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Biomedical subjects

W Lewis

Publications and source records attributed to W Lewis.

At least 73 records · Page 4Linked to original sources
PubMed1990

Actin isoform mRNA alterations induced by doxorubicin in cultured heart cells.

Cultured rat myocardial cells (CMC) were incubated with adriamycin (ADR), an antineoplastic which causes dilated cardiomyopathy (COCM). CMC were exposed to 10(-7) M to 10(-5) M ADR for 24 hours, harvested, and CMC RNA was extracted. Extracted RNA underwent electrophoresis, transfer to nitrocellulose filters, and hybridization with radiolabeled cDNA probes which were specific for the actin isoforms (alpha, beta, and gamma) and isotypes (alpha sk = alpha skeletal; alpha c = alpha cardiac). RNA from CMC exposed to 10(-7) M ADR yielded a strong signal for mRNA coding for alpha c actin when probed with the isotype-specific cDNA. Hybridization signal was reduced in CMC extracts at 10(-6) M ADR. In CMC extracts at 10(-5) M ADR, the alpha c actin mRNA again hybridized. The cDNAs which were specific for beta and gamma actin isoforms yielded hybridization signals in extracts from CMC exposed to 10(-7) M and 10(-6) M ADR. These signals were reduced in extracts of CMC at 10(-5) M ADR. ADR's dose-related effect on the expression of alpha c actin in CMC is specific and suggests that ADR may have effects on regulation of CMC alpha c actin polypeptides and mRNA.

Actins↗
PubMed1990

Adriamycin cardiotoxicity in vivo. Selective alterations in rat cardiac mRNAs.

Adriamycin (ADR) is an antineoplastic agent with a side-effect of dilated cardiomyopathy. The present study examined ADR-induced changes in cardiac mRNA in vivo. Sprague-Dawley female rats (300 to 400 g) received from 2 to 8 mg/kg of ADR intraperitoneally. After 1 to 6 days, rats were killed and RNA was extracted from heart or gastrocnemius muscle by acid guanidinium-phenol-chloroform extraction. RNA underwent agarose electrophoresis, transfer to nitrocellulose, and hybridization with [32P]-cDNA probes specific to mRNA coding for alpha cardiac (alpha c) actin, alpha skeletal (alpha sk) actin, beta (beta) actin, and glyceraldehyde-3-phosphate dehydrogenase (G3PD). Results showed that alpha c actin mRNA levels in heart extracts were lowest at day 3 after injection, with a 60% decrease at 8 mg/kg ADR. beta actin and G3PD mRNAs decreased 28% and 21%, respectively. In gastrocnemius muscle extracts, both alpha sk actin and G3PD mRNAs decreased 30%. Results suggest a selective effect of ADR on depressing alpha c actin mRNA in the rat heart. Such changes may relate to clinical ADR-induced heart muscle disease.

Actins↗
PubMed1989

Characterization of a panel of somatic cell hybrids for subregional mapping along 11p and within band 11p13. Subdivision of the WAGR complex region.

The short arm of chromosome 11 carries genes involved in malformation syndromes, including the aniridia/genitourinary abnormalities/mental retardation (WAGR) syndrome and the Beckwith-Wiedemann syndrome, both of which are associated with an increased risk of childhood malignancy. Evidence comes from constitutional chromosomal aberrations and from losses of heterozygosity, limited to tumor cells, involving regions 11p13 and 11p15. In order to map the genes involved more precisely, we have fused a mouse cell line with cell lines from patients with constitutional deletions or translocations. Characterization of somatic cell hybrids with 11p-specific DNA markers has allowed us to subdivide the short arm into 11 subregions, 7 of which belong to band 11p13. We have thus defined the smallest region of overlap for the Wilms' tumor locus bracketed by the closest proximal and distal breakpoints in two of these hybrids. The region associated with the Beckwith-Wiedemann syndrome spans the region flanked by two 11p15.5 markers, HRAS1 and HBB. These hybrids also represent useful tools for mapping new markers to this region of the human genome.

Antibodies, Monoclonal↗
PubMed1988

Acute altitude exposure and altered acid-base states. I. Effects on the exercise ventilation and blood lactate responses.

This study examined the influence of acute altitude (AL) exposure alone or in combination with metabolic acid-base manipulations on the exercise ventilatory and blood lactate responses. Four subjects performed a 4 min, 30 W incremental test to exhaustion at ground level (GL) and a 4 min, 20 W incremental test during three acute exposures to a simulated altitude of 4200 m; (i) normal (NAL), (ii) following 0.2 g.kg-1 ingestion of sodium bicarbonate (BAL), and (iii) following 0.5 g.day-1 ingestion of acetazolamide for 2 days prior to exposure (AAL). VE.VO2-1 increased progressively throughout the incremental tests at AL and the minimum value was not related to a change in the blood lactate response. In contrast, the VE.VCO2-1 decreased initially to reach a minimum value at the same power output for each altitude trial and was related to a lactate threshold defined by a log-log transformation (r = 0.78). This transformation of the blood lactate data was not influenced by the altered acid-base states. The relative exercise intensity corresponding to both a delta lactate of 1 mM and an absolute lactate of 4 mM was significantly increased during the AAL (79.9 +/- 12.9 and 93.9 +/- 13.7% VO2max, respectively) compared with NAL (59.1 +/- 5.5 and 78.0 +/- 5.8% VO2max, respectively). These data suggest that strong relationships exist between the ventilatory and blood lactate response during AL exposure and altered acid-base states. Further, it is concluded that, unless the acid-base status is known, the use of an absolute or delta lactate value to compare submaximal exercise should be interpreted with caution.

Acetazolamide↗
PubMed1988

Acute altitude exposure and altered acid-base states. II. Effects on exercise performance and muscle and blood lactate.

This study examined the influence of the respiratory alkalosis of acute altitude (AL) exposure alone or in combination with metabolic acid-base manipulations on exercise performance and muscle and blood lactate accumulation. Four subjects exercised for 10 min at 50% and 75% and to exhaustion at 90% of ground level (GL) VO2max, and at the same relative exercise intensities during three exposures to a simulated altitude of 4200 m; (i) normal (NAL), (ii) following 0.2 g.kg-1 ingestion of sodium bicarbonate (BAL), and (iii) following 0.5 g.day-1 ingestion of acetazolamide for 2 days prior to exposure (AAL). Muscle and blood lactate values were similar throughout exercise for GL and NAL. Although muscle lactates were similar among AL conditions blood lactate was reduced for AAL and increased following exhaustive exercise for BAL compared with NAL. Time to exhaustion at 90% VO2max was increased for NAL (10.4 +/- 1.6 min) compared with GL (7.1 +/- 0.2 min). Performance time was decreased for AAL (6.3 +/- 2.8 min) compared with NAL and BAL (12.4 +/- 4.2 min). These data suggest that the induced respiratory alkalosis of acute AL exposure may enhance exercise performance at high relative intensities. In contrast, the ingestion of acetazolamide before AL exposure would have detrimental effects on performance. The mechanism responsible for these changes may relate to the possible influence of altered extracellular acid-base states on intracellular hydrogen ion accumulation and lactate release.

Acid-Base Equilibrium↗
PubMed1988

Lactate dehydrogenase activity in cultured neonatal rat heart cells exposed to doxorubicin.

Doxorubicin (Adriamycin, ADR) is an anthracycline antineoplastic with the serious side effect of dose-related cardiomyopathy. A model of ADR cardiotoxicity was created to examine some subcellular toxic effects of ADR with cultured cardiac myocytes (CMCs) exposed to 1 x 10(-7) to 1 x 10(-5) M ADR for 24 to 48 hr. Lactate dehydrogenase (LDH) activity was monitored in the CMC medium to monitor CMC damage as a function of ADR concentration. A four- to eightfold elevation of LDH activity in medium of CMCs exposed to 1 x 10(-6) to 1 x 10(-5) M ADR was found. No change in LDH activity was detected in medium of CMCs exposed to 1 x 10(-7) M ADR or in control CMCs after 24 or 48 h ADR exposure. Data suggest a dose-dependent effect of ADR on LDH activity in CMC medium. Serial monitoring of LDH in media of ADR-exposed CMCs may correlate with other evidence of ADR cardiotoxicity in vitro.

Animals↗
PubMed1988

Alpha-actin synthesis changes in cultured cardiac myocytes: relationship to anthracycline structure.

Four anthracyclines (AAs) were examined comparatively to determine effects on actin isoform synthesis in vitro. Cultured cardiac myocytes (CMCs) were incubated for 24 hours with 35 microCi sulfur 35-labeled methionine and 10(-10) to 10(-5) mol/L doxorubicin hydrochloride (Adriamycin) (ADR), daunomycin (DM), 5-iminodaunorubicin IDR), or 3'-deamino-3'-(3-cyano-4-morpholinyl)doxorubicin (MRA-CN). CMCs were harvested in buffered Triton X-100 and homogenized. Proteins in the extracts were fractionated by centrifugation. Equal protein quantities were subjected to sodium dodecyl sulfate-polyacrylamide gel electrophoresis, to two-dimensional electrophoresis, and to autoradiography. AAs caused a dose-dependent decrease in radiolabeling of CMC proteins in Triton-soluble and -insoluble fractions of the extracts. ADR and DM (10(-6) mol/L each) and IDR (10(-5) mol/L) decreased radiolabeling of CMC polypeptides including alpha-actin. In polypeptides extracted in the Triton X-100-soluble pool, the effect on CMC alpha-actin synthesis was greater than the effect on beta- or gamma-actin. CMC alpha-actin synthesis was susceptible to ADR and to DM in a dose-dependent fashion. Contrastingly, alpha-actin radiolabeling was not altered by exposing CMCs to 10(-5) mol/L MRA-CN. Decreased sarcomeric actin isoform synthesis in vitro may reflect forms of subcellular damage in this model of anthracycline cardiomyopathy.

Actins↗
PubMed1988

The effects of excess body fat on fine motor performance following physical exertion.

This study evaluated the effects of excess body fat on fine motor performance prior to and following moderate and heavy intensities of physical exertion. An attempt was made to demonstrate a reduction in psychomotor performance, postexercise, among obese non-fit subjects who might be seen as occupationally unsuitable for certain military or civilian operational roles. One hundred healthy males (mean age +/- S.D. = 29.1 +/- 6.0 years) volunteered for the study. Motor performance was assessed using the Canadian National Research Council tracometer, a device which integrates choice reaction time and pursuit tracking on a step-input subject-paced pursuit tracking task. These measurements were taken prior to and following moderate and heavy treadmill exercise (at 6 METs and 9 METs, which produced (mean +/- S.D.) heart rates of 130 +/- 15 bpm and 173 +/- 17 bpm, respectively). When the subjects were classified according to % body fat (desirable less than or equal to 14.9%; overfat 15-24.9%; obese greater than or equal to 25%), there were no significant differences in postexercise motor performance among these groups. For all groups, the moderate exercise had no effect on tracometer performance, while heavy exercise led to an immediate deterioration in performance followed by a slight improvement. In this particular experimental protocol, postexercise fine motor performance was not significantly influenced by excess body fat.

Adult↗
PubMed1987

Actin synthesis in cultured cardiac myocytes: comparative effects of doxorubicin, dactinomycin, and plicamycin.

Cultured neonatal rat myocardial cells (CMC) were incubated with 10(-8) to 10(-5) mol/L doxorubicin (ADR), dactinomycin (ACT), and plicamycin (MIT), respectively, in medium containing 35 mu Ci sulfur 35-labeled methionine to determine comparative effects on myocardial contractile protein synthesis. Cells were harvested in 2 mmol/L Tris buffer with 0.1% Triton X-100, homogenized, and fractionated by centrifugation. Aliquots of the extracts containing equivalent amounts of protein were applied to 8% to 15% gradient sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). Similar aliquots were subjected to isoelectric focusing and to gel electrophoresis in the second dimension. All electrophoretic gels were autoradiographed. A concentration-dependent effect of ADR, ACT, and MIT on protein and on actin synthesis was found in cultured myocytes with decreased density of radiolabeled actin band in CMC exposed to either 10(-5) mol/L ADR, or from 10(-8) to 10(-5) mol/L ACT, or from 10(-7) to 10(-5) mol/L MIT. Autoradiographs of two-dimensional gels focused actin isoforms but showed substantial decreases of all actin isoforms in CMC extracts from 10(-7) mol/L ACT. ACT and MIT each decreased CMC protein synthesis by 20% at 10(-8) mol/L. At 10(-6) mol/L ADR, synthesis of alpha-actin was diminished preferentially compared with beta and gamma. Synthesis of all actin isoforms was diminished at 10(-5) mol/L ADR. The effect of MIT and ACT on CMC actin and protein synthesis in heart cells is not as specific as the effect of ADR on CMC actin and protein synthesis.

Actins↗
PubMed1987

Actin isoform synthesis by cultured cardiac myocytes. Effects of doxorubicin.

Cultured neonatal rat myocardial cells (CMC) were incubated with 10(-10) M to 10(-5) M doxorubicin (adriamycin, ADR) and [35S]methionine to determine incorporation of radiolabeled methionine into myocardial contractile proteins. Cells were harvested after 24 hours homogenized, and subjected to centrifugation. Equivalent amounts of extracted protein were applied to 8 to 15% gradient sodium dodecylsulfate polyacrylamide gel electrophoresis. Similar aliquots were subjected to isoelectric focusing and to 2-dimensional gel electrophoresis. Electrophoretic gels were autoradiographed. Polypeptide bands on sodium dodecylsulfate polyacrylamide gel electrophoresis and autoradiograms were quantitated densitometrically. No effect of ADR on CMC actin or protein synthesis was seen from 10(-10) M to 10(-7) M ADR. ADR decreased protein synthesis in CMC by 31% at 10(-6) M and by 59% at 10(-5) M ADR. Autoradiograms of two-dimensional gels showed decreased radiolabeling of alpha-actin at 10(-6) M ADR compared to beta and gamma. Decreased CMC actin synthesis initiated at 10(-6) M ADR resulted in selective decrease in synthesis of the alpha-isoform. This in vitro observation may relate to poor contractility in ADR heart muscle disease.

Actins↗
PubMed1986

Cardiac actin interactions with doxorubicin in vitro.

Purified bovine cardiac G-actin was interacted with doxorubicin (Adriamycin, ADR), in absence of potassium or magnesium to study ADR's effects on actin polymerization. Actin with ADR (10(-6) M) was incubated with polylysine-coated polystyrene beads and filaments formed were visualized by negative staining electron microscopy (NSEM). ADR-induced actin polymerization was assessed biochemically by ultracentrifugation and analysis of protein content of the supernatant solution. Kinetic assays of turbidity of actin were performed which showed that ADR induced formation of stubby actin polymers which bound to the beads and differed ultrastructurally from the longer actin filaments induced by KCl + MgCl2. Actin content in the supernatant solution decreased after centrifugation (0.8 mg/ml in G-actin to 0.45 mg/ml in actin incubated with 10(-4) M ADR). ADR (10(-4) M) caused increased turbidity of actin of similar magnitude to that induced by actin + KCl + MgCl2. Data support the hypothesis that ADR induces polymerization of cardiac actin in vitro but this polymerization has characteristics which are different from actin polymerization induced by salts.

Actin Cytoskeleton↗
PubMed1986

Decreased fibronectin levels in aqueous humor after corneal injury.

Fibronectin plays an important role in wound healing and cell differentiation. The present study measures fibronectin levels in aqueous humor from injured corneas. In response to transcorneal freezing treatments, a thickened scar-like matrix is deposited on the posterior surface of rabbit corneas. This posterior collagenous layer (PCL) is visible grossly and has a uniform diameter. Aqueous humor from eyes with established posterior corneal scarring has significantly less fibronectin compared with control eye aqueous humor. Tissue culture experiments show that corneal endothelial cells from control eyes and PCL-associated cells from injured eyes produce similar amounts of fibronectin. The marked decline in fibronectin levels in aqueous humor in scarred corneas supports the hypothesis that fibronectin plays a role in the pathological events which result from corneal injury.

Animals↗
PubMed1986

Characterization and modulation of human lymphokine (interleukin 2) activated killer cell induction.

Culture of human peripheral blood mononuclear cells with purified interleukin 2 (IL-2) results in the induction of a cytotoxic population of cells capable of lysing autologous tumor cells and natural killer (NK) cell resistant tumor cell lines. The current study was undertaken to characterize biological agents which might modulate the induction of lymphokine (IL-2) activated killer (LAK) cells and to optimize culture conditions for LAK cell induction. Preliminary studies were undertaken to characterize optimal time and IL-2 concentration for induction of LAK cell activity. Subsequently, we demonstrated that: (a) LAK cell induction is inhibited at high (2.5 X 10(6)/ml) cell concentrations and this phenomenon is due to the presence of monocytes; (b) depletion of monocytes allows LAK cell induction at 5-10-fold higher cell concentrations without altering the extent or range of LAK-cell activity; (c) interleukin 1 enhances and alpha- and beta-interferons inhibit IL-2 induced proliferation, without altering LAK cell induction; and (d) gamma-interferon alters neither IL-2 induction of proliferation nor LAK cell activity.

Cytotoxicity, Immunologic↗
PubMed1986

Effects of acute tachycardia on left ventricular adenine nucleotide levels and subsequent tolerance to ischemia.

Electrophysiologically guided surgical procedures for the ablation of supraventricular and ventricular dysrhythmias often require prolonged periods of tachycardia to complete intraoperative mapping studies. It is unknown whether tachycardia depletes the myocardium of high-energy compounds or alters subsequent tolerance to ischemia. In the present study, 12 anesthetized dogs were paced from the right ventricle at a cycle length of 250 msec for 60 minutes. In seven animals, drill biopsy specimens were taken from the left ventricular free wall for analysis of adenine nucleotide levels and their breakdown products before and after pacing and after 20 minutes of recovery from pacing. In the remaining five animals, the heart was made totally ischemic immediately after tachycardia and the time to the onset of ischemic contracture was determined and compared to that of five nonpaced control dogs. Acute tachycardia resulted in no significant reduction in adenine nucleotide levels compared to control values. Furthermore, in hearts rendered totally ischemic after tachycardia, the mean time to ischemic contracture was 65.6 +/- 1.3 minutes versus 63.6 +/- 2 minutes in nonpaced control animals (no significant difference). These data show that pacing-induced tachycardia in the normal heart does not decrease adenine nucleotide levels or affect subsequent tolerance to ischemia. These results may be clinically relevant to patients without coronary artery disease who undergo operative procedures necessitating prolonged periods of tachycardia for intraoperative mapping to identify the site of arrhythmogenesis.

Adenine Nucleotides↗