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Biomedical subjects

C J Wensing

Publications and source records attributed to C J Wensing.

At least 37 records · Page 2Linked to original sources
PubMed1988

Investigations of arterio-venous anastomoses in the spermatic cords and blood supply, oxygen consumption and testosterone production of scrotal and abdominal testes in the pig.

This study has investigated blood flow from the testicular artery to the pampiniform plexus in the spermatic cord of pigs. Testosterone levels, oxygen tension and the degree of acidity were measured in arterial and venous blood vessels of scrotally and abdominally located testes. Haemoglobin oxygen saturation was derived from the oxygen dissociation curve. Blood flow to abdominal and scrotal testes and epididymides was measured using the radioactive microsphere technique. Average blood flow to the scrotal testes and epididymides was 21 and 8 ml/min, respectively, in normal pigs. In unilaterally cryptorchid pigs average blood flow to the scrotal testis and epididymis was 23 and 6 ml/min, respectively, and to the abdominal testis and epididymis 4.2 and 1 ml/min. In pigs with bilateral scrotal testes oxygen consumption was 16 mumol O2/min/100 g. In unilaterally cryptorchid pigs oxygen consumption by the scrotal testis was 18 mumol O2/min/100 g, compared with 10 mumol O2/min/100 g by cryptorchid testes. From the percentage oxygen saturation in the various blood vessels it was calculated that 29-42% of testicular arterial blood was flowing through arteriovenous anastomoses between the testicular artery and the pampiniform plexus in the spermatic cord, thus bypassing the capillary net of the abdominal testes of unilaterally and bilaterally cryptorchid pigs. These results were supported by the testosterone measurements. In the spermatic cord of scrotal testes no blood bypassed the capillary net of the testes.

Animals↗
PubMed1988

The embryology of testicular descent.

A description is given of the role of the gubernaculum testis in the migration of the testis from the intra-abdominal to the scrotal position. The morphological differences in the process between carnivores, ungulates and man on the one hand and rodents on the other are stressed. The importance of gubernacular outgrowth, gubernacular regression as well as the importance of intra-abdominal pressure is emphasized. The effects of some forms of abnormal gubernacular development on testicular descent are described. The hormonal factors possibly involved in the regulation of the gubernacular reaction are evaluated. LH-RH, gonadotropins, AMH and testosterone seem not to be responsible for gubernacular outgrowth but a low molecular weight fraction of a fetal testicular extract, called descendin, is stimulatory to gubernacular cells. There are indications that testosterone plays a role in the initiation of gubernacular regression.

Animals↗
PubMed1988

In vitro model of the first phase of testicular descent: identification of a low molecular weight factor from fetal testis involved in proliferation of gubernaculum testis cells and distinct from specified polypeptide growth factors and fetal gonadal hormones.

The gubernaculum testis is the connective tissue organ that causes the testis to descend. How the process of testicular descent is regulated is not fully understood. Current hypotheses postulate that a nonandrogenic fetal testicular factor controls the first phase of descent, that is characterized by growth of the gubernaculum and transabdominal migration of the testis. When gonadal extracts from fetuses with ages corresponding to the first phase of testicular descent (50, 60, and 75 days) were tested on gubernacular cells, the growth stimulatory effect of testicular extracts exceeded the effect of both ovarian extract and fetal calf serum. Gonadal extracts from 80-, 90-, and 100-day-old fetuses showed only a minor sex difference. No sex difference or age-dependent changes were detected when fetal gonadal extracts were tested on murine 3T3 cells. Polypeptide growth factors (epidermal growth factor, insulin, fibroblast growth factor, platelet-derived growth factor, and transforming growth factor-beta) were tested for growth stimulatory activity and had only minor effects on gubernaculum cells. Fetal testicular hormones (anti-Müllerian hormone, inhibin, and androgenic steroids) did not induce initiation of DNA synthesis at concentrations that are highly bioactive in typical target systems. When testicular samples were dialyzed, the high mol wt fraction (greater than 3500) had lower growth stimulatory activity in gubernaculum cells, but not 3T3 cells. Bioactivity of ovarian extracts and fetal calf serum was not diminished after dialysis. The low mol wt fraction (less than 3500) of testicular extract was distinctly stimulatory to gubernaculum cells but not 3T3 cells, and the low mol wt fraction of ovarian extracts did not stimulate growth in either cell type. It was concluded that the fetal porcine testis during the first phase of testicular descent contains low mol wt factor(s) to which gubernaculum cells and not 3T3 cells are responsive. The bioactive fraction probably contains the factor(s) that initiate testicular descent. We suggest the name descendin for this new activity.

Androgens↗
PubMed1988

Reduction of testicular blood flow and focal degeneration of tissue in the rat after administration of human chorionic gonadotrophin.

The effect of 100 IU human chorionic gonadotrophin (hCG) on testicular capillary blood flow was studied in adult male rats using a 133Xe clearance method and a radioactive microsphere technique. To investigate the role of Leydig cells in regulation of testicular blood flow after treatment with hCG, rats were pretreated with ethane dimethylsulphonate (EDS) which selectively destroys mature Leydig cells. Six hours after treatment with hCG, testicular blood flow decreased in control and hypophysectomized rats to 25-50% of normal values, but not in EDS-pretreated animals. Prostaglandin E2 levels were also determined 6 h after an injection of hCG. A 300-fold increase in the concentration of prostaglandin E2 occurred in normal testis tissue. This rise was markedly inhibited if EDS was given 3 days before administration of hCG. Furthermore, 6 h after administration of hCG, the filling of the testicular capillary bed with methylacrylate was decreased, while in control rats and rats treated with EDS and hCG, complete filling of the capillaries was seen. Cell degeneration in some subcapsular seminiferous tubules was observed 6-10 days after treatment with hCG. The results suggest that the hCG-induced precapillary vasoconstriction, probably mediated (in part) by prostaglandins, causes reduction in testicular blood flow 6 h after administration of hCG, and may result in cell damage.

Animals↗
PubMed1988

Chronic GnRH administration in prepubertal male pigs. A model to evaluate the effects of GnRH treatment in cryptorchidism.

The effect of chronic pulsatile low-dose GnRH treatment on the juvenile testis and associated structures was evaluated in relation to hormonal parameters in the peripheral blood in the pig. Starting at 8 weeks of age, male pigs (crossbreds of Dutch Landrace and Yorkshire breeds) were injected 6 times daily im with 0, 75 or 250 ng GnRH/kg body weight during 4 weeks. Immediately after the treatment period, a GnRH stimulation test with 750 ng GnRH/kg iv was carried out. Samples for plasma LH, FSH, testosterone and 5 alpha DHT measurement were obtained weekly (basal level) and after GnRH stimulation. The pigs were castrated at 12 weeks of age and the weights and lengths of the testis, epididymis and cremaster muscle were recorded. Intratesticular testosterone and 5 alpha DHT concentrations were determined, and the testis and epididymis were evaluated for histological changes. Basal plasma hormone concentrations, intratesticular androgen concentrations and the response of the pituitary gland to stimulation had not been affected by GnRH treatment. Pigs receiving the higher treatment dose of GnRH showed less increase in testosterone levels in response to the stimulation dose at 12 weeks of age than the other pigs. Morphologically, no changes were observed in the epididymis and cremaster muscle after GnRH treatment and no signs of reactivation of structures that can provoke testicular descent could be seen. The development of the seminiferous epithelium was more advanced in the GnRH-treated groups, apparently in a dose-dependent manner.

Animals↗
PubMed1987

The ultrastructure of normal fetal and neonatal pig testis germ cells and the influence of fetal decapitation on the germ cell development.

The development of germ cells in the male pig was investigated ultrastructurally in normal and decapitated fetuses. The age ranged respectively from 30 days p.c. till one month after birth and from 52 days p.c. until birth. The ultrastructural organization of the germ cells changes dramatically between 30 days p.c. and 52 days p.c. which coincides with the formation of 'true' sex cords. From 52 days p.c. onwards the morphology is rather stable: cells show a 'hydrated' appearance and typical cell bridges. There is no obvious difference in the ultrastructure of germ cells in decapitated animals, their normal littermates and control animals. Therefore germ cell development in the pig is likely to be insensitive to gonadotropins during the fetal period. The development of pig germ cells follows closely the pattern described for several species. Quantitatively there is an increase in the ratio of germ cell/Sertoli cell per cross sectional diameter in the decapitated animals.

Animals↗
PubMed1986

Testicular descent in the rat and a comparison of this process in the rat with that in the pig.

Testicular descent in mammals with a saclike cremaster muscle and in those with a striplike cremaster muscle differs morphologically as well as topographically. In spite of this, functional interpretations are sometimes extrapolated from species to species without defining precisely the different structures involved in this process. This has resulted in several unnecessary conflicting opinions on the mechanism of testicular descent. In this study the anatomical changes of the structures involved in the process of testicular descent in the rat are described and these data are compared with similar data on the pig. It appears that the major changes in the process in both species are 1) the outgrowth of gubernacular mesenchyme, 2) subsequent regression of this mesenchyme, and 3) development and growth of the cremaster muscle. If the structures involved are properly defined the homology of the changes in both species becomes evident.

Animals↗
PubMed1986

Age-related effects of transection of the testicular blood vessels on subsequent testicular development in the pig.

Pigs of different ages were studied to assess the effect of age on the development of the testes after intra-abdominal transection of the testicular artery and vein. Transection of the testicular artery and vein at different stages of sexual development had a variable effect on the growth and differentiation of the testes. Transection performed at a young age (2 months) had no effect on the development of the testes (previous study). The animals used in this study were between 3 and 12 months (adult) at the time of surgical intervention. Their testes appeared to be more sensitive to disturbance of the main blood supply. The alternative vascular pedicle (vasal artery) was unable to adapt sufficiently to the increased physiological requirements of the testis during development in more than 50% of the animals. The results obtained from adult males indicate that intra-abdominal transection of the testicular vessels invariably has a deleterious effect on the testis.

Age Factors↗
PubMed1986

Some histochemical and ultrastructural observations on the early foetal pig testis.

Testes of foetal pigs between 26 to 35 days post coitum (p.c.) were investigated histochemically and ultrastructurally. Diaphorase and delta 5-3 beta-hydroxysteroid dehydrogenase activities were studied using, respectively, NADH and pregnenolone and dihydroxy androsterone as substrates. Ultrastructurally, attention was focused on the development of mesenchymal cells and on the sustentacular cells in the primitive sex cords in an attempt to detect the origin of Leydig cells. Histochemically there is a concentration of activity toward the interstitium with increasing age. Also the reactions increase in intensity. Ultrastructurally no evidence for Leydig cell development from Sertoli cells could be observed. Mesenchymal cells between the sex cords show a development toward Leydig cells. This is absent in mesenchymal cells in the future tunica albuginea. Before 30 days p.c. no 'true' Leydig cells can be observed morphologically. The role of the rough endoplasmic reticulum/mitochondrial complex, which is present in many mesenchymal and sustentacular cells, is discussed.

3-Hydroxysteroid Dehydrogenases↗
PubMed1985

Development of pituitary gonadotropic cells in the pig fetus and the effect of luteinizing hormone-releasing hormone administration.

Pituitary gonadotropic development in fetal pigs has been studied immunocytochemically. From 50 days postcoitum (p.c.) until 90 days p.c. the volume density of luteinizing hormone (LH) immunoreactive cells increased from 0.12% to 0.61% of the glandular mass of the anterior part of the pituitary gland. From 90 to 100 days p.c. a steep increase to 4.5% was found. A single injection of long-acting luteinizing hormone-releasing hormone (LHRH) to the fetus at 75 days p.c. inhibited this developmental pattern. Pulsatile administration of LHRH agonist to fetuses from 70 to 73 days p.c. had no significant effect on the volume density of LH immunoreactive cells, whereas pulsatile administration from 70 to 80 days p.c. and from 95 to 105 days p.c. inhibited the normal increase of this parameter. It is concluded that from 70 days p.c. onwards the development of fetal gonadotropic cells can be manipulated by exogenous LHRH.

Animals↗
PubMed1985

Descent of the testis in the fetal calf. A summary of the anatomy and process.

The descent of the testis in the fetal calf is reviewed, and the role in that process of the swelling reaction of the gubernaculum testis is discussed. The testes of 30 Dutch Friesian fetuses were examined by dissection and light microscopy of sections prepared from chemically and frozen-fixed specimens. The gubernaculum remains unattached to the scrotal fasciae until descent is completed. Shortening of the intra-abdominal gubernaculum and displacement of the testis begins at fetal week 11; the swelling reaction of the gubernaculum occurs between weeks 14 and 15. The testis is at the deep inguinal ring by week 15, and by week 20 it is in the scrotal position and the gubernaculum has regressed. It is proposed that the swelling of the gubernaculum dilates the vaginal ring and enlarges the inguinal canal. The clinical importance of these anatomical relationships and changes is discussed.

Animals↗
PubMed1985

Testicular organogenesis in the fetal calf: interstitial endocrine (Leydig) cell development.

The development of the interstitial endocrine (Leydig) cells of the fetal testis in the calf is described and correlated with a swelling reaction of the gubernaculum and normal, prenatal descent of the testis. An hydroxysteroid dehydrogenase (HSD) procedure is used to determine the onset of functional activity for the interstitial endocrine cells (IEC). The NADH control procedure was strongly positive for the IECs at all ages investigated, indicating that these cells utilize the pyridine nucleotide as a coenzyme for oxireduction conversions. The 3 alpha- and 3 beta-HSD reactions were strongly positive and lightly positive, respectively, demonstrating that these cells contain the HSDs commonly utilized in the early steroidogenesis. TEM revealed structural evidence of this differentiating steroidogenic capability within IECs. During the period of the swelling reaction there is a functional IEC population, but there is no evidence presented by this study for a causal relationship of the gubernacular swelling reaction and subsequent normal descent of the testis into the scrotum.

3-Hydroxysteroid Dehydrogenases↗
PubMed1985

Testosterone secretion during gubernacular development and testicular descent in the dog.

Serum testosterone concentrations ranged from 0.24 to 1.45 nmol/l between Day 53 post coitum (p.c.) until Day 40 post partum (p.p.) and did not show variations that could be correlated with the process of testicular descent. The intratesticular androgen appeared to be mainly testosterone, its concentration being about 5000-fold higher than that in serum whereas 5 alpha-dihydrotestosterone could not be demonstrated. The intratesticular testosterone concentration at the initiation of gubernacular regression (Day 0) was apparently, but not significantly, higher than at Day 49 p.c. and at Day 40 p.p. The ability of the neonatal canine testis to synthesize testosterone was indicated by increased serum testosterone concentrations after hCG stimulation.

Animals↗
PubMed1985

Functional arterio-venous anastomoses between the testicular artery and the pampiniform plexus in the spermatic cord of rams.

Blood flow to the testis, haemoglobin oxygen saturation and testosterone concentration in arterial and venous testicular blood vessels were studied in Texel rams in the breeding and non-breeding season. Blood flow in the proximal and distal testicular artery was measured electromagnetically. The mean flow in the proximal testicular artery was 18.5 ml/min and in the distal testicular artery 7.5 ml/min, and there was no detectable seasonal influence. Haemoglobin oxygen saturation and testosterone concentration were measured in the saphenous artery and vein, the distal testicular artery and vein, and in the proximal testicular vein. The haemoglobin oxygen saturation in the proximal testicular vein was significantly higher than in the distal testicular vein in both seasons. The mean testosterone concentration was significantly lower in the proximal testicular vein than in the distal testicular vein in both seasons. Based on haemoglobin oxygen saturation and testosterone data, it was calculated that between 28 and 46% of the testicular arterial blood was bypassing the testis and was directly flowing through arterio-venous anastomoses towards the pampiniform plexus in the spermatic cord of conscious rams. In anaesthetized rams 55 and 64% of the blood was flowing directly from the testicular artery to the pampiniform plexus based on blood flow data. Transfer of testosterone and oxygen by passive diffusion from the testicular artery to the pampiniform plexus and vice versa in the spermatic cord was not detected.

Animals↗
PubMed1984

Leydig cell development in the pig testis during the late fetal and early postnatal period: an electron microscopic study with attention to the influence of fetal decapitation.

The ultrastructure of fetal and postnatal pig Leydig cells was studied from 75 days postcoitum (p.c.) to 1 month after birth. Additionally, decapitated fetuses from 75 days p.c. until birth were used to study the effect of deprivation of gonadotrophins on the ultrastructure of Leydig cells. Normal Leydig cell development was characterized by a change in smooth endoplasmic reticulum (SER). Next to branched tubular SER, whirls of elaborate and tightly packed SER membranes appeared. The amount of SER increased with age but decreased slightly before the end of the observation period. Rough endoplasmic reticulum (RER) was a minor component. Large bundles or whirls of intermediate filaments were abundant until just before birth; thereafter, they decreased drastically. Peroxisome-like structures and crystalloid bodies were observed with increasing frequency from 75 days p.c. and 20 days postpartum onward. Polygonal lysosome-like dense bodies transformed into complex membranous structures especially after birth. Giant mitochondria occurred in the late fetal and postnatal period. From 75 days p.c. onward fully developed Leydig cells were scarce in testes of decapitated fetuses. Leydig cell characteristics disappeared toward the end of the fetal period; only the cell shape, the large bundles or whirls of intermediate filaments, some scarce polygonal lysosome-like dense bodies, and RER remained, but SER was negligible. Progressive hemorrhages apparent in situ were correlated positively with fetal age. The dependency of Leydig cells upon LH began between 60 and 75 days postcoitum.

Animals↗