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Biomedical subjects

J C Daniel

Publications and source records attributed to J C Daniel.

At least 73 records · Page 4Linked to original sources
PubMed1976

Changes in type of collagen synthesized by chick fibroblasts in vitro in the presence of 5-bromodeoxyuridine.

Chick embryo fibroblasts cease to synthesize their normal collagen product when grown in the presence of the thymidine analogue, 5-bromodeoxyuridine (BrdU). The drug causes an alteration of synthesis from the normal Type I collagen (alpha1 (I)2alpha2) to a mixture of Type I and Type I trimer (alpha1(I)3). While the significance of the synthesis of Type I trimer is unclear, it has been noted that chondrocytes synthesize this collagen type following in vitro senescence and in the presence of BrdU. Since BrdU may cause a switching in the temporal pattern of collagen biosynthesis in chondrocytes and in fibroblasts it is proposed that BrdU may alter the normal regulatory controls acquired by the cells during the course of their differentiation. The synthesis of type I trimer might provide a marker for such a break-down in a wide variety of cell types.

Bromodeoxyuridine↗
PubMed1976

Blastokinin and analogous proteins.

The paper is a review of recent work with blastokinin, a uterine-specific protein of rabbit, and includes consideration of patterns of synthesis, induction by progestagens, metal-binding capacity, translation of its RNA message, possible changes in the molecule, and comparison with the "cone" protein of the oviduct. Other uterine proteins have been identified in the rabbit by their enzymatic or hormonal activity and shown to be distinct from blastokinin though present in the uterine lumen at the same time. Proteins which are temporally or chemically analogous to blastokinin in other species are discussed, including the question of whether a blastokinin-like protein occurs in women. Discussion of the comparative significance of such proteins must await a clearer definition of their function.

Animals↗
PubMed1976

Continuity of a rabbit antigen between generations.

The rabbit uterine protein, blastokinin, is detectable as an antigen in both male and female genital tract tissues, in preimplantation embryos, and in lungs from late fetal stages, immatures, and adults. Thus, it serves as an example of how an antigen of normal tissue exists in a developmental progression from one generation to the next.

Animals↗
PubMed1975

Alterations in uterine and serum esterases in pregnant mammals.

Uterine flushings, endometrial extracts, and serum from estrous and pregnant rabbits were analyzed by acrylamide gel electrophoresis for esterase activity. Two bands of enzyme activity in uterine findings were detectable on days 4 through 7 after coitus. No activity was detectable in washings from nonpregnant animals or on days 1 to 3 of pregnancy. Esterase activity was detectable in endometrial extracts of all rabbits. The intensity and complexity of the esterase activity markedly increased on day 3 and persisted through day 7 after coitus, during which time nine to ten electrophoretic bands were apparent, compared with four bands in extracts from estrous animals. Serum from pregnant rabbits showed two basic patterns. High esterase activity, concentrated in four major bands, was seen in some sera, while other serum samples showed little esterase activity. No consistent correlation was apparent, however, between the stage of gestation and the serum esterase pattern. In contrast, analysis of mouse serum prior to and after mating showed consistent, reproducible changes in esterase profiles, noticeable about 7 days after coitus and becoming increasingly pronounced until parturition. Changes in mouse serum included both marked enhancement of some esterase activities and concomitant diminution in others with increasing gestation time.

Animals↗
PubMed1975

Termination of pregnancy after accelerated lactation in the rat. III. Effects of hormonal treatments.

The relationship was investigated of the hormones associated with pregnancy and lactation and the termination of pregnancy that occurs when rats mated at the post-partum oestrus are allowed to suckle a large litter after implantation. The primary cause for pregnancy termination was found to be an insufficient level of progesterone with the possible need for a primary or synergistic dose of oestrogen. The progesterone deficiency was not due to the high levels of prolactin present in nursing rats, since pregnancy termination could not be produced by prolactin administration in the absence of accelerated lactation, and could not be prevented by blocking prolactin secretion after accelerated lactation. Administration of LH to rats after accelerated lactation did prevent termination of pregnancy.

Adrenocorticotropic Hormone↗
PubMed1975

Termination of pregnancy after accelerated lactation in the rat. IV. Relationship to 20alpha-hydroxysteroid dehydrogenase activity and plasma progesterone concentration.

The activity of 20alpha-hydroxysteroid dehydrogenase (20alpha-HSD) was assayed in the ovaries of rats after accelerated lactation to determine its relationship to the decrease in progesteron secretion that occurs. When rats were sjbjected to accelerated lactation on Day 9 of pregnancy, activity of the enzyme was only slightly increased by Day 10, but had risen to twice the control level by Day 11, and three times the control level by Day 12. Administration of LH or progesterone prevented the increase in enzyme activity. Progesterone concentration had decreased considerably before the time at which any significant increase in 20alpha-HSD activity was detected. These findings are discussed in relation to the role of 20alpha-HSF in regulating progesterone levels in the rat.

Animals↗
PubMed1974

Influence of external potassium on the synthesis and deposition of matrix components by chondrocytes in vitro.

The effect of a high external potassium concentration on the synthesis and deposition of matrix components by chondrocytes in cell culture was determined. There is a twofold increase in the amount of chondroitin 4- and 6-sulfate accumulated by chondrocytes grown in medium containing a high potassium concentration. There is also a comparable increase in the production of other sulfated glycosaminoglycans (GAG) including heparan sulfate and uncharacterized glycoprotein components. The twofold greater accumulation of GAG in the high potassium medium is primarily the result of a decrease in their rate of degradation. In spite of this increased accumulation of GAG, the cells in high potassium fail to elaborate appreciable quantities of visible matrix, although they do retain the typical chondrocytic polygonal morphology. Although most of the products are secreted into the culture medium in the high potassium environment, the cell layer retains the same amount of glycosaminoglycan as the control cultures. The inability of chondrocytes grown in high potassium to elaborate the typical hyaline cartilage matrix is not a consequence of an impairment in collagen synthesis, since there is no difference in the total amount of collagen synthesized by high potassium or control cultures. There is, however, a slight increase in the proportion of collagen that is secreted into the medium by chondrocytes in high potassium. Synthesis of the predominant cartilage matrix molecules is not sufficient in itself to ensure that these molecules will be assembled into a hyaline matrix.

Animals↗