Recognition molecule associated carbohydrate inhibits postsynaptic GABA(B) receptors: a mechanism for homeostatic regulation of GABA release in perisomatic synapses

Extracellular matrix molecules are important cues in the shaping of nervous system structure and function. Here, we describe a novel mechanism by which the HNK-1 carbohydrate carried by recognition molecules regulates perisomatic inhibition in the hippocampus. Neutralization of HNK-1 activity by an HNK-1 antibody results in GABA(B) receptor-mediated activation of K(+) currents in CA1 pyramidal cells, which elevates extracellular K(+) concentration and reduces evoked GABA release in perisomatic inhibitory synapses. This mechanism is supported by pharmacological analysis in hippocampal slices and data showing that the HNK-1 carbohydrate binds to GABA(B) receptors and inhibits GABA(B) receptor-activated K(+) currents in a heterologous expression system. We suggest that the HNK-1 carbohydrate is involved in homeostatic regulation of GABA(A) receptor-mediated perisomatic inhibition by suppression of postsynaptic GABA(B) receptor activity.     

Axonal regeneration from CNS neurons in the cerebellum and brainstem of adult rats: correlation with the patterns of expression and distribution of messenger RNAs for L1, CHL1, c-jun and growth-associated protein-43

Some neurons in the brain and spinal cord will regenerate axons into a living peripheral nerve graft inserted at the site of injury, others will not. We have examined the patterns of expression of four molecules thought to be involved in developmental and regenerative axonal growth, in the cerebellum and brainstem of adult rats, following the implantation into the cerebellum of peripheral nerve grafts. We also determined how the expression patterns observed correlate with the abilities of neurons in these regions to regenerate axons. Three days to 16 weeks after insertion of living tibial nerve autografts, neurons which had regenerated axons into the graft were retrogradely labelled from the distal extremity of the graft with cholera toxin conjugated to horseradish peroxidase, and sections through the cerebellum and brainstem were processed for visualization of transported tracer and/or hybridized with riboprobes to detect messenger RNAs for the cell recognition molecules L1 and CHL1 (close homologue of L1), growth-associated protein-43 and the cellular oncogene c-jun. Retrogradely labelled neurons were present in cerebellar deep nuclei close to the graft and in brainstem nuclei known to project to the cerebellum. Neurons in these same nuclei were found to have up-regulated expression of all four messenger RNAs. Individual retrogradely labelled neurons also expressed high levels of L1, CHL1, c-jun or growth-associated protein-43 messenger RNAs (and vice versa), and every messenger RNA investigated was co-localized with at least one other messenger RNA. Purkinje cells did not regenerate axons into the graft or up-regulate L1, CHL1 or growth-associated protein-43 messenger RNAs, but there was increased expression of c-jun messenger RNA in some Purkinje cells close to the graft. Freeze-killed grafts produced no retrograde labelling of neurons, and resulted in only transient and low levels of up-regulation of the tested molecules, mainly L1 and CHL1.These findings show that cerebellar deep nucleus neurons and precerebellar brainstem neurons, but not Purkinje cells, have a high propensity for axon regeneration, and that axonal regeneration by these neurons is accompanied by increased expression of L1, CHL1, c-jun and growth-associated protein-43. Furthermore, although the patterns of expression of the four molecules investigated are not identical in regenerating neuronal populations, it is probable that all four are up-regulated in all neurons whose axons regenerate into the grafts and that their up-regulation may be required for axon regeneration to occur. Finally, because c-jun up-regulation is seen in Purkinje cells close to the graft, unaccompanied by up-regulation of the other molecules investigated, c-jun up-regulation alone cannot be taken to reliably signify a regenerative response to axotomy.     

The use of tissue-engineered skin (Apligraf) to treat a newborn with epidermolysis bullosa.

BACKGROUND: Inherited epidermolysis bullosa (EB) is a mechanobullous disorder. The Dowling-Meara variant, a subtype of EB, is characterized by widespread blister formation that may include the oral cavity and nails. Many patients with the Dowling-Meara phenotype are at increased risk of sepsis and death during infancy. The treatment of EB is generally supportive. The tissue-engineered skin used (Apligraf) is a bilayered human skin equivalent developed from foreskin. It is the only Food and Drug Administration-approved skin equivalent of its kind. It is approved for the treatment of venous ulcers of the lower extremities. It has also been used to treat acute wounds, such as graft donor sites and cancer excision sites. OBSERVATION: To our knowledge, we describe the first case in which a newborn with EB, Dowling-Meara variant, was treated with bilayered tissue-engineered skin. The areas treated with the tissue-engineered skin healed faster than the areas treated with conventional therapy. Most of the areas treated with tissue-engineered skin have remained healed, without developing new blisters. These areas appear to be more resistant to trauma. CONCLUSIONS: Our early success with tissue-engineered skin in this patient may have a significant impact on the future treatment of neonates with EB simplex. Future studies are needed to determine if the beneficial effects of tissue-engineered skin are reproducible in other neonates with EB simplex and in patients of all ages with different subtypes of EB.     

Experimental modification of postnatal cerebellar granule cell migration in vitro

Histotypic migration of [³H]thymidine pulse-labeled granule cell neurons in cerebellar folium explants was monitored in the presence of antibodies to cell adhesion molecules and quantified by automatic image analysis. When explants were cultured in the presence of monovalent antibody fragments to cell adhesion molecules L1 and N-CAM, an inhibition of cell migration of33.3 ± 4.4% and 13.9 ± 2.1%, respectively, was observed. In the presence of an equimolar mixture of monovalent antibody fragments to L1 antigen and N-CAM no additive effects in inhibition of cell migration were seen. Antibodies to the L2 carbohydrate epitope which is common to L1, N-CAM and other cell surface glycoproteins showed a similarly small effect on cell migration as antibodies to N-CAM. Monoclonal antibodies to cell surface antigen M2 and polyclonal antibodies to mouse liver membranes reacting with the surface of all cerebellar cell types did not alter the migratory behavior of granule cells. Cultivation of explants in the presence of neuraminidase, ganglioside binding toxins, as well as glycosaminoglycans and glycosaminoglycan degrading enzymes, also did not modify the extent of cell migration under the culture conditions used.     

Rapid percutaneous tracheostomy

We describe a new method of performing percutaneous tracheostomy rapidly and safely using a specialized instrument kit. The technique permits the safe insertion of a full-sized 7.0 (ID) or 7.5 mm (ID) cuffed cannula into the trachea within 1-2 min, through the membranous second intercartilagenous space. Animal studies have demonstrated a superior healing process compared to that seen after conventional tracheostomy techniques.     

Near infrared spectroscopy for controlling the quality of distal leg perfusion in remote access cardiopulmonary bypass

The prevention of leg ischemia is necessary in all patients undergoing femoral artery cannulation for extracorporeal circulation. Near infrared spectroscopy (NIRS) is an established non-invasive method for measuring tissue oxygen saturation. Ten patients underwent robotically assisted endoscopic coronary surgery or ASD repair on the arrested heart using aortic endo-occlusion catheters. They were monitored by transcutaneous NIRS (placed on both lower legs) for quality control of distal leg perfusion during femoral access cardiopulmonary bypass. The baseline NIRS values were 61 (52–80) on the cannulated side versus 70 (53–80) on the contralateral leg (p = n.s.). During clamping of the femoral artery for installation of the remote access perfusion system the tissue oxygen saturation dropped to 38 (18–58) (p = 0.001 vs baseline) while it remained stable on the contralateral leg. After successful implantation of the distal leg perfusion the NIRS values normalized to similar amounts on both legs. We conclude that transcutaneous NIRS of the lower legs might be a useful non-invasive tool for monitoring leg perfusion in patients undergoing extracorporeal circulation via the femoral vessels.     

On some neurotic difficulties in nursing mothers

Psychiatric Quarterly -