Direct effect of the luteinizing hormone releasing hormone analog D-Trp6-Pro9-Net-LHRH on rat testicular steroidogenesis

The luteinizing hormone releasing hormone analog D-Trp⁶-Pro⁹-Net-LHRH (LHRH_a) inhibits rat testicular testosterone secretion. To determine whether LHRH_a decreases serum testosterone concentrations solely by inhibiting gonadotropin secretion or, in addition, by influencing directly testicular testosterone biosynthesis, we examined the effects of LHRH_a on the activities of 5 key testicular steroidogenic enzymes. Thirty hypophysectomized, hCG treated rats were given either LHRH_a (1 μg sc/day) or saline during 7 days. The LHRH_a treated animals exhibited a significant decrease of serum testosterone when compared to the control group (498 ± 37 ng/dl vs 2044 ± 105 ng/dl, mean ± SEM, P 〈0.001). 17-Hydroxyprogesterone serum levels were also decreased in the LHRH_a treated rats (61 ± 6 ng/dl vs 93 ± 7 ng/dl, P 〈0.005), while serum progesterone levels were similar in both groups of animals. These changes in steroid concentrations were associated with decreases in the musomal enzyme activities of 17-hydroxylase (37 ± 9 vs 654 ± 41 pmol/mg protein/min, P 〈0.001), 17, 20-desmolase (103 ± 9 vs 522 ± 47 pmol/mg protein/min, P 〈0.001), 3β-hydroxysteroid dehydrogenase (1.7 ± 0.02 vs 4.1 ± 0.1 nmol/mg protein/min, P 〈0.001), aromatase (95 ± 7 vs 228 ± 6 pmol/mg protein/ min, P 〈0.001) and 17-ketosteroid reductase (167 ± 9 vs 290 ± 18 pmol/mg protein/min, P 〈0.01) in the LHRH_a treated animals. These findings indicate that LHRH_a can inhibit directly rat testicular testosterone biosynthesis.     

Cell cycle analysis and synchronization of the TN-368 insect cell line

Summary A cell cycle analysis of theTrichoplusia ni (TN-368) insect cell line is described. By means of autoradiography and percent labeled metaphase data, the cell cycle parameters were determined to be as follows: S, 4.5 hr; G₂, 8.5 hr; M, 0.5 hr; G₁, 1.0 hr; the total cell time being 14.5 hr. A synchronization procedure using 50mm thymidine in a double block procedure was used to provide a method of obtaining a large number of cells in particular cell cycle phases, especially S and G₂. This work was supported in part by U.S. Environmental Protection Agency Grant R-802516.     

Succinate-cytochrome c reductase activity and lipids in diapause and non-diapause Anthonomus grandis from different latitudes

Succinate-cytochrome c reductase (SCR) activity and fat content were compared for diapausing and non-diapausing boll weevils, Anthonomus grandis, collected from various latitudes. Thoracic mitochondrial SCR activity was unaffected by diapause; however, the SCR activity of abdominal mitochondria was reduced by 50% in diapausing weevils and the fat content increased by 2-fold. Diapausing weevils from the southernmost latitude showed the lowest SCR activity and the lowest fat content and were distinct from the other diapausing groups. No correlation was found between northern latitudes and SCR activity during diapause. The significance of the results is discussed from the standpoint of food quality and the evolution of diapause in the boll weevil.     

Prolactin increases the density of striatal dopamine receptors in normal and hypophysectomized male rats

Administration of prolactin to adult male rats, by s.c. injection, significantly increases the density of the striatal dopamine (DA) receptors, without altering the apparent affinity of the receptors for [³H]spiroperidol. Larger doses of prolactin are required to increase the density of the striatal DA receptors in hypophysectomized rates compared to normal rats. These results suggest that prolactin might be the common mediator of the increase in striatal DA receptor density produced by either estrogen or haloperidol administration. Monitoring and/or altering prolactin levels might be informative in neurologic or psychiatric disorders involving striatal DA neurotransmission.     

The role of the conjugated carbonyl of cytochalasin A in contractility inhibitions

A study of the mechanism of action of cytochalasin A (CA) in relation to its structural features and to its selective inhibition of certain contractile processes has been initiated. Quantitative structure-function analyses with several CA-related cytochalasins — including synthetic 21, 22-dihydro-CA (DHCA), the 22-β-mercaptoethanol CA-adduct, (CA-2ME), and the 22-dithiothreitol CA-adduct (CA-DTT) — have been carried out in a temperature sensitive gel-sol extract from Ehrlich ascites tumor cells. Each drug congener was purified to homogeneity by HPLC prior to biological testing. The undiminished inhibitory indices of DHCA and CA-2ME $\text{(}\text{ID}{}_{\mathrm{5\; 0}}\text{? 3.7 × 10}{}^{\mathrm{?7}}\text{M}\text{)}$ overrules the prior circumstantial evidence accumulated for the obligatory electrophilic interaction of this drug, at its α-β-unsaturated ketone region, with presumptive receptor nucleophiles.     

Brain water and electrolytes in response to respiratory acidosis and brain edema in the mutant mouse,Jimpy

Compared to littermate controls, unstressed Jimpy mice have higher brain water, sodium, potassium and chloride contents and lower carbonic anhydrase activity. When stressed by CO₂ to produce a respiratory acidosis or by injection of distilled water to produce brain edema, the Jimpy mouse brain has water and ionic responses essentially like those in controls.     

Proliferation of pulmonary endothelial cells: Time-lapse cinematography of growth to confluence and restitution of monolayer after wounding

A fundamental characteristic of vascular endothelium is that it exists as a monolayer, a condition that must be met in both vascular growth and repair. Maintenance of the monolayer is important both for the exchange of nutrients and for interactions between blood solutes and endothelial enzymes and transport systems. We have used time-lapse cinematography to compare proliferative behavior of bovine pulmonary endothelial cells in (1) establisment of a monolayer from a low-density seed (7.5 × 10⁴ cells in a 60 mm dish) and (2) restitution of a confluent monolayer (approx. 2.9 × 10⁶ cells in a 60 mm dish) following a mechanical wound (removal of cells from an area 5 × 15 mm by scraping). Culture 2 was not refed after wounding. In culture 2, approx. 30% of the cells accounted for repopulation (confluence in 40 hr). In culture I, all cells entered into division. Participating cells of culture 2 began division immediately (69 divisions/filmed area in 10 hr, vs. four divisions in culture I). Interdivision times (IDT) were longer and relatively constant in culture I until near confluence; none were < 10 h, whereas in 2, 24% of the IDT's were ≤ 10 hr. Remarkably, IDTs of culture 2 decreased steadily until confluence was re-established. Cell migration in culture 1 was multidirectional while direction of migration in culture 2 was always into the wound area. Mean migration rate (MIG) in culture 2 was related to the site of origin of the cells, those dividing farthest from the unwounded area had fastest MIGs. Neither culture formed more than a single layer of cells. Although the cell kinetics of cultures 1 and 2 differed, the same goal, confluence, was achieved in either case.     

A comparison of esterolytic mechanisms of several sulfhydryl proteases

A comparison was made of the esterolysis reactions catalyzed by chymopapain, papaya peptidases A and B, several asclepains of both the A and B families, ficin, and bromelain. Michaelis parameters for a series of aryl mesyl glycinates were measured and plotted versus the relevant Hammett σ values. All enzymes exhibited the same response to the substrates used.     

Resolution of microbial mixtures by free flow electrophoresis

Summary The resolution of bacterial mixtures by free flow electrophoresis (FFE) was not affected by the position of the microbes on the growth curve and approximately 70% of the individual cells applied were recovered as viable cells. The dependence of bacterial electrophoretic mobility on the pH, salt concentration, and viscosity of the electrolyte was determined. Suspending media and running electrolyte were developed which allowed collection of samples of>99% purity within two minutes of introduction of a mixture of Escherichia coli and Staphylococcus aureus. Most bacterial strains migrated in a single band, although some migrated in more than one band. Escherichia coli was resolved from each of 10 different species. The considerable variation in mobility found in 21 different E. coli strains, however, appears to preclude use of FFE as a method of species identification.