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1.
J Appl Microbiol ; 120(3): 588-99, 2016 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-26726754

RESUMO

AIMS: Recent studies have demonstrated RAMP, a complete starter feed, to have beneficial effects for animal performance. However, how RAMP may elicit such responses is unknown. To understand if RAMP adaptation results in changes in the rumen bacterial community that can potentially affect animal performance, we investigated the dynamics of rumen bacterial community composition in corn-adapted and RAMP-adapted cattle. METHODS AND RESULTS: During gradual acclimation of the rumen bacterial communities, we compared the bacterial community dynamics in corn and RAMP-adapted using 16S rRNA gene amplicon sequencing. Significant shifts in bacterial populations across diets were identified. The shift in corn-adapted animals occurred between adaptation step3 and step4, whereas in RAMP-adapted cattle, the shift occurred between step2 and step3. As the adaptation program progressed, the abundance of OTUs associated with family Prevotellaceae and S24-7 changed in corn-adapted animals. In RAMP-adapted animals, OTUs belonging to family Ruminococcaceae and Lachnospiraceae changed in abundance. CONCLUSIONS: Rumen bacteria can be acclimated faster to high concentrate diets, such as RAMP, than traditional adaptation programs and the speed of bacterial community acclimation depends on substrate composition. SIGNIFICANCE AND IMPACT OF THE STUDY: These findings may have implications for beef producers to reduce feedlot costs, as less time adapting animals would result in lower feed costs. However, animal feeding behavior patterns and other factors must be considered.


Assuntos
Ração Animal/análise , Bactérias/metabolismo , Bovinos/microbiologia , Rúmen/microbiologia , Animais , Bactérias/classificação , Bactérias/genética , Bactérias/isolamento & purificação , Bovinos/metabolismo , Dieta/veterinária , Rúmen/metabolismo
2.
J Anim Sci ; 96(5): 1996-2011, 2018 May 04.
Artigo em Inglês | MEDLINE | ID: mdl-29733420

RESUMO

Three experiments evaluated the effects of corn oil removal using centrifugation in ethanol plants, on animal performance and digestion characteristics by finishing cattle fed by-products. In Exp. 1, 225 crossbred steers (300 ± 9.1 kg) were utilized in a randomized block design with a 2 × 2 + 1 factorial arrangement of treatments. Factors consisted of oil concentration [de-oiled (DO) or full fat (FF)] and by-product type [condensed distillers solubles (CDS) or modified distillers grains plus solubles (MDGS)] compared to a corn-based control. Fat concentration was 6.0% for DO CDS, 21.1% for FF CDS, 9.2% for DO MDGS, and 11.8% for FF MDGS. No oil concentration by by-product type interactions (P ≥ 0.17) were observed. There were no differences in DMI, ADG, or G:F between DO and FF CDS (P ≥ 0.29) or DO and FF MDGS (P ≥ 0.58). No differences (P ≥ 0.25) due to oil concentration were observed for carcass characteristics. Experiment 2 was a 5 × 5 Latin Square digestion trial with treatments similar to Exp. 1. Fat concentration was 8.7% or 15.4% for DO or FF CDS and 9.2% or 12.3% for DO or FF MDGS. Intake and total tract digestibility of fat were greater (P ≤ 0.02) for FF CDS compared with DO CDS. Digestible energy (megacalorie per kilogram), adjusted for intake, was greater (P = 0.02) for steers fed FF CDS compared to DO CDS. Average ruminal pH for cattle fed FF MDGS was greater than DO MDGS (P = 0.06). In Exp. 3, 336 yearling, crossbred steers (352 ± 19 kg) were utilized in a randomized block design with a 2 × 3 + 1 factorial arrangement of treatments. Factors included oil concentration (DO or FF) and inclusion [35%, 50%, and 65% wet distillers grains plus solubles (WDGS)] along with a corn-based control. The fat concentrations of DO and FF WDGS were 7.9% and 12.4%, respectively. A linear interaction (P < 0.01) was observed for DMI, which produced different slopes for DO and FF WDGS. No linear or quadratic interactions were observed for BW, ADG, or G:F (P ≥ 0.31). For the main effect of oil concentration, there were no statistical differences (P > 0.19) for final BW, ADG, or G:F. No statistical differences were observed for all carcass traits (P ≥ 0.34). Corn oil removal via centrifugation had minimal impact on finishing performance suggesting that cattle fed DO by-products will have similar performance to cattle fed FF by-products in dry-rolled and high-moisture corn diets.


Assuntos
Ração Animal/análise , Bovinos/fisiologia , Animais , Bovinos/crescimento & desenvolvimento , Óleo de Milho , Dieta/veterinária , Digestão , Grão Comestível , Trato Gastrointestinal/metabolismo , Masculino , Distribuição Aleatória , Zea mays
3.
J Clin Invest ; 69(3): 499-506, 1982 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-6801089

RESUMO

Acidosis inhibits the hydroosmotic response to vasopressin. Since prostaglandins are known to modulate vasopressin-stimulated water flow we investigated the role of endogenous prostaglandin E2(PGE2) production in the pH-dependent response of the toad urinary bladder to vasopressin. Graded acidification of the serosal medial resulted in a progressive decline in vasopressin-stimulated water flow from 26.6 +/- 0.5 mg/min at pH 8.4 to 1.7 +/- 0.6 at pH 6.9. In these bladders basal PGE2 synthesis increased from 5.09 +/- 0.51 pmol/min per g hemibladder at pH 8.4 to 18.8 +/- 2.8 at pH 6.9. The addition of that concentration of PGE2 produced by the bladder at pH 7.4 (4 nM) to bladders at pH 8.4 resulted in 62-71% of the inhibition usually seen at pH 7.4; these data suggest that basal PGE2 production per se and not other products of prostaglandin synthesis or other pH-dependent events is responsible for the effect of acidosis. Preincubation with prostaglandin synthesis inhibitors reversed in major part the effect of serosal acidification on the response to submaximal concentrations of vasopressin and completely abolished the effect of pH on near maximal concentrations of the hormone. An increase in PGE2 synthesis after vasopressin was not seen at any pH. These studies establish that increased basal PGE2 synthesis plays a critical role in the pH dependence of the hydroosmotic response to vasopressin and demonstrate that factors that modulate the response to vasopressin may exert this effect by changing the basal rate of prostaglandin synthesis.


Assuntos
Concentração de Íons de Hidrogênio , Prostaglandinas E/fisiologia , Bexiga Urinária/efeitos dos fármacos , Vasopressinas/farmacologia , Acidose/fisiopatologia , Animais , Bufo marinus , Dinoprostona , Feminino , Osmose/efeitos dos fármacos , Prostaglandinas E/biossíntese
4.
J Anim Sci ; 95(8): 3639-3653, 2017 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-28805922

RESUMO

Four experiments evaluated the use of a complete starter feed (RAMP; Cargill Corn Milling, Blair, NE) for grain adaptation. In Exp. 1, 229 yearling steers (397 ± 28.4 kg BW) were used to compare a traditional adaptation program (CON) with adapting cattle with RAMP in either a 1- (RAMP-1RS) or 2- (RAMP-2RS) ration system. From d 23 to slaughter, cattle were fed a common finishing diet. In Exp. 2, 390 yearling steers (341 ± 14 kg BW) were used to compare accelerated grain adaptation programs with RAMP with 2 control treatments where RAMP was blended with a finishing diet containing either 25 (CON25) or 47.5% (CON47) Sweet Bran (Cargill Corn Milling) in 4 steps fed over 24 d to adapt cattle. Rapid adaptation treatments involved feeding RAMP for 10 d followed by a blend of RAMP and a 47% Sweet Bran finishing diet to transition cattle with 3 blends fed for 1 d each (3-1d), 2 blends fed for 2 d each (2-2d), or 1 blend fed for 4 d (1-4d). From d 29 to slaughter, all cattle were fed a common finishing diet. In Exp. 3, 300 steer calves (292 ± 21 kg BW) were used to compare the CON47 and 1-4d adaptation programs with directly transitioning cattle from RAMP, which involved feeding RAMP for 10 d and then switching directly to F1 on d 11 (1-STEP). From d 29 until slaughter, F2 was fed to all cattle. In Exp. 4, 7 ruminally fistulated steers (482 ± 49 kg BW) were used in a 35-d trial to compare the CON47 and 1-STEP adaptation programs. Ruminal pH and intake data from the first 6 d of F1and first 6 d of F2 were used to compare adaptation systems. Adaptation with RAMP-1RS and RAMP-2RS increased ( < 0.01) G:F compared with cattle adapted using CON in Exp. 1. Feeding RAMP-1RS increased ADG ( = 0.03) compared with CON. Intakes were similar ( = 0.39) among treatments. Daily gain, DMI, G:F, and carcass traits were similar ( > 0.11) among treatments in Exp. 2. Daily gain, DMI, and G:F were not different ( > 0.20) among treatments on d 39 or over the entire feeding period in Exp. 3. When F1 or F2 was being fed, DMI was similar ( ≥ 0.40) for CON47 and 1-STEP in Exp. 4. When F1 or F2 was being fed, 1-STEP cattle had lower average ruminal pH ( ≤ 0.03) and greater time below a pH of 5.3 ( ≤ 0.03). Using RAMP for grain adaptation improved performance compared with traditional adaptation. Rapid adaptation with RAMP decreased pH, but no performance differences were observed between long and rapid RAMP adaptation programs. Therefore, cattle started on RAMP do not require extensive adaptation before feeding a finishing diet with Sweet Bran.


Assuntos
Ração Animal/análise , Bovinos/fisiologia , Dieta/veterinária , Adaptação Fisiológica , Criação de Animais Domésticos , Fenômenos Fisiológicos da Nutrição Animal , Animais , Digestão , Grão Comestível , Masculino , Zea mays
5.
J Anim Sci ; 93(7): 3613-22, 2015 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-26440029

RESUMO

Two studies were conducted to optimize use of alkaline-treated corn stover and wheat straw and distillers grains as partial corn replacements. In Exp. 1, a finishing experiment used 30 pens (12 steers/pen) of calf-fed steers (initial BW = 374 ± 23.9 kg) with a 2 × 2 + 1 factorial arrangement of treatments with 6 replications per treatment. Factors were grind size, where corn stover was processed through a 2.54- or 7.62-cm screen, and chemical treatment (corn stover either fed in native, non-treated form [NT; 93.4% DM] or alkaline treated [AT; 5% CaO hydrated to 50% DM]). No interactions (P ≥ 0.38) were noted between grind size and chemical treatment. Feeding AT compared with NT improved (P ≤ 0.02) final BW, ADG, and G:F. Reducing grind size improved (P ≤ 0.01) ADG and G:F, and no interaction with chemical treatment was observed. Steers fed AT had similar DMI, ADG, G:F, and carcass characteristics compared with a 5% roughage control that contained 15 percentage units (DM basis) more corn. In Exp. 2, 60 individually fed steers (initial BW = 402 ± 61.4 kg) were randomly assigned to 10 diets. Six treatments evaluated 10, 25, or 40% dry-rolled corn (DRC), which was replaced with either a 2:1 or 3:1 ratio (DM basis) of modified distillers grains plus solubles (MDGS) and treated corn stover analyzed as a 2 × 3 factorial. An additional 3 treatments were added where a 3:1 ratio of MDGS:straw were compared with a 3:1 ratio of MDGS:stover. As DRC increased, G:F (P = 0.06) quadratically increased for 3:1 MDGS:stover diets. Increasing DRC increased (P = 0.07) G:F in treated stover diets, regardless of ratio. Increasing DRC increased (P = 0.10) ADG for 3:1 ratios for both straw and stover. Reducing grind size, feeding a maximum of 20% treated crop residue, and maintaining at least 25% corn in the diet are strategies for optimizing cattle performance when replacing dry-rolled and high-moisture corn with treated crop residues and distillers grains.


Assuntos
Ração Animal/análise , Dieta/veterinária , Aumento de Peso/efeitos dos fármacos , Zea mays/química , Animais , Bovinos , Grão Comestível , Manipulação de Alimentos , Masculino
6.
Int J Radiat Oncol Biol Phys ; 41(1): 139-50, 1998 Apr 01.
Artigo em Inglês | MEDLINE | ID: mdl-9588929

RESUMO

PURPOSE: Investigation of normal tissue sparing in pulsed brachytherapy (PB) relative to continuous low-dose rate irradiation (CLDR) by adjusting pulse frequency based on tissue repair characteristics. METHOD: Using the linear quadratic model, the relative effectiveness (RE) of a 20 Gy boost was calculated for tissue with an alpha/beta ratio ranging from 2 to 10 Gy and a half-time of sublethal damage repair between 0.1 and 3 h. The boost dose was considered to be delivered either in a number of pulses varying from 2 to 25, or continuously at a dose rate of 0.50, 0.80, or 1.20 Gy/h. RESULTS: The RE of 20 Gy was found to be identical for PB in 25 pulses of 0.80 Gy each h and CLDR delivered at 0.80 Gy/h for any alpha/beta value and for a repair half-time > 0.75 h. When normal tissue repair half-times are assumed to be longer than tumor repair half-times, normal tissue sparing can be obtained, within the restriction of a fixed overall treatment time, with higher dose per pulse and longer period time (time elapsed between start of pulse n and start of pulse n + 1). An optimum relative normal tissue sparing larger than 10% was found with 4 pulses of 5 Gy every 8 h. Hence, a therapeutic gain might be obtained when changing from CLDR to PB by adjusting the physical dose in such a way that the biological dose on the tumor is maintained. The normal tissue-sparing phenomenon can be explained by an increase in RE with longer period time for tissue with high alpha/beta ratio and fast or intermediate repair half-time, and the RE for tissue with low alpha/beta ratio and long repair half-time remains almost constant. CONCLUSION: Within the benchmark of the LQ model, advantage in normal tissue-sparing is expected when matching the pulse frequency to the repair kinetics of the normal tissue exposed. A period time longer than 1 h may lead to a reduction of late normal tissue complications. This theoretical advantage emphasizes the need for better knowledge of human tissue-repair kinetics.


Assuntos
Braquiterapia/métodos , Modelos Biológicos , Lesões Experimentais por Radiação/fisiopatologia , Radiobiologia/métodos , Cicatrização/fisiologia , Animais , Humanos , Eficiência Biológica Relativa , Fatores de Tempo
7.
Neuropharmacology ; 31(3): 307-9, 1992 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-1321360

RESUMO

Inhibition of calcium-evoked [3H]ACh release by different classes of calcium channel blockers was compared among calcium-naive synaptosomes from chick, frog and rat forebrain tissues. In all three species, [3H]ACh release was insensitive to nifedipine (0.03-3 microM) but was completely inhibited by cadmium (IC50 range = 0.7-1.7 microM) or cobalt (190-350 microM). In contrast, the peptide omega-conotoxin revealed marked species heterogeneity in that [3H]ACh release was potently blocked in chick and rat synaptosomes (IC50 congruent to 1 nM), whereas frog tissue was notably resistant (IC50 greater than 100 nM). Together, these data provide functional evidence for pharmacological heterogeneity among presynaptic calcium channels that subserve [3H]ACh release.


Assuntos
Acetilcolina/metabolismo , Canais de Cálcio/efeitos dos fármacos , Prosencéfalo/metabolismo , ômega-Conotoxinas , Animais , Bloqueadores dos Canais de Cálcio/farmacologia , Galinhas , Exocitose/efeitos dos fármacos , Técnicas In Vitro , Masculino , Peptídeos Cíclicos/farmacologia , Prosencéfalo/efeitos dos fármacos , Rana pipiens , Ratos , Ratos Endogâmicos , Especificidade da Espécie , Sinaptossomos/efeitos dos fármacos , Sinaptossomos/metabolismo
8.
Proc Biol Sci ; 268(1474): 1381-6, 2001 Jul 07.
Artigo em Inglês | MEDLINE | ID: mdl-11429138

RESUMO

We present evidence that a relatively widespread and common bat from South East Asia comprises two morphologically cryptic but acoustically divergent species. A population of the bicoloured leaf-nosed bat (Hipposideros bicolor) from Peninsular Malaysia exhibits a bimodal distribution of echolocation call frequencies, with peaks in the frequency of maximum energy at ca. 131 and 142 kHz. The two phonic types are genetically distinct, with a cytochrome b sequence divergence of just under 7%. We consider the mechanisms by which acoustic divergence in these species might arise. Differences in call frequency are not likely to effect resource partitioning by detectable prey size or functional range. However, ecological segregation may be achieved by differences in microhabitat use; the 131kHz H. bicolor is characterized by significantly longer forearms, lower wing loading, a lower aspect ratio and a more rounded wingtip, features that are associated with greater manoeuvrability in flight that may enable it to forage in more cluttered environments relative to the 142 kHz phonic type. We suggest that acoustic divergence in these species is a consequence of social selection for a clear communication channel, which is mediated by the close link between the acoustic signal and receptor systems imposed by the highly specialized nature of the hipposiderid and rhinolophid echolocation system.


Assuntos
Quirópteros/fisiologia , Ecolocação , Animais , Comportamento Animal , Evolução Biológica , Especificidade da Espécie
9.
Radiother Oncol ; 59(3): 273-80, 2001 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-11369068

RESUMO

BACKGROUND AND PURPOSE: Radiobiological studies suggest equivalent biological effects between continuous low dose rate brachytherapy (CLDR) and pulsed brachytherapy (PB) when pulses are applied without interruption every hour. However, radiation protection and institute-specific demands requested the design of a practical PB protocol substituting the CLDR boost in breast cancer patients. An office hours scheme was designed, considering the CLDR dose rate, the overall treatment time, pulse frequency and tissue repair characteristics. Radiobiological details are presented as well as the logistics and technical feasibility of the scheme after treatment of the first 100 patients. MATERIALS AND METHODS: Biologically effective doses (BEDs) were calculated according to the linear quadratic model for incomplete repair. Radiobiological parameters included an alpha/beta value of 3 Gy for normal tissue late effects and 10 Gy for early normal tissue or tumour effects. Tissue repair half-time ranged from 0.1 to 6 h. The reference CLDR dose rate of 0.80 Gy/h was obtained retrospectively from analysis of patients' data. The treatment procedure was evaluated with regard to variations in implant characteristics after treatment of 100 patients. RESULTS: A PB protocol was designed consisting of two treatment blocks separated by a night break. Dose delivery in PB was 20 Gy in two 10 Gy blocks and, for application of the 15 Gy boost, one 10 Gy block plus one 5 Gy block. The dose per pulse was 1.67 Gy, applied with a period time of approximately 1.5 h. An inter-patient variation of 30% (1 SD) was observed in the instantaneous source strength. Taking also the spread in implant size into account, the net variation in pulse duration amounted to 38%. CONCLUSION: An office hours PB boost regimen was designed for substitution of the CLDR boost in breast-conserving therapy on the basis of the BED. First treatment experience shows the office hour regimen to be convenient to the patients and no technical perturbations were encountered.


Assuntos
Braquiterapia , Neoplasias da Mama/radioterapia , Feminino , Humanos , Pulso Arterial , Eficiência Biológica Relativa
10.
Med Phys ; 22(6): 755-65, 1995 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-7565364

RESUMO

An approach to a solution of two major problems in operating Annular Phased Arrays in deep body hyperthermia is presented: an E-field sensor capable of measuring phase and amplitude at 70 MHz and the concept of a power transmission factor to determine the effective amplitude of each applicator. In the four-waveguide Phased Array operating at 70 MHz, which is in clinical use at the department of Radiotherapy of the Academic Medical Center (AMC), the incident fields of the waveguides were scanned in phase and amplitude over the complete aperture midplane, inside an elliptical and a square phantom filled with saline. As a check on the application of the superposition principle, superpositions of the incident fields were compared with the electric field in the measured interference set-ups. With all four applicators radiating at equal amplitude and in phase, the maximum difference over the complete midplane of the phantom between superimposed and measured interference scans was 20% and 10 degrees in the elliptical phantom, and 20% and 30 degrees in the square phantom. After having determined nominal amplitude and phase patterns by a vector probe, any interference set-up can be superimposed from measurement of the actual incident field of each applicator. Therefore, the availability of a vector sensor as described here will contribute to solve a problem of hyperthermia quality assurance: the performance evaluation of Phased Arrays.


Assuntos
Hipertermia Induzida/normas , Modelos Estruturais , Ondas de Rádio , Humanos , Hipertermia Induzida/instrumentação , Hipertermia Induzida/métodos , Matemática , Controle de Qualidade
11.
Phys Med Biol ; 36(4): 461-74, 1991 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-2047396

RESUMO

An experimental study is described, leading to the design of a near-field electromagnetic radiation probe. A passive field probe with fibre-optic link has been constructed for use in hyperthermia phantoms, i.e. for measurements in lossy media--saline was used in this study as a simulation of biological tissue. The realization of a closed electric circuit on the probe proved to be a major influence on the sensitivity and dynamic range of the probe. The experiments also independently confirmed the dipole length, frequency variations between 5 and 110 MHz and the temperature of the probe as important parameters.


Assuntos
Hipertermia Induzida/instrumentação , Desenho de Equipamento , Tecnologia de Fibra Óptica , Humanos , Modelos Estruturais , Cloreto de Sódio , Soluções
12.
IEEE Trans Biomed Eng ; 42(7): 694-8, 1995 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-7622152

RESUMO

There are a number of potential advantages to be gained by using an array of applicators in hyperthermia treatments compared with single applicator systems. These advantages include the possibility of greater spatial control of power deposition and conformability to nonplanar sites. Arrays of applicators can be driven either coherently or incoherently. In the case of coherent operation, an added advantage is the ability to steer power deposition by varying the phases of the antennas. In this study, we investigated the relative merits of the two modes of operation when a 2 x 2 planar array of current sheet applicators is used. The effective field size (EFS) of the array was calculated using a Gaussian beam representation of the applicators on a layered model in which the fat layer had its thickness varied. Good agreement was obtained between the square of the electric field distribution (E2) and quantitative experimental results. It is shown that when the planar array is used with a fat layer greater than about 2 mm present, it should be driven incoherently as this results in a significantly larger EFS than that obtained when the array is driven coherently.


Assuntos
Hipertermia Induzida/instrumentação , Hipertermia Induzida/métodos , Modelos Biológicos , Humanos
13.
Br J Radiol ; 71(844): 433-7, 1998 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-9659137

RESUMO

Hypoxic clonogenic cells are an important contributory factor in tumour radioresistance. The objective of the present study was to evaluate whether hyperbaric oxygen enhances tumour radiosensitivity, using a conventionally fractionated irradiation schedule, and whether the radiosensitizing potential is different from carbogen. Experiments were performed using the rhabdomyosarcoma R1H model transplanted subcutaneously in the flank of WAG/Rij rats. A total of 30 X-ray fractions of 2 Gy were given either in air, normobaric carbogen or high pressure oxygen (HPO) (240 kPa, 2.37 atm) without anaesthesia. The time taken to achieve complete remission was 38.7 +/- 3.6 days, 36.7 +/- 2.7 days and 32.4 +/- 4.1 days for air, normobaric carbogen and HBO, respectively. The differences between air and HBO (p = 0.002) and carbogen and HBO (p = 0.015) were significant. Use of carbogen and HBO produced the same local control probability at 150 days and this was significantly higher than local control under ambient conditions (p < 0.0001). It was concluded that the time to achieve complete remission of the rat rhabdomyosarcoma R1H can be shortened by HBO. Furthermore, both HBO and carbogen give higher local control probabilities than treatment under ambient conditions when used with a conventionally fractionated radiation schedule.


Assuntos
Dióxido de Carbono/uso terapêutico , Oxigenoterapia Hiperbárica , Oxigênio/uso terapêutico , Radiossensibilizantes/uso terapêutico , Rabdomiossarcoma/radioterapia , Animais , Intervalo Livre de Doença , Fracionamento da Dose de Radiação , Masculino , Transplante de Neoplasias , Ratos , Ratos Endogâmicos , Rabdomiossarcoma/patologia
14.
J Anim Sci ; 89(8): 2582-91, 2011 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-21383040

RESUMO

Crossbred yearling steers (n=80; 406 ± 2.7 kg of BW) were used to evaluate the effects of S concentration in dried distillers grains with solubles (DDGS) on growth performance, carcass characteristics, and ruminal concentrations of CH(4) and H(2)S in finishing steers fed diets based on steam-flaked corn (SFC) or dry-rolled corn (DRC) and containing 30% DDGS (DM basis) with moderate S (0.42% S, MS) or high S (0.65% S, HS). Treatments consisted of SFC diets containing MS (SFC-MS), SFC diets containing HS (SFC-HS), DRC diets containing MS (DRC-MS), or DRC diets containing HS (DRC-HS). High S was achieved by adding H(2)SO(4) to DDGS. Ruminal gas samples were analyzed for concentrations of H(2)S and CH(4). Steers were fed once daily in quantities that resulted in traces of residual feed in the bunk the following day for 140 d. No interactions (P ≥ 0.15) between dietary S concentration and grain processing were observed with respect to growth performance or carcass characteristics. Steers fed HS diets had 8.9% less DMI (P < 0.001) and 12.9% less ADG (P=0.006) than steers fed diets with MS, but S concentration had no effect on G:F (P=0.25). Cattle fed HS yielded 4.3% lighter HCW (P = 0.006) and had 16.2% less KPH (P=0.009) than steers fed MS. Steers fed HS had decreased (P=0.04) yield grades compared with steers fed MS. No differences were observed among treatments with respect to dressing percentage, liver abscesses, 12th-rib fat thickness, LM area, or USDA quality grades (P ≥ 0.18). Steers fed SFC had less DMI (P < 0.001) than steers fed DRC. Grain processing had no effect (P > 0.05) on G:F or carcass characteristics. Cattle fed HS had greater (P < 0.001) ruminal concentrations of H(2)S than cattle fed MS. Hydrogen sulfide concentration was inversely related (P ≤ 0.01) to ADG (r=-0.58) and DMI (r=-0.67) in cattle fed SFC, and to DMI (r=-0.40) in cattle fed DRC. Feeding DDGS that are high in dietary S may decrease the DMI of beef steers and compromise the growth performance and carcass characteristics of feedlot cattle.


Assuntos
Ração Animal/análise , Bovinos , Dieta/veterinária , Grão Comestível/química , Manipulação de Alimentos/métodos , Enxofre/química , Fenômenos Fisiológicos da Nutrição Animal , Animais , Composição Corporal/efeitos dos fármacos , Ingestão de Alimentos , Masculino , Metano , Rúmen/metabolismo , Compostos de Sulfidrila , Enxofre/farmacologia
17.
Biofeedback Self Regul ; 12(2): 71-92, 1987 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-3122851

RESUMO

This paper reviews multicomponent behavioral medicine studies that contain cost-effectiveness and or cost-benefit data relevant to the field of biofeedback and relaxation training, primarily when assisted by biofeedback, with or without stress management, in the treatment of psychosomatic illness and pain. A model for evaluating biofeedback treatment is presented. Cost-effectiveness data concerning reduction in physician visits and/or medication use, decrease in medical care costs to patients, reduction in hospital stays and rehospitalization, reduction of mortality, and enhanced quality of life are reviewed. Evidence suggests that multicomponent behavioral medicine treatments are cost-effective on all dimensions reviewed. Cost/benefit ratios range between 1:2 and 1:5, with a median of 1:4. Evidence that could increase the cost effectiveness of biofeedback is reviewed.


Assuntos
Biorretroalimentação Psicológica , Análise Custo-Benefício , Transtornos Psicofisiológicos/terapia , Terapia Combinada , Humanos , Tempo de Internação , Qualidade de Vida , Terapia de Relaxamento/economia
18.
Mol Ecol ; 5(2): 239-49, 1996 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-8673270

RESUMO

Distinguishing between primary and secondary intergradation among differentiated populations, and the relative importance of drift and selection, are persistent problems in evolutionary biology. An historical perspective on population interactions can provide insight into the nature of contacts, and thus help resolve these questions. Continuously distributed populations of Anolis marmoratus from the island of Basse Terre in the Guadeloupean archipelago of the Lesser Antilles show a striking degree of geographic variation in morphology. Initial surveys of mtDNA variation from throughout the Guadeloupean Archipelago revealed one case where levels of sequence difference and phylogenetic relationships of alleles from morphologically differentiated populations from the east coast of Basse Terre were consistent with primary intergradation. In this paper, I examine the genetic population structure of a series of populations spanning this north-south cline in morphological variation to test the hypothesis of primary intergradation. Sequences of the mitochondrial cytochrome-b gene from 50 individuals representing five populations spanning the cline were obtained and fourteen unique haplotypes (differing by 2% or less) were detected. Patterns of nucleotide substitution among haplotypes do not deviate from neutral expectation indicating no effect of selection at the level of mtDNA sequences. Estimates of population structure and gene flow were made using both summary statistics for nucleotide diversity (Nst) and cladistic methods. The results are sensitive to the choice of gene flow model, and this is discussed in detail. Mitochondrial variation in the northern populations may not be at equilibrium, and the phylogeny of alleles is consistent with a recent increase in effective population size. Estimates of nucleotide diversity, gene flow, and the phylogenetic relationships of haplotypes indicate that the southern-most population (representing the extreme of morphological variation along this cline) has been relatively isolated from populations to the north and has experienced a reduced effective population size. The apparent clinal variation between the southern population and the others may therefore reflect secondary contact and introgression rather than primary intergradation.


Assuntos
Lagartos/genética , Animais , Sequência de Bases , DNA/genética , DNA Mitocondrial/genética , Ecossistema , Evolução Molecular , Variação Genética , Genética Populacional , Haplótipos , Lagartos/anatomia & histologia , Lagartos/classificação , Dados de Sequência Molecular , Filogenia , Índias Ocidentais
19.
Neurochem Res ; 16(10): 1175-85, 1991 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-1795760

RESUMO

Calcium-naive synaptosomes were used to assess the effects of divalent cations on [3H]acetylcholine release from rat hippocampal homogenates. Following equilibration with calcium-free buffer (containing 10 microM EGTA), calcium reversibly increased [3H]acetylcholine efflux (up to five-fold) while causing no measurable efflux of lactate dehydrogenase. When substituted for calcium, strontium and barium behaved similarly although barium exhibited three-fold greater efficacy. In the presence of elevated potassium, 4-aminopyridine or tetraethylammonium, the secretagogue efficacy of calcium (but not barium) was markedly increased. The release-promoting effects of both cations were inhibited by lanthanum, magnesium, cadmium, and omega-conotoxin but were insensitive to nifedipine and cobalt (both 10 microM). In addition, stimulation of muscarinic cholinergic autoreceptors substantially inhibited both calcium and barium-evoked [3H]acetylcholine release. Taken together, these results indicate that cation-evoked transmitter release from calcium-naive synaptosomes is subject to normal neuroregulatory mechanisms and therefore should be useful for investigating presynaptic modulation of neuronal exocytosis.


Assuntos
Acetilcolina/metabolismo , Bário/farmacologia , Cálcio/farmacologia , Ácido Egtázico/farmacologia , Hipocampo/metabolismo , Sinaptossomos/metabolismo , Animais , Cátions Bivalentes , Hemicolínio 3/farmacologia , Cinética , Masculino , Fisostigmina/farmacologia , Ratos , Ratos Endogâmicos , Sinaptossomos/efeitos dos fármacos , Trítio
20.
Genetica ; 112-113: 383-98, 2001.
Artigo em Inglês | MEDLINE | ID: mdl-11838777

RESUMO

Hypotheses for divergence and speciation in rainforests generally fall into two categories: those emphasizing the role of geographic isolation and those emphasizing the role of divergent selection along gradients. While a majority of studies have attempted to infer mechanisms based on the pattern of species richness and congruence of geographic boundaries, relatively few have tried to simultaneously test alternative hypotheses for diversification. Here we discuss four examples, taken from our work on diversification of tropical rainforest vertebrates, in which we examine patterns of genetic and morphological variation within and between biogeographic regions to address two alternative hypotheses. By estimating morphological divergence between geographically contiguous and isolated populations under similar and different ecological conditions, we attempt to evaluate the relative roles of geographic isolation and natural selection in population divergence. Results suggest that natural selection, even in the presence of appreciable gene flow, can result in morphological divergence that is greater than that found between populations isolated for millions of years and, in some cases, even greater than that found between congeneric, but distinct, species. The relatively small phenotypic divergence that occurs among long-term geographic isolates in similar habitats suggests that morphological divergence via drift may be negligible and/or that selection is acting to produce similar phenotypes in populations occupying similar habitats. Our results demonstrate that significant phenotypic divergence: (1) is not necessarily coupled with divergence in neutral molecular markers; and (2) can occur without geographic isolation in the presence of gene flow.


Assuntos
Adaptação Biológica/genética , Evolução Biológica , Lagartos , Modelos Biológicos , Aves Canoras , África , Animais , Austrália , DNA Mitocondrial , Feminino , Variação Genética , Lagartos/genética , Masculino , Fenótipo , Filogenia , Seleção Genética , Aves Canoras/genética , Clima Tropical , Vertebrados/genética
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