Biomedical subjects

L S Jen

Publications and source records attributed to L S Jen.

At least 37 records · Page 2Linked to original sources

PubMed1993

Parasagittal patches in the granular layer of the developing and adult rat cerebellum as demonstrated by NADPH-diaphorase histochemistry.

The development of nicotinamide adenine dinucleotide phosphate diaphorase (NADPH-d) activity in the rat cerebellum was studied histochemically. NADPH-d reactivity was observed in the internal granular layer and some Purkinje cells by the end of first postnatal week (PW1). By PW2, the staining was localized in the granular layer (GL) and the molecular layer (ML), but not in the Purkinje cell layer. The staining in GL and ML increased further, and parasagittally organized NADPH-d patches in GL were recognizable by PW3. These patches were more distinct and almost adult-like by PW4. These results provide the first evidence of a patchy organization of NADPH-d activity in GL and suggest that NADPH-d plays an important role in the maturation and function of the cerebellum.

Amino Acid Oxidoreductases↗

PubMed1993

Injury-resistant retinal ganglion cells that are rich in cytochrome oxidase.

Previous studies have demonstrated that the vast majority of retinal ganglion cells (RGCs) die one month after optic nerve transection. However, a small percentage do not degenerate. The present study examined one aspect of the chemical nature of these surviving RGCs using cytochrome oxidase (CO) as a neuronal marker in whole-mounted retinae. In the normal retina, 4.3% of the total population of RGCs show high CO activity. One month after optic nerve transection, 37% of the CO-positive RGCs counted in the control retinae survive and, because they stain with CO, must be metabolically active. Previous studies have shown that only up to 10% of the total RGC population survive optic nerve transection. The implication of our results is that the CO-positive RGCs, as a subpopulation, are more resistant to injury than the general population of RGCs.

Animals↗

PubMed1992

Development of parvalbumin immunoreactive neurons in normal and intracranially transplanted retinas in the rat.

Retinas from embryonic day 14 Sprague-Dawley rats were transplanted to the midbrain or cerebral cortex of newborn (P0) rats of which the right eye was enucleated at the time of transplantation. Parvalbumin immunoreactive (PV-I) neurons were studied in the developing retinal transplants, and in the remaining retina of the host, as well as in normal retinas. PV-I neurons were identifiable in retinas of normal and host rats from postnatal day 5 (P5) onward, with the PV-I somata primarily in the inner half of the inner nuclear layer and in the ganglion cell layer. An adult-like distribution of PV-I neurons was attained at P35, as judged by cell packing density, intensity of immunostaining, laminar distribution and soma size of subpopulations of PV-I cells. A similar time course of development and distribution of PV-I somata was observed in the retinal transplants, except for some minor differences such as a slight delay in PV-I cells achieving their final distribution. These findings provide evidence that PV-I neurons can survive, differentiate and mature according to predetermined programmes intrinsic to the retinal tissue following transplantation to a new and foreign environment.

Animals↗

PubMed1992

Development of gamma-aminobutyric acid-immunoreactive neurons in normal and intracranially transplanted retinas in rats.

Retinas from embryonic day 14 Sprague-Dawley rats were transplanted intracranially to the midbrain or cortex of newborn (P0) rats with right eyes enucleated at the time of transplantation and the gamma-aminobutyric acid (GABA) immunoreactivity in developing retinal transplants, host as well as normal retinas, was studied. The results showed that GABA-immunoreactive neurons were identified in retinas of normal and host rats from the day of birth (P0) onward and that their somata were distributed primarily in the inner half of the internal nuclear layer and in the ganglion cell layer. The adult pattern of GABA immunoreactivity was first observed at P16 when several immunoreactive sublaminae were clearly identifiable in the inner plexiform layer. In contrast, gamma-aminobutyric acid-immunoreactive somata could not be identified in retinal transplants until P4, with a significant reduction in the density and number of GABAergic neurons detected by P12. Moreover, only two immunoreactive sublaminae were observed in the inner plexiform layer in all transplants at P12, as well as in more mature stages. These results suggest that significant changes occurred in the GABA system of the transplanted retina, despite the fact that the overall pattern of organization of the GABAergic neurons and their processes in the retinal transplants was comparable to that of the normal retina.

Animals↗

PubMed1991

Development of choline acetyltransferase-immunoreactive neurons in normal and intracranially transplanted retinas in rats.

Retinas from embryonic day 14 (E14) Sprague-Dawley rats were transplanted to the tectum of newborn (P0) recipient rats, and the distribution pattern of choline acetyltransferase immunoreactivity (ChAT-I) in developing transplants was studied and compared with those observed in the retinas of normal developing rats. In normal retinas, ChAT-I cells were first identified in restricted regions in the ganglion cell layer (GCL) at P4, but were found to cover the entire GCL by P6. A second population of ChAT-I cells was detected in the inner nuclear layer (INL) at P8, and they were observed in most parts of the INL on P10 when two immunoreactive sublaminae began to appear in the inner plexiform layer (IPL). The adult pattern of having two distinct populations of ChAT-I cells, organized in mirror symmetrical fashion in the inner retinal layers was basically established by P12. The time course of development and overall distribution pattern of ChAT-I cells in developing retinal transplants on the whole were very similar to those observed in normal retinas. The first identification of these cells and the establishment of their final distribution pattern were made at stages corresponding to P4 and P12 of normal developing retinas respectively. However, ChAT-I somata were located in the INL at a much earlier stage compared with their counterparts in the normal retina, and a transient population of immunoreactive cells with their processes extending to retinal layers other than the IPL was observed in some transplants from P6 to P10. These features were not observed in normal developing retinas. These results suggest that the development of cholinergic neurons, especially the expression of their characteristic antigen and their final distribution pattern is largely determined by programmes which are intrinsic to the original retinal tissue, despite some minor deviation or variation in the developmental process which may occur under certain abnormal conditions.

Animals↗

PubMed1991

Elimination of transient dendritic spines in ipsilaterally projecting retinal ganglion cells in rats with neonatal unilateral thalamotomy.

Using the DiI and intracellular Lucifer Yellow labeling techniques in the rat, we have demonstrated that the unilateral neonatal thalamotomy does not result in retention of transient dendritic spines of ipsilaterally projecting retinal ganglion cells (IPRGCs), although the thalamotomy is known to retain the normally transient IPRGCs (Chan et al., Dev. Brain Res., 49 (1989) 265-274). These results suggest that the process of elimination or retraction of transient dendritic spines occurs in retinal ganglion cells during development regardless of whether they make connections with appropriate or inappropriate loci in the visual targets, and/or a decrease in interactions with neighboring retinal ganglion cells.

Aging↗

PubMed1990

The cholinergic system in retinal transplants in rats.

Retinas from embryonic day 13 or 14 Sprague-Dawley albino rats were transplanted to the brainstem of newborn rats with unilateral eye enucleation at birth. Two months after the transplantation, the activity and distribution of acetylcholinesterase and choline acetyltransferase were studied using histochemical and immunocytochemical methods respectively. Results obtained showed that the staining patterns of these two cholinergic enzymes in the retinal transplants were essentially the same as those observed in the retinas of normal rats and in the control retinas of the recipient animals. The similarities in the distribution of these two cholinergic enzymes in these retinas suggest that the cholinergic system in the retinal transplants is likely to be functional.

Acetylcholinesterase↗

PubMed1990

Preservation of the entire population of normally transient ipsilaterally projecting retinal ganglion cells by neonatal lesions in the rat.

The number of ipsilaterally projecting retinal ganglion cells (IPRGCs) in developing normal rats and rats which received unilateral thalamic lesion and monocular enucleation at birth was studied using wheat germ agglutinin conjugated to horseradish peroxidase (WGA-HRP) as a retrograde neuronal marker. The results showed that the number of IPRGCs labelled in day-21 rats which received lesions at birth was comparable to the highest number of IPRGCs observed in normal rats on day 0 (day of birth). These results suggest that the entire population of IPRGCs which had their axons already grown in or near to their target structures on day 0 can be rescued by neonatal lesions.

Aging↗

PubMed1990

Factors affecting neurite outgrowth of occipital cortical explants.

The effects of various substrata including laminin, collagen gel, collagen I, and human amniotic basement membrane on neurite outgrowth of occipital cortical and diencephalic explants were studied. The results showed that the extent and pattern of growing neurites of cortical explants varied considerably depending on the substrata used. While an elaborated network of growing neurites was observed when cortical explants were plated on laminin, the most extensive neurite outgrowth was observed when collagen gel was used as the substratum. In contrast, diencephalic explants did not grow on most of the substrata. The significance of the findings are discussed.

Amnion↗

PubMed1989

Cytochrome oxidase activity in retinas transplanted to the brainstem in rats.

Fetal retinas were transplanted to the brainstem of newborn rats and their morphological features were examined using the cytochrome oxidase histochemical method at maturity. The results showed that the inner segments of photoreceptors, outer and inner plexiform layers as well as ganglion cells with large somata were moderately to darkly stained for cytochrome oxidase. This pattern is basically the same as that observed in the normal retina, suggesting that cytochrome oxidase can be used not only for revealing spatial but also functional organization of retinal transplants.

Animals↗

PubMed1989

Postnatal development of the ipsilaterally projecting retinal ganglion cells in normal rats and rats with neonatal lesions.

The postnatal development of normal and anomalous uncrossed retinofugal projections in albino rats was studied using horseradish peroxidase and lectin-conjugated horseradish peroxidase as retrograde neuronal tracers. In normal rats, the number of ipsilaterally projecting retinal ganglion cells (IPRGCs) decreased continuously from more than 3000 cells on the day of birth (day 0) to slightly more than 1000 on postnatal day 5. In contrast, the number of IPRGCs in rats which received either unilateral eye enucleation or thalamectomy at birth increased abruptly to more than 4000 after 24 h on postnatal day 1, thereafter the number decreased rapidly reaching an adult level of slightly more than 2000 on postnatal day 5. The overall pattern of changes of the number, density and distribution of the IPRGCs was similar in rats which received eye enucleation or thalamectomy, although minor differences regarding the number of cells labelled in the temporal and nasal parts of retinas in rats with different lesions were detected. These findings imply that a neonatal lesion such as monocular enucleation or unilateral thalamectomy may not only result in retention of normally transient IPRGCs but also cause an increased number of IPRGCs by misrouting, rerouting or collateral sprouting of optic axons at the optic chiasma that could significantly affect the developing optic pathway. Furthermore, the differential effects of the two types of neonatal lesions upon the IPRGCs provide further evidence to previous findings that different mechanisms might be involved in generating the anomalously enlarged uncrossed retinofugal projections in rodents.

Aging↗

PubMed1989

Cytochrome oxidase activity in the rat retina following unilateral thalamic lesion.

The present study has investigated the cytochrome oxidase (CO) activity in retinas of normal rats and rats which received central lesions at birth or young adult stage. The results show that a thalamic lesion which injured the retinal ganglion cell axons in young adult rats led to severe loss of CO activity in the ganglion, inner and outer plexiform layers in the retina contralateral to the lesion as compared to those of normal rats. In contrast, distinct CO-reactive bands and cells were clearly observed in corresponding laminae in retinas in which almost the entire population of retinal ganglion cells was eliminated by a neonatal thalamic lesion. These results indicate that retinal ganglion cells contribute significantly to the CO activity observed in the inner retinal laminae under normal but not under abnormal conditions, and suggest that considerable changes in the activity of the remaining neurons and possibly reorganization of neural circuitry within the retina in rats which received neonatal lesions has taken place, as revealed by CO histochemistry.

Animals↗

PubMed1989

The origin and terminal arbors of individual uncrossed retinogeniculate fibers in rabbits.

The distribution and morphology of individual uncrossed retinogeniculate fibers in both normal and monocularly enucleated adult Dutch-belted rabbits were studied using horseradish peroxidase and wheat germ agglutinin conjugated to horseradish peroxidase as neuronal markers. The results showed that the uncrossed retinogeniculate fibers were distributed almost entirely in the ipsilateral segment of the dorsal nucleus of the lateral geniculate body, and the extent of terminal distribution of the fibers observed in rabbits with one eye enucleated during the young adult stage was essentially the same as that in the normal rabbit. Most of the uncrossed retinogeniculate fibers appeared to arise as collateral branches of optic tract fibers which were apparently destined for the pretectum or the superior colliculus. The uncrossed retinogeniculate fibers labeled by the wheat germ agglutinin conjugated to horseradish peroxidase passed through the dorsal nucleus of the lateral geniculate body without any branching until they reached the ipsilateral segment. There they could be divided into several morphological types although the possibility that they may represent different classes of a continuum cannot be ruled out.

Animals↗

PubMed1989

Light-evoked cortical activity produced by illumination of intracranial retinal transplants: experimental studies in rats.

We have investigated whether information relayed through intracranial retinal transplants can elicit responses in the visual cortex of host rats. Embryonic retinae were transplanted over the midbrain of neonatal rats. Four to eight weeks later, the transplants were exposed and stimulated with light flashes. This photic stimulation elicited both evoked responses and multi-unit activity in area 18a of the visual cortex. Pathway tracing studies using horseradish peroxidase showed that these responses are transmitted to the cortex via the superior colliculus, the lateral division of the lateral posterior nucleus of the thalamus, and possibly the medial portion of the dorsal lateral geniculate nucleus. It is suggested that this pathway may be involved in complex transplant-mediated visual behaviors.

Animals↗

PubMed1988

Enlargement of uncrossed retinal projections in the albino rat: additive effects of neonatal eye removal and thalamectomy.

The present study in the albino rat investigates the effects of neonatal unilateral eye removal and/or thalamectomy upon the number of ipsilaterally projecting retinal ganglion cells (IPRGCs), using retrograde fluorescent labelling and electron microscopy. The results show that neonatal unilateral eye removal and thalamectomy result in a significant increase in the number of aberrant IPRGCs as compared to that observed in normal rats, and the effects of the two different neonatal lesions appear to be additive. These findings strongly suggest that there are at least two subpopulations of IPRGCs, which normally do not exist in mature albino rats, but which can be preserved into adulthood by neonatal enucleation or thalamectomy. The data also suggest that about 70% of the entire population of IPRGCs, most of which normally exist only transiently in neonatal retinas, can be retained in rats which receive both unilateral eye removal and thalamectomy at the neonatal stage.

Animals↗

PubMed1986

Intercollicular fibers terminating in the superficial layers of the superior colliculus: a WGA-HRP study in the rat.

The intercollicular pathway in the albino rat was studied using a lectin, wheat germ agglutinin, conjugated to horseradish peroxidase (WGA-HRP) as a pathway tracer and a modified HRP histochemistry method. The results showed that a small number of intercollicular fibers were observed in the rostral half of the superficial layers and the caudal half of the intermediate layers of the superior colliculus, while the majority of the intercollicular fibers were distributed in the intermediate and deep layers in the rostral half of the colliculus. The fibers which terminated in the superficial layers of the colliculus were studied in some detail and were subdivided into 4 different morphological types. These results suggest that the intercollicular projection is more broadly distributed in the superior colliculus than has been reported previously in most of the mammalian species studied, and the optic portion of the colliculus receives direct input from different morphological types of intercollicular neurons located on the opposite side of the midbrain.

Animals↗

PubMed1986

The cells of origin of the aberrant recrossed retinotectal projection in the rat.

The cells of origin of the aberrant recrossed retinotectal projection induced by neonatal unilateral eye enucleation and collicular lesion in rats were studied using horseradish peroxidase and fluorescent dyes as pathway tracers. The results showed that labelled ganglion cells which gave rise to the recrossed retinotectal projection were distributed in almost the entire area of the remaining retina. However, more labelled cells were observed in the nasal than in the temporal half of the retina, and very few cells contributing to the recrossed projection were located in the lower temporal retinal crescent where cells of the uncrossed retinotectal fibers were heavily concentrated. In addition, a small number of recrossed retinotectal fibers were found to arise from ganglion cells which simultaneously sent out uncrossed retinotectal fibers terminating in the same remaining colliculus.

Animals↗

PubMed1986

Displaced retinal ganglion cells in normal rats and rats with one eye enucleated at birth.

The displaced retinal ganglion cells in normal rats and rats with left eye enucleated at birth were studied using the fluorescent dye Fast blue as neuronal marker. The dye was introduced to the right optic tract of the rats 7 days before perfusion. Frozen coronal sections of the brains and retinal whole-mounts from all rats were examined under ultraviolet illumination. In the normal rat, the displaced cells constituted 0.91% and 2.07% of the entire population of cells projecting to the contralateral and ipsilateral side of the brain, respectively. While the contralaterally projecting displaced cells were widely distributed in the retina, the ipsilateral ones concentrated mainly in the temporal retinal crescent in all rats studied. However, an increase in the number of the ipsilaterally projecting displaced cells was detected in unilaterally enucleated rats as compared to that observed in normal animals.

Animals↗