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PubMed2003

Determinants of meat quality: tenderness.

Meat quality is a term used to describe a range of attributes of meat. Consumer research suggests that tenderness is a very important element of eating quality and that variations in tenderness affect the decision to repurchase. The present paper highlights recent information on the factors that affect tenderness. While the precise aetiology is not fully understood, a number of factors have been shown to affect tenderness. Of these factors, postmortem factors, particularly temperature, sarcomere length and proteolysis, which affect the conversion of muscle to meat, appear most important. However, it is now becoming clear that variation in other factors such as the muscle fibre type composition and the buffering capacity of the muscle together with the breed and nutritional status of the animals may also contribute to the observed variation in meat tenderness.

Animals↗

PubMedDate not supplied

Transpiration and canopy conductance in a eucalypt plantation using shallow saline groundwater.

Tree water use and canopy conductance were monitored in a 20-year-old Eucalyptus grandis W. Hill ex Maiden and Eucalyptus camaldulensis Dehnh. plantation shown to be using shallow saline groundwater. Annual water use, obtained from two years of heat pulse measurements of daily water use, was approximately 300 mm for both species with a winter minimum and a weak maximum in spring. Canopy conductance obtained from the ratio of daily water use to daily mean vapor pressure deficit (VPD) was low during summer, but rose to high values in winter. Diurnal variation in stomatal conductance was recorded in late summer and spring. Stomatal conductance increased with radiation but showed no evidence of a relationship with VPD. Canopy conductance was generally less than half the observed stomatal conductance on a leaf area basis, and usually declined steadily through the day, showing a strong inverse relationship with VPD. For both species, a decoupling coefficient (Omega) of 0.1 to 0.3 was obtained from canopy conductance and climate observations, and a higher value of Omega was derived from canopy and stomatal conductances. The difference in Omega values is interpreted as demonstrating the inclusion of a soil to leaf conductance within the canopy conductance estimates. Soil to leaf conductance is smaller than both stomatal and aerodynamic conductances, and effectively limits water use by the plantation. The observed variation in soil to leaf conductance is consistent with resistance to water movement to the roots increasing as the soil in the vicinity of the active roots dries as a result of water uptake during the day. Plantations may be useful for transpiring shallow ground-water to control rising water tables and salinity, but their effectiveness as water users will be reduced as the water table is drawn down in soils of low hydraulic conductivity. Plantations irrigated with pumped groundwater or drainage water may provide a more efficient disposal system where these water sources are available.

Journal Article↗

PubMed2004

Genetic diversity in Tetrachaetum elegans, a mitosporic aquatic fungus.

Tetrachaetum elegans Ingold is a saprobic aquatic hyphomycete for which no sexual stage has yet been described. It occurs most commonly during the initial decay of tree leaves in temperate freshwater habitats and typically sporulates under water. Dispersal of the aquatic fungus takes place primarily in the water column and has a large passive component. Differences in substrate composition (e.g. quality of leaf litter) may also play a role in the distribution of different species or genotypes. The population genetic structure of T. elegans was studied using amplified fragment length polymorphism (AFLP) multilocus fingerprints. The populations were isolated from the leaf litter of three different tree genera, sampled in nine streams distributed throughout a mixed deciduous forest. Molecular markers were developed for 97 monosporic isolates using four selective primer pairs. A total of 247 fragments were scored, of which only 32 were polymorphic. Significant stream differentiation was detected for the isolates considered in this study. Analysis of molecular variance revealed that 20% of the genetic variation observed was the result of differences between streams. No correlation between genetic and geographical distances was found but a few multilocus genotypes were observed in different locations. Altogether these results suggest that environmental barriers play a role in the population structure of this aquatic fungus. No clear-cut effect of leaf litter composition on genetic variation could be demonstrated. Finally, tests of linkage disequilibrium between the 32 polymorphic AFLP loci as well as simulations did not provide a final answer regarding clonality in T. elegans. Indeed, it was possible to reject linkage equilibrium at different sampling levels and show that full linkage was unlikely.

Analysis of Variance↗

PubMedDate not supplied

Apolipoprotein E polymorphisms affect atherosclerosis in young males. Pathobiological Determinants of Atherosclerosis in Youth (PDAY) Research Group.

Investigators in eight communities collected aortas, right coronary arteries, blood and liver samples, and associated information from 720 young males, aged 15-34 years, who died of external causes. Genotypes for apolipoprotein (apo) E isoforms (E2, E3, and E4) were determined from hepatic DNA by restriction isotyping (restriction enzyme isoform genotyping) of amplified apo E sequences. Pathologists graded the arteries for atherosclerotic lesions, and a central laboratory measured lipoprotein cholesterol concentrations. Allele frequencies were different between blacks and whites (p less than 0.0001). E2 and E4 frequencies were higher and E3 frequency was lower in blacks than in whites. Among the common genotypes in both whites and blacks, E2E3 heterozygotes had the lowest levels of total serum cholesterol and low density lipoproteins, E3E4 had the highest levels, and E3E3 had intermediate levels. Apo E genotypes differed in mean percent surface area involvement with lesions in the thoracic aorta and the abdominal aorta of both whites and blacks (p less than or equal to 0.0002). Among the common genotypes, E2E3 heterozygotes had the least involvement of both thoracic and abdominal aortas with lesions, E3E4 had the greatest involvement (with the exception of the thoracic aorta in whites), and E3E3 had intermediate involvement. Apo E genotype accounted for 5.7% in whites and 5.9% in blacks of the observed variation in lesions for the thoracic aorta, and for 5.9% in whites and 7.0% in blacks for the abdominal aorta. Adjusting for cholesterol levels did not change apo E genotypic effects appreciably, an observation suggesting that genotypic effects on arterial lesions may not be mediated entirely by changes in serum cholesterol concentrations.

Adolescent↗

PubMed1996

Value of Doppler echocardiography in the detection of low-grade rejections after cardiac transplantation.

Modifications of the diastolic parameters pressure half-time (PHT) and isovolumic relaxation time (IVRT), recorded using cardiac Doppler echocardiography (CDE), were studied in 23 heart transplant recipients and compared to the results of 345 endomyocardial biopsies (EMB) performed on the same day. Two different protocols, analyzing respectively (1) a decrease of 20% or more in IVRT and/or PHT with respect to the mean and (2) a decrease of 20% or more in IVRT and/ or PHT with respect to its preceding value, were used to evaluate the efficiency of CDE in diagnosing mild and moderate rejections. When a mild rejection was detected by EMB, a statistically significant decrease was found in the average CDE parameter values of the patient population. However, these variations were weak and did not differ from the spontaneous variations observed in each patient in the absence of rejection. Thus, it is not surprising that the sensitivity of CDE in the detection of mild rejections was very low (45%) using the most sensitive protocol (variations of the parameters from their preceding value). We conclude that CDE alone does not seem to be sufficient to perform the noninvasive diagnosis of low-grade rejections and must be complemented by other noninvasive methods.

Adult↗

PubMed1994

Volume changes in protein evolution.

We have determined the variations in volume that occur during evolution in the buried core of three different families of proteins. The variation of the whole core is very small (approximately 2.5%) compared to the variation at individual sites (approximately 13%). However, by comparing our results to those expected from random sequences with no correlations between sites, we show that the small variation observed may simply be a manifestation of the statistical "law of large numbers" and not reflect any compensating changes in, or global constraints upon, protein sequences. We have also analysed in detail the volume variations at individual sites, both in the core and on the surface, and compared these variations with those expected from random sequences. Individual sites on the surface have nearly the same variation as random sequences (24% versus 28% variation). However, individual sites in the core have about half the variation of random sequences (13% versus 30%). Roughly, half of these core sites strongly conserve their volume (0 to 10% variation); one quarter have moderate variation (10 to 20%); and the remaining quarter vary randomly (20 to 40%). Our results have clear implications for the relationship between protein sequence and structure. For our analysis, we have developed a new and simple method for weighting protein sequences to correct for unequal representation, which we describe in an Appendix.

Algorithms↗

PubMed2002

Seasonal effects on the air-water carbon dioxide exchange in the Hooghly estuary, NE coast of Bay of Bengal, India.

Monthly variation of CO2 fugacity (fCO2) in surface water and related atmospheric exchanges were measured in the Hooghly estuary which is one of the most important estuaries, since it is fed by one of the world's largest rivers, the Ganges with a flow of 15,646 m3 s-1 (1.6% of the world's combined river flow). Carbon dioxide fluxes averaged over the entire estuary are in the range of -2.78 to 84.4 mmol m-2 d-1. This estuary acts as a sink for CO2 during monsoon months and seasonal variation of its flux is controlled by dilution of seawater by river water. Since the solubility of CO2 and the disassociation of carbonic acid in estuarine water are controlled by temperature and salinity, the observed variations of CO2 fluxes are compared with those predicted from seasonal changes in temperature, salinity and the ratio of gross primary production to community respiration using empirical equations with an explained variability of 55%.

Air↗

PubMed1995

Prediction of cathodal iontophoretic transport of various anions across excised skin from different vehicles using conductivity measurements.

Solute concentration, buffer concentration, applied pH and buffer constituents affect the cathodal iontophoresis of salicylate, benzoate and butyrate across excised skin. Experiments were conducted in which the iontophoretic flux of salicylate was measured across excised human skin with variations in salicylate concentration, donor solution pH, buffer concentrations and buffer consitutents. The conductivity of these solutes and of solutions described in studies on the iontophoresis of benzoate and butyrate were then measured. The observed variations in salicylate, benzoate and butyrate fluxes across a range of conditions were found to be related to the ratio of specific conductance of the solutes in deionized distilled water to that in the buffer solution containing the solutes. The present results suggest that conductivity of solutes in vehicle solutions is one means of predicting the iontophoretic flux of solutes from different vehicle compositions.

Biological Transport↗

PubMed1973

Genetic factors in determining bone mass.

This investigation was undertaken to evaluate possible genetic determinants of bone mass with the premise that inheritance of bone mass could be of etiologic importance in osteoporosis. Bone mass and width measurements were made with the photon absorption technique on the right radius of 71 juvenile and 80 adult twin paris. The variance of intrapair differences of bone mass in monozygotic (MZ) juvenile twins was 0.0013 g(2)/cm(2) compared to 0.0052 g(2)/cm(2) in the dizygotic (DZ) twins. For the adult twins the variance of intrapair differences in bone mass was 0.0069 for MZ and 0.0137 for DZ twins. Similar results were obtained for bone width. The significantly larger variation in intrapair differences in DZ twins indicates that these traits have significant genetic determinants. These intrapair differences were found to increase with age, suggesting that genetic-environmental interaction also contributes to the observed variation in bone mass. These data provide evidence that bone mass does have significant genetic factors, which alone or in conjunction with environmental factors may predispose persons to the development of osteoporosis.

Adolescent↗

PubMed2005

Patient surveillance after curative-intent surgery for rectal cancer.

The follow-up of patients with rectal cancer after potentially curative resection has significant financial and clinical implications for patients and society. The ideal regimen for monitoring patients is unknown. We evaluated the self-reported practice patterns of a large, diverse group of experts. There is little information available describing the actual practice of clinicians who perform potentially curative surgery on rectal cancer patients and follow them after recovery. The 1795 members of the American Society of Colon and Rectal Surgeons were asked, via a detailed questionnaire, how often they request 14 discrete follow-up modalities in their patients treated for cure with TNM stage I, II, or III rectal cancer over the first five post-treatment years. 566/1782 (32%) responded and 347 of the respondents (61%) provided evaluable data. Members of the American Society of Colon and Rectal Surgeons typically follow their own patients postoperatively rather than sending them back to their referral source. Office visit and serum CEA level are the most frequently requested items for each of the first five postoperative years. Endoscopy and imaging tests are also used regularly. Considerable variation exists among these highly experienced, highly credentialed experts. The surveillance strategies reported here rely most heavily on relatively simple and inexpensive tests. Endoscopy is employed frequently; imaging tests are employed less often. The observed variation in the intensity of postoperative monitoring is of concern.

Adult↗

PubMed2005

Chromosomal location polymorphism of major rDNA sites in two Mediterranean populations of the killifish Aphanius fasciatus (Pisces: Cyprinodontidae).

The chromosomes of the Mediterranean killifish, Aphanius fasciatus from two populations, the Lagoon of Venice (LV, 15 specimens) and the Lagoon "Stagnone di Marsala" (Sicily) (SM, 48 specimens), have been investigated using conventional Ag-staining and fluorescent in situ hybridization (FISH) with 18S rDNA probe. The two methods revealed variation in the number of major rDNA sites ranging from 8 to 14 (LV) and from 1 to 4 (SM) per individual. The fact that each individual possessed its own number of sites implies that observed variation was structural. Moreover, overlapping of silver staining and FISH patterns demonstrated that all ribosomal genes were transcriptionally active in each specimen.

Animals↗

PubMed1987

Disease staging and PMCs. Can they improve DRGs?

Since the adoption of Medicare's Prospective Payment System (PPS), critics have raised concerns about the degree of variation in cost per case due to variability in severity of illness within DRGs. Using hospital (Part A) costs for all Medicare beneficiaries hospitalized in Michigan during 1982, this paper applies multivariate techniques to test the ability of two state-of-the-art case-mix measures to either replace or act as a severity modifier to DRGs. When compared with DRGs, neither Patient Management Categories (PMCs) nor Disease Staging explains any more of the variation in costs. Results show that DRGs explain 33%, while PMCs and Disease Staging explain 26% and 17%, respectively. The use of either alternative in tandem with DRGs explains only 1-2% more of the observed variation; however, both PMCs and Disease Staging identify subgroups of patients with significantly different costs. These findings suggest that the alternatives may prove modestly useful as DRG modifiers by identifying classes of patients that do not belong. More importantly, they offer a measure of "unrelated comorbidity" that may improve the performance of DRGs.

Costs and Cost Analysis↗

PubMed1989

Mutational changes in physiochemical cell surface properties of plant-growth-stimulating Pseudomonas spp. do not influence the attachment properties of the cells.

Bacteriophage-resistant mutant strains of the root-colonizing Pseudomonas strains WCS358 and WCS374 lack the O-antigenic side chain of the lipopolysaccharide, as was shown by the loss of the typical lipopolysaccharide ladder pattern after analysis by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. These strains differed from their parent strains in cell surface hydrophobicity and in cell surface charge. The observed variation in these physicochemical characteristics could be explained by the differences in sugar composition. The mutant strains had no altered properties of adherence to sterile potato roots compared with their parental strains, nor were differences observed in the firm adhesion to hydrophilic, lipophilic, negatively charged, or positively charged artificial surfaces. These results show that neither physicochemical cell surface properties nor the presence of the O-antigenic side chain plays a major role in the firm adhesion of these bacterial cells to solid surfaces, including potato roots.

Antigens, Bacterial↗

PubMed2000

Persistent pulmonary hypertension of the newborn in the era before nitric oxide: practice variation and outcomes.

OBJECTIVES: In the era before widespread use of inhaled nitric oxide, to determine the prevalence of persistent pulmonary hypertension (PPHN) in a multicenter cohort, demographic descriptors of the population, treatments used, the outcomes of those treatments, and variation in practice among centers. STUDY DESIGN: A total of 385 neonates who received >/=50% inspired oxygen and/or mechanical ventilation and had documented evidence of PPHN (2D echocardiogram or preductal or postductal oxygen difference) were tracked from admission at 12 Level III neonatal intensive care units. Demographics, treatments, and outcomes were documented. RESULTS: The prevalence of PPHN was 1.9 per 1000 live births (based on 71 558 inborns) with a wide variation observed among centers (.43-6.82 per 1000 live births). Neonates with PPHN were admitted to the Level III neonatal intensive care units at a mean of 12 hours of age (standard deviation: 19 hours). Wide variations in the use of all treatments studied were found at the centers. Hyperventilation was used in 65% overall but centers ranged from 33% to 92%, and continuous infusion of alkali was used in 75% overall, with a range of 27% to 93% of neonates. Other frequently used treatments included sedation (94%; range: 77%-100%), paralysis (73%; range: 33%-98%), and inotrope administration (84%; range: 46%-100%). Vasodilator drugs, primarily tolazoline, were used in 39% (range: 13%-81%) of neonates. Despite the wide variation in practice, there was no significant difference in mortality among centers. Mortality was 11% (range: 4%-33%). No specific therapy was clearly associated with a reduction in mortality. To determine whether the therapies were equivalent, neonates treated with hyperventilation were compared with those treated with alkali infusion. Hyperventilation reduced the risk of extracorporeal membrane oxygenation without increasing the use of oxygen at 28 days of age. In contrast, the use of alkali infusion was associated with increased use of extracorporeal membrane oxygenation (odds ratio: 5.03, compared with those treated with hyperventilation) and an increased use of oxygen at 28 days of age. CONCLUSIONS: Hyperventilation and alkali infusion are not equivalent in their outcomes in neonates with PPHN. Randomized trials are needed to evaluate the role of these common therapies.

Administration, Inhalation↗

PubMed1997

Light exposure induces ubiquitin conjugation and degradation activities in the rat retina.

PURPOSE: To evaluate the consequences of light exposure on retinal ubiquitin (Ub) conjugation and degradation. METHODS: Two-month-old Long Evans pigmented rats were exposed to constant light (180 foot-candles) or were left in complete darkness for 18 hours. Rats used for cyclic light and diurnal rhythm experiments were removed from their light cycles at different times (24-hour clock): 0700 (before the light was turned on), 1000 (3 hours into the light cycle), 1000D (continued in the dark cycle), 1900 (before the light was turned off), 2200 (3 hours into the dark cycle), and 2200L (continued in the light cycle). The retinas were examined for Ub conjugation, adenosine triphosphate-Ub-dependent degradation, levels of Ub messenger RNA, and localization of Ub immunocytochemistry. RESULTS: There was a statistically significant increase in Ub conjugation and degradation in retinas isolated from light-exposed animals compared with degradation in retinas of dark-adapted animals. However, no significant differences were observed in the levels of Ub messenger RNA from cyclic light, or light-exposed or dark-adapted retinas, suggesting that light-stress-induced changes do not reflect increased transcriptional activity. The daily variations observed in Ub conjugation and degradation suggest that these processes are probably the result of a circadian rhythm. Results of immunohistochemical studies revealed that Ub and its conjugates were uniformly distributed throughout the retinal cell layers in light- and dark-adapted retinas. However, in light-exposed retinas, a strong positive immunoreactivity was observed in the inner retina, specifically in horizontal and ganglion cells. CONCLUSIONS: These results suggest that light exposure may play a role in inducing Ub-conjugating activity in certain retinal cells. Furthermore, the results support the hypothesis that Ub is a stress protein that plays an important role in protecting cells under stress conditions.

Adenosine Triphosphate↗

PubMed2004

Thermal acclimation and seasonal variations of erythrocyte size in the Andean mouse Phyllotis xanthopygus rupestris.

Seasonal hematological adjustments in small mammals may include changes in the number and size of the red cells or changes in other linked blood parameters. The direction and magnitude of these changes vary in different species. We hypothesized that the observed variations of the red cell adjustments could be directly related to the magnitude of the seasonal temperature differential, and predicted that the annual red cell size variation in rodents from environments with marked seasonal changes would tend to disappear, if the animals were raised under milder and constant environments. To test this idea, we got field blood samples from the Andean species Phyllotis xanthopygus rupestris enduring a winter-summer thermal differential of at least 20 degrees C. These animals had significantly smaller erythrocytes during the winter. Contrary to our prediction, their offspring born and raised under constant temperature conditions showed a similar trend. Unless the effective environmental cue differed from the one we used, these results favor the idea of a genetically determined annual red cell size variation that occurs independent of thermal acclimation and acclimatization.

Acclimatization↗

PubMed2004

Linkage disequilibrium for different scales and applications.

Assessing the patterns of linkage disequilibrium (LD) has become an important issue in both evolutionary biology and medical genetics since the rapid accumulation of densely spaced DNA sequence variation data in several organisms. LD deals with the correlation of genetic variation at two or more loci or sites in the genome within a given population. There are a variety of LD measures which range from traditional pairwise LD measures such as D' or r2 to entropy-based multi-locus measures or haplotype-specific approaches. Understanding the evolutionary forces (in particular recombination) that generate the observed variation of LD patterns across genomic regions is addressed by model-based LD analysis. Marker type and its allelic composition also influence the observed LD pattern, microsatellites having a greater power to detect LD in population isolates than SNPs. This review aims to explain basic LD measures and their application properties.

Algorithms↗

PubMed2006

Comparison of SAT-1 foot-and-mouth disease virus isolates obtained from East Africa between 1971 and 2000 with viruses from the rest of sub-Saharan Africa.

Foot-and-mouth disease serotype SAT-1 seems to be endemic in many sub-Saharan African countries. Phylogenetic analysis using the 1D gene of 51 SAT-1 isolates from East, West and southern Africa indicated the presence of at least 6 lineages and 11 genotypes with linkages between various geographical regions of the subcontinent. Differences were observed between countries in East Africa, the main focus of this study, with individual countries suffering outbreaks from isolates belonging to various genotypes, which is evidence of reintroduction of strains and long-term circulation of outbreak viruses. The amount of variation observed has significant implications for disease control on the subcontinent.

Africa South of the Sahara↗