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Biomedical subjects

J Tamás

Publications and source records attributed to J Tamás.

At least 19 recordsLinked to original sources
PubMed1993

New Gaba-containing analogues of human growth hormone-releasing hormone (1-30)-amide: I. Synthesis and in vitro biological activity.

Analogues of human growth hormone-releasing hormone (1-30)-amide have been developed. All analogues have been modified in position 27 with Nle and with Gaba in position 30. Additional D-amino-acids have been inserted in the GHRH(1-30)-NH2 sequence: A-1741: Nle27,Gaba30-GH-RH(1-30)-NH2 A-495: D-Ala2,Nle27,Gaba30-GH-RH(1-30)-NH2 A-515: D Ala2,Leu15,Nle27,Gaba30-GH-RH(1-30)-NH2 A-527: D-Ala2,D-Arg11,Leu15,Nle27,Gaba30-GH-RH(1-30)-NH2. Our analogues were synthesized by solid phase peptide synthesis and were tested is two different in vitro systems and in rat pituitary cell cultures. A-495 and A-1741 were found to be the most active in releasing GH, however they showed different activities in the two different test systems. A-495 exhibited higher potency in the superfusion system (1.63 fold potency of the GHRH (1-29)-amide), while A-1741 evoked higher GH release from cultured pituitary cells (1.5-2.5 times higher than the GH-RH(1-44)-amide). The other analogues (A-515 and A-527) were found to be equipotent to the standard molecule. We can conclude that Nle27 and Gaba30 substitutions appeared to be a good modification in in vitro test systems, and Gaba30 substitution served as a good spacer during the synthesis, since it made the coupling of the C-terminal amino acids easier and produced quantitative coupling. In addition to the advantageous properties in the synthesis these modifications with or without D-Ala at the N-terminus increased the in vitro biological activity to 1.5-2.5 fold of the GHRH molecule.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1992

Bioavailability of methionine-hydroxy-analog free acid and S-methyl-methionine in the growing rat.

The biological utilization of DL-methionine (MET), DL-methionine-hydroxy-analog and DL-S-methyl-methionine-sulphonium-chloride (SMM) was tested in rat growth assay. Weight gain, feed efficiency, protein efficiency ratio (PER), net protein ratio (NPR) and net protein utilization (NPU) were applied as criteria. A test diet containing soybean meal as sole protein source was fortified with MET, MHA or SMM at 1.5 and 3.0 g/kg levels, respectively. All fortifications had a significant (p < 0.05) positive influence on weight gain, feed conversion and protein utilization. SMM showed the highest activity. MET and MHA were almost equally well utilized at 3.0 g/kg fortification level, however MHA proved slightly less efficient at 1.5 g/kg level than MET.

Animal Feed↗
PubMed1992

[Mass spectrometry of pipecuronium bromide and some related compounds].

The mass spectral behaviour of the bis-quaternary salt pipecuronium bromide and some related Cn+ A-n type ammonium salts (n = 1, 2, 3) has been studied and compared. Under EI-MS conditions the evaporation of the samples preceded by in situ dealkylation led to formation of alkyl bromide and amine bases. It has been demonstrated that this technique, completed with quantitation of the relative amount of the decomposition products is applicable to get structure information about the basis part as well as the number and positions of the quaternary centres and the substituents at these centres. The FAB mass spectra of these mono-, bis- and this quaternary ammonium salts were found to be very interesting and provide direct structural information about the salt. They exhibit primary Cn+ intact cations and (Cn+ A-n + 1)+ single charged cluster ions and also fragments characteristic of partial structures at the quaternary centres.

Androstane-3,17-diol↗
PubMed1989

Identification of in vitro metabolites of 3-ethyl-2,6-dimethyl-4H-pyrido(1,2a)pyrimidin-4-one.

(2-14C)3-Ethyl-2,6-dimethyl-4H-pyrido(1,2a)pyrimidin-4-one is metabolized in vitro by liver microsomes to at least 12 metabolites. The metabolites were isolated and purified by thin-layer chromatography and high-performance liquid chromatography and identified by mass spectrometry and nuclear magnetic resonance spectroscopy. The mostly mono- and dihydroxylated isomers were distinguished on the bases of their electron ionization mass spectra and the metastable daughter ion spectra of selected ions.

Analgesics↗
PubMed1989

Acute toxicological experiment of T-2 toxin in rabbits.

Rabbits were treated with a single oral dose (1, 2, 4, 6, 8, 10 or 15 mg/kg body mass) of T-2 fusariotoxin. Doses of 4 mg or higher killed the animals in 24 to 48 h. As opposed to the controls, in the treated rabbits gross pathological and histopathological examinations revealed acute catarrhal gastroenteritis, necrosis of lymphoid cells of the gastrointestinal mucosa, centrolobular dystrophy of the liver, necrosis of cells of the mononuclear phagocyte system (MPS) in the liver, tubulonephrosis, focal dystrophy of the adrenal cortex, lymphocyte depletion involving both T- and B-cell-dependent zones of the lymphoid organs (spleen, lymph, ampulla ilei), and depletion and necrosis of the myelopoietic cell colonies of the bone marrow. Similar but milder changes were observed in surviving rabbits exsanguinated 48 h after treatment. In addition to the direct damage done to the digestive tract mucosa and liver, the toxin severely damaged the cells participating in humoral and cell-mediated immunity and in the local defence of the intestinal mucosa, and markedly impaired phagocytosis and granulocytopoiesis. In another experiment rabbits were given oral doses of 2 mg/kg body mass T-2 toxin daily for several days. One rabbit was killed by bleeding every day. In rabbits killed beyond day 7 there was subacute catarrhal gastritis, emaciation, and hypertrophy of the adrenal cortex.

Animals↗
PubMed1988

Mass spectrometric characterization of some human metabolites of flumecinol.

The mass spectrometric behaviour of six human metabolites formed by hydroxylation in various positions of the alpha-ethyl group or/and on the phenyl ring of 3-trifluoromethyl-alpha-ethyl-benzyhydrol (flumecinol) and seven related compounds has been studied. The electron impact mass (EI) spectra of these compounds show significant and characteristic effects of substituents, but many of them suffer from weakness or even from absence of the M+. peak owing to the very facile primary loss of the alpha-aliphatic chain, i.e. no direct information can be obtained about the size of the molecule and that of this chain. It is demonstrated for derivatives possessing a hydroxylated alpha-ethyl group that the difficulties in structural characterization due to the lack or weakness of M+. and [M + H]+ peaks in their EI and chemical ionization mass spectra, respectively, can be overcome by studying their silyated or boronated derivatives. Furthermore, silyation enables us to obtain a clear base for distinction of the primary and secondary alcohols of this type.

Benzhydryl Compounds↗
PubMed1988

Transnitrosating activity of N-nitroso-N-methyl-p-toluenesulfonamide in rats and human gastric juice.

N-nitroso-N-methyl-p-toluenesulfonamide (NMTS, diazald, CAS 80-11-5) is a widely used compound for laboratory production of diazomethane. The present results showed that the noncarcinogenic NMTS reacts as a transnitrosating agent with amino nitrogen of secondary amines and amide both in vitro (human gastric juice) and in vivo (rats) to yield N-nitroso compounds. Since all compounds formed (NMOR, NDMA, NPIP, NPZ, NMU) are known animal carcinogens, caution should be taken by users handling NMTS.

Amides↗
PubMed1987

Metabolism of flumecinol in humans.

1. The metabolism of 14C-flumecinol (3-trifluoromethyl-alpha-ethyl-benzhydrol) was studied in volunteers after a single oral dose of 100 mg (11.1 MBq; 300 microCi). Radioactivity excreted in urine was 78.8 +/- 6.0% of dose and in faeces was 12.0 +/- 5.3% dose in 120 h. 2. Unchanged flumecinol was not excreted in urine, but was present in faeces unconjugated (1.2% dose) and as conjugates of glucuronic and sulphuric acids (10.8% dose). 3. Enzymic hydrolysis showed that all urinary metabolites were conjugated with glucuronic and/or sulphuric acids (77.8% dose). Unconjugated urinary metabolites were not found. 4. The major route of flumecinol metabolism was hydroxylation of the alkyl side chain and/or the phenyl group followed by conjugation. 5. Both the CF3-group and the skeleton of the original compound remained intact during metabolism.

Adult↗
PubMed1983

Identification of guanine and adenine adducts in DNA alkylated by dibromodulcitol in vitro and in vivo.

DNA reacted with dibromodulcitol in neutral solution yielded 3- and 7-alkyl substituted purines after hydrolysis at neutral pH-value at 37 degrees C. The alkylated products were identified by mass spectrometry and by comparison of their UV absorption spectra and chromatographic properties on thin-layer chromatography (TLC) and various columns with those of the corresponding galactitylpurine derivatives obtained by synthetic route from alkylation of the appropriate nucleic bases or nucleosides. The labelled alkylpurines occurring in DNA of Yoshida tumour cells treated with [3H]dibromodulcitol in vivo were also identified by co-chromatography of labelled DNA hydrolysate with synthetic 3- and 7-alkyl substituted purines. On the basis of the same chromatographic behaviour 3-(1-deoxy-3,6-anhydrogalactit-1-yl)adenine, 7-(1-deoxygalactit-1-yl)guanine, 7-(1-deoxy-3,6-anhydrogalactit-1-yl)guanine and 1,6-di(guanin-7-yl)-1,6-dideoxygalactitol were identified as main alkylated products in tumor cell DNA after in vivo treatment with dibromodulcitol.

Adenine↗