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Biomedical subjects

A Gopalakrishna

Publications and source records attributed to A Gopalakrishna.

10 recordsLinked to original sources
PubMed1989

Calcium ion binding to delta- and to beta-crystallins. The presence of the "EF-hand" motif in delta-crystallin that aids in calcium ion binding.

Abnormal levels of endogenous calcium ions are known to induce eye lens opacity, and a variety of causative factors has been proposed, including calcium-mediated aggregation and precipitation of the lens proteins crystallins. We have specifically looked in some detail at the interaction of Ca2+ with various crystallins and its consequences. Lenses incubated in solutions containing 10 mM Ca2+ or 5 mM Tb3+ opacified. Fluorescence titration of crystallins with TbCl3 revealed that this ion binds to delta- and beta-crystallins in solution. Equilibrium dialysis showed that four Ca2+ ions bind to one delta-crystallin tetramer with an affinity of 4.3 x 10(3) M-1. Analysis of the amino acid sequence of delta-crystallin reveals the presence of a calmodulin-type "helix-loop-helix" or "EF-hand" calcium ion binding conformational motif in the region comprising residues 300-350. This is a novel feature of the molecule not reported so far. No other crystallins appear to have this motif. beta-Crystallin also binds four Ca2+ ions/aggregate unit of mass 160 kDa, with an affinity of 2.6 x 10(3) M-1, presumably in the midregion of the molecule that is rich in anionic and polar residues. Circular dichroism spectroscopy shows that the binding of calcium ion leads to subtle conformational changes in the molecules, notably in the tertiary structure.

Amino Acid Sequence↗
PubMed1985

An objective study of the dimensions of the ischial pressure point and its correlation to the occurrence of a pressure sore.

A simple non-invasive technique has been used to study the dimensions of the ischial pressure point in normal and paraplegic individuals. The same technique charts the surface area of the gluteal impression. The data obtained in these two groups of patients (normal and paraplegic) have been analysed to see if it is possible to predict the greater susceptibility of certain individuals to suffer from pressure sores over the ischial tuberosity.

Buttocks↗
PubMed1984

Middle ear function in cleft palate.

This study is based on an impedence audiometric evaluation of three groups of patients-20 with un-operated cleft palate, 28 normal subjects as controls and 20 operated cleft palate patients. Four major parameters have been analysed: middle ear pressure, static compliance, acoustic reflex and tympanometry. It was confirmed that in the normal child Eustachian tube function improves with growth and the critical age when the middle ear pressure becomes normal in almost all the normal children is 5 to 6 years. This process of improvement is disturbed in the presence of a cleft palate. Poor Eustachian tube function, evidenced by persistent negative middle ear pressure, continues to be commonly seen in the older subjects with un-operated cleft palates. The static compliance that reflects the elasticity of the conducting mechanism of the middle ear is poorer in cleft palate patients. It was also observed that when the cleft palate had been repaired before the age of 6 years, Eustachian tube function improved significantly in the older age group as shown by the lower incidence of negative middle ear pressure and Eustachian tube block. The high incidence of serous otitis media is apparently unaffected by surgery on the cleft palate and is responsible for some degree of hearing loss encountered in the older patients with operated cleft palates. Thus the incidence of hearing loss as studied by acoustic reflex is higher in all age groups in the presence of a cleft palate.

Acoustic Impedance Tests↗
PubMed1982

The use of de-epithelialised "turn over" flaps in the hand.

Two examples are presented of the application of the principles of de-epithelialised "turn over" flaps in the hand. These flaps were used to resurface a post-infective volar skin defect on a finger and to correct an adduction contracture in the first web space of the hand. The reasons for their use and their advantages are briefly discussed.

Adult↗