Mediation by nitric oxide of TRH-, but not metoclopramide-stimulated TSH secretion in humans

In order to establish whether nitric oxide (NO) participates in the regulation of thyroid stimulating hormone (TSH) secretion in humans, seven normal men were treated with a placebo (normal saline) or the NO synthase inhibitor L-NAME, given at doses (40 micrograms kg-1 injected plus 50 micrograms kg-1 infused i.v.) previously found to be unable to change blood pressure. Experiments were carried out either in basal conditions or during stimulation of TSH secretion with an i.v. injection of 200 micrograms thyrotropin releasing hormone (TRH) or 10 mg of the dopaminergic antagonist metoclopramide (MCP). Administration of L-NAME did not change the basal secretion of TSH or the TSH response to MCP, but significantly reduced the TSH increase induced by TRH. These data fail to provide evidence of NO involvement in regulation of basal TSH secretion. NO also appears to be without effects on the dopaminergic control of TSH secretion. In contrast, the inhibitory effect of L-NAME on TRH-induced TSH secretion suggests the mediation by NO of the TSH-releasing action of TRH.     

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.     

Patterns of drug-induced cardiovascular pathology in the beagle dog: relevance for humans

In toxicity studies, the examination of tissue sections for pathological changes is the principle method for the identification of organ toxicity and characterisation of the hazard of novel drugs for humans. Study of the patterns of pathological alterations also represents an important means of developing an understanding of the mechanism of toxicity. However as pathological change frequently represents a final common expression of diverse processes, additional functional information is often required for a clear understanding of the mechanisms of toxicity. This is exemplified in the evaluation of the effects of drugs on the beagle dog cardiovascular system where an understanding of mechanisms is crucial in the assessment of human risk. Particular patterns of drug-induced structural change in the myocardium or blood vessels are frequently linked to specific mechanisms of toxicity. However, assessment based on the interpretation of patterns of cardiovascular pathology alone may be misleading. Quite different changes in cardiac and vascular function or direct cellular toxicity may also be manifest by pathological features in common. Therefore, a clear understanding of mechanism frequently requires additional in vivo or in vitro physiological, pharmacological, biochemical or other mechanistic information. The beagle dog remains an important model for the study of cardiovascular toxicity because in this species, haemodynamic changes and pathological alterations can be related in a way that provides the basis for the safe study in humans of novel drugs with cardiovascular activity.     

Hydroxyethyl starch antibodies in humans: incidence and clinical relevance

Hydroxyethyl starch (HES) is a plasma expander used for perioperative i.v. fluid management, as well as for resuscitation from trauma and shock. HES is very well tolerated, and the incidence of anaphylactic reactions is lower than with dextran or gelatin. Dextran anaphylaxis is caused by circulating dextran-reactive antibodies (ABs) of the immunoglobin G (IgG) class found in most adults. Histamine release from mast cells induces adverse reactions after gelatin infusion. The cause of adverse reactions due to HES is not yet clear. To investigate AB formation due to HES, we collected sera of 1004 patients at least 14 days after starch administration. Using a highly sensitive enzyme-linked immunoabsorbent assay technique, we found one patient with a low 1:10 titer of HES-reactive ABs (immunoglobin M [IgM] class). Despite repeated HES infusions, no clinical reaction could be detected in this patient. On the basis of a binomial distribution, a one-tailed confidence interval (99%) was used to calculate the percentage of the occurrence of ABs in general with maximum of 33 in 10,000 persons (IgM) and 23 in 10,000 persons (IgG). We suggest that HES-reactive ABs are extremely rare and that they do not necessarily induce anaphylaxis. Other mechanisms may be responsible for adverse reactions due to HES. Implications: The frequency of antibody formation due to hydroxyethyl starch, a commonly used plasma expander, was prospectively investigated in 1004 patients. Only one patient showed transient antibody formation, which was not harmful to the patient. This low antigenicity could explain the excellent tolerance of hydroxyethyl starch compared with other plasma expanders.     

A TrkA-selective, fast internalizing nerve growth factor-antibody complex induces trophic but not neuritogenic signals

Nerve growth factor (NGF) is a neurotrophin that induces neuritogenic and trophic signals by binding to TrkA and/or p75 receptors. We report a comparative study of the binding, internalization, and biological activity of NGF versus that of NGF in association with an anti-NGF monoclonal antibody (mAb NGF30), directed against the C termini of NGF. NGF.mAb complexes do not bind p75 effectively but bind TrkA with high affinity. After binding, NGF. mAb complexes stimulate internalization faster and to a larger degree than NGF. NGF.mAb-induced activation of TrkA, Shc, and MAPK is transient compared with NGF-induced activation; yet NGF and NGF. mAb afford identical trophic responses. In contrast, NGF induces Suc-1-associated neurotrophic activating protein phosphorylation and neuritogenic differentiation, but NGF.mAb does not. Thus, an absolute separation of trophic and neuritogenic function is seen for NGF.mAb, suggesting that biological response modifiers of neurotrophins can afford ligands with selected activities.     

Departure from neutrality at the mitochondrial NADH dehydrogenase subunit 2 gene in humans, but not in chimpanzees

To test whether patterns of mitochondrial DNA (mtDNA) variation are consistent with a neutral model of molecular evolution, nucleotide sequences were determined for the 1041 bp of the NADH dehydrogenase subunit 2 (ND2) gene in 20 geographically diverse humans and 20 common chimpanzees. Contingency tests of neutrality were performed using four mutational categories for the ND2 molecule: synonymous and nonsynonymous mutations in the transmembrane regions, and synonymous and nonsynonymous mutations in the surface regions. The following three topological mutational categories were also used: intraspecific tips, intraspecific interiors, and interspecific fixed differences. The analyses reveal a significantly greater number of nonsynonymous polymorphisms within human transmembrane regions than expected based on interspecific comparisons, and they are inconsistent with a neutral equilibrium model. This pattern of excess nonsynonymous polymorphism is not seen within chimpanzees. Statistical tests of neutrality, such as TAJIMA's D test, and the D and F tests proposed by FU and LI, indicate an excess of low frequency polymorphisms in the human data, but not in the chimpanzee data. This is consistent with recent directional selection, a population bottleneck or background selection of slightly deleterious mutations in human mtDNA samples. The analyses further support the idea that mitochondrial genome evolution is governed by selective forces that have the potential to affect its use as a "neutral" marker in evolutionary and population genetic studies.     

Perforin is essential for control of ectromelia virus but not related poxviruses in mice

Lack of perforin renders the relatively resistant mouse strain C57BL/6 highly susceptible to the natural mouse pathogen ectromelia virus, a cytopathic orthopoxvirus. This is indicated by increased mortality, elevated virus titers and pathology in liver and spleen, and increased levels of liver enzymes in blood. Cowpox virus on the other hand is more virulent in the presence of perforin than in its absence. An additional lack of granzyme A which together with perforin is a constituent of cytoplasmic granules from cytotoxic T cells increases the virulence of cowpox virus.     

Guanfacine and clonidine, alpha 2-agonists, improve paired associates learning, but not delayed matching to sample, in humans

The present study compares the effects of two alpha 2-agonists, clonidine (0.5, 2, and 5 micrograms/kg, p.o.) and guanfacine (7 and 29 micrograms/kg, p.o.) in young healthy volunteers on their performance in visual paired associates learning (PAL) and delayed matching to sample (DMTS) visual short-term recognition memory tests. In the PAL test, clonidine 2 and guanfacine 29 micrograms/kg improved the subjects' performance. In the DMTS test, clonidine at 5 micrograms/kg delay-dependently impaired performance accuracy, and at 2 and 5 micrograms/kg it also slowed responses. Guanfacine had no effect on DMTS test performance. Clonidine 5 and guanfacine 29 micrograms/kg equally increased subjective feelings of sedation and reduced blood pressure. The results suggest that both clonidine and guanfacine facilitated PAL learning by improving "frontal strategies," but only clonidine disrupted "mneomonic processing" decreasing DMTS accuracy. The greater selectivity of guanfacine for alpha 2A-adrenoceptor subtype may explain the different profile of action of the drugs.     

Generation of lymphokine-activated killer activity in rodents but not in humans is nitric oxide dependent

The role of nitric oxide (NO) in the generation of lymphokine-activated killer (LAK) cells was investigated. Here we report that L-arginine analog NG-monomethyl-L-arginine (NMMA), a specific inhibitor of nitric oxide synthase, prevents LAK cell generation from cultured rat splenic cells. Accumulated NO endproduct nitrite (NO2-), as measured in the supernatants of rat splenic cells, correlated well with the generation of LAK cells. In contrast, cell proliferation induced by rIL-2 or by Con A was not affected by NMMA. Similarly, phenotypic expression of CD25 in rIL-2-stimulated cultures was unaffected. Furthermore, we could not observe differences in percentages of CD5-CD8+ cells (NK and LAK cell phenotype markers in rats) between rIL-2-stimulated cultures performed in the presence or absence of NMMA. LAK cell generation could no longer be blocked if NMMA was added to the rat cell cultures 24 hr after rIL-2 stimulation. To further confirm the role of NO in LAK cell generation, rat splenic cells were cultured in medium without L-arginine. Under such conditions rIL-2 could not induce LAK cell generation. Hemoglobin, which is a scavenger of NO, also inhibited LAK cell generation. Finally, addition of sodium nitroprusside (SNP) which releases NO in cultures was able to overcome blocking effects of NMMA. To attempt the identification of NO-producing cells, lysosomotropic agent, L-leucine methyl ester (LME), was used. Generation of LAK cell activity was virtually abolished in cell cultures treated with LME. Addition of SNP to cultures, however, sufficed to restore LAK cell generation. These results suggest that LAK cell precursors depend on a exogenous NO supply from other cell types in order to display their full cytotoxic potential. Similar results were also obtained by using mouse splenocytes as responder cells. In contrast, NMMA did not affect generation of LAK cells from human peripheral blood or spleen mononuclear cells.     

Happily hopeless: Adaptation to a permanent, but not to a temporary, disability.

Objective: The authors tracked patients with either irreversible or reversible colostomies over a 6-month period, beginning a week after the procedure, to examine how they adapted hedonically over time. Based on prior research and theorizing, the authors hypothesized that, paradoxically, those with irreversible colostomies would adapt more fully, and become happier, than would those with colostomies that were potentially reversible. Design: The authors contacted 107 patients who had recently received either a colostomy or ileostomy. The initial interviews were conducted while patients were still in the hospital recovering from their surgery. Consenting participants were mailed surveys at three time points: 1 week after release from the hospital, 1 month after release, and 6 months after release. Main Outcome Measures: The surveys included measures of life satisfaction and perceived quality of life. Results: As predicted, overall life satisfaction and quality of life increased with time for patients with permanent, but not temporary, ostomies. Conclusion: These findings suggest that knowing an adverse situation is temporary can interfere with adaptation, leading to a paradoxical situation in which people who are better off objectively are worse off subjectively. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The flavin-containing monooxygenase 2 gene (FMO2) of humans, but not of other primates, encodes a truncated, nonfunctional protein

Flavin-containing monooxygenases (FMOs) are NADPH-dependent flavoenzymes that catalyze the oxidation of heteroatom centers in numerous drugs and xenobiotics. FMO2, or "pulmonary" FMO, one of five forms of the enzyme identified in mammals, is expressed predominantly in lung and differs from other FMOs in that it can catalyze the N-oxidation of certain primary alkylamines. We describe here the isolation and characterization of cDNAs for human FMO2. Analysis of the sequence of the cDNAs and of a section of the corresponding gene revealed that the major FMO2 allele of humans encodes a polypeptide that, compared with the orthologous protein of other mammals, lacks 64 amino acid residues from its C terminus. Heterologous expression of the cDNA revealed that the truncated polypeptide was catalytically inactive. The nonsense mutation that gave rise to the truncated polypeptide, a C --> T transition in codon 472, is not present in the FMO2 gene of closely related primates, including gorilla and chimpanzee, and must therefore have arisen in the human lineage after the divergence of the Homo and Pan clades. Possible mechanisms for the fixation of the mutation in the human population and the potential significance of the loss of functional FMO2 in humans are discussed.     

Interleukin-6 stimulates coagulation, not fibrinolysis, in humans

The role of IL-6 as a mediator of haemostatic changes during severe inflammation is controversial. To assess the effect of IL-6 on haemostasis we conducted a controlled cross-over study in eight patients with metastatic renal cell cancer. In all subjects coagulation and fibrinolysis were monitored during and after a 4-h infusion of either 150 micrograms recombinant human (rh) IL-6, or during infusion of saline (control study). Mean maximum IL-6 concentrations were 1418.0 +/- 755.8 pg/ml. Compared to the control study, rhIL-6 induced activation of coagulation as reflected by a 190 +/- 55% increase in the plasma levels of thrombin-antithrombin III complexes (p < 0.001) and by a 24 +/- 11% increase in the plasma levels of in the prothrombin activation fragment F1 + 2 (p < 0.001). In contrast, fibrinolysis was not affected. We conclude that in severe inflammation IL-6 may contribute to the activation of coagulation, whereas other factors mediate changes in fibrinolysis.     

Ketoconazole attenuates the cortisol response but not the subjective effects of smoked cocaine in humans

Attenuation of hypothalamo-pituitary-adrenal (HPA) function in laboratory rodents has been found to reduce the reinforcing effects of cocaine. To examine whether attenuation of HPA function reduces the effects of cocaine in humans, one female and seven male 'crack' cocaine abusers were pretreated with three doses of ketoconazole (0, 600, 1200 mg), an inhibitor of adrenocorticoid biosynthesis, 1 h before receiving cocaine. Three doses of smoked cocaine (0, 12, 50 mg) were administered in counterbalanced order under each ketoconazole condition. Ketoconazole dose-dependently reduced cocaine-induced cortisol, but not adrenocorticotropin (ACTH) release, and attenuated the cocaine-induced increase in heart rate and blood pressure. Plasma ACTH levels were more predictive of blood pressure changes than either cocaine or cortisol levels. Suppression of cortisol secretion was not associated with a reduction in ratings of the subjective effects of cocaine. These results support a role for the HPA axis in the cardiovascular effects of cocaine, but do not support a role for the HPA axis in the subjective effects of cocaine. To the extent that self-administration can be predicted by subjective effects, these results further argue that the HPA axis does not play a critical role in cocaine self-administration by humans.     

Prolonged fasting in humans results in diminished plasma choline concentrations but does not cause liver dysfunction

The potential antiatherogenic actions of the angiotensin II receptor antagonist, losartan were investigated in apolipoprotein (apo) E deficient mice, an animal model with severe hypercholesterolemia and extensive atherosclerosis. In these animals accelerated atherosclerosis is associated with increased lipid peroxidation which may play a crucial role in the build up of the atherosclerotic lesions. Administration of losartan (25mg/kg/d) to the apo E deficient mice for a 3-month period increased the plasma renin activity 3.5-fold compared to the placebo group. Losartan increased the resistance of LDL to CuSO4-induced oxidative modification as shown by a significant reduction in the LDL content of malondialdehyde by 55% compared to placebo, as well as by the prolongation of the lag time required for LDL oxidation, from 60 min in the placebo-treated mice to more than 140 min in the losartan-treated mice. Losartan reduced significantly the mean atherosclerotic lesion area by 80% compared to the placebo group. We conclude that losartan inhibits LDL lipid peroxidation in the apo E deficient mice and this effect may have an important role in the attenuation of the accelerated atherosclerosis.