Biomedical subjects

J Bilotta

Publications and source records attributed to J Bilotta.

25 records · Page 2Linked to original sources

PubMed1989

Spatiospectral properties of goldfish retinal ganglion cells.

1. Responses of single ganglion cells from isolated goldfish retinas were recorded during presentation of various spatial and spectral stimuli. Each cell was classified along several spatial [spatial summation class, spatial contrast sensitivity function (CSF), and response to contrast] and spectral (Red-ON, Red-OFF or Red-ON/OFF, and spectral opponency/nonopponency) dimensions. 2. Linearity of spatial summation was determined from responses to contrast-reversal sinusoidal gratings positioned at various locations across the receptive field of the cell. CSFs were derived from responses to sinusoidal gratings of various spatial frequencies and contrasts, drifting across the cell's receptive field at a rate of 4 Hz. Response to contrast was determined from responses to variations in contrast of a sinusoidal grating of optimal spatial frequency. Spectral classifications were based on responses to monochromatic stimuli presented separately to the center and surround portions of the receptive field. 3. Linearity of spatial summation (X-, Y-, and W-like) was independent of the cell's spectral properties; for example, an X-like cell could be classified as either a Red-ON, Red-OFF, or Red-ON/OFF center cell and as spectrally opponent or nonopponent. 4. There were differences in response to contrast across spectral categories. Red-OFF center cells were very sensitive to contrast compared with Red-ON center cells. Spectrally nonopponent cells were more responsive to contrast than spectrally opponent cells. 5. There were dramatic differences across the spectral categories in relative sensitivity to low spatial frequency stimuli; however, the spatial resolution (i.e., sensitivity to high spatial frequencies) of each spectral classification appeared to be similar.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1987

Endorphinergic modulation of immune function: potent action of the dipeptide glycyl-L-glutamine.

Glycyl-L-glutamine (GLG), the carboxy terminal dipeptide of B-endorphin, inhibits brainstem neuronal activity. It also occurs along with B-endorphin in pituitary secretory vesicles suggesting a neurosecretory role for this dipeptide. We have evaluated potential immunoregulatory actions of this compound using the Phytohemaglutinin (PHA) blastogenesis and the concanavalin A (ConA) suppressor cell induction assays. GLG in low doses (10(-12) M) enhanced the response of human lymphocytes to PHA induced blastogenesis, however; with higher doses of the dipeptide (10(-7) M) immunosuppression was consistently observed. In the suppressor cell induction assay, when GLG was used together with ConA, we observed a dose-dependent inhibition of suppressor activity. These results clearly indicate that GLG produces a dose dependent bidirectional modulation of at least two indicies of immune function, and confirm the presence of a second pituitary peptide with the potential for potent immunomodulatory action.

Concanavalin A↗

PubMed1987

Contributions of short-wavelength cones to goldfish ganglion cells.

There are conflicting reports about the existence and nature of a short-wavelength cone (S-cone) contribution to ganglion cells in the goldfish retina. The present study sought to resolve these discrepancies by examining the S-cone contribution while recording from single ganglion cells in the excised, isolated goldfish retina. The effect of variations in the retinal preparation (gas content and type of background lighting during recording) on the S-cone input was also examined. Cells were classified into one of three types based on the responses at light onset and offset, when responses were driven only by the long-wavelength cone system (L-cones) of the receptive field's center (L+/-(on-excitation/off-inhibition), L-/+, and L+/+). With rare exceptions, the threshold spectral sensitivities of the centers and surrounds of cells that possessed opposite on and off responses (L+/- and L-/+) exhibited S-cone contributions, either prior to and/or during chromatic adaptation of the middle- and long-wavelength cones; the S-cone response was antagonistic to the L-cone input. The L+/+ center cells also contained a S-cone input, but it was synergistic to the L-cone input at suprathreshold intensities. These findings were robust across all of the retinal preparations employed. The discrepancies in the previous work were probably due to the incomplete classification of cells because of the use of threshold responses only.

Adaptation, Physiological↗

PubMed1986

Modulation of human T-cell suppressor activity by beta endorphin and glycyl-L-glutamine.

beta-endorphin (10(-7) M) induced suppressor cell activity in human peripheral blood lymphocyte cultures comparable to that of concanavalin A (Con A) (60 micrograms/ml). beta-endorphin and Con A, when used together during the induction portion of the suppressor assays, displayed synergistic activity. In contrast, glycyl-L-glutamine, the carboxy terminal dipeptide of beta-endorphin, inhibited development of Con A induced suppressor activity. It appears that the previously reported suppressive effects of beta-endorphin on immune function may be achieved by activation of specific suppressor T cell populations.

Concanavalin A↗

PubMed1984

Renal pressor effect of ethanol in the isolated perfused rat kidney.

These experiments were performed to detect changes in renal function produced by acute infusions of small amounts of ethanol into the isolated kidney of the rat. Ethanol was infused for 10 min beginning at 40 min to reach a final concentration of approximately 80 mg/100 ml in the recirculating perfusate. Control kidneys were perfused for 90 min without the addition of ethanol. Control and ethanol infused kidneys were compared with respect to the following measurements: glomerular filtration rate, urine volume, urine protein concentration, pressure and fractional excretion of sodium, chloride, potassium, calcium and magnesium. Ethanol concentration in the perfusate was measured by gas chromatography. The only parameter affected by these concentrations of ethanol was pressure. During the ten min ethanol infusion, the pressure in the system rose significantly (P less than 0.01) from 110 +/- 0.3 to 120 +/- 2.8 mmHg. After the ethanol infusion, the pressure decreased towards pre-ethanol levels at a faster rate than the decrease in ethanol concentration in the perfusate.

Animals↗

PubMedDate not supplied

Cone contributions to the photopic spectral sensitivity of the zebrafish ERG.

Microspectrophotometry studies show that zebrafish (Danio rerio) possess four cone photopigments. The purpose of this study was to determine the cone contributions to the zebrafish photopic increment threshold spectral-sensitivity function. Electroretinogram (ERG) b-wave responses to monochromatic lights presented on a broadband or chromatic background were obtained. It was found that under the broadband background condition, the zebrafish spectral-sensitivity function showed several peaks that were narrower in sensitivity compared to the cone spectra. The spectral-sensitivity function was modeled with L - M and M - S opponent interactions and nonopponent S- and U-cone mechanisms. Using chromatic adaptation designed to suppress the contribution of the S-cones, a strong U-cone contribution to the spectral-sensitivity function was revealed, and the contributions of the S-cones to the M - S mechanism were reduced. These results show that the b-wave component of the ERG receives input from all four cone types and appears to reflect color opponent mechanisms. Thus, zebrafish may possess the fundamental properties necessary for color vision.

Adaptation, Physiological↗

PubMedDate not supplied

ERG assessment of zebrafish retinal development.

Research has shown that adult zebrafish have a complex visual system, with two possible opponent mechanisms. Anatomically, zebrafish retina develops in a sequential manner and is immature at hatching. The purpose of the present study was to assess zebrafish retinal development using the electroretinogram (ERG). ERG responses to visual stimuli were obtained from 4-5, 6-8, 13-15, and 21-24 days postfertilization (dpf) zebrafish. Individual waveforms were assessed and compared across the four age groups. Spectral-sensitivity functions were calculated for the a- and b-wave components of the ERG response. Results showed that the ERG waveforms and spectral-sensitivity functions varied with age. While the 21-24 dpf subjects had an ERG waveform that was similar to that of adults, the younger subjects did not. Although there were modest differences in the a-wave spectral sensitivity, substantial differences were found in the b-wave spectral sensitivities across the ages. There was a consistent strong response to ultraviolet wavelengths, while across the remaining parts of the spectrum, there was a gradual increase in sensitivity with age. Also, the 21-24 dpf subjects appear to have adult-like U- and S-cone functions, but were missing the L-M and the M-S opponent mechanisms found in the adult. These results support the findings of the anatomical studies and demonstrate that the zebrafish is a useful model for examining the development of retinal function.

Animals↗