Improved gene transfer to neuroblastoma cells by a monoclonal antibody targeting RET, a receptor tyrosine kinase.

Receptor-mediated gene transfer is an effective strategy among nonviral vector systems. It is, however, crucial to develop various types of monoclonal antibodies satisfying both the binding specificity for cell targeting and the capacity of endocytosis required for gene transfer. In the present study, we generated a novel monoclonal antibody (NBL-1) to RET, a receptor tyrosine kinase expressed in both neuroblastoma cells and cells present in substantia nigra, a responsive locus of Parkinson's disease. NBL-1, when added to the culture medium of the neuroblastoma cells, was incorporated by endocytosis in a wortmannin-sensitive manner. Using a biotinylated NBL-1 complexed with plasmid DNAs based on electrostatic interaction through avidin-conjugated polylysines, exogenous luciferase genes were expressed in neuroblastoma cells at a more than 10-fold higher level. The expression level of the gene based on NBL-1 was comparable to that obtained by a geneporter system, an improved nonviral gene transduction method. Furthermore, the NBL-1-based gene transfer mediated the formation of more than 20-fold higher numbers of drug-resistant colonies. In contrast, RET-negative cells, which included HeLa, HT1080, Caco-2, and Colo205 cells, did not show any increased expression of an exogenous gene by NBL-1. These data suggest that the RET molecules enable selective gene transduction, and that NBL-1 may possibly be applied to gene therapy for neuroblastomas and Parkinson's disease.

Effect of voluntary exercise on maximal oxygen uptake in young female Fischer 344 rats.

The effect of voluntary exercise on maximal oxygen uptake (VO2 max) was studied in young female Fischer 344 rats. After 10 weeks of wheel-running training, the absolute VO2 max and VO2 max relative to body mass increased without a decline in body mass. The running speed eliciting VO2 max, heart and soleus muscle mass, and succinate dehydrogenase (SDH) activity in the soleus muscle also increased. These results suggest that voluntary exercise is an effective means of increasing the aerobic exercise capacity of young female Fischer 344 rats.

The effect of D-amphetamine, clonidine, and yohimbine on human information processing.

Twelve subjects were tested with D-amphetamine, yohimbine, clonidine, and a placebo on a task with two levels of stimulus and two levels of response complexity. The purpose of this study was to test the hypothesis that noradrenergic drugs affect early stimulus processes. D-amphetamine speeded reaction time (RT), clonidine slowed it, and yohimbine had no effect. D-amphetamine and yohimbine decreased N1 latency and clonidine increased it. D-amphetamine and yohimbine decreased P3 latency and clonidine increased it but, in each case, only when latency estimates were based on single trials, not on averages. D-amphetamine's effect on RT, not P3, as measured by the average, is consistent with previous results. Single trial measures appear more sensitive. Speeding of N1 and single-trial P3 data indicate that noradrenergic drugs affect processing of early (visual) information. D-amphetamine's speeding of single-trial P3 estimates was attributed to its noradrenergic actions. Yohimbine's speeding of P3 without changing RT is consistent with neural net (parallel) simulations but not with a serial model. These findings support the assumption that different neurotransmitters modulate specific cognitive processes.

Drugs and human information processing.

Human performance on a choice-reaction time task (Eriksen task) has been simulated by a neural network. In simulations, the network captures many features of normal performance. In addition, changing gain in different layers produces changes that simulate different drug-induced changes. Data from a similar choice-reaction time task have been reanalyzed to test some of the predictions derived from changing gain in different layers. Clonidine antagonizes norepinephrine and acetylcholine activities and changes speed-accuracy tradeoff (i.e., increased frequency of errors at any specified reaction time). That is predicted when gain is reduced in lower layers (attention layer and input layer) of the network. By contrast, manipulating dopamine activity (with pimozide and amphetamine) changes reaction time without changing speed-accuracy tradeoff functions. That is predicted when gain is changed in the output layer of the network.

Scopolamine effects on visual information processing, attention, and event-related potential map latencies.

We measured performance and event-related brain potential (ERP) map latencies in 12 subjects during four visual discrimination tasks to compare the timing of scopolamine effects on information processing and attention. "Topographic component recognition" found ERP map latencies at times of best fit with a component model map. This "common topography" criterion minimized topographic differences among conditions to facilitate latency interpretations. Scopolamine slowed N1 latency in all tasks, and P3 and reaction time in some tasks. The drug delayed responses to easy targets more than to hard targets. It also induced a disproportionate N1 delay for unilateral high spatial frequency gratings. Both effects reflect a scopolamine-induced impairment when processing targets that usually capture attention. Scopolamine also impaired accuracy for unilateral high spatial frequency gratings, and for gratings presented at probable locations, confirming and extending previous findings. Scopolamine-induced P1 and N1 delays showed that visual processing was affected. Several results were inconsistent with a serial stage model. We suggest that scopolamine both delays selected processes and impairs a processing mode based on automatic capture of attention, inducing more serial processing.

Beyond drug effects and dependent variables: the use of the Poisson-Erlang model to assess the effects of D-amphetamine on information processing.

Several studies have shown that d-amphetamine (DAMP) speeds mean reaction time (RT). However, the use of mean RT may obscure important aspects of the drug response. Therefore we applied the Poisson-Erlang (PE) stochastic model of choice reaction time proposed by Pieters (1985) to the RT distribution. This model proposes that the RT distribution is generated by two states: Processing (P) and Distraction (D). RT represents the sum of the time spent in each of these states. P is the time taken to complete a set of cognitive operations which are required to give a correct response. D represents the time taken by all other activities. RTs were collected using a task (SERS) in which stimulus and response complexity each had two levels, easy and hard. Subjects were tested pre- and postdrug. Drug conditions were: placebo, 10 mg d-amphetamine (DAMP), 4 mg of the dopamine agonist, pimozide, and a combination of DAMP and pimozide (COMBO). Parameters of the model were derived using methods described by Pieters. Four measures were analyzed: Processing Time (PT); Mean Time per distraction (XTD); Distraction Rate (DR); and Total Distraction Time per trial (TDT). Mean RT is also presented. Analyses of the effects of task conditions on the parameters of the model were made using the predrug sessions. Mean RT was increased by both stimulus and response complexities as was PT. TDT was increased by the task conditions. The PE measures did not change over days. DAMP speeded mean RT. However, this effect did not interact with the task factors. DAMP speeded processing and reduced distraction. Processing was speeded only in the hard response condition, distraction time was reduced only in the easy response condition. The results indicate that the PE model can be successfully applied to fast RT tasks. More importantly, the parameters of the model revealed important pharmacological effects that were not apparent in mean RT. DAMP speeds cognitive operations related to motor preparation and reduces the effects of distraction. Consistent with past studies there are no indications that DAMP interacted with stimulus processing. The distraction effect appears to be mediated by an increase in the rate of distraction and a decrease in the average time of these distractions.