Effect of high-frequency electrical stimulation of the auditory nerve in an animal model of cochlear implants

HYPOTHESIS

Electrical stimulation of the cochlea at high rates induces significant adaptation of the auditory nerve.

BACKGROUND

A new development of cochlear implants is the use of speech processors delivering electrical pulses on the implanted electrodes at high rates, such as 1,000 pulses per second (pps) and above. Such a stimulation mode allows subjects with cochlear implants to reach excellent understanding of speech.

METHODS

Long Evans-rats received implantation of stimulating electrodes in the left cochlea. Two hundred-millisecond trains of short (20 microns) monophasic pulses were delivered in 50% duty cycle at 500 microA above threshold. The pulse rate in the train was increased from 100 pps to 1,500 pps. Electrically evoked auditory brainstem responses (EABR) were recorded. The amplitude of the compound action potential of the auditory nerve to each single pulse in the train was measured as the first vertex positive wave (WAVE I) of the EABR.

RESULTS

At 100 and 200 pps, WAVE I amplitudes to each pulse were large and remained stable throughout the pulse train. For increasing pulse rates, WAVE I amplitudes progressively decreased during the first 40 to 50 ms of the train and reached 80% at 300 pps to 15% at 1,500 pps of the maximal amplitude observed for the first pulse in the train.

CONCLUSIONS

The decrease of the WAVE I amplitude in response to high-rate pulsatile stimulation reflects an adaptation of the auditory nerve due, at least in part, to the refractory period of auditory nerve fibers.

A comparative study of intravenous accelerated streptokinase dose regimen with conventional dose regimen for coronary thrombolysis

The aim of this study is to test the patency rate and safety of the accelerated streptokinase dose regimen for coronary thrombolysis compared with the conventional one. One hundred and four patients entering three hospitals up to 12 hours after the onset of definite acute myocardial infarction were randomizely treated with intravenous accelerated streptokinase dose regimen (1.5 million units/30 min) (group A, 47 cases) and conventional dose regimen (1.5 million units/60 min) (group B, 57 casese). The reperfusion rate of infarct-related arteries determined by clinical evidence of reperfusion was 76.6% (36/47) in group A VS 61.4% (35/57) in group B. There was significant difference in reperfusion rates among patients within 6 hours after the onset of chest pain: 87.9% (29/33) in group A VS 67.4 (29/43) in group B (P < 0.05). The incidence of mild bleeding, allergic reaction, hypotension was 12.8% (6/47), 4.3% (2/47), 12.8 (6/47) respectively in group A vs 21.1 (12/57), 3.5 (2/57), 17.5% (10/57) respectively in group B. Compared to conventional dose regimen, intravenous accelerated streptokinase dose regimen for coronary thrombolysis seems to improve reperfusion rate markedly without increasing adverse events such as bleeding, allergic reaction and hypotension. It suggests that accelerated streptokinase therapy deserves more extensive investigation.

[Study on correlation between postures and gastroesophageal reflux]

Simultaneous esophageal and gastric manometry and intraesophageal pH monitoring were performed in 12 patients with gastroesophageal reflux diseases in order to compare the frequency and mechanism of reflux in upright and supine postures. It was found that there was no differences in the number of reflux episodes, acid clearance time and percentage time of pH below 4 (P > 0.05). Frequency of reflux associated with lower esophageal sphinter relaxation (LESR) and gastric press increase was similar in two postures (P > 0.05). The results suggest that upright reflux may be as important as supine reflux in the development of reflux esophagitis. The main machanism of reflux in the two postures is LESR. Increase of gastric press may be a factor leading to gastroesophageal reflux.

[Clinical features and CT diagnostic criteria for diffuse axonal brain injury]

The clinical and computed tomographic features of 117 patients with severe closed head injury were analysed. We put forward the CT diagnostic criteria of diffuse axonal injury (DAD)i.e. (1) single or multiple small intraparenchymal hemorrhages in the cerebral hemispheres (< 2 cm in diameter); (2) intraventricular hemorrhage; (3) hemorrhage in the corpus callosum; (4) small focal areas of hemorrhage adjacent to the third ventricle (< 2 cm in diameter); (5) brain stem hemorrhage. Our patients were divided into DAI group and non-DAI group according to the set of criteria. Traffic accidents were the main injury cause in patients with DAI. GCS on admission in patients with DAI were significantly lower than those in patients without DAI. The incidence of diffuse brain swelling in patients with DAI significantly higher than that in non-DAI patients, whereas the incidences of skull fracture and epidual hematoma were respectively significantly lower than those in non-DAI patients. There was no significant difference between the incidences of subarachnoid hemorrhage and subdual hematoma in the two groups. The incidence of poor outcome in DAI group was significantly higher than that in non-DAI group, although there was no significant difference between the mortalities in the two groups. Because DAI is a very important factor worsening the outcome of head-injured patient, it is very important to make a diagnosis as soon as we can. However, the clinical manifestations of DAI are not specific and DAI does not show directly on CT, so it is difficult to make a diagnosis. The CT diagnostic criteria of DAI we put forward now are practicable, though they are not perfect.

[Comparison of secondary ischemia tolerance between free skin flap and island skin flap raised on the buttock of the pig]

OBJECTIVE

This study was to compare skin viability of the free skin flap and the island skin flap in the pig.

METHODS

The comparison was made between the 8 cm x 11 cm surgically denervated free skin flap and the pedicle island skin flap raised contralaterally on the buttock of 50 pigs. The free flap and the pedicle flap were subjected to 2 h of primary warm ischemia followed by 12 h of reperfusion and 0, 2, 4, 6, 10 h of secondary warm ischemia (n = 10). Skin viability was assessed 7 days after secondary ischemia.

RESULTS

Pedicle skin flaps tolerated up to 10 h secondary ischemia without skin necrosis. However, incidences of flap failure (partial or total) in free flaps subjected to 0, 2, 4, 6, 10 h of secondary ischemia were 0, 10%, 50%, 80%, 100%, respectively. In a separate experiment, skin blood flow was studied in contralateral free skin flaps and pedicle island flaps (n = 20) subjected to 4 h of secondary ischemia. The skin reperfusion was very slow in 8 out of 20 free skin flaps at 1, 5 h after secondary is chemia, and the mean skin blood flow measured by 15 microns microspheres in these 8 free skin flaps was only 8% of their contralateral pedicle skin flaps. The mean skin blood flow in the remaining 12 free skin flaps was 76% of their contralateral pedicle skin flap.

CONCLUSION

These observations were interpreted to indicate that buttock free skin flaps in the pig were less tolerant to secondary ischemia compared with their contralateral pedicle skin flaps subjected to the same ischemic protocol, and this reduced ischemic tolerance in free skin flaps was associated with compromised skin blood flow.

The Src-homology domain 2-bearing protein tyrosine phosphatase-1 inhibits antigen receptor-induced apoptosis of activated peripheral T cells

Restimulation of Ag receptors on peripheral T lymphocytes induces tyrosine phosphorylation-based signaling cascades that evoke Fas ligand expression and induction of Fas-mediated programmed cell death. In view of the role for the Src homology domain 2-bearing protein tyrosine phosphatase-1 (SHP-1) in modulating TCR signaling, we investigated the influence of SHP-1 on TCR-mediated apoptosis by assaying the sensitivity of peripheral T cells from SHP-1-deficient viable motheaten (mev) mice to cell death following TCR restimulation. The results of these studies revealed mev peripheral T cells to be markedly more sensitive than wild-type cells to induction of cell death following TCR stimulation. By contrast, PMA/ionophore and anti-Fas Ab-induced apoptotic responses were no different in mev compared with wild-type activated cells. Enhanced apoptosis of TCR-restimulated mev lymphocytes was associated with marked increases in Fas ligand expression as compared with wild-type cells, but was almost abrogated in both mev and wild-type cells by Fas-Fc treatment. Thus, the increased sensitivity of mev T cells to apoptosis following TCR restimulation appears to reflect a TCR-driven phenomenon mediated through up-regulation of Fas-Fas ligand interaction and induction of the Fas signaling cascade. These findings, together with the hyperproliferative responses of mev peripheral T cells to initial TCR stimulation, indicate that SHP-1 modulation of TCR signaling translates to the inhibition of both T cell proliferation and activation and, as such, is likely to play a pivotal role in regulating the expansion of Ag-stimulated T cells during an immune response.

[The expression of proliferating cell nuclear antigen and alpha smooth muscle actin in papillary muscles of the patient with rheumatic heart disease and its significance]

OBJECTIVES

To reveal the change of chronic rheumatic cardiomyocyt phenotype and its relationship with myocardium fibrosis.

METHODS

The papillary muscles samples were obtained from patients with rheumatic heart disease during mitral valve replacement. Normal papillary muscles samples obtained from adult and fetal heart during autopsy in control group. The specimens were examined using immunohistochemistry and immunoelectron microscopy observation with monoclonal antibody of antiproliferating cell nuclear antigen (PCNA) and anti-alpha smooth muscles actin (alpha-SMA), and imaging analysis was performed.

RESULTS

The interstitial fibrosis (24.7% +/- 3.05%) and the ratio between inner and outer diamater of arteriolas (0.405 +/- 0.035) in rheumatic myocardium were higher significantly than those in normal myocardium. Immunohistochemical PCNA expression was not only in interstitial but also in hypertrophic cardiomyocytes of rheumatic heart disease. The positive expression in rheumatic myocardium increased. There were a lot of rough endoplasmic reticula, ribosomes and Golgi bodies in cytoplasm of PCNA and alpha-SMA positive cells. The degree of PCNA and alpha-SMA positive expression was increased with enlargement of fibrosis areas.

CONCLUSIONS

There is not only a high expression of PCNA and alpha-SMA in the myocardium of patients with rheumatic heart disease but also in fetal myocardium. We suggested that pathological myocardial cells are constructive phenotype and synthetive phenotype. PCNA and alpha-SMA positive expression cells are in the proliferating stage, they take part in fibrotic progress and vascular reconstruction in the myocardium.

Loss of PTEN expression leading to high Akt activation in human multiple myelomas

Mouse plasma cell tumor (PCT) and human multiple myeloma (MM) are terminal B-cell malignancies sharing many similarities. Our recent work demonstrated that activation of the insulin-like growth factor receptor (IGF-IR)/insulin receptor substrate (IRS)/phosphatidylinositol 3' kinase (PI 3'K) pathway was evident in the tumor lines derived from both species. Although PI 3'K activity was higher in mouse tumor lines than that in human tumors, activation of Akt serine/threonine kinase was markedly lower in mouse lines. This discrepancy prompted us to test the status of PTEN tumor suppressor gene, as it has been shown to be a negative regulator of PI 3'K activity. Although all the mouse lines expressed intact PTEN, 2 of the 4 human lines (Delta47 and OPM2) possessing the highest Akt activity lost PTEN expression. Sequencing analysis demonstrated that the PTEN gene contains a deletion spacing from exon 3 to exon 5 or 6 in the Delta47 line and from exon 3 to 7 in the OPM2 line. Restoration of PTEN expression suppressed IGF-I-induced Akt activity, suggesting that loss of PTEN is responsible for uncontrolled Akt activity in these 2 lines. Despite the expression of PTEN with the concomitant low Akt activity in all mouse PCT lines, their p70S6K activities were generally higher than those in 3 human MM lines, arguing for specific negative regulation of Akt, but not p70S6K by PTEN. These results suggest that p70S6K and Akt may be differentially used by the plasma cell tumors derived from mice and humans, respectively.

Contents of sulfur amino acids, and cystathionine beta-synthase and gamma-lyase activities in various tissues from agkistroden blomhoffi (mamushi)

The concentrations of sulfur-containing amino acids, taurine, cystathionine, methionine and cystine, as well as cystathionine beta-synthase and gamma-lyase activities in various tissues of Agkistrodon blomhoffi (mamushi) were measured. The concentration of taurine in examined tissues was greater than the concentration of other sulfur-containing amino acids. The concentration of cystathionine in various tissues was also much higher than those of methionine and cystine, but the concentration of cystathionine in the brain was lower than that of methionine. In all tissues examined in this study, cystathionine beta-synthase activity was much higher than that of cystathionine gamma-lyase. The ratios of cystathionine beta-synthase to gamma-lyase activities in various tissues were 5.6 to approximately 85.6. The concentration of sulfur-containing amino acids in muscle and skin divided into eight portions of the body were also determined. The concentrations of methionine and cystine in each portion of muscle and skin were almost the same, but the concentrations of taurine and cystathionine in each portion of the body were varied.

An experimental study on the mechanism of anisodamini hydrobromidum in treating acute ischemic renal failure

In order to explore the mechanism of anisodamini hydrobromidum (654-2) in treating acute ischemic renal failure, the model of acute ischemic renal failure in white New Zealand rabbits was established to dynamically observe and statistically analyze the intracellular concentration changes of free calcium ([Ca2+]i) and inositol triphosphate (IP3). The results showed that the levels of [Ca2+]i and IP3 in acute renal failure group were higher than those in control group (P < 0.01). However, the levels of [Ca2+]i and IP3 in 654-2 treated group were significantly lower than those in acute renal failure group (P < 0.001). It was concluded that 654-2 could alleviate Ca(2+)-overload in renal histocytes in acute ischemic renal failure. The protective mechanism is associated with intracellular reduction of IP3.

Effect of phorbol ester on cAMP-dependent protein kinase activity in cardiomyocytes

Cardiomyocytes isolated from neonatal rats were treated with phorbol-12-myristate-13-acetate (PMA) ranging from 10(-11) to 10(-7) mol/L for 20 min, causing cytosol protein kinase A (PKA) activity to decrease while particulate PKA activity increase in a concentration-dependent manner. The change of PKA activity induced by PMA was abolished completely by pretreatment of polymyxin B or depletion of protein kinase C (PKC). Type II PKA activity in particulate fraction was enhanced remarkably, while that of type I PKA was not altered when the cells were treated with 100 nmol/L PMA. The results suggested that subcellular distribution and activity of PKA in cardiomyocytes may be regulated by PKC.

Contribution to the regulation of virus replication in cells latently infected with human immunodeficiency virus 1

Monocytes/macrophages have been known to play an important role in the initiation and propagation of human immunodeficiency virus 1 (HIV-1) infection. To analyze the function of these cells during the clinical asymptomatic period of infection, we examined the effect of murine peritoneal macrophages and human peripheral blood macrophages on two cell lines latently infected with HIV-1, a promonocytic cell line, U1, and a T-cell line, ACH-2. Monokines of the murine peritoneal macrophages induced significant viral expression in U1, but not in ACH-2 cells. Experiments employing transient transfection of U937 and CEM cells with HIV long terminal repeat (LTR)-chloramphenicol acetyl transferase (CAT) plasmids indicated that the effect of these monokines was due to specific activation of the HIV LTR. In contrast, supernatants of human macrophages induced viral expression in both ACH-2 and U1 cells. These results suggest that several monokines are active in regulating the transition from the clinical asymptomatic period of HIV infection to progression to acquired immunodeficiency syndrome (AIDS).

Partition of transient and sustained inhibitory glycinergic input to retinal ganglion cells

Physiological and pharmacological properties of possible subtypes of the native glycine receptor were investigated in retinal neurons using whole-cell voltage-clamp techniques. Two discrete inhibitory glycine responses were identified in ganglion cells. The responses could be distinguished pharmacologically: one was sensitive to strychnine and the other to 5,7-dichlorokynurenic acid. The two responses had different kinetics: the former had a fast onset and fast desensitization, whereas the latter had a slower onset and was much more sustained. The physiological and pharmacological distinctions suggest that the responses are mediated by different receptors. These receptors transduce glycinergic synaptic signals to ganglion cells, where they serve as low- and high-pass filters, respectively, of EPSPs.

[A preliminary study of human Y chromosome specific short tandem repeat loci]

OBJECTIVE

To understand the allele structure and reveal genetic polymorphism of Y chromosome specific short tandem repeat (Y-specific STR) loci in Chinese Han population.

METHODS

The authors used a set of five Y-specific STR loci which were tetrameric tandem repeat loci chosen from the Genome Database. EDTA-blood specimens were collected from the unrelated individuals. DNA was extracted by Chelex method and amplified by the polymerase chain reaction (PCR). The PCR products were analyzed using both the PAGE horizontal electrophoresis with discontinuous buffer system and the automated fluorescence detection approach.

RESULTS

The authors observed that the alleles at the five Y-specific STR loci were composed of some complex repeat structures. They successfully prepared a set of human allele ladders for the typing of the five Y-specific STRs and demonstrated the polymorphisms at the five Y-specific STR loci in Chinese Han population.

CONCLUSION

Y-specific STRs are good genetic markers for the purpose of analysis of genetic relationship between populations. This preliminary study not only reveals allele frequencies and haplotype distribution of Y-specific STR in Chinese Han population, but also indicates a reference population for detecting male migration events and for reconstructing paternal history.

[Influence of aging and sex on chromosome 21 segregation in human lymphocytes]

OBJECTIVE

To determine the influence of aging and sex on the segregation of chromosome 21.

METHODS

Lymphocytes were obtained from healthy donors of different ages, both sexes, and were treated with cytochalasin B. Binucleated cells were hybridized with chromosome 21 specific probe, and simultaneously, chromosome 21 loss and non-disjunction were detected.

RESULTS

The coefficients of correlation between age and binucleated cells containing 4, 2 and 6 signals were -0.35(P<0.01), 0.18 and 0.38(P<0.01) respectively. The coefficients of correlation between age and nondisjunction of chromosome 21 and micronuclei were 0.56(P<0.01) and 0.70(P<0.01) respectively.

CONCLUSION

There is a significant increase with age in the number of micronuclei and missegregation. Nondisjunction of chromosome 21 is much more frequent than loss in vivo and in vitro. No significant difference in nondisjunctioin between male and female was noted. Age effect is more significant in female than in male.

[Chromosome aberration of pollen mother cell of broccoli (Brassica oleralea var. Italica) induced by space flight]

OBJECTIVE

To study the cytogenetic effect of space flight on broccoli seeds and the mechanism of mutations of the plant.

METHOD

Dry seeds of broccoli were sent to the space on board a recoverable satellite for 8 days. After recovery the seeds were planted in the field. Chromosome behaviour of pollen mother cell (PMC) samples were observed following the method of ZHU Cheng, 1982. Pollen samples were stained and embeded in lacto-phenol fuchsin for fertility determination.

RESULT

Unequal chromosome numbers of broccoli's PMC were found in the diakinesis stage, such as reducing n = 6, 7 or increasing n = 11 (earth-control number is n = 9); inversion or translocation of chromosomes occurred, and lagging chromosome were found in the anaphase and telophase of PMC meiosis growing rate and growing potential of the seeds were observed after recovery.

CONCLUSION

Leaves cexaceous decrease and aberrations in the chromosome of PMC are found in broccoli after space flight.

Contribution of an auxin to the uptake of nickel and cadmium in maize seedlings

Maize seedlings were cultured in nickel or cadmium contaminated sand treated with alpha-naphthylacetic acid (NAA). The effects of NAA on nickel and cadmium uptake in roots, shoots, and subcellular fractions (cell wall, nuclei and remained parts of seedling cells) were determined. The data showed growth promotion when NAA was applied at low concentrations and inhibition at high concentrations. Uptake of nickel and cadmium content increased concurrently in roots and shoots. In the subcellular fraction, nickel and cadmium was greatest in the cell wall. The changes in growth had greatest correlation with nickel and cadmium content in the subcellular fraction.

[Effects of specific antibodies against the cell surface protein P1 of streptococcus mutans MT 6R upon adhered streptococci]

The sera and saliva were obtained from BALB/C mice by injection of the cell surface protein P1 and Freud's adjuvant. High antibody titers were showed in the sera and saliva by an enzyme-linked immunosorbent assay. The cells of S. mutans (serotype c, e and f) adhered on saliva-coated hydroxyapatite could be detached by the antibodies of the protein P1 of S. mutans MT 6R including in the sera and saliva (P < 0.05), but the antibodies had no influence on the cells of S. cricetus AHT, S. sobrinus OMZ176, S. sobrinus 6715 and S. rattus BHT (P > 0.05).

Effects of polysaccharides (FI0-c) from mycelium of Ganoderma tsugae on proinflammatory cytokine production by THP-1 cells and human PBMC (II)

AIM

To study the effects of water-soluble polysaccharides. FI0-c, and its sulfated derivative, FI0-c-S, on production of human proinflammatory cytokines, interleukin-1 alpha (IL-1 alpha) and tumor necrosis factor alpha (TNF alpha).

METHODS

The herbal polysaccharides were modified by chlorosulfornic acid in dimethyl sulfoxide (Me2SO). Cytokine production was measured by radioimmunoassay, mRNA for the cytokines was measured by semi-quantitative RT-PCR.

RESULTS

FI0-c 4 mg/L itself induced IL-1 alpha production by THP-1 cells without stimulants, such as lipopolysaccharides (LPS) and phorbol myristate acetate (PMA). On the other hand, FI0-c and FI0-c-S inhibited the IL-1 alpha production by THP-1 cells with these stimulants. FI0-c and FI0-c-S significantly upregulated TNF alpha production by THP-1 cells without stimulants or at a low dose of LPS 10 mg/L and PMA 200 nmol/L, whereas these polysaccharides markedly downregulated the TNF alpha production by a high dose of LPS 100 mg/L and PMA. Human peripheral blood mononuclear cells (PBMC) responded to FI0-c and FI0-c-S in IL-1 alpha and TNF alpha production in a fashion similar to THP-1 cell responses. FI0-c 4 mg/L downregulated high-dose LPS- and PMA-induced IL-1 alpha or TNF alpha mRNA and their protein production by THP-1 cells.

CONCLUSION

The water-soluble polysaccharides of Ganoderma tsugae mycelium have bidirectional immunomodulatory effects on cytokine production in different cell stimulatory conditions. Chemical modification of this polysaccharide changed the intensity of regulatory effect on cytokine production.

Preliminary studies on tin miners' lung cancer tissue related genes by differential display mRNA

OBJECTIVE

To study the genes related to tin miners' lung cancer tissue.

METHOD

Differential display mRNA.

RESULTS

Thirty cDNA fragments which differentially expressed in lung cancer tissues and the same patient's normal lung tissues were discovered. Among these, 16 expressed in lung cancer tissues, not in normal lung tissues; fourteen expressed on the contrary. Six cDNA fragment sequence was determined. Five sequences CG2, CG7, CG8, CA5 and CC6 had less than 75% homology with known sequences in GenBank BLAST, so they were believed to be new sequences which we have recorded in Genbank. Only one fragment coded CG3 had homology up to 95% with human ribosome protein L27a gene.

CONCLUSIONS

mRNA differential display provides a unique and powerful experimental system to study differential gene expression in tin miners' lung cancer tissues and the same patient's normal lung tissues. Using the system, differential expression of 30 cDNA fragments was observed. Six of them may be used to study the molecular mechanism of miners' radon-associated lung cancer.