Preliminary study of in vivo autofluorescence of nasopharyngeal carcinoma and normal tissue

BACKGROUND AND OBJECTIVE

In nasopharyngeal cancer, conventional white light endoscopy does not provide adequate information to detect the flat/small lesion and identify the margin of observable tumor. In the present study, we evaluate the potential of light-induced fluorescence spectroscopic imaging for the localization of cancerous nasopharyngeal tissue.

STUDY DESIGN/MATERIALS AND METHODS

We built a multiple channel spectrometer specifically for the investigation of fluorescence collected by a conventional endoscopic system. Nasopharyngeal fluorescence were measured in vivo from 27 subjects during the routine endoscopy. The biopsy specimens for histologic analysis were taken from the tissue sites where the fluorescence were measured.

RESULTS

Two algorithms to discriminate the nasopharyngeal carcinoma from normal tissue were created based on the good correlation between the tissue autofluorescence and histologic diagnosis. For the two-wavelength algorithm, carcinoma can be differentiated from normal tissue with a sensitivity and specificity of 93% and 92%, respectively. For the three-wavelength algorithm with compensation of variation of blood content in tissue, a sensitivity of 98% and specificity of 95% were achieved.

CONCLUSION

Fluorescence endoscopic imaging used with the algorithms developed in this report is an efficient method for detecting the nasopharyngeal carcinoma.

Correlation of pure tone audiogram results and hearing benefit of tympanoplasty for chronic suppurative otitis media

The aim of this study was to evaluate the correlation between pure tone audiogram results and the subjective sensation of hearing benefit of patients who had tympanoplasty for chronic suppurative otitis media. This is a prospective study of 115 patients who had tympanoplasty between 1992 and 1994. The outcome, including a pure tone audiogram and the subjective sensation of hearing benefit, was evaluated at 1 year after operation. There were 63 (55%) patients with subjective hearing benefit after the tympanoplasty. The subjective sensation of hearing benefit correlated with the magnitude of the air conduction (AC) threshold reduction, and increased from 39% for an AC reduction of less than or equal to 10 dB to 100% for an AC reduction of more than 30 dB. The effect of the interaural AC threshold difference on the subjective sensation of hearing was not significant; improvement was felt by 92% of patients when the operated ear became the better hearing ear, and by 73% of patients when the operated ear remained the worse hearing ear. There was considerable discrepancy between the subjective hearing benefit and the pure tone audiogram results. A combination of parameters, including the air-bone gap, the AC threshold, and the subjective hearing change, is recommended in reporting the results of tympanoplasty.

Stretch-activated and background non-selective cation channels in rat atrial myocytes

1. Stretch-activated channels (SACs) were studied in isolated rat atrial myocytes using the whole-cell and single-channel patch clamp techniques. Longitudinal stretch was applied by using two patch electrodes. 2. In current clamp configuration, mechanical stretch of 20 % of resting cell length depolarised the resting membrane potential (RMP) from -63.6 +/- 0.58 mV (n = 19) to -54.6 +/- 2.4 mV (n = 13) and prolonged the action potential duration (APD) by 32.2 +/- 8.8 ms (n = 7). Depolarisation, if strong enough, triggered spontaneous APs. In the voltage clamp configuration, stretch increased membrane conductance in a progressive manner. The current-voltage (I-V ) relationship of the stretch-activated current (ISAC) was linear and reversed at -6.1 +/- 3.7 mV (n = 7). 3. The inward component of ISAC was abolished by the replacement of Na+ with NMDG+, but ISAC was hardly altered by the Cl- channel blocker DIDS or removal of external Cl-. The permeability ratio for various cations (PCs:PNa:PLi = 1.05:1:0.98) indicated that the SAC current was a non-selective cation current (ISAC,NC). The background current was also found to be non-selective to cations (INSC,b); the permeability ratio (PCs:PNa:PLi = 1.49:1:0.70) was different from that of ISAC,NC. 4. Gadolinium (Gd3+) acted on INSC,b and ISAC,NC differently. Gd3+ inhibited INSC,b in a concentration-dependent manner with an IC50 value of 46.2 +/- 0.8 microM (n = 5). Consistent with this effect, Gd3+ hyperpolarised the resting membrane potential (-71.1 +/- 0.26 mV, n = 9). In the presence of Gd3+ (0.1 mM), stretch still induced ISAC,NC and diastolic depolarisation. 5. Single-channel activities were recorded in isotonic Na+ and Cs+ solutions using the inside-out configuration. In NMDG+ solution, outward currents were abolished. Gd3+ (100 microM) strongly inhibited channel opening both from the inside and outside. In the presence of Gd3+ (100 microM) in the pipette solution, an increase in pipette pressure induced an increase in channel opening (21.27 +/- 0.24 pS; n = 7), which was distinct from background activity. 6. We concluded from the above results that longitudinal stret in rat atrial myocytes induces the activation of non-selective cation channels that can be distinguished from background channels by their different electrophysiology and pharmacology.

Permeability characteristics of monovalent cations in atrial myocytes of the rat heart

We investigated the permeability of Cs+ and Na+ through various ion channels in rat atrial myocytes using the whole-cell voltage-clamp technique. With isotonic CsCl (140 mM) on both sides of the membrane and nominally [Ca2+]o-free conditions, depolarising clamp pulses induced an increase of outward currents which showed a biphasic time course. Repolarisation to the holding potential induced inward tail currents. With isotonic NaCl, depolarisation also induced outward currents which showed a monotonic decay, but inward tail currents were not observed. Both in NaCl and CsCl, currents were hardly affected by TEA (10 mM), 4-AP (5 mM) and DIDS (100 microM). Nicardipine (1 M) almost completely blocked time-dependent outward currents in isotonic NaCl solution, leaving only time-independent currents which showed linear I-V relationship. In isotonic CsCl conditions, nicardipine blocked outward current considerably, but there still remained time-dependent outward currents and inward tail currents. Addition of E-4031 (2-20 M) which is known as a specific blocker of the rapidly activating delayed rectifier K+ current (IKr) completely blocked these time-dependent outward and inward currents, leaving only a time-independent current. Time-independent currents recorded in the presence of nicardipine and E-4031 were inhibited by GdCl3, which is known to block non-selective cation (NSC) currents. From these results, it was suggested that NSC current in atrial myocytes can be investigated in isotonic Cs+ or Na+ solution in the presence of Ca2+ channel and IKr blockers.

The training of otorhinolaryngologists in Asia

Asian nations differ from one another in population, cultural background, ethnic tradition and economic situation. The training of otorhinolaryngologists in Asia is not in any way uniform. A questionnaire survey of 26 leading institutions in 12 countries/regions was carried out. The emphasis of investigation is towards the training programme for specialists in Otorhinolaryngology and continuous medical education (CME). The response rate of the survey was 100 per cent. The duration of training for otorhinolaryngologists ranges from three to seven years and an exit assessment is held in seven countries/regions. The training programmes are modifications of either the British or the American pattern depending on tradition. Documentation of CME is available in eight countries/regions while a defined cycle has been established in only three. Medical/health authorities or professional societies in each country contribute towards its monitoring. Better communication and sharing of experience will improve the training of otorhinolaryngologists in Asia.

Chinese tonal language rehabilitation following cochlear implantation in children

Cantonese language rehabilitation in 28 prelingually deaf children who underwent cochlear implantation was evaluated. All patients were implanted with multichannel devices and the operations went smoothly. They all had improved scores on audiological assessments and speech perception tests. The speech evaluation tests included the recognition of sounds, vowels, consonants and tone. Sentence recognition and story comprehension were both improved after training for 2 years. Cochlear implantation is a useful measure for the speech rehabilitation of prelingually profound deaf children when hearing aids are of no benefit. The multichannel implant device is of clinical significance in the rehabilitation of those patients using tonal language.

Evidence of enhancement of malate-aspartate shuttle activity in beta cells of streptozotocin-induced non-insulin-dependent diabetic rats

Glucose-induced insulin secretion is selectively impaired in beta cells from animals with non-insulin-dependent diabetes mellitus (NIDDM). This study was performed to clarify whether the malate-aspartate shuttle among the glucose metabolic pathways is intact in beta cells of NIDDM rats. The insulin secretory capacity of the islets and the K(ATP) channel activity in single beta cells were measured in control and NIDDM rats injected with streptozotocin (STZ) during the neonatal period, using a radioimmunoassay and patch-clamp technique. The increase of insulin secretion induced by 11.1 mmol/L glucose or 10 mmol/L dihydroxyacetone (DHA) was significantly reduced in NIDDM islets, suggesting an impaired glycerol-phosphate shuttle. The application of glyceraldehyde (10 mmol/L) in NIDDM or control islets elicited an increase in insulin secretion, but the difference between the 2 groups was indistinguishable. On the contrary, the increase of insulin secretion and the inhibition of K(ATP) channel activity induced by aspartate, which preferentially participates in the malate-aspartate shuttle, were significantly greater in NIDDM versus the control. However, intracellularly applied aspartate in the inside-out mode did not inhibit K(ATP) channel activity. These findings show that malate-aspartate shuttle activity is potentiated in pancreatic beta cells of NIDDM rats, suggesting the development of a compensatory mechanism for the reduced activity of the glycerol-phosphate shuttle in NIDDM.

Long-term sensorineural hearing deficit following radiotherapy in patients suffering from nasopharyngeal carcinoma: A prospective study

BACKGROUND

This was a prospective study to evaluate the effect of radical external irradiation on inner ear function after treatment of nasopharyngeal carcinoma.

METHODS

Pure tone audiograms were performed at regular intervals before, after, and up to 4.5 years following completion of radiotherapy.

RESULTS

Two hundred ninety-four patients (526 ears) were included. Within 3 months after radiotherapy, deterioration of bone conduction threshold at 4 kHz and pure tone average (average of 0.5 kHz, 1 kHz, and 2 kHz) were noted in 164 ears (31%) and 75 ears (14%), respectively. Patients older than 50 years and ears with threshold below 60 dB at 4 kHz before radiotherapy were significant factors (p < 0.01 and p < 0. 001) associated with a 4 kHz loss. In 40% of these ears, recovery was evident at 2 years. With follow-up for 4.5 years, the probability of significant threshold deterioration increased with time.

CONCLUSION

Sensorineural hearing loss started soon after radiotherapy. Early changes could be reversible while the probability of persistent hearing loss continued to increase.

Measurement of nasal geometry by acoustic rhinometry in normal-breathing Asian children

OBJECTIVE

The purpose of this study was to obtain normal values of nasal geometry in Asian children with no nasal problems using the acoustic rhinometry method.

METHOD

Acoustic rhinometric measurement of the nasal fossae was performed in pediatric patients coming for general surgical operations with no nasal problem.

RESULTS

A cohort study of 183 children in an acute care hospital with full elective and emergency surgical services was undertaken. The mean minimal cross-sectional area (MCA), which was functionally important for nasal breathing, was found to be 0.32 cm2 (SD = 0.13) and situated at 1.40 cm (SD = 0.26) from the anterior nare. Normal values for area, length, and volume of the nose in these children as a group and at different ages from 1 to 11 years old were obtained.

CONCLUSIONS

Acoustic rhinometry was found to be well tolerated by the children. The MCA was confirmed to be situated at the anterior part of the nose and had a positive correlation with an increase in age.

Blockade of the delayed rectifier K+ currents, IKr, in rabbit sinoatrial node cells by external divalent cations

We investigated the actions of various divalent cations on the delayed rectifier K+ currents (IKr) in rabbit sinoatrial node cells using the whole-cell voltage-clamp technique in isotonic K+ solutions. External divalent cations decreased the amplitude of currents, accelerated the time course of deactivation and shifted the activation to positive potentials in a dose-dependent manner. The concentrations for half-maximum inhibition of the steady-state currents (KM) obtained at 0 mV were 0.63, 1.36, 1.65 and 2.16 mM for Ni2+, Co2+, Mn2+ and Ba2+, respectively. The effect was voltage dependent (KM decreased e-fold for 12.2-16.8 mV hyperpolarization), but the dependence did not vary significantly among different cations. Acceleration of the time course of current deactivation by the increase of divalent cation concentration was well fitted by the voltage-dependent block model, and the binding rate constant (k1) was obtained. The binding rates for the ions took the following order: Ni2+ >Co2+ >Mn2+ >Ba2+. The degree of the shift of activation occurred in the same order: Ni2+ >Co2+ >Mn2+ >Ba2+. From these results, we conclude that IKr channels are non-selectively blocked by most divalent cations from the external side and that the binding site is located deep inside the channel, resulting in a steep voltage dependence of the blockade.

Jasmine green tea epicatechins are hypolipidemic in hamsters (Mesocricetus auratus) fed a high fat diet

These studies were designed to test the hypolipidemic activity of green tea epicatechins (GTE) isolated from jasmine green tea. In Experiment 1, three groups of hamsters were given a semisynthetic diet containing 200 g lard/kg and 1 g cholesterol/kg for 4 wk. The control group received distilled water, and the other two groups received either 15 g/L green tea water extract (GTWE) or 5.0 g/L GTE solution. Both the GTWE and GTE groups had lower concentrations of serum total cholesterol (TC) and triacylglycerols (TG) than the controls (P < 0.05). In Experiment 2, four groups of hamsters received tap water as the drinking fluid, but they were given the same high fat and cholesterol diet supplemented with 0 (control), 1.1, 3.4 or 5.7 g GTE/kg diet. The hypolipidemic effect of jasmine GTE was dose dependent. In Experiment 3, the time-course of changes in serum TC and TG was monitored in hamsters given the high fat diet supplemented with 5.7 g GTE/kg in comparison with that of controls. The hypolipidemic effects of dietary GTE were evident after feeding for 2 wk. Dietary supplementation of GTE did not affect liver fatty acid synthase. However, GTE-supplemented hamsters had higher fecal excretions of total fatty acids, neutral sterols and acidic sterols compared with the control group. In Experiment 4, hamsters were fed nonpurified diet; the control group drank distilled water, and the GTE group drank distilled water containing 5.0 g GTE/L. No differences in activities of 3-hydroxy-3-methyl glutaryl coenzyme A reductase and intestinal acyl CoA:cholesterol acyltransferase were observed. This study suggests that the hypolipidemic activity of GTE is not due to inhibition of synthesis of cholesterol or fatty acid but is most likely mediated by its influence on absorption of dietary fat and cholesterol.

Blockade of HERG channels expressed in Xenopus oocytes by external H+

We have investigated the effect of external H+ concentration ([H+]o) on the human-ether-a-go-go-related gene (HERG) current (IHERG), the molecular equivalent of the cardiac delayed rectifier potassium current (IKr), expressed in Xenopus oocytes, using the two-microelectrode voltage-clamp technique. When [H+]o was increased, the amplitude of the IHERG elicited by depolarization decreased, and the rate of current decay on repolarization was accelerated. The activation curve shifted to a more positive potential at lower external pH (pHo) values (the potential required for half-maximum activation, V1/2, was: -41.8 mV, -38.0 mV, -33.7 mV, -26.7 mV in pHo 8.0, 7.0, 6.6, 6.2, respectively). The maximum conductance (gmax) was also affected by [H+]o: a reduction of 7.9%, 14.6%, and 22.8% was effected by decreasing pHo from 8.0 to 7.0, 6.6, and 6.2, respectively. We then tested whether this pH effect was affected by the external Ca2+ concentration, which is also known to block HERG channels. When the extracellular Ca2+ concentration was increased from 0.5 mM to 5 mM, the shift in V1/2 caused by increasing [H+]o was attenuated, suggesting that these two ions compete for the same binding site. On the other hand, the decrease in gmax caused by increasing [H+]o was not significantly affected by changing external Ca2+ levels. The results indicate that HERG channels are inhibited by [H+]o by two different mechanisms: voltage-dependent blockade (shift of V1/2) and the decrease in gmax. With respect to the voltage-dependent blockade, the interaction between H+ and Ca2+ is competitive, whereas for the decreasing gmax, their interaction is non-competitive.

Blockade of HERG channels expressed in Xenopus laevis oocytes by external divalent cations

We have investigated actions of various divalent cations (Ba2+, Sr2+, Mn2+, Co2+, Ni2+, Zn2+) on human ether-a-go-go related gene (HERG) channels expressed in Xenopus laevis oocytes using the voltage clamp technique. All divalent cations inhibited HERG current dose-dependently in a voltage-dependent manner. The concentration for half-maximum inhibition (Ki) decreased at more negative potentials, indicating block is facilitated by hyperpolarization. Ki at 0 mV for Zn2+, Ni2+, Co2+, Ba2+, Mn2+, and Sr2+ was 0.19, 0.36, 0. 50, 0.58, 2.36, and 6.47 mM, respectively. The effects were manifested in four ways: 1) right shift of voltage dependence of activation, 2) decrease of maximum conductance, 3) acceleration of current decay, and 4) slowing of activation. However, each parameter was not affected by each cation to the same extent. The potency for the shift of voltage dependence of activation was in the order Zn2+ > Ni2+ >/= Co2+ > Ba2+ > Mn2+ > Sr2+, whereas the potency for the decrease of maximum conductance was Zn2+ > Ba2+ > Sr2+ > Co2+ > Mn2+. The kinetics of activation and deactivation were also affected, but the two parameters are not affected to the same extent. Slowing of activation by Ba2+ was most distinct, causing a marked initial delay of current onset. From these results we concluded that HERG channels are nonselectively blocked by most divalent cations from the external side, and several different mechanism are involved in their actions. There exist at least two distinct binding sites for their action: one for the voltage-dependent effect and the other for reducing maximum conductance.

Lack of allelic association of dopamine D4 receptor gene polymorphisms with Parkinson's disease in a Chinese population

Parkinson's disease (PD) is a neurodegenerative disease caused by a multitude of environmental, neurochemical, and genetic factors. The gene for human dopamine D4 receptor (DRD4) has been considered as a plausible candidate for the pathogenesis of PD. Different dopamine D4 receptor allelic forms have variable affinity toward certain neuroleptics such as clozapine, suggesting a role for dopamine D4 receptors in neurologic disorders. To test the hypothesis that the DRD4 polymorphism is associated with the susceptibility to Parkinson's disease, we have examined differences in allele frequencies of different DRD4 polymorphisms in 101 Chinese patients with PD and in 105 age-matched control subjects in Hong Kong. The DRD4 gene was analyzed by a non-radioactive polymerase chain reaction-based Southern hybridization with chemiluminescence detection. The number of polymorphic 48 base pair tandem repeats in exon 3 was identified in each study subject. The DRD4 alleles with high frequencies in the control subjects are 4-repeat allele (72.4%), 2-repeat allele (21.4%), and 7-repeat allele (3.8%) which accounted for over 97% of the total alleles in the elderly Chinese population. The most prevalent genotype in the control subjects is the 4/4 (47.6%), followed by 4/2 (38.6), 4/7 (7.6%), and 2/2 (3.0%). None of the variable number tandem repeat polymorphism showed evidence for genetic association with Parkinson's disease.

Contribution of Ca2+-activated K+ channels and non-selective cation channels to membrane potential of pulmonary arterial smooth muscle cells of the rabbit

1. Using the perforated patch-clamp or whole-cell clamp technique, we investigated the contribution of Ca2+-activated K+ current (IK(Ca)) and non-selective cation currents (INSC) to the membrane potential in small pulmonary arterial smooth muscle cells of the rabbit. 2. The resting membrane potential (Vm) was -39.2 +/- 0.9 mV (n = 72). It did not stay at a constant level, but hyperpolarized irregularly, showing spontaneous transient hyperpolarizations (STHPs). The mean frequency and amplitude of the STHPs was 5.6 +/- 1. 1 Hz and -7.7 +/- 0.7 mV (n = 12), respectively. In the voltage-clamp mode, spontaneous transient outward currents (STOCs) were recorded with similar frequency and irregularity. 3. Intracellular application of BAPTA or extracellular application of TEA or charybdotoxin suppressed both the STHPs and STOCs. The depletion of intracellular Ca2+ stores by caffeine or ryanodine, and the removal of extracellular Ca2+ also abolished STHPs and STOCs. 4. Replacement of extracellular Na+ with NMDG+ caused hyperpolarization Vm of without affecting STHPs. Removal of extracellular Ca2+ induced a marked depolarization of Vm along with the disappearance of STHPs. 5. The ionic nature of the background inward current was identified. The permeability ratio of K+ : Cs+ : Na+ : Li+ was 1.7 : 1.3 : 1 : 0. 9, indicating that it is a non-selective cation current (INSC). The reversal potential of this current in control conditions was calculated to be -13.9 mV. The current was blocked by millimolar concentrations of extracellular Ca2+ and Mg2+. 6. From these results, it was concluded that (i) hyperpolarizing currents are mainly contributed by Ca2+-activated K+ (KCa) channels, and thus STOCs result in transient membrane hyperpolarization, and (ii) depolarizing currents are carried through NSC channels.

Different contractile properties between intralobar and extralobar pulmonary arteries of the rabbit

In pulmonary circulation, small muscular resistance arteries are known to have different receptor properties and sensitivity to neurotransmitters from those of large elastic conduit arteries. It is, however, not yet certain whether the different properties are primarily due to the diameter or the location of arteries. In the present study, we compared the contractile responses to various agonists among large extralobar (ELPA, diameter: 2-3 mm), large intralobar (ILPA, diameter: 2-3 mm), and small intralobar pulmonary arteries (SPA, diameter: 300-500 microm) of the rabbit. There were no differences in normalized dose-response curves to KCl among three groups. Half maximum doses (EC50 in mM) were 38.0+/-2.0 (n=8, mean+/-SEM) in ELPA, 36.9+/-2.4 (n=10) in ILPA, and 39.0+/-0.9 (n=12) in SPA. Responses to phenylephrine, epinephrine, histamine, serotonin, and PGF2alpha were normalized and expressed as a relative contraction against maximum tension to KCl. In ELPA, the contractile responses to various agents showed the following sequence: KCl>epinephrine>phenylephrine>serotonin>PGF2alpha>histamine. In ILPA and SPA, the sequence was: KCl>histamine>PGF2alpha>serotonin. There was little response to phenylephrine and epinephrine in ILPA and SPA. These results demonstrate that the difference of contractile responses between ELPA and ILPA was more prominent than that between ILPA and SPA, suggesting that the location is more important than the diameter itself in determining the characteristic contractile responses of pulmonary arteries.

Clinicopathological analysis of elective neck dissection for N0 neck of early oral tongue carcinoma

BACKGROUND

The study aims at evaluation of the efficacy of elective neck dissection as a staging and therapeutic procedure for N0 neck of early carcinoma of the oral tongue by whole organ serial sectioning.

METHODS

There were 50 stage I and II patients. The neck dissection specimens were whole organ sectioned in 3-mm intervals for the evaluation of nodal metastasis.

RESULTS

There were 18 (36%) patients with subclinical nodal metastasis. The total number of metastatic nodes were 31 (1%) among all 2,826 nodes being examined. The metastatic foci had a median size of 3 mm and occupied a median of 6% of the cross sectional area of the involved nodes. The ipsilateral level II nodes were the commonest (26%) site of metastasis. Metastatic nodes were present in 34% patients who had negative preoperative radiological assessment and in 20% patients who had negative intraoperative frozen section sampling of neck nodes. Patients with subclinical nodal metastasis had a high incidence of regional recurrence (62%) and low survival (27%) when postoperative radiotherapy was not given after elective neck dissection.

CONCLUSIONS

Ipsilateral level I,II,III neck dissection is an adequate diagnostic procedure for staging of the N0 neck of early oral tongue carcinoma. Its diagnostic role cannot be replaced by the available pre-operative radiological screening and intra-operative frozen section sampling. However, elective selective neck dissection is an effective but not adequate therapeutic procedure, and post-operative adjuvant radiotherapy and chemotherapy have to be considered for all pathologically positive necks.

Otorrhea after grommet insertion for middle ear effusion in patients with nasopharyngeal carcinoma

PURPOSE

To document the incidence of complications after myringotomy and grommet insertion in patients with nasopharyngeal carcinoma. The focus is on the incidence of otorrhea and perforation. The possible risk factors for these conditions and treatment response were studied.

MATERIALS AND METHODS

We reviewed the records on 206 ears of 163 patients who suffered from nasopharyngeal carcinoma and underwent myringotomy and grommet insertion in a 7-year period. The follow-up period ranged from 4 weeks to 78 months (median, 9 months).

RESULTS

The overall incidence of otorrhea in these ears was 38%. Patients with nasopharyngeal carcinoma (NPC) had a significantly high incidence of postoperative discharge (chi2 test, P<.0001) compared with other patients who underwent myringotomy and grommet insertion. The mean interval between myringotomy and otorrhea was 19.8 weeks. Forty-seven per cent of the ears with a discharge developed otorrhea within 1 month. In 42%, the otorrhea responded to treatment and the ears became dry. After extrusion of the grommet, 29% of those ears with otorrhea ended with an eardrum perforation, and 24% of the ears showed recurrent effusion.

CONCLUSIONS

For patients with NPC who underwent myringotomy, there was a significant risk of otorrhea (49%) and persistent perforation (29%), and these complications were difficult to manage. We conclude that myringotomy and grommet insertion should not be routinely offered to NPC patients with middle ear effusion.

Characterization of a functional AT1A angiotensin receptor in pancreatoma AR4-2J cells

Functional angiotensin receptors were characterized in the rat pancreatic acinar cell line AR4-2J. Angiotensin II stimulated a dose-dependent release of amylase and production of inositol phosphates. Results of high-performance liquid chromatography separation of inositol phosphates indicated that angiotensin stimulated the rapid accumulation of inositol 1,3,4-trisphosphate. Angiotensin II and angiotensin III were at least an order of magnitude more potent than angiotensin I in the stimulation of amylase release. The angiotensin II-stimulated amylase release was blocked by losartan, a selective AT1 angiotensin antagonist. The selective AT2 angiotensin receptor ligands CGP42112 did not alter angiotensin II-stimulated amylase released. However, CGP42112 stimulated amylase release at micromolar concentrations with a potency similar to angiotensin I. Analysis of mRNA expression by reverse transcription polymerase chain reaction suggested that AT1A was the predominant type-I angiotensin receptor expressed in the AR4-2J cells.

Endothelium-dependent relaxation induced by hawthorn extract in rat mesenteric artery

The extract prepared from hawthorn (Crataegus fruit) was examined for its relaxant effect in rat isolated mesenteric arteries. Hawthorn extract induced concentration-dependent relaxation of the U46619-precontracted artery with an IC50 of 0.22 +/- 0.02 mg/ml. Removal of the functional endothelium reduced by approximately 85% the maximum relaxant response to hawthorn extract. Pretreatment of the arterial tissues with N(G)-nitro-L-arginine methyl ester (3-10 microM) or methylene blue (3-10 microM) inhibited the relaxation induced by hawthorn extract, while indomethacin (10 microM) had no effect. L-arginine (3 mM) did not affect the relaxation induced by hawthorn extract but partially reversed the effect of 10 microM N(G)-nitro-L-arginine methyl ester. Iberiotoxin (100 nM) slightly but significantly inhibited the relaxant effect of hawthorn extract whilst glibenclamide (3 microM) was ineffective. Glibenclamide at 3 microM reversed the relaxation induced by pinacidil. N(G)-nitro-L-arginine methyl ester and methylene blue markedly inhibited acetylcholine-induced relaxation in endothelium-intact arteries. Hawthorn extract also reduced the contraction induced by phenylephrine (1 microM) or high Ki (60 mM) with respective IC50 values of 0.13 +/- 0.01 mg/ml and 0.11 +/- 0.01 mg/ml. In high K+-contracted arteries, hawthorn extract induced only 55% of relaxation while it caused a complete inhibition of the U46619- or phenylephrine-induced contraction. These results suggest that hawthorn contains active components which cause vasorelaxation in rat isolated mesenteric arteries. Nitric oxide but not other endothelium-derived vasoactive factors was probably involved in the relaxation induced by hawthorn extract.

Dual effect of nitric oxide on the hyperpolarization-activated inward current (I(f)) in sino-atrial node cells of the rabbit

Using the whole-cell voltage-clamp technique, we have investigated the effect of nitric oxide (NO) donor (sodium nitroprusside, SNP) on hyperpolarization-activated inward current, I(f), in isolated rabbit sinoatrial node (SAN) cells. I(f) in the basal state increased when NO was applied but decreased when I(f) was pre-stimulated by isoproterenol (ISO) or by adding cAMP to the pipette solution. Both the stimulatory and the inhibitory effects of NO were abolished by guanylyl cyclase inhibitor, methylene blue (MB), suggesting that the effect of NO is mediated by cGMP. The inhibitory effect of NO was abolished when I(f) was pre-stimulated by 3-isobutyl-1-methylxanthine (IBMX), which is a phosphodiesterase (PDE) inhibitor, or by adding 8Br-cAMP (which is resistant to PDE) to the pipette solution. An analogue of cGMP, 8Br-cGMP, which is a potent stimulator of cGMP-dependent protein kinase (PKG) but has little effect on PDE, did not inhibit I(f) when I(f) was pre-stimulated by ISO. In its basal state, I(f) was still increased by 8Br-cGMP, and this effect was not prevented by the pretreatment with H-7, PKG inhibitor. The effect of acetylcholine (ACh) was not identical to that of NO: I(f) decreased when pre-stimulated not only by ISO, but also by IBMX. The above results suggest that via cGMP, NO exerts a dual effect on I(f): the inhibitory effect is mediated by cGMP-stimulated PDE, and the stimulatory effect may be attributable to direct binding of cGMP to I(f) channels.

Effects of intracellular N+, M2+ and metabolites on C2+-activated K+ channels in pulmonary and ear arterial smooth muscle cells of the rabbit

Hypoxic pulmonary vasoconstriction (HPV) is an important mechanism for matching the ventilation/perfusion ratio in the lung, but the signal transduction pathway through which hypoxia induces vasoconstriction remains unclear. We hypothesized that the decrease in K+ current induced by hypoxia is a key mechanism for HPV, and examined the effects of the substances which are expected to accumulate during hypoxia on the activity of large conductance Ca2+-activated K+ (BKCa) channels. Pulmonary and ear arterial smooth muscle cells were isolated from the rabbit using enzymatic digestion, and large conductance Ca2+-activated K+ current (IBK,Ca) was recorded in symmetrical K+ concentrations using the inside-out mode of the patch-clamp technique. Increasing the Na+ concentration on the intracellular side suppressed IBK,Ca dose dependently: 4.6, 20.9, 35.5 and 44.6 % reduction with 4, 8, 12 and 16 mM Na+, respectively. Mg2+ also reduced IBK,Ca, and the maximum reduction was obtained at 0.5 mM. Lactate, adenosine, ADP and ATP did not significantly affect IBK,Ca. There was no difference between pulmonary and ear arterial smooth muscle cells in their response to the above substances; this finding rules out modulation of BKCa channels by the various factors thought to accumulate during hypoxia as a major mechanism involved in the decrease in the K+ conductance of pulmonary arteries in hypoxia.

Expression of grass carp growth hormone by baculovirus in silkworm larvae

A total of five recombinant Bombyx mori nuclear polyhedrosis viruses (BMNPV) carrying the grass carp (Ctenopharyngodon idellus) growth hormone (GH) cDNA were constructed in this study. Two of them were able to express the hormone up to a level of 12 microgram/ml medium when cultured B. mori cells were infected for 4 days. Inoculation of the viruses into silkworm (B. mori) host significantly increased the level of GH achievable. The amount of hormone produced per larva was estimated to be around 1 mg. The recombinant grass carp GH had immunological and biological activities similar to the native hormone. The N-terminal sequence of the recombinant hormone was the same as the native one, indicating that the fish signal peptide was correctly processed by the insect cells. Silkworm powder prepared from larvae infected with the recombinant virus was used as food supplement for fish. Compared with the control, this dietary supplement was effective in increasing the growth rate of juvenile carp.

Brain-derived neurotrophic factor rapidly potentiates synaptic transmission through NMDA, but suppresses it through non-NMDA receptors in rat hippocampal neuron

Brain-derived neurotrophic factor (BDNF) rapidly enhances synaptic transmission among the hippocampal neurons. In order to examine which component of glutamate receptors participates in synaptic potentiation by BDNF, we have studied the effect of glutamate antagonists on excitatory postsynaptic currents (EPSCs) enhanced by BDNF, using cultured embryonic hippocampal neurons. In the presence of AP5, a N-methyl-D-aspartate (NMDA) antagonist, BDNF depressed the EPSCs. In contrast, BDNF enhanced the EPSCs in the presence of a non-NMDA antagonist CNQX. Our results suggest that BDNF acutely activates synaptic transmission via NMDA, but suppresses it via non-NMDA receptors in the hippocampus.

Somatostatin inhibits (d-Arg6, Pro9-NEt) salmon gonadotropin-releasing hormone- and dopamine D1-stimulated growth hormone release from perifused pituitary cells of chinese grass carp, ctenopharyngodon idellus

In this study, a heterologous radioimmunoassay (RIA) for grass carp GH has been validated and used to monitor the kinetics of GH release from perifused grass carp pituitary cells. To establish the anatomical specificity of GH antiserum used in this RIA, immunohistochemical staining was performed in grass carp pituitary sections. Somatotrophs recognized by this GH antiserum were located mainly in the proximal pars distalis without overlapping with gonadotrophs located in the same area or with lactotrophs located in the rostral pars distalis. The immunoreactivity of somatotrophs was abolished by preabsorbing GH antiserum with purified grass carp GH, suggesting that the possibility of a cross-reactivity of antiserum with other grass carp pituitary hormones is unlikely. Using 125I-labeled carp GH as the RIA tracer, parallelism was observed among the displacement curves of grass carp GH standard, grass carp serum, and culture medium conditioned by grass carp pituitary cells, suggesting that this RIA can be used to quantitate grass carp GH levels in biological samples. Using an in vitro column perifusion system, a superactive gonadotropin-releasing hormone (GnRH) analog (d-Arg6, Pro9-NEt)-sGnRH(sGnRHa, 0.3-30 nM), dopamine (DA, 0.1-10 muM), and the nonselective DA agonist apomorphine (0.1-10 muM) stimulated GH release from grass carp pituitary cells in a dose-dependent manner. The GH-releasing effect of DA was mimicked by the D1 agonists SKF38393 (0.1-10 muM) and SKF77434 (0.1-10 muM), but not by the D2 agonist LY171555 (3 muM). In addition, the GH response to DA (1 muM) was blocked by the D1 antagonist SCH23390 (5 muM) but not by the D2 antagonist (+/-) sulpiride (5 muM), suggesting that the GH-releasing action of DA is mediated through receptors resembling mammalian D1 receptors. Somatostatin-14 (SRIF14, 0.01-100 nM), unlike sGnRHa and DA, induced a dose-dependent suppression on basal GH release. At a high dose (100 nM), SRIF14 also abolished the GH responses to sGnRHa (100 nM), DA (10 muM), and the D1 agonist SKF38393 (3 muM). These results, as a whole, provide evidence that GH release in the grass carp is under the direct regulation of GnRH, DA, and SRIF at the pituitary cell level. The present study also suggests that DA D1 receptors are present in grass carp pituitary cells mediating the GH-releasing action of DA.

Voltage-dependent blockade of HERG channels expressed in Xenopus oocytes by external Ca2+ and Mg2+

1. We expressed the human eag-related gene (HERG), which is known to encode the delayed rectifier K+ current (IKr) in cardiac muscle, in Xenopus oocytes. Using a two-microelectrode voltage clamp technique, the effect of external Ca2+ and Mg2+ on the HERG current (IHERG) was investigated. 2. When [Ca2+]o was increased, the amplitude of outward IHERG elicited by depolarization decreased, and the rate of current onset slowed. The rate of current decay observed on repolarization was greatly accelerated. The threshold and fully activated potential of IHERG shifted to a more positive potential. On the other hand, the inactivation property represented by the negative slope of the I-V curve and the instantaneous conductance of IHERG were little affected by [Ca2+]o. 3. The effect of [Ca2+]o on IHERG can be interpreted using the channel blockade model. The blockade is voltage dependent; smaller dissociation constants (KM) at more negative potentials indicate that block is facilitated by hyperpolarization. KM changes e-fold for 14.5 mV and the fractional electrical distance of the binding site calculated from this value is 0.86. 4. Blockade by a low concentration of Ca2+ (0.5 mM) was inhibited by increasing [K+]o (from 2 to 20 mM), whereas blockade by a high concentration of Ca2+ (5 mM) was not affected by varying [K+]o, indicating that there is competition between permeating ions and blocking ions. 5. The effect of [Mg2+]o on IHERG was qualitatively similar to that of [Ca2+]o, but the potency was lower. 6. These results suggest that external Ca2+ and Mg2+ block the HERG channel in a voltage- and time-dependent manner, resulting in a voltage dependence which has been regarded as a property of the activation gate.

cGMP facilitates calcium current via cGMP-dependent protein kinase in isolated rabbit ventricular myocytes

The effect of guanosine 3',5'-cyclic monophosphate (cGMP) on L-type Ca current (ICa) was investigated in a study of rabbit ventricular myocytes using the whole-cell patch-clamp technique. Intracellular application of cGMP (100 MUm) increased ICa in the absence of isoprenaline or forskolin. 8-Bromo-cGMP (100 muM) and 8-(4-chlorophenylthio)-cGMP (8-pCPT-cGMP, 400 muM), relatively specific stimulators of cGMP-dependent protein kinase (cGMP-PK), also increased ICa. The stimulatory effect of 8-pCPT-cGMP was suppressed by Rp-8-chlorophenylthio-cGMP (400 muM), a phosphodiesterase-resistant cGMP-PK inhibitor. When ICa was increased by bath application of the non-specific phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine (IBMX, 100 muM), 8-pCPT-cGMP (400 muM) resulted in additional stimulation of ICa. In the presence of 8-pCPT-cGMP, additional applications of isoprenaline (1 muM) or forskolin (1 muM) induced a further increase in ICa. From these results, it could be concluded that the activation of cGMP-dependent protein kinase is involved in the facilitation of ICa by cGMP in rabbit ventricular myocytes.

Modulation of voltage-dependent K+ channel by redox potential in pulmonary and ear arterial smooth muscle cells of the rabbit

It has been suggested that hypoxic pulmonary vasoconstriction (HPV) results from the depolarization that is induced by the suppression of K+ current in pulmonary arterial smooth muscle cells (PASMC). We tested the hypothesis that the effect of the cellular redox potential on voltage-sensitive K+ (Kv) current is involved in HPV as a primary sensing mechanism. Kv current in PASMC and ear arterial smooth muscle cells (EASMC) of the rabbit was recorded using the whole-cell patch-clamp technique, and the effect of redox agents [dithiothreitol, DTT and 2,2'-dithio-bis(5-nitropyridine), DTBNP] was tested. Kv current was decreased by DTT, but increased by DTBNP. DTT accelerated the inactivation kinetics, but did not affect steady-state activation and inactivation, whereas DTBNP accelerated activation kinetics. Kv current has a non-inactivating window in the range of from -40 mV to +10 mV. The resting membrane potential measured using the nystatin-perforated-patch method, however, lay between -50 mV and -30 mV and was not depolarized by 5 mM 4-aminopyridine. The membrane-impermeable oxidizing agent DTNB has no effect on Kv current, suggesting that redox modulation sites are intracellular sulphydryl groups. In EASMC, Kv current was decreased by DTT, but increased by DTBNP, indicating that the redox-potential-induced modulation of Kv current in EASMC and in PASMC is the same. It is therefore concluded that Kv current is modulated by the cellular redox potential, but that this modulation is not involved in HPV as a primary sensing mechanism.

Antigenic determination fragments of alpha-momorcharin

Alpha momorcharin is a protein isolated from the bitter gourd. It has a number of biological activities including induction of abortion, inhibition of tumor growth and anti-HIV. All these activities may be related to the ribosome-inhibiting activity of the protein. Repeated use of alphaMMC can elicit an antigenic response which may neutralize its biological activity. To overcome this problem, we need to know which part of the molecule is the antigenic determinant. In this study, we constructed a random fragment expression library from the alphaMMC cDNA and screened it with three anti-alphaMMC sera. A total of 9 positive clones were picked and sequenced. Based on the sequence information obtained, we were able to deduce three regions at which antibodies raised against native alphaMMC seem to interact. These regions are residues 1-14, residues 71-136 and residues 195-222. Mapping of these regions against a 3D model of alphaMMC indicates that they all are located on the surface of the molecule. As residues 71-136 are found to be in close proximity to the active site involved in ribosome inactivation, treatment with a monoclonal antibody directed to this area was shown to be effective in inactivating the inhibitory effect of alphaMMC on in vitro protein synthesis.

Results of surgical salvage of locoregional recurrence of carcinoma of the tongue after radiotherapy failure

The aim of this study was to evaluate the efficacy of surgical salvage of local and nodal recurrence of carcinoma of the oral tongue after radiotherapy failure. Of the 47 patients in this retrospective review (between 1980 and 1992), there were 25 with local recurrence alone, 11 with locoregional recurrence, and 11 with nodal recurrence alone. There was no operative mortality, and 17% of patients had one or more surgical complications, including wound infection, flap necrosis, anastomotic leakage, and chest infection. Twenty-nine (62%) patients developed recurrences in the head and neck region after the salvage operation, and 9 of them had second surgical salvage operations. At the last follow-up, 53% of patients had died of carcinoma of the tongue and the overall 5-year actuarial survival rate was 43%. The 5-year actuarial survival rates were 39% for local recurrence alone, 27% for locoregional recurrence, and 68% for nodal recurrence alone. Surgical salvage had satisfactory results for patients with oral tongue carcinoma after radiotherapy failure. Close follow-up and early surgical intervention are essential for patients primarily treated with radiotherapy.

Variation of the CGG repeat in FMR-1 gene in normal and fragile X Chinese subjects

The fragile X syndrome is believed to be caused by an expansion of a CGG trinucleotide repeat segment in the FMR-1 gene on the fragile X site of the long arm of the X-chromosome. To understand the variation of the CGG repeat in the FMR-1 gene in southern Chinese from the Hong Kong and Guangzhou area, we undertook the present study. A total of 83 normal and three fragile X subjects were examined. In the normal group, 16 distinct alleles, ranging in size from 272 bp to 332 bp with 17 to 37 CGG repeats were detected. A repeat size of 29 was the most frequent. Compared with data collected in the USA, the repeat size observed in this population was somewhat smaller. Whether this discrepancy is due to ethnic difference remains to be determined. The three fragile X patients examined in this study did not have a greatly expanded CGG segment. One of them may be a mosaic with one full and one premutation allele. The other two patients, although having clinical and cytological features of fragile X syndrome, had a CGG repeat size within normal range. To explain this, we infer that the mutation in these patients may be caused by other mechanisms, such as other types of FMR-1 mutation or mutation in another site. It is possible that the expansion of the CGG repeats may not be as frequent a cause of fragile X syndrome in southern Chinese as in other ethnic groups.

Reduced dihydroxyacetone sensitivity and normal sensitivity to glyceraldehyde and oxidizing agent of ATP-sensitive K+ channels of pancreatic beta cells in NIDDM rats

The inhibition of ATP-sensitive K+(KATP) channels in pancreatic beta cells is a key step of insulin secretion induced by glucose. Glucose-induced insulin secretion from the beta cells is selectively impaired in patients with noninsulin-dependent diabetes mellitus (NIDDM) and in animal models of it. In order to clarify the site of this abnormal glucose response, we studied the effects of insulin secretagogues and sulfhydryl oxidizing agent, 2,2'-dithio-bis (5-nitropyridine) (DTBNP), on KATP channels in single beta cells of neonatally streptozotocin-induced NIDDM rats. We used the patch-clamp technique in cell-attached mode (Vpipette = 0 mV). The inhibitory response to glucose of KATP channels was lacking in NIDDM rats, indicating reduced sensitivity to glucose of the channels. Glyceraldehyde (2-5 mM) in the diabetic beta cells elicited the same KATP channel inhibition as that obtained in controls. In contrast, dihydroxyacetone (DHA, 2-10 mM) sensitivity of KATP channels was significantly reduced in the beta cells of NIDDM rats. KATP channels in the diabetic beta cells were rapidly inhibited by 50 microM DTBNP, just as in the normal beta cells, suggesting that KATP channel function was normal. This indicates that one of the sites responsible for impaired glucose-induced insulin secretion in the pancreatic beta cells of NIDDM rats is located in the glycerol phosphate shuttle.

Myelin basic protein is a zinc-binding protein in brain: possible role in myelin compaction

The zinc-binding proteins (ZnBPs) in porcine brain were characterized by the radioactive zinc-blot technique. Three ZnBPs of molecular weights about 53 kDa, 42 kDa, and 21 kDa were identified. The 53 kDa and 42 kDa ZnBPs were found in all subcellular fractions while the 21 kDa ZnBP was mainly associated with particulate fractions. This 21 kDa ZnBP was identified by internal protein sequence data as the myelin basic protein. Further characterization of its electrophoretic properties and cyanogen bromide cleavage pattern with the authentic protein confirmed its identity. The zinc binding properties of myelin basic protein are metal specific, concentration dependent and pH dependent. The zinc binding property is conferred by the histidine residues since modification of these residues by diethyl-pyrocarbonate would abolish this activity. Furthermore, zinc ion was found to potentiate myelin basic protein-induced phospholipid vesicle aggregation. It is likely that zinc plays an important role in myelin compaction by interacting with myelin basic protein.

Assessment of tracheoesophageal speech in a tonal language. A prospective study

BACKGROUND

Tracheoesophageal puncture followed by insertion of a voice prosthesis is an increasingly popular method for voice rehabilitation after total laryngectomy.

OBJECTIVE

To perform a functional assessment of voice produced by means of the Blom-Singer valve in a tonal language (Cantonese).

DESIGN

Prospective study.

SETTING

Hospital referral center.

MAIN OUTCOME MEASURE

A 5-point scoring scale was adopted for 15 test items of speech assessment grouped into 4 categories: phonatory skills, articulation, additional factors, and general judgment. The sum of the scores for the 15 items was the final speech score. The final speech score was rated as poor, satisfactory, or excellent if it was in the range of less than 30, 31 to 45, or 46 to 75, respectively.

RESULTS

Forty-four users of the Blom-Singer valve who had undergone total laryngectomy and primary tracheoesophageal puncture were available for functional assessment. The final speech score was poor in 2 patients (5%), satisfactory in 4 (9%), and excellent in 38 (86%).

CONCLUSION

Chinese patients can speak satisfactory tonal language with the Blom-Singer voice prosthesis.

Effects of volatile anesthetic isoflurane on ATP-sensitive K+ channels in rabbit ventricular myocytes

It has been suggested that volatile anesthetic, isoflurane mediates cardioprotective effects via activation of the ATP-sensitive K+ (KATP) channels. However, no direct evidence has been provided to define whether isoflurane activates cardiac KATP channels using patch-clamp technique. We examined the effects of isoflurane on the KATP channels in rabbit ventricular myocytes by use of patch-clamp technique. Contrary to the results of the in vivo experiments, isoflurane inhibited the channel activity without a change in the single-channel conductance. Isoflurane decreased the channel activity by a decrease in burst duration and an increase in the inter-burst duration. On the other hand, isoflurane diminished the ATP sensitivity of KATP channels, indicating an increased probability of KATP channel opening for a given concentration of ATP after isoflurane anesthesia. The result supports, at least in part, the hypothesis that isoflurane mediates cardioprotective effects via KATP channel activation.

Comprehensive analysis of pharyngeal recurrence of laryngeal carcinoma after total laryngectomy

PURPOSE

This study analyzes the incidence, risk factors, treatment results, and prognosis of local recurrence at the pharynx after total laryngectomy for laryngeal carcinoma.

PATIENTS AND METHODS

The records of 292 patients who underwent total laryngectomy for the treatment of laryngeal carcinoma between January 1978 and December 1990 were reviewed.

RESULTS

Of these 292 patients, there were 24 patients who developed local recurrence at the pharynx. The 5-year actuarial cumulative local recurrence rate was 10%. There were 17 cases of pharyngeal recurrence alone, five cases of pharyngeal and nodal recurrence, one case of pharyngeal and tracheostomal recurrence, and one case of pharyngeal and distant metastasis. Ten (42%) patients were salvaged surgically; the 5-year actuarial survival rate after surgical salvage was 53%. The other 14 patients were treated with palliative treatment, and all died of tumor, with the longest period of survival being 28 months.

CONCLUSION

Surgical salvage of pharyngeal recurrence has acceptable results. Close monitoring of patients is important to have an early diagnosis of salvageable recurrence.

Blockade of the ATP-sensitive potassium channel by taurine in rabbit ventricular myocytes

Using patch-clamp techniques, the effects of taurine on properties of ATP-sensitive K+ (KATP) channel of rabbit ventricular myocytes were examined. Intracellular taurine (20 mM) markedly depressed the KATP channel activity. The taurine concentration for half-inhibition (apparent Kd) was 13.5 mM with a Hill coefficient, n, of 1.3. Intracellular taurine caused channel inhibition without affecting channel inhibition by ATP. In control conditions, the ATP concentration for half-inhibition (Ki) and n were 73 microM and 1.2 (n = 6), respectively. In the presence of taurine, Ki and n were 81 microM and 1.3 (n = 6), respectively. Analysis of the open and closed time distributions showed that taurine decreased the life time of bursts and increased the inter-burst interval and/or reduced the number of functional channels. 2,4-Dinitrophenol (DNP) activated KATP channel after a lag period. This lag period was much longer after pretreatment with taurine (6.6 +/- 1.2 min, n = 5) than in the absence of taurine (2.8 +/- 1.5 min, n = 12). When DNP was removed in the bath solution, channel activity showed a gradual reduction with time and this process was facilitated by the presence of external taurine (20 mM). From these results it is suggested that taurine blocks KATP channel activity in dose-dependent manner and the depletion of taurine during myocardial ischemia contribute to the early activation of the KATP channel.

Sensorineural hearing loss in patients treated for nasopharyngeal carcinoma: a prospective study of the effect of radiation and cisplatin treatment

PURPOSE

The pattern of sensorineural hearing loss (SNHL) after primary treatment for nasopharyngeal carcinoma (NPC) was studied, and the effect of cisplatin, radiotherapy does, and fractionation were evaluated.

METHODS AND MATERIALS

One hundred thirty-two patients, 227 ears, and 1100 audiogram reports were analyzed. Radiotherapy dose ranged from 59.5 to 76.5 Gy. Fifty-two patients received preirradiation cisplatin, total dose 100-185 mg/m(2). Serial postirradiation bone conduction thresholds at 0.5 kHz, 1 kHz, 2 kHz, and 4 kHz were compared with pretreatment thresholds at respective frequencies. Increase of at least 15 dB was considered as significant and was further grouped as transient or persistent SNHL. Univariate and multivariate analyses were performed to identify predicting factors for persistent SNHL.

RESULTS

At median follow-up of 30 months, 24.2% of ears developed persistent SNHL. High frequency was more affected than low frequencies, 22 vs. 5.3%. Males were more affected than females, 29.4 vs. 15.5%, p = 0.0132. Incidence of persistent SNHL increased with age, with 0, 17.2, and 37.4% of patients aged under 30, between 30-50 and over 50 affected, respectively, p = 0.0001. High incidence was found in patient with postirradiation serous otitis media (SOM), 46.9%. Chemotherapy with cisplatin and radiation dose or fractionation had no significant effect. Multivariate analysis confirmed age, sex, and postirradiation SOM as significant prognostic factors for persistent SNHL.

CONCLUSIONS

Transient and persistent SNHL occurred after radiotherapy, more commonly affecting high frequency. A low dose of preirradiation cisplatin did not increase the risk. A dose fractionation effect of radiotherapy was not confirmed in this study.

Risk factors of tracheostomal recurrence after laryngectomy for laryngeal carcinoma

BACKGROUND

Tracheostomal recurrence after total laryngectomy for laryngeal carcinoma has a poor prognosis. The independent risk factors of tracheostomal recurrence are, however, not well documented.

METHODS

This is a multivariate analysis of the risk factors of tracheostomal recurrence after total laryngectomy for 322 laryngeal squamous cell carcinomas. The factors included in the analysis were sex, age, tumor stage, sites of tumor involvement, preoperative airway obstruction, preoperative tracheostomy, extent of surgical resection, radiotherapy, and pathological resection margin.

RESULTS

Seventeen (5%) patients developed tracheostomal recurrence. Univariate analysis showed that preoperative airway obstruction, subglottic involvement, and postcricoid extension were significant factors associated with tracheostomal recurrence. Multivariate analysis using logistic regression method showed that both subglottic and postcricoid involvement were independent predisposing factors for tracheostomal recurrence. The tracheostomal recurrence rates were 2% in patients without the risk factor and 10% in patients with the presence of one or both risk factors.

CONCLUSIONS

Subglottic and postcricoid involvement were independent risk factors for tracheostomal recurrence.

Comprehensive analysis of nodal recurrence of advanced laryngeal carcinoma following surgery

The problems of nodal recurrence after surgical treatment of T3-4 laryngeal carcinoma were analysed. There were 133 N0 and 66 N+ patients. The 5-year actuarial nodal recurrence rate of N0 patients was 18% and N+ patients was 31%. Nodal recurrence was the commonest site of recurrence. The sites of nodal recurrence of N0 patients were at the level II, III, and IV nodes. Both ipsilateral and contralateral nodal recurrences were common. Of those patients who developed nodal recurrence, 63% patients were feasible for surgical salvage. Surgical salvage with radical neck dissection was the preferred treatment for nodal recurrence with 38% 5-year survival rate. The 'watchful waiting policy' in the management of N0 neck is an acceptable option with eventual nodal failure rate of 10% after surgical salvage. Close follow-up of patients is mandatory for the early detection of surgically salvageable nodal recurrence.

Voltage- and time-dependent block of delayed rectifier K+ current in rabbit sino-atrial node cells by external Ca2+ and Mg2+

1. The properties of the delayed rectifier K+ current (IK) of rabbit isolated sino-atrial node cells were investigated in high (140 mM) [K+]o using the whole-cell-clamp technique. 2. Hyperpolarizing clamp pulses from 0 mV induced an instantaneous current jump (I-V relation linear) followed by a time-dependent increase in inward current to a peak, whereas depolarizing clamp pulses induced little outward current. The peak I-V relation showed a strong inward rectification. The inwardly rectifying current was blocked by E-4031. 3. The inward K+ current induced by hyperpolarizing clamp pulses from 0 mV relaxed after reaching its peak. The rate of the relaxation increased as the membrane potential became more negative and concentrations of external Ca2+ or Mg2+ were increased. The steady-state current was smaller as the relaxation of the current accelerated on increasing [Ca2+]o or [Mg2+]o. 4. Depolarizing clamp pulses from -80 mV induced an increase in inward current, reaching a steady state. The amplitude of the steady-state current became smaller and the rate of current increase became slower as [Ca2+]o or [Mg2+]o was increased. 5. The effects of Ca2+ and Mg2+ are well explained by a time- and voltage-dependent blockade of the K+ channel by these ions. The fractional electrical distance of the binding site calculated from the voltage dependence of the blocking rate constant is 0.69 for Ca2+ and 0.88 for Mg2+. The blocking rate constant at 0 mV for Ca2+ is about 15 times faster than that for Mg2+, indicating stronger effects of Ca2+. 6. A re-interpretation of IK in sino-atrial node cells is proposed: there are two independent gates (an activation gate which opens on hyperpolarization and an inactivation gate which closes on hyperpolarization) and a binding site for Ca2+ and Mg2+ inside the channel. Binding of these ions, which is facilitated by hyperpolarization, causes channel blockade, resulting in the observed voltage dependence of IK in physiological concentrations of Ca2+ and Mg2+.

Primary closure of pharyngeal remnant after total laryngectomy and partial pharyngectomy: how much residual mucosa is sufficient?

After total laryngectomy with or without partial pharyngectomy, the remaining pharyngeal defect can be repaired either by primary closure or with additional tissue, depending on the amount of pharyngeal tissue remnant available. The aim of this study was to determine the minimum width of the pharyngeal remnant that could be safely closed primarily without causing difficulty in swallowing. A total of 52 consecutive patients who underwent total laryngectomy were entered into the study. The relaxed and stretched widths of the pharyngeal remnant were measured after removal of the specimen. The widths of the pharyngeal mucosa ranged from 1.5 to 5.0 cm relaxed (mean, 3.24 cm) and from 2.5 to 8.0 cm stretched (mean, 4.83 cm). All neopharynx was reconstructed by closing the pharynx primarily. Seven of the 52 patients developed recurrent tumor with concomitant dysphagia. Two of the 45 patients without recurrence presented with acute dysphagia from food bolus obstruction, and 1 patient developed benign inflammatory stricture following an episode of fish-bone impaction. The narrowest widths of the pharyngeal remnant in this group of 45 were 1.5 cm relaxed and 2.5 cm stretched. As these patients do not have swallowing difficulty, we conclude that in the absence of tumor recurrence, this amount of residual pharyngeal tissue is sufficient both for primary closure of the pharynx and in restoring swallowing function.

The effect of taurine on the activation osmolality of the osmosensitive current in single ventricular myocytes of rabbits

An osmosensitive current was identified in rabbit ventricular cells and the effects of taurine on osmotic stress were examined. The osmosensitive current was measured with the whole-cell patch clamp technique and all known currents were blocked using Ba2+, Cd2+, Ni2+, diltiazem, ouabain, Cs+ and tetraethyl ammonium. When hyposmotic solution (200 mosmol/kg) was applied, the background current increased gradually. This osmosensitive current was dependent on Cl-. When the conductance of the activated current reached three times the control conductance, the osmolality was arbitrarily named the activation osmolality. The activation osmolality was regarded as an indication of cell volume expansion. With 20 mM taurine in the pipette solution, the activation osmolality was lowered significantly. With high [Na+] (32.5 mM) in the pipette solution, the effect of taurine in reducing the activation osmolality was larger than that in low [Na+] (2.5 mM). From these results, we conclude that taurine reduces the activation osmolality and this effect is more pronounced in the presence of high [Na+] in the pipette solution. It is suggested that Na+-dependent taurine transport could be involved in reducing osmotic stress.

Sulfhydryl redox modulates ATP-sensitive K+ channels in rabbit ventricular myocytes

The properties of sulfhydryl redox modulation of the ATP-sensitive K+ K(ATP) channel have been examined in rabbit ventricular myocytes, using the patch-clamp technique. The sulfhydryl oxidizing agent 5.5'-dithio bis-(2-nitro-benzoic acid) (DTNB) induced an inhibition of the channel activity without change in the single channel conductance. DTNB had no effect on the inhibitory action by ATP. Analysis of the open and closed time distributions showed that DTNB decreased the life time of bursts and increased the interburst interval without changes in open and closed time distributions shorter than 5 ms. N-ethylmaleimide (NEM), a substance that reacts with sulfhydryl groups of cysteine residues in proteins, induced an irreversible closure of the channel. The results suggested that changes in the sulfhydryl redox also modulate K(ATP) channel activity of the K(ATP) channel in rabbit ventricular myocytes.

Redox agents as a link between hypoxia and the responses of ionic channels in rabbit pulmonary vascular smooth muscle

Ca(2+)-activated K+ currents (IK(Ca)) and voltage-dependent Ca(2+)-insensitive K+ currents (IK(V)) were recorded using the patch clamp technique to study the pulmonary (PASMC) and ear arterial smooth muscle cells (EASMC) of the rabbit and the possible regulatory mechanisms related to hypoxia. When a hypoxic solution (1 mM Na2S2O4, gassed with 100% N2) was superfused, the activity of Ca(2+)-activated K+ channels (KCa channels) recorded at a pipette potential of -70 mV in cell-attached mode was decreased to 49 +/- 7% in PASMC, whereas EASMC KCa channels did not respond to hypoxia. In inside-out patches (bathed symmetrically in 150 mM KCl), reducing agents such as dithiothreitol (DTT; 5 mM), reduced glutathione (GSH; 5 mM) and NADH (2 mM) decreased KCa channel activity in PASMC, but they did not affect the EASMC KCa channel. However, oxidizing agents such as 5,5'-dithio-bis(2-nitrobenzoic acid) (DTNB; 1 mM), oxidized GSH (GSSG; 5 mM) and NAD (2 mM) increased KCa channel activity in both PASMC and EASMC. In the whole-cell configuration, using a pipette solution containing a high concentration of 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid (BAPTA; 10 mM), PASMC IK(V) were activated by depolarizing step pulses to voltages more positive than -30 mV (holding potential, -80 mV). IK(V) was increased by application of a membrane-permeable oxidizing agent, 2,2'-dithio-bis(5-nitropyridine) (DTBNP; 200 microM), whereas it was decreased by application of DTT (5 mM). From these results, it could be suggested that hypoxic pulmonary vasoconstriction is attributable, at least in part, to a change of cellular redox state, which decreases outward K+ currents. This hypothesis is further supported by the observation that the basal redox state of EASMC KCa channels is more reduced than that of PASMC KCa channels. The distinct responses to hypoxia of pulmonary and systemic arterial smooth muscle could be explained by this difference.

Different modulation of Ca-activated K channels by the intracellular redox potential in pulmonary and ear arterial smooth muscle cells of the rabbit

We investigated the electrical responses of Ca-activated K (KCa) currents induced by hypoxia and reduction or oxidation of the channel protein in pulmonary (PASMC) and ear (EASMC) arterial smooth muscle cells using the patch-clamp technique. In cell-attached patches, in the presence of a high K solution (containing 0.316 microM Ca2+), the activity of KCa channels from PASMC was decreased (by 49 +/- 7% compared to control, pipette potential = -70 mV) by changing to a hypoxic solution (1 mM Na2S2O4, aeration with 100% N2 gas). EASMC channels did not respond to hypoxia. In order to investigate the possible mechanisms involved, using inside-out patches bathed symmetrically in 150 mM KCl, we applied redox couples to the intracellular side. Reducing agents, such as dithiothreitol (DDT, 5 mM), reduced glutathione, (GSH, 5 mM), and nicotinamide adenine dinucleotide reduced (NADH, 2 mM) decreased PASMC, but not EASMC, KCa channel activity. However, oxidizing agents such as 5,5'-dithio-bis(2-nitrobenzoic acid) (DTNB, 1 mM), oxidized glutathione (GSSG, 5 mM) and NAD (2 mM) increased KCa channel activity in both PASMC and EASMC. The increased activity due to oxidizing agents was restored by applying reducing agents. From these results, we could suggest that the basal redox state of the EASMC KCa channel is more reduced than that of the PASMC channel, since the response of KCa channels of the EASMC to intracellular reducing agents differs from that of the PASMC. This difference may be related to the different responses of PASMC and EASMC KCa channels to hypoxia.

Effects of adriamycin on ionic currents in single cardiac myocytes of the rabbit

Adriamycin has been widely used as an anticancer drug, but its clinical use is limited by a dose-dependent cardiac toxicity. Proposed mechanisms for the adriamycin-induced cardiomyopathy include increasing the Ca current, inhibiting the Na/Ca exchange and dysfunction of the sarcoplasmic reticulum (SR). Using the whole cell voltage clamp technique in single isolated atrial and ventricular myocytes of the rabbit, we have investigated the effect of adriamycin on various current systems which are related to regulating intracellular Ca concentration: the Ca current, the Na/Ca exchange current and [Ca2+]i-dependent currents (ouabain-induced transient inward current and the inward tail current). Adriamycin, 0.05 mg/ml, increased Ca current (L-type) by 61%. Adriamycin inhibited the inward tail current in a dose-dependent manner between 0.02 and 0.1 mg/ml and when low concentration was used the effect was reversible. Ouabain-induced transient inward current was also suppressed by 0.05 mg/ml adriamycin. Na/Ca exchange current which is partly responsible for inducing [Ca2+]i-dependent currents was, however, not affected by adriamycin, suggesting that the effect adriamycin on [Ca2+]i-dependent currents is due to inhibition of SR function. From these results it is suggested that the increase of Ca current and inhibition of SR function cause adriamycin-induced cardiac toxicity: SR dysfunction not only causes a decrease of myocardial contractility, it can also accelerate the Ca overload process which might originate from the increase of Ca current.

High selectivity of the i(f) channel to Na+ and K+ in rabbit isolated sinoatrial node cells

The ionic selectivity of the hyperpolarization-activated inward current (i(f)) channel to monovalent cations was investigated in single isolated sinoatrial node cells of the rabbit using the whole-cell patch-clamp technique. With a 140 mM K+ pipette, replacement of 90% external Na+ by Li+ caused a -24.5 mV shift of the fully activated current/voltage I/V curve without a significant decrease of the slope conductance. With a 140 mM Cs+ pipette, the i(f) current decreased almost proportionally to the decrease in external [Na+]o as Li+ was substituted. These responses are practically the same as those observed with N-methyl glucamine (NMG+) substitution, suggesting that the relative permeability of Li+ compared with Na+ for the i(f) channel is as low as that of NMG+. When Cs+ or Rb+ was substituted for internal K+, the fully activated I/V relationship for i(f) showed strong inward rectification with a positive reversal potential, indicating low permeability of the i(f) channel for Cs+ and Rb+. These results show that the i(f) channel is highly selective for Na+ and K+ and will not pass the similar ions Li+ and Rb+. Such a high degree of selectivity is unique and may imply that the structure of the i(f) channel differs greatly from that of other Na+ and K+ conducting channels.