bluuebunny/crossref_metadata_2025_split huggingface dataset:
An Update on Reproduction in Yak and Mithun
Authors: Prakash BS , Sarkar M , Mondal M 
Published: July 2008

ContentsYak and mithun are two domesticated herbivores of high economic importance to the farming community living in highlands. Improved yak and mithun production could significantly enhance the living standards of these highlanders. Over the years, their dwindling numbers have been a cause of serious concern. In view of the lack of knowledge on the reproductive physiology of these ruminants, studies have been undertaken to investigate their reproductive endocrinology in recent years. This paper attempts to present the latest information on the endocrine changes associated with their various reproductive processes viz. growth and puberty, oestrous cyclicity and oestrous behaviour, ovulation, and, pregnancy and parturition. The paper also provides the recent developments on research done towards the enhancement of yak and mithun reproductive efficiencies through endocrine and embryo biotechniques.
Proteins Associated With the Early Intrauterine Equine Conceptus
Authors: Hayes MA , Quinn BA , Keirstead ND , Katavolos P , Waelchli RO , Betteridge KJ 
Published: July 2008

ContentsA critical period of early gestation in the mare involves the immobilization (fixation) of the encapsulated conceptus at around days 16–17. We compared the major proteins in the normal equine embryonic capsule and endometrial secretions around the period of fixation with those from pregnancies in the process of termination induced by administration of an analogue of prostaglandin F2α(PGF2α). Uterocalin and β2‐microglobulin (β2M) associated with the embryonic capsule were proteolytically converted to smaller forms during the fixation period. These conversions were similar in conceptuses from control and treated mares. A 17 kDa cationic protein identified as a secretory phospholipase A2 (sPLA2) type IIA was detected bound to normal capsules but increased substantially in response to PGF2α. Two forms of uteroglobin were distinguished by partial amino acid sequences of ∼6 kDa bands in flush fluids from normal pregnant uteri. After administration of PGF2αone immunoreactive form of uteroglobin was preferentially increased. These studies demonstrate that failure of pregnancy in this model is associated with an increase in secretory phospholipase in the capsule and a change in the forms of uteroglobin in the uterine secretions.
Heat Stress, the Follicle, and Its Enclosed Oocyte: Mechanisms and Potential Strategies to Improve Fertility in Dairy Cows
Authors: Roth Z 
Published: July 2008

ContentsReduced reproductive performance of lactating cows during the summer is associated with decreased thermoregulatory competence due to intensive genetic selection for high milk production. This review examines the immediate and delayed effects of heat stress on follicular function and describes some potential strategies for their alleviation. It focuses on how heat stress affects the follicle and its enclosed oocyte, suggesting that perturbations in the follicular microenvironment, to which the oocytes are exposed for long periods of development, reduce their developmental competence. Among the potential alterations are reduction in gonadotropin secretion, alteration in follicular growth, attenuation of dominance, and disruption of steroidogenesis. Evaporative cooling methods are the most common strategy used to alleviate the effect of heat stress; however, there is a compelling need to find additional ways to improve fertility during the summer and autumn. Hormonal treatment to enhance removal of the impaired follicles by synchronization of follicular waves with GnRH and PGF2α is suggested. An alternative method is stimulation of follicular growth by a brief treatment with bST or FSH. Other strategies, such as timed AI and embryo transfer, have been recently used, making the optimization of embryo cryopreservation procedures highly relevant. Protection of the ovarian pool of oocytes from thermal stress via nutritional manipulations or administration of antioxidants or other survival factors should also be considered. A better understanding of the underlying mechanisms by which heat stress impairs fertility may lead to the development of additional approaches to alleviate these effects.
Fertilization and Early Embryonic Development in the Porcine Fallopian Tube
Authors: Brüssow K‐P , Rátky J , Rodriguez‐Martinez H 
Published: July 2008

ContentsFertilization and early embryo development relies on a complex interplay between the Fallopian tube and the gametes before and after fertilization. Thereby the oviduct, as a dynamic reproductive organ, enables reception, transport and maturation of male and female gametes, their fusion, and supports early embryo development. This paper reviews current knowledge regarding physiological processes behind the transport of boar spermatozoa, their storage in and release from the functional sperm reservoir (SR), and of the interactions that newly ovulated oocytes play within the tube during their transport to the site of fertilization. Experimental evidence of an ovarian control on sperm release from the SR is highlighted. Furthermore, the impact of oviductal secretion on sperm capacitation, oocyte maturation, fertilization and early embryo development is stressed.
Mastitis in Post‐Partum Dairy Cows
Authors: Pyörälä S 
Published: July 2008

ContentsTransition from the dry period to lactation is a high risk period for the modern dairy cow. The biggest challenge at that time is mastitis. Environmental bacteria are the most problematic pathogens around parturition. Coliforms are able to cause severe infections in multiparous cows, and heifers are likely to be infected with coagulase‐negative staphylococci. During the periparturient period, hormonal and other factors make the dairy cows more or less immunocompromised. A successful mastitis control programme is focused on the management of dry and calving cows and heifers. Clean and comfortable environment, proper feeding and adequate supplementation of the diet with vitamins and trace elements are essential for maintaining good udder health. Strategies which would enhance closure of the teat canal in the beginning of the dry period and would protect teat end from bacteria until the keratin plug has formed decrease the risk for mastitis after calving. Dry cow therapy has been used with considerable success. Yet, a selective approach could be recommended rather than blanket therapy. Non‐antibiotic approaches can be useful tools to prevent new infections during the dry period, in herds where the risk for environmental mastitis is high. Vaccination has been suggested as a means to support the immune defence of the dairy cow around parturition. In some countries, implementation ofEscherichia colicore antigen vaccine has reduced the incidence of severe coliform mastitis after calving.
Energy Metabolism and Leptin: Effects on Neuroendocrine Regulation of Reproduction in the Gilt and Sow
Authors: Barb CR , Hausman GJ , Lents CA 
Published: July 2008

ContentsIt is well established that reproductive function is metabolically gated. However, the mechanisms whereby energy stores and metabolic cues influence appetite, energy homeostasis and fertility are yet to be completely understood. Adipose tissue is no longer considered as only a depot to store excess energy. Recent findings have identified numerous genes, several neurotrophic factors, interleukins, insulin‐like growth factor binding protein‐5, ciliary neurotrophic factor and neuropeptide Y (NPY) as being expressed by adipose tissue during pubertal development. These studies demonstrated for the first time the expression of several major adipokines or cytokines in pig adipose tissue which may influence local and central metabolism and growth. Leptin appears to be the primary metabolic signal and is part of the adipose tissue‐hypothalamic regulatory loop in the control of appetite, energy homeostasis and luteinizing hormone (LH) secretion. Leptin’s actions on appetite regulation are mediated by inhibition of hypothalamic NPY and stimulation of proopiomelanocortin. Its effects on gonadotropin‐releasing hormone (GnRH)/LH secretion are mediated by NPY and kisspeptin. Thus, leptin appears to be an important link between metabolic status, the neuroendocrine axis and subsequent fertility in the gilt and sow.
Endocrine Regulation of the Establishment of Spermatogenesis in Pigs
Authors: Caires KC , Schmidt JA , Oliver AP , De Avila J , McLean DJ 
Published: July 2008

ContentsSomatic and germ cell maturation precedes the start of spermatogenesis and is coordinated, so efficient spermatogenesis will occur in the adults. The present study was conducted to evaluate endocrine regulation of germ and somatic cell homeostasis in the neonatal boar testis associated with the establishment of spermatogenesis. Testis tissue obtained from 3‐, 5‐, 7‐ and 14‐day‐old piglets were ectopically xenografted onto castrated, immunodeficient nude mice. Grafts were removed 22 weeks later and evaluated for growth and the establishment of spermatogenesis. Recipient mouse testosterone biosynthesis and follicle‐stimulating hormone (FSH) concentrations were also assayed. Testis tissue graft growth was significantly greater in testis grafts from 3‐day donor tissue when compared to all other ages; 5‐, 7‐ and 14‐day‐old donor tissue weights were not significantly different at removal. Follicle‐stimulating hormone concentrations in recipient mice supporting testis grafts from 5‐, 7‐ and 14‐day‐old donor tissues did not differ and were similar to normal physiological levels in age‐matched, intact nude mice. Serum FSH levels were significantly lower in recipient mice supporting testis grafts from 3‐day‐old donor tissue. Radioimmunoassay and biological assay indicated no differences in testosterone production by testis tissue grafts of varying donor age. Porcine testis tissue obtained from 3‐, 5‐, 7‐ and 14‐day‐old neonatal boars were all capable of producing round and elongate spermatids after 22 weeks of grafting, but testis grafts from 14‐day‐old donors had a significantly greater (eightfold) percentage of seminiferous tubules with spermatids compared to all other donor ages (p < 0.05). Cryopreservation did not affect the ability of testis tissue grafts to grow, produce testosterone or establish spermatogenesis when compared to controls (p < 0.05). Collectively, these data demonstrate intrinsic differences in the biological activity of germ and somatic cell populations during neonatal boar testis development associated with the establishment of spermatogenesis.
Male Germ Cell Transplantation
Authors: Dobrinski I 
Published: July 2008

ContentsTransplantation of male germ line stem cells from a donor animal to the testes of an infertile recipient was first described in 1994. Donor germ cells colonize the recipient’s testis and produce donor‐derived sperm, such that the recipient male can distribute the genetic material of the germ cell donor. Germ cell transplantation represents a functional reconstitution assay for male germ line stem cells and as such has vastly increased our ability to study the biology of stem cells in the testis and define phenotypes of infertility. First developed in rodents, the technique has now been used in a number of animal species, including domestic mammals, chicken and fish. There are three major applications for this technology in animals: first, to study fundamental aspects of male germ line stem cell biology and male fertility; second, to preserve the reproductive potential of genetically valuable individuals by male germ cell transplantation within or between species; third, to produce transgenic sperm by genetic manipulation of isolated germ line stem cells and subsequent transplantation. Transgenesis through the male germ line has tremendous potential in species in which embryonic stem cells are not available and somatic cell nuclear transfer has limited success. Therefore, transplantation of male germ cells is a uniquely valuable approach for the study, preservation and manipulation of male fertility in animals.
Somatic Cell Nuclear Transfer in Horses
Authors: Galli Cesare , Lagutina Irina , Duchi Roberto , Colleoni Silvia , Lazzari Giovanna 
Published: July 2008

ContentsThe cloning of equids was achieved in 2003, several years after the birth of Dolly the sheep and also after the cloning of numerous other laboratory and farm animal species. The delay was because of the limited development in the horse of more classical‐assisted reproductive techniques required for successful cloning, such as oocyte maturation andin vitroembryo production. When these technologies were developed, the application of cloning also became possible and cloned horse offspring were obtained. This review summarizes the main technical procedures that are required for cloning equids and the present status of this technique. The first step is competent oocyte maturation, this is followed by oocyte enucleation and reconstruction, using either zona‐enclosed or zona‐free oocytes, by efficient activation to allow high cleavage rates and finally by a suitablein vitroembryo culture technique. Cloning of the first equid, a mule, was achieved using anin vivo‐matured oocytes and immediate transfer of the reconstructed embryo, i.e. at the one cell stage, to the recipient oviduct. In contrast, the first horse offspring was obtained using a completein vitroprocedure from oocyte maturation to embryo culture to the blastocyst stage, followed by non‐surgical transfer. Later studies on equine cloning report high efficiency relative to that for other species. Cloned equid offspring reported to date appear to be normal and those that have reached puberty have been confirmed to be fertile. In summary, horse cloning is now a reproducible technique that offers the opportunity to preserve valuable genetics and notably to generate copies of castrated champions and therefore, offspring from those champions that would be impossible to obtain otherwise.
Breeding Soundness Evaluation and Semen Analysis for Predicting Bull Fertility
Authors: Kastelic JP , Thundathil JC 
Published: July 2008

ContentsBull fertility is influenced by numerous factors. Although 20–40% of bulls in an unselected population may have reduced fertility, few are completely sterile. Breeding soundness refers to a bull’s ability to get cows pregnant. A standard breeding soundness evaluation identifies bulls with substantial deficits in fertility, but does not consistently identify sub‐fertile bulls. In this regard, the use of frozen‐thawed semen (from bulls in commercial AI centres) that meets minimum quality standards can result in pregnancy rates that differ by 20–25 percentage points. Although no single diagnostic test can accurately predict variations in fertility among bulls that are producing apparently normal semen, recent studies suggested that a combination of laboratory tests were predictive of fertility. This review is focused on recent developments in prediction of bull fertility, based on assessments at the molecular, cellular and whole‐animal levels.
Sanitary Procedures for the Production of Extended Semen
Authors: Althouse GC 
Published: July 2008

ContentsSemen is collected and processed from a variety of animal species for use in artificial insemination breeding programmes. Because of the inherent nature of the semen collection process, bacterial contamination of the ejaculate is a common occurrence. Additionally, manipulation of the ejaculate during processing in the laboratory can expose the sample to possible introduction of bacterial contamination. If preventative measures at the stud fail to adequately control these risks, decreases in semen quality, dose longevity and fertility may occur. Multiple mammalian and non‐mammalian sources have been identified as origins of contamination in the stud. Knowledge of these sources has aided the industries in developing strategies that help in controlling the introduction of contaminant bacteria in extended semen. A primary step in minimizing contamination is in the practice of good hygiene by stud personnel. Prudent general sanitation protocols should also be followed in the laboratory, animal housing and semen collection areas. Cleanliness and attention to the actual semen collection process can also aid in reducing bacterial load originating from the stud semen donor. Attentiveness to all of these steps significantly contributes to an overall reduction in the type and amount of bacterial contamination. However, their complete elimination stills remains unavoidable. To address residual bacteria load in the sample, antimicrobials are commonly used in semen extenders intended to promote in vitro sperm longevity beyond that of a few hours. Current research by the animal industries continues in the selection and prudent use of antimicrobials that will lead to the success and sustainability of this modality in controlling bacterial contamination.
Regulation of the Spermatogonial Stem Cell Niche
Authors: Kostereva N , Hofmann M‐C 
Published: July 2008

ContentsSpermatogonial stem cells (SSCs) reside within specialized microenvironments called ‘niches’, which are essential for their maintenance and self‐renewal. In the mammalian testis, the main components of the niche include the Sertoli cell, the growth factors that this nursing cell produces, the basement membrane, and stimuli from the vascular network between the seminiferous tubules. This review focuses on signalling pathways maintaining SSCs self‐renewal and differentiation and describes potential mechanisms of regulation of the spermatogonial stem cell niche.
Selected Aspects of Advanced Porcine Reproductive Technology
Authors: Kikuchi K , Kashiwazaki N , Nagai T , Nakai M , Somfai T , Noguchi J , Kaneko H 
Published: July 2008

Contents In vitro fertilization (IVF) of in vitro matured (IVM) oocytes in pigs has become the most popular method of studying gametogenesis and embryogenesis in this species. Furthermore, because of recent advances in in vitro culture (IVC) of IVM–IVF embryos, in vitro production (IVP) of embryos now enables us to generate viable embryos as successfully as for in vivo‐derived embryos and with less cost and in less time. These technologies contribute not only to developments in reproductive physiology and agriculture but also to the conservation of porcine genetic resources and the production of cloned or genetically modified pigs. However, in IVP, there still remains the problem of abnormal ploidy, which is caused by performing procedures under non‐physiological conditions. In recent years, unique technologies such as intracytoplasmic sperm injection (ICSI) or xenografting of gonadal tissue into immunodeficient experimental animals have been developed to help conserve gamete resources. These technologies combined with IVP are expected to be useful for the conservation of gametes from important genetic resources. Here, we discuss the developmental ability and normality of porcine IVP embryos and also the utilization of ICSI and xenografting in advancing biotechnology in pigs.
Reproductive biology and pollination of Govenia utriculata: A syrphid fly orchid pollinated through a pollen‐deceptive mechanism
Authors: PANSARIN EMERSON R. 
Published: July 2008

AbstractThe reproductive biology and pollination mechanisms of Govenia utriculata (Sw.) Lindl. were studied in a mesophytic semideciduous forest at Serra do Japi, south‐eastern Brazil. The floral visitors and pollination mechanisms were recorded, and experimental pollinations were carried out to determine the breeding system of this species. Populations of G. utriculata growing at Serra do Japi are exclusively visited and pollinated by two species of hoverflies in the genus Salpingogaster (Diptera: Syrphidae) that are attracted by deceit to the flowers of this orchid species. The lip apex and the column base present small brownish and yellow to orange spots that mimic pollen clusters. Govenia utriculata is self‐compatible, but pollinator dependent. Natural fruit set was low (10%), but similar to that of other non‐obligatorily autogamous sympatric orchid species that occur at Serra do Japi and of other fly‐pollinated orchid species pollinated through deceptive mechanisms.
Is the endangeredApium repens(Jacq.) Lag. rare because of a narrow regeneration niche?
Authors: BURMEIER SANDRA , JENSEN KAI 
Published: July 2008

AbstractThe conservation of rare plant species is an important aspect of global biodiversity protection, but in many cases these species and the reasons why they are rare are poorly understood. The perennial umbelliferApium repensis generally regarded to be a rare species all over its European range. We hypothesized that its rarity might be caused by a restricted regeneration niche, that is, highly specific requirements for sexual regeneration, low seed dispersal potential and low endurance capacity of seeds in the ground. We conducted several experimental investigations on its germination ecology, hydrochorous dispersal potential and soil seed bank properties.Apium repensshowed high germination success under a variety of abiotic conditions. Either light or cold‐wet stratification was necessary to stimulate germination. Seeds were able to float for more than 50 days when protected from precipitation, and soil seed bank sampling revealed that at least some seeds ofA. repenswere contained in soil depths of up to 10 cm. Overall, our findings do not support the hypothesis that the rarity ofA. repensis caused by highly specific requirements for its sexual regeneration. Nonetheless, its germination ecology should be considered when designing conservation measures for this endangered species.
Reproductive ecology of medicinally important Kashmir Himalayan species of Digitalis L.
Authors: NAZIR ROMAISA , RESHI ZAFAR , WAFAI BASHIR AHMAD 
Published: July 2008

AbstractReproductive biology, encompassing phenology, floral biology, pollination and breeding systems, was investigated in three pharmaceutically important and anthropogenically exploited species of Digitalis in the montane habitats of the Kashmir Himalaya. Flowers in all three species (Digitalis purpurea, Digitalis grandiflora and Digitalis lanata) are aggregated in racemes. Corollas are characteristically bell shaped enclosing four, didynamously arranged stamens. The stigma is deeply bifid only in D. purpurea. The three species over‐winter as underground tubers and sprouting during the following spring occurs first in D. lanata, followed by D. purpurea and D. grandiflora. Floral bud opening in an inflorescence in all three species occurs sequentially from the bottom upwards in an acropetal succession and male and female phases are temporally separated with basal flowers entering the male phase first followed by the upper flowers in a regular sequence. Only after shedding the pollen grains completely do the flowers shift to the female phase. Resource allocation in all three species is more towards maleness than femaleness during anthesis. The species are principally insect pollinated and selfing is denied because of protandry and spatial separation of the stigma and anthers. Copious amounts of viable pollen grains produced by these species aid in successful pollination, fertilization and seed production. Studies revealed that none of these species operates autogamy because hand‐pollinated flowers with self‐pollen or bagged flowers (foreign pollen excluded) failed to set seed. High seed output in open‐pollinated flowers and high pollen–ovule ratios also indicate the outbreeding nature of these species. Thus, any reduction in the number of individuals constituting a population would significantly reduce the floral display and consequent rewards to the pollinators, with a subsequent influence on seed production. Hence, data on the reproductive biology of overexploited species, such as Digitalis spp., is of pivotal importance in formulating effective conservation strategies.