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Biomedical subjects

W Taylor

Publications and source records attributed to W Taylor.

At least 91 records · Page 5Linked to original sources
PubMed1994

Light-induced phase responses in Gonyaulax are drastically altered by creatine.

The mammalian phosphagen creatine has been shown to shorten the circadian period (tau) of the bioluminescence rhythm in the marine alga Gonyaulax polyedra from 23 to 18 hr. The studies described here concern the interactive effects of creatine and light, mainly on the bioluminescence rhythm. We have found that the tau-shortening effect of creatine is greater in blue light, suggesting that it acts on a blue-sensitive light input pathway. In addition, creatine affects the phase response mechanism in Gonyaulax, which is also known to be mainly blue-sensitive. The responses to 4-hr light pulses are dramatically increased under the influence of creatine. The unusual phase response curve (PRC) of the Gonyaulax circadian system, which has no phase delays in the early night, is changed in the presence of creatine to a more typical type 0 PRC, with delays of up to 12 hr. Creatine also amplifies the cells' phototactic response, suggesting that the blue-sensitive light input pathway is shared by the phase-shifting mechanism of the bioluminescence oscillator and the mechanism responsible for phototaxis.

Animals↗
PubMed1994

An inhibitor of protein phosphorylation stops the circadian oscillator and blocks light-induced phase shifting in Gonyaulax polyedra.

The expression of circadian rhythmicity in Gonyaulax polyedra is strikingly altered by an inhibitor of protein phosphorylation. The effects of 6-dimethylaminopurine (6-DMAP), known to reversibly block cell division in many systems through inhibition of protein kinase activity, are described here for Gonyaulax. Its action appears to be exclusively tonic in nature; in cells continuously exposed, the period is lengthened in a concentration-dependent fashion. Shorter treatments at a higher concentration of 6-DMAP (5 mM) apparently stop the circadian oscillator, but reversibly so, since the rhythm resumes after drug removal with a phase delay approximately equal to the duration of the treatment. Pulses of the inhibitor are effective in causing phase delays at all times of the circadian cycle. In addition, 6-DMAP completely blocks light-induced phase advances and is effective in inhibiting many Gonyaulax protein kinases in vitro.

Adenine↗
PubMed1994

Erythropoietin-augmented isovolemic hemodilution in skull-base surgery. Case report.

Human erythropoietin in concert with intraoperative hemodilution, tumor embolization, and surgical staging was used to manage a red blood cell mass in an anemic Jehovah's Witness patient with a hypervascular meningioma. Erythropoietin (3000 U thrice weekly) and oral iron (1300 mg daily) were given for 1 month prior to surgery, raising the hemoglobin level from 11.8 to 14.1 gm/100 ml. A posterior fossa craniectomy combined with a temporal craniectomy was then performed so that partial petrosectomy, section of the transverse sinus, incision of the tentorium, and exposure of the lesion could be carried out. The first stage of the surgery was terminated immediately prior to tumor mobilization. Isovolemic hemodilution was initiated just before the skin incision. Postoperatively, the hemoglobin concentration dropped to 11.5 gm/100 ml. The erythropoietin dose was doubled and administration of oral iron continued, leading to a hemoglobin level of 14.0 gm/100 ml at 1 month after the first operation. The tumor was embolized using superselective catheterization. The next day, at the second stage of the surgery, the tumor was extirpated, again employing isovolemic hemodilution. By the 4th postoperative day, the hemoglobin level had dropped to 9.4 gm/100 ml. The patient made an uncomplicated recovery. Erythropoietin therapy contributed substantially to the successful outcome of this case. Since erythropoietin has the potential to augment all other forms of autologous banking, its role in elective neurosurgery may become increasingly important in an era of heightened concern about heterologous transfusion.

Blood Transfusion, Autologous↗
PubMed1994

Battered women's experiences in the emergency department.

Objective To determine the perceptions of shelter advocates and battered women regarding the treatment of battered women in emergency departments. Methods Mailed survey of 74 battered women and 49 battered women's advocates from Michigan shelters for abused women during an 8-month period. Results Half of the battered women reported negative experiences in the emergency department, such as feeling humiliated, being blamed for their abuse, having abuse minimized, being given insufficient referrals, and not being identified as battered women. Many of the battered women had, in addition to their battering injuries, physical (39.7%) and mental (37.7%) health problems that could be linked to the abuse they had suffered. A significant positive correlation (r = 0.28) was found between existing physical complaints and number of ED visits in the previous year. Conclusions The data were used to develop appropriate model ED policies and procedures for the identification, treatment, and referral of battered women to meet Joint Commission on Accreditation of Healthcare Organizations guidelines regarding abuse.

Adolescent↗
PubMed1994

Hand-arm vibration syndrome.

The hand-arm vibration syndrome affects workers who perform tasks that generate vibration. Raynaud's phenomenon and sensory impairment of the fingers are the predominant effects. A history of hand-arm vibration (HAV) exposure in a patient with these symptoms should alert the physician to the diagnosis. Referral to a special clinic or hospital department for multiple clinical tests is required to confirm the diagnosis and, using the Stockholm classification, to grade the severity in each hand. The assessment permits the patient to be monitored either for progression of or recovery from the syndrome. Avoidance of further vibration exposure is recommended, together with the prescription of a slow-release calcium channel blocker to improve peripheral circulation. Hand-arm vibration syndrome should be distinguished from carpal tunnel syndrome (CTS), which may have similar symptomatology but requires different treatments. Surgery is contraindicated in the former and should be the last resort for carpal tunnel syndrome in a worker requiring good grip-strength in future employment.

Arm Injuries↗
PubMed1993

Circadian rhythms in prokaryotes: luciferase as a reporter of circadian gene expression in cyanobacteria.

We have used a luciferase reporter gene and continuous automated monitoring of bioluminescence to demonstrate unequivocally that cyanobacteria exhibit circadian behaviors that are fundamentally the same as circadian rhythms of eukaryotes. We also show that these rhythms can be studied by molecular methods in Synechococcus sp. PCC7942, a strain for which genetic transformation is well established. A promoterless segment of the Vibrio harveyi luciferase structural genes (luxAB) was introduced downstream of the promoter for the Synechococcus psbAI gene, which encodes a photosystem II protein. This reporter construction was recombined into the Synechococcus chromosome, and bioluminescence was monitored under conditions of constant illumination following entrainment to light and dark cycles. The reporter strain, AMC149, expressed a rhythm of bioluminescence which satisfies the criteria of circadian rhythms: persistence in constant conditions, phase resetting by light/dark signals, and temperature compensation of the period. Rhythmic changes in levels of the native psbAI message following light/dark entrainment supported the reporter data. The behavior of this prokaryote disproves the dogma that circadian mechanisms must be based on eukaryotic cellular organization. Moreover, the cyanobacterial strain described here provides an efficient experimental system for molecular analysis of the circadian clock.

Circadian Rhythm↗
PubMed1993

Selective regulation of protein kinase C isoenzymes by oleic acid in human platelets.

Cis-unsaturated fatty acids activate soluble protein kinase C (PKC) in vitro and in intact platelets. The following studies were conducted to determine the effects of oleate on individual isoenzymes of PKC in human platelets. Human platelets were found to contain predominantly PKC alpha, beta I, beta II, and delta with minor immunoreactivity for PKC epsilon, zeta, and eta. In intact platelets, sodium oleate caused a time-dependent redistribution of PKC alpha, beta II, and delta from cytosol to membrane fractions with little effects on PKC beta I. On the other hand, PMA and thrombin induced translocation of all four isoenzymes of PKC. In vitro, oleate partially activated (50% of Vmax) purified calcium-dependent PKC (alpha, beta I, and beta II) with an EC50 of 50 microM whereas it fully activated (100% of Vmax) purified calcium-independent PKC (predominantly delta) with an EC50 of 5 microM. The selective effects of oleate on PKC isoenzymes were investigated in platelet cytosol which contains endogenous PKC and its physiologic substrates. Under these conditions, oleate potently activated calcium-independent PKC causing the phosphorylation of the 40-kDa substrate. Activation of calcium-dependent isoforms occurred only at higher concentrations of oleate. Thus, oleate activates multiple isoenzymes of PKC with predominant effects on calcium-independent PKC.

Amino Acid Sequence↗
PubMed1993

Intestinal absorption in patients with rheumatoid arthritis treated with methotrexate.

Twelve patients with rheumatoid arthritis treated for at least 12 months with methotrexate and 11 matched rheumatoid arthritis controls underwent a standard d-xylose absorption test. No patients had any pre-existing clinical of biochemical evidence of malabsorption. No significant difference was observed in the 1 hour plasma d-xylose estimation between methotrexate treated patients and controls. The 2 to 5 hour urinary excretion ratio, however, was significantly lower in the methotrexate-treated group compared with controls indicating a minor degree of malabsorption. Six of the methotrexate treated patients and 5 of the controls underwent endoscopic duodenal biopsy but neither group demonstrated any significant histological changes. In conclusion, methotrexate therapy in patients with rheumatoid arthritis produces mild intestinal malabsorption.

Aged↗
PubMed1993

Ontogeny of rat lung type IV collagenase mRNA expression and collagenolytic activity during the perinatal period.

The extracellular matrix is important in the cellular differentiation and morphogenesis of the lung. The basement membrane (BM), an integral part of the extracellular matrix, is composed primarily of type of IV collagen. The metabolism of type IV collagenase is important in remodeling of BM that occurs during growth. We examined the ontogeny of rat lung type IV collagenase mRNA expression, type IV collagenolytic activity and type IV collagen content during the perinatal period. In addition, the effect of prenatal glucocorticoid (GC) treatment on fetal lung type IV collagenase mRNA expression and type IV collagenolytic activity was studied. Lung polyadenylated RNA was extracted and subjected to Northern blot analysis and laser densitometry after hybridization with human type IV collagenase (approximately 72 kD) and rat actin cDNA probe. Type IV collagenolytic activity and type IV collagen concentration were quantitated by an enzymatic and a radioimmunoassay, respectively. While lung type IV collagenase mRNA to alpha-actin ratio and type IV collagenolytic activity were highest prior to birth (21-day fetus), the lung type IV collagen concentration was lowest at this time. Prenatal GC treatment did not influence type IV collagenase mRNA expression or the collagenolytic activity. A role for fetal lung type IV collagenase in preparation for the neonatal pulmonary vascular and/or alveolar adaptation is proposed.

Animals↗
PubMed1992

Determinants of lung cancer risk among cadmium-exposed workers.

Workers at a cadmium recovery plant in Globe, Colorado, showed an increased risk of lung cancer, which some investigators have attributed to cadmium exposure. We conducted a cohort mortality analysis of this work force and a case-control analysis of the lung cancer cases within this work force in order to assess the probable causes of the lung cancer excess. The Globe plant began as a lead smelter about 1886, switched to arsenic production in 1920, and became a cadmium metal production facility in 1926. Cadmium, arsenic, and cigarette smoking are three potential lung carcinogens found in this workplace. Industrial hygiene data collected from 1943 onward served as the basis for the National Institute for Occupational Safety and Health (NIOSH)-derived exposure algorithm that assigned cadmium exposure estimates to employees based on their work area in the plant and calendar time. Few exposure data existed for substances other than cadmium. Feedstock ore concentrations were used as a surrogate measure of air arsenic levels. The arsenic content of the fines used as feedstock prior to 1940 was considerably higher than that of the fines used after 1940. Smoking histories had been obtained previously for 45% of the workers. A case-control analysis of the 25 cases of lung cancer known to have occurred among these workers through 1982 was conducted using three controls per case, matched by closest data of hire and age at hire. Potential causal agents for lung cancer included cadmium exposure, cigarette smoking, and arsenic exposure. Exposure variables for each case and control included estimated cumulative cadmium exposure in milligram-years per cubic meter, cigarette smoking history, and plant arsenic exposure status at the time of hire. Estimated cumulative cadmium exposures of cases and controls did not differ overall or within the date-of-hire strata. Cases were more than eight times more likely to have been cigarette smokers than were controls. Lung cancer risk in this workplace was more closely related to the period of hire, not to the cumulative cadmium exposure. The period of hire appears to be a surrogate for arsenic exposure as related to feedstock. The measures used here seem to indicate that exposure to arsenic and cigarette particulates, rather than to cadmium particulates, may have caused the increased rate of lung cancer of these workers.

Adult↗
PubMed1992

Diagnostic implications of detection of proteinase K-resistant protein in spleen, lymph nodes, and brain of sheep.

Brain, spleen, and selected lymph nodes from sheep with clinical signs of scrapie were analyzed for presence of proteinase K-resistant protein (PrP-res). Diagnosis of scrapie on the basis of detection of PrP-res was compared with diagnosis on the basis of histologic evaluation of the brain from clinically affected or exposed sheep. Proteinase K-resistant protein was found in every brain that was histologically positive for scrapie, and in addition, was found in the brain of several clinically positive sheep that were not diagnosed as scrapie-positive by histologic evaluation. Proteinase K-resistant protein was also found in 87% of the spleens and lymph nodes from sheep that had PrP-res detected in brain homogenates. Therefore, analysis of sheep brain, spleen, or lymph nodes for PrP-res provided a diagnostic approach that was superior to histologic examination alone for detection of naturally scrapie agent-infected sheep.

Animals↗
PubMed1991

Lessons from hand-arm vibration syndrome research.

This paper addresses many of the salient issues and difficulties encountered in performing Hand-Arm Vibration Syndrome research since its discovery in the early 1900's by Alice Hamilton. The areas discussed and the resulting lessons learned include the medical, epidemiological, and control aspects of HAVS. The authors conclude with a plea to health professionals to be ever vigilant and responsive to the HAVS problem, or else it will continue unabated into the next century, an overall time span of nearly 100 years.

Arm↗
PubMed1991

Practical 3-D radiotherapy planning of brain tumors.

In postoperative radiotherapy of brain tumors it is usually the case that preoperative imaging studies, either CT or MRI, were performed outside of the purview of the radiation therapy department. Thus the target volume is defined in an imaging study that does not lend itself readily for entry to a 3-D treatment planning system. A method is described that adjusts the patient structure defined by scan data to an appropriate position for radiotherapy. Software tools that are simple to use have been incorporated in a 3-D treatment planning program that allows oblique treatment planes to be defined. The program provides beam's-eye-view plots of the fields that are used to overlay simulation films and will automatically describe a field blocking outline that provides a prescribed margin on the target volume or other structures that have been defined. Finally, dose calculations in arbitrary planes through the head are made and isodose plots produced.

Brain Neoplasms↗
PubMed1991

Physical activity, cardiovascular fitness, and adiposity in children.

With cardiovascular fitness (CVF) as the dependent variable, relationships with habitual level of physical activity, age, gender, and body mass index (BMI) were investigated in a sample of 93 high adiposity and 93 low adiposity children, ages 8 to 13. A physical activity score (PAS) was computed for each child from a 2-day observation period. A physical working capacity index from cycle ergometry (PWC170) was the measure of CVF. Low and high adiposity samples were classified by a median split (42.9 mm) on the sum of three skinfold measures (tricep, suprailiac, subscapula). For the high adiposity sample, PAS, age, BMI, and gender were significant and the overall model was significant (p less than .001), accounting for 38% of variance in PWC170. In the low adiposity sample, gender (p less than .04) was significantly related to CVF, but the overall model was not significant (p less than .35). PAS, thus, was a significant predictor of CVF among the high adiposity children, but not the low adiposity children. Mechanisms that may account for this difference include greater work for equal activity among the obese, a ceiling effect on CVF among the low adiposity children, or differences in hormonal or metabolic factors mediating the activity-CVF relationship.

Adolescent↗