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PubMed1994

Base preferences for DNA binding by the bHLH-Zip protein USF: effects of MgCl2 on specificity and comparison with binding of Myc family members.

Studies of the DNA binding specificity of transcription factors belonging to the basic helix-loop-helix (bHLH) family have identified the so-called E-box, CACGTG, as being a high affinity specific binding sequence for this class of DNA binding proteins. Binding sequences for HeLa USF were selected from an initially random population of 20 bp sequences, defining the optimum USF binding sequence as R-5Y-4C-3A-2C-1G+1T+2G+3R+4Y+5. The significance of the flanking bases was further demonstrated by showing that USF and the related proteins c-Myc and Max discriminate between CACGTG-type E-boxes and that the primary means of discrimination appears to be the identity of the nucleotide at +/- 4, the presence of a T at -4 being inhibitory to binding by Myc but not by USF or Max. This suggests one mechanism by which bHLH factors are partitioned between multiple potential binding sequences in the promoters and enhancers of viral and cellular genes. It was also demonstrated that MgCl2 has a significant influence on USF DNA binding specificity. A broader range of USF binding sites was selected in the absence of MgCl2, conforming to the altered half-site consensus gTGaY. Binding studies with specific oligonucleotides demonstrated significantly improved tolerance to sequence variation at positions 1, 4, and to a lesser extent 5, of the GTGRY consensus in the absence of MgCl2. The results indicate that Mg2+ ions have an integral role in the formation of the USF-DNA complex.

Amino Acid Sequence↗
PubMed1990

Rapid methane oxidation in a landfill cover soil.

Methane oxidation rates observed in a topsoil covering a retired landfill are the highest reported (45 g m day) for any environment. This microbial community had the capacity to rapidly oxidize CH(4) at concentrations ranging from <1 ppm (microliters per liter) (first-order rate constant [k] = -0.54 h) to >10 ppm (k = -2.37 h). The physiological characteristics of a methanotroph isolated from the soil (characteristics determined in aqueous medium) and the natural population, however, were similar to those of other natural populations and cultures: the Q(10) and optimum temperature were 1.9 and 31 degrees C, respectively, the apparent half-saturation constant was 2.5 to 9.3 muM, and 19 to 69% of oxidized CH(4) was assimilated into biomass. The CH(4) oxidation rate of this soil under waterlogged (41% [wt/vol] H(2)O) conditions, 6.1 mg liter day, was near rates reported for lake sediment and much lower than the rate of 116 mg liter day in the same soil under moist (11% H(2)O) conditions. Since there are no large physiological differences between this microbial community and other CH(4) oxidizers, we attribute the high CH(4) oxidation rate in moist soil to enhanced CH(4) transport to the microorganisms; gas-phase molecular diffusion is 10-fold faster than aqueous diffusion. These high CH(4) oxidation rates in moist soil have implications that are important in global climate change. Soil CH(4) oxidation could become a negative feedback to atmospheric CH(4) increases (and warming) in areas that are presently waterlogged but are projected to undergo a reduction in summer soil moisture.

Journal Article↗
PubMed1984

Demonstration of renin activity in purified rat Leydig cells: evidence for the existence of an endogenous inactive (latent) form of enzyme.

Previous histochemical studies demonstrated the specific localization of immunoreactive renin-like substance in Leydig cells of rat testes. The studies reported herein demonstrate a specific renin enzyme activity in the two purified populations of Leydig cells (I and II) of mature rat testes. Leydig cells of both populations also exhibited an inactive (latent) renin which was activated by the sulfhydryl reagents dithiothreitol, beta-mercaptoethanol, glutathione, and cysteine but not by limited proteolysis by trypsin, which is a characteristic activating agent for prorenin or inactive renin of the zymogen type. The activation of latent renin by dithiothreitol produced approximately 5-and 10-fold increases in renin activity in Leydig cell populations I and II, respectively. Active and latent renin showed strong affinity to an antirat renin immunoglobulin-Sepharose column, indicating a close immunological relationship of latent renin to active renin. Both active and latent renin from Leydig cell populations (I and II) exhibited the pH optimum of 6.0. The gel filtration of Leydig cell extracts characteristically revealed that the apparent mol wts of active and latent renin were 39,000 and 48,000, respectively. Both active and latent renin in Leydig cells remained almost at similar levels through four continuous subcultures. The activity of latent renin slightly increased during the four consecutive subcultures, while active renin levels remained almost constant.

Animals↗
PubMed2005

Monitoring of trace elements in breast milk sampling and measurement procedures.

The aims of this study were to test analytical procedures for the determination of Cd, Cu, Mn, Pb, Se and Zn in breast milk and to establish optimum sampling conditions for monitoring purposes. Two population groups were analysed: (1) Seven women from Prague whose breast milk was sampled on days 1,2, 3, 4, 10, 20 and 30 after delivery; (2) 200 women from four (two industrial and two rural) regions whose breast milk was sampled at defined intervals. All samples were mineralised in a microwave oven in the mixture of HNO3 + H2O2 and analysed by atomic absorption spectrometry. Conditions for the measurement of the elements under study (i.e. those for the electrothermal atomisation for Cd, Mn and Pb, flame technique for Cu and Zn, and hydride generation technique for Se) were optimized. Using optimized parameters the analysis was performed and the following conclusion has been made: the concentrations of zinc and manganese decreased very sharply over the first days, that of copper slightly increased within the first two days and then slightly decreased, that of selenium did not change significantly. Partial "stabilisation" was achieved after the second decade. No correlation among the elements was found. A significant difference between whole and skim milk was only found for selenium (26% rel. higher in whole milk). The majority concentrations of cadmium and lead were below the detection limit of the method (0.3 microg x l(-1) and 8.2 microg x l(-1), respectively, as calculated for the original sample). To provide biological monitoring, the maintenance of sampling conditions and especially the time of sampling is crucial.

Czech Republic↗
PubMed1991

Protection from arabinofuranosylcytosine and n-mustard-induced myelotoxicity using hemoregulatory peptide pGlu-Glu-Asp-Cys-Lys monomer and dimer.

We have previously shown that the synthetic peptide pGlu-Glu-Asp-Cys-Lys (pEEDCK monomer) inhibits the cytostatic drug-induced proliferation of hematopoietic stem cells CFU-S. Keeping CFU-S quiescent by pEEDCK treatment renders them insensitive to cycle-specific cytostatic drugs and leads to reduced toxicity. Here we show that pEEDCK application during repeated (twice) administration of clinically relevant (nonlethal) 1-beta-D-arabinofuranosylcytosine (Ara-C) doses reduced the percentage of CFU-S in S-phase from 60%-70% to 25%-30% and led to a sustained stem cell number in the bone marrow (BM), whereas unprotected mice had lost about 75% of their CFU-S population. Owing to its cysteine content, the pEEDCK monomer is easily oxidized. The resulting dimer (pEEDCK)2 is a potent stimulator of hematopoiesis. As we show, it can be used for postchemotherapy acceleration of hematologic recovery, similar to the use of recombinant hematopoietic growth factors. A single injection of 30 micrograms/kg pEEDCK monomer to mice 2 hours before the second Ara-C injection retarded onset of neutropenia (by 2 to 3 days) and improved recovery after depression. The quantitative degree of neutropenia was not changed. Postchemotherapy (Ara-C administered twice, followed by N-mustard) infusion of the stimulatory (pEEDCK)2 dimer (1.4 micrograms/kg/d) produced a 4.6-fold increase of progenitor levels (6.7 CFU-GM/1,000 BM cells v 1.45 CFU-GM/1,000 in normal mice) 2 days after the end of the cytostatic treatment when CFU-GM were not detectable in unprotected mice. This increase was followed after several days by strongly elevated granulocyte counts, which remained high for approximately 1 week. Up to 75% of the peripheral leukocytes were mature polymorphonuclear leukocytes (PMN) during this phase. Ara-C (twice) and monomer treatment as above followed by dimer infusion resulted in the complete protection of hematopoiesis. Mice treated with the protective pEEDCK monomer plus stimulatory dimer did not develop the leukocyte depression noted in unprotected animals. The inhibitory monomer appears to keep the stem cell population numerically and qualitatively intact, thus providing optimum target cell conditions for the subsequent stimulator (dimer) treatment. Our results show that the hemoregulatory peptide monomer and dimer can be used for improving the hematologic status of mice treated with clinically relevant doses of cytostatic drugs (antimetabolite and alkylating, alone and in combination). Combining both peptides can prevent occurrence of neutropenia completely. Both peptides can be obtained easily by chemical synthesis and are also active on human cells. They are thus highly promising candidates for application as multilevel hemoprotectors in cancer chemotherapy.

Animals↗
PubMed1990

Therapeutic considerations in the elderly hypertensive. The role of calcium channel blockers.

Hypertension is an extremely common problem in the elderly. The optimum antihypertensive agent to use in this population is not certain. In this paper, the factors influencing the choice of antihypertensive therapy are reviewed. They include efficacy, safety, comorbidity, utility in special populations, drug interaction, dosage schedule, cost, the mechanisms of action of the drug, and the pathophysiology of the patient's hypertension. Calcium channel blockers are effective and safe in the elderly. They improve other conditions frequently seen in that population and, with the exception of cardiac conduction abnormalities associated with some calcium channel blockers, do not adversely affect other comorbid diseases. They work well together with other antihypertensives and as vasodilators, they may be specifically appropriate in elderly hypertensives, whose hypertension is associated with reduced cardiac output and increased peripheral vascular resistance. Once- and twice-a-day preparations are available to foster compliance, but calcium channel blockers are expensive.

Aging↗
PubMed1982

Antigen-mediated release of eosinophil growth stimulating factor from Trichinella spiralis sensitized spleen cells: a comparison of T. spiralis stage-specific antigen preparations.

When non-adherent, Trichinella spiralis-sensitized mouse spleen cells were challenged in vitro with T. spiralis antigens, an eosinophil growth factor (Eo-GSF) was released into the culture medium. This factor was assayed by its ability to initiate eosinophil production in liquid cultures of syngeneic, non-adherent marrow cells obtained from unsensitized mice. Extracts of each parasite stage as well as excretory-secretory (ES) products of adult and muscle larva stages were compared for their ability to stimulate spleen cells to release Eo-GSF. All stages and ES products had this ability but most of the preparations had unique dose-optima and there was a very wide range with regard to the optimum dose (in microgram protein/ml): (i) preadult stage, 1 x 10(-5); (ii) muscle stage ES products, 1 x 10(-3); (iii) muscle stage, 1 x 10(-2); (iv) adult stage, 1 x 10(-2); (v) adult ES products, 1 x 10(-1); and (vi) newborn stage, 1.0. When the Eo-GSF-containing conditioned media derived from spleen cell cultures exposed to the optimum dosages were tested on the same population of marrow cells, three potency groups were identified. The rank order of potency was: muscle stage ES products greater than preadult, newborn and adult stages greater than muscles stage and adult ES products. Preliminary experiments revealed that this ranking was not maintained with regard to the release of neutrophil and macrophage growth factors by these preparations.

Aging↗
PubMed2006

Size relationships between the parasitic copepod, Lernanthropus cynoscicola , and its fish host, Cynoscion guatucupa.

The effects of the size of Cynoscion guatucupa on the size and demographic parameters of their parasitic copepod Lernanthropus cynoscicola were evaluated. Prevalence of copepods increased with host size up to fish of intermediate length, then it decreased, probably because changes in size of gill filaments affect their attachment capability, enhancing the possibility of being detached by respiratory currents. Body length of copepods was significantly correlated with host length, indicating that only parasites of an 'adequate' size can be securely attached to a fish of a given size. The absence of relationship between the coefficient of variability in copepod length and both host length and number of conspecifics, together with the host-size dependence of both male and juvenile female sizes, prevent to interpret this relationship as a phenomenon of developmental plasticity. Therefore, the observed peak of prevalence could reflect the distribution of size frequencies in the population of copepods, with more individuals near the average length. Concluding, the 'optimum' host size for L. cynoscicola could merely be the adequate size for most individuals in the population, depending, therefore, on a populational attribute of parasites. However, its location along the host size range could be determined by a balance between fecundity and number of available hosts, which increases and decreases, respectively, with both host and parasite size.

Animals↗
PubMed2004

Evolution and stability of the G-matrix on a landscape with a moving optimum.

In quantitative genetics, the genetic architecture of traits, described in terms of variances and covariances, plays a major role in determining the trajectory of evolutionary change. Hence, the genetic variance-covariance matrix (G-matrix) is a critical component of modern quantitative genetics theory. Considerable debate has surrounded the issue of G-matrix constancy because unstable G-matrices provide major difficulties for evolutionary inference. Empirical studies and analytical theory have not resolved the debate. Here we present the results of stochastic models of G-matrix evolution in a population responding to an adaptive landscape with an optimum that moves at a constant rate. This study builds on the previous results of stochastic simulations of G-matrix stability under stabilizing selection arising from a stationary optimum. The addition of a moving optimum leads to several important new insights. First, evolution along genetic lines of least resistance increases stability of the orientation of the G-matrix relative to stabilizing selection alone. Evolution across genetic lines of least resistance decreases G-matrix stability. Second, evolution in response to a continuously changing optimum can produce persistent maladaptation for a correlated trait, even if its optimum does not change. Third, the retrospective analysis of selection performs very well when the mean G-matrix (G) is known with certainty, indicating that covariance between G and the directional selection gradient beta is usually small enough in magnitude that it introduces only a small bias in estimates of the net selection gradient. Our results also show, however, that the contemporary G-matrix only serves as a rough guide to G. The most promising approach for the estimation of G is probably through comparative phylogenetic analysis. Overall, our results show that directional selection actually can increase stability of the G-matrix and that retrospective analysis of selection is inherently feasible. One major remaining challenge is to gain a sufficient understanding of the G-matrix to allow the confident estimation of G.

Adaptation, Biological↗
PubMed1994

Migration cost externality and interregional equilibrium.

"This paper will investigate the characteristics of population allocation between two regions in the presence of migration cost. It will also examine both populations and the non-migration range of the initial population in which migration does not occur, in social optimum and market equilibrium with central government intervention, to reveal migration cost externality, and to propose a remedy for it." The author finds that "migration cost gives the social planner an additional burden of population reallocation, and it has an important effect upon an individual's decisions on migration in a decentralized market mechanism."

Behavior↗
PubMedDate not supplied

Validation of the PTSD checklist in an HMO sample of women.

Although Post-traumatic Stress Disorder (PTSD) is common among patients seeking care at medical clinics, little is known about the performance of screening instruments for this disorder in these settings. Previous studies of acute trauma populations using the PTSD Checklist (PCL) have suggested that scores of 45-50 provide the best discrimination between cases and noncases. We gave the PCL to 1,225 randomly selected women enrolled in an HMO. After interviewing a sample of 261 of these women using a structured, clinician-administered PTSD interview, we compared the results of the PCL to the clinician interviews over a range of possible cut scores using Receiver Operating Characteristic analysis. The optimum balance of sensitivity and specificity for this population was a score of 30, yielding a sensitivity of.82 and specificity of.76. The positive and negative likelihood ratios for this cut score were 3.40 and 0.24, respectively. By comparison, the use of 45 as a cut score would result in very low sensitivity (.36) in this setting. The lower cut score found in this study may indicate that the use of previously published cut scores of 45-50 may not optimize the function of the PCL as a screening tool outside of acute trauma settings due to an unacceptably high number of false negative cases.

Adolescent↗
PubMed1976

Temperature limitation of methanogenesis in aquatic sediments.

Microbial methanogenesis was examined in sediments collected from Lake Mendota, Wisconsin, at water depths of 5, 10, and 18 m. The rate of sediment methanogenesis was shown to vary with respect to sediment site and depth, sampling date, in situ temperature, and number of methanogens. Increased numbers of methanogenic bacteria and rates of methanogenesis correlated with increased sediment temperature during seasonal change. The greatest methanogenic activity was observed for 18-m sediments throughout the sampling year. As compared with shallower sediments, 18-m sediment was removed from oxygenation effects and contained higher amounts of ammonia, carbonate, and methanogenic bacteria, and the population density of methanogens fluctuated less during seasonal change. Rates of methanogenesis in 18-m sediment cores decreased with increasing sediment depth. The optimum temperature, 35 to 42 C, for sediment methanogenesis was considerably higher than the maximum observed in situ temperature of 23 C. The conversion of H2 and [14C]carbonate to [14C]methane displayed the same temperature optimum when these substrates were added to sediments. The predominant methanogenic population had simple nutritional requirements and were metabolically active at 4 to 45 C. Hydrogen oxidizers were the major nutritional type of sediment methanogens; formate and methanol fermentors were present, but acetate fermentors were not observed. Methanobacterium species were most abundant in sediments although Methanosarcina, Methanococcus, and Methanospirillum species were observed in enrichment cultures. A chemolithotropic species of Methanosarcina and Methanobacterium was isolated in pure culture that displayed temperature optima above 30 C and had simple nutritional requirements.

Cell Count↗
PubMed1997

[Cost-effectiveness analysis of the screening strategies for primary angle closure glaucoma].

PURPOSE: To evaluate varlous primary angle clouse glaucoma(PACG)screening strategies by cost effectiveness analysis for choosing the best screening strategy. METHODS: We designed a model of the process of PACG screening, diagnosis, treatment, and estimated variable parameters of this model through literatures reviewed and the results of our study. Then four screening strategiers which are oblique flashlight test, measurement of axial anterior chamber depth (AACD), examination of peripheral anterior chamber depth (PACD), and combination of oblique flashlight test with examination of PACD in series were calculated by computer to obtain the costs for various screening strategies and the quality ajusted life years (QALYs) saved. We performed sensitivity analysis to determine how the variation in the parameter assumptions would affect the calculated cost effectiveness of the various screening strategies. Based on the principle of cost effectiveness, the screening strategy of more cost effective would be chosen. RESULTS: The results showed that no matter what age group, the screening strategy of oblique flashlight test and measuring PACD combined in series is the lowest cost per QALY gained than other strategies. This screening strategy is optimum, next is oblique flashlight test Screening method. We found that screening strategies not only gains QALY, but also is cost saving as well in the range 40-< 70 years old. sensitivity analysis result showed that optimum strategy is still the combined serial strategy, in addition to the capable closure angle ratio of a population with a 10% up and down, the oblique flashlight test became an optimum strategy and the combined serial method became next in > or = 70 years old group. CONCLUSION: The results showed that the oblique flashlight test and measurement of PACD combined in series is an optimum screening strategy. This research suggests that using adequate screening strategy should not only increase the QALYs, but also save the cost for the government and the patients themselves.

Anterior Chamber↗
PubMed2002

Population pharmacokinetics of digoxin in pediatric patients.

Digoxin pharmacokinetics were studied in a pediatric population with an age range of 6 days to 1 year using the population pharmacokinetic approach. Digoxin data were analyzed by mixed-effects modeling according to a one-compartment steady-state pharmacokinetic model using NONMEM software. The final model selected for the population prediction of digoxin clearance in pediatric patients was as follows: [equation: see text] Individual empirical Bayesian estimates were generated on the basis of the population estimates and were used to correlate the optimum dose of digoxin and patient age according to the following equation: [equation: see text] This equation and its derived nomogram may be used for the initial dosing of digoxin in children aged between 0 and 1 year. The use of this nomogram in routine monitoring requires further pharmacokinetic and clinical validation.

Algorithms↗
PubMed2001

Evaluation of a sampling trap for Dermanyssus gallinae (Acari: Dermanyssidae).

Traps made by rectangular pieces of 3 mm thick corrugated cardboard of four different sizes, 200 by 140 (A), 140 by 100 (B), 100 by 70 (C), and 200 by 40 mm (D), were evaluated as a sampling device for the chicken mite, Dermanyssus gallinae (De Geer). Mites were trapped during 2, 4, 6, 8, and 10 d, respectively, in a poultry house heavily infested with the parasite. Significantly greater numbers of mites were collected by trap B. Additionally, significantly more mites were collected during the sampling periods 6-10 d than by 2 and 4 d. However, with regard to trap size and sampling period, trap C, used for 2 d, collected significantly more mites per day and trap area than any of the other traps. Therefore, such a trap was suggested for monitoring population trends of chicken mites in poultry houses. The larger traps contained significantly higher numbers of mites per trap and may therefore be feasible to use in alternative, nonchemical control programs. Optimum sample size, or number of traps required to monitor population trends of D. gallinae, was also calculated. At a relative variability of 20%, and at densities of 2,000-20,000 mites per trap, approximately 11-16 of trap B and 11-19 of trap C would be adequate to monitor mites.

Animals↗
PubMedDate not supplied

The influence of sperm/zona pellucida collision rates on zona binding.

The satisfying success rates reported with intra-cytoplasmic sperm injection (ICSI) urged clinicians and scientists to re-address the emphasis in the management of the male factor patient towards gamete manipulation in order to circumvent the underlying problem causing fertilization failure. We have designed a study to (i) calculate the collision rate of a sperm population with the human zona pellucida, using a mathematical hypothesis and (ii) use the calculated collision rate to evaluate subsequent zona binding results obtained under hemizona assay conditions. Microdroplets were used to co-incubate sperm and human oocytes in order to evaluate zona binding. Using microvolumes, the track followed by sperm, as well as the maximum distance travelled were employed to calculate the collision rate of sperm and zona pellucida. The sperm concentrations of swim up samples were adjusted to 4 x 10(6) and 0.8 x 10(6) sperm ml-1. Five separate droplets each of 20 microliters containing 4 x 10(6) sperm ml-1 (80,000 motile sperm) and 200 microliters containing 0.8 x 10(6) sperm ml-1 (160,000 motile sperm), respectively, were prepared. Both volumes were incubated for 18 h at 37 degrees C. The mean (+/-SD) number of spermatozoa tightly bound to hemizona, incubated in 20 microliters and 200 microliters sperm droplets, was 2444 +/- 612 and 548 +/- 315, respectively (P = 0.0001). The results can be used as a guideline to calculate the optimum insemination concentration needed for a specific sperm population to ensure the maximum collision rates with the oocyte.

Female↗
PubMed1985

Male factor evaluation in in vitro fertilization: Norfolk experience.

Thirty-three patients from the in vitro fertilization (IVF) program at Norfolk are critically reviewed. A battery of tests was designed and an endocrine investigation was carried out on these patients. The fertilization rate for preovulatory oocytes was lower than in the normal male population (39.6% versus 88.6%). When total concentration of sperm with rapidly progressive motility was less than 6 X 10(5), to fertilize several eggs together the fertilization rate was zero. No fertilization was obtained when the number of sperm with rapidly progressive motility recovered after the separation was less than 1.5 X 10(6). The hamster zona-free oocyte penetration test correlated well with the human IVF system. The other parameters investigated did not show good correlation. When fertilization was achieved, the results of the IVF procedure in the series reviewed rendered a 30.8% pregnancy rate per transfer in 26 transfers. Fifty percent of the pregnancies were normal (either ongoing or delivered). Thirty-seven percent were preclinical miscarriages, and 12.5% were clinical abortions. In the abnormal male population, higher concentrations of sperm per egg should be used for insemination for achievement of optimum fertilization rates. Once fertilization is obtained, the results do not differ substantially from the IVF population at large.

Animals↗
PubMed1989

The divergence of a polygenic system subject to stabilizing selection, mutation and drift.

Polygenic variation can be maintained by a balance between mutation and stabilizing selection. When the alleles responsible for variation are rare, many classes of equilibria may be stable. The rate at which drift causes shifts between equilibria is investigated by integrating the gene frequency distribution W2N II (pq)4N mu-1. This integral can be found exactly, by numerical integration, or can be approximated by assuming that the full distribution of allele frequencies is approximately Gaussian. These methods are checked against simulations. Over a wide range of population sizes, drift will keep the population near an equilibrium which minimizes the genetic variance and the deviation from the selective optimum. Shifts between equilibria in this class occur at an appreciable rate if the product of population size and selection on each locus is small (Ns alpha 2 less than 10). The Gaussian approximation is accurate even when the underlying distribution is strongly skewed. Reproductive isolation evolves as populations shift to new combinations of alleles: however, this process is slow, approaching the neutral rate (approximately mu) in small populations.

Alleles↗