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Biomedical subjects

J Gross

Publications and source records attributed to J Gross.

At least 325 records · Page 18Linked to original sources
PubMed1982

[Relation between the density and maturity of red blood cells in the perinatal period in the rat].

Relations between 59Fe incorporation into red blood cells (rbc) and their density was examined in rats during ontogenesis (20th, 21st, 22nd gestational day, 1st, 21st day of life, adults). The incorporation of 59Fe in rbc of different density was measured 24 or 96 h after application. The density separation was carried out by centrifugation of rbc in phthalate esters of known density. The density of rbc increased during ontogenesis (median density 1.093 kg/l on the 20th gestational day and 1.102 kg/l in adult rats). The erythropoietic activity, in terms of 59Fe-incorporation into peripheral rbc, is higher in newborn rats (60-70%) than in adults (30-50%). 59Fe incorporation into pregnant rats and their fetuses is similar to adult nonpregnant rats. In fetuses a relatively high incorporation of 59Fe was found in comparison to their mother. The relationship between density and maturity of rbc is postnatally more evident than in the prenatal period. (59Fe enrichment in cells of low density prenatally: 2.6 +/- 0.5, postnatally: 8.4 +/- 0.5 (1st day of life), 5.8 +/- 0.8 (21st day of life) 28.5 +/- 5.6 (adult male rats). These findings may reflect a simultaneous formation of rbc at different sites or different clonal origin during prenatal period of ontogenesis.

Age Factors↗
PubMed1982

[Effect of hypoxia on the relationship of density and maturity of erythrocytes of newborn, young and adult rats].

Adult male, juvenile and pregnant rats were exposed to repeated hypoxia 8 h daily for 3-9 days in a low pressure chamber (altitude of 5000 m, pO2 = 11.3 kPa and 6000 m, respectively, pO2 = 9.89 kPa). The density distribution curves of the red blood cells (RBC) and the incorporation of 59Fe into cells of different density were determined. In the ontogenesis the density of RBC increases (median density on the first day of life 1.100 kg/l; on the 21st day of life 1.102 kg/l, adult rats 1.103 kg/l). The density difference between the 1st and 4th quartile in which 50% of the cells range was 0.010 kg/l for newborn and juvenile animals and 0.004 kg/l for adult ones. Exposure to hypoxia led iN the animals of the investigated age groups to a rise of the proporborns, 0.004 for juveniles, and 0.002 kg/l for adult rats. The cumulative distribution curves of 59Fe incorporation and density of RBC can be described by the equation (formula: see text). The value alpha characterizes the relation between density, on the one hand, and the maturity and age of cells, on the other. For control and hypoxic animals the following values for alpha have been calculated: for newborns 0.515 and 0.520, for juveniles 0.829 and 0.596 (p less than or equal to 0.01), and for adult rats 0.875 and 0.823. Juvenile animals from in regard to density similar heterogenic cells as newborns after hypoxia. It may be that ontogenetically older cell forming sites or clones are reactivated.

Aging↗
PubMed1981

Self assembly of mixtures of collagen alpha-chains.

As part of an effort to understand the mechanism of assembly of collagen polypeptide chains into triple-helical rod shaped molecules, we have assessed the role of the proportions of alpha 1 to alpha 2 chains in the starting solutions in determining the compositions of renatured collagen. Solutions of different ratios of alpha 1 and alpha 2 chains, one of which was labelled with [14C]- or [3H]glycine, were renatured to form triple-helical, rod-shaped molecules, then cross-linked intramolecularly with formaldehyde. Specific radioactivity measurement and chromatographic elution profiles demonstrated that the composition of the resultant molecules, (alpha 1)3, (alpha 1)2 alpha 2, alpha 1(alpha 2)2 and (alpha 2)3, depended on a relative proportions of alpha chains in the starting solution.

Animals↗
PubMed1981

Inhibition of tumor growth, vascularization, and collagenolysis in the rabbit cornea by medroxyprogesterone.

Medroxyprogesterone, dexamethasone, or cortisone, locally applied in sustained release polymer to rabbit V2 carcinoma implanted in the rabbit cornea, blocked neovascularization and three-dimensional growth of the tumor. These hormones similarly prevented the vascular proliferative response to implants in the rabbit cornea of mouse B-16 melanoma and also the response to implants of polymer containing tumor extract with angiogenesis activity. The inhibitory responses were accompanied by considerable reduction in collagenolytic activity released into culture medium by explants of the two tumors and of the corneal region containing angiogenic hepatoma extract. Morphologic studies revealed extensive three-dimensional disruption of the compact laminated collagenous structure of the cornea by untreated V2 carcinoma. In the presence of hormone the tumor grew slowly as a noninvasive two-dimensional plaque limited to the narrow region of the insertion pocket in the cornea, with no obvious disturbance of structure elsewhere. Cortisone was much les effective than medroxyprogesterone or dexamethasone. Testosterone and estradiol had no effect on the three measured properties. The data suggest that local hormonal interference with neovascularization, collagenase production, and tumor growth can prevent neoplastic invasion and destruction of a dense collagenous connective tissue.

Animals↗
PubMed1981

Influence of prenatal hypoxia on brain development: effects on body weight, brain weight, DNA, protein, acetylcholinesterase, 3-quinuclidinyl benzilate binding, and in vivo incorporation of [14C]lysine into subcellular fractions.

The influence of prenatal hypoxia on subsequent brain development in the young rat was investigated by examining body and brain weight, cerebral cortex wet weight, protein and DNA concentrations, acetylcholinesterase (AChE) activity, 3-quinuclidinyl benzilate (QNB)-binding levels, the relative amounts of protein in various subcellular fractions, and the in vivo incorporation of [14C]lysine into the protein of homogenate and subcellular fractions. Exposure of pregnant females to a mild hypoxia (9.1% O2, 10 h per day for the 9--11 days preceding birth) resulted in a reduced body weight in the pups and days 1 and 5 after birth; total cortical DNA was reduced but brain weight and protein content were unaffected, leading to a higher protein/DNA ratio in prenatally hypoxic pups. By 10 days of age these differences between prenatally hypoxic and control animals were no longer apparent. There were no differences between prenatally hypoxic and control animals in AChE and QNB binding per milligram cortex protein. The relative amount of synaptic membrane protein from the cerebral cortex was reduced at day 1 in prenatally hypoxic animals and the synaptic membrane fraction showed a higher level of incorporation of [14C]lysine on days 1, 5, and 10. The developmental profile of [14C]lysine incorporation showed a peak on day 10 which was higher in prenatally hypoxic rats. By 46 days after birth little difference could be found between prenatally hypoxic and control animals.

Acetylcholinesterase↗
PubMed1981

Creatine in density-fractionated red cells, a useful indicator of erythropoietic dynamics and of hypoxia past and present.

Creatine in density-fractionated red cells is not only a useful criterion of cell age but also an excellent indicator of erythropoietic dynamics particularly under the influence of present and past hypoxia. This is documented on patients with cardiac hypoxia. A histogram is proposed which permits the simultaneous evaluation of four parameters: (1) the creatine concentration of each separate fraction, (2) the absolute density of a given cell fraction, (3) the percentage distribution of cells over the whole gradient and within the different fractions and (4) the general position of the red cell population with respect to its median density, which serves to characterize the overall age of a red cell population. Creatine histograms on fractionated red cells are shown to be useful aids for diagnosis and prognosis in hypoxic clinical states. They may also give retrograde information on past stimulation of erythropoiesis.

Adult↗
PubMed1981

Changes in glucose 6-phosphate dehydrogenase and phosphofructokinase activity during maturation and ageing of red blood cells in children with chronic renal insufficiency.

Red blood cells (RBC) of children with terminal renal insufficiency show a reduction of the apparent 51Cr RBC half-life (16.5 +/- 5.5 days). The enzymatic activities of phosphofructokinase (PFK) and glucose 6-phosphate dehydrogenase (G6PD) in the RBC of these patients do not differ from those in health persons. The RBC of uraemic and healthy children were separated by density gradient centrifugation in dextran medium according to maturity and age. RET count, mean cellular Hb concentration (MCHC), PFK and G6PD activities were determined in the separated cell populations. MCHC increases with increasing cell density while the number of RET decreases. There is a distinct decrease in the G6PD activity of low-density cells compared to high-density cells. The extent of the decrease in enzymatic activity is about the same for healthy persons as for uraemic patients. A more rapid decrease in G6PD activity per unit of time can be assumed when the enzymatic activity is plotted against the distinctly shortened life span of the RBC of the uraemic children. There is a possible relationship between G6PD activity in old RBC and the premature destruction of these cells. PFK activity apparently does not decrease with increasing cell age.

Adolescent↗
PubMed1981

Influence of drugs on the bilirubin UDP-glucuronyltransferase activity and the concentration of Y and Z acceptor proteins in rat liver.

The aim of this paper is to report on the influence of phenobarbital, the combination of phenobarbital/nikethamide, the racemate and (+) isomer of methylphenobarbital on the activity of bilirubin UDP-glucuronyltransferase and the concentration of intrahepatic Y and Z protein in rats. The activity of bilirubin DP-glucuronyltransferase increased after the treatment in all groups. Pretreatment with phenobarbital/nikethamide resulted in the highest enzyme activity, using wet weight as reference. (+) Methylphenobarbital isomer as well as the racemate showed effects similar to those of phenobarbital. The concentration of hepatic Y acceptor protein increased in all pretreated groups by about 30%. The drugs did not increase the concentration of Z protein. The (+) isomer of methylphenobarbital seems better suited as an inductive drug in the prophylaxis of hyperbilirubinemia and in the treatment of nonconjugated hyperbilirubinemia than phenobarbital or phenobarbital/nikethamide since it has no sedative effect.

Animals↗
PubMed1981

The synthesis and release of TSH in the thyroidectomized rat: c) the effect of T3 on hypothyroidism of varying duration.

The effect of thyroid hormones on TSH synthesis and release from the anterior pituitary of the rat, at the various stages of hypothyroidism was studied by injecting L-Triiodothyronine (T3) iv (1.5 microgram/100 g b.w.) to rats 5 days and 3 months post thyroidectomy (Tx-5d and Tx-3m rats). The changes in plasma and pituitary TSH levels, as well as in the metabolic clearance rate (MCR) of the TSH were followed for 3 days after the T3 injection. From these data TSH synthesis and release rates were determined. TSH release was inhibited in both experimental groups between 3 and 24 h after the injection. TSH synthesis was suppressed in the Tx-5d group to 35% of the initial value. However in the Tx-3m group it was stimulated to approximately 270%, 24 h after the T3. The data suggest that thyroid hormones may affect the synthesis of TSH in two opposite pathways, the first through the stimulation of protein synthesis and the second, inhibitory, as part of the feedback mechanism. Under short-term hypothyroidism, when protein synthesis is not yet diminished, the administration of thyroid hormones results in the inhibition of both TSH synthesis and release through the feedback regulation. In prolonged hypothyroidism, however, when protein synthesis is depressed, the effect of thyroid hormones on the stimulation of TSH synthesis predominates.

Animals↗
PubMed1981

Criteria of maturity and age of red blood cells.

Any work on red blood cells requires information about the characteristics of a cell population. Using buoyant density separation of red blood cells (RBC) in a dextran medium during a bleeding anemia of rabbits cell-physiological, ribosomal, mitochondrial and cytoplasmic criteria were estimated in order to select parameters useful for the characterization of a given RBC population according to its developmental stages. Useful criteria for an unknown overall RBC population are reticulocyte count and aspartate amino transferase, or glucose-6-phosphate dehydrogenase activity or creatine concentration. Useful additional criteria for reticulocytes are the mean cellular volume and the RNA concentration.

Animals↗
PubMed1981

[Effect of osmolarity and pH of the medium on the density of red blood cells of newborns and adults].

The influence of osmolarity and pH-value of a buffered saline glucose solution (BSG) on the density of red blood cells (RBC) of human newborns and adults were tested. The median density of RBC increases with increasing osmolarity by 1.2 mg/ml cells per 10 mosmol/l increase of osmolarity. This holds true for newborns and adults. The median density of RBC increases with increasing pH. The density of RBC of newborns increases by 5.7 mg/ml cells per one pH-unit increase, the density of RBC of adults increases by about 10.3 mg/ml cells per one pH-unit increase. These differences are probably caused by different physical-chemical properties of HbF and HbA.

Adult↗
PubMed1980

The metabolism of T4 and T3 in cultured chick-embryo heart cells.

Thyroxine (T4) and tri-iodothyronine (T3) were metabolized in cultured chick-embryo heart cells via inner-ring de-iodination and O-sulfation. The products of T3 metabolism were 3,3'T2, 3'T1, and sulfated esters of T3 and 3,3'T2. The major product of T4 degradation was 3,3',5'-T3 (rT3). ONo T3 was produced from T4. Propylthioracil inhibited the metabolism of T3. Pretreatment of cultures with T3 or T4 enhanced the metabolism of both hormones; actinomycin D and cycloheximide inhibited the stimulatory effect of T3. The stimulation by T3 was linearly related to the log of the concentration of T3 in cells grown in normal chick serum or in cells grown in dehormonized serum. These results suggest that thyroid hormones induced an increased synthesis of the enzymes involved in their metabolism and therefore may regulate their own disposal rate.

Animals↗
PubMed1980

An inexpensive ultrasonic device for intraocular lens power determination.

The Echo-oculometer is a relatively inexpensive ultrasonic device for measuring anterior chamber depth and axial length prior to lens implantation. It is uncomplicated, easy to use and functioned very well in this limited study, giving an average error of 0.98 D when preoperative measurements were compared to postoperative refraction.

Anterior Chamber↗
PubMed1980

Will hyperthermia conquer the elusive hypoxic cell? Implications of heat effects on tumor and normal-tissue microcirculation.

In tumor radiobiology, the hypoxic cell has become especially important because of recent evidence of acute hypoxic regions within experimental tumors. The impact of hyperthermia on the development of acute hypoxia is discussed. Two experiments for studying hyperthermia and hypoxia in tumors are presented. Knowledge of the microenvironment of tumor cells will be necessary to understand and improve tumor control.

Adult↗