Don F. Cameron

Gonadal dysfunction in the spontaneously diabetic BB rat

Diabetes which occurs spontaneously in the BB Wistar rat is associated with reduced fertility, predominantly in breeding males. In the first month of diabetes, there is a significant (p less than 0.05) reduction in serum testosterone associated with a transient decrease of serum LH and the accumulation of lipid in Leydig cells. Between one and three months of diabetes, there is an increase in both serum testosterone and LH and a further deposition of lipid droplets in Leydig cells. From three to six months of diabetes, there is a reduction of serum testosterone similar to age-matched controls, but high serum LH levels persist. Similar levels of LH and testosterone are noted after six months of diabetes, and all BB rats show marked changes in seminiferous tubules. These morphological changes in tubules consist of increased tubular wall thickness, severe germ-cell depletion, and Sertoli-cell vacuolization. Similar morphological changes of testes associated with generalized atrophy are noted in all control rats after 16 months of age. Decreased fertility in the BB rat appears to be associated with a primary disorder of Leydig cells, which precedes changes in seminiferous tubules consistent with accelerated aging. Preliminary data in impotent diabetic men suggest that the BB rat may be a valuable model for investigating human diabetic impotence and infertility.

Ultrastructural Alterations in the Adluminal Testicular Compartment in Men with Varicocele

Testicular biopsies from 21 otherwise healthy men with diagnosed varicocele were processed for light and electron microscopy. Whereas germ cell morphology and tissue architecture of the basal testicular compartment appeared normal, cellular mophology and intercellular associations of the adluminal testicular compartment were variably altered. In affected tubules, spermatid nuclear and acrosomal morphology was abnormal and sloughing was evident. Spermatids were maloriented relative to Sertoli cells, and Sertoli-germ cell junctional complexes appeared to be structurally abnormal. Contradistinctly, Sertoli-Sertoli cell junctional complexes appeared unaffected. Results from this study indicate that testicular disruption in varicocele is a phenomenon of the adluminal compartment, that the Sertoli cell is, in fact, more sensitive to perturbation of the testicular environment than are germ cells, and that the Sertoli cell is the primary intratubular site of alteration leading secondarily to spermatogenic disruption.

Chronic toxicity of dichloroacetate: Possible relation to thiamine deficiency in rats

The chronic use of dichloroacetate (DCA) for diabetes mellitus or hyperlipoproteinemias has been compromised by neurologic and other forms of toxicity. DCA is metabolized to glyoxylate, which is converted to oxalate and, in the presence of adequate thiamine levels, to other metabolites. DCA stimulates the thiamine-dependent enzymes pyruvate dehydrogenase and alpha-ketoacid dehydrogenase. We postulated that the neurotoxicity from chronic DCA administration could result from depletion of body thiamine stores and abnormal metabolism of oxalate, a known neurotoxin. For 7 weeks, rats were fed ad lib. Purina chow and water or chow plus sodium DCA (50 mg/kg or 1.1 g/kg) in water. A portion of the DCA-treated animals also received intraperitoneal injections of 600 micrograms thiamine three times weekly or 600 micrograms thiamine daily by mouth. Thiamine status was assessed by determining red cell transketolase activity and, in a blinded manner, by recording the development of clinical signs known to be associated with thiamine deficiency. At the 50 mg/kg dose, chronic administration of DCA showed no clinical toxicity or effect on transketolase activity. At the 1.1 g/kg dose, however, DCA markedly increased the frequency and severity of toxicity and decreased transketolase activity 25%, compared to controls. Coadministration of thiamine substantially reduced evidence of thiamine deficiency and normalized transketolase activity. Inhibition of transketolase by DCA in vivo was not due to a direct action on the enzyme, however, since DCA, glyoxylate, or oxalate had no appreciable effects on transketolase activity in vitro. After 7 weeks, plasma DCA concentrations were similar in rats receiving DCA alone or DCA plus thiamine, while urinary oxalate was 86% above control in DCA-treated rats but only 28% above control in DCA plus thiamine-treated animals. No light microscopic changes were seen in peripheral nerve, lens, testis, or kidney morphology in either DCA-treated group, nor was there disruption of normal sperm production in the DCA-treated group. We conclude that stimulation by DCA of thiamine-requiring enzymes may lead to depletion of total body thiamine stores and to both a fall in transketolase activity and an increase in oxalate accumulation in vivo. DCA neurotoxicity may thus be due, at least in part, to thiamine deficiency and may be preventable with thiamine treatment.

The Blood-Testis Barrier in Men with Varicocele: A Lanthanum Tracer Study

Testicular biopsy specimens were obtained from 28 otherwise healthy males (22 to 37 years old) with diagnosed varicocele. Tissue was processed for ultrastructural and intercellular tracer studies using lanthanum nitrate. In all cases Sertoli-Sertoli junctional complexes appeared structurally intact and functionally normal on the basis of their ability to occlude lanthanum from the adluminal testicular compartment. Our results indicate that, even in the presence of severe dissolution of the adluminal testicular compartment as evidenced in varicocele, both the basal compartment and the blood-testis barrier remain relatively normal. In varicocele, not only does the blood-testis barrier remain effective in segregating the two testicular compartments, but it appears to act as a device that limits the progression of apical Sertoli cell cytoplasmic degeneration and seminiferous epithelial dissolution, thereby allowing a pool of progenitor germ cells to be maintained and protected in the basal compartment.

Assessment of proteinuria and neuropathy in the nonimmunosuppressed BB diabetic rat after abdominal intratesticular islet transplantation.

Only limited studies are available that assess diabetic complications following islet cell transplantation. Our objectives were to quantitate urine total protein, sural nerve morphometry, and sexual function in the diabetic BB/WOR male rat following islet cell transplantation into the abdominal testis. Success of islet cell transplantation was determined by nonfasting, morning, twice-weekly serum glucose and 12-hr fasting glucose, total glycosylated hemoglobin, and HbA1c after six months of diabetes and prior to death. Results showed that 9 of 16 rats were transplanted successfully for a period of at least six months. Pretransplant glucose was 21.9 +/- 4.67 (SD) mM/L and posttransplant glucose was 6.44 +/- 72 mM/L. The 12-hr fasting glucose ranged from 4.61 to 9.28 mM/L in animals prior to death, and glycosylated hemoglobins were not different from controls. Total urinary protein was significantly (P < 0.01) less than untreated diabetic rats (5.66 +/- 1.96 vs. 16.6 +/- 3.7 mg/24 hr) and not different from controls. Penile reflexes and serum testosterone remained normal in islet cell-transplanted animals. Sural nerve morphometry was normal, with 29.2% fewer abnormalities (paranodal swelling, paranodal demyelination, myelin wrinkling, Wallerian degeneration, and segmental demyelination) than untreated diabetic BB/WOR rats. We conclude that abdominal, intratesticular islet transplantation normalizes fasting blood glucose and glycosylated hemoglobin. In addition, the improvement in metabolic control at six months of diabetes was associated with normal total urinary protein, sural nerve morphometry, and sexual function.

The effect of experimentally-induced renal failure on accumulation of bupropion and its major basic metabolites in plasma and brain of guinea pigs

Dosage regimen adjustments because of poor renal function are often assumed to be unnecessary for extensively metabolized antidepressants. This assumption is being increasingly questioned in recognition of the role of active drug metabolites. The purpose of this study was to assess the steady-state accumulation of the new antidepressant bupropion and its three major basic metabolites in guinea pigs, with and without experimentally-induced renal guinea pigs, with and without experimentally-induced renal failure. Two groups of guinea pigs were treated by intraperitoneal (IP) implantation of mini-osmotic pumps containing bupropion hydrochloride. Immediately after surgery, one group of animals received an injection of uranyl nitrate. After 4 days, all animals were sacrificed by decapitation following blood removal by cardiac puncture. Analysis of plasma and brain samples by high performance liquid chromatography (HPLC) for concentrations of bupropion (BUP) and its major basic metabolites, the erythro-amino alcohol (EB), the threo-amino alocohol (TB) and the hydroxy metabolite (HB) revealed greater accumulation of BUP, TB, and HB in plasma and brain of the animals with renal failure compared to controls. No difference was found between groups in the concentrations of the EB metabolite. As the guinea pig shows a BUP and metabolite plasma concentration profile similar to that seen in human studies, these results suggest that further studies of bupropion and its major metabolites are warranted in patients with impaired renal function to assess possible excessive drug and metabolite accumulation.

Three patterns of extra-testicular venous drainage in the rabbit

SummarySeventy-eight male New Zealand white rabbits were autopsied and found to have variable left extra-testicular venous anatomy. Our observations reveal that in the rabbit the left testis is drained in one of three ways, identified as either A (18%), B (30%) or C (52%) —type drainage. The right testicular vein in all cases drained directly into the inferior vena cava immediately superior to the right iliolumbar vein.In type A drainage, the left testicular vein drained directly into the inferior vena cava at the level of the left iliolumbar vein. In type B drainage, the left testicular vein emptied into the left iliolumbar vein, which in turn drained into the inferior vena cava. In type C drainage both the left testicular and iliolumbar veins anastomosed to form a “lumbotesticular” trunk which emptied directly into the left renal vein.These three patterns of left venous vascular anatomy in the rabbit can be explained on the basis of their embryologic development. Our observations suggest that it is the caudal segment of the left pelvic subcardinal vein and its anastomosis with the caudal cardinal complex which persist as the left testicular vein and that the more cranial segment of this vein, heretofore presumed to remain patent, atrophies to the level of the developing left renal vein.