Functional and anatomical evidence for different dopamine dynamics in the core and shell of the nucleus accumbens in slices of rat brain

BACKGROUND: Chlorambucil (CLB), 2-chlorodeoxyadenosine (2-CDA) and fludarabine (FAMP) are among the most widely used drugs in chronic lymphocytic leukemia (CLL). Therefore we evaluated in vitro sensitivity to these drugs and cross-resistance of purine analogs. In addition, we correlated the in vitro data with the main clinico-hematological variables and surface markers. PATIENTS AND METHODS: Eighty CLL samples obtained from 63 untreated and 17 treated CLL patients were tested in vitro with the MTT assay. Lethal dose (LD)50 values were calculated to determine sensitivity to CLB, 2-CDA and FAMP. RESULTS: Samples were clustered either for a one-log increase of LD50 values or for LD50 threshold values of 3 microM for FAMP, 0.3 microM for 2-CDA and 7 microM for CLB, which correspond to the therapeutically achievable plasmatic levels of these drugs. A higher number of samples sensitive to 2-CDA were identified by the first approach; with the second method the relative order of sensitivity was FAMP > 2-CDA > CLB. Concerning 2-CDA and FAMP cross-resistance, out of 61 samples resistant to 2-CDA, 29.5% were sensitive to FAMP. Conversely, 13.9% out of 43 samples resistant to FAMP were sensitive to 2-CDA. No correlation was found between the main clinico-hematological features and the LD50 values of each drug either considering the whole series or only the untreated cases. In vitro drug sensitivity was also evaluated during the steady-state of the disease and at disease progression in six untreated cases. We observed a mean increase in the LD50 values of about 13, 38 and 22 times for CLB, FAMP and 2-CDA, respectively. Among the treated cases, the LD50 values of both purine analogs and CLB correlated with bone marrow histology. CLL cells expressing CD14, CD11c, CD11b, and FMC7 were more resistant in vitro to purine analogs but not to CLB. CONCLUSIONS: This study suggests that i) the purine analogs exert a greater cytotoxic effect on CLL cells; ii) 2-CDA and FAMP are not cross-resistant in vitro in a percentage of CLL samples, iii) a possible change in LD50 values may be related to modification of the disease status, and iv) the expression of certain surface markers, which are CLL-unrestricted, identifies samples with higher in vitro resistance to purine analogs.     

Blood lead of intravenous drug users

Ethanol, morphine, cocaine and amphetamine were examined in place conditioning. After determination of initial preferences, animals were conditioned with ethanol (1 g/kg), morphine (5 mg/kg), cocaine (5 mg/kg) and amphetamine (5 mg/kg) alone or with combinations of these drugs plus naloxone (1 mg/kg). Naloxone prevented the ability of all drugs used to produce a place preference. The reinforcing properties of ethanol and morphine were reduced by sodium nitroprusside at a dose equal to 1/10 of LD50 given before preference testing. Molsidomine (1/10 LD50 and 1/20 LD50) altered the expression of the conditioned place preference produced by ethanol but not by morphine. Results of the present study suggest the involvement of endogenous opioids and probably of nitric oxide in the rewarding actions of drugs of abuse.     

Application of pharmacokinetically guided dose escalation with respect to cell cycle phase specificity

BACKGROUND: In 1986, the concept of pharmacokinetically guided dose escalation (PGDE) was proposed to predict the maximum tolerated dose (MTD) of an antitumor drug in humans from animal data. We have previously shown that antitumor drugs can be classified into two types, depending on their cytotoxic mechanisms: type 1 drugs, which are cell cycle phase-nonspecific agents, i.e., area under the curve for drug concentration in the plasma versus time (AUC)-dependent drugs; and type 2 drugs, which are cell cycle phase-specific agents, i.e., those that are time dependent. PURPOSE: The validity of the assumption that the AUC at the dose lethal for 10% of mice administered drug (LD10) is equal to the AUC at MTD for humans, the premise on which PGDE is based, was examined for type 1 and 2 drugs. METHODS: Findings in the literature, including those of Collins and co-workers, were retrospectively analyzed. The human/mouse ratios for the AUC were compared with each other and with the human/mouse dose ratios, based on milligram per meter square of body surface area, the measurement currently used in clinical trials of antitumor drugs. For six of the type 1 drugs, the human/mouse ratio for the AUC of total drug (AUC) and that of unbound drug (AUCu), which has been considered a determinant of pharmacologic and toxicologic effects, were also compared. RESULTS: There was an excellent correlation between log AUC at LD10 for mice and log AUC at MTD for humans for type 1 drugs (r = .898), but not for type 2 drugs (r = .677). For type 1 drugs, the correlation between mouse AUC at LD10 and human AUC at MTD was better for unbound drug (r = .961) than for total drug (r = .892). CONCLUSIONS: PGDE is useful for type 1 drugs; differences in protein binding between species should, however, be considered when using this method.     

Bridge-heterologous chemiluminescence enzyme-linked immunosorbent assay of estriol 3-sulfate in pregnancy plasma

A simple capillary zone electrophoresis method is developed for the quantitation of the beta-blocker atenolol and the complementary antihypertensive agents bendroflumethiazide, amiloride, and hydrochlorothiazide in human urine samples. The electrophoretic separation is performed using a 78-cm x 75-micron-i.d. (70-cm effective length) fused-silica capillary. A borate buffer (pH 9) is used as running electrolyte. The sample is hydrostatically introduced for 20 s, and the running voltage is 25 kV at the injector end of the capillary. The analysis of urine samples requires the optimization of solid-phase extraction methods, achieving recoveries > or = 61% for all the drugs and good separation from the urine matrix. The method is successfully applied to the determination of these compounds in pharmaceutical formulations and in urine samples collected after the intake of Neatenol Diu (100 mg atenolol-5 mg bendroflumethiazide) and Kalten (50 mg atenolol-25 mg hydrochlorothiazide-2.5 mg amiloride). The method is validated in terms of reproducibility, linearity, and accuracy.     

Medical therapies for inflammatory bowel disease

Inflammatory bowel disease is a spectrum of disorders whose etiology and pathogenesis are unclear. No therapy is standard; many modalities exist for management. New drugs, improved formulations of existing drugs, combination therapy and biologic agents offer more effective relief and maintain disease remission.     

Differential expression of plasma membrane calcium pump mRNA isoforms in rat osteoblast-like cells

Cryptococcal meningitis is a common infection in patients with AIDS. Using a murine cryptococcosis model, we compared treatment with a new triazole, D0870, and fluconazole. Groups of ICR (Institute for Cancer Research) mice were infected intracerebrally with eight different isolates of Cryptococcus neoformans variety neoformans with different in vitro susceptibilities to fluconazole. For survival studies mice were challenged with two to four times LD(50) or six to nine times LD(50). Treatment was given for 10 days. Mice were observed through to day 30. To assess the effect of treatment on fungal tissue burden, mice received a three to five times LD(50) inoculum and treatment for 10 days. They were sacrificed on day 12 and serial dilutions of brain homogenates were cultured. Fluconazole prolonged survival primarily in isolates which were susceptible in vitro. D0870 prolonged survival in all isolates except one, which was also resistant in vitro to D0870 and fluconazole. Both drugs reduced colony counts of all isolates. D0870 warrants further development for use in cryptococcosis, and appears effective for isolates relatively resistant to fluconazole. There is a relative correlation of in vivo and in vitro susceptibility to D0870 as well as fluconazole.     

Sciatic nerve blockade in infant, adolescent, and adult rats: a comparison of ropivacaine with bupivacaine

BACKGROUND: Ropivacaine is a newly introduced local anesthetic. No data are available regarding its safety, efficacy, or sensory-selectivity in children. The sciatic block duration and systemic toxicity of bupivacaine and ropivacaine were compared among infant, adolescent, and adult rats. METHODS: Infant, adolescent, and adult rats received blocks with ropivacaine or bupivacaine. Nociceptive, proprioceptive, and motor blockade were assessed. Systemic effects (contralateral leg analgesia, seizures, respiratory distress, apnea) were quantified. Plasma local anesthetic concentrations were measured at terminal apnea. RESULTS: Nerve blockade for a given absolute dose lasted longer in infants than in older rats for both drugs. Block duration from ropivacaine generally was the same as or slightly shorter than bupivacaine. There was no difference in sensory-selectivity between the drugs. Doses required to induce all systemic toxicity indices were inversely related to age (e.g., the lethal dose in 50% of animals [LD50] of ropivacaine in infants is 155 mg/kg; in adults it is 54 mg/kg). All indices of toxicity occurred at higher doses per kilogram for ropivacaine than bupivacaine, at all ages (e.g., the LD50 of bupivacaine in infants is 92 mg/kg; in adults it is 30 mg/kg). Plasma concentrations at terminal apnea were higher for ropivacaine than for bupivacaine at all ages, and were higher in infants than in older rats. CONCLUSIONS: Ropivacaine resembles bupivacaine in its local anesthetic effects but has a greater margin of safety. For a given absolute dose, sciatic blockade in infant rats lasts longer than in adolescents or adults. Although the doses (in milligrams per kilogram) causing toxicity were much higher in infants than in adults, this probably does not correspond to a wider therapeutic index.     

Empirical scaling of single oral lethal doses across mammalian species based on a large database

The scaling of administered doses to achieve equal degrees of toxic effect in different species has been relatively poorly examined for noncancer toxicity, either empirically or theoretically. We investigate empirical patterns in the correspondence of single oral dose LD50 values across several mammalian species for a large number of chemicals based on data reported in the RTECS database maintained by the National Institute for Occupational Safety and Health. We find a good correspondence of LD50 values across species when the dose levels are expressed in terms of mg administered per kg of body mass. Our findings contrast with earlier analyses that support scaling doses by the 3/4-power of body mass to achieve equal subacute toxicity of antineoplastic agents. We suggest that, especially for severe toxicity, single- and repeated-dosing regimes may have different cross-species scaling properties, as they may depend on standing levels of defenses and rate of regeneration of defenses, respectively.     

Climate change and the incidence of food poisoning in England and Wales

A study was undertaken to determine the susceptibility or resistance of 9 outbred experimental or commercial poultry lines to Salmonella enteritidis PT4. Young chicks were inoculated either intramuscularly or orally just after hatching. After intramuscular challenge the lines could be divided into susceptible lines (LD 50% < or = 10(2) Salmonella per animal), intermediate lines (LD 50% about 10(4) Salmonella) and resistant lines (LD 50% > 10(5) Salmonella). The results obtained after oral challenge confirmed these 3 groups for both mortality rates and the probability of the presence of salmonellae in the spleen and liver. There was no difference between lines concerning caecal carriage.     

Blockade of the specific lethal effects of narcotic analgesics in the mouse

The capacity of the narcotic antagonists naloxone and nalorphine and the benzodiazepine derivatives diazepam and oxazepam to increase the LD50s of the narcotic analgesics morphine and methadone administered at convulsant doses was eveluated in the mouse. Naloxone produced a dose-related increase in the LD50s of both morphine and methadone. Iiazepam and oxazepam were also effective in increasing the LD50s of the narcotics; this effect was additive with that of naloxone. However, the maximal increase in the LD50s of the narcotics produced by pretreatment with naloxone alone was not increased further by the combined pretreatment of naloxone and a benzodiazepine. The anticonvulsant trimethadione did not elevate the LD50s of methadone, nor did it potentiate the effects of naloxone. These results suggest that the benzodiazepines may reduce the lethality of narcotic analgesics administered at high doses by a mechanism other than by an anticonvulsant effect alone. Therefore, the present results support the conclusion that the capacity to increase the convulsant LD50 of the narcotic analgesics is a general property of the narcotic antagonists.     

Acute toxicity and pharmacokinetics of dibekacin mice

The LD50 values of dibekacin to mice were determined following three different methods of administration, namely, intravenous constant infusion, intravenous bolus injection, and intramuscular injection. The serum levels of dibekacin were pharmacokinetically analyzed. The differences in LD50 values between the methods of administration were discussed from the viewpoints of pharmacokinetics. 1) The LD50 value following the intravenous constant infusion was higher than that following the intravenous bolus injection and approached the level of that following the intramuscular injection, when the infusion rate of the drug was decreased by increasing the infusion period. 2) The biological half-life of dibekacin in mice was 24--45 min. 3) The volume of distribution increased as its dose increased, and a linear correlation was noted between log Vd and log (dose). 4) The difference among the maximum serum concentrations calculated with dibekacin following the administration of LD50 was small, which coincided with the results of the experiment that the serum concentrations of dibekacin at the death following the administration of LD100 were almost the same regardless of the method of administration.     

Defining the role of the bladder-neck sling in the surgical treatment of urinary incontinence in children with neurogenic incontinence

Mother squirrel monkeys stop carrying infants at earlier ages in high-demand (HD) conditions where food is difficult to find relative to low-demand (LD) conditions. To characterize these transitions in psychosocial development, from 10- to 21-weeks postpartum we collected measures of behavior, adrenocortical activity, and social transactions coded for initiator (mother or infant), goal (make-contact or break-contact), and outcome (success or failure). Make-contact attempts were most often initiated by HD infants, but mothers often opposed these attempts and less than 50% were successful. Break-contact attempts were most often initiated by LD infants, but mothers often opposed these attempts and fewer LD than HD infant break-contact attempts were successful. Plasma levels of cortisol were significantly higher in HD than LD mothers, but differences in adrenocortical activity were less consistent in their infants. HD and LD infants also spent similar amounts of time nursing on their mothers and feeding on solid foods. By rescheduling some transitions in development (carry-->self-transport), and not others (nursing-->self-feeding), mothers may have partially protected infants from the immediate impact of an otherwise stressful foraging task.     

Cholestyramine as an adsorbent in acute lindane poisoning: a murine model

STUDY OBJECTIVES: To compare the effectiveness of single-dose cholestyramine versus single-dose activated charcoal in preventing clinical toxicity after acute lindane ingestion. DESIGN: CD-1 mice received lindane by enteral (gavage) and parenteral (intraperitoneal) routes, followed by enteral administration of either cholestyramine (2.25 g/kg) or activated charcoal (2.25 g/kg), with subsequent observation for convulsions and death. MEASUREMENTS: The doses of lindane at which 50% of mice developed convulsions (CD50) and at which 50% of mice died (LD50) were established and compared among control, charcoal-, and cholestyramine-treated groups. RESULTS: For lindane administered by gavage, the differences in the CD50 and LD50 between the control and the activated charcoal groups were not statistically significant. However, a significant difference did exist in both the CD50 and the LD50 between the group receiving cholestyramine and the control group and between the cholestyramine and activated charcoal groups. After IP administration of lindane, the difference in CD50 or LD50 among control, activated charcoal, or cholestyramine groups was not significantly different. CONCLUSION: In the murine model, cholestyramine is more effective than activated charcoal in preventing absorption of lindane, thus preventing convulsions and death. These data support the need for clinical studies to determine whether cholestyramine may be a more effective treatment than activated charcoal for acute lindane ingestions in human beings.     

4-nitro-2-phenoxymethanesulfonanilide (R-805): a chemically novel anti-inflammatory agent

The anti-inflammatory activity of the sulfonanilide, 4-nitro-2-phenoxymethanesulfonanilide (R-805) has been demonstrated in conventional models (carrageenan-induced edema of the rat's paw, UV-induced erythema of guinea-pig skin, adjuvant-induced arthritis of the rat). R-805 differs from most currently available acidic anti-inflammatory drugs in that its functional acidic group is not carboxyl. The relative anti-inflammatory potency of R-805 is comparable to indomethacin. Calculation of acute therapeutic indices (LD50/ED50) for 8 acidic anti-inflammatory drugs show R-805 to possess a more favourable index than the other drugs examined.     

Performance of abamectin bait formulations against German cockroaches (Dictyoptera: Blattellidae)

Commercial and experimental formulations of abamectin-based baits were evaluated in laboratory and field studies against the German cockroach, Blattella germanica (L.). In continuous exposure tests with adult males, toxicity and presumably bait consumption varied with the design of the bioassay. LT50s ranged from approximately 0.9 to > 41 d for an aerosol gel formulation for males deprived of water for 72 h before the test and for undeprived males tested with alternative food and water, respectively. Dry formulations had lower LT50s than water containing formulations for nondeprived males. There was no difference in bait toxicity between males deprived of food or water, but in arena tests, moist formulations were preferred by mixed-stage populations of cockroaches. Powder formulations were more repellent (approximately 14.9%) than moist formulations (approximately 6.4%) in Ebeling choice boxes assays, but all abamectin formulations had positive performance indices. A powder formulation reduced cockroach trap catch in infested apartments more rapidly when applied to 50, rather than 12 sites, even when the same amount of bait was applied per apartment. When applied at approximately 50 sites as a series of thin smears, an aerosol formulation provided nearly an 80% reduction in trap catch. Other abamectin formulations provided substantial, but smaller reductions in trap catch. Abamectin-based baits can reduce German cockroach populations when properly applied.     

Liquid levodopa/carbidopa produces significant improvement in motor function without dyskinesia exacerbation

We performed the first double-blind, crossover comparison between levodopa/carbidopa (LD/CD) in optimized liquid versus tablet doses to measure plasma LD levels and relative effects on disabilities (motor function, fluctuations, and dyskinesias) in patients with Parkinson's disease. Twenty-three subjects with motor fluctuations were optimized with open-label LD/CD tablets and liquid. In a double-dummy design, patients randomly received 2 weeks of liquid and 2 weeks of tablet LD/CD. Twice during each arm, we evaluated patients hourly 9 AM to 4 PM with the use of plasma LD levels, the Unified Parkinson's Disease Rating Scale, a dyskinesia rating scale, and "on-off" ratings. Patients receiving liquid LD/CD ingested significantly higher doses and had significantly improved motor function and total "on" time, without an increase in dyskinesia severity. The number of motor fluctuations in the two phases was not significantly different. LD levels and variability were also equivalent with the two formulations. At optimized dosing, liquid LD/CD offers a means to significantly improve motor disability in patients with Parkinson's disease without exacerbating dyskinesia.     

News from the Society for the Advancement of Women''s Health Research. Put out that light!

The significance of guanine nucleotides and nucleosides in neurodegenerative disorders is suggested by recent reports that these molecules enhance neurite branching and astrocyte proliferation. The objective of this study was to investigate the influence of increased dopamine metabolism, produced by 5-day treatment of rabbits with reserpine (2 mg/kg) or levodopa (LD) (50 mg/kg), on striatal concentrations of guanosine, guanine, and their metabolites. Reserpine treatment decreased striatal guanosine by 41% and increased guanine by 50%, while LD decreased guanosine by 48% (all p < 0.01 vs. vehicle-treated controls). LD also increased guanine by 22% (not statistically significant). Xanthine and uric acid concentrations were unchanged. Because of the neurotrophic properties of guanosine and guanine, changes in striatal concentrations of these purines secondary to increased dopamine (DA) turnover may have relevance for survival of remaining dopaminergic neurons in Parkinson's disease (PD).     

The dependence of the blood level of the oxime HS-6 on the severity of organophosphate poisoning

Atropinised anaesthetised rats were injected i.v. with 4, 6 or 8 X LD50 of the organophosphorous anticholinesterase soman. Subsequent treatment with one dose of HS-6 (100 mg/kg, i.v.) delayed respiratory failure by 1 h or more; a further postponement was obtained when an additional HS-6 infusion was given. At the same infusion rate, HS-6 blood levels after 4 X LD50 soman remained stationary, but rose after the higher soman doses. The rise was greater the higher the soman dose had been. This rapid rise in oxime blood levels after high doses of organophosphate may seriously complicate therapy.     

Anti-cancer drug characterisation using a human cell line panel representing defined types of drug resistance

Differential drug response in a human cell line panel representing defined types of cytotoxic drug resistance was measured using the non-clonogenic fluorometric microculture cytotoxicity assay (FMCA). In total 37 drugs were analysed; eight topoisomerase II inhibitors, eight anti-metabolites, eight alkylating agents, eight tubulin-active agents and five compounds with other or unknown mechanisms of action, including one topoisomerase I inhibitor. Correlation analysis of log IC50 values obtained from the panel showed a high degree of similarity among the drugs with a similar mechanism of action. The mean percentage of mechanistically similar drugs included among the ten highest correlations, when each drug was compared with the remaining data set, was 100%, 92%, 88% and 52% for the topoisomerase II inhibitors, alkylators, tubulinactive agents and anti-metabolites respectively. Classification of drugs into the four categories representing different mechanisms of action using a probabilistic neural network (PNN) analysis resulted in 29 (91%) correct predictions. The results indicate the feasibility of using a limited number of cell lines for prediction of mechanism of action of anti-cancer drugs. The present approach may be well suited for initial classification and evaluation of novel anti-cancer drugs and as a potential tool to guide lead compound optimisation.