Biomedical subjects

Y Ye

Publications and source records attributed to Y Ye.

At least 91 records · Page 5Linked to original sources

PubMed1999

Oxygen delivery does not limit cardiac performance during high work states.

This study tested the hypothesis that the loss of myocardial high-energy phosphates (HEP), which occurs during high cardiac work states [J. Zhang, D. J. Duncker, Y. Xu, Y. Zhang, G. Path, H. Merkle, K. Hendrich, A. H. L. From, R. Bache, and K. Uğurbil. Am. J. Physiol. 268: (Heart Circ. Physiol. 37): H1891-H1905, 1995], is not the result of insufficient intracellular O(2) availability. To evaluate the state of myocardial oxygenation, the proximal histidine signal of deoxymyoglobin (Mb-delta) was determined with (1)H nuclear magnetic resonance spectroscopy (MRS), whereas HEP were examined with (31)P MRS. Normal dogs (n = 11) were studied under basal conditions and during combined infusion of dobutamine and dopamine (20 micrograms . kg(-1). min(-1) iv each), which increased rate-pressure products to >50,000 mmHg. beats. min(-1). Creatine phosphate (CP) was expressed as CP/ATP, and myocardial myoglobin desaturation was normalized to the Mb-delta resonance present during total coronary artery occlusion. This Mb-delta resonance appeared at 71 parts per million downfield from the water resonance. CP/ATP decreased from 2. 22 +/- 0.12 during the basal state to 1.83 +/- 0.09 during the high work state (P < 0.01), whereas DeltaP(i)/CP increased from 0 to 0.21 +/- 0.04 (P < 0.01). Despite these HEP changes, Mb-delta remained undetectable. In contrast, when a coronary stenosis was applied to produce a similar decrease in CP/ATP, Mb-delta reached 0.38 +/- 0.10 of the value present during total coronary occlusion. These data demonstrate that Mb-delta is readily detected in vivo during limitation of coronary blood flow sufficient to cause a decrease of myocardial CP/ATP. However, similar HEP changes that occur at high work states in the absence of coronary occlusion are not associated with a detectable Mb-delta resonance. The findings support the hypothesis that the myocardial HEP changes observed at high work states are not due to inadequate O(2) availability to the mitochondria and emphasize the limitations of interpreting HEP alterations in the absence of knowing the level of myocyte oxygenation.

Animals↗

PubMed1999

[Homozygous deletion of CDKN2/p16 gene in lung cancers].

OBJECTIVE: To study the relationship between CDKN2/p16 gene homozygous deletion and lung cancer progression. METHODS: Improved multiplex PCR technique was applied to detect deletion of CDKN2/p16 gene exon1 and exon2 in 89 cases of lung cancers. RESULTS: Gene deletion rate was increased by the improved PCR technique. Exon 1 and exon 2 deletion rates were 19.1% (17/89) and 22.5% (20/89) respectively, with total rate of exon1 and/or exon2 deletion 25.8% (23/89). Deletion of CDKN2/p16 gene occurred in non-small cell lung carcinoma (NSCLC) and was related to metastasis and progressive stage. CONCLUSION: Abnormality of CDKN2/p16 gene is a genetic factor for NSCLC susceptibility, and may play a role to some extent in NSCLC malignant progression.

Aged↗

PubMed1999

External valvuloplasty technique in deep venous valve insufficiency of the lower limbs.

OBJECTIVE: To evaluate the therapeutic effects of external valvuloplasty technique in deep venous valve insufficiency of the lower limbs. METHODS: External valvuloplasty of the femoral vein valve was performed in 30 patients(41 limbs) with deep venous valve insufficiency of the lower limbs. The patients ranged in age from 16 to 69 years (mean +/- s, 50.8 +/- 9.2). External valvuloplasty of the first pair of superficial femoral vein valve was carried out in all limbs. External valvuloplasty of the second pair of superficial femoral vein valve was added in 7 limbs and valvuloplasty of the common femoral vein valve in 6 limbs. RESULTS: Venous claudication, swelling, aching disappeared in 78.0% limbs (32), obvious improvement was seen in 22.0% (9), and varicosis disappeared in all limbs. Ulcer healing was observed in 80% (8/10) limbs. Deep venous valve sufficiency was shown in 90.2% limbs, and reflux I degree-II degree in 4 by color Doppler. CONCLUSION: External valvuloplasty is an effective method to treat deep venous valve insufficiency of the lower limbs.

Adolescent↗

PubMed1999

[Antisense oligonucleotide attenuates renal tubulointerstitial injury in mice with unilateral ureteral obstruction].

OBJECTIVE: To inhibit the expression of ICAM-1 mRNA with the mouse ICAM-1 phosphorothioate antisense oligodeoxynucleotide (ASON) and to investigate the role of ICAM-1 in the pathophysialogical process of renal injury in unilateral ureteral obstruction (UUO) animal model. METHODS: After unilateral ureteral ligation, the mice were treated with ICAM-1 ASON, which was injected intravenously at the dosage of 1 mg/kg/day every other day for one week. Other mice treated with control oligonucleotide or normal saline solution only were taken as controls. The expression of ICAM-1 protein and the number of Mac-1 positive cells were measured by immunohistochemical staining. The pathological changes of the obstructed kidney in the mice were analyzed by PAS-staining. Total RNA renal tissue was extracted for the analysis of the ICAM-1 mRNA by methods of Northern blotting. RESULTS: The expression of ICAM-1 protein and the number of Mac-1 positive cells were reduced markedly in the obstructed kidneys of the mice treated with the ICAM-1 ASON(110 +/- 14 [symbol: see text]/mm2 vs 270 +/- 13 [symbol: see text]/mm2). The results of Northern blotting also showed marked decrease of the expression of ICAM-1 mRNA in the kidney of the mice after treatment with ICAM-1 ASON. There were marked inflammatory cells infiltration in the tubulointerstitium, markedly dilated tubules, and extraceliular matrix accumulation in the obstructed kidneys on the 7th day after UUO operation. The treatment of ICAM-1 ASON can alleviate the lesions of the obstructed kidney except for the dilation of the tubules. There was no difference in the body weight, liver weight, spleen weight, the level of BUN and SCr, the level of GPT as well as the urine protein of the mice treated with ICAM-1 ASON, compared with those in control Oligodeoxynucleotide-treated and saline-treated mice. CONCLUSIONS: ICAM-1 is a very important factor in the pathogenesis of the UUO animal model. The mouse ICAM-1 ASON has therapeutic effects on the injury of the obstructed kidney without apparent side effects.

Animals↗

PubMed1999

Effects of BRL 55 834 on allergen-induced bronchoconstriction and airway inflammation in sensitized guinea pigs.

OBJECTIVE: To investigate the effects of potassium channel activator on allergen-induced bronchoconstriction and airway inflammation and to discuss which role it plays in asthma therapy. METHODS: Airway insufflation pressure, examination of inflammatory cells in bronchial alveolar lavage fluid, analysis of airway pathology and airway Evans blue dye extravasation measurement were employed to detect airway resistance and airway inflammatory responses. RESULTS: [(3s, 4R)-3, 4-dihydro-2, 2-dimethyl-4-(2-oxopiperidin-l-yl)-6-pentafluoroethyl-2H-1-benzopyran-3-ol] (BRL) 55 834 (8 micrograms/kg) inhibited not only ovalbumin-induced airway insufflation pressure increase but also inflammatory cell infiltration (ICI) in sensitized guinea-pigs; moreover, it did not decrease blood pressure; in contrast to BRL 55 834, single dose of BRL 38 227 (200 micrograms/kg) and verapamil (0.5 mg/kg) had a little effect on ICI; single dose of aminophylline (25 mg/kg) and dexamethasone (1 mg/kg) could not inhibit ICI, but the former could inhibit airway insufflation increase; drugs, besides aminophylline, could reduce microvascular leakage; single dose of BRL 38 227, verapamil and dexamethasone had no inhibition of airway insufflation pressure; BRL 38 227 and verapamil decreased blood pressure markedly. CONCLUSIONS: Selective potassium channel activator BRL 55 834 not only decreases airway resistance, but also inhibit airway inflammation, and both of them are of benefit to asthma therapy.

Animals↗

PubMed1999

[A study on the etiology of Budd-Chiari syndrome].

OBJECTIVE: To investigate the etiology of Budd-Chiari syndrome (BCS) with finding in surgical operation. METHODS: Thirteen patients with BCS undertook direct vision membranectomy and reconstruction of inferior vena cava. The specimens were studied with light microscopy, electron microscope and immunohistochemistry. RESULTS: Membranous occluding changes, which thickness varying from 2 to 20mm, were found in the posthepatic segment of inferior vena cava during the operation. Thrombi in inferior vena cava were found in 7 cases, 3 of them with thrombi evenly extending to the root of hepatic vein. The compromised venous wall showed proliferation of fibrous connective tissue, hyalinization or mucoid degeneration under light microscopy, 9 of the 13 cases showed chronic infiltration of inflammatory cells. Copious collagenous fibers, few endothelial cells and mitochondria swelling were found with electron microscope. No immune complex (IgA, IgG, IgM) was observed by immunohistochemistry. CONCLUSION: It is concluded that in these cases of BCS, occluding and stenosing lesions in the inferior vena cava were the outcome of thrombosis and its sequelae and local inflammation might be one of the reasons of thrombosis. There was no evidence of congenital malformation.

Adult↗

PubMed1999

[Effect of plasminogen activator inhibitor 1 gene transfer into mesangial cells on Extracellular matrix accumulation].

OBJECTIVE: To observe the influence of plasminogen activator inhibitor 1 (PAI-1) overexpression on extracellular matrix (ECM) accumulation of rat mesangial cells. METHODS: PAI-1/GFP green fluorescent protein fusion gene eukaryotic expression vector pCMX-PAI-1-GFP was constructed and delivered into cultured rat mesangial cells by liposome. PAI-1/GFP expression was observed by fluorescent microscope. FN, LN and Type IV collagen levels were measured by Northern blot analysis and ELISA method. RESULTS: Northern blot analysis, SDS-PAGE analysis and Western blot analysis demonstrated that PAI-1/GFP gene can be transcripted and translated in rat mesangial cells. PAI-1/GFP gene can express a specific protein. The recombinant PAI-1/GFP had significant inhibition activity on urokinase-type plasminogen activator and displayed autonomous fluorescence. The PA activity of cell supernatants decreased markedly in gene transfer group. FN, LN and Type IV collagen levels were higher than in a control group. CONCLUSION: Over-expression of PAI-1 gene leads to mesangial ECM accumulation. The changes of PA/PAI-1 activity in supernatants of cultured rat mesangial cells might be the key factor in ECM accumulation regulation.

Animals↗

PubMed1999

[Experimental study on adhesion mechanism of airway inflammation in the pathogenesis of bronchial asthma].

OBJECTIVE: To investigate the adhesive mechanism of airway inflammation in the pathogenesis of asthma. METHODS: The guniea pigs were divided into 2 groups, the asthmatic animal group and the normal animal group. The following tests were performed: (a) The values of sICAM-1, sP-selectin, IL-8 and ECP both in plasma (or serum) and BALF were measured by ELISA. (b) The expressions of ICAM-1 and IL-8 on the bronchial epithelial cells and vascular endothelial cells were measured by immuno-histochemistry staining. (c) The lung functions (VT, Cdyn, R(L)) were tested. RESULTS: (a) The values of sICAM-1, sP-selectin and ECP were elevated both in the plasma and BALF level of asthmatic group (P < 0.01). Additionally, IL-8 of BALF level of asthmatic group was elevated (P < 0.01), while IL-8 of serum level was lower than that of normal group (P < 0.01). (b) The expressions of ICAM-1, IL-8 on the bronchial epithelial and vascular endothelial cells in asthmatic animals were up-regulated (P < 0.01). (c) The lung functions of the asthmatic animals were impaired (V(T), C(dyn) P < 0.01; R(L) P < 0.05). CONCLUSIONS: ALL the results above suggests that ICAM-1, IL-8, P-selectin and ECP are involved in the inflammative adhesive mechanism of asthma.

Animals↗

PubMed1999

[A clinical study on vaccine of Mycobacterium vaccae in treating pulmonary tuberculosis].

OBJECTIVE: To study the effect of vaccine of Mycobacterium vaccae on cell-mediated immunity and on treating patients with pulmonary tuberculosis. METHODS: Seventy cases of pulmonary tuberculosis with smear positive and initial treatment were classified randomly into group I (35 cases) and group II (35 cases), receiving 2HRZS/4HR and 2HRZS/4HR plus vaccine of Mycobacterium vaccae regimens respectively. Thirty-one multi-drug resistant pulmonary tuberculosis cases were classified into group III, receiving 4 - 6 sensitive antituberculous drugs and vaccine of Mycobacterium vaccae. Improvement of clinical symptoms, resolution of pulmonary lesions, negative conversion of sputum and changes of immunological functions were observed. RESULTS: No significant difference in improvement of symptoms was found in group I and group II (P > 0.05), and the improvement rate of clinical symptoms in group III was found more than 50%. X-ray resolution rates in 4th month were 83% and 89%, and cavity reducing rates 40% and 50% respectively in group I and group II, and no significant differences were found (P > 0.05). X-ray resolution rate was 29%, cavity reducing rate 7% and no deteriorated case was found in group III. Sputum negative conversion rates in 1st, 2nd, 3rd and 4th month were 23%, 51%, 83% and 97% respectively in group I, while 31%, 77%, 89% and 100% in group II, and 3%, 16%, 29% and 32% in group III. Significant difference was found between group I and group II in sputum negative conversion rate in 2nd month after treatment (P < 0.05). After treatment, values of lymphocyte transformation test (LTT), CD(3), CD(4) and CD(4)/CD(8) of the above 3 groups were all higher than that before the treatment (P < 0.05), level of tumor necrosis factor decreased in group II and IL-2, IL-6 increased in group III. CONCLUSIONS: Vaccine of Mycobacterium vaccae is a good immunotherapy preparation, which promotes sputum negative conversion and activation of cell-mediated immunity.

Adolescent↗

PubMed1999

[External valvuloplasty for deep venous valve insufficiency of legs].

OBJECTIVE: To study and evaluate the therapeutic effects of external valvuloplasty for deep venous valve insufficiency of the legs. METHODS: External valvuloplasty of the femoral vein valve was performed in 26 patients (37 legs) with deep venous valve insufficiency of the legs. Among them, 12 were male and 14 were female. These patients ranged in age from 16 to 69 years (x +/- s, 50.8 +/- 10.0). External valvuloplasty of the first pair of the superficial femoral vein valve was carried out in all the legs. External valvuloplasty of the second pair of the superficial femoral vein valve was added in 7 legs and valvuloplasty of the common femoral vein valve in 6 legs. RESULTS: Venous claudication, swelling, aching disappeared in 81.1% patients (30/37), obviously improved in 18.9% (7/37) and varicose veins disappeared in all legs. Ulcer healing was seen in 7/9 patients. Deep venous valve sufficiency was demonstrated in 89.2% patients (33/37), and reflux I degrees - II degrees in 4 legs by color Doppler. CONCLUSIONS: External valvuloplasty is effective in treating deep venous valve insufficiency of the legs.

Adolescent↗

PubMed1999

[The level of expression of adhesion molecules CD44v6 and E-cadherin in colorectal cancer and analysis of correlates with metastasis].

OBJECTIVE: To determine the expression of adhesion molecules CD44v6 and E cadherin in colorectal cancer and its relation with metastasis. METHODS: The expression of CD44v6 and E-cadherin in 32 patients with colorectal carcinoma was investigated using immunohistochemical staining, which was performed on surgical specimens. RESULTS: No significant correlation with CD44v6 and histologic type, TNM and Dukes staging was noted, but it was significantly correlated with lymph node and hematogenous metastasis. E-cadherin was strongly expressed in normal epithelium examined. However, E-cadherin expression in colorectal carcinoma was reduced (positive rate 46.9%). Metastatic colorectal carcinoma showed significant reduction (positive rate 20%). CONCLUSION: CD44v6, E-cadherin immunoreactivity are significantly correlated with lymph node and hematogenous metastasis.

Cadherins↗

PubMed1999

[Preoperative arterial infusion chemotherapy of colorectal carcinoma pathological and clinical effects].

OBJECTIVE: To investigate the pathological and clinical effects of preoperative selective intra-arterial infusion chemotherapy on colorectal carcinoma. METHODS: 30 patients with colorectal carcinoma underwent selective regional arterial angiography by Seldinger's method followed by intra-arterial infusion chemotherapy. RESULTS: changes of karyopyknosis, karyorrhexis, coagulation and necrosis of cytoplasm in cancer cells around vascular vessels were found in all cases. Interstitial edema, invasion of inflammatory cells, fibroelastosis around cancer cells, proliferous intima, thrombus and inflammation of vessels were also found at the same sites. CONCLUSIONS: Histological changes are significant after preoperative selective intra-arterial infusion chemotherapy for colorectal carcinoma. This therapy can relieve symptoms.

Adult↗

PubMed1999

[Microelectrode-guided posteroventral medial pallidotomy for Parkinson's disease].

OBJECTIVE: To introduce the methods and effects of microelectrode-guided posteroventral pallidotomy (PVP) for Parkinson's disease. METHODS: 109 patients underwent PVP by microelectrode electrophysiological recording for intraoperative target localization. 45 patients underwent unilateral PVP, 21 patients simultaneous bilateral PVP, 43 patients combined thalamotomy and PVP. Modified Webster Scale was used for objective assessments before and after operation. Postoperative CT scan or MRI was performed to localise lesions. RESULTS: Microelectrode recording usually led to a final pallidotomy lesion position that deviated from the CT stereotactically defined target point. The change rate of targets was 84.7%. PVP significantly and immediately improved all Parkinsonian motor signs and reduced drug-induced motor fluctuations and dyskinesia. The mean Webster Scale was improved by (72.7 +/- 11.3)% in the "on"" state, and (89.3 +/- 8.1)% in the "off" state. No patient showed permanent complications. CONCLUSIONS: Microelectrode-guided PVP was proved to be safe and effective. Bilateral PVP and combined PVP can significantly and immediately abolish all Parkinsonian motor signs. Physiological methods of microelectrode recording can significantly improve the safety and efficacy of PVP, and decrease the rate of complication.

Adult↗

PubMed1998

Subcellular localization of the von Hippel-Lindau disease gene product is cell cycle-dependent.

The von Hippel-Lindau gene product (pVHL) interacts with and inhibits the cellular transcription factor elongin. However, the subcellular localization of pVHL has remained uncertain. Naturally occurring pVHL mutants which fail to interact with elongin have been described in patients with VHL disease or sporadic renal cell carcinoma (RCC). Here, we have examined the cellular expression pattern of endogenous pVHL in different RCC cell lines by immunocytochemistry and confocal microscopy. Both anti-N-terminal and anti-C-terminal pVHL antibodies were able to recognize endogenous wild-type pVHL expressed by the RCC cells studied. A C-terminal truncated VHL mutant expressed by RCC cell line A498 was detected only by the N-terminal antibody but not by the C-terminal antibody as expected. The overall staining patterns of these cell lines are similar, with a predominant nuclear speckled pattern and a moderate cytoplasmic staining in subconfluent cell cultures. Interestingly, when cells reached confluency, more prominent nuclear staining with little or no cytoplasmic expression was observed. By using double labeling with anti-VHL and anti-bromodeoxyuridine (BrdU) antibodies and cell cycle analyses, we found that in the G1/G0-phase, pVHL was localized exclusively in the nucleus associated with distinctive large subnuclear structures, whereas the majority of the cells in S-phase of the cell cycle also showed a diffuse cytoplasmic staining. Our results indicate that subcellular localization of pVHL is regulated in a cell cycle-dependent manner.

Carcinoma, Renal Cell↗

PubMed1998

Genetic deletion of AT2 receptor antagonizes angiotensin II-induced apoptosis in fibroblasts of the mouse embryo.

To examine whether angiotensin II (Ang II) can trigger apoptosis via Ang II type 2 (AT2) receptor, two genotypes of skin fibroblasts cultured from the AT2 receptor gene targeting homozygous (AT2-/-) and wild-type (AT2+/+) mouse embryos, respectively, were studied when exposed to Ang II. In the AT2+/+ fibroblasts, mRNA expression of the AT2 receptor was modulated by Ang II in a dose-dependent manner and apoptosis appeared with the convincing features of internucleosomal DNA fragmentation and DNA content decrease after stimulation with Ang II, whereas Ang II had no significant impact on the AT2-/- fibroblasts due to the AT2 receptor gene deletion. This is the first report using a gene targeting study to demonstrate that Ang II induces apoptosis through the AT2 receptor in the fibroblasts of the mouse embryo.

Angiotensin II↗

PubMed1998

Myeloperoxidase and horseradish peroxidase catalyze tyrosine nitration in proteins from nitrite and hydrogen peroxide.

Nitration of tyrosine residues in proteins occurs in a wide range of inflammatory diseases involving neutrophil and macrophage activation. We report that both myeloperoxidase (MPO) and horseradish peroxidase (HRP) utilize nitrite (NO2-) and hydrogen peroxide (H2O2) as substrates to catalyze tyrosine nitration in proteins. MPO was approximately 10 times more effective than HRP as a nitration catalyst of bovine serum albumin (BSA). Nitration of BSA by MPO did not require chloride as a cofactor. Physiologic levels of chloride did not significantly inhibit nitration by MPO. Oxidation of chloride to hypochlorous acid (HOCl) is catalyzed by MPO but not by HRP, yet HRP also catalyzed nitration from hydrogen peroxide plus nitrite. Therefore, HOCl formation was not obligatory for tyrosine nitration. Although HOCl plus nitrite can nitrate the amino acid tyrosine in simple solutions, protein nitration by HOCl plus nitrite was not observed in heart homogenates, probably due to the presence of multiple alternative targets of both HOCl and HOCl plus nitrite. In contrast, MPO catalyzed nitration of many proteins in rat heart homogenates using NO2- plus H2O2, suggesting that peroxidase-catalyzed nitration of tyrosine could occur in the presence of competing substrates in vivo. HOCl could substitute for H2O2 as the oxidizing substrate for nitration of either BSA or tissue homogenates catalyzed by either peroxidase. Activated neutrophils may generate nitrotyrosine by several mechanisms, including peroxynitrite, HOCl plus nitrite, and a chloride-independent mechanism involving MPO, nitrite, and hydrogen peroxide.

Animals↗

PubMed1998

The cat vertebral column: stance configuration and range of motion.

This study examined the configuration of the vertebral column of the cat during independent stance and in various flexed positions. The range of motion in the sagittal plane is similar across most thoracic and lumbar joints, with the exception of a lesser range at the transition region from thoracic-type to lumbar-type vertebrae. The upper thoracic column exhibits most of its range in dorsiflexion and the lower thoracic and lumbar in ventroflexion. Lateral flexion is limited to less than 5 degrees at all segments. The range in torsion is almost 180 degrees and occurs primarily in the midthoracic region, T4-T11. Contrary to the depiction in most atlases, the standing cat exhibits several curvatures, including a mild dorsiflexion in the lower lumbar segments, a marked ventroflexion in the lower thoracic and upper lumbar segments, and a profound dorsiflexion in the upper thoracic (above T9) and cervical segments. The curvatures are not significantly changed by altering stance distance but are affected by head posture. During stance, the top of the scapula lies well above the spines of the thoracic vertebrae, and the glenohumeral joint is just below the bodies of vertebrae T3-T5. Using a simple static model of the vertebral column in the sagittal plane, it was estimated that the bending moment due to gravity is bimodal with a dorsiflexion moment in the lower thoracic and lumbar region and a ventroflexion moment in the upper thoracic and cervical region. Given the bending moments and the position of the scapula during stance, it is proposed that two groups of scapular muscles provide the major antigravity support for the head and anterior trunk. Levator scapulae and serratus ventralis form the lateral group, inserting on the lateral processes of cervical vertebrae and on the ribs. The major and minor rhomboids form the medial group, inserting on the spinous tips of vertebrae from C4 to T4. It is also proposed that the hypaxial muscles, psoas major, minor, and quadratus lumborum could support the lumbar trunk during stance.

Animals↗

PubMed1998

Responses of anteroventral cochlear nucleus neurons of the unanesthetized decerebrate cat to click pairs as simulated echoes.

To elucidate the contribution of the anteroventral cochlear nucleus (AVCN) to 'echo' processing, this study documents the responses of AVCN neurons to simulated echoes and compares them to those of auditory nerve (AN) fibers. Single unit discharges were recorded from 121 units in the AVCN of 21 unanesthetized decerebrate cats in response to click pairs with inter-click intervals ranging from 1 to 32 ms between 45 and 105 dB SPL re 20 microPa. Units were classified according to the post-stimulus time histogram (PSTH) and excitatory-inhibitory response area (EI-area) schemes. Based on their spontaneous rates (SR), units were subdivided into low- ( < 20 spikes/s) and high- ( > 20 spikes/s) SR groups. A majority of the units exhibited second-click responses whose recovery time courses were similar to those of AN fibers. These units included primary-like, chopper and onset units in the PSTH scheme and Types I, I/III and III units in the EI-area scheme. A minority of the units exhibited responses that were distinct from those of AN fibers, in that they had second-click response recovery times that were either markedly reduced or prolonged. This group of units included those with primary-like, chopper and onset PSTHs and Type I/III and III EI-areas. No significant difference was found in the second-click response among various PSTH or EI-area types. High-SR AVCN units exhibited a decrease in the second-click response with increasing level. In contrast, low-SR AVCN units showed little level-dependent change in the second-click responses. This SR-based difference was similar to that previously found among AN fibers. The present results suggest that, although a majority of AVCN units exhibit similar time courses of second-click response recovery to those of AN fibers, there do exist mechanisms in the cochlear nucleus that can substantially alter this representation. Furthermore, the difference between the second-click response recovery functions of low- and high-SR AVCN units and the consistency of this finding between AVCN and AN suggest that SR represents an important dimension for signal representation in the AVCN neurons.

Acoustic Stimulation↗