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D E Smith

Publications and source records attributed to D E Smith.

At least 73 records · Page 4Linked to original sources
PubMed1999

Competitive inhibition of glycylsarcosine transport by enalapril in rabbit renal brush border membrane vesicles: interaction of ACE inhibitors with high-affinity H+/peptide symporter.

PURPOSE: To examine the inhibitory potential of enalapril [and other angiotensin converting enzyme (ACE) inhibitors] on glycylsarcosine (GlySar) transport by the high-affinity renal peptide transporter. METHODS: Studies were performed in rabbit renal brush border membrane vesicles in which the uptake of radiolabeled GlySar was examined in the absence and presence of captopril, enalapril, enalaprilat, fosinopril, lisinopril, quinapril, quinaprilat, ramipril and zofenopril. RESULTS: Kinetic analyses demonstrated that enalapril inhibited the uptake of GlySar in a competitive manner (Ki approximately 6 mM). Fosinopril and zofenopril had the greatest inhibitory potency (IC50 values of 55 and 81 microM, respectively) while the other ACE inhibitors exhibited low-affinity interactions with the renal peptide transporter. With respect to structure-function, ACE inhibitor affinity was strongly correlated with drug lipophilicity (r = 0.944, p < 0.001 for all ACE inhibitors; r = 0.983, p < 0.001 without enalaprilat, quinaprilat and quinapril). CONCLUSIONS: The data suggest that enalapril and GlySar compete for the same substrate-binding site on the high-affinity peptide transporter in kidney, and that ACE inhibitors can interact with the renal carrier and inhibit dipeptide transport.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1999

Dietary conjugated linoleic acid influences the immune response of young and old C57BL/6NCrlBR mice.

Aging is associated with a decline in the immune response in mammals. Conjugated linoleic acid (CLA) has been suggested to have immunoenhancing properties. We examined the influence of dietary CLA on the immune response of young and old mice. Forty young (4 mo) and 40 old (22 mo) mice consumed ad libitum diets containing 0 or 1 g CLA /100 g for 8 wk. Splenocytes from half of the mice were isolated to evaluate proliferation to concanavalin A (Con A) (0.5, 1.5, 5.0 mg/L) and phytohemagglutinin A (PHA) (5, 20, 40 mg/L) and lipopolysaccharide (LPS) (5, 15, 30 mg/L), natural killer cell (NK) activity and prostaglandin (PG)E2 and interleukin (IL)-2 production. The remaining mice were used to evaluate in vivo delayed-type hypersensitivity (DTH) skin response. There was a significant decline due to age in response to all three mitogens tested (P < 0. 05). CLA supplementation significantly increased all CLA isomers measured in hepatic neutral lipids and phospholipids (P < 0.05). Young mice fed 1% CLA had greater splenocyte proliferation in response to Con A (0.5 and 5.0 mg/L) and PHA (40 mg/L) (P < 0.05) than young mice fed control diet. Old mice fed 1 g CLA/100 g had significantly higher proliferative response to optimal concentrations of Con A (1.5 mg/L) (P < 0.001) than the mice fed the control diet. Old mice fed the control diet had significantly lower splenocyte IL-2 production than the young mice (P < 0.005). CLA-supplemented young mice had significantly higher splenocyte IL-2 production than those fed the control diet (P < 0.05). CLA had no effect on NK cell activity, PGE2 production or DTH in young or old mice. Further studies are needed to determine the mechanism of CLA-induced enhancement of IL-2 production and T cell proliferation.

Aging↗
PubMed1999

Identification of Id2 as a globin regulatory protein by representational difference analysis of K562 cells induced to express gamma-globin with a fungal compound.

A fungus-derived compound (OSI-2040) which induces fetal globin expression in the absence of erythroid cell differentiation was identified in a high-throughput drug discovery program. We utilized this compound to isolate gamma-globin regulatory genes that are differentially expressed in OSI-2040-induced and uninduced cells in the human erythroleukemia cell line K562. Representational difference analysis (RDA) of cDNA revealed several genes that were significantly up- or down-regulated in OSI-2040-induced cells. One gene whose expression was markedly enhanced was the gene for the helix-loop-helix (HLH) transcription factor Id2. Southern analysis of RDA amplicons demonstrated progressive enrichment of Id2 with each successive subtraction of uninduced cDNA from induced cDNA. Northern analysis of OSI-2040-induced K562 cells confirmed that Id2 expression was directly up-regulated coordinately with gamma-globin. Analysis of other inducers of fetal globin demonstrated up-regulation of Id2 with sodium butyrate but not with hemin. Retrovirus-mediated overexpression of Id2 in K562 cells reproduced the enhancement of endogenous globin expression observed with OSI-2040 induction. Functional assays demonstrated that an E-box element in hypersensitivity site 2 is required for Id2-dependent enhancement of gamma-promoter activity. Protein binding studies suggest that alterations in E-box site occupancy by basic HLH proteins may influence this activity, thus expanding the potential role of these factors in globin gene regulation.

Blotting, Northern↗
PubMed1999

Localization of PEPT1 and PEPT2 proton-coupled oligopeptide transporter mRNA and protein in rat kidney.

To determine the renal localization of oligopeptide transporters, Northern blot analyses were performed and polyclonal antisera were generated against PEPT1 and PEPT2, the two cloned rat H+/peptide transporters. Under high-stringency conditions, a 3.0-kb mRNA transcript of rat PEPT1 was expressed primarily in superficial cortex, whereas a 3.5-kb mRNA transcript of PEPT2 was expressed primarily in deep cortex/outer stripe of outer medulla. PEPT1 antisera detected a specific band on immunoblots of renal and intestinal brush-border membrane vesicles (BBMV) with an apparent mobility of approximately 90 kDa. PEPT2 antisera detected a specific broad band of approximately 85 kDa in renal but not in intestinal BBMV. PEPT1 immunolocalization experiments showed detection of a brush border antigen in S1 segments of the proximal tubule and in the brush border of villi from all segments of the small intestine. In contrast, PEPT2 immunolocalization was primarily confined to the brush border of S3 segments of the proximal tubule. All other nephron segments in rat were negative for PEPT1 and PEPT2 staining. Overall, our results conclusively demonstrate that although PEPT1 is expressed in early regions of the proximal tubule (pars convoluta), PEPT2 is specific for the latter regions of proximal tubule (pars recta).

Animals↗
PubMed1999

Glycylsarcosine uptake in rabbit renal brush border membrane vesicles isolated from outer cortex or outer medulla: evidence for heterogeneous distribution of oligopeptide transporters.

Studies were initially performed in rabbit brush border membrane vesicles (BBMV) prepared from whole cortex plus outer medulla. In these studies using combined tissues, two distinct peptide/H+transport systems were found for glycylsarcosine (GlySar) uptake, with one representing a low-affinity/high-capacity system (Vm1 = 974 pmol/mg/10 sec and Km1 = 4819 microM) and the other a high-affinity/low-capacity system (Vm2 = 220 pmol/mg/10 sec and Km2 = 96 microM). Thus, under linear conditions, the high-affinity transporter accounted for about 92% of the total transport of dipeptide. To better define the regional heterogeneity of peptide transporter activity in kidney, subsequent studies were performed in vesicles prepared from separately harvested outer cortical and outer medullary tissue. In BBMV studies prepared from outer cortex, two saturable components were revealed for GlySar transport (low-affinity/high-capacity transport system: Vm1 = 1921 pmol/mg/10 sec and Km1 = 11714 microM; high-affinity/low-capacity transport system: Vm2 = 143 pmol/mg/10 sec and Km2= 138 microM). However, in BBMV studies prepared from outer medulla, only one saturable component was revealed for GlySar transport (high-affinity/low-capacity transport system:Vm2= 168 pmol/mg/10 sec and Km2 = 230 microM). Overall, these studies support the contention that peptides are handled sequentially in kidney (ie, first by low-affinity transporter PEPT1, and then by high-affinity transporter PEPT2) and that PEPT2 is primarily responsible for the renal reabsorption of peptides and peptidomimetics.

Animals↗
PubMed1999

A high throughput platform for systematic evolution of ligands by exponential enrichment (SELEX).

The systematic evolution of ligands by exponential enrichment (SELEX) process is a combinatorial chemistry method for the isolation of nucleic acid ligands (aptamers) that bind to a desired target molecule with high affinity. In order to increase throughput via automation, we have adapted the SELEX process for protein targets to a robotics-compatible microtiter plate format. A remarkable feature of the platform is that targets are immobilized by hydrophobic adsorption onto the plate surface. Hydrophobic immobilization procedures are simple and require no specialized modification of the protein target. This format was tested by manually performing four independent SELEX experiments. All were concluded within 8 rounds of selection and yielded aptamers that bind in solution to their respective protein target, calf intestinal alkaline phosphatase, human alpha-thrombin or human platelet derived growth factor, with equilibrium dissociation constants below 3 x 10-10 M.

Alkaline Phosphatase↗
PubMed1998

Observations of the north polar region of Mars from the Mars orbiter laser altimeter.

Elevations from the Mars Orbiter Laser Altimeter (MOLA) have been used to construct a precise topographic map of the martian north polar region. The northern ice cap has a maximum elevation of 3 kilometers above its surroundings but lies within a 5-kilometer-deep hemispheric depression that is contiguous with the area into which most outflow channels emptied. Polar cap topography displays evidence of modification by ablation, flow, and wind and is consistent with a primarily H2O composition. Correlation of topography with images suggests that the cap was more spatially extensive in the past. The cap volume of 1.2 x 10(6) to 1.7 x 10(6) cubic kilometers is about half that of the Greenland ice cap. Clouds observed over the polar cap are likely composed of CO2 that condensed out of the atmosphere during northern hemisphere winter. Many clouds exhibit dynamical structure likely caused by the interaction of propagating wave fronts with surface topography.

Carbon Dioxide↗
PubMed1998

Relation of self-image to body size and weight loss attempts in black women: the CARDIA study. Coronary Artery Risk Development in Young Adults.

It has been suggested that the prevalence of obesity in black women is high partly because self-image in black women is not strongly dependent on body size. To determine associations between self-image, body size, and dieting behavior among black women, the authors assessed an Appearance Evaluation Subscale (AES) score (range, 1-5), a Body Image Satisfaction (BIS) score (range, 2-11), and reported dieting behavior in a population-based sample of 1,143 black women aged 24-42 years from the fourth follow-up examination (1992-1993) of the Coronary Artery Risk Development in Young Adults (CARDIA) Study. Lower AES and BIS scores indicate poorer self-image and lower body size satisfaction, respectively. After adjustment for age, education, smoking, and physical activity, women in the lowest, middle, and highest tertiles of body mass index (weight (kg)/height (m)2) had mean AES scores of 3.7, 3.3, and 2.9, respectively (p < 0.001), and mean BIS scores of 7.8, 6.7, and 5.9, respectively (p < 0.001). After additional control for body mass index as a continuous variable, both AES and BIS scores were inversely related to ever dieting, current dieting, and previous weight loss of 10 pounds (4.5 kg) or more in all tertiles of body mass index. These results suggest that among black women, a higher body mass index is associated with poorer self-image and lower body size satisfaction and that these perceptions may be an avenue to promoting weight control.

Adolescent↗
PubMed1998

Calorie restriction, stress and the ubiquitin-dependent pathway in mouse livers.

Calorie restriction (R) is the only known method to delay the aging process and extend mean and maximal lifespan in rodents. R has been shown to delay the age-related accumulation of damaged proteins and to protect organisms from various stresses which can produce damaged proteins. Such stresses include irradiation, heat shock, and oxidative stress. The ubiquitin- and ATP-dependent proteolytic pathway (UPP) has been associated with the degradation of abnormal and/or damaged proteins. We examined the effect of diet and oxidative stress on activities of the UPP in supernatants from livers taken from 23-month-old Emory mice which had been exposed to an in-vivo injection of paraquat. Paraquat induces oxidative stress by generating superoxide radicals. In livers from non-stressed animals, steady-state levels of endogenous ubiquitin conjugates, de novo conjugate formation, and E1 and E2 activities were significantly lower in R animals than in control (C) animals. However, after exposure to paraquat, levels of endogenous ubiquitin conjugates were significantly higher in R versus C animals, and de novo conjugate formation and E1 and E2 activities in R animals rose to levels which were indistinguishable from levels of these activities noted in C animals. R was associated with an increased ability to degrade beta-lactoglobulin by the UPP after an oxidative stress was imposed. Ability to degrade beta-lactoglobulin by the C or R livers in non-stressed animals was not significantly different. Taken together, these data indicate that oxidative stress in R animals is associated with enhanced levels of ubiquitin conjugates and that this enhancement may be due to an increase in UPP activity. These data also indicate that the ability to form ubiquitin conjugates and the UPP system does not change with oxidative stress in C animals. The latter is consistent with prior reports that suggests that older C animals may already be in a state of enhanced oxidative stress and that activities of the UPP provide a sensitive indicator of levels of cellular redox status.

Adenosine Triphosphate↗
PubMed1998

The effects of aging and calorie restriction on plasma nutrient levels in male and female Emory mice.

We examined the effect of diet, age (4.5, 13 and 23 months), and sex on plasma levels of retinol, tocopherol, ascorbate, cholesterol, glucose and glycohemoglobin in male and female Emory mice which were fed control (C) and 50% calorie restricted (R) diets. Results showed that C fed animals tended to have higher levels of plasma ascorbate (50-71%), cholesterol (23-71%), glucose (38-81%) and glycohemoglobin (50%). However, these diet differences varied with the age and sex of the animals. Plasma retinol levels were lower only in R males vs. C males (50%). Novel sex-related differences in levels of plasma retinol (2-fold higher in C male mice than in C or R female mice) are described. Aging was associated with trends towards lower levels of plasma ascorbate (14-25%), glucose (34-36%) and glycohemoglobin (47-57%) from 4.5 to 23 months of age. However, these age differences depended upon the diet and sex of the animals. These data suggest that lower plasma levels of glucose, glycosylated hemoglobin and cholesterol may be causally related to the life extension noted in R animals since elevated levels of these moieties have been related to aging. Since oxidative stress is thought to be causally related to aging it appears unlikely that retinol, tocopherol and ascorbate are causally related to R-induced life-extension.

Aging↗
PubMed1998

Disease incidence and longevity are unaltered by dietary antioxidant supplementation initiated during middle age in C57BL/6 mice.

The ability of augmented antioxidant consumption to alter disease incidence, lesion burden and/or longevity was studied in adult male C57BL/6 mice. Mice were fed modified AIN76 diet or modified AIN76 supplemented with vitamin E, glutathione (GSH), vitamin E and GSH, melatonin or strawberry extract starting at 18 months of age. All the mice in this study were heavier than reference populations of male C57BL/6 mice fed NIH-07 or NIH-31, which were maintained without a mid-life change in diet. Fatty liver, focal kidney atrophy and proteinacious casts in the renal tubules were observed more frequently in this study population than in the reference populations. Lesion burden and incidence of specific lesions observed amongst the various groups in this study did not differ. There were no differences observed for longevity of any of the study groups. The longevity observed in this study was similar to that previously reported for male C57BL/6 mice. Thus, diet supplementation with antioxidants initiated during middle age did not appear to affect age-associated lesions patterns, lesion burden or longevity for ad libitum fed male C57BL/6 mice.

Aging↗
PubMed1998

Regional pharmacokinetics of 5-fluorouracil in dogs: role of the liver, gastrointestinal tract, and lungs.

The purpose of this study was to determine the presence and extent of pulmonary elimination for 5-fluorouracil (FUra). A secondary aim was to characterize the relative importance of the liver, gastrointestinal tract, splanchnic region, and lungs toward the overall elimination of FUra. A total of 10 mixed-breed male and female dogs were used in these acute studies in which FUra was administered through a cephalic vein. Six dogs were studied at sequentially escalated dose rates of 0.125, 0.250, 0.500, 0.750, and 1.00 micromol/min/kg (8-fold range); four dogs were studied at sequentially escalated dose rates of 0.0625, 0.250, 0.750, 1.50, and 2.00 micromol/min/kg (32-fold range). Each infusion lasted 2 h, at which time steady-state plasma concentrations were obtained (i.e., portal vein, carotid artery, hepatic vein, and pulmonary artery), perfusion rates were measured (hepatic artery, portal vein, and cardiac output), and pharmacokinetic parameters were directly assessed. Pulmonary elimination of FUra was conclusively demonstrated. Although only 17% of the drug was extracted by the lungs at the lowest dose rate, pulmonary clearance (16.0 ml/min/kg) was on the order of splanchnic clearance (13.5 ml/min/kg), or larger. As the dose rate increased, pulmonary clearance was more easily saturated than splanchnic clearance. Thus, it appears that at increasing dose rates, the splanchnic region becomes a more significant pathway, whereas the lungs have a reduced role in the overall elimination of FUra.

Animals↗
PubMed1998

Aging, calorie restriction and ubiquitin-dependent proteolysis in the livers of Emory mice.

Calorie restriction (R), the only known method to delay the aging process and extend mean and maximal lifespan, has been shown to delay the age-related decline in protein degradation. There are several proteolytic pathways. The ubiquitin- and ATP-dependent proteolytic pathway (UPP) is frequently associated with degradation of damaged abnormal and/or regulatory proteins. We examined the effect of aging and R on supernatants of livers taken from young (4.5 months) and old (23 months) Emory mice. Aging was associated with increased levels of endogenous ubiquitin conjugates, enhanced ability to form high molecular weight conjugates and ubiquitin activating (E1) and ubiquitin conjugating (E2) activity in the control (C) liver supernatants. The age-related increase in levels of endogenous ubiquitin conjugates in liver appears to be primarily due to increased E1 and E2 activities. R prevented the age-related increase in E1 and E2 activity, and thus prevented the age-related increase in levels of ubiquitin conjugates. In spite of the age-related increase in ubiquitin conjugates, no age-related changes in ubiquitin-dependent proteolytic pathway were observed in the C animals. R was associated with an enhanced ability (130%) to degrade beta-lactoglobulin by the ubiquitin-dependent proteolytic pathway in livers from 4.5-month-old animals relative to age-matched C livers. However, rates of the ubiquitin-dependent degradation of beta-lactoglobulin in the 23-month-old C and R animals were indistinguishable. There were no age- or diet-related differences in the ability to degrade another substrate, oxidized ribonuclease (RNase).

Adenosine Triphosphate↗
PubMed1998

Topography of the northern hemisphere of Mars from the Mars Orbiter Laser Altimeter.

The first 18 tracks of laser altimeter data across the northern hemisphere of Mars from the Mars Global Surveyor spacecraft show that the planet at latitudes north of 50 degrees is exceptionally flat; slopes and surface roughness increase toward the equator. The polar layered terrain appears to be a thick ice-rich formation with a non-equilibrium planform indicative of ablation near the periphery. Slope relations suggest that the northern Tharsis province was uplifted in the past. A profile across Ares Vallis channel suggests that the discharge through the channel was much greater than previously estimated. The martian atmosphere shows significant 1-micrometer atmospheric opacities, particularly in low-lying areas such as Valles Marineris.

Atmosphere↗
PubMed1998

Safety and immunogenicity of a candidate therapeutic vaccine, p24 virus-like particle, combined with zidovudine, in asymptomatic subjects. Community HIV Research Network Investigators.

OBJECTIVES: To evaluate the impact of therapeutic immunization with p24 virus-like particle (VLP) and zidovudine (ZDV) on p24 antibody titre (primary endpoint), CD4+ cell counts, cellular responses to the immunogen and recall antigens, and viral load (secondary endpoints) in subjects with asymptomatic HIV infection and CD4+ counts greater than 400 x 10(6) cells/l. DESIGN: A double dummy, double-blind randomized placebo-controlled Phase II trial of the therapeutic vaccine p24-VLP, with or without ZDV. METHODS: ZDV-naive subjects were randomized to one of three groups for 6 months: group A, ZDV 200 mg three times daily plus intramuscular administration of alum adjuvant monthly; group B, ZDV 200 mg three times daily plus p24-VLP (500 microg) in intramuscular alum monthly; group C, placebo capsules plus p24-VLP (500 microg) in intramuscular alum monthly. Subjects were followed for a further 6 months. RESULTS: Sixty-one patients received vaccinations. The mean CD4+ cell counts pretherapy for groups A, B, and C were 605 +/- 25, 668 +/- 43, and 583 +/- 30 x 10(6) cells/l, respectively. Treatment was well tolerated. At both 24 and 52 weeks there were no significant differences between the treatment groups in terms of antibody responses to p24, CD4+ or CD8+ cell counts, viral load, T-cell responses to p24, p17, recall antigen or mitogen, or markers of immune activation, despite induction of antibody and proliferative responses to the carrier protein of the vaccine. CONCLUSION: Vaccination with p24-VLP was well tolerated. p24-VLP either alone or in combination with ZDV did not significantly alter either antibody or proliferative responses to p24, or CD4+ cell number, immune activation or viral load over 12 months.

AIDS Vaccines↗
PubMed1998

Determination of the population pharmacokinetic parameters of sustained-release and enteric-coated oral formulations, and the suppository formulation of diclofenac sodium by simultaneous data fitting using NONMEM.

Data from sustained-release and enteric-coated oral formulations, and the suppository formulation of diclofenac sodium are fitted simultaneously using NONMEM and the general linear model, ADVAN 5. Absorption and disposition parameters, serum levels, and absorption profiles were determined. The in vivo absorption profiles were determined using the program TOPFIT. The in vivo absorption for the sustained-release formulation is slow first order and follows a flip-flop model since disposition rate constants are greater than absorption rate constants. Absorption from the enteric-coated form is essentially complete (> or = 95%) at about 7.5 h, while it is 95% complete at 24 h from the sustained-release formulation. This suggests likely absorption from the colon in the case of the sustained-release formulation since absorption is only 75% complete during the first 10 h. The sustained-release relative bioavailability is 90-99%. Absorption from the suppository is essentially complete at about 4.5 h. However, the relative bioavailability of the suppository formulation is low (55%), since defecation may remove the drug from the absorption site before complete absorption.

Administration, Oral↗
PubMed1998

Targeted intraparenchymal delivery of human NGF by gene transfer to the primate basal forebrain for 3 months does not accelerate beta-amyloid plaque deposition.

Nerve growth factor therapy has been proposed as a potential means of preventing degeneration of basal forebrain cholinergic neurons in Alzheimer's disease and thereby improving cognition. However, NGF has been reported to upregulate expression of the beta-amyloid precursor protein, which in turn could accelerate deposition of "mature" beta-amyloid in the brain. To address this possibility, the brains of 16 adult and aged rhesus monkeys were examined for beta-amyloid plaque deposition in the presence or absence of NGF treatment. Six aged monkeys received intraparenchymal grafts into the cholinergic basal forebrain of autologous cells genetically modified to secrete NGF, six aged monkeys received intraparenchymal grafts of autologous control cells expressing the reporter gene beta-galactosidase, and four adult nonoperated monkeys served as additional controls. All brains were examined for expression of mature beta-amyloid using an antibody recognizing amino acids 1-40 of the beta-amyloid peptide. Amyloid plaques were systematically quantified in representative sections of the temporal, frontal, cingulate, insular, and parietal cortices and in the amygdala and hippocampus. Results disclosed that aging resulted in an increase in amyloid plaque formation: no plaques at all were detected in nonaged monkeys, whereas a mean of 20 +/- 13 plaques per section were present in control-aged monkeys. Aged subjects with intraparenchymal NGF-secreting grafts for 3 months contained a mean of 29 +/- 14 plaques per section, an amount that did not differ significantly from control-aged monkeys (P = 0.66). Thus, 3 months of intraparenchymal NGF delivery did not significantly increase beta-amyloid deposition.

Aging↗