Models and mechanisms of regenerative biology across phylogeny : introduction to a virtual symposium in The Biological Bulletin

Author Posting. © Marine Biological Laboratory, 2011. This article is posted here by permission of Marine Biological Laboratory for personal use, not for redistribution. The definitive version was published in Biological Bulletin 221 (2011): 3-5.This virtual symposium issue of The Biological Bulletin celebrates a major milestone for our publisher, The Marine Biological Laboratory, as it opens the new Eugene Bell Center for Regenerative Biology and Tissue Engineering on its Woods Hole campus. As with recent virtual symposia published by the journal, the current issue brings together a set of invited reviews, original research reports, and a position paper that offers a coherent and current window into some of the major contemporary trends in animal regeneration research

Transmission loss in manatee habitats

The Florida manatee is regularly exposed to high volumes of vessel traffic and other human-related noise because of its coastal distribution. Quantifying specific aspects of the manatee’s acoustic environment will allow for a better understanding of how these animals respond to both natural and human-induced changes in their environment. Transmission loss measurements were made in 24 sampling sites that were chosen based on the frequency of manatee presence. The Monterey-Miami Parabolic Equation model was used to relate environmental parameters to transmission loss in two extremely shallow water environments: seagrass beds and dredged habitats. Model accuracy was verified by field tests at all modeled sites. Results indicated that high-use grassbeds have higher levels of transmission loss for frequencies above 2 kHz compared to low-use sites of equal food species composition and density. This also happens to be the range of most efficient sound propagation inside the grassbed habitat and includes the dominant frequencies of manatee vocalizations. The acoustic environment may play a more important role in manatee grassbed selection than seagrass coverage or species composition, as linear regression analysis showed no significant correlation between usage and either total grass coverage, individual species coverage, or aerial pattern

Effects of anxiety-relieving drugs on unit discharges in hippocampus, reticular midbrain, and pre-optic area in the freely moving rat

The effects on unit discharges of various doses of the compounds chlordiazepoxide, meprobamate, sodium pentobarbital, and diazepam were studied in the unanesthetized, unrestrained rat. Recordings of action potentials were made simultaneously in hippocampus, pre-optic region, and the reticular formation of the midbrain. The doses of chlordiazepoxide were 5, 10, 20 and 40 mg/kg; 5, 10 and 20 mg/kg of sodium pentobarbital; 80, 100 and 120 mg/kg of meprobamate, and finally 5, 10 and 20 mg/kg of diazepam.In the hippocampus, chlordiazepoxide depressed spontaneous activity at every dose used. The reduction ranged from 30 to 50%, but in no case was there inhibition of all discharges. Diazepam also had substantial depressing effects on the activity in this region of the brain. In contrast, sodium pentobarbital had relatively minor effects in the lower dose range, but significant depressing effects at the higher doses. Meprobamate also had comparatively small effects in the hippocampus.In the pre-optic area, chlordiazepoxide and meprobamate depressed spontaneous activity at the higher dose range. There were small effects in the lower dose range. Sodium pentobarbital also had minor depressing effects at all doses. Diazepam caused less depression even at the higher doses than either chlordiazepoxide or meprobamate, and these effects were transient.In the midbrain reticular formation, meprobamate caused substantial depression of spontaneous activity even at the lower doses. Sodium pentobarbital similarly depressed activity, but the onset of effect was less delayed than with meprobamate. Chlordiazepoxide at low doses caused less depression of reticular midbrain neurons than of hippocampal or pre-optic region ones. At high doses, the effect was similar to that of meprobamate.The data suggest the possibility of a mode of action of chlordiazepoxide and diazepam which implicates the hippocampus, whereas in the case of sodium pentobarbital and meprobamate, the mode of action appears to implicate the midbrain reticular area. Such a view is based upon comparison of effects at low doses on spontaneous activity of the three regions investigated.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/33003/1/0000387.pd

A motivational analyses of the reticular activating system

In 51 rats electrode pairs were chronically implanted with spacing 1 mm. apart from rat to rat to make a grid of the tegmentum. In each case three tests were made: a self-stimulation test for positive reinforcement; an escape test for negative reinforcement; and an EEG test for cortical arousal. The main results were these: all points yielding escape at very low thresholds were clustered in the dorso-medial tegmentum just below the tectum and just lateral to the central grey; all points yielding self-stimulation at high rates were clustered ventrally, usually below and lateral to the medial lemniscus; and points yielding arousal at very low thresholds were clustered in the lateral tegmentum, half-way up from the ventral surface.As for interactions between the three effects, all points yielding escape at low thresholds also yield arousal at low thresholds; al points yielding self-stimulation at high rates yielded arousal at moderately high thresholds; and some points yielded both moderate escape and moderate self-stimulation. Finally, there definitely were points which yielded arousal at low thresholds and which yielded no other motivational effects.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/32417/1/0000496.pd

Reinforcing brain stimulation and memory in monkeys

Sixty electrodes were implanted in various structures in the brain of two cynomologous monkeys subsequently trained to perform a three-position delayed response task. Each brain point was tested for the effects of electric stimulation, applied during the retention interval, on delayed response performance and for appetitive and aversive effects. At all points where there was clear evidence of approach or avoidance with respect to the brain stimulus, there was definite impairment of delayed response performance. In six of the twenty cases where there was possible evidence of approach or avoidance, there was impairment of delayed response. In none of the twenty-six cases where there was no evidence of approach or avoidance was there any evidence of impairment. The data were interpreted as indicating that the impairment produced by brain shocks could be accounted for by their appetitive or aversive effects.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/32081/1/0000130.pd

Utah\u27s 1977 Drought

The Utah Drought of 1976-1977 has been characterized as the wettest drought in history. It was produced by the driest winter season of record followed by summer rains which were much wetter than normal in many regions of the state. Stream-flow is highly correlated with winter rather than summer precipitation and therefore the most severe impacts of the drought were related to the record low stream-flow during 1977 plus the ski industry impacts which were directly related to 1976-1977 snowfall. Drought impacts upon several sectors of the economy plus the extensive responses of all levels of government in the form of drought relief programs are described and quantified

Units during habituation, discrimination learning, and extinction

Unit responses were recorded with 62.5 [mu] fine wires implanted chronically in rats. In each animal simultaneous recordings were made from four probes: in hippocampus, midbrain, hypothalamus and preoptic area. Hippocampal units did not respond in a special fashion to novel stimuli and what responses there were did not change during habituation. After this, response increments appeared rapidly in hippocampus during conditioning, and at the same time a difference developed between the hippocampal firing rates induced by the CS+ and CS- control stimulus. In extinction, the responses in hippocampus changed again to a level between the habituation level and the conditioning level. In other words, complete extinction of the increments in firing rates brought on by conditioning 0did not occur.Midbrain units responded to novel stimuli initially, and then showed clear and continuous habituation during the preliminary series of trials. They showed increments in rate of discharge during conditioning; and a difference between patterns of firing induced by CS+ and CS- developed gradually as compared to its rapid appearance in the hippocampus. The midbrain pattern of neuron responses which appeared during conditioning disappeared during extinction.Hypothalamic units showed patterns of neuron responses somewhat similar to those of midbrain units but less pronounced.Preoptic units showed relatively small responses to novel stimuli but these disappeared rapidly during habituation and there were no further responses in the series of conditioning or extinction trials.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/32814/1/0000188.pd

Dissociation of self-stimulation and epileptiform activity

1. 1. Ventrolateral tegmental stimulation caused self-stimulation behavior at very high rates but no epileptiform discharges even with much higher current levels.2. 2. Posterior lateral hypothalamic stimulation caused self-stimulation and (at higher current levels) random spikes which were unrelated to self-stimulation: that is, (a) they did not stop self-stimulation and (b) they appeared even in cases where self-stimulation did not.3. 3. Anterior lateral hypothalamic stimulation and septal region stimulation caused self-stimulation and (at higher intensity levels) organized epileptiform after-discharges which usually caused self-stimulation behavior to cease for a period during, and a few seconds after the abnormal electrical discharges.4. 4. Epithalamic and posterior lateral thalamic stimulation sometimes caused self-stimulation; stimulation of these areas also often caused one or the other of the epileptiform patterns described above.5. 5. For all probes clearly yielding both effects, thresholds for self-stimulation were lower than those for epileptiform discharges during the period of initial tests. However, at a later date (about two months after surgery) epileptiform thresholds were below self-stimulation thresholds in some cases with probes in the anterior lateral hypothalamus or septal area.6. 6. The random spikes provoked by stimulation in the posterior lateral hypothalamus spread preferentially to tegmental and thalamic probes and much less, if at all, to septal or anterior lateral hypothalamic probes. The organized discharges provoked by stimulation of anterior lateral hypothalamus, septal area, and epithalamus spread preferentially to other members of this triadic group.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/32004/1/0000046.pd

A sequential double-label autoradiographic method that quantifies altered rates of regional glucose metabolism

An autoradiographic sequential double-label variant of the deoxyglucose method for measurement of local glucose utilization has been developed. This technique takes advantage of the short half-life of the positron emitter, 18F () relative to that of 14C. Sequential injection of [18F]fluorodeoxyglucose (FDG) and 14C-labeled FDG allows the production of two separable autoradiograms, each of which represents the same 20-[mu]m brain slice, but under potentially different cerebral metabolic states. We have used this technique to demonstrate that ibotenic acid-lesioned rat striatum is selectively refractory to the depressing effects of barbiturate anesthesia upon brain glucose utilization. The described method has applicability to the analysis of small changes in regional cerebral metabolism in localized brain regions and represents a solution to the problem of intersubject variability inherent in conventional approaches to the deoxyglucose method.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/25464/1/0000002.pd