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Biomedical subjects

A Caplan

Publications and source records attributed to A Caplan.

At least 37 records · Page 2Linked to original sources
PubMed1994

A group of chromosomal proteins is specifically released by spermine and loses DNA-binding activity upon phosphorylation.

Biologically relevant concentrations as low as 500 microM spermine led to the specific release of chromatin-associated proteins from nuclei of rice (Oryza sativa) seedlings. Using a southwestern technique, it was shown that several of these proteins bind DNA. This affinity was lost upon in organello phosphorylation by an endogenous kinase. The effect of spermine was very specific. Spermidine was far less effective and putrescine was essentially ineffective in releasing these proteins. The most abundant spermine-released protein was shown to be homologous to the maize HMG1 protein. Our results suggest that spermine induces the release of spermine-released proteins by changing DNA conformation. Binding of these proteins might be sensitive to long-range changes in chromosome structure caused by torsional stress.

Adenosine Triphosphate↗
PubMed1993

Immunoglobulin G binding sites on the human foetal intestine: a possible mechanism for the passive transfer of immunity from mother to infant.

In humans, the prenatal transfer of IgG from mother to foetus is facilitated by a receptor for IgG on the placenta. However, amniotic fluid contains IgG of maternal origin, and transfer of swallowed IgG into the circulation from the foetal intestine represents another potential pathway of passive immunization. In this study we assayed for a foetal intestinal IgG receptor to support the hypothesis of this alternate pathway of antibody transfer. Microvillous membrane (MVM) from small bowel of aborted foetuses (18 weeks gestation) were probed with [125I]IgG to detect specific IgG binding sites. Binding was pH dependent and was maximal at pH 6. Competitive inhibition of the binding of [125I]IgG was noted with the addition of increasing amounts of unlabelled IgG. Scatchard analysis showed one binding site with a dissociation constant of 1.58 x 10(-7), similar to that of the IgG receptor described on the suckling rat intestine. The binding of labelled IgG to the human MVM receptor was Fc mediated. These observations provide evidence for an Fc receptor on the human foetal intestine.

Binding Sites↗
PubMed1992

A semiquantitative scale for histologic grading of articular cartilage repair.

This laboratory has developed a semiquantitative scale for grading the natural healing process of defects drilled into articular cartilage. The scale is composed of four parameters: percent filling of the defect, reconstitution of the osteochondral junction, matrix staining and cell morphology; it has a score range from 0 (best) to 14 (worst). The scale was used to evaluate the healing of defects drilled into rabbit knee articular cartilage at 2, 14, 30, 60 and 120 days after surgery. No statistically significant difference in the graded score was found between the two different defect sizes (2.7 and 1.5 mm). However, the differences in score observed between specimens from different sacrifice times were significant (p less than 0.01). Currently many investigators are manipulating cartilaginous lesions in an attempt to improve healing, and this scale will provide a means for quantitatively comparing results from control and experimental groups.

Animals↗