Distribution of serum creatine kinase activity in young healthy persons

The normal distribution of serum creatine kinase (CK) was determined in 428 men (mean age = 21.5) and 540 women (mean age = 20.2). The bootstrap method was employed to obtain statistical parameters of CK reference range and correlations with physical activity habits, BMI, cigarette smoking and alcohol consumption. CK distribution was non-Gaussian and skewed toward the higher values; 18.9% of the men and 4.6% of the women had values above the upper reference limits defined for the commercial assay kit. The median 97.5 percentile value was 532 u/l for men and 248 u/l for women (95% confidence interval of 384-738 u/l and 184-340 u/l, respectively). A significant correlation was found only between CK and alcohol consumption in men. Myoglobin level in a representative group of subjects correlated well with CK activity for both genders. Our findings define the range of CK values in a healthy, young, heterogeneous population. We suggest that only CK levels above the determined 97.5 percentile should warrant further clinical investigation.

Bayesian variable selection method for censored survival data

A Bayesian variable selection method for censored data is proposed in this paper. Based on the sufficiency and asymptotic normality of the maximum partial likelihood estimator, we approximate the posterior distribution of the parameters in a proportional hazards model. We consider a parsimonious model as the full model with some covariates unobserved and replaced by their conditional expected values. A loss function based on the posterior expected estimation error of the log-risk for the proportional hazards model is used to select a parsimonious model. We derive computational expressions for this loss function for both continuous and binary covariates. This approach provides an extension of Lindley's (1968, Journal of the Royal Statistical Society, Series B 30, 31-66) variable selection criterion for the linear case. Data from a randomized clinical trial of patients with primary biliary cirrhosis of the liver (PBC) (Fleming and Harrington, 1991, Counting Processes and Survival Analysis) is used to illustrate the proposed method and a simulation study compares it with the backward elimination procedure.

Biomarker study of primary nonmetastatic versus metastatic invasive bladder cancer. National Cancer Institute Bladder Tumor Marker Network

A cohort of 109 patients with primary transitional cell carcinomas, stages T2-T3, grade 2 or higher, was identified and further divided into two groups based on lymphatic metastasis at the time of cystectomy (n = 57 cases) or absence of detectable metastatic disease over a minimum of 5 years of follow-up after cystectomy (n = 52). Blocks corresponding to the primary tumor lesions were sectioned and distributed to different laboratories to be analyzed. Immunohistochemistry on deparaffinized tissue sections was conducted for evaluation of p53 nuclear overexpression (monoclonal antibody PAb1801), assessment of proliferative index (Ki-67 antigen-monoclonal antibody MIB1), and microvascular counts (factor VIII-related antigen). DNA content/ploidy studies were performed on material obtained from thick sections. A double-blinded strategy was used for the evaluation of laboratory data versus clinical parameters. The cutoff value for p53 nuclear overexpression was > or =20% of tumor cells displaying nuclear staining. The median values for MIB1 (> or =18% of tumor nuclear cell staining) and microvascular counts (> or =40 microvessels/area screened) were used as cutoff points for these two variables. The assessment of DNA content was conducted by classifying cases as diploid, tetraploid, or aneuploid. Statistical analyses were performed using the Fisher's Exact Test (2-tailed). Results revealed that none of the markers studied had a statistically significant correlation with the end point of the study, i.e., the presence of lymph node metastatic disease, in the cohort of patients studied, although an obvious trend for p53 was noted. It is concluded that alterations of p53, Ki-67 proliferative index, microvascular counts, and ploidy are not strongly associated with lymph node status in patients affected with high-stage, high-grade bladder cancer.

Haptoglobin-related protein as a serum marker in malignant lymphoma

A novel serum 21 kDa haptoglobin-related protein (Hpr) was investigated in patients with malignant lymphoma, to evaluate its correlation with clinical and histologic features at presentation and its possible role as a tumor marker for patient outcome. One hundred fifty eight serum samples were taken from 88 patients with non-Hodgkin's lymphoma (n=58) and Hodgkin's disease (n=30) at presentation and in the course of follow-up. Sera from 61 healthy volunteers served as normal controls. Serum Hpr levels in the lymphoma patients (median 430x10 u/ml, range 0-4000x10 ) were significantly higher than in the control group (median 68x10 u/ml, range 0-180x10 )(p=0.0001). Higher median Hpr values were detected in patients with advanced disease (p=0.013), "B" symptoms (p=0.029) and in males (p=0.053). There was also a significant correlation between Hpr and erythrocyte sedimentation rate (p=0.028). Serial determinations showed a significant decrease of the initial Hpr values obtained after treatment in 41 patients, 38 of whom achieved complete remission. In the follow-up period additional Hpr measurements were taken from 17 patients. Three of them eventually relapsed, and showed increased Hpr levels at the time of relapse. Hpr levels remained low in 11 of 14 patients who maintained complete remission, and increased in three. In conclusion, serum Hpr is a new serum tumor marker of potential use in the clinical setting of lymphoma.

Large sample Bayesian inference on the parameters of the proportional hazard models

This paper considers large sample Bayesian analysis of the proportional hazards model when interest is in inference on the parameters and estimation of the log relative risk for specified covariate vectors rather than on prediction of the survival function. We use a normal prior distribution for the parameters and make inferences based on the derived posterior distribution. The suggested approach is much simpler than alternative Bayesian analyses previously suggested for the proportional hazards models. Using simulated data we compare estimates obtained from the Bayesian analysis with those obtained from the full proportional hazards model and the reduced model after backwards elimination. We show that under a wider range of assumptions, the Bayesian analysis provides reduced estimation errors and improved rejection of noise variables. Finally, we illustrate the methodology using data from a large study of prognostic markers in breast cancer.

Dexamethasone, etoposide, ifosfamide, and cisplatin as second-line therapy in patients with aggressive non-Hodgkin's lymphoma

BACKGROUND

This study analyzed the long term results of a combination of dexamethasone, etoposide, ifosfamide, and cisplatin (DVIP) used at the study center as standard second-line combination therapy in patients with aggressive non-Hodgkin's lymphoma (NHL) after prior exposure to doxorubicin.

METHODS

All drugs were given intravenously for 4 consecutive days. The maximum daily doses of etoposide, ifosfamide, and cisplatin were 75 mg/m2, 1200 mg/m2, and 20 mg/m2, respectively. The dexamethasone dose was 20 mg twice daily. Cycles were repeated every 3 weeks.

RESULTS

Fifty-six patients were included in the study. Partial response was noted in 18 patients (32%) and complete response (CR) in 18 patients (32%). Pretreatment factors that predicted CR were CR with prior therapy (CR in 17 of 34 in patients with a recurrence vs. 1 of 21 in patients with primary refractory NHL) and age (CR in 12 of 25 patients age < or = 65 years vs. 6 of 31 patients age > 65 years). Median time to treatment failure (TTF) and median survival were 11.5 months and 30 months, respectively, for patients with a CR and 3.5 months and 8 months, respectively, for all patients. Five patients (9%) remained disease free for > 24 months. By multivariate analysis, age was the only independent prognostic factor for TTF, whereas age, serum lactate dehydrogenase, and number of extranodal sites were independent predictors for survival. Myelosuppression (median granulocyte nadir and median platelet nadir of 350/mm3 and 77,000/mm3, respectively) was the major toxicity. There was one possible drug-related death associated with myelosuppression.

CONCLUSIONS

DVIP is a relatively safe salvage combination therapy in patients with aggressive NHL. Response to first-line therapy and age are the most important predictors for prognosis after the administration of DVIP. This regimen is highly active in patients with recurrent NHL, but relatively ineffective in patients with primary refractory NHL.

Confidence intervals for the generalized ROC criterion

Receiver operating characteristic (ROC) curves are frequently used to assess the usefulness of diagnostic markers. When several diagnostic markers are available, they can be combined by a best linear combination: that is, when the area under the ROC curve of this combination is maximized among all possible linear combinations. This maximal area is the generalized ROC criterion, which provides a measure of how effective the combination of the markers is. This criterion needs to be estimated from the data, and is usually evaluated against single markers. In the present paper, we provide confidence intervals for the generalized ROC criterion under the assumption of homogeneous covariance matrices, derive an approximation for the heterogeneous covariance matrices case, and evaluate the approximation via a simulation study. Finally, we present an illustrative example.

A simulation study of cross-validation for selecting an optimal cutpoint in univariate survival analysis

Continuous measurements are often dichotomized for classification of subjects. This paper evaluates two procedures for determining a best cutpoint for a continuous prognostic factor with right censored outcome data. One procedure selects the cutpoint that minimizes the significance level of a logrank test with comparison of the two groups defined by the cutpoint. This procedure adjusts the significance level for maximal selection. The other procedure uses a cross-validation approach. The latter easily extends to accommodate multiple other prognostic factors. We compare the methods in terms of statistical power and bias in estimation of the true relative risk associated with the prognostic factor. Both procedures produce approximately the correct type I error rate. Use of a maximally selected cutpoint without adjustment of the significance level, however, results in a substantially elevated type I error rate. The cross-validation procedure unbiasedly estimated the relative risk under the null hypothesis while the procedure based on the maximally selected test resulted in an upward bias. When the relative risk for the two groups defined by the covariate and true changepoint was small, the cross-validation procedure provided greater power than the maximally selected test. The cross-validation based estimate of relative risk was unbiased while the procedure based on the maximally selected test produced a biased estimate. As the true relative risk increased, the power of the maximally selected test was about 10 per cent greater than the power obtained using cross-validation. The maximally selected test overestimated the relative risk by about 10 per cent. The cross-validation procedure produced at most 5 per cent underestimation of the true relative risk. Finally, we report the effect of dichotomizing a continuous non-linear relationship between covariate and risk. We compare using a linear proportional hazard model to using models based on optimally selected cutpoints. Our simulation study indicates that we can have a substantial loss of statistical power when we use cutpoint models in cases where there is a continuous relationship between covariate and risk.

Dynamic treatment allocation adjusting for prognostic factors for more than two treatments

Methods of sequential allocation of one of K treatments to patients, while controlling for important prognostic factors, are developed and compared. We focus on methods that are based on optimality theory (Begg and Iglewicz, 1980, Biometrics 36, 81-90; Atkinson, 1982, Biometrika 69, 61-67), the permuted block procedure (Zelen, 1974, Journal of Chronic Diseases 27, 365-375), and the compromise method (Faraggi and Reiser, 1991, Communication in Statistics, Simulation and Computation 20, 243-254). These methods are extended to the K treatments case and are evaluated in terms of efficiency and balance. It is shown that each method achieved the best results in the criterion it was designed to optimize, i.e., within stratum balance for the permuted block allocation and efficiency for the allocations that are based on optimality theory, but did not do well with other criteria. The compromise method, on the other hand, has good overall properties in terms of both balance and efficiency.

The menstrual cycle and acute appendicitis

OBJECTIVE

To examine the influence of the menstrual cycle on the incidence and presentation of acute appendicitis.

DESIGN

Retrospective study.

SETTING

University hospital, Israel.

SUBJECTS

144 women of child bearing age operated on for suspected acute appendicitis and subdivided according to the menstrual phase during which they presented.

MAIN OUTCOME MEASURES

The final diagnoses, clinical presentation, and laboratory data.

RESULTS

There were no significant differences in the incidence of acute, gangrenous, or perforated appendicitis in patients operated on during the various phases of the menstrual cycle. During menstruation, however, a normal appendix not accompanied by other disease was found significantly more often (p = 0.04). Clinical presentation, physical findings, and laboratory results did not vary throughout the menstrual cycle except for the "classic shifting pain" which was significantly more common during the luteal phase.

CONCLUSIONS

Acute appendicitis occurs randomly during the various phases of the menstrual cycle. The incidence of operations for uninflamed appendixes may be higher during the menstrual phase. Significantly more negative laparotomies are done during the menstrual phase, which suggests the existence of a functional disorder that mimics acute appendicitis.

Brain Stem Auditory Evoked Potentials: Effects of Ovarian Steroids Correlated with Increased Incidence of Bell's Palsy in Pregnancy

To investigate the effect of ovarian steroids on the brain stem during changes of estrogen and progesterone blood levels, we recorded brain stem auditory evoked potentials with increased stimulus rates from 26 women treated for sterility by menotropins (Pergonal and Metrodin). These women were divided into three groups according to their estrogen and progesterone blood levels. The brain stem auditory evoked potential results revealed a significant delay of peak III only, with an increased stimulus rate in the group with the highest estrogen level. Estrogen may cause a brain stem synaptic impairment, presumably because of ischemic changes, and thus also may be responsible for a higher incidence of Bell's palsy during pregnancy.

Brain stem auditory evoked potentials: effects of ovarian steroids correlated with increased incidence of Bell's palsy in pregnancy

To investigate the effect of ovarian steroids on the brain stem during changes of estrogen and progesterone blood levels, we recorded brain stem auditory evoked potentials with increased stimulus rates from 26 women treated for sterility by menotropins (Pergonal and Metrodin). These women were divided into three groups according to their estrogen and progesterone blood levels. The brain stem auditory evoked potential results revealed a significant delay of peak III only, with an increased stimulus rate in the group with the highest estrogen level. Estrogen may cause a brain stem synaptic impairment, presumably because of ischemic changes, and thus also may be responsible for a higher incidence of Bell's palsy during pregnancy.

A neural network model for survival data

Neural networks have received considerable attention recently, mostly by non-statisticians. They are considered by many to be very promising tools for classification and prediction. In this paper we present an approach to modelling censored survival data using the input-output relationship associated with a simple feed-forward neural network as the basis for a non-linear proportional hazards model. This approach can be extended to other models used with censored survival data. The proportional hazards neural network parameters are estimated using the method of maximum likelihood. These maximum likelihood based models can be compared, using readily available techniques such as the likelihood ratio test and the Akaike criterion. The neural network models are illustrated using data on the survival of men with prostatic carcinoma. A method of interpreting the neural network predictions based on the factorial contrasts is presented.

Full dose CHOP chemotherapy in elderly patients with non-Hodgkin's lymphoma

Twenty-eight previously untreated elderly patients (median age 73 years, range 65-88) with aggressive non-Hodgkin's lymphoma were treated with full-dose CHOP chemotherapy between 1989 and 1992. The median of the average relative dose intensity (ARDI) was calculated for the initial cycles needed to achieve a maximal response or to determine progression of disease (1-6 cycles, median 4), as well as for the whole treatment course. For patients aged 65-74, both ARDIs were 0.89. A comparable group of 36 elderly patients who received reduced doses of CHOP from the start, served as a historical control. There was an increase of 11% and 29% in the ARDIs of the full-dose CHOP as compared with the reduced CHOP, in the initial cycles and for the whole treatment course respectively. Grade III-IV leukopenia was the main toxicity observed in 57% of the patients, and 7 patients were hospitalized for fever and leukopenia. There was no treatment-related death. It is concluded that CHOP chemotherapy without initial dose reduction is feasible in patients aged 65-74 years, resulting in high actual dose intensity with a reasonable degree of toxicity.

Discrimination techniques applied to the NCI in vitro anti-tumour drug screen: predicting biochemical mechanism of action

The National Cancer Institute currently tests approximately 400 compounds per week against a panel of human tumour cell lines in order to identify potential anti-cancer drugs. We describe several approaches, based on these in vitro data, to the problem of identifying the primary biochemical mechanism of action of a compound. Using linear and non-parametric discriminant procedures and cross-validation, we find that accurate identification of the mechanism of action is achieved for approximately 90 per cent of a diverse collection of 141 known compounds, representing six different mechanistic categories. We demonstrate that two-dimensional graphical displays of the compounds in terms of the initial three principal components (of the original data) result in suggestive visual clustering according to mechanism of action. Finally, we compare the classification accuracy of the statistical discrimination procedures with the accuracy obtained from a neural network approach and, for our example, we find that the results obtained from the various approaches are similar.

Is the vestibular system affected by middle ear effusion?

The association between middle ear effusion (MEE) and vestibular pathology is controversial. To investigate this point, 50 children with MEE scheduled for myringotomy and grommet, and 20 normal hearing children without MEE scheduled for adenotonsillectomy, underwent vestibular investigations by craniocorpography and rotatory chair, preoperatively and postoperatively. Most of the correlations, preoperative vs. postoperative, and study vs. control groups, were nonsignificant. Assuming that serous labyrinthitis is responsible for vestibular involvement in MEE, the lack of significant vestibular pathology in our study could probably be explained by the fact that no children with acute otitis media episodes or otalgia were included.

Comparison between self-hypnosis, masking and attentiveness for alleviation of chronic tinnitus

The efficacy of self-hypnosis (SH), masking (MA) and attentiveness to the patient's complaints (AT) in the alleviation of tinnitus was evaluated. Forty-five male patients close in age with chronic tinnitus related to acoustic trauma were assigned to three matched subgroups: SH, AT or MA. The therapeutic stimuli in the SH and MA sessions, recorded on audio cassettes, were given to the patients for use when needed. SH significantly reduced the tinnitus severity; AT partially relieved the tinnitus; MA did not have any significant effect.

Stage I-II low grade non-Hodgkin's lymphoma: prognostic factors and treatment results

48 patients with stage I-II low-grade non-Hodgkin's lymphoma were treated by radiation and/or chemotherapy between 1970 and 1986. The histologic types were diffuse lymphocytic well differentiated, eleven patients; nodular lymphocytic poorly differentiated, 28 patients; nodular mixed, nine patients. Complete remission was obtained in 45 patients (94%). Overall survival was 83% and 68% at five and ten years, respectively. Five and ten-year relapse-free survival of complete responders was 71% and 57%, respectively. Univariate analysis of potential prognosticators showed the following to significantly increase the survival rate: one or two sites of disease (p less than 0.01), stage I (p less than 0.02), age less than 65 years (p less than 0.02), complete excision of tumor mass (p less than 0.03), and the use of radiotherapy (p less than 0.02). The extent of radiotherapy field did not affect survival. Multivariate analysis by the stepwise proportional hazards model of Cox showed that the use of radiotherapy was the factor which significantly produced better survival figures (p less than 0.03). It is concluded that two thirds of stage I-II low-grade lymphoma patients are potentially curable; radiotherapy plays a major role in the management.

Cytosine arabinoside and cisplatin for advanced breast cancer. A phase II study of the Cancer and Leukemia Group B

Forty-four women with advanced breast cancer participated in a prospective clinical trial to evaluate the efficacy and toxicity of a regimen consisting of cytosine arabinoside and cisplatin. All patients had previously received chemotherapy. Three patients (7%) responded to therapy with response durations of 153, 160, and 441 days. The median time to disease progression and median survival time in all 44 patients were 2.3 and 5 months, respectively. This regimen had significant toxicity, with most patients experiencing severe or life-threatening hematologic, renal, or infectious complications. This regimen cannot be recommended for previously treated patients with advanced breast cancer.

Phase II study of echinomycin in patients with advanced breast cancer: a report of Cancer and Leukemia Group B protocol 8641

Twenty-five women with advanced histologically documented stage IV recurrent or inoperable breast cancer were enrolled on a phase II study of echinomycin administered at a dose of 1.2 mg/m2 intravenously over 30 minutes weekly for 4 weeks followed by a two week rest period. Seventy-six percent of patients had visceral dominant disease at study entry and all patients had previously received chemotherapy. One of 21 eligible patients had a partial response lasting 147 days. The median survival for this group of patients was 5.9 months and the median time to treatment failure was 1.7 months. Nausea and vomiting was the primary toxic effect and was severe or life-threatening in 43% of patients. Transient elevation of liver enzymes occurred in 30% of patients. Bone marrow suppression was not significant. Echinomycin as employed in this study did not demonstrate significant antitumor activity in previously treated patients with advanced breast cancer.

Twenty-four-hour blood pressure control with isradipine in mild essential hypertension

The hypotensive effect of isradipine was assessed in 26 male patients, aged 40 to 64 years, with hypertension. After withdrawal of previous antihypertensive treatment and a four-week placebo period, patients were randomized into a double-blind active-treatment period of eight weeks to receive either placebo or 1.25 to 2.5 mg isradipine twice daily. Twenty-four-hour ambulatory blood pressure was measured by Accutracker (Suntech, Oxford, England) after the placebo period and at the end of the active-treatment period. In the isradipine group n = 13), both systolic and diastolic blood pressure and number of blood pressure spikes decreased significantly (P less than .0001), whereas there was a significant increase of these variables in the placebo control group (n = 13). The results of this study indicate that, in these subjects, blood pressure control was achieved throughout the 24-h period by monotherapy with isradipine.

The efficacy of oral steroids in the treatment of persistent otitis media with effusion

One hundred thirty-six children with otitis media with effusion of at least 2 months' duration were investigated in a strict, double-blind, randomized prospective study to evaluate the efficacy of oral steroids in the treatment of this disease. The results of our study showed a significant complete and partial recovery from otitis media with effusion in the group treated by a combination of antibiotics (amoxicillin) and oral steroids (prednisone), compared with an amoxicillin-treated group and a placebo-treated group. We believe that this treatment mostly benefits children aged 4 to 10 years without oversized adenoids. The findings of our study imply that a combined course of antibiotics and oral steroids deserves its place as a routine conservative trial before surgery.

Survival of diffuse large cell lymphoma. A multivariate analysis including dose intensity variables

Ninety-five newly diagnosed patients with diffuse large cell lymphoma (DLCL) treated by cyclophosphamide (CTX), doxorubicin (ADM), vincristine (VCR), and prednisone (CHOP regimen) chemotherapy were evaluated for survival factors including dose intensity (DI). DI calculations were done for the initial cycles needed to achieve maximal response. The medians of the relative DI for CTX, ADM, and VCR were 0.9, 0.86, and 0.79, respectively. The median of the average relative DI (ARDI) was 0.83 (range, 0.28 to 1.14). The univariate analysis of potential prognostic variables showed that the following significantly decreased the survival rate: age older than 60 years (P = 0.0005), Stage III to IV (P = 0.02), male sex (P = 0.03), and all four DI variables (CTX, ADM, VCR, and ARDI) less than the median (P = 0.01 to 0.0001). A multivariate analysis by the stepwise proportional hazards model of Cox indicated that the factors predicting a poor prognosis were ARDI less than the median (P = 0.0003) and age older than 60 years (P = 0.02). A multivariate survival analysis of those who achieved complete remission showed ARDI less than the median (P = 0.0003), CTX less than the median (P = 0.02), and Stage III to IV (P = 0.02) to be the most negative factors regarding survival. In conclusion, a high DI in the initial cycles of CHOP chemotherapy for DLCL has a significant positive impact on survival.

Survival of diffuse large cell lymphoma. A multivariate analysis including dose intensity variables

Ninety-five newly diagnosed patients with diffuse large cell lymphoma (DLCL) treated by cyclophosphamide (CTX), doxorubicin (ADM), vincristine (VCR), and prednisone (CHOP regimen) chemotherapy were evaluated for survival factors including dose intensity (DI). DI calculations were done for the initial cycles needed to achieve maximal response. The medians of the relative DI for CTX, ADM, and VCR were 0.9, 0.86, and 0.79, respectively. The median of the average relative DI (ARDI) was 0.83 (range, 0.28 to 1.14). The univariate analysis of potential prognostic variables showed that the following significantly decreased the survival rate: age older than 60 years (P = 0.0005), Stage III to IV (P = 0.02), male sex (P = 0.03), and all four DI variables (CTX, ADM, VCR, and ARDI) less than the median (P = 0.01 to 0.0001). A multivariate analysis by the stepwise proportional hazards model of Cox indicated that the factors predicting a poor prognosis were ARDI less than the median (P = 0.0003) and age older than 60 years (P = 0.02). A multivariate survival analysis of those who achieved complete remission showed ARDI less than the median (P = 0.0003), CTX less than the median (P = 0.02), and Stage III to IV (P = 0.02) to be the most negative factors regarding survival. In conclusion, a high DI in the initial cycles of CHOP chemotherapy for DLCL has a significant positive impact on survival.

Phase II trial of continuous drug infusions in advanced ovarian carcinoma: acivicin versus vinblastine

Sixty-six women with advanced ovarian carcinoma of coelomic epithelial origin were randomly assigned to one of two intravenous single-agent infusion treatment regimens, either acivicin (60 mg/m2/course, administered as a 72-hr infusion) or vinblastine (7.5 mg/m2/course, administered as a 120-hr infusion) every three weeks. All had progressive disease after one to three prior chemotherapeutic regimens. Of 62 patients who were evaluable for response, survival and toxicity, there was one partial response (2%) produced by vinblastine. Median survival was 13 weeks on either treatment arm. Three patients (10%) on the acivicin arm experienced life-threatening myelosuppression. Severe toxicities resulting from this treatment included myelosuppression (26%), neurotoxicity (16%), mucositis (3%) and vomiting (6%). Vinblastine was associated with one lethal pneumonia and five cases of life-threatening myelosuppression (16%); severe toxicities included myelosuppression (58%), genitourinary toxicity (6%), infection (3%), and edema (3%). Neither regimen produces useful clinical results in patients who have relapsed after prior chemotherapy for ovarian carcinoma.

Strain and site dependence of polyploidization of cultured rat smooth muscle

Smooth muscle cell (SMC) growth may play an important role in the pathogenesis of vascular diseases such as atherosclerosis and hypertension. Recent studies have demonstrated that, under different growth stimuli in vivo, SMC may respond by proliferation of diploid cells, polyploidization to the tetraploid (or even octaploid) state, or both. In this study, we used flow cytometry to evaluate the intrinsic tendencies of aortic SMC and nonarterial cells from rats of different strains, ages, and blood pressures to polyploidize in response to in vitro growth stimulation. Significant strain-related differences in polyploidization of aortic SMC were found (P less than 0.001): highest in WKY (normotensive inbred rat related to SHR), intermediate in SHR (genetically hypertensive rat), and lowest in Sprague-Dawley and Fischer (normotensive outbred and inbred rats). Animal age had less or no effect on the degree of polyploidization. Nonarterial cells (venous SMC and lung cells) from WKY and SHR remained essentially diploid, suggesting tissue specificity of in vitro polyploidization. Studies of the growth kinetics of uncloned and clonal populations of aortic SMC revealed decreased proliferation as the ploidy increased in WKY, SHR, and Sprague-Dawley. These findings suggest that genetic strain factors as well as cell type/site of origin significantly influence in vitro polyploidization, whereas animal age and blood pressure do not. The findings also emphasize the need to consider ploidy changes when evaluating in vitro SMC growth kinetics. Further studies will improve understanding of SMC growth regulation and the functional significance of vascular polyploidy.