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PubMed2005

Yeast ATP-binding cassette transporters: cellular cleaning pumps.

Numerous ATP-binding cassette (ABC) proteins have been implicated in multidrug resistance, and some are also intimately connected to genetic diseases. For example, mammalian ABC proteins such as P-glycoproteins or multidrug resistance-associated proteins are associated with multidrug resistance phenomena (MDR), thus hampering anticancer therapy. Likewise, homologues in bacteria, fungi, or parasites are tightly associated with multidrug and antibiotic resistance. Several orthologues of mammalian MDR genes operate in the unicellular eukaryote Saccharomyces cerevisiae. Their functions have been linked to stress response, cellular detoxification, and drug resistance. This chapter discusses those yeast ABC transporters implicated in pleiotropic drug resistance and cellular detoxification. We describe strategies for their overexpression, biochemical purification, functional analysis, and a reconstitution in phospholipid vesicles, all of which are instrumental to better understanding their mechanisms of action and perhaps their physiological function.

ATP-Binding Cassette Transporters↗
PubMed2001

Purification, characterization, immunolocalization and structural analysis of the abundant cytoplasmic beta-amylase from Calystegia sepium (hedge bindweed) rhizomes.

An abundant catalytically active beta-amylase (EC 3.2.1.2) was isolated from resting rhizomes of hedge bindweed (Calystegia sepium). Biochemical analysis of the purified protein, molecular modeling, and cloning of the corresponding gene indicated that this enzyme resembles previously characterized plant beta-amylases with regard to its amino-acid sequence, molecular structure and catalytic activities. Immunolocalization demonstrated that the beta-amylase is exclusively located in the cytoplasm. It is suggested that the hedge bindweed rhizome beta-amylase is a cytoplasmic vegetative storage protein.

Amino Acid Sequence↗
PubMedDate not supplied

Electron microscopic evidence of non-A, non-B hepatitis markers and virus-like particles in immunocompromised humans.

Characteristic pathological alterations of the liver in chimpanzees inoculated with non-A, non-B hepatitis sera have been described, but no corresponding findings have been reported in humans. Electron microscopic studies of the liver biopsy specimens of two homosexual patients with acquired immune deficiency syndrome, one without hepatitis (Patient 1) and one with chronic active hepatitis in remission (Patient 2), revealed the cytoplasmic tubular structures which are characteristic of chimpanzee non-A, non-B hepatitis. A cluster of 23 nm double-shelled particles was also seen in the cytoplasm of a hepatocyte in patient 1 who had received a blood transfusion 8 days before the biopsy. These particles were smaller than the Dane particles, Epstein-Barr virus, cytomegalovirus or herpes simplex virus, and different from hepatitis A virus particles; the antibodies to all of which are found in high concentration in acquired immune deficiency syndrome patients. These observations may reflect the morphologic findings for non-A, non-B hepatitis infection in humans.

Acquired Immunodeficiency Syndrome↗
PubMed1980

Association between intermediate-sized filaments and mitochondria in rat Leydig cells.

The cytoplasmic filamentous structures of the testis Leydig cells have been studied in the rat after double fixation with glutaraldehyde and osmium-potassium ferrocyanide. A good preservation of the cytoplasmic filaments was obtained and their abundance in the rat Leydig cells become apparent. Judging from their diameter (8-11 nm) and general morphology most of the filaments observed belong to the intermediate-sized type. The close association between filament bundles and mitochondria is described. Some images show cross-bridges between individual filaments and mitochondria and their attachment to the mitochondria outer membrane.

Animals↗
PubMed2005

Genetics and adaptation in structured populations: sex ratio evolution in Silene vulgaris.

Theoretical models suggest that population structure can interact with frequency dependent selection to affect fitness in such a way that adaptation is dependent not only on the genotype of an individual and the genotypes with which it co-occurs within populations (demes), but also the distribution of genotypes among populations. A canonical example is the evolution of altruistic behavior, where the costs and benefits of cooperation depend on the local frequency of other altruists, and can vary from one population to another. Here we review research on sex ratio evolution that we have conducted over the past several years on the gynodioecious herb Silene vulgaris in which we combine studies of negative frequency dependent fitness on female phenotypes with studies of the population structure of cytoplasmic genes affecting sex expression. This is presented as a contrast to a hypothetical example of selection on similar genotypes and phenotypes, but in the absence of population structure. Sex ratio evolution in Silene vulgaris provides one of the clearest examples of how selection occurs at multiple levels and how population structure, per se, can influence adaptive evolution.

Adaptation, Biological↗
PubMed2006

Structural changes in human cytomegalovirus cytoplasmic assembly sites in the absence of UL97 kinase activity.

Studies of human cytomegalovirus (HCMV) UL97 kinase deletion mutant (DeltaUL97) indicated a multi-step role for this kinase in early and late phases of the viral life cycle, namely, in DNA replication, capsid maturation and nuclear egress. Here, we addressed its possible involvement in cytoplasmic steps of HCMV assembly. Using the DeltaUL97 and the UL97 kinase inhibitor NGIC-I, we demonstrate that the absence of UL97 kinase activity results in a modified subcellular distribution of the viral structural protein assembly sites, from compact structures impacting upon the nucleus to diffuse perinuclear structures punctuated by large vacuoles. Infection by either wild type or DeltaUL97 viruses induced a profound reorganization of wheat germ agglutinin (WGA)-positive Golgi-related structures. Importantly, the viral-induced Golgi remodeling along with the reorganization of the nuclear architecture was substantially altered in the absence of UL97 kinase activity. These findings suggest that UL97 kinase activity might contribute to organization of the viral cytoplasmic assembly sites.

Cell Membrane↗
PubMedDate not supplied

Pathology of rotavirus infection in suckling mice: A study by conventional histology, immunofluorescence, ultrathin sections, and scanning electron microscopy.

Pathologic changes induced in the small intestine of suckling mice by rotavirus infection were studied by conventional histology, immunofluorescence, scanning electron microscopy, and electron microscopy of ultrathin sections. Infection could be detected within 24 hours in a few mice, but after 2 days it was well established. Swollen, often vacuolated infected cells were found on the sides and tips of villi from which they rapidly became detached; microvilli showed variable irregularity. Immature enterocytes from crypts replaced lost infected cells. By the tenth day very few infected cells could still be found. Both tubular structures and spherical particles occurred in the infected cells. Only tubular structures were found in nuclei.

Animals↗
PubMed1988

Tubuloreticular structures in a papular eruption associated with human immunodeficiency virus disease.

A widespread pruritic papular eruption associated with human immunodeficiency virus has been previously described. Electron microscopic study of lesional skin from a patient who presented with such an eruption showed cytoplasmic tubuloreticular structures in every venular capillary endothelial cell that was studied. The significance of this finding and the possible cause of these structures are discussed. This new finding strongly suggests that this dermatosis is a dermatosis related to acquired immunodeficiency syndrome (AIDS) and may be helpful in confirming the diagnosis of the AIDS-related complex or AIDS in future patients presenting with this dermatosis.

AIDS-Related Complex↗
PubMed1997

Morphological and cytochemical findings in 150 cases of T-lineage acute lymphoblastic leukaemia in adults. German Multicentre ALL Study Group (GMALL).

We evaluated the morphological findings in 150 consecutive cases of T-lineage acute lymphocytic leukaemia (T-ALL). Cytochemistry including PAS staining and acid phosphatase reaction proved of limited value for the diagnosis of ALL. The diagnosis of acute leukaemia was easy to establish in most instances. However, in a few cases the leukaemic cells were difficult to recognize as blasts. The nuclei of such cells showed condensed chromatin and nucleoli were lacking, and was encountered particularly in thymic ALL. Basophilic cytoplasm combined with prominent vacuolization suggestive of mature B-ALL (ALL-L3 type), was observed in 16 cases. Other features, however, such as cell size, polymorphism, chromatin structure, sparse cytoplasm or focal positivity for acid phosphatase, excluded a diagnosis of ALL-L3 in those cases. Distinction from hybrid leukaemia was difficult in 20 cases, because of a low percentage of peroxidase-positive blasts or other features which suggested a separate myeloid leukaemia component. In nine of these the hybrid nature of the leukaemia was considered as certain on the basis of morphology. Seven cases had been diagnosed as biphenotypic with coexpression of myeloid and lymphoid markers by immunological techniques. In conclusion, our analysis showed some serious pitfalls of the morphology in T-ALL, clearly indicating the need for immunological analysis of the leukaemic cells. However, morphology remains an essential component of the diagnostic repertoire, especially when the marrow is difficult to aspirate and in cases with equivocal immunological findings. Furthermore, recognition of a separate myeloid leukaemic component in addition to the lymphatic one requires a morphological analysis.

Adult↗
PubMedDate not supplied

Pseudo-intracellular collagen tangles in human spinal ganglia.

A new structure was found in the spinal ganglia of 6 out of 215 human autopsy cases with various disorders. It was composed of ballooned cells fully packed with fibrillar structures showing the same staining properties as collagen. Ultrastructurally the fibrillar structures were bundles of collagen fibres with a striation of about 70nm periodicity, and they were enclosed by the cell membrane invaginated in a very complex manner into the cytoplasm. This structure, which we named 'pseudo-intracellular collagen tangle', was considered to result from a disturbance in the releasing process of collagen fibre from fibroblasts. The aetiology of the structure is unknown, but it might represent one of regressive or senile changes in human spinal ganglia.

Aged↗
PubMed2004

Preassociation of nonactivated STAT3 molecules demonstrated in living cells using bioluminescence resonance energy transfer: a new model of STAT activation?

Signal transducers and activators of transcription (STATs) are crucial molecules in cytokine signaling. In the conventional model of STAT activation, STAT molecules are recruited from a latent pool of cytoplasmic monomers to the activated cytokine receptor. After binding to the receptor, they get tyrosine-phosphorylated, dissociate from the receptor, and translocate to the nucleus as activation-induced dimers. Recently, several publications questioned this model of STAT activation and showed the existence of preassociated STAT molecules before activation. We were able to demonstrate the existence of these preassociated STAT3 molecules in living mammalian cells using bioluminescence resonance energy transfer. Our results support the new hypothesis that STAT molecules exist in the cytoplasm as dimers or multimers and point to an activation-induced change in STAT3 conformation. Therefore, we propose a new model of STAT activation and discuss a hypothetical structure of "cytoplasmic" STAT dimers as opposed to the known "activation-induced" dimer.

Animals↗
PubMed1991

Occurrence and ultrastructural characterization of bacteria in association with and isolated from Azolla caroliniana.

The occurrence and ultrastructure of bacteria in leaf cavities of symbiotic Azolla caroliniana were examined by transmission electron microscopy. Bacteria were observed in all leaf cavities of Azolla cultures. Five ultrastructurally distinct types of bacteria were observed in each individual leaf cavity. Features used to characterize the bacteria included morphology, cell wall structure, and cytoplasmic organization. At least one gram-positive and as many as four gram-negative types of bacteria reside in leaf cavities of A. caroliniana. The morphological and ultrastructural characteristics of the gram-positive bacterium suggest that it is an Arthrobacter sp. The gram-negative bacteria could not be cultured; therefore, they have not been classified further. Bacterial cell shape and cell wall structure were similar in leaf cavities of different ages, but cell size and cytoplasmic composition varied. The relative contributions of each bacterial type to the total community within individual leaves was determined. Ultrastructural characteristics of bacterial isolates cultured from A. caroliniana in a free-living state were also examined.

Bacteria↗
PubMed1990

Phylogenetic and biochemical evidence for a secondary structure model of a small cytoplasmic RNA from Bacilli.

Small cytoplasmic RNA (scRNA; 271 nucleotides) is an abundant, stable RNA identified in the Gram-positive eubacterium Bacillus subtilis. Several findings suggest an important role of scRNA in protein biosynthesis: it shares structural and biochemical features with the Escherichia coli 4.5S RNA (114 nucleotides), a molecule known to be involved in this process, and it can complement the essential function of 4.5S RNA in vivo. The common apical hairpin motif of scRNA and 4.5S RNA also exists in eukaryotic 7SL RNA, the RNA component of the signal recognition particle. To elucidate the higher-order structure of scRNA, we have combined a phylogenetic approach with a biochemical one. The sequence of scRNA from a thermophilic relative of B. subtilis, Bacillus stearothermophilus, was determined and compared with the B. subtilis scRNA. In addition, the solution structure of B. stearothermophilus scRNA was probed with single- and double-strand-specific nucleases. Both types of analysis support a secondary structure model for scRNA that strongly resembles 4.5S RNA and respective parts of 7SL RNA. The results provide further evidence for the suggestion of a functional relationship between these RNAs.

Bacillus subtilis↗
PubMed1996

Locomotion of neutrophil fragments occurs by graded radial extension.

The only kinematic description of cell locomotion that relates the dynamics of actin filaments to whole cell movement is the graded radial extension (GRE) model for fish keratocytes, which glide without changing their shapes or sizes. To test whether the GRE model is applicable to other cell types, we analyzed the detailed shape changes during locomotion of heat-induced motile fragments of human polymorphonuclear leukocytes (PMNs). These fragments, called cytokineplasts, were loaded uniformly with a fluorescent cytoplasm-staining dye and their motility and shape changes were analyzed by fluorescence-video microscopy and digital image processing. Two-dimensional (2-D) analysis showed that cytokineplasts only changed their shapes and sizes slightly and apparently maintained their roughly circular shapes, whereas fluorescence-intensity analysis revealed distinct changes in their cytoplasmic thickness profiles. Furthermore, small structures on the cytoplasmic margins behaved as predicted by the GRE model, which therefore is probably also applicable to the parental PMNs, which show complex shape changes. This is the first indication that the GRE model operates in non-fish-keratocyte cells and may, therefore, be a universal model of cell locomotion.

Cell Movement↗
PubMed1982

Malignant rhabdoid tumor of the kidney. Histopathology, ultrastructure and comments on differential diagnosis.

Clinical and histopathological features of two cases of malignant rhabdoid tumor of the kidney are presented. One of these cases was also studied by electron microscopy. Histologically, both tumors consisted of an admixture of undifferentiated polygonal or elongated cells and cells with abundant eosinophilic cytoplasm frequently containing hyaline globular structures. Ultrastructurally, these cytoplasmic inclusions were composed of large masses of actin-size and intermediate-size filaments. The poor prognosis of this type of tumor is emphasized and histological criteria for differential diagnosis from other malignant renal tumors of childhood and adolescence are discussed.

Diagnosis, Differential↗