Glutamate decarboxylase in developing rat neocortex: Does it correlate with the differentiation of GABAergic neurons and synapses?

Postnatal development of glutamate decarboxylase was studied in the rat cerebral cortex. Two methods were used: estimation of the enzymatic activity of glutamate decarboxylase in homogenates of developing cortical tissue and visualization of structures containing glutamate decarboxylase-like immunoreactivity. Glutamate decarboxylase-like immunoreactivity appeared first in perikarya and dendrites and only later in axons and axon varicosities. The most rapid increase in the glutamate decarboxylase activity took place during the second postnatal week and this coincided with a rapid increase in the density of axon varicosities containing glutamate decarboxylase-like immunoreactivity but preceded the most rapid phase in the formation of GABAergic synapses by several days. However, there was a change in the characteristics of glutamate decarboxylase which correlated with GABA synaptogenesis: two fractions of glutamate decarboxylase with different sensitivities to the activating effects of Triton X-100 could be distinguished as from about the time when most of the GABAergic synapses are formed.     

Modulation of solubilized brain fucosyltransferase activity by phospholipids

Phospholipids interact on Triton X-100 solubilized GDP-fucose: asialofetuin fucosyltransferase (EC 2.4.1.68) isolated from sheep brain. This enzymatic activity is modulated by charged phospholipids. In particular, phosphatidic acid and analogues markedly inhibit the transfer of fucose from GDP-[14C]fucose. Kinetic studies show that phosphatidic acid interacts as a mixed inhibitor: the velocity and affinity of fucosyltransferase for the GDP-fucose and asialofetuin substrates are strongly decreased. However, this inhibitory effect is not related to stereospecificity, and the different parameters involved in the enzymatic reaction of glycosylation are not modified. The nature of fatty acids and chemical bond (ester or ether) occurring in the carbohydrate chain does not modify the behaviour of phosphatidic acid with respect to fucosyltransferase activity. Further, the physical state of phosphatidic acid (gel phase or liquid crystalline phase) has no influence. However, as the inhibition is closely pH-dependent, these data suggest that phosphatidic acid might directly interact with the active site of the enzyme and induce a conformational change.     

Effects of tetrodotoxin-induced disuse on properties of developing rat gastrocnemius muscle

Our goal was to determine the influence of a complete lack of neuromuscular activity, during a period of rapid muscle growth, on muscle morphology and contractile function. Rats, 21 days old, had one hindlimb paralyzed for a period of 7-9 consecutive days by repetitive implantation of a silastic cuff containing tetrodotoxin (TTX), a specific nerve impulse conduction blocker, around the sciatic nerve. In situ isometric contractile properties of gastrocnemius were measured at 31 days of age, and muscles were subsequently examined histologically. Normal growth during this period resulted in a two- to three-fold increase in muscle weights, mean muscle fiber cross-sectional areas and increases in absolute twitch and tetanic tensions. After inactivity from 21 to 30 days of age, gastrocnemius muscles were smaller, and tetanically weaker, than age-matched controls. The normal cross-sectional area increase of fast-twitch fibers was preferentially affected. Inactive muscles also demonstrated significantly slower twitch responses, had higher twitch:tetanus ratios and relative tensions at 25 Hz than age-matched controls, suggesting a "slower" contractile response. On the other hand, maximum rate of tetanic tension development was elevated. These effects of inactivity appeared to be reversed by resumption of normal activity for 4 days. Neuromuscular inactivity during a relatively short period of rapid muscle growth causes significant muscle morphological and contractile changes, which are most likely reversible.     

Steroid sulfatase activity and expression in mammary myoepithelial cells

PURPOSE: This investigation examined mRNA expression and enzymatic activity of steroid sulfatase (STS) in human mammary myoepithelial cells (MMECs) and MCF-7 cells and assessed the effects of 17-beta estradiol on the activity of STS. METHODS: The mRNA level of STS in MMECs was determined by RT-PCR analysis using specific primers for STS. STS enzymatic activity prior to and after treatment with 17-beta estradiol was determined by measuring 3H-metabolites formed after exposure to [3H]estrone 3-sulfate (E1S) and [3H]dehydroepiandrosterone-sulfate (DHEA-S). RESULTS: Our data demonstrate the presence of STS in the MMECs. Based on RT-PCR analysis, MMECs had slightly lower levels of STS compared to MCF-7 cells. However, sulfatase activity was about 120 times greater in the MMECs than the MCF-7 cells (E1S V(max)=2640nmol/(mg DNAh) compared to 20.9nmol/(mg DNAh)). Exposure to 17-beta estradiol was associated with 70% reduction in E1S sulfatase activity in the MCF-7 cells and 9% increase in the MMECs after 6 days. DISCUSSION: Our studies indicate for the first time the presence of STS in MMECs. This is suggestive of a previously undetermined role for MMECs in converting precursor hormones into active steroid hormones within mammary tissue. In addition, differential response of the MMECs and the MCF-7 cells to estrogen demonstrates differences in hormone metabolism between these two cell types, perhaps related to the absence of estrogen receptors in the MMECs and their presence in the MCF-7 cells. The MMECs may have an important role in hormonal regulation within mammary tissue.     

A Close Relationship between Increases in Galactosyltransferase Activity and the Accumulation of Galactolipids during Plastid Development in Cucumber Seedlings

Changes in the activity of UDP-galactose:diacylglycerol galactosyltransferase(UDGT), a key enzyme in galactolipid biosynthesis, during germinationwere investigated in cucumber (Cucumis sativus L. cv. Aonagajibai)seedlings. After germination, UDGT activity increased duringgrowth in darkness for 4 days, reaching 10 times the activityin ungerminated seeds. Illumination of 4-day-old dark-grownseedlings strongly stimulated the activity. By contrast, inseedlings grown continuously in darkness, the increase in UDGTactivity ceased after 4 days and the activity remained constantthereafter. A similar increase in the specific activity of UDGTwas observed i n the envelope fraction from seedlings, indicatingthat the increase in the enzymatic activity preceded synthesisof other proteins in the envelope membrane. Coincident withthe change in the enzymatic activity, here was an increase inlevels of monogalactosyl diacylglycerol (MGDG) and digalactosyldiacylglycerol (DGDG), two major constituents of chloroplastmembrane lipids, in the germinated seedlings. Cycloheximideinhibited the light-mediated increase in the enzymatic activityby illumination of 4-day-old dark-grown seedlings, and, as aconsequence, it inhibited the accumulation of MGDG and DGDG.It was clear, therefore, that protein synthesis was necessaryduring this activation. Addition of a cytokinin, benzyladenine(BA), stimulated the increase in the UDGT activity. The increasein the UDGT activity caused by BA was accompanied by the accumulationof galactolipids, as in the case of the activation by light.These results suggest that activation of the final reactionin the synthesis of MGDG, which is catalyzed by the galactosyl-transferase,contributes to the accumulation of galactolipids during thedevelopment of the chloroplast membrane. (Received December 3, 1994; Accepted July 3, 1995)     

Developmental regulation of ornithine decarboxylase (ODC) in rat testis: comparison of changes in ODC activity with changes in ODC mRNA levels during testicular maturation.

These studies were undertaken to analyze the changes in testicular ornithine decarboxylase (ODC) mRNA levels and ODC activity in rats from birth to maturity. Levels of ODC mRNA were initially low in animals aged 10-17 days. Beginning at 21 days, ODC mRNA levels began to rise, reaching maximal levels by 40 days (p less than 0.01). The size of the 2.2- and 2.6-kb ODC mRNAs did not appear to change with age, as determined by Northern blot analysis. The increase in ODC mRNA that began at 21 days paralleled the increase in testis weight. This increase in ODC mRNA preceded the appearance of rat protamine-1 mRNA, a germ cell-specific mRNA found in round spermatids, which was first detected on Day 40. In contrast, levels of sulfated glycoprotein-2 mRNA, which, in the testis, is found exclusively in Sertoli cells, were highest at Day 17 and thereafter declined gradually with age. Unlike the increase in ODC mRNA levels, ODC activity was highest in 10-day-old animals and thereafter declined steadily with age, reaching minimal levels by 40 days (p less than 0.01). Thus, the increase in testicular ODC mRNA levels was in marked contrast to the decrease in testicular ODC activity. Incubation of cytosolic extract from 40-day-old animals with that from 10- or 17-day-old animals inhibited ODC activity approximately 50%, when compared to cytosols from 10- or 17-day-old animals. Dialysis of cytosol from 40-day-old animals prior to incubation with cytosol from 10-day-old animals relieved this inhibition.(ABSTRACT TRUNCATED AT 250 WORDS)     

Characterization and modulation of sex steroid metabolizing activity in normal human keratinocytes in primary culture and HaCaT cells

Skin, the largest organ of the human body, synthesizes active sex steroids from adrenal C19 precursor steroids. Normal human breast epidermal keratinocytes in primary culture were used to evaluate the enzymatic activities responsible for the formation and degradation of active androgens and estrogens during keratinocyte differentiation. Enzymatic activities, including 3beta-hydroxysteroid dehydrogenase/Delta5-Delta4 isomerase (3beta-HSD), 17beta-hydroxysteroid dehydrogenase (17beta-HSD), 5alpha-reductase and 3alpha-hydroxysteroid dehydrogenase (3alpha-HSD) were measured using [3H] steroids as substrates. After 10-60 days in culture, no 3beta-HSD activity was detected, but all other activities were measured, demonstrating the ability of keratinocytes to convert androstenedione (4-DIONE) into the potent androgen dihydrotestosterone (DHT). Furthermore, marked changes in enzymatic activity were observed during cell differentiation: 17beta-HSD was first detected during the third week of culture, the level of activity reaching a peak during the fourth week. This peak was followed by a progressive decrease during keratinization. On the other hand, 5alpha-reductase and 3alpha-HSD activities were first detected during the fourth week of culture. The enzymatic activities involved in the formation and degradation of sex steroids were also characterized in the immortalized human keratinocyte cell line HaCaT. It was then found that HaCaT cells possess a pattern of steroid metabolizing enzymes similar to that of human epidermal keratinocytes in culture. Since glucocorticoids are known to exert potent pharmacological effects on the skin, the effect of dexamethasone (DEX) on cell proliferation and enzymatic activities was determined using HaCaT cells. DEX causes a 55% decrease in HaCaT cell proliferation (IC50: 10nM) whereas DEX caused a three- to five-fold stimulation of oxidative 17beta-HSD activity in intact cells in culture (ED50: 30 nM) and this stimulatory effect was competitively blocked by the glucocorticoid antagonist RU486. A four-fold increase in type 2 17beta-HSD mRNA levels was also observed as measured by real-time PCR, correlating with the increase in oxidative activity. No effect of DEX on the other enzymatic activities (3beta-HSD, 5alpha-reductase, and 3alpha-HSD) was observed. Since increased levels of inflammatory cytokines have been detected in some skin diseases then these cytokines might play a role in the differentiation of keratinocytes. In this regard, we found that interleukin-4 (IL-4) induced the expression of 3beta-HSD in HaCaT cells, thus allowing the cells to produce a different set of sex steroids from adrenal C19 precursors. The present data thus indicate that HaCaT cells are a useful model to further study the regulation of the enzymes involved in the metabolism of sex steroids in keratinocytes.     

Regulation of UDP-Galactose:Ceramide Galactosyltransferase and UDP-Glucose:Ceramide Glucosyltransferase After Crush and Transection Nerve Injury

The enzyme activities of ceramide galactosyltransferase and ceramide glucosyltransferase were assayed as a function of time (0, 1, 2, 4, 7, 14, 21, 28, and 35 days) after crush injury or permanent transection of the adult rat sciatic nerve. These experimental models of neuropathy are characterized by the presence and absence of axonal regeneration and subsequent myelin assembly. Within the first 4 days after both injuries, a 50% reduction of ceramide galactosyltransferase-specific activity was observed compared to values found in the normal adult nerve. This activity remained unchanged at 7 days after injury; however, by 14 days the ceramide galactosyltransferase activity diverged in the two models. The activity increased in the crushed nerve and reached control values by 21 days, whereas a further decrease was observed in the transected nerve such that the activity was nearly immeasurable by 35 days. In contrast, the ceramide glucosyltransferase activity showed a rapid increase between 1 and 4 days, followed by a plateau that was 3.4-fold greater than that in the normal adult nerve, which persisted throughout the observation period in both the crush and transection models. [3H]Galactose precursor incorporation studies at 7, 14, 21, and 35 days after injury confirmed the previously observed shift in biosynthesis from the galactocerebrosides during myelin assembly in the crush model to the glucocerebrosides and oligohexosylceramide homologues in the absence of myelin assembly in the transection model. The transected nerves were characterized by a peak of biosynthesis of the glucocerebrosides at 14 days. Of particular interest is the biosynthesis of the glucocerebrosides and the oligohexosylceramides at 7 and 14 days after crush injury.(ABSTRACT TRUNCATED AT 250 WORDS)     

Collateral arteries grow from preexisting anastomoses in the rat hindlimb

Previous findings have suggested that collateral arteries grow from preexisting arteriolar anastomoses ("arteriogenesis"). To investigate whether collateral growth occurs without preceding angiogenesis, we obtained vascular casts and postmortem angiographies 3, 7, and 21 days after unilateral femoral artery occlusion in the rat. Proliferation kinetics were determined after 5'-bromo-2'-desoxyuridin infusion. A preexisting anastomosis was identified. Proliferation of this vessel began 24 h after femoral artery occlusion, increased maximally during the first 3 days, and reached 60% at day 7. Cell division was restricted to preexisting anastomoses and occurred neither in directly neighboring arterial vessels nor in capillaries. Collateral vessels doubled their diameter within 7 days and assumed a typical corkscrew appearance (increase of length: 21%). After 7 days of occlusion, we measured a further increase of length (14%) but no proliferation or increase of diameter. We conclude that arteriogenesis is a biphasic process involving rapid proliferation of preexisting arteriolar shunts followed by pronounced remodeling processes. Arteriogenesis occurs independently of angiogenesis and denotes a separate entity of vascular proliferation.     

Radiation disorder of enzyme synthesis in the perinatal period of ontogeny

A change of enzymatic differentiation in the rat liver during the perinatal developmental period after gamma-irradiation on the 7-9th and 19th days of embryogenesis in doses 0.5, 2 and 6 Gr has been shown on the example of glucose-6-phosphatase (G-6-P-ase) and tyrosine aminotransferase (TAT). The protein-synthesizing machinery was not damaged at these doses. The radiation inhibition of G-6-P-ase synthesis was relieved by the injection of thyroxine. A dependence was shown between the radiation increase of TAT activity and changes in cAMP system (increase of cAMP level, decrease of phosphodiesterase activity, intensification of response of adenylate cyclase complex to biogenic amines). A suggestion is put forward that the radiation damage of the enzymes under study is mediated by a change in the number of hormonal inductors.     

Ovarian steroid metabolism during post-natal development in the normal mouse and in the adult hypogonadal (hpg) mouse

Ovarian steroid metabolism was investigated (i) during development in a normal inbred strain in which post-natal follicle growth has been described and (ii) in adult hypogonadal (hpg) mice which lack GnRH and have very low serum concentrations of gonadotrophins. Tissue was incubated with [3H]pregnenolone or [3H]androstenedione and metabolites separated by t.l.c. or h.p.l.c. Progesterone was the major metabolite formed at all ages while androstenedione was the major androgen. Between 7 and 21 days there was an overall increase in steroidogenic enzyme activity with a peak of 5 alpha-reductase between 21 and 29 days. The major metabolite of progesterone around puberty was 5 alpha-pregnane-3 alpha-ol-20-one. A sharp increase in 20 alpha-hydroxysteroid dehydrogenase was observed after 38 days due, presumably, to the appearance of corpora lutea. Unlike the rat, androstanediol levels were low at all ages. Oestradiol was the major oestrogen formed from androstenedione with a peak of production at 38 days. In the adult hpg mouse metabolism was similar to that of the 7-day normal mouse although 17-ketosteroid reductase and aromatase levels were very low compared to normal animals of any age, indicating that gonadotrophin stimulation is involved in the expression of activity by these enzymes.     

Characterization of a cytosolic fucosylation pathway in Dictyostelium.

FP21 is a 21-kDa fucoprotein which fractionates with the cytosol after high-speed centrifugation of gently lysed Dictyostelium cells. Less than 0.7% of FP21 is associated with vesicles. In proliferating cells, 4 x 10(5) fucosyl moieties/cell are associated with FP21 as anionic, possibly O-linked oligosaccharides equal in size to 4.8 glucose units. FP21 is underfucosylated in a mutant strain (HL250) that depends on extracellular fucose for synthesis of GDP-fucose. To determine the cellular site of FP21 fucosylation, cytosolic and vesicular preparations from strain HL250 were compared for their ability to transfer fucose from GDP-fucose to FP21. Cytosolic preparations fucosylate endogenous FP21 in a time-, concentration-, and divalent cation-dependent fashion, with a Km for GDP-fucose of 1.4 microM. Activity in normal cell cytosol is dependent on exogenous mutant FP21, demonstrating that FP21 is normally fully fucosylated. Both mutant and normal cytosols are also able to alpha-fucosylate a type 1 glycolipid substrate (8-methoxycarbonyloctyl-Gal beta 1-3 beta GlcNAc), but not related substrates, with Km values for the type 1 glycolipid of 0.99 mM and for GDP-fucose of 1.6 microM. Competitive inhibition between FP21 and the type 1 glycolipid shows that the same enzyme fucosylates both substrates. Intact and permeabilized vesicle preparations from wild-type cells are unable to fucosylate FP21 or the type 1 glycolipid by a divalent cation-dependent mechanism, and thus are devoid of FP21-fucosyltransferase. Since control experiments showed that vesicle leakage is minimal during cytosol preparation, these results indicate that FP21 is synthesized and fucosylated in the cytosolic compartment, by an unusual soluble fucosyltransferase.     

Inhibitory role of sex steroid in the regulation of ovarian follicle-stimulating hormone receptors during pregnancy.

The present study was conducted to determine the role of sex steroids in the regulation of FSH receptors in pregnant rats. In the normal physiological condition, FSH bindings per unit ovarian weight (density of binding) and per 2 ovaries (total binding) increased during days 14-21 gestation. Scatchard plot analyses of the binding suggested that the increase in FSH binding was due to an increase in the number of FSH-binding sites. The plasma FSH concentration in pregnant rats was stable during the receptor change. In contrast, the plasma estradiol-17 beta concentration continuously increased from gestation day 14 to 21, and the testosterone level showed a large peak on gestation day 18. Estradiol-17 beta (one silastic plate containing 13 mg crystal)-implanted pregnant rats during 14-21 days of gestation induced significant decreases in the total FSH binding and ovarian weight on gestation day 21. Estradiol administration increased the plasma estradiol level 2.3-fold but did not change the FSH level. Testosterone or 5 alpha-dihydrotestosterone, a nonaromatizable androgen, did not influence the binding level under the same dose treatment. In contrast, continuous treatment with aminoglutethimide (2 plates containing 20 mg crystal), an inhibitor of adrenocortical steroidogenesis, for 7 days significantly increased the total FSH binding without a significant change in the ovarian weight. The plasma titers of estradiol and testosterone in pregnant rats treated with aminoglutethimide were reduced by 37% and 51%, respectively. Aminoglutethimide did not influence plasma FSH levels. These results suggest that circulating estradiol acts as a negative factor in the regulation of ovarian FSH receptors, at least during the second half of pregnancy. Other factor(s) that is (are) independent of sex steroids and FSH may contribute to FSH receptor induction.     

Early locomotor behaviour in genetic stocks of chickens with different growth rates

Reduction in exercise increases the occurrence of lameness in meat-type chickens. Locomotor activity is dramatically reduced during the finishing period in chickens from fast-growing genetic types compared to slow-growing genetic types, but it is not known whether this difference is already present during the starting period and may be influenced by genetic factors. In order to define the effect of genetic origin on early locomotor behaviour, exercise was compared from 1 to 22 days of age in two meat-type chicken stocks differing in growth rate: male broilers (B) which grow fast and are often lame, and male "label rouge" chickens (L) which grow slowly and are rarely lame.Time budget (lying, standing, drinking, eating, walking) was measured by scanning in six repetitions of five birds (density=2.5 birds/m(2)) at 1, 8, 15 and 17 days of age. Standing bouts were analysed by focal sampling at 2-3, 6-7, 13-14 and 20-21 days of age.B chicks spent less time standing than L chicks at 15 days of age (B=13+/-2%, L=24+/-1%, P<0.01) and 17 days of age, and spent more time lying at 17 days of age (B=73+/-3%, L=60+/-4%, P<0.05).The major part (74%) of the total active time observed by focal sampling was linked to feeding activity. At 2 and 3 days, the activity of B chicks was half that of L chicks during standing bouts (duration of walking per bout: 19+/-4 s for B; 45+/-4 s for L, P<0.05). The activity observed by focal sampling during non-feeding bouts at 20-21 days was significantly correlated with the corresponding data recorded at 2-3 days in the same chicks in the B stock but not in the L stock.We concluded that (1) both B and L genetic stocks have the same overall activity during the first 3 days of age (scanning) but they exhibit different organisation and composition of standing bouts (focal sampling). (2) Genetic factors are probably involved in the expression of locomotor behaviour in very young chicks. (3) The correlations between the levels of activity at early and later ages suggest that selection of young mobile broiler chicks might increase activity at a later age and might therefore reduce the occurrence of leg abnormalities.     

Peroxisome development in the metanephric kidney of mouse.

The relationship of enzymatic activity to organelle development and organelle number during differentiation of the metanephric kidney in the mouse was approached from several experimental directions. Biochemical analyses of marker enzymes for peroxisomes (catalase and D-amino acid oxidase), mitochondria (cytochrome oxidase) and lysosomes (acid phosphatase) were performed on kidneys at ages from 17 days prenatal to adult. These data were correlated with a morphometric analysis of populations of peroxisomes and mitochondria in differentiating cells of the proximal tubule. Postnatal development of the metanephric kidney was found to be accompanied by a rapid increase in both the specific activity of catalase and the number of peroxisomes per 100 mu2 in the proximal tubule during the first 4 weeks of postnatal growth. Elaboration of the endoplasmic reticulum (ER) was seen to parallel the increase in number of peroxisomes to which segments of ER were often in close apposition. Extensive interactions between segments of ER and peroxisomes were readily visible in 0.5-mu sections viewed in the high voltage electron microscope. In contrast to peroxisomes, neither mitochondria nor lysosomes followed a similar pattern of net organelle increase, suggesting that a defined population density of mitochondria and lysosomes may exist in the proximal tubule at birth, prior to complete development of the kidney.     

Regulation of alpha-amylase activity in bean stem tissues

α-Amylase activity was assayed in 1-centimeter sections taken from bean (Phaseolus vulgaris var. Kentucky Wonder) hypocotyls and epicotyls at measured distances from the cotyledons. The activity was low throughout the hypocotyl for the first 7 days. An increase was first observed with etiolated hypocotyls in the basal region, becoming higher in the more central regions by 14 to 17 days. By 21 days the activity was highest in the upper region, but had decreased in the lower regions. A comparable pattern was observed for the epicotyl from etiolated seedlings, the activity increasing first in the region closest to the cotyledons. These increases were associated with loss of cells from the pith in the hypocotyl and epicotyl of both dark- and light-grown plants. Since the changes were observed in tissues virtually devoid of starch, it is hypothesized that the control mechanism is related to the cellular disassembly associated with the mobilization of materials released during senescence rather than to a regulation by the enzyme's substrate or products.     

Effects of lactation length and weaning-to-service interval on subsequent farrowing rate and litter size in Landrace and Yorkshire sows in Thailand

The aim of the present study was to investigate the influence of lactation length (LL) on weaning-to-service interval (WSI), and the effect of LL and WSI on the subsequent farrowing rate and litter size among purebred Landrace and Yorkshire sows under tropical conditions. The variation in litter weight at weaning (LWW) was also studied. Data were analyzed from three purebred sow herds located in the central part of Thailand, including sows weaned during the period from January 1993 to December 1996. Data were analyzed with analysis of variance using SAS software. The procedure MIXED was used for analysis of the continuous outcome variables (namely LL, LWW, WSI, number of total born and number of live born piglets). The GLIMMIX macro was used for analysis of the categorical outcome variable, farrowing rate (FR). In the statistical analyses, WSI was grouped into 7 groups, when it was an independent variable, as follows: 1 to 4, 5, 6, 7, 8, 9, to 10, and 11 to 21 days. Lactation length was grouped into 4 groups as follows: 17 to 24, 25 to 27, 28 to 30 and 31 to 35 days. Parities were grouped into 4 groups as follows: 1, 2, 3 + 4, and 5 to 8. Landrace sows had significantly higher LWW (P < 0.001) compared with Yorkshire sows (56.1 vs. 53.6 kg). The LL was significantly (P < 0.05) shorter during the cool season than during the other seasons while no difference was found in LWW between the hot and the cool season. The LL had no effect on WSI, FR and litter sizes. The FR was significantly lower when the WSI was 7 to 10 days than when the WSI was 1 to 6 days. An increase in WSI between Days 9 to 10 and Day 21 resulted in a significant increase in FR. Subsequent litter size decreased by about 0.5 piglets when the WSI increased from 1 to 5 days to 6 to 7 days. Thereafter, litter size increased as the WSI increased from 9 to 10 days to 21 days.     

Role of monoamine oxidase-B in medroxyprogesterone acetate (17-acetoxy-6 alpha-methyl-4-pregnene-3, 20-dione) induced changes in brain dopamine levels of rats

The effect of medroxyprogesterone acetate (MPA) on brain monoamine levels and monoamine oxidase (MAO) activity was studied in adult, healthy, non-pregnant female rats. MpA was injected in a single dose of 100 mg/kg i.m. Dopamine (DA), noradrenaline (NA), 5-hydroxytryptamine (5-HT) levels and MAO activity were estimated fluorometrically in rat brian. No change in DA, NA, 5-HT or MAO activity was observed after 7 days of MPA treatment while a significant decrease in DA levels along with a significant increase in MAO activity was observed after 21 days of MPA treatment. However, there was no change in NA and 5-HT levels after 21 days of MPA administration. The selective reduction of DA by MPA could be due to an increase in MAO-B activity. MPA does not appear to increase MAO-A activity because neither of the specific substrates (NA and 5-HT) of MAO-A was found to be decreased inspite of the increase in MAO activity as estimated by the kynuramine method. These findings suggest the importance of MAO-B also in DA metabolism in rat brain.     

Activity and expression of different members of the caspase family in the rat corpus luteum during pregnancy and postpartum

Studies were designed to examine the expression and activity of four caspases that contribute to the initial (caspases-2, -8, and -9) and final (caspase-3) events in apoptosis in the rat corpus luteum (CL) during pregnancy (days 7, 17, 19, and 21 of gestation), postpartum (days 1 and 4), and after injection (0, 8, 16, 24, and 36 h) of the physiological luteolysin PGF2alpha. In addition, the temporal relationship of caspase expression/activity relative to steroid production and luteal regression was evaluated. During pregnancy, the activity of all four caspases was significantly greater on day 19, before a decline in CL progesterone (P) and CYP11A1 levels at day 21 of gestation. The levels of the caspase-3 active fragment (p17, measured by Western blot) also increased at days 19 and 21 of pregnancy. Immunohistochemical analyses detected specific staining for the caspases in luteal cells (large and small) as well as in endothelial cells. However, the percentage of apoptotic cells did not increase in the CL until postpartum. Following PGF2alpha injection, there was a significant decrease in CL P by 24 h, although the activity of all four caspases did not increase until 36 h posttreatment. The active p17 fragment of caspase-3 also significantly increased at 36 h post-PGF2alpha. These results suggest that an increase in the activity of caspases-2, -8, -9, and -3 is associated with the early events of natural luteolysis at the end of pregnancy. Also, the exogenous administration of the luteolysin PGF2alpha may regulate members of the caspase family.