Alloxan-induced diabetes mellitus in pregnant sheep and chronic fetal catheterization

25 female sheep of the Texel breed were made hyperglycaemic by administration of alloxan monohydrate (ALX) in early pregnancy and 15 ewes served as controls. Average venous glucose levels (mean +/- standard deviation) increased from 3.5 +/- 0.2 to 14.0 +/- 1.8 mmol/l. All hyperglycaemic sheep were treated with long-acting insulin in doses adjusted individually (0.2-1.0 U/kg per day) to keep glucose levels above 8 mmol/l. After a temporary significant increase, maternal venous concentrations of urea and creatinine returned to normal levels. One sheep died on day 6 after administration of ALX. Another hyperglycaemic sheep died at induction of anaesthesia. Eight hyperglycaemic ewes aborted between days 90 and 128 of gestation. Between days 103 and 135 of gestation the remaining hyperglycaemic (n = 15) and control (n = 15) ewes were operated upon and the fetuses were provided with EEG, nuchal EMG and ECG electrodes and catheters in the trachea, amniotic fluid, jugular vein and carotid artery. Use of the chronic sheep preparation for the study of diabetes mellitus and fetal reactions was successful in 10 out of 25 cases, as in the diabetic group postoperative intra-uterine fetal survival varied between 2 and 19 days and in 10 cases was at least 5 days. Postoperative intrauterine fetal survival in the controls was significantly longer and varied between 4 and 28 days, and in 13 cases was at least 5 days. A highly significant correlation (P less than 10-6) between maternal and fetal blood glucose levels was seen.(ABSTRACT TRUNCATED AT 250 WORDS)     

Calcitonin gene-related peptide in human obesity.

We studied plasma calcitonin gene-related peptide (CGRP) levels in obese women before (n = 24) and after (n = 13) weight loss, and in normal weight controls (n = 15). Furthermore, the influence of two isocaloric meals (high carbohydrate vs. high fat) on plasma CGRP concentrations was studied. The CGRP concentration in the obese group (32.26 +/- 2.01 pg/ml) was significantly (p less than 0.0001) higher than in the control group (21.64 +/- 0.15 pg/ml). After weight loss (14.3 +/- 0.72% of original weight) CGRP concentrations remained unchanged. Only the high-fat meal caused a significant (p less than 0.02) rise in CGRP levels. Our results indicate that elevated plasma CGRP levels may constitute a primary phenomenon in obese women, and that fat intake may be associated with increased CGRP secretion.     

Nitrogen assimilation and transport in carob plants

Most of the nitrate reductase activity (80%;) in carob ( Ceratonia siliqua L. cv. Mulata) is localised in the roots. The nitrate concentration in the leaves is relatively low compared to that in the roots, suggesting that nitrate influx into the leaf may be a major factor limiting the levels of nitrate reductase in the shoot. Transport of nitrate from root to shoot appears limited by the entrance of nitrate into the xylem. In order to study this problem, we determined the nitrate concentrations and nitrate reductase activities along the roots of nitrate-grown plants, as well as the composition of the xylem sap and the nitrate levels in the leaves. Some of the the bypocotyl, in order to bypass the loading of nitrate into the xylem of the roots. The results show that the loading of nitrate into the xylem is a limiting step.
The cation and anion concentrations of nitrate- and ammonium-fed plants were similar, showing almost no production of organic anions. In both nitrate- and ammonium-fed plants, the transport of nitrogen from root to shoot was in the form of organic nitrogen compounds. The nitrate reductase activity in the roots was more than sufficient to explain all the efflux of OH⁻ into the root medium of nitrate-fed plants. In carob plants the K-shuttle may thus be operative to a limited extent only, corresponding to between 11 and 27%; of the nitrate taken up. Potassium seems to be the cation accompanying stored nitrate in the roots of carob seedlings, since they accumulate nearly stoichiometric amounts of K⁺ and NO⁻₃.     

Interactions between nitrate and ammonium during uptake by carob seedlings and the effect of the form of earlier nitrogen nutrition

Seedlings of carob ( Ceratonia siliqua L. cv. Mulata) were used in two sets of experiments in order to evaluate; (1) the reciprocal effects of each nitrogen form on net uptake of nitrate and ammonium, and (2) the effect of earlier nitrogen nutrition on ammonium versus nitrate uptake. In the former group of experiments we studied the kinetics of nitrate and ammonium uptake as well as the interference of each of the two forms with net uptake of ammonium and nitrate by both nitrogen depleted and nitrogen fed carob seedlings. On the whole, nitrogen depletion led to increase in both affinity and V_max of the system for both forms of nitrogen, at the same time as the effects of nitrate on uptake of ammonium and vice versa were concentration dependent. In the second group of experiments the effects of earlier nitrogen nutrition on nitrate and ammonium uptake were characterized, and in this case we observed that: (a) if only one form of N was supplied, ammonium was taken up in greater amounts than nitrate; (b) the presence of ammonium enhanced nitrate uptake; (c) ammonium uptake was inhibited by nitrate; (d) there was a significant effect of the earlier nitrogen nutrition on the response of the plants to a different nitrogen source. The latter was evident mainly as regards ammonium uptake by plants grown in ammonium nitrate. The interactions between nitrate and ammonium uptake systems are discussed on the basis of the adaptation to the nitrogen source during early growth.     

Nitrite activation of nitrate reductase in higher plants

Comparative studies of nitrate-activated nitrate reductase (NR-NO₂) and nitrate-induced nitrate reductase (NR-NO₃) (EC 1.6.6.2) indicate that the enzymes differ in structure, heat stability, and pH dependence, but have the same cofactor requirment. NR-NO₂ developes in barley (Hordeum vulgare L. var. Dvir) seedlings as NR-NO₃ disappears. A transition from the active to the inactive form of nitrate reductase takes place. Nitrite seems to activate the inactive form of the enzyme.     

Expression of the first calcitonin/CGRP gene in spontaneous and transplanted rat medullary thyroid carcinoma: a comparison of dot-blot analysis, in situ hybridization, and immunohistochemistry.

Calcitonin (CT) and calcitonin gene-related peptide (CGRP) are encoded by a single gene, the CALC-I gene. They are expressed in the thyroid and in the nervous system by alternative splicing of the pre-messenger RNA derived from the CALC-I gene. In medullary thyroid carcinoma (MTC), a malignancy derived from the calcitonin-producing C-cells in the thyroid, production of calcitonin and CGRP is a common feature. We investigated the CT and CGRP production of four spontaneous MTCs transplanted three to four times and 14 MTC lines transplanted for several years in WAG/Rij rats, a strain with hereditary MTC. The expression of CT and CGRP in the spontaneous and in the transplanted tumors was studied by means of RNA in situ hybridization (RISH), dot-blot analysis, and immunohistochemistry. A down-regulation of CT production in transplanted compared with spontaneous tumors was observed, but an inverse relation between CT and CGRP mRNA content in both spontaneous and transplanted tumors was not observed. In this study, RISH proved to be as sensitive as dot-blot analysis to detect gene expression in tissue samples. The different approaches of analyzing the gene expression in tissue samples (the cellular localization of gene expression by ISH vs the analysis of an extract of a total tissue sample with dot-blot analysis) showed that each technique is equal in value and that they are complementary to each other.     

Glycolate oxidase content of microbodies as affected by nitrate

Glycolate oxidase is loosely held by microbodies obtained from etiolated barley (Hordeum vulgare L.) leaves depleted of nitrate. Defined centrifugation conditions cause the complete detachment of the enzyme from the microbodies. Addition of nitrate to these plants brings about a greater retention of glycolate oxidase by the microbodies. Synthesis of a nitrate-induced protein seems to be responsible for the enhanced retention of glycolate oxidase. Catalase, on the contrary, is strongly attached to the microbodies under all nutritional and experimental conditions considered.     

Enzyme content of plant microbodies as affected by experimental procedures

The content of specific enzymes in microbodies isolated from tobacco Nicotiana rustica, L. leaves may vary according to the procedure followed during the isolation of the organelles. The type of homogenizing medium, its ionic components and the ratio of medium to tissue during homogenization, affect the over-all yield and relative distribution of each microbody enzyme in different ways. The type of density gradient and the initial acceleration of the centrifuge rotor affect also the enzyme content of sedimenting microbodies. These observations explain some of the conflicting results obtained on the determination of the intracellular location of several enzymes.