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Biomedical subjects

L M Johnson

Publications and source records attributed to L M Johnson.

At least 73 records · Page 4Linked to original sources
PubMed1987

Distinct sequence determinants direct intracellular sorting and modification of a yeast vacuolar protease.

We have mapped a sequence determinant in the vacuolar glycoprotein carboxypeptidase Y (CPY) that directs intracellular sorting of this enzyme. Through the study of hybrid proteins, consisting of amino-terminal segments of CPY fused to the secretory enzyme invertase, we have found that the N-terminal 50 amino acids of CPY are sufficient to direct delivery of a CPY-Inv hybrid protein to the yeast vacuole. Our data suggest that this 50 amino acid segment of CPY contains two distinct functional domains; an N-terminal signal peptide followed by a segment of 30 amino acids that contains the vacuolar sorting signal. Deletion of this putative vacuole sorting signal from an otherwise wild-type CPY protein leads to missorting of CPY. Furthermore, examination of the Asn-linked oligosaccharides present on CPY and CPY-Inv hybrid proteins suggests that an additional determinant in CPY specifies the extent to which these proteins are glycosylated in the Golgi complex.

Amino Acid Sequence↗
PubMed1987

Self-governance: treatment for an unhealthy nursing culture.

The concept of participatory management for nurses is based on the premise that nurses' education and experience qualify them for a leading role in the decision making that affects patient care. Rose Medical Center, Denver, initiated a self-governance model in 1980. The Nursing Congress, which is recognized by the board of trustees and the medical executive committee, represents all nursing division employees who have satisfactorily completed the probation period. Its bylaws provide for four officers, three members at large, and representatives from the committees and councils on nursing standards and practice, audit/quality assurance, continuing education and research, career ladders, collaborative practice, human resources, rules and regulations, and bylaws. Since implementing the shared-governance structure, the medical center has documented an annual attrition rate of less than 12 percent, a significant 5-year retention rate, and above-average satisfaction with working conditions. Nursing administrators who seek to improve the working conditions that influence staff retention must avoid thinking that relegates nurses to second-class status and limits their decision-making capacity. This does not mean, however, ignoring the fact that organizational change can be threatening to some individuals. Participatory management models can help nurses translate existing skills into strengths, enabling them to view change as a catalyst for improved conditions. Nursing shortages themselves are not the problem but rather a symptom of the problem, an unhealthy nursing culture. Unless leaders step forward to push for change, the shortage of qualified, talented nurses will persist.

Career Choice↗
PubMed1986

Isolation of yeast mutants defective in protein targeting to the vacuole.

We have constructed a PRC1-SUC2 gene fusion that directs the synthesis in Saccharomyces cerevisiae of a hybrid polypeptide consisting of a 433-residue amino-terminal domain derived from the yeast vacuolar protease carboxypeptidase Y (CPY; EC 3.4.16.1) and a 511-residue carboxyl-terminal domain derived from the secreted yeast enzyme invertase (EC 3.2.1.26). Fractionation data indicated that this amount of CPY primary sequence is sufficient to quantitatively divert invertase to the yeast vacuole. The phenotypic consequence of localizing active invertase to the vacuole has enabled us to select for mutants that "mislocalize" the hybrid protein to the cell surface. The corresponding mutations that lead to this effect are all trans-acting and recessive, and they define at least eight complementation groups. These vacuolar protein targeting (vpt) mutants also exhibit hybrid protein independent defects in wild-type CPY delivery to the yeast vacuole. Precursor forms of CPY accumulate in the mutants and are secreted into the yeast periplasm and extracellular medium. The vpt mutants should provide useful information pertaining to the mechanisms by which yeast cells regulate vacuolar protein traffic.

Carboxypeptidases↗
PubMed1986

Gender, adult structuring of activities, and social behavior in middle childhood.

The study was designed to test the relations among gender, adult-provided activity structure, and social behavior for children in middle childhood. Adult-provided structure was defined as verbally presented rules, guidelines, suggestions, and modeling. Children aged 7-11 years attended a 1-week summer day camp in which activities characterized by high or low adult structure were available. As predicted, girls spent more time in highly structured activities, whereas boys spent more time in low-structure activities. Once in high-structure activities, however, both genders displayed high rates of adult-directed bids for recognition, leadership attempts, and compliance and low rates of peer interaction. In low-structure activities, children directed high rates of leadership and other social behaviors to same-sex peers. Children who chose high-structure activities most often were also most likely to interact with adults in those activities. Those who chose low-structure activities showed the highest rates of interaction with male peers. Sex-typed personality attributes were not related to activity choice. The results are interpreted in a framework encompassing the interactions of "person" attributes, environmental variables, and behavior.

Child↗
PubMed1985

Isolation of the gene encoding yeast DNA polymerase I.

A yeast genomic DNA expression library in lambda gt11 antibody prepared against yeast DNA polymerase I were used to isolate the gene encoding DNA polymerase I. The identity of the DNA polymerase I gene was determined by several criteria. First, the clone-encoded protein is immunologically related to DNA polymerase I. Second, cells containing the gene cloned in the high copy number plasmid YEp24 overproduce the polymerase activity 4- to 5-fold as measured in yeast extracts. Finally, insertion of the gene downstream from a bacteriophage T7 promoter allows synthesis of yeast DNA polymerase I in Escherichia coli. Gene disruption and Southern hybridization experiments show that the polymerase is encoded by an essential, single copy gene. Examination of the germinated spores containing the disrupted gene reveals a defect in nuclear division and a terminal phenotype typical of replication mutants.

Cell Cycle↗
PubMed1983

Hemorrhagic colitis associated with a rare Escherichia coli serotype.

We investigated two outbreaks of an unusual gastrointestinal illness that affected at least 47 people in Oregon and Michigan in February through March and May through June 1982. The illness was characterized by severe crampy abdominal pain, initially watery diarrhea followed by grossly bloody diarrhea, and little or no fever. It was associated with eating at restaurants belonging to the same fast-food restaurant chain in Oregon (P less than 0.005) and Michigan (P = 0.0005) and with eating any of three sandwiches containing three ingredients in common (beef patty, rehydrated onions, and pickles). Stool cultures did not yield previously recognized pathogens. However, a rare Escherichia coli serotype, O157:H7, that was not invasive or toxigenic by standard tests was isolated from 9 of 12 stools collected within four days of onset of illness in both outbreaks combined, and from a beef patty from a suspected lot of meat in Michigan. The only known previous isolation of this serotype was from a sporadic case of hemorrhagic colitis in 1975. This report describes a clinically distinctive gastrointestinal illness associated with E. coli O157:H7, apparently transmitted by undercooked meat.

Adolescent↗
PubMed1983

Influence of perinatal androgenization on the castration response of adult rats.

An unexplained dichotomy exists between the LH (luteinizing hormone) responses to castration of male and female rats, as males show a more prompt increase in serum LH levels. We have tested the hypothesis that neonatal exposure to androgen determines the sexual dimorphism of that response. Control groups of male and female rats were castrated at 60 days of age. Other animals had been castrated at 0 or 25 days of age and then given steroid treatment via testosterone (T) implants from 25 through 60 days of age. At 60 days of age a blood sample was taken from each animal before removal of either the T implant or the gonads. Animals were bled again 24 and 48 h later. Within 24 h after orchidectomy the typical early plateau of plasma LH had occurred, represented by an increment in mean LH concentrations of 316 ng/ml. Orchidectomy at 25 days of age had little or no effect on subsequent response to removal of T. In contrast, neonatal orchidectomy resulted in a markedly diminished response to T removal on Day 60. The response, however, was not reduced to that of normal females. In female rats plasma LH does not increase by 48 h after ovariectomy. Perinatal testosterone propionate (TP) treatment of females partially masculinized (enhanced) the LH response to T implant removal, but only if ovariectomy had been performed prior to puberty (at 0 or 25 days of age).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1983

Union--yes or no?

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Attitude of Health Personnel↗
PubMed1981

Luteinizing hormone in the cat. I. Tonic secretion.

We have used a RIA system for measuring LH in the plasma of domestic cats and characterized the component of LH secretion which is controlled by negative feedback inhibition. Blood samples were collected at 6- to 10-min intervals from animals with chronically indwelling venous cannulae. The inhibitory influence (negative feedback) of gonadal secretion was evidenced by the increased plasma concentrations of LH seen 24 h after castration in 9 animals and within 5 days in all 15 cats. Restoration of negative feedback by either short or long term administration of 17 beta-estradiol reduced LH concentrations to precastration levels. In castrated animals of both sexes, the plasma concentrations of LH fluctuated episodically, with increases occurring at intervals of 20-30 min, presumably a reflection of intermittent periods of LH release. The dynamics of this pattern of LH release were simulated by the iv injection of gonadotropin-releasing hormone. In combination with our additional observation that plasma concentrations of LH decreased rapidly after treatment with four different anesthetic agents, the observations are suggestive of episodic secretion of gonadotropin-releasing hormone in the absence of negative feedback. The mechanisms regulating tonic LH secretion in this reflex ovulator appear to be more sensitive to neural stimuli but qualitatively similar to those previously described for other species in which ovulation occurs spontaneously.

Animals↗