A PCR-RFLP marker in canine von Willebrand factor gene (vWF).
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Alleles↗
Biomedical subjects
Y Suh
Publications and source records attributed to Y Suh.
Secretion of nuclease across the outer membrane of Serratia marcescens and its energy requirements.
Extracellular secretion of Serratia marcescens nuclease occurs as a two-step process via a periplasmic intermediate. Unlike other extracellular proteins secreted by gram-negative bacteria by the general secretory pathway, nuclease accumulates in the periplasm in its active form for an unusually long time before its export into the growth medium. The energy requirements for extracellular secretion of nuclease from the periplasm were investigated. Our results suggest that the second step of secretion across the outer membrane is dependent upon the external pH; acidic pH effectively but reversibly blocks extracellular secretion. However, electrochemical proton gradient, and possibly ATP hydrolysis, are not required for this step. We suggest that nuclease uses a novel mechanism for the second step of secretion in S. marcescens.
Adenosine Triphosphate↗
Inhibition of Serratia marcescens nuclease secretion by a truncated nuclease peptide.
The production of extracellular nuclease (Nuc) from the Serratia marcescens nucA chromosomal locus is inhibited in cells producing the N-terminal portion of Nuc from a multicopy plasmid. This inhibition in trans is not at the level of nucA expression, but rather at the level of secretion of the Nuc protein. Production of the periplasmic protein beta-lactamase (Bla) does not inhibit Nuc production unless fused to the nucA signal peptide and expressed from nucAp. Inhibition by either the truncated Nuc peptide (delta Nuc) or a Bla fusion protein is promoter specific and observed when expressed from nucAp; little inhibition is observed when the same protein is expressed from the lacZpo promoter-operator. This promoter specificity is also true for the secretion of Nuc itself.
Endodeoxyribonucleases↗
Two-step secretion of the Serratia marcescens extracellular nuclease.
The extracellular nuclease of Serratia marcescens is one of a wide variety of enzymes secreted into the growth medium. Its appearance occurs late in the growth of a culture, and its gene, nucA, is transcriptionally regulated in a complex fashion by growth phase and other factors. Pulse-labeling studies reveal that extracellular secretion of nuclease occurs as a two-step process. In the first step, nuclease is rapidly translocated across the cytoplasmic membrane into the periplasm, where it accumulates as a mature active nuclease. A precursor protein, nuclease still carrying its signal sequence, was detected in the presence of carbonyl cyanide m-chlorophenylhydrazone or sodium azide, suggesting that this initial translocation and signal processing step involves an energy-dependent and Sec-dependent pathway in S. marcescens. The second step of secretion across the outer membrane is a slow process requiring between 30 to 120 min, depending on growth conditions.
Biological Transport↗
Hyperadrenocorticism, attenuated inflammation, and the life-prolonging action of food restriction in mice.
Food restriction (FR), which extends life span, is associated with an enhanced diurnal elevation of glucocorticoids. This increase in glucocorticoids may contribute to longevity by chronically enhancing the same protective mechanisms mobilized during acute stress. The objective of this study was to determine if attenuation of inflammation, a presumably protective effect of glucocorticoids, occurs in FR mice. Two-month-old male BALB/c mice were either fed ad lib (AL) or FR (60% AL calories) for 2 months. After one month, the diurnal elevation of plasma corticosterone was threefold higher in FR mice. Two weeks after corticosterone sampling, a hind foot pad of each mouse was injected with 20 microliters of 4% carrageenan. Maximum observed edema did not differ between FR and AL groups, but edema was reduced at onset and fell earlier in FR mice. Results indicate that at least one inflammatory reaction is attenuated by FR and are consistent with the hypothesis that FR enhances a potentially protective glucocorticoid activity.
Adrenal Cortex↗
Hyperadrenocorticism and food restriction-induced life extension in the rat: evidence for divergent regulation of pituitary proopiomelanocortin RNA and adrenocorticotropic hormone biosynthesis.
The increased diurnal elevation of plasma corticosterone (B) induced by food restriction (FR) may play a role in the life span extension of FR. We investigated whether FR alters adrenocorticotropic hormone (ACTH) and proopiomelanocortin (POMC) mRNA levels in plasma and anterior pituitary (AP), since these molecules both regulate and can be suppressed by B. Measurements were made in 3-month-old male Fischer 344 rats that had been ad libitum (AL) or FR (60% of AL calories) since 6 weeks of age. Plasma B was 2-fold higher in FR rats in the PM samples, but did not differ in AM samples. By contrast, plasma ACTH did not differ in the PM samples of FR and AL rats and was 20% lower in AM samples (p < .05) of FR rats. AP content of ACTH was 50% lower in FR rats in both AM and PM samples (p < .01). In contrast, AP contents of POMC and mRNA, primary transcript, and processing intermediate were not reduced in FR rats, and PM content of POMC primary transcript was elevated in FR rats (p < .05). The reduced pituitary and plasma ACTH of FR rats may be the consequence of their elevated plasma B levels. This study also suggests that factors other than elevated ACTH account for FR-induced hyperadrenocorticism. These results also indicate that POMC mRNA and ACTH biosyntheses are differentially regulated in FR rats.
Adrenocorticotropic Hormone↗
Differential secretion of isoforms of Serratia marcescens extracellular nuclease.
Extracellular secretion of the Serratia marcescens nuclease occurs in a two-step process: (i) rapidly to the periplasm via a signal sequence-dependent pathway and then (ii) slowly to the extracellular growth medium without cell lysis. There are two major isoforms of the nuclease in the culture supernatant of S. marcescens. We have isolated, purified, and determined the sequences of both isoforms. The first isoform, the mature nuclease (Sm2), is the result of signal sequence processing. The second isoform (Sm1) has three additional amino acids missing from the N terminus of the mature nuclease. Sm1 starts to appear extracellularly only during prolonged growth of a culture (16 to 48 h), probably because of cell lysis. However, pulse-chase experiments show that it is made early with Sm2 but is not secreted efficiently.
Amino Acid Sequence↗
Equipping and organizing comparative molecular genetics laboratories.
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Cloning, Molecular↗
Chemical probing studies of the hepatitis delta virus (HDV) genomic ribozyme.
We have investigated the higher-order structure of HDV genomic ribozyme using various base-and phosphate-specific chemical probes under native, semi-denaturing and denaturing conditions. The bases of the HDV ribozyme were probed by treatment with dimethylsulfate and carbodiimide. In general, our results are consistent with the proposed pseudoknot model of secondary structure. The involvement of phosphates in hydrogen bonds or ion co-ordination was monitored with ethylnitrosourea.
Base Sequence↗
Nucleotide sequences of the internal transcribed spacers and 5.8S rRNA gene in Canella winterana (Magnoliales; Canellaceae).
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Base Sequence↗
Maltose chemotaxis involves residues in the N-terminal and C-terminal domains on the same face of maltose-binding protein.
The periplasmic maltose-binding protein (MBP) of Escherichia coli is the recognition component of the maltose chemoreceptor and of the active transport system for maltose. It interacts with the Tar chemotactic signal transducer and the integral cytoplasmic-membrane components (the MalF and MalG proteins) of the maltose transport system. Maltose binds in a cleft between the globular N-terminal and C-terminal domains of MBP, which are connected by a moveable hinge. The two domains undergo a large motion relative to one another as the protein moves from the open, unbound state to the closed, ligand-bound state. We generated, by doped-primer mutagenesis, amino acid substitutions that specifically disrupt the chemotactic function of MBP. These substitutions cluster in two well-defined regions that are nearly contiguous on the surface of MBP in its closed conformation. One region is in the N-terminal domain and one is in the C-terminal domain. The distance between the two regions is expected to change substantially as the protein goes from the open to the closed form. These results support a model in which ligand binding brings two recognition sites on MBP into the proper spatial relationship to interact with complementary sites on Tar. Mutations in MBP that appear to cause defects in interaction with MalF and MalG are distributed differently from mutations that primarily affect maltose taxis. We conclude that the regions of MBP that contact Tar and those that contact MalF and MalG are adjacent on the face of the protein opposite the hinge connecting the two domains and that those regions are largely, although perhaps not entirely, distinct.
ATP-Binding Cassette Transporters↗
Disulfide bonds are required for Serratia marcescens nuclease activity.
The role of the two disulfide bonds found in the Serratia marcescens nuclease were tested by site directed mutagenesis and were found essential for nuclease activity, although slight residual activity remained. The requirement for disulfide bond formation may play a role in preventing the lethal action of nuclease while in the bacterial cytoplasm.
Alleles↗
Production of active Serratia marcescens metalloprotease from Escherichia coli by alpha-hemolysin HlyB and HlyD.
Serratia marcescens produces an abundant extracellular metalloprotease. The gene for this protease had previously been cloned and expressed in Escherichia coli, in which no functional protease could be found. However, the protease gene carries the LXGGXGND repeat motif found in alpha-hemolysin and other proteins secreted by homologous systems. Using a dual-plasmid complementation system, we show that the alpha-hemolysin hlyB and hlyD transport determinants are sufficient to allow secretion and activation of a functional metalloprotease species from E. coli, as are the comparable protease secretion functions of Erwinia chrysanthemi. However, strains expressing protease with the hlyBD transport system are unstable and rapidly lose the ability to produce functional protease.
DNA, Bacterial↗
The effects of prenatal nicotine on radial-arm maze performance in rats.
Studies have revealed lasting cognitive impairments, including deficits in attention and learning, in the offspring of women who smoke. Animal models have shown that prenatal nicotine can induce behavioral impairments, including deficits in learning and memory, and one study showed that only females were impaired on a maze task. The purpose of the present experiment was two-fold: 1) to attempt to replicate the reported sex difference in maze learning and 2) to assess the ability of nicotine-treated subjects to learn a maze that placed particularly heavy demands on their attentional capabilities. Pregnant mothers were given 6.0 mg/kg/day of nicotine in their drinking water. Offspring of both sexes were tested following weaning in an 8-arm-radial maze using a confinement procedure. Results showed that prenatal nicotine treatment produced significant impairments in performance in the radial-arm maze. These impairments were seen in animals of both sexes, a finding which challenges the view that only females prenatally treated with nicotine show deficits in maze learning.
Animals↗
Does the addition of an oral barium tracer improve the ability of the preliminary abdominal radiograph to assess efficacy of colonic cleansing? A prospective randomized controlled evaluation.
BACKGROUND: We investigated whether the ability of preliminary abdominal radiography to assess the adequacy of colonic preparation is improved by the addition of an oral barium tracer to the laxative preparation and the optimal dosage of this tracer. METHODS: A single-blind, randomized controlled evaluation of four parallel groups of adult patients was performed. All patients were scheduled to a receive a double-contrast barium enema at a tertiary care hospital or an outpatient clinic. RESULTS: One hundred nineteen patients were randomized into four groups. There was no significant difference in the ability of plain abdominal radiography to predict the adequacy of the bowel preparation between the control group and the groups given 60 or 150 g of barium tracer. There was an improved correlation between findings of preliminary abdominal radiography and the adequacy of colon preparation between the control group and the group given 240 g of oral barium tracer (67% vs. 90%). CONCLUSION: The use of a large amount (240 g) of oral barium tracer with the colonic preparation improves the ability of preliminary abdominal radiography to predict the adequacy of colonic cleansing.
Administration, Oral↗