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Biomedical subjects

R J Mark

Publications and source records attributed to R J Mark.

At least 19 recordsLinked to original sources
PubMed1995

Pediatric rhabdomyosarcoma of the head and neck.

The optimal treatment for most patients with pediatric rhabdomyosarcoma (RMS) of the head and neck has been shown to be a combination of surgery, chemotherapy and radiation therapy. A retrospective review of patients seen at our institution is presented to analyze the impact of multimodality treatment on survival in 32 pediatric RMS patients. Sixty-five percent (21/32) of the patients were disease free at the most recent follow-up. The 5 year disease free survival was 57% (17/30). Combined modality treatment in 25 patients consisting of chemotherapy, radiation therapy and surgical resection (in 5 patients) rendered 18 (72%) patients free of disease. Only 1 of 7 (14%) patients who underwent surgery alone as primary management was cured. Two of these 7 patients were salvaged, both with combined modality treatment. The Intergroup Rhabdomyosarcoma Study (IRS) protocols have resulted in increased survival in pediatric patients with RMS of the head and neck. Our results reflect the significant improvement since the IRS study was completed.

Adolescent↗
PubMed1995

Craniopharyngioma: treatment in the CT and MR imaging era.

PURPOSE: To determine optimal treatment in patients with craniopharyngiomas. MATERIALS AND METHODS: In 1977-1990, 49 patients (age range, 3-67 years; median age, 35 years; 25 female, 24 male) with craniopharyngiomas were examined. Follow-up was 5-17 years (median, 8 years). Fifteen patients were aged younger than 18 years. RESULTS: All patients underwent surgical resection. Complete resection was achieved in 19. Seven patients underwent additional surgery for recurrent disease. Rate of mortality due to surgical complications was 10% (n = 5). Eight patients had marked perioperative or long-term morbidity. Twenty-five patients judged to have undergone subtotal resection underwent postoperative radiation therapy (RT). RT doses were 4,600-6,287 cGy administered in fractions of 180-200-cGy/d. Actuarial 5-year progression-free survival in patients who underwent complete resection was 63% (12 of 19 patients) versus 96% (24 of 25 patients) in patients who underwent subtotal resection followed by RT (P = .04). No RT dose response was observed. Patient functional status has not been substantially affected by adjuvant RT. CONCLUSION: RT achieves excellent tumor control after subtotal resection of craniopharyngiomas.

Adolescent↗
PubMed1995

Amyloid beta-peptide impairs ion-motive ATPase activities: evidence for a role in loss of neuronal Ca2+ homeostasis and cell death.

The amyloid beta-peptide (A beta) that accumulates as insoluble plaques in the brain in Alzheimer's disease can be directly neurotoxic and can increase neuronal vulnerability to excitotoxic insults. The mechanism of A beta toxicity is unclear but is believed to involve generation of reactive oxygen species (ROS) and loss of calcium homeostasis. We now report that exposure of cultured rat hippocampal neurons to A beta 1-40 or A beta 25-35 causes a selective reduction in Na+/K(+)-ATPase activity which precedes loss of calcium homeostasis and cell degeneration. Na+/K(+)-ATPase activity was reduced within 30 min of exposure to A beta 25-35 and declined to less than 40% of basal level by 3 hr. A beta did not impair other Mg(2+)-dependent ATPase activities or Na+/Ca2+ exchange. Experiments with ouabain, a specific inhibitor of the Na+/K(+)-ATPase, demonstrated that impairment of this enzyme was sufficient to induce an elevation of [Ca2+]i and neuronal injury. Impairment of Na+/K(+)-ATPase activity appeared to be causally involved in the elevation of [Ca2+]i and neurotoxicity since suppression of Na+ influx significantly reduced A beta- and ouabain-induced [Ca2+]i elevation and neuronal death. Neuronal degeneration induced by ouabain appeared to be of an apoptotic form as indicated by nuclear condensation and DNA fragmentation. The antioxidant free radical scavengers vitamin E and propylgallate significantly attenuated A beta-induced impairment of Na+/K(+)-ATPase activity, elevation of [Ca2+]i and neurotoxicity, suggesting a role for ROS. Finally, exposure of synaptosomes from postmortem human hippocampus to A beta resulted in a significant and specific reduction in Na+/K(+)-ATPase and Ca(2+)-ATPase activities, without affecting other Mg(2+)-dependent ATPase activities or Na+/Ca2+ exchange. These data suggest that impairment of ion-motive ATPases may play a role in the pathogenesis of neuronal injury in Alzheimer's disease.

Amyloid beta-Peptides↗
PubMed1994

Postirradiation sarcomas. A single-institution study and review of the literature.

BACKGROUND: With improvement in survival after cancer treatment, it is becoming increasingly important to examine treatment-related morbidity and mortality. Sarcomas can develop in the irradiated field after radiation therapy (RT). The authors undertook a study to estimate the risk, and compared the risk of postirradiation sarcoma (PIS) with other treatment modalities used against cancer. METHODS: Since 1987 the authors have reviewed the records of 1089 patients with head and neck, gynecologic, gastrointestinal, and extremity sarcomas. Of these 1089 patients, 37 had a prior history of RT. RESULTS: Conditions for which these patients received RT included: Hodgkin's disease (2 patients), retinoblastoma (3), non-Hodgkin's lymphoma (2), acne (1), astrocytoma (1), multiple recurrent mixed parotid tumor (1), laryngeal cancer (1), papillary adenocarcinoma of the thyroid (1), bony fibrous dysplasia (1), lymphangioma (1), squamous cell carcinoma of the nasopharynx (1), Ewing's sarcoma (1), choriocarcinoma (1), menorrhagia (4), cervical cancer (6), ovarian cancer (2), breast cancer (7), and hypoplasia (1). RT doses ranged from 3000 to 12,440 cGy. Latency time from RT to the development of PIS averaged 12 years. More than 15,000 patients have received RT for various conditions at our institution since 1955. CONCLUSIONS: From our data and a review of the literature, we estimate the risk of PIS with long-term follow-up to be 0.03-0.8%. From a review of the literature that compared mortality risks of chemotherapy, general surgery, and anesthesia, the risk of PIS appears no worse. Thus, given the large number of patients who can be cured or receive palliative treatment with RT, concern regarding PIS should not be a major factor influencing treatment decisions in patients with cancer.

Adolescent↗
PubMed1994

Sarcomas of the nasal cavity and paranasal sinuses.

Sarcomas of the nose and paranasal sinuses are rare malignancies. Key issues remain unresolved in the management of these tumors, particularly with regard to the role of radiotherapy. To help clarify these issues, 48 consecutive cases of nasal and paranasal sinus sarcomas treated at the University of California, Los Angeles, between 1958 and 1988 were retrospectively reviewed. Six of 16 patients managed initially with surgery alone were cured. All had negative surgical margins and 5 of the 6 had low-grade tumors. Of 5 patients with high-grade lesions treated with surgery only, 1 was rendered free of disease. Twelve patients with positive surgical margins were treated with adjuvant radiotherapy; 5 were cured with this approach. Grade and surgical margin status were found to be significantly related to outcome for sinonasal sarcoma. There were 14 patients with rhabdomyosarcoma; 3 were cured with modern combined-modality therapy. Patients with positive surgical margins should be treated with adjuvant radiotherapy. Surgical therapy is effective for low-grade lesions that are completely excised.

Actuarial Analysis↗
PubMed1992

Breast conservation management of breast tumors 4 cm or larger.

Randomized studies of stage I and II breast cancer have shown that breast conservation treatment is equivalent to modified radical mastectomy in regard to local-regional control and survival. Little has been published on breast conservation for patients with large tumors. We analyzed 68 patients with tumors measuring 4 cm or larger (range, 4 to 12 cm) treated with breast-conserving surgery and radiation therapy. The median follow-up was 46 months; the mean tumor size was 5 cm. The 5-year actuarial local-regional recurrence rate was 8.5%, and the overall survival and disease-free survival rates were 76% and 68%, respectively. We conclude that breast conservation treatment may be a reasonable alternative to mastectomy in patients with tumors 4 cm or larger without compromise in local-regional control or survival, while achieving acceptable cosmesis.

Breast↗
PubMed1992

Mutations in a 19-amino-acid hydrophobic region of the yeast cytochrome c1 presequence prevent sorting to the mitochondrial intermembrane space.

Most mitochondrial proteins destined for the intermembrane space (IMS) carry in their presequence information for localization to the IMS in addition to information for their import. By selecting for mutants in the yeast Saccharomyces cerevisiae that mislocalize an IMS-targeted fusion protein, we identified mutations in the IMS sorting signal of the cytochrome c1 protein. Amino acid substitutions or deletions in a stretch of 19 hydrophobic amino acids of the cytochrome c1 presequence resulted in accumulation of the intermediate form of the cytochrome c1 protein in the matrix. In some cases, the accumulated intermediate appeared to be slowly exported from the matrix, across the inner membrane to the IMS. Our results support the hypothesis that the cytochrome c1 precursor is normally imported completely into the matrix and then exported to the IMS.

Amino Acid Sequence↗
PubMed1992

Nasopharyngeal carcinoma: treatment results with primary radiation therapy.

One hundred three patients with nasopharyngeal carcinoma were treated with radiotherapy at UCLA Medical Center from January 1955 to December 1990. Overall survival, disease-free survival, and local control rates were analyzed. In addition, survival from 1955 to 1978 and from 1979 to 1990 were evaluated. Overall 5- and 10-year actuarial survival rates for all patients were 58% and 47%, respectively. Disease-free survival rates at 3 and 5 years were 45% and 30%, respectively. Local, persistent, or recurrent disease in the nasopharynx was the primary cause of failure, occurring in 32% of patients and correlating with the initial tumor size (T stage). Twenty-four percent of patients developed distant metastases, which correlated with nodal status but not with T stage. Seventy-nine percent of patients failed either locally or distally by 4 years. Sex, race, age, and T and N stage categories were evaluated as prognostic variables in terms of survival. Control of primary disease is important in determining long-term outcome. Modern imaging techniques have greatly assisted in the evaluation of disease extent and treatment options.

Adolescent↗
PubMed1991

Fibrosarcoma of the head and neck. The UCLA experience.

Between 1955 and 1987, twenty-nine patients with the diagnosis of fibrosarcoma of the head and neck were seen at the UCLA Medical Center. Follow-up ranged from 15 to 192 months, with a median of 66 months. Absolute 5-year survival was 62% (13/21). Five of 17 patients treated initially with surgery alone achieved local control and long-term survival. All five had low-grade lesions. Five patients received postoperative radiation therapy because of positive surgical margins. Three were rendered disease free, and all had low-grade lesions. Radiation therapy was used as primary treatment in six patients, four of whom received additional chemotherapy. Of these six, two are disease free with longer than 5-year follow-up. Surgery with and without adjuvant therapy successfully salvaged 42% (5/12) of the patients with local recurrence. Eighty percent (12/15) of the patients with low-grade lesions were ultimately rendered disease free vs only 8% (1/12) of the patients with high-grade histologic features. Seventy-two percent (13/18) of the patients with local recurrence were known to have positive surgical margins. Sixty-eight percent (13/19) of the patients with recurrent disease had high-grade lesions and/or tumor size larger than 5 cm. Tumor grade is the most important prognostic factor followed by tumor size and surgical margin status. Patients with low-grade lesions and adequate surgical margins are treated well with surgery alone. Patients with high-grade lesions or positive surgical margins should receive adjuvant treatment.

Adolescent↗
PubMed1991

Osteogenic sarcoma of the head and neck. The UCLA experience.

Eighteen cases of osteogenic sarcoma of the head and neck were treated at our institution between 1955 and 1987. The patients' ages ranged from 5 to 73 years, with a median age of 28 years. The sex distribution was equal. Follow-up ranged from 1 to 276 months, with a median of 79 months. The primary site of the tumor was the mandible in nine cases, maxilla and paranasal sinuses in six, skull in two, and orbit in one. Six of 18 patients were free of disease with greater than 5 years of follow-up. Four of the six received combined surgery, radiation therapy, and chemotherapy as their primary treatment. Of the five patients treated with surgery alone, four suffered recurrences, one of whom was salvaged with further surgery and chemotherapy. Five patients were treated initially without surgery. They received radiation therapy with or without chemotherapy; all five developed local recurrence. We conclude that osteogenic sarcoma of the head and neck is an aggressive tumor, prone to both local and distant failure. Based on our series and from published experience involving the extremities, osteogenic sarcoma of the head and neck should be managed with multimodality therapy.

Adolescent↗
PubMed1989

Homozygote for Huntington disease.

Four offspring of three different Huntington disease (HD) affected x affected matings were assessed by genetic linkage analysis for possible homozygosity. One individual was found to have a 95% likelihood of being an HD homozygote. The homozygote individual had an age at onset and symptoms which were similar to those of affected HD heterozygote relatives, including some with younger onset. This confirms the observation of Wexler et al. that in HD the homozygote is not more severely afflicted than the heterozygote.

Adult↗
PubMed1978

133Xe uptake by fatty livers.

Of 19 studies on 15 patients with morbid obesity and fatty infiltration of the liver, 16 had increased uptake and retention of 133Xe in the liver following 5-minute rebreathing of 133Xe and oxygen. This observation shows a high correlation with the histologically proven presence of fat in the hepatocytes, and offers a simple, accurate and precise indication of the excess fat in the liver.

Adult↗
PubMed1977

Telephone line transmission of rectilinear radionuclide scans. Report of a pilot project.

The General Electric-Elscint system for telephone line transmission of rectillinear scans has been tested and with certain limitations found to be acceptable in terms of diagnostic accuracy for many scan procedures. The system tested had some logistic disadvantage requiring batch processing of the scans, and making quality control of the scans difficult with the one video data processor available at the reference centre.

Data Display↗
PubMed1972

Dial-a-scan.

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Communication↗