bluuebunny/crossref_metadata_2025 huggingface dataset:
Spike Firing in the Lateral Cerebellar Cortex Correlated With Movement and Motor Parameters Irrespective of the Effector Limb
Authors: Greger Bradley , Norris Scott A. , Thach W. Thomas
Published: January 2004

Neuronal signals in the lateral aspect of the macaque cerebellar cortex were studied during a visually guided reaching task. During the performance of this task, the firing rate of most neurons was significantly modulated when reaching with either the ipsilateral or the contralateral arm. In some of these reach-modulated cells, we found that spike firing was correlated with the direction and speed of the reach. These correlations with motor parameters were present during reaching with either the ipsilateral or the contralateral arm. Based on these observations we suggest that spike firing in the lateral cerebellum was correlated with movement and motor parameters irrespective of the effector limb.
Functional Imaging of the Human Lateral Geniculate Nucleus and Pulvinar
Authors: Kastner Sabine , O'Connor Daniel H. , Fukui Miki M. , Fehd Hilda M. , Herwig Uwe , Pinsk Mark A.
Published: January 2004

In the human brain, little is known about the functional anatomy and response properties of subcortical nuclei containing visual maps such as the lateral geniculate nucleus (LGN) and the pulvinar. Using functional magnetic resonance imaging (fMRI) at 3 tesla (T), collective responses of neural populations in the LGN were measured as a function of stimulus contrast and flicker reversal rate and compared with those obtained in visual cortex. Flickering checkerboard stimuli presented in alternation to the right and left hemifields reliably activated the LGN. The peak of the LGN activation was found to be on average within ±2 mm of the anatomical location of the LGN, as identified on high-resolution structural images. In all visual areas except the middle temporal (MT), fMRI responses increased monotonically with stimulus contrast. In the LGN, the dynamic response range of the contrast function was larger and contrast gain was lower than in the cortex. Contrast sensitivity was lowest in the LGN and V1 and increased gradually in extrastriate cortex. In area MT, responses were saturated at 4% contrast. Response modulation by changes in flicker rate was similar in the LGN and V1 and occurred mainly in the frequency range between 0.5 and 7.5 Hz; in contrast, in extrastriate areas V4, V3A, and MT, responses were modulated mainly in the frequency range between 7.5 and 20 Hz. In the human pulvinar, no activations were obtained with the experimental designs used to probe response properties of the LGN. However, regions in the mediodorsal right and left pulvinar were found to be consistently activated by bilaterally presented flickering checkerboard stimuli, when subjects attended to the stimuli. Taken together, our results demonstrate that fMRI at 3 T can be used effectively to study thalamocortical circuits in the human brain.
Aging and Rhythmical Force Output: Loss of Adaptive Control of Multiple Neural Oscillators
Authors: Sosnoff Jacob J. , Vaillancourt David E. , Newell Karl M.
Published: January 2004

The current study examined the influence of aging on the oscillatory activity of a population of motor units during rhythmical force production. Previously, it has been shown that aging humans have greater low-frequency and less high-frequency electromyographic (EMG) activity during constant and slow ramp force contractions. We hypothesized that more rapid force contractions would reverse the established finding of reduced high- and greater low-frequency EMG activity to greater high- and reduced low-frequency EMG activity in older adults. Intramuscular EMG activity and effector force were recorded while 45 human subjects (20–31 and 60–88 yr of age) rhythmically produced force at four distinct frequencies (1–4 Hz) and two force levels (5 and 25% maximal voluntary contraction). Spectral and coherence analyses were performed on the force output and EMG activity. In the 3- and 4-Hz targets, the older adults had greater 35- to 50-Hz and reduced 0- to 5-Hz EMG activity compared with the young adults. There was greater EMG-force coherence in the 0- to 5-Hz bandwidth for the young subjects. No systematic age difference in the phase relationship between the EMG and force signals were found. Higher frequency force contractions reversed the previously established aging differences in the relative contribution of low- and high-frequency EMG activity. Thus the frequency properties of the task goals channel the relative contribution of low and high EMG activity. Furthermore, it is proposed that aging humans lose the adaptive capability to coordinate the excitatory and inhibitory activity of multiple neural oscillators.
Common Input to Motor Neurons Innervating the Same and Different Compartments of the Human Extensor Digitorum Muscle
Authors: Keen Douglas A. , Fuglevand Andrew J.
Published: January 2004

Short-term synchronization of active motor units has been attributed in part to last-order divergent projections that provide common synaptic input across motor neurons. The extent of synchrony thus allows insight as to how the inputs to motor neurons are distributed. Our particular interest relates to the organization of extrinsic finger muscles that give rise distally to multiple tendons, which insert onto all the fingers. For example, extensor digitorum (ED) is a multi-compartment muscle that extends digits 2–5. Given the unique architecture of ED, it is unclear if synaptic inputs are broadly distributed across the entire pool of motor neurons innervating ED or segregated to supply subsets of motor neurons innervating different compartments. Therefore the purpose of this study was to evaluate the degree of motor-unit synchrony both within and across compartments of ED. One hundred and forty-five different motor-unit pairs were recorded in the human ED of nine subjects during weak voluntary contractions. Cross-correlation histograms were generated for all of the motor-unit pairs and the degree of synchronization between two units was assessed using the index of common input strength (CIS). The degree of synchrony for motor-unit pairs within the same compartment (CIS = 0.7 ± 0.3; mean ± SD) was significantly greater than for motor-unit pairs in different compartments (CIS = 0.4 ± 0.22). Consequently, last-order synaptic projections are not distributed uniformly across the entire pool of motor neurons innervating ED but are segregated to supply subsets of motor neurons innervating different compartments.
Acute Modulation of Adrenal Chromaffin Cell BK Channel Gating and Cell Excitability by Glucocorticoids
Authors: Lovell Peter V. , King Jonathan T. , McCobb David P.
Published: January 2004

Although adrenal glucocorticoids cortisol and corticosterone (CORT) have numerous “genomic” effects on adrenomedullary chromaffin cells, acute modulatory actions remain largely unknown, despite rapid stress-related changes in secretion. We report that 1 μM glucocorticoids rapidly modulate gating of chromaffin cell BK channels and action potential firing. In general, CORT, or the analog dexamethasone (DEX), increased channel activity in inside-out bovine patches, an effect not blocked by the glucocorticoid receptor (GR) antagonist RU38486. By contrast, these steroids could profoundly inhibit BK activation in many rat patches, while facilitating activation in others. We show that BK inhibition arises from a negative shift in the voltage dependence of BK inactivation paralleling that for activation. We report that rat cells characteristically exhibit greater repetitive firing ability than bovine cells in the absence of glucocorticoids. In both species, steroid application typically increased firing responses to smaller current injections, attributable to BK-enhanced repolarization and Na+ channel deinactivation. However, in rat cells, where BK inactivation is generally faster and more complete, glucocorticoids tended to dampen responses to stronger stimuli. Thus, in the context of natural variation in BK gating, glucocorticoids can either promote or limit firing responses. We suggest that steroids exploit BK gating variety to tailor catecholamine output in a species- and context-specific fashion.
Tracking the Moveable Feast: Sonomicrometry and Gastrointestinal Motility
Authors: Adelson David W. , Million Mulugeta
Published: January 2004

Ultrasonomicrometry measures distance between piezoelectric crystals based on transmission time of ultrasound bursts. It allows monitoring of coordinated motion of small and delicate tissues, including gastrointestinal sphincters. Its suitability for motility studies in small animals such as mice suggests that its use in gastrointestinal studies will increase in coming years.
Age-dependent hypothalamic expression of neuropeptides in wild-type and melanocortin-4 receptor-deficient mice
Authors: Arens Janine , Moar Kim M. , Eiden Sandra , Weide Karin , Schmidt Ingrid , Mercer Julian G. , Simon Eckhart , Korf Horst-W.
Published: February 2004

In young (35- to 56-day-old) and middle-aged (9-mo-old) wild-type (+/+) and melanocortin-4 receptor (MC4R)-deficient (+/−, −/−) mice, expressions of neuropeptide Y (NPY), agouti-related protein (AGRP), pro-opiomelanocortin (POMC), and cocaine-and-amphetamine-regulated transcript (CART) were analyzed in the arcuate nucleus (ARC) and adjacent regions comprising the dorsomedial (DMN) and ventromedial (VMN) nucleus. In the ARC of young mice, NPY and AGRP expression increased and POMC and CART expression decreased with body fat content. Adjusting for the influence of body fat content by ANCOVA showed that the levels of NPY, POMC, and CART were highest and of AGRP lowest in young −/− mice. In the middle-aged mice, feedback from body fat content was weakened. For −/− mice ANCOVA revealed higher NPY and AGRP, lower POMC, and unchanged CART expression levels relative to young −/− mice. In the DMN and VMN, POMC and AGRP signals were absent at each age. CART was expressed in the DMN independent of age, fat content, and genotype. For NPY expression, an age-dependent induction was found in the DMN and VMN; it was absent in the young but present in the middle-aged mice, showing close positive correlations between body fat content and the numbers of NPY-labeled cells which were further enhanced in −/− mice. Thus MC4R deficiency augments age-induced NPY expression in the DMN and VMN with no feedback from body fat content. Negative feedback control by body fat content on ARC neuropeptide expression is present in young animals but vanishes with age and is modulated by MC4R deficiency.
Evaluation of common gene expression patterns in the rat nervous system
Authors: Kaiser Sergio , Nisenbaum Laura K.
Published: February 2004

In the postgenomic era, integrating data obtained from array technologies (e.g., oligonucleotide microarrays) with published information on eukaryotic genomes is beginning to yield biomarkers and therapeutic targets that are key for the diagnosis and treatment of disease. Nevertheless, identifying and validating these drug targets has not been a trivial task. Although a plethora of bioinformatics tools and databases are available, major bottlenecks for this approach reside in the interpretation of vast amounts of data, its integration into biologically representative models, and ultimately the identification of pathophysiologically and therapeutically useful information. In the field of neuroscience, accomplishing these goals has been particularly challenging because of the complex nature of nerve tissue, the relatively small adaptive nature of induced-gene expression changes, as well as the polygenic etiology of most neuropsychiatric diseases. This report combines published data sets from multiple transcript profiling studies that used GeneChip microarrays to illustrate a postanalysis approach for the interpretation of data from neuroscience microarray studies. By defining common gene expression patterns triggered by diverse events (administration of psychoactive drugs and trauma) in different nerve tissues (telencephalic brain areas and spinal cord), we broaden the conclusions derived from each of the original studies. In addition, the evaluation of the identified overlapping gene lists provides a foundation for generating hypotheses relating alterations in specific sets of genes to common physiological processes. Our approach demonstrates the significance of interpreting transcript profiling data within the context of common pathways and mechanisms rather than specific to a given tissue or stimulus. We also highlight the use of gene expression patterns in predictive biology (e.g., in toxicogenomics) as well as the utility of combining data derived from multiple microarray studies that examine diverse biological events for a broader interpretation of data from a particular microarray study.
Transcriptional profile of postmortem skeletal muscle
Authors: Sanoudou Despina , Kang Peter B. , Haslett Judith N. , Han Mei , Kunkel Louis M. , Beggs Alan H.
Published: January 2004

Autopsy specimens are often used in molecular biological studies of disease pathophysiology. However, few analyses have focused specifically on postmortem changes in skeletal muscles, and almost all of those investigate protein or metabolic changes. Although some structural and enzymatic changes have been described, the sequence of transcriptional events associated with these remains unclear. We analyzed a series of new and preexisting human skeletal muscle data sets on ≃12,500 genes and expressed sequence tags (ESTs) generated by the Affymetrix U95Av2 GeneChips from seven autopsy and seven surgical specimens. Remarkably, postmortem specimens (up to 46 h) revealed a significant and prominent upregulation of transcripts involved with protein biosynthesis. Additional upregulated transcripts are associated with cellular responses to oxidative stress, hypoxia, and ischemia; however, only a subset of genes in these pathways was affected. Overexpression was also seen for apoptosis-related, cell cycle regulation/arrest-related, and signal transduction-related genes. No major gene expression differences were seen between autopsy specimens with <20-h and 34- to 46-h postmortem intervals or between pediatric and adult cases. These data demonstrate that, likely in response to hypoxia and oxidative stress, skeletal muscle undergoes a highly active transcriptional, and possibly, translational phase during the initial 46-h postmortem interval. Knowledge of these changes is important for proper interpretation of gene expression studies utilizing autopsy specimens.
Nutritional genomics
Authors: Stover Patrick J.
Published: January 2004

The integration of genomics into nutritional sciences has illuminated the complexity of genome responses to nutritional exposures while offering opportunities to increase the effectiveness of nutritional interventions, both clinical and population based. Nutrients elicit multiple physiological responses that affect genome stability, imprinting, expression, and viability. These effects confer both health benefits and risks, some of which may not become apparent until later in life. Nutritional genomics challenges us to understand the reciprocal and complex interactions among the human genome and dietary components in normal physiology and pathophysiology. Understanding these interactions will refine current definitions of benefit and risk and lead to the establishment of dietary recommendations that have a high predictive value, minimize the risk of unintended consequences, and account for the modifying effects of human genetic variation. Furthermore, nutritional genomics will enable the design of effective dietary regimens for the prevention and management of complex chronic disease. This review focuses on new perspectives that have been presented to the nutritional sciences by the advent of genomics, and new challenges that demand attention because of their potential impact on, and immediate translation into, current public health nutrition recommendations and interventions.
Structural Contributions to Short-Term Synaptic Plasticity
Authors: XU-FRIEDMAN MATTHEW A. , REGEHR WADE G.
Published: January 2004

Xu-Friedman, Matthew A., and Wade G. Regehr. Structural Contributions to Short-Term Synaptic Plasticity. Physiol Rev 84: 69–85, 2004; 10.1152/physrev.00016.2003.—Synaptic ultrastructure is critical to many basic hypotheses about synaptic transmission. Various aspects of synaptic ultrastructure have also been implicated in the mechanisms of short-term plasticity. These forms of plasticity can greatly affect synaptic strength during ongoing activity. We review the evidence for how synaptic ultrastructure may contribute to facilitation, depletion, saturation, and desensitization.
A Systematic Review of Several Potential Non-Genetic Risk Factors for Multiple Sclerosis
Authors: Coo H. , Aronson K.J.
Published: January 2004

We reviewed the literature published in the English language to determine the weight of evidence for several potential non-genetic risk factors for multiple sclerosis, including solar ultraviolet radiation (UVR), sex hormones and dietary fat/fatty acids. We ranked the plausibility of each factor and graded the methodological rigour of case-control and cohort studies to determine whether there was a sufficient number of high-quality studies to weigh the evidence. Based on our criteria, the plausibility for solar UVR and sex hormones is good and fair for dietary fat/fatty acids. However, the body of epidemiologic evidence is insufficient for these three sets of risk factors. We did not find a sufficient number of methodologically rigorous studies to weigh the evidence for any of the potential risk factors we examined.
Association between Symptoms Reported in a Population Questionnaire and Future Ischemic Stroke: The ARIC Study
Authors: Chambless Lloyd E. , Toole James F. , Nieto F. Javier , Rosamond Wayne , Paton Catherine
Published: January 2004

The association between computer diagnosis derived from a symptom questionnaire and onset of first hospitalized ischemic stroke during follow-up for up to 11 years has been assessed for 11,804 participants in the Atherosclerosis Risk in Communities Study who had no baseline history of stroke. Of these participants, 578 reported prior positive transient ischemic attack/stroke symptoms, and 265 strokes occurred during the years 1987–1998. Adjusted for age, locale, sex, and race, persons with self-reported baseline symptoms had 2.8 times the hazard rate for incident ischemic stroke of those without symptoms, with 95% confidence interval 1.9–4.1. Greater relative risk was found among younger individuals, women, African-Americans, persons not current smokers, and those with lower white blood cell count.
Cohort Study of Exposure to Environmental Tobacco Smoke and Risk of First Ischemic Stroke and Transient Ischemic Attack
Authors: Iribarren Carlos , Darbinian Jeanne , Klatsky Arthur L. , Friedman Gary D.
Published: January 2004

The independent effect of exposure to environmental tobacco smoke (ETS; passive smoking) on the risk of stroke is not well established. We performed a cohort study among 27,698 lifelong nonsmokers with no prior history of stroke, 62% women, aged 30–85 years at enrollment (1979–1985). Self-reported ETS exposure at home and outside home (in hours/week) and stroke risk factors were collected at a health plan in San Francisco and Oakland. Follow-up for hospitalization and death was available through the end of 2000 (median = 16 years). In multivariate analysis adjusting for age, race/ethnicity, educational attainment, marital status, hypertension, diabetes and serum total cholesterol, ETS exposure at home of 20 h or more/week (in relation to <1 h/week) was associated with a 1.29-fold (95% CI 0.75–2.20) and a 1.50-fold (95% CI 1.07–2.09) increased risk of first ischemic stroke among men and women, respectively. No significant associations were found between ETS exposure outside home and ischemic stroke or between exposure to ETS at home or out of home and the risk of transient ischemic attack. Although potentially important confounders (such as dietary habits) were not included in the analysis, high-level ETS exposure at home was independently associated with increased risk of first ischemic stroke among never-smoking women.
Cognitive Impairment and Dementia 20 Months after Stroke
Authors: Lindén Thomas , Skoog Ingmar , Fagerberg Björn , Steen Bertil , Blomstrand Christian
Published: January 2004

Background and Purpose: Dementia is common after stroke, but the dementia syndrome does not cover the whole spectrum of cognitive impairment. Our aim was to quantify and compare dementia and cognitive impairments in elderly patients 1.5 years after stroke and a matched normal population. Subjects and Methods: We examined dementia and cognitive impairments in 149 out of an initial total of 243 acute stroke patients after a mean 20 months. Inclusion criteria were age ≧70 years, not living in an institution and no previous cerebral lesion. The patients’ mean age was 81 years. Five controls matched by age and gender and fulfilling the same exclusion criteria were selected for each patient (n = 745) from a population-based survey in the same area. Dementia was diagnosed according to the DSM-III-R criteria, and impairments in different dimensions of cognitive function were assessed. Results: The prevalence of dementia was 28% in the stroke patients and 7.4% in the controls (OR 4.7; 95% CI 3.0–7.5). Seventy-two percent of the patients had cognitive impairments compared to 36% in the controls. Cognitive impairments were more common in nondemented stroke patients than in nondemented controls: 61 vs. 31% (OR 3.5; 95% CI 2.3–5.3). The risk increase attributable to stroke was highest for patients below 80 years of age. Conclusions: Stroke confers an increased risk of dementia and cognitive impairments in the elderly, especially in the younger ones. Apraxia is the most frequent neuropsychiatric impairment after stroke. The concept of dementia does not describe cognitive impairments well, since it underestimates their extent not only after stroke but also in normal ageing.
A Follow-Up Analysis of Transient Ischemic Attack Patients Suggests Unsatisfactory Disease Management and Possible Underutilization of Carotid Endarterectomy in Lazio, Italy
Authors: Saitto Carlo , Ancona Carla , Fusco Danilo , Vantaggiato Giampiero , Arcà Massimo , Perucci Carlo A.
Published: January 2004

We evaluated the disease management of transient ischemic attack in patients admitted to Lazio hospitals from July 1997 to June 1998. We assessed the effects of patient characteristics including chronic comorbidities on the use of diagnostic procedures, endarterectomy, and on the risk of adverse cerebrovascular outcome or death. There were 2,608 patients in the study who were followed up over a 18- to 30-month period. Carotid surgery was performed on 1.15% of the subjects, total mortality was 34.7 per 1,000 person-years and adverse cerebrovascular outcome was observed in 38.1 per 1,000 person-years. Chronic comorbidities did affect the mortality rate and the rate of adverse outcome, but not the rate of endarterectomies. Carotid surgery was infrequently performed in study subjects. It seems that this potentially stroke-preventive treatment was not offered to suitable candidates in many instances.
Validity and Reliability of the ‘Ten Questions’ Questionnaire for Detecting Moderate to Severe Neurological Impairment in Children Aged 6–9 Years in Rural Kenya
Authors: Mung’ala-Odera V. , Meehan R. , Njuguna P. , Mturi N. , Alcock K. , Carter J.A. , Newton C.R.J.C.
Published: January 2004

Background: The ‘Ten Questions’ Questionnaire (TQQ) is used to detect severe neurological impairment in children living in resource-poor countries. Its usefulness has been established in Asia and the Caribbean, but there are a few published studies from Africa. We evaluated the TQQ as part of a larger study of neurological impairment in a rural community, on the coast of Kenya. Methods: The study was conducted in two phases from June 2001 to May 2002; in phase one, a community household screening of 10,218 children aged 6–9 years using the TQQ was performed. Phase two involved a comprehensive clinical and psychological assessment of all children testing positive on the TQQ (n = 810) and an equivalent number of those testing negative (n = 766). Data were interpreted using the impairment-specific approach. Results: Overall, the sensitivity rates for screening the different impairments were: cognitive (70.0%), motor (71.4%), epilepsy (100%), hearing (87.4%) and visual (77.8%). All the specificity rates were greater than 96%. However, the positive predictive values were low, and ranged from 11 to 33%. Conclusions: These results are similar to those from other continents and provide evidence that the TQQ can be used to compare the epidemiology of moderate/severe impairment in different parts of the world. Furthermore, the TQQ can be used to screen for moderately/severely impaired children in resource-poor countries; however, the low positive predictive values mean that other assessments are required for confirmation.
Accuracy of Death Certificates for Amyotrophic Lateral Sclerosis Varies Significantly from North to South of Italy: Implications for Mortality Studies
Authors: Ragonese Paolo , Filippini Graziella , Salemi Giuseppe , Beghi Ettore , Citterio Antonietta , D’Alessandro Roberto , Marini Carmine , Monsurrò Maria Rosaria , Aiello Isidoro , Morgante Letterio , Tempestini Antonella , Fratti Cesare , Ragno Michele , Pugliatti Maura , Epifanio Antonio , Testa Daniela , Savettieri Giovanni
Published: January 2004

Objective: To evaluate the accuracy of death certificates (DCs) for amyotrophic lateral sclerosis (ALS) in different parts of Italy. Studies based on DC diagnosis for ALS have shown a reduced mortality comparing northern with southern Italy. These data are in contrast with results from other surveys on the incidence of ALS performed in Italy and other countries. Methods: Archives of neurological clinics from northern (Milano, Monza, Pavia, and Bologna) and southern Italy including islands (Napoli, Sassari, Palermo, and Messina) were searched for patients discharged with a diagnosis of ALS in the period 1970–1995. Subjects affected by definite/probable ALS according to the Scottish Motor Neuron Disease Research Group diagnostic criteria were included. DCs were obtained from the vital statistic bureau. True positive rates (TPRs) and 95% confidence intervals (CIs) for proportions were calculated for northern and southern Italy separately. Multiple logistic regression analysis was performed according to gender, age at onset, age and year of death, and interval between onset and death. Results: We found 651 patients affected by definite/probable ALS; 573 of them had died by December 31, 1996. DCs were available for 566 subjects (411 from northern Italy and 155 from southern Italy). TPR was 66.7% (95% CI 61.9–71.2) for northern Italy and 51.6% (95% CI 43.5–59.7) for southern Italy (χ2 = 10.9, p = 0.001). Logistic regression analysis showed an association between a lower accuracy of DCs and the interval between onset of symptoms and death. TPR calculations considering different death periods (1970–1982 and 1983–1996) showed comparable rates of accuracy over time. Conclusions: Mortality statistics based on official death records do not accurately reflect interregional mortality for ALS in Italy.
Consistency of Primary Brain Tumor Diagnoses and Codes in Cancer Surveillance Systems
Authors: Castillo Monette S. , Davis Faith G. , Surawicz Tanya , Bruner Janet M. , Bigner Sandra , Coons Stephen , Bigner Darell D.
Published: January 2004

High-quality cancer registry data are essential for assessing trends in incidence rates. This study evaluated the consistency of brain tumor surveillance data using a random sample of cases from the Connecticut Tumor Registry. Three neuropathologists independently and blindly reviewed tumor slides from 204 cases and a nosologist blindly reviewed and assigned International Classification of Diseases for Oncology (ICD-O) codes to 326 cases. For the pathology review, absolute concordance was as high as 81% for all primary brain tumors. Absolute concordance rates were high for nerve sheath (89%), meningioma (95%), and pituitary (95%) tumors. Rates were much lower for malignant tumors. ICD-O coding of malignant brain tumors is of relatively high quality with the exception of mixed gliomas and unspecified tumors. A high level of consistency for nonmalignant brain tumor diagnoses suggests that rates for these tumors, when actively reported to a surveillance system, can be of high quality.
Irreversible Inhibition of [3H]Glycine Transport into Channel Catfish Erythrocytes by Thiol Group Modifiers
Authors: McCormick Sara J. , Tunnicliff Godfrey
Published: January 2004

Erythrocytes can take up amino acids from the blood by using a variety of transport systems. GLYT is a key transport protein in the plasma membrane responsible for the Na2+-dependent uptake of glycine needed for glutathione biosynthesis. Certain cysteine-specific compounds, particularly mercuric chloride and 5,5′-dithiobis(2-nitrobenzoate), irreversibly inhibited the [3H]glycine transport via GLYT by red blood cells isolated from channel catfish. Bimolecular rate constants (k2) of 0.556 (mmol/l)–1 min–1 and 0.032 (mmol/l)–1 min–1, respectively, were calculated for the two inhibitors. Addition of 2-mercaptoethanol 1 min after the initiation of inactivation by mercuric chloride stopped further inactivation, but did not reverse the inhibition. The presence of glycine, but not Na+ ions, during the preincubation of the cells with each inhibitor markedly reduced the degree of inhibition. Thus cysteinyl residues within the transport protein appear to be vital for the binding and uptake of glycine by channel catfish erythrocytes.
Effects of HR780, a Novel 3-Hydroxy-3-Methylglutaryl Coenzyme A Reductase Inhibitor, in Watanabe Heritable Hyperlipidemic Rabbits and Cholesterol-Fed Rabbits
Authors: Wajima Teruaki , Makita Shigeki , Oshima Kenichi
Published: January 2004

The aim of this study was to evaluate the effects of (+)-(E)-6S-(2-(4-(4-fluorophenyl)-2-(1-methylethyl)-6-phenylpyridin-3-yl)ethenyl)-4R-hydroxy-3,4,5,6-tetrahydro-2H-pyran-2-one (HR780), a novel 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitor, on hypercholesterolemia in Watanabe heritable hyperlipidemic (WHHL) rabbits and rabbits fed a diet with 1% cholesterol, in comparison with the effects of simvastatin. Each drug was administered orally to WHHL rabbits for 24 weeks and to 1% cholesterol-fed rabbits for 10 weeks. In WHHL rabbits, HR780 at doses of 1, 2.5 and 5 mg/kg/day reduced the plasma total cholesterol level by 15, 24 and 20%, respectively. In contrast, simvastatin at 5 mg/kg/day lowered the level by 23%. In 1% cholesterol-fed rabbits, HR780 (1 and 2.5 mg/kg/day) was found to inhibit the increases in the plasma total cholesterol and phospholipid levels and liver cholesterol contents in a dose-dependent manner. Simvastatin (5 mg/kg/day) also inhibited their increase. Neither HR780 nor simvastatin increased the contents of cholesterol and total bile acid in the gallbladder bile. In conclusion, long-term treatment with HR780 reduced the plasma cholesterol level in WHHL rabbits and 1% cholesterol-fed rabbits, and decreased the liver cholesterol contents in 1% cholesterol-fed rabbits.
Effects of Neuropeptides on the Sumatriptan-Disturbed Circulation in the Optic Nerve Head of Rabbits
Authors: Gaspar M.N. , Fontes Ribeiro C.A. , Cunha-Vaz J.G. , Macedo T.R.A.
Published: January 2004

The purpose of this work was to study ‘in vivo’ the vascular responses of retinal vessels of New Zealand white rabbits to substance P (SP), neurokinin A (NKA), neurokinin B (NKB), senktide, capsaicin (CAPS), and calcitonin gene related peptide (CGRP) before and after selective antagonist administration. We examined the effects of these neuropeptides on the normal circulation in the optic nerve head of the rabbit. Drugs were injected via pars plana through a micropipette system. Ten minutes before perivascular injection of 10 nmol/l sumatriptan (to contract the vessel), a selective antagonist or its solvent was administered. Then, cumulative injection of the agonist was performed. The other eye was used as control. Direct measurement of retinal arteriole diameters was performed using digital angiography. The quantification of the relaxing effect is expressed as percentage related to the precontracted vascular diameter. Microinjection of SP (NK1 receptor agonist) up to 10 nmol/l induced a dose-dependent arteriolar dilating effect [Emax (mean ± SEM) 21.3 ± 2.3%]. After the perivascular preinjection of 1 nmol/l L-668,169 or 1 nmol/l L-733,060 (NK1 receptor antagonists), the SP dose-response curve was shifted to the right. The same results were obtained with NKA (NK2 receptor agonist) which induced the most potent effect of all neuropeptides (Emax 53.3±2.5%). The NK2 receptor antagonists L-659,877 and GR 159897 (1 nmol/l) strongly inhibited this arteriolar vasodilation. As for CGRP, doses up to 10 nmol/l induced a marked vasodilation (Emax 41.1±0.4%) which decreased after microinjection of the selective antagonist CGRP8-37. The NK3 receptor agonists (senktide and NKB) showed a minor vasodilating effect (Emax 5.1±1.2 and 8.0±0.9%, respectively). On the contrary, CAPS showed a marked dose-dependent vasodilating effect (Emax 43.2±2.9%), antagonized by the tachykinin receptor antagonists and CGRP8-37. These results suggest, for the first time, the presence of NK1, NK2, and CGRP receptors on the retinal arteriolar wall of the rabbit.
Overexpression of TRAP in the Enamel Matrix Does Not Alter the Enamel Structural Hierarchy
Authors: Paine Michael L. , Zhu Dan-Hong , Luo Wen , Snead Malcolm L.
Published: January 2004

The secreted, full-length amelogenin is the dominant protein of the forming enamel organ. As enamel mineralization progresses, amelogenin is quickly subjected to proteolytic activity, and eliminated from the enamel environment. Mature enamel contains only traces of structural proteins, including enamelin and the sheath protein ameloblastin. In addition, a proteolytic fragment of amelogenin, known as the tyrosine-rich amelogenin peptide or TRAP, is present in low but isolatable quantities. By overexpressing TRAP during enamel development we sought to determine if such overexpression would result in structural alterations to the mature enamel. We reasoned that overexpressing a protein associated with enamel maturation, at an inappropriate developmental stage, would result in alterations to the enamel protein assembly and hence, alterations in enamel structure and morphology. As judged by transmission and scanning electron microscopy, the enamel formed by overexpressing TRAP showed little morphological differences when compared to the enamel of normal nontransgenic animals. Based on scanning electron-microscopic images, there was modest hypomineralization evident in the interrod enamel of the TRAP-overexpressing animals. However, this finding was inconsistent and inconsequential from a structural and functional perspective. From these results it appears that additional amounts of TRAP protein in the immature enamel matrix are not sufficient to alter the properties of the enamel extracellular matrix to an extent that the hierarchical structure of mature enamel is altered.
Identification of Potential Modifiers of Runx2/Cbfa1 Activity in C2C12 Cells in Response to Bone Morphogenetic Protein-7
Authors: Gu Keni , Zhang Lixin , Jin Taocong , Rutherford R. Bruce
Published: January 2004

Treatment with BMP-7 causes a shift in the differentiation pathway from myoblastic to osteoblastic in C2C12 mouse myoblast precursor cells in vitro. The underlying molecular mechanism is largely unknown. BMP-7 at 200 ng/ml completely inhibited myotube formation in C2C12 cells and dramatically induced alkaline phosphatase activity up to 20-fold when compared to untreated cells by day 12 in culture. The level of Runx2/Cbfa1 mRNA, a bone-specific transcription factor, was also stimulated up to 6-fold by BMP-7 with a peak at 24 h. In addition BMP-7 treatment stimulated a 55-fold increase in osteocalcin mRNA as early as 24 h after treatment. A novel finding was that the expression of the chondrocyte markers Sox9 and type II collagen was increased as well. Runx2/Cbfa1 is a molecular switch for osteoblast differentiation. To initiate the study of modulators of Runx2/Cbfa1, such as kinases and cofactors, during osteoblastic differentiation of C2C12 cells treated by BMP-7 in vitro, microarray analyses of gene expressions were performed. Microarray data suggested that a total of 882 transcripts were either up- or downregulated at least 2-fold. Cluster analyses revealed 76 genes (including ESTs) with expression patterns that paralleled Runx2/Cbfa1. Thirteen of these 76 genes were initially selected as potential transcription modulators for further study; including CCAAT/enhancer binding protein delta, distal- less homeobox 1, forkhead box F2, insulin-like growth factor binding protein 4, an ortholog of human osteoclast stimulating factor 1 and p300/CBP-associated factor. Some transcription modulators have been associated with osteoblastic differentiation or interacted with Runx2/Cbfa1. Most of them have not been extensively studied in osteoblastic differentiation and in relationship to Runx2/Cbfa1. Thus, these studies identify potential regulators for Runx2/Cbfa1 and osteoblast differentiation. In addition, our data revealed for the first time that BMP-7 not only induced the expression of osteoblastic differentiation markers but also stimulated the expression of chondroblastic markers in C2C12 cells.
New Chondrocyte Genes Discovered by Representational Difference Analysis of Chondroinduced Human Fibroblasts
Authors: Yates Karen E. , Forbes Rachel L. , Glowacki Julie
Published: January 2004

This report includes a review of the potential for gene expression analyses to provide new information for solving problems in skeletal repair and regeneration. It focuses on two approaches: high-throughput gene array methods and representational difference analysis (RDA). The principles underlying these methods are presented with experimental tutorials and some applications. Second, this report includes a review of results from applying both approaches to an in vitro model of postnatal chondroinduction by demineralized bone powder (DBP). Human dermal fibroblasts (hDFs) cultured with DBP acquire a chondroblast phenotype and express cartilage-specific matrix proteins after 7 days. We used cDNA macroarrays and RDA to identify the genes that were altered prior to expression of the chondroblast phenotype, i.e., after only 3 days’ culture with DBP. Using a strategy of data management and reduction based upon biological functions, we reported several functional families of genes (cytoskeletal elements, protein synthesis/trafficking, and matrix molecules and their modifiers) that are upregulated during chondroinduction of hDFs. Together with histological and biochemical evidence of the chondroblast phenotype, the gene expression patterns indicate that there are specific stages of induced chondrocyte differentiation in this experimental system. Third, this report includes a new study, in which DBP-regulated genes were used as a data base to derive new information on the cell biology of chondrocytes. The objective was to determine whether a set of genes expressed during induction of chondrocyte differentiation is also expressed by mature articular chondrocytes. Our search of the literature for 59 of the DBP-regulated genes disclosed that expression of 20 of them (33%) had been documented in mature cartilage or chondrocytes. Of the 39 genes not previously documented in cartilage, 11 were tested by RT-PCR and all were found to be expressed in freshly isolated adult human chondrocytes. This review and these new data show how the strategy of high-throughput methods and functional data reduction can expand our knowledge of chondrocyte cell biology.
Forming a Multinucleated Cell: Molecules That Regulate Myoblast Fusion
Authors: Horsley Valerie , Pavlath Grace K.
Published: January 2004

In mammals, cell fusion occurs among a limited number of cell types: sperm and oocytes during fertilization, trophoblasts during placenta formation, macrophages during giant cell and osteoclast formation and myoblasts in the formation of myofibers and myotubes. The molecular mechanisms involved in these membrane fusion events largely are unknown. This review will focus on the known molecules that regulate myoblast fusion with an emphasis on a novel signaling pathway involving the calcium-regulated transcription factor NFATC2 in the regulation of myoblast fusion.
Elevated Vascular Endothelial Growth Factor in Keloids: Relevance to Tissue Fibrosis
Authors: Le Anh D. , Zhang Qunzhou , Wu Yidi , Messadi Diana V. , Akhondzadeh Anita , Nguyen Andrew L. , Aghaloo Tara L. , Kelly A. Paul , Bertolami Charles N.
Published: January 2004

Excessive scar or keloid shares common features of a benign dermal growth. Yet, in contrast to malignant tumor, a keloid does not expand beyond the dermis. What triggers the continuing growth of a benign lesion? Deficient or overabundant levels of vascular endothelial growth factor have been reported to contribute to impaired or excessive wound healing. Although numerous studies have examined the pathophysiology of impaired wounds, little information has been provided on mechanisms of exuberant healing. The molecular basis of keloid formation is governed by the interplay of cellular signaling pathways, specific target gene activation, and the nature of the microenvironment. Recent works have demonstrated an accumulation of hypoxia-inducible factor-1α protein in freshly biopsied keloid tissues, thus providing first evidence that a local state of hypoxia exists in keloids. Our findings and the findings of others support at least two plausible mechanisms implicated in the development of fibrotic wounds, a state of ongoing fibroplasia or inflammation and an excessive accumulation of extracellular matrix. This article will review recent works examining the potential role of vascular endothelial growth factor in keloid pathogenesis with particular focus on its involvement in the two proposed pathological processes, a prolonged inflammation and an altered balance in extracellular matrix metabolism.
Gene Therapy Approaches for Bone Regeneration
Authors: Franceschi Renny T. , Yang Shuying , Rutherford R. Bruce , Krebsbach Paul H. , Zhao Ming , Wang Dian
Published: January 2004

Gene therapy represents a promising approach for delivering regenerative molecules to specific tissues including bone. Several laboratories have shown that virus-based BMP expression vectors can stimulate osteoblast differentiation and bone formation in vivo. Both in vivo and ex vivo transduction of cells can induce bone formation at ectopic and orthotopic sites. Adenovirus and direct DNA delivery of genes encoding regenerative molecules can heal critical-sized defects of cranial and long bones. Although osteogenic activity can be demonstrated for individual BMP vectors, substantial synergies may be achieved using combinatorial gene therapy to express complimentary osteogenic signals including specific combinations of BMPs or BMPs and transcription factors. Further control of the bone regeneration process may also be achieved through the use of inducible promoters that can be used to control the timing and magnitude of expression for a particular gene. Using these types of approaches, it should be possible to mimic natural processes of bone development and fracture repair and, in so doing, be able to precisely control both the amount and type of bone regenerated.
Different Effects of BMP-2 on Marrow Stromal Cells from Human and Rat Bone
Authors: Osyczka Anna M. , Diefenderfer David L. , Bhargave Geeta , Leboy Phoebe S.
Published: January 2004

Bone morphogenetic proteins (BMPs) promote the differentiation of osteoprogenitor cells, and also induce osteogenesis in bone marrow stromal cells (MSC) from rats and mice. However, compared to results with animal models, BMPs are relatively inefficient in inducing human MSC to undergo osteogenesis, and are much less effective in promoting bone formation in human clinical trials. Previous studies indicated that, while human MSC respond to dexamethasone with elevated levels of the osteoblast marker alkaline phosphatase, most isolates of human MSC fail to show alkaline phosphatase induction in response to BMP-2, BMP-4, or BMP-7. Several other genes known to be induced by BMPs are appropriately regulated; thus, human MSC are capable of some BMP-activated signaling. Analysis of the BMP receptors ALK-3 and ALK-6 indicated that, although ALK-6 mRNA was not expressed in human MSC, overexpressing a constitutively active ALK-6 receptor did not induce elevated alkaline phosphatase. Real-time RT-PCR was used to investigate expression of several osteoblast-related transcription factors in MSC after 6 days’ exposure to BMP2 or dexamethasone. Msx-2, a transcription factor that has been reported to inhibit differentiation of osteoprogenitor cells, showed 10-fold elevation in BMP-2-treated human MSC, but not in BMP-2-treated rat MSC. Overexpression of Msx-2 in human and rat MSC, however, did not alter alkaline phosphatase levels, which suggests that absence of BMP-stimulated alkaline phosphatase was not caused by the BMP-2-induced increase in Msx-2. Although Runx2 isoforms have been implicated in control of osteoblast differentiation, levels of this transcription factor were unaffected by BMP treatment. Expression of the FKHR transcription factor, which has been reported to regulate alkaline phosphatase transcription in mouse cells, showed a modest increase in response to BMP-2, but a much greater increase in dexamethasone-treated cells. We propose that BMP regulation of the bone/liver/kidney alkaline phosphatase gene is indirect, requiring expression of new transcription factor(s) that behave differently in rodent and human MSC.
Optimal Degradation Rate for Collagen Chambers Used for Regeneration of Peripheral Nerves over Long Gaps
Authors: Harley B.A. , Spilker M.H. , Wu J.W. , Asano K. , Hsu H.-P. , Spector M. , Yannas I.V.
Published: January 2004

The experimental study of peripheral nerve regeneration has depended heavily on the use of a nerve chamber in which the stumps of the transected nerve are inserted. A large variety of chamber fillings and chamber types have been used in an effort to induce a higher quality of regeneration across the gap initially separating the two stumps. In this study we studied the morphology of nerves regenerated across a 15 mm gap following implantation of a series of five chambers. The chambers were fabricated from type I collagen and possessed identical pore volume fractions as well as average pore diameters, but differed in cross-link density continuously along the series. The residual mass of the implanted chambers at 9 weeks was observed to increase continuously with increasing cross-link density along the series, indicating a continuous decrease in degradation rate. The quality of regenerated nerves, determined by the number of large diameter fibers (A-fibers) per nerve, the average diameter of all axons and the ratio of area occupied by axons (N-Ratio), was superior at an intermediate level of chamber degradation rate. The maximal quality of peripheral nerve regeneration corresponded to an optimal degradation rate with an estimated chamber half-life of approximately 2–3 weeks following implantation. A speculative mechanistic explanation of the observed optimum focuses on the hypothetical role of cell and cytokine traffic that may take place through holes in the chamber generated by the degradation process. The data show the presence of a hitherto unreported optimal chamber degradation rate that leads to regenerated nerves of maximum quality.