9th Chapter of Surgeons' Lecture: the orthopaedic surgeon: historical perspective, ethical considerations and the future.

From a fishing village with colonial surgeons from the East India Company, Singapore is now a medical and business hub servicing the region and beyond in trade and medical education. Orthopaedic Surgery is a young specialty and is the fastest growing sub-specialty in Surgery. Orthopaedic education in Singapore has a structured syllabus and training is coordinated with the Royal Colleges and the American Academy of Orthopaedic Surgeons. Part of the training as Fellows is in the United Kingdom and USA on an HMDP Fellowship. Ethics and Continuing Medical Education need further emphasis. Sub-specialisation in Orthopaedic Surgery is now well-established in Trauma, Adult Reconstructive Surgery, Sports Medicine, Spinal Surgery, Hand Surgery and Rehabilitation Medicine. Ageing in the next millennium with osteoporosis and hip fracture problems of gait and balance need more orthopaedic surgeons to be committed to rehabilitation medicine and voluntary service in the community. There is a need for good role models and knowledge on Quality Assurance, Clinical Pathways and Administration. Appropriate use of high technology and care for the aged in the community with dignity is fundamental to good ethical practice. Selfish, pecuniary interests will destroy the very soul and fabric of medicine.

Solar cycle variability, ozone, and climate

Results from a global climate model including an interactive parameterization of stratospheric chemistry show how upper stratospheric ozone changes may amplify observed, 11-year solar cycle irradiance changes to affect climate. In the model, circulation changes initially induced in the stratosphere subsequently penetrate into the troposphere, demonstrating the importance of the dynamical coupling between the stratosphere and troposphere. The model reproduces many observed 11-year oscillations, including the relatively long record of geopotential height variations; hence, it implies that these oscillations are likely driven, at least in part, by solar variability.

Exostosis presenting as solitary loose body in the ankle of two children.

Two children, aged 5 and 11 years, presented clinically with ankle pain and a mobile bony hard lump in the ankle. Radiological examination revealed a large radio-opaque shadow in relation to the talus. Intraoperatively, a loose body was found. It resembled a detached exostosis with cartilaginous cap and was confirmed histologically as an osteochondroma. In the older child, there was a remnant stalk attached to the lateral surface of the talus. In the younger child, the exostosis probably came from the talus as the osteochondroma could not originate from the epiphyses that form the ankle mortise.

Hangman's fracture in Singapore (1975-1988).

A retrospective study of 33 patients with fracture of the ring of the axis (hangman's fracture) admitted to the Spinal Unit of the Department of Rehabilitation Medicine in the Tan Tock Seng Hospital between 1975 and 1988 was carried out. The aims were to establish the causes, mechanism and outcome of injuries that lead to Hangman's fracture in Singapore. The majority were males (27) and their ages ranged from 16 to 82 with a mean age of 33.7 years. 63.6% (21 cases) were due to road traffic accidents of whom 33% (11 cases) were motorcyclists or pillion riders and 30.3% (10 cases) were drivers or passengers of four wheel vehicles such as cars and vans. Using Effendi et al's classification, we have 21 type I, 11 type II and one type III fractures. Thirteen type I, 6 type II and one type III cases had no neurological deficit on admission. The rest had deficits ranging from tetraparesis to pure bladder dysfunction. After rehabilitation, 28 (84.8%) of them were able to return to gainful employment within a year of their injuries.

A chronic illness characterized by fatigue, neurologic and immunologic disorders, and active human herpesvirus type 6 infection.

OBJECTIVE: To conduct neurologic, immunologic, and virologic studies in patients with a chronic debilitating illness of acute onset. DESIGN: Cohort study with comparison to matched, healthy control subjects. PATIENTS: We studied 259 patients who sought care in one medical practice; 29% of the patients were regularly bedridden or shut-in. MAIN OUTCOME MEASURES: Detailed medical history, physical examination, conventional hematologic and chemistry testing, magnetic resonance imaging (MRI) studies, lymphocyte phenotyping studies, and assays for active infection of patients' lymphocytes with human herpesvirus type 6 (HHV-6). MAIN RESULTS: Patients had a higher mean (+/- SD) CD4/CD8 T-cell ratio than matched healthy controls (3.16 +/- 1.5 compared with 2.3 +/- 1.0, respectively; P less than 0.003). Magnetic resonance scans of the brain showed punctate, subcortical areas of high signal intensity consistent with edema or demyelination in 78% of patients (95% CI, 72% to 86%) and in 21% of controls (CI, 11% to 36%) (P less than 10(-9)). Primary cell culture of lymphocytes showed active replication of HHV-6 in 79 of 113 patients (70%; CI, 61% to 78%) and in 8 of 40 controls (20%; CI, 9% to 36%) (P less than 10(-8], a finding confirmed by assays using monoclonal antibodies specific for HHV-6 proteins and by polymerase chain reaction assays specific for HHV-6 DNA. CONCLUSIONS: Neurologic symptoms, MRI findings, and lymphocyte phenotyping studies suggest that the patients may have been experiencing a chronic, immunologically mediated inflammatory process of the central nervous system. The active replication of HHV-6 most likely represents reactivation of latent infection, perhaps due to immunologic dysfunction. Our study did not directly address whether HHV-6, a lymphotropic and gliotropic virus, plays a role in producing the symptoms or the immunologic and neurologic dysfunction seen in this illness. Whether the findings in our patients, who came from a relatively small geographic area, will be generalizable to other patients with a similar syndrome remains to be seen.

Human herpesvirus 7: antigenic properties and prevalence in children and adults.

The recent isolation of human herpesvirus 7 (HHV-7) from activated CD4+ T lymphocytes of a healthy individual raises questions regarding the prevalence of this virus in humans and its immunological relationship to previously characterized human herpesviruses. We report that HHV-7 is a ubiquitous virus which is immunologically distinct from the highly prevalent T-lymphotropic HHV-6. Thus, (i) only two of six monoclonal antibodies to HHV-6 cross-reacted with HHV-7-infected cells, (ii) Western immunoblot analyses of viral proteins revealed different patterns for HHV-6- and HHV-7-infected cells, (iii) tests of sequential serum samples from children revealed seroconversion to HHV-6 without concomitant seroconversion to HHV-7, and (iv) in some instances HHV-7 infection occurred in the presence of high titers of HHV-6 antibodies, suggesting the lack of apparent protection of children seropositive for HHV-6 against subsequent infection with HHV-7. On the basis of the analyses of sera from children and adults it can be concluded that HHV-7 is a prevalent human herpesvirus which, like other human herpesviruses, infects during childhood. The age of infection appears to be somewhat later than the very early age documented for HHV-6.

Genomic polymorphism, growth properties, and immunologic variations in human herpesvirus-6 isolates.

Fifteen human herpesvirus-6 (HHV-6) isolates from normal donors and patients with AIDS, systemic lupus erythematosis, chronic fatigue syndrome, collagen-vascular disease, leukopenia, bone marrow transplants, Exanthem subitum (roseola), and atypical polyclonal lymphoproliferation were studied for their tropism to fresh human cord blood mononuclear cells, growth in continuous T cell lines, reactivity to monoclonal antibodies, and by restriction enzyme banding patterns. All isolates replicated efficiently in human cord blood mononuclear cells, but mitogen stimulation of the cells prior to infection was required. The ability to infect continuous T-cell lines varied with the isolates. Isolates similar to GS prototype infected HSB2 and Sup T1 cells and did not infect Molt-3 cells, whereas isolates similar to Z-29 infected Molt-3 cells but not HSB2 and Sup T1 cells. Some of the monoclonal antibodies directed against the HHV-6 (GS) isolate showed reactivity with all isolates tested, but others only reacted with HHV-6 isolates similar to the GS isolate and not with those similar to Z-29 isolate. Restriction enzyme analysis using EcoRI, BamHI, and HindIII revealed that HHV-6 isolates from roseola, bone marrow transplant, leukopenia, and an HIV-1-positive AIDS patient from Zaire (Z-29) were closely related but distinct from GS type HHV-6 isolates. Based on the above findings, we propose that, like herpes simplex virus types 1 and 2, the 15 HHV-6 isolates analyzed can be divided into group A (GS type) and group B (Z-29 type).

Characterization of a membrane-associated phosphoprotein of murine cytomegalovirus (pp50) and its immunological cross-reactivity with a human cytomegalovirus protein.

We have identified an abundant 50K phosphoprotein (pp50) in MCMV-infected 3T3-L1 cells and shown by immunofluorescence microscopy and surface-iodination experiments that pp50 is localized to the plasma membrane of the infected cell. Furthermore, the kinetics of its synthesis suggests that it belongs to the early-late class of herpesvirus proteins. Using monoclonal antibodies specific for pp50 to screen a lambda ZAP II expression library constructed from poly(A)+ mRNA of MCMV-infected cells, we have isolated a cDNA clone that synthesizes a truncated form of pp50 as a beta-galactosidase fusion protein. This allowed us to localize the partial pp50 transcript to a region between map coordinates 0.228 and 0.260 of the MCMV genome (Smith strain, Vancouver). Finally, we demonstrated that the MAb 5H10.21A recognizes an antigenic determinant that is conserved between pp50 and a 50K human cytomegalovirus (HCMV) nonstructural protein.

Transactivation of the human immunodeficiency virus promoter by human herpesvirus 6 (HHV-6) strains GS and Z-29 in primary human T lymphocytes and identification of transactivating HHV-6(GS) gene fragments.

Human herpesvirus 6 (HHV-6) can activate the human immunodeficiency virus (HIV) promoter and accelerate cytopathic effects in HIV-infected human T cells. This study examines the regions of the HIV promoter required for HHV-6 transactivation in a heterogeneous population of primary human T lymphocytes with or without antigenic stimulation. Two different strains of HHV-6, GS and Z29, transactivated the HIV promoter. The GS strain transactivated the promoter in both stimulated and resting T cells, while the Z29 strain increased HIV promoter activity only in stimulated T cells. Three DNA clones containing HHV-6(GS) genomic fragments transactivated the HIV promoter in cotransfected T cells. A 21.4-kb DNA clone, pZVB70, showed the highest transactivating ability, while two other DNA fragments, pZVB10 (6.2 kb) and pZVH14 (8.7 kb), showed lower activity. One of these clones, pZVH14, activated the HIV promoter construct containing a mutation in the NF kappa B site. However, this mutated NF kappa B promoter was not transactivated during HHV-6(GS) infection or after cotransfection with pZVB70 or pZVB10. These data indicate that the NF kappa B sites of the HIV promoter are essential for its transactivation during HHV-6(GS) infection. By increasing HIV promoter activity in primary T lymphocytes, HHV-6 may consequently increase HIV replication, leading to an increase in the cytopathic effect on coinfected human T cells.

Identification, characterization, and sequence analysis of a cDNA encoding a phosphoprotein of human herpesvirus 6.

Human herpesvirus 6 (HHV-6)-specific monoclonal antibody (Mab) 9A5D12 reacted with the nucleus of HHV-6 strain GS-infected cells and immunoprecipitated a phosphorylated polypeptide with an approximate size of 41 kDa, designated HHV-6 P41. A 110-kDa polypeptide was also immunoprecipitated by the MAb. These polypeptides were synthesized early in infection, and the synthesis was greatly reduced by phosphonoacetic acid. Polypeptides with identical sizes were recognized by the MAb from cells infected with an additional eight HHV-6 strains. A 2.1-kb cDNA insert was identified from an HHV-6(GS) cDNA library constructed in the lambda gt11 expression system by using MAb 9A5D12. This cDNA insert hybridized specifically with viral DNA from HHV-6 strains GS and Z-29 and with two predominant transcripts with approximate sizes of 2.5 and 1.2 kb from infected cells. The reactivity of the MAb with a fusion protein expressed in the prokaryotic vector suggested that the cDNA encodes a 62- to 66-kDa protein. Analysis of the nucleotide sequence of the cDNA insert revealed a 623-amino-acid-residue single open reading frame of 1,871 nucleotides, with an open 5' end. The predicted polypeptide is highly basic and contains a long stretch of highly hydrophobic residues localized to the carboxy terminus. The amino-terminal half of the predicted HHV-6 protein from the cDNA shows significant homology with the UL44 gene product of human cytomegalovirus, coding for the ICP36 family of early-late-class phosphoproteins. Two TATA boxes are located at nucleotide positions 668 and 722 of the cDNA. In vitro translation of RNA transcribed in vitro from the cDNA resulted in the synthesis of a 41-kDa polypeptide only. This polypeptide was readily immunoprecipitated by MAb 9A5D12, and its partial peptide map was identical to that of the 41-kDa polypeptide detected in infected cells. Together, these results indicate that the HHV-6 P41 is encoded within a gene coding for a larger protein.

Human herpesvirus-6 infection may predispose cells to superinfection by other viruses.

Double infection of cells by HHV-6, Epstein-Barr virus (EBV) and by human immunodeficiency virus (HIV-1) can enhance viral effects though genetic transactivation. It remained to be clarified, however, by which mechanism different viruses may enter the same cell. We have shown that HHV-6 infection of immature lymphoid cells rigidifies the cytoplasmic membrane and causes receptor proteins for viruses such as CD4 for HIV-1 and CR2 for EBV to be expressed. In our experiments, HHV-6 infected cells were superinfected by HIV1 and caused enhanced cell death. The mechanisms by which receptors were expressed after HHV-6 infection appears independent of cell membrane rigidification alone and is suppressed by cycloheximide only to a certain extent.

Human herpesvirus-6 (HHV-6) (short review).

Human Herpesvirus-6 is the etiological agent of Roseola infantum and approximately 12% of heterophile antibody negative infectious mononucleosis. HHV-6 is T-lymphotropic, and readily infects and lyses CD4+ cells. The prevalence rate of HHV-6 in the general population is about 80% (as measured by IFA) with an IgG antibody titer of 1:80. A lower prevalence, however, is observed in some countries. HHV-6 is reactivated in various malignant and non-malignant diseases as well as in Chronic Fatigue Syndrome and transplant patients. Furthermore, elevated antibody titers were also observed in lymphoproliferative disorders, auto-immune diseases and HIV-1 positive AIDS patients. There appears to be some strain variability in HHV-6 isolates. The GS isolates of HHV-6 (prototype) was resistant to Acyclovir, Gancyclovir, but its replication was inhibited by Phosphonoacetic acid and Phosphoformic acid. HHV-7 isolated from healthy individuals showed, by restriction analysis, that 6 out of 11 probes derived from two strains of HHV-6, cross-hybridized with DNA fragments, derived from HHV-7.

Identification of herpes simplex virus infection by immunoperoxidase and in situ hybridization methods.

Seven cases of visceral herpes simplex virus (HSV) infection were observed in five cases of hematopoietic disease and in one case each of a newborn baby and a pregnant woman. These seven cases were studied with an immunoperoxidase method and in situ hybridization. In HSV lesions of squamous epithelium, the immunoperoxidase method using rabbit anti-human HSV revealed positive staining, mainly in the nucleus but with some cytoplasmic staining. DNA in situ hybridization revealed stronger positive staining in the nucleus. In HSV hepatitis positive staining was seen in the nucleus and cytoplasm, both by immunoperoxidase and in situ hybridization methods. In the newborn baby, HSV lesions were observed in the brain only, with numerous positive astrocytes identified by the immunoperoxidase method and a few positive astrocyte nuclei by in situ hybridization. Cultured human fetal fibroblasts from the lung were infected with HSV. The immunoperoxidase method revealed diffuse positive staining in the nucleus and in the cytoplasm whereas in situ hybridization revealed fibrillar positive staining in the nucleus only. Thus, the immunoperoxidase method using rabbit anti-human HSV can detect the presence of HSV protein more sensitively than in situ hybridization, probably because of the greater quantity of HSV protein compared with HSV DNA in infected cells.

Electrophoretic analysis of human herpesvirus 6 polypeptides immunoprecipitated from infected cells with human sera.

Proteins of human herpesvirus 6 (HHV-6) eliciting human antibody responses were examined in serum from healthy adults and patients with AIDS, chronic fatigue syndrome, Hodgkin's disease, and Sjögren's syndrome. HHV-6 IgG antibody titers measured by immunofluorescence (IF) ranged from 1:10 to 1:1280. Lysates of HHV-6-infected and uninfected cells labeled with [35S]methionine, [3H]glucosamine, and 125I were immunoprecipitated with sera and analyzed electophoretically. Sera with IF titers greater than or equal to 1:20 immunoprecipitated greater than 20 [35S]methionine-labeled HHV-6 polypeptides of approximately 26-180 kDa. At least 10 HHV-6 glycoproteins and 8 HHV-6 polypeptides associated with the surfaces of infected cells were recognized by human sera. The approximate molecular masses of glycoproteins immunoprecipitated by human sera were similar to those immunoprecipitated by monoclonal antibodies. The labeling intensity of HHV-6 protein bands increased with increasing IF titer, and the effect was most prominent for HHV-6 glycopolypeptides. No reactivities with specific HHV-6 polypeptide(s) were characteristic of a given patient group. These findings suggest that HHV-6 glycoproteins are good targets for human antibody responses.

A chronic "postinfectious" fatigue syndrome associated with benign lymphoproliferation, B-cell proliferation, and active replication of human herpesvirus-6.

A 17-year-old, previously healthy woman developed an acute "mononucleosis-like" illness with an associated "atypical" pneumonitis, followed by years of debilitating chronic fatigue, fevers, a 10-kg weight loss, night sweats, and neurocognitive symptoms. Thereafter, her sister developed a similar but less severe illness. The patient developed marked, chronic lymphadenopathy and splenomegaly, with associated persistent relative lymphocytosis and atypical lymphocytosis and with thrombocytopenia. After 3 years of illness, a splenectomy was performed, which resulted in some symptomatic improvement, prompt weight gain, and resolution of all hematologic abnormalities. Serial immunologic studies revealed a strikingly elevated number of activated B lymphocytes and a T lymphopenia, which improved but did not return to normal postsplenectomy. No causal association was found with any of several infectious agents that could produce such a lymphoproliferative illness. However, both the patient and her sister had evidence of active infection with the recently discovered human herpesvirus-6. Seven years after the onset of the illness, the patient and her sister remain chronically ill.

Variations in the replication and antigenic properties of human herpesvirus 6 strains.

The Z29 and U1102 strains of human herpesvirus 6 (HHV-6) were compared for their ability to replicate in fresh peripheral blood lymphocytes (PBL) and in continuous T cell lines. The replication of both strains in PBL was enhanced by mitogenic activation of cell growth. U1102 replicated in the continuous T cell lines, J JHAN and HSB-2, whereas no Z29 replication was observed in these cell lines as judged by infectious virus yields, the presence of viral antigens, and viral DNA replication. The two strains were compared with respect to their ability to react in immunofluorescence assays with monoclonal antibodies (MAbs) prepared against the GS strain of HHV-6. These MAbs are directed against six different polypeptides including three glycoproteins. All MAbs reacted with cells infected with the U1102 strain. The Z29-infected cells reacted with four MAbs but failed to react with MAbs specific for an 82- to 105-kDa major surface glycoprotein and with one MAb reactive with a nonglycosylated 180-kDa protein. Taken together, the two strains of HHV-6 exhibit variations with regard to their growth and antigenic properties.