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PubMed2006

Bioactivity of human chorionic gonadotropin produced in frozen-thawed embryo transfer cycles with exogenous hormone replacement.

Human chorionic gonadotropin (HCG) is the glycoprotein hormone in pregnancy. It is known that hCG molecule has a variety of isoforms showing different potency in bioactivity. Taking advantage of rat Leydig cell assay to evaluate hCG bioactivity, we first tried to predict the prognosis of pregnancy in hormone replacement (HR)-cryopreserved embryo transfer cycles. There was no significant difference in serum estradiol (E2) level, immuno-hCG, or bioactive to immunoreactive hCG ratio (b/i) between normal pregnancies and miscarriages at 4 weeks of gestation. Linear regression did not show a significant correlation in E2 or b/i between normal pregnancies and miscarriages. The same analysis was performed on serum samples collected from spontaneously pregnant patients. In normal pregnancies b/i was significantly lower than that in miscarriages while serum E2 was significantly higher. The linear regression analysis was also performed to clarify the correlation between E2 and b/i, and no significant correlation was observed. To confirm the effect of E2 on hCG production, we treated trophoblastic cells with E2. E2 increased the immunoreactivity of hCG to a non-physiologically high concentration; however, it did not change its bioactivity, suggesting that E2 did not change hCG bioactivity by affecting trophoblasts directly. In this study, we presumed it possible to speculate the prognosis of the pregnancy in spontaneous cycles from b/i of hCG, but not in HR cycles. It is suggested that process of hCG secretion could undergo different endocrine regulations between the artificial sex steroid replacement cycles and spontaneous cycles with corpus luteum function.

Animals↗

PubMed1991

Bioactivity of gonadotropins.

It is now certain that both gonadotropins, LH and FSH, are synthesized, stored, and released within the circulation, and excreted as heterologous isoforms that can be distinguished by differences in their bioactive to immunoreactive potential and isoform distribution patterns. The bioactivity (which in this article has been defined as the ability of LH to induce T production in rat interstitial cells and FSH to induce E2 production (via aromatase) in rat Sertoli cells in vitro) results from the ability of gonadotropin isoforms to stimulate postreceptor binding functions upstream from G-protein activation and second messenger stimulation. Within the mix of the heterogeneous isoforms, there could be some that alternatively stimulate Gi protein and inhibit function or some that could stimulate G-protein activation for prolonged periods that extend beyond signal-receptor binding. Methods of separation of isoforms are not yet precise or sophisticated enough to distinguish these isoforms. Therefore, the measurement of in vitro bioactivity measures the sum of stimulatory and inhibitory influences on one defined end result. The immunologic potencies also measure the ability of certain selected antibodies to recognize epitopes on gonadotropin molecules, whether they are biologically active or, by virtue of CHO differences or changes in tertiary structure, biologically inactive. Nonetheless, in many instances, the results have been significantly different, with the bioactivity measurements showing greater excursions in stimulatory or inhibitory paradigms than the immunologic potencies. This has been especially true for FSH. Capitalizing on the usefulness of these methodologic advances, we have reviewed the contribution that measurements of gonadotropin bioactivity have made to our understanding of human puberty, which is a continuum in development from conception to adulthood.(ABSTRACT TRUNCATED AT 400 WORDS)

Aging↗

PubMed1986

Actions of estradiol on the pulsatile secretion of bioactive luteinizing hormone in man.

We evaluated the impact of estradiol on bioactive LH release in normal men by steady-state intravenous infusions of estradiol and oral administration of the antiestrogen tamoxifen HCl. The secretion of biologically active LH was monitored by the rat interstitial cell testosterone bioassay. Estradiol infusions decreased mean plasma bioactive LH concentrations and diminished the bio/immuno LH ratio. Conversely, the antiestrogen tamoxifen increased bioactive LH pulse frequency, bioactive LH pulse amplitude, and the plasma bio/immuno LH ratio. Exogenous injections of GnRH at 2-hr intervals also increased the bio/immuno LH ratio basally. However, tamoxifen attenuated the ability of exogenous GnRH to increase the bio/immuno LH ratio further, indicating attainment of maximal enrichment in LH bioactivity. These complementary observations on the impact of infused estradiol and exogenous antiestrogen indicate that estradiol modulates the pulsatile secretion of LH molecules enriched in biological activity in man.

Adult↗

PubMed1985

Role of insulin and dexamethasone in the expression of bioactivity in rat hepatocytes cultured in a serum-free defined medium.

Previously, we described primary cultures of rat liver cells in a serum-free multihormone defined medium (Am. J. Physiol. 243: E132-E151, 1982). This cell preparation exhibits marked insulin-dependent syntheses of protein, glycogen and lipids (hereafter collectively referred to as "bioactivity" for brevity). In the present studies, the role of different hormones in the expression of insulin's bioactivity was investigated. Hepatocytes from fasted rats, previously maintained in the multihormone glucagon-supplemented medium, were first cultured in the defined medium without the hormones and, subsequently, tested for bioactivity by replacing the missing hormones singly or in combination. Of all the hormones tested (testosterone, estradiol, thyroxine, glucocorticoid steroid and insulin), only insulin, dexamethasone and thyroxine when present individually in the culture medium, showed slight bioactivity (glycogenesis); however, insulin and dexamethasone, when present together, further increased each bioactivity, protein (1.3-fold), glycogen (8-fold) and lipid (1.6-fold) syntheses. The determination of apparent binding parameters of insulin specific receptors using Scatchard plots showed that insulin exposure caused a decrease in receptor concentration (Ro), dexamethasone exposure caused an increase in affinity (Kd), and, compared to insulin alone, treatment with insulin plus dexamethasone increased receptor concentration with no change in apparent affinity. Insulin induced a consistently small, but statistically significant, increase in the average specific activity of the protein-disulfide interchange enzyme, glutathione-insulin transhydrogenase (GIT), with equal distribution between its nonlatent ("readily available") and latent ("cryptic") forms. However, when dexamethasone was present along with insulin, the distribution of GIT was significantly greater in the latent form than in the nonlatent form. Examination by scanning and transmission microscopy showed clear differences, both in the cell surface and intracellular morphology, in the hepatocytes exposed to different hormonal milieu.

Animals↗

PubMed1982

Effect of senescence on the bioactivation of aliphatic halides.

Since the toxicity of xenobiotics is often related to their metabolism, this study was concerned with the relationship between aging and the bioactivation and covalent binding of certain aliphatic halides to microsomal protein and lipid. Hepatic microsomes were isolated from control and phenobarbital induced young (4 mo), adult (11 mo) and senescent (27 mo) Fischer 344 rats. Bioactivation and subsequent covalent binding were studied with 14C-labeled 1,2-dibromoethane, carbon tetrachloride, trichloroethylene, and 1, 1, 2-trichloroethane. With control rats, levels of binding increased slightly between 4 and 11 mo; however the values decreased 50-75% in the 27 mo group compared to the 11 mo group. No significant differences were noted between phenobarbital induced groups with regards to bioactivation of the aliphatic halides and their covalent binding to proteins and lipids. As an explanation for the decreased bioactivation ability in the senescent rats, they were also found to have significantly less hepatic cytochrome P-450 (-35%), NADPH cytochrome C reductase (-31%), and ethyl-morphine N-demethylase activity (-43%) when compared to the 11 mo age group. These differences were reduced when comparisons were made between the various age groups of phenobarbital induced animals. This suppression may indicate a decreased potential for the expression of toxicities requiring bioactivation.

Aflatoxin B1↗

PubMed2001

Serum thyrotropin concentrations and bioactivity during sleep deprivation in depression.

BACKGROUND: One night of sleep deprivation induces a brief remission in about half of depressed patients. Subclinical hypothyroidism may be associated with depression, and changes in hypothalamic-pituitary-thyroid function may affect the mood response to sleep deprivation. We wished to define precisely the status of the hypothalamic-pituitary-thyroid axis of depressed patients during sleep deprivation and the possible relationship of hypothalamic-pituitary-thyroid function to the mood response. METHODS: We studied 18 patients with major depressive disorder and 10 normal volunteers. We assessed mood before and after sleep. We measured serum thyrotropin every 15 minutes during the night of sleep deprivation, thyrotropin bioactivity, the thyrotropin response to protirelin the next afternoon, and other indexes of hypothalamic-pituitary-thyroid function. To determine if the changes were limited to the hypothalamic-pituitary-thyroid axis, we measured serum cortisol, which also has a circadian secretory pattern. RESULTS: Nocturnal serum thyrotropin concentrations were consistently higher in responders, entirely because of elevated levels in the women reponders. Responders had exaggerated responses to protirelin the next afternoon. The bioactivity of thyrotropin in nonresponders was significantly greater than in responders (F(1,8. 99) = 7.52; P =.02). Other thyroid indexes and serum cortisol concentrations were similar among groups. CONCLUSIONS: Depressed patients have mild compensated thyroid resistance to thyrotropin action, not subclinical autoimmune primary hypothyroidism. Sleep deprivation responders compensate by secreting more thyrotropin with normal bioactivity; nonresponders compensate by secreting thyrotropin with increased bioactivity.

Adult↗

PubMed1998

Obliteration of the frontal sinus cavity with bioactive glass.

BACKGROUND: Bioactive glass (BG) is a glass ceramic material. It has been used as surgical bone replacement material in ear and oral surgery, orthopedics, and dentistry. METHODS: Bioactive glass was used as obliteration material in a series of osteoplastic frontal sinus operations on 10 patients suffering from chronic frontal sinusitis, which other, more-conservative treatment modalities had failed to cure. RESULTS: Bioactive glass is easy to handle, and complete obliteration of all sinusal recesses and excavations is easily achieved. No adverse effects of the implant material have been seen over a mean follow-up period of 5.0 years. One patient with a local recurrent infection in the outer table of the sinus was reoperated on 5 months after primary surgery. Repeated postoperative computed tomographic scans analyzed by digital region-of-interest (ROI) selection showed no remarkable changes in the frontal sinus cavities but a slight, yearly decrease in the density of the occlusion material. Laboratory monitoring of patients and histopathologic examination of two postoperative biopsy specimens indicated that the material is well tolerated and stable. CONCLUSIONS: Bioactive glass is a promising and well-tolerated bone graft suitable for osteoplastic frontal sinus operations. Total accurate obliteration of the sinus is achieved with different sizes of granules and blocks. The results of the obliteration are maintained owing to the stability of the material.

Adult↗

PubMed1996

Protein adsorption to a bioactive glass with special reference to precorrosion.

The protein adsorption properties of the bioactive glass S53P4 were studied using albumin, IgG, and fibrinogen solutions (1 mg/mL) as well as diluted plasma, serum, and 1:1:1 mixtures of albumin, IgG, and fibrinogen. The bioactive glass granules (315-500 microns) were used in the experiments without pretreatments or as precorroded with an Si-rich or a Ca,P-rich layer. The protein adsorption properties of S53P4 were compared to a commercial bioactive glass (Bioglass), an inert glass, an experimental glass ceramic, titanium (Ti), and hydroxyapatite (HA). The untreated S53P4 bound in Trisbuffered saline mainly albumin from diluted plasma and serum and the 1:1:1 (1 mg of each) mixture of albumin, IgG, and fibrinogen. No binding of fibrinogen was observed. The omission of NaCl from the buffer used in the experiments increased the number of proteins bound by the S53P4. Most of the albumin bound by the glass could be detached with 0.5-1M NaCl speaking for electrostatic protein bonding. The protein adsorption properties of Bioglass resembled those of S53P4. The Ca,P-rich layer glass, the inert glass, the glass ceramic, HA, and Ti all bound several plasma and serum proteins, including fibrinogen. The Si-rich layer glass showed protein binding properties resembling the untreated glass more than the Ca,P-rich layer glass. The protein adsorption test used in the present study revealed differences in the protein adsorption properties of the studied materials, which may reflect differences in their surface potentials. It also functioned in registration of corrosion-induced changes in the surface properties of the S53P4. As judged by the protein adsorption properties, the untreated S53P4 could have a higher biocompatibility than the two precorroded glasses. Precorrosion, especially the formation of the Ca,P-rich layer, increased the number of proteins bound by the S53P4. Thus, a precorroded glass as compared to the untreated glass could be a better carrier of specific proteins that may be used to improve the biocompatibility of the bioactive glass.

Biocompatible Materials↗

PubMed1997

The influence of alkali and alkaline earths on the working range for bioactive glasses.

Viscosity-temperature dependence has been investigated for glasses in a system where bioactive compositions are found. A glass is called bioactive when living bone can bond to it. In this work, high-temperature microscopy was used to determine viscosity-temperature behaviour for 40 glasses in the system Na2O-K2O-MgO-CaO-B2O3-P2O5-SiO2. The silica content in the glasses was 39-70 wt% % All glasses containing < 54 mol % SiO2 devitrified during the viscosity measurements. Generally, glasses that devitrified contained more alkali but less alkaline earths than glasses with a large working range. A working range is the temperature interval at which forming of a glass can take place. This temperature interval can, for bioactive glasses, be enlarged by decreasing the amount of alkali, especially Na2O, in the glass and by increasing the amount of alkaline earths, especially MgO. Optionally, B2O3 and P2O5 can be added to the glass. An enlarged working range is a prerequisite for an expanded medical use of bioactive glasses as e.g., sintered and blown products, and fibers.

Alkalies↗

PubMed1998

In vitro adsorption and activity of enzymes on reaction layers of bioactive glass substrates.

The effects of physiological biomolecules, particularly proteins, on the reactivity of bioactive glasses is being heavily researched. However, the effects of bioactive glasses on the activity of proteins have received little attention. Activity of horseradish peroxidase (HRP) adsorbed to the silica gel and hydroxycarbonate apatite layers of 45S5 bioactive glass was investigated. Surface reactions were terminated after development of a silica gel layer by the addition of edta to the reaction solution, which completely inhibited calcium phosphate formation. Complete loss of HRP activity on the silica gel layer was found to occur within 21 h while a minimal amount of activity from HCA-adsorbed HRP persisted indefinitely. These results show that bioactive glasses may serve as "friendly hosts" for adsorbed proteins, such as biologically active growth factors. These active peptides then, in turn, may generate an increased cellular response in the surrounding tissue, thereby enhancing the biogenic response.

Adsorption↗

PubMed2000

In vitro bioactive behavior of hydroxylapatite-coated porous Al(2)O(3).

To produce bioactive materials for bone substitutes, two major deposition methods, suspension method and thermal deposition method, were employed to develop bioactive, mechanically strong, and porous ceramics. Hydroxylapatite (HA) has been uniformly coated onto inner pore surfaces of reticulated alumina substrates. It has been found that the in vitro bioactivity of HA coatings was affected by both structural crystallinity and specific surface area. Well-crystallized HA heat-treated at high temperatures has resulted in reduced bioactivity. The bio-reaction rate was found to increase with the surface area of HA. We have found that the stability of the well-crystallized HA is associated with the high driving force required for the formation of hydroxy-carbonate apatite (HCA) phase.

Aluminum Oxide↗

PubMed2000

Bacteriostatic action of a novel four-component bioactive glass.

Bacterial adhesion to biomaterials causing biomaterial-centered infection and poor tissue integration is a problem that limits the extensive use of many biomaterial devices in clinical applications. Bioactive materials are those biomaterials that form a compliant, mechanically stable bond with host tissue. Sol-gel-derived glasses in the three-component system SiO(2)-CaO-P(2)O(5) exhibit bioactivity that is dependent on composition and texture (i.e., specific surface area, pore size, structure, and distribution). The in vitro bioactivity and antibacterial action of a novel sol-gel-derived glass, AgBG, in the system SiO(2)-CaO-P(2)O(5)-Ag(2)O are compared with those of its three-component counterpart, BG. The incorporation of 3-wt % Ag(2)O conferred antimicrobial properties to the glass without compromising its bioactivity. AgBG exhibited a marked bacteriostatic effect on E. coli MG1655 with a minimum inhibiting concentration of 0.2 mg (biomaterial)/mL (culture solution), above which bacterial growth was reduced to 0.01% of that of the control culture. In comparison, BG did not possess antimicrobial properties over the concentration range investigated (0.1-40.0 mg/mL).

Anti-Bacterial Agents↗

PubMed2000

Characterization of bioactive glass-reinforced HAP-polymer composites.

The effect of bioactive glass on the mechanical properties of hydroxyapatite-Ca polyacrylate composites was studied. Powder mixtures of tetracalcium phosphate (TetCP), poly(acrylic-co-itaconic) and bioactive glass (up to 50% by weight) were hot pressed for 30 min at 300 degrees C and 40 kpsi. Tensile strengths, elastic moduli, and microstructures of the composites produced were investigated. Results showed the mechanical properties of these composites were enhanced by the addition of bioactive glass. The highest values of tensile strength and elastic modulus were achieved with the addition of 10% bioactive glass. Composites were immersed in SBF for up to 10 days, then in 1.5 simulated body fluid (SBF) for a week. The changes in the concentrations of Ca, P, and Si ions of these solutions were measured. The microstructures of these composites after SBF immersion were also evaluated. Concentrations of Ca, P, and Si increased with the time of immersion in SBF owing to the formation of an apatite layer on their surfaces as found by SEM with energy-dispersive spectroscopy attachment.

Biocompatible Materials↗

PubMed1989

Bioactive conformation of linear peptides in solution: an elusive goal?

Bioactive peptides of natural origin have, in general, short linear sequences, and are characterized by a large conformational flexibility. It is very difficult to study their conformation in solution since they exist, almost invariably, as a complex mixture of numerous conformers, most of which are extended. The so-called bioactive conformation may be one of them, although the solvents used in solution studies often have properties drastically different from those of the biological system in which the peptide acts. There is, however, no simple way of identifying the bioactive conformation amid the many existing conformers. It is possible to approach a solution to this problem using two distinct strategies: (a) Limiting the conformational freedom of the peptide, e.g., by increasing the viscosity of the solution and decreasing the temperature, in the assumption that the bioactive conformation is, even slightly, more stable than the others. (b) Trying to mimic in solution the physicochemical features of the more reliable receptor models. These two approaches will be illustrated with examples taken mainly from opioid peptides.

Amino Acid Sequence↗

PubMed2006

Effect of oriented or random PEGylation on bioactivity of a factor VIII inhibitor blocking peptide.

Peptides as therapeutic substances are efficient agents in the treatment of several diseases. However, they often have to be chemically modified in order to be suited as therapeutic agent. Conjugation to large carrier molecules is often required. A critical step is the identification of available sites for chemical reaction, without influencing bioactivity. Peptide 238/S1 with the sequence NH(2)-PYWKWQYKYD-COOH previously selected from a combinatorial decapeptide library, has the ability to block inhibitory antibodies against blood clotting factor VIII (FVIII) and therefore, it constitutes a lead for developing a drug to treat patients suffering from development of such antibodies. The aims of this study were (i) to identify sites of the peptide, which are suited for modification without losing bioactivity and (ii) to find out the influence of molecular size of polyethylene glycol (PEG) for bioactivity of the peptide. The contribution of each amino acid residue to biological functionality was investigated by mutational analysis. This method confirmed that the N-terminus is crucial for activity, whereas both lysine residues could be exchanged by other L-amino acids. Using mutational analysis it was possible to identify peptides with higher reactivity compared to the wild type 238/S1. PEGylation experiments demonstrated that conjugation of the peptide to PEG 20,000 resulted in a loss of reactivity, while PEG 5,000 could maintain the bioactivity when conjugated in a site directed manner. The peptide lost its neutralization properties when PEG was coupled to the N-terminus, again indicating that this part of the peptide is important for functionality.

Amino Acid Sequence↗

PubMed2002

In vivo evaluation of a bioactive scaffold for bone tissue engineering.

Revision cases of total hip implants are complicated by the significant amount of bone loss. New materials and/or approaches are needed to provide stability to the site, stimulate bone formation, and ultimately lead to fully functional bone tissue. Porous bioactive glasses (prepared from 45S5 granules, 45% SiO2, 24.5% Na2O, 24.5% CaO, and 6% P2O5) have been developed as scaffolds for bone tissue engineering and have been studied in vitro. In this study, we investigated the incorporation of tissue-engineered constructs utilizing these scaffolds in large, cortical bone defects in the rat simulating revision conditions. With implantation times of 2, 4, and 12 weeks the results were compared to those using the bioactive ceramic scaffold alone. Two tissue-engineered constructs were studied: osteoprogenitor cells that were either seeded onto the scaffold prior to implantation ("primary") or those that were culture expanded to form bonelike tissue on the scaffold prior to implantation ("hybrid"). Defects treated with the hybrid had the greatest amount of bone in the available pore space of the defect over all other groups at 2 weeks (p < 0.05). For both the primary and hybrid groups, woven and lamellar bone was present along the interface of the scaffold and the host cortex and within the porous space of the scaffold at 2 weeks. By 4 weeks, very uniform, lamellar bone was present throughout the scaffold for both tissue-engineered groups. The amount of bone significantly increased over time for all groups while the bioactive ceramic gradually resorbed by 40% at 12 weeks (p < 0.05). Structural properties of the treated long bones improved over time. Long bones treated with the hybrid had an early return in torsional stiffness by 2 weeks. Both tissue-engineered constructs achieved normal torsional strength and stiffness by 4 weeks as compared to the scaffold alone, which achieved this by 12 weeks. Porous, surface modified bioactive ceramic is a promising scaffold material for tissue-engineered bone repair.

Animals↗

PubMed1989

Interfacial analysis of fiber-reinforced bioactive glass dental root implants.

Bioactive glass can form an effective bond with bone. Essential for this connection are the interfacial reactions which lead to the development of a Si-rich film covered by a CaP-rich film. The presence of these layers can be demonstrated clearly by EDX analysis of fiber-reinforced bioactive glass and bulk bioactive glass implants installed for 4 and 16 months in the partial edentulous jaws of beagle dogs. EDX analysis reveals three types of microchemical interface. The first type develops when the implant is bonded to bone. Here, a smooth transition of the CaP profile can be observed between bioactive glass and the bone, thus providing for a compositional gradient between the implant and the surrounding tissues. The second type is seen when the implant surface is surrounded by fibrous tissue. This causes a discontinuity in the CaP profile. The third type is characterized by a gradual decrease in the Ca and P concentrations across the interface, caused by the presence of Ca and P in the fibrous tissue near the implant surface. This suggests that the interface is dynamic in time and transforms to a functionally better optimized interface. EDX analysis does not reveal any metal fiber ion contamination of the outer glass rim of the implant. When stainless-steel or wrought Co-Cr alloy is exposed to the surrounding fluids, the interfacial osteogenesis is disturbed, possibly by a synergistic effect of glass ions and metal ions. Exposure of titanium does not interfere with this osteogenesis. The bone bonding can also be influenced by surgical trauma. However, with precise implantation techniques, an enhancement of bone growth by osteoconductivity can be measured.

Animals↗

PubMed1990

Ca,P-rich layer formed on high-strength bioactive glass-ceramic A-W.

Glass-ceramic A-W, containing crystalline apatite and wollastonite in a MgO-CaO-SiO2 glassy matrix shows high bioactivity as well as high mechanical strength, but other ceramics containing the same kinds of crystalline phases in different glassy matrices do not show the same bioactivity. In order to investigate the bone-bonding mechanism of this type of glass-ceramic, surface structural changes of the glass-ceramics after exposure to simulated body fluid were analyzed with various techniques. A solution with ion concentrations which are almost equal to those of the human blood plasma was used as the simulated body fluid, instead of Tris-buffer solution hitherto used. For analyzing the surface structural changes, thin-film x-ray diffraction was used in addition to conventional techniques. It was found that a bioactive glass-ceramic forms a Ca, P-rich layer on its surface in the fluid but nonbioactive ones do not, and that the Ca, P-rich layer consists of carbonate-containing hydroxyapatite of small crystallites and/or defective structure. These findings were common to those of Bioglass-type glasses. So, we conclude that the essential condition for glass and glass-ceramic to bond to bone is the formation of the surface apatite layer in the body environment but it is not essential to contain apatite within the material. Bioactivity of glass and glass-ceramic can be evaluated in vitro by examining the formation of the surface apatite layer in the simulated body fluid described above.

Apatites↗