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Biomedical subjects

R Longhi

Publications and source records attributed to R Longhi.

At least 91 records · Page 5Linked to original sources
PubMed1989

Antipeptide antibodies toward the extracellular domain of insulin receptor beta-subunit.

In order to investigate structure and function of beta-subunit extracellular portion, four polyclonal antibodies (AP1, AP2, AP3 and AP4) toward peptides comprised in this region were generated. None of them recognizes native human and rat insulin receptor both in vitro and in whole cells. Two antibodies, AP1 and AP2, immunoprecipitate isolated (DTT-reduced) human beta-subunits and bind to human IM-9 cell after alpha-subunit tryptic cleavage. Only AP1 recognizes rat beta-subunit both in vitro and in trypsin treated rat FAD cells. These findings suggest that: (i) the extracellular portion of the insulin receptor beta-subunit is partially covered by the alpha-subunit in human and rat native insulin receptors; (ii) human and rat beta-subunit extracellular domains are different, at least in the amino acid sequence corresponding to residues 785-796 of the human insulin receptor.

Amino Acid Sequence↗
PubMed1989

Denaturation by urea and renaturation of 20 beta-hydroxysteroid dehydrogenase studied by high-performance size exclusion chromatography.

The denaturation by urea and renaturation of 20 beta-hydroxysteroid dehydrogenase, a tetrameric enzyme consisting of four identical subunits, were followed by high-performance size exclusion chromatography to detect intermediates in the processes. During the denaturation process no intermediate form (structured monomers or dimers) between the tetramer and the denatured monomer was observed. During the renaturation process, carried out either with or without NADH, high molecular weight aggregates, native tetramers, and low molecular weight intermediates were evidenced and quantified. The contemporaneous measurement of recovery of activity unambiguously demonstrated that the tetrameric structure is essential for enzymatic activity.

20-Hydroxysteroid Dehydrogenases↗
PubMed1988

Nicotinic acetylcholine receptor: a structural model for alpha-subunit peptide 188-201, the putative binding site for cholinergic agents.

A peptide corresponding to amino acid sequence 188-201 of the alpha-subunit of Torpedo AChR binds alpha-Bgtx. The S-S bridge between Cys 192 and 193 is essential for the binding as Tyr in position 189. The same sequence 188-201 corresponding to human AChR, which instead of Tyr has a Thr in position 189, binds alpha-Bgtx with a much lower efficiency. Monoclonal antibodies raised against Torpedo peptide 188-201 recognize Torpedo AChR and antibodies against Torpedo AChR recognize peptide 188-201 indicating that the synthetic peptide and the corresponding sequence in the native molecule share some immunological epitopes. With computer graphics and energy refinement a molecular model of this peptide has been elaborated.

Amino Acid Sequence↗
PubMed1988

Serotonin and noradrenaline concentrations and serotonin uptake in platelets from hyperphenylalaninaemic patients.

In three untreated patients with phenylketonuria (PKU), three PKU and six hyperphenylalaninaemic (HPA) patients in good metabolic control, the kinetic constants of platelet in vitro uptake of [14C]serotonin (5HT) did not significantly differ from those in 12 control subjects matched for age. The platelet concentrations of endogenous 5HT and noradrenaline (NA), taken as long-term indices of the amount of these amines circulating in plasma, were lower than normal in PKU and HPA patients, whether or not they were kept on a diet. However, a reduction in plasma NA concentrations at the moment of blood collection was seen only in untreated PKU patients. These data indicate that there may be a chronic inhibition of 5HT and possibly of NA synthesis even in PKU or HPA subjects in good metabolic control, with normal psychomotor development and only slightly raised plasma phenylalanine levels.

Adolescent↗
PubMed1988

Pattern reversal visual evoked potentials in phenylketonuria.

The pathogenesis of brain dysfunction in phenylketonuria (PKU) is still under investigation. Hyperphenylalaninaemia results in increased turnover of myelin. In order to demonstrate the derangement of myelinization in PKU we studied the visual evoked potentials (VEP) in 14 PKU patients and in 20 normal subjects. VEP findings were correlated with the metabolic control of the disease and with the electroencephalographic findings. VEP were more sensitive than the EEG in detecting a neurological dysfunction. VEP are influenced by dietary control and are normal only in children with good metabolic control.

Adolescent↗
PubMed1987

The binding site for alpha-bungarotoxin resides in the sequence 188-201 of the alpha-subunit of acetylcholine receptor: structure, conformation and binding characteristics of peptide [Lys] 188-201.

In order to study where the binding site of cholinergic agents is in the sequence of the alpha-subunit of nicotinic acetylcholine receptor (AChR), we have synthetized 3 peptides with an amino acid sequence corresponding to the following sequences of the alpha-subunit of Torpedo californica AChR: 125-143, 158-167, [Lys] 188-201. For binding studies the peptides were immobilized on Sepharose 4B. Only the peptide [Lys] 188-201 binds 125I-alpha-bungarotoxin (alpha-Bgtx) with Kd of 1.03 microM. The binding of 125I-alpha-Bgtx to the peptide is reduced by 85% after reduction of the S-S bridge present between 192-193 cysteines indicating that an intact disulfide bond is important for toxin binding. The 125I-alpha-Bgtx binding is inhibited by curare, decamethonium, hexamethonium but not by carbamylcholine and Naja naja siamensis alpha-toxin and P15 toxin. All these data provide direct evidence that the sequence 188-201 of the alpha-subunit of AChR binds alpha-Bgtx and that this binding has a pharmacological profile similar to that of nicotinic acetylcholine receptor.

Amino Acid Sequence↗
PubMed1987

Pattern-reversal visual evoked potentials in phenylketonuric children.

Pattern-reversal visual evoked potentials (PR-VEPs) and EEG were recorded in 14 phenylketonuric (PKU) children on a low-phenylalanine (phe) diet; the data obtained were correlated with metabolic parameters, namely, the actual phe plasma level, the mean phe plasma level in the last year, an the beginning of the diet. PR-VEPs seem to be more sensitive than EEG in detecting neurophysiological derangements in these subjects; in fact PR-VEPs were pathological in six patients while EEG detected three; no significant alterations were found in the neurophysiological tests among the children with good metabolic control, and only one child was abnormal among the six on an early dietetic regimen; in contrast, six of the nine subjects presenting with high mean phe plasma levels (greater than 10 mg/100 ml) and five of the eight whose diet started after the 2nd month of life showed pathological PR-VEPs.

Adolescent↗
PubMed1987

[Cardiac tolerance of a beta 2-sympathomimetic spray in 37 asthmatic adults monitored by Holter recording].

Thirty-seven asthmatic adults (27 women, 10 men), aged 28 to 70 yrs (mean 50. yrs), in a stable condition, were studied to assess the cardiac tolerance of B2SM sprays. These patients had no cardiac arrhythmia (checked by echocardiography), no hypertension and no hyperthyroidism. Two thirds had severe asthma, and 16 suffered from chronic asthma. After their condition was stabilized, they continued their previous treatment, consisting of theophylline (34 cases), moderate corticotherapy (19 cases), atropine spray (14 cases). Holter monitoring was performed before and 3 days after the institution of treatment by Fenoterol spray at 1,600 micrograms per day in 4 doses at fixed times. Gasometry was tested immediately before and during the protocol. Before B2SM treatment, 26 patients had a normal Holter, 11 had an abnormal first recording (4 important atrial ectopic beats (EBs), 5 ventricular EBs, 1 associating the two), 1 patient had an episode of ventricular tachycardia (VT). With Fenoterol, we observed (with no clinical manifestation) the aggravation of 1 pre-existing atrial EBs and 2 ventricular EBs. Two patients had a short episode of tachycardia but the role of Fenoterol was uncertain: one case was an elderly hypoxaemic patient and in the second a high theophylline level (20 mg/l) was found. The arrhythmogenic property peculiar to B2SM in spray form seems low at the dose we used. However in this study and in certain circumstances, such as hypoxemia, metabolic acidosis, or theophylline overload, the use B2SM may have contributed, together with other factors, to induce disquieting infraclinical cardiac dysrhythmia. We stress that this short-term study involved stable asthmatic patients under surveillance in hospital conditions.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1987

[Variations in venous physiology in the healthy subject. Postural and venous occlusion plethysmography studies].

The principal characteristic of the venous network is its distensibility, the reason for its role as blood reservoir and cardiovascular adaptation system. This distensibility varies continuously as a function of venous tone, of neurocardiovascular adaptation and of the method used for its determination. The importance of variability of venous physiology was investigated by postural and venous occlusion plethysmography. Two series of tests were performed in 3 healthy volunteers, each being treated over one month: one series involved 19 determinations during May 1985, the other 14 determinations in December 1985. Two plethysmographic methods were employed: conventional venous occlusion plethysmography in decubitus with compression of 50 mm Hg and postural plethysmography with venous occlusion only, using gravity force during variations in position of subjects. Venous filling, a function of venous distensibility, varied between 16.7 and 17.8% during venous occlusion and 23.9 and 31.7% during postural plethysmography. Emptying half-life was from 20.7 to 40.7%. Emptying rate was, by the 6th second, 17.3 to 21.6% for venous occlusion and 27.3 to 32.3% for postural plethysmography. A relation was not found between results for the two methods, suggesting that they explore different phenomena. Variability of venous physiology parameters is marked, modulations being due to general or local factors, the former acting on both legs simultaneously: exterior temperature, neurocardiovascular physiology, digestion, stress, relaxation. Factors can have their effects reduced by differential study of the two limbs.(ABSTRACT TRUNCATED AT 250 WORDS)

Adaptation, Physiological↗
PubMed1986

Clinical experience and results of treatment with suprofen in pediatrics. 5th communication: a single-blind study on antipyretic effect and tolerability of suprofen syrup versus metamizole drops in pediatric patients.

In a single-blind study, 60 children in two age groups (30 patients: 6 months to 3 years; 30 patients: 3 years to 12 years), were orally treated with either alpha-methyl-4-(2-thienyl-carbonyl)phenylacetic acid (suprofen, Suprol), syrup 10 mg/ml or metamizole drops 50% for a maximum period of 4 days, up to 4 times a day. The children presented with high fever due to bacterial or virus infections. Body temperature, pulse rate, and respiratory rate were evaluated at the beginning and then 30 min, 1, 1 1/2, 2, 3, 4, 5, and 6 h after the first administration of the respective drug. Significant differences between the drugs were found for all variables; this demonstrated that with suprofen the antipyretic effect set in more rapidly than with the reference drug. No side-effects were observed in children treated with suprofen syrup. Two patients showed adverse effects, i.e. sweating and hypotension, during the treatment with metamizole. Due to its good antipyretic effect and good tolerability, suprofen appears to be particularly useful for symptomatic treatment of pediatric patients with fever caused by bacterial or virus infections.

Adolescent↗