Showing papers by "Public Health Research Institute published in 1977"

Retinal projections in larval, transforming and adult sea lamprey, Petromyzon marinus

Abstract: Unilateral enucleations were performed on larval, transforming and adult sea lampreys Following 5 to 11 days survival, the animals were sacrificed and the brains were processed using a modified Fink-Heimer technique In larvae, contralateral optic projections were found to the posterior one-third of the dorsal thalamus, the pretectum, and the optic tectum No ipsilateral projections were present in the larvae In enucleated transforming and adult lampreys, degenerating axons were observed in the optic chiasm and bilaterally in the optic tracts Retinal efferents projected bilaterally to a lateral neuropil region ("tractus opticus") in the posterior one-half of the dorsal thalamus Contralaterally, a conspicuous dorsomedial cell group (lateral geniculate nucleus) also received a projection Contralateral projections to the superficial layers of the pretectum and optic tectum were observed Ipsilateral retinal projections to the pretectum and optic tectum in transforming and adult lampreys were restricted to a small zone at the ventrolateral margins of the pretectum and tectum The changes in distribution of retinofugal projections during transformation appear to be occurring at the same time that the eye differentiates into its adult form

The mapping of mutations in tRNA and cytochrome oxidase genes located in the cap-par segment of the mitochondrial genome of S. cerevisiae.

Abstract: 1. Two mutants have been isolated which carry mutations in mitochondrial tRNA genes; one in the aspartyl-tRNA gene and the other in one of the threonyl-tRNA genes. The mutant tRNAs are unable to be charged with their respective amino acids. 2. These two mutations are located on the mitochondrial genome in the cap-par segment. Analyses of genetic recombination frequencies and co-retention and co-deletion frequencies of markers in petite strains yield an unambiguous gene order cap-asp-oxi 1-thr 1-oxi 2-par. 3. Two loci involved in the specification of cytochrome oxidase (oxi1 and oxi2) show an average recombination frequency of 14% in pairwise crosses involving mutations of both loci. Although the two loci have a related function and are genetically linked they are shown to be separated by at least one tRNA gene. 4. Pairwise intralocus crosses involving mit- mutations within either the oxi1 or oxi2 locus yield recombination frequencies <0.02–3.2%. However, no unique order could be derived for 19 oxi 1 and 6 oxi 2 mutations based on these data. In addition, the separation of mutant alleles within a single locus as the result of petite mutation was very rare. Consequently, attempts to order mutations within the locus from an analysis of the flanking markers in petites where separation occurred, provided only limited resolution. 5. A discussion is presented of the limitations of the current mitochondrial genetic mapping techniques when applied to the fine resolution of glycerol negative mit- and syn- mutations.

Neutron activation analysis of biologically essential trace elements in environmental specimens using pyrrolidinedithiocarbamate extraction

Abstract: A new radiochemical group separation method using APDC reagent in the extraction procedure has been developed. The method has been applied to the radiochemical separation for activated biological samples and also to the preconcentration technique for sea water samples. The transition elements are extracted into chloroform phase from the pH 3.0 aqueous phase and only manganese is subsequently extracted from the pH 7.0 aqueous phase. The validity of the method is demonstrated by analyzing the NBS standard reference materials. In the specimens preconcentrated from the sea water samples adjusted pH to 5.5, vanadium, manganese, copper and zinc can be determined.

New bile alcohols II: Synthesis and mass spectra of C26 bile alcohols

Abstract: The synthesis of (23α-) and (23β-)24-nor-5β-cholestane-3α,7α,23,25-tetrols (VII-a and VII-b) and 24-nor-5β-cholestane-3α,7α,25,26-tetrol (VIII) is described. Dehydration of 24-nor-5β-cholestane-3α,7α,25-triol (II) (synthesized from methyl chenodeoxycholate via a Grignard reaction) with acetic anhydride and acetic acid yielded two unsaturated compounds. These were oxidized with osmium tetroxide to produce a mixture of 24-nor-5β-cholestane-3α,7α-diacetoxy-23ξ,25-diol (V) and 24-nor-5β-cholestane-3α,7α-diacetoxy-25,26-diol (VI). After separating these diols (V and VI) by column chromatography, each compound was hydrolyzed with KOH to give 24-nor-5β-cholestane-3α,7α,23ξ,25-tetrol (VII) and 24-nor-5β-cholestane-3α,7α,25,26-tetrol (VIII), respectively. Two isomers of the tetrol (VII) were separated using alumina column chromatography (VII-a and VII-b).

Ochre suppression in salmonella typhimurium

Abstract: A bacterial strain was constructed which permitted positive selection for ochre suppressor mutations as well as for the loss of suppressor function. A derivative bearing an ochre suppressor mutation was selected following mutagenesis with N-methyl-N-nitroso-N'-nitroguanidine. The suppressor-bearing strain was treated with nitrous acid to eliminate suppressor function by mutation, and a strain lacking suppressor activity was selected. The selected strain which had lost suppressor function was then subjected to mutagenesis to induce a second suppressor mutation. The alternating sequence (induction of an ochre suppressor mutation → induction of a mutation eliminating ochre suppressor activity) was repeated 29 and one-half times in a single strain. Some of the suppressor mutations were tentatively mapped at four locations on the chromosome. The first suppressor mutation selected maps at about minute 30 on the chromosome. The second suppressor selected maps at approximately minute 60, while the third suppressor maps nearby, possibly as far as minute 72. Among the subsequently selected suppressor mutations, all eleven which were mapped were cotransducible with the gal and nic loci near minute 36 on the chromosome and may represent more than one suppressor gene. Deletions were selected which inactivate two of the ochre suppressor alleles mapping near the gal-nic region, suggesting that one or more such genes are dispensable. Some evidence also suggests that the occurrence of either deletion mutations or transduction-mediated recombination events in the gal-nic region can cause instability of nearby suppressor alleles.