Baccatin III induces assembly of purified tubulin into long microtubules.

Baccatin III is widely considered to be an inactive derivative of Taxol. We have reexamined its effect on in vitro assembly of tubulin under a variety of conditions. We found baccatin III to be active in all circumstances in which Taxol is active: it assembled GTP-tubulin, GDP-tubulin, and microtubule protein into normal microtubules and stabilized these polymers against cold-induced disassembly. The effect of baccatin III on in vitro microtubule assembly was quantitatively assessed through determination of critical concentrations, which can be used to obtain the apparent equilibrium constants for the addition of tubulin subunits to growing microtubules. The apparent equilibrium constants for the growth reaction for baccatin III-induced GTP-tubulin and GDP-tubulin assembly measured at 37 degrees C were 4.2-4.6-fold less than those measured for Taxol-induced GTP-tubulin and GDP-tubulin assembly. These data indicate that the entire Taxol side chain contributes only about -1 kcal/mol to the apparent standard free energy of microtubule growth at 37 degrees C regardless of the nature of the E site nucleotide. These data also support the idea that the majority of the interactions between Taxol and tubulin that affect this equilibrium occur between the baccatin portion of the molecule and the binding site. We have also observed a structural difference in microtubules formed using baccatin III and Taxol. Baccatin III-induced microtubules were routinely much longer than those assembled by Taxol, even when very high concentrations of baccatin III were employed. One interpretation of these data is that baccatin III and Taxol differ in their abilities to nucleate GTP-tubulin. This difference in activity may have bearing on the large disparity in cytotoxicity of the two molecules.

Computerized realistic simulation: a teaching module for crisis management in radiology.

OBJECTIVE: Computerized realistic simulation technology has been used as a training tool in fields such as aviation and military training and in the nuclear power industry. More recently, it has been adapted for use in anesthesia crisis resource management. We describe the effectiveness of a simulation program like that used by anesthesiology departments that we developed to teach radiologists the principles of crisis management. MATERIALS AND METHODS: A mock CT scanner and patient simulator were used to simulate the environment in which radiologists encounter crises. Twenty-four residents attended the training program, four at each half-day session. Two responded to and two observed an initial crisis, after which they attended a lecture and watched a videotape review. The second pair then participated in a different crisis scenario. The scenario order was randomized. All scenarios were videotaped and randomly reviewed by two physicians not involved with the course. The following behavioral qualities of the participating residents were evaluated using a five-point scale, ranging from poor (1) to excellent (5): global assessment, communication skills, use of support personnel, use of resources, and role clarity. Residents then rated the course on a five-point scale using the following criteria: overall course usefulness, attainment of course goals, realism of scenarios, quality of lecture, and quality of videotape review. RESULTS: The trainees who had attended the lecture and watched the videotape review before participating in a scenario consistently scored higher than those who had not in the following areas (score after training/score before training): global assessment, 4.08/2.50; communication skills, 4.09/2.67; use of support personnel, 4.17/3.00; use of resources, 4.00/2.92; and role clarity, 4.17/2.67. Moreover, the participants gave the course the following average ratings: overall usefulness, 4.93; attainment of course goals, 4.78; realism of scenarios, 4.63; quality of lecture, 4.63; and quality of videotape review, 4.85. CONCLUSION: Although the critical assessment of a teaching method is difficult and subjective by nature, the improvement in behavioral performance scores suggests that simulation technology effectively conveyed the principles of crisis management. The course ratings show that the program was well accepted by participants.

No evidence of malonyldialdehyde formation during reoxygenation injury in vitamin E-deficient rat heart.

Vitamin E is an endogenous antioxidant and is known to afford protection against lipid peroxidation. If lipid peroxidation was an important factor in the pathogenesis of reoxygenation injury in heart, then both the extent of lipid peroxidation and cell injury would be expected to be exacerbated in vitamin E-deficient hearts. To study reoxygenation injury in the present experiments, rat hearts were perfused in the Langendorff mode with a modified Krebs-Henseleit buffer under anoxic conditions for 60 min before resuming normoxic perfusion for 20 min. Creatine phosphokinase (CPK) activity and malonyldialdehyde (MDA), a product of lipid peroxidation, were assayed in the perfusate effluent from hearts during reoxygenation injury. Also, myocardial MDA and vitamin E contents were measured in extracts of freeze-clamped heart tissue obtained immediately before and 2 min after reoxygenation. Experiments were performed on hearts from groups of weanling rats fed either a vitamin E-deficient or vitamin E-supplemented diet (50 I.U. vitamin E/kg) for 5 to 6 weeks. After 5 weeks, the myocardial vitamin-E content was 103.8 +/- 5.3 (n = 5) and 11.5 +/- 1.6 (n = 4) ng/mg protein (mean +/- SEM) in the vitamin E-supplemented and vitamin E-deficient groups respectively. Perfused hearts from both dietary groups showed a peak of enzyme release 2 to 3 min after the reintroduction of oxygen, and enzyme release from vitamin E-deficient hearts was two-fold greater than enzyme release from vitamin E-supplemented hearts.(ABSTRACT TRUNCATED AT 250 WORDS)

Cardiopulmonary resuscitation: qualifications and performance of housestaff and trained internists.

Eighty-six physicians in the Internal Medicine Department of the Mount Sinai Medical Center were evaluated on attitudes and knowledge of basic and advanced cardiac life support. Information was gathered over a one-week period using a self-administered questionnaire. Eighteen (21%) of the respondents did not know of the availability of basic and advanced cardiac life support courses at this institution. Of the physicians who had never taken either course, 8 (25%) stated it was because it was not offered at a convenient time or place. All housestaff officers were noted to have completed both courses, a percentage much higher than that of the trained internists (p less than .0001). Previous formal training in cardiac life support was found to be associated with a higher level of confidence in the ability to administer cardiac lifesaving techniques (p less than .0001) and a higher overall knowledge score (p = .003). We determined that the housestaff officers in internal medicine were the physicians most qualified to perform resuscitation efforts because of their completion of life support courses, their confidence in administering these techniques, and their greater overall knowledge. Wider publicity on the availability of cardiac life support courses, more convenient scheduling of such courses, and mandatory certification in basic life support for all physicians, with additional certification in advanced cardiac life support for physicians with extensive ward responsibility, are needed.

Transfusion history, T cell subsets and natural killer cytotoxicity in patients with colorectal cancer.

Blood transfusions are associated with clinical phenomena which are attributable to immune suppression. Since suppression of immune function is associated with a high risk of spontaneous malignancies, we studied T cell subsets and natural killer (NK) cytotoxicity in colorectal cancer patients and correlated the results with patients' transfusion histories. Twelve percent (14) of the 115 patients had been transfused an average of 19 years previously. Recipients of blood transfusions had low levels of peripheral lymphocytes (p = 0.191), T cells (p = 0.015), helper cells (p = 0.016) and suppressor cells (p = 0.2651) compared to previously untransfused patients. NK cytotoxicity was also significantly reduced in transfusion recipients although NK cell numbers were comparable in both groups. These results support previous studies indicating that blood transfusions cause lifelong immune modulation in the recipient. Since blood transfusions have numerous beneficial effects and immune modulation is often beneficial, longitudinal studies are necessary to define the lifetime risks and benefits.

The prognostic significance of natural killer cytotoxicity in patients with colorectal cancer.

We evaluate the prognostic significance of preoperative natural killer (NK) cytotoxicity for K562 cells and its relationship to other prognostic factors in 102 patients with colorectal cancer who underwent curative resections between February 1984 and February 1985. The 18 patients who had recurrences within two years of surgery had significantly higher numbers of preoperative peripheral blood suppressor/cytotoxic and NK cells and significantly lower preoperative NK cytotoxicity than disease-free patients. Low preoperative NK cytotoxicity was predictive of recurrence independent of age, sex, hematocrit, procedure, blood loss, duration of surgery, Dukes' stage, specimen length, tumor size, tumor differentiation, and post-operative therapy. Low levels of in vitro NK-cell cytotoxicity may identify a subgroup of patients at high risk for recurrence.

Perioperative blood transfusion associated with infectious complications after colorectal cancer operations.

We prospectively studied 168 consecutive patients with colorectal cancer to identify perioperative determinants of infectious complications. All patients received preoperative bowel preparation with laxatives, enemas, oral neomycin and erythromycin base, and intravenous cefazolin. Age, sex, admission hematocrit value, operative procedure, specimen length, duration of operation, blood loss, transfusions, tumor size, tumor differentiation, nodal status, and Dukes' stage were evaluated in relation to infectious complications using multivariate analysis. Infectious complications developed in 24 of the 168 patients in the study (14 percent) and these accounted for the four deaths. Blood transfusion (p = 0.0100) and admission hematocrit value (p = 0.0191) were significantly related to postoperative infectious complications. Low admission hematocrit values appeared to protect patients from infectious complications. Patients who had postoperative infectious complications received 2.14 +/- 2.75 units of blood compared with 0.82 +/- 1.37 units in patients without infectious complications (p = 0.0005). Although blood transfusion was associated with high operative blood loss, prolonged procedures, and large specimens (p less than 0.005), none of these factors was significantly associated with infectious complications (p greater than 0.10). Blood transfusion is immunosuppressive in other clinical situations and may be a more significant factor affecting postoperative immune function and susceptibility to infectious complications than previously recognized.

Unnecessary blood transfusions in elective colorectal cancer surgery.

In this 3-year study, we analyzed the transfusion pattern of 288 patients undergoing potentially curative resection of colorectal cancer to determine the magnitude and causes of unnecessary blood transfusions. Transfusions were considered unnecessary if the preoperative hematocrit exceeded 36 percent or the discharge hematocrit exceeded 33 percent. Twenty-five percent of the units of blood administered were unnecessary by these criteria. Excessive intraoperative transfusion (67 patients) and the practice of administering blood in pairs of units (33 patients) without reevaluating the hematocrit between successive units accounted for 90 percent of unnecessary transfusions. This study indicated that determination of the hematocrit immediately before administration of each unit of blood will reduce blood consumption of elective colon resections by 25 percent.