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Biomedical subjects

C A Phillips

Publications and source records attributed to C A Phillips.

At least 19 recordsLinked to original sources
PubMed1995

The minimal gene complement of Mycoplasma genitalium.

The complete nucleotide sequence (580,070 base pairs) of the Mycoplasma genitalium genome, the smallest known genome of any free-living organism, has been determined by whole-genome random sequencing and assembly. A total of only 470 predicted coding regions were identified that include genes required for DNA replication, transcription and translation, DNA repair, cellular transport, and energy metabolism. Comparison of this genome to that of Haemophilus influenzae suggests that differences in genome content are reflected as profound differences in physiology and metabolic capacity between these two organisms.

Antigenic Variation↗
PubMed1995

Phosphatidylinositol 3-kinase activity is not essential for CD28 costimulatory activity in Jurkat T cells: studies with a selective inhibitor, wortmannin.

The interaction of CD28 with its counter-receptor, B7-1 (CD 80), on antigen-presenting cells induces a co-signal in T cells required to promote antigen-dependent interleukin-2 (IL-2) production and to prevent clonal anergy. CD28 stimulation causes both protein-tyrosine kinase and phosphatidylinositol3-kinase (PI3-K) activation, suggesting a possible role for these enzyme activities in CD28 co-signal transduction. Here, we investigate the effect of wortmannin, a selective and irreversible PI3-K inhibitor on CD28 co-signaling events in the Jurkat T cell line. Wortmannin added to cell cultures partially inhibits CD28-induced tyrosine phosphorylation of the putative p110 catalytic subunit of PI3-K, but does not block CD28-induced association of the p85 PI3-K regulatory subunit with the CD28 receptor. Wortmannin inhibits in a dose-dependent manner both total cellular PI3-K activity and CD28-induced receptor-associated PI3-K activity. Wortmannin (1 microM) inhibits cellular PI3-K activity by 90% with complete inhibition achieved at 10 microM. The inhibitory effect of wortmannin on cellular PI3-K activity is prolonged ( > 18 h), suggesting that the drug is not readily metabolized by Jurkat T cells. Wortmannin, at concentrations that blocked PI3-K activity, fails to inhibit the synergistic effect of CD28 on IL-2 secretion in the presence of phorbol 12-myristate 13-acetate and ionomycin. These data demonstrate that CD28-induced signaling events other than the activation of PI3-K catalytic activity contribute to the control of IL-2 secretion.

Androstadienes↗
PubMed1995

Irreversible inhibition of human natural killer cell natural cytotoxicity by modification of the extracellular membrane by the adenine nucleotide analog 5'-p-(fluorosulfonyl)benzoyl adenosine.

Extracellular adenine nucleotides are inhibitors of the human natural killer cell line NK3.3 natural cytotoxicity activity. Natural cytotoxicity was inhibited approximately 26% by 1 mM ATP and 21% by 1 mM ADP. 5'-Adenylyl imidodiphosphate, a nonhydrolyzable ATP analog, inhibited natural cytotoxicity by 41% at a concentration of 1 mM and > 97% at a concentration of 10 mM. In contrast, AMP was not inhibitory. Adenosine was a weak inhibitor of natural cytotoxicity and may represent an alternate regulatory pathway. Removal of the nucleotides resulted in the restoration of control levels of natural cytotoxicity activity. The affinity label 5'-p-(fluorosulfonyl)benzoyladenosine (5'-FSBA) is a synthetic analog of ATP or ADP containing an electrophilic fluorosulfonyl group capable of covalently modifying proteins at adenine di- and triphosphate nucleotide-binding sites. Natural cytotoxicity was irreversibly inhibited by modification of the extracellular membrane of NK3.3 cells by 5'-FSBA. This inhibition was concentration dependent with an I50 approximately 100 microM and complete inhibition at 1 mM. Modification of NK3.3 by 5'-FSBA did not affect the formation of effector-target cell conjugates; however, granule release was inhibited. This targets the site of inhibition by 5'-FSBA modification to a pathway preceding granule release. Irreversible, covalent modification of surface adenine nucleotide-binding proteins by 5'-FSBA provides a probe to study the role of specific adenine nucleotide-binding proteins in the extracellular regulation of natural killer cytolytic activity by adenine nucleotides.

Adenosine↗
PubMed1995

Walking when utilizing a sensory feedback system and an electrical muscle stimulation gait orthosis.

Electrical muscle stimulators (EMS) have been combined with a reciprocating gait orthosis (RGO) to produce an EMS-RGO system for constant velocity ambulation exercise in a spinal cord injured (SCI) individual. The objective of this study is to evaluate an auditory feedback system (AFS) used by the SCI subject when ambulating with the EMS-RGO. Three different types of auditory signals (M = metronome alone, MSL = metronome plus stride length information, and NONE = no auditory feedback) were examined at three different constant walking velocities (WV1 = 0.64 kph, WV2 = 1.22 kph, and WV3 = 1.80 kph). The experimental design was 3 x 3 full factorial with repeated measures, and the dependent variable was the absolute error (AE) of walking distance (absolute value of the distance the subject walked in one minute subtracted from the target distance). A block diagram and circuit schematic of the AFS is provided. The results indicate that at WV1 there is no significant difference of AE among the three auditory conditions (M, MSL and NONE). At WV2, the AE for the NONE auditory condition is significantly greater than the AE for M and MSL (p < 0.05). At WV3, the AE for the NONE auditory condition is significantly less than the AE for M and MSL (p < 0.05). Finally, there was no significant difference in AE between both the M and MSL auditory conditions at any of the three walking velocities. This study indicates that an adequate sensory feedback system for constant velocity control of ambulation in this SCI subject consists of metronome only auditory feedback.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1995

The revised velocity-strain relationship: phase-plane analysis of left ventricular function and dysfunction.

Cyclical cardiac mechanical performance has been described by plotting mid-wall left ventricular circumferential velocity or strain rate (V) as a function of instantaneous mid-wall strain (epsilon). This results in individual velocity-strain (V-epsilon) parameters. For any given individual, a standard velocity-strain plot is represented by a sinusoidally varying strain and strain rate. Three standard velocity-strain variables are then defined. The peak velocity, or peak strain rate (VM), the cycle strain at VM (epsilon M), and the system time constant (tau M). The individual velocity-strain parameters are then divided by these standard V-epsilon parameters to result in normalized V-epsilon parameters for both cardiac systole and cardiac diastole. Thirty-six patients were evaluated, consisting of four groups: Normals (N = 15 patients), Compensated Volume Overload (CVO = 6 patients), Decompensated Volume Overload (DVO = 9 patients) and Congestive Cardiomyopathy (CCM = 6 patients). Five individual velocity-strain parameters significantly differentiate the CCM group from the N group. However, they do not differentiate CVO group and DVO group from the N group. Two standard-epsilon parameters and one normalized V-epsilon parameter significantly differentiated the CVO group and the DVO group from the N group. Two standard V-epsilon parameters and one normalized V-epsilon parameter significantly differentiated the CCM group from the N group. It is recommended that future phase-plane analyses of non-linear cardiac phenomena include both standardization and normalization techniques.

Adult↗
PubMed1995

Separating population structure from population history: a cladistic analysis of the geographical distribution of mitochondrial DNA haplotypes in the tiger salamander, Ambystoma tigrinum.

Nonrandom associations of alleles or haplotypes with geographical location can arise from restricted gene flow, historical events (fragmentation, range expansion, colonization), or any mixture of these factors. In this paper, we show how a nested cladistic analysis of geographical distances can be used to test the null hypothesis of no geographical association of haplotypes, test the hypothesis that significant associations are due to restricted gene flow, and identify patterns of significant association that are due to historical events. In this last case, criteria are given to discriminate among contiguous range expansion, long-distance colonization, and population fragmentation. The ability to make these discriminations depends critically upon an adequate geographical sampling design. These points are illustrated with a worked example: mitochondrial DNA haplotypes in the salamander Ambystoma tigrinum. For this example, prior information exists about restricted gene flow and likely historical events, and the nested cladistic analyses were completely concordant with this prior information. This concordance establishes the plausibility of this nested cladistic approach, but much future work will be necessary to demonstrate robustness and to explore the power and accuracy of this procedure.

Ambystoma↗
PubMed1994

CD28 signal transduction: tyrosine phosphorylation and receptor association of phosphoinositide-3 kinase correlate with Ca(2+)-independent costimulatory activity.

The interaction of CD28 with its counter-receptor, B7, induces a cosignal in T cells required to prevent clonal anergy and to promote antigen-dependent interleukin-2 production. The molecular basis of the CD28 cosignal is not well understood but involves the activation of protein tyrosine kinase(s) (PTK). In this report we demonstrate that CD28 cross-linking on Jurkat T leukemic cells causes the activation of at least two PTK pathways. A CD28-induced, p56lck kinase-independent pathway causes tyrosine-phosphorylation of a 110-kDa substrate while recruitment of p56lck kinase activity is apparently required for CD28-induced tyrosine-phosphorylation of 97- and 68-kDa substrates as well as CD28-induced increases in intracellular calcium. The tyrosine phosphorylation of p110, but not p97 or p68, correlated with CD28 calcium-independent costimulatory activity. The pp110 molecule was tentatively identified as the catalytic subunit of phosphoinositide (PI)-3 kinase based upon its coimmunoprecipitation with the p85 regulatory subunit of PI-3 kinase. PI-3 kinase protein and catalytic activity were found complexed with the CD28 receptor if the receptor was "activated" by cross-linking on the surface of intact cells prior to detergent solubilization. The kinetics of association of PI-3 kinase with the "activated" CD28 receptor was rapid, occurring within 30 s of receptor cross-linking and was stable for at least 30 min. Analysis of the CD28 cytoplasmic peptide sequence revealed a putative PI-3 kinase src homology 2 binding motif and CD28 tyrosine phosphorylation site, DYMNM. Tyrosine phosphorylation of CD28 was detected in pervanadate-treated Jurkat B2.7 cells, but not untreated cells. Pervanadate-induced tyrosine phosphorylation of CD28 correlated with receptor association of PI-3 kinase in the absence of CD28 cross-linking, suggesting that CD28 association with PI-3 kinase uses a tyrosine phosphorylation-dependent mechanism. These data provide a model for CD28 signal transduction and support a role for PI-3 kinase in mediating the CD28 calcium-independent, cyclosporin A-insensitive costimulatory signal.

Amino Acid Sequence↗
PubMed1994

Management of the third stage of labor: a survey of practice among Texas obstetricians.

Available evidence shows that the benefits of routine oxytocic administration in the third stage of labor far outweigh the potential risks. In 1990, T.F. Baskett, MD, reviewed the routine use of oxytocic drugs by Canadian obstetricians in the management of the third stage of labor. With Dr Baskett's permission, we sent a similar questionnaire to 1500 obstetricians in Texas: 1000 practiced in urban areas and 500 practiced in rural areas of the state. Ninety-four percent of Texas obstetricians answering the survey used oxytocics routinely in managing the third stage of labor. However, only 14.9% administered the oxytocics before delivery of the placenta, in contrast to 92.1% who gave oxytocics after the delivery of the placenta. Oxytocin was the chosen oxytocic drug for routine third-stage management (95%) as well as for postpartum hemorrhage (73.3%). Of the physicians surveyed, 55.9% used 15-methyl prostaglandin F2a (Hemabate) to treat postpartum hemorrhage refractory to other drugs within the past year. Of the respondents, 14.3% had managed acute uterine inversion during the past year. Thus, Texas obstetricians use Oxytocin routinely in the management of the third stage of labor, but few are converted to active management.

Attitude of Health Personnel↗
PubMed1993

Identification and partial characterization of an ectoATPase expressed by human natural killer cells.

An extracellular membrane-associated ectoATPase has been identified on the human natural killer cell line NK3.3. The enzyme is distinct from other classes of ATPases, kinases, and phosphatases. NK3.3 ectoATPase demonstrated a Km for ATP of 41 microM and a Vmax of 0.2 mumol/min and required both Ca2+ and Mg2+ for maximal activity. Purine and pyrimidine nucleotides were competitive inhibitors of the catalytic reaction. Inhibition increased with the addition of increasing negative charge of the phosphate side chain and was also dependent on contributions from the nucleoside. NK3.3 ectoATPase activity was inhibited by reaction with the affinity label [p-(fluorosulfonyl)benzoyl]-5'-adenosine (5'-FSBA), which is shown to modify the enzyme at or near the ATP-binding domain. Photoaffinity labeling of intact NK3.3 cells with [alpha-32P]-8-azidoATP demonstrated an ATP-binding protein of 68-80 kDa unique to NK3.3 cells. A positive correlation was observed between the ability of the various nucleotides to block photoincorporation into the 68-80-kDa protein and their ability to inhibit ectoATPase activity. NK3.3 cells which were made ectoATPase-deficient by reaction with 5'-FSBA demonstrated that this enzyme does not have a major role in the protection of this cytolytic effector cell from the possible lytic effects of extracellular ATP.

Adenosine Triphosphatases↗
PubMed1993

Effect of megestrol acetate on quality of life in a dose-response trial in women with advanced breast cancer. The Cancer and Leukemia Group B.

PURPOSE: The impact of the side effects of megestrol acetate on the quality of life of noncachectic women with advanced breast cancer was studied in a dose-response clinical trial of the Cancer and Leukemia Group B (CALGB 8741). Side effects of appetite increase and weight gain at higher doses were predicted to have a negative effect on quality of life. PATIENTS AND METHODS: Stage IV breast cancer patients were randomized to receive either 160, 800, or 1,600 mg/d of megestrol acetate. Quality of life was assessed in 131 patients at trial entry and at 1 and 3 months while on treatment, by telephone interview, using the following measures: the Functional Living Index-Cancer (FLIC), Rand Functional Limitations Scale, Rand Mental Health Inventory (MHI), the Body Image Subscale, and linear analog scales of drug side effects. RESULTS: At 3 months, women treated with 160 mg/d reported less severe side effects (P < .0005), better physical functioning (FLS, P < .0005), less psychologic distress (MHI, P = .008), and an improvement in overall quality of life (FLIC, P = .003) from the time of study entry as compared with those treated with 1,600 mg/d. Patients who received the 800-mg/d dose fell between the low- and high-dose arms in reported intensity of drug side effects, but responded similarly to those in the 160-mg/d group in terms of physical functioning, psychologic distress, and overall quality of life. CONCLUSION: Unless additional follow-up data demonstrate a survival advantage at higher doses, the 160-mg/d dose is optimal, achieving maximal treatment effect with the fewest side effects and better quality of life.

Appetite↗
PubMed1993

Beta-[3H]funaltrexamine-labeled mu-opioid receptors: species variations in molecular mass and glycosylation by complex-type, N-linked oligosaccharides.

We previously showed that under defined conditions beta-[3H]funaltrexamine (beta-[3H]FNA) covalently labeled mu-opioid receptors with high specificity in bovine striatal membranes. beta-[3H]FNA-labeled mu-opioid receptors migrated as a broad band with a molecular mass range of 68-97 kDa. It is controversial whether beta-FNA binds irreversibly to mu-opioid receptors in other species. In this study, we demonstrated that beta-[3H]FNA also labeled mu-opioid receptors with high specificity in brain membranes of the guinea pig, rat, and mouse. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis and fluorography revealed that in each species beta-[3H]FNA specifically bound to a protein in which labeling was greatly reduced by naloxone. These labeled receptors had broad molecular mass ranges, and the molecular masses were different among these species, in the order of cow > guinea pig > rat > mouse. Membranes were subjected to solubilization with 2% Triton X-100 and wheat germ lectin (WGL) affinity chromatography. N-Acetylglucosamine eluted a peak of radioactivity. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis and fluorography showed that in all four species the mu receptor was the only protein labeled with beta-[3H]FNA in the WGL eluate. The molecular masses of labeled mu-opioid receptors were 70-88 kDa (median, 77 kDa) for the cow, 66-80 kDa (median, 72 kDa) for the guinea pig, 60-75 kDa (median, 67 kDa) for the rat, and 60-72 kDa (median, 66 kDa) for the mouse. In addition, we investigated the nature of the carbohydrate moieties linked to the receptor protein and whether the species variation in the molecular mass was due to variable degrees of glycosylation. The bovine WGL eluate was treated with various glycosidases. Neuraminidase treatment decreased the receptor molecular mass by 6-7 kDa, whereas alpha-mannosidase had no effect. Removal of N-linked carbohydrates at asparagine residues by peptide-N4-[N-acetyl-beta-glucosaminyl]asparagine amidase (N-Glycanase) resulted in a much sharper specifically labelled protein band of 43 kDa. These results indicate that mu-opioid receptors are heavily glycosylated and the major carbohydrate moieties are of the complex type, N-linked to asparagine. After the WGL eluates for the four species were treated with N-Glycanase, the labeled receptors became much sharper bands with very similar molecular masses, i.e., 43 kDa for the cow and guinea pig, 39 kDa for the rat, and and 40 kDa for the mouse.(ABSTRACT TRUNCATED AT 400 WORDS)

Amidohydrolases↗
PubMed1992

CD28-induced T cell activation. Evidence for a protein-tyrosine kinase signal transduction pathway.

CD28 is a 44-kDa homodimeric receptor expressed on the majority of T cells. Engagement of the CD28 receptor by soluble anti-CD28 mAb in conjunction with PMA causes the induction of lymphokine/cytokine production and proliferation in resting T cells via signal transduction pathways independent of the TCR. The precise nature of the biochemical events that occur after perturbation of the CD28 receptor remain unclear. We report evidence for the coupling of CD28 to a protein-tyrosine kinase pathway. Multivalent cross-linking of the CD28 receptor or stimulation by soluble CD28 mAb plus PMA, but not PMA or soluble CD28 mAb alone, reproducibly caused the rapid (within 2 min) tyrosine phosphorylation of a 100-kDa cellular substrate. In some experiments, additional cellular substrates of 110, 85, 74, 68, 56, 43, and 29 kDa were also observed. The tyrosine phosphorylation of these substrates was completely inhibited by 12 h pretreatment of T cells with herbimycin A, a selective inhibitor of src-family protein-tyrosine kinases. Pretreatment of T cells with herbimycin was without effect on CD28 surface expression but did inhibit CD28 mAb plus PMA-induced IL-2 mRNA levels, IL-2R(CD25) up-regulation, and cell proliferation. The inhibition of IL-2 mRNA levels was likely at the level of transcription, because herbimycin inhibited NF-AT, AP-1, and CD28RC but not NF-kappa B or OCT-1 binding activities to their respective IL-2 enhancer region sequences. Herbimycin did not inhibit PMA-dependent events including CD69 surface expression, NF-kappa B nuclear binding activity or the level of CD25 induced by PMA alone, supporting the notion that herbimycin is acting to inhibit a CD28 initiated or regulated protein-tyrosine kinase pathway(s).

Antigens, CD↗
PubMed1992

Antiquity of clonal salamander lineages revealed by mitochondrial DNA.

The existence of clonally reproducing vertebrates has often served as a foil in attempts to explain the near-ubiquity of sexual reproduction in eukaryotes, but the absence of recombination, with its attendant limitation of new genotypes to those produced through mutations, restricts the adaptive ability of clonal organisms. It has been argued, therefore, that clonal vertebrate taxa have short lifespans. Variation in mitochondrial DNA (mtDNA) within clonal populations is interpreted instead as reflecting multiple, although limited, independent hybridization events. On the basis of an analysis of an average of 373 nucleotide pairs, we report here that the mtDNA of clonal, hybrid, gynogenetic mole salamanders (Ambystoma, Ambystomatidae) differs by 5% or more from mtDNA of their closest possible sexual relatives (A. jeffersonianum, A. laterale and A. texanum). Assuming usual rates of mtDNA divergence, these lineages have persisted for about 5 million years, far longer than estimated for other clonal vertebrate populations. The low mtDNA variability in the clonal lineages suggests that they have undergone population reductions during the Pleistocene.

Ambystoma↗
PubMed1992

Velocity of mammalian skeletal muscle contraction as a function of fiber type, activation, initial length and temperature.

Multiple stepwise regression analyses techniques were applied to develop modifications of the Hill force-velocity equation. Specifically, predictive models of the Hill a coefficient, the Hill b coefficient, and isometric strength P0 were developed for the following set of variables: the fraction of slow-twitch fibers (X), the recruitment magnitude (A), the initial muscle length (L), and the muscle temperature (T). Results indicate that the Hill a and Hill b coefficients and isometric strength P0 can be predicted with a high degree of accuracy. The utility of the equation is that it would allow development of a computer program to control the velocity of contraction of muscles with differing fiber compositions and lengths such as are found in the leg.

Animals↗
PubMed1992

A noninvasive protocol for anterior temporal lobectomy.

We report the results of a protocol for choosing candidates for temporal lobectomy using a standard battery of objective tests without intracranial electrodes. We assigned each test a level of importance, and an algorithm was used to determine whether temporal lobectomy could be performed. Fifty-one patients (total pool, 103 patients) met protocol requirements and had an anterior temporal lobectomy with a mean follow-up of 39.4 months (range, 21 to 64 months), most remaining on anticonvulsant therapy. Eighty percent are seizure free, 12% have less than 3 seizures per year or only nocturnal seizures, and 8% have greater than 80% reduction in seizure frequency. One-third of patients who failed protocol criteria did not have temporal lobe seizures when studied with intracranial electrodes. We analyzed and modified the algorithm after comparing these patients with others who were poor candidates for temporal lobectomy. We conclude that this protocol is effective and recommend using such an objective algorithm.

Action Potentials↗