Search PubMed⌕ Search

Biomedical subjects

R A Field

Publications and source records attributed to R A Field.

At least 55 records · Page 3Linked to original sources
PubMed1991

Isolation and partial characterisation of ACV synthetase from Cephalosporium acremonium and Streptomyces clavuligerus. Evidence for the presence of phosphopantothenate in ACV synthetase.

delta-(L-alpha-Aminoadipoyl)-L-cysteinyl-D-valine (ACV) synthetase was isolated and partially characterised from Cephalosporium acremonium CO728 and Streptomyces clavuligerus. The purification procedure resulted in a 745- and 277-fold increase in specific enzyme activity, respectively. Both enzymes had similar apparent molecular masses of ca. 300 kdaltons by SDS-polyacrylamide electrophoresis, under reducing and denaturing conditions, and in excess of 600 kdaltons in the native state by gel filtration. Attempts to obtain an N-terminal amino acid sequence of ACV synthetase from C. acremonium were unsuccessful, hence internal amino acid sequence data were obtained after tryptic digestion of the protein. Phosphopantothenic acid was shown to be associated with the enzyme from both sources, which suggests the possible involvement of pantothenate as a 'swinging arm' in the formation of the tripeptide ACV.

Acremonium↗
PubMed1990

Bone ossification and carcass characteristics of wethers given silastic implants containing estradiol.

Administration of growth promotants with estrogenic activity via hastening closure of the growth plate could have an economic impact on lambs because closure results in ovine carcasses being classified as yearlings. Twelve wether lambs approximately 12 mo old were given silastic implants filled with estradiol-17 beta and allotted randomly to be slaughtered 30, 60, 90, or 220 d after implantation to determine time of growth plate closure in relation to date of implanting. Seven comparable wethers not implanted served as controls. Four wethers implanted at 2 mo of age and slaughtered 220 d later also were included. Implanted wethers had serum concentrations of estradiol averaging 13.9 pg/ml over the 220-d implant period; controls averaged 2.7 pg/ml. Estradiol implants increased carcass maturity scores but fat deposition was not altered. Growth plate widths decreased (P less than .05) as wethers grew older and implants were in place for longer periods of time. Metacarpal growth plates in 12-mo-old lambs were completely ossified 220 d after implanting, but control wethers and wethers implanted at 2 mo maintained growth plate widths. Neither metacarpal nor metatarsal bone lengths differed (P less than .05) between control and implanted wethers. Growth plate ossification was not complete until 570 d of age in implanted lambs, even though bone length had stopped increasing by 408 d. Therefore, even though estradiol and other growth stimulants with estrogenic activity increase rate of ossification of the metacarpal growth plate, bone length or mature size is not limited.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
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

Influence of age and testosterone levels on masculine development in rams.

Fifty wethers and 51 spring-born rams were divided into five groups and slaughtered at different seasons of the year at average ages of 271, 361, 459, 557 or 652 d to determine the age and season at which differences in secondary sex characteristics could be detected. Serum testosterone concentrations and testes weights were low in January when the rams were 271 d of age and again in April at 361 d of age. By July, at 459 d of age, testosterone concentrations and testes weights had peaked and then decreased the following November at 557 d and February at 652 d. In contrast with plasma testosterone concentrations and testes weights, buckiness scores, splenius to semimembranosus or semitendinosus muscle ratios, splenius muscle weights and neck and shoulder percentages were not seasonal. All of these measures increased significantly up to July and continued to increase slowly, but not significantly, thereafter. Muscle color and texture scores and rib eye color scores tended to increase in a linear manner for both rams and wethers as age increased. Subcutaneous fat from rams was yellower and softer than that from wethers over all age groups. Ram fat firmness did not change (P greater than .05) with age, and the only significant change in ram fat color was between the groups at 271 and 361 d of age. Overall, season of year coupled with higher levels of serum testosterone was related to initial development of secondary sex characteristics in ram lambs.

Adipose Tissue↗
PubMed1989

Influence of gender, breed and age on maturity characteristics of sheep.

Fifty-one ewes, 50 wethers and 51 rams of Finn x whiteface or Suffolk x whiteface breeding were slaughtered at an average age of 271, 361, 459, 557 or 652 d to study changes in maturity characteristics with changes in age. When metacarpal epiphyseal cartilage (growth plates) ossifies with age, break joints on the distal end of the metacarpals fuse and the end of the bone then appears as a spool joint rather than as a break joint. This fusion occurs earlier chronologically in ewes than in rams or wethers. Most Finn x whiteface-cross ewes, which normally reach reproductive maturity earlier than Suffolk x whiteface-cross ewes, exhibited ossified metacarpal growth plates by 459 d of age; break joints of Suffolk x whiteface crosses were not fused until 557 d of age. Both breed groups of rams exhibited fused joints by 557 d of age, but only 3 of 10 wethers exhibited spool joints at 652 d of age. Microscopic examination showed that even in these three wethers the epiphyseal growth plate could still be detected. Yearling 2-yr-old classifications of sheep from teeth were not gender-dependent within the discrete age classes of this study. About half the sheep in each gender group were classified as yearlings at 459 d of age and about half in each group were classified as 2-yr-olds by 652 d of age. Stepwise multiple regression equations to estimate age of sheep in days were developed. Overall maturity, lean color and texture and rib bone maturity were the best carcass measures of maturity. Maturity scores for characteristics of the break joint did not enter any of the equations studied. When eye lens weight was included in equations with the best measures of carcass maturity, accuracy of estimates for age of sheep was improved.

Age Determination by Teeth↗
PubMed1987

A comparison by magnetic circular dichroism of compound X and compound II of horseradish peroxidase.

The chlorite product of horseradish peroxidase, compound X, is shown by magnetic circular dichroism (MCD) spectroscopy in the temperature range 1.6-50 K to have a very similar haem structure to compound II under the same conditions (pH 10.7). Both are concluded to contain the Fe(IV) = 0 group. The MCD spectrum also detects an unusual species, absorbing at wavelengths between 600 and 750 nm, that has magnetic properties different from those of the ferryl haem group. It is suggested that this is a species at the same oxidation level as ferryl haem but with the porphyrin ring having suffered a one-electron oxidation, i.e. [Fe(III) P.+].

Chlorine↗
PubMed1987

Effects of maternal undernutrition during early pregnancy on growth, muscle cellularity, fiber type and carcass composition in lambs.

Seventy-two Rambouillet ewes were fed one of two different levels of energy and protein during gestation to determine the effects of maternal undernutrition on growth and development in their offspring. Levels of energy and protein for the two groups of ewes were: 70% of National Research Council (NRC) requirements 30 d prior to breeding and the first 100 d of gestation and then alfalfa hay fed at 70% of the average consumed by group 2, and 100% of NRC requirements 30 d prior to breeding and throughout gestation. Dissection data from the leg and muscle characteristics were recorded for each lamb. Neither dissected muscle and fat percentages nor proximate analyses of dissected muscles was influenced by ewe undernutrition during early pregnancy. However, the reduced conception rate, increased embryonic/fetal mortality, decreased birth weights and increased lamb mortality resulted in a severe reduction in kilograms of lamb per ewe bred. Feeding ewes 70% of NRC requirements during gestation resulted in lambs with heavier semitendinosus muscle weights, larger muscle fiber diameters and shorter sarcomere lengths than in lambs from adequately fed ewes. No influence of ewe diet, birth type or sex was observed for proportions of muscle fiber type (beta R, alpha R or alpha W). Therefore, low level feeding of ewes during early gestation had no detrimental effects on the carcass or muscle fiber characteristics of their lambs at slaughter.

Animal Nutritional Physiological Phenomena↗
PubMed1985

Characteristics of male fallow deer muscle at a time of sex-related muscle growth.

Muscle characteristics of male fallow deer undergoing neck muscle enlargement as the mating season (rut) approached were studied. Five commercially-raised males were slaughtered prerut and five were slaughtered 11 weeks later, just before the rut began. During this period, increases in individual muscle weight were not the same: two of the three neck muscles studied grew more rapidly than the average, whereas the back and two hind leg muscles grew more slowly. The splenius, the neck muscle that grew the most apparently in response to a rise in plasma testosterone, was studied. Cryosections were cut and stained for myofibrillar ATPase so that the muscle fiber classes--slow oxidative (type I), fast oxidative-glycolytic (type IIA) and fast glycolytic (type IIB)--could be distinguished. The IIB class was absent from the splenius and the occurrence of I and IIA fibers did not change during the period of splenius growth. However, the splenius of fallow deer increased in activity of NADH-tetrazolium oxidoreductase at the fiber peripheries as the rut approached. Further, fiber areas increased markedly during the period of growth, with type I fibers doubling in area and type IIA nearly trebling. Thus, the endocrinal and/or neural changes associated with the rut differentially affected these fiber types, and since type IIA fibers outnumbered type I by nearly 2 to 1, muscle enlargement is clearly dominated by the former class. Fiber areas were normally distributed for both fiber types, prerut and at the start of the rut, and coefficients of variation were similar. These results suggest that all fibers within a type are equally liable to grow during the growth period.

Acclimatization↗
PubMed1984

Effects of breed and intake level on growth and feed efficiency in ram lambs.

Effects of breed and intake level on growth and feed efficiency in ram lambs were tested with 52 Rambouillet, 46 Dorset and 53 Finnish Landrace (Finn) rams. Rams were individually fed at 100, 85 or 70% of ad libitum or at maintenance. The experimental diet contained 79% digestible dry matter (DM), 3.28% N and 2.95 Mcal metabolizable energy/kg DM. Rams were serially slaughtered every 35 d for 175 d. The efficiency of deposition of body weight, protein, energy and trimmed cuts was determined by breed and intake level over constant time, weight, fat and maturity intervals. Ranking of the breeds for feed efficiency depended upon both the interval and the criterion of evaluation. Efficiency of protein and trimmed cut gain was positively related to mature size in the time and weight intervals, but all differences in efficiency were small in the fat or maturity intervals. Gross energetic efficiency did not differ greatly among breeds in any interval. Dorsets appeared to have a somewhat greater propensity to fatten than the other breeds and to be less able to retain N at a fixed N intake. In the constant time interval, maintenance requirements were estimated to be 115 kcal/kg.75, and the estimated partial efficiencies of energy deposition in fat and protein were .49 and .26, respectively.

Animal Feed↗
PubMed1981

Near-infrared reflectance determination of fat, protein, and moisture in fresh meat.

Near-infrared spectral absorption properties were determined for emulsified and ground meat samples. Six corrected log numbers associated with the optical responses of 6 filters in the InfraAlyzer were used as multiple independent variables in regression equations. Dependent variables for the equations were moisture, determined by oven-drying; fat, determined by Goldfisch extraction; and protein, determined by the Kjeldahl method. InfraAlyzer log values, replicated 4 times on each emulsified beef sample and 3 times on each ground lamb sample, increased as the samples were warmed from the heat generated in the sample drawer. Variation in temperature of the meat samples were partially responsible for differences in constant terms and in regression coefficients for equations developed on data from different replications of a sample. Multiple correlation coefficients for fat ranged from 0.91 to 0.94 in emulsified meat and from 0.83 to 0.85 in ground meat; for moisture, 0.90-0.94 and 0.83-0.85, respectively; and for protein, 0.80-0.85 and 0.72-0.77, respectively. Overall, near-infrared reflectance shows promise as a rapid method for determining composition of meat. Nevertheless, some aspects of near-infrared reflectance require further attention.

Animals↗
PubMed1979

Conjunctival capillary fragility: a preliminary study.

Conjunctival capillary fragility (CCF) and skin capillary fragility (SCF) were studied by a negative-pressure suction cup method in 25 normal subjects and 38 diabetic patients with diabetic retinopathy. The CCF was significantly higher (P less than .001) in patients with diabetic retinopathy than in normal subjects; there was no significant difference in the SCF.

Adult↗
PubMed1977

Protein utilization of mechanically deboned meat by growing rats.

The protein quality of mechanically deboned red meat was investigated using amino acid analysis, protein efficiency ratio and the slope ratio technique. Nine different meat products were studied utilizing Sprague-Dawley weanling albino rats. Protein quality of the mechanically deboned meat varied greatly with the amount of lean left on the bones prior to mechanical deboning. Deboned meat which contained more lean, and less collagen, was superior in protein quality to the deboned meat obtained from bones which contained less lean and more collagen. Total sulfur amino acids (cystine and methionine) and isoleucine were the most limiting amino acids in all nine of the meat products when compared with lactalbumin. The contents of total sulfur amino acids and isoleucine, as well as the ratio of essential amino acids to total amino acids, reflected the protein quality of the meat.

Amino Acids↗
PubMed1975

Amino acid profile of bovine bone during growth.

The amino acid profile of bovine bones at 2, 25 and 130 months of age was examined and the data were expressed as amino acid residues per 1000 total amino acid residues recovered. As age advance proline and hydroxyproline significantly increased in whole bone (P less than .01), while valine, tyrosine, methionine and histidine decreased (P less than .01). To a lesser extent phenylalanine and glutamic acid decreased with increasing age (P greater than .05). A substantial increase (P less than .05) in glycine and arginine, and a considerable decrease (P less than .05) in valine, tyrosine, methionine and histidine occurred between young (2 months) and intermediate (25 months) age bovine bone. The largest differences in amino acid distribution during growth were observed in bones from the young and intermediate age groups. Lower amounts of glycine were present in lumbar vertebra (P less than .05), whereas the highest amount of glycine was found in sacral vertebra when vertebra, ribs and femurs were compared. Proline and hydroxyproline residues were highest in the rib and femur. Vertebrae often contained higher levels of threonine, arginine, histidine, lysine and aspartic acid than either the rib or femur.

Age Factors↗