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Biomedical subjects

M D Collins

Publications and source records attributed to M D Collins.

At least 253 records · Page 14Linked to original sources
PubMed1992

4-Methylpyrazole partially ameliorated the teratogenicity of retinol and reduced the metabolic formation of all-trans-retinoic acid in the mouse.

Oral administration of retinol (50 mg/kg) to NMRI mice on day 11 of gestation (vaginal plug = day 0) led to the metabolic formation of high quantities of all-trans retinoic acid and all-trans-4-oxoretinoic acid, both known as potent teratogenic agents in the mouse. A 96% reduction of the area under the concentration-versus-time-curve (AUC) of metabolically generated all-trans retinoic acid in maternal plasma, and an 84% decrease in the embryonic AUC were observed when mice had been pretreated with the alcohol dehydrogenase inhibitor 4-methylpyrazole. A similar reduction was observed for the major metabolite of all-trans retinoic acid in the mouse, all-trans-4-oxoretinoic acid. However, 4-methylpyrazole pretreatment decreased the AUC of retinol by 10% in maternal plasma and 15% in embryo. Treatment with retinol alone resulted in 55.6%, 43.9% and 56.0% skeletal anomalies of the forelimbs, hindlimbs and craniofacial structures, respectively. Pretreatment with 4-methylpyrazole lowered the retinol induced skeletal defects to 31.3%, 24.0% and 31.3%, respectively, in the forelimb, hindlimb and craniofacial region. Typical retinoid-induced malformations for gestational day 11, e.g. bent or reduced zeugopod or stylopod elements, or cleft palate, were significantly reduced by 4-methylpyrazole pretreatment but were still detected in significantly higher prevalence than in control mice. These data suggest that the teratogenic activity of a single high dose of vitamin A in mouse is partially but not exclusively dependent on the metabolic activation of retinol to all-trans retinoic acid. Thus it could be hypothesized that retinol is either a proximate teratogen or a coteratogen with all-trans retinoic acid.

Abnormalities, Drug-Induced↗
PubMed1992

Murine teratology and pharmacokinetics of the enantiomers of sodium 2-ethylhexanoate.

A mouse model for the induction of exencephaly with sodium (+/-)-2-ethylhexanoate has been developed using multiple administration regimes. With three consecutive administrations at one-half-day intervals, the most sensitive time to induce exencephaly was Gestational Days 8-9. Using the racemic substance it was determined that the SWV strain was more sensitive to the induction of exencephaly than the C57BL/6NCrlBR strain. The enantiomers of 2-ethylhexanoic acid were separated via preparative HPLC to greater than 99.8% optical purity, and greater than 99% purity according to a gas chromatographic analysis. It was demonstrated that the (R)-enantiomer is a more potent teratogen than the (S)-enantiomer for the induction of exencephaly as well as malformations of other organ systems. Pharmacokinetic analyses for each of the enantiomers were performed in maternal plasma, maternal muscle, and embryo. The pharmacokinetics showed that the peak concentration (Cmax) for both enantiomers in the three compartments was approximately equivalent and was attained within 15 min following the third administration. The area under the concentration versus time curve values for the two enantiomers were approximately 10% higher for the (R)-antipode because of a slightly slower elimination of this compound. There was negligible (or no) racemization of the two enantiomers in the biological samples. The results suggest that teratologic differences in the enantiomers of sodium 2-ethylhexanoate are not due to differences in the concentrations of these antipodes in the embryo, but more likely result from the specific interaction of the enantiomers with chiral molecules in the embryo.

Abnormalities, Drug-Induced↗
PubMed1992

Quantitative plasma disposition of retinol and retinyl esters after high-dose oral vitamin A administration in the cynomolgus monkey.

A solid-phase extraction technique followed by automated high-performance liquid chromatography sample elution was successfully used to evaluate the effect of three pharmaceutical parameters on the plasma profile of various forms of vitamin A after an oral dose to cynomolgus monkeys. The three parameters evaluated were the chemical form of vitamin A (retinol versus retinyl acetate), the vehicle (acetone/Tween 20/water versus acetone/soybean oil), and the retinol dose (2, 10, and 50 x 10(3) retinol equivalents/kg). The form of the administered compound, retinol or retinyl acetate, appeared to have no major effect on the formation of nonpolar retinoids. The ester profile in plasma differed depending on whether the dose was administered in the water-based or the oil-based vehicle. Irrespective of the vehicle type the predominant retinoid formed was retinyl palmitate/oleate. However, retinol doses in the water-based vehicle formed relatively high concentrations of retinyl laurate and retinyl myristate but no retinyl linolenate. The retinol dose in the oil-based vehicle formed consistent, but relatively minor, concentrations of retinyl linolenate, higher relative concentrations of retinyl linoleate, and no retinyl laurate or myristate. The dose of retinol administered had an impact on the diversity of the nonpolar retinoid profile. The low dose led to the presence of almost exclusively retinyl palmitate/oleate and retinyl stearate, whereas at higher doses the other retinyl esters became major retinol constituents.(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Oral↗
PubMed1992

Phylogenetic analysis of Alloiococcus otitis gen. nov., sp. nov., an organism from human middle ear fluid.

The partial 16S rRNA sequence of an unknown bacterium that was originally isolated from middle ear fluids of children with persistent otitis media was determined by reverse transcription. A comparison of this sequence with sequences from other gram-positive species having low guanine-plus-cytosine contents revealed that this bacterium represents a new line of descent, for which the name Alloiococcus otitis gen. nov., sp. nov., is proposed. The type strain is strain NCFB 2890.

Base Composition↗
PubMed1992

Phylogenetic interrelationships of members of the genera Aeromonas and Plesiomonas as determined by 16S ribosomal DNA sequencing: lack of congruence with results of DNA-DNA hybridizations.

The phylogenetic interrelationships of members of the genera Aeromonas and Plesiomonas were investigated by using small-subunit ribosomal DNA (rDNA) sequencing. Members of the genus Aeromonas formed a distinct line within the gamma subclass of the Proteobacteria. Plesiomonas shigelloides also clustered within the confines of the gamma subclass of the Proteobacteria but exhibited a closer association with members of the family Enterobacteriaceae than with members of the family Aeromonadaceae. Species of the genus Aeromonas exhibited very high levels of overall sequence similarity (ca. 98 to 100%) with each other. Several of the relationships derived from an analysis of the rDNA sequence data were in marked disagreement with the results of chromosomal DNA-DNA pairing experiments. Diagnostic rDNA signatures that have possible value for differentiating most Aeromonas species were discerned.

Aeromonas↗
PubMed1992

Phylogenetic analysis of some Aerococcus-like organisms from urinary tract infections: description of Aerococcus urinae sp. nov.

Partial 16S ribosomal ribonucleic acid sequences of five Aerococcus-like organisms originally isolated from patients with urinary tract infections were determined using reverse transcriptase in order to clarify their taxonomic position. Analysis of the sequence data revealed that the clinical isolates represent a hitherto unknown line of descent within the genus Aerococcus. A new species, Aerococcus urinae, is proposed for these isolates. The type strain is NCFB 2893.

Base Sequence↗
PubMed1992

Use of the polymerase chain reaction and oligonucleotide probes for the rapid detection and identification of Carnobacterium species from meat.

The polymerase chain reaction (PCR) was used selectively to amplify specific rDNA sequences of Carnobacterium divergens, C. mobile, C. piscicola and C. gallinarum in purified DNA extracts, crude cell lysates and food samples. The PCR products were visualized by agarose gel electrophoresis and identified, at species level, by hybridization reactions with three specific oligonucleotide probes for C. divergens, C. mobile and C. piscicola/C. gallinarum designed from 16S rRNA sequence data. The PCR was sufficiently sensitive to amplify DNA from a single bacterium to detectable levels after 30 cycles of amplification. Both radioactive (32P) and non-radioactive alkaline phosphatase labelled probes was able to detect the PCR products. Detection was highly specific and the probes did not hybridize with DNA samples from any other of the bacterial species tested. These methods enabled the rapid and specific detection and identification of carnobacteria from pure cultures and samples of meat.

Base Sequence↗
PubMed1992

Analysis of operons encoding 23S rRNA of Clostridium botulinum type A.

Southern hybridization analysis of Clostridium botulinum type A chromosomal DNA indicated the presence of six copies of the 23S rRNA gene. Fragments of DNA encoding 23S rRNA were amplified by polymerase chain reaction and cloned in Escherichia coli. Three clones examined by restriction enzyme and sequence analysis were found to be derived from different operons. Sequence determination of the entire insert of two clones revealed nine nucleotide changes in the genes coding for 23S rRNA (99.7% sequence identity) between operons encoded on the same chromosome, showing microheterogeneity in the rRNA operons of this organism.

Base Sequence↗
PubMed1992

Development of a polymerase chain reaction-probe test for identification of Alloiococcus otitis.

A rapid polymerase chain reaction test was developed for specific identification of the human middle ear pathogen Alloiococcus otitis. Primers for the enzymatic amplification reaction were designed from highly specific sequences within the 16S rRNA gene. In addition, a confirmatory test based on hybridization of the polymerase chain reaction products to a specific internal probe was developed.

Bacteriological Techniques↗
PubMed1991

Phylogenetic analysis of some LL-diaminopimelic acid-containing coryneform bacteria from human skin: description of Propionibacterium innocuum sp. nov.

A new species, Propionibacterium innocuum, is proposed to accommodate strains of coryneform bacteria from human skin with phenotypic characters similar to those of the classical propionibacteria but differing in exhibiting primarily aerobic respiration and possessing a unique cell wall composition in which LL-diaminopimelic acid and arabinose occur together. The partial 16S rRNA sequence confirms an affinity with the genus Pro-pionibacterium and indicates that the species represents a distinct line within the genus. The type strain of Propionibacterium innocuum is NCTC 11082.

Actinomycetales↗
PubMed1991

A phylogenetic analysis of an atypical leuconostoc: description of Leuconostoc fallax sp. nov.

The 16S rRNA sequence of an unknown leuconostoc originally isolated from sauerkraut was investigated by reverse transcription. A comparison of the sequence with those from other lactic acid bacteria revealed the unknown organism represents a new albeit peripheral line within the genus Leuconostoc sensu stricto. A new species, Leuconostoc fallax, is proposed for this organism. The type strain is DSM 20189.

Base Sequence↗
PubMed1991

Transplacental distribution of weak acids in mice: accumulation in compartments of high pH.

The transplacental distribution of three weak acids was measured in mice on gestational day 11. The ratio of drug concentration in maternal, embryonic, and extraembryonic compartments compared to maternal plasma followed a consistent hierarchy such that amniotic fluid greater than or equal to exocoelomic fluid greater than embryo greater than embryo plasma greater than maternal skeletal muscle. This distribution pattern correlates well with pH in these compartments and suggests that pH gradients between compartments are an influential factor in determining weak acid drug disposition during pregnancy.

Acids↗
PubMed1991

The effect of administration time on malformations induced by three anticonvulsant agents in C57BL/6J mice with emphasis on forelimb ectrodactyly.

Exposure of C57BL/6J mice to three anticonvulsant derivatives, namely, dimethadione, sodium valproate, and sodium diphenylhydantoin, each induced postaxial forelimb ectrodactyly. The agents were administered at gestational days 9, 9 1/3, 9 2/3, and 10. It was determined that administration at day 9 2/3 induced the highest percentage of forelimb ectrodactyly for each of the three agents. The forelimb ectrodactyly response in the C57BL/6J strain was compared with the A/J strain (Collins et al., Teratology, 41:61-70, 1990); it was found that the C57BL/6J strain was more sensitive to dimethadione and the A/J strain was more sensitive to diphenylhydantoin and sodium valproate. The position of vertebral defects induced by sodium valproate correlated with the time of drug administration. The overall syndrome of malformations induced by the three anticonvulsant agents was relatively similar in the two mouse strains and differed between each of the anticonvulsant agents.

Abnormalities, Drug-Induced↗
PubMed1991

Influence of dose and pharmaceutical formulation of vitamin A on plasma levels of retinyl esters and retinol and metabolic generation of retinoic acid compounds and beta-glucuronides in the cynomolgus monkey.

Retinoid concentrations were analyzed in plasma of nonpregnant female cynomolgus monkeys after oral administration of retinol or retinyl acetate at doses of 2, 10, or 50 mg (as retinol) per kilogram body weight dissolved in acetone/soybean oil (1/9) or acetone/Tween 20/water (1/5/4). All-trans-retinoic acid, 13-cis-retinoic acid, all-trans-4-oxoretinoic acid, and 13-cis-4-oxoretinoic acid as well as the conjugates of retinol and all-trans-retinoic acid with beta-D-glucuronic acid represented major polar plasma retinoids after high doses of vitamin A. The relative bioavailability of vitamin A as well as the biotransformation to more polar retinoids was independent of the molecular form of vitamin A (retinol or retinyl acetate) used for dosing. After administration of 2 mg/kg and, in particular, after a 10 mg/kg dose, the metabolic formation of polar retinoids in plasma was much more extensive with the detergent-based vehicle compared to the oil-based vehicle. At 50 mg/kg, comparable metabolism was observed for both forms. Polar metabolites of retinol were increased in a more than linear fashion with the detergent-based vitamin A preparations between 2 and 10 mg/kg and with the oil-based preparations between 10 and 50 mg/kg. Since retinoic acid compounds have previously been shown to be potent teratogens in various animal species and humans, their metabolic formation may be of significance for the teratogenic activity of high doses of vitamin A. In addition to the dose, the pharmaceutical preparation of vitamin A could therefore be a major determinant of the developmental toxicity of vitamin A.

Animals↗
PubMed1991

Intrageneric relationships of Enterococci as determined by reverse transcriptase sequencing of small-subunit rRNA.

The 16S ribosomal ribonucleic acid (rRNA) sequences of eleven Enterococcus species were determined by reverse transcription in an attempt to clarify their intrageneric relationships. Comparative analysis of the sequence data revealed the presence of several species groups within the genus. The species E. avium, E. malodoratus, E. pseudoavium and E. raffinosus formed a distinct group as did E. durans, E. faecium, E. hirae and E. mundtii and the pair of species E. casseliflavus and E. gallinarum. Of the remaining species, E. cecorum, E. columbae, E. faecalis and E. saccharolyticus formed distinct lines of descent within the genus, whereas E. solitarius displayed a closer affinity with Tetragenococcus halophilus than with other enterococcal species.

Base Sequence↗