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Biomedical subjects

D R White

Publications and source records attributed to D R White.

At least 55 records · Page 3Linked to original sources
PubMed1989

Relationship between calcium, cyclic AMP, ATP, and intracellular pH and the capacity of hamster spermatozoa to express hyperactivated motility.

Capacitation of hamster caudal spermatozoa at a density of 1 x 10(6)/ml is associated with a progressive rise in cAMP levels that precedes the onset of hyperactivated motility. This increase is not expressed by caput spermatozoa incubated under identical conditions. Both the incidence of hyperactivation and the rise in cAMP levels are severely attenuated in the absence of exogenous calcium. Neither factor is restored to control levels by the addition of the phosphodiesterase inhibitor IBMX, although in the presence of exogenous calcium, this reagent increased cAMP levels, stimulated percentage motility and advanced the appearance of hyperactivation. Treatment of spermatozoa at a density of 1 x 10(6)/ml with the calmodulin antagonist, calmidazolium (CZ), caused severe disruption of sperm motility and abolished hyperactivation, while causing only a slight reduction in cAMP content. Addition of IBMX in the presence of CZ elevated cAMP content to levels higher than normally observed during capacitation but did not restore either coordinated or hyperactivated motility. To determine both the mechanisms responsible for this elevation of cAMP content and the changes that occur during epididymal maturation to facilitate the expression of this increase, the free cytosolic calcium concentration, ATP levels, and intracellular pH of caput and caudal cells were compared. The calcium content of caudal spermatozoa rose significantly at a time when cAMP levels were increasing, while ATP content and intracellular pH fell. However, the inability of caput spermatozoa to express a rise in cAMP content was not due to deficiencies in any of these factors. These results indicate a positive role for the cAMP rise in the expression of hyperactivated motility and that the fundamental control mechanism governing both these events may be the influx of calcium that accompanies capacitation in this species.

Adenosine Triphosphate↗
PubMed1989

Phase I study of vincristine and escalating doses of etoposide.

A phase I trial of vincristine and etoposide was designed following the identification of a potentially synergistic antitumor effect in a murine model. The dose of vincristine was fixed (0.5 mg daily for 3 days). Etoposide was given at 1 of 3 total dose levels (250, 500, or 750 mg/m2) per treatment. Each dose was given in 3 equal fractions and each fraction was given daily for 3 days, i.e., 83.3 mg/m2/d x 3d, 166.7 mg/m2/d x 3d, or 250 mg/m2/d x 3d. A total of 31 patients were entered into study including 10, 18, and 3 patients treated at the 250, 500, and 750 mg/m2 dose levels, respectively. Dose-limiting toxicity occurred at the 750 mg/m2 level, in which Grade 4 myelosuppression developed in all of the patients. Life-threatening gram negative sepsis occurred in two of these patients and both required platelet transfusions. Grade 3-4 WBC toxicity was observed in 9 of 16 (56%) evaluable patients treated at the 500 mg/m2 level, but reversal of toxicity was generally rapid with repeat courses given at 3 week intervals in most patients. Non-hematologic toxicity was negligible. Objective responses were observed in 2 of 4 patients with Hodgkin's disease. The starting dose of etoposide recommended for phase II trials of this agent in combination with vincristine is 500 mg/m2; dose escalation may be possible in some patients.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1989

Influence of epididymal maturation on cyclic AMP levels in hamster spermatozoa.

Whilst in their native epididymal fluid, sperm from the caput epididymis of the rat and hamster contain significantly (P less than 0.01) greater amounts of cAMP than do sperm from the cauda epididymis. The cAMP levels in both cell types from these species underwent a rapid increase concomitant with dilution to a density of 20 x 10(6)/ml. Further analyses in the hamster indicated that this increase was calcium-dependent, and could be enhanced by treatment with the calmodulin antagonist, calmidazolium. Dilution of hamster sperm to a concentration of 1 x 10(6)/ml was not associated with a rapid rise in cAMP levels. This effect was shown to be due to the dilution of a component in epididymal plasma. When incubated at this lower density, the cAMP content of hamster caput sperm remained low over a 3 h period, whilst similarly treated caudal sperm exhibited a progressive rise in cAMP levels. Thus, in contrast to other species, cAMP does not appear to play a pivotal role in acquisition of the capacity for movement during epididymal maturation in the rat and hamster. However, this nucleotide may be involved in the post-ejaculatory modifications of motility which accompany the terminal stages of capacitation.

Animals↗
PubMed1989

GR 38032F (GR-C507/75): a novel compound effective in the prevention of acute cisplatin-induced emesis.

We evaluated, in a multi-center trial, the safety and efficacy of GR 38032F (GR-C507/75), a novel and selective serotonin antagonist, in preventing acute emesis in chemotherapy-naive patients receiving treatment with regimens containing high-dose cisplatin (greater than or equal to 100 mg/m2). Eighty-five patients were randomized to receive GR 38032F, 0.18 mg/kg, either every six or every eight hours for three doses, beginning 30 minutes before cisplatin. Patients were evaluated for emetic episodes (vomiting or retching) over a 24-hour period following cisplatin. All patients were evaluable for toxicity and 83 were evaluable for efficacy. The overall antiemetic response rate was 75% (55% complete response [CR], 20% major response). No difference in antiemetic control between the two administration schedules was noted. Patients with histories of heavy ethanol use had significantly better antiemetic control (74% CR) than modest or non-drinkers (33% CR). Toxicity of GR 38032F was modest and independent of administration schedule. The most common adverse events included mild hepatic transaminase elevations, self-limited diarrhea, dry mouth, headache, and mild sedation. Our data indicate that GR 38032F is a safe and effective agent in the control of acute cisplatin-induced nausea and vomiting. Additional trials exploring dosing, schedule, and comparison to standard antiemetic agents are indicated.

Acute Disease↗
PubMed1989

Chemoinfusion of the hepatic artery for metastases to the liver.

During a five year period, 69 patients were treated for carcinoma of the liver (seven primary tumors and 62 metastatic tumors) with 5-fluorodeoxyuridine (5-FUDR) administered through a hepatic artery (n = 62) or portal vein (n = 3) implantable infusion pump. Ten patients proved to have previously unsuspected extrahepatic nodal metastases at laparotomy for pump insertion. 5-FUDR was given in 14 day cycles for three months. At the end of that period and at three month intervals thereafter (mean follow-up time of 18 months, a range of one to 60 months), patients were evaluated with roentgenograms of the chest, liver function tests, carcinoembryonic antigen levels, radionuclide scans and computed tomography. Thirty-five patients had a partial response, nine had stabilization of the disease and 25 had progression of the disease (five during therapy, who were given mitomycin C). Median regression was 6.8 months (a range of three to 18 months). Six of the 35 partial responders, three of the nine patients with stabilization and ten of the 25 patients with progression had extrahepatic visceral disease. Survival time averaged 18.4 months (a range of five to 60 months) for the partial responders, 12.6 months (a range of two to 40 months) for patients with stabilization and seven months (a range of one to 17 months) for those with progression of the disease.

Adult↗
PubMed1989

Low-dose ara-C therapy for acute myelogenous leukemia in elderly patients.

Forty-four evaluable patients with untreated acute myelogenous leukemia received twice-daily subcutaneous injections of low-dose ara-C (10 mg/m2) for less than or equal to 42 days. The median age was 72 years (range 53-87); 42 of 44 patients were greater than or equal to age 60. Ten patients (23%) had complete responses with a median duration of 9.9 months. Median survival was 3 months (range 0.6-31.2+) for all patients, and 19.5 (range 7.9-31.2+) for patients who attained complete responses. Cytoreduction occurred slowly with low-dose ara-C and five of ten patients who achieved complete remission did not develop marrow aplasia. Toxicity was predominantly related to infections associated with granulocytopenia. Nonhematologic toxicity was limited. Low-dose ara-C as used in this trial results in a complete response rate and a duration of response similar to those achieved with other treatments in elderly patients, but with reduced toxicity.

Aged↗
PubMed1988

Amelioration of vincristine neurotoxicity by glutamic acid.

Neurotoxicity is the principal limiting side effect of the widely used antitumor agent, vincristine. Following evaluation of glutamic acid as a potential modifier of vincristine toxicity in preclinical studies in mice and a preliminary clinical trial, a prospective, double-blind, placebo-controlled, randomized trial was conducted by the Piedmont Oncology Association. Of 87 patients entered into the study, 84 were evaluable, including 42 patients who were randomly assigned to receive vincristine 1.0 mg/m2 weekly for six doses and 42 patients who were assigned to receive glutamic acid 500 mg orally three times daily plus vincristine. The following neurotoxic signs and symptoms were evaluated before each dose of vincristine: reflex changes, paresthesias, constipation, strength, and mental changes. Loss of the Achilles tendon reflex, an objective parameter, was noted in 19 percent of patients receiving glutamic acid and 42 percent of control subjects (p = 0.03). Development of moderate to severe paresthesias, a subjective parameter, occurred in 19 percent of the glutamic acid group and 36 percent of the placebo group (p = 0.09). Overall moderate neurotoxicity (6 units or more), determined by adding the grade of each neurotoxic parameter for the weekly clinic visit in which maximum neurotoxicity occurred, was observed in 21 percent of patients receiving glutamic acid and 43 percent of those in the control group (p = 0.04). Hematologic and gastrointestinal side effects occurred with similar frequency in the two groups. The administration of glutamic acid has decreased vincristine-induced neurotoxicity without any attendant side effects.

Adult↗
PubMed1988

Phase II trial of high-dose cytosine arabinoside and cisplatin in recurrent squamous carcinoma of the head and neck. A Piedmont Oncology Association Study.

Fifteen patients with recurrent squamous carcinoma of the head and neck received high-dose cytosine arabinoside (ara-C) (3 g/m2) and cisplatin (100 mg/m2) every 3 weeks in an attempt to explore the dose-dependent synergy between these two agents. A partial response was attained in one patient; there were no complete responses. The major toxicity was myelosuppression. With the current schedule, high-dose ara-C failed to improve the response rate achieved with cisplatin alone.

Adult↗
PubMed1988

The effects of adult human tissue composition on the dosimetry of photons and electrons.

A reassessment of the composition of several types of adult human tissues has been completed. Principal findings relating to the compositions of 30 selected tissues will be discussed and comparisons with previously reported data will be highlighted. The effects of tissue composition on the dosimetry of photons and electrons are evaluated by considering attenuation and energy absorption coefficients for photons and the stopping and scattering powers of electrons over the energy interval 0.01-50 MeV. Calculated results for the tissues compared to pure water are presented.

Adult↗
PubMed1988

Does mother know best? Maternal assessment of relative fetal size in utero.

The accuracy of pregnant womens' impressions of the size of their babies in utero relative to their previous babies has been assessed in 140 parous women. The women who thought their babies would be bigger gave birth to babies weighing a mean of 0.30 kg more than their previous babies (P less than 0.01) and the women who thought their babies would be smaller were delivered of babies weighing a mean of 0.22 kg less than their previous babies (P less than 0.01).

Birth Weight↗
PubMed1987

Phase I study of high-dose cytosine arabinoside and etoposide in patients with advanced malignancies.

Cytosine arabinoside (ara-C) and etoposide (VP-16) display synergy in the laboratory. Twenty-six patients participated in a phase I study of high-dose ara-C in combination with VP-16. The dose of VP-16 was held constant at 50 mg/m2 as an intermittent infusion over 33 h; escalating doses of ara-C were given as infusions during hours 9-12 and 21-24. Myelosuppression was the dose-limiting toxicity and occurred with doses considerably less than those expected from studies of the two drugs as single agents. The suggested initial doses for phase II trials with this schedule are 750 mg/m2 X 2 doses of ara-C and 50 mg/m2 of VP-16. Nonhematologic toxicity was minimal; therefore, further dose escalation is feasible in patients in whom myelosuppression is acceptable.

Adult↗
PubMed1987

Treatment of advanced colorectal carcinoma with actinomycin D, vincristine, methyl-CCNU, and methotrexate.

Twenty patients with advanced colorectal carcinoma were treated with combination chemotherapy consisting of actinomycin D, vincristine, methyl-CCNU, and methotrexate. Fourteen patients had received prior chemotherapy with 5-fluorouracil (5-FU). No complete responses and only one partial response were observed for an overall response rate of 5%. The combination of actinomycin D, vincristine, methyl-CCNU, and methotrexate at the doses and schedule used was of no value in the treatment of patients with metastatic colorectal carcinoma.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1987

Antiemetic therapy in patients treated with high-dose cytosine arabinoside.

The antiemetic efficacy of metoclopramide (MCP) was evaluated in 33 consecutive patients treated with high-dose cytosine arabinoside (HiDAC), greater than or equal to 3 g/m2, a highly emetogenic agent increasingly used in patients with hematologic malignancies for which no previous formal antiemetic trials have been reported. Administration of MCP in conjunction with prophylactic diphenhydramine resulted in major antiemetic responses (0-2 episodes of emesis in the 24 h after therapy) in 23 of 33 (70%) patients. The addition of lorazepam (LZP) to MCP resulted in major antiemetic response in 7 or 8 (88%) patients who failed to respond to MCP alone. Major side effects were extrapyramidal reactions (5%) and moderate diarrhea (18%). MCP alone or in conjunction with LZP is effective antiemetic therapy in patients treated with HiDAC.

Adolescent↗
PubMed1987

Average soft-tissue and bone models for use in radiation dosimetry.

Average tissue compositions have been derived for seven groups of soft tissues found in "Reference Man". The analyses took into account some 40 soft tissues comprising the adult human. Different groups of soft tissues were selected to provide average tissue compositions of practical value in radiation dosimetry. In addition, as more reliable skeletal tissue data are now available, an updated tabulation is given of average bone formulations. Elemental compositions and mass and electron densities are tabulated for all of the derived systems.

Bone and Bones↗
PubMed1987

Vinblastine infusion in non-Hodgkin's lymphomas: lack of total cross-resistance with vincristine.

Historically, vinblastine given by intravenous bolus injection has not been an effective treatment for non-Hodgkin's lymphomas; vincristine has displayed greater activity. Also, vinblastine has generally been considered to be cross-resistant with vincristine in such patients. In an attempt to overcome these obstacles, a protracted infusion of vinblastine was administered (0.5-1.5 mg/m2 per day for 5 days) and repeated every 3 weeks. Partial responses were observed in 4 of 29 (14%) patients with a variety of non-Hodgkin's lymphoma lasting 2.4, 2.4, 5.5, and 9.0 months. Just prior to treatment the responding patients had received and eventually become refractory to vincristine. These data show a lack of total cross-resistance between vinblastine and vincristine which might have important therapeutic implications in this disease.

Adult↗
PubMed1986

Clinical trial of folinic acid to reduce vincristine neurotoxicity.

In a murine model system, folinic acid demonstrated host-protective properties during administration of repetitive and lethal doses of vincristine (VCR). Subsequently, folinic acid was evaluated in patients receiving VCR during an adjuvant chemotherapy program for stage II carcinoma of the breast. The toxicities, cumulative VCR dosage, and percentage of ideal dosage observed in 18 patients receiving folinic acid have been compared with those observed in 70 patients who previously received VCR without folinic acid in the same chemotherapy program. All patients ideally were intended to receive VCR 1.0 mg/m2 weekly for 6 weeks, with dose modification for neurotoxicity. Treatment patients received folinic acid 800 mg PO daily in three divided doses during the 6-week course. The degree of neurotoxic manifestations of VCR was similar in the treatment and comparison patients. Absent to mild neurotoxicity was observed in approximately 70% of patients in both groups; moderate or greater neurotoxicity occurred in about 30% of patients in both groups. Full dosage (6.0 mg/m2) was attained in 7 (39%) treatment patients and 17 (24%) comparison patients (P = 0.21). The mean percentage of the ideal dosage of VCR was 73.7 +/- 28.7 in patients receiving folinic acid and 76.1 +/- 20.5 in those given only VCR (P = 0.69). Hematologic toxicities were similar in both groups, but nausea occurred more frequently in the folinic acid group. Folinic acid in this dose and schedule afforded no protection from the neurotoxic side effects of VCR.

Adult↗
PubMed1986

Moderate-dose vincristine infusion in refractory breast cancer.

Continuous infusion of vincristine at the maximally tolerated infusion dosage of 0.5 mg/m2/day for 5 days has been investigated in 15 patients with refractory breast cancer. Infusion courses were repeated every 3 weeks in the absence of disease progression or prohibitive toxicity. Progressive disease was observed in 14 patients. A partial response lasting 2 months occurred in a patient with pulmonary and skin metastases who had previously received vincristine by bolus injection. Toxicity consisted primarily of mild neurotoxicity of similar degree to that expected with bolus injection. Thrombocytopenia occurred, but was uncommon. The cumulative response rate at this dosage level (2/16, 13%) in our phase I-II trials indicates very limited clinical activity of vincristine infusion in advanced, refractory metastatic breast cancer.

Adult↗