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R J Russell

Publications and source records attributed to R J Russell.

At least 73 records · Page 4Linked to original sources
PubMed1995

Citrate synthase from the hyperthermophilic Archaeon, Pyrococcus furiosus.

The gene encoding the enzyme citrate synthase has been cloned and sequenced from the hyperthermophilic Archaeon Pyrococcus furiosus, and the derived amino acid sequence has been phylogenetically compared with citrate synthases from archaeal, bacterial and eukaryal organisms. The gene has been over-expressed in Escherichia coli to produce an active enzyme that has then been characterized with respect to its kinetic, oligomeric and hyperthermostable properties. A structurally-based sequence alignment was made to the citrate synthase from the thermophilic Archaeon Thermoplasma acidophilum, the crystal structure of which we have determined recently. From this alignment, a homology-modelled structure for the P.furiosus citrate synthase was generated and analysed.

Amino Acid Sequence↗
PubMed1995

Does fortune favour the bald? Psychological correlates of hair loss in males.

In order to investigate the relationship between male hair loss and psychological distress, 182 men were recruited who had a wide range of ages and hair loss varying from none to severe. Care was taken to ensure that hair loss and age were uncorrelated in the sample. Multiple regression was used to predict possible consequences of baldness, controlling for age, and examining the interaction between baldness and age to see if consequences were especially severe in cases of premature baldness. Increasing degrees of hair loss were associated with loss of self-esteem, depression, introversion, neuroticism and feeling unattractive. These effects were more marked for young men in the case of self-esteem, introversion and feeling unattractive.

Adult↗
PubMed1995

Use of antibiotics to prevent hepatitis and typhlitis in male scid mice spontaneously infected with Helicobacter hepaticus.

The use of antibiotic combinations to prevent acute and progressive chronic hepatitis and proliferative typhlitis associated with Helicobacter hepaticus infection in male scid/NCr mice was evaluated. The drug combinations used were amoxicillin-metronidazole-bismuth, tetracycline-metronidazole-bismuth, amoxicillin-neomycin, neomycin alone, and amoxicillin alone. Treatments were administered per os for 14 days beginning at 4 weeks of age. All mice remained clinically normal throughout the study. Specimens from mice were evaluated histologically at 21, 60, 90, and 120 days after initiation of the antibiotic treatments. Results of histologic examination and use of special stains indicated that the antibiotic regimens containing amoxicillin prevented progressive chronic hepatitis and typhlitis. Helical bacteria were not observed histologically in the liver or cecum of amoxicillin-treated mice. Helical bacteria were observed in the liver and cecum of untreated mice and in the cecum of mice treated with antibiotic regimens not containing amoxicillin. Untreated mice and those treated with amoxicillin were evaluated by culture for presence of H. hepaticus at 60 and 90 days and by polymerase chain reaction at 90 days after initiation of the antibiotic treatment. All untreated mice were test-positive by fecal/cecal culture, and three of five were positive by polymerase chain reaction. All mice treated with amoxicillin were negative for H. hepaticus by results of culture and polymerase chain reaction. The oral administration of amoxicillin to young scid mice via the drinking water prevents hepatitis and typhlitis caused by H. hepaticus.

Amoxicillin↗
PubMed1994

The crystal structure of citrate synthase from the thermophilic archaeon, Thermoplasma acidophilum.

BACKGROUND: The Archaea constitute a phylogenetically distinct, evolutionary domain and comprise organisms that live under environmental extremes of temperature, salinity and/or anaerobicity. Different members of the thermophilic Archaea tolerate temperatures in the range 55-110 degrees C, and the comparison of the structures of their enzymes with the structurally homogolous enzymes of mesophilic organisms (optimum growth temperature range 15-45 degrees C) may provide important information on the structural basis of protein thermostability. We have chosen citrate synthase, the first enzyme of the citric acid cycle, as a model enzyme for such studies. RESULTS: We have determined the crystal structure of Thermoplasma acidophilum citrate synthase to 2.5 A and have compared it with the citrate synthase from pig heart, with which it shares a high degree of structural homology, but little sequence identity (20%). CONCLUSIONS: The three-dimensional structural comparison of thermophilic and mesophilic citrate synthases has permitted catalytic and substrate-binding residues to be tentatively assigned in the archaeal, thermophilic enzyme, and has identified structural features that may be responsible for its thermostability.

Amino Acid Sequence↗
PubMed1994

Purification, molecular cloning and heterologous expression of a glutathione S-transferase from the Australian sheep blowfly (Lucilia cuprina).

Three glutathione S-transferases from Lucilia cuprina (Australian sheep blowfly) pupae were purified by affinity chromatography and anion-exchange chromatography. One isoenzyme was composed of M(r)-24,800 subunits, and two isoenzymes had subunits of M(r) 23,900. The M(r)-23,900 subunits showed immunological identity and were immunologically distinct from the M(r)-24,800 subunits. All three enzymes were active with the substrate 1-chloro-2,4-dinitrobenzene and had low activity with 1,2-dichloro-4-nitrobenzene. A cDNA clone encoding a M(r)-23,900 subunit (LuGST1) was isolated and sequenced. The sequence has close similarities (> 81%) to that of GSTs from the fruitfly Drosophila melanogaster and Musca domestica (housefly). The deduced amino acid sequence of the Lu GST1 subunit showed no significant similarity to that of the mammalian GSTs to the Alpha, Mu and Pi classes, but shows some similarity (33%) over the first 100 residues with the rat subunit 12 Theta-class GST. Southern blots of genomic DNA hybridized with the LuGST1 cDNA identified many hybridizing fragments. Taken together, these data indicated that the L. cuprina genome contains multiple glutathione S-transferase genes.

Amino Acid Sequence↗
PubMed1994

Insecticide resistance and malathion carboxylesterase in the sheep blowfly, Lucilia cuprina.

Resistance to the organophosphorus insecticide malathion in genetically related strains of the Australian sheep blowfly Lucilia cuprina was examined. Separate lines of blowflies were established by homozygosis of the fourth chromosome of the parental RM strain. Both the RM and the derived resistant (der-R) strains are approximately 100 times more resistant to malathion than the related susceptible der-S strain, resistance being correlated with a 45- to 50-fold increase in a malathion carboxylesterase (MCE) activity. MCE has a pH optimum ranging between 6.6 and 8.0 and is strongly inhibited by the carboxylesterase inhibitors triphenyl phosphate, paraoxon, and diisopropylfluorophosphate. Subcellular fractionation revealed that MCE was localized predominantly to the cytosol and mitochondria in both resistant and susceptible blowflies. A single MCE was purified to homogeneity from RM blowflies. It has a pI of 5.5, is a monomer of 60.5 kDa, and hydrolyzes malathion with a Vmax of 755 nmol/min/mg protein and a Km of 11.0 microM. L. cuprina have thus evolved a remarkable MCE which is faster and more efficient at hydrolyzing a specific insecticide than any other insect esterase vet described.

Amino Acid Sequence↗
PubMed1994

A cluster of esterase genes on chromosome 3R of Drosophila melanogaster includes homologues of esterase genes conferring insecticide resistance in Lucilia cuprina.

We identify an esterase isozyme in Drosophila melanogaster, EST 23, which shares biochemical, physiological, and genetic properties with esterase E3, which is involved in resistance to organophosphate insecticides in Lucilia cuprina. Like E3, the D. melanogaster EST 23 is a membrane-bound alpha-esterase which migrates slowly toward the anode at pH 6.8. Both enzymes have similar preferences for substrates with shorter acid side chain lengths. Furthermore, on the basis of their high sensitivity to inhibition by paraoxon and their insensitivity to inhibition by eserine sulfate, both enzymes were classified as subclass I carboxylesterases. The activity of each enzyme peaks early in development and, again, in the adult stage. Both enzymes are found in the male reproductive system and larval and adult digestive tissues, the latter being consistent with a role for these enzymes in organophosphate resistance. Fine structure deficiency mapping localized Est 23 to cytological region 84D3 to E1-2 on the right arm of chromosome 3. Moreover, we show that the genes encoding three other esterase phenotypes also map to the same region; these phenotypes involve allozymic differences in EST 9 (formerly EST C), ali-esterase activity, defined by the hydrolysis of methyl butyrate, and malathion carboxylesterase activity, defined by hydrolysis of the organophosphate malathion. This cluster corresponds closely to that encompassing E3 and malathion carboxylesterase on chromosome 4 in L. cuprina, the homologue of chromosome 3R in D. melanogaster.

Animals↗
PubMed1994

A cluster of at least three esterase genes in Lucilia cuprina includes malathion carboxylesterase and two other esterases implicated in resistance to organophosphates.

Three distinct malathion carboxylesterase (MCE) phenotypes have been identified among strains of Lucilia cuprina. The high-activity phenotype shows 1.6- and 33-fold more MCE specific activity than the intermediate- and low-activity phenotypes, respectively. Flies with high MCE activity are 1000-fold more resistant to malathion than flies with either low or intermediate MCE phenotypes, which are equally susceptible. High and low MCE specific activity are allelic and encoded by the Rmal gene on chromosome 4. Rmal is clustered within one map unit of two other esterase genes, Rop1 and E9, which are implicated in resistance to other organophosphate insecticides. Intermediate MCE specific activity is also inherited within the cluster, although its allelism to Rmal, Rop1, or E9 is unclear. The cluster does not contain the gene for the hemolymph esterase E4, which maps 6.1 map units from Rop1, on the other side of the bubbled wing marker. The cluster appears to be homologous to part of a tandem array of 11 esterase genes on chromosome 3R of Drosophila melanogaster.

Animals↗
PubMed1994

Analysis of the genetic contamination of salt-sensitive Dahl/Rapp rats.

Genetic contamination of Dahl/Rapp salt-sensitive rats (SS/JrHsd) was recently discovered in animals received from Harlan Sprague Dawley, Inc, the main supplier of this strain to researchers in the United States. We were interested in determining how this problem occurred and the extent of contamination in the breeding colony in hopes of quickly correcting the problem and reestablishing the supply of this important model of genetic hypertension. DNA was extracted from whole blood obtained from each rat in the Harlan foundation colony and their offspring, the pedigree expansion colony. Several microsatellite-based genetic markers that were polymorphic between the normal and contaminant alleles were used to test these two colonies. All 10 breeder pairs in the foundation colony were tested at six different loci and found to be homozygous for the normal allele in each case. All 60 members of the pedigree expansion colony were also tested, and several rats carrying contaminant alleles were found, thus localizing the origin of the contamination to this colony. We offer several recommendations regarding precautions researchers using inbred animals should take in designing future experiments.

Alleles↗
PubMed1993

Crystallization and preliminary crystallographic study of citrate synthase from the thermophilic Archaeon Thermoplasma acidophilum.

Single crystals of citrate synthase from the Archaeon Thermoplasma acidophilum were obtained in two forms using the hanging drop vapour diffusion method and polyethylene glycol 3350 as precipitant. Type 1 crystals belong to the orthorhombic space group P222(1), with unit cell dimensions a = 80.9 A, b = 103.8 A, c = 98.3 A and one dimer in the asymmetric unit. Type 2 crystals belong to the monoclinic space group P2(1), with unit cell dimensions a = 53.8 A, b = 173.8 A, c = 86.7 A and beta = 97.1 degrees and two dimers in the asymmetric unit.

Citrate (si)-Synthase↗
PubMed1993

Evolutionary genetics of Drosophila esterases.

Over 30 carboxylester hydrolases have been identified in D. melanogaster. Most are classified as acetyl, carboxyl or cholinesterases. Sequence similarities among most of the carboxyl and all the cholinesterases so far characterised from D. melanogaster and other eukaryotes justify recognition of a carboxyl/cholinesterase multigene family. This family shows minimal sequence similarities with other esterases but crystallographic data for a few non-drosophilid enzymes show that the family shares a distinctive overall structure with some other carboxyl and aryl esterases, so they are all put in one superfamily of/beta hydrolases. Fifteen esterase genes have been mapped in D. melanogaster and twelve are clustered at two chromosomal sites. The constitution of each cluster varies across Drosophila species but two carboxyl esterases in one cluster are sufficiently conserved that their homologues can be identified among enzymes conferring insecticide resistance in other Diptera. Sequence differences between two other esterases, the EST6 carboxyl esterase and acetylcholinesterase, have been interpreted against the consensus super-secondary structure for the carboxyl/cholinesterase multigene family; their sequence differences are widely dispersed across the structure and include substantial divergence in substrate binding sites and the active site gorge. This also applies when EST6 is compared across species where differences in its expression indicate a difference in function. However, comparisons within and among species where EST6 expression is conserved show that many aspects of the predicted super-secondary structure are tightly conserved. Two notable exceptions are a pair of polymorphisms in the substrate binding site of the enzyme in D. melanogaster. These polymorphisms are associated with differences in substrate interactions in vitro and demographic data indicate that the alternative forms are not selectively equivalent in vivo.

Amino Acid Sequence↗
PubMed1993

Oral Candida in HIV infection and AIDS: new perspectives/new approaches.

Oral candidosis has become an increasingly important problem in HIV-infected individuals. At present, the small body of published literature on the characterization of the Candida strains and species found in HIV+ patients is full of confusion and contradictions. Some of these difficulties are the result of the methodological shortcomings of a number of the techniques that have been used. Examples of the problems that may be encountered on primary isolation and subculture are described and the drawbacks associated with the systems used to date for phenotyping Candida are quoted. While molecular characterization techniques would appear to offer a reliable and objective alternative, they too have their strengths and weaknesses. An attempt is made to summarize the progress that has been made recently in the detection and identification of Candida albicans and also the non-albicans species from HIV-infected individuals. What emerges is that the commensal Candida species that inhabit the oral cavities of HIV+ patients are subjected to a number of significant pressures that probably promote the selection of organisms with unusual phenotypes and genotypes. These Candida are more difficult to characterize and behave differently compared to their counterparts in HIV- individuals. It is clear that uncovering the factors that are important for the selection of treatment regimens and will be predictive of outcome will not be easy. Candida organisms are neither as benign nor as simple as once thought.

AIDS-Related Opportunistic Infections↗
PubMed1993

DNA fingerprinting for genetic monitoring of inbred laboratory rats and mice.

DNA fingerprinting using a nonisotopically labeled minisatellite probe provided a valuable technique for genetic monitoring/quality control of laboratory rodents. Each of 12 inbred rat strains had a unique fingerprint pattern, and colonies separated for over 20 years had identical or nearly identical patterns. Strain LOU/Iap, which is known to have been genetically contaminated in the past, was clearly different from strain LOU/CN, supporting previous findings of studies using biochemical markers. Inbred strains of mice were also found to differ from each other. The F1 hybrid between C57BL/6 and CBA/Ca could not be distinguished from C57BL/6 by using DNA fingerprints, although they could be distinguished by using biochemical markers. Some congenic strains differed from their inbred partner. A suspected genetic contamination of MRL/Mp-lpr mice could not be detected in a sample of the breeding colony by using biochemical markers; however, DNA fingerprints from the suspect animals clearly demonstrated genetic segregation. DNA fingerprinting will be of particular value in investigating suspected problems as only a small sample of fresh, frozen, or ethanol-preserved tissue is needed. Thus, the actual suspect animals can be studied, rather than samples from a breeding colony from which contaminated animals may already have been eliminated.

Animals↗
PubMed1992

Molecular analysis of the lethal(1)B214 region at the base of the X chromosome of Drosophila melanogaster.

Approximately 50 kb of genomic DNA was isolated from polytene chromosome bands 19F1 and 2 of Drosophila melanogaster. Bands 19F1 and 2 are in the immediate vicinity of the beta-heterochromatin at the base of the X chromosome and encompass the little fly-like and lethal(1)B214 complementation groups. The cloned DNA consists of an approximately 21 kb stretch of unique or low copy number sequence that is bounded by repetitive elements interspersed with further unique sequences. The presence of repeated sequences is characteristic of regions within and adjacent to beta-heterochromatin. At least part of a tRNA gene cluster is present within the 50 kb of cloned DNA. The cloned region also produces at least 18 discrete size classes of developmentally regulated poly(A)+ RNA species. A 2 kb EcoRI fragment (E10), which lies in the 21 kb stretch of unique sequence, generates seven of these transcripts (of sizes 3.5, 3.35, 2.1, 2.0, 1.5, 1.2 and 1.0 kb) in wild-type flies. However, a small deletion of approximately 75 bp in E10 in a lethal(1)B214 mutant allele is associated with alterations in the production or processing of all seven of these transcripts. These data identify E10 sequences as belonging to the lethal(1)B214 gene and suggest that the wild-type lethal(1)B214 gene encodes multiple transcripts. Furthermore, no transcripts of the same size and having the same developmental profile as those generated by the wild-type E10 fragment were identified by probes covering the remainder of the cloned region. This suggests that at least the larger transcripts hybridizing to E10 are partly transcribed from sequences located outside the cloned region, which indicates that the lethal(1)B214 gene extends for more than 20 kb and contains other transcriptionally active sequences within it.

Animals↗
PubMed1992

Reduced azole susceptibility of oral isolates of Candida albicans from HIV-positive patients and a derivative exhibiting colony morphology variation.

Approximately 50% (15/28) of a selection of oral isolates of Candida albicans from separate individuals infected with the human immunodeficiency virus (HIV) exhibited low susceptibility to ketoconazole as determined by hyphal elongation assessment. Nine of these isolates exhibited colony morphology variation or switching at 37 degrees C, of which six expressed low ketoconazole susceptibility. To determine whether colony morphology variation could give rise to derivatives with reduced azole susceptibility, several high-frequency switching variants of three HIV-patient isolates were recovered and assessed. All but one of the variants expressed similar azole susceptibility profiles to their respective parental strains. However, the C. albicans derivative 132ACR expressed significantly reduced susceptibility to ketoconazole in comparison to its parental strain 132A. In whole cells, on the basis of total growth the switched derivative 132ACR was markedly less susceptible than its parental isolate 132A to ketoconazole at 10 microM. A much smaller difference was observed with fluconazole at 10 microM, with the switched derivative 132ACR exhibiting a threefold lower susceptibility compared with the parental isolate 132A. The incorporation of [14C]acetate in control and azole-treated cells of both organisms was higher for the parental strain. When cell lysates of strain 132A and its derivative 132ACR were incubated with [14C]mevalonic acid and ketoconazole, the IC50 for 14C-label incorporation into C-4 demethyl sterols was fivefold higher for lysates of the switched derivative 132ACR compared with those of the parental strain 132A. With fluconazole the IC50 value for the derivative 132ACR was 25-fold higher than for strain 132A. The 14-sterol demethylase of the switched derivative 132ACR was possibly less sensitive to azole inhibition than that of the enzyme of strain 132A. These studies indicated that colony morphology variation in vitro can generate derivatives with stable, reduced azole susceptibility without prior exposure to azoles.

Candida albicans↗
PubMed1991

Informed consent for cardiopulmonary resuscitation in elderly patients.

OBJECT: to determine if a semistructured interview would enable elderly patients to give adequately informed consent for cardiopulmonary resuscitation (CPR). METHOD: one hundred consecutive patients admitted to Wakari assessment and rehabilitation unit for the elderly, who satisfied study criteria, were randomly allocated to receive a detailed discussion on CPR or to act as controls. Subsequently knowledge about CPR was tested in both groups. RESULTS: of the 49 study subjects, 27 (55%) wished to have CPR in the event of a cardiac arrest. After the interview knowledge about the CPR was significantly better in the study group than the controls, but there was still a lack of appreciation of the possible complications and an overly optimistic view of the likely outcome. CONCLUSIONS: careful explanation of the procedures involved in CPR does increase knowledge and assist in making an informed decision. However, the decision may still be based on poor understanding of the likely outcome and possible complications.

Aged↗