Negative extrathoracic pressure ventilation for phrenic nerve palsy after paediatric cardiac surgery.

OBJECTIVE--To investigate the feasibility of negative extrathoracic pressure ventilation as a respiratory support following phrenic nerve palsy after cardiac surgery. DESIGN--An uncontrolled pilot study. PATIENTS--14 patients aged one week to 30 months (median 5.3 months) with phrenic nerve palsy diagnosed by phrenic nerve conduction tests and diaphragmatic electromyograms. Four had bilateral and 10 unilateral palsy. Before treatment all required oxygen and 10 were receiving positive pressure ventilation. One of the patients with bilateral and four of the patients with unilateral palsies had undergone a plication before negative pressure ventilation was started. INTERVENTION--Treatment was started 6-65 days (median 23) after operation with a newly designed system which included a Perspex chamber, which gave easy access to the child, and an elastic latex neck seal. Continuous negative pressure was used in conjunction with intermittent positive pressure ventilation while continuous or intermittent negative pressure ventilation was used in extubated infants. RESULTS--All four patients with bilateral palsy survived with long-term intermittent negative pressure ventilation and did not require further surgery. Of the 10 with unilateral lesions, seven required no further surgery, two underwent plication, and one had a re-plication. Three patients with unilateral palsy died of non-respiratory causes. The duration of positive pressure ventilation after starting negative pressure ranged from 0 to 23 days (median 6). Treatment with negative pressure lasted for 3-241 days (median 32) and was predominantly administered off the intensive care unit, including at home. CONCLUSIONS--Negative pressure ventilation may be an alternative to positive airway pressure ventilation in the management of phrenic nerve palsy. A multicentre randomised controlled trial is now required to assess further the role of negative pressure ventilation in phrenic nerve palsy.     

Neurotropic Virus-Host Relationship Alterations Due to Variation in Viral Genome as Studied by Electron Microscopy

A series of experiments has been described in which litters of suckling rats were inoculated either with wild-type reovirus type III or one of two of its temperature-sensitive (ts) mutants. While the wild-type virus produced an acute, fatal syndrome, the ts mutants were substantially less neurovirulent. Of the ts mutant-inoculated animals, a large percentage of the surviving (chronic) animals given ts mutant B showed an unobstructive hydrocephalus ex vacuo whereas chronic ts mutant C animals showed no visible nervous system disease. The ts mutants persisted within the central nervous system (CNS) for 6 to 8 weeks, after which they could not be detected either virologically, immunologically or morphologically. In another set of experiments, organized CNS explants were studied following infection with either measles virus or the neuroadapted Mantooth strain of SSPE virus, a variant of measles. Wild measles (Edmonston strain) exerted an acute destructive effect, but SSPE virus had a tendency to enter into coexistence with the tissue without destroying its organotypic nature. These relationships are somewhat reminiscent of the neuropathologic conditions caused by these two viruses in man. Since the reovirus type III ts mutants possess both genetic and morphologic defects and in many instances cause CNS conditions different from that induced by the wild-type virus, it has been proposed that a comparable situation may exist after measles and SSPE virus infection. SSPE virions of the strain studied were found to be defective in certain viral components which may have contributed to the lower neurovirulence and its entering into a chronic relationship with the CNS, in contrast to the acute destructive nature of measles infection. The findings are discussed in terms of relevance to other chronic CNS diseases, particularly multiple sclerosis, in which the possiblity exists that a mutant virus is operative.     

Multiple sclerosis: serum-induced demyelination in vitro. A light and electron microscope study

Primary demyelination has been documented in organotypic cultures of mouse spinal cord exposed to 25% myelinotoxic sera from 2 patients with multiple sclerosis (MS). Between 10% and 90% of the original population of myelinated axons were involved. Younger cultures were more severely affected than older ones. Myelin degeneration was seen to involve the transformation of the regular 12 nm periodicity into smudged areas with an amorphous or finely-lamellated structure. The myelinolysis was accompanied by an active overgrowth of oedematous astrocytic processes which surrounded affected fibres and phagocytosed the degenerating myelin. This progressed until naked axons, invested by swollen astrocytic cytoplasm, remained. A number of oligodendrocytes in each MS serum-exposed culture underwent either acute or subacute destruction. The former occurred during the first few hours of exposure. The latter began after about 4 hr and was completed by 72 hr. Affected oligodendrocytes were phagocytosed following their ensheathment by astrocytic processes. Neurons and astrocytes did not degenerate. The myelin and oligodendrocyte lesions produced by MS serum in vitro are essentially identical to those effected by EAE serum from animals inoculated with whole white matter, except that the phenomena are slower and less widespread. The findings have been compared with patterns seen in human MS plaques and in animal demyelinating conditions.     

Chronic relapsing experimental allergic encephalomyelitis in SJL mice following the adoptive transfer of an epitope-specific T cell line

Chronic relapsing experimental allergic encephalomyelitis (CREAE) was induced in SJL mice following the adoptive transfer of a T cell line derived from mice immunized with a synthetic peptide corresponding to residues 89-100 of the guinea pig myelin basic protein (MBP) molecule. This cell line proliferated to both the peptide and MBP and induced CREAE characterized by a series of relapses with eventual stabilization. Central nervous system (CNS) inflammation and demyelination were prominent neuropathologic features of both the acute and relapsing phase of the disease. The chronic phase was characterized by CNS lesions containing chronically demyelinated fibers with remyelination and some fiber drop-out, but little inflammation. The induction of CREAE in SJL mice by a cell line specific for residues 89-100 demonstrates that T cell recognition of this epitope is required for successful disease induction in this strain of mouse.     

The long term culture of bulk-isolated bovine oligodendroglia from adult brain

Oligodendroglia isolated from adult bovine brain by the method of Farooq et al. could be plated on polylysine-coated plastic dishes with an efficiency of 55–80%, and maintained in culture for as long as 4 months. The addition of cytosine arabinoside to the nutrient medium resulted in cultures that were approximately 90% oligodendroglia and 10% large fibroblasts. From 50 g of white matter 100 − 160 × 10⁶ oligodendroglia, containing approximately 6–10 mg protein, could be obtained in culture. These small round cells started to send out processes at 5 days in vitro and by 2 weeks they formed an extensive network of processes. By immunofluorescence, all cells of this morphology were positive for galactocerebroside (GC) and myelin basic protein (MBP), and negative for glial filament protein and fibronectin. Most of the large flat cells were positive for fibronectin and negative for GC, MBP and glial filament protein. As the cultures aged the oligodendroglia tented to clump and blebs formed on the surface of both perikarya and processes. By 4 months they showed evidence of degeneration and detached from the substrate. Electron microscopic examination showed that the cells had the appearance typical of oligodendroglia in situ. The somata were round to elliptical, with eccentrically placed nuclei, and were larger than freshly isolated cells. They grew directly on the substrate or on the surface of the fibroblasts. In older cultures the cells formed tight nests. The somata were enveloped by sheets of oligodendrocyte cytoplasm, sometimes having a myelin-like appearance. Gap junctions and small desmosomes were seen between oligodendroglial processes and between oligodendroglia and fibroblasts. The cytoplasm was characterized by a prominent Golgi apparatus, many mitochondria and lysosomes, scattered rough endoplasmic reticulum, free ribosomes, frequent centrioles and an abundance of microtubules. In cells from older cultures large vacuoles were common, and rarely they had multilamellar walls with alternating major and minor dense lines resembling myelin.     

Antisera to different glycolipids induce myelin alterations in mouse spinal cord tissue cultures

To study the demyelinative effects of antibodies to glycolipids, well-myelinated cultures of mouse spinal cord tissue were exposed to antisera against galactocerebroside and two gangliosides (GM₁ and GM₄), as well as to anti-white matter antiserum. The demyelinative process was evaluated by morphologic and biochemical techniques. Cultures exposed to anti-white matter and anti-galactocerebroside antisera showed the most marked changes. These consisted of a decrease in the number of oligodendroglial cells and dissolution and phagocytosis of myelin. Concomitantly, the activity of 2′,3′-cyclic nucleotide-3′-phosphohydrolase (CNPase) was decreased by 60–70%. This occured within 24 h of exposure to a relatively low concentration of serum (10%). Cultures exposed to anit-GM₁ and anti-GM₄ antisera showed similar changes but to a lasser degree. The CNPase activity was decreased about 30% within 48 h of exposure to a 25% concentration of these antisera. This diminution represents about a 20% loss of myelin, an observation corroborated by electron microscopy where myelin but not oligodendroglial cell was observed. Therefore, in addition to anti-galactocerebroside activity, which was previously found to be the major antibody responsible for the demyelinating activity induced by anti-whole CNS tissue antiserum, these data suggest that antibodies to gangliosides like GM₁ and GM₄ might also play a role in immune-mediated demyelination, including perhaps, the human demyelinating diseases.     

Immunocytochemical studies for the localisation of measles antigens in multiple sclerosis plaques and measles virus-infected CNS tissue.

Actively demyelinating central nervous system (CNS) lesions from a patient with acute multiple sclerosis (MS) were tested for measles antigens using peroxidase-conjugated antimeasles antibody. No evidence of measles antigens was found. Similarly reacted tissue from 2 patients with chronic MS also revealed no evidence of measles antigens. Identically treated and simultaneously tested measles-infected CNS cultures and human SSPE brain tissue stained strongly for measles antigens. The possible reasons underlying the failure to detect measles antigens in MS are discussed.