Ascorbate-like factor from embryonic brain. Role in collagen formation, basement membrane deposition, and acetylcholine receptor aggregation by muscle cells.
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Animals↗
Biomedical subjects
E Bachar
Publications and source records attributed to E Bachar.
Ciliary ganglia and spinal cord explants release an ascorbate-like compound which stimulates proline hydroxylation and collagen formation in muscle cultures.
A low-molecular-weight factor from embryonic rat brain stimulates collagen production in rat muscle cultures. This effect is associated with increased hydroxylation of proline residues in collagenous proteins produced by the cells. Here, we show that increased hydroxylation (22-and 7.5-fold) was also observed with extracts of rat embryonic spinal cord and extracts of the rat pheochromocytoma cell line PC12. A 5-25-fold stimulation in proline hydroxylation was obtained when muscle cells were cocultured with chick ciliary ganglia or with embryonic rat spinal cord explants. Medium conditioned by rat spinal cord explants also increased prolyl hydroxylation. Incubation of the muscle-nerve cocultures with ascorbate oxidase markedly reduced the observed increase in proline hydroxylation. These results show that the cultured explants release a factor which promotes proline hydroxylation and collagen production by muscle. This factor seems to be ascorbic acid or an ascorbate-like compound.
Animals↗
Collagen-stimulating factor from embryonic brain has ascorbate-like activity and stimulates prolyl hydroxylation in cultured muscle cells.
Embryonic rat-brain extract contains a collagen-stimulating factor which enhances the production of collagen types I, III, IV and V by cultured rat muscle cells. Here we report on the partial characterization and possible mechanism of action of a low-molecular-mass fraction with ascorbate-like activity isolated from embryonic rat brain extracts. This activity eluted very close to ascorbate when filtered through Bio-Gel P-2 and Sephadex G-10. The peak of biological activity showed properties of a reducing agent. Both the biological and reducing activities were lost when the fraction was treated with the enzyme ascorbate oxidase. This factor enhanced in a time-dependent manner, the secretion of procollagen, pulse-labeled with [3H] proline. Incubation of the muscle cultures with the factor increased by 15-fold the ratio of hydroxyproline to proline residues in secreted macromolecules over controls. A fourfold increase in the above ratio was obtained for the cellular proteins. Crude homogenates from control and factor-stimulated cultures were tested for prolyl hydroxylase activity using [3H](Pro-Gly-Pro)n as a substrate. Cultures treated with the collagen-stimulating factor showed a 5-50-fold increase in prolyl hydroxylation activity compared to controls. No effect on prolyl hydroxylation was found when the factor was added in vitro to either control or stimulated enzyme preparations. Our results suggest that the collagen-stimulating factor contains ascorbate-like activity which promotes the secretion of collagenous proteins by increasing hydroxylation of proline residues in their polypeptide backbone.
Animals↗
Protection of enkephalins from enzymatic degradation utilizing selective metal-chelating inhibitors.
Metal ion-chelating agents inhibited enkephalin degradation by a rat striatal membrane-associated endopeptidase termed 'enkephalinase'. The combination of a hydrophobic dipeptidyl moiety and a transition metal-chelating moiety in the same molecule resulted in very efficient and selective inhibitors of enkephalinase. The mercaptoacetyl dipeptides (2-mercaptoacetyl-Leu-Phe and 2-mercaptoacetyl-Phe-Leu) and the N-phosphorylated dipeptides (phosphoryl-Leu-Phe and phosphoramidon) inhibited enkephalinase with IC50 values of 15, 70, 0.3 and 1 nM respectively, but were much less potent against the aminopeptidase and angiotensin converting enzyme, two other metalloenzymes implicated in the degradation of the enkephalins in brain. The inhibition of enkephalinase, using phosphoryl-Leu-Phe as a selective inhibitor, resulted in a 4 fold increase in the amount of enkephalin recovered following K+ depolarization of rat striatal slices.
Aminopeptidases↗
Validity of students' ratings of clinical instructors.
The validity of students' rating of clinical instruction was correlated with students' performance in a clinical examination. One-way analysis of variance showed that the students' ratings discriminated among instructors, and that the instructors were a significant source of variance in their students' adjusted examination scores on a written clinical simulation. There was no significant correlation between students' performance in the examinations and their ratings of the clinical instructors.
Clinical Competence↗
Orientation towards freedom in normals, psychotics and psychosomatic patients.
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Adult↗
Multiple regression analysis predictor models in exotropia surgery.
We developed a statistical model based on multiple regression analysis from a sample population of 30 patients with intermittent exotropia who underwent bilateral recession of the lateral recti muscles. We also identified predictor variables, which accounted for most of the change in deviation per millimeter of surgery performed. The application of multiple regression analysis to the problem of exotropia may be limited by variation in predictor variables according to sample population, multicollinearity, measurement unreliability, and the unproven assumption that the preoperative calculation of effect per millimeter correlates well with postoperative clinical success. Controlled clinical trials are needed to determine the value of multiple regression analysis in exotropia surgery. Discriminant analysis may represent an alternative statistical technique with application to this particular problem.
Humans↗
Penetrating keratoplasty in Lesotho.
Sixty-four Basotho patients underwent therapeutic penetrating keratoplasty in Lesotho, a developing African nation. The overall long-term success rate of 60.7% was comparable to similar series in developed countries. Analysis of variables found to significantly affect graft outcome included size of graft, anterior segment pathology, postoperative iris adhesion to graft wound, and onset of graft rejection during hospitalization or after discharge. McCarey-Kaufman medium was found to be highly successful for corneal storage up to seven days, and corneal transplantation across racial lines was not associated with increased immune rejection reactions.
Adolescent↗
[Factors affecting performance in Israel specialty board examinations].
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Certification↗
Comparative study of Hebrew University-Hadassah Medical School participation in education council ofr foreign medical graduates (ECFMG) examination.
The achievements of the 874 (55%) medical graduates of Hebrew University-Hadassah School who took the ECFMG examination from 1962, when it was introduced in Israel, to 1972, were compared with those of candidates from other schools during the same period. The achievement level of candidates was high: usually above the 90th percentile rank position; 80 to 85% of its candidates passed the examination (compared to about 40% from all other schools); and the frequency distribution of ECFMG examination scores of HUHMS candidates in 1965 revelas a similarity to the achievements in American medical schools. The difference between the percentage of candidates passing the ECFMG examination from year to year supports the contention that the level of difficulty of the examinations varies. Candidates taking the examination after several years of clinical experience do not perform better. Since only 19% of all HUHMS graduates have gone abroad for postgraduate training, and only 11% have remained abroad for 4 or more consecutive years, participation in ECFMG has not been reflected in an increase in 'brain drain'.
Curriculum↗
The impact of parental death versus separation from parents on the mental health of Israeli adolescents.
Early research suggested that the loss of a parent during childhood can lead to depression and other psychopathology in children and adults. More recent research has differentiated between loss due to death and separation from parents and has questioned the link between early parental death and psychopathology. We examined the hypothesis that separation from parents has a more detrimental effect than the death of a parent on the mental health of adolescents in the community. Israeli adolescents (N = 844) with a mean age of 16.7 +/- 1.0 years (mean +/- SD) participated in this study. Seventy reported that a parent did not live at home during one of three 5-year periods until they reached the age of 15; 37 reported the death of a parent and 777 were from intact families. All participants completed the Brief Symptom Inventory (BSI), General Well Being Schedule (GWB), Parental Bonding Instrument (PBI), and Perceived Social Support Family/ Friends Scales (PSS-Fam and PSS-Fr). Adolescents who had experienced separation from parents had more psychiatric symptoms (BSI), expressed a lower sense of well-being (GWB), experienced less support from their family (PSS-Fam), and felt less cared for and more controlled by their parents (PBI) compared with those belonging to intact families. The death of a parent was not associated with significantly different scores on these variables. When we controlled for parental bonding (PBI) and perceived social support from family (PSS-Fam), the differences between the separation group and the intact family group were no longer significant. The psychological impact of separation from parents involves a greater risk for psychopathology than the death of a parent. The quality of the relationship with the parents moderates the negative impact of separation from them.
Adolescent↗