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B C Nisula

Publications and source records attributed to B C Nisula.

At least 37 records · Page 2Linked to original sources
PubMed1989

Effect of alcohol on the interaction of cortisol with plasma proteins, glucocorticoid receptors and erythrocytes.

Alcohol ingestion stimulates glucocorticoid secretion in animals and normal men. It is generally believed that this effect is mediated through the pituitary-adrenal axis. To investigate its mechanism, we focussed on the effects of ethanol on cortisol binding to plasma proteins and to glucocorticoid receptors, and on cortisol uptake by erythrocytes. Addition of ethanol (up to 800 mg/dl) decreased cortisol binding to albumin and corticosteroid-binding globulin (CBG), causing an increase in the plasma unbound component. Ethanol also decreased cortisol binding to glucocorticoid receptors in normal human peripheral lymphocytes. The uptake of cortisol by erythrocytes was not affected at ethanol concentrations as high as 2000 mg/dl. These results provide new insight to ethanol effects in vivo. The stimulatory effect of ethanol on the pituitary-adrenal axis appears to be attributable in part to a relative ineffectiveness of cortisol in cortisol-responsive cells consequent to ethanol's ability to diminish cortisol binding to glucocorticoid receptors. A compensatory increase in ACTH secretion in response to the relative hypoglucocorticoid state perceived by corticotrophs would result in maintenance of elevated plasma unbound cortisol and cytosol cortisol levels. We conclude that altered interactions of cortisol with its receptors and transport proteins could be pathophysiological components of the changes in adrenocortical function induced by ethanol ingestion.

Blood Proteins↗
PubMed1989

Metabolic fate of human choriogonadotropin.

Review of the literature reveals a number of recent insights concerning the metabolic fate of human choriogonadotropin (hCG). In man, only a fraction (21.7%) of the circulating hCG molecules is excreted in urine. Results from animal studies indicate that the retained hCG is taken up by various tissues, principally kidney, liver, and ovary, where degradation occurs. Ovarian uptake is receptor mediated and saturable. Hepatic uptake of hCG is not preceded by desialylation, and blockade of hepatic receptors for galactose-terminated glycoproteins does not impair hepatic accumulation of hCG. Kidney uptake is quantitatively the most important; parenchymal metabolism, as well as excretion in urine constitute major renal components of hCG disposal. The intracellular products of hCG catabolism in kidney include certain fragments of the hCG molecule that exhibit relative resistance to processing by degradative enzymes. These products are fragments of the hCG beta subunit that lack the hCG beta carboxyterminal antigenic determinant, but retain an hCG beta core antigenic determinant, and, thus, they are designated beta-core molecules. Both kidney from hCG-infused rat and urine from pregnant women contain beta-core molecules in great abundance, in fact, in greater abundance than hCG, itself. Structural characterizations of the beta-core purified from pregnancy urine indicate a mol. wt of about 10,000 and an absence of sialic acid, galactose, and carboxyterminal peptide region, including O-linked oligosaccharides. Human volunteers given purified hCG or hCG beta by infusion excrete beta-core in their urines, which establishes the existence of catabolic pathways in humans for the production of beta-core. Thus, urinary excretion of beta-core may reflect an important fate for the metabolic products of hCG degradation.

Chorionic Gonadotropin↗
PubMed1989

Effects of hyperthyroidism on binding proteins for steroid hormones.

Sex hormone binding globulin (SHBG) and corticosteroid binding globulin (CBG) binding capacities were examined weekly in eight normally cycling women and three women taking birth control pills during a 5-week baseline period and after daily ingestion of 75 micrograms of L-triiodothyronine (T3) for 30 days. The SHBG binding capacity increased whereas the CBG binding capacity decreased after T3 therapy. The binding capacities of proteins for steroid hormones were measured in 18 hyperthyroid subjects (Graves' disease) prior to and after 3 months of antithyroid drug therapy. SHBG binding capacity in hyperthyroid men or women was higher, and CBG binding capacity lower than those in euthyroid subjects. Thus, during hyperthyroidism, binding capacities of sex hormone binding globulin and corticosteroid binding globulin vary in opposite directions. A statistically significant correlation between the ratio of the sex hormone binding globulin to the corticosteroid binding globulin and triiodothyronine levels was found (P less than 0.01). Therefore the ratio of the sex hormone binding globulin to the corticosteroid binding globulin might be potentially useful as a biochemical index of thyroid hormone action in peripheral tissues.

Adult↗
PubMed1989

Structure-kinetic relationships of choriogonadotropin and related molecules.

To assess how profound differences in carbohydrate and/or polypeptide structures affect parameters of plasma disappearance of glycoprotein hormones, we calculated and compared the initial volume of distribution, rate constants, and metabolic clearance rates of several highly purified human choriogonadotropin (hCG) analogues in monkeys. hCG, deglycosylated hCG, desialylated hCG, or core fragment of hCG-beta purified from pregnancy urine (beta-core) was administered as a rapid intravenous injection to adult male cynomolgus monkeys (n = 3/group). The metabolic clearance rates of deglycosylated hCG, beta-core fragment, and desialylated hCG were increased 15-, 47-, and 152-fold, respectively, over that of hCG. Their corresponding initial volumes of distribution, however, remained essentially unchanged compared with that of hCG and approximated the estimated plasma volume. In contrast, the fast and slow rate constants of plasma disappearance of the hCG analogues were increased as much as 18- and 23-fold, respectively, relative to those of hCG. These studies of structure-kinetic relationships in primates show that major carbohydrate and polypeptide modifications of a glycoprotein hormone cause profound changes in the rate constants of the disappearance curves without changes in the initial volume of distribution.

Animals↗
PubMed1989

Stimulation of testosterone production in the cynomolgus monkey in vivo by deglycosylated and desialylated human choriogonadotropin.

Modifications of carbohydrate structures of hCG, such as deglycosylation or desialylation, have been shown to reduce the biological activity of the hormone derivatives in vivo. We posed the question of whether deglycosylated hCG (dg-hCG) and desialylated hCG (ds-hCG) would behave as agonists at the LH/CG receptor in the primate in vivo, as this would bear on their potential clinical utility as LH/CG agonists or antagonists. Thus, we administered large doses (approximately 3 nmol) of highly purified dg-hCG, ds-hCG, hCG, or normal saline as a rapid iv injection to adult male cynomolgus monkeys (n = 3/group). Mean areas under the curves of plasma T over the first 6 h achieved with dg-hCG and ds-hCG were about 5-fold, significantly (P less than 0.05) greater than that in the saline controls and not significantly (P greater than 0.05) different from that in hCG-injected animals. Despite comparable plasma T responses in the first 6 h, mean plasma concentrations of ds-hCG, dg-hCG, and hCG differed dramatically among the groups. Plasma ds-hCG and dg-hCG levels were undetectable by 15 and 180 min, respectively, while the mean plasma hCG level was more than 2.10 nmol/L at 360 min. These data indicate that 1) dg-hCG is a full agonist at the LH/CG receptor in the primate in vivo, despite having minimal intrinsic activity in the rat Leydig cell adenyl cyclase assay and being able to near-completely antagonize hCG action therein; and 2) ds-hCG is a full agonist in the monkey in vivo, capable of stimulating a full testicular response over 6 h, despite being cleared from the circulation in 15 min. We conclude that the signal transduction system at the monkey LH/CG receptor is capable of achieving full steroidogenesis despite dramatically shortened exposure to stimulus or exposure to a stimulus with markedly reduced adenyl cyclase-stimulating activity in vitro.

Animals↗
PubMed1989

Carbohydrate composition of beta-core.

beta-Core is a major component of the hCG-related molecules found in pregnancy urine. We previously have purified the beta-core molecule and have deduced portions of its carbohydrate structure based on lectin binding data. In the present study we used recently developed technology to determine the carbohydrate composition of beta-core and hCG beta (CR119). For direct compositional analysis, parallel samples were hydrolyzed in trifluoroacetic acid and analyzed for sialic acid and neutral sugars without prior derivatization. Separation of the monosaccharides was achieved by HPLC on a Dionex CarboPac column eluted at high pH, and the resolved monosaccharides were quantified by pulsed amperometric detection. The amounts of sugar that were found relative to peptide indicated the presence of two N-linked oligosaccharides per molecule on both beta-core and hCG beta. hCG beta contained additional sugars consistent with the presence of four O-linked oligosaccharides. Compared to hCG beta, beta-core contained negligible sialic acid, galactose, or N-acetylgalactosamine. The compositional data suggest that beta-core does not contain N-acetylglucosamine at the nonreducing end of the molecule, whereas the trimannosyl-chitobiose core is apparently intact at both glycosylation sites, consistent with the ability of the molecule to bind to Concanavalin-A. Comparable fucose contents and abilities of beta-core and hCG beta to bind to Lens culinaris indicate a similar extent of fucosylation on the internal N-acetylglucosamine in both molecules. We propose that the N-linked oligosaccharides on beta-core closely resemble the underlying N-linked structures of hCG beta with the antennary sialic acid, galactose, and N-acetylglucosamine removed.

Carbohydrate Conformation↗
PubMed1989

Circadian variation of thyrotropin in childhood.

We evaluated the circadian variation of serum TSH in 96 normal children, aged 5-18 yr. Blood samples were obtained hourly for 24 h, and serum TSH was measured using an immunoradiometric assay with a sensitivity of 0.2 mU/L and an intraassay coefficient of variation of 4.9%. The nadir serum TSH value, defined by the three consecutive hourly TSH concentrations having the lowest mean, occurred between 1000 and 1900 h, while the peak TSH value, defined by the three consecutive hourly TSH concentrations having the greatest mean, occurred between 2100 and 0600 h. The mean nadir serum TSH was 1.6 +/- 0.1 mU/L, and the mean peak TSH was 3.7 +/- 0.2 mU/L. The mean nocturnal TSH surge (percent increase in TSH from nadir to peak) was 144% (95% confidence limits, 50-300%) and did not correlate with serum T4, free T4, or T3 concentrations. Seventy-six children were given TRH (7 micrograms/kg). The mean peak serum TSH after TRH was 16.0 +/- 1.1 mU/L (95% confidence limits, 9.0-42.0 mU/L), and it occurred by 30 min after TRH administration in 92% of the children. The absolute peak nocturnal serum TSH and peak post-TRH serum TSH values correlated significantly (r = 0.62; P less than 0.001), while age, gender, and pubertal status did not correlate with either the nocturnal TSH surge or the TSH response to TRH. We conclude that normal children have a circadian variation of serum TSH characterized by a nocturnal TSH surge, and that the peak of serum TSH, which occurs at night, correlates with the peak serum TSH level after TRH administration.

Adolescent↗
PubMed1989

Metabolic clearance rate and urinary clearance of purified beta-core.

We injected a highly purified preparation of the beta-core molecule, a fragment of hCG beta excreted in pregnancy urine, into five men and three women to determine its kinetic parameters, MCR, and urinary clearance. The beta-core molecule was distributed in an initial volume [1950 +/- 156 (mean +/- SEM) mL/m2 body surface area] approximately equal to the estimated plasma volume. Its disappearance was multiexponential on a semilogarithmic plot, with a rapid phase t1/2 of 3.5 +/- 0.7 min and a slow phase t1/2 of 22.4 +/- 4.2 min. The transit time (the mean time spent by a molecule of beta-core in transit) was 20.6 +/- 2.1 min. The MCR was 192.0 +/- 8.0 mL/min.m2 body surface area. About 5% of the injected dose of beta-core was excreted into the urine in the first 30 min after injection, and low levels of excretion persisted for up to 7 days. The urinary clearance rate of beta-core was 13.7 +/- 1.4 mL/min.m2, accounting for about 8% of the elimination of beta-core from the plasma. The beta-core immunoreactivity in serum and urine was characterized by gel filtration and three independent RIA systems to show that its properties were indistinguishable from those of the injected beta-core. Serum levels of beta-core in pregnant women were less than 0.2 ng/mL, while the amounts excreted in their urine were as much as 5 mg/day. Based on these clearance parameters of beta-core in normal subjects, less than 0.2% of the beta-core excreted in pregnancy urine is derived by urinary clearance of plasma beta-core. Therefore, more than 99% of the beta-core excreted in pregnancy urine is derived from beta-core in a compartment separate from plasma. In particular, these data indicate that there is relatively little placental secretion of beta-core into plasma and that placental secretion does not account for the vast majority of beta-core in pregnancy urine. These findings are consistent with previous data that point to renal parenchymal degradation of hCG and hCG beta as the major source of urinary beta-core in pregnancy.

Adult↗
PubMed1988

Incidence of early loss of pregnancy.

We studied the risk of early loss of pregnancy by collecting daily urine specimens from 221 healthy women who were attempting to conceive. Urinary concentrations of human chorionic gonadotropin (hCG) were measured for a total of 707 menstrual cycles with use of an immunoradiometric assay that is able to detect hCG levels as low as 0.01 ng per milliliter, with virtually 100 percent specificity for hCG in the presence of luteinizing hormone. Our criterion for early pregnancy--an hCG level above 0.025 ng per milliliter on three consecutive days--was determined after we compared the hCG levels in the study group with the levels in a comparable group of 28 women who had undergone sterilization by tubal ligation. We identified 198 pregnancies by an increase in the hCG level near the expected time of implantation. Of these, 22 percent ended before pregnancy was detected clinically. Most of these early pregnancy losses would not have been detectable by the less sensitive assays for hCG used in earlier studies. The total rate of pregnancy loss after implantation, including clinically recognized spontaneous abortions, was 31 percent. Most of the 40 women with unrecognized early pregnancy losses had normal fertility, since 95 percent of them subsequently became clinically pregnant within two years.

Abortion, Spontaneous↗
PubMed1988

Erythrocyte-associated component of blood cortisol.

We propose that erythrocyte-associated cortisol is one of the significant components of blood cortisol that should be taken into account in studies of the physiology and pathophysiology of cortisol transport. We suggest that the model system used for determination of the erythrocyte partitioning coefficient may have applications in studies of the uptake of cortisol by tissues.

Erythrocytes↗
PubMed1988

Purification of beta-core fragment from pregnancy urine and demonstration that its carbohydrate moieties differ from those of native human chorionic gonadotropin-beta.

Pregnancy urine contains large quantities of hCG, free beta-subunit, free alpha-subunit, and a population of fragments of beta-subunit known as beta-core. This beta-core population, which can account for as much as 70% of the total beta-immunoreactivity in pregnancy urine, is of interest as both a normal metabolite of pregnancy and a potential marker for malignancy. We have purified the beta-core fragment from pregnancy urine (P-core) and have characterized it with respect to size and carbohydrate composition. P-Core was purified by chromatography on Sephadex G-100, Concanavalin A (Con A)-Sepharose, DEAE-Sephacel, and Sephadex G-75 (superfine). The purified P-core has an apparent mol wt of 17,500 and 17,000, as determined by gel filtration on Sephadex G-75 (superfine) and sodium dodecyl sulfate-polyacrylamide gel electrophoresis under nonreducing conditions, respectively. The sialic acid content of P-core was assayed chemically and was less than 0.07 mumol sialic acid/mumole P-core. For comparison to P-core, we have prepared a trypsin fragment of beta-subunit that retains the beta-core immunological determinant recognized by SB6 antiserum and lacks the carboxy-terminal immunological determinant. We have designated this beta-core molecule as T-core (tryptic fragment of beta-subunit) to distinguish it from the beta-core molecule that we have purified from pregnancy urine (i.e. P-core). Most of the P-core and T-core molecules bind to Con A (84% and 86%, respectively). The Con A-bound material was used for subsequent characterizations. Neither P-core nor T-core binds to DEAE using conditions under which intact hCG beta binds to DEAE. A variety of agarose-bound lectins were used to further investigate the carbohydrate nature of the Con A-bound P-core and T-core molecules. The lectin binding data indicate that the antennae on P-core do not contain appreciable sialic acid or galactose, in contrast to the antennae on T-core, which contain both. We conclude that P-core, the naturally occurring beta-core fragment in pregnancy, has been processed to a form in which nearly all of the sialic acid and galactose residues are removed, but the Con A-binding site (consisting of the core sugars) and most of the core fucose are retained.

Carbohydrate Conformation↗
PubMed1988

A radioimmunoassay for the core fragment of the human chorionic gonadotropin beta-subunit.

We developed a RIA for the beta-core fragment of hCG that is excreted in the urine of pregnant women and some patients with cancer. We purified beta-core from crude commercial preparations of hCG (of which beta-core is a major constituent) derived from pregnancy urine and used this purified beta-core material to immunize rabbits. One antiserum (RW25) was particularly useful in that a RIA with purified beta-core as both radioligand and reference preparation had high sensitivity for beta-core detection and low cross-reactivity with other hCG-related molecules and glycoprotein hormones. The cross-reactivities of purified hCG (CR125), hCG beta (CR125), and hCG alpha (CR125) preparations were in each instance less than 3 x 10(-3) (wt/wt). The cross-reactivities of purified pituitary glycoprotein hormones were in each instance less than 2 x 10(-4) (wt/wt). Using the RW25 RIA, virtually all beta-core immunoreactivity in pregnancy urine eluted from Sephadex G-100 in a position coincident with that of purified beta-core. Urine from men and nonpregnant women contained very low levels of beta-core immunoreactivity (less than 6.5 micrograms/L), while urine from pregnant women and patients with testicular cancer or other neoplasms had levels of beta-core immunoreactivity ranging as high as 26,000 micrograms/L. We conclude that the improved specificity of our beta-core RIA will facilitate studies of the physiology and cancer biology of beta-core molecules.

Adolescent↗
PubMed1988

Beta-core fragments are contaminants of the World Health Organization Reference Preparations of human choriogonadotrophin and its alpha-subunit.

Highly purified preparations of human choriogonadotrophin (hCG), hCG alpha and hCG beta, including those preparations which are being distributed by the World Health Organization as International Standards, cross-reacted in a new radioimmunoassay with increased relative specificity for the beta-core fragment of hCG. A major portion of the beta-core immunoreactivity in the hCG and hCG alpha preparations eluted from Sephadex G-100 in a position (approximate apparent molecular size 15,000-18,000) corresponding to that of purified beta-core fragment prepared from pregnancy urine. However, in the case of hCG beta-subunit preparations, virtually all of the beta-core cross-reacting material eluted from Sephadex G-100 in the same fractions as the native hCG beta-subunit. Quantitatively, the cross-reacting beta-core material accounts for less than 1% (w/w) of the total hCG or subunit immunoreactivity, as measured by conventional radioimmunoassays. The presence of the beta-core fragments as discrete molecular components of the hCG and hCG alpha preparations should be borne in mind when these preparations are used to calibrate new radioimmunoassays for hCG-related molecules.

Chorionic Gonadotropin↗
PubMed1987

Similarity of the clearance rates of free alpha-subunit and alpha-subunit dissociated from intact human chorionic gonadotropin, despite differences in sialic acid contents.

It is well known that the MCR of proteins can be influenced by their carbohydrate structure; i.e. the presence of terminal galactose on proteins results in uptake by hepatic receptors for galactose-terminated glycoproteins. Thus, a protein with its galactose residues covered or removed exhibits a far longer half life in plasma than one with its galactose residues exposed. The free alpha-subunit of human CG (hCG) has been shown to have a different carbohydrate composition than does the alpha-subunit dissociated from the intact hormone. In our laboratory, analysis of alpha-subunits isolated from pregnancy urine indicated that the alpha-subunit dissociated from hCG (hCG alpha) contains primarily monosialylated oligosaccharides, whereas the free alpha-subunit contains more than one sialic acid per oligosaccharide. This difference in the degree of sialylation prompted us to examine the clearance rates of these two subunits. Accordingly, free alpha and hCG alpha were purified by affinity chromatography and labeled with 125I. The labeled subunits were injected iv into rats and serum samples were removed at various time intervals over a 2-h period. The amount of [125I]alpha-subunit remaining in the serum was determined by immunoprecipitation using an antiserum to hCG alpha. The disappearance curves for the two subunits were indistinguishable and could be analyzed by a biexponential model. The t 1/2 of the faster component was 5 min, while the t 1/2 of the slower component was 74 min. In order to determine whether or not terminal galactose was present on either the hCG alpha or the free alpha-subunit, the labeled molecules were subjected to lectin column chromatography using Ricin or peanut lectin linked to agarose. Both of these lectins bind galactose but have different specificities with respect to the penultimate sugar. Both subunit preparations contained only minor amounts of material which could bind or either lectin. However, after desialylation, both hCG alpha and free alpha bound extensively to Ricin, indicating the presence of penultimate galactose residues in both. We conclude that terminal galactose residues are not present on the oligosaccharides of either hCG alpha or free alpha-subunits, and that the difference observed in the sialic acid contents of the two subunits does not affect their rates of clearance.

Animals↗
PubMed1987

Erythrocyte-associated cortisol: measurement, kinetics of dissociation, and potential physiological significance.

It is well known that a portion of the cortisol in blood is associated with erythrocytes. This study was conducted to determine the quantity of cortisol associated with erythrocytes under physiological conditions and to assess the potential availability of that cortisol for tissue uptake. The erythrocyte-associated cortisol was determined from the volume of plasma measured using [125I]human serum albumin, the concentration of cortisol in plasma, and the total concentration of cortisol in blood. The plasma unbound cortisol fraction was determined by ultrafiltration and was used to calculate a partitioning coefficient that describes the distribution of cortisol between erythrocyte-associated and plasma unbound components. The cortisol partitioning coefficient (erythrocyte-associated cortisol concentration divided by plasma unbound cortisol concentration) did not vary significantly over a wide range of cortisol levels, nor was it affected by the presence or absence of corticosteroid-binding globulin. The cortisol partitioning coefficient in six normal men averaged 2.62 +/- 0.16 (mean +/- SD). Computer analysis of the distribution of cortisol among blood components indicated that at all cortisol levels, the proportion of blood cortisol associated with erythrocytes would exceed that which is plasma unbound or albumin-bound. The rate of dissociation of cortisol from erythrocytes was measured to determine if the kinetics of dissociation would be consistent with the tissue availability of erythrocyte-associated cortisol. Indeed, the half-time of dissociation was extremely rapid (less than 2.3 s). These results indicate that erythrocyte-associated cortisol is a substantial component of blood cortisol and that erythrocytes may serve as a major conduit for the transport of cortisol to the tissues.

Adult↗
PubMed1986

Modulation of thyroid parameters by exogenous thyroxine in familial dysalbuminemic hyperthyroxinemia.

A patient with familial dysalbuminemic hyperthyroxinemia (FDH) was given graded doses of exogenous thyroxine (0.2 mg/d for 2 weeks; 0.4 mg/d for 2 weeks; 0.6 mg/d for 2 weeks) to study modulation of various thyroid parameters. The plasma concentration of the serum transport proteins, thyroxine binding globulin (TBG), sex hormone binding globulin (SHBG), and cortisol binding globulin (CBG) as well as serum thyroxine (T4), triiodothyronine (T3), absolute free thyroxine (FT4), and serum protein binding of T4 tracer were measured. At the end of T4 treatment, T4 and T3 were increased by 151% and 78%, respectively. The FT4 increased (157%), while the percent dialyzable free T4 fraction (DFT4) showed no significant change. SHBG, a protein sensitive to thyroid hormone (TH) action, increased 148% (from 0.23 to 0.57 micrograms/dL) after treatment but this concentration was still in the normal range; TBG and CBG decreased by about 16%. Analysis of the electrophoretic 125I-T4 distribution pattern in serum during T4 treatment showed essentially no change in TBG-bound T4 (percent tracer carriage X total T4), while there was a progressive increase in albumin-bound T4 (341% increase over pretreatment value) and a lesser increase in prealbumin (TBPA)-bound T4 (187%). These observations describing alterations in TH action, serum T4-protein binding, and the failure of percent DFT4 to increase with elevation in serum total T4 are of clinical significance in evaluating thyroid function parameters in FDH patients undergoing TH treatment.

Adult↗
PubMed1986

Effect of physical conditioning on measures of thyroid hormone action.

Serum thyroid function tests (T4, T3, rT3 and TSH levels) and measures of peripheral thyroid hormone action (serum dopamine-beta-hydroxylase activity (DBH) and sex hormone binding globulin (SHBG] were determined in 6 women before and one month after initiating an aerobic physical conditioning program. The same measurements were made in a control group of 6 women who did not increase their activity during this time. In physically conditioned subjects, the resting heart rate decreased from 65.1 +/- 3.9 (mean +/- SE) at baseline to 58.0 +/- 2.9 beats per minute after one month (P less than 0.025), indicating an appreciable state of physical conditioning was achieved. However, there were no statistically significant changes in thyroid function test, serum DBH or SHBG levels in either the physically conditioned or the control group. These data indicate that being physically conditioned has a negligible effect on thyroid status.

Adult↗