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Biomedical subjects

M Roberto

Publications and source records attributed to M Roberto.

At least 19 recordsLinked to original sources
PubMed1989

Damage of the auditory system associated with acute blast trauma.

This paper reviews the results of several studies on the effects of blast wave exposure on the auditory system of the chinchilla, the pig, and the sheep. The chinchillas were exposed at peak sound pressure levels of approximately 160 dB under well-controlled laboratory conditions. A modified shock tube was used to generate the blast waves. The pigs and sheep were exposed under field conditions in an instrumented hard-walled enclosure. Blast trauma was induced by the impact of a single explosive projectile. The peak sound pressure levels varied between 178 and 209 dB. All animals were killed immediately following exposure, and their temporal bones were removed for fixation and histologic analysis using light microscopy and scanning electron microscopy. Middle ears were examined visually for damage to the conductive system. There were well-defined differences in susceptibility to acoustic trauma among species. However, common findings in each species were the acute mechanical fracture and separation of the organ of Corti from the basilar membrane, and tympanic membrane and ossicular failure.

Animals↗
PubMed1988

Scar formation following impulse noise-induced mechanical damage to the organ of Corti.

The terminal stages of the healing process of the organ of Corti in the chinchilla following exposure to blast-waves at 160 dB peak SPL, were studied by scanning electron microscopy (SEM) and by surface preparation technique. Extensive lesions of the sensory epithelia consisting in the absence of the OHC's, Deiter cells and Hensen cells, were replaced by scar tissue formed by single, flat, irregularly polygonal cells, arising from the Claudius cell area sealing off the endolymphatic spaces. When the pillar cells have been destroyed the scar epithelium from the Claudius cells has reached the IHC's, which show a remarkable resistance to acoustic trauma. Their presence in a large healed area may be the only remnants of a previous sensory region. When even the IHC's are absent, the entire organ of Corti can be replaced both by Claudius cells and by inner sulcus cells covering the denuded basilar membrane without any clear morphological difference between the two cellular sources.

Animals↗
PubMed1987

Beta-blockers: a new therapeutic approach to Raynaud's disease.

Thirty-six patients with Raynaud's disease (RD) were treated with a low dosage of beta-blockers, atenolol (50 mg/day) or propranolol (20 mg/day). Previous data have suggested that the pathophysiology of RD may be mediated by presynaptic beta-adrenoceptors. In this research we report that chronic beta-blocker treatment, at low dosage, can prevent the cold-induced vasospasm. The majority of patients (28) responded to atenolol, and 8 patients refractory to atenolol responded to propranolol.

Adrenergic beta-Antagonists↗
PubMed1985

Impact noise and the equal energy hypothesis.

The equal energy hypothesis (EEH) was evaluated over a limited range of conditions by exposing four groups of chinchillas to impact noise (200-ms B duration) presented at a fixed rate of four impacts per second. The intensity of the impacts (107-125 dB peak SPL) and the duration (120-1.87 h) of the four exposure conditions were counterbalanced so that the four groups received the same total energy. The traumatic power of the exposures was assessed by measuring the threshold shift of the auditory evoked response and the amount of hair cell loss. Exposure between 107 and 119 dB were consistent with the EEH in that they produced roughly the same amount of permanent threshold shift (less than 20 dB) and hair cell loss (less than 20%). However, the 125-dB exposure produced substantially more threshold shift and hair cell loss than the three lower intensities. Thus, the EEH may be applicable only at lower impact intensities; above a "critical intensity" the amount of damage increases significantly.

Animals↗
PubMed1984

Altered regulator mechanisms of presynaptic adrenergic nerve: a new physiopathological hypothesis in Raynaud's disease.

The effect of isoprenaline infusion (1 gamma/min) on blood flow in the extremities was studied in 15 Raynaud's disease (RD) patients and 9 healthy controls. A highly significant (P less than 0.0005) decrease in blood flow was seen in the RD subjects. It is suggested that an increased presynaptic beta receptor response to cold and emotional stimulus may be involved in the physiopathogenesis of RD.

Adolescent↗
PubMed1979

[Study of the wave-form of the stapedial reflex in response to sonorous stimuli of different intensity].

The threshold of the acoustic reflex and its pattern in response to different intersity stimuli, was investigated by means of the signal-averaging technique in 10 normal ears. Trains of tone bursts between 100 and 0 dB HL were used. The frequencies tested were 500, 1000, 2000 and 4000 Hz. In all subjects the pattern of the acoustic reflex for stimuli between 110 and 100 dB HL was biphasic, with an initial positive plateau followed by a longer negative one. For stimuli < 80 dB HL the pattern of the reflex was monophasic, characterized by a single positive peak (latency between 120 and 170 msec).

Acoustic Impedance Tests↗
PubMedDate not supplied

Quantitative evaluation of postnatal bone growth in the auditory ossicles of the dog.

The postnatal bone growth (appositional and internal) in the auditory ossicles and in the tibia of three mongrel dogs was studied by means of tetracycline and alizarin labeling. The appositional growth is characterized by an increase in the external dimensions of the auditory ossicles within the first month of postnatal life. No trace of bone deposition was found after this period of time. The patterns of internal growth are: 1) the rate of primary osteon formation shows the same value in the incus and malleus; 2) these values are always less than those in the primary osteons of the diaphysis of the tibia of the same dog; 3) the time required for the formation of these osteons in the auditory ossicles, like in the other parts of the skeleton, increases significantly with age.

Animals↗