Effect of the CO2 milliwatt laser on neuroma formation in rats

BACKGROUND AND OBJECTIVE

The purpose of this study was to determine whether the milliwatt laser can suppress neuroma formation at the end of a divided nerve.

STUDY DESIGN/MATERIALS AND METHODS

The peripheral nerves of eight rats were transected with microscissors and the cross-sectional area of their proximal ends was irradiated using the CO2 milliwatt laser. The power ranges used were similar to those applied to weld neural tissue.

RESULTS

None of the eight irradiated nerve ends formed a neuromatous bulb and only one of them regenerated into the surrounding tissues. Histologically, these nerve ends did not show the disorganized picture of classic neuromas. On morphometric measurements, they contained less connective tissue than the control nerve ends (P < 0.001) and their nerve fibers were larger in diameter (P < 0.001) and better myelinated (P < 0.001).

CONCLUSION

These findings in rats show that the CO2 milliwatt laser has the ability to suppress neuroma formation at the end of a divided nerve.

[Diagnostic studies in patients and relatives with hereditary neuromuscular diseases]

Preclinical and prenatal diagnosis as well as detection of healthy carriers is now theoretically possible for more than 200 monogenic inherited neurological and neuromuscular diseases and practically performed in many of them. However, it has to be made a condition, that the diagnosis in the index patient is secured by all clinical and laboratory methods available today, and that the specific mutation has been localized or even sequenced, and of course the families must give their full consent to the examinations. It is important to submit material for the different laboratory investigations from patients and their relatives as early as possible [biopsies, blood samples for DNA, etc.], at least for rapidly progressive diseases with a poor prognosis. In order to obtain very high probabilities in diagnostic predictions a family has to be examined either with mutation-specific DNA-probes and/or with probes for closely linked polymorphic DNA-markers. This requires a close cooperation between genetic services and DNA-laboratories on the one hand and the family doctors, specialists and clinics on the other. Specific strategies are discussed for hereditary sensory and motor neuropathy [HMSN la or Charcot-Marie-Tooth disease], Duchenne und Becker muscular dystrophy and childhood spinal muscular atrophies.

Interactions of a very long chain fatty acid with model membranes and serum albumin. Implications for the pathogenesis of adrenoleukodystrophy

Adrenoleukodystrophy (ALD) is an inherited disorder of fatty acid metabolism marked by accumulation of very long chain saturated fatty acids (VLCFA), especially the 26-carbon acid, hexacosanoic acid (HA), in membranes and tissues. We have studied interactions of 13C-enriched HA with model membranes (phospholipid bilayer vesicles) and bovine serum albumin (BSA) by 13C NMR spectroscopy to compare properties of HA with those of typical dietary fatty acids. In phospholipid bilayers the carboxyl group of HA is localized in the aqueous interface, with an apparent pKa (7.4) similar to other fatty acids; the acyl chain must then penetrate very deeply into the membrane. Desorption of HA from vesicles (t1+2 = 3 h) is orders of magnitude slower than shorter chain fatty acids. In mixtures of vesicles and BSA, HA partitions much more favorably to phospholipid bilayers than typical fatty acids. BSA binds a maximum of only 1 mole of HA at one binding site. Calorimetric experiments show strong perturbations of acyl chains of phospholipids by HA. We predict that disruptive effects of VLCFA on cell membrane structure and function may explain the neurological manifestations of ALD patients. These effects will be further amplified by slow desorption of VLCFA from membranes and by the ineffective binding to serum albumin.

The myotubular myopathies: differential diagnosis of the X linked recessive, autosomal dominant, and autosomal recessive forms and present state of DNA studies

Clinical differences exist between the three forms of myotubular myopathy. They differ regarding age at onset, severity of the disease, and prognosis, and also regarding some of the clinical characteristics. The autosomal dominant form mostly has a later onset and milder course than the X linked form, and the autosomal recessive form is intermediate in both respects. These differences are, however, quantitative rather than qualitative. Muscle biopsy studies of family members are useful in some cases, and immunohistochemical staining of desmin and vimentin may help distinguish between the X linked and autosomal forms. Determining the mode of inheritance and prognosis in individual families, especially those with a single male patient, still poses a problem. Current molecular genetic results indicate that the gene for the X linked form is located in the proximal Xq28 region. Further molecular genetic studies are needed to examine the existence of genetic heterogeneity in myotubular myopathy and to facilitate diagnosis.

X-linked adrenoleukodystrophy presenting as neurologically pure familial spastic paraparesis

The familial spastic paraplegias (FSPs) are heterogeneous neurologic disorders that are known to occur clinically as "pure" or "complicated" forms. Although some of the complicated FSPs have been linked to specific metabolic defects, the pure forms of this disorder remain idiopathic and are considered to be primary system degenerations. We report the case of a 28-year-old man who has evidenced a neurologically pure spastic paraparesis since age twenty-five. Consistent with this diagnosis were the findings of magnetic resonance imaging, which revealed atrophy of the thoracic spinal cord without evidence for white matter disease in the cerebrum, cerebellum, or brainstem. His 32-year-old brother has also evidenced progressive spastic paraparesis since age 30, but his case is confounded by a severe head injury at age 24 that caused a skull fracture and a focal demyelinating lesion of the right frontal lobe. Both patients have had hypogonadism, requiring treatment with testosterone, since age 20. Measurement of plasma levels of very long-chain fatty acids (VLCFA) revealed that both brothers had concentrations diagnostic of adrenoleukodystrophy; their mother had plasma VLCFA levels in the heterozygous range. We conclude that neurologically pure FSP can be an early manifestation of adrenoleukodystrophy and that levels of plasma VLCFA should be determined for all cases of FSP in which X-linked inheritance appears tenable. These considerations may have bearing on the ongoing linkage studies for these disorders.

Adrenoleukodystrophy: a scoring method for brain MR observations

PURPOSE

To develop a scoring method for brain observations in patients with X-linked adrenoleukodystrophy.

METHODS

One hundred seventy-five brain MR scans in 83 male subjects less than 20 years of age with proved biochemical defects were reviewed. A severity score (0 to 34), based on a point system derived from location and extent of disease and the presence of focal and/or global atrophy, was calculated for each exam.

RESULTS

Fifty-five of the 83 patients showed MR findings consistent with adrenoleukodystrophy. Two major patterns were observed. A posterior pattern (mean score, 9; range, 0.5 to 25) was present in 80% of patients, and an anterior pattern (mean score, 10; range, 2 to 18) was present in 15% of patients. Serial MR imaging, positive for adrenoleukodystrophy in 34 patients (mean follow-up, 23 months; range, 2 months to 6 years 11 months), showed progressive disease in 52%, progressive disease with subsequent stabilization in 18%, stable disease in 24%, and minimal improvement in 6%.

CONCLUSION

The adrenoleukodystrophy MR severity scoring method is a measure that can be used with standard MR images. When used in conjunction with clinical parameters, this scoring method may help define better the natural history of adrenoleukodystrophy and monitor response to developing therapies.

Childhood cerebral form of adrenoleukodystrophy: short-term effect of bone marrow transplantation on brain MR observations

PURPOSE

To report the serial brain MR observations in patients with childhood-onset cerebral adrenoleukodystrophy 1 to 2 years after bone marrow transplantation.

METHODS

Eight boys with childhood-onset cerebral adrenoleukodystrophy have undergone successful transplantation at our institution. Seven patients (mean age, 8 years 10 months; range, 5 years 3 months to 11 years 9 months) had serial MR studies before and after transplantation. An MR severity score (0 to 34) based on disease location and the presence or absence of focal atrophy was calculated for each patient scan.

RESULTS

Posttransplantation serial MR showed improvement in two patients, stabilization in three patients, and worsening of MR signal changes in two patients. The patient with the most striking progression had systemic graft-versus-host disease. Although the adrenoleukodystrophy MR severity score did not change in three patients after transplantation, two of these patients did show improved margination of disease.

CONCLUSION

Bone marrow transplantation can affect brain MR observations in childhood-onset cerebral adrenoleukodystrophy. Although brain MR findings do not typically resolve, they do seem to stabilize, which is an improvement over the natural MR history of the disease.

RFLP variation and genealogical distance, multivariate distance, heterosis, and genetic variance in oats

Patterns of restriction fragment length polymorphisms (RFLPs) have been proposed as estimators of genetic diversity among breeding lines and as predictors of heterosis and genetic variance. We evaluated these proposals by using a set of nine elite oat lines crossed in a diallel mating design without reciprocals. RFLP analysis was conducted using HindIII-digested DNA and a total of 107 probes from three different sources: 14 heterologous wheat cDNA clones, 17 oat genomic clones, and 76 oat cDNA clones. Of the 77 probes that produced high-quality autoradiographs, 26 detected polymorphisms among this set of lines, with an average of 2.6 variants per probe. RFLP-based genetic distance (FD) was calculated from these data by using Nei and Li's measure of genetic similarity, and was compared with two other measures of genetic divergence. Genealogical distance (GD (*)) was obtained from the coefficients of parentage based on known parental pedigrees, and multivariate distance (DI) was calculated by using the first five principal components of the parental correlation matrix for 12 agronomic traits. FD was significantly correlated with GD (*) (r=0.63, P<0.01), but not with DI (r=-0.05). Cluster analysis based on these three distance estimates did not produce equivalent groupings, but the FD and GD (*) clusters were more similar to each other than to the DI clusters. These results indicate that: (1) sufficient variation exists for further application of RFLP technologyto oats, (2) RFLPs could provide accurate estimates of genetic divergence among elite oat lines, and (3) it is unlikely that dispersed markers can predict heterosis or population genetic variance in oats. Further investigations will require more parental lines, a larger set of markers, and more information on the linkage relationships between RFLP markers and loci controlling the trait of interest.

Biosynthesis of the unusual amino acid (4R)-4-[(E)-2-butenyl]-4-methyl-L-threonine of cyclosporin A. Identification of 3(R)-hydroxy-4(R)-methyl-6(E)-octenoic acid as a key intermediate by enzymatic in vitro synthesis and by in vivo labeling techniques

The biosynthesis of (4R)-4-[(E)-2-butenyl]-4-methyl-L-threonine (abbreviation: Bmt, systematic name: 2(S)-amino-3(R)-hydroxy-4(R)-methyl-6(E)-octenoic acid) is proposed to involve two principal phases: the formation of a polyketide backbone and a subsequent transformation process to the final product. Here we report on the identification of 3(R)-hydroxy-4(R)-methyl-6(E)-octenoic acid as the end product of the first phase. The primary indication of 3(R)-hydroxy-4(R)-methyl-6(E)-octenoic acid as the key intermediate in the proposed biosynthetic route came from in vivo labeling studies with [1-13C,18O2]acetate, demonstrating retention of 18O in the 3-hydroxy group. Final identification of this intermediate in in vitro polyketide assays with enriched enzyme fractions of Tolypocladium niveum was achieved after development of highly sensitive and specific detection methods and by use of synthetic reference substances. Two additional methylated in vitro products could be detected and characterized as 4(R)-methyl-(E,E)-2,6-octadienoic acid and 4(R)-methyl-6(E)-octenoic acid by liquid chromatography-mass spectrometry analysis and comparison with synthetic reference samples. Their relevance for Bmt biosynthesis is discussed. Bmt polyketide synthase shows optimal activity at substrate concentrations of 200 microM acetyl-CoA, 150 microM malonyl-CoA, and 200 microM S-adenosylmethionine, around pH 7 and at 35 degrees C. Interestingly the Bmt backbone is released from the enzyme as a coenzyme A thioester, suggesting that subsequent transformation to Bmt takes place upon this activated intermediate.

Neuroanatomy of Rett syndrome: a volumetric imaging study

Rett syndrome is a pediatric neurological disorder of unknown etiology defined by the presence of severe neurodevelopment decline, acquired microcephaly, dementia, abnormalities of movement, autistic behavior, and seizures in young female children. In this study, the neuroanatomy of 11 females with Rett syndrome and 15 age- and gender-matched control subjects was investigated in vivo with quantitative neuroimaging techniques. Compared to control subjects, the patients with Rett syndrome were found to have significantly reduced cerebral volume; evidence of greater loss of gray matter in comparison to white matter; regional variation in cortical gray matter, with the frontal regions showing the largest decrease; and reduced volume of the caudate nucleus and midbrain, even when taking into account general reduction in the size of the brain. In addition, there was no evidence of an ongoing degenerative process in this sample of girls with Rett syndrome. The consistency of these data with results from neuropathological investigations points to the need for continued quantitative neuroimaging studies of children with this condition. In particular, research employing serial longitudinal scans of very young children manifesting early signs of the clinical syndrome holds promise for helping to elucidate the neuropathological pathways leading to the debilitating clinical manifestations of Rett syndrome.

Neurochemical alterations in Rett syndrome

The Rett syndrome (RS) is a neurological disorder associated with severe mental deficiency and neurological manifestations of cortical and extrapyramidal dysfunction. The present report is (1) a postmortem brain study that compares the levels of choline acetyltransferase (ChAT) activity and the binding density of selected neurotransmitter receptors in four cases of RS and five normal controls of similar age and (2) a study of cerebrospinal fluid (CSF) concentrations of the endogenous tridecapeptide neurotensin in 12 RS patients and 8 controls of similar age. The level of ChAT activity was lower in many cortical and subcortical regions in the RS brains as compared to control levels. The number of NMDA, AMPA, mu opioid and neurotensin binding sites, as well as CSF concentrations of neurotensin, did not differ significantly from control levels. The results suggest that changes in specific neurotransmitter systems, particularly cholinergic neurons, in the thalamus, cerebellum and basal ganglia may underlie the progressive deterioration in motor and cognitive function characteristic of this disorder.

Stress-induced polymorphous ventricular tachyarrhythmias in two brothers: unusual pattern of inheritance in the long QT syndrome

Two brothers, 10 and 9 years old, are reported who were treated for years with antiepileptic drugs until the cardiac origin of their syncopal attacks was discovered. Our findings are consistent with the diagnosis of long QT syndrome, although no other family members are affected and only intermittent and mostly borderline QT prolongation could be found. Diagnostic difficulties and genetic implications are discussed.

CONTRIBUTION OF THE Na+/H+ ANTIPORTER TO THE REGULATION OF INTRACELLULAR pH IN A CRAYFISH STRETCH RECEPTOR NEURONE

Regulation of intracellular pH (pHi) following acidosis induced by NH4+/NH3 exposures was re-investigated in a crayfish stretch receptor neurone using H+- and Na+-selective microelectrodes. All experiments were performed in nominally HCO3-/CO2-free salines. From studies in Na+-free saline and from electrochemical calculations, we concluded that pHi regulation was dependent on extracellular Na+ concentration ([Na+]o). The half-maximal rate of pHi recovery had an apparent Michaelis-Menten constant of 21 mmol l-1 [Na+]o. The use of this experimental approach and an improved technique enabled us to observe pHi regulation even in Cl-- free saline, in contrast to earlier findings. In addition, amiloride (2 mmol l-1) inhibited the maximum rate of pHi recovery by about 80 %, SITS (1 mmol l- 1) by about 20 %. The results strongly suggest the operation of two separate pHi-regulating mechanisms, a Na+-dependent HCO3-/Cl- antiporter (probably the Na+/H+/HCO3-/Cl- antiporter described earlier) and a Na+/H+ antiporter. Both mechanisms have been described in crayfish ganglion cells and muscle fibres, but the individual contribution to pHi regulation varies considerably in these preparations. Functional aspects of the pHi-regulating mechanisms in relation to ionic changes during the moulting cycle are discussed.

Compound heterozygosity for metachromatic leukodystrophy and arylsulfatase A pseudodeficiency alleles is not associated with progressive neurological disease

Several allelic mutations at the arylsulfatase A (ASA) locus cause substantial deficiencies of this lysosomal enzyme. Depending on the genetically determined degree of the deficiency, the clinical outcome may be very different--either metachromatic leukodystrophy (MLD), a lethal lysosomal storage disorder affecting the nervous system, or, more frequently, the so-called pseudodeficiency (PD), which has no apparent clinical consequence. Because of compound heterozygosity for MLD and PD, 1/1,000 individuals in the population have low residual enzyme activities, which are intermediate between those of MLD patients and those of PD homozygous normal individuals. In order to assess whether PD/MLD compound heterozygotes bear a health risk, we examined clinically and biochemically 16 individuals with this genotype. Of these subjects, two had neurological symptoms and two showed lesions, without clinical symptoms, in magnetic resonance imaging of the brain. None of these symptoms was progressive, nor did they resemble those of MLD. Nerve conduction velocities were normal in these probands, and they secreted only low amounts of sulfatide in the urine. We conclude that the observed neurological symptoms are unrelated to the ASA genotype and that PD/MLD compound heterozygotes are not at an increased risk for developing progressive nervous system diseases.

Linkage of Van der Woude syndrome (VWS) to REN and exclusion of the candidate gene TGFB2 from the disease locus in a large pedigree

Van der Woude syndrome (VWS) is an autosomal dominant disorder associated with one or more of the following features: clefting of the primary or secondary palate, hypodontia or lower lip pits. It has been estimated to account for 2% of all cases of cleft lip and palate. VWS is one of the rare disorders in which clefting of the primary and secondary palate may be seen to segregate as components associated with the same gene. Because of its autosomal dominant inheritance, VWS is readily accessable to linkage analysis as a preliminary step in the identification of the molecular abnormality underlying the clefting effect in the primary and secondary palate. A reported linkage between REN and VWS has promoted us to use pHRnX3.6 (REN) and several markers surrounding REN for a linkage analysis in a large Swiss family. In a second step, linkage analysis was performed to study restriction fragment length polymorphisms for the candidate gene TGFB2 and other loci recently mapped to the candidate region 1q32-1q41. Evidence for linkage (theta = 0.00, lod score = 3.01) between REN and VWS could be confirmed in this pedigree. TGFB2 demonstrated recombination with the disease locus and is unlikely to be causative in VWS. The results of a multipoint linkage analysis showed that VWS was flanked by D1S65 and TGFB2 at a maximum location score of 20.3.

Putative X-linked adrenoleukodystrophy gene shares unexpected homology with ABC transporters

Adrenoleukodystrophy (ALD) is an X-linked disease affecting 1/20,000 males either as cerebral ALD in childhood or as adrenomyeloneuropathy (AMN) in adults. Childhood ALD is the more severe form, with onset of neurological symptoms between 5-12 years of age. Central nervous system demyelination progresses rapidly and death occurs within a few years. AMN is a milder form of the disease with onset at 15-30 years of age and a more progressive course. Adrenal insufficiency (Addison's disease) may remain the only clinical manifestation of ALD. The principal biochemical abnormality of ALD is the accumulation of very-long-chain fatty acids (VLCFA) because of impaired beta-oxidation in peroxisomes. The normal oxidation of VLCFA-CoA in patients' fibroblasts suggested that the gene coding for the VLCFA-CoA synthetase could be a candidate gene for ALD. Here we use positional cloning to identify a gene partially deleted in 6 of 85 independent patients with ALD. In familial cases, the deletions segregated with the disease. An identical deletion was detected in two brothers presenting with different clinical ALD phenotypes. Candidate exons were identified by computer analysis of genomic sequences and used to isolate complementary DNAs by exon connection and screening of cDNA libraries. The deduced protein sequence shows significant sequence identity to a peroxisomal membrane protein of M(r) 70K that is involved in peroxisome biogenesis and belongs to the 'ATP-binding cassette' superfamily of transporters.

Genotype/phenotype association in cystic fibrosis: analyses of the delta F508, R553X, and 3905insT mutations

A striking clinical phenomenon of cystic fibrosis is the heterogeneous disease expression. It must therefore be assumed that the nature of the mutations associated with cystic fibrosis might partly determine the phenotypic manifestations. The relation between the cystic fibrosis mutations delta F508, R553X, and 3905insT and clinical parameters such as sweat test electrolytes, age at chronic Pseudomonas aeruginosa colonization, Chrispin-Norman x-ray scores, and relative underweight have been investigated in 45 patients homozygous for delta F508 (delta F2), in 12 compound heterozygotes for delta F508/R553X (delta F1/RX1), in three R553X homozygotes (RX2), and in 13 patients compound heterozygous for delta F508/3905insT (delta F16). We have found significant differences between the genetically defined subgroups concerning the mean age at onset and the cumulative incidence of chronic P. aeruginosa colonization and Chrispin-Norman x-ray scores. The significant results as well as some trends regarding the relative underweight demonstrate a milder clinical course in R553X heterozygotes and more severe disease in the delta F16 group compared to delta F508 homozygotes. The three patients homozygous for R553X presented with a two-stage course showing mild progression before P. aeruginosa infection and as severe a course as the delta F16 patients after P. aeruginosa colonization at the age of 12 y. The findings presented here indicate that specific mutations can influence the severity and progression of the disease, implicating the importance of mutation and haplotype analyses. However, wide variations within the genetically homogeneous subgroups illustrate that other determinants of the clinical status do exist.

Mutations in the 70K peroxisomal membrane protein gene in Zellweger syndrome

The peroxisomal membrane protein, with a relative molecular mass of 70,000 (M(r) 70K) (PMP70), is an important component of peroxisomal membranes and an ATP-binding cassette protein. To investigate its possible involvement in Zellweger syndrome (ZS), an inborn error of peroxisome assembly, we cloned and sequenced cDNAs for human PMP70 and mapped the gene to chromosome 1. Amongst 32 probands with ZS or related disorders, we found two mutant PMP70 alleles in single ZS probands from the same complementation group. One allele has a donor splice site mutation and the second a missense mutation. Our results suggest that PMP70 plays an important role in peroxisome biogenesis and that mutations in PMP70 may be responsible for a subset of ZS patients.