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Biomedical subjects

G Crosby

Publications and source records attributed to G Crosby.

At least 37 records · Page 2Linked to original sources
PubMed1993

Myocardial perfusion following acute subarachnoid hemorrhage in patients with an abnormal electrocardiogram.

To test the hypothesis that acute subarachnoid hemorrhage is associated with abnormal myocardial perfusion, we assessed myocardial blood flow with thallium scintigraphy in 19 patients with a confirmed subarachnoid hemorrhage and an abnormal electrocardiogram. A thallium scan was performed at the bedside of each patient 3 +/- 2 days (mean +/- SD) after subarachnoid hemorrhage and subsequently was analyzed both qualitatively and quantitatively. Patients averaged 58 +/- 13 yr of age and 68% had one or more cardiac risk factors. The neurologic condition of patients on the day of the scan was II (median; range I-V) on the standard 5-point scale of Botterell. Abnormalities on a standard 12-lead electrocardiogram obtained on the same day as the scan consisted of repolarization changes in most patients; 10 had T wave inversions and 8 had nonspecific ST segment changes. Thirty-two percent (n = 6) of patients had an abnormal thallium scan. There were, however, no features of the clinical history, electrocardiogram pattern, or neurologic condition that were associated with a positive scan. For instance, 2 of 4 patients with diffuse deeply inverted T waves had a normal thallium scan, whereas the scan was abnormal in 2 of 8 patients with minor nonspecific electrocardiographic abnormalities. The thallium scan was also positive in neurologically intact (grade I) as well as severely injured (grade V) patients. Thus, abnormal myocardial perfusion and possibly myocardial ischemia occur frequently following subarachnoid hemorrhage, but no specific electrocardiographic characteristic identifies patients with a perfusion abnormality.

Acute Disease↗
PubMed1992

Effect of SCH 39166, a novel dopamine D1 receptor antagonist, on [3H]acetylcholine release in rat striatal slices.

SCH 39166 is a novel and selective dopamine D1 receptor antagonist. It has been reported to have potential antipsychotic properties and reduced extrapyramidal side-effect liabilities (EPS). The current studies investigated the pharmacological effects of SCH 39166 on striatal cholinergic function in order to further characterize its dopamine D1 receptor selectivity and to address its EPS liability. Electrically stimulated [3H]acetylcholine (ACh) release from rat striatal slices was measured and comparisons were made between SCH 39166, SCH 23390, (-)-sulpiride, haloperidol or apomorphine on their effect on [3H]ACh release. Results indicated that apomorphine inhibited [3H]ACh release from striatal slices (IC50 = 0.31 microM). (-)-Sulpiride and haloperidol completely reversed the inhibition of [3H]ACh release seen with apomorphine. In contrast, SCH 39166, as well as, SCH 23390 did not reverse the inhibition of [3H]ACh release induced by apomorphine. These findings indicate that dopamine D2 receptors are primarily involved in modulation of [3H]ACh release. Furthermore, selective dopamine D1 receptor antagonists, such as SCH 39166, are ineffective in modulating striatal [3H]ACh release, suggesting that striatal cholinergic hyperactivity and possibly EPS will not be a consequence of dopamine D1 receptor blockade.

Acetylcholine↗
PubMed1992

Selective effects of pentobarbital and halothane on c-fos and jun-B gene expression in rat brain.

The effects of pentobarbital and halothane anesthesia on the expression in brain of the immediate-early genes c-fos and jun-B were investigated. Pentobarbital-anesthetized rats (n = 10) received a single intraperitoneal injection of pentobarbital 65 mg/kg in a vehicle of 40% propylene glycol and 10% ethanol and then were placed in a plexiglass box flushed continously with 100% oxygen at 5 l/min. Halothane-anesthetized rats (n = 10) received an intraperitoneal injection of vehicle only and were transferred to a box flushed continuously with oxygen plus 1.5% halothane. Unanesthetized control rats (n = 10) received an intraperitoneal injection of vehicle and were placed in a box flushed continuously with 100% oxygen. Four additional rats received no intraperitoneal injection but were handled and otherwise treated identically to the control group, and six others had a femoral arterial catheter inserted for blood pressure and blood gas measurements. Five animals from the control and both anesthetized groups were killed at 30 and 120 min postinjection and their brains rapidly removed and frozen. The messenger ribonucleic acid transcription products of the genes c-fos, jun-B, and beta-actin from whole cerebral hemispheres were analyzed autoradiographically after Northern blot hybridization with 32P-labeled deoxyribonucleic acid probes. Relative levels of c-fos and jun-B messenger ribonucleic acid were determined from optical density measurements of the autoradiographic bands, with beta-actin measurements being used to correct for sample-to-sample variation. Rats became immobile within minutes of drug administration and remained anesthetized until they were killed.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

[3H]SCH 39166, a new D1-selective radioligand: in vitro and in vivo binding analyses.

SCH 39166 [(-)-trans-6,7,7a,8,9, 13b-hexahydro-3-chloro-2-hydroxy-N-methyl-5H-benzo-[d]naphtho[2, 1b]azepine] has recently been described as a selective D1 antagonist and has entered clinical trials for the treatment of schizophrenia. The tritiated analogue of this compound, [3H]SCH 39166, has now been synthesized and characterized for its in vitro and in vivo binding profiles. [3H]SCH 39166 binds to D1 receptors in a saturable, high-affinity fashion, with a KD of 0.79 nM. In competition studies, D1-selective antagonists like SCH 23390 displaced the binding of [3H]SCH 39166 with nanomolar affinities, whereas antagonists of other receptors exhibited poor affinity. In vivo, [3H]SCH 39166 bound to receptors in rat striatum in a fashion suggestive of D1 selectivity. Further, when the time course for the binding of [3H]SCH 39166 was compared with the behavioral time course of the unlabeled compound, the two durations of action were virtually indistinguishable. Similar studies were performed for SCH 23390 and its tritiated analogue, but the in vivo binding of this radioligand exhibited a duration of action far greater than the behavioral activity of the unlabeled drug. In concert, these data demonstrate that [3H]SCH 39166 selectively labels D1 receptors in vitro and in vivo, and that this drug is superior for in vivo imaging of the D1 receptor.

Animals↗
PubMed1990

Subarachnoid clonidine reduces spinal cord blood flow and glucose utilization in conscious rats.

The authors investigated the spinal blood flow and metabolic effects of subarachnoid clonidine in conscious rats prepared with chronically implanted subarachnoid catheters. For the blood flow experiments, rats received saline (n = 7) or clonidine 20 nmol (7 micrograms; n = 6), 100 nmol (27 micrograms; n = 5), or 400 nmol (107 micrograms; n = 7) intrathecally. Another group of rats received clonidine 400 nmol intravenously (n = 4). Spinal glucose utilization was measured in rats that received either saline (n = 5) or clonidine 100 nmol (n = 5) intrathecally. Spinal cord blood flow (SCBF) and glucose utilization were measured in five gray and three white matter areas of lumbar spinal cord 15 min after drug administration with the autoradiographic iodo-[14C]-antipyrine and 2-[14C]-deoxyglucose methods, respectively. Physiologic differences between the groups were minor. Rats in the blood flow experiments that received clonidine 100 nmol had a slightly lower arterial PO2 level (70 +/- 1 vs. 82 +/- 3 mmHg; P less than 0.05), whereas those in the glucose utilization group were mildly hypocarbic (PCO2 27 +/- 1 vs. 32 +/- 2 mmHg; P less than 0.01) relative to control animals. Only animals that received 400 nmol clonidine intrathecally had significant analgesia, as assessed by the tail-flick test. One control animal for the metabolism experiments was technically unsatisfactory and was excluded from data analysis. Subarachnoid clonidine reduced both SCBF and glucose utilization. In spinal gray matter, the largest decreases in flow (32-44%; P less than 0.01) occurred with 20 nmol clonidine, whereas flow decreased least (12-27%) with the 400-nmol dose.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

Ventricular performance and glucose uptake in rats during chronic hypobaric hypoxia.

To identify changes of ventricular performance and their relationship to myocardial glucose uptake in Sprague-Dawley rats exposed to hypobaric hypoxia, radionuclide angiocardiograms (n = 34) and 2-[14C]deoxyglucose (2-[14C]DG) autoradiography (n = 14) were performed on rats maintained either for two weeks in air at 380 mmHg (hypoxic group), two weeks in hypobaric hypoxia followed by two weeks of air (recovered group), or in air (control group). Right ventricular ejection fraction (RVEF) was 66% +/- 2% (mean +/- s.e.m.) in controls, 40% +/- 3% during hypoxia, and 60% +/- 2% in recovered rats. LVEF remained unchanged. In controls, RV 2-[14C]DG uptake was 77% +/- 3% of LV uptake. During hypoxia, 2-[14C]DG uptake increased. This increase was greater within the RV than the LV and septum (85 +/- 16% versus 51 +/- 10%, p less than 0.005). The alterations of RV 2-[14C]DG uptake correlated with systolic pulmonary artery pressure (r = 0.77, p = 0.002).

Animals↗
PubMed1989

Hypertension does not cause spontaneous hemorrhage of intracranial arteriovenous malformations.

The authors measured blood pressure changes non-invasively in 56 conscious, unpremedicated patients with cerebral arteriovenous malformations (AVMs) during preparation for proton beam therapy. The procedure requires six injections of local anesthetic and application of a stereotactic frame by fixation into the outer table of the skull, and has been used during the past 20 yr to treat over 1,000 patients with cerebral AVMs. No effort was made to control blood pressure. Blood pressure increased during administration of the local anesthetic and application of the frame. Maximum systolic and mean arterial pressures averaged 160 +/- 17 and 118 +/- 7 mmHg (mean +/- SD), respectively. This represented an average increase of 44 mmHg (38%) in systolic pressure and 32 mmHg (37%) in mean blood pressure at some point during the procedure (P less than 0.01 compared with pretreatment control pressures). Systolic pressure increased more than 60 mmHg in 21% of patients. Nevertheless, none of these 56 patients nor any of the more than 1,000 patients treated in similar fashion suffered a clinically evident AVM hemorrhage during the procedure. Since the treatment protocol has not changed materially during the past 20 yr, the authors assume that most patients treated in this fashion developed a similar degree of hypertension and conclude from this large clinical experience that moderate arterial hypertension does not precipitate spontaneous hemorrhage of intracranial AVMs.

Adult↗
PubMed1989

Regional brain glucose utilization in the conscious rat exposed to prolonged hypobaric hypoxia.

Because of the physiologic and metabolic changes that occur during acclimatization, we hypothesized that LCGU may be normal during prolonged hypoxia. We exposed five Sprague-Dawley rats to hypoxia (air at 380 mm Hg) for 2 weeks (hypoxic group) and six rats to 2 weeks of hypoxia followed by 2 weeks of recovery in room air (recovered group). Six control rats breathed room air (control group). Regional brain glucose utilization was measured in awake animals by using 2-[C]deoxyglucose autoradiography. Glucose utilization was comparable in the control and recovered groups and in most brain regions of hypoxic animals. Glucose utilization was decreased slightly in 10 of 12 gray matter regions examined and was 20 to 25% lower (p <0.05) in the olfactory and auditory cortices, the caudate nucleus, and the superior olive of the hypoxic group. White matter glucose utilization was unchanged. Hypoxic rats, compared to controls, had a lower PaO2 (53 +/- 3 vs. 76 +/- 3 mm Hg, mean SEM, respectively), a lower PaCO2 (22 +/- 1 vs. 36 +/- 2 mm Hg), and a higher mean pulmonary artery pressure (46 +/- 3 vs. 14 +/- 3 mm Hg) and hematocrit (61 +/- 2% vs. 48 +/- 1%; p <0.005 for all comparisons). Pulmonary hypertension and polycythemia persisted in recovered rats. Arterial pressure, pH, and plasma glucose were unaffected. Therefore, while acute hypoxia may increase glucose utilization in most brain structures, prolonged exposure does not.

Journal Article↗
PubMed1988

Local spinal cord glucose utilization in conscious and halothane-anaesthetized rats.

The authors used the 2-[14C]deoxyglucose method to study local spinal and cerebral glucose utilization simultaneously during 1.2 per cent halothane anaesthesia in adult Sprague-Dawley rats. In conscious animals (n = 5) the rate of glucose utilization in lumbar spinal gray matter was about 50 per cent lower than that of cerebral cortex. Halothane anaesthesia (n = 6) reduced spinal cord and cerebral metabolic rate. Spinal glucose utilization was reduced 12-35 per cent, but this was less than the 45-70 per cent decrease halothane produced in 8 of 16 cerebral structures examined and was independent of the hypotension produced. These results indicate that halothane is a spinal metabolic depressant but that its effects on this tissue are substantially less than those it has on many cerebral structures.

Anesthesia, Inhalation↗
PubMed1988

Selective affinity of the benzodiazepines quazepam and 2-oxo-quazepam for BZ1 binding site and demonstration of 3H-2-oxo-quazepam as a BZ1 selective radioligand.

Quazepam and 2-oxo-quazepam are novel benzodiazepines containing a trifluoroethyl substituent on the ring nitrogen at position #1. Detailed competition binding experiments (25 to 30 concs.) at 4 degrees C were undertaken with these compounds versus 3H-flunitrazepam using synaptic membranes from rat cortex or cerebellum. Unlike other benzodiazepines, both quazepam and 2-oxo-quazepam distinguished two populations of 3H-flunitrazepam binding sites in rat cortex which were present in roughly equal proportions and for which the compounds displayed a greater than 20-fold difference in affinity. In cerebellum, no such discrimination of sites was noted for 2-oxo-quazepam, but quazepam did distinguish a small, low affinity (15% of total) population of sites. 3H-2-oxo-quazepam was prepared and used in competition studies to substantiate the conclusion that these compounds discriminate two populations of benzodiazepine sites in rat cortex. This new radioligand was shown to specifically label BZ binding sites with high affinity in a saturable manner. The competition experiments were then conducted using 3H-2-oxo-quazepam at a radioligand concentration sufficiently low (0.5 nM) to ensure that only the higher affinity binding sites which 2-oxo-quazepam discriminates would be occupied. Competition experiments in both cortex and cerebellum under these conditions indicated single site binding for unlabelled quazepam and 2-oxo-quazepam in every instance. This suggests that 3H-2-oxo-quazepam should be a useful new tool for selectively labeling and studying the BZ1 population of benzodiazepine binding sites.

Animals↗
PubMed1988

Effect of profound hypermagnesemia on spinal cord glucose utilization in rats.

The purpose of our study was to investigate the effect of hypermagnesemia on spinal metabolic rate. The 2-[14C]deoxyglucose technique was used to measure regional glucose utilization in the lumbar spinal cord of paralyzed, mechanically ventilated rats receiving 70% nitrous oxide and an intravenous infusion of either saline (n = 5) or magnesium sulfate (n = 5). Plasma magnesium concentrations were 6.75 +/- 0.5 and 0.9 +/- 0.5 mM (p less than 0.01) in hypermagnesemic and control rats, respectively. Hypermagnesemic rats were hypotensive (88 +/- 1 vs. 130 +/- 4 mm Hg, p less than 0.01) but blood pressure remained within the autoregulatory range. Glucose utilization was reduced 26-45% in spinal gray matter and 53-63% in spinal white matter during hypermagnesemia. We conclude that magnesium is a potent spinal metabolic depressant and that this action, which is unusually prominent in spinal white matter, is a plausible explanation for the recently reported beneficial effect of magnesium therapy during spinal cord ischemia.

Animals↗
PubMed1986

Fatty acid metabolism and mitochondrial proteins in the C57BL/6J-dy2Jdy2J dystrophic mice.

Measurements of [1-14C]oleoyl CoA oxidation in homogenates and isolated mitochondria of skeletal muscles, hearts and livers from dystrophic C57BL/6J mice and unaffected litter-mates indicate that rates are lower in dystrophic mitochondria, but are comparable in whole homogenates. These findings are not due to differences in the endogenous concentrations of the fatty CoA esters. Qualitative and quantitative differences in the molecular weight distribution of the proteins in the mitochondria and post-mitochondrial supernatants are found in the skeletal muscles with increases in the post-mitochondrial supernatant and decreases in the mitochondria in dystrophic samples. We suggest that these results are due to increased leakiness of the mitochondrial membranes in dystrophic muscles. Such differences were not observed in preparations from normal animals.

Animals↗
PubMed1985

Local cerebral glucose utilization in the homozygous Brattleboro rat.

The [14C]deoxyglucose technique was used to measure brain glucose utilization in homozygous male Brattleboro and age-matched Long-Evans control rats. Brattleboro homozygotes had significantly higher daily water intakes and plasma osmolalities and significantly lower body weights than controls. Glucose utilization for the brain as a whole and for 46 discrete brain structures was not significantly different for the two strains. Our results indicate that vasopressin is not essential for the maintenance of overall brain glucose utilization in resting, awake rats.

Animals↗
PubMed1985

Local spinal cord blood flow and glucose utilization during spinal anesthesia with bupivacaine in conscious rats.

The author studied in conscious rats the local spinal blood flow (SCBF) and metabolic effects of intrathecally administered bupivacaine. Fourteen rats received 0.75% bupivacaine, 15 microliters, through a chronically implanted lumbar subarachnoid catheter. Twelve control animals were treated identically, except that they received only an equal volume of saline intrathecally. Ten minutes after intrathecal drug injection, either local SCBF or glucose utilization was measured in the lumbar spinal cord of seven experimental and six control animals with the quantitative autoradiographic iodo-[14C]antipyrine or 2-[14C]deoxyglucose methods, respectively. Intrathecal bupivacaine produced a limp tail, absent hindlimb withdrawal to pinch, and 25-30 min of analgesia on the tail-flick test. Mean arterial blood pressure decreased 14% (P less than 0.01) after bupivacaine was administered, but there was no change in arterial blood gases, pH, or rectal temperature. Subarachnoid bupivacaine reduced both local SCBF and glucose utilization, but the SCBF effect was larger. Local SCBF decreased 27-34% (P less than 0.01) in all five spinal gray and three white matter areas measured, and there was little regional variability in the response. The reduction in spinal glucose utilization was regionally selective and less marked. For example, glucose utilization decreased 15% (P less than 0.05) and 21% (P less than 0.05) in lateral and anterior spinal white matter, respectively, but only decreased approximately 3% in laminae I-III and dorsal white matter (P greater than 0.1). A trend toward metabolic depression was also evident in laminae VIII (-15%, P = 0.06), VII (-13%, P = 0.09), and IV-VI (-11%, P greater than 0.1).(ABSTRACT TRUNCATED AT 250 WORDS)

Anesthesia, Spinal↗