Biomedical subjects

M J Stark

Publications and source records attributed to M J Stark.

At least 55 records · Page 3Linked to original sources

PubMed1994

Characterisation of the S-adenosylmethionine decarboxylase (SAMDC) gene of potato.

S-adenosylmethionine decarboxylase (SAMDC) is involved in the biosynthesis of the polyamines, spermidine and spermine. Recently, we reported the isolation of a putative cDNA clone of the SAMDC clone of potato (Plant Mol Biol 20; 641-651). In order to confirm that the potato genes does encode SAMDC, a complementation experiment with a yeast strain that possesses a null mutation in the SAMDC gene was performed. The yeast strain contains a deletion-insertion mutation in the SAMDC gene and has an absolute requirement for the addition of exogenous spermidine for growth. When the full-length potato cDNA was expressed in the mutant yeast strain there was no longer a requirement for exogenous spermidine. Immunoblotting experiments suggest that the potato SAMDC gene product has an apparent molecular mass of 39 kDa. Expression of the SAMDC gene was high in the young and actively dividing tissues and low in the mature and non-dividing tissues of both vegetative and reproductive organs. Additionally, isolation and characterisation of the corresponding genomic clone is reported. The gene has one intron in its 5'-untranslated sequence but otherwise the transcribed portion is identical to the cDNA clone.

Adenosylmethionine Decarboxylase↗

PubMed1994

Developing an outpatient prospective payment system based on APGs for the Iowa Medicaid program.

This article describes the development of an outpatient prospective payment system (PPS) based on ambulatory patient groups (APGs) for the Iowa Medicaid Program. Currently, hospitals in Iowa are reimbursed for outpatient services on the basis of cost. Because of concern about escalating costs, the Iowa General Assembly mandated development of a hospital outpatient payment system to promote efficient use of resources and high quality care. The first use of APGs for payment across the full spectrum of services will be a testing ground that should have long term implications for outpatient prospective payment and quality improvement efforts.

Ambulatory Care↗

PubMed1994

The linear-plasmid-encoded toxin produced by the yeast Pichia acaciae: characterization and comparison with the toxin of Kluyveromyces lactis.

The toxin produced by Pichia acaciae was purified and its properties compared to those of the toxin from Kluyveromyces lactis. Like this toxin, the P. acaciae toxin is a protein comprised of three subunits (molecular masses 110, 39 and 38 kDa) with an associated chitinase activity and a pH optimum between 7.0 and 7.5. P. acaciae toxin also caused G1 cell cycle arrest. Of the thirteen recessive alleles that provided resistance in Saccharomyces cerevisiae to K. lactis toxin, only three also conferred resistance to P. acaciae toxin. Similarities and differences in the interactions of the two toxins with yeast cells are discussed.

Cell Cycle↗

PubMed1994

Two Saccharomyces cerevisiae genes which control sensitivity to G1 arrest induced by Kluyveromyces lactis toxin.

The Kluyveromyces lactis toxin causes an arrest of sensitive yeast cells in the G1 phase of the cell division cycle. Two complementary genetic approaches have been undertaken in the yeast Saccharomyces cerevisiae to understand the mode of action of this toxin. First, two sequences conferring toxin resistance specifically in high copy number have been isolated and shown to encode a tRNA(Glu3) and a novel polypeptide. Disruption of the latter sequence in the yeast genome conferred toxin resistance and revealed that it was nonessential, while the effect of the tRNA(Glu)3 was highly specific and mediated resistance by affecting the toxin's target. An alpha-specific, copy number-independent suppressor of toxin sensitivity was also isolated and identified as MATa, consistent with the observation that diploid cells are partially resistant to the toxin. Second, in a comprehensive screen for toxin-resistant mutants, representatives of 13 complementation groups have been obtained and characterized to determine whether they are altered in the toxin's intracellular target. Of 10 genes found to affect the target process, one (KTI12) was found to encode the novel polypeptide previously identified as a multicopy resistance determinant. Thus, both loss of KTI12 function and elevated KTI12 copy number can cause resistance to the K. lactis toxin.

Adaptor Proteins, Signal Transducing↗

PubMed1993

Both isoforms of protein phosphatase Z are essential for the maintenance of cell size and integrity in Saccharomyces cerevisiae in response to osmotic stress.

The sequences of two genes encoding the protein-serine/threonine-phosphatases PPZ1 and PPZ2 from Saccharomyces cerevisiae have been determined. The molecular masses of PPZ1 and PPZ2 are 77.5 and 78.5 kDa, respectively, and each protein consists of two distinct domains. The C-terminal half of each molecule is 93% identical in PPZ1 and PPZ2, and comprises the protein-phosphatase catalytic domain, while the N-terminal halves, which are rich in serine and asparagine (PPZ1) or serine and arginine (PPZ2), are only 43% identical. Both N-termini start with the amino acids Met-Gly-Asn, suggesting that after removal of the initiating methionine, the N-terminal glycine of the mature protein is myristoylated. Disruption of the gene encoding either PPZ1 or PPZ2 leads to an increase in cell size and cell lysis, the latter being more pronounced in cells disrupted in PPZ1. Haploid cells carrying a double disruption of PPZ1 and PPZ2 genes also show a marked increase in cell size and cell lysis, which can be significantly reduced by the addition of 1 M sorbitol to the growth medium. These results suggest that PPZ1 and PPZ2 play a role in regulating osmotic stability.

Alleles↗

PubMed1993

Drug use and cigarette smoking in applicants for drug abuse treatment.

Whereas smoking rates have declined in the last three decades from around 40% to under 30%, the rates for substance abuse clients remain at a plateau almost three times as high. In order to examine the relations between nicotine and drug use, applicants for drug abuse treatment were surveyed about their cigarette smoking. Results indicated that 85% of applicants were smokers. Also, it was found that for smokers, frequency and type of drug use were associated with amount of cigarette use. Among the five categories of primary drugs surveyed, heroin users had the highest levels of smoking. Additionally, frequency of primary drug use and frequency of overall drug use correlated with cigarette smoking. Within categories of primary drug, frequency of use was related to severity of nicotine dependence for marijuana only. Given the possible association between severity of illicit drug use and smoking found in this study, it behooves treatment organizations to help clients overcome their nicotine dependence.

Adult↗

PubMed1993

Cigarette smoking and methadone dose levels.

Cigarette smoking has been shown to increase consequent to the acute administration of methadone. This suggests the possibility that differences in maintenance dose levels might be associated with differential smoking rates. It is of special concern that higher maintenance levels of methadone may lead to more cigarette smoking because of the putative beneficial effects of higher doses on illicit drug use, treatment retention, and the like. Two experiments were conducted to test the hypothesis that higher maintenance doses of methadone are related to more cigarette smoking. Smoking was measured by self-report and expired carbon monoxide, and the amounts were correlated with subjects' methadone dose levels. The results showed smoking rates of 85% and that self-reported smoking significantly correlated (r = -.52) with CO. Maintenance doses, however, were not correlated with smoking levels. This suggests that the acute effects of methadone on smoking are nullified as clients habituate to dose level, and that decisions regarding appropriate methadone dosage can be made on other grounds.

Adult↗

PubMed1992

Kluyveromyces lactis killer system: ORF1 of pGKL2 has no function in immunity expression and is dispensable for killer plasmid replication and maintenance.

To functionally characterize the genes encoded by the larger killer plasmid pGKL2 from Kluyveromyces lactis a previously developed in-vivo recombination system was exploited. An in-vitro modified version of the cytoplasmically expressible LEU2 gene cartridge (LEU2*) flanked by appropriate pGKL2 segments was used to replace the central part of the ORF1 region of pGKL2. Transformation of a Leu- killer strain resulted in the expected disruption of ORF1 in the resident pGKL2. The Leu+ transformants obtained can be assigned to three classes. Class I carries both killer plasmids, pGKL1/2, and the recombinant pGKL2 derivative termed pRKL2. Class II and III additionally harbor palindrome and hairpin-like plasmids, respectively. Upon subculturing of class I transformants under selective pressure, segregation of the native pGKL2 and the recombinant pRKL2 eventually occurs resulting in total loss of pGKL2. No differences concerning killer and immunity phenotype between a pRKL2-harboring strain and the native pGKL2-carrying recipient could be detected. Thus pGKL2 ORF1 is dispensable for both expression of killer/immunity phenotypes and for the replication and maintenance of the K. lactis killer plasmids.

Immunity↗

PubMed1992

Protein A-calmodulin fusions: a novel approach for investigating calmodulin function in yeast.

A novel gene fusion approach which may be of more general use has been developed for investigating the function of calmodulin in the budding yeast Saccharomyces cerevisiae. By fusing a portion of the Staphylococcus aureus spa gene (encoding protein A) to CMD1, the S. cerevisiae gene encoding calmodulin, we have generated a yeast calmodulin with an affinity tag able to bind immunoglobulins. The chimaeric protein A-calmodulin (ProtA-CaM) polypeptide functions in vivo and shows Ca(2+)-dependent binding to calmodulin target proteins. The spa-CMD1 fusion has been used (i) to prepare (by affinity chromatography) a fraction of yeast proteins which interact with calmodulin, (ii) to isolate genes encoding calmodulin target proteins by direct screening of an expression library, and (iii) to visualize calmodulin-binding proteins in crude extracts by Western blot analysis.

Amino Acid Sequence↗

PubMed1991

Kluyveromyces lactis toxin has an essential chitinase activity.

The Kluyveromyces lactis toxin is a protein containing three subunits (alpha, beta and gamma) which causes sensitive yeast cells to arrest proliferation in the G1 phase of the cell cycle. Despite the toxin's complex structure, the gamma subunit appears to be the only component required for it to arrest proliferation since intracellular expression of the gamma polypeptide alone in a sensitive yeast strain mimics the effect of the exogenous native toxin. The toxin alpha subunit shows sequence similarity to a variety of chitinases and here we report that the toxin is a potent exochitinase. The exochitinase activity is absolutely required for its biological activity against sensitive Saccharomyces cerevisiae cells and allosamidin, a specific inhibitor of chitinases, abolishes the biological activity of the toxin. However, since the alpha subunit is not required for the G1 arrest induced by the toxin, the chitinase activity of the toxin cannot be directly responsible for the ultimate effect of the toxin and most likely plays a role in the initial interaction of the toxin with sensitive cells.

Acetylglucosamine↗

PubMed1991

Protein phosphatase 2Bw and protein phosphatase Z are Saccharomyces cerevisiae enzymes.

cDNAs encoding three protein phosphatases, termed PP2Bw (Da Cruz e Silva, E.F. and Cohen, P.T.W. (1989) Biochim. Biophys. Acta 1009, 293-296), PPZ1 and PPZ2 that have been isolated from a Clontech 'rabbit brain' library are shown to be Saccharomyces cerevisiae clones. PPZ1 and PPZ2 are two novel yeast phosphatases showing 93% amino acid sequence identity to one another. PPZ1 shows approx. 60% sequence identity to S. cerevisiae or mammalian PP1 and approx. 40% identity to S. cerevisiae or mammalian PP2A. These and other observations suggest that the two isoforms of PPZ have functions distinct from those of PP1.

Amino Acid Sequence↗

PubMed1991

A psychoeducational approach to methadone maintenance treatment: a survey of client reactions.

STAR, a methadone clinic in Portland, Oregon employs a psychoeducational approach in an attempt to provide coherent, comprehensive treatment in meeting diverse client needs. Two hundred and thirty-eight STAR clients completed a 133 item survey as part of an evaluative review of the efficacy of the psychoeducational model. Clients were asked about their perceived treatment needs and expectations, drug use, criminality, mental and physical health, social and economic stability, and their sense of self-worth and life satisfaction. Respondents reported that receiving methadone was the most useful and best liked aspect of treatment, followed by individual counseling, and education and skill classes. Clients indicated low rates of criminal behavior and drug use, but acknowledged high rates of psychological symptoms including depression, anxiety, and irritability, and rated as very important the need to reduce drug use and to improve health, to achieve a sense of life satisfaction, to enhance feelings about self and relationships, especially those with their children. A majority of the respondents had less than adequate income, and a substantial minority had less than a high school education. Longer time in treatment at STAR was associated with reduced heroin and cocaine use and improvements in social, economic and legal realms. The discussion focuses on implications for methadone treatment in general and possible modifications of the STAR program.

Activities of Daily Living↗

PubMed1991

Analysis of the response of Saccharomyces cerevisiae cells to Kluyveromyces lactis toxin.

The response of Saccharomyces cerevisiae cells to the toxin produced by certain strains of Kluyveromyces lactis was studied. The toxin caused an arrest of sensitive cells in the unbudded (G1) phase of the cell cycle, consistent with the accumulation of cells with an unreplicated (G1) content of DNA in treated populations. However, toxin-treated cells were not proficient for mating. The effects of the toxin were dependent on its continuous presence for over an hour and removal of cells into fresh medium at earlier times prevented inhibition. Following toxin treatment, cells increased in volume and continued to synthesize protein and RNA, suggesting that they were able to continue growth in the absence of division. However, several lines of evidence suggested that the toxin does not simply block proliferation in G1, but that another continuous or post-G1 event is also affected. Possible models to explain these observations are discussed.

DNA Replication↗

PubMed1990

Toxin arrest.

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Killer Factors, Yeast↗

PubMed1990

Saccharomyces cerevisiae protein phosphatase 2A performs an essential cellular function and is encoded by two genes.

Two genes (PPH21 and PPH22) encoding the yeast homologues of protein serine-threonine phosphatase 2A have been cloned from a Saccharomyces cerevisiae genomic library using a rabbit protein phosphatase 2A cDNA as a hybridization probe. The PPH genes are genetically linked on chromosome IV and are predicted to encode polypeptides each with 74% amino acid sequence identity to rabbit type 2A protein phosphatase, indicating once again the extraordinarily high degree of sequence conservation shown by protein-phosphatases from different species. The two PPH genes show less than 10% amino acid sequence divergence from each other and while disruption of either PPH gene alone is without any major effect, the double disruption is lethal. This indicates that protein phosphatase 2A activity is an essential cellular function in yeast. Measurement of type 2A protein phosphatase activity in yeast strains lacking one or other of the genes indicates that they account for most, if not all, protein phosphatase 2A activity in the cell.

Alleles↗

PubMed1990

"Hello, may we help you?" A study of attrition prevention at the time of the first phone contact with substance-abusing clients.

The problem of early attrition from treatment is pervasive throughout community mental health and is particularly high for substance-abusing clients. In spite of the severity of this problem and the potential for successful interventions, there have not been many studies that attempt to reduce the dropout rate of drug abusers. The purpose of this research was to test the effectiveness of attrition prevention procedures at the time of the client's first phone contact with the clinic. Callers were either given an appointment or told to come to the clinic the same day. A second variable was the presence or absence of an experimenter-initiated dialogue designed to help subjects predict possible obstacles to attendance and to generate potential solutions to those barriers. Subjects in the same day conditions showed at a higher rate than those given appointments, but the addition of the dialogue had no effect on client behavior. The results are discussed in terms of how mental health professionals can find cost effective interventions that prevent drug abuse treatment dropout.

Adult↗

PubMed1990

Psychopathology and personality characteristics in different forms of substance abuse.

Sixteen opiate, 16 amphetamine, 34 cocaine, and 29 marijuana abusers were administered the Million Clinical Multiaxial Inventory and the SCL-90R symptom checklist at treatment admission. Results showed that the combined drug group had levels of psychopathology that were significantly higher than those of a normative psychiatric sample. The four drug groups differed significantly from one another on four scales of the SCL-90R, with the amphetamine group differing from the others on two of the scales. These findings reveal high levels of psychopathology and considerable heterogeneity of symptoms within and across groups of substance abusers at treatment admission.

Adolescent↗

PubMed1989

Remarkable similarities between yeast and mammalian protein phosphatases.

Protein phosphatase activities in extracts of the yeast Saccharomyces cerevisiae showed remarkable similarities to the mammalian type 1, type 2A and type 2C enzymes. Similarities included their substrate specificities, including selectivity for the alpha-and beta-subunits of muscle phosphorylase kinase, sensitivity to okadaic acid and to mammalian inhibitor 1 and inhibitor 2, and requirement for divalent cations. The results suggest that the function and regulation of these enzymes has been highly conserved during evolution and indicate that the improved procedure for identifying and quantitating protein phosphatases [(1989) FEBS Lett. 250,000,000] may be applicable to all eukaryotic cells.

Animals↗