Renal 25-hydroxyvitamin D-3 1 alpha-hydroxylase in guinea-pig: activity variations during development and pregnancy

The renal 25-hydroxyvitamin D-3-1 alpha-hydroxylase (1 alpha-hydroxylase) activity and circulating levels of 1,25-dihydroxyvitamin D (1,25(OH)2D) were measured in pregnant guinea-pigs and their offspring. Serum levels of 1,25(OH)2D were significantly elevated in pregnant guinea-pigs but the renal enzyme activity was not different from non-pregnant animals. The fetal renal 1 alpha-hydroxylase activity was about 6-fold higher than the maternal level, whereas circulating 1,25(OH)2D was low. Treatment with pharmacological doses of 1,25(OH)2D3 increased circulating 1,25(OH)2D and depressed the renal 1 alpha-hydroxylases both in the mother and the fetus. In newborn guinea-pigs the enzyme activity was up to 10-times that seen in adults. It declined over the first 3 weeks, showing no difference between the sexes. In sexually mature animals the males had a significantly higher 1 alpha-hydroxylase activity than the female. However, this higher enzyme activity was not correlated to serum testosterone. Around the time the animals reached sexual maturity serum 1,25(OH)2D increased in both sexes. In the males this rise was correlated to an increase in serum testosterone. It is concluded that the maternal renal 1 alpha-hydroxylase activity is unchange in late pregnancy, compared to non-pregnant females. The data indicate that the fetus produces 1,25(OH)2D, and may contribute to the maternal circulating 1,25(OH)2D. The sex difference in 1 alpha-hydroxylase activity previously demonstrated is manifest at about the time of puberty.     

Neonatal effect of clomiphene and o,p'-DDT on hepatic oxidative metabolism of male rats.

The hepatic oxidative metabolism of dehydroepiandrosterone (DHA) and aminopyrine has been investigated in adult rats of both sexes treated neonatally with either clomiphene citrate (100 mug on day 3) or o,p'-DDT (1 mg daily on days 2-3). The rates of 16 alpha-, 7 alpha- and 7 beta-hydroxylase activities of DHA and the N-demethylase activities of aminopyrine in hepatic microsomes of normal males were significantly (p less than 0.05) higher than those of females. Treatment with clomiphene citrate reduced significantly (p less than 0.05) the 16 alpha-hydroxylase activities of males and appeared to suppress the 7 alpha-hydroxylase and N-demethylase activities to a lesser extent. Neonatal o,p'-DDT also reduced these hepatic oxidative activities. Neither treatment affected the 7 beta-hydroxylase activities. On the other hand, no significant differences in these activities were observed between the control and the treated females, all of which had persistent vaginal estrus. Therefore, it appears that treatment of male neonates with these weak estrogenic compounds antagonizes the androgen-mediated expression of the DHA-16alpha-hydroxylase activity in liver.     

The effects of sex,age and diet of mice and gerbils on susceptibility to Microphallus pygmaeus (Digenea: Microphallidae)

Molan A. L. and James B. L. 1984. The effects of sex, age and diet of mice and gerbils on susceptibility to Microphallus pygmaeus (Digenea: Microphallidae). International Journal for Parasitology14: 521–526. Mature male mice (40–100-day-old) and gerbils (60–150-day-old) harbour significantly more Microphallus pygmaeus than their female counterparts. Adult worms from male mice and gerbils consistently contain more eggs than those from females but the differences are not significant. No sex differences in worm recovery occur in immature or ageing mice and gerbils. Seventy-day-old mice and gerbils of both sexes harbour significantly more worms with a higher egg production than immature and ageing animals. The worm burden of sucklings, however, is higher than in weanlings and mature mice and gerbils of both sexes fed on cow's milk harbour significantly more worms than those fed on a normal pellet diet.     

Sex differences in the activity of mice: modulation by postnatal gonadal hormones

A series of six experiments was performed to examine the influence of postnatal-gonadal-hormone exposure on home-cage activity in Rockland-Swiss albino mice. Intact females were more active than their male counterparts and gonadectomy in adulthood, while reducing levels of the behavior in both sexes, did not eliminate the gender difference. Males that were castrated on the day of birth were more active than animals castrated 5, 10, or 25 days later. Also, females treated with testosterone propionate on the day of birth were less active than oil-treated controls and females exposed to the steroid 10 days after birth. Thus, perinatal exposure to gonadal hormones suppresses adult levels of home-cage activity in mice.     

Ommochrome deficiency in an albino strain of a terrestrial isopod, Armadillidium vulgare.

In order to clarify the cause of ommochrome deficiency in an albino strain of the terrestrial isopod, Armadillidium vulgare, levels of xanthommatin, 3-hydroxykynurenine, 3-hydroxyanthranilic acid and tryptophan in whole body extracts of the albino and the wild type individuals were determined together with enzyme activities of kynurenine-3-hydroxylase, kynureninase and tryptophan-2,3-dioxygenase. Xanthommatin could not be detected in the albinos. The levels of 3-hydroxykynurenine and 3-hydroxyanthranilic acid were determined by high-performance liquid chromatography (HPLC) with electrochemical detection and were markedly low in the albinos compared with the wild type individuals. In contrast to those, the tryptophan levels determined by HPLC with fluorescence detection did not differ significantly between the two phenotypes. In the albino A. vulgare, kynurenine-3-hydroxylase activity was lower and kynureninase activity was higher than in the wild type, although the differences were not statistically significant. Tryptophan-2,3-dioxygenase activity in the albinos was less than 10% that in the wild type. Thus, ommochrome deficiency in the albino A. vulgare is considered to be caused by the extremely low activity of tryptophan-2,3-dioxygenase.     

Ommochrome Deficiency in an Albino Strain of a Terrestrial Isopod,Armadillidium vulgare

In order to clarify the cause of ommochrome deficiency in an albino strain of the terrestrial isopod, Armadillidium vulgare, levels of xanthom-matin, 3-hydroxykynurenine, 3-hydroxyanthranilic acid and tryptophan in whole body extracts of the albino and the wild type individuals were determined together with enzyme activities of kynurenine-3-hydroxylase, kynureninase and tryptophan-2,3-dioxygenase. Xanthommatin could not be detected in the albinos. The levels of 3-hydroxykynurenine and 3-hydroxyanthranilic acid were determined by high-performance liquid chro-matography (HPLC) with electrochemical detection and were markedly low in the albinos compared with the wild type individuals. In contrast to those, the tryptophan levels determined by HPLC with fluorescence detection did not differ significantly between the two phenotypes. In the albino A. vulgare, kynurenine-3-hydroxylase activity was lower and kynureninase activity was higher than in the wild type, although the differences were not statistically significant. Tryptophan-2,3-dioxygenase activity in the albinos was less than 10% that in the wild type. Thus, ommochrome deficiency in the albino A. vulgare is considered to be caused by the extremely low activity of tryptophan-2,3-dioxygenase.     

Differential effect of dopamine on mitosis in early postnatal albino and pigmented rat retinae

Insufficient levels of L-DOPA, released from the retinal pigment epithelium (RPE), in albino animals are considered responsible for the abnormal development of the underlying neural retina. L-DOPA normalizes retinal neurogenesis by reducing levels of cell proliferation either by acting on the cells directly or by being converted into dopamine. Here we report the effects of dopamine on mitosis in early postnatal neural retinae from albino and pigmented rats, using 4D (x, y, z and time) confocal microscopy. Exogenous dopamine significantly prolongs mitosis in retinae from albino, but not pigmented, animals. As fewer cells move into and divide in the ventricular zone (VZ) in the presence of dopamine, we conclude that the overall cell cycle is affected. The D1 receptor blocker, SCH 23390, inhibits these effects. Thus, the differential effects of dopamine on neural retinae from pigmented and albino rats in vitro must result from the activation of D1 receptors, which are present in the retina from birth. Immunohistochemical labeling of D1 receptors shows that the pattern of their distribution is similar between pigmentation phenotypes, but levels of expression may be elevated in albinos. Labeling is most intense in the inner plexiform layer but is present throughout the neuroblastic layer. These findings are discussed in light of previous reports of reduced catecholamine levels in the albino retina.     

A reliable radiochromatographic assay technique for hepatic microsomal 16 alpha-hydroxylase activity towards oestrone 3-sulphate. Comparison between pigmented and non-pigmented mature guinea pigs.

A reliable procedure for the assay of liver microsomal 16 alpha-hydroxylation of oestrone 3-sulphate has been developed for the guinea pig. It is based on the rapid, quantitative separation of oestradiol and oestriol by Sephadex LH-20 columns after the chemical reduction and enzymic hydrolysis of the incubation products. Microsomal preparations and incubation conditions that optimized 16 alpha-hydroxylation of oestrone 3-sulphate were employed. Under these circumstances, reduction of the substrate at C-17 and hydrolysis of the sulphate were minimized. Conditions were established that yielded reaction linearity with respect to time and microsomal concentration. This hydroxylation had an absolute requirement for NADPH, which could not be satisfied by NADH. Apparent Km values for oestrone 3-sulphate and NADPH, under the conditions used, were 14 microM and 0.17 mM respectively. 16 alpha-Hydroxylase activity was present in the liver microsomal fraction from heavily pigmented, female English Shorthaired guinea pigs. Much lower activity was detected in mature pigmented males and albino females. No activity could be demonstrated in mature, albino males.     

Circadian Rhythm of Outside-Nest Activity in Wild (WWCPS), Albino and Pigmented Laboratory Rats

The domestication process of the laboratory rat has been going on for several hundred generations in stable environmental conditions, which may have affected their physiological and behavioural functions, including their circadian system. Rats tested in our ethological experiments were laboratory-bred wild Norway rats (WWCPS), two strains of pigmented laboratory rats (Brown Norway and Long Evans), and two strains of albino rats (Sprague-Dawley and Wistar). Rats were placed in purpose-built enclosures and their cycle of activity (time spent actively outside the nest) has been studied for one week in standard light conditions and for the next one in round-the-clock darkness. The analysis of circadian pattern of outside-nest activity revealed differences between wild, pigmented laboratory, and albino laboratory strains. During daytime, albino rats showed lower activity than pigmented rats, greater decrease in activity when the light was turned on and greater increase in activity when the light was switched off, than pigmented rats. Moreover albino rats presented higher activity during the night than wild rats. The magnitude of the change in activity between daytime and nighttime was also more pronounced in albino rats. Additionaly, they slept outside the nest more often during the night than during the day. These results can be interpreted in accordance with the proposition that intense light is an aversive stimulus for albino rats, due to lack of pigment in their iris and choroid, which reduces their ability to adapt to light. Pigmented laboratory rats were more active during lights on, not only in comparison to the albino, but also to the wild rats. Since the difference seems to be independent of light intensity, it is likely to be a result of the domestication process. Cosinor analysis revealed a high rhythmicity of circadian cycles in all groups.     

Number and Distribution of Mouse Retinal Cone Photoreceptors: Differences between an Albino (Swiss) and a Pigmented (C57/BL6) Strain

We purpose here to analyze and compare the population and topography of cone photoreceptors in two mouse strains using automated routines, and to design a method of retinal sampling for their accurate manual quantification. In whole-mounted retinas from pigmented C57/BL6 and albino Swiss mice, the longwave-sensitive (L) and the shortwave-sensitive (S) opsins were immunodetected to analyze the population of each cone type. In another group of retinas both opsins were detected with the same fluorophore to quantify all cones. In a third set of retinas, L-opsin and Brn3a were immunodetected to determine whether L-opsin⁺cones and retinal ganglion cells (RGCs) have a parallel distribution. Cones and RGCs were automatically quantified and their topography illustrated with isodensity maps. Our results show that pigmented mice have a significantly higher number of total cones (all-cones) and of L-opsin⁺cones than albinos which, in turn, have a higher population of S-opsin⁺cones. In pigmented animals 40% of cones are dual (cones that express both opsins), 34% genuine-L (cones that only express the L-opsin), and 26% genuine-S (cones that only express the S-opsin). In albinos, 23% of cones are genuine-S and the proportion of dual cones increases to 76% at the expense of genuine-L cones. In both strains, L-opsin⁺cones are denser in the central than peripheral retina, and all-cones density increases dorso-ventrally. In pigmented animals S-opsin⁺cones are scarce in the dorsal retina and very numerous in the ventral retina, being densest in its nasal aspect. In albinos, S-opsin⁺cones are abundant in the dorsal retina, although their highest densities are also ventral. Based on the densities of each cone population, we propose a sampling method to manually quantify and infer their total population. In conclusion, these data provide the basis to study cone degeneration and its prevention in pathologic conditions.     

Seasonal change and sex difference in drug-metabolizing activity in frog liver microsomes

The drug-metabolizing activities (aminopyrine N-demethylase and p-nitroanisole O-demethylase activities) have been measured at monthly intervals throughout the year in liver microsomes of male and female Japanese bullfrogs, Rana catesbeiana. The aminopyrine N-demethylase activity based on cytochrome P-450 of both sexes was significantly higher in May-July (spring-summer) than in August-October (summer-autumn). On the contrary, the p-nitroanisole O-demethylase activity based on cytochrome P-450 of males was significantly higher in July-October (summer-autumn) than in May-June (spring). However, there was no seasonal changes in the O-demethylase activity in females. There were significant differences between males and females in the N-demethylase activity in August-October and in the O-demethylase activity in May-June (or July-October).     

Antioxidant enzymatic systems in pigment tissue of amphibia

Superoxide dismutase, catalase, glutathione peroxidase, and glutathione reductase activities in pigmented and unpigmented liver tissues of frog and albino rat, respectively, were studied. Our results show that pigmented tissue is lacking in manganese superoxide dismutase activity and that the main enzymatic activity utilized in the cytosol by pigmented cells to reduce the hydrogen peroxide to water is represented by catalase; on the contrary, for the same reaction, the cells of albino rat liver primarily utilize the glutathione peroxidase activity. Both a low glutathione peroxidase activity and a low glutathione reductase activity were found in pigmented tissue of frog liver when compared with unpigmented tissue of rat liver. In light of our results, we also report a hypothetical interrelationship between melanin and reduced glutathione: We believe that in pigmented cells the melanin could act as a reducing physiological agent replacing the glutathione in the reduction of hydrogen peroxide. This reducing action of melanin could cause a diminished need for GSH and therefore could provoke the low glutathione peroxidase and reductase activities in pigmented tissue.     

L-Dopa and the Albino Riddle: Content of L-Dopa in the Developing Retina of Pigmented and Albino Mice

Background

The absence or deficiency of melanin as in albinos, has detrimental effects on retinal development that include aberrant axonal projections from eye to brain and impaired vision. In pigmented retinal pigment epithelium (RPE), dihydroxyphenalanine (L-Dopa), an intermediate in the synthetic path for melanin, has been hypothesized to regulate the tempo of neurogenesis. The time course of expression of retinal L-Dopa, whether it is harbored exclusively in the RPE, the extent of deficiency in albinos compared to isogenic controls, and whether L-Dopa can be restored if exogenously delivered to the albino have been unknown.

Methodology/Principal Findings

L-Dopa and catecholamines including dopamine extracted from retinas of pigmented (C57BL/6J) and congenic albino (C57BL/6J-tyr^c2j) mice, were measured throughout development beginning at E10.5 and at maturity. L-Dopa, but not dopamine nor any other catecholamine, appears in pigmented retina as soon as tyrosinase is expressed in RPE at E10.5. In pigmented retina, L-Dopa content increases throughout pre- and postnatal development until the end of the first postnatal month after which it declines sharply. This time course reflects the onset and completion of retinal development. L-Dopa is absent from embryonic albino retina and is greatly reduced in postnatal albino retina compared to pigmented retina. Dopamine is undetectable in both albino and pigmented retinas until after the postnatal expression of the neuronal enzyme tyrosine hydroxylase. If provided to pregnant albino mothers, L-Dopa accumulates in the RPE of the fetuses.

Conclusions

L-Dopa in pigmented RPE is most abundant during development after which content declines. This L-Dopa is not converted to dopamine. L-Dopa is absent or at low levels in albino retina and can be restored to the RPE by administration in utero. These findings further implicate L-Dopa as a factor in the RPE that could influence development, and demonstrate that administration of L-Dopa could be a means to rescue developmental abnormalities characteristic of albinos.     

Developmental regulation of hepatic testosterone hydroxylases: simultaneous activation and repression of constitutively expressed cytochromes P450 in senescent rats

The aging process is generally associated with marked decreases in the activities of numerous enzymes as well as lower levels of sex hormones such as testosterone. We therefore examined testosterone metabolism in liver microsomes from individual 3- and 24-month-old male rats. Although the old rats exhibited lower 16 alpha-, 6 beta-, and 2 alpha-hydroxylase activities than the young rats, the old rats had a higher 7 alpha-hydroxylase activity. Immunoquantitation of P450a, a known 7 alpha-hydroxylase, showed that the level of this protein was elevated in the old rats, and was correlated with 7 alpha-hydroxylase activity. The mRNA for P450a was measured with a cDNA probe and its level was fivefold higher in the old rats, whereas levels of mRNA coding for a 6 beta-hydroxylase P450 were markedly decreased. The increased expression of cytochrome P450a demonstrates that the observed common decrease in cytochrome P450-catalyzed activities with senescence is not a universal phenomenon. Thus, constitutive expression of specific cytochrome P450 genes is repressed or activated in senescent rats.     

Biotransformation in Egyptian spiny mouse Acomys cahirinus

The activities of several representative biotransformation enzymes were determined in male and female spiny mouse tissues. Cytochrome P450 monooxygenase activity toward benzo(a)pyrene was significantly greater in female spiny mouse intestine than in males. Activity toward benzphetamine in both sexes was high in the liver, with little activity in the kidney and intestine. Sulfotransferase activity was high in kidney and intestine of female spiny mice but undetectable in the same tissues in males. Hepatic glutathione s-transferase activity towards 1-chloro-2,4-dinitrobenzene in females was significantly higher than in males. UDP-Glucuronosyltransferase activity toward 1-naphthol in both sexes in the kidney was significantly higher than hepatic and intestinal activity. Intestinal N-acetyltransferase activity towards 2-aminofluorene and β-naphthylamine was significantly greater in females than males. No consistent relation appeared to exist between biotransformation activities in spiny mouse and those in other related rodent species.     

Plumage phenotypes and mate preferences in Japanese quail 2. sexual imprinting

Mate selection, with emphasis on early social (sexual imprinting) and subsequent long-term social experience, was studied in a randombred population of Japanese quail consisting of wildtype (W), redhead (R) and Albino (A) plumage colors. Early social experiences involved situations where flocks of the various plumage colors were maintained either separately or intermingled.Initial mate preferences were determined from a series of paired choice-tests between plumage phenotypes. Wildtype and redhead females exhibited no preferences, while albino hens preferred albino males. Preferences exhibited by albino males depended on sexual imprinting; those with no other experience preferred albinos and redheads to wildtypes, whereas those raised with other morphs did not distinguish among phenotypes. Redhead and wildtype males while avoiding albino hens, did not distinguish between redhead and wildtype hens.Combinations of the plumage color-social experience flocks (A&R; A&W; R&W) were housed for long-term observations of mate selection. Albino hens mated only albino males. Redhead and wildtype hens having previous experience with albinos mated more frequently with albino males than those lacking such experience. Redhead and wildtype hens showed no preference between redhead and wildtype males. Albino males did not distinguish among female plumage colors, whereas redhead and wildtype males avoided albino hens, and mated equally with redhead and wildtype hens. In a series of nonsimultaneous choice trials, redhead and wildtype females were mated significantly more than albinos. These results demonstrate the influence of genetic mechanisms, sexual imprinting and subsequent long-term social experiences on the optimization of mate selection.     

Evidence for high levels of androgen in peripheral plasma during postnatal development in a marsupial: the gray short-tailed opossum (Monodelphis domestica).

Plasma samples were assayed for androgen in gray short-tailed opossums (Monodelphis domestica) on the day of birth and at selected ages through adulthood. Levels of androgen in mixed-sex plasma pools of animals 4 and 8 days of age were higher than in either sex at all other ages examined. At postnatal Days 16, 30, and 60 (weaning), levels of androgen were equivalent in males and females and as high as in adult males. In both sexes, androgen levels were lower at postnatal Day 84 (juveniles) than at younger ages; after puberty, levels were significantly higher in males than in females. These findings are discussed with respect to similarities and differences between marsupials and eutherians in hormonal environment during the perinatal period and with respect to the possible role of androgens in sexual differentiation of the gray opossum brain.     

Variation with reproductive status of PGE₂receptor immunoreactivities in the Bostrichthys sinensis olfactory system

The role of PGE(2) as a putative sex pheromone in Chinese black sleeper Bostrichthys sinensis was investigated, using immunocytochemistry and how the immunoreactivities of the prostaglandin E(2) (PGE(2) ) receptor subtypes EP(1) , EP(2) , EP(3) and EP(4) varied with reproductive status in the olfactory system was determined. The results showed that PGE(2) receptors were present in the whole of the olfactory system of B. sinensis, and that the number of receptors was linked to the reproductive status of the fish. The densities of EP(1) immunoreactivity in the olfactory epithelium of mature fish were significantly (P < 0·01) higher than those in immature fish of both sexes, and the densities of EP(2) and EP(3) immunoreactivities in mature fish were higher (but not significantly) than those in immature fish of both sexes. In the olfactory nerve, the density of EP(2) immunoreactivity in mature fish was higher (but not significantly) than that in immature fish in both sexes. In the olfactory bulb, the densities of EP(1-4) immunoreactivities in mature females were significantly (P < 0·05 or <0·01) higher than those in immature females, and the density of EP(4) immunoreactivity in mature males was significantly (P < 0·01) higher than that in immature males. As far as is known, the present study is the first report of the immunoreactivities of PGE(2) receptor subtypes in the olfactory system of a teleost, and offers new findings regarding the role of PGE(2) as sex pheromone and hormone in the reproductive behaviour and pheromonal communication of B. sinensis.     

Expression of hepatic microsomal cholesterol 7 alpha-hydroxylase activity in lean and obese Zucker rats

The activity of hepatic microsomal cholesterol 7 alpha-hydroxylase was studied in genetically obese and lean Zucker rats. The liver microsomal cholesterol 7 alpha-hydroxylase activity in fatty Zucker rats (fa/fa) is about 50% to 70% lower than that of the lean (Fa/-) rats of the same sex, when animals were sacrificed at the middle of the dark cycle. When rats were sacrificed at the middle of the light cycle, cholesterol 7 alpha-hydroxylase activity was the same as in the dark cycle in obese rats of both sexes, but was 65% lower in lean rats. However, cholesterol 7 alpha-hydroxylase activity was stimulated by the treatment with cholestyramine in both obese and lean rats. Our results suggested that the diurnal regulation of cholesterol 7 alpha-hydroxylase activity is lost in obese rats but was present under cholestyramine treatment in the genetically obese strain of rats.     

Role of glutathione in the regulation of hepatic cholesterol 7 alpha-hydroxylase, the rate-limiting enzyme of bile acid biosynthesis

The effect of in vivo variation of hepatic glutathione (using diethyl maleate and L-cysteine) on in vitro cholesterol 7 alpha-hydroxylase activity was studied in male Sprague-Dawley rats. Cholesterol 7 alpha-hydroxylase activity in glutathione-depleted rats (ca. 10% of control glutathione) was significantly reduced compared to that in vehicle-injected controls. While L-cysteine treatment of glutathione-depleted animals increased glutathione levels somewhat (ca. 20% of control glutathione), they were still significantly less than control levels. Similarly, cholesterol 7 alpha-hydroxylase activity in the partially glutathione replete animals was approximately 50% greater than that in the glutathione-depleted animals, but still significantly less than that in the controls. The rate of 7 alpha-hydroxylation of cholesterol was found to be dependent on liver glutathione content. The calculated maximal rate was 34.4 picomoles/mg/min with a half maximal activity at 1.89 mumoles glutathione/gm liver. These results suggest that hepatic glutathione may be an important modulator of in vivo activity of cholesterol 7 alpha-hydroxylase.