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Biomedical subjects

J Hirt

Publications and source records attributed to J Hirt.

9 recordsLinked to original sources
PubMed2003

Inhibitors of 20-hydroxyeicosatetraenoic acid reduce renal vasoconstrictor responsiveness.

20-Hydroxyeicosatetraenoic acid (20-HETE) is a cytochrome P450-derived constrictor eicosanoid produced by the preglomerular vasculature where it contributes to regulation of tone. Removal of the tonic inhibitory influence of nitric oxide (NO) has been reported to increase renal 20-HETE release. Because inhibition of NO synthesis enhances responses to vasoconstrictor agents, we examined a contribution for increased 20-HETE generation. In the rat kidney perfused with Krebs' buffer, responses to U46619 (9,11-dideoxy-9alpha,11alpha-methanoepoxy PGF2alpha), a thromboxane A2 mimetic, were compared before and after 50 microM L-nitroarginine (L-NA) to inhibit NO synthase. L-NA raised perfusion pressure (PP) from 79 +/- 3 to 190 +/- 7 mm Hg and enhanced constrictor responsiveness to U46619. U46619 (10, 30, 100, and 300 ng) increased PP by 7 +/- 1, 17 +/- 2, 50 +/- 7, and 67 +/- 7 mm Hg, respectively, before L-NA and 15 +/- 1, 37 +/- 7, 68 +/- 10, and 85 +/- 11 mm Hg, respectively, after L-NA, which did not increase 20-HETE efflux from the kidney. Nonetheless, an inhibitor of omega-hydroxylase, dibromododecencyl methylsulfonimide (DDMS), which reduced 20-HETE release, normalized the enhanced responsiveness to U46619. When PP was elevated with phenylephrine, vasoconstrictor responses to U46619 were similarly enhanced, an effect that was also prevented by DDMS. DDMS and an antagonist of 20-HETE, 20-HEDE [20-hydroxyeicosa-6(Z), 15(Z)-dienoic acid], also reduced vasoconstrictor responses to U46619 in the absence of elevation of PP. Because 20-HETE inhibits K+ channels, we examined the effects of K+ channel inhibitors on vasoconstrictor responses and showed that both tetraethylammonium (TEA) and charybdotoxin enhanced renal vasoconstrictor responses to U46619. However, the inhibitory effects of 20-HEDE on vasoconstrictor responses remained after treatment with TEA. These results support a role for 20-HETE vasoconstrictor responses but suggest an action independent of K+ channels.

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗
PubMed2003

Toxoplasmic lymphadenitis--clinical and serologic profile.

OBJECTIVE: To study the serologic profile of several types of test for toxoplasmosis, in order to contribute to the interpretation of antibody kinetics. METHODS: The clinical and serologic features of 120 cases of lymphadenopathy with known time of clinical onset were studied during 18 months postinfection. Antibody kinetics was determined by Sabin-Feldman dye test, complement fixation with light antigen, IgM immunofluorescent antibody test, and IgM immunosorbent agglutination assay (IgM-ISAGA). Cell-mediated immunity was evaluated by the toxoplasmin skin test. RESULTS: Seventy-five female patients aged 11-54 years (median 27 years) and 45 male patients aged 3-59 years (median 17 years) were studied, 85% of whom were under 30 years of age. Cervical lymph nodes were involved throughout, generally on both sides, with more than one affected ganglion group in 88%. The predominant symptom was asthenia (69%), which persisted in some cases for several months. A negative Sabin-Feldman dye test in a lymphadenopathy with more than three weeks' evolution excludes a toxoplasma etiology. A positive Sabin-Feldman dye test with negative IgM-ISAGA almost invariably excludes recent infection. The Sabin-Feldman dye test was positive in 94% of patients with titers higher than 1 : 16 000 within the first three months. The IgM-ISAGA yielded 98% of positive results, of which 94% were high titers. Titers >/= 1 : 160 in the IgM immunofluorescent antibody test and complement fixation were found to be highly indicative of recent infection, since 87% and 91%, respectively, were found within the first three months. A negative skin test plus positive serology values indicates recent infection. CONCLUSION: Our results indicate that estimation of time of infection on the basis of serologic results is improved by the simultaneous application of several tests, and correlates closely with the presence of clinical lymphadenitis.

Adolescent↗
PubMed2000

Photoinduced electron-transfer reactions with quinolinic and trimellitic acid imides: experiments and spin density calculations(1)

The regioselectivity of photoinduced electron-transfer (PET) reactions of unsymmetrical phthalimides is controlled by the spin density distribution of the intermediate radical anions. ROHF ab initio calculations were found to be most suitable for atomic spin density analysis. Intramolecular PET reactions of quinolinic acid imides were studied with the potassium butyrate and hexanoate 1a,b and a cysteine derivative 3. The photocyclizations products 2a,b and 4 were formed with moderate regioselectivities (68:32, 57:43, and 81:19) showing preferential ortho cyclization. The intermolecular reaction of potassium propionate and potassium isobutyrate with N-methylquinolinic acid imide (5) yielded as addition products the dihydropyrrolo[3,4-b]pyridines 6a,b with slight ortho regioselectivity (55:45). In contrast to these low regioselectivities, the PET reaction of potassium propionate with the methyl ester of N-methyltrimellitic acid imide (9) yielded solely the para addition product 10. Likewise, the intramolecular photoreaction of the cysteine derivative 7 gave a 75:25 (para/meta) mixture of regioisomeric cyclization products 8. The regioselectivity originates from donor-acceptor interactions prior to electron transfer and differences in spin densities in the corresponding imide radical anions. The results of DFT and ab initio calculations for the radical anions of the quinolinic acid imide (11(*)(-)) and the methyl ester of trimellitic acid imide (12(*)(-))( )()were in agreement with the latter assumption: spin densities in 11(*)(-) were higher for the imido ortho carbon atoms (indicating preferential ortho coupling); for 12(*)(-) the spin densities were higher for the imido para carbon atoms (indicating preferential para coupling). These correlations became more significant when the additional spin densities at the carbonyl oxygen and the adjacent carbon atoms were taken into account. The cyclization selectivities for 2, 4, and 8 deviate from the intermolecular examples probably because of ground-state and solvent effects.

Journal Article↗
PubMed1999

Richness and diversity of parasite communities in European eels Anguilla anguilla of the River Rhine, Germany, with special reference to helminth parasites.

A total of 121 European eels (Anguilla anguilla) from 2 sampling sites on the River Rhine were investigated in respect of their parasite communities. Special attention was given to the swim bladders, intestines, gills and fins of the fish. Twelve different parasite species were found to live in and on the eels. Data from each sampling site were kept separate. Parasites found in descending order of prevalence were: Anguillicola crassus, Trypanosoma granulosum, Myxobolus sp., Paratenuisentis ambiguus, Pseudodactylogyrus sp., Bothriocephalus claviceps, Myxidium giardi, Pomphorhynchus laevis, Trichodina sp., Raphidascaris acus, Acanthocephalus lucii and Acanthocephalus anguillae. Significantly different prevalences were reported for L3 larvae of A. crassus, adult P. ambiguus, B. claviceps and Myxobolus sp. at the 2 sampling sites. The highest number of parasite species was recorded from the intestine, which contained up to 6 different helminths. The coexistence of the acanthocephalans P. laevis and P. ambiguus, which showed clear patterns of distribution within the intestine of the respective hosts, was reported for the first time. Up to 3 different helminth species were found in the intestine of individual fish. Among those, acanthocephalans were the most prevalent worms with the eel-specific parasite P. ambiguus as the dominant species not only of the intestinal but also of the total component communities. Both infra and component communities exhibited low diversity and were dominated by this single species. The evenness reached only approximately 50% or less and it remained unclear why the helminth communities of the eels from the River Rhine with its huge catchment area exhibit such a low parasite diversity and high dominance.

Air Sacs↗
PubMed1993

Growth hormone response to clonidine in neuroleptic-free patients with multidagnostically defined schizophrenia.

The role of alpha 2-adrenergic receptor sensitivity in schizophrenia was examined by measuring growth hormone (GH) response after the intravenous administration of clonidine (1.3 micrograms/kg) in 26 healthy control subjects and 26 neuroleptic-free, acutely psychotic patients with at least 1 out of 11 possible diagnoses of schizophrenia derived from a multidiagnostic psychopathological assessment. GH responses were significantly (0.01) lower than control values in schizophrenias defined by E. Bleuler, M. Bleuler, Schneider, Langfeldt, Taylor and Abrams, and Cloninger, but not in DSM-III, World Health Organization, Feighner, Kraepelian, and Research Diagnostic Criteria (RDC) schizophrenias. Eight patients with RDC schizoaffective disorder also had a blunted response. However, there were no correlations with any symptom measures. There were no differences between paranoid and nonparanoid patients, although there was a significant difference between nonparanoid patients and control subjects. These findings support the presence of noradrenergic dysfunction in some patients within the schizophrenia syndrome, possibly those whose illnesses have an affective component. The study also illustrates the need for simultaneous investigation of several different sets of diagnostic criteria for schizophrenia in neurobiological research.

Adolescent↗