NMDA receptor-mediated refinement of a transient retinotectal projection during development requires nitric oxide

We recently developed a simple new method which is designed to separate and concentrate bacteria from a sample by centrifugation in a gel system. Bacterial enzyme activity is then detected inside the gel without further manipulation using a colorimetric or fluorogenic substrate. The method provides a rapid, direct means of detecting bacteria in clinical samples, dispensing with the 24-h period normally required to isolate colonies on agar. Various applications of the method are described below, e.g. screening of negative urine samples, identification of Escherichia coli in urine samples, identification of Staphylococcus aureus in blood culture broths and detection of oxacillin-resistant S. aureus in blood culture broths. The advantages of the gel system and other applications are discussed.     

Mechanism of selective motor neuronal death after exposure of spinal cord to glutamate: involvement of glutamate-induced nitric oxide in motor neuron toxicity and nonmotor neuron protection

In this study, we analyzed the mechanism of selective motor neuronal death, a characteristic of amyotrophic lateral sclerosis, using embryonic rat spinal cord culture. When dissociated cultures were exposed to low-level glutamate (Glu) coadministered with the Glu transporter inhibitor L-trans-pyrrolidine-2,4-decarboxylate (PDC) for 24 hours, motor neurons were selectively injured through N-methyl-D-aspartate (NMDA) and alpha-amino-3-hydroxy-5-methylisoxazole-4-propionate (AMPA)/kainate receptors. Nitric oxide synthase (NOS) inhibitors attenuated this toxicity, and long-acting nitric oxide (NO) donors damaged motor neurons selectively. Nonmotor neurons survived after exposure to low-dose Glu/PDC, but Glu-induced toxicity was potentiated by coadministration of an NO-dependent guanylyl cyclase inhibitor. In addition, 8-bromo-cyclic GMP, a soluble cyclic GMP analogue, rescued nonmotor neurons, but not motor neurons, exposed to high-dose Glu/PDC. Twenty-four hours' incubation with PDC elevated the number of neuronal NOS-immunoreactive neurons by about twofold compared with controls, and a double-staining study, using the motor neuron marker SMI32, revealed that most of them were nonmotor neurons. These findings suggest that selective motor neuronal death caused by chronic low-level exposure to Glu is mediated by the formation of NO in nonmotor neurons, which inversely protects nonmotor neurons through the guanylyl cyclase-cyclic GMP cascade. Induction of neuronal NOS in nonmotor neurons might enhance both the toxicity of motor neurons and the protection of nonmotor neurons, which could explain the pathology of amyotrophic lateral sclerosis.     

The role of nitric oxide in ischemia-reperfused heart

The objective of this study was to estimate the dominance variance for postweaning gain in Limousin cattle. Data included 215,326 records of postweaning gain from 205 to 365 d, provided by the North American Limousin Foundation. Parental dominance subclasses were formed and related using the method of Hoeschele and VanRaden. Variance components were estimated using Method R based on six samples of 50%. Fixed effects in the model included contemporary group and covariates for inbreeding and breed composition (percentage Limousin). Heterozygosity was negatively correlated with breed composition (< -.99) and was therefore not included in the model. Two types of contemporary groups used as original groups from the National Cattle Evaluation were partially based on breed composition. Original contemporary groups that were too homogeneous for breed composition were replaced by herd-year-sex classes. Two models were used with the two data sets. Model 1 contained the fixed effects described above and an additive genetic effect. Model 2 included a dominance effect in addition to the effects contained in Model 1. In total, four combinations of contemporary group x model were used. Dominance variance was computed as being four times the estimated parental subclass variance. Estimates for inbreeding depression and breed composition (percentage Limousin) were all small and not greatly affected by inclusion of dominance effects or changes in contemporary groups. Estimates of the additive variance (expressed as percentage of the phenotypic variance) were only slightly affected, with values between 20 and 21%. Dominance estimates were highly affected when passing from original (10%) and to alternative contemporary groups (18%). Such large values may indicate that dominance is important for postweaning gain. Results showed the advantage of an individual dominance approach based on sire-dam combinations; therefore, expected gains through the use of specific combination ability as a part of the mating selection criteria for growth might be high.     

The role of nitric oxide in hepatic metabolism

Nitric oxide (NO) may regulate hepatic metabolism directly by causing alterations in hepatocellular (hepatocyte and Kupffer cell) metabolism and function or indirectly as a result of its vasodilator properties. Its release from the endothelium can be elicited by numerous autacoids such as histamine, vasoactive intestinal peptide, adenosine, ATP, 5-HT, substance P, bradykinin, and calcitonin gene-related peptide. In addition, NO may be released from the hepatic vascular endothelium, platelets, nerve endings, mast cells, and Kupffer cells as a response to various stimuli such as endotoxemia, ischemia-reperfusion injury, and circulatory shock. It is synthesized by nitric oxide synthase (NOS), which has three distinguishable isoforms: NOS-1 (ncNOS), a constitutive isoform originally isolated from neuronal sources; NOS-2 (iNOS), an inducible isoform that may generate large quantities of NO and may be induced in a variety of cell types throughout the body by the action of inflammatory stimuli such as tumor necrosis factor and interleukin (IL)-1 and -6; and NOS-3 (ecNOS), a constitutive isoform originally located in endothelial cells. Another basis for differentiation between the constitutive and inducible enzymes is the requirement for calcium binding to calmodulin in the former. NO is vulnerable to a plethora of biologic reactions, the most important being those involving higher nitrogen oxides (NO2-), nitrosothiol, and nitrosyl iron-cysteine complexes, the products of which (for example, peroxynitrite), are believed to be highly cytotoxic. The ability of NO to react with iron complexes renders the cytochrome P450 series of microsomal enzymes natural targets for inhibition by NO. It is believed that this mechanism provides negative feedback control of NO synthesis. In addition, NO may regulate prostaglandin synthesis because the cyclooxygenases are other hem-containing enzymes. It may also be possible that NO-induced release of IL-1 inhibits cytochrome P450 production, which ultimately renders the liver less resistant to trauma. It is believed that Kupffer cells are the main source of NO during endotoxemic shock and that selective inhibition of this stimulation may have future beneficial therapeutic implications. NO release in small quantities may be beneficial because it has been shown to decrease tumor cell growth and levels of prostaglandin E2 and F2 alpha (proinflammatory products) and to increase protein synthesis and DNA-repair enzymes in isolated hepatocytes. NO may possess both cytoprotective and cytotoxic properties depending on the amount and the isoform of NOS by which it is produced. The mechanisms by which these properties are regulated are important in the maintenance of whole body homeostasis and remain to be elucidated.     

The role of nitric oxide in vascular biology and pathobiology

Brain natriuretic peptide (BNP) is a novel cardiac hormone secreted predominantly from the ventricle. We examined the plasma levels of BNP and atrial natriuretic peptide (ANP) in 13 patients with aortic stenosis undergoing corrective surgery. Preoperative plasma BNP and ANP levels correlated highly with preoperative left ventricular end-systolic wall stress (ESS) (r = 0.96, p < 0.0001 and r = 0.95, p < 0.0001, respectively). Moreover, between preoperative and late postoperative states, the difference of the plasma levels of BNP and ANP correlated with the difference of ESS. In two patients with elevated ESS and quite high preoperative plasma BNP (> 1000 pg/ml), rapid decrease of the plasma level after operation was observed. These results suggest that synthesis and secretion of BNP and ANP are stimulated by the increase of left ventricular end-systolic wall stress in patients with aortic stenosis.     

The role of nitric oxide in passive avoidance learning

The role of nitric oxide on passive avoidance learning was studied by administering L-arginine or D-arginine to male rats in a passive avoidance paradigm. L-Arginine administered into the lateral brain ventricle at a dose of 1.25 microg showed a tendency to increase the passive avoidance latency, and 2.5 microg exerted almost maximal action, but the action gradually increased still further up to 20 microg tested. D-Arginine had no action. Peripheral administration (intraperitoneal) of L-arginine facilitated the consolidation of passive avoidance learning in a dose-dependent manner. A significant increase in passive avoidance response was obtained following an injection of 100 mg/kg L-arginine. When L-arginine was given i.c.v. with a selected dose of 5 microg, 30 min prior to a learning trial, the latency of the passive avoidance response was likewise lengthened. However, when L-arginine was given 30 min before the 24-hr testing (retrieval), it was ineffective. It was also ineffective when given 6 hr after the training trial. However, when L-arginine was administered immediately following the training trial, the action in improving the consolidation could be detected 6 hr after the training trial. Nitro-L-arginine, which blocks nitric oxide synthase, can also block the facilitation of consolidation caused by the nitric oxide donor L-arginine. The nitric oxide synthase inhibitor per se in different doses had no action on the learning of a passive avoidance task. The results indicate that nitric oxide is able to facilitate the learning and consolidation of memory in a passive avoidance paradigm, but it is ineffective in retrieval processes. The results also suggest that, under the experimental circumstances used, nitric oxide is involved only in the facilitated learning and memory processes caused by pharmacological effect of L-arginine, and not involved in normal learning processes.     

The role of NMDA receptors in the slow neuronal degeneration of Parkinson's disease

Parkinson's disease is a disorder, in which neurons of various neuronal systems degenerate. Furthermore, in such degenerating neurons, the cytoskeleton seems to be affected. In this respect, Parkinson's disease resembles Alzheimer's disease. Since it has been shown, that elevated levels of intracellular calcium can disrupt the cytoskeleton and that the stimulation of glutamate (NMDA) receptors can cause high intracellular concentrations of calcium, it has been suggested, that the stimulation of glutamate receptors plays a role in the slow degeneration in Alzheimer's and Parkinson's disease. In case of the degeneration of the dopaminergic nigrostriatal system in Parkinson's disease, neurons that contain calcium binding protein appear to be less vulnerable than the neurons that lack it, suggesting that calcium binding protein might protect these neurons from degeneration by preventing that cytosolic calcium concentrations increase excessively. And, since there is in the nigrostriatal system a glutamatergic afferent pathway (the prefrontonigral projection) and since dopaminergic nigrostriatal neurons contain postsynaptic NMDA receptors, glutamatergic excitation may play a role in the degeneration of the nigrostriatal system in Parkinson's disease. If so, it may be possible to protect the neurodegeneration of these dopaminergic neurons by NMDA receptor antagonists.     

The role nitric oxide and other neurotransmitter in canine penile erection

The role on nitric oxide and its relative factors (cGMP, cAMP, methylene blue) was studied in canine erection induced by stimulating pelvic nerves, and the effect of cholinergic neuroeffectors and the sinusoidal endothelium was also observed in this experiment. The results indicate that intracavernous injection of nitric oxide can evoke a penile tumescence, which is similar to that of the neurostimulation. The results also suggest that the cholinergic nerves and the sinusoidal endothelium are involved in erection, and the effect of the former must depend on mediation of the latter. The study supports that cholinergic and nonadrenergic noncholinergic (NANC) neuroeffectors take part in penile erection, and nitric oxide may be one of chief NANC neurotransmitters.     

The role of endogenous nitric oxide in the gastroprotective action of morphine

Morphine in a dose of 1 mg/kg s.c. decreased mucosal lesions induced by 100% ethanol or acidified aspirin by 79% and 85%, respectively, in rats. When the animals were pretreated with NG-nitro-L-arginine (40 mg/kg i.v.), the mucosal lesions were aggravated in both tests and the gastroprotective action of morphine decreased to 17% and 20%, respectively. This decrease in morphine protection was antagonized by L-arginine but not by D-arginine in the case of ethanol-induced lesions; however, L-arginine failed to restore the gastroprotective effect of morphine when the mucosal damage was induced by acidified aspirin. The protective action of either prostaglandin E2 (0.1 mg/kg orally) or cysteamine (50 mg/kg orally) was not influenced by NG-nitro-L-arginine (L-NNA). When L-NNA was given simultaneously with either indomethacin (10 mg/kg p.o.) or N-ethyl-maleimide (50 mg/kg s.c.), compounds which also reduced the gastroprotective action of morphine, almost complete inhibition of the gastroprotective action of morphine against 100% ethanol-induced lesions was observed as a result of the addition of the inhibitory activities of the latter substances. These results suggest that: (1) Endogenous nitric oxide is likely to be involved in the gastroprotective action of morphine. (2) The protective action of nitric oxide is independent of both mucosal prostaglandins and sulfhydryls.     

The reorganization of motor units in motor neuron disease

We studied 78 patients with motor neuron disease (MND) using concentric needle electromyography. Analysis on weak and maximal effort was performed using our own, fully automated, computer method, EMG-LAB. In addition to the conventional parameters of single motor unit action potentials (MUAPs) and interference pattern, new criteria were applied: the range of the acting motor units and the functional recruitment order. A total of 375 muscles of MND patients and 120 control muscles were investigated. The electromyographic data were analyzed separately in five groups of muscles, classified A, B, C, D, and E according to their clinical condition. Those results allowed us to discern six neurophysiological stages (N(0,1,2,3,4,5)) from the early to the most advanced phase. It has been confirmed that reinnervation in MND is adequate to compensate for the loss of over 50% of motor neurons but it is only a transitory phase in the morbid course. At stages N(O-5), the electrophysiological data reflect structural and functional integrity of the functioning motor units. Evaluation of not only single MUAPs but also of the full range of acting motor units and their recruitment order allowed a deeper look into the underlying pathophysiological mechanisms.     

The role of endothelial nitric oxide synthase expression in the development of pulmonary hypertension in chronically hypoxic infant swine

OBJECTIVE: Our goal was to determine the role of pulmonary endothelial nitric oxide synthase expression in the development of pulmonary hypertension in infants with congenital cyanotic heart disease. METHODS: Two groups of 4-week-old piglets were studied. In one group, the piglets were raised in an environment of 10% oxygen from 2 days of age (cyanotic, n = 6), and in the other group the piglets were raised at room air (control, n = 5). Pulmonary hemodynamics were measured in vivo for each animal, and peripheral lung biopsy specimens were obtained for Western blot analysis with the use of antiendothelial nitric oxide synthase antibody and for activity analysis with the use of the tritiated L-arginine assay. RESULTS: The piglets in the chronically hypoxic group had significant increases in mean pulmonary arterial pressure (44.0 +/- 3.8 mm Hg vs 14.8 +/- 1.2 mm Hg in controls, p = 0.0007) and pulmonary vascular resistance (7272.0 +/- 871.1 dyne x cm x sec(-5) vs 1844.5 +/- 271.2 dyne x cm x sec(-5) in controls, p = 0.002). These changes in the pulmonary hemodynamics of the hypoxic piglets were accompanied by a twofold increase in the expression of pulmonary endothelial nitric oxide synthase (p = 0.0043) but no corresponding increase in nitric oxide synthase activity. CONCLUSIONS: Raising infant piglets in an environment of 10% oxygen for 4 weeks results in significant pulmonary arterial hypertension accompanied by increased expression of nitric oxide synthase within the lung endothelium. Furthermore, the increased levels of nitric oxide synthase within the lungs of the hypoxic swine were not accompanied by a proportional increase in enzyme activity. These findings suggest that the development of pulmonary hypertension in infants with congenital cyanotic disease is not due to decreased expression of endothelial nitric oxide synthase, but instead may be related to a decreased ability of the enzyme to produce sufficient nitric oxide.     

NMDA receptors play an anti-aggregating role in human platelets

We Describe a case of ovarian serous cystadenoma having Sertoli-Leydig cell tumor, well differentiated, in the cystic septum. Well differentiated Sertoli-Leydig cell tumor coexisting with other tumor, including serous tumor, has not yet been described. In all cases of Sertoli-Leydig cell tumor with heterologous components or other tumors, the androblastomatous components are intermediately or poorly differentiated. The present case revealed a well differentiated Sertoli-Leydig cell tumor arising in a septum of serous cystadenoma, as a circumscribed nodule. With these findings, we discuss the possibility of this Sertoli-Leydig cell tumor, considered a mural nodule, which is well established in cystic common epithelial tumors of the ovary.     

The role of neuronal and endothelial nitric oxide synthase in retinal excitotoxicity

PURPOSE: Nitric oxide synthase (NOS) plays an essential role in neuronal function and is critical in the brain for normal and pathologic responses to glutamate. The role of NOS in the retina is less well understood. The retina provides an experimental system in which the intrinsic circuitry is well defined; retinal excitotoxic damage has been well characterized. METHODS: To determine whether neuronal NOS (nNOS) and endothelial NOS (eNOS) are critical in excitotoxic damage in the retina, nNOS- and eNOS-deficient mice were subjected to intravitreal injections of N-methyl-D-aspartate (NMDA) or to arterial occlusions. RESULTS: Retinal ganglion cells in the nNOS-deficient mouse were relatively resistant to NMDA and to arterial occlusion. In contrast, the damage in the eNOS-deficient mouse retina was not distinguishable from that in control animals. Preinjection with an NOS inhibitor was partially protective. CONCLUSIONS: The presence of nNOS is a prerequisite for the full expression of excitotoxicity in the retina; eNOS does not appear to play a significant role.     

Involvement of mechanisms dependent on NMDA receptors, nitric oxide and protein kinase A in the hippocampus but not in the caudate nucleus in memory

The effects of the NMDA receptor antagonist AP5, the nitric oxide synthase (NO) inhibitor NO-arg or the protein kinase A (PKA) inhibitor KT5720 on memory were evaluated. Rats bilaterally implanted in the CA1 region of the dorsal hippocampus were trained and tested in a step-down inhibitory avoidance task, and rats unilaterally implanted in the left posteroventral region of the caudate nucleus were trained and tested in a cued water maze task. Previous findings from this and other laboratories had found that lesions or pharmacological treatments of these sites significantly altered memory of these two tasks. Immediately after training, animals received intrahippocampal or intracaudate 0.5 microliter microinfusions of saline, AP5, NO-arg or KT5720. All three drugs impaired retention of inhibitory avoidance, but did not affect retention of the cued water maze. The findings suggest that NMDA receptor-, NO- and PKA-mediated processes in the dorsal hippocampus, but not in the caudate nucleus, are involved in memory.     

The role of nitric oxide in mechanisms of the nephrotoxic effect of verografin

A clinic based cross-sectional study was conducted at Immunoprophylaxis Clinic at Govt. Medical College, Nagpur. Mothers of 217 children were interviewed for infant feeding practices. In 62.67% of children, breast-feeding was initiated within 24 hrs. after birth. About 22% mother used prelacteal feed and 70% mothers preferred demand feeding. Prominent area of concern includes discarding of colostrum, low exclusive breast feeding rate, delayed weaning and early termination of breast feeding. Further improvement in present day infant feeding practices is possible by emphasising on the health education component of existing nutritional programmes.     

The role of nitric oxide in vivo feline erection under hypoxia

Previous in vitro studies have demonstrated that the cavernous relaxation under hypoxia does not involve the endothelium dependent mechanism. However, the mechanism of nitric oxide pathway under hypoxia are not fully evaluated or understood yet in vivo. The changes of intracavernous pressure to various vasoactive substances were monitored in 45 mature male cats in vivo under normoxia and hypoxia (pH: 7.03, PO2: 25.52 mmHg, PCO2: 84.66 mmHg). L-arginine and SNAP (s-nitroso-n-acetyl-penicillamine) produced cavernous relaxation under normoxia, but not under hypoxia (n = 19, P < 0.01). The L-arginine-induced relaxations were inhibited by L-NAME (N omega-nitro-1-arginine-methyl-ester) or methylene blue under normoxia (n = 19, P < 0.01). The cavernous relaxation was 58% suppressed under hypoxia compared to normoxia with 10(-3) M/0.2 ml of acetylcholine (n = 22, P < 0.01). Moreover, L-NAME attenuated the acetylcholine-induced relaxation under normoxia, but not under hypoxia (n = 22, P < 0.05). Epinephrine suppressed the acetylcholine-induced relaxation in both conditions (n = 10, P < 0.01), while indomethacin significantly potentiated the acetylcholine-induced relaxation under normoxia compared to hypoxia (n = 6, P < 0.05). However, none of these substances responded in severe hypoxia (PO2 < 15 mmHg, n = 3). These results suggest that erectile and contractile responses are attenuated under hypoxia. The endothelium derived relaxation via nitric oxide does not play a role in cavernous relaxation under definitive hypoxia with acidosis like in ischemic priapism (PO2 < 30 mmHg, pH < 7.25).     

The role of inducible nitric oxide synthase in cardiac allograft rejection

Rats were exposed to either a footshock stimulus (FS) or emotional stimulus (ES, forced perception of another rat receiving footshocks) during a daily 10-min session for 5 consecutive days. The consequences of FS and ES on their behavioural responsiveness were assessed at different post-stress intervals using a small open-field. FS induced a decrease in ambulation, rearing and sniffing and an increased immobility in the small open field. These effects were present in rats tested immediately after the last session and remained present for at least 15 days. In contrast, ES induced a transient decrease in ambulation and rearing immediately after the last session, but in the period from half an hour until at least 15 days after the stimulus experience, an increase in ambulation, rearing and sniffing was observed. Exposure to one footshock per session for 5 consecutive days or to 10 footshocks in a single session also resulted in a long-lasting reduction in ambulation and sniffing and an increase in immobility. The former regime did not influence the behavioural response of ES rats, but the latter resulted in an increase in ambulation, rearing and sniffing in ES rats. Naloxone (1 mg/kg s.c.) pretreatment antagonized the increased behavioural activity of the ES rats whereas the activity of control and FS animals was not affected, suggesting an involvement of endogenous opioid systems in the behavioural responses observed in ES rats. It is suggested that the behavioural responses of the ES and FS animals are regulated by different mechanisms.