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Biomedical subjects

R Thun

Publications and source records attributed to R Thun.

At least 19 recordsLinked to original sources
PubMed2004

Sensitive fluorimetric method based on sequential injection analysis technique used for dissolution studies and quality control of prazosin hydrochloride in tablets.

This report introduces a fully automated flow system for drug-dissolution studies based on the coupling of the sequential injection analysis (SIA) technique with a conventional dissolution apparatus. The methodology described was used for monitoring of dissolution profiles of prazosin hydrochloride (PRH) in pharmaceutical formulation. The very sensitive fluorimetric detection of PRH was performed at lambda(ex)=244 nm (lambda(em)>or=389 nm). Under the optimal conditions, the calibration curve was linear over the range 0.02-2.43 mg x l(-1) of PRH with R.S.D. 1.89, 1.23, and 1.80% (n=10) when determining 0.02, 1.22, and 2.43 mg x l(-1) of PRH in standard solutions, respectively. Equation of the calibration curve was calculated giving the following values: F=4.108 c-3.9 (n=6), r=0.9996. Detection limit was calculated 0.007 mg x l(-1) of PRH. The dissolution test of Deprazolin tablets was programmed for 60 min, with a continuous sampling rate of 70 h(-1) under conditions required by USP 26. Results obtained by SIA technique compared well with HPLC standard method.

Chromatography, High Pressure Liquid↗
PubMed2004

[Suppression of cycling activity in sheep using parenteral progestagen treatment].

The objective of this study was to evaluate the effect of two synthetic progestagen preparations Chlormadinone acetate (CAP, Chronosyn, Veterinaria AG Zürich) and Medroxyprogesterone acetate (MPA, Nadigest, G Streuli & Co. Uznach) on cycling activity and fertility in sheep. A flock of 28 non pregnant white alpine sheep was randomly divided into three groups, A (n = 10), B (n = 9) and C (n = 9). During a period of 4 weeks the cycling activity was confirmed by blood progesterone analysis. Thereafter, the animals of group A were treated with 50 mg CAP, those of group B with 140 mg MPA and those of group C with physiological saline solution. All injections were given intramuscularly. Suppression of endogenous progesterone secretion lasted from 28 to 49 days (mean = 39 days) in group A and from 42 to 70 days (mean = 50 days) in group B. The synchronization effect of both preparations was unsatisfactory as the occurrence of first estrus was distributed over a period of 3 weeks in group A and 4 weeks in group B. These findings could also be confirmed by the lambing period which lasted 52 days in group A and 36 days in group B. Control animals lambed within 9 days due to the synchronizing effect of the ram. The first fertile estrus was observed 36 days (group A) and 45 days (group B) after the treatment. In group A all 10 animals and in groups B and C 8 of 9 ewes each became pregnant. Parenteral progestagen application with CAP and MPA is a simple, safe and reversible method of estrus suppression in the sheep. The minimal suppressive duration of 4 (CAP) and 5 weeks (MPA) is not sufficient when a period of 3 months (alpine pasture period) is desired.

Animals↗
PubMed2004

[Body condition and frequency of ovarian cysts in Brown Swiss cows during the first 40 days of lactation].

For this investigation 50 Brown Swiss cows from 21 different farms were used. Twenty-five peripartal overconditioned cows (back fat thickness > 38 mm) were compared with 25 peripartal not overconditioned animals (back fat thickness < 38 mm). On days 20, 30 and 40 post partum the ovaries were examined sonographically and 10, 15, 20, 30 and 40 days after calving plasma concentrations of progesterone and 17-beta estradiol were determined. In peripartal overconditioned animals 12 ovarian cysts were found while only one cyst was present in not overconditioned cows (P < 0.05). At first examination all ovarian cysts were classified by ultrasound as follicle theca cysts (progesterone < 0.5 ng/ml plasma). Follow examinations resulted in 3 cysts which persisted as theca cysts while 8 cysts became luteinized and 2 cysts completely regressed. There was no indication of increased plasma progesterone and/or estradiol concentrations in overconditioned cows with higher fat deposit before of ovarian cysts had occurred.

Adipose Tissue↗
PubMed2004

[The influence of centrifugation on quality and freezability of stallion semen].

The aim of the present study was to investigate the influence of various centrifugation methods on sperm loss and quality of frozen-thawed semen. From at a total of 8 Warmblood stallions of the National Stud Farm in Avenches, 3 ejaculates each were collected and seminal plasma was removed using 3 different centrifugation regimes. In method I (reference method) centrifugation occurred by a speed of 600 x g during 10 minutes. In method II 1000 x g was used during 2 minutes while in method III centrifugation was performed by 2000 x g during 2 minutes. After centrifugation 90%, of the supernatant was removed and sperm loss calculated. After resuspension of the pellet with freezing medium, functional membrane integrity was evaluated by HOS-test and motility determined. In frozen-thawed semen motility, viability as well as functional membrane integrity (HOS-test) and acrosome status using chlortetracyclinassay (CTA) were assessed. Our results demonstrate that mean sperm loss (I, 1.9%; II, 8.7%; III, 3.7%) was significantly (P < 0.05) different between the three centrifugation regimes. Regarding semen quality of frozen-thawed semen, HOS in method III (52.1%) was significantly lower than in methods I (55.5%) and II (55.3%). Evaluation of the acrosome status by CTA showed that more than 70% of sperm cells were capacitated and 25% capacitated and acrosome reacted. From our results we conclude that sperm loss and functional membrane integrity (HOS-test) in frozen-thawed semen were significantly influenced by the centrifugation regime. Therefore, stallion semen should be centrifuged at 600 x g during 10 minutes before freezing in order to obtain low sperm loss and a good quality of frozen-thawed semen.

Acrosome↗
PubMed2003

Seasonal changes of semen quality and freezability in Franches-Montagnes stallions.

The objective of this study was to investigate seasonal changes of semen quality parameters in Franches-Montagnes stallions and to compare the freezability of ejaculates collected in autumn and winter. Experiments were performed using 15 stallions from the National Stud Farm in Avenches (Switzerland). Ejaculates were collected and evaluated every month during 1 year as well as cryopreserved in autumn and winter (September to February). In fresh semen the gel-free volume, concentration, motility and morphology (normal sperm, major defects, vacuoles and acrosome defects) were evaluated and in frozen-thawed semen the motility as well as the viability (SYBR-14/PI) were performed. To analyse seasonal differences four periods of 3 months each were defined as autumn (September, October, November), winter (December, January, February), spring (March, April, May) and summer (June, July, August). During the 1-year experiment all fresh semen quality parameters demonstrated a clear seasonal and individual pattern. The gel-free volume was significantly (P<0.05) higher in spring and summer compared to autumn and winter while sperm concentration was significantly (P<0.05) lower in spring than at any other time of the year. Total sperm number was significantly (P<0.05) higher and sperm motility significantly (P<0.05) lower in summer than in other seasons. Regarding sperm morphology, normal sperm was significantly (P<0.05) higher in autumn than in winter and summer and major defects were lowest (P<0.05) in autumn. In frozen-thawed semen motility was significantly (P<0.05) improved in the ejaculates collected in autumn compared to winter, while viability showed no obvious differences. Our results clearly demonstrate that individual and seasonal differences occurred in semen quality of Franches-Montagnes stallions. Ejaculates collected in autumn (September, October, November) demonstrated good quality, especially regarding sperm morphology, and were more suitable for cryopreservation because of better motility in frozen-thawed semen collected during autumn than in winter.

Animals↗
PubMed2003

Seasonal changes in semen quality and freezability in the Warmblood stallion.

The objective of this study was to investigate seasonal changes in stallion semen quality and to determine the best time for semen cryopreservation. Experiments were performed using 10 Warmblood stallions from the National Stud Farm in Avenches (Switzerland). Ejaculates were collected and frozen every other week during 1 year from January to December 1999. Volume, concentration, and motility, and the number of morphologically normal sperm and sperm with major defects (abnormal heads, acrosome defects, nuclear vacuoles, proximal droplets, abnormal midpieces) were evaluated. For all frozen-thawed semen samples motility as well as viability (SYBR-14/PI) was tested, and the hypoosmotic swelling test (HOS) was performed. To analyze seasonal differences 4 periods of 3 months each were defined: autumn (September, October, November), winter (December, January, February), spring (March, April, May) and summer (June, July, August). During the 1 year experiment all semen quality parameters showed a clear seasonal pattern. The volume, total sperm count and motility in fresh semen were significantly higher (P<0.05) in summer than in winter, while sperm concentration was significantly lower in summer compared to the other seasons. Regarding morphology, normal sperm was significantly lower (P<0.05) in summer than at any other time of the year and higher values (P<0.05) were found for major defects in summer than in spring and autumn. In frozen-thawed semen motility was significantly (P<0.05) improved in autumn when compared to spring and summer. Viability was lowest in summer and differed significantly (P<0.05) from other seasons. The HOS test revealed significantly more (P<0.05) membrane damaged spermatozoa in winter than in spring, summer and autumn. Our results demonstrate that in our climatic conditions clear seasonal differences occur in semen quality of fresh and frozen-thawed semen and that cryopreservation of stallion semen should preferably be performed in autumn.

Acrosome↗
PubMed2003

[The castration of male lambs by immunization against GnRH].

The objective of this study was to evaluate the effect of a GnRH-vaccine in the ram lamb. Experiments were performed using 20 male lambs, randomly divided into a test (GnRH-immunization) and control group (physiological NaCl-solution). At a body weight of 20 kg (age 2-3 months) and three weeks later, all animals of the test group received 2 ml of Improvac (CSL Limited, Parkville, Victoria, Australia). The body weight as well as the blood testosterone concentration were measured weekly for 16 weeks. Thereafter, blood samples for testosterone analysis were taken monthly in immunized lams only. After the booster injection testicular growth was suppressed and plasma testosterone remained at low values < 0.1 ng/ml for at least 12 weeks. The mean corresponding testosterone concentrations for the control lambs ranged between 0.1 and 0.9 ng/ml plasma. An increase of testosterone was observed in 8 of 10 immunized animals between 3 to 7 months after the booster dose. The control lambs showed a tendency for better growth rate than vaccinated animals, but the difference was not significant. Our results demonstrate that in prepubertal ram lambs two immunizations with Improvac, three weeks apart, can suppress testosterone secretion and testicular growth at least for three months after the booster injection. For a suppression of reproductive function longer than three months after the second vaccination, a third immunization is needed at this time or when testicular growth is beginning.

Animals↗
PubMed2002

[The transactional stress model for the animal keeper].

A health problem of an animal or a group of animals represents a potential stress situation for the animal keeper. In this article, the transactional stress model, which was developed in social psychology was applied on the animal keeper and shows, how he perceives the influence of animal care. If veterinary help is considered relevant, it may lead to an improved coping, which affects the health of the animal keeper and the animal as well. This viewpoint leads to a cycle, in which cause, success, coping and utility are closely linked together.

Animal Husbandry↗
PubMed2001

Semen characteristics after vasectomy in the ram.

The objective of this study was to monitor the changes in semen characteristics in vasectomized rams and to determine if infertility was present 14 days after vasectomy. Experiments were performed using five cross-breed rams, aged between 18 and 30 months. Semen was collected weekly by artificial vagina from 2 months before to 5 months after vasectomy. After sexual rest for 10 days, vasectomy was performed by the cranial midscrotal approach. In all ejaculates the volume, concentration, total sperm number, motility and morphology (normal spermatozoa, loose heads) were determined and sperm viability (SYBR-14/PI) was evaluated in all semen samples collected after vasectomy. In the first ejaculate obtained 14 days post vasectomy all rams showed a significant (P < 0.05) drop in mean volume (from 1.2 to 0.5 mL), total sperm count (from 5176.8 to 51.1 x 10(6)) and morphologically normal sperm (from 84.1 to 15.7%), when compared to the last prevasectomy collection. We could also demonstrate a positive correlation (r = 0.89) between the individual cumulative total number of spermatozoa after vasectomy and the scrotal circumference measured before vasectomy. Sperm motility and viability could never be demonstrated after vasectomy and normal spermatozoa continuously decreased concomitant with an increase in loose heads. On post mortem examination 5 months after surgery, spermatocele formation and multiple sperm granulomas were present in all five rams. Our results show that in the first ejaculate collected by artificial vagina 14 days after vasectomy, no motile and viable spermatozoa could be detected. Despite weekly collections during a 5-month period after sterilization, azoospermia could never be achieved.

Animals↗
PubMed2001

Influence of Eqvalan (ivermectin) on quality and freezability of stallion semen.

The objective of this study was to evaluate the effect of Eqvalan (ivermectin) on stallion semen quality and freezability. Experiments were performed using 22 Freiberger stallions, randomly divided into a control and test group. Semen was collected once a week for 17 weeks from October 1997 to February 1998. Eqvalan was given orally to all stallions of the test group at a therapeutic dose of 0.2 mg ivermectin/kg. Besides measuring the scrotal width, ejaculates were collected to determine the volume, concentration, and the motility and morphology (normal sperm, major defects, vacuoles and acrosome defects). In addition, the motility and viability (fluorescence staining with propidium iodide/SYBR-14) were tested in all frozen-thawed semen samples. During the experimental period, stallions treated with Eqvalan had significantly better concentration (P < 0.0001) and motility (P < 0.0001) in fresh semen compared to control animals. After freezing-thawing, the motility (P < 0.0001) and viability (P = 0.0003) of semen also increased significantly for treated stallions. Regarding morphology, normal sperm (P < 0.0001), major defects (P = 0.0027) and vacuoles (P = 0.0236) were significantly better in the Eqvalan group. In addition to group differences we also observed a time effect on morphological parameters as shown by a decrease of normal sperm and an increase of major defects in both groups during the experiment. Our results demonstrate that a single oral application of Eqvalan did not negatively influence the quality and freezability of stallion semen in the nonbreeding season. Rather, it seems that Eqvalan has a favorable effect on stallion fertility as most sperm parameters examined were significantly improved in treated animals compared to control.

Animals↗
PubMed2001

[Hydrosalpinx in a goat].

A two year old Swiss Alpine goat was referred to our clinic because of sterility. Ultrasound examination revealed a nonechogenic area cranially to the urinary bladder. As hydrometra was suspected, the goat was treated repeatedly with PGF2 alpha. Success of this therapy, however, was unsatisfactory and estrus was therefore induced by progesterone in combination with eCG and the goat mated. As conception failed and ultrasonography remained unchanged, laparoscopy was performed and a fluid filled structure could be located in the region of the right oviduct. After ovariohysterectomy and histo-pathological examination of the genital organs hydrosalpinx was diagnosed on both sides.

Animals↗
PubMed2000

Characterisation of the enzymatic 4-O-acetylation of sialic acids in microsomes from equine submandibular glands.

Microsomes prepared from equine submandibular glands and incubated with tritium-labelled AcCoA incorporated acid-insoluble radioactivity in a manner dependent on time, protein, membrane integrity and AcCoA concentration, with incorporation being optimal at 37 degrees C and pH 6.6. Under the experimental conditions used a K(M) of 32.1 microM for AcCoA and a V(max) of 1.2 pmol/mg protein x min was obtained. The incorporation of acid-insoluble radioactivity was also inhibited by CoA in a competitive manner (K(i)=240 microM), as well as by para-chloromercuribenzoate, 3'-dephospho-CoA, 5'-IDP, 5'-ADP, beta-NAD and 4,4'-diisothiocyanatostilbene-2,2'-disulfonate. We demonstrate here that this incorporation of radioactivity into endogenous sialic acid is due to the action of an AcCoA:sialate-4-O-acetyltransferase [EC 2.3.1.44]. Radio thin-layer chromatography analyses of propionic acid-released sialic acids showed that the incorporation of radioactivity correlated with the formation of a radiolabelled species that co-migrated with authentic Neu4,5Ac2. Saponification experiments using NaOH, mouse hepatitis virus strain S and Influenza C/JJ/50 virus also showed that the transfer of [3H]acetyl groups from [3H]AcCoA to endogenous sialic acid acceptors was occurring exclusively at carbon 4 of the pyranose ring.

Acetyl Coenzyme A↗
PubMed2000

[Bovine herpes mammillitis: clinical symptoms and serologic course].

Bovine herpes mammillitis was diagnosed in a dairy herd with udder and teat skin lesions. Clinical symptoms seen in 6 cows consisted of round dry areas at the teats as well as large red and painful areas with crust formation at the teats, the teat basis and the udder. Diagnosis was verified by demonstrating numerous virus particles with the typical herpes structure and by BHV-2 serum neutralization test. Prevalence of BHV-2 in the herd was determined by using BHV-2 SNT at 7 occasions during a period of 15 months. The relatively low BHV-2 SNT-titres as well as the seasonal increase of BHV-2 titres and seroprevalence in the month of September were indicative of a chronic and latent BHV-2 infection in the herd.

Animals↗
PubMed1996

[Relationship between cortisol and testosterone during resting conditions, after acute stress and hormone stimulation in steers].

In this study the relationship between peripheral concentrations of cortisol and testosterone was investigated in 7 adult bulls under resting conditions as well as after sexual and hormonal stimulation. The animals were kept under natural photoperiods of 16L:8D and for hormone determinations blood was withdrawn from an indwelling jugular vein catheter every 30 minutes for 24 and 48 h, respectively. Evaluation of the hormonal profiles revealed that both steroids are secreted episodically characterized by irregular, short term fluctuations with high individual variability. A clear circadian rhythm with high levels in the morning and during the day and low concentrations in the evening and during night was observed for cortisol only. Concentrations of both steroidal hormones were not significantly correlated with each other. Intense sexual stimulation (mounting several times with ejaculation) during 30 minutes caused a rapid increase of cortisol without affecting testosterone secretion. After intravenous application of 1500 IU hCG and 0.5 mg GnRH a sharp rise of testosterone concentrations occurred with high values remaining for several hours but leaving the circadian cortisol pattern unchanged. The intravenous injection of 5 mg PGF2 alpha stimulated both the cortisol and testosterone secretion. Results from this investigation show that cortisol and testosterone are secreted episodically without any interrelationship under resting conditions. Sexual stress induced an increase of cortisol which did not inhibit testosterone secretion and high testosterone levels did neither influence the cortisol pattern. The concomitant increase of cortisol and testosterone after PGF2 alpha suggests a central (hypothalamus/hypophysis) action for prostaglandin.

Animals↗
PubMed1996

[Measurement of stress parameters in farm animals using active telemetry].

We investigated the effect of an acute stressor on body temperature and heart rate in cows. Both parameters were recorded by active telemetry. For the experiments, five cyclic Brown Swiss cows were used, each of them exposed to an acute stressor during estrus and the luteal phase of the cycle. The stressor consisted in restraining the cows in a crush for hoof treatments. During the 2-hour stress period and for additional 6 hours, body temperature and heart rate were measured every 10 minutes. Control animals remained in their accustomed environment during the whole experiment of 8 hours. The course of body temperature and heart rate was clearly influenced by the stressor. While heart rate was maximal already at the beginning of the stress period, the body temperature showed highest values only one hour after stress and then continuously decreased. Changes in body temperature and heart rate under stress differed significantly from the values of control animals. Both parameters are reliable indicators of stress in the bovine species. The transmitters used in this investigation allowed us to register exact data without manipulation of the animal, which could possibly falsify the results. This advantage as well as the functional longevity of the transmitters (ca. 6 months) make active telemetry a useful tool for stress research in farm animals.

Animals↗
PubMed1996

[Gynecomastia in a goat buck].

A 3-year old horned buck of the Toggenburger breed was referred to our clinic with signs of gynecomastia. Cytogenetic abnormalities could not be detected in the karyogram and compared to control animals the buck had normal plasma concentrations of testosterone and estradiol but not prolactin. Hyperprolactinemia has been considered the cause of gynecomastia leaving the semen quality undisturbed.

Animals↗
PubMed1995

Influence of endometrial cysts on conception rate of mares.

A total of 259 normally fertile mares were examined gynecologically by means of rectal palpation and ultrasonography in order to record the presence of uterine cysts and pregnancy. The incidence of endometrial cysts was 22.4%. Of the 95 cysts observed during the trial, 87.4% were located in the middle and posterior segments of both uterine horns. The size of all endometrial cysts ranged between 3 and 48 mm. When all mares were assigned to three age groups, A < 7 years (n = 116), B 7-14 years (n = 117) and C > 14 years (n = 26), a significant (P < 0.01) increase in the number of endometrial cysts was observed with advancing age (4.3%, 29.1% and 73.1%, respectively). The pregnancy rates at Days 14 and 40 were significantly (P < 0.01) lower in mares with cysts (77.6% and 71.4%) compared to mares without cysts (91.5% and 88.0%). This suggests that the presence of uterine cysts plays an important role in the reduction of fertility of Thoroughbred mares.

Animals↗