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Results for “balancing selection”

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At least 1,207 records · Page 67Linked to original sources

PubMed1988

Cotrel-Dubousset instrumentation.

Cotrel-Dubousset Instrumentation (CDI) presents a diversified posterior implant system applicable in any situation requiring posterior spinal instrumentation. It acts in the three dimensions of the spine, frontal-sagittal-axial. Correct hook site selection and direction provide spinal balance in three dimensions. The double major idiopathic scoliosis is an appropriate model on which to learn the principles of usage of CDI Results of CDI in a wide variety of spinal pathology have been excellent. There is a learning curve for CDI, hook placement being the most significant. Pitfalls and complications can be avoided.

Bone Screws↗

PubMed2001

Mass balance for on-line alphakLa estimation in activated sludge oxidation ditch.

The capacity of an aeration system to transfer oxygen to a given activated sludge oxidation ditch is characterised by the alphakLa parameter. This parameter is difficult to measure under normal plant working conditions. Usually this measurement involves off-gas techniques or static mass balance. Therefore an on-line technique has been developed and tested in order to evaluate alphakLa. This technique deduces alphakLa from a data analysis of low cost sensor measurement: two flow meters and one oxygen probe. It involves a dynamic mass balance applied to aeration cycles selected according to given criteria. This technique has been applied to a wastewater treatment plant during four years. Significant variations of the alphakLa values have been detected while the number of blowers changes. This technique has been applied to another plant during two months.

Environmental Monitoring↗

PubMedDate not supplied

Insect cold hardiness: a Canadian perspective.

The cold climates and diverse environments of Canada have allowed key studies of insect cold hardiness that developed and widened the understanding of this subject. For example, freezing tolerance, chilling tolerance, freezing resistance, supercooling, cryoprotectants and other features can be combined in many different ways, reflecting a wide range of adaptations. Many other factors interact with and influence cold hardiness, such as habitats and their selection, and water and energy balances. These findings suggest several topics that would be especially fruitful for further study in northern Canada.

Journal Article↗

PubMed1999

[The efficacy on natural extrinsic stain of Colgate whitening dentifrice--eight-week study].

OBJECTIVE: To assess the effect on natural extrinsic dental stain by use of a dentifrice containing 1% tetrasodium polyphosphate (TSPP), 7% sodium tripolyphosphate (STPP), 0.243% sodium fluoride and 10% high cleaning silica (HCS) over an eight-week period was compared to a sodium fluoride/silica placebo dentifrice without stain removal ingredients. METHODS: Ninety one subjects were selected and stratified into two balanced groups randomly assigned to use the test dentifrice or the placebo dentifrice. The two groups were well balanced with regard to their mean baseline stain index scores, gender and tobacco habits. Subjects were instructed to brush their teeth twice daily (morning and evening) for one minute with their assigned dentifrice and a commercially available soft bristled toothbrush. Extrinsic dental stain examinations, which included mean stain area and mean stain intensity, were conducted at baseline, four and eight weeks. The same dental examiner conducted examinations on the subjects at each examination. RESULTS: After eight-week use of their assigned products, those subjects in the TSPP/STPP/HCS dentifrice group demonstrated a statistically significant (P = 0.0001) stain reduction of 37.1%, as compared to the fluoride placebo dentifrice group without stain removal ingredients. CONCLUSION: The use of a dentifrice containing 1% tetrasodium polyphosphate, 7% sodium tripolyphosphate, 0.243% sodium fluoride and 10% high cleaning silica is effective in reducing natural extrinsic dental stain, when compared to a placebo fluoride dentifrice.

Adolescent↗

PubMed2006

Intestinal colonisation, microbiota and future probiotics?

The human intestine is colonized by a large number of microorganisms, collectively termed microbiota, which support a variety of physiological functions. As the major part of the microbiota has not yet been cultured, molecular methods are required to determine microbial composition and the impact of specific dietary components including probiotics. Probiotics are viable microbial food supplements, which have a beneficial impact on human health. Health-promoting properties have been demonstrated for specific probiotic products. The most significant demonstrations for probiotic efficacy include prevention and treatment of antibiotic associated diarrhea, rotavirus diarrhea and allergy prevention. Lactobacillus rhamnosus GG (=ATCC 53103) and Bifidobacterium lactis Bb12 are the among the best-characterized and most studied probiotic strains with demonstrated impact on human health. New complex targets for probiotics include irritable bowel syndrome and Helicobacter pylori infection. For future probiotics the most important target is a demonstrated clinical benefit supported by knowledge on the mechanistic actions in the microbiota of the target population. Molecular and genomics-based knowledge of the composition and functions of the microbiota, as well as deviations from the balanced microbiota, will advance the selection of new and specific probiotics. Potential combinations of specific probiotics may prove to be the next step to reduce the risk on intestinal diseases and reconstruct specific microbial deviations.

Bifidobacterium↗

PubMed1987

Bacterial adherence to respiratory tract mucosa--a dynamic interaction leading to colonization.

Normally, the mucosa of the nasooropharynx, trachea, and, perhaps, the major bronchi is colonized with aerobic and anaerobic microbes. This epithelial surface coexists with the microbial flora and is not overgrown with it. Moreover, the physiologic functions of the mucosa--including a protective barrier, mucociliary clearance and humidification, and warming of respired air--are not impeded. How this flora is controlled and what is amiss when virulent or pathogenic bacteria can cause infection are fascinating questions. A balance is maintained during health in which epithelial cell integrity--a function of proper nutrition, available secretory immunoglobulins and glycoproteins, and ciliary motion--resists the microbe's attempt to attach via specialized receptors (pili) or by proteolytic destruction of local proteins. These interactions are reviewed in detail. When colonization is excessive and aspiration of more microbes into the lower airway occurs, infection is more probable. Certain bacteria such as Streptococcus pneumoniae and Hemophilus influenzae, which are associated with chronic bronchitis, illustrate a mechanism in which the host-microbial balance may be upset by selective impairment of a host protein, secretory IgA1. Alternatively, viral infection or cilotoxic microbes (mycoplasma) can favor colonization of bacteria when mucosal clearance mechanisms are impaired. Last, mucosal integrity can be breached by noxious gases or inflammation that may allow bacteria entry into the submucosal that provides a nidus for infection.

Animals↗

PubMed1986

Genetic relationship of human populations and ethnic differences in reaction to drugs and food.

Using gene frequency data for a large number of protein and blood group loci and restriction-site data for mitochondrial DNA, we studied the genetic variation within and between the three major races of man, Caucasoid, Negroid, and Mongoloid. In all the three major races, about 50 percent of structural loci seem to be polymorphic at the electrophoretic level, and the average heterozygosity is about 14 percent. The genetic variation between the three major races is small compared with that within the races. However, even this small interracial variation seems to be the result of geographic isolation for 40,000 to 110,000 years. Genetic distance analysis indicates that Amerindian and Australoid are genetically closer to Mongoloid than to Caucasoid and Negroid, as expected. It is indicated that the evolutionary mechanism of ethnic differences in reaction to drugs and food should be studied with the knowledge that different groups of human populations have been separated for a long time in the evolutionary process. The geographic distributions of the genes for lactose absorption and aldehyde dehydrogenase-I isozyme deficiency suggest that they have existed for a very long time in human populations and that genetic drift has been an important factor in the geographic differentiation of the frequencies of these genes. By contrast, the variant alleles at the pseudocholinesterase locus seem to be maintained by the balance between mutation and weak selection.

Aldehyde Dehydrogenase↗

PubMed1986

[NAPROS--a semiautomatic, user-friendly anesthesia protocol system].

NAPROS is a semiautomatic inexpensive and easy to use anaesthetic record system. It is based on an ACORN (BBC-Model B) micro-computer that is linked to an non-invasive arterial pressure monitor (DINAMAP 845a) and an inhalation narcotic monitor (Engstroem EMMA) for automatic collection of the measured data. The following functions have been implemented: automatic registration of cardiovascular data and concentration of narcotic inhalation agents; input of drugs, fluid input or fluid output, laboratory values, events and comments of the anaesthetist; collection of administrative data and data concerning the preoperative state of the patient; graphic or numeric representation of fluid-balances; survey of all or selected drugs that have been administered up to that time; possibility for recalling dosage information for drugs and infusions; parallel printing of all collected data as a preliminary anaesthetic record; printing of a final anaesthetic report at the end of anaesthesia.

Anesthesiology↗

PubMed1982

Neuroleptic-induced lateral asymmetry of visual evoked potentials in schizophrenia.

Electrophysiological studies have shown asymmetric brain reactivity in schizophrenia, supporting the hypothesis of left hemisphere hyperarousal in this disease. It may be assumed, therefore, that neuroleptic treatment restores hemispheric balance in schizophrenic patients by selectively suppressing the hyperactive left hemisphere. This hypothesis was tested in the present study which compared bilaterally recorded visual evoked potentials (VEP) in 9 non-medicated patients and 29 schizophrenics treated with various neuroleptic drugs, as well as in 34 normal controls. In medicated patients later VEP components showed enhancement over the right hemisphere as a function of the overall dose (chlorpromazine equivalent) of neuroleptics. Reversed asymmetry was seen in drug-free patients. In view of this result, some amendments of the concept of left hemisphere hyperactivity in schizophrenia are proposed.

Adolescent↗

PubMedDate not supplied

[Effect of a 140-day flight on the amino acid content of the blood of cosmonauts].

The results of studying 17 free amino acids in the plasma of the 140-day Salyut-6 crewmembers are presented. The measurements were carried out by means of a Hitachi KLA-3B amino acid analyzer. The data obtained give evidence that the dietary uptake of amino acids before and during flight should be better controlled, the dietary content of amino acids should be enriched with certain amino acids (primarily methionine and cystine) and more adequately balanced. It is recommended to select space diets on an individual basis, taking into consideration anthropometric and metabolic characteristics of cosmonauts.

Amino Acids↗

PubMed1982

Unilateral Versus bilateral electroconvulsive shock in albino rats: comparison of behavioral symptomatology and neocortical reactivity changes.

Electrophysiological studies have shown asymmetric brain reactivity in schizophrenia, supporting the hypothesis of left hemisphere hyperarousal in this disease. It may be assumed, therefore, that neuroleptic treatment restores hemispheric balance in schizophrenic patients by selectively suppressing the hyperactive left hemisphere. This hypothesis was tested in the present study, which compared bilaterally recorded visual evoked potentials (VEP) in 9 nonmedicated patients and 29 schizophrenics treated with various neuroleptic drugs, as well as in 34 normal controls. In medicated patients later VEP components showed enhancement over the right hemisphere as a function of the overall dose (chlorpromazine equivalent) of neuroleptics. Reversed asymmetry was seen in drug-free patients. In view of this result, some amendments of the concept of left hemisphere hyperactivity in schizophrenia are proposed.

Animals↗

PubMed1995

An emergent model of orientation selectivity in cat visual cortical simple cells.

It is well known that visual cortical neurons respond vigorously to a limited range of stimulus orientations, while their primary afferent inputs, neurons in the lateral geniculate nucleus (LGN), respond well to all orientations. Mechanisms based on intracortical inhibition and/or converging thalamocortical afferents have previously been suggested to underlie the generation of cortical orientation selectivity; however, these models conflict with experimental data. Here, a 1:4 scale model of a 1700 microns by 200 microms region of layer IV of cat primary visual cortex (area 17) is presented to demonstrate that local intracortical excitation may provide the dominant source of orientation-selective input. In agreement with experiment, model cortical cells exhibit sharp orientation selectivity despite receiving strong iso-orientation inhibition, weak cross-orientation inhibition, no shunting inhibition, and weakly tuned thalamocortical excitation. Sharp tuning is provided by recurrent cortical excitation. As this tuning signal arises from the same pool of neurons that it excites, orientation selectivity in the model is shown to be an emergent property of the cortical feedback circuitry. In the model, as in experiment, sharpness of orientation tuning is independent of stimulus contrast and persists with silencing of ON-type subfields. The model also provides a unified account of intracellular and extracellular inhibitory blockade experiments that had previously appeared to conflict over the role of inhibition. It is suggested that intracortical inhibition acts nonspecifically and indirectly to maintain the selectivity of individual neurons by balancing strong intracortical excitation at the columnar level.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗

PubMed1993

Efficacy and tolerability of brodimoprim in otitis.

Eighty adult patients affected by acute bacterial otitis media were selected and randomized into two balanced groups of treatment: 1) brodimoprim 200 mg tablets at the dosage of 2 tablets in single dose on the first day and one tablet on the following days; 2) josamycin 500 mg tablets at the dosage of 3 tablets/day. The average duration of treatment was 8 days: all patients completed the trial. The symptoms were evaluated by score method (on the 3rd, 7th and on the last day of therapy) and a thermometric curve was made daily. Microbiological examination of the exudate was performed in the patients with auricular discharge (28), at the beginning of the treatment and 7 days after the end of therapy. The tolerability was assessed through registration of side effects. Brodimoprim resulted more effective in the reduction of hypoacusis and tinnitus; other symptoms demonstrated higher percentage reductions in the group under brodimoprim therapy. Bacteriological exams were negative at the second checkup, except in 6 patients (3 per group). Side effects were reported in 5 patients (12.5%) treated with brodimoprim and in 9 (22.5%) treated with josamycin. Abnormal values in laboratory tests were not observed.

Acute Disease↗

PubMed1993

Efficacy and tolerability of brodimoprim in bacterial otitis media in children. Controlled study versus cefaclor.

78 pediatric patients affected by acute otitis media were selected and randomized into two balanced groups of treatment: brodimoprim, at the dosage of 200 mg once-a-day on the first day and of 100 mg once-a-day on the following days, and cefaclor at a dosage of 40 mg/Kg/day in three doses. Brodimoprim resulted more efficacious in the reduction of symptoms, especially hypoacusis and tinnitus (p < 0.05 between treatments); tympanometry showed a higher number of normalizations in the brodimoprim group, without significant differences between treatments. Both drugs resulted active against most of isolated bacterial strains. Side effects were reported in 4 patients treated with brodimoprim and in 6 patients in the control group.

Acute Disease↗

PubMedDate not supplied

Selective stimulatory actions of corticotropin-releasing factor ligands on correlates of energy balance.

Acute administration of corticotropin-releasing factor (CRF) results in anorexic and sympathomimetic effects that suggest efficacy in chronic models of energy balance. The present studies employed a broad spectrum energy balance indices in lean and genetically obese Zucker rats in order to fully characterize the pharmacological efficacy of CRF and a CRF binding protein (CRF-BP) ligand inhibitor, CRF(6-33), which is thought to liberate CRF from CRF-BP. Acute administration of CRF(6-33) significantly increased CRF(2) receptor density by 10% within the ventromedial hypothalamic (VMH) nucleus of Zucker lean rats and decreased density by 10% in Zucker obese rats. A single infusion of CRF(6-33) increased nonshivering thermogenesis by 25-30% as measured by proton conductance in brown adipose tissue of both lean and obese rats. Chronic CRF(6-33) infusion suppressed body weight gain and elevated core temperature irrespective of genotype while increasing motor activity in obese rats without altering heart rate or blood pressure. Taken together, these results document strain-dependent, long-term effects of a CRF-BP ligand inhibitor on a select subset of physiological and behavioral measures of increased energy expenditure.

Adipose Tissue, Brown↗

PubMed2002

Dispersal, kin competition, and the ideal free distribution in a spatially heterogeneous population.

In this paper, we reanalyze simple models of the evolution of dispersal in a heterogeneous landscape. Previous analyses concluded that without temporal variability, dispersal can evolve only if it is not costly and if it is conditional on the habitat. If both conditions hold, these models predict that selection on dispersal should lead to balanced dispersal between habitats (the number of immigrants equals the number of emigrants in each habitat). To evaluate the generality of these conclusions, we extended the analysis of these models to finite populations. This requires us to establish fitness measures for finite class-structured populations. These fitness measures allow us to take kin competition into account. Our analysis shows that even without temporal variability, conditional dispersal and the absence of a dispersal cost are not necessary conditions for dispersal to evolve. In the absence of a dispersal cost, we predict that selection on conditional dispersal will always lead to panmixia and not simply to balanced dispersal. When dispersal is costly, we show that the ideal free distribution (IFD) and balanced dispersal do not occur. Our results show that the deviations from IFD are of the order of the dispersal cost. We propose an approach to test our predictions.

Biological Evolution↗

PubMed1998

In vivo selection for intronic splicing signals from a randomized pool.

Retroviruses utilize balanced splicing to express multiple proteins from a single primary transcript. A number of cis -acting signals help maintain this balance, including the branch point sequence (BPS), polypyrimidine tract (PPyT) and sequences within the downstream exon. In general, regulated splicing requires weak splicing signals and we have previously shown the same requirement for the simple retrovirus, avian sarcoma virus (ASV). Here we take advantage of the requirement for balanced splicing in retroviral replication to examine the sequence constraints of an intronic splicing element. Selection for replication competence makes it possible to amplify and identify functional sequences from a pool of all possible sequences. In this report we examine the role of pyrimidines within the PPyT. Our results provide in vivo confirmation that the functional strength of a PPyT is related to its length and uridine content and that the PPyT plays a role in the second step of the splicing reaction. We also show that the minimal distance between the 3'-splice site and the BPS in this system is 16 nt. With modification, the selection system described here can be used to examine the sequence constraints of other exonic or intronic splicing elements in vivo .

Base Sequence↗

PubMed2003

Selective activation of Src family kinases and JNK by low levels of chromium(VI).

Inhaled hexavalent chromium (Cr(VI)) promotes pulmonary disease and lung cancer through poorly defined mechanisms. These mechanisms were studied in A549 lung epithelial cells to investigate the hypothesis that nontoxic Cr(VI) exposures selectively activate cell signaling that shifts the balance of gene transcription. These studies demonstrated that nontoxic doses of Cr(VI) (10 microM) increased reactive oxygen species and selectively activated c-Jun N-terminal kinase (JNK), relative to ERK or p38 MAP kinase. In contrast, only toxic, nonselective levels of exogenous oxidants stimulated JNK. However, JNK activation in response to Cr(VI) and exogenous H(2)O(2) (1 mM) shared requirements for intracellular thiol oxidation, activation of Src family kinases, and p130(cas) (Cas). Cr(VI) did not mimic H(2)O(2)-mediated stimulation of JNK in fibroblasts containing only Src and did not activate Src or Yes in A549 cells. Instead, Fyn and Lck were activated in A549 cells, indicating activation of specific Src family kinases in response to Cr(VI). Finally, Cr(VI) was demonstrated to directly activate purified Fyn in vitro and the majority of this activation did not require oxidant generation. These data suggest that nontoxic levels of Cr(VI), which can shift patterns of gene transcription, are selective in their activation of cell signaling and that Cr(VI) can directly activate Src family kinases independently of reactive oxygen species generation.

Cells, Cultured↗