Nef genes of SIV

Molecular clones of SIVmac were constructed that differed only in sequences within the nef gene. DEAE-transfection of viral DNA containing an open from of nef yielded virus that replicated with similar kinetics and to a similar extent in macaque peripheral blood lymphocyte (PBL) cultures as virus with a deletion or stop codon within nef. Rhesus monkeys that received each kind of molecularly cloned virus became infected. Our results additionally suggest that mutant forms of virus are selected in vitro while open, functional forms are selected in vivo. In animals infected with virus containing a stop codon within nef, reversion of the stop codon to a coding codon was demonstrated in five of five clones analyzed. These results indicate that nef is playing some role crucial to the virus life cycle in vivo.     

Increased H-2Dd expression following infection by a molecularly cloned ecotropic MuLV

The biological consequences of radiation leukemia virus (RadLV) infection include the stimulation of H-2D^d antigen expression in resistant mouse strains and thymoma induction in susceptible strains. In an effort to understand the genetic basis of these phenomena, the integrated ecotropic RadLV genome has been examined in a number of primary RadLV-induced tumors, as well as thymomas adapted to in vitro passage; considerable heterogeneity was observed. Examination of these polymorphic viral sequences should help define the viral gene(s) involved in the biological effects of RadLV infection; toward this end, integrated RadLV genomes were molecularly cloned and examined. The genomes and their flanking sequence were characterized by restriction enzyme analysis. Three unique viral genomes were obtained which represent four integration sites. The three RadLV genomes are shown to carry polymorphisms of the original tumor. Following DNA transfection, one of the three genomes replicated in and reinfected both mouse thymocytes and fibroblasts, but not mink fibroblasts in vitro. Virus encoded by the other two DNA genomes could not be recovered following transfection into any of the three cell types. One of these two apparently defective retroviruses encodes a truncated p15E molecule, while the other has elongated long terminal repeats (LTRs). The non-defective ecotropic isolate was collected from in vitro tissue culture supernatants, concentrated, and used to infect mice. Thymocytes of infected, resistant mice were shown to express elevated levels of H-2D^d antigen as early as 12 days post infection, a hallmark of RadLV infection. Offprint requests to: G. D. Brown.     

Effects of dl-2-Amino-5-Phosphonovalerate on Metabolism of Catecholamines in Synaptosomes from Rat Brain

Incubation of synaptosomes from rat brain with DL-2-amino-5-phosphonovalerate (APV) stimulated an increased release of dopamine, and this effect was strictly dependent on the extrasynaptosomal calcium level. APV increased biosynthesis of dopamine from tyrosine by 30%, whereas monoamine oxidase activity was inhibited by 30%. When synaptosomes were incubated with radioactive dopamine, APV caused a large decrease in incorporation of label into 3,4-dihydroxyphenylacetic acid but greatly increased incorporation into norepinephrine and its N-methyl derivatives. Quantification of dopamine and its metabolites in synaptosomes, using electrochemical detection, indicated that the presence of APV resulted in changes in the absolute levels of the aforementioned dopamine metabolites similar to the changes in radiolabel incorporation. Omission of Ca2+ from the extrasynaptosomal medium greatly diminished the APV-induced changes in catecholamine metabolism. The metabolic changes appear to largely result from an increased intrasynaptosomal Ca2+ level due to the APV-induced increase in calcium permeability of the plasma membrane.     

Phenotypic variation during micropropagation of the chimeralRhododendron ‘President Roosevelt’

The putative periclinal chimeraRhododendron xlimbatum President Roosevelt was used to study the origin of shoots in vitro. Genotypic segregation readily occurred in vitro. Numerous phenotypes were observed, although most shoots were either entirely green or maintained the original variegation pattern. Derivatives of the third apical layer were rarely involved in shoot formation. A reversed chimeral form was isolated. Adventitious shoots were usually miniaturized and rapidly proliferating, but axillary shoots had thicker stems, larger leaves and proliferated more slowly. Corolla tissue produced stunted, leafy shoots; no variegated shoots were produced from floret explants. In shoot tip cultures the addition of 40M 2iP without IBA resulted in the greatest number of shoots. Explant choice was the most critical factor for maintenance of foliar variegation.     

Fluorescence lifetimes of dimers and higher oligomers of bacteriochlorophyll c from Chlorobium limicola

Fluorescence lifetimes have been measured for bacteriochlorophyll (BChl) c isolated from Chlorobium limicola in different states of aggregation in non-polar solvents. Two different homologs of BChl c were used, one with an isobutyl group at the 4 position, the other with n-propyl. Species previously identified as dimers (Olson and Pedersen 1990, Photosynth Res, this issue) decayed with lifetimes of 0.64 ns for the isobutyl homolog, 0.71 ns for n-propyl. Decay-associated spectra indicate that the absorption spectrum of the isobutyl dimer is slightly red-shifted from that of the n-propyl dimer. Aggregates absorbing maximally at 710 nm fluoresced with a principal lifetime of 3.1 ns, independent of the homolog used. In CCl₄, only the isobutyl homolog forms a 747-nm absorbing oligomer spectrally similar to BChl c in vivo. This oligomer shows non-exponential fluorescence decay with lifetimes of 67 and 19 ps. Because the two components show different excitation spectra, the higher oligomer is probably a mixture of more than one species, both of which absorb at 747 nm.Abbreviations BChl bacteriochlorophyll - Chl chlorophyll - % MathType!MTEF!2!1!+-% feaafeart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGGipm0dc9vqaqpepu0xbbG8F4rqqrFfpeea0xe9Lq-Jc9% vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x% fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaeq4Xdm2aaW% baaSqabeaacaaIYaaaaaaa!3777!\[\chi ^2 \] chi-square - FWHM full-width at half-maximum     

Phylogenetic systematic evaluation of a classification of the Zoogonidae Odhner, 1902 (Cercomeria: Trematoda: Digenea: Plagiorchiiformes)

A recent systematic study of the digenean family Zoogonidae presented a series of cladograms, which are the product of phylogenetic systematic, or cladistic, analysis. However, one of the two subfamilies and nine of the 21 genera recognised in that study lacked putative synapomorphies, a requirement for phylogenetic systematic studies. This study presents a re-analysis of the database for the zoogonids, based on rigorous application of phylogenetic systematic methods. A new phylogenetic tree is presented, which better fits the original data than the published tree (with a consistency index of 52.3% vs. 46.3%). Four subfamilies, three monophyletic and one of uncertain status, and 10 genera could be recognised phylogenetically. This would affect the nomenclatorial status of one-third (26) of the species in the family. However, it is recommended that another analysis, based on more characters, be carried out before nomenclatorial changes are proposed.     

Substance P affects the GABAergic system in the hypothalamo-pituitary axis

In the present work we examined the effect of the neutralization of endogenous substance P by the administration of an anti-substance P serum (ASPS) on GABA concentration in the anterior pituitary in hyperprolactinemic conditions induced by 5-hydroxytryptophan or by grafting anterior pituitaries. ASPS reduced the increase in the anterior pituitary GABA concentration induced by hyperprolactinemia. In vitro experiments showed that substance P inhibited K⁺-evoked GABA efflux from hypothalamic fragments and decreased GABA concentration in the anterior pituitary but ASPS increased it. Our results demonstrate that substance P modifies hypothalamic GABA release and anterior pituitary GABA concentration and suggest that an interaction exists between substance P and GABA.     

A Metachromatic Dye-Atpase Method for The Simultaneous Identification of Skeletal Muscle Fiber Types I, IIA, IIB and IIC

The histochemical demonstration of quantitative differences in myofibrillar ATPase activity at the selective pH optima of the various types of human skeletal muscle fibers is the most widely used technique for their differentiation. The basis of the reaction is the deposition of insoluble salts of inorganic phosphate cleaved from ATP by myofibrillar ATPase(s) followed by substitution of the phosphates with less soluble chromogenic salts. Doriguzzi and associates reported using metachromatic dyes to demonstrate quantitative differences in phosphate deposition among different fiber types. Following routine ATPase histochemistry and staining with either azure A or toluidine blue, fibers with low ATPase activity (and low phosphate content) were stained metachromatically while fibers with high ATPase activity (and high phosphate content) were orthochromatic with the intensity of color proportional to the content of insoluble phosphate. The metachromasia was readily lost after immoderate washing in aqueous solutions or routine dehydration in ethanol, with consequent diminished fiber type distinction. A critical modification of this technique is reported in which incubation of frozen sections of human skeletal muscle in ATP-containing medium is carried out at room temperature (22-24 C), rather than the usual 37 C., followed by a revised washing and dehydration protocol. With these modifications, the four human skeletal muscle fiber types (types I, HA, IIB, and IIC) can be identified rapidly and reliably in single sections, obviating the need for examination of serial sections. The tinctorial differentiation allows fiber type identification even in black and white photographs.     

The Compatibility of d-Pinitol and 1d-1-O-Methyl-Muco-Inositol with Malate Dehydrogenase Activity

Pinitol (1d -3-O-methyl-chiro-inositol) and 1d -1-O-methyl-muco-inositol, two cyclitols wide-spread in the plant kingdom, were isolated from plant sources in order to test their compatibility with malate dehydrogenase activity. Both compounds had no inhibitory effect on malate dehydrogenase from Rhizophora mangle in a range of 100 to 1000 mol . m^?3. Their influence on malate dehydrogenase activity from different plant sources (Rh. mangle L., Mesembryanthemum crystallinum L., Cicer arietinum L. and Spinacia oleracea L.) was also small and similar to that observed for a number of well established compatible solutes (e.g. proline, glycine betaine). A possible role of cyclitols as cryoprotectants or radical scavengers is discussed.