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Biomedical subjects

M C Gebhardt

Publications and source records attributed to M C Gebhardt.

At least 109 records · Page 6Linked to original sources

Extraosseous osteosarcoma presenting with intestinal hemorrhage: case report and literature review.

A 23-year-old man presented with intestinal bleeding due to an extraosseous osteosarcoma of the jejunum. A lesion was also found in the deltoid muscle, and other metachronous soft tissue sites developed subsequently. The presence of malignant osteoid was documented by immunohistochemical studies of one of the lesions. The patient died of metastatic disease 19 months after diagnosis, despite surgical resections and adjuvant chemotherapy. This unique presentation is discussed, and the literature concerning extraosseous osteosarcoma is reviewed.

Adult↗

Magnetic resonance imaging in a patient with soft tissue sarcoma of the leg.

A patient with a high grade malignant fibrous histiocytoma of the leg is presented. Staging studies included a 99mTc diphosphonate bone scan, an arteriogram, a computed tomogram (CT) and a proton (1H) magnetic resonance imaging (MRI) study. By manipulating imaging parameters to enhance contrast between normal and neoplastic tissues, the latter technique more accurately delineated the extent of the soft tissue sarcoma than the other imaging modalities. Although spatial resolution of MRI is inferior to that of CT, it is likely that MRI will provide important information relative to surgical staging and preoperative planning that is not available from current imaging techniques.

Female↗

Prostaglandin E2 synthesis by human primary and metastatic bone tumors in culture.

Prostaglandin E2 (PGE2) is known to stimulate osteolysis in vitro and has been implicated in mediating bone resorption in several animal and human tumors. Little attention has yet to be directed toward local humoral control (including PGE2) of bone resorption in primary and metastatic bone tumors. For investigation of whether histologically identified areas of osteolytic or osteoblastic bone tumors differentially secrete PGE2 under in vitro conditions, culture media from explants of central and peripheral areas of tissue were sterilely collected from 13 surgical specimens of primary and metastatic bone tumors and assayed for (PGE2) radioimmunoassay. The results indicate a marked heterogeneity in the concentration of immunoreactive (I-PGE2) synthesis by tumors of different as well as similar cell type. PGE2 production was time-dependent in culture, and at 72 hours substantial increases were apparent compared to cultures of non-neoplastic fascia controls. Significantly higher levels of I-PGE2 were found in cultures derived from "bone-destructive" tumors. No difference in I-PGE2 synthesis was found between explants of peripheral versus central tissue of the same tumors. PGE2 is synthesized in culture by bone tumors characterized as destructive of bone at higher levels than "bone-forming" tumors, and this synthesis is inhibited by indomethacin.

Bone Neoplasms↗

Desmoplastic fibroma of bone. A report of eight cases and review of the literature.

Desmoplastic fibroma of bone is a rare benign tumor consisting of thin, wavy fibroblasts set in an abundant matrix of collagen fibers. At times it is difficult to distinguish desmoplastic fibroma from other fibrous lesions, especially low-grade fibrosarcomas. Fewer than eight cases have been previously reported. We have reviewed the diagnostic and therapeutic findings of eighty additional cases. Six patients had the lesions located in an extremity and two had an axial lesion. The average age of the patients was twenty-five years (range, twelve to fifty-six years) and all of the patients had more than two years of follow-up (range, two to seventeen years). The radiographic findings in all but one patient were of a purely lytic, honeycombed lesion that often widened the bone, and was metaphyseal in long bones. The tumor replaced the medullary cavity with a grayish-white, rubbery to firm tissue that was often, but not always, contained by a rim of periosteal reactive bone. Histologically, the features were: (1) prominent loose bundles of fibrous tissue composed of slim, spindle-shaped fibroblasts with wavy, elongated nuclei; (2) variable amounts of bands of collagen fibers; and (3) absence of mitoses or atypical cells. Areas of metaplastic bone were found only around sites, of pathological fractures. The biology of desmoplastic fibroma is different from that of other benign fibrous lesions in that the lesion is very destructive locally and often recurs after incomplete excision. It is also distinguished from low-grade malignant lesions (for example, fibrosarcoma) in that metastases have never been reported. In our series an intralesional excision was initially performed in six of the eight patients and a marginal resection, in two. There were four recurrences, treated by a marginal resection in two patients and repeat curettage in one. The recurrence in the fourth patient required an amputation above the knee after two additional intralesional procedures had been unsuccessful. Wide or marginal resection appears to be the treatment of choice when the lesion is located in a site that can be resected without significant loss of function. In other areas, an attempt at curettage, instillation of phenol, and bone-grafting seems to be warranted, resorting to more radical procedures only if this fails to control local disease.

Adolescent↗

Bone tumors in children. Differential characteristics and treatment.

Recognition of benign bone tumors in children is important so that they can be distinguished from malignant tumors, which pose a far more significant risk. Treatment is relatively uncomplicated for benign lesions, but malignant tumors present a significant challenge to the orthopedist, medical oncologist, and radiotherapist. Currently, strides are being made toward improving the survival rate and quality of life of bone sarcoma patients. Newer diagnostic techniques, such as magnetic resonance imaging, and improved research techniques, such as flow cytometry, may lead to further understanding of the nature of these virulent tumors. Improvement in biomechanical designs for metallic joint implants and further understanding of bone transplantation biology should result in better functional restoration in these patients.

Adolescent↗

NMR imaging of forearms in healthy volunteers and patients with giant-cell tumor of bone.

Serial proton nuclear magnetic resonance (NMR) images of distal upper extremities were obtained in four healthy volunteers and four patients with giant cell tumor of the distal radius. The steady-state-free-precession (SSFP) data collection technique and an 8-cm bore superconducting magnet (1.44 tesla) were used. All images demonstrated high spatial resolution and excellent soft-tissue contrast. In patients with giant cell tumor, the NMR images revealed bone marrow replacement by tumor, cortical bone thinning, and cortical bone destruction. The extent of tumor involvement was clearly delineated by the NMR images and corresponded to radiographic and surgical findings. NMR signal intensity was lower in tumors, suggesting altered relaxation times. These findings demonstrate that proton NMR imaging can provide high-resolution images of extremities and detect tumors by changes in both anatomic structure and relaxation times.

Adult↗

Effect of Corynebacterium parvum in prevention and reversal of atrophy of the liver following portacaval shunt.

Since it has been demonstrated that the administration of Corynebacterium parvum is associated with increased hepatocyte proliferation in both normal and regenerating livers, it seemed appropriate to determine whether the use of this agent would affect the hepatic atrophy which occurs following end-to-side portacaval shunts. When administered at shunting, liver weight and liver deoxyribonucleic acid failed to decrease to the same extent as that occurring in untreated, shunted rats. An increase in liver deoxyribonucleic acid synthesis was observed following portacaval shunt only in treated rats. Corynebacterium parvum administration to portacaval shunt rats with livers demonstrating marked atrophy 15 to 18 days following shunting resulted in the reversal of such atrophy. There was an increase in liver weight and deoxyribonuclei acid to the extent that those values were equal to, or greater than, those of livers from nonshunted rats. By increasing the number of cells within liver, Corynebacterium parvum administration prevents or reverses the decrease in liver size, that is, atrophy, which occurs after portacaval shunts were performed.

Animals↗

Presurgical window of carboplatin and surgery and multidrug chemotherapy for the treatment of newly diagnosed metastatic or unresectable osteosarcoma: Pediatric Oncology Group Trial.

PURPOSE: Relapse remains a significant problem in patients with metastatic osteosarcoma. The response to carboplatin of patients with newly diagnosed metastatic or unresectable osteosarcoma was assessed in an upfront phase II window, which was followed-up by surgery and intensive multiagent chemotherapy. PATIENTS AND METHODS: Thirty-seven patients, ages 3 to 23 years with histologically confirmed diagnoses of osteosarcoma, were treated between January 1992 and November 1994 with carboplatin 1,000 mg/m2 per dose administered as a 48-hour continuous infusion. Two courses were administered in 3-week intervals, depending on marrow recovery. After radiographic reevaluation, patients underwent surgical removal of tumor (if feasible) and then 40 weeks of chemotherapy with high-dose methotrexate, ifosfamide, doxorubicin, and cisplatin. RESULTS: One of the 37 evaluable patients demonstrated a partial response to carboplatin; there were no complete responses. Patients were additionally analyzed by the response of pulmonary metastases to therapy and the extent of tumor necrosis of the primary lesion. By these criteria, 8 of 37 (22%) of patients showed a response at one or more sites, whereas 20 of 37 (54%) had unequivocal disease progression. Severe myelosuppression was the major toxicity. The projected 3-year event-free and overall survival rates were 23.9% and 31.9%, respectively. Only 1 of 17 patients with unresectable disease or distant bone metastases remains alive, in contrast to 6 of 17 patients with the lung as their only metastatic site and two of three patients with resected regional bone metastases. CONCLUSIONS: Continuous-infusion carboplatin demonstrated limited activity as an upfront agent in patients with metastatic osteosarcoma at diagnosis, even at doses that result in severe and prolonged myelosuppression. Patients with isolated pulmonary metastases or resectable bone metastases have a longer median survival time and greater chance of long-term survival than do patients with unresectable bone disease, for whom the prognosis remains dismal.

Adolescent↗

Percutaneous biopsy of pyogenic infection of the spine in children.

Three boys had percutaneous biopsies of pyogenic infections of the spine guided by computed tomography (CT). All had typical features of chronic vertebral osteomyelitis, i.e., narrowing of disc space, destruction of the contiguous vertebral endplates, sclerosis of vertebral bodies, and soft tissue swelling as noted on radiographs, CT, and magnetic resonance imaging (MRI). All three had back pain; one was asymptomatic at the time of the biopsy. Culture of the biopsy material grew Staphylococcus aureus in two cases and Salmonella group B in one. If blood cultures are negative, a biopsy of the vertebral body is recommended in order to determine the activity of the process and the type of organism, and its susceptibility to antibiotics. CT-guided percutaneous biopsy is an alternative to open surgical biopsy.

Adolescent↗

Polyploidization induced by acridine orange in mouse osteosarcoma cells.

This study was undertaken to clarify the in vitro effect of acridine orange (AO) on the cell kinetics of mouse osteosarcoma cells, as well as the mechanism of cell growth inhibition induced by AO. A mouse osteosarcoma cell line (MOS), established from a radiation-induced mouse osteosarcoma, was cultured under exposure to 0.05, 0.5, 5, and 50 micrograms/ml of AO, either continuously or for 10 minutes. The cell kinetic analysis was performed using the following parameters: tumor cell growth by trypan blue exclusion test, mitotic activity, DNA synthetic activity by BrdU labeling and DNA ploidy by cytofluorometry. The results showed that continuous exposure to 5 and 50 micrograms/ml of AO or 10 minute exposure to 50 micrograms/ml of AO quickly killed the tumor cells within 12 hours, whereas continuous exposure to 0.5 microgram/ml of AO or 10 minute exposure to 5 micrograms/ml of AO gradually inhibited tumor cell growth. Under the latter conditions, mitotic activity was rapidly and completely inhibited within 48 hours but DNA synthetic activity was not completely inhibited even after 96 hours. DNA ploidy analysis demonstrated that most of the tumor cells arrested at the S-G2 phase after 12 hours, followed by G2 phase arrest after 24 hours and progressive DNA synthesis to a higher DNA ploidy class after 48 to 96 hours. We therefore concluded that a high concentration of AO has a strong cytocidal effect due to cytotoxicity whilst a moderate concentration of AO induces progressive and synchronous polyploidization by mitotic inhibition without DNA damage in MOS cells. We presume that this in vitro effect on MOS cells may be caused by protein synthetic inhibition after transfer RNA inactivation caused by AO binding.

Acridine Orange↗