The discrimination between magnesium and manganese by serum proteins.

Magnesium and manganese have proved physically and functionally interchangeable in many isolated biological systems investigated in vitro. This lack of discrimination contrasts sharply with the high biological specificity exhibited by intact mammals under a large variety of conditions. The dichotomy between intact animals and their isolated systems might be due at least partially to presence vs. absence of an intact circulation. Hence the capability of mammalian plasma to discriminate between the alkaline earth and the transition metal was investigated by means of equilibrium dialysis, exchange, ultrafiltration, ultracentrifugation, and zone electrophoresis. The states of the respective elements are thus contrasted as follows: (a) Magnesium is partially bound, manganese totally. (b) Magnesium is nonselectively bound by serum proteins, manganese selectively by a beta(1)-globulin. (c) Under conditions approaching physiological, the two metals do not interchange. This is interpreted as indicating that the plasma proteins contribute to biological specificity by discriminating between a trace metal and a macronutrient.

A prepubertal surge of thyrotropin precedes an increase in thyroxine and 3,5,3'-triiodothyronine in normal children.

The variations in plasma levels of TSH, T4, T3, and rT3, during the pubertal period, were studied in 647 school students from the urban area of Santiago in Chile (47% males and 53% females) with ages ranging between 7.5 and 15 yr. The subjects were grouped by age in consecutive intervals of 6 months each, and pubertal development was determined in every subject. TSH showed a significant increase, reaching a peak in the 9- to 9.5-yr interval. The same was found for T3 and T4, which reached a peak by 10 and 11 yr. The T4/T3 ratio did not show any significant variation with age. After 9.5 yr, a decrease in rT3 and increase in the T4/rT3 ratio was found. The TSH peak preceded the onset of clinical pubertal development, while the T3 and T4 peaks coincided with this onset. The variations in rT3 suggest an increase of peripheral conversion of T4 to T3. These transient events, not described until now, could be termed thyroidarche and could have a significant effect on pubertal growth and development.

Primary hyperaldosteronism in essential hypertensives: prevalence, biochemical profile, and molecular biology.

There is evidence that primary aldosteronism (PA) may be common in patients with essential hypertension (EH) when determinations of serum aldosterone (SA), plasma renin activity (PRA), and the SA/PRA ratio are used as screening. An inherited form of primary hyperaldosteronism is the glucocorticoid-remediable aldosteronism (GRA) caused by an unequal crossing over between the CYP11B1 and CYP11B2 genes that results in a chimeric gene, which has aldosterone synthase activity regulated by ACTH. The aim of this study was to evaluate the prevalence of PA and the GRA in 305 EH patients and 205 normotensive controls. We measured SA (1-16 ng/dL) and PRA (1-2.5 ng/mL x h) and calculated the SA/PRA ratio in all patients. A SA/PRA ratio level greater than 25 was defined as being elevated. PA was diagnosed in the presence of high SA levels (>16 ng/dL), low PRA levels (<0.5 ng/mL x h), and very high SA/PRA ratio (>50). Probable PA was diagnosed when the SA/PRA ratio was more than 25 but the other criteria were not present. A Fludrocortisone test was done to confirm the diagnosis. GRA was differentiated from other forms of PA by: the aldosterone suppression test with dexamethasone, the high levels of 18-hydroxycortisol, and the genetic detection of the chimeric gene. In EH patients, 29 of 305 (9.5%) had PA, 13 of 29 met all the criteria for PA, and 16 of 29 were initially diagnosed as having a probable PA and confirmed by the fludrocortisone test. Plasma potassium was normal in all patients. The dexamethasone suppression test was positive for GRA in 10 of 29 and 18-hydroxycortisol levels were high in 2 of 29 patients who had also a chimeric gene. In normotensive subjects, 3 of 205 (1.46%) had PA, and 1 of 205 had a GRA. In summary, we found a high frequency of normokalemic PA in EH patients. A high proportion of PA suppressed SA with dexamethasone, but only a few had a chimeric gene or high levels of 18-hydroxycortisol. These results emphasize the need to further investigate EH patients.

Salt-wasting congenital adrenal hyperplasia: detection of mutations in CYP21B gene in a Chilean population.

The steroid 21-hydroxylase deficiency (21OHD) is the most frequent cause of congenital adrenal hyperplasia. We have characterized the disease-causing mutations in the 21-hydroxylase genes of 63 patients with salt-wasting congenital adrenal hyperplasia from a Chilean population of Hispanic origin, a group that has been scarcely evaluated. Using allele-specific PCR, lesions were identified in 97 chromosomes out of 126 tested (77%). The most frequent findings were the gene deletion or large gene conversion (LGC) = 22.9%, I2 splice = 19%, R357W = 12.7%, and Q319X = 10.5%. We did not find alleles with the mutation F308insT and we found three alleles with the cluster E6. The frequency of the point mutation R357W was at least two times more frequent than the one found in Caucasians populations, but similar to that communicated in Asian populations; this finding may be explained by the Asian ancestry of our South-Amerindian population. The frequency of Q319X was also high, similar only to those patients studied in Italy and in a neighboring Argentinian population. In summary, this is a genetic characterization of 21OHD made in an almost pure Hispanic population in Latin America. The high frequency of deletion of CYP21B gene, I2 splice, R357W, and Q319X mutations probably reflects the European-Caucasian-Spanish influence of the conquerors, mixed with Amerindians of Asian ancestry and modulated by other European immigrations.

An alternative ELISA for T4 determination based on idiotype anti-idiotype interaction and a latex method for anti-idiotype monoclonal antibody selection.

This paper is the first report on the use of an idiotype-anti-idiotype monoclonal antibody reaction to develop an enzyme immunoassay for thyroxine (T4). We have developed a monoclonal antibody against T4, named 1F10 of IgG1 subclass and KA 5.21 x 10(8) M-1 which was used to obtain anti-idiotypic monoclonal antibodies. Anti-idiotypic antibodies were selected by a novel method, a passive agglutination assay with the idiotype monoclonal 1F10 absorbed on latex particles and subsequently characterized by RIA. One of these anti-idiotype antibodies, named 5B3--type beta antibody--of IgG1 subclass, was used to develop an enzyme-linked T4 idiotype-anti-idiotype immunosorbent assay. The T4 calibration curve, using the 1F10 idiotypic antibody adsorbed to solid phase and the 5B3 anti-idiotypic antibody conjugated to alkaline phosphatase (ALP), shows adequate performance in the range between 0.7-25 micrograms% of the analyte. The reliability of the proposed method is demonstrated by the correlation coefficient r = 0.74, found between T4 measured by RIA and our assay, with a panel of sera from euthyroid, hypothyroid and hyperthyroid individuals. The correlation coefficient was r = 0.93 within assays and r = 0.88 between assays. These results provide the basis for a new non isotopic assay for the study and diagnosis of T4-related human disease and provides a model to develop immunoassays for other haptens and small molecules of clinical interest.

Comparative study of size, total protein, fibrinogen and 5-HT content of human and canine platelet density subpopulations.

The size, total protein, fibrinogen and 5-HT content were evaluated in density subpopulations of human and canine platelets fractionated in linear arabinogalactan gradients. The methodology was assessed to ascertain that platelet separation was by density and to discard artifactual changes and platelet release during the procedure. EDTA or PGE1 increased the size of human PRP-platelets, but not of dog platelets. In humans, high density (HD) platelets were 1.26 times larger and contained 1.88 times more fibrinogen, 2.23 times more 5-HT and 1.37 times more protein than low density (LD) platelets; in dogs, these density cohorts did not differ in protein content, but LD platelets were 1.29 times larger and had 1.33 times more fibrinogen and 5-HT than HD platelets. These findings suggest that cell density is mostly dependent on the protein content per unit volume of platelets (and not on dense bodies). The differences in fibrinogen and 5-HT content between HD and LD cohorts in humans and dogs may be related to platelet age. The difference in volume between HD and LD platelets in dogs is of uncertain interpretation.

Platelet 5-hydroxytryptamine increases with platelet age in dogs.

Thrombocytopenia was induced in mongrel dogs by two mechanisms: immunologically, by intravenous injection of heterologous antiplatelet antibody, and non-immunologically, by circulating the blood through glass beads in anesthetized animals. The platelet content of 5-HT was monitored before and during the recovery of the blood platelet counts. This period is associated with the normalization of the mean platelet survival time and with a progressive increase in the mean age of the circulating platelet population. A continuous increment in platelet 5-HT closely followed the increase in platelet counts in both models of thrombocytopenia, and a strong correlation was found between the platelet age and 5-HT content. These findings support the concept that platelets accumulate 5-HT during their physiological aging process, contradicting the notion that a negative balance in 5-HT content results at the end of their physiological lifespan in circulation. These results are not in conflict with the concept that circulating platelets release and re-uptake 5-HT.

Ketoconazole alters cyclosporine pharmacokinetic profile and may predispose to acute rejection.

Ketoconazole (KET) is frequently used as a cyclosporine (CyA)-sparing agent. Adequate exposure to CyA is critical to avoid acute rejection (AR) or chronic rejection (CR). We compared the pharmacokinetic profiles of nine stable renal transplant patients on CyA before and after conversion to KET (200 mg/d of KET simultaneous with CyA). The CyA doses were adjusted to achieve similar drug exposures. The mean dose reduction of CyA while on KET was 83% from 3.2 +/- 0.9 to 0.6 +/- 0.2 (P <.000). Addition of KET produced a significant decrease in the absorption parameters of CyA and an increased elimination half-life. Coefficient of variation (CV) of AUC was significantly increased. Serum creatinine (SCr) at 3 months after switch remained the same. One patient experienced a grade I AR episode (11%). There were no adverse effects related to KET. Although addition of KET to CyA can significantly decrease the CyA dose, the observed pharmacokinetic changes involved decreased absorption and increased CV, which may respectively relate to AR and CR. The 11% AR rate observed is of concern. We do not recommend switching patients to KET as this may imply an increased risk of late AR or CR.

Y chromosome sequences in Turner's syndrome: association with virilization and gonadoblastoma.

UNLABELLED: The presence of Y chromosome fragments in patients with Turner's syndrome is known to increase the risk of gonadoblastoma and virilization. Y chromosome material is detected in up to 6% of patients with Turner's syndrome by karyotype. By DNA analysis, Y chromosome sequences have been reported in 0-60% of patients. The putative gonadoblastoma gene has been mapped to the pericentromeric region of the Y chromosome increasing the interest in studying these sequences. AIMS: 1. To determine the frequency of occult Y chromosome sequences in patients with Turner's syndrome. 2. To analyze the clinical implications of Y sequences detected by karyotype and occult Y sequences. STUDY DESIGN: Cross-sectional study of 58 patients with Turner's syndrome (30 45,X; two with structural anomalies; 26 mosaic [two of whom were 45,X/46,XY]). SRY, TSPY and DYZ3 sequences were amplified by PCR using genomic DNA from peripheral blood. RESULTS: All three Y chromosome sequences were found in one out of 56 patients whose karyotype was not suggestive of having Y chromosome material and in one patient with 45,X/46,Xr(X) karyotype. The patients with the ring chromosome and 45,X/46,XY karyotype underwent surgery and were found to have a gonadoblastoma and dysgerminoma. The four patients with Y chromosome material had non-virilized female genitalia. CONCLUSIONS: Analysis by PCR was more sensitive in detecting Y chromosome sequences than conventional karyotype. The presence of Y material was not associated with virilization. We confirmed the association of Y fragments and gonadoblastoma at an early age.