Astroglia—Neuron interactions that promote long-term neuronal survival

Besides intrinsic determinants of cell growth, epigenetic signals have been proposed to regulate development and maintenance of neurons. Here we provide evidence that cerebral astrocytes contribute significantly to the set of environmental influences that are required for long-term survival of neurons derived from the mammalian central nervous system. Cerebral astrocytes in serum-free culture express diffusible and non-diffusible neuron-supporting signals, including cell-adhesive neurite growth-promoting glycoproteins, diffusible neurotrophic factors as well as membrane-bound molecules that mediate cell contact interactions. The combination and synergistic interaction of these environmental signals markedly enhance the survival of brain neurons. While astroglia-derived cell-adhesive substrates that include a high molecular weight complex consisting of laminin β-chains and proteoglycan (Matthiessen et al., 1989) stimulate neurite outgrowth, they fail to enhance long-term neuronal survival when additional neurotrophic and cell-contact interactions are lacking. Astrocytes release a diffusible neurotrophic activity that, when permanently applied, maintains long-term survival of central neurons in culture. The soluble neurotrophic activity seems to interact synergistically with cell-bound signals which are also required for long-term survival and which are expressed by astrocytes and neurons, but not by fibroblasts. Among neurons from different brain areas, such as hippocampus, cerebral cortex and septum, regional differences in their responsiveness to the astroglial neurotrophic activity have been observed.     

Effect of weightlessness on the development of the nervous system and peripheral analyzers inXenopus laevis larvae

The study was carried out within the framework of a Russian-Canadian experiment aboard the Bion-10 satellite. The volume and surface area of the gray and white matter and ventricles of the brain, retina, olfactory placodes, the VIII nerve ganglia, and vascular plexus were measured inXenopus laevis which had been in a state of weight-lessness for 2 weeks since their hatching. Zero gravity was found to stimulate the growth of nerve processes, to increase the surface of the vascular plexus, and to impede the development of the retina, olfactory placodes, and VIII nerve ganglia. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 119, N ^o 6, pp. 650–653, June, 1995 Presented by N. K. Permyakov, Member of the Russian Academy of Medical Sciences     

Hypertension and sleep apnoea

SUMMARY  Epidemiological data indicate a link between sleep-disordered breathing and elevation of arterial pressure. Previous studies suggest increased activity of the sympathetic nervous system in patients with sleep apnoea. The response of muscle sympathetic nerve activity was further investigated in normal, awake subjects following exposure to 20 minutes of asphyxia. Sympathetic nerve traffic increased during exposure and remained elevated even after the return to room air breathing. These findings raise the possibility that this sustained elevation of sympathetic nerve traffic could play a role in the development of daytime hypertension in patients with sleep-disordered breathing.     

Central nervous system involvement in arthrogryposis multiplex congenita: Overview of causes,diagnosis, and care

Arthrogryposis or AMC, arthrogryposis multiplex congenita, is defined as multiple congenital joint contractures in more than two joints and in different body areas. The common cause of all AMC is lack of movement in utero, which in turn can have different causes, one of which is CNS involvement. Intellectual disability/CNS involvement is found in approximately 25% of all AMC. AMC with CNS involvement includes a large number of genetic syndromes. So far, more than 400 genes have been identified as linked to AMC, with and without CNS involvement. A number of neonatally lethal syndromes and syndromes resulting in severe disability due to CNS malfunction belong to this group of syndromes. There are several X‐linked disorders with AMC, which are primarily related to intellectual disability. A number of neuromuscular disorders may include AMC and CNS/brain involvement. Careful clinical evaluation by a geneticist and a pediatrician/pediatric neurologist is the first step in making a specific diagnosis. Further investigations may include MRI of the brain and spinal cord, electroencephalogram, blood chemistry for muscle enzymes, other organ investigations (ophtalmology, cardiology, gastrointestinal, and genitourinary systems). Nerve conduction studies, electromyogram, and muscle pathology may be of help when there is associated peripheral nervous system involvement. But most importantly, genetic investigations with targeted or rather whole exome or genome sequencing should be performed. A correct diagnosis is important in planning adequate treatment, in genetic counselling and also for future understanding of pathogenic mechanisms and possible new treatments. A multidiciplinary team is needed both in investigation and treatment.     

Neurotransmitter characteristics of brain grafts: striatal and septal tissues form the same laminated input to the hippocampus

In previous experiments we have studied the development of grafts of embryonic septal tissues implanted alongside the hippocampal formation of neonatal rats. In the present study we examined intracerebral implants of corpus striatum, a brain region that contains acetylcholinesterase-positive cells and does not normally project to the hippocampal formation, in order to evaluate the possibility that neurotransmitter identity may be involved in mechanisms guiding patterns of afferent growth and connectivity. Implant cavities were made in the entorhinal cortices of neonatal rat recipients and 3-6 days later embryonic striatal tissues were grafted to these preformed cavities. Implants were examined with acetylcholinesterase histochemistry one month after implantation. Grafts of embryonic striatal tissues did not survive implantation when the implant was introduced at the same time as the cavity was made. Grafts of corpora striata containing acetylcholinesterase-positive neurons were found in 7 of 11 rats in the delayed implant paradigm and, in all but one of these animals, acetylcholinesterase was present within those terminal laminae in the ipsilateral hippocampus and dentate gyrus that normally receive cholinergic input from the septal area. These findings suggest that cues underlying the development of specific connections between native (and implanted) septal efferents and hippocampal target neurons may be recognized by ingrowing acetylcholinesterase-reactive fibers from striatal implants.     

Developmental changes in the behavioral and autonomic effects of kappa opioid receptor stimulation of the midbrain periaqueductal gray

Kappa opioid receptors stimulation with U50,488 is known to modulate behaviors during the early postnatal period, but the specific neuroanatomical locus of many of these effects is unexplored. In the present study, we infused U50,488 into the midbrain periaqueductal gray (PAG) and investigated the effects of this drug on behavior and heart rate of 1-, 2-, and 3-week-old rats. U50,488 increased activity most potently in 1- and 2-week-old subjects. Ultrasonic vocalization (USV) production was increased in 1-week-old subjects, but not in 2- or 3-week-old pups. Heart rate changes were similarly seen in younger aged subjects. At 1 week, U50,488 decreased heart rate, but at 2 weeks it increased heart rate. There was no effect of this drug on heart rate at 3 weeks. At 1 week, USVs were more potently elicited from dorsal than lateral PAG infusion sites. No other site-specific effects within the PAG were seen. The age-related decline in behavioral effects elicited by U50,488 is consistent with other published reports, and to the extent that kappa receptor activity mediates infant separation responses, implicates the PAG as a modulator of those responses.     

Effect of relaxation training on cardiac parasympathetic tone

To examine the hypothesis that the relaxation response is associated with an increase in cardiac parasympathetic tone, the frequency components of heart rate variability during relaxation training were investigated in 16 college students. Electrocardiograms and pneumograms were recorded during a 5-min baseline period followed by three successive 5-min sessions of the autogenic training (relaxation) or by the same periods of quiet rest (control), while subjects breathed synchronously with a visual pacemaker (0.25 Hz). Although neither the magnitude nor the frequeney of respiration showed a significant difference between relaxation and control, the amplitude of the high-frequency component of heart rate variability increased only during relaxation (p= .008). There was no significant difference in the ratio of the low-frequency (0.04–0.15 Hz) to the high-frequency amplitudes. The increased high-frequency amplitude without changes in the respiratory parameters indicates enhanced cardiac parasympathetic tone. Thus, our results support the initial hypothesis of this study. Enhanced cardiac parasympathetic tone may explain an important mechanism underlying the beneficial effect of the relaxation response.     

Effects of signaled and unsignaled stressor on ECG T-wave amplitude

Thirty-six human subjects were exposed to noise (noxious US) under one of the following signal (CS) conditions: signaled stressor (SS), unsignaled stressor (NS) and a truly random control group (RS). Changes in ECG T-wave amplitude were used to index the stress response and the greatest change in amplitude occurred in the SS group. T-wave amplitude change was compared to HR change as an index of sympathetic stimulation and the former proved the more sensitive. The increased sympathetic responding in the SS condition suggests that a reliable signal may serve a physiologically adaptive purpose.