Leptin activation of Stat3 in the hypothalamus of wild-type and ob/ob mice but not db/db mice

Mare's colostrum was collected and examined for the presence of trypsin inhibitors. It was found to contain a low level of trypsin inhibitor which could be denatured by 2.5% trichloroacetic acid and, therefore, it clearly differs from the acid-resistant colostral inhibitor of Artiodactyla and Carnivora. This finding is exceptional for a species that concentrates IgG in the colostrum and whose newborn absorbs colostral proteins non-selectively by the gut. It appears that the presence of colostral trypsin inhibitor is not essential for the transmission of maternal immunity via the colostrum and the gut.     

Specificity of leptin action on elevated blood glucose levels and hypothalamic neuropeptide Y gene expression in ob/ob mice

Correction of the obese state induced by genetic leptin deficiency reduces elevated levels of both blood glucose and hypothalamic neuropeptide Y (NPY) mRNA in ob/ob mice. To determine whether these responses are due to a specific action of leptin or to the reversal of the obese state, we investigated the specificity of the effect of systemic leptin administration to ob/ob mice (n = 8) on levels of plasma glucose and insulin and on hypothalamic expression of NPY mRNA. Saline-treated controls were either fed ad libitum (n = 8) or pair-fed to the intake of the leptin-treated group (n = 8) to control for changes of food intake induced by leptin. The specificity of the effect of leptin was further assessed by 1) measuring NPY gene expression in db/db mice (n = 6) that are resistant to leptin, 2) measuring NPY gene expression in brain areas outside the hypothalamus, and 3) measuring the effect of leptin administration on hypothalamic expression of corticotropin-releasing hormone (CRH) mRNA. Five daily intraperitoneal injections of recombinant mouse leptin (150 micrograms) in ob/ob mice lowered food intake by 56% (P < 0.05), body weight by 4.1% (P < 0.05), and levels of NPY mRNA in the hypothalamic arcuate nucleus by 42.3% (P < 0.05) as compared with saline-treated controls. Pair-feeding of ob/ob mice to the intake of leptin-treated animals produced equivalent weight loss, but did not alter expression of NPY mRNA in the arcuate nucleus. Leptin administration was also without effect on food intake, body weight, or NPY mRNA levels in the arcuate nucleus of db/db mice. In ob/ob mice, leptin did not alter NPY mRNA levels in cerebral cortex or hippocampus or the expression of CRH mRNA in the hypothalamic paraventricular nucleus (PVN). Leptin administration to ob/ob mice also markedly reduced serum glucose (8.3 +/- 1.2 vs. 24.5 +/- 3.8 mmol/l; P < 0.01) and insulin levels (7,263 +/- 1,309 vs. 3,150 +/- 780 pmol/l), but was ineffective in db/db mice. Pair-fed mice experienced reductions of glucose and insulin levels that were < 60% of the reduction induced by leptin. The results suggest that in ob/ob mice, systemic administration of leptin inhibits NPY gene overexpression through a specific action in the arcuate nucleus and exerts a hypoglycemic action that is partly independent of its weight-reducing effects. Furthermore, both effects occur before reversal of the obesity syndrome. Defective leptin signaling due to either leptin deficiency (in ob/ob mice) or leptin resistance (in db/db mice) therefore leads directly to hyperglycemia and the overexpression of hypothalamic NPY that is implicated in the pathogenesis of the obesity syndrome.     

Effects of leptin on corticotropin-releasing factor (CRF) synthesis and CRF neuron activation in the paraventricular hypothalamic nucleus of obese (ob/ob) mice

The effects of leptin on the levels of CRF messenger RNA (mRNA) in the paraventricular hypothalamic nucleus (PVN), on the activation of the PVN CRF cells, and on the plasma levels of corticosterone were investigated in lean (+/?) and obese (ob/ob) C57BL/6J male mice. Murine leptin was s.c. infused using osmotic minipumps. The treatment period extended to 7 days, and the daily dose of leptin delivered was 100 microg/kg. The mice were killed either in a fed state or following 24 h of total food deprivation. The starvation paradigm was employed to enhance the activity of the hypothalamic-pituitary-adrenal axis in obese mice. In situ hybridization histochemistry was performed to determine the PVN levels of CRF mRNA and the arcuate nucleus levels of neuropeptide Y mRNA. The activity of the PVN CRF cells was estimated from the number of PVN cells colocalizing CRF mRNA and the protein Fos. Leptin led to a reduction in body weight gain and fat deposition. These effects were seen in both +/? and ob/ob mice and were observed to be particularly striking in obese mutants, in which leptin also caused an important reduction in food intake. Leptin also was found to affect plasma levels of corticosterone. It lowered the high corticosterone levels of obese mutants, an effect that appeared more evident in food-deprived than in fed mice. Finally, leptin prevented the induction of CRF synthesis in the PVN and the activation of the PVN CRF neurons observed in food-deprived ob/ob mice and hindered the elevation of arcuate nucleus neuropeptide Y synthesis in ob/ob mice. Together these results suggest a role for leptin in the excessive response of the hypophysiotropic CRF system of the ob/ob mouse.     

Neuropeptide Y and luteinizing hormone releasing hormone synergize to stimulate the development of cellular follicle-stimulating hormone in the hamster adenohypophysis

Luteinizing hormone releasing hormone (LHRH) stimulates the development of cellular FSH immunoreactivity in the perinatal hamster adenohypophysis. Because neuropeptide Y (NPY) can act directly on rat adenohypophysial cells to stimulate FSH and LH release and potentiate the stimulatory effect of LHRH on FSH and LH release, we investigated the effects of NPY alone and in combination with a low, ineffective dose of LHRH on inducing cellular FSH immunoreactivity in the neonatal hamster adenohypophysis. Neonatal female pituitary glands were grafted beneath the right renal capsules of hypophysectomized-ovariectomized adult hamster hosts with a catheter implanted in the external jugular vein. After treatment, hosts were decapitated and graft tissue was stained for FSH and LH immunoreactivity. The mean percentage of adenohypophysial cells that stained for FSH was low (2.8%) in grafts in hosts infused continuously with heparinized saline vehicle for 7 days. In other hosts, peptides were pulsed through the catheter every 12 h for 7 days. The mean percentage of FSH cells also was low after pulsing 6 ng LHRH or 2 micrograms NPY but increased substantially when the two peptides were pulsed simultaneously. No differences in the mean percentage of LH cells existed between any of the groups. The results demonstrate that NPY and LHRH can synergize to induce cellular FSH immunoreactivity in the neonatal female hamster.     

Failure of stationary but not of flying honeybees (Apis mellifera) to respond to magnetic field stimuli.

Trained individual honeybees (Apis mellifera) to feed to repletion from a well of sucrose solution so constructed that shock could be delivered when the proboscis was in contact with the solution. If shock was signaled by vibration of the substrate or by an airstream, the animals learned readily to avoid it by breaking contact briefly, but there was no response to change (either constant or time-varying) in the ambient magnetic field. When, however, a magnetic field anomaly in the region of the food well signaled to flying animals that contact would be punished with shock, hesitation to settle was greater in presence than absence of the anomaly. Parallel results were obtained with light, to which flying Ss clearly responded but to which stationary Ss hardly responded at all. We conclude that stationary bees detect magnetic field stimuli but do not process them successfully in the training situation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Responses of leptin to short-term fasting and refeeding in humans: a link with ketogenesis but not ketones themselves

We investigated the response of leptin to short-term fasting and refeeding in humans. A mild decline in subcutaneous adipocyte ob gene mRNA and a marked fall in serum leptin were observed after 36 and 60 h of fasting. The dynamics of the leptin decline and rise were further substantiated in a 6-day study consisting of a 36-h baseline period, followed by 36-h fast, and a subsequent refeeding with normal diet. Leptin began a steady decline from the baseline values after 12 h of fasting, reaching a nadir at 36 h. The subsequent restoration of normal food intake was associated with a prompt leptin rise and a return to baseline values 24 h later. When responses of leptin to fasting and refeeding were compared with that of glucose, insulin, fatty acids, and ketones, a reverse relationship between leptin and beta-OH-butyrate was found. Consequently, we tested whether the reciprocal responses represented a causal relationship between leptin and beta-OH-butyrate. Small amounts of infused glucose equal to the estimated contribution of gluconeogenesis, which was sufficient to prevent rise in ketogenesis, also prevented a fall in leptin. The infusion of beta-OH-butyrate to produce hyperketonemia of the same magnitude as after a 36-h fast had no effect on leptin. The study indicates that one of the adaptive physiological responses to fasting is a fall in serum leptin. Although the mediator that brings about this effect remains unknown, it appears to be neither insulin nor ketones.     

Expression of LECAM-1 and LFA-1 on pre-B lymphoma cells but not on preneoplastic pre-B cells in SL/KH mice

BACKGROUND AND OBJECTIVES: The efficacy of operatively administered spinal neostigmine to provide analgesia and that of different antiemetics to prevent neostigmine-related nausea and vomiting were evaluated in patients undergoing tibial or ankle reconstruction. METHODS: One hundred patients were randomized to five groups (n = 20). The intravenous antiemetic test drug (except propofol) was given as premedication in the holding room, after intravenous midazolam, 0.05 mg/kg. The subarachnoid drugs administered were 20 mg bupivacaine (0.5%) in conjunction with 100 micrograms neostigmine, except for the saline group (S group), which received bupivacaine and saline. The S group, the neostigmine group (N group), and the propofol group (P group) received saline as the intravenous test drug. The droperidol group (D group) received intravenous droperidol 0.5 mg, and the metoclopramide group (M group) received intravenous metoclopramide 10 mg. The P group had a continuous intravenous propofol infusion (2-4 mg/kg/hr), started 10 minutes after the spinal injection. Nausea, emetic episodes, and the need for analgesic (disclofenac) or antiemetic medication were recorded for the first 24 hours following surgery and scored by a 10-cm visual analog scale (VAS). RESULTS: Subarachnoid neostigmine 100 micrograms did not affect subarachnoid bupivacaine analgesia as measured by time to first rescue analgesic in most patients, but it decreased the overall 24-hour visual analog scale (VAS) scores and the need for postoperative analgesics in 24 hours (P < .001). The incidence of intraoperative nausea and vomiting was higher in the N, D, and M groups than in the S group (P < .001). Following surgery, the 3-hour VAS assessment for emesis was higher for the N, P, and M groups than for the S group (P < .05). The overall 24-hour assessment was similar among groups. CONCLUSIONS: Subarachnoid neostigmine reduced postoperative pain scores and analgesic requirements. Whether it prolonged the duration of action of diclofenac or enhanced the mechanisms involved in spinal analgesia cannot be determined from these data. Although propofol and droperidol appeared to be more effective during and after surgery, respectively, all neostigmine groups were associated with a high consumption of antiemetics.     

Endothelial and epithelial cells do not respond to complexes of peptidoglycan with soluble CD14 but are activated indirectly by peptidoglycan-induced tumor necrosis factor-alpha and interleukin-1 from monocytes

Peptidoglycan (PGN) activates macrophages through membrane CD14 (an endotoxin receptor) and binds to both soluble and membrane CD14. Since soluble CD14-lipopolysaccharide (LPS) complexes activate CD14-negative endothelial and epithelial cells, this study tested whether soluble CD14-PGN complexes activate human umbilical vein endothelial cells and epithelial-like U373 cells to secrete interleukin (IL)-6, express vascular cellular adhesion molecule-1, and translocate nuclear factor-kappaB. In contrast to LPS, endothelial, epithelial, and other cells of non-hemopoietic origin were unresponsive to PGN through soluble or membrane-bound CD14, whereas cells of hemopoietic origin were responsive to both PGN and LPS. PGN, similarly to LPS, activated endothelial and epithelial cells indirectly in the presence of 2%-4% blood, by inducing secretion of both tumor necrosis factor-alpha and IL-1 from monocytes. These results reveal different mechanisms of CD14 function and cell activation for LPS and PGN and also demonstrate strong indirect activation of endothelial and epithelial cells by both PGN and LPS.     

Overexpression of the cardiac Na+/Ca2+ exchanger increases susceptibility to ischemia/reperfusion injury in male, but not female, transgenic mice

Influx of Ca2+ into myocytes via Na+/Ca2+ exchange may be stimulated by the high levels of intracellular Na+ and the changes in membrane potential known to occur during ischemia/reperfusion. This increased influx could, in turn, lead to Ca2+ overload and injury. Overexpression of the cardiac Na+/Ca2+ exchanger therefore may increase susceptibility to ischemia/reperfusion injury. To test this hypothesis, the hearts of male and female transgenic mice, overexpressing the Na+/Ca2+ exchange protein, and hearts of their wild-type littermates, were perfused with Krebs-Henseleit buffer and subjected to 20 minutes of ischemia and 40 minutes of reperfusion. Preischemic left ventricular developed pressures and +dP/dtmax, as well as -dP/dtmin, were higher in the male transgenic hearts compared with wild-type, implying a role for Na+/Ca2+ exchange in the contraction, as well as the relaxation, phases of the cardiac beat. Postischemic function was lower in male transgenic than in male wild-type hearts (7+/-2% versus 32+/-6% of preischemic function), but there was no difference between female transgenic and female wild-type hearts, both at approximately 30% of preischemic function. To assess whether this male/female difference was due to female-specific hormones such as estrogen, the hearts of bilaterally ovariectomized and sham-operated transgenic females were subjected to the same protocol. The functional recoveries of ovariectomized female transgenic hearts were lower (17+/-3% of preischemic function) than those of wild-type and sham-operated transgenic females. The lower postischemic functional recovery in the male transgenic and female ovariectomized transgenic hearts correlated with lower recoveries of the energy metabolites, ATP and phosphocreatine, as measured by 31P nuclear magnetic resonance spectroscopy. Alternans were observed during reperfusion in male transgenic and female ovariectomized transgenic hearts only, consistent with intracellular Ca2+ overload. Western analyses showed that alterations in the expression of the Na+/Ca2+ exchange or L-type Ca2+ channel proteins were not responsible for the protection observed in the female transgenic hearts. In conclusion, in males, overexpression of the Na+/Ca2+ exchanger reduced postischemic recovery of both contractile function and energy metabolites, indicating that the Na+/Ca2+ exchanger may play a role in ischemia/reperfusion injury. From the studies of females, however, it appears that this exacerbation of ischemia/reperfusion injury by overexpression of the Na+/Ca2+ exchanger can be overcome partially by female-specific hormones such as estrogen.     

Neuropeptides and thirst: The temporal response of corticotropin-releasing hormone and neurotensin/neuromedin N gene expression in rat limbic forebrain neurons to drinking hypertonic saline.

The authors have demonstrated in rats that the ingestion of hypertonic saline for 5 days provides an increasingly complex dehydrating stimulus to the rats. Initially, the stimulus leads to cellular dehydration, but extracellular dehydration develops as ingestion continues beyond 3 days. The initial cellular dehydration provokes modifications to corticotropin-releasing hormone and neurotensin/neuromedin N messenger RNAs (mRNAs) in some neurons of the limbic forebrain, changes that are either maintained or are modified as extracellular dehydration develops. These changes in mRNA content occur in neurosecretory neurons as well as in neurons in hypothalamic and telencephalic regions associated with behavior and autonomic regulation. The authors propose that alterations in peptide mRNAs are allied to altered neuronal signaling processes that direct the different components of the homeostatic response to dehydration. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Competitive and non-competitive NMDA antagonists block the development of antinociceptive tolerance to morphine, but not to selective mu or delta opioid agonists in mice

N-Methyl-D-aspartate (NMDA) receptor antagonists have been shown to block the development of antinociceptive tolerance to morphine. Assessment of the effects of NMDA antagonists on development of antinociceptive tolerance to selective opioid mu (mu) and delta (delta) agonists, however, has not been reported. In these experiments, selective mu and delta receptor agonists, and morphine, were repeatedly administered to mice either supraspinally (i.c.v.) or systemically (s.c.), alone or after pretreatment with systemic NMDA antagonists. Antinociception was evaluated using a warm-water tail-flick test. Repeated i.c.v. injections of mu agonists including morphine, fentanyl, [D-Ala2, NMePhe4, Gly-ol]enkephalin (DAMGO) and Tyr-Pro-NMePhe-D-Pro-NH2 (PL017) or [D-Ala2, Glu4]deltorphin, a delta agonist, or s.c. injections of morphine or fentanyl, produced antinociceptive tolerance as shown by a significant rightward displacement of the agonist dose-response curves compared to controls. Single injections or repeated administration of MK801 (a non-competitive NMDA antagonist) or LY235959 (a competitive NMDA antagonist) at the doses employed in this study did not produce behavioral toxicity, antinociception or alter the acute antinociceptive effects of the tested opioid agonists. Consistent with previous reports, pretreatment with MK801 or LY235959 (30 min prior to agonist administration throughout the tolerance regimen) prevented the development of antinociceptive tolerance to i.c.v. or s.c. morphine. Neither NMDA antagonist, however, affected the development of antinociceptive tolerance to i.c.v. fentanyl, DAMGO, or [D-Ala2, Glu4]deltorphin. Additionally, MK801 pretreatment did not affect the development of antinociceptive tolerance to i.c.v. PL017 or to s.c. fentanyl. Further, MK801 pretreatment also did not affect the development of tolerance to the antinociception resulting from a cold-water swim-stress episode, previously shown to be a delta-opioid mediated effect. These data lead to the suggestion that the mechanisms of tolerance to receptor selective mu and delta opioids may be regulated differently from those associated with morphine. Additionally, these findings emphasize that conclusions reached with studies employing morphine cannot always be extended to 'opiates' in general.     

Cortisol in physiological concentrations acts within minutes to modify effects of prolactin and growth hormone on prostaglandin secretion: importance of effect in modulating cellular responses to calcium and cyclic nucleotides

We propose that intracellular prostaglandins (PGs) are essential for the final expression of the effects of second messengers in most cells. We suggest that the amounts of PGs required are very small (in the picomolar range) and are much lower than those used in most current PG studies. We suggest that while therapeutic levels of inhibitors of PG synthetase may be adequate to block the overflow of PGs from cells, they are in most cases unlikely to reduce intracellular PGs sufficiently to test the role of such PGs. We propose that there is a basal level of PG synthesis unaffected by hormones but that above this level PG synthesis is regulated by the interplay between physiological levels of cortisol, prolactin, growth hormone and thyroid hormones. For the most part prolactin seems to stimulate PG synthesis and cortisol to inhibit it: cortisol has, however, no inhibitory effect on basal PG synthesis. In reducing prolactin-stimulated PG synthesis cortisol is 1000-2000 times more potent than indomethacin on a molar basis. We suggest that the regulation of intracellular PG levels is the mechanism of the so-called "permissive" actions of these hormones. These concepts could prove important in the understanding of many aspects of physiology and pathophysiology including diurnal and seasonal changes in hormone responsiveness. They are also relevant to the use of established drugs and the design of new ones.     

Changes of plasma levels of human growth hormone with age in relation to mammary tumour appearance in whey acidic protein/human growth hormone (mWAP/hGH) transgenic female and male mice

Plasma levels of human growth hormone (hGH) were determined in female and male transgenic mice with human growth hormone fusion gene driven by the promoter of mouse whey acidic protein (mWAP/hGH) at 3, 6 and 9 months of age and at mammary tumour appearance. In female transgenic mice developing mammary tumours, the plasma hGH level decreased markedly upon tumour appearance, which was associated with little change in body weight. In contrast, the hGH level changed little in transgenic male mice with tumours. In female and male transgenic mice without mammary tumours, the pattern of the change of hGH levels was variable; some showed high levels at all three time points (3, 6, and 9 months) and others had none or high levels at one or two time points.     

Hyperphosphorylated p107 and p130 bind to T-antigen: identification of a critical regulatory sequence present in RB but not in p107/p130

The retinoblastoma tumor suppressor RB and its related proteins, p107 and p130, are targets of several viral oncoproteins, including SV40 large T-antigen (T-Ag) and adenovirus E1A. T-Ag and E1A each contains an LXCXE-peptide motif through which binding to the conserved 'A/B pocket' present in RB, p107 and p130 is achieved. The LXCXE-binding activity of RB, we have previously shown, is inhibited by phosphorylation at Thr 821 and 826 in the C-terminal region of RB. Thr 821 and its surrounding sequence is unique to RB and not found in p107 or p130. Interestingly, hyperphosphorylation of p107 does not disrupt its ability to bind T-Ag or to inhibit the transactivating function of E1A. Insertion of a fourteen amino acid sequence of RB containing Thr 821 into p107 prevents binding of T-Ag and E1A to phosphorylated p107. These results show that the RB sequence surrounding Thr 821 plays a critical role in the regulation of the 'A/B pocket' function. In addition, these data indicate that the protein binding functions of RB and p107 are not equivalently regulated by phosphorylation.     

Development of survival responsiveness to brain-derived neurotrophic factor, neurotrophin 3 and neurotrophin 4/5, but not to nerve growth factor, in cultured motoneurons from chick embryo spinal cord

During embryonic development, most neuronal populations undergo a process usually referred to as naturally occurring neuronal death. For motoneurons (MTNs) of the lumbar spinal cord of chick embryos, this process takes place in a well defined period of time, between embryonic days 6 and 10 (E6-E10). Neurotrophins (NTs) are the best characterized family of neurotrophic factors and exert their effects through activation of their specific Trk receptors. In vitro and in vivo studies have demonstrated that rodent motoneurons survive in response to BDNF, NT3, and NT4/5. In contrast, the trophic dependencies of chicken motoneurons have been difficult to elucidate, and various apparently conflicting reports have been published. In the present study, we describe how freshly isolated motoneurons from E5.5 chick embryos did not respond to any neurotrophin in vitro. Yet, because motoneurons were maintained alive in culture in the presence of muscle extract, they developed a delayed specific survival response to BDNF, NT3, and NT4/5 that is clearly dose-dependent, reaching saturation at doses of 100 pg/ml. This trophic response correlated with increasing expression of the corresponding functional receptors TrkB and TrkC. Moreover, TrkB receptor is able to become autophosphorylated and to activate classical intracellular signaling pathways such as the extracellular signal-regulated protein kinase when it is stimulated with its cognate ligand BDNF. Therefore, our results reconcile the reported differences between in vivo and in vitro studies on the ability of chicken MTNs to respond to some members of the neurotrophin family of trophic factors.