Ultrastructural changes in rat livers perfused in vitro and in vivo with a high dose of methotrexate.

Methotrexate is an antifolate that is widely used in the treatment of malignant tumours and other diseases. The present study was undertaken to examine the short-term effects of high doses of methotrexate (HD-MTX) on the ultrastructure and metabolic activity of isolated rat livers. The authenticity of the drug-induced changes was substantiated by the concomitant use of in vivo experiments. Isolated rat livers were infused with HD-MTX via the portal vein for 3 hours (total dose for each liver 2000 mg). For in vivo experiments, each rat received a single intravenous injection of a maximum tolerated dose of MTX (100 mg/kg body weight) that allowed the animals to survive for 3 days. At the end of each experimental period, MTX-treated and control livers were processed for light microscopy (LM), scanning (SEM) and transmission electron (TEM) microscopy. Oxygen consumption and thyroxine metabolism were measured in treated and control isolated livers. With the exception of a few minor differences, the structural changes in the hepatocytes after MTX treatment in vitro and vivo were similar. There were focal changes consisting of disruption of normal hepatic plates and swelling and vacuolation of the hepatocytes, with no clear evidence of restriction to a specific hepatic zone. SEM revealed striking changes in the plasma membrane, the microvillar system, intercellular junctions and the sinusoidal endothelium. TEM revealed disorganized endoplasmic reticulum, dispersion of the polyribosomes, a variety of mitochondrial changes, and glycogen redistribution. In MTX-treated isolated rat livers, the uptake of tetraiodothyronine (T4) was not affected, but triiodothyronine (T3) release was impaired. Oxygen consumption was increased in livers treated with MTX. Employing an organotypic liver perfusion model in conjunction with the in vivo experiment and the use of SEM, TEM and hepatic thyroxine measurements, this investigation revealed that infusion of HD-MTX induced early ultrastructual changes in cell membrane, intercellular junctions and cell organelles and disturbance in the functional integrity of the hepatocytes in isolated rat liver.

Isomerism of the right atrial appendages: clinical, anatomical, and microscopic study of a long-surviving case with asplenia and ciliary abnormalities.

This study describes a case of isomerism of the right atrial appendages (bilateral morphologically right atrial appendages associated with complex congenital cardiac lesions) with ciliary abnormalities. Detailed investigation included gross anatomic dissection, review of the clinical history, and light, confocal, and electron microscopy. Clinically, this 40-year-old, long-surviving male patient had relatively good health until 4 years before death, which was due to cardiac failure. Surgical intervention consisted only of a Blalock-Taussig shunt (anastomosis of the right subclavian artery to the right pulmonary artery) at 6 years of age. Despite the presence of complex cardiac malformations and asplenia, his longevity may be attributed to the connection of the pulmonary veins to the atrium without pulmonary venous obstruction, pulmonary valvar stenosis rather than atresia, no significant atrioventricular valve regurgitation, and no serious infections during his life. Microscopic examination of bronchial epithelium revealed a narrow, disorganized epithelium with abundant goblet cells and short, angulated cilia with a random orientation and possibly an abnormal central microtubule doublet. These abnormalities were not present in controls, and have been noted in primary ciliary dyskinesia (PCD) or Kartagener's syndrome. Because this syndrome has classically been thought to cause random lateralization resulting in a mirror-imaged arrangement of the organs, the occurrence of truly isomeric patterns is not widely recognized. Whereas polysplenia and left bronchial isomerism have been reported to occur in immotile cilia syndrome, this is the first report to present detailed postmortem anatomic evidence of isomerism of the right atrial appendages, right bronchial isomerism, and asplenia in association with microscopy suggesting ciliary abnormalities.

An ultrastructural study of the phagocytic activity of astrocytes in adult rat brain.

The role of adult astrocytes in the removal of cell debris and foreign particles following injury to the brain is controversial. This study was undertaken to elucidate the response of adult astrocytes to needle injury of the rat cerebral cortex, using a suspension of colloidal carbon as a marker for phagocytosis. Either a single or 2 successive injections of colloidal carbon suspension were made into the cerebral cortex. The animals were allowed to survive for periods of from 1 to 30 d. Unequivocal involvement of astrocytes in the removal of carbon particles was evident only in those brains which had been subjected to 2 successive injections of carbon. The particles were located in membrane-bound vacuoles and were subsequently sequestered in lysosomes. Carbon-containing astrocytes were observed in the immediate vicinity of the lesion, in the adjacent parenchyma, around blood vessels and abutting carbon-containing macrophages. This study demonstrates that adult astrocytes are involved in phagocytosis, but only as a second line of defence. The possible significance of carbon-laden astrocytes further away from the site of the lesion is discussed.

Electron and light microscopy of pancreatic islets of Langerhans isolated by Trowell's T8 medium.

The isolation and purification of high yields of islets of Langerhans are important areas of investigation. Although it is well established that warm and cold ischemia affect islet yield and function, little information is available about the damage that occurs during the digestion period. We used Trowell's T8 medium and conventional Hank's balanced salt solution to obtain high yields of islets with morphologically-intact cells. Light and electron microscopy were used to characterize the islets isolated by the two media. Results reveal that the islets isolated by Trowells T8 medium were less fragmented and had better fine-structural integrity than those isolated by the conventional medium.

Ultrastructural and hormonal metabolic studies of rat liver maintained in vitro by perfusion at 30 degrees C and 37 degrees C: a time course study by TEM, SEM and RIA.

Isolated rat liver perfusion system has been extensively used for metabolic and functional studies. Results derived from the application of this system may reflect true biochemical changes but they may also be associated with some structural changes. This study was undertaken to correlate the cytological changes and functional integrity of isolated rat liver perfused in vitro at normal physiological temperature (37 degrees C) and 30 degrees C, using a non-recirculating system. The livers were perfused for 3 hours with modified Ham's F10 culture medium supplemented with thyroxine hormone (T4). The hepatocyte structural integrity was studied by light microscopy, transmission and scanning electron microscopy. The triiodothyronine (T3) and T4 hormones in the perfusion medium and the effluent fractions were assessed by radioimmunoassay. The livers perfused at 30 degrees C remained morphologically intact at the ultrastructural level for 3 hours whilst at 37 degrees C, hepatocytes in the centrilobular zone exhibited marked structural alterations. The percentage of T4 uptake was significantly higher (P less than 0.01) in livers perfused at 30 degrees C (50.8 +/- 7.7% vs 38 +/- 7.7%, 37 degrees C), but the net T3 output (3.16 +/- 1.04 micrograms) and the conversion of T4 to T3 (4 +/- 0.62%) were significantly higher (P less than 0.001) in livers perfused at 37 degrees C in comparison to livers perfused at 30 degrees C (1.61 +/- 0.84 micrograms and 1.68 +/- 0.76%, respectively). In conclusion, at 30 degrees C the hepatic T4 uptake is not inhibited, but the rate of T4 to T3 conversion has decreased, additionally the livers remain morphologically well preserved throughout the experimental period.(ABSTRACT TRUNCATED AT 250 WORDS)

Fine structural study of the spinal cord and spinal ganglia in mice afflicted with a hereditary sensory neuropathy, dystonia musculorum.

Dystonia musculorum in mice is a hereditary autosomal recessive disorder, characterized by a progressive neuromuscular incoordination. This paper describes the ultrastructural changes in the spinal cord and compares and correlates the results with changes in the spinal ganglia in dystonic mice. Ganglion cells exhibited various stages of degeneration and pyknosis. The dorsal roots of the spinal nerves showed severe degeneration and loss of myelinated fibres accompanied by fibrosis, whilst the ventral roots appeared normal. Nerve cells within the dorsal and intermediate grey matter (laminae I to VII) of the spinal cord showed chromatolysis, atrophy, and necrosis. Boutons exhibited glycogen accumulation or an increase in their electron density. Axonal changes consisted of focal swellings, marked accumulation of neurofilaments, membranous and dense bodies, and disintegration of axoplasm. Myelin sheath degeneration of Wallerian type and degenerating axons were prominent in the dorsal, lateral and ventral white columns of the spinal cord. Glial reactions in the spinal cord were limited to mild hypertrophy and hyperplasia of astrocytic processes. The process of phagocytic activity was not intense in spite of the presence of an abundance of degenerating myelin and cell debris. This study showed that the ultrastructural changes in the spinal cord are more severe than those seen with routine light microscopy. The detection of definite neuronal degeneration of the dorsal root ganglia and spinal cord suggests that the defect apparently operates at the level of cell bodies, as well as axons, of the primary and second order sensory neurons.

The histological and the histopathological pattern of conjunctival rhinosporidiosis associated with papillomavirus infection.

The present study describes for the first time, the clinical, light and electron microscopic findings of two cases of conjunctival rhinosporidiosis. One was with concurrent infection of papillomavirus. Investigations at the ultrastructural level have provided additional information on the development of Rhinosporidium seeberi and would suggest that the formation of the wall of this organism is a continuous morphological and biochemical spectrum throughout its cytological maturation. The current observation on the wall formation is probably a modification of the classical pattern as an environmental protection carried out by the fungus against the virus. In contradistinction to the usual histopathological picture of rhinosporidiosis, the case with the viral infection lacked the characteristic marked inflammatory reaction. This finding, together with the relatively short interval of the frequent recurrences of this lesion, have led us to postulate the presence of a localised acquired immune deficiency state. It is possible that this local immune deficiency may be caused by an immunosuppression mechanism. This is probably mediated by papillomavirus and/or due to the weak antigenicity of the host virus-infected cells which contain only copies of viral DNA in an unintegrated form.

Rhinosporidium seeberi and papovavirus infection of the conjunctiva: a clinical and ultrastructural study.

The present study describes, for the first time, the clinical and the ultrastructural findings of a rare case presented with concurrent conjunctival infection of Rhinosporidium seeberi and a papovavirus. In contradistinction to previous reports, the present case lacked the characteristic granulomatous inflammatory reaction of rhinosporidiosis. This finding, together with the frequent recurrence of the lesion, led us to postulate the presence of a Local Acquired Immune Deficiency State (LAIDS). This Local AIDS may be caused by an immunosuppression mechanism which is probably mediated by papovavirus.

Ultrastructural study of phagocytic activities of young astrocytes in injured neonatal rat brain following intracerebral injection of colloidal carbon.

The cellular reaction to injury in the mature central nervous system (CNS) has been extensively studied in both man and animals, while a detailed study of the reaction of the immature CNS to injury is lacking in the literature. This study was undertaken to elucidate the response of young astrocytes following injection injury to developing brain. Colloidal carbon was applied because it is a suitable marker for phagocytosis, it is nontoxic, and it is readily identifiable by light and electron microscopy. The cerebral cortex of the neonatal rat was injected with 0.1 microliter of colloidal carbon solution. The animals were allowed to survive from 1 hour to 30 days postoperation. The brains were fixed by vascular perfusion and processed for light and electron microscopy. Carbon particles were ingested in membrane-bound vacuoles and sequestered in lysosomes of young astrocytes. Astrocytes, loaded with carbon particles, were identified after 4 days, and were seen in abundance between 10 to 21 days postoperation. Carbon-laden astrocytes were seen in the immediate vicinity of the site of the injection; in the surrounding, apparently normal, neuropil; and in the perivascular regions. This study demonstrates the ability of young astrocytes to engulf foreign particles injected into the developing brain. The presence of carbon particles in astrocytes located further away from the site of injection is discussed.

Morphological changes in the isolated rat liver perfused in a non-recirculating system: scanning and transmission electron microscopy.

Isolated perfused rat livers have been used for various studies, but detailed investigation into the structural integrity of hepatocytes of this system is lacking. In this study, isolated rat livers were perfused in vitro with oxygenated Krebs-Ringer bicarbonate buffer solution, for 2 minutes and 1, 2, 3, and 4 hour(s) at 37 degrees C, using a non-recirculating perfusion system. The perfused livers were processed for semithin section light microscopy, transmission electron microscopy, and scanning electron microscopy. Sectional areas of cell deaths were measured by a camera-tracing assembly from 1.5 microns thick Araldite sections stained with toluidine blue. Progressive nuclear and cytoplasmic changes, leading to cell death, occurred in the hepatocytes of the centrilobular zone, during the 2nd, 3rd, and 4th hour of the perfusion at a rate of 9.03% +/- 1.5%, 38.7% +/- 2.7%, and 55.1% +/- 5.9% (mean +/- standard deviation) of the total sectional areas respectively. Midzonal hepatocytes showed normal basophilic staining but exhibited loss of glycogen granules, loss of microvilli, development of aqueous vacuoles and formation of blebs. The fine structures of cell organelles, glycogen granules, microvilli and plasma membrane of the cells in the periportal zone were well preserved throughout the experimental period. For further quantitative, metabolic and functional studies using isolated rat liver perfused with Krebs-Ringer solution, it is evident from the present investigation that the periportal zone represents the functional region of the hepatic lobule. Whilst progressive changes, leading to cell death, occurred in the centrilobular zone.

Neuronal and oligodendrocytic response to cortical injury: ultrastructural and cytochemical changes.

A needle wound was made in the adult rat cerebral cortex. Responses of neurons and oligodendrocytes at the site of injury were followed over a period of 450 days and correlations made between morphological and enzyme cytochemical changes to clarify some phenomena previously unresolved. Evidence from acid phosphatase activity in degenerating neurons showed no increase in the number of cytochemically stained lysosomal profiles nor changes in the subcellular localization of the acid phosphatase reaction product. Our observations indicated that the majority of dying neurons were not digested by their own acid phosphatase 'autodigestion' but by the process of heterodigestion. The time-course study revealed that not all the traumatized neurons were eliminated but some persisted permanently in an attenuated 'atrophic' state. The atrophic neurons were small in size with low cytoplasmic-nuclear ratios and exhibited low levels of glucose-6-phosphatase and cytochrome oxidase activities. The acid phosphatase activity was slightly increased as evidenced by cytochemically stained hypertrophic Golgi cisternae and a slight increase in the number of lysosomes. The low level of enzyme activities concerned with carbohydrate metabolism reflected the low metabolic activity in atrophic neurons whilst an increase in Golgi-lysosomal enzyme activity suggested some anabolic process necessary for their survival. Oligodendrocytes displayed only minor changes in morphology, and their glucose-6-phosphatase and cytochrome oxidase activities were normal, suggesting that these cells have little or no involvement in the repair of a cerebral wound. The absence of significant changes in lysosomal acid phosphatase activity indicated a minimal role, if any, of oligodendrocytes in the process of phagocytosis.

Brain phagocytes: source of high acid phosphatase activity.

A stab wound was produced in the adult rat cerebral cortex, and the progress of enzyme cytochemistry of phagocytosis was studied over 450 days. Light- and electron-microscopic observations were made to establish the origin of high acid phosphatase activity commonly seen at the site of brain lesions. Cells with phagocytic potential became differentiated and activated by the presence of degenerating neurons. The Golgi-lysosomal system of the phagocytes became elaborated, as evidenced by thiamine pyrophosphatase and acid phosphatase activities, the synthesis of acid phosphatase was increased, and the enzyme then secreted into the digestive vacuoles containing dead cells to be digested. Progress of the digestive process resulted in the accumulation of large amounts of acid phosphatase reaction product within the digestive vacuoles. The results showed that the phagocytes were the only detectable source of increased acid phosphatase activity at the site of injury in the cerebral cortex. In contrast to the phagocytes, newly formed multi-nucleated giant cells exhibited weak acid phosphatase, and intense cytochrome oxidase activities, the difference between the two cells reflecting the functional characteristics of each.

Ultrastructural study of enzymes in reactive astrocytes: clarification of astrocytic activity.

Enzymes in reactive of the cerebral cortex were examined at the ultrastructural level in an attempt to resolve some conflicting aspects of astrocytic activity. Correlations between morphological and enzyme changes after injury established that the apparent increase in oxidative enzyme activity was exclusively mitochondrial and not an artefactual reaction product resulting from anoxic cellular damage. Pronounced glucose-6-phosphatase activity within cisternae of an increased amount of the granular endoplasmic reticulum was related to increased glycogen. Further evidence from acid phosphatase activity indicated that astrocytes played a minimal role in phagocytosis.

Ultrastructural demonstration of glucose 6-phosphatase in cerebral cortex.

A two-stage fixation technique has been developed to obtain morphological preservation and retention of glucose 6-phosphatase (G6-Pase) activity for its demonstration in rat cerebral cortex. The technique was then employed to localize the enzyme in the cortex where it produced a dense reaction over the well developed granular endoplasmic reticulum cisternae in nerve cells and oligodendrocytes which contrasted with a thin reaction in astrocytes. Other membranous organelles showed no reaction.

Ultrastructural demonstration of cytochrome oxidase via cytochrome C in cerebral cortex.

A procedure for the ultrastructural cytochemical localization of cytochrome oxidase via cytochrome c in the cerebral cortex is described. Vascular perfusion fixation by formaldehyde and glutaraldehyde of different concentrations and mixtures of the two gave varying results. A mixture of 4% formaldehyde and 0.5% glutaraldehyde gave the best combination of ultrastructural preservation and retention of enzyme activity. Histochemical methods were examined for optimum incubation conditions, based on the oxidative polymerization of 3,3'-diaminobenzidine (DAB) to an osmiophilic product. The reaction product was discretely localized within intercristate and the intermembrane space of mitochondria. The staining pattern was the same in nerve cells and in neuroglia and their processed. The DAB reaction product was also found in mitochondria of the endothelial cells.