Activity of nuclear RNA polymerases in the liver of rats of different ages after phenobarbital administration

DNA-dependent RNA-polymerases of nuclei isolated from the liver of rats aged 3- and 24 months were studied in different periods after phenobarbital administration. It is shown that 4h after single intraperitoneal injection of the preparation (80 mg per 1 kg of the body mass) to young animals the activity of the RNA-polymerase I rises, it remains higher, the following 12-20 h and then returns to the initial level. The activity of RNA-polymerases II and III under these conditions 16 h later remains higher the following 8 h and 24 h later the activity of the first enzyme returns to the initial value and that of the second one becomes still more. In old rats (24 months) the activity of all three classes of RNA-polymerases is lower than in young ones and increases only 48 h later. Under long-term administration of phenobarbital (40 mg per 1 kg of the body mass daily, 4 days) the activity of RNA-polymerase I was the same as in the intact animals of the corresponding ages and the activity of RNA-polymerases II and III increased both in young and old rats. Single administration of the preparation increases the liver mass in the young animals 24 h later and in the old ones--48 h later. Long-term administration of the preparation enhances its mass both in young and old animals, but its relative increase is more expressed in rats at the age of 3 months.     

Effects of age on morphology,protein synthesis and secretagogoue-evoked secretory responses in the rat lacrimal gland

This study investigated changes in the morphology and protein synthesis and protein and peroxidase secretion due to peptidergic and aminergic stimulation from rat lacrimal gland acinar cells of 3–5, 9, 12, 20 and 24 month old rats. There was a marked reduction in the presence of Golgi apparatus in the acinar cells of glands from the 24 month old rats coupled to dilatation and degeneration of rough endoplasmic reticulum, when compared to that in the acinar cells of glands from 3–5 and 12 month old rats. Following incorporation of tritiated leucine for 360 min (6 h), the amount of newly synthesised protein in acinar cells of the 12 month old rats was significantly (p < 0.01) higher than that in the acinar cells of 3–5 month old animals. However, at 20 months the amount of newly synthesised protein in these acinar cells was significantly (p < 0.01) reduced to less than that in acinar cells of both the 3–5 and 12 month old animals. Immunohistochemical and immunofluorescence studies identified the presence of substance P (SP), vasoactive intestinal peptide (VIP), histamine and 5-hydroxytryptamine (5-HT) in the lacrimal glands of 3–5 month old rats. Stimulation by either SP, VIP, histamine or 5-HT resulted in significant increases in total protein output and peroxidase release from acinar cells of the 3–5 month old rats. However, all responses to the secretagogues were reduced with ageing from 3–5 to 24 months of age. The results indicate that ageing is associated with alteration in the ability of acinar cells to synthesise and secrete proteins.     

Effect of graded doses of tri-iodothyronine on ventricular myosin ATPase activity and isomyosin profile in young and old rats.

Ventricular myosin ATPase activity, V1 isomyosin content and serum T3 (tri-iodothyronine) values decrease with age in male Fischer 344 rats. To determine if the age decrement in ATPase activity and V1 isomyosin content are caused by decreased T3 levels or an age-related decrease in V1 isomyosin induction by T3, 3-, 12- and 24-month-old male Fischer 344 rats were given constant T3 infusions by osmotic minipump. Rats at all ages were given 0.75, 5 and 15 micrograms(/100 g per 24 h) doses of T3, whereas 12- and 24-month-old rats were given an additional 0.4 microgram dose. In control rats, T3 levels decreased from 97 +/- 2.7 at 3 months to 75 +/- 4.7 ng/100 ml at 24 months. Likewise, Ca2+-activated myosin ATPase activity decreased from 1.04 +/- 0.05 to 0.68 +/- 0.05 mumol of Pi/min per mg of protein, and the relative proportion of V1 of isomyosin decreased from 90 +/- 4.0 to 26 +/- 2.0%. The lowest (0.4 microgram) T3 dose, which was sufficient to restore T3 levels in 24-month-old animals to 3-month control values, abolished the age decrement in myosin ATPase activity and markedly increased the proportion of V1 isomyosin present in the ventricle. These findings indicate that the senescent ventricle responds readily to small doses of T3 and strongly suggest that the age decrement in serum T3 levels is sufficient to contribute to the age-related decrease in myosin ATPase activity and V1 isomyosin content. Since these parameters correlate with ventricular contractility, the age decrement in T3 levels may also contribute to the decreased ventricular contractility and cardiac output observed in senescent rats.     

The streaming of the submandibular gland. II: Parenchyma and stroma advance at the same velocity

Thirty young male rats aged 7 weeks, weighing 200 g, were injected with 18.5 kBq g-1 (0.5 microCi g-1) body weight tritiated thymidine [3H]TdR (specific activity 185 GBq). The rats were then killed in groups of five, at the following times: 1 hour, and 14, 30, 60, 90, and 120 days. Autoradiograms of sections through the submandibular gland were prepared, and the location of labelled cells in tubular and acinar cross sections was recorded. The nuclear content of each cross section was defined as its 'class'. In this numbering system, narrow tubuli, e.g. intercalated ducts are of low class, and wider tubuli, e.g. striated ducts, of high class. One hour after labelling most labelled tubular cells were found in low class cross sections, i.e. intercalated ducts and narrow granular ducts. Striated ducts were not labelled. From then onward labelled cells entered wider tubuli, e.g. striated ducts. The advancing labelled epithelium was accompanied by labelled stroma. Both cell types traversed 0.089 classes per day. In acini, labelled cells advanced in the opposite direction, starting from acinar cross sections of high class and ending in class-1 cross sections.     

Influence of unilateral castration and increased plane of nutrition on sexual development of Holstein bulls. II. Histologic development of the testes

Sixty-five Holstein bull calves were assigned in an experiment to determine the effects of unilateral castration (UC) at 1 week of age and of two levels of nutrition after 6 months on reproductive development to 16 months. Five animals were killed at 1 wk and half the remainder UC at that age. Groups of 5 in all factorial groups were killed at 2, 4, 8 and 16 months. Tubular diameter increased with age (P<.01) and at 8 and 16 months with UC (P<.01). Epithelial area at 8 and 16 months increased with age and UC (P<.01). The percents of tubular and intertubular tissue varied with age (P<.01) with the tubular tissue having its highest value at 8 months. Indexes of both total tubular and intertubular tissue were increased with age and UC (P<.01). The number of type A spermatogonia per cross section of stage 1 tubules of 16-month bulls was increased by UC (P<.05).     

Peculiarities of urea distribution in tissues of rats of different age

The content of urea was studied in protein-free filtrates of the liver kidneys, skeletal muscles, myocardium, spleen, brain tissues and blood serum as well as in urine of 1, 3, 6, 12 and 24-month rats. It is shown that at the age of 6 months the content of urine in most tissues under study is significantly decreased (by 42-73%), at the age of 12 months in the spleen and at the age of 24 months in the brain tissues as compared to the one-month animals. The level of urine decrease in the liver and brain tissues of 24-month animals is less pronounced than in other tissues, that corresponds to age peculiarities of their protein metabolism. A decrease of blood consumption per weight unit and a relative increase in the amount of nitrogen excreted with urine are observed with ageing. The arginase activity in the liver decreases essentially only in 3-month animals. A conclusion is drawn that peculiarities of food consumption and the character of changes in the urea content in tissues and urine are adaptation manifestation of an age decrease in the intensity of nitrogen metabolism and protein demand of the organism.     

Age-related differences in serum melatonin and pineal NAT activity and in the response of rat pineal to a 50-Hz magnetic field.

In a previous study we have shown that exposure to a 50-Hz sinusoidal magnetic field decreased serum melatonin concentration and pineal enzyme activities in young rats (9 weeks). In the present study we looked for the effect of a magnetic field of 100 microT on serum melatonin and pineal NAT activity in aged rats and compared them to young rats. We hypothesized that aging may change sensitivity of rats to a magnetic field. Two groups of Wistar male rats [aged rats (23 months) and young rats (9 weeks)] were exposed to 50-Hz magnetic fields of 100 microT for one week (18h/day). The animals were kept under a standard 12:12 light: dark cycle with a temperature of 25 degrees C and a relative humidity of 45 to 50%. Control (sham-exposed) animals were kept in a similar environment but without exposure to a magnetic field. The animals were sacrificed under red dim light. Serum melatonin concentration and pineal N-acetyltransferase (NAT) and hydroxyindole-O-methyltransferase (HIOMT) activities were studied. Our results showed that sinusoidal magnetic fields altered the production of melatonin (28% decrease; P <0.05) through an inhibition of pineal NAT activity (52% decrease; P <0.05) in the young rats whereas no effect was observed in aged ones. On the other hand, when comparing data from control animals between young and aged rats, we observed that serum melatonin level and NAT activity, but not HIOMT activity, decreased in aged rats (decrease by about 38% and 36% respectively). Our data strongly suggest that old rats are insensitive to the magnetic field.     

The streaming of the submandibular gland II: parenchyma and stroma advance at the same velocity

Abstract Thirty young male rats aged 7 weeks, weighing 200 g, were injected with 18.5 kBq g⁻¹ (0.5 μCi g⁻¹) body weight tritiated thymidine [³H]TdR (specific activity 185 GBq). The rats were then killed in groups of five, at the following times: 1 hour, and 14, 30, 60, 90, and 120 days. Autoradiograms of sections through the submandibular gland were prepared, and the location of labelled cells in tubular and acinar cross sections was recorded. The nuclear content of each cross section was defined as its 'class'. In this numbering system, narrow tubuli, e.g. intercalated ducts are of low class, and wider tubuli, e.g. striated ducts, of high class. One hour after labelling most labelled tubular cells were found in low class cross sections, i.e. intercalated ducts and narrow granular ducts. Striated ducts were not labelled. From then onward labelled cells entered wider tubuli, e.g. striated ducts. The advancing labelled epithelium was accompanied by labelled stroma. Both cell types traversed 0.089 classes per day. In acini, labelled cells advanced in the oposite direction, starting from acinar cross sections of high class and ending in class-1 cross sections.     

Effect of Aging on the Metabolism of Pyruvate and 3-Hydroxybutyrate in Nonsynaptic and Synaptic Mitochondria from Rat Brain

Abstract: Age-dependent changes in the oxidative metabolism in nonsynaptic and synaptic mitochondria from brains of 3, 12, and 24-month-old rats were investigated. When pyruvate and malate were used in conjunction as substrates, a significant reduction in State 3 respiration was observed in both mitochondrial populations from 12-and 24-month-old rats compared with 3-month-old animals. A similar age-dependent reduction in the oxidation of [1-¹¹C]pyruvate was also observed in nonsynaptic and synaptic mitochondria from senescent rats. Pyruvate dehydrogenase complex activity (both active and total) was, however, not decreased in the two mitochondrial populations from brains of 3, 12, and 24-month-old rats. When DL-3-hydroxybutyrate plus malate were used as substrates, a decrease in State 3 respiration was observed only in synaptic mitochondria from 24-month-old rats compared with 3- month-old animals. Similarly, an age-dependent reduction in the oxidation of 3-hydroxy[3-¹¹C]butyrate was also observed only in synaptic mitochondria from 12-and 24-month-old rats. However, a significant reduction in the activities of ketone body-metabolizing enzymes, namely, 3-hydroxybutyrate dehydrogenase, 3-ketoacid CoA transferase, and acetoacetyl-CoA thiolase was observed in both mitochondrlal populations from 12- and 24-month-old rats compared with 3 month-old animals. These findings show that specific alterations in oxidative metabolism occur in nonsynaptic and synaptic mitochondria from aging rats. The data also suggest that in addition to alterations in enzyme activities, permeability of anions (e.g. pyruvate) across the inner mitochondrial membrane may be altered in nonsynaptic and synaptic mitochondria from senescent animals.     

Effect of aging on monoamines and their metabolites in the rat brain

Concentrations of dopamine (DA), norepinephrine (NE), serotonin (5-HT) and their acid merabolites were assayed in specific brain areas of Wistar rats of various ages. DA and its metabolite 3,4-dihydroxyphenylacetic acid (DOPAC) were significantly lower in striatum and mesolimbic areas of old (24 mos) rats than young adult (3 mos), but not mature (12 mos) rats. The decrease of homovanillic acid (HVA) was significant in mesolimbic areas but not in striatum. Neither cortical NE nor its metabolite methoxydroxyphenylglycol sulphate (MHPG-SO₄) were significantly changed by aging. 5-HT and 5-hydroxyindoleacetic acid (5-HIAA) in the brainstem showed a tendency to a decrease and increase respectively in aged animals compared with young adults, but the differences were not statistically significant. However, the ratio of 5-HIAA to 5-HT concentrations was significantly higher in aged animals. The conclusion can be drawn that, in these brain areas, DA is more vulnerable to aging than NE and 5-HT, the metabolism of the latter being even enhanced.     

Stimulation of spermatocyte development in prepubertal rats by the Sertoli cell steroid, 3 alpha-hydroxy-4-pregnen-20-one

The effect of 3 alpha-hydroxy-4-pregnen-3-one (3HP), a Sertoli cell steroid, on spermatogenesis was examined in normal and gonadotropin-suppressed rats, through s.c. as well as direct intratesticular injections. Early experiments employing normal prepubertal male rats indicated that 3HP, when administered at 65 micrograms/100 g BW daily for 15 days, was capable of stimulating pachytene spermatocyte number to 149% of untreated control numbers. It was of interest to determine if this effect could be amplified in gonadotropin-suppressed animals. Neonatally estrogenized rats (500 micrograms estradiol benzoate in 0.1 ml oil at 2 days) were treated on alternate days with 3HP (100 micrograms/100 g BW) for 3 wk, starting at 7 days of age. This treatment significantly increased the number of spermatocytes per tubule cross section from 17.3 +/- 1.9 (in estradiol benzoate-only animals) to 47.1 +/- 7.9 (p less than 0.01). In a similar study, 100 micrograms/100 g BW of testosterone propionate could stimulate spermatocyte number to only 15.1 +/- 2.2 cells per tubule cross section versus estradiol benzoate-only numbers. A single intratesticular injection of 3HP (2 ng in 2.0 microliters oil) in Methallibure-treated rats resulted in a significant increase in late pachytene spermatocyte numbers from 0.77 +/- 0.12 in Methallibure-only-treated rats to 1.70 +/- 0.10 (p less than 0.001) cells per tubule cross section in 28-day-old rats. However, in this study, no other progesterone metabolite or androgenic steroid (testosterone, 5 alpha-dihydrotestosterone, or 5 alpha-androstan-3 alpha, 17 beta-diol) tested was capable of this level of germ cell stimulation. In conclusion, 3HP appears to have a direct effect on germ cell development within the testis at levels much lower than those shown to be effective for androgens. It does not appear that this effect is mediated through the conversion of 3HP to any C21 or C19 steroids, and appears to be the first report of a Sertoli cell steroid with a possible role in the process of mammalian spermatogenesis.     

Effect of free radicals on adenosine A(2A) and dopamine D2 receptors in the striatum of young adult and aged rats

Parkinson's disease (PD) is a prevalent age-related motor dysfunction resulting from the hyperactivity of the indirect striatal pathway, which is controlled in an antagonistic manner by inhibitory dopamine D2 and facilitatory adenosine A(2A) receptors. Thus, dopamine precursors like l-DOPA are the standard therapy and A(2A) antagonists are now tested as anti-parkinsonians. Increased free radicals levels occur on aging and are proposed to be a contributing factor for PD. We now tested if free radicals affected A(2A) and D2 receptors in striatal membranes of young adult (2 months) and old (24 months) rats. The A(2A) receptor antagonist [3H]SCH 58261 bound to striatal membranes with a KD of 0.9 nM and a Bmax of 953 fmol/mg protein in young rats and with a KD of 0.8 nM and a Bmax of 725 fmol/mg protein in aged rats (24% decrease). The D2 receptor antagonist [3H]raclopride bound to striatal membranes with a KD of 4.0 nM and a Bmax of 598 fmol/mg protein in young rats and with a KD of 4.3 nM and a Bmax of 368 fmol/mg protein in aged rats (38% decrease). Exposure of striatal membranes to a free radical generation system (2 mM FeSO4 and 4 mM ascorbate) caused a similar decrease of [3H]SCH 58261 (35%) and [3H]raclopride (37%) binding in young adult rats but caused a greater decrease of [3H]SCH 58261 (49%) than of [3H]raclopride (20%) binding in aged rats. Thus, in aged rats, there is an unbalance of A(2A)/D2 receptor density favouring A(2A) receptors, which is restored on exposure to free radicals. This supports the hypothesis that the effectiveness of A(2A) receptor antagonists as anti-parkinsonians, demonstrated in young adult animals, may not be affected by a modified A(2A)/D2 receptor density in aged individuals suffering from exposure to increased free radical levels, as occurs in PD.     

Role of the glycerophosphate shunt in regulating oxidation of cytoplasmic NADH and ATP synthesis by liver mitochondria during rat ontogeny

The activity of alpha-glycerophosphate dehydrogenase rate of alpha-glycerophosphate oxidation and ATP synthesis were determined in the liver mitochondria of 1, 3, 12 and 24-month old rats in norm and two days after thyroxin daily administration in a dose of 0.25 mg per 100 g of body mass. The value of the studied parameters decreases with the age, most considerably--from one to three months and then--from 3 to 24-month age. This evidence for the fact that the role of glycerophosphate shuttle in the energy supply of cells falls with ageing; thyroxin administration evoked almost a two-fold increase of the mentioned parameters in one-month rats and more than three-fold in 12 and 24-month animals. A decrease in the alpha-glycerophosphate dehydrogenase activity with ageing is supposed to be connected with the thyroid gland function.     

Frequency of the stages in the cycle of the seminiferous epithelium in the rat

This study determined the optimum number of tubules to be counted per testis cross section, and the number of animals per treatment group, when changes in stage frequencies in the cycle of the seminiferous epithelium are criteria for assessing effects of treatment on spermatogenesis. A data base of 9,672 observed and staged tubules was collected from testicular cross sections of 15 Sprague-Dawley rats. A significant variation between animals was found for the frequencies of Stages I, II, IV, VI, VIII, and XIII. Computer simulation was used to randomly select different combinations of animal and tubule numbers from the observed data. Stage frequency means from each simulation experiment were compared statistically to observed mean frequencies. A model that used data from all 14 stages was analyzed. The following conclusions were made: a) a minimum of 200 tubule cross sections/testis is recommended for estimating stage frequencies; b) for a fixed number of tubules scored, the number of animals sampled is more important than the number of tubules per animal in reducing variance; c) to detect a difference of 2 standard deviations from the mean with a 2% error rate and examining 200 tubules/testis, at least 12 animals must be used per group when assessing all 14 stages; d) when individual stages are examined using 10 animals per group, only Stage VII has 80% or greater power of test (alpha = 0.05) to detect a frequency difference; e) pooling stages into 3-4 groups is recommended to improve the power of detecting a treatment difference.     

Age and food restriction alter the porphyrin concentration and mRNA levels for 5-aminolevulinate synthase in rat Harderian gland.

The effects of age and food restriction on the porphyrin concentration in Harderian glands were studied in male Fisher 344 rats. Harderian gland porphyrin concentrations increased with age; this was statistically significant in 20 month old animals compared with 3 month old animals. Food restriction (by 40%) prevented the age-associated rise in porphyrins; thus, in 20 month old food restricted rats had porphyrin concentrations similar to those found in young animals. In a second experiment, we correlated the age-associated rise in Harderian gland porphyrin concentrations with an increase in mRNA levels for 5-aminolevulinate synthase (ALV-S). Both the porphyrin concentration and ALV-S mRNA rose at 12 and 18 months of age, but decreased by 24 months of age. It is concluded that, a) porphyrin biosynthesis in the Harderian glands increases up to 20 months of age but decreases in rats that are 24 months old, and b) food restriction prevents the porphyrin rise associated with age in the Harderian gland of male Fisher 344 rats.     

Age-related effects of the neuromodulator D-serine on neurotransmission and synaptic potentiation in the CA1 hippocampal area of the rat

The effects of the co-agonist of the N-methyl-D-aspartate receptor (NMDAr) D-serine on glutamatergic neurotransmission and synaptic potentiation were studied in the CA1 hippocampal field of young (3-5 months old) and aged (25-27 months old) Sprague-Dawley rats using ex vivo extracellular electrophysiological recording techniques. Exogenous d-serine depressed fast neurotransmission mediated by the alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid/kainate subtype of glutamate receptors in young but not in aged rats by acting on inhibitory glycinergic interneurons. In contrast, D-serine dose-dependently enhanced NMDAr-mediated synaptic responses in both groups of animals, but with a larger magnitude in aged rats, thus preventing the age-related decrease in NMDAr activation. D-serine also increased the magnitude of long-term potentiation in aged but not in young rats. Finally, D-serine levels were dramatically reduced in hippocampal tissues of aged rats. Taken together, these results indicate a weaker activation of the NMDAr glycine modulatory site by endogenous D-serine in aged animals, which accounts for a reduced NMDAr contribution to synaptic plasticity in ageing.     

Reproduction in females of the little free-tailed bat, Tadarida (Chaerephon) pumila, in the eastern Transvaal, South Africa

Little free-tailed bats (2-9/month) were collected over 15 months in the eastern Transvaal lowveld (latitude 24 degrees 59'S). There was an extended but distinct breeding season of 8 months per year. Females appeared to be polyoestrous and able to bear 3 pregnancies per breeding season. There was a progressive decrease in the magnitude of the three birth peaks during the breeding season, with a concomitant slight loss in birth synchronization. Gestation period was approximately 60 days and one young per female was the rule, with implantation occurring only in the right uterine horn of the bicornuate uterus. It is suggested that offspring are weaned before the age of 21 days, and that female become sexually mature in the following breeding season at the age of 5-12 months.     

Effect of repeated stress and administration of phenobarbital on the lymphoid tissue and on protein metabolism in the lymphocytes of infant and adult rats

Further study of the response to chronic stress stimulation in the early postnatal phase showed that the i.p. injection of physiological saline (stress stimulation) induced lymphopenia, a 50% decrease in the incorporation of 3H-leucine into isolated lymphocytes and a decrease in the weight of the thymus in 7-day-old male rats. No such changes were observed in adult animals. If repeated doses of phenobarbital were administered to stressed young rats, however, lymphopenia did not occur and the rate of the incorporation of 3H-leucine into isolated lymphocytes was not different from the control value; the protein content of the lymphocytes was significantly raised, however. In adult animals, phenobarbital increased the rate of incorporation of 3H-leucine into the lymphocytes. The repeated administration of phenobarbital reduced the weight of the thymus in both young and adult animals, but a decrease in spleen weight was recorded only in the young animals. A single i.p. injection of ACTH or dexamethasone caused lymphopenia and slowed down the incorporation of 3H-leucine into the lymphocytes of both young and adult animals. The results show that the striking decrease observed in the rate of the liver metabolism of corticosterone in suckling young rats not injured by repeated stress stimulation is accompanied by significant changes in the lymphoid tissue.