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PubMed1983

Sexual selection and fertility.

Genetic models are analyzed in which sexual selection is combined with fertility selection. In these models, the sexual selection acts on males, the fertility selection on either males, females or both sexes. The phenotypes thus selected may be determined either by dominant and recessive alleles or by each homozygous and heterozygous genotype. Polymorphisms of dominant and recessive phenotypes can be maintained in equilibrium by a balance between sexual and fertility selection. Generally fertility selection has a greater effect than viability selection in determining the point of equilibrium. The dominant phenotype is maintained at a lower frequency when at a fertility disadvantage than when at a viability disadvantage. When about 20% or more of the females mate preferentially, the models show that equilibria will be established at very different frequencies depending on whether fertility selection acts on males, females or both sexes. These results, applied to data of preferential mating of melanic two-spot ladybirds, predict differences in fertility which can be use to test the models. Symmetric models of preferences for each genotype also give rise to polymorphisms if the heterozygotes obtain an overall advantage.

Animals↗

PubMed1996

Dietary beta-carotene elevates plasma steady-state and tissue concentrations of beta-carotene and enhances vitamin A balance in preruminant calves.

Preruminant calves are regarded as a model for studying beta-carotene bioavailability in humans. The objectives of this trial were to determine the relationship between multiple beta-carotene doses and plasma steady-state concentration, accumulation in selected tissues, and vitamin A balance in liver. Seventy newborn Holstein calves in six treatments (n = 10/treatment) were fed a complete milk replacer diet low in vitamin A and supplemented with beta-carotene doses of 0, 0.23, 0.46, 0.92, 1.84 or 3.68 mumol/(kg body wt.d) for 28 d. Ten calves were killed on d 1. Plasma beta-carotene increased in relation to log transformations of dose and time (P < 0.05) in all supplemented calves and steady state was attained after 4 wk. For doses up to 0.92 mumol/(kg body wt.d), the dose-response relationship was linear. A dose-dependent accumulation of beta-carotene was found for liver, heart, lungs, adrenals and adipose tissue. All-trans-beta-carotene was the only isomer in plasma and adrenals and the predominant isomer in the remaining tissues. In liver, vitamin A increased with beta-carotene uptake. Hepatic balance between vitamin A accumulation and loss was achieved at beta-carotene intake of 0.36 mumol/(kg body wt.d) for a calf of 45 kg. It is concluded that preruminant calves within 1 mo of age utilize beta-carotene as a source of vitamin A, and that for testing bioavailability of beta-carotene sources, doses up to 0.92 mumol beta-carotene/(kg body wt.d) are most appropriate.

Adipose Tissue↗

PubMed1989

Effect of guar gum on mineral balances in NIDDM adults.

The self-selected diet of 16 subjects with non-insulin-dependent diabetes mellitus (NIDDM) was supplemented for 6 mo with either a granolalike bar containing 35.5 g carbohydrate and 6.6 g guar gum/bar or a placebo bar containing carbohydrate but no guar gum. Subjects consumed a mean of 4.8 bars/day. Average guar gum consumption at the end of the study was 31.7 g/day. One week before and at the end of the study, subjects were admitted to a metabolic ward and fed a controlled diet similar to their self-selected diet. Food, feces, and urine were composited for analysis of iron, zinc, copper, calcium, magnesium, and manganese. Eight subjects consuming the guar gum supplement and 6 subjects consuming the placebo bar completed collections for mineral balance. Neither consumption of guar gum nor placebo bar significantly changed apparent mineral balance for iron, copper, zinc, calcium, manganese, or magnesium from prestudy levels to 6-mo levels, and no significant differences were observed between the two groups. With the exception of copper, men consumed significantly more minerals than women. We conclude that consumption of guar gum by patients with NIDDM does not adversely affect apparent mineral balance.

Calcium↗

PubMed1983

The selection of fusion levels in thoracic idiopathic scoliosis.

From the material and data reviewed in our study of 405 patients, it appears that postoperative correction of the thoracic spine approximately equals the correction noted on preoperative side-bending roentgenograms. Selective thoracic fusion can be safely performed on a Type-II curve of less than 80 degrees, but care must be taken to use the vertebra that is neutral and stable so that the lower level of the fusion is centered over the sacrum. The lumbar curve spontaneously corrects to balance the thoracic curve when selective thoracic fusion is performed and the lower level of fusion is properly selected. In Type-III, IV, and V thoracic curves the lower level of fusion should be centered over the sacrum to achieve a balanced, stable spine.

Adolescent↗

PubMed1990

Clinical application of dynamic posturography for evaluating sensory integration and vestibular dysfunction.

The assessment of sensory organization in balance control by dynamic posturography is unique compared with clinical maneuvers and other vestibular or neurologic testing. It was designed to isolate the relative contributions of visual, somatosensory, and vestibular feedback, and thus to assess the overall function of the balance control system in adaptively selecting between available sensory information for orientation cues to serve as a reference to earth vertical. Rather than serving as a test for specific pathologic conditions, the utility of posturography is in screening for balance disorders and in functionally defining different types of sensory deficits or central disorders. This functional information can be used to define restrictions or high-risk environments for patients, to guide rehabilitative balance therapy, and to monitor progression of recovery from a disease process.

Adolescent↗

PubMed2006

Surgical treatment of basal cell carcinomas using standard postoperative histological assessment.

SUMMARY Surgical treatment of basal cell carcinomas using postoperative histological assessment is routinely practised in Australia. The efficacy of the procedure depends on key decisions made by the surgeon. The first is case selection that requires an understanding of the limitations of the procedure. The tumour border is then identified and a margin added. The margin selected should achieve the desired balance between incomplete excision rate and mean tissue sacrifice. There is an inverse relationship between these parameters; achieving a 5% incomplete excision rate requires a mean tissue sacrifice of over 4 mm. Factors affecting margin selection are discussed, unfortunately none allows a dramatic reduction in mean tissue sacrifice. The final decision involves interpreting and acting on the histological examination of the excised specimen. Tumour recurrence is rare (less than 2% at 5 years) if the tumour is clear of the surgical margin. The visualized histological margin required to ensure complete excision varies with histological technique and tumour properties. Routine reporting of histological margin in millimetres or horizontal sectioning is recommended. Tumour recurrence averages 38% when the histological margin is involved. The merits of careful clinical follow up of incompletely excised tumours or immediate re-excision are discussed.

Biopsy, Needle↗

PubMed2004

Balancing false positives and false negatives for the detection of differential expression in malignancies.

A basic problem of microarray data analysis is to identify genes whose expression is affected by the distinction between malignancies with different properties. These genes are said to be differentially expressed. Differential expression can be detected by selecting the genes with P-values (derived using an appropriate hypothesis test) below a certain rejection level. This selection, however, is not possible without accepting some false positives and negatives since the two sets of P-values, associated with the genes whose expression is and is not affected by the distinction between the different malignancies, overlap. We describe a procedure for the study of differential expression in microarray data based on receiver-operating characteristic curves. This approach can be useful to select a rejection level that balances the number of false positives and negatives and to assess the degree of overlap between the two sets of P-values. Since this degree of overlap characterises the balance that can be reached between the number of false positives and negatives, this quantity can be seen as a quality measure of microarray data with respect to the detection of differential expression. As an example, we apply our method to data sets studying acute leukaemia.

False Negative Reactions↗

PubMed2006

Single dose vaccine based on biodegradable polyanhydride microspheres can modulate immune response mechanism.

This study focuses on the development of single dose vaccines based on biodegradable polyanhydride microspheres that have the unique capability to modulate the immune response mechanism. The polymer system employed consists of copolymers of 1,6-bis(p-carboxyphenoxy)hexane and sebacic acid. Two copolymer formulations that have been shown to provide extended release kinetics and protein stability were investigated. Using tetanus toxoid (TT) as a model antigen, in vivo studies in C3H/HeOuJ mice demonstrated that the encapsulation procedure preserves the immunogenicity of the TT. The polymer itself exhibited an adjuvant effect, enhancing the immune response to a small dose of TT. The microspheres provided a prolonged exposure to TT sufficient to induce both a primary and a secondary immune response (i.e., high antibody titers) with high-avidity antibody production, without requiring an additional administration. Antigen-specific proliferation 28 weeks after a single immunization indicated that immunization with the polyanhydride microspheres generated long-lived memory cells and plasma cells (antibody-secreting B cells) that generally do not occur without maturation signals from T helper cells. Furthermore, by altering the vaccine formulation, the overall strength of the T helper type 2 immune response was selectively diminished, resulting in a balanced immune response, without reducing the overall titer. This result is striking, considering free TT induces a T helper type 2 immune response, and has important implications for developing vaccines to intracellular pathogens. The ability to selectively tune the immune response without the administration of additional cytokines or noxious adjuvants is a unique feature of this delivery vehicle that may make it an excellent candidate for vaccine development.

Animals↗

PubMed1983

Density-dependent selection incorporating intraspecific competition. II. A diploid model.

A diploid model is introduced and analyzed in which intraspecific competition is incorporated within the context of density-regulated selection. It is assumed that each genotype has a unique carrying capacity corresponding to the equilibrium population size when only that type is present. Each genotypic fitness at a single diallelic autosomal locus is a decreasing function of a distinctive effective population size perceived as a result of intraspecific competition. The resulting fitnesses are both density and frequency dependent with selective advantage determined by a balance between genotypic carrying capacity and sensitivity to intraspecific competition. A major finding is that intergenotypic interactions may allow genetic variation to be more easily maintained than in the corresponding model of purely density-dependent selection. In addition, numerical study confirms the possible existence of multiple interior equilibria and that neither overdominance in fitness nor carrying capacity is necessary for stability. The magnitude of the equilibrium population size and optimization principles are also discussed.

Alleles↗

PubMed1997

Conditions for protected inversion polymorphism under supergene selection.

Conditions for protected inversion polymorphism under the operation of both karyotype and supergene selection in a viability model have been analytically determined. When supergene selection (the effect of recombination in homokaryotypes lowering the mean fitness of their offspring) is acting on gene arrangements and there is no karyotype selection, it is demonstrated that a polymorphic stable equilibrium is reached by the population, which is a function of only the recombination effects in homokaryotypes. Under both supergene and karyotype selection the degree of dominance (h) of karyotype selection is critical to produce a protected inversion polymorphism. In general, the opportunity for protected polymorphism increases as the degree of dominance decreases. For small s values, the conditions for protected polymorphism are r > 2sh and c > 2s(h-1), where r and c are the average loss of viability for offspring of ST/ST and IN/IN homokaryotypes, respectively. These findings suggest that supergene selection may be an important balancing mechanism contributing to the maintenance of inversion polymorphism.

Chromosome Inversion↗

PubMed1990

Effects of moderate dietary phosphorus restriction on intestinal absorption and external balances of phosphorus and calcium in growing female rabbits.

The effects of moderate dietary P restriction on intestinal net fluxes and external balances of P and Ca were studied in growing female albino rabbits that were fed a P-deficient diet for 10 consecutive days while they were housed in metabolism cages. Intestinal P secretion occurred during the first 24 h of P restriction and thereafter changed to absorption. During recovery, when the rabbits were consuming a normal diet, P absorption was significantly greater than either prerestriction control values or than in a separate group of time control rabbits. Phosphorus balance was negative during the 1st day of P restriction but thereafter became positive. This pattern occurred because intestinal P secretion changed to absorption and because urinary losses of P were negligible. Intestinal Ca absorption increased within 24 h of P restriction, reached maximal values by 4 days, and remained elevated for each of the remaining 6 days that dietary P was low. It also was elevated compared to P-sufficient time controls for 8 days after replenishment of dietary P. Despite increased intestinal absorption, Ca balance was significantly reduced during P restriction because of substantial hypercalciuria. Thus, selective dietary P restriction reduced the positive balances of both P and Ca that are characteristic of growth. We conclude that in growing rabbits moderate dietary P restriction induces both intestinal and renal adaptations that conserve this mineral; concomitantly, positive Ca balance is reduced. With dietary P replenishment, adaptations persist to restore the positive mineral balances that were lost because of dietary P restriction during growth.

Animals↗

PubMed2026

Reducing haystacks to needles - ViralClust: A Nextflow pipeline to cluster viral sequences.

BACKGROUND: The rapid accumulation of viral genome sequences presents major challenges for downstream analysis tools, including tools for multiple sequence alignments, phylogeny, and genome/alignment visualization, due to computational constraints and sampling biases caused by outbreak-driven over-representation. Selecting representative genomes through clustering offers a principled alternative to random subsampling, yet choosing appropriate clustering strategies remains non-trivial and context-dependent. RESULTS: Here, we present ViralClust, a modular Nextflow pipeline for bias-aware representative selection from large viral genome datasets. ViralClust integrates five distinct clustering algorithms (CD-HIT-EST, SUMACLUST, VSEARCH, MMSeqs2, and HDBSCAN) within a unified workflow, enabling direct comparison of clustering outcomes and flexible adaptation to diverse biological questions, considering a balanced phylogenetic distribution of the selected sequences. We evaluated ViralClust on six RNA and DNA virus datasets ranging from 632 to 156,586 sequences and spanning genome lengths from 890 to 197,185 nucleotides. Across all datasets, clustering reduced dataset size by ~95 % or more while preserving genetic diversity across species, genera, and families, and effectively mitigating biases introduced by outbreaks, partial genomes, and sequence orientation artifacts. CONCLUSIONS: By supporting whole-genome clustering and scalable representative selection, ViralClust enables efficient and reproducible downstream analyses that would otherwise be computationally infeasible. Rather than offering a prescriptive, guided analysis engine, our framework functions as a flexible comparative collection of complementary strategies, allowing users to empirically evaluate trade-offs and choose the ideal method tailored to their specific analytical endpoints.

Bioinformatics↗

PubMed1980

Dark adaptation within the receptive field centre of rat retinal ganglion cells.

1. Recordings from single axons of retinal ganglion cells in the rat's optic tract were used to determine whether bleaching a small area of the receptive field reduced sensitivity globally or locally, near the bleached photoreceptors. 2. When a suprathreshold test spot was alternated between two equally sensitive positions, the ganglion cell gave an approximately balanced response. The balance was upset if a small-spot bleach was selectively applied to one position. Recovery of the balanced condition was rapid. 3. Varying the duration of a constant illuminance bleach varied the duration of the imbalance following the bleach. 4. The recovery of sensitivity after small-spot bleaches was measured both at the location of the bleach and also at another location, initially equally sensitive. The recovery at the bleached location lagged recovery at the unbleached location; but even in the bleached location, the return of sensitivity was rapid. 5. Recovery of sensitivity after half-field bleaches was measured in the bleached and unbleached halves of the receptive field. Recovery in the bleached half lagged that in the unbleached half. 6. A comparison between the effects of a small-spot bleach and a half-field bleach of the same strength show that the duration of dark adaptation depends on the area of the bleach.

Action Potentials↗

PubMed1989

Analytical applications of circular dichroism.

The goal of the present research has been to develop a selective analytical detection procedure for the easy identification and assay of drugs and related substances present in complex mixtures, without a chromatographic separation step or other work up. The detector of choice is circular dichroism (CD) spectropolarimetry which has the appropriate balance between degree of analytical selectivity and breadth of application. Applications that are described are selected from work carried out in the context of forensic, clinical, and pharmaceutical chemistries, and specifically include discussions of the analyses of enantiomeric mixtures of nicotine and cocaine, the D and E vitamins, and cholesterol and other steroids.

Animals↗

PubMed2006

Molecular evolution of plant immune system genes.

Molecular population genetic studies are providing new perspectives on the evolution of genes that confer resistance to pathogens and herbivores. Here, we compare the evolutionary history of different components of the defense response (detection, signaling and response) and of genes with parallel function in plants and Drosophila. A review of the literature indicates that the dominant form of selection acting on defense genes (balancing, positive and purifying) differs among components of defense. Sampling of particular classes of genes and genes from non-model organisms, however, remains limited. Future studies combining molecular evolutionary analyses with ecological genetic and functional analyses should better reveal how natural selection has shaped defense gene evolution.

Animals↗

PubMed1999

The role of rehabilitation in the treatment of balance disorders.

The vestibular system registers changes in head position, gravity, vibration, acceleration and deceleration. This information is then transmitted to the central nervous system, where additional information from the visual and auditory systems, muscles, tendons, joints and skin, serve to regulate and maintain the equilibrium and orientation of the system. Vision plays the most obvious part in continual monitoring of the environment. Distances, speeds of linear and angular movement, and changes of direction, can all be estimated with experience and be integrated in the central nervous system with those received by other sensory systems. Light touch and pressure receptors in the skin detect bodily contact with the environment and are an essential source of data in walking, cycling, motoring, flying and other activities. Proprioception provides data regarding the instantaneous mechanical disposition of the musculoskeletal system as it relates to the force of gravity acting upon it. The functional recovery that occurs after unilateral vestibular lesions is referred to as "vestibular compensation" and consists of all the processes of neurological reorganization that allow recovering balance after a unilateral vestibular lesion. Exercises are particularly useful in helping patients to overcome disturbances, associated with balance disorders. The purpose of these selected exercises is to build up a tolerance mechanism in the brain, which will compensate for the unequal balance of the two ears.

Exercise↗

PubMed2003

Positive assortative mating with selection restrictions on group coancestry enhances gain while conserving genetic diversity in long-term forest tree breeding.

Selection and mating principles in a closed breeding population (BP) were studied by computer simulation. The BP was advanced, either by random assortment of mates (RAM), or by positive assortative mating (PAM). Selection was done with high precision using clonal testing. Selection considered both genetic gain and gene diversity by "group-merit selection", i.e. selection for breeding value weighted by group coancestry of the selected individuals. A range of weights on group coancestry was applied during selection to vary parent contributions and thereby adjust the balance between gain and diversity. This resulted in a series of scenarios with low to high effective population sizes measured by status effective number. Production populations (PP) were selected only for gain, as a subset of the BP. PAM improved gain in the PP substantially, by increasing the additive variance (i.e. the gain potential) of the BP. This effect was more pronounced under restricted selection when parent contributions to the next generation were more balanced with within-family selection as the extreme, i.e. when a higher status effective number was maintained in the BP. In that case, the additional gain over the BP mean for the clone PP and seed PPs was 32 and 84% higher, respectively, for PAM than for RAM in generation 5. PAM did not reduce gene diversity of the BP but increased inbreeding, and in that way caused a departure from Hardy-Weinberg equilibrium. The effect of inbreeding was eliminated by recombination during the production of seed orchard progeny. Also, for a given level of inbreeding in the seed orchard progeny or in a mixture of genotypes selected for clonal deployment, gain was higher for PAM than for RAM. After including inbreeding depression in the simulation, inbreeding was counteracted by selection, and the enhancement of PAM on production population gain was slightly reduced. In the presence of inbreeding depression the greatest PP gain was achieved at still higher levels of status effective number, i.e. when more gene diversity was conserved in the BP. Thus, the combination of precise selection and PAM resulted in close to maximal short-term PP gain, while conserving maximal gene diversity in the BP.

Computer Simulation↗

PubMed2000

Dietary change, energy balance and body weight regulation among migrating students.

This study was conducted to examine how subjects modulate their food intake and energy balance when they migrate from a low energy density food intake pattern to one of high energy density. It was hypothesised that an increase in the energy density of food consumed would result in increased body weight of the migrating subjects unless food intake and energy balance could be modulated. Food selection, food intake, basal metabolic rate (BMR) and anthropometric measurements were made on 53 female and 56 male newly arrived overseas students. All subjects were from Malaysia, but the data was collected at Oxford Brookes University where the subjects were studying. Food intake using 3-day food diaries and food frequency questionnaires (FFQs). BMR and anthropometric measurements including body weight were measured on arrival in the UK and after 3 and 6 months' stay. Student's t-tests and analysis of variance (ANOVA) were used to compare the data. A significant difference (P < 0.05) was found between the energy density of the foods consumed in Malaysia and after 3 and 6 months in the UK. There was also a significant decrease (P < 0.05) in protein consumed. However, there were no differences in total energy intake. From results of the FFQs, differences were found in food selection due mainly to the lack of availability of certain foods in UK supermarkets. No significant differences were found in the BMR and anthropometric measurements made at the start of the study and later assessments. It appears that Malaysian students are able to remain in energy balance and are weight stable at least during the first 6 months of residence in the UK, despite the wider choice of energy dense food available. This suggests that at least in the short term, subjects are able to modulate their food intake in response to changes in the energy densities and free choice of food.

Adult↗