Alkaline pH and internal calcium increase Na+ and K+ effluxes in LK sheep red blood cells in Cl--free solutions

We examined the effects of pH, internal ionized Ca (Ca2+i), cellular ATP, external divalent cations and quinine on Cl-independent ouabain-resistant K+ efflux in volume-clamped sheep red blood cells (SRBCs) of normal high (HK) and low (LK) intracellular K+ phenotypes. In LK SRBCs the K+ efflux was higher at pH 9.0 (350%) than at pHs 7. 4 and 6.5, and was inhibited by external divalent cations, quinine, and cellular ATP depletion. The above findings suggest that the increased K+ efflux at alkaline pH is due to the opening of ion channels or specific transporters in the cell membrane. In addition, K+ efflux was activated (100%) when Ca2+i was increased (+A23187, +Ca2+o) into the microm range. However, in comparison to human red blood cells, the Ca2+i-induced increase in K+ efflux in LK SRBCs was fourfold smaller and insensitive to quinine and charybdotoxin. The Na+ efflux was also higher at pH 9.0 than at pH 7.4, and activated (about 40%) by increasing Ca2+i. In contrast, in HK SRBCs the K+ efflux at pH 9.0 was neither inhibited by quinine nor activated by Ca2+i. These studies suggest the presence in LK SRBCs, of at least two pathways for Cl--independent K+ and Na+ transport, of which one is unmasked by alkalinization, and the other by a rise in Ca2+i.

Exploring the relationship between inpatient facility and physician services

OBJECTIVES

Medicare hospitalizations involve both facility and physician services. Although several studies analyze hospital-level variations in Medicare inpatient facility and inpatient physician services per admission, few studies directly explore the relationship between these services. Theoretically, inpatient facility and physician services may be complements or substitutes. That is, an increase in facility services may lead to an increase or decrease in physician services and vice versa. This article contributes to the existing literature by exploring directly the relationship between facility and physician services.

METHODS

Medicare physician claims were linked to inpatient hospital stays using data from the Medicare hospital cost reports, the Medicare Patient Analysis and Review file, and the Medicare National Claims History System.

RESULTS

In multivariate regression analyses, the (partial) correlations between facility and physician services were positive, which is consistent with complementarity. Standardized regression coefficients indicate that physician services are the single most important determinant of facility services; however, facility services are a less important determinant of physician services. A 10% increase in physician services is associated with at least a 3.0% increase in facility services.

CONCLUSIONS

Proposals that reduce inpatient physician expenditures also would reduce facility expenditures in the long-run.

Adenovirus E1A specifically blocks SWI/SNF-dependent transcriptional activation

Expression of the adenovirus E1A243 oncoprotein in Saccharomyces cerevisiae produces a slow-growth phenotype with accumulation of cells in the G1 phase of the cell cycle. This effect is due to the N-terminal and CR1 domains of E1A243, which in rodent cells are involved in triggering cellular transformation and also in binding to the cellular transcriptional coactivator p300. A genetic screen was undertaken to identify genes required for the function of E1A243 in S. cerevisiae. This screen identified SNF12, a gene encoding the 73-kDa subunit of the SWI/SNF transcriptional regulatory complex. Mutation of genes encoding known members of the SWI/SNF complex also led to loss of E1A function, suggesting that the SWI/SNF complex is a target of E1A243. Moreover, expression of E1A in wild-type cells specifically blocked transcriptional activation of the INO1 and SUC2 genes, whose activation pathways are distinct but have a common requirement for the SWI/SNF complex. These data demonstrate a specific functional interaction between E1A and the SWI/SNF complex and suggest that a similar interaction takes place in rodent and human cells.

The impact of practicing in multiple hospitals on physician profiles

Although physicians are all too familiar with the psychologic impact of having multiple responsibilities, the associated impact on practice styles has not been examined systematically. To provide some data on the effects of "work dispersion," we examined the hypothesis that the inpatient resource use of physicians would rise with the number of hospitals in which they work. Data for 1991 from Medicare's National Claims History File were used to profile a sample of attending physicians (n = 33,756) in seven states. The attending physician "profile" was the case mix-adjusted relative value of all physician services (regardless of who delivered them) that were delivered during each patient's hospital stay. Relative value was measured in relative value units, used by Medicare in determining physician payments. The authors then categorized physicians in terms of the number of hospitals to which they admitted patients. Physician profiles were adjusted further to control for geography, physician specialty, and characteristics of the physician's primary (ie, most used) hospital. One third of the physicians in the sample had admissions to more than one hospital. Physicians working in one hospital had inpatient practice profiles 2.1% below the sample mean. Additional hospital affiliations were associated with progressively higher profiles: two hospitals, 2.3% above the mean; three hospitals, 4.5% above; four hospitals, 8.2% above; and five or more hospitals, 11.5% above (all P < 0.01). The practice of medicine in more than one hospital is associated with higher inpatient profiles and shows a dose-response relationship. Physicians and policy makers will need to consider carefully whether there are any associated benefits to justify the increased cost.

Some techniques for the analysis of work sampling data

Work sampling is an observational technique that produces counts representing the number of times that an individual has been observed performing each of several tasks. These data are collected using either systematic or random times of observation, and typically exhibit correlation between repeated observations on the same individual, with the degree of correlation being a function of the amount of time elapsed between measurements. Using several recently developed statistical techniques, we illustrate how it is possible to carry out analyses of these nominal outcomes that account for the correlation between repeated outcomes. We use description of a work sampling study to motivate the techniques and we compare empirically results from analyses based on several different underlying assumptions.

Screening for social and environmental problems in a VA primary care setting

Social workers are in an ideal position to identify and treat social and environmental problems early in the continuum of care. Information on these problems will facilitate informed decision making on the development and reallocation of resources to better meet patients needs. This study assessed the social and environmental problems of 132 patients seen in a primary care clinic at a university-affiliated Veterans Affairs (VA) medical center. The most prevalent social problems were financial difficulties, personal stress, family problems, legal concerns, and employment concerns. When asked, nearly one-third of all respondents requested social work services or information about services related to their problems. The findings suggest a clear need for social work interventions in VA primary care clinics that focus on both psychosocial problems.

Occupational asthma caused by FD&C blue dye no. 2

We report the case of a 55-year-old male who experienced cough, dyspnea, wheezing, and nasal congestion immediately upon exposure to FD&C Blue Dye No. 2 (Indigotine) at work. The patient had worked for 10 years mixing and grinding powdered synthetic red, yellow, and blue dyes for use in foods; symptoms had occurred for 2 years and only with exposure to Indigotine (C16H8N2Na2O8S2), a free flowing blue powder. Prick testing to Indigotine (20 mg/mL) was negative. ELISA failed to detect specific IgE, IgA, IgM, or IgG to Indigotine-HSA conjugates. Bronchial challenge was done according to the method of Pepys et al. beginning with 4 x 10(-4) lactose dilution of Indigotine powder. After 5 minutes of exposure to 4 gm Indigotine/100 gm lactose, the patient developed dyspnea and audible wheezing. At 20 minutes postexposure, there was a 20% decline in FEV1 from prechallenge baseline; no late phase response was observed. A second bronchial challenge with sodium sulfate, the major nondye product additive was negative. To our knowledge, this is the first documented case of occupational asthma due to FD&C Blue Dye No. 2. The pathogenesis is uncertain but does not appear to be IgE mediated.

Impact of the nutritional regimen on protein catabolism and nitrogen balance in patients with acute renal failure

BACKGROUND

Patients with acute renal failure are in substantial negative nitrogen balance as a result of their extremely high protein catabolic rates. We prospectively evaluated a series of patients with acute renal failure managed with continuous venovenous hemofiltration to determine which nutritional and nonnutritional variables might influence protein catabolism and nitrogen balance.

METHODS

Forty consecutive patients (aged 52 +/- 20 years; mean +/- SD) were monitored for 357 treatment days (average treatment duration 8.9 +/- 8.6 days). All data (including nutritional regimen, laboratory values, APACHE II score, administered blood products, hemofiltration parameters, and medications) were collected daily.

RESULTS

For all patients, the mean normalized protein catabolic rate was 1.4 +/- 0.5 g/kg per day. The rate did not differ between those who received nutrition support and those who did not. The net nitrogen deficit was less in those patients receiving nutrition support (-6.0 +/- 5.2 vs -14.0 +/- 5.6 g N/d; p = .02). Using regression techniques (adjusted for the within-person correlation and the previous day's normalized protein catabolic rate), the level of protein and energy provision and the interaction between protein and energy provision were predictive of the normalized protein catabolic rate. Predicted values, using this equation, suggest that at low protein administration rates (< 1 g/kg per day), increasing energy provision may reduce the protein catabolism. However, at this level of protein provision, patients remain in negative nitrogen balance. At protein administration rates necessary to achieve nitrogen balance (approximately 1.5 to 1.8 g/kg per day), protein catabolism may increase. Providing relatively low levels of energy may diminish the magnitude of this increase.

CONCLUSION

These results suggest that the optimal nutritional regimen for patients with acute renal failure may require a high-protein (approximately 1.5 to 1.8 g/kg per day) and a relatively low-energy (approximately 25 to 35 kcal/kg per day) content.

Monoaminergic influences on temporal patterning of sexual behavior in male rats

We evaluated the effects of the serotonin (5-HT) presynaptic uptake blocker fluoxetine (FLX) and the dopamine (DA)/noradrenaline (NE) releaser amantadine (AMA), separately and in combination, on the temporal patterning of male rat sexual behavior. FLX alone increased intermount-bout intervals, time-outs, grooming time, ejaculation latency, number of mounts per mount bout, and number of mount bouts per ejaculation. AMA alone had the opposite effect on these measures. Additionally, AMA, when given in combination with FLX, completely reversed the FLX-induced deficits in copulatory behavior. We interpret our results as suggesting an interaction between 5-HT and catecholamines in the temporal patterning of male rat copulatory behavior.

Cyclic AMP signaling is required for function of the N-terminal and CR1 domains of adenovirus E1A in Saccharomyces cerevisiae

We have constructed yeast vectors in which derivatives of the adenovirus E1A gene are expressed from the GAL1 promoter. Cells expressing E1A289 grow poorly and accumulate cells with a 1C DNA content. Using a series of E1A deletion mutants, we have identified three regions within the E1A protein that are necessary for the G1 growth phenotype; each deletion partially relieves the growth defect. These deletions span residues 4-25, 38-60 and 140-186, which fall within the N-terminal, CR1 and CR3 domains of E1A respectively. Expression of the first 82 residues of E1A, spanning just the N-terminal and CR1 domains, strongly inhibits yeast cell growth in G1 showing that these domains can function independently of other domains of E1A. Using this strong growth inhibition, we isolated a yeast mutant in the net1 gene that conferred resistance to the expression of E1A1-82. The mutant was insensitive to expression of both E1A1-82 and full length E1A, but remained sensitive to the toxicity caused by over-expression of a Gal4p-VP16 fusion. Finally, we found that the function of E1A in yeast depends on the cyclic AMP signaling pathway, providing a striking parallel with the action of E1A at the c-fos promoter in mammalian cells. These results suggest that a genetic analysis of the yeast model system will provide relevant new insights into mechanisms of gene regulation by E1A proteins.

Clinical and cytogenetic findings in seven cases of inverted duplication of 8p with evidence of a telomeric deletion using fluorescence in situ hybridization

We report on the clinical and cytogenetic findings in 7 cases of inverted duplication of region 8p11.2p23. The phenotype of inv dup (8p) compiled from this series and the literature (N = 29) consists of severe mental retardation (100%), minor facial alterations (97%), agenesis of the corpus callosum (80%), hypotonia (66%), orthopedic abnormalities (58%), scoliosis/kyphosis (40%), and congenital heart defect (26%). A telomeric deletion of region 8p23.3-pter was confirmed in 3 of our cases studied using fluorescent in situ hybridization with a telomeric probe for 8p. Thus, these karyotypes are inv dup del(8) (qter-->p23.1::p23.1-->p11.2:). Our findings suggest that most cases of inv dup(8p) probably have a telomeric deletion.

Primary care physician productivity: the physician factor

OBJECTIVES

To model physician productivity as a function of clinic (support system) characteristics and physician characteristics and to model the time a physician spends with the patient as a function of patient characteristics.

DESIGN

Observational study.

SETTING

A general medicine clinic of a university-affiliated Veterans Affairs medical center.

PATIENTS

A cohort of 2,520 patients having 2,721 consecutive outpatient visits to 56 physicians.

MAIN OUTCOME MEASURES

Physician productivity defined as patients seen/physician/hour and time (minutes) spent with the patient.

RESULTS

Physicians saw a mean (+/- SD) of 1.62 +/- 0.68 patients/hour. Clinic characteristics explained 8.2% of the variability of session-specific physician productivity. Controlling for clinic characteristics, a factor representing the physician explained an additional 55.4%. A model for overall physician productivity, using physician characteristics, explained 84.9% of the variance, and time spent with the patient was an important predictor. Modeling physician time with patients, patient characteristics accounted for only 7% of the variability. Controlling for patient characteristics, the individual physician again provided the greatest explanatory power, an additional 22.8% of the variability.

CONCLUSIONS

Physicians' practice patterns, rather than clinic or patient characteristics, may account for most of the variation in physician productivity. Given the magnitude of the influence of individual practice patterns, interventions to increase productivity need to consider methods to affect physician behavior.

Improving compliance among women with abnormal Papanicolaou smears

OBJECTIVE

To determine whether a clinic-based intervention, consisting of motivational brochures and a tracking system, increases adherence to recommendations for treatment in women with abnormal Papanicolaou smears.

METHODS

Three pairs of clinics--two family planning clinics, two family practice clinics, and two dysplasia clinics--were randomized within pairs either to provide the intervention or to maintain usual contact procedures with women having abnormal Papanicolaou smears. Baseline adherence rates were assessed through chart review during 3 randomly selected months of the previous year. Intervention clinics received the tracking system and motivational brochures, which were sent to women on notification of their cervical abnormalities. Comparison clinics also used the tracking system but did not include the brochures when notifying women of their abnormalities. Adherence rates were assessed prospectively for approximately 100 consecutive nonpregnant women with abnormal Papanicolaou smears (inflammatory benign atypia, or cervical intraepithelial neoplasia I, II, or III) at each clinic.

RESULTS

Within clinics, baseline adherence rates ranged from 34-69% for atypia and 33-88% for dysplasia. For dysplasia patients, the overall analysis indicated a significant increase in adherence for the intervention clinics (P = .03); however, for atypia patients, the observed difference was not statistically significant (P = .23). Extensive analyses of the data from family planning clinics indicated that women receiving the intervention were more likely to obtain follow-up treatment (odds ratio [OR] 2.6, 95% confidence interval 1.15-5.85). There was a suggestion that the intervention could have a greater effect among African-American women (OR 15.7) compared with white women (OR 1.8) (P = .09). White women, those with dysplasia, nonsmokers, and nulliparas were most likely to adhere to treatment recommendations.

CONCLUSION

A motivational brochure can enhance adherence to treatment recommendations among women with abnormal Papanicolaou smears. Future studies should focus on techniques for enhancing adherence among more resistant participants.

Geographic variations in physician service utilization

This article investigates the geographic variation in Medicare physician services by type of service. Using 1990 Medicare beneficiary samples, age-sex-race adjusted population based physician service rates are computed. Physician services are measured using relative value units (RVUs)from the Medicare feeschedule. There is substantial variation across the states in utilization levels (Florida 38 percent above the U.S. mean; Vermont and Montana 29 percent below the mean) and a much greater range at the metropolitan area level. With the exception of major surgery, urban area benefciaries generally receive higher amounts of most evaluation and management services (particularly consultations), imaging services, and diagnostic testing. If volume performance standards (or an entitlement cap) were established at a state or area level, policymakers would have to address issues of geographic variation.

Service mix in the hospital outpatient department: implications for Medicare payment reform

OBJECTIVE

To determine if implementation of a PPS for Medicare hospital outpatient department (HOPD) services will have distributional consequences across hospital types and regions, this analysis assesses variation in service mix and the provision of high-technology services in the HOPD.

DATA

HCFA's 1990 claims file for a 5 percent random sample of Medicare beneficiaries using the HOPD was merged, by hospital provider number, with various HCFA hospital characteristic files.

STUDY DESIGN

Hospital characteristics examined are urban/rural location, teaching status, disproportionate-share status, and bed size. Two analyses of HOPD services are presented: mix of services provided and the provision of high-technology services. The mix of services is measured by the percentage of services in each of 14 type-of-service categories (e.g., medical visits, advanced imaging services, diagnostic testing services). Technology provision is measured by the percentage of hospitals providing selected high-technology services.

FINDINGS/CONCLUSIONS

The findings suggest that the role hospital types play in providing HOPD services warrants consideration in establishing a PPS. HOPDs in major teaching hospitals and hospitals serving a disproportionate share of the poor play an important role in providing routine visits. HOPDs in both major and minor teaching hospitals are important providers of high-technology services. Other findings have implications for the structure of an HOPD PPS as well. First, over half of the services provided in the HOPD are laboratory tests and HOPDs may have limited control over these services since they are often for patients referred from local physician offices. Second, service mix and technology provision vary markedly among regions, suggesting the need for a transition to prospective payment. Third, the organization of service supply in a region may affect service provision in the HOPD suggesting that an HOPD PPS needs to be coordinated with payment policies in competing sites of care (e.g., ambulatory surgical centers).

Influence of hormones on platelet intracellular calcium

The pathophysiology of thromboembolic disease associated with estrogen therapy is poorly understood. There are innumerable calcium-dependent activities involved in platelet function. To determine whether platelet calcium levels are affected by exogenous hormones, intracellular calcium and release were studied in platelets in various hormonal environments and findings were correlated with platelet adhesion and aggregation. Platelet intracellular calcium concentration and release was significantly decreased in women ingesting tamoxifen compared to controls and significantly increased, as was platelet adhesion, in oral contraceptive users. Platelets incubated ex vivo with estradiol had increased intracellular calcium and release but there was decreased adhesion to fibronectin. Intracellular calcium concentration and release were not affected when platelets were incubated with tamoxifen. Adhesion to collagen III was increased in tamoxifen-incubated platelets. Only oral contraceptive users had increased sensitivity to aggregating agents. This data suggests that 17 beta estradiol, progesterone, and tamoxifen likely have a nongenomic effect on platelet intracellular calcium and calcium release and that platelet calcium levels are closely related to the degree of platelet adhesion and aggregation in vivo.

Reassembly of the 66 kD neurofilament protein in vitro following isolation and purification from bovine spinal cord

NF-66, also known as alpha-internexin, has been characterized as a 66 kD mammalian neurofilament (NF) protein whose expression in developing rat brain precedes that of the low molecular weight NF protein (NF-L). NF-66 is thought to assemble into 10 nm diameter intermediate filaments in vitro, although the precise nature of the assembly process remains obscure. Likewise, the ability of NF-66 to polymerize with the low (NF-L), middle (NF-M), and high (NF-H) M(r)NF proteins has not been defined. This investigation describes the reassembly of bovine NF-66 regarding its formation into 10 nm diameter filaments as well as its potential for polymerization with other type IV intermediate filaments. NF-66 and the NF triplet proteins were isolated from bovine spinal cord using established biochemical extraction and isolation procedures (Balin et al., Brain Res 556:181-195, 1991), and purified by a combination of high performance liquid chromatography (HPLC) (DEAE anion exchange and hydroxylapatite column chromatography) and gel elution strategies. In vitro reassembly experiments revealed that NF-66 formed approximately 10 nm diameter filaments of varying length; immunoelectron microscopy demonstrated labeling of these filaments by a monoclonal antibody to intermediate filament antigen (IFA), a polyclonal antibody against rat NF-66 and by a monoclonal antibody generated against the core region of NF-M but cross-reactive with NF-66. This report is the first investigation to look at the in vitro interaction between NF-66 and other type IV intermediate filament proteins (NF-H, -M, and -L) and establishes that NF-66 forms heteropolymeric filaments with these other neurofilament proteins, as confirmed by double immunolabeling. These studies suggest that NF-66 could provide a nucleation site for the polymerization of later-expressed proteins during neuronal development.

Predicting inpatient costs with admitting clinical data

Hospital cost-containment programs should themselves be cost-effective, targeting high-cost physicians (which requires adjusting for case mix) and patients (which requires early identification). In this study, clinical data available within 24 hours of admission from an electronic medical record system were used to develop statistical models to predict hospital costs. In this retrospective analysis of clinical data and diagnosis-related groups (DRGs), study subjects were 2,355 patients admitted for at least 1 day to the medicine service at an urban teaching hospital with sophisticated electronic medical records. Of these 2,355 patients, 1,663 (71%) had one of the 41 most common DRGs. Predictive models were derived on a random subset of two thirds of the patients and were validated on the remaining third. The following patient data were obtained: admission and prior diagnostic test results, diagnoses, vital signs; demographic data; prior inpatient and outpatient visits; tests and treatments ordered within 24 hours of admission (discretionary data); DRGs; and total inpatient costs (estimated from charges). Diagnosis-related groups explained 24% of the variance in total costs in the derivation patient set and 16% in the validation set. When only nondiscretionary data were used, the models retained only clinical laboratory results and prior diagnoses, explaining 20% of the derivation set variance in total costs and 16% in the validation set. Adding DRGs increased the variance explained in the derivation set to 34%, but decreased to 24% in the validation set. Adding discretionary data substantially increased the explained variance in the derivation and validation patient sets. The models' median predicted costs underestimated true costs by 10% to 13%, with the lowest error in the models using all types of variables. Clinical data gathered during routine clinical care can be used to adjust for case mix and identify high-cost patients early in their hospital stays, when they could be targeted by cost-containment interventions.

A comparison of HIV risk between women and men who inject drugs

Although there is growing evidence of differences between women and men who inject drugs (IDUs) in terms of level of risk for HIV infection, very little research has been conducted specifically addressing the risk practices of women IDUs. This study formed part of a national study of HIV infection risks in IDUs and the purpose of the present analysis was an exploration of gender differences in HIV risk practices, focusing on the HIV risk practices of IDU women. 1,245 IDUs from the inner city area of Sydney took part in this study. Of these, 908 were men and 331 were women. Notable results were that female respondents were more likely to report sharing needles, they injected heroin more times in a typical using month and were more likely to have shared with someone they later found out was HIV seropositive. Female respondents also reported more sexual partners than men, were more likely to engage in prostitution, and were more likely to have sexual partners who were themselves IDUs. The results provide support for the proposition that women who inject drugs may be at greater risk of HIV infection through both their drug taking and their sexual practices. Further research is needed to explore the reasons underlying the risk practices of women who inject drugs and an understanding of these factors needs to be incorporated into HIV risk-reduction and drug harm-reduction policies and programs.

Visual and quantitative computerized assessment of disease severity on peripheral angiograms

PURPOSE

This study was designed to determine and compare the intra- and interobserver variability of visual and computerized assessment of peripheral arterial disease (PAD) severity from lower extremity angiograms, and to correlate quantitative angiographic measures with clinical predictors of PAD.

PATIENTS AND METHODS

Peripheral angiograms of 13 segments from the ilio-femoral-popliteal system were evaluated on two separate occasions by nine radiologists and with a quantitative computerized method. In a separate study, images from 18 patients undergoing diagnostic lower extremity angiography were analyzed with use of quantitative angiography and the results were compared with clinical and lipid risk factors.

RESULTS

The data demonstrate that computerized assessment of peripheral angiograms is associated with lower intra- and interobserver variability than visual assessment of the same films. Despite this, there was excellent intraobserver and good interobserver agreement on the presence or absence of a severe lesion with visual assessment. Quantitative computerized measures of disease severity correlate with several known predictors of large vessel PAD.

CONCLUSION

Computerized assessment of peripheral angiograms may be a useful tool in the clinical and investigational evaluation of PAD.

Paradoxical influence of estrogenic hormones on platelet-endothelial cell interactions

Controversies abound in the literature about the safety and efficacy of tamoxifen and estrogen. We studied the effect of these 2 hormonal agents on factors involved in in vitro thrombogenesis: platelets and endothelial cells. Endothelial cells were derived from human umbilical veins and platelets were obtained from premenopausal and postmenopausal women, women on oral contraceptives, postmenopausal women on hormone replacement therapy, men, and patients with breast cancer who had been taking adjuvant tamoxifen for more than 1 year. The interaction of platelets with endothelial cell matrix was measured in 2 systems: 1) in a flow chamber at low shear rate and, 2) with 51Cr labeled platelets in a "static" culture system. In the static system, platelets from women on tamoxifen exhibited decreased platelet adherence to endothelial cell matrix whether they were grown in tamoxifen or control conditions, when compared to platelets from premenopausal women. When flow (25 sec-1) was added these differences were negated. Neither tamoxifen nor 17 beta estradiol had an effect on endothelial cell proliferation or platelet aggregation. Adhesion of platelets at low shear was not altered when platelet rich plasma was incubated with tamoxifen nor when endothelial cells were grown in tamoxifen. In contrast, incubation of platelets in 17 beta estradiol decreased platelet adhesion at low shear rate, however, there was no effect on platelet adhesion when endothelial cells were grown in 17 beta estradiol. We conclude that in early stages of thrombus formation as measured in vitro, tamoxifen may not have a detrimental effect and estrogen may be protective.