Measurement of glycated hemoglobin and glycated albumin in umbilical cord: evaluation of the glycemic control indicators in neonates.

OBJECTIVE: As neonatal blood contains a high proportion of fetal hemoglobin (HbF), it is difficult to use high-performance liquid chromatography (HPLC) method, latex-immunoturbidimetry (LA) method and enzymatic methods, which determine hemoglobin A(1C) (HbA(1C)) in order to provide the glycemic control indicators of neonates. In this study, we evaluated glycated hemoglobin (GHb) and glycated albumin (GA) as appropriate indicators of the glycemic control in the neonatal period. STUDY DESIGN: Umbilical cord blood samples collected during delivery were subjected to measurements of GHb (HPLC methods using two different instruments, LA method, enzymatic method and affinity method) and serum GA. RESULT: HbA(1C) levels determined by the HPLC method, the LA method and the enzymatic method were as low as <3.0% in all the cases. Although GHb determined by the affinity method was 3.6 ± 0.2%, this method may not measure accurately the values of glycated HbF plus glycated HbA. Serum GA was 9.4 ± 1.1%. CONCLUSION: We speculate that serum GA, but not GHb, could be used as glycemic control indicators in neonates.

Spontaneous reversal of the developmental aging of normal human cells following transcriptional reprogramming.

AIM: To determine whether transcriptional reprogramming is capable of reversing the developmental aging of normal human somatic cells to an embryonic state. MATERIALS & METHODS: An isogenic system was utilized to facilitate an accurate assessment of the reprogramming of telomere restriction fragment (TRF) length of aged differentiated cells to that of the human embryonic stem (hES) cell line from which they were originally derived. An hES-derived mortal clonal cell strain EN13 was reprogrammed by SOX2, OCT4 and KLF4. The six resulting induced pluripotent stem (iPS) cell lines were surveyed for telomere length, telomerase activity and telomere-related gene expression. In addition, we measured all these parameters in widely-used hES and iPS cell lines and compared the results to those obtained in the six new isogenic iPS cell lines. RESULTS: We observed variable but relatively long TRF lengths in three widely studied hES cell lines (16.09-21.1 kb) but markedly shorter TRF lengths (6.4-12.6 kb) in five similarly widely studied iPS cell lines. Transcriptome analysis comparing these hES and iPS cell lines showed modest variation in a small subset of genes implicated in telomere length regulation. However, iPS cell lines consistently showed reduced levels of telomerase activity compared with hES cell lines. In order to verify these results in an isogenic background, we generated six iPS cell clones from the hES-derived cell line EN13. These iPS cell clones showed initial telomere lengths comparable to the parental EN13 cells, had telomerase activity, expressed embryonic stem cell markers and had a telomere-related transcriptome similar to hES cells. Subsequent culture of five out of six lines generally showed telomere shortening to lengths similar to that observed in the widely distributed iPS lines. However, the clone EH3, with relatively high levels of telomerase activity, progressively increased TRF length over 60 days of serial culture back to that of the parental hES cell line. CONCLUSION: Prematurely aged (shortened) telomeres appears to be a common feature of iPS cells created by current pluripotency protocols. However, the spontaneous appearance of lines that express sufficient telomerase activity to extend telomere length may allow the reversal of developmental aging in human cells for use in regenerative medicine.

Close relationship between serum concentrations of 1,5-anhydroglucitol and uric acid in non-diabetic male subjects implies common renal transport system.

BACKGROUND: 1,5-Anhydroglucitol is found in food. We determined factors other than glucosuria that affect serum 1,5-anhydroglucitol (1,5-AG) concentration. METHODS: The relationships between serum 1,5-AG concentration and metabolic parameters were investigated in 158 males with normal glucose tolerance verified by an oral glucose tolerance test. RESULTS: Serum uric acid was positively correlated to 2-h plasma glucose and serum 1,5-AG concentrations. Serum 1,5-AG levels were not different between hyperuricemic and normouricemic subjects, though those with normouricemia had lower 2-h plasma glucose concentrations than subjects with hyperuricemia. The association between 1,5-AG and uric acid in serum was still evident after adjustment with 2-h plasma glucose concentration. Multivariate regression analyses demonstrated that serum uric acid was an independent variable related to serum 1,5-AG and vice versa. CONCLUSIONS: 1,5-AG and uric acid may share in part a common renal tubular transport system, independent of glucose excretion.

Effects of thyroid hormone on serum glycated albumin levels: study on non-diabetic subjects.

Glycated albumin (GA) is used alongside glycated hemoglobin (HbA(1C)) as an indicator of glycemic control. Although serum GA levels are affected mainly by plasma glucose, they are also influenced by serum albumin metabolism. Thyroid hormone is known to promote albumin catabolism, and it is thus thought to affect serum GA levels. In the present study, the effects of thyroid hormone on serum GA measurements were investigated in patients with thyroid dysfunction. Six patients with untreated hypothyroidism and 17 patients with untreated thyrotoxicosis were investigated. Patients who had anemia or diabetes were excluded. A total of 25 non-diabetic, euthyroid individuals were enrolled as controls. HbA(1C), serum GA, thyroid-stimulating hormone (TSH), free triiodothyronine (T(3)), and free thyroxine (T(4)) levels were measured in all these subjects, and their relationships were examined. Although no intergroup differences were observed for HbA(1C), serum GA was significantly higher among patients with hypothyroidism than controls, and significantly lower among patients with thyrotoxicosis. Serum GA had a significant positive correlation with serum TSH and significant inverse correlations with free T(3) and free T(4). Thyroid hormone levels are inversely associated with serum GA levels. Cautions are necessary when evaluating serum GA levels in patients with thyroid dysfunction.

Fine mapping and DNA fiber FISH analysis locates the tobamovirus resistance gene L3 of Capsicum chinense in a 400-kb region of R-like genes cluster embedded in highly repetitive sequences.

The tobamovirus resistance gene L(3) of Capsicum chinense was mapped using an intra-specific F2 population (2,016 individuals) of Capsicum annuum cultivars, into one of which had been introduced the C. chinense L(3) gene, and an inter-specific F2 population (3,391 individuals) between C. chinense and Capsicum frutescence. Analysis of a BAC library with an AFLP marker closely linked to L(3)-resistance revealed the presence of homologs of the tomato disease resistance gene I2. Partial or full-length coding sequences were cloned by degenerate PCR from 35 different pepper I2 homologs and 17 genetic markers were generated in the inter-specific combination. The L(3) gene was mapped between I2 homolog marker IH1-04 and BAC-end marker 189D23M, and located within a region encompassing two different BAC contigs consisting of four and one clones, respectively. DNA fiber FISH analysis revealed that these two contigs are separated from each other by about 30 kb. DNA fiber FISH results and Southern blotting of the BAC clones suggested that the L(3) locus-containing region is rich in highly repetitive sequences. Southern blot analysis indicated that the two BAC contigs contain more than ten copies of the I2 homologs. In contrast to the inter-specific F2 population, no recombinant progeny were identified to have a crossover point within two BAC contigs consisting of seven and two clones in the intra-specific F2 population. Moreover, distribution of the crossover points differed between the two populations, suggesting linkage disequilibrium in the region containing the L locus.

Isolation and characterization of the three Waxy genes encoding the granule-bound starch synthase in hexaploid wheat.

Complete genomic DNA sequences of three homoeologous Waxy structural genes, located on the chromosomes 7A, 4A, and 7D in hexaploid wheat (Triticum aestivum L. cv. Chinese Spring), were separately determined and analyzed. Those structural genes in lengths from start to stop codon were 2781bp in Wx-7A, 2794bp in Wx-4A, and 2862bp in Wx-7D, each of which consisted of 11 exons and ten introns. They were closely similar to one another in the nucleotide sequences, with 95.6-96.3% homology in mature protein regions, 88. 7-93.0% in transit-peptide regions, and 70.5-75.2% in the introns. These wheat Waxy genes were GC-rich when compared with standard values for plant genomes reported so far. This was reflected in the extremely high G/C occupation frequency at the third position of the codons in the coding regions. The sequence divergence in the exon regions was mostly due to the substitution of nucleotides, whereas that found in the introns was attributed to substitution, insertion and/or deletion of nucleotides. Only the Wx-4A gene contained a trinucleotide insertion (CAA) in the region encoding the transit peptide. Most of the substitutions observed in the exon regions were categorized as synonymous, and higher sequence similarities (96.5-97. 4%) were conserved at the protein level. The phylogenetic tree obtained in terms of the amino acid sequence variations showed a well-resolved phylogenetic relationship among wheat Waxy genes and those from other plants.

[The effects of pleasantness of verbal messages on perceived deceptiveness in romantic relationships].

The present study examined the effects of pleasantness expressed in verbal messages on their perceived deceptiveness. The hypothesis was that pleasant messages are perceived as less deceptive than neutral or unpleasant ones. To test the hypothesis, three types of messages were constructed: pleasant, neutral, and unpleasant. Sixty-seven university students answered the questionnaire in which they rated, on seven-point semantic differential scales, perceived deceptiveness in one of the three types of messages. The result indicated that the unpleasant messages were perceived as the most deceptive, while the pleasant ones the least deceptive. The computer program "GPOWER" was used in order to obtain appropriate sample size.

Downregulation of protein kinase C by phorbol ester increases expression of epidermal growth factor receptors in transformed trophoblasts and amplifies human chorionic gonadotropin production.

Epidermal growth factor (EGF) and its homologue, transforming growth factor-alpha (TGF-alpha), regulate human chorionic gonadotropin (hCG) synthesis in the human placenta. The current study was designed to investigate the involvement of the protein kinase C pathway in EGF-mediated hCG-beta production by JAr choriocarcinoma cells. Downregulation of protein kinase C activity by chronic exposure to the phorbol ester, phorbol 12,13-dibutyrate (PDB), produced a greater increase in hCG-beta secretion than did activation of protein kinase C activity by short-term exposure to PDB. Pretreatment with the protein kinase C inhibitors calphostin and chelerythrine also resulted in enhanced basal and EGF-stimulated hCG-beta production. Individual concentrations (5 nM EGF and 500 nM PDB) that maximally stimulated hCG production, were additive in combination. The additive effect of PDB on EGF-induced hCG-beta secretion was mediated in part by increased JAr cell EGF-receptor concentrations detected by Western blot and Scatchard analyses. The results suggest that EGF and PDB stimulate hCG production in JAr cells by different but interactive mechanisms. It is speculated that downregulation of protein kinase C stimulates basal and EGF-mediated hCG-beta production by uninhibiting other signalling pathways that regulate hCG-beta secretion in trophoblasts.

[Color Doppler signal enhancement with SH/TH-508 in pancreatic tumors].

In this report, we showed the efficacy of a new contrast agent (SH/TA-508, Schering AG, Germany) for color Doppler imaging of the pancreatic tumors. In pancreatic ductal cancer, no enhancement of the lesion was observed, but vascular invasion by cancer became to be easily evaluated. On the other hand, hypervascular tumors such as islet cell tumor and cystadenocarcinoma, were increased in color Doppler signals of vessels by SH/TA-508. We concluded that SH/TA-508 was useful for evaluating the vascular invasion by pancreatic cancer as well as vascularity of hypervascular mass and solid component of cystic neoplasma.

Eicosanoid secretion by human endothelial cells exposed to normal pregnancy and preeclampsia plasma in vitro.

Eicosanoids play an important role in the pathogenesis of preeclampsia. The major eicosanoid metabolite reported to be secreted by endothelial cells, the vasodilator prostacyclin, is generally reduced in preeclampsia. By contrast, it was shown previously that prostacyclin secretion by cultured human umbilical vein endothelial (HUVE) cells is increased significantly after exposure to blood from preeclamptic women. In the current study, eicosanoid profiles in conditioned media from HUVE cells incubated with pregnancy plasma were analyzed by high-performance liquid chromatography, thin layer chromatography and quantitative radio- and enzyme immunoassays. More prostaglandin F2alpha, prostacyclin and 8-isoprostane were secreted after exposure to plasma from preeclamptic women than plasma from matched, normal pregnant patients. Predominant secretion of the vasoconstrictor prostaglandin F2alpha by HUVE cell cultures and a stimulatory effect of preeclampsia plasma on eicosanoid biosynthesis underscore the importance of bioactive lipids in the vasospasm associated with clinical preeclampsia.

Human umbilical vessels and cultured umbilical vein endothelial and smooth muscle cells lack detectable protein and mRNA encoding estrogen receptors.

OBJECTIVE: To identify and characterize estrogen receptors in human umbilical vascular tissues and in cultured cells derived from the human umbilical vein. METHODS: Human umbilical vein endothelial (HUVE) and human umbilical vein smooth muscle (HUVSM) cells were isolated. Immunohistochemical, radioligand binding. Western immunoblotting, and reverse transcription-polymerase chain reaction (RT-PCR) methods were used to detect estrogen receptors in vascular tissues and in cells derived from the umbilical cord. RESULTS: Estrogen receptor protein was not detected in either umbilical vessel tissue or in isolated HUVE or HUVSM cells. Messenger RNAs for the classic estrogen receptor (alpha) and estrogen receptor beta isoforms also were undetectable by RT-PCR. CONCLUSION: These findings suggest that the effects of estradiol observed in this widely used vascular model are mediated by very low concentrations of receptors that evade standard methods of detection. Alternatively, this steroid may affect umbilical vascular cells through mechanisms that do not involve the classic genomic estrogen-receptor pathway.

Elevated nonesterified fatty acid concentrations in severe preeclampsia shift the isoelectric characteristics of plasma albumin.

We previously hypothesized that the endothelial cell dysfunction observed in women with preeclampsia might be caused by an imbalance between circulating very low density lipoproteins and a cytoprotective pI 5.6 isoform of albumin, referred to as toxicity preventing albumin (TxPA). An accurate simplified method was developed to quantify TxPA in small volumes of pregnancy plasma by gel electrofocusing. This assay revealed that circulating TxPA concentrations in women with severe preeclampsia were significantly reduced compared to those in normal pregnant women and women with benign transient hypertension of pregnancy. Nonesterified fatty acids (NEFA) and triglycerides were elevated in plasma from women with severe preeclampsia compared to those in plasma from the two control groups. The inverse correlation between TxPA and NEFA values led us to analyze the NEFA bound to plasma albumin. Gas chromatography and mass spectrometry demonstrated no qualitative differences in the specific fatty acids bound to plasma albumin in severe preeclamptic and normal pregnant women. However, the quantity of NEFA bound to albumin was greater in preeclampsia plasma (2.5 mol NEFA/mol albumin) compared to that in normal pregnancy plasma (0.8 mol NEFA/mol albumin), accounting for the acidic pI shift observed in albumin from the former patients. Functional assays demonstrated that human very low density lipoprotein particles were toxic to human umbilical vein endothelial cells in vitro, but this toxicity was prevented by the addition of TxPA albumin to the culture medium.

Maternal and fetal modulators of lipid metabolism correlate with the development of preeclampsia.

The pregnancy syndrome preeclampsia is associated with placental dysfunction, dyslipidemia, and endothelial cell activation, and is a major cause of maternal and fetal morbidity and mortality. In this report, a nested case-control study of matched preeclamptic and normal pregnant women was used to investigate the association of maternal and fetal modulators of lipid metabolism with pregnancy outcome. Maternal body mass index (BMI), triglyceride levels, and nonesterified fatty acid (NEFA) concentrations were all significantly increased in women who developed preeclampsia (P < .01). Human placental lactogen (hPL), which is secreted by the syncytiotrophoblast layer of the fetal placenta and reportedly has lipolytic activity, also was found to be elevated in women with preeclampsia (P < .01). By contrast, hemoglobin levels were not found to be statistically different between the two groups of women, indicating that the increased plasma lipids and hPL were not a result of hemoconcentration in preeclamptic patients. The results suggest a multihit hypothesis for the pathophysiology of preeclampsia in which maternal obesity and a placental lipolytic hormone (hPL) converge to adversely affect free fatty acid concentrations in the maternal circulation.

Distribution between protein-bound and free forms of plasma cortisol in the gilt and fetal pig near term.

Thirty-five time-dated pregnant gilts were used to document plasma levels of total and free cortisol, corticosteroid-binding globulin (CBG) binding capacity, and percent distribution of cortisol among protein-bound (CBG and albumin) and free forms in the fetal pig during the last 24 days of gestation. Plasma from fetal pigs on days 110-114 of gestation (gestation length 114 days) had significantly higher levels of total cortisol (p < 0.01), percent albumin-bound and free cortisol (p < 0.10), and free cortisol concentration (p < 0.05) compared to samples on days 90, 100 and 105. Fetal plasma CBG binding capacity increased (p < 0.05) linearly from day 100 to 114. Fetal pigs located in the cervical region of the uterus had lower (p < 0.05) total and free cortisol and higher (p < 0.05) albumin and total protein concentrations compared to fetuses in the middle and oviductal regions. Total, percent free and free cortisol concentrations in maternal plasma on days 105-114 were greater (p < 0.10) than that measured on days 12-100 of gestation. These results suggest that the developmental patterns of plasma cortisol and CBG in the prenatal pig are directly related and highly similar to those of another precocious species, the sheep.

Aromatase gene expression and its exon I usage in human breast tumors. Detection of aromatase messenger RNA by reverse transcription-polymerase chain reaction.

The expression of aromatase in human breast tumors has been studied by the reverse-transcription polymerase chain reaction (RT-PCR) method on 70 breast tissue specimens. An RT-PCR analysis using two oligonucleotide primers derived from the exon II of the human aromatase gene revealed that aromatase mRNA was detected in all but three tissue specimens. Furthermore, primer-directed RT-PCR was performed to determine the exon I usage in aromatase mRNA in these breast tumor specimens. The analysis has revealed that exons I.3 and PII are the two major exon Is present in aromatase mRNA isolated from breast tumors, suggesting that promoters I.3 and II are the major promoters driving aromatase expression in breast cancer and surrounding adipose stromal cells. The RT-PCR analysis also detected two products, I.3A (334 bp in length) and I.3B (222 bp in length), when it was carried out using a primer derived from exon I.3 and a reverse primer derived from exon II. The nucleotide sequences of these products have been determined and indicate that I.3A contains a region which was previously thought to be an intron. In addition, RT-PCR analyses of RNA isolated from eight pairs of breast tumor and neighboring normal tissue specimens were performed to evaluate the exon I usage and the distribution of I.3A- and I.3B-containing aromatase RNA messages in breast tumor and neighboring normal tissues. The results suggest that I.3B- and I.3A-containing messages are mainly present in breast tumor and neighboring normal tissues, respectively. Finally, the exon I/promoter usage for aromatase expression in eight cell lines (skin fibroblast, MCF-7, MDA-MB-231, T-47D, SK-BR-3, JAR, OVCAR-3, and human adipose stromal cells) was examined by primer-directed RT-PCR analyses. These studies provide a basis for further evaluation of the control mechanism of aromatase expression and estrogen biosynthesis in breast tumors.

Interleukin-6 secretion in vitro is up-regulated in ectopic and eutopic endometrial stromal cells from women with endometriosis.

An in vitro model developed to compare human endometrial and endometriosis stromal cells was used to examine basal and stimulated expression of interleukin (IL-6). Stromal cells isolated from normal endometrium (NE) exhibited the lowest level of IL-6 secretion (84 pg/10(6) cells-48 h), whereas those cells isolated from endometriosis implants (EI) secreted the highest concentration of this inflammatory cytokine (46,284 pg/10(5) cells-48 h; P < 0.01). Eutopic endometrial stromal cells from women with endometriosis (EE) expressed an intermediate concentration of IL-6 (831 pg/10(6) cells-48 h). Stimulation of the various cultures with IL-1 beta dramatically augmented stromal cell production of IL-6. The mean concentrations of stimulated IL-6 secretion were 16,257, 37,800, and 264,290 pg/10(5) cells-48 h for NE, EE, and EI cells, respectively (P < 0.03). Exposure of the cell cultures to 10 nmol/L estradiol had little direct effect on IL-6 production. The results indicate that endometrial stromal cells isolated from tissues of women with and without endometriosis express IL-6 under basal and cytokine-stimulated conditions. Differential responsiveness among the three cell sources indicates that NE, EE, and EI cells have intrinsic quantitative differences in cytokine regulation.

[The screening of hepatitis virus and its efficacy].

1. Infection of hepatitis A virus (HAV) was prevented with hepatitis A vaccine. High risk groups of HAV infection should be inoculated this vaccine because Japanese peoples less than 40 years old didn't have immunity for HAV. 2. Infection of hepatitis E virus (HEV) was scarcely observed in Japan. 3. Infection of hepatitis B virus (HBV) by blood transfusion was eradicated after the screening with anti-HBc antibody for blood donors. And maternal transmissions of HBV and infections of HBV in hospital were protected by HB-globulin and hepatitis B vaccine. 4. Infection of hepatitis D virus (HDV) was protected by HB-globulin and hepatitis B vaccine. 5. Infection of hepatitis C virus (HCV) by blood transfusion markedly decreased after the screening with anti-HCV for blood donors. We can't prevent a maternal transmission of HCV but its frequency is low (about 10%). And acute hepatitis C due to an infection of HCV in hospital can be prevented by the treatment with interferon in the Workmen's Accident Compensation Insurance.

Quantitative analysis of Lewis antigens on erythrocytes by flow cytometry.

We have developed a method for the quantitative analysis of Lewis antigens on human red blood cells (RBC) using immunofluorescence labeling and flow cytometry. Initially, Lewis a and Lewis b (Le(a) and Le(b)) antigens were labeled with monoclonal anti-Le(a) or anti-Le(b) antibodies followed by labeling with the fluorescein isothiocyanate (FITC)-conjugated second antibody. This method was not sensitive enough to identify the Lewis antigens on RBC, although the FITC method is very commonly used for antigens on white blood cells. Next, we selected the enhanced labeling technique using the avidin-biotin procedure. Biotinylated anti-mouse IgM was used for the second label and the reaction with R-phycoerythrin (RPE)-conjugated streptavidin followed to produce the fluorescence. The method was found to be effective for our objectives. From the results analyzed by the enhanced labeling technique, differences were not found in either the levels of the antigen-positive percentage and the peak mean channel of Le(a) antigens on RBC in the groups of blood type O and A (in ABO system). On the other hand, both the levels of Le(b) antigens on RBC were higher in the groups of blood type O than in those of blood type A. We found both Le(a) and Le(b) antigens on RBC from a few blood type O subjects. We conclude that enhanced labeling and flow cytometry constitute a useful technique for the determination of Lewis antigens on RBC and that this method enables the precise quantification of such antigens.

Squirrel monkey corticosteroid-binding globulin: primary structure and comparison with the human protein.

Squirrel monkey (Saimiri sciureus) corticosteroid-binding globulin (CBG) is the product of a 1.6-kilobase mRNA in the liver. Analyses of two overlapping cDNAs revealed that the squirrel monkey CBG precursor comprises 406 amino acids, the first 22 residues of which exhibit 91% identity with the human CBG leader sequence. The mature form of squirrel monkey CBG, therefore, very likely comprises 384 amino acids and has a polypeptide mol wt of 42,854. Compared to human CBG, the squirrel monkey protein contains an additional residue (threonine) at position 144, and the two proteins exhibit 86% sequence identity if this is taken into account. Squirrel monkey CBG contains five consensus sites for N-glycosylation, four of which are located in analogous positions in human CBG, and has two cysteine residues in the same relative positions as the cysteines in human CBG. Unlike CBG in most other species, squirrel monkey CBG appears to circulate as a dimer, and its affinity for glucocorticoids is remarkably low. We, therefore, expressed cDNAs for human and squirrel monkey CBGs in Chinese hamster ovary (CHO) cells and compared the physico-chemical properties of the products with those of the corresponding serum proteins. Squirrel monkey CBG is produced by CHO cells as a dimer, and its subunit size heterogeneity is similar to that associated with CBG in serum. In addition, the cortisol-binding affinity of squirrel monkey CBG produced by CHO cells is similar to that of the natural protein and is 5- to 8-fold lower than that of natural or recombinant human CBG. Mutants in which a threonine at position 144 was either added to human CBG or subtracted from squirrel monkey CBG were also expressed in CHO cells. This demonstrated that this additional amino acid in the squirrel monkey CBG sequence may actively contribute to its propensity for spontaneous dimerization, but does not account for its relatively low steroid-binding affinity.

Aromatase gene is amplified in MCF-7 human breast cancer cells.

The levels of the aromatase gene and its expression in MCF-7 human breast cancer cells and seven additional cultured cells were investigated. Using normal human foreskin fibroblasts as the control, the aromatase gene appeared to be amplified in MCF-7 cells as shown by Southern and DNA slot blot analyses utilizing human placental aromatase cDNA as the probe. However, the promoter I.1 and the first exon of the aromatase gene were not amplified in MCF-7 cells based on results obtained from DNA slot blot analysis using oligonucleotide probes having sequences derived from those regions of human aromatase gene. Aromatase was expressed at a very low level in this cell line as indicated by Northern blot analysis to measure the level of aromatase mRNA, immunoprecipitation analysis to measure the level of aromatase protein, and aromatase activity measurement. Furthermore, nucleotide sequence analysis of the aromatase cDNA obtained from MCF-7 cells by PCR techniques, revealed no sequence difference from that of the enzyme expressed in placenta. These results lead us to conclude that the expression of aromatase in MCF-7 cells is under the control of an unusual promoter and aromatase gene expression is repressed at the transcriptional level in these cells.