Effectiveness of wet and dry mercury vapour suppressant systems in a faculty of dentistry clinic.

The objective of this study was to determine the effectiveness of a liquid and a dry commercial mercury vapour suppressant system. Measurements were made in a student dental clinic, using a mercury vapour detector for periods up to 76 weeks. The two products examined were Mercon vap liquid in a stock jar and the Mercon tainer dry jar system. Amalgam scrap jars were removed from the study when the mercury vapour concentration in the jars exceeded the arbitrary cut-off criterion of 0.05 mg Hg m(-3). Results showed that the mercury vapour concentration in the liquid system exceeded the cut-off criterion in 44 weeks or less, whereas the dry system remained below the detection limit (0.01 mg Hg m(-3)) for the maximum measurement period of 76 weeks. It was concluded that the dry system is more effective and reliable than the liquid system. The reliability of the liquid system may be influenced by contact of amalgam scrap with the portion of the inner wall of the jar that is not covered by liquid. It is proposed that amalgam scrap contaminates the wall with mercury during its insertion.

Documented arterial gas embolism after spinal epidural injection.

We report the case of a 90-year-old man with syncope, arrhythmia, cardiac ischemia, and neurologic deficit after undergoing spinal epidural injection for control of pain related to post-herpetic neuralgia. The diagnosis of arterial gas embolus was made after air was identified in the left ventricle of the heart on an abdominal computed tomographic scan. Emergency physicians should consider and rapidly diagnose this rare but potentially fatal complication of spinal epidural puncture.

Characterization of the protein encoded by gene UL49A of herpes simplex virus type 1.

Herpes simplex virus type 1 (HSV-1) gene UL49A potentially encodes a primary translation product of 91 residues with a signal sequence at the N terminus and a membrane anchor domain near the C terminus. Mutants were generated in this gene and utilized to characterize the encoded protein on SDS-PAGE as a 6.7 kDa species which fractionated with infected cell membranes, was a relatively abundant virion component, and was not detectably O-glycosylated. The protein was identified by microsequencing as a 68 residue polypeptide formed by removal of 23 residues from the N terminus of the primary translation product. Cleavage of the signal sequence was also demonstrated by in vitro transcription and translation in the presence of microsomal membranes. The UL49A protein was efficiently solubilized along with envelope proteins by treatment of virions with a non-ionic detergent but only in the presence of a reducing agent, suggesting that it may be an envelope protein that is disulphide-linked to the tegument. It is apparent from mutational analysis that the 10 amino acid residues at the C terminus are not essential for synthesis of the protein, signal sequence cleavage, targeting to membranes and virions, linkage to the tegument and growth of virus in cell culture.

HSV Entry and Spread.

This chapter deals with assays commonly used to follow herpes simplex virus type 1 (HSV-1) entry into and spread between cells in tissue culture These are complex processes, known to involve several of the 20 or more HSV-encoded membrane proteins (see refs. 1 and 2 for recent reviews). HSV entry is mediated by a number of proteins on the surface of the virus particle. Recognition of and binding to target cells are known to involve at least three glycoproteins-gB, gC, and gD. gC mediates the initial interaction with cells, recognizing heparan sulfate proteoglycans on the cell surface. gB also interacts with heparan sulfate proteoglycans, and can substitute for gC in gC negative viruses. This initial, heparin-sensitive attachment to cells is relatively weak, and is followed by a more stable attachment to cells, apparently mediated by gD. Following attachment, the virus particle fuses with the cell membrane to mediate entry. Fusion is known to require gB and gH/gL, and possibly also gD, but their precise functions are uncertain. The roles of other virus-encoded membrane proteins in entry are unclear, but it is possible that different proteins may be required for entry into different cell types.

Isolation and characterization of two herpes simplex virus type 1 variants containing duplication of sequences within the unique long component of their genomes.

This paper reports the first spontaneous isolation of two DNA duplication variants in the unique long (UL) component of herpes simplex virus type 1 (HSV-1) strain 17+ genome, one (1719) with a duplication of 7.5 kb DNA sequences centered around OriL and the other (1740In) with a 356 bp DNA duplication between the UL19 (MCP) and UL20 open reading frames (ORFs). The variant 1719 is stable with the rare isolation of a wild type (strain 17+) genome presumably generated by the excision of the duplicated sequences during homologous recombination. Because of the 7.5 kb duplication, UL29 (DBP) is diploid and UL30 (DNA pol) is present as one complete and one partial copy. Although duplication in the variant 1740In involved sequences from the UL20 ORF, the virus produces an intact UL20 gene product. Both variants show normal growth characteristics when compared with the parental viruses. DNA duplications in these variants suggest a link between replication and recombination in HSV-1.

Characterization of the UL10 gene product of herpes simplex virus type 1 and investigation of its role in vivo.

On the basis of predicted amino acid sequence characteristics, herpes simplex virus type 1 gene UL10 is thought likely to encode a membrane protein with eight potential transmembrane regions. Previously, a protein with an apparent M(r) 47,000 on SDS-PAGE was identified as a product of this gene. Here we have further characterized this protein, and show that it is modified by N-linked glycosylation, associates with membranes from infected cells, and is a component of the virus particle. It is not essential for virus growth in tissue culture. To investigate its role in vivo a deletion mutant lacking the majority of the UL10 open reading frame was constructed (UL10-del). The in vitro growth properties of this virus were consistent with previous studies; it grew to give slightly lower yields than wild-type and revertant viruses, and had no apparent temperature-sensitive or host range phenotype. In vivo, in a mouse model, UL10-del was capable of establishing a latent infection, although it was impaired for growth at the periphery, and for spread to and/or growth within the nervous system relative to wild-type or revertant viruses.

The myristylated virion proteins of herpes simplex virus type 1: investigation of their role in the virus life cycle.

Herpes simplex virus type 1 (HSV-1) gene UL11 encodes a myristylated virion protein. In this paper we have characterized the UL11 product further and investigated its role in the virus life cycle. Wild-type HSV-1 strain 17syn+ expresses three electrophoretically distinguishable UL11 polypeptide species. Analysis of single plaque isolates demonstrated that two virus populations exist within the 17syn+ stock: a major population encoding only the two higher Mr species, and a minor population encoding the lowest Mr species alone. DNA sequence analysis suggests that the latter polypeptide differs from the former ones at a single amino acid residue only. The UL11 polypeptides are synthesized as delayed early gene products and are phosphorylated in vitro. Following subcellular fractionation of infected cells, they are found predominantly associated with membranes. Within the virus particle, they appear to reside within the tegument. An insertion mutant containing the lacZ gene from Escherichia coli within the UL11 open reading frame is viable in tissue culture, although it gives smaller plaques and is impaired for growth compared to the wild-type parent or revertant viruses; it does not have a temperature-sensitive or host-range phenotype. Thus, although required for efficient replication, the myristylated HSV-1 virion protein, in contrast to those of many other viruses, is not essential for virus growth in tissue culture.

Investigation of herpes simplex virus type 1 genes encoding multiply inserted membrane proteins.

The herpes simplex virus type 1 genome contains four open reading frames (ORFs) which are predicted to encode hydrophobic proteins with the potential to cross a membrane several times. The products of these genes (genes UL10, UL20, UL43 and UL53) have not previously been identified. To investigate the role of these proteins in the virus life cycle, we attempted to inactivate the genes individually by inserting the lacZ gene from Escherichia coli within the ORFs. Using this approach we have isolated insertion mutants for UL10 and UL43, as well as a deletion mutant lacking the majority of the UL43 ORF. The growth of the UL10-lacZ virus was slightly impaired in tissue culture compared to that of the wild-type virus parent, whereas the growth of the UL43 mutants was indistinguishable from that of wild-type virus. Furthermore, deletion of the majority of the UL43 ORF did not impair the ability of the virus to replicate in vivo at the periphery, or to spread to and replicate within the nervous system, in a mouse ear model. Repeated attempts to isolate lacZ insertion mutants for UL20 and UL53 were unsuccessful, suggesting that these genes may be essential for virus growth, at least in tissue culture. Using antipeptide sera, the products of genes UL10 and UL20 have been detected.

Gene UL11 of herpes simplex virus type 1 encodes a virion protein which is myristylated.

We have investigated whether herpes simplex virus (HSV) contains structural polypeptides which are modified by myristic acid. We demonstrate that herpes simplex virions contain a family of myristylated proteins, Mr approximately 13,000 to 16,000. These were mapped, using HSV-1/HSV-2 intertypic recombinants, to 0.130 to 0.204 map units on the virus genome. Using anti-peptide sera, raised against the carboxyterminus of the predicted UL11 gene product, we have established that the myristylated virion polypeptides are products of the viral gene UL11.

Occupational strain and the incidence of coronary heart disease.

The hypothesis that men in high "strain" occupations have an increased risk of developing coronary heart disease was tested during an 18-year follow-up study from 1965-1983 of a cohort of 8,006 men of Japanese ancestry in Hawaii. There were no significant associations between the incidence of coronary heart disease and the individual job components of high psychologic demands and low job control or for the high strain interaction of these two characteristics. There were, in fact, trends of associations opposite to that predicted by the job strain model which were of borderline significance in multivariate analyses. Stratified analyses by level of acculturation showed similar inverse associations of job strain and coronary heart disease for the more Westernized men and no association for the more traditional men. There were also no significant associations among the various job characteristics and the major risk factors for coronary heart disease in this cohort. The disagreement of these results with those from other studies may be due to methodologic differences of using men whose usual and current occupations were the same in this study compared with using only current occupation in the other studies, the use of different methods of measuring job strain, or the possibility that men in this cohort perceive or react to occupational strain differently.

The products of gene US11 of herpes simplex virus type 1 are DNA-binding and localize to the nucleoli of infected cells.

We have used antisera raised against synthetic oligopeptides to characterize the protein products from herpes simplex virus type 1 gene US11. These antisera recognized predominantly polypeptides of apparent molecular weight 21,000 and 22,000, but also polypeptides of apparent molecular weight 17,500, 15,000, 14,000 and 11,000. Tryptic peptide fingerprint analysis confirmed that these polypeptides were all closely related. The 21,000 and 22,000 molecular weight polypeptides were shown to be DNA-binding proteins, and immune electron microscopy demonstrated their strong localization within nucleoli of infected cells.

Serum Fc gamma-receptor-like molecules in primary biliary cirrhosis: a possible immunoregulatory mechanism.

Functionally active Fc gamma-receptor-like molecules were isolated from normal human serum by affinity chromatography and shown to have an apparent molecular weight (MW) of approximately 60,000 as assessed by SDS-polyacrylamide gel electrophoresis. These low MW Fc gamma-receptor-like molecules were found to be significantly reduced in whole serum, and in all of six serum fractions, obtained from patients with primary biliary cirrhosis (PBC). A high MW IgG-binding factor, with partial Fc gamma-receptor-like activity, was also found in PBC serum. This factor was also observed to a lesser extent in normal serum. Detailed analysis of this factor suggests that it is a large macromolecule consisting of antigen (unknown). IgG class antibody and 60K Fc gamma-receptor-like molecules. Binding of serum Fc gamma R-like molecules to immune complexes may account for the apparent reduction in Fc gamma-receptor-like activity observed in whole PBC serum. These macromolecules may play an important role in immunoregulation.