Study of ultrasonic contrast agents using a dual-frequency band technique

We have developed a dual-frequency band technique to study frequency-dependent phenomena associated with ultrasonic contrast agents. Our technique uses a superimposed high-frequency (10 MHz) broad-band ultrasound (US) pulse to investigate contrast agent interaction with a low-frequency (e.g., 0.5 MHz) ultrasonic field. Our digitally controlled system has the ability to produce two colinear, confocal US pulses at different center frequencies, to adjust the relative phasing and pulse repetition frequency of each pulse, and to acquire digital backscatter data. A series of experimental studies demonstrated that the high-frequency backscatter signal responded to several phenomena induced in contrast agent particles by the low-frequency beam. These phenomena included radial pulsations, nonlinear oscillations and depletion. Initial results also demonstrated a relative phase shift between the high- and low-frequency signals; this shift is due to a difference in sound velocity at these frequencies, and it may convey information about the contrast agent concentration.

Specific phenotypic restoration of an attenuated virus by knockout of a host resistance gene

To produce disease, viruses must enter the host, multiply locally in host tissues, spread from the site of entry, and overcome or evade host immune responses. At each stage in this infectious process, specific microbial and host genes determine the ultimate virulence of the virus. Genetic approaches have identified many viral genes that play critical roles in virulence and are presumed to target specific components of the host innate and acquired immune response. However, formal proof that a virulence gene targets a specific protein in a host pathway in vivo has not been obtained. Based on cell culture studies, it has been proposed that the herpes simplex virus type 1 gene ICP34.5 (ICP, infected cell protein) enhances neurovirulence by negating antiviral functions of the IFN-inducible double-stranded RNA-dependent protein kinase R or PKR [Chou, J., Chen, J.J., Gross, M. & Roizman, B. (1995) Proc. Natl. Acad. Sci. USA 92, 10516-10520]. Herein, we show that a virus that has been attenuated by deletion of ICP34.5 exhibits wild-type replication and virulence in a host from which the PKR gene has been deleted. We show that restoration of virulence is specific to ICP34.5 and PKR by using additional host and viral mutants. The use of recombinant viruses to infect animals with null mutations in host defense genes provides a formal genetic test for identifying in vivo mechanisms and targets of microbial virulence genes.

Transcriptional control of the human plasma membrane phospholipid scramblase 1 gene is mediated by interferon-alpha

Interferons (IFNs) mediate their diverse biologic activities through induction of the expression of multiple genes. Whereas the mode of action of certain of these IFN-regulated genes has been well characterized, most of the molecular and cellular events underlying the constellation of biologic responses to the IFNs remain unresolved. This study showed that the newly identified PLSCR1 gene for phospholipid scramblase, previously implicated in remodeling of plasma membrane phospholipids, is regulated at the transcriptional level by IFN-alpha. Analysis of 5' flanking genomic sequence in reporter constructs showed that transcriptional control of PLSCR1 was entirely regulated by a single IFN-stimulated response element located in the first exon. A similar induction of PLSCR1 by IFN-alpha2a was also observed in a variety of other human tumor cell lines as well as in human umbilical vein endothelial cells. In these cell lines, the marked IFN-alpha2a-induced increase in PLSCR1 protein expression, ranging as high as 10-fold above basal levels, was not accompanied by increased cell surface exposure of phosphatidylserine, suggesting that remodeling of the cell surface requires both exposure to IFN and a second yet-to-be identified event to stimulate plasma membrane phospholipid scramblase activity and to mobilize phosphatidylserine to the cell surface. (Blood. 2000;95:2593-2599)

2-5A antisense directed against telomerase RNA produces apoptosis in ovarian cancer cells

OBJECTIVE

RNase L is converted to an active form upon binding short 2',5'-oligoadenylates (2-5A). To direct RNase L to an RNA target, 2-5A is attached to an antisense oligonucleotide (2-5A antisense). This chimera can be directed against telomerase-an RNA-protein complex that elongates telomeric DNA and is involved in cellular immortalization. Our objective is to investigate the effect of 2-5A antisense by targeting telomerase RNA (hTR) in the ovarian cancer cell line, HEY-1B.

METHODS

Baseline RNase L levels and telomerase activities were measured in both HEY-1B and normal ovarian epithelial cells (NOE). Cells were treated daily with chimeric oligonuclotides (ODN) directed against four different hTR sites, or control ODNs including nonchimeric antisense, 2-5A fused to a mismatched sequence, or inactive 2-5A fused to antisense. At 48 h, apoptosis was evaluated using the TUNEL assay. After six daily ODN administrations, telomerase activity was redetermined, and at 7 days viability counts were obtained.

RESULTS

Both cell lines expressed similar levels of RNase L. Hey-1B displayed telomerase activity while NOE did not. After 7 days of transfection, 2-5A antisense ODNs caused profound cell death in the HEY-1B cells, but not in the NOE cells. This effect was seen regardless of hTR target site, and ODN controls showed no significant decrease in cell viability in either cell line. HEY1B cells treated with 2-5A antisense against hTR showed a decrease in telomerase activity and a profound induction of programmed cell death.

CONCLUSIONS

The results suggest that 2-5A antisense directed against telomerase RNA results in apoptotic cell death in ovarian cancer cells, but not normal ovarian epithelial cells. The 2-5A antisense strategy may hold a considerable advantage over the conventional antisense approach in targeting cancer-causing genes.

Activation of p38 mitogen-activated protein kinase and c-Jun NH(2)-terminal kinase by double-stranded RNA and encephalomyocarditis virus: involvement of RNase L, protein kinase R, and alternative pathways

Double-stranded RNA (dsRNA) accumulates in virus-infected mammalian cells and signals the activation of host defense pathways of the interferon system. We describe here a novel form of dsRNA-triggered signaling that leads to the stimulation of the p38 mitogen-activated protein kinase (p38 MAPK) and the c-Jun NH(2)-terminal kinase (JNK) and of their respective activators MKK3/6 and SEK1/MKK4. The dsRNA-dependent signaling to p38 MAPK was largely intact in cells lacking both RNase L and the dsRNA-activated protein kinase (PKR), i. e., the two best-characterized mediators of dsRNA-triggered antiviral responses. In contrast, activation of both MKK4 and JNK by dsRNA was greatly reduced in cells lacking RNase L (or lacking both RNase L and PKR) but was restored in these cells when introduction of dsRNA was followed by inhibition of ongoing protein synthesis or transcription. These results are consistent with the notion that the role of RNase L and PKR in the activation of MKK4 and JNK is the elimination, via inhibition of protein synthesis, of a labile negative regulator(s) of the signaling to JNK acting upstream of SEK1/MKK4. In the course of these studies, we identified a long-sought site of RNase L-mediated cleavage in the 28S rRNA, which could cause inhibition of translation, thus allowing the activation of JNK by dsRNA. We propose that p38 MAPK is a general participant in dsRNA-triggered cellular responses, whereas the activation of JNK might be restricted to cells with reduced rates of protein synthesis. Our studies demonstrate the existence of alternative (RNase L- and PKR-independent) dsRNA-triggered signaling pathways that lead to the stimulation of stress-activated MAPKs. Activation of p38 MAPK (but not of JNK) was demonstrated in mouse fibroblasts in response to infection with encephalomyocarditis virus (ECMV), a picornavirus that replicates through a dsRNA intermediate. Fibroblasts infected with EMCV (or treated with dsRNA) produced interleukin-6, an inflammatory and pyrogenic cytokine, in a p38 MAPK-dependent fashion. These findings suggest that stress-activated MAPKs participate in mediating inflammatory and febrile responses to viral infections.

Antisense cancer therapy: the state of the science

Over the last few years, antisense technology has emerged as an exciting and promising strategy in the fight against cancer. The antisense concept is to selectively bind short, modified DNA or RNA molecules to messenger RNA in cells and prevent the synthesis of the encoded protein. As anticancer agents, these molecules can be targeted against a myriad of genes involved in cell transformation, cell survival, metastasis, and angiogenesis. Indeed, the list of possible antisense targets increases as the knowledge of the genetic basis of oncogenesis expands. One aim of this review is to focus on those antisense cancer drugs that have entered human clinical trials. At least four of these compounds are currently in phase II trials, including those targeting protein kinase C-alpha, bcl-2, c-raf, and the R1-alpha subunit of protein kinase A. A new development in antisense chemistry (peptide nucleic acids) is discussed, along with alternative antisense-related strategies (ribozymes and 2-5A-antisense) designed to overcome some of the challenges of this already encouraging technology.

The antiviral enzymes PKR and RNase L suppress gene expression from viral and non-viral based vectors

Expression of transfected genes is shown to be suppressed by two intracellular enzymes, RNase L and protein kinase PKR, which function in interferon-treated cells to restrict viral replication. RNase L(-/-) or PKR(-/-) murine embryonic fibroblasts produced enhanced levels of protein from transfected genes compared with wild-type cells. Increased expression of exogenous genes in RNase L(-/-) cells correlated with elevated levels of mRNA and thus appeared to be due to enhanced mRNA stability. Plasmid encoding adenovirus VA RNAs was able to further enhance accumulation of the exogenous gene transcript and protein, even in cells lacking PKR. In contrast to the increased expression of transfected genes in cells lacking RNase L or PKR, expression of endogenous host genes was unaffected by the absence of these enzymes. In addition, a dominant-negative PKR mutant improved expression from a conventional plasmid vector and from a Semliki Forest virus derived, self-replicating vector. These results indicate that viral infections and transfections produce similar stress responses in mammalian cells and suggest strategies for selectively increasing expression of exogenous genes.

Interferon action in triply deficient mice reveals the existence of alternative antiviral pathways

Antiviral proteins encoded by the interferon (IFN)-stimulated genes provide a front-line defense against viral infections. In particular, PKR, RNase L, and Mx are considered to be the principal proteins through which IFNs mount an antiviral state. To determine whether alternative antiviral pathways exist, RNase L-/- mice and PKR-/- mice were crossed onto an Mx1(-/-) background to generate a strain of triply deficient (TD) mice. After infections with encephalomyocarditis virus, the TD mice died 3-4 days earlier than infected, wild-type mice. However, there was an IFN dose-dependent increase in survival times after encephalomyocarditis virus infections for both the TD and wild-type mice. Mice that were deficient for PKR or RNase L showed intermediate survival times between those of the TD and wild-type mice. Surprisingly, cultured embryonic fibroblasts lacking RNase L, PKR, or both proteins were still able to mount a substantial residual antiviral response against encephalomyocarditis virus or vesicular stomatitis virus after IFN-alpha treatments. These results confirm the antiviral functions of RNase L and PKR in vivo but also provide unequivocal evidence for the existence of novel, innate immune pathways against viruses.

High-resolution ultrasonic imaging of blood flow in the anterior segment of the eye

PURPOSE

To develop a noninvasive technique to visualize and measure blood flow in the iris and ciliary body.

METHODS

Echo data from 50-MHz ultrasound scans of the iris and ciliary body of rabbits were digitized using a new "swept scan" modality. The method makes use of spatial oversampling to identify regions with scatterers whose range changes with time. The data allowed construction of high-resolution B-mode images with embedded flow information. Pulsatility over the cardiac cycle was evaluated by sending a series of pulses along a single line of sight containing a vessel of interest. Local blood flow and changes over the cardiac cycle before and after application of atropine were quantified.

RESULTS

Flow was identified in the radial vessels and major arterial circle of the iris. Vessels with lumens as small as 40 microm in diameter and flow velocities as low as 0.6 mm/sec were measured. Change in blood velocity over the cardiac cycle was determined to be approximately 27%. Peak systolic velocity after administration of topical atropine increased by 72%.

CONCLUSIONS

This technique allowed visualization of flow using the same type of very-high-frequency transducer now widely used for imaging the anterior segment. The technique can also be used at lower frequencies for more posterior tissues with similar improvement of resolution over Doppler. The ability to examine flow in the anterior segment of the eye offers a new tool for study of glaucoma, hypotony, tumors, and other disorders.

A comparison of ultrasonic beams for thermal treatment of ocular tumors

OBJECTIVE

This study examined the relative merits of different ultrasonic beams and exposure modalities for treating ocular melanomas.

METHODS

Simulations were conducted to evaluate temperature patterns and lesion shapes induced by intense-ultrasound treatment of ocular tumors. In-vitro insonification experiments were conducted in bovine lenses.

RESULTS

Simulated hyperthermia exposures did not effectively treat tumor margins because of thermal conduction into nearby fluid-like media. Standard high-intensity focused beams produced narrow lesions during 2-s exposures. A high-intensity, multi-lobed beam, produced by a transducer with strip electrodes, generated asymmetric lesions with a single large dimension; this lesion shape could expedite the production of lesion matrices within large tumors. In-vitro cataract shapes were consistent with simulation results for focused high-intensity beams.

CONCLUSIONS

Thermal conduction and perfusion can cause underheating of tumor margins during hyperthermia unless special beam designs are used. The strip-electrode transducer configuration promises to expedite treatment of extended tumor volumes.

Very high-frequency ultrasound corneal analysis identifies anatomic correlates of optical complications of lamellar refractive surgery: anatomic diagnosis in lamellar surgery

OBJECTIVE

To examine the utility of very high-frequency (VHF) ultrasound scanning in determining the anatomic changes and correlates of optical complications in lamellar refractive surgery.

STUDY DESIGN

Case series.

PARTICIPANTS

Cases analyzed included marked asymmetric astigmatism postautomated lamellar keratoplasty (ALK), image ghosting despite normal videokeratography post-ALK, uncomplicated myopic laser in situ keratomileusis (LASIK), and hyperopic LASIK with regression.

METHODS

A prototype VHF ultrasound scanner (50 MHz) was used to obtain sequences of parallel B-scans of the cornea. Digital signal processing techniques were used to measure epithelial, stromal, and flap thickness values in a grid encompassing the central 4 to 5 mm of the cornea, enabling pachymetric mapping of each layer with 2-micron precision.

MAIN OUTCOME MEASURE

The appearance of the corneas in VHF ultrasound images and thickness values of individual corneal layers determined from VHF ultrasound data.

RESULTS

VHF ultrasound resolved the epithelial, stromal cap, or flap and residual stromal layers 1 year after lamellar surgery. Asymmetric stromal tissue removal was differentiated from stromal cap irregularity. Epithelium acted to compensate for asymmetry of the stromal surface about the visual axis and for localized surface irregularities. Irregularities in the epithelial-stromal interface accounted for image ghosting present despite apparently normal videokeratography. Epithelial thickening was shown after uncomplicated myopic LASIK. Hyperopic LASIK demonstrated relative epithelial thickening localized to the region of ablation accounting for refractive regression.

CONCLUSIONS

VHF ultrasound shows promise as a sensitive method of determining the anatomic correlates of optical complications in lamellar refractive surgery.

Alternative function of a protein kinase homology domain in 2', 5'-oligoadenylate dependent RNase L

RNase L is the 2',5'-oligoadenylate (2-5A)-dependent endoribonuclease that functions in interferon action and apoptosis. One of the intriguing, albeit unexplained, features of RNase L is its significant homology to protein kinases. Despite the homology, however, no protein kinase activity was detected during activation and RNA cleavage reactions with human RNase L. Similarly, the kinase plus ribonuclease domains of RNase L produced no detectable protein kinase activity in contrast to the phosphorylation obtained with homologous domains of the related kinase and endoribonuclease, yeast IRE1p. In addition, neither ATP nor pA(2'p5'A)3was hydrolyzed by RNase L. To further investigate the function of the kinase homology in RNase L, the conserved lysine at residue 392 in protein kinase-like domain II was replaced with an arginine residue. The resulting mutant, RNase LK392R, showed >100-fold decreases in 2-5A-dependent ribonuclease activity without reducing 2-5A- or RNA-binding activities. The greatly reduced activity of RNase LK392Rwas correlated to a defect in the ability of RNase L to dimerize. These results demonstrate a critical role for lysine 392 in the activation and dimerization of RNase L, thus suggesting that these two activities are intimately linked.

Identification of genes differentially regulated by interferon alpha, beta, or gamma using oligonucleotide arrays

The pleiotropic activities of interferons (IFNs) are mediated primarily through the transcriptional regulation of many downstream effector genes. The mRNA profiles from IFN-alpha, -beta, or -gamma treatments of the human fibrosarcoma cell line, HT1080, were determined by using oligonucleotide arrays with probe sets corresponding to more than 6,800 human genes. Among these were transcripts for known IFN-stimulated genes (ISGs), the expression of which were consistent with previous studies in which the particular ISG was characterized as responsive to either Type I (alpha, beta) or Type II (gamma) IFNs, or both. Importantly, many novel IFN-stimulated genes were identified that were diverse in their known biological functions. For instance, several novel ISGs were identified that are implicated in apoptosis (including RAP46/Bag-1, phospholipid scramblase, and hypoxia inducible factor-1alpha). Furthermore, several IFN-repressed genes also were identified. These results demonstrate the usefulness of oligonucleotide arrays in monitoring mammalian gene expression on a broad and unprecedented scale. In particular, these findings provide insights into the basic mechanisms of IFN actions and ultimately may contribute to better therapeutic uses for IFNs.

2',5'-Oligoadenylate-antisense chimeras cause RNase L to selectively degrade bcr/abl mRNA in chronic myelogenous leukemia cells

We report an RNA targeting strategy, which selectively degrades bcr/abl mRNA in chronic myelogenous leukemia (CML) cells. A 2', 5'-tetraadenylate activator (2-5A) of RNase L was chemically linked to oligonucleotide antisense directed against either the fusion site or against the translation start sequence in bcr/abl mRNA. Selective degradation of the targeted RNA sequences was demonstrated in assays with purified RNase L and decreases of p210(bcr/abl) kinase activity levels were obtained in the CML cell line, K562. Furthermore, the 2-5A-antisense chimeras suppressed growth of K562, while having substantially reduced effects on the promyelocytic leukemia cell line, HL60. Findings were extended to primary CML cells isolated from bone marrow of patients. The 2-5A-antisense treatments both suppressed proliferation of the leukemia cells and selectively depleted levels of bcr/abl mRNA without affecting levels of beta-actin mRNA, determined by reverse transcriptase-polymerase chain reaction (RT-PCR). The specificity of this approach was further shown with control oligonucleotides, such as chimeras containing an inactive dimeric form of 2-5A, antisense lacking 2-5A, or chimeras with altered sequences including several mismatched nucleotides. The control oligonucleotides had either reduced or no effect on CML cell growth and bcr/abl mRNA levels. These findings show that CML cell growth can be selectively suppressed by targeting bcr/abl mRNA with 2-5A-antisense for decay by RNase L and suggest that these compounds should be further explored for their potential as ex vivo purging agents of autologous hematopoietic stem cell transplants from CML patients.

Ultrasonic evaluation of the vitreous and retina

Ultrasonic evaluation of the vitreous body augments and complements visual and clinical assessment in any condition in which some form of media opacity exists, eg, cornea, lens, hemorrhage, or subretinal mass. The appearance of the eye in hypotony, the presence of foreign material, the pattern of hemorrhage, and the presence of a detached retina or choroid are all identifiable and their diagnosis may be of critical importance to patient management. Patterns of diabetic retinopathy and ocular tumors are usually characteristic using conventional 10 MHz ultrasound. The use of Very High Frequency (VHF or UBM) ultrasound can identify ciliary body detachment or other retroiridal pathology, such as tumors and cysts.

Impact of RNase L overexpression on viral and cellular growth and death

The biologic actions of interferons (IFNs) are complex and involve multiple biochemical mechanisms, including the 2-5A system, a regulated RNA decay pathway. The 2-5A system is implicated in the antipicornavirus activity of IFN and in the control of apoptosis. To further investigate involvement of the 2-5A system in the control of viral and cellular growth and death, human RNase L cDNA was stably expressed in murine 3T3 cells from a constitutive cytomegalovirus (CMV) promoter. A clonal cell line, 3T3/pLZ, was isolated that overexpressed RNase L by >100-fold compared with levels of the endogenous murine RNase L. Interestingly, human RNase L levels in 3T3/pLZ cells decreased 3-fold as cells entered a confluent, growth arrest state, suggesting autoregulation. Overexpression of human RNase L greatly enhanced both the cell growth inhibitory activity of IFN and the proapoptotic activity of staurosporine. Furthermore, high levels of RNase L suppressed the replication of diverse viruses: encephalomyocarditis virus, vesicular stomatitis virus, human parainfluenza virus-3, and vaccinia virus. Additional reductions in viral growth were obtained by treating 3T3/pLZ cells with IFN (a + beta) before infections. These results directly demonstrate the anticellular and antiviral potential of the 2-5A system.

The Shape of Bowman's Layer in the Human Cornea

PURPOSE

The aim of this investigation was to derive a mathematical model for Bowman's layer, the interface between the epithelium and stroma, in the human cornea.

METHODS

The central epithelial thickness distribution within 14 normal human corneas was measured in vivo using high frequency ultrasonic digital signal processing with a measurement precision of 2 microns. The results per eye were averaged and incorporated into existing algorithms for the estimation of the shape of the anterior surface of Bowman's layer using terminology in accordance with Baker's equation.

RESULTS

The average radius of Bowman's layer was 7.34 mm (SE +/- 0.17 mm). Descriptions of this boundary ranged from a steepening or prolate ellipse to a hyperbola. However, the typical Bowman's layer is hyperbolic with a shape factor, p = -0.22 (SE +/- 1.81).

CONCLUSION

The results support previous cadaver studies where Bowman's layer was found to be steeper than the anterior corneal surface but disagree with the concept that the average Bowman's layer is akin to a prolate ellipse. The hyperbolic nature of the average Bowman's layer has the potential to influence the optical performance of the eye.

Advances in ophthalmic ultrasound

New ultrasound technologies, including three-dimensional imaging, tissue characterization, and very high frequency (50 MHz) ultrasound, have become available recently. We demonstrate how these technologies can be used alone and together to improve the use of ultrasound for diagnosis of ocular pathology.

How cells respond to interferons

Interferons play key roles in mediating antiviral and antigrowth responses and in modulating immune response. The main signaling pathways are rapid and direct. They involve tyrosine phosphorylation and activation of signal transducers and activators of transcription factors by Janus tyrosine kinases at the cell membrane, followed by release of signal transducers and activators of transcription and their migration to the nucleus, where they induce the expression of the many gene products that determine the responses. Ancillary pathways are also activated by the interferons, but their effects on cell physiology are less clear. The Janus kinases and signal transducers and activators of transcription, and many of the interferon-induced proteins, play important alternative roles in cells, raising interesting questions as to how the responses to the interferons intersect with more general aspects of cellular physiology and how the specificity of cytokine responses is maintained.

The vaccinia virus A18R DNA helicase is a postreplicative negative transcription elongation factor

Loss of vaccinia virus A18R gene function results in an aberrant transcription profile termed promiscuous transcription, defined as transcription within regions of the genome which are normally transcriptionally silent late during infection. Promiscuous transcription results in an increase in the intracellular concentration of double-stranded RNA, which in turn results in activation of the cellular 2-5A pathway and subsequent RNase L-catalyzed degradation of viral and cellular RNAs. One of three hypotheses could account for promiscuous transcription: (i) reactivation of early promoters late during infection, (ii) random transcription initiation, (iii) readthrough transcription from upstream promoters. Transcriptional analysis of several viral genes, presented here, argues strongly against the first two hypotheses. We have tested the readthrough hypothesis by conducting a detailed transcriptional analysis of a region of the vaccinia virus genome which contains three early genes (M1L, M2L, and K1L) positioned directly downstream of the intermediate gene, K2L. The results show that mutation of the A18R gene results in increased readthrough transcription of the M1L gene originating from the K2L intermediate promoter. A18R mutant infection of RNase L knockout mouse fibroblast (KO3) cells does not result in 2-5A pathway activation, yet the virus mutant is defective in late viral gene expression and remains temperature sensitive. These results demonstrate that the A18R gene product is a negative transcription elongation factor for postreplicative viral genes.

Targeted therapy of human malignant glioma in a mouse model by 2-5A antisense directed against telomerase RNA

Telomerase is the RNA-protein complex which elongates telomeric DNA (TTAGGG)n and appears to play an important role in cellular immortalization. The almost exclusive expression of telomerase in tumor cells, and not in most normal cells, offers an exciting opportunity for therapy by inhibiting its function. Here, we have investigated the effect of inhibition of telomerase on the growth and survival of human malignant glioma cells in vitro and in vivo by using a 19-mer antisense oligonucleotide against human telomerase RNA linked to a 2',5'-oligoadenylate (2-5A). 2-5A antisense functions by activating the endoribonuclease, RNase L, resulting in the degradation of single stranded, targeted RNA. We have shown that the 2-5A antisense treatment effectively suppressed tumor cell growth and survival in vitro. Furthermore, treatment of tumors grown in nude mice with the antisense oligonucleotide inhibited survival of the tumor cells. TUNEL assays suggest that this effect is mediated through the induction of apoptosis. Targeting telomerase RNA with 2-5A antisense, therefore, may represent an effective and novel approach for treatment of a broad range of cancers.

Targeting RNase L to human immunodeficiency virus RNA with 2-5A-antisense

In an attempt to develop a lead for the application of 2-5A-antisense to the targeted destruction of human immunodeficiency virus (HIV) RNA, specific target sequences within the HIV mRNAs were identified by analysis of the theoretical secondary structure. 2-5A-antisense chimeras were chosen against a total of 11 different sequences: three in the gag mRNA, three in the rev mRNA and five in the tat mRNA. 2-5A-antisense chimera synthesis was accomplished using solid-phase phosphoramidite chemistry. These chimeras were evaluated for their activity in a cell-free assay system using purified recombinant human RNase L to effect cleavage of 32P-labelled RNA transcripts of plasmids derived from HIV NL4-3. This screening revealed that of the three 2-5A-antisense chimeras targeted against gag mRNA, only one had significant HIV RNA cleavage activity, approximately 10-fold-reduced compared to the parent 2-5A tetramer and comparable to that reported for the prototypical 2-5A-anti-PKR chimera, targeted against PKR mRNA. The cleavage activity of this chimera was specific, since a scrambled antisense domain chimera and a chimera without the key 5'-monophosphate moiety were both inactive. The 10 other 2-5A-antisense chimeras against tat and rev had significantly less activity. These results imply that HIV gag RNA, like PKR RNA and a model HIV tat-oligoA-vif RNA, can be cleaved using the 2-5A-antisense approach. The results further imply that not all regions of a potential RNA target are accessible to the 2-5A-antisense approach.

Very high frequency ultrasound analysis of a new phakic posterior chamber intraocular lens in situ

PURPOSE

To use very high frequency ultrasound scanning for in situ analysis of a new phakic posterior chamber intraocular lens (No-Touch; International Visions Inc, Cincinnati, Ohio).

METHODS

In this pilot study, very high frequency ultrasound (50 MHz) wide-angle (15 mm) full anterior segment scans were obtained in two patients who had undergone phakic posterior chamber intraocular lens implantation into legally blind eyes with normal anterior segment anatomy.

RESULTS

Very high frequency ultrasound B-scan images delineated the phakic posterior chamber intraocular lens within the posterior chamber. The relations to the sulci were clearly imaged. Anatomic relations of the phakic posterior chamber intraocular lens optic and haptics were visualized in both static (light/dark) and kinetic (distance/accommodative) states.

CONCLUSION

Very high frequency ultrasound wide-angle scanning provides a unique tool to noninvasively evaluate the eye preoperatively and the static and kinetic relations of this new refractive device within the posterior chamber.

Correlation of high-frequency ultrasound backscatter with tumor microstructure in iris melanoma

OBJECTIVE

This study aimed to correlate histologic characteristics with high-frequency ultrasound backscatter spectra in malignant melanomas of the iris.

DESIGN

The study design was a cohort (case series) study of patients diagnosed with iris melanoma in the authors' clinic.

PARTICIPANTS

Sixteen patients with iris melanoma participated.

INTERVENTION

The patients were scanned with a 50-MHz ultrasound unit equipped for digitization of raw echo data. Spectral parameter images representing the spatial distribution of size and concentration of tissue inhomogeneities were produced.

MAIN OUTCOME MEASURES

The variation of spectral properties within and between tumors was determined. In the two tumors in this series for which histologic material was available, the authors compared scatterer concentration and size with histology and mathematically modeled the effect of melanocyte distribution on spectra.

RESULTS

Ultrasound scattering characteristics differed considerably among tumors. Where histology was available, acoustic parameters correlated with the size and number of melanocytes present.

CONCLUSIONS

Iris melanomas exhibited a wide range in acoustic backscatter properties. Whereas characteristics such as vascularity and necrosis might contribute to this, in the two cases examined here, backscatter characteristics could be largely accounted for by melanocyte distribution. A better understanding of the relationship of histology to noninvasive ultrasound data will enhance the diagnostic utility of this technique.

Nuclease-resistant composite 2',5'-oligoadenylate-3', 5'-oligonucleotides for the targeted destruction of RNA: 2-5A-iso-antisense

A new modification of 2-5A-antisense, 2-5A-iso-antisense, has been developed based on a reversal of the direction of the polarity of the antisense domain of a 2-5A-antisense composite nucleic acid. This modification was able to anneal with its target RNA as well as the parental 2-5A-antisense chimera. The 2-5A-iso-antisense oligonucleotide displayed enhanced resistance to degradation by 3'-exonuclease enzyme activity such as that represented by snake venom phosphodiesterase and by that found in human serum. 2-5A-Iso-antisense was able to effect the degradation of a synthetic nontargeted substrate, [5'-32P]pC11U2C7, and two targeted RNAs, PKR and BCR mRNAs, in a cell-free system containing purified recombinant human 2-5A-dependent RNase L. These results demonstrated that the novel structural modification represented by 2-5A-iso-antisense provided a stabilized biologically active formulation of the 2-5A-antisense strategy.

The role of 2'-5' oligoadenylate-activated ribonuclease L in apoptosis

Apoptosis of viral infected cells appears to be one defense strategy to limit viral infection. Interferon can also confer viral resistance by the induction of the 2-5A system comprised of 2'-5' oligoadenylate synthetase (OAS), and RNase L. Since rRNA is degraded upon activation of RNase L and during apoptosis and since both of these processes serve antiviral functions, we examined the role RNase L may play in cell death. Inhibition of RNase L activity, by transfection with a dominant negative mutant, blocked staurosporine-induced apoptosis of NIH3T3 cells and SV40-transformed BALB/c cells. In addition, K562 cell lines expressing inactive RNase L were more resistant to apoptosis induced by decreased glutathione levels. Hydrogen peroxide-induced death of NIH3T3 cells did not occur by apoptosis and was not dependent upon active RNAse L. Apoptosis regulatory proteins of the Bcl-2 family did not exhibit altered expression levels in the absence of RNase L activity. RNase L is required for certain pathways of cell death and may help mediate viral-induced apoptosis.

RNase L dimerization in a mammalian two-hybrid system in response to 2',5'-oligoadenylates

RNase L, a key enzyme in the anti-viral activity of interferons, requires activation by 2',5'-linked oligoadenylates (2-5A) to cleave viral and cellular single-stranded RNA. Here we demonstrate that 2-5A causes formation of stable dimers of RNase L in intact human cells as measured with a mammalian two-hybrid system. Hybrid proteins consisting of the GAL4 DNA binding domain fused to RNase L and the VP16 transactivation domain fused to RNase L were able to associate and drive transcription of a reporter gene, but only after cells were transfected with 2-5A. Several functional forms of 2-5A, such as p3A2'p5'A2'p5'A, were capable of activating transcription in human HeLa cells. In contrast, p3A2'p5'A, which can neither activate nor dimerize RNase L, did not induce gene expression. Evidence for the involvement of the C-terminal region of RNase L in dimerization was obtained by expressing truncated forms of RNase L. These findings describe a convenient, high-throughput screening method for RNase L activators which could lead to the discovery of novel anti-viral and anti-cancer agents.

Progress in interferon and cytokine biology

The 15th Annual Meeting of the International Society for Interferon and Cytokine Research was held on October 19-24, 1997, at the Sheraton San Diego Hotel and Marina. In this meeting Bryan Williams and Robert Silverman review the scientific highlights of the proceedings. Interferon regulatory factors (IRFs) were among the major topics discussed at this meeting. Fortunately, the scientific program of the meeting, organized by Tom Cesario (U.C., Irvine), was sufficiently interesting to hold cytokine biologists in darkened halls away from the splendid marina and sunny San Diego skies.

Imaging and spectrum analysis of contrast agents in the in vivo rabbit eye using very-high-frequency ultrasound

We have conducted initial studies that demonstrated the feasibility of employing ultrasonic contrast agents with very-high-frequency ultrasound (VHFU), using wideband transducers with center frequencies near 40 MHz. These studies were undertaken with an ultimate objective of quantifying perfusion in vessels in the eye and other organs. We expanded the model developed by Lizzi et al. (1983) to incorporate the scattering characteristics from encapsulated bubbles, such as contrast agents. Our analysis shows how the spectral slopes and intercepts measured from contrast agents are related to factors that include the radii and concentration of contrast-agent particles. We conducted in vitro experiments to validate the theoretical predictions and obtained excellent agreement. We obtained in vivo VHFU data from the eyes of anesthetized rabbits before and after injection of Albunex and Aerosomes. Digitally computed B-mode images demonstrated echo enhancement within the ciliary body and its processes. The magnitudes of these enhancements were quantified using calibrated spectrum-analysis techniques.

Regulation of human immunodeficiency virus replication by 2',5'-oligoadenylate-dependent RNase L

Activation of RNase L by 2',5'-linked oligoadenylates (2-5A) is one of the antiviral pathways of interferon action. To determine the involvement of the 2-5A system in the control of human immunodeficiency virus type 1 (HIV-1) replication, a segment of the HIV-1 nef gene was replaced with human RNase L cDNA. HIV-1 provirus containing sense orientation RNase L cDNA caused increased expression of RNase L and 500- to 1,000-fold inhibition of virus replication in Jurkat cells for a period of about 2 weeks. Subsequently, a partial deletion of the RNase L cDNA which coincided with increases in virus production occurred. The anti-HIV activity of RNase L correlated with decreases in HIV-1 RNA and with an acceleration in cell death accompanied by DNA fragmentation. Replication of HIV-1 encoding RNase L was also transiently suppressed in peripheral blood lymphocytes (PBL). In contrast, recombinant HIV containing reverse orientation RNase L cDNA caused decreased levels of RNase L, increases in HIV yields, and reductions in the anti-HIV effect of alpha interferon in PBL and in Jurkat cells. To obtain constitutive and continuous expression of RNase L cDNA, Jurkat cells were cotransfected with HIV-1 proviral DNA and with plasmid containing a cytomegalovirus promoter driving expression of RNase L cDNA. The RNase L plasmid suppressed HIV-1 replication by eightfold, while an antisense RNase L construct enhanced virus production by twofold. These findings demonstrate that RNase L can severely impair HIV replication and suggest involvement of the 2-5A system in the anti-HIV effect of alpha interferon.

Three-dimensional ultrasound imaging. Clinical applications

OBJECTIVE

The aim of this report is to describe the technology of three-dimensional (3-D) ultrasonic imaging and its impact on improved diagnosis and monitoring of ocular disease.

DESIGN

The authors reviewed techniques for acquiring and displaying 3-D ultrasound data of the eye.

PARTICIPANTS

The authors applied these techniques to representative individual cases, including a choroidal hemorrhage, a ciliary body melanoma, a ciliary body detachment, a displaced posterior chamber intraocular lens, and topographic analysis of a normal cornea.

INTERVENTION

A computer-controlled motion system was used to perform very high-frequency (VHF) (50-MHz) and conventional (10-MHz) digital 3-D ultrasound data collection. The scanning system allowed digitization of ultrasound data from a series of parallel planes. The 3-D data could be manipulated interactively to obtain two-dimensional images in any plane through the scan volume. The 3-D images were constructed by volume rendering and could be positioned for viewing from a variety of perspectives. The 3-D ultrasound parameter images representing acoustic scatterer properties were generated by spectrum analysis of digitized echo data. Color maps representing the contour and thickness of the epithelium and stroma of the central corneal were generated by digital signal processing of 3-D echo data.

RESULTS

Quantitative volume measurement and biometric techniques enhanced the diagnostic and treatment planning information content in 3-D ultrasound images. The location and extent of hemorrhage and clots within the suprachoroidal space were shown with solid modeling. Volume changes in ciliary body melanoma over time were documented and 3-D ultrasound parameter image changes associated with radiation therapy observed. In ciliary body detachment, the extent of the detachment was shown. Solid modeling of a posterior chamber intraocular lens showed misplacement of the haptic in relation to the lens capsule remnants. Keratopachymetric maps showed the range and variance of thickness and local radius of curvature measurements in the cornea.

CONCLUSIONS

Quantitative volume measurement and biometric tools combined with segmentation of 3-D ultrasound images improve diagnostic and treatment planning informational content of 3-D ultrasound images through improved localization of tissue structures.

A swept-scanning mode for estimation of blood velocity in the microvasculature

In contrast to previous systems in which an ultrasonic pulse was repeatedly directed to a discrete line of sight, a new method has been developed to continuously scan over a region in order to rapidly assess blood velocities in superficial small blood vessels. Using this technique, which we call swept-scan, a high frequency transducer can rapidly translate across a region of interest, and sensitive maps of blood velocity in small blood vessels can be constructed. This system has been applied to flow mapping in the anterior segment of the eye, which is clinically significant in cases of trauma and glaucoma. No previous imaging technique has been capable of estimating blood velocities within this region in a clinically useful manner. With this new technique, each 2-D scan of the eye can be obtained in an interval on the order of 1 second, and blood flow through the iris and ciliary body can be detected in vessels as small as 40 microns. A major implication of this new technique is that a wall filter can be applied continuously to the return from all regions, thus eliminating the transient response that occurs along each line of sight in traditional Doppler systems.

Interferon action and apoptosis are defective in mice devoid of 2',5'-oligoadenylate-dependent RNase L

2',5'-Oligoadenylate-dependent RNase L functions in the interferon-inducible, RNA decay pathway known as the 2-5A system. To determine the physiological roles of the 2-5A system, mice were generated with a targeted disruption of the RNase L gene. The antiviral effect of interferon alpha was impaired in RNase L-/- mice providing the first evidence that the 2-5A system functions as an antiviral pathway in animals. In addition, remarkably enlarged thymuses in the RNase L-/- mice resulted from a suppression of apoptosis. There was a 2-fold decrease in apoptosis in vivo in the thymuses and spleens of RNase L-/- mice. Furthermore, apoptosis was substantially suppressed in RNase L-/- thymocytes and fibroblasts treated with different apoptotic agents. These results suggest that both interferon action and apoptosis can be controlled at the level of RNA stability by RNase L. Another implication is that the 2-5A system is likely to contribute to the antiviral activity of interferon by inducing apoptosis of infected cells.

A bipartite model of 2-5A-dependent RNase L

The 2-5A-dependent RNase (RNase L) is a tightly regulated endoribonuclease of higher vertebrates that is catalytically active only after engaging unusual effector molecules consisting of the 2',5'-linked oligoadenylates, p1-3A(2'p5'A)>/=2 (2-5A). Progressive truncations from either terminus have provided insight into the structure, function, and regulation of RNase L. We determined that deletion of the N-terminal 335 amino acids of RNase L, about 45% of the enzyme, produced a constitutively active endoribonuclease, thus effectively eliminating the requirement for 2-5A. The truncated nuclease had 6-fold lower catalytic activity against an oligo(rU) substrate than wild type RNase L. However, the two enzymes showed identical RNA cleavage site preferences with an mRNA as substrate. The repressor function required only the last three of a series of nine ankyrin-like repeats present in the N-terminal part of RNase L. In contrast, the entire ankyrin repeat region was necessary and sufficient for 2-5A binding activity. Deletion of a 10-amino acid sequence near the C terminus of RNase L, between residues 710 and 720, eliminated both the catalytic and RNA substrate binding functions of the enzyme. The ability to bind native RNase L in response to 2-5A required amino acid sequences near both termini of the protein. A bipartite model for the structure of RNase L emerged in which the regulatory functions of the molecule are located in the N-terminal half, while the catalytic domain is present in the C-terminal half.

Correlation of selective modifications to a 2',5'-oligoadenylate-3',5'-deoxyribonucleotide antisense chimera with affinity for the target nucleic acid and with ability to activate RNase L

The use of an antisense oligonucleotide to address a specific targeted RNA sequence and subsequent localized activation of the 2-5A-dependent RNase (RNase L) to effect selective RNA degradation is a new approach to the control of gene expression called 2-5A-antisense. The previously reported biological activity of the 2-5A:AS chimeric oligonucleotide [p5'(A2'p)3A-antiPKR1], directed against nucleotides 55-73 of the coding sequence of the PKR mRNA, has been used as a point of reference to examine the effect of introducing mismatches into the chimeric oligonucleotide, altering the chain length of the antisense domain of the chimeras, removal of the 5'-monophosphate moiety, shortening the 2',5'-oligoadenylate domain, and substitution of 3',5'-linked 2'-deoxyadenosine nucleotides for the 2-5A domain. The general formula for the novel chimeric oligonucleotides is p5'(A2'p)3A2'p(CH2)4p(CH2)4p(5'N3'p)mN, where N is any nucleoside and m is any integer. When the biological activity of these new chimeric oligonucleotides was compared to that of the parent chimera, 2-5A-aPKR, for their ability to effect target PKR RNA cleavage in a cell-free and in an intact cell assay, it was determined that there was a close correlation between the activity of 2-5A-antisense chimeras and their affinity (Tm) for a targeted nucleic acid. In addition, there was also a close correlation between activity of the 2-5A-antisense chimeras and their ability to activate the 2-5A-dependent RNase L.

Targeting RNA decay with 2',5' oligoadenylate-antisense in respiratory syncytial virus-infected cells

Treatment of human cells with 2',5' oligoadenylate covalently linked to antisense (2-5A-antisense) results in the selective cleavage of targeted RNA species by 2-5A-dependent RNase L. Here we show that 2-5A-antisense containing stabilizing modifications at both termini are effective in suppressing the replication of respiratory syncytial virus (RSV) in human tracheal epithelial cells. The affinity of 2-5A-antisense for different regions in the RSV M2 and L mRNAs was predicted from a computer-generated model of the RNA secondary structure. The most potent 2-5A-antisense molecule caused a highly effective, dose-dependent suppression of RSV yields when added to previously infected cells. In contrast, control oligonucleotides, including an inactive dimeric form of 2-5A linked to antisense, 2-5A linked to a randomized sequence of nucleotides, and antisense molecules lacking 2-5A, had minimal effects on virus replication. The specificity of this approach was shown by reverse transcriptase-coupled PCR analysis of RSV M2, P, and N mRNA and of cellular glyceraldehyde-3-phosphate dehydrogenase mRNA. The RSV M2 mRNA amounts were depleted after treating RSV-infected cells with 2-5A-antisense targeted to this mRNA, whereas the amounts of the other RNA species were unchanged. These studies demonstrate that 2',5' oligoadenylate covalently linked to antisense (2-5A-antisense) can effectively suppress RSV replication by directing the cellular RNase L to selectively degrade an essential viral mRNA.

Improved system for sonographic imaging and biometry of the cornea

We developed a programmable motion system for high-frequency (50 MHz) ultrasonographic imaging of the cornea. The system permits a variety of scanning modes, including arc scans matched to the approximate radius of curvature of the cornea. This approach allows high-precision biometry (+ or - 2 microm) over a much larger region of the cornea than the 3 mm central zone obtainable with conventional rectilinear scanning. Using 60 degree wide meridional arc scans covering each clock-hour of a rabbit cornea, we obtained data over an 8 mm wide central zone and produced maps representing the thickness of the corneal epithelium.

Ophthalmic, ultrasonographic findings in primary central nervous system lymphoma with ocular involvement

PURPOSE

To describe and classify ophthalmic, ultrasonographic findings in patients with primary central nervous system lymphoma with ocular involvement.

METHODS

B- and A-scan ultrasonography was performed on the eyes of 13 patients with primary central nervous system lymphoma with ocular involvement.

RESULTS

In seven patients, the eyes were the site of initial involvement. In the other six patients, both ocular and central nervous system disease were present at the initial evaluation. All patients had abnormal ultrasonographic findings. The most common were vitreous debris (n = 10), choroidal-scleral thickening (n = 6), and widening of the optic nerve (n = 4). Elevated chorioretinal lesions (n = 3) and retinal detachment (n = 2) were also found.

CONCLUSION

Ophthalmic ultrasonography is a useful adjunctive diagnostic technique for characterizing ocular involvement in lymphoma. Ocular lymphoma may present as chorioretinitis, vitreitis and nonspecific uveitis; it produces characteristic, but nonspecific findings on ultrasonography. The diagnosis of ocular involvement is an important factor in determining treatment.

Correlation of ultrasound parameter imaging with microcirculatory patterns in uveal melanomas

Previous studies demonstrated a correlation between acoustic backscatter parameters and survival in ocular melanoma. The histologic presence of microvascular networks in ocular melanoma is also associated with death from metastases. This study tests the hypothesis that melanomas grouped on the basis of these microvascular patterns are separable by ultrasound spectrum analysis. We scanned 40 melanomas using a 10-MHz ultrasound unit equipped for digitization of radio frequency data. After enucleation, tumors were sectioned in planes corresponding to the ultrasonographic examination and stained to demonstrate microcirculation. Acoustic spectral parameters were compared between 14 melanomas with a nevuslike microcirculation and 26 with foci of high-risk microvascular structures. Smaller scatterer size, lower acoustic concentration and greater spatial variability were found to correlate with high-risk microvascular patterns and areas of cystic degeneration. We suggest that nonvascular extracellular matrix components associated with microvessels may be responsible for the correlation of acoustic parameters with microvascular pattern and distribution.

Ultrasonically induced hyperthermia for adjunctive treatment of intraocular malignant melanoma

PURPOSE

This report describes results of a prospective pilot trial to evaluate the safety and efficacy of hyperthermia as an adjunct to enucleation or brachytherapy in the treatment of patients with intraocular malignant melanoma.

METHODS

Twenty-five patients with intraocular malignant melanomas were treated with ultrasonically induced hyperthermia. In 14 patients, hyperthermia was administered before enucleation (median follow-up period, 44 months), and in 11 patients, hyperthermia was used as an adjunct to brachytherapy (median follow-up period, 79 months).

RESULTS

Patient survival in each group was compared with that of a control group treated with enucleation or brachytherapy alone, using Kaplan-Meier and Cox analysis. Taking into account the simultaneous effects of tumor size and location, the relative risk ratios and 95% confidence bounds associated with adjunctive hyperthermia were 1.68 (range, 0.60-4.72) and 0.68 (range, 0.16-2.89) for the enucleation and brachytherapy groups, respectively.

CONCLUSIONS

Patients receiving adjunctive hyperthermia with brachytherapy showed increased survival, whereas those receiving hyperthermia before enucleation showed decreased survival. Neither trend was statistically significant in this small series. The synergism of hyperthermia with radiation may offer the possibility of improved tumor management.

Iridoschisis: high frequency ultrasound imaging. Evidence for a genetic defect?

AIMS

To elucidate changes in the anatomy of the anterior chamber associated with iridoschisis, a rare form of iris atrophy, and their potential contribution to angle closure glaucoma.

METHODS

Both eyes of a 71-year-old woman with bilateral iridoschisis and fibrous dysplasia and her asymptomatic 50-year-old daughter were scanned with a very high frequency (50 MHz) ultrasound system.

RESULTS

The symptomatic patient exhibited diffuse changes in the iris stoma with an intact posterior iris pigmented layer in both eyes. These changes were clinically compatible with the lack of iris transillumination defects. Additionally, iris bowing with a resultant narrowing of the angle occurred. The asymptomatic daughter showed discrete, but less severe iris stromal changes.

CONCLUSION

This is the first detailed study of high frequency ultrasonic imaging of the iris in iridoschisis. The observed structural changes suggest angle narrowing by forward bowing of the anterior iris stroma may be a mechanism of IOP elevation in this condition. The ultrasonic detection of iris changes in the asymptomatic daughter of the symptomatic patient and the association of iridoschisis with fibrous dysplasia suggest a possible genetic component in the pathogenesis of this condition.

A mammalian 2-5A system functions as an antiviral pathway in transgenic plants

Resistance to virus infections in higher vertebrates is mediated in part through catalysis of RNA decay by the, interferon-regulated 2-5A system. A functional 2-5A system requires two enzymes, a 2-5A synthetase that produces 5'-phosphorylated, 2',5'-linked oligoadenylates (2-5A) in response to double-stranded RNA, and the 2-5A-dependent RNase L. We have coexpressed these human enzymes in transgenic tobacco plants by using a single plasmid containing the cDNAs for both human RNase L and a low molecular weight form of human 2-5A synthetase under control of different, constitutive promoters. Expression of the human cDNAs in the transgenic plants was demonstrated from Northern blots, by specific enzyme assays, and by immunodetection (for RNase L). Infection of leaves, detached or in planta, of the coexpressing transgenic plants by tobacco mosaic virus, alfalfa [correction of alfafa] mosaic virus, or tobacco etch virus resulted in necrotic lesions. In contrast, leaves expressing 2-5A synthetase or RNase L alone and leaves containing the plasmid vector alone produced typical systemic infections. While alfalfa mosaic virus produced lesions only in the inoculated leaves regardless of the concentration of virus in the inoculum, high, but not low, levels of tobacco etch virus inoculum resulted in escape of virus to uninoculated leaves. Nevertheless, there was a substantial reduction of tobacco etch virus yield as measured by ELISA assay in the coexpressing transgenic plants. These results indicate that expression of a mammalian 2-5A system in plants provides resistance to virus infections.

Elevated levels of 2',5'-linked oligoadenylate-dependent ribonuclease L occur as an early event in colorectal tumorigenesis

RNA decay in IFN-treated cells is controlled by 2'5'-linked oligoadenylate (2-5A)-dependent RNase (RNase L), a uniquely regulated endoribonuclease that requires short 5'-phosphorylated, 2-5A for its activity. Because RNase L is also implicated in the regulation of cell proliferation, we monitored its expression in colorectal adenocarcinomas and noncancerous polyps from familial adenomatous polyposis patients. Elevated levels of RNase L mRNA and activity were found in 17 of 20 tumors compared with corresponding normal mucosa. An mAb against RNase L revealed elevated amounts of this RNase in sections of the tumors, largely in the base of the villi. The occurrence of elevated levels of RNase L seems to be an early event in colorectal tumorigenesis, suggesting that control of RNA turnover is an important step in tumor progression. These data also indicate that regulating RNase L activity may be a useful strategy in treating colorectal carcinomas.

Respiratory syncytial virus induces interleukin-10 by human alveolar macrophages. Suppression of early cytokine production and implications for incomplete immunity

Respiratory syncytial virus (RSV) causes repeated infections thought to be due to an ineffective immune response. We examined the hypothesis that incomplete immunity may result, in part, from RSV-infected alveolar macrophage production of IL-10 which can interfere with the production of immunoregulatory cytokines. We also assessed whether RSV induced the expression of the 2',5' oligoadenylate (2-5A)-dependent RNase L, an endoribonuclease involved in the antiviral activities of interferons. Human alveolar macrophages were exposed to medium (uninfected control), RSV, LPS, and RSV + LPS then were assessed for expression of the cytokines TNF-alpha, IL-1 beta, IL-8, IL-10, as well as 2-5A-dependent RNase L. LPS up-regulated the expression of protein and mRNA for all cytokines. RSV stimulated the protein levels of TNF-alpha, did not alter IL-1 beta, and decreased IL-8. RSV markedly stimulated protein expression of IL-10 and 2-5A-dependent RNase L. RSV had minor effects on the steady state mRNA levels of TNF-alpha, IL-1 beta, and IL-8, yet potently induced IL-10. Cells costimulated with RSV + LPS demonstrated reduced protein and mRNA levels of TNF-alpha, IL-1 beta, IL-8 but synergistically increased IL-10 levels compared to RSV- or LPS-activated cells. Kinetic analysis indicated that RSV induced a delayed and sustained increase in IL-10 transcripts. Furthermore, RSV-infected alveolar macrophage supernatants suppressed IL-1 beta and IL-8 production by LPS-stimulated alveolar macrophages as did recombinant IL-10. Anti-IL-10 neutralized these effects. These studies indicate that RSV is capable of suppressing production of early immunoregulatory cytokines through induction of IL-10 perhaps mediated by 2-5A-dependent RNase L (or other endoribonucleases) accounting for the ineffective immune response to this virus.

High frequency ultrasound imaging in pupillary block glaucoma

BACKGROUND

The diagnosis of pupillary block glaucoma requires sufficient clarity of the ocular media. This is particularly important for assessment of both the presence and patency of an iridotomy, and the determination of central anterior chamber depth.

METHODS

High frequency ultrasonography was used in three patients with suspected pupillary block to determine iris configuration, posterior chamber volume, and ciliary body conformation.

RESULTS

All patients demonstrated high frequency ultrasonographic findings consistent with pupillary block: iris bombé, a formed posterior chamber, and a lack of anterior rotation of the ciliary processes.

CONCLUSION

High frequency ultrasound imaging appears to be a valuable adjunct in making or corroborating the diagnosis of pupillary block glaucoma.

Synthesis and biological activities of a phosphorodithioate analog of 2',5'-oligoadenylate

To enhance the resistance of 2-5A (pppA2'p5'A2'p5'A) to degradation by exo- and endonucleases, a phosphorodithioate analog was synthesized using a solid-phase phosphite triester approach with N6-benzoyl-5'-O-dimethoxytrityl-3'-O-t-butyldimethylsilyladenosine 2'-[S-(beta-thiobenzoylethyl)-pyrrolidinophosphorothioamidit e]. 5'-Monophosphorylation was accomplished with 2-[2-(4,4'-dimethoxytrityloxy)-ethylsulfonyl]ethyl-(2-cyanoe thyl)-(N,N- diisopropyl)-phosphoramidite. The resulting product, p5'A2'(s2p)- 5'A2'(s2p)5'A, was approximately 10-fold less effective as an activator of purified human recombinant 2-5A-dependent RNase than was 2-5A itself. This loss of activation ability was related directly to the loss of binding ability of the phosphorodiothioate analog. As predicted, p5'A2'(s2p)5'A2' (s2p)5'A was stable to snake venom phosphodiesterase and the nucleolytic activities of both human lymphoblastoid CEM cell extracts and human serum, under conditions that led to facile degradation of parent 2-5A. This nuclease stability permitted the observation of the CEM cell extracts and human serum phosphatase activity which led to 5'-dephosphorylation of p5'A2'(s2p)5'A2'(s2p)5'A.