Biomedical subjects

H B Li

Publications and source records attributed to H B Li.

46 records · Page 3Linked to original sources

PubMed1990

Synaptic organization of neurotensin immunoreactive amacrine cells in the chicken retina.

Immunohistochemistry was utilized to investigate the light and electron microscopic localization of neurotensinlike immunoreactive (NT) amacrine cells in the chicken retina. The NT cells possess oval cell bodies (7 microns in diameter) that are located in either the second or third tier of cells from the border of the inner nuclear and inner plexiform layers. The processes of such cells extend into the inner plexiform layer where they ramify as a narrow plexus in sublamina 1 and as a broad plexus in sublaminas 3 and 4. Additionally, stained processes are observed occasionally within sublamina 5. At the ultrastructural level, NT-positive somas exhibit a rather dense and evenly distributed peroxidase reaction product throughout their cytoplasm. The nucleus of NT amacrine cells possess a round, unindented nuclear membrane. NT-immunoreactive processes in the inner plexiform layer interact synaptically only with non-NT cells. NT processes receive synaptic input mainly from the processes of amacrine cells and to a lesser degree from bipolar cells. The large majority of NT-stained varicosities form presynaptic contacts onto the processes of amacrine cells, but are also presynaptic to bipolar cell axon terminals. Moreover, each of the above synaptic relationships can be identified in each of sublaminas 1 and 3 to 4 of the inner plexiform layer. In addition, NT processes are presynaptic to processes devoid of synaptic vesicles that may originate from ganglion cells. Finally, NT processes occasionally form synaptic contacts onto somas situated in the most proximal row of the inner nuclear layer.

Animals↗

PubMed1987

Immunocytochemical localization of LANT-6-like immunoreactivity within neurons in the inner nuclear and ganglion cell layers in vertebrate retinas.

LANT-6 is a hexapeptide (H-Lys-Asn-Pro-Tyr-Ile-Leu-OH) isolated from chicken small intestine, which resembles the COOH-terminal half of neurotensin, except for the amino acid substitutions Lys/Arg and Asn/Arg. The present report concerns the immunocytochemical staining of vertebrate retinas using an antiserum directed against LANT-6. In the retinas from goldfish, bird and turtle, cells in both the inner nuclear and ganglion cell layers were labeled, but in the frog no cells were labeled specifically and in the rat only cells in the ganglion cell layer were labeled. Labeled cell bodies in the inner nuclear layer gave rise to processes which were seen primarily within the following laminas of the inner plexiform layer (IPL): in the goldfish, lamina 3; chicken, laminae 1, 3 and 4; and turtle, laminae 3, 4 and 5. The cell bodies of the labeled neurons in the ganglion cell layer gave rise to dendrites which entered the IPL and axons which descended to the optic fiber layer. The cells with LANT-6-like immunoreactivity were distributed in both the central and peripheral parts of the retina in all the species examined except frog. Measured by radioimmunoassays, the levels of LANT-6-like-immunoreactivity in extracts of turtle, chicken, and goldfish retinas were 5-30 times those for neurotensin-like immunoreactivity, however no LANT-6-like immunoreactivity was detected in frog. Multiple chromatographic analyses indicated that while the LANT-6-like immunoreactivity in chicken retina was indistinguishable from synthetic LANT-6, LANT-6-like immunoreactivity in turtle and goldfish retinas was primarily associated with large molecular forms. Treatment of turtle LANT-6-like immunoreactivity with pepsin, an enzyme known to mimic processing for neurotensin precursors, yielded 3 major peptides, one of which co-chromatographed with synthetic LANT-6. The present immunocytochemical localization of LLI within cells in the inner nuclear and ganglion cell layers, coupled with the biochemical characterization of LANT-6 in the vertebrate retinas and brains, suggests that neuropeptides such as LANT-6 may play a role in visual processing both within the retina and within the visual pathways to the brain.

Animals↗

PubMed1986

Colocalization of immunoreactive substance P and neurotensin in amacrine cells of the goldfish retina.

Using an immunohistochemical double-label technique, neurotensin and substance P immunoreactivity were localized to amacrine cells in the goldfish retina. Both peptides were found in a single population of unistratified amacrine cells branching in sublamina 3 of the inner plexiform layer. A monostratified amacrine cell branching in sublamina 1 contained only substance P immunoreactivity and a bistratified cell branching in sublaminae 1 and 3 contained only neurotensin immunoreactivity.

Animals↗

PubMed1986

The light microscopic localization of substance P- and somatostatin-like immunoreactive cells in the larval tiger salamander retina.

Light microscopic immunocytochemistry was utilized to localize the populations of substance P (SP)- and somatostatin (SOM)-like immunoreactive cells in the larval tiger salamander retina. Of 104 SP-immunostained cells observed, 82% were Type 1 amacrine cells. Another 8% of the SP-cells were classified as Type 2 amacrine cells, while 10% of the SP-cells had their cell bodies located in the ganglion cell layer and were designated as displaced amacrine cells. Each type of SP-like immunoreactive cell was observed in the central and peripheral retina. SP-immunopositive processes were observed in the inner plexiform layer as a sparse plexus in sublamina 1 and as a denser network of fibers in sublamina 5. Seventy-eight percent of the 110 somatostatin-immunopositive cells observed were designated as Type 1 amacrine cells. Another 12% of SOM-cells were classified as displaced amacrine cells, while only two SOM-immunopositive Type 2 amacrine cells were observed. Nine percent of the SOM-cells were designated as interplexiform cells, based on their giving rise to processes distributing in the outer plexiform layer as well as processes ramifying in the inner plexiform layer. Each type of SOM-immunoreactive cell was observed in the central and peripheral retina, with the exception of the Type 2 amacrine cells, whose somas were only found in the central retina. Lastly, SOM-immunopositive processes in the inner plexiform layer appeared as a fine plexus in sublamina 1 and as a somewhat denser network of fibers in sublamina 5.

Ambystoma↗

PubMed1985

The presence of three neuroactive peptides in putative glycinergic amacrine cells of an avian retina.

Amacrine cells are retinal interneurons which serve to mediate transmission between bipolar and ganglion cells. To date, in addition to several classical neurotransmitters, a number of neuroactive peptides have been localized to these cells. We have previously demonstrated in the chicken that both peptide-transmitter and peptide-peptide colocalization exists in some amacrine cells. In this report, we show that 3 neuroactive peptides (enkephalin, neurotensin and somatostatin) are present in subpopulations of amacrine cells which also possess a high affinity uptake system for glycine. These observations suggest that the simultaneous visualization by autoradiography of [3H]glycine-uptake and immunocytochemistry of peptides may be useful for distinguishing between different types of putative glycinergic amacrine cells.

Animals↗

PubMed1985

Localization of enkephalin-like immunoreactive amacrine cells in the larval tiger salamander retina: a light and electron microscopic study.

Immunohistochemistry was utilized to examine the light and electron microscopic localization of enkephalin-like (enk) immunoreactive amacrine cells in the larval tiger salamander retina. The vast majority of enk-immunoreactive cells were typical amacrine cells whose round or oval cell bodies (14-16 microns) were situated in the innermost cell row of the inner nuclear layer. A relatively small number of enk-stained oval cell bodies (14-22 microns) were located in the ganglion cell layer and were designated as those of displaced amacrine cells. Enkephalin immunostaining was observed in the inner plexiform layer as a fine plexus in sublamina 1 and as a dense network of fibers in sublamina 5. In both the center and periphery of the retina the density of typical enk-amacrine cells was determined to be 250 +/- 16.36 cells per mm2 surface area of the retina. At the ultrastructural level typical enk-stained amacrine cells possessed a round, indented nuclear membrane. Enk-immunoreactive processes sometimes contained dense-core vesicles (60-115 nm) in addition to a rather homogeneous population of small, round, agranular synaptic vesicles (25-35 nm). In sublamina 1 the processes of enk-amacrine cells were presynaptic to amacrine and bipolar cells. They also contacted processes devoid of synaptic vesicles which possibly arise from ganglion cells. As the postsynaptic element in sublamina 1, they received synaptic input from amacrine cells. In sublamina 5 the processes of enk-amacrine cells were presynaptic to amacrine cells, bipolar cells, and the somas of cells situated in the ganglion cell layer.(ABSTRACT TRUNCATED AT 250 WORDS)

Ambystoma↗

PubMed1985

The coexistence of two neuroactive peptides in a subpopulation of retinal amacrine cells.

Amacrine cells are axonless interneurons of the vertebrate retina. Over the past few years many neuroactive peptides have been localized to these cells. We have previously demonstrated that a neuropeptide and a classical transmitter are colocalized in some amacrine cells. In this report, we show that two neuroactive peptides, which probably arise from different precursors, also coexist in some amacrine cells. Although some amacrine cells contain only enkephalin or neurotensin, others contain both of these neuroactive peptides.

Animals↗

PubMed1985

The signature hypothesis: co-localizations of neuroactive substances as anatomical probes for circuitry analyses.

The recent discoveries that a neuron in the vertebrate retina may contain more than one neuroactive substance (transmitter or neuropeptide) raise the possibility that within each class of neurons, every morphologically and physiologically distinct cell type may be uniquely identified and categorized by the neuroactive substances that it contains. This article examines the evidence to-date for such a conjecture and discusses some of its potential applications and implications.

Animals↗

PubMedDate not supplied

Substance P-immunoreactive neurons in hamster retinas.

Light-microscopic immunocytochemistry was utilized to localize the different populations of substance P-immunoreactive (SP-IR) neurons in the hamster retina. Based on observation of 2505 SP-IR neurons in transverse sections, 34% were amacrine cells whose pear-shaped or round cell bodies (7-8 microm) were situated in the inner half of the inner nuclear layer (INL) or in the inner plexiform layer (IPL), while 66% of SP-IR somata (6-20 microm) were located in the ganglion cell layer (GCL) which were interpreted to be displaced amacrine cells and retinal ganglion cells (RGCs). At least three types of SP-IR amacrine cells were identified. The SP-IR processes were distributed in strata 1, 3, and 5 with the densest plexus in stratum 5 of the inner plexiform layer. In the wholemounted retina, the SP-IR cells were found to be distributed throughout the entire retina and their mean number was estimated to be 4224 +/- 76. Two experiments were performed to clarify whether any of the SP-IR neurons in the GCL were RGCs. The first experiment demonstrated the presence of SP-IR RGCs by retrogradely labeling the RGCs and subsequently staining the SP-IR cells in the retina using immunocytochemistry. The second experiment identified SP-IR central projections of RGCs to the contralateral dorsal lateral geniculate nucleus. This projection disappeared following removal of the contralateral eye. The number of SP-IR RGCs was estimated following optic nerve section. At 2 months after sectioning the optic nerve, the total number of SP-IR neurons in the GCL reduced from 4224 +/- 76 to a mean of 1192 +/- 139. Assuming that all SP-IR neurons in the GCL which disappeared after nerve section were RGCs, the number of SP-IR RGCs was estimated to be 3032, representing 3-4% of the total RGCs. In summary, findings of the present study provide evidence for the existence of SP-IR RGCs in the hamster retina.

Animals↗

PubMedDate not supplied

A highly sensitive spectrophotometric method with solid-phase extraction for the determination of methylmercury in human hair.

Methylmercury is the most toxic among the mercury species. In order to provide a quick method to screen samples for methylmercury, a highly sensitive spectrophotometric method was established. The method was based on formation of the red complex of methylmercury with thio-Michler's ketone, which can be extracted with n-butanol. The organic layer was determined at a maximum absorption wavelength of 564 nm. The Lambert-Beer law was obeyed for methylmercury from 1.00 x 10(-7) mol/L to 2.00 x 10(-5) mol/L with a correlation coefficient of 0.9992. The detection limit was 3 x 10(-8) mol/L. The method was used to determine methylmercury in human hair. The recovery was from 94% to 102%, and the relative standard deviation was 2.5%. The results agreed with those obtained by gas chromatography with electron capture detection.

Benzophenones↗