Nitric oxide and cerebral ischemia.
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Animals↗
Biomedical subjects
M A Moskowitz
Publications and source records attributed to M A Moskowitz.
Hypertension in mice lacking the gene for endothelial nitric oxide synthase.
Nitric oxide (NO), a potent vasodilator produced by endothelial cells, is thought to be the endothelium-dependent relaxing factor (EDRF) which mediates vascular relaxation in response to acetylcholine, bradykinin and substance P in many vascular beds. NO has been implicated in the regulation of blood pressure and regional blood flow, and also affects vascular smooth-muscle proliferation and inhibits platelet aggregation and leukocyte adhesion. Abnormalities in endothelial production of NO occur in atherosclerosis, diabetes and hypertension. Pharmacological blockade of NO production with arginine analogues such as L-nitroarginine (L-NA) or L-N-arginine methyl ester affects multiple isoforms of nitric oxide synthase (NOS), and so cannot distinguish their physiological roles. To study the role of endothelial NOS (eNOS) in vascular function, we disrupted the gene encoding eNOS in mice. Endothelium-derived relaxing factor activity, as assayed by acetylcholine-induced relaxation, is absent, and the eNOS mutant mice are hypertensive. Thus eNOS mediates basal vasodilation. Responses to NOS blockade in the mutant mice suggest that non-endothelial isoforms of NOS may be involved in maintaining blood pressure.
Amino Acid Oxidoreductases↗
Autoradiographic visualisation of [3H]5-carboxamidotryptamine binding sites in the guinea pig and rat brain.
We have investigated the distribution of [3H]5-carboxamidotryptamine ([3H]5-CT) binding sites by in vitro autoradiography on sections of guinea-pig and rat brain. In saturation studies, the ligand recognised a saturable, homogeneous population of binding sites with an affinity ranging from 0.19-0.45 nM depending on the region. The labelling pattern was heterogeneous, and the displacement pattern with different competing drugs selective for different 5-HT receptor subtypes was complex. [3H]5-CT appeared to label 5-HT1B/5-HT1D sites in the substantia nigra, globus pallidus and caudate/putamen, as the binding in these regions was displaced by the 5-HT1B/1D receptor selective agents sumatriptan, CP-122,288 and GR-127,935. In the hippocampus and lateral septum, the very dense [3H]5-CT binding was displaced with high affinity by the 5-HT1A receptor selective agonist 8-hydroxy-dipropylaminotetralin ((+/-)-8-OH-DPAT), dihydroergotamine and 5-HT. In contrast the affinity of the 5-HT1 receptor antagonists spiperone and methiothepine was much lower than their previously published potency at 5-HT1A receptors. The affinity of agonists, taken together with the fact that the distribution of these [3H]5-CT sites overlaps that of [3H]8-OH-DPAT binding sites in serial sections, suggest that these sites correspond to 5-HT1A receptors. Their atypical properties deserve further investigations. While [3H]5-CT binding at 5-HT1B/1D sites and these atypical 5-HT1A sites was inhibited by the GTP analogue 5'-beta, gamma-imidotriphosphate, [3H]5-CT binding in the superficial cortical layers and in midline thalamic nuclei was insensitive to this agent. It was however displaced by low concentrations of spiperone, clozapine and methiothepine, but not by sumatriptan, CP-122,288, GR-127,935 or dihydroergotamine. This binding profile is similar to that of 5-HT7 receptors, while the spatial distribution of these sites matches the known distribution of 5-HT7 messenger RNA. We did not find evidence of [3H]5-CT labelling to 5-HT5 receptors, in spite of their reported high affinity for this ligand. It is concluded that [3H]5-CT, in the presence of selective blockers, can be used to investigate the properties of 5-HT1A, 5-HT1B/1D and 5-HT7 receptors in the rodent brain, although further studies are required to explain the atypical features of [3H]5-CT binding in 5-HT1A receptors containing regions.
Animals↗
Induction of nitric oxide synthase activity in rodent brain following middle cerebral artery occlusion.
The conversion of L-[3H]arginine to L-[3H]citrulline in the absence of calcium can be used to assay selectively the activity of inducible nitric oxide synthase (NOS) in rat spleen homogenates 6 h after lipopolysaccharide administration. Using similar assay conditions, changes in inducible NOS activity were measured within ischemic brain tissue between 2 h and 7 days following permanent middle cerebral artery (MCA) occlusion in Sprague-Dawley rats and SV-129 mice. Total (constitutive and inducible) NOS activity was measured in the presence of 0.5 mM CaCl2. Whereas total NOS activity in rat decreased dramatically to 16% and 6% of baseline 6 and 12 h after MCA occlusion, inducible NOS activity remained undetectable before 2 days after occlusion, became maximal at 3 days, and decreased to less than 10% of maximal iNOS activity at 7 days. In the mouse, total NOS activity decreased after MCA occlusion but inducible NOS activity was undetectable from 2 h to 4 days after occlusion. Sustained NO production by inducible NOS activity does not contribute to ischemic injury within 24 h after MCA occlusion, but may contribute to infarct maturation 2-4 days after ischemia in some but not all species.
Animals↗
Cerebrovascular alterations in mice lacking neuronal nitric oxide synthase gene expression.
Nitric oxide (NO) is known to mediate increases in regional cerebral blood flow elicited by CO2 inhalation. In mice with deletion of the gene for neuronal NO synthase (NOS), CO2 inhalation augments cerebral blood flow to the same extent as in wild-type mice. However, unlike wild-type mice, the increased flow in mutants is not blocked by the NOS inhibition, N omega-nitro-L-arginine, and CO2 exposure fails to increase brain levels of cGMP. Topical acetylcholine elicits vasodilation in the mutants which is blocked by N omega-nitro-L-arginine, indicating normal functioning of endothelial NOS. Moreover, immunohistochemical staining for endothelial NOS is normal in the mutants. Thus, following loss of neuronal NOS, the cerebral circulatory response is maintained by a compensatory system not involving NO.
Acetylcholine↗
Genetically modified fibroblasts producing NGF protect hippocampal neurons after ischemia in the rat.
The neuroprotective effect of nerve growth factor (NGF) on the pyramidal cells in the vulnerable CA1-CA2 sectors of the hippocampus was investigated in a rat model of transient forebrain ischemia. A genetically modified fibroblast line that secretes high levels of NGF was implanted 7 days before induction of ischemia between the hippocampal CA1-CA2 subfields in the right hemisphere. Rats were then subjected to 10 min of cerebral ischemia in a four vessel occlusion model. Morphological changes in the CA1 and CA2 subfields were evaluated 7 days after ischemia. Animals in the NGF-protected group had significantly higher numbers of normal appearing neurons in the right CA1 and CA2 regions, compared with their non-implanted left hemispheres, to non-implanted animals or to animals implanted with non-modified cells. The data confirmed that NGF can protect CA1-CA2 hippocampal neurons from ischemic damage by implantation of genetically engineered cells producing NGF.
Animals↗
[3H]sumatriptan labels both 5-HT1D and 5-HT1F receptor binding sites in the guinea pig brain: an autoradiographic study.
We have used in vitro autoradiography to visualize [3H]sumatriptan binding sites in sections of guinea-pig and rat brain. In saturation studies, this ligand recognized a single saturable population of high affinity binding sites in all regions examined (pKD = 8.3-9.3). While 5-HT and the sumatriptan derivative CP-122,288 (5-methyl-aminosulfonylmethyl-3-(N-methylpyrrolidin-2R-yl-me thyl)- 1 H-indole) competed for [3H]sumatriptan binding sites with a high affinity and monophasic profile, displacement experiments with 5-carboxamidotryptamine revealed the existence of 2 classes of binding sites. The high affinity component (pKD = 9.2-9.9) probably corresponded to 5-HT1B (rat) or 5-HT1D (guinea-pig) receptors. The intermediate affinity (pKD = 5.7-7.3) of the other component, taken together with their high affinity for [3H]sumatriptan, was similar to that of the cloned 5-HT1F receptor. The regional distribution of the 5-HT1B/1D [3H]sumatriptan binding sites was in agreement with previously published studies (striatonigral system, hypothalamus, central gray, superficial layer of the superior colliculus) and corresponded to the pattern of serotonin-5-O-carboxymethyl-glycyl [125I]tyrosinamide labeling in consecutive sections. [3H]sumatriptan binding sites with a low affinity for 5-CT predominated in the intermediate neocortical layers, the claustrum (in the guinea-pig only), the mammillary nuclei, most of the thalamic nuclei and the principal oculomotor nucleus (in the guinea-pig only). This distribution is very similar to that of 5-HT1F mRNA, indicating further the identity of these sites with 5-HT1F receptors. Very high densities of 5-HT1F sites were also found in the rat parafascicular nucleus. Some regions, such as the caudate/nucleus, the lateral geniculate nuclei and the spinal trigeminal nucleus appeared to contain both 5-HT1B/1D and 5-HT1F binding sites. Ketanserin had a low affinity for [3H]sumatriptan binding sites in all guinea-pig brain regions, compatible with the presence of the 5-HT1D beta subtype. An exception was the substantia nigra, where a significant proportion of sites displayed an intermediate affinity for this compound, suggesting the presence of 5-HT1D chi receptors. [3H]5-HT labeled 5-HT1F sites in the claustrum and intermediate cortical layers in the guinea-pig. However these data show that [3H]sumatriptan, in the presence of 10 nM 5-carboxamidotryptamine, is a more suitable radioligand to study the distribution of 5-HT1F binding sites.
Animals↗
Newspaper reporting of the medical literature.
OBJECTIVE: To examine whether the media are providing information to the public about important medical advances in a timely manner and whether the degree of importance is associated with other aspects of newspaper reporting (presence, extent, and prominence). DESIGN: The authors explored the amount, extent, prominence, and timeliness of newspaper coverage received by New England Journal of Medicine and JAMA articles published in 1988, by searching ten leading U.S. newspapers. The journal articles were independently rated based on the public's need to know the medical information contained in the article. The intraclass reliability coefficient for this need-to-know importance score was 0.77. MEASUREMENTS AND MAIN RESULTS: Overall, 35% of the journal articles received newspaper coverage (276/786). The articles were frequently covered by more than one newspaper [extensive coverage (161/276, 58%)] and often appeared on the front page [prominent coverage (42/276, 15%)]. Articles considered most important to the public (92/786, 12%) received more extensive and prominent coverage than did less important articles (p < 0.01). More than three fourths of the newspaper stories appeared within two days of the journal article's issue date. Stories about the most important articles appeared sooner than did those about the less important articles (p < 0.0001). CONCLUSIONS: Articles reported in two prominent medical journals are often viewed as being important to the public, and these articles are receiving newspaper coverage that is extensive, prominent, and timely. This is particularly true for those articles considered most important to the public.
Information Services↗
Ambulatory care casemix measures.
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Ambulatory Care↗
The non-peptide neurokinin-1 antagonist, RPR 100893, decreases c-fos expression in trigeminal nucleus caudalis following noxious chemical meningeal stimulation.
The effect of RPR 100893, a selective and specific neurokinin-1 antagonist, or its enantiomer RPR 103253 was examined on c-fos antigen expression in brain stem and upper cervical cord 2 h after intracisternal capsaicin injection (30.5 micrograms/ml) in pentobarbital-anesthetized Hartley guinea-pigs. Positive cells were counted at three levels corresponding to obex, -2.25 mm and -6.75 mm in 18 sections (50 microns). Immunoreactivity was strongly expressed within laminae I and IIo of trigeminal nucleus caudalis, area postrema and the leptomeninges. Moderate labeling was present in the nucleus of the solitary tract and the medullary lateral reticular nucleus, whereas few positive cells were found in the ventral portion of the medullary reticular nucleus and Rexed laminae III-V and X. The distribution of labeled cells was consistent with previously reported results following subarachnoid placement of the noxious agents, blood or carrageenin. Pretreatment with RPR 100893 (1, 10 and 100 micrograms/kg, i.v.) but not its enantiomer (100 micrograms/kg, i.v.) 30 min prior to capsaicin injection significantly reduced the number of positive cells in the trigeminal nucleus caudalis (P < 0.01) in a dose-dependent manner, but not within area postrema or nucleus of the solitary tract. These results indicate that (i) the instillation of capsaicin into the subarachnoid space is an effective stimulus for the induction of c-fos antigen within trigeminal nucleus caudalis, presumably through activation of trigeminovascular afferents, and (ii) the neurokinin-1 antagonist RPR 100893 reduces the number of positive cells selectively within this nucleus. The findings are significant because drugs which alleviate vascular headaches decrease the number of c-fos-positive cells within trigeminal nucleus caudalis following noxious meningeal stimulation. Hence, strategies aimed at blocking the neurokinin-1 receptor may be useful for treating migraine and cluster headache.
Animals↗
The importance of severity of illness adjustment in predicting adverse outcomes in the Medicare population.
The importance of using risk-adjusted mortality rates to measure quality of care is well-established. However, mortality rates may be an insensitive measure of quality for surgical patients since death is a relatively rare outcome. This study used Medicare files to identify, through chart abstraction, clinical postoperative complications of four surgical procedures (n = 8126) that could serve as measures of quality. Disease-specific severity of illness models using a moderate number of clinical variables and admission MedisGroups score models computed from approximately 250 clinical variables were compared in predicting postoperative adverse events. Initial differences between the two models disappeared upon cross-validation. Validated R-squareds and C statistics from models using half the data were generally positive, suggesting that these models had real, although modest, predictive power. We have shown that severity of illness on admission plays a role in predicting adverse events of surgery. Risk-adjusted outcomes may potentially be useful in screening for quality shortfalls.
Aged↗
Cerebrovascular responses under controlled and monitored physiological conditions in the anesthetized mouse.
Control of physiological parameters such as respiration, blood pressure, and arterial blood gases has been difficult in the mouse due to the lack of technology required to monitor these parameters in small animals. Here we report that anesthetized and artificially ventilated mice can be maintained under physiological control for several hours with apparently normal cerebrovascular reactivity to hypercapnia and mechanical vibrissal stimulation. SV-129 mice were anesthetized with urethane (750 mg/kg i.p.) and alpha-chloralose (50 mg/kg i.p.), intubated, paralyzed, and artificially ventilated. Respiratory control was maintained within physiological range by reducing the inspiratory phase of the respiratory cycle to < 0.1 s and by adjusting end-tidal CO2 to give a PCO2 of 35 +/- 3 mm Hg. In these mice, mean arterial pressure (95 +/- 9 mm Hg), heart rate (545 +/- 78 beats/min), and arterial pH (7.27 +/- 0.10) could be maintained for several hours. Body temperature was kept at 36.5-37.5 degrees C. We observed stable regional CBF (rCBF) measurements (as determined by laser-Doppler flowmetry) when systemic arterial blood pressure was varied between 40 and 130 mm Hg. Hypercapnia led to a 38 +/- 15% (5% CO2) and 77 +/- 34% (10% CO2) increase in rCBF. Mechanical stimulation of contralateral vibrissae for 1 min increased rCBF by 14 +/- 4%. Changes in rCBF compare favorably with those observed previously in another rodent species, the Sprague-Dawley rat. After placement of a closed cranial window, cerebrovascular reactivity to hypercapnia and whisker stimulation was intact and well maintained during 2-h superfusion with artificial CSF.
Anesthesia↗
Neurogenic model of migraine.
Activation of peripheral trigeminal fibers induces neurogenic inflammation in rat dura mater, as well as vascular and mat cell changes. These changes parallel an increase of vasodilating and permeability promoting peptides in venous effluent of the cephalic circulation. The experimental model of electrical trigeminal ganglion stimulation or systemic capsaicin administration has proven effective in detecting cellular activation in brainstem trigeminal nuclei. Animal experimental models of trigeminovascular activation and the effects of antimigraine drugs on functional and morphological consequences of such activation provide the background for further models and for developing pharmacological strategies in this field.
Animals↗
Suppression by the sumatriptan analogue, CP-122,288 of c-fos immunoreactivity in trigeminal nucleus caudalis induced by intracisternal capsaicin.
1. The effects of an intravenously administered sumatriptan analogue were examined on c-fos-like immunoreactivity (c-fos-LI), a marker of neuronal activation, evoked within trigeminal nucleus caudalis (TNC) and other brain stem regions 2 h after intracisternal injection of the irritant, capsaicin (0.1 ml, 0.1 mM), in pentobarbitone-anaesthetized Hartley guinea-pigs. 2. C-fos-LI was assessed in eighteen serial sections (50 microns) using a polyclonal antiserum. A weighted average, reflecting total expression within lamina I, IIo of TNC was obtained from three representative levels (i.e., at -0.225 mm, -2.475 mm and -6.975 mm.). 3. Capsaicin caused significant labelling within lamina I, IIo, a region containing axonal terminations of small unmyelinated C-fibres, as well as within the nucleus of the solitary tract, area postrema and medial reticular nucleus. A similar distribution of positive cells was reported previously after intracisternal injection of other chemical irritants such as autologous blood or carrageenin. 4. Pretreatment with a conformationally restricted sumatriptan analogue (with some selectivity for 5-HT1B and 5-HTID receptor subtypes) CP-122,288, reduced the weighted average by approximately 50-60% (P < 0.05) in lamina I, IIo at > or = 100 pmol kg-1, i.v., but did not decrease cell number within area postrema, nucleus of the solitary tract or medial reticular nucleus. A similar pattern was reported previously following sumatriptan, dihydroergotamine or CP-93,129 administration after noxious meningeal stimulation. 5. We conclude that modifications at the amino-ethyl side chain of sumatriptan dramatically enhance the suppression of c-fos expression within TNC, a finding consistent with its remarkable potency against neurogenic plasma protein extravasation within dura mater. CP-122,288 and related analogues may serve as an important prototype for drug development in migraine and related headaches.
Animals↗
Attenuation by valproate of c-fos immunoreactivity in trigeminal nucleus caudalis induced by intracisternal capsaicin.
1. Valproic acid, useful in the treatment of migraine, is an inhibitor of gamma aminobutyric acid (GABA) aminotransferase and activator of glutamic acid decarboxylase. Its mechanism in migraine remains obscure. The effects of valproic acid (2-propylpentanoic acid) were examined on the number of cells expressing c-fos-like immunoreactivity (c-fos-LI), a marker of neuronal activation, within the trigeminal nucleus caudalis (lamina I, IIo, TNC) 2 h after intracisternal injection of the irritant, capsaicin (0.1 ml; 15.25 micrograms ml-1), in urethane-anaesthetized Hartley guinea-pigs. Positive cells were counted in eighteen sections (50 microns) at three representative levels (rostral, middle and caudal) within lamina I, IIo of the TNC in 90 animals. 2. Numerous cells were labelled after capsaicin instillation (244 +/- 25; 1 ml; 15.25 mM) but not after capsaicin vehicle (11 +/- 1). Positive cells were also found within the medial reticular nucleus, the area postrema and the nucleus of the solitary tract. A similar distribution has been demonstrated previously after application of intracisternal irritants such as autologous blood or carrageenin. 3. Valproate (> or = 10 mg kg-1, i.p.) reduced labelled cells by 52% (P < 0.05) in lamina I, IIo but not within the area postrema, the nucleus of the solitary tract or the medial reticular nucleus. A similar finding was obtained previously after administration of sumatriptan, dihydroergotamine or the NK1 receptor antagonist RPR 100,893. 4. Pretreatment with bicuculline (30 micrograms kg-1; i.p.), a GABAA antagonist, but not phaclofen (1 mg kg-1) a GABAB antagonist, reversed the effect of valproate and increased c-fos positive cells within lamina I, IIo. Somewhat paradoxically, bicuculline by itself (30 micrograms kg-1 i.p.) decreased the number of labelled cells suggesting that more than a single GABAergic mechanism can suppress c-fos expression. 5. We conclude that the mechanism of action of valproate is mediated via GABAA receptors. Since valproate decreases both c-fos expression and as previously shown, neurogenic inflammation within the meninges, the GABAA receptor complex might provide an important target for drug development in migraine and related headaches.
Animals↗
Peripheral GABAA receptor-mediated effects of sodium valproate on dural plasma protein extravasation to substance P and trigeminal stimulation.
1. The GABA transaminase inhibitor and activator of glutamic acid decarboxylase, valproic acid is being used for the treatment of migraine. Its mechanism of action is unknown. We tested the effects of sodium valproate and GABAA-agonist muscimol on dural plasma protein ([125I]-bovine serum albumin) extravasation evoked by either unilateral trigeminal ganglion stimulation (0.6 mA, 5 ms, 5 Hz, 5 min) or substance P (SP) administration (1 nmol kg-1,i.v.) in anaesthetized Sprague-Dawley rats. 2. Intraperitoneal (i.p.) injection of sodium valproate or muscimol, but not baclofen (< or = 10 mg kg-1, i.p.) dose-dependently reduced dural plasma protein extravasation caused either by electrical trigeminal stimulation (ED50: 6.6 +/- 1.4 mg kg-1, i.p., and 58 +/- 18 micrograms kg-1, i.p. for valproate or muscimol, respectively) or by intravenous substance P administration (ED50: 3.2 +/- 1.4 mg kg-1, i.p. and 385 +/- 190 micrograms kg-1, i.p. for valproate or muscimol, respectively). 3. Valproate (6.6 mg kg-1, i.p.) or muscimol (58 micrograms kg-1, i.p.) had no effect on mean arterial blood pressure or heart rate when measured for 30 min after i.p. administration. 4. The GABAA-antagonist bicuculline (0.01 mg kg-1, i.p.) completely reversed the effect of valproate and muscimol on plasma extravasation following electrical stimulation or substance P administration, whereas the GABAB-receptor antagonist, phaclofen (0.01-1 mg kg-1, i.p.) did not. Bicuculline or phaclofen, given alone, did not alter the plasma extravasation response after either electrical stimulation or SP administration. 5. Valproate decreased plasma extravasation following substance P administration in adult animals, neonatally treated with capsaicin by a bicuculline-reversible mechanism. This suggests that GABAA receptors are not found primarily on those afferent neurones or fibres which are sensitive to capsaicin treatment in neonatal rats.6. We conclude that sodium valproate blocks plasma extravasation in the meninges through GABAA mediated postjunctional receptors probably within the meninges. The dosages required are comparable to those used clinically. Agonists and modulators at the GABAA receptor may become useful for the development of selective therapeutic agents for migraine and cluster headache.
Animals↗
Postoperative adverse events of cholecystectomy in the Medicare population.
We explored the use of postoperative adverse events of cholecystectomy as possible screens for poor quality of care. Retrospective analysis of clinical data abstracted from hospital charts between 1985-1986 was conducted on a random sample of 3,182 cholecystectomy cases. Severity of illness models were developed predicting adverse events following cholecystectomy in patients with and without bile duct exploration. Outcome measures included 17 nonfatal adverse events and death within 30 days of admission. Adverse event rates were 23.2% for cases with bile duct exploration and 14.4% for cases without bile duct exploration. Cross-validated R-squareds and C-statistics showed that models had real, although modest, predictive power. We conclude that clinically meaningful adverse events of cholecystectomy can be successfully identified through chart abstraction.
Aged↗
Effects of cerebral ischemia in mice deficient in neuronal nitric oxide synthase.
The proposal that nitric oxide (NO) or its reactant products mediate toxicity in brain remains controversial in part because of the use of nonselective agents that block NO formation in neuronal, glial, and vascular compartments. In mutant mice deficient in neuronal NO synthase (NOS) activity, infarct volumes decreased significantly 24 and 72 hours after middle cerebral artery occlusion, and the neurological deficits were less than those in normal mice. This result could not be accounted for by differences in blood flow or vascular anatomy. However, infarct size in the mutant became larger after endothelial NOS inhibition by nitro-L-arginine administration. Hence, neuronal NO production appears to exacerbate acute ischemic injury, whereas vascular NO protects after middle cerebral artery occlusion. The data emphasize the importance of developing selective inhibitors of the neuronal isoform.
Amino Acid Oxidoreductases↗