Structural and functional variability among DQ β alleles of DR2 subtypes

Homozygous lymphoblastoid cell lines representing various Dw subtypes of DR2 were examined for polymorphism at the DQ locus by molecular and cellular techniques. The subtypes studied included Dw2, Dw12, and a group heterogenous by cellular typing that we shall refer to as non-Dw2/non-Dw12. Restriction fragment length polymorphism analysis of cell lines representing these subtypes revealed DQ -specific patterns consistent with cellular typing. Two-dimensional gel electrophoresis of DQ molecules from representative cell lines revealed a structural polymorphism of DQ among the three subtypes. The DQ chain migrated to a position that was unique to each subtype and was consistent among various representative cell lines of each subtype. Nucleotide sequence analysis of cDNA clones of DQ from Dw2, Dw12, and non-Dw2/non-Dw12 lines confirmed that the variability resided at the genetic level. Variability was found in the form of numerous scattered nucleotide substitutions throughout the first domain of these alleles. The DQ gene of the non-Dw2/non-Dw12 cell line AZH was further found to be almost identical with the DQ gene of a DR1 line (Bell et al. 1985b), implicating a common evolutionary origin of these alleles. The only difference between these two sequences was due to an apparent gene conversion event at amino acid 57. T-cell cloning experiments resulted in the derivation of Epstein-Barr virus-specific, DQw1-restricted clones that proliferated against only those cell lines that exhibited the DQ gene common to AZH and the DR1 cell line. Thus, the polymorphism among DQ alleles within DR2 results in subtype-specific restriction.     

Blidingia ramifera stat. nov. (Chlorophyta): a new marine alga for eastern North America

Blidingia minima var. ramifera is reported for the first time in eastern North America. It occurs in the Gulf of St. Lawrence, Nova Scotia and in Maine. In the estuary of the West and Rights Rivers (Antigonish Harbour, Nova Scotia) it is the most common intertidal alga and during its maximum growth period (June-August) covers 75–90% of the intertidal zone for several km of shoreline at the mouth of the Rights River. In culture, spore germination and early development were typical of the taxon as described from Europe. The taxon is raised to specific status as Blidingia ramifera stat. nov. Blidingia subsalsa is confirmed from New England based on observations of spore germination in plants from Maine and Connecticut.     

Calcium-Dependent Release of Tyrosine in Brain Elicited by Stimulation of Neuropeptide Receptors

We sought to establish whether the endogenous opiate-receptor agonist Met-enkephalin (m-ENK) selectively modulates the release of endogenous tyrosine (Tyr) from brain slices prepared from the corpus striatum (CS). Amino acids (AAs) released from slices of CS and, for comparison, cerebral cortex (Cx) were measured by HPLC. Incubation of slices with m-ENK (1-10 microM) increased the basal release of Tyr (up to 293% of control) from CS, but not Cx, whereas other nonneurotransmitter AAs, phenylalanine (Phe) and valine (Val), were unchanged. The release of the putative neurotransmitter AAs glutamate (Glu), taurine (Tau), and glycine (Gly) were similarly increased by 50-150% with m-ENK in slices of CS, but not Cx. The enhanced release of AAs by m-ENK was prevented by removal of extracellular Ca2+ or by preincubation with the opiate receptor antagonist naloxone. Neuronal depolarization by potassium (5-55 mM) in the presence of Ca2+ did not affect the release of Tyr, whereas release of neurotransmitter AAs such as gamma-aminobutyric acid (GABA) were markedly increased. The increase in basal Tyr release by m-ENK was not the result of a decreased uptake of Tyr. Relative to slices, the basal release of Tyr, Phe, and Val from a synaptosomal (P2) preparation of CS was small (8-51%) compared to that of GABA, Gly, Glu, and Tau (49-123%). Nonetheless, m-ENK (10 microM) markedly increased the release of Tyr (to 833%), but not Glu, Gly, and Tau from the P2 fraction.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of stress and beta-funal trexamine pretreatment on morphine analgesia and opioid binding in rats

This study was essentially an in vivo protection experiment designed to test further the hypothesis that stress induces release of endogenous opioids which then act at opioid receptors. Rats that were either subjected to restraint stress for 1 hr or unstressed were injected ICV with either saline or 2.5 micrograms of beta-funaltrexamine (beta-FNA), an irreversible opioid antagonist that alkylates the mu-opioid receptor. Twenty-four hours later, subjects were tested unstressed for morphine analgesia (tail-flick assay) or were sacrificed and opioid binding in brain was determined. [3H]D-Ala2NMePhe4-Gly5(ol)enkephalin (DAGO) served as a specific ligand for mu- opioid receptors, and [3H]-bremazocine as a general ligand for all opioid receptors. Rats injected with saline while stressed were significantly less sensitive to the analgesic action of morphine 24 hr later than were their unstressed counterparts. Beta-FNA pretreatment attenuated morphine analgesia in an insurmountable manner. Animals pretreated with beta-FNA while stressed were significantly more sensitive to the analgesic effect of morphine than were animals that received beta-FNA while unstressed, consistent with the hypothesis that stress induces release of endogenous opioids that would protect opioid receptors from alkylation by beta-FNA. beta-FNA caused small and similar decreases in [3H]-DAGO binding in brain of both stressed and unstressed animals. Stressed rats injected with saline tended to have increased levels of [3H]DAGO and [3H]-bremazocine binding compared to the other groups. This outcome may be relevant to the tolerance to morphine analgesia caused by stress.     

Generation of altered transcripts by retroviral insertion within the c-myb gene in two murine monocytic leukemias

Two murine monocytic leukemia cell lines, WEHI-265 and WEHI-274, were found to carry a rearranged c-myb gene. The rearrangements are due to insertion of a deleted Moloney murine leukemia virus (Mo-MLV) provirus in the 5' region of the c-myb gene and thus are similar to rearrangements in the ABPL tumors (G. L. C. Shen-Ong, M. Potter, J. F. Mushinski, S. Lavu, and E. P. Reddy, Science 226:1077-1080, 1984). In each cell line, the retroviral insertion has induced high levels of two aberrant RNA species, which, as in the ABPL tumors (G. L. C. Shen-Ong, H. C. Morse, M. Potter, and J. F. Mushinski, Mol. Cell. Biol. 6:380-392, 1986), contain both viral (Mo-MLV) and cellular (myb) sequences. Both species lack the sequences encoding the amino terminus of the c-myb protein and thus could encode a protein which, like the v-myb gene products (and the predicted ABPL myb proteins), is truncated at the amino terminus. We have found that the larger (5.3 kilobase [kb]) and more abundant of the tumor-specific myb RNAs was predominantly nuclear, while the smaller species (3.9 kb) was cytoplasmic. Furthermore, our data imply that the 3.9-kb RNA was derived from the 5.3-kb RNA by an additional splice which utilized a cryptic splice acceptor site within the viral gag sequences. On the basis of subcellular distribution and predicted translational potential, we conclude that the 3.9-kb RNA is probably the mRNA which encodes a truncated myb protein. We also show that, due to different insertion points in W265 and W274, the W274 myb RNAs contained sequences from a c-myb exon upstream of the exons represented in the W265 (and ABPL) RNAs. The significance of our findings with regard to transformation by myb in these tumors is discussed.     

Structure and expression of the overlapping ND4L and ND5 genes of Neurospora crassa mitochondria

Summary Genes homologous to the mammalian mitochondrial NADH dehydrogenase subunit genes ND4L and ND5 were identified in the mitochondrial genome of the filamentous fungus Neurospora crassa, and the structure and expression of these genes was examined. The ND4L gene (interrupted by one intervening sequence) potentially encodes an 89 residue long hydrophobic protein that shares about 26% homology (or 41% homology if conservative amino acid substitutions are allowed) with the analogous human mitochondrial protein. The ND5 gene (which contains two introns) encodes a 715 residue polypeptide that shares 23% homology with the human analogue; a 300 amino acid long region is highly conserved (50% homology) in the two ND5 proteins. The stop codon of the ND4L gene overlaps the initiation codon of the downstream ND5 gene, and the two genes are contranscribed and probably cotranslated. A presumed mature dicistronic (ND4L plus ND5) RNA was detected. The postulated mRNA (about 3.2 kb) contains 5 and 3 non-coding regions of about 86 and 730 nucleotides, respectively; this species is generated from very large precursor RNAs by a complex processing pathway. The ND4L and ND5 introns are all stable after their excision from the precursor species.Abbreviations bp base pairs - rRNA ribosomal RNA - ND NADH dehydrogenase - URF unidentified reading frame - kDal kilodaltons; a.a., amino acid     

Electrical Characteristics of the Tonoplast of Cham corallincr. A Study Using Permeabilised Cells

Use of permeabilised cells of Chara corallina provides a uniqueopportunity to study the electrical characteristics of the tonoplastwhilst being able to control ionic conditions on the outsideof the membrane. Current-voltage (I/V) analysis over wide voltagespans, and admittance measurements at 5 Hz showed that manypermeabilised cells had a similar conductance and capacitanceto the tonoplast of intact cells. Cells developed two regionsof negative-slope conductance upon addition of external Cl^–,which suggests the existence of potential-dependent Cl^–channels in the Chara tonoplast. With Cl^– concentrationssimilar to those expected in vivo, the resting potential wasmore sensitive to changes in external K⁺ than Cl^–; however,a decrease in external K⁺ did not significantly alter the shapeof the I/V relation. ¹Present address: Biopysics Laboratory, School of BiologicalSciences, A12, University of Sydney, Sydney, N.S.W., 2006, Australia ²Permanent address: Department of botany, Faculty of Science,University of Tokyo, Hongo, Tokyo 113, Japan (Received May 6, 1987; Accepted September 21, 1987)     

A monoclonal antibody specific for the red-absorbing form of phytochrome

Characterisation of a new monoclonal antibody (mAb), designated LAS 41, directed against 124-kilodalton (kDa) etiolated-oat (Avena sativa L.) phytochrome, indicates that it recognises an epitope unique to the red-light-absorbing form, Pr. In a solid-phase enzyme-linked immunosorbent assay (ELISA), LAS 41 exhibits a seven- to eight-fold higher affinity for Pr than for the far-red-light-absorbing form of phytochrome, Pfr. In addition, in immunoprecipitation assays LAS 41 effectively precipitates 100% of phytochrome presented as Pr but only precipitates a maximum of 24.5% of phytochrome presented as Pfr. These values are indicative of binding exclusively to Pr. Peptide-mapping studies show that LAS 41 recognises and epitope located within a region 6–10 kDa from the aminoterminus of the phytochrome molecule. Since binding of LAS 41 to Pr induces alterations in the spectral properties of Pr, this indicates that at least part of the 4 kDa domain to which the antibody binds is essential for protein-chromophore interaction. Subsequent photoconversion of LAS 41-Pr complexes produces native Pfr spectra, with concomitant production of free antibody and antigen, as shown by a modified ELISA. The specificity of LAS 41 for Pr has facilitated the purification of Pfr which is free of contaminating Pr. This has enabled direct determination of the mole fraction of Pfr established by red light to be 0.874.Abbreviations ELISA enzyme-linked immunsorbent assay - kDa kilodalton - mAb monoclonal antibody - Pfr far-red-absorbing form of phytochrome - Pr red-absorbing form of phytochrome - SDS-PAGE sodium dodecyl sulphate polyacrylamide gel electrophoresis - (A) difference in absorbance (A ₆₆₅ ^Pr –A ₇₃₀ ^Pr )-(A ₆₆₅ ^Pfr –A ₇₃₀ ^Pfr ) - Ar/Afr spectral change ratio (SCR) - max mole fraction of Pfr following saturating red light