A new Zn(II)-selective potentiometric sensor based on 4-tert-butylcalix[4]arene in PVC matrix.

Poly(vinyl chloride) (PVC) based membranes containing 4-tert-butylcalix[4]arene (I) as an electroactive material along with anion excluder sodiumtetraphenylborate (NaTPB) and plasticizer tri-butylphosphate (TBP) have been developed to fabricate a new zinc-selective sensor. Out of various compositions, the best performance was exhibited by the membrane having I, NaTPB, TBP and PVC in the ratio 8:5:100:200 (w/w). The sensor works well in the concentration range 9.8 x 10(-6) to 1.0 x 10(-1) mol dm(-3) with a near-Nernstian slope of 28.0+/-1.0 mV/decade of activity. The detection limit is down to 5.0 x 10(-7) mol dm(-3). The working pH range of this sensor is 2.5-4.3 and it works well in partially non-aqueous medium up to 15% (v/v) (methanol, ethanol and acetone). It exhibits a fast response time of 30s and could be used for more than four months without any considerable change in response characteristics. It has excellent selectivity for Zn(II) over other mono-, bi- and trivalent cations which have been reported to cause interference in the working of other sensors. It has been successfully used as an indicator electrode in the potentiometric titration of Zn(II) against EDTA and also to estimate zinc ions in industrial waste waters.

A copper-selective electrode based on bis(acetylacetone)propylenediimine.

The potentiometric response characteristics of Cu(2+)-selective electrodes based on bis(acetylacetone)propylenediimine (I) combined with anion localizing agent (sodium tetraphenyl borate (NaTPB)) and solvent mediators (dibutyl butyl phosphonate (DBBP), tri-n-butyl phosphate (TBP) and chloronaphthalene (CN)) were investigated. The best results for Cu(2+) sensing was obtained for the electrode membrane containing PVC, I, DBBP and NaTPB in composition 5:100:200:6 (I:PVC:DBBP:NaTPB) (w/w; mg), where the electrode had a Nernstian response (30.0mV/decade) to Cu(2+) within the concentration range 1.0x10(-5) to 1.0x10(-1)M and detection limit of 0.5ppm. The operational pH range of the electrode was 3.3-7.0. Selectivity characteristic of the proposed electrode was also assessed by calculating K(A,B)(Pot) using fixed interference method matched potential method. The sensor has been successfully used in the potentiometric titration of copper ions with EDTA.

Hearing preservation in microvascular decompression for trigeminal neuralgia.

OBJECTIVE/HYPOTHESIS: Sensorineural hearing loss is a disturbing complication of microvascular decompression (MVD) for trigeminal neuralgia with an incidence of 1% to 23.8%. Cerebellar retraction with increasing I-V interpeak latency (IPL) during intraoperative brainstem auditory evoked potentials (BAEP) has been identified as the chief cause of acoustic injury. This study was designed to eliminate cerebellar retraction by a modification of the standard suboccipital craniectomy. STUDY DESIGN: Nine consecutive patients undergoing surgery for trigeminal neuralgia were prospectively selected for this study between 1994 and 1995. METHODS: Preoperative and postoperative audiograms were obtained. Preoperative and intraoperative BAEPs were performed. The surgical modification describes initiating a partial mastoidectomy to enhance early recognition and delineation of the sigmoid and transverse sinuses crucial to maximizing the lateral extent of the craniectomy. The additional exposure gained by this technique allows for improved visualization of the brainstem without cerebellar retraction. RESULTS: All patients were relieved of neuralgic pain. Postoperative IPL values were not significantly different from preoperative values (4.9+/-0.6 vs. 4.7+/-0.3 ms). Maintaining IPL of less than 1.5 ms is considered critical for preventing injury to the auditory nerve. In this study the average increase in postoperative IPL was 0.25 ms for the ipsilateral ear and 0.1 ms for the contralateral ear. CONCLUSIONS: The authors offer a surgical modification of the standard suboccipital craniectomy and furnish intraoperative neurophysiologic data to demonstrate how cerebellar compression can be eliminated and hearing preserved in MVD for trigeminal neuralgia.

Case report and discussion of hearing preservation after translabyrinthine excision of small acoustic tumors.

OBJECTIVE: Since 1991, three separate reports have shown how hearing may be salvaged after translabyrinthine excision of small acoustic tumors. The authors submit yet another report of a complete translabyrinthine excision of a 1.4-cm intracanalicular acoustic tumor with modest hearing preservation. An attempt is made to retrace the steps of the operation and recognize and discuss what particular events may have safeguarded the viability of the cochlea. With the availability of cochlear implantation, there should be added incentive to preserve the cochlear neurones if hair cells cannot be saved. STUDY DESIGN: The study design was a retrospective case review. SETTING: The study was conducted at a primary care hospital. INTERVENTION: Therapeutic and rehabilitative measures were performed. MAIN OUTCOME MEASURES: Hearing preservation was measured. CASE REPORT: A 55-year-old woman presented with a left-sided hearing loss and a 1.4-cm left acoustic tumor completely filling the internal auditory canal (speech reception threshold [SRT] 30 dB, discrimination [Pb] 28%). A successful translabyrinthine excision of the tumor was performed in November 1995. A 1-year postoperative audiogram showed a mixed hearing loss in the left ear with SRT 85 dB and Pb 0%. Average pure-tone threshold for 500 Hz, 1 kHz, and 3 kHz was 50 dB and aided SRT 40 dB with Pb 64%. Postoperative magnetic resonance imaging confirmed complete excision of the tumor. CONCLUSION: An exceptional case of hearing preservation after translabyrinthine excision of a small acoustic tumor illustrates how it may be possible to preserve cochlear hair cells and neurones simultaneously in certain selected cases. A review of the surgical events shows the value of sealing the cochlear duct with bone wax, selectively removing the vestibular nerves with the tumor by sharp dissection, and safeguarding the meatal segment of the anterior inferior cerebellar artery by a limited dural incision.

Effect of 3-[p-(N-2-pyrimidylsulfamoyl)phenyl hydrazono]pentane-2,4-dione on blood parameters of albino rats.

Intramuscular injection of 3-[p-(N-2-pyrimidylsulfamoyl)phenylhydrazono]pentane-2,4-dio ne (compound I) resulted in decrease in haemoglobin and alanine transaminase (ALT) and increase in aspartate transaminase (AST) values in albino rats. The serum glucose was found to decrease and after administration of 14 doses of 5.4 mg kg-1 body wt glucose level also declined significantly. It is concluded that the compound I is a better hypoglycemic than sulfonamide or hydrazone alone.

7-S-glutathionyl-tryptamine-4,5-dione: a possible aberrant metabolite of serotonin.

Tryptamine-4,5-dione (Compound 1) is an in vitro oxidation product of 5-hydroxytryptamine (5-HT). Recent evidence has suggested that aberrant oxidations of 5-HT occur in the central nervous system of individuals with Alzheimer's disease (AD). In the event that Compound 1 is formed as a result of oxidation of 5-HT within serotonergic nerve terminals or axons, it would be expected to be rapidly conjugated by intraneuronal glutathione (GSH) to give 7-S-glutathionyl-tryptamine-4,5-dione (Compound 2). When injected into the brains of laboratory mice, Compound 2 was lethal (LD50 = 21 micrograms) and evoked hyperactivity for the first 30 min following drug administration. Particularly during this hyperactive phase Compound 2 caused a statistically significant decrease in whole brain levels of norepinephrine and 5-HT. Levels of dopamine were also decreased while whole brain concentrations of its metabolites, 3,4-dihydroxyphenylacetic acid and homovanillic acid, were increased significantly. In the presence of GSH, NADPH and ascorbic acid, Compound 2 redox cycled in reactions that catalyzed the oxidation of these cellular reductants by molecular oxygen and formed H2O2 as a byproduct. Compound 2 also reacted with molar excesses of GSH to form more structurally complex glutathionyl conjugates. Several of these conjugates have been isolated and their structures determined using spectroscopic methods. It is conceivable that one or more of these conjugates might serve as analytical markers in a search for evidence in support of the hypothesis that aberrant oxidations of 5-HT occur in the Alzheimer brain. The redox cycling properties of Compound 2 and its facile reactions with cellular nucleophiles such as GSH may represent mechanisms that contribute to the toxicity of this drug.

Further insights into the molecular mechanisms of action of the serotonergic neurotoxin 5,7-dihydroxytryptamine.

Autoxidation and various enzyme-mediated oxidations of the serotonergic neurotoxin 5,7-dihydroxytryptamine (1) give 5-hydroxytryptamine-4,7-dione (2) and 6,6'-bi(5-hydroxytryptamine-4,7-dione) (3) as the major products. When administered into the ventricular system of mice 2 and 3 are general toxins. The LD50 values for 2 (29.6 +/- 0.04 micrograms) and 3 (25.4 +/- 0.30 micrograms) are lower than that for 1 (51.8 +/- 0.28 micrograms). In the presence of cellular reductants (glutathione, cysteine, ascorbate) and molecular oxygen, or when incubated with rat brain homogenate, 2 and 3 redox cycle and form superoxide radical anion, O2.-, as a byproduct. The lethal effects of 2 and 3 when introduced into the brain may in part be due to such redox cycling reactions which deplete oxygen levels and, as a result of Haber-Weiss chemistry deriving from O2.-, form the cytotoxic hydroxyl radical (HO.). Intraventricular administration of 2 and 3 to mice causes only relatively minor and transient (ca. 1 h to 1 day) changes in whole brain levels of dopamine, 5-hydroxytryptamine (from both 2 and 3), acetylcholine, and choline (from 2 only). These changes differ from the profound and long-lasting serotonergic deficit evoked by 1. On the basis of these results a hypothesis has been formulated which proposes that the selective neurotoxicity of 1 derives from its rapid uptake into serotonergic neurons where it is oxidatively converted to 2 and 3. Redox cycling reactions of 2 and 3 then result in the depletion of intraneuronal oxygen and concomitant formation of O2.-. Dismutation of O2.- gives H2O2 which, as a result of transition metal ion-catalyzed Haber-Weiss chemistry, yields HO.. Thus, neuronal damage and death might result from the combined effects of hypoxia and HO. formation.

5,5'-Dihydroxy-4,4'-bitryptamine: a potentially aberrant, neurotoxic metabolite of serotonin.

Previous investigators have detected unknown oxidized forms of 5-hydroxytryptamine (5-HT) in the CSF of Alzheimer's disease (AD) patients. Furthermore, an unidentified autoxidation product of this neurotransmitter is an inhibitor of acetylcholinesterase (AChE), an enzyme compromised in the Alzheimer brain. In this study it is demonstrated that the major product of autoxidation of 5-HT is 5,5'-dihydroxy-4,4'-bitryptamine (DHBT). Central administration of DHBT to mice at a dose of 40 micrograms (free base) evokes profound behavioral responses, which persist until the animals die (approximately 24 h). One hour after central administration of DHBT, the levels of norepinephrine, dopamine, 5-HT, and acetylcholine and their metabolites in whole brain are greatly elevated. Disturbances to the catecholaminergic and serotonergic systems were still evident shortly before the death of animals. DHBT is also shown to be a noncompetitive inhibitor of AChE in vitro. These observations suggest that if DHBT is formed as an aberrant metabolite of 5-HT in the human brain, it could potentially be neurotoxic and contribute to the neuronal degeneration and other neurochemical and neurobiochemical changes associated with AD or perhaps other neurodegenerative diseases.

Haematological and hepatotoxic effects of silken styles of corn in albino rats.

The alterations of haematological parameters in albino rats were studied after oral administration of an aqueous extract of silken styles of corn (Zea maize Linn.) at 50, 100 and 150 mg kg-1 daily for 21 days. The following haematological values were significantly reduced on the 7th and 21st day following extract administration: haemoglobin (Hb), red blood corpuscles (RBC), clotting time (CT), mean corpuscular volume (MCV), haematocrit (Ht), serum glucose, blood urea nitrogen (BUN), cholesterol, aspartate transaminase (AST), alanine transaminase (ALT), calcium, total protein, total albumin and total acid phosphatase; and white blood corpuscles (WBC), mean corpuscular haemoglobin (MCH), mean corpuscular haemoglobin concentration (MCHC), alkaline phosphatase and creatinine increased. The remaining parameters were not significantly affected, except body weight parameters at the two highest doses. The results emphasize that the biochemical changes caused through aqueous extract of silken styles of corn (Zea maize Linn.) are not significantly toxic at low and medium doses (50 and 100 mg kg-1).

Oxidation chemistry and biochemistry of the central mammalian alkaloid 1-methyl-6-hydroxy-1,2,3,4-tetrahydro-beta-carboline.

The electrochemical oxidation of the central mammalian alkaloid 1-methyl-6-hydroxy-1,2,3,4-tetrahydro-beta-carboline (1) has been studied in neutral aqueous solution at a pyrolytic graphite electrode (PGE). Voltammograms of 1 show two closely spaced oxidation peaks, Ia and IIa. At potentials less positive than the peak potential (Ep) for peak Ia, 1 is oxidized to a radical intermediate which dimerizes to give two diastereomers of 5,5'-bi(1-methyl-6-hydroxy-1,2,3,4-tetrahydro-beta-carboline) (5 and 6). At potentials more positive than Ep for peak Ia the putative radical intermediate is further electrooxidized to a C(5)-centered carbocation which reacts with 1 in an ion-substrate reaction to give 5 and 6 or with water to give, ultimately, 1-methyl-1,2,3,4-tetrahydro-beta-carboline-5,6-dione (12). Dimers 5 and 6 give two reversible oxidation peaks at the PGE, the second of which corresponds to peak IIa observed in voltammograms of 1. Because 5 and 6 are easily oxidizable compounds they are only observed as products in the initial stages of the controlled potential electrooxidation of 1. Tyrosinase/O2, human ceruloplasmin/O2, and peroxidase/H2O2 also oxidize 1 to 5, 6, and 12 as the initial products. In the presence of glutathione the electrochemically driven and enzyme-mediated oxidations of 1 result in the formation of 5-S-glutathionyl-1-methyl-6-hydroxy-1,2,3,4-tetrahydro-beta-carboline as a major product. Central administration of diastereomer 5 or 6 to mice evoked behavioral responses similar to those caused by the opioid analgesics. These behavioral effects, which include spatial disorientation and a characteristic ducklike walk, became most pronounced approximately 3 h after drug administration and continued for about 3 days. Neurotransmitter and related metabolite analyses of whole brain reveal that 5 and 6 cause a general increase in dopaminergic and serotonergic activity and a small but significant decrease in cholinergic activity. These transmitter/metabolite disturbances appear to parallel the time course of the observed behavioral effects. The possible roles of in vivo oxidations of 1, an alkaloid which is elevated in mammalian brain following ethanol consumption, in the addictive, behavioral, and neurodegenerative consequences of chronic alcoholism are discussed.

Metrizamide CT scanning in spinal nerve root cysts.

Two cases of lumbosacral root cysts of different etiology are reported. Their specific radiographic features are described using the combined technique of metrizamide myelography followed by computerized tomography of the spine. The terminology of intraspinal cysts is reviewed and their distinguishing features discussed.

Intraspinal cysts: a classification and literature review.

Advances in radiologic technology have allowed the identification of a variety of cystic lesions of spinal nerve roots. Failure to appreciate the different characteristics of these cysts has led to a confusion in terminology, with different terms often being used to describe the same lesion. In an attempt at clarification, the literature is reviewed and a simplified classification of spinal cysts presented. The distinguishing features of each type of cyst, its investigation, and appropriate treatment are discussed.

Polarography of some 3-arylazo-3-bromopentane-2,4-diones.

The polarographic reduction of 3-arylazo-3-bromopentane-2,4-diones has been studied at different concentrations and pH. These compounds give a single 2-electron transfer and well-defined diffusion-controlled irreversible waves. The effect of fourteen substituents (electron-donating and electron-withdrawing) has been determined. A correlation between half-wave potential and Hammett substituent-constant has been established.

Quantitative treatment of substituent effects in the polarographic investigations of some potential antineoplastic 2-amino-4-aryl-5-phenylazothiazoles.

Polarographic reduction of 2-amino-4-aryl-5-phenylazothiazoles takes place in a single 2-electron transfer, giving a diffusion-controlled irreversible wave in the pH range 2.0-10.0. Substituents in the 4-position of the thiazole moiety shift the half-wave potential through conjugation of the system. A correlation of E(sol;1 2 ) with the Brown and Hammett substituent constant has also been established.

Studies on the polarographic reduction of the azomethine bond in the products of beta-keto-esters coupled with aryldiazonium chlorides.

The products of coupling beta-keto-esters with aryldiazonium chlorides have been studied polarographically and give a single well-defined 4-electron diffusion-controlled irreversible wave in the pH range 2.0-11.0. The effect of electron-donating and electron-withdrawing substituents and the correlation between the half-wave potential and Hammett substituent constant have been studied.

Polarographic reduction of some potential antidiabetic compounds with more than one reduction site.

The polarographic reduction of a number of N'-guanylarylazopyrazole nitrates has been studied over a range of concentration and pH values. The effect of substituent groups on the value of the half wave potential has been determined.

Studies on the electrocapillary curves of anionic surfactants in presence of non-ionic surfactants.

Polyoxyethylated non-ionic surfactants such as Tween 20, Tween 40, Nonidet P40 and Nonex 501 have been supposed to be associated with cationic characteristics. Studies on the effect of these surfactants on the electrocapillary curves of the anionic surfactants Aerosol IB, Manaxol OT and sodium lauryl sulphate (SLS), show that the electrocapillary maxima shift towards positive potentials. The order of adsorption of the anionic surfactants is SLS > Manaxol OT > Aerosol IB while the shift in maxima is in the order Aerosol IB ~ Manaxol OT > SLS which confirms association of cationic characteristics with the micelles of these non-ionic surfactants. The magnitude of the shift in electrocapillary maxima is Nonex 501 > Nonidet P40 > Tween 20 > Tween 40 which may be the order of magnitude of the positive charge carried by these non-ionic surfactants.