Biomedical subjects

R J McCormick

Publications and source records attributed to R J McCormick.

At least 37 records · Page 2Linked to original sources

PubMed1995

Pre-bending of a promoter sequence enhances affinity for the TATA-binding factor.

TATA-binding protein (TBP) binds the minor groove of the TATA element with the DNA bent 80 degrees towards the major groove. A constrained minicircle strategy has been used to test the effect of DNA topology on the affinity of TBP for the TATA element. We report here that TBP bound to DNA which was slightly pre-bent towards the major groove with 100-fold higher affinity than unbent (linear) DNA of identical sequence and 300-fold higher affinity than DNA pre-bent towards the minor groove. Similar discrimination was observed with the holo-TFIID transcription complex. DNA topology, particularly bending, is determined by many factors including chromatin in cells and may, through changes in the affinity of the TATA factor, be important in the control of transcription.

DNA↗

PubMed1995

Collagen characteristics of skin, fell, and epimysium from rams, wethers, and zeranol-implanted ram lambs.

Eighteen spring-born Columbia ram, wether, and zeranol-implanted ram lambs were examined to determine the influence of castration or zeranol implantation on collagen characteristics of skin, fell, and epimysium and possible relationships between collagen properties of each tissue and difficulty of pelt removal. Pelt removal force was lower in wethers than in rams (P < .05) and intermediate for zeranol-implanted rams. Collagen concentration in skin of rams was greater (P < .05) than that in wethers or implanted rams, but percentage of heat-soluble collagen in skin was higher in implanted rams. Percentage of type III collagen in skin was highest in rams and lowest in wethers (P < .05); that in the skin of implanted rams was intermediate. The fell of wethers contained a higher (P < .05) collagen concentration, higher insoluble collagen amount, and lower percentage of soluble collagen than that of rams or implanted rams. The fell had a lower percentage of type III collagen than that of rams (P < .05). Epimysium collagen concentration of rams and wethers was higher (P < .05) than that of implanted rams; however, percentage of soluble collagen was higher for the implanted rams than for the other classes. Type III collagen percentage in the epimysium did not differ by animal class (P < .05). Zeranol-implanted ram lambs had a higher percentage of soluble collagen in all tissues examined than did non-implanted rams and force required for pelt removal was reduced in implanted rams.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1994

Fibronectin self-association is mediated by complementary sites within the amino-terminal one-third of the molecule.

The formation of a fibrillar fibronectin (FN) extracellular matrix requires self-association of FN dimers. In this report, we show that the major sites for self-association are the amino-terminal repeats I1-5 and the first type III repeats. Recombinant FNs and fragments were generated by baculovirus expression of cysteine-rich domains and by bacterial expression of type III repeats as fusion proteins with maltose binding protein. When recombinant polypeptides were immobilized on microtiter wells, FN bound to 70-kDa amino-terminal fragment and to fusion proteins containing repeats III1-2 and III1-6 but not to other type III repeats. Similar results were obtained with a gel overlay assay. Binding was concentration-dependent and saturable. The amino-terminal binding site for III1-2 was further localized to repeats I1-5. Therefore, at least two different sites for FN-FN interaction reside near the amino terminus of the molecule. A model for the regulation of FN matrix assembly is proposed based on intramolecular interactions between these amino-terminal sites.

Amino Acid Sequence↗

PubMed1994

Regional differences in LV collagen accumulation and mature cross-linking after myocardial infarction in rats.

To determine the extent of and any regional differences in remodeling response of the extracellular matrix (ECM) to myocardial infarction (MI), moderate-to-large transmural infarcts were surgically produced in left ventricular (LV) free wall of rats. Animals were killed 13 wk after surgery. In comparison to age-matched controls, infarction was associated with an overall increase in heart weight, which included hypertrophy of both the right ventricle and LV. Although the remaining viable myocardium in LV free wall was significantly reduced, the interventricular septum was hypertrophied some 30% compared with control tissues (247 +/- 9 vs. 189 +/- 8 mg). Collagen concentration more than doubled in remaining viable free wall (8.92 +/- 0.59 vs. 3.95 +/- 0.25 mg/100 mg, P < 0.0001), and a smaller but still highly significant 27% increase occurred (P < 0.01) in the more remote septum. Degree of covalent cross-linking of collagen fibrils as assessed by hydroxylysylpyridinoline (HP) concentration also revealed regional differences in response of the ECM to infarction. Although HP concentration was increased 60% in viable free wall (P < 0.05) post-MI, it was unchanged in the septum. With respect to collagen characteristics of the transmural infarct per se, the scar exhibited still further increases in both collagen and HP concentrations compared with the already elevated values for these two parameters in viable free wall. The results indicate that any evaluation of the remodeling response of viable myocardium post-MI must include not only the myocyte but also the ECM, the principal component of which is collagen.

Amino Acids↗

PubMed1993

Copper deficiency alters collagen types and covalent cross-linking in swine myocardium and cardiac valves.

Dietary copper deficiency induces alterations of connective tissue metabolism that are associated with lesions in cardiovascular and other organ systems. To determine the impact of copper deficiency on characteristics of collagen in porcine myocardium and cardiac valves, weaned pigs were fed diets with adequate or deficient levels of copper. Although dietary copper did not affect the concentration of collagen in either myocardium or bicuspid valves, the degree of collagen cross-linking, as assessed by the level of hydroxylysylpyridinoline, was lower in both tissues of copper-deficient pigs. Proportions of type III collagen were increased in the left ventricle and bicuspid valves of copper-deficient pigs. Copper deficiency induced extensive remodeling, however, of the collagen fraction of cardiac interstitium. Reduction in left ventricular collagen cross-linking may provide the stimulus for the development of cardiac hypertrophy, which characterizes severe copper deficiency, by increasing the compliance of the ventricular wall. The shift in the phenotypic profile of collagen that is associated with this cardiac hypertrophy indicates synthesis of new collagen, which could affect collagen cross-linking irrespective of copper status.

Animals↗

PubMed1993

Age and training alter collagen characteristics in fast- and slow-twitch rat limb muscle.

This study evaluated the single and interactive effects of age and training status on selected collagen parameters in two rodent locomotor skeletal muscles contrasting in fiber type composition. Gastrocnemius (GAST) and soleus (SOL) muscles from both trained (10 wk of daily treadmill running) and sedentary young adult (5-mo-old), middle-aged (15-mo-old), and old (23-mo-old) female Fischer 344 rats were evaluated for concentrations of collagen (measured by hydroxyproline concentration ([OH-Pro])) and of the predominant nonreducible lysine aldehyde-derived collagen cross-link hydroxylysylpyridinoline ([HP]). Maximal aerobic capacity was significantly elevated in all three trained groups compared with sedentary age-matched control groups. Slow-twitch SOL had a significantly higher [OH-Pro] than fast-twitch GAST (P < 0.05). Although aging had no effect on [OH-Pro] in GAST, in SOL a significant increase with age was seen (P < 0.02). In sedentary rats both GAST and SOL [HP] increased with age, with this increase being more pronounced for SOL. Additionally, although training had no effect on the aging-associated increase in GAST [HP], it prevented the rise seen in SOL. The observed training-induced reduction in SOL [HP] presumably reflects exercise recruitment and subsequent stimulation of collagen synthesis and degradation rates in this muscle. We conclude that both aging and training affect the extracellular matrix in rodent limb skeletal muscle.

Aging↗

PubMed1993

Mechanisms and physiological implications of leucocyte chemoattraction into periovulatory ovine follicles.

Leucotactic polypeptide was isolated from follicular-conditioned incubation media by ultrafiltration and reverse-phase high performance liquid chromatography. The bioactive fraction was subjected to amino acid analysis and shown to be abundant in glycine, proline and hydroxyproline. These amino acid residues are common to repetitive sequences of alpha collagens. Synthetic collagen-like peptides composed of repeating triplets of glycine, proline and hydroxyproline (GPH x 3, GPH x 9) were active in attracting white blood cells as measured in vitro using a linear under-agarose assay. Accumulation of leucocytes within extravascular spaces of the theca interna was induced by intrafollicular injection of GPH x 3 or bacterial collagenase. Intrafollicular administration of affinity-purified GPH x 3 antibodies during the immediate preovulatory period inhibited thecal extravasation of leucocytes, but did not negate follicular rupture. However, serum concentrations of progesterone were depressed in antibody-treated animals throughout the ensuing luteal phase. This luteal defect was counteracted by injecting leucocytes into the preovulatory follicle. It is concluded that periovulatory follicles of the sheep secrete collagen-like leucotactic peptides. Once drawn into the follicle, resident inflammatory cells are apparently involved in transforming it into a fully functional corpus luteum.

Animals↗

PubMed1993

Growth and slaughter characteristics of ram and wether lambs implanted with zeranol.

Forty-nine Columbia ram and wether lambs born in April 1990 and 46 born in April 1991 were studied to determine the effects of zeranol implants on growth, difficulty of pelt removal, and carcass characteristics. Implanting ram and wether lambs once (1990) or twice (1991) with 12 mg of zeranol did not change live weight or ADG but gain/feed decreased (P < .05) in ram lambs slaughtered at approximately 50 kg. Testes weight was reduced approximately 50% by implanting. Two implants reduced (P < .05) the force needed to pull the pelt from the hind legs of ram lambs, but implanting tended to increase the force required to pull the pelt from wether lambs. Data for pelt weight, force required to pull the pelt, percentage of the carcass in the shoulder or splenius muscle, and Warner-Bratzler shear values showed that zeranol implants resulted in ram lambs becoming more like wethers and wether lambs becoming more like rams. Implanting with zeranol did not affect closure of the metacarpal growth plate in ram or in wether lambs. Difficulty of pelt removal can be reduced by implanting ram lambs with 12 mg of zeranol at approximately 114 d of age and reimplanting zeranol 28 d later.

Age Factors↗

PubMed1993

Intramuscular collagen characteristics of ram, wether, and zeranol-implanted ram lambs.

Eighteen spring-born Columbia ram, wether, and zeranol-implanted ram lambs were studied to determine the influence of castration or zeranol implants on intramuscular collagen (IMC) properties and muscle shear force values. Warner-Bratzler shear force values for longissimus muscle were greatest for ram lambs, intermediate for implanted rams, and least for wethers (P < .05). Nonreducible collagen crosslink concentration was greater in IMC of rams and implanted rams (P < .05). The IMC from rams compared with that from wethers contained proportionately more Type III than Type I collagen (P < .05); values for implanted rams were intermediate. Heat-soluble muscle collagen concentration was greater for rams and implanted rams than for wethers (P < .05); however, insoluble collagen concentration did not differ by treatment. Muscle collagen concentrations were not different for rams, wethers, or implanted rams. Increased shear force values in rams were associated with elevated collagen crosslink concentration and increased proportion of Type III collagen. Greater concentration of soluble collagen in ram IMC neither diminished nor diluted IMC crosslinking. The proportion of heat-labile collagen in the fractions did not reflect the IMC crosslinking profile for ram and wether lambs. Zeranol implantation modified IMC characteristics of rams such that shear force values and some collagen properties were similar to those of wethers.

Adipose Tissue↗

PubMed1992

Sequence analysis of leukocyte chemoattractant peptides secreted by periovulatory ovine follicles.

Cells of the white blood series infiltrate ovarian follicles during the ovulatory process. A segment of the wall of periovulatory ovine follicles was incubated and conditioned media subjected to ultrafiltration. Leukocyte chemoattractant activity of media was measured using a linear under-agarose migration assay. Bioactivity was recovered following filtration through a 3000 molecular weight cut-off membrane. Filtrate was then fractionated by reverse phase high performance liquid chromatography. Peptides recovered from two fractions with significant chemoattractant activity were sequenced. One fraction contained 16 amino acid residues with repeating triplets of Gly-X-Y, where X and Y were often proline and hydroxyproline, respectively. Because this motif is characteristic of alpha collagens, and since thecal collagen is degraded during the mechanics of ovulation, it appears that this chemoattractant is derived from the connective tissue matrix of the follicle. Peptide isolated from the other bioactive chromatographic fraction was 15 amino acids in length, and rich in glycine, but did not contain imino acids. To our knowledge this is the first report of purification of leukocyte chemoattractants of reproductive tissue origin. Resident follicular granulocytes and mononuclear cells are capable of secreting a broad spectrum of potent chemicals that could be involved in the mechanisms of ovulation and luteinization.

Amino Acid Sequence↗

PubMed1992

Enzymatic and nonenzymatic cross-linking of collagen and elastin.

Knowledge regarding the steps and mechanisms related to the intra- and interchain cross-linking of collagen and elastin has evolved steadily during the past 30 years. Recently, effort has been directed at identifying the location and types of cross-links that are found in collagen and elastin. There are two major groups of cross-links: those initiated by the enzyme lysyl oxidase and those derived from nonenzymatically glycated lysine and hydroxylysine residues. The formation of enzymatic cross-links depends on specific enzymes, amino acid sequences, and quaternary structural arrangements. The cross-links that are derived nonenzymatically occur more adventitiously and are important to pathobiological processes. Considerable progress has been made in elucidating the pathways of synthesis for several of the enzymatically mediated cross-links, as well as possible mechanisms regulating the specificity of cross-linking. Although less is known about the chemistry of cross-links arising from nonenzymatically glycated residues, recent progress has also been made in understanding possible biosynthetic pathways and control mechanisms. This review focuses on such progress and hopes to underscore the biological importance of collagen and elastin cross-linking.

Animals↗

PubMed1992

Enhanced degradation of collagen within apical vs. basal wall of ovulatory ovine follicle.

Electron microscopic examination of ovulatory ovine follicles indicated that dissolution of thecal collagen was enhanced along the follicular circumference adjacent to the ovarian serosa. Concentrations of hydroxyproline were correspondingly lower within apical than basal tissues. Collagenolytic activity of tissue homogenates and extracts was assessed by monitoring radioactive peptide release from cocultured collagen fibrils. Collagenase inhibitors were separated from enzyme by sequential extraction of follicular homogenates with detergent and heating. Enzymatic activities of homogenates and heat extracts of apical and basal tissues increased toward ovulation. A distinction between apex and base was not attributed to significant differences in homogenates; however, collagenolytic activity of heat extracts of apical tissue was selectively elevated (i.e., extraction was evidently required to effectively dissociate collagenase from thecal fibrils, making more enzyme available for substrate digestion). Activity of detergent extracts was restored by dithiothreitol and iodoacetamide (which inactivate tissue inhibitors of metalloproteinases), and collagenolysis induced by heat extracts was augmented by aminophenylmercuric acetate (a stimulator of latent collagenases). Nonetheless, variations between apex and base invoked by these compounds were relative. It therefore appears that active collagenase is more tightly bound within the extracellular matrix of the follicular apex than enzyme associated with basal tissue. This phenomenon might serve to preferentially favor enzymatic catabolism of collagen in that region, thereby dictating the ovarian site of follicular rupture.

Animals↗

PubMed1992

Aging- and training-induced alterations in collagen characteristics of rat left ventricle and papillary muscle.

We evaluated the single and interactive effects of aging and exercise training on selected parameters of myocardial interstitium in both the left ventricle (LV) and LV papillary muscle of female Fischer 344 specific pathogen-free rats. Ten weeks of treadmill running resulted in significant LV hypertrophy as well as elevated plantaris muscle citrate synthase activity in both young adult (5-mo-old) and senescent (23-mo-old) trained animals (YT, young trained; OT, old trained) compared with age-matched sedentary controls (YC, young control; OC, old control). Proline and hydroxyproline pools were significantly higher (both P less than 0.05) in 23-mo-old vs. 5-mo-old papillary muscles. Degree of maturation (nonreducible cross-linking) of LV collagen was evaluated by measurement of hydroxylysylpyridinoline concentration ([HP]). In a comparison of YC with OC rats, ventricular [HP] increased approximately fivefold from 0.059 +/- 0.007 to 0.285 +/- 0.018 (SE) mol HP/mol collagen (P less than 0.001). Whereas training had no effect on ventricular [HP] in young adult rats, it significantly reduced LV collagen cross-linking in OT rats (0.131 +/- 0.027) so that HP values in this group were less than one-half of those observed in OC rats. Because both collagen concentration and degree of cross-linking are thought to affect muscle stiffness characteristics, we conclude that the observed changes should be considered in any explanation for aging- and training-induced alterations in LV and papillary muscle contractile indexes.

Aging↗

PubMed1991

Dose-dependent effects of indomethacin on ovulation in the sheep: relationship to follicular prostaglandin production, steroidogenesis, collagenolysis, and leukocyte chemotaxis.

A few recent investigations have indicated that it is possible for mammalian ovulation to progress to completion in the absence of a preovulatory rise in ovarian prostanoid production and that the antiovulatory mode of action of antiinflammatory agents (e.g., indomethacin) could be independent of their ability to inhibit the cyclooxygenase pathway of arachidonate metabolism. Mature ewes were treated during the preovulatory period with a systemic dosage of indomethacin that either consistently did (500 mg) or did not (100 mg) prevent follicular rupture. With both dosages, the rise in follicular production of prostaglandin F2 alpha following the surge in secretion of LH was negated. Indomethacin did not affect periovulatory patterns of change in follicular tissue concentrations of estradiol-17 beta, testosterone, or progesterone. The 500-mg dose of indomethacin inhibited collagen breakdown within the follicular wall as deduced from measurement of tissue levels of hydroxyproline. In vitro secretion of a follicular leukotactic agent and accumulation of extravascular white blood cells within the theca interna of periovulatory follicles were also suppressed by the ovulation-inhibiting dose of indomethacin. It appears that the blockage of ovulation induced by indomethacin in the sheep is largely unrelated to its capacity to suppress follicular prostaglandin biosynthesis; rather, it is more directly associated with effects on follicular collagenolysis and leukocyte chemoattraction.

Animals↗

PubMed1991

Effects of age, castration, and season on difficulty of pelt removal in lambs.

Sixty-four white-faced rams and wethers were dressed with the aid of a commercial pelt puller. The effects of age, castration, and season on difficulty of pelt removal and pelt damage were evaluated. Lambs were divided into two age groups (5 and 12 mo) within gender (ram and whether) and season (spring and fall). A greater force (P less than .05) was required to remove pelts from rams than from wethers in both 5- and 12-mo-old groups. Older lambs slaughtered in the fall required more force (P less than .05) to remove their pelts than did those slaughtered in the spring, but differences by season did not exist for 5-mo-old lambs. The difference between rams and wethers in percentage of live weight that was closely shorn pelt weight was not significant (P greater than .05). The area of grain crack in the flank expressed as a percentage of total area of the skin was lower (P less than .05) for skins from 5-mo-old lambs and ram lambs than it was for skins from 12-mo-old lambs and wether lambs, respectively. Factors involved in difficulty of pelt removal in ram lambs included crosscut shoulder weight, fat firmness, and carcass weight. Difficulty of pelt removal in wether lambs was best predicted by including crosscut shoulder weight and bodywall thickness in multiple regression equations.

Age Factors↗

PubMed1990

Effect of plane of nutrition and age on carcass maturity of sheep.

One hundred twenty ewe and wether lambs were fed high (76% TDN, 12.3% crude protein) or low (70.6% TDN, 16.1% crude protein) energy diets and slaughtered at average ages of 261, 356 or 469 d. High planes of nutrition for lambs at 356 or 469 d of age resulted in heavier carcasses, thicker fat depth and higher flank streaking scores compared to lambs fed low planes of nutrition. Rib bone, break joint and overall maturity scores were not influenced (P greater than .05) by diet. Metacarpal and metatarsal bones from lambs fed high planes of nutrition were slightly longer and heavier and required more force to break (P less than .05) compared with bones from lambs fed low planes of nutrition. The majority of the ewes fed high or low planes of nutrition had fused growth plates and possessed spool joints by 469 d; none of the wethers had spool joints. An additional 27 wethers were slaughtered at an average of 480, 578 or 662 d. Rib bone, break joint and overall maturity scores were not different (P greater than .05) for animals fed the high or low energy diets, but bone weight and shaft break force values were higher for those fed high energy diets. At 662 d of age, only 20% of the wethers on each dietary regimen possessed fused growth plates. Overall, plane of nutrition in market-weight lambs and yearlings had very little influence on the presence or absence of a break joint or on other bone maturity scores.(ABSTRACT TRUNCATED AT 250 WORDS)

Age Factors↗

PubMed1989

Effects of a solution of a succinic aldehyde on elastomeric impressions.

This study investigates the effect of a 10 per cent solution of a succinic aldehyde on impressions of three representative elastomeric materials. For each material ten specimens were required for each of six immersion periods ranging from 10 min to 72 h at 23 degrees C and including immediate and delayed immersions. Control groups, each of five specimens, were investigated in air and water. The specimens were formed against a standard ruled block (ADA No. 18). Before and after immersion/storage the impression surface of each specimen was assessed, scored and measured to determine dimensional stability and any attenuation and loss of detail. The results indicate that following all immersion/storage periods there was no loss of detail. Whereas dimensional changes of c. -0.5 per cent and +1.0 per cent were observed for the addition and condensation cured silicones, respectively, after 72 h immersion in the solution, zero dimensional changes were observed following the recommended immersion period for sterilization (4 h). However, with the polyether impressions, a 4 per cent expansion occurred after 4 h in the test solution and 9 h in the aqueous control. No significant differences were found between data relating to immediate and delayed immersions. It is concluded that the immersions in the test solution had no effect on surface detail; only the silicone impressions exhibited acceptable dimensional stability during prolonged immersions (4-72 h) in the test solutions and aqueous control, and that the polyether specimens withstood immersion in the test solution for the 10-min period recommended for disinfection.

Aldehydes↗

PubMed1989

Myofibrillar and nonmyofibrillar myocardial proteins of copper-deficient rats.

Myofibrillar and nonmyofibrillar proteins from hearts of copper-adequate (n = 9) and copper-deficient (n = 10) rats were compared. Male weanling Long-Evans rats were fed copper-deficient or copper-adequate diets for 9 wk. Twelve additional rats were fed similar diets and cardiac tissue was evaluated by transmission electron microscopy. Ventricular myocytes were glycerinated and homogenized in 0.1 M KCl and 1.5% Triton X-100, and suspensions were centrifuged at 1100 x g. The supernatant was removed and designated Triton X-100-soluble non-myofibrillar protein, and the pellet was resuspended and recentrifuged several times to obtain myofibrillar protein. Sodium dodecyl sulfate--polyacrylamide gel electrophoresis (SDS-PAGE) analysis was conducted on both protein fractions. Densitometer scans of SDS-PAGE pherograms of myofibrillar protein revealed no significant difference between copper-adequate and copper-deficient groups. Similar analysis of nonmyofibrillar protein revealed a consistent decrease or diminished level of a 23-kDa polypeptide among copper-deficient rat hearts. These results may be consistent with the findings that demonstrated fragementation of mitochondrial cristae and an increased area occupied by mitochondria in copper-deficient rat hearts.

Analysis of Variance↗