Ionophore-mediated Ca2+ countertransport: role of Na+, Li+ or H+ gradient

Summary In an artificial system, the ionophore A23187, which transports Ca²⁺ but not Na⁺, is able to mediate the uphill translocation of Ca²⁺ from one aqueous medium to another across an organic immiscible phase, provided that a Na⁺, Li⁺ or H⁺ gradient is imposed on the system. Therefore, in the process known as Na-Ca countertransport, the downhill influx of Na⁺ may not be necessary for causing Ca²⁺ extrusion against its electrochemical gradient.     

Ionomycin-mediated calcium transport in rigid and fluid liposomes

The antibiotic ionophore ionomycin translocates Ca from an aqueous medium into or across an organic immiscible phase. At pH 8.0, ionomycin translocates less Ca than A23187, the effects of these ionophores being additive to one another. The capacity of ionomycin to translocate Ca across the organic phase is dramatically decreased when the pH of the aqueous media is reduced from 8.0 to 7.5 or lower values. Ionomycin also mediates Ca exchange-diffusion in liposomes, the magnitude of such a process being greater in fluid than in rigid liposomes. At a physiological pH (7.4), ionomycin is unexpectedly as potent as A23187 in mediating Ca transport in fluid liposomes. These findings suggest that the capacity of ionophores to translocate Ca across model membranes depends on both the transverse and lateral mobility of the ionophoretic molecules. The relative importance of the latter phenomenon itself largely depends on the stoichiometry of the Ca-ionophore complex.     

The distribution of hydroxycinnamic acid amides in flowering plants

Hydroxycinnamic acid amides have been identified as the main phenolic constituents in the reproductive organs of a range of flowering plants.     

Secondary trisomy 1 q due to a reciprocal maternal translocation]

The authors report a case of partial trisomy 1 q due to a maternal balanced translocation : t(1 ; 4) (q 32 : p 16). The evocative malformations of trisomy 1 q and monosomy 4 p are discussed and compared to seven others from the literature. Then the interest of the chromosomical prenatal diagnosis and the significance of familial genetic studies are showed.     

Evidence for a gonadal nonsteroidal factor that specifically inhibits release of luteinizing hormone in ewes.

Bilaterally ovariectomized ewes were used to investigate the effect of systemic administration (i.v.) of charcoal-treated aqueous luteal extracts from ovine corpora lutea on plasma concentrations of pituitary gonadotrophins. Jugular blood samples were taken every 15 min at least 5 h before (control period) and 5 h after (treatment period) injection. In Expt 1, the administration of luteal extract from corpora lutea of days 70-76 of pregnancy, but not of the extract prepared from muscular tissue, resulted in a significant decrease of mean concentrations of luteinizing hormone (LH) (P < 0.02) and frequency of LH pulses (P < 0.01). Plasma follicle-stimulating hormone (FSH) concentrations were not affected by injections of either extract. These findings provide the first demonstration of the presence of a nonsteroidal factor in the corpus luteum of midpregnancy that selectively suppresses the secretion of LH. In Expt 2, mean concentrations of LH and FSH and frequency of LH pulses were unaffected by injections of luteal extracts from ovine corpora lutea of days 10-12 of the oestrous cycle or day 15 of pregnancy. These data suggest that some factor(s), probably from the fetoplacental endocrine unit, is required to ensure the production of a significant quantity of the luteal LH-inhibiting factor after day 15 of pregnancy. In Expt 3, treatment of luteal extract from corpora lutea of day 70 of pregnancy with proteolytic enzymes destroyed the LH-inhibiting activity, suggesting the proteic nature of the luteal LH-inhibiting factor. In Expt 4, plasma concentrations of LH were not affected by injection of charcoal-treated extract prepared from fetal cotyledonary tissue of days 110-120 of pregnancy suggesting that the LH-inhibiting factor exclusively originates from the corpus luteum during pregnancy. These experiments provide the first direct evidence for the existence of a potent nonsteroidal factor of luteal origin that specifically inhibits pulsatile secretion of LH, without influencing FSH release in female animals. We propose the term LH-release-inhibiting factor (LH-RIF) to describe this activity.     

In vivo activation of blood and arterial prophospholipase by an activator of blood platelet origin]

When partially purified platelet-rat lysate is injected in the rat aorta, transformation of prophospholipase into phospholipase is observed. Blood prophospholipases are activated almost entirely during about 15 minutes; aortic phospholipase are entirely activated for a longer time.     

Genetic structure of a tribal population, the Yanomama Indians. XIII. Dental microdifferentiation.

Data are presented on the frequency of the following eight dental traits in 635 Yanomama and 65 Makiritare Indians: upper central incisor rotation or winging, shoveling of maxillary incisors, maxillary molar hypocone reduction, Carabelli's trait, mandibular molar cusp number, mandibular molar cusp pattern rotation of second lower premolar, and pattern of second lower premolar cusps. Yanomama dentition is unusual in the high frequency of six cusps on the mandibular molars. There is marked dental microdifferentiation between villages; significant agreement was observed between a matrix of pairwise "dental distances" based on six morphological traits and corresponding matrices based on 11 genetic systems and on geographic location.     

Purification of rat adipose tissue lipoprotein lipase by affinity chromatography.

Lipoprotein lipase (EC 3.1.1.3) from rat adipose tissue was purified by affinity chromatography with heparin-Sepharose. Elution was carried out with buffered solutions of increasing NaCl molarity. Proteins without affinity for heparin were eluted with 0.5 M NaCl, while lipoprotein lipase activity was eluted as two peaks with 1.16 M NaCl (In earlier work on human adipose tissue (Etienne et al. (1974) C.R. Acad. Sc. Paris 279, 1487-1490) two fractions with lipoprotein lipase activity were also obtained). Phospholipase activity was detected in the fraction eluted with buffered 0.5 M NaCl and containing proteins without affinity for heparin. On feeding the fasting rats with fresh cream or glucose two peaks were also obtained, but the first peak had clearly increased while the second one had remained virtually unchanged.