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Biomedical subjects

K J Shaw

Publications and source records attributed to K J Shaw.

At least 73 records · Page 4Linked to original sources
PubMed1990

Resistance to aminoglycoside antibiotics in gram-negative bacilli and staphylococci isolated from blood. Report from a European collaborative study. The ESGAR Study Group (European Study Group on Antibiotic Resistance).

The incidence of resistance to gentamicin, tobramycin, amikacin and netilmicin was determined by the microdilution method in Mueller-Hinton broth among blood culture isolates consecutively collected in 37 laboratories in 14 European countries. The distribution of bacteria was similar in each laboratory, Escherichia coli and staphylococci predominating. Resistance levels varied between laboratories but they were higher to all four antibiotics in Southern Europe than in Central and Northern Europe. Aminoglycoside resistance was usually associated with production of aminoglycoside-modifying enzymes, ANT(2"), AAC (3)-V, AAC (6')-I predominating in Gram-negative bacilli and APH (2") + AAC (6') and ANT (4')-I in staphylococci.

Aminoglycosides↗
PubMed1990

Fetal responses to external stimuli.

The fetus is clearly able to respond to various external stimuli. The nature of the response is related to gestational age, intact neurologic function, and also the behavioral state of the fetus. Of the various modalities described herein, vibroacoustic stimulation utilizing an artificial larynx appears to be clinically useful in both ante- and intrapartum management. The positive predictive value is excellent (greater than 99 per cent). The fetus who responds to the stimulus with an acceptable acceleration is uniformly nonacidotic. Like many other tests of fetal health, vibroacoustic stimulation is less useful in predicting fetuses in distress, as many fail to respond and yet show no signs of compromise. It is evident that there is no single test that is without false-positives; thus accurate assessment of fetal health will depend upon utilization of a variety of biophysical parameters.

Acoustic Stimulation↗
PubMed1989

Isolation, characterization, and DNA sequence analysis of an AAC(6')-II gene from Pseudomonas aeruginosa.

The gene encoding a 6'-N-acetyltransferase, AAC(6')-II, was cloned from Pseudomonas aeruginosa plasmid pSCH884. This gene mediates resistance to gentamicin, tobramycin, and netilmicin but not amikacin or isepamicin. The DNA sequence of the gene and flanking regions was determined. The 5'- and 3'-flanking sequences showed near identity to sequences found abutting a variety of different genes encoding resistance determinants. It is likely that the current structure arose by the integration of the 572-base-pair sequence containing the AAC(6')-II gene into a Tn21-related sequence at the recombinational hot spot, AAAGTT. We have compared the sequence of the AAC(6')-II gene to genes of other 6'-N-acetyltransferases. An AAC(6')-Ib protein (encoded by the aacA4 gene; G. Tran Van Nhieu and E. Collatz, J. Bacteriol. 169:5708-5714, 1987) that results in resistance to amikacin but not gentamicin was found to share 82% sequence similarity with the AAC(6')-II protein. We speculate that these two genes arose from a common ancestor and that the processes of selection and dissemination have led to the observed differences in the spectrum of aminoglycoside resistance.

Acetyltransferases↗
PubMed1989

Use of plasmid analysis and determination of aminoglycoside-modifying enzymes to characterize isolates from an outbreak of methicillin-resistant Staphylococcus aureus.

We compared disk susceptibility, plasmid analysis, aminoglycoside resistance patterns, and DNA hybridization for their usefulness in characterizing isolates from a hospital outbreak of methicillin-resistant Staphylococcus aureus. Fifteen isolates were susceptible (group 1) and 28 were resistant (group 2) to gentamicin. A total of 15 of 15 (100%) group 1 and 22 of 28 (79%) group 2 isolates carried a 21.5-megadalton plasmid. All group 2 isolates and none of the group 1 isolates possessed a 33-megadalton plasmid. Aminoglycoside resistance pattern determinations revealed the presence of the ANT(4')-I enzyme (aminoglycoside 4' adenyltransferase) in all group 1 isolates but was unable to demonstrate presence of this enzyme in group 2 organisms. The APH(2") + AAC(6')-II enzyme (aminoglycoside 2" phosphotransferase plus 6' acetyltransferase) was found in all of the group 2 isolates but in none of the group 1 isolates. Use of DNA hybridization revealed the presence of the ANT(4')-I enzyme in both groups (group 1, 14 of 15; group 2, 26 of 28). In this hospital outbreak, we found good correlation between disk susceptibility, plasmid profile, aminoglycoside resistance patterns, and DNA hybridization results. It was difficult to predict the presence of the ANT(4')-I enzyme in the presence of the bifunctional [APH(2") + AAC(6')-II] enzyme by the aminoglycoside resistance pattern method because of overlap of the substrate profile.

Anti-Bacterial Agents↗
PubMed1989

Human decidua is a major source of renin.

Plasma prorenin levels are elevated in normal pregnant women. Current evidence suggests renin production by tissues of the uteroplacental unit contribute to this elevation. The purpose of this investigation was to define the source of renin biosynthesis within the human uteroplacental unit and to characterize the renin produced. RNA extraction and Northern blot analysis consistently demonstrated renin mRNA expression in uterine lining both in the pregnant (decidua) and nonpregnant states (endometrium) and in fetal chorion laeve, which is inseparable from the decidua. In contrast, renin mRNA expression was not detected in basal plate and intertwin chorion (which is separate from decidua), amnion, myometrium, or placental villi. The total renin content in decidual homogenates was two- to threefold greater than in endometrial homogenates, and cultured human decidual cells produced significantly more total renin than cultured human endometrial cells, suggesting that pregnancy enhanced renin production by the cells lining the uterus. Immunoblot analysis and [3H]leucine incorporation identified 47,000-mol wt prorenin as the major form of renin produced by cultured human decidual cells. These studies indicate that maternal decidua is the major source of prorenin in the uteroplacental unit.

Adult↗
PubMed1988

Regulated secretion of MuGM-CSF in Saccharomyces cerevisiae via GAL1:MF alpha 1 prepro sequences.

Murine granulocyte-macrophage colony-stimulating factor (GM-CSF) was expressed in Saccharomyces cerevisiae using a novel regulated secretion system. This system involves the fusion of the GAL1 upstream regulatory region to the signal sequence of the alpha mating pheromone, and the integration of this GAL1:MF alpha 1 prepro:MuGM-CSF construct into the yeast chromosome. These constructs were very stable under both selective and nonselective conditions: after 30 generations of growth no plasmid loss was observed. The expression and secretion of MuGM-CSF were analyzed by biological assays and Western blots of yeast culture medium and yeast cell extracts. Expression of MuGM-CSF was regulated by galactose induction. In addition, expression levels were proportional to the number of tandem copies of the gene inserted into the yeast chromosome.

Animals↗
PubMed1986

Synthesis and antitumor activities of unsymmetrically substituted 1,4-bis[(aminoalkyl)amino]anthracene-9,10-diones and related systems.

A number of unsymmetrically substituted 1,4-bis[(aminoalkyl)amino]anthracene-9,10-diones have been synthesized and evaluated for their antitumor activity against L1210 in vitro and in vivo. The high activity of several compounds observed in vitro was not paralleled by comparable activity in vivo. The activities of the substituted 1,4-bis[(aminoalkyl)amino]anthracene-9,10-diones as inhibitors of cell growth were generally much higher than those of the related 1-[(aminoalkyl)amino]-4-methoxyanthracene-9,10-diones, and this correlated with the relative abilities of compounds of the two types to interact with calf thymus DNA.

Animals↗
PubMed1986

Studies of the free faecal amines of infants with gastroenteritis and of healthy infants.

The free primary amines present in the faeces of 44 infants (1-18 months) with gastroenteritis have been examined by field desorption mass spectrometry of the lactone form of their fluorescamine derivatives without their prior separation. p-Tyramine, 2-phenylethylamine, the diamines, putrescine and cadaverine and several of their acyl derivatives were common constituents, but a number of other amines were also characterised. Using thin layer chromatography and field desorption mass spectrometry of the amine dansyl derivatives a comparative study was made of the faecal amines of 13 selected infants with gastroenteritis (diarrhoea) and of 13 healthy infants. p-Tyramine, the most abundant amine, was significantly higher (p = 0.02) in the sick infants. The overall presence of p-tyramine was more significantly related to the diet of the infants. Faecal tyramine was low in breast fed infants but significantly higher (p = 0.01) in infants fed cow's milk.

Amines↗
PubMed1986

Mosaic variegated trisomy (42,XY/43,XY, + variable) in a male pigtail macaque monkey.

We identified an infant male pigtail macaque monkey with a bizarre karyotype which, to the best of our knowledge, has never before been reported in any species. Examination of 107 nuclei from cultured lymphocytes revealed 81 (75.7%) to be trisomic, but with the supernumerary chromosome varying from cell to cell, trisomy 16 being the most common. A small percentage (11.2%) of the nuclei had a normal 42,XY karyotype, and the balance, with the exception of one apparent monosomic (possibly a technical artifact), had multiple chromosome abnormalities. Examination of cultured skin fibroblasts revealed a similar karyotype. We called this karyotype a mosaic variegated trisomy. At birth, the animal had a cleft lip and palate and situs inversus of the heart. He subsequently showed significant developmental delay and apparent mental retardation. There were no clinical symptoms of hematological malignancy, which often have associated acquired chromosome abnormalities such as those described here. The animal survived for 2 yr and 8 mo under intensive care.

Animals↗
PubMed1985

Porcine granulosa cell production of plasminogen activator: disparity between the effects of hCG and pFSH.

Fibrinolytic activity in porcine follicular fluid and plasminogen activator production by porcine granulosa cells in response to gonadotropins is described. Fibrinolytic activity was determined using a solid phase assay in which 125I-fibrinogen was coupled to latex beads. Urokinase plus plasminogen served as the standard. Porcine follicular fluid contained protease inhibitors as evidenced by its ability to inhibit the activity of an urokinase-plasminogen standard. Removal of these inhibitors by acid precipitation revealed plasminogen-dependent and -independent fibrinolytic activity. Cultured granulosa cells produced plasminogen activator in amounts that increased over time. This pattern was most significant in cells stimulated by hCG. Cells incubated with hCG produced significantly more plasminogen activator when compared to those cells cultured in absence of gonadotropin. The enhancement was most marked during the second 48 hrs in culture (p = 0.032). FSH was found to have no stimulatory effect on plasminogen activator production by cultured porcine granulosa cells.

Animals↗
PubMed1984

Effects of altered 5'-flanking sequences on the in vivo expression of a Saccharomyces cerevisiae tRNATyr gene.

Deletion mutations ending in the 5'-flanking sequences of the Saccharomyces cerevisiae SUP4-o gene have been analyzed for their effects on gene expression. This ochre-suppressing tRNATyr gene was cloned into a S. cerevisiae centromeric plasmid, and its level of in vivo expression was monitored by observing the suppressor phenotype of the gene after transformation into S. cerevisiae. A deletion mutant that retains only four base pairs of the 5'-flanking sequence is profoundly deficient in expression; deletion mutants extending to positions -18, -17, -16, or -15 are moderately deficient; deletion mutants extending to positions -36 or -27 are slightly defective; and mutants retaining more than 60 base pairs of the original 5'-flanking DNA are expressed normally. In some cases, the cloning procedure led to the introduction of multiple BamHI linkers at the SUP4-o-vector fusion site, and in one instance, the resulting structure dramatically affects gene function: the presence of three linkers abutting a -18 deletion completely inhibits the in vivo expression of SUP4-o. In contrast, three linkers that abut a -77 deletion have no effect on in vivo expression. The template properties of these plasmids in a homologous in vitro transcription system parallel the levels of in vivo expression, suggesting that the mutations predominantly affect transcription. The data demonstrate that there are significant functional constraints on the 5'-flanking sequences of this RNA polymerase III-transcribed gene. The dramatic effects of the multiple linker insertion at position -18 suggest that there may be extensive melting of the DNA in this region during normal transcription initiation.

Chromosome Deletion↗
PubMed1981

Organization and regulation of the ilvGEDA operon in Salmonella typhimurium LT2.

A total of 102 isoleucine- and isoleucine-valine-requiring (ilv) mutants induced by insertion of the transposable element Tn10 have been classified to cistron by growth requirement, cross-feeding behavior, and enzyme assays. The mutations are in a polycistronic operon transcribed in the order ilvGEDA and in a monocistronic operon ilvC. Analysis of distal gene expression in these polar insertion mutants revealed the existence of two constitutive interval promoters, one preceding ilvE and the other preceding ilvD.

Chromosome Mapping↗
PubMed1980

The ilvG gene is expressed in Escherichia coli K-12.

Three genes code for isozymes of acetohydroxy acid synthase (AHAS) in Escherichia coli K-12. To test the previously published supposition that one of them, ilvG, is silent in ilvO+ strains, we isolated mutants which had deletions of various lengths in the ilvGEDA operon. Some of these mutants have severely reduced levels of AHAS activity. We conclude that ilvG is expressed in ilvO+ strains but is deleted in these mutants. In addition, we find that AHAS II, the ilvG gene product, is sensitive to feedback inhibition by valine. We hypothesize that ilvO- mutations are ilvG frameshift mutations which render AHAS II valine resistant and enhance transcription of distal genes.

Acetolactate Synthase↗
PubMed1980

Salmonella typhimurium mutants defective in acetohydroxy acid synthases I and II.

An analysis of transposon-induced mutants shows that Salmonella typhimurium possesses two major isozymes of acetohydroxy acid synthase, the enzymes which mediate the first common step in isoleucine and valine biosynthesis. A third (minor) acetohydroxy acid synthase is present, but its significance in isoleucine and valine synthesis may be negligible. Mutants defective in acetohydroxy acid synthase II (ilvG::Tn10) require isoleucine, alpha-ketobutyrate, or threonine for growth, a mutant defective in acetohydroxy acid synthase I (ilvB::Tn5) is a prototroph, and a double mutant (ilvG::Tn10 ilvB::Tn5) requires isoleucine plus valine for growth.

Acetolactate Synthase↗
PubMed1980

Substrate channeling: alpha-ketobutyrate inhibition of acetohydroxy acid synthase in Salmonella typhimurium.

Excess alpha-ketobutyrate inhibited the growth of Salmonella typhimurium LT2 by inhibiting the acetohydroxy acid synthase-catalyzed synthesis of alpha-acetolactate (a valine precursor). As a result, cells were starved for valine, and both ilvB (encoding acetohydroxy acid synthase I) and ilvGEDA (ilvG encodes acetohydroxy acid synthase II) were derepressed. The addition of valine reversed the effects of alpha-ketobutyrate.

Acetolactate Synthase↗