Biomedical subjects

P Gil-Loyzaga

Publications and source records attributed to P Gil-Loyzaga.

At least 19 recordsLinked to original sources

PubMed2006

[Presbycusis: neural degeneration and aging on the auditory receptor of C57/BL6J mice].

Presbycusis is a progressive hearing impairment associated with aging, characterized by hearing loss and a degeneration of cochlear structures. In this paper we analyze the effects of aging on the auditory system of C57/BL6J mice, with electrophysiological and morphological studies. With this aim the auditory potentials of mice aging 1, 3, 6, 9, 12, 15, 18, 21 and 24 months were recorded, and then the morphology of the cochleal were analyzed. Auditory potentials revealed an increase in wave latencies, as well as a decrease in their amplitudes during aging. Morphological results showed a total Corti's organ degeneration, being replaced by a flat epithelial layer, and a total absence of hair cells.

Aging↗

PubMed2005

One-month administration of hydroxytyrosol, a phenolic antioxidant present in olive oil, to hyperlipemic rabbits improves blood lipid profile, antioxidant status and reduces atherosclerosis development.

The present study analysed the effects of hydroxytyrosol (HT) on blood lipids, antioxidant status and the progression of aortic lesions in hyperlipemic rabbits. Sixty-four rabbits were distributed into eight groups of animals (n = 8). Animal groups C, A and H were fed for 1-month with a control diet containing sunflower oil (C), an atherogenic diet (A) high in saturated fat and cholesterol or the A diet together with HT, respectively. The other five groups were fed for 2-months with diets C or A (groups CC or AA, respectively), or for 1-month with the A-diet followed by a further month with diet C, extra virgin olive oil diet (O) or diet C with HT (groups AC, AO and AH, respectively). Four milligram of HT/kg body weight were used in the study. Fifty and 42% decrease in total cholesterol and triacylglycerols, respectively, and a 2.3-fold increase in HDL-cholesterol were observed in the AH group but not in the H group. The HT-supplemented groups improved their antioxidant status and reduced the size of atherosclerotic lesions measured as intimal layer areas of the aortic arch when compared with control animals. We conclude that HT supplementation may have cardioprotective effects in vivo.

Animals↗

PubMed2005

Effects of ovariectomy and growth hormone administration on body composition and vascular function and structure in old female rats.

UNLABELLED: Aging and estrogen-deprivation induce deleterious effects on body composition and vascular function in females. On the other hand, growth hormone (GH), whose production is reduced by age, exerts several vascular effects. The aim of this study was to investigate the effect of long-term estrogen deprivation and GH administration on body composition, vascular function and structure in aged female rats. METHODS: Twelve female Wistar rats were ovariectomized at 10 months of age. At 20 months of age, half of the ovariectomized rats were treated with GH for 4 weeks. The remaining ovariectomized rats animals and one group of six intact females were used as control groups. After the treatment period, animals were sacrificed and Specific Gravity Index (SGI) and periuterine fat weigh, as well as vascular reactivity and morphometry in aortic rings, were studied. RESULTS: No significant differences were found in SGI and periuterine fat weigh between ovariectomized and intact control rats. SGI was significantly increased by GH, and periuterine fat was reduced by the treatment. Dose-dependent relaxing responses to acetylcholine and isoproterenol were significantly diminished in ovariectomized rats as compared with intact animals, and GH treatment improved these responses. Ovariectomized animals showed significantly higher contracting responses to phenylephrine, acetylcholine + L-NAME and angiotensin-I than intact rats, and treatment with GH reduced them significantly. Media cross-sectional area was increased in ovariectomized rats as compared to intact animals, and GH reduced this area, but differences did not reach significance. CONCLUSION: GH has beneficial effects in body composition and endothelial function in old ovariectomized female rats.

Acetylcholine↗

PubMed2005

Neuroplasticity in the auditory system.

An increasing interest on neuroplasticity and nerve regeneration within the auditory receptor and pathway has developed in recent years. The receptor and the auditory pathway are controlled by highly complex circuits that appear during embryonic development. During this early maturation process of the auditory sensory elements, we observe the development of two types of nerve fibers: permanent fibers that will remain to reach full-term maturity and other transient fibers that will ultimately disappear. Both stable and transitory fibers however, as well as developing sensory cells, express, and probably release, their respective neuro-transmitters that could be involved in neuroplasticity. Cell culture experiments have added significant information; the in vitro administration of glutamate or GABA to isolated spiral ganglion neurons clearly modified neural development. Neuroplasticity has been also found in the adult. Nerve regeneration and neuroplasticity have been demonstrated in the adult auditory receptors as well as throughout the auditory pathway. Neuroplasticity studies could prove interesting in the elaboration of current or future therapy strategies (e.g.: cochlear implants or stem cells), but also to really understand the pathogenesis of auditory or language diseases (e.g.: deafness, tinnitus, dyslexia, etc.).

Animals↗

PubMed2003

Body composition and vascular effects of growth hormone administration in old female rats.

Aging is associated with alterations in cardiovascular system and changes in body composition. The aim of this study was to investigate the effect of GH on body composition, vascular function and structure in old female rats. Old (20 months) and adult (4 months) female Wistar rats were used. One group of old animals was treated with GH (2 mg/kg/day) for four weeks. Periuterine fat weight, specific gravity index (SGI), dose response to Acetylcholine, Isoprenaline, Phenylephrine and Acetylcholine in the presence of L-NAME and vascular morphology in aortic rings, were studied. Old rats showed increased fat weight and decreased SGI (p<0.05) as compared to adult animals. GH reduced fat weight (p<0.05) and tended to increase SGI (NS). Old rats showed impaired vasodilatation to Acetylcholine and Isoprenaline (p<0.05), and GH improved these responses (p<0.05). Contraction response to Phenylephrine was higher in old than in adults rats (p<0.05), but GH did not show any effect. Contraction induced by Acetylcholine+L-NAME was higher in old rats than in adults, and GH tended to reduce this response, although not significantly. Aortic media area was increased in old rats, and GH reduced this parameter (p<0.05). In conclusion, GH shows beneficial effects on body composition, vascular function and morphology in old female rats.

Adipose Tissue↗

PubMed2002

Sensitivity to glutamate neurotoxicity in different developmental periods of the rat cochlea.

Cochlear neurotoxicity induced by the intraperitoneal administration of monosodium glutamate (MSG) has been analyzed during the postnatal development of the auditory receptor of the rat. The animals were treated with MSG during two postnatal periods. The electrophysiological recordings showed that MSG treatment produced a decrease in the 8th nerve compound action potential. The effect was more marked in the animals treated between the 9th and 12th postnatal day than in the others, with a qualitative decrease in neuronal density in the spiral ganglion. These results suggest that there is a period of maximum sensitivity to the cochlear neurotoxicity induced by MSG in the postnatal development of the rat.

Action Potentials↗

PubMed2002

Abnormal cochlea linked to deafness in transgenic mice expressing human cytokeratin K8.

The cytokeratin intermediate filaments have a relevant role in the proliferation and differentiation processes of epithelial cells. To provide information about the role of K8 cytokeratin during the auditory receptor differentiation, two groups of adult mice were used: TGK8-4 transgenic and control animals. The TGK8-4 transgenic mice contained 12 kb of K8 human cytokeratin (HK8) locus (Casanova et al., 1995, 1999). The functional activity of the auditory receptor was analyzed by auditory thresholds. Morphological studies demonstrate that the auditory receptors of the TGK8-4 transgenic mice are highly immature. Immunocytochemical studies were made by using two monoclonal antibodies: CAM 5-2 (recognizing K8 human cytokeratin) and Troma-1 (recognizing both mouse and human K8 cytokeratin). These demonstrated significant differences between the auditory receptors of the transgenic mice and the control mice. These functional and morphological differences clearly suggest that K8 cytokeratin has a relevant role during the differentiation and tridimensional organization of the sensory and the supporting cells of the auditory receptor.

Animals↗

PubMed2002

Transitional expression of OX-2 and GAP-43 glycoproteins in developing rat cochlear nerve fibers.

The OX-2 and GAP-43 glycoproteins are two proteins involved in neuronal cell-to-cell interaction and/or growing of dendrites and axons. Therefore, for the auditory receptor the expression of these proteins could provide information on the afferent and efferent nerve fiber organization. The expression and distribution of OX-2 and GAP-43 were analyzed during the auditory receptor development and maturation (from embryonic day E13 to postnatal day P22). Both glycoproteins were early recognized in the cochleae of E13 rats. Then, they slowly but progressively disappeared, being absent when the animals reached the P22 postnatal day. At E13, a weak OX-2 expression was restricted to the perikaryon of the spiral ganglion neurons, while in the same period a strong GAP-43 immunostaining was found in both the neuronal perikaryon and the neurites. During the rat embryonic period (E13 to birth) the expression of both glycoproteins appeared progressively restricted to the neurites. During the rat postnatal period (P0 to P22), OX-2 and GAP-43 exhibited a dissimilar distribution pattern. The OX-2 glycoprotein appeared in the afferent, efferent and fibers of the auditory nerve, while the GAP-43 glycoprotein only appeared in the efferent nerve fibers. Present data suggest that OX-2 and GAP-43 could act as two complementary glycoproteins during the development, organization, and maturation of the cochlear nerve fibers. While both glycoproteins could participate in axonal growing and orientation, OX-2 could also be involved in a similar process for auditory dendrites.

Animals↗

PubMed2001

Changes in the cochlear dopaminergic system of the aged rat.

The levels of dopamine (DA) and its metabolites 3,4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA) have been quantified in cochleae of male and female rats aged 3, 6, 9, 12, 19 and 24 months. Animals were exposed for 1 h, under general anesthesia, to: (1) silence (basal conditions) or (2) white noise at 90 dB SPL. Afterwards, the concentrations of DA, DOPAC and HVA were determined by HPLC with electrochemical detection in homogenates of individual cochleae. In basal conditions, the cochlear concentrations of DA, DOPAC and HVA in aged females were higher than in adult ones. The concentrations of DA and DOPAC were also higher in aged males with respect to adult ones. A decrease in DA and an increase in DOPAC and HVA concentrations, with respect to silence, were detected when adult animals were exposed to noise. Meanwhile, aged animals showed either a noise-induced increase or no modification of DA and DOPAC with respect to basal levels. Present results suggest age-related failures in DA release and metabolizing mechanisms within the cochlea, together with a compensatory DA synthesis increase. However, the possibility of an initial damage in the primary auditory neurons which could also stimulate the synthesis of DA must not be excluded. Present age-related changes could indicate that the cochlear dopaminergic innervation is affected during the aging process. Since this innervation plays an important role in both the modulation and the protection of the primary auditory neurons, its metabolic alteration could profoundly modify the auditory process.

3,4-Dihydroxyphenylacetic Acid↗

PubMed2001

Galectine-1 expression in cochleae of C57BL/6 mice during aging.

Presbycusis is a progressive hearing loss related to the aging process associated with auditory receptor degeneration. Adult animals exhibited galectine-1 (GAL-1) expression in epithelial cells of the inner and outer spiral sulci and Hensen cells, which was absent from the sensory and supporting cells. The progressive age-related degeneration of auditory receptor was analyzed using an anti-GAL-1 monoclonal antibody on cochleae of C57BL/6 mice (1-24 months old). Mice < or = 9 months old showed adult and healthy auditory receptors, with a similar GAL-1 expression along the time. Conversely, animals > 1 year old exhibited a sensory degeneration at the cochleae basal coil that progressively reached the middle coil. Older animals (18-24 months old) showed a single layer epithelium that replaced the auditory receptor. The age-related degenerative process of the auditory receptor involves sensory but also supporting cells, which are both substituted by epithelial non-specialized cells.

Aging↗

PubMed2001

Cochlear microphonic potentials: a new recording technique.

A new instrumentation and a particular method for detecting and recording cochlear microphonic potentials (CMPs) are described here. The CMPs were recorded in rats by means of pure tones (4,000, 2,000, 1,000, 500, and 250 Hz) and intraepidermic electrodes; the electrocochleography technique was avoided. An experimental design that included the use of a glutamatergic agonist (kainic acid [KA]) and an aminoglycoside antibiotic (kanamycin [KANA]) was carried out to demonstrate the origin of the recorded potential. Morphological studies showed that KA selectively eliminated the afferent type I dendrites of the spiral ganglion, while the administration of KANA resulted in the absence of outer hair cells. When CMPs were recorded after KA administration, no alterations were detected. In contrast, KANA administration resulted in the absence of any selective electrophysiological activity corresponding to CMPs. All these results were compared with the recording of the compound action potential of the eighth nerve obtained by electrocochleography. These findings and the great specificity of the reproduction of the sound stimulus confirm that the CMPs can be recorded by the new equipment.

Acoustic Stimulation↗

PubMed2000

Ultrastructural evidence of the protective effect of Na+/H+ exchange inhibition on the in vitro damage induced by ischaemia reperfusion in the interventricular septum of the rabbit heart.

We investigated the effects of the Na+/H+ antiporter inhibitor, dimethylamiloride, on myocardial injury after 1 h global ischaemia and 30 min. reperfusion in the isolated arterially perfused interventricular septum of the rabbit heart. After ischaemia and reperfusion challenge, dimethylamiloride significantly increased the recovery of developed tension in a dose-dependent manner, and significantly decreased the maximal increase in resting tension. Ultrastructural analysis of myocytes submitted to the experimental in vitro model supported functional maintenance of physiologically-like conditions. Where myocardial portions were submitted to ischaemic conditions and reperfusion, myocyte cell damage reached usual characteristics of infarct-like induced lesions. Intracellular oedema, severe disruption of myofibrils with loss of muscle striation and both swelling and fragmentation of mitochondria were the main characteristics observed. Dimethylamiloride treatment clearly modifies ultrastructural findings towards the normalization of cell shape and structure, only a slight-middle intracellular oedema and contraction bands were found. On the basis of the present results, we suggest that the protective effects exhibited by dimethylamiloride on the ischaemic myocardium are compatible with its Na+/H+ antiporter inhibition properties, they diminish Na+ accumulation and then either Ca2+ overload or non-exocytotic noradrenaline release during the ischaemia and reperfusion challenge.

Amiloride↗

PubMed2000

Serotonergic innervation of the organ of Corti.

The olivocochlear efferent system of the mammalian cochlea, which is divided into two lateral and medial bundles, contains numerous neuroactive substances (acetylcholine, GABA, dopamine, enkephalins, dynorphins and CGRP). These have been located at the brainstem in neurons belonging to the lateral superior olive (lateral efferent system) or in neurons of the periolivary region around the medial superior olive and the trapezoid body (medial efferent system). All of these substances were found in well-characterized projections corresponding to lateral and medial nerve fibres and terminals which connect to the type I afferent dendrites and the outer hair cells, respectively. All could be involved in the modulation of the auditory process, as is suggested by the cochlear turnover increases observed in some of them (i.e. enkephalins or dopamine) induced by sound stimulation. Recently, the presence and distribution of serotonin-containing fibres has been included in the long list of cochlear neuroactive substances. However, its highly particular peripheral pattern of distribution together with the lack of response to sound stimulation could suggest that serotonergic fibres constitute a previously unknown cochlear innervation.

Animals↗

PubMed1999

Noise stimulation decreases the concentration of norepinephrine in the rat cochlea.

The present study was designed to analyze, by using high performance liquid chromatography (HPLC), the effect of acoustic stimulation on the cochlear concentration of norepinephrine (NE). Independently of the rat strain (Long-Evans or Wistar strains), NE concentration decreased about 18% when animals were exposed to white noise (90 dB SPL for 1 h). The same decrease was observed in animals perfused by aortic pathway to remove the blood, indicating that this decrease corresponds exclusively to a neurophysiological process. In fact, these findings could indicate that noise stimulation is involved in the NE release from sympathetic fibers innervating the cochlea. This likely release of NE supports that sympathetic fibers play a functional role in cochleae exposed to noisy situations.

Acoustic Stimulation↗

PubMed1999

Trimetazidine prevents cochlear lesions induced by intraperitoneal and perilymphatic administration of kainic acid.

The protective activity of trimetazidine (TMZ) against cochlear neurotoxicity induced by intraperitoneal and intracochlear administration of kainic acid (KA) has been analyzed. The amplitude of the CAP N1 wave was significantly higher in KA rats pretreated with TMZ, independently of the administration route, than in those only treated with KA. However, CAP N1 amplitude of both TMZ pretreated and non-pretreated animals was always lesser than the N1 wave amplitude observed in the control group. The CAP N1 latency did not show any significant difference between KA and TMZ+KA groups except at high intensities of 8 and 12 kHz. As a complementary control, we have demonstrated that the intraperitoneal administration of TMZ (5 mg/kg) alone did not affect either the electrophysiological activity or the morphology of the auditory nerve. Morphological results fit well with electrophysiology. Some isolated swollen afferent fibers were observed in TMZ+KA cochleae, the swollen dendrites being sparser than in the KA only treated animals. In TMZ+KA animals, the cochlear apical coils were less affected than the basal coils. Our results are in agreement with recent clinical studies and suggest that TMZ could be an active drug on cochlear impairment linked to hypoxic-ischaemic syndromes.

Animals↗

PubMed1999

Sequential changes in anti-GAL-1 staining of the rat organ of Corti following amikacin exposure.

Hair cell loss and a non-functional epithelial reorganization appeared in the organ of Corti after acoustic or toxic damage. Moreover, in the drug damaged organ of Corti, transient atypical cells were recently described with characteristics of both immature hair cells and/or non-sensory epithelial cells. The phenotype of these atypical cells has been now investigated by using the galectine 1 (GAL-1) antibody. In the normal organ of Corti, this antibody recognizes all the epithelial cells except the sensory hair cells and their supporting cells. At PD 21, transient atypical cells were not stained by GAL-1 antibody, suggesting that they were originated from hair cells or their supporting cells. Later, the organ of Corti was substituted by an epithelial scare, GAL-1 stained. This study also emphasizes the particular resistance of the cochlear apex to degeneration after antibiotic intoxication.

Amikacin↗

PubMed1999

Decalcification by ascorbic acid for immuno- and affinohistochemical techniques on the inner ear.

An ascorbic acid decalcifying solution was applied to immuno- and affinohistochemical studies on the inner ear. Rat inner ears fixed in 4% paraformaldehyde in PBS or in 2% acetic acid in ethanol solutions were adequately decalcified in an ascorbic acid solution, at a temperature of 4 degrees C. The decalcifying solution was prepared with 1% ascorbic acid and 0.84% sodium chloride in distilled water (pH 2.5-2.6). The decalcification time was in a direct relationship to the specimen calcification. In this study, two neuroactive substances (gamma-aminobutyric acid and calcitonin gene-related peptide), neurofilaments, and the galectine endogenous lectin were successfully detected immunohistochemically.

Animals↗

PubMed1999

Parotid gland tissue is able partially to assume pituitary functions under the influence of hypothalamic factors: in vivo and in vitro studies.

To test whether salivary tissue can secrete pituitary hormones, female Sprague-Dawley rats were hypophysectomized (hypox) and the following were transplanted to the sella turcica: parotid gland (group 3, n=33), adrenal gland (group 4, n=30), muscle (group 5, n=24). Group 2 (n=21) had the sella turcica filled with dentist's cement. In addition a group of rats (group 1, n=22) remained intact as controls. All groups were followed for 8 months. Daily vaginal smears showed normal cyclicity in controls and constant dioestrus in all hypox groups. Blood samples, taken once every 30 days before and after LHRH stimulation, showed significantly lower (P<0.001) plasma LH values in all hypox groups compared with controls. In group 3, a gradual and significant increase (P<0.05) was observed in the LH response to LHRH in parallel with a partial recovery of oestrous smears. No LH modification was observed in the other hypox groups. Plasma prolactin (PRL) levels were also very low in all hypox groups and were unaltered throughout the study. At the end of the experiments, half the animals were killed by decapitation and the hypothalamic-pituitary areas carefully dissected, homogenized and analysed for LH and PRL content. The remaining animals were perfused with 4% paraformaldehyde to obtain fixing of the whole body tissues. Hypothalamic and transplant areas were carefully dissected, frozen, cut and submitted to immunochemical procedures. LH content in the graft of group 3 animals was markedly (P<0.001) lower than in the control pituitary, but significantly higher (P<0.05) than in the other hypox groups. Immunochemistry showed LH and PRL positive cells in the graft of group 3 animals, whereas neither positive cells, nor LH content were observed in the parotid gland in situ. Experiments were completed with in vitro cultures of parotid glands in the presence or absence (controls) of synthetic hypothalamic hormones or rat hypothalamic extracts. After 1.5 weeks of culture, a significantly higher LH concentration (P<0.05) was observed in the wells treated with synthetic hypothalamic hormones (216+/-46 pg/ml vs 41+/-6 pg/ml in controls). When hypothalamic extracts were used, the LH levels increased more markedly (1834+/-190 pg/ml vs 36+/-6 pg/ml in controls) and those values were maintained during 3 weeks of culture. Immunostaining of these cultures showed a positive LH reaction in the epithelial cells found in the hypothalamic extract-treated wells. Both in vivo and in vitro studies confirm the transdifferentiation of parotid gland tissue to pituitary hormone-producing cells under hypothalamic influence.

Adrenal Glands↗