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Biomedical subjects

S B Smith

Publications and source records attributed to S B Smith.

At least 73 records · Page 4Linked to original sources
PubMed1998

Candidate gene analysis of GH1 for effects on growth and carcass composition of cattle.

We present an approach to evaluate the support for candidate genes as quantitative trait loci (QTLs) within the context of genome-wide map-based cloning strategies. To establish candidacy, a bacterial artificial chromosome (BAC) clone containing a putative candidate gene is physically assigned to an anchored linkage map to localise the gene relative to an identified QTL effect. Microsatellite loci derived from BAC clones containing an established candidate gene are integrated into the linkage map facilitating the evaluation by interval analysis of the statistical support for QTL identity. Permutation analysis is employed to determine experiment-wise statistical support. The approach is illustrated for the growth hormone 1 (GH1) gene and growth and carcass phenotypes in cattle. Polymerase chain reaction (PCR) primers which amplify a 441 bp fragment of GH1 were used to systematically screen a bovine BAC library comprising 60,000 clones and with a 95% probability of containing a single copy sequence. The presence of GH1 in BAC-110R2C3 was confirmed by sequence analysis of the PCR product from this clone and by the physical assignment of BAC110R2C3 to bovine chromosome 19 (BTA19) band 22 by fluorescence in situ hybridisation (FISH). Microsatellite KHGH1 was isolated from BAC110R2C3 and scored in 529 reciprocal backcross and F2 fullsib progeny from 41 resource families derived from Angus (Bos taurus) and Brahman (Bos indicus). The microsatellite KHGH1 was incorporated into a framework genetic map of BTA19 comprising 12 microsatellite loci, the erythrocyte antigen T and a GH1-TaqI restriction fragment length polymorphism (RFLP). Interval analysis localised effects of taurus vs. indicus alleles on subcutaneous fat and the percentage of either extractable fat from the Iongissimus dorsi muscle to the region of BTA19 harbouring GH1.

Animals↗
PubMed1998

Lithium chloride does not inhibit the proliferation of L6 myoblasts by decreasing intracellular free inositol.

We conducted a series of experiments to determine whether lithium chloride (LiCl) inhibited the proliferation of L6 myoblasts by reducing the availability of intracellular free inositol. After the myoblasts were plated in DMEM + 10% fetal bovine serum (FBS) for 24 h, medium was replaced with DMEM + 10% FBS containing 0 (control), 5, 10, or 20 mM LiCl. Cell number, protein content, and [3H]thymidine incorporation into DNA were determined at 24-h intervals. Control cells exhibited a 3.8-fold increase in cell number by 96 h in culture. Although 5 mM LiCl did not affect the rate or extent of proliferation, 10 and 20 mM LiCl caused 36 and 86% decreases, respectively (P < .05), in cell number by 96 h in culture. The effects of LiCl could not be overcome by the addition of free inositol (up to 20 mM) to the medium. Lithium chloride caused 4.6- and 7.3-fold increases (P < .05) in lactate dehydrogenase activity in culture media after 96 h of exposure to 10 and 20 mM LiCl, respectively, indicating loss of viability after chronic treatment. However, the acute effects of LiCl after 24 h of treatment were reversible, as indicated by a rapid resumption of proliferation following removal of LiCl. Concentrations of 5, 10, and 20 mM LiCl caused 4.7-, 8.2-, and 9.1-fold increases (P < .05), respectively, in the accumulation of [3H]inositol within the inositol monophosphate pool. Treatment of cells with 10 and 20 mM LiCl also increased (P < .05) label recovered as inositol bisphosphate. Rather than depress phosphoinositide synthesis, the addition of 10 and 20 mM LiCl dose-dependently increased (P < . 05) the incorporation of [3H]inositol into phosphatidylinositol and phosphatidylinositol-4-phosphate. These results indicate that LiCl does not decrease proliferation of L6 myoblasts via a depletion in the intracellular free inositol pool. Instead, LiCl may block the hydrolysis of phosphatidyl inositides.

Animals↗
PubMed1998

Physiological adaptations in adipose tissue of Brahman vs Angus heifers.

Nonpregnant yearling Brahman (n = 12) and Angus (n = 12) heifers were equally allocated to two dietary treatments in a replicated study to examine responses in lipid metabolism to nutritional treatments consisting of a moderate energy diet (2.0 Mcal ME/kg) fed at maintenance and a 2.5 x maintenance high-energy diet (2.4 Mcal ME/kg) fed for 30 d. In vitro lipogenesis and the activities of lipoprotein lipase (LPL) and hormone-sensitive lipase (HSL) were determined in perianal subcutaneous adipose tissue biopsies at the start and end of the trial. At the start of the trial, breeds had similar (P > .10) rates of lipogenesis and LPL activity. Brahman had greater (P < .05) HSL activity than Angus at the start of the trial and tended (P < .07) to have greater HSL activity at the end. Diet did not influence (P > .10) HSL activity. Heifers on the high-energy, higher-intake diet had greater lipogenesis (P < .001) and LPL activity (P < .01) than those on the moderate-energy diet. Inclusion of body condition score (BCS) nested within breed as a covariate explained breed differences for lipogenesis (P < .05). Thus, by including the covariate, the two breeds had similar (P > .10) rates of lipogenesis at the end of the trial. When adjusted for BCS nested within breed, Brahman had greater (P < .05) LPL activity than Angus.

Adaptation, Physiological↗
PubMed1998

Recombinant bovine somatotropin (rbST) administration to creep-fed beef calves increases muscle mass but does not affect satellite cell number or concentration of myosin light chain-1f mRNA.

Our objective in this study was to determine the effect of recombinant bovine somatotropin (rbST) on indices of muscle development in creep-fed beef calves. Crossbred steer calves were assigned to one of two treatment groups: control (sham-injected; n = 12) or rbST-treated (.09 mg x kg(-1) x d(-1); n = 12). Calves were injected every 14 d starting at d 28 of age and were weaned at 205 d of age. Supplemental creep feed was supplied free access to all calves to compensate for an expected increased protein and energy requirement in calves given rbST. Biopsy (d 100) and slaughter (d 206) samples of semitendinosus muscle were evaluated for satellite cell, myofiber nuclei numbers, and myosin light chain (MLC-1f) mRNA quantification. Myofiber nuclei and satellite cell numbers per 100 myofibers and MLC-1f mRNA:rRNA ratios at 100 and 206 d of age were not different (P > .10) between control and rbST-treated calves. Total gain, ADG, quality grade, femur length, percentage kidney, pelvic, and heart fat, dressing percentage, plasma IGF-I, and plasma urea nitrogen concentrations did not differ (P > .10) between control and rbST-treated calves. However, rbST-treated calves had larger longissimus muscle areas (P < .03), less marbling (P < .001), higher carcass conformation scores (P < .04), greater mass of separated muscle (P < .03), more ground meat (P < .01), and heavier carcass weights (P < .05) than control calves. Thus, rbST treatment increased muscle characteristics while nuclei number and MLC-1f mRNA concentrations remained the same, implying that the additional muscle growth was in a normal fashion.

Animal Feed↗
PubMed1997

Analysis of esterification of retinoids in the retinal pigmented epithelium of the Mitf-vit (vitiligo) mutant mouse.

PURPOSE: Mice homozygous for the vitiligo mutation of the microphthalmia (Mitf) gene have a retinal degeneration characterized by slow loss of photoreceptor cells and compromised retinal pigment epithelial (RPE) structure and function. The levels of retinyl esters, which are essential for generation of 11-cis-retinaldehyde for the formation of rhodopsin, were reported previously to be elevated by 6 weeks postnatally in the RPE of vitiligo mutant mice. The purpose of the present study was to determine whether this elevation was due to increased activity of lecithin:retinol acyl transferase (LRAT) the enzyme that converts all-trans-retinol to retinyl esters. METHODS: Retinoids extracted from the RPE and neural retina of mutant and normal mice ages 2, 4, 6 and 8 weeks were analyzed by reversed-phase HPLC. The esterification capacity of the RPE to convert 3H-retinol to 3H-retinyl ester was determined by HPLC in mutant and normal mice at 3 and 9 weeks. RESULTS: Retinyl ester levels were elevated significantly in the mutant RPE as early as postnatal week 2 and were four-fold greater by 8 weeks. The esterification assay indicated no significant differences between mutants and controls at 3 weeks. At 9 weeks, the esterification activity of the mutant RPE was significantly reduced compared to controls rather than elevated. CONCLUSIONS: The data suggest that the accumulation of retinyl esters is not due to increased LRAT activity. Alternative explanations for the retinyl ester accumulation are discussed.

Acyltransferases↗
PubMed1997

The p38/reactivating kinase mitogen-activated protein kinase cascade mediates the activation of the transcription factor insulin upstream factor 1 and insulin gene transcription by high glucose in pancreatic beta-cells.

Insulin upstream factor 1 (IUF1), a transcription factor present in pancreatic beta-cells, binds to the sequence C(C/T)TAATG present at several sites within the human insulin promoter. Here we isolated and sequenced cDNA encoding human IUF1 and exploited it to identify the signal transduction pathway by which glucose triggers its activation. In human islets, or in the mouse beta-cell line MIN6, high glucose induced the binding of IUF1 to DNA, an effect mimicked by serine/threonine phosphatase inhibitors, indicating that DNA binding was induced by a phosphorylation mechanism. The glucose-stimulated binding of IUF1 to DNA and IUF1-dependent gene transcription were both prevented by SB 203580, a specific inhibitor of stress-activated protein kinase 2 (SAPK2, also termed p38 mitogen-activated protein kinase, reactivating kinase, CSBP, and Mxi2) but not by several other protein kinase inhibitors. Consistent with this finding, high glucose activated mitogen-activated protein kinase-activated protein kinase 2 (MAPKAP kinase-2) (a downstream target of SAPK2) in MIN6 cells, an effect that was also blocked by SB 203580. Cellular stresses that trigger the activation of SAPK2 and MAPKAP kinase-2 (arsenite, heat shock) also stimulated IUF1 binding to DNA and IUF1-dependent gene transcription, and these effects were also prevented by SB 203580. IUF1 expressed in Escherichia coli was unable to bind to DNA, but binding was induced by incubation with MgATP, SAPK2, and a MIN6 cell extract, which resulted in the conversion of IUF1 to a slower migrating form. SAPK2 could not be replaced by p42 MAP kinase, MAPKAP kinase-2, or MAPKAP kinase-3. The glucose-stimulated activation of IUF1 DNA binding and MAPKAP kinase-2 (but not the arsenite-induced activation of these proteins) was prevented by wortmannin and LY 294002 at concentrations similar to those that inhibit phosphatidylinositide 3-kinase. Our results indicate that high glucose (a cellular stress) activates SAPK2 by a novel mechanism in which a wortmannin/LY 294002-sensitive component plays an essential role. SAPK2 then activates IUF1 indirectly by activating a novel IUF1-activating enzyme.

Amino Acid Sequence↗
PubMed1997

Ionic effects on the elasticity of single DNA molecules.

We used a force-measuring laser tweezers apparatus to determine the elastic properties of lambda-bacteriophage DNA as a function of ionic strength and in the presence of multivalent cations. The electrostatic contribution to the persistence length P varied as the inverse of the ionic strength in monovalent salt, as predicted by the standard worm-like polyelectrolyte model. However, ionic strength is not always the dominant variable in determining the elastic properties of DNA. Monovalent and multivalent ions have quite different effects even when present at the same ionic strength. Multivalent ions lead to P values as low as 250-300 A, well below the high-salt "fully neutralized" value of 450-500 A characteristic of DNA in monovalent salt. The ions Mg2+ and Co(NH3)63+, in which the charge is centrally concentrated, yield lower P values than the polyamines putrescine2+ and spermidine3+, in which the charge is linearly distributed. The elastic stretch modulus, S, and P display opposite trends with ionic strength, in contradiction to predictions of macroscopic elasticity theory. DNA is well described as a worm-like chain at concentrations of trivalent cations capable of inducing condensation, if condensation is prevented by keeping the molecule stretched. A retractile force appears in the presence of multivalent cations at molecular extensions that allow intramolecular contacts, suggesting condensation in stretched DNA occurs by a "thermal ratchet" mechanism.

Cobalt↗
PubMed1997

Folding-unfolding transitions in single titin molecules characterized with laser tweezers.

Titin, a giant filamentous polypeptide, is believed to play a fundamental role in maintaining sarcomeric structural integrity and developing what is known as passive force in muscle. Measurements of the force required to stretch a single molecule revealed that titin behaves as a highly nonlinear entropic spring. The molecule unfolds in a high-force transition beginning at 20 to 30 piconewtons and refolds in a low-force transition at approximately 2.5 piconewtons. A fraction of the molecule (5 to 40 percent) remains permanently unfolded, behaving as a wormlike chain with a persistence length (a measure of the chain's bending rigidity) of 20 angstroms. Force hysteresis arises from a difference between the unfolding and refolding kinetics of the molecule relative to the stretch and release rates in the experiments, respectively. Scaling the molecular data up to sarcomeric dimensions reproduced many features of the passive force versus extension curve of muscle fibers.

Amino Acid Sequence↗
PubMed1997

Dietary whole cottonseed depresses lipogenesis but has no effect on stearoyl coenzyme desaturase activity in bovine subcutaneous adipose tissue.

The primary objective of this study was to determine the effect of long-term feeding of whole cottonseed (WCS) on lipogenesis and stearoyl-coenzyme A desaturase activity in growing steers. Brangus steers were fed either a control, cornbased diet (n = 11) or 30% WCS (n = 12). The 30% WCS contributed an estimated 6.6% additional lipid to the diet. Steers fed the added WCS had greater live weights (P = 0.04) and kidney, pelvic, and heart fat (P = 0.005). Subcutaneous fat thickness was not different (P = 0.20) between treatment groups, although WCS elicited an increase in the proportion of large diameter subcutaneous adipocytes. The rate of [U-14C]acetate incorporation into fatty acids in subcutaneous adipose tissue was reduced by dietary WCS (171.4 vs 122.1 nmol x 100 mg adipose tissue-1 x 2 hr-1, P = 0.03), indicating that the increased dietary fat depressed de novo lipogenesis. Hepatic desaturase activity was much lower than that of subcutaneous adipose tissue, a feature common to cattle. We anticipated that added WCS also would depress stearoyl-coenzyme A desaturase activity in subcutaneous adipose tissue and liver due to its cyclopropene fatty acid content. Instead, desaturase activity was numerically (although not significantly) greater in liver (P = 0.37) and adipose tissue (P = 0.23).

Adipose Tissue↗
PubMed1997

Delayed rhodopsin regeneration and altered distribution of interphotoreceptor retinoid binding protein (IRBP) in the mi(vit)/mi(vit) (vitiligo) mouse.

Rhodopsin regeneration requires attachment between the retinal pigment epithelium (RPE) and rod outer segments; however, in experimentally induced retinal detachment, rhodopsin regeneration can be restored partially upon addition of IRBP (interphotoreceptor retinoid binding protein). The mi(vit)/mi(vit) (vitiligo) mutant mouse, a model of slowly progressing photoreceptor cell degeneration, has a marked elevation of IRBP at 4 weeks as well as progressive detachment of the retina. The purpose of this study was to determine whether this mutant is capable of regenerating rhodopsin within a few hours following an intense light bleach. Rhodopsin regeneration was determined spectrophotometrically in mice after an intense one hour light bleach followed by 0,1,2,4 or 24 h of dark recovery. IRBP was localized immunohistochemically in fixed frozen tissue at the light microscopic level and in LR Gold embedded tissue at the ultrastructural level. Rhodopsin regeneration experiments indicated that rhodopsin levels following 0,1,2 and 4 h dark-recovery were significantly less in mi(vit)/mi(vit) mutants compared with controls. Immunohistochemical detection of IRBP indicated an altered distribution of the protein in the mutant mice compared with controls. There was accumulation in the region of the inner segments in mutant retinas rather than distribution only to the RPE/OS apical regions as in controls. The data suggest that regeneration of rhodopsin is reduced by 4 weeks postnatally in the mi(vit)/mi(vit) mouse. There is partial detachment of the retina at this age; and IRBP, thought to be essential for proper functioning of the visual cycle, is aberrantly distributed in this mutant.

Animals↗
PubMed1997

Prepartum protein restriction does not alter norepinephrine-induced thermogenesis or brown adipose tissue function in newborn calves.

We examined the effect of prepartum protein restriction on thermogenesis and several aspects of perirenal (brown) adipose tissue (BAT) in newborn calves. Lipid synthesis and morphology also were compared between BAT and sternum (white) adipose tissue. During the last 140 d of gestation, heifers were fed isocaloric diets containing adequate (10.4%) or restricted (average of 6.8%, dry matter basis) levels of protein. Body condition scores and weight gain during gestation were significantly lower in heifers fed the restricted-protein diet. However, newborn calf birth weight, calf BAT weight and composition, and calf thermoneutral metabolic rates were not affected by prepartum protein restriction. Similarly, visceral organ weights, except for lung plus trachea, were not affected (P > 0.10) by prepartum protein treatment. Peak metabolic rates were not affected (P > 0.10) by prepartum protein treatment and on average were twice the thermoneutral metabolic rates. Consistent with this, BAT of calves from heifers fed adequate- or restricted-protein diets did not differ in lipid synthesis, cellularity, or uncoupling protein mRNA:28S rRNA ratios. Although both perirenal and sternum adipocytes were mostly unilocular, perirenal adipocytes contained numerous large mitochondria with well-differentiated cristae; sternum adipocytes contained a small number of mitochondria with poorly developed cristae. Fatty acid biosynthesis from acetate was high in BAT (55-57 nmol acetate incorporated.100 mg-1.h-1) but barely detectable in sternum adipose tissue. Conversely, fatty acid biosynthesis from glucose was 80-110% higher in sternum adipose tissue than in BAT (4.5 vs 2.1-2.5 nmol glucose incorporated.100 mg-1.h-1). Thus maternal protein restriction severely affected heifers but had no effect on neonatal calf thermogenesis or BAT function.

Adipose Tissue, Brown↗
PubMed1997

Bone registration method for robot assisted surgery: pedicle screw insertion.

A registration method that identifies bone geometry with respect to a robotic manipulator arm is presented. Although the method is generally applicable to many orthopaedic internal fixation procedures, it was only demonstrated for the insertion of pedicle screws in vertebral bodies for spine fixation. The method relies upon obtaining an impression of the vertebral bodies. Computerized tomography (CT) scans of both vertebrae and mould are reconstructed using a computer aided engineering (CAE) system. From the reconstructions, the surgeon is able to do preoperative planning including selection of pedicle screw diameter, direction of screw through pedicle, point of entry and length of engagement. The three-dimensional models are than meshed to determine positions of the surgeon's preoperative plan relative to the mould. Intra-operative positions are defined in space by a mechanical fixture rigidly attached to the mould and designed to allow a manipulator end-effector to recognize the global coordinates of the in vivo spine. The theory and methodology were validated using a five-axis manipulator arm. This initial presentation assumes and allows no relative motion between vertebrae in vivo.

Bone Screws↗
PubMed1997

Live animal performance, carcass traits, and meat palatability of calf- and yearling-fed cloned steers.

Two groups of Brangus steers produced by nuclear transplantation cloning were used in parallel studies investigating the impact of calf- and yearling-feeding. The first group (n = 8) were fed as calves (CF; n = 4) or yearlings (YF; n = 4) to a constant age end point of 16 mo. The second group (n = 10) were fed as calves (CF; n = 5) or yearlings (YF; n = 5) to a constant live weight end point (530 kg). When slaughtered at the same age, CF and YF steers did not differ (P > .05) in feedlot ADG, but the CF steers were heavier and had higher dressing percentages, numeric yield grades, and quality grades (P < .05). Top loin steaks from the groups of steers did not differ (P > .05) in palatability traits. When fed to a constant live weight, the YF steers gained more rapidly (P < .05) and had lower (P < .05) numeric yield grades than did CF steers. Again CF steers had higher (P < .05) dressing percentages. There was no difference (P > .05) between the treatments in carcass quality grade or meat palatability characteristics. Thus, when finished to a constant weight end point, YF steers gained more rapidly, with no adverse effects on carcass quality grade or palatability traits; however, CF steers consistently produced higher dressing percentages, largely due to greater external fatness.

Aging↗
PubMed1997

Effect of patient position on the consistency of placing the rearfoot at subtalar neutral.

The ability of foot care specialists to place a rearfoot at the subtalar neutral position is important for the care of patients who require foot orthosis prescription, fabrication, and management. Although some clinicians perform this procedure with the patient in the prone position, others prefer a seated or standing approach. This study examined whether patient position and preferred patient position influence the ability of clinicians to place a subject's rearfoot at the subtalar neutral position. The results suggest the following: a clinician's ability to find the subtalar neutral position is better with a seated subject; clinicians do not necessarily perform better assessments on a subject in a position corresponding to their patient position preference; and clinicians who prefer their patients prone generally have more flexible and reproducible observations. In addition, the findings suggest that the nature and relative importance of the tactile and visual cues used by clinicians to place a rearfoot at the subtalar neutral position warrant further exploration.

Adult↗
PubMed1996

Real-time imaging of the reorientation mechanisms of YOYO-labelled DNA molecules during 90 degrees and 120 degrees pulsed field gel electrophoresis.

Pulsed field gel electrophoresis (PFGE) techniques have been developed to overcome the limitations of conventional electrophoresis and to increase the separation to DNA chromosomes of few megabase pairs in size. Despite of the large success of these techniques, the various separation protocols employed for PFGE experiments have been determined empirically. However, a deep understanding of the molecular mechanisms of motion responsible for DNA separation becomes necessary for the rational optimization of these techniques. This paper shows the first clear observations of individual molecules of DNA during the reorientation process in 90 degrees PFGE and 120 degrees PFGE. Real-time visualization of the DNA dynamics during PFGE was possible with the use of an epi-illumination fluorescence microscope specifically equipped to run these experiments and by staining the DNA with YOYO-1 (1,1'-(4,4,7,7-tetramethyl-4,7-diazaundecamethylene)-bis-4-[3-meth yl -2,3-dihydro-(benzo-1,3-oxazole)-2-methyl-idene]-quinolinium tetraiodide). This dye forms a very stable, highly fluorescent complex with double-stranded DNA and dramatically improves the quality of the DNA images. The results of computer simulations used to reproduce the molecular mechanisms of motion as well as the DNA separation features are also discussed.

Benzoxazoles↗