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At least 271 records · Page 15Linked to original sources
PubMed1986

Aster-free spindle poles in insect spermatocytes: evidence for chromosome-induced spindle formation?

Tipulid spermatocytes form normally functioning bipolar spindles after one of the centrosomes is experimentally dislocated from the nucleus in late diakinesis (Dietz, R., 1959, Z. Naturforsch., 14b:749-752; Dietz, R., 1963, Zool. Anz. Suppl., 23:131-138; Dietz, R., 1966, Heredity, 19:161-166). The possibility that dissociated pericentriolar material (PCM) is nevertheless responsible for the formation of the spindle in these cells cannot be ruled out based on live observation. In studying serial sections of complete cells and of lysed cells, it was found that centrosome-free spindle poles in the crane fly show neither pericentriolar-like material nor aster microtubules, whereas the displaced centrosomes appear complete, i.e., consist of a centriole pair, aster microtubules, and PCM. Exposure to a lysis buffer containing tubulin resulted in an increase of centrosomal asters due to aster microtubule polymerization. Aster-free spindle poles did not show any reaction, also indicating the absence of PCM at these poles. The results favor the hypothesis of chromosome-induced spindle pole formation at the onset of prometaphase and the dispensability of PCM in Pales.

Animals↗
PubMed1986

A novel mitotic spindle pole component that originates from the cytoplasm during prophase.

Several unique aspects of mitotic spindle formation have been revealed by investigation of an autoantibody present in the serum of a patient with the CREST (calcinosis, Raynaud's phenomenon, esophageal dysmotility, schlerodacytyly, and telangiectasias) syndrome. This antibody was previously shown to label at the spindle poles of metaphase and anaphase cells and to be absent from interphase cells. We show here that the serum stained discrete cytoplasmic foci in early prophase cells and only later localized to the spindle poles. The cytoplasmic distribution of the antigen was also seen in nocodazole-arrested cells and prophase cells in populations treated with taxol. In normal and taxol-treated cells, the microtubules appeared to emanate from the cytoplasmic foci and polar stain, and in cells released from nocodazole block, microtubules regrew from antigen-containing centers. This characteristic distribution suggests that the antigen is part of a microtubule organizing center. Thus, we propose that a prophase originating polar antigen functions in spindle pole organization as a coalescing microtubule organizing center that is present only during mitosis. Characterization of the serum showed reactions with multiple proteins at 115, 110, 50, 36, 30, and 28 kD. However, affinity-eluted antibody from the 115/110-kD bands was shown to specifically label the spindle pole and cytosolic foci in prophase cells.

Autoantibodies↗
PubMed1997

Mitotic spindle poles are organized by structural and motor proteins in addition to centrosomes.

The focusing of microtubules into mitotic spindle poles in vertebrate somatic cells has been assumed to be the consequence of their nucleation from centrosomes. Contrary to this simple view, in this article we show that an antibody recognizing the light intermediate chain of cytoplasmic dynein (70.1) disrupts both the focused organization of microtubule minus ends and the localization of the nuclear mitotic apparatus protein at spindle poles when injected into cultured cells during metaphase, despite the presence of centrosomes. Examination of the effects of this dynein-specific antibody both in vitro using a cell-free system for mitotic aster assembly and in vivo after injection into cultured cells reveals that in addition to its direct effect on cytoplasmic dynein this antibody reduces the efficiency with which dynactin associates with microtubules, indicating that the antibody perturbs the cooperative binding of dynein and dynactin to microtubules during spindle/aster assembly. These results indicate that microtubule minus ends are focused into spindle poles in vertebrate somatic cells through a mechanism that involves contributions from both centrosomes and structural and microtubule motor proteins. Furthermore, these findings, together with the recent observation that cytoplasmic dynein is required for the formation and maintenance of acentrosomal spindle poles in extracts prepared from Xenopus eggs (Heald, R., R. Tournebize, T. Blank, R. Sandaltzopoulos, P. Becker, A. Hyman, and E. Karsenti. 1996. Nature (Lond.). 382: 420-425) demonstrate that there is a common mechanism for focusing free microtubule minus ends in both centrosomal and acentrosomal spindles. We discuss these observations in the context of a search-capture-focus model for spindle assembly.

Animals↗
PubMed2004

Dynein/dynactin regulate metaphase spindle length by targeting depolymerizing activities to spindle poles.

During cell division metaphase spindles maintain constant length, whereas spindle microtubules continuously flux polewards, requiring addition of tubulin subunits at microtubule plus-ends, polewards translocation of the microtubule lattice, and removal of tubulin subunits from microtubule minus-ends near spindle poles. How these processes are coordinated is unknown. Here, we show that dynein/dynactin, a multi-subunit microtubule minus-end-directed motor complex, and NuMA, a microtubule cross-linker, regulate spindle length. Fluorescent speckle microscopy reveals that dynactin or NuMA inhibition suppresses microtubule disassembly at spindle poles without affecting polewards microtubule sliding. The observed uncoupling of these two components of flux indicates that microtubule depolymerization is not required for the microtubule transport associated with polewards flux. Inhibition of Kif2a, a KinI kinesin known to depolymerize microtubules in vitro, results in increased spindle microtubule length. We find that dynein/dynactin contribute to the targeting of Kif2a to spindle poles, suggesting a model in which dynein/dynactin regulate spindle length and coordinate flux by maintaining microtubule depolymerizing activities at spindle poles.

Animals↗
PubMed2000

A New Late Middle Cambrian Paleomagnetic Pole for the Ellsworth Mountains, Antarctica.

A paleomagnetic study of the late Middle to possibly early Late Cambrian Liberty Hills Formation in the Ellsworth Mountains, Antarctica, reveals a stable magnetization with positive fold and reversal tests. The paleopole is based on 16 sites from volcanic and sedimentary rocks and lies at lat 7.3 degrees N and long 326.3 degrees E (A95=6.0&j0;). The new paleomagnetic data support the view that the Ellsworth Mountains are part of a microplate-the Ellsworth-Whitmore Mountains crustal block-that rotated independently of the main Gondwana continental blocks during breakup. The Liberty Hills pole differs from both previous poles recovered from Cambrian rocks in the Ellsworth Mountains and from the available Gondwana reference pole data. Our pole indicates a more northerly prebreakup position for the Ellsworth Mountains than previously suggested, contradicting the overwhelming geologic evidence for a prebreakup position close to southern Africa. The reasons for this are uncertain, but we suggest that problems with the Gondwana apparent polar wander path may be important. More well constrained, early Paleozoic paleomagnetic data are required from the Ellsworth Mountains and the Gondwana continents if the data are to constrain further the Middle-Late Cambrian location of the Ellsworth-Whitmore Mountains block.

Journal Article↗
PubMed2002

Single upper-pole percutaneous access for treatment of > or = 5-cm complex branched staghorn calculi: is shockwave lithotripsy necessary?

BACKGROUND AND PURPOSE: Percutaneous nephrolithotomy for staghorn calculi is reported to have a residual stone rate of 28%, while shockwave lithotripsy alone results in residual stones in approximately 50% of cases. Combination therapy, sandwich therapy, and multiple percutaneous accesses have also been advocated for staghorn stones. We believe these stones can often be removed with a staged procedure via a single upper-pole percutaneous access using flexible nephroscopy and the holmium:YAG laser. Our experience is reviewed. PATIENTS AND METHODS: The hospital records of patients having a cumulative stone burden > or =5 cm who underwent percutaneous nephrolithotripsy (PCNL) for a single complex staghorn calculus were reviewed. There were 15 male and 34 female patients having 45 complete and 7 partial staghorn calculi constituting a mean stone burden of 6.7 cm (range 5.0-10.0 cm). A calix was punctured that would provide access to the majority of the involved calices. Thirty-five renal units were approached through a single upper-pole percutaneous access, and four and six renal units were accessed through single middle or lower-pole calices, respectively. The remaining seven renal units were treated with multiple percutaneous accesses. RESULTS: In the renal units having only a single access, a mean of 1.6 (range 1-3) procedures were required to achieve stone-free status. The mean operating room time was 2.9 hours (range 2.0-3.5 hours). For the second PCNL, the mean operating room time was 63 minutes (range 30-90 minutes). Two patients (two renal units) had residual stones <1 cm in diameter. One refused additional surgery, and the other is awaiting further treatment. The mean estimated blood loss was 238 mL (range 50-800 mL), with only one procedure (2.2%) necessitating a blood transfusion. One (2.8%) hydrothorax developed among the 35 upper-pole puncture cases. Six patients had transient oral temperature readings >101 degrees F with negative blood cultures. Other early complications included single cases of leg cellulitis, atrial fibrillation, and noncardiac chest pain. There were no delayed surgical complications. Patients were discharged from the hospital a mean 2 days (range 1-10 days) after the first PCNL. CONCLUSION: Use of flexible nephroscopy with holmium:YAG laser lithotripsy and Nitinol basket stone extraction has allowed us to render staghorn-containing renal units stone free in a mean of 1.6 procedures. Of the 45 renal units treated through a single percutaneous access, 43 (95%) were rendered stone free. The holmium:YAG laser appears to be a safe lithotrite for the kidney, as no complications occurred from its use.

Adult↗
PubMed2001

SPO21 is required for meiosis-specific modification of the spindle pole body in yeast.

During meiosis II in the yeast Saccharomyces cerevisiae, the cytoplasmic face of the spindle pole body changes from a site of microtubule initiation to a site of de novo membrane formation. These membranes are required to package the haploid meiotic products into spores. This functional change in the spindle pole body involves the expansion and modification of its cytoplasmic face, termed the outer plaque. We report here that SPO21 is required for this modification. The Spo21 protein localizes to the spindle pole in meiotic cells. In the absence of SPO21 the structure of the outer plaque is abnormal, and prospore membranes do not form. Further, decreased dosage of SPO21 leaves only two of the four spindle pole bodies competent to generate membranes. Mutation of CNM67, encoding a known component of the mitotic outer plaque, also results in a meiotic outer plaque defect but does not block membrane formation, suggesting that Spo21p may play a direct role in initiating membrane formation.

Alleles↗
PubMed1999

Neovascularization at the vascular pole region in diabetic glomerulopathy.

BACKGROUND: Diabetic nephropathy is associated with renal structural changes involving all of the compartments. Most characteristic is the diabetic glomerulopathy. Studies of the histological changes during the early phases of nephropathy have included the glomerulopathy and also the juxtaglomerular structures. Neovascularization, well-known in diabetic retinopathy, has also been observed in the kidney. The present study concerns estimates of frequency of neovascularization at the vascular pole region in early stages of diabetic nephropathy. METHODS: Extra efferent arterioles at the glomerular vascular pole were detected during measurements of the vascular pole area applying 1-microm serial sections through kidney biopsies. It was observed that more than one efferent arteriole existed occasionally. The present study was carried out with the aim of estimating the frequency of this phenomenon in diabetic patients and in non-diabetic controls, the diabetic patients categorized according to the level of albumin excretion rate. RESULTS: Neovascularization was first observed in IDDM patients with microalbuminuria. Some of the cases presented the phenomenon in all of the glomeruli studied. As the examinations of many kidney biopsies continued the phenomenon was observed also in the non-diabetic control group and in one IDDM patient with normoalbuminuria. However, the frequency was statistically highly significantly increased in patients with elevated albumin-excretion. Within this group a strong correlation between frequency of neovascularization and the severity of diabetic glomerulopathy is seen. CONCLUSIONS: The vascular abnormality localized to the vascular pole region is observed occasionally in the normal kidney, but the frequency is increased in patients with diabetic glomerulopathy. The abnormality may develop as a consequence of a long-standing diabetic glomerulopathy and might lead to less pronounced elevation of albumin excretion.

Adolescent↗
PubMed2002

Fate of the retained ureteral stump after upper pole heminephrectomy in duplex kidneys.

PURPOSE: We review the long-term outcome of retained ureteral stumps in children undergoing heminephrectomy for nonfunctioning upper pole moieties in duplex kidneys. MATERIALS AND METHODS: The medical records of 50 patients who underwent 50 upper pole heminephrectomies for a nonfunctioning upper pole moiety of a duplex kidney between January 1990 and December 2000 were reviewed retrospectively. RESULTS: Median patient age at heminephrectomy was 2.5 years (range 3 weeks to 16.5 years) and median followup was 6 years (range 1 to 11). Indications for heminephrectomy in the 50 renal units were obstructive ureterocele in 25 (50%) cases, ectopic ureter in 15 (30%), obstructive megaloureter in 5 (10%) and reflux nephropathy in 5 (10%). A total of 48 (96%) of the corresponding ureters were taken down as low as possible and transfixed through the heminephrectomy incision. Residual stump excision was required in 5 (10%) of the 50 units for recurrent urinary tract infection due to vesicoureteral reflux. CONCLUSIONS: Our long-term followup suggests that the majority of patients with residual ureteral stumps after upper pole heminephrectomy do not require stump resection.

Adolescent↗
PubMed1999

Modified Antia-Buch repair for full-thickness upper pole auricular defects.

Various reconstructive techniques have been described for repair of full-thickness upper pole auricular defects. The wedge excision commonly used for treatment of upper pole tumors allows excision and reconstruction in a single stage. However, this technique suffers from major deficiencies. We apply the concept of crescentic scaphal excision and the Antia-Buch advancement-rotation flap principle to repair various full-thickness upper pole auricular defects resulting from excision of skin lesions in eight consecutive patients. The technique achieves a natural auricular shape in three dimensions with minimal disruption of the anatomic landmarks and avoids conspicuous scars. It has several advantages over the original Antia-Buch repair and other techniques used for reconstruction of full-thickness upper pole auricular defects.

Aged↗
PubMed2005

Percutaneous access to upper pole renal stones: role of prone 3-dimensional computerized tomography in inspiratory and expiratory phases.

PURPOSE: We evaluated the role of noncontrast, prone position, inspiratory and expiratory 3-dimensional spiral computerized tomography (PIE-CT) for preoperative planning of percutaneous treatment in patients with complex upper pole renal calculi. MATERIALS AND METHODS: In this pilot study a total of 6 renal units in 4 women and 1 man with complex upper pole calculi who were candidates for percutaneous nephrolithotomy were evaluated with thin section PIE-CT. With the patient imaged in the prone position percutaneous access was simulated under 4 potential access conditions, including subcostal and intercostal, in inspiration and expiration. Each potential access was then deemed transpleural or extrapleural and minimally angulated or severely angulated cephalad. RESULTS: PIE-CT was performed uneventfully in all patients. Ideal nonangulated extrapleural percutaneous access was deemed possible in 5 of 6 renal units. However, inspiratory plus expiratory phases were necessary to identify the most suitable access site. In 2 renal units only 1 safe access site was identified. No pulmonary complications were noted in any of these patients. In 1 renal unit no suitable access could be identified and this patient was treated with laparoscopic caliceal diverticulectomy. CONCLUSIONS: Thin section PIE-CT offers 3-dimensionally rendered images that clearly demonstrate anatomical relationships among the kidney, calculi, pleura, diaphragm, ribs and surrounding organs. In this pilot study PIE-CT provided useful data for planning urological intervention for complex upper pole renal stones. This study also suggests that generalizations regarding the safety of upper pole access in the inspiratory or expiratory phase are not warranted.

Exhalation↗
PubMed2005

Prospective, randomized trial comparing shock wave lithotripsy and ureteroscopy for lower pole caliceal calculi 1 cm or less.

PURPOSE: The optimal management of lower pole renal calculi is controversial. We compared shock wave lithotripsy (SWL) and ureteroscopy (URS) for the treatment of patients with small lower pole stones in a prospective, randomized, multicenter trial. MATERIALS AND METHODS: A total of 78 patients with 1 cm or less isolated lower pole stones were randomized to SWL or URS. The primary outcome measure was stone-free rate on noncontrast computerized tomography at 3 months. Secondary outcome parameters were length of stay, complication rates, need for secondary procedures and patient derived quality of life measures. RESULTS: A total of 67 patients randomized to SWL (32) or URS (35) completed treatment. The 2 groups were comparable with respect to age, sex, body mass index, side treated and stone surface area. Operative time was significantly shorter for SWL than URS (66 vs 90 minutes). At 3 months of followup 26 and 32 patients who underwent SWL and URS had radiographic followup that demonstrated a stone-free rate of 35% and 50%, respectively (p not significant). Intraoperative complications occurred in 1 SWL case (unable to target stone) and in 7 URS cases (failed access in 5 and perforation in 2), while postoperative complications occurred in 7 SWL and 7 URS cases. Patient derived quality of life measures favored SWL. CONCLUSIONS: This study failed to demonstrate a statistically significant difference in stone-free rates between SWL and URS for the treatment of small lower pole renal calculi. However, SWL was associated with greater patient acceptance and shorter convalescence.

Adult↗
PubMed2005

Risk of injury to adjacent organs with lower-pole fluoroscopically guided percutaneous nephrostomy: evaluation with prone, supine, and multiplanar reformatted CT.

PURPOSE: To assess the risk of injury to organs near the kidney during lower-pole fluoroscopically guided percutaneous nephrostomy by evaluation of prone, supine, and multiplanar reformatted computed tomography (CT). MATERIALS AND METHODS: Eighty-three patients who underwent prone and supine CT examinations were identified retrospectively. The expected path of nephrostomy tube placement to the lower-pole calyx was simulated on prone and supine axial images and multiplanar CT reformations. Intervening organs along this path were considered at risk for injury and were recorded for each kidney (N = 166). RESULTS: The risk of organ injury as determined on multiplanar reformatted prone images (n = 5) and supine images (n = 0) was significantly less (P < .05) than determined on axial prone images (n = 25) or supine images (n = 10). The colon was the only organ identified to be at risk for injury during the simulated lower-pole percutaneous nephrostomy placement; spleen and liver were not seen along the nephrostomy path on axial or multiplanar reformatted images. CONCLUSION: Lower-pole fluoroscopically guided percutaneous nephrostomy carries a low risk of visceral injury, and the risk of injury is overestimated by evaluation of axial CT images alone compared with oblique parasagittal reformations.

Adult↗
PubMed1982

Incorporation of diaminopimelic acid into the old poles of Escherichia coli.

The surface stress theory of the ontogeny of the bacterial rod depends critically on whether the old poles continue to incorporate new material into the stress-bearing murein. If insertion of peptidoglycan continues, then seemingly the shape must become gradually rounder due to the surface stress resulting from the internal hydrostatic pressure. We have reanalysed our earlier experimental data by classifying grains with respect to distance from the nearest pole, and not from the cell centre as was done previously, and conclude that old poles do incorporate new diaminopimelic acid residues. This eliminates the model we have proposed for Gram-positive rods, which assumed diffuse growth on the cylindrical sides and that poles once formed would be rigid. The new results are consistent with another model (presented elsewhere) in which insertion of new murein occurs all over the surface, although not equally. This new model leads to elongation and division if the energetics of wall expansion is altered by the cell in a control region at a particular point of the cycle by the cell.

Amino Acids, Diamino↗
PubMed1995

Pole-tracking algorithms for the extraction of time-variant heart rate variability spectral parameters.

Various algorithms of autoregressive (AR) recursive identification make it possible to evaluate power spectral distribution in correspondence with each sample of a time series, and time-variant spectral parameters can be calculated through the evaluation of the pole positions in the complex z-plane. In traditional analysis, the poles are obtained by zeroing the denominator of the model transfer function, expressed as a function of the AR coefficients. In this paper, two algorithms for the direct updating and tracking of movements of poles of an AR time-variant model on the basis of the innovation given to the coefficients are presented and investigated. The introduced algorithms are based upon 1) the classical linearization method and 2) a recursive method to compute the roots of a polynomial, respectively. In the present paper, applications in the field of heart rate variability (HRV) signal analysis are presented and efficient tools are proposed for quantitative extraction of spectral parameters (power and frequency of the low-frequency (LF) and high-frequency (HF) components) for the monitoring of the action of the autonomic nervous system in transient patho-physiological events. These computational methods seem to be very attractive for HRV applications, as they inherit the peculiarity of recursive time-variant identification, and provide a more immediate comprehension of the spectral process characteristics when expressed in terms of poles and AR spectral components.

Algorithms↗
PubMed2003

Electric poling and electromechanical characterization of 0.1-mm-thick sensor films and 0.2-mm-thick cable layers from piezoelectric poly(vinylidene fluoride-trifluoroethylene).

Piezoelectric polymers have been proposed for many sensor and actuator applications. Among these, piezoelectric polymer films with thicknesses between several tens and a few hundreds of micrometers as well as coaxial cables with piezoelectric polymer layers are highly suitable and attractive for the detection of mechanical loads. In addition to good piezoelectric properties, materials for such sensors should have high mechanical strength. Therefore, the most common materials are nonporous piezoelectric polymers, such as polyvinylidene fluoride (PVDF) or its copolymer with trifluoroethylene (P(VDF-TrFE)). Here, P(VDF-TrFE) polymer films as well as the operating principle and the geometry of piezoelectric polymer cables are described. As active piezoelectric cable layer, P(VDF-TrFE) (76/24) was employed. After electrical poling with one or more point-to-cable corona discharges, the polarization in the P(VDF-TrFE) layer was investigated. Poling parameters, such as electric field and poling time, were varied. The resulting polarization was characterized with measurements of polarization profiles across the film or the cable-layer thickness as well as with the determination of other electromechanical quantities. The optimized poling process yields good piezoelectric properties in the piezoelectric polymer layers as well as useful sensor properties of the piezoelectric polymer cable, which are assessed and discussed.

Journal Article↗
PubMed2002

RacA, a bacterial protein that anchors chromosomes to the cell poles.

Eukaryotic chromosomes are anchored to a spindle apparatus during mitosis, but no such structure is known during chromosome segregation in bacteria. When sister chromosomes are segregated during sporulation in Bacillus subtilis, the replication origin regions migrate to opposite poles of the cell. If and how origin regions are fastened at the poles has not been determined. Here we describe a developmental protein, RacA, that acts as a bridge between the origin region and the cell poles. We propose that RacA assembles into an adhesive patch at a centromere-like element near the origin, causing chromosomes to stick at the poles.

Bacillus subtilis↗
PubMedDate not supplied

Distal patellar pole fractures. A proposed common mechanism of injury.

A variety of names has been given to disorders of the inferior pole of the patella occurring in young athletic individuals and several different causes have been proposed for these disorders. Occasionally a direct blow will cause fracture of the inferior pole of the patella, but the only other mechanism which seems to be responsible is subluxation or dislocation. Ten cases of distal patellar pole fracture secondary to dislocation or subluxation of the patella are reported. From these cases and an extensive review of the literature it is concluded that patellar subluxation or dislocation is the usual common mechanism of distal patellar pole fractures in young, active individuals and that adequate treatment of this problem must address the patellar instability as well as the fracture.

Adolescent↗