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Biomedical subjects

M C Wallace

Publications and source records attributed to M C Wallace.

At least 73 records · Page 4Linked to original sources
PubMed1994

Venous congestion: an MR finding in dural arteriovenous malformations with cortical venous drainage.

PURPOSE: To present the MR findings of intracranial dural arteriovenous malformations with cortical venous drainage, emphasizing the parenchymal changes. METHODS: Conventional MR and x-ray angiograms in 13 patients with dural arteriovenous malformations and cortical venous reflux were reviewed. The site of the shunt, location of the venous reflux, and presence of venous stenosis were assessed on the angiograms. Parenchymal changes, dilated vessels, and venous occlusive disease were assessed on MR. RESULTS: On MR, 10 of the 13 patients (77%) had dilated pial vessels. Two patients had hydrocephalus. Two patients presented with parenchymal bleeds, one with a subdural component, both remote from the nidus. Two patients presented with subarachnoid hemorrhage. One patient had a parenchymal bleed 9 months after presentation. Venous occlusion was evident on MR in 2 patients. Diffuse white matter edema in the cerebellar or cerebral hemispheres was present on MR in 4 patients and correlated with neurologic deficits. In 2 of these 4 patients, gadolinium enhancement was seen in the periphery of the involved hemisphere. CONCLUSIONS: On MR a surplus of pial vessels suggests a dural arteriovenous malformation with cortical venous drainage. The MR finding of white matter edema deep in the cerebral or cerebellar hemispheres is direct evidence of a venous congestion.

Adult↗
PubMed1993

Separable regulatory elements governing myogenin transcription in mouse embryogenesis.

Expression of the myogenic helix-loop-helix (HLH) protein myogenin in muscle cell precursors within somites and limb buds is among the earliest events associated with myogenic lineage determination in vertebrates. Mutations in the myogenin promoter that abolish binding sites for myogenic HLH proteins or myocyte enhancer factor-2 (MEF-2) suppressed transcription of a linked lacZ transgene in subsets of myogenic precursors in mouse embryos. These results suggest that myogenic HLH proteins and MEF-2 participate in separable regulatory circuits leading to myogenin transcription and provide evidence for positional regulation of myogenic regulators in the embryo.

Animals↗
PubMed1993

Cell-permeant Ca2+ chelators reduce early excitotoxic and ischemic neuronal injury in vitro and in vivo.

We report the characterization of the first successful treatment of neuronal ischemic injury in vivo by cell-permeant Ca2+ chelators. The chelators attenuated glutamate-induced intracellular Ca2+ increases and neurotoxicity in neuronal explant cultures. When infused intravenously in rats, permeant fluorescent BAPTA analogs accumulated in neurons in several brain regions. BAPTA-AM, infused in vivo, reduced Ca(2+)-dependent spike frequency adaptation and post-spike train hyperpolarizations in CA1 neurons taken from treated animals. This effect was reproduced by direct injections of BAPTA into untreated neurons. The effects of three different chelators (BAPTA, 5,5'-difluoro BAPTA, and 4,4'-difluoro BAPTA) on Ca(2+)-dependent membrane excitability varied with their Ca2+ affinity. When the chelators' permeant forms were used to treat rats prior to the induction of focal cortical ischemia, they were highly neuroprotective, as gauged by significant reductions in cortical infarction volumes and neuronal sparing. The chelators' protective effects in vivo also reflected their affinity for Ca2+. This report provides the most direct evidence to date that intracellular Ca2+ excess triggers early neurodegeneration in vivo and contributes a novel therapeutic approach to neuronal ischemia of potential clinical utility.

Animals↗
PubMed1993

The 48-month increment of root caries in an urban population of older adults participating in a preventive dental program.

The purpose of this study was to determine the effect of a 48-month preventive dental program on the incidence of root caries in an urban, geriatric, noninstitutionalized population residing in an optimally fluoridated area. The 466 participants were randomly assigned to one of three groups at baseline. Group A (control): 171 subjects using a placebo mouthrinse daily; group B: 147 subjects receiving semiannual applications of a topical APF gel (1.2% F-) with the daily use of a placebo mouthrinse; group C: 148 subjects using a fluoridated mouthrinse daily, ACT (0.05% F-). At baseline, the numbers of surfaces at risk, and decayed and filled surfaces were recorded. After 48 months, in addition, the number of reversed and new lesions were determined, and the incremental DMFS calculated. The data were analyzed by ANCOVA. The incremental DMFS were: A = 0.91, B = 0.27, C = 0.26. The incremental DMFS in groups B and C were significantly lower than in group A (P < .05). The number of reversed lesions in group C (1.53 +/- 2.03) was significantly greater than in group A (1.11 +/- 1.74) and group B (1.01 +/- 1.86) (P < .05). The number of new lesions in group B (1.36 +/- 2.00) was significantly less than in group A (1.99 +/- 2.65) (P < .05). The daily use of the fluoride mouthrinse significantly increased the number of reversed lesions.

Acidulated Phosphate Fluoride↗
PubMed1993

Role of angiography following aneurysm surgery.

The postoperative angiograms in 66 patients who underwent craniotomy for clipping of 78 cerebral aneurysms were reviewed. Indications for urgent postoperative angiography included neurological deficit or repeat subarachnoid hemorrhage. Routine postoperative angiograms were carried out in the remaining patients. Postoperative angiograms were reviewed to determine the incidence of unexpected findings such as unclipped aneurysms, residual aneurysms, and unforeseen major vessel occlusions. Logistic regression analysis was used to test if the following were factors that predicted an unexpected finding on postoperative angiography: aneurysm site or size; the intraoperative impression that residual aneurysm was left or a major vessel was occluded; intraoperative aneurysm rupture; opening or needle aspiration of the aneurysm after clipping; or development of a new neurological deficit after surgery. Kappa values were calculated to assess the agreement between some of these clinical factors and unexpected angiographic findings. Unexpected residual aneurysms were seen in three (4%) of the 78 occlusions. In addition, three aneurysms were completely unclipped (4%); these three patients were returned to the operating room and had their aneurysms successfully obliterated. There were nine unexpected major vessel occlusions (12%); six of these resulted in disabling stroke and two patients died. Of six major arteries considered to be occluded intraoperatively and shown to be occluded by postoperative angiography, two were associated with cerebral infarction. Logistic regression analysis showed that a new postoperative neurological deficit predicted an unforeseen vessel occlusion on postoperative angiography. Factors could not be identified that predicted unexpected residual aneurysm or unclipped aneurysm. The inability to predict accurately the presence of residual or unclipped aneurysm suggests that all patients should undergo postoperative angiography. Since a new postoperative neurological deficit is one factor predicting unexpected arterial occlusion, intraoperative angiography may be necessary to help reduce the incidence of stroke after aneurysm surgery. With study of more patients or of factors not examined in this series, it may be possible to select cases more accurately for intraoperative or postoperative angiography.

Adult↗
PubMed1992

Superselective angiography of a spinal dural arteriovenous fistula having a common segmental origin with the artery of Adamkiewicz.

The artery of Adamkiewicz infrequently originates from the same radicular vessel that also supplies a dural arteriovenous fistula. This variant is not adequately emphasized in the neuroradiological literature. Awareness of this entity is essential to prevent catastrophic complications during embolization. We report such a case, and our experience with attempted embolization. We are unaware of any previously reported instance of such an attempt being made.

Adult↗
PubMed1992

Autoradiographic analysis of 3H-MK-801 (dizocilpine) in vivo uptake and in vitro binding after focal cerebral ischemia in the rat.

The clinical utility of N-methyl-D-aspartate (NMDA) receptor antagonists is now being assessed in ischemic brain injury in humans. The uptake and retention of NMDA receptor antagonists in ischemic tissue will influence the design of clinical trials. The effects of permanent occlusion of the middle cerebral artery, induced 15 minutes prior to isotope administration, on the uptake of 3H-MK-801 (dizocilpine) have been assessed in the rat with quantitative autoradiography. In a group of three rats at 15 minutes after the intravenous administration of 3H-MK-801, the level (mean +/- standard error of the mean) of isotopic tracer in the ischemic cortex and striatum was markedly less than that in the contralateral hemisphere (ipsilateral vs. contralateral caudate nucleus: 22 +/- 4 vs. 84 +/- 11 pmol/gm, p less than 0.01). In contrast, in a group of five rats at 60 minutes after the intravenous administration of 3H-MK-801, the level of isotopic tracer in the ischemic cortex and striatum was greater than that in the contralateral hemisphere (ipsilateral vs. contralateral caudate nucleus: 52 +/- 8 vs. 32 +/- 4 pmol/gm, p less than 0.05). There were no significant alterations in the specific binding of 3H-MK-801 in vitro in ischemic tissue at equivalent times. The early uptake of 3H-MK-801 into the central nervous system is dominated by the level of cerebral blood flow, whereas at later times after administration enhancement of MK-801 binding by elevated extracellular glutamate concentrations appears to be more important in determining the level of the drug in ischemic tissue.

Animals↗
PubMed1991

Venous thromboembolism after brain tumor surgery: a retrospective review.

We retrospectively reviewed the incidence rate of clinical postoperative deep vein thrombosis and/or pulmonary embolism in 1703 patients undergoing initial craniotomy for meningioma, glioma, or cerebral metastasis. The incidence rate of clinical thromboembolic complications was 1.59% for all tumor groups within the first 4 weeks of surgery. Patients undergoing surgery for meningiomas had a statistically significant increased risk of thromboembolism despite fewer overall perioperative risk factors, when compared with the other tumor groups. The tumor-specific incidence rates of deep vein thrombosis and/or pulmonary embolism for meningioma, glioma, and metastasis were 3.09%, 0.97%, and 1.03%, respectively. Whether this difference was a result of increased surgical time or an inherent property of meningiomas could not be ascertained.

Adult↗
PubMed1990

Blood and urinary profiles of free-ranging desert mule deer in Arizona.

As a corollary to a more comprehensive study on their ecology, we documented blood and urinary profiles for 10 free-ranging desert mule deer (Odocoileus hemionus crooki) (five males, five females) captured by net-gun shot from a helicopter during February 1988 in Saguaro National Monument, Arizona. Pursuit with the helicopter for netting deer ranged from 3 to 15 min. Blood profiles included seven hematological characteristics and 12 serum chemistries, electrolytes, hormones and enzymes. Urine samples were assayed for urea nitrogen, creatinine, sodium, potassium, calcium and phosphorus. Urinary data were compared as ratios to creatinine. Serum cholesterol was greater (P less than 0.05) in males than females. Pursuit time was correlated with serum non-esterified fatty acids (r = 0.67, P less than 0.05) and influenced urinary specific gravity (r2 = 0.77, P less than 0.004), urea nitrogen: creatinine (r2 = 0.79, P less than 0.005), and potassium: creatinine (r2 = 0.42, P = 0.08) ratios. Increasing specific gravity was related to urinary creatinine concentration (r2 = 0.72, P less than 0.008). All deer exhibited acute adrenal stimulation, accompanied by elevated serum creatine phosphokinase and urinary potassium: creatinine ratios, which were indicative of acute excitement and muscle trauma associated with the capture process. We demonstrated that urinary data are a valuable supplement to serum data in demonstrating effects of intense physical exertion, and both forms of data emphasize the need to assess capture-related excitability as a source of variation in blood and urine characteristics of free-ranging desert mule deer.

Animals↗
PubMed1989

Alterations in the N-methyl-D-aspartate receptor complex following focal cerebral ischemia.

The functional integrity of the N-methyl-D-aspartate receptor complex following focal cerebral ischemia in the rat has been examined at a time when brain tissue is irreversibly damaged. Twelve hours after unilateral permanent middle cerebral artery occlusion, [3H]-MK-801 binding was not significantly altered in the ischemic cerebral cortex compared to sham-operated animals. Moreover, the enhancement of [3H]MK-801 binding by exogenous glutamate was preserved in an area of the brain that was permanently damaged by the ischemic insult.

Animals↗