OBJECTIVETo observe the influence of lead exposure on the activity of nitric oxide synthase (NOS) in different brain regions of rat.

METHODSBy establishing a series of rat models exposed to different low levels of lead (drinking water containing 0.025%, 0.050%, 0.075% of lead acetate) during developing period, NOS activities in hippocampus, cerebellum, cerebral cortex and brain stem were studied.

RESULTSOn the 21st day after birth, NOS activities in hippocampus of three levels of lead exposed groups [(1.53 +/- 0.20), (1.66 +/- 0.23), (1.88 +/- 0.32) U/mg pro respectively], and in cerebellum [(0.87 +/- 0.24), (0.85 +/- 0.09), (0.91 +/- 0.18) U/mg pro respectively] were significantly lower than those of control group [(2.36 +/- 0.18), (1.41 +/- 0.18) U/mg pro, respectively, P < 0.01]. NOS activities in cerebral cortex of 0.075% group [at 7, 14, 21 d of age [(1.29 +/- 0.14), (1.03 +/- 0.15), (0.69 +/- 0.10) U/mg pro] were significantly lower than those in control group [(2.54 +/- 0.31), (1.64 +/- 0.22), (1.24 +/- 0.14) U/mg pro respectively], and 0.025% group [(2.42 +/- 0.19), (1.59 +/- 0.17), (1.27 +/- 0.12) U/mg pro respectively], and 0.050% group [(2.56 +/- 0.53), (1.77 +/- 0.19), (1.24 +/- 0.10) U/mg pro respectively, P < 0.05]. There were no significant differences among control, 0.025%, and 0.050% groups (P > 0.05). Lead exposure had no influence on NOS activity in brain stem at the same age (P > 0.05).

CONCLUSIONNOS activities in hippocampus, cerebellum and cerebral cortex were inhibited by low level lead exposure and the degree of the effect was related to Pb exposure time and/or level of Pb exposed.

Animals ; Brain ; drug effects ; enzymology ; Brain Stem ; drug effects ; enzymology ; Cerebellum ; drug effects ; enzymology ; Cerebral Cortex ; drug effects ; enzymology ; Dose-Response Relationship, Drug ; Female ; Hippocampus ; drug effects ; enzymology ; Lead ; toxicity ; Nitric Oxide Synthase ; metabolism ; Rats ; Rats, Sprague-Dawley ; Time Factors

OBJECTIVE: To determine the distribution and influence of lysosomal neuraminidase (Neul), protective protein/cathepsin A (PPCA) and beta-galactosidase (beta-gal) in the inner ear of the mouse, and to observe their auditory alterations in enzyme deficiency. METHODS: Six wild type (2 months postnatal) (Neu1+/+, PPCA+/+ and beta-gal+/+) mice were used, and Neu1, PPCA and beta-gal homozygous (Neu1-/-, PPCA-/- and beta-gal-/-) mice at the same age used as control in this experiment. The auditory thresholds were examined through the auditory brainstem responses (ABR) to click, which tone pips were 8, 16, and 32 kHz. The mice were intracardically perfused with 4% paraformaldehyde. The bulla were further fixed in 4% paraformaldehyde, processed and sectioned with paraffin embedded method. Immunohistochemistry was used to determine the cellular localizations of Neu1, PP-CA, and beta gal in the inner ear. RESULTS: There was a similar distributive pattern of Neu1, PPCA and betagal in the inner ear. Neu1 intense staining was observed in the cochlear spiral ganglion cells, spiral limbus, spiral ligament, vestibular ganglion cells, cristae, maculae hair cells, and weak staining in inner hair cells, outer hair cells, supplying cells of the organ of Corti and stria vascularis. The intense staining of PPCA and beta-gal were observed in the spiral ganglion and vestibular ganglion cells, and weak staining in the spiral limbus, spiral ligament, stria vascularis and organ of Corti. The inner ear exhibited no staining when Neul, PPCA and beta-gal were deficient, respectively. A positive staining of PPCA and beta-gal was presented in Neu1-/- mice, and as well as Neu1 and PPCA in beta-gal-/- mice. However, the staining of Neu1 was not presented, and only very weak staining of beta-gal in PPCA-/- mice. The auditory thresholds of Neul, PPCA, and beta-gal mice were elevated for 60-69 dB, 40-48 dB, and 7-10 dB above those of wildtype littermates, respectively. CONCLUSION Neu1 PPCA and beta-gal are distributed in the inner ear of mouse, and the three enzymes also form a lysosomal multi-enzyme complex in the inner ear. The respective enzyme deficiencies can induce the hearing the loss of different levels.
Animals ; Auditory Threshold ; Cathepsin A ; genetics ; metabolism ; Ear, Inner ; enzymology ; Evoked Potentials, Auditory, Brain Stem ; physiology ; Hearing Loss, Sensorineural ; enzymology ; genetics ; Lysosomes ; enzymology ; Mice ; Mice, Knockout ; Neuraminidase ; genetics ; metabolism ; beta-Galactosidase ; genetics ; metabolism

OBJECTIVETo investigate the effect of noise on the antioxidant enzymes of cochleae.

METHODS16 male pigmented guinea pigs (250 - 300 g) were randomly divided into 2 groups, control group and noise group. Each group had 8 animals. The animals in noise group were performed auditory evoked brainstem responses (ABR) recording before and after exposure to a continuous noise (4 kHz, octave band, 100 dB, SPL) 8 h/d for 3 consecutive days. Immediately at the end of the third day's noise exposure after ABR recording, guinea pigs were decapitated. Both the right and the left cochlea with the bony capsule removed were homogenized, and the supernatants were prepared for assays. Reactive oxygen species (ROS), superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GSH-Px) were measured.

RESULTSROS level of the noise group [(281.2 +/- 3.5) U/mg pro] was significantly higher than that of the control group [(273.0 +/- 3.2) U/mg pro, P < 0.05] and SOD, CAT and GSH-Px activities of the noise group [(206.5 +/- 5.1) NU/mg pro, (47.0 +/- 9.0) U/g pro, (14.1 +/- 2.5) U/mg pro respectively] were significantly lower than that of the control group [(221.8 +/- 4.8) NU/mg pro, (60.8 +/- 9.9) U/g pro, (21.1 +/- 3.1) U/mg pro respectively, P < 0.05].

CONCLUSIONNoise may damage the defensive system of antioxidant enzymes in cochlea.

Animals ; Antioxidants ; analysis ; pharmacology ; Catalase ; metabolism ; Cochlea ; enzymology ; Evoked Potentials, Auditory, Brain Stem ; Glutathione Peroxidase ; metabolism ; Guinea Pigs ; Male ; Noise ; adverse effects ; Superoxide Dismutase ; metabolism

The distribution of the nerve growth factor (NGF), the glial fibrillary acidic protein (GFAP) and the ciliary neurotrohic factor (CNTF) was performed in coronal sections of the mesencephalon, rhombencephalon and spinal cord in the developing Mongolian gerbils. Generally, NGF specifically recognizes neurons with the NGF receptor, whereas GFAP does the glia, and CNTF does the motor neurons. The receptor expression was examined separately in gerbils between embryonic days 15 (E15) and postnatal weeks 3 (PNW 3). The NGF-IR was first observed in the spinal cord at E21, which might be related to the maturation. The GFAP reactivity was peaked at the postnatal days 2 (PND2), while the highest CNTF-reaction was expressed at PNW 2. The GFAP stains were observed in the aqueduct and the spinal cord, which appeared to project laterally at E19. The CNTF was observed only after the birth and found in both the neurons and neuroglia of the substantia nigra, mesencephalon, cerebellum and the spinal cord from PND1 to PNW3. These results suggest that NGF, GFAP and CNTF are important for the development of the neurons and the neuroglia in the central nervous system at the late prenatal and postnatal stages.
Animals ; Brain Stem/enzymology/*metabolism ; Ciliary Neurotrophic Factor/*metabolism ; Embryonic and Fetal Development/physiology ; Female ; Gerbillinae/*embryology ; Glial Fibrillary Acidic Protein/*metabolism ; Immunohistochemistry/veterinary ; Mesencephalon/embryology/metabolism ; Nerve Growth Factor/*metabolism ; Pregnancy ; Rhombencephalon/embryology/metabolism ; Spinal Cord/embryology/*metabolism

AIMTo explore the relationship between evoked potentials (EPs) and chronic anoxic brain damage by chronic intermittent hypoxia (CIH), and provide theory evidence for diagnosis and treatment of anoxic encephalopathy.

METHODSBAEP and SLSEP were recorded in rat model with CIH (hypoxia group) and rat with normoxia (normal group). Morris water maze was used to observe learning and memory ability. Immunohistochemical method was used to investigate the expression levels of caspase-3 in brain tissue.

RESULTSThe peak latency (PL) of wave I, III, V and the interpeak latency (IPL) of wave III - V, I - V in BAEP in hypoxia group were much longer than that of in normal group (P < 0.05). The PL of wave N1, P1 of SEP in hypoxia group were much longer than that of in normal group (P < 0.05). In the water mase test, the escape latency (EL) of hypoxia group was much longer than normal group (P < 0.01). The number of caspase-3 positive cells in hypoxia group was much larger than that of in normal group (P < 0.05). There was a positive correlation among BAEP, SLSEP, the number of caspase-3 positive neuron and EL of water mase.

CONCLUSIONThe alteration of BAEP and SLSEP has an apparent correlation with chronic anoxic brain damage. This provides theory evidence for diagnosis and treatment of anoxic encephalopathy.

Animals ; Brain ; enzymology ; pathology ; physiopathology ; Caspase 3 ; genetics ; metabolism ; Chronic Disease ; Evoked Potentials, Auditory, Brain Stem ; physiology ; Evoked Potentials, Somatosensory ; physiology ; Hypoxia, Brain ; physiopathology ; Male ; Maze Learning ; Random Allocation ; Rats ; Rats, Sprague-Dawley

The relationship between the hypertension and the aging process of hearing organ was investigated. Twenty Wistar 3-month old rats and 20 Wistar 12-month old rats, 20 spontaneously hypertensive rat stroke-prone (SHRSP) 3-month old rats and 20 SHRSP 12-month old rats free of middle ear infections as observed under otomicroscopy, with normal tympanic membrane and auricle reflex, were selected to be divided into two experimental groups and two control groups respectively. The tail artery blood pressure was measured non-invasively. The threshold of auditory brain-stem response (ABR) was measured by Spirit evoked potential meter. The LDH and ChE staining in the inner ear was performed and the optical density was analyzed by the HPIAS analysis system. The results showed that there was no difference in the ABR thresholds, the activities of LDH and ChE between Wistar 3-month old group and SHRSP 3-month old group (P > 0.05). The mean value of ABR threshold and the activities of LDH and ChE in the Wistar 12-month old group at relevant sections were significantly greater than those in the two 3-month old groups (P < 0.05), whereas the mean value of ABR threshold and the activities of LDH and ChE in the SHRSP 12-month old group at relevant sections were significantly higher than those in the 3-month old control group (P < 0.01). It was concluded that presbycusis existed in the Wistar 12-month old group rats. The glycogenosis and the abnormal secretion of neural transmitter were discerned after hypertension. All the above factors may worsen the aging of the hearing system.
Aging ; Animals ; Cholinesterases ; metabolism ; Cochlea ; metabolism ; physiopathology ; Evoked Potentials, Auditory, Brain Stem ; Female ; Hypertension ; complications ; enzymology ; physiopathology ; L-Lactate Dehydrogenase ; metabolism ; Male ; Presbycusis ; etiology ; physiopathology ; Rats ; Rats, Inbred SHR ; Rats, Wistar

OBJECTIVETo investigate the alterations in auditory brainstem evoked responses (ABRs) and the changes of carboplatin-induced ototoxicity in the cochlear oxidant/antioxidant systems and otoprotection by an antioxidant lipoate.

METHODSMale wistar rats were divided into four groups and treated as follows: 1) vehicle (saline) control, 2) carboplatin (256 mg/kg, i.p.), 3) lipoate (100 mg/kg, i.p.), 4) lipoate + carboplatin. Post-treatment ABRs were performed after four days and rats were sacrificed with their cochleae harvested and analyzed.

RESULTSCarboplatin significantly elevated ABR threshold above the pretreatment thresholds. Lipoate+carboplatin treated rats showed decreased elevation of hearing threshold. Carboplatin significantly depleted cochlear reduced to oxizized glutathione (GSH/GSSG) ratio, whereas lipoate+carboplatin treatment increased GSH/GSSG ratio. Carboplatin significantly decreased cochlear copper zinc-superoxide dismutase (CuZn-SOD), catalase (CAT), glutathione peroxidase (GSH-Px), glutathione reductase (GR) and glutathione-S-transferase (GST) activities and enzyme protein expressions and a significant increase in Mn-SOD activity, protein expression and malondialdehyde (MDA) level. Cochlear antioxidant enzyme activities, enzyme protein expressions and MDA level were partially restored in lipoate+carboplatin treated rats, compared to carboplatin alone.

CONCLUSIONCarboplatin-induced ototoxicity is related to impairment of cochlear antioxidant system and otoprotection conferred by lipoate is associated with partial sparing of the cochlear antioxidant defense system.

Animals ; Antioxidants ; pharmacology ; Auditory Threshold ; drug effects ; Carboplatin ; Catalase ; metabolism ; Cochlea ; drug effects ; enzymology ; metabolism ; Evoked Potentials, Auditory, Brain Stem ; drug effects ; Glutathione ; metabolism ; Glutathione Disulfide ; metabolism ; Glutathione Peroxidase ; metabolism ; Glutathione Reductase ; metabolism ; Glutathione Transferase ; metabolism ; Hearing Loss, Sensorineural ; chemically induced ; Lipid Peroxidation ; Male ; Malondialdehyde ; metabolism ; Protective Agents ; pharmacology ; Rats ; Rats, Wistar ; Superoxide Dismutase ; metabolism ; Thioctic Acid ; pharmacology

The aim of the present study was to investigate the effect of tetramethylpyrazine (TMP) on the changes of respiration and expression of neuronal nitric oxide synthase (nNOS) in brainstem induced by hypoxia in the rats. Hypoxia was induced by inhalation of 8% O2-balanced N2.The electromyogram (EMG) of diaphragm was monitored to evaluate the respiratory response of the rats to hypoxia. The immunohistochemical staining technique was used to study the change of the expression of nNOS in the brainstem during hypoxia. In the rats of hypoxia group, a successive process of response, excitatory followed by inhibitory, was produced. Twenty min after hypoxia, a significant inhibition of respiration occurred, which was characterized with a marked decrease in the inspiratory duration, the respiratory frequency, and the amplitude of inspiration and a prolongation of expiratory duration (P<0.05). In the rats of pretreated with TMP, the respiratory activity was not obviously depressed (P>0.05). In the rats of hypoxia group, the level of nNOS immunoreactivity was enhanced remarkably in the lateral reticular nucleus, nucleus of trapezoid, hypoglossal nucleus and the facial nucleus compared with the control group (P<0.05). In the rats of pretreated with TMP, the nNOS level increased further in the nuclei mentioned above (P<0.05). The results obtained indicate that TMP can reverse the inhibitory effect of hypoxia on respiration in the rats and that nNOS may be involved in the respiratory protective action of TMP.
Animals ; Brain Stem ; enzymology ; physiopathology ; Female ; Hypoxia ; physiopathology ; Male ; Nitric Oxide Synthase Type I ; genetics ; metabolism ; Pyrazines ; pharmacology ; Random Allocation ; Rats ; Rats, Sprague-Dawley ; Respiration ; drug effects ; Respiratory Insufficiency ; prevention & control