Deoxyribonucleic Acid Homologies Among Some Pseudomonas Species

Phylogenetic relationships among a number of strains belonging to the genus Pseudomonas were explored by the use of in vitro deoxyribonucleic acid (DNA) hybridization. The fluorescent nomenspecies (P. fluorescens, P. putida, P. aeruginosa, P. cichorii, P. syringae, and related species), as well as the nonfluorescent species P. stutzeri, P. mendocina, P. alcaligenes, and P. pseudoalcaligenes, were shown to belong to a single DNA homology complex which is isolated from other Pseudomonas species that have been studied [P. cepacia (= P. multivorans), P. caryophylli, P. marginata (= P. alliicola), P. pseudomallei, P. acidovorans, P. testosteroni, P. solanacearum, P. diminuta, P. facilis, P. delafieldii, P. saccharophila, P. palleronii]. A limited numerical analysis of the phenotypic properties of the examined strains supported, with some exceptions, their previous allocation to nomenspecies and biotypes. The internal structure and nomenclature of the "P. fluorescens homology complex" are discussed.     

Assembly of the sarcoplasmic reticulum proteins in differentiating rat skeletal muscle cell cultures: localization by immunofluorescence of sarcoplasmic reticulum proteins in differentiating rat skeletal muscle cell cultures

Immunofluorescent staining techniques were used to study the distribution of the Ca(2) + Mg(2+)-dependent ATPase and calsequestrin in primary cultures of differentiating rat skeletal muscle cells, grown for different periods of time under various culture conditions. In mononucleated myoblasts calsequestrin was detected after 45 h in culture whereas the ATPase was not detected until 60 h. After cell fusion began, both proteins could be identified in all multinucleated cells. Myoblasts grown for longer than 60 h in low Ca(2+) medium contained calsequestrin and the ATPase, even though they were unable to fuse. These studies at the cellular level confirm biochemical findings on the biosynthesis of calsequestrin and the ATPase. Immunofluorescent staining of myoblasts showed that calsequestrin first appears in a well-defined region of the cell near one end of the nucleus. At later times, the staining occupied progressively larger regions adjacent to the nucleus and took on a fibrous appearance. This suggests that calsequestrin first accumulates in the Golgi region and then gradually spreads throughout the cell. In contrast, the ATPase appeared to be concentrated in many small patches or foci throughout the cytoplasm and was never confined to one particular region, although some parts of the cell often stained more intensely than others. In multinucleated cells, alternating dark and fluorescent strands parallel to the longitudinal axis of the cells were evident.     

Termination of early gestation with a vaginal polysiloxane device impregnated with (15S)-15 methyl prostaglandin F2alpha methylester

An investigation of the abortifacient activity of (15S)-15 methyl prostaglandin F2alpha methyl ester released from a vaginal polysiloxane device was performed in eleven pregnant women of 49 days gestation or less. Bleeding and contractions were induced in all women, but only seven aborted their pregnancies. Five subjects received a vaginal device impregnated with 3 mg of drug and two aborted fetal tissue. Six women were given a vaginal device containing 5 mg of drug and five aborted fetal tissue. Ten of the patients had significant side effects, nausea, emesis, diarrhea and chills. Six women expelled the device prior to the termination of therapy. This prostaglandin analogue, when administered from a vaginal polysiloxane device in early gestation was an effective abortifacient but was accompanied by systemic side effects and a high incidence of expulsion of the device prior to its scheduled removal.     

Role of cryptic genes in microbial evolution

Cryptic genes are phenotypically silent DNA sequences, not normally expressed during the life cycle of an individual. They may, however, be activated in a few individuals of a large population by mutation, recombination, insertion elements, or other genetic mechanisms. A consideration of the microbial literature concerning biochemical evolution, physiology, and taxonomy provides the basis for a hypothesis of microbial adaptation and evolution by mutational activation of cryptic genes. Evidence is presented, and a mathematical model is derived, indicating that powerful and biologically important mechanisms exist to prevent the loss of cryptic genes. We propose that cryptic genes persist as a vital element of the genetic repertoire, ready for recall by mutational activation in future generations. Cryptic genes provide a versatile endogenous genetic reservoir that enhances the adaptive potential of a species by a mechanism that is independent of genetic exchange.      

Regulation of protein accumulation in cultured cells.

1. A technique is described whereby protein synthesis, protein breakdown and net protein accumulation are measured separately in monolayer cultures of mammalian cells. All rates are expressed as microgram of protein per 18 h incubation. 2. Under most incubation conditions with either L6 rat myoblasts or T47D human breast carcinoma cells the rates of protein accumulation, determined directly, agreed with the rates obtained by subtracting protein breakdown from protein synthesis. 3. Foetal calf serum, human and bovine colostrum, human milk and insulin increased protein accumulation in both cell lines, mainly as a consequence of effects on protein synthesis. 4. NH4Cl, in addition to inhibiting protein breakdown in both cell lines in the presence and in the absence of serum, stimulated protein synthesis in L6 myoblasts. 5. Leupeptin slightly inhibited protein breakdown without affecting protein-synthesis rates. 6. Cycloheximide almost completely inhibited protein synthesis, but restricted the net loss of cell proteins under most conditions because protein-breakdown rates were also decreased. 7. The assumptions, limitations and potential application of this technique for evaluating changes in protein turnover are described.     

Insulin inhibition of protein degradation in cell monolayers

Protein degradation has been measured in confluent monolayers of eleven lines of contact-inhibited cells and ten transformed lines as the rate of release of trichloroacetic acid-soluble radioactivity after prelabeling cell protein with [³H]leucine. Insulin, at concentrations from 10^?12 M to 10^?6 M, has been added at the beginning of the 4-hour degradation period to detect selective effects of this hormone as an inhibitor of the inducible proteolysis occurring in serumfree medium. In addition insulin binding measurements have been performed on selected cell lines in an attempt to relate receptor properties to insulin action. Substantial effects of insulin are found in most cells with a selective inhibition at low insulin concentrations noted in several of the transformed lines. The difference in insulin sensitivity is not entirely definitive because temperature-sensitive transformation mutants of NRK cells are not more sensitive to insulin at a temperature where they show the transformed phenotype. Although insulin receptors on different cell lines have similar binding properties, two of the hepatomas used, H35 and MH₁C₁, show inhibition of protein degradation at insulin concentrations where receptor occupancy is extremely low. Calvarial osteoblast-like cells have a high rate of protein degradation which can be reduced by growth factors but not by insulin. The lack of an insulin response is a consequence of poor insulin binding to the cells. Insulin binds to the osteogenic sarcoma cells in substantial amounts. However, its normal action to inhibit the induced proteolysis is restricted because with these cells no increase of proteolysis occurs in serum-free medium. Generally higher rates of protein degradation are observed in the contact-inhibited lines than the transformed cells. We suggest that this difference may provide a selective growth advantage to transformed cells.     

Pathways of fructose conversion into glucose in foetal rat liver

1. Glucose, formed from [1-(14)C]fructose or [6-(14)C]fructose in rat-liver slices, has been isolated as gluconate and degraded to give the radioactivity in C-1, C-2-5 and C-6. 2. By using this method it has been shown that, in liver from foetal rats younger than 20 days, glucose is formed from fructose without splitting of the molecule by the aldolase reaction. The rate of glucose formation from fructose in liver from these foetuses is approximately half of the rate in adult liver. 3. The direct conversion of fructose into glucose in foetal rat liver is not via sorbitol as in seminal vesicles, as this pathway cannot be detected. 4. When liver slices are incubated with [U-(14)C]fructose of high specific activity, the labelled intermediates are similar whether from liver from 18-day foetal, newborn or adult rats. 5. These findings are discussed with reference to the changing pathways of fructose metabolism during perinatal development of the liver in the rat.     

Signal transduction mechanism for the stimulation of the sarcolemmal Na+−Ca2+ exchanger by insulin

The signal transduction pathway for insulin-mediated activation of sarcolemmal Na⁺–Ca²⁺ exchange was examined. Insulin stimulated Na⁺–Ca²⁺ exchanger activity in a dose-dependent manner, with the EC50 being about 0.7 U/l. The insulin effect was blocked by the protein kinase inhibitor, staurosporine, indicating possible involvement of a protein kinase in insulin action. Also, the relationship between the insulin effect and activation of a G protein, was examined by testing the effects of 5 guanylyl imidodiphosphate (Gpp(NH))p) on Na⁺–Ca²⁺ exchange in, the presence and absence of insulin. When exchanger activity was assayed at a calcium concentration of 40 M, insulin alone had no effect whereas ATP and Gpp(NH)p increased exchanger activity. However, insulin responsiveness was restored in vesicles preloaded with either ATP or Gpp(NH)p, suggesting that insulin may act through a combination of G protein coupling and protein phosphorylation to enhance Na⁺–Ca²⁺ exchanger activity. We conclude that calcium overload in the diabetic heart may involve a defect in acute activation of the exchanger by insulin.