International Journal of Neuroscience

TAN, ÜNER

doi: 10.1080/00207450500403306pmid: 16644515

A new reflex is described: middle-finger extensor reflex elicited by percussion of tendon insertion of musculus extensor digitorum communis in forearm. Following percussion using a reflex hammer, two EMG responses from the belly of the muscle were recorded: a short latency monosynaptic reflex with a latency of 31.4 ± 1.5 ms (M1), and a long-latency middle-finger reflex with a mean latency of 64.8 ± 6.31 ms (M2), the former being a monosynaptic extensor reflex, and the latter belonging to a spino-cortico-spinal reflex circuitry. It was suggested that the middle-finger extensor reflex elicited by radial nerve afferents and efferents (C7–C8) would be of clinical and theoretical importance.

TREMERE, LIISA A.; PINAUD, RAPHAEL

doi: 10.1080/00207450600592073pmid: 16644516

Inhibitory and excitatory transmission have been shown to be two dominant forces in the process of injury-induced cortical reorganization. However, the contributions of each individual neurotransmitter system have been difficult to characterize, mainly because they often affect overlapping domains of the reorganizing cell's receptive field (RF). The present work differentiates the effects of either neurotransmitter system by studying reorganizing neurons where pharmacological intervention directed at glutamatergic or GABAergic networks affected spatially non-overlapping subfields within a cell's RF. Microiontophoresis was used to apply glutamate and bicuculline, a selective GABA-A receptor antagonist, to cells in the deafferented cortex at various post-amputation times, that ranged from 2 to 37 weeks. It was found that at all post-amputation times studied, glutamate increased the neural activity that could be evoked from mechanical stimulation over the wound area, in addition to decreasing the threshold for activation. Disinhibition with bicuculline application often lowered the response threshold for subfields within the reorganized RF, usually located on the digits, and could also expand RF area. Interestingly, the effects of GABAergic transmission to the process of reorganization appeared later than those mediated through glutamatergic networks. These findings suggest that recruitment of inhibition in reorganizing cells relies on activity-dependent mechanisms, with reinstatement of GABAergic transmission being secondary to the formation of novel glutamatergic drives.

YILMAZ, M. BERTAN; KOÇ, A. FİLİZ; KASAP, HALİL; GÜZEL, A. İRFAN; SARICA, YAKUP; SÜLEYMANOVA, DİLARA

doi: 10.1080/00207450600592099pmid: 16644517

Friedreich's ataxia (FRDA), the most common subtype of early onset hereditary spinocerebellar ataxia (SCA), is an autosomal recessive neurodegenerative disorder caused by unstable GAA tri-nucleotide expansions in the first intron of FRDA gene located at 9q13-q21.1 position. Results of GAA repeat polymorphism in 80 Turkish SCA patients and 38 family members of 11 typical FRDA patients were reported. GAA triplet repeat size ranged from ∼7 to 34 in normal alleles and from ∼66 to 1300 in mutant alleles. Twenty six patients were homozygous for GAA expansion and size of expanded alleles differed from ∼425 to 1300 repeats. Children 2 and 6 years old (showing no ataxia symptoms) of one family had homozygous GAA expansions reaching ∼925 repeats. All 11 families studied had at least 1 afflicted child and 9 parents and 2 siblings were carrier (heterozygous) with mutant alleles ranging from 66 to 850 repeats. Family studies confirmed the meiotic instability and stronger effect of expansion in the smaller alleles on phenotype and a negative correlation between GAA repeat expansion size and onset-age of the disease.

HIRABAYASHI, KIYOKO; KOMAGATA, MASASHI; YAMADA, JINZO; ISSHIKI, ATSUSHI; WATANABE, YASUO

doi: 10.1080/00207450600592115pmid: 16644518

This article investigated the time response of COX II induction by traction of the cauda equina assessed by a quantified RT-PCR method. Under deep GOI anesthesia, male Wistar rats were fixed in the prone position and a laminectomy of the dorsal part of the first and second sacral vertebrae was performed. Following, COX II-mRNA levels in the cervical, thoracic, lumbar, sacral, and caudal segments were measured at 2, 4, 6, and 24 h after traction by a quantified RT-PCR method. After cauda equina traction, significant levels of COX II mRNA were detected in all segments of the spinal cord examined. Maximum levels in each segment were determined 4 h after traction of the cauda equina. Particularly in the sacrocaudal segments significantly higher levels of COX II mRNA were measured 24 h after traction. These results indicate that significant induction of spinal COX II mRNA was caused by cauda equina traction and that such induction plays a regulatory role in the nociceptive pain pathway.

ZEHRA MINBAY, FATMA; EYIGOR, OZHAN; ÇAVUSOGLU, ILKIN

doi: 10.1080/00207450600592123pmid: 16644519

The present study assessed if kainic acid activates oxytocinergic neurons and this activation is blocked by 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX). Dual immunohistochemistry for oxytocin and c-Fos showed that oxytocin neurons in SON and PVN express c-Fos following kainic acid administration, a significant increase when compared to the control group. Administration of CNQX prior to kainic acid caused a significant reduction. The results suggested the participation of non-NMDA receptors in the regulation of oxytocin neurons because the administration of kainic acid activates these neurons and this activation is blocked by CNQX administration.

ERBAŞ, BAHAR; ÜRESIN, YAĞIZ; ÖZEK, MEHMET; DOĞRU-ABBASOĞLU, SEMRA

doi: 10.1080/00207450600592131pmid: 16644520

This study investigated the effects of renin-angiotensin system (RAS) blockade on stress-induced changes of serum vascular endothelial growth factor (VEGF) and nitric oxide (NO) in mice. Chronic stress increased the serum NO levels significantly compared to control group (p = .0172). Valsartan, an angiotensin II receptor antagonist, alone, did not make significant difference versus control group. In chronic stress + valsartan group, serum NO levels decreased nonsignificantly compared to chronic stress group. There was a nonsignificant increase in serum VEGF levels after chronic stress. Valsartan alone or with chronic stress did not significantly affect the serum VEGF levels. In conclusion, there was no correlation between NO and VEGF changes during the stress response. In this respect, there may be other mechanisms to explain the stress-induced NO increase.

MILLER, JULIE M.; PLISKIN, NEIL H.

doi: 10.1080/00207450600592164pmid: 16644521

The progression of cognitive decline in Alzheimer's disease (AD) was studied by examining patterns of test performance on successive administrations of the Mattis Dementia Rating Scale (DRS) in a sample of 63 participants who were diagnosed with probable AD. Assessments were performed at intervals ranging approximately from 3 to 38 months apart. Results indicated that the pattern of progression and sequence of neuropsychological decline in AD is influenced by sex and age of disease onset. Results offered support for the clinical staging of AD and further substantiated the clinical utility of the Mattis Dementia Rating Scale in staging degree of dementia.

KARARIZOU, E.; DAVAKI, P.; KARANDREAS, N.; DAVOU, R.; VASSILOPOULOS, D.

doi: 10.1080/00207450600592180pmid: 16644522

In elderly patients, peripheral neuropathies are common and may lead to disability. In order to investigate the relative incidence of different polyneuropathies in the elderly focusing on the contribution of nerve biopsy to their diagnosis, the authors studied 74 patients over 65 years of age with clinical, laboratory, electrophysiological, and sural nerve biopsy findings of different types of polyneuropathy. Vasculitic polyneuropathy seemed to be the most common cause of disabling neuropathy in the elderly, followed by paraneoplasia and diabetes. The possible diagnosis of idiopathic axonal neuropathy in the nine cases with neuropathy of unknown origin is discussed.

CREWS, RYAN T.; KAMEN, GARY

doi: 10.1080/00207450600592198pmid: 16644523

This article investigated whether mental imagery training could reduce the detrimental effects produced by limb disuse. Subjects learned a task requiring fifth finger abduction. Motor-evoked potentials (MEPs) were obtained from the abductor digiti minimi muscle using transcranial magnetic stimulation. The arm was casted and the experimental group then practiced using imagery. After seven days, variable error scores increased. The immobilization treatment decreased MEP scores in both groups, with no difference between groups. It is concluded that limb immobilization produces a decrement in the area of motor cortex dedicated to this muscle as a result of disuse. Imagery failed to ameliorate the disuse-related changes.

ARDILA, ALFREDO; SURLOFF, CHERI

doi: 10.1080/00207450600592206pmid: 16644524

Different types of writing disorders associated with brain pathology have been described. Limited mention the writing disturbances associated with prefrontal pathology, however, is found. Clinical observations of patients not only with focal prefrontal pathology but also with other conditions affecting the frontal system (e.g., traumatic head injury, dementia) confirm the assumption that these patients present an overt decrease in the ability to express ideas in writing. It is proposed that complex aspects of writing, such as planning, narrative coherence, and maintained attention, are significantly disturbed in cases of impairments of executive functions. Frontal lobe patients not only have difficulties in keeping the effort required for writing, but also to organize the ideas in the written texts. The term dysexecutive agraphia is proposed to refer to this writing disorder. Three illustrative cases are presented. It is finally suggested that questions regarding the ability to write should be included in dementia questionnaires and executive functioning testing.