PubMed Health⌕ Search

Biomedical subjects

G Herman

Publications and source records attributed to G Herman.

At least 55 records · Page 3Linked to original sources
PubMed1983

Effects of high levels of DNA adenine methylation on methyl-directed mismatch repair in Escherichia coli.

Two methods were used in an attempt to increase the efficiency and strand selectivity of methyl-directed mismatch repair of bacteriophage lambda heteroduplexes in E. coli. Previous studies of such repair used lambda DNA that was only partially methylated as the source of methylated chains. Also, transfection was carried out in methylating strains. Either of these factors might have been responsible for the incompleteness of the strand selectivity observed previously. In the first approach to increasing strand selectivity, heteroduplexes were transfected into a host deficient in methylation, but no changes in repair frequencies were observed. In the second approach, heteroduplexes were prepared using DNA that had been highly methylated in vitro with purified DNA adenine methylase as the source of methylated chains. In heteroduplexes having a repairable cI/+ mismatch, strand selectivity was indeed enhanced. In heteroduplexes with one chain highly methylated and the complementary chain unmethylated, the frequency of repair on the unmethylated chain increased to nearly 100%. Heteroduplexes with both chains highly methylated were not repaired at a detectable frequency. Thus, chains highly methylated by DNA adenine methylase were refractory to mismatch repair by this system, regardless of the methylation of the complementary chain. These results support the hypothesis that methyl-directed mismatch repair acts to correct errors of replication, thus lowering the mutation rate.

Adenine↗
PubMed1981

A tentative explanation of the stimulatory effect of methylxanthines (pentoxifylline and isobutylmethylxanthine) on the secretory process in rat extraorbital lacrimal gland.

In the present paper we report the effect of two methylxanthines (pentoxifylline and isobutylmethylxanthine) on the protein secretion in a model of exocrine gland (rat lacrimal gland). Both compounds are able to increase the protein release. This effect is dependent on the calcium concentration gradient between the extra- and intracellular media. The larger the difference, the greater the pentoxifylline or isobutylmethylxanthine effect. Moreover, pentoxifylline and isobutylmethylxanthine can potentiate the norepinephrine or isoproterenol effect by inhibiting phosphodiesterases (even in the absence of calcium). All these data suggest pentoxifylline and isobutylmethylxanthine can act on the cell functions in two ways: (a) by a calcium-dependent mechanism, either by increasing the influx of calcium into the cell or by mobilizing the pool of intracellular calcium; (b) by a mechanism independent of calcium and dependent on a system involving cyclic nucleotides. The first possibility seems to be very attractive for further investigations of the mechanism of action of pentoxifylline and especially when this drug is used to affect the cell motility or deformability controlled by calcium.

1-Methyl-3-isobutylxanthine↗
PubMed1980

Vesicovaginal fistulas in childhood.

Six instances of childhood vesicovaginal fistulas are reviewed. Emphasis is on avoidance of such occurrences. Management should be by careful co-optation and individual closure of layers. Success was ultimately achieved in all patients.

Child↗
PubMed1979

Nondelay in vesicovaginal fistula repair.

Current attitudes toward closure of vesicovaginal fistulas have engendered a period of delay of three to six months prior to surgical closure. We believe that such delay is unwarranted, and describe our experiences with the closure of these fistulas as soon as the diagnosis is made. We consider our success to be good and therefore advocate a more direct approach to these injuries.

Adult↗
PubMed1978

Distinctive features for short-term memory of consonants in noise.

Wickelgren's (1966) short-term memory paradigm was used to investigate distinctive features of consonants in noise; 18 English consonants paired with the vowel /a/ were presented to 3 normal listeners in a CV context. Ss were tested in a quiet sound field at most comfortable listening level in experimental conditions of (1) quiet, (2) speech and noise at 0, (3) --5, and (4) --10 db S/N. Errors in auditory perception were eliminated from the data analysis and only errors in short-term memory recall were used as input to INDSCAL analysis. Results revealed that few errors were made in the quiet condition, but that all the noise conditions had deleterious effects on features.

Adult↗
PubMed1977

Normal-hearing subjects' perception of speech through one-third octave bands.

Perceptual features of consonants were investigated from normally-hearing Ss' confusions of stimuli perceived through one-third-octave bands; 12 Ss were paid to respond to CVs consisting of 17 consonants, each paired with the vowels /i, a, u/ and filtered through one-third-octave bands centered at 0.5, 1, 2, 3.15 and 4 kc/s and one critical band (500 c/s wide) centered at 3.15 kc/s. An earlier cursory analysis of distinctive features in these data (Chari, N.C.A., Herman, G. and Danhauer, J.L. "Perception of one-third octave-band filtered speech." J. Acoust. Soc. Am., 1977, 61, 576-580) showed that while place features were severely affected by the filtering, manner and voicing features were not. The data were submitted in the present study to INDSCAL for a more a-posteriori investigation of the features and their weights by the Ss. Results showed some differences in the features and their weights across the various filter bands, but that they were similar to those found earlier for hearing-impaired Ss having losses corresponding to frequency cut-offs in this study.

Adult↗
PubMed1975

Regulation of protein secretion and metabolism in rat salivary glands. Effects of norepinephrine and carbachol on the glycogenolysis in submaxillary glands.

Carbachol and norepinephrine induce glycogen breakdown in rat submaxillary glands incubated in vitro. These effects are suppressed by specific inhibitors of cholinergic receptors (atropine, a muscarinic blocker) and of adrenergic receptors (propranolol, a beta-blocker and phentolamine, an alpha-blocker). The beta-adrenergic effect seems to be mediated through the adenosine 3':5'-monophosphate system, whereas the alpha-adrenergic and cholinergic effects are dependent of Ca2+ influx into cell. In the two latter systems, it is suggested that a direct activation of phosphorylase b kinase by calcium takes place. These data clearly indicate that glycogenolysis in rat submaxillary glands in vitro can be independently affected by sympathetic and parasympathetic agents via specific receptors.

Animals↗