The identification of unbranched enzyme kinetic mechanisms by computer analysis of qualitative information: Logic of the method

The paper describes the logic of a computer method for identifying unbranched enzyme kinetic mechanisms on the basis of observed initial velocity and product inhibition patterns (Cleland, 1963). The method establishes initially an acceptable order of reactant addition and release, proceeds to list all the mechanisms consistent with that order and the data, and finally determines which of these can also explain data which require either non-competitive or dead-end inhibition.     

Seasonal changes in plasma testosterone and ejaculatory capacity in squirrel monkeys (Saimiri sciureus)

Seasonal changes in body weight, plasma testosterone and ejaculatory capacity were observed in five intact and two testosterone-implanted castrated squirrel monkeys for a total of 13 months. Electroejaculation was employed for obtaining data concerning ejaculation. In the intact animals, there were significant increases in body weight, ejaculate volume and plasma testosterone during the breeding season. With the exception of one animal, there was also a decrease in ejaculation latency during the season. Seasonal differences in the sperm count and sperm motility were not observed. Testosterone-implanted castrates showed changes in both ejaculate volume and ejaculation latency similar to those seen in intact monkeys during the breeding season. The body weight and plasma testosterone of the castrates remained quite constant throughout the year. Supported by NIH grants HD 00778, MH 21178 and MH 23645.     

Studies of ribosomal proteins of yeast species and their hybrids gel electrophoresis and immunochemical cross-reactions

Summary The cytoplasmic ribosomal proteins (r-proteins) of seventeen yeast species of the genera Saccharomyces and Kluyveromyces were analyzed by one-dimensional gradient polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulphate. The electrophoretic patterns of cytoplasmic r-proteins from different species display extensive differences in both the 40S and the 60S subunit. Relatedness of species suggested by r-protein patterns correlates well with that based on DNA/DNA homology (Bicknell and Douglas 1970). Immunochemical cross-reactions and antibiotic susceptibility tests were also used to compare different species.Analyses of r-proteins from two different interspecific hybrids showed that their ribosomes were hybrid, containing r-proteins from both parents. These findings are discussed in relation to the evolution of yeast species and the regulation of expression of r-proteins in cucaryotes.     

A new species of Eugenia (Myrtaceae) from Venezuela

Eugenia mcvaughii is described from a forest remnant of the Jardin Botánico of Caracas, Venezuela. Found also in the hills adjacent to Caracas, it may be considered as an endemic species of the Interior Coastal Cordillera.     

New species from the summit of Cerro Guaiquinima,Venezuela

Three new species,Lubaria szczerbanii (Rutaceae),Croton guaiquinimae (Euphorbiaceae), andStomatochaeta colveei (Asteraceae), are described from the summit of Cerro Guaiquinima, Venezuela. The generic affinities betweenLubaria andMyllanthus, and betweenStomatochaeta andStenopadus are discussed.     

Random recirculation of small T lymphocytes from thoracic duct lymph in the mouse

The migration of ⁵¹Cr-labeled nylon-wool separated mouse thoracic duct T cells has been followed in order to determine whether there is a circulation of small (nondividing) T cells through the small intestine. Approximately 6% of the injected dose of T-TDL localized in the small intestine (minus Peyer's patches). Experiments revealed that this gut-localizing cell population consisted almost entirely, if not exclusively, of lymphoblasts present in mouse T-TDL. When lymphoblasts and small lymphocytes from mouse T-TDL were separated by velocity sedimentation, and the migration of separated fractions was studied, we found large cells (66% blasts) migrated well to the gut but poorly to the lymph nodes, whereas small cells (2% blasts) showed minimal migration to the gut but localized randomly in lymph nodes and spleen. The in vivo distribution of small cells from T-TDL was similar to that of T-PLN. Furthermore, the recirculatory patterns of both ⁵¹Cr-labeled T-TDL and T-PLN were found to be identical as accessed by their rate of recovery in the thoracic duct lymph of recipient mice. These results support the notion that the vast majority of T-TDL and T-PLN are part of a common pool of recirculating T cells which recirculate randomly through lymph nodes and spleen and not the small intestine.     

New taxa from the Avila and Naiguatá Mountains,Venezuela

Ten new species (Billbergia manarae, Croizatia naiguatensis, Croton huberi, Rinorea oraria, Anaectocalyx manarae, Linociera avilensis, Cynanchum beatricis, C. manarae, Matelea costanensis, and M. manarae) are described in preparation for the forthcoming Flora of Avila and Naiguatá.     

Immobilization of tyrosinase within polyacrylamide gels

The enzyme tyrosinase (E.G. 1.14.18.1) has been immobilized in a polyacrylamide gel and intermittently assayed for enzyme activity over a period of 19 days using phenol as the substrate. The results of these studies indicate that the immobilized enzyme could be incorporated into a system to detect phenol and related compounds that are found in industrial effluents and as surface water contaminants.