摘要:

We have determined for the X chromosomes of 10 laboratory strains and the Y chromosomes of 4 of them both the total number of ribosomal units and the relative percentages of uninterrupted (ins‐), type 1 (ins1: with distinction between small ins1S and large ins1L) and type 2 (ins2) interrupted ribosomal units.These studies were made with the DNA extracted from third instar larval diploid tissues (brains and imaginal discs) of X/X female lines or XNO−/Y male lineages (devoid of X ribosomal genes) whose members possess copies of the same initial X or Y chromosome.Between the X chromosomes as well as the Y chromosomes an ⋍ 2‐fold variation was observed in the total number of ribosomal genes: from ⋍ 200 to 420 for the X chromosomes and from ⋍ 150 to 330 for the Y ones.The Y chromosomes are devoid of insertion 1 interrupted units, but one can observe some variation in the percentage and hence the absolute numbers of uninterrupted and insertion 2 interrupted units.Among the X chromosomes a very large variation exists between the percentage and absolute number of all the ribosomal unit types; it is to be noted especially that the number of uninterrupted units, which are the only kind of ribosomal genes actively transcribed, can vary from about 20 to 140 without any differences in the development of the differ

ISSN:0248-4900    

DOI:10.1111/j.1768-322X.1988.tb00722.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

The quantitative characteristics of chromosomal nucleolus‐organizing regions (NORs) and some other nucleolar components were studied on ultra‐thin sections of pig embryo kidney cells (PK cells). It was shown that: 1) nucleoli‐per‐cell volumes were 3 times smaller in the G0 period than in the G2 period; 2) the number of fibrillar centers (FCs) per cell in the G0 period, the G2 period, and at metaphase was equal to 7, 33.7, and 8, respectively; 3) mean volumes of individual FCs in the G0 period (0.033±0.005 μm3), G2 period (0.014±0.001 μm3), and at metaphase (0.04±0.05 μ3) were significantly different; 4) the total volumes of FCs calculated per haploid set of chromosomes were practically the same in the G0 (0.105 μm3) and G2 (0.107 μm3) periods, but were twice as large as those at metaphase (0.04–0.05 μm3). These data show that partial activation and inactivation of ribosomal genes in interphase PK cells are not accompanied by a considerable change in the total volume of FCs and may be due to the fragmentation and fusion of individual FCs. Complete inactivation of ribosomal genes in mitosis results in a decrease of total volumes of FCs per cell; 5) in G0 and G2 periods the total volume of the dense fibrillar component per nucleolus is practically proportional to the nucleolus volume (r = 0.99);6) in the G2 period, the nucleolus volume is also proportional to the number of FCs (r = 0.99;7) the volume of the dense fibrillar component within individual fibrillar complexes is not a constant one. This is indirect evidence for a different level of NOR functional activity in different NO‐chrom

ISSN:0248-4900    

DOI:10.1111/j.1768-322X.1988.tb00723.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

It has been established that following removal of the micronucleus inParamecium tetraurelia, the amicronucleate cell line enters a depression period, characterized by slow growth rate and oral abnormalities, at normal growth temperature (27°C). Such cell lines gradually recover in growth rate and stomatogenesis. In the present study, 4 recovered amicronucleate cell lines were challenged with high temperatures (35°C, 36°C, and 36.5°C). They exhibited growth rate reduction and abortive cytokinesis at 35°C and 36°C, and died at 36.5°C. In addition, they demonstrated oral defects similar to those observed in the depression period: disruption of the regular oral membranellar pattern, reduction in the length of the oral apparatus, and impaired phagocytosis (food vacuole formation). These high temperature‐induced abnormalities were largely restricted to amicronucleates, and were rare or seen to a much lesser extent in sister micronucleate cell lines. This study demonstrates the participation of the micronucleus in conferring thermotolerance on the cells. It is hypothesized that the micronucleus specifies heat‐shock proteins to maintain the integrity of oral and somatic cytoskeletal elements at high t

ISSN:0248-4900    

DOI:10.1111/j.1768-322X.1988.tb00724.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

A high‐speed microcinematographic study was performed on the biflagellate unicellular algaDunaliella. A frame‐by‐frame analysis has shown that the two flagella never beat at the same frequency. For a better characterization of the bending pattern of the two flagella, a new automated method of image analysis has been developed. The method allowed an automatic acquisition of a line characterizing theDunaliellaflagellum and its mathematical modelling. From this model, some binding parameters could be automatically measured, which have permitted determination of the velocities of formation and propagation of flagellar waves and the variation of the curvature radius of the bends between the two flagella. Both flagella showed a similar pattern of ciliary beat. The most important difference was the lengthening of the initiation phase for the slower fla

ISSN:0248-4900    

DOI:10.1111/j.1768-322X.1988.tb00725.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

This paper reports the suitability of culturing a line of dog kidney epithelial cells, MDCK, in the presence of a serum substitute, Ultroser G. Serial subcultivation with this product was possible for at least 10 passages without any change in cell shape and size, saturation density, dome‐forming ability, transepithelial resistance, and growth curve. Adhesion of newly plated cells to plastic was somewhat lower than in fetal calf serum but the trypsin‐harvesting kinetics were essentially the same. However, the membrane ion transport systems was alterd: cell sodium influx was greatly diminished, suggesting a deep change in the amiloride‐sensitive Na+channels: sodium efflux was highly enhanced (both active and pas

ISSN:0248-4900    

DOI:10.1111/j.1768-322X.1988.tb00726.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

In order to study the expression of the morphological and functional characteristics of human thyroid cells, 3‐dimensional cultures were carried out in collagen gel. This substrate allows the cells to retain their organization in follicles with a normal polarity. Cellular polarities appeared normal at the time of collagen embedding, but there was a delay of 4–5 days in culture before the maximal TSH stimulation of125I−uptake and of cAMP accumulation occurred. In normal and adenoma‐derived cells,125I−uptake, which could be increased by TSH, was demonstrated. cAMP accumulated in the culture medium and thyroglobulin was secreted into the follicle lumen. Of the 4 differentiated carcinomas for which the 72‐hr uptake of125I−was measured, only 2 displayed slight125I−uptake and response to TSH. Thus, human thyroid cells exhibit better morphological and functional differentiation in collagen gel culture than in monolayer culture. Furthermore, in a variety of pathological cases studied, the expression of specific characteristics in culture varied in a fashion similar to differences

ISSN:0248-4900    

DOI:10.1111/j.1768-322X.1988.tb00727.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

The human colon cancer cell line Caco‐2 culturedin vitrodisplayed morphological differentiation which was shown to be a growth‐related event. We have investigated this phenomenon further in relation to the cell surface glycosaminoglycans produced by growing (5‐day,i.e., prior to differentiation) and confluent (9‐day,i.e., after morphological and functional differentiation) cultures. Neosynthesized [35S]glycosaminoglycans were purified on DEAE‐cellulose; at confluency, they were bound more strongly to the column than the corresponding fractions from the growing cells. Analysis of Kavvalues of heparan sulfate and chondroitin sulfates from growing and confluent cells indicated an increase in chain length of both glycosaminoglycans in morphologically differentiated cells. Heparan sulfate was the main35S‐labeled glycosaminoglycan of the cell surface of both 5‐day and 9‐day cultures. Paper chromatography of the unsaturated disaccharides obtained by chondroitinase digestion showed that chondroitin sulfate chains were primarily 6‐sulfated in the 2 studied extracts. Heparan sulfate chains were isolated as chondroitinase‐resistant material and treated with nitrous acid. Analysis of N‐ and O‐sulfate group‐related radioactivity showed an increase in the amount of35S‐label in the form of N‐sulfate groups and an increase in the O‐35S‐sulfation pattern in heparan sulfate from morphologically differentiated cells. Thus, the structural features of both chondroitin sulfates and heparan sulfate were significantly different when the growing cells beca

ISSN:0248-4900    

DOI:10.1111/j.1768-322X.1988.tb00728.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

The occurence of GABA‐containing cells in the rat entero‐pancreatic system was investigated by using anti‐GABA‐glutaraldehyde antibodies at the light and electron microscope level. In the pancreas, the B cells showed intense immunoreactivity, contrary to non‐B and exocrine cells. Moreover, post‐embedding immunogold staining was localised mostly in mitochondria, close to rough endoplasmic reticulum and in the nucleus. The insulin granules appeared non‐significantly stained, which suggests the lack of cosecretion of GABA together with insulin. In the duodenum, GABA immunoreactivity was detected in certain endocrine cell types, suggesting a possible interaction with this amino acid. The well established GABAergic innervation in the enteric system was also confirmed by im

ISSN:0248-4900    

DOI:10.1111/j.1768-322X.1988.tb00729.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Tritiated auxin applied by an agar block on the wheat coleoptile tip for 2 hr was covalently fixed to adjacent protein by treatment with 1‐(3‐dimethylaminopropyl)‐3‐ethylcarbodiimide hydrochloride (DCC). The density of labelled auxin in the nucleus, the cell wall, the cytoplasm, and the vacuole was determined by autoradiography. Localization of tritiated auxin was studied at high resolution at the tonoplast and the plasmalemma lining the transverse (distal and proximal) and the longitudinal walls. The radioactivity along the tonoplast was always less than along the plasma membrane. The distribution of3H‐auxin was different across the longitudinal and transverse regions of the plasmalemma. The labelling was distributed asymmetrically on the longitudinal plasma membrane with a peak observed on the external surface. Tritiated auxin was distributed more symmetrically on the distal and the proximal plasma membranes. Our results are in agreement with the hypothesis that there are 2 different specific binding sites on the plasmalemma. The ratio of auxin present at the proximal and distal regions of the plasmalemma

ISSN:0248-4900    

DOI:10.1111/j.1768-322X.1988.tb00730.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

We describe a procedure for disassembling rat liver rough microsomes, which allows the purification of the rough endoplasmic reticulum (ER) membrane. Membrane‐bound ribosomes and adsorbed proteins are first detached by washing rough microsomes with 5 mM Na‐pyrophosphate. In a second step, the vesicle membrane is opened by digitonin, with concomitant release of the luminal content. The purification is monitored at each step by electron microscopy, and by assaying chemical constituents (protein, phospholipid, RNA) and marker enzymes for the main subcellular organelles. The final membrane preparation is representative of the ER, since it contains 24.1% of the liver glucose 6‐phosphate with a relative specific activity of 14.2. Contaminants represent less than 5% of its protein content. SDS‐polyacrylamide gel electrophoresis, followed by immunoblot analysis, reveals that the ribophorins I and II, two established markers of the rough (d) domain are still present in the final membrane preparation. It also containes the docking protein (or signal recognition particle receptor) and protein disulfide isomerase, and has conserved the functional capacity to remove co‐ and post‐translationally the signal peptide of pre‐secretory proteins. The membrane preparation is suitable for studies on the polypeptide composition of

ISSN:0248-4900    

DOI:10.1111/j.1768-322X.1988.tb00731.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY