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Biomedical subjects

N Tian

Publications and source records attributed to N Tian.

27 records · Page 2Linked to original sources
PubMed1991

Spectral characteristics of electroretinogram in X-linked dichromats--a preliminary study.

Spectral characteristics of X-linked Dichromats (13 protanopes, 20 deuteranopes) were studied with spectral ERG. The results are as follows: The maximal spectral response of the b-wave in protanopes tended to shift toward the short wavelength side and the sensitivity to long wavelengths decreased obviously. The ratio value of the amplitude in 500 nm and in 620 nm (500/620) was greater in the protanope than that in the normal subject. Like the normals, the maximal response of the b-wave in deuteranopes appeared at 550-570 nm. Though the differences between the normals and deuteranopes in the ratio values (600/620 and b/a at 520 nm) were found by means of analysing a, b wave responses at each wavelength, most of the ratio values (600/620 or b/a at 520 nm) overlapped between the normals and deuteranopes. We established the discriminant function or score made up by the combination of two ratios basing on Fisher's rule, which can raise the diagnostic rate for deuteranopes.

Adolescent↗
PubMed1991

Contrast sensitivity in amblyopia.

Contrast sensitivity function (CSF) for sinusoid gratings of varying spatial frequencies was determined for each eye of 21 cases with unilateral amblyopia. The CSF of all amblyopic eyes, except one, showed reduced sensitivity when compared with the non-amblyopic eye of the same person. The curve showed reduction more significantly at middle and high spatial frequencies. The cut-off frequency was shifted toward lower spatial frequencies. The relationship between CSF and various degree of amblyopia was also discussed.

Adolescent↗
PubMed1990

[Contrast sensitivity in open-angle glaucoma].

The contrast sensitivity function (CSF) was determined with vertical stationary sinusoidal gratings of 6 spatial frequencies of 0.5, 1, 3, 6, 11.4 and 22.8 cycles/degree in 31 patients (50 eyes) with open-angle glaucoma. The data of CSF were compared with visual acuity and visual field determinations. It was found that CSF could be abnormal in subjects with visual acuities of 1.0 or better and normal visual fields; the patterns of CSF loss were varied, and there was a linear correlation between the area of the visual field and the CSF value. The results suggested that the measurement of CSF provided basis for the judgment of visual functional changes in the clinical observation of glaucoma.

Adolescent↗
PubMedDate not supplied

Functional properties of a metabotropic glutamate receptor at dendritic synapses of ON bipolar cells in the amphibian retina.

Perforated patch-voltage and current-clamp recordings were obtained from ON bipolar cells in the amphibian retinal slice preparation. The currents produced by the photoreceptor transmitter were compared to the currents produced by selective metabotropic glutamate agonists: L-2-amino-4-phosphonobutyrate (L-AP4, APB) and IS,3R 1-amino-1,3 cyclopentanedicarboxylic acid (1S, 3R ACPD). Both agonists produced currents that were very similar to that produced by the photoreceptor transmitter in terms of conductance and reversal potential. The similarities suggest that the metabotropic glutamate receptors are functionally localized to the synaptic region of ON bipolar dendrites. The synaptic conductance rarely exceeded the non-synaptic conductance. The mean input resistance of ON bipolar neurons was 770 M omega in the light and 1.2 G omega in the dark. The average light-regulated synaptic conductance was 57% of the non-synaptic conductance. The L-AP4 regulated conductance averaged 77% of the non-synaptic conductance, while the 1S, 3R ACPD regulated conductance averaged 95% of the non-synaptic conductance. This balance between synaptic and non-synaptic conductance indicates that the synapse will not shunt the cell and the conductance ratio serves to maximize incremental gain at the photoreceptor to ON bipolar synapse. This conductance mechanism makes the ON bipolar cell well equipped to relay rod signals.

Aminobutyrates↗