Biomedical subjects

K H Ma

Publications and source records attributed to K H Ma.

4 recordsLinked to original sources

PubMed1990

Aural tuberculosis.

Tuberculous otitis media can present with very nonspecific clinical features. Five cases of tuberculous otitis media are reviewed over a period of 5 years. Significant clinical findings included the presence of abundant granulation tissue in mastoids with good pneumatization, cervical lymphadenopathy, profound hearing loss, facial palsy, and foci of tuberculous infection at other sites. Histologic examination of granulation tissue showed tuberculoid granulomata in all cases. The mycobacteria could be identified in two of the biopsies but not on cultures. Other conditions that give rise to tuberculoid granulomata should be searched for in cases where the myobacteria cannot be identified. In one case, diagnosis was delayed because the operative specimen was neither histologically examined nor sent for culture. Persistent otorrhea and recurring granulomata after mastoidectomy provided other important clinical features. All cases responded well to antituberculous chemotherapy. Surgery is indicated nowadays for facial palsy, subperiosteal abscess, fistula formation, labyrinthitis, intracranial complication, or infrequency for resistant mycobacterial infection caused by the non-tuberculous mycobacteria.

Adolescent↗

PubMed1988

Facial nerve tumours or 'all that palsies is not Bell's'.

Most cases of facial nerve palsy are idiopathic, that is to say, Bell's palsy. A few cases are due to tumours on the facial nerve. Early diagnosis will avoid extensive tissue destruction with loss of hearing and lead to satisfactory facial reinnervation. Five cases are presented. In three, there was a significant delay in diagnosis. A facial nerve tumour generally presents as a paralysis of slow onset and the degree of paralysis often fluctuates. Diagnosis can be made in most cases by high resolution CT.

Adolescent↗

PubMed1988

Osteoradionecrosis of the temporal bone: a surgical technique of treatment.

Osteoradionecrosis of the temporal bone is a well-documented complication of radiotherapy to the ear, with potentially lethal complications. Three cases of advanced disease, treated surgically, are presented. In two of these, subtotal petrosectomy with blind-sac closure of the external auditory canal was carried out via an anterior approach. The enclosed space was obliterated with pedicled temporalis muscle. Primary healing took place. One case was similarly obliterated using a prolonged posterior incision. The wound broke down, requiring a microvascular free flap for closure. Radiotherapy jeopardizes the viability of skin flaps. An anterior incision bases the flap behind on the occipital and postauricular arteries. When radiotherapy has been used, this incision has theoretical and practical advantages over a standard posterior incision.

Bone Diseases↗

PubMed1985

The reactivity of the sulphydryl groups of chorismate mutase/prephenate dehydratase--a bifunctional enzyme of phenylalanine biosynthesis in Escherichia coli K12.

The reaction of N-ethylmaleimide with chorismate mutase/prephenate dehydratase (chorismate pyruvatemutase/prephenate hydrolyase (decarboxylating) EC 5.4.99.5/EC 4.2.1.51) from Escherichia coli K12, which leads to the preferential inactivation of the prephenate dehydratase activity (Gething, M-J.H. and Davidson, B.E. (1977) Eur. J. Biochem. 78, 111-117), was found to involve only the sulphydryl groups of the enzyme. Determination of the reactivities of the four different cysteine residues indicated that the reaction was not specific for a single residue, although two residues (Cys-216 and Cys-374) were more reactive than the others. The amount of inhibition of the prephenate dehydratase activity approximated in extent to the sum of the stoichiometries of the individual reactions of N-ethylmaleimide with these two cysteine residues. In the presence of either phenylpyruvate, the product of the prephenate dehydratase activity, or cis-aconitate, a competitive inhibitor with respect to prephenate, the prephenate dehydratase activity was substantially protected from inactivation. This protection was concomitant with a significant decline in the reactivities of both Cys-216 and Cys-374. These results are interpreted as indicating that both of these cysteine residues are at, or near to, the prephenate dehydratase active site and are possibly essential for the prephenate dehydratase activity of the enzyme.

Amino Acid Sequence↗