Activation of interferon-regulated, dsRNA-dependent enzymes by human immunodeficiency virus-1 leader RNA.

Human immunodeficiency virus-1 (HIV-1) leader RNA, which contains double-stranded regions due to inverted repeats, was shown to activate the dsRNA-dependent enzymes associated with the interferon system. HIV-1 leader RNA produced in vitro using SP6 RNA polymerase was characterized using probes for antisense and sense-strand RNA. The RNA preparation was free from significant levels of antisense RNA. HIV-1 leader RNA was shown to activate dsRNA-dependent protein kinase in a cell-free system from interferon-treated HeLa cells. Affinity resins, consisting of HIV-1 leader RNA covalently attached to cellulose, immobilized and activated dsRNA-dependent protein kinase and 2-5A-synthetase. HIV-1 leader RNA, therefore, may be a contributing factor in the mechanism by which interferon inhibits HIV replication.     

Nucleotide sequence of IS492, a novel insertion sequence causing variation in extracellular polysaccharide production in the marine bacterium Pseudomonas atlantica.

The complete nucleotide sequence of insertion element IS492, which causes reversible inactivation of extracellular polysaccharide production in the marine bacterium Pseudomonas atlantica, is presented. Insertion of IS492 results in the EPS- phenotype, and excision results in restoration of EPS+. DNA sequencing of the site of insertion in the eps locus showed that insertion of IS492 generates a 5-base-pair repeat and that its excision is precise. IS492 is 1,202 nucleotides in length and contains one large open reading frame encoding a protein of 318 amino acids, a candidate for transposition function. No similarity between IS492 and other transposable elements has been found. Unlike the situation with other insertion sequences, no direct or inverted repeats exist at the termini of IS492.     

Fine needle aspiration of metastatic and hematologic malignancies clinically mimicking pancreatic carcinoma.

The fine needle aspiration (FNA) cytology findings in 19 cases of hematopoietic and metastatic neoplasms that radiographically mimicked primary pancreatic carcinoma are reported. These cases represented 11% of 176 malignant diagnoses in a series of 304 pancreatic FNAs. The cytologic diagnoses included 7 non-Hodgkin's lymphomas, 2 Hodgkin's lymphomas, 6 small cell carcinomas (4 lung, 1 gallbladder, 1 skin), 3 squamous cell carcinomas (2 cervix, 1 esophagus) and 1 hepatocellular carcinoma. In six cases the pancreatic lesion was the initial presentation of malignant disease. These included five lymphomas, which probably involved peripancreatic lymph nodes, and a metastatic small cell carcinoma of pulmonary origin. Recognition of unusual morphologic features of pancreatic carcinoma raised the possibility of extrapancreatic malignancies. Electron microscopy and immunocytochemistry performed on FNA specimens were helpful in selected cases. The FNA diagnosis of hematopoietic and metastatic neoplasms that clinically mimic pancreatic carcinoma prompts appropriate clinical studies and treatment and eliminates the need for open pancreatic biopsy and/or resection.     

Endurance-training-induced cellular adaptations in respiratory muscles

Controversy exists concerning the adaptability of mammalian respiratory muscles in response to endurance training. We examined the effects of 8 wk of progressive treadmill exercise (45 min/day 5 days/wk) on the biochemical adaptations of rat diaphragm and intercostal muscles. Female Sprague-Dawley rats were randomly assigned to a sedentary control (n = 10) or an exercise-training group (n = 10). Endurance training resulted in an enhanced oxidative capacity in the anterior costal diaphragm as evidenced by a 29% increase (P less than 0.05) in the activity of succinate dehydrogenase (SDH) in trained animals compared with controls (4.15 +/- 0.13 vs. 3.21 +/- 0.17 mumol.g-1.min-1). Similarly, SDH activity in the intercostal muscles was 32% greater (P less than 0.05) in the trained animals than in the untrained animals (1.72 +/- 0.11 vs. 1.30 +/- 0.06 mumol.g-1.min-1). In contrast, the crural region of the diaphragm showed no significant increase (P greater than 0.05) in oxidative capacity as a result of the training program (3.28 +/- 0.12 vs. 3.13 +/- 0.18). Furthermore, training did not alter (P less than 0.05) lactate dehydrogenase activity in the intercostals or in the crural or the costal diaphragm. These data demonstrate that the oxidative capacity of the costal diaphragm and the intercostal muscles can be enhanced by increasing respiratory loads via regular endurance exercise. We speculate that the lack of metabolic adaptation in the crural region of the diaphragm was not due to limited plasticity of the fibers in this area but to failure to the exercise-training program to provide the appropriate stimulus for cellular adaptation.     

Effect of N-ethylmaleimide on beef and rat liver vitamin K1 epoxide reductase

There is little difference in the extent of inactivation of beef liver microsomal vitamin K1 epoxide reductase by N-ethylmaleimide (NEM) whether or not the microsomes are pre-treated with dithiothreitol (DTT). The rat liver microsomal enzyme, however, is inactivated by NEM to a much greater extent if the microsomes are pre-treated with DTT. The beef liver enzyme activity is protected from NEM inactivation by the substrate, vitamin K1 epoxide. Ping-pong kinetics are exhibited by the beef liver enzyme. These results support a mechanism for vitamin K1 epoxide reductase in which the function of the required dithiol is to reduce an active site disulfide bond; however, the geometry of the active sites of the enzyme from rat and beef may be different.     

Effect of traY amber mutations on F-plasmid traY promoter activity in vivo.

We have examined the effect of the F plasmid TraY protein on tra gene expression in vivo. Expression was assayed as alkaline phosphatase activity in cells containing a traY phi(traA'-'phoA)hyb operon under traY promoter control. Amber mutations in traY significantly reduced alkaline phosphatase activity. Since nonsense polarity effects were minimal, if they occurred at all, these data provide the first direct evidence that TraY regulates tra gene expression.     

Effects of decreased atmospheric deposition on the sulfur budgets of two Dutch moorland pools

The chemical composition of surface waters of two Dutch moorland pools and of incident precipitation, was monitored from 1982 to 1990. For this period, sulfur and water budgets were calculated using a hydrochemical model developed for well-mixed non-stratifying lakes. Total atmospheric deposition of S decreased significantly after 1986 at both locations. A model describing the sulfur budget in terms of input, output and reduction/oxidation processes predicted a fast decrease of pool water SO₄ ²⁻ concentrations after a decrease of atmospheric input. However, SO₄ ²⁻ concentrations in the surface water was lowered only slightly or remained constant. Apparently a source within the lake caused the unexpectedly high SO₄ ²⁻ concentrations. The possible supply of SO₄ ²⁻ from the sediment through regulation by (K-)Al-SO₄ containing minerals or desorption of SO₄ ²⁻ from positively charged surfaces in the sediment was evaluated. Solubility calculations of pore water with respect to alunite, basaluminite and jurbanite indicated that SO₄ ²⁻ concentration was not regulated by these minerals. It is suggested here (1) that desorption of SO₄ ²⁻ from peaty sediments may account for the estimated SO₄ ²⁻ supply provided that the adsorption complex is periodically recharged by partial oxidation of the upper bottom sediments and (2) that because of exposure of a part of the pool bottom to the atmosphere during dry summers and subsequent oxidation of reduced S, the amount of SO₄ ²⁻ may be provided which complements the decreasing depositional SO₄ ²⁻ input. In future research these two mechanisms need to be investigated.     

Chaetomella acutiseta produces chaetomellic acids A and B which are reversible inhibitors of farnesyl-protien transferase

Chaetomellic acids A and B, isolated from Chaetomella acutiseta, are specific inhibitors of farnesyl-protein transferase that do not inhibit geranylgeranyl transferase type 1 or squalene synthase. Chaetomellic acids A and B are reversible inhibitors, resemble farnesyl diphosphate and probably inhibit FPTase by substituting for farnesyl diphosphate. Chaetomellic acid production appears to be widespread within the genus Chaetomella. Correspondence to: R. B. Lingham