Actinomycin D and cycloheximide actions on activity of some intestinal enzymes of adult hamster

Actinomycin D, at a dose of 0.25 micrograms/g body wt, produced slight increases in intestinal enzymatic activity on hamsters. At a high dose (1.5 micrograms/g body wt), actinomycin D produced inhibition of lactase activity, whereas maltase, sucrase and alkaline phosphatase activity decreased in males and increased in females. Cycloheximide (1.5 micrograms/g body wt), produced no changes in enzymatic activity. In the male and female hamster, the different actions of the antibiotic can be explained by the variations in the cortisol release produced by stress.     

Estimation of the mechanical parameters of the human respiratory system

A numerical algorithm has been developed for the estimation of the mechanical parameters of the human respiratory system. In order to estimate the pulmonary resistance and the dynamic pulmonary elastance, the transpulmonary pressure and the airflow at the mouth or nose are expanded in Chebyshev series. The nonlinear mathematical lung model and a set of measurements for airflow and pressure are then handled by the numerical technique. The lung model includes a component to account for turbulent flow in the larynx and trachea. This contribution presents an alternative method for lung parameter estimation and differs from most existing methods in that it does not need measurements for the tidal volume. It therefore eliminates the use of a body plethysmograph. The method may also find potential application to various other parameter identification problems.     

Effect of nonanoic acid and other short chain fatty acids on exchange properties in embryonic axes of Cicer arietinum during germination

Nonanoic acid, which inhibits germination in several seeds, enhanced ion efflux from embryonic axes of Cicer arietinum L., especially at temperatures above 25°C. Other short chain fatty acids had little effect on germination and ion leakage. Nonanoic acid also decreased uptake of ⁸⁶Rb⁺ and ²²Na⁺ and increased efflux of both isotopes from the embryonic axes into the incubation solution. Fusicoccin, which stimulates early germination in C. arietinum , counteracted the effects of nonanoic acid at both 25 and 30°C. These results suggest that nonanoic acid affects the integrity of plasmalemma and other membrane systems. Nonanoic acid thus inhibits cell elongation during early germination by disturbing ion exchange and inhibiting water uptake.     

Addition of an androgen-free epididymal protein extract increases the ability of immature hamster spermatozoa to fertilize in vivo and in vitro

The fertility of spermatozoa from the different epididymal segments of hamsters was tested by in-vivo insemination. Caput and proximal corpus spermatozoa were non-fertile; spermatozoa from the distal corpus epididymidis fertilized 13% (38/290) oocytes and those from the proximal and distal cauda epididymidis 71 and 87%, respectively. When tested by in-vitro insemination, distal corpus spermatozoa penetrated 44% of oocytes while those from the distal cauda fertilized 87% of oocytes. Spermatozoa from the distal corpus recovered in Medium BMOC fertilized 13% (28/219) of oocytes in vivo, while those mixed with an epididymal protein preparation (0.8 mg protein/ml) fertilized 24% (49/204; P less than 0.01) of oocytes. When distal corpus spermatozoa were inseminated in vivo with 0.8 mg epididymal protein preparation 34% (31/90) oocytes were fertilized and only 22% (23/103; P less than 0.05) oocytes were fertilized when the proteins were obtained from epididymides of animals castrated for 30 days. When distal corpus spermatozoa were preincubated for 5 h in medium without (control) or with protein preparation (0.8 or 1.6 mg protein/ml), a significant increase in in-vitro oocyte penetration was found (25 compared with 45%; P less than 0.05) when the protein was present at 1.6 mg/ml. These results confirm and extend previous observations suggesting a role for androgen-dependent glycoproteins secreted by the epididymis in the acquisition of fertilizing ability that occurs during sperm maturation.     

In vitro fertilization with normal development in the sheep

Ovine tubal (n = 87) and ovarian in vitro matured oocytes (n = 99) were fertilized in vitro with ejaculated spermatozoa capacitated for 8 h in modified defined medium buffered with Hepes. High levels of fertilization were obtained as assessed by development to two-to six-cell stage within 40 h (75. 8% for ovulated and 62. 6% for in vitro matured oocytes). Electron microscope analysis of oocytes 20–22 h after insemination indicated that in vitro fertilization approximated the in vivo events. Embryos (two- to six-cell) were transferred surgically to the oviducts of pseudopregnant rabbits. Three days later, 42 (from ovulated oocytes) and 15 (from in vitro matured oocytes) embryos were recovered; 26 (61. 9%) and 10 (66. 6%), respectively, had cleaved at least once. Embryos incubated in vivo (n = 20 from ovulated oocytes; n = 9 from in vitro matured oocytes) were transferred surgically to the uteri of seven and four recipient ewes resulting in four and two pregnancies, respectively, from which three and one, respectively, have been maintained ( > 3 months). The first lamb resulting from the in vitro fertilization of an ovulated oocyte was born. In addition, six embryos (two- to four-cell) from tubal oocytes and ten embryos (two- to six-cell) from in vitro matured oocytes were directly transferred to the oviducts of two and three ewes, respectively. Two pregnancies resulting from in vitro matured fertilized oocytes are in progress ( > 3 months).     

Ultrastructural differentiation of glandular stomach (proventriculus) in chick embryo

Cytochemical characterization of mucosubstances of chick glanular stomach (proventriculus) changes from 15 days of development to postnatal and adult stages was studied. To corroborate these data cytochemical, ultrastructural and ultracytochemical study of chick embryo proventriculus from 7 to 20 days of development was performed. At the 7th day several layers of undifferentiated cells formed an epithelium which covered the walls of the glandular stomach. Mocosubstances were not found. Between the 9th and 5th day a single layer of cylindrical cells was encountered forming invaginations which originated deep glands. Three types of cells were separated from the above mentioned layer, dark, clear and undifferentiated. The dark cells had organelles which are involved in protein synthesis and the clear ones were rich in mitochondria. Argentaffine cells appeared at 15th day instead mucosubstances formed a thin coat on the epithelium at 9th day which increased at the end of development in the apical cytoplasm and gland cells. These observations demonstrate that proventriculus of chick embryo has ultrastructurally differentiated cells involved with enzymatic and hydrochloric acid secretion after the 9th day. These progressive events are correlated with the digestion process of yolk during embryogenesis. At the end of development the proventriculus has completely organized the glandular layer.     

Looking for probes of gated channels: studies of the inhibition of glucose and choline transport in erythrocytes

Two seemingly contradictory sets of observations have been made in studies of biological transport, which are essential for our understanding of the transport mechanism: carriers are integral membrane proteins, which span the membrane and are not free to rotate across the membrane; carriers appear to function like a ferryboat, with a substrate binding site moving back and forth from one side of the membrane to the other. To reconcile these facts, it is necessary to postulated gated channels connecting the substrate site with the two membrane surfaces: the channels are arranged so that as one opens the other closes, with the result that the substrate site is alternately accessible from opposite sides of the membrane. Based on these properties, the following distinguishing features of molecules specifically bound in the channels may be predicted: if sufficiently bulky, they inhibit transport; they bind outside the substrate site (though adjacent to it), they bind asymmetrically either to the outward-facing carrier and on the outer surface of the membrane, or to the inward-facing carrier and on the inner surface of the membrane. The asymmetrical inhibition of the glucose and choline transport systems of erythrocytes by various inhibitors is examined, and the behavior in every case is found to conform with these criteria. From the results it may be concluded that the glucose carrier binds cytochalasin B in the inner gated channel and phloretin and tetrathionate in the outer gated channel.(ABSTRACT TRUNCATED AT 250 WORDS)     

Clathrin-associated proteins contain bound nucleotide

An alcohol dehydrogenase isolated from Zymomonas mobilis was found to be activated by ferrous ions but not by zinc, after inactivation with metal-complexing agents. Cobaltous ions also re-activated to a lesser extent. It is suggested that in this species the alcohol dehydrogenase naturally contains iron. Kinetic studies on the iron-treated enzyme indicate an 'alcohol activation' phenomenon, which may have physiological relevance in overcoming product inhibition during fermentation.     

Electro-optical measurements on aqueous suspension of purple membrane from Halobacterium halobium

The permanent dipole moment, polarizability, and the retinal angle of Halobacterium halobium purple membranes were determined at different pH values. All of the parameters have a maximum between pH 5 and 6. There is a reversal in the direction of the permanent dipole moment near pH 5. The value of permanent dipole moment was determined to be 60 D/protein at pH 6.6, and the value obtained for polarizability was 3 X 10(-28) Fm2/membrane fragment. The retinal angle of all-trans retinal was 0.8 degrees smaller than that of the 13-cis conformation.