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Biomedical subjects

D Dixon

Publications and source records attributed to D Dixon.

At least 91 records · Page 5Linked to original sources
PubMed1987

Lack of benefit of adjunctive chemotherapy in stage I malignant melanoma: a Southwest Oncology Group Study.

In 1975, the Southwest Oncology Group initiated an adjuvant study in localized malignant melanoma testing the value of aggressive chemotherapy using carmustine, hydroxyurea, and dacarbazine versus a control arm. Median disease-free survival was 7.1 years for the control arm and 6 years for the treatment arm. Survival was identical for both arms with 65% of the patients alive at 6 years. We conclude that carmustine, hydroxyurea, and dacarbazine chemotherapy is of no value as adjuvant treatment for localized melanoma.

Adult↗
PubMed1987

Variables predicting response to high dose cytosine arabinoside therapy in patients with refractory acute leukemia.

The cytotoxic effect of cytosine arabinoside (ara-C) is presumably mediated by cytosine arabinoside 5'-triphosphate (ara-CTP). We tested for a correlation between intracellular ara-CTP pharmacokinetics and clinical response among 51 patients who received high dose ara-C (3 g/m2 at 12-hr intervals) as therapy for refractory acute leukemia. After accounting for pretreatment clinical variables that correlated with response, measurement of ara-CTP pharmacokinetics added significant prognostic information. This provides a rationale for manipulation of schedules of high dose ara-C administration in those patients whose pharmacokinetic characteristics are inconsistent with response to an every 12-hr schedule.

Acute Disease↗
PubMed1986

Antibodies isolated by using cloned surface antigens recognize antigenically related components of Legionella pneumophila and other Legionella species.

We studied the antigenic cross-reactivity of surface proteins among various strains of Legionella pneumophila and other Legionella species by using a novel method of antibody purification. Anti-bacterial antibodies in hyperimmune sera were adsorbed to and eluted from the surface of recombinant E. coli cells that express individual L. pneumophila antigens on their surface. These affinity-purified antibodies were then used to probe protein immunoblots prepared from the test strains to detect cross-reactive domains. We found that antigenic proteins are generally conserved in all L. pneumophila serogroups. Although some of these antigenic domains are shared with members of other Legionella species, they are associated with proteins of different molecular mass. Our approach to the study of antigenic cross-reactivity has potential advantages over similar studies that use either monoclonal antibodies or monospecific antibodies prepared by immunization with purified antigens.

Animals↗
PubMed1986

Erythrocyte polyamine levels during intravenous feeding of patients with colorectal carcinoma.

Changes in erythrocyte (RBC) polyamines were studied during total parenteral nutrition (TPN) in 16 colorectal carcinoma patients and six patients with noncancerous diseases. RBC putrescine (PTC), spermidine (SPD), and spermine (SPM) were analyzed before and at the completion of preoperative TPN in each patient. Before TPN, nutritional status, based on a history of weight loss and plasma albumin, prealbumin and retinol-binding protein levels, were similar for the two groups. Initial RBC PTC, SPD, and SPM levels were also similar for both groups. Preoperative TPN induced significant increases in RBC PTC levels (P less than 0.001) and RBC PTC:SPD ratios (P less than 0.005) of the cancer patients while no significant polyamine changes were observed in the other group. Host response to nutritional therapy was monitored with plasma prealbumin and retinol-binding protein levels which did not change significantly in either group.

Colonic Neoplasms↗
PubMed1986

Immunologic relationship between platelet membrane glycoprotein GPIIb/IIIa and cell surface molecules expressed by a variety of cells.

A polyclonal antiserum to platelet membrane glycoprotein GPIIb/IIIa was used to detect antigenically related molecules on a diverse panel of human cells. Umbilical vein endothelial cells, erythroleukemic HEL cells, and diploid fetal lung GM1380 fibroblasts expressed GPIIb/IIIa-related molecules, as judged by immunofluorescence and immunoprecipitation of surface-labeled proteins. The GPIIb and GPIIIa subunits were both present and were of similar molecular weight in these cell types. These molecules were synthetic products of the cells, as shown by immunoprecipitation of intrinsically labeled proteins. Promyeloid U937 cells could be induced by 4 beta-phorbol 12-myristate 13-acetate to synthesize and express GPIIb/IIIa-related molecules on their cell surface. The GPIIb/IIIa-related molecules were not precisely identical in the various cell types, based on slight differences in electrophoretic mobility and their failure to react with monoclonal antibodies specific for each subunit of platelet GPIIb/IIIa. These results suggest the existence of a widely distributed family of GPIIb/IIIa-related molecules. This family of "cytoadhesins" may share a common function in cellular adhesive reactions.

Antibodies, Monoclonal↗
PubMed1986

Exoantigen test for Cladosporium bantianum, Fonsecaea pedrosoi, and Phialophora verrucosa.

Exoantigens from 10-day-old cultures of 100 isolates of pathogenic and saprophytic dematiaceous fungi were analyzed by the exoantigen test. Antisera to Cladosporium bantianum ATCC 10958, Fonsecaea pedrosoi CDC AMO-B06, and Phialophora verrucosa CDC AMO-C12 were prepared in New Zealand rabbits immunized with soluble antigens from 1-month-old cultures. Absorbed and nonabsorbed antisera and exoantigens from the same organisms were used as reference reagents. Serologic reactions were analyzed in terms of the presence or absence of lines of identity or nonidentity. These reactions allowed presumptive differentiation of C. bantianum, F. pedrosoi, and Phialophora verrucosa from other dematiaceous fungi, including Cladosporium spp. (28 isolates), Exophiala spp. (18 isolates), Fonsecaea spp. (17 isolates). Lecythophora hoffmannii (4 isolates), Phaeoannellomyces werneckii (3 isolates), Phialophora spp. (17 isolates), Wangiella dermatitidis (9 isolates), and Rhinocladiella spp. (4 isolates).

Animals↗
PubMed1986

High-dose glucocorticoid treatment of resistant myeloma.

Intermittent, high-dose dexamethasone treatment was given to 49 consecutive patients with refractory multiple myeloma. In patients who were unresponsive to previous treatment, the response rate of 27% was similar to that achieved with the VAD regimen, which combines the same schedule of dexamethasone with vincristine and doxorubicin given by continuous infusion. Among patients with relapses, VAD chemotherapy induced remissions in 11 of 17 patients (65%), whereas dexamethasone alone induced remissions in 4 of 19 (21%). The median survival of all patients responding to either treatment, 22 months, was longer than that from any previous program for treatment of resistant myeloma. These findings indicate the value of frequent dexamethasone administration in patients unresponsive to standard therapy and show the major role of vincristine and doxorubicin given by continuous infusion in patients with relapses. They also suggest different mechanisms for primary and secondary resistance to chemotherapy.

Aged↗
PubMed1985

Crayfish motor nerve terminal's response to serotonin examined by intracellular microelectrode.

Measurements of resting potential and action potential in presynaptic branches of the excitatory motor axon to the crayfish opener muscle were made with intracellular microelectrodes during application of serotonin (10(-9)-10(-3) M). A 5-min exposure to 10(-6) M serotonin produced enhancement of excitatory junction potentials (EJPs) lasting about 1 h. The membrane potential of the presynaptic terminal was depolarized by about 5 mV; the depolarization subsided within 1/2 h. Concomitant reduction in amplitude of the presynaptic action potential, not accompanied by spike broadening, was observed. The presynaptic depolarization, and the enhancement of EJPs, were dependent on the presence of extracellular sodium but not extracellular calcium. A possible mechanism for serotonin's effect involves initial entry of sodium into the nerve terminal, with consequent increased availability of intracellular calcium. The subsequent long-lasting phase of EJP enhancement may result from an additional effect on the metabolism of the nerve terminal.

Action Potentials↗
PubMed1985

Perceived sexual satisfaction and marital happiness of bisexual and heterosexual swinging husbands.

This study compared the sexual satisfaction and marital happiness of 50 bisexual and 50 heterosexual married male volunteers. All participants chosen were in swinging marriages. Age, length of current marriages, and socioeconomic status were matched and controlled between samples. The bisexual sample reported: (a) significantly more frequent orgasms with females, from masturbation, and from all sexual activities combined; and (b) a significantly greater incidence of orgasms from fantasies or dreams. Although both samples gave high ratings to their sexual satisfaction and marital happiness, both measures were rated significantly higher by the heterosexual males.

Adult↗
PubMed1985

Prognostic implications of tumor cell DNA and RNA content in multiple myeloma.

Flow cytometric studies of bone marrow DNA and RNA content were conducted in 71 previously untreated patients with multiple myeloma. There was a progressive increase in response rate with rising plasma cell RNA content. The DNA-derived ploidy level also affected chemotherapy sensitivity: only one of 11 patients with either hypodiploidy or biclonal DNA stemlines responded. DNA-RNA-defined marrow plasmacytosis was the only tumor mass-related variable adversely affecting remission induction. Survival was longer in patients with low tumor burden and favorable DNA features. The availability of objective and quantitative pretreatment variables associated with both initial response and survival should permit a risk-based selection of patients for novel treatment approaches.

Bone Marrow↗
PubMed1984

Chlorotetracycline fluorescence is a quantitative measure of the free internal Ca2+ concentration achieved by active transport. In situ calibration and application to bovine cardiac sarcolemmal vesicles.

Chlorotetracycline (CTC) fluorescence is shown to be a competent and quantitative measure of the free internal calcium concentration, [Ca2+]i, obtained by ATP supported active uptake by bovine cardiac sarcolemmal (SL) vesicles. The fluorescence response of CTC to [Ca2+]i is calibrated by pre-equilibrating the vesicles with known Ca2+ concentrations and then diluting into a Ca2+-free medium containing CTC. The experiments show that CTC comes into equilibrium with the internal Ca2+ more rapidly than the latter can passively leak from the vesicles. The amplitude of the fluorescence increase is proportional to the Ca2+ concentration with which the vesicles are pre-equilibrated. This constitutes a calibration procedure for the use of CTC fluorescence as a quantitative measure of the free internal Ca2+ concentrations achieved in active transport. This method is applied to the determination of the average free Ca2+ concentrations achieved in ATP-energized uptake with sarcolemmal vesicles. Under optimal conditions an initial rate of 13 mM/min (37 nmol/mg/min) is observed. Uptake reaches a maximum corresponding to 70 mM (179 nmol/mg). Half-maximal values are obtained after 5 min of reaction. The mechanism of the CTC response to free internal Ca2+ concentration is discussed and is compared with measurements of vesicle-associated 45Ca2+.

Animals↗
PubMed1984

Susceptibility testing of filamentous fungi to amphotericin B by a rapid radiometric method.

A rapid, radiometric method was developed to determine the susceptibility of filamentous fungi to amphotericin B. The rapid, radiometric method depended on measurement of the inhibition of 14CO2 production in the presence of amphotericin B. Thirty isolates of filamentous fungi were tested by the rapid, radiometric method and a reference agar dilution method. There was 93% agreement between the two methods when an 80% or greater decrease in CO2 production was used to calculate the minimal inhibitory concentration with the rapid, radiometric method. Minimal inhibitory concentrations, based on 80% decrease of CO2 production, were achieved within 24 h of incubation with all of the fungi tested.

Amphotericin B↗
PubMed1983

Improved complete remission rates and survival for patients with large cell lymphoma treated with chemoimmunotherapy. A Southwest Oncology Group Study.

Between 1974 and 1977, 652 patients with non-Hodgkin's lymphoma without prior chemotherapy were randomized to 1 of 3 combination chemotherapy programs designed to induce complete remission (CR): COP-bleomycin (180 patients), CHOP-bleomycin (232 patients) or CHOP plus immunotherapy with Bacillus Calmette Guerin (BCG) (240 patients). With mature follow-up, the major effect of BCG immunotherapy was observed in patients with large cell lymphomas (diffuse or nodular "histiocytic") and not in other common lymphoma subtypes. CR rate for 65 patients with large cell lymphoma treated with CHOP-BCG was 68% compared to 48% in 61 patients treated with CHOP-bleomycin (P = 0.02) (two-tailed test) or 44% for 45 patients treated with COP-bleomycin (P = 0.02). CR duration for both CHOP-based regimens was similar and superior to that produced by COP-bleomycin (P = 0.03). Survival of patients with large cell lymphoma treated with CHOP-BCG was better than that observed with CHOP-bleomycin (P = 0.02) or COP-Bleomycin (P = 0.002). Although the explanation for the favorable effect of BCG remains unclear, further clinical trials to evaluate the combination of chemotherapy and other "biologic response modifiers" is warranted for patients with lymphoma.

Antineoplastic Agents↗
PubMed1983

The combined modality therapy of diffuse histology non-Hodgkin's lymphoma with cyclophosphamide, adriamycin, vincristine, prednisone (CHOP) and total body irradiation.

The combination of cyclophosphamide, adriamycin, vincristine, and prednisone (CHOP) alternating with total body irradiation (TBI) has been shown earlier to be effective therapy in patients with malignant lymphoma who have received prior chemotherapy and/or radiation therapy. A limited institutional pilot study was therefore done by the Southwest Oncology Group between October 1977, and November 1978 to test the benefit of this program in previously untreated persons with Stages 3 and 4 diffuse histology non-Hodgkin's lymphoma. Eleven evaluable patients with the following histologies were treated: 7 poorly differentiated, 2 with histiocytic, 1 with mixed lymphoma and 1 with well-differentiated morphology. CHOP was given in the following manner: cyclophosphamide 400 mg/M2 IV day 1, adriamycin 40 mg/M2 IV day 1, vincristine 2 mg IV day 1, and Prednisone 100 mg po daily X 5. Forty-five rad total body irradiation was delivered in three fractions on days 21, 23 and 25. Chemotherapy was repeated on day 42, etc., until four cycles of CHOP and three cycles TBI (135R) were delivered. Responses were seen in 8/11 patients (6 CR and 2 PR); 5 persons are currently alive and 6 are dead. Two of the living patients are alive with disease and the remainder are in unmaintained remission. Two persons died with no response and one died in complete remission of an unrelated illness. The median duration of remission is 15 months and the median survival for all patients is 48 months. The therapy was well tolerated with a mean nadir leukocyte count of 3,020 X 10(9)/microliters (range 1.2-5.5) and a mean nadir platelet count of 188 X 10(9)/microliters (range 016-270). As delivered, this program is capable of producing durable remissions and needs to be verified in a larger series of patients.

Adult↗
PubMed1983

Lobster muscle and synapse respond to cortisol, a vertebrate hormone.

Cortisol (0.28 mumol X L-1) applied to lobster (Homarus americanus) neuromuscular preparations produces a hyperpolarization in muscle fibers and an increase in amplitude of excitatory postsynaptic potentials. The effect appears to be surface-mediated, because of its rapid onset (within seconds). It is also Na+-K+ ATPase dependent, because ouabain blocks the effects. The effects are relatively short-lasting, and gradually subside within 15 min. The increase in excitatory postsynaptic potentials is attributed in part to increased quantal output of transmitter, and not to changes in muscle fiber membrane resistance. The effects of cortisol on neuromuscular transmission and membrane potential indicate that cortisol may have a physiological role in crustaceans.

Animals↗