A system of coordinated autonomous robots for Lagrangian studies of microbes in the oceanic deep chlorophyll maximum.

The deep chlorophyll maximum (DCM) layer is an ecologically important feature of the open ocean. The DCM cannot be observed using aerial or satellite remote sensing; thus, in situ observations are essential. Further, understanding the responses of microbes to the environmental processes driving their metabolism and interactions requires observing in a reference frame that moves with a plankton population drifting in ocean currents, i.e., Lagrangian. Here, we report the development and application of a system of coordinated robots for studying planktonic biological communities drifting within the ocean. The presented Lagrangian system uses three coordinated autonomous robotic platforms. The focal platform consists of an autonomous underwater vehicle (AUV) fitted with a robotic water sampler. This platform localizes and drifts within a DCM community, periodically acquiring samples while continuously monitoring the local environment. The second platform is an AUV equipped with environmental sensing and acoustic tracking capabilities. This platform characterizes environmental conditions by tracking the focal platform and vertically profiling in its vicinity. The third platform is an autonomous surface vehicle equipped with satellite communications and subsea acoustic tracking capabilities. While also acoustically tracking the focal platform, this vehicle serves as a communication relay that connects the subsea robot to human operators, thereby providing situational awareness and enabling intervention if needed. Deployed in the North Pacific Ocean within the core of a cyclonic eddy, this coordinated system autonomously captured fundamental characteristics of the in situ DCM microbial community in a manner not possible previously.

Preliminary study of the behavioral effects of LBS-neuron implantation on seizure susceptibility following middle cerebral artery occlusion in the rats.

Neural transplantation is a promising treatment strategy that can restore the motor, sensory and cognitive functions in the rat middle cerebral artery occlusion (MCAO) model of stroke. In particular, neuronal cells derived from a human teratocarcinoma cell line, called hNT neurons or LBS neurons (clinical grade preparation), are effective in improving behavioral recovery after stroke. In the elderly, epilepsy is a common sequela of stroke, especially if the infarction involves cerebral cortex. However, the effect of implanting neural cells on seizure susceptibility in the MCAO model has not yet been determined. The purpose of this study was to determine the susceptibility to pentylenetetrazol (PTZ)-induced seizures in normal, MCAO-lesioned and MCAO-lesioned rats in which the LBS neurons were injected. Adult, male Sprague-Dawley rats were subjected to 60 min of MCAO using the intraluminal filament technique followed 3-4 weeks later by transplantation of 80,000 LBS-neurons into the ipsilateral cortex. Susceptibility to PTZ-induced seizures was tested 4-6 weeks post-transplant at doses of 35, 50 and 70 mg/kg, administered subcutaneously. Latency to the first lethal response, latency to first generalized seizure, duration of the first generalized seizure, and the number of generalized seizures in an hour post-PTZ treatment observation period was determined. Even thought there was a tendency for groups that underwent MCAO to be more susceptible to seizures, there were no statistically significant differences between the groups and no differences between MCAO alone and MCAO animals in which cells had been implanted. While grafted cells were identified in all but one injected animal, the results suggest that the grafts may not have been healthy either from immunological rejection or PTZ-induced injury. These results suggest that while placing cells within the cortex does not reduce seizure susceptibility, it also does not increase the incidence of seizures. Further investigations are warranted.

Lithium exposure enhances survival of NT2N cells (hNT neurons) in the hemiparkinsonian rat.

Lithium (Li +) treatment of NTera2/D1 (or hNT Neurons) in culture increases tyrosine hydroxylase (TH) expression in this cell-line [Zigova et al., (1999) Exp. Neurol., 157, 251-258]. It is not known if these Li + treated cells maintain TH expression once transplanted into the striatum of the hemiparkinsonian rats. hNT neurons were either treated with 1 mm LiCl or left untreated and then transplanted into the striatum of Sprague-Dawley rats. Some cells were exposed to the lithium for 24 h in culture while others were exposed only briefly (2-3 h) just prior to transplantation. We also examined whether Li + treatment of the animal after transplantation (0.24% w/w lithium carbonate in chow) was effective in increasing neuronal survival. One week after transplantation, the animals were perfused with 4% paraformaldehyde and immunocytochemistry was performed on 30 micro m sections through the transplant. Human nuclear matrix antigen immunostaining demonstrated that there was significantly better survival of cells in the group treated briefly with lithium compared to all other groups. Brief exposure to lithium resulted in a greater expression of TH in situ as well. Neuron specific enolase immunohistochemistry showed that there was extensive fibre outgrowth in all groups. These results suggest that brief Li + exposure may enhance survival to over 60% and increase TH expression of hNT Neurons transplanted in the hemiparkinsonian rat nearly three-fold.

Effects of middle cerebral artery occlusion on spontaneous activity and cognitive function in rats.

The middle cerebral artery occlusion (MCAO) in the rat is a commonly used model to evaluate new therapeutic strategies for the treatment of ischemic stroke. However, many such studies rely on short-term neurological examination and infarct volume as endpoint measures while neglecting more long-term functional assessments. In this study, we examined whether there were changes in passive avoidance behavior, spontaneous behavioral patterns across the light-dark cycle, and motor coordination as measured on the rotorod test 1 month after Sprague-Dawley rats had undergone MCAO. Compared to age-matched controls, fewer animals in the MCAO group remained on the platform during the passive avoidance retention test (p < .03). Significant differences between the groups were observed in the spontaneous activity during the initial portions of both the light and dark testing periods, when the test situation was new (p < .01 to .05, depending on the variable examined). Any differences on the rotorod test failed to gain statistical significance. These results suggest that at least the passive avoidance test and measures of spontaneous activity are sensitive to ischemia-induced damage over a more prolonged survival period and therefore may be appropriate measures for long-term effectiveness of new treatments.