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PubMed1996

Epidermal ultrastructure of the southern right whale calf (Eubalaena australis).

An ultrastructural analysis by transmission and scanning electron microscopy was carried out on normal epidermis of six southern right whale (Eubalaena australis) calves which stranded over a period of several months at Peninsula Valdes, Argentina. This was undertaken to 1) provide the first normal skin ultrastructural data on this highly endangered species which is known to display skin pathology in some instances, and 2) to elucidate further the integumentary specializations which have developed in diving marine mammals. Southern right whale lipokeratinocytes demonstrated parakeratosis and numerous intracellular lipid bodies, keratin and melanosomes, as reported for other cetacean species, but showed several unique ultrastructural features as well. These included a high prevalence of intranuclear inclusion bodies resembling small fragments of cytoplasmic keratin, and close structural relationship between cytoplasmic lipid droplets and the nucleus. The subcellular morphology supported the concept of possible nuclear import of cytoplasmic keratin and lipid metabolites through enlargements of the nuclear pore complex or other disruptions of the nuclear envelope. The light microscopy and scanning electron microscopy also revealed an irregular contour of the lipokeratinocytes which comprised the thick stratum externum, and surface flaking of the outermost cells which were covered by stubby microvillous-like remnants of intercellular junctions. These results thus suggest that the long-tem aquatic evolution of this cetacean species has resulted in a number of integumentary specializations and that investigation of their submicroscopic cytology may help elucidate the general cell biology of nuclear-cytoplasmic interactions.

Animals↗
PubMed1989

Plasmodium falciparum antigens associated with membrane structures in the host erythrocyte cytoplasm.

Hybridomas were made from mice immunized with plasma membranes from erythrocytes infected with Plasmodium falciparum. Among the monoclonal antibodies produced, a series reacted with antigens in the host cell cytoplasm. Immunoelectron microscopy, along with indirect fluorescent antibody double labeling experiments, were used to further localize the antigens to membrane structures (presumably Maurer's clefts) in the erythrocyte cytoplasm. The epitopes thus localized are found on three parasite proteins (20 kDa, 29 kDa, and 45 kDa) and one parasite glycoprotein (45 kDa). They are likely to be part of a transport system for the parasite.

Animals↗
PubMed1975

Electron microscopic examinations of a conjunctival squamous cell carcinoma before and during beta-irradiation.

An electron microscopic study was performed on a conjunctival squamous cell carcinoma in an 82-year-old man. Biopsies were taken before and during beta-irradiation and the morphologic features of nonirradiated tumor cells were compared to those after application of 10,000 rad. There occur striking changes in the nucleus and the cytoplasm after irradiation. The nuclei show hypertrophic and electron-dense nucleoli as well as altered chromatin structures. The cytoplasm of many cells appears destroyed and contains numerous vacuole-like structures, as well as swollen mitochondria. It is of interest that numerous normal lymphoid cells were present within the irradiated tumor.

Aged↗
PubMed1991

Ultrastructural changes associated with reversal of chloroquine resistance by verapamil in Plasmodium chabaudi.

Reversal of chloroquine (CQ) resistance by verapamil, a Ca2+ antagonist, has been shown in CQ-resistant human and rodent malaria parasites. Here, we report ultrastructural changes associated with this phenomenon in CQ-resistant Plasmodium chabaudi (AS strain) after infected mice were administered CQ and verapamil. At parasitaemias of 5-7%, CQ at 6 mg/kg caused little morphological effect on CQ-resistant parasites. In contrast, co-administration of CQ and verapamil at 50 mg/kg induced swelling of food vacuoles with clumped pigment at 2.5 h. Morphological changes other than food vacuole enlargement occurred at 21 and 45 h: disappearance of endoplasmic reticulum, formation of myelin structures, focal cytoplasmic vacuolization and coarse clumping of electron-dense material in nuclei. These structural changes appeared to be very similar to those observed in CQ-sensitive P. chabaudi in mice injected with CQ alone or CQ plus verapamil. On the other hand, verapamil at 50 mg/kg alone did not induce any effect on both CQ-sensitive and CQ-resistant P. chabaudi. These results suggest that swelling of the food vacuoles is an initial event associated with reversal of CQ-resistance by verapamil.

Animals↗
PubMed1998

The distribution of SMN protein complex in human fetal tissues and its alteration in spinal muscular atrophy.

Spinal muscular atrophy (SMA) is a common autosomal recessive neuromuscular disorder characterized by degeneration of motor neurons of the spinal cord and muscular atrophy. SMA is caused by alterations to the survival of motor neuron (SMN) gene, the function of which has hitherto been unclear. Here, we present immunoblot analyses showing that normal SMN protein expression undergoes a marked decay in the postnatal period compared with fetal development. Morphological and immunohistochemical analyses of the SMN protein in human fetal tissues showed a general distribution in the cytoplasm, except in muscle cells, where SMN protein was immunolocalized to large cytoplasmic dot-like structures and was tightly associated with membrane-free heavy sedimenting complexes. These cytoplasmic structures were similar in size to gem. The SMN protein was markedly deficient in tissues derived from type I SMA fetuses, including skeletal muscles and, as previously shown, spinal cord. While our data do not help decide whether SMA results from impaired SMN expression in spinal cord, skeletal muscle or both, they suggest a requirement for SMN protein during embryo-fetal development.

Animals↗
PubMed1989

[Electron microscopic studies of fine structure on the oral spirochetes].

Of the strains isolated from periodontitis patients in this laboratory, seven pure cultures with different characteristics were subjected to a scanning electron microscope and transmission electron microscope (negative staining, thin section and freeze-etching method were employed) for the cell morphology investigations. The following results were obtained; 1) Cells were thin, long and twisted to make thme spirals. Some differences were observed in cell length and width, even though in a same isolated strain. 2) It was obvious that the basic cell structure of oral spirochetes consisted of the following seven parts; i.e., outer envelope, axial fibrils, main body, cytoplasm, nucleous structure, ribosomes and fine fibrils. 3) The specific structures, which should be called tubulous and/or ring-like structures, were shown in certain strains. They obviously located at the cell surface of oral spirochetes. 4) Outer envelope, which locates at the most outside layer of the cell, composed with two membranous structures holding one fine granular structures in it, and fold completely the main body and axial fibrils. 5) It was noted that the one end of axial fibrils locating at the space between outer envelope and main body fused with main body resulting in formation of a specific disk-like structure. 6) The surface of the main body was double-layered membranous structures. 7) Nucleous structure, ribosomes, and fine fibrils which were slender than axial fibrils were in the cytoplasm.

Humans↗
PubMed2000

Virus morphogenesis of Helicoverpa armigera nucleopolyhedrovirus in Helicoverpa zea serum-free suspension culture.

Helicoverpa armigera single nucleopolyhedrovirus (HaSNPV) replication in Helicoverpa zea serum-free suspension culture was studied in detail and the sequence of virus morphogenesis was determined by transmission electron microscopy. By 16 h post-infection (p.i.), virus replication was observed in the virogenic stroma by the appearance of nucleocapsids. Polyhedron formation was detected by 24 h p.i. and the polyhedron envelope (PE) was completely formed by 72 h p.i. PE morphogenesis of HaSNPV is significantly different compared to the extensively studied Autograph californica (Ac)MNPV. In AcMNPV-infected cells, fibrillar structures are found in both cytoplasm and nuclei, and the fibrillar structures in nuclei are in close association with maturing polyhedra during PE formation. Fibrillar structures that resemble the AcMNPV fibrillar structures were detected only in the cytoplasm of HaSNPV-infected cells and appeared to interact with calyx precursors there, but their role in PE formation is unclear. However, prominent calyx precursor structures of various shapes and sizes were observed in the nuclei of HaSNPV-infected cells as well, and they appeared to interact with polyhedra during PE formation. Both the calyx precursor structure and the cytoplasmic fibrillar structure were detected only after HaSNPV virion occlusion had started, indicating that they might have a role in formation of PE. Similar calyx precursor structures and cytoplasmic fibrillar structures were observed in both serum-supplemented and serum-free suspension cultures, as well as in HaSNPV-infected larval tissues, indicating that the structures observed are not cell culture artefacts.

Animals↗
PubMedDate not supplied

Alcohol dehydrogenases, aldehyde dehydrogenases, and related enzymes.

Several new structures have recently been determined for dehydrogenases which are involved in alcohol metabolism. These structures give new insight into catalytic properties, structure-function relationships, and evolutionary connections. They also explain the structural basis for known metabolic deviations. Among alcohol dehydrogenases, the first primary structures for human enzyme forms have been reported (the beta 1, gamma 1, and "atypical" beta-chains). These structures explained functional properties and enzymatic differences, showed separate and parallel events of isozyme divergence, and suggested differential gene activations. Similarly, for aldehyde dehydrogenases, the first cytoplasmic isozyme structures have been reported in man and horse. The data showed positions of functionally important residues, and established clear differences between the mitochondrial and cytoplasmic isozymes of aldehyde dehydrogenase. For sorbitol dehydrogenase, the first complete structure which establishes a relationship with other "long" alcohol dehydrogenases in a scheme exhibiting both structural divergence and functional convergence has also been reported. Finally, glucose dehydrogenase has been structurally linked with sorbitol dehydrogenase, extending the scheme and adding further enzymes to the group of "short" alcohol dehydrogenases.

Alcohol Oxidoreductases↗
PubMed1964

"GERMINATION TUBE" GROWTH IN ESCHERICHIA COLI MICROCULTURES.

Hoffman, Heiner (New York University, New York, N.Y.), and Michael E. Frank. "Germination tube" growth in Escherichia coli microcultures. J. Bacteriol. 88:1151-1154. 1964.-Analysis of extensive time-lapse photomicrographic records of Escherichia coli microcultures uncovered two cases in which there occurred aberrant cell growth resembling a germination tube. Although previously observed by a number of investigators in gram-positive bacteria, the present observations appear to constitute the first time-lapse photomicrographic record concerning a gram-negative form. In the first case, with photographs taken at 15-sec intervals, the cell initially exhibited a clublike deformation, and the "germ tube" then issued from the club head. The "tube" had developed into a separate cell by the time the photographic record was concluded. In the second case, with the photographs taken at 1-min intervals over a longer period of time, the "germ tube" cell assumed a plastic dumbbell-like form after separation from its sister. It is suggested that the phenomenon results from a disturbance in cell-wall synthesis, while cytoplasmic growth continues unabated.

Cell Division↗
PubMed1991

Origin of unenveloped capsids in the cytoplasm of cells infected with herpes simplex virus 1.

In cells infected with herpes simplex viruses the capsids acquire an envelope at the nuclear membrane and are usually found in the cytoplasm in structures bound by membranes. Infected cells also accumulate unenveloped capsids alone or juxtaposed to cytoplasmic membranes. The juxtaposed capsids have been variously interpreted as either undergoing terminal deenvelopment resulting from fusion of the envelope with the membrane of the cytoplasmic vesicles or undergoing sequential envelopment and deenvelopment as capsids transit the cytoplasm into the extracellular space. Recent reports have shown that (i) wild-type virus attaches to but does not penetrate cells expressing glycoprotein D (G. Campadelli-Fiume, M. Arsenakis, F. Farabegoli, and B. Roizman, J. Virol. 62:159-167, 1988) and that (ii) a mutation in glycoprotein D enables the mutant virus to productively infect cells expressing the wild-type glycoprotein (G. Campadelli-Fiume, S. Qi, E. Avitabile, L. Foa-Tomasi, R. Brandimarti, and B. Roizman, J. Virol. 64:6070-6079, 1990). If the unenveloped capsids in the cytoplasm result from fusion of the cytoplasmic membranes with the envelopes of viruses transiting the cytoplasm, cells infected with virus carrying the mutation in glycoprotein D should contain many more unenveloped capsids in the cytoplasm inasmuch as there would be little or no restriction in the fusion of the envelope with cytoplasmic membranes. Comparison of thin sections of baby hamster kidney cells infected with wild-type and mutant viruses indicated that this was the case. Moreover, in contrast to the wild-type parent, the mutant virus was not released efficiently from infected cells. The conclusion that the unenveloped capsids are arrested forms of deenveloped capsids is supported by the observation that the unenveloped capsids were unstable in that they exhibited partially extruded DNA.

Animals↗
PubMed1992

Structure and function in rhodopsin. Studies of the interaction between the rhodopsin cytoplasmic domain and transducin.

Structural requirements for the activation of transducin by rhodopsin have been studied by site-specific mutagenesis of bovine rhodopsin. A variety of single amino acid replacements and amino acid insertions and deletions of varying sizes were carried out in the two cytoplasmic loops CD (amino acids 134-151) and EF (amino acids 231-252). Except for deletion mutant delta 137-150, all the mutants bound 11-cis-retinal and displayed normal spectral characteristics. Deletion mutant delta 236-239 in loop EF caused a 50% reduction of transducin activation, whereas deletion mutant delta 244-249 and the larger deletions in loop EF abolished transducin activation. An 8-amino acid deletion in the cytoplasmic loop CD as well as a replacement of 13 amino acids with an unrelated sequence showed no transducin activation. Several single amino acid substitutions also caused significant reduction in transducin activation. The conserved charged pair Glu-134/Arg-135 in the cytoplasmic loop CD was required for transducin activation; its reversal or neutralization abolished transducin activation. Three amino acid replacements in loop EF (S240A, T243V, and K248L) resulted in significant reduction in transducin activation. We conclude that 1) both the cytoplasmic loops CD and EF are required for transducin activation, and 2) effective functional interaction between rhodopsin and transducin involves relatively large peptide sequences in the cytoplasmic loops.

Amino Acid Sequence↗
PubMed2006

Two conformational states in the crystal structure of the Homo sapiens cytoplasmic ribosomal decoding A site.

The decoding A site of the small ribosomal subunit is an RNA molecular switch, which monitors codon-anticodon interactions to guarantee translation fidelity. We have solved the crystal structure of an RNA fragment containing two Homo sapiens cytoplasmic A sites. Each of the two A sites presents a different conformational state. In one state, adenines A1492 and A1493 are fully bulged-out with C1409 forming a wobble-like pair to A1491. In the second state, adenines A1492 and A1493 form non-Watson-Crick pairs with C1409 and G1408, respectively while A1491 bulges out. The first state of the eukaryotic A site is, thus, basically the same as in the bacterial A site with bulging A1492 and A1493. It is the state used for recognition of the codon/anticodon complex. On the contrary, the second state of the H.sapiens cytoplasmic A site is drastically different from any of those observed for the bacterial A site without bulging A1492 and A1493.

Animals↗
PubMed1982

Cytoplasmic microtubule-associated proteins: phosphorylation at novel sites is correlated with their incorporation into assembled microtubules.

We have analyzed the detailed structure and cytoplasmic distribution of cytoplasmic microtubule-associated proteins. The procedure used to identify these proteins, based on preparation of detergent-extracted cytoskeletons, permits separation of fractions containing assembled and unassembled microtubule proteins. We show that two of these proteins, 69 and 80 kd, are closely related to one another and that each protein is present as a set of structurally related polypeptides with differing isoelectric points. In both neuroblastoma and pheochromocytoma cells, several of the isoelectric variants are greatly enriched in the fraction containing assembled microtubule components. Their differential distribution is correlated with phosphorylation at novel sites on the protein. These results support the possibility that covalent modification of a cytoskeletal component may specify its functional state.

Animals↗
PubMed1996

Study of the three-dimensional images of potyvirus-induced cytoplasmic inclusions using confocal laser scanning microscopy.

The three-dimensional structure of the cytoplasmic inclusions in leaves of Cucurbita pepo L. infected with a Singapore isolate of zucchini yellow mosaic virus (ZYMV-S) was studied using a confocal laser scanning microscope. The cytoplasmic inclusions were found to be linear filamentous structures that varied in thickness and length. The formation of the inclusions probably begins when finely-pointed linear filamentous structures aggregate into bundles forming flat parallel arrays, or diverge into triangular shaped inclusions. Some cytoplasmic inclusions appeared as twisted tubules with empty central cores. The average length and width of the inclusions ranged from 9.4 +/- 0.3 to 20.1 +/- 0.4 microns and from 2.1 +/- 0.1 to 3.7 +/- 0.1 microns. respectively. Confocal laser scanning microscopy is useful for the in situ exploration of three-dimensional structures of cytoplasmic or nuclear inclusions in plant virus infected cells.

Cytoplasm↗
PubMed1991

New structural features of the flagellar base in Salmonella typhimurium revealed by rapid-freeze electron microscopy.

The structure of the flagellar base in Salmonella typhimurium has been studied by rapid-freeze techniques. Freeze-substituted thin sections and freeze-etched replicas of cell envelope preparations have provided complementary information about the flagellar base. The flagellar base has a bell-shaped extension reaching as far as 50 nm into the bacterial cytoplasm. This structure can be recognized in intact bacteria but was studied in detail in cell envelopes, where some flagella lacking parts of the bell were helpful in understanding its substructure. Structural relationships may be inferred between this cytoplasmic component of the flagellum and the recently described flagellar intramembrane particle rings as well as the structures associated with the basal body in isolated, chemically fixed flagella.

Flagella↗
PubMed2002

Detection of Chlamydophila pneumoniae in mouse respiratory ciliated epithelium using targeted sections of the lung tissue.

Chlamiophila pneumoniae were detected in targeted sections of mouse lung tissue by means of transmission electron microscopy and immunofluorescent staining. Incorporation of microorganisms into the axonemal matrix of cilia was observed 24 h after infection. The ciliary axoneme was characterized by pronounced swelling. At the late stages Chlamiophila pneumoniae were present in cytoplasmic vacuoles. Structural abnormalities and dysfunction of mucociliary clearance followed by incorporation of Chlamiophila pneumoniae into the cytoplasm of epitheliocytes were revealed in the early stage of infection. The proposed method allows studying the very early events of Chlamiophila pneumoniae infection.

Animals↗
PubMed2000

Three subunit a isoforms of mouse vacuolar H(+)-ATPase. Preferential expression of the a3 isoform during osteoclast differentiation.

Vacuolar H(+)-ATPase (V-ATPase) is a multi-subunit enzyme with a membrane peripheral catalytic (V(1)) and an intrinsic (V(o)) sector. We have identified three cDNA clones coding for isoforms of mouse V(o) subunit a (a1, a2, and a3). They exhibit 48-52% identity with each other and high similarity to subunit a of other species. The a1 isoform was mainly expressed in brain and liver. The a2 isoform was observed in heart and kidney in addition to brain and liver. Transcripts for the a3 isoform were strongly expressed in heart and liver. The a3 isoform was induced during osteoclast differentiation, and localized in the plasma membrane and cytoplasmic filamentous structures. In contrast to a3, the a1 isoform was constitutively expressed and localized in the cytoplasmic endomembrane compartments of the same cells. These findings suggest that the a3 isoform is a component of the plasma membrane V-ATPase essential for bone resorption.

Amino Acid Sequence↗
PubMedDate not supplied

Ultrastructural changes induced in Walker carcinosarcoma by treatment with dihematoporphyrin ester and light in animals with diabetes mellitus.

The purpose of this study was to evaluate by electron microscopy the tumoral fine structure changes induced by photodynamic therapy (PDT) in diabetic animals. Walker -256 carcinosarcoma harvested from animals with/without diabetes mellitus exposed to PDT (Photofrin II/5 mg/kg and 24 hrs later He-Ne laser irradiation/632.8 nm; 10 mW) and examined by electron microscopy showed different degrees of lesions in the nucleus and cytoplasmic fine structure. The ultrastructural changes induced by PDT in animals with diabetes mellitus bearing carcinosarcoma are characterized by: lysis of chromatin situated on the central zone of nucleus; swelling and vacuolization of mitochondria; formation of phagosome--like structures; myelin figures; degenerescence and disappearance of cytoplasmic organelles. Summing up, the data presented in this work demonstrate that the exposure to three doses of PDT produces changes in tumoral fine structure, increases survival rate and reduces incidence of carcinosarcoma in rats with diabetes mellitus.

Alloxan↗