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Biomedical subjects

B J Johnson

Publications and source records attributed to B J Johnson.

14 recordsLinked to original sources
PubMed1979

Utilization of a radioiodinated bile salt for kinetic studies and hepatic scintigraphy. Studies in nonhuman mammals.

An 125I- or 131I-labeled bile salt derivative, cholylglycyliodohistamine, has been synthesized and purified. The bile salt derivative is rapidly cleared from the circulation when injected intravenously into rats and rabbits. Ten minutes after injection, approximately 50% of the recovered bile salt derivative was in the jejunum and ileum, and 36% was found in the liver. Sixty minutes after injection, 99% of the recovered radioactivity was found in the luminal gastrointestinal tract. The isotope was cleared from the circulation of rabbits with a t1/2 of approximately 2 min. Hepatic scintigraphy using rabbits demonstrated rapid uptake by the liver and excretion into the intestine. Quantitative analysis of scintigraphy showed an uptake rate of 14%/min and a subsequent excretory rate of 4.6/min.

Animals↗
PubMed1978

Mobilization of colonic kallikrein following pelvic nerve stimulation in the atropinized cat.

1. Pelvic nerve stimulation (p.n.s.) in cats induces atropine-resistant colonic vasodilatation and colonic contraction. The effects of this on cat colon are mimicked by synthetic bradykinin infusions. The present study examines the effect of p.n.s. on the activation of kallikrein, the kinin-forming enzyme present in colonic tissue and its effects on the plasma kinin system in the atropinized cat.2. Mean level (+/- S.D.) of mucosal kallikrein was found to be about 37 times higher in unstimulated colonic mucosa (300 +/- 100 ng bradykinin equivalents min(-1)g(-1)) than in the underlying muscle (8.2 +/- 6.3 ng bradykinin equiv min(-1)g(-1)).3. After a p.n.s. of 5 min, mean kallikrein level in colonic muscle was 7.3 +/- 3.5 ng bradykinin equiv min(-1)g(-1), which was not significantly different from the control muscle kallikrein. However, there was an 86% fall in mucosal kallikrein to 41.3 +/- 34.7 ng bradykinin equiv min(-1)g(-1) after 5 min p.n.s., indicating a rapid activation and secretion of mucosal kallikrein.4. Secretion of mucosal kallikrein was paralleled by specific depletion of plasma kininogen, the precursor of active kinin in blood draining the colon. The mean plasma kininogen level fell to 79 and 68% of the prestimulated value (3.1 +/- 1.1 S.D. mug bradykinin equiv per ml. plasma) after 5 and 10 min p.n.s. respectively. Total plasma protein and haematocrit remained unaltered excluding non-specific changes due to protein extravasation or haemodilution and indicating utilization of the plasma kinin precursor.5. Following 2 hr p.n.s., raised levels of kallikrein were detected in both colonic muscle (28 +/- 2.0 bradykinin equiv min(-1)g(-1)) and mucosa 434 +/- 118 ng bradykinin equiv min(-1)g(-1)). Preliminary studies using a kallikrein inhibitor indicated that the increased kallikrein levels originated from plasma.6. Direct stimulation of the parasympathetic pelvic nerve in the atropinized cat thus produced activation of the plasma kinin system in the colon and formation of free kinins may be responsible for the mucosal vasodilatation and strong motor contraction which is not blocked by large doses of atropine. The observation that prolonged stimulation causes extravasation of plasma kallikrein, a potential inflammatory mediator, into the tissues may be of clinical significance.

Animals↗
PubMed1977

Complement fixing site of human IgG1.

A number of chemical modifications were made to purified human IgG1. The effects of these modifications on the complement activity of the immunoglobulin were studied using aggregation on latex and measuring the consumption of the complement by CH50-quantitation. Tryptophan and tyrosine are implicated in the complement fixing site of this human immunoglobulin, and an arginine moiety probably provides a binding site for the complement.

Adsorption↗
PubMed1977

Lipid-protein interactions: detergent binding to L-glutamic acid dehydrogenase.

A nonionic detergent was found to bind to the enzyme L-glutamic acid dehydrogenase [L-glutamate:nicotinamide adenine dinucleotide phosphate oxidoreductase (deaminating) EC 1.4.1.3]. The amount bound was 17 moles of detergent/mole of enzyme, which, however, was not sufficient for the enzyme to be included in a detergent micelle.

Chromatography, Gel↗
PubMed1977

Interrelation between two anticomplement cobra venom factors isolated from crude Naja naja cobra venom.

Two moieties occurring in crude Naja naja cobra venom were found to possess anticomplement activity. Both materials possessed similar molecular weights and specific activities but dissimilar elution profiles upon ion-exchange chromatography. The anticomplement activities of these materials were maintained upon digestion with neuraminidase, and their elution profiles from cation-exchange chromatography became identical after this treatment. It was concluded that the differences between the two anticomplement materials were due to their different sialic acid contents.

Animals↗
PubMed1977

An 125I radioimmunoassay for primary conjugated bile salts.

Cholylglycylhistamine, a derivative of cholic acid, has been synthesized and characterized. This derivative has been iodinated using Na125I and chloramine-T and purified free from unlabeled cholylglycylhistamine. Application of this iodinated bile salt derivative to radioimmunoassay of bile salts in human serum is reported. Antibody titers have uniformly increased over titers used in tritium-based assays; some antibodies are usable in dilutions of 1:80,000. The radioimmunoassay described here was found to measure predominantly the primary conjugated bile salts. Sensitivity has been maintained, with the least detectable amount being 0.5 pmoles per assay tube. Normal values in human serum are 3.47 +/- 2.16 (SD) nmoles per ml.

Animals↗
PubMed1976

Lipid-protein interactions: enhancement of enzyme activity of L-glutamic acid dehydrogenase by nonionic detergents.

Five nonionic detergents enhanced the activity of L-glutamic acid dehydrogenase [L-glutamate:nicotinamide adenine dinucleotide phosphate oxidoreductase (deaminating) (EC 1.4.1.3)]. These detergents activated the enzyme toward alpha-ketoglutaric acid reduction, causing a decrease in the sensitivity of the enzyme to allosteric regulation by guanosine 5-triphosphate. There was also a diminution of the enhancing effect of the modifier adenosine 5-diphosphate on the enzyme's L-glutamic acid dehydrogenase activity. These detergents may cause a conformational change in the enzyme, and this change could lead to an increase in the binding of the substrates for the alpha-ketoglutaric acid reduction. Accompanied with this conformational change would be a decrease in the binding of the modifier guanosine 5'-triphosphate, with no concomitant change in the binding of the adenosine 5'-diphosphate modifier.

Adenosine Diphosphate↗
PubMed1976

Investigations of the complement-fixing sites of immunoglobulins.

Indirect evidence for the complement-fixing site of human IgG1 has been found by using chemical modification of the immunoglobulin. These results implicate the amino acid residues, tryptophan, tyrosine, and arginine. Furthermore, by the use of synthetic peptides it has been shown that the area surrounding the tryptophan and tyrosine at positions 277 and 278 probably constitutes the locus of the complement-fixing site of human IgG1. By analogy, the tryptophan at position 488 of human IgM is implicated in the complement-fixing site of this immunoglobulin. Evidence for this is presented by a peptide which mimics the sequence 487-491 of human IgM and possesses the ability to consume complement. The relative complement-fixing ability of this peptide is 200 times less effective than human IgG1.

Amino Acid Sequence↗
PubMed1976

Studies on the antigenic determinants of the Thy-1.2 alloantigen as expressed by the murine lymphoblastoid line S-49.1 TB-2-3.

Sialic acid has been shown to be part of the antigenic determinant of the Thy-1.2 alloantigen as expressed by the murine cell line S-49.1 TB-2-3 (S-49). This conclusion is based on the loss of cytotoxic inhibitory activity by the action of neuraminidase on the Thy-1.2 alloantigen. Also, sialic acid has the ability to inhibit the cytotoxic assay of AKR anti-C3H Thy-1.2 serum for S-49 cells. Further evidence for the protein nature of the Thy-1.2 alloantigen is apparent by trypsin digestion. Possibly the Thy-1.2 alloantigen as expressed on S-49 cells is a glycoprotein.

Animals↗
PubMed1975

The protein nature of the Thy-1.2 alloantigen as expressed by the murin lymphoblastoid line S-49.1 TB-2-3.

This preliminary study was undertaken to investigate the chemical nature of the Thy-1.2 antigen expressed on the murine cell line S-49.1 TB-2-3 (S-49). The presence of the Thy-1.2 antigen was indicated by the inhibition of AKR anti-C3-Thy-1.2 serum induced lysis of 51Cr-primed target cells. It was found that limited digestion of S-49 cells with crude papain yielded a Thy-1.2-containing solution. The protein nature of the Thy-1.2 antigen obtained in this manner was indicated by changes after proteolytic digestion. Separate digestions with crystalline papain, insolubilized papain, and insolubilized protease all destroyed the Thy-1.2 activity. These results suggest that the protein moiety is necessary for Thy-1.2 activity.

Absorption↗