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Biomedical subjects

E Straus

Publications and source records attributed to E Straus.

At least 37 records · Page 2Linked to original sources
PubMed1982

Post-translational processing of cholecystokinin in pig brain and gut.

A sequential extraction method employing methanol extraction of the COOH-terminal fragments of cholecystokinin (CCK) from pig tissues followed by HCl extraction of intact CCK and its NH2-terminal fragments is described. Radioimmunoassay of extracts and their fractionation by Sephadex chromatography and HPLC demonstrate that the distributions of COOH-terminal and NH2-terminal immunoreactivities among various regions of brain are similar and independent of the concentrations in individual regions. The distribution in gut differs from that in brain. Greatest concentrations of CCK immunoreactivity are located in cortical tissue in the brain and in duodenal mucosa in gut. Both brain and gut contain CCK octapeptide (CCK8) and an NH2-terminal fragment that is likely to be desoctapeptide-CCK33. Intact CCK33 is extractable from gut but not from brain. Brain contains another NH2-terminal immunoreactive molecule lacking COOH-terminal immunoreactivity that may be a peptide with a COOH-terminal extension, as has been described for gastrin, or one that may not be derived from a CCK33-like precursor. This peptide is much less prominent in gut, or may be nonexistent there. The failure to find CCK33 in the brain and the presence in the brain of this as-yet-uncharacterized NH2-terminal peptide raises the question as to whether the differences between neuronal and mucosal tissues are a consequence of differences in post-translational processing or in the DNA templates.

Animals↗
PubMed1982

The effects of bile salts on the radioimmunoassay of hormonal peptides.

The effect of bile salts on RIAs of secretin, glucagon, insulin, and gastrin have been studied. Increasing concentrations of the sodium salts of taurocholic, glycochenodeoxycholic, taurochenodeoxycholic, glycocholic, and taurodeoxycholic acids progressively inhibit the binding of 125I-secretin to specific antibody, resulting in significant lowering of the B/F ratio at concentrations as low as 0.04 mM and almost complete inhibition at concentrations above 2.4 mM. The nonspecific inhibition by taurodeoxycholate results in a B/F vs. concentration curve resembling a secretion standard curve. The binding of 125I-secretin to charcoal is also inhibited by increasing concentrations of bile salts, although this effect is less marked than their effects on the immune reaction. The binding of 125I-glucagon, 125I-insulin, and 125I-gastrin to specific antisera is also inhibited by sodium taurocholate. Insulin binding is least affected. However, gastrin binding is inhibited by sodium taurocholate at a concentration as low as 0.2. The binding of 125I-insulin and 125I-gastrin to charcoal is also inhibited by sodium taurocholate. Thus bile salts interfere in the RIA of hormonal peptides by inhibiting both the immune reaction and the binding of labeled antigen to charcoal. These nonspecific effects must therefore be considered in RIA of body fluids containing high concentrations of bile salts. Treatment of plasma samples with anionic-binding resins can eliminate interference caused by high bile salt concentrations. However, these resins will also remove anionic hormonal peptides such as gastrin.

Bile Acids and Salts↗
PubMed1981

Nature of immunoreactive CCK in rat and pig brain.

Two major classes of immunoreactive cholecystokinin peptides (iCCK) have been identified in rat and pig brains: (1) large basic peptides (Big iCCK) resembling pCCK33 in size and charge; (2) small acidic peptides (Small iCCK) resembling the COOH-terminal fragments of CCK. Boiling 0.1 N HCl maximally extracts Big iCCK; boiling 0.1 N NaOH maximally extracts Small iCCK. The differences in hormonal forms removed by these extractions are not likely to be due to enzymatic conversion during the extraction procedures. Fractionation on Sephadex G50 and starch gel electrophoresis combined with radioimmunoassay using 3 antisera of different specificities: (1) directed towards the NH2-terminus of pCCK33; (2) produced by immunization with CCK8; (3) produced by immunization with CCK4; are consistent with the hypothesis that a major fraction of Big iCCK may represent intact CCK with a COOH-terminus extension as has recently been suggested for gastrin, a molecule having a COOH-terminal pentapeptide identical with that of CCK.

Animals↗
PubMed1981

Cholecystokinin and enkephalin levels following ethanol administration in rats.

Using radioimmunoassay, cholecystokinin and enkephalin levels were determined in the brain and gut of rats following ethanol administration. Acute or chronic administration of ethanol did not affect the cholecystokinin or enkephalin content of rat brain cortex, hypothalamus, striatum or proximal small bowel. This contrasts with the reports of altered levels of several classical neurotransmitters following ethanol administration.

Animals↗
PubMed1981

Recovery of secretin in acid small intestinal lumen perfusates in the rabbit.

Immunoreactive secretin concentrations were measured in femoral venous plasma and in intestinal perfusates during acid and neutral perfusion of small intestinal segments in anesthetized rabbits. Steady-state plasma and luminal secretin concentrations were less than 20 pg/ml. Duodenal perfusion with with 0.1 N hydrochloric acid stimulated peak plasma immunoreactive secretin concentrations of 200 - 300 pg/ml within five minutes. Acid stimulated plasma concentrations remained constant during 30 minutes of perfusion. Secretin output into the acid perfusate (2000 - 4000 pg/min) accompanied the release into plasma. Subsequent perfusion with a neutral solution resulted in a rapid return to steady-state plasma and luminal secretin concentrations. Sequential acid perfusion of the ileum, jejunum, and duodenum stimulated similar concentrations of secretin in plasma and luminal perfusates.

Animals↗
PubMed1981

Clinical applications of the radioimmunoassay of secretory tuberculoprotein.

A radioimmunoassay that measures a specific secretory tuberculoprotein was used to detect Mycobacterium tuberculosis in 9 of 30 liquid cultures of sputum. The accumulation of immunoreactive material in liquid cultures containing isoniazid was shown to reflect in vitro susceptibility of mycobacteria to the antibiotic effects of the drug.

Bacterial Proteins↗
PubMed1981

Extraction and immunochemical characterization of cholecystokinin-like peptides from pig and rat brain.

Two major classes of immunoreactive cholecystokinin peptides (iCCK) have been identified in rat and pig brains: (i) large basic peptides (big iCCK) resembling the 33-amino acid porcine cholecystokinin (pCCK33) in size and charge; (ii) small acidic peptides (small iCCK) resembling the COOH-terminal fragments of CCK. Boiling 0.1 M HCl maximally extracts big iCCK; boiling 0.1 M NaOH maximally extracts small iCCK. The differences in hormonal forms removed by these extractants are not likely to be due to enzymatic conversion during the extraction procedures. Fractionation on Sephadex G-50 and starch gel electrophoresis combined with radioimmunoassay using three antisera of different specificities--(i) directed towards the NH2 terminus of pCCK33, (ii) produced by immunization with COOH-terminal fragment CCK8, (iii) produced by immunization with COOH-terminal fragment CCK4--are consistent with the hypothesis that a major fraction of big iCCK may represent intact cholecystokinin with a COOH-terminal extension, as has recently been suggested for gastrin, a molecule having a COOH-terminal pentapeptide identical with that of cholecystokinin.

Animals↗
PubMed1981

Alkaline extraction and characterization of cholecystokinin-immunoreactivity from rat gut.

Generally some variation of neutral or acid extractants has been used to recover immunoreactive cholecystokinin (CCK) from gut as well as from brain. Recovery of CCK in 0.1 N NaOH extracts from gut mucosa, gut muscle, or whole gut ranged up to threefold higher than in similar water or 0.1 N HCl extracts, although the reverse was the case for the extraction of secretin from the same tissue. CCK-immunoreactive peptides from rat gut were found to resemble a CCK-33-like peptide, sulfated CCK-12 and CCK-8, as well as smaller COOH-terminal fragments, which are larger than the C-terminal tetrapeptide amide. The fraction of immunoreactivity in the form of a CCK-33-like peptide was greater, although the total recovery was less, in acid extractants of whole gut. Proper interpretation of dynamic changes in gut CCK in response to fasting, feeding, and other laboratory manipulations requires efficient extraction of total immunoreactivity.

Animals↗
PubMed1981

Mucosal secretin content in postmortem tissues.

Since human tissues are generally obtained at autopsy performed some hours after death, it is necessary to extrapolate from the observed concentration what the values might have been antemortem. In this study, we investigated the changes of secretin in gastrointestinal mucosa in man and rats under differing conditions postmortem. Although considerable secretin can be recovered from mucosal tissue even after extended postmortem delay, these studies demonstrate the importance of low postmortem body temperature and rapid removal and extraction of tissues after opening of the peritoneal cavity to maximize recovery.

Animals↗
PubMed1980

Cholecystokinin-converting enzymes in brain.

Crude extracts of porcine cerebral cortical tissue convert cholecystokinin (CCK) to its COOH-terminal fragments, the dodecapeptide (CCK-12) and the octapeptide (CCK-8). The Sephadex G-75 void volume eluate of the crude extract cleaves the arginine-isoleucine bond and effects conversion only to CCK-12; the Sephadex G-50 void volume eluate of the same extract cleaves the arginine-aspartate bond as well, so that both CCK-12 and CCK-8 are end products. Thus, there are at least two enzymes; the one involved in the conversion to CCK-12 is of larger molecular radius than the other. The Km for the cleavage of CCK at the arginine-isoleucine bond by the Sephadex G-75 void volume eluate enzyme is 1.1 X 10(-6) M; the Km for trypsin cleavage of the same bond is 4.7 x 10(-6) M. The lower Vmax for the brain enzyme (1.5 x 10(-11) mol/min per g of extract) compared with trypsin (66 x 10(-11) mol/min per g of trypsin) simply reflects the lesser degree of purify of the brain extract than of the highly purified trypsin.

Amino Acid Sequence↗
PubMed1980

Further characterization of brain cholecystokinin-converting enzymes.

The brain cholecystokinin-converting enzymes that cleave intact cholecystokinin to its COOH-terminal dodecapeptide and octapeptide also cleave the synthetic dipeptides Arg-Ile (or Arg-Val or Arg-Leu) and Arg-Asp, respectively. Thus, they are not hormone-specific enzymes but are bond-specific. Ultracentrifuge studies demonstrate that there is Arg-Ile hydrolase activity associated with a protein greater in molecular weight than gamma globulin and that both Arg-Ile and Arg-Asp hydrolase activities are associated with one or more proteins between albumin and gamma globulin in molecular weight.

Animals↗
PubMed1980

Radioimmunoassay of tuberculoprotein derived from Mycobacterium tuberculosis.

A radioimmunoassay was developed for constituent of the purified-protein derivative obtained from cultures of Mycobacterium tuberculosis. Crossreacting immunoreactive material was detected in cultures of other mycobacterial species, but no immunoreactivity was present in cultures of various fungal and bacterial species. The development of specific radioimmunoassays for tuberculoproteins offers a new research and diagnostic approach.

Antigens, Bacterial↗