Biomedical subjects

R Sormunen

Publications and source records attributed to R Sormunen.

48 records · Page 3Linked to original sources

PubMed1992

Low intracellular pH induces redistribution of fodrin and instabilization of lateral walls in MDCK cells.

We have studied the effect of intracellular pH on the establishment and maintenance of the cellular polarity in MDCK cells by utilizing nigericin which causes lowering of the cytoplasmic pH. At pH below 6.5, MDCK cells lost their polarized morphology and became roundish, with an increased apical area and shortened and unstable lateral walls. The lateral wall marker proteins uvomorulin and Na,K-ATPase remained segregated to the lateral walls in the acidified cells, as shown by immunofluorescence microscopy. Fodrin, on the other hand, was released from its normal basolateral residence and was found in the cytoplasm. Actin, which normally co-localizes with fodrin along the basolateral walls, showed a dotty distribution in the cytoplasm of acidified cells, while stress fibers remained intact. Microtubular network appeared flattened, but the Golgi complex retained its apical position. The pH change-induced alterations were readily reversible, as the normal basal-apical polarity (columnar shape, distinct apical and lateral domains with apposing and stiff lateral membranes) was reformed within 10 minutes after restoring the normal pH gradient across the cell membrane. This coincided with the translocation of fodrin from the cytoplasm to the lateral walls. The results show that lowering of intracellular pH leads to temporary segregation of fodrin from the other components of the membrane skeleton assembly, and that association of fodrin with the lateral walls seems to be a prerequisite for their close apposition and for the maintenance of normal basal-axial polarity.

Animals↗

PubMed1992

Different organizational states of fodrin in cultured MDCK cells are induced by treatment with low pH, calmodulin antagonist TFP, and tumor promoter PMA.

We have investigated the molecular mechanisms underlying dynamic organization of the fodrin network by treating the epithelial MDCK cells with various agents affecting intracellular pH, intracellular calcium ion concentration, intracellular calmodulin, and protein kinase C (PKC) activity. Elevation of intracellular calcium level by A23187 or treatment with trifluoperazine (TFP), a calmodulin inhibitor, did not have any drastic effect on the fodrin distribution as judged by immunofluorescence microscopy. A long-term incubation with phorbol-12-myristate-13-acetate (PMA), a protein kinase C activator, in contrast, released fodrin from the lateral walls of the MDCK cells, leading to a diffuse cytoplasmic distribution. TFP, along with PMA, accelerated destabilization of the fodrin skeleton. Treatment with TFP alone rapidly released the cells from the substratum, which, however, could be prevented by PMA. We have previously shown that lowering of intracellular pH (< 6.5) leads to a removal of fodrin from its basolateral residence (Eskelinen et al., 1992) and that this translocation is reversed upon returning normal pH. We now show that the rebuilding of the membrane skeleton can be prevented if TFP is added to the acidified cells. Moreover, in TFP-treated acidified cells, fodrin shows a clusterlike organization similar to that observed in resting lymphocytes. We also noticed that interconversions between these different organizational states of fodrin are independent of the intracellular calcium concentration. Thus manipulation of the intracellular pH and treatment with TFP and PMA reveals different organizational states of the fodrin skeleton. This suggests that fodrin may participate in PMA-, TFP- and pH-sensitive signal transduction pathways.

Acids↗

PubMed1992

Localization, cellular morphology and respiratory capacity of "brown" adipose tissue in newborn reindeer.

1. The localization and cellular morphology of adipose tissue was studied by light, fluorescence and electron microscopy in reindeer between 2 weeks pre partum and 4.5 months post partum during calving, and the subsequent growth period. The respiratory capacity of the adipose tissue was examined in terms of morphometric mitochondrial volume and cytochrome-c oxidase or succinate dehydrogenase activity. 2. Adipose tissue was located at specific anatomical sites in the newborn reindeer (from 0 to 2 days of age). The perirenal-abdominal depot was the largest location (32%) followed by the inter(pre)scapular (18%) and sternal (12%) depots. Internal depot dominated over external or peripheral depots (66-34%). The locations of adipose tissue were largely similar in foetal, newborn and young reindeer. 3. The adipose tissue of the newborn reindeer had all the typical cell morphological characteristics of brown adipose tissue: abundant mitochondria, multilocular fat, high vascularization and a dense spot-like sympathetic innervation between the adipocytes. In the young reindeer, however, it resembled white adipose tissue, being almost totally unilocular with few mitochondria. 4. There was a significant correlation between morphometric mitochondrial volume and cytochrome-c oxidase activity (r = 0.848) in the adipose tissue. Mitochondrial volume, cytochrome-c oxidase and succinate dehydrogenase activity were highest after birth and decreased to almost an undetectable level during the first month. A parallel decrease occurred in the amount of brown adipose tissue from birth (1-2%) to the age of about one month (0.3%). 5. It is concluded that the distinct cell morphological features and high respiratory capacity of the adipose tissue indicate the presence of brown adipose tissue at specific anatomical locations in newborn reindeer. A marked progression towards the characteristics of white adipose tissue then takes place at the same locations during the first month. The results suggest the fundamental significance of brown adipose tissue for non-shivering thermogenesis in newborn reindeer.

Adipose Tissue, Brown↗

PubMed1991

Immunohistochemical localization of 17 beta-hydroxysteroid dehydrogenase in the human endometrium during the menstrual cycle.

Immunoaffinity-purified polyclonal anti-rabbit antibody against human placental 17 beta-hydroxysteroid dehydrogenase (17HSD) was used to localize 17HSD in frozen sections of 21 human endometrial tissue specimens, taken at different stages of the menstrual cycle, and in the human placenta. The presence and distribution of estrogen and progesterone receptors were also analyzed in endometrial specimens using commercial immunohistochemical techniques. In addition, 17HSD was localized by immunoelectron microscopy in the endometrium and the placenta. In the endometrium, immunostaining of 17HSD appeared in the cytoplasm of surface epithelial and gland cells during the early and midluteal phase. During the late luteal phase, it gradually disappeared. No immunostaining was observed in the endometrium during the follicular phase of the menstrual cycle. The changes in staining intensity of 17HSD were associated with changes in the concentration of serum progesterone as judged by radioimmunoassay. An apparent inverse correlation between 17HSD expression and the concentrations of estrogen and progesterone receptors was observed. These results strongly support the concept that progesterone induces an increase in the amount of 17HSD, in the glandular and surface epithelial cells of the human endometrium. In the human term placenta, 17HSD immunostaining was detected exclusively in the cytoplasm of syncytiotrophoblasts. In immunoelectron microscopic studies of the endometrium and placenta, 17HSD staining was observed in the cytoplasm and it was associated with cytoplasmic membranes unrelated to the endoplasmic reticulum.

17-Hydroxysteroid Dehydrogenases↗

PubMed1991

Effect of prolonged experimental distension on the function and ultrastructure of the canine urinary bladder.

Urinary bladder distension was induced for 10 hours in dogs and micturition tests were made before over-stretching, immediately afterwards and 5 days later. Compliance and residual urine had increased and maximum pressure during voiding had decreased immediately after retention, but returned to normal after 5 days. Biopses for light microscopic and electronmicroscopic investigation taken from the anterior wall of the bladder on the fifth day showed submucosal haemorrhages and some necrosis. The consistent finding on electron microscopy was Schwann cell oedema, which was seen within the cytoplasm and between the cytoplasmic processes of the Schwann cells. Axonal degeneration was also a common finding. These anatomical changes, although found at the moment of functional recovery, may be linked to impaired conductivity of the nerves in the bladder wall, at least partly, causing its impaired function. Recovery of function occurs quite rapidly in healthy bladders.

Animals↗

PubMed1991

Coated endosomal vesicles: sorting and recycling compartment for transferrin in BHK cells.

We have investigated receptor-mediated endocytosis of transferrin (Tf) in baby hamster kidney (BHK) cells, using fluorescence and electron microscopy, and by carrying out colocalization experiments with clathrin antibodies and a fluorescently tagged glycolipid. Early during internalization, Tf was found in small vesicles (100-150 nm in diameter) located at the cell periphery. The ligand remained associated with such vesicles when the latter concentrated towards the cell center, before ending up in the juxtanuclear area. Throughout this vesicular trafficking pathway, clathrin colocalized with Tf. We conclude that Tf is processed intracellularly via small coated endosomal vesicles (CEV) and is not delivered into large tubular endosomes (CURL; compartment for uncoupling receptors and ligands), typical for ligand trafficking to lysosomes. By determining the kinetics of Tf internalization and by comparing the flow of Tf to that of a fluorescent glycolipid, it can also be concluded that CEVs display sorting and recycling properties, implying that small vesicles can be shed from or fuse with CEVs. Acidic pH does not prevent the formation of CEVs, but their intracellular movement, towards the cell center, is impeded.

4-Chloro-7-nitrobenzofurazan↗

PubMed1990

Reduced glucose-6-phosphorylase and NADPH generating enzyme activities associated with glibenclamide induced hypoglycemia and hypoinsulinemia in genetically obese mice.

Addition of phenobarbital, an inducer of the liver mixed function oxidase system, to sulphonylurea regimen improves insulin sensitivity and intracellular glucose handling in patients with non-insulin dependent diabetes mellitus. The inducer also activates liver NADPH synthesis and its availability for mono-oxygenase reactions. In this study we further evaluated the mutual relationship between glucose and drug metabolism and the effect of sulphonylurea therapy by using genetically obese female mice. The mice were treated with glibenclamide, phenobarbital or both. Glibenclamide reduced blood glucose and plasma insulin levels indicating improved insulin sensitivity in the mice. Total glucose phosphorylating, delivering and NADPH generating enzyme activities were reduced together with decreased microsomal protein content and the amount of smooth endoplasmic reticulum in the liver. Phenobarbital had an opposite effect: the drug induced liver drug metabolism and increased hepatic glucose phosphorylating and NADPH generating enzyme activities. Treatment with glibenclamide seems to reduce serum immunoreactive insulin levels, microsomal enzyme function and NADPH generating enzyme activities in genetically obese mice.

Animals↗

PubMed1989

Malotilate prevents accumulation of type III pN-collagen, type IV collagen, and laminin in carbon tetrachloride-induced pulmonary fibrosis in rats.

Orally administered malotilate was studied as a protective antifibrotic agent with respect to experimentally induced pulmonary fibrosis in rats using immunohistochemical methods. Specific antibodies raised in rabbits against the aminoterminal propeptide of human type III procollagen and against two basement membrane proteins, the 7S domain of human type IV collagen and the P1 fragment of human laminin, were used for the immunohistochemical analysis, and the result was confirmed by morphometry. Intraperitoneally injected carbon tetrachloride significantly increased the volume densities of reticulin fibers, type III pN-collagen, type IV collagen, and laminin, whereas treatment with malotilate completely normalized these. Binding of the antibodies to rat antigens was also demonstrated by immunoelectron microscopy in which the collagen fibers with a typical periodic pattern were labeled positively with rabbit antitype III procollagen, whereas the amorphous basement membrane material reacted positively with rabbit antitype IV collagen and antilaminin, indicating good, specific cross-reactivity between these antibodies and the rat antigens. It is concluded that malotilate prevents the accumulation of type III pN-collagen and two basement membrane proteins, type IV collagen and laminin, in experimental pulmonary fibrosis, and can potentially be developed to provide a useful drug for preventing pulmonary fibrosis in humans.

Animals↗

PubMed1989

Immunoelectron microscopic localization of laminin, type IV collagen, and type III pN-collagen in reticular fibers of human lymph nodes.

We studied the ultrastructural distribution of laminin, type IV collagen, and the amino terminal pro-peptide of type III collagen (type III pN-collagen) in normal human lymph nodes. After fixation with freshly prepared 4% paraformaldehyde mixed with 0.1% glutaraldehyde, cryoultramicrotomy proved to preserve the antigenicity of these proteins better than embedding in Lowicryl K4M. Sections were treated with rabbit antibodies against the 7S domain of human type IV collagen, the fragment P1 of human laminin, and the amino terminal pro-peptide of human type III pro-collagen, followed by anti-rabbit IgG conjugated to 10-nm colloidal gold. Laminin and type IV collagen were seen in the basement membrane structures of the blood vessels and in the walls of sinuses. The amorphous material between the collagenous fibers in locations corresponding to reticular fibers also contained laminin and type IV collagen. The amino terminal pro-peptide of type III pro-collagen was present in the collagenous fibers in reticular fibers and in the walls of blood vessels and sinuses. Therefore, a significant number of the type III collagen molecules in these fibers must have retained their amino terminal pro-peptide. These results indicate that the basement membrane proteins laminin and type IV collagen are genuine components of reticular fibers, as suggested earlier by immunohistochemical studies at the light microscopic level.

Basement Membrane↗

PubMed1989

Cathepsin B immunoreactive neurons in rat brain. A combined light and electron microscopic study.

The regional distribution and cellular localization of the lysosomal proteinase cathepsin B was studied by use of monospecific antiserum. The application of the peroxidase-antiperoxidase technique at the light microscopic level revealed cathepsin B immunoreactive neurons in many brain areas. A strong immunoreaction was found in pyramidal cells of the cortex, large neurocytes of the septal region, some hippocampal neurons and magnocellular nerve cells of the hypothalamus. Immunogold labeling on ultrathin cryosections of rat neocortex revealed the enzyme protein to be associated with lysosomes.

Animals↗

PubMed1988

Bronchiolo-alveolitis with pulmonary basal lamina injury in a rheumatoid patient during gold treatment.

A 47-year-old housewife presented with nonproductive cough, progressive breathlessness and intermittent fever during gold treatment, originally prescribed for seropositive polyarthritis, which later fulfilled the criteria for systemic lupus erythematosus (SLE). An open lung biopsy showed abundant interstitial edema with mononuclear inflammatory cells and some eosinophils, and slight bronchiolitis. The picture was nonspecific but suggestive of hypersensitivity pneumonitis. Electron microscopy revealed splitting and local disappearance of the basal laminae of the alveolar capillaries, venules and alveolar epithelium. This injury was confirmed by immunohistochemical staining for type IV collagen and laminin, the major components of basal laminae. In most macrophages there was lysosomal electron dense granular material, i.e. aurosomes, which gave the spectrum of gold in electron microprobe analysis. After the gold treatment was stopped the pulmonary symptoms gradually decreased during several months and no permanent lung disease remained. Whereas the pulmonary manifestation could have been due to her underlying disease we discuss in this study the possibility of its being gold induced.

Alveolitis, Extrinsic Allergic↗

PubMed1987

Effect of distension on function and nervous ultrastructure in the canine urinary bladder.

Canine bladders were distended for 4 h at 100 cm H2O to study the effects of distension on bladder function and structure. A micturition study was performed before overstretching, immediately after distension and 5 days after it. Bladder function was impaired immediately after distension, compliance and residual urine were increased and the maximum pressure during voiding decreased. The function returned to normal after 5 days. Overstretching caused diffuse or focal submucosal haemorrhages, only rarely fibrosis or necrosis of bladder wall. Electron microscopic changes of the bladder peripheral nerves were slight, the consistent finding being oedema in areas of outer mesoaxons and between cytoplasmic processes of Schwann cells. This change was sometimes accompanied by a rupture of the surrounding basement membrane. Axonal lysis was observed in one case. It is concluded that these anatomical changes, although found at the moment of functional recovery, may be linked to impaired conductivity of nerves in the bladder wall causing, at least partly, its impaired function. This may further decrease bladder instability and after urinary retention cause prolonged micturition problems. Functional recovery occurs, however, quite rapidly in healthy bladders.

Animals↗