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H Callesen

Publications and source records attributed to H Callesen.

66 records · Page 4Linked to original sources
PubMed1988

A semiquantitative and rapid radioimmunosorbent assay of luteinizing hormone for early prediction of time of ovulation in cattle.

A radioimmunoassay (RIA) for bovine luteinizing hormone (LH) is presented. It is based on the binding of the second antibody to polystyrene vials. Less than 4 h is required to estimate the hormone level in the plasma. LH content is determined by comparing unknown plasma samples to relevant control plasma to identify the preovulatory LH surge. Of 182 samples, 176 (97%) were found to contain either more or less LH than the control plasma, and 12 out of 13 (92%) LH surges were identified using the immunosorbent RIA. The method can be used for early prediction of ovulation in cattle, and it may be used to time aspiration of oocytes.

Journal Article↗
PubMed1988

Preovulatory evaluation of the superovulatory response in donor cattle.

Dairy cows and heifers (n = 134) were induced to superovulate with exogenous gonadotrophins. In 103 animals, peripheral plasma concentrations of progesterone (P4) and luteinizing hormone (LH) were measured during the preovulatory period. On the basis of these measurements, normal and deviating profiles of P4 and LH were defined. A high degree of correlation existed between the normality of the two profiles; when the P4 profile was normal, the probability for the LH profile also to be normal was greater than 10:1. This relationship was utilized to evaluate donors based on four preovulatory measurements of P4. When used on 31 animals used for collection of eggs, a superior superovulatory response was encountered in animals with normal vs deviating P4 profiles (eggs recovered: 7.2 +/- 1.1 vs 0.5 +/- 0.3, P < 0.001; transferable embryos: 4.4 +/- 0.9 vs 0.3 +/- 0.2, P < 0.01). It is concluded that evaluation of donors by measurements of progesterone in plasma at four preovulatory sampling points allows for the early exclusion of donors with inferior embryo yield.

Journal Article↗
PubMed1988

Ultrastructure of in-vivo fertilization in superovulated cattle.

Heifers were induced to superovulate by treatment with PMSG or FSH. Subsequently, oestrus was induced with prostaglandins and artificial insemination was performed. Ova were collected from the oviducts and their ultrastructural features were related to an estimated time of ovulation based on the time of the LH peak. With the insemination schedule used, the estimated time of ovulation defined the time at which fertilization was expected to occur. The ova were characterized as unfertilized, fertilized or possibly fertilized, and a sequence of nuclear and cytoplasmic changes associated with fertilization was revealed. Within 4 h after the estimated time of ovulation formation of the female and male pronucleus was initiated, and at 5-7 h swelling of the pronuclei occurred. At 19 h the pronuclei were closely apposed and synkaryosis was seen, and at 23 h the first two-cell stage was obtained. Within 2-3 h after the estimated time of ovulation cortical granule release, development of conspicuous Golgi complexes, and transformation of the smooth endoplasmic reticulum occurred. At approximately 7 h parallel arrays of annulate lamellae appeared. In one third of the unfertilized ova deviant oocyte maturation was noticed.

Animals↗
PubMed1987

Ultrastructure of the final nuclear maturation of bovine oocytes in vitro.

Cumulus-oocyte complexes were obtained from cow ovaries by aspiration from small (1-6 mm in diameter) antral follicles after slaughter. Complexes with a compact multilayered cumulus investment were cultured and subsequently processed for electron microscopy after various periods of culture. By morphological criteria the oocytes could be divided into the following sequence of meiotic stages. The oocyte nucleus I stage was characterized by a spherical nucleus located peripherally in the ooplasm while undulation of the nuclear envelope and initial chromatin condensation was seen at the oocyte nucleus II stage. The oocyte nucleus breakdown stage was characterized by formation of long slender projections from the nuclear envelope in which the envelope doubled back on itself, appearance of dense areas and haphazardly oriented microtubules in the nucleus, marked condensation of the chromatin, and dissolution of the nuclear envelope into irregular vesicles and tubules. The condensed chromatin I stage was characterized by the location of condensed chromatin configuration and uniformly oriented microtubules in a dense area peripherally in the ooplasm while the final condensed chromatin II stage was characterized by a gradual invasion of condensed chromatin configurations into a dense area combined with the presence of the first polar body in the perivitelline space.

Animals↗
PubMed1987

In vivo development of in vitro fertilized bovine oocytes matured in vivo versus in vitro.

In vivo developmental potentials of in vivo and in vitro matured oocytes fertilized in vitro were assessed in cattle. One-cell stages produced from in vivo matured oocytes developed into a pregnancy when transferred to the ampulla part of oviducts of synchronized heifers. In vitro matured oocytes achieved high penetration and cleavage rates but did not develop into pregnancies when transferred to synchronized heifers.

Animals↗
PubMed1987

Premature ovulations in superovulated cattle.

The incidence and consequences of premature ovulations in superovulated cattle were studied. These ovulations, presumably induced by the luteinizing hormone content of the gonadotrophin preparation used, were found in 17 of 133 (13%) stimulated cows and heifers used as oocyte donors. In general this group of donors exhibited deviating periovulatory patterns of plasma hormone profiles (progesterone, estradiol17beta and LH), estrus behaviour, follicular steroidogenesis of progesterone and estradiol-17beta, and oocyte meiosis. It is concluded that superovulated donor cattle exhibiting premature ovulations constitute a group of poor oocyte donors that also must be considered as inferior embryo donors.

Journal Article↗
PubMed1987

Pregnancy resulting from cattle oocytes matured and fertilized in vitro.

Follicular oocytes (n = 81) collected from cattle at a local slaughterhouse were matured and fertilized in vitro. Of 27 ova 19 (70%) were penetrated by spermatozoa and 40/54 (74%) inseminated ova transferred surgically to the oviducts of a synchronized heifer were recovered by non-surgical flushing of the uterine horns 6 days later. Of the 40 ova 15 (38%) were at the morula, early blastocyst or diminutive morula stages. Culture in vitro sustained further development of all embryos and 9 were expanding or expanded blastocysts. One pregnancy resulted from non-surgical transfer of 2 blastocysts. The results demonstrate that immature oocytes from cattle can be matured and fertilized in vitro, subsequently develop to the blastocyst stage, and develop into a normal pregnancy after non-surgical transfer.

Animals↗
PubMed1986

Ultrastructural features of preovulatory oocyte maturation in superovulated cattle.

Cows and heifers were induced to superovulate by treatment with PMSG or FSH. The ultrastructural features of the oocytes were related to the time of the LH peak and the progesterone/oestradiol-17 beta ratios in the follicular fluid. At 0-2 h after the LH peak the perivitelline space developed; at 9-12 h there was disconnection of the junctions between cumulus cell projections and oolemma, and the concomitant breakdown of the oocyte nucleus; at approximately 15 h there were spatial rearrangements in the ooplasm of (a) mitochondrial clusters from a peripheral to an even distribution and (b) vesicles from an even distribution to a more central location; at approximately 19 h there was abstriction of the first polar body with dislocation of mitochondrial clusters and vesicles towards the site of polar body formation; at 21-22 h there was migration of cortical granules to solitary positions along the oolemma and decrease in the sizes of Golgi complexes and, on some occasions, the smooth endoplasmic reticulum. These ultrastructural changes were accompanied by an increase in progesterone/oestradiol ratios in the follicular fluids. It is concluded that preovulatory oocyte maturation in gonadotrophin-stimulated cattle comprises nuclear as well as cytoplasmic changes accompanied by steroidogenic changes in the follicle, each of which are closely related to the time of the LH peak. However, some variation existed between animals, between follicular and oocyte maturation and even within oocytes between nuclear and cytoplasmic maturation.

Animals↗
PubMed1983

Endocrine profiles and egg quality in the superovulated cow.

Plasma progesterone- and LH concentrations were studied in lactating dairy cows around the superovulatory heat. The pattern of both hormones accurately reflected the donor animals' endocrine balance and could be used to evaluate and predict the subsequent potentials or quality of a given animal as embryo- and oocyte donor. It was the general impression that both PMSG- and FSH treatment caused endocrine changes in progesterone- and LH patterns that would account for improper oocyte- and embryo development.

Animals↗
PubMedDate not supplied

In vivo versus in vitro produced bovine ova: similarities and differences relevant for practical application.

This present review describes some differences and similarities between bovine embryos produced in vivo and in vitro. The first part outlines the respective environments during maturation, fertilisation and early embryonic development of the two types of embryos and compares their morphological, biochemical and genomic characteristics. Results from comparative studies on embryo metabolism and gene expression reveal that most parameters are similar, but some significant differences of presumptive importance for normal development have been described. Morphologic and kinetic differences between in vitro and in vivo produced embryos are also well documented. However, improved culture conditions have been reported to minimise the differences. The second part focuses on the practical consequences of the differences in relation to embryo selection, cryopreservation, sanitary risks and pregnancy following transfer as well as normality of calves. Lower viability following transfer and increased susceptibility to cryopreservation of in vitro produced embryos is discussed. Finally and most importantly, reported evidence of increased sanitary risks and abnormal foetal development associated with in vitro produced embryos is presented.

Animals↗
PubMedDate not supplied

Rendez-vous in the oviduct: implications for superovulation and embryo transfer.

The meeting between the maternal and paternal gametes is dependant upon a number of complicated processes. On the maternal side it involves maturation of the oocytes under the influence on both peripheral and follicular endocrine factors. Deviations in the normal pattern of maturation will lead to ovulation of inferior oocytes. On the paternal side the transport of spermatozoa in the female genital tract following mating is an area of great importance. The establishment of the sperm reservoir in the isthmus is dependant upon a number of factors (intracellular calcium concentrations, oligo-saccharides, change in estradiol: progesterone ratio in the afferent blood supply). Alterations of the normal micro-environment may disturb both binding, release and transport as a whole. The process of fertilization occurs in the ampullar region of the oviduct and it involves several well tuned steps: binding to the zona pellucida where the acrosome reaction takes place, penetration, fusion between the oolemma and the sperm plasma membrane, activation with the release of the cortical granules, decondensation of the sperm chromatin, pronucleus formation and finally syngamy where the two pronuclei fuses. The egg will experience the first cleavage shortly thereafter. Superovulation may disturb a number of these processes including oocyte maturation (arrest at MI) and sperm and zygote transport in the oviduct caused by the deviant endocrine environment, thus leading to a higher incidence of lack of fertilization and poor embryos quality.

Acrosome Reaction↗