An inquiry into the source of stereospecificity of lactate dehydrogenase using substrate analogues and molecular modeling.

Lactate dehydrogenase catalyzes the stereospecific hydride transfer to and from the re face of the nicotinamide coenzyme. The demonstrated probability of transfer to the si face of less than 2 x 10(-8) indicates that the free energy of any diastereotopic transition state leading to a si transfer must be over 10 kcal/mol greater than the free energy for transfer to or from the re face. The general notion of closed, desolvated active sites suggests the a priori hypothesis that steric hindrance prevents the nicotinamide ring from assuming a conformation that would lead to transfer of the pro-S hydrogen. In this paper we report that the probability of transfer of the pro-S proton is less than 9 x 10(-7) with 3-pyridinealdehyde adenine dinucleotide as coenzyme and less than 4 x 10(-7) during the lactate dehydrogenase catalyzed disproportionation of glyoxylate. Examination of the crystal structure of lactate dehydrogenase further suggests that steric exclusion does not enforce the extreme stereospecificity of the reaction. An electrostatic interaction with the macrodipole associated with the alpha 2F helix is suggested as a potential molecular source of the stereospecificity.     

Repetitive sequences of the sea urchin genome: Distribution of members of specific repetitive families

Three repetitive sequence families from the sea urchin genome were studied, each defined by homology with a specific cloned probe one to a few hundred nucleotides long. Recombinant λ-sea urchin DNA libraries were screened with these probes, and individual recombinants were selected that include genomic members of these families. Restriction mapping, gel blot, and kinetic analyses were carried out to determine the organization of each repeat family. Sequence elements belonging to the first of the three repeat families were found to be embedded in longer repeat sequences. These repeat sequences frequently occur in small clusters. Members of the second repeat family are also found in a long repetitive sequence environment, but these repeats usually occur singly in any given region of the DNA. The sequences of the third repeat are only 200 to 300 nucleotides long, and are generally terminated by single copy DNA, though a few examples were found associated with other repeats. These three repeat sequence families constitute sets of homologous sequence elements that relate distant regions of the DNA.     

Sporulation of Marteilioides branchialis n. sp. (Paramyxea) in the Sydney rock oyster, Saccostrea commercialis: an electron microscope study.

The ultrastructure of sporulation of a new parasite, Marteilioides branchialis (Paramyxea), in the Sydney Rock oyster, Saccostrea commercialis, is described. The development is typical of other Paramyxea whereby a stem cell internally cleaves a secondary cell contained within a vacuole. It differs from other species in the phylum in that each secondary cell produces a single spore composed of two concentric cells, one within a vacuole of the other. This type of sporulation represents the simplest of all known Paramyxea. Infection results in focal gill lesions and was observed concurrently with an epizootic of another paramyxean, Marteilia sydneyi.     

Sydney epilepsy incidence study to measure illness consequences: the SESIMIC observational epilepsy study protocol

Background  

Epilepsy affects an estimated 50 million people and accounts for approximately 1% of days lost to ill health globally, making it one of the most common, serious neurological disorders. While there are abundant global data on epilepsy incidence, prevalence and treatment, there is a paucity of Australian incidence data. There is also a general lack of information on the psychosocial impact and socioeconomic consequences of a new diagnosis of epilepsy on an individual, their family, household, and community which are often specific to the health and social system of each country.     

Methods for producing twins in cattle

During January and February 1972 we added 100 Fishman units of beta-glucuronidase per ml of diluted semen to 331 bull ejaculates and compared the nonreturn results with 368 ejaculates without the enzyme. From February 1972 until September 1975 21′663 first inseminations were performed with semen containing beta-glucuronidase, and 20′263 without the enzyme.The analysis of variance of the nonreturn results shows that there are significant differences between years resp. months but not between the two treatments.