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PubMed1993

The anatomy of the P lymphocyte.

This paper describes the basic morphologic criteria for identifying the P lymphocyte. The P cell is a stimulated atypical lymphocyte that is found in schizophrenics and some of their relatives. This cell is suggested as a tentative laboratory indicator of the schizophrenia process. The main identifying features of the cell are its high cytoplasmic basophilia and leptochromatic nuclear structure. Furthermore, the cytoplasm often contains vacuoles and the nuclear shape is often irregular with one or more nucleoli visible. Color micrographs are used to illustrate the cell features.

Chromatin↗
PubMed2006

Mutation S233L in the 1B domain of keratin 1 causes epidermolytic palmoplantar keratoderma with "tonotubular" keratin.

Epidermolytic palmoplantar keratoderma (EPPK) is an autosomal dominant genodermatosis characterized by epidermolytic hyperkeratosis restricted to the palm and sole epidermis. The disorder is normally associated with dominant-negative mutations in the keratin 9 (K9) gene; however, a small number of cases have been reported where causative mutations were identified in the K1 gene. Here, we present two unrelated Dutch EPPK families with striking ultrastructural findings: tubular keratin structures in the cytoplasm of suprabasal cells. Similar structures were reported previously in a German EPPK family and were termed "tonotubular" keratin. After excluding the involvement of the K9 gene by complete sequencing, we identified a novel mutation, S233L, at the beginning of the 1B domain of K1 in both families. Protein expression studies in cultured cells indicated pathogenicity of this mutation. This is the first report of a genetic defect in this domain of K1. The unusual gain-of-function mutation points to a subtle role of the 1B domain in mediating filament-filament interactions with regular periodicity.

Humans↗
PubMed1995

The appearance of cytoplasmic membranes of Escherichia coli cells in freeze-fracture electron microscopy after stringent and relaxed response.

Guanosine-5'-diphosphate-3'-diphosphate (ppGpp), an effector for many metabolic pathways, is synthesized by the relA gene product after amino acid limitation. Studies of stringent controlled Escherichia coli CP78 (relA+) and relaxed controlled E. coli CP79 (relA-) were carried out to test whether these strains differ in the appearance of their cytoplasmic membranes after induction of stringent and relaxed response. Cytoplasmic membrane structures of the cells were investigated by freeze-fracture electron microscopy after cooling the cells. The obtained micrographs showed a net-like distribution of the particles in the cytoplasmic membranes of relaxed controlled cells whereas such a pattern was not detectable in the stringent controlled counterparts.

Amino Acids↗
PubMed1996

Peptidoglycan synthesis and structure in Staphylococcus haemolyticus expressing increasing levels of resistance to glycopeptide antibiotics.

The structures of cytoplasmic peptidoglycan precursor and mature peptidoglycan of an isogenic series of Staphylococcus haemolyticus strains expressing increasing levels of resistance to the glycopeptide antibiotics teicoplanin and vancomycin (MICs, 8 to 32 and 4 to 16 microg/ml, respectively) were determined. High-performance liquid chromatography, mass spectrometry, amino acid analysis, digestion by R39 D,D-carboxypeptidase, and N-terminal amino acid sequencing were utilized. UDP-muramyl-tetrapeptide-D-lactate constituted 1.7% of total cytoplasmic peptidoglycan precursors in the most resistant strain. It is not clear if this amount of depsipeptide precursor can account for the levels of resistance achieved by this strain. Detailed structural analysis of mature peptidoglycan, examined for the first time for this species, revealed that the peptidoglycan of these strains, like that of other staphylococci, is highly cross-linked and is composed of a lysine muropeptide acceptor containing a substitution at its epsilon-amino position of a glycine-containing cross bridge to the D-Ala 4 of the donor, with disaccharide-pentapeptide frequently serving as an acceptor for transpeptidation. The predominant cross bridges were found to be COOH-Gly-Gly-Ser-Gly-Gly-NH2 and COOH-Ala-Gly-Ser-Gly-Gly-NH2. Liquid chromatography-mass spectrometry analysis of the peptidoglycan of resistant strains revealed polymeric muropeptides bearing cross bridges containing an additional serine in place of glycine (probable structures, COOH-Gly-Ser-Ser-Gly-Gly-NH2 and COOH-Ala-Gly-Ser-Ser-Gly-NH2). Muropeptides bearing an additional serine in their cross bridges are estimated to account for 13.6% of peptidoglycan analyzed from resistant strains of S. haemolyticus. A soluble glycopeptide target (L-Ala-gamma-D-iso-glutamyl-L-Lys-D-Ala-D-Ala) was able to more effectively compete for vancomycin when assayed in the presence of resistant cells than when assayed in the presence of susceptible cells, suggesting that some of the resistance was directed towards the cooperativity of glycopeptide binding to its target. These results are consistent with a hypothesis that alterations at the level of the cross bridge might interfere with the binding of glycopeptide dimers and therefore with the cooperative binding of the antibiotic to its target in situ. Glycopeptide resistance in S. haemolyticus may be multifactorial.

Amino Acid Sequence↗
PubMed1990

Developmental changes of synapsin I subcellular localization in rat cerebellar neurons.

Synapsin I, one of the major synaptic proteins, is thought to associate with synaptic vesicles and to play a regulatory role in neurotransmitter release. In mature neurons, it is concentrated almost exclusively in presynaptic nerve endings. Here, we studied the subcellular localization of synapsin I during the development of rat cerebellar cortices by immunocytochemistry, using anti-synapsin I antibodies and found that during the development of rat cerebellar cortices it tentatively exists in the dendritic growth cones of immature internal granule cells and in the axonal growth cones of mossy fibers as well as mature presynaptic endings. Also, we found that synapsin I, in the axonal and dendritic growth cones does not necessarily associate with vesicles, but rather with fuzzy filamentous structures in the cytoplasm. In search of the structure of synapsin I in vivo, we employed the quick-freeze, deep-etch technique after immunogold labeling. Synapsin I seems to thereby connect synaptic vesicles or anchor them to cytoskeletons in presynaptic endings.

Animals↗
PubMed1978

Role of chelation and water binding of calcium in dormancy and heat resistance of bacterial endospores.

The possible relationship between the water binding by bacterial endospores and their dormancy and heat resistances has been examined in terms of the coordination characteristics of the spore-bound calcium. Stabilities of the calcium complexes of typical cytoplasmic and structural spore components were determined by potentiometric equilibrium pH measurements in model systems consisting of DPA, glycine, alanine, glutamic acid, alanyl-glutamic acid, triglycine, and tetraglycine. The Ca++-form and H+-form spores of Clostridium botulinum 33A were investigated in vivo with respect to their water sorption and heat-resistance characteristics. The results suggest that the complexing of calcium and Ca(II)-DPA may be biologically significant for spore resistance and dormancy at the following three levels: (1) complexing with spore cytoplasmic pool constituents consistent with the idea of a metal-chelate cross-linked cytoplasm or spore cement stabilizing the essential biological macromolecules, (2) complexing with structural components of the spore as indicated by the interaction with model peptides, and (3) coordination with water to produce an apparently dehydrated environment in the spore as evident from the much greater water-sorption capacity of the Ca++-form spores vs the much smaller water sorption of the H+-form spores. Interestingly enough, DPA itself, in the absence of metal ion, showed some interaction with di-, tri-, and tetrapeptides and a weak but detectable interaction with amino acids. Although the exact mode of the DPA-peptide interaction is not clear, it is attractive to speculate about its possible involvement in the control of spore dormancy and resistance.

Absorption↗
PubMed1982

A unique class of compound, guanosine-nucleoside tetraphosphate G(5')pppp(5')N, synthesized during the in vitro transcription of cytoplasmic polyhedrosis virus of Bombyx mori. Structural determination and mechanism of formation.

Two structurally different classes of oligonucleotides accumulate in vitro in cytoplasmic polyhedrosis virus (CPV) transcription mixtures in molar excess as compared to the completed RNA products. The first class consists of oligonucleotides which correspond to the 5'-terminal sequence of the virus mRNAs (referred to as initiator oligonucleotides). The major species of initiator oligonucleotides are (p)ppApG and (p)ppApGpN together with smaller amounts of homologous capped structures (Furuichi, Y. (1981) J. Biol. Chem. 256, 483-493). In addition to initiator oligonucleotides, CPV transcription mixtures yielded a second new class of compounds which were radiolabeled by [alpha-32P]GTP and resistant to phosphatase digestion. Their structures were identified as G(5')pppp(5')A, G(5')pppp(5')C, G(5')pppp(5')G, and G(5')pppp(5')U. With the exception of G(5')pppp(5')G, these compounds have not been observed previously. The mechanism of synthesis of these unique compounds was elucidated as pppG + pppN leads to GppppN + PPi. The reaction resembles, in principle, a guanylylation reaction which occurs during cap formation in CPV and other eukaryotic mRNA syntheses. It is likely that these compounds are formed in a similar way by a condensation reaction involving a viral guanylyltransferase-pG intermediate complex and ribonucleoside triphosphate. When the amounts of G(5')pppp(5')N were measured, it was found that G(5')pppp(5')N reached maximum concentrations (0.4 to 0.7 microM) shortly after the onset of RNA synthesis (1 h) and these levels were maintained or diminished gradually. By contrast, mRNA and (p)ppApG were continuously synthesized. The relative molar ratios of total G(5')pppp(5')N and (p)ppApG versus mRNA were comparable (74:24:1 and 30:27:1 during 1 to 4 h transcription, respectively). The results imply that these unusual compounds G(5')pppp(5')N as well as initiator oligonucleotides may be produced reiteratively during initiation when RNA chain elongation and capping are uncoupled.

Animals↗
PubMed1994

Epstein-Barr virus recombinant molecular genetic analysis of the LMP1 amino-terminal cytoplasmic domain reveals a probable structural role, with no component essential for primary B-lymphocyte growth transformation.

Previous recombinant Epstein-Barr virus molecular genetic experiments with specifically mutated LMP1 genes indicate that LMP1 is essential for primary B-lymphocyte growth transformation and that the amino-terminal cytoplasmic and first transmembrane domains are together an important mediator of transformation. EBV recombinants with specific deletions in the amino-terminal cytoplasmic domain have now been constructed and tested for the ability to growth transform primary B lymphocytes into lymphoblastoid cell lines. Surprisingly, deletion of DNA encoding EHDLER or GPPLSSS from the full LMP1 amino-terminal cytoplasmic domain (MEHDLERGPPGPRRPPRGPPLSSS) had no discernible effect on primary B-lymphocyte transformation. These two motifs distinguish the LMP1 amino-terminal cytoplasmic domain from other arginine-rich membrane proximal sequences that anchor hydrophobic transmembrane domains. Two deletions which included the ERGPPGPRRPPR motif adversely affected but did not prevent transformation. This arginine- and proline-rich sequence is probably important in anchoring the first transmembrane domain in the plasma membrane, since these mutated LMP1s had altered stability and cell membrane localization. The finding that overlapping deletions of the entire amino-terminal cytoplasmic domain do not ablate transformation is most consistent with a model postulating that the transmembrane and carboxyl-terminal cytoplasmic domains are the likely biochemical effectors of transformation.

Amino Acid Sequence↗
PubMed1975

The outer membrane of Proteus mirabilis. I. Isolation and characterization of the outer and cytoplasmic membrane fractions.

1. The crude envelope preparation obtained by sonication of Proteus mirabilis cells in the presence of lysozyme was separated into outer and cytoplasmic membrane fractions by sucrose density gradient centrifugation. The outer membrane fraction accounted for about two thirds of the dry weight of the envelope preparation. 2. In thin sections, the outer and cytoplasmic membrane fractions were shown to consist of vesicles bounded by a single trilaminar membrane, but those of the outer membrane were considerably smaller and were frequently open, forming C-shaped structures. The cytoplasmic membrane vesicles were cleaved by freeze fracturing to expose fracture faces studded with particles, while the outer membrane fragments resisted cleavage. 3. The outer membrane fraction consisted of protein (similar to 40%), lipopolysaccharide (similar to 36%) and lipid (similar to 18%) and had a density of about 1.22 g/cm3. The cytoplasmic membrane fraction consisted mostly of protein (similar to 56%) and lipid (similar to 38%), had a density of about 1.16 g/cm3, and contained almost all the NADH oxidase, succinate and D-lactate dehydrogenase activities of the crude envelope preparation. 4. Electrophoresis in polyacrylamide gels containing sodium dodecylsulfate revealed over 20 polypeptide bands in the cytoplasmic membrane fraction and only 6-7 in the outer membrane fraction. The outer membrane electrophorogram was dominated by a major band (mol. wt 40 000) which was resolved into two bands when electrophoresed in an acidic gel system. Amino acid analysis revealed a higher content of polar amino acids in the protein moiety of the outer membrane.

Amino Acids↗
PubMed1994

A novel gene whose expression is regulated by the response-regulator, SphR, in response to phosphate limitation in Synechococcus species PCC7942.

In Synechococcus species PCC7942, the production of a subset of proteins is induced when it is grown in a phosphate-limited medium. We previously suggested that a pair of cyanobacterial two-component regulatory proteins, SphS (sensory-kinase) and SphR (response-regulator), may be involved in this particular response to phosphate limitation. Here it was found that a protein with an apparent molecular mass of 33 kDa became particularly abundant when the total cellular proteins from cells grown in a phosphate-limited medium were analysed by SDS-PAGE. A deletion mutant lacking both the sphS and the sphR genes failed to produce this 33 kDa protein in response to phosphate limitation. Thus it was reasonable to assume that this protein is a member of the group of proteins involved in the Synechococcus phosphate regulatory circuit (hence, it was named SphX). The SphX protein was purified to near homogeneity, and the corresponding structural gene was cloned. The determined nucleotide sequence revealed that the sphX gene encodes a novel protein with a calculated molecular mass of 36,374 Da, which was demonstrated to be located in the cytoplasmic membrane. Structural features of the sphX promoter were then clarified by determining its transcription start site, from which transcription was triggered in response to phosphate limitation. Furthermore, the putative response-regulator, SphR, was demonstrated to bind to the upstream region of the sphX promoter by means of in vitro DNase I footprinting. From these results, we conclude that the sphX gene is a member of the Synechococcus phosphate regulatory circuit, in which the two signal-transduction components, SphS and SphR, are crucially involved as transcriptional regulators. The SphX protein may play a role in phosphate assimilation in Synechococcus.

Amino Acid Sequence↗
PubMed1988

Antibody to galactocerebroside alters organization of oligodendroglial membrane sheets in culture.

Antibodies to galactocerebroside (GalC) cause major changes in the organization of the membrane sheets elaborated by murine oligodendroglia in culture. Exposure of oligodendroglia to rabbit anti-GalC IgG for 15 min followed by fluoresceinated second antibodies results in patches of surface GalC staining; when second antibodies are applied after 2 hr of anti-GalC, the pattern of staining on membrane sheets is solid and wrinkled. Anti-GalC exposure for 24 hr results in contracted membrane sheets. No membrane contraction is detected in cultures treated with anti-sulfatide IgM or anti-proteolipid protein IgG. In cultures exposed to anti-GalC continuously for 4-7 d, there is a marked decrease in numbers of extended membrane sheets with an accompanying increase in contracted sheets. This effect is reversible upon removal of anti-GalC from the culture media. By scanning electron microscopy, normally flat membrane sheets appear ruffled after 2 hr of anti-GalC treatment; by 24 hr, contracted membrane sheets consist entirely of bulbous protrusions. Oligodendrocyte membranes exposed to anti-sulfatide for 24 hr are not contracted but are covered with bulbous protrusions. The organization of underlying membrane structures was examined in relation to membrane patching and sheet contraction. In membranes with patching induced by exposure to anti-GalC for 15 min, the anti-GalC: GalC complexes are localized over cytoplasmic MBP domains, with the unstained areas located above cytoplasmic microtubular structures. Membrane sheets that are contracted in response to anti-GalC exposure for 6-24 hr show intense GalC staining over microtubular structures. Anti-GalC exposure does not change metabolism of GalC; in cultures incubated with 3H-galactose and anti-GalC for 24 hr, there are no alterations in GalC labeling compared with control cultures. In summary, these results provide direct evidence that interaction between surface glycolipids and external antibodies can initiate a sequence of events leading to dramatic changes within the oligodendrocyte.

Animals↗
PubMed1975

An ultrastructural study of mixed hepatoblastoma with osteoid elements.

A case of mixed hepatoblastoma with osteoid elements was studied by light and electron microscopy. The ultrastructure of the epithelial elements showed a lack of differentiation and simple cytoplasmic organelles. However, an occasional cytoplasmic crystalloid structure were seen. The ultrastructure of the osteoid foci showed fibroblast-like cells capable of collagen formation, clearly distinguishable from the epithelial elements. These cells had neoplastic characteristics of nuclear pleomorphism and high nucleo-cytoplasmic ratio. These findings support the belief that hepatoblastoma arises from a multipotential blastema capable of both epithelial and mesenchymal differentiation, with the osteoid elements being an intrinsic neoplastic component of the tumor.

Carcinoma, Hepatocellular↗
PubMed2001

Molecular identification of smg-4, required for mRNA surveillance in C. elegans.

Premature termination codons trigger a process in eukaryotes known as nonsense mediated decay or mRNA surveillance, resulting in the rapid decay of the aberrant transcript. Studies in C. elegans have shown this system is mediated by seven smg genes and can prevent the accumulation of toxic, truncated peptides. Here we report the cloning of smg-4 by physical mapping and functional rescue assays. The minimal rescuing activity is found within a genomic operon, encoding a novel protein. The final exon of the gene is alternatively spliced for expression of two different isoforms. Although no known genes were found to exhibit significant homology to smg-4, a novel conserved domain has been identified by alignment with sequences defined by expressed sequence tags (ESTs) from a variety of organisms. Furthermore, we describe a homolog from C. briggsae, which will rescue C. elegans smg-4 mutants. The C. elegans gene has been fused to green fluorescent protein (GFP). This SMG-4:GFP fusion exhibits nuclear accumulation and diffuse cytoplasmic staining, and further localizes to what appear to be perinuclear and cytoplasmic punctate structures.

Alternative Splicing↗