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Biomedical subjects

A Horvath

Publications and source records attributed to A Horvath.

At least 55 records · Page 3Linked to original sources
PubMed1989

Isolation of tyrosine-melanocyte-stimulating hormone release-inhibiting factor 1 from bovine brain tissue.

Although Tyr-melanocyte-stimulating hormone release-inhibiting factor 1 (MIF-1) (Tyr-Pro-Leu-Gly-NH2) can exert a number of biological actions in the brain and elsewhere, it has never been isolated from any tissue. Accordingly, we attempted to purify it from acetic acid extracts of bovine brain tissue by gel filtration chromatography and several different high performance liquid chromatographic systems. Peptide content was followed by a specific and sensitive radioimmunoassay with an antibody that was generated against synthetic Tyr-MIF-1. In each of the five applied high performance liquid chromatographic systems, the immunoreactive fractions coincided exactly with the elution time of synthetic Tyr-MIF-1 in the control runnings. The structure of the isolated peptide was identified by microsequence analysis as the tetrapeptide Tyr-Pro-Leu-Gly-NH2 and shown to be biologically active.

Animals↗
PubMed1989

Flow cytometric analysis of lymphoma and lymphoma-like disorders.

The use of flow cytometry (FC) represents the most recent advance in the phenotypic analysis of lymphocyte subsets, and has emerged as a valuable adjunct in the diagnosis of malignant non-Hodgkin's lymphoma (NHL). In a review of over 200 cases of nodal and extranodal suspected lymphomas studied in the Immunophenotyping Laboratory at the University of New Mexico, the diagnostic utility of FC was assessed. Among cases of NHL, FC was able to confirm a morphologic diagnosis of lymphoma and determine B or T cell lineage in greater than 85% of the samples submitted. Difficulty in lineage determination in the remaining cases of morphologic NHL was multifactorial. Among cases of reactive lymph nodes and Hodgkin's disease, FC showed no characteristic patterns, although several cases exhibited phenotypic profiles suggestive of B or T cell clonality. When combined with routine morphologic review and accompanied by other specialized diagnostic techniques when necessary, the use of FC represents a precise and reproducible method for rapidly and easily studying lymphoproliferative disorders in solid tissue.

Flow Cytometry↗
PubMed1988

Diffusion of HIV-1 virus into non-habitual categories at risk in European countries.

The ECP Working Group on AIDS has evaluated the available data on seropositivity to HIV-1 supplied by research groups in 12 Eastern and Western European countries. The period covered is 1985 and 1986. A significantly elevated incidence of seropositives was observed in both females and males in heterosexual contact with members of high risk groups. In contrast heterosexuals with no such contact had an incidence below 1%. For male homosexuals from Italy, Denmark and Switzerland the trend was no detectable increase in prevalence from 1985 to 1986. Hungary and Poland now have a few per cent seropositive male homosexuals, but no seropositives were found in a group of Polish drug abusers.

Bisexuality↗
PubMed1988

Effect of hormone-induced premature parturition on hemoglobin switching in sheep.

This study examines the effect of premature delivery on the switch from fetal (alpha 2 tau 2) to adult (alpha 2 beta 2) Hb, in lambs in which premature parturition was induced by the intrafetal infusion of ACTH or corticotropin releasing hormone. Of 10 chronically cannulated ovine fetuses given ACTH at the rate of 79 ng/min for a 15 min period every 2 h starting at days 125 (n = 9) or 126 (n = 1) of gestation, three died in utero at days 131, 131, and 130, respectively. The remaining seven were born alive at 133 +/- 1.6 days. Five control fetuses, treated with vehicle (0.9% NaCl, wt/vol) only were delivered at 149 +/- 2.7 days of gestation, which is not significantly different from the duration of pregnancy in other chronically cannulated lambs in this flock. Hb switching, as measured by the globin synthesis ratio, beta/alpha, was complete at term in the control lambs. The beta/alpha globin synthesis ratio of the prematurely delivered lambs was not accelerated by birth, and was similar to that of control fetuses of the same gestational age still in utero. The four lambs surviving premature birth more than 70 days did not complete the switch to normal adult Hb until after 220 days postconception.

Adrenocorticotropic Hormone↗
PubMed1988

Structural specificity of MIF-1 and Tyr-MIF-1 in augmenting GABA-stimulated benzodiazepine receptor binding.

The possibility of a linkage between endogenous peptides and the GABA-benzodiazepine system has been greatly strengthened by reports that the brain peptides MIF-1(Pro-Leu-Gly-NH2) and Tyr-MIF-1(Tyr-Pro-Leu-Gly-NH2) augment GABA-stimulated benzodiazepine binding. We evaluated the actions of fragments and analogs of these small peptides on GABA-stimulated benzodiazepine binding in mouse cortical brain membranes. Fragments of Tyr-MIF-1, several compounds related to MIF-1, or several analogs of Tyr-MIF-1 had no effect on binding. These results demonstrate the specificity of the effects of MIF-1 and Tyr-MIF-1 on GABA-stimulated benzodiazepine binding.

Animals↗
PubMed1987

Nonleukemic granulocytic sarcoma of the heart: a report of a fatal case.

We report the clinical and pathological features of a cardiac fatality caused by granulocytic sarcoma in a young adult man with no evidence of leukemia involving bone marrow or peripheral blood. At autopsy, walls of the four cardiac chambers were massively infiltrated by tumor, resulting in a cardiac weight of almost three times normal. Routine cytochemical stains plus immunoperoxidase staining for OKM1 confirmed the diagnosis. Although subclinical cardiac infiltrates are commonly detected at autopsy in patients with acute nonlymphoblastic leukemia (ANLL), massive cardiac granulocytic sarcoma in the absence of bone marrow disease has not been previously described. Cytochemical and immunological methods of diagnosing granulocytic sarcoma in fixed tissues are reviewed.

Adult↗
PubMed1987

Carrier-mediated transport of vasopressin across the blood-brain barrier of the mouse.

A brain to blood carrier-mediated transport system for arginine vasopressin (AVP) was investigated in mice after intraventricular injection of iodinated AVP and varying amounts of unlabeled material or candidate inhibitors. Residual activity in the brain detected after decapitation was used as the main determinant of transport activity. The half-time disappearance of iodinated AVP from the brain was 12.4 min, the Vmax was 1.41 nmol/g-min, and the apparent Km was 28.7 nmol/g. A 30-nmol dose of AVP, mesotocin, arginine vasotocin, pressinoic amide, pressinoic acid, tocinoic acid, and lysine vasotocin, but not oxytocin, lysine vasopressin, AVP free acid, tocinoic amide, Tyr-MIF-1, or cyclo Leu-Gly, significantly (P less than 0.05) inhibited the transport of iodinated AVP out of the brain. The 30 nmol dose of AVP had no effect on the transport of iodide or iodotyrosine out of the brain. High-performance liquid chromatography showed that 59.2% of the radioactivity found in the blood 2 min after an i.c.v. injection of labeled AVP eluted at the same position as labeled AVP compared with 68.8% of radioactivity eluting at that position after material was infused i.v. for 2 min. This indicates that intact peptide is transported across the blood-brain barrier and that most of the degradation of AVP occurs during circulation in the blood. Calculations based on the appearance of radioactivity in the periphery showed that 56.2% of the material injected centrally would have been transported into the periphery by 10 min. This appearance of material in the periphery was inhibited by the simultaneous injection of an excess of unlabeled peptide. Water loading significantly decreased the brain to blood transport rate of AVP by 40%. It is concluded that a saturable system exists for brain to blood transport of AVP and some structurally similar peptides.

Animals↗
PubMed1985

In the central role of GnRH in the regulation of reproductive functions: mechanism of action and practical results.

The regulation of reproductive functions is influenced by several hormones. The hypothalamic hormone GnRH has a central role in reproduction. Several superactive and inhibitory analogs of GnRH synthesized in our laboratory showed use in animal breeding. GnRH was suggested to be degraded by the hypothalamus itself and also by the pituitary. We have used cultured fetal hypothalamic cells, and cultured pituitary cells to study the storage, the release and the action of this neuropeptide. It was found that neither the cultured hypothalamic nor the pituitary cells degrade GnRH, and pretreatment of these cultured cells with steroids do not induce GnRH degradation. The basal GnRH secretion from the cultured hypothalamic cells was increased by steroid pretreatment while the neurotransmitter induced GnRH release did not change. At the pituitary level it was found that GnRH regulates its own effect by priming or desensitizing gonadotropin release depending on the pretreatment time or the concentration of GnRH. The self-regulatory action of GnRH follows a similar pattern for both LH and FSH release.

Animals↗
PubMed1983

Comparative cytotoxic and cytokinetic effects of the epipodophyllotoxins 4'-demethylepipodophyllotoxin-9-(4,6-O-2-ethylidene-beta-D-glucopyranoside) and 4'-demethylepipodophyllotoxin-9-(4,6-O-2-thenylidene-beta-D-glucopyranoside) and their metabolites on human leukemic lymphoblasts.

We compared the effects of the epipodophyllotoxins 4'-demethylepipodophyllotoxin-9-(4,6-O-2-ethylidene-beta-D-glucopyranoside) (VP-16-213) and 4'-demethylepipodophyllotoxin-9-(4,6-O-2-thenylidene-beta-D-glucopyranoside) (VM-26) and several of their derivatives on cell cycle progression and viability of human leukemic lymphoblasts (CCRF-CEM). The cis-(picro)-lactone derivatives, like both VP-16-213 and VM-26, produced G2-phase arrest and cytotoxicity, but only at concentrations 100 times greater than required with the parent compounds. The epiaglycone derivative showed potent cytotoxicity: at 100 to 250 nM, it reduced cloning efficiency by 50%, an effect requiring 25 to 40 nM VM-26 and 340 to 425 nM VP-16-213. In contrast to VM-26 and VP-16-213, the epiaglycone arrested cells in M, consistent with evidence that it, like podophyllotoxin, is an inhibitor of microtubule assembly. At concentrations resulting in 50% cell kill and an increase of cells in M, however, the epiaglycone produced little change in the proportion of cells in G1 or early S phase, while podophyllotoxin produced a shift of cells to mid- and late S. The hydroxy acid derivatives, although found in detectable quantities in patients' urine and serum, were inactive in vitro. Structural differences among the compounds account for their different biochemical and cell kinetic effects and, hence, different cytotoxic activities. Because the epiaglycone is a potent compound and combines activities of both the podophyllotoxins and 4'-demethyl derivatives, further studies of its cytotoxicity are indicated.

Cell Cycle↗
PubMed1982

Suppression of ovulation in the rat by an orally active antagonist of luteinizing hormone-releasing hormone.

A synthetic antagonist of luteinizing hormone-releasing hormone blocked ovulation in rats in a dose-dependent manner when given by gavage on the afternoon of proestrus. Ovulation was delayed for at least 1 day in all animals given 2 milligrams of antogonist and in some of the animals treated with 1 or 0.5 milligram. Oral administration of 2 milligrams also blocked the preovulatory surge of luteinizing hormone. This demonstration that antagonists of luteinizing hormone-releasing hormone can have oral antiovulatory activity clearly enhances their therapeutic potential.

Administration, Oral↗