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Biomedical subjects

D H Lewis

Publications and source records attributed to D H Lewis.

At least 37 records · Page 2Linked to original sources
PubMed1997

Functional brain imaging with cerebral perfusion SPECT in cerebrovascular disease, epilepsy, and trauma.

Functional brain imaging with cerebral perfusion single-photon emission computed tomography (SPECT) has practical and important applications for use by neurosurgeons in the evaluation of cerebrovascular disease, stroke, epilepsy, and trauma. The radiopharmaceuticals used in SPECT enable one to image a "snapshot" of regional cerebral blood flow. The findings on SPECT can be the most sensitive and unique descriptors of dynamic alterations in brain function due to the aforementioned disorders. Used in conjunction with other imaging modalities such as magnetic resonance imaging, CT, and neurodiagnostic tests such as EEG and TCD, the brain blood flow images enhance the ability of the neurosurgeon to determine the perfusion status of the brain.

Brain↗
PubMed1997

Clinical outcome of patients with intermediate probability lung scans during six-month follow-up.

UNLABELLED: A retrospective review of a consecutive series of patients with intermediate probability (IP) ventilation/perfusion lung scans was performed to evaluate: the frequency of documented thromboembolic (TE) disease, either pulmonary embolism (PE) or deep-venous thrombosis (DVT), at time of presentation; the prevalence of new diagnoses of TE disease during 6-mo follow-up; and occurrence of mortality during the same follow-up interval. METHODS: Radiologic and clinical records for all patients who had ventilation/perfusion lung scans reported as IP or indeterminate during a 7-yr period were reviewed. TE disease at presentation or during follow-up was identified from results of pulmonary angiography, chest CT, lower extremity Doppler ultrasound and venography, and repeat lung scans. Occurrence of mortality and cause of death were determined by medical record review. RESULTS: Of 164 patients studied, 36 (22%) had TE disease confirmed at initial presentation (PE = 19; DVT only = 17), and four others (2%) developed evidence of TE disease during follow-up, two with PE and two with DVT. Prevalence of TE disease was significantly greater in patients with matching perfusion/chest radiographic abnormalities and ventilation/perfusion mismatches (0.5-1.5 segmental equivalents) than in those with various patterns of matching ventilation/perfusion defects (31% versus 14%, p < 0.01). Twenty-eight patients (18%) died during follow-up, but recurrent PE was implicated in only one death in a patient with angiographically-confirmed PE at initial presentation. Among the 116 patients who did not receive long-term anticoagulation after their initial lung scans, 22 (19%) died, none of whom had PE confirmed or suspected as a contributing cause. CONCLUSION: The prevalence of new or recurrent TE disease is low in patients with IP lung scans who are appropriately evaluated and managed after their initial presentation. No evidence of significant mortality secondary to untreated PE was found in the study group.

Female↗
PubMed1996

Altered glutathione levels in ischemic and postischemic skeletal muscle: difference between severe and moderate ischemic insult.

The purpose of the present study was to investigate how the duration of ischemia and reperfusion affect the glutathione (GSH) levels in skeletal muscle and to assess the presence of oxidative stress by quantitating oxidized glutathione (GSSG) and the ratio of GSSG/GSH. The amounts of GSH and GSSG were quantitated in the tibialis anterior muscle of the rat hind limb after 2 and 4 hours of tourniquet ischemia and after 1 and 5 hours of reperfusion, and the levels were compared to those in nonischemic control tibialis anterior muscles. In muscles subjected to 2 hours of ischemia, the levels of GSH, GSSG, and the ratio GSSG/GSH did not differ significantly from those of nonischemic controls. After 4 hours of ischemia without reperfusion, the GSH levels were slightly increased, compared to controls (p < 0.05). After 1 hour of reperfusion following 4 hours of ischemia, the levels of GSH decreased by 50% compared to control (p < 0.01), and still after 5 hours of reperfusion the levels of GSH were 50% lower than control levels. The GSSG/ GSH ratio did not change during 1 and 5 hours of reperfusion compared to control. A major finding in this study was that, during reperfusion after severe ischemia of 4 hours, there was a marked depletion of glutathione, which was not seen after a moderate ischemic insult of 2 hours.

Animals↗
PubMed1996

Diagnostic imaging: its role in evaluating chest, abdominal, and musculoskeletal infections.

Imaging studies can provide essential information when infection is suspected. Chest radiography remains the best radiographic screening tool for intrathoracic infections. Computed tomographic (CT) scanning is preferred for evaluation of solid-organ abscesses, peritoneal abscesses, and associated malignant tumors or adenopathy. Ultrasonography is used primarily in evaluation of the gallbladder, biliary system and, increasingly, the appendix. Magnetic resonance imaging is highly sensitive in detecting osteomyelitis.

AIDS-Related Opportunistic Infections↗
PubMed1995

A method for producing microbe-free Amyloodinium ocellatum (Brown) with Percoll.

A method for collecting microbe-free Amyloodinium ocellatum from infected red drum (Sciaenops ocellatus) is described. Surface contamination of trophonts removed from fish by osmotic shock was reduced by washing the preparation with antibiotic containing saltwater and Percoll density gradient purification. The resulting tomont preparation was free of external contamination. Sterile, infective dinospores excysted from the tomonts after 72 h incubation at 26 degrees C in antibiotic containing 30 ppt saltwater.

Animals↗
PubMed1995

Sandwich enzyme-linked immunosorbent assay for Vibrio vulnificus hemolysin to detect V. vulnificus in environmental specimens.

Vibrio vulnificus hemolysin, purified by quantitative isoelectric focusing, was used to prepare rabbit and goat anti-hemolysin. The resulting antibodies were used as capture and detector antibody reagents in a sandwich enzyme-linked immunosorbent assay (ELISA) to detect V. vulnificus in environmental samples. By this technique, 4 laboratory-maintained V. vulnificus strains and 33 environmental V. vulnificus isolates were detected. Also, the technique distinguished five other Vibrio species from V. vulnificus, and when it was used in combination with colistin-polymyxin-cellobiose agar, 31 non-V. vulnificus isolated were excluded. This sandwich ELISA compared favorably with the current Food and Drug Administration standard immunoassay in confirming presumptive V. vulnificus colonies from environmental specimens: oysters, sediment, and seawater. Among 340 presumptive V. vulnificus colonies, the sandwich ELISA detected 95% of the confirmed V. vulnificus colonies. Equally important, the technique correctly distinguished 99% of the non-V. vulnificus colonies. The sandwich ELISA offers time-saving and labor-saving advantages over the currently accepted immunoassay.

Animals↗
PubMed1994

Effect of hypoxic hypoxia and ritanserin on capillary flow and oxygenation in rabbit skeletal muscle.

This study examined capillary flow and oxygenation in rabbit skeletal muscle during hypoxic hypoxia (inspired oxygen fraction = 0.10) and after administration of ritanserin (highly selective 5-Hydroxytryptamine-2-receptor antagonist). Capillary flow (hydrogen clearance) or oxygen pressure was measured with a multiwire micro-electrode which was placed on the surface of the left vastus medialis muscle. For measurement of regional microcirculatory blood flow a laser-Doppler flowmeter probe was placed on the contralateral muscle. An experimental sequence with normoxaemia (arterial PO2 12.5 kPa), followed by hypoxaemia (arterial PO2 3.9 kPa) and thereafter sustained hypoxaemia (arterial PO2 4.0 kPa) during which ritanserin (0.035 mg kg-1 i.v.) was administered, was used. During hypoxaemia a decrease was seen in mean arterial pressure (MAP) by 27%, capillary flow by 25%, muscle oxygen pressure by 32% and laser-Doppler flowmetry (LDF) flow by 24%. After the administration of ritanserin the mean arterial pressure was further reduced by 7%, whereas the capillary flow increased by 59% and the muscle oxygen pressure by 31%. The LDF flow remained unchanged. These results demonstrate that, in this animal model, a decrease in skeletal muscle capillary flow and oxygenation during hypoxaemia can be reversed by the administration of ritanserin, despite a further reduction in blood pressure.

Animals↗
PubMed1994

The effect of mannitol on reperfusion after severe induced subtotal ischemia of the leg. A hemodynamic, biochemical and metabolic study in a pig hind limb model.

Revascularization of acutely ischemic muscle tissue is followed by edema, decreased oxygen utilization, increased vascular resistance and massive efflux of intracellular compounds indicating loss of cellular integrity, with resultant irreversible damage. In this pig hindlimb study, 8 pigs were submitted to standardized subtotal ischemia of one leg and mannitol was administered i.v. prior to and during 2.5 hours of reperfusion. Compared to 9 controls, the mannitol treated pigs had increased blood flow to the legs, increased oxygen consumption and decreased release of intracellular compounds (CK). This indicates that mannitol attenuates the ischemia/reperfusion syndrome. Muscle energy metabolic parameters showed a similar response to ischemia for both mannitol-treated pigs and controls and no differences in recovery were detected during 2.5 hours of reperfusion between the groups.

Animals↗
PubMed1994

White matter ischemia on brain SPECT.

Four patients were shown to have ischemic injury to the posterior limb of the internal capsule on brain SPECT with 99mTc-HMPAO. These findings were later corroborated by transmission CT scans in three patients. In the interpretation of high-resolution SPECT imaging of regional cerebral blood flow, it is important to inspect the deep white and gray matter activity for asymmetry and perfusion deficits. The blood flow to the diencephalon, which is critical for brain function, can be imaged with high-resolution brain SPECT. The early ascertainment of ischemic changes in the diencephalon may lead to important patient management decisions.

Adult↗
PubMed1993

Immunization of rabbits with enterotoxigenic E. coli colonization factor antigen (CFA/I) encapsulated in biodegradable microspheres of poly (lactide-co-glycolide).

We have searched for an effective oral delivery system for a purified enterotoxigenic Escherichia coli (ETEC) fimbrial adhesin, CFA/I, which elicits anti-colonization immunity. Purified CFA/I antigen encapsulated in biodegradable polymer microspheres of poly (DL-lactide-co-glycolide) (PLG) induced a vigorous, systemic CFA/I IgG antibody response in rabbits immunized once via intragastric tube; oral, unencapsulated CFA/I induced little or no circulating antibody. CFA/I-specific, S-IgA coproantibody was detected in one of three rabbits fed with the CFA/I-PLG microsphere vaccine. We conclude that PLG microspheres protected CFA/I from degradation in the stomach and effectively delivered the antigen for processing by the host's immune system.

Adhesins, Escherichia coli↗
PubMed1993

Hyperemic receptive aphasia on neuroSPECT.

NeuroSPECT of regional cerebral blood flow (rCBF) with Tc-99m HMPAO demonstrated left temporoparietal hyperemia in two patients with acute receptive aphasia. This finding prompted further testing with electroencephalography that added to the impression of ictal dysphasia. The differential diagnosis in one case included complicated migraine. NeuroSPECT depicts blood flow abnormalities in acute aphasic disorders, either due to ischemia, which is most commonly the cause, or due to hyperemia secondary to migraine or epilepsy. The treatment and prognosis of these latter conditions differ from stroke, and thus SPECT plays a role in patient management.

Adult↗