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Biomedical subjects

J Silberring

Publications and source records attributed to J Silberring.

At least 91 records · Page 5Linked to original sources
PubMed1979

RIA system programming by means of kinetic parameters.

Insulin-125I antibody reaction was optimized by physical-chemical parameters. After the activation energies Ea and Ed for association and dissociation, respectively were calculated from the experimental data, the theoretical values of the reaction rate constants ka and kd were determined as well as equilibrium constants K. By means of the empirical formulae, the approximate incubation time for the RIA kit and maximal percent of insulin-125I binding to antibody (%B) in relation to temperature were computed. The proposed method may be applied to the new antigen-binder systems preparation (new antibodies, shortening of the incubation time, temperature changes, influence of different ions and kind of buffer).

Animals↗
PubMed1976

Control of the RIA method as viewed from the standpoint of the investigation on the kinetics of the insulin-125 I-antibody reaction.

In this paper attempts were made towards the optimalization and the control of some parameters of the RIA reaction. Basing on the law mass action, as well as on the Scatchard's and Sip's equations, the equilibrium constants for the reversible reaction: insulin-125I-antibody for different incubation temperatures were calculated. Moreover a characteristic of the antiinsulin antibody by means of the "alpha"heterogeneity coefficient was done, as well as the values of the thermodynamic function increments were calculated, which made possible to point out explicitly the optimal shape of the standard curve.

Insulin Antibodies↗
PubMedDate not supplied

Quantitation and identification of two cholecystokinin peptides, CCK-4 and CCK-8s, in rat brain by HPLC and fast atom bombardment mass spectrometry.

A sensitive HPLC method has been described for quantitation of two cholecystokinin (CCK) peptides in discrete rat brain regions. Separation and quantitation was performed by the reversed-phase HPLC combined with electrochemical detection. Analytical recoveries of the tetrapeptide (CCK-4) and octapeptide-sulphate (CCK-8s) were 96% and 94%, respectively. The between assay coefficient of variation (CV) was less than 3% for both peptides. The within-assay CV was 4% and 6% for CCK-4 and CCK-8s and the detection limit was 2 and 10 pmol/mL, respectively. For identification of structures, the peptides were fractionated by semi-preparative HPLC using a novel SMART system for micropurification. The fractions were analysed by fast atom bombardment mass spectrometry (FAB MS) which confirmed the presence of both CCK-4 and CCK-8s in the rat brain tissue.

Amino Acid Sequence↗
PubMedDate not supplied

Proteinergic profiles in cerebrospinal fluid from alcoholic subjects.

Minute amounts of cerebrospinal fluid samples from alcoholics were subjected to separation by HPLC-molecular sieving, combined with multispectral UV analysis of the acquired data. A significant difference in the protein/polypeptide pattern within the molecular weight range of 7-10 kDa has been observed between samples, taken directly after detoxification and 2 weeks later. Spectral analysis of the results suggests that the components are of peptidergic nature. On the other hand, albumin content did not differ significantly, suggesting that the blood-brain barrier was not affected. An enzyme marker, dynorphin converting enzyme, remained unchanged in both groups.

Adult↗
PubMedDate not supplied

Kinetics and metabolism of 2-chloro-2'-deoxyadenosine and 2-chloro-2'-arabino-fluoro-2'-deoxyadenosine in the isolated perfused rat liver.

2-Chloro-2'-deoxyadenosine (CdA), a newly developed anticancer drug, has been tested in phase II trials in the treatment of lymphoproliferative disorders. 2-Chloro-2'-arabino-fluoro-2'-deoxyadenosine (CAFdA), an acid stable derivative of CdA with promising anti-lymphoproliferative activity, has been suggested as a potentially effective oral drug. In the present study, we investigated the metabolism of CdA and CAFdA in isolated perfused rat liver. The liver was recycled with a perfusate containing CdA or CAFdA (2-200 micrograms/ml) for 3.5 h. The elimination half-lives were concentration-dependent for both CdA and CAFdA. The elimination rate of CAFdA was slower than that of CdA, suggesting that CAFdA is more stable than CdA against deglycosylation by hepatic enzymes. The amount of 2-chloroadenine (CAde), the major metabolite of CdA and CAFdA, increased proportionally with time and dose. The first passage effect was approximately 50% both for CdA and CAFdA. Less than 1% of CdA and CAFdA were recovered as intact drug in the bile during the experiment and less than 1% of CdA and 0.1% of CAFdA were found as CAde in the bile, respectively. The structural identity of metabolites present in the perfusates was verified utilizing electrospray ionization mass spectrometry.

Adenine Nucleotides↗
PubMedDate not supplied

Analgesic and convulsant effects of guanidinoethylmercaptosuccinic acid (GEMSA)--a potent enkephalin convertase inhibitor.

We studied behavioral effects of the intraventricularly and intrathecally administered guanidinoethylmercaptosuccinic acid (GEMSA) - a potent inhibitor of enkephalin convertase. When given intraventricularly in doses of 3 and 6 micrograms, GEMSA elicited analgesia; after doses of 12.5 and 25 micrograms the explosive motor behavior and convulsions occurred. Following the intrathecal administration of GEMSA (12.5, 25 and 50 micrograms), an increase in the tail-flick latency was observed; moreover that drug potentiated analgesic effects of the intrathecally applied Met5-enkephalin-Arg6-Phe7 and Met5-enkephalin-Arg6-Gly7-Leu8. All the above effects of GEMSA were significantly attenuated by naloxone. The rats subjected to chronic pain showed a weaker analgesic response to the intrathecally injected GEMSA. The 3H-GEMSA binding to enkephalin convertase in the spinal cord of these rats produced only a slight increase in KD; besides, no changes in the enzyme activity were observed. The study shows that GEMSA has a potent pharmacological action in the central nervous system. Furthermore, this effect is partly due to the influence of GEMSA on endogenous opioid peptide systems, possibly on proenkephalin A.

Analgesics↗
PubMedDate not supplied

Enkephalin convertase in the rat spinal cord.

3H-Guanidinoethylmercaptosuccinic acid (3H-GEMSA) a very selective inhibitor of enkephalin convertase, binds to the crude rat spinal cord homogenates saturably, reversibly and with high affinity. Scatchard analysis revealed two classes of binding sites with KD: 4.5 nM and 215 nM. A plot of dissociation experiment was nonlinear with the T1/2: 2 min and 6 min, respectively. 3H-GEMSA binding sites are evenly distributed throughout the rat spinal cord and their high density might suggest a physiological significance of enkephalin convertase in that tissue.

Animals↗
PubMedDate not supplied

Micropurification and amino acid sequence of beta-casomorphin-8 in milk from a woman with postpartum psychosis.

Milk was obtained from a woman with acute postpartum psychosis and with ongoing lactation. Defatted samples were subjected to micropurification and collected fractions were analyzed by means of their beta-casomorphin-8 immunoreactivity. Immunoreactive material with the same chromatographic properties as synthetic human beta-casomorphin-8 was determined by amino acid sequence analysis to be Tyr-Pro-Phe-Val-Glu-Pro-Ile-Pro. Its molecular mass was determined by fast atom bombardment-mass spectrometry to be 962.3 Da. These determinations, which ultimately identify the immunoreactive material as human beta-casomorphin-8, represent the first structural identification of a beta-casomorphin peptide from a body fluid.

Acute Disease↗
PubMedDate not supplied

The difference in stress-induced analgesia in C57BL/6 and DBA/2 mice: a search for biochemical correlates.

The level of opioid peptides: beta-endorphin and dynorphin, binding to the mu and kappa opioid receptors and the analgesic response of those endogenous opioid systems to stress were investigated in two strains of mice: C57BL/6 (C57) and DBA/2 (DBA). The nociceptive threshold of DBA mice was higher than that of C57 mice. KD values for spinal mu receptors were lower in C57, while KD for cerebral kappa receptors were higher in this strain. DBA mice have significantly higher concentrations of dynorphin in the hypothalamus and neurointermediate lobe of the pituitary. Stress-induced analgesia was much greater in C57 than in DBA mice. In the hypothalamus both stress procedures depressed the concentrations of beta-endorphin in C57, and dynorphin in DBA mice. The level of beta-endorphin increased in the neurointermediate lobe in C57 and in anterior lobe of the pituitary in DBA mice. In the spinal cord both stress procedures depressed the dynorphin level. The above data indicate that C57 and DBA mice differ in the endogenous opioid peptide content, stress-induced alteration and opioid receptor affinity, the effects which might correlate with their different responses to environmental factors and pharmacological agents.

Analgesia↗
PubMedDate not supplied

Degradation of the labelled beta-endorphin is an important factor of direct RIA in the human and rat plasma.

Degradation of iodinated beta-endorphin in human and rat plasma was investigated, using different proteinase inhibitors. This degradation affects the radioimmunoassay quality. Additional blank tubes were also prepared during assay procedure to avoid the effect of 125-I-beta-endorphin adsorption on the dextran-coated charcoal in the presence and absence of plasma proteins, what avoids underestimation of the beta-endorphin level in plasma samples. Based on the above observations, the sensitive and direct radioimmunoassay of beta-endorphin was developed in human and rat plasma.

Animals↗