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Biomedical subjects

H R Lindner

Publications and source records attributed to H R Lindner.

At least 37 records · Page 2Linked to original sources
PubMed1981

The ontogeny of the thyrotropin-thyroid axis in early bovine embryos.

T4 and T3 formation and their response to TSH, cAMP, and prostaglandin E2 (PGE2) stimulation were studied by RIA in cultured bovine fetal thyroids from 130 embryos of 1.2-25.0 cm crown-rump length (CRL). T4 and T3 were found in all of the freshly isolated glands studied, and their concentrations increased significantly (P less than 0.05) during a 24-h incubation of glands from fetuses with a CRL greater than 8.0 cm. The release of T4 (nanograms per mg tissue), but not of T3, increased consistently with CRL (r = 0.64; P less than 0.05). The addition of TSH (0.5 mU) to the culture medium induced a 2- to 3-fold increase in the secretion of T4, but not of T3, by glands of fetuses with a CRL of 3.0-25.0 cm (P less than 0.05). Dibutyryl cAMP (10(-4) M) and PGE2 (10(-4) M) had comparable effects. A combination of TSH and theophylline (1 mM) or of TSH and dibutyryl cAMP significantly enhanced the T4 released by cultured tissue into the medium (P less than 0.05) over that induced by either agonist, but the combined effect was not fully additive. The total PGE2 in the tissue and medium was not changed by the addition of 0.5 mU TSH, and indomethacin had no effect on TSH-induced T4 secretion. The data show that thyroids of fetuses that have reached a CRL of 3.0 cm have the enzymatic capacity to produce both T4 and T3, and T4 is the dominant product formed. While exogenous PGE2 at high concentrations stimulates fetal T4 secretion, it does not mediate the actions of TSH and cAMP on the fetal thyroid.

Adenosine↗
PubMed1981

Iodine metabolism and the effect of TSH in thyroid glands of early bovine embryos.

The ontogeny of the thyrotrophin-thyroid axis during the first trimester was studied in 104 bovine embryonic thyroids taken from foetuses of crown-rump length 1.4 to 19.2 cm (25-120 days). The uptake of labelled iodine in vitro in the absence or presence of TSH was measured. The per cent incorporation of radioiodine into iodotyrosines and iodothyronines in the presence and absence of TSH was also studied. It was found that the foetal tissue displayed radioiodine uptake by 25 days of foetal life and the uptake increased with age. TSH caused a further increase in radioiodine uptake in foetuses of 40 days or older. Incorporation of radioiodine into MIT and DIT was apparent at 25 days and into T3 and T4 by 40 days of foetal life. Addition of TSH increased the proportion of total radioiodine found as DIT and thyroxine in foetuses of 40 days older. This TSH stimulation of radioiodine incorporation increased with age. However, the proportion of radioiodine found as MIT and T3 was not affected before 120 days of foetal life. This was in marked contrast to the adult thyroid where the proportion of radioiodine found as T3 was increased by the addition of TSH. It is concluded that the foetal thyroid can respond to TSH by at least 40 days of foetal life and that this response differs from that seen in the adult.

Animals↗
PubMed1980

An assay for urinary estriol-16 alpha-glucuronide based on antibody-enhanced chemiluminescence.

An immunoassay for estriol-16 alpha-glucuronide in pregnancy urine is described that utilizes antibody-enhanced chemiluminescence. The steroid glucuronide was covalently conjugated with the chemiluminescent marker aminobutyl-ethyl-isoluminol. The light yield of this conjugate upon oxidation was augmented by specific antibody, and this effect was inhibited by addition of the homologous steroid glucuronide (10-100 pg) in a dose-dependent manner. The assay does not require separation of bound and free ligand and proved satisfactory with respect to sensitivity, precision and accuracy. Assay results obtained by radioimmunoassay and chemiluminescence immunoassay were in good agreement (r = 0.98; n = 25).

Antibody Specificity↗
PubMed1980

An immunoassay for plasma cortisol based on chemiluminescence.

An immunoassay procedure for the determination of cortisol in human plasma is described, which utilizes chemiluminescence as the end point. A cortisol-isoluminol conjugate serves as the chemiluminescent marker. The light emission by this conjugate upon oxidation is delayed by prior incubation with anti-cortisol IgG, but not by unrelated gamma-globulin. This delayed light emission was inhibited by cortisol in a dose-dependent manner, with a linear range of 20-1000 pg steroid/assay tube. A competitive protein binding assay based on this procedure was applied to methylene chloride extracts of cortisol from normal and pathological human plasma (2-40 micrograms/100 ml). Cortisol values obtained by this procedure agreed well with those obtained by radioimmunoassay, using the same antiserum with tritiated cortisol as the label (r = 0.98). The chemiluminescence immunoassay is comparable to radioimmunoassay with regard to sensitivity, specificity, precision and accuracy. The advantage of the new assay procedure is that it obviates the need for counting radioactivity and for separation of bound and free ligand.

Humans↗
PubMed1980

Role of steroid hormones and prostaglandins in the regulation of DNA synthesis by decidual cells in culture.

The effect of oestrogen and progesterone on prostaglandin synthesis and on DNA synthesis by rat decidual cells was studied in a culture system. The cells were explanted from deciduoma either during the proliferation phase (namely on the 5th day of leukocytic smear, Day L5:"L5 cells") or during the maintenance phase ("L8 cells") and examined on the second day of culture. Oestradiol-17 beta (7 X 10(-11) M) and progesterone (6 X 10(-8) M) significantly inhibited accumulation of PGE by cells explanted on Day L5: L8-cell cultures showed no significant response to oestradiol and the progesterone effect was markedly reduced. Progesterone stimulated [3H]thymidine incorporation into cells explanted on Day L5, but had no effect on L8-cultures. Other inhibitors of PG synthesis, namely cortisol, flufenamic acid and indomethacin, also had a stimulatory effect on DNA synthesis by L5 cells. PGE2 (5-10 micrograms/ml) inhibited DNA synthesis in control, indomethacin-treated and progesterone-treated L5-cell cultures, suggesting that the progesterone-induced stimulation of DNA synthesis may be in part be due to its inhibitory effect on PGE accumulation by decidual cells. The possibility is discussed that during the proliferation phase of decidual development in vivo, the rate of DNA synthesis may be influenced by steroid-induced changes in PGE content of the tissue.

Animals↗
PubMed1980

Significance of prostaglandins in the regulation of cyclic events in the ovary and uterus.

We examined the role of prostaglandins in three pivotal events of the female reproductive cycle: ovulation, luteolysis, and menstruation. Four general approaches were adopted, using in vivo and in vitro models: use of inhibitors of cyclooxygenase and of PG action; immunoneutralization of individual prostaglandins; administration of exogenous prostaglandins; and attempts to correlate PG levels in tissues and body fluids to physiologic events. It can be concluded that prostaglandins or related metabolites of arachidonic acid are essential in laboratory rodents for follicular rupture and the release of a fertilizable oocyte, but not for other LH actions on the follicle that are mimicked by PG or for the neuroendocrine triggering of ovulation. PGs control the cyclic regression of the corpus luteum and appear also to be implicated in the decidual reaction and in the menstrual shedding of the endometrium in primates. Some aspects of the control of follicular PG formation and of PG action were analyzed. Gonadotropins stimulate follicular PG synthesis by a steroid-independent cyclic nucleotide-mediated induction of cyclooxygenase. Both the thecal and granulosa cell compartments show this response. An effect of the phytolectin conconalavin A on ovarian PG synthesis is described. The response of follicular cells to prostaglandin E2 exhibits the phenomenon of desensitization and is influenced by agents modifying the structure and function of cytoskeletal elements. Evidence is put forward for the view that abrogation by PGF2 alpha of the stimulatory action of LH on luteal adenylate cyclase is the biochemical basis of the luteolytic action of this prostaglandin. While the precise mechanism of PG action on the endometrium remains to be defined, PG-synthetase inhibitors have already found useful applications in the management of menstrual disorders, such as functional dysmenorrhea and menorrhagia. The role in ovarian and uterine physiology of the more recently discovered labile arachidonate metabolites, such as the endoperoxides, prostacyclin, and thromboxanes, has not yet been adequately explored.

Animals↗