Expression of α1-adrenergic receptor subtypes in heart cell culture

Three ₁AR subtypes have been cloned so far and are designated as _1a, _1b, and _1d. Organspecific distribution pattern and subtype-specific effects are known but not fully understood. To address a cell-type specific expression pattern in the heart we investigated expression pattern of ₁AR subtypes on RNA and proteinlevel in heart tissue, cultured cardiomyocytes and nonmyocytes of the rat. Each ₁ARsubtype mRNA was present in neonatal and adult rat heart culture but the relative distribution pattern was significantly different. While the _1aAR subtype is preferentially expressed in adult cardiomyocytes, the _1bAR subtype was preferentially expressed in the nonmyocyte cell fraction. The RTPCR results were confirmed by Westernblotting (_1b) and immunocytochemical studies. Incubation with an ₁agonist (phenylephrine) for 72 h led to a significant reduction of the _1bAR in neonatal heart cell culture on both mRNA and protein level. In contrast, incubation with an ₁antagonist (prazosin) induced a 1.6 fold upregulation of the _1aAR mRNA without significant effects on radioligand binding and functional assay. The results indicate a distribution pattern of the ₁AR subtype which is specific for cell type and ontogeny of the rat heart and may be regulated by adrenergic agents.     

Expression of estrogen receptor α and β in rat astrocytes in primary culture: effects of hypoxia and glucose deprivation

Estrogen replacement therapy could play a role in the reduction of injury associated with cerebral ischemia in vivo, which could be, at least partially, a consequence of estrogen influence of glutamate buffering by astrocytes during hypoxia/ischemia. Estrogen exerts biological effects through interaction with its two receptors: estrogen receptor alpha (ERα) and estrogen receptor beta (ERβ), which are both expressed in astrocytes. This study explored effects of hypoxia and glucose deprivation (HGD), alone or followed by 1 h recovery, on ERα and ERβ expression in primary rat astrocyte cultures following 1 h exposure to: a) 5 % CO(2) in air (control group-CG); b) 2 % O(2)/5 % CO(2) in N(2) with glucose deprivation (HGD group-HGDG); or c) the HGDG protocol followed by 1 h CG protocol (recovery group-RG). ERα mRNA expression decreased in HGDG. At the protein level, full-length ERα (67 kDa) and three ERα-immunoreactive protein bands (63, 60 and 52 kDa) were detected. A significant decrease in the 52 kDa band was seen in HGDG, while a significant decrease in expression of the full length ERα was seen in the RG. ERβ mRNA and protein expression (a 54 kDa single band) did not change. The observed decrease in ERα protein may limit estrogen-mediated signalling in astrocytes during hypoxia and recovery.     

Surface receptors: Are they involved in transformation of spermatozoa of Ascaris?

Exposure of the spheroidal spermatozoa of Ascaris suum to an extract of the male accessory gland causes their transformation into ameboid cells. We have investigated the mechanism of this transformation, also termed activation, by labeling the proteins of accessory gland extracts with fluorescein isothiocyanate (FITC) or [125I], followed by qualitative localization of the sperm activating substances (SAS) and quantitative measurements of [125I]-SAS binding. Fluorescent patches of FITC-conjugated SAS were localized at the spermatozoan surface and were concentrated primarily at the posterior region. Few fluorescent patches were detectable in the region of the newly formed pseudopodia following transformation. Although spermatozoan transformation occurs within 2-5 min after exposure to SAS, the fluorescent patches became more distinct after a minimum of 8 min and reached maximum density at 15-30 min. Spermatozoa activated with [125I]-SAS became radioactively labeled in direct proportion to the amount of available [125I]-SAS until a saturation level was reached. SDS-polyacrylamide gel electrophoresis combined with autoradiography indicated that the cells bind two SAS components, of small (9,000 MW) and large (56,000 MW) sizes. These same two components were also detectable in a membrane fraction, obtained by differential centrifugation, of the spermatozoa after incubation with [125I]-SAS. binding of the two SAS components was not inhibited by preincubation of the spermatozoa with trypsin or Concanavalin A; however, the 56,000 MW component of SAS was not detectable in autoradiograms of spermatozoa incubated with periodic acid (1.6-10 mM) treated SAS. Such cells also failed to transform into ameboid spermatozoa. These results indicate that the two components of SAS that bind to the spermatozoan surface are possibly responsible for inducing the cell transformations associated with activation.     

Estrogen receptor α and β are involved in the activation of lordosis behavior in estradiol-primed rats

The present study was designed to assess the participation of estrogen receptors alpha (ERα) and beta (ERβ) in the short-term facilitation of lordosis behavior in ovariectomized (ovx), estradiol (E₂) primed rats. In experiment 1, dose response curves for PPT and DPN (ERα and ERβ agonists, respectively) facilitation of lordosis behavior (lordosis quotient and lordosis score) were established by infusing these agonists into the right lateral ventricle (icv) in female rats injected 40 h previously with 5 μg of E₂ benzoate. PPT doses of 0.08 and 0.4 ng produced high lordosis quotients starting at 30 min and continuing at 120 and 240 min post-injection. DPN induced high levels of lordosis behavior at all times tested. However, the intensity of lordosis induced by both agonists was weak. In experiment 2, we tested the involvement of each ER in facilitation of lordosis by icv infusion of MPP (ERα-selective antagonist) or PHTPP (ERβ-selective antagonist) prior to infusion of 2 ng of free E₂. Icv infusion of either MPP or PHTPP 30 min before free E2 significantly depressed E₂ facilitation of lordosis. The results suggest that both forms of ER are involved in the short-latency facilitation of lordosis behavior in E₂-primed rats.     

Expression pattern of estrogen receptors α and β and G-protein-coupled estrogen receptor 1 in the human testis

Estrogen signaling is considered to play an important role in spermatogenesis, spermiogenesis and male fertility. Estrogens can act via the two nuclear estrogen receptors ESR1 (ERα) and ESR2 (ERβ) or via the intracellular G-protein-coupled estrogen receptor 1 (GPER, formerly GPR30). Several reports on the localization and expression of all three receptors in the human testis have been published but are controversial particularly in case of ERα. Contrary to previous studies, we decided therefore to evaluate expression of all three receptors in the testis by a number of different methods and in comparison with MCF-7 cells. Using qPCR, we could show that mRNA expression of ERα is considerably lower and expression of ERβ and GPER much higher in the testis than in MCF-7 cells. RT-PCR after laser-assisted microdissection of tubular and interstitial compartments from normal and Sertoli cell only syndrome testes plus in situ hybridization and immunohistochemical analyses of the same samples demonstrated that there is very low expression of ERα in germ cells and in single interstitial cells, very high expression of ERβ in germ cells and Sertoli cells and high expression of GPER in interstitial cells and less in Sertoli cells.     

Are G-protein-coupled receptors involved in mediating larval settlement and metamorphosis of coral planulae?

Larvae of the scleractinian coral Pocillopora damicornis are induced to settle and metamorphose by the presence of marine bacterial biofilms, and the larvae of Montipora capitata respond to a combination of filamentous and crustose coralline algae. The primary goal of this study was to better understand metamorphosis of cnidarian larvae by determining what types of receptors and signal-transduction pathways are involved during stimulation of metamorphosis of P. damicornis and M. capitata. Evidence from studies on larvae of hydrozoans suggests that G-protein-coupled receptors (GPCRs) are good candidates. Settlement experiments were conducted in which competent larvae were exposed to neuropharmacological agents that affect GPCRs and their associated signal-transduction pathways, AC/cAMP and PI/DAG/PKC. On the basis of the results of these experiments, we conclude that GPCRs and these pathways do not mediate settlement and metamorphosis in either coral species. Two compounds that had an effect on both species, forskolin and phorbol-12-myristate-13-acetate (TPA), may be acting on other cellular processes not related to GPCRs. This study strengthens our understanding of the underlying physiological mechanisms that regulate metamorphosis in coral larvae.     

The taste of monosodium glutamate (MSG), L-aspartic acid, and N-methyl-D-aspartate (NMDA) in rats: are NMDA receptors involved in MSG taste?

Monosodium glutamate (MSG) is believed to elicit a unique taste perception known as umami. We have used conditioned taste aversion assays in rats to compare taste responses elicited by the glutamate receptor agonists MSG, L-aspartic acid (L-Asp), and N-methyl-D-aspartate (NMDA), and to determine if these compounds share a common taste quality. This information could shed new light upon the receptor mechanisms of glutamate taste transduction. Taste aversions to either MSG, L-Asp or NMDA were produced by injecting rats with LiCl after they had ingested one of these stimuli. Subsequently, rats were tested to determine whether they would ingest any of the above compounds. The results clearly show that a conditioned aversion to MSG generalized to L-Asp in a dose-dependent manner. Conversely, rats conditioned to avoid L-Asp also avoided MSG. Conditioned aversions to MSG or L-Asp generalized to sucrose when amiloride was included in all solutions. Importantly, aversions to MSG or L-Asp did not generalize to NMDA, NaCl or KCl, and aversions to NMDA did not generalize to MSG, L-Asp, sucrose or KCl. These data indicate that rats perceive MSG and L-Asp as similar tastes, whereas NMDA, NaCl and KCl elicit other tastes. The results do not support a dominant role for the NMDA subtype of glutamate receptors in taste transduction for MSG (i.e. umami) in rats.     

The role of δ-opioid receptor subtypes in cocaine- and methamphetamine-induced place preferences

The effects of δ-receptor antagonists on cocaine- and methamphetamine-induced place preferences were examined in rats. Cocaine- and methamphetamine-induced place preferences were significantly attenuated by naltrindole (NTI: a non-selective δ-opioid receptor antagonist). Furthermore, naltriben (NTB: a selective δ₂-opioid receptor antagonist), but not 7-benzylidenenaltrexone (BNTX: a selective δ₁-opioid receptor antagonist), attenuated the cocaine- and methamphetamine-induce place preferences. These results suggest that δ-opioid receptors, particularly δ₂-opioid receptors, may be involved in the reinforcing effects of cocaine and methamphetamine.     

Expression and function of heregulin-α and its receptors in the mouse mammary gland

Heregulin-α (HRGα) is a cytokine secreted by the mammary mesenchyme, adjacent to lobuloalveolar structures. To understand the role of HRGα and its receptors in mammary glands, and the underlying mechanisms, we performed this study to determine the expression and localization of HRGα and its receptors ErbB2 and ErbB3. We also determined the role of HRGα in the development of mammary glands, β-casein expression and secretion, Rab3A protein expression and the phosphorylation of HRGα signaling molecules using confocal laser scanning microscopy, tissue culture, capillary electrophoresis, Western blotting and enzyme-linked immunosorbent assays. We found that a peak was on pregnancy day 15. Changes of ErbB2 and ErbB3 expression were positively and linearly correlated with HRGα, indicating that HRGα positively regulates ErbB2 and ErbB3 expression. During pregnancy, HRGα enhanced the phosphorylation of STAT5, p42/p44, p38, PKC and Rab3A protein expression, stimulated the proliferation and differentiation of the ductal epithelial cells of mammary glands, and increased and maintained the expression and secretion of β-casein. During lactation, HRGα enhanced the phosphorylation of STAT5 and p38, inhibited the phosphorylation of PKC and Rab3A protein expression, maintained the morphology of the mammary glands and increased the secretion of lactoprotein to reduce the expression of β-casein in mammary epithelial cells. During involution, HRGα induced the phosphorylation of STAT3 and Rab3A protein expression, and inhibited the phosphorylation of PKC to stimulate the degeneration of mammary epithelial cells. It also inhibited the secretion of β-casein, resulting in increased levels of β-casein in mammary epithelial cells.     

Prolactin-induced parental hyperphagia in ring doves: are glucocorticoids involved?

Hyperphagia is a prominent component of the parental behavior repertoire in male and female ring doves and is necessary in order for parents to successfully provision their growing young. Although previous studies implicate both prolactin and the endogenous glucocorticoid, corticosterone, in parental hyperphagia, the functional interactions between these two hormones in regulating changes in feeding activity have not been characterized. These studies examined the possibility that prolactin's orexigenic effects are mediated through the increased secretion of corticosterone. Twice-daily intracerebroventricular (icv) injection of prolactin increased plasma corticosterone concentration in non-breeding doves of both sexes, with males exhibiting more pronounced effects than females. To further test the importance of glucocorticoid signaling in prolactin-induced feeding responses, changes in food intake were investigated in icv prolactin-treated, non-breeding doves following icv infusion of the glucocorticoid receptor antagonist RU38486 or propylene glycol vehicle. No attenuation of prolactin-induced hyperphagia was observed in either sex following co-administration of RU38486 at a dose shown previously to block dexamethasone-induced feeding in doves. These findings suggest that elevated corticosterone titers in blood may contribute to the hyperphagia observed in response to prolactin, but corticosterone signaling through a mammalian-type glucocorticoid receptor is not essential.     

SOM230 inhibits insulin-like growth factor-I action in mammary gland development by pituitary independent mechanism: mediated through somatostatin subtype receptor 3?

Somatostatin analogs (SAs) treat acromegaly by lowering pituitary GH secretion, which, in turn, lowers systemic IGF-I. The profound systemic effect is often greater than expected in the face of only partial GH suppression. Here we report that the SA SOM230 can also act by a nonpituitary-mediated inhibition of IGF-I action. SOM230 inhibited mammary development in intact and hypophysectomized female rats, a process requiring IGF-I. IGF-I overcame this inhibition. SOM230 also inhibited other actions of IGF-I (inhibition of apoptosis, phosphorylation of insulin receptor substrate-1, and cell division). SOM230 did not reduce IGF-I mRNA abundance in mammary gland but did stimulate IGF binding protein 5 (IGFBP5). IGFBP5 was 3.75 times higher in mammary epithelium of SOM230 than in placebo animals (P < 0.001). Administration of IGFBP-5 also inhibited GH-induced mammary development (P < 0.001). Measurement of sstr(1-5) (somatostatin subtype receptor) by real-time RT-PCR revealed that the mammary glands had an abundance of sstr(3) and lower amounts of sstr(4) and sstr(5) but no sstr(1) or sstr(2.) That mammary development was also inhibited to a lesser degree than SOM230 by octreotide, whose main action is through sstr(2), strongly suggests that sstr(3) is at least in part mediating the effects of the SAs. We conclude that 1) SAs inhibit IGF-I action in the mammary gland through a novel nonpituitary mechanism; 2) IGFBP-5, here shown to inhibit pubertal mammary development, might mediate the effect; and 3) Measurement of available sstr receptors in the mammary gland suggests that sstr(3) mediates the SA activity, but sstr(5) is also a possible mediator.     

Is somatostatin or a somatostatin-like peptide involved in central nervous system control of gastric secretion?

Intracisternal injection of octapeptide analogs of somatostatin (SS), Cys-Phe-Phe-D-Trp-Lys-Thr-Phe-Cys (des-AA1,2,4,5,12,13-[D-Trp8]SS (ODT8-SS)) and Cys-Phe-Phe-D-Trp-Lys-Thr-Phe-D-Cys, increased the volume and the acid output of gastric secretion in rats. ODT8-SS given intravenously did not affect basal gastric secretion. The gastrosecretory effect of ODT8-SS, administered intracisternally is dose-dependent (0.01-1 micrograms), long acting, reversible, specific, and abolished by vagotomy, or systemic injection of atropine or SS. SS (5-10 micrograms) or [D-Trp8]SS (1 microgram) had no effect on gastric secretion when given intracisternally. These results demonstrate that some octapeptide SS analogs, unlike SS or other SS analogs, have the capability to act in the brain to induce a vagal dependent stimulation of gastric secretion.     

Plasmid- and chromosome-encoded redundant and specific functions are involved in biosynthesis of the siderophore anguibactin in Vibrio anguillarum 775: a case of chance and necessity?

We report the identification of a novel chromosome cluster of genes in Vibrio anguillarum 775 that includes redundant functional homologues of the pJM1 plasmid-harbored genes angE and angC that are involved in anguibactin biosynthesis. We also identified in this cluster a chromosomal angA gene that is essential in anguibactin biosynthesis.     

Hemocyanin and the branchial heart complex of Sepia officinalis: are the hemocytes involved in hemocyanin metabolism of coleoid cephalopods?

Cytobiological experiments using isotopic- and cytochemical-labeled Sepia hemocyanin as well as immunocytochemical localization of the respiratory pigment were carried out to investigate the function of the hemocytes in hemocyanin metabolism of the common cuttlefish Sepia officinalis. For comparison, the rhogocytes (ovoid cells) of the branchial heart complex were included in this study. Hemocyanin molecules were immunocytochemically detected in the lysosomal compartment of the rhogocytes and, at lower levels, in adhesive and circulating hemocytes. (125)I-labeled Sepia hemocyanin was taken up by the rhogocytes only, whereas gold- and/or fluorescein-labeled Sepia hemocyanin was solely taken up by the adhesive and the circulating hemocytes, even though the level of uptake is different. There are also differences in the uptake of pure gold particles and/or fluorescein between rhogocytes and hemocytes. These findings give evidence that circulating and adhesive hemocytes of the branchial heart complex are not involved in hemocyanin turnover, but are a component of the cellular defense and detoxification system of adult coleoid cephalopods.     

Male sterility in flowering plants: are plant growth substances involved?

Male sterility in flowering plants is of tremendous importance not only in molecular and developmental studies of stamen and pollen grains and evolutionary studies on the origin of dioecy, but also in its commercial application in hybrid seed production. This paper reviews the literature on the possible involvement of plant growth substances (PGSs) in male sterility, and in normal stamen and pollen development. Different experimental approaches on a number of male sterile systems and normal plants have shown that nearly all PGSs, i.e., gibberellins, cytokinins, auxin, abscisic acid, and ethylene, directly or indirectly influence the expression of male sterility. Analyses of endogenous PGSs have revealed that in male sterile plants the level and/or metabolism of more than one PGS is affected. These studies support the suggestion that it is the relative ratio of various PGSs, rather than any one substance, that is critical for normal stamen and pollen development. It is also proposed that gene-regulated male sterility is likely mediated through an altered balance of endogenous PGSs in developing flowers and stamens.     

Kidney atrophy vs hypertrophy in diabetes: which cells are involved?

One of the first structural changes in diabetic nephropathy (DN) is the renal enlargement. These changes resulted in renal hypertrophy in both glomerular and tubular cells. Shrink in the kidney size, which described as kidney atrophy resulted from the loss of nephrons or abnormal nephron function and lead to loss of the kidney function. On the other hand, increase in kidney size, which described as hypertrophy resulted from increase in proximal tubular epithelial and glomerular cells size. However overtime, tubular atrophy and tubulointerstitial fibrosis occurs as subsequent changes in tubular cell hypertrophy, which is associated with the infiltration of fibroblast cells into the tubulointerstitial space. The rate of deterioration of kidney function shows a strong correlation with the degree of tubulointerstitial fibrosis. A consequence of long-standing diabetes/hyperglycemia may lead to major changes in renal structure that occur but not specific only to nephropathy. Identifying type of cells that involves in renal atrophy and hypertrophy may help to find a therapeutic target to treat diabetic nephropathy. In summary, the early changes in diabetic kidney are mainly includes the increase in tubular basement membrane thickening which lead to renal hypertrophy. On the other hand, only renal tubule is subjected to apoptosis, which is one of the characteristic morphologic changes in diabetic kidney to form tubular atrophy at the late stage of diabetes.