ISSN:0248-4900    

DOI:10.1111/j.1768-322X.1990.tb00886.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Summary—Depending on the author and the animal or plant origin of the material under study, the term “nucleolonema” is used in different contexts and thus indicates nucleolar ultrastructures that are different. In this paper, we attempt to clarify this state of affairs and to propose a definition for the plant cell nucleo

ISSN:0248-4900    

DOI:10.1111/j.1768-322X.1990.tb00887.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Summary—Nuclear rings are cell structures found at the nuclear cortex wedged between the nuclear envelope and the chromatin fiber network. In previous publications we have dealt with their morphology, relationships with the nuclear membranes, chromatin fibers and cytoskeletal filaments; and more recently, with their measurements at high electron microscope resolution. In this article we have calculated the mass and molecular weight of 336 isolated nuclear rings from human circulating lymphocytes using a photometric procedure and polystyrene latex spheres as the standard for weight calibration. Our results show a range of mass of 0.4–35.5 × 10−16g (equivalent to 0.2–21.2 × 108Da with a positively skewed distribution (median: 3.3 × 10−16g or 2.0 × 108Da). Mass and volume of nuclear rings were highly correlated. In addition, it was possible to calculate the area, the whole mass and the mass per unit area of the nuclear envelope present in the center of the nuclear rings. The mass of this area also shows a lognormal distribution (median of mass/unit area: 37.3 × 10−8pg/nm2or 1.9 × 105Da/nm2). We discuss the significance of this results as parameters for the characterization of the nuclear rings and their possible implications for a new interpretation of nuclear cortex architecture, nucleocytoplasmic traffic and macromolecule segregation between the two main

ISSN:0248-4900    

DOI:10.1111/j.1768-322X.1990.tb00888.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Summary—The response of microtubules to treatment with vinca alkaloids was investigatedin vivoandin situin the embryonic nervous system of mice. For this purpose we used rotatory cultures of post‐implanted embryos in a serum medium containing the alkaloid combined with immunofluorescence using a tubulin‐specific polyclonal antibody on high molecular weight polyethylene glycol embedded semithin sections.In mitotic cells, kinetochore microtubules were seen to be more resistant to the action of vinca alkaloids than interpolar microtubules. Increasing drug concentrations induced an increasing rate of mitosis together with an increasing rate of disassembly of the cytoplasmic microtubule complex, suggesting a probable relation between these events.In bipolar neuroepithelial cells at interphase, a small pool of microtubules was resistant to the vinca alkaloids. These microtubules were located near the centriolar apparatus associated with the primary cilium; they were short, curly and bent. Disruption of the cytoplasmic microtubule complex did not alter the shape of the bipolar neuroepithelial cells.In the axonal profiles, a drug‐stable pool of microtubules were not disrupted by the alkaloids and were also short. They seem to act as microtubule organizing centres.These observations suggest vinca alkaloids seem to actin vivomuch more by inducing, at a given concentration, the disruption of a particular group of microtubules without altering the others. The fact that these drugs affect the number, but not the length, of the microtubules raises the hypothesis that these drugs act on microtubules by a mechanism similar to that described as “dynamic ins

ISSN:0248-4900    

DOI:10.1111/j.1768-322X.1990.tb00889.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Summary—The distribution of blood‐borne immunoglobulins G (IgG) was studied in the cerebral cortex, pineal gland, spinal cord and dorsal root ganglia of normal Lewis rats using the detection of autologous anti‐horseradish peroxidase (HRP) antibodies. This detection was performed by means of light and electron microscopy. This study demonstrated that, in the cerebral cortex and the spinal cord microcirculations, endothelial cells are a restrictive barrier against IgG while IgG are able to diffuse into the perivascular parenchyma of the pineal gland and spinal ga

ISSN:0248-4900    

DOI:10.1111/j.1768-322X.1990.tb00890.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Summary—Using the whole cell voltage‐clamp technique and a Cl free and Na free Ba methane sulfonate solution, stage V and VIXenopusoocytes demonstrated a Ba current (endogenous component) with a peak amplitude average of 6 nA (6 ± 2 nA). When oocytes were injected with crustacean skeletal muscle mRNA, an additional component of IBacould be detected (exogenous IBa). The latter current could be distinguished from the native one by several electrophysiological means: a peak amplitude average of 90 nA (90 ± 4 nA), activation potential threshold, steady state inactivation properties and sensitivity to Ca blockers. As shown by Jdaïâa and Guilbault in crustacean skeletal muscle fibres, exogenous IBacould be divided into two components: a “fast component” and a “slow component” probably passing through two types of Ca channels (fast and slow) since the peak Ba current voltage relationship was biphasic and the fast component of exogenous IBawas less sensitive than the slow to nifedipine. The features of the newly synthesized channels incorporated in theXenopusoocyte membrane suggest that they may be associated with fast and slow channels, previously described in many preparations, particularly in crustacean skeleta

ISSN:0248-4900    

DOI:10.1111/j.1768-322X.1990.tb00891.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Summary—The distribution of calbindin D28k in the digestive system and the urinary bladder of the toad was investigated using immunohistochemistry and Western blotting. By analogy with mammals and birds, the protein was expected to be located preferentially in the duodenal part of the intestine. Interestingly, absorptive cells of the duodenum were totally devoid of calbindin D28k while the colon contained high amounts of the calcium‐binding protein. This reversed polarity of calbindin D28k content in the toad intestine should obviously correspond to a different scheme of calcium absorption regulation between amphibians and higher vertebrates. Calbindin D28k containing neuroendocrine‐like cells were found scattered in the proximal parts of the gut with a similar distribution to what has been described in rat and chick intestine. The oesophagus, the stomach, and the intrinsic nervous sytem of the intestine were negative. No significant amounts of the proteins were found in the urinary bladder, which is known to be a site of Ca2+active tran

ISSN:0248-4900    

DOI:10.1111/j.1768-322X.1990.tb00892.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Summary—Digestive mucus of sea‐water adapted eels has been observed and analyzed by the scanning electron microscope (SEM) after rapid freezing at liquid nitrogen temperature followed by freeze‐drying. No chemical procedures were used in this technique. This allowed the maintenance of the mucous coating.Preliminary X‐ray microanalysis carried out on freeze‐fractured and freeze‐dried samples of the oesophagus showed a decrease of K+and an increase of Ca2+and Cl−from the basal part of the mucous cell towards its the apical part. This technique has proven to be satisfactory for it prevents translocation and loss of diffusible elementsin situand allows X‐ray microanal

ISSN:0248-4900    

DOI:10.1111/j.1768-322X.1990.tb00893.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Summary—In order to gain a better understanding of the role of ecto‐NAD+glycohydrolase, an enzyme predominantly associated with phagocytic cells, we have studied its fate in murine macrophages (splenic, resident peritoneal and Kupffer cells) during phagocytosis of opsonized or mannosylated latex beads. In parallel, we have also monitored nucleotide pyrophosphatase, another ectoenzyme of macrophages. Phagosomes were isolated by flotation in a discontinuous sucrose gradient and the enzyme activities were determined with fluorometric methods. Low levels of NAD+glycohydrolase and nucleotide pyrophosphatase could be measured associated with the phagosomal fractions,eg, respectively less than 4.5% and 10% in spleen macrophages. The phagosomal activities originate from the plasma membrane,iethey were latent and inactivation of ecto‐NAD+glycohydrolase with the diazonium salt of sulfanilic acid resulted in a marked decrease of this enzyme activity in the phagosomal fractions. Pre‐labelling of the cell surface by [3H]‐galactosylation indicated that NAD+glycohydrolase is internalized to a lesser extent than an average surface‐membrane unit. These results indicate that if ecto‐NAD+glycohydrolase of macrophages can be internalized to a limited extent during phagocytosis of opsonized or mannosylated latex beads, this enzyme appears to be predominantly excluded from the surface area involved in the uptake of s

ISSN:0248-4900    

DOI:10.1111/j.1768-322X.1990.tb00894.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Summary—InDrosophila melanogasterthe tandemly arranged repetitive sequences coding for 18S and 28S rRNA are heterogenous at the level of the spacers between units and insertions that interrupt many 28S rRNA genes. This heterogeneity contrasts with the homogeneity of the regions transcribed into 18S and 28S rRNA. Homogenization and evolution of repetitive genes are usually explained by conversion, amplification events or unequal crossovers. In this paper we studied the change in rDNA patterns associated with partial reversion ofbobbedmutations. In most cases, no increase in rDNA gene number, but a new repartition of gene types were foun

ISSN:0248-4900    

DOI:10.1111/j.1768-322X.1990.tb00895.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY