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Biomedical subjects

R L West

Publications and source records attributed to R L West.

At least 37 records · Page 2Linked to original sources
PubMed1997

Carcass characteristics, the calpain proteinase system, and aged tenderness of Angus and Brahman crossbred steers.

We used 69 steers of varying percentage Brahman (B) breeding (0% B, n = 11; 25% B, n = 13; 37% B, n = 10; 50% B, n = 12; 75% B, n = 12; 100% B, n = 11) to study the relationship between carcass traits, the calpain proteinase system, and aged meat tenderness in intermediate B crosses. Calpains and calpastatin activities were determined on fresh longissimus muscle samples using anion-exchange chromatography. The USDA yield and quality grade data (24 h) were collected for each carcass. Longissimus steaks were removed and aged for 5 or 14 d for determination of shear force and 5 d for sensory panel evaluation. Even though some yield grade factors were affected by the percentage of B breeding, USDA yield grades did not differ (P > .15) between breed types. Marbling score and USDA quality grade decreased linearly (P < .01) with increasing percentage of B breeding. Shear force after 5 and 14 d of aging was higher (P < .05) in the 100% B steers than in all other breed types, which were not significantly different. Sensory panel tenderness and connective tissue scores decreased linearly (P < .05) with increasing B breeding. A quadratic effect was also noted for tenderness and connective tissue scores; 37% B steers received the highest scores. A similar response was found in mu-calpain activities; the 37% B steers had the highest activities. Conversely, calpastatin activity increased linearly (P < .01) with increasing percentage B breeding. These data show strong linear relationships between calpastatin activity (positive), marbling score (negative), and percentage B breeding, suggesting a possible combined effect of these traits on aged tenderness of intermediate Brahman crosses.

Animals↗
PubMed1997

Consumer evaluation of beef of known categories of tenderness.

A study was conducted to determine consumer perceptions of beef top loin steaks of known shear force and to evaluate how buying trends were modified by the tenderness and price variations of these steaks. Strip loins were cut into a 2.54-cm-thick steaks, and the center steak from each strip loin was used to determine Warner-Bratzler shear force. The remaining steaks were placed into one of the following shear force categories based on that shear force and color-coded accordingly: 1) 2.27 to 3.58 kg (Red); 2) 4.08 to 5.40 kg (White); and 3) 5.90 to 7.21 kg (Blue). Randomly recruited consumers were allowed to evaluate steaks and then purchase steaks based on their findings. A $1.10/kg price difference was placed between each category. Results of the analysis indicated that consumers were able to differentiate between the three categories of tenderness (P < .05). In addition, consumers gave higher (P < .05) juiciness and flavor ratings to Red steaks than to Blue steaks. Overall satisfaction was higher (P < .05) for Red steaks than for the other two categories of steaks. The following percentages of steaks were purchased: 1) Red, 94.6%; 2) White, 3.6%; and 3) Blue, 1.8%. These results suggest that consumers could discern between categories of tenderness and were willing to pay a premium for improved tenderness.

Animals↗
PubMed1996

An application of prefrontal cortex function theory to cognitive aging.

The purpose of this review is to extend the existing application of the frontal lobe hypothesis of cognitive aging beyond the limited work on inhibitory control (F. N. Dempster, 1992) to include memory processes supported by the prefrontal cortex. To establish a background for this analysis, I review existing models of prefrontal cortex function and present a synthesized model that includes a general function of temporal integration, supported by 4 specific processes: prospective memory, retrospective memory, interference control, and inhibition of prepotent responses. I found the frontal lobe hypothesis to perform well, with the exception of an inability to account for age-related declines in item recall and recognition memory, possibly a result of age-related declines in medial temporal function.

Aged↗
PubMed1995

Hypomethylation of the amyloid precursor protein gene in the brain of an Alzheimer's disease patient.

Aberrant expression of the amyloid precursor protein (APP) gene may contribute to the beta-amyloid deposition seen in Alzheimer's disease and Down syndrome patients. Genomic DNA was isolated from human brain tissue and digested with HpaII, an enzyme sensitive to CpG methylation. Southern-blot analysis revealed the absence of methylation at a site in the APP gene of an Alzheimer's disease subject. This site was methylated in a nondemented subject and a subject with a non-Alzheimer's type of dementia (Pick's disease). This is the first report of an epigenetic defect in an Alzheimer's disease patient and the observation suggests that hypomethylation of the APP gene may be one of several factors contributing to aberrant gene expression in Alzheimer's disease.

Aged↗
PubMed1994

Diagnosis of inflammatory myopathy by percutaneous needle biopsy with demonstration of the focal nature of myositis.

Inflammatory myopathies are a group of acquired disorders with histologic features of inflammation and nonspecific myopathic changes in the muscle fibers. Up to 25% of patients with clinical features of polymyositis reportedly have no inflammatory changes in their muscle biopsy specimens, but the absence of inflammatory infiltrates does not exclude an inflammatory myopathy. However, whether the lack of inflammation is caused by sampling variation or by a total lack of demonstrable inflammation in a particular patient has been unclear in the literature. The authors diagnosed polymyositis in six patients who underwent percutaneous muscle biopsy using a Bergstrom needle. Through one skin incision, the needle was inserted into different areas within the muscle compartment, obtaining three or four concurrent specimens from each patient. In all cases of needle biopsy, adequate tissue was obtained for histochemical and electron microscopic examination. All patients tolerated the procedure well and resumed normal daily activities the morning after biopsy. Although we saw inflammatory changes in at least one biopsy specimen from each patient, one or more of the remaining specimens contained no evidence of inflammation. This illustrates that inflammatory infiltrates can be focal in polymyositis. Because a specific diagnosis of inflammatory myopathy cannot be made in the absence of demonstrable inflammation, the diagnostic yield of multiple percutaneous needle biopsy specimen is potentially higher than that of the traditional single biopsy specimen obtained with the open surgical method.

Adult↗
PubMed1993

Activity memory and aging: the role of motor retrieval and strategic processing.

This study examined the role of retrieval and encoding mechanisms in the magnitude of age differences in the recall of subject-performed tasks (SPTs). Eighty older (60-79 years old) and 80 younger adults (18-26 years old) were tested in 1 of 4 conditions by varying modality at both encoding and retrieval. The role of list organization in reducing age differences in SPT recall was also examined. The results suggested that older adults' SPT recall improves when motor processing is enhanced by list organization. Age differences in recall were reduced for an organized list when motor processing occurred during retrieval or encoding, but age differences in recall of an unorganized list remained under most conditions. Discrepant results in the literature concerning the magnitude of age differences in SPT recall could be due in part to differences in list characteristics, such as organization, that have not been fully explored.

Adolescent↗
PubMed1992

Sequence and methylation in the beta/A4 region of the rabbit amyloid precursor protein gene.

Alzheimer's disease is characterized by the accumulation of the beta/A4 fragment of the amyloid precursor protein in the hippocampal regions of the brain. We report here the isolation of genomic clones carrying exons 15, 16 and 17 of the beta/A4 coding region of the rabbit amyloid precursor protein gene. The complete sequence of these exons predicts that all three peptides are identical to their human counterparts. An unexpectedly high concentration of CpG dinucleotides seen in exon 15 were conserved and continued into the intron 15 region. MspI/HpaII southern blot analysis revealed the presence of a number of methylated CpG dinucleotides in the cloned region of the gene. These data suggest that the rabbit amyloid precursor protein gene could provide a new and useful model for the study of this important gene.

Amino Acid Sequence↗
PubMed1992

Everyday memory performance across the life span: effects of age and noncognitive individual differences.

Gerontologists have long been concerned with the impact of individual-difference factors on memory. This study used a large sample (N = 2,495) of adult volunteers aged 18 to 90 years to determine if a set of individual-difference variables--vocabulary, education, depression, gender, marital status, and employment status--mediates the effects of aging on a wide range of laboratory-analogue tests of everyday memory. The data indicated that age was consistently the most significant predictor of memory performance, followed by vocabulary and gender. Vocabulary totally mediated age effects on a prose memory measure, and partial mediation of aging effects--primarily by vocabulary and gender--was observed on 5 other memory tests. These data suggest that when health samples of volunteers serve as research subjects, these individual differences can affect some memory test scores, but age remains the best overall predictor of memory performance.

Adolescent↗
PubMed1991

Age differences in the recall of actions and cognitive activities: the effects of presentation rate and object cues.

In studies of activity memory, age differences have been found in the recall of cognitive activities (sustained mental activities that subjects solve during acquisition) but not in recall of Subject-Performed Tasks (one-step actions that subjects enact during acquisition). To understand the reasons for the discrepant findings, both types of item were included in a study examining the effects of object cues, rate of presentation, and aging. Variations in presentation rate or use of objects did not account for the different findings on the two item types. Even when presentation rate and object cues were matched, larger age differences were found for recall of cognitive activities than of SPTs. Age differences were also affected by the interaction of item type, presentation rate, and the presence of objects during encoding. To identify the variables controlling age differences, more analysis is needed of the features of activities to be remembered.

Adolescent↗
PubMed1991

The association of memory complaint with computer-simulated everyday memory performance.

The relationship of memory self-report to self-rated depression and to actual performance on computer-simulated everyday memory tasks was investigated in 125 normal adults. Canonical correlation analyses demonstrated that self-rated memory performance and objective computer-simulated everyday memory performance shared from 27.9% to 29.4% of common variance. These data provide initial concurrent validity for a new memory self-report scale, the MAC-S. Results are discussed in relation to psychometric factors important in the design and validation of self-report memory scales.

Adolescent↗
PubMed1991

Factors influencing intermuscular fat and other measures of beef chuck composition.

Carcasses from 59 steers produced from the mating of Braford, Simbrah, Senepol, and Simmental bulls to Brahman- and Romana Red-sired cows and Brahman bulls mated to Angus cows were used in this study. Effects of sire breed and feeding calves vs yearlings on fat depots in the chuck, when steers were fed to 1.0 cm external fat, were determined. Breed of sire and feeding calves vs yearlings had no effect (P greater than .05) on percentage of intermuscular fat. However, carcasses from Braford-sired steers had a higher (P less than .05) percentage of dissectable subcutaneous fat on the chuck than did those from other breed groups. Carcasses from Simmental-sired steers were superior (P less than .05) to those from Braford-sired steers in USDA yield grade and had a higher average marbling score (P less than .05) than the Simbrah-sired group. Estimated kidney, pelvic, and heart (KPH) fat was higher (P less than .05) in carcasses from Brahman-, Simbrah-, and Senepol-sired steers than in Braford-sired steers. Steers fed as calves had higher percentages (P less than .05) of KPH fat and major chuck muscles than did those fed as yearlings. The best single predictor of percentage of intermuscular fat within the chuck was adjusted fat over the ribeye (R2 = .46).

Adipose Tissue↗
PubMed1991

The effect of breed of sire and age at feeding on muscle tenderness in the beef chuck.

Steers (n = 59) produced from the mating of Braford, Simbrah, Senepol, and Simmental bulls to Brahman- and Romana Red-sired cows and Brahman bulls to Angus cows were used in this study. Effects of sire breed and age at feeding on muscle tenderness in the major muscles of the chuck when steers were fed to 1.0 cm 12th rib fat were determined. There were no muscle tenderness effects due to sire breed group, with the exception of the serratus ventralis muscle, which was more tender in Brahman- and Braford-sired steers than in Simmental-sired steers. Additionally, the supraspinatus muscle from the yearlings was lower in shear value than that from the calves. The Brahman-sired steers had serratus ventralis muscles with higher percentages (P less than .05) of intramuscular fat than those of Braford-, Simbrah-, and Simmental-sired steers. Fat deposited within the muscle or between muscles in the chuck was not related to muscle tenderness as measured by Warner-Bratzler shear values. Also, percentages of intramuscular fat of the triceps brachii, serratus ventralis, or supraspinatus muscles were not influenced (P greater than .05) by age at feeding.

Adipose Tissue↗
PubMed1990

Age differences in everyday memory: laboratory analogues of telephone number recall.

Three experiments were conducted to examine age differences in memory for telephone numbers by adults ranging from 18 to 85 years of age. In the first 2 studies, using visual simultaneous presentation, age declines in immediate recall were evident on 10-digit numbers, but not on 3-digit numbers. With 7-digit numbers, the youngest group performed significantly better than the oldest (70-85 years) group. In the second study, more marked age declines occurred when subjects had to redial a number after a busy signal. The third experiment replicated the observed aging pattern with auditory sequential presentation. Also, chunked presentation of local telephone numbers resulted in high performance for old and young in sequential recall. The findings were discussed in relation to task processing demands and practical issues related to telephone number recall.

Adolescent↗
PubMed1990

Name recall performance across the adult life-span.

Everyday name-recall tests were administered to 1205 adults ranging in age from 18 to 90 years. They were asked to recall sets of four, six, or 14 names of individuals who introduced themselves on videotape. Immediate recall, acquisition, and delayed retention were examined. The results showed consistent age-related declines in name recall. Declines in performance were more evident on sets of 14 names rather than four or six names. Age deficits remained across several acquisition trials within the set of 14 names. The largest declines were evident for the old-old (over 70), although there were also significant performance differences, on some analyses, between the young and middle-aged groups. Changes in performance were less apparent during the middle-aged years (40-60 years). Name recall was related to individual differences factors, reaction time and paired-associate memory for names. The value of assessment and intervention with name recall was stressed.

Adult↗