Biomedical subjects

Z Chiti

Publications and source records attributed to Z Chiti.

3 recordsLinked to original sources

PubMed2006

An integrated, temporal study of the behavioural, electrophysiological and neuropathological consequences of murine prion disease.

We have conducted an integrated study of ME7 prion disease by examining the electrophysiological and neuropathological features of hippocampal slices from behaviourally characterised C57Bl/6J mice 12, 14, 16, 18, 20 and 24 weeks after intracerebral micro-injection of ME7 or normal brain homogenate. We describe the pathogenesis of ME7 as a three-stage process. STAGE ONE: PrPSc deposition, synaptic pathology and abnormal synaptic plasticity. STAGE TWO: Onset of behavioural changes, exemplified by an increase in open-field activity, enhancement of the slow AHP and development of vacuolation. Membrane depolarisation is also an early feature, but its exact timing remains to be confirmed. STAGE THREE: Clinical disease, substantial neurodegeneration and further disruption of the action potential profile. We suggest that the mechanisms underlying the electrophysiological changes of Stages one and two may provide novel approaches to treatment of prion disease, and that those seen in Stage three may be relevant to neurodegenerative diseases more generally.

Action Potentials↗

PubMed2002

Effect of darkness on inner retinal hypoxia in diabetes.

It has been postulated that diabetic retinopathy might be initiated by hypoxia during the hours of darkness. Oscillatory potentials, which reflect inner retinal function, are reduced in diabetic patients. We tested the effect of oxygen inhalation on the amplitude of these oscillatory potentials after dark adaptation in seven patients with type 2 diabetes and eight controls. We found that the decreased oscillatory potentials induced by dark adaptation in the diabetic patients increased during oxygen inhalation to an amplitude that was not significantly different from that of the controls before oxygen. Oscillatory potentials in the controls were unaffected by oxygen. This finding strengthens support for the suggestion that diabetic patients might benefit from sleeping with night-time illumination.

Administration, Inhalation↗

PubMed2001

The s-cone PHNR and pattern ERG in primary open angle glaucoma.

PURPOSE: To compare the sensitivity of the photopic negative response (PhNR) from the shortwave (S)-sensitive and the long (L)- and medium (M)-wave-sensitive cone electroretinograms (ERGs), with the pattern electroretinogram (PERG) in the early stages of primary open-angle glaucoma (POAG). METHODS: Eighteen patients under treatment for diagnosed POAG and 19 normal control subjects were investigated. S-cone ERGs were elicited using adaptation to 650-nm light to suppress L-cone activity, and substitution between 450 nm and 535 nm to silence M-cone response at luminances higher than rod saturation. PhNRs from the L&M-cone pathways were elicited by a 200-msec pulse of red light (650 nm) on a continuous blue (450 nm) background. PERGs were recorded in accordance with the International Society for Clinical Electrophysiology of Vision (ISCEV) standard. RESULTS: Each method showed a statistically significant difference in the two groups. The S-cone PhNR was the most sensitive test and provided the most statistically significant results, with the largest area enclosed by the receiver operating characteristic (ROC) curve. CONCLUSIONS: The findings indicate that all three types of ERG may be useful in glaucoma investigation. The L- and M-cone PhNRs may have a role in monitoring established glaucoma. The previously reported high sensitivity of the PERG was confirmed. Extensive diffuse damage to S-cone bipolar and bistratified ganglion cells appears to occur at a very early stage in POAG, owing to a pressure-related mechanism, and the S-cone PhNR was the most sensitive test. It may in future have an important role in diagnosis and monitoring of early glaucoma. Further investigation of this possibility is recommended.

Aged↗