A MORPHOMETRIC STUDY OF THE REMOVAL OF PHENOBARBITAL-INDUCED MEMBRANES FROM HEPATOCYTES AFTER CESSATION OF TREATMENT

It is well known that phenobarbital (PB) treatment produces an increase in the amount of cytoplasmic membranes of hepatocytes, with a parallel enhancement in the activity of drug-metabolizing enzymes. However, little is known about how the induced membranes are removed after the drug treatment is stopped. To consider this problem, the recovery of rat hepatocytes from PB induction (five daily injections, 100 mg/kg) was followed morphometrically. Treatment with PB produced a cellular enlargement (26%) due to increases in the volume of the cytoplasmic matrix (20%) and the volume (100%) and surface area (90%) of the smooth-surfaced endoplasmic reticulum (SER). The volume of the nuclei and the surface area of the Golgi apparatus were also increased, but no changes were detected in the volumes of the mitochondria or peroxisomes. The SER membranes induced by the PB were removed within 5 days after the end of the treatment period. During this period of membrane removal, we observed an increase in the volume (800%) and number (96%) of autophagic vacuoles without a change in dense bodies. A morphometric analysis of the content of the autophagic vacuoles showed that the endoplasmic reticulum membranes were preferentially removed, and from this we conclude that the formation of autophagic vacuoles was not a random process. Our findings show that the removal of excess cytoplasmic membranes is associated with an increase in autophagic activity and thus demonstrates the presence of a specific cellular mechanism which may be responsible for the bulk removal of PB-induced membranes.     

Morphometric analysis of the ultrastructural changes in rat liver induced by the peroxisome proliferator SaH 42-348

The changes occurring in hepatocytes of F-344 male rats during a 3-wk treatment with a hypolipidemic agent, 1-methyl-4-piperidyl-bis [p- chlorophenoxy]acetate (SaH 42-348), have been evaluated by morphometric and biochemical methods. The twofold increase in liver weight resulted from a significant increase in hepatocyte cytoplasm as well as a moderate increase in the number of liver cells. The peroxisome population and SER played an overwhelming part in the hypertrophy of hepatocytic cytoplasm. The relative volume and the surface density of peroxisomes volume resulted from an increased ninefold and sevenfold, respectively. The increase in the collective peroxisome volume resulted from an increase in both the number and the average volume of peroxisomes. The SER also demonstrated a substantial increase in these values. The relative volume and surface density of mitochondria were not significantly altered in comparison to controls, while these values for RER decreased onefold. Studies on the lobular distribution of cytoplasmic organelles before and during treatment revealed that the relative volume and surface density of peroxisomes and SER increased from periportal to centrilobular cells of the hepatic lobule, whereas mitochondrial values decreased from periportal to centrilobular cells. The RER values were fairly constant in different parts of the hepatic lobule. The increase in peroxisome and SER volume and surface area was first evident within the first 3 days of SaH 42-348 treatment and these values continued to increase, reaching a steady state within 2 wk. The time course of increase in catalase and carnitine acetyltransferase activities correlated with the morphometric data on the peroxisomes. After cessation of SaH 42-348 treatment, the peroxisome values decreased rapidly within the first 3 days and reached control levels within 1 wk. Moderate reduction in SER values occurred after withdrawal of the drug, but these values remained higher than controls even after 2 wk, suggesting that the reduction in the amount of circulating peroxisome proteins may result in empty SER channels. On the 4th day of drug withdrawal a significant increase in the relative volume and surface density of lysosomes was observed, suggesting that these organelles may play some part in the removal of cellular membranes. However, the rapid reduction in peroxisome values after SaH 42-348 withdrawal appears to be due to cessation of enhanced peroxisome protein synthesis.     

The pineal gland of the gerbil,Meriones unguiculatus

Summary By means of morphometric analytical procedures, a diurnal rhythm in the cellular volume of gerbil pinealocytes was determined. This rhythm has been attributed primarily to a change in the cytoplasmic volume of the pinealocytes which is low during the daylight hours and increases to reach a peak during the middle of the dark period. At the ultrastructural level, six cytoplasmic components of the pinealocytes were found to exhibit a rhythm: free cytoplasm, smooth endoplasmic reticulum (SER), rough endoplasmic reticulum (RER) and ribosomes, secretory vesicles, microtubules, and mitochondria. The presumptive secretory vesicles and the microtubules reached a peak in volume one hour before lights-off. It is suggested that lights-on and lights-off both signal a decrease in size and/or number of the secretory vesicles. The SER and RER/ribosomes reached their peak volume one hour after lights-off which is interpreted as indicating a peak in indoleamine synthesis and protein synthesis, respectively. The volume of free cytoplasm exhibits two peaks; one occurs one hour before lights-off while the second peak occurs in the middle of the dark phase. It is suggested that, although part of the secretory product of the pinealocyte may be present in dense-cored vesicles, other locations could include the free cytoplasm and clear secretory vesicles.Supported by NSF grant #PCM 77-05734     

A quantitative electron microscopic analysis of the membrana granulosa of rat preovulatory follicles

The ultrastructure of the membrana granulosa (MG) of rat preovulatory follicles was examined using stereological techniques. Organelles studied were nuclei, mitochondria, lipid droplets (LD), lysosomes, and smooth and rough endoplasmic reticulum (SER, RER). The peripheral region of the MG contained the greatest volume of mitochondria, LD and SER, organelles associated with steroidogenesis. The volume of RER, an organelle associated with protein production, was greatest in the cumulus oophorus. These results corroborate previous analyses and demonstrate that the rat MG is composed of discrete subregions.     

Observations on the role of smooth endoplasmic reticulum in glucocorticoid-induced hepatic glycogen deposition

We have studied by quantitative electron microscopy the relationship of specific hepatic cellular organelles to glycogen synthesis using dexamethasone, a potent synthetic glucocorticoid, to induce glycogen deposition in livers of adrenalectomized rats. Chemical and ultrastructural glycogen determinations revealed that the livers of fasted adrenalectomized rats had very low glycogen levels. Dexamethasone caused a time-related increase in hepatic glycogen which was the result of increases in the number of hepatocytes depositing glycogen and the amount of glycogen in each cell. The surface density of smooth endoplasmic reticulum (SER) in centrilobular and periportal hepatocytes also increased after treatment with dexamethasone; this increase preceded glycogen deposition. The newly deposited glycogen was spatially associated with membranes of SER, and a continued increase in SER surface density was correlated temporally with the increasing glycogen volume density. In both centrilobular and periportal hepatocytes, the suface density of rough endoplasmic reticulum (RER) initially decreased after dexamethasone administration but later increased. These data support the hypothesis that dexamethasone-induced enhancement of SER is functionally associated with the increase in glycogen, and that although the initial increase in SER may occur through transformation of RER to SER, later increases in SER require synthesis of new membranes.     

Effects of clofibrate (alpha-p-chlorophenoxyisobutyryl-ethyl-ester) on male rat liver

In male rats, fed 0.5% clofibrate in their diet for 8 days and 21 days, the ultrastructural morphometric alterations of the hepatocytes were evaluated and compared with the biochemical data. The morphologic alterations of the microbodies were particularly related to the changes of the catalase activity of the liver homogenates. The results showed a marked hypertrophy of the liver and an increase in the volume of the individual hepatocyte. The numerical density and, even more pronounced, the volume density of the microbodies increased excessively during the treatment. The numerical density of the mitochondria decreased markedly after 21 days of administration. The surface of the rough endoplasmic reticulum showed a significant decrease, whereas the surface of the smooth endoplasmic reticulum showed a hypertrophy. The catalase activity of the liver homogenates increased 2-fold after 8 days and remained at this new steady-state after 21 days of treatment. The results suggest that the enzyme content of the microbodies changed after treatment with clofibrate, and support the suggestion that clofibrate may induce the synthesis of a yet unidentified peroxisomal protein.     

Zonal changes in the rat liver following an acute dose of phenobarbitone: An ultrastructural,morphometric and biochemical correlation

Alterations in the liver of rats 6 h after a dose of phenobarbitone have been studied by subcellular fractionation, conventional electron microscopy and morphometric analysis. The area immediately surrounding the central vein was the only area to undergo any alterations. There was a morphometrically measurable but not observable cellular hypertrophy of 71% whilst the hepatocyte complement of rough endoplasmic reticulum (RER) and smooth endoplasmic reticulum (SER) was increased by 72% and 93% respectively. The increases in RER and SER were not apparent by observation and it is assumed that they have been diluted by the cell hypertrophy to 1% and 22% which must be below the threshold for detection by subjective observation. Following subcellular fractionation and measurement of microsomal protein, there was no significant difference in the level of microsomes isolated from control or treated rats. Therefore, the morphometrically measured increase in RER and SER would appear to be restricted to a relatively small population of hepatocytes adjacent to the central vein. Such an increase would represent only a small percentage of total microsomes in a homogenate and would almost certainly be masked by variation in animals and techniques. Disruption of RER was also observed in hepatocytes that would proliferate their SER should phenobarbitone treatment have been continued. Therefore this RER disruption would seem in no way to interfere with the process of membrane and enzyme synthesis.     

Morphometric analysis of hepatocytes from rats subjected to compound 48/80-induced anaphylactic shock

Morphometric and biochemical techniques were used to analyze hepatic glycogen, endoplasmic reticulum, and mitochondrial matrix granules in rats treated with compound 48/80 to induce an anaphylactic-like state of shock. Thirty minutes after insult there was a significant decrease in glycogen and mitochondrial matrix granules, an increase in rough endoplasmic reticulum (RER), and no change in smooth endoplasmic reticulum (SER). Less glycogen in experimental rats substantiated a previously described glycogenolytic response to compound 48/80. The decrease in matrix granules implies a loss and/or shift in intramitochondrial calcium as occurs in epinephrine-induced glycogenolysis in the rat. Since other glycogenolytic agents, e.g. glucagon, and starvation stimulate an increase in SER presumably from RER, the present morphological data suggest the increase in RER may precede proliferation of SER from RER.     

Isolation of a subfraction of rough endoplasmic reticulum closely associated with mitochondria : Evidence for its role in cytochrome P450 synthesis

A subfraction of rough endoplasmic reticulum (RER) structurally associated with mitochondria (mito-RER complexes) was isolated from crude nuclear fractions of rat liver homogenate. When apocytochrome P450 synthesis (which presumably occurs in RER) and mitochondrial heme synthesis was dissociated by concomitant treatment of rats with phenobarbital and cobaltous chloride, apocytochrome P450 accumulated predominantly in mito-RER complexes. These data suggest that cytochrome P450 synthesis requires structural interaction of mitochondria and RER.     

Comparison of components of the testis interstitium with testosterone secretion in hamster, rat, and guinea pig testes perfused in vitro

Components of the testis and cytoplasmic organelles in Leydig cells were quantified with morphometric techniques in hamster, rat, and guinea pig. Testosterone secretory capacity per gram of testis and per Leydig cell in response to luteinizing hormone (LH) (100 ng/ml) stimulation was determined in these three species from testes perfused in vitro. Numerous correlations were measured among structures, and between structures and testosterone secretion, to provide structural evidence of intratesticular control of Leydig cell function. Testosterone secretion per gm testis and per Leydig cell was significantly different in the three species: highest in the guinea pig, intermediate in the rat, and lowest in the hamster. The volume of seminiferous tubules per gm testis was negatively correlated, and the volumes of interstitium, Leydig cells, and lymphatic space per gm testis were positively correlated with testosterone secretion. No correlations were observed between volumes of blood vessels, elongated spindleshaped cells, or macrophages per gm testes and testosterone secretion. The average volume of a Leydig cell and the volume and surface area of smooth endoplasmic reticulum (SER) and peroxisomes per Leydig cell were positively correlated, and the volume of lysosomes and surface area of inner mitochondrial membrane per Leydig cell were negatively correlated with testosterone secretion. No correlations were observed between volume and surface area of rough endoplasmic reticulum (RER), Golgi apparatus, and lipid, and volume of ribosomes, cytoplasmic matrix, and the nucleus with testosterone secretion per Leydig cell. These results suggest that Leydig cell size is more important than number of Leydig cells in explaining the difference in testosterone-secreting capacity among the three species, and that this increase in average volume of a Leydig cell is associated specifically with increased volume and surface area of SER and peroxisomes. An important unresolved question is what is the role of peroxisomes in Leydig cell steroidogenesis.     

Stereological analysis of hepatic fine structure in the Fischer 344 rat. Influence of sublobular location and animal age

Stereological analysis of hepatic fine structure in Fischer 344 male rats at 1, 6, 10, 16, 20, 25, and 30 mo of age revealed differences in the amounts and distributions of hepatocellular organelles as a function of sublobular location or animal age. Between 1 and 16 mo of age, both the centrolobular and periportal hepatocytes increased in volume by 65 and 35%, respectively. Subsequently, the cell volumes declined until the hepatocytes of 30-mo-old rats approached the size of those found in the youngest animals. Regardless of animal age, the centrolobular cells were consistently larger than the corresponding periportal hepatocytes. The cytoplasmic and ground substance compartments reflected similar changes in their volumes, although there was no significant alteration in the nuclear volume. The volumes of the mitochondrial and microbody compartments increased and decreased concomitant with the changes in average hepatocyte size. Both lobular zones in the 30-mo-old rats contained significantly smaller relative volumes of mitochondria than similar parenchyma in 16-mo-old animals. The volume density of the dense bodies (lysosomes) increased markedly in both lobular zones between 1 and 30 mo of age, confirming reports of an age-dependent increase in this organelle. The surface area of the endoplasmic reticulum in the centrolobular and periportal hepatocytes reached its maximum level in the 10-mo-old rats and subsequently declined to amounts which approximated those measured in the 1-mo-old animals. This age-related loss of intracellular membrane is attributable to a significant reduction in the surface area of the smooth-surfaced endoplasmic reticulum (SER) in animals beyond 16 mo of age. The amount of rough-surfaced endoplasmic reticulum (RER) in the periportal parenchymal cells was unaffected by aging, but the centrolobular hepatocytes of 30-mo-old animals contained 90% more RER than similar cells in the youngest rats. The centrolobular parenchyma contained more SER and the portal zones more RER throughout the age span studied. These quantitative data suggest that (a) certain hepatic fine structural parameters undergo marked changes as a function of animal age, (b) there exists a gradient in hepatocellular fine structure across the entire liver lobule, and (c) there are remarkable similarities in hepatocyte ultrastructure between very young and senescent animals, including cell size and the amount of SER.     

Phenobarbital-induced alterations in the activities of the transport and hydrolytic components of the glucose-6-phosphatase system in smooth and rough subfractions of the rat hepatic endoplasmic reticulum

We have examined the influence of the phenobarbital-induced proliferation of the hepatic endoplasmic reticulum (ER) on the activities of the components of the glucose-6-phosphatase system, i.e., the enzyme, the glucose-6-P translocase (T1), and the phosphate translocase (T2). Young male rats were injected ip twice daily for 4 days with 4 mg/100 g body wt of phenobarbital (PB) or an equivalent volume of saline solution. On the fifth day, the rats were killed and smooth (SER) and rough (RER) fractions of the ER were isolated from liver homogenates. Kinetic constants for glucose-6-P hydrolysis by the system and enzyme were determined and used to calculate the kinetic constants for glucose-6-P transport. T2 activity was approximated by assaying the pyrophosphatase activity at pH 6.0 in intact microsomes. Three times more SER protein was recovered from livers of PB-treated rats. PB-treatment did not alter total liver enzyme activity, but total liver T1 activity was decreased to 59% of the control value. Maximal specific activities of the system, enzyme and T1 were all reduced by PB treatment to 44% of control values in the RER and to 68% of control values in the SER. PB treatment reduced the apparent activity of T2 in RER and SER to 35 and 49% of the respective control values. In the SER from both groups of rats, T1 activity or apparent T2 activity divided by enzyme activity was about 55% of the corresponding ratio in the RER. Our analysis of these data suggests that the lower activities of T1 and T2 in the smooth ER are the results of suppression by some intrinsic component localized in the smooth membrane. Accordingly, the reduction in total liver T1 activity and, therefore, system activity in PB-treated rats reflects the redistribution of the glucose-6-P translocase from the RER to the more abundant SER membrane where it is less active. The possibility is discussed that a higher cholesterol content within the SER membrane is responsible for the lower transport activities.     

The Ultrastructure of Circulating Hemolymph Cells of the Marine Snail Cerithidea californica (Gastropoda: Prosobranchiata)

Two morphologically distinct blood cell-types, the granulocyte and hyalinocyte, are found in the hemolymph circulation of the marine prosobranch Cerithidea californica. Granulocytes, measuring 12.7 µ (9.0–15.0 µ) in diameter, possess well-defined ectoplasmic and endoplasmic regions of the cytoplasm, granules of moderate to heavy electron density, tubular rough endoplasmic reticulum (RER), short vesicles of smooth endoplasmic reticulum (SER), and a large cytoplasm to nucleus ratio. Two morphological variants of this cell-type are distinguished depending upon the presence or absence of dense granules or RER. Hyalinocytes, measuring 5.3 µ (4.0–8.0 µ) in diameter, are distinguished from gran ulocytes by possessing a smaller cytoplasm to nucleus ratio and a general lack of dense cytoplasmic granules and SER.     

A morphological study of rat liver cells after the administration of phenobarbital and ziksorin]

Male Wistar rats were inducted with phenobarbital and ziksorin. The inducing effect has been shown by hepatocyte hypertrophy involving the cytoplasm and nuclei. After phenobarbital injection cytoplasmic hypertrophy was due to redistribution of the plastic material in favour of the smooth-surface endoplasmic reticulum (SER). This redistribution occurred with the decrease of the energy forming and external synthetic functions of hepatocytes. After ziksorin injection SER hyperplasia was combined with proportional hyperplasia of the whole cytoplasmic organelles of the liver cells. This points to more optimal response of hepatocytes after ziksorin induction as compared with phenobarbital. Therefore, ziksorin can be recommended for clinical practice if it is necessary to stimulate processes of reparative regeneration in the liver.     

The Characterization of Tubulin in CNS Membrane Fractions

Abstract— Rough endoplasmic reticulum (RER), smooth endoplasmic reticulum (SER), and a plasma membrane (PM) fraction enriched in synaptic membranes were isolated from rat forebrain. The proteins in these membrane fractions were analyzed by two-dimensional gel electrophoresis (2DGE) in the isoelectric range of 5.1 to 6.0 by a modification of the O'Farrell procedure. Proteins were detected by Coomassie Brilliant Blue staining of the electrophoretograms. The results of these analyses were compared with 2DGE analysis of cytosol proteins, with particular attention given to tubulin subunits and actin. The RER contained one major protein (53K 5.4) in the β-tubulin region with a molecular weight of 53,000 and an isoelectric point of 5.4. The SER contained at least two major proteins in the β-tubulin region; one with a migration identical to 53K 5.4 and other proteins with slightly higher apparent molecular weights and more acidic isoelectric points (54K, 5.4 to 5.3), identical to cytoplasmic β-tubulin. The PM fraction also contained multiple overlapping proteins (54K, 5.4 to 5.3) in the β-tubulin area and a trace amount of the 53K 5.4 protein. The proteins in the β-tubulin region were removed from the 2DGE electrophoretogram and digested by Staphylococcus aureus V8 protease, and the peptides separated on one-dimensional polyacrylamide gels. The peptide patterns of 53K 5.4 protein from RER and SER were almost identical and differed significantly from the cytoplasmic β-tubulin pattern; however, the peptide maps of the PM and SER β-tubulin region were identical to the cytoplasmic β-tubulin. The 2DGE analysis of RER did not contain proteins in the region of cytoplasmic α-tubulin. SER and PM contained proteins in the α-tubulin region with a similar, but not identical, peptide analysis to cytoplasmic α-tubulin. Significant amounts of actin were detected in 2DGE analysis of SER and PM, and the peptide analysis of the actin was identical to the cytoplasmic actin analysis. The RER fraction contained only trace amounts of actin. The cytosol and all membrane fractions contained a protein (68K 5.6) found among microtubule-associated proteins, as judged by molecular weight and isoelectric point. Several proteins present in all membrane fractions (61K 5.1 and 58K 5.1) bound to concanavalin A agarose.     

COTTON EMBRYOGENESIS: THE EARLY DEVELOPMENT OF THE FREE NUCLEAR ENDOSPERM

An electron microscope study was made of the central cell and the development of the free nuclear endosperm surrounding the zygote and synergids during the first three days after pollination. The cytoplasm of the central cell, concentrated around the partially-fused polar nuclei, contains many ribosomes, mitochondria and large, dense, starch-containing plastids, some dictyosomes and lipid bodies, and long, single cisternae of rough endoplasmic reticulum (RER) that frequently terminate in whorls. Dense, core-containing microbodies are closely associated with the RER. After fertilization the cytoplasm of the 2-and 4-nucleate endosperm shows an increase in number of dictyosomes, and in amount of RER which becomes stacked in arrays of parallel cisternae. Cup-shaped plastids are associated with many long, helical polysomes. Perinuclear aggregates of dense, granular material also appear after fertilization. Granular aggregates and helical polysomes disappear after the first few divisions of the primary endosperm nucleus. During the second and third days of development there is an increase in dictyosome number and RER proliferation, and endosperm nuclei become deeply lobed. Concurrently, there is a sharp decline in the starch and lipid reserves of the central cell and elaborate transfer walls are formed at the micropylar end of the embryo sac and on the outer surface of the degenerating synergid. The transfer walls contain groups of small, membrane-bound vesicles, and are associated with large numbers of mitochondria and with the smooth endoplasmic reticulum.     

Quantitative study of hepatocytes from minipigs and minipig fetuses exposed to ethanol in vivo

The effect of ethanol on hepatocytes from pregnant minipigs and their half-term fetuses was studied with the aid of morphometric methods. In the pregnant minipigs the hepatocytes of the ethanol-treated animals showed a significant increase in the volume density of mitochondria, autophagic vacuoles, Golgi complexes and smooth endoplasmic reticulum, and a significant decrease of glycogen. In the half-term fetuses the hepatocytes of ethanol-exposed animals showed no significant change in the volume density of mitochondria, peroxisomes, autophagic vacuoles, Golgi complexes, smooth endoplasmic reticulum or glycogen, and no significant change in the surface density of granular endoplasmic cisternae. The present investigation indicates that in the maternal hepatocyte certain cytoplasmic components are quantitatively changed by ethanol, whereas the volume and surface densities of identical components in the fetal hepatocyte are unaffected. The significance of these results is discussed.     

Seasonal changes of the Leydig cells of viscacha (Lagostomus maximus maximus). A light and electron microscopy study

The Leydig cells of viscacha (seasonal rodent) show cytoplasmic hypertrophy and regional distribution during the breeding period (summer-autumn). The dominant organelles are smooth endoplasmic reticulum (SER) and mitochondria. A moderately well-developed Golgi, abundant lipid inclusions, dense bodies like lysosomes in different stages, and centrioles are observed. Extensive or focal desmosome and gap-like junctions between neighbouring Leydig cells are present. These cells exhibit an evident hypotrophy and an increase in the number of dense bodies during the gonadal regression in winter (July and August). Cells in different stages of involution are observed in this period. Their nuclei are irregular and heterochromatic. The cytoplasm contains few mitochondria. The vesicular SER is scarse. Irregular and large intercellular spaces with microvilli and amorphous material are present. The junctional complexes are absent. The nuclear and cytoplasmic volume and development of SER and mitochondria increase during the recovery period (spring). The lipid inclusions decrease. Dilatations of the intercellular space with microvilli and limited by focal desmosome-like junctions are observed. In conclusion, the Leydig cells of Lagostomus maximus maximus show deep changes alongside the reproductive cycle. The photoperiod variations, through pineal hypothalamus pituitary axis and the hormone melatonin, are probably responsible for them. Moreover, the fall of serum and tubular testosterone would be one of the factors responsible for gonadal regression.     

Filaments associated with the endoplasmic reticulum in the streaming cytoplasm of Chara corallina

Perfused Chara cells capable of resuming ATP-dependent cytoplasmic streaming in low free Ca++ solutions have been examined by electron microscopy for myosin-like filaments. Filaments 44 nm in diameter and up to 3 micron in length have been found associated with the endoplasmic reticulum that along with mitochondria, microbodies and dictyosomes from the endoplasm becomes immobilised around the sub-cortical actin bundles when ATP is depleted. Such endoplasmic filaments have not been detected in association with mitochondria or microbodies and they have not been found in the stationary cortex. These filaments are extracted from the perfused cell by ATP unless motility-inhibiting levels of cytochalasin B are present. The filaments are not detectable in cells inactivated in solutions containing high (10(-4) M) Ca++ concentrations even when the Ca++ level is subsequently lowered. Consistent with their being required for motility, cytoplasmic streaming cannot be effeiciently reactivated by ATP in such filament-depleted cells. The possibility is discussed that the filaments contain myosin and that the endoplasmic reticulum with which they are associated has a major role in generating and transmitting the motive force for streaming.     

An ultrastructural and morphometric study of pre- and post-hatching satellite cells in lumbar sensory ganglia of Gallus gallus domesticus L

An electron microscopic study of satellite cells in the sensory lumbar ganglia from 12 pre- and post-hatching stages of Gallus gallus domesticus L., between the 5th and 120th d, was undertaken. A combined light and electron microscopic morphometric analysis was made in 10 and 18 d embryos and in 8, 35, 61, and 120 d post-hatching specimens. RER, SER, Golgi complex, mitochondria, free ribosomes, cell expansions, pinocytotic vesicles, subsurface cisternae and adhering, gap, and tight junctions are described from the different stages considered. Although a continuous increase in nuclear and cytoplasmic volumes is observed, there is a tendency towards a decrease in the cytoplasm/nucleus and nerve cell/satellite cell volume ratios.