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Biomedical subjects

B A Smith

Publications and source records attributed to B A Smith.

At least 127 records · Page 7Linked to original sources
PubMed1989

Arteriovenous malformations of the small intestine.

Arteriovenous malformations of the small intestine are an uncommon cause of gastrointestinal hemorrhage. When we reviewed the records of 406 patients admitted to the hospital because of gastrointestinal blood loss, we found nine patients who had AVMs of the small intestine. We have developed an algorithm that presents a rational diagnostic approach to patients with hemorrhage from the small intestine. Single contrast barium roentgenograms were not helpful in this series. Endoscopy is not helpful unless the scope can be passed to the area of involvement. Arteriography is the most helpful diagnostic maneuver and should be considered early in the work-up for suspected intestinal AVMs. In addition, arteriography can be useful in localizing the precise area of bleeding so that resection can be limited to the involved areas.

Aged↗
PubMed1989

Relationships of sire scrotal circumference to offspring reproduction and growth.

Reproductive and growth data were obtained on 779 and 564 yearling beef heifers and bulls, respectively, that had sires with yearling scrotal circumference data at the San Juan Basin Research Center, Hesperus, CO. Partial regression coefficients of reproductive and growth traits on inbreeding (FXC) and age of the individual and adjusted scrotal circumference of sire (SCSI) were obtained. Growth and reproductive traits of heifers and growth and breeding soundness traits of bulls were analyzed. Separate analyses for each sex were performed, but least squares models were similar. Models included fixed effects of breed, birth year (BY), age of dam (AOD) and the covariates FXC, age (day of birth in heifer analyses) and SCSI. Scrotal circumference of sire was adjusted for age, FXC, AOD and BY using values obtained in a separate analysis. Seminal traits improved as age increased, and there was a seasonal effect present for age of puberty. Inbreeding had a detrimental effect on reproductive traits. Partial regression coefficients for the reproductive traits on SCSI were: age of puberty, -.796 d/cm; age of first calving, -.826 d/cm; julian day of first calving, -.667 d/cm; julian day of second calving, .597 d/cm; most probable producing ability, .132 %/cm; percent sperm motility, -.74 %/cm; percent primary sperm abnormalities, .08 %/cm; percent secondary sperm abnormalities, .92 %/cm; percent normal sperm, -1.28 %/cm; total breeding soundness examination score, .28 units/cm and scrotal circumference, .306 cm/cm. A heritability of .39 was obtained for scrotal circumference.

Age Factors↗
PubMed1989

Estimation of genetic parameters among breeding soundness examination components and growth traits in yearling bulls.

Data on breeding soundness examinations (BSE) and performance traits were obtained on 549 yearling beef bulls at the San Juan Basin Research Center, Hesperus, Co from 1976 to 1984. Genetic parameters estimated for components of BSE included percent motility (PMOT), percent primary abnormalities (PPRIM), percent secondary abnormalities (PSEC), percent normal sperm (PNOR), scrotal circumference (SC) and BSE score (BSESC). Performance traits included birth weight, weaning weight, yearling weight and average daily gain. The least squares model included birth year, age of dam and breed as fixed effects, sire/breed as a random variable, and age and percent inbreeding as covariates. Paternal half-sib estimates of heritability were PMOT, .08 +/- .07; PPRIM, .31 +/- .09; PSEC, .02 +/- .05; PNOR, .07 +/- .06; BSESC, .10 +/- .06 and SC, .40 +/- .09. Phenotypic correlations among BSE components and growth traits were generally favorable. Genetic correlations involving percent secondary abnormalities were highly variable with large standard errors. Seminal traits improved as age increased and became poorer as inbreeding increased.

Age Factors↗
PubMed1989

Estimation of genetic parameters among reproductive and growth traits in yearling heifers.

Growth and reproductive data were obtained on 779 beef heifers at the San Juan Basin Research Center, Hesperus, Co. Genetic parameters were estimated for age of puberty (AOP), age of first calving (AOC), julian day of first calving (DOC), julian day of second calving (DOSC), birth weight, weaning weight, yearling weight, and average daily gain from weaning to yearling and to cycling weights. The least squares model included birth year, age of dam and breed as fixed effects, sire/breed as a random variable, and day of birth and percent inbreeding as covariates. Day of birth was not included in the analyses of AOC, DOC or DOSC. Paternal half-sib estimates of heritability were: AOP, .10 +/- .17; AOC, .01 +/- .12; DOC, .09 +/- .13 and DOSC, .36 +/- .18. Genetic and phenotypic correlations were generally favorable, but genetic correlations were variable with large standard errors. Inbreeding had a detrimental effect on reproductive traits, and a seasonal effect was present for AOP.

Age Factors↗
PubMed1988

Permeability of a heparin-polyvinyl alcohol hydrogel to thrombin and antithrombin III.

The diffusivities of thrombin and antithrombin III in a heparin-polyvinyl alcohol hydrogel were estimated and used to demonstrate that diffusion limits the effectiveness of the immobilized heparin in the interior of such hydrogels. Diffusivities were calculated from permeabilities and partition coefficients measured with films in a diffusion chamber apparatus. The diffusion coefficients were estimated to be 6 +/- 4 X 10(-8) cm2/s for thrombin and 4 +/- 2 X 10(-8) cm2/s for antithrombin III in 10% gel membranes with or without immobilized heparin. Using the diffusivity of thrombin and a Thiele-type modulus, the effectiveness factor of a spherical heparin-PVA bead used to accelerate the inactivation of thrombin by antithrombin III was found to be 4-9% (diameter range 250-150 micron). While indicating that diffusion of thrombin limited the full utilization of the immobilized heparin, these values for the effectiveness factor could not completely account for the low apparent heparin activity (0.2%) in a thrombin time test of heparin-PVA "beads" (J. Biomed. Mater. Res., 17, 359 (1983]. Other factors such as the immobilization chemistry or the diffusion of thrombin-antithrombin III complex must be considered for a full explanation of the thrombin time results.

Animals↗
PubMed1988

Salutary effects of CG-4203, a novel, stable prostacyclin analog, in hemorrhagic shock.

Prostacyclin (PGI2) is a potent vasodilator, an inhibitor of platelet aggregation, and a membrane-stabilizing agent that has been shown to exert beneficial effects in a variety of models of ischemia and circulatory shock. However, the use of PGI2 is limited by its instability and rapid biodegradation. We studied the effects of a novel, stable prostacyclin analog, CG-4203, in a murine model of hemorrhagic shock. Hemorrhaged rats treated with CG-4203 maintained postreinfusion mean arterial blood pressure (MABP) at significantly higher values than rats receiving only the vehicle (final MABP 101 +/- 3 vs. 75 +/- 5 mm Hg, p less than 0.01). CG-4203 was also found to attenuate the increase in plasma cathepsin D activity (p less than 0.01), as well as the plasma accumulation of free amino-nitrogen compounds (p less than 0.05). Furthermore, the plasma activity of a myocardial depressant factor (MDF) was significantly lower in CG-4203-treated hemorrhaged rats than in rats receiving the vehicle (25 +/- 2 vs. 54 +/- 7 U/ml, p less than 0.01). In addition, CG-4203 exerted an anti-proteolytic action in pancreatic homogenates and inhibited platelet aggregation in platelet-rich plasma. However, CG-4203, at concentrations expected during treatment of shock, failed to have an immediate or delayed vasodilator effect in rat aortic rings, and thus vasodilation is not an important aspect of the antishock effects of CG-4203. Our results suggest that inhibition of platelet aggregation, as well as the antiproteolytic and membrane-stabilizing actions, could mediate the beneficial effects of CG-4203 in hemorrhagic shock.

Animals↗
PubMed1988

New attachment achieved by guided tissue regeneration in beagle dogs.

This study tested the effects of using a Gore-Tex periodontal material on new connective tissue attachment in beagle dogs with natural periodontitis. Seven female beagle dogs with advanced periodontitis were selected and given thorough root debridement. Under general anesthesia four weeks later, mucoperiosteal flaps were raised involving all mandibular premolars and first molars. Gore-Tex periodontal material was adapted to all premolars, and the flaps were sutured tightly, keeping the material covered. The first molars acted as controls, receiving only surgery. Some material was removed in one month, while other materials were removed eight to 10 weeks after surgery. All dogs were sacrificed at three months. After processing, descriptive histology and histometrics were carried out, evaluating new connective tissue attachment, bone response and epithelial downgrowth. Results were statistically analyzed, using paired t tests. They showed new connective tissue attachment with cementum deposition in areas where the material was used. Also, the epithelial downgrowth was reduced in these areas. In the controls, minimal connective tissue attachment was found, with the area healing by a long junctional epithelium. Statistical analysis showed significant differences (P less than 0.05) favoring experimental areas both in the increase of new connective tissue attachment and in the decrease of epithelial downgrowth. No differences were found between areas where the material was removed in one month or left longer in place. No difference in bone response was found. Gore-Tex material was effective in blocking gingival epithelial downgrowth and connective tissue proliferation, promoting new attachment according to the principle of "guided tissue regeneration."

Alveolar Process↗
PubMed1988

Use of the novel cardiotonic and vasodilator agent pimobendan in traumatic shock.

The effect of 4,5-dihydro-6-[2-(4-methoxyphenyl)-1H-benzimidazol-5-yl]-5-methyl- 3(2H)- pyridazinone (pimobendan, UD-CG 115 BS), a novel positive inotropic and vasodilator agent, was studied in a severe model of murine traumatic shock. Noble-Collip drum trauma produced a shock state characterized by a significantly reduced mean arterial blood pressure (MABP), a 5-fold increase in plasma cathepsin D and myocardial depressant factor (MDF) activities, and a survival time of 80 +/- 12 min. Administration of pimobendan (100 micrograms/kg, i.v. bolus) significantly prolonged the survival time to 175 +/- 24 min (p less than 0.01). Although plasma cathepsin D was not affected by pimobendan, this agent significantly attenuated the accumulation of MDF activity in the plasma when compared to animals receiving only its vehicle (37 +/- 6 vs 61 +/- 9 U/ml, p less than 0.05). Additionally, pimobendan inhibited platelet aggregation in cat platelet rich plasma, but failed to have an antiproteolytic effect in cat pancreatic homogenates. These results suggest that cardiotonic and vasodilator activities combined with inhibition of platelet aggregation could mediate the beneficial effects of pimobendan in traumatic shock.

Animals↗
PubMed1988

Beneficial actions of antagonism of peptide leukotrienes in hemorrhagic shock.

The peptide leukotrienes are biologically active eicosanoids which have recently been implicated as possible mediators of anaphylactic, endotoxic, traumatic, and splanchnic artery occlusion shock. We studied the effects of a novel selective peptide leukotriene antagonist, L-649,923, in a rat model of hemorrhagic shock. Hemorrhaged rats treated with L-649,923 (1 mg/kg/h) maintained post-reinfusion mean arterial blood pressure (MABP) at significantly higher values than rats receiving either 0.9% NaCl or a lower dose (0.2 mg/kg/h) of L-649,923 (final MABP 97 +/- 4 vs 60 +/- 5, p less than 0.01; vs 60 +/- 4 mm Hg, p less than 0.01, respectively). Both doses of L-649,923 attenuated the increase in plasma cathepsin D activity (p less than 0.01). L-649,923, at 1 mg/kg/h, also attenuated the plasma accumulation of free amino-nitrogen compounds (p less than 0.05). Furthermore, the plasma activity of a myocardial depressant factor (MDF) was significantly lower in rats treated with L-649,923 (1 mg/kg/h) than in rats receiving the lower dose of the drug or the vehicle (36 +/- 5 U/ml vs. 61 +/- 4 U/ml, p less than 0.01; and 60 +/- 3 U/ml, p less than 0.01, respectively). Furthermore, L-649,923 does not inhibit platelet aggregation in platelet rich plasma. Our data suggest that peptide leukotrienes are important mediators of hemorrhagic shock and that blockade of leukotriene-induced vasoconstriction may underlie the beneficial effects of L-649,923 in hemorrhagic shock.

Animals↗
PubMed1987

Negative and positive regulation by a short segment in the 5'-flanking region of the human cytomegalovirus major immediate-early gene.

To analyze the significance of inducible DNase I-hypersensitive sites occurring in the 5'-flanking sequence of the major immediate-early gene of human cytomegalovirus (HCMV), various deleted portions of the HCMV immediate-early promoter regulatory region were attached to the chloramphenicol acetyltransferase (CAT) gene and assayed for activity in transiently transfected undifferentiated and differentiated human teratocarcinoma cells, Tera-2. Assays of progressive deletions in the promoter regulatory region indicated that removal of a 395-base-pair portion of this element (nucleotides -750 to -1145) containing two inducible DNase I sites which correlate with gene expression resulted in a 7.5-fold increase in CAT activity in undifferentiated cells. However, in permissive differentiated Tera-2, human foreskin fibroblast, and HeLa cells, removal of this regulatory region resulted in decreased activity. In addition, attachment of this HCMV upstream element to a homologous or heterologous promoter increased activity three- to fivefold in permissive cells. Therefore, a cis regulatory element exists 5' to the enhancer of the major immediate-early gene of HCMV. This element negative modulates expression in nonpermissive cells but positively influences expression in permissive cells.

Cell Line↗
PubMed1987

Renal hemodynamics and functional changes during the transition from fetal to newborn life in sheep.

The effects of delivery on renal function and renal hemodynamics were studied in conscious and chronically instrumented fetal sheep. Each fetus was studied 1 h before delivery and 1, 4, and 24 h following delivery by cesarean section. Delivery was not associated with significant changes in plasma renin activity, plasma angiotensin II, plasma aldosterone, and plasma arginine vasopressin concentrations when determined 1 h after birth. On the other hand, the transition from fetal to newborn life was accompanied by significant increases in plasma epinephrine and norepinephrine concentrations. No significant changes in renal blood flow velocity or in renal vascular resistance were observed during the transition from fetal to newborn life; percent changes in renal blood flow velocity and renal vascular resistance values were respectively 15.4 +/- 11 and -2.4 +/- 1.0% at 1 h, 4.0 +/- 8.0 and 5.8 +/- 9.1% at 4 h, and 3.2 +/- 8.0 and 9.7 +/- 13% at 24 h. No significant changes in urinary flow rate, urine osmolality, free water clearance, and osmolar clearance were observed in the first 24 h following delivery. On the other hand, glomerular filtration rate increased 3-fold from 3.3 +/- 0.4 ml/min in fetuses to 10.1 +/- 1.2 ml/min in newborn lambs at 24 h of age. This rise in glomerular filtration rate was associated with significant decreases in urinary sodium excretion (UNaV) (from 36 +/- 7 to 13 +/- 3 microEq/min) and fractional excretion of sodium (FENa) (from 7.6 +/- 0.9 to 1.1 +/- 0.3%).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1987

Cell proliferation after flap surgery, root conditioning and fibronectin application.

This study evaluated the effects of citric acid demineralization and autologous fibronectin application on cell proliferation after mucoperiosteal flap surgery. Three adult rhesus monkeys were used. After flaps were raised, the roots were surgically exposed and planed. Surfaces on the experimental sides were decalcified with citric acid, and after thorough rinsing, the inner aspect of the flaps and the roots were bathed with 1 ml of autologous plasma fibronectin in normal saline (400 micrograms m/ml) and the flaps sutured. Contralateral teeth, acting as controls, were treated only with the surgical procedure. One hour prior to sacrifice, the animals were injected with an intravenous injection of tritiated thymidine (1 microCi/gm body weight). Surgeries were staggered to produce the following time periods: 3, 7, 15, 21 and 28 days. After processing, autoradiographs were obtained for evaluation, and labeled cells were counted in five compartments at 400 x: (1) oral epithelium, (2) crevicular area, (3) supracrestal connective tissue, (4) coronal periodontal membrane and (5) coronal bone marrow. Forty tissue sections per procedure (20 slides per tooth) were counted and means obtained for the three monkeys. Differences between experimental and control values were statistically evaluated for each component, at each time interval, using pairwise t tests. Fibronectin-treated areas showed significantly increased cellular proliferation (P less than 0.01) during the first 2 weeks, affecting mainly all the supracrestal tissues. Histologically, the establishment of a well-organized fibrinous clot at 3 days was noted in these areas. Results show a faster healing after surgery with the use of citric acid and fibronectin. It was concluded that citric acid followed by fibronectin enhanced cellular proliferation.

Animals↗
PubMed1987

Effect of citric acid and various concentrations of fibronectin on healing following periodontal flap surgery in dogs.

The purpose of this histologic and histometric study was to examine the effect of citric acid and increasing concentrations of fibronectin on new connective tissue attachment following periodontal flap surgery. Full thickness, mucoperiosteal flaps were elevated in six healthy mongrel dogs. Two to 3 mm of alveolar bone were removed along the buccal aspect of the teeth in the mandible and into the interproximal areas of each surgical site. Cementum was removed from the exposed root surfaces and reference notches were inscribed into the roots at the margin of the recontoured bone. Citric acid, pH 1.0, was applied to the instrumented root surfaces for 3 minutes and rinsed with sterile saline. Both the root surfaces and the inner surface of the flap were then bathed in either sterile saline or increasing concentrations (0.38, 0.75 and 1.5 mg/ml saline) or exogenous fibronectin. All the flaps were returned to their original preoperative positions, secured using figure 8 sutures with 4-0 braided silk and allowed to heal. Two dogs per time-point were sacrificed at 1, 2 and 6 weeks after surgery. Block specimens of the surgical sites were demineralized and serial sections prepared for histologic and histometric evaluations. Histologically, tissue sections were examined for: (1) epithelial proliferation and attachment, (2) periodontal fiber organization and maturation, (3) inflammatory cell types, (4) presence or absence of new cementum deposition and (5) degree of vascularity of the tissues. Histometric measurements were taken: (1) from the root surface notch to the apical extent of the junctional epithelium and (2) from the apical extent of the junctional epithelium to the free gingival margin.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗