Biomedical subjects

G Favaro

Publications and source records attributed to G Favaro.

14 recordsLinked to original sources

PubMed2005

In situ fluorimetry: a powerful non-invasive diagnostic technique for natural dyes used in artefacts Part I. Spectral characterization of orcein in solution, on silk and wool laboratory-standards and a fragment of Renaissance tapestry.

In this paper the potentialities of spectrophotometric and fluorimetric techniques for identifying the materials used in artistic textiles are investigated. A portable non-destructive instrument suitable to record fluorescence spectra on surfaces was set up and successfully experienced. A naturally occurring dye, orcein, which was widely used in antiquity for textile dyeing, has been spectrally characterized in both solution and powder. Laboratory samples of wool and silk orcein-dyed threads were analysed before and after ageing. An original fragment of Renaissance tapestry was also analysed. The textile (wool) and the colourant (orcein) were recognised by comparison with the data from the laboratory samples.

Animals↗

PubMed2005

Traceability of Asiago mountain cheese: a rapid, low-cost analytical procedure for its identification based on solid-phase microextraction.

The traceability of Asiago mountain cheese was established by analyzing samples of herbaceous species, milk, and cheese of mountain origin using the head-space solid-phase microextraction sampling procedure coupled with gas chromatography-mass spectrometry. As preliminary work had highlighted the characteristic presence of sesquiterpenes in Asiago mountain cheese, these species were considered effective markers of mountain origin. Systematic qualitative analysis, carried out using a carboxen/polydimethylsiloxane fiber, revealed several sesquiterpenes in mountain herbage and milk, in particular beta-caryophyllene and alpha-humulene, in Asiago mountain cheese, confirming sesquiterpenes as markers of cheese produced from animals grazing on mountain pastures. Analysis was performed on 19 samples of herbage, 8 of milk, and 8 of cheese, collected in summer from 4 mountain farms on the Asiago plateau. For quantitative analysis of caryophyllene in cheese, polydimethylsiloxane fiber sampling, coupled with the standard addition method to eliminate matrix effect, was preferred. The amount of beta-caryophyllene found ranged from 21 to 65 microg/kg.

Altitude↗

PubMed2002

An artificial intelligence approach to classify and analyse EEG traces.

We present a fully automatic system for the classification and analysis of adult electroencephalograms (EEGs). The system is based on an artificial neural network which classifies the single epochs of trace, and on an Expert System (ES) which studies the time and space correlation among the outputs of the neural network; compiling a final report. On the last 2000 EEGs representing different kinds of alterations according to clinical occurrences, the system was able to produce 80% good or very good final comments and 18% sufficient comments, which represent the documents delivered to the patient. In the remaining 2% the automatic comment needed some modifications prior to be presented to the patient. No clinical false-negative classifications did arise, i.e. no altered traces were classified as 'normal' by the neural network. The analysis method we describe is based on the interpretation of objective measures performed on the trace. It can improve the quality and reliability of the EEG exam and appears useful for the EEG medical reports although it cannot totally substitute the medical doctor who should now read the automatic EEG analysis in light of the patient's history and age.

Adult↗

PubMed2001

Competition between vibrational relaxation and photochemistry: relevance of vibronic quantum effects.

Two molecules showing photochemistry but no fluorescence have been investigated at 80 K in a rigid matrix regarding the behavior of the quantum yield for bond fragmentation as a function of the vibrational/vibronic level and electronic excited state. A new equation was developed to determine the photochemical quantum yield under ambient conditions (80 K). The levels/bands involved were those within a given vibrational progression, in different progressions as well as in combination. The yield was low (phi = 0.1) with excitation into the n = 0 level of S1 but very rapidly increased with excitation into higher levels whether they were harmonics or combination levels. A parallel result was observed upon excitation into S2. Vibrational relaxation/deactivation occurs only between levels of the same vibrational progression. Deactivation from the 0 level of S2 does not occur via levels of S1. The photochemically active modes correspond to the vibrational modes present in the region of the molecule where bond breakage occurs. These results add further proof of the complex nature and number of processes that can occur within excited states of photochemically active molecules.

Journal Article↗

PubMed2000

Photochromic behavior of 2,2-spiro-adamantylidene-2H-naphtho

The photokinetic behavior of a photochromic compound, 2,2-spiro-adamantylidene-2H-naphtho[1,2-b]pyran (Py), has been investigated by using monochromatic irradiation in the UV and visible ranges. An unusually complex photochemistry occurs whereby two colored forms (o-quinone-allides) are produced, one of which is thermoreversible whereas the other is not thermoreversible but photoreversible. These are the result of ring opening of the pyran C-O bond to a short lived open-form intermediate which converts to the two different colored forms by twisting around different C-C bonds. Their spectra and molar absorption coefficients were obtained in acetonitrile solution. The kinetic parameters of the thermal bleaching (rate constant and activation energy) and photobleaching (quantum yield) were measured. A plausible reaction mechanism is proposed. Based on this mechanism, mathematical methods were devised which were capable of analyzing the system during its dynamic evolution and evaluating the quantum yields of the colorforming photoreactions.

Journal Article↗

PubMed1996

Down-regulation of evoked synaptic release in rat neuromuscular junction.

Spontaneous and evoked synaptic transmission were studied at the rat extensor digitorum longus (EDL) neuromuscular junction in the presence of CGIIIA mu-conotoxin, a peptide which suppresses action potential in the sarcolemma, while not affecting impulse conduction along motor nerve fibers. The binomial parameters m (mean quantal content) and n (number of units involved in evoked quantal release) increased as a function of extracellular Ca++ ([Ca++]o), up to the physiological concentration (2 mM). Additional Ca++ failed to induce a statistically significant increase in either m or n, while the probability of activation (p) did increase, approaching unity at 4 mM [Ca++]o. In cut EDL preparations, without CGIIIA, the relation between end-plate potential amplitude and [Ca++]o resembled that for quantal content in unlesioned, CGIIIA-treated muscles. In contrast, normal preparations exposed to 0.5 mg/ml d-tubocurarine were much more responsive to Ca++ variations, with a significant end-plate potential amplitude increase in the presence of 4 mM [Ca++]o. However, in curarized preparation the evoked release was remarkably affected by repetitive stimulation, while in the absence of postsynaptic blockers release levels were more stable. We suggest that the stimulatory effect of extracellular Ca++ on evoked release at the mammalian neuromuscular junction might normally be depressed under physiological conditions, possibly by a down-regulation mechanism involving presynaptic nicotinic receptors. Such inhibition would increase nerve transmission efficiency during prolonged motor terminal activity.

Animals↗

PubMed1990

Efficacy of ganglioside treatment in reducing functional alterations induced by vincristine in rabbit peripheral nerves.

Vincristine (VCR) administration to rabbits resulted in severe electrophysiologic alterations of peripheral nerves. Sciatic nerve conduction velocity, compound action potential (CAP) amplitude, and area under the CAP waveform were all reduced in a dose-dependent fashion. In addition, the pattern of conduction velocity of both motor and sensory fibers was altered and shifted toward slow conduction classes. Simultaneous treatment with gangliosides limited significantly the changes in electrophysiologic parameters induced by VCR. It is suggested that gangliosides be given in the clinical setting as protection for the peripheral nerves against the side effects of antiblastic therapy.

Action Potentials↗

PubMed1989

Functional evaluation of acute vincristine toxicity in rat skeletal muscle.

Vincristine sulfate (VCR) was administered intravenously to rats at doses of 0.25, 0.5, and 0.75 mg/kg. During the first week following VCR treatment, extensor digitorum longus (EDL) muscle contraction strength and fiber electrophysiologic parameters were measured. At all doses tested, VCR strongly reduced twitch and tetanic tension. EDL fiber resting membrane potential was affected in a dose-dependent manner, and membrane depolarization was associated with the loss of excitability. Local membrane hyperpolarization by intracellular current application restored the capacity to produce action potential (AP). However, to elicit APs with a normal rate of rise, polarizing current had to be maintained for 3-5 minutes, indicating that the removal of Na+ channel inactivation followed a slow kinetics. Minor alterations in spontaneous synaptic transmission and in evoked transmission during high-frequency repetitive stimulation were seen only at the highest dose. It is suggested that VCR impairs skeletal muscle function by affecting primarily the contractile apparatus, whereas sarcolemmal alterations are evident at increased doses of the drug.

Action Potentials↗

PubMed1989

Spontaneous and nerve-evoked quantal transmission in regenerated motor terminals.

Quantal acetylcholine release was studied in sciatic nerve-extensor digitorum longus muscle preparations from normal rats and in reinnervated muscles at different times following peroneus nerve crush. The efficiency of nerve-evoked transmission was regained almost completely at a time (20 days after crush) when the secretory response to increased extracellular K+ was very weak. This suggests that K+-induced secretion might be activated through mechanisms at least partially different from those involved in the response to nerve stimulation.

Animals↗

PubMed1988

Adaptation of sarcolemmal action potential mechanisms to chronic depolarization in denervated skeletal muscle.

Action potential properties were studied in rat extensor digitorum longus fibers, at different times after locally setting the membrane to a holding potential of -90 mV. Whereas in normal muscles holding potential duration had little effect on the action potential, the holding potential duration markedly influenced membrane excitability in the fibers previously depolarized by increasing the K+ concentration of the bathing medium. In this case, when the holding potential was prolonged from 20 to 180 s, action potential overshoot, maximum rate of rise, and maximum rate of fall increased 1.8-, 3.1-, and 1.8-fold, respectively. In the denervated muscle, overshoot and maximum rate of fall were dependent on the duration of holding potential application until denervation day 6, whereas maximum rate of rise was affected throughout the duration of this study (15 days of denervation). However, 180-s application of -90 mV holding potential elicited about a 2-fold increase of maximum rate of rise in the earlier denervation stages, and only a 1.5-fold increase at later times. These observations suggest that ultra-slow processes of Na+ conductance inactivation were less effective after 6 days of denervation. Correspondingly, extensor digitorum longus fibers acquired the ability to generate action potentials at a depolarized holding potential. The partial removal of ultra-slow Na+ inactivation after muscle denervation could substantially contribute to a general process of membrane adaptation, resulting in the capacity of voltage-dependent ion channels to operate in a condition of chronic depolarization.

Action Potentials↗

PubMed1988

General toxicity and peripheral nerve alterations induced by chronic vincristine treatment in the rabbit.

The effects of five 0.3 mg/kg intravenous administrations of vincristine (VCR) at weekly intervals were studied in the rabbit. Body weight gain was impaired starting from the first injection, while gross signs of motor paralysis and hair loss initiated from the third week. At the end of the observation period blood analysis revealed normocytic normochromic anemia, elevated serum creatine kinase, and low serum alkaline phosphatase, whereas all the tested parameters related to liver and kidney functions where within normal limits. The decreased number of red blood cells was the consequence of a complete, although reversible, blockade of staminal hematopoietic activity. Two important indexes of peripheral nerve function were clearly altered at the end of the treatment: (i) the sciatic nerve conduction velocity in vitro was 27% reduced and (ii) the latency between sciatic nerve stimulation and extensor digitorum longus (EDL) twitch in vivo was 34% prolonged. The usefulness of the rabbit as an animal model to study side-effects of VCR treatment is discussed.

Alkaline Phosphatase↗

PubMed1988

Ganglioside treatment of vincristine-induced neuropathy. An electrophysiologic study.

A 5-week treatment with vincristine (0.20 or 0.25 mg/kg, i.v., once/week) in the rabbit produced a peripheral neuropathy characterized by both morphologic and electrophysiologic alterations. In particular, electrophysiologic recordings demonstrated that the amplitude, area and conduction velocity of compound action potential (CAP) were consistently reduced in a dose-dependent manner. The simultaneous daily administration of 50 mg/kg ganglioside mixture counteracted significantly this functional impairment, area and amplitude of the monophasic CAP being maintained closer to control values. These results suggest that the loss of functional nerve fibers can be reduced, in vincristine-induced neuropathy, by ganglioside treatment.

Action Potentials↗

PubMed1987

Maturation, dystrophic changes and the continuous production of fibers in skeletal muscle regenerating in the absence of nerve.

To investigate how much skeletal muscle depends on influences coming from peripheral nerve, we studied muscle regeneration induced by bupivacaine in the permanently denervated soleus muscle of adult rats. Using light and electron microscopy, we studied the extent of maturation attained by regenerated myofibers and their ability to regenerate again after repeated bupivacaine injury. Morphometric analyses showed that within the first two weeks after injury, the regenerated denervated fibers increased in diameter, matured and then became atrophic. By electron microscopy the morphological characteristics of mature fibers are evident, but final differentiation into adult fiber types is not attained. This is in keeping with previously reported biochemical results. A new phase of massive regeneration occurred when bupivacaine treatment was repeated, thus demonstrating that regenerated myofibers devoid of innervation keep their intrinsic ability to regenerate after injury. Spontaneous though scanty regeneration also occurred in denervated regenerated muscle at late stages, when atrophy and dystrophy of fibers became prominent. Concomitantly the relative number of myosatellite cells remained high. These morphological observations further support the hypothesis that fiber regeneration participates in the maintenance of chronically denervated muscles.

Animals↗

PubMedDate not supplied

Peripheral nerve regeneration through a novel bioresorbable nerve guide.

A nerve guide made of a benzyl ester of hyaluronic acid (HYAFF11p75) was used to bridge 8 mm gaps in rat tibial nerves. Histologic observations indicated that this biomaterial provoked only a transient, modest inflammatory response, and the resorption rate was compatible with the nerve regeneration processes. Phagocytosis of the biomaterial began after neoangiogenesis and cell migration had taken place from both stumps into the nerve guide material. For comparison, the regeneration achieved was evaluated in nerve guides made of either HYAFF11p75 or Silastic, and in nerves repaired with the autograft technique. Recovery was assessed in vivo 90 days after implantation by measuring the nerve compound action potential (CAP) and conduction velocity (NCV) of the regenerated tibial nerve. The results demonstrate that the nerve guide tubes made of HYAFF11p75 were able to support and direct axonal growth, thereby suggesting a possible use for such biomaterial in the management of short nerve gaps in human pathology.

Animals↗