Showing papers by "University of Naples Federico II published in 1983"

Preferred conformations of peptides containing α,α‐disubstituted α‐amino acids

Abstract: The conformational preferences of linear peptides containing α,α-disubstituted α-amino acids, derived from the crystal structures of 28 compounds, are reviewed. In particular, the sensitivity of peptide conformation to the geometry of these unusual amino acids is underlined. We also consider possible future directions of research, which, we hope, will result in a complete understanding of the structures adopted by peptaibol antibiotics.

Abnormalities of Calcium Metabolism in Essential Hypertension

Abstract: Calcium metabolism has been investigated in patients with essential hypertension and normal renal function to evaluate the renal calcium handling and the reported increase in renal calcium loss. In 55 hypertensive and 55 sex- and age-matched healthy normotensive subjects creatinine clearance, serum total and ionized calcium, plasma parathyroid hormone and 24 h urinary excretion of calcium, sodium and cAMP were measured. In a subgroup of 20 hypertensive patients and 20 controls the fasting calcium excretion rate was also measured. Both 24 h and fasting calcium excretion rates were higher in the hypertensive group; so also were plasma parathyroid hormone and urinary cAMP. Serum total and ionized calcium levels were not different in the two groups. After intravenous calcium infusion (15 mg 3 h-1 kg-1) in seven hypertensive patients and controls, the hypertensive patients excreted more calcium at all serum calcium concentrations. These results support the hypothesis of primary renal calcium leak in essential hypertension. Enhanced urinary calcium excretion rate may cause compensatory parathyroid overactivity.

An Adaptive Model Following Control for Robotic Manipulators

Abstract: On developpe un systeme de commande adaptative avec poursuite de modele pour des robots manipulateurs, a l'aide de la theorie de l'hyperstabilite

Comparative study of the arterial and lacunary systems of the ventricular myocardium of elasmobranch and teleost fishes

Abstract: The typical fish heart has a spongy trabeculated ventricular myocardium (spongiosa) supplied by the venous blood of the intertrabecular spaces (lacunae); hence it is called a "venous heart." However, in some fishes a more complex ventricular muscle is found (mixed type), in which the spongiosa is covered by an outer layer of densely arranged myocardial bundles (compacta). The compacta receives oxygenated blood from the coronary vessels. The objective of this study was to investigate relations between myoarchitecture and blood supply with an emphasis on the hitherto unexplored, putative vascular connections between the arterial and the lacunary circuits. Using histological methods combined with vascular cast techniques and India ink injections, it was possible to define four different types of ventricular myocardium and its microvasculature. In some of them an intramural network arises from the subepicardial arterial system supplying the compacta and also is distributed to the spongiosa. Extensive arterio-luminal vessels connect this coronary bed with the lacunary circuit of the spongiosa, so realizing the first evolutionary step of the Thebesian system. The highest development of these connections is found in some very active pelagic fishes. The functional morphology of these vascular patterns is discussed in relation to the phylogenetic and functional context of the fish heart. It appears that the concept of the piscine heart as a typical "venous" type is an oversimplified generalization, at least on morphological grounds.

Prospective study of X-linked progressive muscular dystrophy in Campania

Abstract: Within the Campania region of southern Italy a prospective study on X-linked progressive muscular dystrophy was conducted over a period of 12 years from 1969 to 1980, inclusive. The mean incidence rate was 21.7 per 100,000 male livebirths for Duchenne muscular dystrophy (DMD) cases and 3.2 per 100,000 male livebirths for Becker muscular dystrophy (BMD) cases. The familial cases were 38.5% among the DMD patients and 50% among the BMD patients. Myocardial involvement appeared in DMD patients at about 6 years of age in a high percentage of cases and increased progressively until the last years of life, when cardiac damage occurred in 95% of cases. The percentage of myocardial involvement in BMD patients was very low before 13 years of age, but increased progressively until 20 years, when cardiac damage occurred in 80% of cases studied; severe cardiomyopathy did not occur before the age of 21. The data reported also include the effects of age on physical performance, serum creatine kinase activity and serum myoglobin levels, the types of cardiac damage, and the causes of death.

Cloning and sequencing of a full length cDNA coding for human retinol-binding protein

Abstract: We have isolated and sequenced a cDNA clone coding for human Retinol Binding Protein. The sequence indicates that Retinol Binding Protein is synthesized as a single polypeptide chain precursor which is then matured to the secreted protein by removal of a leader peptide. Southern and Northern blot analysis suggest that the gene is present in one or few copies per haploid genome and is transcribed in a single mRNA species.

Some representational issues in default reasoning

Abstract: Although most commonly occurring default rules are normal when viewed in isolation, they can interact with each other in ways that lead to the derivation of anomalous default assumptions. In order to deal with such anomalies it is necessary to re-represent these rules, in some cases by introducing non-normal defaults. The need to consider such potential interactions leads to a new concept of integrity, distinct from the conventional integrity issues of first order data bases. The non-normal default rules required to deal with default interactions all have a common pattern. Default theories conforming to this pattern are considerably more complex than normal default theories. For example, they need not have extensions, and they lack the property of semi-monotonicity. Current semantic network representations fail to reason correctly with defaults. However, when viewed as indexing schemes on logical formulae, networks can be seen to provide computationally feasible heuristics for the consistency checks required by default reasoning.

Ovarian activity and reproduction in the frog, Rana esculenta

Abstract: Rana esculenta specimens were collected, during the last 13 years, in well-defined areas around Naples. The annual ovarian cycle shows distinct phases of recrudescence (starting September; vitellogenesis), breeding (late March-early July; egg deposition and active oogenesis) and quiescence (July-August; no follicular growth). Previtellogenic follicles are recruited for vitellogenesis in early September and in between two successive ovulatory waves. Breeding congregations are generally formed after a heavy rain fall and eggs are laid in standing waters, temporary or permanent. A maximum of three clutches of eggs is produced during the breeding season, at roughly monthly intervals. All mature females reproduce to some extent. Ovarian weight and clutch size are positively correlated to body weight. Depending upon the body size, the potential clutch size ranges from 1000 to 3500 eggs during the first wave of ovulation and it is notably smaller in the successive wave(s) of ovulation. Egg masses and tadpoles are left unprotected and mortality is high. The life cycle from the fertilized egg to completion of metamorphosis is 2 months and oogenesis in the ovary starts in the larva before the onset of metamorphic climax. Young females hatching from the first clutch of eggs may reach sexual maturity and breed in May the following year; those hatching from the last clutch require nearly 20 months to reach sexual maturity. The importance of some endocrine and exocrine factors for the regulation of ovarian activity and reproduction is discussed.

Male sexual function after abdominoperineal resection for rectal cancer.

Abstract: In a series of 26 male patients undergoing abdominoperineal resection of the rectum for malignant disease, a detailed history of sexual function was obtained, using a questionnaire before and 12 months after the operation. The overall incidence of sexual dysfunction was 61.5 per cent, total and partial erectile impotence being, respectively, both 27 per cent. Taking age into account, among men of the youngest age group (41-48 yrs), incidence of complete and partial erectile impotence was 14 per cent. In the middle age group (49-57 yrs), 22 per cent reported total and 33 per cent reported partial erectile impotence, whereas in patients of the oldest group (58-65 yrs), total erectile impotence was present in 40 per cent and partial in an additional 30 per cent. The extent of the disease (Dukes' stage) was found to be of no value as a prognostic index of postoperative sexual dysfunction. It is concluded that the age of the patients is the most important factor related to sexual activity after abdominoperineal resection for cancer.

Dissociation between transformed and differentiated phenotype in rat thyroid epithelial cells after transformation with a temperature-sensitive mutant of the Kirsten murine sarcoma virus.

Abstract: Differentiated rat thyroid epithelial cells, infected in vitro with a temperature-sensitive mutant of the Kirsten murine sarcoma virus, expressed at the permissive temperature (33 degrees C) some phenotypic properties typical of transformed cells, including morphological features, colony formation in agar, and induction of tumors in newborn animals. Specific functional markers of these differentiated cells, i.e., synthesis/secretion of thyroglobulin, synthesis of thyroglobulin mRNA and iodide uptake, were blocked during growth at 33 degrees C. Normal morphology, failure to grow in agar, and the requirement of hormones for optimal growth were all restored after shifting to the temperature nonpermissive for transformation (39 degrees C), though the typical differentiated functions remained blocked. Infection with a leukemia helper virus clone (Moloney or Kirsten murine leukemia virus) did not lead to the loss of the differentiated phenotype of rat epithelial thyroid cells, thus demonstrating that the loss of the differentiated phenotype is caused by the sarcoma virus component. These results indicate that the expression of some of the phenotypic properties of transformed differentiated rat thyroid epithelial cells is under the direct control of the p21 thermosensitive activity, whereas the block in the expression of two typical differentiation markers of thyroid epithelial cells is irreversible and probably controlled by different mechanisms.

Sequence of human haptoglobin cDNA: evidence that the alpha and beta subunits are coded by the same mRNA.

Abstract: We have isolated and sequenced a cDNA clone coding for human haptoglobin. Our sequence shows that haptoglobin is very likely synthesized as a single polypeptide chain which is then cleaved at an Arg residue to generate its two characteristic alpha and beta subunit. Southern blot analysis suggests that there are at least two copies of the haptoglobin gene per haploid genome.

A quasi-one-dimensional analysis of vertical JFET devices operated in the bipolar mode

Abstract: “Bipolar operation”, namely forward-basing the gate-source diode of a JFET, has been proposed in the literature as a means to reduce the on-state resistance of such devices. In this paper, the physics of bipolar operation of power JFET's is analysed in detail and closed-form solutions of its output characteristics are derived as a function of the device geometry and of physical parameters of the semiconductor. From that model, it turns out that the low value of the saturation voltage originates from the existence of an high-density electron-hole plasma that fills the space between source and drain. In the active region of the output characteristics, the control of the gate current the drain current is due to the possibility to control the level of majority-carrier injection from the source transition. The closed-form expression for the current gain allows to identify the structure parameters that affect it. It shown that, under suitable conditions, a substantial current amplification can be observed. The model has been found to be in good agreement with the results obtained on experimental devices.

Circannual rhythms of plasma luteinizing hormone, follicle‐stimulating hormone, testosterone, prolactin and cortisol in prepuberty

Abstract: For a period of four years we have been studying 106 healthy males and 66 healthy females, aged 6-10, by cross-sectional design, to look for evidence of a circannual rhythm in LH, FSH, testosterone, PRL, and cortisol secretion. Plasma samples were taken at 0800 h and all hormones were measured by RIA. A cosine function was fitted to the single data to indicate any significant circannual (about 1 year) rhythm and to estimate its parameters: mesor, amplitude, and acrophase. Annual changes were validated in the secretion of: LH (annual crest time in January in both sexes), testosterone (studied only in males, annual crest time in July), and PRL (significant rhythm only in females with annual crest time in March). FSH and cortisol did not show an annual rhythm in both sexes. Our data suggest that sex influences the circannual hormonal rhythms from prepuberty onwards.

Friedreich's ataxia: electrophysiological and histological findings

Abstract: Electromyography was performed, and motor and sensory nerve conduction velocities were measured in 19 patients definitely affected by Friedreich's ataxia. Biopsy of the sural nerve was also performed in 9 patients. Most patients presented a moderate to severe loss of motor units, a significant increase in mean duration of motor unit potentials, and in the incidence of polyphasic potentials. Short-lasting spontaneous activity was rarely seen. Conduction velocity along the motor and sensory fibres of the median and tibial nerves was moderately slowed, while distal conduction time to muscle was significantly increased and the sensory orthodromically-evoked response markedly reduced. Intraoperative electrophysiological recordings obtained during biopsy of the sural nerve in 4 patients were consistent with the changes conventionally observed in the median, tibial and sural (6 patients) nerves. Quantitative histology revealed a reduced number of total myelinated fibres with a severe loss of large fibres, and a moderate loss of fibres of less than 7 microns in diameter. In teased nerve fibre preparations, the most evident abnormality consisted of fibres with uniformly short internodal length, while signs of remyelination were less prominent. Signs of active axonal degeneration were rarely observed in electron microscopy. Electrophysiological and histological findings were uniformly distributed, and the changes were neither related to the duration nor to the severity of the clinical condition.

Universal unfolding of Hamiltonian systems: From symplectic structure to fiber bundles

Abstract: The problem of the global Lagrangian description of a dynamical system which has a global Hamiltonian description is considered; the motion of a charged particle in the field of a static magnetic monopole is a prototype of such dynamical problems. The symplectic structure on the (cotangent bundle of the) manifold is associated with a closed but not necessarily exact two-form. In conventional language this means that the tensor field inverse to the symplectic metric is divergence free but not necessarily expressible globally as the curl of a vector field; and hence the usual passage to Hamilton's principle and the Lagrangian can be carried out in patches but not necessarily globally. Generalizing techniques developed elsewhere, we show that the fundamental expression for the action integral is like the surface integral of the closed but not necessarily exact antisymmetric tensor field (two-form) rather than like the line integral of a vector field (one-form). This naturally leads to the path-space formalism in which the action functional depends not only on a point in configuration space but also a path from a chosen fixed point terminating in the relevant point in configuration space. We then show how this is a "universal unfolding" and how the topological obstructions in the configuration-space description are circumvented in the path-space description. The path-space description contains redundancies and they can be reduced; locally the new manifold is obtained by associating an angle of rotation [a U(1) fiber] with each configuration-space point, but globally there would be a nontrivial fiber-bundle structure. These questions naturally carry over to the quantum theory of such systems and it is shown how quantization conditions arise. The structure of the quantum-theory formalism for such systems is analyzed. The considerations are applied to the monopole problem where the enlarged space in which the Lagrangian description is possible is explicitly identified as the manifold of the group SU(2).

Thermal and rheological properties of blends of polystyrene and thermotropic liquid crystals

Abstract: The rheological and thermal properties of composites of polystyrene (F'S) and two liquid crystalline low-molecular-weight additives have been studied. Both additives act as plasticizers as evidenced by decreases in the glass transition and the melt viscosity. In addition both are miscible with PS over a broad range of concentrations. Partial phase diagrams of the two systems are presented and discussed.

The relationship between glycosylated haemoglobin levels and various degrees of glucose intolerance.

Abstract: To assess the use of glycosylated haemoglobin to discriminate between various degrees of glucose intolerance, glycosylated haemoglobin levels were determined in 107 subjects (48 males and 59 females, age range 18–80 years). Following a 75 g oral glucose tolerance test and according to World Health Organization criteria, subjects were classified as normal (n=32), diabetic (n=46) or as having impaired glucose tolerance (n=29). Mean glycosylated haemoglobin levels were 5.8±1.3% (range 4%–9%) in normal subjects, 7.1±1.7% in subjects with impaired glucose tolerance (range 4.1%–10.1%) and 10.1±2.6% (range 4.7%–18.8%) in diabetic patients. The difference between the groups was highly significant (p<0.01). Twelve per cent of normal subjects exceeded and 52% of subjects with impaired glucose tolerance fell below 7.4% (mean ± 2SD, considered as the upper limit of normal values). A significant correlation was observed between glycosylated haemoglobin values and fasting blood glucose (r=0.68, p<0.01). These results provide evidence that glycosylated haemoglobin levels are influenced by slightly reduced carbohydrate tolerance. Glycosylated haemoglobin may be a useful test to improve the specificity of the oral glucose load to select and to follow-up subjects with impaired glucose tolerance.

Physical degradation by water clustering in epoxy resins

Abstract: Water uptakes in sorption experiments on thin sheets of epoxy resins have been explained on the basis of theoretical models. The occurrence of an irreversible void formation process at higher humidities induces strong deviations from the Flory–Huggins analysis. This phenomenon can be successfully explained on the basis of cluster formation.

Relationships between Octanol-Water Partition Data, Chromatographic Indices and Their Dependence on pH in a Set of Nonsteroidal Anti-Inflammatory Drugs

Abstract: Octanol/water partition and distribution coefficients of a set of nonsteroidal anti-inflammatory drugs were measured. Relationships between partition data at different pH values and dissociation constants are discussed. Log k′ values were determined by reversed-phase high-performance liquid chromatography (HPLC) on bonded octyl and octadecylsilane supports at different pH values using various organic modifiers in the mobile phase. The log k′ values exhibited linear relationships with methanol concentration in the mobile phase. Octanol/water partition data correlated well with the extrapolated log k′ indices to zero methanol concentration (solvent regression equations) and with the corresponding Rm indices measured on octyl and octadecyl reversed phases thin layer chromatography (HPTLC). Nature of the slopes and the intercepts of the relationships is discussed. It is shown that the HPLC and HPTLC methods are useful alternatives for the determination of partition data.

Valsalva Maneuver in the Assessment of Baroreflex Responsiveness in Borderline Hypertensives

Abstract: Baroreceptor function was assessed by (1) the reflex response during Valsalva maneuver, (2) phenylephrine injection, and (3) increase in neck tissue pressure by a neckchamber in 15 borderline hyperten