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PubMed2007

Sex ratio variance and the maintenance of environmental sex determination.

Although variation in population sex ratios is predicted to increase the extinction rate of clades with environmental sex determination (ESD), ESD is still seen in a wide array of natural systems. It is unclear how this common sex-determining system has persisted despite this inherent disadvantage associated with ESD. We use simulation modelling to examine the effect of the sex ratio variance caused by ESD on population colonization and establishment. We find that an accelerating function of establishment success on initial population sex ratio favours a system that produces variance in sex ratios over one that consistently produces even sex ratios. This sex ratio variance causes ESD to be favoured over genetic sex determination, even when the mean global sex ratio under both sex-determining systems is the same. Data from ESD populations suggest that the increase in population establishment can more than offset the increased risk of extinction associated with temporal fluctuations in the sex ratio. These findings demonstrate that selection in natural systems can favour increased variance in a trait, irrespective of the mean trait value. Our results indicate that sex ratio variation may provide an advantage to species with ESD, and may help explain the widespread existence of this sex-determining system.

Computer Simulation↗
PubMed1991

The occurrence and functions of ultradian rhythms.

Ultradian oscillations with periods between 5 min and 4 h have been described in cell-free extracts, single-celled eukaryotes, cultured cells and embryos. Whereas some of these potentially oscillatory systems (e.g. glycolysis) may only exhibit this type of behaviour rarely if at all in vivo, other ultradian oscillators in lower eukaryotes are rhythms and probably have timekeeping functions. Rhythms with ultradian periods of 10 min to 20 h in oxygen consumption and carbon dioxide production have also been studied in endotherm animals: these rhythms may be modified by variations of environmental parameters and by circadian and infradian synchronizers. Interspecies and interstrain differences strongly suggest that these rhythms are endogenous and have a genetic origin. We suggest that the temporal organization of biochemical and physiological processes facilitates optimization of thermodynamic maintenance of the organism within the random fluctuations of its physicochemical environment and contributes to genetic selection.

Animals↗
PubMed1995

Development of an autoflow cruise control system for a centrifugal pump.

To improve the ease of driving a centrifugal pump that is afterload dependent, we have developed an automatic flow control system for the Terumo Capiox centrifugal pump system. This system consists of an autoflow cruise control system with a safety cutoff. The Capiox Pump Console 3000 was controlled by a personal computer through a serial communication line. In the usual manual mode, the motor speed knob works as a pump speed control, and in the autoflow mode, the same knob works as a blood flow rate control. After selecting and obtaining the desired flow rate, the mode was changed from manual to autoflow mode. In the autoflow mode, the computer compares the desired flow rate with the actual flow measured by an ultrasonic Doppler flowmeter and adjusts the motor rotational speed accordingly. During both in vivo and in vitro testing, this autoflow mode was able to return the changed flow that was disrupted by either clamping and declamping of the tubing or by the bolus injection of a vasomotor drug to the selected flow rate within 10 s without any significant fluctuation. In conclusion, the newly developed computer controlled autoflow system was able to produce a reliable and effective flow regulation for a centrifugal pump.

Animals↗
PubMed1997

Restriction pattern variability of respiratory syncytial virus during three consecutive epidemics in Denmark.

A PCR-based assay was used to distinguish between respiratory syncytial virus (RSV) group A and B in order to analyze their prevalence in Denmark in three consecutive epidemics during the winters of 1992/93, 1993/94 and 1994/95. A total of 96 RSV strains isolated from hospitalized children were examined, showing alternation of group prevalence. Furthermore, the genetic variability of the RSV isolates was illustrated by restriction enzyme analysis of PCR products originating from a part of the F and G proteins that has been reported to be highly variable. We found that, in general, different genome types predominated each year, some types being present in consecutive epidemics, indicating a contribution of strains circulating unattended between outbreak seasons, while others seemed to disappear or became undetectable, being replaced by emerging types. Some of the genome types found seemed related to strains isolated up to more than two decades ago in other parts of the world. This indicates that the temporal fluctuation in predominance of genome types presumably caused by selective pressure exerted by host immunity is due to the favoring of strains from a pool of globally circulating, genetically relatively stable genome types, rather than a molecular evolution in strains induced or directed by immunoselective pressure.

Animals↗
PubMed1996

Elevated TNF-alpha production by peripheral blood monocytes of weight-losing COPD patients.

The inflammatory cytokines, tumor necrosis factor-alpha (TNF-alpha) and interleukin-1-beta (IL-1 beta), have been associated with accelerated metabolism and protein turnover following exogenous administration in normal humans. We hypothesized that these inflammatory cytokines might contribute to the weight-losing process in patients with chronic obstructive pulmonary disease (COPD). COPD patients were identified prospectively as "weight losers" (WL; n = 10) if they reported > 5% weight loss during the preceding year or as "weight stable" (WS; n = 10) if their body weight fluctuated < or = 5%. Age-matched healthy volunteers were selected as the control group (C; n = 13). Monocytes were isolated from a peripheral blood sample, cultured, and exposed to lipopolysaccharide (LPS). The concentration of TNF-alpha and IL-1 beta in the monocyte supernatant was measured using a four layer enhanced ELISA. No significant difference in LPS-stimulated IL-1 beta production was found in the three study populations. However, LPS-stimulated TNF-alpha production (mean [range] ng/ml) by monocytes was significantly higher in the WL COPD patients (20.2 [6.3 to 44.8]), compared with WS patients (6.9 [1.5 to 16.6]), and C subjects (5.7 [0 to 61.8]). This difference was not maintained at 6 mo follow-up in the absence of ongoing weight loss. Definition of a causal relationship between TNF-alpha production and weight loss will require further understanding of the relationship between energy metabolism and TNF-alpha production in these patients.

Aged↗
PubMed2005

Thermal cycling and the optical and electrical characterization of self-assembled multilayer nile blue A-gold thin films.

Some laser applications produce high power densities that can be dangerous to equipment and operators. We have fabricated thin-film coatings by using molecular electrostatic self-assembly to create a spectrally selective absorbing coating that is able to withstand thermal fluctuations from -20 degrees C to 120 degrees C. We made the thin-film coatings by alternating deposition of an organic dye and gold colloidal nanoparticles onto glass substrates. Nile Blue A perchlorate, with a maximum absorbance slightly above 632 nm, was chosen as the organic dye. Strong coupling between the dye molecules and the gold nanoparticles provides a redshift that increases as the film's thickness is increased. The incorporation of the gold colloidal nanoparticles also decreases the resistivity of the film. The resistivity of the film was measured with a four-point probe and found to be approximately 10 omega/cm for the two samples measured. Atomic-force microscopy was used to show that film thickness increased 2.4 nm per bilayer. The optical properties of the film were measured at the end of every 5 thermal cycles from -20 degrees C to 120 degrees C, and negligible degradation was observed after 30 cycles.

Journal Article↗
PubMed1989

Hypertension in the surgical patient: management of blood pressure and anesthesia.

Although hypertension has always been a high risk factor during anesthesia and surgery, risk can be reduced by preoperative control of blood pressure, evaluation of the patient to determine risk factors that can exacerbate blood pressure rises, and continuation of preoperative antihypertensive therapy. Patient hemodynamics must be monitored to manage blood pressure fluctuations and signs of ischemia as early as possible. Selection of anesthetic and adjuvant agents must be tailored to the patients, the agents must be administered carefully and in a timely fashion, and the anesthesiologist must be aware of the relevant variables. Increased knowledge of the pathophysiology of hypertension, antihypertensive therapy, and the development of new anesthetics and muscle relaxants with minimum hemodynamic effects has helped minimize complications related to perioperative hypertension.

Anesthesia↗
PubMed1989

[Relationships between patterns of dyad relations and its change and mutual understanding of psychological traits].

The link between dyad friendship pattern and properties of mutual understanding was explored using the seventh graders as subjects. In Study 1, 42 mutual (MP) and 47 unilateral (UP) friendship pairs were selected. Each partner in each pair was asked to choose five dispositional traits which deemed to describe properly (1) self, (2) partner, and (3) self perceived by partner respectively from 30 traits. Five kinds of criteria to delineate mutual understanding were devised. MP, as opposed to UP, showed greater mutual understanding and recognized not only partners' attractive traits but receiving desirable estimation from partners. MP were also aware of sharing weak points. In Study 2, conducted four-months after Study 1, stable pairs (20 maintained mutual, MM) and vacillating ones (six growing mutual, GM; 11 decayed mutual, DM) were selected. For each of these pairs, the degree of fluctuations in mutual understanding was analyzed. Results showed DM became to see partner as having negative traits, besides to assume receiving negative evaluation from the partner, while MM sustained high degree of mutual understanding.

Adolescent↗
PubMed1975

The variability of innate darkness preference in mice: an evaluation of Ungar's design.

This study attempted to elucidate the controversy surrounding the experiments of Ungar examining the effects of scotophobin on dark preference in mice. The behavior of 45 noninjected mice in the type of maze described by Ungar was examined. Seven subsequent tests were conducted for dark box time (DBT) and motor activity. In general, the results indicated that DBT in all subpopulations of mice selected according to different criteria on the preference test fluctuated during the course of experimentation. Further, on the basis of the present data, the problem of summation effects from combined probabilities in the series of independent comparisons was readily apparent, so that the probability of obtaining significant differences between groups was increased as the results of Ungar's data analysis. A strong relationship between motor activity and DBT was also obtained, suggesting that other, nonspecific factors may influence motor activity and shorten the elevation of DBT.

Animals↗
PubMed1975

[The influence of bemegride on frog spinal cord root potentials].

The effect of the convulsant bemegride (beta-ethyl-beta-methyl-glutharimide) on the electronic potentials in the frog spinal roots was investigated in situ. Intravenous injection of the bemegride subconvulsant doses (6.8 +/- 2.7 mg/kg) depressed rapidly the electrotonic dorsal root potentials (DRP) evoked by a stimulation of the adjacent dorsal root (DR) or the ventral root (VR). They were reduced by 55--67% 3-6 min after the bemegride injection. The effect of bemegride was reversible and the DRP amplitude restored its initial value within an hour. Ventral root potentials after bemegride injection revealed only greater amplitude fluctuations. A conclusion is made that bemegride is a selective and potent depressor of the primary afferent depolarization in the frog spinal cord.

Animals↗
PubMed1979

Acne vulgaris. Current concepts of pathogenesis and treatment.

Although the basic cause of acne vulgaris remains unknown, considerable data that concern its pathogenesis and that have been accumulated in recent years allow a rational and therapeutically successful approach to the management of this disorder. To date, there is no single treatment for acne. Therapy must be individualized, with appropriate variations and modifications as the degree or severity of this disorder fluctuates. Today, this goal can be achieved by proper selection of available medications, coupled with the cooperation of the patient, and the knowledge, continued interest, and enthusiasm of the physician and his staff.

Acne Vulgaris↗
PubMed1978

The influence of corticotherapy on mitogen induced lymphocytotoxicity in bronchial asthma.

In a previous study the hyperreactive lymphocytes in bronchial asthma (BA) have been documented by mitogen induced cell-mediated cytotoxicity (MICC). Since MICC was considerably low in patients receiving substantial doses of steroids, further investigation was conducted. BA patients were divided into three groups: the first was given daily steroids, the second was given steroids on alternate days and the third consisted of a longitudinal follow-up study on the same individual being on different doses of steroids. Mixture of blood lymphocytes, phytohemagglutinin and Cr51 labeled target cells (P815/DBA2) were incubated in ratio 10:1 for 12 hours. Subsequently the cytotoxic potential of effector lymphocytes was detected by measuring the Cr51 in the supernatant of reacting cells. It was observed that cytotoxic correction index (CCI = Patient/Control Cytotoxic Index) was significantly lower among those in the first group and when the dose of Prednisone or its equivalent exceeded 40 mg/day. Comparison of the CCI between patients from the first and second groups supports alternate day corticotherapy in BA. Considerable fluctuation of CCI was apparent in the third group. Selected high doses of steroids suppressed MICC. This effect is reversible and offers a new practical in vitro guidance for monitoring an adequate dose of steroids in vivo.

Adrenal Cortex Hormones↗
PubMed1994

Weight cycling. National Task Force on the Prevention and Treatment of Obesity.

OBJECTIVE: To address concerns about the effects of weight cycling and to provide guidance on the risk-to-benefit ratio of attempts at weight loss, given current scientific knowledge. DATA SOURCES: Original reports obtained through MEDLINE and psychological abstracts searches for 1966 through 1994 on weight cycling, "yo-yo dieting," and weight fluctuation, supplemented by a manual search of bibliographies. STUDY SELECTION: English-language articles that evaluated the effects of weight change or weight cycling on humans or animals. DATA EXTRACTION: Studies were reviewed by experts in the fields of nutrition, obesity, and epidemiology to evaluate study design and the validity of the authors' conclusions based on published data. DATA SYNTHESIS: The majority of studies do not support an adverse effect of weight cycling on metabolism. Many observational studies have shown an association between variation in body weight and increased morbidity and mortality. However, most of these studies did not examine intentional vs unintentional weight loss, nor were they designed to determine the effects of weight cycling in obese, as opposed to normal-weight, individuals. CONCLUSIONS: The currently available evidence is not sufficiently compelling to override the potential benefits of moderate weight loss in significantly obese patients. Therefore, obese individuals should not allow concerns about hazards of weight cycling to deter them from efforts to control their body weight. Although conclusive data regarding long-term health effects of weight cycling are lacking, nonobese individuals should attempt to maintain a stable weight. Obese individuals who undertake weight loss efforts should be ready to commit to lifelong changes in their behavioral patterns, diet, and physical activity.

Body Composition↗
PubMedDate not supplied

A retrospective study of the fluctuation in serum levels of anti-cyclic citrullinated peptide antibody in patients with rheumatoid arthritis.

OBJECTIVE: To investigate the fluctuation in serum levels of anti-cyclic citrullinated peptide antibody (anti-CCP) retrospectively in patients with rheumatoid arthritis (RA). METHODS: Serum levels of anti-CCP were measured retrospectively in 131 patients with RA and 90 patients with non-RA rheumatic diseases using a commercially available kit. All sera were collected from patients during the 22-year period, 1982-2004. To analyze the fluctuation in anti-CCP levels, 17 RA patients were selected on the basis of showing a significantly higher anti-CCP level in a serum sample taken at the first visit (> 80 U/ml), and availability of preserved serum samples that had been taken from each patient at 10 time points. RESULTS: The test gave a sensitivity of 88% (115/131) and a specificity of 81% (73/90). The longitudinal study of 17 RA patients showed that anti-CCP levels were elevated at the first visit in 12 (71%) patients and then decreased gradually, whereas those in the other five (29%) patients fluctuated substantially. In both cases, anti-CCP levels tended to fluctuate in parallel with the erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) level, reflecting the spontaneous aggravation of arthritis and the efficacy of anti-rheumatic drugs. The courses of three representative RA patients are illustrated in detail along with their therapeutic regimens, and these further confirm the correlation of anti-CCP levels with laboratory parameters (ESR and CRP) as well as the activity of arthritis. CONCLUSION: Measurement of serum anti-CCP levels was found to be useful for not only the diagnosis but also the management of RA.

Antibodies, Antinuclear↗
PubMed1993

Double-blind, placebo-controlled, crossover study of duodenal infusion of levodopa/carbidopa in Parkinson's disease patients with 'on-off' fluctuations.

Ten patients with Parkinson's disease suffering severe motor fluctuations completed a double-blind, placebo-controlled, crossover trial of duodenal infusion of levodopa/carbidopa to determine if this technique improved the duration of functional time by reducing plasma levodopa level variability. With infusion, seven patients experienced increased functional "on" hours and decreased number of "off" episodes; however, two patients were slightly worse and one patient experienced no benefit. All 10 patients had significantly decreased variability in levodopa levels permitting better titration of levodopa dosage to individual requirements. Five patients continued to use infusion 12 to 20 months after completion of this study. Selected patients with Parkinson's disease who experience severe motor fluctuations may benefit from duodenal infusion with an improved and prolonged response to medication.

Administration, Oral↗
PubMed2000

Diffusional mechanism of strong selection in ostwald ripening

The purpose of this paper is to show through a systematic asymptotic analysis that fluctuations, accounted for as a diffusional perturbation in the Lifshitz-Slyozov-Wagner (LSW) model of Ostwald ripening, provides, as conjectured previously by Meerson [Phys. Rev. E 60, 3072 (1999)], a "strong" selection of the limiting solution, out of a one-parameter family of similarity solutions with a finite support, as the sole attractor of time evolution. Throughout the latter, the previously described weak selection of other similarity solutions of that family, by the initial conditions with finite supports, occurs as intermediate time asymptotics. The respective mechanism is traced first for a simple instance of the LSW model with linear characteristic equations (integer power in the particle growth rate law equals -1), beginning with the analysis of steady states in the perturbed problem in similarity variables and weak selection in the unperturbed problem, followed by a detailed asymptotic analysis of the time-dependent perturbed problem, and generalized next for an arbitrary integer power in the range [-1,2]. The approximate asymptotic solutions obtained are compared with the exact numerical ones.

Journal Article↗
PubMed2006

Adaptive genetic complementarity in mate choice coexists with selection for elaborate sexual traits.

Choice of genetically unrelated mates is widely documented, yet it is not known how self-referential mate choice can co-occur with commonly observed directional selection on sexual displays. Across 10 breeding seasons in a wild bird population, we found strong fitness benefits of matings between genetically unrelated partners and show that self-referential choice of genetically unrelated mates alternates with sexual selection on elaborate plumage. Seasonal cycles of diminishing variation in ornamentation, caused by early pairing of the most elaborated males, and influx of increasingly genetically unrelated available mates caused by female-biased dispersal, lead to temporal fluctuations in the target of mate choice and enabled coexistence of directional selection for ornament elaboration with adaptive pairing of genetically unrelated partners.

Adaptation, Physiological↗
PubMed2003

Seasonal acclimatisation of muscle metabolic enzymes in a reptile (Alligator mississippiensis).

Reptiles living in heterogeneous thermal environments are often thought to show behavioural thermoregulation or to become inactive when environmental conditions prevent the achievement of preferred body temperatures. By contrast, thermally homogeneous environments preclude behavioural thermoregulation, and ectotherms inhabiting these environments (particularly fish in which branchial respiration requires body temperature to follow water temperature) modify their biochemical capacities in response to long-term seasonal temperature fluctuations. Reptiles may also be active at seasonally varying body temperatures and could, therefore, gain selective advantages from regulating biochemical capacities. Hence, we tested the hypothesis that a reptile (the American alligator Alligator mississippiensis) that experiences pronounced seasonal fluctuations in body temperature will show seasonal acclimatisation in the activity of its metabolic enzymes. We measured body temperatures of alligators in the wild in winter and summer (N=7 alligators in each season), and we collected muscle samples from wild alligators (N=31 in each season) for analysis of metabolic enzyme activity (lactate dehydrogenase, citrate synthase and cytochrome c oxidase). There were significant differences in mean daily body temperatures between winter (15.66+/-0.43 degrees C; mean +/- S.E.M.) and summer (29.34+/-0.21 degrees C), and daily body temperatures fluctuated significantly more in winter compared with summer. Alligators compensated for lower winter temperatures by increasing enzyme activities, and the activities of cytochrome c oxidase and lactate dehydrogenase were significantly greater in winter compared with summer at all assay temperatures. The activity of citrate synthase was significantly greater in the winter samples at the winter body temperature (15 degrees C) but not at the summer body temperature (30 degrees C). The thermal sensitivity (Q(10)) of mitochondrial enzymes decreased significantly in winter compared with in summer. The activity of mitochondrial enzymes was significantly greater in males than in females, but there were no differences between sexes for lactate dehydrogenase activity. The differences between sexes could be the result of the sex-specific seasonal demands for locomotor performance. Our data indicate that biochemical acclimatisation is important in thermoregulation of reptiles and that it is not sufficient to base conclusions about their thermoregulatory ability entirely on behavioural patterns.

Acclimatization↗