Male Sprague-Dawley rats exposed to in utero di(n-butyl) phthalate: dose dependent and age-related morphological changes in Leydig cell smooth endoplasmic reticulum.

When 100 mg/kg/day of di(n-butyl) phthalate (DBP) was intragastrically administered to pregnant Sprague-Dawley rats throughout gestation days 12 to 21, the male pups had similar body weights with no apparent physical differences (e.g., litter size, sex ratio) compared to that of the vehicle group. However, prominent age-related morphological alterations in the smooth endoplasmic reticulum (sER) of testicular Leydig cells (LCs) were observed once these animals reached puberty. At weeks 5 to 7, the abundant sER with non-dilated cisternae was distributed in LCs. Subsequently, although the number of LCs significantly increased, the amount of sER was significantly decreased at 9 to 14 weeks of age and had disappeared at 17 weeks. In contrast, the number of LCs and the amount of sER in LCs of the lower dose groups (10, 30, and 50 mg/kg/day) were similar to those of the vehicle group. Further, serum testosterone levels in the 100 mg/kg dose group were significantly lower during 5 to 17 weeks of age. While their luteinizing hormone (LH) level was significantly lower at 5 to 7 weeks of age, it became significantly higher during 9 to 17 weeks. The amount of sER in LCs decreased with age with the increase in LCs proliferation and serum LH levels in rat exposed in utero to DBP in a dose-dependent manner.

Role of syntaxin 18 in the organization of endoplasmic reticulum subdomains.

The presence of subdomains in the endoplasmic reticulum (ER) enables this organelle to perform a variety of functions, yet the mechanisms underlying their organization are poorly understood. In the present study, we show that syntaxin 18, a SNAP (soluble NSF attachment protein) receptor localized in the ER, is important for the organization of two ER subdomains, smooth/rough ER membranes and ER exit sites. Knockdown of syntaxin 18 caused a global change in ER membrane architecture, leading to the segregation of the smooth and rough ER. Furthermore, the organization of ER exit sites was markedly changed concomitantly with dispersion of the ER-Golgi intermediate compartment and the Golgi complex. These morphological changes in the ER were substantially recovered by treatment of syntaxin-18-depleted cells with brefeldin A, a reagent that stimulates retrograde membrane flow to the ER. These results suggest that syntaxin 18 has an important role in ER subdomain organization by mediating the fusion of retrograde membrane carriers with the ER membrane.

Ethanol-related increases in degenerating bodies in the Purkinje neuron dendrites of aging rats.

Chronic ethanol consumption in aging rats results in regression of Purkinje neuron (PN) dendritic arbors ([Pentney, 1995 Measurements of dendritic pathlengths provide evidence that ethanol-induced lengthening of terminal dendritic segments may result from dendritic regression. Alcohol Alcohol. 30, 87-96]), loss of synapses (Dlugos and Pentney, 1997), dilation of the smooth endoplasmic reticulum (SER), and the formation of degenerating bodies within PN dendrites ([Dlugos, C.A., 2006a. Ethanol-Related Smooth Endoplasmic Reticulum Dilation in Purkinje Dendrites of Aging Rats. Alcohol., Clin. Exp. Res. 30, 883-891,Dlugos, C.A., 2006b. Smooth endoplasmic reticulum dilation and degeneration in Purkinje neuron dendrites of aging ethanol-fed female rats. Cerebellum. 5, 155-162]). Dilation of the SER and the formation of degenerating bodies may be a predictor of dendritic regression. Ethanol-induced effects on mitochondria may be involved as mitochondria cooperate with the SER to maintain calcium homeostasis. The purpose of this study was to determine whether degenerating body number and mitochondrial density and structure are altered by chronic ethanol treatment in PN dendrites. Male, Fischer 344 rats, 12 months of age, were fed an ethanol or pair-fed liquid diet, or rat chow for a period of 10, 20, or 40 weeks (15 rats/treatment; 45 rats/treatment duration). Ethanol-fed rats received 35% of their calories as ethanol. At the end of treatment, all animals were euthanized, perfused, and tissue prepared for electron microscopy. The densities of degenerating bodies and mitochondria, mitochondrial areas, and the distance between the SER and the mitochondria were measured. Results showed that there was an ethanol-related increase in degenerating bodies compared to controls at 40 weeks. Ethanol-induced alterations to mitochondria were absent. Correlation of the present results with those of previous studies suggest that degenerating bodies may be formed from membrane reabsorption during dendritic regression or from degenerating SER whose function has been compromised by dilation.

Smooth endoplasmic reticulum dilation and degeneration in Purkinje neuron dendrites of aging ethanol-fed female rats.

The effects of chronic ethanol consumption on the extensive Purkinje neuron (PN) dendritic arbor of male rats include dilation of the smooth endoplasmic reticulum (SER) and dendritic regression. The purpose of the present study was to examine the molecular layer of female rats for the presence of ethanol-related SER dilation and evidence of degeneration within the PN dendritic arbor. Twenty-one 12-month-old Fischer 344 female rats (n = 7/treatment group) received a liquid ethanol, liquid control, or rat chow diet for a period of 40 weeks. Ethanol-fed rats received 35% of their dietary calories as ethanol. Pair-fed rats received a liquid control diet that was isocaloric to the ethanol diet. Chow-fed rats received standard laboratory rat chow ad libitum. At the end of treatment, tissues from the anterior and posterior lobes of the cerebellar vermis were viewed and photographed with the electron microscope. The diameters of SER profiles were measured and the density of degenerating bodies within the PN dendritic arbor was quantitated. In the posterior lobe, ethanol-related SER dilation was apparent. In the anterior lobe, the density of degenerating bodies within PN dendritic shafts was significantly increased but SER dilation in PN dendritic shafts was absent. These results confirm that SER dilation and dendritic degeneration in PN dendrites may precede and contribute to ethanol-related regression in female rats. In addition, comparison of these results with data obtained in male rats from a previous study suggests that PN dendrites in females may be more sensitive to the effects of ethanol.

Analyses of smooth endoplasmic reticulum of cerebellar parallel fibers in aging, ethanol-fed rats.

The smooth endoplasmic reticulum (SER), a calcium storage organelle, is essential for normal neuronal function. Dilation of the SER is pathologic and a threat to neuronal calcium homeostasis. Dilation of the SER has been reported within the dendrites of cerebellar Purkinje neurons of aging rats after lengthy ethanol treatment. Ethanol-related alterations of parallel fiber SER have not been investigated despite the fact that such dilation may precede and contribute transsynaptically to SER dilation and degeneration in Purkinje neuron dendrites. Male Fischer 344 rats (n = 120; age = 12 months old) were randomly divided into three dietary groups (40 rats per group) and fed rat chow, the AIN-93M liquid control diet, or the AIN-93M liquid ethanol diet (without water) for 5, 10, 20, or 40 weeks (30 rats per time point). Sections from posterior vermal lobules were viewed with the electron microscope. Maximum and minimum diameters of parallel fiber SER profiles were measured. Ethanol-related dilation of parallel fiber SER was not found after 5, 10, 20, or 40 weeks of treatment. Age-related dilation of parallel fiber SER profiles did occur. These findings support the suggestions that (1) parallel fiber SER, unlike the SER in Purkinje neurons, is insensitive to ethanol and (2) the mechanisms by which ethanol and aging alter cerebellar function and structure are different.

Diethylstilbestrol increases intracellular calcium in lens epithelial cells.

The effects of diethylstilbestrol (DES) on steady-state intracellular calcium concentration ([Ca(2+)](i)) and resting Ca(2+) influx were examined in primary cultures of bovine lens epithelial cells using conventional fluorometric techniques (Fura-2). At low concentrations (10 microM), DES usually induced relatively rapid increases in [Ca(2+)](i) that occurred over an interval of 10-50 s and that persisted for several minutes in the continued presence of the drug. In about 10% of the cells, cyclic oscillations in [Ca(2+)](i) were seen after adding 10 microM DES. At higher concentrations (100 microM), the drug induced more prolonged increases in [Ca(2+)](i) lasting several minutes. DES did not affect Mn(2+) quench determinations of resting Ca(2+) influx, and neither 100 microM GdCl(3), which blocked resting Ca(2+) influx, nor low [Ca(2+)](o) solutions substantially diminished the influence of DES on [Ca(2+)](i). Pretreatment of cells with the smooth endoplasmic reticulum Ca(2+) ATPase (SERCA) inhibitors cyclopiazonic acid (CPA) or thapsigargin completely abolished the effect of 10 microM DES on [Ca(2+)](i), while the IP(3) receptor blocker 2-aminoethoxydiphenyl borane (2-APB) had no effect. These results indicate that DES releases CPA-sensitive stores of intracellular Ca(2+), perhaps by inhibiting SERCA-dependent Ca(2+) sequestration.

Fibrates induce hepatic peroxisome and mitochondrial proliferation without overt evidence of cellular proliferation and oxidative stress in cynomolgus monkeys.

There is little primate risk factor data in the literature evaluating the relationship between proposed mechanisms of PPAR agonist-induced hepatocarcinogenesis at clinically relevant therapeutic exposures. These studies were conducted to characterize the hepatic effects of fenofibrate and ciprofibrate in the cynomolgus monkey. Male cynomolgus monkeys were given fenofibrate (250, 1250 or 2500 mg/kg/day) or ciprofibrate (3, 30, 150 or 400 mg/kg/day) for up to 15 days. The highest doses used were approximately 4 times (fenofibrate) and 9.4 times (ciprofibrate) the human therapeutic exposure for these agents based on AUC (area under the curve). For both compounds, there was a treatment-related increase in liver weight and periportal hepatocellular hypertrophy, which was related to increases in peroxisomes (up to 2.8 times controls) and mitochondria (up to 2.5 times controls). An increase in smooth endoplasmic reticulum probably contributed to the hypertrophy. There was no indication of cell proliferation as determined by the number of mitotic figures and this was confirmed by evaluating cell proliferation by immunohistochemical staining for the Ki-67 antigen. Consistent with the findings by light microscopy, there was no treatment-related effect on the level of mRNA for proteins known to be involved in the control of hepatocyte cell division or apoptosis (e.g. P21, Cyclin D1, PCNA, CDKN1A). Furthermore, there was minimal indication of oxidative stress. Thus, there was no evidence of lipofuscin accumulation, and there was no remarkable increase in the mRNA levels for most proteins known to respond to oxidative stress (e.g. catalase, glutathione peroxidase). A mild induction in the mRNA levels of cellular beta-oxidation and detoxification enzymes (e.g. acyl CoA oxidase, thioredoxin reductase) was observed. Collectively, the data from these studies suggest that the primate responds to PPARalpha agonists in a manner that is different from the rodent suggesting that the primate may be refractory to PPAR-induced hepatocarcinogenesis.

Cell density and growth-dependent down-regulation of both intracellular calcium responses to agonist stimuli and expression of smooth-surfaced endoplasmic reticulum in MC3T3-E1 osteoblast-like cells.

A two-dimensional intracellular Ca(2+) ([Ca(2+)](i)) imaging system was used to examine the relationship between [Ca(2+)](i) handling and the proliferation of MC3T3-E1 osteoblast-like cells. The resting [Ca(2+)](i) level in densely cultured cells was 1.5 times higher than the [Ca(2+)](i) level in sparsely cultured cells or in other cell types (mouse fibroblasts, rat vascular smooth muscle cells, and bovine endothelial cells). A high resting [Ca(2+)](i) level may be specific for MC3T3-E1 cells. MC3T3-E1 cells were stimulated with ATP (10 microM), caffeine (10 mM), thapsigargin (1 microM), or ionomycin (10 microM), and the effect on the [Ca(2+)](i) level of MC3T3-E1 cells was studied. The percentage of responding cells and the degree of [Ca(2+)](i) elevation were high in the sparsely cultured cells and low in densely cultured cells. The rank order for the percentage of responding cells and magnitude of the Ca(2+) response to the stimuli was ionomycin > thapsigargin = ATP > caffeine and suggests the existence of differences among the various [Ca(2+)](i) channels. All Ca(2+) responses in the sparsely cultured MC3T3-E1 cells, unlike in other cell types, disappeared after the cells reached confluence. Heptanol treatment of densely cultured cells restored the Ca(2+) response, suggesting that cell-cell contact is involved with the confluence-dependent disappearance of the Ca(2+) response. Immunohistological analysis of type 1 inositol trisphosphate receptors and electron microscopy showed distinct expression of inositol trisphosphate receptor proteins and smooth-surfaced endoplasmic reticulum in sparsely cultured cells but reduced levels in densely cultured cells. These results indicate that the underlying basis of confluence-dependent [Ca(2+)](i) regulation is down-regulation of smooth-surfaced endoplasmic reticulum by cell-cell contacts.

Effects of repeated exposures to xenon on rat adrenal cortex ultrastructure.

Xenon has many properties of the ideal anaesthetic and it has been proposed to replace classic volatile anaesthetics. Although some studies demonstrated that xenon does not induce gross morphological changes in major organs, little is known on its possible ultrastructural effects. The present study investigates the subcellular effects of repeated exposures to 70% xenon on rat adrenal cortex in comparison with N2O. Animals were divided into four groups: xenon-exposed, N2O-exposed, sham-exposed and controls. Exposed rats were placed into a sealed cage to breathe the respective gas mixture for 2.5 h/day for a week. Specimens of adrenal cortex for electron microscopy and blood samples for determination of corticosterone plasma levels were taken at the end of the last exposure or one week after the last exposure (recovery). Adrenal cortex from N2O- and sham-exposed rats mainly showed dilation of endoplasmic reticulum, whereas xenon-exposed rats also exhibited several cells with lipid droplets appearing subdivided into smaller droplets, irregular in shape and size. In all experimental groups, corticosterone plasma levels increased in comparison to controls. Both ultrastructural and hormonal changes were not detected anymore after one week from the last exposure. These findings indicate that xenon is able to induce subcellular changes in rat adrenal cortex, mainly at the level of lipid structures. The transient changes induced by xenon suggest that this gas can be regarded as a safer anaesthetic.

Specialization of midgut cells for synthesis of male isoprenoid pheromone components in two scolytid beetles, Dendroctonus jeffreyi and Ips pini.

Endodermal or midgut cells have only recently been recognized as the site of pheromone synthesis in bark beetles. Midgut cells are not only specialized for digestion, but they have also been recruited to form isoprenoid compounds that function as pheromone components in Ips pini and Dendroctonus jeffreyi. Male bark beetle midgut cells are competent to produce isoprenoid pheromones after feeding or stimulation by juvenile hormone (JH) III. Competent midgut cells share many ultrastructural features with cells that do not secrete isoprenoid pheromone, but they are distinguished from these by abundant and highly ordered arrays of smooth endoplasmic reticula. During secretion, both midgut cells that produce pheromone and cells that do not are characterized by the presence of apical extrusions (apocrine secretion) rather than the presence of vesicles that fuse with the apical membrane and undergo exocytosis (eccrine secretion). Pheromone-producing cells of the midgut do not represent a population of cells that are distinct from cells involved in digestion. All, or most, midgut cells of male I. pini and D. jeffreyi can secrete pheromones as well as digestive enzymes.

Caffeine stimulates Ca(2+) entry through store-operated channels to activate tyrosine hydroxylase in bovine chromaffin cells.

The ability of caffeine-induced store Ca(2+) mobilization to activate tyrosine hydroxylase was studied in bovine adrenal chromaffin cells. Caffeine increased tyrosine hydroxylase activity over 10 min with an EC(50) of 3 mm and maximum effect at 20 mm. The maximum response to caffeine was substantial, being almost one third that of the strongest agonists acetylcholine and PACAP-27, about half that for K(+) and similar to that for histamine. In contrast, catecholamine secretion evoked by caffeine was small, being less than 10% of the response to strong agonists. Caffeine-induced tyrosine hydroxylase activation was not mimicked or prevented by phosphodiesterase inhibition with isobutylmethylxanthine, nor was it mimicked by an equimolar concentration of sucrose. However, the effect of caffeine was prevented by depleting intracellular Ca(2+) stores by thapsigargin pretreatment, and reduced substantially by removing extracellular Ca(2+), by blocking Ca(2+) channels with Co(2+) or Ni(2+), or by inhibiting store-operated channels with 2-aminoethyl diphenylborate. It was not affected by inhibiting Ca(2+) entry through voltage-operated Ca(2+)-channels or by tetrodotoxin. The effect of caffeine was mimicked by acute thapsigargin treatment or by depleting intracellular Ca(2+) stores in Ca(2+)-free buffer and then reintroducing extracellular Ca(2+). The results indicate that mobilizing store Ca(2+) with caffeine is a very effective mechanism for activating tyrosine hydroxylase and that the majority of this response depends on extracellular Ca(2+) entry through store-operated channels. They also suggest that extracellular Ca(2+) entry through such channels regulates cellular responses differently to Ca(2+) entry through voltage-operated Ca(2+) channels.

The Clara cells activated by acetaminophen.

Many high mountaineers die of acute mountain sickness in the high mountains of Nepal during their adventure. Most of them administer acetaminophen (AP) as an analgesic. Various cells with higher expression of cytochrome P-450 (CYP) would metabolize AP and lead to cellular impairment. CYP is a major enzyme system in the metabolism of xenobiotics in different organs of the human being including in Clara cells of the lungs. Clara cells contain the highest concentration of CYP. We injected AP to C57BL/6J mice to examine the toxicity of AP in Clara cells. In 8 hours Clara cells show more prominent apical protrusion with edematous smooth endoplasmic reticulum (sER), reduced secretary granules, and edema. We speculate that using AP in a high mountain area might be harmful for Clara cells being a trigger of high altitude sickness.

Polychlorobiphenyls inhibit skeletal muscle differentiation in culture.

Polychlorinated biphenyls (PCBs) are ubiquitous and persistent pollutants whose role in developmental toxicity is of great concern. The observation that the offspring of PCB-exposed mothers (both in humans and rodents) display reduced body mass prompted us to investigate the effects of commercial mixtures of PCB congeners (Aroclor 1232, 1254, and 1262) on differentiation of both a myogenic cell line and primary myogenic cell cultures. The fusion of L6 myoblasts into multinucleated myotubes and the increase of creatine kinase (CK) activity were dose-dependently inhibited by Aroclor 1254 at concentrations (0.1-4 microg/ml) that caused no effect on cell density. Ultrastructural analysis demonstrated that Aroclor 1254 also prevented the accumulation of contractile filaments while inducing hypertrophy of the smooth endoplasmic reticulum and appearance of membrane-filled autophagosomes. Half-maximal inhibition (IC50) of CK activity accumulation occurred at 0.01 microg/ml for Aroclor 1262, 2 microg/ml for Aroclor 1254, and 8 microg/ml for Aroclor 1232. Aroclor-dependent inhibition of myogenic differentiation was also shown by the reduced expression and nuclear accumulation of beta-galactosidase in primary cultures of fetal myoblasts from transgenic mice expressing this reporter gene under the control of the myosin light chain promoter. These data show that skeletal muscle differentiation is specifically impaired by PCBs and may explain the reported depression of body mass growth in PCB-exposed offspring at birth. Furthermore, myogenic cell cultures are highly sensitive to PCBs and allow the detection of biological effects of environmental levels of these pollutants.

New features of renal lesion induced by stroma free hemoglobin.

This study focused on the subacute renal lesions resulting from the infusion of stroma free hemoglobin (SFH), which remains under evaluation as a potential blood substitute despite limited renal toxicity observed in acute infusion. Four groups of rats received different doses of SFH (0.03, 0.48, 0.96, and 1.46 g, respectively) and were monitored, on alternate days, for their glomerular filtration rate over the course of 10 days. Another group of 6 rats receiving 0.96 g SFH was sacrificed at day 10 for examination of renal morphology. The low dose (0.03 g) of SFH infusion did not alter the creatinine clearance (Clcr) over 10 days. The Clcr decreased in rats receiving 0.48 g SFH but fully recovered at day 10. A persistent decrease in Clcr was observed in the groups of rats receiving 0.96 and 1.68 g of SFH. Tubular necrosis was the most prominent renal lesion distributed in the proximal tubules, especially in the convoluted segment of the juxtamedullary nephrons. Pearls' stained cytoplasmic granules and electron-dense lysosomal granules were found in surviving proximal tubules. Necrosis was the predominant mechanism of cell death. This study revealed for the first time proliferation of smooth endoplasmic reticulum in the proximal tubules after SFH treatment, where it appeared as nodular aggregates of tubulovesicular structures. The effect of SFH on the proximal tubule appeared to be a direct toxicity, and this toxicity was shown to be dose dependent. The presence of reversible toxicity indicated that a safety limit dosage for SFH infusion exists and that tolerance dose of SFH can be determined for clinical applications.

Role of p97 and syntaxin 5 in the assembly of transitional endoplasmic reticulum.

Transitional endoplasmic reticulum (tER) consists of confluent rough and smooth endoplasmic reticulum (ER) domains. In a cell-free incubation system, low-density microsomes (1.17 g cc(-1)) isolated from rat liver homogenates reconstitute tER by Mg(2+)GTP- and Mg(2+)ATP-hydrolysis-dependent membrane fusion. The ATPases associated with different cellular activities protein p97 has been identified as the relevant ATPase. The ATP depletion by hexokinase or treatment with either N-ethylmaleimide or anti-p97 prevented assembly of the smooth ER domain of tER. High-salt washing of low-density microsomes inhibited assembly of the smooth ER domain of tER, whereas the readdition of purified p97 with associated p47 promoted reconstitution. The t-SNARE syntaxin 5 was observed within the smooth ER domain of tER, and antisyntaxin 5 abrogated formation of this same membrane compartment. Thus, p97 and syntaxin 5 regulate assembly of the smooth ER domain of tER and hence one of the earliest membrane differentiated components of the secretory pathway.

PCB 128-induced ultrastructural lesions in the rat liver.

PCB 128 (2,2',3,3',4,4'-hexachlorobiphenyl) prepared in 4% corn oil and mixed in diets was given to weanling Sprague-Dawley rats. The animals were placed in eight groups, each comprising 10 males or 10 females; each group received a diet that contained 0.05, 0.5 or 5 ppm PCB. Ten animals of each gender that served as the controls were given diets mixed with only corn oil. Thirteen weeks after the commencement of dosing, animals were euthanized and liver specimens were harvested and prepared for transmission electron microscopy. The architecture of the liver parenchymal cell was indistinguishable in the animals of the lowest concentration group from those in the controls. However, smooth endoplasmic reticulum profiles increased, and abnormal mitochondria were noted in the liver of rats, regardless of gender, from 0.5 and 5 ppm groups. Based on our previous work, PCB 128 is estimated to be equally toxic as PCB 153, another di-ortho substituted PCB congener.

PCB congener 126-induced ultrastructural alterations in the rat liver: a stereological study.

Hepatocyte cytoplasmic alterations were morphometrically determined in male and female Sprague-Dawley rats fed PCB congener 126 (3,3',4,4',5-pentachlorobiphenyl) in concentrations of 0.1, 1.0, 10, 100 ppb or corn oil in diets for 13 weeks. A dose-dependent increase (P < 0.05) in the volume fraction of smooth endoplasmic reticulum (SER) and mitochondria was measured in the hepatocytes of the females. However, these cells of the male rats contained a significantly greater baseline volume fraction of SER compared to that in the females. Statistical differences were not detected in the volume fractions of rough endoplasmic reticulum, peroxisomes or lipid droplets of the hepatocytes in either the males or females. We conclude the increase in mitochondrial volume was a necessary cellular adaptation to meet the heightened energy demands by the SER to produce the necessary enzymes to detoxify the PCB. Morphometric analysis rather than a descriptive methodology allowed for a more accurate determination of the liver pathology induced by PCB 126.

Chronic ethanol-initiated apoptosis in hepatocytes is induced by changes in membrane biogenesis and intracellular transport.

The outcome of chronic ethanol consumption recorded in liver by in situ staining of the genomic DNA in fragmented nuclei indicates the course of cellular events that has been coined as apoptosis or programmed cell death. Hence, we designed the study to determine which ethanol-induced modification of the cellular make-up is responsible for the hastening the cell damage. The in vitro assays were performed with cellular organelles and cytosol prepared from hepatocytes derived from rats subjected to 9 weeks of chronic alcohol consumption. The results were compared with the pair-fed controls receiving isocaloric liquid diet. In the initial phase of the studies, we established that the process of apoptosis was not triggered by the aberrant activity of neutral or acidic sphingomyelinase. The hepatocytes derived from alcohol and control diets manifested equal enzymatic activity. The de novo synthesis of sphingoid bases and ceramides in the alcohol-derived sample of endoplasmic reticulum was reduced, but the in situ apoptosis was up to 36-fold higher than in the control. Also, the isolated hepatocytes contained a 2- to 4-fold higher amount of nucleosomal fragments in the cytosolic extracts. The endosomes from liver hepatocytes of ethanol-consuming rats, in the presence of the cytosol and mitochondria from pair-fed controls, disclosed 2 to 3 times higher apoptotic potential than sample consisting of ethanol-derived fractions only, and 3 to 5 times higher than the control-derived fractions. The substantial increase in apoptosis, as recorded in the amount of DNA fragments released to the cytosol from the fresh nuclei, was also recorded when the microsomal membranes of endoplasmic reticulum and Golgi were incubated in the conditions with preserved intracellular transport. The maximal 20-fold increase of apoptotic activity was recorded in the incubation mixtures of ethanol-derived endoplasmic reticulum-Golgi membranes with control-derived cytosol in the presence of the ATP generating system. Results infer that the intracellular transport vesicles, generated from ethanol-modified membranes in the presence of the substrates that are available in the cytosol of the control hepatocytes, activate the apoptotic activity in the in vitro system. This interpretation is supported by the results of analysis of the clathrin-coated transport vesicles that, in contrast to nonclathrin transport vesicles, contain a sizable accumulation of ceramides that are known to induce apoptosis.

Conformational changes of the smooth endoplasmic reticulum are facilitated by L-glutamate and its receptors in rat Purkinje cells.

The intraventricular administrations of L-glutamate or trans-1-amino-1,3-cyclopentanedicarboxylic acid (t-ACPD), which is an agonist for the metabotropic glutamate receptor, induced conformational changes of the smooth endoplasmic reticulum (SER) to form lamellar bodies, consisting of stacks of flattened cisterns in Purkinje cell dendrites of the rat cerebellum. The formation of lamellar bodies by t-ACPD or by anoxia was blocked by pretreatment of L(+)-2-amino-3-phosphonopropionic acid (L-AP3), which is an antagonist for the metabotropic glutamate receptor. Injections of N-methyl-D-aspartic acid (NMDA) and amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA)/kainate, which are categorized as acting on ionotropic receptors of glutamate, did not cause the formation of lamellar bodies, although kainate condensed the dendritic cytoplasm and produced a swelling of surrounding astrocytes. The cisterns of lamellar bodies formed by t-ACPD were long and formed regular stacks. Many intercisternal bridges were arranged with a center-to-center distance of about 25 nm between apposed cisterns. The bridges appeared as short tubes about 15 nm in diameter and in length, a clear center of which linked the lumen of their cisterns. The present results revealed that an excess release of excitatory transmitter by brief anoxia activates metabotropic glutamate receptors, which transform the networks of SER that normally release Ca2+ widely to the neuronal cytoplasm into lamellar bodies. Large Ca2+ storage pools of lamellar bodies are formed by the association of opposing molecules that belong to different cisterns and may protect excess release of Ca2+ from their reservoirs.

PCB congener 77-induced ultrastructural alterations in the rat liver: a quantitative study.

Liver alterations were estimated morphometrically in male and female Sprague-Dawley rats that were fed PCB congener 77 (3,3',4,4'-tetrachlorobiphenyl) in concentrations of 0.01, 0.1, 1, 10 ppm or corn oil in diets for 13 weeks. A dose-dependent increase in the volume of smooth endoplasmic reticulum (SER) and an elevation in the volume of mitochondria following administration of the highest congener concentration (10 ppm) were estimated in the female rats. Hepatocytes of the male rats contained a significantly greater baseline volume of both SER and mitochondria compared to that in the females. A statistically significant (P < 0.05) change in the volumes of either SER or mitochondria in the PCB-fed males was not revealed. The authors concluded that the increase in mitochondrial volume was probably a necessary cellular adaptation to meet the heightened energy demands required by the SER to detoxify the PCB. The use of morphometric rather than a descriptive methodology allowed for a better determination of the hepatic alterations induced by PCB 77.