bluuebunny/crossref_metadata_2025_split huggingface dataset:
Characterization of human sperm N‐acetylglucosaminidase
Authors: Perez Martinez S. L. , Menendez Helman R. J. , Zitta K. S. , Brandelli A. , Miranda P. V. 
Published: June 2007

Summary N‐acetylglucosaminidase (NAG) is particularly active in mammalian spermatozoa and appears to be involved in fertilization. Although it is assumed that this enzyme is acrosomal, previous results from our laboratory suggest the presence of NAG at the sperm plasma membrane level. The present study attempted to analyse the subcellular distribution of this enzyme in human spermatozoa. Sperm were incubated under different conditions and NAG activity measured in the soluble extracts and cell pellets using a specific fluorometric substrate. A significant proportion of NAG activity was released when sperm were incubated in culture medium, suggesting a weak association with the plasma membrane. This location was confirmed by western blot analysis of plasma membrane fractions and immunofluorescence on non‐permeabilized sperm, which showed a positive signal mainly on the acrosomal domain. The distribution of NAG activity between plasma membrane and acrosome was analysed after cell disruption by freezing and thawing. Triton X‐100 stimulated sperm and epididymal NAG activity but not the enzyme obtained from other sources. In addition, biotinylated human recombinant NAG was able to bind to human sperm. Finally, after sperm incubation under capacitating conditions, NAG total activity increased and the sperm enzyme lost its ability to be stimulated by Triton X‐100. The possible connection of these results with sperm maturation, capacitation and NAG participation in primary binding to the zona pellucida, was discussed.
Drosophila spermatogenesis: insights into testicular cancer
Authors: Hime G. R. , Loveland K. L. , Abud H. E. 
Published: June 2007

SummaryGeneticists have a long history of studying reproduction in the fruitfly, Drosophila melanogaster, and in recent years it has become apparent that many of the genes that regulate invertebrate reproduction have been conserved through vertebrate evolution. As with other higher eukaryotes, spermatogenesis in Drosophila is characterized by a regenerative germline stem cell population that divides asymmetrically to produce mitotic spermatogonia which will eventually differentiate into spermatocytes. Germline tumours consisting of undifferentiated germ cells have been associated with both loss‐of‐function mutations and ectopic gene expression. While the genesis of these tumours may not be identical to human germ cell tumours many of the genes that regulate stem cell proliferation and aberrant over‐proliferation in the Drosophila testis provide candidate molecules that may underlie the genetic programmes that contribute to human testicular oncogenesis.
Relationship between sperm apoptosis signalling and oocyte penetration capacity
Authors: Grunewald S. , Said T. M. , Paasch U. , Glander H.‐J. , Agarwal A. 
Published: June 2007

SummaryHuman sperm have been documented to display apoptosis‐like features such as externalization of phosphatidylserine (EPS), disruption of the transmembrane mitochondrial potential (MMP) and activation of caspases. Our aim was to evaluate possible association between activation of the apoptosis cascade in human sperm and its oocyte penetration capacity using the zona free hamster oocyte penetration assay (SPA). Semen specimens from 76 unselected donors were subjected to double density gradient centrifugation followed by incubation under capacitating conditions for 3 h and SPA. Apoptosis signalling was monitored by assessment of EPS, disruption of MMP and activation of caspase‐3 by flow cytometry. Semen samples with subnormal SPA values (<20% penetrated oocytes) contained significantly higher amounts of spermatozoa with EPS, disrupted MMP and activated caspase‐3 compared with those samples with normal SPA values (>20% penetrated oocytes, p < 0.01). All three apoptosis markers showed a significantly negative correlation with the percentage of penetrated oocytes (p < 0.01). Apoptosis‐related signalling appears to have a negative association with sperm–oocyte penetration. The exclusion of sperm presenting with those apoptosis‐related features during assisted reproduction may improve success rates of procedures such as intrauterine insemination and in vitro fertilization.
KIT and RAS signalling pathways in testicular germ cell tumours: new data and a review of the literature
Authors: Goddard N. C. , McIntyre A. , Summersgill B. , Gilbert D. , Kitazawa S. , Shipley J. 
Published: June 2007

SummaryTesticular germ cell tumours (TGCTs) are the leading cause of cancer deaths in young male Caucasians. Identifying changes in DNA copy number can pinpoint genes involved in tumour development. We defined the smallest overlapping regions of imbalance in TGCTs using array comparative genomic hybridization analysis. Novel regions, or regions which refined those previously reported, were identified. The expression profile of genes from 12p, which is invariably gained in TGCTs, and amplicons defined at 12p11.2‐12.1 and 4q12, suggest KRAS and KIT involvement in TGCT and seminoma development, respectively. Amplification of these genes was not found in intratubular germ cell neoplasia adjacent to invasive disease showing these changes, suggesting their involvement in tumour progression. Activating mutations of RAS genes (KRAS or NRAS) and overexpression of KRAS were mutually exclusive events. These, correlations between the expression levels of KIT, KRAS and GRB7 (which encodes an adapter molecule known to interact with the KIT tyrosine kinase receptor) and other reported evidence reviewed here, are consistent with a role for activation of KIT and RAS signalling in TGCT development. In order to assess a role for KIT in seminomas, we modulated the level of KIT expression in TCam‐2, a seminoma cell line. The likely seminomatous origin of this cell line was supported by demonstrating KIT and OCT3/4 overexpression and gain of 12p material. Reducing the expression of KIT in TCam‐2 through RNA inhibition resulted in decreased cell viability. Further understanding of KIT and RAS signalling in TGCTs may lead to novel therapeutic approaches for these tumours.
In vivo administration of doxazosin in rats highly decreases serum circulating levels of testosterone through a mechanism involving the testicular renin–angiotensin system
Authors: De La Chica‐Rodríguez S. , Cortés‐Denia P. , Ramírez‐Expósito M. J. , Arias de Saavedra J. M. , Sánchez‐Agesta R. , Del Cármen Pérez M. , Martínez‐Martos J. M. 
Published: June 2007

SummaryMen are at greater risk of cardiovascular and renal diseases than women. Several hypertensive rat models also exhibit gender differences in blood pressure. Although the mechanisms responsible for these gender differences are not clear, androgens have been shown to promote hypertension. Testosterone is produced by Leydig cells under the regulation of catecholamines acting through both α‐ and β‐adrenoceptors. Some investigators have postulated a putative role of angiotensin II (AngII) in modulating the action of gonadotropin in Leydig cells, inhibiting testosterone production. In the present work, we analysed the potential mechanism by which the testicular renin–angiotensin system (RAS) decreases the serum circulating levels of testosterone after the in vivo administration of the long‐acting selective α1‐adrenergic receptor antagonist doxazosin. RAS was analysed through assessment of the activity of its proteolytic regulatory enzymes. We can conclude that the testicular testosterone production, at least in rat, is regulated by catecholamines through a mechanism involving α1‐adrenergic receptors and RAS, with a putative role for AngIII. Because doxazosin is usually used as a pharmacological therapy in the treatment of hypertension and benign prostatic hyperplasia, our results could also indicate that its benefits are due, at least in part, to decreased serum circulating levels of testosterone.
DNA damage response in human testes and testicular germ cell tumours: biology and implications for therapy
Authors: Bartkova J. , Rajpert‐De Meyts E. , Skakkebæk N. E. , Lukas J. , Bartek J. 
Published: June 2007

SummaryDNA damage response (DDR) is emerging as a physiological anti‐cancer barrier in early stages of cancer development, as shown for several types of solid cancers derived from somatic cells. Here we discuss our recently published and unpublished results on the exceptional paucity of such constitutive activation of the DDR machinery in human testicular germ cell tumours (TGCTs), including their common pre‐invasive stage of carcinoma in situ (CIS). Our conclusions are supported by immunohistochemical analyses of multiple markers of activated DNA damage signalling, such as the phosphorylated ATM and Chk2 checkpoint kinases and phosphorylated histone H2AX. We propose that the unique lack of DDR activation in TGCTs reflects the biology of their cell of origin, the gonocyte. Furthermore, we propose that the lack of DDR activation avoids the pressure to select for mutations in DDR genes such as p53 or ATM, and the resulting intact DDR machinery may have implications for the exceptional curability of TGCTs by DNA damaging therapies.
Non‐tumoural parenchyma in Leydig cell tumours: pathogenetic considerations
Authors: Cajaiba M. M. , Reyes‐Múgica M. , Rios J. C. S. , Nistal M. 
Published: June 2007

SummaryLittle is known about the pathogenesis of Leydig cell tumours (LCTs) of the testis. The observation of several associated dysgenetic features in the non‐tumoural parenchyma and in the contralateral testes of men with testicular germ cell neoplasms has served as the basis to propose that there may be a common mechanism for different male reproductive disorders. However, the possible relationship between LCTs and other testicular lesions has not been explored. Here we describe the presence of primary lesions in the non‐tumoural parenchyma of testes with LCT, from which we try to establish possible pathogenetic associations. We studied the non‐tumoural parenchyma adjacent to 16 LCT specimens. Parameters as Leydig cell hyperplasia (LCHY), qualitative evaluation of the germinal epithelium and spermatogenesis, the presence of Sertoli cell‐only tubules (SCOT), and the Sertoli cell nuclear morphology were consistently assessed in all cases. SCOT associated with Sertoli cell dysgenetic morphology was the most frequent finding, present in 50% of the cases. Another interesting finding was the presence of LCHY in four cases (25%). Abnormal spermatogenesis was found in 81.25% of the cases, and it consisted of lesions of the adluminal or basal compartments of seminiferous tubules. The occurrence of either dysgenetic Sertoli cells or LCHY adjacent to LCTs could represent primary anomalies, resulting from a common insult also involved in tumourigenesis. The abnormalities in spermatogenesis observed here are likely to represent consequences of either tumour compression or abnormal hormonal production. The significance of these associations merits further investigation regarding a common pathogenesis.
Genomic and expression profiling of human spermatocytic seminomas: pathogenetic implications
Authors: Looijenga Leendert H.J. , Stoop Hans , Hersmus Remko , Gillis Ad J. M. , Wolter Oosterhuis J. 
Published: June 2007

SummaryTraditionally, germ cell tumours (GCTs) have been classified based on their histological appearance, i.e. the differentiation of lineages. Various subtypes of seminomas have been identified in a number of classification systems, including anaplastic and spermatocytic seminoma. Here we present conclusive evidence that spermatocytic seminomas are GCTs with a separate pathogenesis from seminoma, and should therefore not be considered as a variant of seminoma. Moreover, the different putative animal models, either spontaneous or induced, are discussed in the context of their value as model for human GCTs. The canine seminomas are currently considered as the most informative model for human spermatocytic seminomas.
Low coronary driving pressure early in the course of myocardial infarction is associated with subendocardial remodelling and left ventricular dysfunction
Authors: Koike Marcia Kiyomi , De Carvalho Frimm Clovis , Cúri Mariana 
Published: June 2007

SummarySubendocardial remodelling of the left ventricular (LV) non‐infarcted myocardium has been poorly investigated. Previously, we have demonstrated that low coronary driving pressure (CDP) early postinfarction was associated with the subsequent development of remote subendocardial fibrosis. The present study aimed at examining the role of CDP in LV remodelling and function following infarction. Haemodynamics were performed in Wistar rats immediately after myocardial infarction (MI group) or sham surgery (SH group) and at days 1, 3, 7 and 28. Heart tissue sections were stained with HE, Sirius red and immunostained for α‐actin. Two distinct LV regions remote to infarction were examined: subendocardium (SE) and interstitium (INT). Myocyte necrosis, leucocyte infiltration, myofibroblasts and collagen volume fraction were determined. Compared with SH, MI showed lower CDP and LV systolic and diastolic dysfunction. Necrosis was evident in SE at day 1. Inflammation and fibroplasia predominated in SE as far as day 7. Fibrosis was restricted to SE from day 3 on. Inflammation occurred in INT at days 1 and 3, but at a lower grade than in SE. CDP correlated inversely with SE necrosis (r = −0.65, P = 0.003, at day 1), inflammation (r = −0.76, P < 0.001, at day 1), fibroplasia (r = −0.47, P = 0.04, at day 7) and fibrosis (r = −0.83, P < 0.001, at day 28). Low CDP produced progressive LV expansion. Necrosis at day 1, inflammation at days 3 and 7, and fibroplasia at day 7 correlated inversely with LV function. CDP is a key factor to SE integrity and affects LV remodelling and function following infarction.
Functional convergence in regulation of net CO2 flux in heterogeneous tundra landscapes in Alaska and Sweden
Authors: SHAVER G. R. , STREET L. E. , RASTETTER E. B. , VAN WIJK M. T. , WILLIAMS M. 
Published: June 2007

Summary

Arctic landscapes are characterized by extreme vegetation patchiness, often with sharply defined borders between very different vegetation types. This patchiness makes it difficult to predict landscape‐level C balance and its change in response to environment.
Here we develop a model of net CO2 flux by arctic landscapes that is independent of vegetation composition, using instead a measure of leaf area derived from NDVI (normalized‐difference vegetation index).
Using the light response of CO2 flux (net ecosystem exchange, NEE) measured in a wide range of vegetation in arctic Alaska and Sweden, we exercise the model using various data subsets for parameter estimation and tests of predictions.
Overall, the model consistently explains ~80% of the variance in NEE knowing only the estimated leaf area index (LAI), photosynthetically active photon flux density (PPFD) and air temperature.
Model parameters derived from measurements made in one site or vegetation type can be used to predict NEE in other sites or vegetation types with acceptable accuracy and precision. Further improvements in model prediction may come from incorporating an estimate of moss area in addition to LAI, and from using vegetation‐specific estimates of LAI.
The success of this model at predicting NEE independent of any information on species composition indicates a high level of convergence in canopy structure and function in the arctic landscape.
Costs and benefits of fruiting to future reproduction in two dormancy‐prone orchids
Authors: SHEFFERSON RICHARD P. , SIMMS ELLEN L. 
Published: June 2007

SummaryReproduction is expected to occur at a cost to survival, growth or future reproduction. However, trade‐offs in long‐lived, clonal herbs have proven difficult to assess, particularly when they are prone to adult dormancy.We assessed the costs of fruiting in a study of two species of lady's slipper orchid,Cypripedium candidumandC. parviflorum, growing sympatrically in a wet meadow in north‐eastern Illinois, USA, from 2000 to 2005.First, we characterized flowering and fruiting in both populations. We found some differences between species, with 68.6 ± 5.7% (mean ± SE) and 43.5 ± 1.4% of sprouting plants flowering, while 33.6 ± 10.0% and 33.5 ± 8.1% of flowering plants fruited inC. candidumandC. parviflorum, respectively.Next, we tested the survival, sprouting and flowering response to current fruiting using multistate mark–recapture statistics. The best‐fit model posited no cost of fruiting. However, according to a model parsimonious with the best‐fit model, fruiting may have resulted in a small cost to survival visible primarily in small‐sized individuals ofC. parviflorum(decrease from 0.846 in non‐fruiting but flowering plants to 0.824 in fruiting plants). In all cases, fruiting resulted in an increased probability of future flowering, suggesting that reproduction may have a higher priority in resource allocation than survival.Finally, we tested the effects of fruiting on future fruiting using logistic regression for two years in which fruiting was particularly high, but detected no change in the probability of fruiting after fruiting.Fruiting may increase in response to internal cues, perhaps related to nutrient uptake or storage, in addition to the obvious effects of pollination. The result may be that plants with greater access to nutrients or with greater stored reserves are more likely to flower each season. We suggest a need for further research exploring the internal mechanisms governing fruiting response in long‐lived, clonal herbs.
Biological Flora of the British Isles: Cirsium dissectum (L.) Hill (Cirsium tuberosum (L.) All. subsp. anglicum (Lam.) Bonnier; Cnicus pratensis (Huds.) Willd., non Lam.; Cirsium anglicum (Lam.) DC.)
Authors: DE VERE NATASHA 
Published: June 2007

Summary

This account reviews information on all aspects of the biology of Cirsium dissectum (L.) Hill that are relevant to understanding its ecological characteristics and behaviour. The main topics are presented within the standard framework of the Biological Flora of the British Isles: distribution, habitat, communities, responses to biotic factors, responses to environment, structure and physiology, phenology, floral and seed characters, herbivores and disease, history and conservation.
Cirsium dissectum (meadow thistle) is a perennial, rhizomatous herb found in moist, nutrient poor grasslands and heathlands in north‐west Europe. It is readily distinguishable from other Cirsium species in the British Isles but has been considered a subspecies of C. tuberosum, along with C. filipendulum, in some other areas of Europe.
It is susceptible to being out‐competed by species that are able to increase biomass more rapidly. At more productive sites, greater nutrient availability increases the proportion of rosettes that flower, as well as rosette turnover. Seeds germinate readily under a range of conditions in the growth room and greenhouse but seedlings are very rarely found in the field. An examination of its population dynamics reveals that clonal propagation is the dominant form of reproduction, with the low number of seedlings primarily caused by very low establishment rates in vegetation stands.
Cirsium dissectum is relatively tolerant of drought and shade even though it is found in moist grasslands. At very low pH it suffers from ammonium and aluminium toxicity. As it has suffered habitat loss through drainage and succession, C. dissectum has declined in the British Isles and it is now endangered in Germany and the Netherlands.
The general transition metal (Tro) and Zn2+(Znu) transporters inTreponema pallidum: analysis of metal specificities and expression profiles
Authors: Desrosiers Daniel C. , Sun Yong Cheng , Zaidi Akbar A. , Eggers Christian H. , Cox David L. , Radolf Justin D. 
Published: June 2007

SummaryAcquisition of transition metals is central to the struggle between a bacterial pathogen and its mammalian host. Previous studies demonstrated thatTreponema pallidumencodes a cluster‐9 (C9) ABC transporter (troABCD) whose solute‐binding protein component (TroA) ligands Zn2+and Mn2+with essentially equal affinities. Bioinformatic analysis revealed thatT. pallidumencodes an additional C9 transporter (tp0034–36) orthologous to Zn2+‐uptake (Znu) systems in other bacteria; the binding protein component, ZnuA, contains a His‐rich tract characteristic of C9 Zn2+‐binding proteins. Metal analysis and metal‐reconstitution studies demonstrated that ZnuA is a Zn2+‐binding protein; parallel studies confirmed that TroA binds Zn2+, Mn2+and Fe. Circular dichroism showed that ZnuA, but not TroA, undergoes conformational changes in the presence of Zn2+. Using isothermal titration calorimetry (ITC), we demonstrated that TroA binds Zn2+and Mn2+with affinities approximately 100‐fold greater than those previously reported. ITC analysis revealed that ZnuA contains multiple Zn2+‐binding sites, two of which are high‐affinity and presumed to be located within the binding pocket and His‐rich loop. Quantitative reverse transcription polymerase chain reaction oftroandznutranscripts combined with immunoblot analysis of TroA and ZnuA confirmed that both transporters are simultaneously expressed inT. pallidumand that TroA is expressed at much greater levels than ZnuA. Collectively, our findings indicate thatT. pallidumprocures transition metalsviathe concerted utilization of its general metal (Tro) and Zn2+(Znu) transporters. Sequestration of periplasmic Zn2+by ZnuA may free up TroA binding capacity for the importation of Fe and Mn2+.
The ammonium‐inactivated cyanobacterial glutamine synthetase I is reactivated in vivo by a mechanism involving proteolytic removal of its inactivating factors
Authors: Galmozzi Carla V. , Fernández‐Avila M. Jesús , Reyes José C. , Florencio Francisco J. , Muro‐Pastor M. Isabel 
Published: June 2007

SummaryThe Synechocystis sp. PCC 6803 glutamine synthetase type I (GS) activity is controlled by a process that involves protein–protein interaction with two inactivating factors (IF7 and IF17). Following addition of ammonium, the genes encoding these proteins, gifA and gifB, respectively, are derrepressed, leading to the synthesis of IF7 and IF17 and consequently GS is inactivated. Upon ammonium removal, the GS activity rapidly returns to the initial level within 20 min. In this study, we analyse the mechanism underlying GS reactivation and find that this process involves IF7 and IF17 degradation. We show that the presence of ammonium as nitrogen source enhances IF17 but not IF7 stability independently of gif gene transcription. Studies with Synechocystis crude extracts under different conditions revealed that IF7 and IF17 display different stabilities in vitro. We found that IF7 is degraded in vitro by the activity of metalloproteases. Furthermore, the involvement of soluble processing metallopeptidases in IF7 degradation has also been demonstrated in vivo, by analysing Synechocystis mutant strains devoid of genes of the prp family. Finally, using a Synechocystis strain lacking GS type I, we establish the crucial role of the target protein GS for in vivo IF7 and IF17 stability.