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Biomedical subjects

M S Clegg

Publications and source records attributed to M S Clegg.

At least 19 recordsLinked to original sources
PubMed2006

The effect of exposure to irrigant solutions on apical dentin biofilms in vitro.

This study assessed the effectiveness of different concentrations of sodium hypochlorite (NaOCl), 2% chlorhexidine (CHX) (Vista Dental Products, Racine, WI), and BioPure MTAD (Dentsply Endodontics-Tulsa Dental, Tulsa, OK). Intracanal contents were collected from 10 patients diagnosed with chronic apical periodontitis. The samples were cultured on hemisections of root apices to generate a polymicrobial biofilm. Each biofilm was separately immersed in 6% NaOCl, 3% NaOCl, 1% NaOCl, 2% CHX, 1% NaOCl followed by BioPure MTAD, and sterile phosphate buffered solution (PBS). SEM analysis showed 6% NaOCl and 3% NaOCl were capable of disrupting and removing the biofilm; 1% NaOCl and 1% NaOCl followed by MTAD were capable of disrupting the biofilm, but not eliminating bacteria; 2% CHX was not capable of disrupting the biofilm. Viable bacteria could not be cultured from specimens exposed to 6% NaOCl, 2 % CHX, or 1% NaOCl followed by BioPure MTAD. These results indicate that 6% NaOCl was the only irrigant capable of both rendering bacteria nonviable and physically removing the biofilm.

Biofilms↗
PubMed2004

Cardiac abnormalities induced by zinc deficiency are associated with alterations in the expression of genes regulated by the zinc-finger transcription factor GATA-4.

Zinc (Zn) deficiency during pregnancy results in a wide variety of developmental abnormalities. The objective of this study was to determine if expression of cardiac developmental genes regulated by Zn-finger transcription factors could be modulated during dietary Zn deficiency. Rats were fed 0.5 (low Zn) or 90 (controls) microg Zn/g diet throughout pregnancy. Fetal development was examined and RNA isolated at gestation day (GD) 13 and 20. Cardiac abnormalities were detected at GD 20 in 82% of fetuses from dams fed low Zn diets compared with only 2% in controls. Cardiac developmental gene expression regulated by the Zn-finger transcription factor, GATA-4, was measured by quantitative reverse transcriptase-polymerase chain reaction (RT-PCR). In GD 13 and 20 hearts, two genes critical for heart development, alpha-myosin heavy chain (alpha-MHC) and cardiac troponin I (cTnI), were down-regulated in Zn-deficient fetuses. Expression of alpha-MHC was 66 and 40% lower at GD 13 and 20, respectively, in fetuses from dams fed low Zn diets compared with fetuses from control dams (p<0.05). Fetal cardiac TnI RNA levels were reduced 40 and 45% at GD 13 and 20 in the Zn-deficient group compared with controls (p<0.05). Fetal cardiac transcript levels of GATA-4 and MHox, a gene regulated by a helix-loop-helix transcription factor, whose expressions are not Zn-dependent, were unaffected by diet. These data indicated that alterations in gene regulation might be an underlying mechanism of cardiac abnormalities. Dysfunction of other Zn-dependent transcription factors may be an integral part of the extensive teratogenesis associated with Zn deficiency.

Abnormalities, Multiple↗
PubMed2001

Retinol binding protein expression is induced in HepG2 cells by zinc deficiency.

Zinc (Zn) deficiency is often associated with low plasma vitamin A (retinol) concentrations. It has been suggested that the reduction in plasma retinol is secondary to reduced liver retinol binding protein (RBP) synthesis. In the present study, RBP expression was determined in HepG2 cells cultured in either Zn adequate media or chelated media containing varying concentrations of Zn. Levels of RBP mRNA increased in a time- and Zn concentration-dependent manner such that 0.5 microM Zn-treated cells exhibited a >7.5-fold increase while cells treated with 15 microM Zn were increased 2.9-fold at 72 h compared to controls. RBP protein also progressively increased by 72 h to levels >8-fold and 3-fold higher than controls, in 0.5 microM and 15 microM Zn-treated cells, respectively. The increase in RBP occurred without any change in DNA concentration between groups through 72 h. The Zn deficiency-induced elevations in RBP transcript levels could be reversed within 24-48 h of repletion in Zn adequate media. Thus, the reductions in plasma retinol observed in Zn deficiency are in part a direct consequence of the deficiency.

Actins↗
PubMed2001

A decrease in intracellular zinc level precedes the detection of early indicators of apoptosis in HL-60 cells.

Low extracellular zinc concentrations have been associated with the induction of apoptosis. To assess the relationship between intracellular zinc concentration and the rate of apoptosis, cells were grown in media containing 0.5, 25, or 50 microM zinc and analyzed by flow cytometry or fluorescence microscopy. Cells grown in 0.5 microM zinc medium over 48 h showed a successive decrease in intracellular zinc concentration measured by the zinc-specific fluorophore, zinquin. After 18 h in 0.5 microM zinc medium, rhodamine 123 retention decreased. However, the addition of 10 microM zinc to the 0.5 microM medium before 16 h in culture restored rhodamine retention in the cells. After 30 h there was an increase in the number of cells cultured in 0.5 microM zinc medium that bound annexin V-FITC. These data indicated that decreased intracellular zinc concentration preceded early markers of apoptosis, with alterations in mitochondrial transmembrane potential preceding the loss of polarity in the cell membrane.

Annexin A5↗
PubMed2001

Short-term zinc deficiency affects nuclear factor-kappab nuclear binding activity in rat testes.

We reported previously that feeding zinc-deficient diets for 14 d altered the oxidant defense system in the testes of young male rats and increased levels of lipid, protein and DNA oxidation in this tissue. In this study, we investigated the early involvement of oxidative stress in zinc deficiency-induced testicular pathology. Weanling male rats (17 d old) were given free access to a control (25 microg Zn/g) or a zinc-deficient (0.5 microg Zn/g) diet, or restricted access to the control diet at a level of intake similar to that of rats fed the 0.5 microg Zn/g diet (restricted group) for 7 d. Rats fed the low zinc diet were characterized by low testes zinc and alkaline phosphatase activity compared with ad libitum and restricted controls. Testes protein and lipid oxidation variables did not differ among the groups. Higher than normal (P < 0.05) activities of CuZn (CuZnSOD) and Mn (MnSOD) superoxide dismutases were observed in the low zinc group. Glutathione peroxidase and glutathione reductase activities did not differ among the groups. Total glutathione concentrations were lower in the low zinc and restricted groups than in the control group (P < 0.05). The testes nuclear binding activities of two transcription factors sensitive to oxidants [nuclear factor (NF)-kappaB and AP-1] were assessed. AP-1 nuclear binding activity did not differ among the groups, but NF-kappaB nuclear binding activity was lower in the low zinc group than in the control groups (P < 0.05). We suggest that the reduction in NF-kappaB binding reflects an early response to zinc deficiency-induced oxidative stress.

Animals↗
PubMed2000

Zinc-deficient rat embryos have increased caspase 3-like activity and apoptosis.

Caspase activity is a hallmark of apoptosis. Given that maternal zinc (Zn) deficiency results in apoptosis in the rat embryo, we assessed caspase activity in Zn-deficient embryos. Mid-gestation rat embryos were collected from dams fed either a Zn-deficient (0.5 Zn/g) diet ad libitum, or a Zn-adequate (25 microg Zn/g) diet ad libitum or pair fed to dams fed the Zn-deficient diet. Embryos from dams fed the Zn-adequate diet had a normal level of cell death, while embryos from the dams fed the Zn-deficient diet had either increased or normal levels of cell death. Zn-deficient embryos displaying increased cell death had increased caspase activity. Embryos with normal levels of cell death, regardless of maternal diet, had similar caspase activities. Thus, Zn-deficiency-induced apoptosis in vivo is associated with increased caspase activity.

Animals↗
PubMed2000

Zinc deficiency induces oxidative stress and AP-1 activation in 3T3 cells.

It has been postulated that one mechanism underlying zinc deficiency-induced tissue alterations is excessive cellular oxidative damage. In the present study we investigated if zinc deficiency can induce oxidative stress in 3T3 cells and trigger select intracellular responses that have been associated to oxidative stress. Cells were exposed to control media or to chelated media containing 0.5, 5, or 50 microM zinc for 24 or 48 h. The oxidative status of the cells was evaluated as an increase in the fluorescence of the probe 5(or 6)-carboxy-2'7'-dichlorodihydrofluorescein diacetate (DCDCDHF). After 24 and 48 h of exposure, the fluorescence intensity was significantly higher (4- to 15-fold) in the 0.5 and 5 microM Zn groups compared to the 50 microM Zn and control groups. The activity of the antioxidant enzymes CuZn (CuZnSOD) and Mn (MnSOD) superoxide dismutases was significantly higher in the 0.5 and 5 microM Zn cells compared to the 50 microM Zn and control groups at both the 24 and 48 h time points. These higher activities were associated with higher levels of MnSOD mRNA. After 24 h in culture, the level of activated AP-1 was markedly higher in the 0.5 and 5 microM Zn cells than in the control (72 and 58%, respectively) and 50 microM Zn cells (73 and 60%, respectively). NF-kappaB binding activity was lower in the 0.5 and 5 microM Zn cells than in controls. Thus, oxidative stress is induced by zinc deficiency in 3T3 cells. This oxidative stress results in an upregulation of oxidant defense mechanisms.

3T3 Cells↗
PubMed2000

Paraparesis, hypermanganesaemia, and polycythaemia: a novel presentation of cirrhosis.

Progressive myelopathy is a rare complication of chronic hepatic disease which has never been reported in the paediatric age group. We describe the 11 year course of an adolescent male with hepatic myelopathy caused by cryptogenic micronodular cirrhosis. His condition has been associated with persistent polycythaemia and extraordinary increases of whole blood manganese, with magnetic resonance imaging evidence of manganese deposition within the basal ganglia and other regions of the brain. The patient has developed neither liver failure nor parkinsonism. The pathophysiological bases of this multiorgan system disorder are described.

Adolescent↗
PubMed1998

Copper, lysyl oxidase, and extracellular matrix protein cross-linking.

Protein-lysine 6-oxidase (lysyl oxidase) is a cuproenzyme that is essential for stabilization of extracellular matrixes, specifically the enzymatic cross-linking of collagen and elastin. A hypothesis is proposed that links dietary copper levels to dynamic and proportional changes in lysyl oxidase activity in connective tissue. Although nutritional copper status does not influence the accumulation of lysyl oxidase as protein or lysyl oxidase steady state messenger RNA concentrations, the direct influence of dietary copper on the functional activity of lysyl oxidase is clear. The hypothesis is based on the possibility that copper efflux and lysyl oxidase secretion from cells may share a common pathway. The change in functional activity is most likely the result of posttranslational processing of lysyl oxidase. Copper is essential for organic cofactor formation in amine oxidases such as lysyl oxidase. Copper-containing amine oxidases have peptidyl 2,4,5 tri(oxo)phenylalanine (TOPA) at their active centers. TOPA is formed by copper-catalyzed oxidation of tyrosine, which takes place as part of Golgi or trans-Golgi processing. For lysyl oxidase, recent evidence (Science 1996;273:1078-84) indicates that as an additional step, a lysyl group at the active center of lysyl oxidase reacts with TOPA or its precursor to form lysyl tyrosylquinone.

Animals↗
PubMed1998

The influence of manganese deficiency on serum IGF-1 and IGF binding proteins in the male rat.

Young male rats subjected to a dietary manganese (Mn) deficiency respond to the deficiency by reducing their growth rate. The growth hormone (GH)/insulin-like growth factor (IGF) axis is critical for linear growth; this system is exquisitely sensitive to the nutritional state of the animal. In this study, we examined circulating GH, IGF-1, and insulin levels in Mn-deficient (-Mn; fed a 0.5 microg Mn/g diet) and sufficient (+Mn; fed a 45 microg Mn/g diet) male Sprague-Dawley rats. Additionally, we examined the distribution of circulating IGF binding proteins (IGFBPs) in animals of both dietary groups as these proteins modulate IGF-1 action in vivo and in vitro, and have been demonstrated to be altered in a number of nutritional and physiological states. Body weight was significantly reduced in -Mn relative to +Mn rats. Consistent with other studies, daily food intake was not altered. However, cumulative food intake (over 3 months) was marginally lower in -Mn versus +Mn animals. -Mn animals displayed lower circulating concentrations of IGF-1 (66% of control levels) and insulin (60% of control levels) despite having significant elevations in circulating GH levels relative to +Mn animals (140% of control levels). The IGFBP profile of -Mn animals reflected their elevated GH status, as we observed increased binding of tracer (125I-IGF-1) to the circulating IGFBP-3 complex (120% of control binding) using native chromatography techniques. Interestingly, the lower circulating insulin concentrations of -Mn animals did not result in dramatic elevations in lower-molecular-weight binding proteins. In summary, we demonstrate that in young male rats, Mn deficiency is associated with alterations in IGF metabolism. These alterations may contribute to the growth and bone abnormalities observed in -Mn animals.

Animals↗
PubMed1997

Incorporation of copper into lysyl oxidase.

Lysyl oxidase is a copper-dependent enzyme involved in extracellular processing of collagens and elastin. Although it is known that copper is essential for the functional activity of the enzyme, there is little information on the incorporation of copper. In the present study we examined the insertion of copper into lysyl oxidase using 67Cu in cell-free transcription/translation assays and in normal skin fibroblast culture systems. When a full-length lysyl oxidase cDNA was used as a template for transcription/translation reactions in vitro, unprocessed prolysyl oxidase appeared to bind copper. To examine further the post-translational incorporation of copper into lysyl oxidase, confluent skin fibroblasts were incubated with inhibitors of protein synthesis (cycloheximide, 10 microg/ml), glycosylation (tunicamycin, 10 microg/ml), protein secretion (brefeldin A, 10 microg/ml) and prolysyl oxidase processing (procollagen C-peptidase inhibitor, 2.5 microg/ml) together with 300 microCi of carrier-free 67Cu. It was observed that protein synthesis was a prerequisite for copper incorporation, but inhibition of glycosylation by tunicamycin did not affect the secretion of 67Cu as lysyl oxidase. Brefeldin A inhibited the secretion of 67Ci-labelled lysyl oxidase by 46%, but the intracellular incorporation of copper into lysyl oxidase was not affected. In addition, the inhibition of the extracellular proteolytic processing of prolysyl oxidase to lysyl oxidase had minimal effects on the secretion of protein-bound 67Cu. Our results indicate that, similar to caeruloplasmin processing [Sato and Gitlin (1991) J. Biol. Chem. 266, 5128-5134], copper is inserted into prolysyl oxidase independently of glycosylation.

Bone Morphogenetic Protein 1↗
PubMed1997

Comparative effects of essential and nonessential metals on preimplantation mouse embryo development in vitro.

It is well recognized that deficiencies of essential trace elements during early development can result in structural abnormalities and/or embryonic death. Recently, there has been increasing interest in the concept that small excesses of essential metals can also have negative effects on the developing embryo. We hypothesized that, with respect to toxicity, metals with similar physico-chemical properties would act by similar mechanisms to influence the preimplantation embryo. In the current study we investigated the influence of four essential (Cu, Mn, Fe, Zn), and eight nonessential (Cr, Hg, Pb, V, Al, Ag, Cd, As) metals on mouse preimplantation embryonic development. Two cell stage mouse embryos were cultured for 72 h in media containing varying metal concentrations (0.05 - 200 microM). Embryo cell differentiation and proliferation were respectively assessed by scoring for blastocyst formation and final embryo cell number. Both nonessential and essential metals were embryotoxic at relatively low concentrations. However, in contrast to our expectations, at similar molar concentrations, redox active essential metals were less toxic than non-redox active nonessential metals. These data suggest that direct metal binding to critical membrane sites and/or intracellular ligands, including protein and nucleic acids, may trigger abnormal development and death prior to metal-associated oxidative damage.

Animals↗
PubMed1997

Serum concentrations of zinc and copper in bull terriers with lethal acrodermatitis and tail-chasing behavior.

OBJECTIVE: To establish similarities or differences in tissue concentrations of zinc, copper, and iron in Bull Terriers with lethal acrodermatitis (LAD) and tail-chasing behavior (TCB) and to confirm the suspicion that copper is involved in the etiopathogenesis of LAD. SAMPLES: Serum samples from 29 Bull Terriers (9 control dogs, 6 dogs with LAD, 14 dogs with TCB), and liver and kidney specimens from 2 dogs and 1 and 4 dogs with LAD or TCB, respectively. PROCEDURE: Serum, liver, and kidney mineral (zinc, copper, and iron) concentrations in Bull Terriers with LAD or TCB and in a group of control dogs were analyzed, using flame atomic absorption after wet ashing technique. RESULTS: Serum zinc and copper concentrations were lower (P < 0.05) in dogs with LAD, compared with values for control dogs and dogs with TCB. Liver zinc and copper concentrations were similar to serum values. Kidney zinc and copper concentrations were similar among the 3 groups. Serum, liver, and kidney iron concentrations had a wide range of variability within all 3 groups. CONCLUSION: Copper deficiency is associated with LAD. The primary cause of LAD may be copper deficiency, with zinc involved secondarily, or combined zinc and copper deficiencies. The role of ion deficiency in TCB was not clarified. CLINICAL RELEVANCE: Serum zinc and copper concentrations should be determined when LAD is suspected.

Acrodermatitis↗
PubMed1996

Modulation of lysyl oxidase by dietary copper in rats.

Lysyl oxidase levels were estimated in rat tissues using an enzyme-linked immunosorption assay (ELISA) and a functional assay standardized against known amounts of purified lysyl oxidase. High concentrations of lysyl oxidase (> or = 150 micrograms/g of tissue or packed cells) were detected in connective tissues, such as tendon and skin. Values for aorta, kidney, lung and liver ranged from 30 to 150 micrograms/g of tissue; values for skeletal muscle and diaphragm were < 30 micrograms/g tissue. Purified rat skin lysyl oxidase catalyzed the release of 50-100 Bq of tritium per micrograms enzyme in assays that used 3H-elastin-rich substrates. In dense connective tissues, good agreement was obtained for the values from ELISA and those derived from measurements of functional activity in aorta, lung, skin and tendon (r2 > 0.9). When egg white-based experimental diets containing 2 or 10 micrograms/g added copper were fed to weanling rats, values for skin lysyl oxidase functional activity in the group fed 2 micrograms/g added copper were one-third to one-half the values for skin lysyl oxidase functional activity in rats fed 10 micrograms/g copper. This reduction in lysyl oxidase activity, however, had minimal effect on indices of collagen maturation in rat skin, e.g., collagen solubility in neutral salt and dilute acid or the levels of acid stable cross-links. Moreover, copper deficiency did not influence the steady-state levels of lysyl oxidase specific mRNA in rat skin or the apparent amounts of lysyl oxidase in rat skin as determined by ELISA. These observations underscore that the concentration of lysyl oxidase is relatively high in dense corrective tissues, and although decreasing dietary copper influences functional activity, there is little apparent effect on the production of lysyl oxidase protein.

Administration, Oral↗
PubMed1996

Mineral values of selected plant foods common to southern Burkina Faso and to Niamey, Niger, west Africa.

Wild and cultivated fruits, leaves, nuts, seeds, spices and vegetables from southern Burkina Faso and Niamey, Niger, were analysed for their copper, iron, magnesium, manganese and zinc concentrations and compared to imported, exotic reference foods found within the study area. The species analysed covered a broad spectrum of local diet; 33 were wild and 16 were cultivated. The edible wild plants were often the highest in mineral concentrations. Five species analysed, exhibited consistently high mineral values, specifically, Adansonia digitata, Boerhavia diffusa, Cerathoteca sesamoides, Sclerocarya birrea and Xylopia sp. The latter was particularly high in zinc, an observation which suggests that there may be a solid rationale for local traditions which recommended its consumption during pregnancy and lactation. Respondents indicated that during times of drought, wild plants were not consumed in the volume they once were, due to changes of infrastructure and in famine relief programmes.

Adult↗
PubMed1995

Zinc deficiency-induced anorexia influences the distribution of serum insulin-like growth factor-binding proteins in the rat.

Zinc (Zn) deficiency can result in severe growth retardation in mammals, and in a number of animal model systems it leads to low circulating insulin-like growth factor-I (IGF-I) concentrations. Using a weanling male rat model and a number of feeding schemes, we show that in addition to lower circulating IGF-I concentrations, Zn deficiency leads to alterations in the distribution of serum IGF-binding proteins (IGFBPs). Serum from Zn-deficient animals labeled in vitro with [125I]IGF-I displayed three peaks of tracer activity: 150 kd (IGFBP-3), 37 kd (IGFBP-2 and -1), and 8 kd (free [125I]IGF-I). Relative to controls, Zn-deficient animals demonstrated more tracer binding in the 37-kd region, whereas less was found in the 150- and 8-kd peaks. Serum from chronically calorie-restricted fed animals displayed [125I]IGF-I binding profiles similar to Zn-deficient serum, implicating Zn deficiency-induced anorexia as the principle factor underlying both the lower circulating IGF-I and the alterations in IGFBP profiles. Concentrations of IGFBP-4 were unaffected by diet manipulation based on sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE)/Western ligand blot (WLB) analysis.

Animals↗
PubMed1991

Influence of hypertension and dietary copper on indexes of copper status in rats.

The Dahl salt-sensitive rat was used to investigate the effect of hypertension on indexes of copper status and to determine the extent to which dietary manipulation of copper attenuated, or exacerbated, the rate of sodium chloride-induced hypertension. Weanling salt-sensitive rats were fed, in a 2 x 3 factorial design, one of six diets that contained one of three levels of copper (2.0 micrograms/g marginal, 12 micrograms/g adequate, or 50 micrograms/g supplemental) and either control (0.4%) or high (4%) levels of sodium. Diets were fed to the rats for 11 weeks. Rats fed the high sodium diets were characterized by high plasma copper concentrations and ceruloplasmin activities compared with their respective control sodium rats. The magnitude of the sodium-induced rise in plasma copper and ceruloplasmin was affected by dietary copper intake; however, dietary copper intake had no effect on the development of hypertension in the high sodium groups. These results suggest that altered copper metabolism is secondary, rather than primary, to the development of sodium chloride-induced hypertension in the salt-sensitive rat. Red blood cell superoxide dismutase activity was reduced in rats fed the low copper diets compared with the adequate and supplemented copper groups. At the lower levels of copper intake, sodium chloride-induced hypertension increased red blood cell superoxide dismutase activity in a manner consistent with the plasma copper and ceruloplasmin changes observed. However, at adequate or supplemental levels of dietary copper, red blood cell superoxide dismutase activity plateaued, suggesting possible saturation of copper at sites of hematopoeisis.

Animals↗