Phosphodiester bond cleavage outside mitochondria is required for the completion of protein import into the mitochondrial matrix

The present studies show that hydrolysis of a phosphodiester bond, most likely ATP, is a distinct, second step required to complete import of the F1-ATPase beta-subunit into the mitochondria. This step follows a membrane potential-dependent first step. We show, using an inhibitor of adenine nucleotide transport and the analogue beta,gamma-AMP-PCP, that the activity required for this phosphodiester hydrolysis-dependent completion of protein import resides outside the mitochondrial inner membrane. This activity is proposed to act on the precursor at the site of translocation either to render it competent or to catalyze its vectorial movement directly through the import apparatus. This activity shares properties ascribed to proteins of the heat-shock family, which are proposed to participate in the ATP-dependent refolding of partially denatured proteins and nascent peptides.     

Behavior ofPseudomonas fluorescens within the hydrodynamic boundary layers of surface microenvironments

Phase, darkfield, and computer-enhanced microscopy were used to observe the surface microenvironment of flow cells during bacterial colonization. Microbial behavior was consistent with the assumptions used previously to derive surface colonization kinetics and to calculate surface growth and attachment rates from cell number and distribution. Surface microcolonies consisted of closely packed cells. Each colony contained 2ⁿ cells, where n is the number of cell divisions following attachment. Initially, cells were freely motile while attached, performing circular looping movements within the plane of the solid-liquid interface. Subsequently, cells attached apically, maintained a fixed position on the surface, and rotated. This type of attachment was reversible and did not necessarily lead to the formation of microcolonies. Cells became irreversibly attached by progressing from apical to longitudinal attachment. Longitudinally attached cells increased in length, then divided, separated, moved apart laterally, and slid next to one another. This resulted in tight cell packing and permitted simultaneous growth and adherence. After approximately 4 generations, individual cells emigrated from developing microcolonies to recolonize the surface at new locations. Surface colonization byPseudomonas fluorescens can thus be subdivided into the following sequential colonization phases: motile attachment phase, reversible attachment phase, irreversible attachment phase, growth phase, and recolonization phase.     

Susceptibility and resistance of ruminal bacteria to antimicrobial feed additives

Susceptibility and resistance of ruminal bacterial species to avoparcin, narasin, salinomycin, thiopeptin, tylosin, virginiamycin, and two new ionophore antibiotics, RO22-6924/004 and RO21-6447/009, were determined. Generally, antimicrobial compounds were inhibitory to gram-positive bacteria and those bacteria that have gram-positive-like cell wall structure. MICs ranged from 0.09 to 24.0 micrograms/ml. Gram-negative bacteria were resistant at the highest concentration tested (48.0 micrograms/ml). On the basis of their fermentation products, ruminal bacteria that produce lactic acid, butyric acid, formic acid, or hydrogen were susceptible and bacteria that produce succinic acid or ferment lactic acid were resistant to the antimicrobial compounds. Selenomonas ruminantium was the only major lactic acid-producing bacteria resistant to all the antimicrobial compounds tested. Avoparcin and tylosin appeared to be less inhibitory (MIC greater than 6.0 micrograms/ml) than the other compounds to the two major lactic acid-producing bacteria, Streptococcus bovis and Lactobacillus sp. Ionophore compounds seemed to be more inhibitory (MIC, 0.09 to 1.50 micrograms/ml) than nonionophore compounds (MIC, 0.75 to 12.0 micrograms/ml) to the major butyric acid-producing bacteria. Treponema bryantii, an anaerobic rumen spirochete, was less sensitive to virginiamycin than to the other antimicrobial compounds. Ionophore compounds were generally bacteriostatic, and nonionophore compounds were bactericidal. The specific growth rate of Bacteroides ruminicola was reduced by all the antimicrobial compounds except avoparcin. The antibacterial spectra of the feed additives were remarkably similar, and it appears that MICs may not be good indicators of the potency of the compounds in altering ruminal fermentation characteristics.     

The association between spontaneous pyelonephritis and maturity-onset diabetes mellitus in male MM mice

Blood glucose and glucose tolerance tests demonstrated that many male MM mice are diabetic. Serial urine sampling showed that the diabetes occurred only in mature MM males and consisted of a single self-limiting episode. Histological examination of the pancreas, together with measurements of body weight, glycosylated haemoglobin and plasma insulin, revealed that the diabetes was of the maturity-onset insulin-resistant type. Bacteriological examination of the urine samples showed that urinary tract infection, a known feature of male MM mice, occurred in the diabetics but only after the onset of hyperglucosuria. It was concluded that the high urinary glucose levels of diabetic MM males are of prime importance in the aetiology of the renal infection which occurs rarely in non-diabetic MM males or in other strains in the colony. An infectious aetiology for the diabetes per se was excluded by the existence of diabetes in germfree MM males.     

Correlation of adenosine receptor affinities and cardiovascular activity

Binding affinities of 28 adenosine analogs at A1 adenosine receptors (rat whole brain membranes, [3H]N6-cyclohexyladenosine, CHA), and at A2 adenosine receptors (rat striatal membranes, [3H]NECA) were compared to their EC25 values for decreasing heart rate and increasing coronary flow in the isolated rat heart. Heart rate (an A1 response) correlated with A1 binding affinity (r2 = 0.71, p less than 0.0001) but not with A2 binding affinity (r2 = 0.007, n.s.); conversely, coronary flow (an A2 response) correlated with A2 binding affinity (r2 = 0.83, p less than 0.0001) but not with A1 binding affinity (r2 = 0.05, n.s.). These results confirm that the brain A1 and A2 receptors, studied by binding methods, bear close similarities to their respective counterparts in the heart, studied by means of functional responses.     

Chloroplast photooxidation inhibits the expression of a set of nuclear genes

Summary Mutations or herbicides which inhibit the accumulation of carotenoid pigments in higher plants also result in the arrest of chloroplast development at a very early stage. The cause is extensive photooxidative damage within the chloroplast in the absence of protective carotenoids. Because the extent of photooxidation is dependent upon light intensity, normal chloroplast development can occur when carotenoid-deficient seedlings are grown in very dim light. Normal accumulation of chloroplastic and cytosolic mRNAs encoding chloroplast proteins proceeds only under permissive dim light conditions. Illumination with higher intensity light causes rapid chlorophyll photooxidation and the loss of two cytosolic mRNAs coding for proteins destined for the chloroplast, but does not affect another light-regulated cytosolic mRNA encoding a cytosolic protein. This experimental system may have uncovered a mechanism which coordinates the expression of genes in different cellular compartments.Abbreviations LHCP light-harvesting chlorophyll a/b protein - SSu small subunit - RuBP fibulose 1,5-bisphoshate - PEP phosphoenolpyruvate     

Optimizing the expression of chimeric genes in plant cells

Summary The Serratia marcescens chiA gene encodes a secreted chitinase activity which contributes to the fungal growth inhibition exhibited by this bacterium. The coding region from the chiA gene was fused to the promoter and 3 polyadenylation region of the Agrobacterium nopaline synthase gene. Site-directed mutagenesis of specific nucleotides surrounding the initiating AUG of the coding sequence of this chimeric gene resulted in up to an eight-fold increase in the amount of chitinase protein detected in transformed plant tissue. Analysis of the chiA mRNA indicated that these nucleotides also affected mRNA levels. At least 50% of the chitinase protein produced in transformed tobacco cells was the same molecular weight as the S. marcescen secreted protein.     

Semiquantitative estimates of Al and other cations in the leaf tissues of some Al-accumulating species using electron probe microanalysis

Electron probe microanalysis of transverse sections was used to provide semiquantitative estimates of Al and other cations in the leaf tissues of some Al-accumulating plants of the cerrado vegetation of central Brazil. Concentrations of Al were generally higher than those of other cations in the phloem elements of these plants growing on dystrophic as well as fertile acid soils. When one of the Al-accumulating species,Vochysia thyrsoidea, was grown in a calcareous soil, the concentration of Al in the phloem elements of leaves was lower than that of Ca and K though the cotyledons showed higher concentrations of Al than those of other cations.     

The impact of augmentation mammaplasty: a follow-up study

Seventy-five women who had undergone augmentation mammaplasty responded to a questionnaire that obtained their perceptions of five areas of their personal and relationship functioning: (1) body and self-image, (2) attractiveness, (3) sensual sensitivity of breasts, (4) sexual life, and (5) relationship with partner. The women's perceptions of these areas before and after surgery were obtained retrospectively (between 3 months and 3 years after surgery). The 54 women in consistent relationships reported positive effects of the surgery on their relationship, although not to the extent that they had anticipated. However, regardless of this finding, these women perceived surgery to have had significant positive effects on their attractiveness, as well as on their body and self-image. Postoperatively, the partners of these women were viewed as having a significantly greater interest in sexual activity, as perceiving the women to be significantly more attractive, and as believing that the sexual relationship was significantly enhanced. The 21 women who were not in a consistent relationship also reported positive postoperative changes, although these were not statistically significant. Neither the women's age, length of time since surgery, nor the duration of the woman's relationship had any effect on the positive changes reported. The quantitative and qualitative data underscored the highly positive benefits of breast augmentation for the respondents.     

Radiosensitization in multifraction schedules. I. Evidence for an extremely low oxygen enhancement ratio

Stable monolayers of contact-inhibited C3H 10T1/2 cells were used in multifraction radiation experiments to measure the oxygen enhancement ratio (OER) at low doses/fraction under conditions where cell cycle effects (repopulation, redistribution) were minimal. Consistent with there being a dose-dependent reduction in the OER at low doses, an extremely low OER of 1.34 was measured after 20 fractions of 1.7 Gy every 12 h. The sparing effects of fractionating radiation doses were not apparent for cells irradiated under hypoxic conditions (i.e., multifraction survivals were lower than acute single-dose values) until doses exceeding 15 Gy were reached. This result suggested a deficiency in the recovery from sublethal and/or potentially lethal damage might exist after hypoxic irradiations, thereby reducing the OER. The capacity to repair potentially lethal damage was found to be nearly the same after hypoxic as compared to aerobic irradiations. However, there was an apparent absence of sublethal damage repair by 10T1/2 cells between two hypoxic irradiations which could be a major contributing factor to the extremely low OER value measured in this multifraction schedule.