Synthesis and antiviral activity of 5'-deoxypyrazofurin

In searching for derivatives of pyrazofurin that could display antiviral properties by means that do not require C-5' phosphorylation, 5'-deoxypyrazofurin (3) has been synthesized in six steps from methyl5-deoxy-2,3-O-isopropylidene-beta-D-ribofuranoside (4). Compound 3 was evaluated for antiviral activity against a large number of viruses including herpes-, pox-, myxo-, toga-, arena-, rhabdo-, picorna-,reo-, and retroviruses. Compound 3 proved active against respiratory syncytial virus (in HeLa cells), vaccinia virus (in embryonic skin-muscle fibroblast cells), vesicular stomatitis virus (in HeLa cells), and influenza A virus (in Madin-Darby canine kidney cells) at concentrations (ranging from 4 to 20 micrograms/mL) that were nontoxic to the confluent host cell cultures.

Radiation pattern of a focused transducer: a numerically convergent solution

The radiation pattern of a focused transducer is reexamined. The radiation field is divided into an illuminated zone and a shadow zone. A numerically convergent solution of the pressure distribution in terms summations of Bessel functions is provided. This solution is computationally more advantageous than earlier results where a double or single integral in the complex plane is required. The pressure amplitude differs from earlier reports slightly for off-axis locations at low frequency. This difference may have significance for backscatter coefficient determination where scatterers are assumed present over a time-gated volume. The solution for a flat disk radiator is obtained as a limiting case.

Evoked ink release in Aplysia produces inhibition of the siphon withdrawal reflex in neighboring conspecifics

Aplysia californica exhibit a dramatic defensive reaction, the release of a cloud of dark purple ink, in response to noxious stimuli. Although the neural control of this behavior has been studied rather extensively, the functional significance of the inking response is not well understood. We have found that ink released by animals that are subjected to noxious stimuli rapidly induces inhibition of the tail-elicited siphon withdrawal reflex in neighboring Aplysia. Further experiments indicated that the inhibitor is the ink itself, and not some other substance released by the donor animals. Finally, we examined whether ink-induced inhibition of siphon withdrawal might be a secondary consequence of an elevated competing response such as increased locomotion. We found that locomotion is not affected by the concentrations of ink we employed, indicating that the ink probably modulates the withdrawal reflex directly. Because the neural circuits responsible for both tail-elicited siphon withdrawal and the inking response have already been partly delineated, one can now bring the neurobiological advantages of Aplysia to bear on the ethologically important issue of signaling between conspecifics.

Effects of insulin on fatty acid reesterification in healthy subjects

The effects of insulin on triacylglycerol/fatty acid cycling (fatty acid reesterification) were studied in 12 normal subjects during euglycemic hyperinsulinemia with the use of stable isotope dilution analysis ([2H5]glycerol and [1-13C]palmitate) in combination with indirect calorimetry. During basal conditions, 5.6 +/- 0.6 mumol.kg-1 x min-1 of fatty acid were released of which approximately 3.3 mumol.kg-1 x min-1 were oxidized and approximately 2.2 mumol.kg-1 x min-1 were reesterified. A minority of the recycled fatty acid, (0.8 +/- 0.4 mumol.kg-1 x min-1) never left the intracellular space before being reesterified (intracellular triacylglycerol/fatty acid cycling), whereas the majority (1.2 +/- 0.4 mumol.kg-1 x min-1) were first released into the extracellular space and then reesterified in various organs (extracellular triacylglycerol/fatty acid cycling). In response to insulin, fatty acid release declined by 71% (from 5.6 +/- 0.6 to 1.6 +/- 0.2 mumol.kg-1 x min-1). Fatty acid oxidation (measured by indirect calorimetry) declined by 55% (from 3.3 +/- 0.3 to 1.5 +/- 0.3 mumol.kg-1 x min-1) and total triacylglycerol/fatty acid cycling was completely suppressed (from 2.2 to 0.0 mumol.kg-1 x min-1). Fatty acid release, oxidation, total and extracellular triacylglycerol/fatty acid cycling all correlated positively with plasma fatty acid concentrations. These data showed that insulin profoundly suppressed fatty acid release, oxidation as well as reesterification of those fatty acids that had entered the extracellular compartment. They suggested that physiological concentrations of insulin suppressed extracellular fatty acid reesterification primarily by inhibiting lipolysis.

Computer-aided diagnosis in chest radiography. Preliminary experience

RATIONALE AND OBJECTIVES

Computer-aided diagnosis (CAD) schemes for chest radiography are being developed with which to alert radiologists to possible lesions, and thus potentially improve diagnostic accuracy. However, CAD schemes have not been tested on a large number of clinical cases. The authors identify design parameters that would be required for development of an intelligent workstation.

METHODS

Computer-aided diagnosis programs were applied for the automated detection of lung nodules, cardiomegaly, and interstitial infiltrates to 310 consecutive chest radiographs, and were analyzed for potential usefulness and limitations. Computer-aided diagnosis output was evaluated by radiologists and physicists for accuracy and technical problems, respectively.

RESULTS

Approximately 70% of the results were judged to be potentially acceptable; however, the number of false-positive findings was relatively high. Technical problems included failure to detect subtle abnormalities and the occurrence of false-positive detections caused by normal anatomical structures.

CONCLUSION

Computer-aided diagnosis has the potential to be a valuable aid to radiologists in clinical practice, if certain technical problems can be overcome and if optimal operating points can be defined for clinical use.

[Oral anticoagulation for prevention of thromboembolism in non-rheumatic atrial fibrillation: indications, effectiveness and risk]

Oral anticoagulation in patients with rheumatic heart disease for prevention of systemic thromboembolism is accepted clinical practice. The incidence of stroke in patients with nonrheumatic atrial fibrillation is about five times the rate of patients in sinus rhythm. However, contradictory findings in several small retrospective studies have precluded determination of a gold standard for patients with nonrheumatic atrial fibrillation so far. Recently, the results of five prospective, placebo-controlled studies in patients with nonrheumatic atrial fibrillation treated with anticoagulation have been published. A consistent risk reduction of thromboembolism ranging from 37 to 87% in patients treated with warfarin was reported. This risk reduction occurred in excess of a relatively low incidence of intracerebral and/or fatal bleeding complications. The efficacy of prevention of thromboembolism was comparable for high intensity anticoagulation (International Normalized Ratio (INR) 2.8-4.2) and low dose anticoagulation (INR 1.5-2.7). However, fatal and/or intracerebral bleedings only occurred with INR > or = 2.6. In subgroup analysis, recent congestive heart failure, arterial hypertension, and previous apoplex or arterial thromboembolism were independent clinical predictors of increased risk for thromboembolism, whereas results in patients with chronic and intermittent atrial fibrillation were comparable. In 69 patients with lone atrial fibrillation, no single event occurred in the follow-up period. Thus, lone atrial fibrillation does not seem to carry an increased risk for stroke when strict criteria for diagnosis of lone atrial fibrillation are applied. In two of the five studies, aspirin was additionally randomized. Since contradictory findings resulted, the role of aspirin for prophylaxis of stroke still needs to be determined.(ABSTRACT TRUNCATED AT 250 WORDS)

Expression of insulin-like growth factor-I (IGF-I) and IGF-II and the IGF-I, IGF-II, and insulin receptor genes and localization of the gene products in the human ovary

We examined the expression of the genes encoding the insulin-like growth factors (IGFs) and their receptors (r) and the localization of their gene products in specific cellular compartments of the human ovary. mRNA was localized by in situ hybridization with specific human 35S-labeled antisense RNA probes, and protein was detected by immunocytochemistry with specific antisera. We studied 34 follicles (10 ovaries), which included both dominant and small antral follicles. In dominant follicles, no IGF-I mRNA was seen in either thecal or granulosa cells (GC), but IGF-Ir mRNA was expressed in GC. In contrast, abundant IGF-II mRNA was found exclusively in GC, whereas the IGF-IIr gene was expressed in both thecal cells and GC. Insulin receptor mRNA was widely distributed and expressed in all cell types, including stromal cells. Small antral follicles contained both IGF-I and IGF-II mRNA, which was restricted to thecal cells. Although IGF-Ir message was detected only in GC, IGF-IIr mRNA was expressed in both granulosa and thecal cells. As in dominant follicles, insulin receptor mRNA was found in thecal, granulosa, and stromal cells. No IGF-I immunoreactivity was seen in either dominant or small antral follicles; however, immunostaining for the other gene products demonstrated that each of these proteins colocalized with its corresponding mRNA. Thus, the relative distribution of ligand and receptor transcripts and protein in cellular compartments of the human ovary observed in this study supports the presence of an intraovarian IGF system and suggests that both autocrine and paracrine mechanisms of IGF action occur between GC and thecal cells. We conclude that 1) IGF-II, rather than IGF-I, is the principal IGF in human ovarian follicles, being synthesized in thecal cells in small antral follicles and in GC in dominant follicles; 2) in small antral follicles, IGF-II acts in an autocrine fashion in thecal cells and in a paracrine fashion in GC; 3) in dominant follicles, granulosa-derived IGF-II acts in an autocrine manner in GC; and 4) the presence of transcripts and proteins corresponding to the IGF and insulin receptors in cellular compartments of human ovaries may also provide target sites for the action of circulating ligands with a potential extraovarian role in the regulation of folliculogenesis.

Rate-equilibria relationships in intramolecular proton transfer in human carbonic anhydrase III

Maximal turnover rates for the dehydration of HCO3- catalyzed by the zinc metalloenzyme carbonic anhydrase III are limited by a proton transfer to zinc-bound hydroxide in the active site. We have used site-directed mutagenesis to place a proton donor, histidine, at position 64 and used 18O exchange between CO2 and water measured by mass spectrometry to determine the rates of intramolecular proton transfer to the zinc-bound hydroxide. In a series of site-specific mutants, the values of pKa of the zinc-bound water ranged from approximately 5 to 9. The rate constants for proton transfer obeyed a Brønsted correlation and showed sharp curvature characteristic of facile proton transfers. Application of Marcus rate theory shows that this proton transfer has the small intrinsic energy barrier (near 1.5 kcal/mol) characteristic of rapid proton transfer between nitrogen and oxygen acids and bases, but has an observed overall energy barrier (near 10 kcal/mol), indicating the involvement of accompanying, energy requiring processes such as solvent reorganization or conformational change.

Hepatic polysomes that contain apoprotein B mRNA have unusual physical properties

To characterize the association of the mRNA for apoprotein B (apoB) with ribosomes, rat hepatic cytoplasmic extracts were fractionated by density gradient centrifugation. On linear sucrose gradients, the sedimentation velocity of the 14.4-kilobase apoB mRNA was retarded compared to the mRNAs for other hepatic proteins, which were concentrated in fractions containing the bulk of the polysomes. This unusual distribution of apoB mRNA could not be explained by cotranslational association of nascent apoB peptides with lipids, based on experiments using either detergents to delipidate proteins or puromycin to release nascent peptides from polysomes. The results were also not the result of the editing of apoB mRNA, since the sucrose gradient distributions of both edited and nonedited forms were similar. In contrast, the distribution of a 3'-truncated apoB mRNA (apoB-42, 5.8 kilobases) expressed in rat hepatoma cells resembled that of mRNA of a typical hepatic protein. As opposed to the sedimentation velocity results, on equilibrium density gradients most hepatic apoB mRNA was found in the fraction that contained polysomes. Based on these data, the elongation rate of nascent apoB, and the calculated translational yield of apoB mRNA, we conclude that the majority of rat hepatic apoB mRNA must be part of polysomal complexes with unusual physical properties related to the presence of sequence(s) in the 3'-region of the message. These sequences may either be primary determinants of structural features or binding sites for protein factors that effect conformational changes.

Comparison of intimal thickening of Chinese and New Zealand coronary arteries

Coronary arteries from forensic autopsies on 170 Chinese subjects aged 0 to 60 years were compared with those of 301 New Zealand individuals of corresponding ages to explore the reasons for the lower incidence of coronary artery disease in Chinese people. Intimal thickening progressed more rapidly in Chinese subjects up to the age of 30 years, but more slowly in the older age groups. The most striking difference was the much reduced lipid content of the intima and the better formed luminal surface of Chinese arteries of older subjects. These observations are consistent with the known dietary and plasma lipid differences between the peoples of China and the Western world, and they offer further evidence of the damaging effect of lipid and macrophages on the formation of an elastin membrane at the luminal surface of the intima subjacent to the endothelial cells.

Cooperative DNA binding of p53 with TFIID (TBP): a possible mechanism for transcriptional activation

The p53 tumor-suppressor gene product, a sequence-specific DNA-binding protein, has been shown to act both as a transcriptional activator and repressor in vivo and in vitro. Consistent with its roles in regulating transcription are recent observations that p53 binds directly to the TATA box-binding protein (TBP) subunit of the basal transcription factor TFIID. Here, we show that p53 cooperates with either recombinant TBP or partially purified TFIID in binding to a DNA fragment containing both a specific p53-binding site (RGC) and a TATA box (RGC-TATA). Surprisingly, both TBP and TFIID also stimulate p53 binding to DNA containing a specific p53-binding site but lacking a TATA box. These data are supported by the observation that p53 and Drosophila TBP combinatorily activate transcription in vivo. Our results suggest that p53 activates transcription through the formation of a more stable p53-TFIID-promoter complex. We also examined whether p53 might affect the ability of TBP or TFIID to interact with DNA containing a TATA box but lacking a p53-binding site. Although p53 strongly inhibited the interaction of TBP with such DNA, it had virtually no effect on TFIID binding. Thus, transcriptional repression by p53 may require additional functions other than inhibiting TBP binding.

Photosensitized cleavage and cross-linking of pBR322 DNA with khellin and visnagin

The naturally occurring furanochromones khellin and visnagin have received considerable attention, largely because of their vasodilatory properties and of their ability (particularly that of khellin) to induce skin pigmentation upon ultraviolet light treatment of patients suffering from vitiligo. There are conflicting statements in the literature on whether or not they are capable of cross-linking DNA photochemically. Supercoiled and linear pBR322 DNA was used to probe this reaction. The results showed that both khellin and, to a greater extent, visnagin photosensitized DNA cross-linking. In addition, both photosensitizers induced extensive DNA cleavage.

The importance of a substantial elastic lamina subjacent to the endothelium in limiting the progression of atherosclerotic changes

This study examines the hypothesis that progressive intimal thickening and atherosclerosis in the larger pulsatile arteries arise from failure to maintain, subjacent to the endothelial cells, a substantial elastin membrane, a component which has been shown to be of special structural significance. The internal thoracic arteries of 293 subjects of all ages up to 60 years were compared histologically with the anterior descending coronary arteries of the same individuals by light- and electronmicroscopy and immunoperoxidase staining for macromolecules. The internal thoracic arteries usually developed a new robust reduplicated internal elastic lamina at an early age, no further intimal thickening, and no significant entry of lipid or cells to the intima. The coronary arteries showed areas of rapid intimal thickening with poor and incomplete reduplicated internal elastic laminae, entry of lipid, macrophages, and other cells to the intima. The reduplicated internal elastic laminae appeared to be formed primarily by the endothelial cells themselves. An elastin membrane subjacent to the endothelial cells appears to be essential. It provides a secure attachment for the cells and a barrier to the entry of macromolecules and cells to the intima. Its absence is associated with progressive intimal thickening and atherosclerosis.

Initiation codon mutations in the Chlamydomonas chloroplast petD gene result in temperature-sensitive photosynthetic growth

The chloroplast petD gene encodes subunit IV of the cytochrome b6/f complex and is required for photosynthetic electron transport. We have created Chlamydomonas strains in which the initiation codon of the petD gene has been changed to AUU or AUC. These mutants can grow photosynthetically at room temperature, but not at 35 degrees C. The accumulation of subunit IV during photosynthetic or heterotrophic growth at room temperature is reduced to 10-20% of the wild-type level; petD mRNA abundance is reduced to approximately 50% of the wild-type amount. Pulse labeling experiments indicate that at room temperature, subunit IV translation proceeds at 10-20% of the wild-type rate. Cells grown heterotrophically at 35 degrees C accumulate < 5% as much subunit IV as wild-type cells grown under the same conditions, and < 1% as much subunit IV as wild-type cells grown at room temperature. We conclude that translation initiation in these mutants is inefficient, leading to decreased translation and accumulation of subunit IV. At 35 degrees C, translational inefficiency leads directly or indirectly to insufficient accumulation of subunit IV to support photosynthetic growth.

Immunosuppression in murine brucellosis

Brucellosis in mice results in a distinct immunosuppression which may be abrogated by immunomodulators, such as levamisole, bestatin, interleukin-2 (IL-2) and Polyporus umbellatus. The data presented here provide evidence that immunosuppression in addition to infection of target tissues and allergic reactions (including types 3 and 4) contributes to the pathogenesis of brucellosis. The present study also provides some basic data regarding the value of this animal model, and criteria for observing the effect of therapy on chronic brucellosis.

Neutrophil-mediated endothelial angiotensin-converting enzyme dysfunction: role of oxygen-derived free radicals

We examined the mechanisms whereby phorbol 12-myristate 13-acetate (PMA)-activated rabbit peritoneal neutrophils [polymorphonuclear leukocytes (PMN)] altered endothelial-bound angiotensin-converting enzyme (ACE) activity in cultured bovine pulmonary arterial endothelial cells (EC). PMA or PMN alone had no effect on ACE activity. When PMN were coincubated with PMA (10 ng/ml) for 4 h in Earle's salt solution, endothelial ACE activity was decreased by 87%. No EC cytotoxicity was observed at this time as determined by 51Cr release from prelabeled EC. Activated PMN-mediated decreased ACE activity was inhibited by catalase (2,000 U/ml) but not by superoxide dismutase (300 U/ml). The decrease in ACE activity was also inhibited by the hydroxyl radical scavenger dimethylthiourea (5 mM) but not mannitol (5 mM), which does not cross cell membranes. Pretreatment of EC with the iron chelator deferoxamine mesylate (1-10 mM) for 4 h attenuated the PMN-mediated decrease in ACE activity, as did the thiol reducing agent, 2-mercaptoethanol (0.1 mM), and the myeloperoxidase inhibitor, cyanide (5 mM), but not azide (1-50 mM). Treatment with the proteinase inhibitor phenylmethylsulfonyl fluoride, with human alpha-antitrypsin, or with the nitric oxide synthase inhibitor N omega-nitro-L-arginine had no effect on PMN-mediated ACE dysfunction. These results suggest that PMN-mediated ACE dysfunction may be due to the production of hydrogen peroxide by PMN and its subsequent conversion into hydroxyl radicals.

Effects of hydrogen peroxide on membrane fluidity and Ca(2+)-transporting ATPase activity of rabbit myocardial sarcoplasmic reticulum

This study was to investigate the effects of hydrogen peroxide on membrane fluidity and Ca(2+)-ATPase activity of rabbit myocardial sarcoplasmic reticulum (SR). The membrane fluidity of SR was monitored by measuring the changes in the steady state fluorescence anisotropies (rs) using diphenylhexatriene as a probe. The Ca(2+)-ATPase activity was determined by assaying the amount of inorganic phosphate (Pi) released from ATP. It was found that the membrane fluidity (rs: 0.154 +/- 0.014 vs 0.113 +/- 0.010, P < 0.01) and Ca(2+)-ATPase activity (3.1 +/- 1.3 vs 25.3 +/- 2.4 mumol Pi.h-1/mg protein, P < 0.01) were reduced in SR exposed to H2O2 (2 mmol.L-1) for 40 min. Catalase 20 micrograms.ml-1 completely prevented the SR damages caused by H2O2. H2O2 jeopardized the SR in a concentration- and time-dependent manner as measured by changes in rs values and Ca(2+)-ATPase activities, which were negatively correlated (r = 0.981, P < 0.01). These results suggest that H2O2 produces dysfunctions of the rabbit myocardial SR, and that the alteration of membrane fluidity may be one of the mechanisms responsible for the decrease of Ca(2+)-ATPase activity.

Assembly of adenovirus-specific nuclear inclusions in lytically infected HeLa cells: an ultrastructural and cytochemical study

Adenoviruses (Ads) are nuclear DNA viruses that remodel host nuclear structure and function and induce formation of a variety of nuclear inclusions within which Ad DNA is replicated and transcribed. In this study, we have examined inclusion assembly by electron microscopy of samples stained conventionally or with bismuth to detect phosphoproteins. Small dense fibrillar bodies (DFBs) appeared very early associated with interchromatin granule (ICG) clusters. Somewhat later, similar DFBs lay near amorphous, loosely fibrillar structures that were moderately electron dense and showed little bismuth deposition. These clear fibrillar bodies (CFBs) enlarged and DFBs became embedded in their surface. At later stages, CFBs and DFBs were again dissociated. DFBs seen very early were poor in phosphoproteins, but later DFBs, whether embedded in the CFBs or lying near them, were intensely bismuth stained. DFBs and CFBs were less prominent once assembled virions were seen. At this late stage, virions were generally associated with moderately dense, slightly bismuth positive, irregularly shaped fibrillar inclusions that have previously been identified as viral genome storage sites. In addition, very dense fibrillar bodies, consisting usually of an electron-dense fibrillar shell and a less dense fibrogranular core, were observed at all but the earliest stages of infection, often at some distance from CFBs. There was also a major reorganization of host components during infection, including chromatin condensation, reduction of nucleolar volume and aggregation of the fibrillar regions at the nucleolar surface, and increased prominence of ICG clusters. A model is proposed for the assembly of Ad replication factories.

Interaction and influence of phenylalanine-198 and threonine-199 on catalysis by human carbonic anhydrase III

Site-directed mutants of human carbonic anhydrase III were used to examine the role of Thr-199 and its interaction with Phe-198 in the catalyzed hydration of CO2. Threonine-199 is a hydrogen bond acceptor for the zinc-bound water, and Phe-198 forms part of the hydrophobic side of the active-site cavity of carbonic anhydrase III. Catalytic activity for a total of five single and double mutants at residues 198 and 199 was determined by stopped-flow spectrophotometry and 18O exchange between CO2 and water measured by mass spectrometry. The replacement Thr-199-->Ala resulted in a 4-fold decrease in the kcat/Km for hydration of CO2. We tested the hypothesis that the 25-fold increase in the kcat/Km for hydration of CO2 accompanying the replacement Phe-198-->Leu in isozyme III is caused by changes in the interaction of Thr-199 with the zinc-bound water or the transition state for catalysis. Comparison of hydration of CO2 by the single and double mutants of isozyme III containing the replacements Thr-199-->Ala and Phe-198-->Leu was consistent with an interaction between these two sites.

A highly sensitive probe for guanine N7 in folded structures of RNA: application to tRNA(Phe) and Tetrahymena group I intron

A nickel complex has been shown to promote conformation-specific oxidation of guanosine in polynucleotide RNA. In all cases, reaction was strictly dependent on the solvent exposure and surface properties of guanine N7. Modification of native tRNA(Phe) (yeast) was detected at G18, G19, G20, and Gm34 and concurred with predictions based on its crystal structure. Additional guanine derivatives became exposed to oxidation only after the tRNA unfolded in the absence of Mg2+. Reaction of the Tetrahymena group I intron RNA (L-21 ScaI) also compared favorably to its three-dimensional model by appropriately identifying guanosine residues in hairpin loops, duplex termini, and the essential cofactor binding site. These results complemented prior data generated by hydroxyl radical, and in combination they served to distinguish the solvent accessibility of sugar backbone and base positions in guanosine residues. Most importantly, this nickel complex exhibited greater selectivity than either dimethyl sulfate or RNase T1 for characterizing tRNA(Phe) and intron RNA.