Morphine regulation of a novel uridine diphosphate glucuronosyl-transferase in guinea pig pups following in utero exposure.

The uridine diphosphate glucuronosyltransferases (UGTs) catalyze conjugation reactions between various substrates and glucuronic acid, UDPGA (uridine diphosphate glucuronic acid), within the endoplasmic reticulum. Conjugation with UDPGA (glucuronidation) is an important pathway in the elimination, detoxification, and activation of compounds including steroid hormones, xenobiotics, and quaternary ammonium substrates. The guinea pig, which has a placental structure and a glucuronidation profile for morphine that are similar to the human, serves as a good small animal model to study the ontogeny of UGTs and the effect of in utero exposure to morphine on UGTs. We examined type 2 UGTs expressed in the guinea pig using amplification and cloning of partial cDNAs from liver RNA. Sequence analysis revealed a novel UGT2 (subsequently named UGT2A3),(2) that has a 64% amino acid sequence similarity to a known UGT2.(3) Full-length cDNAs were isolated from a guinea pig liver cDNA library. Tissue distribution of UGT2A3 using Northern blot analysis showed expression of three distinct size UGT2A3 mRNAs with unique expression in liver and small intestine. UGT2A3 mRNA is expressed at high levels in liver and lower levels in kidney and small intestine. In utero exposure to chronic intermittent morphine resulted in the up regulation of mRNA in 7-day-old female pups' liver and kidney as determined by quantitative RT-PCR analysis. The conjugation profile for UGT2A3 using stable expression in CHO cells and thin-layer chromatography demonstrated active conjugation of phenolic substrates. Regulation of UGTs by in utero morphine exposure may play an important role in fetal development.

Contour curvature analysis: hyperacuities in the discrimination of detailed shape.

Curvature discrimination thresholds were measured for a wide range of stimulus curvatures and sizes. Results are compared with an ideal processor of curvature to provide relative efficiencies. The results lead to three major findings. (i) Curved lines may be processed with the same precision as straight lines for decisions of shape, demonstrating a new class of hyperacuity. (ii) High relative efficiencies are obtained for all curved lines with an orientation range of less than 40 deg. (iii) This performance is not however consistent with common processing for straight and curved lines. The results are discussed, and two or possibly three separate processes are suggested as the basis for detailed shape perception.

Collinearity tolerance of cells in areas 17 and 18 of the cat's visual cortex: relative sensitivity to straight lines and chevrons.

Collinearity tolerance and length dependence of orientation tuning were compared in cells recorded from areas 17 and 18 of the lightly anaesthetised cat's visual cortex. Orientation tuning and interaction between receptive field halves of the same cells are reported in the preceding paper and elsewhere (Hammond and Andrews, 1978a, b). In confirmation of previous work, increase in stimulus length was associated with sharper orientation tuning in all simple and hypercomplex cells, and in most complex cells even in the absence of length summation. Cells in areas 17 and 18 were more sharply tuned for chevrons was noticeably skewed compared with tuning for straight lines. In area 17, the best response was always obtained with a straight line of optimal orientation. The two halves of the receptive fields of some cells in area 18 had dissimilar preferred orientations. Even in cells whose receptive field halves were similarly tuned, broadly tuned, or apparently untuned for orientation, simultaneous stimulation of both halves of the receptive field led to substantial sharpening of tuning. In cells with dissimilarly tuned half fields, the skew in chevron tuning was predictable from the orientation tuning of each half of the receptive field. Two area 18 cells responded consistently better to a chevron stimulus than to a straight line of any orientation.

Orientation tuning of cells in areas 17 and 18 of the cat's visual cortex.

Sharpness and symmetry of orientation tuning were quantitatively investigated and compared in ninety-seven cells from areas 17 and 18 of the lightly-anaesthetised feline visual cortex. Halfwidths of orientation tuning at half-height ranged between 5 degrees and 73 degrees for long stimuli, with an extreme exception at 111 degrees (excluding untuned cells). There was a tendency for cells in area 18 to be more broadly tuned than those in area 17, due largely to the relatively sharp tuning of area 17 simple cells. Confirming previous work, simple cells were more sharply tuned than complex cells in area 17. In area 18, there was no clear distinction in sharpness of tuning between complex type 1 cells (equated with area 17 simple cells), complex type 2 cells (equated with area 17 complex cells), or hypercomplex cells. Approximately 60% of cells in both areas were asymmetrically tuned for orientation: ratios of half-widths to either side of the optimal orientation ranged from 1.0-3.0, exceptionally 5.8. Asymmetry of tuning was more marked in area 18 than in area 17, except that area 18 complex type 2 cells as a group were relatively symmetrically tuned for orientation. Occasional cells with different preferred orientations for opposite directions of motion, for each peak of a bimodal response to a single direction, or for each half of the receptive field were also observed. The latter are described in the following paper.

Interaction between receptive field halves of cells in area 18 of the cat's visual cortex.

Interaction between receptive field halves has have investigated in cells from area 18 of the visual cortex of cats light anesthestised with N(2)O/O(2) supplemented with pentobarbitone. Interaction within receptive field halves may be facilitatory additive, partially additive, or subtractive, and the organization in one half-field is not predictable from that in the other. Interaction between half-fields may be facilitatory, additive, partially additive, or subtractive and can not be predicted from interaction within halves.

Gene expression during the development of Bacillus subtilis bacteriophage phi 29. I. Analysis of viral-specific transcription by deoxyribonucleic acid-ribonucleic acid competition hybridization.

The ribonucleic acid (RNA) specified by bacteriophage phi29 was analyzed to determine its composition at various times in the viral lytic cycle. Although viral-specific RNA was detected immediately after infection, a large increase in the rate was observed at 10 min when DNA synthesis began. phi29 was found to resemble other viruses in that gene expression occurred in two stages which could be defined temporally as "early" and "late." Early RNA appeared before the onset of viral deoxyribonucleic acid (DNA) replication and accounted for approximately 40% of the viral genetic potential. This RNA was also present late in the infectious cycle because of the slow turnover rate of phi29-specific RNA (approximately 10 min half-life) and the continued synthesis of much early viral RNA throughout infection. Late RNA was first detected at approximately the same time as viral DNA replication, although late transcription was not dependent upon DNA synthesis. This RNA was only partially displaced by early RNA in the appropriate competition experiments, suggesting that it contained sequences not present in the early class. Expression of viral genes was sensitive to rifamycin throughout the lytic cycle, the sensitivity resulting from a dependence upon the rifamycin phenotype of the host RNA polymerase.

Mesopic increment threshold spectral sensitivity of single optic tract fibres in the cat: cone-rod interaction.

1. Mesopic increment threshold spectral sensitivities of sixty-six on-centre and twenty-five off-centre ganglion cells in the cat were determined by recording from single fibres of the left optic tract at a level posterior to the optic chiasma.2. All units were monocularly driven; receptive fields were located almost exclusively in the right visual half-fields within 30 degrees of the area centralis, but with slight overlap across each retinal mid line to the left half-fields. The extent of field spread to the right temporal hemi-retina was significantly larger than that to the left nasal hemi-retina. Field centre diameters ranged from less than 0.25 degrees for central units to 2 degrees for more peripheral units.3. At high mesopic adaptation of 1 log cd/m(2) all responsive units (forty-four fibres) received mixed cone-rod input. Threshold curves could always be fitted by the absorption spectra of visual pigment 556 together with varying contributions from visual pigment 507, each derived from the Dartnall nomogram.4. Of forty-seven fibres analysed under low mesopic background (0 log cd/m(2)) 92% received similar cone-rod input, being fitted predominantly by visual pigment 507 with slight cone contamination. The remaining 8% received pure rod input and could be matched by visual pigment 507 alone.5. In conclusion, the cat retina presumably contains a single class of cones with absorption maxima at 556 nm, and a single class of rods. Discrepancy between the presumed rod absorption maximum (502 nm) and the low-mesopic sensitivity maxima of tract fibres (507 nm) is considered in terms of tapetal reflectivity, and absorption by ocular media. Both mechanisms input to the great majority of retinal ganglion cells. At high mesopic levels the cone mechanism predominates. At low mesopic levels the rod mechanism predominates. A small proportion of ganglion cells within the central 30 degrees of the retina receive input only from rods, and in these the rod mechanism saturates completely below 1 log cd/m(2).

Suprathreshold spectral properties of single optic tract fibres in cat, under mesopic adaptation: cone-rod interaction.

1. Responses of 122 on-centre or off-centre ganglion cells in cat to suprathreshold monochromatic stimulation have been analysed under mesopic adaptation with white light, recording from their single fibres in the optic tract at a level posterior to the chiasma. Fields described are monocularly driven, located in the right half-fields of either eye, and are all within 30 degrees of the area centralis.2. Retinal receptors are of two types, viz. 556 nm cones and 502 nm rods. At high mesopic adaptation (1 log cd/m(2)) all units receive mixed cone-rod input. Under low mesopic adaptation (0 log cd/m(2)) the great majority receive mixed input; a few receive pure rod input. These results are in agreement with the threshold data (Andrews & Hammond, 1970).3. Peaks of spectral response curves of units, to suprathreshold monochromatic stimuli of different wave-length but equal quantum flux, fall primarily between 550 and 560 nm for high mesopic adaptation, and between 500 and 520 nm for low mesopic adaptation. Peak position depends on the degree of rod or cone contamination, in units treated under high or low mesopic levels respectively.4. Units with cone-rod input to the field centre receive similar but antagonistic cone-rod input to the surround. In units with pure rod input to the field centre, only rods input to the surround.5. Cone and rod components of on-centre discharges are identifiable in terms of colour sensitivity and latency. The cone component is primarily a short-latency, high-frequency, excitatory transient; the rod component is a longer latency, lower frequency, maintained phase of excitation.6. Less direct evidence indicates that cone and rod input to the field surround give rise to inhibitory components of comparable latency, magnitude and time course.7. The identified cone and rod components of responses are used in further experiments to show that cone and rod input have different spatial organization both in the receptive field centre and in the surround.8. The boundary between the field centre and surround for rods has a diameter on average about twice as large as that for cones. This organization is such that the field centre for rods substantially overlies the cone surround.9. Changes in receptive field organization occur within the mesopic range, associated with the changeover from cone to rod vision.10. It is suggested that the difference between cone and rod input in the mesopic range may form the basis of the cat's ability behaviourally to discriminate between colours.