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Biomedical subjects

R A Berg

Publications and source records attributed to R A Berg.

At least 181 records · Page 10Linked to original sources
PubMed1979

Congenital vs acquired deafness: differences in reading and mathematics levels.

Measures of reading ability and math skills were taken in 22 adults who were either congenitally deaf or had acquired deafness in the second or third year of life. Both groups were equivalent with respect to I.Q., education level and degree of loss. The following tests were administered: (1) the performance scale of the Weschler Adult Intelligence Scale, (2) the math section of the Wide Range Achievement Test, (3) the Reading Comprehension subtest of the Peabody Individual Achievement Test, and (4) the Raven Test of Progressive Matrices. There were no significant differences between the two groups on reading level, but a significantly higher math level was found in the congenital group. It was suggested that the pathology in the acquired group may have affected other neural centers in addition to the auditory, or that the acquired group may have been handicapped by the possibility of switching from one coding system (auditory) to another (visual), while in the congenital group the coding remained confined to the visual mode.

Achievement↗
PubMed1977

Kinetics for the secretion of procollagen by freshly isolated tendon cells.

Fibroblasts isolated by enzymic digestion of chick embryo tendons were incubated for several hours in suspension under conditions in which they were in steady state in terms of the synthesis and secretion of procollagen. Under these conditions, the cells synthesized and secreted about 630 microgram of procollagen/10(9) cells/h. The cells were labeled with [14C]proline for 15 to 120 min and then the kinetics of secretion were followed by chasing the label and assaying the 14C-peptides digestible by collagenase in the cells and in the medium. The results demonstrated that secretion of collagenase-digestible peptides did not follow the kinetics of a single first order process but suggested at least two pseudo-first order process with half-times of 14 and 115 min. The [14C]procollagen secreted during 0 to 30 min and 90 to 120 min of chase was the same in terms of the ratio of pro-alpha1 to pro-alpha2 chains, the size of the pro-alpha chains, the extent of interchain disulfide bonding, the extent of prolyl hydroxylation, and the degree of helicity as tested by resistance to pepsin digestion. Addition of ascorbic acid to the incubation medium increased slightly the extent of prolyl hydroxylation but did not alter the kinetics of secretion. The results suggested that the kinetics of secretion are influenced by a two-compartment system in which at least one metabolic pool contributing to the secretory process is present as a "side pocket."

Animals↗
PubMed1977

Hydroxylation of (Pro-Pro-Gly)5 and (Pro-Pro-Gly)10 by prolyl hydroxylase. Evidence for an asymmetric active site in the enzyme.

Previous studies with 14C-labeled synthetic peptides demonstrated that prolyl hydroxylase, which synthesizes the hydroxyproline in collagen, preferentially hydroxylates the fourth triplet from the NH-terminal end of the peptide (Pro-Pro-Gly)5. In the experiments reported here, the prolyl hydroxylase reaction was investigated further by preparing chemically modified derivatives of (Pro-Pro-Gly)5 and by synthesizing 14C-labeled preparations of (Pro-Pro-Gly)10. Essentially, the same kcat value was found for the hydroxylation of (Pro-Pro-Gly)5, N-acetyl-(Pro-Pro-Gly)5, (Pro-Pro-Gly)5 methyl ester, (Pro-Pro-Gly)10, and for larger polypeptide substrates of the enzyme. It appeared therefore that preferential hydroxylation of specific triplets in peptides of the structure (Pro-Pro-Gly)n cannot be explained by differences in the kinetic constants for individual triplets. Hydroxylation of 14C-labeled preparations of (Pro-Pro-Gly)10 demonstrated that the ninth triplet was preferentially hydroxylated over any other triplet. The results were best explained by the hypothesis that prolyl hydroxylase has an asymmetric active site in which binding subsites are located adjacent to but not symmetrical with the catalytic subsite.

Amino Acid Sequence↗
PubMed1977

The clinical value of pediatric herniography.

We review the herniography experience at a community hospital. Twenty-nine patients, aged 4 weeks to 6 years, were examined. Herniography was most often helpful (25 of 29 patients) in determining the need for exploration of the clinically normal side in the patient with a unilateral hernia. By herniography, patients with a right inguinal hernia were found to have a left sac in 47% of cases; whereas with a clinical left inguinal hernia, the incidence of right sacs was 67%. Herniography was also useful (four of 29 patients) as a diagnostic aid in children with a history of hernia but inconclusive physical findings. In all patients explored, the roentgenographic findings were confirmed at surgery.

Child↗
PubMed1975

Ascorbate increases the synthesis of procollagen hydroxyproline by cultured fibroblasts from chick embryo tendons without activation of prolyl hydroxyla.

An improved procedure was developed to extract prolyl hydroxylase from tendon cells of chick embryos with detergent, and improved assays were developed for both the activity of the enzyme and the amount of enzyme protein. Freshly isolated tendon cells were found to contain approx. 100 mug of enzyme protein per 10(8) cells and 40-50% of the enzyme protein was active. When the cells were cultured, they were found to contain the same amount of enzyme protein but only 15-20% of the enzyme protein was active. Gel filtration of cell extracts indicated that the active form of prolyl hydroxylase in freshly isolated tendon cells and incultured tendon cells had the same apparent size and the same activity per mug of immunoreactive protein as enzyme which was shown to be a tetramer. The inactive form was found to have about the same apparent size as subunits of the enzyme. When freshly isolated cells were incubated for 2 h in the presence of 40 mug per ml of ascorbate, there was a slight increase in the rate of hydroxyproline synthesis. In cultured cells, ascorbate at a concentration of 40 mug per ml caused a 2-fold increase in the rate of hydroxyproline synthesis within 30 min. However, ascorbate did not icrease the activity of prolyl hydroxylase in extracts from either cell system. Therefore it appears that the influence of ascorbate on synthesis of procollagen hydroxyproline by the cells studied here must be ascribed to a cofactor effect on the hydroxylation reaction similar to that observed with purified enzyme, and it does not involve "activation" of inactive enzyme protein to active enzyme as has been observed in cultures of L-929 and 3T6 mouse fibroblasts.

Animals↗
PubMed1975

Two improved methods for preparing ferritin-protein conjugates for electron microscopy.

Two improved procedures were developed for activating ferritin so that the ferritin could be covalently linked to antibodies. One procedure involved use of a water-soluble carbodiimide and N-hydroxysuccinimide to prepare ferritin-containing activated esters. The other involved activation of the ferritin with excess glutaraldehyde. The ferritin-antibody conjugates prepared with the two procedures were shown to have a number of properties which made them suitable for locating antigenic components in cells.

Animals↗
PubMed1975

Further characterization of embryonic tendon fibroblasts and the use of immunoferritin techniques to study collagen biosynthesis.

Morphological studies were carried out on fibroblasts from chick embryo tendons, cells which have been used in a number of recent studies on collagen biosynthesis. The cells were relatively rich in endoplasmic reticulum and contained a well-developed Golgi complex comprised of small vesicles, stacked membranes, and large vacuoles. Techniques were then devised for preparing cell fragments which were penetrated by ferritin-antibody conjuates but which retained the essential morphological features of the cells. Finally, the new procedures were employed to develop further information as to how collagen is synthesized. As reported elsewhere, preliminary studies with ferritin-labeled antibodies showed that prolyl hydroxylase was found in the endoplasmic reticulum of freshly isolated fibroblasts and that procollagen is found in both the cisternae of the endoplasmic reticulum and the large Golgi vacuoles. In the experiments described here, the cells were manipulated so that amino acids continued to be incorporated into polypeptide chains but assembly of the molecule was not completed because hydroxylation of prolyl and lysyl residues was prevented. The results indicated that these manipulations produced no change in the distribution of prolyl hydroxylase. Examination of the cells with ferritin conjugated to antibodies which reacted with protocollagen, the unhydroxylated form of procollagen, demonstrated that protocollagen was retained in the cisternae of the endoplasmic reticulum during inhibition of the prolyl and lysyl hydroxylases. Assays for prolyl hydroxylase with an immunologic technique demonstrated that although the enzyme is found within the endoplasmic reticulum, it is not secreted along with procollagen. The observations provided further evidence for a special role for prolyl hydroxylase in the control of collagen biosynthesis.

Animals↗
PubMed1973

Collagen synthesis: localization of prolyl hydroxylase in tendon cells detected with ferritin-labeled antibodies.

An improved procedure was employed for linking ferritin to antibodies against prolyl hydroxylase, the enzyme that synthesizes the hydroxyproline in collagen. By electron microscopy, the enzyme was then found to be localized in cisternae of the rough endoplasmic reticulum of embryonic tendon cells; this indicates that hydroxylation of proline occurs while newly synthesized polypeptides are fed into the cisternae.

Animals↗