Identification of a cDNA for the plastid-located geranylgeranyl pyrophosphate synthase from Capsicum annuum: correlative increase in enzyme activity and transcript level during fruit ripening

Geranylgeranyl pyrophosphate synthase is a key enzyme in plant terpenoid biosynthesis. Using specific antibodies, a cDNA encoding geranylgeranyl pyrophosphate synthase has been isolated from bell pepper (Capsicum annuum) ripening fruit. The cloned cDNA codes for a high molecular weight precursor of 369 amino acids which contains a transit peptide of approximately 60 amino acids. In-situ immunolocalization experiments have demonstrated that geranylgeranyl pyrophosphate synthase is located exclusively in the plastids. Expression of the cloned cDNA in E. coli has unambiguously demonstrated that the encoded polypeptide catalyzes the synthesis of geranylgeranyl pyrophosphate by the addition of isopentenyl pyrophosphate to an allylic pyrophosphate. Peptide sequence comparisons revealed significant similarity between the sequences of the C. annuum geranylgeranyl pyrophosphate synthase and those deduced from carotenoid biosynthesis (crtE) genes from photosynthetic and non-photosynthetic bacteria. In addition, four highly conserved regions, which are found in various prenyltransferases, were identified. Furthermore, evidence is provided suggesting that conserved and exposed carboxylates are directly involved in the catalytic mechanism. Finally, the expression of the geranylgeranyl pyrophosphate synthase gene is demonstrated to be strongly induced during the chloroplast to chromoplast transition which occurs in ripening fruits, and is correlated with an increase in enzyme activity.     

Metastatic spindle-cell carcinoma. Cytologic features and differential diagnosis

Fine needle aspiration biopsies of tumors can yield a variety of spindle cells derived from several types of neoplasms. Among these is a rare lesion known as a "spindle-cell carcinoma" or "pseudosarcoma," which may represent a transformation of a preexisting squamous-cell carcinoma that has been subjected to radiotherapy or solar damage. The cytologic, histologic and ultrastructural features of a case of metastatic spindle-cell carcinoma of the rib subjected to fine needle aspiration are presented, and other spindle-cell tumors that should be considered in the differential diagnosis are discussed.     

Cytogenetic characterization of 20 lymphoblastoid lines derived from human individuals differing in bleomycin sensitivity

Summary Forty lymphoblastoid (lymphoid) lines were established from 42 volunteer blood donors, including healthy individuals and patients with head and neck carcinomas. Each peripheral blood sample was split into two portions, one for the establishment of a lymphoid line and the other for short-term culture, which was used to estimate bleomycin sensitivity by cytogenetic procedures. Twenty lymphoid lines were selected at random to compare bleomycin sensitivity with data obtained from short-term lymphocyte cultures. In each set, bleomycin sensitivity of lymphoid cells was similar to that of the lymphocytes. The lymphoid lines, which can be propagated for an unlimited supply of relatively homogeneous cellular material, will be useful for a variety of future investigations. This investigation was supported by grants from the John S. Dunn Foundation, Houston, TX, the Esther Knispel Fund administered by The University of Texas M. D. Anderson Cancer Center, Houston, TX, and Department of Health and Human Services PHS grant DE 07007.     

Molecular characterization of three Mhc class II B haplotypes in the ring-necked pheasant

We investigated the class II B genes in free-ranging population of the ring-necked pheasant Phasianus colchicus by a combination of restriction fragment length polymorphism (RFLP), polymerase chain reaction (PCR), and DNA sequencing. Special attention was paid to the variation in the second exon, which encodes the peptide-binding ₁-domain. The population was introduced, but it still exhibited major histocompatibility complex polymorphism with at least three segregating class II B haplotypes and consequently six genotypes. We found two class II B genes associated with each haplotype. The class II B genes of birds had until then only been molecularly characterized in the domestic chicken. the pheasant genes were highly variable, although one of the amplified sequences was found in two different haplotypes. Taken together, the most polymorphic positions (residues 37 and 38) were not identical in any of the predicted protein sequences, but all except one of the motifs had already been foud in the domestic chicken. Structurally important features in mammalian class II B genes were generally conserved also in the pheasant sequences, but the loss of a potential salt bridge constituent (Arg₇₂) in several sequences may suggest a slightly different structure of the adjacent parts of the peptide-binding groove. The pheasant genes are most closely related to the so called B-LBII family in the chicken, indicating that this represents a major line of development among avian class II B genes.The nucleotide sequence data reported in this paper have been submitted to the EMBL nucleotide sequence database and have been assigned the accession numbers X75403-X75407. Correspondence to: H. Wittzell, Department of Theoretical Ecology, Ecology Building, Lund University, S-223 62 Lund, Sweden.     

Volume regulation by flounder red blood cells in anisotonic media

The nucleated high K, low Na red blood cells of the winter flounder demonstrated a volume regulatory response subsequent to osmotic swelling or shrinkage. During volume regulation the net water flow was secondary to net inorganic cation flux. Volume regulation the net water flow was secondary to net inorganic cation flux. Volume regulation after osmotic swelling is referred to as regulatory volume decrease (RVD) and was characterized by net K and water loss. Since the electrochemical gradient for K is directed out of the cell there is no need to invoke active processes to explain RVD. When osmotically shrunken, the flounder erythrocyte demonstrated a regulatory volume increase (RVI) back toward control cell volume. The water movements characteristic of RVI were a consequence of net cellular NaCl and KCl uptake with Na accounting for 75 percent of the increase in intracellular cation content. Since the Na electrochemical gradient is directed into the cell, net Na uptake was the result of Na flux via dissipative pathways. The addition of 10(-4)M ouabain to suspensions of flounder erythrocytes was without effect upon net water movements during volume regulation. The presence of ouabain did however lead to a decreased ration of intracellular K:Na. Analysis of net Na and K fluxes in the presence and absence of ouabain led to the conclusion that Na and K fluxes via both conservative and dissipative pathways are increased in response to osmotic swelling or shrinkage. In addition, the Na and K flux rate through both pump and leak pathways decreased in a parallel fashion as cell volume was regulated. Taken as a whole, the Na and K movements through the flounder erythrocyte membrane demonstrated a functional dependence during volume regulation.     

cDNAs encoding members of a family of proteins related to human sterol carrier protein 2 and assignment of the gene to human chromosome 1 p21----pter.

Sterol carrier protein 2 (SCP2) is believed to play a key role in intracellular lipid movement. Here we report the cloning and nucleotide sequences of cDNAs encoding SCP2-related proteins of 58.85 kD and 30.8 kD and the assignment of the SCP2 gene to human chromosome 1 p21-pter. The SCP2-related proteins share common deduced carboxyl amino acid sequences with SCP2 and the cDNAs have a common 3' untranslated nucleotide sequence. The mRNAs encoding these proteins increased in a coordinate fashion as human placental cytotrophoblasts differentiated into syncytiotrophoblasts in culture. Our observations document the existence of a family of related proteins encoded by the human SCP2 gene.