Severe type I protein C deficiency in a compound heterozygote for Y124C and Q132X mutations in exon 6 of the PROC gene

We report the genetic abnormalities in the protein C genes of a Spanish child with neonatal purpura fulminans and disseminated intravascular coagulation, associated with undetectable protein C levels. Direct sequencing of the nine protein C gene exons and their splice junctions indicated that the proband is a compound heterozygote with two mutant protein C gene alleles, Y124C and Q132X, that do not express protein C in plasma. The Y124C mutation was inherited from the mother and is due to a novel A to G transition at nucleotide 3416, which results in the substitution of cysteine for tyrosine 124, a highly conserved amino acid in EGF-like domains. The paternal inherited mutation (Q132X) is a C to T transition at nucleotide 3439, which replaces glutamine 132 with a Stop codon signal. This mutation, if expressed, should result in the synthesis of a truncated protein of 131 amino acids. Y124C or Q132X are present in the heterozygous state in the asymptomatic parents and siblings of the proband, all of which have half the normal plasma levels of protein C. Q123X has also been identified in families where type I PC deficiency is inherited as a clinically dominant trait. Therefore, the presence of the same mutation in a family showing a clinically recessive pattern of inheritance indicates that other factors, apart from the type of protein C gene mutation, are responsible for the clinical expression of protein C deficiency.

A novel polymorphism (6376 G/T) in intron 7 of the human protein C gene

A novel polymorphism (6376 G/T) in intron 7 (17) of the human PROC gene has been identified by direct DNA sequencing. Restriction analysis with the use of mutagenic primers indicate that the allele frequencies are 0.17 (allele T) and 0.83 (allele G), with a calculated heterozygosity of 28%.

A sensitive enzyme immunoassay for angiotensin II in serum

A sensitive and specific enzyme immunoassay for measuring angiotensin II (AII) has been developed as a convenient alternative to a radioimmunoassay. An antiserum to AII was prepared using AII conjugated by carbodi-imide to rabbit serum albumin, and coated on to microwell plates. The labelled antigen was prepared from AII and horseradish peroxidase using the periodate method. This enzyme immunoassay was a simple two-step procedure: 0.1 ml of AII-extracted plasma was incubated for 1 h at 37 degrees C; and 1 ml of labeled AII was incubated for 1 h at 37 degrees C. Bound horseradish peroxidase activity was then determined using o-phenylenediamine as chromogen by measuring the absorbance at 492 nm. The lower detection limit of the assay was 3.5 pmol l-1. Between- and within-assay RSD values were 8.8-18.3% and 6.9-17%, respectively, for concentrations of 10-40 pmol l-1. The accuracy of the assay, determined by recovery and linearity experiments, was 89-106% for recovery and 91-126% for parallelism. The results obtained by the present ELISA method were well correlated with those obtained by an established radioimmunoassay (n = 10, r = 0.96, intercept = 0.9 and slope = 1.02). This assay is easy to perform, rapid and does not require radioisotopes; thus it could be widely applied in clinical laboratories.

Levels of L-T3 in maternal and foetal compartments following experimental modifications of the maternal thyroid state in rats

In pregnant female rats, concentrations of tri-iodo-L-thyronine in maternal serum, amniotic fluid and placental tissue after 15, 18 and 20 days of gestation were measured by homologous radioimmune-analysis. The three experimental groups of pregnant rats were: 1) euthyroid (or control), 2) hypothyroid, provoked by iodine-deficient diet for two months before conception and during gestation, 3) hyperthyroid, provoked by subcutaneous injections of L-thyroxine during gestation. Maternal serum L-T3 was measured in order to check the thyroid state. Significant decreases in L-T3 concentrations were found at all stages of gestation in the amniotic fluid of hypothyroid group. The hormonal concentrations in the placental tissues were correlated with the different treatments (decreased in hypothyroid state and increased in hyperthyroid state). This could suggest that the transfer of maternal iodothyronines to the foetus influences its foetal thyroid development.

5' Deiodinase activity in brain regions of adult rats: modifications in different situations of experimental hypothyroidism

In the central nervous system, type II 5' deiodinase (5'D-II) is highly regulated, as judged by the dramatic changes in enzyme levels observed after abrupt alterations in thyroid status. In this work, the 5'-DII activity has been studied in different situations of experimental hypothyroidism (propylthiouracil, methimazole, thyroidectomy, and low iodine diet), in various brain regions (pituitary, cerebellum, brain stem, hypothalamus, cortex, and whole brain) in adult rats. Propylthiouracil and methimazole significantly increase the activity in all brain regions. These increases are higher in rats treated with methimazole. Thyroidectomy significantly increases the activity in cortex and pituitary. A low iodine diet significantly increases in all brain regions except in the hypothalamus. The concentration of triiodothyronine (T3) studied in the major brain regions remained unchanged. The results obtained show a compensatory mechanism in pituitary and other brain regions in order to maintain the T3 levels in brain tissue.

[Comparison of homologous and heterologous standard curves using TR-FIA for the determination of total T4 in the rat]

A homologous standard curve for rat T4 measurement has been compared to heterologous standard curves, by a time resolved fluoroimmunoassay (TR-FIA). Homologous standard curves have been carried out starting from rat serum in the absence of thyroid hormone by using Samuel's technique. The security criteria (sensitivity, inter and intraassay precision, and accuracy), were measured and compared between the homologous and heterologous test. Analysis of variance and slopes between homologous and heterologous standard curves showed homogeneous variances, the differences in the slopes being not significant.

Influence of thyroid hormone deficiency in DNA contents in different areas of adult rat brain

We have studied DNA concentrations in various regions of the adult rat brain in prolonged hypothyroidism of different origin. In both normal and hypothyroid rats hypophysis, cerebellum and hypothalamus contained the highest concentrations of DNA. Hypothyroidism produced a slight decrease in DNA content but this effect varied according to the different regions. These variations were due to changes in their maturation period, a critical and specific target for thyroid hormone action after birth.

Renin-angiotensin system in thyroidectomized rats at different periods of development

The relationship between the renal function and some components of the renin-angiotensin system has been studied in hypothyroid rats thyroidectomized surgically at different periods of their life. Changes in plasma renin concentration (PRC) depending on the period hypothyroidism were induced. Results showed that the renin release control could result from an equilibrium between the reduced beta-adrenergic activity and the marked natriuresis observed in hypothyroidism. A reduction in plasma angiotensinogen concentration (PAC), due to a decrease in its hepatic production, was observed in thyroidectomized animals. PAC reduction was independent of the hypothyroidism induction period. Alterations in plasma renin activity (PRA) were a consequence of PRC and PAC changes in thyroidectomized animals, as an increase in fractional sodium excretion (FENa) time course dependent, was found in these rats.

[L-thyroxine and L-triiodothyronine in the cerebral tissues of the adult rat. Effect of hypothyroidism]

The L-thyroxine and L-triiodothyronine concentrations in several brain areas (cerebral cortex, brain stem, hypothalamus, total brain and hypophysis) in normal and hypothyroid rats have been studied. Results show that L-thyroxine values at tissue level are inferior in the hypothyroid group, although non-significant with respect to the control group, whereas L-triiodothyronine presents values similar to the hypothyroid group and its control in all the brain regions studied with the exception of hypophysis. These results show that in hypothyroid situations exist a compensatory mechanism for maintaining the adequate L-triiodothyronine levels in several brain areas, although the serum levels are strongly decreased in hypothyroid animals.

Immunological characterization of L-triiodothyronine and L-thyroxine labelled with rhodamine B isothiocyanate

In the present work the label of L-T3 and L-T4 with RBITC have been developed by means of a relatively easy procedure. A purification by TLC, previously optimized, offers the possibility of obtaining a good recovery of conjugates T3 and T4-RBITC. The immunoreactivity of conjugates was calculated by a formulas especially designed for this purpose. This formulas could be applied to any molecule labelled with fluorescent compounds.

The Subunit Structure of Potato Tuber ADPglucose Pyrophosphorylase

ADPglucose pyrophosphorylase has been extensively purified from potato (Solanum tuberosum L.) tuber tissue to study its structure. By employing a modified published procedure (JR Sowokinos, J Preiss [1982] Plant Physiol 69: 1459-1466) together with Mono Q chromatography, a near homogeneous enzyme preparation was obtained with substantial improvement in enzyme yield and specific activity. In single dimensional sodium dodecyl sulfate polyacrylamide gels, the enzyme migrated as a single polypeptide band with a mobility of about 50,000 daltons. Analysis by two-dimensional polyacrylamide gel electrophoresis, however, revealed the presence of two types of subunits which could be distinguished by their slight differences in net charge and molecular weight. The smaller potato tuber subunit was recognized by antiserum prepared against the smaller spinach leaf 51 kilodalton ADPglucose pyrophosphorylase subunit. In contrast, the anti-54 kilodalton raised against the spinach leaf subunit did not significantly react to the tuber enzyme subunits. The results are consistent with the hypothesis that the potato tuber ADPglucose pyrophosphorylase is not composed of a simple homotetramer as previously suggested, but is a product of two separate and distinct subunits as observed for the spinach leaf and maize enzymes.

Molecular Characterization of the Brittle-2 Gene Effect on Maize Endosperm ADPglucose Pyrophosphorylase Subunits

Activity of the enzyme ADPglucose pyrophosphorylase is known to be reduced in maize (Zea mays L.) endosperm mutants at two independent loci, Shrunken-2 (Sh(2)) and Brittle-2 (Bt(2)). Spinach leaf ADPglucose pyrophosphorylase has previously been shown to comprise two subunits of 51 and 54 kilodaltons. Anti-bodies raised to each of the two subunits of spinach leaf ADPglucose pyrophosphorylase were found to cross-react to different bands on Western blots prepared from polyacrylamide gel electrophoresis separated wild-type maize endosperm proteins. The anti-spinach leaf 51 kilodalton subunit antibody cross-reacted with a 55 kilodalton maize endosperm protein and the anti-spinach leaf 54 kilodalton subunit antibody cross-reacted with a 60 kilodalton maize endosperm protein. These immunological reactions were observed in maize endosperm extracts and with a highly purified preparation of maize endosperm ADPglucose pyrophosphorylase. Mutant bt(2) endosperm lacked the 55 kilodalton subunit while mutant sh(2) endosperm lacked the 60 kilodalton subunit on Western blots. These results suggest that the maize endosperm ADPglucose pyrophosphorylase is made up of two immunologically dissimilar subunits and that the bt(2) and sh(2) mutations cause reduction in ADPglucose pyrophosphorylase activity through the lack of one of these two subunits. An ADPglucose pyrophosphorylase cDNA clone antigenically selected from a rice seed cDNA expression library was found to hybridize strongly with a cDNA corresponding to a maize endosperm transcript which is absent in a W64A bt(2) mutant. Thus, the bt(2) mutant causes the absence not only of the small subunit but of the corresponding transcript. Bt(2) is implicated as the structural gene for the small (54 kilodalton) subunit of maize endosperm ADPglucose pyrophosphorylase.

Serum activity of the key gluconeogenic enzymes in carbon-tetrachloride-induced experimental hepatotoxicity

Serum activity has been measured in three of the key enzymes in the gluconeogenic pathway in rats subjected to experimental hepatotoxicity after intraperitoneal administration of carbon tetrachloride. The levels of phosphoenolpyruvate carboxykinase (PEPCK) and fructose-1,6-biphosphatase (FBPase) showed a similar behavior to the transaminase (AST and ALT), increasing markedly with respect to the controls at 12 h after administration of the poison, reaching their maximum peak of activity at between 24 and 36 h, and returning to normal values at 96 h. The activity of glucose-6-phosphatase was not significantly modified throughout the treatment. These results seem to demonstrate that the determination of the serum activity of PEPCK and FBPase could be a sensitive and specific marker of hepatic cytolysis.

Immunocytochemical Localization of ADPglucose Pyrophosphorylase in Developing Potato Tuber Cells

The subcellular localization of ADPglucose pyrophosphorylase, a key regulatory enzyme in starch biosynthesis, was determined in developing potato tuber cells by immunocytochemical localization techniques at the light microscopy level. Specific labeling of ADPglucose pyrophosphorylase by either immunofluorescence or immunogold followed by silver enhancement was detected only in the amyloplasts and indicates that this enzyme is located exclusively in the amyloplasts in developing potato tuber cells. Labeling occurred on the starch grains and, in some instances, specific labeling patterns were evident which may be related to sites active in starch deposition.

The encoded primary sequence of a rice seed ADP-glucose pyrophosphorylase subunit and its homology to the bacterial enzyme

Rice seed ADP-glucose pyrophosphorylase cDNA clones were isolated by screening a lambda expression library prepared from rice endosperm poly(A+) RNA with a heterologous antibody raised against the spinach leaf enzyme and subsequently by nucleic acid hybridization. One cDNA plasmid, possessing about 1650 nucleotides, was shown by both DNA and RNA sequence analysis to contain the complete ADP-glucose pyrophosphorylase coding sequence of 483 amino acids. The primary sequence displayed a putative leader peptide presumably required for transport of this nuclear encoded protein into the amyloplasts, a differentiated starch containing plastid. The leader peptide, however, showed little sequence homology with transit peptides displayed by other known nuclear encoded proteins localized in the chloroplasts. A comparison of the primary sequence of the putative mature subunit to the Escherichia coli pyrophosphorylase showed two regions displaying significant homology. These two conserved regions contain residues shown previously to be essential for the allosteric regulation and catalytic activity of the E. coli enzyme. Differences in the primary sequences of the plant and bacterial enzyme may reflect the distinct nature of the allosteric effectors that control these enzymes.

Influence of thyroidectomy on serum and pituitary FSH in control and orchidectomized rats

The influence of hypothyroidism on both pituitary and serum FSH has been studied in male rats thyroidectomized in early stages of development. To know whether FSH alterations are produced by changes of the gonadal feed-back system or by a direct effect of thyroid hormones upon pituitary synthesis, estradiol, testosterone and testicular weight were measured. The result showed a decrease of biological and immunological activity of pituitary FSH in thyroidectomized rats. Serum FSH levels were also low. The deficiency of FSH production cannot be attributed to an alteration of the gonadal feed-back systems, since (1) in thyroidectomized rats, estradiol and testosterone were lower than in the controls, (2) signs of tubular atrophy were found in the testes and hence it could be expected that inhibin is low, and (3) in the absence of gonadal factors (induced by orchidectomy) thyroidectomized rats also showed a decrease of pituitary FSH. The present data suggest that the decrease of FSH can be attributed to a direct effect of thyroid hormones on pituitary FSH production.

Effect of low-iodine diet and propylthiouracil on glycolytic enzymes in brain areas of adult rats

Glycolytic activity of five brain areas in the rat was studied under two hypothyroid states: (1) induced by low-iodine diet from weaning, and (2) induced by propylthiouracil. The areas studied were the anterior cortex, amygdala, hypothalamus, septum and hippocampus. A low-iodine diet induced a decrease of pyruvate kinase activity in three region and of phosphofructokinase in the hippocampus, while hexokinase increased in both the amygdala and septum. Propylthiouracil treatment produced an increase in hexokinase activity in the hypothalamus and septum, and a decrease in the anterior cortex, while phosphofructokinase decreased significantly in the hippocampus. No significant changes of lactate dehydrogenase activity were observed. The correlation between the results and type of hypothyroidism is discussed.