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At least 397 records · Page 22Linked to original sources
PubMed1978

Study of pole assembly in Bacillus subtilis by computer reconstruction of septal growth zones seen in central, longitudinal thin sections of cells.

The septal growth of Bacillus subtilis 168/s has been studied by making a number of observations from thin sections of cells from exponentially growing cultures. The process was initiated by the formation of a new cross wall under a preexisting layer of cylindrical wall. An annular notch appeared to cut through the overlying wall and presumably allowed the cross wall to split into two layers of peripheral wall. During this initial notching process, two raised bands of wall material were produced which resembled those previously observed in morphological studies of Streptococcus faecalis. Through an improved fixation technique, it was possible to preserve the bands seen in B. subtilis to the extent that they were used as markers to study the subsequent stages of septal growth. These stages included (i) the continued displacement of the two bands from the cross wall (as the two nascent polar surfaces enlarged and as the diameter of the cross wall decreased), (ii) the closure of the cross wall, and (iii) the final severance of the common cross wall connection between two completed poles. To study this process in a more quantitative manner, three-dimensional reconstructions of the envelope observed between pairs of the raised bands were made from axial thin sections of cells. The process of reconstruction was based on a technique by which x, y coordinates were taken from thin sections and were rotated around the cell's central axis. These reconstructions were used to estimate the surface area or volume of the reconstructed zones or their parts. A round of septal growth was then simulated by arranging 118 reconstructions in order of increasing surface area or volume. The topology of the process was studied by noting how various measurements of septal thickness, length, surface area, and volume varied as a function of increasing septal zone size. This analysis was based on several assumptions, of which three of the most important are: (i) the bands produced by the initial notching process are markers which separate septal from cylindrical wall growth; (ii) a septal zone observed between pairs of bands is made up of two nascent poles and a single cross wall; and (iii) as septal zones develop in terms of relative age they increase in size (volume or surface area) or amount of wall. The data suggested that the S. faecalis model of surface growth (in which polar growth occurs through a regulated constrictive separation and expansion of a cross wall) also seems applicable to the pattern of septal growth observed here for B. subtilis. This was indicated from measurements which showed that increases in the size of nascent polar surfaces were correlated with decreases in cross wall diameter. An explanation of these observations may be that decreases in cross wall diameter were due to a progressive splitting of the cross wall that removed surface from the outer circumference of the cross wall and converted it into new polar surface. Calculations further suggested that if the poles of B. subtilis were made by this model a sizeable and variable increase in surface area of the cross wall would also be required to convert these separating cross wall layers into two curved polar structures. Measurements of wall thickness taken from various locations within septal zones indicated that while the thickness of the polar wall of B. subtilis was constant over its surface, the width of the cross wall varied considerably during a round of synthesis. Again, one of the simplest explanations compatible with these observations and those previously made in S. faecalis is that the B. subtilis cross wall is brought to a constant thickness (possibly by remodeling or precursor addition) before or during separation. Although most observations made from the reconstruction of the septal zones of B. subtilis may fit the S. faecalis model of surface growth, differences in the pattern of septal growth were seen when the two organisms were compared. These have been discussed in terms of differences in the regulation of their respective septal growth sites and basic mechanisms of wall assembly and modification.

Bacillus subtilis↗
PubMed1993

The essential mitotic target of calmodulin is the 110-kilodalton component of the spindle pole body in Saccharomyces cerevisiae.

Two independent methods identified the spindle pole body component Nuf1p/Spc110p as the essential mitotic target of calmodulin. Extragenic suppressors of cmd1-1 were isolated and found to define three loci, XCM1, XCM2, and XCM3 (extragenic suppressor of cmd1-1). The gene encoding a dominant suppressor allele of XCM1 was cloned. On the basis of DNA sequence analysis, genetic cosegregation, and mutational analysis, XCM1 was identified as NUF1/SPC110. Independently, a C-terminal portion of Nuf1p/Spc110p, amino acid residues 828 to 944, was isolated as a calmodulin-binding protein by the two-hybrid system. As assayed by the two-hybrid system, Nuf1p/Spc110p interacts with wild-type calmodulin and triple-mutant calmodulins defective in binding Ca2+ but not with two mutant calmodulins that confer a temperature-sensitive phenotype. Deletion analysis by the two-hybrid system mapped the calmodulin-binding site of Nuf1p/Spc110p to amino acid residues 900 to 927. Direct binding between calmodulin and Nuf1p/Spc110p was demonstrated by a modified gel overlay assay. Furthermore, indirect immunofluorescence with fixation procedures known to aid visualization of spindle pole body components localized calmodulin to the spindle pole body. Sequence analysis of five suppressor alleles of NUF1/SPC110 indicated that suppression of cmd1-1 occurs by C-terminal truncation of Nuf1p/Spc110p at amino acid residues 856, 863, or 881, thereby removing the calmodulin-binding site.

Binding Sites↗
PubMed1985

Does actin produce the force that moves a chromosome to the pole during anaphase?

Chromosomes move towards spindle poles because of force produced by chromosomal spindle fibres. I argue that actin is involved in producing this force. Actin is present in chromosomal spindle fibres, with consistent polarity. Physiological experiments using ultraviolet microbeam irradiations suggest that the force is due to an actin and myosin (or myosin-equivalent) system. Other physiological experiments (using inhibitors in "leaky" cells or antibodies injected into cells) that on the face of it would seem to rule out actin and myosin on closer scrutiny do not really do so at all. I argue that in vivo the "on" ends of chromosomal spindle fibre microtubules are at the kinetochores; I discuss the apparent contradiction between this conclusion and those from experiments on microtubules in vitro. From what we know of treadmilling in microtubules in vitro, the poleward movements of irradiation-induced areas of reduced birefringence (arb) can not be explained as treadmilling of microtubules: additional assumptions need to be made for arb movements toward the pole to be due to treadmilling. If arb movement does indeed represent treadmilling along chromosomal spindle fibre microtubules, treadmilling continues throughout anaphase. Thus I suggest that chromosomal spindle fibres shorten in anaphase not because polymerization is stopped at the kinetochore (the on end), as previously assumed, but rather because there is increased depolymerization at the pole (the "off" end).

Actins↗
PubMed1997

Experimental evidence of a plant meridian system: V. Acupuncture effect on circumnutation movements of shoots of Phaselus vulgaris L. pole bean.

When the first unifoliolate leaf of Phaselus vulgaris L. cv. Kentucky wonder pole bean was at the expended stage, two needles were inserted into opposite sides of the stem near the unifoliolate bud and left there for the entire experiment. Changes of the period of circumnutation movement at the shoots of Phaselus vulgaris L. pole bean were measured. Results from two separate experiments are reported in this communication. In the first experiment, the mean period of the ultradian rhythms of the horizontal circumnutation movement of shoots was reduced significantly (p = 0.0022) from 124.2 minutes in controls to 116.3 minutes in the treated plants. The average period of the ultradian rhythms of circumnutation movement in the treated and the untreated groups from the second experiments were 96.7 and 132.1, minutes respectively, which was statistically significant (p < 0.0001). This study demonstrates for the first time that acupuncture markedly shortens the period lengths of the ultradian rhythms of circumnutation movement of the shoots of the Phaselus vulgaris L. pole bean.

Acupuncture Therapy↗
PubMed1986

Obstruction of the upper-pole moiety in renal duplication in adults: CT evaluation.

Delineation of the presence and anatomy of an obstructed, nonfunctioning upper-pole duplex system often requires multiple imaging techniques. Computed tomography (CT) was used to evaluate duplex systems in five adult patients. Independent of renal function, CT allowed assessment of the presence of a duplex system, determination of whether the system was obstructed, assessment of the quantity of residual parenchyma in the upper-pole system, determination of whether the ectopic ureter was intravesical or extravesical, and assessment of the retroperitoneum to look for unusual causes of upper-pole ureteral obstruction.

Adult↗
PubMed1994

Visual response properties of single neurons in the temporal pole of behaving monkeys.

1. The responses of single neurons in the anterior part of the temporal cortex in monkeys, mainly the temporopolar cortex, area 36, and the most anterior part of area TE of von Bonin and Bailey (1947) (these areas were designated here as the temporal pole), were examined during the performance of a visual recognition memory task. The visual stimulus (sample stimulus) was presented when the monkey pressed a lever. The same sample stimulus was presented one to four times and, thereafter, a new stimulus was presented. The monkeys were trained to discriminate the new stimulus from the sample stimulus and to release the lever in response to the new stimulus. We used colored photographs of natural objects (human faces, monkeys, foods, and non-food objects) as complex visual stimuli or computer-generated two-dimensional shapes (a red square, a green circle, etc.) as simple visual stimuli. 2. In total, the activity of 311 neurons was recorded, and 225 of these responded to at least one visual stimulus. All visually responsive neurons were located in the ventral part of the temporal pole including the banks of the superior temporal sulcus. 3. The relationship between the monkey's eye movements and visual responses was investigated. Visual response properties, such as the number of spikes, onset latency, and response duration, were stable regardless of the monkey's eye positions and movements if the eyes were directed to the display. We also examined the receptive field property of neurons (n = 3). The neurons tested in the temporal pole tended to have a large receptive field (24 x 24 degrees). 4. The neurons tended to respond to different stimuli in different magnitudes. In each case, the maximal responses were elicited by complex, colored photographs, whereas simple, two-dimensional colored shapes elicited little or no responses. In 21% of the cases (47/225), the magnitude of the maximal response was significantly larger than for any of the other responses. 5. An achromatic version of the stimulus that induced the maximal response was tested in 53 neurons. About 80% of the neurons (41/53) responded to the achromatic stimulus at a magnitude that was not significantly different from the response to the original stimulus. In 12 neurons, the removal of color did significantly decrease the magnitude of the response. When other colors were tested, 3 of 9 neurons were found to code for color. 6. In 21 of these 53 neurons, a portion (the left-, right-, upper-, or lower-half) of the stimulus was also tested.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1998

Single stones of the lower pole of the kidney. Comparative results of extracorporeal shock wave lithotripsy and percutaneous nephrolithotomy.

OBJECTIVE: To assess the effectiveness of extracorporeal shock wave lithotripsy (ESWL) and percutaneous nephrolithotomy (PCN) as a treatment for stones of the lower pole of the kidney and to compare their morbidity according to the stone size. METHODS: We retrospectively studied 739 patients treated for a single stone of the lower pole. Group I consisted of 666 patients treated by ESWL and group II consisted of 73 patients treated by PCN. RESULTS: These were assessed at 3 months for 587 ESWL patients (88%) and at day 1 for all PCN patients on renal tomography or ultrasonography. Respectively in groups I and II, 335 patients (57%) and 53 patients (72.6%) were stone-free (p = 0.01). For medium-size (10-20 mm) stone patients, stone-free represented 102 patients (44%) and 29 patients (72.5%) in groups I and II respectively (p = 0.001). For smaller stones (< 10 mm), stone-free represented 231 patients (69%) and 21 patients (84%) in groups I and II respectively (p = 0.12). Morbidity rate was less with ESWL than with PCN. CONCLUSIONS: PCN achieves better results than ESWL for single stone of the lower pole with statistical significance for middle-size stones but with higher morbidity.

Adolescent↗
PubMed1992

Alpha-1-antitrypsin (PI) subtypes in Russians and Poles.

alpha-1-antitrypsin (PI) subtypes were studied in Poles and Russians. The frequencies of the PI alleles were similar in the two populations, with the exception of the Z allele, whose frequency was significantly lower in Poles. The M3 allele frequency, which is highly heterogeneous in European populations, has medium frequencies in Poles and Russians.

Adult↗
PubMed2001

Cell lineages and tissue boundaries in cardiac arterial and venous poles: developmental patterns, animal models, and implications for congenital vascular diseases.

Multiple cell populations with different embryological histories are involved in the morphogenesis of the cardiac arterial and venous poles as well as in the correct alignment and connection of the developing vessels with the cardiac chambers. Formation of the aorta and the pulmonary trunk is a complicated process orchestrated via a specific sequence of highly integrated spatiotemporal events of cell proliferation, migration, differentiation, and apoptosis. The peculiar susceptibility of this intricate cell network to be altered explains the frequency of congenital cardiovascular diseases of the arterial and venous poles. We review this topic from the "vascular point of view," putting major emphasis on (1) the existence of different cell lineages from which smooth muscle cells of the aorticopulmonary trunk can be derived, (2) the establishment of cell/tissue boundaries in the cardiovascular connecting regions, and (3) the animal models that can mimic human congenital defects of the arterial and venous poles of the heart.

Animals↗
PubMedDate not supplied

Skiers' thumb injuries associated with flared ski pole handles.

Three skiers presented for treatment of significant thumb injuries sustained while skiing. Each patients was using a strapless ski pole handle with a flared thumb support. These skiers felt their interphalangeal (IP) joint flexion was blocked by the flare of their ski pole handle, causing their protruding thumb tip to be the point of initial impact, thus leading to their injury. Prior to use of any ski pole handle, full flexion of the gloved thumb IP joint should be verified.

Adult↗
PubMed2005

Valois, a component of the nuage and pole plasm, is involved in assembly of these structures, and binds to Tudor and the methyltransferase Capsuléen.

Using the Capsuleen (Csul) methyltransferase as bait in the yeast two-hybrid system, we have identified a novel Drosophila protein containing multiple WD repeats and encoded by the valois (vsl) gene, which acts in pole plasm function. Vls is homologous to human MEP50, which forms a complex with the PRMT5 methyltransferase--the human homologue of Csul. We found that Vls localizes to the nuage in the nurse cells and to the pole plasm in the oocyte. Moreover vls is required for the synthesis and/or stability of Oskar and the localization of Tudor (Tud) in both the nuage and at the posterior pole of the oocyte. Furthermore, we show that Vls and a fragment of Tud interact directly in binding assay. As the PMRT5/MEP50 complex is involved in ribonucleoprotein complex assembly, we hypothesize that the Vls complex may play a similar function in assembling the nuage in nurse cells and the polar granules in the oocyte.

Amino Acid Sequence↗
PubMed1989

Multiple steps in the localization of bicoid RNA to the anterior pole of the Drosophila oocyte.

The anterior region of the Drosophila embryonic pattern is determined by a gradient of the bicoid (bcd) protein. The correct formation of this gradient requires the localization of bcd RNA to the anterior pole of the egg. Here we use a wholemount in situ technique to examine the process of bcd RNA localization during oogenesis and embryogenesis. While bcd protein becomes distributed in a gradient that extends throughout the anterior two thirds of the early embryo, bcd RNA remains restricted to a much smaller region at the anterior pole. The difference between these distributions indicates that the shape of the protein gradient must depend to some extent on the posterior movement of the protein after it has been synthesized. Four distinct phases of bcd RNA localization can be distinguished during oogenesis. Between stages 6 and 9 of oogenesis, the RNA accumulates in a ring at the anterior end of the oocyte. During the second phase, in stage 9-10a follicles, the RNA also localizes to the apical regions of the nurse cells, demonstrating that the nurse cells possess an intrinsic polarity. As the nurse cells contract during stages 10b-11, all of the bcd RNA becomes localized to the cortex at the anterior end of the oocyte. During a final phase that must occur between stage 12 of oogenesis and egg deposition, the RNA becomes localized to a spherical region that occupies a slightly dorsal position at the anterior pole.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Differential pathways of recruitment for centrosomal antigens to the mitotic poles during bipolar spindle formation.

As cells enter mitosis, centrosomes undergo many transformations and become associated with different molecules in a stage-specific manner. We have developed a protocol for immunofluorescence staining with four antibody probes that can help us to follow the interaction of centrosomal components during mitosis. The cells were first stained with a human autoimmune serum (5051); a monoclonal anti-phosphocentrosomal antibody (CHO3); and an antitubulin antibody. Localization of the antibodies was detected using rhodamine-, fluorescein- and AMCA-conjugated second antibodies, respectively. After photographing marked mitotic cells, coverslips were soaked with 0.2 M glycine-HCl at pH 1.0 for 1 h to release all antibodies bound to the structures. The same cells were re-stained with a human autoantibody (SP-H) specific for spindle poles and a fluorescein-conjugated second antibody. This allowed us to compare the subcellular distribution of three kinds of centrosomal antigens in a single cell. Mitotic PtK1 cells treated with either nocodazole or taxol included microtubule-containing cytoplasmic foci and parallel bundles of short microtubules at the cell periphery. All the centrosomal antibodies stained the same one or two dots corresponding to structures labeled by the tubulin antibody. CHO3 also revealed extra cytoplasmic foci, whereas the SP-H antigen was additionally localized at one end of the free microtubule bundles. As the microtubules reorganized into bipolar spindles during the recovery from drug treatment, the CHO3 and SP-H antigens coalesced into the spindle poles where the 5051 antigen was located, suggesting that centrosomal antigens become associated with spindle poles through very different recruitment pathways.

Alkaloids↗
PubMed1993

Identification of a 102 kDa protein (cytocentrin) immunologically related to keratin 19, which is a cytoplasmically derived component of the mitotic spindle pole.

The mAb RK7, previously shown to recognize keratin 19, was also found to cross-react with a biologically unrelated 102 kDa protein, which becomes associated with the poles of the mitotic apparatus. This newly identified protein, called cytocentrin, is a stable cellular component, may be at least in part phosphorylated, and displays a cell cycle-dependent cellular localization. In interphase cells, it is diffusely distributed in the cytosol and shows no affinity for cytoplasmic microtubules. It becomes localized to the centrosome in early prophase, prior to nuclear envelope breakdown, separation of replicated centrosomes, and nucleation of mitotic apparatus microtubules. During metaphase, cytocentrin is located predominately at the mitotic poles, often appearing as an aggregate of small globular sub-components; it also associates with some polar microtubules. In late anaphase/early telophase cytocentrin dissociates entirely from the mitotic apparatus and becomes temporarily localized with microtubules in the midbody, from which it disappears by late telophase. In taxol-treated cells cytocentrin was associated with the center of the miniasters but also showed affinity for some cytoplasmic microtubules. Studies employing G2-synchronized cells and nocodazole demonstrated that cytocentrin can become associated with mitotic centrosomes independently of tubulin polymerization and that microtubules regrow from antigen-containing foci. We interpret these results to suggest that cytocentrin is a cytoplasmic protein that becomes specifically activated or modified at the onset of mitosis so that it can affiliate with the mitotic poles where it may provide a link between the pericentriolar material and other components of the mitotic apparatus.

Amino Acid Sequence↗
PubMed1998

SPC72: a spindle pole component required for spindle orientation in the yeast Saccharomyces cerevisiae.

The monoclonal antibody 78H6 recognises an 85 kDa component of the yeast spindle pole body. Here we identify and characterise this component as Spc72p, the product of YAL047C. The sequence of SPC72 contains potential coiled-coil domains; its overexpression induced formation of large polymers that were strictly localised at the outer plaque and at the bridge of the spindle pole body. Immunoelectron microscopy confirmed that Spc72p was a component of these polymers. SPC72 was found to be non-essential for cell growth, but its deletion resulted in abnormal spindle positioning, aberrant nuclear migration and defective mating capability. Precisely, deletion of SPC72 resulted in a decreased number of astral microtubules: early in the cell cycle only few were detectable, and these were unattached to the spindle pole body in small-budded cells. Later in the cell cycle few, if any, remained, and they were unable to align the spindle properly. We conclude that Spc72p is not absolutely required for nucleation per se, but is needed for normal abundance and stability of astral microtubules.

Amino Acid Sequence↗
PubMed1982

Ultrastructural studies in the Rhodophyta. I. Development of mitotic spindle poles in Apoglossum ruscifolium, Kylin.

The ultrastructure of somatic mitosis in the germlings of Apoglossum ruscifolium, Kylin, fixed from its natural habitat, was examined to investigate spindle-pole development and the role of the 'polar ring'. It was found that the polar ring originates from a special nuclear pore raised above a small projection of the nuclear envelope. The initiation of mitotic polarity takes the form of changes in the nuclear envelope. These are: close crowding of pores, heavy deposition of electron-opaque material and attachment of microtubules. No such phenomena are to be observed in the equatorial regions of the nuclear envelope, which persists throughout mitosis. The next stage is the development of 'clear zones', which become filled with microtubules excluding all other structures, notably ribosomes, at both poles. At pre-metaphase, microtubules begin to be extended from the clear zones through polar fenestrae in the nuclear envelope into the nucleus itself. With subsequent development of the intranuclear spindle, the microtubules in the clear zones show signs of degeneration. At metaphase, the polar regions of the nuclear envelope begin to return to their normal condition. After metaphase, the polar rings degenerate. Thus it is primarily the nuclear envelope, via its polar modifications, which begins the organization of the mitotic spindle. The capabilities of nuclear pores are summarized. In the Discussion, the polar rings are compared with procentrioles; since they appear to have a passive role in spindle-pole organization, it is suggested that they may represent an evolutionary stage prior to the procentriole. The origin of the centriole ultimately from a nuclear pore is presented as an hypothesis. It is concluded to be unlikely that the polar ring is a degenerate centriole, and therefore it is proposed that the red algae never had centrioles in the course of their evolution. Thus the view of the non-flagellate ancestry of the red algae is supported.

Metaphase↗
PubMed2006

Real-time monitoring of all-optical poling by two-beam second-harmonic generation.

We demonstrate a simple method for monitoring all-optical poling in real time. The poling pattern created by the writing beam at the fundamental frequency and the seed beam at the second-harmonic frequency is reconstructed by two-beam second-harmonic generation because of the writing beam and an additional probe beam at the fundamental frequency. When the probe beam is sufficiently weak, it does not distort the poling process. The method provides a significantly stronger signal than monitoring based on a probe beam alone.

Journal Article↗
PubMed2006

A curvature-mediated mechanism for localization of lipids to bacterial poles.

Subcellular protein localization is a universal feature of eukaryotic cells, and the ubiquity of protein localization in prokaryotic species is now acquiring greater appreciation. Though some targeting anchors are known, the origin of polar and division-site localization remains mysterious for a large fraction of bacterial proteins. Ultimately, the molecular components responsible for such symmetry breaking must employ a high degree of self-organization. Here we propose a novel physical mechanism, based on the two-dimensional curvature of the membrane, for spontaneous lipid targeting to the poles and division site of rod-shaped bacterial cells. If one of the membrane components has a large intrinsic curvature, the geometrical constraint of the plasma membrane by the more rigid bacterial cell wall naturally leads to lipid microphase separation. We find that the resulting clusters of high-curvature lipids are large enough to spontaneously and stably localize to the two cell poles. Recent evidence of localization of the phospholipid cardiolipin to the poles of bacterial cells suggests that polar targeting of some proteins may rely on the membrane's differential lipid content. More generally, aggregates of lipids, proteins, or lipid-protein complexes may localize in response to features of cell geometry incapable of localizing individual molecules.

Bacillus subtilis↗