The Wilson–Cowan model, 36 years later

The Wilson–Cowan model of interacting neurons (1973) is one of the most influential papers published in Biological Cybernetics (Kybernetik). This paper and a companion paper published in 1972 have been cited over 1000 times. Rather than focus on the microscopic properties of neurons, Wilson and Cowan analyzed the collective properties of large numbers of neurons using methods from statistical mechanics, based on the mean-field approach. New experimental techniques to measure neuronal activity at the level of large populations are now available to test these models, including optical recording of brain activity with intrinsic signals and voltage sensitive dyes, and new methods for analyzing EEG and MEG. These measurement techniques have revealed patterns of coherent activity that span centimetres of tissue in the cerebral cortex. Here the underlying ideas are reviewed in a historic context. This note was written by Alain Destexhe and Terry Sejnowski, the Editors-in-Chief of the Journal of Computational Neuroscience and Neural Computation, on the occasion of the appearance of Volume 100 of Biological Cybernetics.     

The Evolution of Virulence in RNA Viruses under a Competition–Colonization Trade-Off

RNA viruses exist in large intra-host populations which display great genotypic and phenotypic diversity. We analyze a model of viral competition between two viruses infecting a constantly replenished cell pool. We assume a trade-off between the ability of the virus to colonize new cells (cell killing rate or virulence) and its local competitiveness (replicative success within coinfected cells). We characterize the conditions that allow for viral spread by means of the basic reproductive number and show that a local coexistence equilibrium exists, which is asymptotically stable. At this equilibrium, the less virulent competitor has a reproductive advantage over the more virulent colonizer reflected by a larger equilibrium population size of the competitor. The equilibria at which one virus outcompetes the other one are unstable, i.e., a second virus is always able to permanently invade. We generalize the two-virus model to multiple viral strains, each displaying a different virulence. To account for the large phenotypic diversity in viral populations, we consider a continuous spectrum of virulences and present a continuum limit of this multiple viral strains model that describes the time evolution of an initial continuous distribution of virulence without mutations. We provide a proof of the existence of solutions of the model equations, analytically assess the properties of stationary solutions, and present numerical approximations of solutions for different initial distributions. Our simulations suggest that initial continuous distributions of virulence evolve toward a distribution that is extremely skewed in favor of competitors. At equilibrium, only the least virulent part of the population survives. The discrepancy of this finding in the continuum limit with the two-virus model is attributed to the skewed equilibrium subpopulation sizes and to the transition to a continuum. Consequently, in viral quasispecies with high virulence diversity, the model predicts collective virulence attenuation. This result may contribute to understanding virulence attenuation, which has been reported in several experimental studies.     

The Madagascan Maastrichtian bryozoans of Ferdinand Canu – Systematic revision and scanning electron microscopic study

In 1922, the first taxonomic work on Maastrichtian bryozoans from Madagascar was published in the Annales de Paléontologie by Ferdinand Canu. Canu described 25 species, 17 of which were regarded as new but the material has never been revised until now. Here we employ scanning electron microscopy (SEM) to illustrate Canu's material and revise the taxonomy. Based on this revision, 23 species, comprising eight cyclostomes and 15 cheilostomes, are recognized. A new genus, Fehiborypora, is introduced for the cribrimorph Cribilina (?) labiatula, and two new species are described: ‘Plagioecia’ antanihodiensis sp. nov. and ‘Escharoides’ charbonnieri sp. nov. Galeopsis parvipora is synonymized with Crustoporina prona Stoliczka. All bryozoan species found are encrusters on echinoids or oysters.     

The Antarctic psychrophile, Chlamydomonas subcaudata, is deficient in state I–state II transitions

State I-State II transitions were monitored in vivo and in vitro in the Antarctic, psychrophillic, green alga, Chlamydomonas subcaudata, as changes in the low-temperature (77 K) chlorophyll fluorescence emission maxima at 722 nm (F722) relative to 699 nm (F699). As expected, the control mesophillic species, Chlamydomonas reinhardtii, was able to modulate the light energy distribution between photosystem II and photosystem I in response to exposure to four different conditions: (i) dark/anaerobic conditions, (ii) a change in Mg2+ concentration, (iii) red light, and (iv) increased incubation temperature. This was correlated with the ability to phosphorylate both of its major light-harvesting polypeptides. In contrast, exposure of C. subcaudata to the same four conditions induced minimum alterations in the 77 K fluorescence emission spectra, which was correlated with the ability to phosphorylate only one of its major light-harvesting polypeptides. Thus, C. subcaudata appears to be deficient in the ability to undergo a State I-State II transition. Functionally, this is associated with alterations in the apparent redox status of the intersystem electron transport chain and with higher rates of photosystem I cyclic electron transport in the psychrophile than in the mesophile, based on in vivo P700 measurements. Structurally, this deficiency is associated with reduced levels of Psa A/B relative to D1, the absence of specific photosystem I light-harvesting polypeptides [R.M. Morgan et al. (1998) Photosynth Res 56:303-314] and a cytochrome b6/f complex that exhibits a form of cytochrome f that is approximately 7 kDa smaller than that observed in C. reinhardtii. We conclude that the Antarctic psychrophile, C. subcaudata, is an example of a natural variant deficient in State I-State II transitions.     

Secular Trends in Measures of Cephalo-Facial Traits among Bengalee Boys Aged 7.0–16.0 Years from Kolkata between 1982–1983 and 1999–2001

While a large number of studies on secular trends have been performed on measures of stature, weight, trunk and limb dimensions, subcutaneous fatness and body composition, etc., less attention has been paid to cephalo-facial traits. This study reports on secular trends in five cephalo-facial traits (head length, head breadth, head circumference, bizygomatic breadth and morphological facial height) and two indices (cephalic index and facial index) in Bengalee Hindu boys between ages 7.0 and 16.0 years. The data set comes from two cross-sectional growth surveys carried out among the students of one particular Kolkata (formerly Calcutta) boys school with an interval of about 20 years (1982–1983 and 1999–2001). Identical protocol with respect to sampling, data collection, measuring technique and data analysis has been followed in both surveys. Except for morphological facial height (which showed negative secular trends), the other four cephalo-facial traits showed positive secular trends with varying magnitudes over the two decades. Cephalic index did not reveal any consistent pattern of change, while facial index showed a declining trend in the later survey.     

An Epidemiological Survey of Blood Lead Level in Tibetan Youth 10–18 Years Old in Songpan,China

There are few studies on Tibetan youth’s blood lead level (BLL) and environmental pollution in China. The objective of this project was to conduct a preliminary investigation on the blood lead level of Tibetan youth. Chinese Han youth’s BLL was also investigated as a control group. A total of 846 Tibetan youth and 785 Han youth were tested for BLL from September to October in 2007. Both of the mean BLL (6.4 μg/dL) and the frequency of high BLL (≥10 μg/dL) of Tibetan youth (7.7%, 65 of 846) were lower than those of Han youth (6.7 μg/dL; 13.2%, 104 of 785). But they are still higher compared with the BLL of youth in developed countries (1.1 μg/dL; USA 2005 census). The BLL of boys was significantly higher than that of girls, both in Tibetan and Han youth (p = 0.033 and p = 0.000, respectively). The study shows that Chinese Han and Tibetan youth's lead poisoning prevention and treatment lags far behind developed countries. These findings have implications for environmental health policy.     

The life – history of the peach silver mite,Aculus fockeui (Acari: Eriophyidae) in Egypt

The peach silver mite Aculus fockeui (Nalepa and Trouessart) successfully developed from egg to adult stage when reared on a nectarine or peach leaflet attached with soft lateral divided branch dipped in test tube at different constant temperatures and 70% r.h. The effect of temperature on the development, reproduction and population growth was investigated. Below 20°C all activity ceased and by 33°C the adult began to slow down and cease all activity. At least of 34% of the generation time was spent in the egg stage at 29°C. Adult longevity decreased with increasing temperature. Fecundity was highest at 29°C with 43.16 eggs per female. Life table parameters showed that the population of A. fockeui on nectarine leaves multiplied 30.04 times in a generation time of 18.49 days at 29°C, while the population on peach leaves increased 13.87 times in a generation time of 19.18 days under the same conditions.     

Association of Serum Calcium and Hypertension Among Adolescents Aged 12–17 Years in the Rural Area of Northeast China

Calcium plays an important role in regulating body homeostasis. Several studies have reported the association between serum calcium and cardiovascular disease in adults. However, studies assessing the relationship between serum calcium and hypertension were limited, especially in subject populations of adolescents. The aim of the present study was to examine the association of serum calcium levels and blood pressure levels among adolescents in the rural area of Northeast China. A total of 2,023 students participated in this study, including 894 boys and 1,129 girls, aged from 12 to 17 years old. We measured the body weight, height, systolic blood pressure (SBP), diastolic blood pressure (DBP), and serum calcium concentrations of all eligible subjects, and the body mass index (BMI) was calculated from body weight and height. Childhood hypertension was defined as SBP and/or DBP ≥95th percentile for age and gender. According to the results of multivariable linear and logistic regression analysis, we found that higher serum calcium levels were positively associated with childhood hypertension. In comparison with serum calcium levels ≤2.37 mmol/L, the multivariable odds ratio (95 % confidence interval) of hypertension among adolescents with serum calcium levels ≥2.53 mmol/L was 1.89 (1.41–2.53; P trend?<?0.001). In addition, higher serum calcium levels were also positively associated with average difference in SBP and DBP; the average differences (95 % confidence interval) were 4.22 (2.74–5.83; P trend?<?0.001) and 2.23(1.00–3.46; P trend?<?0.001), respectively. In conclusion, higher serum calcium concentrations were found to have an association with higher blood pressure levels and higher prevalence of hypertension in the young population.     

Acquisition of Visuomotor Abilities and Intellectual Quotient in Children Aged 4–10 Years: Relationship with Micronutrient Nutritional Status

Lethargy, poor attention, and the high rate and severity of infections in malnourished children affect their educational achievement. We therefore studied the association between visuomotor abilities and intelligence quotient (IQ) and their relationship with iron, zinc, and copper. A cross-sectional study was carried out on a sample of 89 healthy children (age range, 4-10 years). Evaluations of visuomotor ability and IQ were performed with the Developmental Test of Visual Motor Integration (VMI) and the Scale for Measurement of Intelligence for children aged 3-18 years, respectively. Nutritional status was assessed using anthropometry and biochemical assessments, which included serum ferritin, zinc and copper levels, and Hb. The sample was classified as having low or normal VMI scores: 47 children (52.8%, mean age 7 +/- 1.5 years) had low VMI, and 42 (47.2%, mean age 7 +/- 2.06 years) had normal VMI. There were no statistically significant differences in socioeconomic and cultural condition between both groups. We found significantly higher serum copper and ferritin levels in normal as compared to low VMI, but we did not find any differences with zinc. IQ was significantly higher in normal vs low VMI children. The fact that children with abnormal VMI presented low mean serum copper and ferritin concentrations could indicate that copper and iron deficiencies in this sample could be related with visuomotor abilities.     

The Vulture in the Sky and the Hominin on the Land: Three Million Years of Human–Vulture Interaction

ABSTRACT

Vultures and humans have been sympatric for millions of years and evidence from the archaeological and historical records suggests interdependence over long periods. Like other species, early hominins probably used these birds to locate carcasses in the landscape. With the evolution of large-bodied and more encephalized hominins, the quest for high-quality food would have intensified. Vultures used as beacons for meat may have been particularly important to hominins dispersing out of Africa, facilitating the occupation of new landscapes. Neanderthals and prehistoric modern humans incorporated vulture parts into their culture, and while the symbolic and ritualistic significance of the birds may have varied through time and across cultures, their link with positive life forces is apparent. More recently, the intensification of farming and modern sanitary restrictions, as well as the spread of human populations, has led to the radical decline in vulture populations throughout the world. Without commitments by governments to fund vulture conservation programs, the ability to preserve many species may be limited over the long term. In this review paper we discuss the ability of vultures to act as beacons signaling meat in the landscape and our changing relationships with these enigmatic birds through a shared history. Within this narrative, we outline why vultures are fundamental to maintaining our ecosystem and should therefore be protected.     

Evaluation of Essential Trace and Toxic Elements in Biological Samples of Normal and Night Blindness Children of Age Groups 3–7 and 8–12 Years

The most common cause of blindness in developing countries is vitamin A deficiency. The World Health Organization estimates 13.8 million children to have some degree of visual loss related to vitamin A deficiency. The causes of night blindness in children are multifactorial, and particular consideration has been given to childhood nutritional deficiency, which is the most common problem found in underdeveloped countries. Such deficiency can result in physiological and pathological processes that in turn influence biological samples composition. Vitamin and mineral deficiency prevents more than two billion people from achieving their full intellectual and physical potential. This study was designed to compare the levels of Zn, Mg, Ca, K, Na, As, Cd, and Pb in scalp hair, blood, and urine of night blindness children age ranged 3–7 and 8–12 years of both genders, comparing them to sex- and age-matched controls. A microwave-assisted wet acid digestion procedure was developed as a sample pretreatment, for the determination of As, Ca, Cd, K, Pb, Mg, Na, and Zn in biological samples of night blindness children. The proposed method was validated by using conventional wet digestion and certified reference samples of hair, blood, and urine. The concentrations of trace and toxic elements were measured by atomic absorption spectrophotometer prior to microwave-assisted acid digestion. The results of this study showed that the mean values of As, Cd, Na, and Pb were significantly higher in scalp hair, blood, and urine samples of male and female night blindness children than in referents (p?<?0.001), whereas the concentrations of Zn, Ca, K, and Mg were lower in the scalp hair and blood but higher in the urine samples of night blindness children. These data present guidance to clinicians and other professional investigating deficiency of essential mineral elements in biological samples (scalp hair and blood) of night blindness children.     

The role of spin in biological processes: O2, NO,nucleobases, nucleosides,nucleotides and Watson–Crick base pairs

The experimental electron affinities of adenine, guanine, cytosine, thymine and uracil have been determined from reduction potentials and negative ion photoelectron spectra. Updated values for purine, pyrimidine and other nitrogen heterocyclics, which have not been measured in the gas phase, are presented. The electron affinity of Watson–Crick guanine–cytosine is estimated empirically. The experimental values are consistent with quantum mechanical semi-empirical multiconfiguration configuration interaction calculations. The bulk hydration energies of the nucleobase anions, 2.34 eV, determined from the experimental data and sequential anion hydration energy difference of about 0.20(5) eV suggest that 10–15 water molecules complete the hydration shell. The electron affinities for the formation of doublet and quartet anions of the nucleobases, nucleosides, nucleotides and Watson–Crick base pairs are calculated. We postulate that low-lying quartet anion states and their spin distribution can and will participate in electron conduction, radiation damage, oxidation damage and repair, strand breakage and protein synthesis.     

The Effect of Synbiotic Supplementation on Growth Parameters in Mild to Moderate FTT Children Aged 2–5 Years

Synbiotic (probiotic bacteria and prebiotic) has beneficial effects on the gastrointestinal tract. This study was designed to investigate the effect of synbiotic supplementation on the growth of mild to moderate failure to thrive (FTT) children. A randomized, triple-blind, placebo-controlled trial was conducted involving 80 children aged 2–5 years with mild to moderate FTT, who were assigned at random to receive synbiotic supplementation (10⁹ colony-forming units) or placebo for 30 days. The weights, height, and BMI were recorded in a structured diary, and the questionnaires were completed to monitor the numbers of infection episodes, gastrointestinal problems, admission to hospital, and appetite improvement during the study. Sixty-nine children completed the study. There were no differences in the demographic characteristic between the two groups. The mean weight was similar at baseline. After 30 days of intervention, the mean weight of the participants in the synbiotic group increased significantly than those in the placebo group (600?±?37 vs. 74?±?32 g/month P 0.000). BMI changes in synbiotic and placebo group were 0.44 and 0.07 kg/m², and that the differences among the two groups were significant.(P 0.045) Furthermore, the height increment in synbiotic and placebo group was 0.41 and 0.37 cm respectively with no significant difference (P 0.761). Administration of 30-day synbiotic supplementation may significantly improve weight and BMI in Iranian children with mild to moderate FTT, but there is no effect on the height in this study. Further studies should be designed to found out the effect of synbiotic on growth parameters in undernourished and well-nourished children.

     

The Level of Passive Voice Comprehension in the 4–5 Years Old Russian Children Reflects in the ERP’s

Journal of Evolutionary Biochemistry and Physiology - The passive voice acquisition and thematic-role assignment is the key point in the process of complex grammar comprehension. The same semantic...