AB1099 CORONAVIRUS INFECTION IN PATIENTS WITH SYSTEMIC LUPUS ERYTHEMATOSUS (CASE SERIES)

Background

SARS -CoV 2 infection (Covid -19) has a wide range of Clinical and laboratpry symptoms typical for rheumatic diseases, in particular systemic lupus erythematosus (SLE).

Objectives

Analysis of the course of Сovid-19 in patients with SLE and the influence of antirheumatic drugs on its outcomes.

Methods

A retrospective analysis of 12 patients with SLE previously observed in the rheumatology department and had Covid-19 in 2020-2021. Average age of patients (83% women) is 41 years (24-59 years old), duration of SLE - 11 years (3-25 years). 10 patients had low SLE activity, 1 - moderate, 1 - high. In anamnesis 8 patients had hematological disorders, 4 - secondary antiphospholipid syndrome (APS) with thrombosis, 3 - cerebrovasculitis, 5 - lung damage, 3 - lupus nephritis. All patients were treated with glucocorticosteroids (GCs) (the average dose 2 1/4 tablets per day), 10 (66,7%) - with hydroxychloroquine (HCQ), 4 (33,3%) – with immunosuppressants: 2 - mycophenolate mofetil, 1 - methotrexate, 1 – cyclophosphamide. 3 (25%) patients received rituximab (RTM) 2-3 months before the onset of COVID-19. 9 (75%) patients received outpatient treatment, 5 of them had a mild infection (3 - without lung damage, 2 - with lung damage - CT 1), 4 - had a moderate course, 3 (25%) - were admitted to the hospital,1 - to the intensive care unit.

Results

Patients were divided into 3 groups for SLE therapy. The first group (6 patients) was treated with GCs (average dose of 1 1/2 tab.) and HCQ (200-400 mg). All of them had mild to moderate course of infection without complications. Exacerbation of SLE was noted in 3 (50%) patients: 2 had capillarities, psycho-emotional lability, deterioration of laboratory parameters, 1 (with secondary APS) developed deep vein thrombosis of the legs and an exacerbation of lupus nephritis a month after. The second group (3 patients) received GCs (average dose 2 1/4 tab.) and immunosuppressants. In 2 patients the course of Covid-19 was mild, in 1 - moderate. Exacerbation of SLE was noted in 2 patients: 1 had headaches, high titers of ANA and anti-DNA, 2nd - a severe exacerbation (hematological disorders, lupus nephritis with impaired renal function). The third group (3 patients) received GCS (average dose 5 tab.) and rituximab. 2 patients received RTM for 2 years, the last infusion was carried out for 3 months before the onset of an infection. Their course of Covid-19 was moderate with CT-2 lung damage and mild respiratory failure. There were no exacerbations of SLE after recovery. The 3rd patient initially had a high activity of SLE with nephrotic syndrome, arterial hypertension, batterfly rash, arthritis, fever, which required high doses of GCs and 2 rituximab infusions of 500 and 1000 mg. A month later, a severe COVID-19 developed with 70% lung damage, severe respiratory failure (SpO2 - 80%), and cytokine storm syndrome. He was treated with GCS, anticoagulants, tocilizumab, immunoglobulin, followed by recovery. Mild and moderate course of COVID-19 was observed in 92% of patients with SLE, in 8% - severe. Exacerbation of SLE after infection occurred in 41% of cases with no lethal outcomes.

Conclusion

Patients with low activity SLE on small doses of GCs and HCQ tolerate COVID-19 relatively easily. The high activity of SLE and the use of rituximab contribute to the severe course of COVID-19 with damage to the lungs and respiratory failure, so the use of anti-B-cell therapy during a pandemic is undesirable. The effect of immunosuppressants is controversal. Exacerbation of SLE after COVID-19 in 41% of all patients requires monitoring of laboratory parameters and observation by a rheumatologist for at least six months after recovery from infection.

Disclosure of Interests

None declared

AB1276 NON-INTERFERON THERAPY OF CHRONIC HEPATITIS C IN A PATIENT WITH SYSTEMIC LUPUS ERYTHEMATOSUS AND SECONDARY SJÖGREN SYNDROME - CASE REPORT

Background:

Hepatitis C virus infection is one of the most significant public health problems in the world. To date, the problem of selection of therapy is very relevant for patients with autoimmune diseases and chronic hepatitis C [1]. Patients with systemic lupus erythematosus (SLE) are forced to take different doses of steroids, often in combination with immunosuppressants (mycophenolate mofetil, azathioprine, etc.) even in the case of long-term remission. Such therapy for many years can contribute to the reactivation of hepatitis C.

Objectives:

To describe a clinical case of the effectiveness of the combined use of interferon-free therapy and therapy of steroids in a patient with SLE, secondary Sjogren syndrome and chronic hepatitis C.

Methods:

56 years-old woman was admitted to the rheumatology department of Clinical Hospital No. 1 in December 2018 with the debut of SLE: photosensitivity, aphthous stomatitis, arthritis, pleurisy, sicca syndrome, leukopenia, ANA 1: 2560, antibodies to dsDNA 55.95 IU / ml, positive antiSS-A (Ro). At the same time, it became known that she was infected with hepatitis C virus in 1985 presumably. At the time of hospitalization, anti-HCV was positive, the virus genotype was 1b, the activity of the process was low (HCV RNA 6.6x104, AST 33 U/L and ALT 25 U/L). The patient was prescribed corticosteroids (methylprednisolone 16 mg/day) and hydroxychloroquine 400 mg/day. In January 2019, after gastroenterologist, hematologist and infectious disease specialist advise, it was decided to conduct the patient a specific interferon-free antiviral therapy for chronic hepatitis C (a 24-week course with asunaprevir and daclatasvir), given the potential long-term glucocorticoid therapy, with the prospect of treating the patient with cytotoxic drugs, and the possibility of reactivation of chronic hepatitis C amid of immunosuppressive therapy for SLE and Sjogren syndrome.

Results:

Low-disease activity of SLE was achieved in a month, and after 24-week course of antiviral therapy, there was no increase in SLE activity, and positive laboratory and clinical dynamics were noted.

Conclusion:

Thus, the use of interferon-free therapy of chronic hepatitis C in patients with systemic lupus erythematosus and secondary Sjogren syndrome shows possible ways to safe treatment of this disease in patients with diffuse connective tissue diseases.

References:

[1]Xiaobo Zhu, Mingqi Wang, Mei Liu, Xinghao Yu & Peng Huang. Efficacy and safety of direct-acting antivirals for treatment-naive patients with genotype 1 hepatitis C virus infection. Per Med. October 2019. 16 (5): 421 doi: 10.2217/pme-2018-0121.

Acknowledgments:

Supported by the “Russian Academic Excellence Project 5-100”

Disclosure of Interests:

None declared

Megestrol Acetate for Cachexia and Anorexia in Advanced Non-small Cell Lung Cancer: A Randomized Study Comparing Two Different Doses

Background

The primary aim of the study was to compare two different dose levels of megestrol acetate, administered for cancer-related anorexia and cachexia for 3 months.

Methods

From August 1996 to December 2000, 119 patients with advanced non-small cell lung cancer were randomized to take 160 mg/day or 320 mg/day of megestrol acetate for 3 months at the Gülhane Military Medicine Academy of Ankara, Turkey. Patients were controlled at biweekly periods.

Results

There were 59 patients in the single dose arm (group 1) and 60 patients in the twice a day dose arm (group 2). The mean percentages of weight loss were 16.9% and 16.7% in group 1 and 2, respectively. In the first and the second month of weight gain, there were no significant differences in the two groups (P = 0.23 and P = 0.11). In the third month, weight gain was significantly higher in group 2 than in group 1 (P = 0.038). Toxicity was similar for both dose levels.

Conclusions

Megestrol acetate can be safely and effectively given to patients with advanced non-small cell lung cancer. Although lower doses of megestrol acetate can be effective for anorexia and cachexia, the higher dose level seems to be more efficient.

Determination of parameters affecting the use of complementary and alternative medicine in cancer patients and detection of prevalence of use

This study was conducted to find out the frequency of complementary and alternative medicine (CAM) use that could lead to troubles in patient health and in applied standard therapy protocols when used improperly, which method is used, the reasons for use and from which resources the information about this topic were obtained. A questionnaire consisting of 28 questions was applied to 195 patients with cancer diagnosis by a face-to-face interview. The obtained data were assessed with SPSS 11.5 program. Out of 195 cancer patients, 100 (51.3%) were using CAM and 48.7% (n=95) were not. The most commonly used agent was nettle (72%). This was followed by herbal teas (21%), grape molasses (20%) and black seed (20%). The frequency of CAM use was found higher in those under age 50, in literate people, in those working during the diagnosis stage and having disease at the later stage. While CAM was commonly recommended by friends and relatives of the patients (73%), this ratio was only 5% for health professionals. While 51.3% of all patients were gathering information about CAM, 75% of those actually using CAM gathered information about it. Whilst information was gathered mostly from the relatives of patients and tamperers (47%), it can be gathered from physicians only with a ratio of 10%. Cancer patients use CAM and they gather information mainly from unreliable sources rather than physicians. Although the primary information source should be physicians, the ratio for this was very low (10%). We suggest that physicians should spend more time in gathering correct information and sharing them with their patients for a better guidance.

Patterns of care for lung cancer in radiation oncology departments of Turkey

PURPOSE

To determine the patterns of care for lung cancer in Turkish radiation oncology centers.

METHODS AND MATERIALS

Questionnaire forms from 21 of 24 (87.5%) centers that responded were evaluated.

RESULTS

The most frequent histology was non-small cell lung cancer (NSCLC) (81%). The most common postoperative radiotherapy (RT) indications were close/(+) surgical margins (95%) and presence of pN2 disease (91%). The most common indications for postoperative chemotherapy (CHT) were ">/= IB" disease (19%) and the presence of pN2 disease (19%). In Stage IIIA potentially resectable NSCLC, the most frequent treatment approach was neoadjuvant concomitant chemoradiotherapy (CHRT) (57%). In Stage IIIA unresectable and Stage IIIB disease, the most frequent approach was definitive concomitant CHRT (91%). In limited SCLC, the most common treatment approach was concomitant CHRT with cisplatin+etoposide for cycles 1-3, completion of CHT to cycles 4-6, and finally prophylactic cranial irradiation in patients with complete response (71%). Six cycles of cisplatin + etoposide CHT and palliative thoracic RT, when required, was the most commonly used treatment (81%) in extensive SCLC. Sixty-two percent of centers did not have endobronchial brachytherapy (EBB) facilities.

CONCLUSION

There is great variation in diagnostic testing, treatment strategies, indications for postoperative RT and CHT, RT features, and EBB availability for LC cases. To establish standards, national guidelines should be prepared using a multidisciplinary approach.

Unresectable huge sternal and mediastinal metastasis of follicular thyroid carcinoma; radiotherapy as first-line and palliative therapy

Distant metastases as initial manifestation of follicular thyroid carcinoma is rare. We report a case of an unusual initial presentation of follicular thyroid carcinoma on follow-up. A 52- year-old woman presented with a 12-month history of progressively enlarging mass in the anterior chest wall. The mass was fixed to the chest wall, measuring 12 x 10 cm in diameter. Computed tomography demonstrated a lobulated soft-tissue mass (17 x 11 x 6 cm) destructing sternum and extending into the anterior mediastinum. There was no lung metastasis. Invasion of tumor to the ascending aorta, superior vena cava, and right atrium could not be excluded. Multiple lymph nodes were observed in the supraclavicular regions. Ultrasonography of the thyroid gland showed 46 x 37 mm nodule in the left lobe with milimetric gross calcifications and cystic-necrotic areas. Hyperthyroidism was detected. Biopsy from this nodule and the sternal mass revealed typical histology of follicular carcinoma. She was considered inoperable. Since there was huge tumor burden and iodinated contrast exposure for several times during evaluation, we decided to treat the patient with external beam radiotherapy (EBRT) rather than radioiodine as first-line therapy. After a course of conventional radiation with 50 Gy in 25 fractions over 4 weeks, encompassing the thyroid bed and the gross disease, tumor regressed remarkably in 6 months. In conclusion, when surgical resection is not possible, EBRT may be used for palliative purpose to obtain local control for extensive disease as first-line therapy. The indications of EBRT for differentiated thyroid cancer still remain poorly defined.

Epithelial-mesenchymal transition (EMT) and activated extracellular signal-regulated kinase (p-Erk) in surgically resected pancreatic cancer

BACKGROUND

EMT or transformation to the mesenchymal phenotype plays an important role in tumor invasion and metastasis. In vitro data suggest that mesenchymal transformation may correlate with the activation of PI3 kinase and Ras/Erk pathways. We investigated the expression of EMT markers (low E-cadherin, high fibronectin, and vimentin) and their association with p-Erk in resected pancreatic cancer.

METHODS

Clinical data/surgical specimens from 34 consecutive pancreatic cancer patients (pts) who underwent pancreatectomy were included. Immunohistochemical staining was performed on formalin-fixed paraffin-embedded tissues using monoclonal antibodies against vimentin, fibronectin, E-cadherin, and p-Erk. The results were correlated with clinicopathological parameters and survival. Survival analysis (log-rank test, Cox proportional hazard model), categorical data analysis (Pearson's chi-square, Fisher's exact test) and Kendall's tau were performed at a significance level of 0.05.

RESULTS

The patient population was formed from 13 males and 21 females, with a median age of 66 years (range 38-84 years); American Joint Committee on Cancer (AJCC) stage 1 (n = 2), 2 (n = 27), 3 (n = 5); histological grade 1 (n = 4), 2 (n = 13), 3 (n = 16), 4 (n = 1). Median survival was 15 months (95% CI: 11-24 months). Fibronectin overexpression correlated with the presence of vimentin (p = 0.0048) and activated Erk (p = 0.0264). There was a borderline association of fibronectin with worsening grade (p = 0.06). A negative association between vimentin and E-cadherin was noted (p = 0.0024). Increased fibronectin or vimentin and decreased E-cadherin correlated with poor survival.

CONCLUSION

EMT is associated with poor survival in surgically resected pancreatic adenocarcinoma. A correlation between activated Erk and fibronectin was identified that may open avenues for targeted therapy for this subgroup.

A single institution experience with neuroendocrine tumors

15164

Background: ABSTRACT Introduction: . The aim of this study was to analyze demographic, therapy, tumor and clinical outcomes of all cases of neuroendocrine cancer at a tertiary cancer and determine the the markers that may better correlate with outcomes than histologic grade. Patients and Methods: With IRB approval , 126 charts with a diagnosis of neuroendocrine carcinoma were identified between 1–1-1999 and 1–1-2004. Ninety-five cases were selected on the basis of complete availability of baseline, therapy and at least one time point of followup data. Patient demographics, therapy details, TNM stage, tumor marker and survival data were collected. Tumors were graded as well, moderate and poorly differentiated and by site of origin. We attempted to correlate the outcome with NCAM(neural cell adhesion molecule-CD56) status, which is a homophylic binding glycoprotein to have a role in cell adhesion. Descriptive statistics and frequency tables were used to describe the data and kaplan meier methods were used to estimate the median survival. Results: There were 28 patients with lung primaries, 25 had primaries in the gut (extra pancreatic),11 had pancreatic primaries, 31 cases had unknown primaries or primaries at sites other than the lungs or the gastrointestinal tract. The estimated median survival for the whole sample was 34 months.(95% C I :20,54) and the 2 year survival rate was 55.3 %.The estimated median survival for CD56 positive group was 11 months(95% C.I :3,38) and that for CD 56 unknown group was 36(95% C .I :20,n/a). A significant difference in survival between CD56 positive group and CD56 unknown was found,based on log-rank test>(P=.02). Baseline characteristics were as follows: M:F 48:47; 19 were well differentiated, 4 were moderately differentiated and 36 of 95 tumors were poorly differentiated, the differentiation was not known in 36 cases. Surgery with curative intent was done in 52 of the patients(54.74%) and 52 received (54.74%)t chemotherapy, 4 patients(4.2%) received chemoembolization and 2 patients(2.1%) received local ablative treatments. Conclusion: These data summarize our instutions experience with this rare malignancy. In our data survival was as expected in the literature and further investigation of the CD 56 status of all patients is underway.

No significant financial relationships to disclose.

Safety and efficacy of transdermal fentanyl in patients with cancer pain: phase IV, Turkish oncology group trial

We have performed a prospective evaluation of the efficacy, safety and convenience of the transdermal therapeutic system - fentanyl (TTS-F) in Turkish cancer patients when it was newly available in Turkey. Ninety-nine patients with historically confirmed malignancy and pain entered the study; the mean age was 55.1 (16-58) years. The study duration was 28 days. Transdermal therapeutic system - fentanyl was used in opioid-naïve or pre-treated patients. Most patients reported a decrease in pain severity. Use of rescue medication decreased from day 4 to day 28. The majority of patients rated patch convenience of use as excellent. A total of 22.2% of patients experienced adverse events that were either probably related or very likely to be related to the study drug. The majority of the adverse events mentioned were related to the digestive system. Eighteen serious adverse events were reported by 13 patients. Six events were doubtfully related, and 12 events were not related to the study drug. Four patients died during the trial. None of these deaths was attributed to the study drug. In conclusion, the trial showed that TTS-F is easily managed, effective and will help to enable the appropriate opioid administration to patients who are suffering from cancer pain in Turkey.

The effects of tangential radiotherapy on lung clearance in breast cancer patients

PURPOSE

The aim of this study was to investigate the effects of tangential radiotherapy (RT) on lung clearance in the patients with breast cancer by using (99m)Tc-DTPA aerosol scintigraphy.

MATERIAL AND METHODS

Thirty-three female patients [non-smoker: 20, ex-smoker: 13] performed surgery and systemic chemotherapy for breast carcinoma [47+/-13 years] were included in the study. All patients underwent (99m)Tc-DTPA aerosol scintigraphy prior to RT (pre RT), midway through RT (mid RT) and after RT (post RT). Total dose was 50 Gy in modified radical mastectomy and 60 Gy in lumpectomy (2 Gy/fraction). Posterior dynamic images of lungs were obtained immediately after the inhalation of (99m)Tc-DTPA aerosol.

RESULTS

Pulmonary function tests were normal in three measurements for all cases. In the ex-smokers, there was no significant difference among pre RT, mid RT and post RT clearance values in both lungs. Pre RT lung clearance in non-smoker group did not differ from that in ex-smokers. However, the lung clearance for non-smoker group showed significantly increase following RT.

CONCLUSION

In this study, we observed that tangential radiotherapy caused an increase in the lung clearance in the cases of non-smokers even in non-irradiated lung, and that the effect of RT on lung clearance was closely depended on smoking habit before RT.

Experimental lens-sparing optimization in therapeutic orbital irradiation with electron beams

There has been a number of approaches in the literature for therapeutic malignant and benign orbital irradiation. All techniques intend to deliver a homogenous dose to the orbital and retroorbital target volume while sparing the lens of excessive dose. In this experimental lens-sparing study, 4 MeV and 12 MeV anterior electron irradiation has been used with cerrobend shielding circular blocks of varying diameter and thickness placed on a thin Mylar at the distal tip of the electron applicator to spare the lens. The first phase of the study in water phantom has been designed to determine the shield thickness and diameter constant for 4 MeV and 12 MeV electron beams. After optimizing the lens dose by water phantom, the second phase of our study has been designed to measure doses at lens and other specific localizations in randophantom under same conditions with 4 MeV and 12 MeV electron beams. By this technique lens accumulated 18.56% of prescribed dose and lateral aspects of the lens received 44.59% of the prescribed dose in 4 MeV electron irradiation, whereas this was 13.86% and 44.80%, respectively in 12 MeV electron irradiation. The technique used is found to be an extremely simple and effective technique allowing an easier setup with excellent dose distribution characteristics with lens sparing applicable to orbital irradiation practice.

Total skin electron beam therapy for cutaneous T-cell lymphoma: Turkish experience with translational technique

Mycosis fungoides is the most common form of cutaneous T-cell lymphoma. In our department, between January 1995 to January 2001, we treated eleven patients with mycosis fungoides by total body skin electron irradiation to evaluate its influence. According to our knowledge, our department is the only center in Turkey capable of applying total skin electron beam therapy. Total skin electron beam therapy was applied by using the "translational technique". Daily doses (4 Gray) were given in a total of seven fractions according to the conventional fractionation scheme. There were 6 patients with stage I disease, 3 patients with stage II and 2 patients with stage IV disease. Except stage IV patients, we obtained good cutaneous results. According to our observation, in early stage mycosis fungoides total body skin electron irradiation can provide good cutaneous response, but for stage IV only moderate pallation can be obtained.

Retrospective analysis of 74 cases of seminoma treated with radiotherapy

BACKGROUND

Standard post-orchiectomy radiotherapy (RT) is accepted as a standard management option for stage I seminoma.

METHODS

Retrospective evaluation of 74 patients with stage I seminoma was performed according to the Royal Marsden staging system. All of the patients underwent RT in the Radiation Oncology Department of Gülhane Military Medical Academy between 1974 and 1995. The median age of patients was 27 years (range, 20-56). Radiotherapy was applied to all of the patients after orchiectomy for adjuvant purposes. Sixty-nine patients underwent RT while five patients who had recurrence received chemotherapy following radiotherapy.

RESULTS

After a mean follow-up period of 54 months, the 5-year overall survival rate was 98.61%, which complied with the literature. The disease-free survival rate was 90.54%. According to the World Health Organization toxicity scale, acute enteritis was 9.4% for grade I and 5.4% for grade II, while nausea/vomiting was 36.4% for grade I and 5.4% for grade II.

CONCLUSION

To avoid acute toxicity related to RT, prognostic risk factors should be well-known and patients with low risk factors should be monitored carefully after orchiectomy. RT should be directed to the para-aortic +/- ipsilateral pelvic lymph nodes in high risk patients. Although post-orchiectomy RT is a traditional management option for clinical stage I seminoma, the results of RT should be well-known to compare it with other treatment options (e.g. RPLND, adjuvant chemotherapy and surveillance).

Evaluation of radiation carcinogenesis risk in vertebral hemangioma treated by radiotherapy

The purpose of this study is to report carcinogenesis risk factor evaluation in vertebral hemangioma patients treated by radiotherapy. Between 1975 and 1995, 29 patients received 20-30 Gy total irradiation dose using conventional fractionation scheme. All the patients had measurements with thermoluminescent dosimeters (TLD 100 ), placed on multiple randophantom sites in vivo within the irradiated volume, to verify irradiation accuracy and calculate carcinogenesis risk factor. Twenty nine still-alive patients who had a minimum 6-year and maximum 26-year follow-up (median 14.34 years) have been evaluated by carcinogenic radiation risk factor on the basis of tissue weighting factors as defined by International Commission on Radiological Protection Publication 60. Reasonable pain relief has been obtained in all 29 patients. Calculated mean carcinogenesis risk factor is 0.6% for single irradiation portals and 0.9% for double irradiation portals in the whole group, whilst no secondary cancer has been detected. Radiotherapy is an effective treatment modality in relieving pain of vertebral hemangioma patients. Estimated secondary cancer risk factor for this benign neoplasm irradiation is not as high as can be feared.

Can radiotherapy be a treatment option for elderly women with invasive vulvar carcinoma without radical surgery?

PURPOSE OF THE INVESTIGATION

To evaluate the impact of radiotherapy after limited surgery in vulvar carcinoma.

METHODS

Between March 1980 and January 2000, 22 patients older than 60 years and suffering from invasive vulvar carcinoma were treated with limited surgery and radiotherapy at Gülhane Military Medicine Academy. These are the subjects of this review.

RESULTS

The median age of the patients was 67 (range 60 to 78 years). Median follow-up was 35 months (range 12 to 60 months). Local recurrence rate was 18%. Median time to local failure was 12 months (range 8 to 14 months). Two patients with local failure also developed lung metastases. Five-year survival rate was 60% and cause-specific survival rate was 69%. No treatment delay or death related to treatment was observed.

CONCLUSIONS

Radiotherapy and conservative surgery can be an alternative to radical surgery with less morbidity in elderly patients.

Evaluation of dose homogenization and radiation carcinogenesis risk in total body irradiation for bone marrow transplantation

The purpose of this study is to report on the dose homogeneity in total body irradiated patients undergoing Bone Marrow Transplantation (BMT), and carcinogenic risk in surviving patients. Between 1987 and 2001, 105 patients received hyperfractionated (6 fractions in 3 days) 12 Gy Total Body Irradiation (TBI) in our institution with lateral opposed fields. All the patients had measurements with thermoluminiscence dosimetry (TLD100) placed on seven bilateral body sites in vivo, controlled by the randophantom measurements to verify reasonable dose homogeneity achievement. The comorbid effects in the whole TBI conditioning group with at least three months post BMT follow-up were noted and surviving patients who had a minimum 5-year and maximum 14-year follow-up (median 7.8 years) have been evaluated for carcinogenic radiation risk on the basis of tissue weighting factors as defined by ICRP 60. Reasonable dose homogeneity by lateral opposed beam TBI has been obtained in all 105 patients in whom lateral TLD100 measurement means were within +5% of the planned doses. Calculated carcinogenesis risk factor was 11.34% for males and 12.40% for females, and no second-cancer has been detected whilst radiation-induced 5 cataracts and 10 interstitial pneumonia comorbidities were noted. Dose homogenization can be well achieved for hyperfractionated lateral-beam TBI with acceptable comorbidities and estimated second-cancer risk is significant but relatively low compared to the risk from the clinical indications for TBI.

Postoperative radiotherapy for ganglioglioma; report of three cases and review of the literature

Gangliogliomas are rare tumors of the central nervous system. The definite role of postoperative radiotherapy has not been established. In studying three cases who underwent radiotherapy after subtotal resection, we evaluated the clinical, pathological, radiological features with follow-up of mean 8.1 years. All of three patients were male, and mean age was 22.3 years. All of the cases have temporal lobe lesions and, except for one, they all have seizures. Radiotherapy was given to all patients after surgery. Parallely opposed local fields were used. A total of 54 Gy in 5.5 weeks was given to the mid-plane using a Co-60 tele-therapy device. No recurrence, no new symptoms, and no new neurological deficiency were detected during follow-up.

An optimization method for reference dose point of rectum in brachytherapy of gynecological neoplasms

Rectum reference dose points have a direct impact on the morbidity seen in gynecological intracavitaty radiotherapy. The aim of this study is to obtain less morbidity by marking rectum with radio opaque solution. Fourteen patients with gynecological cancer who underwent external radiotherapy received 15 Gray (Gy) intracavitary radiotherapy. During the internal radiotherapy planning, radio opaque solution has been administered into the rectum to observe it on lateral radiogram. Thus rectum reference dose point and five points were marked at sites nearest to the sources. Nucletron Planning system was used for obtaining three-dimensional planning. After therapy patients were followed at every three months. Median follow-up was 18 months. Most frequently observed morbidities were grade 1-2 rectitis and cystitis in six patients. As a result, more accurate rectum dose values and less factors causing dose changing can provide better results for gynecological intracavitary brachytherapy.

Endovascular radiotherapy for stenosis after percutaneous transluminal coronary angioplasty

The rate of restenosis after percutaneous transluminal coronary angioplasty ranges from 30% to 60%. Despite numerous trials, no effective pharmacological therapy has been found. This late effect can be reduced by endovascular radiotherapy. In animal models of restenosis after balloon injury, there is marked reduction of neointimal proliferation when the injured vessel is irradiated, using a variety of radiation sources and delivery systems. Early human trials did not focus on the importance of source selection and calibration. Other aspects which should be carefully determined are source selection and responsibilities of the treatment team. These matters are reviewed and discussed.

Recognition of 16S rRNA by ribosomal protein S4 from Bacillus stearothermophilus

Protein S4 is essential for bacterial small ribosomal subunit assembly and recognizes the 5' domain (approximately 500 nt) of small subunit rRNA. This study characterizes the thermodynamics of forming the S4-5' domain rRNA complex from a thermophile, Bacillus stearothermophilus, and points out unexpected differences from the homologous Escherichia coli complex. Upon incubation of the protein and RNA at temperatures between 35 and 50 degrees C under ribosome reconstitution conditions [350 mM KCl, 8 mM MgCl2, and 30 mM Tris (pH 7.5)], a complex with an association constant of > or = 10(9) M(-1) was observed, more than an order of magnitude tighter than previously found for the homologous E. coli complex under similar conditions. This high-affinity complex was shown to be stoichiometric, in equilibrium, and formed at rates on the order of magnitude expected for diffusion-controlled reactions ( approximately 10(7) M(-1) x s(-1)), though at low temperatures the complex became kinetically trapped. Heterologous binding experiments with E. coli S4 and 5' domain RNA suggest that it is the B. stearothermophilus S4, not the rRNA, that is activated by higher temperatures; the E. coli S4 is able to bind 5' domain rRNA equally well at 0 and 37 degrees C. Tight complex formation requires a low Mg ion concentration (1-2 mM) and is very sensitive to KCl concentration [- partial differential[log(K)]/partial differential(log[KCl]) = 9.3]. The protein has an unusually strong nonspecific binding affinity of 3-5 x 10(6) M(-1), detected as a binding of one or two additional proteins to the target 5' domain RNA or two to three proteins binding a noncognate 23S rRNA fragment of the approximately same size. This binding is not as sensitive to monovalent ion concentration [- partial differential[log(K)]/partial differential(log[KCl]) = 6.3] as specific binding and does not require Mg ion. These findings are consistent with S4 stabilizing a compact form of the rRNA 5' domain.

Comparison of granulocyte-colony, stimulating factor and granulocyte macrophage-colony stimulating factor in the treatment of chemotherapy extravasation ulcers

The results of perilesional granulocyte macrophage-colony stimulating factor and granulocyte-colony stimulating factor application in a patient with chemotherapy extravasation ulcers are reported. A 64-year-old patient with recurrent ovarian carcinoma was admitted to our department in February 1999. In June 1998, six cycles of chemotherapy were applied to the patient after surgery. At the first cycle, two ulcers appeared on both lower arms related to doxorubicin extravasation despite all interventions. When the patient was admitted to in our department, we observed an ulcer on the distal part of the right lower arm with a dimension of 1.5x2 cm and another on the proximal portion of the left lower arm with a dimension of 2.5x3 cm. Of those ulcers, the bigger and deeper one on the left was treated with weekly 400 mcg granulocyte macrophage-colony stimulating factor subcutaneously for three weeks. The lesion completely disappeared in the fourth week. The other ulcer that was left for control on the right arm was treated with weekly 48 M.U. granulocyte-colony stimulating factor for four weeks. This ulcer did not reduce in size. As a result granulocyte-colony stimulating factor did not affect the healing of chemotherapy extravasation ulcers, as did granulocyte macrophage-stimulating factor.

Structural Basis of Binding of High-Affinity Ligands to Protein Kinase C: Prediction of the Binding Modes through a New Molecular Dynamics Method and Evaluation by Site-Directed Mutagenesis

The structural basis of protein kinase C (PKC) binding to several classes of high-affinity ligands has been investigated through complementary computational and experimental methods. Employing a recently developed q-jumping molecular dynamics (MD) simulation method, which allows us to consider the flexibility of both the ligands and the receptor in docking studies, we predicted the binding models of phorbol-13-acetate, phorbol-12,13-dibutyrate (PDBu), indolactam V (ILV), ingenol-3-benzoate, and thymeleatoxin to PKC. The "predicted" binding model for phorbol-13-acetate is virtually identical to the experimentally determined binding model for this ligand. The predicted binding model for PDBU is the same as that for phorbol-13-acetate in terms of the hydrogen-bonding network and hydrophobic contacts. The predicted binding model for ILV is the same as that obtained in a previous docking study using a Monte Carlo method and is consistent with the structure-activity relationships for this class of ligands. Together with the X-ray structure of phorbol-13-acetate in complex with PKCdelta C1b, the predicted binding models of PDBu, ILV, ingenol-3-benzoate, and thymeleatoxin in complex with PKC showed that the binding of these ligands to PKC is governed by a combination of several highly specific and optimal hydrogen bonds and hydrophobic contacts. However, the hydrogen-bonding network for each class of ligand is somewhat different and the number of hydrogen bonds formed between PKC and these ligands has no correlation with their binding affinities. To provide a direct and quantitative assessment of the contributions of several conserved residues around the binding site to PKC-ligand binding, we have made 11 mutations and measured the binding affinities of the high-affinity PKC ligands to these mutants. The results obtained through site-directed mutagenic analysis support our predicted binding models for these ligands and provide new insights into PKC-ligand binding. Although all the ligands have high affinity for the wild-type PKCdelta C1b, our site-directed mutagenic results showed that ILV is the ligand most sensitive to structural perturbations of the binding site while ingenol-3-benzoate is the least sensitive among the four classes of ligands examined here. Finally, we have employed conventional MD simulations to investigate the structural perturbations caused by each mutation to further examine the role played by each individual residue in PKC-ligand binding. MD simulations revealed that several mutations, including Pro11 --> Gly, Leu21 --> Gly, Leu24 --> Gly, and Gln27 --> Gly, cause a rather large conformational alteration to the PKC binding site and, in some cases, to the overall structure of the protein. The complete abolishment or the significant reduction in PKC-ligand binding observed for these mutants thus reflects the loss of certain direct contacts between the side chain of the mutated residue in PKC and ligands as well as the large conformational alteration to the binding site caused by the mutation.

Prostate specific antigen in the female body: its role in breast cancer prognosis

Prostate-specific antigen, a 33 kDa serine protease, is found at high concentrations in seminal plasma and prostate epithelial cells. It is currently used for the diagnosis and monitoring of prostate carcinoma. However, several investigators have demonstrated nonprostatic sources of prostate specific antigen, including amniotic fluid, breast milk, breast cyst fluid, nipple aspirate fluid, and breast tumor cytosol. Studies have revealed that a high prostate-specific antigen level in tumors of women with breast cancer is associated with good prognosis. This finding is analyzed in this manuscript.

Evaluation of a minimal experimental design for determination of enzyme kinetic parameters and inhibition mechanism

The advent of combinatorial chemistry has led to a deluge of new chemical entities whose metabolic pathways need to be determined. A significant issue involves determination of the ability of new agents to inhibit the metabolism of existing drugs as well as its own susceptibility for altered metabolism. There is need to estimate the enzyme inhibition parameters and mechanism or mechanisms of inhibition with minimal experimental effort. We examined a minimal experimental design for obtaining reliable estimates of K(i) (and V(max) and K(m)). Simulations have been applied to a variety of experimental scenarios. The least experimentally demanding case involved three substrate concentrations, [S], for the control and one substrate-inhibitor pair, [S]-[I]. The control and inhibitor data (with 20% coefficient of variance random error) were simultaneously fit to the full nonlinear competitive inhibition equation [simultaneous nonlinear regression (SNLR)]. Excellent estimates of the correct kinetic parameters were obtained. This approach is clearly limited by the a prior assumption of mechanism. Further simulations determined whether SNLR would permit assessment of the inhibition mechanism (competitive or noncompetitive). The minimal design examined three [S] (control) and three [S]-[I] pairs. This design was successful in identifying the correct model for 98 of 100 data sets (20% coefficient of variance random error). SNLR analysis of metabolite formation rate versus [S] permits a dramatic reduction in experimental effort while providing reliable estimates of K(i), K(m), and V(max) along with an estimation of the mechanism of inhibition. The accuracy of the parameter estimates will be affected by the experimental variability of the system under investigation.

Role for the C-terminus in agonist-induced mu opioid receptor phosphorylation and desensitization

Determining which domains and amino acid residues of the mu opioid receptor are phosphorylated is critical for understanding the mechanism of mu opioid receptor phosphorylation. The role of the C-terminus of the receptor was investigated by examining the C-terminally truncated or point-mutated mu opioid receptors in receptor phosphorylation and desensitization. Both wild-type and mutated receptors were stably expressed in Chinese hamster ovary (CHO) cells. The receptor expression was confirmed by receptor radioligand binding and immunoblottting. After exposure to 5 microM of DAMGO, phosphorylation of the C-terminally truncated receptor and the mutant receptor T394A was reduced to 40 and 10% of that of the wild-type receptor, respectively. Mutation effects on agonist-induced desensitization were studied using adenylyl cyclase inhibition assays. The C-terminally truncated receptor and mutant receptor T394A both showed complete loss of DAMGO-induced desensitization, while the mutant T/S-7A receptor only lost part of its ability to desensitize. Taken together, these results suggest that the C-terminus of the mu opioid receptor participates in receptor phosphorylation and desensitization with threonine 394, a crucial residue for both features. DAMGO-induced mu opioid receptor phosphorylation and desensitization are associated and appear to involve both the mu opioid receptor C-terminus and other domains of the receptor.

Split-course radiotherapy with or without concurrent or sequential chemotherapy in non-small cell lung cancer

In our department we designed a three-armed study to compare the effects of sequential and concurrent chemoradiotherapy in locally advanced non-small cell lung cancer. Each treatment arm consisted of 15 patients with histologically confirmed stage III non-small cell lung cancer. In group 1, the main treatment approach was split-course radiotherapy alone. In group 2, 6 mg/m2 of cisplatin was applied daily and concurrently with split-course radiotherapy. In group 3, two cycles of etoposide, ifosfamide, and cisplatin chemotherapy, which ended three weeks before split-course radiotherapy, was applied. Overall response rates were 40%, 66%, and 53% in groups 1, 2, and 3, respectively. Median survival was 10, 11, and 10 months for groups 1, 2, and 3 respectively. Results are discussed in the light of the literature.

A successful and simplified filgrastim primed single apheresis method without large volume apheresis for peripheral blood stem cell collection

BACKGROUND

There is a tendency to use only one apheresis collection to reduce the morbidity and the cost of peripheral blood stem cell collection. We studied whether rapid and complete engraftment could be achieved by single apheresis by using only Filgrastim without large volume apheresis in previously treated patients.

METHODS

Engraftment of single apheresis in 25 patients was compared with those of multiple apheresis in 26 patients; 52% of patients in the single apheresis group and 62% of patients in the multiple apheresis group were heavily pretreated. All patients received 10-15 microg/kg/day of Filgrastim starting on day 14 after 3-4 cycles of induction chemotherapy. Apheresis was performed using Cobe Spectra on day 4, 5 or 6 in the single apheresis group and every other day in the multiple apheresis group after day 3.

RESULTS

The median collection volume was 250 ml (250-300 ml) in the single apheresis group and 750 ml (200-1500 ml) in the multiple apheresis group. The median CD34(+) cell number was not significantly different in the two groups (11.79 vs. 9.38x10(6)/kg). The median times to achieve leukocytes > or =1x10(9)/l and platelets > or =50x10(9)/l counts were 10 days (8-21 days) and 15 days (9-38 days) in the single apheresis group vs 11 days (8-23 days) and 20 days (10-32 days) in the multiple apheresis group, respectively (p<0.05). Antibiotic use was less in the single apheresis group than the multiple apheresis group (9 vs. 12 days, p<0.05).

CONCLUSION

Adequate numbers of peripheral stem cells were harvested by G-CSF in a single apheresis without large volume apheresis even in heavily pretreated patients. Rapid and complete engraftment occurred in all patients and it was faster in single than multiple apheresis.

Agonist-induced, G protein-dependent and -independent down-regulation of the mu opioid receptor. The receptor is a direct substrate for protein-tyrosine kinase

The mu opioid receptor (MOR) has been shown to desensitize after 1 h of exposure to the opioid peptide, [D-Ala(2), N-MePhe(4), Gly-ol(5)]enkephalin (DAMGO), largely by the loss of receptors from the cell surface and receptor down-regulation. We have previously shown that the Thr(394) in the carboxyl tail is essential for agonist-induced early desensitization, presumably by serving as a primary phosphorylation site for G protein-coupled receptor kinase. Using a T394A mutant receptor, we determined that Thr(394) was also responsible for mu opioid receptor down-regulation. The T394A mutant receptor displayed 50% reduction of receptor down-regulation (14.8%) compared with wild type receptor (34%) upon 1 h of exposure to DAMGO. Agonist-induced T394A receptor down-regulation was unaffected by pertussis toxin treatment, indicating involvement of a mechanism independent of G protein function. Interestingly, pertussis toxin-insensitive T394A receptor down-regulation was completely inhibited by a tyrosine kinase inhibitor, genistein. Tyrosine kinase inhibition blocked wild type MOR down-regulation by 50%, and the genistein-resistant wild type MOR down-regulation was completely pertussis toxin-sensitive. Following DAMGO stimulation, MOR was shown to be phosphorylated at tyrosine residue(s), indicating that the receptor was a direct substrate for tyrosine kinase action. Mutagenesis of the four intracellular tyrosine residues resulted in complete inhibition of the G protein-insensitive MOR internalization. Therefore, agonist-induced MOR down-regulation appears to be mediated by two distinct cellular signal transduction pathways. One is G protein-dependent and GRK-dependent, which can be abolished by pertussis toxin treatment of wild type MOR or by mutagenesis of Thr(394). The other novel pathway is G protein-independent but tyrosine kinase-dependent, blocked by genistein treatment, and one in which Thr(394) has no regulatory role but phosphorylation of tyrosine residues appears essential.

Fifteen cases of male breast carcinoma treated between 1980 and 1995

Male breast carcinoma is a rare malignity. In Turkey, as in other countries, there are insufficient studies on male breast cancer. In the Radiation Oncology Department, Gülhane Military Medical Academy, we treated 15 cases of male breast cancer versus 1393 female breast cancer. Two of the cases had stage I, nine had stage II, and the remaining four had stage III disease. Median age was 52. All patients had definitive external beam radiation therapy with daily 200 cGy fractionation, following surgery. Median follow-up was 227 months. Five year survival rate was found to be 60% for all stages. Our evaluations of the pathologic findings, management, and treatment outcome were compared with literature.

In vivo chiro-inositol metabolism in the rat: a defect in chiro-inositol synthesis from myo-inositol and an increased incorporation of chiro-[3H]inositol into phospholipid in the Goto-Kakizaki (G.K) rat

We report our comparative studies of myo- and chiro-[3H]inositol distribution in control nondiabetic Wistar and spontaneous nonobese insulin-resistant Type II diabetic G.K. rat tissues following 78-h labeling period. From various tissue extracts, free inositols, inositol phosphates, and inositol phospholipids were isolated and analyzed. Our findings demonstrate (1) a significant difference in the metabolism of myo- and chiro-inositol in normal Wistar and G.K. rats, (2) a severe defect in conversion of myo-[3H]inositol to chiro-[3H]inositol at the inositol phospholipid level of insulin-sensitive tissues of the G.K. rat, (3) an increased incorporation of myo-[3H]inositol into purified inositol phospholipids of the G.K. rat consistent with a decreased conversion to chiro-[3H]inositol, (4) the presumed presence of a pathway which incorporates chiro-[3H]inositol into inositol phospholipids, and which is overactive in the G.K. rat compared to the Wistar rat, and (5) no or minimal conversion of chiro-[3H]inositol to myo-[3H]inositol.

Agonist-induced desensitization of the mu opioid receptor is determined by threonine 394 preceded by acidic amino acids in the COOH-terminal tail

To identify the structural determinants necessary for mu opioid receptor desensitization, we serially ablated potential phosphorylation sites in the carboxyl tail of the receptor and examined their effects on [D-Ala2,N-Me-Phe4,Gly-ol5]enkephalin (DAMGO)-induced desensitization. First, we replaced Thr394 with alanine (T394A) and stably expressed this mutant receptor in Chinese hamster ovary cells. The T394A receptor did not desensitize after 1 h of treatment with DAMGO, indicating that Thr394 is required for agonist-induced early desensitization. To test whether Thr394 was the only residue necessary, we investigated the importance of 7 potential phosphorylation sites between residues 363 and 383, which were all replaced by alanines with the Thr394 maintained. This mutant (AT) showed partial loss of desensitization (30%), which was attributable to the Ala mutation at Thr383, since complete desensitization was achieved by restoring Thr383 (ATT). These results suggest that Thr394 is the primary recognition site for G protein-coupled receptor kinases, but Thr383 is also required for complete agonist-induced desensitization. The specificity of Thr394 as the primary initiation site appears to be dependent on the preceding acidic amino acid stretch, because in a mutant in which glutamic acid residues at 388, 391, and 393 were replaced by glutamines (EQ), agonist-induced desensitization was completely abolished, identical to the T394A mutant.

Prostate rhabdomyosarcoma in a young adult: a case study

Prostate rhabdomyosarcoma is a very rare malignancy in young adults. This case study presents an 18-year-old adult with prostate rhabdomyosarcoma treated with a combined regimen of radiotherapy and chemotherapy.

Protective effect of vitamin A on acute radiation injury in the small intestine

The objective of this study was to examine the influence of vitamin A on the development of early radiation-induced reactions in the rat small intestine. The early effects of intraoperative gamma-radiation on the small bowel utilizing the terminal ileum of Sprague-Dawley rats and the protective effect of supplemental vitamin A on acute radiation injury were investigated. Three groups were included in the study: group I (10 rats) was the surgical control group; group II (13 rats) underwent only intraoperative irradiation; and group III (10 rats) was the vitamin A plus irradiation group. Exteriorized terminal ileal segments of groups II and III were exposed to a single fraction of 20 Gy of intraoperative gamma-irradiation. On the seventh postoperative day, terminal ileal segments of all rats were resected and histopathologically evaluated for ulceration, enteritis cystica profunda, atypical epithelial regeneration, fibrosis, vascular sclerosis, and inflammatory process. Although none of the above findings were present in the surgical control group, group III rats experienced less severe effects than group II rats. The results suggest the early side effects of radiation may be prevented by vitamin A supplementation.

Agonist-induced functional desensitization of the mu-opioid receptor is mediated by loss of membrane receptors rather than uncoupling from G protein

The effects of acute exposure of the opioid peptide [D-Ala2,N-MePhe4, Gly-ol5]enkephalin (DAMGO) on the mu-opioid receptor were examined in Chinese hamster ovary (CHO) K-1 and baby hamster kidney stable transfectants. In the CHO cell line, acute 1-hr treatment with DAMGO decreased the density of receptors without affecting the affinity or proportion of agonist-detected sites and attenuated the ability of the agonist to inhibit forskolin-stimulated cAMP accumulation. In contrast, similar 1-hr treatment of baby hamster kidney cells did not affect receptor density or agonist ability to inhibit cAMP accumulation, but longer duration of agonist exposure resulted in a reduction in membrane receptor, identical to the CHO cells. These results suggested that for the mu-opioid receptor, alteration in receptor density was the major determinant for the observed agonist-induced desensitization. Consistent with this notion, the ratio of the DAMGO concentration yielding half-maximal occupation of the mu receptor to that yielding half-maximal functional response was < 1. This suggests the necessity for a high mu receptor occupancy rate for maximal functional response, so that any loss of cell surface opioid-binding sites was a critical determinant in reducing the maximal response. This hypothesis was further supported by the observation that irreversible inactivation of fixed proportions of opioid-binding sites with beta-chlorn-altrexamine demonstrated that there were few spare receptors, which is in contrast to what has been reported for other G protein-coupled receptors, including the delta-opioid receptor. Taken together, these data suggest that the opioid agonist DAMGO has a high affinity for the mu receptor but must occupy > 70% of the available receptors to generate the maximal second messenger-linked response.

Comparison of multileaf collimation and shield alloy blocks on an irregular target volume

Multileaf collimation (MLC) is a crucial component dynamic conformal radiotherapy and can be used as a replacement for conventional blocks. The most appropriate volumetric approach for the lesion's shape is achieved by MLC by conforming the prescribed dose to the critical structure or normal tissue dose. In this study, the edge effects of dose profiles on an irregular radiation field obtained by MLC and shield alloy blocks drawn by a water-phantom system were compared. We used a SL25 linac machine with MLC consisting of 40 pairs of opposing leaves and conventional alloy block shielding on a water phantom system. We found no significant edge effect difference between MLC and conventional shielding, but MLC showed clear advantages over conventional blocks in terms of time-saving, repeatability, and reliability.

Characterization of the properties of cocaine in blood: blood clearance, blood to plasma ratio, and plasma protein binding

As part of a study to examine cocaine disposition and interaction with ethanol, it was necessary to characterize various properties of cocaine in the blood of the experimental animal. All studies were conducted using blood from healthy adult male Sprague-Dawley rats. Cocaine was incubated in whole blood at 37 degrees C at concentrations of 500-4000 ng/mL. The apparent first-order rate constant for cocaine loss was independent of concentration. Blood clearance, calculated assuming blood volume to be 64 mL/kg, was estimated to be 0.056 +/- 0.003 mL/(min.kg); a value considerably smaller than estimates of systemic clearance. The addition of NaF increased the rate of loss to form benzoylecgonine, as a result of increased chemical degradation and as a consequence of increased pH (to pH 8.0 over 30 h). This NaF-enhanced degradation was abolished when NaF was added to blood buffered to pH 7.4. Ethanol had no influence on cocaine degradation, and there was no evidence of cocaethylene (ethylcocaine) formation. Blood to plasma ratios determined in spiked and authentic samples were constant (0.94-1.05 and 0.99-1.03, respectively) and independent of concentration (100-1500 ng/mL) and pH (7.2-7.6). This ratio was not influenced by NaF or ethanol. The unbound fraction (fu) of cocaine determined in spiked plasma varied from 0.62 to 0.63 over the concentration range (75-2025 ng/mL). Ethanol had no effect on binding. The values for fu determined from authentic blood samples taken from rats dosed intravenously with cocaine (10 mg/kg) ranged from 0.67 to 0.69 (over the concentration range 300-1500 ng/mL). Cocaine plasma protein binding was independent of concentration but depended upon plasma pH (fu, 0.765 and 0.486, at pHs 7.0 and 7.8, respectively.

Structural analysis of the light subunit of the Entamoeba histolytica galactose-specific adherence lectin

Adherence of Entamoeba histolytica trophozoites to colonic mucins and resistance to lysis by the membrane attack complex of complement are mediated by a galactose- and N-acetyl-D-galactosamine-specific cell-surface lectin. This lectin is a heterodimeric glycoprotein of heavy (170 kDa) and light (35/31 kDa) subunits. In this work, the amino acid sequence and membrane anchor of the light subunit were analyzed. The light subunit cDNA encoded a protein with a calculated molecular mass of 32 kDa containing two potential sites for N-linked glycosylation and putative amino- and carboxyl-terminal signal sequences characteristic of glycosylphosphatidylinositol (GPI)-anchored proteins. No classical carbohydrate-binding domains common to C- or S-type eukaryotic lectins were detected by sequence analysis of either the heavy or light subunits, leaving the location of the ligand-binding site of the lectin unknown. Analysis of restriction enzyme-digested E. histolytica DNA by Southern blotting was consistent with the presence of more than one light subunit gene. Two light subunit isoforms of 31 and 35 kDa were identified by SDS-polyacrylamide gel electrophoresis analysis of affinity-purified lectin, and the isoforms were shown on two-dimensional gel analysis to form distinct 170/35- and 170/31-kDa heterodimers. The amino acid compositions and cyanogen bromide peptide patterns of the two light subunit isoforms were nearly identical. The 35-kDa isoform labeled more efficiently than the 31-kDa isoform with [3H]glucosamine, while only the 31-kDa isoform labeled with [3H]myristate and [3H]palmitate. Nitrous acid deamination released lipid from the 31-kDa isoform, which co-migrated on thin layer chromatography with acylphosphatidylinositol, a component of some GPI anchors. Gas chromatography and mass spectrometry of the deamination product from the 31-kDa subunit identified both myo- and chiro-inositols, supporting the presence of a GPI membrane anchor. The covalent association of a transmembrane protein with a GPI-anchored protein, as suggested by the cDNA sequences of the lectin heavy and light subunits, is novel and suggests unique roles for the two subunits in the pathogenesis of amebiasis.