The respiratory inhibitor antimycin A specifically binds Fe(III) ions and mediates utilization of iron by the halotolerant alga Dunaliella salina (Chlorophyta)

It is demonstrated that Antimycin A (AA), a respiratory inhibitor produced by Streptomyces bacteria, forms lipophylic complexes with Fe(III) ions. Spectroscopic titration indicates that Fe(III) ions interact with 2AA molecules. At growth-limiting Fe concentrations, AA mediates Fe uptake and promotes growth and chlorophyll synthesis better than other Fe chelators in the halotolerant alga Dunaliella salina. It is proposed that AA enhances Fe bioavailability in hypersaline solutions by formation of lipophylic Fe-AA complexes which are taken-up and utilized by the algae. The results suggest that the respiratory inhibitor AA can affect Fe metabolism in microorganisms.     

Fertility determinants in the oil region of Mexico

This study analyzes fertility determinants in the oil region of Mexico, consisting of the states of Veracruz, Tabasco, and Campeche. Data are from the 1980 Mexican census and the unit of analysis is the municipio. The regression models, in which the dependent variables of children ever born and child-woman ratio are examined, reveal religious variables to be most significant, with greater fertility for non-Catholics and persons with no religion than for Catholics. Also of great importance are economic variables. Literacy and urbanization, both "classical" Mexican fertility variables, reduce fertility. There are major differences among three urban/rural and three indigenous language subsamples. Results are discussed vis-a-vis demographic theories and prior research.     

SV40 immortalizes myogenic cells: DNA synthesis and mitosis in differentiating myotubes

Primary skeletal muscle myoblasts have a limited proliferative capacity in cell culture and cease to proliferate after several passages. We examined the effects of several oncogenes on the immortalization and differentiation of primary cultures of rat skeletal muscle myoblasts. Retroviruses containing a SV40 large T antigen (LT) gene very efficiently immortalize myogenic cells. The immortalized cell lines retain a very high differentiation capacity and form, in the appropriate culture conditions, a very dense network of muscle fibers. As in primary culture, cell fusion is associated with the synthesis of large amounts of muscle-specific proteins. However, unlike normal myoblasts (and previously established myogenic cell lines), nuclei in the multinucleated fibers of SV40-immortalized cells synthesize DNA and enter mitosis. Thus, withdrawal from DNA synthesis is not obligatory for cell fusion and biochemical differentiation. Using a retrovirus coding for a temperature-sensitive SV40 LT, myogenic cell lines were produced in which the SV40 LT could be inactivated by a shift from 33 degrees C to 39 degrees C. The inactivation of LT induced massive cell fusion and synthesis of muscle proteins. The nuclei in those fibers did not synthesize DNA, nor did they undergo mitosis. This approach enabled the reproducible establishment of myogenic cell lines from very small populations of myoblasts or single primary myogenic clones. Activated p53 also readily immortalized cells in primary muscle cultures, however the cells of eight out of the nine cell lines isolated had a fibroblastic morphology and could not be induced to form multinucleated fibers.     

Calcium is necessary for light excitation in barnacle photoreceptors

Summary Illumination of barnacle (Balanus amphitrite) photoreceptors is known to increase the membrane permeability to sodium and Ca²⁺ ions resulting in a depolarizing receptor potential. In this report, we show that lanthanum (La³⁺), a known inhibitor of Ca-binding proteins, reversibly eliminates the receptor potential of barnacle photoreceptors when applied to the extracellular space. Similar reversible elimination of the light response was obtained by removing extracellular Ca²⁺ by application of the calcium chelating agent EGTA. Iontophoretic injection of Ca²⁺, but not K⁺ into the cells protected both the transient and the steady-state phases of the receptor potential from elimination by EGTA while only the transient phase was protected in the presence of La³⁺. The EGTA experiments suggest that internal Ca²⁺ is necessary for light excitation of barnacle photoreceptors while the La³⁺ experiments suggest that La³⁺-sensitive inward current is necessary to maintain excitation during prolonged light.Abbreviations EGTA ethylenglyol-bis-(-aminoethylether) N, N, N¹, N¹-tetraacetate - BAPTA bis-(0-aminophenoxy)-ethane-N, N, N¹, N¹-tetraacetic acid - DMSO dimethyl sulfoxide - trp transient receptor potential - nss no steady state - ASW artificial sea water     

Amine Accumulation in Acidic Vacuoles Protects the Halotolerant Alga Dunaliella salina Against Alkaline Stress

Amines at alkaline pH induce in cells of the halotolerant alga Dunaliella a transient stress that is manifested by a drop in ATP and an increase of cytoplasmic pH. As much as 300 millimolar NH₄⁺ are taken up by the cells at pH 9. The uptake is not associated with gross changes in volume and is accompanied by K⁺ efflux. Most of the amine is not metabolized, and can be released by external acidification. Recovery of the cells from the amine-induced stress occurs within 30 to 60 minutes and is accompanied by massive swelling of vacuoles and by release of the fluorescent dye atebrin from these vacuoles, suggesting that amines are compartmentalized into acidic vacuoles. The time course of ammonia uptake into Dunaliella cells is biphasic—a rapid influx, associated with cytoplasmic alkalinization, followed by a temperature-dependent slow uptake phase, which is correlated with recovery of cellular ATP and cytoplasmic pH. The dependence of amine uptake on external pH indicates that it diffuses into the cells in the free amine form. Studies with lysed cell preparations, in which vacuoles become exposed but retain their capacity to accumulate amines, indicate that the permeability of the vacuolar membrane to amines is much higher than that of the plasma membrane. The results can be retionalized by assuming that the initial amine accumulation, which leads to rapid vacuolar alkalinization, activates metabolic reactions that further increase the capacity of the vacuoles to sequester most of the amine from the cytoplasm. The results indicate that acidic vacuoles in Dunaliella serve as a high-capacity buffering system for amines, and as a safeguard against cytoplasmic alkalinization and uncoupling of photosynthesis.     

Hydrolysis of polyphosphates and permeability changes in response to osmotic shocks in cells of the halotolerant alga dunaliella

The effects of osmotic shocks on polyphosphates and on the vacuolar fluorescent indicator atebrin have been investigated to test whether acidic vacuoles in the halotolerant alga Dunaliella salina have a role in osmoregulation. Upshocks and downshocks induce different patterns of polyphosphate hydrolysis. Upshocks induce rapid formation of new components, tentatively identified as 5 or 6 linear polyphosphates, formed only after upshocks with NaCl and not with glycerol, indicative of compartmentation of Na⁺ into the vacuoles. Conversely, downshocks induce a slower transient accumulation of tripolyphosphates, indicating activation of a different hydrolytic process within the vacuoles. Osmotic shocks do not lead to release of atebrin from acidic vacuoles, indicating that they do not induce a major intravacuolar alkalinization. However, osmotic shocks induce transient permeability changes measured by amine-induced atebrin release from vacuoles. Hypoosmotic shocks transiently increase the permeability (up to 20-fold), whereas hyperosmotic shocks induce a rapid drop in permeability. Electron micrographs of osmotically shocked cells also reveal transient changes in the surface and internal organelles of D. salina cells. It is suggested that hyperosmotic and hypoosmotic shocks induce different changes within acidic vacuoles and in the organization and/or composition of the plasma membrane in Dunaliella.     

Bulb mite,Rhizoglyphus robini (Astigmata: Acaridae) as an experimental animal

Rhizoglyphus robini Claparède (Acari: Astigmata: Acaridae) is proposed as a model laboratory animal for biological, ecological, physiological and toxicological studies. The mite is easy and inexpensive to rear, quite fecund, convenient to manipulate, and may rapidly be raised to gram quantities. Examples are presented of its use in soil pest ecology and control studies, and in physiological, biochemical and toxicological investigations. Efforts to explore the induction of detoxification systems by various chemicals, and a demonstration of its control by solarization, are also described.     

A light-dependent dicyclohexylcarbodiimide-sensitive Ca-ATPase activity in chloroplasts which is not coupled to proton translocation

The early observation of light-dependent Ca-ATPase activity in chloroplast thylakoids [Avron, M. (1962) J. Biol. Chem. 237, 2011-2017] has been reinvestigated. It is demonstrated that in contrast to light-triggered Mg-ATP activity, Ca-ATPase activity is strictly dependent on delta microH+, the transthylakoid membrane electrochemical potential gradient, since (a) there is an absolute requirement for continuous illumination; (b) electron-transport mediators that catalyze proton uptake, like phenazinemethosulphate, methylviologen of ferricyanide, are essential and (c) uncouplers inhibit the activity. The Ca-ATPase activity is essentially unaffected by dithiols, but is inhibited by CF0-CF1 inhibitors including tentoxin, dicyclohexylcarbodiimide and antisera to CF1. Addition of Ca-ATP to thylakoids does not induce delta pH or delta psi (the electrical potential gradient) formation either in the light or following preillumination with dithiols, demonstrating that it is not coupled to proton translocation. It is also demonstrated that Ca-ATP or Ca-ADP does not induce a proton leak through CF0-CF1. It is concluded that the Ca-ATPase activity in chloroplast thylakoid reflects a partial reaction of ATP synthesis catalyzed by CF0-CF1, which is internally uncoupled from proton translocation but is dependent on energization by a transmembrane delta microH+.     

Potential antiradiation drugs containing no nitrogen, and related compounds

Capabilities are reported of di- and higher sulfides (RSnR') terminated by sulfinate functions [-S(O)O-] for protecting mice against otherwise lethal effects of ionizing radiation. With the use of congeners, structure-activity correlations are developed for the effects of esterification of the sulfinate function, of changing the length of the chain of sulfur atoms, of reduction to a mercapto sulfinate, and of changing the substituents R and R' to chiral and other types of groups. Neither a trisulfide nor a sulfinate by itself was significantly radioprotective. The key requirement for radio-protection in the series appears to be the presence of a sulfur function (-Sn-) from which a thiol can be engendered by a neighboring-group effect of an electron-donating group; sulfoxide functions may afford alternatives to sulfinate functions as such neighboring groups. The relevance of structure-activity relations to the chemical and biological mechanisms involved in the radioprotective activities is discussed.