Search PubMed⌕ Search

Biomedical subjects

J Gross

Publications and source records attributed to J Gross.

At least 397 records · Page 22Linked to original sources
PubMed1976

Species specificity of guinea pig erythropoietin.

Various stimuli (hypoxic hypoxia, bleeding, carbon monoxide hypoxia and cobalt administration), well known to increase erythropoietin plasma level in many species including man, failed to increase the erythropoietin activity in plasma of guinea pigs when measured in the polycythaemic mice assay. Nevertheless, the plasma of these guinea pigs stimulated the erythropoiesis in polycythaemic guinea pigs which, however, failed to respond to rat erythropoietin. From this it was concluded that not only the erythropoietin, but also the erythropoietin responsive cells in the bone marrow of guinea pigs are species specific. Bilateral nephrectomy in guinea pigs exposed to hypoxia prevented the increase in the erythropoietin plasma level, thus suggesting that, similarly as in other species, also in guinea pigs the kidney is the main organ of erythropoietin elaboration. The species specificity of guinea pig erythropoietin - erythropoiesis system is an interesting exception among mammals, since the erythropoietin of a large number of species belonging to this class was demonstrated to lack species specificity.

Animals↗
PubMed1975

The covalent structure of collagen. Amino acid sequence of alpha1-CB5 glycopeptide and alpha1-CB4 from chick skin collagen.

The amino acid sequences of chick skin alpha1-CB4 and alpha1-CB5 have been determined by automated Edman degradation of the intact peptides and of their tryptic and chymotryptic peptides. The two peptides contain 47 and 37 residues and comprise residues 56 to 102 and 103 to 139, respectively, of the alpha1(I) chain. In addition, alpha1-CB5 is the major hexose-containing peptide, previously reported to be active in mediating platelet aggregation. A comparison of the sequence with previously reported data on the homologous region of the rat skin alpha1(I) chain indicates that there are only three interspecies differences, or a sequence identity of 96%.

Amino Acid Sequence↗
PubMed1975

Covalent structure of collagen: amino acid sequence of alpha1-CB3 of chick skin collagen.

The amino acid sequence of alpha1-CB3, a peptide containing 149 residues obtained from the central portion of the alpha1(I) chain of chick skin collagen by cyanogen bromide cleavage, has been determined. As in the other sequences from the helical region of collagen chains, the repeating triplet Gly-X-Y extends throughout the length of the peptide. These data allow a comparison of the sequence to that of alpha1-CB3 from calf and rat skin collagens. As compared with calf, the chick peptide contains 14 amino acid differences, whereas it contains 17 residue differences from the rat peptide. Thus, the sequence identity level is 91 and 89 percent, respectively, in comparison to the calf and rat peptides. These values are significantly greater than the value of 97 percent observed between the peptide of the two mammalian species and reflect the greater phylogenetic distance of the species compared.

Amino Acid Sequence↗
PubMed1975

Covalent structure of collagen: amino acid sequence of alpha1-CB6A of chick skin collagen.

The amino acid sequence of chick skin collagen alpha1-CB6A, a peptide containing 107 residues obtained from the helical region near the carboxy-terminus of the alpha1(I) chain by cyanogen bromide cleavage, has been determined. This was accomplished by automated Edman degradation of the hydroxylamine-produced fragments and of the tryptic peptides prepared with and without prior maleylation. The data show that this portion of the alpha1(I) chain from chick skin is identical in 90 percent of the residues to the corresponding peptide region of calf skin collagen reported previously.

Amino Acid Sequence↗
PubMed1975

The amino acid sequence of chick skin collagen alpha1-CB7.

The amino acid sequence of chick skin collagen alpha1-CB7, the 268 CNBr peptide from the helical portion of the alpha1 chain, has been determined by automatic and manual degradation of tryptic and chymotryptic peptides, and of the COOH-terminal fragment produced by cleavage with animal collagenase. The resulting sequence shows 94% identity with that of the corresponding peptide from calf skin collage (Fietzek, P. P., Rexrodt, F. W., Hopper, K. E., and Kühn, K. (1973), Eur. J. Biochem. 38, 396). The bond cleaved by animal collagenase has been identified as Gly-Ile at residues 221-222 of alpha1-CB7.

Amino Acid Sequence↗
PubMed1975

Inhibition of the response of mouse thyroid to tryrotropin induced by chronic triiodothyronine treatment.

Administration of 1 mU bovine TSH iv to mice resulted, within 1 hour, in the increase of the serum T4 level from 32 +/- 1.4 ng/ml to 53 +/- 2.6 ng/ml (Mean +/- SE, n = 24). Treatment with 1 mug triiodothyronine (T3) per day, for 10 days, abolished the responsiveness of the thyroid to TSH, as measured by thyroxine (T4) release. Thyroidal response to TSH was measured also in vitro. The basal hormonal release was 4.66 +/- 0.55 ng T4 and 0.98 +/- 0.15 ng T3 per thyroid per 3 h (n = 30). In the presence of bovine TSH (0.2 mU/ml) the hormonal secretion increased 3-fold for T4 and 2.5-fold for T3. Thyroids from mice pretreated with T3 for 10 days showed almost no response to TSH. Partial refractoriness to TSH was already significant 5 days after T3 pretreatment. Responsiveness to TSH was restored 3 days after T3 withdrawal or after 3 daily injections of 10 mU bovine TSH, concomitant with the last 3 days of T3 pretreatment. These results indicated that the prolonged absence of an adequate level of trophic hormone may be the cause of thyroidal unresponsiveness to acute TSH treatment. With 20 mU of TSH, cAMP levels rose from 4 +/- 0.5 picomoles to 80 +/- 9.3 picomoles per thyroid (n = 6). In mice subjected to 10 days of T3 pretreatment the response was markedly reduced: 20 +/- 3 picomoles/ thyroid. Thyroids of the T3-treated mice responded normally to 1 mM DBcAMP in vitro. From these results it was concluded that the impaired responsiveness of the thyroids to TSH occurs at a step prior to cAMP accumulation.

Animals↗
PubMed1975

The effect of elevated doses of thyrotropin on mouse thyroid.

In the course of validating the McKenzie assay it was found that large doses of bovine or rat TSH have a retarding effect on hormonal secretion from the thyroid. TSH in doses less than 10 mU had a maximal effect on thyroidal secretion at about 2-3 h after administration. Doses of TSH in excess of 10 mU caused the peak of secretion to appear at about 9-10 h and caused, as well, a decreased thyroidal iodine release at earlier times. This effect was not due to changes in the pattern of iodocompounds secreted by the thyroid or to a change in the clearance of the blood [125I] thyroxine. An estimate of the integrated secretion with time was linear with log dose up to 100 mU TSH. This pattern of response to TSH is also seen when colloid droplet formation is the parameter studied. cAMP accumulation shows a different pattern of response to TSH. Control levels of cAMP were 1-2 pmoles/mg thyroid. Doses of TSH smaller than 5 mU caused no significant increase in cAMP. With a further increase in TSH up to 200 mU per mouse, cAMP levels increased linearly with the log of TSH and reached 400 pmoles/mg thyroid. Theophylline administered together with large doses of TSH increased the level of the thyroidal cAMP and further decreased the release of iodocompounds at 2 h. These results indicate that there may be an intrathyroidal mechanism which prevents a surge of secretion of thyroid hormones with acute changes in blood TSH levels. The mechanism sensitive to excess TSH is probably associated with steps in thyroidal activation between the accumulation of cAMP and colloid droplet formation.

Animals↗
PubMed1975

[Separation of reb blood cells in the isopyknic dextran and albumin density gradient].

The separation of red blood cells according to their maturity and age was compared in the isopyknic dextran and albumin density gradients, and the quality of separation was appraised by selected criteria (density distribution curves, accumulation of reticulocytes, activity of G-6-PD). The achieved quality of separation, as measured by the quotient of G-6-PD activity in the cells of lower density/G-6-PD activity in cells of higher density is of equal value in the two media. In the dextran gradient, separation of old cells seems to be accomplished more readily, while albumin affords better separation of young erythrocytes. The reticulocytes are in both media 4-5 mg/ml lighter than the total cell population. When shifting pH from 7.4 to 6.8 both in erythrocytes and reticulocytes the density decreases by 3-6 mg/ml irrespective of the type and pretreatment of the separation medium.

Albumins↗
PubMed1974

Brain hyaluronidase: changes in activity during chick development.

Development of embryonic chick brain is characterized by high levels of hyaluronidase activity and of hyaluronate, both of which decrease rapidly soon after the chick hatches. By analogy to other systems, it is proposed that the sequence of hyaluronate production and its enzymatic removal may have a developmental role in brain formation.

Animals↗