Intermediate clinical and radiological results of cervical TDR (Mobi-C) with up to 2 years of follow-up

The interest in cervical total disc replacement (TDR) as an alternative to the so-far gold standard in the surgical treatment of degenerative disc disease (DDD), e.g anterior cervical discectomy and fusion (ACDF), is growing very rapidly. Many authors have established the fact that ACDF may result in progressive degeneration in adjacent segments. On the contrary, but still theoretically, preservation of motion with TDR at the surgically treated level may potentially reduce the occurrence of adjacent-level degeneration (ALD). The authors report the intermediate results of an undergoing multicentre prospective study of TDR with Mobi-C prosthesis. The aim of the study was to assess the safety and efficacy of the device in the treatment of DDD and secondary to evaluate the radiological status of adjacent levels and the occurrence of ossifications, at 2-year follow-up (FU). 76 patients have performed their 2-year FU visit and have been analyzed clinically and radiologically. Clinical outcomes (NDI, VAS, SF-36) and ROM measurements were analyzed pre-operatively and at the different post-operative time-points. Complications and re-operations were also assessed. Occurrences of heterotopic ossifications (HOs) and of adjacent disc degeneration radiographic changes have been analyzed from 2-year FU X-rays. The mean NDI and VAS scores for arm and neck are reduced significantly at each post-operative time-point compared to pre-operative condition. Motion is preserved over the time at index levels (mean ROM = 9 degrees at 2 years) and 85.5% of the segments are mobile at 2 years. HOs are responsible for the fusion of 6/76 levels at 2 years. However, presence of HO does not alter the clinical outcomes. The occurrence rate of radiological signs of ALD is very low at 2 years (9.1%). There has been no subsidence, no expulsion and no sub-luxation of the implant. Finally, after 2 years, 91% of the patients assume that they would undergo the procedure again. These intermediate results of TDR with Mobi-C are very encouraging and seem to confirm the efficacy and the safety of the device. Regarding the preservation of the status of the adjacent levels, the results of this unconstrained device are encouraging, but longer FU studies are needed to prove it.

Functional and molecular ultrasound imaging: concepts and contrast agents

Contrast-enhanced ultrasound has shown convincing results for monitoring vessel morphology, surrogate markers of vascularization and changes in molecular marker expression in oncological and cardiovascular diseases. Ultrasound contrast agents have the ability to increase the backscattering signal intensity of an ultrasound pulse. An interesting class of ultrasound contrast agents are gas filled microbubbles, which can be synthesized by external bubble encapsulation using sugar matrices or microspheres consisting of lipids or polymers with or without surfactant and by selecting gases with low blood solubility and diffusion coefficient such as perfluorocarbons or sulphur hexafluoride. Ultrasound contrast agents can be classified according to the rigidity of their shell. Soft-shell microbubbles are coated with a thin monolayer of surfactant molecules such as palmitic acid or phospholipids and are very sensitive to pressure changes. Hard-shell microbubbles have a rigid shell made of polymers such as polycyanoacrylate, which dramatically increases their stability. Depending on the acoustic properties of the microbubbles and on the purpose of the examination either destructive or non destructive methods are preferred for their detection. Microbubbles can be detected by destructive and non-destructive methods. Both soft- and hard-shell microbubbles coated with target-specific molecules can also be used for molecular imaging. Using target-specific approaches, the expression of several angiogenic markers such as VEGFR2, alphavbeta3 Integrins, ICAM, and E-selectin has been investigated in neoplastic and vascular diseases. This article summarizes the synthesis and properties of contrast agents as well as the indications, limitations and future potential of contrast-enhanced functional and molecular ultrasound.

Lifetime prevalence of mood and anxiety disorders in twin pairs discordant for schizophrenia

There have been long questions about the relationship of schizophrenia to other mental disorders. Lifetime DSM-III-R diagnoses of mood and anxiety disorders in twins with clinically diagnosed schizophrenia (n = 24) and their non-affected co-twins (n = 24) were compared with twins from pairs without schizophrenia (n = 3327) using a sample from the Vietnam Era Twin Registry. Schizophrenic probands had significantly elevated rates of all included disorders (bipolar disorder, major depression, dysthymia, generalized anxiety disorder, panic disorder, and PTSD) compared with controls (P<0.01). The odd ratios comparing co-twins of schizophrenic probands with controls was greater than three for every disorder, but did not attain statistical significance. A similar pattern was observed when analyses were restricted to only monozygotic twins (n = 12). Consistent with other studies, schizophrenics appeared to have higher rates of a range of mental disorders. Our results suggest that schizophrenia per se represents a risk factor for other psychiatric disorders, but the absence of significantly elevated risk among non-schizophrenic co-twins suggested that family environmental and/or genetic factors that contribute to risk of schizophrenia do not increase the risk of mood and anxiety disorders to the same extent that the risk of these other disorders is increased by the presence of schizophrenia.

[Cerebral nocardiosis cured by repeated stereotaxic punctures and antibiotic therapy]

We report the case of a 58-year old man who had been on corticosteroid therapy for several months and presented with cerebral nocardiosis. Computerized tomography showed multiple brain abscesses. As the neurological status was getting worse, several stereotactic needle aspirations were performed, resulting in decompression of the brain and permitting bacteriological examination of the pus. Antibiotic therapy based on sensitivity tests was administered, and cure was obtained in the 4th month of treatment.

Effect of doxorubicin on mouse hybridoma B cells: stimulation of immunoglobulin synthesis and secretion

The purpose of these studies was to investigate whether the cell-differentiating effect of anthracyclines can trigger an over-production and secretion of molecules that may interfere with the tumor-host relationship. We exposed mouse hybridoma B-cells, which are devoted to immunoglobulin production, to doxorubicin (10-40 ng/ml). We found that most doxorubicin-treated cells secreted 3- to 5-fold higher amounts of immunoglobulin than untreated cells, along with an accumulation of 50% of them in the G2+M phase of the cell cycle. The antigenic specificity of the immunoglobulin and its size pattern as determined by polyacrylamide gel electrophoresis were similar whether or not cells were treated with doxorubicin. The enhancement of immunoglobulin secretion by doxorubicin was associated with an increase of the intracellular pool of heavy and light chains of the immunoglobulin. Furthermore, an elevated synthesis of immunoglobulin was observed. The synthesis of other proteins also appeared to be modified in these circumstances. These data suggest that doxorubicin can potentiate the biological functions of target cells when used at low concentrations, elevating the production and secretion of effector molecules that interfere with the tumor-host relationship.

Bilateral extradural haematoma. Report of two cases

Two cases of bilateral extradural haematomas are reported. In case I, the haematomas developed simultaneously and were probably due to a tear in the sagittal sinus. In case II, the haematomas developed sequentially and were demonstrated by serial CT scannings after the removal of a seemingly unilateral lesion. A review of the literature points out the rarity of this condition which had been described even before the CT era, with varying clinical presentations and unusually poor surgical results. The advent of the CT has made the diagnosis of simultaneous bilateral extradural haematomas easier and is regarded as a significant factor in the improvement of the prognosis noted in recent reports. However, the possibility of delayed bilateral extradural haematomas escaping detection in the initial CT should be emphasized. This unusual clinical presentation stresses the value of a routine use of serial CT scannings in the acute phase of head injuries.

Lumbo-peritoneal shunt in non-hydrocephalic patients. A review of 41 cases

A population of 41 non-hydrocephalic patients in whom a lumbo-peritoneal shunt (LPS) was inserted for various conditions is reviewed. 19 had persistent cerebro-spinal fluid rhinorrhoea following cranial injury, basal skull surgery or of unknown origin, 3 had recalcitrant benign intra-cranial hypertension, 14 had a persistent bulging craniotomy site after operations for intra-cranial tumours or head trauma, 4 had syringomyelia and 1 had a postoperative cervical meningocele. There was no shunt-related mortality. LPS was effective in treating the initial symptomatology in 31 patients. Further revision or removal of LPS were needed on 9 occasions in 8 patients showing shunt-related mechanical or infectious complications or persistent postural headaches. This report demonstrates the safety of the LPS procedure experienced in another population of 146 patients with communicating hydrocephalus operated on in the meantime. According to the authors' experience, the versatility of the clinical applications of LPS seems well established. LPS should be considered when a CSF diversion is required in patients showing absent or minimal ventricular enlargement in the CT scan.

Chromosomal changes associated with resistance to doxorubicin: correlation with tumorigenicity

Chromosome analysis was performed on Friend leukemia cells sensitive and resistant to doxorubicin. With increasing levels of resistance, increased numbers, of metacentric chromosomes and several chromosomal markers were observed. When sensitive cells were exposed to a toxic dose of doxorubicin, multiple chromosomal breaks were observed in 62% of cells. In contrast, when doxorubicin resistant cells were exposed to cytotoxic concentrations, the pulverization phenomenon was not observed. This striking difference suggests a different mechanism for cytotoxicity in sensitive and resistant cells. Moreover, when logarithmically growing cells were grafted subcutaneously in DBA2 mice, the tumorigenic property was related to the level of doxorubicin resistance.

Characterization of two murine monoclonal antibodies (P10, P12) directed against different determinants on human blood platelet thrombospondin

Thrombospondin, a 450-kDa glycoprotein composed of three disulphide linked chains, is located in human blood platelet alpha-granules and is released from platelets upon stimulation. This glycoprotein is thought to play a major role in platelet aggregation. The aim of this study was to characterize two monoclonal antibodies (P10 and P12) directed against human blood platelet thrombospondin. When the released material obtained after stimulation of platelets with thrombin in the presence of 2 mM calcium was immediately treated with EDTA, labelled with 125I and incubated with monoclonal antibodies P10 and P12, both immunoprecipitated a major labelled protein band with a molecular mass of 160 kDa and a weaker band at 146 kDa, as analysed on reduced dodecyl sulphate/polyacrylamide gels. The major band corresponds in molecular mass to the thrombospondin subunits. If, however, the released material was left in the presence of Ca2+ for 48 h, then the main band was at 130 kDa and in addition one minor protein band (75 kDa) was immunoprecipitated by P10 whereas P12 recognized two minor protein bands (75 and 60 kDa). When P10 and P12 were incubated with 125I-labelled platelet releasates treated for 48 h at 4 degrees C with 10mM EDTA, three major protein bands (160, 146 and 130 kDa) were immunoprecipitated in addition to the minor bands mentioned above. These results indicate that thrombospondin is probably degraded by the endogenous platelet calcium-dependent protease. Investigation of tryptic peptide fragments of thrombospondin isolated by fast protein liquid chromatography showed that 125I-labelled antibody P10 bound to 400-kDa and 120-kDa fragments whereas 125I-labelled P12 only recognized a 400-kDa fragment. Competition studies involving solid-phase antibody binding and double antibody sandwich assays showed that P10 and P12 were directed against different determinants of thrombospondin. Purified thrombospondin, isolated in the presence of calcium, either directly or after treatment with EDTA, haemagglutinated trypsinized, formaldehyde-fixed sheep erythrocytes identically. The haemagglutination activity of EDTA-treated thrombospondin was inhibited by P10 and enhanced by P12. On the other hand, P10 and P12, despite their binding to calcium-treated thrombospondin, had no effect on its haemagglutination activity. Monoclonal antibodies P10 and P12 could be useful tools to investigate the role of thrombospondin in platelet aggregation.

Cytogenetic modifications of Friend leukemia cells resistant to adriamycin

Chromosome analysis was performed on adriamycin-sensitive and resistant Friend leukemia cells. Resistance to ADM is associated with an increased number of metacentric chromosomes. With increasing level of drug resistance additional metacentric chromosomes and several chromosomal markers were observed. Furthermore, the C-banding patterns and the heterochromatin distribution differed in resistant, as compared to sensitive cells. When sensitive cells were exposed to a toxic dose of ADM, multiple chromosomal breaks were observed in 62% of cells. In contrast, when ADM resistant cells were exposed to cytotoxic concentrations, the pulverization phenomenon was not observed and 75-80% of cells were without breaks. This striking difference suggests a different mechanism for cytotoxicity in sensitive and resistant cells.

Virus-related pathology: is the continued presence of the virus necessary?

This chapter examines the effect of viruses in inducing modifications in chromosomes, immune system interactions, and cell metabolism to support such a hypothesis that virus may no longer be present when the pathology appears. When vaccines were available to protect the population against the major epidemics, then chronic, recurrent, or persistent infections came into focus. Viruses are everywhere and all organisms are permanently exposed to them. The result of this contact depends on the particular moment a t which a given cell is exposed to the virus. Rubella, for example, provokes a very benign disease in adults, but can induce abnormalities in the differentiating fetus. Although interferon is active against virus aggression, excess interferon has a toxic effect and can block differentiation. The capacity of several viruses to act as cellular mutagens by modifying chromosomes is well established, whatever the molecular mechanism may be. Mutations at the cellular level were carefully analyzed for their tumorigenic potential.

Treatment of cerebrospinal fluid rhinorrhea by percutaneous lumboperitoneal shunting: review of 15 cases

Fifteen patients with recalcitrant cerebrospinal fluid (CSF) fistula underwent the insertion of a lumboperitoneal shunt. The shunt consists of a two-piece Silastic tube and has been used in a population of 150 patients with communicating hydrocephalus, persistent postoperative meningocele, and benign intracranial hypertension. The spinal catheter is introduced subcutaneously and no flushing device is used. We studied three groups: 9 patients had a history of head trauma, and 7 of these had undergone one or several ineffective direct approaches to the dural leak. Four patients presented with a presumably congenital fistula. Two patients had persistent rhinorrhea due to previous intracranial procedures. Indium-111 cisternography was performed in 10 patients before lumboperitonel (LP) shunting and failed in 2 of those to document the site of leakage. Twelve patients showed cessation of rhinorrhea after LP shunting. In 4 of these, shunt-related complications responded to shunt removal with no further recurrence of rhinorrhea. Two patients underwent revision of the shunt. In 3 patients, the LP shunt failed to control the CSF leak and further intracranial procedures were indicated. The LP shunt provides an attractive and technically simple solution when direct methods of treatment have failed. Additionally, LP shunting should be considered as a primary mode of treatment in elderly patients or when impairment of CSF dynamics is documented by radionuclide cisternography and computed tomographic scanning. When an LP shunt is ineffective, shunt function should be checked by isotopic studies before additional surgery is performed.

Depression of reverse transcriptase activity by hybridoma supernatants: a potential problem in screening for retroviral contamination

Murine hybridoma cell lines generally produce retroviral particles (type A and/or type C), often in large numbers. We have measured reverse transcriptase activity in the supernatant of some 30 hybridoma lines of murine origin and found that the observed activity expressed as pmoles of [3H]-dGMP incorporated into an acid insoluble polymer, is frequently much lower than would be expected from the amount of retrovirus seen by electron microscopy in the corresponding cells. We demonstrate that this reduction is due to the presence of a nuclease which degrades the high molecular weight product but is not due to a change in the reverse transcriptase activity. This nuclease activity may be associated with mycoplasma contamination of the cell lines.

Retroviral antigens on gs- chf- leukocytes

It has recently been suggested that the endogenous retroviruses present in many different species might be involved during stimulation of the immune system of their hosts. We have now studied the expression of two avian retroviral antigens p27 and gp85 in chicken lymphoid cells by indirect immunofluorescence (IIF) and by complement-dependent microcytotoxicity (CDM). We have now found that these viral antigens are expressed in peripheral blood leukocytes of adults and embryos and in splenic and bursal lymphocytes of Spafas gs- chf- chickens but they are not expressed in fibroblasts cultured from the feather follicles of the same individual adult birds nor in fibroblasts cultured from embryos of the same flock. The differential expression of viral antigens in leukocytes may be related to a specific property or function of these cells.

Nuclear processing of viral high-molecular-weight RNA in cells infected with herpes simplex virus type 1

Nuclear RNA isolated from cells infected by herpes simplex virus type 1, strain F, was fractionated on formamide-sucrose gradients into two major classes, greater and less than 45S. These two classes of labeled nuclear RNA were hybridized to viral DNA fragments generated by digestion with the restriction enzymes HindIII and BglII. Early in infection, only a few DNA fragments hybridized to RNA, with slight differences between the two classes. Late in infection, all DNA fragments hybridized, showing that all viral RNA was present in large precursor molecules greater than 14 kilobases. The fragments that correspond to late gene products hybridized more of the small RNA than the large RNA. This suggests that the mRNA corresponding to late genes accumulated after the large precursors have been cleaved. Large (greater than or equal to 45S) and small (< 45S) nuclear RNA and cytoplasmic RNA from cells late in infection were hybridized in excess to in vitro-labeled HindIII M and L fragments. More than 50% of the HIndIII M fragment annealed with the large nuclear RNA, but only 36% of it annealed with the cytoplasmic RNA. The HindIII L fragment hybridized large nuclear RNA and cytoplasmic RNA to the same extent (30% and 26%). These results suggest that RNA complementary to the HindIII M fragment, which is the template for immediate early polypeptides, was regulated in the nuclei at the posttranscriptional level. This seems to suggest that temporal regulation of RNA cleavage occurs in the nucleus.

Herpes simplex type 1 infection of nonpermissive rat XC cells

Herpes simplex virus type 1 (HSV-1) infection of non permissive XC cells (a rat cell line transformed by Rous sarcoma virus) was studied. Using virus labeled with 3H-thymidine it was shown that adsorption is similar to that in a permissive system. By electron microscopy enveloped particles were observed in cytoplasmic vesicles in XC cells but not in the permissive system. However input viral DNA was degraded both in non permissive cells (XC) and permissive cells (HEp-2) and the degradation products were found incorporated into cellular DNA in the first case or into viral DNA in the second case. In the non permissive XC cells, it was possible to detect a small amount of incorporation of radioactive precursors into the viral DNA, identified by its buoyant density in CsCl of 1.726 g/cm3 and by hybridization with viral DNA. This DNA has the size of the native viral genome and its uptake of radioactive precursors was only partially inhibited by phosphonoacetic acid, a specific inhibitor of HSV-DNA polymerase. With permissive HEp-2 cells in the presence of such inhibitor, the obtained data are roughly the same as with XC cells, both in the presence or in the absence of phosphonoacetic acid. These results suggest that the observed viral DNA synthesis in XC cells is not a true replication but, further, a repair synthesis and, also, that the same events might take place in the permissive system before the onset of viral DNA replication.

[Immunochemical evidence for the specific binding of putrescine to plasma proteins including fibronectin]

Human plasma contains proteins capable of binding 14C putrescine by the action of Ca++ activated transglutaminase. These proteins have molecular weights from 32 to 220 K and above. One of these (with a molecular weight of 220 K) has been identified as fibronectin by the use of an antifibronectin antiserum. Evidence for a protein with a molecular weight identical to that of fibronectin has been obtained on PAGE analysis of the precipitate formed on incubating human serum with antipolyamine antiserum.

[Modification of human adenovirus type 7 after culture in guinea pig brain cells in vitro]

Multiplication of human adenovirus 7 (Ad7) is restricted in subcultures of adult Guinea Pig brain cells. It was however possible to recover enough infectious virus to purify it, and to study its properties. Several properties are similar to that of Ad 7 produced in HeLa cells but differences in sensitivity to cesium chloride and in its polypeptide composition were found.

Replication cycle of Newcastle disease virus in three host cells of different permissiveness

Various degrees of permissiveness for NDV have been described in different cell lines. In the present work three systems were investigated: bovine kidney (MDBK) cells, chick embryo (CE) cells and mouse L cells producing 50 to 100 p.f.u., 2 to 10 p.f.u. and less than 0.1 p.f.u./cell, respectively. Analysis of the radioactive virus messenger RNAs (vmRNAs) accumulating in actinomycin D-treated cells throughout the infection cycle revealed that, except for the absence of one 18S vmRNA species in L cells, all vmRNA components were formed in the three cell types, although variations occurred in their total and relative amounts from one cell type to another. Kinetic studies of vmRNA synthesis confirmed the absence of one 18S vmRNA species in L cells and also showed that the labelling rate of this vmRNA component is higher in CE cells. Virus proteins synthesized in the infected cells were labelled with 14C-amino acids and analysed by polyacrylamide gel electrophoresis. All the major NDV polypeptides were formed as expected in both CE and MDBK cells but only traces were detected in L cells. In contrast in a cell-free translation system from wheat germ, all of the NDV major proteins were synthesized using RNA extracted from the three infected cell types. Moreover, the total radioactivity incorporated into NDV proteins was twice as great with CE cell RNA and five times as great with L cell RNA than with equivalent quantities of RNA from MDBK cells.

Isolation and characterisation of a defective measles virus from a subacute sclerosing panencephalitis patient

A cytopathic measles virus was isolated from a brain biopsy of a subacute sclerosing panencephalitis (SSPE) patient. The agent could be transferred to Vero cells by cocultivation, but the infectivity always remained cell-associated -ie, a defective virus infection. The cell-associated nature of the virus was retained through 25 passages in Vero cells. Intracerebral inoculation of hamsters (2-6 days old) with the cocultured Vero cells gave rise to 100% mortality in 5-7 days. The virus retained its cell-associated nature after passage in hamsters. Electron microscopy of the brain and Vero cocultures showed the presence of virus-like ribonucleoparticles mainly in the nucleus. The presence of viral antigens in the nucleus, cytoplasm, and on the plasma membranes was confirmed by immunofluorescence. Using a combination of immunological and biochemical techniques, it was shown that all the viral proteins were synthesized with the exception of the haemagglutinin. Inclusion of the fusion inhibitor SV4814 (CBZ-D phenylalanine-L-phenylalanine-L-arginine-NO2) in the culture medium led to the elimination of the SSPE infection.

The use of a measles latex reagent for the determination of measles antibodies and in a specific test for multiple sclerosis

Measles virus antigens covalently linked to latex spheres were used for measuring measles-specific antibodies in a direct agglutination test either in microtitre plates or as a rapid slide-agglutination test. The titres were compared to that obtained by conventional assays. The measles-latex spheres were also used as the antigen for a radio-immuno assay. By incorporating a 14C-radioactive marker into the measles-latex spheres their interaction with lymphocytes from multiple sclerosis and control patients was determined. Lymphocytes from multiple sclerosis patients reacted with a higher percentage of beads at low bead/lymphocyte ratios compared with controls, whereas the reverse was found when the ratio of beads was increased.

Poly (A) polymerase activity in L cells following encephalomyocarditis virus infection

Poly (A) polymerase activity has been measured in crude cytoplasmic extracts of mouse L cells infected with encephalomyocarditis (EMC) virus. After infection there is first a decrease in enzyme activity followed by an increase which itself precedes detectable virus RNA and protein synthesis. The activity of the enzyme then declines before the release of mature virions and cell death take place. The early inhibition of poly (A) polymerase activity is correlated with the virus-induced shut-off of cellular protein synthesis but it is not due to inhibition of the synthesis of cellular enzyme and occurs in the absence of virus replication. The poly (A) polymerase is not synthesized after infection and modification of its activity can be reversed late in the virus cycle. These results indicate that host poly (A) polymerase activity can be regulated by the virus and further show that there is a correlation between the modification of poly (A) polymerase activity and the biosynthesis of poly (A).

The preparation of latex particles with covalently bound polyamines, IgG and measles agglutinins and their use in visual agglutination tests

Carboxylated latex particles were substituted with side arms terminating in primary amine and hydrazine groups. The particles were coupled to aldehyde groups generated on glycoproteins which were treated with sodium periodate. Particles having the alipathic primary amine putrescine hapten as the sole substituent and particles linked to glycoproteins such as measles agglutinins and IgG were used to detect the presence of the corresponding antibodies or antigens in biological fluids by agglutination tests.

Inhibition of viral RNA methylation in herpes simplex virus type 1-infected cells by 5' S-isobutyl-adenosine

5' S-isobutyl-adenosine (SIBA), a structural analogue of S-adenosylhomocysteine, reversibly blocks the multiplication of herpes simplex type 1 virus. In the presence of SIBA, viral protein synthesis is inhibited. After removing SIBA the synthesis of proteins starts rapidly again. The new polypeptides are mainly alpha proteins (Honess and Roizman, J. Virol. 14:8-19, 1974,), normally the first to be synthesized after infection. The rapid synthesis of proteins after release of inhibition seems to be directed by mRNA formed in the presence of SIBA as indicated by experiments using actinomycin D but which was undermethylated as shown by analysis of methyl groups on RNA. SIBA inhibits the methylation of mRNA and especially that of the 5' cap. Capping of mRNA thus seems to be essential for efficient translation. The analogue affected various methylations to different extents.

[Presence in immunostimulated cells of an RNA molecule utilizable as template for reverse transcriptase of avian myeloblastosis virus (AMV)]

Cytoplasmic RNA extracted from antigen stimulated immunocompetant cells is transcribed in vitro into DNA by the RNA directed DNA polymerase from avian myeloblastosis virus, in the absence of any added primer. Cytoplasmic RNA from other organs of the same animal, from non-stimulated immunocompetent cells, or from cells in tissue culture is not transcribed in the absence of exogenous primer.

Size of the poly(A) sequences in encephalomyocarditis virus RNA

Poly(A) sequences were demonstrated in the RNA of encephalomyocarditis (EMC) virus by affinity chromatography on poly(U)-Sepharose, treatment with RNases, and determination of the ability of the RNA to prime for reverse transcription. The size of the poly(A) sequences was estimated as 10-20 nucleotides in length by determination of the fraction resistant to pancreatic RNases plus T1 RNases, followed by analysis of electrophoretic mobility on polyacrylamide gels and of the AMP-to-adenosine ratio after alkaline hydrolysis. The poly(A) sequences are located at the 3' end of the RNA as shown by mild digestion by snake venom phosphodiesterase.

Vesicular stomatitis virus (measles) pseudotypes: tool for demonstrating defective measles infections

Mixed infection of Vero cells with measles and vesicular stomatitis viruses gives rise to phenotypically mixed infections virus particles possessing the properties of pseudotypes. Similar results were obtained when vesicular stomatitis virus was used to superinfect a defective measles system.