The medical school curriculum committee revisited.

Numerous study commissions have contended that departmental territoriality and lack of coordinated planning are stagnating contemporary medical education. As a cure, these commissions have recommended the creation of centralized academic management units empowered to oversee revitalization of the curriculum through a series of reforms, including better definition of graduation competencies, community-based training, interdisciplinary courses, problem-based learning, and modernization of evaluation strategies. To determine the extent to which these recommendations were being adopted, in 1990 the authors sent a questionnaire on curriculum committee functions, current innovation efforts, and future priorities to academic administrators and members of medical school curriculum committees at 143 North American medical schools. Responses were received from administrators (primarily associate deans for academic affairs) at 118 schools and committee members (primarily faculty) at 111 schools. Recommendations for enhancing curriculum committee effectiveness were also elicited. The authors conclude that centralization of curricular management has occurred at very few institutions, and that the commonly mentioned reforms are being adopted at a modest pace. The results are analyzed in light of theories of the institutional change process and strategies for introducing educational innovations into established institutions.

The effect of unilateral testicular torsion on the contralateral testicle in prepubertal Chinese hamsters.

Recent studies of experimental testicular torsion in rats, rabbits, and guinea pigs have demonstrated conflicting evidence regarding contralateral testicular damage. Those studies in which cellular damage has been found are postulated to result from an immunological mechanism whereby the blood-testis barrier is disrupted with subsequent autoantibody formation. In this study, the histologic and immunologic effects of testicular torsion on the contralateral testicle were investigated in prepubertal Chinese hamsters. Four study groups were established; (1) Left orchiectomy only, (2) sham surgery (scrotal incision), (3) 720 degrees left testicular torsion with left orchiectomy 24 hours later, (4) 720 degrees torsion of left testicle with detorsion after 24 hours. The initial procedure was performed at 1 month of age with subsequent biopsies of the contralateral testicle at 1 week, 1 month, and 6 months after the initial procedure. Testicular tissue was examined for immunofluorescent activity using fluorescent labeled goat anti-hamster IgG. Positive controls were established by rabbit immunization (rabbit anti-hamster immunoglobulin) which was subsequently combined with fluorescent labeled goat antirabbit IgG. There was no appreciable difference in immunologic activity between control and experimental animals. Representative sections were examined histologically and no tubular damage was demonstrated and active spermatogenesis was noted at 6 months in all groups. We believe that our results support the premise that testicular torsion in the prepubertal period has no effect on the contralateral testicle.

Membrane-bound intranuclear inclusions in the Leydig cell of the Chinese hamster (Cricetulus griseus).

Membrane-bound intranuclear inclusions have been described, for the first time, in the Leydig cell of the Chinese hamster (Cricetulus griseus). The inclusions were not found in the 1-day-old animal, rarely found prior to sexual maturity, and commonly found in the sexually mature animals. The incidence of inclusions increases with aging. Their size and content varies greatly. They are surrounded by a single membrane and completely enclosed by nucleoplasm. Their close association with nuclear invaginations of cytoplasmic material, and their content of cytoplasmic structures along with some exhibiting the presence of trimetaphosphatase reaction product, suggest a cytoplasmic origin. This phenomenon involves the migration of cytoplasmic structures into the nucleus followed by detachment on the nucleoplasmic side. The presence of the inclusions is not an indication of an abnormality of the Leydig cell. The Leydig cell of the Chinese hamster may be an excellent model to study factors that initiate inclusion formation, and to determine the functional role of membrane-bound intranuclear inclusions.

Effects of trypan blue on thyroid secretion: localization of trypan blue within the colloid space and phagolysosomes of thyroid follicles.

Trypan blue was previously shown to directly inhibit thyroid secretion following TSH stimulation. Inhibition of both colloid droplet formation and thyroglobulin proteolysis was demonstrated. By observing the characteristic bright red fluorescence of the dye-protein complex, we have demonstrated that trypan blue rapidly enters the colloid space and combines with thyroglobulin. In addition, the dye in association with thyroglobulin has been demonstrated within phagosomes and phagolysosomes by centrifugation of the lysosomal (P15) fraction on both sucrose and Percoll density gradients. Lability or latency of the dye with the phagolysosomal contents was demonstrated and the dye was found in association with thyroglobulin by column chromatography. It is proposed that the complexing of trypan blue to thyroglobulin alters its attachment to specific follicular cell receptors, inhibits pinocytosis, and, thus, thyroid hormone secretion.

Two types of paracrystalline inclusions in the Leydig cell of the Chinese hamster (Cricetulus griseus).

The ultrastructure of two types of paracrystalline inclusions is described, for the first time, in the Leydig cell of the Chinese hamster (Cricetulus griseus). The subunit of both types of inclusions consists of 5-nm-wide microfilaments differing only in the arrangement and shape of the microfilaments. The electron-dense microfilaments of the type A inclusion are usually in a serrated pattern with an equidistant 5-nm interval separating them. The type B inclusion has pairs of straight microfilaments separated by a 5-nm interval. Other microfilaments course at right angles to the paired units. Both types of inclusions are absent in the newborn, rarely found in the sexually immature, and commonly found in the sexually mature and aged animals. Both inclusions are found in the cytoplasm of Leydig cells, but only the A inclusion is found in the nucleoplasm. Their functional role is not yet determined, but the inclusions are commonly found in Leydig cells whose ultrastructural characteristics indicate normal steroidogenesis.

Melatonin's inhibition of pituitary, adrenal, testicular and accessory gland growth in male golden hamsters: pineal dependence and organ differences with shielding and intracranial surgery.

Testes, accessory glands, pituitaries and adrenal glands from 101 male Golden Hamsters (55-65 days old) were weighed after 4 weeks of daily injections of vehicle or 25 microgram or 2500 microgram of melatonin, and 32-33 days after surgery. The surgical groups within each injection group were: (1) nonoperated (NO), (2) sham-pinealectomized (S), (3) sham-pinealectomized with black plastic shielding of the pineal region (S + Pl), (4) pinealectomized (PX), and (5) pinealectomized with black plastic shielding of the pineal region (PX + Pl). All injections were made between L11 and L11.75 in a fixed LD14:10 daily photoperiod. Absolute and relative organ weights were significantly depressed by 25 but not 2500 microgram melatonin. This effect of low dose melatonin was blocked by pinealectomy (PX, PX + Pl) in all four organ groups, but was blocked as well by the sham-operation (S, S + Pl) only in the case of the adrenal glands. Effects and organ weights in S animals were not modified in the S + Pl animals. But in vehicle-injected groups the S + Pl animals had significantly lower accessory organ weights in comparison with those of NO and S groups. These results aid in the further definition of the mechanisms of melatonin's physiological actions as a chemical mediator within neuroendocrine timing controls, and show that the mechanisms for melatonin's actions can differ in relation to eventual endpoint target tissue or organ studied.

Physical and hormonal evaluation of transsexual patients during hormonal therapy.

The optimal hormonal therapy for transsexual patients is not known. The physical and hormonal characteristics of 38 noncastrate male-to-female transsexuals and 14 noncastrate female-to-male transsexuals have been measured before and/or during therapy with various forms and dosages of hormonal therapy. All patients were hormonally and physically normal prior to therapy. Ethinyl estradiol was superior to conjugated estrogen in suppression of testosterone and gonadotropins but equal in effecting breast growth. The changes in physical and hormonal characteristics were the same for 0.1 mg/d and 0.5 mg/d of ethinyl estradiol. The female-to-male transsexuals were well managed with a dose of intramuscular testosterone cypionate of 400 mg/month, usually given 200 mg every two weeks. The maximal clitoral length reached was usually 4 cm. Higher doses of testosterone did not further increase clitoral length or suppression of gonadotropins; lower doses did not suppress the gonadotropins. Based on the information found in this study, we recommend 0.1 mg/d of ethinyl estradiol for the noncastrate male-to-female transsexual and 200 mg of intramuscular testosterone cypionate every two weeks for the noncastrate female-to-male transsexual.

Effects of trypan blue on thyroid secretion. Inhibition of purified cathepsin D from bovine thyroid.

Previous studies have demonstrated that trypan blue directly inhibits thyroid secretion when the dye is administered in vitro or in vivo. To further study the mechanisms of inhibition, cathepsin D (EC 3.4.23.5) (thyroidal acid proteinase) has been purified from bovine thyroid. Trypan blue inhibited the proteolysis of both 125I-labeled thyroglobulin and 125I-labeled hemoglobin in both crude lysosomal enzyme preparation and purified endopeptidase and the inhibition was competitive. Inhibition was also observed when the dye was allowed to prebind to either purified enzyme or purified substrate. Inhibition of cathepsin D is shown to account for part of the inhibition of thyroid secretion.

Ultrastructural and cytochemical effects of trypan blue on TSH stimulation of thyroid follicular cells.

Ultrastructural and cytochemical techniques were used to study the effects of trypan blue on the response of mouse-thyroid cells to exogenous stimulation by thyroid stimulating hormone (TSH). The dye delayed the response to TSH resulting in decreased colloid-droplet formation in the apical region of the cells. The dye did not stop the shift of trimetaphosphatase activity from lysosomes to phagolysosomes. The duration of the TSH-induced response was shorter in the dye treated thyroids. Small vesicles, with trimetaphosphatase reaction product, were found near Golgi elements, phagolysosomes, and the plasma membrane facing rhe intercellular space of adjacent follicle cells. Their enzyme activity was not affected by exposure to the dye. These data indicate that the primary effect of trypan blue on the response of thyroid follicle cells to TSH stimulation was reduced endocytosis in the apical region resulting in fewer colloid droplets.

A new familial syndrome of 46,XY gonadal dysgenesis with anomalies of ectodermal and mesodermal structures.

Two 46,XY phenotypic female siblings, aged 1 1/2 and 8 1/2 years, have peculiar facies, cardiac, renal, musculoskeletal, and ectodermal anomalies, short stature, streak gonads, and mild developmental delay. Previous reported cases of 46,XY gonadal dysgenesis have not had major associated malformations. These children present a new constellation of anomalies unlike those seen in other types of gonadal dysgenesis and represent a new familial syndrome of 46,XY gonadal dysgenesis.

Ultrastructural classification of paracrystalline inclusions in untreated and estrogen treated human Leydig cells.

Ultrastructural examination of untreated and estrogen-treated human testes revealed for the first time five types of paracrystalline inclusions in the cytoplasm of Leydig cells. The distinctions between each type of inclusion were based on longitudinal and cross-sectional ultrastructure. The inclusions were not found in Leydig cells containing Reinke crystals, nor were different types of inclusions found in the cytoplasm of the same cell. One form of inclusion or Reinke crystals were occasionally found in the nucleus. Some Leydig cells with intranuclear inclusions contained the same or a different type of inclusion in the cytoplasm. The present study revealed five types of paracrystalline inclusion in contrast to the one or two types described in previous reports. A possible explanation for this difference is that earlier investigators based their observations on small pieces of tissue obtained from biopsy, while the present data were obtained by studying many regions of each testis. All five types of paracrystalline inclusions were found in relatively normal as well as azoospermic (estrogen-treated) testes.

Use of osmium-ferrocyanide treatment for improved lysosomal acid trimetaphosphatase reaction and subcellular detail in thyroid follicular cells.

The histochemical reaction for acid trimetaphosphatase in addition to secondary tissue treatment with an osmium-ferrocyanide mixture was used to study lysosomes and phagolysosomes in the mouse thyroid gland. The osmium-ferrocyanide postfixation enhanced reaction product localization, reduced diffuse reaction, and improved membrane contrast. In addition, the ultrathin tissue sections did not require heavy metal staining, thus eliminating potential stain artifacts due to precipitation. In view of the improved tissue preservation and enzyme localization, it is suggested that osmium-ferrocyanide postfixation be used after the acid trimetaphosphatase method.

Direct effects of trypan blue on thyroid secretion.

Trypan blue directly inhibited in vitro thyroid secretion (butanol soluble 125I release to the media) induced by both thyroid stimulating hormone (TSH) and dibutyryl cAMP. Intracellular colloid droplet counts were also decreased. Inhibition was directly proportional to dye concentration and could be overcome by supramaximal TSH and dibutyryl cAMP. Inhibition could be observed as early as 20 min of incubation, was not increased by preincubation, and could even be demonstrated after TSH in vivo. Trypan blue, in vivo, produced similar inhibition of thyroid secretion. Incubation of 125I-thyroglobulin with lysosomal enzymes revealed inhibition with much lower concentrations of dye. Inhibition of lysosomal enzyme(s) would not appear to explain the marked decreases in colloid droplets, and this may represent two separate effects of trypan blue on thyroid secretion.

The ultrastructural response of human Leydig cells to exogenous estrogens.

The effect of long term treatment with estrogens alone or along with medroxyprogesterone acetate on the Leydig cell ultrastructure was studied in testes from males undergoing surgery for sexual reassignment. The testes were fixed for electron microscopy by a perfusion method to insure uniform preservation. The morphological features were not the same in all the treated testes. Therefore, the cells found in the intertubular region were classified into three groups: (A) Leydig cells very similar to controls; (B) Absence of typical Leydig cells, but with cells having increased microfilaments, abundant smooth endoplasmic reticulum and some lipid droplets; (C) Absence of any cell type possessing abundant smooth endoplasmic reticulum, but having varying amounts of microfilaments and pigmentation. It is suggested that some of the cell types found in the intertubular region are dedifferentiated Leydig cells. This study indicates that the human testis from transsexuals of reproductive age is an appropriate model to study the indirect and direct effects of estrogens on the ultrastructure of cell types found in the human testes.

PIP: Transsexual men exposed long-term to exogenous female hormones (estrogens and medroxyprogesterone acetate) were studied to determine any ultrastructural changes in the light or electron microscopic structure of Leydig cells from perfused human testes after long-term treatment with exogenous hormones lasting from 2-8.5 years. 14 photomicrographs form the core of this report. Morphological features were not the same in all of the treated testes. Hence, cells found in the intertubular region were classified into 3 groups: 1) Leydig cells very similar to controls; 2) absence of typical Leydig cells, but with cells having increased microfilaments, abundant smooth endoplasmic reticulum, and some lipid droplets; and 3) absence of any cell type possessing abundant smooth endoplasmic reticulum, but having varying amounts of microfilaments and pigmentation. In all, 6 patients were studied, and 2 fell into each of the 3 groups. Perhaps some of the cell types found in the interubular region were dedifferentiated Leydig cells. Nevertheless, this study shows that the human testes from transsexuals of reproductive age are appropriate models for studying the indirect and direct effects of estrogens on the ultrastructure of cell types found in human testes.

An ultrastructural study of Schwann cell response to axonal degeneration.

Adult Sprague-Dawley rats were used to prepare isolated and distal segments of ovarian, vagus and saphenous nerves. Isolated segments were prepared by cutting between double ligatures followed by retracting and anchoring the proximal and distal segments 0.5 cm or more away from the isolated piece. After various intervals between 3 and 123 days and rats were perfused with buffered glutaraldehyde and nerves were processed for electron microscopic examination. Cross sections of isolated and distal segments of all nerves displayed an abundance of mostly circular profiles containing microtubules and filaments that were indistinguishable from those in unmyelinated nerve fibers. Many such profiles were nested against perinuclear Schwann cell cytoplasm, others were present in isolated clusters enclosed only by basement membrane. Examples of continuity between the nerve-like profiles and perinuclear cytoplasm of Schwann cells were found in longitudinal sections. In time, the number of such processes gradually diminished, but 123 days after transection they still could be found. It was concluded that Schwann cells in isolated and distal segments of transected nerves develop great numbers of small cylindrical processes that are arranged in bundles parallel to the long axis of the degenerated nerve. These processes had an arrangement of cytoplasmic organelles similar to axons of the proximal segment and the contralateral nerve. However the processes differed from most mature axons in that they were not ensheathed by Schwann cell cytoplasm with a mesaxon.

Ultrastructural study of the nerve plexus accompanying the ovarian artery and vein in the rat.

The ultrastructural characteristics of the nerve plexus that accompanies the ovarian vessels of the rat were studied. The nerve fibers were primarily unmyelinated with less than 5% myelinated. Two types of neuronal cell bodies were found along these nerves. They were located at variable distances along the nerve bundle. The first and more numerous was a larger cell type similar to the autonomic postganglionic neuron. The second and smaller cell type had granulated vesicles throughout the cytoplasm. Synapses of the axodendritic type and synapses between the neuronal cell bodies were found. Most of the synapses possessed agranular vesicles. The presence of neuronal cell bodies is an important characteristic to consider in evaluating denervation of the ovary by interruption of this nerve plexus.

Permeability of ovarian follicles and capillaries in mice.

The permeability of ovarian capillaries and follicles in prepubertal and sexually mature (proestrus and metestrus) randomly bred Swiss Albino female mice (SCH:ARS HA ICR strain) was studied by intravenous injection of either ferritin or horseradish peroxidase (HRP), followed by examination with light and electron microscopes. The study revealed that capillaries in the interstitial and perifollicular regions were provided with a continuous endothelium that had constant permeability characteristics irrespective of sexual maturity or phase of the estrous cycle. Horseradish peroxidase left the capillaries primarily through interendothelial cell junctions and was present in all follicles within 30 seconds after administration of the tracer. Ferritin, on the other hand, was absent from endothelial cell junctions, and left the capillaries, at a slower rate than HRP, via cytoplasmic vesicular transport. Both tracers were found in the granulosa cells but rarely in the oocytes. The tracers reached the oocyte through the intercellular spaces between granulosa cells. These findings demonstrate that the follicular apparatus of the mouse is permeable to ferritin and HRP, and that follicular regions such as the basal lamina of the follicle and the zona pellucida do not stop or retard the passage of either tracer.