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Biomedical subjects

R N Gates

Publications and source records attributed to R N Gates.

At least 19 recordsLinked to original sources
PubMed1999

Comparison of Tifton 85 and Coastal bermudagrasses for yield, nutrient traits, intake, and digestion by growing beef steers.

A study was undertaken to compare Tifton 85 (T85) and Coastal (CBG) bermudagrasses for effects of cultivar and age at harvest on yields of DM and digestible DM, in vitro digestion, nutrient content, cell wall composition, in situ digestion kinetics, and feed intake and digestion by growing beef steers. In Exp. 1, T85 and CBG forages staged for growth in May or July of 1993 were harvested at 3, 4, 5, 6, 7, and 8 wk from subplots. Tifton 85 bermudagrass had 7.1% greater DM yield, 18.2% higher (P < .05) digestible DM yield, and 7.1% greater IVDMD than CBG, and, after 5 wk of forage growth, IVDMD of both T85 and CBG decreased with increased age at harvest (P < .05). In Exp. 2, T85 and CBG forages staged for growth in July 1997 were harvested at 2, 3, 4, 5, 6, and 7 wk from subplots. Even though T85 had higher concentrations of NDF and ADF than CBG, T85 had 34.1% higher DM yield, 47.9% higher digestible DM, 55.0% higher digestible NDF, 91.7% higher digestible ADF, greater IVDMD, in vitro NDF and ADF disappearances, and higher in situ DM and NDF digestion (P < .05). Coastal bermudagrass had higher concentrations of lignin and lower concentrations of total neutral sugars, arabinose, glucose, and xylose than T85 (P < .05). In vitro digestibilities of DM, NDF, and ADF were lower and concentrations of ADF and lignin were greater for 7- vs 6-wk harvests of both T85 and CBG (P < .05). In Exp. 3, T85 and CBG forages staged for growth in July 1997 were harvested as hay at 3, 5, and 7 wk from .8-ha pastures and fed to 36 individually penned growing beef steers (initial BW = 244 kg) to quantify ad libitum intake without supplementation. Tifton 85 bermudagrass had lower concentrations of lignin and ether-linked ferulic acid and greater concentrations of NDF, ADF, hemicellulose, and cellulose than CBG (P < .05). Steers fed T85 had higher (P < .05) digestion of DM, OM, NDF, ADF, hemicellulose, and cellulose than steers fed CBG. Digestion of NDF, ADF, hemicellulose, and cellulose decreased (P < .05) with increased age at harvest for both cultivars. In conclusion, T85 produced more DM and had more digestible nutrients in vitro, in situ, and in vivo than CBG, and 3 and 5 wk of growth would be recommended ages to harvest either cultivar.

Animal Nutritional Physiological Phenomena↗
PubMed1998

Side-to-side aorto-Gore-Tex central shunt.

BACKGROUND: This report details our experience in 13 patients with a technical modification of the standard central shunt. METHODS: The study was performed using a retrospective chart review approach. In our operation, the aorto-Gore-Tex (W.L. Gore & Assoc, Flagstaff, AZ) anastomosis is created in a side-to-side fashion with the free end of the Gore-Tex shunt being oversewn. RESULTS: All patients had echocardiographic evidence of shunt patency in the immediate postoperative period, and there have been no cases of late shunt occlusion at a mean follow-up period of 10 months. CONCLUSIONS: We believe this approach will yield patency rates equivalent to or better than those of the standard central shunt. The technique has the advantage of creating a short, straight-lying shunt that is less likely to kink or be injured on repeated sternotomy and in which flow may be more reliable.

Aorta↗
PubMed1998

Protein and energy value of pearl millet grain for mature goats.

We conducted two studies to assess the protein and energy value of pearl millet grain (Pennisetum glaucum [L.] R. Br.) for mature goats. In Exp. 1, 15 2-yr-old male castrated goats were gradually introduced over a 4-mo period to three all-grain diets consisting of 100% corn (Zea mays L.), 50:50 corn:pearl millet, and 100% pearl millet. After the adjustment to all-grain feeds, the goats were fed the diets in metabolism crates for 2-d adjustment and 7-d total collection periods. For Exp. 2, complete diets containing the three grain treatments (corn, 50:50 corn:pearl millet, and pearl millet) as 40% of the total DM as fed (the remainder was mainly alfalfa meal and mineral supplement) were balanced to contain 16% crude protein (CP) and 2.24 Mcal digestible energy (DE)/kg on an air-dry basis. Twelve mature (4- to 6-yr-old) buck goats were randomly assigned to diets and fed in pens for 14 d and then moved to metabolism crates for 10-d adjustment and 10-d total collection periods. In Exp. 1, DM intake was unaffected by dietary treatment, but digestibility of DM and organic matter was lowest (P < .10) in goats fed 100% pearl millet. Digestibility of complete diets also decreased (P < .10) as corn was replaced by 50 or 100% pearl millet, but DM intake increased (P < .10) on the 100% millet diet. In both experiments, substituting pearl millet for corn had no effect on nitrogen retained by the goats. Metabolizable energy of pearl millet was only 92% that of corn, but ME intake was similar when the grains were fed as 40% of the dietary DM. Pearl millet has potential as a major energy feed for goats in areas where it can be economically produced.

Animal Feed↗
PubMed1998

Intake, milk yield, and digestion by dairy cows fed diets with increasing fiber content from bermudagrass hay of silage.

Lactating dairy cows were offered diets containing increasing quantities of Tifton 85 bermudagrass hay or silage and increasing dietary neutral detergent fiber (NDF) to determine effects of method of bermudagrass storage and dietary fiber content on intake, milk yield, and nutrient digestion. Bermudagrass was added as hay or silage at the rate of 8.5, 15.9, or 23.3% of dietary dry matter and was substituted for an equal quantity of corn silage. The method of bermudagrass storage did not affect intake [20.8 vs. 20.3 (+/- 0.3) kg/d for bermudagrass hay and silage diets; respectively], but an increase in the amount of bermudagrass and NDF in the diet did reduce intake. Dietary NDF concentration was well above minimum recommendations of the National Research Council. Milk yield was not altered by method of bermudagrass storage but declined as dietary NDF increased. Digestion of NDF tended to be lower for bermudagrass silage than for bermudagrass hay. An increase in the amount of bermudagrass in the diet improved digestion of dietary dry matter, acid detergent fiber, and NDF; however, milk yield declined because total intake declined. Improved NDF digestion caused by added bermudagrass hay or silage was confirmed by in vitro analyses. High quality bermudagrass hybrids could potentially be used in diets of lactating dairy cows because of the good digestion characteristics and relatively small effects on intake despite the high dietary fiber content. Tifton 85 bermudagrass may serve as a forage alternative for lactating dairy cows.

Animals↗
PubMed1997

The Fontan procedure in adults.

BACKGROUND: A retrospective clinical study was performed to document the course of adult patients undergoing the Fontan procedure. METHODS: Between 1982 and 1994, 21 adults aged 18 to 40 years (mean age, 27 +/- 7 years) underwent a Fontan procedure. Anatomic diagnosis was tricuspid atresia in 9, double-inlet left ventricle in 4, and various single ventricles in 8. Four underwent a right atria-right ventricle connection, 13 had a right atria-pulmonary artery connection, and 4 had a lateral-tunnel Fontan. Three of these 4 had a snare-adjustable atrial septal defect. Preoperative risk factors assessed were left ventricular end-diastolic pressure greater than 10 mm Hg, ejection fraction lower than 0.45, mean pulmonary artery pressure higher than 15 mm Hg, transpulmonary gradient greater than 10 mm Hg, pulmonary artery abnormalities, and atrioventricular valve regurgitation. Mean preoperative risk score was 1.6 /-1.1. Mean New York Heart Association class was 2.6 +/- 0.5. RESULTS: The operative mortality rate was 5% (1/21). Six patients (30%) had a major complication, four being prolonged effusions. One patient was lost to follow-up; the remaining 20 have been followed for a mean of 7.4 +/- 3.8 years. At follow-up, mean New York Heart Association class was 1.7 +/- 0.5. There has been one late death (5%) at 9 2/3 years, which was probably due to ventricular arrhythmia. Three patients (16%) have required and survived reoperation. During follow-up, 7 patients (37%) have had development of atrial arrhythmias requiring medication, and 2 have been treated for ventricular arrhythmias. CONCLUSIONS: These results indicate that properly selected adults can undergo the Fontan procedure with low morbidity and mortality. However, late-developing arrhythmias, need for reoperation, and decreasing ventricular function are serious problems that mandate careful follow-up.

Adult↗
PubMed1997

Nutritional value of pearl millet for lactating and growing goats.

Studies were conducted to assess nutritional value of pearl millet grain (Pennisetum glaucum [L] R. Br.) for lactating and growing goats. Three complete diets containing either 40% corn, 40% pearl millet, or 40% corn and pearl millet mixed 1:1 (wt/wt) were balanced to contain 16% crude protein and 2.24 Mcal DE/kg on an air-dry basis. Forty-five does were blocked by kidding date and randomly assigned to diets for a 7-wk investigation. Feed intake and milk production were unaffected (P > .25) by treatment, and they averaged 2.86 and 2.47 kg daily, respectively. Thirty-three growing goats were blocked by sex and fed the same diets for 15 wk. Daily growth rate and feed to gain ratio were depressed (P < .05) by 25.4 and 19.0%, respectively, when corn was completely replaced with pearl millet. Digestion coefficients for DM, GE, CP, and NDF were reduced by over 10 percentage units with partial or complete replacement of corn by pearl millet. Ruminal acetate and ratio of acetate to propionate increased (P < .05) but butyrate, propionate, and ammonia were depressed (P < .05) with the pearl millet diets. Growing goats consumed 43 meals daily. They consumed 26.9, 32.6, 27.4, and 13.1% of their ration during the morning (0600 to 1200), afternoon (1200 to 1800), evening (1800 to 2400), and night (2400 to 0600), respectively. Pearl millet is a useful energy feed for mature, but not for growing, goats.

Acetates↗
PubMed1997

Performance of Angus and Brangus cow-calf pairs grazing Alicia bermudagrass and common bermudagrass-dallisgrass pastures.

This research was designed to examine genotype x environment interactions in cow-calf growth performance of grazing animals. Angus and Brangus cow-calf pairs (minimum of six per breed) were allowed to rotationally graze (14-d intervals) treatment pastures from approximately May through early October in each of 2 yr. Treatment pastures contained relatively pure stands of Alicia bermudagrass (AP) or a mixed stand of common bermudagrass and dallisgrass (CDP). Forage allowance was equalized, using "put-and-take" cow-calf pairs, among forage and breed types at the initiation of each 14-d grazing interval. Forage samples were obtained in each paddock at the initiation of each grazing interval. Forage CP concentration was greater (P < .05; 13.5 vs 11.6%) and NDF concentration was less (P < .05; 63.8 vs 70.6%) for CDP than for AP. Daily weight loss was similar for Angus and Brangus cows, but it was greater (P < .05) for cows grazing AP than for cows grazing CDP. Calf ADG during the grazing season was 35% greater (P < .05) for CDP than for AP pastures and was 23% greater (P < .01) for Brangus than for Angus calves. Relative performance of Angus and Brangus cow-calf pairs was consistent between forages; no breed x forage interactions were observed.

Animal Feed↗
PubMed1997

Yield, composition, and in vitro digestibility of temperate and tropical corn hybrids grown as silage crops planted in summer.

Following the harvest of corn silage crops that were planted in spring, second crops of one temperate and four tropical corn hybrids were planted under conditions of minimum tilling in four replications on August 3, 1992 and harvested on October 11, 1992 (yr 1). During the 2nd yr, second crops were planted on July 21, 1993 and harvested on October 19, 1993. Dry matter yields of the hybrids ranked similarly for both years but differed among hybrids, ranging from 7800 to 11,430 kg/ha (yr 1) and from 8470 to 13,150 kg/ha (yr 2). The temperate hybrid yielded 20% (yr 1) and 26% (yr 2) less than the lowest yielding tropical hybrid. The proportion of grain in the dry matter (DM) differed across hybrids, ranging from 14.3 to 32.2% during yr 1 and from 18.0 to 32.4% during yr 2. Composition of the DM, excluding grain, also differed for the hybrids: acid detergent fiber ranged from 38.0 to 42.2% during yr 1 and 40.0 to 48.8% during yr 2; in vitro digestible DM ranged from 60.9 to 65.1% during yr 1 and from 53.0 to 64.6% during yr 2. The temperate hybrid was the highest in acid detergent fiber and the lowest in in vitro digestible DM. Lower digestibility during yr 2 was attributed to disease, which infected 24.9 to 40.4% of the foliage of tropical hybrids and 84.3% of the temperate hybrid. Whole plant DM digestibilities differed narrowly in yr 1 (68.8 to 70.4%) but differed widely in yr 2 (62.2 to 69.9%). There were important differences among yields and compositions of tropical hybrids planted in summer, but all were superior to the temperate hybrid.

Agriculture↗
PubMed1997

Effects of dietary forage source and amount of forage addition on intake, milk yield, and digestion for lactating dairy cows.

Lactating cows were used to determine the effects of increasing forage content from alfalfa (Medicago sativa L.) hay or Tifton 85 bermudagrass (Cynodon sp.) hay or Tifton 85 bermudagrass (Cynodon sp.) hay on dry matter intake (DMI), milk yield, and nutrient digestion. Forage proportions and neutral detergent fiber (NDF) content of diets were (dry basis) 1) 45% corn (Zea mays L.) silage (control), 33.5% NDF; 2) 15% bermudagrass hay and 30% corn silage, 39.5% NDF; 3) 30% bermudagrass hay and 15% corn silage, 46.6% NDF; 4) 15% alfalfa hay and 30% corn silage, 35.5% NDF; or 5) 30% alfalfa hay and 15% corn silage, 33.5% NDF. The DMI was greater with alfalfa diets than with bermudagrass diets, with low hay diets than with high hay diets, and with the control diet than with the hay diets. Digestibility of NDF in bermudagrass diets was greater than that in alfalfa diets, in high hay diets than in low hay diets, and in hay diets than in the control diet. In vitro NDF digestion was most rapid for bermudagrass hay, intermediate for corn silage, and slowest for alfalfa hay. Results suggest that NDF from bermudagrass was digested more completely and rapidly than was NDF from corn silage or alfalfa, which improved the rate of passage despite the high NDF content of diets containing bermudagrass. Milk yield followed trends for DMI. The control diet and diets containing alfalfa elicited the greatest DMI and milk yield, but DMI per 100 kg of body weight for Holsteins was equal for diets containing either bermudagrass or alfalfa. High quality bermudagrass can be used in rations for lactating dairy cows.

Animal Feed↗
PubMed1996

Evidence of improved microvascular perfusion when using antegrade and retrograde cardioplegia.

BACKGROUND: The maximum degree of microvascular distribution of cardioplegic solution is considered important to achieve optimum myocardial protection. This study attempts to demonstrate that the addition of retrograde cardioplegia to antegrade cardioplegia improves overall microvascular perfusion. METHODS: Explanted human hearts (n = 6) were treated with cold cardioplegic arrest and bicaval cardiectomy. Blood cardioplegia (37 degrees C) containing colored microspheres (color A for antegrade, color B for retrograde) was simultaneously infused antegrade at a pressure of 80 mm Hg and retrograde at a pressure of 40 mm Hg for 2 minutes. The ventricular myocardium was then sampled at three sites to determine absolute and relative cardioplegic microvascular flow. RESULTS: Of the total microvascular capillary flow, 27% to 32% was found to be the contribution of retrogradely delivered cardioplegia. CONCLUSIONS: Despite being delivered simultaneously and at a lower pressure, retrograde cardioplegia contributed substantially to overall microvascular perfusion. This suggests that antegrade cardioplegia alone does not perfuse all available myocardial capillaries and that the addition of retrograde cardioplegia enhances overall microvascular distribution and perfusion.

Cardioplegic Solutions↗
PubMed1995

Aortic to right ventricular shunt for pulmonary atresia and intact ventricular septum.

Acute or chronic myocardial ischemia may develop in patients with pulmonary atresia with intact ventricular septum and right ventricular-dependent coronary circulation. In such cases an aorta to right ventricle shunt may be used to reverse this ischemia. This report summarizes our experience with the placement of an aortic to right ventricular shunt in 5 patients. The shunts were made of Gore-Tex and ranged from 4 mm to 8 mm. Associated procedures were bidirectional Glenn (n = 2) and Fontan (n = 2). All 5 patients survived the procedure with documented early graft patency and no evidence of ischemia.

Aorta↗
PubMed1995

Can improved microvascular perfusion be achieved by using both antegrade and retrograde cardioplegia?

BACKGROUND: The complete and uniform distribution of cardioplegia to the microvasculature of the heart is considered critical for myocardial protection. This study explores the hypothesis that enhanced microvascular perfusion can be achieved by using both antegrade and retrograde cardioplegia. METHODS: Infant piglet hearts (n = 15) were arrested with antegrade blood cardioplegia, excised, and fixed with 2.5% glutaraldehyde by retrograde perfusion. Hearts were then perfused retrograde with an inert intracapillary marker (NTB-2). Six of these hearts served as controls (group 1) to anatomically demonstrate the degree of capillary perfusion achieved by the retrograde delivery route. Nine experimental hearts (group 2) underwent a subsequent infusion of antegrade blood cardioplegia to wash out NTB-2 capillaries coperfused by both the antegrade and retrograde delivery techniques. Sections of the left ventricular free wall and anterior-mid interventricular septum were taken and examined by light microscopy at four separate sites (average, 126 capillaries per section). RESULTS: In control hearts, 91.9% +/- 0.9% of ventricular capillaries and 91.4% +/- 5.8% of septal capillaries were perfused by retrograde cardioplegia. After antegrade blood cardioplegia washed out group 2 hearts, 14.0% +/- 4.1% of capillaries in the ventricle still contained NTB-2, as did 12.5% +/- 5.4% of capillaries in the septum. CONCLUSIONS: In this experimental model, antegrade blood cardioplegia did not coperfuse (and therefore washout) 12.5% to 14% (p < 0.05) of capillaries perfused by retrograde cardioplegia. This suggests that an additional 12.5% to 14% of capillaries within the myocardium may receive cardioplegia if retrograde cardioplegia is used in addition to antegrade cardioplegia. We conclude that by combining both antegrade and retrograde cardioplegia, there is a potential for enhanced overall microvascular perfusion.

Animals↗
PubMed1995

The regional capillary distribution of retrograde blood cardioplegia in explanted human hearts.

Warm retrograde blood cardioplegia is frequently used for myocardial protection, despite experimental studies questioning the adequacy of capillary flow to the right ventricle and septum. The capillary distribution of retrograde blood cardioplegia in the human heart is unknown. Hearts from eight transplant recipients with the diagnosis of idiopathic or dilated cardiomyopathy were arrested in situ with cold blood cardioplegia and excised with the coronary sinus intact. Within 20 minutes of explanation, colored microspheres mixed in 37 degrees C blood cardioplegia were administered through the coronary sinus at a pressure of 30 to 40 mm Hg for 2 minutes. Twelve transmural myocardial samples were taken horizontally at the level of midventricle and apex to determine regional capillary flow rates. When retrograde warm blood cardioplegia was administered at a rate of 0.42 +/- 0.06 ml/gm/min, the left ventricle, the septum, the posterior wall of the right ventricle, and the apex consistently received capillary flow rates in excess of their metabolic requirements. The capillary perfusion of anterior and lateral walls of the right ventricle was marginally adequate to sustain aerobic metabolism. In explanted human hearts, retrograde blood cardioplegia provides adequate capillary flow to the left ventricle, the septum, the posterior wall of the right ventricle, and the apex; however, capillary flow to the anterior and lateral walls of the right ventricle is marginal. This study delineates the tenuous balance between supply and demand for right ventricular protection with warm continuous retrograde blood cardioplegia.

Capillaries↗
PubMed1995

Coronary sinus ostial occlusion during retrograde delivery of cardioplegic solution significantly improves cardioplegic distribution and efficacy.

UNLABELLED: This study documents the gross flow characteristics and capillary distribution of cardioplegic solution delivered retrogradely with the coronary sinus open versus closed. METHODS: Five explanted human hearts from transplant recipients were used as experimental models. Hearts served as their own controls and received two doses of warm blood cardioplegic solution, each containing colored microspheres. The first dose was delivered through a retroperfusion catheter with the coronary sinus open and the second dose was delivered with the sinus occluded. Capillary flow was measured at twelve ventricular sites and gross flow was measured by examining coronary sinus regurgitation, thebesian vein drainage, and aortic effluent (nutrient flow). RESULTS: Coronary sinus ostial occlusion allowed for a significant decrease in total cardioplegic flow (1.74 +/- 0.40 ml/gm versus 1.06 +/- 0.32 ml/gm; p < 0.05) to occur while maintaining an identical intracoronary sinus pressure. Ostial occlusion also resulted in an increase in the ratio of nutrient flow/total cardioplegic flow from 32.3% +/- 15.1% to 61.3% +/- 7.9% (p < 0.05). A statistically significant improvement in capillary flow was found at the midventricular level in the posterior intraventricular septum and posterolateral right ventricular free wall. This improvement was also documented for the intraventricular septum and right ventricle at the level of the apex. CONCLUSION: Coronary sinus occlusion during retrograde cardioplegia significantly improves cardioplegic delivery to the right ventricle and posterior intraventricular septum. Furthermore, the technique affords a significant improvement in nutrient cardioplegic flow while reducing the overall volume of cardioplegic solution administered.

Capillaries↗
PubMed1995

Monensin and ammoniation or urea supplementation of bermudagrass hay diets for steers.

One growth trial using crossbred beef steers (297 +/- 2 kg, Exp. 1) and one metabolism trial using Holstein steers (405 +/- 14 kg, Exp. 2) were conducted to evaluate effects of ammoniation (3% of hay DM, added as anhydrous NH3) vs urea supplementation with or without monensin supplementation of mature 'Alicia' bermudagrass hay-based diets for steers. Ammoniation (P < .05), but not urea (P = .26) or monensin (P = .70) supplementation, increased ADG in Exp. 1. In Exp. 2 ammoniation increased hay DMI (P < .05), but urea (P = .88) or monensin (P = .16) had no effect. Supplementation with either monensin (P < .05) or urea (P < .05) decreased ruminal total VFA concentrations. Monensin also decreased the ruminal acetate:propionate ratio (P < .001) and increased ruminal pH (P < .05). Addition of urea to the concentrate supplement decreased the rate of concentrate intake. Both the rate (P < .05) and the potential extent (P < .001) of ruminal forage in situ DM and NDF disappearance were increased by ammonia treatment. Dietary interactions (P < .10) were detected between monensin and ammoniation for rate and potential extent of in situ NDF disappearance and between monensin and urea supplementation (P < .05) for ruminal total free amino acid concentrations. Decreased concentrations of VFA and lower forage digestibilities observed with monensin supplementation in Exp. 2 may explain the failure of monensin to affect ADG in Exp. 1.

Ammonia↗
PubMed1995

Ventricular effluent of retrograde cardioplegia in human hearts has traversed capillary beds.

BACKGROUND: In human hearts, as much as two thirds of retrograde cardioplegia is shunted through thebesian and arteriosinusoidal channels into the ventricular cavities. This ventricular effluent is believed to have bypassed the myocardial capillary beds and is therefore considered nonnutritive. METHODS: To test this hypothesis, we studied the explanted hearts from 9 cardiac transplant recipients with the diagnosis of idiopathic cardiomyopathy. These hearts were arrested in situ with cold blood cardioplegia and excised with the coronary sinus intact. The left and right coronary ostia and the coronary sinus then were cannulated. Colored microspheres (15 +/- 5 microns) mixed in 37 degrees C blood cardioplegia were administered through the coronary sinus at a pressure of 30 to 40 mm Hg. Effluents from the coronary arteries and ventricular chambers were collected and analyzed for microsphere concentration. RESULTS: Approximately 80% of retrograde cardioplegia solution was recovered in the ventricular chambers. Nearly 40% of this ventricular chambers effluent had traversed capillary beds and, thus, we believe has nutritive properties. Almost all of the coronary artery effluent of retrograde cardioplegia solution had traversed capillary beds. The total nutritive fraction of retrograde warm blood cardioplegia in this explanted human heart model was approximately 55%. CONCLUSIONS: These findings suggest that the ventricular chamber effluent of retrograde blood cardioplegia contributes to the metabolic homeostasis of the arrested human heart.

Capillaries↗