The experience to use a modified en bloc excision technique in vitrectomy for diabetic traction retinal detachment

Modified en bloc excision is a technique in which all posterior hyaloid is excised except the portions essential for membrane dissection. Then, bimanual dissection techniques allow excision of retained fibrovascular membrane "en bloc" with hyaloid. In a consecutive series of 16 eyes with diabetic traction retinal detachment treated with this technique, visual acuity of 5/200 or better was obtained in 11 (69%) of the cases, and complete macula reattachment was noted in 14 (87%) of 16 eyes. The final visual acuity was improved in 12 (75%) cases. While this surgical technique allows a higher rate of anatomic success and less postoperative morbidity, visual results remain limited by irreversible alteration in retinal function.

Biphasic dispersion of clones containing Purkinje cells and glia in the developing chick cerebellum

The cerebellum is a highly conserved structure which exhibits patterns of gene expression and axonal connections that are organized into parasagittal domains. These aspects of the mature cerebellum are presaged during embryonic development by the expression patterns of vertebrate homologs of Drosophila segmentation genes. We wished to determine whether the parasagittal domains of gene expression are compartments of lineage restriction. To this end, a clonal analysis of the chick cerebellum was conducted with a complex retroviral library. From embryonic day (E) 8 to E12, clones derived from the more medial portion of the cerebellar ventricular zone (VZ) were observed to spread preferentially in the mediolateral direction, crossing the boundaries of the parasagittal domains of gene expression. In late embryonic and posthatch periods, VZ clones were found to comprise Purkinje cells, glial cells, or both types of cells. At these later times, clonally related glial cells formed tight parasagittal clusters, while clonally related Purkinje cells were scattered extensively in the anteroposterior direction. We propose that a subset of the cerebellar VZ clones, those with medial origins, undergoes a biphasic dispersion: an early phase of mediolateral dispersion and a late phase of anteroposterior dispersion. This novel pattern of clonal dispersion suggests that the cerebellar VZ is not partitioned into parasagittal domains of lineage restriction. It leaves open the possibility that the later dispersion along the anteroposterior axis results from the parasagittal patterns of gene expression in the developing cerebellar cortex.

Cytogenetic aspects of the Canadian early and mid-trimester amniotic fluid trial (CEMAT)

Cytogenetic results from a large multicentre randomized controlled study of 2108 amniotic fluids obtained at 11+0-12+6 weeks (EA) and 1999 fluids at 15+0-16+6 weeks (MA) were compared. There was no statistically significant difference in the rate of chromosome abnormalities (EA =1.9 per cent; MA=1.7 per cent) or level III mosaicism (EA=0.2 per cent; MA= 0.2 per cent) between the groups. Level I and Level II mosaicism occurred more frequently in MA. Maternal cell contamination was not significantly different between the groups, but maternal cells only were analysed from one bloody EA fluid. The number of repeat amniocenteses because of cytogenetic problems was 2.2 per cent in the EA group compared with only 0.3 per cent in the MA group. On average, culture of EA fluids required one day more than MA fluids. Although both culture success (97.7 per cent) and accuracy (99.8 per cent) were high for patients randomized to the EA group, routine amniocentesis prior to 13 weeks' gestation is not recommended for clinical reasons including an increased risk of fetal loss and talipes equinovarus.

Rationale, design, and baseline results of the Pravastatin-to-Simvastatin Conversion Lipid Optimization Program (PSCOP)

A program designed to increase the percentage of patients at a Department of Veterans Affairs health system who meet their cholesterol goals as recommended by the National Cholesterol Education Program (NCEP) is described, and baseline results are reported. Patients with an active prescription for pravastatin between February 4 and June 4, 1997, were identified for conversion to simvastatin by means of the Pravastatin-to-Simvastatin Conversion Lipid-Optimization Program; 1361 patients were eligible for conversion. Each patient was mailed a survey for determining risk factors for coronary heart disease (CHD) and NCEP-recommended low-density lipoprotein (LDL) cholesterol goal and was asked to provide a fasting blood sample for determination of lipid profile, liver function, and serum creatine phosphokinase concentration. The patients were asked to make a follow-up laboratory visit six to seven weeks after they had started taking simvastatin. The percentage change from baseline and the percentage of patients who meet their LDL cholesterol goal before and after the conversion will be determined. A total of 1115 patients were converted to simvastatin. Only 35.4% of patients taking pravastatin to prevent a second CHD-related event met or exceeded their LDL cholesterol goal. Only 36.2% of patients with two or more CHD risk factors who were taking pravastatin for primary prevention met or exceeded their LDL cholesterol goal. In a veterans population, less than half of patients receiving a 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitor had LDL cholesterol concentrations that met goals recommended by the NCEP.

Catheter microwave ablation therapy for cardiac arrhythmias

This article describes three microwave catheter antennas for percutaneous cardiac ablation. A particular design feature of these antennas is that there is no reflected microwave current from the antenna flowing up the transmission line. Thus, it minimizes heating of the coaxial cable. The power reflection coefficients are very low (4% or less) in phantom equivalent materials. These antennas can also serve as bipolar electrodes for sensing endocardiac electrograms. Our studies in dogs, during both cardiopulmonary bypass and closed-chest operations via the femoral vein, have shown microwave energy greater than 200 joules (J) delivered to the heart through a split-tip dipole catheter antenna can produce irreversible block of the heart rhythms. This energy was achieved either by increasing the delivered power from 20 to 40 watts or by increasing the treatment duration from 7 to 11 s (210 to 330 J per application). It produced an endocardium temperature of about 65 degrees C. We found that the percutaneous, transcatheter microwave system is capable of inducing AV blocks consistently in dogs using the flexible, curved tip, split-tip catheter antenna. In addition, our studies have shown that the width and height of SAR distributions for cap-choke and split-tip catheter antennas are similar for the same antenna length. The cap-slot design had a much longer SAR distribution compared to the others. Moreover, a longer (4 mm) split-tip antenna can also induce larger lesions. These results suggest that it could be possible to ablate a ventricular tachycardia focus using the 4 mm split-tip as well as the cap-slot microwave catheter antennas.

Locally advanced nasopharyngeal cancer: long-term outcomes of radiation therapy

PURPOSE

To investigate the clinical manifestations and treatment outcomes in patients with stage T4M0 nasopharyngeal carcinoma.

MATERIALS AND METHODS

Findings in 179 patients (age range, 13-78 years) with American Joint Committee on Cancer stage T4M0 nasopharyngeal carcinoma treated from January 1983 to February 1992 with a minimum follow-up of at least 5 years were reviewed. Of the 179 patients, 166 (92.7%) had World Health Organization type II or III disease. Forty-one patients (22.9%) had no lymph nodal involvement; 138 patients (77.1%) had metastatic nodal involvement in the neck. All patients underwent radiation therapy; 39 patients also received different forms of chemotherapy. The radiation therapy doses were usually 70-74 Gy administered to the primary tumor over 7 or 8 weeks, 70-74 Gy to the neck region in patients with nodal involvement, or 50-60 Gy administered to the neck region over 5 or 6 weeks in patients without neck nodal involvement.

RESULTS

In 100 patients, radiation therapy failed in the primary tumor alone (n = 28), neck nodes alone (n = 5), and distant metastases alone (n = 43) or at a combination of sites (n = 24). The cumulative failure rates for the primary tumor, neck metastases, and distant metastases were 25.1% (n = 45), 14.0% (n = 25), and 33.0% (n = 59), respectively. The 5-year primary disease-free, distant disease-free, and overall survival rates were 68.7%, 56.5%, and 28.6%, respectively. Results of salvage treatment for relapse were unsatisfactory.

CONCLUSION

In about three-tenths of patients, T4M0 nasopharyngeal carcinoma can be cured with conventional high-dose radiation therapy.

Multicenter comparison of PCR assays for detection of human herpesvirus 8 DNA in semen

Reported prevalences of human herpesvirus 8 (HHV-8) (Kaposi's sarcoma-associated herpesvirus) in semen have ranged widely. This is possibly due to differences in assay sensitivity, geographic or population-based differences in the true presence of the virus in semen, and PCR contamination. This study assessed interlaboratory sensitivity and reproducibility in the analysis of blinded experimental panels, each consisting of 48 specimens and being composed of semen specimens from different healthy artificial-insemination donors (n = 30) and human immunodeficiency virus (HIV)-infected patients (n = 7) plus positive (n = 4) and negative (n = 7) controls. The experimental panels analyzed in each laboratory were identical except for being independently coded. Of 10 experiments done in five laboratories, 5 experiments from three laboratories had evidence of PCR contamination; all instances of contamination were in the context of nested PCR procedures. In the experiments with no false-positive results, HHV-8 DNA was detected in three (8%) of the 37 semen specimens (two from artificial-insemination donors and one from an HIV-positive patient) but in only 3 (1.6%) of the 184 PCRs in which these specimens were analyzed. This suggests that HHV-8 DNA is present in semen at concentrations that can be too low to allow its consistent detection. This study emphasizes the importance of performing blinded, multi-institution experiments to provide a coherent basis for comparing results and to motivate standardization of methods.

MRI compatibility and visibility assessment of implantable medical devices

We have developed a protocol to evaluate the magnetic resonance (MR) compatibility of implantable medical devices. The testing protocol consists of the evaluation of magnetic field-induced movement, electric current, heating, image distortion, and device operation. In addition, current induction is evaluated with a finite element analysis simulation technique that models the effect of radiofrequency fields on each device. The protocol has been applied to several implantable infusion pumps and neurostimulators with associated attachments. Experiments were performed using a 1.5-T whole-body MR system with parameters selected to approximate the intended clinical and worst case configuration. The devices exhibited moderate magnetic field-induced deflection and torque but had significant image artifacts. No heating was detected for any of the devices. Pump operation was halted in the magnetic field, but resumed after removed. Exposure to the magnetic field activated some of the neurostimulators.

High rate of clinical complete response to weekly outpatient neoadjuvant chemotherapy in oral carcinoma patients using a new regimen of cisplatin, 5-fluorouracil, and bleomycin alternating with methotrexate and epirubicin

BACKGROUND

A Phase II trial was initiated to evaluate the response to and toxicity of a new regimen of weekly outpatient neoadjuvant chemotherapy in patients with oral carcinoma.

METHODS

Patients with previously untreated squamous cell carcinoma of the oral cavity were eligible for this trial. The neoadjuvant chemotherapy was comprised of cisplatin, 25 mg/m2, 5-fluorouracil, 1000 mg/m2, and bleomycin, 10 mg/m2, mixed in normal saline as a 24-hour intravenous (i.v.) infusion, alternating with methotrexate, 30 mg/m2, and epirubicin, 30 mg/m2, as an i.v. bolus (PFB/ME) on a weekly schedule for 8-12 weeks. In patients with American Joint Committee on Cancer Stage IV disease who completed neoadjuvant chemotherapy, surgery was preferred to radiotherapy, unless patients refused surgery.

RESULTS

A total of 40 patients (82.5% with Stage IV disease) with previously untreated oral carcinoma were enrolled. The median size of the primary tumor was 7 cm (range, 3-13 cm). Fifty percent of patients had tumor penetrating through the oral mucosa to the cheek skin and 62.5% had bony destruction. Detectable cervical lymph nodes were noted in 77.5% of patients. After neoadjuvant weekly chemotherapy, 22 patients (55%) showed complete response (CR) and 15 patients (37.5%) showed partial response, for an overall response rate of 92.5%. World Health Organization Grade 3/4 toxicity included mucositis (7.5%), leukopenia (25%), anemia (10%), and thrombocytopenia (2.5%). Eleven of 33 patients with Stage IV disease underwent surgery, and pathologic CR (2 patients) or microscopic residual tumor (4 patients) was noted (54.5%).

CONCLUSIONS

The results of the current study indicate that a weekly PFB/ME neoadjuvant chemotherapy regimen is highly effective for the treatment of patients with oral carcinoma. In addition, this regimen has low toxicity. The authors believe that implementation of this regimen into a multimodality therapy protocol deserves further study.

Cardiac pheochromocytoma: resection after diagnosis by 111-indium octreotide scan

Cardiac pheochromocytoma is an exceedingly rare and unusual clinical entity. Only 37 previous surgically treated adult patients were found in review of the surgical literature. We report the case of a 13-year-old boy who had a cardiac pheochromocytoma that was localized by the 111-indium diethylenetriamine pentaacetic acid octreotide scintigraphy scan and confirmed by magnetic resonance imaging after computed tomographic and B1-iodine-metaiodobenzylguanidine scans had failed. At operation, a 6-cm pheochromocytoma of the left atrium was found and successfully resected with reconstruction of the left atrium using autologous pericardium.

Chronic creatine kinase elevation not associated with HMG-CoA reductase inhibitor treatment

OBJECTIVE

To report a case of chronically elevated creatine kinase (CK) concentration that is possibly associated with renal insufficiency and prostatic carcinoma. The goal is to raise awareness among clinicians who monitor CK concentrations in patients receiving hydroxymethylglutaryl-coenzyme A (HMG-CoA) reductase inhibitors.

CASE SUMMARY

Because of an elevated CK concentration, a 64-year-old African-American man with a history of chronic heart disease and renal insufficiency was assessed for possible myositis relating to his treatment with HMG-CoA reductase inhibitors. However, an association between the elevated enzyme concentration and drug treatment could not be clearly established. The patient was subsequently diagnosed with prostatic cancer and underwent a radical retropubic prostatectomy. The CK enzyme concentration declined following the surgery despite continuation of the drug therapy.

DISCUSSION

CK is relatively nonspecific because of its wide distribution in human tissues. Although several findings of elevated CK concentrations, particularly the CK-BB isoenzyme, in patients with carcinoma or chronic renal insufficiency have been documented, these may not be common knowledge among clinicians. This case report provides an example of an unusually high CK enzyme concentration that may be linked to prostatic carcinoma and renal insufficiency.

CONCLUSIONS

It is important to be aware of different causes for CK enzyme concentration elevation, especially when it is used as a monitoring parameter during HMG-CoA reductase inhibitor treatment. In a case of persistent elevated CK enzyme concentration without evidence of myositis, renal insufficiency may be a contributing factor and malignancy must be ruled out.

Brain energy stores in C57BL/6 mice after C. parvum injection

Activation of the immune system has been associated with the development of fatigue of unknown cause. We were interested in brain energy stores (e.g., phosphocreatine (PCr) and creatine kinase) after immune activation to investigate whether this system was altered. In this model, fatigue (defined as > 50% reduction in spontaneous running) was induced in C57BL/6 mice after a single injection of Corynebacterium parvum antigen. Maximal fatigue (about 86% reduction on day 10 post injection) was associated with reduced (about 29%) brain PCr/gamma-ATP and increased creatine kinase levels (approximately 31%), suggesting an active process of brain ATP depletion and replenishment. These findings need to be further delineated to establish the relationship between immune activation, reduced brain energy pools and fatigue.

Trabecular bone architecture in the distal radius using magnetic resonance imaging in subjects with fractures of the proximal femur. Magnetic Resonance Science Center and Osteoporosis and Arthritis Research Group

To determine whether magnetic resonance (MR)-derived measures of trabecular bone architecture in the distal radius are predictive for prevalent hip fractures, 20 subjects with hip fractures and 19 age-matched postmenopausal controls were studied. Bone mineral density (BMD) measures at the hip (dual-energy X-ray absorptiometry, DXA) and the distal radius (peripheral quantitative computed tomography, pQCT) were also obtained. We compared the MR-based structural measures derived in the radius with those in the calcaneus of the same patients. In the radius, images were acquired at an in-plane resolution of 156 microm and a slice thickness of 0.5 mm. Stereologic measures such as the apparent trabecular thickness (app. Tb.Th), fractional trabecular bone volume (app. BV/TV), trabecular spacing (app. Tb.Sp) and trabecular number (app. Tb.N) were derived from the images. Measures of app. Tb.Sp and app. Tb.N in the distal radius showed significant (p<0.05) differences between the two groups, as did hip BMD measures. However, radial trabecular BMD measures showed only a marginal difference (p = 0.05). Receiver operating curve analysis was used to determine the diagnostic efficacy of BMD, structural measures and a combination of the two. The area under the curve (AUC) for total hip BMD was 0.73, and for radial trabecular BMD was 0.69. AUC for most of the measures of trabecular bone structure at the distal radius was lower than for hip BMD measures; however, AUC for app. Tb.N at the radius was 0.69, comparable to trabecular BMD using pQCT. The AUC for combined BMD (hip) and structure measures was higher (0.87) when radius and calcaneus structure was included. Measures of trabecular architecture derived from MR images combined with BMD measures improve the discrimination between subjects with hip fractures and normal age-matched controls.

Fractal analysis of proximal femur radiographs: correlation with biomechanical properties and bone mineral density

Conventional radiography and fractal analysis were used to quantify trabecular texture patterns in human femur specimens and these measures were used in conjunction with bone mineral density (BMD) to predict bone strength. Radiographs were obtained from 51 human femur specimens (25 male, 26 female). The radiographs were analyzed using three different fractal geometry based techniques, namely semi-variance, surface area and Fourier analysis. Maximum compressive strength (MCS) and shear stress (MSS) were determined with a material testing machine: BMD was measured using quantitative computed tomography (QCT). MCS and MSS both correlated significantly with BMD (MCS: R = 0.49-0.54; MSS: R = 0.69-0.72). Fractal dimension also correlated significantly with both biomechanical properties (MCS: R = 0.49-0.56; MSS: R = 0.47-0.54). Using multivariate regression analysis, the fractal dimension in addition to BMD improved correlations versus biomechanical properties. Both BMD and fractal dimension showed statistically significant correlation with bone strength. The fractal dimension provided additional information beyond BMD in correlating with biomechanical properties.

The effect of converting from pravastatin to simvastatin on the pharmacodynamics of warfarin

Forty-six adult patients maintained on warfarin therapy were converted from pravastatin to simvastatin. Mean international normalized ratio (INR) significantly increased from 2.42 to 2.74, p = 0.002. Although warfarin doses were reduced in 7 patients and increased in 4 patients following the post-conversion INR measurements, the pre- and postconversion median weekly warfarin dose of all 46 patients did not differ significantly. The number of patients with an INR > 3.0 increased significantly from 6 to 16 following the conversion. There was no report of unusual episodes of bleeding. The results indicate that antihyperlipidemic therapy can be changed safely from pravastatin to simvastatin in patients who are taking warfarin concomitantly. Additional anticoagulation monitoring is not necessary in institutions where patients are followed in formal anticoagulation clinics.

Granule cell raphes and parasagittal domains of Purkinje cells: complementary patterns in the developing chick cerebellum

The extensive migration of granule cells and the parasagittal organization of Purkinje cells are two prominent features of cerebellar development. Using granule cell markers, we observed that the inward migration of a subset of granule cells occurs in streams that appear to be restricted to specific areas in the developing chick cerebellum. These streams are organized into a stereotypical series of parasagittal linear arrays, similar to the "granule cell raphes" described previously by . Similar raphes were found in the developing cerebellum of other avian species but not in the mouse cerebellum. During the period when granule cell raphes are apparent, Purkinje cells appear to be segregated into discrete parasagittal domains, interrupted by Purkinje cell-poor areas that correspond to the granule cell raphes. Purkinje cells in each domain exhibit a domain-specific expression profile of genes, including Bmp-7, EphA5/Cek-7, EphA4/Cek-8, and several chick homologs of Drosophila segmentation genes. From embryonic day 12 (E12) to E15, most of these genes gradually cease to be expressed differentially in parasagittal stripes, concurrent with the disappearance of the granule cell raphes by E15-E16. The spatial and temporal correlations of granule cell raphes and Purkinje cell parasagittal domains suggest a novel interaction between these two cell types and a potentially critical period of parasagittal patterning of the chick cerebellum.

Proximal femur: assessment for osteoporosis with T2* decay characteristics at MR imaging

PURPOSE

To use T2* measurements at magnetic resonance (MR) imaging to investigate the trabecular structure of the hip in women with and women without osteoporotic hip fractures and to compare this technique with bone mineral density (BMD) measurements in the diagnosis of fractures.

MATERIALS AND METHODS

T2* maps of the proximal femur were obtained at 1.5 T in 23 postmenopausal study patients with osteoporotic hip fractures, 27 age-matched healthy postmenopausal control subjects, and five healthy premenopausal control subjects. A modified gradient-recalled acquisition in the steady state, or GRASS, sequence was used with echo times of 4-40 msec at 4-msec increments. T2* values were measured in five regions of interest: femoral neck, the Ward triangle, trochanter, intertrochanteric region, and total proximal femur. Additionally, BMD measurements of the hip were obtained with dual x-ray absorptiometry.

RESULTS

Significant differences between T2* measurements were obtained in all three groups (P < .05). BMD measurements of the hip also showed significant differences (P < .05). For T2* and BMD measurements, odds ratios and areas under the curve in receiver operating characteristic analysis were comparable. Correlations between 1/T2* values and BMD were significant (P < .05). T2* measurements in the proximal femur showed regional variations.

CONCLUSION

MR imaging decay characteristics of bone marrow could be used to differentiate between postmenopausal women with and those without osteoporotic hip fractures.

Unusually high frequency of a 69-bp deletion within the carboxy terminus of the LMP-1 oncogene of Epstein-Barr virus detected in Burkitt's lymphoma of Turkish children

Burkitt's lymphoma (BL) in Turkish children is commonly associated with Epstein-Barr virus (EBV) infection. The C-terminus of the latent membrane protein 1 (LMP-1) of EBV is essential for transformation and the 30-bp deletion detected in this region has been implicated to be associated with a more aggressive malignant phenotype. To understand the molecular mechanisms underlying EBV pathogenesis in BL of Turkish children, we analyzed 30-bp deletion and 33-bp variable repeat regions of the LMP-1 gene from paraffin-embedded tumor tissues of 30 BL patients (mean age 5.9 years). Primer pairs spanning the 30-bp deletion and 33-bp repeat regions were designed for amplification by polymerase chain reaction (PCR). The PCR-amplified products were analyzed by gel electrophoresis, Southern blot hybridization, and DNA sequencing. Twenty-eight (93%) of 30 BL biopsy samples were EBV positive as determined by PCR. Variable copy numbers (ranging from 4.5 to 7) of the 33-bp repeat of LMP-1 gene were detected in these EBV-containing tumor samples. To determine the frequency of the 30-bp deletion of the LMP-1 gene, we sequenced the amplimers encompassing this region. Analyses of DNA sequence of 28 Turkish BLs have disclosed four patterns: the first (32% (9/28)) is identical to B95-8 with no deletion, the second (11% (3/28)) is identical to Asian NPC CAO strain with 30-bp deletion, the third (46% (13/28)) is prevalent in Turkish BLs with a longer deletion (69 bp), and the fourth (11% (3/28)) consists of a mixture of 30-bp and 69-bp deletion. The occurrence of high frequency of the 69-bp deletion appears to have no correlation with the disease site. Mutations found in the CAO strain were also detected in the Turkish BL clustering at the amino acids 322, 334, 338 and 342; whereas mutations specific for Turkish BL were clustered at amino acids 326, 352 and 361. To assess the EBV genotype with the changes in C-terminus of LMP-1 gene, we performed genotyping by PCR to differentiate type A and B strain. All 28 patients were infected by type A EBV. Such a high frequency of the larger size (69 bp) deletion has never been reported. Ascertaining the role of this deletion in BL pathogenesis will require further study.

Congenital nasal pyriform aperture stenosis and single central maxillary incisor: CT and MRI findings

The authors report five cases of congenital nasal pyriform aperture stenosis (CNPAS). Four cases are presented as neonatal nasal obstruction and also have single central maxillary incisor (SCMI). Computed tomography examination indicates three of the SCMI are unerupted and one is erupted. The fifth case has an erupted SCMI and short stature. The associated SCMI in CNPAS is believed to be more than an isolated anomaly. Awareness of the associated features of CNPAS among the radiologist and otolaryngologist may help the diagnosis and treatment of the patient.

[Computer-assisted structure analysis of trabecular bone in the diagnosis of osteoporosis]

Osteoporosis is characterized by reduced bone mass and a deterioration of bone structure which results in an increased fracture risk. The purpose of this review is to evaluate structure analysis techniques in the diagnosis of osteoporosis. Several imaging techniques were applied to analyze trabecular bone, such as conventional radiography, high-resolution computed tomography (HR-CT) and high-resolution magnetic resonance imaging (HR-MRI). The best results were obtained using high-resolution tomographic techniques. The highest spatial resolutions in vivo were achieved using HR-MRI. These studies show that texture parameters and bone mineral density predict bone strength and osteoporotic fractures in a complementary fashion. Combining both techniques yields the best results in the diagnosis of osteoporosis.

Gadolinium-enhanced MRI in neuro-Behçet disease

Gadolinium-enhanced MRI is a practical method to evaluate the active lesion of Behçet disease and the response to treatment. This case was presented as a slow-growing brainstem tumor clinically and radiographically.

Activation of human herpesvirus 8 (HHV-8) thymidine kinase (TK) TATAA-less promoter by HHV-8 ORF50 gene product is SP1 dependent

Human herpesvirus 8 (HHV-8) is a newly discovered virus closely associated with Kaposi's sarcoma and primary effusion lymphomas. When they occur in patients with AIDS, these B-cell lymphomas frequently harbor another human herpesvirus, Epstein-Barr virus (EBV). To determine the molecular mechanisms of the regulation of early gene expression by the immediate-early gene products of HHV-8 and to assess possible molecular interactions between HHV-8 and EBV, we studied the regulation of the HHV-8 thymidine kinase (TK) promoter in cell lines harboring either or both viruses. The constitutive chloramphenicol acetyltransferase (CAT) activity of the TK promoter was low in all six cell lines tested. A putative immediate-early gene product of HHV-8 ORF50, which is a homolog of EBV BRLF1, was cloned into an expression vector and tested for its transactivating capacity. In the presence of 12-O-tetradecanoyl-phorbol-13-acetate (TPA), the CAT activity of the TK promoter was increased 7- to 720-fold by cotransfection with the ORF50 clone in EBV-producing cell lines (Ramos/AW, P3HR-1, and BC-1) but not in EBV-negative cell lines (BCBL-1 and Ramos), nor in the latently EBV-infected cell line Raji. The TK promoter contains three consensus SP1- and two AP1-binding sites. In electrophoretic mobility shift assays, the cellular factor SP1, but not AP1, was found to bind specifically to the TK promoter. To determine whether the increased CAT activity resulted from the interaction of SP1 with the ORF50 gene product, we introduced mutations into two SP1-binding sites. Both mutated SP1 sites had reduced SP1-binding activity and greatly decreased TK promoter responsiveness to ORF50 transactivation, suggesting that upregulation of TK promoter by ORF50 is SP1 dependent.