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Biomedical subjects

L L Smith

Publications and source records attributed to L L Smith.

At least 91 records · Page 5Linked to original sources
PubMed1995

DNA damage as assessed by 32P-postlabelling in three rat strains exposed to dietary tamoxifen: the relationship between cell proliferation and liver tumour formation.

Tamoxifen was administered in the diet (420 p.p.m.) to female F344 (Fischer), Wistar (LAC-P) and LEW (Lewis) rats to determine for each strain the early morphological and biochemical changes associated with the subsequent development of liver cancer. Hepatic DNA damage, as determined by 32P-postlabelling, showed a cumulative increase with time from 500 adducts/10(8) nucleotides at 30 days to almost 3000 adducts/10(8) nucleotides after 180 days, with little difference between strains at this time point. A significant strain difference was found in the number of adducts present in the Fischer rats at 90 days, compared to the Wistar and Lewis strains. There was a marked strain differences in the time to development of liver tumours. After 6 months treatment, both Wistar and Lewis rats had tumours while none were seen in the Fischer animals. After 11 months, all of the Wistar and Lewis rats had developed liver carcinoma, while the Fischer rats developed liver carcinoma by 20 months. Depression in cell proliferation, relative to age-matched controls, was seen in the livers of Fischer rats after six months of exposure to tamoxifen, in contrast to an increase in the Wistar and Lewis rats. This observation is consistent with the promotion of foci to tumours and the subsequent progression of tumours to carcinomas in the latter two strains. These data may assist in establishing the possible risk factors, such as extent of DNA damage and increased liver cell proliferation, to women with long-term prophylactic exposure to tamoxifen.

Animals↗
PubMed1995

32P-postlabelled DNA adducts in liver obtained from women treated with tamoxifen.

32P-Postlabelling of DNA extracted from the livers obtained from seven women receiving tamoxifen (20 mg either once or twice daily) was compared with liver DNA from seven individuals not receiving this drug. In all but one of the treated women, tamoxifen and its N-desmethyltamoxifen metabolite could be detected in liver extracts by high performance liquid chromatography; none was detected in control samples. The total level of 32P-postlabelled DNA adducts extracted from the tamoxifen treated women ranged between 18-80 adducts/10(8) nucleotides. The pattern of 32P-postlabelled adducts was not the same as those seen in rats dosed with this drug. There was no significant difference in the level of DNA damage between the tamoxifen treated and control groups. Although only a small number of subjects has so far been examined it appears that women are less susceptible to liver DNA damage caused by tamoxifen than rats.

Adult↗
PubMed1995

Alpha-v beta-3 integrin expression in normal and atherosclerotic artery.

Recent evidence suggests that alpha v beta 3 integrin is a critical molecule in several processes involved in atherosclerosis progression and in restenosis, eg, smooth muscle cell (SMC) migration and angiogenesis. While several ligands for this integrin are known to be present in atherosclerotic plaque, little is known about the presence of alpha v beta 3 integrin at this site. In the present study, we have examined alpha v beta 3 expression in normal and atherosclerotic arteries. Thirty-six coronary artery segments from the recipient hearts of 24 patients undergoing heart transplantation were classified into two groups: nonatherosclerotic diffuse intimal thickening (DIT) and atherosclerotic plaques. Serial frozen sections were examined immunohistochemically with four different monoclonal antibodies directed against human alpha v beta 3 complex or the beta 3 subunit and with cell markers for SMCs, macrophages, and endothelial cells. The endothelium along the lumen of both DIT and plaque arteries showed high expression of alpha v beta 3. The media of both DIT and plaque arteries showed less intense but extensive expression of alpha v beta 3. Immunoprecipitation and reverse-transcribed polymerase chain reaction (RT-PCR) analyses performed on extracts from the aortic media confirmed the presence of alpha v beta 3 in the media. In the intima of both DIT and plaque arteries, alpha v beta 3 expression generally colocalized with SMCs but rarely with macrophages. The microvessels in the adventitia as well as in the plaque showed prominent expression of alpha v beta 3, in contrast to low expression in similar-sized microvessels of the skin.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

Methylene chloride: an inhalation study to investigate toxicity in the mouse lung using morphological, biochemical and Clara cell culture techniques.

Single exposures of mice to methylene chloride (MC) cause vacuolation and necrosis of the bronchiolar Clara cells which subsequently recover normal morphology on continued exposure. Both cytochrome P-450 (CYP)- and glutathione S-transferase (GST)-dependent metabolism of MC are known to occur. The current studies have investigated the metabolism of MC in mouse lung using inhibitors of both GST and CYP-dependent routes of metabolism, the consequences of metabolic inhibition on the Clara cell vacuolation, and any changes in cell proliferation, assessed in vitro, in Clara cells cultured from exposed individuals. Vacuolated bronchiolar cells were seen in mice exposed to 2000 and 4000 ppm MC but were not seen at lower concentrations, while addition of the CYP inhibitor, piperonyl butoxide, significantly reduced the bronchiolar cell vacuolation seen following exposure to 2000 ppm MC. Treatment of mice with the glutathione depletor, buthionine sulphoximine, had no effect on the number of vacuolated bronchiolar cells following MC. Exposure of mice to 1000 ppm MC and above for 6 h caused a burst of DNA synthesis in bronchiolar Clara cells cultured in vitro from the lungs of exposed animals. The results suggest that the Clara cell vacuolation following MC exposure is mediated via CYP metabolism, that depression of the CYP metabolic pathway occurs following exposure, and that Clara cell vacuolation may have a priming role in stimulating cell proliferation in the unaffected cell population.

Administration, Inhalation↗
PubMed1994

On the relationship between the mitochondrial inner membrane anion channel and the adenine nucleotide translocase.

The mitochondrial inner membrane anion channel (IMAC) is a transport pathway which is believed to be involved in mitochondrial volume homeostasis. The protein, however, has not been identified. In this paper, we examine the relationship between IMAC and the adenine nucleotide translocator. Many inhibitors of the adenine nucleotide translocase are shown to block IMAC, including Cibacron blue 3GA, bromcresol green, alizarin red S, agaric acid, palmitoyl-CoA, and the fluorescein derivatives erythrosin B, erythrosin isothiocyanate, rose bengal, and eosin Y. The following evidence suggests that Cibacron blue, agaric acid, and palmitoyl-CoA inhibit by binding to a common site. 1) They all only partially block the transport of small anions such as Cl-, NO3-, and HCO3-, but completely block the transport of larger anions such as malonate. 2) They decrease the IC50 values of each other in a manner consistent with competitive binding. 3) N-Ethylmaleimide decreases their IC50 values by a similar extent. 4) Inhibition by all shows no dependence on matrix pH and only a small dependence on medium pH. It is suggested that these agents may selectively bind to an open state of IMAC and inhibit by decreasing its conductance. The physiological nucleotides CoA, NAD+, NADH, NADP+, NADH, and ATP do not inhibit; in fact, IMAC is shown to transport ATP. Despite these similarities between IMAC and the adenine nucleotide translocase, IMAC appears to be a separate entity, since some of the IC50 values differ by up to 8-fold, and carboxyatracyloside, the most selective inhibitor of the adenine nucleotide translocase, has no effect on IMAC. In addition, IMAC is also able to transport AMP, while the adenine nucleotide translocase does not.

Anions↗
PubMed1994

Effect of leuprolide acetate in patients with moderate to severe functional bowel disease. Double-blind, placebo-controlled study.

Moderate to severe functional bowel disease results in debilitating abdominal pain, nausea, intermittent vomiting, early satiety, bloating, abdominal distension, and/or altered bowel habits. Because it occurs approximately 20-30 times more frequently in women than in men and its symptoms often coincide with the menstrual cycle, we hypothesized that reproductive steroids may antagonize diseased nerves of the gastrointestinal tract, enhancing the expression of symptoms. No effective or consistent therapy has existed for these patients. We prospectively investigated the effect of a gonadotropin-releasing hormone analog, leuprolide acetate, in 30 women with symptoms of moderate to severe functional bowel disease. The study was phase II, randomized, double blind, and placebo controlled. Lupron Depot 3.75 mg (which delivers a continuous low dose of drug for one month) or placebo were given intramuscularly monthly for three months. Symptom scores were assessed at each four-week visit. Follicle-stimulating hormone, luteinizing hormone, estradiol, and progesterone levels were assessed before and after therapy. Patients treated with low-dose leuprolide improved progressively and significantly in scores for nausea, vomiting, bloating, abdominal pain, and early satiety, and for overall symptoms (P < 0.01-0.05). All hormone levels decreased significantly (P < 0.05) except luteinizing hormone (P = 0.054).

Adult↗
PubMed1994

Genotoxicity of tamoxifen, tamoxifen epoxide and toremifene in human lymphoblastoid cells containing human cytochrome P450s.

The clastogenicity of tamoxifen and toremifene was tested in six human lymphoblastoid cell lines each expressing increased monooxygenase activity associated with a specific transfected human cytochrome P450 cDNA (CYP1A1, CYP1A2, CYP2D6, CYP2E1 or CYP3A4). The chemicals were also tested in a cell line (MCL-5) expressing elevated native CYP1A1 and containing transfected CYP1A2, CYP2A6, CYP2E1 and CYP3A4 and epoxide hydrolase, and in a cell line containing only the viral vector (Ho1). Dose-related increases in micronuclei were observed when cells expressing 2E1, 3A4, 2D6 or MCL-5 cells were exposed to tamoxifen. The positive responses in the cell lines were in the order MCL-5 > 2E1 > 3A4 > 2D6. Toremifene also gave positive results with 2E1, 3A4 and MCL-5 cells, although the responses were less marked and the positive effects required higher doses than with tamoxifen. A synthesized epoxide of tamoxifen was also tested in these cell lines and produced similar increases in the incidences of micronucleated cells. The increases in the responses observed with the epoxide were greater than with tamoxifen or toremifene. The P450 isoenzyme activities in these cells were in a range similar to those of human tumour-derived cell lines. Microsomes (1A1, 2A2, 2A6, 2B6, 2E1, 3A4 and 2D6) from these cells all metabolized tamoxifen. The major metabolite detected by HPLC was N-desmethyltamoxifen, and 4-hydroxytamoxifen was also detected in cells with cytochrome P450 2E1 and 2D6. These results are consistent with the following conclusions. (1) Tamoxifen requires metabolic activation to DNA-reactive species by specific CYP monooxygenases in order to exert its genotoxic effects. (2) The positive clastogenic effects elicited in lymphoblastoid cells by tamoxifen epoxide suggest that the genotoxic (and possibly the carcinogenic) effects of tamoxifen may be due to one or more epoxide metabolites that are generated intracellularly, probably in close proximity to the nucleus. (3) Tamoxifen is more genotoxic than toremifene.

Biotransformation↗
PubMed1994

A comparative study of tamoxifen metabolism in female rat, mouse and human liver microsomes.

The metabolisms of tamoxifen in female rat, mouse and human liver microsomal preparations were compared. Rat, mouse and human liver microsomes were incubated with tamoxifen in the presence of NADPH and MgCl2 and the metabolites formed were analysed by on-line HPLC-electrospray ionization MS. The major metabolites formed by rat liver microsomes were 4-hydroxytamoxifen, 4'-hydroxytamoxifen, N-desmethyltamoxifen and tamoxifen N-oxide. In addition, two epoxide metabolites, 3,4-epoxytamoxifen and 3',4'-epoxytamoxifen, and their hydrolysed derivatives, 3,4-dihydrodihydroxytamoxifen and 3',4'-dihydrodihydroxytamoxifen, have been identified. The pattern of the main metabolites obtained with human liver microsomes resembles qualitatively that of rat liver microsomes. The major differences between rat and human liver microsomes were that the amount of hydroxylated metabolites were much lower in human and only traces of 3,4-epoxytamoxifen and the corresponding dihydrodihydroxy derivative were detected. No 3',4'-epoxytamoxifen was detected in human liver microsomes. The four major metabolites were also formed in much larger amounts and with faster rates of formation by mouse liver microsomes, though tamoxifen N-oxide clearly predominated in this species. Polar metabolites, 3,4-dihydroxytamoxifen and 4-hydroxytamoxifen N-oxide, which were undetectable in rat and human, were formed in significant amounts in mouse microsomes. As in human microsomes, there was only one epoxide metabolite, 3,4-epoxytamoxifen, produced by mouse liver microsomes at levels lower than that found in rat. The faster rate of metabolism and the production of polar metabolites may indicate the ability of mouse to detoxify tamoxifen by rapid elimination compared with rat and human. The production of a larger amount of potentially reactive epoxide metabolites in rat may be responsible for the liver carcinogenesis in this species.

Animals↗
PubMed1994

The impact of a repeated bout of eccentric exercise on muscular strength, muscle soreness and creatine kinase.

The purpose of this study was to determine if there were any beneficial or detrimental effects regarding delayed onset muscle soreness (DOMS), serum creatine kinase (CK), and maximum concentric strength at 80% of 1-RMconc, if a bout of eccentric exercise was repeated at 48 h after an initial bout. A secondary purpose was to determine whether unaccustomed eccentrics might affect plasma cholesterol (TC). Twenty-six men were randomly assigned to a control (Group 1) or experimental group (Group 2). Both groups performed three sets (12 repetitions per set) of the eccentric phase of a chest press, at 80% of one repetition maximum (1-RMconc); Group 2 repeated this exercise 48 h later. DOMS and CK were measured before, and every 24 h for 8 days after; TC was measured before, and every 24 h for 4 days. Maximum strength during the concentric phase of a chest press (1-RMconc) was measured before and at 48-h intervals after. A repeated measures analysis of variance revealed a significant time effect (P < 0.05) for DOMS, CK and strength, but no significant difference between groups (P < 0.05). An interesting finding was the significant (P < 0.05) reduction in TC at 24, 48 and 72 h, after exercise in both groups, which we hypothesized was associated with cellular repair. From these results we concluded that when a bout of eccentrics is repeated 48 h after an initial bout, there is no change in the characteristic time-course and/or intensity of DOMS, CK or 1-RMconc.

Adult↗
PubMed1994

Pulmonary embolism: confirmation with venous duplex US as adjunct to lung scanning.

PURPOSE: To assess the prevalence of deep venous thrombosis with venous duplex ultrasonography (US) in patients who underwent radionuclide lung scanning for evaluation of clinically suspected pulmonary embolism (PE) and to assess the clinical usefulness of this type of US in the selection of patients for anticoagulant therapy. MATERIALS AND METHODS: Two hundred eighty-five lung scan and duplex US examinations in 267 consecutive patients seen between January 1987 and June 1990 with clinical evidence of PE (151 men and 134 women, aged 17-98 years [mean, 57 years]) were retrospectively reviewed. Lung scans were divided into four groups: normal, depicting up to 30% probability of PE, indeterminate or intermediate probability of PE, and greater than 90% probability of PE. RESULTS: Thrombotic disease was confirmed with US in seven (21%) of 33 patients with normal lung scans and in 64 (25%) of 252 patients with abnormal lung scans. CONCLUSION: Venous duplex Doppler US is a useful adjunct to lung scanning in patients with signs and/or symptoms of PE.

Adolescent↗
PubMed1994

The effects of athletic massage on delayed onset muscle soreness, creatine kinase, and neutrophil count: a preliminary report.

It was hypothesized that athletic massage administered 2 hours after eccentric exercise would disrupt an initial crucial event in acute inflammation, the accumulation of neutrophils. This would result in a diminished inflammatory response and a concomitant reduction in delayed onset muscle soreness (DOMS) and serum creatine kinase (CK). Untrained males were randomly assigned to a massage (N = 7) or control (N = 7) group. All performed five sets of isokinetic eccentric exercise of the elbow flexors and extensors. Two hours after exercise, massage subjects received a 30-minute athletic massage; control subjects rested. Delayed onset muscle soreness and CK were assessed before exercise and at 8, 24, 48, 72, 96, and 120 hours after exercise. Circulating neutrophils were assessed before and immediately after exercise, and at 30-minute intervals for 8 hours; cortisol was assessed before and immediately after exercise, and at 30-minute intervals for 8 hours; cortisol was assessed at similar times. A trend analysis revealed a significant (p < 0.05) treatment by time interaction effect for 1) DOMS, with the massage group reporting reduced levels; 2) CK, with the massage group displaying reduced levels; 3) neutrophils, with the massage group displaying a prolonged elevation; and 4) cortisol, with the massage group showing a diminished diurnal reduction. The results of this study suggest that sports massage will reduce DOMS and CK when administered 2 hours after the termination of eccentric exercise. This may be due to a reduced emigration of neutrophils and/or higher levels of serum cortisol.

Adult↗
PubMed1994

Is your colleague chemically dependent?

Don't shrug off signs of possible impairment--the problem is more common than you might think. Knowing how to recognize and report it can literally make the difference between life and death.

Confidentiality↗
PubMed1993

The epidemiology of bacillary angiomatosis and bacillary peliosis.

OBJECTIVE: To determine environmental risk factors for bacillary angiomatosis-bacillary peliosis (BAP), and to confirm infection with Rochalimaea species. DESIGN: Case-control study. SETTING: Community and university hospitals and clinics. PATIENTS: Case patients (N = 48) had biopsy-confirmed BAP. Controls (N = 94) were matched to patients by institution and by human immunodeficiency virus (HIV) serological status. MAIN OUTCOME MEASURES: Clinical information was obtained from medical records. Subjects were queried about environmental exposures. Univariate odds ratios (ORs) with 95% confidence intervals (CIs) were determined. Bivariate analyses were performed on variables associated with disease by univariate analysis. DNA from 22 available case-patient tissues and from 22 control tissues was amplified with the polymerase chain reaction (PCR) using primers designed to detect Rochalimaea species. RESULTS: We identified five HIV-negative, immunocompetent case patients; one HIV-negative, immunodeficient case patient; and 42 HIV-positive case patients. There were no significant differences between case patients and controls by race, sex, age, or risk factors for HIV infection. Owning a cat (OR, 2.8; CI, 1.4 to 5.8) and history of a recent cat lick (OR, 1.95; CI, 1.0 to 3.8), cat scratch (OR, 3.7; CI, 1.7 to 8.0), or cat bite (OR, 3.9; CI, 1.8 to 8.9) were associated with disease in the univariate analysis. In bivariate analyses, only the variables representing traumatic contact with a cat (bite or scratch) remained associated with disease. No other environmental exposure was associated with disease. The PCR amplified a DNA fragment of the size expected for Rochalimaea species in all 22 case-patient tissue specimens. CONCLUSIONS: These data suggest that BAP is a new zoonosis associated with both traumatic exposure to cats and infection with Rochalimaea species or a closely related organism.

Adult↗
PubMed1993

Induction of CYP2B1 and 3A1, and associated monoxygenase activities by tamoxifen and certain analogues in the livers of female rats and mice.

Previous studies suggest long-term feeding of tamoxifen (Z-1-[4-(2-dimethylamino-ethoxy)phenyl]1,2-diphenyl-1-butane) to rats gives rise to liver tumours, while mice are resistant. The effects of tamoxifen on cytochrome P450 isoenzymes and associated monoxygenase activities in the livers of female Fischer rats and C57Bl/6 and DBA/2 mice have been compared. Total microsomal cytochrome P450 was not induced in the livers of rats given tamoxifen (45 mg/kg daily for 4 days) and was in fact significantly reduced after 3 days treatment. In contrast, there was a 30-60-fold increase in the metabolism of benzyloxy- and pentoxyresorufins to resorufin. Ethoxyresorufin O-deethylase was induced only 2.5-fold. The regio- and stereo-specific hydroxylation of testosterone following tamoxifen pretreatment of rats showed a general time- and dose-dependent induction. 6 beta- and 16 alpha-hydroxylation of testosterone together with oxidation to androstenedione were increased 2-3-fold while 2 beta-hydroxylation was induced only marginally, suggesting that tamoxifen produces a mixed pattern of induction with a significant phenobarbitone-like component. No induction of the 2 beta- or 6 beta-hydroxylation pathway occurred in either mouse strain. In rats, immunoblotting experiments with polyclonal antibodies raised against CYP2B1 or 3A1 showed that tamoxifen pretreatment resulted in 2-3-fold increases in both CYP2B1, 2B2 and 3A1 proteins, relative to controls. Immunohistochemistry of rat liver sections showed a centrilobular localization of these induced proteins. Similar patterns of induction as measured by immunoblotting experiments and testosterone hydroxylation were seen following the administration of structurally related analogues, toremifene and droloxifene (3-hydroxytamoxifen), thought to be non-carcinogenic in the rat. No induction of these monooxygenase activities was seen in C57Bl/6 mice and only small increases in benzyloxy and pentoxyresorufin metabolism were in DBA/2 mice. It is suggested that the induction of cytochrome P450-dependent activities by tamoxifen may result in accelerated liver metabolism of this drug with important implications for the disposition of tamoxifen in vivo and also for its metabolic conversion to genotoxic metabolite(s). The difference in inducibility of cytochrome P450-dependent monooxygenase activities between rats and mice offers a plausible and testable hypothesis that the difference in tamoxifen metabolism between the two species may contribute to their carcinogenic response to tamoxifen.

Animals↗
PubMed1993

Popliteal-tibial bypass grafts in the management of limb-threatening ischemia.

OBJECTIVES: To ascertain the cumulative rates of primary graft patency and limb salvage and the frequency of proximal arterial disease progression in patients with autologous saphenous vein bypass grafts that originate from the popliteal artery and whose operative indication was limb-threatening ischemia. DESIGN: Five-year retrospective study with follow-up that ranged from less than 1 month to 60 months. SETTING: Tertiary care center. PATIENTS: Twenty-four threatened limbs in 23 patients were reviewed. Surgical indications included gangrene in 15 limbs (63%), rest pain in seven limbs (29%), and a nonhealing ulcer in two limbs (8%). Patients with previous ipsilateral infrainguinal arterial reconstructive procedures were excluded. Mean patient age was 66 years, and 18 patients 78% had insulin-dependent diabetes mellitus. MAIN OUTCOME MEASURES: Percentages of primary graft patency and limb salvage were determined by the life-table method. Proximal arterial disease progression was assessed via follow-up arteriography or segmental limb pressures. RESULTS: The cumulative rates of primary graft patency and limb salvage at 1, 3, and 5 years were 73%, 59% and 59%, and 87%, 57%, and 57%, respectively. No patient developed proximal arterial disease progression that required intervention during the study period. CONCLUSIONS: The cumulative rates of primary graft patency and limb salvage were essentially the same, which indicated poorly collateralized limbs that are solely dependent on the graft. There did not appear to be a critical progression of proximal arterial disease that would warrant a more proximal graft origin. A short autologous saphenous vein graft that originates from the above-knee or below-knee popliteal artery is a durable bypass.

Aged↗
PubMed1993

17O nuclear magnetic resonance spectra of steroids.

The 17O NMR spectra of cholesterol and 31 other steroid alcohols, esters, ketones, and acids enriched by synthesis with 17O from H2(17)O have been observed under ordinary operating conditions, and correlations between 17O chemical shift and structure have been adduced. Spectra-structure correlations for these steroids are in conformity with those previously adduced with simpler compounds by others.

Acids↗