No increase in carcinogen-DNA adducts in the lungs of monkeys exposed chronically to marijuana smoke.

Rhesus monkeys exposed to marijuana smoke either 7 or 2 days/weeks (HI and LO groups, respectively), or ethanol-extracted marijuana smoke for 7 days/week (EM) or sham treatment (SH) for 1 year were sacrificed 7 months following the last exposure. Pulmonary levels of carcinogen-DNA adducts were determined. Although mean or median adduct levels were not statistically different, 15 of 22 adduct measures were highest in the EM group and lowest 12 of 22 times in the SH group. The levels of aromatic carcinogen-DNA adducts seem no higher in the lungs of animals exposed to marijuana smoke than in untreated animals. Ethanol-extracted marijuana may have effects greater than marijuana itself.     

Acute effects of chlorpromazine in a monkey operant behavioral test battery.

The effects of acute chlorpromazine treatment were assessed using a complex operant test battery (OTB) containing five tasks thought to depend upon processes associated with short-term memory and attention [delayed-matching-to-sample (DMTS)], color and position discrimination [conditioned position responding (CPR)], motivation [progressive ratio (PR)], time perception [temporal response differentiation (TRD)], and learning [incremental repeated acquisition (IRA)]. Adult male rhesus monkeys were tested 15 min after IV injection of saline or chlorpromazine (0.010, 0.030, 0.100, or 0.175 mg/kg). Behavioral endpoints measured included percent task completed, response rate or latency, and response accuracy. The order of task sensitivity to disruption by chlorpromazine was TRD = PR = IRA = DMTS = CPR in which sensitivity was defined as a significant alteration in any aspect of task performance. Chlorpromazine slowed response rates in all tasks except TRD but did decrease accuracy in that task. These effects were similar to those noted in previous studies of acute chlorpromazine treatment. Specific motoric effects suggested decreased task initiation at doses that left general motor ability intact. This finding is similar to that noted in parkinsonism caused by chronic chlorpromazine treatment.     

Acute effects of d-amphetamine in a monkey operant behavioral test battery

The acute effects of d-amphetamine were assessed using a battery of complex food-reinforced operant tasks that included responding in delayed matching-to-sample (DMTS, n = 6), conditioned position responding (CPR, n = 7), progressive ratio (PR, n = 8), temporal response differentiation (TRD, n = 4), and incremental repeated acquisition (IRA, n = 9) tasks. Performance in these tasks is thought to depend upon specific brain functions such as short-term memory and attention (DMTS), color and position discrimination (CPR), motivation to work for food (PR), time perception (TRD), and learning (IRA). d-Amphetamine sulfate (0.01-1.0 mg/kg IV), given 15-min pression produced significant dose-dependent decreases in the number of reinforcers obtained in each task. Response accuracy was significantly decreased at doses of 0.3 and 1.0 mg/kg for TRD and at 1.0 mg/kg for CPR when compared to saline injections. Accuracy was not consistently affected in the DMTS or IRA tasks. Response rates decreased or response latencies increased significantly at doses of 0.3 and 1.0 mg/kg in the PR and DMTS tasks. A dose of 0.1 mg/kg for the IRA and TRD tasks, 0.3 mg/kg for DMTS and 1.0 mg/kg for the CPR tasks significantly decreased percent task completed. Thus, the relative sensitivities of these tasks for detecting d-amphetamine behavioral effects were IRA = TRD greater than PR = DMTS greater than CPR.(ABSTRACT TRUNCATED AT 250 WORDS)     

Quantitation of complex brain function in children: preliminary evaluation using a nonhuman primate behavioral test battery

The performance of twenty children (3-11 years of age) in a complex operant test battery (OTB) was evaluated. The operant schedules, or tasks, used in the OTB were identical to those originally designed and currently used to assess complex brain function in nonhuman primate laboratory animals (monkeys). The OTB consisted of five operant tasks: 1) Progressive-Ratio [PR]; 2) Conditioned-Position Responding [CPR]; 3) Temporal Response Differentiation [TRD]; 4) Delayed Matching-to-Sample [DMTS] and 5) Incremental Repeated Acquisition [IRA]. These operant tasks are thought to engender responding indicative of processes associated with: 1) motivation; 2) color and position discrimination; 3) time-perception; 4) short-term memory and attention; and 5) learning, respectively. The parameters for each of the tasks in the OTB were optimized for use in the clinical setting to assess cognitive function in children. In the small population studied, performance in the IRA, DMB and TRD tasks was age related. Of the four 6-yr-olds studied, only those categorized as having either learning disabilities (LD, n = 1) or attention deficit disorders (ADD, n = 2) did not complete the "learning" task. By comparison of human and monkey performance in the OTB, we also hope to validate the use of laboratory animal models in research efforts designed to yield insight into complex human brain function. It is also hoped that assessment of children's performance in the tasks in the OTB will assist in the diagnosis and treatment of certain childhood disorders such as learning disabilities and/or attention deficit disorders.     

Benzodiazepine-like behavioral effects following withdrawal from chronic delta-9-tetrahydrocannabinol administration in rats

Chronic exposure to cannabis extract or delta-9-tetrahydrocannabinol (THC) has been reported to produce hippocampal neuropathology in rats, as well as classical "hippocampal" behavioral deficits. In an attempt to replicate and extend these findings, male rats were exposed to THC for 13 consecutive weeks, beginning in early adolescence. Drugs were administered five consecutive days a week (Monday through Friday). There were five dose levels: vehicle control, 5, 10, or 20 mg/kg, p.o., and 20 mg/kg THC four days a week (Monday-Thursday), followed by 60 mg/kg on Friday. Following THC exposure, all animals were withdrawn from drugs for seven weeks prior to behavioral testing. Three behavioral tasks previously shown to be sensitive to hippocampal damage were assessed. These were habituation of open-field activity, 24-hr passive avoidance response retention, and complex maze performance. A fourth task, emergence latency, was also included because it has been determined to be sensitive to "anxiety" levels. To facilitate interpretation of the complex maze data, two additional experiments are also reported. One experiment tested rats exposed to trimethyltin (TMT, a potent hippocampal neurotoxicant) on the complex maze. The second assessed the affects of chronic/acute benzodiazepine (BZ) exposure upon maze performance. Test results did not suggest that chronic THC exposure produced behavioral deficits resembling those seen following hippocampal damage. Habituation rates in an activity monitor were identical for all exposure groups, and there was no passive avoidance retention deficit. Further, while TMT caused pronounced abnormalities in the complex maze, chronic THC exposure at the two highest dose levels significantly improved maze performance, similar to BZ effects on this task. Chronic THC also appeared to reduce freezing on the emergence task, another anxiolytic-like effect. These results support other reports of persistent long-term behavioral effects of chronic THC exposure. However, they suggest that some behavioral effects may more closely resemble the effects of minor tranquilizers rather than hippocampal damage.     

Implication of the C-terminal domain of nef protein in the reversion to pathogenicity of attenuated SIVmacBK28-41 in macaques

We have analyzed the nef gene sequences amplified from 12 macaques presenting various patterns of infection with SIVmacBK28-41, a clone derived from attenuated SIVmacBK28. We have observed seven mutation hot spots at positions 56, 75, 432, 588, 680, 699, and 779. The major alteration was a thymidine insertion at position 699, leading to a frameshift in the SIVmacBK28-41 nef gene and changing the last 15 amino acids of Nef into a 31-amino-acid-long C-terminal domain nearly identical to that encoded by pathogenic SIVmac239 and SIVmac251. The insertion was found at early time points in proviruses obtained from rapid progressor macaques, after 2 years postinfection in progressors, and rarely or only after 4 years postinfection in nonprogressors. Fixation of the other mutations occurred only after insertion of thymidine 699. Phylogenetic analysis demonstrated that the nef genes isolated from progressors evolved from the allele present in SIVmacBK28-41 to alleles present in SIVmac239 or SIVmac251, whereas nef sequences from nonprogressors stayed clustered with that of the inoculated molecular clone. These data stress the importance of the C-terminal extremity of the Nef protein of SIVmac239 or SIVmac251 in viral pathogenesis.     

Comparison of the 5-hydroxytryptamine3 (serotonin) antagonist ondansetron (GR 38032F) with high-dose metoclopramide in the control of cisplatin-induced emesis

To compare ondansetron (GR 38032F), a 5-hydroxytryptamine3-receptor antagonist, with metoclopramide in the prophylaxis of acute cisplatin-induced emesis, we conducted a double-blind crossover study in 97 patients scheduled to receive cisplatin (80 to 100 mg per square meter of body-surface area) for treatment of cancer. None had received chemotherapy before this trial. Among the 76 patients who satisfactorily completed both parts of the study, complete or nearly complete control of emesis (i.e., no episodes of emesis occurred, or only one or two) was achieved in 57 of 76 treatments (75 percent) with ondansetron and in 32 of 76 treatments (42 percent) with metoclopramide (P less than 0.001). Ondansetron was also more effective in controlling acute nausea, as assessed with a visual-analogue scale (P = 0.019) or a graded scale (P = 0.024). There was a significant preference among patients for ondansetron (55 vs. 26 percent; P = 0.006). Dystonic reactions were observed during three treatments with metoclopramide; both agents were otherwise well tolerated. We conclude that ondansetron is more effective than metoclopramide in the control of cisplatin-induced nausea and vomiting, and that this suggests that serotonin is an important mediator of this side effect.     

Evaluation of hematopoietic potential generated by transplantation of muscle-derived stem cells in mice

Muscle tissue of adult mice has been shown to contain stem cells with hematopoietic repopulation ability in vivo. To determine the functional characteristics of stem cells giving rise to this hematopoietic activity, we have performed hematopoietic reconstitution experiments by the use of muscle versus marrow transplantation in lethally irradiated mice and followed the fate of transplanted cells by Y-chimerism using PCR and fluorescence in situ hybridization (FISH) analysis. We report here that transplantation of murine muscle generate a major hematopoietic chimerism at the level of CFU-C, CFU-S, and terminally-differentiated cells in three generations of lethally irradiated mice followed up to 1 year after transplantation. This potential is totally abolished when muscle grafts were performed by the use of muscle from previously irradiated mice. As compared to marrow transplantation, muscle transplants were able to generate similar potencies to give rise to myeloid, T, B, and natural killer (NK) cells. Interestingly, marrow stem cells that have been generated in primary and then in secondary recipients were able to contribute efficiently to myofibers in the muscle tissue of tertiary recipients. Altogether, our data demonstrate that muscle-derived stem cells present a major hematopoietic repopulating ability with evidence of self-replication in vivo. They are radiation-sensitive and similar to marrow-derived stem cells in terms of their ability to generate multilineage hematopoiesis. Finally, our data demonstrate that muscle-derived hematopoietic stem cells do not lose their ability to contribute to myofiber generation after at least two rounds of serial transplantation, suggesting a potential that is probably equivalent to that generated by marrow transplantation.     

Incremental repeated acquisition in the rat: acute effects of drugs

Rats lever pressed for food and learned new response sequences on three levers. At the beginning of each daily session, responses on only one of the levers produced food. After meeting criterion on one lever, the task was "incremented" so that sequential responses on two levers were required and so on up to five sequential responses. Each new required response was added in front of the previously performed sequence. Sequences of lever presses required to produce food changed each session. Following establishment of stable acquisition behavior, the acute effects of d-amphetamine (0.30-3.0 mg/kg), diazepam (0.125-4.0 mg/kg), morphine (0.30-10.0 mg/kg), pentobarbital (1.0-17.5 mg/kg), and chlorpromazine (0.10-3.0 mg/kg) were examined. All drugs decreased the number of response sequences completed in a dose-dependent fashion. Response rates generally decreased at or below those doses that caused an increase in errors. For d-amphetamine, the profound disruption of incremental repeated acquisition behavior was primarily due to drug-induced perserverative responding. Pentobarbital and chlorpromazine increased errors both when the sequence was incremented and within the sequence whereas diazepam only increased errors when the sequence was incremented. Morphine generally increased within sequence errors without affecting errors when the sequence was incremented.