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PubMed1998

Fertile offspring derived from mammalian eggs lacking either animal or vegetal poles.

In all animals so far tested, removing either pole of the undivided egg prevents normal development: embryos may arrest early, lack organs, or the adults may be sterile. These experiments have shown that spatial patterning of the egg is of utmost importance for subsequent development. However, the significance of spatial patterning in mammalian eggs is still controversial. To test the importance of egg polarity in the mouse a substantial amount of material either from the animal (polar body-associated) or the vegetal (opposite) pole of the fertilised egg was removed. One pole of the egg was cut away manually with a glass needle and the eggs were allowed to develop in vitro. Both kinds of surgical operation permit the development of blastocysts, which, after transfer to the uteri of pseudo-pregnant foster mothers, can produce viable offspring. Furthermore, these develop into fertile adult mice. I conclude that mouse eggs have no essential components that are localised uniquely to the animal or the vegetal pole and, therefore, do not rely for their axial development on maternal determinants that are so localised in the fertilised egg. Thus the mammalian egg appears to be very unusual in the animal kingdom in that it establishes the embryonic axes after the zygote has begun development.

Animals↗
PubMed1999

F-actin marks the rhizoid pole in living Pelvetia compressa zygotes.

Spatial and temporal changes in F-actin during polarity establishment in Pelvetia compressa zygotes were investigated using vital staining with rhodamine phalloidin (RP). F-actin was localized to a patch in the cortex of young zygotes. When unilateral light was applied to induce a growth axis (photopolarization) in a population of zygotes, the cortical F-actin patches localized at the shaded pole (rhizoid pole of growth axis). Treatments that prevented photopolarization prevented localization of F-actin patches to the shaded pole. When the direction of the light treatment was reversed, the previous growth axis was abandoned and a new axis was established in the opposite direction. The F-actin patch repositioned to the new rhizoid pole within minutes of light reversal, indicating that F-actin was an immediate marker of the nascent growth axis. Repositioning probably occurred by disassembly of the initial patch and reassembly of a new one. The patch grew in size as zygotes developed, eventually becoming a ring just prior to rhizoid outgrowth. The rhizoid emerged at the site of the F-actin ring and, following germination, the ring was located in the subapical zone of the elongating tip.

Actins↗
PubMed2004

Multiple mechanisms regulate NuMA dynamics at spindle poles.

The large coiled-coil protein NuMA plays an essential role in organizing microtubule minus ends at spindle poles in vertebrate cells. Here, we use both in vivo and in vitro methods to examine NuMA dynamics at mitotic spindle poles. Using fluorescence recovery after photobleaching, we show that an exogenously expressed green-fluorescent-protein/NuMA fusion undergoes continuous exchange between soluble and spindle-associated pools in living cells. These dynamics require cellular energy and display an average half-time for fluorescence recovery of approximately 3 minutes. To explore how NuMA dynamics at spindle poles is regulated, we exploited the association of NuMA with microtubule asters formed in mammalian mitotic extracts. Using a monoclonal antibody specific for human NuMA, we followed the fate of human NuMA associated with microtubule asters upon dilution with a hamster mitotic extract. Consistent with in vivo data, this assay shows that NuMA can be displaced from the core of pre-assembled asters into the soluble pool. The half-time of NuMA displacement from asters under these conditions is approximately 5 minutes. Using this assay, we show that protein kinase activity and the NuMA-binding protein LGN regulate the dynamic exchange of NuMA on microtubule asters. Thus, the dynamic properties of NuMA are regulated by multiple mechanisms including protein phosphorylation and binding to the LGN protein, and the rate of exchange between soluble and microtubule-associated pools suggests that NuMA associates with an insoluble matrix at spindle poles.

Animals↗
PubMed1996

The spacer protein Spc110p targets calmodulin to the central plaque of the yeast spindle pole body.

Yeast calmodulin (CaM) was found to be localized to the microtubule organizing centre, the spindle pole body. The spindle pole body is a multi-layered structure consisting of outer, central and inner plaques. In this paper, we report that a fraction of CaM is in association with the central plaque of the spindle pole body. This localization is dependent on the calmodulin-binding site of another spindle pole body component, Spc110p, which serves as a spacer connecting the inner plaque with the central plaque. Since the CaM-binding site of Spc110p is located near the carboxy terminus, Spc110p-dependent localization of calmodulin defines the orientation of Spc110p with the carboxy terminus towards the central plaque and the amino terminus towards the inner plaque. This orientation of Spc110p was confirmed using antibodies specific for the amino-terminal end of Spc110p, which predominantly labelled the inner plaque. In addition, synthetic peptides corresponding to the calmodulin-binding site of Spc110p bound to calmodulin with a Kd in the nanomolar range and nearly independent of Ca2+.

Amino Acid Sequence↗
PubMed1999

The nucleolar phosphoprotein B23 redistributes in part to the spindle poles during mitosis.

B23 is a major phosphoprotein in the interphasic nucleolus where it is involved in the assembly of pre-ribosomes. Using several cultured animal cells, we report that, in addition to the known redistribution of the protein during mitosis, B23 also becomes associated with mitotic spindle poles starting from early prometaphase onwards. Colocalization of B23 with the protein NuMA (Nuclear Mitotic Apparatus protein) was studied in mitotic cells and taxol-arrested cells. During the onset of mitosis, we observed that a fraction of B23 associates with, and dissociates from, the poles later than NuMA. At metaphase, both proteins are colocalized at the poles. The polar redistribution of both B23 and NuMA is mediated by microtubules. In taxol-treated cells, B23 is associated with the microtubule minus ends in the center of mitotic asters together with NuMA. Association of B23 with microtubule minus ends of mitotic asters was further confirmed with an in vitro assay, where B23 was found by western blotting to co-sediment with taxol-induced microtubule asters formed in a mitotic cell extract. Immunolabeling demonstrated that B23 and NuMA were both present at the center of the asters. Furthermore, an additional hyperphosphorylated form of B23 appeared when microtubule asters formed and associated with the asters. Immunodepletion of B23 from the mitotic extract revealed that taxol-induced microtubule asters were still observed in B23-immunodepleted mitotic extract, indicating that the presence of B23 at the poles is unlikely to be essential for spindle formation or stabilisation.

Animals↗
PubMed2000

S. pombe sporulation-specific coiled-coil protein Spo15p is localized to the spindle pole body and essential for its modification.

Spindle pole bodies in the fission yeast Schizosaccharomyces pombe are required during meiosis, not only for spindle formation but also for the assembly of forespore membranes. The spo15 mutant is defective in the formation of forespore membranes, which develop into spore envelopes. The spo15(+)gene encodes a protein with a predicted molecular mass of 223 kDa, containing potential coiled-coil regions. The spo15 gene disruptant was not lethal, but was defective in spore formation. Northern and western analyses indicated that spo15(+) was expressed not only in meiotic cells but also in vegetative cells. When the spo15-GFP fusion gene was expressed by the authentic spo15 promoter during vegetative growth and sporulation, the fusion protein colocalized with Sad1p, which is a component of spindle pole bodies. Meiotic divisions proceeded in spo15delta cells with kinetics similar to those in wild-type cells. In addition, the morphology of the mitotic and meiotic spindles and the nuclear segregation were normal in spo15delta. Intriguingly, transformation of spindle pole bodies from a punctate to a crescent form prior to forespore membrane formation was not observed in spo15delta cells. We conclude that Spo15p is associated with spindle pole bodies throughout the life cycle and plays an indispensable role in the initiation of spore membrane formation.

Amino Acid Sequence↗
PubMed1990

The transition of cells of the fission yeast beta-tubulin mutant nda3-311 as seen by freeze-substitution electron microscopy. Requirement of functional tubulin for spindle pole body duplication.

A previous fluorescence light-microscopic study showed that the fission yeast cold-sensitive beta-tubulin mutant nda3-311 was arrested with rod-like condensed chromosomes in a mitotic state at the restrictive temperature. Upon transfer to the permissive temperature, a spindle was formed and the nucleus was divided. In the present study, we employed freeze-substitution electron microscopy to examine the ultrastructure of arrested and released nda3-311 cells. In arrested cells, a single, displaced nucleus was seen with a single spindle pole body. Therefore, spindle pole body duplication seemed to require functional beta-tubulin. The nuclear membrane was highly deformed with a leaf-like profile in cross-section, possibly due to an interaction with the rod-like, condensed chromosomes. Upon transfer to the permissive temperature, the spindle pole duplicated and the daughter spindle pole bodies rapidly migrated to the opposite ends of the nucleus, accompanied by the formation of the mitotic spindle. Elongation of the nuclear envelope occurred with concomitant spindle extension, as in a wild-type mitosis. The deformed nuclear membrane became smooth and described a convex curve. The numerous vacuoles that are seen in the arrested cells decreased in number and increased in size. Septation was completed, leaving the two divided nuclei in one half of the cell. Hexagonally arranged microtubules, apparently forming the mitotic spindle, were observed in a cross-section of a cell after return to the permissive conditions.

Freezing↗
PubMed2003

Separate vertical wiring for the fixation of comminuted fractures of the inferior pole of the patella.

Comminuted and displaced fractures of the inferiorole of the patella are not easy to reduce and it is difficult to fix the fragments soundly enough to allow early movement of the knee. We have evaluated the clinical effectiveness of the separate vertical wiring technique in acute comminuted fractures of the inferior pole of the patella. A biomechanical study was also performed using ten pairs of embalmed cadaver knees. A four-part fracture was made on the inferior pole of the patella and fixed by two separate vertical wires on one side and two pull-out sutures after partial patellectomy on the other. The ultimate load to failure in the first group was significantly higher than in the second (250.1+/- 109.7 N v 69.7 +/- 18.9 N, p < 0.002), as was the stiffness (279.9 +/- 76.4 N/mm v 23.2 +/- 11.4 N/mm, p < 0.001). The separate wire technique was used in 25 patients with comminuted fractures of the inferior pole of the patella who were followed up for a mean period of 22 months (10 to 50). All the fractures healed at a mean of seven weeks (6 to 10). No breakage of a wire or infection occurred. The mean grading at the final follow-up was 29.5 points (27 to 30) using the Böstman method. This technique preserved the length of the patella, fixed the comminuted fragments of the inferior pole and avoided long-term immobilisation of the knee.

Adolescent↗
PubMed2003

Optimal poling of nonlinear photonic crystals for frequency conversion.

Nonlinear photonic crystals formed by two-dimensional periodic poling of the quadratic susceptibility chi(2) can support quasi-phase-matched harmonic generation. The frequency-conversion efficiency depends on the photonic crystal's poling pattern through certain Fourier coefficients of the poling function. A procedure is described for finding those poling patterns that are most efficient for any specific quasi-phase-matched frequency-conversion scheme.

Journal Article↗
PubMed2003

Static and dynamic profile of the electric field within the bulk of fused silica glass during and after thermal poling.

We use the electric-field-induced second-harmonic (EFISH) technique to characterize, for the first time to our knowledge, the profile of the electric field induced within the bulk of fused silica glass samples both during and after thermal-poling treatment. During thermal poling, the initially homogeneous electric field decays exponentially from the anodic to the cathodic surface. After the poling treatment, a permanent electric field is induced within the bulk of the sample. It also decays exponentially from a positive value on the anodic surface to a negative value on the cathodic surface. The exponential decay constant depends on the thickness of the sample, the poling time, and the temperature. The temperature evolution of this constant makes it possible to retrieve the activation energy of the rapidly moving ionic species. This ensemble of observations indicates that modifications to models previously proposed are necessary.

Journal Article↗
PubMed2006

Cross-phase-modulation nonlinearities and holographic solitons in periodically poled photovoltaic photorefractives.

We show that the nonlinearity in periodically poled photovoltaic photorefractives can be solely of the cross-phase-modulation type. The effects of self-phase modulation and asymmetric energy exchange, which exist in homogeneously poled photovoltaic photorefractives, can be considerably suppressed by the periodic poling. Finally, we demonstrate numerically that periodically poled photovoltaic photorefractives can support Thirring-type ("holographic") solitons, which to our knowledge have never been observed.

Journal Article↗
PubMedDate not supplied

Simplified upper pole nephrectomy: initial experience.

OBJECTIVE: To assess the results of an upper pole nephrectomy technique on 5 children. MATERIALS AND METHODS: Upper pole nephrectomy was performed on 5 children, including 4 females and 1 male. Age ranged from 3 to 6 years old. The technique was performed without initial dissection of the renal pedicle. The upper pole is incised and removed. Upon its complete dissection, the segment that drains the upper pole is easily identified, clamped and sectioned. RESULTS: Three children with ureterocele and 2 with ectopic ureter underwent this procedure. There was no intra- or postoperative complication with this technique. DSMA scintigraphy showed no decrease in renal function in the remaining kidney following the procedure. CONCLUSION: The polar nephrectomy technique is simple, and has the advantage of not approaching the renal hilum, which makes surgery less laborious and prevents risk of renal damage, hemorrhage and decreased function in the remaining renal portion.

Child↗
PubMed1990

Importance of prenatal detection of hydronephrosis of the upper pole.

To determine the impact of prenatal detection on neonates with hydronephrosis of the upper pole of a duplex collecting system, we reviewed 40 such cases seen between June 1982 and April 1989. This six-per-year rate contrasts with fewer than one case per year that was seen at our hospital from 1947 to 1977. Nineteen patients had an ectopic ureterocele, and 21 had an ectopic ureter without a ureterocele. Thirty-three (83%) were girls. Thirty-three cases were discovered because of abnormal findings on a prenatal sonogram, and 20 of those infants were asymptomatic. In the 33 patients whose prenatal sonographic findings were abnormal, the sonogram was diagnostically precise for hydronephrosis of the upper pole of a duplex collecting system in only 39%. This imprecision did not adversely affect management or outcome. Postnatal sonography modified the prenatal diagnosis in 75% of these 33 patients. Voiding cystourethrography was the most sensitive and precise imaging technique for detecting both ureterocele and reflux. Lower pole reflux was almost twice as common when an ectopic ureterocele was present (63%) than when one was not (33%). Prenatal sonographic detection of hydronephrosis of the upper pole of a duplex collecting system decreased the proportion of neonates presenting with urinary tract infection and urosepsis because of prophylactic antibiotics initiated at birth and continued until surgical correction. Precise prenatal diagnosis was not needed for effective surgical treatment.

Humans↗
PubMed2001

Duplicated collecting system with lower pole ureteropelvic junction obstruction.

Two examples of the rare case of complete duplicated collecting system with lower pole ureteropelvic junction obstruction are described. Ureteropelvic junction obstruction (UPJO) and duplicated collecting systems seldom occur in combination. Complete duplication of the ureter may be asymptomatic or recognized when complications develop as a result of reflux into the lower pole ureter or obstruction of the upper pole with an ectopic ureterocele. It is difficult to choose an optimal therapy due to the high variability in function, degree of obstruction, damage and potential for regeneration in growing kidneys. The diagnosis and management of UPJO of the lower pole in complete duplicated collecting systems are discussed.

Female↗
PubMed2005

Quantitative morphology of the scapula: normal variation of the superomedial scapular angle, and superior and inferior pole thickness.

This study examined the normal variation of the superomedial scapular angle and the thickness of the superior and inferior scapular borders. Scapulae of 53 cadaver shoulders were dissected free from all soft tissue. A line was drawn from the most superior to the most inferior point on each scapula, and the scapulae were cut along this line to obtain cross sections. The supero-medial scapular angle (alpha) was measured with a goniometer from the cross section as a ABC: through the inferior tip (A), base of the spine (B), and superior tip (C). Superior and inferior pole thickness was measured with a digital caliper from the thickest portions on the cross section of the poles. Average superomedial angle was 139 degrees +/- 6 degrees (range: 125 degrees - 156 degrees). Average thickness for the superior and inferior poles was 3.9 +/- 0.9 mm (range: 2.1 - 8.3 mm) and 7.5 +/- 1.5 mm (range: 4 - 11 mm), respectively. The thickness of both superior and inferior poles was significantly different between male and female specimens (P < .05), with male scapulae having the higher values.

Aged↗
PubMed1999

Lower pole caliceal stone clearance after ESWL: the effect of infundibulopelvic angle.

Extracorporeal Shock Wave Lithotripsy (ESWL) represents the first choice therapy for renoureteral stone disease. Clinical controversy exists concerning the efficacy of ESWL for lower pole kidney stones. Nowadays, the factors that hinder the spontaneous passage of stone debris that results from ESWL of lower caliceal stone are the gravity-dependent position of the lower pole calices and particular features of the inferior-pole collecting system anatomy. We studied the influence of the lower infundibulo-pelvic in the success of ESWL of lower caliceal stones 10-20 millimeters in size in 50 patients with STORZ MODULITH SL-20 machine. At the mean follow-up of 6 months, only 44 per cent of the patients presenting with an infundibulo-pelvic angle of les than 90 degrees became stone free. On the other hand, 86 per cent of the patients presenting with an infundibulo-pelvic angle of greater than 90 degrees became stone free. Our data suggest that acute infundibulo-pelvic angle of the lower pole hinders the spontaneous passage of fragments after ESWL.

Humans↗
PubMed2001

A role for left temporal pole in the retrieval of words for unique entities.

Both lesion and functional imaging studies have implicated sectors of high-order association cortices of the left temporal lobe in the retrieval of words for objects belonging to varied conceptual categories. In particular, the cortices located in the left temporal pole have been associated with naming unique persons from faces. Because this neuroanatomical-behavioral association might be related to either the specificity of the task (retrieving a name at unique level) or to the possible preferential processing of faces by anterior temporal cortices, we performed a PET imaging experiment to test the hypothesis that the effect is related to the specificity of the word retrieval task. Normal subjects were asked to name at unique level entities from two conceptual categories: famous landmarks and famous faces. In support of the hypothesis, naming entities in both categories was associated with increases in activity in the left temporal pole. No main effect of category (faces vs. landmarks/buildings) or interaction of task and category was found in the left temporal pole. Retrieving names for unique persons and for names for unique landmarks activate the same brain region. These findings are consistent with the notion that activity in the left temporal pole is linked to the level of specificity of word retrieval rather than the conceptual class to which the stimulus belongs.

Adult↗
PubMed2002

Ureteroscopic treatment of lower pole calculi: comparison of lithotripsy in situ and after displacement.

PURPOSE: Ureteroscopic management is a viable option for lower pole calculi less than 2 cm. Recently a technique was described to displace the calculus into a more accessible calix using a nitinol basket or grasper before lithotripsy. We compared the efficacy and safety of this technique with in situ treatment of small and intermediate lower pole calculi. MATERIALS AND METHODS: We retrospectively reviewed the records of 95 ureteroscopy cases performed at our institution from January 1997 through August 2001 for renal calculi located only in the lower pole. Preoperative patient characteristics, stone size, operative details, complications and outcomes were compared for calculi treated in situ and those displaced before treatment. RESULTS: Adequate followup was available on 78 patients. Patients in the displacement group were statistically older, more often had a preoperative indwelling ureteral stent and had a mean operative time that was 16 minutes longer (p = 0.04). Average stone diameter in the in situ and displacement groups was 8 and 10.3 mm., respectively (p = 0.04). In patients with radiographic followup greater than 1 month complete success was obtained for 77% of stones 1 cm. or less treated in situ versus 89% treated with displacement first (p = 0.43). For calculi greater than 1 cm. complete success was obtained for 2 of the 7 (29%) treated in situ versus all 7 (100%) treated with displacement (p = 0.005). CONCLUSIONS: When treating lower pole calculi 1 to 2 cm. via ureteroscopy, a higher success rate can be obtained with displacement into a more accessible calix before treatment.

Adult↗