Anion secretion by the isolated rabbit pancreas

The isolated rabbit pancreas secretes a fluid containing chloride and bicarbonate in about equal concentrations. Replacement of bicarbonate by acetate, phosphate or isethionate, replacement of Na⁺ by Li⁺ and addition of ouabain to the bathing medium of the pancreas inhibit the secretion of fluid, chloride and bicarbonate in a similar fashion and by maximally 100%. Replacement of chloride by isethionate inhibits fluid secretion by maximally 50%, chloride secretion by 90% and bicarbonate secretion by 20%. It is concluded that fluid secretion is based on a Na⁺-gradient-dependent bicarbonate influx or proton efflux in the ductular cell, and that the secretion of chloride is secondary to that of bicarbonate.     

Microscopic anatomy of the ovary ofAlouatta caraya

The microscopic structure of theAlouatta caraya ovary is studied in different ages and reproductive stages. The most significant feature seems to be the presence in adult ovaries of abundant glandular interstitial tissue which occupies both the cortex and medulla. It seems to be derived from the theca interna of atretic follicles. Discrete luteinized masses are present in the medulla in all the ovaries observed. Invaginations of the surface epithelium are seen only in infant and juvenile ovaries. The development of cystic follicles seems to be a common pathway of atresia.     

The identification of trihydroxyeicosatrienoic acids as products from the incubation of arachidonic acid with washed blood platelets

Arachidonic acid is converted by washed platelets from man, horse and dog into a mixture of 8, 9, 12-trihydroxyeicosa-5, 10, 14-trienoic acid and 8, 11, 12-trihydroxyeicosa-5, 9, 14-trienoic acid (termed 8, 9, 12-THETA and 8, 11, 12-THETA respectively and THETA collectively). Gas chromatographic — mass spectrometric evidence of structure is discussed.     

Dimers of nicotinamide adenine dinucleotide: New evidence for the structure and the involvement in an enzymatic redox process

The composition and the structure of the product from the known electrochemical dimerization of the NAD⁺ have been conclusively demonstrated. A detailed analysis of the ¹H and ¹³C nmr spectra has in fact led to the conclusion that the product contains three diastereoisomeric dimers of the 4,4′-tetrahydrobipyridyl type. Furthermore, the cytoplasmic fraction obtained from a standard mitochondrial preparation of rat liver has been shown to catalyze the oxygen uptake by the dimers. A 1 : 1 molar ratio of the reagents in the redox process is indicated by manometric data on oxygen uptake complemented by spectrophotometric analysis of the oxidized substrates, suggesting that H₂O₂ is the reduction product. NAD⁺ was identified as the oxidation product by an enzymatic method.     

Guanosine 5′-triphosphate and guanosine 5′-[βγ-imido]triphosphate effect a collision coupling mechanism between the glucagon receptor and catalytic unit of adenylate cyclase

1. GTP, but not p[NH]ppG (guanosine 5′-[βγ-imido]triphosphate), abolishes the sensitivity of glucagon-stimulated adenylate cyclase to the lipid-phase separations occurring in the outer half of the bilayer in liver plasma membranes from rat. 2. When either GTP or p[NH]ppG alone stimulate adenylate cyclase, the enzyme senses only those lipid-phase separations occurring in the inner half of the bilayer. 3. Trypsin treatment of intact hepatocytes has no effect on the basal, fluoride-, GTP- or p[NH]ppG-stimulated adenylate cyclase activity. However, ¹²⁵I-labelled-glucagon specific binding decays with a half-life matching that of the decay of glucagon-stimulated adenylate cyclase activity. 4. When GTP or p[NH]ppG are added to assays of glucagon-stimulated activity, the half-life of the trypsin-mediated decay of activity is substantially increased and the decay plots are no longer first-order. 5. Trypsin treatment of purified rat liver plasma membranes abolishes basal and all ligand-stimulated adenylate cyclase activity, and ¹²⁵I-labelled-glucagon specific binding. 6. Benzyl alcohol activates the GTP- and p[NH]ppG-stimulated activities in an identical fashion, whereas these activities are affected differently when glucagon is present in the assays. 7. We suggest that guanine nucleotides alter the mode of coupling between the receptor and catalytic unit. In the presence of glucagon and GTP, a complex of receptor, catalytic unit and nucleotide regulatory protein occurs as a transient intermediate, releasing a free unstable active catalytic unit. In the presence of p[NH]ppG and glucagon, the transient complex yields a relatively stable complex of the catalytic unit associated with a p[NH]ppG-bound nucleotide-regulatory protein.     

A statistical investigation of the time-sampling methods in studying primate behavior

Two commonly used time-sampling techniques in studying animal behavior, namely, fixed interval time point technique and fixed interval time span technique have been investigated, in which their statistical properties and the estimators for frequency and duration have been discussed. Three simple numerical examples have been used to illustrate the calculation of estimates. Finally, a sketch of a stochastic approach to the problem and the resultant estimators are presented, in which all the possible transitions are considered. Therefore, both total frequency and duration of a certain behavior can be estimated by summing up the estimators during each fixed intervening interval with only two end-points being observed.     

Effects of cAMP,theophylline, imidazole,and 4-(3,4-dimethoxybenzyl)-2-imidazolidone on the leaf movement rhythm of Trifolium repens—a test of the cAMP-hypothesis of circadian rhythms

The period length of the leaf movement rhythm of Trifolium repens L. is lengthened by continuously offered cAMP (0.5–1.0 mol m^-3) and theophylline (0.5–4 mol m^-3). At the higher concentrations this effect is more pronounced and the rhythm damps out faster. Imidazole (0.5 and 1 mol m^-3) has no effect on the period length; however, after 5 mol m^-3 the rhythm is abolished. Offered as 4 h pulses the resulting phase response curves for cAMP and imidazole are similar and show delays of up to 4 h during the day position of the leaves. Theophylline pulses lead to delays of up to 5 h during closure and advances of up to 3 h during opening. No phase shift is brought about by 4-(3,4-dimethoxybenzyl)-2-imidazolidone. The results do not support the cAMP-model of the circadian clock which has been proposed by Cummings (J. theor. Biol. 55, 455–470; 1975). The effect of the substances tested could, however, be based upon influences on the transport of Ca²⁺.Abbreviations ATP adenosine triphosphate - cAMP cyclic adenosine 35 monophosphate - AMP adenosine 5 monophosphate - AC adenyl cyclase - PDE phosphodiesterase - LL continuous light