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PubMedDate not supplied

[Change in the structural organization of Mycobacterium rubrum cells upon the action of ethidium bromide].

The action of ethidium bromide on Mycobacterium rubrum cells was studied. The culture growth was found to depend on ethidium bromide (EB) concentration in the medium. The reaction of EB with nucleoid DNA was shown to be specific and changes in the nucleoid structure were detected. Low EB doses (ca. 2 micrograms/ml) caused DNA despiralization in many cells. The process was reversible, which accounted for the elevated ability of reactivation at low EB doses. A higher EB dose (ca. 5-10 micrograms/ml and more) made the nucleoid structure coarser and denser in most cells and the nucleoid broke down to small fragments. As a result, due to the pool of enzymes present in the cells prior to EB addition, secondary changes developed. They involved all the cellular structures as well as the metabolism of lipids, polyphosphates, and glycogen. As a rule, these changes were incompatible with the cell viability.

DNA, Bacterial↗
PubMed2002

Internal shearing within the hearing organ evoked by basilar membrane motion.

The vibration of the hearing organ that occurs during sound stimulation is based on mechanical interactions between different cellular structures inside the organ of Corti. The exact nature of these interactions is unclear and subject to debate. In this study, dynamic structural changes were produced by stepwise alterations of scala tympani pressure in an in vitro preparation of the guinea pig temporal bone. Confocal images were acquired at each level of pressure. In this way, the motion of several structures could be observed simultaneously with high resolution in a nearly intact system. Images were analyzed using a novel wavelet-based optical flow estimation algorithm. Under these conditions, the reticular lamina moved as a stiff plate with a center of rotation in the region of the inner hair cells. Despite being enclosed in several types of supporting cells, the inner hair cells, together with the adjacent inner pillar cells, moved in a manner signifying high compliance. The outer hair cells displayed radial motion indicative of cellular bending. Together, these results show that shearing motion occurs between several parts of the organ, and that structural relationships within the organ change dynamically during displacement of the basilar membrane.

Animals↗
PubMed1997

The phosphatidyl-myo-inositol anchor of the lipoarabinomannans from Mycobacterium bovis bacillus Calmette Guérin. Heterogeneity, structure, and role in the regulation of cytokine secretion.

Lipoarabinomannans are major mycobacterial antigens capable of modulating the host immune response; however, the molecular basis underlying the diversity of their immunological properties remain an open question. In this study a new extraction and purification approach was successfully applied to isolate ManLAMs (lipoarabinomannans with mannosyl extensions) from bacillus Calmette Guérin leading to the obtention of two types of ManLAMs namely parietal and cellular. Structurally, they were found to differ by the percentage of mannooligosaccharide caps, 76 and 48%, respectively, and also, thanks to a new analytical method, by the structure of the phosphatidyl-myo-inositol anchor lipid moiety. A novel fatty acid in the mycobacterium genus assigned to a 12-O-(methoxypropanoyl)-12-hydroxystearic acid was the only fatty acid esterifying C-1 of the glycerol residue of the parietal ManLAMs, while the phosphatidyl unit of the cellular ManLAMs showed a large heterogeneity due to a combination of palmitic and tuberculostearic acid. Finally, parietal and cellular ManLAMs were found to differentially affect interleukin-8 and tumor necrosis factor-alpha secretion from human dendritic cells. We show that parietal but not cellular ManLAMs were able to stimulate tumor necrosis factor-alpha secretion from dendritic cells. From these studies we propose that the 1-[12-O-(methoxypropanoyl)-12-hydroxystearoyl]-sn-glycerol part is the major cytokine-regulating component of the ManLAMs. It seems likely that modification of the ManLAM lipid part, which may occur in hostile environments, could regulate macrophagic mycobacterial survival by altering cytokine stimulation.

Antigens, Bacterial↗
PubMed1991

Structure of the yeast endoplasmic reticulum: localization of ER proteins using immunofluorescence and immunoelectron microscopy.

The endoplasmic reticulum (ER) and other secretory compartments of Saccharomyces cerevisiae have biochemical functions that closely parallel those described in higher eukaryotic cells, yet the morphology of the yeast organelles is quite distinct. In order to associate ER functions with the corresponding cellular structures, we localized several proteins, each of which is expected to be associated with the ER on the basis of enzymatic activity, biological function, or oligosaccharide content. These marker proteins were visualized by immunofluorescence or immunoelectron microscopy, allowing definition of the S. cerevisiae ER structure, both in intact cells and at the ultrastructural level. Each marker protein was most abundant within the membranes that envelop the nucleus and several were also found in extensions of the ER that frequently juxtapose the plasma membrane. Double-labeling experiments were entirely consistent with the idea that the marker proteins reside within the same compartment. This analysis has permitted, for the first time, a detailed characterization of the ER morphology as yeast cells proceed through their growth and division cycles.

Cell Cycle↗
PubMed1979

A stereological ultrastructural study of stimulated peritoneal macrophages in the germ-free mouse.

Peritoneal macrophage ultrastructure was analysed stereologically in germ-free mice given a single intraperitoneal injection of sterile, pyrogen-free saline. Thus the stimulant was non-particulate, non-antigenic and inorganic, and effects of immune reactions were minimal. Macrophages were recovered 1, 6, 24 and 72 h after stimulation. A sequence of structural alterations is reported which may be fundamental to macrophage activation. The plasma membrane and nuclear envelope increased in area within only 1 h of saline injection. During the next 5 h loss of plasma membrane, probably by pinocytosis, caused cellular "rounding" and clear-cut alteration in surface configuration. At the same time lysosome-like granules enlarged but decreased in number. By 24 h most cellular structures and compartments (including the plasma membrane) were enlarged. Morphological evidence of nuclear activation accompanied a rather modest enlargement of the nucleus at this stage. The RER hypertrophied last and must, therefore, be judged sufficient in resident macrophages to support the initial growth response which results after stimulation. Thus hypertrophy was observed eventually in every structure examined. Even the minimally activated macrophages resident in the peritoneum of germ-free mice respond readily to stimulation.

Animals↗
PubMed1981

[Cellular effects of anesthetics].

Anesthetic drugs have multiple effects on cellular structures and functions. Among these are membrane perturbations, cell division, DNA synthesis, disruption of microtubules and microfilaments, phagocytosis and cell locomotion. Some of these effects are reversible, and directly correlated to concentration and length of exposure; other, however, seriously compromise cellular integrity and vital functions. A review of the literature and current work are presented.

Anesthetics↗
PubMedDate not supplied

[Influence] of enzymatic treatment on Junin virus--Vero cells interaction].

The chemical nature of cellular structures involved in the attachment of Junin virus (wild type XJC13 and host range mutant Cl 67) to Vero cells was investigated. Enzyme treatment of cells before virus infection indicated that whereas lipids are not directly involved in virus attachment, cellular proteins play a significant role in early interaction with JV. Moreover aromatic residues, leucine and basic amino acid seem to actively participate in this interaction with different affinity for the assayed strains.

Animals↗
PubMed1999

Structural and functional consequences of antigenic modulation of red blood cells with methoxypoly(ethylene glycol).

We previously showed that the covalent modification of the red blood cell (RBC) surface with methoxypoly(ethylene glycol) [mPEG; MW approximately 5 kD] could significantly attenuate the immunologic recognition of surface antigens. However, to make these antigenically silent RBC a clinically viable option, the mPEG-modified RBC must maintain normal cellular structure and functions. To this end, mPEG-derivatization was found to have no significant detrimental effects on RBC structure or function at concentrations that effectively blocked antigenic recognition of a variety of RBC antigens. Importantly, RBC lysis, morphology, and hemoglobin oxidation state were unaffected by mPEG-modification. Furthermore, as shown by functional studies of Band 3, a major site of modification, PEG-binding does not affect protein function, as evidenced by normal SO4- flux. Similarly, Na+ and K+ homeostasis were unaffected. The functional aspects of the mPEG-modified RBC were also maintained, as evidenced by normal oxygen binding and cellular deformability. Perhaps most importantly, mPEG-derivatized mouse RBC showed normal in vivo survival ( approximately 50 days) with no sensitization after repeated transfusions. These data further support the hypothesis that the covalent attachment of nonimmunogenic materials (eg, mPEG) to intact RBC may have significant application in transfusion medicine, especially for the chronically transfused and/or allosensitized patient.

Animals↗
PubMed1999

A novel family of Ig-like receptors for HLA class I molecules that modulate function of lymphoid and myeloid cells.

We review what is presently known about structure, cellular distribution, biochemical characteristics, and function of a new family of human cell-surface receptors referred to as immunoglobulin-like transcripts (ILTs), leukocyte Ig-like receptors (LIRs), or monocyte/macrophage Ig-like receptors (MIRs). These receptors are genetically, structurally, and functionally related to a group of natural killer (NK) cell receptors for HLA class I molecules known as killer cell Ig-like receptors (KIRs). Distinct ILT/LIR/MIR isotypes are differentially expressed on lymphocytes, monocytes, macrophages, dendritic cells, and granulocytes; at least some of them recognize HLA class I molecules. Whereas some isotypes either inhibit or induce cell activation, others may be secreted as soluble receptors. ILT/LIR/MIR receptors may allow all immune cells to monitor class I expression on other cells and to respond in its absence, just as NK cells do. In addition, they may contribute to homeostasis by establishing activation thresholds that can be overcome only by relevant triggering stimuli and not by bystander cells.

Antibodies, Monoclonal↗
PubMed2000

Cellular turnover and extracellular matrix remodeling in female reproductive tissues: functions of metalloproteinases and their inhibitors.

Female reproductive tissues possess a unique ability to accommodate a remarkable amount of cell turnover and extracellular matrix (ECM) remodeling following puberty. Cellular structures within ovary, uterus, and mammary tissue not only change cyclically in response to ovarian hormones but also undergo differentiation during pregnancy, and eventually revert to that resembling the pre-pregnant stage. Cell proliferation, apoptosis, invasion, and differentiation are integral cellular processes that are precisely regulated in reproductive tissues, but become dysregulated in pathologies such as cancer. Explicit reorganization of ECM and basement membranes is also critical to preserve the form and function of these tissues. Here we review the evidence that coordinated spatiotemporal expression patterns of matrix metalloproteinase (MMP) genes and their tissue inhibitors (TIMPs) are important in cell and ECM turnover of the ovary, uterus, and mammary tissues. We discuss how perturbation in these gene families may impact the biology of these reproductive tissues and the factors implicated in the control of MMP and TIMP gene expression. The observed trends in MMP and TIMP expression involved in ovarian and mammary carcinomas are also presented.

Animals↗
PubMed1996

Structural and functional changes in diabetic glomerulopathy.

Diabetic nephropathy is characterized by glomerular basement membrane thickening and mesangial expansion. Immunohistochemical studies of diabetic kidneys showed an increased collagen type IV synthesis and deposition in the mesangial matrix, while the glomerular heparan sulfate proteoglycan content was decreased. In nodular glomerulosclerosis massive deposition of collagens III and VI appears, possibly indicating irreversibility of the pathological process. These structural changes seem to be the underlying cause for the alterations of renal functions like persistent albuminuria and proteinura. In a recent study significant glomerular infiltration by macrophages at all stages of glomerulosclerosis was observed. The pathogenesis of the multitude of cellular, structural, and functional abnormalities in diabetic nephropathy is likely to be multifactorial, involving chronic hyperglycemia as well as genetic determinants. In vitro studies with cultured glomerular cells have indicated that hyperglycemia induces transforming growth factor beta, a matrix-producing cytokine. The hyperglycemia-induced cytokine production may involve protein kinase C activation and/or the formation of advanced glucosylation end products. The elucidation of the pathogenesis of diabetic nephropathy may suggest new ways for therapeutic interventions.

Animals↗
PubMed1999

[Oxidation mechanisms and anti-oxidation in HIV infected patients--effect on disease progression].

Recently it has been proposed that reactive oxygen species (ROS) are involved in pathogenesis of many human diseases. An elevated level of these molecules causes oxidative stress and is toxic for living cells. Oxidative stress is the reason of many damages of cellular structures, as result of free radical reactions with proteins, lipids, nucleic acids etc. In most of human diseases overproduction of ROS is characteristic for early stage of disease. Some of infectious factors, e.g. viruses can cause oxidative stress by disturbance of cellular antioxidants system or induction of oxidative reactions. There is some evidence of presence of oxidative stress in early stage of HIV infection (glutathione and other antioxidants loss in serum and decreased activity of antioxidant enzymes). All these metabolic disturbances may be involved in AIDS pathogenesis, for example through incorrect induction of lymphocyte apoptosis, tumours related to AIDS and high rate of HIV mutation. This suggests a possible, important role of oxidative stress in AIDS pathogenesis and that administration of antioxidant drugs, by HIV infected patients, may offer protection against mechanisms responsible for lymphocyte apoptosis and AIDS related carcinogenesis.

Acquired Immunodeficiency Syndrome↗
PubMed2001

Structures involved in production, secretion and injection of the venom produced by the caterpillar Lonomia obliqua (Lepidoptera, Saturniidae).

The number of accidents caused by injection of the venom of Lonomia obliqua caterpillars in Southern Brazil has increased in the last years. Even though this kind of envenomation has an important social and medical impact, nothing is known about the cellular structures responsible for the production and secretion of this venom. Here we identify and analyse morphological structures possibly responsible for the production and secretion of the active principles of the venom, as well as the histological relationship of these structures with the urticating spines of L. obliqua. Detailed microscopic observations showed that: (a) L. obliqua has a complex tegument, with several cuticular specializations, (b) there are no pores along the tegument neither in the spines and (c) the spines bear a hollow canal--where the venom is deposited--and an area that can be easily broken when touched, releasing the venom. Histological and histochemical techniques revealed that: (a) there is no single gland cell that produces the venom, (b) a secretory epithelium, composed of cells containing vesicles that increase in size and number as they reach the apical region, underlies the tegument and the spines and is responsible for secretion of the venomous substances and (c) the venom is deposited in the subcuticular space and at the tips of the spines.

Animals↗
PubMed1988

The arthropod gap junction and pseudo-gap junction: isolation and preliminary biochemical analysis.

The hepatopancreas of the crayfish, Procambarus clarkii, contains an unusual abundance of gap junctions, suggesting that this tissue might provide an ideal source from which to isolate the arthropod-type of gap junction. A membrane fraction obtained by subcellular fractionation of this organ contained smooth septate junctions, zonulae adhaerentes, gap junctions and pentalaminar membrane structures (pseudo-gap junctions) as determined by electron microscopy. A further enrichment of plasma membranes and gap junctions was achieved by the use of linear sucrose gradients and extraction with 5 mM NaOH. The enrichment of gap junctions correlated with the enrichment of a 31 Kd protein band on polyacrylamide gels. Extraction with greater than or equal to 20 mM NaOH or greater than or equal to 0.5% (w/v) Sarkosyl NL97 resulted in the disruption and/or solubilization of gap junctions. Negative staining revealed a uniform population of 9.6 nm diameter subunits within the gap junctions with an apparent sixfold symmetry. Using antisera to the major gap junctional protein of rat liver (32 Kd) and to the lens membrane protein (MP 26), we failed to detect any homologous antigenic components in the arthropod material by immunoblotting-enriched gap junction fractions or by immunofluorescence on tissue sections. The enrichment of another membrane structure (pseudo-gap junctions), closely resembling a gap junction, correlated with the enrichment of two protein bands, 17 and 16 Kd, on polyacrylamide gels. These structures appeared to have originated from intracellular myelin-like figures in phagolysosomal structures. They could be distinguished from gap junctions on the basis of their thickness, detergent-alkali insolubility, and lack of association with other plasma membrane structures, such as the septate junction. Pseudo-gap junctions may be related to a class of pentalaminar contacts among membranes involved in intracellular fusion in many eukaryotic cell types. We conclude that pseudo-gap junctions and gap junctions are different cellular structures, and that gap junctions from this arthropod tissue are uniquely different from mammalian gap junctions of rat liver in their detergent-alkali solubility, equilibrium density on sucrose gradients, and protein content (antigenic properties).

Animals↗
PubMed1979

Structural aspects of the permeability of the microvascular endothelium.

This article reviews recent findings and current views concerning the structural aspects of microvascular permeability. The vascular endothelium is considered as a simple squamous epithelium which has acquired a remarkably high permeability to water and water soluble solutes (including macromolecules) through a characteristic process of differentiation of its cells. In terms of cellular structures, this differentiation involves an unusually large population of plasmalemmal vesicles. The evidence so far obtained indicates that these vesicles function as (1) mass-carriers of fluid and solutes across the endothelium and as (2) generators of transendothelial channels by concomitant fusion (followed by fission) with both domains (luminal and tissular) of the plasmalemma. The endothelial fenestrae of visceral capillaries are initially transendothelial channels subsequently collapsed to minimal length. The intercellular junctions of the endothelium are not detectably permeable to tracers of diam. greater than or equal to 18--20 A in capillaries, but are focally open to probes of 50--60 A diam. in postcapillary (pericytic) venules. A correlation is attempted between transendothelial channels (and fenestrae) and the pore systems postulated by the pore theory of capillary permeability. The channels appear to function as either small or large pores depending on the porosity of their associated diaphragms and on the size of local strictures along their pathway. Two main components are recognized in the analysis of capillary permeability: 1) a basic component comparable to that of other simple epithelia and involving transport across the plasmalemma and probably along the intercellular junctions (for molecules of diam. greater than or equal to 10 A); and a differentiated component which involves plasmalemmal vesicles and their derivatives (transendothelial channels and fenestrae). The postulated pores of the capillary endothelium are part of this differentiated component. The special situation found in postcapillary venules (focally open junctions) seems to be related to the role played by these vessels in inflammatory reactions.

Animals↗
PubMed1980

High resolution optical microscopy of animal tissues by the use of sub-micrometer thick sections and a new stain.

The introduction of 1 micron-thick sections from plastic embedded material represents a great technical improvement for the study of tissues under the optical microscope. However, even sections of this thickness appear too thick when observed with oil immersion objectives of high numerical aperture. The extremely shallow depth of field of these lenses allows them to differentiate several focal planes within a one micron thick section. This in turn results in ghost images being formed from out of focus structures, a problem particularly vexing when photomicrography is attempted. To circumvent this difficulty, we reduced the thickness of the sections down to an optimum of 0.4 micron. These thinner sections do require a very energetic stain to give enough contrast to the cellular structures; Stevenel Blue, a stain recently adapted for plastic sections [del Cerro et al., Microsc. Acta 83, (2), 117--121 (1980)] proved to be the most suitable for this purpose of several stains tested. In summary, submicrometer thick sections stained with Stevenel Blue allow to reach the limits of visibility permitted by the best available objectives and effectively merge the realm of optical microscopy with that of low power electron microscopy.

Animals↗
PubMed1990

Occurrence and developmental consequences of aberrant cellular organization in meiotically mature human oocytes after exogenous ovarian hyperstimulation.

The extent to which fertilization failure in in vitro inseminated human oocytes obtained from hyperstimulated ovaries was associated with alterations in cellular structure and cytoplasmic organization was examined by a combination of DIC, fluorescence, time-lapse video, and transmission electron microscopy. Detailed analysis of meiotically mature preovulatory (uninseminated) oocytes, and of oocytes that failed to fertilize in vitro, indicated that between 10% and 15% of grossly normal-appearing MII-stage oocytes displayed one of the following cellular perturbations: 1) a subtle change in organelle distribution, 2) a small region(s) of intracellular cytolysis, 3) a massive aggregation of SER tubules, 4) an accumulation of vesicles presumed to be of SER origin, 5) a change in the structural organization of the cortical cytoplasm and overlying plasma membrane, 6) a sudden and rapid internalization of perivitelline fluid by means of an apparently aberrant process of endocytosis, and 7) a premature and partial exocytosis of cortical granules. The description of these disorders is discussed with respect to the developmental consequences for the oocyte.

Cell Degranulation↗
PubMed1994

CMV-induced class II antigen expression in various rat organs.

Cytomegalovirus (CMV) is thought to trigger acute or chronic allograft rejection by inducing the expression of MHC class II antigens in the graft. This induction may be mediated by gamma-interferon or directly by CMV. In this study, we have investigated which structures in the rat kidney, liver, and heart are responsive to CMV-induced class II expression in vivo. Rats were infected with rat CMV, the organs were harvested during the acute phase of infection, and the virus was demonstrated by culture from each organ. Direct CMV antigen detection was performed on frozen sections to demonstrate the detailed localization of CMV in the organs. In the kidney, CMV antigens were found in the vascular endothelium, in tubular cells, and scattered in the glomeruli. In the liver, the vascular structures and parenchyma contained CMV antigens. In the heart, CMV antigens were seen only in the capillary endothelium. Class II antigen expression was demonstrated by a monoclonal antibody and immunoperoxidase techniques. The induction of class II molecules was recorded in exactly the same cellular structures as those in which CMV antigens were detected.

Animals↗