Complete nucleotide sequence and characterization of a cryptic plasmid from Lactobacillus helveticus subsp. jugurti

A small cryptic plasmid, pLJ1, was isolated from Lactobacillus helveticus subsp. jugurti and was cloned into Escherichia coli HB101 by using pBR329 as a vector. Plasmid pLJ1 was 3,292 base pairs long and had single restriction endonuclease sites for PvuII, KpnI, AvaII, Acci, HindIII, and EcoRI. In a maxicell system, pLJ1 produced a protein of about 41 kilodaltons.     

Ontogenesis of gastrin cells in the pyloric antrum and duodenum of the mouse

Summary Ontogenesis of gastrin cells was studied in the pyloroduodenal mucosa of the mouse using anti-human G17 serum, R-1301, and anti-human G34(1–15) serum, R-2703. R-1301-immunostained cells first appeared in the pyloric mucosa of 14-day-old fetuses. Cells stained with both R-1301 and R-2703 appeared immediately after birth, and gradually increased in number to the adult level. Most R-1301-reactive cells were also reactive to R-2703, whereas some cells that reacted with R-1301 exhibited very weak or no reaction with R-2703. The discrepancy between these two immunoreactivities is discussed.In the duodenum, a considerable number of R-1301-reactive cells were present from the perinatal stage and through out adult development. A few R-2703-reactive cells were seen in the duodenum of young mice but not of the adult.     

Deletion of a phenylalanine in the N-terminal region of human cytochrome P-450(17 alpha) results in partial combined 17 alpha-hydroxylase/17,20-lyase deficiency

Steroid 17 alpha-hydroxylase and 17,20-lyase activities reside within the same polypeptide chain (cytochrome P-450(17 alpha)), and consequently human 17 alpha-hydroxylase deficiencies are characterized by defects in either or both of these activities. Human mutants having these deficiencies represent an excellent source of material for investigation of P-450(17 alpha) structure-function relationships. The CYP17 gene from an individual having partial combined 17 alpha-hydroxylase/17,20-lyase deficiency has been characterized structurally and the homozygous mutation found to be the deletion of the phenylalanine codon (TTC) at either amino acid position 53 or 54 in exon 1. Reconstruction of this mutation into a human P-450(17 alpha) cDNA followed by expression in COS 1 cells led to production of the same amount of immunodetectable P-450(17 alpha) protein as found with expression of the normal human P-450(17 alpha) cDNA. However, 17 alpha-hydroxylase activity of this mutant protein measured in intact cells was less than 37% of that observed upon expression of the wild-type enzyme, whereas 17,20-lyase activity of the mutant was less than 8% of that observed with the normal enzyme. When estimated in intact cells, the Km for 17 alpha-hydroxylation of progesterone was increased by a factor of 2 in the mutant enzyme, whereas the Vmax was reduced by a factor of 3. In order to estimate the kinetic parameters for the 17,20-lyase reaction, microsomes were isolated from transfected COS 1 cells to enrich for this activity. Surprisingly, the specific activity of the mutant 17 alpha-hydroxylase in microsomes was 3-fold less than that observed in intact cells, indicating that the structure of mutant P-450(17 alpha) was dramatically altered upon disruption of COS 1 cells. Apparently the deletion of a single phenylalanine in the N-terminal region of P-450(17 alpha) alters its folding in such a way that both enzymatic activities are dramatically decreased, leading to the partial combined deficiency observed in this individual.     

The influence of glycosylation on the fate of renin expressed in Xenopus oocytes

It has been recently reported that, in Xenopus oocytes injected with the mRNA for human renin, this secretory renal glycoprotein acquires phosphomannosyl residues on its asparagine-linked oligosaccharide chains, remains intracellular and undergoes a proteolytic cleavage which removes the prosegment. To understand the influence of glycosylation on the fate of renin in Xenopus oocytes and whether it is specific for human renin, we have expressed human renin and mouse Ren1 renin, which are glycosylated at two and three selected asparagine residues, respectively, and mouse Ren2 renin, which is not glycosylated, in Xenopus oocytes. The majority of human and Ren1 renins remained intracellular and underwent proteolytic cleavage, whereas mouse Ren2 renin was secreted efficiently. When human and Ren1 renins were expressed in oocytes treated with tunicamycin, both were secreted efficiently. A mutant of human renin, which had amino-acid substitutions at both glycosylation sites, was also secreted efficiently, whereas that mutated at one of the two sites was not. These results indicate that the majority of all of the glycosylated renin molecules remain intracellular and undergo proteolytic cleavage, probably due to the acquisition of phosphomannosyl residues, and the human renin remains intracellular if it is only glycosylated at one of the two sites.     

Double Infection,Recombination, and Segregation of Two R Factors,R 100 and Rts1, and Their Possible Bearing on the Genetic Structure of R 100

Applying the observation by Yokota et al (1969) that a cell doubly harboring an R factor (R100) and a temperature sensitive R factor (Rts1) produces segregant R factors with various resistance patterns, a total of 271 segregant R factors were obtained. There were 163 resistant to (sul, str, kan), 39 resistant to (sul, str, cml, kan), 62 resistant to (sul, str, tet, kan) and finally 7 resistant to (tet, kan). More than 90% of the former 3 segregants were fi⁺ and the remainder, including all of the (tet, kan) segregants, were fi^?. Some fi^? segregants with the former 3 resistance patterns and all of the (tet, kan) segregants were nontransmissible. All of these segregants were still temperature sensitive. Based upon the results of three experiments; (a) the growth at 43 C to observe linked loss of the kan gene and the genes derived from R 100, (b) a conjugal analysis of the relevant resistant markers, and (c) a transductional analysis of these same markers, several conclusions were made. The 2 R factors both consisting of a circle were supposed to have recombined to form a larger circle which then further resulted in the final formation of smaller circles. The possible bearing of these observations and conclusions on the genetic structure of R 100 was discussed.     

Heligmosomoides polygyrus infection reduces severity of type 1 diabetes induced by multiple low-dose streptozotocin in mice via STAT6- and IL-10-independent mechanisms

Some parasitic helminths are known to protect their hosts from allergic and autoimmune disorders. Here, we tested the effects of a gastrointestinal nematode, Heligmosomoides polygyrus (Hp), on streptozotocin (STZ)-induced type 1 diabetes (T1D) in mice. Hp infection significantly suppressed hyperglycemia induced by multiple low-dose administration of STZ, but did not affect hyperglycemia induced by single high-dose administration of STZ. In the multiple low dose model, Hp infection prevented a decrease in pancreatic islet size. The augmentation of TNF-α and IL-1β expression in the pancreas was abrogated by Hp infection. The genetic absence of IL-10 or STAT6 did not abrogate the anti-hyperglycemic effect of Hp. Hp has a suppressive effect on immune mechanism-mediated experimental T1D via Th2 polarization-independent mechanisms.