PubMed Health⌕ Search

Biomedical subjects

A-R Günzel-Apel

Publications and source records attributed to A-R Günzel-Apel.

10 recordsLinked to original sources
PubMed2006

Concentrations of progesterone, prolactin and relaxin in the luteal phase and pregnancy in normal and short-cycling German Shepherd dogs.

Twenty-two nonpregnant and 19 pregnant German Shepherd dogs were assigned to either a control group or a suspected short-cycling group, based on the interestrous interval (> or = 6 month and < 5 month, respectively) and data from previous pregnancies. Blood serum concentrations of progesterone and prolactin were determined from days 5 to 60 (day 0 = ovulation) for characterization of luteal function. In pregnant bitches, placental integrity was additionally assessed by relaxin concentrations. The nonpregnant, suspected short-cycling bitches had significantly lower progesterone concentrations than the controls, indicating decreased luteal activity both in the autonomous and prolactin-dependent period. In the pregnant suspected short-cycling bitches, unavoidable progesterone supplementation prevented assessment of luteal function; it may have suppressed prolactin secretion (significantly lower prolactin concentrations from days 20 to 60, compared with the pregnant control group), but deficient prolactin secretion affecting luteal function cannot be excluded. The significantly lower relaxin concentrations, together with a high incidence of embryonic death found in the pregnant, suspected short-cycling group, may indicate loss of placental integrity and may have caused decreased prolactin concentrations.

Animals↗
PubMed2006

Morphology of canine placental sites after induced embryonic or fetal death.

Although spontaneous and medically induced canine embryonic or fetal death and "resorption" are clinically well documented, morphological studies of these processes are still missing. The objective of this study was therefore a detailed morphological investigation of canine placental sites after embryonic or fetal death. In five pregnant beagle bitches, embryonic or fetal death was induced by cloprostenol and cabergoline or by aglepristone. Two dogs served as untreated controls. Between Days 30 and 33 of gestation, the bitches were ovariohysterectomized, placental sites were fixed and examined by different methods. Morphological features of placental sites after both treatments were similar, finally leading to a complete disappearance of the placental labyrinth. Although there was an increase in the number of cells in the glandular chambers (superficial endometrial glands) expressing lysozyme after induced fetal death, signs of phagocytosis were absent in these cells, and no increased infiltration of maternal stroma by macrophages (compared to normal placental sites at the same time of gestation) occurred. We inferred that fetal and placental tissues were lysed, but no phagocytosis by genuine or "functional" macrophages was detectable. Further investigations are needed for a more detailed understanding of the morphological processes occurring after embryonic or fetal death in the dog.

Animals↗
PubMed2006

Influence of cooling rates and addition of Equex pasta on cooled and frozen-thawed semen of generic gray (Canis lupus) and Mexican gray wolves (C. l. baileyi).

A current priority for the preservation of the endangered Mexican gray wolf (Canis lupus baileyi) is the development of a sperm-based genome resource bank for subsequent use in artificial insemination. To optimize the quality of cryopreserved sperm, the procedures involved in processing semen before and during freezing need to be improved. The aim of this study were to examine the effects of: (i) different cooling periods before freezing and (ii) addition of Equex pasta (Minitüb, Tübingen, Germany) on the characteristics of sperm from the generic gray wolf and the Mexican gray wolf after cooling and cryopreservation. For Mexican wolf sperm, cooling for 0.5 and 1.0 h had a less detrimental effect on cell morphology than cooling for 2.5 h, whereas the slower cooling rate (2.5 h) had a less detrimental effect on functional parameters and seemed to cause less damage to plasma membrane and acrosome integrity than 0.5 and 1.0 h. For the generic gray wolf, cooling semen for 2.5 h had less detrimental effect on plasma membrane integrity and viability; together with the 0.5 h cooling time, it yielded the highest percentages of intact acrosomes. As previously shown in the domestic dog, Equex pasta had no beneficial effect on sperm characteristics in either wolf species.

Acrosome↗
PubMed2005

Effects of the dopamine agonist cabergoline on the pulsatile and TRH-induced secretion of prolactin, LH, and testosterone in male beagle dogs.

In the present study, the pulsatile serum profiles of prolactin, LH and testosterone were investigated in eight clinically healthy fertile male beagles of one to six years of age. Serum hormone concentrations were determined in blood samples collected at 15 min intervals over a period of 6 h before (control) and six days before the end of a four weeks treatment with the dopamine agonist cabergoline (5 microg kg(-1) bodyweight/day). In addition, the effect of cabergoline administration was investigated on thyrotropin-releasing hormone (TRH)-induced changes in the serum concentrations of these hormones. In all eight dogs, the serum prolactin concentrations (mean 3.0 +/- 0.3 ng ml(-1)) were on a relatively constant level not showing any pulsatility, while the secretion patterns of LH and testosterone were characterised by several hormone pulses. Cabergoline administration caused a minor but significant reduction of the mean prolactin concentration (2.9 +/- 0.2 ng ml(-1), p < 0.05) and did not affect the secretion of LH (mean 4.6 +/- 1.3 ng ml(-1) versus 4.4 +/- 1.7 ng ml(-1)) or testosterone (2.5 +/- 0.9 ng ml(-1) versus 2.4 +/- 1.2 ng ml(-1)). Under control conditions, a significant prolactin release was induced by intravenous TRH administration (before TRH: 3.8 +/- 0.9 ng ml(-1), 20 min after TRH: 9.1 +/- 5.9 ng ml(-1)) demonstrating the role of TRH as potent prolactin releasing factor. This prolactin increase was almost completely suppressed under cabergoline medication (before TRH: 3.0 +/- 0.2 ng ml(-1), 20 min after TRH: 3.3 +/- 0.5 ng ml(-1)). The concentrations of LH and testosterone were not affected by TRH administration. The results of these studies suggest that dopamine agonists mainly affect suprabasal secretion of prolactin in the dog.

Administration, Oral↗
PubMed2005

Volume regulatory function and sperm membrane dynamics as parameters for evaluating cryoprotective efficiency of a freezing extender.

In the past years a series of functional assays has been developed to determine the structural, morphological and functional integrity of the plasma membrane and sperm acrosomal membrane. Cell volume regulation is an important physiological function crucial for the success of cryopreservation. In this study, the effects induced by freezing-thawing were judged by evaluating the functional characteristics of frozen-thawed semen samples submitted to secondary stress such as osmotic challenge or incubation under capacitating conditions, following cryopreservation. Prior to freezing, dog semen samples were diluted in the presence or absence of Equex STM Paste, which contains sodium dodecyl sulphate (SDS) as the active ingredient. Cell volume regulation and capacitation and calcium ionophore-induced membrane dynamics were assessed in freshly diluted and frozen-thawed semen samples by electronic volume measurement and flow cytometry. Cryopreservation led to a disturbance of the volume regulatory function and to a rapid decrease in the proportion of acrosome-reacted live spermaotozoa. Extender containing Equex STM Paste had a protective effect on isotonic cell volume, on regulatory function under hypertonic conditions, and on the proportion of live acrosome-reacted cells. The evaluation of the functional state of sperm submitted to secondary stress after freezing-thawing leads to a more subtle characterization of sperm function and helps improve the cryoprotective efficiency of the extender.

Acrosome↗
PubMed2004

Role of potassium channels, the sodium-potassium pump and the cytoskeleton in the control of dog sperm volume.

Response to osmotic shock is an important aspect of mammalian sperm physiology. In this study we recorded volume changes of dog spermatozoa at 39, 33, and 25 degrees C under isotonic conditions and following hypotonic shock. Cell volume measurements were performed electronically in saline solutions of 300 and 150 mOsmol kg(-1), and Percoll-washed preparations were compared with unwashed samples. The involvement of potassium channels in volume control was tested by treatment with quinine, while the involvement of the plasma membrane Na(+)-K+ pump was tested by treatment with ouabain. The role of the cytoskeleton was investigated by treatment with colchicine and cytochalasin D. The number of cell populations observed varied with temperature and tonicity. In both types of sperm preparations, between two and three populations were present under isotonic conditions at 25 degrees C whereas at 39 and 33 degrees C only one population was detected. Hypotonic stress at the higher temperatures caused the single population to swell, whereas at 25 degrees C it resulted in a population of cells whose modal volume was similar to that of the middle isotonic sub-population. Both quinine and the cytoskeletal inhibitors markedly increased swelling both under hypotonic conditions at 39 degrees C and under isotonic conditions at 25 degrees C. However, little or no effect of ouabain was observed. We conclude that in dog spermatozoa swelling in response to hypotonic conditions is minimised through the activity of potassium channels and the presence of an intact cytoskeletal network. Under isotonic conditions at 25 degrees C, a considerable proportion of the sperm population is already swollen; this swelling varies between individual males and appears to be due to lowered cytoskeletal and potassium channel activity.

Animals↗
PubMed2004

Kinetics of protein tyrosine phosphorylation in sperm selected by binding to homologous and heterologous oviductal explants: how specific is the regulation by the oviduct?

Essential steps of the capacitation process take place in the oviductal isthmus. A crucial step in the process of capacitation is the phosphorylation of membrane proteins. The aims of this work were (1) to study the effect of dog sperm binding to oviductal epithelium on tyrosine phosphorylation and (2) to investigate the specificity of regulation of molecular changes by the oviduct of different species by comparing the numbers of canine sperm bound to heterologous (porcine) and homologous epithelium, and the kinetics of tyrosine phosphorylation. Semen was collected from four healthy dogs and washed through a Percoll gradient. Explants, small pieces of epithelium, were cut from porcine and estrous bitch oviducts. During 6 h of coincubation in Tyrode medium, the numbers of bound sperm were counted by microvideographic observation, and the state of tyrosine phosphorylation was determined immunocytochemically after 3, 30, 90, 180 and 360 min. Canine sperm bound in similar numbers to homologous and heterologous explants. Increasing tyrosine phosphorylation of tail proteins and subsequent phosphorylation of sperm head proteins were observed. Binding occurred mainly in sperm with non-phosphorylated heads (approximately 2% phosphorylated), while higher proportions of head-phosphorylated cells were found in unbound populations (approximately 40-60%;P<0.05). The head phosphorylation progressed significantly during incubation in unbound spermatozoa (P<0.05), while it was suppressed in bound suspensions. The rate of tyrosine phosphorylation of sperm tail proteins was higher in cells bound to explants than in unbound cells or in those incubated in control medium. There were no significant differences with respect to the kinetics of tyrosine phosphorylation between the two coincubation systems. These observations support the hypothesis that spermatozoa with non-phosphorylated heads preferentially attach to epithelial cells. Tyrosine phosphorylation of sperm head proteins and capacitation are delayed in spermatozoa in close contact with oviductal epithelium. This mechanism appears to be species-independent, as sperm bound similarly to pig and dog oviduct explants, and similar phosphorylation kinetics were observed in both types of tissue.

Animals↗
PubMed2004

Morphological changes and proliferative activity in the oviductal epithelium during hormonally defined stages of the oestrous cycle in the bitch.

The aim of the present study was to investigate morphological changes and proliferative activities in the epithelium of the canine oviduct with regard to the part of the oviduct - possibly indicating the existence of a locally restricted sperm reservoir - and the stage of the oestrous cycle. Nine healthy adult nulliparous bitches were submitted to ovariohysterectomy at three stages of the cycle: anoestrus (n = 3), late follicular phase (n = 3) and mid-luteal phase (n = 3). The whole oviduct ranging from the utero-tubal junction (UTJ) to the infundibulum (IN) was collected, divided into UTJ, IN plus six segments of equal length, i.e. eight oviductal specimens per animal were studied by light microscopy. Morphological characteristics of ovaries and endometrium were recorded macroscopically and verified histologically. The height of oviduct epithelial cells and percentage of ciliated cells (CC) were assessed and the respective data analysed statistically. Proliferative activity was immunohistochemically visualized by means of Ki-67 antigen detection. Blood was collected and concentrations of oestradiol-17beta and progesterone (P(4)) were measured. Within the IN and five of the six tissue samples collected from the ampulla and isthmus in anoestrous bitches, the oviductal surface epithelium consisted of low cuboidal cells demonstrating a uniform dark staining intensity. Only a very few scattered lighter staining CC could be detected. Under the influence of oestrogens during late follicular phase, the oviductal epithelium was highly differentiated. Lighter stained CC with apically located nuclei were easily distinguishable from basophilic secretory cells with apical cytoplasmic protrusions. Cell height and percentage of CC were significantly higher than in anoestrus (p <or= 0.05). During mid-luteal phase, high levels of P(4) were associated with differentiated and dedifferentiated cells as well as cells in regression seen in the mucosal folds of all samples. The percentage of CC and cell height were significantly lower than during late follicular phase (p <or= 0.05). Further signs of dedifferentiation consisted of a loss of cilia, a pinching off of the apical cytoplasm as well as the presence of debris and macrophages within the oviductal lumen. In the oviductal part of UTJ and the caudal isthmus hormone-dependent variations in cellular morphology were less distinct. Changes in cell height were minimal and did not differ significantly throughout the oestrous cycle. Hypertrophic cells with large nuclei were predominantly present at these sites, but did not consistently demonstrate signs of ciliation or secretion. Sporadic proliferating activity, visualized by means of Ki-67 antigen, was mainly seen in some cells of the late follicular phase samples. Thus, overall proliferative activity is generally very low or may occur within a relatively short period of time. It therefore cannot be excluded, that periods exhibiting higher mitotic rates are not included in the present study. It should, however, be mentioned that cells demonstrating morphological signs of apoptosis can only be seen very sporadically within a few specimens during mid-luteal phase, thus, reflecting low proliferative capacities and minimal cellular turnover found during this study. The results of the present study strongly indicate that oestrogens cause hypertrophy and differentiation, whereas P(4) induces gradual dedifferentiation or regression of the oviductal epithelium. Furthermore, they reveal clearly visible changes in the morphology of the tubal epithelium during the oestrous cycle. Depending on the tubal segment, these are, however, variably expressed. Whether the low degree of cellular variation of the UTJ and caudal isthmus is caused by specific hormone concentrations at these sites or specific regulatory mechanisms and may be associated with specific functional properties such as the formation of a locally restricted sperm reservoir needs further investigations.

Animals↗
PubMed2003

Seeking mathematical strategies in sperm function analysis: between scylla and charybdis?

During the last decades, essential progresses in reproductive biotechnology were achieved, implying development of special spermatological techniques. The major problem was to set up simple, rapid, precise and adequate evaluation methods. The key aspect to be considered in all assays of sperm fertilizing function is capacitation. As not all spermatozoa respond to fertilizing conditions in a similar manner, it seems to be logical to assess samples via their response to these specific conditions. For the spermatological practice, the sensitivity of methodology for assessment and analysis of data with respect to differences in individual response, in heterogeneity of the population, and proper temporal characterization of the response is crucial for the improvement of evaluation procedures. Currently, most used statistical analytical tools in spermatology do not always fulfil these essential sensitivity requirements. We structured our paper concerning different fields of mathematical science (distribution analysis, fractal geometry, functional approximation and differentiation) related to the modern insights in sperm function analysis. The spectrum of methods we are going to review in this paper is restricted to basic ideas to illustrate how the accuracy and sensitivity of sperm evaluation assays may be improved by applying adequate elementary tools of the mathematical analysis.

Animals↗