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Biomedical subjects

M J Homer

Publications and source records attributed to M J Homer.

At least 37 records · Page 2Linked to original sources
PubMed1993

Dinitrogenase reductase- and MgATP-dependent maturation of apodinitrogenase from Azotobacter vinelandii.

The requirements for iron-molybdenum cofactor (FeMo-co) activation of apodinitrogenase from Azotobacter vinelandii strain UW97, which lacks dinitrogenase reductase activity as assayed by substrate reduction, have been examined. Activation of apodinitrogenase from strain UW97 by FeMo-co requires the addition of both dinitrogenase reductase and MgATP. When the same apodinitrogenase is pretreated with dinitrogenase reductase and MgATP and then partially purified, however, it does not require these components for activation by FeMo-co. This suggests that dinitrogenase reductase and MgATP are involved in processing apodinitrogenase to a FeMo-co activatable form. This processing step coincides with a change in the subunit composition of apodinitrogenase from alpha 2 beta 2 to a form with an additional subunit (gamma) attached. The apodinitrogenase with the associated gamma subunit is apparently the form of the protein that is competent for activation by FeMo-co.

Adenosine Triphosphate↗
PubMed1993

Breast conservation therapy for early stage breast carcinoma with outstanding 10-year locoregional control rates: a case for aggressive therapy to the tumor bearing quadrant.

PURPOSE: Between 1982 and 1988 233 American Joint Committee on Cancer Stage I and II invasive breast carcinomas were prospectively treated in 225 women with conservative tumor excision, careful assessment of histopathological margins, and dose-adjusted irradiation to maximum doses of 70 Gy to the tumor bearing quadrant of the breast. METHODS AND MATERIALS: The pathological stages at presentation were T1N0 and T1N1 in 57% and 13% and T2N0 and T2N1 in 19% and 10% of the patients, respectively. All patients were irradiated according to a policy that, beyond the 50 Gy to the whole breast and draining lymphatics, the tumor-bearing quadrant was boosted in adjustment to the histopathological margin. Normal tissue margins of < 2 mm were considered positive, margins 2-5 mm close, and margins > 5 mm negative and were boosted with 20, 15, and 10 Gy, respectively. Patients in whom the margin could not be assessed were re-excised or boosted to 20 Gy. Re-excisions with no residual carcinoma were not boosted. Most patients boosted to 20 Gy to the tumor-bearing quadrant received interstitial 192-Ir implantations. RESULTS: The actuarial local control rates in the treated breast were 97.5% at 10 years with three recurrences having occurred at a median of 4.5 years after completion of radiotherapy. An additional two patients failed regionally outside the irradiation portals. The overall and disease-free survival of the whole group is 87.5% and 77%, respectively. CONCLUSION: The approach to breast conservation therapy followed in this study has resulted in outstanding local control rates and suggests that there may be a subset of patients that could be irradiated to the tumor bearing quadrant only.

Adult↗
PubMed1993

The nifY product of Klebsiella pneumoniae is associated with apodinitrogenase and dissociates upon activation with the iron-molybdenum cofactor.

Apodinitrogenase, which lacks the iron-molybdenum cofactor at its active site, is an oligomer that contains an additional protein not found in the active dinitrogenase tetramer. This associated protein in Klebsiella pneumoniae is shown to be the product of the nifY gene. When apodinitrogenase is activated by the addition of the iron-molybdenum cofactor, NifY dissociates from the apodinitrogenase complex. The conditions for this dissociation are described. Finally, there are aspects of the dissociation and insertion process in K. pneumoniae that are different from that in Azotobacter vinelandii.

Amino Acid Sequence↗
PubMed1992

Nonpalpable breast microcalcifications: frequency, management, and results of incisional biopsy.

In a series of 500 consecutive needle localizations, there were 165 biopsies for benign microcalcifications without a mass. An incisional biopsy was performed in 49 of these cases (30%). Follow-up mammograms were available for review in 39 of the cases. The average length of follow-up was 32 months. In no case did malignancy develop at the biopsy site. When an incisional biopsy is performed, careful follow-up mammography is an alternative to a repeated needle localization and biopsy in selected cases.

Biopsy↗
PubMed1992

Prebiopsy needle localization. Methods, problems, and expected results.

The use of mammography to screen patients for the presence of early breast cancer results in the detection of nonpalpable lesions. As screening becomes more widespread, the number of needle localizations performed will continue to increase. This procedure requires involvement of the radiologist, surgeon, and pathologist. Close cooperation between these disciplines will ensure optimal patient care.

Breast↗
PubMed1989

In situ breast cancer: a multidisciplinary approach.

The approach to these lesions is being reexamined in light of results with conservative surgery for invasive breast cancers. According to available data, the invasive potential of in situ lesions varies. Mammographic and pathologic findings may differentiate patients who will benefit from lumpectomy (with or without radiotherapy) from those requiring mastectomy.

Breast Neoplasms↗
PubMed1989

Residual breast carcinoma after biopsy: role of mammography in evaluation.

The records of 21 consecutive patients referred for breast-conservation treatment of early-stage mammary carcinoma contained insufficient histopathologic documentation of adequate resection margins after tumor excision at other hospitals. All patients underwent postbiopsy mammography before reexcision of the tumor bed. In 12 of the 21 cases, there was pathologic evidence of macroscopic or microscopic residual tumor. In seven of the 12 cases, there was no clinical or mammographic evidence to suggest residual carcinoma. The findings indicate that mammography is insufficient to evaluate the completeness of tumor excision in the absence of histopathologic documentation.

Biopsy↗
PubMed1989

The relationship of mammographic microcalcification to histologic malignancy: radiologic-pathologic correlation.

Forty consecutive cases of nonpalpable breast carcinoma presenting on the mammogram as microcalcifications without an associated mass were reviewed. The precise relationship between the mammographic microcalcification and the histologic carcinoma was determined in each case. In 25 cases (63%), the mammographic calcium was confined to the tumor, and in 13 cases (33%), the calcification was present both within the tumor and contiguous to the tumor margin. In two cases (5%), the calcium was not contained within the tumor but was located next to it. In one of these cases, the calcium was within 4 mm of the malignant neoplasm and in the other it was within 13 mm. No difference was seen between the appearance of the calcifications located within the tumor and the appearance of calcification next to the tumor. Precise histologic analysis revealed that microcalcifications that had prompted biopsy were confined to the tumor in 63%, within and contiguous to the tumor in 32%, and within 13 mm of the tumor in 5%.

Breast Neoplasms↗
PubMed1987

Disappearing breast masses caused by compression during mammography.

Two cases are described in which a palpable mass and a nonpalpable mass disappeared during the performance of mammography. The disappearance is presumed to be caused by cyst rupture, resulting from the firm compression used to perform the examination. This occurrence can create confusing clinical and radiographic situations, and radiologists should be aware that occasional cyst rupture may occur.

Adult↗
PubMed1987

Preoperative needle localization of lesions in the lower half of the breast: needle entry from below.

For preoperative localization of lesions in the lower part of the breast, an inferior approach provides the shortest skin-to-lesion distance. This paper describes the successful inferior approach in 48 of 49 consecutive localizations. No special grid localization device is needed. This technique permits accurate localization of small foci of microcalcifications and other nonpalpable breast lesions.

Breast Diseases↗