Antioxidant treatment ameliorates germ cell apoptosis induced by a high-dose ionizing irradiation in rats.

BACKGROUND: Exposure to ionizing radiation results in cytotoxic and genotoxic effects caused mainly by the oxidative damage. In the present study, we investigated the radioprotective effect of novel antioxidant cocktail on germ cell apoptosis and spermatogenesis in rats subjected to whole body radiation (WBIR). METHODS: Adult male rats weighing 250-270 g were divided into four groups, eight rats each. Group 1 served as untreated control, group 2 received an IP single dose of antioxidant cocktail (1 ml). Group 3 was exposed to a WBIR (6 Gy). Group 4 received antioxidant cocktail before WBIR. Rats from each group were killed after 48 h. MDA levels were measured in serum (TBARS assay). Johnsen's criteria and the number of germinal cell layers were used to categorize spermatogenesis. TUNEL assay was used to determine germ cell apoptosis. Statistical analysis was performed using one-way ANOVA test. RESULTS: WBIR resulted in histological testicular damage (decrease in Johnsen's criteria, p < 0.05) that was accompanied by a significant increase in germ cell apoptosis, expressed as the number of apoptotic cells per 100 tubules (AI-1 apoptotic index) and the number of positive tubules per 100 tubules (AI-2 apoptotic index). Treatment with antioxidant cocktail resulted in a significant decrease in germ cell apoptosis (33% decrease in AI-1, p < 0.05 and 34% decrease in AI-2, p < 0.05) that was accompanied by an improved spermatogenesis (increase in Johnsen's criteria, p < 0.05). CONCLUSIONS: In a rat model of WBIR, antioxidant treatment ameliorates oxidative stress-induced testicular damage, decreases germ cell apoptosis and improves spermatogenesis.

Accelerated cell turnover 48 h after intestinal ischemia is NOTCH independent.

AIM OF THE STUDY: Notch signaling plays important roles in maintaining intestinal epithelial homeostasis. When Notch signaling is blocked, proliferation ceases and epithelial cells become secretory. The purpose of the present study was to evaluate the role of Notch signaling pathway following intestinal ischemia-reperfusion (IR) injury in a rat model. MATERIALS AND METHODS: Male Sprague-Dawley rats were randomly divided into four experimental groups: Sham-24 and Sham-48 rats underwent laparotomy and were killed 24 or 48 h later, respectively; IR-24 and IR-48 rats underwent occlusion of SMA and portal vein for 30 min followed by 24 or 48 h of reperfusion, respectively. Enterocyte proliferation and enterocyte apoptosis were determined at killing. Notch-related gene and protein expression were determined using Real Time PCR, Western blotting and immunohistochemistry 48 h followed IR. MAIN RESULTS: IR-48 rats demonstrated significantly increased rates of cell proliferation and increased cell apoptosis in both jejunum and ileum compared to Sham rats. IR-48 rats exhibited a significant decrease in Notch-1 protein expression (Western blot) that was coincided with a significant decrease in the number of Notch-1 positive cells (immunohistochemistry) in jejunum (35% decrease, p < 0.05) and ileum (twofold decrease, p < 0.05) as well as Hes-1 positive cells in jejunum (28% decrease, p < 0.05) and ileum (31% decrease, p < 0.05) compared to Sham-48 rats. CONCLUSIONS: Forty-eight hours following intestinal IR in rats, accelerated cell turnover was associated by inhibited Notch signaling pathway. Intestinal stem cells differentiation toward secretory progenitors rather than differentiation toward absorptive cells is important at this phase of intestinal recovery.

Fenofibrate reduces intestinal damage and improves intestinal recovery following intestinal ischemia-reperfusion injury in a rat.

PURPOSE: Fenofibrate (FEN) is known as a nuclear receptor activator which regulates many pathophysiological processes, such as oxidative stress, inflammation, and leukocyte endothelium interactions. Recent studies have demonstrated an anti-oxidant, anti-inflammatory, and anti-ischemic role of FEN in the attenuation of ischemia-reperfusion (IR) injury in the kidney, liver, brain, and heart. The purpose of the present study was to examine the effect of FEN on intestinal recovery and enterocyte turnover after intestinal IR injury in rats. METHODS: Male Sprague-Dawley rats were divided into four experimental groups: (1) sham rats underwent laparotomy, (2) sham-FEN rats underwent laparotomy and were treated with intraperitoneal (IP) FEN (20 mg/kg); (3) IR rats underwent occlusion of both the superior mesenteric artery and the portal vein for 30 min followed by 24 h of reperfusion, and (4) IR-FEN rats underwent IR and were treated with IP FEN immediately before abdominal closure. Intestinal structural changes, Park's injury score, enterocyte proliferation, and enterocyte apoptosis were determined 24 h following IR. The expression of Bax, Bcl-2, p-ERK, and caspase-3 in the intestinal mucosa was determined using real-time PCR, Western blot, and immunohistochemistry. RESULTS: Treatment with FEN resulted in a significant decrease in Park's injury score in jejunum (32 %) and ileum (33 %) compared to IR animals. IR-FEN rats also demonstrated a significant increase in mucosal weight in jejunum (23 %) and ileum (22 %), mucosal DNA (38 %) and protein (65 %) in jejunum, villus height in jejunum (17 %) and ileum (21 %), and crypt depth in ileum (14 %) compared to IR animals. IR-FEN rats also experienced significant proliferation rates as well as lower apoptotic indices in jejunum and ileum which was accompanied with higher Bcl-2 levels compared to IR animals. CONCLUSIONS: Treatment with fenofibrate prevents intestinal mucosal damage and stimulates intestinal epithelial cell turnover following intestinal IR in a rat model.

Effect of taurine on intestinal recovery following intestinal ischemia-reperfusion injury in a rat.

PURPOSE: Taurine (TAU) is a sulfur-containing amino acid that is involved in a diverse array of biological and physiological functions, including bile salt conjugation, osmoregulation, membrane stabilization, calcium modulation, anti-oxidation, and immunomodulation. Several studies have established that treatment with TAU significantly protects cerebral, cardiac and testicular injury from ischemia-reperfusion (IR). The purpose of the present study was to examine the effect of TAU on intestinal recovery and enterocyte turnover after intestinal IR injury in rats. METHODS: Male Sprague-Dawley rats were divided into four experimental groups: (1) Sham rats that underwent laparotomy, (2) Sham-TAU rats that underwent laparotomy and were treated with intraperitoneal (IP) TAU (250 mg/kg); (3) IR-rats that underwent occlusion of both superior mesenteric artery and portal vein for 30 min followed by 48 h of reperfusion, and (4) IR-TAU rats that underwent IR and were treated with IP TAU (250 mg/kg) immediately before abdominal closure. Intestinal structural changes, Park's injury score, enterocyte proliferation and enterocyte apoptosis were determined 24 h following IR. The expression of Bax, Bcl-2, p-ERK and caspase-3 in the intestinal mucosa was determined using Western blot and immunohistochemistry. RESULTS: Treatment with TAU resulted in a significant decrease in Park's injury score compared to IR animals. IR-TAU rats also demonstrated a significant increase in mucosal weight in jejunum and ileum, villus height in jejunum and ileum and crypt depth in ileum compared to IR animals. IR-TAU rats also experienced significantly lower apoptotic indices in jejunum and ileum which was accompanied by a higher Bcl-2/Bax ratio compared to IR animals. CONCLUSIONS: Treatment with taurine prevents gut mucosal damage and inhibits intestinal epithelial cell apoptosis following intestinal IR in a rat.

Drosophila divalent metal ion transporter Malvolio is required in dopaminergic neurons for feeding decisions.

Members of the natural resistance-associated macrophage protein (NRAMP) family are evolutionarily conserved metal ion transporters that play an essential role in regulating intracellular divalent cation homeostasis in both prokaryotes and eukaryotes. Malvolio (Mvl), the sole NRAMP family member in insects, plays a role in food choice behaviors in Drosophila and other species. However, the specific physiological and cellular processes that require the action of Mvl for appropriate feeding decisions remain elusive. Here, we show that normal food choice requires Mvl function specifically in the dopaminergic system, and can be rescued by supplementing food with manganese. Collectively, our data indicate that the action of the Mvl transporter affects food choice behavior via the regulation of dopaminergic innervation of the mushroom bodies, a principle brain region associated with decision-making in insects. Our studies suggest that the homeostatic regulation of the intraneuronal levels of divalent cations plays an important role in the development and function of the dopaminergic system and associated behaviors.

Social behavior and comparative genomics: new genes or new gene regulation?

Molecular analyses of social behavior are distinguished by the use of an unusually broad array of animal models. This is advantageous for a number of reasons, including the opportunity for comparative genomic analyses that address fundamental issues in the molecular biology of social behavior. One issue relates to the kinds of changes in genome structure and function that occur to give rise to social behavior. This paper considers one aspect of this issue, whether social evolution involves new genes, new gene regulation, or both. This is accomplished by briefly reviewing findings from studies of the fish Haplochromis burtoni, the vole Microtus ochrogaster, and the honey bee Apis mellifera, with a more detailed and prospective consideration of the honey bee.

Behavioral plasticity in honey bees is associated with differences in brain microRNA transcriptome.

Small, non-coding microRNAs (miRNAs) have been implicated in many biological processes, including the development of the nervous system. However, the roles of miRNAs in natural behavioral and neuronal plasticity are not well understood. To help address this we characterized the microRNA transcriptome in the adult worker honey bee head and investigated whether changes in microRNA expression levels in the brain are associated with division of labor among honey bees, a well-established model for socially regulated behavior. We determined that several miRNAs were downregulated in bees that specialize on brood care (nurses) relative to foragers. Additional experiments showed that this downregulation is dependent upon social context; it only occurred when nurse bees were in colonies that also contained foragers. Analyses of conservation patterns of brain-expressed miRNAs across Hymenoptera suggest a role for certain miRNAs in the evolution of the Aculeata, which includes all the eusocial hymenopteran species. Our results support the intriguing hypothesis that miRNAs are important regulators of social behavior at both developmental and evolutionary time scales.

The foraging gene, behavioral plasticity, and honeybee division of labor.

In recent years, the honeybee has emerged as an excellent model for molecular and genetic studies of complex social behaviors. By using the global gene expression methods as well as the candidate gene approach, it is now possible to link the function of genes to social behaviors. In this paper, I discuss the findings about one such gene, foraging, a cGMP-dependent protein kinase. The involvement of this gene in regulating division of labor is discussed on two independent, but not mutually exclusive levels; the possible mechanisms for PKG action in regulating behavioral transitions associated with honeybee division of labor, and its possible involvement in the evolution of division of labor in bees.

Satiation differentially affects performance in a learning assay by nurse and forager honey bees.

When not satiated prior to training, there were no differences between foragers and nurse honey bees in the acquisition of an appetitively based conditioned response in an olfactory associative learning assay, but when satiated foragers showed faster acquisition than did nurses. Satiation-related differences between foragers and nurses were more a function of behavioral state than age, because satiated precocious foragers also showed faster acquisition rates than did satiated nurse bees, despite their similar ages. Tests of sucrose responsiveness and retention of conditioned responses indicate that the observed performance differences between nurses and foragers were more likely due to differential sensitivity of sensory and motor processes related to satiation rather than differences in cognitive ability.

Influence of gene action across different time scales on behavior.

Genes can affect natural behavioral variation in different ways. Allelic variation causes alternative behavioral phenotypes, whereas changes in gene expression can influence the initiation of behavior at different ages. We show that the age-related transition by honey bees from hive work to foraging is associated with an increase in the expression of the foraging (for) gene, which encodes a guanosine 3',5'-monophosphate (cGMP)-dependent protein kinase (PKG). cGMP treatment elevated PKG activity and caused foraging behavior. Previous research showed that allelic differences in PKG expression result in two Drosophila foraging variants. The same gene can thus exert different types of influence on a behavior.

cGMP-dependent changes in phototaxis: a possible role for the foraging gene in honey bee division of labor.

Division of labor in honey bee colonies is influenced by the foraging gene (Amfor), which encodes a cGMP-dependent protein kinase (PKG). Amfor upregulation in the bee brain is associated with the age-related transition from working in the hive to foraging for food outside, and cGMP treatment (which increases PKG activity) causes precocious foraging. We present two lines of evidence in support of the hypothesis that Amfor affects division of labor by modulating phototaxis. We first show that a subset of worker bees involved in the removal of corpses from the hive had forager-like brain levels of Amfor brain expression despite being middle aged; age-matched food-handlers, who do not leave the hive to perform their job, had low levels of Amfor expression. This finding suggests that occupations that involve working outside the hive are associated with high levels of Amfor in brain. Secondly, foragers were much more positively phototactic than hive bees in a laboratory assay, and cGMP treatment caused a precocious onset of positive phototaxis. The cGMP effect was not due to a general increase in behavioral activity; cGMP treatment had no effect on locomotor activity under either constant darkness or a light:dark regime. The cGMP effect also was not due to changes in circadian rhythmicity; cGMP treatment had no effect on age at onset of locomotor circadian rhythmicity or the period of rhythmicity. The effects of Amfor on phototaxis are not related to peripheral processing; electroretinogram analysis revealed no effect of cGMP treatment on photoreceptor activity and no differences between untreated hive bees and foragers. The cAMP/PKA pathway does not appear to be playing a similar role to cGMP/PKG in the honey bee; cAMP treatment did not affect phototaxis and gene expression analysis revealed task-related differences only for the gene encoding the regulatory subunit, but not the catalytic subunit, of PKA. Our findings implicate one neural process associated with honey bee division of labor that can be affected by naturally occurring changes in the expression of AMFOR: