bluuebunny/crossref_metadata_2025_split huggingface dataset:
The control of reproductive diapause in Nebria salina (Coleoptera: Carabidae)
Authors: Telfer G. , Butterfield J. E. L. 
Published: July 2004

Abstract.  1. Adult male and female Nebria salina were collected in summer, when in reproductive diapause, and subjected to three different photoperiod regimes, LD 18:6 h, LD 12:12 h, and LD 6:18 h, to assess the role of light regimes on sexual development.2. Two alternative hypotheses were tested: (i) development rates increase in response to time restriction and (ii) development rate is at a maximum on the day length approximating to that in the field during reproduction.3. Gonad development was assessed after 1 and 2 months' exposure to the experimental day lengths. In female N. salina, photoperiod and length of time of exposure both influenced reproductive development. Females required at least 2 months' exposure to photoperiods of ≤ LD 12:12 h to mature. Development of the ovary did not take place on LD 18:6 h, irrespective of the length of exposure. Sexual development occurred in all the males after 2 months, irrespective of photoperiod.4. At the end of the study the activity of the remaining beetles was measured and compared. Significantly higher activity levels were measured in periods of darkness, and consequently beetles exposed to the two shorter day lengths were found to be more active than those kept on the longest photoperiod. Comparing the 3‐h period 06.00 – 09.00, the last 3 h of darkness for all three regimes, activity was significantly higher on LD 12:12 h and LD 6:18 h than on the LD 18:6 h regime.5. In order to place the experimental studies in context with the life cycle under natural conditions, pitfall traps were used to compare the seasonal activity of N. salina in the field.
The significance of overlapping plant range to a putative adaptive trade‐off in the black bean aphid Aphis fabae Scop
Authors: Tosh C. R. , Morgan D. , Walters K. F. A. , Douglas A. E. 
Published: July 2004

Abstract.  1. This study continues to explore the analysis of a putative adaptive trade‐off in the utilisation of host plants Vicia faba and Tropaeolum majus by the aphid, Aphis fabae. These plants are utilised exclusively by the subspecies Aphis fabae fabae and A. f. mordwilkoi respectively, and this plant‐use system has been studied previously as a potential source of disruptive selection.2. Here the potential of these two host plants to generate disruptive selection is considered given common utilisation of the abundant host plant, Rumex obtusifolius, by both subspecies.3. The life history of subspecific clones is quantified in the laboratory on V. faba, T. majus, and R. obtusifolius at various temperatures and used to parameterise a temperature‐driven simulation model of aphid population development.4. Accuracy of the model is tested using a field experiment, and fitness of clones on specific and common host is simulated using temperature data from a number of English sites.5. The model gives a close quantitative fit to field data and makes the following predictions: performance of A. f. fabae is higher on the specific host than the common host under all tested thermal regimes; and performance of A. f. mordwilkoi is superior on the specific host in warm years but inferior in cold years.6. Given the great abundance of R. obtusifolius relative to T. majus, the model predicts that the plant utilisation system has little potential to consistently promote hybrid dysfunction. This adds further weight to the assertion that the plant utilisation system studied can offer little insight into the evolutionary processes involved in subspecific differentiation and probably contains a host plant/host plants acquired after the evolution of reproductive barriers.
Disturbance and investment: developmental responses of tropical lotic midges to repeated tube destruction in the juvenile stages
Authors: Mckie Brendan G. 
Published: July 2004

Abstract.  1. Investment in silken tubes may give tubicolous chironomid larvae more to lose than non‐tube building taxa when physical disturbances or the actions of other organisms induce dispersal. In this study, two chironomid species from flood‐prone Australian tropical streams were subjected to repeated experimental destruction of their larval and pupal tubes in laboratory experiments, with life‐history parameter responses recorded.2. When subjected to the tube destruction treatments, Echinocladius martini (Orthocladiinae), whose larvae construct branched loose silken tubes in fast flow, showed no reduction in survivorship to adult, whereas Polypedilum australotropicus (Chironominae), which builds compact tightly woven tubes incorporating detrital material within pool leaf packs, showed reduced survivorship of about 25%.3. For both species, tube destruction reduced pupal duration, regardless of whether destruction occurred in the larval stage only, or in both the larval and pupal stages. This may be a response to the risks of exposure outside tubes in nature, particularly for pupae, which are incapable of spinning silk.4. Tube destruction caused little or no reduction in adult size, longevity, or female fecundity (oocyte number) for either species, but oocyte development and size was retarded in E. martini females, reflecting the energetic and nutritive costs of the tube destruction treatments.5. Contrasts in the responses of the two species reflect differences in tube‐building behaviour and in situ habitat use. These results demonstrate that tube loss can affect the fitness of individual chironomids, though both species proved generally resilient, which may reflect their long‐term exposure to variable tropical lotic conditions.
Cold tolerance in obligate and cyclical parthenogens of the peach‐potato aphid, Myzus persicae
Authors: Vorburger Christoph 
Published: July 2004

Abstract.  1. Many aphids form mixed populations of cyclical and obligate parthenogens. This is puzzling, because all else being equal, obligate parthenogens should outcompete cyclical parthenogens due to the two‐fold cost of sex. Yet cyclical parthenogens produce frost‐resistant, diapausing eggs in autumn, while obligate parthenogens spend the winter as active stages. Frost resistance thus represents a short‐term advantage to sexual reproduction mediated by winter temperatures, which may promote this coexistence.2. Because obligate parthenogens overwinter as active stages, there may be selection for increased cold tolerance compared to cyclical parthenogens. This has the potential to gradually erode the advantage of sexually producing eggs.3. Four obligately and four cyclically parthenogenetic lines of Myzus persicae (Sulzer) (Hemiptera: Aphididae) were collected from each of two areas differing in winter severity, and their survival after exposure to a severe experimental frost (14 h at −9 °C), as well as their reproductive performance at a low (10 °C) and a high (20 °C) temperature were compared.4. There was significant variation among lines in survival after the experimental frost, but this variation was neither related to their reproductive mode, nor to their area of origin. Similarly, neither reproductive mode nor origin had a significant effect on reproductive performance, independent of temperature. The average slope of the response to variation in temperature was also similar for both reproductive modes, despite the fact that slopes differed significantly among lines.5. Within the limits of extrapolating from laboratory experiments, it is concluded that in M. persicae, the active stages of obligate parthenogens are not better adapted to cold temperatures than those of cyclical parthenogens.
Internal structure of developing aucuba fruit as a defence increasing oviposition costs of its gall midges Asphondylia aucubae
Authors: Imai Kensuke , Ohsaki Naota 
Published: July 2004

Abstract.  1. Damage to juvenile plant tissues can cause reductions in fitness. Therefore, plants are expected to have evolved various defences for juvenile organs; however, so far, little attention has been paid to mechanical defence, as they have been considered to constrain the growth of juvenile organs. This study revealed that the dioecious tree Aucuba japonica uses mechanical defences to protect young developing fruit from the gall midge Asphondylia aucubae.2. Young fruit of A. japonica have a hard layer of endocarp covering the integument. Midges oviposit on the surface of the integument, where larval chambers are later formed. The endocarp gradually becomes cracked as the embryo sac develops.3. Oviposition by the midges is successful only when the ovipositors happen to pass through cracks in the endocarp. Thus, to successfully lay eggs, midges must insert the ovipositor repeatedly. This should decrease the fecundity of the midges, and subsequently their infectiousness, because their adult lifespan is short and they do not consume food during this time.4. Expansion of the cracks in the endocarp simplifies oviposition over time; however, the embryo sac continues to grow, increasing its volume relative to that of the ovule. This appears to deplete available space and tissue used in the construction of larval chambers, gradually making the fruit less susceptible to midge attacks.5. The temporary nature of this defence should prevent it from constricting the growth of young fruit. This exemplifies a novel strategy for a mechanical defence of young developing plant tissues.
The Puzzling Increase in the Underpricing of Seasoned Equity Offerings
Authors: Kim Kenneth A. , Shin Hyun‐Han 
Published: July 2004

AbstractUsing a sample of over 3,000 seasoned equity offerings (SEOs) from 1983 to 1998, we test the hypothesis that the U.S. Securities and Exchange Commission's Rule 10b‐21, which disallows the covering of short positions with newly issued SEOs, makes pre‐offer stock prices less informative, which, in turn, causes the new seasoned equity to be priced at a discount. Consistent with the hypothesis, we find that the year the rule went into effect coincides with the year from which we begin observing significant SEO discounts. Further, we find that ex ante uncertainty and SEO discounts are positively related. We also conduct tests specifically related to short selling, and we also consider an exhaustive set of alternative explanations for the discounts. Based on all of the evidence, we conclude that it is the rule that makes issue discounts larger in the 1990s.
Mixed Messages: Open‐Market Repurchases Following Stock Acquisitions
Authors: Howell Jann C. , Payne Janet D. 
Published: July 2004

AbstractManagement decisions and market reactions to those decisions do not occur in isolation. Despite this fact, little or no research has examined two events when they occur in a sequence, even when theory suggests that those two events convey opposite signals. We examine firms that do a stock‐based acquisition then announce an open‐market repurchase program. These two actions, according to the signaling theory, signal conflicting valuation errors. This paper is the first to examine a sequence of events that convey seemingly conflicting signals. Among other results, we find that repurchasers who had previously made a stock‐based acquisition have a less positive market reaction than do otherwise comparable repurchasers with no previous acquisition. These results indicate that the market reactions to events are tempered by previous information‐releasing events.
Equity Ownership and Firm Value: Evidence from Targeted Stock Repurchases
Authors: Chang Saeyoung , Hertzel Michael 
Published: July 2004

AbstractIn contrast to the negative average abnormal return associated with the announcement of a control‐related targeted repurchase (greenmail transaction), we find that the announcement of a noncontrol‐related targeted repurchase is associated with a positive and significant average abnormal return. Cross‐sectional analysis indicates that the change in firm value at the announcement of a noncontrol‐related targeted repurchase is negatively related to the resulting changes in both insider ownership and outside blockholdings. We also find significant differences in announcement‐period stock price effects depending on the identity of the selling shareholder.
Informed Trading Around Earnings Announcements: Another Look
Authors: Whalen Dennis J. , Collver Charles D. 
Published: July 2004

AbstractThis study is an empirical test of the Easley, O'Hara, and Srinivas (1998) multimarket sequential trade model of stock and option markets. We employ two approaches to determine the information content of signed stock and option trades executed around quarterly earnings announcements. The first approach expands the vector autoregression (VAR) technique of Hasbrouck (1991a) to include signed option trade volumes and inter‐trade durations. Estimates from the VAR models provide insight into whether both equity and option trades are viewed as informative by the equity specialist. The second approach focuses on the information content of the earnings releases to determine whether signed equity and option trades executed prior to the announcements are informed. Results indicate that although informed traders prefer to transact in both markets around earnings announcements, option market transactions contain no incremental information.
The Effect of Demand on Stock Prices: Evidence from Index Fund Rebalancing
Authors: Biktimirov Ernest N. 
Published: July 2004

AbstractI examine the effect of demand on stock prices by analyzing the conversion of the TIPs 35 and TIPs 100 exchange‐traded funds into the i60 Fund. This conversion occurred at the Toronto Stock Exchange on March 6, 2000. Forty stocks of the TIPs 100 Fund that were not members of the new units of the i60 Fund were sold to complete this conversion. I find that a decrease in demand produced a permanent stock price decline, which was accompanied by significant abnormal trading volume. The results provide support for the downward‐sloping demand curve hypothesis.
A central role for the mast cell in early phase vasculitis in the Brown Norway rat model of vasculitis: a histological study
Authors: Vinen Catherine S. , Turner David R. , Oliveira David B. G. 
Published: July 2004

SummaryAdministration of mercuric chloride (HgCl2) to Brown Norway rats causes Th2‐dominated autoimmunity with raised immunoglobulin E concentrations and gut vasculitis, both of which are T‐cell dependent, peak at 14 days after starting HgCl2 and then spontaneously resolve. If animals are re‐challenged with HgCl2 6 weeks after initial exposure, they are resistant to autoimmunity, developing only attenuated disease. Recently, a separate phase of early caecal vasculitis was described beginning 24 h after initiating HgCl2 and prior to caecal entry of T cells. Previous work suggested this early vasculitis was αβ T‐cell independent and implied a role for mast cells. We further tested this hypothesis by performing a histological study during the first 93 h following HgCl2 challenge defining the precise relationship between gut mast cell degranulation and appearing caecal vasculitis. We also studied whether early caecal vasculitis enters a resistant phase upon re‐challenge with HgCl2. We show a direct correlation between mast cell degranulation and early caecal vasculitis following initial HgCl2 challenge. We demonstrate resistance to re‐challenge in this phase of injury, with results at re‐challenge also showing a correlation between mast cell degranulation and early caecal injury.
Activity of lung neutrophils and matrix metalloproteinases in cyclophosphamide‐treated mice with experimental sepsis
Authors: Hirsh Mark , Carmel Julie , Kaplan Viktoria , Livne Erella , Krausz Michael M. 
Published: July 2004

SummarySepsis in patients receiving chemotherapy may result in acute respiratory distress syndrome, despite decreased number of blood neutrophils [polymorphonuclear neutrophils (PMNs)]. In the present study, we investigated the correlation of cyclophosphamide (CY)‐induced neutropenia with the destructive potential of lung PMN in respect to formation of septic acute lung injury (ALI). Mice were treated with 250 mg/kg of CY or saline (control) and subjected to cecal ligation and puncture (CLP) or sham operation. ALI was verified by histological examination. Lung PMNs and matrix metalloproteinases (MMPs) were assessed by flow cytometry and gelatin zymography. CLP in CY‐treated mice induced a typical lung injury. Despite profound neutropenia, CY treatment did not attenuate CLP‐induced ALI. This might relate to only a partial suppression of PMN: CY has significantly reduced PMN influx into the lungs (P = 0.008) and suppressed their oxidative metabolism, but had no suppressive effect on degranulation (P = 0.227) and even induced MMP‐9 activity (P = 0.0003). In CY‐untreated animals, peak of CLP‐induced ALI coincided with massive PMN influx (P = 0.013), their maximal degranulation (P = 0.014) and activation of lung MMP‐9 (P = 0.002). These findings may indicate an important role of the residual lung PMN and activation of MMP‐9 in septic lung injury during CY chemotherapy.
Metalloproteinases, insulin‐like growth factor‐I and its binding proteins in aortic aneurysm
Authors: Panek Bogusław , Gacko Marek , Pałka Jerzy 
Published: July 2004

SummaryAbdominal aortic aneurysm is accompanied by the impairment of collagen metabolism in arterial wall. Metalloproteinases and collagen‐stimulating factors play an important role in the maintenance of balance between collagen biosynthesis and degradation in tissues. Insulin‐like growth factor‐I (IGF‐I) plays a major role in the stimulation of collagen biosynthesis. Its activity and bioavailability to target cells are modulated by IGF binding proteins (IGFBPs). The potential role of these factors in the mechanism of collagen metabolism deregulation in aortic aneurysm is the purpose of this study. Therefore, we have compared the content of collagen, gelatinolytic activity, IGF‐I, IGFBP‐1 and IGFBP‐3 in normal human aorta and aortic aneurysm. The content of hydroxyproline (representing collagen content) in the proteins of aortic aneurysm was found to be similar to that found in normal aorta. Taking into account that some of the hydroxyproline may be derived from collagen degradation products (CDPs), they were separated and hydroxyproline was determined. It has been found that CDP‐derived hydroxyproline content in aortic aneurysm was increased as compared with normal aorta, suggesting an increased collagen degradation. In contrast, zymography showed a decrease of collagenolytic activity in aortic aneurysm tissue, but an increase in mural thrombus, compared to respective controls. IGF‐I concentration in aortic aneurysm was decreased, while the concentrations of BP‐1 and BP‐3 were both increased compared to control. The data suggest that increased collagen degradation in aortic aneurysm is due to the increase in collagenolytic activity in mural thrombus accompanying aneurysm tissue. It suggests that the mural thrombus may play a critical role in the pathogenesis of abdominal aortic aneurysm.
Role of Lewis A and Lewis B Blood Group Antigens in Helicobacter pylori Infection
Authors: Rothenbacher Dietrich , Weyermann Maria , Bode Günter , Kulaksiz Murrat , Stahl Bernd , Brenner Hermann 
Published: July 2004

ABSTRACTBackground and aims.  We investigated the prevalence of Helicobacter pylori infection in a large group of women to determine whether there was an association of current infection status with Lewis blood group antigen A and B phenotype.Methods.  Between November 2000 and November 2001, mothers were recruited after delivery of their offspring at the Department of Gynecology and Obstetrics at the University of Ulm, Ulm, Germany. The H. pylori infection status of the women was determined by 13C urea breath test. Their Lewis A and Lewis B phenotype was determined using standard laboratory techniques.Results.  In total, 22.2% of the 712 women included in the study (mean age 30.7 years) had a current H. pylori infection. The prevalence of infection varied from 15.5% in women of German nationality to 75.0% in women of Turkish nationality (p < .001). Most women (68.1%) had a Le(a–b+) phenotype. The prevalence of H. pylori infection in women with Le(a–b+) phenotypes was lower than in other women (p = .02). In multivariate analysis, the odds ratio (OR) for a current H. pylori infection given Le(a–b+) was 0.56 [95% confidence interval (CI) 0.33–0.95] compared to women with Le(a–b–).Conclusion.  Le(a–b+) blood group phenotype in combination with secretor status may hinder colonization of H. pylori in the population studied.
Total Family Unit Helicobacter pylori Eradication and Pediatric Re‐Infection Rates
Authors: Farrell Stephen , Milliken Irene , Doherty Gary M. , Murphy Jane L. , Wootton Steven A. , McCallion William A. 
Published: July 2004

ABSTRACTBackground.  Re‐infection with Helicobacter pylori is more common in children than adults, and it is generally accepted that the family unit plays a significant role in primary childhood infection. We investigated whether the family unit plays a significant role in pediatric re‐infection and if eradication of H. pylori from the entire family reduces the risk of childhood re‐infection.Methods.  Fifty families, each with an H. pylori‐infected pediatric index case (mean age 9.48 years), were recruited. A 13carbon urea breath test was performed on all family members in the same house as the index case. Each family unit was randomized into a ‘family unit treatment’ group (all infected family members treated) or an ‘index case treatment’ group (index case only treated).Results.  At long‐term follow‐up (mean 62.2 months), there were three re‐infected children in the ‘index case treatment’ group compared with one in the ‘family unit treatment’ group. The re‐infection rate was 2.4% per patient per year in the ‘index case treatment’ group and 0.7% per patient per year in the ‘family unit treatment’ group (p = .31).Conclusions.  This study is the first to evaluate the effect of total family unit H. pylori eradication on pediatric re‐infection rates and reports the longest period of re‐infection follow‐up in children. In childhood, re‐infection with H. pylori is not significantly reduced by family unit H. pylori eradication.
A Novel In Vitro Infection Model of Helicobacter pylori Using Mucin‐Producing Murine Gastric Surface Mucous Cells
Authors: Takahashi Tetsufumi , Matsumoto Tsukasa , Nakamura Masahiko , Matsui Hidenori , Kiyohara Hiroaki , Sasakawa Chihiro , Yamada Haruki 
Published: July 2004

ABSTRACTBackground.  Helicobacter pylori is found within the gastric surface mucous gel layer and in the epithelial surface. Gastric cancer cells have been used in experimental H. pylori infection in vitro, although cancer cells have some abnormalities in cellular properties. The aim of this study was to develop an in vitro H. pylori infection model using normal gastric surface cells that produce gastric mucin.Materials and methods.  Normal murine gastric surface mucous cells (GSM06) were cultured by the liquid interface method using a serum‐free medium and a collagen gel containing a fibroblast cell line (L929) and infected with H. pylori. Infection by H. pylori was assessed by enumerating the colony‐forming units (CFU) of H. pylori adhered to GSM06 cells and by transmission electron microscopy. The production of mucin was determined by a lectin binding assay, sugar analysis, and MUC5AC gene expression.Results.  GSM06 cells cultured under these conditions produced mucin containing N‐acetylgalactosamine and MUC5AC as the core protein. Significantly higher numbers of H. pylori adhered to GSM06 cells under mucin‐producing conditions than under nonproducing conditions. Microscopic observation showed a filamentous structure resembling a type IV secretion system apparatus formed between the surface of GSM06 cells and H. pylori.Conclusions.  This study demonstrates a novel in vitro H. pylori infection model using mucin‐producing murine GSM06 cells for early stages of infection.