摘要:

The cytoskeleton of rat neurohypophysial cells as seen in resinless sections is an irregular three‐dimensional lattice of short strands of cytoplasmic matrix (the microtrabeculae) that interconnect parallel arrays of neurotubules, neurofilaments, abundant neurosecretory granules, and other membrane‐bound organelles including the plasma membrane. This morphological finding suggests that the cytoplasmic ground substance constitutes a cytoskeletal continuum that may be the ultrastructural expression of a motile apparatus responsible for neurosecretory granule movement and hormone release in the neurohypophy

ISSN:0248-4900    

DOI:10.1111/j.1768-322X.1984.tb00227.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

Human and bovine vascular endothelial cells from the umbilical vein and the aorta, respectively, were cultured in the presence of EDGF (a growth factor prepared from bovine retina) on plastic or on extracellular matrix (ECM). Both EDGF and ECM are required to allow the maximal proliferation of human cells and their organization in a typical monolayer. Conversely, bovine aortic endothelial cells grow perfectly in the absence of both factors in 6% fetal calf serum. However, a requirement for EDGF can also be demonstrated in low serum conditions, or in cells at high passage number. ECM had no growth promoting activity by itself. Thrombin acts similarly to EDGF on bovine serum‐starved cells. EDGF prolongs the in vitro lifespan of both types of cells. Cells at all stages still synthesize factor VIII antigen as revealed by immunofluorescence. Thus EDGF, like other growth factors from brain, FGF or ECGF, may have an important role in angiogenesis, a critical problem in pathological retina

ISSN:0248-4900    

DOI:10.1111/j.1768-322X.1984.tb00228.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

Three phorbol esters: phorbol‐12,13‐dibutyrate (PDB), 12‐0‐tetradecanoylphorbol‐13‐acetate (TPA) and phorbol‐12,13‐diacetate (PDA) were added at various concentrations (10(1)‐10(4) ng/ml) to the culture medium of rabbit mammary explants. The three phorbol esters inhibited the mitogenic signals of insulin, EGF and prolactin. They also prevented the induction of casein synthesis and casein mRNA accumulation by prolactin. In all cases, the most potent inhibitor was PDB. PDB did not alter the binding of prolactin to its receptors. The three phorbol esters added to mammary cell membranes with prolactin prevented the generation of the hormonal relay which specifically stimulates casein gene transcription when added to isolated nuclei. These data suggest that phorbol esters act directly at the membrane level where they interrupt the transfer of the hormonal messages, through a mechanism which may not be related to their

ISSN:0248-4900    

DOI:10.1111/j.1768-322X.1984.tb00229.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

Prolactin and arachidonic acid increase milk casein secretion in mammary gland slices. These effects do not necessitate Ca2+ in the incubation medium. Prolactin does not modify the influx or the efflux of 45Ca2+. The Ca2+ channel blocking agent D600 (6 micrograms/ml) decreases the stimulatory effect of prolactin on casein secretion, but does not interfere in the stimulatory effect of arachidonic acid. The calmodulin inhibitor trifluoperazine (100 microM) inhibits stimulation of casein secretion by both prolactin and arachidonic acid. From these data, it is concluded that a flow of Ca2+ from the outside into the cell is not a requisite for the stimulation of casein secretion. However, stimulation by prolactin, but not stimulation by arachidonic acid, requires Ca2+ movement through calcium pathways. Intracellular transport of Ca2+ seems necessary for the stimulation of secretion.

ISSN:0248-4900    

DOI:10.1111/j.1768-322X.1984.tb00230.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

Separation by velocity sedimentation at unit gravity according to the STAPUT system of Miller and Phillips was applied to a population of rabbit megakaryocytes previously enriched by density gradient centrifugation. By this means, 80,000 to 100,000 megakaryocytes with 100% purity were collected in eight fractions according to size for a sedimentation velocity of 52 to 30 mm/hr. DNA‐Feulgen cytophotometric measurements show significant correlation between megakaryocyte size and ploidy. The study of the eight purified fractions is of particular interest because it reflects megakaryopoiesis evolution. The different stages of megakaryocyte maturation of each fraction were analysed by transmission and scanning electron microscopy and were correlated to ploidy level. Thrombopoietic megakaryocytes with grape‐like appearance were found in ploidy fractions 8n to 128n. Cytophotometric determinations of nucleohistones revealed several populati

ISSN:0248-4900    

DOI:10.1111/j.1768-322X.1984.tb00231.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

Incubation in a culture medium with and without TSH of 16 day‐old foetal thyroid glands induces hypertrophy of the Golgi apparatus which may be correlated with a considerable increase in the number of secretory vesicles. A stereological study performed during the first 6 hr of incubation showed that: vesicle secretion was biphasic; vesicle secretion was heterogeneous with two different populations of vesicles; When TSH (20 mU and 80 mU) was added to the medium, the volume density of the follicular lumina increased; at least during the first 6 hr TSH seemed to be necessary to the formation of follicular lumin

ISSN:0248-4900    

DOI:10.1111/j.1768-322X.1984.tb00232.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

The dimensions of the various regions of the flagellum and the length of each of the dense fibres has been determined by transmission electron microscopy of a large number of spermatozoa from ten men. The overall mean length of the flagellum was 60.5 micron, and its diameter diminished from 0.88 micron in the midpiece to 0.17 micron at the terminal filament. The midpiece and terminal filament as measured in longitudinal sections had variable lengths among spermatozoa (3.4 +/‐ 0.5 (S.D.) micron and 3.1 +/‐ 1.0 micron respectively). Stereological analysis was used to estimate the length of the principal piece (53 micron) and the dense fibres. These latter fibres were of unequal length and extended along 60% of the length of the principal piece. They fell into 3 groups with respect to their lengths: (i) fibres 3 and 8 were short (6 micron); (ii) fibres 4, 2 and 7 were of medium length (17, 18 and 21 micron respectively); and (iii) the longest fibres were 5, 6, 9 (31, 32 and 31 micron respectively) and fibre 1 which was a little longer (35 micron). Although there was variation in the length of the various fibres among spermatozoa, the order of their termination was relatively constant. The relationship between these quantitative data regarding the structural characteristics of the dense fibres and the shape of the flagellar wave is discus

ISSN:0248-4900    

DOI:10.1111/j.1768-322X.1984.tb00233.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

The ontogeny of the chondriome was studied in the developing kidney of fetuses and newborn rats and compared to its maturation in jejunum cells of adult rats. The tissues were immersed in a double lead and copper citrate solution which stains mitochondria selectively. Thick sections (0.3‐0.5 micron) were observed with a standard transmission electron microscope (80‐100 kV). Mitochondria have in developing cells a shape different from those in mature cells and seem to increase in number and volume during development. In the undifferentiated stages of both jejunum and nephron, the mitochondria are small, spherical and scattered throughout the cytoplasm with no particular orientation. As jejunal cells migrate towards the villus tip, the mitochondria orient themselves in the apical‐basal direction; those of the proximal nephron become parallel to the lateral cell membranes. The morphological communications found in adult renal cells are much less prominent in the jejunum. With maturation, the close association between membranes, mitochondria and the endoplasmic reticulum takes place in both epithelia. Our studies suggest that the mitochondrial mass is increased by a continuous process of addition of sub‐units and that the chondriome development appears to be more analogous to the growth, differentiation and modification of the endoplasmic reticulum system. The chondriome also seems to reach a certain stage of development before the onset of the organ f

ISSN:0248-4900    

DOI:10.1111/j.1768-322X.1984.tb00234.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

Follicles from adult rat thyroid glands were isolated by digestion with collagenase followed by sieving. Electron microscopic studies have shown that basement membrane was present around each one of the isolated follicles. Follicles were cultured in vitro with or without thyrotropin and fibronectin. When cultured in a medium free of thyrotropin, basement membrane remained around them, while it was lacking in presence of this hormone.

ISSN:0248-4900    

DOI:10.1111/j.1768-322X.1984.tb00235.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

Lutropin (LH) and human choriogonadotropin (hCG) share the same receptor and stimulate testosterone production in porcine Leydig cells in primary culture. Cells were pulsed with [125I]LH or [125I]hCG. During the chase, more than 80% of cell‐bound LH consisted in internalized material which was degraded and excreted (half‐time: 25 min) NH4Cl largely inhibited this degradation. On the contrary, hCG remained essentially bound to the cell surface and was not degraded by the cells with or without NH4Cl up to 160

ISSN:0248-4900    

DOI:10.1111/j.1768-322X.1984.tb00236.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY