Intraspecific cross-protection in mice immunized with irradiated Schistosoma mansoni cercariae

Several laboratory-maintained strains of Schistosoma mansoni were tested for their relative immunogenicity or susceptibility to anti-schistosome immunity in irradiated cercaria-immunized mice. A total of 11 strains and substrains were used; 7 were of Puerto Rican origin, 3 from Brazil, and 1 from Egypt. Mice were immunized by percutaneous exposure to 50-krad-irradiated cercariae. Immunity was assessed following challenge with cercariae of the homologous or a heterologous strain. The results showed that the choice of either the challenge or immunizing strains was not critical in the development of significant levels of protection. Extensive degrees of cross-protection developed in all intrastrain combinations tested.     

The genetic variation of compatibility in Biomphalaria glabrata and Schistosoma mansoni

Interactions between different Biomphalaria glabrata stocks and Schistosoma mansoni strains were studied. A series of inbred stocks of B. glabrata were characterized as to genetic variations in susceptibility at different ages to a series of different S. mansoni strains. A series of inbred strains of S. mansoni were characterized as to genetic variations in infectivity for B. glabrata stocks at different ages. Also described is a process of selection for substrains from a single S. mansoni isolate that differ genetically in snail infectivity.     

Energization and activation of inorganic carbon uptake by light in cyanobacteria

The requirement of the inorganic carbon (C_i) transport system for light in cyanobacteria was investigated in Anabaena variabilis by the filtering centrifugation technique and in a mutant (E₁) isolated from Anacystis nidulans using a gas exchange system. C_i transport capability increased with time of preillumination and decreased following darkening. Full activity could not be obtained by operating either photosystem II (PSII) or photosystem I alone. 3(3,4 Dichlorophenyl)-1,1 dimethylurea strongly inhibited C_i uptake. Very low activity of PSII was sufficient to activate C_i uptake. However, in the presence of dithiothreitol PSII activity was not required. We conclude that light may be required to activate as well as to energize C_i uptake in cyanobacteria.     

Hormonal regulation of estradiol biosynthesis, aromatase activity, and aromatase mRNA in rat ovarian follicles and corpora lutea

To determine the molecular basis for changes in aromatase (P450arom) activity in rat ovarian follicles and corpora lutea, seven clones for rat P450arom cDNA have been identified and isolated from a rat granulosa cell λgtll cDNA expression library using a 62 mer deoxyoligonucleotide probe (derived from an amino acid sequence of purified human placental aromatase) and a human placental P450arom cDNA probe. One of the rat P450arom cDNA clones contained an insert 1.2 kb in size. Both the human 1.8 kb cDNA and the rat 1.2 kb cDNA probes hybridized to a single species of P450arom mRNA that was 2.6 kb in size. Northern blot analysis revealed that corpora lutea isolated on day 15 of pregnancy contained high amounts of P450arom mRNA, whereas granulosa cells of antral follicles of hormonally primed, hypophysectomized rats (i.e., those from which mRNA was isolated to construct the cDNA library) contained only low amounts of P450arom mRNA. The lower amounts of P450arom in granulosa cells of preovulatory follicles in the estradiol-follicle-stimulating hormone primed hypophysectomized rats were unexpected because follicles incubated in medium containing testosterone substrate produce more estradiol than do corpora lutea isolated on day 15 of pregnancy and incubated under similar conditions. Additional studies will determine the hormonal events responsible for the elevated amounts and constitutive maintenance of P450arom mRNA and aromatase activity in luteal cells in vivo and in vitro.     

Creation of a test plasmid for detecting G-C-to-T-A transversions by changing serine to arginine in the active site of beta-lactamase.

Oligonucleotide-directed mutagenesis of the beta-lactamase gene, bla, on pBR322 was used to change the codon for the active-site serine 70, AGC, to CGC, coding for arginine. Escherichia coli cells carrying the mutant plasmid, pGD104, were sensitive to ampicillin, indicating that the arginine-containing enzyme is inactive. We characterized the reversion of the mutant bla gene by a number of mutagens and in different genetic backgrounds and demonstrated that full ampicillin resistance can be restored only by a G-C-to-T-A transversion occurring at the first base of the codon. Thus, reversion of the mutant bla gene is diagnostic for G-C-to-T-A transversions, and bacteria carrying pGD104 can be used as test strains to detect the occurrence of this mutation.     

Mouse glandular kallikrein genes. Structure and partial sequence analysis of the kallikrein gene locus

Mouse glandular kallikreins are encoded by a family of closely linked genes which are located on chromosome 7 at a site corresponding to the genetically defined Tam-1, Prt-4, and Prt-5 loci. We have characterized 24 kallikrein genes by genomic cloning and restriction mapping of 310 kilobase pairs of BALB/c mouse DNA. Most of these genes are highly homologous, have the same exon/intron organization, and are linked in clusters of up to 11 genes. Partial sequence analysis of the kallikrein genes has facilitated identification of those members of the family for which protein sequence data exist and assignment of those which are pseudogenes or encode proteins of unknown function. We find that a maximum of 14 mouse kallikrein genes have the potential to encode functional proteins.