The role of the genitofemoral nerve and calcitonin gene-related peptide in congenitally cryptorchid mutant TS rats

We investigated whether previous gubernacular denervation in TS rats changes the gubernacular contractile response to or binding capacity of calcitonin gene-related peptide receptors. In TS rats there is excessive calcitonin gene-related peptide in the genitofemoral nerve and 85% of the male rats have cryptorchidism. TS rats and controls underwent genitofemoral nerve transection or sham operation at day 0. On day 3 gubernacula were cultured with or without calcitonin gene-related peptide to observe contractions. Gubernacular frozen sections were incubated with 125iodine calcitonin gene-related peptide with or without unlabeled calcitonin gene-related peptide. Exposed x-ray films were quantified by computerized densitometry. In the sham operated controls contractility increased from 15 to 55% by adding calcitonin gene-related peptide compared with 5% and 10%, respectively, in the TS rats. After genitofemoral nerve denervation exogenous calcitonin gene-related peptide increased contractility to 90% in controls and 75% in TS rats. Previous genitofemoral nerve transection increased specific 125iodine calcitonin gene-related peptide binding 21% in controls and about 100% in TS rats. Genitofemoral nerve transection in TS rats restored gubernacular contractile response to calcitonin gene-related peptide in vitro and doubled the binding capacity of calcitonin gene-related peptide receptors.

Characterization of the gubernacular contractile response to calcitonin gene-related peptide in the mouse

Calcitonin gene-related peptide (CGRP) has no effect on quiescent skeletal muscle, but cultured neonatal mice gubernacula show rhythmic contractions in response to CGRP. This study investigated whether these contractions (1) require calcium ions, (2) are activated via acetylcholine receptors, or (3) require dihydropyridine receptors. Gubernacula (n = 20 for each experiment) from male mice aged 7 days old were preincubated for 30 minutes in aerated culture medium (Krebs-Henseleit solution) with (1) up to 1.8 mmol/L of calcium with or without CGRP (714 nmol/L), (2) up to 5.0 mumol/L of curare with CGRP and calcium (1.8 mmol/L), or (3) up to 1 mumol/L of nifedipine with CGRP and calcium. Then they were placed on agar-coated grids over the same compound solutions, and observed for 2 days by video camera to see contractions. Of gubernacula cultured with calcium (1.8 mmol/L) and CGRP, 90% showed contractions, which decreased to 20% without CGRP (P < .001) and 15% without calcium (P < .001). Only 5% of gubernacula cultured without both CGRP and calcium showed contractions. Also these contractions in response to CGRP depended on calcium concentrations in a dose-dependent manner. Curare did not suppress contractions. With increasing dose of nifedipine, the percentage of gubernacula contracting decreased from 95% to 0%. These results suggest that developing mouse gubernacular contractions in response to CGRP require influx of calcium ions to the sarcoplasm via dihydropyridine receptors in a similar manner to contractions of immature cardiac or smooth muscles, and these contractions are not activated via acetylcholine receptors.

Voiding cystourethrography in boys: does the presence of the catheter obscure the diagnosis of posterior urethral valves?

OBJECTIVE

In voiding cystourethrography, the urethral catheter may or may not be left in place during voiding. The main argument for removing the catheter is that the diagnosis of posterior urethral valves may be missed because the catheter can hold open the valve, efface it, and render it invisible. However, if the catheter does not prevent the diagnosis of urethral disease, it is preferable to leave it in place. The catheter makes it possible to repeat the procedure easily if necessary, and using it to drain the bladder provides information about ureteric obstruction in the presence of vesicoureteric reflux. Accordingly, the purpose of this study was to determine whether leaving the urethral catheter in place throughout voiding cystourethrography affects the efficacy of the procedure for the diagnosis of posterior urethral valves.

MATERIALS AND METHODS

Three radiologists reviewed the preoperative voiding cystourethrograms obtained in 48 boys who ranged in age from 1 day to 10 years old (mean, 1.5 years). All patients had a diagnosis of posterior urethral valves made at cystoscopy, which was used as the gold standard. The voiding cystourethrogram was obtained with a catheter in place during voiding in 28 (58%) of the 48 boys, without a catheter in 17 (35%), and with and then without a urethral catheter during the voiding phase of the study in three (6%).

RESULTS

Posterior urethral valves were detected on 25 (89%) of the 28 voiding cystourethrograms obtained with a urethral catheter in place and in 15 (88%) of the 17 voiding cystourethrograms done without a urethral catheter. The five children in whom posterior urethral valves had been diagnosed by cystoscopy but were not detected on voiding cystourethrography had no dilatation of the posterior urethra nor any other evidence of obstruction; these were possibly false-positive cystoscopic diagnoses.

CONCLUSION

Our results show that a urethral catheter does not obscure posterior urethral valves in boys and need not be removed routinely during the voiding phase of voiding cystourethrography.

Physiological effects in vitro of calcitonin gene-related peptide on gubernacular contractility with or without denervation

The gubernaculum in neonatal rats has been shown previously by direct observation to contract rhythmically in response to exogenous calcitonin gene-related peptide (CGRP), but the physiological properties of these contractions were unknown. In the first study the authors investigated gubernacular contractility in vitro using a strain gauge to see if there were characteristics of skeletal or smooth muscle. Both the frequency and the amplitude of contractions were significantly enhanced by CGRP, and isotonic tension of the gubernaculum and the duration of contractions were also increased after CGRP. The effect of CGRP on gubernacular contractions appeared several minutes after adding CGRP, and it was independent of the acetylcholine action, which induced only a single twitch response of the gubernaculum. In the second study the authors investigated the effect on gubernacular contractility of prior transection of the genitofemoral nerve (GFN), which contains CGRP. Vigorous contractions occurred in 85% of denervated gubernacular compared with 46% of controls (P < .01). These data provide the first quantitative evidence of rhythmic gubernacular contractions, and suggest that CGRP enhances gubernacular contractility by a direct effect independent of acetylcholine. Further, the contractile properties resemble those of differentiated cardiac muscle or primitive embryonic skeletal muscle. GFN transection enhances the gubernacular contractile response to exogenous CGRP, which is consistent with the GFN being the normal source of CGRP for the gubernaculum in vivo.

Pyloromyotomy: comparison between laparoscopic and open surgical techniques

Several reports have appeared in the literature recently describing various techniques of performing pyloromyotomy laparoscopically. Although there is no doubt that this is now technically feasible, there are unanswered questions with regard to its safety, efficacy, and potential benefits or otherwise to the patient. In an attempt to resolve some of these issues, we compared the results in 37 infants who underwent open pyloromyotomy with 26 who underwent laparoscopic pyloromyotomy. The two groups were similar in terms of sex, age, weight, and presenting pH, although they could not be randomized. The time from feeding to discharge was less for the laparoscopic group (1.4 days) compared with the open group (1.8 days) (p = 0.04). Postoperative vomiting was not significantly different between the two groups. The operating time was identical for groups, 29 min vs 27 min. There were 3 complications in the open surgical group and 1 in the laparoscopic group. On the criteria measured, our results suggests that laparoscopic pyloromyotomy is at least as good as conventional surgery, and offers the potential benefits of shortened hospital stay and minimal cosmetic deformity.

Human chorionic gonadotropin (hCG) fails to stimulate gonocyte differentiation in newborn mouse testes in organ culture

The primitive germ cells within the postnatal testis differentiate through several steps to form primary spermatocytes, which are required for postpubertal spermatogenesis. It is postulated that this germ cell development is controlled by the hypothalamic-pituitary-gonadal axis. To study the effect of human chorionic gonadotropin (hCG) on postnatal testicular germ cell differentiation, especially on gonocytes, newborn mouse testes (n = 75) were cultured for 7 days in vitro. The synthetic serum-free medium contained either hCG or exogenous human recombinant müllerian inhibiting substance (MIS) plus transferrin, insulin and retinoic acid (TIRA). Fetal calf serum 10% (FCS) was used for control medium. Thirty-eight newborn mouse testes were cultured with hCG (0.1 to 2.0 IU/ml). The percentages of differentiated type-A spermatogonia were not significantly increased compared with synthetic medium alone (NS, p > 0.05), but were only 5 to 7% (p < 0.001) of that of serum-containing medium. By contrast, normal transformation from gonocytes to type-A spermatogonia occurred in newborn mouse testes (n = 10) cultured with serum-free medium containing exogenous MIS. The percentage of differentiated type-A spermatogonia was approximately 77% (NS, p > 0.05) of those seen in serum-containing medium. These findings demonstrate that the transformation of gonocytes to type-A spermatogonia is regulated by MIS, rather than hCG. As early germ cell transformation is deficient in boys with cryptorchidism, the role of hCG in the treatment of infertility associated with undescended testes should be reevaluated.

Absence of normal sexual dimorphism of the genitofemoral nerve spinal nucleus in the mutant cryptorchid (TS) rat

Sexual dimorphism of the genitofemoral nerve spinal nucleus has been demonstrated in normal rodents. Calcitonin gene-related peptide is a neurotransmitter, present in the genitofemoral nerve, that has been implicated in the regulation of gubernacular migration and inguinoscrotal testicular descent. A combination of retrograde fluorescent labelling of the genitofemoral nerve and immunohistochemistry for calcitonin gene-related peptide was used in 1-3-day-old mutant TS rats with 85% incidence of congenital cryptorchidism and an absence of the normal sexual dimorphism of the genitofemoral nerve spinal nucleus was demonstrated. There was no significant difference between male and female nuclei with respect to fluorescent-labelled neurones as well as those immunoreactive for calcitonin gene-related peptide, in contrast to an obvious sexual dimorphism present in normal control animals. This lack of normal sexual dimorphism of the genitofemoral nerve nucleus is likely to be important in the pathogenesis of cryptorchidism in this animal model.

Capsaicin increases the frequency of cryptorchidism in flutamide-treated rats

Capsaicin, a specific neurotoxin that irreversibly results in degeneration of sensory C fibers of the peripheral nerves, was investigated for its ability to affect testicular descent. In particular, we investigated the ability of prenatal flutamide, postnatal capsaicin or combined prenatal flutamide with postnatal capsaicin to induce undescended testes in rats. Within these treatment groups the frequency of maldescent was 42% in the animals treated prenatally with flutamide, 32% with postnatal capsaicin, and 100% with prenatal flutamide and postnatal capsaicin. Of interest, it was found that all animals that received capsaicin had maldevelopment of the scrotum. Our data suggest that capsaicin increased the frequency of cryptorchidism in rats prenatally treated with flutamide, perhaps by inhibition of scrotal development. These findings indicate that sensory nerves to the scrotum may affect scrotal development and testicular descent.

Calcitonin gene-related peptide receptors in the gubernaculum of normal rat and 2 models of cryptorchidism

We investigated calcitonin gene-related peptide binding in the gubernaculum from a normal rat, a TS rat (congenitally cryptorchid from unknown causes) and a flutamide rat (cryptorchid secondary to prenatal antiandrogen treatment). Gubernacular sections from 2-day-old male pups were incubated with 125iodine-calcitonin gene-related peptide with various concentrations of unlabeled calcitonin gene-related peptide. After exposure to x-ray film, developed film was quantified by computerized densitometry. The binding analysis showed that concentrations of calcitonin gene-related peptide receptors were 22.9 +/- 2.12, 13.5 +/- 1.70 and 30.3 +/- 2.63 (mean plus or minus standard error of mean, fmol./mg. polymer) for each rat, respectively, and there were significant differences between the normal and TS rats (p < 0.01), and the normal and flutamide rats (p < 0.05). However, there was no significant difference in the dissociation constant among the 3 models. This result shows that deficiency and excess of calcitonin gene-related peptide binding in the gubernaculum are associated with cryptorchidism. Calcitonin gene-related peptide released from the genitofemoral nerve may regulate its own receptor concentration to control gubernacular motility in vivo.

Transabdominal testicular descent is really ovarian ascent

Some investigators have suggested that testicular descent relative to the ovary is actually caused by the relative upward growth of the structures adjacent to the testis and that in the early phase of descent the testis is anchored to the inguinal region as the embryo enlarges. This concept was founded on results from the dissection of human fetuses. In this study the development of the urogenital system in fetal mice is examined using scanning electron microscopy to determine the distance between the bladder neck and the lower pole of the gonad. The results of this study confirm that transabdominal descent of the testis relative to the ovary is in one sense really ascent of the ovary in the fetal mouse, while the testis is anchored to the inguinal region by the developed gubernaculum. The testis shows real movement at the beginning of the inguinoscrotal phase of testicular descent at birth.

The effect of flutamide on testicular descent in rats examined by scanning electron microscopy

The effect of prenatal flutamide exposure on testicular descent was investigated by using scanning electron microscopy (SEM) in prenatal and postnatal rats. In 20-day-old fetal rats, SEM showed no significant difference in the degree of gubernacular development or testicular descent relative to the kidney between flutamide-treated (74.5 +/- 2.2 U) and control rats (73.3 +/- 1.5 U); however, there was significant inhibition in oestrogen-treated rats (44.3 +/- 2.2 U) (P < .001). (The distance between the kidney and the bladder neck was standardized to 100 U.) In 5-day-old rats, SEM showed inhibited downward growth of the processus vaginalis in flutamide-treated rats. The length of processus vaginalis below the inguinal ligament was 32.8 +/- 2.4 U in flutamide-treated rats and 51.7 +/- 1.8 U in controls (P < .001). In 30- to 35-day-old mature rats, the frequency of cryptorchidism was 41.3% for flutamide-treated rats and 0% for controls (P < .001). Some cryptorchid testes were located in the lower abdominal cavity (10.9%); others were in the suprainguinal position (26.1%) or on the line of descent in the inguinal region (4.3%). In the flutamide-treated group, no testes were located in the posterior abdominal cavity, near the kidney. These results suggest that transabdominal descent of the testis is independent of androgen action, but that androgens control inguinoscrotal descent of the testis by regulating gubernacular migration and the growth of the processus vaginalis.

Prenatal androgen blockade with flutamide inhibits masculinization of the genitofemoral nerve and testicular descent

Prenatal androgen blockade with the antiandrogen flutamide inhibits the inguinoscrotal phase of testicular descent. The evidence suggests that androgens may act indirectly via the sexually dimorphic genitofemoral nerve (GFN) to control this phase. Rats were exposed to flutamide on gestational days 16 through 19. Seven-day-old rats were subjected to retrograde fluorescent labelling of the GFN combined with immunohistochemistry for calcitonin gene-related peptide (CGRP), a neurotransmitter found in the GFN. Fluorescent-labelled and CGRP-immunoreactive neurons in the GFN spinal nucleus were quantified. Sexual dimorphism of the GFN nucleus was absent in the flutamide-treated rats but obviously present in control rats. Furthermore, control male nuclei had 24% more CGRP-immunoreactive neurons and 12% more fluorescent-labelled neurons than did flutamide-treated male nuclei. This study shows that prenatal androgen blockade with flutamide inhibits masculinization of the GFN, with significant reduction of its CGRP content. This supports the proposal that androgens act via the GFN, with CGRP as the second messenger, to control inguinoscrotal testicular descent.

Ontogeny of gubernacular contraction and effect of calcitonin gene-related peptide in the mouse

The mouse gubernaculum undergoes inguinoscrotal migration in the first postnatal week and also shows rhythmic contractions in organ culture in response to calcitonin gene-related peptide (CGRP). This study aimed to investigate the ontogeny of gubernacular contractile activity and effect of CGRP in organ culture in relation to the normal time of migration. Two hundred eighty gubernacula from male mice of 17 and 19 days' gestation, and of postnatal days 0,2,4,7, 10, and 14 were studied. Half were cultured with CGRP 714 nmol/L, and the other half were cultured without CGRP as controls. All were examined daily (for 7 days) for contractions. In the control group, the cumulative percentages of contractile gubernacula increased from 5% to 100% with age; in the CGRP group, these values ranged from 65% to 100%. There were significant differences between the two groups from prenatal day 17 to postnatal day 4 (P values ranged from less than .001 to less than 0.05, respectively). With increasing age in the CGRP group, the highest contractile rates were observed at the fewest number of days in culture. From prenatal day 17 to postnatal day 4, the gubernaculum had increasing endogenous contractility, but there was low endogenous contractility without exogenous CGRP. Contractility of gubernacula was enhanced strongly by exogenous CGRP, and the culture days of the peak contractile rates lined up in the reverse order. These results suggest that the days of optimal gubernacular contraction with CGRP in vitro are in keeping with the days of natural migration in vivo. This is consistent with the hypothesis that CGRP (released from the genitofemoral nerve) is important for gubernacular migration.

Hormonal control of testicular descent and the cause of cryptorchidism

This paper briefly reviews the literature on testicular descent and presents new observations from the authors' laboratory which suggest new ways of looking at old problems. There is now good evidence that testicular descent occurs in two morphologically and hormonally distinct phases. Relative 'transabdominal migration' of the testis compared with the ovary occurs at 10-15 weeks of gestation in the human and 'inguinoscrotal' migration occurs at 26-35 weeks of gestation. We have proposed previously that the first phase is controlled by Müllerian inhibiting substance although this remains controversial. The second phase is androgen dependent and is possibly mediated indirectly through the release from the genitofemoral nerve (GFN) of the neuropeptide calcitonin gene-related peptide (CGRP). Recently we have used three different rodent models of undescended testis to determine the involvement of the GNF and/or CGRP. The testicular feminization mouse with complete androgen resistance and the rat exposed prenatally to the antiandrogen flutamide have a deficiency of CGRP in the GFN. In contrast, the mutant trans-scrotal rat which has normal androgen levels has an excess of CGRP in the GFN. All cryptorchidism models, despite their different primary cause, have in common an abnormality of the GNF and/or CGRP which is consistent with the hypothesis that normal testicular descent in the rodent may be mediated by the GFN.

The gubernaculum in adult female, adult male and TFM male mice

There is still controversy over whether androgens are involved in gubernacular migration during descent of the testis, prompting a review of anatomical events controlled by androgens. The gubernacular position in adult female, male, and testicular feminized male (TFM) mice (with complete androgen resistance) was observed macroscopically to determine its caudal limit and whether the adult TFM male still contained guvernacular bulk. The length of the processus vaginalis was measured, and the presence of a differentiated cremaster muscle was determined histologically. In 10 adult female mice there was neither a processus vaginalis nor a cremaster muscle, and the gubernaculum (round ligament of the ovary) attached to the external inguinal ring. In 10 adult TFM mice the gubernaculum ended at or just beyond the external ring, and was present in an amount corresponding to its size at the end of the outgrowth phase of development, with secondary infiltration by fat. The processus vaginalis was poorly developed, the cremaster muscle was undifferentiated, and there was no eversion of the cremaster sac. In 10 normal adult male mice the gubernaculum and testis had migrated to the scrotum, and the gubernaculum had regressed fully. Because gubernacular development in the androgen-resistant mouse cases after termination of transabdominal testicular migration, the anatomy of the adult confirms that, in the mouse, normal androgenic function is essential for eversion of the cremaster sac and gubernacular migration beyond the groin to the genital folds.

The tammar wallaby (Macropus eugenii) and the Sprague-Dawley rat: comparative anatomy and physiology of inguinoscrotal testicular descent

Inguinoscrotal testicular descent in the tammar wallaby (Macropus eugenii) and the Sprague-Dawley rat was studied by macroscopic dissection, histological evaluation and organ culture bioassay. In 3 or 4 d Sprague-Dawley rats (n = 10) the gubernacular tip bulged free from the surrounding tissues, particularly with the application of abdominal pressure. Microscopic examination revealed that only the body of the gubernaculum is connected posteriorly to the pubic region. In contrast, macroscopic dissection of male tammar wallabies (n = 17) revealed a densely adherent distal gubernacular attachment to the inside of the fibrous scrotal bulge while the body of the gubernaculum was less firmly attached. These attachments were present throughout the process of testicular descent, illustrating an important anatomical difference between these species. The gubernaculum from the tammar wallaby pouch young was studied in organ culture with rat calcitonin gene-related peptide for 4 d. Rhythmic gubernacular contractions similar to those documented previously in the rat were not observed. The hypothesis proposed in the rat for the control of inguinoscrotal gubernacular migration via the genitofemoral nerve and its neurotransmitters may not be applicable in marsupial mammals.

The role of intra-abdominal pressure in cryptorchidism

The effect of intra-abdominal pressure was investigated in the rat, in which the testes normally descend on or about the 21st day of age. In newborn rats less than 5 days old, the entire anterior abdominal wall musculature was excised from the level of the umbilicus to the xiphoid process. The proximal attachment of the gubernaculum also was incised bilaterally. The abdomen was re-explored on the 28th day to examine the position of the testes. Ninety-five male animals survived. The 4 testes held by adhesions and the 12 with testicular atrophy were excluded from the analysis. A combination of abdominal muscle excision and transection of the proximal gubernaculum (A) reduced the number of descended testes to 19 of 45 (42%). Transection of the gubernaculum alone (B) resulted in 30 of 43 (70%) descended testes. Where an abdominal defect was created without cutting the gubernaculum (C), 34 of 36 (96%) testes descended, which is similar to sham-operated (D) controls 50 of 50 (100%). There was a significant difference between groups A and B (p < 0.025), A and C (p < 0.005) and B and C (p < 0.025). These results show that the gubernacular attachment to the testis and the intra-abdominal pressure act synergistically to aid testicular descent in the rat.

Germ cell development in neonatal mouse testes in vitro requires müllerian inhibiting substance

To study the effect of müllerian inhibiting substance on testicular germ cell development, especially on gonocytes, whole testes (156) from newborn mice were cultured for 1 to 7 days in vitro. The synthetic medium contained either 10% fetal calf serum, which itself contains endogenous müllerian inhibiting substance, or transferrin, insulin and retinoic acid. Human recombinant müllerian inhibiting substance, rabbit antiserum against müllerian inhibiting substance and/or normal rabbit serum was added to some cultures. The cultured testes were fixed in Stieve's fixative and stained with hematoxylin and eosin, and the numbers and types of germ cells per tubule were counted under a light microscope. Preliminary studies showed that germ cell development in newborn mouse testes was similar in vitro to that observed in vivo, except for delay in vitro. Normal germ cell maturation from gonocytes to primary spermatocytes occurred in testes cultured with 10% fetal calf serum only (i), 10% fetal calf serum plus müllerian inhibiting substance plus anti-müllerian inhibiting substance antibody (ii), 10% fetal calf serum plus normal rabbit serum (iii) and transferrin, insulin and retinoic acid plus müllerian inhibiting substance (iv). Maturation from gonocytes to A-type spermatogonia was arrested in testes cultured with 10% fetal calf serum plus anti-müllerian inhibiting substance antibody (p < 0.01), transferrin, insulin and retinoic acid alone (p < 0.001) and transferrin, insulin and retinoic acid plus müllerian inhibiting substance plus anti-müllerian inhibiting substance antibody (p < 0.001). The results are consistent with the hypothesis that müllerian inhibiting substance may be involved in postnatal gonocyte development and suggest that it may be useful to treat infertility associated with undescended testes.