Reinstatement of LH surges by serotonin neuroleptics in aging, constant estrous rats

Aged rats in constant estrous (CE) were treated with drugs which effect monoamine metabolism in an attempt to restore the positive-feedback response to estrogen. Prior to treatment, the rats were ovariectomized so as to eliminate indirect effects of drug: ovary interaction which might alter the steroid environment. They then received silastic capsules containing estradiol 17β, SC, immediately (IME, immediate implant group) or 4 weeks after surgery (DEL, delayed implant group), to provide a constant, stable source of estrogen, mimicking the CE condition. Blood samples were taken 3 days after estrogen capsules were implanted to determine if the exogenous steroid induced LH surges in IME or DEL rats. LH surges occurred in 80% of DEL rats, but no IME rats suggesting that a 30-day hiatus from ovarian steroids restored the positive-feedback response in previously acyclic rats. Progesterone (0.5 mg) administered at 1100 hr increased the size of the surge in DEL rats but did not change serum LH levels in IME rats. After 3 days of estrogen exposure, hypothalamic content of serotonin was significantly lower (p <0.05) in DEL rats vs. IME rats, while norepinephrine was not different in either group. Differential effects of estrogen on norepinephrine were not apparent in IME or DEL rats. The changes in serotonin metabolism following estrogen treatment in DEL rats occurred with the onset of LH surges, suggesting a functional correlation. On the other hand, serotonin levels did not change in response to estrogen in IME rats, and LH surges were absent as well. Monoamine neuroleptics were administered to IME rats in an attempt to reestablish positive feedback. I-Dihydroxyphenylalanine (l-DOPA; 200 mg/kg at 1100 hr) stimulated LH surges in 31% of the rats; however, its effectiveness was diminished (8% responding with LH surges) by pretreatment with p-chlorophenylalanine (pCPA; 250 mg/kg at 1600 hr, 19 hours before l-DOPA). LH surges were reinstated in the majority (77%) of IME rats following combined treatment with pCPA + 5-hydroxytryptophan (5-HTP; 50 mg/kg at 1100 hr, 43 hours after pCPA). Since this combination of pCPA + 5-HTP enhances sensitivity to serotonin signals, the drugs may have restored the facilitatory effect of serotonin on LH secretion which is lost in aging constant estrous rats. In conclusion, loss of the positive-feedback response in aging female rats may follow changes in monoamine metabolism resulting from life-long exposure to estrogen. Although metabolic changes occur in all hypothalamic monoamines, this study suggests that a major deficit with regard to this feedback loss residues with serotonin.     

Sister chromatid exchange and chromosome aberrations in mice after in vivo exposure of green S--a food colorant.

Sister chromatic exchanges (SCE) and chromosome aberrations (CA) in mice after in vivo exposure of Green S were carried out following single acute treatment. Except for the lowest dose (25 mg/kg body weight) a significant increase in the SCEs were observed in all the other doses (50, 100, and 200 mg/kg) tested. In CA study two higher doses (200 and 400 mg/kg) showed a significant increase in CA when compared with control. The minimum effective dose which induced SCE and CA was 50 and 200 mg/kg of body weight, respectively. The trend tests for the evidence of dose response effects were also significant for both SCE and CA. No significant differences were observed in cell replication kinetic (RI) analysis. A significant increase in the mitotic index (MI) was also observed in the highest dose (400 mg/kg) tested when compared with control. Thus the present study indicates that Green S can induce both SCE and CA in vivo in bone marrow cells of mice.     

梗死灶周围心肌C3G蛋白表达增加参与了异丙肾上腺素诱导的梗死后心脏重塑恶化的发病机制

 目的 通过观察梗死灶周围心肌C3G蛋白的表达及异丙肾上腺素(ISO)对其的影响,探讨梗死灶周围心肌C3G蛋白是否参与了异丙肾上腺素诱导的梗死后心脏重塑恶化的发病机制。方法 按Litwin方法建立心肌梗死(心梗)及假手术模型。 术后7天仍存活的雄性SD大鼠分为心梗组,假手术组,心梗ISO组,假手术ISO组。其中,心梗组及假手术组给予生理盐水5ml/kg每三天一次, 腹腔注射,至干预后12周;心梗ISO组及假手术ISO组给予ISO 5mg/kg每三天一次, 腹腔注射,余方法同上。免疫印迹检测梗死灶周围心肌C3G 蛋白的表达。结果 干预后12周, 梗死灶周围心肌C3G蛋白表达积分光密度标化值分别为：心梗组（1.14±0.29, n=8）, 假手术组（0.90±0.10,n=6）, 心梗ISO组（1.51±0.18,n=10 ）, 假手术ISO组（0.97±0.26, n=8）。心梗组较假手术组、 心梗ISO组较假手术ISO组、及心梗ISO组较心梗组梗死灶周围心肌C3G蛋白的表达均显著增高（P＜0.05）。 结论 梗死灶周围心肌C3G蛋白表达显著增加, 而ISO可使C3G蛋白表达更显著增加; C3G蛋白表达增加参与了梗死后心室重塑,缺血性心肌病及心力衰竭的发病机制,且C3G蛋白表达进一步增加参与了ISO诱导的梗死后心室重塑,缺血性心肌病及心力衰竭恶化的发病机制。     

Mutagenicity of zidovudine, lamivudine, and abacavir following in vitro exposure of human lymphoblastoid cells or in utero exposure of CD-1 mice to single agents or drug combinations

Experiments were performed to investigate the impact of zidovudine (AZT), lamivudine (3TC), and abacavir (ABC) on cell survival and mutagenicity in two reporter genes, hypoxanthine-guanine phosphoribosyltransferase (HPRT) and thymidine kinase (TK), using cell cloning assays for assessing the effects of individual drugs/drug combinations in (1) TK6 human lymphoblastoid cells exposed in vitro and (2) splenic lymphocytes from male CD-1 mice exposed transplacentally on days 12-18 of gestation. In TK6 cells, dose-related increases in HPRT and TK mutant frequencies were found following 3 days of exposure to AZT or 3TC alone (33, 100, or 300 microM), or to equimolar amounts of AZT-3TC. Compared with single drug exposures, AZT-3TC coexposures generally yielded enhanced elevations in HPRT and TK mutant frequencies. Mutagenicity experiments with ABC alone, or in combination with AZT-3TC, were complicated by the extreme cytotoxicity of ABC. Exposure of cells either to relatively high levels of AZT-3TC short-term (100 microM, 3 days), or to peak plasma-equivalent levels of AZT-3TC for an extended period (10 microM, 30 days), resulted in similar drug-induced mutagenic responses. Among sets of mice necropsied on days 13, 15, or 21 postpartum, Hprt mutant frequencies in T-cells were significantly elevated in the AZT-only (200 mg/kg bw/day) and AZT-3TC (200 mg AZT + 100 mg 3TC/kg bw/day) groups at 13 days of age. These results suggest that the mutagenicity by these nucleoside analogs is driven by cumulative dose, and raises the question of whether AZT-3TC has greater mutagenic effects than AZT alone in perinatally exposed children.     

(-)-nicotine ameliorates corticosterone's potentiation of N-methyl-d-aspartate receptor-mediated cornu ammonis 1 toxicity

Hypercortisolemia, long-term exposure of the brain to high concentrations of stress hormones (i.e. cortisol), may occur in patients suffering from depression, alcoholism, and other disorders. This has been suggested to produce neuropathological effects, in part, via increased function or sensitivity of N-methyl-d-aspartate (NMDA)-type glutamate receptors. Given that cigarette smoking is highly prevalent in some of these patient groups and nicotine has been shown to reduce toxic consequences of NMDA receptor function, it may be suggested that nicotine intake may attenuate the neurotoxic effects of hypercortisolemia. To investigate this possibility, organotypic hippocampal slice cultures derived from rat were pre-treated with corticosterone (0.001-1 microM) alone or in combination with selective glucocorticoid receptor antagonists for 72-h prior to a brief (1-h) NMDA exposure (5 microM). Pre-treatment with corticosterone (0.001-1 microM) alone did not cause hippocampal damage, while NMDA exposure produced significant cellular damage in the cornu ammonis (CA)1 subregion. No significant damage was observed in the dentate gyrus or CA3 regions following NMDA exposure. Pre-treatment of cultures with corticosterone (0.1-1 microM) markedly exacerbated NMDA-induced CA1 and dentate gyrus region damage. This effect in the CA1 region was prevented by co-administration of the glucocorticoid receptor antagonist RU486 (>or=1 microM), but not spironolactone (1-10 microM), a mineralocorticoid receptor antagonist. In a second series of studies, both acute and pre-exposure of cultures to (-)-nicotine (1-10 microM) significantly reduced NMDA toxicity in the CA1 region. Co-administration of cultures to (-)-nicotine (1-10 microM) with 100 nM corticosterone prevented corticosterone's exacerbation of subsequent CA1 insult. This protective effect of (-)-nicotine was not altered by co-exposure of cultures to 10 microM dihydro-beta-erythroidine but was blocked by co-exposure to 100 nM methyllycaconitine, suggesting the involvement of nicotinic acetylcholine receptors possessing the alpha7* subunit. The present studies suggest a role for hypercortisolemia in sensitizing the hippocampal NMDA receptor system to pathological activation and indicate that prolonged nicotine exposure attenuates this sensitization. Thus, it is possible that one consequence of heavy smoking in those suffering from hypercortisolemia may be a reduction of neuronal injury and sparing of cellular function.     

Efficacy of micafungin alone or in combination against experimental pulmonary aspergillosis.

Mortality from invasive pulmonary aspergillosis approaches 80% with few useful therapeutic options available. In these studies, we examined the efficacy of micafungin (MICA) alone or in combination with other antifungals in a model of pulmonary aspergillosis in immunosuppressed DBA/2 mice infected intranasally with conidia of Aspergillus fumigatus 10AF. In the initial study, groups of mice were given saline, or 1, 3 or 10 mg kg(-1) of MICA b.i.d., s.c. All saline controls, and 90% of untreated mice succumbed to infection. The efficacy of MICA was difficult to assess because of an apparent toxicity at 10 mg kg(-1). MICA given at 1 mg/kg significantly prolonged survival over the saline controls (P = 0.008). MICA at 3 or 10 mg kg(-1) versus the saline controls approached significance. No treatment regimen differed in efficacy. The efficacy of combination therapy was assessed, with mice given either no treatment, MICA at 1 mg/kg/dose, 0.8 mg kg(-1) of intravenous amphotericin B (AMB), 100 mg kg(-1) of oral itraconazole (ICZ), or 100 mg/kg/dose of twice-daily subcutaneous nikkomycin Z (NIK). AMB alone and MICA + AMB or MICA +NIK significantly prolonged survival (P < 0.05 - 0.02) over that of the controls. ICZ alone, ICZ+MICA and NIK alone did not significantly prolong survival. MICA alone at 1 mg/kg approached significance in prolonging survival. The combination of MICA and ICZ appeared to be potentially antagonistic. Although AMB+MICA was efficacious, no synergistic activity was noted for any of the regimens. Overall, these results indicate that MICA has moderate activity against pulmonary aspergillosis and might be useful in combination with conventional AMB.     

The effects of L-carnitine on the combination of, inhalation anesthetic-induced developmental, neuronal apoptosis in the rat frontal cortex

The anesthetic gas nitrous oxide (N2O) and the volatile anesthetic isoflurane (ISO) are commonly used in surgical procedures for human infants and in veterinary and laboratory animal practice to produce loss of consciousness and analgesia. Recent reports indicate that exposure of the developing brain to general anesthetics that block N-methyl-D-aspartate (NMDA) glutamate receptors or potentiate GABA(A) receptors can trigger widespread apoptotic neurodegeneration. In the present study, the question arises whether a relatively low dose of ISO alone or its combination with N2O entails significant risk of inducing enhanced apoptosis. In addition, the role of L-carnitine to attenuate these effects was also examined. Postnatal day 7 (PND-7) rat pups were exposed to N2O (75%) or a low dose of ISO (0.55%) alone, or N2O plus ISO for 2, 4, 6 or 8 h with or without L-carnitine. The neurotoxic effects were evaluated 6 h after completion of anesthetic administration. No significant neurotoxic effects were observed for the animals exposed to N2O or ISO alone. However, enhanced apoptotic cell death was apparent when N2O was combined with ISO at exposure durations of 6 h or more. Co-administration of L-carnitine (300 or 500 mg/kg, i.p.) effectively protected neurons from the anesthetic-induced damage. These data indicate that 6 h or more of inhaled anesthetic exposure consisting of a combination of N2O and ISO results in enhanced neuronal apoptosis, and L-carnitine effectively blocks the neuronal apoptosis caused by inhalation anesthetics in the developing rat brain.     

Ameliorative effect of vitamin C on the haematological changes induced by exposure of chlorpyriphos and lead acetate in Wistar rats

The present study was designed to evaluate the effects of chlorpyriphos, lead acetate and vitamin C alone and in combinations, on various haematological parameters in Wistar rats. Rats of 150–200 g body weight were divided into eight groups of six animals each and were subjected to various daily oral treatment regimes for 98 days. Group C served as control receiving only corn oil, group CP received chlorpyriphos at 5.5 mg/kg in corn oil and group L received lead acetate at100?ppm in water, whereas animals in group CP + L received a combination of chlorpyriphos at 5.5 mg/kg in corn oil and lead acetate at 100 ppm in water. Group VC received vitamin C at 100 mg/kg in water; group CP + VC received a combination of chlorpyriphos at 5.5 mg/kg and vitamin C at 100 mg/kg; group L + VC received lead acetate at 100 ppm in water and vitamin C at 100 mg/kg and group CP + L + VC received chlorpyriphos at 5.5 mg/kg, lead acetate at 100 ppm in water and vitamin C at 100 mg/kg. Blood samples were collected on days 0, 30, 60 and 98 post exposure and analysed for packed cell volume (PCV), total erythrocyte count (TEC), haemoglobin (Hb), erythrocyte sedimentation rate (ESR), total leucocyte count (TLC) and differential leucocyte count. A significant decrease in TEC, PCV and Hb and a significant increase in ESR values were observed. However, lead acetate caused an increase in TLC while chlorpyriphos resulted in a decrease in TLC. Both of these toxicants potentiated toxicity of each other. The study demonstrated that treatment of chlorpyriphos- and lead-treated rats with vitamin C significantly altered some of the important haematological parameters revealing the protective effect of this vitamin against haematological alterations induced by chlorpyriphos and lead.     

Physiologic responses of cross-linked hemoglobin in endotoxin-treated rats

Purified human cross-linked hemoglobin (alpha alpha Hb) as well as recombinant human hemoglobin is undergoing clinical trials in the setting of acute blood loss and perioperative hemodilution. We have previously demonstrated that in rabbits with circulating plasma Hb, such as alpha alpha Hb, infusion of endotoxin (LPS) impairs myocardial contractility which results in hypotension, tissue hypoperfusion and increased mortality. The untoward cardiovascular effects occurring after the combined infusion of LPS and alpha alpha Hb in this model are similar to those reported for other agents that inhibit nitric oxide (NO) availability. To determine if the deleterious effects of alpha alpha Hb and LPS were species specific, we performed similar studies in rats. Anesthetized Sprague-Dawley rats received LPS (4 mg/kg or 40 mg/kg) alone or in combination with alpha alpha Hb (0.7 g/kg). Mean arterial blood pressures (MAP) increased in the group that received alpha alpha Hb alone (105 +/- 8 to 120 +/- 7 mm Hg, p = 0.2) and a decrease was noted in the groups that received low dose LPS (4 mg/kg, p = 0.5) and high dose LPS (40 mg/kg, p = 0.016). MAP in rats treated with the LPS at either dose combined with alpha alpha Hb remained unchanged. Levels of urine nitrite, which was measured as a surrogate marker for plasma NO, were significantly decreased at 2 hr in groups that received the combination of alpha alpha Hb and LPS at 4 mg/kg (p = 0.022) and 40 mg/kg (p = 0.003). No significant decrease was observed in animals treated only with alpha alpha Hb (p = 0.21) or LPS (4 mg/kg; p = 0.78 and 40 mg/kg; p = 0.65). Survival was evaluated during 72 hr in animals that were infused with high dose LPS (40 mg/kg) alone or in combination with alpha alpha Hb and then allowed to recover. The survival of rats treated with LPS alone or the combination was 29% at the end of 24 hr and was 100% for rats receiving only alpha alpha Hb. The data suggest that the toxicity of alpha alpha Hb appears to be a species specific phenomenon.     

Lack of antiviral activity of ketoconazole alone or in combination with the acyclic nucleoside ganciclovir against a herpes virus type 2 infection in mice

Ketoconazole and ganciclovir were tested for antiviral activity, each alone and in combination, against a herpes simplex virus type 2 (HSV-2) systemic infection in Swiss-Webster mice. When given once daily for 5 days starting 24 hr after infection, the ED50 for ketoconazole either alone or in combination was greater than 60 mg/kg; for ganciclovir, the ED50 was 7.1 mg/kg alone and 10.8 mg/kg in combination. Thus, ketoconazole did not potentiate or antagonize the antiviral activity of an acyclic nucleoside. Consequently, AIDS patients could perhaps receive ketoconazole and ganciclovir simultaneously for fungal and viral opportunistic infections without interference with their respective efficacies.     

Profound effects of combining choline and piracetam on memory enhancement and cholinergic function in aged rats

In an attempt to gain some insight into possible approaches to reducing age-related memory disturbances, aged Fischer 344 rats were administered either vehicle, choline, piracetam or a combination of choline or piracetam. Animals in each group were tested behaviorally for retention of a one trial passive avoidance task, and biochemically to determine changes in choline and acetylcholine levels in hippocampus, cortex and striatum. Previous research has shown that rats of this strain suffer severe age-related deficits on this passive avoidance task and that memory disturbances are at least partially responsible. Those subjects given only choline (100 mg/kg) did not differ on the behavioral task from control animals administered vehicle. Rats given piracetam (100 mg/kg) performed slightly better than control rats (p<0.05), but rats given the piracetam/choline combination (100 mg/kg of each) exhibited retention scores several times better than those given piracetam alone. In a second study, it was shown that twice the dose of piracetam (200 mg/kg) or choline (200 mg/kg) alone, still did not enhance retention nearly as well as when piracetam and choline (100 mg/kg of each) were administered together. Further, repeated administration (1 week) of the piracetam/choline combination was superior to acute injections. Regional determinations of choline and acetylcholine revealed interesting differences between treatments and brain area. Although choline administration raised choline content about 50% in striatum and cortex, changes in acetylcholine levels were much more subtle (only 6–10%). No significant changes following choline administration were observed in the hippocampus. However, piracetam alone markedly increased choline content in hippocampus (88%) and tended to decrease acetylcholine levels (19%). No measurable changes in striatum or cortex were observed following piracetam administration. The combination of choline and piracetam did not potentiate the effects seen with either drug alone, and in certain cases the effects were much less pronounced under the drug combination. These data were discussed as they relate to possible effects of choline and piracetam on cholinergic transmission and other neuronal function, and how these effects may reduce specific memory disturbances in aged subjects. The results of these studies demonstrate that the effects of combining choline and piracetam are quite different than those obtained with either drug alone and support the notion that in order to achieve substantial efficacy in aged subjects it may be necessary to reduce multiple, interactive neurochemical dysfunctions in the brain, or affect activity in more than one parameter of a deficient metabolic pathway.     

A beta 25-35-induced depression of long-term potentiation in area CA1 in vivo and in vitro is attenuated by verapamil

The effect of intracerebroventricular (icv) injection of A beta 25-35 and/or intraperitoneal (ip) application of the L-type calcium channel (VDCC) blockers verapamil or diltiazem were examined in vivo. To by-pass possible systemic actions of these agents, their effects on long-term potentiation (LTP) in the CA1 region of the in vitro hippocampal slice preparation were also examined. Application of A beta 25-35 (10 nmol in 5 microl, i.c.v.) significantly impaired LTP in vivo, as did IP injection of verapamil (1 or 10 mg/kg) or diltiazem (1 or 10 mg/kg). In the in vitro slice preparation, LTP was also depressed by prior application of A beta 25-35 (500 nmol), verapamil (20 microM), or diltiazem (50 microM). Combined application of A beta 25-35 and verapamil in either the in vivo or in vitro preparation resulted in a significant reversal of the LTP depression observed in the presence of either agent alone. However, co-application of diltiazem and A beta 25-35 failed to attenuate the depression of LTP observed in the presence of either agent alone in vivo or in vitro. Since LTP is a cellular correlate of memory and A beta is known to be involved in Alzheimer's disease (AD), these results indicate that verapamil, a phenylalkylamine, may be useful in the treatment of cognitive deficits associated with AD.     

Inhibitors of lipoxygenase increase the ovulation rate in the in-vitro perfused luteinizing hormone-stimulated rabbit ovary

In order to determine whether leukotrienes, products of the lipoxygenase pathway, are involved in ovulation, pairs of rabbit ovaries were treated with the lipoxygenase inhibitors nordihydroguaiaretic acid (NDGA) and caffeic acid (CA) while being perfused in vitro. The control ovaries from each rabbit received luteinizing hormone (LH) (1.5-2.25 micrograms ml-1) while the contralateral ovaries were treated with LH + NDGA (100 microM) or LH + CA (100 microM). The numbers of ovulations from both the LH + NDGA- and LH + CA-treated ovaries were significantly higher (P less than 0.05) than from their respective LH-stimulated controls. Treatment with NDGA alone in the perfusate did not cause any ovulation, while CA alone caused one ovulation from one of six ovaries perfused. Ovarian tissue levels of prostaglandins after 7 h of perfusion with LH + NDGA or with LH alone showed that, in five of the six ovaries perfused in this group, the tissue levels of PGE2, 6-keto-PGF1 alpha and PGF2 alpha were higher in the presence of NDGA. The mean differences were significant (P less than 0.05) for prostacyclin but not significant (P greater than 0.05) for PGE2 and PGF2 alpha. Our interpretation of the findings is that, when used for blocking the lipoxygenase pathway, NDGA and CA increase the substrate availability for the cyclo-oxygenase pathway of arachidonic acid metabolism, resulting in a net increase in prostaglandins. The increased ovarian levels of prostaglandins, especially prostacyclin, may cause the observed increase in ovulation rate. Consequently, although the leukotrienes may be involved in the mechanism of ovulation in the rabbit, their effects appear to be less pronounced than those of prostaglandins.     

Antithrombotic and platelet function inhibiting effects of ML3000, a new antiinflammatory drug with COX/5-LOX inhibitory activity

DESIGN: The studies reported were designed to evaluate the effects of ML3000 on platelet aggregation and platelet-induced thrombin generation in human platelet rich plasma and its antithrombotic effect in a rat thrombosis model. ML3000 is a potent inhibitor of both COX-1/2 and 5-LOX with demonstrated antiinflammatory activity and a low incidence of GI mucosal injury in animal and human studies. METHODS AND RESULTS: The antithrombotic activity of ML3000 (10, 30 and 100 mg/kg) and aspirin (30 and 100 mg/kg) was measured in the mesenteric venules of rats using the laser-induced thrombus model. Both ML3000 and aspirin, at all doses tested, showed significant antithrombotic activity. The mean number of laser injuries necessary to induce a thrombus that blocked the vessel was 1.93 +/- 0.28 in the control group, 3.3 +/- 0.53, 3.6 +/- 0.14 or 4.07 +/- 0.37 in the groups treated with ML3000 at 10, 30 or 100 mg/kg p.o. and 3.4 +/- 0.55 or 3.9 +/- 0.3 in the groups treated with Aspirin at 30 or 100 mg/kg p.o. The antithrombotic activity in this model was significant up to 12 h post-administration of 100 mg/kg ML3000 or Aspirin. The aggregation inhibiting activity of ML3000 (1-100 microg/ml) and indomethacin (1 microg/ml) was studied using the following inducing agents: ADP (1 and 2 microM), epinephrine (25 and 50 microM), collagen (0.5 and 1 microg/ml), and the thromboxane mimetic U46619 (0.8 and 1.6 microM). Aggregation inhibitory activity was observed with ML3000 in all assays except with the higher concentration of U46619 at 1.6 microM. Indomethacin (1 microg/ml) inhibited aggregation in all assays. CONCLUSIONS: ML3000 has significant antithrombotic activity and a marked platelet aggregation inhibiting effect. Given its demonstrated antiinflammatory activity, platelet function inhibition, and antithrombotic effects along with a lack of effect on the GI mucosa, ML3000 may offer an alternative to the combination of a COX-2 inhibitor and aspirin in arthritis patients at risk for cardiovascular disease.     

Mu 1 opioid receptor involvement in maternal behavior

Previous studies have demonstrated that morphine inhibits the display of maternal behavior in lactating rats. Whether morphine exerts its actions specifically at the mu receptor has not yet been determined. The present study examined this possibility by evaluating whether naloxonazine, an irreversible and selective antagonist of the mu 1 opioid receptor subtype, is able to attenuate morphine's disruptive effect on maternal behavior in primiparous lactating rats. Experiment 1 compared the ability of naloxonazine (AZINE) and naloxone (NAL) to block the action of morphine (MOR) on maternal care. Virgin, Sprague-Dawley rats were mated in our colony and on day 3 postpartum (parturition, day 0) all rats received jugular catheters. On day 6 the mothers received one of the following treatments: MOR alone (10 mg/kg, SC, N = 10); MOR (10 mg/kg, SC) 24 hr after AZINE pretreatment (10 mg/kg, IV, N = 10); MOR (10 mg/kg, SC) 24 hr after NAL pretreatment (10 mg/kg, IV, N = 8); or MOR (10 mg/kg, SC) immediately after NAL (0.5 mg/kg, SC, N = 10). MOR alone completely disrupted maternal behavior (0% responded) which was blocked by prior NAL administration (100%). AZINE pretreatment 24 hr earlier partially blocked MOR disruption of MB (40% responded; significantly different from MOR alone). The response of rats pretreated 24 hr earlier with NAL did not differ from MOR alone. AZINE blocked MOR's effect on pup retrieval to an even greater degree (70% responded vs. 10% in MOR alone). Experiment 2 determined the ability of AZINE to interfere with varying doses of MOR on maternal behavior.(ABSTRACT TRUNCATED AT 250 WORDS)     

The genotoxic effect of potassium metabisulfite using chromosome aberration, sister chromatid exchange, micronucleus tests in human lymphocytes and chromosome aberration test in bone marrow cells of rats

Potassium metabisulfite (PMB) is used as an antimicrobial substance in many kinds of foods. In the present study, the effects of PMB on chromosome aberrations (CAs), sister chromatid exchanges (SCEs), and micronucleus (MN) formation in human lymphocytes and as well as its effect on CAs in bone marrow cells of rats were investigated. The human lymphocytes were treated with 25, 50, 100, and 200 microg/ml of PMB for 24 and 48 hr. PMB was also intraperitoneally (ip) injected to the rats as a single dose of 150, 300, and 600 mg/kg body weight (b.w.) for 12 and 24 hr before sacrifice. PMB induced abnormalities such as structural and numerical (total) CAs, SCEs, and MN formations in a dose dependent manner in the lymphocytes of the 24- and 48-hr treatment periods. In addition, PMB showed a cytotoxic effect by decreasing the replication index (RI), mitotic index (MI) and nuclear division index (NDI) in a dose dependent manner in human lymphocytes. The compound induced CA as well and decreased the MI in bone marrow cells of rats. It might be concluded that PMB had a high genotoxic and cytotoxic risk.     

Chronic ascorbate potentiates the effects of chronic haloperidol on behavioral supersensitivity but not D2 dopamine receptor binding.

Ample behavioral evidence suggests that ascorbate parallels the action of haloperidol, a widely used neuroleptic. To determine the extent to which this parallel extends to chronic treatment, 21 days of exposure to ascorbate (100 or 500 mg/kg) alone or combined with haloperidol (0.5 mg/kg) were assessed on stereotyped behavior and neostriatal D2 dopamine receptor binding in rats. Our results indicate that when challenged with the dopamine agonist, apomorphine (0.5 mg/kg), animals chronically treated with haloperidol or high-dose ascorbate alone display a supersensitive sniffing response relative to controls, while animals chronically treated with the combination of haloperidol and high-dose ascorbate display a further potentiation of sniffing relative to the haloperidol groups. In addition, [3H]spiperone saturation studies showed, as expected, an up-regulation of striatal D2 dopamine receptors in rats treated with haloperidol as reflected by a change in receptor density (Bmax) but not affinity (KD). Ascorbate treatment, however, had no effect on D2 receptor density or the distribution of [3H]apomorphine in whole brain. Even though chronic treatment with the haloperidol-high-dose-ascorbate combination produced an up-regulation of striatal D2 dopamine receptors, this treatment did not cause a further up-regulation relative to haloperidol alone nor did it have any effect on [3H]apomorphine distribution. Taken together, these findings indicate that although chronic ascorbate produces behavioral supersensitivity to apomorphine through central mechanisms, they appear to differ from those induced by chronic haloperidol.     

Antimicrobial effects of varied combinations of meropenem, sulbactam, and colistin on a multidrug-resistant Acinetobacter baumannii isolate that caused meningitis and bacteremia

Meropenem (MEM; 2 g/8 hr; minimum inhibitory concentration [MIC] = 256 mg/L) plus sulbactam (SUL; 1 g/8 hr; MIC = 128 mg/L) (two-drug-therapy period), and subsequent additional intravenous colistin (COL; 2.5 mg/kg/12 hr) and intraventricular (COL, 5 mg/day; MIC = 1 mg/L) (three-drug-therapy period) were sequentially used in a patient with postneurosurgery bacteremic meningitis due to a multidrug-resistant Acinetobacter baumannii (MDRAB) isolate (AB(1)). We detected 4- to 32-fold increases in peak or trough cerebrospinal fluid bactericidal titer and serum bactericidal titer in three-drug-therapy period when comparing to those in two-drug-therapy period. The time-kill study with MEM, SUL, and COL alone or varied combinations (all at 1 x MIC) against AB(1) and another genetically nonrelated MDRAB isolate (AB(134) [MICs of MEM = 64 mg/L, SUL = 16 mg/L, and COL = 1 mg/L]) was performed. The two-drug combinations (MEM + SUL, MEM + COL, and SUL + COL) each elicited different inhibitory effect on AB(1) and AB(134) at 6 hr. Bacterial regrowth at 24 hr was observed in the experiments in which the MDRAB isolate was inhibited earlier by COL alone (AB(1) and AB(134)), by MEM plus SUL (AB(1)), and by MEM plus COL (AB(134)), but not in SUL plus COL, and MEM + SUL + COL. Combined use of COL with MEM and/or SUL may provide good therapeutic options, even though MEM and SUL are in vitro resistance to the MDRAB.     

Stimulation by vasoactive intestinal polypeptide of muscarinic receptor-mediated catecholamine secretion from isolated guinea pig adrenal medullary cells

The effects of vasoactive intestinal polypeptide (VIP) on catecholamine (CA) secretion by isolated guinea pig adrenal medullary cells were studied. VIP (1 microM) alone induced only a slight secretion of CA, but it stimulated ACh-induced CA secretion. At concentrations of 0.01-1 microM, it stimulated muscarine-induced CA secretion, but not nicotine-induced CA secretion. It did not affect high K+ or Ca2+ ionophore-induced CA secretion. The stimulatory effect of VIP on muscarine-induced CA secretion was observed at muscarine concentrations of 2 200 microM and was detectable after 2 min incubation.     

Regulation of intracellular pH in rat renal inner medullary thin limbs of Henle's loop

Regulation of intracellular pH (pHi) was studied in isolated rat renal inner medullary thin limbs of Henle's loop in bicarbonate/phosphate-buffered medium with high pCO2, high osmolality ( congruent with670 mosmol/kg H2O; 270 mM urea; 180 mM NaCl), organic osmolytes, and a pH of 6.8 to approximate the physiological in vivo environment. The pH-sensitive fluorescent dye 2',7'-bis(2-carboxyethyl)-5,6-carboxyfluorescein (BCECF) was used to measure pHi. Resting pHi was always acid and significantly more acid in descending thin limb (DTL) cells than in ascending thin limb (ATL) cells from pure or mixed-type thin limbs. Resting pHi was slightly but significantly higher in both DTLs and ATLs in high osmolality ( approximately 670 mosmol/kg H2O) than in low osmolality ( approximately 290 mosmol/kg H2O) medium but not when sucrose replaced urea. In both DTLs and ATLs the rate of recovery of pHi following additional acidification with an NH4Cl pulse was reduced by Na+ removal from the medium and by the addition of 60 microM HOE642 (an inhibitor of the Na+/H+ exchanger, NHE1), 55 microM S1611 (inhibitor of Na+/H+ exchanger, NHE3), 1 microM bafilomycin A1 (an inhibitor of vacuolar H+ -ATPase), or 20 microM Schering 28080 (an inhibitor of H+ -K+ -ATPase) to the medium. Resting pHi was also reduced by 60 microM HOE642, 55 microM S1611, and 20 microM Schering 28080. In both DTLs and ATLs, RT-PCR revealed message for NHE1, NHE3, and vacuolar H+ -ATPase; immunocytochemistry demonstrated the expression of the protein for NHE1 (basolateral membrane), NHE3 (luminal membrane), and H+ -K+ -ATPase (luminal membrane). These data suggest that pHi in rat inner medullary thin limbs is regulated by urea and by basolateral and luminal H+ extrusion via NHE1, NHE3, vacuolar H+ -ATPase, and H+ -K+ -ATPase.