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1.
Indian J Otolaryngol Head Neck Surg ; 76(3): 2480-2489, 2024 Jun.
Article in English | MEDLINE | ID: mdl-38883531

ABSTRACT

Purpose: Yakshagana is a type of folk-art theatre portraying mythological and historical stories. It includes artists who play predominantly percussion instruments besides cymbals and harmonium. Professional musicians exposing themselves to deafening sounds are prone to develop noise-induced complications. [1] One such professional in the coastal districts of Karnataka state is a Yakshagana himmela (backstage) artist. There is no reported literature concerning these artists' hearing health and problems. Hence, the proposed study was aimed at developing, validating and assessing the Knowledge, Attitude and Practice (KAP )of Yakshagana Mela artists towards Music-Induced Hearing Loss (MIHL), a possible risk factor of their profession. Method: This study was carried out on 139 yakshagana mela artists with a mean age of 41.63 years. It was conducted in two phases. In the first phase, an expert committee discussion was conducted to verify, modify and validate the questionnaire. The second phase included the administration of the developed questionnaire on the artists. Results: The sum scores for each domain of KAP were computed. Scores above 80% were defined as good knowledge, practice, and a positive attitude. The findings of the study revealed that more than half of the participants demonstrated inadequate knowledge (63.3%) and negative attitude (63.7%), but a fair level of practice (65.4%). Conclusion: From the outcome of the present study, it can be inferred that in spite of being in a profession with a high risk of MIHL, the participants considered hearing health as their least priority. The study illustrates the need for initiating hearing and conservation programs to improve awareness & combat music induced hearing loss in this population.

2.
J Otol ; 18(1): 63-69, 2023 Jan.
Article in English | MEDLINE | ID: mdl-36820160

ABSTRACT

Background: Classic dichotic listening tests using speech stimuli result in right ear advantage, due to the dominant crossed pathway for speech and language. It is presumed that similar crossed dominance could exist for non-speech stimuli too. Hence, this is an attempt to develop and validate the dichotic non-speech test using environmental stimuli and explore the effect of focused attention on this test. Materials and method: Three lists of dichotic stimuli were created using these sounds with fifteen tokens in each list. Four professionals and non-professionals validated these materials. Normative estimation was obtained by administering the newly developed test on 70 adults and 70 children using a free-recall and forced-recall condition. Result: The results showed a significant difference between the left ear and right scores where the left ear score was better than the right, depicting left ear advantage (LEA) for free recall condition in both groups. In the forced recall condition, LEA was not seen; rather the mean score was significantly higher in the attended ear, irrespective of the stimuli presented to the right or left ear. The test-retest reliability in free recall was good in both the ears and moderate for forced right ear conditions. Conclusion: The novel test consistently showed LEA with good reliability and can be used to assess the hemispheric asymmetry in normal subjects and also in test batteries for the clinical population.

3.
Int J Pediatr Otorhinolaryngol ; 108: 22-25, 2018 May.
Article in English | MEDLINE | ID: mdl-29605359

ABSTRACT

BACKGROUND AND PURPOSE: Comprehensive management for communication disorders in individuals with CLP was provided in a community based program in two rural districts in Tamilnadu, India. This program provides services at the community to empower the families about CLP and treatment options. OBJECTIVE: To document the caregiver perceptions' of communication status and needs in children with repaired CLP. METHOD: Six Focus Group Discussions were conducted in Thiruvannamalai and Cuddalore districts in Tamil Nadu, India. Participants were 55 Caregivers of children (5-12 years of age) with repaired CLP. RESULTS: Most participants were concerned about their child's communication and few expressed concerns about specific errors in speech observed in their children. The caregivers recognized the need for and were willing to avail speech correction services. The focus group discussions highlighted some factors that need to be considered while planning a service delivery program for speech correction. The caregivers' expressed inability to independently carryout home training programs attributing it the lack of cooperation from their children. However they were open to receiving services if it was logistically convenient. CONCLUSION: This study provided the caregiver perceptions' of needs relating to communication in children with CLP. These need to be incorporated in the existing program to develop a model for speech intervention that would be feasible, sustainable and have good compliance.


Subject(s)
Cleft Lip/complications , Cleft Palate/complications , Communication Disorders/epidemiology , Health Services Needs and Demand/statistics & numerical data , Speech Disorders/epidemiology , Caregivers/psychology , Child , Child, Preschool , Communication , Communication Disorders/etiology , Female , Focus Groups , Humans , India , Language , Male , Speech , Speech Disorders/etiology , Speech Perception/physiology
4.
Indian J Plast Surg ; 50(3): 295-301, 2017.
Article in English | MEDLINE | ID: mdl-29618865

ABSTRACT

BACKGROUND AND AIM: A community-based rehabilitation programme, Sri Ramachandra University-Transforming Faces project, was initiated to provide comprehensive management of communication disorders in individuals with CLP in two districts in Tamil Nadu, India. This community-based programme aims to integrate hospital-based services with the community-based initiatives and to enable long-term care. The programme was initiated in Thiruvannamalai (2005) district and extended to Cuddalore (2011). The aim of this study was to identify needs related to speech among children with CLP, enroled in the above community-based programme in two districts in Tamil Nadu, India. DESIGN: This was a cross-sectional study. PARTICIPANTS AND SETTING: Ten camps were conducted specifically for speech assessments in two districts over a 12-month period. Two hundred and seventeen individuals (116 males and 101 females) >3 years of age reported to the camps. METHODS: Investigator (SLP) collected data using the speech protocol of the cleft and craniofacial centre. Descriptive analysis and profiling of speech samples were carried out and reported using universal protocol for reporting speech outcomes. Fleiss' Kappa test was used to estimate inter-rater reliability. RESULTS: In this study, inter-rater reliability between three evaluators revealed good agreement for the parameters: resonance, articulatory errors and voice disorder. About 83.8% (n = 151/180) of the participants demonstrated errors in articulation and 69% (n = 124/180) exhibited abnormal resonance. Velopharyngeal port functioning assessment was completed for 55/124 participants. CONCLUSION: This study allows us to capture a "snapshot" of children with CLP, living in a specific geographical location, and assist in planning intervention programmes.

5.
Int J Audiol ; 55(12): 715-722, 2016 12.
Article in English | MEDLINE | ID: mdl-27686575

ABSTRACT

OBJECTIVE: The parents/caregivers of a newborn play a pivotal role in the process of hearing screening and intervention. The decisions taken by them depend on their knowledge and attitude. The purpose of this study was to review the literature systematically on knowledge and attitude of parents/caregivers towards infant hearing loss and newborn hearing screening. DESIGN: A systematic search was conducted using electronic databases for the periods from 1990 to March 2016. Two authors scrutinized the studies and extracted the data based on predetermined criteria. STUDY SAMPLE: Ten studies. RESULTS: Ear discharge was correctly identified as a risk factor for hearing loss along with measles, drugs/medication, family history, congenital causes and noise exposure. The studies revealed mixed results for knowledge about newborn hearing screening. Overall, the parents/caregivers showed positive attitudes towards hearing screening and intervention options. However, due to heterogeneity in the studies, it's hard to derive a conclusion. CONCLUSIONS: The present review sheds light on the common areas of misconception among parents/caregivers about risk factors of infant hearing loss and newborn hearing screening. The review also draws attention to the need to have more studies exploring this knowledge and attitude of parents/caregivers among diverse populations.


Subject(s)
Caregivers/psychology , Health Knowledge, Attitudes, Practice , Hearing Tests/psychology , Neonatal Screening/psychology , Parents/psychology , Female , Hearing Loss/diagnosis , Hearing Loss/psychology , Hearing Tests/methods , Humans , Infant, Newborn , Male , Neonatal Screening/methods , Surveys and Questionnaires
6.
Ann Hum Genet ; 80(1): 11-9, 2016 Jan.
Article in English | MEDLINE | ID: mdl-26620415

ABSTRACT

Mutations in the gap-junction gene Cx30 (Connexin30, GJB6) are a known cause of hearing loss. Here, we report our findings on a large multigeneration family in which severe to profound sensorineural hearing impairment is associated with a variety of skin-related anomalies. Genome-wide analysis of the family showed that the locus maps to chromosome region 13ptel-q12.1 and that a novel mutation, p.N54K, in Cx30, cosegregates with the phenotype. Unlike wild-type Cx30, p.N54K Cx30 is predominantly localized in the cytoplasm and does not permit transfer of neurobiotin, suggesting improper cellular localization and abolishment of gap-junction activity.


Subject(s)
Connexins/genetics , Hearing Loss, Sensorineural/genetics , Skin Diseases, Genetic/genetics , Biotin/analogs & derivatives , Biotin/metabolism , Connexin 30 , DNA Mutational Analysis , Female , Genetic Linkage , Humans , Ichthyosis/genetics , Keratoderma, Palmoplantar, Diffuse/genetics , Male , Pedigree , Phenotype
7.
Acta Crystallogr Sect E Struct Rep Online ; 67(Pt 9): o2354, 2011 Sep 01.
Article in English | MEDLINE | ID: mdl-22058969

ABSTRACT

The title compound, C(13)H(10)OS(2), exhibits twists between the central C(3)O and ethene residues [O-C-C-C torsion angles = -8.4 (3) and 11.8 (3)°], and between the ethene and adjacent thio-phenyl residues [C-C-C-C torsion angles = -4.2 (3) and 10.5 (3)°]. As a result, the mol-ecule is non-planar, the dihedral angle formed between the terminal thio-phenyl groups being 15.45 (10)°. The presence of C-H⋯O inter-actions involving the bifurcated carbonyl O atom leads to supra-molecular arrays in the ac plane. These are linked into a three-dimensional architecture by C-H⋯π inter-actions involving both thio-phenyl residues.

8.
Indian J Otolaryngol Head Neck Surg ; 63(1): 32-9, 2011 Jan.
Article in English | MEDLINE | ID: mdl-22319714

ABSTRACT

Total thyroidectomy (TT) is a surgical procedure which involves complete removal of the thyroid gland, usually done in massive goitre compressing the trachea and esophagus, hyperthyroidism and carcinoma of thyroid gland. Laryngeal nerve damage is one of the most feared complications after TT which can lead to permanent changes in voice. Recent research suggests the occurrence of voice changes without any visible laryngeal nerve damage. Present study attempts to compare the pre and post-operative voice characteristics in individuals with total thyroidectomy without any laryngeal nerve damage. A total of 27 subjects (21 females and 6 males) who underwent total thyroidectomy participated in the study. Their recorded phonation of vowel/a/was subjected to two types of analyses viz. Perceptual analysis (using CAPE-V rating scale) and Acoustic analysis (using Multi Dimensional Voice Profile). Results of perceptual analysis indicated slight decrease in overall severity, roughness and breathiness and a slight increase in strainness, in only males. Acoustic analysis findings supported perceptual results with minimal changes in most of the parameters. The results suggest that after total thyroidectomy, in the absence of visible laryngeal nerve damage, functional changes in voice are minimal and temporary in nature. This study provides an insight to Otolaryngologists and Speech Language Pathologists about the voice characteristics in individuals with thyroidectomy, enabling them to formulate appropriate therapy protocol for this population. It further attempts to sensitize surgeons and physicians on the need for referral of this population to Speech Language Pathologist in the event of dysphonia.

9.
Indian J Palliat Care ; 17(3): 238-40, 2011 Sep.
Article in English | MEDLINE | ID: mdl-22346050

ABSTRACT

Buccal carcinoma is one of the most common malignant neoplasms among all oral cancers in India. Understanding the role of speech language pathologists (SLPs) in the domains of evaluation and management strategies of this condition is limited, especially in the Indian context. This is a case report of a young adult with recurrent squamous cell carcinoma of the buccal mucosa with no deleterious habits usually associated with buccal mucosa carcinoma. Following composite resection, pectoralis major myocutaneous flap reconstruction, he developed severe oral dysphagia and demonstrated unintelligible speech. This case report focuses on the issues of swallowing and speech deficits in buccal mucosa carcinoma that need to be addressed by SLPs, and the outcomes of speech and swallowing rehabilitation and prognostic issues.

10.
Int J Pediatr Otorhinolaryngol ; 64(2): 105-10, 2002 Jun 17.
Article in English | MEDLINE | ID: mdl-12049823

ABSTRACT

OBJECTIVE: To find out the prevalence and causes of hearing impairment among children of school-entry age, in rural areas of coastal south India. METHODS: The study adopted the World Health Organization (WHO) guidelines viz., "The Prevalence of Ear and Hearing Disorders Protocol". A total of 855 children studying in the first year of school were examined using a Portable Pure Tone Audiometer and an Otoscope. Children with hearing impairment were re-examined to find out the type of hearing impairment. Mothers of all children were interviewed in their homes, in order to obtain details of socio-economic status, family history and history of consanguinity. RESULTS: Hearing impairment was detected in 102 children (11.9%) and impacted wax was found to be the most common cause of hearing impairment (86.3%). On re-testing, it was predominantly conductive hearing impairment (81.6%) observed among 74 of these children. The prevalence of hearing impairment was significantly lower among children belonging to high socio-economic status (P=0.0036). CONCLUSIONS: Hearing impairment and preventable ear diseases were found to be important health problems among children of school-entry age group in this region. Regular screening of children of school-entry age will ensure that children begin their school-life without this disability.


Subject(s)
Hearing Disorders/diagnosis , Hearing Disorders/epidemiology , Age Distribution , Child , Child, Preschool , Ear Diseases/diagnosis , Ear Diseases/epidemiology , Female , Humans , India/epidemiology , Male , Otoscopes , Population Surveillance , Prevalence , Probability , Risk Factors , Rural Population , Sampling Studies , Sex Distribution
11.
J Biol Chem ; 261(29): 13617-23, 1986 Oct 15.
Article in English | MEDLINE | ID: mdl-3020038

ABSTRACT

Modelling studies with beta-endorphin have clearly demonstrated that an amphiphilic secondary structural segment is a salient feature of the biologically active conformation of this 31-residue opioid peptide hormone. Here, we have initiated the synthesis of peptide models using unnatural building blocks by designing a beta-endorphin analogue (peptide 6) in which the hydrophilic linker region between the NH2-terminal enkephalin (residues 1-5) and the COOH-terminal helix (residues 10-28, sequence identical to that of peptide 3 in region 13-31, Fig. 1) consists of four units of gamma-amino-gamma-hydroxymethylbutyric acid connected by isopeptidic linkages. Peptide 6 has physical properties similar to that of peptide 3, as shown by surface monolayer and circular dichroism studies. The binding affinities of the two peptides to delta- and mu-receptors are also similar. In rat vas deferens assays, the present model is equipotent to peptide 3. The most striking result of all is the potent analgesic activity displayed by peptide 6 when injected intracerebroventricularly into mice. The potencies of peptides 6 and 3 are comparable in these assays. These studies clearly illustrate that one can use unusual building blocks to construct structural regions of synthetic analogues and still preserve the biological activity of peptide hormones.


Subject(s)
Endorphins/chemical synthesis , Peptides/chemical synthesis , Analgesics , Animals , Endorphins/metabolism , Endorphins/pharmacology , Indicators and Reagents , Male , Muscle Contraction/drug effects , Peptides/metabolism , Peptides/pharmacology , Protein Conformation , Rats , Rats, Inbred Strains , Receptors, Opioid/metabolism , Structure-Activity Relationship , Vas Deferens/drug effects , beta-Endorphin
12.
Biochemistry ; 23(16): 3590-8, 1984 Jul 31.
Article in English | MEDLINE | ID: mdl-6477886

ABSTRACT

The compound 2-bromo-3-(p-hydroxyphenyl)-1-propene (I) is a substrate of dopamine beta-hydroxylase from adrenal medulla, and the product has been identified by mass spectrometry as 2-bromo-3-hydroxy-3-(p-hydroxyphenyl)-1-propene (II). Compound I also inactivates dopamine beta-hydroxylase in a mechanism-based fashion. Thus, in acetate buffer at pH 5.0, inactivation by I exhibits saturation kinetics with a KD = 4.5 microM and kinact = 0.09 min-1. The inactivation is strictly dependent on O2 and a reducing agent (ascorbate or ferrocyanide) and is irreversible with no reactivation occurring upon prolonged dialysis or passage through a gel filtration column. The observed rate of inactivation at [I] = 4.5 mM (pH 5.5) increases from 0.045 to 0.17 min-1 when [O2] is increased from 0.25 to 1.2 mM. Norepinephrine affords competitive protection against inactivation of enzyme by I. In initial velocity experiments, I is a linear competitive inhibitor vs. tyramine. The log Kis vs. pH profile is flat while the log kinact vs. pH profile has an inflection corresponding to a group with a pKa of 5.7 +/- 0.1. These data demonstrate that an enzymic group in its protonated form is involved in the inactivation reaction and not in the binding of I to the enzyme. In addition, inactivation requires a catalytically competent enzyme, inasmuch as no inactivation occurs when Cu2+-free enzyme is incubated with I in the presence of ascorbate and O2.(ABSTRACT TRUNCATED AT 250 WORDS)


Subject(s)
Dopamine beta-Hydroxylase/antagonists & inhibitors , Phenols/pharmacology , Adrenal Medulla/enzymology , Animals , Apoenzymes/antagonists & inhibitors , Cattle , Chromaffin Granules/enzymology , Copper/pharmacology , Hydrogen-Ion Concentration , Kinetics , Oxidation-Reduction , Phenols/chemical synthesis
13.
J Biol Chem ; 259(11): 6925-30, 1984 Jun 10.
Article in English | MEDLINE | ID: mdl-6547138

ABSTRACT

Three substrate analogs of dopamine beta-hydroxylase, viz. 2-X-3-(p-hydroxyphenyl)-1- propenes (where X = Br, Cl, H), have been synthesized, and all behave as substrates requiring O2 and ascorbate for the enzyme-catalyzed hydroxylation reaction. The products have been characterized by mass spectrometry as the respective 2-X-3-hydroxy-3-(p-hydroxyphenyl)-1- propenes . The relative kcat values for these compounds at pH 5.5, 0.25 mM O2 are 49 min-1 (2-H), 8.6 min-1 (2-Cl), and 7.0 min-1 (2-Br). All three compounds have the characteristics of mechanism-based inhibitors of dopamine beta-hydroxylase since incubation of enzyme with these compounds under turnover conditions leads to a time-dependent loss of activity. The kinact values at pH 5.5, 0.25 mM O2 are 0.08, 0.20, and 0.51 min-1, respectively, for the 2-Br-, 2-Cl-, and 2-H-substituted analogs. No reactivation was observed after exhaustive dialysis of enzyme inactivated by 2-Br-3-(p-hydroxyphenyl)-1-propene, suggesting irreversible inactivation of dopamine beta-hydroxylase.


Subject(s)
Dopamine beta-Hydroxylase/antagonists & inhibitors , Phenols/pharmacology , Adrenal Medulla/enzymology , Animals , Ascorbic Acid/metabolism , Cattle , Chromatography, High Pressure Liquid , Kinetics , Mass Spectrometry , Oxygen/metabolism , Phenols/chemical synthesis
14.
J Biol Chem ; 259(3): 1607-15, 1984 Feb 10.
Article in English | MEDLINE | ID: mdl-6319404

ABSTRACT

Dopamine beta-hydroxylase was incubated with p-hydroxybenzyl cyanide, ascorbate, and O2 and the products of the hydroxylation reaction were monitored by high performance liquid chromatography. At early times, p-hydroxymandelonitrile was the sole product but this compound slowly decomposed to p-hydroxybenzaldehyde and cyanide. Dopamine beta-hydroxylase was also inhibited under these reaction conditions but the amount of cyanide produced was insufficient to account for the extent of enzyme inhibition. Incubation of dopamine beta-hydroxylase with [ring-3H]p-hydroxybenzyl cyanide, ascorbate, and O2 resulted in incorporation of detectable radiolabel into enzyme only when 100% O2 (0.4 X Km) was present. The amount of incorporated radiolabel was substoichiometric with respect to enzyme subunits (approximately 30%) and also did not correlate with the total amount of inhibited dopamine beta-hydroxylase. These data suggest two different modes of inhibition: covalent-adduct formation at early times and inhibition due to cyanide generated at the active site. Separate K14CN binding studies with dopamine beta-hydroxylase corroborated the latter suggestion since 2 mol of cyanide were bound per tetramer. Tyramine stabilized [14C]cyanide binding to dopamine beta-hydroxylase, consistent with the lack of enzyme reactivation observed under certain conditions (Colombo, G., Giedroc, D. P., Rajashekhar, B., and Villafranca, J. J. 1984) J. Biol. Chem. 259, 1601-1606). EPR data for dopamine beta-hydroxylase-bound Cu2+ directly demonstrated that a quaternary complex with tyramine and cyanide was formed, since the spectrum of dopamine beta-hydroxylase-Cu2+-tyramine-cyanide is distinct from that of dopamine beta-hydroxylase-Cu2+-cyanide and dopamine beta-hydroxylase-Cu2+-tyramine. A comprehensive mechanism for dopamine beta-hydroxylase inhibition by benzyl cyanides is presented.


Subject(s)
Acetonitriles/pharmacology , Dopamine beta-Hydroxylase/antagonists & inhibitors , Animals , Cattle , Electron Spin Resonance Spectroscopy , Kinetics , Protein Binding , Substrate Specificity , Tyramine/pharmacology
15.
J Biol Chem ; 259(3): 1593-600, 1984 Feb 10.
Article in English | MEDLINE | ID: mdl-6693426

ABSTRACT

A series of benzyl cyanide analogs have been studied as substrates and inhibitors of dopamine beta-hydroxylase to extend our initial report (Baldoni, J. M., and Villafranca, J. J. (1980) J. Biol. Chem. 255, 8987-8990) which showed that p-hydroxybenzyl cyanide was a suicide substrate of dopamine beta-hydroxylase. Thus, the appVmax values for benzyl cyanide analogs decrease in the order p-OH greater than m-OH greater than H much greater than p-OCH3,m-OCH3; the m-OH, m-OCH3 and p-OCH3 analogs are competitive inhibitors versus tyramine in initial velocity studies. The Vmax values for tyramine and p-hydroxybenzyl cyanide are nearly identical at saturating O2 and ascorbate (pH 5.0, 37 degrees C) but the Km for O2 is 0.14 and 2.8 mM, respectively, with tyramine and p-hydroxybenzyl cyanide. Studies of the pH dependence of log V/K for tyramine show two pKa values of 5.2 and 5.8 while for m-hydroxybenzyl cyanide the values are 5.3 and 5.9. The log Vmax profile shows one pKa of 5.9 with tyramine as substrate. Thus, nearly identical enzymic groups are involved in binding and/or catalysis with these two substrates. All the benzyl cyanide analogs are suicide inactivators of dopamine beta-hydroxylase. With m-hydroxybenzyl cyanide, the partition between catalysis and inactivation (kcat/kinact) changed from approximately 600 to approximately 17 as the pH varied from 5.0 to 6.7. The log kinact versus pH profile shows one pKa value of 6.0, suggesting that an enzymic group must be deprotonated for maximal inactivation. Copper was essential for the suicide inactivation of dopamine beta-hydroxylase by benzyl cyanides and kinetic studies of partially inhibited dopamine beta-hydroxylase (approximately 50%) showed that inactive enzyme molecules were completely inactive. The following papers in this series discuss the partial reactivation of suicide-inhibited dopamine beta-hydroxylase and the stoichiometry of inactivation by benzyl cyanide analogs.


Subject(s)
Benzyl Compounds/pharmacology , Cyanides/pharmacology , Dopamine beta-Hydroxylase/metabolism , Adrenal Medulla/enzymology , Animals , Cattle , Copper/analysis , Hydrogen-Ion Concentration , Kinetics , Oxygen Consumption , Structure-Activity Relationship , Substrate Specificity
16.
J Biol Chem ; 259(3): 1601-6, 1984 Feb 10.
Article in English | MEDLINE | ID: mdl-6693427

ABSTRACT

Several ring-substituted benzyl cyanides lead to inactivation of dopamine beta-hydroxylase during catalysis. With m-hydroxybenzyl cyanide, maximal inactivation occurs when an enzyme group with a pK alpha of 6.0 +/- 0.2 is ionized (Colombo, G., Rajashekhar, B., Giedroc, D. P., and Villafranca, J.J. (1984) J. Biol. Chem. 259, 1593-1600). This paper reports studies conducted to determine the stability of inactivated dopamine beta-hydroxylase. Inactivation of the enzyme by m-hydroxybenzyl cyanide at pH 6.4 is halted by lowering the pH to approximately 5.0 with acetate, fumarate, pyridine, or phosphate buffer in the presence of tyramine. However, if tyramine is omitted, reactivation occurs. The extent of reactivation is dependent upon the final pH value and buffer used to adjust the pH. Reactivation is observed as the pH is lowered from 6.4 to below 5.7 with acetate, fumarate, or HCl. With phosphate, reactivation occurs at any pH value from 6.9 to 4.5 but is greater at lower pH values. Thus, inactivation and reactivation have opposite pH dependencies. Also, reactivation is dependent upon the elapsed time of inactivation. At early times, no reactivation is observed when phosphate is used to adjust the pH, but reactivation is observed later in the inactivation reaction. Reactivation to 100% of the original activity does not occur under these conditions. These data suggest at least two inactivation mechanisms by benzyl cyanides: 1) formation of a tightly bound or covalent adduct between dopamine beta-hydroxylase and enzyme-bound mandelonitrile (or a rearranged form of this molecule), and 2) reversible inhibition resulting from cyanide binding to enzyme-Cu2+. Studies with radiolabeled p-hydroxybenzyl cyanide as well as EPR studies of dopamine beta-hydroxylase-Cu2+ are reported in the following paper.


Subject(s)
Benzyl Compounds/pharmacology , Cyanides/pharmacology , Dopamine beta-Hydroxylase/antagonists & inhibitors , Adrenal Medulla/enzymology , Animals , Cattle , Dopamine beta-Hydroxylase/metabolism , Enzyme Activation , Hydrogen-Ion Concentration , Kinetics , Structure-Activity Relationship
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