bluuebunny/crossref_metadata_2025 huggingface dataset:
Taurine Replacement Prevents Apoptosis In Experimental Diabetic Neuropathy
Authors: Pop‐Busui R , Sullivan K , Russel J , Feldman E , Stockert C , Larkin D , Greene D , Stevens M.
Published: March 2003

The pathophysiology of diabetic neuropathy (DN) is complex involving both metabolic and vascular deficits. Recent data have implicated a potential role for programmed cell death (PCD) in the development of experimental DN (EDN). Oxidative stress has emerged as a leading candidate in the development of nerve blood flow (NBF) and nerve conduction deficits. We have previously shown that replacement of the endogenous antioxidant taurine in the nerve of streptozotocin‐diabetic (STZ‐D) rats corrects neuro‐vascular dysfunction, prevents deficits in Na,K‐ATPase activity and attenuates motor and sensory NCV slowing. The aims of this study were to examine the hypothesis that oxidative stress‐mediated mitochondrial dysfunction may promote the activation of PCD pathways in STZ‐D rats and to determine whether these effects could be attenuated by taurine. Dorsal root ganglion (DRG) neurons were extracted from perfused control (C), STZ‐D and STZ‐D rats given a 1% taurine supplemented diet for 6 weeks. STZ‐D induced a significant decrease in sensory nerve conduction velocity (SNCV) and NBF vs controls and these deficits were corrected by taurine. Lumbar and sacral DRG were sectioned at 10 mm intervals and slides were prepared from two different sampling sites. Apoptosis was detected by TUNEL staining. 150 or more DRG nuclei were counted per animal. In STZ‐D rats 21.3 ± 4.9% of DRG nuclei were found to be TUNEL positive as compared with 2.9 ± 2.1% in controls (p < 0.05). Taurine replacement markedly attenuated apoptosis since only 6.5 ± 2.9% neurons were TUNEL positive. In summary, 6 weeks of STZ‐D increased apoptosis in DRG neurons of STZ‐D rats. This increase in apoptosis could be prevented by replacement of the endogenous antioxidant taurine, implicating a role of taurine depletion in the development of sensory neuron degeneration.
Hedgehog Proteins Play A Role In Peripheral Nerve Regeneration
Authors: Engber Tm , Allendoerfer Kl , Berg A , Drake E , Mahanthappa N , Mozell R , Pepicelli C , Ranciato R , Reilly Jo , Sah D , Wang S , Galdes A.
Published: March 2003

Hedgehog proteins are embryonic induction factors that play a role in the development of the central and peripheral nervous systems. The Hedgehog proteins and their signaling pathway continue to be expressed in the adult nervous system, where their role is not known. In adult peripheral nerve, Sonic Hedgehog (Shh) is expressed in a subset of motor neurons, Desert Hedgehog (Dhh) is expressed in Schwann cells, and the Hedgehog receptor Patched (Ptc) and the Hedgehog‐responsive transcription factor Gli are expressed predominantly in perineurial cells. We have used the mouse sciatic nerve crush model to assess whether the Hedgehog pathway plays a role in nerve regeneration. The sciatic nerve was crushed in adult, male CD‐1 mice, and the expression of Dhh, Ptc‐1, Ptc‐2 and Gli‐1 was examined 1, 3, 7 and 13 days later. The ability of exogenous and endogenous Hedgehog proteins to influence functional recovery after nerve crush was assessed by measuring toe spread and ability to grip with the hindpaws. Little change in expression was seen 1 or 3 days after nerve crush. At 7 days and, to a greater extent, 13 days, there was a pronounced increase in expression of Dhh in Schwann cells and Ptc‐1 in perineurial cells. Expression of Ptc‐2 and Gli‐1 increased not only in the perineurial layer, but also in the endoneurium. Treatment with a Shh‐Ig fusion protein (1 mg/kg s.c. every other day) improved recovery of both toe spread and ability to grip. Conversely, treatment with an anti‐Hedgehog neutralizing antibody (10 mg/kg s.c. every other day) slowed functional recovery, while an isotype control antibody had no effect. These findings suggest that endogenous Hedgehog proteins play a role in promoting regeneration following nerve injury and that administration of exogenous Hedgehog proteins can further accelerate recovery of injured peripheral nerves. Therefore, Hedgehog proteins may be useful in the treatment of nerve injury and peripheral neuropathies.
Effects Of Different Schedules Of Oxaliplatin Treatment On The Peripheral Nervous System And The Auditory Pathway In The Rat
Authors: Cavaletti G , Tredici G , Petruccioli MG , Dondè E , Tredici P , Marmiroli P , Minoia C , Gatti A , Bayssas M , Griffon Etienne G.
Published: March 2003

The dose‐limiting side effect of the second‐generation platinum drug oxaliplatin is peripheral neurotoxicity. In the present study we compared the effect on the peripheral nervous system and on the auditory pathway of the rat of four different schedules of oxaliplatin administration using two cumulative doses (36 and 48 mg/kg) and three different intervals between administrations (twice weekly, five consecutive days on alternate weeks or alternate days).

After oxaliplatin treatment platinum was detected in the kidney, dorsal root ganglia (DRG) and sciatic nerve. The neuropathological examination evidenced DRG nucleolar, nuclear and somatic size reduction with DRG nucleolar segregation in all the treated rats. In the sciatic nerves, mild secondary axonopathy occurred. Sensory nerve conduction velocity was reduced after oxaliplatin treatment, while the auditory pathway was unaffected. After a 5‐week follow‐up period complete recovery of the pathological changes in the DRG and sciatic nerves occurred, although platinum was still detectable in these tissues. In the follow‐up period several oxaliplatin‐treated rats had abdominal bloating due to local toxicity of the intraperitoneally delivered drug. Conclusion: 1) The least toxic schedules are those used in gr.1 and 2; 2) The shorter the interval between injections, the higher the severity of peripheral neuropathy, related primarily to the cumulative l‐OHP dose; 3) The DRG neuronopathy and the nerve damage tend to be reversible; 4) Ototoxicity even with high cumulative doses of oxaliplatin is absent.

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αβ1 Integrins Are Required For Normal Peripheral Nerve Development
Authors: Feltri ML , Quattrini A , Previtali S , Nodari A , Migliavacca B , Graus‐Porta D , Littlewood‐Evans A , Messing A , Mueller U , Wrabetz L.
Published: March 2003

Adhesion to basal lamina is required for Schwann cells (SC) to form normal myelin in peripheral nerves. In human Congenital Muscular Dystrophy (CMD), mutations in laminin 2 (α2 chain) cause a dysmyelinating peripheral neuropathy with slow nerve conduction velocities. The dy2J/dy2J mouse also carries a mutation in the laminin α2 chain, and is considered an animal model for CMD. The dysmyelination in the dy2J/dy2J mouse is dramatic in nerve roots, where SC fail to sort bundles of naked axons. In distal peripheral nerves, myelination can proceed, even if axon/SC interactions and nodes of Ranvier are abnormal. Which of the SC laminin receptors, integrins or dystroglycan mediate these functions is unclear because targeted inactivation of those genes results in embryonic death in mice prior to myelination. Several in vitro studies suggest β1 integrin as a candidate for a role in axon/SC interaction and myelination. To inactivate the β1 integrin gene (mIntb1) in SC only, we produced transgenic mice expressing Cre recombinase using the vector mP0TOT, that activates expression of genes in SC in parallel with P0 during development. By crossing mP0TOT(Cre) mice with mice carrying a mIntb1 flanked by loxP sites of recombination, we produced mice lacking β1 integrin specifically in SC. These mice have a severe dysmyelinating peripheral neuropathy, originating in embryonic nerve development. Although Schwann cells populate the length of forming nerves, and are present in numbers comparable to wildtype nerves, they are unable to penetrate bundles of naked axons in order to sort and ensheath them. In some nerve fascicles, SC can bypass the block, even in the absence of β1 integrin, and myelinate normally. These data show that αβ1 integrins are necessary for normal Schwann cell‐axon interactions, but not for myelination per se. The similarity of this phenotype to that of dy2J/dy2J mouse suggests that αβ1 integrins mediate some of the effects of altered laminin‐2 in impaired CMD peripheral nerves.
Novel MPZ Mutation In A Sporadic CMT Patient
Authors: Bellone E , Cassandrini D , Di Maria E , Balestra P , Grandis M , Mancardi GL , Schenone A , Ajmar F , Mandich P.
Published: March 2003

Mutations in the gene for the major structural protein component of peripheral nerve myelin, myelin protein zero (MPZ), are associated with some forms of hereditary neuropathies such as Charcot‐Marie‐Tooth disease type 1B (CMT1B), Dejerine‐Sottas syndrome (DSS) and congenital hypomyelinating neuropathy (CHN). The common pathological characteristics of these allelic disorders are severe demyelination and remyelination of peripheral nerves. Recently, MPZ mutations were also found in patients with the axonal form of CMT neuropathy (CMT2). We studied a patient with negative familiar history and clinical and electrophysiological features of Charcot‐Marie‐Tooth disease: distal muscle weakness and atrophy, foot deformities (pes cavus), and severely reduced nerve conduction velocities in the motor and sensory nerves. The sural nerve biopsy showed marked loss of myelinated fibers, few onion bulbs, and a high percentage of fibers showing excessive myelin outfoldings. DNA analysis excluded CMT1A duplication by Southern blot and by pulsed field gel electrophoresis methods. SSCP analysis of all six exons of MPZ revealed a shift band in exon 2 in the patient's DNA. No such difference was detected in normal controls. Direct sequencing disclosed a G → A transition at nucleotide position 181. This base substitution predicts the replacement of aspartic acid with asparagine at codon 61. A mutation at the same codon (but different amino acid replacement) was recently identified in a family with the axonal type of CMT, in which the disease was autosomal dominantly inherited. This finding provides further confirmation of the role of MPZ gene in peripheral neuropathies and suggests that MPZ coding region mutations may account for a considerable number of CMT cases which do not involve DNA duplication on 17p11.2‐p12. This research was partially supported by a MURST and an Ateneo grant to FA, by a Ministero della Sanità grant to PM. Our laboratory is a member of the European Charcot‐Marie‐Tooth Consortium co‐ordinated by Prof. Christine Van Broeckhoven.
Genes Differentially Expressed By Schwann Cells Of Motor Versus Sensory Nerves
Authors: Imperiale D , Feltri L , Previtali S , Quattrini A , Ravetti C , Wrabetz L.
Published: March 2003

Charcot‐Marie‐Tooth (CMT) disease includes a heterogeneous group of inherited demyelinating peripheral neuropathies related to genetic defects of myelin‐forming Schwann cells (SC). In CMT, as in other common acquired demyelinating neuropathies (Guillain Barré syndrome, chronic inflammatory demyelinating polyneuropathy), motor nerves are invariably more involved than sensory nerves. Also in transgenic mouse models of peripheral neuropathy, there is a preferential demyelination of motor districts independent of the type of genetic alteration. The basis for differential susceptibility to demyelination is unknown. The aim of this study was to identify differences in gene and protein expression that may underlie the differential susceptibility to demyelination of motor and sensory myelin‐forming SC. Since spinal roots are the only portion of mammalian PNS in which motor and sensory axons are segregated, we extracted RNA from adult rat dorsal (sensory) and ventral (motor) spinal roots and compared corresponding cDNAs by an RNA fingerprint approach. Four differentially displayed bands were isolated. We first characterized the most differentially expressed band, which was highly enriched in sensory roots. Sequence analysis showed that the band encoded a portion of rat sarco/endoplasmic reticulum calcium transporting ATPase type 1 coding sequence (SERCA1). RT‐PCR experiments confirmed SERCA1 enrichment in dorsal sensory roots. SERCA enzymes are ubiquitous calcium regulatory systems in muscle and non‐muscle cells and SERCA1 is selectively enriched in skeletal muscle. To our knowledge, no studies have investigated SERCA isoform expression in peripheral nerve. Identification of a calcium regulatory molecule in SC is interesting, as calcium is essential for the proper structure and function of the nodal and paranodal portions of SC, as well as the myelin sheath. However, calcium homeostasis in SC is relatively unexplored. Experiments to localize SERCA1 transcript and protein in different PNS districts and to clarify its functional role in peripheral nerve are underway.
Role Of Campylobacter Jejuni In Experimental Allergic Neuritis: A Morphological And Biochemical Study
Authors: Laura M , Gregson N , Vita G , Hughes RAC.
Published: March 2003

Objective: The aim of the study was to evaluate if Campylobacter jejuni (C.j.) when used as an adjuvant would be able to produce a different form of Experimental Allergic Neuritis (EAN). We present here some preliminary results. Background: EAN is considered the in vivo model of Guillain‐Barrè Syndrome (GBS), which is often preceded by c.j. infection. EAN can be induced in Lewis rats by immunization with bovine peripheral nerve myelin in complete Freund's adjuvant (CFA), an emulsion formed by oil‐in‐water and dead mycobacteria. An adjuvant is usually necessary for the induction of EAN because it enhances the immunogenicity of the antigen. Clinically EAN is characterized by an acute monophasic course and progressive tail and limb weakness. The pathological finding is represented by marked demyelination affecting the roots and the sciatic nerve. Methods: 4 Lewis rats were immunized with an emulsion containing 2 mg of bovine peripheral myelin and C.j. strain Penner 0:41 in incomplete Freund's adjuvant (IFA). They were compared to 4 controls immunized with the same amount of peripheral myelin in CFA. The clinical course of the disease and the histological pattern of the roots and the sciatic nerve were examined. Anti‐peripheral myelin, anti‐C.jejuni and anti‐GM1 antibodies' reactivity was detected by an ELISA assay. A biochemical study was performed to test the role of cell‐ and humoral‐mediated responses. Results: The Lewis rats immunized with the C.j. as an adjuvant showed a delayed onset and a milder course of disease. Pathology in the roots was characterized by predominant demyelination, whereas the sciatic nerve presented very little signs of damage. Conclusion: This serotype of C.j. appears to be a less effective adjuvant in inducing EAN rather than Mycobacteria. Further studies are necessary to elucidate the pathogenetic mechanisms involved in GBS.
Long‐Term Prognosis Of CIDP: A Study of 49 Patients
Authors: Madia F , Sabatelli M , Lippi G , Quaranta L , Tonali P.
Published: March 2003

In 1975 Dyck et al. (Mayo Clin Proc. 1975, 50:621) reported that 10% of their patients with CIDP died, 28% were confined to wheelchair/bed and 8% were ambulatory and not able to work. More recent papers (Bouchard et al., Neurology 1999, 52:498; Gorson et al., Neurology 1997, 48:321) have reported quite similar data: 27–29% of treated patients need assistance for most activities and 7–10% of patients die. These findings are in contrast with the progressive expansion of therapeutic repertoire observed over the last 25 years. We describe the outcome of 49 patients affected by CIDP observed in our Institute from 1986 to 2000. All patients underwent extensive electrophysiological examination. Sural nerve biopsy was carried out in 45/49 patients. Selection criteria included clear‐cut evidence of conduction blocks or demyelination at pathological examination. Patients were treated with corticosteroids, IVIg, and PE. Patients on refractory to standard therapies received azathioprine or Interferon alpha. Taken as a whole, outcome was good in 84% of our patients: 33 (67%) achieved clinical remission and 8 (17%) improved significantly. 12% of our patients were unresponsive to all treatments. 4% died as the result of progression of the disease to severe quadriplegia with respiratory failure. Patients achieving recovery were separated in two distinct groups: patients showing a remission period after treatment withdrawal (16 patients) and patients needing permanent therapies to maintain improvement (17 patients). In the former group, 8 patients had a monophasic course with a follow‐up of 6 months to 9 years (mean 47 months); 8 patients showed a relapsing‐remitting course with a drug‐free period ranging from 6 months to 20 years, 50% reaching a remission period of at least 5 years. Regarding the latter group, clinical remission while taking therapies lasted 3 months to 4 years. In conclusion, we found that prognosis of CIDP is better than reported in the literature. Selection criteria and different therapeutic approach may explain such discrepancy.
Adult Onset Krabbe Disease Presenting As Complex Form Of CMT, With Peculiar Features On Sural Nerve Biopsy
Authors: Quaranta L , Sabatelli M , Lippi G , Di Trapani G , Lo Monaco M , Madia F , Tonali P.
Published: March 2003

Peripheral neuropathy is a common feature of classic infantile Krabbe disease and is characterised, on pathological ground, by segmental demyelination, reduction of large myelinated fibers, presence of crystalloid and prismatic inclusions within Schwann cells and histocytes. We report a fifty‐nine‐year‐old man who presented a progressive weakness in his distal limb muscles since the age of forty‐seven. At first examination, at the age of 50, there was a slight weakness of small hand muscles and of tibio‐peronei (F = 4, MRC scale) with bilateral pes cavus. Reflexes were moderately brisk with bilateral Babinski sign. There was a slight tongue atrophy. Electrophysiological examination showed generalised slowing of nerve conduction velocities. T2‐weighted magnetic resonance images showed bilateral periventricular hyperintensity of the white matter. A diagnosis of “complex form” of Charcot Marie Tooth disease was made. Over ten years of follow‐up a progressive worsening was observed, particularly in the proximal and distal muscles of his left upper limb. He was intellectually normal. Leukocyte galactocerebroside beta‐galactosidase activity, performed at the age of 59, was absent. On sural nerve biopsy the most striking finding was the presence of uniformly thin myelin sheaths without evidence of de‐remyelination. Myelinated fiber density was moderately reduced. Two brothers suffered from the same disease. Symptoms started at 41 and 47 years and were characterised by progressive weakness in the limbs with death occurring at 61 and 59 years, respectively, due to respiratory failure. Nerve conduction velocity was slowed in both patients. Sural nerve biopsy was performed in one of them, 4 years before death, and disclosed a complete absence of myelinated and unmyelinated fibers. Parents were not consanguineous and did not suffer from neurological diseases. In conclusion our findings show that peripheral neuropathy may be the presenting feature of late‐onset Krabbe disease. We found that hypomyelination rather than demyelination was responsible for slowing of nerve conduction. Our data confirm the only report in the literature (Matsumoto et al., Acta Neuropathol 1996, 92:635) suggesting that hypomyelination may play a role in late‐onset Krabbe disease.
Molecular Diagnosis Of Hereditary Peripheral Neuropathies
Authors: Taroni F.
Published: March 2003

Hereditary peripheral neuropathies are clinically and genetically heterogeneous and include the most common motor and sensory forms (HMSN) as well as the rarer pure motor and pure sensory phenotypes. As a group, Charcot‐Marie‐Tooth (CMT) disease and related neuropathies (Déjérine‐Sottas disease [DSD], congenital hypomyelinating neuropathy [CHN] and hereditary neuropathy with liability to pressure palsies [HNPP]) represent the most common inherited peripheral nerve diseases as well as one of the most common human inherited disorders with a prevalence of ∼20–40:100,000. During the last decade, advances in molecular genetics have greatly increased our understanding of these disorders and significantly changed the clinical approach to them by providing powerful molecular tools for diagnosis. The most common form is demyelinating CMT (CMT1). Based on genetic location and the gene involved, CMT1 is further subcategorized into autosomal dominant (AD) CMT1A (PMP22, 17p11.2) and CMT1B (MPZ, 1q21.2), and X‐linked dominant CMTX (Cx32, Xq13.1). Approx. 3/4 of CMT1 patients belong to the CMT1A subgroup and carry a 1.5‐Mb duplication on chr. 17p11.2 encompassing the myelin protein PMP22 gene. Given the high duplication rate in sporadic cases, the diagnosis of CMT1A should be considered even in the absence of a family history. Furthermore, the reciprocal deletion of the CMT1A 1.5‐Mb tract is commonly (∼80%) observed in HNPP patients. Altogether, detection of these relatively common molecular abnormalities allows diagnosis in the vast majority of CMT1 or HNPP patients. Patients who do not have the CMT1A duplication should be screened initially for Cx32 mutations which are the next most frequent cause of CMT1 accounting for ∼10% of patients. Approx. 4% of cases belong to the CMT1B subgroup, harboring mutations in the myelin protein P0 gene (MPZ). Mutations in the PMP22 gene can be found in a minority of CMT1 patients. Of the remaining cases, some have been demonstrated to carry mutations in the EGR2 gene. Interestingly, mutations in the PMP22, MPZ and EGR2 genes can also cause the more severe early‐onset variants DSD and CHN. A number of loci have been linked to the rare autosomal recessive forms of CMT1. Very recently, mutations in the MTMR2 and NDRG1 genes have been associated with two distinct phenotypes, AR‐CMT1 with myelin outfoldings (CMT4B) and HMSN‐Lom, respectively. Approx. 20–30% of CMT patients exhibit the axonal type CMT2. For the majority of these patients, no molecular test is currently available. Although several loci have been associated with this form, only one disease gene, NF‐L on chr. 8p21, has been thus far identified. However, Cx32 mutations should always be excluded in female patients diagnosed with CMT2. Finally, recent evidences have indicated that mutations in the MPZ gene can be found in ∼5% of AD‐CMT2 families.
Charcot‐Marie‐Tooth Disease: Poor Balance And Rehabilitation
Authors: Vinci P , Perelli SL , Esposito C
Published: March 2003

Charcot‐Marie‐Tooth is an hereditary motor and sensory neuropathy. Although the poor balance presented by most patients is generally considered as the consequence of the involvement of the sensory fibers, with impaired proprioception, in our patients, the sense of position was impaired only at the toes and Romberg sign was positive in only 3% of the cases. Patients with poor balance in stance, were found to have one or more of the following problems: foot rotation in supination, equinus deformity, foot dorsiflexion in presence of weak triceps surae muscles, inversion of the action of the toe extensors, contracture of proximal muscles, pain under the sole. Whereas the disfunction of the sensory fibers, depending on the neuropathy itself, cannot be treated, the other causes of poor balance can be removed by orthotic devices, physiotherapy and surgery. Our protocol of rehabilitation aimed at the improvement of balance includes: 1) foot orthoses in soft polyurethane, with wedges to correct rotation and talus or equinus deformity; 2) proper shoes, with a large sole and a correct amount of heel, varying according to the stage of the diesease and the individual needs; 3) ankle‐foot‐orthoses, either traditional or incorporated in the boot; 4) stretching of the contractured proximal muscles; 5) postural kinesitherapy, aimed at reducing the need of controlling joints from 3 (hip, knee, ankle) to 1 (hip); 6) proprioceptive kinesitherapy, to improve coordination. After this treatment, patients' stance became more steady and harmonic; also gait presented fewer skiddings and sprains over a six month period dramatically decreased.
Ceramide Initiates NF Kappa B‐Mediated Caspase Activation In Neuronal Apoptosis
Authors: Gill JS , Windebank AJ
Published: March 2003

The objective of the present study was to evaluate the role of ceramide in mediating apoptosis of dorsal root ganglion neurons induced by either nerve growth factor withdrawal or treatment with the chemotherapeutic agents suramin and cisplatin. Measurement of ceramide accumulation by mass spectrometry and the diacylglycerol kinase assay revealed elevation of intracellular ceramide only in suramin treated cultures. Ceramide‐mediated neuronal cell death was inhibited by the caspase inhibitor zVAD.fmk. In these experimental models, ceramide accumulation mediated activation and nuclear translocation of the transcription factor NF kappa B and cyclin D1 protein expression. Specific inhibition of NF kappa B using a molecular decoy strategy resulted in increased cell viability accompanied by diminished caspase activity and cyclin D1 expression. Inhibition of NF kappa B did not alter intracellular ceramide levels. Our study suggests that ceramide generation occurs upstream of NF kappa B activation, cell cycle reentry, and caspase activation in the neuronal death pathway.
Successful Generation Of Peripheral Neuropathy With Onion‐Bulb Formation In The Macrophage Scavenger Receptor Class A Knockout Mouse Treated With Isoniazid
Authors: Naba I , Yoshikawa H , Sakoda S , Itabe H , Suzuki H , Kodama T , Yanagihara T.
Published: March 2003

We previously reported successful generation of many onion‐bulbs (OBs) and formation of oxidized phosphatidylcholine after compression injury to the peripheral nerve of mice deficient of macrophage scavenger receptor class A (MSR‐A). In the present study, we employed chemical injury with isoniazid to the peripheral nerve of the MSR‐A knockout mice to investigate the role of the MSR‐A in toxic neuropathy. Peripheral neuropathy has not previously been generated with isoniazid in mice. In the present study, we also noted little histological change after isoniazid administration not only to control littermates but also to the A/J strain mice known to be slow acetylators. Surprisingly, however, we were successful in generating peripheral neuropathy with isoniazid in the MSR‐A knockout mice. Histologically, the predominant feature was the presence of many thinly myelinated fibers with some OBs, which have not been observed in rats with isoniazid neuropathy. Deficiency of the MSR‐A appears to have played an important role in generation of peripheral neuropathy with isoniazid in mice.
Recent progress on the molecular organization of myelinated axons
Authors: Scherer Steven S. , Arroyo Edgardo J.
Published: March 2003

Abstract  The structure of myelinated axons was well described 100 years ago by Ramón y Cajal, and now their molecular organization is being revealed. The basal lamina of myelinating Schwann cells contains laminin‐2, and their abaxonal/outer membrane contains two laminin‐2 receptors, α6β4 integrin and dystroglycan. Dystroglycan binds utrophin, a short dystrophin isoform (Dp116), and dystroglycan‐related protein 2 (DRP2), all of which are part of a macromolecular complex. Utrophin is linked to the actin cytoskeleton, and DRP2 binds to periaxin, a PDZ domain protein associated with the cell membrane. Non‐compact myelin—found at incisures and paranodes—contains adherens junctions, tight junctions, and gap junctions. Nodal microvilli contain F‐actin, ERM proteins, and cell adhesion molecules that may govern the clustering of voltage‐gated Na+ channels in the nodal axolemma. Nav1.6 is the predominant voltage‐gated Na+ channel in mature nerves, and is linked to the spectrin cytoskeleton by ankyrinG. The paranodal glial loops contain neurofascin 155, which likely interacts with heterodimers composed of contactin and Caspr/paranodin to form septate‐like junctions. The juxtaparanodal axonal membrane contains the potassium channels Kv1.1 and Kv1.2, their associated β2 subunit, as well as Caspr2. Kv1.1, Kv1.2, and Caspr2 all have PDZ binding sites and likely interact with the same PDZ binding protein. Like Caspr, Caspr2 has a band 4.1 binding domain, and both Caspr and Caspr2 probably bind to the band 4.1B isoform that is specifically found associated with the paranodal and juxtaparanodal axolemma. When the paranode is disrupted by mutations (in cgt‐, contactin‐, and Caspr‐null mice), the localization of these paranodal and juxtaparanodal proteins is altered: Kv1.1, Kv1.2, and Caspr2 are juxtaposed to the nodal axolemma, and this reorganization is associated with altered conduction of myelinated fibers. Understanding how axon‐Schwann interactions create the molecular architecture of myelinated axons is fundamental and almost certainly involved in the pathogenesis of peripheral neuropathies.
Reduced Ia‐afferent‐mediated Hoffman reflex in streptozotocin‐induced diabetic rats
Authors: Tonra JR , Cliffer KD , Carson SR , Lindsay RM , Bodine SC , DiStefano PS
Published: March 2003

In addition to reduced nerve conduction velocity, diabetic neuropathic patients often exhibit a reduction in the amplitude of the compound muscle action potential elicited by stimulation of the la‐afferent‐mediated reflex pathway (Hoffman or H wave) that can contribute to diminished or absent tendon reflexes. In contrast to nerve conduction velocity deficits, changes in H‐wave amplitudes have not been reproduced in diabetic animal models. Using electrophysiological techniques developed for repeated recordings in individual animals, we report H‐wave deficits in streptozotocin (STZ)‐treated insulin‐dependent diabetic rats. After 4 weeks of diabetes induced by STZ treatment, a 47% reduction in the H‐wave amplitude was demonstrated by recording compound muscle action potentials in foot muscles after stimulation of la afferents. Interestingly, we also demonstrate that the H‐wave amplitude gradually recovers to a 26% deficit after 12 weeks of experimental diabetes. The recovery of the H wave in STZ‐treated rats distinguishes this deficit mechanistically from other STZ‐induced electrophysiological changes and may model a similar recovery of the H wave reported in diabetic patients.
The endoneurial response to microsurgically removed epi‐ and perineurium
Authors: Terho Perttu M. , Vuorinen Ville S. , Röyttä Matias
Published: March 2003

Abstract  The purpose of the study was to examine the response of the endoneurium of the rat sciatic nerve after removal of the epi‐ and perineurium. For this purpose, segments (4–5 mm long) of the whole epi‐ and perineurium around the rat sciatic nerve were microsurgically removed (the peel‐off area) and the endoneurium was left intact. The postoperative changes were followed up to 5 weeks post‐operatively (PO) by histo‐ and immunohistochemical studies. Additionally, neuromorphometric analyses considering the number of Schwann cells, axons, macrophages and endothelial cells were examined in the peel‐off area.

The results showed that at the operative area the central part of the endoneurium (65% of the total area of the endoneurium) remained morphologically intact, but the outer part of the endoneurium (35% of the total area) reacted strongly and showed Wallerian type of degeneration. The number of axons and Schwann cells decreased 3 days PO. However, after 2 weeks the number of Schwann cells increased markedly and the highest number was noted 5 weeks PO. A great number of capillaries were observed in the outer part 1 week PO. A rapid invasion of macrophages was noted at the outer part of the endoneurium immediately after the operation. During the regeneration the endoneurial fibroblasts in the peripheral zone started to form minifascicle‐like formations, which resulted in a distinct dense outer part of the endoneurium. This dense outer zone was preserved up to 5 weeks PO and participated in the formation of a new perineurium‐like structure, but no distinct new perineurium was formed. At the border zone, areas beside the normal epi‐ and perineurium proliferation of preserved perineurial cells were noted, which fused to the outer part of the dense endoneurium. On focal areas, an attachment of the operated area to the adjoining muscle was observed.

This study shows for the first time that despite the microsurgical removal of epi‐ and perineurium, the inner part of the endoneurium stays intact, but in the outer part of the endoneurium marked reactive changes ensue, probably to protect the injured peripheral nerve.
NERVE GROWTH FACTOR RESCUE OF CISPLATIN NEUROTOXICITY IS MEDIATED THROUGH THE HIGH AFFINITY RECEPTOR: STUDIES IN PC12 CELLS AND P75 NULL MOUSE DORSAL ROOT GANGLIA
Authors: Fischer SJ , Podratz JL , Windebank AJ.
Published: March 2003

Nerve growth factor (NGF) rescues dorsal root ganglion neurons and PC12 cells from cisplatin‐induced cell death. Two model systems were used to demonstrate that rescue is mediated through the high affinity NGF receptor. In dorsal root ganglion (DRG) neurons isolated from p75(−/−) and control mice, 20 ng/ml NGF completely prevented cisplatin‐induced death. In PC12 cells, we overexpressed receptor chimeras between the tumor necrosis factor and NGF receptors. We demonstrated that activation of the intracellular domain of Trk A is responsible for the NGF rescue effect.
LIGHT HISTORY INFLUENCES THE SENSITIVITY TO ATRAZINE IN PERIPHYTIC ALGAE
Authors: Guasch Helena , Sabater Sergi
Published: March 2003

This study examines the relationship between light history (i.e. light conditions during colonization) and sensitivity to atrazine for periphyton communities grown on etched glass substrates (colonized for 2–3 weeks) at seven stream and river sites differing in water chemistry and light regime. For each site, taxonomic composition of the community (by microscopic examination and cell counts), pigment composition, and photosynthetic parameters were measured and related to sensitivity to the herbicide. Photosynthetic parameters were estimated from photosynthesis– irradiance (P‐I) curves; the responses of the algae to atrazine were analyzed using short‐term concentration–response tests. Periphyton communities colonizing shaded sites were diatom dominated, had higher percentages of accessory pigments, and were more susceptible to photoinhibition at high light intensities compared to periphyton communities colonizing open sites; communities in the more open sites were dominated by green algae or cyanobacteria. Periphyton communities colonizing open sites were more sensitive to atrazine; the concentration of atrazine needed to inhibit photosynthesis by 50% in the short‐term tests (EC50 values) was correlated with light conditions during colonization. The interaction between treatment factors (light conditions during colonization, irradiance of incubation, and atrazine concentration) was analyzed by three‐way ANOVA. The two‐way interactions were significant, indicating that the response of the periphyton to irradiance during incubation and to atrazine concentration both depend on light history. However, the magnitude of the interaction between light history and atrazine toxicity was attenuated by changes in irradiance during incubation (three‐way ANOVA). This investigation presents evidence that the apparent toxicity of atrazine to lotic periphyton in natural communities is greater for algae that are adapted to high‐light conditions than for those that are adapted to low‐light conditions.
ON‐LINE MONITORING OF CHLOROPHYLL FLUORESCENCE TO ASSESS THE EXTENT OF PHOTOINHIBITION OF PHOTOSYNTHESIS INDUCED BY HIGH OXYGEN CONCENTRATION AND LOW TEMPERATURE AND ITS EFFECT ON THE PRODUCTIVITY OF OUTDOOR CULTURES OF SPIRULINA PLATENSIS (CYANOBACTERIA)
Authors: Torzillo Giuseppe , Bernardini Paola , Masojídek Jirí
Published: March 2003

The saturating pulse fluorescence technique was applied to study photoinhibition of photosynthesis in outdoor cultures of the cyanobacterium Spirulina platensis (Nordstedt) Geitler strain M2 grown under high oxygen and low temperature stress. Diurnal changes in maximum photochemical yield (Fv/Fm), photon yield of PSII (ΔF/F′m), and nonphotochemical quenching (qN) were measured using a portable, pulse‐amplitude–modulated fluorometer. When solar irradiance reached the maximum value, the Fv/Fm and ΔF/F′m ratios of theSpirulina cultures grown under high oxygen stress decreased by 35% and 60%, respectively, as compared with morning values. The depression of the Fv/Fm and ΔF/F′m ratios reached 55% and 84%, respectively, when high oxygen stress was combined with low temperature (i.e. 10° C below the optimal value for growth). Photoinhibition reduced the daily productivity of the culture grown under high oxygen stress by 33% and that of the culture grown under high oxygen–low temperature stress by 60%. Changes in the biomass yield of the cultures correlated well with changes in the daily integrated value of the estimated electron transport rate through the PSII (ΔF/F′m × photon flux density). The results indicate that on‐line chlorophyll fluorescence measurement is a powerful tool for assessing the photosynthetic performance of outdoorSpirulina cultures.
SUBSIDY AND STRESS RESPONSES OF STREAM PERIPHYTON TO GRADIENTS IN WATER VELOCITY AS A FUNCTION OF COMMUNITY GROWTH FORM
Authors: Biggs Barry J. F. , Goring Derek G. , Nikora Vladimir I.
Published: March 2003

Previous studies have shown major differences in the way biomass of stream periphyton is controlled by spatial variations in velocity. We hypothesize that these differences may be the result of different growth forms within the community. Some dense and coherent growth forms (e.g. mucilaginous diatom/cyanobacterial mats) may be resistant to diffusion and also resistant to dislodgment by shear stress. Higher velocities applied to such communities could therefore be expected to enhance biomass accrual by increasing rates of mass transfer, but without greatly increasing losses through sloughing. Conversely, other growth forms (e.g. long filamentous green algae) have an open matrix, and high rates of diffusion into the mats can potentially occur even at low velocity. However, as velocities increase, high skin friction and form drag should lead to higher rates of sloughing. The overall result of these processes should be that maximum biomass occurs at low velocities. This “subsidy‐stress” hypothesis was tested twice with each of three different periphytal growth forms: a coherent, mucilaginous, diatom community; a moderately coherent, stalked/ short, filamentous diatom community; and an open‐weave, long, filamentous green algal community. A monotonic increase in chl a biomass occurred as a function of near‐bed velocities for the first of the two mucilaginous diatom communities investigated. No biomass‐velocity relationship was found, however, with the second mucilaginous community, probably because the waters were highly enriched and mass transfer driven by molecular diffusion was probably high throughout the velocity gradient. Biomass was moderate at low velocities, peaked at near‐bed velocities from 0.18 to 0.2 m·s−1 (∼0.40–0.45 m·s−1 mean column velocity), and then decreased at higher velocities in both of the stalked/ short filament communities of diatoms analyzed. With the long filamentous green algal communities, a monotonic reduction in biomass occurred as a function of increases in velocity. Proliferations greater than 100 mg·m−2 chl a occurred at low near‐bed velocities (i.e. <0.2 m·s−1), after which biomass declined nearly exponentially as a function of increasing velocity to less than 10 mg·m−2 chl a at velocities greater than 0.4 m·s−1. These biomass‐velocity trends support our hypothesis that community growth form determines periphytal responses to spatial variations in velocity within stream reaches.
CELL DIVISION AND MORPHOGENESIS OF THE CENTRIC DIATOM CHAETOCEROS DECIPIENS (BACILLARIOPHYCEAE) II. ELECTRON MICROSCOPY AND A NEW PARADIGM FOR TIP GROWTH
Authors: Pickett‐Heaps Jeremy D.
Published: March 2003

Valve morphogenesis starts when the silica deposition vesicle (SDV) expands across a cleavage furrow covered by an unidentified layer, which may aid in its shaping. A labiate process (LP) is present only in the outer valve of terminal cells in the filament. Before these particular cells form setae, a layered “labiate process apparatus” (LPA) appears on the SDV in the exact center of the forming valve, near the microtubule center arising after cleavage. The LPA thereafter surmounts the lips of the LP as it forms. After the girdle bands separate slightly, two lateral protrusions develop in the corners of the cell. These nascent setae are lined internally by a cylindrical, fibrous band (sleeve), which assembles immediately ahead of the expanding edge of the SDV, very close to the plasmalemma. Then these protrusions, lined by the fibrous band, the SDV, and the forming silica wall, grow through two gaps in the girdle bands. The cytoplasm at the tip of the growing seta is naked. Immediately behind the tip, this fibrous band is adpressed to the plasmalemma and thereby apparently defines the diameter of the seta; it extends to internally ensheath the tipmost edge of the SDV for a short distance, like a tight‐fitting inner sleeve. This structure is considered the major organelle involved in seta morphogenesis. Microtubules (MTs), while present, are variable in extent and disposition within the seta. Turgor pressure is considered irrelevant in driving seta growth. Instead, a new paradigm proposed for tip‐growing cells generally, may apply to seta morphogenesis, as follows. If, as is suspected, the fibrous band contains actin, cycling of this actin (as in animal cells undergoing ruffling or filopodial extension) could drive seta extension via attachment of the band to the just‐formed silica wall. The band is visualized as a molecular treadmill whose support base, the new wall, is being continually extended; extension is controlled and generated strictly at the tip.
HEAT‐SHOCK PROTEIN 90 MAY BE INVOLVED IN DIFFERENTIATION OF THE FEMALE GAMETOPHYTES IN GRIFFITHSIA JAPONICA (CERAMIALES, RHODOPHYTA)
Authors: Lee Yoo Kyung , Kim Soon Hee , Hong Choo Bong , Chah Ok‐Kyong , Kim Gwang Hoon , Lee In Kyu
Published: March 2003

A cDNA library from a mixed population of female and male gametophytes of Griffithsia japonica Okamura was constructed, and a cDNA clone, designated GjFP‐1 (G. japonica female predominant‐1), was isolated by differential screening of the cDNA library. The transcript corresponding to GjFP‐1 was abundant in female gametophytes, but only basal levels of the transcript were detected in male and tetrasporangial thalli. Determination of the nucleotide sequence of GjFP‐1 identified a putative open reading frame encoding 313 amino acids and a 3′ untranslated region of 116 nucleotides. The deduced amino acid sequence of GjFP‐1 for the putative open reading frame shared high homology with the previously reported amino acid sequences of heat shock protein 90 (hsp90). RNA blot hybridization analysis for the transcripts of heat‐shocked G. japonica and DNA hybridization analysis for the genomic DNA of G. japonica with GjFP‐1 as a probe suggested that GjFP‐1 is a cDNA clone for the hsp90 gene in G. japonica.In situ hybridization for the GjFP‐1 transcript again showed a differential specificity of the transcript in female gametophytes. The data reported here suggest a possibility of hsp90 function linked to the development of the female gametophytes in G. japonica.
THE PINGUIOPHYCEAE CLASSIS NOVA, CHROMOPHYTE ALGAE PRODUCING LARGE AMOUNTS OF OMEGA‐3 FATTY ACIDS
Authors: Kawachi M. , Inouye I. , Honda D. , O'kelly C.J. , Bailey J.C. , Bidigare R.R. , Andersen R.A.
Published: March 2003

A new class of algae is proposed for a small group of unusual chromophytes (=heterokont algae). One novel aspect of these organisms is that cells contain large amounts of polyunsaturated fatty acids (41 – 67% of fatty acids), with exceptionally high amounts of EPA (21 – 56% of fatty acids). A second unusual character is that, for at least two genera, the mature flagellum (short, smooth flagellum of other chromophytes) is dominant, and the immature flagellum (long, hairy flagellum of other chromophytes) lacks tripartite hairs and is reduced in size or even absent. Carotenoid analysis shows that the class is characterized by the presence of chlorophylls a and c, fucoxanthin, violaxanthin, antheraxanthin, zeaxanthin, and β‐carotene. The 18S rRNA and rbcL gene sequences show that these organisms form a monophyletic group that is supported by very high bootstrap values. The phylogenetic relationships of the Pinguiophyceae and other classes are not well resolved, however, the relationships among the chromophytes have always been uncertain. The abundance of EPA, known to reduce “bad cholesterol” in humans, suggests this new class may be of significant economic importance.
MOLECULAR SYSTEMATICS OF THE XANTHOPHYCEAE
Authors: Bailey J.C. , McElhinney A. L. , Andersen R.A.
Published: March 2003

Species belonging to the Xanthophyceae have traditionally been classified in six (or seven) orders corresponding to amoeboid, coccoid, filamentous, monadoid, palmelloid and siphonous lines of descent. We have determined plastid rbcL and nuclear 18S rRNA gene sequences for selected coccoid, filamentous and siphonous species. Phylogenetic trees inferred from these data indicate that the orders Mischococcales (coccoid) and Tribonematales (filamentous) are not monophyletic. Instead, our results indicate that coccoid and filamentous life forms have arisen independently in different xanthophyte lineages. Some coccoid and filamentous species are resolved as close allies. For example, in our analyses coccoid and filamentous species possessing bipartite cell walls (e.g., Bumilleria, Ophiocytium, Tribonema, Xanthonema) form a distinct and previously unrecognized lineage within the class. The phylogenetic positions of Asterosiphon, Botrydium and Vaucheria are not robustly resolved, but our data suggest that these siphonous xanthophytes probably do not form a monophyletic group. Our results imply that Vaucheria is only distantly related to other xanthophytes we have examined. Nucleotide sequence divergence values among Vaucheria species were found to be equal to, or greater than, those observed between other xanthophyte species that are classified in different families or orders. Furthermore, our trees do not always support the infrageneric system of classification for Vaucheria species, which is based primarily upon antheridial features.
SEASONAL VARIATIONS IN PHYTOPLANKTON COMMUNITIES OF AN EPHEMERAL POND SYSTEM IN SOUTHEASTERN VIRGINIA
Authors: Kokolis M.R.
Published: March 2003

The Grafton Ponds Natural Area is a 151 hectare preserve in York County, Virginia, approximately 56km north of the City of Norfolk. The preserve contains over 40 ephemeral ponds. These ponds which are filled seasonally by precipitation and groundwater discharge, are typically wet from late fall through late spring or early summer. Pond size varies from 0.1 to 2 ha, and depths range from 4 cm to 3 meters. The first phase of this study was to examine the physical and chemical characteristics of five of these ponds, including pond size and depth, inundation period, water temperature, pH, and phosphate and ammonium concentrations. The second phase, which is currently underway, is to examine the phytoplankton assemblages, relating differences in the phytoplankton populations to the varying physical and chemical characteristics of the ponds. To date, analysis indicates Chlorophytes and Cyanobacteria as dominant groups in the winter and spring with diatoms becoming more abundant in the late summer and fall. Periodic Dinoflagellate blooms also occur. Analysis also indicates rapid turnover of species from month to month.