Fine structure of interphase liver cell nuclei in subacute ethionine intoxication

Neuronal activation affects the organization and protein composition of the nuclear speckles

Nuclear speckles, also known as interchromatin granule clusters (IGCs), are subnuclear domains highly enriched in proteins involved in transcription and mRNA metabolism and, until recently, have been regarded primarily as their storage and modification hubs. However, several recent studies on non-neuronal cell types indicate that nuclear speckles may directly contribute to gene expression as some of the active genes have been shown to associate with these structures. Neuronal activity is one of the key transcriptional regulators and may lead to the rearrangement of some nuclear bodies. Notably, the impact of neuronal activation on IGC/nuclear speckles organization and function remains unexplored. To address this research gap, we examined whether and how neuronal stimulation affects the organization of these bodies in granular neurons from the rat hippocampal formation. Our findings demonstrate that neuronal stimulation induces morphological and proteomic remodelling of the nuclear speckles under both in vitro and in vivo conditions. Importantly, these changes are not associated with cellular stress or cell death but are dependent on transcription and splicing.

Effect of streptozotocin on the ultrastructure of rat pancreatic islets

Our objective was to study the effects of three (30, 40, and 50 mg/kg) doses of Streptozotocin (STZ) on fasting plasma glucose level (FPG) and observe its effects at the cellular level in rat pancreas by electron microscopy. FPG was measured in rats before induction of diabetes and then on 3, 7, and 14 days after induction of diabetes with STZ. Keto diastix urine strips were used to check urine glucose and ketone bodies. Two weeks after the induction of diabetes, the rat pancreas was removed and fixed for light and electron microscopic studies. Three days after induction, the mean FPG level was 112 mg/dl in Group I (30 mg/kg STZ), 217 mg/dl in Group II (40 mg/kg STZ), and 376 mg/dl in Group III (50 mg/kg STZ). Histology was normal in Group I but revealed altered islet structure in Groups II and III. Ultrastructure revealed intact D cells in all three groups. The focal mitochondria and Golgi complex swelling found in A and B cells was occasional in Group I and frequent in Groups II and III. Swelling of other organelles and reduction in the size and number of granules was further observed in Group III. It is our conclusion that the 30-mg/kg body weight STZ produces mild changes while 50 mg/kg proves to be fatal. STZ at 40 mg/kg has a moderate effect on plasma glucose as well as on the islets of Langerhans at a cellular level.

Ultrastructural alterations of the liver of Pekin ducks fed methyl mercury-containing diets

This report describes the ultrastructural alterations of the liver of 24 male and 24 female Pekin ducks fed 0.0, 0.5, 5.0, and 15.0 ppm of methyl mercury chloride (MeHgCl), mixed in a mash diet, for 12 wk. Birds were weighed weekly and observed for neurologic symptoms daily. Samples of blood, liver, kidney, skeletal muscle and brain were analyzed for Hg residue by atomic absorption spectrophotometry. Livers were fixed in situ by perfusion with glutaraldehyde fixative and processed for electron microscopy. The percent decreases in mean body weights between wk 0 and wk 7 were statistically not significant except for males fed 5.0 ppm MeHgCl. Leg paralysis and convulsions in males treated with 15.0 ppm began at wk 5 and in females at wk 8, but were more severe in the latter. The dose-residue response for the three dose levels in all five tissues was linear, with liver and kidney containing the highest and the brain the least amount of Hg. Hepatocytes in 0.5- and 5.0-ppm MeHgCl treatment groups showed little morphologic changes, while liver cells in the 15.0-ppm group had several ultrastructural alterations, including remarkable increase in peribiliary lysosomal bodies. The mitochondria of some hepatocytes exhibited lysis of both inner and outer membranes. Changes also occurred in endothelial and Kupffer cells. These results indicate that dosing Pekin ducks with 15.0 ppm causes ultrastructural alterations indicative of toxic injury to the liver.

Adaptive changes of the rat liver cells induced by repeated intraperitoneal injections of d-galactosamine. II. Light and electron microscopic investigations of hepatocellular nucleolar alterations

The effects of repeated d-galactosamine (GalN) administration - i.e. subacute GalN intoxication - on rat liver cell nucleoli were examined. After an initial intraperitoneal injection of 375 mg GalN/kg body weight the rats were treated with 250 mg GalN/kg body weight daily at intervals between 24 h and 30 days. The rats were sacrificed six h after the last injection by decapitation. Specimens of liver were studied by light and electron microscopy. According to the nucleolar size three stages were to be distinguished. Stage I: decreased nucleolar size after one injection, stage II: increased and maximal nucleolar size after two to five injections, stage III: slightly increased relatively stable nucleolar size after six and more injections. Fine structural observations suggest a nucleolar hyperfunction in subacute GalN intoxication as well as a minor disturbance of the transcription and the transfer of the nucleolar RNA.

Ultrastructural studies of nuclei and nucleoli in psoriatic epidermis, compared with those in normal epidermis

Quantitative and qualitative differences of the nuclear and nucleolar structures in normal and psoriatic (involved and uninvolved) epidermis were revealed with the electron microscope. The size of nuclei and nucleoli was increased, the frequency of nuclear bodies was increased, and the relative amount of heterochromatin was decreased in involved skin compared to normal or uninvolved skin. There was no significant difference between normal skin and uninvolved skin of psoriasis. In addition to these changes, multiple fibrillar centers within nucleoli and small masses of chromatin in the epidermal nucleoplasm were observed very frequently in involved skin, while rarely or not at all in normal and uninvolved skin. These results suggest that involved psoriatic keratinocytes have increased metabolic activity and abnormal protein synthesis, having undergone gene derepression.

Studies on the human corpus luteum. II. Observations on the ultrastructure of luteal cells during pregnancy

The ultrastructure of human corpora lutea obtained during the 6th, 10th, 16th, and 35th week of pregnancy is reported. Differences between the established luteal cell of pregnancy and the transitory luteal cell of the menstrual cycle are noted. In pregnancy the luteal cell is more compartmentalized into a peripheral mass of ER (endoplasmic reticulum) and a central area where mitochondria and Golgi complexes are concentrated. The latter area extends to a cell surface where microvilli face on a perivascular space. Long bundles of filaments are prominent within the luteal cell cytoplasm and, in contiguous cells, appear to arise from adjacent desmosomal regions. Bilateral subsurface cisternae of granular ER at lateral cell borders appear to be areas of specialized junctional surfaces. Certain luteal cells with irregular nuclear membranes are also characterized by vesicular aggregates enclosed within a single membrane. These aggregates are found within the peripheral nucleoplasm or the perinuclear cytoplasm. Their single limiting membrane often appears continuous with either the inner or outer leaflet of the nuclear membrane.

Fine structural alterations of interphase nuclei of lymphocytes stimulated to grwoth activity in vitro

This report describes fine structural changes of interphase nuclei of human peripheral blood lymphocytes stimulated to growth by short-term culture with phytohemagglutinin. Chromatin is found highly labile, its changes accompanying the sequential increases of RNA and DNA synthesis which are known to occur in lymphocyte cultures. In "resting" lymphocytes, abundant condensed chromatin appears as a network of large and small aggregates. Early in the response to phytohemagglutinin, small aggregates disappear during increase of diffuse chromatin regions. Small aggregates soon reappear, probably resulting from disaggregation of large masses of condensed chromatin. Loosened and highly dispersed forms then appear prior to the formation of prophase chromosomes. The loosened state is found by radioautography to be most active in DNA synthesis. Small nucleoli of resting lymphocytes have concentric agranular, fibrillar, and granular zones with small amounts of intranucleolar chromatin. Enlarging interphase nucleoli change chiefly (1) by increase in amount of intranucleolar chromatin and alteration of its state of aggregation and (2) by increase in granular components in close association with fibrillar components.

Electron microscopic and biochemical characteristics of nuclei and nucleoli isolated from rat liver

Rat liver nuclei were freed of cytoplasmic contamination by washing with Triton-X-100 and subsequent centrifugation through 2.2 M sucrose. Electron microscopic examination showed that the outer membranes of the nuclei had been removed, but that the nuclei otherwise resembled the nuclei of intact liver. Morphological studies, chemical estimations of DNA, RNA, and protein and the estimation of cytoplasmic "marker" enzymes suggested that contamination of nuclei by cytoplasmic components was limited. These nuclei were obtained in yields of about 70% and were suitable for the isolation of nucleoli. Nucleoli were isolated by the breaking of the nuclei by ultrasound and subsequent differential centrifugation. In ultrastructural appearance, the isolated nucleoli resembled nucleoli in intact tissue. However, at high magnifications the "granular" component of isolated nucleoli appeared to consist of tightly twisted fibers. The nucleoli could be obtained in yields of at least 30%, and the values for the chemical composition of the isolated nucleoli agreed with values previously reported.

The disorganization of hepatic cell nucleoli induced by ethionine and its reversal by adenine

The structure of nuclei and nucleoli of hepatic cells after short-term ethionine administration was investigated with the electron microscope. By 1(1/2) hr after the injection, a distinct alteration occurred in the nucleoli which was characterized by the appearance of electron-opaque masses in the nucleolonema. After 6-8 hr, the nucleoli showed partial fragmentation into small, dense masses. Large aggregates of interchromatinic granules appeared in the nucleoplasm. Condensation of chromatin became prominent in the nucleoplasm particularly along the nuclear membrane. By 12 hr almost complete fragmentation of nucleoli had occurred. The administration of adenine or methionine at 4 hr prevented the development of nucleolar changes. Also, adenine administration at 8 hr after ethionine completely reversed the nucleolar lesion by 12 hr. After methionine administration at 8 hr, many nucleoli showed incomplete reconstruction with many twisted ropelike structures when viewed 4 hr later. Identical structures were found when adenine was given at 8 hr, and animals were sacrificed 2 hr later. On the basis of this observation, the simplified structures of nucleoli found 2 hr after adenine or 4 hr after methionine appeared to be precursors of the nucleolonema. It is suggested that nucleoli show at least two basic reaction patterns to inhibitors of RNA synthesis, one typified by actinomycin D and one by ethionine.