The main objective of this project was to provide baseline data on faecal parasites of groups of non-human primates from Tambopata Research Center, Tambopata National Reserve, Peru. All primate species found in this area were sampled: red howler monkeys Alouatta seniculus, night monkeys Aotus vociferans, spider monkeys Ateles bezlebuth chamek, brown titi monkeys Callicebus brunneus, white-fronted capuchins Cebus albifrons, brown capuchins Cebus apella, saddleback tamarins Saguinus fuscicollis and squirrel monkeys Saimiri sciureus. Individuals from four howler monkey troops, three brown titi monkey troops, two squirrel monkey troops and one troop each of night monkeys, spider monkeys, brown capuchins, white-fronted capuchins and saddleback tamarins were sampled. Faecal samples were collected from July to October 2002 from 86 individuals. A concentration test was used to analyse faecal samples. Results indicate the presence of various protozoans, Ancyclostoma sp., Ascaris sp., Strongyloides stercoralis, Trichuris trichiura, Prosthenorchis elegans and Schistosoma mansoni.

The expression of glutamate decarboxylase forms, GAD-65 and GAD-67, in GABAergic cells was studied by immunocytochemistry in the retina of the New World monkey, Cebus apella. In the innermost rows of the inner nuclear layer (INL), somata that express GABA correspond to about 45% of the total number of cells in the central retina and about 25% on the periphery. Three subsets of GABAergic amacrine cells were identified along the horizontal meridian: about 5% express only GAD-65 and 40% GAD-67, and approximately 50% contain both forms of GAD. In the INL, GAD-65 immunoreactivity was detected in broad bands around strata 1, 3, and 5. GAD-67 immunoreactivity was observed throughout all strata. Somata that expressed GAD-67 exclusively stratified only in narrow bands around strata 2 and 4 of the INL and colocalized with β2 and β3 subunits of GABA-A receptor. Interplexiform and amacrine cells that express GABA also express tyrosine hydroxylase (TH) or nitric oxide synthase (NOS). GAD-67 colocalized with TH or NOS in presumed amacrine cells of the inner plexiform layer (IPL) and ganglion cell layer (GCL). GAD-65 was expressed in the TH- and NOS-immunoreactive interplexiform and amacrine cells, respectively. Different from what has been described in other mammals, TH and NOS were coexpressed in some neurons, indicating a partial overlap in retinal cell populations containing dopamine or nitric oxide in this primate.

The inhibitory neurotransmitter gamma aminobutyric acid (GABA) has been shown to influence the responses of ganglion cells in the mammalian retina. Consistently, GABAA receptor subunits have been localized to different ganglion cell types. In this study, the distribution of the α1 subunit of the GABAA receptor on the dendrites of midget and parasol ganglion cells was investigated quantitatively in the retina of a New World monkey, the marmoset. Ganglion cells were injected with Neurobiotin in a live in vitro retinal whole-mount preparation. Retinal pieces were then processed with an antibody against the α1 subunit of the GABAA receptor. Strong punctate immunoreactivity indicative of synaptic localization is present in the ON and OFF sublamina of the inner plexiform layer. Many of the immunoreactive puncta coincide with the dendrites of both midget and parasol ganglion cells. Immunoreactive puncta are present on distal and proximal dendrites of ON and OFF cells of both ganglion cell types. On average, parasol cells show a slight increase in the spatial density of immunoreactive puncta with distance from the soma, whereas the density of immunoreactive puncta on midget cells stays even. Parasol ganglion cells show a slightly higher average density of immunoreactive puncta (0.083 puncta/μm dendrite) than midget cells (0.054 puncta/μm dendrite).

Glycine is a major inhibitory neurotransmitter in the mammalian retina and has been shown to influence the responses of ganglion cells. Midget and parasol ganglion cells serve distinct physiological roles in the primate retina and show differences in their response characteristics to light stimuli. In the present study, we addressed the question of whether the expression of glycine receptors differs in midget and parasol ganglion cells. Ganglion cells in the retinae of marmoset and macaque monkeys were injected with Neurobiotin in a live in vitro retinal whole-mount preparation. Retinal pieces were then processed with an antibody against the α1 subunit of the glycine receptor. Strong punctate immunoreactivity indicative of synaptic localization is present in the ON and OFF sublamina of the inner plexiform layer. Many of the immunoreactive puncta coincide with the dendrites of both midget and parasol ganglion cells. Immunoreactive puncta are present on distal and proximal dendrites of ON and OFF cells. These results suggest that ON and OFF midget and parasol cells do not differ with respect to the distribution of the α1 subunit of the glycine receptor.