Ultrastructural changes during nuclear maturation in Bufo arenarum oocytes.

During progesterone-induced nuclear maturation the oocytes of Bufo arenarum undergo a series of nuclear and cytoplasmic changes. The breakdown of heterocellular communications between the follicular cell projections and the oocyte microvilli, and the consequent enlargement of the perivitelline space, were observed at the animal pole. The more evident cytoplasmic feature during nuclear maturation comprised the gathering of glycogen granules in clusters, some phagocytosed by empty vesicles. With respect to the location of these vesicles, some were observed in close proximity to the oolemma and others were freely suspended in the perivitelline space, extruded from the oocyte. Other visible events were the disruption of the annulate lamellae, the formation of an elaborate cortical endoplasmic reticulum and the rearrangement of the cortical granules in a monolayer immediately beneath the oolemma together with aggregates of endoplasmic reticulum cisternae. Our results show that during nuclear maturation the nuclear oocyte changes include a flattening of the spherical oocyte nucleus, its migration towards the surface of the animal pole, the disappearance of the nucleoli and the dissolution of the nuclear envelope.     

Distribution of chromosome breakage point induced by arabinosylcytosine on in-vitro human lymphocytes]

The cytogenetic effects of arabinosyl cytosine on human leukocytes in vitro has been studied using continuous and discontinuous treatments. Optimum activity occurs at the end of the S period. Interchromosomal distribution of breaks is non-random. The hypothesis of a very late replication for some chromatid segments is discussed. The relations between banding and the position of breaks are discussed.     

Ultrastructural events in the cytoplasmic death of lethally-irradiated human lymphocytes.

Normal human peripheral-blood lymphocytes were irradiated with a dose of X-rays and processed for electron microscopic examination at different times after irradiation. A localized protrusion of the plasma membrane of the irradiated lymphocytes was observed in samples fixed as early as 15 min after irradiation, suggesting that the injury to the plasma membrane could have occurred during or immediately after irradiation. This was followed by fenestration of the plasma membrane, rarefaction of the cytoplasm and accumulation of cytoplasmic organelles in the centrosphere region. Localized distention of the outer nuclear envelope occurred after 2 hours and invagination of the inner nuclear membrane after 4 hours of irradiation. By 24 hours, the cytoplasmic and nuclear ultrastructural integrity was lost. The study suggested that, for high doses of X-radiation, the plasma membrane of the human peripheral-blood lymphocytes was the most sensitive target.     

Thiamine prevents X-ray induction of genetic changes in human lymphocytes in vitro

The effects of thiamine (vitamin B1) on the level of spontaneous or radiation-induced genetic changes in human lymphocytes in vitro were studied. Cultured lymphocytes were exposed to increasing concentrations of thiamine (0-500 microg/ml) and irradiated with X-rays. The DNA damage was estimated as the frequency of micronuclei and apoptotic or necrotic morphological changes in fixed cells. The results show that thiamine alone did not induce genetic changes. A significant decrease in the fraction of apoptotic and necrotic cells was observed in lymphocytes irradiated in the presence of vitamin B1 at concentrations between 1-100 microg/ml compared to those irradiated in the absence of thiamine. Vitamin B1 at 1 and 10 microg/ml decreased also the extent of radiation-induced formation of micronuclei. Vitamin B1 had no effect on radiation-induced cytotoxicity as measured by nuclear division index. The results indicate that vitamin B1 protects human cells from radiation-induced genetic changes.     

Ultrastructural changes in adrenergic neurons following chemical sympathectomy

The paper describes the ultrastructural changes of the sympathetic neurons following guanethidine administration in mice. The main characteristics changes, after prolonged administration (1-10 weeks) of guanethidine (Ismelin, Ciba-Geigy, Basel, Switzerland) at doses of 30-50 mg/kg/day i.p. and i.m. were: (1) Mitochondrial damages: swelling and deformation of the mitochondria, with disruption and dispersion of the cristae and condensation or dissolution of the matrix. Membranolysis of the outer and inner mitochondrial membranes. (2) Neural processes: swelling and disorganization of the internal architecture in the postganglionic axonal and dendritic synaptic varicosities. (3) Adrenergic vesicles: disappearance of the granular vesicles in the early stage of the experiment, increase of the coated vesicles in the later stage of treatment. The effect of guanethidine is specific for the postganglionic adrenergic neurons, but the observed destruction is not caused solely by guanethidine; other chemical substances induce the same or similar degeneration in the sympathetic ganglion.     

Ultrastructural changes in murine lymphocytes induced by aflatoxin B1

This investigation sought to determine whether splenic lymphocytes obtained from Balb/C mice exposed to aflatoxin B1 (AFB1) showed any ultrastructural changes which could account for the immunodysfunction attributable to aflatoxins. Lymphocytes obtained from Balb/C mice administered aflatoxin B1 in olive oil daily for three weeks were studied using both transmission and scanning electron microscopy. The lymphocytes demonstrated ultrastructural changes primarily in the mitochondria where marked internal dissociation of the cristae was revealed by transmission electron microscopy. All other cellular organelles were unaffected. No significant alterations in external structure were observed under scanning electron microscopy. The findings of this study indicate that AFB1 administration does not affect the surface topography of lymphocytes, but AFB1, by causing extensive mitochondrial damage, may affect the way in which these cells function. This could be a possible explanation for the immunodysfunction associated with AFB1.Abbreviations AFB1 Aflatoxin B1 - SEM scanning electron microscopy - TEM transmission electron microscopy     

Interaction of human lymphocytes and viruses in vitro.

Interaction between phytohaemagglutinin (PHA) stimulated human lymphocytes and two DNA viruses (adenovirus type 5 and herpes simplex virus type 1) considered to be closely connected with lymphoid tissues has been studied. The fate of the same viruses was investigated also in non-stimulated separated lymphocytes for comparative purposes. To elicit this interaction infectivity titrations, immunofluorescent technique and electron microscopy were used. The production of viral antigens was investigated by complement fixation. It has been shown that in PHA-stimulated lymphocytes from peripheral blood of healthy donors adenovirus type 5 is capable to replicate in its infectious form. Prolongation of the interval between stimulation and infection of cells significantly influenced the dynamics of replication. Non-stimulated lymphocytes produced antigens but no infectious particles.     

Ultrastructural changes in human leukemic cell nuclei

The ultrastructural changes of human leukemic cell nuclei have been investigated. Particular attention is paid to the alteration of the nuclear envelope and its constituents, i.e., the pores and the Zonula Nucleum Limitans which appear constantly involved in these pathologic processes. An alteration of the relationships between the components of the nuclear envelope and the chromatin itself may be responsible for the appearance of the most nuclear changes.     

Ultrastructural aspects of the adherence to target cells of in vitro differentiated lymphocytes.

The specific adherence to target fibroblasts of lymphocytes differentiated in vitro from blast cells after stimulation with pokeweed mitogen was studied under the electron microscope. Lymphocyte pseudopods were seen to penetrate into the target cells forming a close contact between the membranes of the two interacting cells. Microfilaments were the only cytoplasmic components that could be detected within or in the vicinity of the penetrating pseudopods. No morphological signs of secretion could be observed in the contact region. Morphological aspects of the contact region are discussed as related to the lytic mechanism.     

Ultrastructural changes in the rat submaxillary gland following isoprenaline

Summary The ultrastructural appearance of acinar cells of the submaxillary gland have been examined at various time intervals following an injection of isoprenaline; the changes observed in previously untreated rats were compared with those in animals which had received differing periods of chronic treatment. The depletion and re-accumulation of secretory material was found to follow a similar time course irrespective of earlier treatment but there were quantitative differences in magnitude of response. An injection of the drug resulted in almost total depletion of secretory granules in previously untreated animals while in those which had received chronic treatment the depletion was less complete. This difference is discussed in relation to the decline in the hyperplasic response with prolonged drug treatment. The secretory granules showed better preservation of membranes and frequently contained dense configurations after chronic treatment.I am indebted to S. Glanvill, B. Mason, and D. O'Reilly for their skilled assistance.     

Nucleolar changes in human phytohaemagglutinin-stimulated lymphocytes

Summary The nucleoli of lymphocytes from circulating peripheral blood and from phytohaemagglutinin (PHA)-stimulated cultures (from 2 h–96 h) were studied using a silver method, RNA-specific fluorescent staining, and electron microscopy of ultrathin sections. In peripheral blood about 75% of the lymphocytes have one ring-shaped nucleolus composed of a distinct fibrillar centre surrounded by a dense pars fibrillaris and little granular material; the remaining lymphocytes showing two or more small ring-shaped nucleoli. With PHA stimulation, the number of cells with several nucleoli increases first (from 2 h–12 h). Next, cells containing one or, at most, two large nucleoli with nucleolonema devoid of fibrillar centers are seen (from 4 h on). 34 h after PHA, nucleoli of the compact type containing one or more fibrillar centres appear and comprise about 60% of the cells after 72 h. The appearance of more than one nucleolus per cell shortly after PHA administration suggests an activation of additional nucleolar organizer regions (NOR), which fuse to form one or two large nucleoli with nucleolonema. These are then transformed into compact nucleoli. The fibrillar centers stain preferentially with silver. They contain nonchromosomal proteins and may serve as stores for nucleolar proteins. The fusion of activated NORs during the first cell cycle explains the relatively high frequency of satellite associations in first mitoses compared to later mitoses after stimulation.     

Proportion of lymphocytes forming E, EA, and EAC rosettes following treatment with human interferon preparations in vitro

The proportion of lymphocytes forming E, EA, and EAC rosettes after treatment with human interferon preparations in vitro was measured. While interferon increased the percentage of lymphocytes forming E rosettes, the percentage of cells forming EA rosettes was diminished. The proportion of lymphocytes forming EAC rosettes was not altered to any major extent by interferon treatment. The same effects were observed when fibroblast interferon, purified to homogeneity with regard to molecular weight, was used.     

Cytotoxicity of tin on human peripheral lymphocytes in vitro.

The comparative effects of inorganic and organic tin compounds on chromosomes were assessed in human peripheral blood lymphocytes of healthy donors 20-40 years of age. The endpoints observed were chromosomal abnormalities, sister-chromatid exchanges (SCEs) and cell cycle kinetics. The maximum concentrations which reduced the replicative index by about 50%, of stannic chloride and trimethyltin chloride were 40 micrograms and 2 micrograms per culture respectively. The tested doses were 20 micrograms and 10 micrograms of stannic chloride and 1 microgram and 0.5 microgram of trimethyltin chloride. Both doses of stannic chloride induced a much higher frequency of chromosomal abnormalities (P less than 0.05-P less than 0.001) and a greater reduction of cell cycle kinetics than the corresponding relative doses of trimethyltin chloride. The frequencies of SCEs/cell induced by the latter were, however, slightly higher than those induced by the former.