Antagonism of the proinflammatory and pronociceptive actions of canonical and biased agonists of protease-activated receptor-2

BACKGROUND AND PURPOSE

Diverse proteases cleave protease-activated receptor-2 (PAR2) on primary sensory neurons and epithelial cells to evoke pain and inflammation. Trypsin and tryptase activate PAR2 by a canonical mechanism that entails cleavage within the extracellular N-terminus revealing a tethered ligand that activates the cleaved receptor. Cathepsin-S and elastase are biased agonists that cleave PAR2 at different sites to activate distinct signalling pathways. Although PAR2 is a therapeutic target for inflammatory and painful diseases, the divergent mechanisms of proteolytic activation complicate the development of therapeutically useful antagonists.

EXPERIMENTAL APPROACH

We investigated whether the PAR2 antagonist GB88 inhibits protease-evoked activation of nociceptors and protease-stimulated oedema and hyperalgesia in rodents.

KEY RESULTS

Intraplantar injection of trypsin, cathespsin-S or elastase stimulated mechanical and thermal hyperalgesia and oedema in mice. Oral GB88 or par2 deletion inhibited the algesic and proinflammatory actions of all three proteases, but did not affect basal responses. GB88 also prevented pronociceptive and proinflammatory effects of the PAR2-selective agonists 2-furoyl-LIGRLO-NH2 and AC264613. GB88 did not affect capsaicin-evoked hyperalgesia or inflammation. Trypsin, cathepsin-S and elastase increased [Ca(2+) ]i in rat nociceptors, which expressed PAR2. GB88 inhibited this activation of nociceptors by all three proteases, but did not affect capsaicin-evoked activation of nociceptors or inhibit the catalytic activity of the three proteases.

CONCLUSIONS AND IMPLICATIONS

GB88 inhibits the capacity of canonical and biased protease agonists of PAR2 to cause nociception and inflammation.

Bifidobacterium longum NCC3001 inhibits AH neuron excitability

BACKGROUND

Bifidobacterium longum (B. longum) NCC3001 can affect behavior and brain biochemistry, but identification of the cellular targets needs further investigation. Our hypothesis was that the communication with the brain might start with action on enteric sensory neurons.

METHODS

Ileal segments from adult mice were used to create a longitudinal muscle-myenteric-plexus preparation to expose sensory after-hyperpolarizing (AH) neurons in the myenteric plexus to allow access with microelectrodes. The intrinsic excitability of AH neurons was tested in response to the perfusion of conditioned media (B. longum culture supernatant) or unconditioned media (growth medium, MRS).

KEY RESULTS

B. longum conditioned medium significantly reduced the excitability of AH neurons compared to perfusion with the unconditioned medium. Specifically, a reduction was seen in the number of action potentials fired per depolarizing test pulse, the instantaneous and time-dependent input resistances and the magnitude of the hyperpolarization-activated cationic current (Ih ).

CONCLUSIONS & INFERENCES

The probiotic B. longum reduces excitability of AH sensory neurons likely via opening of potassium channels and closing of hyperpolarization-activated cation channels.

Effect of aging on soluble and membrane bound enzymes in rat brain

A number of soluble and membrane associated enzymes of glycolysis, pentose phosphate pathway and other related enzymes were measured in three different brain regions during aging. Enzymes utilizing and synthesizing peroxides were also included. Increasing levels of peroxidative products are known to accumulate in the brain with age. The membrane associated enzymes were found to be the primary focus of damage. Phosphofructokinase and glucose-6-phosphate dehydrogenase exhibited an unusual pattern when measured in whole homogenates. A progressive decrease in the synaptosomal bound hexokinase was found with increasing age. The synaptosomal phosphofructokinase (PFK) also showed a significant decrease with aging. Significant decrease in the incorporation of myoinositol into phospholipids and a loss of activity of membrane bound adenylate cyclase with age indicated that changes must be occurring in the structure of the brain and the loss of cerebral competence in the senescent brain may arise from peroxidative damage to membranes.

Obesity: lessons from evolution and the environment

The 9th Stock Conference acknowledged the complex background of genetic, cultural, environmental and evolutionary factors of obesity. Gene-environment interactions underlie the flexibility in body-weight and body-fat regulation, illustrated by the hunter-gatherers' feast and famine lifestyle, the variation in physical activity over the lifespan being highest at reproductive age, the variation in energy intake through 'eating in the absence of hunger', while running the risk of exceeding the capacity of triacylglyceride storage, leading to lipotoxicity and metabolic problems. Perinatal metabolic programming for obesity via epigenetic changes in response to a 'Western diet' results in production of lipid-poor milk and metabolically efficient pups, contributing to the perpetuation of obesity throughout generations. Evolutionary insight from comparative physiology and ecology indicates that over generations activity-induced energy expenditure has remained the same compared to wild mammals, that energy balance might be dependant on protein balance, while the function of taste changed from detection of poison or energy to social drinking and social behaviour. At present, the impact of assortative mating on obesity prevalence is unambiguously positive. The complexity that appeared can only be fully appreciated by setting the data into the context of our evolutionary history.

Antidiabetic and neuroprotective effects of Trigonella foenum-graecum seed powder in diabetic rat brain

Trigonella foenum-graecum seed powder (TSP) has been reported to have hypoglycemic and hyperinsulinemic action. The objective of the study was to examine the antidiabetic and neuroprotective role of TSP in hyperglycemiainduced alterations in blood glucose, insulin levels and activities of membrane linked enzymes (Na+K+ATPase, Ca2+ATPase), antioxidant enzymes (superoxide dismutase, glutathione S-transferase), calcium (Ca2+) levels, lipid peroxidation, membrane fluidity and neurolipofuscin accumulation in the diabetic rat brain. Female Wistar rats weighing between 180 and 220 g were made diabetic by a single injection of alloxan monohydrate (15 mg/100 g body weight), diabetic rats were given 2 IU insulin, per day with 5% TSP in the diet for three weeks. A significant increase in lipid peroxidation was observed in diabetic brain. The increased lipid peroxidation following chronic hyperglycemia was accompanied with a significant increase in the neurolipofuscin deposition and Ca2+ levels with decreased activities of membrane linked ATPases and antioxidant enzymes in diabetic brain. A decrease in synaptosomal membrane fluidity may influence the activity of membrane linked enzymes in diabetes. The present study showed that TSP treatment can reverse the hyperglycemia induced changes to normal levels in diabetic rat brain. TSP administration amended effect of hyperglycemia on alterations in lipid peroxidation, restoring membrane fluidity, activities of membrane bound and antioxidant enzymes, thereby ameliorating the diabetic complications.

Beneficial effects of Trigonella foenum graecum and sodium orthovanadate on metabolic parameters in experimental diabetes

Oxidative stress in diabetic tissues is accompanied by high-level of free radicals with simultaneously declined antioxidant enzymes status leading to cell membrane damage. The present study was carried out to observe the effect of sodium orthovanadate (SOV) and Trigonella foenum graecum seed powder (TSP) administration on blood glucose and insulin levels, antioxidant enzymes, lipid peroxidation, pyruvate kinase, lactate dehydrogenase and protein kinase C in heart, muscle and brain of the alloxan-induced diabetic rats to see whether the treatment with SOV and TSP was capable of reversing the diabetic effects. Diabetes was induced by administration of alloxan monohydrate (15 mg/100 g body weight), and rats were treated with 2 IU insulin, 0.6 mg/ml SOV, 5% TSP in the diet and a combination of 0.2 mg/ml SOV and 5% TSP separately for 21 days. Blood glucose levels increased markedly in diabetic rats, animals treated with a combined dose of SOV and TSP had glucose levels almost comparable with controls, similar results were obtained in the activities of pyruvate kinase, lactate dehydrogenase, antioxidant enzymes and protein kinase C in diabetic animals. Our results showed that lower doses of SOV (0.2 mg/ml) could be used in combination with TSP to effectively reverse diabetic alterations in experimental diabetes.

Protective effects of 17β estradiol on altered age related neuronal parameters in female rat brain

Biological aging is a fundamental process observed in almost all living beings. During aging the brain experiences structural, molecular, and functional alterations. Aging in females and males is considered as the end of natural protection against age related diseases like osteoporosis, coronary heart disease, diabetes, Alzheimer's and Parkinson's disease. These changes increase during menopausal condition in females when the level of estradiol is decreased. The aim of the present study was to investigate the anti-aging and protective potential of 17β estradiol (E2) treatment on activities of membrane linked ATPases (Na⁺K⁺ ATPase, Ca²⁺ATPase), antioxidant enzymes (superoxide dismutases, glutathione-S-transferases), intrasynaptosomal calcium levels, membrane fluidity and neurolipofuscin in the brain of aging female rats of 3 months (young), 12 months (adult) and 24 months (old) age groups, and to see whether these changes are restored to normal levels after exogenous administration of E2 (0.1 μg/g body weight for one month).The results obtained in the present work revealed that normal aging was associated with significant decrease in the activities of membrane linked ATPases, antioxidant enzymes and an increase in neurolipofuscin, intrasynaptosomal calcium levels in brain of aging female rats. The present study showed that E2 treatment reversed the changes to near normal levels. E2 treatment appears to be beneficial in preventing some of the age related changes in the brain, an important anti-aging effect of the hormone.

The pentose phosphate pathway of glucose metabolism. Measurement of the non-oxidative reactions of the cycle

Methods for the quantitative determination of ribose 5-phosphate isomerase, ribulose 5-phosphate 3-epimerase, transketolase and transaldolase in tissue extracts are described. The determinations depend on the measurement of glyceraldehyde 3-phosphate by using the coupled system triose phosphate isomerase, alpha-glycero-phosphate dehydrogenase and NADH. By using additional purified enzymes transketolase, ribose 5-phosphate isomerase and ribulose 5-phosphate epimerase conditions could be arranged so that each enzyme in turn was made rate-limiting in the overall system. Transaldolase was measured with fructose 6-phosphate and erythrose 4-phosphate as substrates, and again glyceraldehyde 3-phosphate was measured by using the same coupled system. Measurements of the activities of the non-oxidative reactions of the pentose phosphate pathway were made in a variety of tissues and the values compared with those of the two oxidative steps catalysed by glucose 6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase.

Influence of hormones on the nicotinamide nucleotide coenzymes of adipose tissue

The concentrations of the oxidized and reduced forms of the nicotinamide nucleotides were measured in the epididymal fat pads of normal, alloxan-diabetic and hypophysectomized rats. In both alloxan-diabetic rats and hypophysectomized rats the weight of the adipose tissue fell, as did the total content of NADH and NADPH; in addition, NAD(+) was decreased in the alloxan-diabetic group. Of these changes the most marked was in NADPH and this was the only significant difference when the results were expressed as nicotinamide nucleotides/mg. of tissue protein. The concentration of NADPH in the hypophysectomized rats was not altered by treatment with growth hormone but was restored to normal by treatment with thyroxine. These results are discussed in relation to the known effect of these hormonal conditions on lipid synthesis in adipose tissue.

Effect of alloxan-diabetes on multiple forms of hexokinase in adipose tissue and lung

Comparison has been made of the effect of alloxan-diabetes on the multiple forms of hexokinase (EC 2.7.1.1) in adipose tissue and lung. Types I and II hexokinase were distinguished in adipose tissue by their different stabilities to heat treatment, which made it possible to determine the activity of each form spectrophotometrically; additional confirmatory evidence was obtained from starch-gel electrophoresis. Type II hexokinase was markedly depressed in adipose tissue from alloxan-diabetic rats. Lung contained types I, II and III hexokinase, type I predominating. There was no significant change in the pattern of these multiple forms of hexokinase in lung from alloxan-diabetic rats. These results are discussed in relation to current ideas that the insulin-sensitivity of a tissue may be correlated with the content of type II hexokinase.

Insight into the role of inositol phosphoglycans in insulin response and the regulation of glucose and lipid metabolism illustrated by the response of adipocytes from two strains of rats

Differences in biochemical and hormone profiles between two strains of rats provide insights into the relationships between insulin response, inositol phosphoglycans and lipid metabolism in adipose tissue. The results suggest the apparent anomaly of a higher rate of lipogenesis and response to insulin with a lower fat pad weight in the Charles River vs. Harlan Olac group relates to: (i) enzyme pre-programming with IPG-A, (ii) faster turnover of lipid, (iii) effects of leptin and cAMP.

Urinary excretion of inositol phosphoglycan P-type in gestational diabetes mellitus

OBJECTIVE

The mechanisms underlying insulin resistance during normal pregnancy, and its further exacerbation in pregnancies complicated by gestational diabetes mellitus (GDM), are generally unknown. Inositolphosphoglycan P-type (P-IPG), a putative second messenger of insulin, correlates with the degree of insulin resistance in diabetic subjects. An increase during normal pregnancy, in maternal and fetal compartments, has recently been reported.

METHODS

A cross-sectional study was carried out in 48 women with GDM and 23 healthy pregnant women. Urinary levels of P-IPG were assessed spectrophotometrically by the activation of pyruvate dehydrogenase phosphatase in urinary specimens and correlated with clinical parameters.

RESULTS

Urinary excretion of P-IPG was higher in GDM than in control women (312.1 +/- 151.0 vs. 210.6 +/- 82.7 nmol NADH/min/mg creatinine, P < 0.01) with values increasing throughout pregnancy in control subjects (r2 = 0.34, P < 0.01). P-IPG correlated with blood glucose levels (r(2) = 0.39, P < 0.01 for postprandial glycaemia and r2 = 0.18 P < 0.01 for mean glycaemia) and birthweight in the diabetic group (r2 = 0.14, P < 0.01).

CONCLUSIONS

Increased P-IPG urinary excretion occurs in GDM and positively correlates with blood glucose levels. P-IPG may play a role in maternal glycaemic control and, possibly, fetal growth in GDM.

Impact of 5-HT3 receptor blockade on colonic haemodynamic responses to ischaemia and reperfusion in the rat

5-HT(3) receptor antagonists are clinically available for treating patients with irritable bowel syndrome (IBS) but their use is restricted because of a link with some episodes of ischaemic colitis. However, the role of 5-HT3 receptors in regulating colonic blood flow has not been systematically investigated. Thus, we examined acute and chronic treatment with alosetron, a potent and selective antagonist of the 5-HT3 receptor, on baseline colonic blood flow and haemodynamic responses during occlusion and reactive hyperaemia in the pentobarbitone-anaesthetized rat. Colonic haemodynamics were assessed using ultrasonic recordings of superior mesenteric blood flow (MBF) and laser Doppler recordings of colonic vascular perfusion (VP). Blood pressure (BP) was also monitored and in some experiments tissue oxygen was detected polarographically. Alosetron (10, 30, 100 microg kg(-1), i.v.) had no effect on baseline haemodynamics nor responses to nitric oxide synthase inhibition with N(omega)-nitro-l-arginine methyl ester (l-NAME) (16 mg kg(-1)). Arterial occlusion (5 min) reduced MBF (-98.6 +/- 0.6%) and VP (-70.7 +/- 5.4%) followed by a post-occlusion reactive hyperaemia (MBF = +94.5 +/- 19.1%; VP = +60.0 +/- 22.3%) the magnitude of which was unchanged following acute (30 microg kg(-1)) or chronic alosetron administration (0.5 mg kg(-1) twice daily, 5 days). Alosetron did not significantly alter baseline colonic blood flow in the anaesthetized rat; nor did it interfere with vascular control mechanisms activated during occlusion and reactive hyperaemia.

Regulation of glucose utilization and lipogenesis in adipose tissue of diabetic and fat fed animals: effects of insulin and manganese

In order to evaluate the modulatory effects of manganese, high fat diet fed and alloxan diabetic rats were taken and the changes in the glucose oxidation, glycerol release and effects of manganese on these parameters were measured from adipose tissue. An insulin-mimetic effect of manganese was observed in the adipose tissue in the controls and an additive effect of insulin and manganese on glucose oxidation was seen when Mn2+ was added in vitro. The flux of glucose through the pentose phosphate pathway and glycolysis was significantly decreased in high fat fed animals. Although the in vitro addition of Mn2+ was additive with insulin when 14CO2 was measured from control animals, it was found neither in young diabetic animals (6-8 weeks old) nor in the old (16 weeks old). Both insulin and manganese caused an increased oxidation of carbon-1 of glucose and an increase of its incorporation into 14C-lipids in the young control animals; the additive effect of insulin and manganese suggests separate site of action. This effect was decreased in fat fed animals, diabetic animals and old animals. Manganese alone was found to decrease glycerol in both the control and diabetic adipose tissue in in vitro incubations. The results of the effects of glucose oxidation, lipogenesis, and glycerol release in adipose tissue of control and diabetic animals of different ages are presented together with the effect of manganese on adipose tissue from high fat milk diet fed animals.

Polyamines regulate gap junction communication in connexin 43-expressing cells

The control of cell-cell communication through gap junctions is thought to be crucial in normal tissue function and during various stages of tumorigenesis. However, few natural regulators of gap junctions have been found. We show here that increasing the activity of ornithine decarboxylase, or adding polyamines to the outside of cells, increases the level of gap junction communication between various epithelial cells. Conversely, reduction of ornithine decarboxylase activity decreases the level of gap junction communication. This regulation is dependent upon the expression of connexin 43 (Cx43 or Cxalpha1), which is a major connexin expressed in many different cell types, and involves an increase in Cx43 and its cellular re-distribution.

Rapid Notch1 nuclear translocation after ligand binding depends on presenilin-associated gamma-secretase activity

Recent data suggest an intimate relationship between the familial Alzheimer disease gene presenilin 1 (PS1) and proteolytic processing of both the amyloid precursor protein (APP) and the important cell signaling molecule, Notch1. We now show, using mammalian cells transfected with full-length Notch1, that the C terminal domain of Notch1 rapidly translocates to the nucleus upon stimulation with the physiologic ligand Delta and initiates a CBF1-dependent signal transduction cascade. Using this assay, we demonstrate that the same aspartate mutations in PS1 that block APP processing also prevent Notch1 cleavage and translocation to the nucleus. Moreover, we show that two APP gamma-secretase inhibitors also diminish Notch1 nuclear translocation in a dose-dependent fashion. However, Notch1 signaling, assessed by measuring the activity of CBF1, a downstream gene, was reduced but not completely abolished in the presence of either aspartate mutations or gamma-secretase inhibitors. Our results support the hypothesis that similar PS1-related enzymatic activity is necessary for both APP and Notch1 processing, yet suggest that Notch signaling may remain relatively preserved with moderate levels of gamma-secretase inhibition.

Aspartate mutations in presenilin and gamma-secretase inhibitors both impair notch1 proteolysis and nuclear translocation with relative preservation of notch1 signaling

It has been hypothesized that a presenilin 1 (PS1)-related enzymatic activity is responsible for proteolytic cleavage of the C-terminal intracellular protein of Notch1, in addition to its role in beta-amyloid protein (Abeta) formation from the amyloid precursor protein (APP). We developed an assay to monitor ligand-induced Notch1 proteolysis and nuclear translocation in individual cells : Treatment of full-length Notch1-enhanced green fluorescent protein-transfected Chinese hamster ovary (CHO) cells with a soluble preclustered form of the physiologic ligand Delta leads to rapid accumulation of the C terminus of Notch1 in the nucleus and to transcriptional activation of a C-promoter binding factor 1 (CBF1) reporter construct. Nuclear translocation was blocked by cotransfection with Notch's physiologic inhibitor Numb. Using this assay, we now confirm and extend the observation that PS1 is involved in Notch1 nuclear translocation and signaling in mammalian cells. We demonstrate that the D257A and the D385A PS1 mutations, which had been shown previously to block APP gamma-secretase activity, also prevent Notch1 cleavage and translocation to the nucleus but do not alter Notch1 trafficking to the cell surface. We also show that two APP gamma-secretase inhibitors block Notch1 nuclear translocation with an IC(50) similar to that reported for APP gamma-secretase. Notch1 signaling, assessed by measuring the activity of CBF1, a downstream transcription factor, was impaired but not abolished by the PS1 aspartate mutations or gamma-secretase inhibitors. Our results support the hypotheses that (a) PS1-dependent APP gamma-secretase-like enzymatic activity is critical for both APP and Notch processing and (b) the Notch1 signaling pathway remains partially activated even when Notch1 proteolytic processing and nuclear translocation are markedly inhibited. The latter is an important finding from the perspective of therapeutic treatment of Alzheimer's disease by targeting gamma-secretase processing of APP to reduce Abeta production.

Inositol phosphoglycans and the regulation of the secretion of leptin: in vitro effects on leptin release from adipocytes and the relationship to obesity

The ratio of two families of inositol phosphoglycans (IPG-A:IPG-P), insulin second messengers, is raised in non-insulin-dependent diabetes mellitus (NIDDM) and obesity. It is shown here that IPG A type inhibits leptin release from adipocytes, contrasting with the action of insulin (stimulation) and IPG P type (no effect). The significance of inhibitory effects of IPG A type on leptin release is important in relation to obesity and NIDDM in view of the action of leptin in promoting Lep expression and fat oxidation in muscle, in addition to its effects on satiety. Energy conservation and oxidation via interorgan regulation by leptin could be compromised by a rise in the IPG-A:IPG-P ratio.

Binding of bovine papillomavirus type 4 E8 to ductin (16K proteolipid), down-regulation of gap junction intercellular communication and full cell transformation are independent events

The E8 open reading frame of bovine papillomavirus type 4 encodes a small hydrophobic polypeptide that contributes to primary cell transformation by conferring to cells the ability to form foci and to grow in low serum and in suspension. Wild-type E8 binds in vitro to ductin, a component of gap junctions, and this binding is accompanied by a loss of gap junction intercellular communication in transformed bovine fibroblasts. However, through the analysis of a panel of E8 mutants, we show here that binding of E8 to ductin is not sufficient for down-regulation of gap junction communication and that there is no absolute correlation between down-regulation of gap junction communication and the transformed phenotype.

Inositol phosphoglycans and signal transduction systems in pregnancy in preeclampsia and diabetes: evidence for a significant regulatory role in preeclampsia at placental and systemic levels

Measurements have been made of the urinary content of inositol phosphoglycans IPG P-type and IPG A-type, putative insulin second messengers, in preeclampsia, in type I insulin-treated diabetic pregnant women and their matched control subjects, and nonpregnant women of child-bearing age. The content of IPG P-type and IPG A-type was also measured in the placenta from preeclamptic patients and from normal pregnancies. Pregnancy was associated with an increase, approximately twofold, in urinary output of IPG-P-type relative to nonpregnant controls (P<0.01). The 24-h output of IPG P-type in urine in preeclamptic women was significantly higher (2- to 3-fold) than in pregnant control subjects matched for age, parity, and stage of gestation (P<0.02). In contrast, insulin-dependent diabetic pregnant women did not show any significant change in urinary output of IPG P-type or IPG A-type relative to pregnant control subjects. Evidence for a possible relationship and correlation between the urinary excretion of IPG P-type and markers of preeclampsia, including proteinuria (r = 0.720, P<0.01), plasma aspartate transaminase (r = 0.658, P<0.05), and platelet counts (r = 0.613, P<0.05) is presented. A high yield of IPG P-type was extracted from human placenta, in preeclampsia some 3-fold higher (P = 0.03) than the normal value, whereas no IPG A-type (with lipogenic-stimulating activity) was found. Low concentrations of placental IPG A-type were detected relative to IPG P-type using assay systems dependent upon the effect of this mediator on cAMP-dependent protein kinase or on a proliferation assay using thymidine incorporation into DNA of EGFR T17 fibroblasts. It is postulated that the high urinary excretion IPG P-type in preeclampsia reflects high placental levels and relates to the accumulation of glycogen in the placenta. The paracrine effects of placental IPG P-type (stimulation off other endocrine glands and/or endothelial cells) could contribute to the pathogenesis of the maternal syndrome. A possible theoretical link between elevated placental IPG P-type and apoptosis is proposed.

Inositol phosphoglycans in diabetes and obesity: urinary levels of IPG A-type and IPG P-type, and relationship to pathophysiological changes

Measurements have been made, in adult male diabetic patients and control subjects, of the urinary content of inositol phosphoglycans (IPGs), the IPG A-type and IPG P-type forms, which, among other actions, regulate pathways of glucose utilization, lipogenesis, triglyceride formation, and pyruvate dehydrogenase (PDH) activity. Urine samples from the entire diabetic group showed a 2- to 3-fold increase in IPG A-type, and a fall in the IPG P-type:IPG A-type ratio relative to the control group. Subdivision of the diabetic patients into lean IDDM and obese NIDDM groups revealed significant differences in the IPG P-type:IPG A-type ratio between these groups, this ratio decreasing with increases in the body mass index (BMI). Analysis of the relationships among IPGs and HbA1, blood pressure, and BMI indicated that a fall in the IPG P-type:IPG A-type ratio correlated with a rise in the HbA1 (indicative of impaired glycemic control), with increased systolic blood pressure and increased obesity, all factors linked to Syndrome X. There was a parallism between the profile of the IPG P-type:IPG A-type ratio and the well-established pattern of insulin resistance and BMI. In vitro studies of the effects of alterations in the IPG P-type:IPG A-type ratio on the activation of the pyruvate dehydrogenase complex (PDH complex) at the PDH phosphatase reaction demonstrated that IPG A-type forms antagonized the stimulation of the PDH phosphatase by IPG P-type forms, thus having a negative effect on the conversion of PDH to the active, dephosphorylated, form. This observation could provide a mechanism whereby the shifts in the IPG P-type:IPG A-type ratio reported above could change the metabolic pattern from one directed to glucose oxidation to one more directed toward energy conservation and lipid storage.

Notch1 inhibits neurite outgrowth in postmitotic primary neurons

Notch plays an important role in cell fate decisions in uncommitted proliferative cells, including neurogenesis, but is believed to not have a role in postmitotic cells. We have shown previously that Notch1 is highly expressed in embryonal mouse and human brain, but surprisingly it continues to be expressed at low levels in the adult brain. The function of Notch1 in postmitotic neurons in mammals is unknown. To better understand the potential role of Notch1 in mature central nervous system neurons we studied the effect of Notch1 transfection on neurite outgrowth in primary neocortex hippocampal neurons. Transfection at two days in vitro with full length Notch1 inhibited neurite outgrowth. Transfection at five to six days in vitro, after neurite outgrowth was established, led to apparent regression of neurites. These effects were enhanced when truncated constitutively active forms of Notch1 were introduced. Co-transfection with Numb, a physiological inhibitor of Notch, blocked Notch's effect on neurite outgrowth. We also examined whether Notch1 could activate C-promoter binding factor (CBF1) transcription factor using C-promoter binding factor-luciferase constructs, and demonstrated that this signal transduction pathway is present and can be activated in postmitotic neurons. Our results show that in postmitotic neurons Notch1 influences neurite morphology, and can activate its native signal transduction pathway. These data strongly suggest that Notch1 may play a physiologically important role in the central nervous system beyond neurogenesis.

The Alzheimer-related gene presenilin 1 facilitates notch 1 in primary mammalian neurons

The normal functional neurobiology of the Alzheimer's disease (AD) related gene presenilin 1 (PS1) is unknown. One clue comes from a genetic screen of Caenorhabditis elegans, which reveals that the presenilin homologue sel-12 facilitates lin-12 function [D. Levitan, I. Greenwald, Facilitation of lin-12-mediated signalling by sel-12, a Caenorhabditis elegans S182 Alzheimer's disease gene, Nature 377 (1995) 351-355]. The mammalian homologue of lin-12, Notch1, is a transmembrane receptor that plays an important role in cell fate decisions during development, including neurogenesis, but does not have a known function in fully differentiated cells. To better understand the potential role of Notch1 in mammalian postmitotic neurons and to test the hypothesis that Notch and PS 1 interact, we studied the effect of Notch1 transfection on neurite outgrowth in primary cultures of hippocampal/cortical neurons. We demonstrate that Notch1 inhibits neurite extension, and thus has a function in postmitotic mature neurons in the mammalian CNS. Furthermore, we present evidence demonstrating that there is a functional interaction between PS1 and Notch1 in mammalian neurons, analogous to the sel-12/lin-12 interaction in vulval development in C. elegans [D. Levitan, T. Doyle, D. Brousseau, M. Lee, G. Thinakaran, H. Slunt, S. Sisodia, I. Greenwald, Assessment of normal and mutant human presenilin function in Caenorhabditis elegans, Proc. Natl. Acad. Sci. U.S.A. 93 (1996) 14940-14944; D. Levitan, I. Greenwald, Effect of Sel-12 presenilin on Lin-12 localization and function in Caenorhabditis elegans, Development, 125 (1998) 3599-3606]. The inhibitory effect of Notch1 on neurite outgrowth is markedly attenuated in neurons from PS1 knockout mice, and enhanced in neurons from transgenic mice overexpressing wild type PS1, but not mutant PS1. These data suggest that PS1 facilitates Notch1 function in mammalian neurons, and support the hypothesis that a functional interaction exists between PS1 and Notch1 in postmitotic mammalian neurons.

Telephone advice: is it safe?

Telephone advice in health care is always risky. Until the last few years practitioners--with a few exceptions such as poison control personnel--were generally warned not to give telephone advice to anyone. The possibility of harm resulting, and of a lawsuit against the health care provider, was just too great a risk.

Cognitive restructuring in the treatment of social phobia. Efficacy and mode of action

Cognitive restructuring (CR) is commonly used to treat social phobia, although its contribution to treatment efficacy has not been established. CR requires the person to think about and discuss feared social events with his or her therapist and thus entails some degree of exposure to social stimuli. CR also is thought to enhance the efficacy of therapeutic exposure exercises (EXP). Four predictions were tested based on this model: Relative to a control intervention matched for the exposure inherent in CR, CR is more effective in (1) reducing social phobia, (2) reducing negative social cognitions, (3) increasing positive cognitions, and (4) enhancing the effects of subsequent EXP. People with generalized social phobia (N = 60) were randomly assigned to CR followed by EXP or to a control intervention followed by EXP. Support was found for predictions 1 to 3, but not 4.

B7.2 expressed by T cells does not induce CD28-mediated costimulatory activity but retains CTLA4 binding: implications for induction of antitumor immunity to T cell tumors

The B7 family of costimulatory molecules provides the second signal necessary for activation of T cells. In the absence of the second signal, responding T cells become anergic. Although predominantly expressed on professional APCs, recent evidence shows that the B7 molecules are also expressed on T cells. To study the functions of B7 molecules on T cells, we transfected murine B7.1 (CD80) and B7.2 (CD86) cDNAs into the EL4 T cell thymoma cell line and examined the transfectants for their ability to costimulate T cell proliferation in vitro and to induce antitumor immunity in vivo. Here we show that although EL4-B7.1 cells costimulate T cells and induce tumor regression, EL4-B7.2 transfectants failed to costimulate T cell proliferation or induce tumor regression. To understand the cellular basis for this difference, we examined the binding of EL4-B7.1 and EL4-B7.2 to CTLA4 and CD28. Whereas EL4-B7.1 cells bound both CTLA4-Ig and CD28-Ig, EL4-B7.2 transfectants preferentially bound CTLA4-Ig, but not CD28-Ig. Similar binding data were obtained with freshly isolated murine T cells, which have been shown to constitutively express B7.2. Our data suggest, therefore, that B7.2 expressed on T cells may not costimulate but instead inhibit the T cell response by preferential binding to CTLA4.

B7.2 expressed by T cells does not induce CD28-mediated costimulatory activity but retains CTLA4 binding: implications for induction of antitumor immunity to T cell tumors

The B7 family of costimulatory molecules provides the second signal necessary for activation of T cells. In the absence of the second signal, responding T cells become anergic. Although predominantly expressed on professional APCs, recent evidence shows that the B7 molecules are also expressed on T cells. To study the functions of B7 molecules on T cells, we transfected murine B7.1 (CD80) and B7.2 (CD86) cDNAs into the EL4 T cell thymoma cell line and examined the transfectants for their ability to costimulate T cell proliferation in vitro and to induce antitumor immunity in vivo. Here we show that although EL4-B7.1 cells costimulate T cells and induce tumor regression, EL4-B7.2 transfectants failed to costimulate T cell proliferation or induce tumor regression. To understand the cellular basis for this difference, we examined the binding of EL4-B7.1 and EL4-B7.2 to CTLA4 and CD28. Whereas EL4-B7.1 cells bound both CTLA4-Ig and CD28-Ig, EL4-B7.2 transfectants preferentially bound CTLA4-Ig, but not CD28-Ig. Similar binding data were obtained with freshly isolated murine T cells, which have been shown to constitutively express B7.2. Our data suggest, therefore, that B7.2 expressed on T cells may not costimulate but instead inhibit the T cell response by preferential binding to CTLA4.

Biomedical research and the law of informed consent

Awareness of the legal and ethical parameters of nursing practice is a necessity for nurses in all nursing roles, but some of these same legal and ethical considerations take on an increased significance in the area of clinical research. The most predominant legal issue in the research field in terms of both litigation and legal commentary is the issue of informed consent.

Anxiety sensitivity and depression: how are they related?

Anxiety sensitivity is the fear of anxiety-related bodily sensations, which arises from beliefs that the sensations have harmful somatic, psychological, or social consequences. Elevated anxiety sensitivity, as assessed by the Anxiety Sensitivity Index (ASI), is associated with panic disorder. The present study investigated the relationship between anxiety sensitivity and depression. Participants were people with panic disorder (n = 52), major depression (n = 46), or both (n = 37). Mean ASI scores of each group were elevated, compared to published norms. Principal components analysis revealed 3 factors of anxiety sensitivity: (a) fear of publicly observable symptoms, (b) fear of loss of cognitive control, and (c) fear of bodily sensations. Factors 1 and 3 were correlated with anxiety-related measures but not with depression-related measures. Conversely, factor 2 was correlated with depression-related measures but not with anxiety-related measures.

Anxiety sensitivity and depression: how are they related?

Anxiety sensitivity is the fear of anxiety-related bodily sensations, which arises from beliefs that the sensations have harmful somatic, psychological, or social consequences. Elevated anxiety sensitivity, as assessed by the Anxiety Sensitivity Index (ASI), is associated with panic disorder. The present study investigated the relationship between anxiety sensitivity and depression. Participants were people with panic disorder (n = 52), major depression (n = 46), or both (n = 37). Mean ASI scores of each group were elevated, compared to published norms. Principal components analysis revealed 3 factors of anxiety sensitivity: (a) fear of publicly observable symptoms, (b) fear of loss of cognitive control, and (c) fear of bodily sensations. Factors 1 and 3 were correlated with anxiety-related measures but not with depression-related measures. Conversely, factor 2 was correlated with depression-related measures but not with anxiety-related measures.

Reduced resources and liability risks

Cost-containment strategies have meant the loss of many registered nurse positions in health care facilities across Canada. Nurses are concerned about whether there will be enough adequately prepared professional health care staff to ensure safe, competent care consistent with professional nursing standards. Fears have arisen that substituting unregulated health care workers for nurses may pose a risk to the public that will lead to more lawsuits against nurses.

Geographically overlapping Alzheimer's disease registries: comparisons and implications

In the medical and epidemiologic literature, a registry denotes a data base in which registrants share some common characteristic such as disease category. One criticism of registries is that they frequently collect subjects in a haphazard fashion and, hence, are "nonrepresentative of the population purportedly being represented." In this report, we compare two registries: an incident-based Alzheimer's Disease Patient Registry (ADPR) recruiting subjects for epidemiologic studies from a large health maintenance organization; and an Alzheimer's Disease Research Center (ADRC) registry recruiting subjects for phenomenologic, biologic, and pharmacologic studies. While these registries share personnel, overlap geographically, and use similar diagnostic procedures, they differ substantially in their missions and resulting recruitment strategies. We compared these registries with respect to demographic characteristics and cognitive features at subject entry. Subjects enrolled in the incident-based registry are older and report shorter time between symptom onset and recruitment. They are less demented and mirror the general population demographically more closely than do subjects in the other registry. The ADRC registry contains a much greater proportion of subjects with higher educational attainment.

A flat decelerative fetal heart rate tracing with normal fetal heart rate variability

We report two cases for which computer interpretation of nonstress test indicated a flat decelerative trace in spite of normal fetal heart rate variability. Fetal behavioral state in the first case and signal loss in the second case were possibly responsible for this computerized interpretation of the tracings in the absence of fetal distress.

Transplant nephrectomy over 20 years: factors involved in associated morbidity and mortality

Of 1,048 renal transplants performed between 1971 and 1990, transplant nephrectomy was performed in 86 (8.2%). Mean patient age was 33 years (range 3.8 to 66.5). Postoperative complications occurred in 60% of the patients, including wound infection in 20% and major hemorrhage in 4 patients. The external iliac artery was ligated in 4 patients. The incidence and severity of the complications were greater in patients with acute rejection. Four patients died: 1 of ischemic bowel and metastatic carcinoma, 1 of pulmonary embolism, and 2 of sepsis and disseminated intravascular coagulation. The nephrectomy rate increased significantly (p < 0.005) when cyclosporine A was initially introduced. Added care is necessary when new immunosuppressants are used. The majority of our failed transplants were left in situ without compromising overall patient well-being.

Inositolphosphoglycan second messengers

The mechanisms by which cellular receptors can elicit different biological responses in a maturation state-dependent manner is one of the central problems in cell differentiation which remains to be resolved. The signals generated are likely to be due to additional (as yet unknown) transmembrane signalling pathways. In addition, the recent observation that a single growth factor receptor can activate a whole family of different putative second messengers and that the combinatorial interactions and stoichiometric ratios between the different messengers determine the resulting biological activities has opened up a whole new area of cell biology. It has been proposed that membrane GPI-anchors may function in signal transduction. We have recently confirmed the presence of a family of inositolphosphoglycan second messengers. Partial structural data suggests that these second messengers are not derived from known GPI membrane anchors and may thus constitute a novel class of non-protein-conjugated GPI.

Changes in uridine nucleotides and uridine nucleotide sugars in diabetic rat lens: implications in membrane glycoprotein formation

The lens has a very high content of UDP sugars. These are required for glycoprotein and proteoglycan synthesis, as components of fiber cell membranes and the capsule. In diabetes, changes in these sugar nucleotides are related to pathological changes in the basement membranes of cells from non-insulin-requiring tissues. We have investigated whether this is the case in the lens in diabetes and we report here that UDP-sugar levels are, in contrast to the norm in other non-insulin-requiring tissues, decreased at 2 and 4 weeks of diabetes. This is despite an elevation in the precursors of their formation, both of the pyrimidine (PPRibP) and carbohydrate (glucose, glucose 6-phosphate) components. Also reported here is the observation that lens pyrimidine biosynthesis occurs primarily by the de novo route, and that orotate phosphoribosyltransferase and orotidine-5'-phosphate decarboxylase are unchanged in diabetes. We have measured the energy charge of the adenine and uridine nucleotide pools and report both to be compromised under the diabetic condition. The fall in ATP provision is proposed to be responsible for the fall in UTP and hence leads to the recorded decrease in the UDP sugars. These changes are discussed in relation to the change in capsular and fiber cell composition and the functional significance of this in cataract formation.

Effect of oestradiol on the carbohydrate metabolism of immature rat uterus: the role of fructose-2, 6-bis-phosphate and of phosphoribosyl pyrophosphate

Enzymes and metabolic intermediates of glycolysis, pentose phosphate pathway and the tricarboxylic acid cycle were measured in immature rat uterus after treatment with oestradiol. The flux of glucose through alternative pathways was examined. Fructose-2,6-bis-phosphate, the well known regulator of glycolytic pathway, increased after the injection of oestradiol and remained elevated. This increase was accompanied by raised levels of most of glycolytic intermediates and by increase in glycolytic flux. The key enzymes of glycolysis and all the enzymes of pentose phosphate pathway showed a gradual increase in the activity with administration of oestradiol up to 48 hours. Phosphoribosyl pyrophosphate, the metabolite required in nucleotide synthesis, was also elevated. Marked changes in the levels of key metabolic intermediates and the enzyme activities are correlated with the increased nucleic acid, protein and lipid synthesis occurring following oestradiol treatment.

Aspects of the regulation of hepatic phosphoribosyl pyrophosphate formation in the obese (ob/ob) mouse: relationship to the pentose phosphate pathway

The content of phosphoribosyl pyrophosphate (PPRibP) and of intermediates involved in its synthesis has been measured in the livers of obese (ob/ob) mice 2 months and 3-4 months of age, a period of dynamic growth and marked hepatic hypertrophy and hyperplasia, and comparison made with the values found in the lean age-matched control groups. The total hepatic PPRibP content and PPRibP/mg DNA was significantly increased in the 3- to 4-month-old obese mice relative to both the lean control groups and the 2-month-old obese mice, illustrating the significant changes occurring in the obese mouse liver in this transition period. The change in hepatic PPRibP/mg DNA in the obese mice is positively correlated with age (up to 4 months, body weight 60 g) and with parameters linked to the activity of the pentose phosphate pathway. There is no apparent correlation between PPRibP concentration and inorganic phosphate, the energy status of the cell, or the hepatic PPRibP synthetase (EC 2.7.6.1.) activity. The increase in the bioavailability of PPRibP, which is both a substrate and activator of the de novo and salvage pathways of purine and pyrimidine synthesis, is considered in relation to the increased nucleotide requirement associated with the rise in total hepatic RNA, DNA, and adenine nucleotide in the obese mouse.

Outcome profiles in the treatment of unipolar depression

Treatment efficacy is typically evaluated by examining group means and pre-post change scores. Although informative, such analyses may obscure individual or subgroup differences in response (outcome profiles). The present study used two different methods to define treatment outcome profiles--rationally-derived criteria (Frank et al., Archives of General Psychiatry 48, 851-855, 1991) and dynamic clustering--to evaluate four treatments of unipolar depression: behaviour therapy, amitriptyline, psychodynamic psychotherapy and relaxation training (attention placebo). The profiling methods yielded similar results. Regardless of treatment, the majority of patients displayed either a recovery or nonremission outcome profile, with relatively few instances of remission followed by a recurrence of depression. These findings challenge the view that any of the treatments are associated with a strong tendency to relapse, at least over the 3-month follow-up period. To further characterize the major outcome profiles, discriminant analysis was performed. Results indicated that recovery and nonremission profiles differed in that the latter was associated with a longer and more severe index episode and greater neuroticism. A number of variables, including family history of depression and therapists' prediction of outcome, failed to distinguish recovered from unremitted patients.

Pyrimidine nucleotide synthesis in the rat mammary gland: changes in the lactation cycle and effects of diabetes

Measurements have been made of the activities of the enzymes of the de novo and salvage pathways of pyrimidine synthesis (carbamoyl phosphate synthetase II (glutamine) (EC 6.3.5.5); dihydroorotate dehydrogenase (EC 1.3.99.11); the overall activity of Complex II (orotate phosphoribosyl pyrophosphate transferase (EC 2.4.2.10) and orotidine 5-phosphate decarboxylase (EC 4.1.1.23); uracil phosphoribosyltransferase (EC 2.4.2.9)) in the mammary gland of rats at different stages of the lactation cycle and the effects of diabetes on the activity of these enzymes in lactation have been studied. From a consideration of the changes in enzyme activities and the changes in the tissue concentration of phosphoribosyl pyrophosphate, an activator of the de novo pathway and substrate for both the de novo and salvage routes, it is concluded that the de novo pathway is the major route of pyrimidine synthesis in mammary tissue. Diabetes decreases the activity of the enzymes of the de novo pathway; the effects are particularly marked for Complex II. The present results on pyrimidine synthesis are compared to the pattern for purine synthesis previously published.

Phosphoribosyl pyrophosphate formation in the rat adrenal gland in relation to adrenal growth in experimental diabetes

Adrenal growth occurs in experimental diabetes, and evidence exists for increased adrenal function. The concentration of PPRibP has been examined in the rat adrenal gland at various times after induction of diabetes with STZ, in view of the key role it plays in the synthesis of Purs and Pyrs. The PPRibP level was exceptionally high in the adrenal gland and increased faster than the rate of growth during the initial rapid growth phase--the first 7 days after STZ was given; PPRibP synthetase showed a parallel increase. Formation of R5P via the oxidative and nonoxidative segments of the PPP also was measured. The oxidative enzymes, G-6-PD and 6-PGD, increased in parallel with growth during the early phase, but showed a more marked rise during the secondary, slower, growth phase seen 6 wk after STZ was given, when this may be associated with the known sustained rise in plasma corticosteroids. The nonoxidative enzymes of the PPP, an alternate route for the production of R5P, showed smaller changes. The specifically high adrenal concentration of PPRibP may be related to the high Km for PPRibP (250 microM) of the first enzyme of the de novo pathway of Pur synthesis, as such synthesis may be required in the rat to replace the net loss of ATP associated with catecholamine secretion. Factors controlling PPRibP synthetase and their potential relative importance in the adrenal gland have been considered.

Severity of unipolar depression and choice of treatment

The National Institute of Mental Health (NIMH) Treatment of Depression Collaborative Research Program (Elkin et al., Archives of General Psychiatry, 46, 971-982; 1989) reported treatment-by-severity interactions favouring pharmacotherapy for more depressed outpatients, on a minority of relevant comparisons. The present study reports secondary analyses from a similar, preexisting data set in which treatment-by-severity interactions are systematically investigated with depressed outpatients treated either with nondirective psychotherapy, behaviour therapy, pharmacotherapy, or relaxation/placebo. Despite multiple severity measures and variable severity cut scores, no treatment was differentially effective in improving more severely depressed patients. Also, there was little difference across symptom severity levels in the proportions of recovered patients between treatment groups. Finally, dynamic cluster analysis demonstrated that the proportion of pharmacotherapy nonresponders (20%) did not differ from the proportion of nonresponders in behaviour therapy or placebo groups. It is concluded that this failure to replicate the NIMH trial findings can not be attributed to treatment differences, populations or statistical power. The suggestion that pharmacotherapy be the treatment of choice for more severely depressed outpatients appears to be unjustified on the basis of available evidence.

Uridine and cytidine nucleotide synthesis in renal hypertrophy: biochemical differences in response to the growth stimulus of diabetes and unilateral nephrectomy

The effects of unilateral nephrectomy (UN) and streptozotocin (STZ) diabetes on the activities of enzymes involved in uridine and cytidine synthesis in early renal growth (3-14 days after stimulus to growth) have been compared. Measurements were also made of glucose-6-phosphate dehydrogenase (G6PDH) and 6-phosphogluconate dehydrogenase (6PGDH) and of glucose 6-phosphate (G6P), UDP-glucose, and glycogen, in relation to phosphoribosyl pyrophosphate, ribonucleotide, and complex carbohydrate formation. There were striking differences in the activities of CTP synthetase, G6PDH, and 6PGDH in the two conditions, with a three-fold increase in all three enzymes at 3 and 5 days and a two-fold increase above basal values at 14 days of STZ diabetes. The UN group showed no significant change in CTP synthetase at any stage and the activity of G6PDH and 6PGDH only kept pace with renal growth. Changes in routes of uridine synthesis were less marked, with a more rapid rise in carbamoyl-phosphate synthetase (glutamine) and a lesser response of dihydroorotate dehydrogenase in the UN relative to the STZ-diabetic groups. The enzymes of complex II and of uracil phosphoribosyltransferase showed essentially similar patterns during renal hypertrophy in UN and STZ diabetes. The parallel increase in CTP synthetase, G6PDH, and 6PGDH in the kidney in diabetes, also known to increase in growth situations in hepatomas and in renal tumors, is discussed in relation to hormone signals involved in renal growth. The importance of the concentration of CTP, and thus of CTP synthetase, in the CTP-cytidyltransferase reaction, an enzyme with a high Km for CTP, makes the present observation of the striking increase in CTP synthetase in STZ diabetes of particular interest in relation to phosphatidylcholine formation and hormone signal transduction.

Peritoneum-preserving radical nephrectomy in a patient on continuous ambulatory peritoneal dialysis

We describe a pararectus retroperitoneal approach for radical nephrectomy in a patient on chronic ambulatory peritoneal dialysis. This approach allows early ligation of the renal pedicle pre-operatively and immediate resumption of peritoneal dialysis post-operatively.