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Biomedical subjects

R Perez

Publications and source records attributed to R Perez.

At least 145 records · Page 8Linked to original sources
PubMed1990

Location of neurons projecting to the retina in mammals.

In this study, horseradish peroxidase (HRP) was used as a retrograde tracer in order to investigate the existence of centrifugal pathways to the retina in mammals and to locate the somas of the retinopetal neurons. After the application of HRP to the stump of the cut optic nerve in monkeys, cats, guinea-pigs and rabbits, labeled neurons were located in various areas. The largest number of labeled neurons was found bilaterally in the hypothalamus in the premammillary area, and some neurons were also found slightly more rostral and dorsally towards the posterior hypothalamic area. At the mesencephalic-metencephalic junction, a few labeled neurons were observed in the dorsal raphe nucleus and more ventrally in the tegmental area situated between the medial longitudinal fascicle and the superior cerebellar peduncle. Furthermore, labeled neurons were found in the contralateral medial pretectal area in guinea-pigs, in the ipsilateral tegmental mesencephalic reticular formation in monkeys, in the laterodorsal tegmental nucleus in rabbits, and in the dorsal hypothalamic area near the nucleus of the anterior commissure in monkeys. We were unable to find labeled cells in the dorsal raphe nucleus or in the hypothalamus in rabbits or in the above-mentioned tegmental area in guinea-pigs. These divergences may be due to species differences or may simply be false-negative results due to the known difficulty of using the currently available tracers to label retinopetal neurons.

Animals↗
PubMed1989

Binding properties of biotinylated epidermal growth factor to its receptor on cultured cells and tissue sections.

A biotinylated derivative of murine epidermal growth factor (EGF) was prepared by covalent attachment of the terminal amino group of EGF to N-biotinyl-epsilon-aminocaproyl-N-hydroxysuccinimide. The stoichiometry of biotin incorporation was in the range of one biotin moiety per EGF molecule. The biotinylated EGF (biotinyl-epsilon-caproyl-EGF, BioEGF) binds to EGF receptors on intact Ehrlich ascites carcinoma (EAC) cells with an affinity similar to that of native EGF and displays the same mitogenic activity as EGF in a soft agar test system with normal rat kidney (NRK) cells. BioEGF was visualized on cultured cells and tissue sections of a head and neck tumour by commercial streptavidin/avidin detection systems. Cytochemical analyses of certain tumour forms can be easily performed using the BioEGF probe.

Animals↗
PubMed1989

Effect of chronic stress on ENU-induced tumors.

The relation of stress to cancer is the subject of considerable controversy. We studied the possible influence of chronic stress on the time of development and frequency of tumors induced in rats after a single exposure to ethylnitrosourea during prenatal life. Time of development, localization, incidence, type, and size of tumors were similar in stressed rats and in controls. Our results in this paradigm do not support the hypothesis that chronic stress exerts a potentiating effect on carcinogenesis.

Animals↗
PubMed1989

Factors affecting beta 2-microglobulin plasma concentration during hemodialysis.

We studied ten patients on hemodialysis (HD) treated in sequence with cuprophan (CU), ethylenevinylalcohol (EVAL), polyacrylonitrile (A-69) and polysulphone (PSP) membrane dialyzers. beta 2-microglobulin (beta 2m) was measured by radioimmunoassay in plasma and dialysate samples. Plasma concentrations were corrected for changes in extracellular volume (ECV). We also studied adsorption in vitro by incubating the above membranes with I-125-labelled beta 2m. There were no changes in beta 2m plasma concentration after HD with CU dialyzers, but a significant decrease was observed with the other membranes tested. Filtration of beta 2m across the dialyzer was absent with CU and minimal with EVAL. However, large amounts were recovered from dialysate with the high-permeability dialyzers, AN-69 and PSP. In vitro studies showed that maximal adsorption capacity was obtained with AN-69 (13%) compared to 9% with CU, 4% with EVAL and 7% with PSP. In summary, beta 2m clearance with PSP is achieved through greater removal of this protein by mass transport across the membrane. The mechanism by which beta 2m is removed from blood during AN-69 dialysis seems to include both adsorption to and filtration by the membrane itself.

Adolescent↗
PubMed1988

A phase I trial of recombinant human gamma interferon (IFN-gamma 4A) in patients with advanced malignancy.

We report a Phase I study in 39 cancer patients of the tolerance and biologic activity of 47 intravenous (i.v.), intramuscular (i.m.), and subcutaneous (s.c.) treatments with recombinant methional gamma interferon (IFN-gamma 4A) which most closely resembles the natural material produced by T lymphocytes. Patients were treated with IFN-gamma 4A 5 days a week for 2 weeks. After a 2-week rest period, patients were placed on the same dose of drug three times a week. The most common side effects--fever, chills, malaise, myalgias, and nausea and vomiting--were seen with all routes of administration. Reversible increases in hepatic transaminase and decrease in granulocytes counts were seen. The dose-limiting toxicities observed were malaise and orthostatic hypotension. The maximum tolerated dose was 500-1,000 micrograms/M2/day. The t1/2 of IFN-gamma 4A in the circulation was 20 min after i.v. injection. No blood levels were detected after i.m. or s.c. injection. Antibody against IFN-gamma 4A increased in three patients. A complete response was observed in one patient with pulmonary metastases from renal cell carcinoma.

Adult↗
PubMed1987

Susceptibility of Rickettsia conorii and R. rickettsii to pefloxacin, in vitro and in ovo.

The activity of pefloxacin against Rickettsia conorii and R. rickettsii was determined by several methods. The mean survival time of embryonated eggs infected with R. conorii was increased by pefloxacin 50 micrograms/egg; plaque formation in Vero cells was inhibited by 1 mg/l. In a microplate assay, the MIC of pefloxacin was 0.5 mg/l for R. conorii and 1 mg/l for R. rickettsii. The results support the use of pefloxacin in treating spotted fever rickettsioses.

Animals↗
PubMed1986

In vitro susceptibility of Rickettsia conorii to ciprofloxacin as determined by suppressing lethality in chicken embryos and by plaque assay.

We tested the susceptibility of Rickettsia conorii to ciprofloxacin, a new quinolone antibiotic. A final concentration of 1 microgram/g of egg was effective in suppressing chicken embryo lethality, and a concentration of 0.25 micrograms/ml inhibited plaque formation in a plaque assay; however, a concentration of 0.5 microgram/ml was necessary to obtain rickettsiacidal activity. These results support the idea that ciprofloxacin could be of clinical use in treating Mediterranean spotted fever.

Animals↗
PubMed1986

Renal metabolism during four types of lactic acidosis in the dog including anoxia.

The present study was undertaken to evaluate the metabolic response of the kidney to lactic acidosis. Four types of lactic acidosis were induced in the dog: infusion of lactic acid, infusion of lactic acid with phenformin, administration of phenformin alone, and hypoxia by breathing 95% nitrogen. In all groups of animals, the same degree of acidosis was observed with plasma bicarbonate ranging from 12.8 to 14.9 mM. Plasma lactate concentration ranged from 3.0 to 8.1 mumol/mL. Renal ammoniagenesis failed to be influenced by lactic acidosis. As a matter of fact, it fell during anoxia. The extraction of glutamine by the kidney rose except during anoxia where it fell. The renal production of alanine rose during the infusion of lactic acid with and without phenformin. This coincided with the extraction of glutamine. The renal extraction of lactate rose in all forms of acidosis as well as the production of pyruvate. In the renal cortical tissue, the concentration of malate, pyruvate, and lactate rose. Alanine also rose except during anoxia. An important fall in cytosolic redox potential (NAD+/NADH lactate dehydrogenase) was observed, as well as a fall in mitochondrial redox (NAD+/NADH beta-hydroxybutyrate dehydrogenase). Lactate also accumulated in the liver and in the muscle. We propose that the kidney is unable to respond to lactic acidosis in terms of ammonia production and that this phenomenon is explained by transamination of pyruvate and glutamate into alanine and also by the observed fall in cytosolic redox potential. It is likely that renal gluconeogenesis is also inhibited and this is reflected by the rise in the concentration of malate in the kidney.(ABSTRACT TRUNCATED AT 250 WORDS)

Acidosis↗
PubMed1985

Inhibition of herpes simplex virus type 1 penetration by cytochalasins B and D.

Internalization of herpes simplex virus type 1 (HSV) KOS strain by HEp-2 cells was reversibly inhibited by pretreatment of cells with cytochalasins B and D. Internalization of virus following preincubation at 4 degrees C and temperature shift to 37 degrees C was normally preceded by a 5 to 8 min lag period and was complete within 20 to 30 min. A similar lag period followed HSV addition at 37 degrees C. Cytochalasin D was fivefold more active on HSV entry than cytochalasin B, with 50% inhibition at 2 microM and 10 microM respectively. Inhibition was completely reversible, such that all cell-bound infectious virus was recovered upon removal of cytochalasin. In conjunction with previous reports, the activity of cytochalasin on HSV entry suggests that a change in cytoskeletal structure following virus attachment triggers a microfilament activity important for internalization of HSV by HEp-2 cells.

Cell Line↗
PubMed1985

The metabolic response of the kidney to acute sodium lactate alkalosis.

In vivo studies were performed in the dog to verify if sodium lactate had an important effect on the metabolism of glutamine by the kidney. The animals were infused with 0.6 M sodium lactate to induce acute metabolic alkalosis with plasma bicarbonate of 29.7 mM. During these experiments, it was demonstrated that the renal uptake of glutamine increased by 46%, while the renal production of ammonia was unchanged. The renal production of alanine rose from 6.0 to 16.8 mumol/min. Plasma concentration of lactate increased from 1.3 to 19.2 mM, while that of pyruvate increased from 0.075 to 0.454 mM. In the renal tissue, alpha-ketoglutarate, malate, oxaloacetate, lactate, pyruvate, citrate, and alanine increased significantly. Similar changes were found in the liver and skeletal muscle. The observed changes are best described by transamination of pyruvate and glutamate under the influence of alanine aminotransferase (GPT). It can be calculated that this reaction was responsible for 76% of the production of ammonia from glutamine, the latter being necessary to provide glutamate for the synthesis of alanine. Dogs infused with 0.3 M sodium bicarbonate instead of sodium lactate with the same degree of acute metabolic alkalosis, showed a depression of 40% in the renal uptake of glutamine with a 38% decrease in renal ammoniagenesis and a 20% fall in the production of alanine. The present studies demonstrate that the production of ammonia from glutamine is not necessarily related to changes in acid-base balance, but may be associated with biochemical alterations related to the synthesis of alanine by the kidney.

Alanine↗
PubMed1985

Sequential hypertonic dialysis.

We have investigated the usefulness and practicability of the so-called sequential hypertonic dialysis in 2 selected patients with severe hemodialysis-induced hypotension; 190 mmol/l of sodium dialysate during the 1st and 3rd h and 132 mmol/l throughout the 2nd and 4th h were used, with a Drake-Willock-Bi proportionating unit, which was electronically modified for the purpose of the study. Crossover was made, patients serving as their own controls in two consecutive cycles: 3 weeks conventional hemodialysis followed by 4 weeks sequential hypertonic dialysis, using high-flux dialyzers. At the end of sequential hypertonic dialysis a greater weight loss was achieved (p less than 0.001) with absolute stability of blood pressure. There were no significant changes in plasma osmolality and plasma volume during sequential hypertonic dialysis when compared with conventional hemodialysis. Dialysis symptoms and complications were less frequently recorded during sequential hypertonic dialysis (p less than 0.001). At the end of each sequential hypertonic dialysis period, hemoglobin, potassium, and phosphate plasma levels improved significantly and plasma sodium concentrations remained within the normal range. We conclude that sequential hypertonic dialysis is an easy and routine feasible procedure with our methodology. It is possible to achieve the ideal dry weight with no symptomatic hypotension. Sequential hypertonic dialysis constitutes an alternative to sequential ultrafiltration in selected patients, as it minimizes the falloff in plasma volume and osmolality observed during conventional hemodialysis.

Adult↗