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1.
Ramakrishna A. Bangaru Yatish K. Bansal A. R. M. Rao T. P. Gandhi 《Journal of chromatography. B, Analytical technologies in the biomedical and life sciences》2000,739(2)
A rapid, simple and sensitive reversed-phase high-performance liquid chromatographic (HPLC) method has been developed for the measurement of acyclovir concentrations in human plasma and its use in bioavailability studies is evaluated. Unchanged acyclovir has been quantified without the introduction of an internal standard using the present method. Human plasma proteins were selectively precipitated by the addition of 7% perchloric acid to spiked plasma samples or to the plasma samples obtained after acyclovir administration to human volunteers and the mixture was spun at 1000 g for 10 min. The supernatant was directly injected into a Novaflex C18 column and detected at 254 nm. The mobile phase consisted of octane sulfonic acid buffer (pH 2.5) and methanol (92:08). The limit of quantitation for acyclovir in plasma was 20 ng/ml, which enabled the determination of the area under the curve (AUC) more precisely, that is, it is much closer to its extrapolated value. The present method has been successfully applied to samples from bioavailability studies. 相似文献
2.
Behavioral and physiological effects of chronic 2,450-MHz microwave irradiation of the rat at 0.5 mW/cm2 总被引:2,自引:0,他引:2
J A D'Andrea J R DeWitt O P Gandhi S Stensaas J L Lords H C Nielson 《Bioelectromagnetics》1986,7(1):45-56
Adult male Long-Evans rats were intermittently exposed to 2450 MHz CW microwaves at an average power density of 0.5 mW/cm2 for 90 days. The resulting SAR was 0.14 W/kg (range 0.11 to 0.18 W/kg). The animals were exposed 7 h/day, 7 days/wk, for a total of 630 h in a monopole-above-ground radiation chamber while housed in Plexiglas holding cages. Daily measures of body mass and food and water intake indicated no statistically significant effects of microwave exposure. Monthly assessment of reactivity to electric footshock, levels of cholinesterase and sulfhydryl groups in blood, and 17-ketosteroids in urine revealed no reliable differences between 14 sham-exposed and 14 microwave-exposed rats. After the 90 days of exposure, seven rats, randomly chosen from each group, were assessed for open-field behavior, shuttlebox performance, and schedule-controlled (IRT schedule) lever pressing for food pellets. Statistically significant differences between microwave-exposed and sham-exposed rats were observed in shuttlebox performances and lever pressing. Post mortem measures of mass of several organs and microscopic examination of adrenal tissue revealed no differences between the two groups of animals. 相似文献
3.
Effect of fenitrothion (phosphorothioic acid, 0,0-dimethyl 0-4-nitro-m-tolyl ester), an organophosphorous insecticide, on
membrane permeability employing the leakage of betacyanin and electrolytes as the criteria were studied in beet root(Beta vulgaris) discs. The leakage of both betacyanin and electrolytes increased with increasing concentrations (10–150 ppm) of fenitrothion
in the incubation medium. At 0.33 mM the increase in electrolyte leakage was approximately linear for the first 6h, while
the increase in betacyanin leakage started with a lag of about 2 h. Long term incubation (24 h) showed a biphasic nature (in
the semilog plot) for the increase in betacyanin leakage, while the increase in electrolyte leakage appeared more complex.
In the control sample, the Arrhenius plots (25–50°C) of leakage showed a break at 40°C. In treated samples no break was observed,
but the slope decreased (for both electrolyte and betacyanin leakage) as compared to the respective slopes in the control
in the temperature region greater than 40°C. The results are discussed in terms of the possible effect of the insecticide
on the active transport in plant membranes 相似文献
4.
5.
Studies on the lipozyme-catalyzed synthesis of butyl laurate 总被引:4,自引:0,他引:4
The effects of temperature, speed of agitation, enzyme concentration, etc., on butyl laurate synthessis using Mucor miehei lipase (Lipozymetrade mark) have been studied. Although the soluble enzyme was quite thermcstable in aqeous solution, it deactivated rapidly at and above 40 degrees C in the presence of butanol. This enzyme immobilized on an anion-exchange resin (Lipozymetrade mark) showed enhanced stability (as compared to the soluble form) to denaturation by butanol under the same conditions. The denaturation of M. miehei lipase was found to be a function of the butanol concentration in the aqueous phase, and rapid denaturation takes place at the concentration corresponding to its saturation at that temperature. (c) 1995 John Wiley & Sons, Inc. 相似文献
6.
Xiaohong Liu Jan Sejbal George Kotovych R. Rao Koganty Mark A. Reddish Linda Jackson Sham S. Gandhi Aubrey J. Mendonca B. Michael Longenecker 《Glycoconjugate journal》1995,12(5):607-617
Translation of an immune response into therapy is probably the toughest task in designing vaccines for cancer due to the heterogeneity of the cell surface antigens which display tremendous variations in glycoforms. Consequently, a small segment (antigen) of the cancer-associated mucin, in spite of generating antigen-specific immune responses, may be limited in therapeutic value. It is important that the synthetic segment resembles the native cancer-associated mucin in both structure and conformation. Synthetic cancer associated mucin derived 16 amino acid peptide GVTSAPDTRAPAPGSTA and its partially glycosylated forms have demonstrated specific binding to two monoclonal antibodies, B27.29 and BCP8, raised against the native cancer associated mucin, MUC-1 and a MUC-1 derived synthetic peptide, respectively. In spite of the structural similarities at the core peptide level of both glycosylated and unglycosylated peptides, it appears that partial glycosylation does not inhibit and even slightly enhances binding to the MAb B27.29 indicating that the glycosylated synthetic peptide more closely resembles the native mucin epitope recognized by MAb B27.29. From molecular dynamic simulations using NMR derived distance constraints, both glycosylated and unglycosylated peptides have shown a type I turn involving the same amino acids in both glycosylated and unglycosylated peptides. The GalNAc attached to the threonine (T3) and serine (S4) in the 16 amino acid sequence has not imposed any conformational changes to the peptide backbone nor has offered severe steric resistance to the binding of either antibody to the glycopeptides as indicated by hapten inhibition studies. Nevertheless, all peptides have displayed glycosylation dependent specificities in binding to these antibodies, i.e. the glycosylated peptides demonstrated relative higher affinities to the native mucin antibody B27.29 while the unglycosylated peptide is more specific to the MAb BCP8. Immune responses generated by these synthetic glycopeptides are highly specific in recognizing the native cancer associated mucin. 相似文献
7.
Saccade-related burst neurons (SRBNs) in the monkey superior colliculus (SC) have been hypothesized to provide the brainstem
saccadic burst generator with the dynamic error signal and the movement initiating trigger signal. To test this claim, we
performed two sets of open-loop simulations on a burst generator model with the local feedback disconnected using experimentally
obtained SRBN activity as both the driving and trigger signal inputs to the model. First, using neural data obtained from
cells located near the middle of the rostral to caudal extent of the SC, the internal parameters of the model were optimized
by means of a stochastic hill-climbing algorithm to produce an intermediate-sized saccade. The parameter values obtained from
the optimization were then fixed and additional simulations were done using the experimental data from rostral collicular
neurons (small saccades) and from more caudal neurons (large saccades); the model generated realistic saccades, matching both
position and velocity profiles of real saccades to the centers of the movement fields of all these cells. Second, the model
was driven by SRBN activity affiliated with interrupted saccades, the resumed eye movements observed following electrical
stimulation of the omnipause region. Once again, the model produced eye movements that closely resembled the interrupted saccades
produced by such simulations, but minor readjustment of parameters reflecting the weight of the projection of the trigger
signal was required. Our study demonstrates that a model of the burst generator produces reasonably realistic saccades when
driven with actual samples of SRBN discharges.
Received: 25 October 1994/Accepted in revised form: 20 June 1995 相似文献
8.
The rate of electron transfer through Photosystem I (reduced 2,6-dichlorophenol indophenol (DCIPH2 → methylviologen) in a low-salt thylakoid suspension is inhibited by Mg2+ both under light-limited and the light-saturated conditions, the magnitude of inhibition being the same. The 2,6-dichlorophenol indophenol (DCIP) concentration dependence of the light-saturated rate in the presence and in the absence of Mg2+ shows that the overall rate constant of the photoreaction is not altered by Mg2+. With N,N,N′,N′-tetramethyl-p-phenylenediamine or 2,3,5,6-tetramethylphenylenediamine as electron donor only the light-limited rate, not the light-saturated rate, is inhibited by Mg2+ and the magnitude of inhibition is the same as with DCIP as donor. The results are interpreted in terms of heterogeneous Photosystem I, consisting of two types, PS I-A and PS I-B, where PS I-A is involved in cation-regulation of excitation energy distribution and becomes unavailable for DCIPH2 → methyl viologen photoelectron transfer in the presence of Mg2+. 相似文献
9.
R H Lenox J L Meyerhoff O P Gandhi H L Wray 《Journal of cyclic nucleotide research》1977,3(5):367-379
Techniques of in-vivo microwave irradiation to inactivate brain enzymes in rats were varied as to exposure configuration and output power. The rate at which metabolism was stopped was studied in various regions of the rat brain, using changes in levels of cyclic AMP and phosphodiesterase activity. Exposure times required to obtain stabilized levels of cyclic AMP varied in different brain regions, i.e., hypothalamus, cortex and cerebellum. Levels of cyclic AMP in selective regions of the brain decreased as more rapid inactivation was achieved. The authors identify important sources of variability of present microwave inactivation systems and the need for improved control of signficant microwave parameters. 相似文献
10.