Two new mimosaceous trees from the American Tropics

Piptadenia (sect.Pityrocarpa)leucoxylon is described from the lower Orinoco basin in Venezuela, andPithecellobium (sect.Samanea)foederale from Distrito Federal, Brazil. Figures, diagnoses, and discussion of kinship are presented for each.     

Testing for bacterial resistance to arsenic in monitoring well water by the direct viable counting method.

Direct viable counting of metal-resistant bacteria (DVCMR) has been found to be useful in both enumerating and differentiating metal-resistant and metal-sensitive strains of bacteria. The DVCMR bioassay was used to detect effects of low and high concentrations of arsenic and arsenicals on bacterial populations in groundwater. The level of resistance of the bacterial populations to arsenate was determined by the DVCMR bioassay, and the results showed a linear correlation with the total arsenic concentrations in the monitoring well water samples; no correlation was observed by culture methods with the methods employed. Bacteria resistant to 2,000 micrograms of arsenate per ml were isolated from all monitoring well water samples studied. Strains showed similar antibiotic and heavy-metal profiles, suggesting that the arsenic was not a highly selective pressure for arsenic alone. The monitoring well water samples were amended with arsenate and nutrients to determine the biotransformation mechanisms involved. Preliminary results suggest that bacteria indigenous to the monitoring well water samples did not directly transform, i.e., precipitate or volatilize, dissolved arsenic. It was concluded that arsenic contamination of the groundwater can be monitored by the DVCMR bioassay.     

A comparison of histological and non-histological indices of atresia and follicular function

Histological indices of atresia for bovine follicles greater than or equal to 5 mm in diameter were compared with potential non-histological indices of atresia such as opaqueness of the exposed surface of non-excised follicles, concentrations of steroids in follicular fluid (FF) and specific binding of gonadotropins by granulosal cells. Each non-excised follicle was classified as clear (n=86), intermediate (n=79), or opaque (n=115), on the basis of the appearance of its exposed surface. A section of tissue from each follicle was evaluated histologically for atresia and assigned to one of the following categories: non-atretic, intermediately atretic, strongly atretic, or luteinized-atretic. Concentrations of estradiol (E), progesterone (P), and testosterone (T) and capacity of granulosal cells to bind radioactive ovine follicle-stimulating hormone (oFSH) and human chorionic gonadotropin (hCG) were determined for each follicle. Overall incidence of atresia was similar for clear (n=66%), intermediate (60%), and opaque (72%) follicles. Opaque follicles, however, were more likely to be strongly atretic (42%) than were clear (21%) or intermediate (23%) follicles. Non-atretic and intermediately atretic follicles had similar concentrations of E, P, and T and similar capacities to bind gonadotropins. Strongly atretic and luteinized-atretic follicles contained a higher concentration of P, lower E, and a reduced capacity of granulosal cells to bind oFSH than non-atretic and intermediately atretic follicles. A ratio of P:E in FF greater than or equal to 10 usually (greater than 90%) indicated that a follicle was atretic. However, lesser ratios of P:E did not accurately indicate whether follicles were atretic.(ABSTRACT TRUNCATED AT 250 WORDS)     

Diatoms in sediment cores in Utah Lake,Utah, U.S.A.

Diatoms from sediment cores taken from Provo Bay, Geneva and midlake sites in Utah Lake, Utah County, Utah were studied. Algal communities from strata at four centimeterintervals of the cores were analyzed. This study has demonstrated that the diatom flora in Utah Lake has changed through time and that the diatom communities of Provo Bay are floristically unique from those of the main body of the lake.     

The Role of Calcium and Calmodulin in Carrot Somatic Embryogenesis

The role of Ca²⁺ and calmodulin in carrot somatic embryo formationwas examined. Embryogenic cell clumps were induced to form embryosin medium containing 0–3 mM Ca²⁺. Embryo formation wasnot affected until the concentration of Ca²⁺ was lower than200 µM and after this threshold was reached the percentof embryo formation decreased with lower Ca²⁺ concentrations.Treatment of developing embryos with either verapamil or nifedipine,Ca²⁺ -channel blockers, or the Ca²⁺ ionophore A23187 [GenBank] , inhibitedembryo formation. These results suggest that exogenous Ca²⁺or the maintenance of Ca²⁺ gradients are required for properembryo development. Analysis of membrane-associated Ca²⁺ andtotal membrane distribution using the fluorescent dyes chlorotetracyclineand N-phenyl-1-napthylamine, respectively, indicated changesin the distribution of membranes during embryogenesis withoutany significant alterations in the concentration of Ca²⁺ associatedwith the membranes. In heart- and torpedo-stage embryos, calmodulin-Ca²⁺complexes were localized in regions containing the developingmeristems of both the cotyledon tips and rhizoid regions whiletotal calmodulin protein appeared to be more uniformly distributed.Calmodulin mRNA levels increased slightly when cell clumps wereinduced to form embryos. (Received July 7, 1993; Accepted September 27, 1993)     

Vibrio species associated with mortality of sharks held in captivity

Two urease-positiveVibrio spp. were isolated from a brown shark (Carcharhinus plumbeus) that died in captivity at a national aquarium. Morphological, biochemical, and molecular genetic studies revealed one of the isolates to beV. damsela; the other isolate was unique and has been classified asV. carchariae sp. nov. BothV. damsela andV. carchariae were found to be virulent for spiny dogfish (Squalus acanthias), causing death in less than 18 hours after intraperitoneal injection of ca. 4×10⁶ cells.V. damsela was strongly cytotoxic for Y1 adrenal cell monolayers;V. carchariae exhibited weak cytotoxicity for Y1 cells.V. damsela contained cryptic plasmids and both isolates were urease positive.V. carchariae was able to utilize urea as sole source of carbon and nitrogen.