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Biomedical subjects

M Riley

Publications and source records attributed to M Riley.

At least 55 records · Page 3Linked to original sources
PubMed1996

Growth, carcass, and tenderness characteristics of virgin, spayed, and single-calf heifers.

Fifty-three Angus/Gelbvieh rotationally crossed heifers were slaughtered after 100 d on a high-concentrate diet. The average slaughter age for each of three different groups was 31, 33, or 35 mo, which falls within the USDA's 30- to 42-mo age range for animals producing "B" maturity carcasses. Each age group consisted of five or six heifers that had never been bred (virgin), six heifers ovariectomized at 1 yr of age (spayed), and six heifers that had weaned calves approximately 120 d postpartum (single-calf). Slaughter weight was higher (P < .05) for the virgin heifers but total weight gain in the feedlot was similar among the three groups. Single-calf heifers fed 100 d after weaning calves tended to be fatter than virgin or spayed heifers. Carcass maturity scores for the single-calf, virgin, and spayed heifers were different (P < .05); single-calf heifers produced carcasses that appeared older and spayed heifers produced carcasses that appeared younger. Maturity scores coupled with lighter and shorter metacarpal bone weights indicated single-calf heifers matured earlier (P < .05) than the other groups. Panel tenderness and Warner-Bratzler (WB) shear values of rib roasts from virgin, spayed, and single-calf heifers were determined. No differences among groups of heifers existed but scores within each group varied greatly. Marbling score was correlated (P < .05) with panel tenderness and shear force and the hydroxylysylpyridinium (HP) crosslink of muscle collagen was correlated (P < .05) with shear values. Because no significant (P < .05) correlation existed between HP in bone collagen or HP or WB shear values in muscle, we concluded that collagen maturation processes in muscle and bone occur independently. With the exception of differences in bone maturity scores, few meaningful differences in characteristics of virgin, spayed, and single-calf heifers existed, but these maturity differences could change carcass grade and influence value.

Amino Acids↗
PubMed1995

Intravenous methylmethacrylate following cemented total hip arthroplasty.

Both cemented and noncemented techniques have been used for total hip arthroplasty (THA). Each technique has advantages and disadvantages. Among the disadvantages of cemented THA are several perioperative complications, such as intraoperative cardiac or respiratory failure and hypotension, called "cement implantation syndrome," and extrusion of cement beyond the confines of the medullary canal. Cement extrusion can be the result of overreaming of the femoral canal and cortical perforation. This is a worrisome finding, as the risk of subsequent femoral fracture at the site of perforation is increased. Extruded cement, however, does not always indicate a problem. Extruded cement located within the femoral venous system, intravenous methylmethacrylate, for example, is not associated with long-term complications. While uncommon, it is important to differentiate this finding from the more serious cortical perforation. We report four examples of intravenous methylmethacrylate following THA and describe the imaging features that allow differentiation of this entity from the more significant finding of cortical perforation.

Aged↗
PubMed1995

The emergence of a highly transmissible lineage of cbl+ Pseudomonas (Burkholderia) cepacia causing CF centre epidemics in North America and Britain.

The rapid increase in Pseudomonas (Burkholderia) cepacia infection in cystic fibrosis (CF) patients suggests epidemic transmission, but the degree of transmissibility remains controversial as conflicting conclusions have been drawn from studies at different CF centres. This report provides the first DNA sequence-based documentation of a divergent evolutionary lineage of P. cepacia associated with CF centre epidemics in North America (Toronto) and Europe (Edinburgh). The involved epidemic clone encoded and expressed novel cable (Cbl) pili that bind to CF mucin. The sequence of the cblA pilin subunit gene carried by the epidemic isolates proved to be invariant. Although it remains to be determined how many distinct, highly transmissible lineages exist, our results provide both a DNA sequence and chromosomal fingerprint that can be used to screen for one such particularly infectious, transatlantic clone.

Amino Acid Sequence↗
PubMed1995

Gene products of Escherichia coli: sequence comparisons and common ancestries.

Sequences of 1,862 chromosomally encoded Escherichia coli K12 proteins were examined to identify genes likely to have arisen by duplication of genes in an ancestral chromosome. The criteria for sequence relatedness were an alignment of at least 100 amino acid residues and a PAM distance (number of accepted point mutations per 100 residues separating two sequences) below 250. A total of 971 of the 1,862 proteins examined were found in 2,329 sequence-related pairs that met these criteria. Most proteins of the sequence-related pairs were related in cellular function, as judged by biochemical and/or physiological features. Many of the pairs of proteins could be grouped into sequence-related families. If such groupings were generated from ancestral genes by duplication and divergence events, through these sequence comparisons we can identify putative ancestral sequences of the present-day genes of E. coli and other organisms. The results suggest that the 971 paralogous genes could have been derived from only 204 ancestral genes. We have also shown that the process of duplication and divergence is not the exclusive mechanism of evolution of all E. coli genes. Indeed, the relationships among the sequences of multiple (in the sense of redundant) enzymes indicate that nearly half could have arisen either by convergent evolution or by lateral transfer. Therefore, not all functionally related genes need arise by duplication and divergence.

Bacterial Proteins↗
PubMed1995

Follow-up validation study of the Victorian Congenital Malformations Register.

OBJECTIVE: To determine whether there has been an improvement in ascertainment of malformations in the Victorian Congenital Malformations Register (VCMR). METHODOLOGY: The medical records of 500 children under 4 years of age admitted consecutively to two paediatric teaching hospitals in Victoria in 1992 were viewed to determine whether these cases had been notified to the Register. RESULTS: Over three-quarters of the defects recorded had been notified to VCMR. There was 100% ascertainment of chromosomal anomalies and a high proportion of major structural malformations were notified. CONCLUSION: This study repeats the validation study completed in 1986 and shows marked improvement in ascertainment of malformations in the VCMR by 1992.

Child, Preschool↗
PubMed1995

Widespread protein sequence similarities: origins of Escherichia coli genes.

To learn more about the evolutionary origins of Escherichia coli genes, we surveyed systematically for extended sequence similarities among the 1,264 amino acid sequences encoded by chromosomal genes of E. coli K-12 in SwissProt release 26 by using the FASTA program and imposing the following criteria: (i) alignment of segments at least 100 amino acids long and (ii) at least 20% amino acid identity. Altogether, 624 extended alignments meeting the two criteria were identified, corresponding to 577 protein sequences (45.6% of the 1,264 E. coli protein sequences) that had an extended alignment with at least one other E. coli protein sequence. To exclude alignments of questionable biological significance, we imposed a high threshold on the number of gaps allowed in each of the 624 extended alignments, giving us a subset of 464 proteins. The population of 464 alignments has the following characteristics expressed as median values of the group: 254 amino acids in the alignment, representing 86% of the length of the protein, 33% of the amino acids in the alignment being identical, and 1.1 gaps introduced per 100 amino acids of alignment. Where functions are known, nearly all pairs consist of functionally related proteins. This implies that the sequence similarity we detected has biological meaning and did not arise by chance. That a major fraction of E. coli proteins form extended alignments strongly suggests the predominance of duplication and divergence of ancestral genes in the evolution of E. coli genes. The range of degrees of similarity shows that some genes originated more recently than others. There is no evidence of genome doubling in the past, since map distances between genes of sequence-related proteins show no coherent pattern of favored separations.

Algorithms↗
PubMed1994

Anaerobic threshold in patients with chronic cardiac failure due to ischaemic heart disease.

OBJECTIVES: Anaerobic threshold was measured to examine its relationship with venous lactate levels and the reproducibility of gas exchange methods. METHODS: Twenty patients with chronic cardiac failure due to ischaemic heart disease underwent two successive treadmill tests with measurements of respiratory gas exchange. RESULTS: An anaerobic threshold was demonstrated in 78 p. 100 of tests, by plotting either VE/VO2 or VCO2/VO2, and reproducibility between the two tests was satisfactory. Peripheral venous lactate levels did not increase from rest to the end of the exercise stage prior to the anaerobic threshold, but did increase significantly thereafter. Where an anaerobic threshold could be demonstrated, it was reproducible and correlated strongly with peak achieved VO2. CONCLUSION: However, as measurement of anaerobic threshold requires exercise to 90 p. 100 maximum VO2, it may be preferable to continue until limiting symptoms, and use peak achieved VO2 as the end point. Anaerobic threshold is a reproducible measure of anaerobic exercise capacity.

Anaerobic Threshold↗
PubMed1994

Stress in midwifery: a comparison of midwives and nurses using the Work Environment Scale.

Previous research into midwifery has identified a number of potential sources of stress without attempting to understand the variables that might contribute to it. The study sample was drawn from a population of registered nurses and midwives and compares the work environment of 29 midwives with 180 nurses, using the Work Environment Scale Questionnaire. Significant differences were found between midwives and nurses for involvement, supervisor support, autonomy, work pressure and clarity of roles. These results have the potential for forming the basis of future research.

Analysis of Variance↗
PubMed1994

Ventilatory and heart rate responses after exercise in chronic cardiac failure.

1. To determine if the recovery period after exercise is abnormal in chronic cardiac failure, we studied 15 patients with stable chronic cardiac failure, and 14 normal subjects during and after symptom-limited maximal treadmill exercise. 2. In patients, O2 consumption fell exponentially from 16.8 (13.7-20.0) ml min-1 kg-1 at peak exercise to 6.0 (5.2-6.7) ml min-1 kg-1 at 3 min of recovery and in control subjects it fell from 30.2 (27.0-33.5) ml min-1 kg-1 to 6.7 (5.9-7.4) ml min-1 kg-1 (mean and 95% confidence intervals). The associated decay constants were slower in patients [0.70 (0.58-0.83) min-1 versus 0.93 (0.81-1.05) min-1 in control subjects (P < 0.01, t-test)]. 3. CO2 consumption kinetics displayed similar abnormalities [(k: 0.55 (0.41-0.69) min-1 versus 0.71 (0.59-0.83) min-1, P < 0.05)] and heart rate kinetics showed a similar trend [(k: 0.53 (0.33-0.74) min-1 versus 0.76 (0.62-0.89) min-1, P = 0.08]. 4. We conclude that patients with cardiac failure recover more slowly from exercise than normal subjects, and that this may further impair their ability to perform exercise, with consequent effect on quality of life.

Aged↗
PubMed1994

Antigens of Lyme disease of spirochaete Borrelia burgdorferi inhibits antigen or mitogen-induced lymphocyte proliferation.

Modulation of cellular immune responses by the spirochaete Borrelia burgdorferi, the bacteria that causes Lyme disease, was demonstrated. When cultured in the presence of sonicated Borrelia preparation (Bb), the mitogen- or antigen-stimulated proliferative responses of normal lymphocytes were consistently lowered. Bb caused the greatest reduction in Concanavalin A (ConA) or antigen-stimulated proliferation, where almost 100% reduction in proliferation could be achieved. Bb also reduced phytohemagglutinin-M (PHA) or pokeweed mitogen (PWM)-stimulated peripheral blood lymphocyte (PBL) proliferation, with the PWM proliferation being the least affected. This regulatory activity was not due to toxicity and was determined to be caused by Bb protein antigens. The degree of the proliferation reduction was directly proportional to both Bb quantity and length of exposure to lymphocytes. IL-2 production was significantly reduced from Bb-exposed lymphocytes. The entry of lymphocytes into the proliferating phases of the cell cycle was also shown to be blocked. These results have demonstrated an immune suppressive mechanism of B. burgdorferi. The magnitude of host immune responses may be dependent on the degree of suppression which is related to the spirochaete quantity and their length of presence in the host.

Antigens, Bacterial↗
PubMed1994

Gas exchange responses to constant work rate exercise in chronic cardiac failure.

OBJECTIVE: To examine the time course of changes in minute oxygen consumption and other gas exchange variables and heart rate during constant work rate exercise in patients with chronic cardiac failure. DESIGN: Treadmill exercise with on line measurement of gas exchange and a target duration of 10 minutes. SUBJECTS: Seven men in New York Heart Association class II, six in class III, and seven controls. MAIN OUTCOME MEASURES: Gas exchange variables and heart rate were averaged for the final two minutes of exercise. Time constants were calculated for the increase in all variables. RESULTS: Consumption of oxygen at the end of exercise (VO2) was similar in class II patients (mean (95% confidence interval (95% CI) 14.9 (13.6 to 16.1) ml kg-1 min-1), class III patients (13.2 (11.2 to 15.1) ml kg-1 min-1), and controls (13.3 (12.5 to 14.2) ml kg-1 min-1). The patients reached this VO2 more slowly with longer exponential time constants of 0.82 (0.59 to 1.04) min in class II and 1.19 (0.86 to 1.51) min in class III, than the 0.49 (0.35 to 0.64) min in the controls. Time constants of other gas exchange variables and heart rate were also longer in patients. By analysis of covariance, peak VO2 accounted for the between group difference in the time constant for VO2, suggesting that circulatory factors may be an important cause of the delayed kinetics. CONCLUSIONS: A delayed rise in VO2 in response to exercise may be responsible for subnormal values of VO2 early in exercise in patients with chronic cardiac failure.

Aged↗
PubMed1993

Effectiveness of programme for reducing cardiovascular risk for men in one general practice.

OBJECTIVES: To assess the effectiveness of a programme for reducing cardiovascular risk in men in terms of clinical measurements and perceptions of patients. DESIGN: Collection of paired data on men attending well person clinics over three to five years. Questionnaire to determine changes in risk related habits. SETTING: Well person clinics in rural general practice with five partners in mid-Wales. SUBJECTS: The first 687 men seen in the clinic: analysable data obtained on 520. Initial age range 28-60 years. MAIN OUTCOME MEASURES: Analysis of serum cholesterol concentration (mmol/l) and blood pressure (mm Hg). Changes in diet, exercise, smoking, and drinking. RESULTS: Mean (SD) cholesterol concentration for all subjects increased from 5.8 (1.0) to 6.0 (1.0), p < 0.001. Overall percentage of ideal weight and mean systolic blood pressure also increased. Mean diastolic blood pressure was unchanged at 84 mm Hg. Professed dietary change, age, and number of visits all had significant effects on final cholesterol concentration. Those seen more often showed a significant decrease in cholesterol concentrations (in those seen more than twice mean (SD) initial value 6.7 (0.9) mmol/l v final value 6.5 (1.0) mmol/l, p < 0.001). Those over 45 years at start of study showed a significant decrease in diastolic blood pressure (mean (SD) initial value 89 (9) mm Hg v final value 86 (7) mm Hg, p < 0.001). CONCLUSIONS: These clinics are not effective in achieving a reduction in mean cholesterol concentration or blood pressure, despite evidence that the message of reduction in risk had been successfully transmitted. Success was achieved in older patients and those in whom a definite problem was identified. Identification of high risk groups and clinical case finding with appropriate long term follow up may be more cost effective in reducing cardiovascular risk than non-specific screening of the whole population.

Adult↗
PubMed1993

Metabolic responses to graded exercise in chronic heart failure.

To determine if exercise intolerance and fatigue in chronic heart failure could be exacerbated by an abnormal metabolic response to exercise, we studied 12 patients with stable chronic heart failure and 12 normal volunteers during symptom-limited maximal treadmill exercise. Peak VO2 was 17.2 (15.1-19.2) ml.kg-1 x min-1 in patients and 29.9 (26.3-33.5) in controls (mean and 95% confidence intervals; P < 0.0001, t-test). Overall, levels in peripheral venous blood of glucose, glycerol and free fatty acids were greater in patients, although the differences became less marked with increasing exercise intensity. Noradrenaline was elevated in patients at rest, but the peak exercise response was similar to controls. Responses of adrenaline, insulin and glucagon were similar in both groups. We conclude that depletion of the levels of circulating substrates is not contributory to exercise intolerance and fatigue in chronic heart failure. Greater levels of glycerol and free fatty acids may be mediated by excess sympathetic nervous system activity, reflected in elevated noradrenaline levels.

Aged↗
PubMed1993

Functions of the gene products of Escherichia coli.

A list of currently identified gene products of Escherichia coli is given, together with a bibliography that provides pointers to the literature on each gene product. A scheme to categorize cellular functions is used to classify the gene products of E. coli so far identified. A count shows that the numbers of genes concerned with small-molecule metabolism are on the same order as the numbers concerned with macromolecule biosynthesis and degradation. One large category is the category of tRNAs and their synthetases. Another is the category of transport elements. The categories of cell structure and cellular processes other than metabolism are smaller. Other subjects discussed are the occurrence in the E. coli genome of redundant pairs and groups of genes of identical or closely similar function, as well as variation in the degree of density of genetic information in different parts of the genome.

Bacterial Proteins↗
PubMed1993

Respiratory gas exchange and metabolic responses during exercise in McArdle's disease.

During normal progressive exercise, the gas exchange anaerobic threshold occurs when CO2 production (VCO2) and ventilation (VE) increase so as to depart from a linear relationship to O2 consumption (VO2). This is thought to represent a gas exchange response to metabolic acidosis due to lactate accumulation. Patients with McArdle's disease have previously been reported to exhibit a steepened ventilatory response relative to VCO2, despite an inability to produce lactate. However, the VCO2 response has not been studied. We therefore investigated the VCO2-VO2 and VE-VO2 relationships in seven McArdle's disease patients and seven control subjects during symptom-limited maximal treadmill exercise. Analysis of gas exchange showed that whereas all control subjects had an easily identifiable anaerobic threshold, four of the patients had none and the other three displayed an attenuated threshold. The occurrence of the threshold in one patient was associated with a small rise in lactate and in another patient with an abrupt rise in leg discomfort, suggesting a pain response. Ammonia and the purine metabolite hypoxanthine were elevated during exercise in all patients, suggesting that ammonia may be a product of adenosine monophosphate degradation. Free fatty acid levels were also elevated, and a shift toward utilization of lipid may contribute to abnormal gas exchange responses. It is concluded that lactic acidosis contributes to the gas exchange anaerobic threshold but that other factors, such as discomfort, may be involved in the excess Ve seen during heavy exercise.

Adolescent↗
PubMed1993

Representations of metabolic knowledge.

Construction of electronic repositories of metabolic information is an increasingly active area of research. Encoding detailed knowledge of a complex biological domain requires finely honed representations. We survey representations used for several metabolic databases, including Eco-Cyc, and reach the following conclusions. Representation of the metabolism must distinguish enzyme classes from individual enzymes, because there is not a one-to-one mapping from enzymes to the reactions they catalyze. Individual enzymes must be represented explicitly as proteins, e.g., by encoding their subunit structure. The species variation of metabolism must be represented. So must the substrate specificity of enzymes, which may be treated in several ways.

Databases, Factual↗