bluuebunny/crossref_metadata_2025 huggingface dataset:
The functional cobalamin (vitamin B12)–intrinsic factor receptor is a novel complex of cubilin and amnionless
Authors: Fyfe John C. , Madsen Mette , Højrup Peter , Christensen Erik I. , Tanner Stephan M. , de la Chapelle Albert , He Qianchuan , Moestrup Søren K.
Published: October 2003

Imerslund-Gräsbeck syndrome (I-GS, megaloblastic anemia 1) is an autosomal recessive disorder characterized by intestinal cobalamin (vitamin B12) malabsorption and proteinuria. I-GS–causing mutations are found in either of 2 genes encoding the epithelial proteins: cubilin and amnionless (AMN). Cubilin recognizes intrinsic factor (IF)–cobalamin and various other proteins to be endocytosed in the intestine and kidney, respectively, whereas the function of AMN is unknown. Here we show that cubilin and AMN colocalize in the endocytic apparatus of polarized epithelial cells and copurify as a tight complex during IF-cobalamin affinity and nondenaturing gel filtration chromatography. In transfected cells expressing either AMN or a truncated IF-cobalamin–binding cubilin construct, neither protein alone conferred ligand endocytosis. In cubilin transfectants, cubilin accumulated in early biosynthetic compartments. However, in cells cotransfected with AMN and the cubilin construct, cubilin trafficked to the cell surface and endosomes, and the cells exhibited IF-cobalamin endocytosis and lysosomal degradation of IF. These data indicate that cubilin and AMN are subunits of a novel cubilin/AMN (cubam) complex, where AMN binds to the amino-terminal third of cubilin and directs subcellular localization and endocytosis of cubilin with its ligand. Therefore, mutations affecting either of the 2 proteins may abrogate function of the cubam complex and cause IG-S.
Endothelial progenitor cells in infantile hemangioma
Authors: Yu Ying , Flint Alan F. , Mulliken John B. , Wu June K. , Bischoff Joyce
Published: October 2003

Infantile hemangioma is an endothelial tumor that grows rapidly after birth but slowly regresses during early childhood. Initial proliferation of hemangioma is characterized by clonal expansion of endothelial cells (ECs) and neovascularization. Here, we demonstrated mRNA encoding CD133-2, an important marker for endothelial progenitor cells (EPCs), predominantly in proliferating but not involuting or involuted hemangioma. Progenitor cells coexpressing CD133 and CD34 were detected by flow cytometry in 11 of 12 proliferating hemangioma specimens from children 3 to 24 months of age. Furthermore, in 4 proliferating hemangiomas, we showed that 0.14% to 1.6% of CD45– nucleated cells were EPCs that coexpressed CD133 and the EC marker KDR. This finding is consistent with the presence of KDR+ immature ECs in proliferating hemangioma. Our results suggest that EPCs contribute to the early growth of hemangioma. To our knowledge, this is the first study to show direct evidence of EPCs in a human vascular tumor.
Aggregation of β2 integrins activates human neutrophils through the IκB/NF-κB pathway
Authors: Kim Cheol Hyeon , Lee Kyoung-Hee , Lee Choon-Taek , Kim Young Whan , Han Sung Koo , Shim Young-Soo , Yoo Chul-Gyu
Published: October 2003

Neutrophils are now considered central to the pathogenesis of most forms of acute lung injury. Neutrophils do not cause damage while suspended in the bloodstream; however, a release of cytotoxic agents occurs when neutrophils are adherent to endothelium, epithelium, or extracellular matrix proteins in the interstitium. Such neutrophil adherence is mediated predominantly through β2 integrins (CD11/CD18) on its surface. This study was undertaken to investigate whether the IκB/nuclear factor (NF)-κB cascade is involved in this β2 integrin-mediated activation of human neutrophils. β2 Integrin Mac-1 (CD11b/CD18) aggregation was induced by antibody cross-linking of the integrins on the cell surface. β2 Integrin aggregation induced interleukin-1β and tumor necrosis factor-α production, which suggests the activation of neutrophils by β2 integrin. IκBα was markedly degraded at 1 h, and NF-κB–DNA-binding activity markedly increased 2 h after β2 integrin aggregation, which activated IκB kinase activity at 1 h. β2 Integrin-induced cytokine production was suppressed by MG132 or SN50 pretreatment, which blocked the activation of NF-κB. These findings suggest that the activation of human neutrophils by β2 integrin aggregation is mediated through the activation of the IκB/NF-κB pathway.
Bilateral Prophylactic Oophorectomy and Ovarian Cancer Screening Following BRCA1/BRCA2 Mutation Testing
Authors: Schwartz Marc D. , Kaufman Elizabeth , Peshkin Beth N. , Isaacs Claudine , Hughes Chanita , DeMarco Tiffani , Finch Clinton , Lerman Caryn
Published: October 2003

Purpose: Despite the widespread availability of genetic testing for BRCA1/BRCA2 mutations, little is known about the impact of testing on ovarian cancer prevention and screening. For mutation testing to effect cancer mortality, positive test results must be followed by appropriate behavior change. In this study, we prospectively examined the impact of BRCA1/2 testing on the utilization of prophylactic oophorectomy and ovarian cancer screening.

Participants and Methods: Participants were 289 high-risk women who underwent genetic counseling and testing for alterations in the BRCA1/2 genes. We measured self-reported receipt of bilateral prophylactic oophorectomy (BPO) and utilization of CA-125 and transvaginal ultrasound (TVU) in the year following testing, and examined the impact of test results on these outcomes. In addition, we examined the role of sociodemographic, medical, family history, and psychological variables on the receipt of BPO, CA-125, and TVU.

Results: Twenty-seven percent of mutation carriers, 5% of uninformative patients, and 2% of noncarriers received a BPO in the year following testing. In addition to test results, perceived risk for ovarian cancer and family history of ovarian cancer independently predicted receipt of BPO. The receipt of a positive test result was associated with increased utilization of CA-125 and TVU. Additional predictors included perceived risk for ovarian cancer (both CA-125 and TVU) and state anxiety (CA-125).

Conclusion: These results demonstrate the significant behavioral impact of receiving a positive BRCA1/2 test result. The increased rate of oophorectomy among mutation carriers suggests that testing for BRCA1/2 mutations may ultimately impact ovarian cancer mortality.
F-18 Fluorodeoxyglucose Positron Emission Tomography in the Evaluation of Distant Metastases From Renal Cell Carcinoma
Authors: Majhail Navneet S. , Urbain Jean-Luc , Albani Justin M. , Kanvinde Mangesh H. , Rice Thomas W. , Novick Andrew C. , Mekhail Tarek M. , Olencki Thomas E. , Elson Paul , Bukowski Ronald M.
Published: October 2003

Purpose: We conducted a study to evaluate the role of F-18 fluorodeoxyglucose (FDG) positron emission tomography (PET) in the detection of distant metastases from renal cell carcinoma (RCC).

Materials and Methods: Twenty-four patients with histologically proven clear-cell RCC undergoing surgical evaluation for possible resection of recurrent disease were investigated. All patients had suspected distant metastases based on conventional anatomic imaging techniques (computed tomography and magnetic resonance imaging). A total of 36 distant metastatic sites were identified. Pathology for all sites was obtained by biopsy or after surgical resection.

Results: Histologically documented distant metastases from RCC were present in 33 sites (21 patients). Overall sensitivity, specificity, and positive predictive value of FDG-PET for the detection of distant metastases from RCC was 63.6% (21 of 33), 100% (three of three), and 100% (21 of 21), respectively. The mean size of distant metastases in patients with true-positive FDG-PET was 2.2 cm (95% CI, 1.7 to 2.6 cm) compared with 1.0 cm in patients with false-negative FDG-PET (95% CI, 0.7 to 1.4 cm; P = .001).

Conclusion: FDG-PET is not a sensitive imaging modality for the evaluation of metastatic RCC and may not adequately characterize small metastatic lesions. However, positive FDG-PET is predictive for the presence of RCC in lesions imaged, may complement anatomic radiologic imaging modalities, and may alleviate the need for a biopsy in selected situations. A negative FDG-PET, however does not rule out active malignancy.
Temporarily Deferred Therapy (watchful waiting) for Men Younger Than 70 Years and With Low-Risk Localized Prostate Cancer in the Prostate-Specific Antigen Era
Authors: Carter Corey A. , Donahue Timothy , Sun Leon , Wu Hongyu , McLeod David G. , Amling Christopher , Lance Raymond , Foley John , Sexton Wade , Kusuda Leo , Chung Andrew , Soderdahl Douglas , Jackman Stephen , Moul Judd W.
Published: October 2003

Purpose: Watchful waiting (WW) is an acceptable strategy for managing prostate cancer (PC) in older men. Prostate-specific antigen (PSA) testing has resulted in a stage migration, with diagnoses made in younger men. An analysis of the Department of Defense Center for Prostate Disease Research Database was undertaken to document younger men with low- or intermediate-grade PC who initially chose WW.

Patients and Methods: We identified men choosing WW who were diagnosed between January 1991 and January 2002, were 70 years or younger, had a Gleason score ≤ 6 with no Gleason pattern 4, had no more than three positive cores on biopsy, and whose clinical stage was ≤ T2 and PSA level was ≤ 20. We analyzed their likelihood of remaining on WW, the factors associated with secondary treatment, and the influence of comorbidities.

Results: Three hundred thirteen men were identified. Median follow-up time was 3.8 years. Median age was65.4 years (range, 41 to 70 years). Ninety-eight patients remained on WW; 215 proceeded to treatment. A total of 57.3% and 73.2% chose treatment within the first 2 and 4 years, respectively. Median PSA doubling time (DT) was 2.5 years for those who underwent therapy; those remaining on WW had a median DT of 25.8 years. The type of secondary treatment was associated with the number of patient’s comorbidities (P = .012).

Conclusion: Younger patients who choose WW seemed more likely to receive secondary treatment than older patients. PSA DTs often predict the use of secondary treatment. The number of comorbidities a patient has influences the type of secondary therapy chosen. The WW strategy may better be termed temporarily deferred therapy.
Clinical Features and Outcome of Primary Effusion Lymphoma in HIV-Infected Patients: A Single-Institution Study
Authors: Simonelli Cecilia , Spina Michele , Cinelli Roberta , Talamini Renato , Tedeschi Rosamaria , Gloghini Annunziata , Vaccher Emanuela , Carbone Antonino , Tirelli Umberto
Published: October 2003

Purpose: To describe the clinical features and outcome of HIV-associated primary effusion lymphoma (PEL) and to compare them with those of the other HIV-associated non-Hodgkin’s lymphomas (NHLs).

Patients and Methods: From April 1987 to June 2002, 277 patients with HIV infection and systemic NHL were diagnosed and treated in our institution. Clinical features and outcome of PEL patients were compared with the features and outcomes of 162 patients belonging to the following histologic subtypes: plasmoblastic lymphoma of oral cavity (PBLOC, n = 11), immunoblastic lymphoma (IBL, n = 76), and centroblastic B-cell lymphoma (CBCL, n = 75).

Results: Among the 277 NHL patients, PEL was diagnosed in 11 patients (4%). Eight of 11 patients were treated with a cyclophosphamide, doxorubicin, vincristine, and prednisone (CHOP)–like regimen. Complete remission was reached in 42% of patients, with a median survival time of 6 months. When the clinical features and outcome of 11 PEL patients were compared with the other three groups of patients affected by NHL, at the onset of the disease, no statistically significant differences were observed in demographic data, CD4 absolute number, HIV viremia plasma levels, and clinical characteristics. When we compared the outcome of PEL patients with the CBCL group, a statistically significant worse outcome was observed; however, the clinical outcome of PEL patients was not significantly different from the outcome observed in the other two groups (PBLOC and IBL groups).

Conclusion: PEL is a rare HIV-associated NHL type occurring as a late manifestation of HIV infection with a poor clinical outcome and a shorter overall survival compared with CBCL patients.
The Outcome of Liver Transplantation in Patients With Hepatocellular Carcinoma in the United States Between 1988 and 2001: 5-Year Survival Has Improved Significantly With Time
Authors: Yoo Hwan Y. , Patt Cary H. , Geschwind Jean-Francois , Thuluvath Paul J.
Published: October 2003

Purpose: We hypothesized that the outcome of liver transplantation in patients with hepatocellular carcinoma (HCC) has improved over the past decade because of the application of published criteria for patient selection. In this study, we compared the outcome of liver transplantation in patients with and without HCC at different time periods using the United Network for Organ Sharing data.

Patients and Methods: We excluded children, patients with multiple organ transplantation or retransplantation, and those with incomplete survival data. The study period was arbitrarily divided into three time intervals: 1987 to 1991, 1992 to 1996, and 1997 to 2001.

Results: During the study period, 985 patients with HCC (HCC group), and 33,339 without HCC underwent liver transplantation (control group). Kaplan-Meier patient and graft survivals were significantly lower for the HCC group compared with the control group. Cox regression analysis (after adjusting for other confounding variables) confirmed a lower patient survival in the HCC group (1-year survival, 77.0% v 86.7%; hazard ratio [HR], 1.7; 95% CI, 1.5 to 2.0; P < .0001) compared with the control group (5-year survival, 48.2% v 74.7%; HR, 2.2; 95% CI, 1.9 to 2.4; P < .0001); HCC was an independent predictor of survival. Kaplan-Meier analysis showed a significant improvement in 5-year patient survival with time in patients with HCC (1987 to 1991, 25.3%; 1992 to 1996, 46.6%; 1997 to 2001, 61.1%; P < .0001). During the same period, there was only minimal improvement in survival among the control group.

Conclusion: Five-year survival of patients transplanted for HCC is excellent, with a steady improvement in survival over the past decade. It is possible that the published criteria for patient selection may have contributed to the better outcome.
Dose-Dependent Switch in Response of Gonadotropin-Releasing Hormone (GnRH) Neurons to GnRH Mediated through the Type I GnRH Receptor
Authors: Xu Chun , Xu Xu-Zhi , Nunemaker Craig S. , Moenter Suzanne M.
Published: October 2003

Pulsatile release of GnRH provides central control of reproduction. GnRH neuron activity is likely synchronized to produce hormone pulses, but the mechanisms are largely unknown. One candidate for communication among these neurons is GnRH itself. Cultured embryonic and immortalized GnRH neurons express GnRH receptor type I (GnRHR-1), but expression has not been shown in adult GnRH neurons. Using mice that express green fluorescent protein (GFP) in GnRH neurons, we tested whether adult GnRH neurons express GnRHR-1. GFP-positive (n = 42) and -negative neurons (n = 22) were harvested from brain slices, and single-cell RT-PCR was performed with cell contents. Fifty-two percent of the GnRH neurons tested expressed GnRHR-1, but only 9% of non-GnRH hypothalamic neurons expressed GnRHR-1; no false harvest controls (n = 13) were positive. GnRHR-1 expression within GnRH neurons suggested a physiological ultrashort loop feedback role for GnRH. Thus, we examined the effect of GnRH on the firing rate of GnRH neurons. Low-dose GnRH (20 nm) significantly decreased firing rate in 12 of 22 neurons (by 42 ± 4%, P < 0.05), whereas higher doses increased firing rate (200 nm, five of 10 neurons, 72 ± 26%; 2000 nm, nine of 13 neurons, 53 ± 8%). Interestingly, the fraction of GnRH neurons responding was similar to the fraction in which GnRHR-1 was detected. Together, these data demonstrate that a subpopulation of GnRH neurons express GnRHR-1 and respond to GnRH with altered firing. The dose dependence suggests that this autocrine control of GnRH neurons may be not only a mechanism for generating and modulating pulsatile release, but it may also be involved in the switch between pulse and surge modes of release.
Expression and Distribution of MAL2, an Essential Element of the Machinery for Basolateral-to-Apical Transcytosis, in Human Thyroid Epithelial Cells
Authors: Marazuela Mónica , Martín-Belmonte Fernando , García-López María Angeles , Aranda Juan F. , de Marco María C. , Alonso Miguel A.
Published: October 2003

Polarized transport of newly synthesized proteins to the apical surface of epithelial cells takes place by a direct pathway from the Golgi or by an indirect route involving the delivery of the protein to the basolateral surface, followed by its endocytosis and transport across the cell. The indirect pathway, named transcytosis, is also used to translocate external material across the cell. MAL, a raft-associated integral membrane protein required for the direct apical route, is known to be expressed in the thyroid epithelium. MAL2, a member of the MAL protein family, has been recently identified as an essential component of the machinery for the transcytotic route in human hepatoma cells. Herein, we have investigated the expression and distribution of MAL2 in the human thyroid. MAL2 mRNA species were detected in the thyroid. Immunohistochemical analysis of thyroid follicles indicated that, in contrast to MAL, which predominantly distributed to the Golgi region, MAL2 distributed to the apical membrane. Biochemical analysis in primary thyrocyte cultures indicated that MAL2 exclusively resides in raft membranes. Confocal immunofluorescence analysis of thyrocyte cultures revealed that MAL2 predominantly localized in a subapical endosome compartment that was positive for Rab11a. Alterations in MAL2 expression, distribution, and appearance were found in specific types of follicular cell-derived carcinomas. Although the role of MAL2 has not been directly addressed in this study, the simultaneous expression of MAL and MAL2 suggests that traffic to the apical membrane in thyrocytes may rely on MAL for the direct route and on MAL2 for the transcytotic pathway.
Does Cortisol Inhibit Pulsatile Luteinizing Hormone Secretion at the Hypothalamic or Pituitary Level?
Authors: Breen Kellie M. , Karsch Fred J.
Published: October 2003

Elevations in glucocorticoids suppress pulsatile LH secretion in sheep, but the neuroendocrine sites and mechanisms of this disruption remain unclear. Here, we conducted two experiments in ovariectomized ewes to determine whether an acute increase in plasma cortisol inhibits pulsatile LH secretion by suppressing GnRH release into pituitary portal blood or by inhibiting pituitary responsiveness to GnRH. First, we sampled pituitary portal and peripheral blood after administration of cortisol to mimic the elevation stimulated by an immune/inflammatory stress. Within 1 h, cortisol inhibited LH pulse amplitude. LH pulse frequency, however, was unaffected. In contrast, cortisol did not suppress either parameter of GnRH secretion. Next, we assessed the effect of cortisol on pituitary responsiveness to exogenous GnRH pulses of fixed amplitude, duration, and frequency. Hourly pulses of GnRH were delivered to ewes in which endogenous GnRH secretion was blocked by estradiol. Cortisol, again, rapidly and robustly suppressed the amplitude of GnRH-induced LH pulses. We conclude that, in the ovariectomized ewe, cortisol suppresses pulsatile LH secretion by inhibiting pituitary responsiveness to GnRH rather than by suppressing hypothalamic GnRH release.
The Evolutionarily Conserved Gonadotropin-Releasing Hormone II Modifies Food Intake
Authors: Kauffman Alexander S. , Rissman Emilie F.
Published: October 2003

GnRH is an evolutionarily conserved peptide of which there are multiple structural variants. One form, GnRH II, is the most widespread in vertebrates, but its primary function remains unclear. In female musk shrews, administration of GnRH II, but not GnRH I, reinstates mating behavior previously inhibited by food restriction. Because this finding suggests that the function of GnRH II may be linked to energetic status, we tested whether GnRH II directly affects food intake. Adult female musk shrews were maintained on ad libitum feeding or food restricted for 48 h, after which they were infused centrally with GnRH I (1 μg), GnRH II (1 μg), or saline. Food intake was recorded 90 min, and 3, 6, 24, and 48 h after infusion. GnRH II administration, but not saline or GnRH I, reduced 24-h food intake in ad libitum animals. Short-term food intake (90 min and 3 h) of both ad libitum and underfed shrews receiving GnRH II was also reduced by as much as 33%, relative to the food intake of saline-infused controls. GnRH I infusion did not affect short-term food intake differently than saline infusion in shrews fed ad libitum. In underfed females, GnRH I had an effect on short-term food intake that was intermediate to saline and GnRH II. We conclude that, in addition to its permissive role in regulating reproduction, GnRH II may also modulate food intake in mammals. Because GnRH II is present in primate brain, it may also serve a similar function in humans.
Androgens Promote Maturation and Signaling in Mouse Oocytes Independent of Transcription: A Release of Inhibition Model for Mammalian Oocyte Meiosis
Authors: Gill Arvind , Jamnongjit Michelle , Hammes Stephen R.
Published: October 2003

Normal fertility in females depends upon precise regulation of oocyte meiosis. Oocytes are arrested in prophase I of meiosis until just before ovulation, when meiosis, or maturation, is triggered to resume. Whereas sex steroids appear to promote maturation in fish and amphibians, the factors regulating mammalian oocyte maturation have remained obscure. We show here that, similar to lower vertebrates, steroids may play a role in promoting the release of meiotic inhibition in mammals. Specifically, testosterone induced maturation of mouse oocytes arrested in meiosis, as well as activation of MAPK and cyclin-dependent kinase 1 signaling. These responses appeared to be transcription independent and might involve signaling through classical androgen receptors expressed in the oocytes. Our results are the first to show that sex steroids can modulate meiosis in mammalian oocytes and suggest a model whereby dominant ovarian follicles in mammals may produce sufficient androgen and/or other steroids to overcome constitutive inhibitory signals and allow oocyte maturation and subsequent ovulation to occur.
The potential to induce glial differentiation is conserved betweenDrosophilaand mammalian glial cells missing genes
Authors: Iwasaki Yasuno , Hosoya Toshihiko , Takebayashi Hirohide , Ogawa Yasuhiro , Hotta Yoshiki , Ikenaka Kazuhiro
Published: October 2003

Drosophila glial cells missing (gcm) is a key gene that determines the fate of stem cells within the nervous system. Two mouse gcm homologs have been identified, but their function in the nervous system remains to be elucidated. To investigate their function, we constructed retroviral vectors harboring Drosophila gcm and two mouse Gcm genes. Expression of these genes appeared to influence fibroblast features. In particular, mouse Gcm1 induced the expression of astrocyte-specific Ca2+-binding protein, S100β, in those cells. Introduction of the mouse Gcm1 gene in cultured cells from embryonic brains resulted in the induction of an astrocyte lineage. This effect was also observed by in utero injection of retrovirus harboring mouse Gcm1 into the embryonic brain. However, cultures from mouse Gcm1-deficient mouse brains did not exhibit significant reductions in the number of astrocytes. Furthermore,in situ hybridization analysis of mouse Gcm1 mRNA revealed distinct patterns of expression in comparison with other well-known glial markers. The mammalian homolog of Drosophila gcm, mouse Gcm1, exhibits the potential to induce gliogenesis, but may function in the generation of a minor subpopulation of glial cells.
TheDUETgene is necessary for chromosome organization and progression during male meiosis inArabidopsisand encodes a PHD finger protein
Authors: Reddy Thamalampudi Venkata , Kaur Jagreet , Agashe Bhavna , Sundaresan Venkatesan , Siddiqi Imran
Published: October 2003

Progression through the meiotic cell cycle is an essential part of the developmental program of sporogenesis in plants. The duet mutant of Arabidopsis was identified as a male sterile mutant that lacked pollen and underwent an aberrant male meiosis. Male meiocyte division resulted in the formation of two cells instead of a normal tetrad. In wild type, male meiosis extends across two successive bud positions in an inflorescence whereas in duet, meiotic stages covered three to five bud positions indicating defective progression. Normal microspores were absent in the mutant and the products of the aberrant meiosis were uni- to tri-nucleate cells that later degenerated, resulting in anthers containing largely empty locules. Defects in male meiotic chromosome organization were observed starting from diplotene and extending to subsequent stages of meiosis. There was an accumulation of meiotic structures at metaphase 1, suggesting an arrest in cell cycle progression. Double mutant analysis revealed interaction with dyad, a mutation causing chromosome cohesion during female meiosis. Cloning and molecular analysis of DUET indicated that it potentially encodes a PHD-finger protein and shows specific expression in male meiocytes. Taken together these data suggest that DUET is required for male meiotic chromosome organization and progression.
Bowl is required downstream of Notch for elaboration of distal limb patterning
Authors: de Celis Ibeas Jesus M. , Bray Sarah J.
Published: October 2003

In the Drosophila leg, activation of Notch leads to the establishment of the joints that subdivide the appendage into segments. We find that mutations in bowl result in similar phenotypes to Notch,causing fusion and truncations of tarsal segments (tarsomeres) and, like its close relative Odd-skipped, Bowl is produced in response to Notch signalling at a subset of segment boundaries. However, despite the fact that bowl mutant clones result in fusion of tarsomeres, Bowl protein is only found at the t1/tibial and t5/pretarsal boundaries, not at tarsomere joints. One hypothesis to reconcile these data is that bowl has a role at an earlier stage in tarsal development. We therefore investigated the effects of bowl mutations on the expression of leg `gap' genes that confer regional identity on the developing leg. Several of these genes have altered expression in bowl mutant cells. For example, bric-a-brac2 is normally expressed in the central part of the tarsus domain but expands into distal and proximal regions in bowl clones. Conversely, ectopic bowl leads to a reduction in bric-a-brac2, with a concomitant expansion of proximal (t1) and distal (t5) tarsomere fates. The bowl gene is therefore required for the elaboration of pattern in the tarsus and its effects suggest a progressive model for the determination of P/D identities. This mechanism might be important in the diversification of arthropod limbs, because it explains how segmented tarsomeres could have arisen from an ancestral limb with an unsegmented tarsus.
Mutation ofweak atrium/atrial myosin heavy chaindisrupts atrial function and influences ventricular morphogenesis in zebrafish
Authors: Berdougo Eli , Coleman Hope , Lee Diana H. , Stainier Didier Y. R. , Yelon Deborah
Published: October 2003

The embryonic vertebrate heart is composed of two major chambers, a ventricle and an atrium, each of which has a characteristic size, shape and functional capacity that contributes to efficient circulation. Chamber-specific gene expression programs are likely to regulate key aspects of chamber formation. Here, we demonstrate that epigenetic factors also have a significant influence on chamber morphogenesis. Specifically, we show that an atrium-specific contractility defect has a profound impact on ventricular development. We find that the zebrafish locus weak atrium encodes an atrium-specific myosin heavy chain that is required for atrial myofibrillar organization and contraction. Despite their atrial defects, weak atrium mutants can maintain circulation through ventricular contraction. However, the weak atrium mutant ventricle becomes unusually compact,exhibiting a thickened myocardial wall, a narrow lumen and changes in myocardial gene expression. As weak atrium/atrial myosin heavy chainis expressed only in the atrium, the ventricular phenotypes in weak atrium mutants represent a secondary response to atrial dysfunction. Thus, not only is cardiac form essential for cardiac function, but there also exists a reciprocal relationship in which function can influence form. These findings are relevant to our understanding of congenital defects in cardiac chamber morphogenesis.
Ebf gene function is required for coupling neuronal differentiation and cell cycle exit
Authors: Garcia-Dominguez Mario , Poquet Christophe , Garel Sonia , Charnay Patrick
Published: October 2003

Helix-loop-helix transcription factors of the Ebf/Olf1 family have previously been implicated in the control of neurogenesis in the central nervous system in both Xenopus laevis and the mouse, but their precise roles have remained unclear. We have characterised two family members in the chick, and have performed a functional analysis by gain- and loss-of-function experiments. This study revealed several specific roles for Ebf genes in the spinal cord and hindbrain regions of higher vertebrates, and enabled their precise positioning along the neurogenic cascade.

During neurogenesis, cell cycle exit appears to be tightly coupled to migration to the mantle layer and to neuronal differentiation. We show that antagonizing Ebf gene activity allows the uncoupling of these processes. Ebf gene function is necessary to initiate neuronal differentiation and migration toward the mantle layer in neuroepithelial progenitors, but it is not required for cell cycle exit. Ebf genes therefore appear to be master controllers of neuronal differentiation and migration, coupling them to cell cycle exit and earlier steps of neurogenesis.

Mutual activation between proneural and Ebf genes suggests that besides their involvement in the engagement of differentiation, Ebf genes may also participate in the stabilisation of the committed state. Finally,gain-of-function data raise the possibility that, in addition to these general roles, Ebf genes may be involved in neuronal subtype specification in particular regions of the CNS.
Dissection of floral induction pathways using global expression analysis
Authors: Schmid Markus , Uhlenhaut N. Henriette , Godard François , Demar Monika , Bressan Ray , Weigel Detlef , Lohmann Jan U.
Published: October 2003

Flowering of the reference plant Arabidopsis thaliana is controlled by several signaling pathways, which converge on a small set of genes that function as pathway integrators. We have analyzed the genomic response to one type of floral inductive signal, photoperiod, to dissect the function of several genes transducing this stimulus, including CONSTANS, thought to be the major output of the photoperiod pathway. Comparing the effects of CONSTANS with those of FLOWERING LOCUS T, which integrates inputs from CONSTANS and other floral inductive pathways, we find that expression profiles of shoot apices from plants with mutations in either gene are very similar. In contrast, a mutation in LEAFY, which also acts downstream of CONSTANS, has much more limited effects. Another pathway integrator, SUPPRESSOR OF OVEREXPRESSION OF CO 1, is responsive to acute induction by photoperiod even in the presence of the floral repressor encoded by FLOWERING LOCUS C. We have discovered a large group of potential floral repressors that are down-regulated upon photoperiodic induction. These include two AP2 domain-encoding genes that can repress flowering. The two paralogous genes, SCHLAFMÜTZE and SCHNARCHZAPFEN, share a signature with partial complementarity to the miR172 microRNA, whose precursor we show to be induced upon flowering. These and related findings on SPL genes suggest that microRNAs play an important role in the regulation of flowering.
The effect of elevated intraocular oxygen on organelle degradation in the embryonic chicken lens
Authors: Bassnett Steven , McNulty Richard
Published: October 2003

In the vertebrate lens, nuclei and other cytoplasmic organelles are degraded in fiber cells situated in the center of the tissue. This is believed to ensure the transparency of the tissue. The mechanism that triggers this process is unknown. We hypothesized that standing gradients of oxygen generated within the tissue may serve as a spatial cue for organelle degradation. To examine this possibility, we incubated fertilized chicken eggs under hyperoxic (50% O2) or normoxic (21% O2)conditions. Hyperoxic treatment was initiated on the seventh day of embryonic development (E7), five days before organelle degradation normally commences in the lens core. Hyperoxia was maintained until E17. Under normoxic conditions,the partial pressure of oxygen (PO) within the vitreous compartment was low. Direct measurement of PO using an optode oxygen sensor indicated values of 1.3 kPa and 0.4 kPa for the mid- and anterior vitreous, respectively. Similarly, treatment with pimonidazole, a bio-reductive hypoxia marker, led to the formation of immuno-positive protein adducts within the lens, suggesting that the embryonic lens is chronically hypoxic in situ. Following hyperoxic treatment, vitreous PO significantly increased, although pimonidazole staining in the lens was not markedly affected. Confocal microscopy of slices prepared from hyperoxic lenses revealed a significant increase in the size of the lens relative to age-matched normoxic controls. By E13, an organelle-free zone(OFZ) was present in the center of normoxic and hyperoxic lenses. However, in hyperoxic lenses, the OFZ was consistently smaller, and the distance from the lens surface to the border of the OFZ significantly larger, than in normoxic controls. These observations suggest that hyperoxia delays organelle breakdown and are consistent with a model in which hypoxia in the deep cortical layers of the normal lens serves as a trigger for the organelle loss process.
Bone formation is not impaired by hibernation (disuse) in black bears Ursus americanus
Authors: Donahue Seth W. , Vaughan Michael R. , Demers Laurence M. , Donahue Henry J.
Published: October 2003

Disuse by bed rest, limb immobilization or space flight causes rapid bone loss by arresting bone formation and accelerating bone resorption. This net bone loss increases the risk of fracture upon remobilization. Bone loss also occurs in hibernating ground squirrels, golden hamsters, and little brown bats by arresting bone formation and accelerating bone resorption. There is some histological evidence to suggest that black bears Ursus americanus do not lose bone mass during hibernation (i.e. disuse). There is also evidence suggesting that muscle mass and strength are preserved in black bears during hibernation. The question of whether bears can prevent bone loss during hibernation has not been conclusively answered. The goal of the current study was to further assess bone metabolism in hibernating black bears. Using the same serum markers of bone remodeling used to evaluate human patients with osteoporosis, we assayed serum from five black bears, collected every 10 days over a 196-day period, for bone resorption and formation markers. Here we show that bone resorption remains elevated over the entire hibernation period compared to the pre-hibernation period, but osteoblastic bone formation is not impaired by hibernation and is rapidly accelerated during remobilization following hibernation.
Limits to sustained energy intake VI. Energetics of lactation in laboratory mice at thermoneutrality
Authors: Król E. , Speakman J. R.
Published: October 2003

The limits to sustained energy intake are important because of their implications for reproductive output, foraging behaviour and thermoregulatory capabilities. Recent attempts to elucidate the nature of the limits to sustained energy intake have focused on peak lactation, which is the most energetically demanding period for female mammals. The hypothesis that performance of lactating animals is limited peripherally by the capacity of mammary glands to produce milk has received the most attention. However, some empirical data cannot be explained by the peripheral limitation hypothesis. Here, we present a novel hypothesis that the limits to sustained energy intake at peak lactation are imposed by the capacity of the animal to dissipate body heat generated as a by-product of processing food and producing milk. To test the heat dissipation limit hypothesis we challenged reproducing MF1 laboratory mice (N=67) with a reduced potential heat flow between the animal and the environment by exposing them to 30°C (thermoneutral zone). We compared their food intake and reproductive output at peak lactation with animals studied previously at 21°C (N=71) and 8°C (N=15). Mice lactating at 30°C had a significantly lower mean asymptotic food intake (12.4 g day-1) than those at 21°C (23.5 g day-1) and 8°C (28.6 g day-1). On average, mice at 30°C raised significantly fewer (9.8) and smaller (6.1 g) pups than those at 21°C (11.3 pups; 7.0 g per pup) and smaller pups than those at 8°C(9.6 pups; 7.3 g per pup). Consequently, mean litter mass at 30°C (56.0 g)was significantly lower than at 21°C (77.1 g) and at 8°C (68.7 g). The mean rate of litter mass increase at 30°C (2.1 g day-1) was also lower than at 21°C (3.1 g day-1). The reduced food intake and low reproductive output in mice lactating at 30°C are consistent with the heat dissipation limit hypothesis.
Limits to sustained energy intake VII. Milk energy output in laboratory mice at thermoneutrality
Authors: Król E. , Speakman J. R.
Published: October 2003

The limits to sustained energy intake at peak lactation could be imposed peripherally, by the capacity of the mammary glands, or centrally, by the capacity of the animal to dissipate body heat generated as a by-product of processing food and producing milk. To distinguish between the two hypotheses,we examined milk energy output at peak lactation in MF1 laboratory mice exposed to 30°C (N=12), 21°C (N=10; published data)and 8°C (N=10; published data). The peripheral limitation hypothesis predicts that milk energy output will remain constant at different temperatures, while the heat dissipation limit hypothesis predicts a decline in milk energy output as temperature increases. Since estimates of milk energy output in small mammals can vary depending on the calculation method used, we evaluated the milk energy output of mice (N=24) using four different methods: (1) as the difference between metabolizable energy intake and daily energy expenditure of the female, (2) from female water turnover, (3) from pup water turnover and (4) from the energy budget of the litter. We assessed these four methods by comparing their accuracy, precision and sensitivity to changes in parameters involved in the calculations. Methods 1, 3 and 4 produced similar estimates of milk energy output, while those derived from female water turnover were significantly lower and more variable. On average, mice at 30°C exported significantly less energy as milk (87.7 kJ day–1) than mice at 21°C (166.7 kJ day–1) and 8°C (288.0 kJ day–1). This reduction in milk energy output at 30°C was caused by a significant decline in both milk flow (20.0 g day–1, 12.9 g day–1 and 8.5 g day–1 at 8°C, 21°C and 30°C, respectively) and gross energy content of milk (14.6 kJ g–1, 13.1 kJ g–1 and 10.5 kJ g–1 at 8°C, 21°C and 30°C, respectively). Milk produced at 30°C contained significantly less total solids (34.4%) than milk at 21°C (40.9%) and 8°C (41.5%) and significantly less fat(20.0%) than milk at 21°C (26.4%) and 8°C (30.3%). The reduced milk energy output in mice exposed to 30°C, paralleled by their reduced food intake and low reproductive output, argues against the peripheral limitation hypothesis and provides strong support for the heat dissipation limit hypothesis.
Three-dimensional hindlimb kinematics of water running in the plumed basilisk lizard (Basiliscus plumifrons)
Authors: Hsieh S. Tonia
Published: October 2003

Much of what is known about tetrapod locomotion is based upon movement over solid surfaces. Yet in the wild, animals are forced to move over substrates with widely varying properties. Basilisk lizards are unique in their ability to run across water from the time they hatch to adulthood. Previous studies have developed mechanical models or presented theoretical analyses of running across water, but no detailed kinematic descriptions of limb motion are currently available. The present study reports the first three-dimensional kinematic descriptions of plumed basilisk lizards (Basiliscus plumifrons) running across water, from hatchling (2.8 g) to adult (78 g)size range. Basilisks ran on a 4.6 m-long water track and were filmed with two synchronized high-speed cameras at 250 frames s–1 and 1/1250 s shutter speed. All coordinates were transformed into three dimensions using direct linear transformation. Seventy-six kinematic variables and six morphological variables were measured or calculated to describe the motion of the hindlimb, but only 32 variables most relevant to kinematic motion are presented here.

Kinematic variation among individuals was primarily related to size differences rather than sprint speed. Although basilisk lizards applied some of the same strategies to increase running velocity across water as other tetrapods do on land, their overall kinematics differ dramatically. The feet exhibit much greater medio-lateral excursions while running through water than do those of other lizards while running on land. Also, whereas the hindlimb kinematics of other lizards on land are typically symmetrical (i.e. limb excursions anterior to the hip are of similar magnitude to the limb excursions aft of the hip), basilisks running through water exhibit much greater excursions aft than they do anterior to the hip. Finally, ankle and knee flexion in early stance is a defining feature of a tetrapod step during terrestrial locomotion; yet this characteristic is missing in aquatic basilisk running. This may indicate that the basilisk limb acts primarily as a force producer – as opposed to a spring element – when locomoting on a highly damping surface such as water.
Intrapopulational variation in the standard metabolic rate of insects:repeatability, thermal dependence and sensitivity (Q10) of oxygen consumption in a cricket
Authors: Nespolo R. F. , Lardies M. A. , Bozinovic F.
Published: October 2003

Studies focusing on physiological variation among individuals, and its possible evolutionary consequences, are scarce. A trait can only be a target of natural selection if it is consistent over time, that is, a trait must be repeatable. In ectotherms it has been suggested that standard metabolic rate(MR) is related to Darwinian fitness, since it reflects energy usage and expenditure. The metabolic rate of the cricket Hophlosphyrum griseuswas determined at three ambient temperatures. Repeatability of MR was estimated by product–moment correlation on residuals of body mass, as well as the thermal sensitivity of MR on an individual basis (individual Q10). The MR of H. griseus was significantly repeatable(r=0.53) and highly dependent on ambient temperature, and its sensitivity (Q10) was dependent on the temperature range. Our estimation of MR repeatability was high in comparison to published studies in vertebrates. Ours is the second report of repeatability (i.e. consistency over time of an individual's performance ranking within a population) of any aspect of energy metabolism in an insect, and also the first study to report significant repeatability of MR.

Individual Q10 values revealed important interindividual variation, which reflects the existence of intrapopulational variability in the thermal sensitivity of MR. In addition, individual Q10 values were negatively correlated between temperature ranges. This means that crickets having low Q10 at low temperatures, presented high Q10 at high temperatures, and vice versa. Our results suggest that MR could be of selective value in insects, showing consistency over time and intrapopulational variability in its thermal dependence. Nevertheless, its heritability remains to be determined.
Motor control of locomotor hindlimb posture in the American alligator(Alligator mississippiensis)
Authors: Reilly Stephen M. , Blob Richard W.
Published: October 2003

Crocodilians are unusual among quadrupedal tetrapods in their frequent use of a wide variety of hindlimb postures, ranging from sprawling to a more erect high walk. In this study, we use synchronized kinematic videos and electromyographic recordings to test how the activity patterns of hindlimb muscles in American alligators (Alligator mississippiensis Daudin)differ between sprawling and more upright postures.

Previous force platform analyses suggested that upright posture in alligators would require greater activation by hindlimb extensors to counter increases in the flexor moments exerted about joints by the ground reaction force during upright stance. Consistent with these predictions, ankle extensors (gastrocnemius) and knee extensors (femorotibialis internus and iliotibialis 2) exhibit increases in signal intensity during the use of more upright stance. Bone loading data also predicted that activation patterns for hip adductors spanning the length of the femur would not differ between sprawling and more upright posture. Correspondingly, motor patterns of the adductor femoris were not altered as posture became more upright. However, the adductor puboischiofemoralis externus 3, which inserts far proximally on the femur, displays significant increases in burst intensity that could contribute to the greater femoral adduction that is integral to upright posture.

In contrast to patterns in alligators, in mammals EMG burst intensity typically decreases during the use of upright posture. This difference in the motor control of limb posture between these taxa may be related to differences in the relative sizes of their feet. Alligator feet are large relative to the hindlimb and, as a result, the ground reaction force shifts farther from the limb joints during upright steps than in mammals, increasing flexor moments at joints and requiring alligator extensor muscles to exert greater forces to keep the limb in equilibrium. However, several alligator hindlimb muscles show no differences in motor pattern between sprawling and upright posture. The wide range of motor pattern modulations between different postures in alligators suggests considerable independence of neural control among the muscles of the alligator hindlimb.
Propulsive impulse as a covarying performance measure in the comparison of the kinematics of swimming and jumping in frogs
Authors: Nauwelaerts Sandra , Aerts Peter
Published: October 2003

Animals have to modulate their locomotor behavior according to changes in external circumstances. The locomotor requirements are expected to be most extreme for species that move through different physical environments, such as water versus land.

In this study, we examine the use of the propulsive impulse as a covariate in the comparison of the kinematics of locomotion of a semi-aquatic frog Rana esculenta, across land and through water. We focused on the propulsive phase because it is functionally the most significant phase of the locomotor cycle in both jumping and swimming, and it is also the most comparable.

The frog alters the joint angles of its legs in order to adjust its performance (i.e. impulse) within both locomotor modes. The kinematics and this modulation of the propulsive phase differ between the two modes; however,we found that the impulse ranges of swimming and jumping do not fully overlap. Possible explanations for this include larger lateral forces during swimming,a reduced force transmission due to a lower external load during swimming and reduced muscle recruitment due to differences in coordination patterns.