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B R Sitaram

Publications and source records attributed to B R Sitaram.

17 recordsLinked to original sources
PubMed1999

Studies on the relationship between structure and electrophoretic mobility of alpha-helical and beta-sheet peptides using capillary zone electrophoresis.

The electrophoretic behaviour of a series of 33 different synthetic peptides has been investigated using free solution high-performance capillary zonal electrophoretic (HPCZE) methods. The dependency of the electrophoretic mobility, mu(em), on the peptide charge, q, and on the charge-to-size ratio parameter, zeta, determined according to several electromobility models, have been examined. Significant divergences from linearity in the mu(em) vs. q or the mu(em) vs. zeta plots were noted for several peptides, possibly due to the proclivity of specific arrangements of their amino acid sequences to assume preferred alpha-helical or beta-sheet conformational features rather than random coil structures under the HPCZE conditions. These results provide further demonstration of the facility of HPCZE procedures to probe the effects of compositional, sequential and conformational differences of closely-related peptides and their consequences on their physicochemical behaviour in solution.

Electrophoresis, Capillary↗
PubMed1996

Determination of delta 9-tetrahydrocannabinol levels in brain tissue using high-performance liquid chromatography with electrochemical detection.

delta 9-Tetrahydrocannabinol (delta 9-THC) is the major psychoactive component of cannabis. To assist in investigating the mechanism(s) of action of delta 9-THC, a convenient method for determining its levels in brain tissue is required. We now describe a method for determining nanogram quantities of delta 9-THC in rat brain tissue. The method employs solvent extraction with methanol-hexane-ethyl acetate, followed by analysis using liquid chromatography with electrochemical detection. Overall recoveries were greater than 80%. The relationship between the peak-height ratio for processed standards extracted in the presence of tissue (delta 9-THC/internal standard) and the amount of delta 9-THC added was shown to be linear within the range of concentrations examined. Quantitative measurements of delta 9-THC in different brain regions following the intravenous administration of delta 9-THC are presented as examples of the applications of this method.

Animals↗
PubMed1995

Nyctohemeral rhythm in the levels of S-adenosylmethionine in the rat pineal gland and its relationship to melatonin biosynthesis.

Liquid chromatographic techniques that permit the simultaneous analysis of S-adenosylmethionine, melatonin, and its intermediary metabolites N-acetyl-5-hydroxytryptamine and 5-hydroxytryptamine within individual pineal glands have been developed. S-Adenosylmethionine has been shown to undergo a marked nyctohemeral rhythm in the pineal gland of the rat, with maximal levels occurring during the light period and minimal levels during the dark period. Detailed studies of the temporal relationships between the levels of S-adenosylmethionine and those of melatonin and its intermediary metabolites suggest that an association exists between the levels of S-adenosylmethionine and the status of the biosynthesis of melatonin. Exposure of animals to continuous light and the administration of the beta-adrenoreceptor antagonist propranolol were both found to inhibit the induction of melatonin synthesis and prevent the reduction in the levels of S-adenosylmethionine during the dark period. As a corollary the induction of melatonin biosynthesis following the administration of the beta-adrenoreceptor agonist isoproterenol during the light period was accompanied by a marked decrease in the levels of S-adenosylmethionine in the pineal gland. The significance of the link between the nyctohemeral rhythms in the levels of S-adenosylmethionine and the biosynthesis of melatonin in the pineal gland is discussed in the context of the therapeutic efficacy of S-adenosylmethionine as an antidepressant.

Animals↗
PubMed1993

Ion-pair extraction and liquid chromatographic analysis of morphine in rat brain and plasma.

A highly efficient and reproducible two-step liquid-liquid ion-pair extraction technique for the isolation of morphine from biological samples is described. A rapid normal phase high-performance liquid chromatographic procedure coupled with amperometric electrochemical detection has also been developed for subsequent quantification of morphine. Extraction involves the disruption of brain tissue or plasma in methanol, centrifugation, evaporation and reconstitution in ethyl acetate containing 10 mM di-(2-ethylhexyl) phosphoric acid, a liquid cation-exchanger, and back-extraction into 170 mM orthophosphoric acid. An acidic eluent consisting of acetonitrile-76 mM orthophosphoric acid-ammonia buffer (pH 3.0) (15:85, v/v) in combination with a strong cation-exchange column allows complete separation of morphine and the internal standard, nalbuphine. The limit of detection for morphine is 1.3 ng on-column.

Animals↗
PubMed1992

The role of procaine in adverse reactions to procaine penicillin in horses.

Procaine penicillin is a commonly used antibiotic in equine medicine but its use is associated with a substantial incidence of adverse reactions. Soluble procaine concentrations were determined by HPLC in several commercially available procaine penicillin preparations, including some that were involved in adverse reactions. The mean (+/- SEM) soluble procaine concentrations in the veterinary preparations was 20.18 +/- 5.07 mg/ml, which was higher than the concentration in the only procaine penicillin preparation for use in humans in Australia of 7.3 mg/ml. Heating the veterinary procaine penicillin preparations to 50 degrees C for 1 day led to a significant (P less than 0.01) increase in the amount of soluble procaine. Heating to 50 degrees C for 7 days also produced a significant (P less than 0.02) increase. Soluble procaine tended to return to baseline concentrations when veterinary procaine penicillin preparations were heated to 50 degrees C for 2 days then stored for 7 days at room temperature. Administration of procaine HCl intravenously (IV) at 2, 5, and 10 mg/kg produced behavioural, locomotor and vascular reactions, which were clinically similar to those reported in adverse reactions to procaine penicillin. The more severe reactions occurred at higher doses, although different horses responded variably at the same dose. Some adverse reactions lead to recumbency but none were fatal. The blood procaine concentrations 1 min after IV administration averaged 19.0 +/- 12.6 and 25.3 +/- 16 micrograms/ml at 2.5 mg/kg and 5 mg/kg, respectively. Ten min after administration, blood procaine concentrations were significantly higher (P less than 0.001) in the 5 mg/kg group than in the 2.5 mg/kg group. Intramuscular (IM) procaine HCl at 5 mg/kg produced significantly lower (P less than 0.001) blood concentrations than similar IV doses, and, in contrast to the IV doses, the amount of procaine in the blood was significantly higher 5 and 10 min after administration than it was after 1 min. Mild excitatory reactions in 4/5 horses were noted 5 to 10 min after IM administration. Administration of diazepam 20 s before procaine HCl prevented the excitatory adverse reaction in 2/2 horses, but administration after the procaine did not influence the outcome.

Animals↗
PubMed1990

Observations on the metabolism of the psychotomimetic indolealkylamines: implications for future clinical studies.

Although the psychotomimetic indolealkylamines N,N-dimethyltryptamine, 5-methoxy-N,N-dimethyltryptamine, and 5-hydroxy-N,N-dimethyltryptamine have been unequivocally identified in human body fluids, evidence relating their concentration to the presence of psychotic illness in humans remains controversial. A series of studies on the metabolism of the compounds in the rat have highlighted the rapidity and with which these are metabolized and renally excreted. The implications of our observation for the interpretation of past clinical studies and the design of future ones is discussed.

Animals↗
PubMed1987

Gas chromatographic-mass spectroscopic characterisation of the psychotomimetic indolealkylamines and their in vivo metabolites.

The use of liquid chromatography with on-line fluorescence detection has formed the basis for the separation, characterisation and quantitation of a number of metabolites of the psychotomimetic indolealkylamines N,N-dimethyltryptamine and 5-methoxy-N,N-dimethyltryptamine formed both in vitro and in vivo. Verification of the identity of metabolites has previously been facilitated by the combined use of a number of analytical techniques including multidimensional liquid chromatography and stop-flow spectroscopic analysis. We now describe the combination of liquid chromatography with gas chromatography-mass spectrometry for the unequivocal verification of a number of structurally characteristic metabolites of the psychotomimetic indolealkylamines.

Animals↗
PubMed1987

Study of metabolism of psychotomimetic indolealkylamines by rat tissue extracts using liquid chromatography.

The use of a series of liquid chromatographic techniques involving cation-exchange, reverse-phase and normal-phase chromatography has permitted the separation and characterisation of a number of metabolites of the psychotomimetic indolealkylamines N,N-dimethyltryptamine and 5-methoxy-N,N-dimethyltryptamine which were isolated following incubation of these compounds with rat tissue extracts. In liver, kidney and brain tissue extracts the routes of metabolism identified included oxidative deamination, N-demethylation, O-demethylation and N-oxidation. The quantitative significance of individual routes of metabolism in these tissues was assessed using N,N-dimethyltryptamine as a substrate.

Animals↗
PubMed1987

In vivo metabolism of 5-methoxy-N,N-dimethyltryptamine and N,N-dimethyltryptamine in the rat.

Following intraperitoneal administration, 5-methoxy-N,N-dimethyltryptamine and N,N-dimethyltryptamine are subject to both a very rapid uptake into, and clearance from, all tissues examined. The current studies in vivo confirm previous in vitro observations that the routes involved in the metabolism of these compounds include oxidative deamination, N-demethylation, O-demethylation, and N-oxidation. The analysis of metabolic profiles in various tissues led to the identification of the N-oxides as major metabolites. The successful inhibition and redirection of metabolism away from the indole acids towards the parent compounds and their structurally unique metabolites were demonstrated in animals pretreated with iproniazid.

Adrenal Glands↗
PubMed1985

Bufotenine reconsidered.

Bufotenine given intravenously to a medically trained volunteer subject correlated with the appearance of profound perceptual and emotional changes which were of short duration. The compound rapidly disappeared from the blood and metabolites quickly appeared in the urine of the subject.

Bufotenin↗
PubMed1984

Information content and one point mutations in DNA.

It has been suggested recently that data on mutations in human haemoglobin is consistent with the hypothesis that evolution takes place in the direction of increasing informational entropy of DNA. We argue that the mutation data sheds no light on the above hypothesis and show how the data can be understood in terms of random mutation of the bases in DNA.

Base Sequence↗
PubMed1984

Effect of oxygen on the induction of tryptophan hydroxylase by adrenergic agents in organ cultures of rat pineal glands.

Rat pineal glands, cultured under 95% air and 5% CO2, lost 50% of their tryptophan hydroxylase activity within 5 h. This loss was accelerated by the addition of cycloheximide or puromycin to the medium. Activity was, however, largely maintained in 95% O2 and 5% CO2. Under these conditions, L-noradrenaline (100 microM), L-isoproterenol (10 microM), and dibutyryl cyclic AMP (1 mM) induced enzyme activity. They failed to do so when 95% air and 5% CO2 was used. Noradrenaline induced serotonin N-acetyltransferase activity with either atmosphere.

Animals↗
PubMed1983

The ion-pair extraction, purification, and liquid chromatographic analysis of indolealkylamines in human urine.

A highly efficient ion-pair extraction technique for the isolation of tryptamine, 5-hydroxytryptamine, and their mono- and N,N-dimethylated derivatives from aqueous media is described. The technique has been used to isolate nanogram quantities of both N, N-dimethyltryptamine and 5-hydroxy-N, N-dimethyltryptamine from large volumes of urine. A rapid and efficient normal-phase liquid chromatographic procedure has also been developed for the subsequent purification of indolealkylamines isolated from urine. The methods described have been used in the measurement of the urinary excretion of 5-hydroxy-N, N-dimethyltryptamine. Analyses were performed by liquid chromatography using a cation-exchange column with online fluorescence detection. Further characterization was achieved by stop-flow spectroscopic analysis of the LC eluant.

Bufotenin↗