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Biomedical subjects

M M Jacobs

Publications and source records attributed to M M Jacobs.

47 records · Page 3Linked to original sources
PubMed1976

Studies on the isolation and chemical properties of porcine follicle-stimulating hormone.

Porcine follicle-stimulating hormone (pFSH) has been prepared from acetone dried pituitary glands. The acetone powder was initially extracted in pH 5 ethanol-acetate buffer (40% ethanol and acetate at 0.5 ionic strength) containing 0.02% PMSF. The gonadotropin rich fraction, obtained in the 80% ethanol precipitate, was dissolved in 0.12 M NH4HCO3, heated at 60 degrees for 3 min, cooled, and centrifuged. The supernatant was lyophilized for chromatography on QAE-Sephadex, then Sephadex G-100. The pFSH obtained has a biological activity of 15 X NIH-FSH-P-1 and 2.1% sialic acid. The amino acid analysis is characterized by high lysine, aspartic acid, and glutamic acid with notable amounts of threonine, proline, and half-cystine.

Amino Acids↗
PubMed1975

Factors affecting the initial extraction of ovine gonadotropins.

The method of tissue homogenization as well as the solvents used for extraction influenced the protein yield, the specific activity of the oLH and oFSH, and the total units of each hormone recovered. Use of the Tekmar homogenizer (Method 2) produced a fivefold increase in the total yield of oLH per Kg glands (2390 units, Method 2; 474 units, Method 1) and the relative potency of this partially purified LH from the 80% ethanol precipitate was increased (0.16 times NIH-LH-S18, Method 2). By combining the aqueous extraction--ammonium sulfate precipitation with a subsequent ethanolic acetate extraction (Methods 3 and 4) the combined yields provided a 2.4-fold increase in oLH and 1.4-fold increase in oFSH. Thus the total units recovered of oFSH and oLH can be increased simply by changing the methods of homogenization and extraction.

Ammonium Sulfate↗
PubMedDate not supplied

Dual regulation of human syncytial adenylyl cyclase.

The dual (stimulatory and inhibitory) regulation of adenylyl cyclase was studied in syncytiotrophoblast basal membranes prepared from term human placenta. Stimulation of adenylyl cyclase activity with GTP, non-hydrolyzable GTP analogs, isoproterenol and PGE1 was observed, confirming the presence of an intact stimulatory pathway in these membranes. Investigations of the inhibitory pathway revealed tight coupling of the G-protein, Gi alpha, to catalytic adenylyl cyclase, with high doses of GTP producing 80 per cent inhibition of GTP/forskolin-stimulated activity. Confirming Gi alpha involvement, pertussis toxin (PTX) treatment of basal membranes augmented the responses of adenylyl cyclase to both GTP and forskolin. In addition, immunoblotting of basal membrane proteins revealed the presence of the G-protein subunits, Gs alpha, Gi alpha, and G beta/gamma. The response of adenylyl cyclase was measured to a series of agonists known to inhibit adenylyl cyclase in other tissues, however a reproducible inhibitory effect was produced only by somatostatin (approximately 80 per cent). Treatment of basal membranes with PTX caused a degree of reversal of the somatostatin-mediated adenylyl cyclase inhibition. However, the intoxication was insufficient to restore GTP/forskolin-stimulated activity.

Adenylate Cyclase Toxin↗
PubMedDate not supplied

[Study of tensile bond strength of 3 different adhesive systems associated with composites on dentinal surfaces].

The aim of this in vitro study was to compare the tensile bond strength of 3 different bonding systems, associated to composite resins, bonded to dentinal surfaces. Forty-four dentinal surfaces were obtained from recently extracted human molars. A standardized smear layer was obtained and the surfaces were divided in 3 groups: G1) self etch + microhybrid composite; G2) single-component adhesive + phosphoric acid + microhybrid composite and G3) conventional system (acid + primer + bond) + microhybrid composite. Specimens made of composite resin were constructed in the shape of an inverted truncated cone with 3 mm of diameter. Tensile bond strength test was performed at the speed of 0.5 mm/min, and the results were expressed in MPa. The analysis of variance ANOVA (p < 0.05) determined that the type of bonding system used influenced tensile bond strength. Tukey's test, however, showed that the results of the comparison between G2 and G3 were the only statistically significant ones, with G2 showing greater values of tensile bond strength.

Composite Resins↗
PubMedDate not supplied

Fetal pulmonary beta-adrenergic receptors: characterization in the human and in vitro modulation by glucocorticoids in the rabbit.

At least two developmental responses necessary to prepare the fetal lung to serve as a gas-exchange organ, the release of surface-active material and the reabsorption of alveolar water, can be stimulated by beta-adrenergic agonists. The sensitivity of these responses increases dramatically in late gestation. beta-Adrenergic receptors can be identified by radioligand binding and are present in human fetal lung as early as 16 weeks of gestation. The temporal relationship of the increases in both pulmonary beta-receptors and plasma-free cortisol in the fetal rabbit during gestation suggests that endogenous glucocorticoids may cause increased concentration of pulmonary beta-receptors. Treatment of pregnant rabbits at 24 or 25 days of gestation results in precocious increases in both fetal lung beta-receptors and agonist-specific, high-affinity binding. The increase in receptor concentration with glucocorticoid is not dependent on other endocrine response inasmuch as 0.1 microM dexamethasone increases beta-receptor concentrations at 24 and 48 hours of incubation in cultures of fetal rabbit lung organ. This effect of glucocorticoid to increase beta-receptor concentration and high-affinity binding may explain the increased fetal pulmonary beta-adrenergic response at term and may be responsible in part for the reduction in neonatal respiratory syndrome seen after antenatal glucocorticoid therapy.

Adenylyl Cyclases↗