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At least 451 records · Page 25Linked to original sources
PubMed1995

Morphometric analysis of ventral mesencephalic neurons retrogradely labeled with Fluoro-Gold following injections in the shell, core and rostral pole of the rat nucleus accumbens.

Morphologically distinct subsets of mesotelencephalic neurons were sought following retrograde transport of Fluoro-Gold from iontophoretic injections relatively restricted to the medial shell, core or rostral pole subterritories of the nucleus accumbens. The diameter and lengths of Fluoro-Gold immunolabeled dendrites of medial shell-projecting neurons were less than those of core and rostral pole-projecting neurons.

Animals↗
PubMed1987

Vegetal pole cells and commitment to form endoderm in Xenopus laevis.

In order to compare their states of commitment with their normal developmental fate, single vegetal pole cells from early Xenopus embryos were labeled and transplanted into the blastocoels of host embryos. In a previous study we showed, using this single cell transplantation assay, that vegetal pole cells become committed to endoderm by the early gastrula stage. In this paper we examine some properties of the commitment process. First, we show that it is gradual. When vegetal blastomeres are taken from progressively older embryos an increasing number of them enter only the endoderm, until by the early gastrula stage they all do. Second, we show that commitment can continue in vitro when an appropriate tissue mass is present. We suggest that commitment to form endoderm may be, in the right conditions, a cell autonomous process.

Animals↗
PubMed1984

Centrosomes and mitotic poles.

The original theory of the centrosome as the 'reproductive organ' of the cell provides a logical explanation of the mitotic poles and the accuracy of cell division. No alternative explanation has replaced it. The historical problem was the failure to identify centrosomes as compact physical bodies in a great many kinds of cells. In this essay, I consider the evidence that centrosomes are flexible bodies; they may take on alternative forms and their forms determine the shapes of mitotic poles and other organizers of microtubular structures. Compact corpuscular centrosomes are not necessary and would not be expected in cases where microtubules clearly do not originate from point sources. A model of the flexible centrosome is introduced and the speculation that the centrosome is a bearer of morphological information is considered.

Animals↗
PubMed1992

Computer modeling of pole formation in cell division.

The regular position of spindle poles in bi- and multipolar cell divisions is interpreted as the result of expanding caps on the surface of cell nuclei first proposed by Mazia in 1986. In a computer model it is shown that expanding caps position their centers with the maximal distance between them, which is in complete accordance with findings in experimentally influenced cell divisions in which multiple poles are formed.

Cell Division↗
PubMed1981

Effect of some cholinergic drugs on the conditioned pole jump response in rats.

Rats were trained to pole jump to a buzzer as the conditioned response. Cholinergic agents, oxotremorine and physostigmine significantly depressed this response. The effect was blocked by atropine. Nicotine and carbachol failed to modify the conditioned pole jump response. It is suggested that the central muscarinic inhibitory receptors are involved in the action of these drugs.

Animals↗
PubMed1994

Evaluation of bradykinesia induction by SM-9018, a novel 5-HT2 and D2 receptor antagonist, using the mouse pole test.

Induction of bradykinesia by SM-9018, a novel 5-HT2 and D2 antagonist, was compared with that of other neuroleptics using the pole test in mice. Neuroleptics including SM-9018, haloperidol, chlorpromazine, and thioridazine dose dependently induced bradykinesia in the pole-descending behavior of mice with relative potencies consistent with those for catalepsy induction. SM-9018 was about 70 times weaker than haloperidol and twice as weak as thioridazine in inducing bradykinesia. Other CNS drugs such as barbiturates and antidepressants had no effects. Haloperidol-induced bradykinesia was significantly attenuated by a cholinergic muscarinic antagonist (i.e., trihexyphenidyl) and 5-HT2 antagonists (i.e., ritanserin and cyproheptadine) whereas that caused by SM-9018 was relatively resistant to the 5-HT2 antagonists. These findings suggest that SM-9018 is weaker than other neuroleptics in inducing extrapyramidal side effects and that the 5-HT2 blocking activity of SM-9018 may contribute to its atypical neuroleptic property.

Animals↗
PubMed1989

Centrosomes, and not nuclei, initiate pole cell formation in Drosophila embryos.

An injection of aphidicolin into early Drosophila embryos inhibits DNA synthesis and nuclear division, while centrosome replication and many other aspects of the mitotic cycle continue. If aphidicolin is injected at nuclear cycle 7-8, the normal migration of nuclei to the embryo cortex is completely inhibited. In most of these embryos, however, centrosomes continue to migrate in a coordinated manner to the cortex, where they reorganize tubulin, actin, and the overlying plasma membrane. Remarkably, the centrosomes that migrate to the posterior pole of such embryos initiate pole cell formation in the absence of nuclei. These observations demonstrate that centrosomes alone are able to direct a major reorganization of the cortical cytoskeleton when they arrive at the surface of the embryo. They also suggest that the coordinated movement of nuclei to the embryo cortex is mediated by forces acting on the centrosome rather than on the nucleus itself.

Actins↗
PubMed1990

Gamma-tubulin is a component of the spindle pole body that is essential for microtubule function in Aspergillus nidulans.

We have recently discovered that the mipA gene of A. nidulans encodes gamma-tubulin, a new member of the tubulin superfamily. To determine the function of gamma-tubulin in vivo, we have created a mutation in the mipA gene by integrative transformation, maintained the mutation in a heterokaryon, and determined the phenotype of the mutation in spores produced by the heterokaryon. The mutation is lethal and recessive. It strongly inhibits nuclear division, less strongly inhibits nuclear migration, and, as judged by immunofluorescence microscopy, causes a reduction in the number and length of cytoplasmic microtubules and virtually a complete absence of mitotic apparatus. We conclude that gamma-tubulin is essential for microtubule function in general and nuclear division in particular. Immunofluorescence microscopy of wild-type hyphae with affinity-purified, gamma-tubulin-specific antibodies reveals that gamma-tubulin is a component of interphase and mitotic spindle pole bodies. We propose that gamma-tubulin attaches microtubules to the spindle pole body, nucleates microtubule assembly, and establishes microtubule polarity in vivo.

Alleles↗
PubMed1991

oskar mRNA is localized to the posterior pole of the Drosophila oocyte.

Mutants of the maternal posterior-group genes of Drosophila lack posterior body pattern elements and germ cells, both of which form through the action of determinants localized to the posterior pole of the oocyte. We report that transcripts of one of these genes, oskar, become localized to the posterior pole of oocytes shortly after the oocyte begins to differentiate visibly. Analysis of various posterior-group mutants reveals that localization of oskar mRNA is an early step in the posterior localization pathway. In addition, we find that nonsense oskar mutations disrupt osk mRNA localization, while missense oskar mutations do not.

Amino Acid Sequence↗
PubMed1991

Unique oscillatory activity related to visual processing in the temporal pole of monkeys.

To examine the role of the temporal pole of monkeys in visual processing, the activity of single neurons was extracellularly recorded while the monkey performed a visual discrimination task. Various colored photographs were used as visual stimuli. We found neurons with oscillatory activity coupled to visual stimuli in the ventral part of the temporal pole. Oscillatory activity tended to be elicited by objects familiar to the monkey, such as familiar human faces, familiar foods and familiar non-food objects related to the experiment. The frequencies of oscillations changed depending upon the nature of the visual stimulus. The results suggest that oscillatory activity generated by the activation of a certain circuit is involved in the recognition of complex visual stimuli, leading to the production of certain psychological states.

Animals↗
PubMed1993

Assembly and functions of the spindle pole body in budding yeast.

The spindle pole body (SPB) serves as the centrosome in yeasts and in a variety of other lower eukaryotes. In Saccharomyces cerevisiae, this organelle controls the assembly of all microtubules in the cell, acting not only as a pole of the mitotic or meiotic spindle but also as the site from which cytoplasmic microtubules emanate. The distinctive structure of the SPB has permitted definition of discrete stages in its duplication and behavior at all stages of the yeast life cycle. In association with genetic analyses, studies of the yeast SPB are providing insights into the mechanisms that control centrosomal behavior in this model eukaryote.

Cell Cycle↗
PubMed1992

The influence of spatial polarization distribution on spot poled PVDF membrane hydrophone performance.

The influence of spatial polarization distribution on spot poled PVDF membrane hydrophone performance was calculated and then experimentally verified using a one-dimensional model based on acoustic wave propagation through a layered medium. It is shown that the sensitivity of the hydrophone is markedly dependent on the spatial polarization distribution. It is also shown that there can be a significant difference between the voltage sensitivities measured in the same hydrophone probe depending on which electrode is actually facing the acoustic source. The measurements carried out in the frequency range 1-20 MHz indicate that this difference, while negligible below 2 MHz, may exceed 1.6 dB at higher frequencies. The model developed can also be used to determine the "effective" piezoelectric constant d33 of the PVDF material as a continuous function of frequency. Moreover, the model predicts the existence of a negative slope in the frequency response of the spot poled membrane hydrophone. The experimental confirmation of this prediction underscores the importance of using swept frequency methods during calibration measurements.

Electricity↗
PubMed1989

The scaphoid allograft: a new operation for treatment of the very proximal scaphoid nonunion or for the necrotic, fragmented scaphoid proximal pole.

This is a preliminary report of eight cases in which an allograft was used to replace half of the scaphoid. The indications for the procedure include the following: (1) Severe necrosis with fragmentation of the proximal pole, (2) Very proximal pole nonunion with small (less than 20% of the bone), unreconstructable proximal fragments, and (3) One case of severely comminuted intra-articular fracture of the scaphotrapezial joint and basal joint of the thumb caused by a gunshot wound. The Herbert scaphoid screw was used to provide rigid fixation. Follow-up ranged from 8 to 30 months. The result was good in six of eight patients. It should be emphasized that this is a preliminary report of the early experience with a new operation for salvage of difficult scaphoid fracture problems.

Bone Screws↗
PubMedDate not supplied

Zonal turnover of cell poles of Bacillus subtilis.

Turnover of cell walls of Bacillus subtilis occurs in three distinct phases: a lag phase, a relatively rapid phase persisting for 2-3 generations and a much slower phase continuing for several additional generations. A lectin probe revealed that cell pole material was lost during the slow phase of turnover and that the loss of wall occurred in zones, beginning at the cylinder-pole junction and continuing to the cell tip. This is in contrast to cell wall turnover in cylinders where turnover occurs randomly at many surface sites.

Acetylglucosamine↗
PubMed1991

Control and function of terminal gap gene activity in the posterior pole region of the Drosophila embryo.

We have studied the genetic requirement for the normal expression of the terminal gap genes huckebein (hkb) and tailless (tll) and their possible function in the posterior pole region of the Drosophila embryo. At the early blastoderm stage, both genes are expressed in largely coextensive expression domains. Our results show that in the posterior region of the embryo both the activation and the control of the spatial limits of tll and hkb expression are critically dependent on torso (tor) activity, which is thought to be a crucial component of a cellular signal transduction pathway provided by the terminal maternal system. Furthermore, the spatial control of hkb and tll expression does not require mutual interactions among each other, nor does it require regulatory input from other gap genes which are essential for the establishment of segmentation in the trunk region of the embryo ("central gap genes"). Therefore, the terminal gap genes have unique regulatory features which are distinct from the central gap genes. In the absence of terminal gap gene activities, as in hkb and tll mutant embryos, the expression domains of the central gap genes expand posteriorly, indicating that the terminal gap gene activities prevent central gap gene expression in the posterior pole region of the wildtype embryo. This, in turn, suggests that the terminal gap gene activities prevent metamerization by repression of central gap genes, thereby distinguishing the segmented trunk from the nonsegmented tail region of the embryo.

Animals↗
PubMed1993

Mitotic spindle pole separation.

Eukaryotic cells utilize a microtubular spindle to segregate chromosomes during mitosis. Chromosome segregation requires the timely separation of the mitotic spindle poles to which the chromosomes are attached. Recent studies at the molecular and cellular levels have provided new insights into the mechanism and regulation of this process. On the one hand, the process now seems more complex, as redundant mechanisms apparently overlap in function during cell division. On the other hand, some of these processes may be acting continuously during the various stages of spindle pole separation, suggesting an underlying simplicity.

Journal Article↗
PubMed2006

Sealed with a Kiz: How Plk1 ensures spindle pole integrity.

The kinase Plk1 plays multiple roles in regulating mitotic progression, including stabilization of spindle poles, but its substrates are largely unknown. A new study by Yamamoto and coworkers has identified a centrosomal protein, Kizuna (Kiz), as a mitotic substrate of Plk1 (Oshimori et al., 2006). Phosphorylation of Kiz ensures the integrity of spindle poles in the face of severe pulling forces exerted by the chromosome-attached spindle microtubules.

Amino Acid Sequence↗