Rutin promotes activation and reduces apoptosis of primordial follicles by regulating Akt phosphorylation after in vitro culture of ovine ovarian tissue.

The aims of this study were to analyze the effects of different concentrations of rutin on primordial follicle survival and development after in vitro culture of sheep ovarian tissue, and to verify the possible involvement of the phosphatidylinositol-3-kinase/protein kinase B (PI3K/Akt) pathway in the rutin actions. Ovarian fragments were fixed for histological analysis (fresh control) or cultured in α-minimum essential medium alone (α-MEM+: control medium) or in α-MEM+supplemented with different concentrations of rutin (0.1; 1 or 10 µg/mL) for 7 days. Inhibition of the PI3K activity was performed in fragments cultured with 50 µM LY294002. Thereafter, immunohistochemistry was performed to evaluate the expression of cleaved caspase-3 (apoptosis) and Akt phosphorylation (p-Akt). The results showed that 1 µg/mL rutin has a greater percentage of normal follicles (P < 0.05) than those of α-MEM+ and other rutin treatments. In addition, 1 µg/mL rutin maintained the follicular apoptosis similar (P > 0.05) to that of the fresh control and lower than α-MEM+ and 10 µg/mL rutin. All rutin concentrations increased (P < 0.05) follicular activation compared to fresh control and α-MEM+. Furthermore, follicular and oocyte diameters increased (P < 0.05) only after culture with 1 µg/mL rutin. After PI3K inhibition, there was a reduction (P < 0.05) of rutin follicular effects. In conclusion, rutin at 1 µg/mL reduces apoptosis, promotes activation and growth of sheep primordial follicles through the modulation of the PI3K/Akt signaling pathway after in vitro culture of ovine ovarian tissue.

Epigallocatechin-3-gallate (EGCG) reduces apoptosis of preantral follicles through the phosphatidylinositol-3-kinase/protein kinase B (PI3K/AKT) signaling pathway after in vitro culture of sheep ovarian tissue.

The aims of this study were to analyze the effects of different concentrations of epigallocatechin-3-gallate (EGCG) on the primordial follicle survival and development after in vitro culture of ovarian tissue, and to verify the possible involvement of the phosphatidylinositol-3-kinase/protein kinase B (PI3K/AKT) pathway in the EGCG actions in the sheep ovary. Ovarian fragments were fixed for histological analysis (fresh control) or cultured in α-minimum essential medium alone (α-MEM+: control medium) or with different concentrations of EGCG (0.01; 0.1; 1; 10 or 100 µg/mL) for 7 days. Inhibition of PI3K activity was performed in fragments cultured with 1 µg/mL EGCG plus LY294002. Thereafter, immunohistochemistry was performed to evaluate the expression of cleaved caspase-3 and AKT phosphorylation (p-AKT). The results showed that 1 µg/mL EGCG maintained the follicular survival similar (P > 0.05) to that of the fresh control and higher (P < 0.05) than that of the α-MEM+ and other EGCG treatments. No difference (P > 0.05) in the follicular activation was observed. However, both follicle and oocyte diameters increased after in vitro culture with 1 µg/mL EGCG compared to other treatments (P < 0.05), except for 10 µg/mL EGCG (P > 0.05). After PI3K inhibition, there was an increase (P < 0.05) of the follicular apoptosis and a reduction of p-AKT immunolocalization. In conclusion, EGCG at 1 µg/mL reduces apoptosis of preantral follicles through the PI3K/AKT pathway after in vitro culture of sheep ovarian tissue.

Use of protocatechuic acid as the sole antioxidant in the base medium for in vitro culture of ovine isolated secondary follicles.

This study evaluated the effect of the protocatechuic acid (PCA) as the sole antioxidant in the base medium for in vitro culture of ovine secondary follicles. Secondary follicles (200-230 µm) were isolated and cultured in α-minimal essential medium supplemented with BSA, insulin, glutamine and hypoxanthine (α-MEM: antioxidant-free medium) or α-MEM also added by transferrin, selenium and ascorbic acid (α-MEM+: with antioxidant) or α-MEM added by PCA (56.25; 112.5; 225; 450; or 900 µg/ml). Moreover, after culture, oocytes were matured and the chromatin configuration and DNA fragmentation were evaluated. After 12 days, the treatment containing 56.25 µg/ml PCA showed higher percentage of normal follicles than control medium or the other treatments (p < .05), except for 900 µg/ml PCA (p > .05). The antrum formation was significantly higher in treatments containing 56.25, 112.5 or 900 µg/ml PCA, compared to the α-MEM and similar (p > .05) to the other treatments. The rates of fully grown oocytes (≥110 µm) were similar (p > .05) among all treatments containing PCA and α-MEM+, and those were superior (p < .05) than α-MEM, except for 450 µg/ml PCA (p > .05). GSH levels and mitochondrial activity were higher (p < .05) in α-MEM+ than in α-MEM and similar (p > .05) to all PCA treatments. The rates of meiotic resumption and DNA fragmentation were similar (p > .05) among α-MEM+ and 56.25 µg/ml PCA. In conclusion, PCA at 56.25 µg/ml as the sole antioxidant added to the medium for ovine isolated secondary follicle culture maintains follicular survival, GSH and active mitochondria levels, meiotic developmental competence and DNA integrity of cultured oocytes.

Amburana cearensis leaf extract maintains survival and promotes in vitro development of ovine secondary follicles.

The antioxidant properties of Amburana cearensis extract may be a useful substitute for standard cell culture medium. Thus, the aim of this study was to evaluate the effect of this extract, with or without supplementation, on in vitro survival and development of sheep isolated secondary follicles. After collection of the ovaries, secondary follicles were isolated and cultured for 18 days in α-MEM+ supplemented with bovine serum albumin, insulin, transferrin, selenium, glutamine, hypoxanthine and ascorbic acid (control medium) or into medium composed of different concentrations of A. cearensis extract without supplements (Amb 0.1; 0.2 or 0.4 mg/ml) or A. cearensis extract supplemented with the same substances described above for α-MEM+ supplementation. The A. cearensis supplemented medium was named Amb 0.1+; 0.2+ or 0.4+ mg/ml. There were more morphologically normal follicles in Amb 0.1 or Amb 0.4 mg/ml than in the control medium (α-MEM+) after 18 days of culture. Moreover, the percentage of antrum formation was significantly higher in Amb 0.1 or Amb 0.2 mg/ml than in α-MEM+ and Amb 0.1+ mg/ml, and similar to the other treatments. All A. cearensis extract media induced a progressive and significant increase in follicular diameter throughout the culture period. In conclusion, this study showed that 0.1 mg/ml of this extract, without supplementation, maintains follicular survival and promotes the development of ovine isolated secondary follicles in vitro. This extract can be an alternative culture medium for preantral follicle development.

Immunolocalization of melatonin and follicle-stimulating hormone receptors in caprine ovaries and their effects during in vitro development of isolated pre-antral follicles.

The expression of melatonin type 1 (MT1) and FSH (FSHR) receptors in caprine ovaries and the effects of these hormones on the in vitro development of isolated pre-antral follicles were evaluated. Follicles (≤200 µm) were cultured for 12 days in α-MEM (control) or melatonin (100 or 1000 pg/ml) or sequential melatonin medium (100 pg/ml: from day 0 to day 6; 1000 pg/ml: from day 6 to day 12; experiment 1) and in control or sequential FSH (100 ng/ml from day 0 to day 6; 500 ng/ml from day 6 to day 12) or sequential melatonin or this latter plus sequential FSH (experiment 2). MT1 and FSHR expressions were observed in granulosa cells from secondary and antral follicles. The oocytes from primordial and primary follicles also express FSHR. Sequential melatonin increased the percentage of normal follicles and oocyte recovery compared with the control or melatonin (1000 pg/ml) at day 12. In experiment 2, all the treatments increased the normal follicles and growth compared with the control. In conclusion, this study demonstrated the presence of MT1 and FSHR in caprine ovaries. The addition of increased concentrations of melatonin (sequential medium) or FSH can be used to promote the in vitro development of caprine pre-antral follicles.

Atrial stretch delays gastric emptying of liquids in awake rats.

AIMS: We previously reported that mechanical atrial stretch (AS) by balloon distention increased gastric tonus in anesthetized rats. The present study evaluated the effect of AS on the gastric emptying of a liquid test meal in awake rats and its underlying neural mechanisms. MAIN METHODS: Anesthetized male rats received a balloon catheter into the right atrium and a gastrostomy cannula. The next day, mean arterial pressure (MAP), heart rate (HR), central venous pressure (CVP), and cardiac output (CO) were continuously monitored. After the first 20min of monitoring (basal interval), the balloon was either distended or not (control) with 30, 50, or 70µl saline for 5min. Fifteen minutes later, the rats received the test meal (glucose solution with phenol red), and fractional gastric dye retention was determined 10, 20, or 30min later. KEY FINDINGS: Heart rate and CVP values were transiently increased by 50 or 70µl AS but not 30µl AS, whereas gastric emptying was slower after 30, 50, or 70µl AS than after sham distention. Subdiaphragmatic vagotomy or splanchnicotomy+celiac ganglionectomy and capsaicin, ondansetron, hexamethonium, L-NAME, and glibenclamide treatment prevented the AS-induced delay in gastric emptying, whereas atropine and guanethidine treatment failed to prevent it. SIGNIFICANCE: Atrial stretch inhibited the gastric emptying of liquid via non-adrenergic and non-cholinergic pathways that activate nitric oxide-K(+)ATP channels.

Atrial stretch increases the gastric tonus of anesthetized rats.

AIMS: We assessed the effects of right atrial stretch on gastric tone and neuro-humoral pathways involved in this phenomenon. MAIN METHODS: Anesthetized male rats were submitted for monitoring of the mean arterial pressure (MAP) and central venous pressure (CVP). A balloon catheter positioned into the stomach monitored by plethysmography the gastric volume (GV). All rats were monitored for 55-min. After the first 20-min of monitoring (basal period), rats were either submitted to a 5-min interval of atrial stretch (AS) or maintained as controls. An intra-atrial balloon catheter was distended with 30, 50, or 70 microL of saline. GV and hemodynamic data were also monitored for a further 30-min. Another set of rats, either previously submitted to subdiaphragmatic vagotomy or splanchnicectomy plus celiac ganglionectomy or maintained as controls (sham), were also submitted to AS. Each subset consisted of six rats. The plasma level of the atrial natriuretic peptide (ANP) was measured in another group of rats. Data were compared by ANOVA followed by Bonferroni's test. KEY FINDINGS: In control rats, the GV, MAP, and CVP remained at stable levels throughout the studies. In addition to increase the CVP, AS also decreased (P<0.05) the GV by 14%, 11.5%, and 16.5% in the 30, 50, and 70 microL groups, respectively. Vagotomy prevented the GV decrease. In contrast, the AS decreased (P<0.05) the GV by 21.3% in splanchnicectomized rats. SIGNIFICANCE: AS decreased the GV of rats in a volume-dependent manner, a phenomenon prevented by vagotomy but enhanced by celiac ganglionectomy.

Evaluation of gastrointestinal motility in awake rats: a learning exercise for undergraduate biomedical students.

Current medical curricula devote scarce time for practical activities on digestive physiology, despite frequent misconceptions about dyspepsia and dysmotility phenomena. Thus, we designed a hands-on activity followed by a small-group discussion on gut motility. Male awake rats were randomly submitted to insulin, control, or hypertonic protocols. Insulin and control rats were gavage fed with 5% glucose solution, whereas hypertonic-fed rats were gavage fed with 50% glucose solution. Insulin treatment was performed 30 min before a meal. All meals (1.5 ml) contained an equal mass of phenol red dye. After 10, 15, or 20 min of meal gavage, rats were euthanized. Each subset consisted of six to eight rats. Dye recovery in the stomach and proximal, middle, and distal small intestine was measured by spectrophotometry, a safe and reliable method that can be performed by minimally trained students. In a separate group of rats, we used the same protocols except that the test meal contained (99m)Tc as a marker. Compared with control, the hypertonic meal delayed gastric emptying and gastrointestinal transit, whereas insulinic hypoglycemia accelerated them. The session helped engage our undergraduate students in observing and analyzing gut motor behavior. In conclusion, the fractional dye retention test can be used as a teaching tool to strengthen the understanding of basic physiopathological features of gastrointestinal motility.

Sildenafil delays the intestinal transit of a liquid meal in awake rats.

Sildenafil slows down the gastric emptying of a liquid test meal in awake rats and inhibits the contractility of intestinal tissue strips. We studied the acute effects of sildenafil on in vivo intestinal transit in rats. Fasted, male albino rats (180-220 g, N = 44) were treated (0.2 mL, iv) with sildenafil (4 mg/kg) or vehicle (0.01 N HCl). Ten minutes later they were fed a liquid test meal (99m technetium-labeled saline) injected directly into the duodenum. Twenty, 30 or 40 min after feeding, the rats were killed and transit throughout the gastrointestinal tract was evaluated by progression of the radiotracer using the geometric center method. The effect of sildenafil on mean arterial pressure (MAP) was monitored in a separate group of rats (N = 14). Data (medians within interquartile ranges) were compared by the Mann-Whitney U-test. The location of the geometric center was significantly more distal in vehicle-treated than in sildenafil-treated rats at 20, 30, and 40 min after test meal instillation (3.3 (3.0-3.6) vs 2.9 (2.7-3.1); 3.8 (3.4-4.0) vs 2.9 (2.5-3.1), and 4.3 (3.9-4.5) vs 3.4 (3.2-3.7), respectively; P < 0.05). MAP was unchanged in vehicle-treated rats but decreased by 25% (P < 0.05) within 10 min after sildenafil injection. In conclusion, besides transiently decreasing MAP, sildenafil delays the intestinal transit of a liquid test meal in awake rats.