bluuebunny/crossref_metadata_2025 huggingface dataset:
Quantitative analysis of flagellar movement in hyperactivated and acrosome‐reacted golden hamster spermatozoa
Authors: Ishijima Sumio , Baba Shoji A. , Mohri Hideo , Suarez Susan S.
Published: August 2002

Caudal epididymal spermatozoa of golden hamsters were incubated in capacitation medium. Their movement patterns changed as they became hyperactivated and underwent the acrosome reaction. To understand the basic mechanism by which changes in movement pattern are brought about, digital image analysis was carried out on the flagellar movements recorded with a video system. The degree of flagellar bending increased with incubation time, especially in the proximal midpiece. The hyperactivated spermatozoa had remarkably asymmetrical flagellar waves of large amplitude because either the bends in the same direction as the hook of the head (referred as the “pro‐hook bend”) or the bends in the opposite direction to the hook of the head (referred as the “anti‐hook bend”) extremely increased their curvature; whereas, the acrosome‐reacted spermatozoa had relatively symmetrical flagellar waves of large amplitude because both the pro‐ and anti‐hook bends remarkably increased their curvature. Beat frequency significantly decreased while wavelength of flagellar waves increased after hyperactivation and further after the acrosome reaction. These results suggest that both extreme pro‐ and anti‐hook bends are essential in the acrosome‐reacted spermatozoa even though beat frequency decreased markedly.Mol. Reprod. Dev. 61: 376–384, 2002. © 2002 Wiley‐Liss, Inc.
Localization of plasminogen in the extracellular matrix of hamster eggs: Exogenous activation by streptokinase
Authors: Jiménez‐Díaz María , Roldán Mariela , Miceli Dora C.
Published: August 2002

The plasminogen activator (PA)/plasminogen/plasmin proteolytic system has begun to be taken into account in the fertilization process. In this study, we demonstrated the presence of plasminogen in the extracellular matrix (ECM) of hamster oocytes by indirect immunofluorescence and immunoperoxidase assays using human anti‐plasminogen. Plasminogen appeared first on the zona pellucida (ZP) of ovarian oocytes and later on the plasma membrane (PM) of oviducal eggs. This would suggest that oviducal oocytes modulate the expression of plasminogen binding sites on the PM. Human plasminogen as well as that of other species, known to be activated by streptokinase (SK), is rapidly converted to a plasmin‐SK complex. We demonstrated the rapid formation of a SK‐plasminogen complex that yields plasmin in the blood plasma of hamsters. Both the in vivo and in vitro SK treatment of eggs from superovulated female hamsters caused a decreased in the ZP dissolution time (ZPdt), probably either due to the proteolytic effect of plasmin or due to the SK‐Plasminogen. Extracellular proteolysis assays carried out on agar–casein plates confirmed the proteolytic activity of SK‐incubated eggs; the controls, on the contrary, failed to display a halo. These studies show that (1) superovulated hamster eggs contain plasminogen in their ECM, (2) oviducal eggs exhibit plasminogen on their PMs, indicating the presence of their corresponding binding sites, (3) in hamsters, SK, a non‐enzymatic exogenous protein would be capable of activating ECM plasminogen to plasmin, and (4) the complex SK‐plasminogen and/or the plasmin are capable of changing the ZPdt with α‐chymotrypsin. Mol. Reprod. Dev. 61:528–535, 2002. © 2002 Wiley‐Liss, Inc.
Effect of extracellular matrix proteins on in vitro testosterone production by rat Leydig cells
Authors: Diaz Emilce S. , Pellizzari Eliana , Meroni Silvina , Cigorraga Selva , Lustig Livia , Denduchis Berta
Published: August 2002

The aim of this study was to detect the effect of extracellular matrix (ECM) proteins on rat Leydig cell shape, adhesion, expression of integrin subunits and testosterone production, in vitro. Leydig cells isolated from adult rats were cultured on plates uncoated or coated with different concentrations of laminin‐1, fibronectin, or type IV collagen in the presence or absence of hCG for 3 or 24 hr. A significant increase of cell adhesion and of α3, α5, and β1 integrin subunit expression was observed when cells were cultured on ECM proteins, compared to those grown on uncoated plates. Leydig cells cultured on glass coverslips coated with ECM proteins for 24 hr exhibited elongated shapes with long cell processes (spreading), while cells cultured on uncoated plates showed few cell processes. A significant decrease in testosterone production was observed when basal and hCG‐stimulated Leydig cells were cultured for 3 or 24 hr on plates coated with type IV collagen (12 and 24 μg/cm2) compared to uncoated plates. A significant though a slighter decrease in testosterone production was also observed in cells cultured on plates coated with fibronectin (12 and 24 μg/cm2), compared to uncoated plates. Laminin‐1 did not modify testosterone production under basal or hCG stimulated conditions. These results suggest that ECM proteins are able to modulate Leydig cell steroidogenesis, in vitro. Mol. Reprod. Dev. 61:493–503, 2002. © 2002 Wiley‐Liss, Inc.
Effect of 6‐dimethylaminopurine on electrically activated in vitro matured porcine oocytes
Authors: Grupen Christopher G. , Mau James C. , McIlfatrick Stephen M. , Maddocks Simon , Nottle Mark B.
Published: August 2002

The effect of the protein kinase inhibitor, 6‐dimethylaminopurine (6‐DMAP), on the maturation promoting factor (MPF) activity, pronuclear formation, and parthenogenetic development of electrically activated in vitro matured (IVM) porcine oocytes was investigated. Oocytes were activated by exposure to two DC pulses, each of 1.5 kV/cm field strength and 60 μsec duration, applied 1 sec apart. In the first experiment, subsequent incubation with 2 or 5 mM 6‐DMAP for 3 hr increased the incidence of blastocyst formation compared with no treatment, whereas incubation with 2 or 5 mM 6‐DMAP for 5 hr did not. In the proceeding experiments, oocytes exposed to 6‐DMAP were incubated with 2 mM of the reagent for 3 hr. Assaying histone H1 kinase activity in the second experiment revealed that the levels of active MPF in electrically activated oocytes treated with 6‐DMAP were depleted more rapidly and remained depleted for longer compared with electrical activation alone. The kinetics of MPF activity following 6‐DMAP treatment were similar to that found in inseminated oocytes in the third experiment. The effect of 6‐DMAP was correlated with an increased incidence of parthenogenetic blastocyst formation. A fourth experiment was undertaken to examine the diploidizing effect of 6‐DMAP. Electrically activated oocytes treated with 6‐DMAP and cytochalasin B, either alone or in combination, displayed a higher incidence of second polar body retention compared with those that were untreated or treated with cycloheximide alone. After 6 days of culture in vitro, parthenotes exposed to 6‐DMAP, either alone or in combination with cytochalasin B, formed blastocysts at a greater rate compared with those exposed to cytochalasin B alone, cycloheximide alone or no treatment. The combined 6‐DMAP and cytochalasin B treatment induced the highest rate of blastocyst formation (47%), but the numbers of trophectoderm and total cells in these blastocysts were lower compared with those obtained following exposure to 6‐DMAP alone. These results suggest that the increased developmental potential of 6‐DMAP‐treated parthenotes may be attributable to the MPF‐inactivating effect of 6‐DMAP, rather than the diploidizing effect of 6‐DMAP. Mol. Reprod. Dev. 62: 387–396, 2002. © 2002 Wiley‐Liss, Inc.
Paternal influence on the time of first embryonic cleavage post insemination and the implications for subsequent bovine embryo development in vitro and fertility in vivo
Authors: Ward Fabian , Rizos Dimitrios , Corridan Doreen , Quinn Katherine , Boland Maurice , Lonergan Patrick
Published: August 2002

The objectives of this study were: (1) to evaluate the effect of sire on the time from insemination to first cleavage following insemination in vitro and the relationship of this parameter to field fertility and (2) to establish the relationship between the kinetics of cleavage in vitro and oocyte developmental competence for bulls of known field fertility. Frozen semen from six bulls with 150‐day non‐return rates ranging from 57–78% was used. In experiment 1, after insemination with semen from one of the six bulls, presumptive zygotes were transferred to IVC in droplets of synthetic oviduct fluid. Droplets were examined at 24, 27, 30, 33, 36, 42, and 48 hr after insemination and the number of cleaved oocytes was recorded. Blastocyst yield was recorded on Days 6‐, 7‐, and 8‐post insemination. In experiment 2, culture droplets were examined at 30, 36, and 48 hr after insemination. At each time point, the number of cleaved embryos was recorded and these embryos were transferred into new droplets and were cultured separately for the duration of the experiment. The proportion of embryos developing to the blastocyst stage was recorded for each of the groups for each bull. The best predictor of field fertility was a model containing 33‐hpi‐cleavage percentage only (r = 0.689, P < 0.0001). There was also a significant correlation between blastocyst yield and non‐return rate, with Day 7 blastocyst yield having the highest correlation (r = 0.356), although this was relatively low in comparison. In experiment 2, irrespective of sire, a significantly higher proportion of those early‐cleaving oocytes (before 30 hpi) developed to blastocysts than those cleaving later. In most cases, a higher proportion of blastocysts derived from early‐cleaving oocytes hatched from the zona pellucida suggesting that such blastocysts are of superior quality to those derived from late‐cleaving oocytes. In conclusion these data confirm our earlier observations that earliest cleaving zygotes are more competent in terms of development to the blastocyst stage than those that cleave later. This phenomenon is independent of the sire used. However, we have demonstrated that the kinetics of early embryonic development as measured by the timing of the first cleavage division post insemination vary between different bulls and that these differences can be used to discriminate between bulls of high and low bull field fertility. Mol. Reprod. Dev. 60: 47–55, 2001. © 2001 Wiley‐Liss, Inc.
Capacitation dependent activation of tyrosine phosphorylation generates two sperm head plasma membrane proteins with high primary binding affinity for the zona pellucida
Authors: Flesch F.M. , Wijnand E. , van de Lest C.H.A. , Colenbrander B. , van Golde L.M.G. , Gadella B.M.
Published: August 2002

The recognition and binding of sperm cells to the zona pellucida (the extracellular matrix of the oocyte) are essential for fertilization and are believed to be species specific. Freshly ejaculated sperm cells do not bind to the zona pellucida. Physiologically this interaction is initiated after sperm activation in the female genital tract (capacitation) via a yet unknown mechanism, resulting in the binding of a receptor in the apical sperm plasma membrane to the zona pellucida. In order to mimic this biochemically, we isolated zona pellucida fragments from gilt ovaries to prepare an affinity column with the intact zona pellucida structure and loaded this column with solubilized apical plasma membranes of boar sperm cells before and after in vitro capacitation. With this technique we demonstrated that two plasma membrane proteins of capacitated boar sperm cells showed high affinity for zona pellucida fragments. Further analysis showed that these proteins were tyrosine phosphorylated. Plasma membrane proteins from freshly ejaculated sperm cells did not exhibit any zona pellucida binding proteins, likely because these proteins were not tyrosine phosphorylated. Mol. Reprod. Dev. 60: 107–115, 2001. © 2001 Wiley‐Liss, Inc.
Male sterile mutant casanova gives clues to mechanisms of sperm–egg interactions in Drosophila melanogaster
Authors: Perotti Maria‐Elisa , Cattaneo Fabio , Pasini Maria E. , Vernì Fiammetta , Hackstein Johannes H.P.
Published: August 2002

The plasma membrane of the spermatozoa of Drosophila melanogaster contains two integral proteins with glycosidase activity, β‐N‐acetylglucosaminidase and α‐D‐mannosidase. Biochemical analysis and ultrastructural cytochemistry of spermatozoa of the autosomal male sterile mutant casanova reveal that at least one of these enzymes, β‐N‐acetylglucosaminidase, is crucial for sperm–egg interactions. casanova sperm are motile, morphologically normal, are transferred to the female at mating, but are unable to fertilize the eggs. The mutation was localised by deficiency mapping to the chromosomal region 95E8‐F7. Fluorimetric assays showed that the mutant's sperm have the same level of α‐D‐mannosidase activity as wild‐type sperm, whereas β‐N‐acetylglucosaminidase activity reaches only 51% of the wild‐type level. The biochemical characteristics of α‐D‐mannosidase and of the residual β‐N‐acetylglucosaminidase are the same as in wild‐type males. Ultrastructural localization of the enzymes indicated that casanova spermatozoa lacks β‐N‐acetylglucosaminidase on the plasma membrane covering the acrosome, whereas the location of this glycosidase at the terminal part of the sperm tail is indistinguishable from the wild‐type situation. The results strongly suggest that in Drosophila the β‐N‐acetylglucosaminidase of the plasma membrane covering the acrosome functions as a receptor for the glycoconjugates on the egg surface. We named the putative egg receptor EROS. This is the first evidence for an egg/sperm recognition system in insects. The mechanism is similar to those known from higher animals. Mol. Reprod. Dev. 60: 248–259, 2001. © 2001 Wiley‐Liss, Inc.
Proteome analysis of rat spermatogonia: Reinvestigation of stathmin spatio‐temporal expression within the testis
Authors: Guillaume Elisabeth , Evrard Bertrand , Com Emmanuelle , Moertz Ejvind , Jégou Bernard , Pineau Charles
Published: August 2002

Stathmin is a protein known to be involved in various cell processes including cell proliferation and differentiation. It has already been described in the testis but its recent identification using a proteomic approach in mitotic spermatogenetic stem cells named spermatogonia (Guillaume et al., 2000) has lead us to reinvestigate its expression within the testis. Stathmin and its mRNAs were studied in isolated cells by Western and Northern blots and in situ using immunohistochemistry. We demonstrated that stathmin is indeed expressed in spermatogonia, and that it is also intensively expressed in the meiotic spermatocytes and in the first generations of spermatids. Furthermore, we showed aggregations of the protein in the cytoplasm of the later generations of spermatids preceding its elimination at the time of spermiation. Our Northern blots reveal the presence of two stathmin transcripts of 1.1 and 3.2 kb within the testis from the fetal stage onwards, in spermatogonia, spermatocytes, and spermatids. However, the 3.2 kb RNA transcript was barely detectable in the spermatids. Stathmin expression is known to be associated with microtubule dynamics. Therefore, its expression in the germ line is most probably related to the extremely complex structural cellular rearrangements occurring in germ cells during spermatogenesis. However, the exact role of stathmin and the reason of the existence of two transcripts in the male germ lineage awaits further investigation. Mol. Reprod. Dev. 60: 439–445, 2001. © 2001 Wiley‐Liss, Inc.
Molecular cloning of Odf3 encoding a novel coiled‐coil protein of sperm tail outer dense fibers*†
Authors: Petersen Christoph , Aumüller Gerhard , Bahrami Masoud , Hoyer‐Fender Sigrid
Published: August 2002

The outer dense fibers (ODF) are the main cytoskeletal structures of the sperm tail found in animals with internal fecundation. They consist of at least 14 polypeptides from which only a few are identified due to difficulties in isolation of the protein components. Here we report the isolation and molecular characterization of Odf3, encoding a novel protein of rat sperm ODF. Odf3 is transcribed in testes and more specifically in spermatids but it is also expressed in epididymides and brain suggesting a possible involvement in building of the cellular cytoskeleton. Odf3 encodes a putative protein of ∼110 kDa. Secondary structure predictions indicated that ODF3 is a coiled‐coil protein. The identification of coiled‐coil proteins as constituents of outer dense fibers reveals a model for ODF formation. Mol. Reprod. Dev. 61: 102–112, 2002. © 2002 Wiley‐Liss, Inc.
Apoptosis and brain development
Authors: Roth Kevin A. , D'Sa Cleta
Published: August 2002

Neuronal cell death in the embryonic brain was first recognized almost a century ago. Its significance for normal nervous system development and function has been a major focus of neuroscientific investigation ever since. Remarkable progress has been made in defining the cellular processes controlling neuronal cell death and studies performed over the last ten years have revealed extensive homology between the molecules regulating programmed cell death in Caenorhabditis elegans and apoptosis in mammalian cells. Targeted gene disruptions of members of the bcl‐2 and caspase gene families have demonstrated particularly significant roles for bcl‐x, bax, caspase‐9 and caspase‐3 in mammalian brain development. As expected from previous studies of synapse‐bearing neurons and neurotrophic factors, reduced neuronal cell death in mice bearing mutations in key pro‐apoptotic molecules resulted in increased numbers of neurons in a variety of neuronal subpopulations. However, targeted gene disruptions also demonstrated a heretofore underappreciated significance of neural precursor cell death and immature neuron death in nervous system development. Pathological activation of apoptotic death pathways may lead to neuroanatomic abnormalities and possibly to developmental disabilities. MRDD Research Reviews 2001;7:261–266. © 2001 Wiley‐Liss, Inc.
T2‐shortening by strongly magnetized spheres: A chemical exchange model†
Authors: Brooks Rodney A.
Published: August 2002

It is shown that a chemical exchange model can reproduce nuclear magnetic relaxation caused by diffusion of water molecules near strongly magnetized particles. The agreement is based on the similarity (but not equivalence) of the respective “visit‐limiting” mechanisms in the echo‐limited regime. The model leads to a single equation that predicts relaxation behavior in both the motional‐averaging and visit‐limited regimes. When combined with the static‐dephasing regime equation, the result is a simple theory (for spheres) that covers the entire range of diffusion times. Magn Reson Med 47:388–391, 2002. Published 2002 Wiley‐Liss, Inc.
T1 quantification with inversion recovery TrueFISP
Authors: Scheffler Klaus , Hennig Jürgen
Published: August 2002

A snapshot FLASH sequence can be used to acquire the time course of longitudinal magnetization during its recovery after a single inversion pulse. However, excitation pulses disturb the exponential recovery of longitudinal magnetization and may produce systematic errors in T1 estimations. In this context the possibility of using the TrueFISP sequence to detect the recovery of longitudinal magnetization for quantitative T1 measurements was examined. Experiments were performed on different Gd‐doped water phantoms and on humans. T1 values derived from inversion recovery TrueFISP were in excellent agreement with the single‐point method even for flip angles up to 50°. In terms of T1 accuracy and SNR, the proposed method seems to be superior to the conventional inversion recovery snapshot FLASH technique. Magn Reson Med 45:720–723, 2001. © 2001 Wiley‐Liss, Inc.
Trabecular bone volume fraction mapping by low‐resolution MRI
Authors: Fernández‐Seara M.A. , Song H.K. , Wehrli F.W.
Published: August 2002

Trabecular bone volume fraction (TBVF) is highly associated with the mechanical competence of trabecular bone. TBVF is ordinarily measured by histomorphometry from bone biopsies or, noninvasively, by means of high‐resolution microcomputed tomography and, more recently, by micro‐MRI. The latter methods require spatial resolution sufficient to resolve trabeculae, along with segmentation techniques that allow unambiguous assignment of the signal to bone or bone marrow. In this article it is shown that TBVF can be measured under low‐resolution conditions by exploiting the attenuation of the MR signal resulting from fractional occupancy of the imaging voxel by bone and bone marrow, provided that a reference signal is available from a marrow volume devoid of trabeculation. The method requires accurate measurement of apparent proton density, which entails correction for various sources of error. Key among these are the spatial nonuniformity in the RF field amplitude and effects of the slice profile, which are determined by B1 field mapping and numerical integration of the Bloch equations, respectively. By contrast, errors from variations in bone marrow composition (hematopoietic vs. fatty) between trabecular and reference site are predicted to be small and usually negligible. The method was evaluated in phantoms and in vivo in the distal radius and found to be accurate to 1% in marrow volume fraction. Finally, in a group of 12 patients of varying skeletal status, TBVF in the calcaneus was found to strongly correlate with integral bone mineral density of the lumbar vertebrae (r2 = 0.83, p < 0.0001). The method may fail in large imaging objects such as the human trunk at high magnetic field where standing wave and RF penetration effects cause intensity variations that cannot be corrected. Magn Reson Med 46:103–113, 2001. © 2001 Wiley‐Liss, Inc.
Effect of black blood MR image quality on vessel wall segmentation
Authors: Thomas Jonathan B. , Rutt Brian K. , Ladak Hanif M. , Steinman David A.
Published: August 2002

Black blood MRI has become a popular technique for measuring arterial wall area as an indicator of plaque size. Computer‐assisted techniques for segmenting vessel boundaries have been developed to increase measurement precision. In this study, the carotid arteries of four normal subjects were imaged at seven different fields of view (FOVs), keeping all other imaging parameters fixed, to determine whether spatial resolution could be increased at the expense of image quality without sacrificing precision. Wall areas were measured via computer‐assisted segmentation of the vessel boundaries performed repeatedly by two operators. Analysis of variance (ANOVA) demonstrated that the variability of wall area measurements was below 1.5 mm2 for in‐plane spatial resolutions between 0.22 mm and 0.37 mm. An inverse relationship between operator variability and the signal difference‐to‐noise ratio (SDNR) demonstrated that semi‐automatic segmentation of the wall boundaries was robust for SDNR >3, defining a criterion above which subjective image quality can be degraded without an appreciable loss of information content. Our study also suggested that spatial resolutions higher than 0.3 mm may be required to quantify normal wall areas to within 10% accuracy, but that the reduced SNR associated with the higher resolution may be tolerated by semi‐automated wall segmentation without an appreciable loss of precision. Magn Reson Med 46:299–304, 2001. © 2001 Wiley‐Liss, Inc.
Contractile properties of adjacent segments of single human muscle fibers
Authors: Wilkins John T. , Krivickas Lisa S. , Goldstein Richard , Suh Dongwon , Frontera Walter R.
Published: August 2002

A comparison of the contractile properties of adjacent segments of single human muscle fibers may help to explain the interaction among nuclear domains within the myofiber. Biopsy samples were obtained from the vastus lateralis muscle of 20 healthy untrained women (age 18–79 years). Single fibers (n = 38) were dissected and cut into halves (segments A and B). Segment diameter and depth were measured using an image analysis system. Maximal force (Po) was recorded during activation with calcium (pCa 4.5). Maximal unloaded shortening velocity (Vo) was calculated using the slack test. Myosin heavy chain (MyHC) expression was determined using sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS‐PAGE). A significant difference (∼7%) in Po was seen between adjacent segments expressing type I MyHC that could not be attributed to differences in fiber size. Significant differences were observed in Vo even after adjusting for fiber type. A positive correlation was seen in Po (concordance coefficient Rho_C = 0.803) and Vo (Rho_C = 0.690) between segments, but concordance was less than perfect in both cases. Possible explanations for nonuniformity of contractile properties include random variations in physiological systems or variability of protein expression among nuclear domains. © 2001 John Wiley & Sons, Inc. Muscle Nerve 24: 1319–1326, 2001
Obtaining force–frequency curves with a single 3‐second train of stimuli
Authors: Meyers B.M. , Nguyen J. , Cafarelli E.
Published: August 2002

We devised a method to assess the force–frequency relationship (FFR) in human skeletal muscle that involved delivery of a single 2.8‐s train of shocks directly to the femoral nerve. This increasing‐frequency train (IFT) was based on a power function, with a range of stimulation frequencies beginning at 5 Hz and rising to 100 Hz. We compared the IFT to a standard series of constant‐frequency trains (CFT) under two conditions. Force–frequency curves were examined, first in response to altered muscle length and second, following fatigue. There was no leftward shift in the curve when the knee extensors were shortened, although maximal force increased. In contrast, we observed a rightward shift in the curve after fatigue with both protocols; the frequency required to develop 50% of maximal force increased by 48% (P < .01) with CFT and 58% (P < .001) with an IFT. The CFT produced an irregular pattern of low‐frequency fatigue recovery. In the IFT, low‐frequency fatigue was greatest at the onset of recovery and decreased linearly until 120 s. These experiments show that the IFT protocol reveals alterations in muscle performance similar to the more traditional CFT. However, it requires only 2.8 s to administer and was judged more tolerable by 70% of our subjects. This suggests that the IFT may be an effective alternative for determining the FFR in human muscle for clinical and experimental purposes. © 2001 John Wiley & Sons, Inc. Muscle Nerve 24: 1332–1338, 2001
Peripheral neuropathy in young‐old and old‐old patients
Authors: Verghese J. , Bieri P.L. , Gellido C. , Schaumburg H.H. , Herskovitz S.
Published: August 2002

Diabetes is said to account for most cases of neuropathy in the elderly. We reviewed records of 223 young‐old (65–79 years) and 77 old‐old (≥80 years) patients referred for evaluation of neuropathic symptoms over a 9‐year period. We prospectively validated our findings in 102 consecutive elderly (77 young‐old) patients receiving intensive evaluation for neuropathy. Diabetes was the most common cause of neuropathy (41%), but was less common in the old‐old (25% versus 46%, P < 0.001). Idiopathic neuropathies were more common in the old‐old (39% versus 9%, P < 0.001). Alcoholic and nutritional neuropathies were uncommon in the old‐old. Electrophysiological studies showed that most patients had an axonal type of neuropathy. Sural and peroneal response amplitudes were poorly correlated with age. We obtained similar results in our prospective study. The distribution of causes of neuropathies in young‐old and old‐old patients, in a hospital‐based sample, is age‐related. Future studies need to include the old‐old to better understand the nature of neuropathy in the elderly. © 2001 John Wiley & Sons, Inc. Muscle Nerve 24: 1476–1481, 2001
Finite deformation analysis of geomaterials
Authors: Jeremić Boris , Runesson Kenneth , Sture Stein
Published: August 2002

The mathematical structure and numerical analysis of classical small deformation elasto–plasticity is generally well established. However, development of large deformation elastic–plastic numerical formulation for dilatant, pressure sensitive material models is still a research area.

In this paper we present development of the finite element formulation and implementation for large deformation, elastic–plastic analysis of geomaterials. Our developments are based on the multiplicative decomposition of the deformation gradient into elastic and plastic parts. A consistent linearization of the right deformation tensor together with the Newton method at the constitutive and global levels leads toward an efficient and robust numerical algorithm. The presented numerical formulation is capable of accurately modelling dilatant, pressure sensitive isotropic and anisotropic geomaterials subjected to large deformations. In particular, the formulation is capable of simulating the behaviour of geomaterials in which eigentriads of stress and strain do not coincide during the loading process.

The algorithm is tested in conjunction with the novel hyperelasto–plastic model termed the B material model, which is a single surface (single yield surface, affine single ultimate surface and affine single potential surface) model for dilatant, pressure sensitive, hardening and softening geomaterials. It is specifically developed to model large deformation hyperelasto–plastic problems in geomechanics.

We present an application of this formulation to numerical analysis of low confinement tests on cohesionless granular soil specimens recently performed in a SPACEHAB module aboard the Space Shuttle during the STS‐89 mission. We compare numerical modelling with test results and show the significance of added confinement by the thin hyperelastic latex membrane undergoing large stretching. Copyright © 2001 John Wiley & Sons, Ltd.
A shear‐dilation‐based model for evaluation of hydraulically stimulated naturally fractured reservoirs
Authors: Rahman M. K. , Hossain M. M. , Rahman S. S.
Published: August 2002

The role of shear dilation as a mechanism of enhancing fluid flow permeability in naturally fractured reservoirs was mainly recognized in the context of hot dry rock (HDR) geothermal reservoir stimulation. Simplified models based on shear slippage only were developed and their applications to evaluate HDR geothermal reservoir stimulation were reported. Research attention is recently focused to adjust this stimulation mechanism for naturally fractured oil and gas reservoirs which reserve vast resources worldwide. This paper develops the overall framework and basic formulations of this stimulation model for oil and gas reservoirs. Major computational modules include: natural fracture simulation, response analysis of stimulated fractures, average permeability estimation for the stimulated reservoir and prediction of an average flow direction. Natural fractures are simulated stochastically by implementing ‘fractal dimension’ concept. Natural fracture propagation and shear displacements are formulated by following computationally efficient approximate approaches interrelatingin situstresses, natural fracture parameters and stimulation pressure developed by fluid injection inside fractures. The average permeability of the stimulated reservoir is formulated as a function of discretized gridblock permeabilities by applying cubic law of fluid flow. The average reservoir elongation, or the flow direction, is expressed as a function of reservoir aspect ratio induced by directional permeability contributions. The natural fracture simulation module is verified by comparing its results with observed microseismic clouds in actual naturally fractured reservoirs. Permeability enhancement and reservoir growth are characterized with respect to stimulation pressure,in situstresses and natural fracture density applying the model to two example reservoirs. Copyright © 2002 John Wiley & Sons, Ltd.
BPH with coexisting overactive bladder dysfunction—an everyday urological dilemma
Authors: Knutson Tomas , Edlund Christer , Fall Magnus , Dahlstrand Christer
Published: August 2002

The aim of this study was to use a systematic schedule, including urodynamics, to describe the rate of coexisting overactive bladder (OB) in patients with bladder outlet obstruction (BOO) caused by benign prostatic hyperplasia (BPH). We also identified differences between the patients with pure BOO compared with those with BOO combined with OB (BOO + OB). One hundred and sixty‐two men referred to our clinic due to LUTS were included. Patients with a history that might affect their bladder function were excluded. After cystometry and pressure–flow studies, the patients were divided into pure BOO and BOO + OB. Of the 162 men, 55% had pure BOO. BOO + OB was found in 45%. Age, s‐PSA, voided volume, and obstruction grade differed significantly between the groups. The patients with BOO + OB were older, had a higher s‐PSA, voided smaller volumes, and were more obstructed. We found no differences in TRUS‐volume, Q‐max, IPS score, or PVR. There was a strong association between OB and BOO, the percentage of OB increasing with increased obstruction. TRUS‐volume, Q‐max, IPS score, and PVR did not predict whether the patients had a combined BOO + OB or not. These findings indicate that BOO is a progressive disease, which in time causes pronounced obstruction and perhaps in itself contributes to the development of OB. Neurourol. Urodynam. 20:237–247, 2001. © 2001 Wiley‐Liss, Inc.
1‐13C glucose magnetic resonance spectroscopy of pediatric and adult brain disorders
Authors: Blüml Stefan , Moreno Angel , Hwang Jong‐Hee , Ross Brian D.
Published: August 2002

With protocols designed for use in a clinical environment we investigated the feasibility and diagnostic potential of 13C MRS after 1‐13C labeled glucose infusion. 13C MRS brain examinations were performed in 27 subjects (17 children and pediatric patients, six adult patients, and four adult controls), using a standard 1.5 T clinical MR scanner. 1‐13C glucose, 99% enriched (20% w/v) was administered intravenously (690 or 210 mg/kg body weight) or orally (730 mg/kg). Cerebral 13C‐enrichment patterns and time courses were compared. 1‐13C glucose appeared in brain spectra within 2.5–15 min, with ensuing enrichment of its metabolites. No complications were encountered. When data obtained in patients were compared with controls, striking abnormalities in hepatic encephalopathy and in premature brain were observed, consistent with reduced cerebral glucose metabolism. Abnormalities in the 13C enrichment pattern were also observed in pediatric patients with leukodystrophies and mitochondrial disorders. In this preliminary survey, we conclude that 13C MRS in combination with glucose infusion is safe and efficient and provides new insights into the pathophysiology of brain disorders. Copyright © 2001 John Wiley & Sons, Ltd.

Abbreviations used:

Ala

alanine

ALD

adrenoleukodystrophy

Asp

aspartate

CACH

childhood ataxia with diffuse central nervous system hypomyelination

Glc

glucose

Gln

glutamine

Glu

glutamate, HE, hepatic encephalopathy

HCO3−

bicarbonate

i.v.

intravenous

Lac

lactate

mI

myo‐inositol

NAA

N‐acetylaspartate

TCA

tricarboxylic acid.
Combined diffusion weighting and CSF suppression in functional MRI
Authors: Andersson Linda , Bolling Max , Wirestam Ronnie , Holtås Stig , Ståhlberg Freddy
Published: August 2002

In this study, EPI pulse sequences with diffusion weighting for reduction of contributions from large vessels and inversion pulses in order to minimize the effects of CSF pulsations and CSF partial volume effects were developed for BOLD contrast investigations in functional MR imaging. One inversion recovery echo‐planar imaging (IR‐EPI) pulse sequence and one IR‐EPI with additional diffusion weighting (DW‐IR‐EPI) were developed and compared to a standard gradient‐echo EPI sequence in a cortical stimulation experiment in nine healthy volunteers. Stimulation of motor cortex was performed using a semi‐complex finger‐tapping paradigm in seven periods of alternating rest and stimulation. Comparison between the three pulse sequences was made by measuring the activated volume in each subject, as well as by calculating the relative signal increase during stimulation. Due to different baseline signal‐to‐noise levels in the images generated by the three pulse sequences, artificial noise was added so that the comparative investigation could be performed independently of the noise level. The activated volume was 128 ± 73 pixels (mean ± SD) using the standard EPI pulse sequence, 31 ± 12 pixels using IR‐EPI and 15 ± 13 pixels when DW‐IR‐EPI was employed. The relative signal increase was 5.7 ± 1.1% using standard EPI, 11.5 ± 3.1% using IR‐EPI and 9.9 ± 2.4% using DW‐IR‐EPI. The activated volume obtained with the addition of extra noise, i.e. at equal S/N, was 70 ± 50 pixels using the standard EPI, and when using IR‐EPI, the activated volume was 28 ± 13 pixels. At equal S/N, the signal increase was 7.3 ± 1.4% using standard EPI and 12.0 ± 3.6% using IR‐EPI. In BOLD contrast imaging, a combination of diffusion weighting and inversion recovery appeared to reduce false activation caused by CSF pulsation and blood flow in large vessels. Copyright © 2002 John Wiley & Sons, Ltd.
An adaptive load balancing scheme for web servers
Authors: Aweya James , Ouellette Michel , Montuno Delfin Y. , Doray Bernard , Felske Kent
Published: August 2002

This paper describes an overload control scheme for web servers which integrates admission control and load balancing. The admission control mechanism adaptively determines the client request acceptance rate to meet the web servers' performance requirements while the load balancing or client request distribution mechanism determines the fraction of requests to be assigned to each web server. The scheme requires no prior knowledge of the relative speeds of the web servers, nor the work required to process each incoming request. Copyright © 2002 John Wiley & Sons, Ltd.
On the geodetic number of a graph
Authors: Chartrand Gary , Harary Frank , Zhang Ping
Published: August 2002

For two vertices u and v of a graph G, the set I(u, v) consists of all vertices lying on some u − v geodesic in G. If S is a set of vertices of G, then I(S) is the union of all sets I(u, v) for u, v ∈ S. The geodetic number g(G) is the minimum cardinality among the subsets S of V(G) with I(S) = V(G). It is shown that if G is a graph of order n and diameter d then g(G) ≤ n − d + 1 and this bound is sharp. For positive integers r, d, and k ≥ 2 with r ≤ d ≤ 2r, there exists a connected graph G of radius r, diameter d, and g(G) = k. Also, for integers n, d, and k with 2 ≤ d < n, 2 ≤ k < n, and n − d − k + 1 ≥ 0, there exists a graph G of order n, diameter d, and g(G) = k. It is shown, for every nontrivial connected graph G, that g(G) ≤ g(G × K2). A sufficient condition for the equality of g(G) and g(G × K2) is presented. A graph F is a minimum geodetic subgraph if there exists a graph G containing F as an induced subgraph such that V(F) is a minimum geodetic set for G. Minimum geodetic subgraphs are characterized. © 2002 John Wiley & Sons, Inc.
A comparative analysis of several formulations for the generalized minimum spanning tree problem
Authors: Feremans Corinne , Labbé Martine , Laporte Gilbert
Published: August 2002

This article describes eight formulations for the Generalized Minimum Spanning Tree Problem (GMSTP). Relationships between the polytopes of their linear relaxations are established. It is shown that four of these polytopes are strictly included in the remaining ones. This analysis suggests which formulations should be preferred for the construction of a branch‐and‐cut algorithm and for the evaluation of heuristics. © 2002 John Wiley & Sons, Inc.
Estradiol‐induced phosphorylation of ERK1/2 in explants of the mouse cerebral cortex: The roles of heat shock protein 90 (Hsp90) and MEK2
Authors: Sétáló György , Singh Meharvan , Guan Xiaoping , Toran‐Allerand C. Dominique
Published: August 2002

Confocal laser scanning microscopy was used to identify the cells within organotypic slice cultures of the developing mouse cerebral cortex that respond to estradiol treatment by phosphorylation of ERK1 and ERK2. Estrogen‐responsive cells resembled neurons morphologically and expressed the neuronal marker microtubule‐associated protein 2B. The intracellular distribution of the phospho‐ERK signal was both cytoplasmic and nuclear, but inhibition of protein synthesis abolished the appearance of the nuclear signal. ERK1and ERK2 also coimmunoprecipitated with heat shock protein 90 (Hsp90) in the cerebral cortical explants. Geldanamycin effectively disrupted this association and prevented ERK phosphorylation. Surprisingly, MEK2 but not MEK1 was the principal mediator of estradiol‐induced activation of ERK. Our data demonstrate the requirement for Hsp90 in estrogen‐induced activation of ERK1 and ERK2 by MEK2 in the developing mouse cerebral cortex and also provide insight into alternative mechanisms by which estradiol may influence cytoplasmic and nuclear events in responsive neurons via the MAP kinase cascade. © 2002 Wiley Periodicals, Inc. J Neurobiol 50: 1–12, 2002
Sexual dimorphism in neuromuscular junction size on a muscle used in courtship by green anole lizards
Authors: O'Bryant Erin L. , Wade Juli
Published: August 2002

The green anole lizard exhibits seasonal courtship behavior that is sexually dimorphic. This courtship consists of the extension of a bright red throat fan (dewlap) associated with head‐bobbing display behavior. While males extend their dewlaps in aggressive encounters as well as in courtship, females use their considerably smaller dewlaps much less frequently and mainly in agonistic encounters. In parallel, a number of components of the neuromuscular system controlling dewlap extension are greater in males than in females during the breeding season, including dewlap motoneuron soma size and muscle fiber size and number. These features do not seem to change substantially in adulthood, despite a dramatic decline in dewlap use during the nonbreeding season. We explored the morphology of this neuromuscular system in more detail in the present experiment in males and females during both the breeding and nonbreeding seasons. Fiber and whole muscle length (approximately perpendicular to the fibers) were measured. Acetylcholinesterase histochemistry was used to visualize neuromuscular junctions (NMJs), and the surface area and density of NMJs were assessed for each animal. During the breeding season, NMJ size was larger in males than in females, but NMJ density along each fiber was equivalent between the sexes. In addition, whole muscle length and that of individual muscle fibers, was larger in males than in females. However, when corrected for body size, the sex difference in muscle fiber length disappeared. In the nonbreeding season, the sexual dimorphisms were maintained, suggesting that these features do not change substantially due to differences in circulating testosterone or a difference in use across seasons. Overall, these results are consistent with the idea that enhanced NMJ size is a relatively stable feature of the dewlap muscle in adulthood that either facilitates or is a consequence of using a larger muscle to extend a bigger dewlap in males compared to females. © 2002 Wiley Periodicals, Inc. J Neurobiol 50: 24–30, 2002
GABA and development of the Xenopus optic projection
Authors: Ferguson Shane C. D. , McFarlane Sarah
Published: August 2002

In the developing visual system of Xenopus laevis retinal ganglion cell (RGC) axons extend through the brain towards their major target in the midbrain, the optic tectum. Enroute, the axons are guided along their pathway by cues in the environment. In vitro, neurotransmitters have been shown to act chemotropically to influence the trajectory of extending axons and regulate the outgrowth of developing neurites, suggesting that they may act to guide or modulate the growth of axons in vivo. Previous work by Roberts and colleagues (1987) showed that populations of cells within the developing Xenopus diencephalon and midbrain express the neurotransmitter gamma amino butyric acid (GABA). Here we show that Xenopus RGC axons in the midoptic tract grow alongside the GABAergic cells and cross their GABA immunopositive nerve processes. Moreover, RGC axons and growth cones express GABA‐A and GABA‐B receptors, and GABA and the GABA‐B receptor agonist baclofen both stimulate RGC neurite outgrowth in culture. Finally, the GABA‐B receptor antagonist CGP54626 applied to the developing optic projection in vivo causes a dose‐dependent shortening of the optic projection. These data indicate that GABA may act in vivo to stimulate the outgrowth of Xenopus RGC axons along the optic tract. © 2002 Wiley Periodicals, Inc. J Neurobiol 51: 272–284, 2002
Telomerase and oligodendrocyte differentiation
Authors: Caporaso Gregg L. , Chao Moses V.
Published: August 2002

Myelin in the mammalian central nervous system (CNS) is produced by oligodendrocytes, most of which arise from oligodendrocyte precursor cells (OPCs) during late embryonic and early postnatal development. Both external and internal cues have been implicated in regulating OPC exit from the cell cycle and differentiation into oligodendrocytes. In this study, we demonstrate that differentiation of cultured OPCs into mature oligodendrocytes is associated with lower levels of activity of telomerase, the ribonucleoprotein that synthesizes telomeric DNA at the ends of chromosomes. Differentiation is also associated with lower levels of mRNA encoding the catalytic subunit of telomerase (TERT), whereas no difference is seen in the expression of its telomeric template RNA component (TR). These data suggest a possible role for telomerase during normal growth and differentiation of oligodendrocytes that may be relevant to the mechanism of myelination in the CNS. © 2001 John Wiley & Sons, Inc. J Neurobiol 49: 224–234, 2001
A parallel balance scheme for banded linear systems
Authors: Golub Gene H. , Sameh Ahmed H. , Sarin Vivek
Published: August 2002

A parallel algorithm is proposed for the solution of narrow banded non‐symmetric linear systems. The linear system is partitioned into blocks of rows with a small number of unknowns common to multiple blocks. Our technique yields a reduced system defined only on these common unknowns which can then be solved by a direct or iterative method. A projection based extension to this approach is also proposed for computing the reduced system implicitly, which gives rise to an inner–outer iteration method. In addition, the product of a vector with the reduced system matrix can be computed efficiently on a multiprocessor by concurrent projections onto subspaces of block rows. Scalable implementations of the algorithm can be devized for hierarchical parallel architectures by exploiting the two‐level parallelism inherent in the method. Our experiments indicate that the proposed algorithm is a robust and competitive alternative to existing methods, particularly for difficult problems with strong indefinite symmetric part. Copyright © 2001 John Wiley & Sons, Ltd.
Woven fabric composites—part II: Characterization of macro‐crack initiation loads for global damage analysis
Authors: Choi Jaehyon , Tamma Kumar K.
Published: August 2002

In Part 2, finite element techniques are developed to additionally investigate the global damage of woven fabric composites, focusing on plain weaves. The homogenized elastic properties of the original undamaged and the damaged woven fabric composites from the micromechanical homogenization and the micromechanical progressive damage analysis investigated earlier in Part 1 are subsequently employed in the present global damage analysis. The theory of continuum damage mechanics is utilized in the global damage analysis. The damage variables, the most important material properties of the continuum damage mechanics, are measures of average material degradation at a macro‐mechanics scale. In the present study, these damage variables are calculated numerically using the results from the micromechanical damage analysis in Part 1, instead of being obtained experimentally. Subsequently, a finite element formulation for the global damage analysis of woven fabric composites is developed to predict the initiation loads of macro‐cracks. Copyright © 2001 John Wiley & Sons, Ltd.