Extraparenchymal neurocysticercosis: report of five cases and review of management

Neurocysticercosis due to parenchymal cysts carries a good prognosis regardless of therapy. Extraparenchymal neurocysticercosis (including ventricular, spinal, and subarachnoid types) carries a poorer prognosis. Most extraparenchymal cases present with hydrocephalus. Medical treatment alone in doses and schedules developed for parenchymal disease is frequently unsuccessful. For ventricular disease, most cases can be managed with shunting procedures either alone or together with the administration of antiparasitic agents (e.g., praziquantel or albendazole), without extirpation of the cysts. Subarachnoid disease was formerly associated with a case fatality rate of about 50%. However, with the combination of shunting procedures for hydrocephalus, antiparasitic agents, and, in some cases, surgical extirpation of the cysts, the prognosis is much improved. Spinal cysticercosis can be either leptomeningeal (which responds like subarachnoid disease) or intramedullary. For all forms of neurocysticercosis, the role of antiparasitic agents needs to be better defined.

Moloney murine sarcoma virus MuSVts110 DNA: cloning, nucleotide sequence, and gene expression

We have cloned Moloney murine sarcoma virus (MuSV) MuSVts110 DNA by assembly of polymerase chain reaction (PCR)-amplified segments of integrated viral DNA from infected NRK cells (6m2 cells) and determined its complete sequence. Previously, by direct sequencing of MuSVts110 RNA transcribed in 6m2 cells, we established that the thermosensitive RNA splicing phenotype uniquely characteristic of MuSVts110 results from a deletion of 1,487 nucleotides of progenitor MuSV-124 sequences. As anticipated, the sequence obtained in this study contained precisely this same deletion. In addition, several other unexpected sequence differences were found between MuSVts110 and MuSV-124. For example, in the noncoding region upstream of the gag gene, MuSVts110 DNA contained a 52-nucleotide tract typical of murine leukemia virus rather than MuSV-124, suggesting that MuSVts110 originated as a MuSV-helper murine leukemia virus recombinant during reverse transcription rather than from a straightforward deletion within MuSV-124. In addition, both MuSVts110 long terminal repeats contained head-to-tail duplications of eight nucleotides in the U3 region. Finally, seven single-nucleotide substitutions were found scattered throughout MuSVts110 DNA. Three of the nucleotide substitutions were in the gag gene, resulting in one coding change in p15 and one in p30. All of the remaining nucleotide changes were found in the noncoding region between the 5' long terminal repeat and the gag gene. In NIH 3T3 cells transfected with the cloned MuSVts110 DNA, the pattern of viral RNA expression conformed with that observed in cells infected with authentic MuSVts110 virus in that viral RNA splicing was 30 to 40% efficient at growth temperatures between 28 and 33 degrees C but reduced to trace levels above 37 degrees C.

Nickel mutagenesis: alteration of the MuSVts110 thermosensitive splicing phenotype by a nickel-induced duplication of the 3' splice site

We investigated DNA damage caused by carcinogenic metals in a murine sarcoma virus (MuSV)-based mutagenicity assay in which mutations targeted to v-mos expression can be selected. Nickel chloride treatment of NRK cells (termed 6m2 cells) infected with MuSVts110, a retrovirus conditionally defective in viral RNA splicing and cell transformation, caused the outgrowth of transformed "revertants" with changes in the MuSVts110 RNA splicing phenotype. Cadmium and chromium treatment of 6m2 cells resulted in the selection of a second class of revertants with what appeared to be frameshift mutations allowing the translation of a readthrough gag-mos protein. In both classes of metal-induced revertants, viral gene expression was distinct from that observed in revertants arising in untreated 6m2 cultures, arguing that metal treatment did not simply enhance the rate of spontaneous reversion. In one representative nickel revertant line the operative nickel-induced mutation affecting MuSVts110 RNA splicing was a duplication of 70 bases surrounding the 3' splice site. The effect of this mutation was to direct splicing to the most downstream of the duplicated 3' sites and concomitantly relax its characteristic thermosensitivity. These data establish the mutagenic potential of nickel and provide the first example of a defined nickel-induced mutation in a mammalian gene.

IL-2 dose regulates TNF-alpha mRNA transcription and protein secretion in human peripheral blood lymphocytes

TNF-alpha is an inducible cytokine with widely divergent effects on numerous target tissues. Secretion and response to TNF-alpha appear to be required in cellular immune function including that of classical cytotoxic T cell development, non-MHC restricted cytotoxicity, and the mixed lymphocyte reaction. In addition, production of TNF-alpha has been implicated in a number of pathophysiologic processes involving lymphocytes. In this report, we have investigated the regulation of TNF-alpha in normal lymphocytes stimulated with IL-2. Our results demonstrate that the level of TNF-alpha gene expression can be determined by the quantity of IL-2 present during lymphocyte activation. The increased steady-state levels of TNF-alpha mRNA were attributable to an enhanced rate of nuclear transcription. TNF-alpha secretion increased with escalating IL-2 dose in parallel to that of mRNA production. The modulation of TNF-alpha gene expression by IL-2 concentration has been previously unrecognized and may be an important mechanism in normal immunohomeostasis, cellular dysregulations involving TNF production, and the dose-dependent toxicities observed with high-dose IL-2 immunotherapy.

Activation of cryptic splice sites in murine sarcoma virus-124 mutants

We have examined splice site activation in relation to intron structure in murine sarcoma virus (MuSV)-124 RNA. MuSV-124 contains inactive murine leukemia virus env gene splice sites (termed 5' env and 3' env) as well as cryptic sites in the gag and v-mos genes (termed 5' gag and 3' mos) which are activated for thermosensitive splicing by a 1,487-base intronic deletion in the MuSV-124 derived MuSVts110 retrovirus. To determine conditions permissive for splice site activation, we examined MuSV-124 mutants deleted in the 1,919-base intron bounded by the 5' gag and 3' mos sites. Several of these deletions activated thermosensitive splicing either at the same sites used in MuSVts110 or in a previously unreported temperature-sensitive splice event between the 5' gag and 3' env sites. These data suggested that the thermosensitive splicing phenotype characteristic of MuSVts110 required neither a specialized intron nor selection of a particular 3' splice site. The 3' env and 3' mos sites were found to compete for splicing to the 5' gag site; the more upstream 3' env site was exclusively used in MuSV-124 mutants containing both sites, whereas selection of the 3' mos site required removal of the 3' env site. Branchpoint sequences were found to have a potential regulatory role in thermosensitive splicing. Insertion of a beta-globin branchpoint sequence in a splicing-inactive MuSV-124 mutant activated efficient nonthermosensitive splicing at the 3' mos site, whereas a mutated branchpoint activated less efficient but thermosensitive splicing.

Regulation of RNA splicing in gag-deficient mutants of Moloney murine sarcoma virus MuSVts110

We investigated whether the MuSVts110 gag gene product (P58gag) can regulate the novel growth temperature dependence of MuSVts110 RNA splicing. MuSVts110 mutants with either frameshifts or deletions in the gag gene were tested for their ability to maintain the MuSVts110 splicing phenotype. Only small decreases in splicing efficiency and no changes in the thermosensitivity of viral RNA splicing were observed in MuSVts110 gag gene frameshift mutants. Deletions within the gag gene, however, variably decreased MuSVts110 splicing efficiency but had no effect on its thermosensitivity. Another class of MuSVts110 splicing mutants generated by treatment of MuSVts110-infected cells with NiCl2 was also examined. In these "nickel revertants," P58gag is made, but splicing of the viral transcript is nearly complete at all growth temperatures. The splicing of "tagged" viral RNA transcribed from a modified MuSVts110 DNA introduced into nickel revertant cells remained thermosensitive, arguing against trans effects of viral gene products on splicing efficiency. These experiments indicated that neither the MuSVts110 P58gag protein nor any other viral gene product acts in trans to regulate MuSVts110 splicing.

Chromosomal changes in cell lines from mouse tumors induced by nickel sulfide and methylcholanthrene

Rhabdomyosarcomas were induced in mice by intramuscular injections of crystalline nickel sulfide and 3-methylcholanthrene. At early passage, karyotypes were performed by G-banding for four nickel sulfide cell lines and for three 3-methylcholanthrene cell lines. Six cell lines were near-diploid and one nickel sulfide line was near-tetraploid. Three of the nickel sulfide cell lines were characterized by a rearranged marker chromosome which was present in a majority of the cells of each line. The rearrangements leading to the formation of marker chromosomes were different in each nickel sulfide cell line but involved chromosome 4 in two of the nickel sulfide cell lines. Extra copies of chromosome 15 were present in two nickel sulfide cell lines. Possible rearrangement and/or gene activation was examined for the c-mos oncogene on chromosome 4 and the c-myc oncogene on chromosome 15, but no alteration or activation was observed. None of the 3-methylcholanthrene cell lines contained rearranged marker chromosomes; however, one MCA cell line did contain large numbers of double minutes. In all cell lines, minichromosomes (small atypical acrocentric chromosomes) were observed that contained distinct centromeric regions but no other G-positive bands.

Activation of thermosensitive RNA splicing and production of a heat-labile P85gag-mos kinase by the introduction of a specific deletion in murine sarcoma virus-124 DNA

Murine sarcoma virus ts110 (MuSVts110) is a conditionally transformation-defective MuSV mutant lacking 1,487 bases found in its wild-type parent, MuSV-349 (MuSV-124). Expression of the MuSVts110 v-mos gene product, P85gag-mos, requires splicing of the viral transcript to align the gag and mos genes in frame. However, this splice event is restricted to growth temperatures of 33 degrees C or lower. No splicing of the viral RNA, no production of P85gag-mos, and, hence, no cell transformation is observed at growth temperatures above 33 degrees C. To determine whether thermosensitive splicing is an intrinsic property of To determine whether thermosensitive splicing is an intrinsic property of MuSVts110 RNA specified by the 1,487-base deletion or a result of a cellular defect, we examined an "equivalent" or MuSVts110 DNA (designated ts32 DNA) constructed by combining wild-type MuSV-124 DNA fragments with a synthetic oligonucleotide to yield an otherwise wild-type viral DNA containing the same 1,487-base deletion as authentic MuSVts110. As observed in control cells (6m2 cells) infected with the authentic MuSVts110 virus, NIH 3T3 cells transfected with ts32 DNA appeared morphologically transformed when grown at 33 degrees C, but were converted to a more normal, flattened shape within a few hours of a shift to 39 degrees C. In concert with these morphological changes, both the processing of the ts32 RNA transcripts and the production of ts32 p85gag-mos kinase were found to be optimal at growth temperatures from 28 to 33 degrees C, but dramatically reduced at 37 to 41 degrees C. Like authentic P85gag-mos, the ts32 P85gag-mos kinase activity was rapidly inactivated by brief exposure to 39 degrees C. These results suggested that the MuSVts110 equivalent is functionally indistinguishable from authentic MuSVts110 and that the novel temperature-sensitive splicing of MuSVts110 transcripts is specified by an intrinsic property of the viral RNA.

Exploitation of a thermosensitive splicing event to study pre-mRNA splicing in vivo

The spliced form of MuSVts110 viral RNA is approximately 20-fold more abundant at growth temperatures of 33 degrees C or lower than at 37 to 41 degrees C. This difference is due to changes in the efficiency of MuSVts110 RNA splicing rather than selective thermolability of the spliced species at 37 to 41 degrees C or general thermosensitivity of RNA splicing in MuSVts110-infected cells. Moreover, RNA transcribed from MuSVts110 DNA introduced into a variety of cell lines is spliced in a temperature-sensitive fashion, suggesting that the structure of the viral RNA controls the efficiency of the event. We exploited this novel splicing event to study the cleavage and ligation events during splicing in vivo. No spliced viral mRNA or splicing intermediates were observed in MuSVts110-infected cells (6m2 cells) at 39 degrees C. However, after a short (about 30-min) lag following a shift to 33 degrees C, viral pre-mRNA cleaved at the 5' splice site began to accumulate. Ligated exons were not detected until about 60 min following the initial detection of cleavage at the 5' splice site, suggesting that these two splicing reactions did not occur concurrently. Splicing of viral RNA in the MuSVts110 revertant 54-5A4, which lacks the sequence -AG/TGT- at the usual 3' splice site, was studied. Cleavage at the 5' splice site in the revertant viral RNA proceeded in a temperature-sensitive fashion. No novel cryptic 3' splice sites were activated; however, splicing at an alternate upstream 3' splice site used at low efficiency in normal MuSVts110 RNA was increased to a level close to that of 5'-splice-site cleavage in the revertant viral RNA. Increased splicing at this site in 54-5A4 viral RNA is probably driven by the unavailability of the usual 3' splice site for exon ligation. The thermosensitivity of this alternate splice event suggests that the sequences governing the thermodependence of MuSVts110 RNA splicing do not involve any particular 3' splice site or branch point sequence, but rather lie near the 5' end of the intron.

Analysis of metal-induced mutations altering the expression or structure of a retroviral gene in a mammalian cell line

Carcinogenic metal compounds, with the exception of chromium(VI), have been found to be poorly mutagenic in both prokaryotic and mammalian cell mutagenesis assays, yet they are clearly clastogenic (Hansen and Stern, 1984). Thus, the role of metals as initiators in carcinogenesis has been difficult to delineate. In an effort to develop a model system capable of assaying DNA damage caused by carcinogenic metals, we have investigated the role of NiCl2, CdCl2, Na2CrO4, and NMU in a murine sarcoma virus-infected mammalian cell line in which expression of the retroviral v-mos gene is growth-temperature regulated. This cell line, designated 6m2, contains a single-copy, stably integrated, mutant Moloney murine sarcoma virus DNA (designated MuSVts110) and is temperature sensitive for morphological transformation due to a conditionally defective viral RNA-splicing event that in turn regulates expression of the viral transforming gene. Mutations affecting the viral DNA in 6m2 cells can be detected if these alterations lead to changes in the structure or expression of the transforming protein encoded by the MuSVts110 v-mos gene. Analysis of the viral proteins from 6m2 'revertant' cell lines (as defined by reversion to the transformed phenotype at all growth temperatures) selected after treatment with the above agents showed that NiCl2, NMU, and Na2CrO4 each induced a different yet specific type of mutation. NiCl2 and NMU each altered the temperature sensitivity of viral RNA splicing, possibly due to base substitution mutations, but did so to distinctly different extents. Na2CrO4 affected the structure of the viral proteins by inducing what appear to be short frameshift mutations that resulted in the temperature-dependent translation of a novel virus-encoded transforming protein, P100gag-mos. CdCl2 also induced frameshift mutations but, in one case, induced a mutation which may result from a deletion of about 300 bases within the MuSVts110 DNA.

Nickel-induced heritable alterations in retroviral transforming gene expression

Determination of the mutagenic effects of carcinogenic nickel compounds has been difficult because, like many metals, nickel is poorly or nonmutagenic in procaryotic mutagenicity assays. We attempted to characterize nickel-induced genetic lesions by assessing the effect of nickel chloride on the conditionally defective expression of the v-mos transforming gene in normal rat kidney cells infected with the Murine sarcoma virus mutant ts110 (MuSVts110) retrovirus. MuSVts110 contains an out-of-frame gag gene-mos gene junction that prevents the expression of the v-mos gene at the nonpermissive temperature (39 degrees C). In MuSVts110-infected cells (6m2 cells) grown at 33 degrees C, however, this defect can be suppressed by a splicing event that restores the mos reading frame, allowing the expression of a gag-mos fusion protein which induces the transformed phenotype. The capacity to splice the viral transcript at 33 degrees C, but not at 39 degrees C, is an intrinsic property of the viral RNA. This property allowed us to target the MuSVts110 genome using a positive selection scheme whereby nickel was used to induce genetic changes which resulted in expression of the transformed phenotype at 39 degrees C. We treated 6m2 cells with NiCl2 and isolated foci consisting of cells which had reverted to the transformed phenotype at 39 degrees C. We found that brief nickel treatment increased the reversion frequency of 6m2 cells grown at 39 degrees C sevenfold over the spontaneous reversion frequency. The nickel-induced revertants displayed the following heritable characteristics: They stably maintained the transformed phenotype at 39 degrees C; unlike the MuSVts110 RNA in 6m2 cells, the nickel-induced revertant viral RNA could be spliced efficiently at 39 degrees C; as a consequence of the enhanced accumulation of spliced viral RNA, the nickel-induced revertants produced substantial amounts of the transforming v-mos protein P85gag-mos at 39 degrees C; the nickel-induced revertant P85gag-mos serine kinase, like the parental 6m2 P85gag-mos kinase, was found to be rapidly inactivated at 39 degrees C; however, in the nickel-induced revertants, overproduction of P85gag-mos allowed the transformed state to be maintained; and even though viral RNA processing was much changed, no rearrangements of the viral DNA in the nickel-induced revertant cells were detected by partial restriction analysis.

Isoniazid prophylaxis in hepatitis B carriers

Both tuberculosis and hepatitis B are endemic in southeast Asia and are common among refugees to the United States from that region. Isoniazid, used for the prophylactic treatment of tuberculosis, is a potentially hepatotoxic drug. Carriers of the hepatitis B virus are likely to have some degree of liver damage due to their chronic infection. We hypothesized that prophylactic treatment of carriers with isoniazid would cause greater liver damage, as measured by serum alanine aminotransferase (ALT) levels, than would such therapy of noncarriers. Cross-sectional and longitudinal studies of the southeast Asian refugee population in Philadelphia failed to support this hypothesis. Isoniazid did not cause greater hepatotoxicity in hepatitis B carriers than in noncarriers. Although carriers had higher ALT levels than noncarriers, both groups experienced transient ALT elevations during the first 2 months of isoniazid prophylactic therapy. Therefore, we concluded that chronic infection with hepatitis B virus is not a contraindication to the prophylactic use of isoniazid.

Molecular basis underlying phenotypic revertants of Moloney murine sarcoma virus MuSVts110

We examined the molecular basis for phenotypic reversion in cells infected with a transformation mutant of murine sarcoma virus, MuSVts110. In MuSVts110-infected NRK cells (6m2 cells), the manifestation of the transformed phenotype at 33 degrees C and the normal phenotype at 39 degrees C is governed by thermosensitive splicing of the MuSVts110 primary transcript, a 4.0-kilobase (kb) RNA which contains the gag and mos genes joined out of frame. At 33 degrees C, selectively, the 4.0-kb RNA is processed to a spliced 3.5-kb RNA in which the gag and mos genes are rejoined in a continuous open reading frame, thus allowing synthesis of the P85gag-mos-transforming protein. In contrast, the MuSVts110 revertant cell lines (designated 54-5A4 and 204-3) appear transformed at all growth temperatures from 33 to 39 degrees C and express a P100gag-mos-transforming protein from an apparently unprocessed 4.0-kb viral RNA. In the current study we established both by S1 nuclease analysis and primer extension sequencing that the revertant 54-5A4 and 204-3 4.0-kb viral RNAs suffered a 5-base deletion at the intron-exon border of the 3' splice site. The effect of this deletion is twofold. First, because of the damage to the 3' splice site, the revertant viral 4.0-kb RNAs cannot be processed to the spliced 3.5-kb RNA and, consequently, cannot be translated to P85gag-mos. Second, the 5-base deletion excises an in-frame stop codon positioned at the intron-exon border in the parental RNA and restores the original mos gene reading frame. The net effect is to produce a continuous open reading frame from the gag, alternate mos, and authentic mos gene reading frames which are fused together in the revertant 4.0-kb RNA. This continuous open reading frame can be translated into the P100gag-mos-transforming protein at any growth temperature.

Early initiation of DNA synthesis in G1 phase HeLa cells following fusion with red cell ghosts loaded with S-phase cell extracts

A modification of polyethylene glycol-mediated cell fusion procedure has been described and standardized for red blood cell mediated microinjection of proteins into cells in suspension. Using this procedure, proteins are routinely introduced into 50% of the target cells. We have applied this microinjection procedure to introduce cytoplasmic extracts obtained from S-phase HeLa cells into HeLa cells synchronized in G1. This experiment resulted in an accelerated entry of the G1 cells into S phase as measured by the incorporation of [3H]thymidine. This technique may provide a means to identify and characterize the S-phase factors responsible for the induction of DNA synthesis.

Translation of messenger RNA from rat epididymis and identification of poly(A)RNA coding for acidic epididymal glycoprotein

Different proteins are secreted by the various regions of rat epididymis. We have examined the messenger RNA dependence of this varied gene expression by cell-free translation of poly(A)RNA extracts from initial segment, caput plus corpus, and cauda. Labeled translation products were analyzed by polyacrylamide gel electrophoresis under denaturing conditions. Poly(A)RNA from initial segment coded for several unique bands of labeled protein, including a 23,000 MW protein that may correspond to an initial segment protein reported previously to be regulated by testicular fluid factors. Messenger RNA encoding 20,000 MW protein believed to be alpha-lactalbumin, was most abundant in caput but also present in initial segment. Acidic epididymal glycoprotein (AEG) was identified previously by immunoperoxidase staining in epithelial cells of caput, corpus, and cauda. AEG was not readily identified on electrophoresis of total translated proteins, but when concentrated by immunoprecipitation with purified AEG antibody prior to electrophoresis, AEG appeared in both caput plus corpus, and in cauda poly(A)RNA translations.