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Biomedical subjects

H R Gilbert

Publications and source records attributed to H R Gilbert.

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

A respirometric technique for evaluating velopharyngeal closure in children.

Respirometric quotients, indices of velopharyngeal closure, were determined from oral and nasal air volumes measured separately but simultaneously. Ten children aged 6-10 years were the subjects. The quotients were significantly lower for speech stimuli involving nasal sounds than for those involving nonnasal sounds. In contrast to the quotients obtained in previous research with children, the quotients obtained in this study were close to, but not in excess of, unity.

Child↗
PubMed1980

A fluorescent probe for conformational changes in skeletal muscle G-actin.

Actin from rabbit skeletal muscle has been modified with the fluorescent label N-iodoacetyl-N'-(5-sulfo-1-naphthyl)ethylenediamine (1,5-I-AEDANS). Under conditions where the actin is in the unpolymerized form (G-actin), the addition of Mg2+ or KCl results in enhancement of the fluorescence. Titration of the labeled G-actin with Mg2+ at varying concentrations of CaCl2 gives, by extrapolation, a value for the dissociation constant for Mg2+ of 35 microM in the absence of Ca2+ and a calculated value of 10 microM for Ca2+ in the absence of Mg2+. The two metal ions compete with each other. The fluorescence enhancement induced by Mg2+ is reversed by the addition of Ca2+ and both processes are time-dependent, indicating a reversible conformational change of G-actin as a consequence of addition of divalent metal. KCl also enhances the fluorescence of the labeled G-actin but does not appear to compete with the divalent metal ion. The enhancement of the fluorescence is very rapid and any conformational change induced by KCl is probably different from that induced by divalent metal ions. Finally, it is shown that loss of fluorescence of the labeled G-actin may be associated with inactivation of the actin.

Actins↗
PubMed1980

Speaking fundamental frequency in three groups of hearing-impaired individuals.

The purpose of the present investigation was to provide speaking fundamental frequency data for three groups: 4-6, 8-10, and 16-25-yr-old hearing-impaired individuals. The hearing-impaired children between the ages of 4 to 6 and 8 to 10 yr exhibited mean speaking fundamental frequency values that were 55 Hz and 41 Hz higher, respectively, than values obtained for normally hearing children of similar ages. Fundamental frequency values for postpubescent hearing-impaired males and females were 20 Hz and 30 Hz higher, respectively, when compared to values reported in the literature for normally hearing individuals of similar age and sex.

Adolescent↗
PubMed1979

Spectral properties of fricative consonants in children.

Twenty-one preadolescent children were asked to produce stimulus words with the fricatives /f/, /v/, /s/, /z/, /s/, and /3/ in various phonetic environments. Results indicated that the major resonances were higher than values reported for both male and female adult speakers. Also significant differences existed among the major resonances of the consonants studied.

Child↗
PubMed1978

Malate dehydrogenases. The lack of evidence for dissociation of the dimeric enzyme in kinetic analyses.

The kinetic parameters of beef heart cytoplasmic and pig heart mitochondrial malate dehydrogenases have been examined over a wide range of enzyme concentration. No significant changes are observed in these properties. In conjunction with active enzyme sedimentation and sedimentation equilibrium experiments, it is concluded that there is no evidence for dissociation of the dimeric enzyme at any enyzme level in the kinetic analyses. Thus, if dissociation occurs, it must be too slow to be of significance in determining the kinetic properties of the enzyme. It is shown that unless a subunit and its dimeric form have identical kinetic and substrate binding characteristics, the kinetic parameters should change as a function of enzyme concentration.

Animals↗
PubMed1978

Speaking fundamental frequency characteristics of institutionalized adults with Down's syndrome.

Mean speaking fundamental frequency was obtained from 16 institutionalized adults with Down's syndrome (8 males, 8 females) and from 16 nonretarded adults of similar age and sex. Both male and female adults with Down's syndrome exhibited a higher mean speaking fundamental frequency than did the nonretarded adults of the same sex. This finding does not support early reports of a characteristically low-pitched voice among Down's syndrome individuals.

Adult↗
PubMed1976

Phosphofructokinase. III. Correlation of the regulatory kinetic and molecular properties of the rabbit muscle enzyme.

It is shown that the degree of regulatory kinetic behavior of rabbit muscle phosphofructokinase increases at a given pH and lower temperatures, as well as at a given temperature and lower pH values. It is also shown that the regulatory kinetic behavior which appears at lower pH values is inherent in the tetrameric (active) form of the enzyme. We conclude that a portion of the mechanism proposed previously (Bock, P.E., and Frieden, C. (1976) J. Biol. Chem. 251, 5630-5636) to describe the pH and temperature-dependent inactivation or reactivation may also be used to explain the pH and temperature-dependent regulatory kinetic behavior. According to this proposal, two rapidly equilibrating forms of the enzyme, which differ in the degree of protonation of specific residues, differ in their ability to bind substrates. While the protonated form of the enzyme subsequently becomes inactive by isomerization and dissociation, this process is too slow to affect the kinetic results, making direct comparisons between the association-dissociation behavior and regulatory kinetic behavior invalid. The time dependence of the processes of inactivation or reactivation in the presence or absence of ligands and of the appearance of regulatory kinetic behavior is discussed in relation to their possible role in metabolic regulation.

Allosteric Regulation↗
PubMed1975

Speech characteristics of miners with black lung disease (pneumoconiosis).

Speech samples were obtained from 10 miners with diagnosed black lung disease and 10 nonminers who had never worked in a dusty environment and who had no history of respiratory diseases. Frequency, intensity and durational measures were used as a basis upon which to compare the two groups. Results indicated that four of the six pausal measures, vowel duration, vowel intensity variation and vowel perturbation differentiated the miners from the nonminers. The results indicate that black lung disease may affect not only respiratory physiology associated with speech production but also laryngeal physiology.

Humans↗
PubMed1974

Indentification of an intestinal sodium and calcium-dependent phosphatase stimulated by parathyroid hormone.

Previous reports suggest that the site of the energy-dependent intestinal calcium transport against an electropotential and concentration gradient is located along the basal-lateral membrane of the mucosal cell. Accordingly, basal-lateral membranes were prepared from rat intestinal homogenates in order to identify the enzyme mediating this step in the transport process. An alkaline phosphatase was delineated which utilized ATP as a substrate and was dependent on both Na(-) and Ca(++) with optimum enzyme activity at 200 mM and 0.04 mM, respectively. Furthermore, the activity of the enzyme was demonstrated to decrease with the advance in age of the animal and to decrease with removal of the parathyroid glands, consistent with a decreased rate of (45)Ca release from mucosal cells under the same experimental conditions. Calcium binding to basal-lateral membrane fragments was also sodium dependent and enhanced by the prior administration of parathyroid extract. The consistent correlation between the rate of calcium transport across the basal-lateral membrane of the mucosal cell and the activity of this Na, Ca-dependent phosphatase under a variety of experimental conditions suggest that this enzyme may mediate the parathyroid hormone-sensitive active transport of calcium across the intestine.

Adenosine Triphosphate↗