Out-of-Hospital Cardiac Arrest in a Teaching Hospital in Hong Kong: Descriptive Study Using the Utstein Style

Objective

To describe, using the Utstein template, the characteristics of patients presenting with out-of-hospital cardiac arrest to a university teaching hospital in the New Territories of Hong Kong, and to evaluate survival.

Design

Prospective study.

Setting

The emergency department of a teaching hospital in the New Territories, Hong Kong.

Participants

Patients older than 12 years with non-traumatic out-of-hospital cardiac arrest who were transported to the hospital between 1 July 2002 and 31 December 2002.

Main outcome measures

Demographic data, characteristics of cardiac arrest and response time intervals of the emergency medical service presented according to the Utstein style, and also survival to hospital discharge rate.

Results

A total of 124 patients were included (49.2% male; mean age 71.9 years). The majority of cardiac arrests occurred in patients' home. The overall bystander cardiopulmonary resuscitation (CPR) rate was 15.3% (19/124). The most common electrocardiographic rhythm at scene was asystole, whilst pulseless ventricular tachycardia (VT)/ventricular fibrillation (VF) was found in 18.0%. The overall survival was 0.8% (1/124), and survival to hospital discharge was significantly higher for patients with VF or pulseless VT than those patients with other rhythms of cardiac arrest (11.1% versus 0%). The median witnessed/recognised collapse to defibrillation time was 14 minutes. The median prehospital time interval from collapse/recognition to arrival at hospital was 33 minutes.

Conclusion

The prognosis of out-of-hospital cardiac arrest in Hong Kong was poor. Major improvements in every component of the chain of survival are necessary.

Features discriminating SARS from other severe viral respiratory tract infections

This study investigated the discriminatory features of severe acute respiratory syndrome (SARS) and severe non-SARS community-acquired viral respiratory infection (requiring hospitalization) in an emergency department in Hong Kong. In a case-control study, clinical, laboratory and radiological data from 322 patients with laboratory-confirmed SARS from the 2003 SARS outbreak were compared with the data of 253 non-SARS adult patients with confirmed viral respiratory tract infection from 2004 in order to identify discriminatory features. Among the non-SARS patients, 235 (93%) were diagnosed as having influenza infections (primarily H3N2 subtype) and 77 (30%) had radiological evidence of pneumonia. In the early phase of the illness and after adjusting for baseline characteristics, SARS patients were less likely to have lower respiratory symptoms (e.g. sputum production, shortness of breath, chest pain) and more likely to have myalgia (p < 0.001). SARS patients had lower mean leukocyte and neutrophil counts (p < 0.0001) and more commonly had “ground-glass” radiological changes with no pleural effusion. Despite having a younger average age, SARS patients had a more aggressive respiratory course requiring admission to the ICU and a higher mortality rate. The area under the receiver operator characteristic curve for predicting SARS when all variables were considered was 0.983. Using a cutoff score of >99, the sensitivity was 89.1% (95%CI 82.0–94.0) and the specificity was 98.0% (95%CI 95.4–99.3). The area under the receiver operator characteristic curve for predicting SARS when all variables except radiological change were considered was 0.933. Using a cutoff score of >8, the sensitivity was 80.7% (95%CI 72.4–87.3) and the specificity was 94.5% (95%CI 90.9–96.9). Certain clinical manifestations and laboratory changes may help to distinguish SARS from other influenza-like illnesses. Scoring systems may help identify patients who should receive more specific tests for influenza or SARS.

The Role of RCAS1 and oxytocinase in immune tolerance during pregnancy

OBJECTIVES

To determine and compare the level of RCAS1 (receptor-binding cancer antigen expressed in SiSo cells) in placentas at term as well as oxytocinase/cystine amino peptidase (CAP) serum level a few days before labor in order to evaluate their possible role in the regulation of maternal immune response during pregnancy and in initiation of labor.

METHODS

We estimated the RCAS1 content in 44 placental tissue samples, using Western blot method. We also assessed CAP serum level by its enzymatic activity, using L-cystine-di-beta-naphthylamide as a synthetic substrate. The statistical analysis was performed using Shapiro-Wilk procedure. Student's t test was applied to compare the differences between parametric data. A value of p < 0.05 was considered significant.

RESULTS

RCAS1 was found in all placental tissue samples examined. The differences in the RCAS1 relative amount depended on the onset of labor, with the highest level in induced labor and the lowest in spontaneous labor. The differences were also observed in the CAP serum level with the highest level in pregnant women whose labor was induced.

CONCLUSIONS

We have observed a link between the expression of the two proteins examined and the onset of the labor. Therefore, we posit that RCAS1 and CAP may play a role in the downregulation of the maternal immune response during pregnancy and may participate in the initiation of the labor.

Antimicrobial peptides derived from heme-containing proteins: hemocidins

Deprived of heme and partially unfolded hemoglobin, myoglobin and cytochrome c display microbicidal activity against a broad spectrum of microorganisms with half maximal lethal dose estimated at micromolar concentrations. The intact proteins were ineffective. Antibacterial activity of these apohemoproteins was also sustained after digestion to approximately 50 amino acids long peptides but further fragmentation abolished microbicidal properties. The most active fragment of apomyoglobin (corresponding to 56-131 region) showed a pronounced effect on the E. coli membrane permeabilization and its action was sensitive to salt as well as to divalent cations concentrations. The membrane-directed effect was specific toward bacteria but no lipopolysaccharide binding properties were observed. No hemolytic properties, even at high peptide concentrations were found; however, a slight but dose-independent cytotoxic effect was observed on fibroblasts and hepatoma cells. The presented data suggest a 'carpet-like' mechanism of the membrane-directed activity and may result from exceptional abilities of hemoprotein-derived peptides to form alpha-helical structures. We postulate that the antimicrobial peptides obtained from the heme-containing proteins should be named hemocidins, in contrast to, e.g., hemorphins displaying opioid-like activity.

Performance specification for lower limb orthotic devices

OBJECTIVE

To establish the range of forces and moments applied to lower limb orthoses during ambulation by routine users.

DESIGN

Well-established gait analysis techniques were used to determine the loading at the major joints. It was assumed that the joint moments were transmitted by the orthosis encompassing any particular joint. Two hundred and five assessments of 164 patients were successfully completed by a consortium of four gait laboratories in Europe. The orthosis specification and patient clinical data were also recorded.

BACKGROUND

The design and development of orthoses has occurred largely by evolution rather than by formal engineering methods. In particular, formal design has been hampered by a lack of information on the forces and moments applied during ambulation.

METHODS

A standard gait analysis procedure was employed to capture the data. In-house biomechanical models were used to calculate the joint loading. Data were normalised with respect to patient weight and leg length.

RESULTS

It was found that the median maximum normalised ankle moment transmitted by an ankle foot orthosis was 0.15 and the maximum knee moment was 0.09. The greatest moment transmitted by the hip joint of a hip knee ankle foot orthosis was also 0.09. There was a wide variation in the data due to differences in the impairments of the test subjects.

CONCLUSION

It is possible to estimate the loads transmitted by an orthosis using established gait analysis procedures without the need for load measurement transducers. There is now a need both to collect a larger representative dataset and to perform validation studies with transducers.

Self-starting mode locking in a Cr:forsterite laser by use of non-epitaxially-grown semiconductor-doped silica films

We demonstrate RF sputtered, non-epitaxially-grown semiconductor nanocrystallite-doped silica films for mode locking a Cr:forsterite laser. We controlled the size and the optical properties of the nanocrystallites by varying the ratio of InAs to SiO(2) during fabrication. Femtosecond pump-probe measurements were performed to characterize the nonlinear optical properties of these films, revealing their lower saturation fluences. Using the InAs-doped silica films as saturable absorbers permitted self-starting Kerr-lens mode locking (KLM), generating pulses of 25-fs duration with 91-nm spectral bandwidth at 1.3 microm . We also describe saturable-absorber mode-locked operation without KLM and investigate its dependence on intracavity dispersion.

Antibacterial peptides of the moth Galleria mellonella

The work describes purification and biochemical characterization of two inducible antimicrobial peptides from the hemolymph of Galleria mellonella. The peptides were isolated by a sequence of reversed-phase chromatography steps from the hemolymph of larvae immunized with viable bacteria. The first peptide is a member of the cecropin family while the second one is rich in proline residues and has a unique sequence.

Antibacterial peptides of the moth Galleria mellonella

The work describes purification and biochemical characterization of two inducible antimicrobial peptides from the hemolymph of Galleria mellonella. The peptides were isolated by a sequence of reversed-phase chromatography steps from the hemolymph of larvae immunized with viable bacteria. The first peptide is a member of the cecropin family while the second one is rich in proline residues and has a unique sequence.

Molecular cloning and biochemical characterisation of proteases from Staphylococcus epidermidis

We report the complete coding sequence and the partial amino acid sequence (determined by chemical sequencing) of Staphylococcus epidermidis extracellular cysteine (Ecp) and serine (Esp) proteases. The first enzyme shows an extended sequence similarity to Staphylococcus aureus cysteine protease (staphopain) and the second one resembles the serine protease produced by that species. The region directly upstream of the sequence coding for the mature protein in both enzymes displays significant homology to the profragments encoded by sspB and sspA, respectively, thus suggesting that the characterised enzymes may also be produced as proproteins. Furthermore, we report some biological properties of the cysteine protease, contributing to a better understanding of its role as a possible virulence factor. The proteolytic activity of this enzyme was rapidly and efficiently inhibited by human alpha-2-macroglobulin; however, human kininogen as well as cystatins (A, C and D) were not inhibitory. Moreover, the protease was capable of inactivating, by limited proteolysis, both alpha-1-antitrypsin and HMW-kininogen, but neither alpha-1-antichymotrypsin nor antithrombin III.

Arginine-specific cysteine proteinase from porphyromonas gingivalis as a convenient tool in protein chemistry

RgpB, a cysteine proteinase produced by Porphyromonas gingivalis, exhibits proteolytic activity selectively directed against peptide bonds containing an arginine residue in the P1 position. Here we show that this enzyme can be used for very efficient and specific protein cleavage. RgpB is highly active even at high concentrations of denaturing agents, including urea (up to 6 M) and SDS (0.1%), both of them being commonly used for solubilization of insoluble proteins and peptides. Moreover, RgpB is able to digest polypeptide chains in buffers supplemented with 1% Triton X-100, 1% octyl or decylpyranoside, detergents employed for the enzymatic digestion of proteins transferred onto nitrocellulose membranes. These features render RgpB a suitable tool for use in protein chemistry.

Reconstitution of hepatitis C virus protease activities in yeast

The hepatitis C virus (HCV) protease genes (NS2/3 and NS3) were expressed in yeast with their natural substrates fused to a ligand-dependent transcriptional activator, the retinoic acid receptor (RARbeta). RARbeta can activate transcription in yeast cells in response to retinoic acids. We hypothesized that cis-cleavage at the NS2-3 or NS3-4A junctions by the appropriate HCV proteases would release RARbeta, thereby activating transcription of a reporter gene. Our results from Western blot analyses and reporter gene activation indicate that the wild-type NS2/3 and NS3 enzymes are catalytically active in yeast cells, whereas mutations in the catalytic domain of NS2(C993V) and NS3(S1165A) lead to inactive enzymes. We conclude that HCV NS2/3 and NS3 protease activities can be reconstituted in yeast.

Different catalytic properties and inhibitor responses of the goldfish brain and ovary aromatase isozymes

The brain and ovarian aromatase isozymes of goldfish (Carassius auratus) are encoded by different CYP19 genes. This study measured aromatase activity in the goldfish brain tissues. For a direct comparison of the properties of the two aromatase isozymes, Chinese hamster ovary cells were stably transfected with brain- and ovary-derived cDNAs (respectively, p450 arom B and -A) and the properties of the expressed isozymes were compared. The kinetic parameters of the two isozymes were determined using androstenedione and testosterone as substrates and compared to those of human aromatase. Inhibition profile analyses on the two isozymes were performed using seven inhibitors [4-hydroxyandrostenedione, 7 alpha-(4'-amino)phenylthio-1,4-androstadiene-3,17-dione, bridge (2,19-methyleneoxy)androstene-3,17-dione, aminoglutethimide (AG), CGS 20267, ICI D1033, and vorozole]. Except for AG, the compounds tested were found to be much stronger inhibitors against the ovary enzyme than the brain enzyme. In addition, the ovary isoform was more sensitive to two phytoestrogens, chrysin and 7,8-dihydroxyflavone, than the brain form. These studies reveal that catalytic properties of the goldfish aromatase isoforms are significantly different from those of human aromatase. In addition, differences in the K(i) values of aromatase inhibitors for the two goldfish isoforms suggest structural variance in the active sites of these isozymes.

Porphyromonas gingivalis DPP-7 represents a novel type of dipeptidylpeptidase

A novel dipeptidylpeptidase (DPP-7) was purified from the membrane fraction of Porphyromonas gingivalis. This enzyme, with an apparent molecular mass of 76 kDa, has the specificity for both aliphatic and aromatic residues in the P1 position. Although it belongs to the serine class of peptidases, it does not resemble other known dipeptidylpeptidases. Interestingly, the amino acid sequence around the putative active site serine residue shows significant similarity to the C-terminal region of the Staphylococcus aureus V-8 endopeptidase. The genes encoding homologues of DPP-7 were found in genomes of Xylella fastidiosa, Shewanella putrefaciens, and P. gingivalis. It is likely that at least in P. gingivalis, DPP-7 and its homologue, in concert with other di- and tripeptidases, serve nutritional functions by providing dipeptides to this asaccharolytic bacterium.

Effect of antimicrobial apomyoglobin 56-131 peptide on liposomes and planar lipid bilayer membrane

The horse apomyoglobin 56-131 peptide is a convenient object for studies on the recently discovered antimicrobial activities of haem-binding protein fragments called haemocidins. The purpose of this study was to determine the effect of this peptide on planar lipid bilayer membranes and on liposomes of different lipid compositions. Micromolar concentrations of the apomyoglobin 56-131 fragment disrupt phosphatidylserine/phosphatidylethanolamine planar lipid bilayers without discrete conductance changes. The observed detergent-like action is dependent on peptide concentration; the lower amount of peptide resulted in longer bilayer lifetime. The cholesterol has an inhibitory effect on peptide-induced liposome lysis as shown by calcein release from liposomes. Additionally, there was considerable lytic activity on liposomes formed from anionic lipids of the sort found in bacterial membranes. Circular dichroism (CD) experiments showed that the peptide had a disordered structure in aqueous solutions and folds gradually to form helices in both membrane-mimetic trifluoroethanol solutions as well as in liposome suspensions. The features of the apomyoglobin 56-131 fragment that are similar to the cationic antimicrobial peptides acting in a 'carpet-like' manner are discussed.

A T-cell-selective interleukin 2 mutein exhibits potent antitumor activity and is well tolerated in vivo

Human interleukin 2 (IL-2; Proleukin) is an approved therapeutic for advanced-stage metastatic cancer; however, its use is restricted because of severe systemic toxicity. Its function as a central mediator of T-cell activation may contribute to its efficacy for cancer therapy. However, activation of natural killer (NK) cells by therapeutically administered IL-2 may mediate toxicity. Here we have used targeted mutagenesis of human IL-2 to generate a mutein with approximately 3,000-fold in vitro selectivity for T cells over NK cells relative to wild-type IL-2. We compared the variant, termed BAY 50-4798, with human IL-2 (Proleukin) in a therapeutic dosing regimen in chimpanzees, and found that although the T-cell mobilization and activation properties of BAY 50-4798 were comparable to human IL-2, BAY 50-4798 was better tolerated in the chimpanzee. BAY 50-4798 was also shown to inhibit metastasis in a mouse tumor model. These results indicate that BAY 50-4798 may exhibit a greater therapeutic index than IL-2 in humans in the treatment of cancer and AIDS.

Cloning and characterization of a novel human histone deacetylase, HDAC8

Histone deacetylases (HDACs) are a growing family of enzymes implicated in transcriptional regulation by affecting the acetylation state of core histones in the nucleus of cells. HDACs are known to have key roles in the regulation of cell proliferation [Brehm, Miska, McCance, Reid, Bannister and Kouzarides (1998) Nature (London) 391, 597-600], and aberrant recruitment of an HDAC complex has been shown to be a key step in the mechanism of cell transformation in acute promyelocytic leukaemia [Grignani, De Matteis, Nervi, Tomassoni, Gelmetti, Cioce, Fanelli, Ruthardt, Ferrara, Zamir et al. (1998) Nature (London) 391, 815-818; Lin, Nagy, Inoue, Shao, Miller and Evans (1998), Nature (London) 391, 811-814]. Here we present the complete nucleotide sequence of a cDNA clone, termed HDAC8, that encodes a protein product with similarity to the RPD3 class (I) of HDACs. The predicted 377-residue HDAC8 product contains a shorter C-terminal extension relative to other members of its class. After expression in two cell systems, immunopurified HDAC8 is shown to possess trichostatin A- and sodium butyrate-inhibitable HDAC activity on histone H4 peptide substrates as well as on core histones. Expression profiling reveals the expression of HDAC8 to various degrees in every tissue tested and also in several tumour lines. Mutation of two adjacent histidine residues within the predicted active site severely decreases activity, confirming these residues as important for HDAC8 enzyme activity. Finally, linkage analysis after radiation hybrid mapping has localized HDAC8 to chromosomal position Xq21.2-Xq21.3. These results confirm HDAC8 as a new member of the HDAC family.

A yeast screen system for aromatase inhibitors and ligands for androgen receptor: yeast cells transformed with aromatase and androgen receptor

Endocrine disruptors are hormone mimics that modify hormonal action in humans and animals. It is thought that some endocrine disruptors modify estrogen and androgen action in humans and animals by suppressing aromatase activity. Aromatase cytochrome P450 is the key enzyme that converts C19 androgens to aromatic C18 estrogenic steroids. We have developed a novel aromatase inhibitor screening method that allows us to identify antiaromatase activity of various environmental chemicals. The screen was developed by coexpressing the human aromatase and the mouse androgen receptor in yeast cells, which carry the androgen-responsive ss-galactosidase reporter plasmid. Functional expression of aromatase in yeast has been demonstrated using the [3H]-water release assay with intact cells as well as with yeast microsomes. The aromatase activity could be blocked by known aromatase inhibitors such as aminoglutethimide (AG). Yeast-produced androgen receptors were able to transactivate a yeast basal promoter linked to an androgen-responsive element in response to androgens. The resultant triple yeast transformant responded to the treatment of testosterone, androstenedione, or 5 alpha-dihydrotestosterone (5 alpha-DHT). In the absence of the aromatase inhibitor AG, transcriptional activation was observed only for the nonaromatizable androgen 5 alpha-DHT. However, the two aromatizable androgens (testosterone and androstenedione) induced the reporter activity in the presence of AG. Using this yeast-based assay, we confirmed that two flavones, chrysin and alpha-naphtholflavone, are inhibitors of aromatase. Thus, this yeast system allows us to develop a high-throughput screening method, without using radioactive substrate, to identify aromatase inhibitors as well as new ligands (nonaromatizable androgen mimics) for the androgen receptors. In addition, this screening method also allows us to distinguish nonandrogenic aromatase inhibitors from inhibitors with androgenic activity. This yeast screening method will be useful to screen environmental chemicals for their antiaromatase activity and for their interaction with androgen receptor.

Size-exclusion chromatography performed in capillaries. Studies by liquid chromatography-mass spectrometry

Miniaturization of the chromatographic column led to increased sensitivity and shortened time of analysis. In our work we applied 300 microm I.D. capillaries packed with a novel stationary phase Superdex Peptide for the size-exclusion chromatography, capable of separating molecules within the mass range of 0.1-7 kDa. Here we proved that such capillary columns can operate effectively at high sensitivity. Several peptide mixtures were efficiently chromatographed and analyzed on line with electrospray ionization mass spectrometry as a detection technique. A CNBr peptide map, derived from human globin alpha subunit, was effectively separated using this method. These fragments are difficult to elute from the reversed-phase column at low pH, therefore, such approach can be considered as a complementary to other separation techniques, in particular for analyzing hydrophobic components and complex mixtures.

Prolyl tripeptidyl peptidase from Porphyromonas gingivalis. A novel enzyme with possible pathological implications for the development of periodontitis

Porphyromonas gingivalis possesses a complex proteolytic system, which is essential for both its growth and evasion of host defense mechanisms. In this report we characterized, both at a protein and genomic level, a novel peptidase of this system with prolyl tripeptidyl peptidase activity. The enzyme was purified to homogeneity, and its enzymatic activity and biochemical properties were investigated. The amino acid sequence at the amino terminus and of internal peptide fragments enabled identification of the gene encoding this enzyme, which we refer to as PtpA for prolyl tripeptidyl peptidase A. The gene encodes an 82-kDa protein, which contains a GWSYGG motif, characteristic for members of the S9 prolyl oligopeptidase family of serine proteases. However, it does not share any structural similarity to other tripeptidyl peptidases, which belong to the subtilisin family. The production of prolyl tripeptidyl peptidase may contribute to the pathogenesis of periodontal tissue destruction through the mutual interaction of this enzyme, host and bacterial collagenases, and dipeptidyl peptidases in the degradation of collagen during the course of infection.

Heat shock proteins (HSP70) as biomarkers in ecotoxicological studies

Hsp70, so-called stress proteins, were studied in the centipede Lithobius mutabilis when exposed in laboratory tests to different concentrations of the insecticide dimethoate (DMT; 0, 0.012, 0.111 mg kg-1 dwt), the detergent linear alkilobenzene sulfonate (LAS; 0, 16, 80, 400, 2000, 10,000 mg kg-1 dwt), and copper (Cu; 0, 56, 167, 500, 1000, 1500 mg kg-1 dwt) and in the field in captured animals from polluted (2 and 4 km from a zinc-and-lead smelter) and unpolluted (35 and 40 km from the smelter) areas. Hsp70 in centipedes were also tested for seasonal differences (March and September) in field-captured animals and for a temperature effect under laboratory conditions (5, 15, and 25 degrees C). Moreover, hsp70 were examined in housefly (Musca domestica) pupae after rearing larvae on food medium contaminated with DMT or LAS. Hsp70 were found in all animals tested, including controls, and their levels were not clearly related to the laboratory treatment with chemicals or temperature or to the degree of contamination in polluted areas. In centipedes from unpolluted areas, a significant seasonal difference in hsp70 content was found. The problems with using hsp70 as a universal biomarker in ecotoxicological studies are discussed.

Drosophila ecdysone receptor functions as a constitutive activator in yeast

Transcriptional activation of the Drosophila ecdysone receptor (EcR) was studied in yeast cells, which carry a reporter plasmid containing the ecdysone response element in the absence or presence of its heterodimeric partners, ultraspiracle protein (USP) or human retinoid X receptor (RXRalpha). High constitutive transcriptional activation was detected in the yeast strain expressing EcR, but not USP or RXRalpha in the absence of ponasterone or muristerone A. Incubation of these ligands with yeast cells coexpressing EcR and USP or RXRalpha did not enhance the constitutive transcriptional activity. However, specific ligand binding using [3H]ponasterone A as a radioactive ligand was detected only in yeast extracts prepared from the yeast strain coexpressing EcR and USP, but not from yeast strains expressing only EcR or USP. The ligand binding characteristics of the EcR/USP complexes were similar to those reported in an insect cell line with a Kd value of 1.8 nM for [3H]ponasterone A. These data are in contrast to mammalian cell transfection studies, and indicate that the EcR is the only member of the nuclear receptor superfamily of ligand-activated transcription factors which functions as a constitutive transcriptional activator in yeast, although the EcR/USP complexes exhibit normal ligand binding properties.

Identification of amino acid residues required for a specific interaction between Src-tyrosine kinase and proline-rich region of phosphatidylinositol-3' kinase

The binding of ligand to B-cell antigen receptors (BCR) leads to the activation of receptor-associated Src-family kinases and phosphatidylinositol-3' kinase (PI-3 kinase). Although it has been demonstrated that SH3 domains of several Src-family kinases interact with PI-3 kinase by binding to a proline-rich region of PI-3 kinase in vitro, there is no direct evidence to support their interaction in vivo. Thus, we utilized the yeast two-hybrid assay to reconstitute this protein-protein interaction. This genetic screen clearly indicates that the interaction between SH3 domain of Fyn and the proline-rich region (residues: 80-104) of PI-3 kinase is highly specific. Mutational analysis revealed that amino acid residues Asp92, Tyr93, Arg96 and Thr97 of the SH3 domain of Fyn are essential for interacting with the proline-rich peptide of PI-3 kinase.

Isolation, antimicrobial activities, and primary structures of hamster neutrophil defensins

Hamster (Mesocricetus auratus) neutrophil granules contain at least four microbicidal peptides belonging to the defensin family. These compounds were purified from granule acid extracts by reverse-phase chromatography and termed HaNP-1 to -4 (hamster neutrophil peptide). HaNP-1 and HaNP-3 revealed the most bactericidal activity, with a 50% inhibitory concentration of 0.3 to 0.8 microg/ml for Staphylococcus aureus and Streptococcus pyogenes strains. The HaNP-4 was always isolated in concentrations exceeding about 10 times the concentrations of other hamster peptides, but its antibacterial activity as well as that of HaNP-2 was relatively lower, probably as a result of conserved Arg residue substitutions. Other microorganisms were also tested, and generally, hamster defensins exhibited less potency against gram-negative bacteria. The amino acid sequence of hamster defensins showed a high percentage of identity to the sequence of mouse enteric defensins, reaching about 60% identical residues in the case of HaNP-3 and cryptdin 3.

Evidence for the presence of different alpha-1-proteinase inhibitor genes products in mouse plasma

The plasma alpha-1-proteinase inhibitor (API) of three mouse species Mus domesticus, M. caroli and M. pahori was isolated. Each of the species isoforms were then separated by chromatofocusing; however, no significant differences in association rate constants toward human neutrophil elastase and bovine chymotrypsin were observed. The amino-acid sequence of the P'1-P'15 C-terminal fragments of the API variants indicate that mouse plasma contains at least two different active API isoforms in the case of M. domesticus (five API genes) but only one active API isoform in M. pahori and M. caroli (one API gene).

Hamster antithrombin III: purification, characterization and acute phase response

Antithrombin III was purified to homogeneity from hamster plasma by affinity chromatography on heparin-agrose, ion-exchange chromatography on Mono Q and size-exclusion chromatography on TSK G3000SWG column with 50% yield. The molecular mass of hamster antithrombin III was estimated at 62.5 kDa and the absorption coefficient (A280 nm 1%, 1 cm) at 6.48 (in 0.1 M sodium phosphate pH 7.0). Several isoforms of the inhibitor were detected with the pI in range of 4.95-5.25. The protein contains all residues characteristic for complex-type carbohydrate chains. The N-terminal amino acid sequence shows 84% of identity to mouse and 76% to human analogue. The hamster antithrombin III gives low immunological cross-reactivity with antibodies to human antithrombin III. Initiation of the acute phase response only slightly affected the plasma concentration of inhibitor (+/- 10% within 72-h period). The kinetic data suggest high efficiency in bovine and human thrombin inhibition. In summary, the study shows only similarities between hamster and other mammal antithrombins.

Differential transcriptional regulation of the apoAI gene by retinoic acid receptor homo- and heterodimers in yeast

Several members of the nuclear receptor superfamily including RXR (retinoid X receptor) bind to a specific retinoic acid response element (site A) of the apoAI promoter. However, transcriptional activation of the apoAI gene by different homo- and heterodimeric forms of RXR or RAR (retinoic acid receptors) cannot be evaluated in mammalian cells, which contain endogenous RXR or RAR. In order to circumvent this limitation, we assessed the DNA-binding activities and transcriptional activation of different homo- and heterodimers of these receptors in yeast. Electrophoretic mobility shift assays (EMSA) demonstrated that yeast expressed RARalpha does not bind to site A of the apoAl promoter, whereas binding of RARbeta to site A is ligand-dependent. Both RARalpha and RARbeta form heterodimers with RXRalpha and bind to site A with high affinity. These DNA-binding studies correlate with the transcriptional data, which indicated that RARbeta but not RARalpha activates transcription from site A in response equally well to 9-cis and all-trans retinoic acids. 9-cis RA is a more potent ligand than all-trans RA to activate transcription via RXR/RAR heterodimers. We conclude that this yeast expression system is a useful tool to elucidate the 'transactivation code' for apoAl site A via specific combinations of different homo and heterodimeric versions of RXR and RAR.

Transcriptional regulation of the apoAI gene by hepatic nuclear factor 4 in yeast

Hepatocyte Nuclear Factor 4 (HNF-4), a liver-enriched orphan receptor of the nuclear receptor superfamily, is required for the expression of a wide variety of liver-specific genes including apoAI. To explore the possibility that site A of the apoAI gene enhancer might also be the target for HNF-4 without the interference of endogenous mammalian cell proteins that also bind to site A, we tested the ability of HNF-4 to activate transcription from site A in yeast cells. Electrophoretic mobility shift assays (EMSA) and Scatchard plot analysis demonstrated that yeast produced HNF-4 binds to site A with an affinity two times higher than that of yeast produced RXR alpha. Mapping analysis indicated that the 5' portion of site A containing two imperfect direct repeats (TGAACCCTTGACC) and the sequence of the trinucleotide spacer (CCT) between these imperfect repeats are critical determinants for selective binding and transactivation by HNF-4. Similar observations were obtained when these mutated versions of site A were evaluated by transient cotransfection assays in CV1 cells. We conclude that the unique structural determinants of site A in conjunction with the differential binding affinity of HNF-4 for site A may play a fundamental role in apoAI gene regulation.

Retinoid X receptor homodimers function as transcriptional activators in yeast

The possibility that different retinoids activate transcription from a specific retinoic acid (RA)-responsive element known as site A via different homo and heterodimeric versions of RA receptors cannot be evaluated in mammalian cells because they contain endogenous RA receptors (RAR). However, this limitation can be overcome by using yeast cells, which do not contain endogenous RAR, to study retinoid signaling pathways. Here, we describe heterologous expression of the human retinoid X receptor (RXR alpha) in yeast and hormone-dependent activation of a reporter construct containing site A upstream from a yeast promoter fused to the lacZ gene of Escherichia coli. Western blot analysis of yeast extracts containing RXR alpha revealed a distinct immunoreactive polypeptide co-migrating with the mammalian-produced RXR alpha. Electrophoretic mobility shift assays demonstrated that RXR alpha produced in yeast binds efficiently to site A in the absence of 9-cis-RA. However, transcription activation experiments showed that RXR alpha transactivates a yeast basal promoter linked to site A only in the presence of 9-cis-RA. We conclude that RXR alpha homodimers bind to site A in the absence of 9-cis-RA, but function as ligand-dependent transactivators in yeast cells. This retinoid-responsive transcription unit created in yeast cells provides a powerful genetic tool for the systemic unraveling of the synergistic interactions between RXR alpha and its heterodimeric partners.

Expression of functional chicken oviduct progesterone receptors in yeast (Saccharomyces cerevisiae)

The cDNAs encoding full-length chicken oviduct progesterone receptor B (PRB) and a truncated receptor (C1C2) lacking the amino-terminal domain were expressed in yeast (Saccharomyces cerevisiae) using a ubiquitin fusion system. The expression of the fusion protein is under the control of a copper-responsive yeast metallothionein promoter, and the fusion protein is subsequently cleaved by the yeast host enzyme to produce receptor protein. Western immunoblot analyses of yeast extracts containing full-length PRB revealed a polypeptide co-migrating with authentic chicken oviduct PRB. Using a polyclonal antibody (907) directed against the "hinge" region of the authentic chicken progesterone receptor, a 42-kDa polypeptide was detected by Western analysis in yeast extracts containing C1C2 receptors. Standard hormone binding assays indicated that these receptors produced in yeast cells exhibited steroid binding affinity and specificity characteristic of the authentic chicken progesterone receptor. To test for progesterone receptor-mediated activation of transcription in yeast, reporter plasmids were constructed to transform yeast cells expressing PRB or C1C2 receptors. The reporter gene contained two copies of a progesterone response element upstream of the yeast proximal CYC1 promoter fused to the beta-galactosidase gene of Escherichia coli. The induction of beta-galactosidase activity by PRB and C1C2 was strictly dependent on specific ligand and the presence of a progesterone response element. However, overproduced C1C2 receptors had an adverse effect on the transcription of the lacZ gene. It was found that when overproduced C1C2 was activated by progesterone, an inhibitory effect on normal yeast cell growth was evident. These observations suggest that C1C2 is a potent trans-acting factor in yeast and that the amino-terminal domain of the chicken progesterone receptor may play a role in selective modulation of target gene activation.

Mutational analysis of the chicken progesterone receptor

Oligonucleotide-directed site mutagenesis was used to prepare a series of chicken progesterone receptor deletion mutants in an attempt to elucidate structure-function relationships of the receptor. These mutants spanned the entire 659-amino acid coding region of the A form of the receptor. The ability of these mutants to bind progesterone was analyzed following in vitro transcription and translation. Results obtained indicate that a large portion of the protein ranging from amino acid 420 to the extreme carboxyl terminus is necessary to maintain the protein in a conformation which is capable of binding hormone. Following transient cotransfection of mutant receptor proteins into CV-1 cells along with a reporter gene containing an authentic GRE/PRE (PRE-TK-CAT), our results indicated that any deletion throughout the entire molecule results in a decrease in transcriptional activation. Most of these decreases result from an inability of the mutant receptor proteins to bind DNA or hormone. However, two areas of the receptor have been identified which are unrelated to either DNA or hormone binding but markedly affect the ability of the receptor to transactivate target genes.

Regulation of spermatogenesis: the shark testis model

Spermatogenesis is a unique developmental sequence dependent on FSH and androgen. Due to the complex organization of the mammalian testis, however, mechanistic details of regulation are largely unknown. Using the dogfish shark (Squalus acanthias) in which there is a cystic mode of spermatogenesis and a topographic separation of different germ cell stages within the testis, we have obtained new information of general relevance on stage-related biochemical and morphological changes and have proposed a model in which steroids serve as parahormonal regulators of the spermatogenic progression. In addition, techniques developed for culturing staged spermatocysts (intact Sertoli/germ cell units) and isolated, staged Sertoli cells demonstrate the usefulness of this model for studying spermatogenic regulation under defined conditions in vitro.

A novel steroid-binding protein in the testis of the dogfish Squalus acanthias

In an earlier study, we identified and characterized a testicular estrogen receptor in the spiny dogfish (Squalus acanthias); however, in this species estrogen receptors were located exclusively in nuclear subfractions. We describe here a nonreceptor, sex hormone-binding protein (SBP) present in Squalus testicular cytosol and distinguishable in its physicochemical characteristics from both the estrogen receptor and serum SBP of the same species. Cytosol (100,000g supernatant) was prepared by differential centrifugation of testicular homogenates and incubated with [3H]estradiol (E2) or [3H]testosterone (T) (10-15 nM +/- 100-fold excess radioinert competitor) to determine total and nonspecific bound radioactivity. The testicular SBP had a broad specificity: E2 = T greater than progesterone greater than 5 alpha-dihydrotestosterone greater than estrone, but diethylstilbestrol was not an effective competitor. It displayed a high affinity for both E2 and T (Kd = 2.2-2.5 X 10(-9) M), sedimented at 8-10 S in both low- and high-salt sucrose gradients, and migrated more slowly than BSA during polyacrylamide disc gel electrophoresis. The testicular SBP-E2 complex was relatively stable (t1/2 = 160 min) compared to the serum SBP-E2 complex (t1/2 = less than 30 min). The testicular SBP was not found in nuclear subfractions nor did it bind to DNA-cellulose affinity columns. Its intratesticular distribution was stage-dependent: Zone III (mature spermatids) greater than Zone II (spermatocytes) greater than Zone I (stem cells and spermatogonia). Moreover, increased binding activity corresponded exactly to the hypertrophy and differentiation of Sertoli cells in the same zones, pointing to this cell as the possible site of SBP synthesis.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of short days on aromatization and accumulation of nuclear estrogen receptors in the hamster brain

Exposure of hamsters to short days increases sensitivity to the negative feedback effects of testosterone (T) but decreases responsiveness to the behavioral effects of the hormone. Since T is metabolized in the brain to 5 alpha-dihydrotestosterone (DHT) and estradiol, which differentially affect gonadotropin secretion and sex behavior, it is reasonable to postulate that daylength can modulate neural responses by quantitative or qualitative alterations in T metabolism and subsequent receptor binding of active hormone. Experiments reported here focused on aromatization and the nuclear accumulation of estrogen receptors. Adult male hamsters were maintained for 6-12 wk in long (14:10 LD) or short (8:16 LD) daily photoperiods. Both intact and castrated animals were used to assess direct effects of short days versus changes due to short-day-induced testicular regression. Discretely dissected regions of the brain (preoptic area, POA; hypothalamus, HTH; and corticomedial amygdala, CMA) or limbic blocks (LIM) comprised of all three regions were assayed for estrogen-synthesizing activity (aromatase) and estrogen-binding activity (receptors). Aromatase was estimated in vitro by conversion of [7-(3)H] androstenedione to [3H] estrogen and in vivo by measuring increases in nuclear estrogen receptor levels after injection of aromatizable androgen. Receptor-binding activity was assayed in crude cytosolic and nuclear extracts by incubating samples with [3H] estradiol +/- 100-fold excess inert estradiol, and separating free and bound steroids by Sephadex LH-20 gel filtration. When aromatase was assayed in homogenates prepared from discrete brain regions of individual hamsters, significantly lower activity was found in the HTH of short-day animals than in long-day controls. This effect was seen in both intact and castrated animals, which indicates that it was not mediated by the testis. Decreased enzyme activity in the POA and CMA of short-day hamsters was not significant, nor was there an effect of castration independent of short days. Low levels of nuclear estrogen receptors were present in LIM of intact males, but these were reduced after castration or concomitant with testicular regression after short-day exposure. This suggests that the hamster testis normally secretes estrogen or aromatizable androgen. A single injection of estradiol or aromatizable androgen (T or androstenedione) increased nuclear receptors in LIM of castrated animals. Cytosolic receptors were not different in short-day vs. long-day hamsters, nor were there differences in nuclear receptor levels after a single estradiol injection.(ABSTRACT TRUNCATED AT 400 WORDS)

Tissue and species specificity of unmasked nuclear acceptor sites for the estrogen receptor of Squalus testes

The testicular estrogen receptor of the shark Squalus acanthias is restricted to nuclear subfractions when tissue is homogenized in low salt buffers and adheres tightly to nuclei and DNA-cellulose even when exposed to high salt conditions. Therefore, we examined the binding characteristics of this receptor to chromatin subfractions from homologous and heterologous tissues. Squalus chromatin linked to cellulose and partially deproteinized by 0-8 M guanidine hydrochloride (GuHCl) gave extraction patterns similar to those obtained with mammalian and avian chromatin. Chromatin as prepared in our laboratory contained no bound estrogen receptor. The binding pattern of the [3H]estradiol-labeled nuclear estrogen receptor to chromatin fractions from Squalus testicular zones I/II (containing spermatogonia, spermatocytes, and high receptor levels) revealed maximal binding activity (acceptor sites) on chromatin previously extracted with 2-4 M GuHCl (350% increase over unextracted chromatin), with a 40% decrease from maximal binding at 5-8 M GuHCl. By contrast, binding to chromatin from zone III (containing spermatozoa and little or no detectable receptor) showed no major peak and 4 times less binding at 3 M GuHCl-extracted chromatin. We have previously shown that zones I and II contain the majority of testicular receptors and, presumably, are the primary sites of estrogen action, whereas receptor activity in zone III is minimal (less than 5%), indicating a secondary or nontarget tissue. Squalus testicular [3H]estradiol-receptor complexes bound minimally to rabbit uterine chromatin. Likewise, [3H]estradiol-receptor complexes from rabbit uterus, Squalus oviduct, or mouse testis bound minimally to Squalus testicular chromatin. Thus, maximal binding occurred only with Squalus zones I/II chromatin and Squalus testicular receptor. The binding of [3H]estradiol-receptor complexes to testicular chromatin (zones I/II) was of high affinity (Kd = 1.9 X 10(-10) M) and low capacity and was optimal in the presence of 150 mM KCl, but was unaffected by the addition of urea in an amount similar to that of Squalus body fluids (300 mM). [3H]Estradiol binding to chromatin required undenatured receptor and was competitively inhibited by radioinert estradiol-receptor complexes, confirming saturability of acceptor sites. The affinity of the Squalus estrogen receptor for homologous chromatin was in the same range as that reported for other systems, despite the unusual nuclear extractability characteristics of Squalus receptor. This study provides new evidence for tissue and species specificity of receptor binding to chromatin acceptor sites.

Stage-dependent changes in steroidogenic enzymes and estrogen receptors during spermatogenesis in the testis of the dogfish, Squalus acanthias

In the spiny dogfish (Squalus acanthias), germ cells and adjacent steroidogenic elements are topographically segregated within the testis according to stage of development. In the experiments reported here, we have taken advantage of this favorable anatomical arrangement to demonstrate stage-specific variations in steroidogenic enzymes and estrogen receptor number. The testes of Squalus collected in July-November were sectioned transversely and further subdivided into three zones as follows: I) germinal bed plus immature lobules with spermatogonia; II) lobules with primary or secondary spermatocytes; III) lobules with spermatids or mature spermatozoa. The morphology of these zones was verified by light microscopy and, in a separate study, by electron microscopy. Through the course of spermatogenesis, Sertoli cells increased dramatically in size and in the abundance of steroidogenic organelles. By contrast, interstitial tissue was sparse in all stages of development, and only relatively undifferentiated Leydig-like cells were present. Microsomes prepared from each zone were incubated with [3H] progesterone, [3H]17 alpha-hydroxyprogesterone, or [3H]androstenedione to evaluate androgen and estrogen biosynthetic potentials. Based on product formation, 17 alpha-hydroxylase and C-17,20-lyase activities increased progressively from less mature to more mature regions (zone III greater than II greater than I), whereas aromatase was greatest in regions undergoing meiosis or early spermiogenesis (zone II). These enzymes were not detected in semen, although C21 substrates were converted to unidentified polar metabolites in high yield. Estrogen receptors were concentrated in immature zones (zone I greater than II greater than III), and the percentage of occupied receptors revealed the same distribution. Semen and epigonal tissues were receptor negative. We conclude that Sertoli cells are responsible for steroidogenesis in Squalus testis and that hormone production is keyed to the spermatogenic cycle. The data are consistent with an important role for androgens during spermatid maturation and/or after sperm release, but reveal that estrogen actions are expressed primarily during early spermatogenic stages. This report demonstrates the usefulness of unconventional animal models for obtaining new information of general relevance.

Characterization of estrogen receptors in the hamster brain

Although the hamster is frequently used as an experimental animal for studying reproductive neuroendocrinology and sex behavior, estrogen receptors (ER) in the central nervous system have not been fully characterized. Using Sephadex LH-20 gel filtration and DNA-cellulose affinity chromatography, estrogen binding macromolecules having the physicochemical properties of classical ER were identified in cytosolic and nuclear extracts of brain tissues. These receptors exhibited high affinity for estradiol (Kd = 10(-9) M), limited capacity (30-50 fmol/g tissue), and estrogen specificity; however, competition studies indicate that brain and uterine ER have different binding kinetics. The neuroanatomic distribution of ER was similar in males and females with highest levels in the limbic brain and consistently low levels in remaining forebrain and mid/hindbrain. No sex differences in receptor number or other binding parameters were evident. Sucrose gradient centrifugation showed that cytosolic ER sedimented in the 7-8S region of a 5-20% linear gradient (no salt), whereas nuclear ER had a sedimentation coefficient of 5S under high ionic strength. On DNA-cellulose affinity columns, these receptors had an elution maximum of 0.18 M NaCl. After a single injection of estradiol, nuclear ER increased and cytosolic ER were depleted. The lower estradiol binding affinity and receptor levels in hamster brain as compared to the rat are consistent with observed species differences in neural sensitivity to estrogen. We expect these data in hamsters, a markedly photosensitive species, to provide a basis for future studies examining the role of receptors in mediating the effects of day-length on steroid dependent feedback and behavioral responses.

Exclusive nuclear location of estrogen receptors in Squalus testis

An estrogen (E)-binding molecule having both occupied and unoccupied sites is restricted to nuclear subfractions in the testis of the spiny dogfish (Squalus acanthias). We investigated the hypothesis that a species characterized by high body-fluid osmolarity (1010 mosM) has an estrogen receptor (ER) that binds to chromatin with high affinity and consequently resists redistribution during tissue processing. Although the steroid binding and sedimentation properties of the Squalus nuclear ER conformed to those of classical ER, its elution maximum from DNA-cellulose was unusually high (0.55 M NaCl). A tendency to adhere tightly to cell nuclei was reflected in the high salt concentration (0.43 M KCl) required to extract 50% of the receptors from the nuclear compartment during homogenization and in the stability of the nuclear ER population in the presence of high concentrations of a nonionic solute (urea) or increased buffer volume. Mixing and redistribution experiments showed that nuclear ER could be quantitatively and qualitatively measured in cytosolic extracts, ruling out the possibility that soluble receptors were being masked. Although Squalus oviduct ER was similar to that of testis, ER in the testis and liver of a related elasmobranch (Potamotrygon) that maintains osmotic equilibrium at 300 mosM more closely resembled mammalian ER in its elution maximum from DNA-cellulose (0.22 M NaCl) and cytosolic/nuclear ratios in low-salt buffers. We conclude that Squalus testis has a single ER pool located exclusively in the nuclear compartment. These observations support a revised concept of steroid action and further indicate that the chromatin affinity of the hormone-ER complex is an important factor in determining subfractional distribution during tissue processing.

Characterization of an estrogen receptor in the turtle testis

Using DNA-cellulose affinity chromatography, an estrogen-binding component having the properties of a classical estrogen receptor was characterized from testicular cytosol of the freshwater turtle, Chrysemys picta. This putative cytoplasmic receptor exhibited high affinity (Kd = 7.0 X 10(-10) M), low capacity (1-4 fmol/mg protein), and steroid binding that was specific for estrogens. It was not present in plasma, muscle, kidney, or lung. A temperature-dependent conversion of turtle testicular estrogen receptor from 4 to 5 S occurred on DNA-cellulose columns, and resembled that in mammalian testis and other target tissues. After a single injection of estrogen at 3 hr, cytoplasmic receptors were depleted with a concomitant increase of nuclear receptors. Identification in turtle testis of an estrogen-binding macromolecule having the physicochemical properties of mammalian estrogen receptors is further evidence that receptors have been widely conserved in many tissue types through vertebrate phylogeny and supports the idea that the testis is an important target of estrogen action.

Estradiol binding activity in epididymal cytosol of the turtle, Chrysemys picta

Estrogen binding activity was investigated in the epididymis of the turtle, Chrysemys picta using DNA-cellulose affinity chromatography. A component binding estradiol-17 beta specifically with high affinity (Kd:8.0 X 10(-10) M) and limited capacity (20 fmol/mg protein) was demonstrated in the epididymal cytosol. In addition, binding of estradiol-17 beta was sensitive to excess (100-fold) diethylstilbestrol or natural estrogens (estradiol-17 beta, estrone, and estriol) but not to progesterone or androgens (testosterone and 5 alpha-dihydrotestosterone). The specific estrogen binding macromolecules eluted from DNA-cellulose columns sedimented at 4-5 S in linear 5-20% sucrose gradients. These characteristics suggest the presence of an estrogen receptor in this androgen target organ.

The differentiation of Leydig cells, steroidogenesis, and the spermatogenetic wave in the testis of Necturus maculosus

The study of seminiferous tubule--Leydig cell interactions in relation to specific germ cell stages during the cycle of the seminiferous epithelium is extremely difficult in most mammalian species due to the continual presence of different spermatogenetic stages in the testis from the onset of puberty. The problem is also compounded by the uniform distribution of both seminiferous tubules and interstitial tissue throughout the entire testis. This difficulty can be circumvented, however, by studying certain species where there is a topographical distribution of germ cell stages within the testis. The urodele amphibian Necturus maculosus exhibits a breeding cycle during which a longitudinal wave of spermatogenesis occurs along the length of the testis, resulting in a spatial and temporal segregation of differentiating germ cells. Moreover, this topographical pattern of spermatogenesis is also reflected in the degree of development of adjacent Leydig cells. This anatomical arrangement allows distinct testicular regions to be obtained using a dissecting microscope. The isolated zones, containing germ cells and Leydig cells in various stages of development, were analyzed for 17 alpha-hydroxylase, C-17,20-lyase, and aromatase activities (key enzymes for the synthesis of androgens and estrogen), estrogen binding, and cytochrome P-450 content. Functional parameters were then correlated with the morphology of Leydig cells in the various zones observed by both light and electron microscopy. It was found that there existed a distinct correlation between the state of differentiation of the leydig cells, their steroidogenic potential, and the distribution of estrogen receptors. These results in Necturus indicate indicate in this species, at least, the steroidal microenvironment of different germ cell associations may be quite specific.

Estrogen receptors in the turtle brain

Estrogen binding activity in the CNS of the freshwater turtle, Chrysemys picta, was investigated using DNA-cellulose affinity chromatography. An estrogen binding component (EBC) with the characteristics of an estrogen receptor species was demonstrated in the brain cytosol extracts from both sexes. This EBC exhibited high affinity (K d = 10 -10 M), low capacity (n = 0.8 to 6.0 fmol/mg cytosol protein) and binding specificity. The bound estradiol-17 beta which adhered to DNA-cellulose was sensitive to excess synthetic and natural estrogens (DES, E2, E1 and E3) but not to progesterone and androgens (5 alpha- DHT and T). Specific estradiol-17 beta binding was not detected in plasma or non-target tissues such as lung, kidney and muscle. The topographic distribution of cytoplasmic EBC was similar in males and females, with binding highest in the hypothalamus-preoptic areas (HPOA) followed by the remaining forebrain (RFB). The mid/hindbrain (HB), consisting of the optic lobes, cerebellum and underlying brain stem had significantly lower concentrations of EBC. Monthly data (from May to October) suggest that variations in EBC concentrations occur during the year.