The importance of glucose for the freezing tolerance/intolerance of the anuran amphibians Rana catesbeiana and Bufo paracnemis.

Several species of terrestrially hibernating frogs, turtles and insects have developed mechanisms, such as increased plasma glucose, anti-freeze proteins and antioxidant enzymes that resist to freezing, for survival at subzero temperatures. In the present study, we assessed the importance of glucose to cryoresistance of two anuran amphibians: the frog Rana catesbeiana and the toad Bufo paracnemis. Both animals were exposed to -2 degrees C for measurements of plasma glucose levels, liver and muscle glycogen content, haematocrit and red blood cell volume. Frogs survived cold exposure but toads did not. Blood glucose concentration increased from 40.35 +/- 7.25 to 131.87 +/- 20.72 mg/dl (P < 0.01) when the frogs were transferred from 20 to -2 degrees C. Glucose accumulation in response to cold exposition in the frogs was accompanied by a decrease (P < 0.05) in liver glycogen content from 3.94 +/- 0.42 to 1.33 +/- 0.36 mg/100 mg tissue, indicating that liver carbohydrate reserves were probably the primary carbon source of glucose synthesis whereas muscle carbohydrate seems unimportant. In the toads, the cold-induced hyperglycaemia was less (P < 0.05) pronounced (from 27.25 +/- 1.14 to 73.72 +/- 13.50 mg/dl) and no significant change could be measured in liver or muscle glycogen. Cold exposition had no effect on the haematocrit of the frogs but significantly reduced (P < 0.01) the haematocrit of toads from 20.0 +/- 2.1% to 5.8 +/- 1.7% due to a decreased red blood cell volume (from 1532 +/- 63 to 728 +/- 87 mm3). When toads were injected with glucose, blood glucose increased to levels similar to those of frogs and haematocrit did not change, but this failed to make them cryoresistent. In conclusion, the lack of cold-induced glucose catabolism may not be the only mechanism responsible for the freeze intolerance of Bufo paracnemis, a freeze-intolerant species.

The importance of glucose for the freezing tolerence/intolerence of the anuran amphibians Rana catesbeiana and Bufo paracnemis

Several species of terrestrially hibernating frogs, turtles and inserts have developed mechanisms, such as increased plasma glucose, anti-freeze proteins and antioxidant enzymes that resist to freezing, for survival at subzero temperatures. In the present study, we assessed the importance of glucose to cryoresistance of two anuran amphibians: the frog Rana catesbeiana and the toad Bufo paracnemis. Both animals were exposed to -2 degrees Celsius for measurements of plasma glucose levels, liver and muscle glycogen content, haematocrit and red blood cell volume. Frogs survived cold exposure but toads did not. Blood glucose concentration increased from 40.35 + 7.25 to 131.87 + 20.72 mg/dl (P < 0.01) when the frogs were transferred from 20 to -2 degrees Celsius. Glucose accumulation in response to cold exposition in the frogs was accompanied by a decrease (P < 0.05) in liver glycogen content from 3.94 + 0.42 to 1.33 + 0.36 mg/100 mg tissue, indicating that liver carbohydrate reserves were probably the primary carbon source of glucose synthesis whereas muscle carbohydrate seems unimportant. In the toads, the cold-induced hyperglycaemia was less (P < 0.05) pronounced (from 27.25 + 1.14 to 73.72 + 13.50 mg/dl) and no significant change could be measured in liver or muscle glycogen. Cold exposition had no effect on the haematocrit of the frogs but significantly reduced (P < 0.01) the haematocrit of toads from 20.0 + 2.1 per cent to 5.8 + 1.7 per cent due to a decreased red blood cell volume (from 1532 + 63 70 728 + 87 mm3). When toads were injected with glucose, blood glucose increased to levels similar to those of frogs and haematocrit did not change, but this failed to make them cryoresistent. In conclusion, the lack of cold-induced glucose catabolism may not be the only mechanism responsible for the freeze intolerance of Bufo paracnemis, a freeze-intolerant species.

Chronic immobilization-induced stress increases plasma testosterone and delays testicular maturation in pubertal rats.

We investigated whether chronic stress, applied from prepuberty to early puberty, interferes with the spermatogenic and androgenic testicular functions. Male pubertal rats (40 days old) were immobilized 6 h per day for 15 days. Plasma concentrations of corticosterone, prolactin and testosterone were significantly augmented following immobilization, whereas plasma luteinizing hormone decreased and follicle-stimulating hormone was not altered. Acute immobilization (5 min) increased prolactin and testosterone levels in control rats but caused a significantly higher increase in these hormones when superimposed on chronic stress. A lower extent of testicular maturation was observed in pubertal rats immobilized from prepuberty.

Streptozotocin-induced diabetes: significant changes in the kinetic properties of the soluble form of rat bone alkaline phosphatase.

A soluble form of an alkaline phosphatase, obtained from the osseous plate of streptozotocin-induced diabetic rats, was purified 90-fold with a yield of 26%. The calculated Mr of the purified enzyme was 80,000 by denaturing polyacrylamide gel electrophoresis and 160,000 by gel filtration on Sephacryl S-300, suggesting a dimeric structure for its native form. In the absence of metal ions, the p-nitrophenylphosphatase activity of the purified enzyme was 4223.1 U/mg. Magnesium or calcium ion concentrations up to 2 mM increased the specific activity of the enzyme to 9896.5 and 10,796.2 U/mg, respectively. The enzyme was stimulated to a lesser extent by MnCl2 (5390.1 U/mg) and CoCl2 (5088.2 U/mg). The purified soluble alkaline phosphatase showed a broad substrate specificity, and among the less hydrolyzed substrates were pyrophosphate (1517.6 U/mg) and bis-p-nitrophenylphosphate (499.6 U/mg). The enzyme was relatively stable at 45 degrees for periods as long as 180 min, but was denatured rapidly above 50 degrees, following first order kinetics with T1/2 values ranging from 3.5 to 57.7 min. The results reported herein suggested that the soluble form of alkaline phosphatase from streptozotocin-induced diabetic rats had its kinetic properties altered, apparently as a consequence of changes in metal-binding properties.

Decreased spermatogenic and androgenic testicular functions in adult rats submitted to immobilization-induced stress from prepuberty

We investigated whether chronic stress applied from prepuberty to full sexual maturity interferes with spermatogenic and androgenic testicular functions. Male Wistar rats (40 days old) were immobilized 6 h a day for 60 days. Following immobilization, plasma concentrations of corticosterone and prolactin increased 135 per cent and 48 per cent, respectively, while plasma luteinizing hormone and testosterone presented a significant decrease of 29 per cent and 37 per cent, respectively. Plasma concentration of follicle-stimulating hormone was not altered in stressed rats. Chronic stress reduced the amount of mature spermatids in the testis by 16 per cent and the spermatozoon concentration in the cauda epididymidis by 32 per cent. A 17 per cent reduction in weight and a 42 per cent decrease in DNA content were observed in the seminal vesicle of immobilized rats but not in its fructose content. The growth and secretory activity of the ventral prostate were not altered by chronic stress.

Low-intensity ultrasound energy applied to the testes of aged rats.

Previous studies from our laboratory have shown that low-intensity ultrasound applied to the scrotum of prepubertal rats causes a 62% increase in plasma testosterone, suggesting a possible stimulation of LH receptors and/or the enzymes controlling the steroidogenic process. The purpose of the present study was to investigate whether low-intensity ultrasound has a stimulatory effect on the androgenic activity of aged testes. In addition to plasma testosterone, LH and FSH, the testicular spermatogenic status was also analysed. Ultrasound applied to the scrotum of aged rats did not stimulate sperm production, which was significantly reduced compared to sexually mature animals, and failed to re-establish the steroidogenic testicular function, which was decreased by 74%, suggesting an inherent loss of gonadal steroidogenic competence.

Decreased spermatogenic and androgenic testicular functions in adult rats submitted to immobilization-induced stress from prepuberty.

We investigated whether chronic stress applied from prepuberty to full sexual maturity interferes with spermatogenic and androgenic testicular functions. Male Wistar rats (40 days old) were immobilized 6 h a day for 60 days. Following immobilization, plasma concentrations of corticosterone and prolactin increased 135% and 48%, respectively, while plasma luteinizing hormone and testosterone presented a significant decrease of 29% and 37%, respectively. Plasma concentration of follicle-stimulating hormone was not altered in stressed rats. Chronic stress reduced the amount of mature spermatids in the testis by 16% and the spermatozoon concentration in the cauda epididymidis by 32%. A 17% reduction in weight and a 42% decrease in DNA content were observed in the seminal vesicle of immobilized rats but not in its fructose content. The growth and secretory activity of the ventral prostate were not altered by chronic stress.

Ultrasound stimulation of rat testes damaged by busulfan.

The purpose of the present study was to investigate whether or not low-intensity ultrasound exposure (20 mW/cm2 average intensity) accelerates the repair of rat germinal epithelium damaged by an antispermatogenic agent. The results from analysis of testicular weight and DNA content, sperm production and epididymal sperm concentration showed that the time needed for the reestablishment of the spermatogenic process following busulfan treatment was not reduced by ultrasound energy suggesting that, in contrast to many other mammalian tissues, the seminiferous epithelium is refractory to ultrasound stimulation.

Effects of guanethidine-induced sympathectomy on the spermatogenic and steroidogenic testicular functions of prepubertal to mature rats.

Selective chemical sympathectomy of the internal genital organs of prepubertal to mature male Wistar rats was performed by chronic treatment with low doses of guanethidine. Sympathetic denervation caused an increase in intratesticular progesterone levels in prepubertal and early pubertal rats in addition to a decrease in androstenedione and testosterone levels in prepubertal animals, thus indicating a decrease in the conversion of progesterone into androgen, probably by blocking the steroidogenic enzymatic pathway at the 17 alpha-hydroxylase/17, 20 desmolase level. A lower degree of testicular maturation, probably related to reduced androgen activity, was observed in prepubertal and early pubertal sympathectomized rats. Concentration of spermatozoa, on the other hand, was increased in the enlarged cauda epididymidis of late pubertal and mature denervated animals. This result is discussed in terms of the impairment of epididymal mechanisms of seminal emission, fluid resorption and spermatozoal disposal.

Direct effect of low-intensity pulsed ultrasound on pubertal rat seminal vesicle.

Pubertal male Wistar rats were submitted to bilateral castration and killed 7 or 14 days later; an additional group of castrated rats was submitted to ultrasound stimulation of the ventral region lying above the accessory sex glands, for 20 min a day from the 7th to the 14th day postcastration. Control intact rats were age-matched to the different treated groups. Seminal vesicle growth and secretory activity were investigated on the basis of weight and fructose content, respectively. A progressive fall in seminal vesicle weight was observed over a period of 7 (83% decrease) to 14 (92% decrease) days following castration; ultrasound treatment beginning on the 7th day prevented this additional weight reduction. Castration caused also a marked decrease (50-60%) in the fructose content of the seminal vesicle and the ultrasound energy promoted a partial recovery of the secretory activity of the gland. The results revealed a direct ultrasound stimulation of the seminal vesicle secretory activity in pubertal rats deprived of testicular androgens.

The hypophyseal-testicular axis and sex accessory glands following chemical sympathectomy with guanethidine of pre-pubertal to mature rats.

Selective chemical sympathectomy of the internal sex organs of prepubertal to mature male Wistar rats was performed by chronic treatment with low doses of guanethidine. Plasma testosterone and luteinizing hormone and the intratesticular level of testosterone were determined. The weight and fructose content of seminal vesicle and ventral prostate were also investigated. The results showed that sympathetic innervation is related to the control of the hypophyseal-testicular axis as well as to the growth and potential secretory activity of the male sex accessory glands.

Time-dependent effects of lead on rat reproductive functions.

The effects of exposure to lead on endocrine function and the reproductive parameters were studied in pubertal rats treated with 1.0 g l-1 lead acetate in drinking water for 20 days (subacute group) or 9 months (chronic group) in addition to i.v. injections of lead acetate (0.1 mg 100 g-1 body wt.) every 10 (subacute group) or 15 days (chronic group). Although basal levels of testosterone were higher both in plasma and in testes of acutely intoxicated animals, the circulating levels of luteinizing hormone (LH) were not affected in either group, nor was the LH-releasing hormone content of the median eminence. The density of [125I]LH/human chorionic gonadotrophin (hCG) binding sites in testicular homogenates was reduced by saturnism in both groups, concomitant with a significantly increased apparent affinity constant of the hormone-receptor complex. These data can be viewed as the result of a mixture of specific lead toxicity (e.g. at the enzyme level) with other more general actions (e.g. at the level of the hypothalamus-pituitary-testicular axis).

The male reproductive organs in experimental Chagas' disease. III. Plasma testosterone and accessory sex glands in the acute phase of the disease.

Male Wistar rats were injected i.p. with 2 x 10(5) trypomastigotes of the Bolivia strain. Fifteen days later, few parasite nests were observed in the fibromuscular layer surrounding the seminal vesicle acini of chagasic animals and no parasites were detected in the testis and ventral prostate. A significant decrease was observed in the absolute weight and fructose content of the seminal vesicle and ventral prostate of chagasic rats, which also presented a sharp decrease in plasma testosterone levels.

Sexual development of male Wistar rats.

1. Sexual development was investigated in male Wistar rats from 22 to 97 days of age by morphometric, biochemical and radioimmunological methods. 2. The first significant increase of plasma testosterone (T) occurred from 40 to 50 days of age and a progressive enhancement was observed thereafter to a maximum at 76 days (5.4 +/- 0.9 ng/ml). From that time onward, plasma T was gradually depressed to adult levels at 97 days of age (2.0 +/- 0.3 ng/ml). Plasma prolactin increased in parallel to T, reaching a maximum at 76 days (9.2 +/- 0.9 ng/ml) and attaining a lower plateau by 83 to 97 days of age (5.0 +/- 0.5 ng/ml). A small but significant increase was observed in plasma luteinizing hormone from 22 to 83 days of age. Plasma follicle stimulating hormone was high at 22 days, increased to a maximum at 40 days (15.4 +/- 0.6 ng/ml) and fell slowly to a lower plateau by 76 to 97 days of age. 3. Fructose content in the ventral prostate increased abruptly from 50 to 63 days of age (148.8 +/- 19.8 micrograms) and no significant change was observed thereafter. A progressive increase in the seminal vesicle fructose content was observed from 40 to 63 days (45.6 +/- 2.8 micrograms) when a plateau was reached. 4. The evolution of the germinal epithelium was investigated in cross-sections of seminiferous tubules analyzed at random for the presence of the most advanced germ cell and also for sperm production (estimated by the number of spermatids in stages 15 to 18 of spermiogenesis).(ABSTRACT TRUNCATED AT 250 WORDS)

Sexual development of male Wistar rats

1. Sexual development was investigated in male Wistar rats from 22 to 97 days of age by morphometric, biochemical and radioimmunological methods. 2. The first significant increase of plasma testosterone (T) occurred from 40 to 50 days of age and a progressive enhancement was observed thereafter to a maximum at 76 days (5.4 +/- 0.9 ng/ml). From that time onward, plasma T was gradually depressed to adult levels at 97 days of age (2.0 +/- 0.3 ng/ml). Plasma prolactin increased in parallel to T, reaching a maximum at 76 days (9.2 +/- 0.9 ng/ml) and attaining a lower plateau by 83 to 97 days of age (5.0 +/- 0.5 ng/ml). A small but significant increase was observed in plasma luteinizing hormone from 22 to 83 days of age. Plasma follicle stimulating hormone was high at 22 days, increased to a maximum at 40 days (15.4 +/- 0.6 ng/ml) and fell slowly to a lower plateau by 76 to 97 days of age. 3. Fructose content in the ventral prostate increased abruptly from 50 to 63 days of age (148.8 +/- 19.8 micrograms) and no significant change was observed thereafter. A progressive increase in the seminal vesicle fructose content was observed from 40 to 63 days (45.6 +/- 2.8 micrograms) when a plateau was reached. 4. The evolution of the germinal epithelium was investigated in cross-sections of seminiferous tubules analyzed at random for the presence of the most advanced germ cell and also for sperm production (estimated by the number of spermatids in stages 15 to 18 of spermiogenesis).(ABSTRACT TRUNCATED AT 250 WORDS)

Stimulation of prepubertal, pubertal and adult rat testis with low-intensity pulsed ultrasound.

Testes of prepubertal, pubertal and adult Wistar rats were stimulated with low-intensity pulsed ultrasound for 20 min a day, for 7 days. No significant changes were found in the spermatogenic activity as well as in plasma LH and FSH levels following ultrasound treatment. The testicular androgenic activity, however, was significantly increased in prepubertal treated animals, in addition to a significant increase in seminal vesicle growth and secretory activity. In spite of normal androgenic levels, pubertal treated rats presented also an increase in the seminal vesicle secretory activity, thus suggesting a direct action of ultrasound on the gland.

Prepubertal development of rat prostate and seminal vesicle following chemical sympathectomy with guanethidine.

1. The internal genital organs of prepubertal, 21-day old male Wistar rats were sympathectomized by ip injection of guanethidine (G), at doses of 5 mg/kg per day (N = 10) or 10 mg/kg per day (N = 10), for 20 days. Controls (N = 10) received saline. 2. Plasma testosterone level (measured by radioimmunoassay) decreased significantly in sympathectomized rats from 4.11 +/- 0.57 to 1.76 +/- 0.37 ng/ml (5 mg/kg G) and to 1.17 +/- 0.26 ng/ml (10 mg/kg G). Plasma levels of luteinizing and follicle-stimulating hormones and of prolactin were unaltered. 3. Chemical denervation caused a significant decrease in ventral prostate wet weight from 74.3 +/- 5.5 to 59.3 +/- 4.7 mg (5 mg/kg G) and to 54.6 +/- 4.1 mg (10 mg/kg G) and in seminal vesicle wet weight from 36.5 +/- 6.8 to 31.7 +/- 5.2 mg (5 mg/kg G) and to 21.3 +/- 1.6 mg (10 mg/kg G). 4. The potential secretory activity of the prostate (measured in terms of fructose content) decreased significantly in guanethidine-treated rats from 0.38 +/- 0.02 to 0.30 +/- 0.02 mg/g (5 mg/kg G) and to 0.20 +/- 0.02 mg/g (10 mg/kg G). The seminal vesicle fructose content (0.33 +/- 0.04 mg/g for controls), however, was not altered by chemical denervation. 5. Our data suggested that sympathetic neurons may be involved in the control of LH receptors, at least in the prepubertal phase of sexual development. They may also be directly related to growth and secretory activity of the male accessory sex glands.

Prepubertal development of rat prostate and seminal vesicle following chemical sympathectomy with guanethidine

1. The internal genital organs of prepubertal, 21-day old male Wistar rats were sympathectomized by ip injection of guanethidine (G), at doses of 5 mg/kg per day (N = 10) or 10 mg/kg per day (N = 10), for 20 days. Controls (N = 10) received saline. 2. Plasma testosterone level (measured by radioimmunoassay) decreased significantly in sympathectomized rats from 4.11 +/- 0.57 to 1.76 +/- 0.37 ng/ml (5 mg/kg G) and to 1.17 +/- 0.26 ng/ml (10 mg/kg G). Plasma levels of luteinizing and follicle-stimulating hormones and of prolactin were unaltered. 3. Chemical denervation caused a significant decrease in ventral prostate wet weight from 74.3 +/- 5.5 to 59.3 +/- 4.7 mg (5 mg/kg G) and to 54.6 +/- 4.1 mg (10 mg/kg G) and in seminal vesicle wet weight from 36.5 +/- 6.8 to 31.7 +/- 5.2 mg (5 mg/kg G) and to 21.3 +/- 1.6 mg (10 mg/kg G). 4. The potential secretory activity of the prostate (measured in terms of fructose content) decreased significantly in guanethidine-treated rats from 0.38 +/- 0.02 to 0.30 +/- 0.02 mg/g (5 mg/kg G) and to 0.20 +/- 0.02 mg/g (10 mg/kg G). The seminal vesicle fructose content (0.33 +/- 0.04 mg/g for controls), however, was not altered by chemical denervation. 5. Our data suggested that sympathetic neurons may be involved in the control of LH receptors, at least in the prepubertal phase of sexual development. They may also be directly related to growth and secretory activity of the male accessory sex glands

Kinetic properties of osseous plate alkaline phosphatase from diabetic rats.

1. Increased levels of bone alkaline phosphatase activity were observed in diabetic rats. These animals exhibited impaired bone development without concomitant alterations of the sequence of cellular transformations. 2. Alkaline phosphatase activity was delayed in diabetic rats but the kinetic parameters for the hydrolysis of p-Nitrophenylphosphate (PNPP) were virtually the same observed for controls (N = 1.2 and K0.5 = 43 microM). 3. Alkaline phosphatase from diabetic rats had a better affinity (K0.5 = 38 microM) for magnesium ions than controls (K0.5 = 91 microM). 4. Zinc ions affected alkaline phosphatase activity from control and diabetic rats in the same way (K0.5 = 10 microM).

Alcohol-induced alterations in the palate epithelium of the rat fetus.

Maternal alcoholism (ethanol and sugar cane brandy) during gestation induces delayed cellular growth and differentiation in fetal rat palate epithelium, with increased nuclear, cytoplasmic and cellular volumes, increased epithelial and keratin thickness and decreased cellular numerical density.