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Biomedical subjects

A Negi

Publications and source records attributed to A Negi.

At least 109 records · Page 6Linked to original sources
PubMed1982

Effects of biological stimuli on the viscosity of the vitreous.

Changes in the physical properties of the vitreous induced by various biological stimuli were investigated with Cannon-Fenske kinematic and cone-plate rotary viscometers. Heating greatly decreased the viscosity of the human vitreous, the critical temperature being between 50 degrees C and 60 degrees C. Freezing also affected the viscosity, but less so than heating. Viscosity of hyaluronic acid was also decreased by heating to approximately 60 degrees C. Preliminary incubation with hyaluronidase made the viscosity of both the vitreous and hyaluronic acid heat-stable. Lens extraction decreased vitreous viscosity markedly, suggesting a decrease of hyaluronic acid concentration and/or a lowering of hyaluronic acid molecular weight. Vitreous haemorrhage resulted in decreased vitreous viscosity. Cryoretinopexy at the level employed in this study induced little change in vitreous viscosity, while retinal diathermy caused a moderate decrease. In the course of vitreous haemorrhage and retinal diathermy, a return towards normal of the viscosity was observed, suggesting the presence of local hyaluronic acid production.

Aged↗
PubMed1982

Pressure profile of ophthalmic surgical procedures: an experimental study on the rabbit eye.

A balloon sensor was implanted in the posterior wall of the rabbit eye, and pressure fluctuation during several surgical procedures was monitored. Temporary IOP increase during digital massage sometimes reached near 100 mm Hg. Pressure increase during incision on the cornea was quite high, while corneal suturing, lens extraction, iridectomy, and open-sky vitrectomy induced minor fluctuating pressure on the posterior wall. Diathermy coagulation and scleral incision during simulated retinal detachment surgery increased IOP, exceeding 50 mm Hg and sometimes reaching 100 mm Hg.

Animals↗
PubMed1981

Effects of intraocular irrigating solutions on the electroretinographic b-wave.

We studied the effects of physiologic saline, lactated Ringer's solution, and BSS (balanced salt solution) on the electroretinogram of the rabbit in vitro. The b-wave amplitudes decreased when the retina was incubated in lactated Ringer's solution or BSS. These amplitudes recovered to 60% to 70% of the original level when the retina was re-immersed in the control medium. With physiologic saline, the b-wave amplitude recovered only to about 30% after 20 minutes of incubation, and recovery was nil after 60 minutes of incubation time. Extended contact with physiologic saline produced permanent damage to the retina. Bicarbonate ion and glucose were shown to be essential for maintaining the ERG amplitude.

Animals↗
PubMed1981

Ion movement in and out of the vitreous space after vitrectomy. An experimental study on the in vivo eyecup preparation of rabbits.

Osmotic pressure and ion movements in and out of the vitreous space after open-sky vitrectomy were studied in the in vivo eyecup of rabbits. The osmotic pressure of several hypo-osmotic solutions rose over a period of time by the penetration of ions from the surrounding tissue; increases in the concentration of sodium, chloride, potassium, and calcium were documented. Appearance and disappearance of ions were independent of the total osmolarity and depended on the concentration gradient for each ion.

Animals↗
PubMed1980

Application of twin flash stimuli for some mascular diseases isolation of local responses by twin flashes.

Double flash ERG was examined for patients with visual loss from macular and optic nerve disorders, and the responses were compared. K values (= (B1-B2))/B1 x 100) of the former were larger than normal values when the stimulus intervals were between 200 and 500 mseconds, and abnormality of K values seemed to correspond to the functional impairment of macula. On the other hand, K values of the patients with optic nerve diseases remained in the normal range. These facts indicate that double flash ERG is a very useful method to estimate the cone function clinically, and can be employed as a routine examination for patients with suspected cone dysfunction.

Adult↗