Immunoregulatory T-cell defects in B-cell chronic lymphocytic leukemia: cause or consequence of the disease? The contributory role of decreased availability of interleukin 2 (IL-2)

Several phenotypic and functional defects have been described within the residual T-lymphocyte population of patients with B-cell chronic lymphocytic leukemia (B-CLL), particularly in those in the more advanced stages of the disease. In this study, we review these abnormalities and discuss their possible effects on the course of the illness. Particular emphasis is devoted to the role of interleukin 2 (IL-2) in B-CLL. Evidence is provided that the IL-2 released by B-CLL T-lymphocytes may be utilized by the neoplastic B-cell clone that expresses the IL-2 receptor and that decreased availability of IL-2 may play a contributory role in some of the T-cell defects encountered in B-CLL.     

The cucumber mosaic virus 1a protein regulates interactions between the 2b protein and ARGONAUTE 1 while maintaining the silencing suppressor activity of the 2b protein

The cucumber mosaic virus (CMV) 2b viral suppressor of RNA silencing (VSR) is a potent counter-defense and pathogenicity factor that inhibits antiviral silencing by titration of short double-stranded RNAs. It also disrupts microRNA-mediated regulation of host gene expression by binding ARGONAUTE 1 (AGO1). But in Arabidopsis thaliana complete inhibition of AGO1 is counterproductive to CMV since this triggers another layer of antiviral silencing mediated by AGO2, de-represses strong resistance against aphids (the insect vectors of CMV), and exacerbates symptoms. Using confocal laser scanning microscopy, bimolecular fluorescence complementation, and co-immunoprecipitation assays we found that the CMV 1a protein, a component of the viral replicase complex, regulates the 2b-AGO1 interaction. By binding 2b protein molecules and sequestering them in P-bodies, the 1a protein limits the proportion of 2b protein molecules available to bind AGO1, which ameliorates 2b-induced disease symptoms, and moderates induction of resistance to CMV and to its aphid vector. However, the 1a protein-2b protein interaction does not inhibit the ability of the 2b protein to inhibit silencing of reporter gene expression in agroinfiltration assays. The interaction between the CMV 1a and 2b proteins represents a novel regulatory system in which specific functions of a VSR are selectively modulated by another viral protein. The finding also provides a mechanism that explains how CMV, and possibly other viruses, modulates symptom induction and manipulates host-vector interactions.     

In vivo cellular responses to electrophoretically applied dynorphin in the rat hippocampus

Recent immunohistochemical and radioimmunochemical observations have demonstrated a differential distribution of immunoreactive dynorphin (DYN) in rat brain. The presence of DYN immunoreactivity in a major intrinsic fiber pathway within the rat hippocampus (the mossy fiber system) has led us to evaluate the possible role of DYN and other closely related peptides in this structure. Single cell activity and hippocampal field potentials have been recorded from the CA1-CA3 cellular fields in halothane or urethane anesthetized rats. DYN, DYN1-13, DYN1-8, and alpha-neo-endorphin had an excitatory effect on most CA1-CA3 neurons encountered as has been previously observed for opiates and other opioid peptides. This response could be blocked by naloxone or by co-administration of Mg++ ion suggesting an indirect (synaptic) mechanism of excitation similar to that hypothetized for enkephalin. A significant number of CA3 neurons, however, exhibited a non-naloxone sensitive inhibitory response to DYN, related opioid peptides, and the kappa agonist WIN 35-197 (ethylketocyclazocine). Field potential analysis of CA1-CA3 neuronal responses to mossy fiber activation also indicated an excitatory, Mg++ reversible, action of iontophoretically applied DYN. These observations support our cytochemical and assay studies indicating diverse opioid systems within the rat hippocampus. In addition, these functional studies are congruent with other evidence suggesting multiple opioid mechanisms in this structure.     

Susceptibility of neuroactive peptides to aminopeptidase digestion is related to molecular size.

Peptide fragments derived from the NH₂-terminus of corticotropin were found to exhibit widely differing degrees of stability to degradation by aminopeptidase M. Corticotropin itself was 135 times more stable than its NH₂-terminal pentapeptide, and similar differences in stability were observed with peptides derived from the B-chain of bovine insulin. Enkephalin linked covalently to the A-chain of bovine insulin was at least 100 times more stable than the pentapeptide. The results demonstrate that the molecular size of a peptide is one factor that determines its NH₂-terminal stability.     

Cytochrome b, the var 1 protein, and subunits I and III of cytochrome c oxidase are synthesized without transient presequences in Saccharomyces cerevisiae

The N-termini of four mitochondrial translation products, the var 1 protein, cytochrome b, and subunits I and III of cytochrome c oxidase have been characterized in Saccharomyces cerevisiae and compared with the known DNA sequences of the respective structural genes. The four mature proteins correspond to the predicted primary translation products and retain the formylated methionine residue. Thus, subunit II of cytochrome c oxidase studied previously [Pratje et al. (1983) EMBO J.2, 1049-1054] is so far the only mitochondrial translation product carrying a N-terminal-extended transient presequence in S. cerevisiae.     

Onset of changes in phospholipid fatty acid composition and prostaglandin synthesis following dietary manipulation with n-6 and n-3 fatty acids in the rat

A synthetic diet preparation supplemented with 10% by weight of either safflower oil, hydrogenated coconut oil containing 3% safflower oil, or 'max EPA' fish oil was fed to rats over a 8-week period. Serial measurements of serum fatty acids, serum thromboxane B2 and urinary prostaglandin excretion were taken during the treatment period to assess the rate of change in fatty acid composition and prostaglandin synthesis following dietary manipulation. There was no significant change in weight gain between the dietary groups during the treatment period. Significant changes in serum fatty acids occurred within 48 h of treatment, with the 'max EPA' oil group having arachidonic acid levels reduced by 23% (P less than 0.01) compared to the coconut oil group. Conversely, rats fed safflower oil had an 18% enhancement of arachidonic acid during the same time period. Whole blood synthesis of thromboxane B2 was significantly depressed (P less than 0.01) after 48 h in rats fed 'max EPA' oil compared to the safflower oil or coconut oil groups. This suppression reached a maximum of 65% (P less than 0.001) after 7 days of dietary 'max EPA' oil treatment. The safflower oil and coconut oil-fed groups showed the same levels of serum thromboxane B2 production over the treatment period. Urinary excretion of both 6-ketoprostaglandin F1 alpha and prostaglandin E2 varied significantly (P less than 0.01) between the groups after 7 days of dietary treatment. Rats fed 'max EPA' oil had depressed urinary prostanoid excretion compared to the safflower and coconut oil groups which remained very similar to each other. After the 8-week treatment period rats were killed and the phospholipid fatty acid composition and prostaglandin-generating capacity of platelets, aorta and renal tissue was examined. Prostanoid production by kidney cortex and medulla and segments of aorta was consistently suppressed in rats fed 'max EPA' oil. These observations correlated well with changes in the phospholipid fatty acid profiles in these tissues. This study shows rapid changes in serum fatty acids and thromboxane B2 generation following dietary manipulation, while changes in urinary excretion or prostanoid metabolites occur only after a longer time period.     

Atrial natriuretic factor alters autonomic interactions in the control of heart rate in conscious rats

Regulation of heart rate was studied in rats receiving either i.v. saline at 64 microL/min or synthetic 28-residue rat atrial natriuretic peptide (ANF) at a dose sufficient to decrease mean arterial blood pressure by 10%. Autonomic influences were deduced from steady-state heart rate responses of each group to propranolol, atropine, or propranolol and atropine combined. A multiplicative model of heart rate control was used to derive quantitatively from the data the modulation of intrinsic heart rate by sympathetic and parasympathetic mechanisms. Animals receiving ANF showed a lower heart rate than control animals. This relative bradycardia was abolished by atropine. Blocking of sympathetic effects with propranolol had no effect on basal heart rate in either group, and atropinization led to significant increases in heart rate in both groups of rats. Mathematical analysis of the results showed that the bradycardia produced by ANF was due predominantly to a reduced intrinsic heart rate and to enhanced vagal inhibition of postganglionic sympathetic activity. Parasympathetic contribution to heart rate in the absence of sympathetic activity was negligible in control rats and small during ANF. We conclude that the major influences of ANF on heart rate control are a decrease of intrinsic heart rate and enhanced parasympathetic inhibition of postganglionic presynaptic sympathetic activity.     

Evidence for two uroporphyrinogen decarboxylase isoenzymes in human erythrocytes

In animals and plants, uroporphyrinogen decarboxylase catalyzes the stepwise decarboxylations of uroporphyrinogen, the precursor of heme and chlorophyll. To better understand its metabolic roles, we characterized the enzyme purified to electrophoretic homogeneity (about 11,000-fold) from human erythrocytes by a novel uroporphyrin-sepharose affinity chromatographic method. Native polyacrylamide disc gel electrophoresis of the purified enzyme preparation showed two bands detected by staining either for protein or with uroporphyrin-I. Each individual protein eluted from the gel when subjected to re-electrophoresis on SDS-polyacrylamide gel, appeared as a single protein band with molecular masses of approximately 54,000 and approximately 35,000 daltons respectively. Both proteins were able to catalyze all four decarboxylation steps, though the ratios of enzyme activity using octa-, hepta-, hexa- to pentacarboxylic porphyrinogen substrates were distinctly different. Also, their kinetic analysis with heptacarboxylic porphyrinogen-I substrate provided distinctly different apparent Michaelis constants. This provides the first evidence that decarboxylations of uroporphyrinogen to coproporphyrinogen are catalyzed by two isoenzymes.