Modelling phytoplankton-virus interactions: phytoplankton blooms and lytic virus transmission.

A dynamic reaction-diffusion model of four variables is proposed to describe the spread of lytic viruses among phytoplankton in a poorly mixed aquatic environment. The basic ecological reproductive index for phytoplankton invasion and the basic reproduction number for virus transmission are derived to characterize the phytoplankton growth and virus transmission dynamics. The theoretical and numerical results from the model show that the spread of lytic viruses effectively controls phytoplankton blooms. This validates the observations and experimental results of Emiliana huxleyi-lytic virus interactions. The studies also indicate that the lytic virus transmission cannot occur in a low-light or oligotrophic aquatic environment.

The impact of water storage capacity on plant dynamics in arid environments: A stoichiometric modeling approach.

Plants in arid environments have evolved many strategies to resist drought. Among them, the developed water storage tissue is an essential characteristic of xerophytes. To clarify the role of water storage capacity in plant performance, we originally formulate a stoichiometric model to describe the interaction between plants and water with explicit water storage. Via an ecological reproductive index, we explore the effects of precipitation and water storage capacity on plant dynamics. The model possesses saddle-node bifurcation and forward or backward bifurcation, and the latter may lead to the emergence of alternative stable states between a stable survival state and a stable extinction state. Numerical simulations illustrate the persistence and resilience of plants regulated by soil conditions, precipitation and water storage capacity. Our findings contribute to the botanical theory in the perspectives of environmental change and plant water storage traits.

Effect of Soil Temperature on Reproduction of Root-knot Nematodes in Flue-cured Tobacco with Homozygous Rk1 and/or Rk2 Resistance Genes.

Most commercial flue-cured tobacco cultivars contain the Rk1 resistance gene, which provides resistance to races 1 and 3 of Meloidogyne incognita and race 1 of M. arenaria. A number of cultivars now possess a second root-knot resistance gene, Rk2. High soil temperatures have been associated with a breakdown of root-knot resistance genes in a number of crops. Three greenhouse trials were performed from 2014 to 2015 investigate the effect of high soil temperature on the efficacy of Rk1 and/or Rk2 genes in reducing parasitism by a population of M. incognita race 3. Trials were arranged in randomized complete block design in open-top growth chambers set at 25°, 30°, and 35°C. Plants were inoculated with 3,000 eggs and data were collected 35 days post-inoculation. Galling, numbers of egg masses and eggs, and reproductive index were compared across cultivar entries. Nematode reproduction was reduced at 25°C and 30°C on entries possessing Rk1 and Rk1Rk2 compared to the susceptible entry and the entry possessing only Rk2. However, there were often no significant differences in reproduction at 35°C between entries with Rk1 and/or Rk2 compared to the susceptible control, indicating an increase of root-knot nematode parasitism on resistant entries at higher temperatures. Although seasonal differences in nematode reproduction were observed among experiments, relative differences among tobacco genotypes remained generally consistent.

Effect of nutrient supply on cell size evolution of marine phytoplankton.

The variation of nutrient supply not only leads to the differences in the phytoplankton biomass and primary productivity but also induces the long-term phenotypic evolution of phytoplankton. It is widely accepted that marine phytoplankton follows Bergmann's Rule and becomes smaller with climate warming. Compared with the direct effect of increasing temperature, the indirect effect via nutrient supply is considered to be an important and dominant factor in the reduction of phytoplankton cell size. In this paper, a size-dependent nutrient-phytoplankton model is developed to explore the effects of nutrient supply on the evolutionary dynamics of functional traits associated with phytoplankton size. The ecological reproductive index is introduced to investigate the impacts of input nitrogen concentration and vertical mixing rate on the persistence of phytoplankton and the distribution of cell size. In addition, by applying the adaptive dynamics theory, we study the relationship between nutrient input and the evolutionary dynamics of phytoplankton. The results show that input nitrogen concentration and vertical mixing rate have significant effects on the cell size evolution of phytoplankton. Specifically, cell size tends to increase with the input nutrient concentration, as does the diversity of cell sizes. In addition, a single-peaked relationship between vertical mixing rate and cell size is observed. When the vertical mixing rate is too low or too high, only small individuals are dominant in the water column. When the vertical mixing rate is moderate, large individuals can coexist with small individuals, so the diversity of phytoplankton is elevated. We predict that reduced intensity of nutrient input due to climate warming will lead to a trend towards smaller cell size and will reduce the diversity of phytoplankton.

Towards objective measurement of reproductive performance of traditionally managed goat flocks in the drylands of Ethiopia.

Reproductive performance is a key determinant for the efficiency of goat production. Regular monitoring of reproductive efficiency is essential to assess management and to avoid financial losses due to poor performance. To allow more objective measurement and comparisons over time, we propose a novel quantitative approach for defining annual reproductive performance by combining common performance indicators into a goat flock index. Commonly used reproductive performance measures were collected from 242 goat flocks in four districts in dryland of Ethiopia between July 2018 and February 2019. Principal component analysis (PCA) was performed to identify biologically meaningful latent components that explain annual reproductive output (ARO) and annual reproductive wastage (ARW). Together with the remaining annual reproductive performance measures, the ARO and ARW components were included in a PCA to derive an algorithm for a goat annual reproductive performance index (G-ARPI). One component representing variation in kidding interval, PCARO1 and PCARW1 was extracted and normalized to a 10-scale value. The flocks were classified into good performing (15.63%) with index > 8.5, moderately performing (48.21%) with index values ranging from 6.5 to 8.5 and poor performing (36.16%) with index < 6.5. Good performing flocks have higher scores for reproductive output measures, lower scores for reproductive wastage and lower kidding interval. The proposed G-ARPI can be used as an objective tool to compare reproductive performance between management systems, evaluate the costs of poor reproductive management and will be useful for economic models that aim to identify the most cost-efficient intervention option and monitor the impact of interventions. We present here the index for goat production in dryland systems in Ethiopia; the approach can easily be adapted to other production systems elsewhere.

Postnatal germ cell development in cryptorchid boys.

Cryptorchidism is associated with infertility in adulthood. Early orchiopexy is suggested to reduce the risk. Information is lacking on the potential link between infant germ cell maturation and the risk of future infertility. The objective of the study was to evaluate age-related germ cell development in cryptorchidism. Immunostaining for markers of germ cell development (octamer-binding transcription factor 3/4 [OCT3/4], placental alkaline phosphatase [PLAP], KIT proto-oncogene [C-KIT], podoplanin [D2-40], Lin-28 homolog A [LIN28], and G antigen 7 [GAGE-7]) was performed in testicular biopsies from 40 cryptorchid boys aged 4-35 months. Germ cell numbers and distributions were evaluated in cross sections of seminiferous tubules, with and without immunostaining. OCT3/4, D2-40, and LIN28 were generally expressed in the early stages of germ cell development, as shown by positive expression in germ cells in the central region of seminiferous tubules. In contrast, PLAP and GAGE-7 were expressed in both central and peripheral parts of the tubules in the early stages of development and expressed mainly in a peripheral position with advancing age. Germ cell maturation was delayed in this study population as compared with that observed in our previous study on germ cell markers in a healthy population. The number of GAGE-7-positive germ cells per tubular cross section obtained by immunostaining was significantly higher than that obtained by standard hematoxylin and eosin staining. Double immunostaining revealed heterogeneity in germ cell development in cryptorchid testes. These results shed light on the pathophysiology of germ cell development in boys with cryptorchidism.

Dynamics of a nutrient-phytoplankton model with random phytoplankton mortality.

This study formulates a stochastic nutrient-phytoplankton model which incorporates the effect of white noise on phytoplankton growth. The global existence and uniqueness of a positive solution, stochastic boundedness, and stochastically asymptotic stability are well explored. A stochastic ecological reproductive index R0s is formulated to characterize the global dynamics. The theoretical analysis demonstrates that, if R0s<1, then phytoplankton dies out with probability one; if R0s>1 and some other conditions hold, then there exists an invariant and asymptotically stable density of the system and the approach involves integral Markov semigroups theory. Numerical simulations are presented to illustrate the analytical findings and to investigate the long-time effect of water temperature, light, nutrients, and environmental noise on the dynamic evolution of phytoplankton.

Postnatal germ cell development in cryptorchid boys / 亚洲男科学杂志(英文版)

Cryptorchidism is associated with infertility in adulthood. Early orchiopexy is suggested to reduce the risk. Information is lacking on the potential link between infant germ cell maturation and the risk of future infertility. The objective of the study was to evaluate age-related germ cell development in cryptorchidism. Immunostaining for markers of germ cell development (octamer-binding transcription factor 3/4 [OCT3/4], placental alkaline phosphatase [PLAP], KIT proto-oncogene [C-KIT], podoplanin [D2-40], Lin-28 homolog A [LIN28], and G antigen 7 [GAGE-7]) was performed in testicular biopsies from 40 cryptorchid boys aged 4-35 months. Germ cell numbers and distributions were evaluated in cross sections of seminiferous tubules, with and without immunostaining. OCT3/4, D2-40, and LIN28 were generally expressed in the early stages of germ cell development, as shown by positive expression in germ cells in the central region of seminiferous tubules. In contrast, PLAP and GAGE-7 were expressed in both central and peripheral parts of the tubules in the early stages of development and expressed mainly in a peripheral position with advancing age. Germ cell maturation was delayed in this study population as compared with that observed in our previous study on germ cell markers in a healthy population. The number of GAGE-7-positive germ cells per tubular cross section obtained by immunostaining was significantly higher than that obtained by standard hematoxylin and eosin staining. Double immunostaining revealed heterogeneity in germ cell development in cryptorchid testes. These results shed light on the pathophysiology of germ cell development in boys with cryptorchidism.

Two-generation reproductive toxicity of lufenuron in SD rats / 中国职业医学

OBJECTIVE: To obtain information on the toxicity of lufenuron on the reproduction ability and the growth and development of offspring in female and male rats through two-generation reproduction toxicity study. METHODS: The specific pathogen free healthy SD rats were randomly divided into control group and low-, medium-and high-dose lufenuron groups, with 60 rats in each group, half females and half males. Rats in the low-, medium-and high-dose lufenuron groups were respectively fed with lufenuron at the dose of 5.0, 20.0 and 80.0 mg/(kg body weight·day) for 8 weeks before mating. The control group was fed with standard foot. The reproductive index, brain and reproductive organ coefficients and pathological changes were observed in P and F1 parents. The birth and growth indexes of the offspring were measured. RESULTS: i) P generation: from the 14 th day, the female rats in the medium-dose group had lower body weight than that of the female control group(P<0.05); from the 35 th day, the body weight was lower than that of the female low-dose group(P<0.05). From the 14 th day, the female rats in the high-dose group had lower body weight than that of the other three female groups(P<0.05). From the 14 th day, the male rats in the medium-and high-dose groups had lower body weight than that of the male control group and low-dose group(P<0.05). The body weight of pregnant rats in the parental high-dose group was lower than that of the control group, low-dose group, and medium-dose group at day 0, 7, 14, 19 of the pregnancy duration(P<0.05). The body weight of pregnant rats in the parental medium-dose group was lower than that of the low-dose group on day 0 of the pregnancy duration, and lower than that of the control and low-dose groups on day 7 and 14(P<0.05). The conception rate, the new-borne survival rates and the feeding survival rate of female rats in the high-dose group was lower than that of the other three female groups(P<0.008). The new-borne feeding survival rate of female rats in the medium-dose group was lower than that of the control group and low-dose group(P<0.008). The organ coefficients of brain in female rats in the medium-and high-dose groups were higher than that of the female control group and low-dose group(P<0.05). The organ coefficients of brain and testis in male rats in the medium-and high-dose groups were higher than that of the control group and low-dose group(P<0.05). The organ coefficient of epididymis in male rats in the high dose group was lower than that of the other three male groups(P<0.05). ii) F1 generation: the body weight of female rats in the low-and medium-dose group was higher than that of the female control group on the 42 th day(P<0.05). The body weight of male rats in the low-dose group was higher than that of the male control group on the 42 th, 49 th, and 56 th days(P<0.05). The body weight of male rats in the medium-dose group was higher than that of the male control group on the 14 th, 21 th, 42 th, 49 th, and 56 th days(P<0.05). The new-borne survival rate in the low-dose group was lower than that of the control group(P<0.017). The body weight of new-borne rats in the high-dose group on day 4 of birth was lower than that in the other three female groups(P<0.05). iii) F2 generation: the body weight of male rats in the male medium-dose group was lower than that in the control group on day 21 of birth(P<0.05). CONCLUSION: The reproductive and developmental toxicity of lufenuron is found in rats in the medium-and high-dose groups. Toxicities including low body weight, conception rate, new-borne survival rate and feeding survival rate are found in P generation; low body weight and feeding survival rate are found in F1 generation; low body weight is found in male F2 generation. The no-observed-adverse-effects levels of lufenuron in two-generation reproductive study are 5.87 mg/(kg·d) for females and 5.09 mg/(kg·d) for males in SD rats.

EVALUATION OF THE ANTIGENICITY AND IMMUNOGENICITY OF Eimeria tenella BY REPRODUCTIVE INDEX AND HISTOPATHOLOGICAL CHANGES OF CECAL COCCIDIOSIS VIRULENT LIVE VACCINE IN BROILER CHICKENS.

BACKGROUND: The development of vaccine to control coccidiosis caused by Eimeria tenella (E. tenella) in chickens is intensifying because of the increasing threat of drug resistance to anticoccidial agents. It is important, therefore, to develop a reliable standard method for the assessment of vaccine afficacy particularly antigenicity and immunogenicity become crucial. Evaluation of E. tenella antigenicity and immunogenicity to some low doses can be reflected by reproductive index and histopathological changes. MATERIALS AND METHODS: The complete random design of research was used in this study. Sixty of two weeks old broilers were divided into four groups and each group composed 15 replications. The group 1 was chicken group without virulent E. tenella oocyst inoculation. The group 2, 3 and group 4 were chicken group inoculated with virulent E. tenella oocyst at doses of 1.0 x 102, 2.0 x 102, 3.0 x 102, respectively. Then all chicken groups were challenged with E. tenella oocyst at doses of 1.0 x 103. Observation of research that represented antigenicity and immunogenicity was clinical sign, reproductive index, histopathological changes. RESULTS: On virulent E. tenella inoculation step, some clinical signs such as appetite, weakness, and diarrhea were very slight on all chicken groups. While on challenge test step, there were no clinical signs of all chicken groups except the group 1. For the reproductive index of virulent E. tenella inoculation step, there were no significantly differences in all chicken groups except the group 1. As reproductive index, the same result pattern was seen for histopathological changes. CONCLUSION: The low number virulent E. tenella had low reproductive index and few histopathological changes effect that represents a promising strategy to prevent cecal coccidiosis in chickens.

Ecología y reproducción de Opsanus beta (Actinopterygii: Batrachoididae) en la Laguna de Alvarado, Veracruz, México / Ecology and reproduction of Opsanus beta (Actinopterygii: Batrachoididae) in the Alvarado Lagoon, Veracruz, Mexico

Resumen Opsanus beta es un habitante permanente del Sistema Lagunar de Alvarado, a pesar de participar en la transferencia energética entre los distintos componentes, no hay información sobre los aspectos ecológicos y reproductivos de esta especie. El presente trabajo se desarrolló, con la finalidad de evaluar aspectos de la biología como estacionalidad, alimentación, proporción de sexos, índice gonadosomático, hepatosomático y factor de condición para ambos sexos, así como la fecundidad y la relación peso-longitud, durante el período de abril 2008 a diciembre 2012. Se registraron los parámetros de temperatura ambiental y del agua, profundidad, salinidad, oxígeno disuelto y pH en cada uno de los seis sitios de recolecta que se ubicaron en el sistema. El análisis de los parámetros ambientales no mostró diferencias significativas entre los años del período de estudio, la salinidad registrada a lo largo del estudio correspondió a un ambiente oligohalino, el resto de los parámetros fisicoquímicos presentó variaciones que pueden explicarse por el patrón climático en el área. Se capturó un total de 519 organismos, 311 (59.9 %) machos y 208 (41.1 %) hembras, el comportamiento de la longitud patrón en los distintos meses muestra que en los machos, la longitud promedio es mayor que en las hembras. El espectro trófico se compone de 13 tipos alimenticios, destacan los crustáceos, moluscos y peces, adicionalmente se observó la práctica de canibalismo en los meses de marzo y abril. Los estadios de maduración gonádica más avanzados se registraron en los meses de noviembre a marzo para los machos, y de noviembre a febrero para las hembras. El IGS registró los valores más altos en los meses de noviembre a abril, el IHS y el FC presentaron un comportamiento inverso al IGS. La fecundidad de esta especie varía de 96 a 428 ovocitos por hembra. La relación peso-longitud por sexo y temporada presentó una mayor tasa de crecimiento (b) para los machos que para las hembras, y un crecimiento de tipo alométrico negativo. La información biológica y ecológica de O. beta en el SLA permite reconocer que esta especie es importante por el papel ecológico que juega en la estructura y dinámica de sus comunidades acuáticas y puede ser utilizada en la propuesta de manejo y aprovechamiento sustentable de este ecosistema.

Abstract Opsanus beta is a permanent species in the Alvarado Lagoon System (ALS), Veracruz, and eventhough it is not of economic importance, it might be actively involved in the energy transfer of the system. Currently, there is no information about the reproductive and ecological characteristics of this common fish, so this work aimed to evaluate those aspects, and to contribute with some ecological features. For this, a total of six sampling sites were selected and studied from April 2008 to December 2012. Per site, we determined fish seasonality, feeding, sex ratio, gonadosomatic index, hepatosomatic and condition factors for both sexes, as well as the fecundity and length-weight relationships. We also considered some environmental parameters such as temperature, water temperature, depth, salinity and pH. Our results on the environmental parameters analysis did not show significant differences for the study period; besides, salinity data confirmed an oligohaline environment, and the rest of the physico-chemical parameters, varied in accordance with the climatic pattern in the area. We captured a total of 519 fishes, 311 (59.9 %) males and 208 (41.1 %) females; the proportion of males resulted favorable against females throughout the study. The standard length found along the study period showed that the average was higher in males than in females. The trophic spectrum was composed of 13 food items, principally crustaceans, molluscs and fishes; in addition, cannibalism was observed over young individuals during March and April. The most advanced stages of gonadal maturation were recorded from November to March for males, and from November to February in females; generally, the Gonadosomatic index (IGS) recorded the highest values from November to April. The Hepatosomatic Index (IHS) and the Condition Factor (FC) presented an inverse relationship with the Gonadosomatic index (IGS). The fecundity of this species ranged from 96 to 428 oocytes per female. The weight-length relationship by sexes and seasons, showed a higher growth rate for males than for females, and an allometric growth type. The biological and ecological information of O. beta in ALS evidenced the importance of this species and its ecological role in the structure and dynamics of these aquatic communities. This species may be used as a model for future proposals dealing with the management and sustainable use of this ecosystem.

The association between subclinical mastitis around calving and reproductive performance in grazing dairy cows.

The objective of this study was to evaluate the effect of subclinical mastitis (SCM) on calving-to-first-service interval (CFS), calving-to-conception interval (CC), and on the number of services per conception (S/C) in grazing Holstein and Normande cows. Primiparous (n=43) and multiparous (n=165) cows were selected from five dairy herds. Two composite milk samples were aseptically collected from each cow at drying-off, and then every week during the first postpartum month. One sample was used for somatic cell count (SCC), and the other one for bacteriological analysis. Cows were followed up to 300 d after calving. Non-parametric and parametric survival models, and negative binomial regression were used to assess the association between SCM, evaluated by SCC and milk culture, and reproductive indices. Staphylococcus aureus, CNS, and Streptococcus uberis were the most frequent isolated pathogens. Subclinical mastitis in the first month of lactation was not associated with CFS; however, the CC interval was longer in cows with SCM compared to healthy cows, the former also had a higher number of S/C.

Reproduction of Meloidogyne incognita Race 3 on Flue-cured Tobacco Homozygous for Rk1 and/or Rk2 Resistance Genes.

Most commercial tobacco cultivars possess the Rk1 resistance gene to races 1 and 3 of Meloidogyne incognita and race 1 of Meloidogyne arenaria, which has caused a shift in population prevalence in Virginia tobacco fields toward other species and races. A number of cultivars now also possess the Rk2 gene for root-knot resistance. Experiments were conducted in 2013 to 2014 to examine whether possessing both Rk1 and Rk2 increases resistance to a variant of M. incognita race 3 compared to either gene alone. Greenhouse trials were arranged in a completely randomized design with Coker 371-Gold (C371G; susceptible), NC 95 and SC 72 (Rk1Rk1), T-15-1-1 (Rk2Rk2), and STNCB-2-28 and NOD 8 (Rk1Rk1 and Rk2Rk2). Each plant was inoculated with 5,000 root-knot nematode eggs; data were collected 60 d postinoculation. Percent galling and numbers of egg masses and eggs were counted, the latter being used to calculate the reproductive index on each host. Despite variability, entries with both Rk1 and Rk2 conferred greater resistance to a variant of M. incognita race 3 than plants with Rk1 or Rk2 alone. Entries with Rk1 alone were successful in reducing root galling and nematode reproduction compared to the susceptible control. Entry T-15-1-1 did not reduce galling compared to the susceptible control but often suppressed reproduction.

Bovine viral diarrhea virus (BVDV) infection in dairy cattle herds in northeast Thailand.

Bovine viral diarrhea virus causes a wide range of clinical manifestation with subsequent economic losses in dairy production worldwide. Our study of a population of dairy cattle in Thailand based on 933 bulk tank milk samples from nine public milk collection centers aimed to monitor infective status and to evaluate the effect of the infection in cows as well as to examine the reproductive performance of heifers to provide effective recommendations for disease control in Thailand. The results showed a moderate antibody-positive prevalence in the herd (62.5 %), with the proportion of class-3 herd, actively infected stage, being 17.3 %. Fourteen persistently infected (PI) animals were identified among 1196 young animals from the class-3 herds. Most of the identified PI animals, 11/14, were born in one sub-area where bovine viral diarrhea virus (BVDV) investigation has not been performed to date. With respect to reproductive performance, class-3 herds also showed higher median values of reproductive indices than those of class-0 herds. Cows and heifers in class-3 herds had higher odds ratio of calving interval (CI) and age at first service (AFS) above the median, respectively, compared to class-0 herds (OR = 1.29; P = 0.02 and OR = 1.63; P = 0.02). Our study showed that PI animals were still in the area that was previously studied. Furthermore, a newly studied area had a high prevalence of BVDV infection and the infection affected the reproductive performance of cows and heifers. Although 37.5 % of the population was free of BVDV, the lack of official disease prevention and less awareness of herd biosecurity may have resulted in continuing viral spread and silent economic losses have potentially occurred due to BVDV. We found that BVDV is still circulating in the region and, hence, a national control program is required.

The dynamics of temperature and light on the growth of phytoplankton.

Motivated by some lab and field observations of the hump shaped effects of water temperature and light on the growth of phytoplankton, a bottom-up nutrient phytoplankton model, which incorporates the combined effects of temperature and light, is proposed and analyzed to explore the dynamics of phytoplankton bloom. The population growth model reasonably captures such observed dynamics qualitatively. An ecological reproductive index is defined to characterize the growth of the phytoplankton which also allows a comprehensive analysis of the role of temperature and light on the growth and reproductive characteristics of phytoplankton in general. The model provides a framework to study the mechanisms of phytoplankton dynamics in shallow lake and may even be employed to study the controlled phytoplankton bloom.

In vivo and in vitro study of the function of the left and right bovine ovaries.

Inequality in function of the left and right bovine ovaries and uterine horns was evaluated in two separate experiments. In the first experiment (in vivo), the relationship between the left and right ovarian activities and reproductive indices was evaluated. Therefore, the total number of 1284 randomly chosen lactating dairy cows were examined from Day 50 to 60 postpartum, and according to the presence of an active CL on the ovaries, they were divided into 502 LCL3-cows and 782 RCL3-cows (cows with an active CL on the left [L] or right [R] ovary, respectively). To induce estrus synchronization and investigate the effects of PGF2α administration on the incidence of estrus in both LCL3-cows and RCL3-cows, the cows were treated with one luteolytic dose of PGF2α and were inseminated after observed estrus (via visual observation lasting at least 30 minutes three times a day). To investigate the effects of side of ovulation at the time of PGF2α administration on reproductive parameters, pregnancy diagnosis was performed 28 days after insemination (using ultrasound) and 42 days after insemination (using transrectal palpation). The results showed that the percentage of the RCL3-cows was greater than the LCL3-cows (60.9% vs. 39.1%, respectively). Furthermore, ovulations switching from the left to right ovary in two successive ovulations were greater than those that switched from the right to left ovary. On the other hand, the sex ratio (male percentage) in the right uterine horn was greater than that of the left one. In the second experiment (in vitro), the developmental potential of bovine oocytes derived from the left (L-oocytes) and right (R-oocytes) ovaries after in vitro embryo production and heterogeneity in the developmental competence of L-oocytes and R-oocytes using the brilliant cresyl blue staining test as a selection criterion were evaluated. Results of the in vitro experiment showed that the percentage of cleavage and blastocyst rate of R-oocytes were greater (P < 0.001) than those of L-oocytes. Moreover, it appears that the side of ovaries had greater effects on the developmental competence of oocytes than other factors associated with heterogeneity in the developmental competence of oocytes, which can be detected by the brilliant cresyl blue test. In conclusion, the results of the in vivo study confirmed the observations in previous studies in which the right ovarian response (distribution of ovulation) was superior to that of the left ones. Interestingly, the in vitro experiments for the first time clearly showed that more ovulation on the right side is not the only reason for this unequal activity. In fact, in cattle, the greater developmental potential of oocytes originating from right ovaries may cause superior activity of the right side, and the effect is even higher than the differences in ovulation response between the left and right ovaries.

Relationship between blood lead level and male reproductive hormones in male lead exposed workers of a battery factory: A cross-sectional study.

BACKGROUND: The reproductive system is one of the organs that are affected by lead. Lead can cause loss of libido and fertility in men, and menstrual disturbances and spontaneous abortion in woman. OBJECTIVE: The purpose of this cross-sectional study was assessment of dose-response relationship between blood lead level (BLL) and sex hormones levels in lead exposed male workers. MATERIALS AND METHODS: One hundred and thirteen male workers enrolled. All workers had at least 6 months of lead exposure and no history of diseases or conditions affecting reproductive system. Blood lead level and hormones levels measured with atomic absorption spectrophotometer and radioimmunoassay method, respectively. RESULTS: Average duration of exposure was 15.92±6.95 years. Mean BLL was 41.41µg/dl±16.99. All of the sex hormones values were in normal range. Pearson correlation showed that sex hormones levels had no significant correlation with blood lead level. Also, there was no significant difference in sex hormones levels between workers with BLL <40µg/dl and workers whose BLL was >40 µg/dl. CONCLUSION: This study showed that BLL cannot serve as a predictor of male sex hormonal changes. However, it is not possible to rule out the effect of lead on the reproductive system after long-term exposure.

Edad y crecimiento del híbrido de tilapia Oreochromis niloticus x Oreochromis aureus (Perciformes: Cichlidae) en la represa “Zimapán” Hidalgo, México

Age and growth of the hybrid tilapia Oreochromis niloticus x Oreochromis aureus (Perciformes: Cichlidae) in the dam “Zimapan” Mexico. Studies on age and growth in fishes are essential to establish models on population dynamics. The previos issues were determined in this study by scale growth analyses. Between September 2003 and May 2004, 382 organisms were captured using gill and atarraya nets. Eight samples were developed every month a long this study. Standard length in centimeters (Le), total weight in grams (Pt), scale length in centimeters (Lesc) and growth rings were determined. The size and weight ranged from 38 to 232mm (Le) and 8.7 to 311.9g (Pt), respectively. The growth rings analyses reveal four age groups, being the sec-ond group the most representative with 34.3% of the total sampled. The scale ring analyses showed two growth rings, one develops between November-January and the other between April-May, in good correlation with low temperature and gonad development, respectively. The growth parameters were established as: L∞=281.1mm, W∞=877.1g, K=0.33 and T0=0.88year -1. The growth curves based on length and weight were described by using the von Bertalanffy model: Le =28.11[1-e-0.33(t+0.88)] and Pt =877.17[1-e-0.33(t+0.88)]³. Finally, it is concluded that commercial catches in this dam are between a year and year and half-old when exploited. Rev. Biol. Trop. 59 (2): 761-770. Epub 2011 June 01.

La edad y crecimiento de la tilapia Oreochromis niloticus x Oreochromis aureus fueron determinados por medio de la lectura de escamas. Un total de 382 individuos fueron capturados mediante el uso de redes agalleras y atarrayas. Ocho recolectas mensuales se llevaron a cabo entre septiembre 2003-mayo 2004; se registraron los datos de longitud estándar en cm. (Le), el peso total en g (Pt) y se obtuvieron muestras de escamas para registrar el largo de la escama en mm. (Lesc) y el número de anillos de crecimiento formados. Las tallas y pesos de recolecta variaron entre 38 a 232mm (Le) y de 8.7 a 311.9g de peso total (Pt) respectivamente. El recuento de los anillos anuales en escamas, permitió establecer cuatro grupos de edad, siendo el grupo de edad 2 el más representativo, con un 34.3% de la población muestreada. El cálculo de los incrementos marginales del crecimiento mensual de las escamas, sugirió la formación de dos anillos, uno de ellos se forma en los meses de noviembre-enero y otro en los meses de abril-mayo, los cuales coinciden con la época de bajas temperaturas y de madurez gonádica respectivamente. Los parámetros de crecimiento quedaron establecidos en: L∞=281.1mm, W∞=877.1g, K=0.33 y T0=0.88/año. Las curvas de crecimiento en longitud y peso se describieron mediante las ecuaciones de von Bertalanffy: Le=28.11 [1- e-0.33(t+0.88)] y Pt=877.17 [1-e-0.33(t+0.88)]³. Finalmente, se concluyó que los peces que se explotan en la represa mediante captura comercial presentan entre un año y año y medio de edad.

Efeito da fotoperiodicidade na taxa de prenhez em ratos isogênicos (F344) / Effect of photoperiodicity in the pregnancy rate of isogenic rats (F344)

O uso de animais isogênicos apresenta grandes vantagens experimentais, como uniformidade fenotípica e genotípica (reduzindo o número de animais em experimentos) e histocompatibilidade, permitindo, assim, o acúmulo de informações e a repetibilidade dos experimentos. A linhagem isogênica de Rattus norvegicus Fischer 344 existe há 90 anos, entretanto pouco se sabe sobre as razões de seu baixo índice reprodutivo. O presente estudo demonstrou que ratos Fischer F344 são fotorresponsivos quanto à reprodução, tendo seus índices de prenhezes acrescidos com o aumento do fotoperíodo. Os melhores índices são obtidos quando os machos são submetidos a 14 horas de luz e fêmeas a 16 horas de luz, indicando dimorfismo sexual na fotorresponsividade.

The use of isogenic animals presents great experimental advantages, as phenotypic and genotypic uniformity (reducing the number of experimental animals) and histocompatibility, thus allowing, the accumulation of information, and the repeatability of the experiments. The isogenic strain of Rattus norvegicus Fischer 344 has existed for 90 years, however the reasons of its low reproductive index are not knew. The present study has demonstrated that Fischer F344 rats are photoresponsive regarding reproduction, having improved its pregnancy index with the increase of the photoperiod. The best indexes were achieved when the males had been submitted to 14 hours of light and females to 16 hours of light, indicating sexual dimorphism in photoresponsivity.

Intraspecific Variability of Rotylenchulus reniformis from Cotton-growing Regions in the United States.

Reniform nematode (Rotylenchulus reniformis) is a major pest of cotton in the southeastern United States. The objective of this study was to examine the variation of reniform nematode populations from cotton-growing locations in the United States where it is prevalent. Multivariate analysis of variance and discriminant analysis were used to determine the variability of morphology in males and immature females. Reproduction indices of populations were measured on selected soybean and cotton genotypes in the greenhouse. High variability in morphometrics and reproduction was observed within all the populations, and several differences were found among populations. DNA sequences of the nuclear ribosomal first internal transcribed spacer region (ITS1) were compared among populations from the United States and to sequences of populations from Brazil, Colombia, Honduras, and Japan. No polymorphic nucleotide sites were observed among the amphimictic populations. Only a parthenogenic population from Japan was distinct. The phenotypic polymorphism of the species in the United States could impact the effectiveness of management strategies based on host plant resistance.