Schwann cell-axon interactions in Charcot-Marie-Tooth disease

The consequences of the molecular defects in myelin genes are manifest from the time of birth in most patients, as assessed either electrodiagnostically or pathologically. Reduction in nerve conduction velocity is present from the first weeks of life, but the clinical manifestations have been recognized as predominantly distal and dominated by distal muscle atrophy. The recent advances in understanding the molecular defects involved present a paradox: the molecular abnormalities are found in intrinsic Schwann cell proteins, not in distal axons. Thus, the interactions between Schwann cells and axons have been the focus of much attention. Here, we present findings on the effects of Schwann cell phenotype on the exon and how abnormalities in myelin alter the axonal cytoskeleton. The clinical importance of Schwann cell-axon interactions extends beyond Charcot-Marie-Tooth disorders. The same principles may apply in the CNS, for example, in multiple sclerosis.

Ganglioside GM1 mimicry in Campylobacter strains from sporadic infections in the United States

To determine whether GM1-like epitopes in Campylobacter species are specific to O serotypes associated with Guillain-Barré syndrome (GBS) or whether they are frequent among random Campylobacter isolates causing enteritis, 275 random enteritis-associated isolates of Campylobacter jejuni were analyzed. To determine whether GM1-like epitopes in Campylobacter species are specific to O serotypes associated with Guillan-Barre syndrome (GBS) or whether they are frequent among random Campylobacter isolates causing enteritis, 275 enteritis-associated isolates, randomly collected in the United States, were analyzed using a cholera-toxin binding assay [corrected]. Overall, 26.2% of the isolates were positive for the GM1-like epitope. Of the 36 different O serotypes in the sample, 21 (58.3%) contained no strains positive for GM1, whereas in 6 serotypes (16.7%), >50% of isolates were positive for GM1. GBS-associated serotypes were more likely to contain strains positive for GM1 than were non-GBS-associated serotypes (37.8% vs. 15.1%, P=.0116). The results suggest that humans are frequently exposed to strains exhibiting GM1-like mimicry and, while certain serotypes may be more likely to possess GM1-like epitopes, the presence of GM1-like epitopes on Campylobacter strains does not itself trigger GBS.

The test for severe impairment: validity with the Dementia Rating Scale and utility as a longitudinal measure

The Test for Severe Impairment (TSI; Albert & Cohen, 1992) was compared to the Dementia Rating Scale (DRS; Mattis, 1988) on nursing home patients identified with cognitive impairment. Construct validity, criterion validity, and reliability on repeated, longitudinal testing were determined. The TSI was also compared with the shortened form of the Boston Naming Test (Mack, Freed, Williams, & Henderson, 1992). Results show that the TSI is a valid tool of different cognitive domains and is useful in longitudinal settings where repeat testing is required. Moreover, although the TSI was a test designed for late stage assessment, it is a comparable measure with the DRS and can be used across the different levels of cognitive impairment in dementia.

Urban-rural differences in Medicare in Missouri

Health Care Financing Administration's (HCFA) administrative data were analyzed to examine urban-rural differences in the characteristics of Medicare beneficiaries, their utilization of medical care, the providers of services, and selected outcomes in Missouri. As compared to the residents of urban areas, the residents of the rural counties were a little poorer, had equal access to health care, and utilized more health care services; but the cost of major services was lower.

Motor nerve terminal degeneration provides a potential mechanism for rapid recovery in acute motor axonal neuropathy after Campylobacter infection

We investigated the possible mechanisms of paralysis and recovery in a patient with the acute motor axonal neuropathy (AMAN) pattern of the Guillain-Barré syndrome. The AMAN pattern of GBS is characterized clinically by acute paralysis without sensory involvement and electrodiagnostically by low compound motor action potential amplitudes, suggesting axonal damage, without evidence of demyelination. Many AMAN patients have serologic or culture evidence of recent Campylobacter jejuni infection. Pathologically, the most severe cases are characterized by wallerian-like degeneration of motor axons affecting the ventral roots as well as peripheral nerves, but some fatal cases have only minor changes in the roots and peripheral nerves, and some paralyzed patients with the characteristic electrodiagnostic findings of AMAN recover rapidly. The mechanism of paralysis and recovery in such cases has been uncertain. A 64-year-old woman with culture-proven Campylobacter upsaliensis diarrhea developed typical features of AMAN. She improved quickly following plasmapheresis. Her serum contained IgG anti-GM1 antibodies. The lipopolysaccharide of the organism bound peanut agglutinin. This binding was blocked by cholera toxin, suggesting that the organism contained the Gal(beta1-3)GalNAc epitope of GM1 in its lipopolysaccharide. Motor-point biopsy showed denervated neuromuscular junctions and reduced fiber numbers in intramuscular nerves. In contrast, the sural nerve biopsy was normal and skin biopsy showed normal dermal and epidermal innervation. In AMAN the paralysis may reflect degeneration of motor nerve terminals and intramuscular axons. In addition, the anti-GM1 antibodies, which can bind at nodes of Ranvier, might produce failure of conduction. These processes are potentially reversible and likely to underlie the capacity for rapid recovery that characterizes some cases of AMAN.

A prospective study of suramin-induced peripheral neuropathy

Suramin is an investigational drug that has shown therapeutic activity in hormone-refractory metastatic prostate cancer in Phase I/II trials. Dose-limiting neurotoxicity remains the most serious complication of suramin treatment. We performed a prospective study to define the incidence, severity, characteristics, and dose relationships of suramin-induced peripheral neuropathy. Twenty-two patients who received suramin in a Phase-I trial underwent baseline and serial follow-up neurological evaluations consisting of history, examination, nerve conduction studies and quantitative sensory testing (QST). Suramin was administered intravenously in escalating dosages by using a 5-day schedule (repeated monthly), with the dose, determined by a population pharmacokinetic model, to accomplish 30-min post-infusion concentrations of 300 micrograms ml-1 (cohort I), 350 micrograms m-1 (cohort II) and 400 micrograms ml-1 (cohort III). Twelve patients developed a mild, axonal, length-dependent, sensory-motor poly-neuropathy. Three other patients developed a subacutely progressive, functionally disabling, demyelinating neuropathy; sural nerve biopsy in two patients showed lymphocytic inflammation. These three patients improved after drug discontinuation and plasmapheresis. Although there was no apparent correlation between the cumulative dose and the severity of the neuropathy, no patient from cohort I, but 88% of patients from cohorts II and III, developed neuropathy. We conclude that when suramin is used at peak concentrations of > or = 350 micrograms ml-1 its administration is associated with two patterns of neuropathy, a distal axonal neuropathy and an inflammatory demyelinating neuropathy that is partially reversible. Neurological monitoring for development of neuropathy will improve the safety of suramin use in future clinical studies.

Acute motor axonal neuropathy: an antibody-mediated attack on axolemma

The acute motor axonal neuropathy (AMAN) form of the Guillain-Barre syndrome is a paralytic disorder of abrupt onset characterized pathologically by motor nerve fiber degeneration of variable severity and by sparing of sensory fibers. There is little demyelination or lymphocytic inflammation. Most cases have antecedent infection with Campylobacter jejuni and many have antibodies directed toward GM1 ganglioside-like epitopes, but the mechanism of nerve-fiber injury has not been defined. In 7 fatal cases of AMAN, immunocytochemistry demonstrated the presence of IgG and the complement activation product C3d bound to the axolemma of motor fibers. The most frequently involved site was the nodal axolemma, but in more severe cases IgG and C3d were found within the periaxonal space of the myelinated internodes, bound to the outer surface of the motor axon. These results suggest that AMAN is a novel disorder caused by an antibody- and complement-mediated attack on the axolemma of motor fibers.

Modulation of neonatal rat myeloid kinetics resulting in peripheral neutrophilia by single pulse administration of Rh granulocyte-macrophage colony-stimulating factor and Rh granulocyte colony-stimulating factor

Rh granulocyte-macrophage (GM) colony-stimulating factor (CSF) and rh granulocyte (G) CSF have been demonstrated to induce proliferation and maturation of myeloid stem cells and release of mature polymorphonucleocytes (PMNs) from human and animal adult bone marrows. Unfortunately, reduced bone marrow progenitor cells, neutrophil storage pool (NSP) depletion and peripheral neutropenia are characteristic of human and animal newborn bone marrows. We investigated the effect of administering intraperitoneal rhGM-CSF and rhG-CSF to Sprague-Dawley newborn rats (less than 36 h). Newborn rats treated with intraperitoneal CSF (3.0 micrograms/kg) demonstrated significant leukocytosis at 6 and 24 h: rhGM-CSF vs. control, WBC (10(3)/mm3), at 6 h, 8.0 +/- 0.5 vs 4.3 +/- 0.9 (p less than or equal to 0.003), and at 24 h, 7.7 +/- 1.7 vs. 3.8 +/- 0.2 (p less than or equal to 0.008); rhG-CSF vs. control WBC (10(3)/mm3) at 6 h, 6.6 +/- 1.2 vs 4.3 +/- 0.1 (p less than or equal to 0.03), and at 24 h, 8.1 +/- 0.2 vs. 3.75 +/- 0.2 (p less than or equal to 0.003). The absolute neutrophil count was also significantly elevated at 6 h following intraperitoneal CSF (3.0 micrograms/kg): RhGM-CSF vs. control 1,827 +/- 25 vs. 379 +/- 10 (p less than or equal to 0.001); rhG-CSF vs. control, 1,698 +/- 40 vs. 371 +/- 10.1 (p less than or equal to 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Real-time, three-dimensional echocardiography: feasibility and initial use

The purpose of this article is to review new approaches to three-dimensional acquisition and presentation of echocardiographic data. New three-dimensional phased-array devices hold great promise for the development and application of new descriptors for left ventricular performance, myocardial perfusion, and other important indices of cardiac function.

Lymphokines: enhancement by granulocyte-macrophage and granulocyte colony-stimulating factors of neonatal myeloid kinetics and functional activation of polymorphonuclear leukocytes

Colony-stimulating factors, such as the granulocyte-macrophage and the granulocyte colony-stimulating factors (GM-CSF and G-CSF), are glycoproteins with biologic specificity defined by their ability to support proliferation and differentiation of hematopoietic cells of various lineages. Their physiologic activities include stimulation and proliferation of early stem cell precursors and functional activation of mature peripheral effector cells. Recently produced recombinant human (rh) GM-CSF and G-CSF have been demonstrated to regulate hematopoietic neutrophil progenitor colony growth; to stimulate the release of bone marrow neutrophil storage pools; and to prime mature effector functions, including chemotaxis, oxidative metabolism, phagocytosis, C3bi receptor expression, and antibody-dependent cytotoxicity in adults. We examined the effects of rh-GM-CSF on priming superoxide release and chemotaxis of neonatal (cord) polymorphonuclear leukocytes (PMNs) and of rh-G-CSF and rh-GM-CSF on bone marrow neutrophil egress in the neonatal rat. A time-response evaluation of the effect of rh-GM-CSF revealed enhanced release of superoxide by PMNs. PMN chemotaxis also was enhanced by rh-GM-CSF, with a maximal response occurring earlier than enhanced superoxide release. Intraperitoneal administration of rh-G-CSF or rh-GM-CSF to 1-day-old rats resulted in significant increases in white blood cell counts and significant early neutrophilia. Bone marrow examination revealed that the neutrophilia was secondary to egress and mild depletion of the neutrophil storage pool but that the neutrophil storage pool later returned to normal. These preliminary studies suggest that rh-GM-CSF and rh-G-CSF prime neonatal effector function and induces significant PMN egress and neutrophilia.(ABSTRACT TRUNCATED AT 250 WORDS)

Mortality of workers at acetylene production plants

To reduce the risk of explosion oxyacetylene cylinders are filled with a spongy mass, acetone is added to saturate the mass, and acetylene is pumped into the cylinder. The first cylinders manufactured before 1936 used a kapok filling topped off with about 16 oz of crocidolite asbestos, with a metal gauze thimble inserted to reduce risk of flash back. Cylinders must be examined annually. The use of crocidolite ceased in 1972 and other fillings have been adopted since 1970; kapok cylinders now constitute less than 5% of the total stock. To assess possible hazards, a mortality study of workers first employed between 1935 and 1975 and followed up to December 1984 was undertaken. Simulation tests showed low concentrations of asbestos in the air even in the earliest period. The population studied consisted of 370 workers at the Bilston plant in the West Midlands, 611 at the 14 other plants in England and Wales, and 120 in Scotland. No deaths occurred from mesothelial tumours but there was an excess of deaths from cancer, particularly lung cancer, cancer of the stomach, and cancer of the pancreas, the latter accounting for eight deaths. Risks appeared to be concentrated at the Bilston plant. The importance of these findings is discussed.

Chemically modified collagen: a natural biomaterial for tissue replacement

Glutaraldehyde crosslinking of native or reconstituted collagen fibrils and tissues rich in collagen significantly reduces biodegradation. Other aldehydes are less efficient than glutaraldehyde in generating chemically, biologically, and thermally stable crosslinks. Tissues crosslinked with glutaraldehyde retain many of the viscoelastic properties of the native collagen fibrillar network which render them suitable for bioprostheses. Implants of collagenous materials crosslinked with glutaraldehyde are subject long-term to calcification, biodegradation, and low-grade immune reactions. We have attempted to overcome these problems by enhancing crosslinking through bridging of activated carboxyl groups with diamines and using glutaraldehyde to crosslink the epsilon-NH2 groups in collagen and the unreacted amines introduced by aliphatic diamines. This crosslinking reduces tissue degradation and nearly eliminates humoral antibody induction. Covalent binding of diphosphonates, specifically 3-amino-1-hydroxypropane-1, 1-diphosphonic acid (3-APD), and chondroitin sulfate to collagen or to the crosslink-enhanced collagen network reduces its potential for calcification. Platelet aggregation is also reduced by glutaraldehyde crosslinking and nearly eliminated by the covalent binding of chondroitin sulfate to collagen. The cytotoxicity of residual glutaraldehyde--leaching through the interstices of the collagen fibrils or the tissue matrix--and of reactive aldehydes associated with the bound polymeric glutaraldehyde can be minimized by neutralization and thorough rinsing after crosslinking and storage in a nontoxic bacteriostatic solution.

Disability scales: assessment of reliability

Modified or newly developed disability scales have to be assessed for their validity in terms of an appropriate standard and for reproducibility--inter- and intraobserver variability and intrasubject variability. For ordinal scales with more than two points or categories, correlation or regression coefficients are appropriate estimates of validity. An assessment of the sensitivity and specificity of such a scale is not feasible. Indices of proportion agreement or correlation analysis are frequently used to assess the reproducibility of disability scales. These procedures do not, however, correct for chance-expected agreement between two or more sets of observations. In a study of a 31-point ADL (activities of daily living) index used to measure the level of disability in patients with chronic diseases, scores independently rated by two observers were strongly correlated (r = 0.962), yet the two sets of observations were significantly different. An estimate of kappa statistic, that corrects for chance agreement, showed that there was in fact a poor (36.3%) overall agreement between the observers. It is concluded that the correlation coefficient often overestimates the degree of true agreement, may conceal significant disagreements, and may give misleading information about reproducibility. The kappa statistic should always be used in the assessments of reproducibility of disability scales. Agreement between more than two sets of observations can also be assessed by estimating kappa.