Seasonal Variability in Otariid Energetics: Implications for the Effects of Predators on Localized Prey Resources

Otariids, like other wild mammals, contend with a wide variety of energetic demands across seasons. However, due to the cryptic behaviors of this marine group, few studies have been able to examine longitudinal energetic costs or the potential impact of these costs on seasonal or annual prey requirements. Here we evaluated the changes in energy demand and intake of female California sea lions (Zalophus californianus) during reproductive (n=2 sea lions) and nonreproductive (n=3) periods. Monthly measurements included resting metabolic rate, blood hormone levels, body condition (blubber thickness and body mass), and caloric intake for adult sea lions throughout molting, late pregnancy, lactation, and postweaning. We found that maintenance energy demands decreased from 32.0 to 23.1 MJ d(-1) before pupping, remaining stable at 19.4+/-0.6 MJ d(-1) during lactation and postweaning. Energy intake rates to meet these demands showed marked changes with activity level and the reproductive cycle, reaching a peak intake of 3.6 times baseline levels during lactation. Translating this into prey demands, we find that 20,000 reproductively active females on San Nicolas Island rookeries would maximally require 4,950 metric tons of Pacific whiting during a month of the breeding season. This localized impact is reduced significantly with postbreeding dispersal and demonstrates the importance of considering spatial and temporal factors driving the energetic requirements of predators when designing marine protected areas.

Elastic path controller for assistive devices

Robotic assistive devices that constrain motion along pre-defined paths are useful in reducing maneuvering efforts by human. This paper introduces an Elastic Path Controller (EPC) that adds "elasticity" to the path following and enables dynamic modification of the paths. This permits the users to compensate for changes in the environment such as introduction of new obstacles or for errors in position sensing. The experiments performed on a Scooter cobot show that users can learn to use this novel tool to modify and design guiding paths in a relatively simple way. The operators use the EPC by pushing/pulling against the guided paths to produce the desired deformations. Then, by just dropping the forces and trusting the path controller, they will be brought back to the guided paths.

Abnormal sterol metabolism in holoprosencephaly: studies in cultured lymphoblasts

BACKGROUND

Holoprosencephaly (HPE) is the most common structural malformation of the developing forebrain in humans. The aetiology is heterogeneous and remains unexplained in approximately 75% of patients.

OBJECTIVE

To examine cholesterol biosynthesis in lymphoblastoid cell lines of 228 patients with HPE, since perturbations of cholesterol homeostasis are an important model system to study HPE pathogenesis in animals.

METHODS

An in vitro loading test that clearly identifies abnormal increase of C27 sterols in lymphoblast-derived cells was developed using [2-(14)C] acetate as substrate.

RESULTS

22 (9.6%) HPE cell lines had abnormal sterol pattern in the in vitro loading test. In one previously reported patient, Smith-Lemli-Opitz syndrome was diagnosed, whereas others also had clearly reduced cholesterol biosynthesis of uncertain cause. The mean (SD) cholesterol levels were 57% (15.3%) and 82% (4.7%) of total sterols in these cell lines and controls, respectively. The pattern of accumulating sterols was different from known defects of cholesterol biosynthesis. In six patients with abnormal lymphoblast cholesterol metabolism, additional mutations in genes known to be associated with HPE or chromosomal abnormalities were observed.

CONCLUSIONS

Impaired cholesterol biosynthesis may be a contributing factor in the cause of HPE and should be considered in the evaluation of causes of HPE, even if mutations in HPE-associated genes have already been found.

Comparison of processes and intermediate outcomes between South Asian and European patients with diabetes in Blackburn, north-west England

BACKGROUND

Diabetes and its complications are more prevalent among South Asians than people of European origin and there is some evidence that patients of South Asian origin with diabetes receive poorer quality care.

METHODS

Longitudinal study of patients with diabetes in Blackburn, UK. Processes of care indicators [measurement of blood pressure (BP), cholesterol and glycosolated haemoglobin (HbA1c)] and values of these intermediate outcomes were extracted for all patients registered on a diabetes information system for the period 1995-2001. Differences in processes of care indicators and intermediate outcomes between ethnic groups were estimated after adjusting for the potential confounding factors of sex, age and socioeconomic status (SES). Generalized estimating equations were used to model trends and to test for differences in trends over time.

RESULTS

Process of care was similar in South Asian and European patients. Mean BP and cholesterol concentration fell during the study period. South Asians had a higher level of HbA1c throughout the study period. South Asians had lower levels of BP and cholesterol in 1995 but the differences diminished or were abolished over time. SES did not explain differences between ethnic groups. Analyses stratified by baseline levels of intermediate outcomes (above or within target) demonstrated improvements among above target patients were greater among European patients.

CONCLUSIONS

Processes of care indicators are similar in diabetic patients of South Asian and European origin, irrespective of SES. However, there are worrying differences in improvements over time in the intermediate outcomes, and glycaemic control remained poorer among patients of South Asian origin patients throughout.

Ventricular tachycardia in nonpostoperative pediatric patients: role of radiofrequency catheter ablation

Experience concerning radiofrequency catheter ablation (RFCA) of ventricular tachycardia (VT) in pediatric patients is limited. In adults, success rates vary widely based on the etiology of the VT. Highest success rates have been achieved in patients without structural heart disease. Between March 1998 and December 1999, five young patients (age, 5 months to 15 years; body weight, 5.5-61.6 kg) underwent RFCA for VT at our institution [structurally normal heart (n = 4), preoperative tetralogy of Fallot (n = 1)]. Monomorphic VT was present in four children, and an infant with MIDAS syndrome had polymorphic VT. Clinical presentation varied: palpitations, n = 2, congestive heart failure, n = 3. All patients had been proven to be unresponsive to one to six (median, three) antiarrhythmic drugs. In all five patients, VT could be successfully eliminated by RFCA after a total of nine (range, 1-4) procedures. Activation mapping and pace mapping were used to identify the anatomical substrate, which was located in the right ventricle/right ventricular outflow tract in all four patients with monomorphic VT and in the left ventricular septum/left ventricular free wall in the infant with polymorphic VT. There were no significant complications in any patient. During follow-up (20-42 months), all patients are in normal sinus rhythm. Left ventricular function recovered in all three patients who had initially presented with congestive heart failure. RFCA can be effective, safe, and life saving in children with medically resistant VT who have not been operated on for congenital heart disease, even when the VT is polymorphic. Although the number of patients is small, RFCA may be the treatment of choice for symptomatic VT in pediatric patients.

Spatial perturbation caused by a badger (Meles meles) culling operation: implications for the function of territoriality and the control of bovine tuberculosis (Mycobacterium bovis)

1. The spatial organization of a badger population (North Nibley) is described before and after it was subjected to a UK Ministry of Agriculture, Fisheries and Food badger removal operation (BRO) intended to control bovine tuberculosis. Comparison is made with an undisturbed badger population (Woodchester Park). 2. The Woodchester Park population was organized in group territories with clearly defined boundaries that remained stable during the 3 years of study (1995-97). In North Nibley, however, the badgers' spatial organization was severely perturbed in the first year and, to a lesser extent, also in the second year after the BRO, with badgers using latrines further away from their setts. This resulted in enlarged social group ranges that were difficult to define and overlapped considerably. 3. The disturbance was observed in the removal groups, those immediately adjacent, as well as those at a distance of one or two social groups from the removal area, with an unexpected indication that the latter groups may have been the most affected. 4. The apparent increase in the size of the group ranges in North Nibley was likely to have been caused by an increased proportion of badgers making extra-group excursions in the aftermath of the BRO. 5. Initial recolonization was almost exclusively by females. 6. Although such perturbation might be expected to facilitate disease transmission between badger social groups, there was no evidence that any infectious animals had survived the BRO. However, there were further cattle breakdowns in the area. 7. The behaviour of badgers after the BRO also provided an opportunity to test predictions made by competing hypotheses about the main determinants of the badger's socio-spatial behaviour.

Aromatase inhibition and inactivation

Aromatase is the key enzyme in the synthesis of estrogens and mediates the conversion of androstenedione and testosterone to estrone and estradiol. Because of the importance of estrogen in stimulating breast cancers, the inhibition of estrogen synthesis is a logical approach to treatment. Aromatase is an excellent target for inhibition, because it is the last step in steroid biosynthesis, and, therefore, there are no important downstream enzymes to be affected. In addition, although aromatase is a P-450 enzyme and shares common features with other enzymes in this class, such as liver metabolizing enzymes and steroidogenic enzymes, it has unique features in the aromatizing reaction, features that are amenable to the development of selective inhibition. The approach we took to develop the first aromatase inhibitors was to design substrate analogues based on the structure of androstenedione. Some of these inhibitors, such as 4-hydroxyandrostenedione [4-OHA (later known as formestane)], also cause enzyme inactivation. Instead of being released at the end of the reaction, the substrate analogue remains bound. Therefore, the inhibitor is not required to be present at all times to maintain inhibition, and it has high enzyme specificity. Subsequently, other investigators have taken a different approach to developing compounds based on inhibitors of P-450 enzymes. High selectivity has been achieved with some of these reversible inhibitors. We have developed a unique animal model with human tumors to compare the antitumor efficacy of antiestrogens and aromatase inhibitors and to optimize their use in sequence and combination as a guide for future clinical trials.

Class I major histocompatibility complex anchor substitutions alter the conformation of T cell receptor contacts

An immunogenic peptide (GP2) derived from HER-2/neu binds to HLA-A2.1 very poorly. Some altered-peptide ligands (APL) of GP2 have increased binding affinity and generate improved cytotoxic T lymphocyte recognition of GP2-presenting tumor cells, but most do not. Increases in binding affinity of single-substitution APL are not additive in double-substitution APL. A common first assumption about peptide binding to class I major histocompatibility complex is that each residue binds independently. In addition, immunologists interested in immunotherapy frequently assume that anchor substitutions do not affect T cell receptor contact residues. However, the crystal structures of two GP2 APL show that the central residues change position depending on the identity of the anchor residue(s). Thus, it is clear that subtle changes in the identity of anchor residues may have significant effects on the positions of the T cell receptor contact residues.

Synthesis of 7beta-sulfur analogues of paclitaxel utilizing a novel epimerization of the 7alpha-thiol group

Paclitaxel analogues with a sulfur group at the 7beta position were required for SAR studies. Attempts to generate these compounds by displacing a 7alpha leaving group with sulfur nucleophiles were unsuccessful. Instead, these compounds were successfully prepared from a 7beta-thiol intermediate that was obtained by a base-catalyzed epimerization of the 7alpha-thiol derivative. The epimerization presumably proceeds through a thioaldehyde intermediate and exhibits the opposite stereochemical preference of its oxygen counterpart.

A physical activity screening measure for use with adolescents in primary care

OBJECTIVE

To develop a reliable and valid physical activity screening measure for use with adolescents in primary care settings.

STUDY DESIGN

We conducted 2 studies to evaluate the test-retest reliability and concurrent validity of 6 single-item and 3 composite measures of physical activity. Modifications were based on the findings of the 2 studies, and a best measure was evaluated in study 3. Accelerometer data served as the criterion standard for tests of validity.

RESULTS

In study 1 (N = 250; mean age, 15 years; 56% female; 36% white), reports on the composite measures were most reliable. In study 2 (N = 57; mean age, 14 years; 65% female; 37% white), 6 of the 9 screening measures correlated significantly with accelerometer data. Subjects, however, had great difficulty reporting bouts of activity and distinguishing between intensity levels. Instead, we developed a single measure assessing accumulation of 60 minutes of moderate to vigorous physical activity. Evaluated in study 3 (N = 148; mean age, 12 years; 65% female; 27% white), the measure was reliable (intraclass correlation, 0.77) and correlated significantly (r = 0.40, P<.001) with accelerometer data. Correct classification (63%), sensitivity (71%), and false-positive rates (40%) were reasonable.

CONCLUSION

The "moderate to vigorous physical activity" screening measure is recommended for clinical practice with adolescents.

Synthesis, structure proof, and biological activity of epothilone cyclopropanes

[structure--see text] A semisynthetic route to epothilone cyclopropanes from epothilones A and B is described. Of significance, the deoxygenation of the 12, 13-epoxide to give the corresponding olefin was achieved with high efficiency. The title compounds (8, 9) were active in both tubulin polymerization and cytotoxicity assays, which is in direct contrast to a previously published report. These results provide further evidence that the role of the 12,13-epoxide of epothilones is largely conformational and argue against some of the current pharmacophore models.

Sequence stratigraphy and architecture of the Late Pleistocene Lagniappe delta complex, northeast Gulf of Mexico

During the last fourth-order glacial-interglacial cycle (e.g. post oxygen isotope stage 5) the Lagniappe Delta system located in the northeast Gulf of Mexico, prograded several tens of miles seaward along two main NE-SW and N-S trending fairways. The delta complex is underlain by a well-developed calcareous shale-rich condensed section that was deposited during isotope stage 5. The delta complex comprises many progradational lobes that were deposited during fifth-order sea-level falls and during the fourth-order maximum lowstand and early rise of sea level associated with isotope stages 4 to 2. Each significant fifth-order sea level fall developed a sequence boundary with an unconformity updip and a correlative conformity downdip on which a delta lobe was deposited. Autocyclic processes also lead to deposition of numerous lobes through lobe switching. During the maximum sea-level lowstand, deep erosion related to the development of an extensive incised valley system occurred across the top of the prograding wedges that were deposited during relative sea-level fall (the falling stage systems tract) and modified all of the previous updip unconformities. The base of the incised valley system, and its correlative downdip conformity, form the main fourth-order sequence boundary. It is on this surface that the last part of the delta complex was deposited during the maximum lowstand and early rise of sea-level. Thus, during the last fourth-order cycle, several fifth-order ‘initial’ sequence boundaries and one fourth-order ‘final’ sequence boundary were formed. Infilling of the incised valley system occurred mainly during the early and late rise of sea-level (isotope stages 2 and younger), prior to a major landward shift of deltaic sedimentation in response to the rapid eustatic rise in sea level during isotope stage 1.

Six months of in-practice experience with a high Dk lotrafilcon a soft contact lens

Recent innovations in research and development have brought two new high Dk soft contact lens materials to the market. The purpose of this study was to report the performance of one of these materials, lotrafilcon A, among a large and diverse number of patients and routine practices. Five hundred and forty seven patients were fitted with study lenses by 62 investigators in six countries and followed for 3-6 months of up to 30 nights extended wear. Clinical results showed good visual acuity, lens surfaces, biomicroscopy findings, and lens fit throughout the study. Patients rated the lens highly and were satisfied with the lens. Practitioners may expect good results among their patients who are appropriate candidates for this lens.

An embedded decisional model of stress and coping: implications for exploring treatment decision making by women with breast cancer

Treatment decision making by women with breast cancer has been recognized to be an inherently stressful process. However, past decisional theory and research has failed to fully elucidate the personal, transactional, and relational nature of choice behaviour. The purpose of this paper is to explore an embedded decisional model of stress and coping that locates key assumptions of Janis & Mann's (1977) conflict-theory model of decision making within Lazarus & Folkman's (1984) transactional framework. Through combining decisional and stress and coping theories, a model is developed that addresses the theoretical limitations of the conflict-theory model and provides greater specificity within decision-making research. The paper examines the complexity of treatment decision making within the context of the constructs of causal antecedents, primary appraisal, secondary appraisal, coping, and adaptational outcomes. Examples specific to women with breast cancer are provided to illustrate the potential application of the embedded model. The implications of this inclusive and comprehensive decisional theory for future knowledge development and research in the area of treatment decision making are also discussed.

Cytotoxic sesquiterpenoids from Ratibida columnifera

Bioassay-directed fractionation of the flowers and leaves of Ratibida columnifera using a hormone-dependent human prostate (LNCaP) cancer cell line led to the isolation of 10 cytotoxic substances, composed of five novel xanthanolide derivatives (2-4, 7, and 8), a novel nerolidol derivative (9), and three known sesquiterpene lactones, 9alpha-hydroxy-seco-ratiferolide-5alpha-O-angelate+ ++ (1), 9alpha-hydroxy-seco-ratiferolide-5alpha-O-(2-methylbut yrate) (5), 9-oxo-seco-ratiferolide-5alpha-O-(2-methylbutyrate) (6), as well as a known flavonoid, hispidulin (10). On the basis of its cytotoxicity profile, compound 5 was selected for further biological evaluation, and was found to induce G1 arrest and slow S traverse time in parental wild type p53 A2780S cells, but only G2/M arrest in p53 mutant A2780R cells, with strong apoptosis shown for both cell lines. The activity of 5 was not mediated by the multidrug resistance (MDR) pump, and it was not active against several anticancer molecular targets (i.e., tubulin polymerization/depolymerization, topoisomerases, and DNA intercalation). While these results indicate that compound 5 acts as a cytotoxic agent via a novel mechanism, this substance was inactive in in vivo evaluations using the murine lung carcinoma (M109) and human colon carcinoma (HCT116) models.

An embedded decisional model of stress and coping: implications for exploring treatment decision making by women with breast cancer

Treatment decision making by women with breast cancer has been recognized to be an inherently stressful process. However, past decisional theory and research has failed to fully elucidate the personal, transactional and relational nature of choice behaviour. The purpose of this paper is to explore an embedded decisional model of stress and coping that locates key assumptions of Janis and Mann's conflict-theory model (CTM) of decision making within Lazarus and Folkman's transactional framework. Through combining decisional and stress and coping theories, a model is developed that addresses the theoretical limitations of the CTM and provides greater specificity within decision-making research. The paper examines the complexity of treatment decision making within the context of the constructs of causal antecedents, primary appraisal, secondary appraisal, coping and adaptational outcomes. Examples specific to women with breast cancer are provided to illustrate the potential application of the embedded model. The implications of this inclusive and comprehensive decisional theory for future knowledge development and research in the area of treatment decision making are also discussed.

Comparison between a short and a conventional blade periodontal curet: an in vitro study

This in vitro study was done to compare a short-blade, long-shank (test) curet designed for deeper pockets of incisors and a conventional Gracey 1/2 curet regarding (a) their ability to remove root surface material at different pocket depths, and (b) their effect on root surface roughness. 2 groups of 12 senior dental hygiene students used either the randomly assigned test or conventional curet for a defined period on maxillary and mandibular incisors in a cross-over experimental design. Extent of root debridement was determined by assessing the removal of black enamel paint on root surfaces within pockets using a computerized video routine and root surface roughness measured using a profilometer. When each surface of the root was analyzed separately at 2-mm increments, the test instrument exhibited superior material removal on all surfaces at the 4-6 mm CAL (p-values<0.001). However, the test curet caused a rougher surface than the conventional curet on all surfaces (p<0.001), with a mean difference of 0.27 microm. While it is assumed that the ability of the test instrument to debride the root surface of deeper pockets more thoroughly is clinically more important than the rougher root surfaces it produces, this can only be assessed by further studies in vivo.

Aromatase inhibitors and their antitumor effects in model systems

The potential of aromatase (estrogen synthetase) within the breast to provide a significant source of estrogen mediating tumor proliferation is suggested by studies reporting 4- to 6-fold higher estrogen levels in tumors than in plasma of postmenopausal patients with breast cancer. Recent studies in our laboratory have identified aromatase and its mRNA in tumor epithelial cells using immunocytochemistry and in situ hybridization. In addition, significant aromatase activity, which was stimulated 7-fold by dexamethasone, was measured in metastatic cells isolated from a breast cancer patient. Increase in proliferation, as measured by proliferating cell nuclear antigen immunostaining in tumor sections and by thymidine incorporation into DNA in response to testosterone, was observed in histocultures of breast cancer samples. This latter effect could be inhibited by 4-hydroxyandrostenedione. These results imply that intratumoral aromatase has functional significance and may be an important target for successful inhibitor treatment of breast cancer patients. To investigate treatment strategies with aromatase inhibitors and antiestrogens, we developed an intratumoral aromatase model to simulate the hormone responsive postmenopausal breast cancer patient. Tumors of estrogen receptor positive human breast carcinoma cells (MCF-7) transfected with the human aromatase gene are grown in ovariectomized nude mice. These cells synthesize sufficient estrogen to stimulate tumor formation. We have utilized this model to investigate the effects on tumor growth of the antiestrogens, tamoxifen and ICI 182780, and the aromatase inhibitors, letrozole and anastrozole (arimidex), alone and in combination. Both the aromatase inhibitors and the antiestrogens were effective in suppressing tumor growth. However, letrozole was significantly more effective than the antiestrogens. When the aromatase inhibitors were combined with the antiestrogen, tamoxifen, tumor growth was suppressed to about the same extent as with the aromatase inhibitors alone. Furthermore, the results do not suggest any benefit from combining tamoxifen with the pure antiestrogen, ICI 182780. Thus sequential use of these agents is likely to be more advantageous to the patient in terms of longer duration of effective treatment.

Theological reflection in the supervision of pastoral care

Reviews some elements of group supervision in preparation for the ministry of pastoral care and suggests five steps in theologically processing a case study. Reflects on the Word of God as an interpretive resource to provide meaning to life experiences. Suggests four ways demonstrating how the habit of an interpretive approach and theological reflection can enrich the Christian community.

Aromatase and its inhibitors

Inhibitors of aromatase (estrogen synthetase) have been developed as treatment for postmenopausal breast cancer. Both steroidal substrate analogs, type I inhibitors, which inactivate the enzyme and non-steroidal competitive reversible, type II inhibitors, are now available. 4-hydroxyandrostenedione (4-OHA), the first selective aromatase inhibitor, has been shown to reduce serum estrogen concentrations and cause complete and partial responses in approximately 25% of patients with hormone responsive disease who have relapsed from previous endocrine treatment. Letrozole (CGS 20, 269) and anastrozole (ZN 1033) have been recently approved for treatment. Both suppress serum estrogen levels to the limit of assay detection. Letrozole has been shown to be significantly superior to megace in overall response rates and time to treatment failure, whereas anastrozole was found to improve survival in comparison to megace. Both were better tolerated than the latter. The potential of aromatase within the breast as a significant source of estrogen mediating tumor proliferation and which might determine the outcome of inhibitor treatment was explored. Using immunocytochemistry and in situ hybridization, aromatase and mRNAarom was detected mainly in the epithelial cells of the terminal ductal lobular units (TDLU) of the normal breast and also in breast tumor epithelial cells as well as some stromal cells. Increase in proliferation, measured by increased thymidine incorporation into DNA and by PCNA immunostaining in response to testosterone was observed in histocultures of breast cancer samples. This effect could be inhibited by 4-OHA and implies that intratumoral aromatase has functional significance. An intratumoral aromatase model in the ovariectomized nude mouse was developed which simulated the hormone responsive postmenopausal breast cancer patient. This model also allows evaluation of the efficacy of aromatase inhibitors and antiestrogens in tumors of estrogen receptor positive, human breast carcinoma cells transfected with the human aromatase gene. Thus, the cells synthesized estrogen which stimulated tumor formation. Both aromatase inhibitors and antiestrogens were effective in suppressing tumor growth in this model. However, letrozole was more effective than tamoxifen. When the aromatase inhibitors were combined with tamoxifen, tumor growth was suppressed to about the same extent as with the aromatase inhibitors alone. Thus, there was no additive or synergistic effects of combining tamoxifen with aromatase inhibitors. This suggests that sequential treatment with these agents is likely to be more beneficial to the patient in terms of longer response to treatment.

An in vitro comparison of thermoplasticised gutta-percha obturation techniques with cold lateral condensation

This study compared the apical sealing ability, obturation time and extrusion of gutta-percha and sealer when root canals were obturated using either cold lateral condensation or one of the three methods using thermoplasticised gutta-percha (Alpha Seal, Thermafil or JS Quick Fill) in vitro. One hundred and thirty-one root canals from 78 extracted human teeth were used; 116 canals were divided into five groups so that they were balanced with respect to prepared canal anatomy, and the remaining 15 canals were used as positive and negative controls. The canals in the first four groups were prepared with hand files using the step-down technique to a standard apical size and flare. The last group was prepared using engine-driven rotary nickel-titanium files (McSpadden) to a similar apical size and flare. One of the four obturating techniques was used to fill the canals in each of the first four groups. The fifth group was obturated using the Alpha Seal technique. The roots were immersed in india ink, demineralised and rendered transparent to assess the extent of maximum lincar dye penetration. The Alpha Seal groups had the highest number of specimens without any leakage. There was a significant difference in the proportions of specimens that did not leak when the Alpha Seal (P < 0.01) and cold lateral condensation groups (P < 0.05) were compared with JS Quick Fill. Cold lateral condensation had a higher proportion of specimens with leakage in canals with curvature greater than 20 degrees than in canals with curvatures less than 20 degrees (P < 0.05). The curvature of canals had no effect on the sealing ability of the other techniques. The method of canal preparation had no effect on the sealing ability of Alpha Seal. Alpha Seal, Thermafil and JS Quick Fill were significantly quicker to perform than cold lateral condensation.

Aromatase expression in the human breast

The plasma levels of free estradiol are very low in postmenopausal women. However, concentrations of estrogens within breast tissue have been reported to be higher than in plasma and similar to plasma concentrations in premenopausal women. One mechanism by which this may occur is for breast cells to synthesize estrogens themselves and produce high concentrations locally. Thus, tumor aromatase may be a significant source of estrogen which stimulates tumor growth. To address the question of the importance of this pathway, we have investigated the expression of aromatase within the normal breast and breast cancers. Because conventional biochemical assays for measuring aromatase activity require relatively large amounts of tissue, we developed an immunocytochemical method using a monoclonal antibody to determine the expression of aromatase. The method can be applied to sections of tumors embedded in paraffin blocks as routinely prepared for pathology. Since we have previously shown that mRNA for aromatase (P450 arom) and the protein are expressed in the same cells of the human placenta, we used in situ hybridization of sequence specific probes to P450 arom mRNA in breast tissue as one method to verify the specificity of the immunocytochemical detection of the enzyme. Both immunocytochemistry and in situ hybridization identified aromatase enzyme and mRNA expression in the epithelial cells of the terminal ductal lobula units (TDLU) and surrounding stromal cells of the normal human breast, and in the tumor epithelial cells and stromal cells of breast cancers. In addition, evidence for the functional significance of tumor aromatase was indicated by a correlation between aromatase activity and expression of proliferating cell nuclear antigen (PCNA) in the tumor, and by increased thymidine incorporation into DNA in response to testosterone in tumors in histoculture which had high aromatase activity but not in those with low activity. The findings suggests that estrogen produced locally is important in enhancing proliferation of the tumor.