Biomedical subjects

S M Morris

Publications and source records attributed to S M Morris.

At least 91 records · Page 5Linked to original sources

PubMed1996

Apoptotic and anti-proliferative effects of fumonisin B1 in human keratinocytes, fibroblasts, esophageal epithelial cells and hepatoma cells.

Fumonisin B1 is associated with various animal and human carcinomas and toxicoses, including leukoencephalomalacia, hepatocarcinoma, pulmonary edema and esophageal carcinoma. We have examined the cellular effects of fumonisin B1 in vitro using cellular model systems relevant to potential human target tissues. Although fumonisin B1 has been described as a mitogen in Swiss 3T3 cells based on stimulation of [3H]thymidine incorporation, in the current work it was found that fumonisin B1 inhibited incorporation of [3H]thymidine by cultured neonatal human keratinocytes and HepG2 human hepatocarcinoma cells at 10(-7) and 10(-4) M respectively. Fumonisin B1 also inhibited clonal expansion of normal human keratinocytes and HET-1A human esophageal epithelial cells at 10(-5) M and growth in mass culture of normal human fibroblasts at 10(-7) M. The clonogenicity of normal human keratinocytes decreased to 45.5% of controls after exposure to 10(-4) M fumonisin B1 for 2 days. However, no differences in the cell cycle distribution of cultured keratinocytes was noted after exposure to 10(-5) M fumonisin B1 for 40 h. The viability of normal human keratinocytes and HET-1A cells decreased as a result of fumonisin B1 treatment, as determined by a fluorescein diacetate/propidium iodide flow cytometric cell viability assay. Fumonisin B1-treated keratinocytes released nucleosomal DNA fragments into the medium 2-3 days after exposure to 10(-4) M fumonisin B1 and increased DNA strand breaks were detected in attached keratinocytes exposed to 0-10(-4) M fumonisin B1 using a terminal deoxynucleotidyl transferase-based immunochemical assay system. Furthermore, fumonisin B1-treated keratinocytes and HET-1A cells developed morphological features consistent with apoptosis, as determined by phase contrast microscopy, fluorescent microscopy of acridine orange stained cells and electron microscopy. These results are consistent with the occurrence of fumonisin B1-mediated apoptosis in vitro.

3T3 Cells↗

PubMed1996

Comparison of the performance characteristics of three generations of membrane oxygenators: Univoxregistered, Univoxreqistered Goldtrademark and SpiralGoldtrademark.

With continuous enhancement in oxygenator design, the question is raised as to how these changes actually impact the performance of the oxygenator. The recent addition of two new oxygenators by the Bentley Division of Baxter Healthcare Corporation provided us with a unique opportunity to compare the performance of each device and isolate the impact of each design change on performance. While the basic design and flow patterns have remained the same, application of the Duraflo II treatment has produced the Univox Gold and a change in the fibre-winding technique has produced the SpiralGold. This study compared the effects of heparin coating (Univox to Univox Gold) and fibre-winding (Univox Gold to SpiralGold) on gas and heat transfer and resistance to blood flow (pressure drop). Six oxygenators of each model were evaluated utilizing an in vitro single pass circuit, which first conditioned bovine blood to the Association for the Advancement of Medical Instrumentation (AAMI) venous standards. Blood flows of 4.0, 5.0, 6.0 and 7.0 l/min, FiO2 values of 1.0, 0.8 and 0.6, and gas-to-blood flow ratios of 0.5, 1.0 and 1.5 were chosen as test variables. Data generated included oxygen transfer, carbon dioxide transfer, arterial pO2, resistance to blood flow, and coefficient of heat exchange. The results indicate that the Duraflo II treatment does not have a significant effect on gas and heat transfer or resistance to blood flow. The fibre-winding technique employed with the new SpiralGold, however, has improved significantly gas exchange and arterial pO2 when compared with the previous Univox models. Resistance to blood flow and coefficient of heat exchange were not affected significantly by the winding technique.

Carbon Dioxide↗

PubMed1995

Cloning of the promoter-regulatory region of the murine growth hormone receptor gene. Identification of a developmentally regulated enhancer element.

The growth hormone (GH) receptor is essential for the actions of GH on postnatal growth and metabolism. To identify DNA sequences involved in the regulation of transcription of the murine GH receptor gene, a 17-kilobase genomic clone containing the 5'-flanking region, exon 1, and part of intron 1 of the murine GH receptor gene was isolated. Utilizing primer extension and ribonuclease protection assays, two major transcription start sites were identified in RNA from liver of male, female, and pregnant mice. Transient transfection studies using a reporter gene demonstrated promoter activity in a variety of eukaryotic cells. Deletional analysis and DNA-protein binding assays led to the identification of a 30-base pair enhancer element located about 3.4 kilobases upstream of the transcription start sites. Computer analysis of the nucleotide sequence of the enhancer element did not reveal any potential DNA binding motifs for known transcription factors, and this DNA element failed to exhibit binding activity for some common transcription factors. Analysis of both functional activity and DNA-protein binding activity of this enhancer element in adult and fetal hepatocytes suggests that this DNA element may play a role in the developmental expression of the GH receptor gene.

Animals↗

PubMed1995

Programmed cell death and mutation induction in AHH-1 human lymphoblastoid cells exposed to m-amsa.

One role of programmed cell death (apoptosis) is the removal of cells with DNA damage from the population. Certain cells, however, are able to suppress the signals for apoptotic cell death and maintain viability. This suggests that the susceptibility of a cell to either undergo apoptosis or escape from the apoptotic death pathways may be an important factor in chemical mutagenesis. In order to provide insight into the role of apoptosis in the recovery of chemically induced mutants, AHH-1 cells were exposed to the chromosomal mutagen, m-amsa, and the percentage of cells undergoing apoptosis or necrosis quantified by flow cytometry. Logistic regression analysis revealed that the primary manner of cell death was by apoptosis. Two specific-locus mutations assays, the tk and the hprt, were utilized as markers for cells with DNA damage and that retained clonogenicity under conditions known to induce apoptosis. Analysis of variance indicated that the concentration-dependent increase in the mutant fraction at the tk locus was significant and the result of the recovery of clones with the slow-growth phenotype. Because this phenotype is thought to reflect chromosomal mutations, these results are consistent with the survival and clonogenicity of damaged cells. This suggests that the ability to recover mutant cells may be influenced by the suppression of or an escape from the apoptotic death pathways.

Amsacrine↗

PubMed1995

Prevention of cataracts by nutritional and metabolic antioxidants.

Among aging disabilities, the one associated with the progressive decline of vision is functionally most disadvantageous. Cataracts are one of the more common causes of such visual disability. Several predisposing factors have been identified in the genesis of this disease. While it is perhaps a multifactorial process, significant developments have taken place in recent years suggesting that oxygen radicals are involved in the development of this aging manifestation. Antioxidant enzymes, such as catalase and superoxide dismutase, have been demonstrated to protect the lens cell membrane from oxidative stress as reflected by the prevention of the Na(+)-K(+)-ATPase-dependent pump deterioration due to oxyradical-dependent oxidation of its proteins and lipids. From the nutritional point of view, antioxidants such as ascorbate and vitamin E also offer significant protection to the lens against damage due to oxidative stress. Evidence regarding the protective effect of these nutrients has been based on lens organ culture studies in the presence of active oxygen, generated photochemically as well as enzymatically. The experiment involving photochemical environs simulate the status of the eye during the photopic vision. In vivo, the effectiveness of ascorbate against cataracts has been tested in rat pups developing cataracts under the oxidative influence of sodium selenite. Certain antioxidants produced metabolically also may be useful in protecting against cataracts. Pyruvate produced in glucose metabolism seems to be an important antioxidant. The efficacy of this compound has been tested within in vitro organ culture as well as in vivo, the latter experiments being done with selenite-treated rats. There is a hope that these and other nutritional and metabolic antioxidants may one day be useful in delaying or even preventing cataract formation in human beings.

Animals↗

PubMed1995

Enhancement of macrophage microbicidal activity: supplemental arginine and citrulline augment nitric oxide production in murine peritoneal macrophages and promote intracellular killing of Trypanosoma cruzi.

The generation of nitric oxide (NO) is largely responsible for the intracellular killing of Trypanosoma cruzi by activated macrophages. The present study was carried out to determine whether the production of NO by activated murine macrophages cultured in physiologic levels of arginine can be augmented by increasing the availability of arginine, the substrate for NO biosynthesis. Increased exogenous arginine or citrulline resulted in a significant increase in NO production and complete clearance of the parasites by activated macrophages. As citrulline fully substituted for arginine in supporting NO production and trypanocidal activity, these results demonstrate the expression of a highly active citrulline-NO cycle in activated macrophages and that levels of arginine in plasma are limiting with respect to both NO production and trypanocidal activity in these cells. The results indicate that increasing plasma substrate levels for both arginine and NO biosynthesis may represent a means of enhancing microbicidal activity in vivo.

Animals↗

PubMed1995

Sources of arginine for induced nitric oxide synthesis in the isolated perfused liver.

Hepatocytes can be stimulated to express high levels of inducible nitric oxide synthase (iNOS), which utilizes arginine for nitric oxide (NO) synthesis. Hepatocytes also synthesize and catabolize arginine, an intermediate in the urea cycle, raising the possibility that the urea pathway may provide substrate for hepatic NO synthesis. To identify the sources of arginine for iNOS, we measured the release of NO-2 + NO-3 and urea in isolated rat livers perfused in a recirculation model with a Krebs-Henseleit-bicarbonate buffer containing either no added amino acid, arginine, or precursors for urea synthesis. To induce iNOS expression, rats were injected with killed Corynebacterium parvum (C. parvum) or with endotoxin. In livers from C. parvum- and endotoxin-treated rats, we found that 1) an intracellular source of arginine exists that provides substrate to iNOS; 2) additional exogenous arginine increase NO synthesis, demonstrating that endogenous arginine is insufficient for maximal NO synthesis; and 3) an increase in the rate of endogenous arginine synthesis within the urea cycle is inefficient in increasing NO synthesis, demonstrating the independence of the two pathways in the liver.

Animals↗

PubMed1995

Immunocytochemical study of the degradation of elastic fibers in a living extracellular matrix.

We used ultrastructural and immunocytochemical technique to follow the movement of human neutrophil elastase (HNE) and porcine pancreatic elastase (PPE) through a living extracellular matrix produced by cultured smooth muscle cells and to compare the effect of the two elastases on elastic fibers in situ. Although both enzymes solubilize elastin purified from these cultures at similar rates, PPE solubilized 11.5 times more elastin from the intact cultures than did HNE. The difference in the rate of elastin solubilization from the cultures parallels the degree of elastic fiber degradation and the emphysema-inducing potency of the two elastases when they are instilled into animal lungs. Immunohistochemical studies employing antibodies to HNE and PPE revealed that PPE penetrates the smooth muscle cell cultures more readily than does HNE. Because the amount of elastin in these cultures increases with increasing distance from the free surface, the lesser amounts of elastin solubilized by HNE may be partly due to poor penetration of HNE into the living extracellular matrix, resulting in limited access to elastin substrate. Ultrastructural and immunocytochemical studies indicated, however, that even when HNE does have access to elastin substrate, it is less efficient than PPE at penetrating and degrading individual elastic fibers.

Animals↗

PubMed1995

Expression of the citrulline-nitric oxide cycle in rodent and human pancreatic beta-cells: induction of argininosuccinate synthetase by cytokines.

Nitric oxide (NO) may be a mediator of beta-cell damage in insulin-dependent diabetes mellitus. beta-Cells express the inducible form of NO synthase (iNOS) and produce large amounts of NO upon exposure to cytokines. iNOS requires the amino acid arginine for NO formation. It has been shown in other cell types that interferon-gamma (IFN gamma) and bacterial lipopolysaccharide induce the enzyme argininosuccinate synthetase (AS), enhancing the capacity of these cells to regenerate arginine from citrulline and maintain NO production in the presence of low arginine concentrations. To characterize the messenger RNA (mRNA) expression of AS in insulin-producing cells, RINm5F cells (RIN cells) were exposed to interleukin-1 beta (IL-1 beta) or to tumor necrosis factor-alpha plus IFN gamma. After 4-6 h, there was a significant and parallel induction of AS and iNOS mRNA. IL-1 beta-induced AS and iNOS mRNA expression was prevented by an inhibitor of the activation factor NF-kappa B pyrrolidine diaminoguanidine, an inhibitor of gene transcription (actinomycin D), and a blocker of protein synthesis (cycloheximide), suggesting coregulation of AS and iNOS by cytokines. RIN cells exposed to IL-1 beta in the presence of citrulline but the absence of arginine had increased AS enzyme activity and produced NO, demonstrating that cytokine-induced AS mRNA expression is accompanied by increased AS activity. Both adult rat islets exposed to IL-1 beta and human pancreatic islets cultured in the presence of IL-1 beta, tumor necrosis factor-alpha, and IFN gamma were able to use citrulline to regenerate arginine and produce NO. Taken as a whole, the present data suggest that regulation of AS activity may play a role in modulation of NO production in both rodent and human insulin-producing cells.

Animals↗

PubMed1995

The diversion of mentally ill persons from jails to community-based services: a profile of programs.

OBJECTIVES: A major proposal for appropriately treating persons with mental illnesses who have been arrested is to divert them from jail to community-based mental health programs. However, there are few available definitions, guidelines, and principles for developing effective diversion programs. The goal of this research was to determine the number and kinds of jail diversion programs that exist, how they are set up, and which types of programs are effective. METHODS: On the basis of information gathered during a national mail survey (n = 1263) and follow-up telephone survey of 115 responding jails, 18 sites were selected for on-site interviews based on perceived effectiveness and presence of a formal diversion program. RESULTS: Data are presented from a national sample of jail diversion programs (n = 18). Key factors for developing diversion programs and descriptors of effective programs are presented. CONCLUSIONS: It is clear that controlled, longitudinal studies of these programs' effectiveness, using client-based and organizational outcome measures, are badly needed.

Case Management↗

PubMed1995

Prevention of oxidative damage to rat lens by pyruvate in vitro: possible attenuation in vivo.

Studies have been conducted to assess the possible preventive effect of pyruvate against lens protein oxidation and consequent denaturation and insolubilization. Rat lens organ culture system was used for these studies. The content of water insoluble proteins (urea soluble) increased if the lenses were cultured in medium containing hydrogen peroxide. Incorporation of pyruvate in the medium prevented such insolubilization. The insolubilization was associated primarily with loss of gamma crystallin fraction of the soluble proteins. PAGE analysis demonstrated that insolubilization is related to -S-S- bond formation which was preventable by pyruvate. Since pyruvate is a normal tissue metabolite the findings are considered pathophysiologically significant against cataract formation. This was apparent by the prevention of selenite cataract in vivo by intraperitoneal administration of pyruvate.

Adenosine Triphosphate↗

PubMed1994

Induction of mutations at the hypoxanthine phosphoribosyl transferase (HPRT) locus in AHH-1 human lymphoblastoid cells.

Cells from the human lymphoblastoid cell line, AHH-1, were exposed to two direct-acting mutagens, ethyl methanesulfonate (EMS) and ethyl nitrosourea (ENU), and to three carcinogens that require metabolic activation to an electrophile, benzo[a]pyrene (B(a)P), 6-aminochrysene (6-AC), and 6-nitrochrysene (6-NC); mutation induction at the HPRT locus was quantified by resistance to 6-thioguanine (6-TGr). Exposure of AHH-1 cells to either EMS or ENU resulted in a concentration-dependent increase in mutant frequency at the HPRT locus. When AHH-1 cells were exposed to B(a)P, the increase in mutant frequency at the HPRT locus was marginally significant linearly and significant quadratically. The 32P-postlabeling assay revealed the formation of DNA adducts derived from (+/-)anti-benzo[a]pyrene-trans-7,8-dihydrodiol-9,10-epoxide which may account for the increase in 6-TGr clones. Although DNA adducts could be detected by the 32P-postlabeling assay in both 6-NC- and 6-AC-treated AHH-1 cells, exposure to 6-AC or 6-NC did not result in a concentration-dependent increase in mutant frequency at the HPRT locus. Our results are consistent with the results of previous studies which indicate that EMS and ENU are effective inducers of 6-TGr clones as is B9(a)P when activated to an electrophile. In 6-NC- and 6-AC-exposed cells, low levels of N-hydroxy-6-aminochrysene-derived adducts were detected in only 6-NC-exposed cells. No 6-aminochrysene-1,2-dihydrodiol-derived adducts were detected following 6-NC or 6-AC exposure. Minimal metabolic activation of 6-NC or 6-AC by AHH-1 cells may account for the lack of a positive mutagenic response for either 6-AC or 6-NC.

Alkylating Agents↗

PubMed1994

Regulation of gene expression of branched-chain keto acid dehydrogenase complex in primary cultured hepatocytes by dexamethasone and a cAMP analog.

The present study demonstrates that dexamethasone and 8-(4-chlorophenylthio)adenosine 3',5'-monophosphate (CPT-cAMP), a cAMP analog, increase the substrate flux through branched-chain keto acid dehydrogenase (BCKDH) in primary rat hepatocytes cultured in defined medium. Maximum response (2.7-fold increase in flux) was observed when hepatocytes were cultured with 1 microM dexamethasone plus 50 microM CPT-cAMP for 24 h. This increase in the flux rate was accompanied by significant increases in both the basal and total activities of BCKDH (2.2- and 2.0-fold, respectively), without any significant change in the activity state of this enzyme. The increase in BCKDH activity was the result of increased protein mass of E1 alpha (3.2-fold), E1 beta (2.9-fold), and E2 (1.6-fold) subunits of BCKDH, indicating that E2 is the limiting subunit for the expression of BCKDH. The relative abundance of mRNAs encoding the E1 alpha, E1 beta, and E2 subunits of BCKDH increased by 7.4-, 21.7-, and 4.8-fold, respectively. We conclude that increased flux through BCKDH in hepatocytes cultured with dexamethasone and CPT-cAMP is due to increased expression of BCKDH subunit genes. However, nonstoichiometric expression of individual subunits and the corresponding mRNAs suggests regulation of BCKDH also at translational and post-translational steps.

3-Methyl-2-Oxobutanoate Dehydrogenase (Lipoamide)↗

PubMed1994

The role of programmed cell death in the toxicity of the mutagens, ethyl methanesulfonate and N-ethyl-N'-nitrosourea, in AHH-1 human lymphoblastoid cells.

In order to determine the pathway for cell death in alkylating agent-exposed human lymphoblastoid cells, AHH-1 cells were exposed to either ethyl methanesulfonate (EMS) or ethyl nitrosourea (ENU) and the effect on relative cell growth and plating efficiency quantified. Flow cytometric (FCM) assays were utilized to quantify cell viability and to determine if cell death occurred through necrosis or apoptosis. As expected, exposure to the simple ethylating agents resulted in concentration-dependent decreases in plating efficiencies at each time interval after exposure (Days 0, 2, 3 and 7). EMS exposure did not significantly affect the relative cell growth, in contrast to ENU exposure, which inhibited cell growth. The FCM viability assay, based on light scatter characteristics, revealed that exposure to either alkylating agent resulted in a significant reduction in the percentage of viable cells. The results of the FCM dye-exclusion assays revealed that while necrosis occurred in EMS- and ENU-exposed cells, the primary manner of cell death was apoptosis. AHH-1 cells were stained with propidium iodide and fluorescein diacetate, the population of cells sorted electronically and the cell type (necrotic, apoptotic or viable) confirmed morphologically. Our results clearly indicate that exposure to EMS or ENU results in the movement of AHH-1 cells into the pathway for apoptosis and cell death.

Apoptosis↗

PubMed1994

Coinduction of nitric oxide synthase and argininosuccinate synthetase in a murine macrophage cell line. Implications for regulation of nitric oxide production.

In macrophages and other cell types, bacterial lipopolysaccharide and certain cytokines stimulate nitric oxide (NO) production via expression of the inducible isoform of nitric oxide synthase (NOS). Citrulline, which is the coproduct of NOS-catalyzed metabolism of arginine, can be recycled to arginine by the action of argininosuccinate synthetase and argininosuccinate lyase, which are present at high levels in hepatocytes and renal tubular cells but normally at very low levels in other cell types such as macrophages. The present study demonstrates that lipopolysaccharide and interferon-gamma, which induce NOS in the murine macrophage cell line RAW 264.7, also coinduce activity and mRNA for argininosuccinate synthetase, which is limiting for arginine synthesis. Argininosuccinate lyase activity and mRNA abundance are unaffected. Induction of argininosuccinate synthetase is not blocked by NG-monomethyl-L-arginine, a potent inhibitor of NOS, indicating that argininosuccinate synthetase induction is not the consequence of depleting cellular arginine levels by NOS. Because plasma levels of arginine are limiting for NO synthesis, enhanced cellular capacity to regenerate arginine from citrulline could play a significant role in regulating NO production, especially under conditions where the inducible isoform of NOS is expressed.

Amino Acid Oxidoreductases↗

PubMed1994

New insights into the regulation of inducible nitric oxide synthesis.

Recent studies have identified the induction of nitric oxide (NO) synthesis in many cell types as part of the host response to sepsis and inflammation. Induced NO can have a variety of effects which may be detrimental or beneficial during sepsis or inflammation, depending on amount, duration, and anatomic site of synthesis. As arginine is the only physiological nitrogen donor for NO synthesis, metabolism of this amino acid may play an important role in regulation of NO synthesis during sepsis. This review will discuss the roles NO plays in sepsis and the potential impact of arginine metabolism on NO synthesis.

Animals↗

PubMed1993

The genetic toxicology of 5-fluoropyrimidines and 5-chlorouracil.

The halogenated pyrimidines were synthesized in the 1950s as potential anti-tumor agents after the discovery that certain tumors preferentially incorporated uracil rather than thymine into the DNA. The fluorinated derivatives are widely recognized today as effective treatment modalities, especially with tumors of the head, neck and breast. Mechanistically, efficacy of the fluorinated pyrimidines results from the ability of these compounds to incorporate into RNA and inhibit its maturation to those forms necessary for cellular metabolism and from the inhibition of the enzyme, thymidylate synthetase, which controls the biosynthesis of thymine and DNA synthesis. The 5-fluoropyrimidines can incorporate into DNA, but the contribution of this phenomenon to the overall efficacy of this class of chemotherapeutic agents is not totally resolved. Evidence exists that this class of compounds possesses the properties to induce genotoxic effects, both in bacterial and eukaryotic cells. Most notably, these effects include the induction of cellular toxicity and the induction of chromosome aberrations. The biology and chemistry of the chlorinated pyrimidines were first explored as a possible means of sensitizing the DNA to ionizing radiation in a manner similar to the sensitization observed when DNA incorporates bromodeoxyuridine. This approach was not utilized clinically. The genetic toxicology of this compound became important with the discovery of the ribonucleoside in the effluents of sewage treatment plants. Evidence is now available that the chlorinated pyrimidines, upon conversion to deoxyribonucleosides, are effective mutagens, clastogens and toxicants, as well as extremely effective inducers of sister-chromatid exchanges.

Animals↗

PubMed1993

Electron microscopic study of human lung tissue after in vitro exposure to elastase.

Much of the experimental evidence supporting the hypothesis that pulmonary emphysema results from an imbalance between elastases and anti-elastases in the lung comes from animal models. The present study was designed to examine the effects on human lung tissue of the two elastases that have been most widely used to produce these animal models. Lung tissue was exposed in vitro to human neutrophil elastase (HNE) or porcine pancreatic elastase (PPE). Although both enzymes solubilized protein at similar rates, PPE solubilized elastin five times faster than did HNE. Ultrastructurally, HNE-exposed tissue exhibited fewer damaged elastic fibers as well as some fibers that were damaged at the edges, whereas the interior of the fiber appeared intact. Elastic fibers showing damage only at the periphery were not seen in tissue exposed to PPE. Immunocytochemical studies in which antibodies to HNE and PPE were applied to thin sections of Lowicryl-embedded tissue indicated that both of these elastases could be detected in association with elastic fibers, but only in areas of the fiber that showed morphological evidence of elastase injury. Both HNE and PPE removed fibronectin from basement membranes (as determined by loss of binding of fibronectin antibodies after exposure to elastase), but neither elastase was detected on basement membrane. Loss of epithelial cells usually accompanied elastic fiber damage by HNE but not PPE.

Animals↗