A Nomograph for Calculating the Optimal Frequency for Dielectrophoresis and the Characteristic Frequency of the β-Dispersion of Cell Membrane Vesicles

The first stage of the two-stage cell electrofusion technique involves the dielectrophoretic apposition, in an AC field, of protoplasts suspended in a medium of relatively low specific conductivity. A frequency at which the maximum dielectrophoretic force is exerted is given by the characteristic frequency for the dielectric relaxation by a Maxwell-Wagner type of mechanism. We provide a nomograph for the rapid calculation of this frequency.     

Frequency of bird hybrids: does detectability make all the difference?

The number of hybrids recorded in the field may be biased because these data may simply reflect the detectability of a hybrid pairing. A questionnaire was constructed for assessing the detectability of natural avian hybrids. Ratings from 17 independent experienced observers were subjected to factor analysis and all observers loaded onto the same single factor. The reliability was extremely high (Cronbachs alpha=0.96). Initially, I found a weak positive and significant correlation between the number of hybrids and their detectability index (r_s=0.268; P=0.015; n=81). However, the respective correlations within three orders and one family containing enough hybrids for analysis revealed non-significant results. Significant differences existed among orders with respect to both detectability and hybrid frequency. At the family level, differences existed in detectability, but not in the number of hybrids recorded. Furthermore, I found no publication bias. These results suggest a general influence of detectability and on higher taxonomic levels, and that either detectability or the number of hybrids vary between orders possibly due to phylogenetic effects. Data about hybrids should be used in a cautious manner in analyses across a wide range of species, but seem unbiased when restricted to analyses within orders and families. As a rule of thumb, distinctness of hybrids seems to be a function of the plumage difference between the hybridising species.Communicated by F. Bairlein     

Frequency of the cystic fibrosis ΔF508 mutation in a large sample of the French population

Summary We have determined the frequency of the cystic fibrosis (CF) ΔF508 mutation in a large sample of CF patients originating from different areas of France, including the greater Paris, Brittany, Alsace, Lorraine and Rh?ne-Alpes regions. A total of 422 CF chromosomes were studied, and the defect was found to account for 75% of the mutant alleles. In the course of the survey, a rare nucleotide sequence polymorphism leading to an isoleucine to valine substitution at position 506 of the CF transmembrane conductance regulator protein has been characterized in an unaffected individual. Our data enable the evaluation of the probabilities that a chromosome negative for the ΔF508 mutation carriers another CF defect.     

Frequency of the ΔF508 mutation on cystic fibrosis chromosomes in Denmark

Summary We have investigated the frequency of the ΔF508 mutation on cystic fibrosis (CF) chromosomes in Denmark. Of 304 chromosome tested, 86.8% have the ΔF508 mutation. The majority of the chromosomes with this mutation are found on chromosomes with the XV2c/KM19 haplotype B (97.3%), whereas 15/16 chromosomes with haplotype C have another mutation, confirming that only very few mutations will account for the majority of CF genes in the Danish population.     

Frequency Dependence of Electrical Coupling in Deiters″ Cells of the Guinea Pig Cochlea

Immunolabeling with antibodies against connexins 26 and 30 showed that, in the guinea pig cochlea, supporting Deiters″ cells are massively interconnected and form an orderly network within the organ of Corti. In paired patch-clamp recordings the coupling ratio (CR) of adjacent Deiters″ cells at the apex of the cochlea (～0.31) was 3-fold smaller than in isolated cell pairs due to shunting afforded by multicellular connectivity. With sinusoidal current stimuli the delay in signal propagation between adjacent cells increased with increasing frequency whereas the amplitude did not change significantly up to 200 Hz (corner frequency F_c ～220 Hz). Depolarizing voltage commands applied to an outer hair cell (OHC) elicited outward potassium currents in the OHC and inward currents in the abutting Deiters″ cells, supplying direct evidence for potassium buffering in the organ of Corti. Computational analysis indicates that electrical signals injected into a Deiters″ cell are transmitted across a network segment spanning 8 cell diameters. Thus electrical coupling in the organ of Corti is unlikely to influence the selectivity of frequency filtering performed mechanically by the mammalian cochlea.     

Frequency response of the electroreceptors (“small pit organs”) of the catfish,Ictalurus nebulosus LeS

Summary By electrophysiologically recording the spikes from the ramus lateralis ventralis nervi vagi of the catfishIctalurus nebulosus LeS., we determined the frequency response of the electroreceptors (small pit organs) in unanaesthetized, freely swimming specimens. The response frequency domain we were able to measure ranged from 0,03 to 25 Hz. We found a peak of greatest sensitivity at about 3 to 7 Hz (Fi. 5), using a stimulus with a current density of 5 × 10^–4A/mm² in water with a specific resistance of 20 Ohm. m. The threshold current density of the small pit organs in a homogeneous sinusoidally varying electric field (3 Hz) proved to be 3 × 10^–5 A/mm².

---

Zusammenfassung Durch Ableitung von Nervenimpulsen vom ramus lateralis ventralis nervi vagi beim Zwergwels,Ictalurus nebulosus LeS., versuchten wir den Frequenzbereich der Electroreceptoren (small pit organs) bei frei herumschwimmenden, nicht narkotisierten Tieren zu bestimmen. Der wirksame Frequenzbereich, in dem Bestimmungen vorgenommen werden konnten, erstreckte sich von 0,03 bis 25 Hz. Die Empfindlichkeitskurve der small pit organs erreichte einen Gipfel bei Frequenzen von 3–7 Hz (Fig. 5). Die Reizstromdichte betrug dabei 5 × 10^–4A/mm²; der spezifische Wasserwiderstand war 20 Ohm. m. Es stellte sich heraus, daß die Schwellenstromdichte der small pit organs im homogenen elektrischen Wechselstromfeld (3 Hz) 3 × 10^–5 A/mm² betrug.

---

---

We wish to thank Prof. S. Dijkgraaf for his stimulating interest, and Mr. W. J. G. Loos for making the drawings.     

Gene Frequency Distribution of the BoLA-DRB3 Locus in Saavedreño Creole Dairy Cattle

The objective of this study is to describe the gene frequency distribution of the bovine lymphocyte antigen (BoLA)-DRB3 locus in Saavedreño Creole dairy cattle and to compare it with previously reported patterns in other cattle breeds. One hundred and twenty-five Saavedreño Creole dairy cattle were genotyped for the BoLA-DRB3.2 allele by polymerase chain reaction and restriction fragment length polymorphism. Twenty-two out of 53 previously identified BoLA-DRB3.2 alleles were detected, with gene frequencies ranging from 0.4 to 16.8%. Seventy percent of the variation corresponded to the seven most frequent alleles (BoLA-DRB3.2*7, *8, *11, *16, *27, *36, and *37). The studied population exhibits a high degree of expected heterozygosity (h _e = 0.919). The F _IS index did not show significant deviation from Hardy-Weinberg equilibrium. However, the neutrality test showed an even gene frequency distribution. This result could be better explained assuming balancing selection instead of neutral or positive selection for one or a few alleles. In conclusion, the results of this study demonstrated that BoLA-DRB3.2 is a highly polymorphic locus in Saavedreño Creole dairy cattle, with significant variation in allele frequency among cattle breeds.     

Effect of Long-Term Exposure to a Randomly Varied 50 Hz Power Frequency Magnetic Field on the Fertility of the Mouse

A double blind study on BALB/c mice was conducted to examine the effects of extremely low-frequency electromagnetic fields on fertility. The mice were continuously exposed or sham-exposed from conception for two generations to magnetic fields varying between 0.5 and 77?μT. Biological parameters related to fertility were evaluated. Serum testosterone levels and mass of testes and adrenals were determined. No significant difference was found between the sham-exposed and exposed groups for all the biological endpoints, except for sperm motility. A significant difference between the two groups was found prior to the swim-up test with quantitative analysis of sperm motility as well as after the swim-up test for quantitative and qualitative analysis of sperm motility. ELF-EMFs significantly decreased the number of living sperm and the quality of movement of sperm, although these adversities did not impact on the outcome of the other parameters investigated.     

Does Climate or Habitat Affect the Frequency of Cooperative Brood Rearing in Canada Geese?

Canada geese ( Branta canadensis ) are unusual because individuals use either of two different brood-rearing behaviors: cooperative broods (two or more merged broods attended by more than three parents) or two-parent families. We tested whether cooperative broods form in response to habitat or climatic conditions by examining variation in cooperative brood frequencies among Canada geese nesting in Connecticut from 1982 to 1996. Percent of goslings raised in cooperative broods ranged from 0 to 100% at a given site in different years, but the pattern of annual variation was different at each site. The sites were in close proximity to each other and had similar climates; thus, the differences in annual variation among sites was not likely to be a response to climatic conditions. Cooperative brood frequencies also varied among sites in each individual year, but sites with the most gang brooding in one year often had the least the next. Such would not be expected if gang brooding occurred in response to non-ephemeral habitat characteristics. Sites where gang brooding occurred and where it did not have similar food resources and predation risks. These findings failed to support the hypotheses that gang broods form in response to food competition or predation. Sites where gang broods occurred had more parent geese and more goslings than sites where they did not occur. Furthermore, the proportion of goslings raised in gang broods was correlated with the number of goslings and parents at the site. Our results support the hypothesis that gang broods form from the inadvertent mixing of goslings. This single factor, however, was not sufficient to account for all of the observed variation in gang brooding frequencies.     

Heterozygosity for a Hypomorphic Polβ Mutation Reduces the Expansion Frequency in a Mouse Model of the Fragile X-Related Disorders

The Fragile X-related disorders (FXDs) are members of the Repeat Expansion Diseases, a group of human genetic conditions resulting from expansion of a specific tandem repeat. The FXDs result from expansion of a CGG/CCG repeat tract in the 5’ UTR of the FMR1 gene. While expansion in a FXD mouse model is known to require some mismatch repair (MMR) proteins, our previous work and work in mouse models of another Repeat Expansion Disease show that early events in the base excision repair (BER) pathway play a role in the expansion process. One model for repeat expansion proposes that a non-canonical MMR process makes use of the nicks generated early in BER to load the MMR machinery that then generates expansions. However, we show here that heterozygosity for a Y265C mutation in Polβ, a key polymerase in the BER pathway, is enough to significantly reduce both the number of expansions seen in paternal gametes and the extent of somatic expansion in some tissues of the FXD mouse. These data suggest that events in the BER pathway downstream of the generation of nicks are also important for repeat expansion. Somewhat surprisingly, while the number of expansions is smaller, the average size of the residual expansions is larger than that seen in WT animals. This may have interesting implications for the mechanism by which BER generates expansions.     

RF Energy Absorption in Human Bodies Due to Wearable Antennas in the 2.4 GHz Frequency Band

Human exposure to electromagnetic fields produced by two wearable antennas operating in the 2.4 GHz frequency band was assessed by computational tools. Both antennas were designed to be attached to the skin, but they were intended for different applications. The first antenna was designed for off-body applications, i.e. to communicate with a device placed outside the body, while the second antenna model was optimized to communicate with a device located inside the body. The power absorption in human tissues was determined at several locations of adult male and female body models. The maximum specific absorption rate (SAR) value obtained with the off-body antenna was found on the torso of the woman model and was equal to 0.037 W/kg at 2.45 GHz. SAR levels increased significantly for the antenna transmitting inside the body. In this case, SAR values ranged between 0.23 and 0.45 W/kg at the same body location. The power absorbed in different body tissues and total power absorbed in the body were also calculated; the maximum total power absorbed was equal to 5.2 mW for an antenna input power equal to 10 mW. Bioelectromagnetics. 2020;41:73–79 © 2019 Wiley Periodicals, Inc.     

Frequency sensitivity in Hodgkin–Huxley systems

 The frequency sensitivity of weak periodic signal detection has been studied via numerical simulations for both a single neuron and a neuronal network. The dependence of the critical amplitude of the signal upon its frequency and a resonance between the intrinsic oscillations of a neuron and the signal could account for the frequency sensitivity. In the presence of both a subthreshold periodic signal and noise, the signal-to-noise ratio (SNR) of the output of either a single neuron or a neuronal network present the typical characteristics of stochastic resonance. In particular, there exists a frequency-sensitive range of 30–100 Hz, and for signals with frequencies within this range the SNRs have large values. This implies that the system under consideration (a single neuron or a neuronal network) is more sensitive to the detection of periodic signals, and the frequency sensitivity may be of a functional significance to signal processing. Received: 26 October 1999 / Accepted in revised form: 25 July 2000     

Frequency of the C34T mutation of the AMPD1 gene in world-class endurance athletes: does this mutation impair performance?

The C34T mutation in the gene encoding for the skeletal muscle-specific isoform of AMP deaminase (AMPD1) is a common mutation among Caucasians (i.e., one of five individuals) that can impair exercise capacity. The purpose of this study was twofold. First, we determined the frequency distribution of the C34T mutation in a group of top-level Caucasian (Spanish) male endurance athletes (cyclists and runners, n = 104). This group was compared with randomly selected Caucasian (Spanish) healthy (asymptomatic) nonathletes (n = 100). The second aim of this study was to compare common laboratory indexes of endurance performance (maximal oxygen uptake or ventilatory thresholds) within the group of athletes depending on their C34T AMPD1 genotype. The frequency of the mutant T allele was lower (P < 0.05) in the group of athletes (4.3%) compared with controls (8.5%). On the other hand, indexes of endurance performance did not differ (P > 0.05) between athlete carriers or noncarriers of the C34T mutation (e.g., maximal oxygen uptake 72.3 +/- 4.6 vs. 73.5 +/- 5.9 ml.kg(-1).min(-1), respectively). In conclusion, although the frequency distribution of the mutant T allele of the AMPD1 genotype is lower in Caucasian elite endurance athletes than in controls, the C34T mutation does not significantly impair endurance performance once the elite-level status has been reached in sports.     

Gender-Dependent Frequency–Spatial Organization of the Brain Cortex Activity during Convergent and Divergent Thinking: I. Analysis of the EEG Power

The frequency–spatial organization of the brain cortex activity of men and women was studied during convergent (CTh) and divergent (DTh) thinking by means of EEG power mapping in a broad frequency band. Right-handed 17- to 23-year-old students (36 men and 30 women) participated in the study. Mental arithmetic was used as a model of CTh. Functional changes in the EEG patterns in the ₁ and ₁ frequency bands were distinct in CTh: the activation of the frontal cortical regions with a predominant involvement of right-hemispheric mechanisms of sustained attention was characteristic of the men, whereas, in the women, desynchronization of the ₁ rhythm was shifted to the caudal part of the cortex with a stronger left-hemispheric control over the calculating operations. This difference may be indicative of the involvement of different attention mechanisms and, consequently, the predominant use of the verbal or visuospatial strategies of CTh in men and women. Regardless of the gender, DTh was accompanied by an increase in the EEG power in the ₂ band. The successful performance of a divergent task was determined by different frequency components of the brain activation in men and women. In men, successful performance was associated with a substantial increase in the power of the ₂ rhythm and weak EEG desynchronization in the ₁ band; in women, successful performance was characterized by a lower increase in the amplitude of the ₂ oscillations as compared to noncreative persons and stronger EEG desynchronization in the ₁ band. The reciprocal changes in the power of the ₁ and ₂ rhythms in men and women during successful DTh may reflect the difference in interactions between cortical and subcortical structures in the regulation of voluntary, involuntary, and differential attention.     

The Effect of the X-Monosome Cell Clone Frequency on Anthropometric Variation in Patients with Shereshevsky–Turner Syndrome

Using methods of mathematical statistics the relationships were determined between 31 anthropometric traits (ATs) and the frequency of the X-monosome cell clone in 53 patients with either 45,X-monosomy or mosaic forms (45,X/46,XX) of the Shereshevsky–Turner syndrome (STS). AT variations were studied in patients untreated with growth hormone and in 25 control fertile healthy women. In 29 patients, the degree of mosaicism was assessed by interphase FISH analysis using X-centromer-specific DNA probe hybridized to the cell nuclei of two types of tissues differing in embryonic origin (lymphocytes and oral epithelium, originating from meso- and ectoderm, respectively). The level of X-monosome mosaicism had a substantial effect on some AT, which depended similarly on the proportion of X-monosome cells in tissues of different embryonic origin. Statistically significant negative correlations were revealed between the size of X-monosome clone and 13 height–weight, longitudinal, and circumference traits, whereas positive correlations were characteristic of seven mostly width traits. Eleven ATs showed no correlation with the X-monosome cell clone. Discriminant analysis of all ATs, whose variations depended on the frequency of X-monosome cell clone, was found to be an essential tool for precise classification of both STS patients with different degree of mosaicism and healthy women. Based on these results, the set of ATs characteristic of the STS phenotype was identified.     

Frequency of micronuclei in 4–8 cell mouse embryos generated after maternal gamma-irradiation in the presence and in the absence of vitamin C

The objective of this investigation was to evaluate the frequency of chromosomal aberrations expressed as micronuclei (MN) in 4–8 cell embryos generated by gamma-irradiation of female mice in the absence and in the presence of vitamin C. Female NMRI mice were whole body exposed to 4 Gy gamma-irradiation after intraperitoneal (i.p.) injection of pregnant mare’s serum gonadotrophin (PMSG) followed by injection of human chorionic gonadotrophin (HCG) and mating with non-irradiated NMRI male mice. Pregnant animals were sacrificed and embryos flushed from the oviducts and fixed on slides. Cells were treated for MN observation using standard method. To investigate the protective effect of vitamin C (ascorbic acid) on the frequency of MN, 100 mg/kg vitamin C was i.p. injected 1 h before irradiation. Results show that the frequency of MN generated in the embryos of irradiated mother compared to those of control in the non-irradiated group increased dramatically (P < 0.001). Frequency of MN in embryos generated in irradiated female mice treated with vitamin C dramatically and statistically decreased relative to the frequency observed in the irradiation only group (P < 0.001). This decrease returned the combined treatment group to a level that was not statistically different from the controls (P > 0.05). Thus, irradiation of preovulatory stage oocytes leads to stable chromosome abnormalities expressed as micronuclei in successive preimplantation embryos. Vitamin C reduces these clastogenic effects of radiation in preovulatory oocytes and thus the reduced frequency of MN in embryos is probably due to its antioxidation and radical scavenging properties.     

Frequency distribution of the <Emphasis Type="Italic">G/A</Emphasis> alleles of the β-fibrinogen gene in the Lebanese population

Fibrinogen is a plasma protein that has been reported to be associated with an increased risk of atherothrombotic diseases and venous thrombosis. The most common polymorphism that has been studied so far in different populations is the G-455-->A polymorphism in the promoter region of the beta-fibrinogen gene. We studied 160 healthy unrelated Lebanese individuals for the prevalence of -455G/G, -455G/A and -455A/A genotypes of the beta-fibrinogen gene and the frequency of G and A alleles using a reverse hybridization PCR assay. The prevalence of the G/G, G/A, and A/A genotypes were found to be 60.6, 31.9 and 7.5%, respectively. The frequency of the G and A alleles were found to be 0.77 and 0.23, respectively. As compared to other ethnic groups, the Lebanese individuals were found to have a relatively high prevalence of the A allele which may predispose them to develop cardiovascular diseases as well as thrombotic events. This study provides additional unique genetic information pertaining to the Lebanese population.     

Mutations in Elongation Factor Ef-1α Affect the Frequency of Frameshifting and Amino Acid Misincorporation in Saccharomyces Cerevisiae

A mutational analysis of the eukaryotic elongation factor EF-1 alpha indicates that this protein functions to limit the frequency of errors during genetic code translation. We found that both amino acid misincorporation and reading frame errors are controlled by EF-1 alpha. In order to examine the function of this protein, the TEF2 gene, which encodes EF-1 alpha in Saccharomyces cerevisiae, was mutagenized in vitro with hydroxylamine. Sixteen independent TEF2 alleles were isolated by their ability to suppress frameshift mutations. DNA sequence analysis identified eight different sites in the EF-1 alpha protein that elevate the frequency of mistranslation when mutated. These sites are located in two different regions of the protein. Amino acid substitutions located in or near the GTP-binding and hydrolysis domain of the protein cause suppression of frameshift and nonsense mutations. These mutations may effect mistranslation by altering the binding or hydrolysis of GTP. Amino acid substitutions located adjacent to a putative aminoacyl-tRNA binding region also suppress frameshift and nonsense mutations. These mutations may alter the binding of aminoacyl-tRNA by EF-1 alpha. The identification of frameshift and nonsense suppressor mutations in EF-1 alpha indicates a role for this protein in limiting amino acid misincorporation and reading frame errors. We suggest that these types of errors are controlled by a common mechanism or closely related mechanisms.