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Biomedical subjects

J Powers

Publications and source records attributed to J Powers.

At least 37 records · Page 2Linked to original sources
PubMed1998

A nematode kinesin required for cleavage furrow advancement.

Dividing cells need to coordinate the separation of chromosomes with the formation of a cleavage plane. There is evidence that microtubule bundles in the interzone region of the anaphase spindle somehow control both the location and the assembly of the cleavage furrow [1-3]. A microtubule motor that concentrates in the interzone, MKLP1, has previously been implicated in the assembly of both the metaphase spindle and the cleavage furrow [4-6]. To gain insight into mechanisms that might underlie interdependence of the spindle and the cleavage furrow, we used RNA-mediated interference (RNAi) to study the effects of eliminating MKLP1 from Caenorhabditis elegans embryos. Surprisingly, in MKLP1(RNAi) embryos, spindle formation appears normal until late anaphase. Microtubule bundles form in the spindle interzone and the cleavage furrow assembles; anaphase and cleavage furrow ingression initially appear normal. The interzone bundles do not gather into a stable midbody, however, and furrow contraction always fails before complete closure. This sequence of relatively normal mitosis and a late failure of cytokinesis continues for many cell cycles. These and additional results suggest that the interzone microtubule bundles need MKLP1 to encourage the advance and stable closure of the cleavage furrow.

Animals↗
PubMed1998

Transport of axl2p depends on erv14p, an ER-vesicle protein related to the Drosophila cornichon gene product.

COPII-coated ER-derived transport vesicles from Saccharomyces cerevisiae contain a distinct set of membrane-bound polypeptides. One of these polypeptides, termed Erv14p (ER-vesicle protein of 14 kD), corresponds to an open reading frame on yeast chromosome VII that is predicted to encode an integral membrane protein and shares sequence identity with the Drosophila cornichon gene product. Experiments with an epitope-tagged version of Erv14p indicate that this protein localizes to the ER and is selectively packaged into COPII-coated vesicles. Haploid cells that lack Erv14p are viable but display a modest defect in bud site selection because a transmembrane secretory protein, Axl2p, is not efficiently delivered to the cell surface. Axl2p is required for selection of axial growth sites and normally localizes to nascent bud tips or the mother bud neck. In erv14Delta strains, Axl2p accumulates in the ER while other secretory proteins are transported at wild-type rates. We propose that Erv14p is required for the export of specific secretory cargo from the ER. The polarity defect of erv14Delta yeast cells is reminiscent of cornichon mutants, in which egg chambers fail to establish proper asymmetry during early stages of oogenesis. These results suggest an unforeseen conservation in mechanisms producing cell polarity shared between yeast and Drosophila.

Amino Acid Sequence↗
PubMed1998

Induction of heat shock protein 27 by hydroxyurea and its relationship to experimental metastasis.

Treatment of tumor cells with hydroxyurea (HU) has been shown to increase the experimental metastatic potential of these cells. We have previously described the induction of stress proteins (antioxidants) by HU in B16 murine melanoma cells and their relationship to the metastatic process. We have now investigated the induction by HU of another set of stress proteins, the heat shock proteins, and their role in experimental metastasis. HU markedly increased the cellular content of heat shock protein (hsp) 27 but not of hsp 90, 72/73, or 60 as measured by immunoblotting. The induction of hsp27 protein was preceded by a specific increase in hsp27 mRNA. Furthermore, HU-treated cells were more thermotolerant. To investigate the functional role of hsp27, human hsp27 cDNA was constitutively overexpressed in B16 cells at levels seen in HU-treated cells. In separate experiments, we induced a global increase in hsps by heat shock. Neither the hsp27 transfectants nor the heat-shocked cells demonstrated an increase in their experimental metastatic capacity. We conclude that hsp27 protein is increased by HU by the specific induction of hsp27 mRNA in B16 melanoma cells but increased hsp27 protein is not responsible for the increase in experimental metastasis. Since high levels of hsp27 are associated with metastatic disease in breast and ovarian cancers, but not in our experimental system, the functional role of hsp27 in metastasis requires further study.

Animals↗
PubMed1998

A quantitative rationale for investing in healthcare facilities.

When considering investing in its facilities, a healthcare organization should determine its competitive position by quantifying factors such as average age of plant, inpatient days, occupancy rates, and inpatient versus outpatient revenue. Average age of plant in years (AAP) can be compared with inpatient days per 1,000 population to determine an organization's AAP relative to the market and thus whether investment is warranted. Occupancy rates per facility can be compared to the total of all unoccupied beds in an organization to determine if some facilities should be consolidated or closed. Understanding the relationship between revenue trends and the number of projects undertaken to address shifts in inpatient and outpatient volumes can help providers create the optimal environment for patient care delivery.

Age Factors↗
PubMed1997

Long-term effects of home visitation on maternal life course and child abuse and neglect. Fifteen-year follow-up of a randomized trial.

CONTEXT: Home-visitation services have been promoted as a means of improving maternal and child health and functioning. However, long-term effects have not been examined. OBJECTIVE: To examine the long-term effects of a program of prenatal and early childhood home visitation by nurses on women's life course and child abuse and neglect. DESIGN: Randomized trial. SETTING: Semirural community in New York. PARTICIPANTS: Of 400 consecutive pregnant women with no previous live births enrolled, 324 participated in a follow-up study when their children were 15 years old. INTERVENTION: Families received a mean of 9 home visits during pregnancy and 23 home visits from the child's birth through the second birthday. DATA SOURCES AND MEASURES: Women's use of welfare and number of subsequent children were based on self-report; their arrests and convictions were based on self-report and archived data from New York State. Verified reports of child abuse and neglect were abstracted from state records. MAIN RESULTS: During the 15-year period after the birth of their first child, in contrast to women in the comparison group, women who were visited by nurses during pregnancy and infancy were identified as perpetrators of child abuse and neglect in 0.29 vs 0.54 verified reports (P<.001). Among women who were unmarried and from households of low socioeconomic status at initial enrollment, in contrast to those in the comparison group, nurse-visited women had 1.3 vs 1.6 subsequent births (P=.02), 65 vs 37 months between the birth of the first and a second child (P=.001), 60 vs 90 months' receiving Aid to Families With Dependent Children (P=.005), 0.41 vs 0.73 behavioral impairments due to use of alcohol and other drugs (P=.03), 0.18 vs 0.58 arrests by self-report (P<.001), and 0.16 vs 0.90 arrests disclosed by New York State records (P<.001). CONCLUSIONS: This program of prenatal and early childhood home visitation by nurses can reduce the number of subsequent pregnancies, the use of welfare, child abuse and neglect, and criminal behavior on the part of low-income, unmarried mothers for up to 15 years after the birth of the first child.

Adolescent↗
PubMed1997

A multidisciplinary approach to occipital pressure ulcers related to cervical collars.

Pressure ulcers related to cervical collars are a common difficult-to-manage complication of cervical immobilization in the trauma patient. After many cases of occipital pressure ulcers occurred at our institution, a multidisciplinary task force was formed to look at this issue. The group was to identify causes for this problem and develop a plan to decrease the occurrence of pressure ulcers related to cervical immobilization. The problem involved three areas that needed improvement. These were: nursing care, the type of collar used, and the lengthy process of clearing C-spines. The group developed objectives, goals, and interventions to resolve these concerns. The task force developed a protocol for nursing care, changed to a different type of cervical collar, and developed a protocol for clearing cervical spine films. Through the use of a multidisciplinary approach, the development of protocols and a new product, pressure ulcers related to cervical collars have been eliminated in our institution. In addition, patients are staying in cervical collars half the time as before the protocol was implemented.

Braces↗
PubMed1997

Risk factors for aboriginal low birthweight, intrauterine growth retardation and preterm birth in the Darwin Health Region.

Risk factors for Aboriginal low birthweight (< 2500 g), preterm birth (< 37 weeks' gestation) and intrauterine growth retardation (under the tenth percentile of Australian birthweights for gestational age) were examined in 503 live-born singletons recorded as born to an Aboriginal mother and routinely delivered at the Royal Darwin Hospital between January 1987 and March 1990. Infants born to mothers with body mass index less than 18.5 kg/m2 had five times the risk of having low birthweight and 2.5 times the risk of intrauterine growth retardation. Population-attributable risk percentages suggest that 28 per cent of low birthweight and 15 per cent of growth retardation could be attributed to maternal malnutrition. Risk percentages for maternal smoking of more than half a packet of cigarettes a day were 18 per cent for low birthweight and 10 per cent for growth retardation. For growth retardation, 18 per cent could be attributed to a maternal age under 20 years. Risk factors for preterm birth were predominantly obstetric: the population-attributable risk percentage for pregnancy-induced hypertension was 26 per cent and for other obstetric conditions was 16 per cent. For Aboriginal births in the Darwin Health Region, maternal malnutrition and smoking are key elements in the prevention of low birthweight and intrauterine growth retardation. Teenage pregnancy is an important risk for intrauterine growth retardation, and pregnancy-induced hypertension is a risk for preterm birth.

Adult↗
PubMed1997

Intra-arterial thrombolysis of embolic proximal middle cerebral artery occlusion from presumed atrial myxoma.

The role of thrombolysis in brain ischemia in patients with atrial myxoma is unknown. A patient with acute brain ischemia and previously undiagnosed atrial myxoma recanalized an occluded middle cerebral artery with intra-arterial thrombolysis. Arterial occlusion from presumed myxoma may be amenable to fibrinolysis. Angiography before treatment in patients with atrial myxoma excludes a myxomatous pseudoaneurysm and permits site-specific thrombolytic instillment.

Carotid Arteries↗
PubMed1997

Exercise-rest same-day SPECT sestamibi imaging to detect coronary artery disease.

UNLABELLED: This study examined the results of exercise-rest same-day SPECT protocol in 193 patients, of whom 132 had coronary artery disease (CAD) by angiography (> or = 50% diameter stenosis), and 61 had a low pretest probability of CAD. METHODS: The rest study was combined with first-pass radionuclide angiography using the multicrystal gamma camera in 72 patients. RESULTS: The sensitivity of SPECT was 76% (25/33 patients) in patients with one-vessel, 84% in patients with two-vessel (38/45) and 98% in patients with three-vessel CAD (53/54) (P = 0.01 versus one- or two-vessel CAD). The sensitivity of SPECT in patients with CAD was higher than ST depression (88% versus 28%, P = 0.001). The exercise was submaximal in 53 patients (40%). The perfusion defects were reversible (complete or partial) in 80 patients and fixed in 36 patients. The left ventricular ejection fraction was 50 +/- 12% in patients with reversible defects (n = 44) and 39 +/- 9% in patients with fixed defects (n:19) (P = 0.0004). The normalcy rate in subjects with a low pretest probability of CAD was 95% (53 of 61 subjects). CONCLUSION: The exercise-rest same-day sestamibi protocol provides high diagnostic accuracy for CAD detection. The protocol may eliminate the need for rest studies in patients with normal exercise images, help improve laboratory throughput and lower costs.

Adult↗
PubMed1995

Prognostic value of rest-redistribution tomographic thallium-201 imaging in ischemic cardiomyopathy.

The relation between the presence of viable myocardium by rest-redistribution thallium imaging and prognosis is not well defined. This study examined the prognostic value of rest-redistribution single-photon emission computed tomographic imaging with thallium-201 in patients with coronary artery disease (CAD) and left ventricular (LV) dysfunction. Patients were divided into 2 groups: group 1 patients (n = 47) were treated medically and group 2 patients (n = 38) underwent coronary revascularization. The 2 groups were comparable in the extent of CAD and in LV ejection fraction. Thallium images showed normal tracer uptake in 1 group 1 and 3 group 2 patients, fixed defects in 26 group 1 and 18 group 2 patients, and both reversible and fixed defects in 20 group 1 and 17 group 2 patients (p = NS). Based on analysis of 20 segments/patient, reversible defects were seen in 4 +/- 4 segments/patient in group 1 and 5 +/- 5 segments/patient in group 2 (p = NS). Viable myocardium (defined as normal tracer uptake, reversible defects, or mild fixed defects) was seen in 14 +/- 4 segments/patient in group 1 and 15 +/- 5 segments/patient in group 2 (p = NS). During a mean follow-up of 31 months, there were 16 group 1 (34%) and 6 group 2 (16%) deaths. The annual mortality rate was 13% in group 1 and 6% in group 2. Actuarial survival analysis showed better survival in group 2 than in group 1 (p = 0.056). Thus, viable myocardium in patients with CAD and LV dysfunction is associated with poor prognosis with medical therapy. Coronary revascularization improves prognosis.

Actuarial Analysis↗
PubMed1994

Clinical response to intravenous nitroglycerin infused through polyethylene or polyvinyl chloride tubing.

The effects of polyethylene and polyvinyl chloride (PVC) administration sets on the clinical response to i.v. nitroglycerin were studied. Patients with ischemic heart disease were randomly assigned to receive nitroglycerin solution through either a polyethylene administration set or a PVC set. The rate of the infusion was 5-10 micrograms/min initially and was adjusted upward by 5-10 micrograms/min every 5-10 minutes until anginal symptoms were relieved or an adverse effect limited further increases. The data collected included patient demographics, the indication for nitroglycerin, nitroglycerin dosages, the initial dosage-adjustment time (the time necessary to reach the initial effective dosage), the number of dosage adjustments and the indications for them, the duration of the infusion, the time of tubing changes, the total dose of nitroglycerin, the amounts of sublingual nitroglycerin and i.v. morphine used, and the occurrence of various clinical events. There were 78 courses of therapy in the PVC group and 62 in the polyethylene group. The two groups were comparable in all respects except gender. There were no significant differences between the two groups in any of the primary study variables. Patients who received i.v. nitroglycerin through a PVC administration set had the same clinical response as patients given the drug through a polyethylene set.

Aged↗
PubMed1994

Gastrointestinal hemorrhage and small cell carcinoma.

Despite widespread dissemination of primary lung carcinoma by lymphangitic and hematogenous routes, acute gastrointestinal signs and symptoms are rarely presenting symptoms for bronchogenic carcinoma. We present a patient with small cell carcinoma of the lung who came to medical attention because of a lower gastrointestinal hemorrhage. In the absence of radiographically apparent pulmonary disease, the correct diagnosis was suggested by the biopsy specimens of the colon.

Aged↗
PubMed1993

Neuropathology of lubag (x-linked dystonia parkinsonism).

Lubag is an x-linked recessive dystonia parkinsonism that affects Filipino men originating principally from the Panay Island. Linkage analysis has confirmed the mode of inheritance and localized the disease gene to the proximal long arm of the x-chromosome. We studied the brain of a 34 year old Filipino man affected with lubag. He developed truncal dystonia at age 30, which subsequently generalized. With disease progression, he also presented with parkinsonism including, rigidity, bradykinesia, and impaired balance. His symptoms were largely unaffected by medication and, at age 34, he underwent a right cryothalamotomy. He died suddenly 2 days after the procedure. The principal neuropathological findings were neuronal loss and a multifocal mosaic pattern of astrocytosis restricted to the caudate and lateral putamen. Similar findings have been reported in two other men with dystonia--one Filipino and the other non-Filipino. The similar pathology of the two Filipino men suggests that this is the pathology of lubag. Recognition of this pathology in a non-Filipino man suggests that the mutation causing lubag may not be restricted to the Filipino population.

Adult↗
PubMed1993

Pharmacokinetics of single intravenous and single and multiple dose oral administration of rifampin in mares.

The disposition of rifampin in six healthy mares after single intravenous (i.v.) and oral (p.o.) doses and after seven oral doses of 10 mg/kg administered twice a day was investigated using a high performance liquid chromatographic (HPLC) method. Pharmacokinetic variables for rifampin determined using the HPLC method were comparable to variables reported from earlier studies utilizing a microbiological assay. Desascetylrifampin, a major metabolite of the parent compound, could not be detected in the serum but was detected at low concentrations in urine. Mean trough concentrations of rifampin increased from the first to the second dose of the multiple dose oral study and then remained unchanged through 72 h. At 84 h after the first dose (i.e. 12 h after the final dose) the rifampin concentration was significantly decreased (P = 0.001). The harmonic mean of the half-life of rifampin decreased significantly from 13.3 h after a single oral dose of 7.99 h after the seventh oral dose. The mean serum protein binding of rifampin over the concentration range of 2-20 micrograms/ml was 78%. Mean trough serum concentrations of unbound rifampin after multiple oral doses ranged from 0.67 micrograms/ml at 24 h to 0.40 micrograms/ml at 72 h. The mean unbound serum rifampin concentration at 84 h (i.e., 12 h after the final dose) was 0.30 micrograms/ml. Trough concentrations and the 84-h sample concentration of unbound rifampin exceeded the minimum inhibitory concentration for most gram positive bacterial isolates from horses reported in this study. All organisms with minimum inhibitory concentrations less than 0.125 micrograms/ml were considered susceptible. Based on the pharmacokinetics of rifampin after p.o. administration, we concur with the current dosage recommendation of 10 mg/kg twice a day by mouth. At this dose, most streptococci, Rhodococcus equi, and coagulase-positive staphylococci would be considered susceptible to rifampin.

Administration, Oral↗