Dynamics of metal accumulation in the grasshopper Chorthippus brunneus in contaminated grasslands.
Explore the source record for details and available documents.
Animals↗
Biomedical subjects
M S Johnson
Publications and source records attributed to M S Johnson.
Effect of elevating serum lipids on luteinizing hormone response to gonadotrophin releasing hormone challenge in energy-deficient anestrous heifers.
A study was conducted to evaluate the effect of feeding a bypass fat on luteinizing hormone (LH) response to gonadotrophin releasing hormone (GnRH) in noncyclic Holstein heifers. Twelve cyclic Holstein heifers were fed a complete diet at 40% net energy for maintenance (NE(m)) until cessation of ovarian activity. Based on weights and condition scores, heifers were assigned to either a control or treatment diet containing 0.45 kg bypass fat and fed at an energy level of 85% NE(m). Diet adjustments were made following weekly weighings. GnRH challenges were conducted at four periods: prior to initial energy deprivation, at termination of 40% NE(m) feeding, and twice more at 21-d intervals after 85% NE(m) feeding began. Blood was sampled via a jugular catheter every 15 min for 5 h, and GnRH was injected after the fourth sample. None of the heifers exhibited estrous activity after the initial energy deprivation. Heifers on the bypass fat diet continued to lose weight during the treatment period, while the control heifers gained a slight amount of weight. Baseline and peak concentrations of LH were not significantly affected by time or diet. Time to GnRH-induced LH peak was longer (53 vs 130 min, P < 0.01) after 40% NE(m) and remained greater at all times thereafter. Serum lipid levels increased 82.5% among heifers being fed the bypass fat. Energy restriction had no effect on the magnitude of LH response to GnRH but did delay response time.
Journal Article↗
Relocation of a protease-like gene segment between two retroviruses.
An anomalous sequence in certain lentiviruses was found to be related to a region in a completely different part of the simian retrovirus type I (SRV-I) and its close relative, the hamster intracisternal A particle (IAP-H18). The segment is not present in the human immunodeficiency virus (HIV), which is also a lentivirus, nor is it found in any one of a dozen other retroviruses whose sequences have been reported. These observations imply that a horizontal transfer of newly acquired genetic information has taken place between an SRV-I-type virus and one of the lentivirus type, and that this event occurred more recently than did the divergence of members of this latter group and HIV. Comparison of the viral nucleic acid sequences that encode these segments revealed the presence of imperfect direct nucleotide repeats resembling the retroviral endonuclease cleavage sites at the 5' and 3' ends of these regions.
Amino Acid Sequence↗
Preparing nurse executives for financial management.
Explore the source record for details and available documents.
Administrative Personnel↗
Studies on NADH(NADPH)-cytochrome c reductase (FMN-containing) from yeast: steady-state kinetic properties of the flavoenzyme from top-fermenting ale yeast.
A study of the steady-state kinetics of NADH(NADPH)-cytochrome c reductase (FMN-containing) from ale yeast (M. S. Johnson and S. A. Kuby (1985) J. Biol. Chem. 260, 12341-12350) has led to a postulated three-substrate random-ordered hybrid mechanism, where NAD(P)H and FMN add randomly and very likely in a steady-state fashion, followed by an ordered addition of cytochrome c. Kinetic parameters have been derived from this mechanism. Arrhenius plots showed large differences between NADH and NADPH, as the substrate-reductant. Menadione accelerated cytochrome c reduction and also O2 uptake, but vitamin K1 and coenzyme Q10 were ineffective as electron mediators, possibly as a result of their insolubility. With NADPH as the substrate-reductant, the order of the rate of reduction of electron acceptors was ferricyanide greater than DCIP greater than cytochrome c greater than oxygen; with menadione, the specificity sequence was cytochrome c greater than ferricyanide greater than DCIP greater than oxygen. With NADH, the order was ferricyanide greater than cytochrome c greater than oxygen greater than DCIP, which changed to cytochrome c greater than ferricyanide greater than oxygen greater than DCIP on addition of menadione. Cytochrome b5 was also reduced in the absence of oxygen. No transhydrogenase activity was observed, but the reduced thionicotinamide analogs of NADH and NADPH acted as substrates. Superoxide dismutase inhibited cytochrome c reduction in air by 50%, but O2-. was not necessary for cytochrome c reduction, as evidenced by the increase in rate in the absence of O2. The product of the reaction with oxygen appeared to be H2O2.
Catalysis↗
Consumer-producer relationships for trace metals in Chorthippus brunneus (Thunberg).
Explore the source record for details and available documents.
Animals↗
A method for the simultaneous alignment of three or more amino acid sequences.
We describe an algorithm for the concurrent comparison of three or more amino acid sequences. The basis of the approach is a progressive evaluation of selected segments from each sequence. Only a small subset of all possible segments from each sequence is compared, and a minimum of information is retained for the trace-back of the alignment. As a result, this method has the advantage of being both rapid and minimally consumptive of computer memory when constructing an alignment. This being the case, there are no practical limits on the length of sequences that may be aligned. A computer program for the alignment of three sequences is described, and this method is compared with two three-sequence extensions of the Needleman and Wunsch variety, including a recently published approach. In addition, we have made simultaneous alignments of sets of four and five sequences with this selected-segment method.
Amino Acid Sequence↗
Computer analysis of retroviral pol genes: assignment of enzymatic functions to specific sequences and homologies with nonviral enzymes.
A computer analysis of the amino acid sequences from the putative gene products of retroviral pol genes has revealed a 150-residue segment that is homologous with the ribonuclease H of Escherichia coli. The segment occurs at the carboxyl terminus of the region assigned to the 90-kDa reverse transcriptase polypeptide. In contrast, a section nearer the amino terminus of this sequence can be aligned with nonretroviral polymerases. The order of activities in the pol gene is thus: polymerase-ribonuclease-endonuclease. On another note, all retroviral endonuclease sequences contain a consensus zinc-binding "finger." This should not be confused with the well-known zinc requirement of reverse transcriptases.
Amino Acid Sequence↗
Repetitive segmental structure of the transducin beta subunit: homology with the CDC4 gene and identification of related mRNAs.
Retinal transducin, a guanine nucleotide regulatory protein (referred to as a G protein) that activates a cGMP phosphodiesterase in photoreceptor cells, is comprised of three subunits. We have identified and analyzed cDNA clones of the bovine transducin beta subunit that may be highly conserved or identical to that in other G proteins. From the cDNA nucleotide sequence of the entire coding region, the primary structure of a 340-amino acid protein was deduced. The encoded beta subunit has a Mr of 37,375 and is comprised of repetitive homologous segments arranged in tandem. Furthermore, significant homology in primary structure and segmental sequence exists between the beta subunit and the yeast CDC4 gene product. The Mr 37,375 beta subunit polypeptide is encoded by a 2.9-kilobase (kb) mRNA. However, there exists in retina other beta-related mRNAs that are divergent from the 2.9-kb mRNA on the basis of oligonucleotide and primer-extended probe hybridizations. All mammalian tissues and clonal cell lines that have been examined contain at least two beta-related mRNAs, usually 1.8 and 2.9 kb in length. These results suggest that the mRNAs are the processed products of a small number of closely related genes or of a single highly complex beta gene.
Amino Acid Sequence↗
Relationships of human protein sequences to those of other organisms.
Explore the source record for details and available documents.
Amino Acid Sequence↗
Evidence against direct involvement of cyclic GMP or cyclic AMP in bacterial chemotactic signaling.
Defects in phosphotransferase chemotaxis in cya and cpd mutants previously cited as evidence of a cyclic GMP or cyclic AMP intermediate in signal transduction were not reproduced in a study of chemotaxis in Escherichia coli and Salmonella typhimurium. In cya mutants, which lack adenylate cyclase, the addition of cyclic AMP was required for synthesis of proteins that were necessary for phosphotransferase transport and chemotaxis. However, the induced cells retained normal phosphotransferase chemotaxis after cyclic AMP was removed. Phosphotransferase chemotaxis was normal in a cpd mutant of S. typhimurium that has elevated levels of cyclic GMP and cyclic AMP. S. typhimurium crr mutants are deficient in enzyme III glucose, which is a component of the glucose transport system, and a regulator of adenylate cyclase. After preincubation with cyclic AMP, the crr mutants were deficient in enzyme II glucose-mediated transport and chemotaxis, but other chemotactic responses were normal. It is concluded that cyclic GMP does not determine the frequency of tumbling and is probably not a component of the transduction pathway. The only known role of cyclic AMP is in the synthesis of some proteins that are subject to catabolite repression.
Adenylyl Cyclases↗
Studies on NADH (NADPH)-cytochrome c reductase (FMN-containing) from yeast. Isolation and physicochemical properties of the enzyme from top-fermenting ale yeast.
Only three major NADPH-nitrotetrazolium blue (NTB) reductases may be detected in a unique top-ale yeast (Saccharomyces cerevisiae, Narragansett strain), which appears to be of a near anaerobic type with the absence of cytochromes c and a/a3 and the presence of cytochromes P-450 and b5. Two of these three major NADPH-NTB reductases possessed NADH-NTB reductase activity; the third was specific for NADPH and was isolated in this laboratory (Tryon, E., Cress, M. C., Hamada, M., and Kuby, S. A. (1979) Arch. Biochem. Biophys. 197, 104-118) vis. NADPH-cytochrome c reductase (FAD-containing). A description of the isolation procedure is provided for one of these two NADH(NADPH)-NTB reductases, viz. NADH(NADPH)-cytochrome c reductase (FMN-containing), which accounts for about one-half of the total cyanide-insensitive menadione-activated respiration of this yeast. This NADH(NADPH)-cytochrome c reductase has been isolated from an extract of an acetone powder of the top-fermenting ale yeast, with an apparent purification of more than 67-fold and a final specific activity of 0.41 and 0.31 mumol/min/mg for NADH- and NADPH-dependent reduction, respectively. The isolated enzyme proved to be homogeneous by electrophoresis on cellulose acetate and on polyacrylamide gels. It had a pI of 5.25 (at gamma/2 = 0.05) and a molecular size under nondenaturing conditions (as determined by chromatography on Sephadex G-100 and Sephacryl S-200) of 70,000 daltons. On denaturation, the enzyme dissociated into two similar, if not identical, subunits which possessed a molecular weight of 34,000 by sodium dodecyl sulfate/urea-polyacrylamide gel electrophoresis and a weight average molecular weight of 35,000 by sedimentation equilibrium in the presence of 4.0 M guanidinium chloride. The absorbance spectrum of NADH(NADPH)-cytochrome c reductase (FMN-containing) showed three maxima at 464, 383, and 278 nm, with extinction coefficients of 9.88, 9.98, and 64.6 mM-1 cm-1, respectively. The reductase, as isolated, contained 0.63 mol of FMN/34,000-dalton subunit, with no metals and one sulfhydryl group/subunit. Its amino acid composition is reported herein. Anaerobic titrations with dithionite or NAD(P)H revealed a two-electron reduction of FMN, with no spectrally observable semiquinone intermediates.(ABSTRACT TRUNCATED AT 400 WORDS)
Amino Acids↗
The synaptic distribution of the retinal input in the superficial layers of the guinea-pig superior colliculus.
An evoked potential consisting of four postsynaptic components was recorded in the guinea-pig superior colliculus following electrical stimulation of the contralateral optic nerve. This potential was generated in response to the activation of four populations of optic nerve fibres with different conduction velocities. Current source-density analysis revealed that the two slower conducting fibre populations synapse in the upper third of the stratum griseum superficiale on dendrites whose cell bodies appear to be found in the lower part of this layer and in the stratum opticum. The two faster conducting populations synapse deeper, near the border of the stratum griseum superficiale and stratum opticum, on neurons with cell bodies that may lie towards the upper part of the stratum griseum superficiale. The locations of these postsynaptic sites correspond to the layers in which the optic nerve terminates as revealed by neuroanatomical tracing techniques. Furthermore, neurons of the shape and orientation predicted by the current source-density analysis were found in the superficial layers by using the Golgi-Cox technique.
Action Potentials↗
The beta subunit of E. coli glycyl-tRNA synthetase plays a major role in tRNA recognition.
The contributions made by the alpha and beta subunits of E. coli glycyl-tRNA synthetase to the recognition of tRNA have been investigated via binding and immunological methods. Using the nitrocellulose filter assay, we have shown that isolated beta subunit, but not the alpha subunit, binds [14C]glycyl-tRNA with an affinity comparable to that of the native enzyme. Further, the data indicate that the beta subunit possesses one binding site for glycyl-tRNA while the native or reconstituted enzyme (alpha 2 beta 2) has two sites. Rabbit antibodies directed at the beta subunit or the holoenzyme inhibit efficiently the ability of the enzyme to aminoacylate tRNA while alpha-subunit antibodies have a smaller effect. Since none of the antisera have an appreciable effect on the ATP-PPi exchange activity of the enzyme under these conditions, the beta-subunit (and holoenzyme) antisera evidently interfere with productive tRNA binding. Taken together, the data indicate that the larger, beta subunit of glycyl-tRNA synthetase plays a major role in tRNA recognition.
Amino Acyl-tRNA Synthetases↗
Studies on sound-induced epilepsy in mice.
The cerebral concentrations of pyridoxal-5'-phosphate and divalent transition metal ions (Cu2+ and Zn2+) are appreciably higher in the seizure-susceptible strain of mouse (DBA/2J) than those in normal strains (CBA/Ca and Parkes ). By injecting metal ions intracranially and pyridoxal-5'-phosphate intraperitoneally, we could render the normal mouse prone to sound-induced epilepsy. The behaviour of the treated seizure-susceptible strain of mouse. The levels of glutamate and aspartate in its inferior colliculus were elevated and the concentration of gamma-aminobutyrate was lowered. Glutaminase inhibitors, 6-diazo-5-oxo-L-norleucine (DON) and 0-diazo-acetyl-L-serine (azaserine), and a transaminase inhibitor, 4-amino-3- isoxazolidone (L-cycloserine), when injected intraperitoneally, protected the seizure-susceptible mouse from undergoing convulsions, whereas pyridoxal-5'-phosphate and methionine sulphoximine, a glutamine synthetase inhibitor, exacerbated its epileptic condition. We propose a possible sequence of biochemical events associated with susceptibility to audiogenic seizures.
Acoustic Stimulation↗
L-cycloserine: a potent anticonvulsant.
The L-isomer of 4-amino-3- isoxazolidinone (L-cycloserine), a potent transaminase inhibitor, was tested for its anticonvulsant action. Intraperitoneal injection of 25 mg kg-1 protects the inbred epileptic mouse (DBA/2J) from convulsions. The drug exerts its protective influence 3 h after administration, and its effect subsides gradually thereafter. A normal mouse (CBA/Ca) can be made prone to sound-induced epilepsy by enhancing its cerebral concentrations of Zn2+ and pyridoxal-5'-phosphate (PLP). Prior administration of 25-50 mg kg-1 L-cycloserine counteracts the convulsive effects of these substances. The pretreated animal is resistant to seizures. The concentrations of glutamate and aspartate in the inferior colliculus of the treated animal are diminished, whereas the concentration of gamma-aminobutyrate is enhanced. The time course of the changes in the amino acid concentrations broadly mirrors the changes in seizure susceptibility following the treatment. Proton nuclear magnetic resonance spectra of a mixture containing equimolar concentrations of L-cycloserine, PLP, and ZnSO4 were obtained. From the resonance peaks of such an adduct, we have ascertained that a molecule of L-cycloserine forms an irreversible Schiff base with the 4-aldehyde group of PLP, and this adduct is stabilized by a zinc ion. The significance of this finding for the anticonvulsant action of the drug is discussed.
Amino Acids↗
Pertussis in nonimmunized postsurgical biliary atresia.
A case of pertussis in a patient who had undergone hepatic portocholecystostomy for biliary atresia is described. It has been recommended that infants with postsurgical biliary atresia forgo immunizations because of the high incidence of "ascending cholangitis." The patient in this study, however, had two characteristics that decreased her susceptibility to ascending cholangitis. This report suggests that patients with postsurgical biliary atresia who undergo hepatic portocholecystostomy rather than hepatic portoenterostomy or do not achieve bile drainage should be immunized according to schedule.
Bile Ducts↗
Divalent transition-metal ions (Cu2+ and Zn2+) in the brains of epileptogenic and normal mice.
The concentrations of Cu2+ and Zn2+ in 3 strains of mice were determined spectrophotometrically. The brain of the inborn audiogenic mouse (DBA/2J) contains higher levels of Zn2+ and Cu2+ than those found in the normal mouse (CBA/Ca or Parkes). Small differences in the metallic content in the whole brains of audiogenic and normal mice are accentuated in the hippocampus and the colliculus.
Acoustic Stimulation↗