Serum concentrations of legacy, alternative, and precursor per- and polyfluoroalkyl substances: a descriptive analysis of adult female participants in the MIREC-ENDO study.

BACKGROUND: Several legacy and emerging per- and polyfluoroalkyl substances (PFAS) have been regulated around the world. There is growing concern over the proliferation of alternative PFAS, as well as PFAS precursors. Biomonitoring data for PFAS are critical for assessing exposure and human health risk. METHODS: We collected serum samples from 289 adult female participants in a 2018-2021 follow-up study of the Maternal-Infant Research on Environmental Chemicals (MIREC) Canadian pregnancy cohort. Samples were analyzed for 40 PFAS using ultra-performance liquid chromatography-tandem mass spectrometry. For those compounds with > 50% detection, as well as the sum of these compounds, we describe serum concentrations and patterns of exposure according to sociodemographic and obstetrical history characteristics. RESULTS: 17 out of 40 PFAS were detected in > 50% of samples with 7 of these detected in > 97% of samples. Median [95th percentile] concentrations (µg/L) were highest for PFOS (1.62 [4.56]), PFOA (0.69 [1.52]), PFNA (0.38 [0.81]), and PFHxS (0.33 [0.92]). Geometric mean concentrations of PFOA and PFHxS were approximately 2-fold lower among those with more children (≥ 3 vs. 1), greater number of children breastfed (≥ 3 vs. ≤ 1), longer lifetime duration of breastfeeding (> 4 years vs. ≤ 9 months), and shorter time since last pregnancy (≤ 4 years vs. > 8 years). We observed similar patterns for PFOS, PFHpS, and the sum of 17 PFAS, though the differences between groups were smaller. Concentrations of PFOA were higher among "White" participants, while concentrations of N-MeFOSE, N-EtFOSE, 7:3 FTCA, and 4:2 FTS were slightly higher among participants reporting a race or ethnicity other than "White". Concentrations of legacy, alternative, and precursor PFAS were generally similar across levels of age, education, household income, body mass index, and menopausal status. CONCLUSIONS: We report the first Canadian biomonitoring data for several alternative and precursor PFAS. Our findings suggest that exposure to PFAS, including several emerging alternatives, may be widespread. Our results are consistent with previous studies showing that pregnancy and breastfeeding are excretion pathways for PFAS.

Adverse birth outcomes related to concentrations of per- and polyfluoroalkyl substances (PFAS) in maternal blood collected from pregnant women in 1960-1966.

BACKGROUND: Prior animal and epidemiological studies suggest that per- and polyfluoroalkyl substances (PFAS) exposure may be associated with reduced birth weight. However, results from prior studies evaluated a relatively small set of PFAS. OBJECTIVES: Determine associations of gestational PFAS concentrations in maternal serum samples banked for 60 years with birth outcomes. METHODS: We used data from 97 pregnant women from Boston and Providence that enrolled in the Collaborative Perinatal Project (CPP) study (1960-1966). We quantified concentrations of 27 PFAS in maternal serum in pregnancy and measured infant weight, height and ponderal index at birth. Covariate-adjusted associations between 11 PFAS concentrations (>75% detection limits) and birth outcomes were estimated using linear regression methods. RESULTS: Median concentrations of PFOA, PFNA, PFHxS, and PFOS were 6.189, 0.330, 14.432, and 38.170 ng/mL, respectively. We found that elevated PFAS concentrations during pregnancy were significantly associated with lower birth weight and ponderal index at birth, but no significant associations were found with birth length. Specifically, infants born to women with PFAS concentrations ≥ median levels had significantly lower birth weight (PFOS: ß = -0.323, P = 0.006; PFHxS: ß = -0.292, P = 0.015; PFOA: ß = -0.233, P = 0.03; PFHpS: ß = -0.239, P = 0.023; PFNA: ß = -0.239, P = 0.017). Similarly, women with PFAS concentrations ≥ median levels had significantly lower ponderal index (PFHxS: ß = -0.168, P = 0.020; PFHxA: ß = -0.148, P = 0.018). CONCLUSIONS: Using data from this US-based cohort study, we found that 1) maternal PFAS levels from the 1960s exceeded values in contemporaneous populations and 2) that gestational concentrations of certain PFAS were associated with lower birth weight and infant ponderal index. Additional studies with larger sample size are needed to further examine the associations of gestational exposure to individual PFAS and their mixtures with adverse birth outcomes.

[The effects of inhaled steroids withdrawal in COPD]. / Impact du sevrage des corticostéroïdes inhalés dans la BPCO.

The key pathophysiological feature of chronic obstructive pulmonary disease (COPD) is an abnormal inflammatory bronchial reaction after inhalation of toxic substances. The priority is the avoidance of such toxic inhalations, but the use of anti-inflammatory drugs also seems appropriate, especially corticosteroids that are the sole anti-inflammatory drug available for this purpose in France. The risks associated with the prolonged use of these parenteral drugs are well known. Inhalation is therefore the optimal route, but inhaled drugs may also lead to adverse consequences. In COPD, there is an inhaled corticosteroids overuse, and a non-satisfactory respect of the guidelines. Consequently, their withdrawal should be considered. We reviewed seven clinical studies dealing with inhaled corticosteroids withdrawal in patients with COPD and found that included populations were heterogenous with different concomitant treatments. In non-frequent exacerbators receiving inhaled corticosteroids outside the recommendations, withdrawal appears to be safe under a well-managed bronchodilator treatment. In patients with severe COPD and frequent exacerbations, the risk of acute respiratory event is low when they receive concomitant optimal inhaled bronchodilators. However, other risks may be observed (declining lung function, quality of life) and a discussion of each case should be performed, especially in case of COPD and asthma overlap.

[The place of inhaled corticosteroids in COPD]. / Place des corticostéroïdes inhalés dans la BPCO.

INTRODUCTION: Clinical trials have provided some evidence of a favorable effect of inhaled corticosteroids on the frequency of exacerbations and on the quality of life of patients with chronic obstructive pulmonary disease (COPD). In contrast, ICS have little or no impact on lung function decline and on mortality. STATE OF THE ART: Inhaled corticosteroids are recommended only in a minority of COPD patients, those with severe disease and repeated exacerbations and probably those with the COPD and asthma overlap syndrome. However, surveys indicate that these drugs are inappropriately prescribed in a large population of patients with COPD. Overtreatment with inhaled corticosteroids exposes these patients to an increased risk of potentially severe side-effects such as pneumonia, osteoporosis, and oropharyngeal candidiasis. Moreover, it represents a major waste of health-care spending. CONCLUSION: Primary care physicians as well as pulmonologists should be better aware of the benefits as well as the side-effects and costs of inhaled corticosteroids.

Long-term reduction in poly(dimethylsiloxane) surface hydrophobicity via cold-plasma treatments.

Poly(dimethylsiloxane), PDMS, a versatile elastomer, is the polymer of choice for microfluidic systems. It is inexpensive, relatively easy to pattern, and permeable to oxygen. Unmodified PDMS is highly hydrophobic. It is typically exposed to an oxygen plasma to reduce this hydrophobicity. Unfortunately, the PDMS surface soon returns to its original hydrophobic state. We present two alternative plasma treatments that yield long-term modification of the wetting properties of a PDMS surface. An oxygen plasma pretreatment followed by exposure to a SiCl4 plasma and an oxygen-CCl4 mixture plasma both cause a permanent reduction in the hydrophobicity of the PDMS surface. We investigate the properties of the plasma-treated surfaces with X-ray photoelectron spectroscopy (XPS) and contact angle measurements. We propose that the plasma treated PDMS surface is a dynamic mosaic of high- and low-contact-angle functionalities. The SiCl4 and CCl4 plasmas attach polar groups that block coverage of the surface by low-molecular-weight groups that exist in PDMS. We describe an application that benefits from these new plasma treatments, the use of a PDMS stencil to form dense arrays of DNA on a surface.

Investigation of arthritic joint destruction by a novel fibroblast-based model.

The key pathologic mechanism in rheumatoid arthritis (RA) is the destruction of cartilage by fibroblasts. In a severe combined immunodeficient (SCID) mouse model, this process can be modulated by gene transfer using invasive LS48 fibroblasts. This study aims to investigate the effect of interleukins (IL) -11 and -12 on cartilage destruction when transferred into LS48, and of IL-15 when transfected into non-invasive 3T3 cells; to compare three transduction systems (a lentiviral vector system, a retroviral vector system, and a particle-mediated gene transfer); and to establish an in vitro cartilage destruction system based on LS48 cells. Transduced fibroblasts were injected into SCID mice knee joints, and disease progression assessed microscopically. Distinctive morphologic pattern revealed invasion of fibroblasts into the articular cartilage by transfected, as well as non-transfected, LS48 cells. IL-12 and IL-15 did not alter swelling or cartilage destruction. Animals treated with IL-11-transfected cells showed reduced cartilage damage but no changes in swelling. Efficacy of gene transfer to establish transfected fibroblasts was shown to be >85% for lentiviral transfer, compared to <10% for retroviral transfer and gene gun. Furthermore, cells were co-incubated with porcine cartilage. Transduction of IL-11 led to a reduction of apoptosis in chondrocytes. These findings suggest that cartilage destruction by invasive fibroblasts can be modulated by gene transfer. Lentiviral vector systems offer the most effective approach for gene transduction. In vitro fibroblast/cartilage co-cultures present a convenient system for the assessment of novel therapeutic strategies toward reduction of articular destruction.

Therapeutic use, efficiency and safety of the proteolytic pineapple enzyme Bromelain-POS in children with acute sinusitis in Germany.

The therapeutic efficiency and safety of the proteolytic enzyme bromelaine obtained from pineapple (Bromelain-POS, Ursapharm GmbH, Saarbrücken, Germany) was evaluated in children under the age of 11 years diagnosed with acute sinusitis. Data from 116 patients from 19 centres located across Germany were analysed in a pharmacoepidemiological cohort study. Patient cohorts were either treated with Bromelain-POS (N = 62), in combination with Bromelain-POS and standard therapies (N = 34), or with standard therapies (N = 20). The primary parameter measuring effectiveness of the different treatment groups was the duration of symptoms. The shortest mean period of symptoms was observed in patients treated with Bromelain-POS alone (6.66 days), followed by the standard therapy (7.95 days) and those treated with a combination of Bromelain-POS and the standard therapy (9.06 days). Patients of the Bromelain-POS monotherapy group showed a statistically significant faster recovery from symptoms (p = 0.005) compared to the other treatment groups. One 10-year-old male patient, with a known pineapple allergy, showed a self-limiting mild allergic reaction. No other unwanted side-effects were reported. This trial documents that the proteolytic pineapple enzyme Bromelain-POS is widely used in the treatment of young children diagnosed with acute sinusitis in Germany and that the use of proteolytic enzymes can benefit such patients.

Cytokine release of whole blood from adult female donors challenged with mistletoe lectin-1 standardised mistletoe extract and E. coli endotoxin or phytohaemagglutinin (PHA).

Cytokine (TNF, alpha, interleukin-6) release of whole blood from healthy donors was challenged with mistletoe extract standardised for mistletoe lectin-1 (sML) and control substances (E. coli endotoxin; phytohaemagglutinin). The rationale of this investigation was non-proven warnings that pro-inflammatory cytokines induce by the application of standardised mistletoe lectins may induce tumor cell proliferation. These investigations provided evidence that non-cytotoxic concentrations of sML did not induced enhanced TNFa or interleukin-6 secretion compared to non-challenged control cells. Cytotoxic concentrations of sML, however, induced significantly higher cytokine levels than the control, obviously due to non-physiological stimuli. Immunomodulation with clinically relevant, low-dose sML incubation did not induce proinflammatory cytokine secretion in vitro.

Why is smoking a risk factor for sudden infant death syndrome?

Smoking is a major risk factor for both Sudden Infant Death Syndrome (SIDS) and respiratory tract infections. Such infections, both viral and bacterial, also increase the SIDS risk. This study investigated the effect of cigarette smoke at two stages of infection: 1) mucosal surface colonization; 2) induction and control of inflammatory responses. For colonization, RSV or influenza A infected cells bound several bacterial species in significantly higher numbers due to increased expression of host cell antigens. Buccal epithelial cells from smokers bound significantly more bacteria. For Staphylococcus aureus, this was associated with increased tar levels. Some SIDS deaths have been proposed to result from high levels of pro-inflammatory mediators elicited by infection and/or cigarette smoke during a developmental period when infants are less able to control inflammatory responses. Inflammatory reponses were compared between blood samples from smokers (n = 42) and non-smokers (n = 60) stimulated with TSST-1 or LPS. Non-smokers had significantly higher IL-6 (P = 0.011), IFN (P = 0.003) and IL-10 (P = 0.000) baseline levels. Non-smokers had higher IFN (P = 0.008) and IL-1 (P = 0.001, 0.007) responses to LPS and higher IL-10 responses to TSST-1 (P < 0.05) and LPS (P < 0.000). This study highlights that smoking increases the SIDS risk by greater susceptibility to viral and bacterial infections and enhanced bacterial binding after passive coating of mucosal surfaces with smoke components. In animal models, IL-10 reduced the lethal effect of staphylococcal toxins. In this study, smokers had lower IL-10 responses toTSST-1 and LPS. Dose response effects of cigarette smoke exposure needs to be established in relation to inflammatory response control and infantile infections.

Evidence for a genetic component in sudden infant death syndrome.

There is increasing evidence that inflammatory responses have been elicited in some Sudden Infant Death Syndrome (SIDS) infants and that these responses are under genetic control. The objective of this study was to investigate the hypothesis that the cytokine responses of SIDS parents (n = 41) differed significantly from control donors (n = 61). Blood samples were stimulated with the staphylococcal toxin TSST-1 and LPS from Eschericia coli and assessed for production of TNF, IL-1, IL-6, IFN and IL-10. In response toTSST-1 (P < 0.02) and LPS (P < 0.002), SIDS parents produced higher levels of IL-1 than the controls. SIDS parents produced higher levels of IFN in response to TSST-1 compared to LPS (P < 0.001) although in response to LPS, the IFN (P = 0.0008) and IL-6 (P < 0.0002) responses of the SIDS parents were lower than those of the controls. For TNF and IL-10, there was little difference between the two groups unless the effect of smoking was considered. As part of this work, a small pilot genotyping study was carried out using DNA from SIDS parents (n = 10), control donors (n = 10) and Bangladeshi subjects (n = 10). An IFN polymorphism (3/3) was found in 40%,15.4% and 0% of donors respectively. Staphylococcal toxins have been identified in SIDS infants therefore this study highlights the importance of assessing IL-1 levels. Determination of cytokine polymorphisms and consideration of interactions between these and environmental factors such as smoking in high, average and low risk ethnic groups will assist in establishing the contribution of these factors to an infant's susceptibility to SIDS.

Standardized mistletoe extract augments immune response and down-regulates local and metastatic tumor growth in murine models.

The immunomodulatory and antimetastatic activity of standardized aqueous mistletoe extract (sME) was evaluated in BALB/c-mice. Regular subcutaneous (s.c.) applications (three times per week for 14 consecutive days; 2, 20, 100 and 500 micrograms per injection and mouse) up-regulated thymocyte and peripheral blood leukocyte counts in tumor-bearing mice. Tumor weight and tumor volume were significantly down-regulated after application of sME doses greater than 20 micrograms per injection. To check the influence of sME treatment on growth of experimental metastases, RAW 117 H 10 lymphosarcoma cells and L-1 sarcoma cells were intravenously inoculated into BALB/c-mice to establish liver and lung colonization, respectively. sME was regularly administered starting 24 hours after tumor cell challenge. Organ colonization was investigated on day 14 after tumor cell inoculation and demonstrated statistically significant (p < 0.05) reductions of experimental liver and lung metastases for sME-treated mice.

Application-dependent immunomodulating and antimetastatic efficacy of thymic peptides in BALB/c-mice.

The immunomodulating and antimetastatic activity of clinically approved, low molecular weight, standardized thymic peptide (TP) preparations was evaluated in BALB/c-mice. Daily applications (subcutaneously, s.c.; intraperitoneally, i.p.; intramusculary, i.m.) of two commercially available TP preparations (7 consecutive days, 10, 50 and 100 micrograms per mouse and injection) up-regulated the thymus weight and thymocyte counts as well as peripheral blood leukocyte and lymphocyte counts in liver metastases-bearing mice. The immunomodulating activity of TP application was most pronounced and statistically significant for thymus weight and counts of thymocytes, leukocytes and lymphocytes after s.c. administration of both TP preparations and concentrations. I.p. and i.m. TP-injections were less effective at reaching statistical significance, however, for defined dosages and parameters, only. To evaluate the influence of TP on experimental liver metastases, RAW 117 lymphosarcoma cells were intravenously inoculated into BALB/c-mice. TP (10, 50, 100 micrograms/mouse) were s.c., i.p. and i.m. administered daily for 7 consecutive days starting 24 hours after tumor cell challenge. Liver colonization was investigated on day 14 after tumor cell inoculation and demonstrated a statistically significant (p < 0.05) reduction of experimental liver metastases for s.c. (both preparations and concentrations) as well as i.p. and i.m. (dose-dependent) TP-treated mice.

Application of standardized mistletoe extracts augment immune response and down regulates metastatic organ colonization in murine models.

The immunomodulatory and antimetastatic activity of standardized aqueous mistletoe extracts from plants grown on fir trees (ME-A) and pine trees (ME-P) were evaluated in BALB/c-mice. Regular subcutaneous (s.c.) and intraperitoneal (i.p.) applications (three times per week for 14 consecutive days; 5 and 50 microg per injection and mouse) upregulated thymus weight and peripheral blood leukocyte counts in tumor bearing mice. To check the influence of ME-A and ME-P treatment on growth of experimental metastases, RAW 117 H 10 lymphosarcoma cells and L-1 sarcoma cells were intravenously inoculated into BALB/c-mice to establish liver and lung colonization. ME-A and ME-P were regularly administered starting 24 h after tumor cell challenge. Organ colonization was investigated on day 14 after tumor cell inoculation and demonstrated statistically significant (P<0.05) reductions of experimental liver and lung metastases for ME-A and ME-P treated mice.

Enhanced aesthetics using provisionalization.

The proper fabrication of provisional restorations is integral to the overall success of restorative dentistry, as these templates are the initial architecture for the completed case. In a clinical setting, restorations may be utilized for an extended period, during which time the clinician and patient must feel confident. Due partially to a new generation of dental materials with unique properties, provisionalization can be predictably achieved. This article reviews the clinical criteria for the fabrication of interim restorations using a light cure/dual phase temporary crown and bridge material (Provipont DC, Ivoclar Vivadent, Amherst, NY) and its effect on the overall success of restorative procedures, including anterior and posterior restorations.

Respiratory burst of human polymorphonuclear leukocytes in response to the galactoside-specific mistletoe lectin.

The phagocytic activity of human polymorphonuclear leukocytes (PMNLs) towards Staphylococcus aureus Cowan 1 was evaluated in chemiluminescence assays. As to check its activating ability, galactoside-specific mistletoe lectin (ML-1) was coincubated with PMNLs which were then challenged with S. aureus. Statistically significant (p < 0.001) chemiluminescent response (correlating with phagocytic activity) could be demonstrated at optimal experimental condition, viz: 1 x 10(6) PMNLs incubated with 0.005 ng ML-1 for 30 and 60 minutes before S. aureus challenge. Other experimental schedules (different timing and PMNL/ML-1 concentrations) did not present with statistically relevant changes in chemiluminescent response. These studies suggest that optimal ML-1 concentrations enhance the phagocytic activity of PMNLs which might be of benefit in thus treated patients as to prevent (or lower the rate of) infections under antineoplastic therapy.

Induction of autoimmunity by immunization of mice with human thyrotropin receptor.

The development of autoimmunity was investigated after repeated immunizations with human thyrotropin receptor (hTSH-R) of five congenic strains of female and male mice. After each immunization, free T3 levels and antibodies to hTSH-R and to six peptides of the hTSH-R were assayed. Our results showed that H-2s and H-2q female mice developed features of autoimmunity such as antibody responses to hTSH-R and to hTSH-R peptides, transient variations in the levels of free T3 thyroid hormone, and lymphocytic infiltrations in their thyroid glands. Concerning the antibody responses to hTSH-R peptides, we found that peptide P1 (352-366) contained a major B cell epitope. Furthermore, strain-specific B cell epitope was exemplified by peptide 92 (12-30) and two male- and female-specific B cell epitopes were located in peptides 91 (32-46) and 93 (316-330), respectively. These features appeared rather related to hyperthyroidism.

Production of Ab2 beta, anti-idiotypic monoclonal antibodies, specific for human thyrotropin receptor.

We had previously selected five monoclonal antibodies (mAb1) upon their specific binding to human thyrotropin (hTSH). These mAbs1, which are specific for two distinct epitopes of the hTSH beta-chain, also inhibit the hTSH binding to human thyroid membrane preparations. We then immunized BALB/c mice with the various mAbs1 in attempt to generate anti-idiotypic Abs (Ab2) directed to the hTSH receptor (hTSHR). Five hybridomas secreting monoclonal antibodies (mAb2) to the hTSHR were selected from one mouse immunized with the mixture of the five mAbs1. These monoclonal antibodies to the hTSHR were selected upon their ability to specifically bind to the hTSHR. Moreover, we showed that binding of mAbs2 to the individual mAbs1 used for immunization was specifically inhibited by hTSH and not by insulin or by human chorionic gonadotrophin, a highly related glycoprotein hormone. The five mAbs2 inhibited the binding of iodine-labeled hTSH to its receptor by 8 to 41%; moreover, two of them stimulated the adenylate-cyclase system of the thyroid cells. With respect to their properties, mAbs2 were classified as mAb2-beta.

Characterization of monoclonal antibodies to the human thyrotropin receptor.

We have produced four monoclonal antibodies (mAbs), 34A, 49G, 11E7, and 12E3, which bind the human TSH receptor (hTSH-R) when expressed on a human thyroid cell line (GEJ), freshly dissociated human and murine thyroid cells, or Chinese hamster ovary cells stably transfected with the hTSH-R gene. These mAbs were obtained after immunization of DBA/1 mice with affinity-purified TSH-binding sites from GEJ cells. Biochemical studies, including sodium dodecyl sulfate-polyacrylamide-gel electrophoresis, Western blot, and immunoprecipitation of solubilized GEJ cell membranes or human thyroid cells showed that most of the mAbs recognized two bands: one located at 46-48 kilodaltons and the other at 86-88 kilodaltons. Inhibition of [125I]hTSH binding to solubilized porcine membranes (TSH-receptor auto-antikörper assay) or Chinese hamster ovary cell membranes previously transfected with hTSH-R gene showed that mAb 34A recognizes the hTSH-binding site of both receptors. In contrast, mAbs 49G, 11E7, and 12E3 recognize a structure located near the hTSH-binding site. Lastly, the ability of these mAbs to stimulate murine thyroid function was investigated by measuring cAMP production and iodide accumulation. The 34A mAb, which fully competes with [125I]TSH for binding to hTSH-R, was able to induce both functions. Conversely, the 12E3 mAb, which was the least potent inhibitor of [125I]TSH binding to hTSH-R-transfected cells had no effect. A relationship was, therefore, established between the capacity of mAb to hTSH-R to inhibit [125I]hTSH binding and their ability to induce thyroid functions.

Differential effect of glycosylation on the expression of antigenic and bioactive domains in human thyrotropin.

Enzymatic deglycosylation of human thyroid-stimulating hormone (hTSH) was shown to result in a mixture of partially and fully deglycosylated forms of the hormone by gel electrophoresis, silver staining and immunoblotting. Radioiodination of the enzymatic digest, followed by gel filtration and concanavalin A-Sepharose chromatography allowed to separate two different forms of partially deglycosylated [125I]hTSH and a fully deglycosylated hormone. The final recovery was of approx. 60% for [125I]hTSH deglycosylated in its beta-subunit, of 30% for [125I]hTSH missing the oligosaccharide in beta and one in alpha but only of 10% for [125I]hTSH deglycosylated in both the alpha- and beta-subunits. Gel electrophoresis under non-denaturing conditions showed that each form migrated distinctly from free subunits and reverse-phase high performance liquid chromatography after reduction and carboxymethylation identified the presence of the two subunits. Mapping of [125I]hTSH derivatives with polyclonal, monoclonal and anti-peptide antibodies allowed to identify two novel glycosylation-independent epitopes preserved in deglycosylated hTSH while the main immunogenic determinant was lost. When assayed in a bioassay with FRTL-5 cells, the hormone deprived of its beta-linked carbohydrate chain was found to be as effective as the native hormone on cAMP production and cell growth. In contrast, the fully deglycosylated derivative proved to stimulate cAMP release but appeared to be definitely less potent on thyroid cell growth. Our findings thus demonstrate that glycosylation of the alpha-subunit but not that of the beta-subunit is essential to express the domains involved in hTSH immunoreactivity as well as those controlling the post-receptor biological activity of the hormone.