Systemic and microcirculatory effects of autologous whole blood resuscitation in severe hemorrhagic shock.
(57/3858)
Systemic and microcirculatory effects of autologous whole blood resuscitation after 4-h hemorrhagic shock with a mean arterial pressure (MAP) level of 40 mmHg were investigated in 63 conscious Syrian golden hamsters. Microcirculation of skeletal skin muscle and subcutaneous connective tissue was visualized in a dorsal skinfold. Shed blood was retransfused within 30 min after 4 h. Animals were grouped into survivors in good (SG) and poor condition (SP) and nonsurvivors (NS) according to 24-h outcome after resuscitation and studied before shock, during shock (60, 120, and 240 min), and 30 min and 24 h after resuscitation. Microvascular and interstitial PO2 values were determined by phosphorescence decay. Shock caused a significant increase of arterial PO2 and decrease of PCO2, pH, and base excess. In the microcirculation, there was a significant decrease in blood flow (QB), functional capillary density (FCD; capillaries with red blood cell flow), and interstitial PO2 [1.8 +/- 0.8 mmHg (SG), 1.3 +/- 1.3 mmHg (SP), and 0.9 +/- 1.1 mmHg (NS) vs. 23.0 +/- 6.1 mmHg at control]. Blood resuscitation caused immediate MAP recompensation in all animals, whereas metabolic acidosis, hyperventilation, and a significant interstitial PO2 decrease (40-60% of control) persisted. In NS (44.4% of the animals), systemic and microcirculatory alterations were significantly more severe both in shock and after resuscitation than in survivors. Whereas in SG (31.8% of the animals) there was only a slight (15-30%) but still significant impairment of microscopic tissue perfusion (QB, FCD) and oxygenation at 24 h, SP (23.8% of the animals) showed severe metabolic acidosis and substantial decreases (>/=50%) of FCD and interstitial PO2. FCD, interstitial PO2, and metabolic state were the main determinants of shock outcome. (+info)
Activation of NMDA receptors in the suprachiasmatic nucleus produces light-like phase shifts of the circadian clock in vivo.
(58/3858)
Although there is substantial evidence that glutamate mimics the effects of light on the mammalian circadian clock in vitro, it has been reported that microinjection of glutamate into the suprachiasmatic nucleus of the hypothalamus (SCN) region in vivo does not result in a pattern of phase shifts that mimic those caused by light pulses. The present study was designed to test the hypothesis that microinjection of NMDA into the SCN would induce light-like phase shifts of the circadian clock through activation of the NMDA receptor. Hamsters housed in constant darkness received microinjections of NMDA through guide cannulas aimed at the SCN region at various times throughout the circadian cycle. Wheel running was monitored as a measure of circadian phase. Microinjection of NMDA resulted in circadian phase shifts, the size and direction of which were dependent on the time of injection. The resulting phase-response curve closely resembled that of light. The circadian response showed a clear dose-dependence at circadian time (CT) 13.5 but not at CT19. Both phase delays and advances induced by NMDA were blocked by coinjection of the NMDA antagonist 2-amino-5-phosphopentanoic acid but were slightly attenuated by the non-NMDA antagonist 6-nitro-7-sulfamoylbenzo[f]quinoxaline-2,3-dione disodium. The ability of NMDA to induce phase shifts was not altered by coinjection with tetrodotoxin. These data are consistent with the hypothesis that activation of NMDA receptors is a critical step in the transmission of photic information to the SCN. (+info)
Neural representation of the taste of NaCl and KCl in gustatory neurons of the hamster solitary nucleus.
(59/3858)
NaCl and KCl are monovalent salts that can be discriminated behaviorally by hamsters on the basis of their tastes. We examined the effects of the passive Na+ channel blocker amiloride on responses to both of these salts in 34 taste-responsive neurons of the nucleus of the solitary tract (NST) in the hamster. The effects of amiloride were assessed with two different, commonly employed stimulus protocols. Additionally, concentration-response functions for each salt were measured in 37 neurons. Cells were characterized by their best response to (in M) 0. 03 NaCl, 0.1 sucrose, 0.003 HCl, 0.001 quinine hydrochloride, and 0. 1 KCl. In neurons classified as NaCl-best, amiloride reversibly blocked responses to both NaCl and KCl. In neurons classified as HCl-best, amiloride had no effect on either stimulus. In sucrose-best neurons, amiloride blocked the response to NaCl but not KCl. These results support the hypothesis that both salts are transduced by at least two different receptor mechanisms. In the NST, information arising from these different inputs is maintained in discrete populations of neurons. In addition to differences in amiloride sensitivity, the cell types also differed in their responses to the salts across concentration. At midrange salt concentrations, NaCl-best neurons were far more responsive to NaCl than KCl, whereas HCl- and sucrose-best neurons responded equivalently to the two salts at all concentrations. Because NaCl- and HCl-best cells cannot by themselves distinguish NaCl from KCl, it is the relative activity across these cell types that comprises the code for taste discrimination. (+info)
Respective role of lipoxygenase and nitric oxide-synthase pathways in plasma histamine-induced macromolecular leakage in conscious hamsters.
(60/3858)
1. Intravital microscopy technique was used to determine the distribution of a fluorescent plasma marker (fluorescein-isothiocyanate-dextran, 150 kD; FD-150) into venular and interstitial compartments of dorsal skin fold preparations in conscious hamsters. 2. One mg kg(-1) histamine (i.v.) caused a biphasic decrease in venular fluorescence due to FD-150 extravasation in all organs (general extravasation). Immediately after injection, the venular fluorescence decreased and plateaued in 60 min. Ninety minutes after histamine injection, venular fluorescence further decreased until 180 min. Prior treatment with indomethacin (0.1 mg kg(-1), i.v.) did not modify the time-course of general extravasation but prevented histamine-induced venule dilatation. 3. Prior treatment with the 5-lipoxygenase activating protein (FLAP) inhibitor, 3-[1-(p-chlorobenzyl)-5-(isopropyl)-3-t-butylthioindol-2-yl]-2,2-d imethyl-propanoic acid sodium (MK-886)(10 microg kg(-1), i.v.), the leukotriene receptor antagonist, benzenemethanol a-pentyl-3-(2-quinolinylmethoxy) (REV-5901)(1 mg kg(-1), i.v.), or the glutathione-S-transferase inhibitor, ethacrynic acid (1 mg kg(-1), i.v.), delayed by 60 min the onset of general extravasation caused by 1 mg kg(-1) histamine. 4. Prior treatment with lipoxygenase pathway inhibitors and N(G)-nitro-L-arginine-methylester (L-NAME)(100 mg kg(-1), i.v.) abolished the general extravasation and venule dilatation induced by 1 mg kg(-1) histamine. 5. Injection of 1 microg kg(-1) (i.v.), of leukotriene-C4 (LTC4) or -D4 (LTD4) induced immediate and sustained general extravasation and reduction in venule diameter, these effects being blocked by REV-5901. 6. Histamine (1 mg kg(-1), i.v.) induced biphasic decline in mean arterial blood pressure (MAP). An initial phase (from 0 to 60 min) was followed by a late phase beginning 90 min after histamine injection. L-NAME (100 mg kg(-1), i.v.) and aminoguanidine (1 mg kg(-1), i.v.) prevented the late phase of histamine-induced hypotension. 7. Thus, plasma histamine can trigger both an immediate cysteinyl-leukotriene (Cys-LT)-dependent and a late nitric oxide (NO)-mediated inflammatory cascade. Although the cyclo-oxygenase (COX) pathway might account for histamine-induced venule dilatation, it would not influence histamine-induced extravasation. (+info)
Roles of bicarbonate, cAMP, and protein tyrosine phosphorylation on capacitation and the spontaneous acrosome reaction of hamster sperm.
(61/3858)
Capacitation is a prerequisite for successful fertilization by mammalian spermatozoa. This process is generally observed in vitro in defined NaHCO3-buffered media and has been shown to be associated with changes in cAMP metabolism and protein tyrosine phosphorylation. In this study, we observed that when NaHCO3 was replaced by 4-(2-hydroxyethyl)1-piperazine ethanesulfonic acid (HEPES), hamster sperm capacitation, measured as the ability of the sperm to undergo a spontaneous acrosome reaction, did not take place. Addition of 25 mM NaHCO3 to NaHCO3-free medium in which spermatozoa had been preincubated for 3.5 h, increased the percentage of spontaneous acrosome reactions from 0% to 80% in the following 4 h. Addition of anion transport blockers such as 4,4'-diiso thiocyano-2, 2'-stilbenedisulfonate (DIDS) or 4-acetomido-4'-isothiocyanatostilbene-2,2'-disulfonic acid (SITS) to the NaHCO3-containing medium inhibited the acrosome reaction, with maximal inhibition at 600 microM, and with an EC50 of 100 microM. Increasing either extracellular or intracellular pH did not induce the acrosome reaction in NaHCO3-free medium. In contrast, addition of 500 microM dibutyryl cAMP (dbcAMP), alone or together with 100 microM 1-methyl-3-isobutylxanthine (IBMX), induced the acrosome reaction in spermatozoa incubated in NaHCO3-free medium. These compounds also partially reversed the inhibition of the acrosome reaction caused by the DIDS or SITS in complete medium. In contrast to these results, IBMX or dbcAMP did not induce acrosome reactions in cells incubated in Ca2+-free medium. When hamster sperm were incubated in the absence of NaHCO3 or in the presence of NaHCO3 and DIDS, cAMP concentrations were significantly lower than the values obtained from sperm incubated in complete medium. Protein tyrosine phosphorylation has also been shown to be highly correlated with the onset of capacitation in many species. During the first hour of capacitation, an increase in protein tyrosine phosphorylation was observed in complete medium. In the absence of NaHCO3, the increase in protein tyrosine phosphorylation was delayed for 45 min, and this delay was overcome by the addition of dbcAMP and IBMX. The induction of the acrosome reaction by calcium ionophore A23187 in NaHCO3-free medium was delayed 2 h, as compared with control medium. This delay was not observed in the presence of dbcAMP and IBMX. Taken together, these results suggest that a cAMP pathway may mediate the role of NaHCO3 in the capacitation of hamster spermatozoa and that protein tyrosine phosphorylation is necessary but not sufficient for complete capacitation. (+info)
Differential activity of diethylstilbestrol versus estradiol as neonatal endocrine disruptors in the female hamster (Mesocricetus auratus) reproductive tract.
(62/3858)
The synthetic estrogen diethylstilbestrol (DES) is a potent neonatal endocrine disruptor in the hamster. To test the specificity of this phenomenon, newborn animals were treated with 100 microgram of either DES or the natural estrogen, estradiol-17beta (E2). Of the two, neonatal DES exposure caused greater morphological disruption throughout the female reproductive tract in prepubertal animals and in adults that either retained their ovaries or were ovariectomized and then given the same levels of chronic E2 stimulation. In the uterus, a characteristic histopathological profile, including enhancement of both hyperplastic and apoptotic activity, was initiated prepubertally and exclusively in the endometrial epithelial cell compartment from the neonatally DES-treated animals and then was promoted by E2 stimulation during adulthood. Interestingly, apoptotic activity was not detected in an area of endometrial epithelium that progressed to the neoplastic state in a DES-exposed animal. Lastly, chronic estrogen induction of lactoferrin was also restricted to the DES-exposed endometrium. We conclude that 1) DES is more active than E2 as a perinatal endocrine disruptor in the hamster and 2) this experimental system should be generally useful as a means to screen compounds for such activity and then probe their mechanism of action. (+info)
Role of tyrosine phosphorylation of flagellar proteins in hamster sperm hyperactivation.
(63/3858)
Despite extensive study of sperm motility, little is known of the mechanism of mammalian sperm hyperactivation. Here we describe a novel method for preparation of rodent sperm flagella and use it to show a correlation between tyrosine phosphorylation of flagellar proteins and hyperactivation of hamster sperm. When hyperactivation was produced by a 3.5-h incubation in a medium supporting capacitation, four major tyrosine-phosphorylated peptides of 90-, 80-, 62-, and 48-kDa mass were detected in flagellar extracts. Incubation with calyculin A, an inhibitor of protein phosphatases 1 and 2A, produced hyperactivation within 40 min but only a single 80-kDa phosphotyrosine-containing flagellar component. Conversely, incubation with inhibitors of either protein kinase A (H8) or protein tyrosine kinase (tyrphostin 47) prevented both hyperactivation and the production of tyrosine-phosphorylated flagellar peptides. These results indicate a strong correlation of hyperactivation with the tyrosine phosphorylation of sperm flagellar peptides, and they strongly implicate an 80-kDa component as a major mediator of the mechanism that produces hyperactivated motility of hamster sperm. (+info)
Hamster sperm protein, p26h: a member of the short-chain dehydrogenase/reductase superfamily.
(64/3858)
For successful fertilization to occur, mammalian spermatozoa must undergo a series of modifications in order to reach and penetrate the oocyte. Some of these modifications occur during passage through the epididymis, the site where spermatozoa acquire their fertilizing ability. We have previously described hamster sperm protein, P26h, which is acquired by spermatozoa during epididymal transit, and have proposed that this protein is involved in sperm-egg binding. In the present study, we report the cloning and characterization of the full-length cDNA encoding hamster P26h. A database search using the predicted hamster P26h amino acid sequence revealed 85% identity with mouse AP27 protein and porcine carbonyl reductase, members of the short-chain dehydrogenase/reductase (SDR) family of proteins. Northern blot analysis revealed a major P26h 1-kilobase transcript in the testis. No signal was detected in other somatic tissues of the hamster. In situ hybridization experiments revealed that the P26h gene was predominantly transcribed in seminiferous tubules of the testis and at a lower level in the corpus epididymidis. The identity of the cloned P26h was confirmed by immunoprecipitating in vitro-translated P26h using polyclonal antiserum raised against purified hamster sperm P26h. Taken together, these results identify P26h as a new member of the SDR family of proteins involved in the processes of mammalian gamete interactions. (+info)