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Biomedical subjects

R L Jacobson

Publications and source records attributed to R L Jacobson.

63 records · Page 4Linked to original sources
PubMedDate not supplied

Species-specific detection of Leishmania in sandflies using an enzyme-linked immunosorbent assay.

A direct enzyme-linked immunosorbent assay (ELISA) using species-specific monoclonal antibodies was developed for the detection and identification of Leishmania in sandflies. A titration of mock-infected Phlebotomus papatasi showed that fewer than 2000 L. major promastigotes could be detected. The percentage of infected P. papatasi collected in the field, as determined by dissection, was compared to that revealed by the ELISA. Both methods gave similar results, irrespective of whether the flies were caught by sticky papers or light-traps. The percentage of infected flies determined by either method was also similar in experimentally infected colony reared sandflies. The ELISA can be carried out using multiple species-specific antibodies, and is as accurate as identification of infected sandflies by microscopical examination. The technique should be useful for identifying sandfly species involved in transmitting different species of Leishmania, and for rapid assessment of leishmanial infection rates in endemic regions.

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PubMedDate not supplied

Cellulase activity of Leishmania major in the sandfly vector and in culture.

The secretion of cellulose-degrading enzymes by Leishmania promastigotes in culture and in the sandfly vector was demonstrated. Two types of activity of cellulase enzyme-complexes were measured: endoglucanases, which randomly cleave cellulose chains and cellobioydrolases, which remove cellobiose from the nonreducing end of the molecule. The assays demonstrated that enzymes with these activities were secreted into the culture medium by Leishmania major, L. donovani, and L. braziliensis. These activities were also found in cultures of Sauroleishmania agamae, Leptomonas seymouri, Herpetomonas muscarum, Crithidia fasciculata and Trypanosoma brucei brucei that had a relatively low endoglucanase activity. Both endoglucanase and cellobiohydrolase activities were found in the gut of L. major-infected Phlebotomus papatasi, while gut preparations of uninfected sandflies had only cellobiohydrolase activity. The similar growth of L. major parasites in medium supplemented with either cellulose or glucose suggests these parasites can utilize cellulose.

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PubMedDate not supplied

Hypertension and acute focal cerebral ischemia. Infarction and edema after occlusion of a middle cerebral artery in cats.

Hypertension was produced in 8 cats by nephrectomy and wrapping the opposite kidney. Subsequent occlusion of one middle cerebral artery caused ischemic infarcts that were larger than those of 8 normotensive cats. The larger infarcts may have been caused by increases of ischemic cerebral edema resulting from changes in the cerebral endothelial barrier induced by hypertension. In addition to increasing the likelihood of strokes, hypertension in humans may predispose toward larger cerebral infarcts.

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PubMedDate not supplied

Tissue pertechnetate and iodinated contrast material in ischemic stroke.

Isotope uptake during static radionuclide scanning and contrast enhancement during CT scanning, which may result from similar pathophysiologic mechanisms after ischemic infarction, were investigated in an animal model. Infarction was produced by transorbital occlusion of the middle cerebral artery in cats killed one, 2, 4, 8, or 16 days later. Sodium pertechnetate containing technetium-99m and 30% methylglucamine iothalamate labeled with I-125 were administered intravenously 60 and 15 min respectively prior to sacrifice. A coronal section through the infarct was parceled into 30 portions which were assayed for concentration of each isotope. Adjacent brain was prepared for histopathologic correlation. Concentrations of the 2 materials were highest in infarcted brain at 4 and 8 days. Strong positive correlation was found between tissue concentrations of the 2 materials in all brain samples. Elevated tissue levels correlated with necrosis, macrophage infiltration, and vascular hyperplasia. The results support the probability that radionuclide scan positivity and CT contrast enhancement reflect the same pathophysiologic development, probably extravasation of the respective labels, after ischemic stroke.

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Cerebrospinal fluid in cerebral hemorrhage and infarction.

Cerebrospinal fluid (CSF) abnormalities were correlated with pathological diagnoses in 61 patients with autopsy-verified intracerebral hemorrhage or cerebral infarction. Lumbar punctures were performed within one week of onset of symptoms. The CSF color and red blood cell counts were the most useful CSF parameters in differentiating between intracerebral hemorrhage and cerebral infarction. In 75% of the patients with intracerebral hemorrhage, the CSF was either grossly bloody or xanthochromic; in 25%, the CSF was clear. In patients with cerebral infarction, the CSF was never grossly bloody; in two patients with hemorrhagic infarction, the CSF was xanthochromic. The CSF pressure, protein values and leukocyte counts were less useful in differentiating intracerebral hemorrhage from cerebral infarction. Cases with hemorrhagic infarction could not be separated from those with ischemic infarction on the basis of CSF analysis. In clear CSF, the polymorphonuclear neutrophilic leukocyte (PNL) counts were never greater than 20 per cubic millimeter. In xanthochromic or cloudy CSF, leukocyte counts, especially PNLs, were frequently elevated, occasionally to the high levels.

Cerebral Cortex↗
PubMedDate not supplied

Brain water alterations after unilateral nephrectomy. A study of regional circulatory factors in squirrel monkeys.

White and regional gray matter distributions of water, blood flow, and the protein tracer pertechnetate were measured in five normal squirrel monkeys. A second group of five monkeys, which had undergone unilateral nephrectomy six months previously, were found at the time of study to have blood pressures similar to those of the control animals but increased brain water and altered distribution of blood flow which was increased in white matter. No alteration of capillary permeability to the protein traces attended these changes, which appeared to be influenced by blood pressure. Nephrectomy without hypertension influences brain water content, perhaps because of an effect on cerebral resistance vessels. In hypertensive encephalopathy renal lesions, as well as intraluminal pressure changes, may be related to cerebral edema.

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