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Biomedical subjects

C E Cook

Publications and source records attributed to C E Cook.

At least 19 recordsLinked to original sources
PubMed2001

Hox genes and the phylogeny of the arthropods.

The arthropods are the most speciose, and among the most morphologically diverse, of the animal phyla. Their evolution has been the subject of intense research for well over a century, yet the relationships among the four extant arthropod subphyla - chelicerates, crustaceans, hexapods, and myriapods - are still not fully resolved. Morphological taxonomies have often placed hexapods and myriapods together (the Atelocerata) [1, 2], but recent molecular studies have generally supported a hexapod/crustacean clade [2-9]. A cluster of regulatory genes, the Hox genes, control segment identity in arthropods, and comparisons of the sequences and functions of Hox genes can reveal evolutionary relationships [10]. We used Hox gene sequences from a range of arthropod taxa, including new data from a basal hexapod and a myriapod, to estimate a phylogeny of the arthropods. Our data support the hypothesis that insects and crustaceans form a single clade within the arthropods to the exclusion of myriapods. They also suggest that myriapods are more closely allied to the chelicerates than to this insect/crustacean clade.

Animals↗
PubMed1999

Hox genes in brachiopods and priapulids and protostome evolution.

Understanding the early evolution of animal body plans requires knowledge both of metazoan phylogeny and of the genetic and developmental changes involved in the emergence of particular forms. Recent 18S ribosomal RNA phylogenies suggest a three-branched tree for the Bilateria comprising the deuterostomes and two great protostome clades, the lophotrochozoans and ecdysozoans. Here, we show that the complement of Hox genes in critical protostome phyla reflects these phylogenetic relationships and reveals the early evolution of developmental regulatory potential in bilaterians. We have identified Hox genes that are shared by subsets of protostome phyla. These include a diverged pair of posterior (Abdominal-B-like) genes in both a brachiopod and a polychaete annelid, which supports the lophotrochozoan assemblage, and a distinct posterior Hox gene shared by a priapulid, a nematode and the arthropods, which supports the ecdysozoan clade. The ancestors of each of these two major protostome lineages had a minimum of eight to ten Hox genes. The major period of Hox gene expansion and diversification thus occurred before the radiation of each of the three great bilaterian clades.

Amino Acid Sequence↗
PubMed1999

A mitochondrial control region and cytochrome b phylogeny of sika deer (Cervus nippon) and report of tandem repeats in the control region.

Sika deer (Cervus nippon Temminck) are endemic to mainland and insular Asia. Numerous subspecies have been named, but they are not quantitatively well defined. Portions of the mitochondrial cytochrome b gene (450 bp) and control region (512 bp) were sequenced from 28 individuals belonging to five sika subspecies and two Cervus elaphus subspecies. Phylogenetic trees constructed using these sequences clearly demonstrated that sika are monophyletic with respect to C. elaphus. A survey of variation in the control region showed that approximately half the variation occurred in a 100-base segment between positions 150 and 250 in the left domain of the control region. Within this region there were three tandemly repeated copies of a 39-base motif. In addition, two of the samples (C. n. aplodontus and C. n. hortulorum) contained, respectively, two and four additional copies of the repeated motif.

Animals↗
PubMed1999

The novel progesterone receptor antagonists RTI 3021-012 and RTI 3021-022 exhibit complex glucocorticoid receptor antagonist activities: implications for the development of dissociated antiprogestins.

We have identified two novel compounds (RTI 3021-012 and RTI 3021-022) that demonstrate similar affinities for human progesterone receptor (PR) and display equivalent antiprogestenic activity. As with most antiprogestins, such as RU486, RTI 3021-012, and RTI 3021-022 also bind to the glucocorticoid receptor (GR) with high affinity. Unexpectedly, when compared with RU486, the RTI antagonists manifest significantly less GR antagonist activity. This finding indicates that, with respect to antiglucocorticoid function, receptor binding affinity is not a good predictor of biological activity. We have determined that the lack of a clear correlation between the GR binding affinity of the RTI compounds and their antagonist activity reflects the unique manner in which they modulate GR signaling. Previously, we proposed a two step "active inhibition" model to explain steroid receptor antagonism: 1) competitive inhibition of agonist binding; and 2) competition of the antagonist bound receptor with that activated by agonists for DNA response elements within target gene promoters. Accordingly, we observed that RU486, RTI 3021-012, and RTI 3021-022, when assayed for PR antagonist activity, accomplished both of these steps. Thus, all three compounds are "active antagonists" of PR function. When assayed on GR, however, RU486 alone functioned as an active antagonist. RTI 3021-012 and RTI 3021-022, on the other hand, functioned solely as "competitive antagonists" since they were capable of high affinity GR binding, but the resulting ligand receptor complex was unable to bind DNA. These results have important pharmaceutical implications supporting the use of mechanism based approaches to identify nuclear receptor modulators. Of equal importance, RTI 3021-012 and RTI 3021-022 are two new antiprogestins that may have clinical utility and are likely to be useful as research reagents with which to separate the effects of antiprogestins and antiglucocorticoids in physiological systems.

Apoptosis↗
PubMed1998

Molecular instability in the COII-tRNA(Lys) intergenic region of the human mitochondrial genome: multiple origins of the 9-bp deletion and heteroplasmy for expanded repeats.

We have identified two individuals from Glasgow in Scotland who have a deletion of one of two copies of the intergenic 9-bp sequence motif CCCCCTCTA, located between the cytochrome oxidase II (COII) and lysine tRNA (tRNA(Lys)) genes of the human mitochondrial genome. Although this polymorphism is common in Africa and Asia, it has not been reported in Northern Europe. Analysis of the mitochondrial DNA control region sequences of these two individuals suggests that they belong to a lineage that originated independently of the previously characterized African and Asian 9-bp deleted lineages. Among the Scottish population we have also identified a maternal lineage of three generations exhibiting heteroplasmy for two, three and four copies of the CCCCCTCTA motif. Polymerase chain reaction amplification across the COII-tRNA(Lys) intergenic region of these individuals gives different ratios of the three product lengths that are dependent on the concentration of the DNA-binding dye crystal violet. To investigate whether changes in repeat number were generated de novo, we constructed clones containing known numbers of the CCCCCTCTA motif. In the presence of high concentrations of crystal violet we obtained two, three and four copies of this motif when the amplification template contained only four copies. Various DNA-binding drugs are known to stabilize bulged structures in DNA and contribute to the process of slipped-strand mispairing during DNA replication. These results suggest that the COII-tRNA(Lys) intergenic region is unstable owing to slipped-strand mispairing. Although sequences containing four copies of the CCCCCTCTA motif are less stable in vitro, we observed an increase in the proportion of mitochondrial genomes with four repeats between-a mother and a daughter in the heteroplasmic lineage. From this we conclude that drift in the germ-line lineage is a main factor in the maintenance or loss of heteroplasmy.

Africa↗
PubMed1998

Characterization of infectious aerosols in health care facilities: an aid to effective engineering controls and preventive strategies.

Assessment of strategies for engineering controls for the prevention of airborne infectious disease transmission to patients and to health care and related workers requires consideration of the factors relevant to aerosol characterization. These factors include aerosol generation, particle size and concentrations, organism viability, infectivity and virulence, airflow and climate, and environmental sampling and analysis. The major focus on attention to engineering controls comes from recent increases in tuberculosis, particularly the multidrug-resistant varieties in the general hospital population, the severely immunocompromised, and those in at-risk and confined environments such as prisons, long-term care facilities, and shelters for the homeless. Many workers are in close contact with persons who have active, undiagnosed, or insufficiently treated tuberculosis. Additionally, patients and health care workers may be exposed to a variety of pathogenic human viruses, opportunistic fungi, and bacteria. This report therefore focuses on the nature of infectious aerosol transmission in an attempt to determine which factors can be systematically addressed to result in proven, applied engineering approaches to the control of infectious aerosols in hospital and health care facility environments. The infectious aerosols of consideration are those that are generated as particles of respirable size by both human and environmental sources and that have the capability of remaining viable and airborne for extended periods in the indoor environment. This definition precludes skin and mucous membrane exposures occurring from splashes (rather than true aerosols) of blood or body fluids containing infectious disease agents. There are no epidemiologic or laboratory studies documenting the transmission of bloodborne virus by way of aerosols.

Aerosols↗
PubMed1996

16 alpha-substituted analogs of the antiprogestin RU486 induce a unique conformation in the human progesterone receptor resulting in mixed agonist activity.

Previously, we have shown that agonists and antagonists interact with distinct, though overlapping regions within the human progesterone receptor (hPR) resulting in the formation of structurally different complexes. Thus, a link was established between the structure of a ligand-receptor complex and biological activity. In this study, we have utilized a series of in vitro assays with which to study hPR pharmacology and have identified a third class of hPR ligands that induce a receptor conformation which is distinct from that induced by agonists or antagonists. Importantly, when assayed on PR-responsive target genes these compounds were shown to exhibit partial agonist activity; an activity that was influenced by cell context. Thus, as has been shown previously for estrogen receptor, the overall structure of the ligand-receptor complex is influenced by the nature of the ligand. It appears, therefore, that the observed differences in the activity of some PR and estrogen receptor ligands reflect the ability of the cellular transcription machinery to discriminate between the structurally different complexes that result following ligand interaction. These data support the increasingly favored hypothesis that different ligands can interact with different regions within the hormone binding domains of steroid hormone receptors resulting in different biologies.

Animals↗
PubMed1995

Structure-activity studies of 2,3,4,4a,5,9b-hexahydroindeno[1,2-c]pyridines as antispermatogenic agents for male contraception.

Analogs of (4aRS,5SR,9bRS)-2-ethyl-2,3,4,4a,5,9b-hexahydro-7-meth yl-5-p- tolyl-1H-indeno[1,2-c]pyridine (Sandoz 20-438, 10a; R1 = ethyl, R2 = R3 = methyl, R4 = H) have been synthesized and tested in mice for their ability to reduce testes weight and disrupt spermatogenesis. The activity was strongly dependent on stereoisomerism and chirality, consistent with a mechanism of action involving interaction with a specific macromolecule. It was affected by changes in the nitrogen substituent and most strikingly by changes in the p-substituent of the 5-aryl ring. A hydrogen, fluorine, hydroxy, or methoxy substituent led to loss of activity, whereas methyl (Sandoz 20-438, 10a), carboxylate (RTI-4587-054, 10k; R1 = ethyl, R2 = methyl, R3 = COOH, R4 = H), ester (RTI-4587-056, 12b; R1 = ethyl, R2 = methyl, R3 = COOMe, R4 = H), formyl (RTI-4587-030, 12i; R1 = ethyl, R2 = methyl, R3 = CHO, R4 = H), or hydroxymethyl (RTI-4587-055, 12g; R1 = ethyl, R2 = methyl, R3 = CH2OH, R4 = H) groups resulted in antispermatogenic compounds. Methyl ester 12b was an effective antifertility agent, without apparent effects on mating, when given orally to male mice at 7-15 mg/kg daily for 35 days. Further evaluation of these compounds as male contraceptive agents and probes for study of spermatogenesis appears warranted.

Administration, Oral↗
PubMed1994

Determination of l-alpha-acetylmethadol, l-alpha-noracetylmethadol and l-alpha-dinoracetylmethadol in plasma by gas chromatography-mass spectrometry.

A method is described for the simultaneous determination of l-alpha-acetylmethadol (LAAM) and its N-demethylated metabolites, l-alpha-noracetylmethadol (norLAAM) and l-alpha-dinoracetylmethadol (dinorLAAM), in plasma by gas chromatography-chemical ionization mass spectrometry. Deuterated internal standards for each analyte serve as carriers and control for recovery during sample purification on a solid-phase extraction column (C18), and subsequent separation and analysis on a DB-17 capillary column. With this method, we have determined levels of LAAM, norLAAM, and dinorLAAM in small volumes of plasma (100 microliters). The limit of quantitation for all analytes was approximately 1.0 ng/g plasma and the limit of detection was approximately 0.5 ng/g plasma. An experimental application is also described where these analytes are quantitated in plasma obtained from rats before, during, and after chronic administration of LAAM-HCl. Since this technique affords a selective and sensitive means of detection of LAAM and its active, N-demethylated metabolites in small samples of blood, it may enable patient compliance to be more easily assessed by allowing samples to be collected by a simple finger-prick technique.

Animals↗
PubMed1994

Comparison in humans of the potency and pharmacokinetics of intravenously injected cocaethylene and cocaine.

Cocaethylene (the ethyl ester of benzoylecgonine) is a product of the interaction between ethanol and cocaine. The results of preclinical studies and of a pilot clinical study have shown cocaethylene to produce pharmacologic effects similar to those of cocaine. However, no information is available concerning the potency and pharmacokinetics of cocaethylene in comparison to those of cocaine in humans. We report the results of a single-blind, crossover study in which six male, healthy, paid volunteers, who were moderate users of cocaine, were intravenously injected with the water soluble fumarate salt of cocaethylene (0.25 mg/kg cocaethylene base) or an equivalent dose of the water soluble hydrochloride salt of cocaine (0.25 mg/kg cocaine base). Each dose was dissolved in normal saline and injected over a 1-min interval. Test sessions were separated by a 1-week interval. The variables measured were: cocaine and cocaethylene plasma concentrations, subjective and cardiovascular effects. The results indicate, that in comparison to cocaine, cocaethylene had a significant smaller elimination rate constant (0.42 versus 0.67 l/h), had a longer elimination half-life (1.68 versus 1.07 h), and induced ratings of "high" and changes in heart rate that were of lower magnitude (65%, and 43%, respectively). During the period of time that pharmacologic effects were present the plasma concentrations of cocaine and cocaethylene were statistically indistinguishable. This finding supports the conclusion that in humans cocaethylene is less potent than cocaine.

Adult↗
PubMed1994

Effects of D-ring substituents on antiprogestational (antagonist) and progestational (agonist) activity of 11 beta-aryl steroids.

The discovery of antiprogestational steroids by the Roussel-Uclaf group not only was a major scientific advance but also opened the way to new methods of fertility control and new therapies for such conditions as cancer. RU486, the prototype of the series, is distinguished by a p-(N,N-dimethylaminophenyl) substituent at the 11 beta- position of the steroid framework, a 4,9-dien-3-one system and 17 beta-hydroxy-17 alpha-propynyl substituents. We examined the effect of varying the 17 alpha- substituent in 17 beta-hydroxy compounds analogous to RU486, the effect of introducing a progesterone side chain at C-17, and the effects of further substitution at C-17 alpha and C-16 alpha on the activity of these latter compounds. These studies indicate an important role for D-ring substituents in determining the balance of agonist/antagonist activity in this series. For example, 17 alpha-acetoxy-17 beta-acetyl substitution gave a potent antagonist, whereas 16 alpha-ethyl-17 beta-acetyl substitution resulted in a compound with potent progestational (agonist) activity. The compounds present opportunities for further interesting and useful biological investigations.

Acetylation↗
PubMed1993

Reversal of activity profile in analogs of the antiprogestin RU 486: effect of a 16 alpha-substituent on progestational (agonist) activity.

16 alpha-Ethyl-17 beta-acetyl substitution in the D-ring of steroids having an 11 beta-aryl-4,9-dien-3-one structure resulted in compounds with strong progestational activity. These compounds caused endometrial proliferation in the uterus of estrogen-primed rabbits with a potency greater than that of progesterone and had no detectable antiprogestational activity in this model. This is in stark contrast with the marked antiprogestational activity in rabbits, rats and humans reported for most 11 beta-aryl-4,9-diene-3-keto steroids such as RU 486 and its 17 beta-acetyl-17 alpha-acetoxy analog, 17 alpha-acetoxy-11 beta-(4-N,N-dimethylaminophenyl)-19-norpregna-4,9-diene- 3,20-dione. Examination of structure activity relationships in combination with computer aided molecular modelling suggests that a binding interaction of the 16 alpha-ethyl group with the progesterone receptor (PR) or the PR-progestin response element complex may play the major role in this reversal of activity profile.

Animals↗