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Biomedical subjects

J Gross

Publications and source records attributed to J Gross.

At least 307 records · Page 17Linked to original sources
PubMed1983

A simple method for the approximation of the behaviour of marker constituents in density-fractionated red blood cells by means of normalized cumulative distribution functions.

The present paper proposes a mathematical approach for the approximation of the relation between the concentration (or activity) of a cell constituent and the cumulative red cell distribution after density gradient centrifugation by means of normalized cumulative distribution functions (NCDF). With only one parameter (easily obtained on a programmable pocket calculator) and the mean concentration of the substance in the total red cell population this functional relation can be described in good approximation. The goodness of fit expressed by v2 (= square of correlation coefficient) to the experimentally obtained data is demonstrated for the cell constituents creatine (v2 = 0.85-0.97), RNA (v2 = 0.82-0.87) and G-6PD (v2 = 0.60-0.95). The method of NCDF is shown to be superior to an exponential function. It permits the estimation of a concentration (or activity) of a cell constituent for any chosen density-fractionated cell portion and thus gives information on the ratio of standardized portions of young: old cells.

Cell Separation↗
PubMed1983

[Sectoring of a university clinic].

UNLABELLED: In 1980 the psychiatric clinic of the University of Hamburg took charge of a catchment area within the city of Hamburg. From this year on the clinic decided to provide half of its in-patient and day clinic capacity (that is 71 beds and 10 day clinic places) for a population of 139,000 living in this region. The effects of this decision are discussed on three levels: - changes in the patient population - opinions and attitudes of the clinic personnel - implications for the organizational structure RESULTS: The proportion of in-patients from the catchment area increased from 20% to 45% due to the clinic taking charge of this region. This increase did not much change the characteristics of the total in-patient population admitted to the clinic, except for a shift towards more older patients and more patients with a diagnosis of dementia or organic psychosis. Around two thirds of the clinic personnel held a predominantly positive view of the clinic's decision to establish a catchment area. Contrary to some hopes the internal structure of the clinic did not change much in response to its newly acquired responsibility for the catchment area. Nevertheless a period of one year seems too short for such changes to occur.

Academic Medical Centers↗
PubMed1983

Dopamine release from striatum slices of rats at different age: influence of hypoxia.

During the maturation and aging of rats the dopamine release from striatum slices shows different dynamics in dependence on the stimuli used. Electrically evoked release is very constant. Amphetamine induced release is fully developed at the age of day 14 and declines after 9 months. The K+ stimulated release develops to a maximum at 10 weeks and decreases thereafter. The stimulus and age dependent inhibition of dopamine release after an 18 h hypoxic exposure may be the result of peroxidative reactions of membranous phospholipid components induced by free radicals. Adult rats exposed to a 200 h hypoxia reveal no change in dopamine release after the last exposure probably in consequence of adaptive processes of physiological protection, among other things, by scavenging of free radicals. Adult rats exposed to long term hypoxia postnatally during the growth spurt period of neuronal structures show an increased dopamine release and no posthypoxic release inhibition. Our data indicate that different mechanisms are operative during hypoxia in animals of different age.

Aging↗
PubMed1982

Separation and characterization of red blood cells from newborns and infants during the first trimenon of life using a dextran density gradient: mean cellular volume and mean cellular haemoglobin concentration.

The adaptation of cell physiological parameters of erythrocytes of the newborn to erythrocytes in later life was studied by cell separation in an isopycnic dextran density gradient. The cell characteristics during the first trimester of life were followed by repeated determinations. The mean cellular haemoglobin concentration of the lightest cells is remarkably less than that of the cells of median density. This is probably due to the ongoing synthesis of haemoglobin in reticulocytes, which are highly concentrated in the top fractions. It was shown that the young cells released from the bone marrow become progressively smaller during this period with a decrease of mean cellular volume (MCV) from 104 micrometer3 at birth to 85 micrometer3 at the end of the first trimester. It has been established that this process commences during the first week of life. No difference concerning the alterations of cell parameters, especially MCV, in premature and mature infants was found. It is therefore probable that these alterations are due to changes in the external milieu following birth.

Cell Separation↗
PubMed1982

Familial hyperthyroidism due to inappropriate thyrotropin secretion successfully treated with triiodothyronine.

A family of three generations is described in which six females had hyperthyroidism secondary to chronic overstimulation of the thyroid by pituitary TSH. In the untreated state, their basal levels of T4 ranged between 14-22 microgram/dl, T3 levels ranged from 205-300 ng/dl, T3 resin uptake ranged from 43-61%, TSH ranged from 5-26 microU/ml, and PRL ranged from 33-75 ng/ml. Basal metabolic rate (BMR) was elevated in all patients (+32 to +100%). There was no evidence of pituitary tumor, In spite of elevated circulating thyroid hormones, TRH stimulated TSH and PRL to 25-57 microU/ml and 120-300 ng/ml, respectively. Serum TSH could be suppressed to normal after 1 week of T3 administration (25 microgram three times per day). Concomitantly, serum T3 and T4 levels fell, and the TSH response to TRH became normal. In contrast, T4 (200 microgram/day) administered for 1 and 4 weeks, respectively, to two patients did not suppress the pituitary-thyroidal axis. A long term therapeutic trial was performed in three patients with T3 and a single morning dose of 25-50 microgram. TSH gradually returned to normal, as did thyroid hormone levels and the BMR. The clinical manifestations of hyperthyroidism regressed, and complete remission was achieved after 2-3 months of T3 therapy, which persists to data as long as medication is continued. The inappropriate TSH secretion of our patients appears to be due to partial unresponsiveness of the thyrotroph to thyroid hormone. It is suggested that either the pituitary T4 monodeiodinase is deficient in our patients, resulting in low intracellular T3 levels, or the thyrotroph has reduced sensitivity to T3 and therefore can shut off TSH only when serum T3 is raised to high levels, albeit intermittently.

Adolescent↗
PubMed1982

Hypoxanthine levels in amniotic fluid: an indicator of fetal hypoxia?

During hypoxia there is an increased formation of hypoxanthine from the consumption of ATP; simultaneously the oxidation into uric acid is decreased. The purpose of this study was to determine possible correlations between hypoxanthine concentrations in the amniotic fluid and states of fetal hypoxia. We obtained 83 amniotic fluid samples from 68 patients during pregnancy or delivery. Hypoxanthine was assayed fluorimetrically according to GARDINER [4]. In the course of pregnancy, hypoxanthine levels in the amniotic fluid rise slightly. A marked increase occurs during delivery (without labor mean = 3.4 +/- 0.9 mumol/l, with labor mean = 7.0 +/- 5.4 mumol/l, p less than 0.02). There is no significant difference in the levels obtained from the first and second stages of labor. In intrauterine fetal death (Fig. 1) and in depressed newborns (Tab. I) there were increased hypoxanthine levels in the amniotic fluid, this was not seen in other complications of pregnancy. Independently from the fetal state increased hypoxanthine concentrations may occur in the amniotic fluid evidently as a consequence of labor activity. Thus the determination of hypoxanthine levels in the amniotic fluid cannot be used for the diagnosis of fetal hypoxia.

Adenosine Triphosphate↗
PubMed1982

Human corneal stroma contains three distinct collagens.

Acetic acid-pepsin extracts of normal human corneal stromas were shown by carboxymethyl cellulose-column chromatography, sodium dodecyl sulfate-slab gel electrophoresis, highly purified collagenase, trypsin sensitivity, and cyanogen bromide peptide mapping to contain types I, III, and IV collagen, with type I by far the predominant species. This degree of collagen heterogeneity in normal human corneal stroma has not been reported previously and may be important in the understanding of wound healing and disease states.

Adolescent↗
PubMed1982

Collagenolytic activity of rabbit V2 carcinoma implanted in the nude mouse.

The relative contribution of host cells and tumor cells to the production of collagenase and its regulation during tumorigenesis were studied with the use of a heterologous rabbit tumor-nude mouse host system. The V2 carcinoma, a malignant neoplasm of the New Zealand White rabbit, behaved as a nonmetastasizing, noninvasive tumor when implanted and grown in the inbred Swiss albino nude mouse. The extracts from both tumors contained similar levels of collagenase. Tumor explants also released enzyme into culture medium in both cases, but the rabbit tumor produced approximately 10 times more collagenase than the nude mouse. Freeze-thawing of the explants or treatment with cycloheximide markedly inhibited the appearance of enzyme in the medium from the rabbit tumor but not from the nude mouse tumor. The relative proportions of mouse- and rabbit-derived collagenase in the nude mouse tumor extracts and culture medium were determined with the use of antibodies specific for rabbit V2 tumor and mouse bone collagenases. Approximately 70% of the nude mouse tumor enzyme was derived from the rabbit tumor, and approximately 30% was derived from the mouse host. These findings indicate that the former might represent stored enzyme carried over during tumor transplantation into the nude mouse, whereas the latter might have originated from stimulation of host cells during tumorigenesis.

Animals↗