Idiopathic reactive hypoglycemia: a role for glucagon?

We previously reported that patients with idiopathic reactive hypoglycemia (plasma glucose concentration lower than 2.5 mmol/L 2-4 h after the ingestion of 75 g of glucose) display reduced or absent counterregulatory response of the glucagon secretion and increased insulin sensitivity. In order to examine the effect of glucagon on the increased insulin sensitivity in these patients, 12 subjects with idiopathic reactive hypoglycemia underwent a two-step hyperinsulinemic (1 mU/kg.min) euglycemic glucose clamp and were compared with 12 normal control subjects matched for age, weight and sex. During the first step of the glucose clamp (only insulin + glucose infusion) the patients with Idiopathic Reactive Hypoglycemia required higher glucose infusion rates to maintain euglycemia than normal subjects (9.09 +/- 0.29 mg/kg. min vs 7.61 mg/kg.min). When basal glucagon secretion was replaced (+ somatostatin and glucagon, second step of the clamp) the glucose infusion rates required to maintain euglycemia in patients with Idiopathic Reactive Hypoglycemia significantly decreased (to 7.17 +/- 0.40 mg/kg.min) and resulted similar to normal subjects (7.64 +/- 0.41 mg/kg.min). Thus, in patients affected by Idiopathic Reactive Hypoglycemia, glucagon secretion may play an important role in the pathogenesis of the increased insulin sensitivity and hypoglycemia.

Changes in central and peripheral nervous system function during hypoglycemia in man: an electro-physiological quantification.

We measured somatosensory evoked potentials (SEP) in normal subjects during acute (group A) and moderately prolonged (group B) hypoglycemia. We considered the following parameters: peripheral conduction velocity (wrist-Erb CV), conduction time (CT) between brachial plexus and the cervical cord (Erb-N13) and central CT from the cervical cord/lower brainstem lemniscal pathway to the cortex (N13-N20). In group A, the electrophysiological parameters did not change significantly throughout the study. In group B, mean N13-N20 CT increased from a basal values of 5.82 +/- 0.11 to 6.22 +/- 0.11 msec at 105 min (p less than 0.02) and 6.33 +/- 0.11 msec at 120 min (p less than 0.05). This study indicates that neither acute nor moderately prolonged hypoglycemia influence the peripheral nerve function in normal subjects and provides evidence that hypoglycemia as low as 2.4 mmol/L, lasting more than 60 min, can significantly increase the conduction time of central somatosensory pathways.

Kinetics of the Hb A to Hb C switch and erythropoietin plasma levels in sheep.

The induction of Hb A (alpha 2 beta A2) and Hb C (alpha 2 beta C2) synthesis in three adult sheep has been sequentially analysed, in relation to the reduction of the haematocrit (Ht) and to the changes of erythropoietin (Epo) concentration in plasma. Hb A production is detected in peripheral reticulocytes when the Ht approaches 70% of its initial value in correspondence with the first rise of EPO plasma level, whereas HB C synthesis appears when the Ht is further reduced to about 50%, at an Epo concentration two to three times higher. The assumption that the cell committed to HB C synthesis is close to the erythroid colony-forming unit (CFU-e) progenitor is also discussed.

A comparison of methods for the detection of hepatitis B virus surface antigen (HBsAg).

Our aim was to check the relative sensitivity of the various commercial kits available on the Italian market for the detection of hepatitis B virus surface antigen (HBsAg) in its two subtypes ay and ad. To this end, panels from different producers were compared by parallel sensitivity assays of several kits. It was found that the kits revealed different sensitivities depending on the panel used, and that sensitivity curves were not parallel. Given the lack of uniformity of response in the various panels currently available, we preferred to use two panels prepared at the Istituto Superiore di Sanità, one for each of the aforementioned subtypes. These HBsAg serial-concentration preparations were used to measure the sensitivity of the different kits on the basis of distinct methodological principles, i.e. RIA, ELISA and RPHA. These are currently considered the most sensitive methodologies and are used for kits classified as belonging to the 3rd generation. For each kit we used the procedure indicated by its manufacturer as being the most sensitive. For some of the kits we adopted all procedures in parallel recommended by respective manufacturers for different conditions of use. Sensitivity was found to be a function of lot, kit, methodology and procedure used. For the RIA and ELISA kits, we also used a modified method in parallel with the normal procedures. This method consisted in presaturating the solid phase in a solution of bovine albumin serum and was generally shown to increase the sensitivity of the kit adopted. For the majority of the kits examined, as well as the direct tests, a confirmatory test was also used, i.e. a specific inhibition test to verify the positivity revealed. In this way an increase in the sensitivity of the sample was also obtained.

Radioimmunoassay detection of HBsAg in hemoderivatives.

The aim of the present paper is that of developing a technique which exploiting a commercial RIA Kit (Ausria II - Abbott) could be employed for the detection of HBsAg also in products different from serum or plasma, such as hemoderivates, even when as negative control is employed the kit, made up of a pool of HBsAg and HBsAb negative plasma. In order to lower the probability of false positive and false negatives the Authors employed, in parallel with the normal Abbott technique, a modified technique, which involves the presaturation of the polystyrene beads with human serum albumin solution. This technique showed to increase the sensitivity relevant to the kit itself. The technique with successive contacts employed by the Authors allowed the carrying out of the confirmation test for those blood derivatives also, which tend to clot, both due to the treatments and for the addition of the reagents employed in the confirmation test. In order the get a better garantee in classifying as "non-reactive" a sample the Authors expect it to be timely to carry out, in addition to the direct test, a confirmation test. Samples with titrated HBsAg additions and showing C/N > 1.5 in the direct test, turned out reactive to the confirmation test. Recovery tests show, even considering the variability of the sensitivity of the kit, according to the batch and the date of use, an indication of the sensitivity of the RIA method for HBsAg detection in hemoderivatives.

Insulin secretion in children with growth retardation.

The effect of tolbutamide administration on insulin secretion was studied in 69 children with growth retardation. Diminished insulin secretion was found in all the patients, compared to the control group. This insulin deficit was most evident in patients with isolated, total GH deficiency and least evident in children with idiopathic short stature. Intermediate values were found in dwarfism due to isolated, partial GH deficiency. These results favour the hypothesis that hypoinsulinism contributes to the somatotropin deficiency in causing growth retardation.

Survey on controls for the presence of HBsAg in products based on hemoderivatives.

In Italy, Health Ministry provisions prohibit the marketing of products based on hemoderivatives unless they have first been controlled for the presence of HBsAg by means of radioimmunoassay. The present survey considers certificates submitted by Pharmaceutical Companies to the Health Department for permission to market their hemoderivative-based products. The results of the survey are discussed, and compared with the data obtained by the AA. in official control analyses, so as to arrive at some conclusion as to the applicability of currently employed RIA methods to HBsAg detection in hemoderivatives.

Study of methods for the detection of HBsAg and HBsAb in hemoderivatives.

For application to the control of hemoderivatives of the methods adopted for the detection of HBsAg and HBsAb in sera or plasma, using radioimmunological kits, it is necessary for the methods to have greater sensitivity and reliability, which can be achieved by employing complementary tests or by modifying certain phases of the normal methods. Particularly in the case of hemoderivatives with a high infectivity risk, application of the normal procedures entails problems of a kind such as to rule out the test altogether or to adversely affect its reliability. The preliminary data obtained with modifications of the methods according to the Abbott AUSRIA II and AUSAB RIA kits are here reported; these data seem to indicate that the reliability of the tests is improved.

Results of a comparative study on insulin radioimmunoassay in 36 Italian laboratories.

An interlaboratory study in which the insulin contents of five plasma samples were estimated in 36 italian laboratories was coordinated by the Istituto Superiore di Sanità (National Institute of Health) and the Consiglio Nazionale delle Ricerche (National Research Council). A rather large between-laboratory variability resulted, though the ranking of samples according to their insulin concentrations was practically the same. A significant dependence of estimates on the method used was established. The analysis of data, aimed at defining the possible reasons of the assay variability, is reported and discussed.