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Biomedical subjects

D Ross

Publications and source records attributed to D Ross.

At least 217 records · Page 12Linked to original sources
PubMed1991

Intraoperative radiotherapy of skull base cancer.

As the head and neck surgeon expands the boundaries of resectability into the skull base, the margin of tumor clearance diminishes. Intraoperative radiotherapy (IORT) can be used as an adjunct to skull base surgery and external beam radiation to enhance local control in areas with close margins or remaining microscopic disease. During the period from May 1982 to May 1988, 25 patients underwent IORT of the skull base following resection and prior to closure to treat microscopic disease in 9 patients, sterilize close margins in 14 patients, and attempt to eliminate remaining gross disease in 2 patients. The types of tumors treated were 13 squamous cell carcinomas, 4 adenoid cystic carcinomas, 3 high-grade mucoepidermoid carcinomas, 3 sarcomas, 1 malignant mixed tumor, and an oncocytic adenocarcinoma. The majority of the tumors either originated in the sinuses or were skull base extensions of oral cavity or oropharyngeal cancers. In 22 patients with 1-year follow-up, IORT prevented local recurrence in 14 (64%) patients. This may represent improved control of local disease in patients who historically have a very dismal prognosis. The indications, techniques, and complications of this exciting therapeutic modality are also reviewed.

Adolescent↗
PubMed1991

Hysteresis of the parathyroid hormone response to hypocalcemia in hemodialysis patients with low turnover aluminum bone disease.

During the study of parathyroid function in 19 hemodialysis patients with low turnover aluminum bone disease, it was observed that serum parathyroid hormone (PTH) levels were higher during the induction of hypocalcemia than during the recovery from hypocalcemia. This type of PTH response has been termed hysteresis. Hypocalcemia was induced during hemodialysis with a calcium-free dialysate. When the total serum calcium level decreased to 7 mg/dL, the dialysate calcium concentration was changed to 3.5 mEq/L and the dialysis session was completed. One week later, hypercalcemia was induced during hemodialysis with a high-calcium dialysate. The mean basal PTH level was 132 +/- 37 pg/mL (normal, 10 to 65 pg/mL; immunoradiometric (IRMA), Nichols Institute, San Juan Capistrano, CA) and increased to a maximal PTH level of 387 +/- 91 pg/mL during hypocalcemia. For the same ionized calcium concentration, the PTH level was higher during the induction of hypocalcemia than during the recovery from hypocalcemia. Conversely, for the same ionized calcium concentration, the PTH level was greater when hypercalcemia was induced from the nadir of hypocalcemia than when hypercalcemia was induced from basal serum calcium. The set point of calcium (defined as the serum calcium concentration required to reduce maximal PTH by 50%) was greater during the induction of hypocalcemia than during the recovery from hypocalcemia (4.44 +/- 0.10 versus 4.25 +/- 0.09 mg/dL; P = 0.03). The mean basal ionized calcium concentration and the mean ionized calcium concentration at the intersection of the two PTH-calcium curves were the same (4.61 +/- 0.13 versus 4.61 +/- 0.12 mg/dL).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1991

Lung transplantation: the pathologic diagnosis of pulmonary complications.

The reliability of bronchoscopy with transbronchial biopsies for the diagnosis of acute graft rejection has recently been questioned. We present our experience with 59 transbronchial and bronchial biopsies and two open-lung biopsies from 12 patients that underwent lung transplantation. The diagnosis of acute rejection was established in 14 biopsies based on the absence of infection and presence of one or more of the following features: perivascular lymphoid infiltrates, usually associated with endothelial swelling; bronchial "acute on chronic" inflammation; and/or angiitis. Problems and potential pitfalls in the diagnosis of acute graft rejection in lung transplant patients are discussed. The biopsies were also sensitive for the diagnosis of cytomegalovirus pneumonitis and fungal infections but were not helpful for the diagnosis of bacterial pneumonias. Indeed, one patient died with Legionella sp. pneumonia diagnosed only on open-lung biopsy after two negative transbronchial biopsies. The significance of other histologic changes, such as nonspecific interstitial pneumonitis, diffuse alveolar damage, acute alveolitis, goblet cell hyperplasia of the bronchial mucosa, and pulmonary infarction, is discussed.

Biopsy↗
PubMed1990

Metabolism of mitomycin C by DT-diaphorase: role in mitomycin C-induced DNA damage and cytotoxicity in human colon carcinoma cells.

The role of DT-diaphorase in bioreductive activation of mitomycin C was examined using HT-29 and BE human carcinoma cells which have high and low levels of DT-diaphorase activity, respectively. HT-29 cells were more sensitive to mitomycin C-induced cytotoxicity than the DT-diaphorase-deficient BE cell line. Mitomycin C induced DNA interstrand cross-linking in HT-29 cells but not in BE cells. Both mitomycin C-induced cytotoxicity and induction of DNA interstrand cross-links could be inhibited by pretreatment of HT-29 cells with dicoumarol. Metabolism of mitomycin C by HT-29 cell cytosol was pH dependent and increased as the pH was lowered to 5.8, the lowest pH tested. Metabolism of mitomycin C by HT-29 cytosol was inhibited by prior boiling of cytosol or by the inclusion of dicoumarol. Little metabolism was detected in BE cytosols. When purified rat hepatic DT-diaphorase was used, metabolism of mitomycin C increased as the pH was decreased and could be detected at pH 5.8, 6.4, 7.0, 7.4, but not at 7.8. Metabolism of mitomycin C was NADH dependent and inhibited by dicoumarol or by prior boiling of enzyme. An approximate 1:1 stoichiometry between NADH and mitomycin C removal was demonstrated and no oxygen consumption could be detected. Metabolism of mitomycin C by purified HT-29 DT-diaphorase was also dicoumarol inhibitable and pH dependent. The major metabolite formed during metabolism of mitomycin C by HT-29 cytosol, purified HT-29, and rat hepatic DT-diaphorase was characterized as 2,7-diaminomitosene. These data suggest that two-electron reduction of mitomycin C by DT-diaphorase may be an important determinant of mitomycin C-induced genotoxicity and cytotoxicity.

Antineoplastic Agents↗
PubMed1990

Metabolism of diaziquone by NAD(P)H:(quinone acceptor) oxidoreductase (DT-diaphorase): role in diaziquone-induced DNA damage and cytotoxicity in human colon carcinoma cells.

Reduction of 2,5-diaziridinyl-3,6-bis(carboethoxyamino)-1,4-benzoquinone (diaziquone; AZQ) by purified rat hepatic DT-diaphorase was NADH and enzyme dependent and was inhibited by prior boiling of the enzyme or by dicumarol. Under aerobic conditions some of the hydroquinone (AZQH2) formed by reduction oxidized to regenerate AZQ and an approximate 1:1 stoichiometry was observed between AZQH2 reoxidized and oxygen consumed. The steady state kinetics of AZQ reduction were consistent with a ping-pong mechanism and a high Km for AZQ. There was no evidence for saturation in the range of 25-200 microM AZQ at 200 microM NADH. AZQ (0-20 microM) induced dicumarol-inhibitable DNA interstrand cross-linking and cytotoxicity in HT-29 human colon carcinoma cells which have high DT-diaphorase activity but not in BE cells which have low DT-diaphorase activity. Extensive metabolism (greater than 90%) of AZQ (100 microM) in HT-29 cytosol occurred, which was either NADH or NADPH dependent and could be inhibited by dicumarol. Little metabolism of AZQ could be detected in BE cell cytosols. DT-diaphorase was purified from HT-29 cells and metabolism of AZQ by this enzyme was confirmed. These data show that AZQ can be metabolized by purified rat hepatic and human HT-29 DT-diaphorase and suggest that in HT-29 cells, DT-diaphorase catalyzed reduction of AZQ represents a bioactivation process leading to the production of genotoxic and cytotoxic metabolites.

Animals↗
PubMed1990

Phenol-induced stimulation of hydroquinone bioactivation in mouse bone marrow in vivo: possible implications in benzene myelotoxicity.

The coadministration of phenol and hydroquinone has been shown to produce myelotoxicity in mice similar to that observed following benzene exposure. One explanation of this phenomenon may be that phenol enhances the peroxidase-dependent metabolic activation of hydroquinone in the mouse bone marrow. Here we report that radiolabeled [14C]hydroquinone and [14C]phenol bind covalently to tissue macromolecules of blood, bone marrow, liver and kidney, when administered intraperitoneally to the mouse in vivo. Substantially more radiolabeled hydroquinone was covalently bound 18 h after administration as compared with that bound after 4 h. Phenol, when administered together with [14C]hydroquinone, significantly stimulated the covalent binding of [14C]hydroquinone oxidation products to blood (P less than 0.001) and bone marrow (P less than 0.05) macromolecules, but had no significant effect on covalent binding of [14C]hydroquinone oxidation products to liver and kidney macromolecules (P greater than 0.05). Catechol, on the other hand, had no effect on the binding of [14C]hydroquinone oxidation products in either bone marrow, kidney or liver (P greater than 0.05). When hydroquinone was administered together with [14C]phenol, a stimulation of the covalent binding of phenol oxidation products to bone marrow macromolecules also occurred (P less than 0.05). In addition, hydroquinone co-administration increased the covalent binding of [14C]phenol oxidation products in kidney and blood (P less than 0.05), but significantly decreased the covalent binding in liver (P less than 0.05). These results suggest that altered pharmacokinetics play a major role in the hydroquinone-dependent stimulation of covalent binding of [14C]phenol oxidation products to extrahepatic tissue macromolecules in vivo. The mechanism underlying the phenol-induced stimulation of binding of [14C]hydroquinone by phenol in blood and bone marrow remains unclear, but stimulation of peroxidase-mediated hydroquinone metabolism may be responsible. The latter may therefore play an important role in benzene-induced myelotoxicity.

Animals↗
PubMed1990

Intraoperative radiotherapy of head and neck cancer.

Intraoperative radiotherapy (IORT) was developed as an adjuvant to surgery and external beam radiation for aggressive, extensive, or recurrent cancers of the head and neck. This report reviews the indications, technique, response, and complications of IORT. From May 1982 to May 1988, 104 patients received 15 to 20 Gy of radiation delivered through a Lucite cone to areas of high risk of recurrence following resection and prior to closure. The indications for treatment were (1) aggressive primary or recurrent cancer; (2) disease fixed to deep muscle, carotid, or bone; or (3) close margins in an effort to preserve vital structures or function. The IORT was effective in preventing local recurrence in 14 (40%) of 35 patients with 2-year follow-up of squamous cell carcinoma. The complication rate was acceptable. Intraoperative radiotherapy appears to be a safe and beneficial adjunctive therapy for cancers that historically have extremely dismal prognoses.

Adolescent↗
PubMed1990

Allograft root replacement for prosthetic endocarditis.

A series of 53 root replacements of the aortic valve for severe endocarditis is presented. The principles of this technique are to remove all abscesses and infected areas likely to drain into the mediastinum, excision of infected tissue down to healthy noninfected tissue, and replacement with an antibiotic-impregnated homograft aortic root. Using this technique there has been a very high rate of cure of this most dreaded complication.

Abscess↗
PubMed1990

Activation and deactivation of quinones catalyzed by DT-diaphorase. Evidence for bioreductive activation of diaziquone (AZQ) in human tumor cells and detoxification of benzene metabolites in bone marrow stroma.

Bioactivation of diaziquone (AZQ) in HT-29 human colon carcinoma cells and detoxification of benzene metabolites in bone marrow stromal cells were used as examples of the potential role of DT-diaphorase in both activation and deactivation processes. HT-29 cell cytosol contained high levels of DT-diaphorase activity and removed AZQ in the presence of either NADH or NADPH. Prior boiling of cytosol, omission of NADH or NADPH or inclusion of dicoumarol, an inhibitor of DT-diaphorase, inhibited removal of AZQ. AZQ-induced cytotoxicity in HT-29 cells was also inhibited by dicoumarol. Chemical reduction of AZQ in a cell free system enhanced formation of a GSH conjugate of AZQ. Two of the major cell types in bone marrow stroma are macrophages and fibroblastoid stromal cells. A fibroblastoid cell line derived from stromal cells contained approximately fourfold higher levels of DT-diaphorase than macrophages. Inclusion of dicoumarol in incubations containing 14C-hydroquinone and the respective stromal cell type, significantly increased covalent binding of radiolabel to macromolecules in stromal fibroblasts but not in macrophages.

Animals↗
PubMed1990

Alcohol and crimes of violence: present issues.

Current issues in alcohol-related violence are highlighted through the examination of correlational studies between alcohol and violent crime. Alcohol is associated with violent crime at a greater than chance level and at a significantly higher level than it is associated with nonviolent crime. Heavy drinking and a verbal argument usually precede the violent act and the victim is as likely as the offender to initiate the altercation. However, it is the precipitator of the altercation who is more likely to be intoxicated. Alcohol and aggression are more strongly related than expected with violent offenders demonstrating psychopathology. Marital violence appears related to alcohol independent of other marital problems. Although there exists a strong correlational relationship between alcohol and violent crime, the nature of the evidence prohibits the establishment of a causal link. In particular, methodological problems, such as a lack of appropriate comparison groups, make it difficult to draw conclusions in this area.

Alcoholic Intoxication↗
PubMed1990

Bone marrow stromal cell bioactivation and detoxification of the benzene metabolite hydroquinone: comparison of macrophages and fibroblastoid cells.

Bone marrow stroma consists predominately of two cell types, macrophages and fibroblastoid stromal cells, which regulate the growth and differentiation of myelopoietic cells via the production of growth factors. We have previously shown that macrophages are more sensitive than fibroblastoid stromal cells (LTF cells) to the toxic effects of the benzene metabolite hydroquinone. In this study, the role of selective bioactivation and/or deactivation in the macrophage-selective effects of hydroquinone was examined. LTF and macrophage cultures were incubated with 10 microM [14C]hydroquinone to examine differential bioactivation. After 24 hr, the amount of 14C covalently bound to acid-insoluble macromolecules was determined. Macrophages had 16-fold higher levels of macromolecule-associated 14C than did LTF cells. Additional experiments revealed that hydroquinone bioactivation to covalent-binding species was hydrogen peroxide dependent in macrophage homogenates. Covalent binding in companion LTF homogenates was minimal, even in the presence of excess hydrogen peroxide. These data suggest that a peroxidative event was responsible for bioactivation in macrophages and, in agreement with this, macrophages contained detectable peroxidase activity whereas LTF cells did not. Bioactivation of [14C]hydroquinone to protein-binding species by peroxidase was confirmed utilizing purified human myeloperoxidase in the presence of hydrogen peroxide and ovalbumin as a protein source. High performance liquid chromatographic analysis of incubations containing purified myeloperoxidase, hydroquinone, and hydrogen peroxide showed that greater than 90% of hydroquinone was removed and could be detected stoichometrically as 1,4-benzoquinone. 1,4-Benzoquinone was confirmed as a reactive metabolite formed from hydroquinone in macrophage incubations using excess GSH and trapping the reactive quinone as its GSH conjugate, which was measured by high performance liquid chromatography with electrochemical detection. The activity of DT-diaphorase, a quinone reductase that has been invoked as a protective mechanism in quinone-induced toxicity, was 4-fold higher in LTF cells than macrophages. These data suggest that the macrophage-selective toxicity of hydroquinone results from higher levels of peroxidase-mediated bioactivation and/or lower levels of DT-diaphorase-mediated detoxification.

Animals↗
PubMed1990

Adjuvant radiation therapy in endometrial carcinoma.

Between 1983 and 1987, 79 patients received radiation therapy in combination with surgery for cancer of the endometrium. The pathology in all cases was adenocarcinoma. Most cases had deep myometrial penetration with moderate or poor differentiation. More than two-thirds of the patients had stage I disease. Twenty-two patients received preoperative radiation, and 57 patients received radiation following surgery. There were 10 recurrences in the 79 patients treated. Most recurrences were from distant disease, and there was only one case of an isolated pelvic recurrence. Adjuvant radiation is well-tolerated, and the failure rate in the pelvis is low, even with aggressive lesions.

Adult↗
PubMed1989

Arterial blood gas changes in panic disorder and lactate-induced panic.

Lactate infusions were conducted in 12 male panic patients and 8 male normal controls with arterial catheters in place to reassess previously reported acid-base changes based on venous blood samples. The analysis of arterial pH, carbon dioxide pressure, and bicarbonate concentration confirmed most venous findings. At baseline, before the infusion, venous blood shows evidence of mixed chronic and acute respiratory alkalosis in patients while arterial blood gasses are most consistent with developing acute respiratory alkalosis. During the infusion both bloods are consistent with mixed metabolic and respiratory alkalosis with the patients hyperventilating more than normal controls and panicking patients hyperventilating more than nonpanicking patients. Arterial blood seems more sensitive than venous blood in detecting baseline differences between panicking and nonpanicking patients. A baseline arterial carbon dioxide pressure of 40 mmHg or higher and an arterial pH below 7.40 may predict no subsequent panic to lactate infusion.

Acid-Base Equilibrium↗