Programmed necrosis - a new mechanism of steroidogenic luteal cell death and elimination during luteolysis in cows

Programmed necrosis (necroptosis) is an alternative form of programmed cell death that is regulated by receptor-interacting protein kinase (RIPK) 1 and 3-dependent, but is a caspase (CASP)-independent pathway. In the present study, to determine if necroptosis participates in bovine structural luteolysis, we investigated RIPK1 and RIPK3 expression throughout the estrous cycle, during prostaglandin F2α (PGF)-induced luteolysis in the bovine corpus luteum (CL), and in cultured luteal steroidogenic cells (LSCs) after treatment with selected luteolytic factors. In addition, effects of a RIPK1 inhibitor (necrostatin-1, Nec-1; 50 μM) on cell viability, progesterone secretion, apoptosis related factors and RIPKs expression, were evaluated. Expression of RIPK1 and RIPK3 increased in the CL tissue during both spontaneous and PGF-induced luteolysis (P < 0.05). In cultured LSCs, tumor necrosis factor α (TNF; 2.3 nM) in combination with interferon γ (IFNG; 2.5 nM) up-regulated RIPK1 mRNA and protein expression (P < 0.05). TNF + IFNG also up-regulated RIPK3 mRNA expression (P < 0.05), but not RIPK3 protein. Although Nec-1 prevented TNF + IFNG-induced cell death (P < 0.05), it did not affect CASP3 and CASP8 expression. Nec-1 decreased both RIPK1 and RIPK3 protein expression (P < 0.05). These findings suggest that RIPKs-dependent necroptosis is a potent mechanism responsible for bovine structural luteolysis induced by pro-inflammatory cytokines.

Synthesis and reception of prostaglandins in corpora lutea of domestic cat and lynx

Felids show different reproductive strategies related to the luteal phase. Domestic cats exhibit a seasonal polyoestrus and ovulation is followed by formation ofcorpora lutea(CL). Pregnant and non-pregnant cycles are reflected by diverging plasma progesterone (P4) profiles. Eurasian and Iberian lynxes show a seasonal monooestrus, in which physiologically persistent CL (perCL) support constantly elevated plasma P4 levels. Prostaglandins (PGs) represent key regulators of reproduction, and we aimed to characterise PG synthesis in feline CL to identify their contribution to the luteal lifespan. We assessed mRNA and protein expression of PG synthases (PTGS2/COX2, PTGES, PGFS/AKR1C3) and PG receptors (PTGER2, PTGER4, PTGFR), and intra-luteal levels of PGE2and PGF2α. Therefore, CL of pregnant (pre-implantation, post-implantation, regression stages) and non-pregnant (formation, development/maintenance, early regression, late regression stages) domestic cats, and prooestrous Eurasian (perCL, pre-mating) and metoestrous Iberian (perCL, freshCL, post-mating) lynxes were investigated. Expression ofPTGS2/COX2, PTGES and PTGER4 was independent of the luteal stage in the investigated species. High levels of luteotrophic PGE2in perCL might be associated with persistence of luteal function in lynxes. Signals for PGFS/AKR1C3 expression were weak in mid and late luteal stages of cats but were absent in lynxes, concomitant with low PGF2αlevels in these species. Thus, regulation of CL regression by luteal PGF2αseems negligible. In contrast, expression of PTGFR was evident in nearly all investigated CL of cat and lynxes, implying that luteal regression, e.g. at the end of pregnancy, is triggered by extra-luteal PGF2α.

Type of Inflammation Differentially Affects Expression of Interleukin 1β and 6, Tumor Necrosis Factor-α and Toll-Like Receptors in Subclinical Endometritis in Mares

Mares that fail to conceive or lose their embryos, without showing typical signs of clinical endometritis, should be suspected of subclinical endometritis (SE). In this study, the question was addressed: does SE fully activate selected mechanisms of innate immunity in mares? For this aim, expression of mRNAs for Toll-like Receptor 2 and 4 (TLR 2/4), interleukin 1β (IL-1β), interleukin 6 (IL-6) and tumor necrosis factor α (TNF) was examined in control mares versus either mares suffering from chronic endometritis (ChE) or subacute suppurative endometritis (SSE). The concentrations of IL-1β, IL-6 and TNF-α in supernatants from endometrial tissue cultures after 4 h incubation were measured using the enzyme immunoassay (EIA) method. Eighty-two warmblood mares, of known breeding history, were enrolled in this study. Based on histopathological assessment, mares were classified as suffering from ChE, SSE or as being healthy. In addition, immuno-localization of both TLR2 and TLR4 as well as TNF-α was investigated in the equine endometria. The mRNA expression of TLR2 (P < 0.01), IL-1β (P < 0.0001), IL-6 (P < 0.0001) and TLR4 and TNF (P < 0.05) was up-regulated in endometria of mares suffering from SSE compared with unaffected mares. Concentrations of IL-6 and TNF-α were increased only in mares exhibiting SSE, compared with unaffected (P < 0.01 for both) and ChE mares (P < 0.05 for both). Immuno-localization of TNF-α and TLRs was confirmed, both in unaffected and SE-affected endometria, and was present in the luminal and glandular epithelia and stromal cells. The severity of inflammation impacts the immune response and fosters activation of innate immunity mechanisms, as observed in the endometria of mares. The intracellular localization of TLRs and TNF-α in the endometria indicates a key role of endometrial epithelial and stromal cells in the immune response and inflammation.

Comparison of the effect of lipopolysaccharide on tumor necrosis factor α (TNF-α) secretion and TNF and TNFR1 mRNA levels in feline endometrium throughout the estrous cycle during pyometra and after medroxyprogesterone acetate treatment

Endotoxins released by Gram-negative bacteria are potent stimulators of tumor necrosis factor α (TNF-α) production. The objectives of this study were to evaluate plasma levels of TNF-α, TNF-α secretion, and mRNA levels of TNF and TNF-α receptor type 1 (TNFR1) following exposure to lipopolysaccharide (LPS). For this, we used cultured endometrial cells or organ cultures, throughout the estrous cycle, after hormone treatment with medroxyprogesterone acetate (MPA), and during pyometra. Plasma TNF-α concentrations were increased in animals at estrus (P < 0.05) compared to other groups. In the LPS-challenged endometrium, secretion of TNF-α by tissues collected during estrus increased (P < 0.001) compared to that of other groups. LPS, alone or combined with TNF-α, upregulated TNF gene expression in the feline endometrium at diestrus (P < 0.001 for both treatments), in queens treated short-term with MPA (P < 0.01 and P < 0.05, respectively) and in queens treated long-term with MPA (P < 0.01 and P < 0.001, respectively). During pyometra, TNF and TNFR1 mRNA were increased only after tissues were challenged with TNF-α and LPS (P < 0.001 and P < 0.01, respectively). When cultured endometrial cells were challenged with LPS, the concentration of TNF-α increased only in epithelial cells after 4 h and 12 h (P < 0.05 and P < 0.01, respectively). Since LPS did not affect stromal cells, but TNF-α increased its own transcript after 2 h (P < 0.01), 4 h (P < 0.05) and 12 h (P < 0.001), we assume that stromal cells are not directly involved in pathogen recognition, as was the case for epithelial cells.

Altered secretion of selected arachidonic acid metabolites during subclinical endometritis relative to estrous cycle stage and grade of fibrosis in mares

Mares that fail to become pregnant after repeated breeding, without showing typical signs of clinical endometritis, should be suspected of subclinical endometritis (SE). Contact with infectious agents results in altered synthesis and secretion of inflammatory mediators, including cytokines and arachidonic acid metabolites, and disturbs endometrial functional balance. To address the hypothesis that SE affects the immune endocrine status of the equine endometrium, spontaneous secretion of prostaglandin E(2) (PGE(2)), prostaglandin F(2α) (PGF(2α)), 6-keto-PGF(1α )(a metabolite of prostacyclin I(2)), leukotriene B(4) (LTB(4)), and leukotriene C(4) (LTC(4)) was examined. In addition, secretion of these factors was examined relative to the grade of inflammation, fibrosis, and estrous cycle stage. Eighty-two warmblood mares, of known breeding history, were enrolled in this study. On the basis of histopathologic assessment, mares were classified as suffering from first-grade SE, second-grade SE, or being healthy. The grade of fibrosis and the infiltration of endometrial tissue with polymorphonuclear leukocytes were examined by routine hematoxylin-eosin staining. In mares suffering from SE, the secretion profiles of PGE(2), 6-keto-PGF(1α), LTB(4), and LTC(4) were changed compared to mares that did not suffer from endometritis. The secretion of PGE(2) and 6-keto-PGF1α was increased, whereas that of LTB(4) and LTC(4) was decreased. Secretion of 6-keto-PGF(1α) was increased in first- and second-grade SE (P < 0.01). The concentration of PGI(2) metabolite was increased only in inflamed endometrium, independently of the inflammation grade, but was not affected by fibrosis. Prostaglandin E(2) secretion was increased in second-grade SE (P < 0.05). The secretion of LTB(4) decreased in both first- and second-grade SE (P < 0.05), whereas secretion of LTC(4) was decreased only in second-grade SE (P < 0.05). Fibrosis did not change the secretion profile of PGE(2), PGF(2α), and 6-keto-PGF(1α) during the course of SE. However, the secretion profile of LTB(4) was affected during the course of fibrosis. Evident divergences between PGE(2) and PGF(2α) profiles and in PGE2:PGF(2α) ratios in the control versus SE mares observed during the course of diestrus contribute to shortened or prolonged interestrous intervals observed clinically in SE mares.

Formation of the early canine CL and the role of prostaglandin E2 (PGE2) in regulation of its function: an in vivo approach

The mechanisms governing corpus luteum (CL) function in domestic dogs remain not fully elucidated. The upregulated expression of cyclooxygenase 2 and prostaglandin (PG) E2 synthase (PGES) at the beginning of the canine luteal phase indicated their luteotrophic roles, and the steroidogenic activity of PGE2 in the early canine CL has been confirmed in vitro. Recently, by applying a cyclooxygenase 2 (COX2)-specific inhibitor (firocoxib [Previcox]; Merial) from the day of ovulation until the midluteal phase, the luteotrophic effects of PGs have been shown in vivo. This is a follow-up study investigating the underlying endocrine mechanisms associated with the firocoxib-mediated effects on the canine CL. Experimental groups were formed with ovariohysterectomies performed on Days 5, 10, 20, or 30 of firocoxib treatments (10 mg/kg bw/24h; TGs = treated groups). Untreated dogs served as controls. A decrease of steroidogenic acute regulatory (STAR) protein expression was observed in TGs. The expression of PGE2 synthase was significantly suppressed in TGs 5 and 10, and both PGE2 and PGF2α levels were decreased in luteal homogenates, particularly from CL in TG 5. Similarly, expression of the prolactin receptor (PRLR) was diminished in TGs 5 and 20. The expression of PGE2 receptors PTGER2 (EP2) and PTGER4 (EP4), the PG- transporter (PGT), and 15-hydroxy PG dehydrogenase (HPGD) was not affected in TGs. Our results substantiate a direct luteotrophic role of PGs in the early canine CL, i.e., by upregulating the steroidogenic machinery. Additionally, the possibility of an indirect effect on PRL function arises from the increased prolactin receptor expression in response to PGE2 treatment in canine lutein cells observed in vitro.

Corpora lutea of pregnant and pseudopregnant domestic cats reveal similar steroidogenic capacities during the luteal life span

In domestic cats, luteal phases of pregnancy and pseudopregnancy (non-pregnant luteal phase) differ in the course and level of plasma progesterone (P4). Therefore, we assumed differences in luteal steroidogenic capacities. Here we present a comprehensive analysis of intraluteal steroid biogenesis in the domestic cat. We quantitatively measured relative mRNA levels of steroidogenic acute regulatory protein (STAR), cytochrome P450 oxidases (CYP), hydroxysteroid dehydrogenases (HSD), steroid reductase (SRD) and enzymes involved in sulfoconjugation of steroids, i.e. sulfotransferase (SULT) and sulfatase (STS). Protein expression was analysed by Western Blot for HSD3B. Additionally, intraluteal steroid contents were determined. During the pseudopregnant luteal phase, expression of STAR (p=0.005), HSD3B1 (p<0.0001), CYP19A1 (p<0.0001) and HSD17B7 (p=0.008) decreased from formation of the corpus luteum (CL) onwards. HSD3B protein expression was highest in the development/maintenance stage of CL and declined during the subsequent luteal phase of pregnancy and pseudopregnancy. This was in accordance with decreasing intraluteal levels of P4, oestrogens and androgens. In contrast, expression of SRD5A1 (p<0.001) increased with progression through stages of the pseudopregnant CL, being indicative of P4 metabolism via an alternate pathway to dihydrotestosterone (DHT). Compared to the formation stage, expression of SULT1E1 was higher in all other luteal stages of pseudopregnancy (p=0.004), implying a potential sulfoconjugation of oestrogens. Expression of CYP11A1 and CYP17A1 was unaffected by the luteal stage (p>0.05), suggesting a permanent capacity of cat CL to convert progestogens via androgen and oestrogen pathways. In general, mRNA expression profiles of steroidogenic enzymes during the pregnant luteal phase reflected the pseudopregnancy profiles. Intraluteal oestrogen (p<0.0001) and androgen (p=0.008) levels were higher in the formation stage compared to the following luteal stages of pseudopregnancy. Concentrations of P4 were higher in the development/maintenance compared to the regression stages (p=0.01). We conclude that cat CL of the same histomorphological stage are characterised by identical steroidogenic capacities independently of an on-going pregnancy.

Validation of reference genes in the feline endometrium

The aim of the study was to find the most stable reference genes from: ACTB, GAPDH, RPL30, CYC, RPL17, RPS7 and YWHAZ in the feline endometrium. Three free software packages, geNorm, NormFinder and BestKeeper were used. In geNorm analysis, the most stable gene was RPS7 (at a primer concentration 1000 nM) or YWHAZ (500 and 250 nM). According to NormFinder and BestKeeper, ACTB (at all examined primer concentrations) followed by RPS7 and CYC were the most stable genes. Based on geNorm results at least two genes from among RPS7, RPL30, ACTB or YWHAZ should be chosen for Real Time-PCR result normalization.

Comparison of the biopsy and cytobrush techniques for diagnosis of subclinical endometritis in mares

BACKGROUND

Endometritis is a major cause of infertility in the mare. Therefore, the diagnosis of this disease is very important in veterinary practice. The objective of this study was to compare bacteriological and cytological results obtained from the mare uterus using biopsy (EB) and cytobrush (CB) techniques and relating these findings to the presence of polymorphonuclear cells (PMNs) in endometrial tissue as the gold standard for detection of endometritis. In particular, we tested the hypothesis that endometrial cytology and microbiology data obtained from material collected using the EB and CB techniques are similar, so that the CB technique could preferentially be used to detect subclinical endometritis in clinical practice.

METHODS

A total of 69 mares suspected of subclinical endometritis because of previous reproductive history and 15 maiden mares were enrolled in this study. Material collected from both EB and CB was smeared on sterile glass slides for cytological examinations and on culture media for microbiological examinations. Bacteriological cultures and cytological samples were classified as negative (no growth or mixed cultures of more than three microorganisms; <2% PMNs) or positive (pure growth of microorganisms; >2% PMNs) for endometritis.

RESULTS

Positive growth was observed in 43% of CB samples and in 54% of EB samples (difference not significant). The growth of β-hemolytic streptococci was always connected with positive cytology. This relationship was not observed for growth of E. coli or for non-pathogenic flora. The sensitivity of bacterial growth and cytology from EB was 0.63 and 0.73 respectively. The sensitivities of bacterial growth and cytology from CB were 0.50 and 0.71 respectively.

CONCLUSION

Microbiological and cytological results obtained from CB are similar to those obtained from EB and based on these findings the CB technique may be recommended for collection of materials from the mare's uterus in clinical practice.

Lipopolysaccharides, cytokines, and nitric oxide affect secretion of prostaglandins and leukotrienes by bovine mammary gland epithelial cells

The aims of this study were to determine the effects of lipopolysaccharides (LPS), tumor necrosis factor (TNF), interleukin 1 alpha (IL-1α), nitric oxide donor (NONOate), or the combination of TNF + IL-1α + NONOate on the following: (i) secretion of prostaglandin (PG)-F(2α), PGE(2), leukotriene (LT)-B(4), and LTC(4) by epithelial cells of the teat cavity and lactiferous sinus of bovine mammary gland; (ii) messenger RNA (mRNA) transcription of enzymes responsible for arachidonic acid (AA) metabolism (prostaglandin-endoperoxide synthase 2 [PTGS2], prostaglandin E synthase [PTGES], prostaglandin F synthase [PGFS], and arachidonate 5-lipooxygenase [ALOX5]); and (iii) proliferation of the cells. The cells were stimulated for 24 h. Prostaglandins and LT were measured by enzyme immunoassay, mRNA transcription of enzymes was determined by real-time reverse transcription polymerase chain reaction, and the cell viability was measured by 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide. All factors increased PG secretion, but the highest stimulation was observed after TNF and IL-1α (P < 0.001). Tumor necrosis factor, NONOate, and TNF + IL-1α + NONOate increased LTB(4) production (P < 0.01), whereas LTC(4) was increased by LPS, TNF, and IL-1α (P < 0.01). Lipopolysaccharides, TNF, IL-1α, and the reagents combination increased PTGS2, PTGES, and PGFS mRNA transcription (P < 0.01), whereas ALOX5 mRNA transcription was increased only by TNF (P < 0.001). Lipopolysaccharides, TNF, IL-1α, NONOate, and the combination of reagents increased the cell number (P < 0.001). Mediators of acute-clinical Escherichia coli mastitis locally modulate PG and LT secretion by the epithelial cells of the teat cavity and lactiferous sinus, which might be a useful first line of defense for the bovine mammary gland. Moreover, the modulation of PG and LT secretion and the changing ratio of luteotropic (PGE(2), LTB(4)) to luteolytic (PGF(2α), LTC(4)) metabolites may contribute to disorders in reproductive functions.

Steroidogenic capacity of the placenta as a supplemental source of progesterone during pregnancy in domestic cats

BACKGROUND

Until recently, the corpus luteum (CL) was considered to be the main source of progesterone (P4) during pregnancy in the domestic cat (Felis catus). However, other possible sources of P4 have not been ruled out. Although feline placental homogenates were found to be capable of synthesizing P4, expression of the respective steroidogenic enzymes has not been investigated at the molecular level. Therefore, in the present study, expression of the two major factors involved in the synthesis of P4 - 3beta-hydroxysteroid dehydrogenase (3betaHSD) and steroidogenic acute regulatory protein (StAR) - was investigated in the feline CL and placenta during the course of pseudopregnancy and pregnancy.

METHODS

The mRNA levels of StAR and 3betaHSD were determined using Real Time PCR and their localizations were determined by immunohistochemistry. Placental P4 concentrations, after ethyl extraction, were measured by EIA.

RESULTS

Luteal 3betaHSD and StAR mRNA levels were strongly time-dependent, peaking during mid-pregnancy. The placental 3betaHSD mRNA level was significantly upregulated towards the end of pregnancy. In the CL, 3betaHSD and StAR protein were localized in the luteal cells whereas in the placenta they were localized to the maternal decidual cells. Placental P4 concentrations were low in early pregnant queens, but increased along with gestational age.

CONCLUSIONS

These results confirm that the placenta is an additional source of P4 in pregnant queens and can thereby be considered as an important endocrine organ supporting feline pregnancy.

mRNA transcription of prostaglandin synthases and their products in the equine endometrium in the course of fibrosis

Accurate regulation of the reproductive cycle and successful implantation depend on proper functioning of the endometrium. The aim of this study was to determine whether mRNA transcription of specific enzymes responsible for prostaglandin (PG) synthesis (prostaglandin-endoperoxide synthase, PTGS-2; prostaglandin F(2α) synthase, PGFS; and prostaglandin E(2) synthases, PGES) and PG concentrations in endometrial extracts would change in moderate (Kenney's Category II) and severe phases of fibrosis (Kenney's Category III; endometrosis), compared with healthy endometrium (Kenney's Category I), during the estrous cycle. Endometrial tissues samples were obtained from mares at the early (n = 12), mid (n = 12) and late (n = 12) luteal phases and the follicular phase (n = 12) of the estrous cycle. Additionally, all endometria were classified microscopically as belonging to Categories I and II or III according to the Kenney classification, resulting in allocation of 4 samples for each subcategory, e.g., mid luteal I, II and III. Relative mRNA transcription was quantified using Real-time PCR. Concentrations of PGE(2) and PGF(2α) in the endometrial extracts were determined using enzyme-linked immunosorbent assay (EIA). In Category I, PTGS-2 mRNA transcription was upregulated at the mid (P < 0.05) and late luteal phases (P < 0.001) and at the follicular phase (P < 0.05) compared to the early luteal phase. PGFS mRNA transcription as well as PGF(2α) concentrations increased at the mid (P < 0.01) and late (P < 0.05) luteal phases compared to the early luteal phase in Category I. PGES mRNA transcription was higher at the mid (P < 0.01) and late luteal phases (P < 0.05) compared to the early luteal and follicular phases in Category I. Prostaglandin E(2) concentration in Category I was higher at the mid luteal phase (P < 0.01) compared to all other phases of the estrous cycle. During incipient endometrosis (Category II) and under full endometrosis (Category III), PTGS-2, PGFS and PGES mRNA transcription and PG concentration were altered compared to the respective estrous phases in healthy endometria (P < 0.05). It may be concluded that serious changes in mRNA transcription of PG synthases and PG production that occur in the equine endometrium during the course of fibrosis in the estrous cycle could be responsible for disturbances leading to disorders of the estrous cycle and early embryo losses.

Experimentally induced mastitis and metritis modulate soy bean derived isoflavone biotransformation in diary cows

The present study compared the changes in isoflavone (daidzein and genistein) and their metabolite (equol and para-ethyl-phenol) concentrations in the blood plasma of cows with induced mastitis and metritis after feeding with soy bean. Sixteen cows were divided into four groups: control for mastitis group, cows with induced mastitis group, control for metritis group, and cows with induced metritis group. All cows were fed a single dose of 2.5 kg of soy bean and then blood samples were taken from the jugular vein for 8 h at predetermined intervals. The concentrations of soy bean-derived isoflavones and their active metabolites were measured in the blood plasma on HPLC system. β-Glucuronidase activity in the blood plasma of cows was measured by fluorometric method. In the blood plasma of cows with induced mastitis and metritis, we found considerably higher concentrations and time-dependent increase in isoflavone metabolites (equol and para-ethyl-phenol) with reference to cyclic cows (P < 0.05). Moreover, we noticed significant decrease of genistein in the blood plasma of the cows with induced metritis compared with control cows (P < 0.05). In addition, in the blood plasma of the cows with induced metritis, we found an increase in β-glucuronidase activity compared with control cows (P < 0.05). In conclusion, health status of the females influenced the concentrations of isoflavone metabolites in the blood plasma of the cows. Experimentally induced mastitis and metritis increased isoflavone absorption, biotransformation and metabolism. Therefore, we suggest that cows with induced mastitis and metritis are more exposed to active isoflavone metabolite actions than healthy cows.

Ovarian steroids modulate tumor necrosis factor-α and nitric oxide-regulated prostaglandin secretion by cultured bovine oviductal epithelial cells

Ovarian steroids assure an optimum environment for the final maturation of oocytes, gamete transport, fertilization, and early embryonic development. The aim of experiment 1 was to examine the influence of ovarian steroids on tumor necrosis factor-α (TNF-α)- or nitric oxide (NO)-regulated prostaglandin (PG), and nitrite/nitrate (NO₂/NO₃) secretion by cultured bovine oviductal epithelial cells (BOECs). BOECs were pretreated with 17β-estradiol (E₂; 10⁻⁹ M) and/or progesterone (P₄; 10⁻⁷ M) for 24 h. For the next 24 h, BOECs were treated with TNF-α (10 ng/mL) or spermine nitric oxide complex (NONOate; 10⁻⁵ M). Prostaglandin F(2α) and PGE₂ secretion was measured in medium by ELISA. The pretreatment of cells with P₄ (progesterone), E₂ (17 β-estradiol), or E₂/P₄ augmented TNF-α-induced PGF(2α) and PGE₂ secretion (P < 0.01). The pretreatment of cells with E₂ or E₂/P₄ increased NONOate-induced PGF(2α) and PGE₂ secretion (P < 0.01). TNF-α induced NO₂/NO₃ production by BOECs. The pretreatment of cells with E₂ augmented only TNF-α-induced NO₂/NO₃ production (P < 0.05). The aim of experiment 2 was to examine the influence of TNF-α, NO, and ovarian steroids on the protein content of enzymes specifically involved in PG and NO production, PG synthases, and NO synthases (NOSs). BOECs were treated with TNF-α (10 ng/mL) or NONOate (10⁻⁵ M). TNF-α increased the protein content of PGG/H synthase, PGF synthase, and PGE synthase (P < 0.05) and endothelial and inducible NOSs (P < 0.05). Nitric oxide increased the protein content of PGF synthase, PGE synthase, endothelial NOS, and inducible NOS (P < 0.05). These results show possible linkage between TNF-α and NO, modulated by ovarian steroids, in the regulation of PG synthesis by BOECs that may be important for triggering the process of oviductal contractions.

Are glucocorticoids auto- and/or paracrine factors in early bovine embryo development and implantation?

We determined the transcript content of three genes involved in the metabolism of glucocorticoids (GC) in bovine in vitro fertilized embryos (2-blastomere stage until hatched blastocyst), trophoblast as well as the oviduct (Day 2-4 of the estrous cycle) and endometrium (Day 16 of the cycle and pregnancy). Since mRNA expression of the glucocorticoid receptor and two enzymes responsible for GC production (11β-HSD1 and 2) was demonstrated in the embryos in all pre-implantation stages as well as in the endometrium and oviduct, it is suggested that GC may serve as auto-/paracrine factors in the development of bovine pre-implantation embryos.

Effects of tumor necrosis factor-alpha and nitric oxide on prostaglandins secretion by the bovine oviduct differ in the isthmus and ampulla and depend on the phase of the estrous cycle

To determine the possible roles of tumor necrosis factor-alpha (TNFalpha) and nitric oxide (NO) in the bovine oviduct, ampulla and isthmus collected during the estrous cycle were exposed for 18 h to TNFalpha, NO donor (NONOate), NO synthase inhibitors (L-NOARG, L-NAME and AMT) and oxytocin (OT) as a positive control. Prostaglandins (PGs) and NO(2)/NO(3) in conditioned media were measured. TNFalpha stimulated PGF(2alpha) secretion on Day 0 (onset of estrus = Day 0) and Days 2-3, in both the ampulla and isthmus, but on Days 18-20 only in ampulla. TNFalpha increased PGE(2) secretion in both fragments in each phase. NONOate did not affect PGF(2alpha) secretion on Days 18-20, whereas this NO donor stimulated PGF(2alpha) secretion in both fragments on Day 0 and Days 2-3. TNFalpha increased NO(2)/NO(3) production in every examined phase in the ampulla and on Days 2-3 in the isthmus. L-NAME lowered NO(2)/NO(3) production regardless of phase or fragment. L-NOARG and AMT lowered NO(2)/NO(3) production in both fragments on Day 0 and Days 2-3. The possible role of TNFalpha, NO or PGs on the oviductal contractility during the early-luteal phase was also examined. Neither TNFalpha nor NONOate influenced contractility in either fragment. Although PGF(2alpha) stimulated the contraction in both fragments, PGE(2) decreased it. When taken together, TNFalpha seems to play some role as a modulator of PGF(2alpha) and PGE(2) production and for transferring the embryo from the oviduct to the uterus by stimulating NO production in the bovine oviduct.

Apoptotic changes in the epithelium germinativum of the cat (Felis catus s. domestica, L. 1758) at different ages and breeding seasons

Apoptosis (programmed cell death) could be considered as a physiological process that takes part in a healthy organism, which helps to maintain organism homeostasis. The visible deterioration of semen quality and the number of germ cells is accompanied by a seasonal decrease of the reproductive activity in some species. This post-effect cascade is caused by apoptosis, which is the primary mechanism responsible for the elimination of germ cells during spermatogenesis. The aim of our study was to assess apoptotic changes in the epithelium germinativum in cat testes at different ages. One hundred and two pairs of testes were obtained from domestic cats aged between 4 months and 10 years. The paraffin-embedded tissue sections were labelled using the Oncogene and Calbiochem Research Products DNA Fragmentation Detection Kit (Cat# QIA21; Darmstadt, Germany), which allows the recognition of apoptotic nuclei in tissue sections with Fragment End Labelling (FragEL) of DNA. The activity of apoptotic processes in cat testes collected from the spring-summer period compared with the autumn-winter season revealed that, 59.42% and 51.51%, respectively, males testes were characterized by insignificant changes. The obtained data revealed a distinctive apoptotic changes in the young animal testes before spermatogenesis onset. An intensification of programmed death cells in the epithelium germinativum in the elder cats (between 3-6 and 6-10 years) was not observed. Apoptotic changes slightly intensified in cats aged between 12 and 36 months.

Morphological features of the seminiferous epithelium in cat (Felis catus, L. 1758) testes

The aim of the present study was to assess the changes in the germinal epithelium in cats of different ages. Routine histological staining was applied to perform morphological and stereological examinations. The animals were divided into five groups according to age: under 8 months (n=28), 8-12 months (n=30), 12-36 months (n=33), 3-6 years (n=14) and older than 6 years (n=13). The appearance of the gonads of the males in the first group varied the most. The seminiferous tubules of the youngest cats consisted of a monolayer of supporting cells and a few spermatogonia. No tubular lumina were present, and the diameters of the seminiferous tubules reached 132.5 microm. We noted the typical arrangement of gametogenic cells with a tubule diameter of 191.83 microm in the second group. We observed multilayer germinal epithelia with the most significant production of gametes and a seminiferous tubule diameter of 202.61 microm in the third group. The diameters of the seminiferous tubules of the forth and fifth groups were 193.38 microm and 191.84 microm, respectively. The obtained data revealed that the most intensive morphological diversification of the seminiferous epithelium in cats occurs at about 7-8 months of age. The diameters of seminiferous tubules were highest in the third group of cats, and the activity of spermatogenesis of this group, expressed as the number of sperm per 10 mm(2), was also the most distinctive. The spermatogenesis process was most evident in cats between 12 and 36 months of age, which was also when the sperm concentration was highest per estimated surface.