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M Bergeron

Publications and source records attributed to M Bergeron.

At least 73 records · Page 4Linked to original sources
PubMed1987

Segmental variations in the organization of the endoplasmic reticulum of the rat nephron. A stereomicroscopic study.

The spatial organization of endoplasmic reticulum (ER) was examined in all segments of rat nephron. Tissues were fixed with glutaraldehyde, impregnated "en bloc" with osmium tetroxide, prepared for and examined by standard (80-100 kV) and high voltage (1 mEV) transmission electron microscopy. In all proximal tubule cells, ER forms a continuous and extensive network of canaliculi and abundant fenestrated saccules which surround mitochondria and cytoplasmic bodies; the cage-like structure of the fenestrated saccules was most evident around the spherical mitochondria of the S3 segment. In the cells of the distal straight and convoluted tubules, the network consists mostly of canaliculi with rare non-fenestrated saccules. The ER network of canaliculi is particularly rich in intercalated cells, in contrast with its rudimentary appearance in the adjacent principal cells of the collecting tubule. In fact, in these cells there are few isolated ER cisternae and they are rarely impregnated. The nuclear envelope is well impregnated in most cells throughout the various segments. Segmental variations in ER organization and its relative abundance are most likely related to the well, established functional heterogeneity of the nephron segments. Moreover, the extensive and unique organization among mitochondria, ER and the basolateral membrane suggests that these three organelles function as a unit which is related to active electrolyte transport. In addition, because of its transepithelial organization, ER may well constitute a transcellular pathway for molecules.

Animals↗
PubMed1987

Polymorphic organization of the endoplasmic reticulum of the Malpighian tubule. Evidence for a transcellular route.

Isosmotic fluid absorption carried out by many mammalian epithelia appears to be similar to the isosmotic secretion of insect epithelia such as the Malpighian tubules, which are responsible for urine formation and osmoregulation. We have studied by electron microscopy (80 kV) the three-dimensional characteristics of organelles in the Malpighian tubules of Rhodnius prolixus using thick sections (0.3-0.5 microns) and uranyl and lead impregnation. The ER presents a different organization in the upper (distal) and lower (proximal) segments of the Malpighian tubule. In distal secretory segment, the ER forms a network made of chains of vesicles having irregular shapes (ca. 0.06 micron in diameter) connected to each other by canaliculi while in the lower absorptive segment, the ER is made of parallel saccules arranged in stacks or whorls in the central region of the cytoplasm. In both segments, the ER network extends throughout the cytoplasm from the basolateral infoldings to the apex between the many mitochondria present in these two areas. A unique feature of these cells, revealed by thick sections, is the presence in each microvillus of either a mitochondrion or an ER canaliculus in continuity with the ER network. The ER does not seem to have any specific association with mitochondria or other organelles. As in the mammalian nephron, this ER organization is most likely related to specific segmental functions and adds support to its potential role as a transcellular epithelial route.

Animals↗
PubMed1986

Approaches to prevention of asbestos-induced lung disease using polyethylene glycol (PEG)-conjugated catalase.

Asbestos-associated damage to cells of the respiratory tract in vitro can be prevented by the simultaneous addition of scavengers of active oxygen species to cultures. To determine if administration of scavenger enzymes to animals and humans is a plausible approach to the prevention of asbestos-induced lung disease, osmotic pumps were filled with various concentrations of PEG-coupled catalase and implanted subcutaneously into Fischer 344 rats over a 28-day period. At 3, 14, and 28 days after implantation of the pumps, the animals were evaluated for levels of catalase in serum and lung. In addition, lung tissue and lavage fluids were examined at 28 days for biochemical and morphologic indications of cell injury, inflammation, and fibrotic lung disease. At all time points examined, the administration of PEG-catalase caused a dosage-dependent increase in serum levels of catalase. The levels of lung catalase were evaluated at 28 days but not at earlier time periods. In comparison to control rats, the amounts of enzymes (lactic dehydrogenase, alkaline phosphatase), protein, and cells in lavage fluids from treated animals were unaltered. Moreover, the lungs showed no evidence of inflammation or fibrotic disease as determined by differential cell counts in lavage and measurement of hydroxyproline. These studies suggest that administration of PEG-catalase does not cause injury or other alterations in lung tissue and can be pursued as a feasible approach to prevention of asbestosis.

Animals↗
PubMed1985

Osmium impregnation of the endoplasmic reticulum correlates with the functional status of prostatic secretory cells.

The ultrastructure of prostatic secretory cells was studied with the osmium impregnation technique in order to determine if the ER reactivity, or its absence, and its three-dimensional organization correspond to specific functions possibly hormono-dependent. Thick sections (0.3 micron) of rat ventral prostate were made after a five-day impregnation with osmium tetroxide and examined by standard transmission electron microscopy at 80 kV. Studies were performed in normal adult rats, between the 3rd and 26th day following castration and in castrated rats treated with 5-alpha-dihydrotestosterone. In normal rats the impregnation technique delineated three secretory cell types (dark, greyish and clear), representing various degrees of reactivity in ER cisternae; however, despite this quantitative variation, they had similar morphological characteristics. In a longitudinal section, the ER network appeared to be made of saccules running parallel along the length of the cell and forming whorl-like patterns around the nucleus. Comparison of sections taken at various angles suggests that the ER network is made of concentric parallel saccules extending from the base to the apex of the cell and encircling the nucleus and the Golgi apparatus like a large multilayered cylinder. Whereas in dark cells the Golgi apparatus contained mostly clear vesicles, it was always heavily impregnated in clear cells. Noteworthy, osmium deposits were rarely observed on the nuclear envelope of secretory cells but were always present in basal cells. After castration, secretory cells became progressively cubic and the most conspicuous cytoplasmic change was observed in association with the ER. The Golgi apparatus decreased markedly in volume and became heavily stained with metallic osmium.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1985

Segmental heterogeneity of enzymatic response during compensatory renal growth.

The activities of DNA polymerase alpha and key enzymes of gluconeogenesis and glycolysis were measured in different segments of the rat nephron at various times (up to 96 hrs) following a unilateral nephrectomy (UNx). Tubule fragments were obtained after collagenase treatment followed by centrifugation on a Percoll gradient. The DNA polymerase alpha activity in control rats showed moderate and similar values in different segmental extracts as well as in the whole kidney extract (1700-1800 mumumole [3H] dAMP/mg DNA). In UNx rats, activity in proximal tubules (PT) measured at 24, 48, 72 and 96 hrs after nephrectomy represented an increase of 60%, 200%, 420% and 370% respectively over control values. Distal tubule fragments (DT) showed only minor increases. The results demonstrate that the proximal tubule accounts for most of the compensatory renal growth (CRG) in the remaining kidney. The gluconeogenic and glycolytic enzymes were confined to the PT and those of glycolysis to the DT fragments. Following UNx, the specific activities of these enzymes were not modified in the remaining kidney; however, the overall activity of gluconeogenesis was increased as a result of the cell hyperplasia occurring in the PT. Our work also illustrates that biochemical studies of CRG on the whole organ may provide misleading information due to the presence of heterogenous cell populations in the mammalian kidney and to their uneven response in CRG.

Animals↗
PubMed1983

Three-dimensional characteristics of the endoplasmic reticulum in the columnar cells of the rat small intestine: an electron microscopy study in thick section.

The endoplasmic reticulum (ER) of the columnar cells of the rat jejunum was studied with a specific block-staining technique and standard transmission electron microscopy. A new three-dimensional model, based on the analysis of stereo pair photographs, is proposed; this model suggests that the endoplasmic reticulum may constitute a transcellular route. Thick sections (0.5-1 micron) of columnar cells were made after a 5-day impregnation with osmium tetroxide and were examined by standard transmission electron microscopy at 80-100 kV. The evolution of the ER during the cellular ascent of cells from the crypt to the top of the villus is toward a greater complexity. At the base of the crypt of Lieberkühn, no definite organization is noted, and most often only the nuclear envelope and canalicular elements are stained. The endoplasmic reticulum of the mature columnar cells forms a continuous network of canaliculi and fenestrated saccules; it extends from the apex, below the microvilli, to the lateral and basal plasma membranes, and sends many projections to the nuclear envelope. In the basal part of the cell, below the nucleus, the ER consists mainly of tubular canaliculi, whereas mostly saccules are observed in the supranuclear part. The canaliculi have a diameter of 40-60 nm. Fenestrated saccules appear to form a continuous tubular structure surrounding mitochondria; the saccules have a thickness of 25-40 nm and possess irregular perforations of 35-60 nm. Finally, in some cells, the endoplasmic reticulum seems to show functional differences as reflected by the absence of reaction in cells adjacent to well-stained cells in the same part of the villus; thus the osmium impregnation technique appears to be a valid tool for studying the ER organization.

Animals↗
PubMed1983

Morphological study of cell organelles during development. I - The nuclear sac and the endoplasmic reticulum on the rat nephron.

The maturation of the endoplasmic reticulum (ER) of rat kidney tubule cells was studied with an osmium impregnation technique. Thick sections (0.3-0.6 micron) of kidney tissue were made after a five-day impregnation with osmium tetroxide and examined by standard transmission electron microscopy at 80-100 kV. Studies were performed on rat foetuses from 18-21 days of gestation, on newborns, and on 2-20 day old animals. At the undifferentiated stage, only a small percentage of the tubule cells were impregnated; in these, the perinuclear sac was stained and a few nuclear pores were already seen. Rudimentary, but thick canalicular projections seemed to originate from the perinuclear sac and become more extensive with maturity. Flattened saccules appeared later and fenestrations were seen in proximal tubule cells only when they seemed to have reached their functional specialization. In some cells, only the Golgi apparatus was stained. In the distal tubule cells, there was also progressive formation of a network consisting first of canaliculi and later of saccules which were rarely fenestrated. The osmium impregnation technique appears to be useful as an index of the ER organization development.

Animals↗
PubMed1983

Morphological study of cell organelles during development II-The mitochondria of the renal and intestinal epithelium.

The ontogeny of the chondriome was studied in the developing kidney of fetuses and newborn rats and compared to its maturation in jejunum cells of adult rats. The tissues were immersed in a double lead and copper citrate solution which stains mitochondria selectively. Thick sections (0.3-0.5 micron) were observed with a standard transmission electron microscope (80-100 kV). Mitochondria have in developing cells a shape different from those in mature cells and seem to increase in number and volume during development. In the undifferentiated stages of both jejunum and nephron, the mitochondria are small, spherical and scattered throughout the cytoplasm with no particular orientation. As jejunal cells migrate towards the villus tip, the mitochondria orient themselves in the apical-basal direction; those of the proximal nephron become parallel to the lateral cell membranes. The morphological communications found in adult renal cells are much less prominent in the jejunum. With maturation, the close association between membranes, mitochondria and the endoplasmic reticulum takes place in both epithelia. Our studies suggest that the mitochondrial mass is increased by a continuous process of addition of sub-units and that the chondriome development appears to be more analogous to the growth, differentiation and modification of the endoplasmic reticulum system. The chondriome also seems to reach a certain stage of development before the onset of the organ function.

Animals↗
PubMed1983

Assessment of the effect of IgG antibodies to ragweed and rye grass on the IgE antibody disc RAST.

The results of the present study indicate that the IgE disc RAST is susceptible to interference by IgG antibodies directed against the same allergens on the disc. Thus removal of IgG antibodies with protein A-Sepharose caused an enhancement of as much as 66% in IgE RAST binding for six sera from treated ragweed and rye grass allergic patients. Furthermore, such interference was shown to vary for a given patient over a period of two years. The use of an alternate support media, matrex-beads linked with excess of ragweed allergen, eliminated the interference effect. The relationship between IgG antibody levels and the interference effect as well as the clinical significance of these findings is discussed.

Absorption↗
PubMed1983

Adenosine deaminase in renal ontogeny and compensatory hypertrophy in the rat.

Recent studies have indicated a possible link between cell proliferation and adenosine deaminase (ADase); the characteristics and specific activity of ADase in the kidney of neonatal rats and unilaterally nephrectomized rats were therefore determined. The enzyme was found to have a molecular weight of 35,000. Two variants with electrophoretic points at pH 4 x 53 (ADase I) and 4 x 63 (ADase II) were resolved by analytical isoelectric focusing. Enzyme activity was high in newborn rats (250 milliunits/mg protein) but declined to about 150 milliunits/mg protein from 20 days old to maturity. Enzyme activity and its biochemical characteristics were not altered in compensatory renal hypertrophy (CRH).

Adenosine Deaminase↗
PubMed1982

Topology of membrane exposure in the renal cortex slice. Studies of glutathione and maltose cleavage.

We measured glycine release from ([2-3H]glycine)-labelled GSH and glucose formation from maltose incubated with rat kidney whole cortex homogenate, thin cortex slices or collagenase-treated tubule fragments. Liberation of glycine was inhibited (74-83%) by serine borate (20 mM), indicating a gamma-glutamyltransferase-dependent hydrolysis of GSH. In whole cortex homogenate, the GSH cleavage activity was 17.4 +/- 0.6 nmol GSH degraded/mg protein per min (mean +/- S.D.); cleavage activity by intact slices was 3.5 +/- 0.7 (P less than 0.001 relative to whole cortex homogenate) and in tubule fragments 9.4 +/- 0.8 (P less than 0.001). Homogenizing the tissue preparation increased cleavage rate in slices about 4-fold (12.4 +/- 2.9; P less than 0.005 relative to intact slice) but did not change the rate in tubule fragments (9.8 +/- 0.5). Maltose cleavage activity in whole cortex homogenate was 512 +/- 22 nmol glucose formed/mg protein per min, in slices 162 +/- 12, and in tubules 884 +/- 48. These findings imply that substrate in the incubation medium has a limited access to the luminal membrane of cortex slices but not of tubule fragments. They further imply that basolateral membrane is preferentially exposed in the slice preparation.

Animals↗
PubMed1982

Neonatal iminoglycinuria: evidence that the prolinuria originates in selective deficiency of transport activity in the proximal nephron.

We investigated the process of neonatal hyperprolinuria in dog and rat. Plasma proline varied only 2-fold in the puppy whereas prolinuria increased up to 12-food from birth to the 10th day declining thereafter to reach adult values (less than 0.1 mumole/mg creatine) by the third wk. Stop-flow analysis in puppies (less than 17 days old, n = 3) and one adult dog revealed that backflux of proline in distal nephron is not the source of neonatal hyperprolinuria. Prolinuria occurs in the Long-Evans rat pup during the first postnatal wk. We measured net uptake of L-proline at low (0.2 mM) and high (5 mM) concentrations by tubule fragments prepared form newborn and adult kidneys. At both concentrations and at initial rates, uptake was similar in newborn and mature tubules; at or near steady-state, tubules of newborn kidney had greater net uptake relative to mature kidney, apparently because efflux is attenuated. A difference in metabolic runout did not explain the difference in proline uptake by newborn kidney. Tubules from pups less than 7 days old did not exclude the competitive inhibitor AIB from interacting with proline uptake at o.2 mM when compared with mature kidney, (p = 0.005). These findings imply that transport of proline on the previously described proline-preferring high-affinity system is deficient in proximal nephron of newborn kidney.

Animals↗