define a short region towards the C-terminal end of Vmw110 that is required for the 135-kDa protein interaction in virus-infected cells and in vitro. We also confirm that the C-terminal region of Vmw110 contains residues that are responsible for the multimerisation of the protein; these sequences are at least partially distinct from those involved in 135-kDa binding. Both multimerisation and 135-kDa protein interaction are required for full viral infectivity, and elimination of these functions affects the normal interactions between Vmw110 and cellular nuclear structures that contain the PML protein.

Cytosolic biosynthesis of GTP and ATP in normal rat pancreatic islets

GTP and ATP are necessary for glucose-induced insulin secretion; however, the biosynthetic pathways of purine nucleotides have not been studied in pancreatic islets. The present work examines the cytosolic pathways of purine nucleotide synthesis using intact rat islets cultured overnight in RPMI 1640 medium containing either [14C]glycine (to label the de novo pathway) or [3H]hypoxanthine (to mark the salvage pathway), with or without mycophenolic acid or L-alanosine (selective inhibitors of cytosolic GTP and ATP synthesis, respectively). Addition of mycophenolic acid decreased total GTP content (mass) by 73-81%; although the incorporation of labeled hypoxanthine into GTP also fell by 87%, the incorporation of glycine did not change. Similarly, L-alanosine decreased ATP mass by 26-33% in the presence of either label; whereas the incorporation of hypoxanthine into ATP fell 59%, the incorporation of glycine was again not significantly decreased. Thus, both the de novo and salvage purine nucleotide biosynthetic pathways are present in rat islets; however, the salvage pathway appears to be quantitatively the more important source of nucleotides. This conclusion was supported by additional studies of the effects on nucleotide content and insulin secretion of various site-specific inhibitors of purine synthesis. These findings have potential relevance to the processes of mitogenesis, cell proliferation and differentiation of islet cells, as well as for the control of insulin secretion.

Facilitation of mating behavior in male hamsters by LHRH and AcLHRH5-10: interaction with the vomeronasal system

An intact vomeronasal organ is important for the reproductive physiology and behavior of many species. Vomeronasal sensory input is known to influence hormone levels especially LH, presumably by prior modulation of LHRH. LHRH has been shown independently to facilitate mating behavior in rodents of both sexes. In this study intracerebroventricular LHRH at a dose of 50 ng substantially relieved mating behavior deficits caused by prepubertal removal of vomeronasal organs from inexperienced male hamsters. Intranasal LHRH at a higher dose did not have this effect. Behavioral responses were recorded 30 mins after peptide or saline injection. The LHRH analog, AcLHRH5-10 which we demonstrate does not induce LH release, did facilitate mating behavior in these tests, suggesting that LHRH peptides may facilitate male mating behavior via an extra-pituitary mode of action.

Nervus terminalis ganglion of the bonnethead shark (Sphyrna tiburo): evidence for cholinergic and catecholaminergic influence on two cell types distinguished by peptide immunocytochemistry

The nervus terminalis is a ganglionated vertebrate cranial nerve of unknown function that connects the brain and the peripheral nasal structures. To investigate its function, we have studied nervus terminalis ganglion morphology and physiology in the bonnethead shark (Sphyrna tiburo), where the nerve is particularly prominent. Immunocytochemistry for gonadotropin-releasing hormone (GnRH) and Leu-Pro-Leu-Arg-Phe-NH2 (LPLRFamide) revealed two distinct populations of cells. Both were acetylcholinesterase positive, but LPLR-Famide-immunoreactive cells consistently stained more darkly for acetylcholinesterase activity. Tyrosine hydroxylase immunocytochemistry revealed fibers and terminal-like puncta in the ganglion, primarily in areas containing GnRH-immunoreactive cells. Consistent with the anatomy, in vitro electrophysiological recordings provided evidence for cholinergic and catecholaminergic actions. In extracellular recordings, acetylcholine had a variable effect on baseline ganglion cell activity, whereas norepinephrine consistently reduced activity. Electrical stimulation of the nerve trunks suppressed ganglion activity, as did impulses from the brain in vivo. During electrical suppression, acetylcholine consistently increased activity, and norepinephrine decreased activity. Muscarinic and, to a lesser extent, alpha-adrenergic antagonists both increased activity during the electrical suppression, suggesting involvement of both systems. Intracellular recordings revealed two types of ganglion cells that were distinguishable pharmacologically and physiologically. Some cells were hyperpolarized by cholinergic agonists and unaffected by norepinephrine; these cells did not depolarize with peripheral nerve trunk stimulation. Another group of cells did depolarize with peripheral trunk stimulation; a representative of this group was depolarized by carbachol and hyperpolarized by norepinephrine. These and other data suggest that the bonnethead nervus terminalis ganglion contains at least two cell populations that respond differently to acetylcholine and norepinephrine. The bonnethead nervus terminalis ganglion appears to differ fundamentally from sensory and autonomic ganglia but does share some features with the neural circuits of forebrain GnRH systems.

Chronic recording of vomeronasal pump activation in awake behaving hamsters

The vomeronasal organs, the receptor organs of the accessory olfactory system, are important in chemical communication. Each organ contains receptor neurons sequestered inside a blind-ending tube with a narrow access duct. Large blood vessels surrounding the vomeronasal lumen act as a pump to draw substances into the lumen, under the control of vasomotor fibers in the nasopalatine nerve. Stimulation of the superior cervical sympathetic ganglion or nasopalatine nerve operates the pump (24) but its schedule of activation in awake behaving animals is unknown. Electrodes, implanted inside the vomeronasal organ capsule of male hamsters, recorded changes in electrical properties accompanying vomeronasal pump activation. Recorded signals were validated by anesthetizing the animals and recording from the same electrodes while driving the pump by nasopalatine nerve stimulation. Recordings in awake behaving animals show that the pump does not operate only in situations where the vomeronasal organ is known to be important. It appears to operate in response to any novel situation where the animal's attention is attracted. The signals recorded suggest that blood vessels are constricted repetitively by bursts of activity in the vasomotor sympathetic nerves each time the pump is triggered, while the underlying level of arousal is reflected in the ongoing sympathetic tone. The low selectivity in operation of the pump may require a greater degree of selectivity in the receptors than previously thought. The ready activation of the pump also suggests that the vomeronasal system may have other functions than the communication of reproductive events.

c-fos expression in vomeronasal pathways of mated or pheromone-stimulated male golden hamsters: contributions from vomeronasal sensory input and expression related to mating performance

The vomeronasal system projects to the accessory olfactory bulb (AOB), to the medial (Me) and posterior medial cortical nuclei (PMCN) of the amygdala, to the bed nucleus of the stria terminalis (BNST), and to other central structures shown to be important in mating behavior, including the medial preoptic area (MPOA). In these experiments c-fos expression was used as a marker of neural activity to identify the contribution of vomeronasal sensory input during mating behavior in male golden hamsters, either intact or with vomeronasal organs removed (VNX). Inexperienced hamsters were either stimulated with a receptive female and allowed to mate, exposed to female hamster vaginal fluid (HVF), which contains stimuli known to act through the VN system, or placed in a clean cage alone. Densely stained Fos-positive nuclei were evident in mated animals in the central VN pathway [AOB, Me, posterior medial BNST (pmBNST)] and a VN target area (MPOA). HVF-exposed animals showed Fos expression in the AOB, Me, and BNST but not MPOA. Unstimulated animals showed almost no activation. Most VNX animals exposed to females did not mate, but performed intense chemoinvestigation. They had few Fos-positive nuclei in any of these areas except the caudal pmBNST. A few VNX animals that did mate had patterns of Fos activation that were similar but less intense than those of intact mating animals, suggesting a selective activation of VN central pathways during mating regardless of VN sensory input. The main olfactory system showed low levels of Fos expression in all animals (stimulated and unstimulated). Fos expression in the MPOA and rostral pmBNST was seen only in mated animals, suggesting that these regions are concerned with mating performance or its consequences, rather than the chemosensory input that triggers it. Fos expression in the caudal encapsulated pmBNST was evident in all groups of animals that performed chemosensory investigation, regardless of VN status or mating, suggesting that this region either directs or responds to chemosensory investigation.

Herpes simplex virus type 1 immediate-early protein Vmw110 binds strongly and specifically to a 135-kDa cellular protein

Herpes simplex virus type 1 encodes five immediate-early gene products, at least three of which are required for fully efficient viral gene expression. One of these three, Vmw110 (or ICPO), is a potent and nonspecific activator of gene expression in transfection assays. Viruses which fail to express functional Vmw110 have a cell-type and multiplicity-dependent defect in viral gene expression. In addition, Vmw110 has been implicated in the reactivation of latent virus in mouse and tissue culture model systems. In this report we show that Vmw110 can be isolated as a fast-sedimenting complex from infected cells and that this complex contains a cellular protein which is immune precipitated in association with Vmw110. This association can be reconstructed by adding purified Vmw110 to lysates of several different cell types. By using a GST fusion protein, we have found that the isolated C-terminal portion of Vmw110 can complex strongly and specifically with a similar cellular protein. The relevance of this observation to the roles of Vmw110 in latent and lytic virus infection is discussed.

Vomeronasal system, LHRH, and sex behaviour

Vomeronasal chemosensory input is important for male hamster mating behavior, especially in inexperienced animals. Experiments reviewed here showed that intracerebroventricular injection of luteinizing hormone-releasing hormone (LHRH) substantially restores mating behavior impaired by removal of vomeronasal organs in inexperienced hamsters. An analogue molecule Ac5-10LHRH, which fails to release luteinizing hormone (LH) from the pituitary, has similar behavioural effects. These findings are consistent with the idea that vomeronasal sensory input may trigger intracerebral release of LHRH which then facilitates mating behaviour. Immunocytochemistry for the immediate-early gene-product Fos, used as an indicator of regional brain activation, indicates a selective activation of central vomeronasal pathways during mating behaviour. Chemosensory and other sensory inputs contribute to activation in medial amygdala and bed-nucleus of stria terminalis, but medial preoptic/anterior hypothalamic area activation appears more closely tied to mating behavior itself. Any of these areas may be sites of interaction between vomeronasal chemosensory input and LHRH-containing cells and fibers.

Small elevations of glucose concentration redirect and amplify the synthesis of guanosine 5'-triphosphate in rat islets

Recent studies suggest a permissive requirement for guanosine 5'-triphosphate (GTP) in insulin release, based on the use of GTP synthesis inhibitors (such as myocophenolic acid) acting at inosine monophosphate (IMP) dehydrogenase; herein, we examine the glucose dependency of GTP synthesis. Mycophenolic acid inhibited insulin secretion equally well after islet culture at 7.8 or 11.1 mM glucose (51% inhibition) but its effect was dramatically attenuated when provided at < or = 6.4 mM glucose (13% inhibition; P < 0.001). These observations were explicable by a stimulation of islet GTP synthesis derived from IMP since, at high glucose: (a) total GTP content was augmented; (b) a greater decrement in GTP (1.75 vs. 1.05 pmol/islet) was induced by mycophenolic acid; and (c) a smaller "pool" of residual GTP persisted after drug treatment. Glucose also accelerated GTP synthesis from exogenous guanine ("salvage" pathway) and increased content of a pyrimidine, uridine 5'-triphosphate (UTP), suggesting that glucose augments production of a common regulatory intermediate (probably 5-phosphoribosyl-1-pyrophosphate). Pathway-specific radiolabeling studies confirmed that glucose tripled both salvage and de novo synthesis of nucleotides. We conclude that steep changes in the biosynthesis of cytosolic pools of GTP occur at modest changes in glucose concentrations, a finding which may have relevance to the adaptive (patho) physiologic responses of islets to changes in ambient glucose levels.