Biomedical subjects

M Parsons

Publications and source records attributed to M Parsons.

At least 73 records · Page 4Linked to original sources

PubMed1996

Breast cancer patients' personality style, age, and treatment decision making.

BACKGROUND: Previous studies have shown that whereas nearly all cancer patients want information, far fewer wish to make treatment decisions. Although breast cancer patients who were given a choice of lumpectomy versus mastectomy and were encouraged to make the decision were believed to do better psychologically, a 1994 study refuted this. Some authors suggest that patient personality style is an important consideration in decisional preference. METHODS: Newly diagnosed breast cancer patients (n = 76) were surveyed within 6 months of surgery. They answered seven questions about patient and physician roles in the decision-making process. Additionally, they completed the Miller Behavioral Style Scale (MBSS), which categorizes "monitors," or information seekers, and "blunters," or information avoiders. Chi-square analyses were used to explore the relationship of personality style and age to treatment decision-making preferences. RESULTS: Although 80% of women wanted a role in decision making, 74% wanted their surgeons to make a recommendation and when given, 94% followed the recommended treatment plan. Monitors and blunters were equally likely to want physician recommendations. Younger women, particularly those under age 40, were more likely to want a physician's recommendation. Of those women who had specific fears about their cancer (76%), only half of them revealed such fears to their doctors. CONCLUSIONS: The notion that health care consumers, particularly younger ones, desire an independent choice of treatment was contradicted in this study. Physicians are encouraged to provide information and to probe regarding the fears of breast cancer patients in order to reduce anxiety while recognizing that treatment recommendations are desired by most women.

Adult↗

PubMed1996

Use of microsatellite loci to classify individuals by relatedness.

This study investigates the use of microsatellite loci for estimating relatedness between individuals in wild, outbred, vertebrate populations. We measured allele frequencies at 20 unlinked, dinucleotide-repeat microsatellite loci in a population of wild mice (Mus musculus), and used these observed frequencies to generate the expected distributions of pairwise relatedness among full sib, half sib, and unrelated pairs of individuals, as would be estimated from the microsatellite data. In this population one should be able to discriminate between unrelated and full-sib dyads with at least 97% accuracy, and to discriminate half-sib pairs from unrelated pairs or from full-sib pairs with better than 80% accuracy. If one uses the criterion that parent-offspring pairs must share at least one allele per locus, then only 15% of full-sib pairs, 2% of half-sib pairs, and 0% of unrelated pairs in this population would qualify as potential parent-offspring pairs. We verified that the simulation results (which assume a random mating population in Hardy-Weinberg and linkage equilibrium) accurately predict results one would obtain from this population in real life by scoring laboratory-bred full- and half-sib families whose parents were wild-caught mice from the study population. We also investigated the effects of using different numbers of loci, or loci of different average heterozygosities (He), on misclassification frequencies. Both variables have strong effects on misclassification rate. For example, it requires almost twice as many loci of He = 0.62 to achieve the same accuracy as a given number of loci He = 0.75. Finally, we tested the ability of UPGMA clustering to identify family groups in our population. Clustering of allele matching scores among the offspring of four sets of independent maternal half sibships (four females, each mated to two different males) perfectly recovered the true family relationships.

Alleles↗

PubMed1995

Trypanosoma congolense: developmental regulation of protein kinases and tyrosine phosphorylation during the life cycle.

In higher eukaryotes, key steps in the control of growth and proliferation are regulated by protein phosphorylation. However, little is known about the role of protein phosphorylation in the developmental cycles of pathogenic protozoa. In Trypanosoma brucei, only the bloodform and procyclic form stages can be obtained in sufficient numbers for biochemical analyses. However, the entire life cycle of Trypanosoma congolense can be generated in vitro, providing sufficient material for analyses of the different developmental stages. The studies reported here provide a series of snapshots documenting the activity of a number of protein serine/threonine kinases and the pattern of tyrosine-phosphorylated proteins throughout the T. congolense developmental cycle. Metacyclic forms and mammalian bloodforms showed similar profiles of protein kinase activity, as did procyclic forms and epimastigotes. Most tyrosine-phosphorylated proteins were shared between all developmental stages, with the exception of a 100-kDa metacyclic-specific species. The developmental changes in molecules involved in protein phosphorylation in the different developmental stages support the concept that changes in protein phosphorylation networks are important correlates of the developmental process in African trypanosomes.

Animals↗

PubMed1995

Pharmacological aspects of acid secretion.

The secretion of gastric acid is regulated both centrally and peripherally. The finding that H2-receptor antagonists are able to reduce or abolish acid secretion due to vagal, gastrinergic, and histaminergic stimulation shows that histamine plays a pivotal role in stimulation of the parietal cell. In the rat, the fundic histamine is released from the ECL cell, in response to gastrin, acetylcholine, or epinephrine, and histamine release is inhibited by somatostatin or by the H3-receptor ligand, R-alpha-methyl histamine. The parietal cell has a muscarinic, M3, receptor responsible for [Ca]i regulation. Blockade of muscarinic receptors by atropine can be as effective as H2-receptor blockade in controlling acid secretion. However, general effects on muscarinic receptors elsewhere produce significant side effects. The different receptor pathways converge to stimulate the gastric H+,K(+)-ATPase, the pump responsible for acid secretion by the stomach. This enzyme is an alpha,beta heterodimer, present in cytoplasmic membrane vesicles of the resting cell and in the canaliculus of the stimulated cell. It has been shown that acid secretion by the pump depends on provision of K+Cl- efflux pathway becoming associated with the pump. As secretion occurs only in the canaliculus, this K+Cl- pathway is activated only when the pump inserts into the canalicular membrane. Transport by the enzyme involves reciprocal conformational changes in the cytoplasmic and extracytoplasmic domain. These result in changes in sidedness and affinity for H3O+ and K+, enabling active H+ for K+ exchange. The acid pump inhibitors of the substituted benzimidazole class, such as omeprazole, are concentrated in the canaliculus of the secreting parietal cell and are activated there to form sulfenamides. The omeprazole sulfenamide, for example, reacts covalently with two cysteines in the extracytoplasmic loops between the fifth and sixth transmembrane and the seventh and eighth transmembrane segments of the alpha subunit of the H+,K(+)-ATPase, forming disulfide derivatives. This inhibits ATP hydrolysis and H+ transport, resulting in effective, long-lasting regulation of acid secretion. Therefore, this class of acid pump inhibitor is significantly more effective and faster acting than the H2 receptor antagonists. K+ competitive antagonists bind to the M1 and M2 transmembrane segments of the alpha subunit of the acid pump and also abolish ATPase activity. These drugs should also be able to reduce acid secretion more effectively than receptor antagonists and provide shorter acting but complete inhibition of acid secretion.

Amino Acid Sequence↗

PubMed1995

Three genes and two isozymes: gene conversion and the compartmentalization and expression of the phosphoglycerate kinases of Trypanosoma (Nannomonas) congolense.

The glycosome, a microbody organelle found only in kinetoplastid protozoa, compartmentalizes the first six enzymes of glycolysis. In order to better understand the regulation and targeting of glycolytic enzymes in trypanosomes, we have cloned and analyzed the three genes of the phosphoglycerate kinase (PGK) complex of Trypanosoma (Nannomonas) congolense. The organization of the genes within the complex is similar to that of Trypanosoma brucei brucei. The nucleotide and amino-acid sequences, including those of the novel high-molecular-weight 56PGK, show substantial cross-species similarity. However, the two downstream genes, c1PGK and c2PGK, encode identical isozymes in T. congolense, while they encode distinct glycosomal and cytoplasmic isozymes in T. brucei. Western analysis also indicated that there are only two isozymes in T. congolense and that these are constitutively expressed. Differential digitonin solubilization of the trypanosomes indicated that 56PGK is primarily localized to the glycosome, as expected, and that c1/c2PGK is cytoplasmic. Northern analysis demonstrates that while 56PGK is constitutively expressed, c1PGK and c2PGK mRNAs are differentially expressed in the T. congolense developmental stages. This work demonstrates that T. congolense has only one PGK isozyme, 56PGK, that is predominantly localized in glycosomes.

Amino Acid Sequence↗

PubMed1995

Crystallisation of alpha-crustacyanin, the lobster carapace astaxanthin-protein: results from EURECA.

Crystallisation of alpha-crustacyanin, the lobster carapace astaxanthin-protein was attempted under microgravity conditions in EURECA satellite using liquid-liquid diffusion with polyethyleneglycol (PEG) as precipitant; in a second reaction chamber phenol and dioxan were used as additives to prevent composite crystal growth. Crystals of alpha-crustacyanin grown under microgravity from PEG were larger than those grown terrestrially in the same apparatus under otherwise identical conditions. On retrieval, the crystals from PEG were shown to be composite and gave a powder diffraction pattern. The second reaction chamber showed leakage on retrieval and had also been subjected to rapid temperature variation during flight. Crystal fragments were nevertheless recovered but showed a powder diffraction pattern. It is concluded, certainly for liquid-liquid diffusion using PEG alone, that, for crustacyanin, although microgravity conditions resulted in an increase in dimensions of crystals, a measurable improvement in molecular ordering was not achieved.

Animals↗

PubMed1994

Translational control mediates the developmental regulation of the Trypanosoma brucei Nrk protein kinase.

The expression and function of eukaryotic protein kinases is highly regulated, primarily through transcriptional and post-translational processes. In this report we demonstrate an unusual mechanism for controlling protein kinase function, translational control. The Trypanosoma brucei Nrk loci encode predicted protein kinases. Here we show that Nrk has protein serine-threonine kinase activity and examine the expression and activity of Nrk during parasite development. While Nrk transcripts were previously found to be constitutively expressed throughout the life cycle, we now find that expression of Nrk protein is highly stage-regulated. Immunoblot analysis revealed that Nrk expression dramatically increased as the parasites differentiated from proliferative slender bloodforms to the non-proliferative stumpy bloodforms. Procyclic form organisms expressed moderate levels of Nrk. Analysis of Nrk activity demonstrated that it too was highest in stumpy bloodforms. Metabolic labeling and pulse-chase analysis demonstrated that Nrk accumulation was highest in stumpy bloodforms and indicated that Nrk abundance is primarily controlled at the level of biosynthesis rather than turnover. All Nrk mRNA was contained in the poly(A)+ fraction, and the 5' ends of the transcript were the same in each developmental stage. Thus, Nrk is under translational control. The strict developmental regulation of the Nrk enzymes within the trypanosome life cycle suggests that the Nrk protein kinase may play a role in parasite differentiation.

Animals↗

PubMed1994

Developmental regulation of pp44/46, tyrosine-phosphorylated proteins associated with tyrosine/serine kinase activity in Trypanosoma brucei.

The pattern of tyrosine-phosphorylated proteins is developmentally regulated in Trypanosoma brucei. To examine the function and regulation of these tyrosine-phosphorylated molecules, monoclonal antibodies were generated using purified tyrosine-phosphorylated proteins as immunogens. Two monoclonal antibodies were obtained. Both react with a set of proteins at 44-46 kDa, collectively referred to as pp44/46, that are phosphorylated on serine and tyrosine. Differentiation of the parasite from slender bloodforms to procyclic forms was accompanied by increased abundance and tyrosine-phosphorylation of pp44/46. The monoclonal antibodies immunoprecipitated protein kinase activity capable of phosphorylating pp44/46 on serine and tyrosine, and myelin basic protein on serine. The data indicate that the prominent tyrosine-phosphorylated proteins induced upon differentiation are either themselves protein kinases or that they are associated with protein kinases.

Animals↗

PubMed1994

The effect of the oxytocin antagonist atosiban on preterm uterine activity in the human.

OBJECTIVE: The purpose of this study was to test the hypothesis that infusion of the oxytocin antagonist atosiban results in decreased preterm uterine activity in the human. STUDY DESIGN: A randomized, double-blind, placebo-controlled trial was performed. One hundred twenty women from 20 to 36 weeks' gestation with a complaint of labor who had more than four uterine contractions per hour after intravenous hydration but no evidence of cervical changes were randomized to receive a 2-hour intravenous infusion of atosiban at a rate of 300 micrograms/min or placebo. Ond hundred-twelve subjects (56 in each arm) were suitable for analysis of efficacy. Both groups remained at bed rest and received hydration. RESULTS: The mean percent decrease in contraction frequency was greater in atosiban subjects compared with controls (55.3% +/- 36.3% vs 26.7% +/- 40.4%, mean +/- SD, p < 0.001). A minimal (< 20%) decrease or an increase in contraction frequency was noted in 25 placebo subjects (45%) and seven atosiban subjects (13%). There was no clinically or statistically significant change in maternal blood pressure or heart rate during the infusion. The only adverse experiences possibly related to the drug were nausea and vomiting in one atosiban patient. CONCLUSION: A 2-hour infusion of the oxytocin antagonist atosiban resulted in a significantly greater decline in contraction frequency compared with controls. Oxytocin appears to play a role in the maintenance of preterm uterine activity in the human.

Adult↗

PubMed1994

The protein phosphatase inhibitor okadaic acid induces defects in cytokinesis and organellar genome segregation in Trypanosoma brucei.

Mitosis and cytokinesis are events that are highly coordinated in most eukaryotic cell cycles. African trypanosomes possess a single mitochondrion and must additionally coordinate the organellar division cycle. Here we report that okadaic acid, a potent and specific inhibitor of protein phosphatases PP1and PP2A, uncouples these cycles in living trypanosomes. Cell cycle analysis of treated cells revealed elevated DNA content. Microscopic examination indicated that okadaic acid treatment yielded multinucleate cells with a single mitochondrial network indicating these cells have undergone mitosis but failed to complete cytokinesis. Immunofluorescence analysis of 5-bromo-2-deoxyuridine incorporation demonstrated that the mitochondrial DNA was replicated but did not segregate. The dose response curve for inhibition of the normal cell cycle paralleled that for the in vitro inhibition of protein phosphatase activities with IC50s of approximately 20 nM okadaic acid. These results suggest the involvement of a PP1/PP2A-like activity in coordinating mitosis, mitochondrial DNA division and cytokinesis in trypanosomes.

Animals↗

PubMed1994

Cell cycle-specific induction of an 89 kDa serine/threonine protein kinase activity in Trypanosoma brucei.

The cell cycle compartmentalization of specific activities of the protozoan parasite Trypanosoma brucei has remained unexplored due to the lack of a cell synchronization protocol. We report here that stationary phase cells stimulated to enter the cell cycle showed significant synchrony through the first cycle. The pattern of tyrosine phosphorylated proteins, known to undergo alterations during trypanosome development, showed only moderate changes as quiescent cells entered the cycle, particularly an increase in a 77 kDa species. However, the activity of an 89 kDa protein kinase (SPK89), previously demonstrated to be restricted to the proliferative stages of the parasite's life cycle, markedly increased as the population entered S phase. Cell sorting experiments demonstrated that SPK89 activity was highest in S phase cells and moderate in G2/M cells. The entry into S phase and increased SPK89 activity did not depend on serum factors but required protein synthesis for a discrete period after stimulation. Various modulators of protein phosphorylation were tested to determine their effects on progression to S and SPK89 activity. Only staurosporine and genistein were effective. However, both of these compounds inhibited virtually all protein phosphorylation and protein synthesis in the parasites. Thus these drugs cannot be used as specific protein kinase inhibitors in trypanosomes.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗

PubMed1993

Trypanosoma cruzi acidic ribosomal P protein gene family. Novel P proteins encoding unusual cross-reactive epitopes.

We have cloned and characterized cDNA molecules that encode members of the acidic ribosomal protein family (TcP proteins) from the protozoan parasite Trypanosoma cruzi. These proteins have been shown to be antigenic in individuals with T. cruzi infection. Unlike other known eukaryotic cells, T. cruzi possesses at least four types of P protein genes TcP0, TcP1, TcP2a, and TcP2b, each of which is present in multiple copies in the genome. These genes are present on at least three different chromosomes. Although the abundance of TcP0, TcP2a, and TcP2b transcripts do not appear to vary among the parasite life-cycle stages, TcP1 is predominantly expressed in the epimastigote (insect) stage. TcP0 has a C-terminal heptapeptide sequence that is similar to those of archaebacterial acidic (P-like) proteins, but the TcP1/P2 proteins terminate with a shared sequence characteristic of the P proteins of higher eukaryotes. The serine residues or other potential phosphorylation sites typically found within the highly charged C-terminal acidic domain are absent in T. cruzi P proteins. Using synthetic peptides, we demonstrated that approximately 80% of T. cruzi-infected individuals produce two distinct but cross-reactive anti-P antibody specificities directed against the C-termini of TcP0 and TcP1/P2. We also expressed the full length (non-fusion) recombinant human P0 and demonstrated that the T. cruzi anti-P antibodies cross-react with the C-terminal residues of human P-proteins. Conversely, human anti-P protein antibodies in sera from patients with SLE cross-react with the C-terminal epitope of T. cruzi TcP1/P2 proteins. The cross-reactivity of anti-TcP antibodies with human P proteins suggests that, through antigenic conservation, TcP proteins may contribute to the development of autoreactive antibodies in Chagas' disease patients.

Amino Acid Sequence↗

PubMed1993

Molecular cloning and characterization of a 42-kDa protein phosphatase of Leishmania chagasi.

Using rabbit serum raised against a potent T cell-stimulating antigen fraction of Leishmania chagasi promastigotes, we have cloned and expressed the Leishmania type 2C serine/threonine protein phosphatase, LcPP2C. LcPP2C was shown to be present as a 42-kDa protein in both the infective promastigote and tissue amastigote stages of L. chagasi and Leishmania amazonensis. DNA hybridization studies established the close conservation of LcPP2C among eight of eight geographically diverse species of Leishmania which cause a spectrum of human diseases. To support the relationship between LcPP2C and mammalian type 2C protein phosphatases observed through predicted amino acid sequence comparisons, we expressed enzymatically active rLcPP2C in Escherichia coli. We demonstrated that purified rLcPP2C readily dephosphorylated [32P]casein, an activity dependent on Mg2+ and insensitive to okadaic acid. In agreement with studies of rat liver PP2C, activity was maintained when Mg+2 was replaced with Mn+2 but not with Ca2+. As these parameters are characteristic of the eukaryotic type 2C serine/threonine protein phosphatases, LcPP2C can be classified as a member of this protein family. We further showed that of the four major classes of eukaryotic serine/threonine protein phosphatases, PP2C-and PP1-like activities, are readily detectable in Leishmania.

Amino Acid Sequence↗

PubMed1993

Protein kinases in divergent eukaryotes: identification of protein kinase activities regulated during trypanosome development.

The role of protein kinases in organisms that diverged early in the eukaryotic lineage is relatively unexplored. In this study, we determined that primitive parasitic protozoa possess multiple protein-serine kinases and inferred the presence of protein-tyrosine kinases through sensitive immunoblotting techniques. To further explore the role of protein kinases in parasite development, we examined the activity of eight renaturable protein kinases during the life cycle of the protozoan parasite Trypanosoma brucei. The activities of six protein-serine/threonine kinases were regulated during development, with several distinct patterns of regulation. In addition, an 89-kDa protein kinase was detected in dividing cells but not in nondividing cells. Our data indicate that even the most primitive eukaryotes possess a large complement of protein kinases, including protein-tyrosine kinases as well as protein-serine/threonine kinases. The data further suggest that protein kinases may play a pivotal role in regulation of proliferation and differentiation in protozoa.

Animals↗

PubMed1993

The C-terminal tripeptide of glycosomal phosphoglycerate kinase is both necessary and sufficient for import into the glycosomes of Trypanosoma brucei.

Glycosomal phosphoglycerate kinase (gPGK) of Trypanosoma brucei differs from the cytoplasmic isozyme (cPGK) in its higher isoelectric point characterized by clusters of positive charges along the polypeptide chain, and a 20 amino acid C-terminal extension ending in serine-serine-leucine (SSL). While a C-terminal SSL tripeptide is apparently not capable of directing luciferase to the peroxisomes in mammalian cells [J. Cell Biol. 108 (1989), 1657-1664], we show here that it is sufficient for the import of luciferase as well as an unrelated protein, beta-glucuronidase, into the glycosomes of T. brucei, as determined by immunoelectron microscopy. The analysis of luciferase-gPGK fusion proteins indicates that the only targeting signal for import of gPGK into the glycosome resides in this C-terminal SSL sequence.

Amino Acid Sequence↗

PubMed1993

Factors associated with use of safer sex practices among college freshmen.

The purpose of this exploratory study was to examine the relationship of knowledge of AIDS, misconceptions about AIDS, knowledge of safer sex practices, perceived susceptibility, and future time perspective to the practice of safer sex behaviors in 352 single, sexually active, college freshmen. Data were analyzed using stepwise multiple regression analysis and discriminant analysis. There were too few black females for analysis. Future time perspective explained the most variance in safer sex practices for black males. Knowledge of AIDS, perceived susceptibility, misconceptions about AIDS, knowledge of safer sex practices, and future time perspective did not explain a significant amount of variance in use of safer sex practices for either white males or females. However, perceived susceptibility and future time perspective differentiated sexually active from nonsexually active white males and females.

Acquired Immunodeficiency Syndrome↗

PubMed1993

A Trypanosoma brucei gene family encoding protein kinases with catalytic domains structurally related to Nek1 and NIMA.

Using polymerase chain reaction technology we cloned a Trypanosoma brucei gene fragment that has a deduced amino acid sequence with a high degree of homology to protein kinase catalytic domains. This clone detects two genes by genomic Southern analysis. These genes, nrkA and nrkB, share a 97% nt sequence homology over their 1.3-kb coding regions. NrkA encodes a 48-kDa protein which possess all 11 protein kinase homology regions. The 279-aa N-terminal catalytic domain has highest homology with Nek1, a bifunctional kinase, and NIMA, a protein serine/threonine kinase. Both alleles at the nrkB locus in T. brucei strain IsTAR 1 encode a truncated protein kinase catalytic domain due the presence of a premature termination codon. However, the TREU667 strain is heterozygous at the nrkB locus, encoding one truncated and one full-length molecule. NrkA and NrkB possess multiple phosphorylation site motifs. Both nrk transcripts are constitutively expressed during parasite development.

Alleles↗

PubMed1993

Characterization of a Trypanosoma brucei nuclear gene encoding a protein homologous to a subunit of bovine NADH:ubiquinone oxidoreductase (complex I).

A Trypanosoma brucei gene has been identified that encodes a protein predicted to be a component of the trypanosome homologue of mitochondrial NADH:ubiquinone oxidoreductase (complex I). High homology was found to a 20-kDa component of the iron-sulfur protein fraction of bovine mitochondrial NADH:ubiquinone oxidoreductase and the products of the ndhK locus of Paramecium tetraurelia mitochondria and the NQO6 locus of Paracoccus denitrificans. The homology extends to several other proteins predicted to function as part of electron transport systems, including the psbG/ndhK gene products of chloroplast and cyanobacterial genomes which are thought to be subunits of a NADH:plastoquinone oxidoreductase involved in chlororespiration. The T. brucei ndhK counterpart is nuclearly encoded. An extended amino terminus of the T. brucei ndhK with structural similarity to mitochondrial presequences indicates that its transfer into mitochondria is likely. Stumpy and slender bloodforms and procyclic forms all possess similar levels of ndhK transcripts despite previous reports of stage-regulated expression of complex I-like activity.

Amino Acid Sequence↗