Calcitonin and vasopressin affect epithelial properties in a renal cell line

We have used a stable clonal variant (D + Sc), isolated from the LLC-PK1 pig kidney-derived cell line and selected for its extensive capacity to form domes, in order to study the hormonal modulation of epithelial permeability in culture. Calcitonin, vasopressin, and other agents that raise intracellular adenosine 3',5'-cyclic monophosphate levels caused a rapid and dramatic decrease in the size and number of domes. This effect was independent of RNA and protein synthesis, and thus appeared unrelated to the production of urokinase, a proteinase synthesized by the cells in response to these agents. Calcitonin caused a decrease in transepithelial electrical resistance, suggesting that the effect of the hormone on domes was due to an increase in the permeability of a paracellular pathway. Thus, in addition to the wellknown effects of vasopressin on collecting duct permeability, part of the in vivo effect(s) of calcitonin and vasopressin on the renal tubule might also involve alterations of epithelial permeability related to those described here.     

Classification of Histoplasma capsulatum isolates by restriction fragment polymorphisms

Twenty isolates of the dimorphic, pathogenic fungus Histoplasma capsulatum were divided into three classes based on comparisons of restriction enzyme digests of their mitochondrial DNA and rDNA. The majority of isolates, including most North American strains and the African H. capsulatum var. duboisii variants, belong to class 2. Isolates from Central America and South America make up class 3. The attenuated Downs strain is the only member of class 1.     

Correlates and implications of breast-feeding practices in Bas Zaire

A sample of 1871 women having a child under 3 years old in Bas Zaire was studied to determine the correlates of breastfeeding practices and to examine the interrelationships among breastfeeding, contraceptive practices and desire for pregnancy. The methods of analysis applied were life table analysis and its multivariate extensions. Most of the findings in this analysis are consistent with current literature on the correlates of the duration of breastfeeding. Maternal education, economic status, age, parity, urban residence, pregnancy, and sex of the index child were significantly related to the length of breastfeeding. Among non-pregnant women, current desire for pregnancy was also related to breastfeeding status when the length of time since birth of the last child was taken into consideration. Rural women were reportedly ready for another pregnancy sooner after the birth of their last child than were urban women. Breastfeeding appears to be the most important means of contraceptive protection in the study population. The effective traditional method of extended postpartum abstinence is not widely prevalent, particularly among the urban sample, and indeed seems to be on the decline. The data presented here also suggest that breastfeeding pratices are changing in this area of Africa where little economic development has occurred in the past 20 years. This research suggests that if current trends continue, fertility levels are likely to increase significantly. The findings also indicate that Bas Zairian mothers want to space their births and for this reason may be receptive to family planning programs that use appropriate strategies.     

Role of progesterone in regulating uteroovarian venous concentrations of PGF2 α and PGE2 during the estrous cycle and early pregnancy in ewes

The role of progesterone in regulation of uteroovarian venous concentrations of prostaglandins F₂ α (PGF₂α) and E₂ (PGE₂) during days 13 to 16 of the ovine estrous cycle or early pregancy was examined. At estrus, ewes were either mated to a fertile ram or unmated. On day 12 postesturus, ewes were laparotomized and a catheter was inserted into a uteroovarian vein. Six mated and 7 unmated ewes received no further treatment. Fifteen mated and 13 unmated ewes were ovariectomized on day 12 and of these, 7 mated and 5 unmated ewes were given 10 mg progesteron sc and an intravaginal pessary containing 30 mg of progesterone. Uteroovarian venous samples were collected every 15 min for 3 h on days 13 to 16 postestrus. Mating resulted in higher mean daily concentrations of PGE₂ in the uterovarian vein than in unmated ewes. Ovariectomy prevented the rise in PGE₂ with day in mated ewes but had no effect in unmated ewes. Progesterone treatment restored PGE₂ in ovariectomized, mated ewes with intact embros. Mating had no effect on mean daily concentrations of PGF₂α or the patterns of the natural logarithm (ln) of the invariance of PGF₂α. Ovariectomy resulted in higher mean concentrations and ln invariances of PGF₂α on day 13 and lower mean concentrations and ln invariances of PGF₂α on days 15 and 16. Replacement with progesterone prevented these changes in patters of mean concentrations and ln variances of PGF₂α following ovariectomy. It is concluded that progesterone regulates the release of PGF₂α from the uterus, maintaining high concentrations while also preventing the occurrence of the final peaks of PGF₂α which are seen with falling concentrations of progesterone. This occurs in both pregnant and non-pregnant ewes. Progesterone is also needed to maintain increasing concentrations of PGE₂ in mated ewes.     

Long-term comparative effect of cholecystokinin and gastrin on mouse stomach, antrum, intestine, and exocrine pancreas

Mice were injected three times a day for 12 days with 300 micrograms/kg body weight of gastrin G17 or 37.5 Ivy dog U/kg body weight of CCK or saline. Other mice were also injected four times an hr for 1 hr with 7.5 micrograms/kg of gastrin, nine Ivy dog U/kg of CCK or saline; 1 hr before killing, they were injected with tritiated thymidine to evaluate the labelling indices in peptic, antral, duodenal, jejunal, and ileal mucosae. Four hours after the first injection of the two peptides, the peptic labelling indices increased while those of intestinal mucosa increased 8 hr after these injections. Long-term injections of CCK had a trophic effect on secretory cells of the digestive tract: the number of gastric zymogenic cells, Paneth cells, and the mucous cells of Brünner glands were hypertrophied. The pepsin, amylase, chymotrypsin, and lysozyme activities increased in stomach, exocrine pancreas, and intestine, respectively. Neither parietal cells nor intestinal enterocytes and hydrolase activities were affected. The trophic effect of long-term injections of gastrin is confirmed on parietal cells and exocrine pancreatic parenchyma and is demonstrated in Paneth cells. Confirming cytological results, pancreatic lipase and amylase activities and intestinal lysozyme activity were increased after gastrin. Although CCK and gastrin have a structural analogy, these two peptides did not affect the same cellular types. A specific action of CCK on the main secretory cells of the digestive mucosa is demonstrated.     

Characterization of Bacteria by Particle Beam Mass Spectrometry

A technique is described for detecting and characterizing bacteria on a single-particle basis by mass spectrometry. The method involves generation of a particle beam of single whole cells which are rapidly volatilized and ionized in vacuum in the ion source of a quadrupole mass spectrometer. The particle beam can be generated, with minimal sample handling, from a naturally occurring aerosol or from a solution of bacteria that can be dispersed as an aerosol. The mass spectrum is generated by successively measuring the average intensities of different mass peaks. The average intensity is obtained by measuring the ion intensity distribution at the particular mass (m/e) for ion pulses from more than 1,000 bacteria particles. Bacillus cereus, Bacillus subtilis, and Pseudomonas putida samples were analyzed to test the capability of the instrument for differentiating among species of bacteria. Significant ion-intensity information was produced over the m/e range of 50 to 300, an improvement over previous pyrolysis-mass spectrometry results. The complex mass spectra contained a few unique peaks which could be used for the differentiation of the bacteria. A statistical analysis of the variations in peak intensities among the three bacteria provided a quantitative measure of the reproducibility of the instrument and its ability to differentiate among bacteria. The technique could lead to a new rapid method for the analysis of microorganisms and could be used for the detection of airborne pathogens on a continuous, real-time basis.     

Characterization of Rhizobia from Ineffective Alfalfa Nodules: Ability to Nodulate Bean Plants [Phaseolus vulgaris (L.) Savi.]

This study was initiated to characterize Rhizobium isolates obtained from root nodules of ineffectively nodulated, field-grown alfalfa (Medicago sativa L.) plants. The purpose was to determine if these isolates possessed characteristics which would explain either their ineffectiveness in N₂ fixation or their apparent ability to tolerate the moderately acid soil conditions from which they originated. Isolates were characterized by analysis of growth rate, 39°C tolerance, acid production on conventional media, and symbiotic performance. All isolates were ineffective in N₂ fixation on alfalfa, and they contained one or more anomalous characteristics. These included either slow growth rate, lack of 39°C tolerance, or lack of acid production on conventional media. Infectiveness tests on a broad range of legumes revealed that the isolates formed root nodules on M. sativa, Medicago lupulina L., and Phaseolus vulgaris (L.) Savi. (common bean). These results provide evidence that, in some situations, ineffective nodulation of M. sativa in the field may be due to the presence of promiscuous, native Rhizobium species.     

Promoter mutations affecting divergent transcription in the Tn10 tetracycline resistance determinant

The tetracycline resistance determinant in transposon Tn10 consists of two genes, the tetA resistance gene and the tetR repressor gene, that are transcribed from divergent overlapping promoters. We determined the levels of pulse-labeled tet messenger RNA in Escherichia coli strains with the Tn10 tet genes on a multicopy plasmid. Addition of the inducer 5a,6-anhydrotetracycline results in a 270- to 430-fold increase in tetA mRNA and a 35- to 65-fold increase in tetR mRNA. As judged by the relative molar amounts of tetA and tetR mRNA synthesized under maximally inducing conditions, the tetA promoter (tetPA) is 7 to 11 times more active than the two tetR promoters (tetPR1 and tetPR2) combined. We characterized ten mutations in tetPA, including nine single-base-pair substitutions and a 30-base-pair deletion. All of the single-base-pair changes reduce the agreement with the consensus sequence for promoters recognized by E. coli RNA polymerase. Mutations in highly conserved nucleotides result in a 200- to 600-fold reduction in tetPA activity in vivo. Unexpectedly, tetPA mutations reduce by two- to fourfold the combined activity in vivo of tetPR1 and tetPR2, in spite of their locations outside the -35 and -10 regions of tetPR1 and tetPR2. For two tetPA mutations, the negative effect on tetPR activity was also demonstrated in tetR- tetPR-lacZ operon fusion strains, thus eliminating the possibility that it is due to variations in either plasmid copy-number or induction efficiency. The pleiotropic effects of tetPA mutations are discussed in terms of the expectation that the overlapping tet promoters compete for RNA polymerase.     

Further characterization of the structural and functional properties of the cross-linked complex between F-actin and myosin S-1

Several structural and functional properties of the covalent complex, formed upon cross-linking of the myosin heads (S-1) to F-actin with 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide, were characterized. The elevated Mg2+-ATPase activity was measured during a 1-month storage of the complex under various conditions. In aqueous medium it showed a rapid time-dependent decrease but it was significantly more stable in the presence of 50% ethylene glycol at -20 degrees C. The ATPase loss most likely reflects a progressive conformational change within the S-1 ATPase site resulting from its greater exposure to the medium, induced by the permanently bound F-actin. The covalent acto-S1 complex was submitted to depolymerization-repolymerization experiments using different depolymerizing agents (0.6 M KI; 4.7 M NH4Cl; low-ionic-strength solution). The depolymerization led to an immediate loss of the enhanced Mg2+-ATPase activity; this activity was almost entirely recovered upon repolymerization of the complex. The protein material formed upon depolymerization of the covalent acto-S1 was analyzed by gel chromatography, gel electrophoresis, analytical ultracentrifugation and electron microscopy. It comprised mainly small-sized actin oligomers associated with the covalently bound S-1 and only a limited amount of free G-actin. The results illustrate the relationships between the filamentous state of actin and its ability to stimulate the Mg2+-ATPase activity of S-1. They also indicate that the binding of S-1 to F-actin is transmitted to several neighbouring actin subunits and strengthens the interactions between actin monomers. Acto-S1 cross-linked complexes were prepared in the presence of tropomyosin and the tropomyosin-troponin system. Under the conditions employed, the regulatory proteins were not cross-linked to actin or S-1 and did not affect the extent or the pattern of S-1 cross-linking to F-actin. Measurements of the elevated Mg2+-ATPase activity of the cross-linked preparations revealed that tropomyosin and the tropomyosin-troponin complex, in the absence of Ca2+, inhibit ATP hydrolysis; the extent of ATPase inhibition (up to 50%) was dependent on the amount of covalently bound S-1, being larger at low level of S-1 cross-linking; the addition of Ca2+ restored the ATPase activity to the control value. The data provide direct evidence that the regulatory proteins can modulate directly the kinetics of ATP hydrolysis by the covalent acto-S1 complex as has earlier been suggested for the reversible complex [Chalovich, J. M. and Eisenberg, E. (1982) J. Biol. Chem. 257, 2432-2437].(ABSTRACT TRUNCATED AT 400 WORDS)     

Insertion of a foreign nucleotide sequence into mitochondrial DNA causes senescence in Neurospora intermedia

The kalilo variants of Neurospora contain a cytoplasmic genetic factor that causes senescence. This factor is a 9.0 kb transposable element (kalDNA) that lacks nucleotide sequence homology with mtDNA and is inserted into the mitochondrial chromosome, often at sites located within the open reading frame in the intron-DNA of the mitochondrial 25S-rRNA gene. Genomes containing the "foreign" DNA insert accumulate during growth, and death occurs as the cells become deficient in functional large and small subunits of mitochondrial ribosomes. The kalDNA transposon may be an "activator" element that causes breaks in mtDNA. Nonsenescing [+] strains of Neurospora do not contain kalDNA.