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At least 505 records · Page 28Linked to original sources
PubMed2003

Nuclear localization of beta-catenin in vegetal pole cells during early embryogenesis of the starfish Asterina pectinifera.

Recently, beta-catenin has been reported to control the expression of morphogenetic genes through the Wnt signaling pathway in invertebrate embryogenesis. In this study, the distribution pattern of beta-catenin during starfish embryogenesis was investigated using immunohistochemistry. In 16-cell stage embryos, beta-catenin began to accumulate in some nuclei at the vegetal pole. During the early cleavage stage, the cells expressing nuclear beta-catenin increased in number in the vegetal pole region of the embryos, and the beta-catenin signal increased in intensity in each nucleus. At the blastula stage, signal for beta-catenin was also found in the cytoplasm of the cells with nuclear beta-catenin. At the vegetal plate stage, almost all vegetal plate cells expressed beta-catenin in both the nucleus and cytoplasm. When the embryos developed to early gastrulae, cells with nuclear beta-catenin were restricted to the archenteron tip, and the signal gradually faded in later stages. The localization and temporal change of beta-catenin expression suggests that beta-catenin has a pivotal role in archenteron formation in starfish embryos.

Animals↗
PubMedDate not supplied

Translocation of a localized maternal mRNA to the vegetal pole of Xenopus oocytes.

A prominent hypothesis in embryology is that localized maternal factors are important in specifying cell fate. There are, however, only a few examples of maternal molecules that have been shown to be localized and very little is known about how such factors are physically localized within an egg (for review see ref. 1). Previously, cDNA clones were obtained for a class of localized maternal mRNAs from Xenopus laevis. These mRNAs are unusual in that they are concentrated at either the animal or vegetal pole of unfertilized eggs. In the present study the synthesis and intracellular distribution of one of them, Vg1, has been examined during oogenesis. The results show that Vg1 mRNA is localized as a crescent at the vegetal pole of mature oocytes. Surprisingly, this mRNA is uniformly distributed in the cytoplasm of immature oocytes. These findings suggest that a single cell, the frog oocyte, has some mechanism for translocating specific RNAs like Vg1. The process that moves Vg1 mRNA is evidently a cytoplasmic localization machinery which is not directly coupled to the synthesis of Vg1 RNA.

Animals↗
PubMed2001

Msps protein is localized to acentrosomal poles to ensure bipolarity of Drosophila meiotic spindles.

The female meiotic spindle is commonly formed in a centrosome-independent manner. Here we report the identification of proteins at acentrosomal poles in the female meiotic spindle of Drosophila. The acentrosomal poles contain at least two proteins, Mini-spindles (Msps) and D-TACC, which are also associated with mitotic centrosomes. These proteins interact with one another and are both required for maintaining the bipolarity of acentrosomal spindles. The polar localization of Msps is dependent on D-TACC and Ncd, a kinesin-like microtubule motor. We propose that the polar localization of Msps mediated by D-TACC and Ncd may be crucial for the stabilization of meiotic spindle bipolarity.

Animals↗
PubMed2005

Planetary science: constant illumination at the lunar north pole.

Images returned by the spacecraft Clementine have been used to produce a quantitative illumination map of the north pole of the Moon, revealing the percentage of time that points on the surface are illuminated during the lunar day. We have used this map to identify areas that are constantly illuminated during a lunar day in summer and which may therefore be in permanent sunlight. All are located on the northern rim of Peary crater, close to the north pole. Permanently sunlit areas represent prime locations for lunar outpost sites as they have abundant solar energy, are relatively benign thermally (when compared with equatorial regions), and are close to permanently shadowed regions that may contain water ice.

Journal Article↗
PubMedDate not supplied

Direct detection of variable tropospheric clouds near Titan's south pole.

Atmospheric conditions on Saturn's largest satellite, Titan, allow the possibility that it could possess a methane condensation and precipitation cycle with many similarities to Earth's hydrological cycle. Detailed imaging studies of Titan have hitherto shown no direct evidence for tropospheric condensation clouds, although there has been indirect spectroscopic evidence for transient clouds. Here we report images and spectra of Titan that show clearly transient clouds, concentrated near the south pole, which is currently near the point of maximum solar heating. The discovery of these clouds demonstrates the existence of condensation and localized moist convection in Titan's atmosphere. Their location suggests that methane cloud formation is controlled seasonally by small variations in surface temperature, and that the clouds will move from the south to the north pole on a 15-year timescale.

Journal Article↗
PubMed2006

No evidence for thick deposits of ice at the lunar south pole.

Shackleton crater at the Moon's south pole has been suggested as a possible site of concentrated deposits of water ice, on the basis of modelling of bi-static radar polarization properties and interpretations of earlier Earth-based radar images. This suggestion, and parallel assumptions about other topographic cold traps, is a significant element in planning for future lunar landings. Hydrogen enhancements have been identified in the polar regions, but these data do not identify the host species or its local distribution. The earlier Earth-based radar data lack the resolution and coverage for detailed studies of the relationship between radar scattering properties, cold traps in permanently shadowed areas, and local terrain features such as the walls and ejecta of small craters. Here we present new 20-m resolution, 13-cm-wavelength radar images that show no evidence for concentrated deposits of water ice in Shackleton crater or elsewhere at the south pole. The polarization properties normally associated with reflections from icy surfaces in the Solar System were found at all the observed latitudes and are strongly correlated with the rock-strewn walls and ejecta of young craters, including the inner wall of Shackleton. There is no correlation between the polarization properties and the degree of solar illumination. If the hydrogen enhancement observed by the Lunar Prospector orbiter indicates the presence of water ice, then our data are consistent with the ice being present only as disseminated grains in the lunar regolith.

Journal Article↗
PubMed2006

Nud1p, the yeast homolog of Centriolin, regulates spindle pole body inheritance in meiosis.

Nud1p, a protein homologous to the mammalian centrosome and midbody component Centriolin, is a component of the budding yeast spindle pole body (SPB), with roles in anchorage of microtubules and regulation of the mitotic exit network during vegetative growth. Here we analyze the function of Nud1p during yeast meiosis. We find that a nud1-2 temperature-sensitive mutant has two meiosis-related defects that reflect genetically distinct functions of Nud1p. First, the mutation affects spore formation due to its late function during spore maturation. Second, and most important, the mutant loses its ability to distinguish between the ages of the four spindle pole bodies, which normally determine which SPB would be preferentially included in the mature spores. This affects the regulation of genome inheritance in starved meiotic cells and leads to the formation of random dyads instead of non-sister dyads under these conditions. Both functions of Nud1p are connected to the ability of Spc72p to bind to the outer plaque and half-bridge (via Kar1p) of the SPB.

Cell Cycle Proteins↗
PubMed2006

Positioning centrosomes and spindle poles: looking at the periphery to find the centre.

Centrosome positioning is tightly controlled throughout the cell cycle and probably shares common regulatory mechanisms with spindle-pole positioning. In this article, we detail the possible mechanisms controlling centrosome and spindle positioning in various organisms both in interphase and mitotic cells, and discuss recent findings showing how microtubule plus-end-associated proteins interact with the cell cortex. We suggest that microtubule plus-end complexes simultaneously regulate microtubule dynamics and microtubule anchoring at the cell periphery to allow proper centrosome and spindle-pole positioning.

Animals↗
PubMed2003

Early targeting of Min proteins to the cell poles in germinated spores of Bacillus subtilis: evidence for division apparatus-independent recruitment of Min proteins to the division site.

The earliest event in bacterial cell division is the assembly of a tubulin-like protein, FtsZ, at mid-cell to form a ring. In rod-shaped bacteria, the Min system plays an important role in division site placement by inhibiting FtsZ ring formation specifically at the polar regions of the cell. The Min system comprises MinD and MinC, which form an inhibitor complex and, in Bacillus subtilis, DivIVA, which ensures that division is inhibited only in the polar regions. All three proteins localize to the division site at mid-cell and to cell poles. Their recruitment to the division site is dependent on localization of both 'early' and 'late' division proteins. We have examined the temporal and spatial localization of DivIVA relative to that of FtsZ during the first and second cell division after germination and outgrowth of B. subtilis spores. We show that, although the FtsZ ring assembles at mid-cell about halfway through the cell cycle, DivIVA assembles at this site immediately before cell division and persists there during Z-ring constriction and completion of division. We also show that both DivIVA and MinD localize to the cell poles immediately upon spore germination, well before a Z ring forms at mid-cell. Furthermore, these proteins were found to be present in mature, dormant spores. These results suggest that targeting of Min proteins to division sites does not depend directly on the assembly of the division apparatus, as suggested previously, and that potential polar division sites are blocked at the earliest possible stage in the cell cycle in germinated spores as a mechanism to ensure that equal-sized daughter cells are produced upon cell division.

Bacillus subtilis↗
PubMed2001

Upper pole heminephrectomy: is complete ureterectomy necessary?

OBJECTIVE: To determine the re-operation rate on the distal ureter after upper pole heminephrectomy with incomplete ureterectomy. PATIENTS AND METHODS: The case notes from one institution were reviewed retrospectively; 60 upper pole heminephrectomies with incomplete ureterectomy were undertaken in 39 girls and 16 boys (mean age at primary surgery 27 months, range 3--88). RESULTS: Thirty-two children (58%) had an antenatal diagnosis while 12 (22%) presented with a urinary tract infection (UTI) and six (11%) with urinary incontinence. Twenty-nine of the 60 renal units (48%) had an associated ureterocele and in nine (15%) the ureter was ectopic. Ten infants (18%) underwent initial puncture of a ureterocele. Five patients (8%), all females, required lower urinary tract re-operation. The indications for secondary surgery were recurrent UTIs in all and a prolapsed ureterocele in one. All five had ultrasonographic evidence of a dilated ureteric stump. Reflux into the retained stump was detected in one child. CONCLUSIONS: The re-operation rate for a redundant ureteric stump in this series was 8%. The risk of injury to the good ureter may outweigh the benefits of a complete ureterectomy.

Child↗
PubMed1999

Retrograde compression screw fixation of acute proximal pole scaphoid fractures.

Seventeen consecutive patients with acute unstable proximal pole scaphoid fractures were managed over the past 5 years with open reduction and internal fixation. Four fractures were displaced, with greater than 1 mm of fragment offset and intercarpal malalignment. The operative technique consisted of a dorsal approach to the scaphoid, radius bone grafting, and freehand retrograde Herbert compression screw fixation. The patients were evaluated at an average of 37 months (range, 12-63 months) after surgery. All fractures healed within 13 weeks (average, 10 weeks). Functional wrist range of motion and grip strength were achieved in all patients. No patients developed osteonecrosis or radioscaphoid arthritis. Open reduction and internal fixation rather than primary casting is a better means of reducing the complications of delayed union, nonunion, and irreparable osteonecrosis that often occur after acute proximal pole scaphoid fracture treated with cast immobilization.

Acute Disease↗
PubMed2002

Management of acute fractures and nonunions of the proximal pole of the scaphoid.

It is my belief that all acute proximal pole fractures should be treated by open reduction and internal fixation, via a dorsal approach. There is no longer any place for conservative treatment of these fractures, because a lengthy period of plaster immobilization is required and there is an unacceptably high risk of nonunion with conservative management. Unfortunately, nonunion of the proximal pole remains a common and disabling problem which demands careful evaluation and treatment. Internal fixation combined with limited cancellous bone grafting produces very satisfactory results in terms of pain relief and function, and clinical results are as good as those reported for more complex procedures involving vascularized grafts and prolonged cast immobilization. While the place for vascularized grafting has yet to be clearly defined, at present it is a technique which should be reserved for cases with long-standing ischaemia or failed previous surgery.

Female↗
PubMedDate not supplied

[Spinal cord stimulation (SCS) using an 8-pole electrode and double-electrode system as minimally invasive therapy of the post-discotomy and post-fusion syndrome--prospective study results in 34 patients].

AIM: Therapy of a pronounced post-discotomy (PDS) and post-fusion syndrome (PFS) is often unsatisfactory because of the complexity and multifactorial pain genesis. If surgical interventions cannot promise relief and if the entire interdisciplinary spectrum of conservative treatment measures is inadequate, the area of neuromodulative procedures offers spinal cord stimulation (SCS). The objective of this study was to examine the therapeutic possibilities of SCS using an 8-pole electrode and double electrode system in PDS and PFS with extensive back-leg pain areas. METHOD: An appropriate SCS system was implanted in 34 patients with PDS and PFS. Follow-up examinations were made prospectively over a period of 24 months using general criteria and psychometric test measuring instruments validated for German-language use. RESULTS: An 8-pole double electrode system was implanted 23 times, a single electrode sufficed in 11 cases. The area of pain was covered in all patients. This required special technical capabilities of the SCS system. The results remained constant over 24 months. The morphine dose could be reduced by at least 50 %. All measuring instruments confirmed a clear reduction in pain and improvement in quality of life as a result of SCS implantation. CONCLUSION: The SCS is an minimally invasive surgical procedure which can enlarge the therapeutical possibilities of pronounced PDS and PFS resistant to other modes of treatment. Special technical possibilities of parameter setting are required to cover the pain areas.

Adult↗
PubMed2003

[Infected upper renal pole in a duplex system with paravaginal abscess].

INTRODUCTION: Diagnosis of afunctional duplex systems may be delayed as they are often associated with misleading and atypical symptoms. A 40-year-old female with no history of urological disease exemplifies this thesis. CASE REPORT: Symptoms at admission were fever with pain in the right flank and lower abdomen. Sonography showed a large unclear structure at the upper pole of the right kidney and a paravaginal abscess, which was drained primarily. Rising temperature led to examination by CT-scan, which revealed a renal abscess of the upper pole, suggesting a right extopic ureter. After percutaneous drainage, further examinations (antegrade pyelography and IVP) confirmed an ectopic, blind-ending duplex ureter with a hydropyonephrotic upper renal system on the right side. Upper poole resection with ureterectomy was performed. CONCLUSIONS: In patients with unclear abscesses in the area of the external genitalia, congenital anomalies of the urinary tract should be considered as an underlying disease.

Abdominal Abscess↗
PubMed2005

Second-harmonic generation in an optically poled azo-dye/polymer film.

The power dependence of the optical poling process of a new azo chromophore in the polymethylmethacrylate matrix at room temperature has been investigated. The existing theory is found to be inconsistent with the experiment. A simple model based on the rate equation is proposed to describe the writing process of the chromophore/polymer system. The measured growth rate and the plateau second-harmonic generation intensity as induced by all optical poling are found to be in good agreement with the prediction of the simple model.

Journal Article↗
PubMed2003

Mapping of zones of altered morphology and chorionic connective tissue cellular phenotype in human fetal membranes (amniochorion and decidua) overlying the lower uterine pole and cervix before labor at term.

OBJECTIVE: The purpose of this study was to determine the location, frequency, and extent of altered fetal membrane morphology before term labor and its relation to myofibroblast activation in their connective tissue layers. STUDY DESIGN: Fetal membranes that were obtained from 10 women who underwent prelabor cesarean delivery at 38 to 39 weeks of gestation underwent biopsy examination with respect to the internal os of the cervix. The thickness of their constituent layers was measured, and the numbers of alpha-smooth muscle actin immunoreactive cells (ie, marker of myofibroblast activation) within the reticular layer were counted. RESULTS: A region that measured 119+/-21cm(2), that exhibited altered morphology of the fetal membranes from the lower uterine pole, and that was characterized by increased connective tissue thickness and decreased thickness of the cellular layers was demonstrated in all patients. In 8 of 10 patients, this region was centered on the location of the Babcock tissue forceps. Within this region was an area of fetal membranes that exhibited alpha-smooth muscle actin immunoreactivity in the cells of the reticular layer and whose number correlated with parameters of altered morphology. CONCLUSION: All patients before labor at term possess an area of fetal membranes that are located in the lower uterine pole that exhibit altered morphology that is associated with myofibroblastic activation in the chorionic connective tissue.

Amnion↗
PubMed1972

Pseudo-Poles in the Theory of Emden's Equation.

It is known that Emden's equation y'' = x(1-m)y(m) has movable singularities where the solution becomes infinite for one-sided approach. If m = (p + 2)/p, p positive integer, the singularities look like poles of order p. In this note expansions in terms of powers and logarithms are obtained from which the nonpolar nature of these "pseudo-poles" becomes evident. Various extensions are considered. Convergence proofs are deferred to a more detailed publication.

Journal Article↗
PubMed1986

Yeast gene required for spindle pole body duplication: homology of its product with Ca2+-binding proteins.

Saccharomyces cerevisiae strains bearing temperature-sensitive alleles of the cell division cycle gene CDC31 are specifically defective in duplication of the spindle pole body, the microtubule-organizing center of yeast. To define the function encoded by CDC31 more fully, we have isolated genomic clones of the gene by selection for complementation of a temperature-sensitive allele. The locus from which the clone was derived was marked by integration of a nutritional marker and found by meiotic mapping to cosegregate with CDC31. The polypeptide sequence of the open reading frame in the CDC31 gene was determined and compared with the sequences of other known proteins. This revealed significant homology with the calmodulins and other members of the Ca2+-binding protein family. On the basis of comparison with these related proteins, it is evident that the CDC31 gene product has at least two binding sites for Ca2+ and is also homologous with other regions of the calmodulin sequence. We propose that Ca2+ fluxes within the yeast cell play a key role in spindle pole body duplication and consequently in the organization of the microtubule arrays.

Amino Acid Sequence↗