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Biomedical subjects

P Campo

Publications and source records attributed to P Campo.

At least 37 records · Page 2Linked to original sources
PubMed1998

Cubic distortion product otoacoustic emissions in young and aged chinchillas exposed to low-frequency noise.

The aim of this study was to examine susceptibility to noise-induced hearing loss in animals with and without age-related hearing loss (AHL), using cubic distortion product otoacoustic emissions (CDPs) to assess the functional status of the outer hair cell (OHC) system. Subjects were young (< or = 3-yr-old) and aged (10- to 15-yr-old) chinchillas. CDP thresholds and input/output (I/O) functions were measured before and after exposure to 95 dB or 106 dB SPL low-frequency noise. The results indicate that (a) aging in the chinchilla is associated with significant elevations of CDP thresholds and depression of CDP I/O functions, (b) noise exposures cause equivalent CDP threshold elevations and amplitude reductions in young animals with normal hearing and older animals with AHL, and (c) CDP threshold and amplitude measures provide information that complements evoked potentials measured from the auditory midbrain.

Aging↗
PubMed1998

[Pre-postoperative neuropsychological evaluation in the surgical treatment of epilepsy].

INTRODUCTION: Epilepsy is one of the most common neurological disorders, affecting about one percent of the world population. Pharmacological treatment fails in one-third of these patients. Surgical intervention has become an accepted treatment option for those patients with seizure disorders that are refractory to conventional therapies. Cortical resection and callosotomy are the most widely accepted methods of surgical intervention. A prerequisite for success in this type of surgical intervention is the preoperative clinical assessment of the epilepsy surgery candidate. DEVELOPMENT: This paper examines the current uses of neuropsychological assessment in an epilepsy surgery program. Several areas are addressed for discussion with respect to the contributions of neuropsychological assessment: the preoperative evaluation of the epilepsy surgery candidates, including the clinical examination of language and memory functions during the Wada test; the neuropsychological changes that result from surgery and the predictive role of neuropsychology in these areas, and prediction for seizure control following surgery. CONCLUSION: Assessment of cognitive functions is an important component of the preoperative evaluation of the epilepsy surgery candidate, and is needed in order to obtain complete diagnostic information.

Epilepsy↗
PubMed1997

Age-related decline of auditory function in the chinchilla (Chinchilla laniger).

The aim of this study was to examine the functional consequences of aging in the chinchilla, a rodent with a relatively long life span and a range of hearing similar to that of humans. Subjects were 21 chinchillas aged 10-15 years, and 23 young controls. Thresholds were determined from auditory evoked potentials (EVPs), and outer hair cell (OHC) functioning was assessed by measuring 2f1-f2 distortion product otoacoustic emissions (DPOAEs). Six cochleas from 11-12-year-old animals were examined for hair cell loss and gross strial pathology. The results show that the chinchilla exhibits a small but significant decline of auditory sensitivity and OHC functioning between 3 and 15 years of age, with high-frequency losses exceeding and growing more rapidly than low-frequency losses. Compared to rodents with shorter life spans, the chinchilla has a rate of loss that is more similar to that of humans, which could make it a valuable model for understanding the etiology of human presbycusis.

Acoustic Stimulation↗
PubMed1997

Evolution of susceptibility of non-typhi Salmonella in a Spanish hospital (1992-1994) and report of a Salmonella ser. Typhimurium isolate resistant to quinolones.

We report the evolution of the antimicrobial resistance of non-typhi Salmonella (1992-1994) in a Spanish hospital in relation with a case of infection due to a fluoroquinolone-resistant strain of Salmonella ser. Typhimurium. None of the isolates were resistant to ciprofloxacin. The resistance to ampicillin has increased from 20.6% (1992) to 29.5% (1994) whereas no significative differences in chloramphenicol and cotrimoxazole susceptibility were noted.

Anti-Infective Agents↗
PubMed1996

Applicability of the L(eq) as a damage-risk criterion: an animal experiment.

Within the European communities, the L(eq8h) is used as a damage-risk criterion (DRC) for hearing protection. The use of such a DRC supposes that sound exposures with equal energy imply equal risk for noise-induced hearing loss (NIHL). The aim of the present study, carried out with guinea pigs, was to test the applicability of the L(eq8h) for estimating the hazard of different noises having the same spectrum and acoustic energy. Therefore, only the temporal structure of noises was a variable (continuous, intermittent, or impulsive) and each noise had a L(eq8h) of 92 dB. The results indicate the L(eq8h) is not an accurate DRC. It overestimates the NIHL for intermittent and short-continuous noises, whereas it seems to be useful for moderate-intensity noises (95 dB) and for the impulse noise (101 dB). Furthermore, the data point out the notion of ¿critical intensity¿ which seems to play a determining role in the transition between metabolic and mechanical mechanisms involved in the acoustic trauma. Since the critical intensity and the existence of two mechanisms are parameters that the L(eq8h) cannot take into consideration, recommendations on the safety program of hearing loss prevention are discussed.

Acoustic Stimulation↗
PubMed1994

Anatomical effects of impact noise.

Four groups of binaural chinchillas were exposed to impact noise (B-duration = 200 ms) ranging from 119 dB to 137 dB peak equivalent SPL at repetition rates of 1/s or 4/s. The duration of exposure was adjusted so that each exposure consisted of equal acoustic energy. Animals were then sacrificed immediately, 24 h or 30 days after the exposure and their cochleas subjected to scanning electron microscopy. For exposures of 119 dB or greater, there appeared to be direct mechanical damage, including large clefts between the third row of outer hair cells and Deiters' cells and fracture of tight cell junctions at the reticular lamina. There was also a progressive increase in cochlear damage over the 30 days of recovery. The patterns of cochlear pathology are compared with hearing losses and cochleograms of chinchillas previously subjected to similar exposures and with results of studies using higher level impulse noise. The results are discussed in terms of 'critical level' for impact and impulse noise.

Acoustic Stimulation↗
PubMed1992

The effect of 'conditioning' on hearing loss from a high frequency traumatic exposure.

The role of high frequency, low level 'conditioning' exposures as moderators of hearing loss from subsequent exposure to the same noise at a higher level was studied using monaural chinchillas. All the animals in the experimental groups were exposed to an octave band noise centered at 4 kHz at 85 dB SPL for 6 h a day for 10 days. One of the experimental groups was allowed to recover for 5 days and the other was allowed to recover for 18 h, prior to the higher level exposure at 100 dB for 48 h. A third group exposed only to the higher level constituted the control group. A comparison of threshold shifts and hair cell loss after 4 weeks of recovery across the three groups revealed: (a) the 5-day recovery group incurred greater threshold shifts than the other two groups; the hair cell loss in this group was greater than in the 18-h recovery group, but the same as in the control group and (b) the 18-h recovery group incurred considerably less threshold shift as well as hair cell loss than the other two groups. The results were also compared with the results from similar exposures using low frequency noise which indicated that the base vs. apex differences in the cochlea appear to extend to the effects of 'conditioning' exposures.

Animals↗
PubMed1991

The effect of 'conditioning' exposures on hearing loss from traumatic exposure.

The role of 'conditioning' exposures as moderators of hearing loss produced by exposure to a higher level noise was explored using chinchillas. Monaural chinchillas were exposed to an octave band of noise centered at 0.5 kHz at 95 dB for six hours/day for ten days. The subjects were allowed to recover to pre-exposure sensitivity and at five days after the last exposure they were re-exposed to the same noise at 106 dB. Thresholds recorded at various time intervals following the second exposure were compared with those recorded in a control group exposed only to the higher level noise. The experimental animals were found to have less threshold shift at all stages of recovery. Results are discussed in the light of results of other related studies and possible mechanisms involved are hypothesized.

Acoustic Stimulation↗
PubMed1991

Development of resistance to hearing loss from high frequency noise.

The effect of interrupted exposure on the development of progressive resistance to hearing loss from exposure to high frequency noise was studied using monaural chinchillas. The animals were exposed to an octave band noise centered at 4 kHz at 85 dB SPL for 6 h a day for ten consecutive days. Hearing thresholds were measured using evoked potential recording before and after each exposure. Results indicated a reduction in threshold shift with repeated exposures. This reduction in threshold shift or 'toughening' was more rapid for the high frequency exposures than the 'toughening' from similar low frequency exposures.

Acoustic Stimulation↗
PubMed1991

The effect of exposure level on the development of progressive resistance to noise.

The effect of exposure level on the development of progressive resistance to temporary threshold shift caused by exposures to an octave band of noise centered at 0.5 kHz was explored using chinchillas. The animals were exposed to either 85, 95 or 100 dB SPL for six hours a day for ten days. Hearing thresholds were recorded electrophysiologically, prior to and after each daily exposure. A trend toward decreasing threshold shift with increase in the number of exposures was seen at all the levels. The amount of threshold shift appeared to depend upon the level as well as the test frequency. The findings are discussed in the light of results of previous studies and possible mechanisms involved in the process of 'toughening' are hypothesized.

Adaptation, Physiological↗
PubMed1981

[Effect of sodium difluoroacetate on retinal lactate levels in diabetic rats].

Our experiments were carried out in normal and streptozotocin-diabetic rats. The effects of sodium difluoroacetate (DFA) at the dose of 40 mg/kg daily were studied on the blood and retinal lactate levels; these effects were compared to those of an identical dose of sodium dichloroacetate (DCA) which is the most known among the pyruvate dehydrogenase activators. DFA and DCA were administered orally by oesophageal tube during 5 months. At these doses, neither DFA nor DCA significantly modified the blood and retinal lactate levels in the normal animals. The blood and retina lactate levels of the non treated diabetic rats were much higher than those of the normal rats; the treatment by DFA and DCA significantly decreased the blood and retina lactate levels in diabetic rats.

Animals↗
PubMed1980

[Hypolactatemic effect of sodium difluoroacetate].

In the anesthetized rat, the intraperitoneal injection of 40 mg/kg sodium difluoroacetate (DFA), an activator of the pyruvate dehydrogenase, counteracted the hyperlactatemia induced by a high dose of phenformin (40 mg/kg) injected concomitantly. In the normal conscious dog, the administration of 150 mg/kg by gastric intubation decreased the blood lactate and pyruvate levels; however, this effect was less marked than that produced by the same dose of sodium dichloroacetate (DCA).

Animals↗
PubMedDate not supplied

Cochlear pathology induced by styrene.

Hair cells, spiral fibers and spiral ganglion cells (SGCs) coming from cochleae of styrene-treated Long-Evans rats were counted in order to assess the extent and location of the cochlear injury after the solvent inhalation. If the hair cells, and more specifically the outer hair cells (OHCs), were undoubtedly the first targets of inhaled styrene, the histological results of the present study would seem to indicate that neurons of the spiral ganglion were also injured with increasing styrene doses. The degenerative process of SGCs and spiral fibers within the osseous lamina was predominant in the middle and mid-basal turn. The electrophysiological data, obtained by recording near-field potentials from the inferior colliculus, reflected the damages of the SGCs and fibers but were not consistent with the histopathological data of the organ of Corti. Because of the weak correlation between the styrene-induced injury at the level of the organ of Corti and that induced at the level of the spiral ganglion, it is likely that two different intoxication routes exist within the cochlea. Such an assumption is discussed in the present paper.

Animals↗
PubMedDate not supplied

Toluene-induced hearing loss: a mid-frequency location of the cochlear lesions.

Inhaled toluene (from 1000 to 2000 ppm, 6 h/day, 5 days/week, 4 weeks) is anototoxic solvent that severely damaged the cochlea in adult Long-Evans rats. Auditory function was tested by recording near field potentials from the inferior colliculus. Surprisingly, the electrophysiologic results did not reflect all the cochlear damage observed by histology. Loss of outer hair cells of the organ of Corti occurred in all toluene-treated rats in middle and mid-apical turns, whereas the basal turn of the cochlea was fairly well preserved. The third row of outer hair cells was more injured than the second row, which itself was more injured than the first row. The locations of the cochlear lesions are reported in the present study with regard to the toluene dose.

Administration, Inhalation↗
PubMedDate not supplied

Combined effects of a simultaneous exposure to noise and toluene on hearing function.

To study the combined effects of noise and toluene on auditory function, three experimental groups of Long-Evans adult rats were used. The first group was exposed to toluene (2000 ppm, 6 h/day, 5 days/week, 4 weeks), the second group to an octave band of noise centered at 8 kHz (92 dB SPL), and the last group to a simultaneous exposure to toluene and noise. Auditory function was tested by recording brainstem (inferior colliculus) auditory-evoked potentials. The auditory deficit induced by the combined exposure exceeded the summated losses caused by toluene alone and by noise alone within the range (2-32 kHz) of test frequencies. The nature of the cochlear damage induced by noise alone (injured stereocilia) or by toluene alone (outer hair cells loss) is different.

Animals↗
PubMedDate not supplied

Combined effects of simultaneous exposure to toluene and ethanol on auditory function in rats.

Three experimental groups and one control group of Long-Evans rats were used to study the combined effects of toluene and ethanol on auditory function. The first experimental group was exposed to toluene vapors (1750 ppm, 6 h/day, 5 days/week, 4 weeks), the second one was daily gavaged with a saline solution of ethanol (4 g/kg, 4 weeks), and the last group was simultaneously exposed to both toluene and ethanol. Auditory function was tested by recording brain stem (inferior colliculus) auditory-evoked potentials for audiometric frequencies ranging from 2 to 32 kHz. Urinary hippuric acid was dosed to check the toluene metabolism during the experiments. Ethanol clearly modified the toluene metabolism in the present experimental conditions. As a result, the hearing loss induced by a simultaneous exposure to both ethanol and toluene was larger than that induced by exposure to toluene alone.

Analysis of Variance↗