Prosimian Galago Research Articles

Tandemly duplicated alpha globin genes of gibbon.

The alpha globin gene locus of the common gibbon (Hylobates lar) was isolated, and it contains two closely linked alpha globin genes that share the same arrangement as that found for the homologous genes of other catarrhine primates. The nucleotide sequences of the gibbon alpha globin genes were determined and compared with the alpha globin gene sequences from other primate species (human, chimpanzee, orangutan, baboon, and rhesus); the prosimian primate, galago, alpha A and alpha B globin genes provided the out-group for this analysis. The degree of divergence for both synonymous and nonsynonymous substitutions among the alpha globin genes are generally smaller for intraspecies than interspecies comparisons, which is indicative of concerted evolution between the paired alpha globin genes of each catarrhine species. The pattern of differences is suggestive of gene conversions. This possibility is supported by both site-by-site and branch-swapping parsimony analyses. The site-by-site parsimony analysis was also used to determine the 3' boundary of each catarrhine species-specific conversion. These alpha globin gene conversion events encompass most of the transcriptional region, including the promoter, exons, introns, and about one-half of the 3'-untranslated region. However, the paired gibbon alpha globin genes show the highest degree of divergence, differing by five nucleotides in their coding regions, three of which encode amino acid replacement substitutions. It appears that the last convergence event between the paired gibbon alpha globin genes is relatively ancient, having occurred approximately 11 million years ago. The remaining 3'-untranslated region and flanking DNAs show no evidence of involvement in any recent conversion event as the parsimony analysis of these sequences group all the alpha 1 globin genes of the different catarrhine species into one clade and all the alpha 2 globin gene of these species into a separate clade. The sequence comparison among the alpha globin genes of different primate species also provides interesting implications regarding the evolution and functional domains of the 3'-untranslated regions.

The β globin gene cluster of the prosimian primate Galago crassicaudatus: Nucleotide sequence determination of the 41-kb cluster and comparative sequence analyses

The nucleotide sequence of the β globin gene cluster of the prosimian Galago crassicaudatus has been determined. A total sequence spanning 41, 101 bp contains and links together previously published sequences of the five galago β-like globin genes (5′-ε-γ-ψη-δ-β-3′). A computer-aided search for middle interspersed repetitive sequences identified 10 LINE (L1) elements, including a 5′ truncated repeat that is orthologous to the full-length L1 element found in the human ε-γ intergenic region. SINE elements that were identified included one Alu type I repeat, four Alu type II repeats, and two methionine tRNA-derived Monomer (type III) elements. Alu type II and Monomer sequences are unique to the galago genome. Structural analyses of the cluster sequence reveals that it is relatively A + T rich (about 62%) and regions with high G + C content are associated primarily with globin coding regions. Comparative analyses with the β globin cluster sequences of human, rabbit, and mouse reveal extensive sequence homologies in their genic regions, but only human, galago, and rabbit sequences share extensive intergenic sequence homologies. Divergence analyses of aligned intergenic and flanking sequences from orthologous human, galago, and rabbit sequences show a gradation in the rate of nucleotide sequence evolution along the cluster where sequences 5′ of the ε globin gene region show the least sequence divergence and sequences just 5′ of the β globin gene region show the greatest sequence divergence.

A projection from the parabigeminal nucleus to the pulvinar nucleus in Galago.

A projection from the parabigeminal nucleus (Pbg) to the striate-recipient zone of the pulvinar nucleus in the prosimian Galago was identified by anterograde and retrograde transport methods. In addition to the pulvinar nucleus, Pbg projections were found to terminate in layers 4 and 5 of the dorsal lateral geniculate nucleus and the central lateral nucleus. All three of these structures project to the superficial layers of the striate cortex. Similarities between the Pbg in mammals and the nucleus isthmi in nonmammals in connections and neurochemistry reinforce the idea that these two nuclei are homologous.

Sublaminar organization within layer VI of the striate cortex in Galago

In this study we examined the organization of projections from the striate cortex to the dorsal lateral geniculate (GL) and pulvinar (PUL) nuclei in the prosimian Galago by using retrograde transport methods. Injections of wheat germ agglutinin-conjugated horseradish peroxidase (WGA-HRP) into the PUL labeled two bands of cells in the striate cortex: the first consisted of large pyramidal cells in the upper half of layer V; the second consisted of small and medium-size pyramidal cells located in the deepest part of layer VI. The location of cells within layer VI coincided with a clear cytoarchitectonic sublayer, VIb, which contains fewer and paler staining cells than VIa. Injections of WGA-HRP involving all layers of the GL produced an uninterrupted band of pyramidal cells distributed throughout layer VI (a and b), including the region labeled after injections into the PUL. Thus as a first approximation, layer VI can be divided into an upper tier (VIa) that projects only to the GL and a lower tier (VIb) that projects to both the GL and PUL. Injections of WGA-HRP that were restricted to one or a few GL layers revealed a further refinement of the subdivisions within layer VI. Injections into the parvicellular and intercalated (or koniocellular) layers of the GL labeled neurons predominantly in the upper half of layer VIa, whereas injections restricted to the magnocellular layers labeled neurons in the lower half of layer VIa and in layer VIb. In order to determine whether individual neurons in layer VIb send axon collaterals to both the GL and PUL, we injected WGA-HRP into one nucleus and fluorescent rhodamine latex beads into the other. In three experiments, we found only one double-labeled cell. In sum, the results provide evidence that layer VI is divided into at least three sublayers: upper VIa, which projects to the intercalated and parvicellular GL layers; lower VIa, which projects to the magnocellular GL layers; and VIb, which sends separate projections to the magnocellular layers of the GL and to the PUL. The segregation observed is sufficiently discrete to propose the existence of multiple, descending pathways from layer VI of the striate cortex that complement those ascending from the GL and PUL.

Structure and Evolution of the U2 Small Nuclear RNA Multigene Family in Primates: Gene Amplification under Natural Selection?

The organization of U2 genes was compared in apes, Old World monkeys, and the prosimian galago. In humans and all apes (gibbon, orangutan, gorilla, and chimpanzee), the U2 genes were organized as a tandem repeat of a 6-kb element; however, the restriction maps of the 6-kb elements in these divergent species differed slightly, demonstrating that mechanisms must exist for maintaining sequence homogeneity within this tandem array. In Old World monkeys, the U2 genes were organized as a tandem repeat of an 11-kb element; the restriction maps of the 11-kb elements in baboon and two closely related macaques, bonnet and rhesus monkeys, also differed slightly, confirming that efficient sequence homogenization is an intrinsic property of the U2 tandem array. Interestingly, the 11-kb monkey repeat unit differed from the 6-kb hominid repeat unit by a 5-kb block of monkey-specific sequence. Finally, we found that the U2 genes of the prosimian galago were dispersed rather than tandemly repeated, suggesting that the hominid and Old World monkey U2 tandem arrays resulted from independent amplifications of a common ancestral U2 gene. Alternatively, the 5-kb monkey-specific sequence could have been inserted into the 6-kb array or deleted from the 11-kb array soon after divergence of the hominid and Old World monkey lineages.

Structure and evolution of the U2 small nuclear RNA multigene family in primates: gene amplification under natural selection?

The organization of U2 genes was compared in apes, Old World monkeys, and the prosimian galago. In humans and all apes (gibbon, orangutan, gorilla, and chimpanzee), the U2 genes were organized as a tandem repeat of a 6-kb element; however, the restriction maps of the 6-kb elements in these divergent species differed slightly, demonstrating that mechanisms must exist for maintaining sequence homogeneity within this tandem array. In Old World monkeys, the U2 genes were organized as a tandem repeat of an 11-kb element; the restriction maps of the 11-kb elements in baboon and two closely related macaques, bonnet and rhesus monkeys, also differed slightly, confirming that efficient sequence homogenization is an intrinsic property of the U2 tandem array. Interestingly, the 11-kb monkey repeat unit differed from the 6-kb hominid repeat unit by a 5-kb block of monkey-specific sequence. Finally, we found that the U2 genes of the prosimian galago were dispersed rather than tandemly repeated, suggesting that the hominid and Old World monkey U2 tandem arrays resulted from independent amplifications of a common ancestral U2 gene. Alternatively, the 5-kb monkey-specific sequence could have been inserted into the 6-kb array or deleted from the 11-kb array soon after divergence of the hominid and Old World monkey lineages.

Cortical connections of MT in four species of primates: Areal, modular, and retinotopic patterns

Cortical connections were investigated by restricting injections of WGA-HRP to different parts of the middle temporal visual area, MT, in squirrel monkeys, owl monkeys, marmosets, and galagos. Cortex was flattened and sectioned tangentially to facilitate an analysis of the areal patterns of connections. In the experimental cases, brain sections reacted for cytochrome oxidase (CO) or stained for myelin were used to delimit visual areas of occipital and temporal cortex and visuomotor areas of the frontal lobe. Major findings are as follows: (1) The architectonic analysis suggests that in addition to the commonly recognized visual fields, area 17 (V-I), area 18 (V-II), and MT, all three New World monkeys and prosimian galagos have visual areas DL, DI, DM, MST, and FST. (2) Measurements of the size of these areas indicate that about a third of the neocortex in these primates is occupied by the eight visual areas, but they occupy a somewhat larger proportion of neocortex in the diurnal marmosets and squirrel monkeys than the nocturnal owl monkeys and galagos. The diurnal primates also have proportionally more neocortex devoted to areas 17, 18, and DL and less to MT. These differences are compatible with the view that diurnal primates are more specialized for detailed object and color vision. (3) In all four primates, restricted locations in MT receive major inputs from short meandering rows of neurons in area 17 and several bands of neurons in area 18. (4) Major feedforward projections of MT are to two visual areas adjoining the rostral half of MT, areas MST and FST. Other ipsilateral connections are with DL, DI, and in some cases DM, parts of inferotemporal (IT) cortex, and posterior parietal cortex. (5) In squirrel monkeys, where injection sites varied from caudal to rostral MT, caudal parts of MT representing central vision connect more densely to DL and IT than other parts. Both DL and IT cortex emphasize central vision. (6) In the frontal lobe, MT has dense connections with the frontal ventral area (FV), but not with the frontal eye field (FEF). (7) Callosal connections of MT are most dense with matched locations in MT of the other hemisphere, rather than with the outer boundary of MT representing the vertical meridian. Targets of sparser callosal connections include FST, MST, and DL.(ABSTRACT TRUNCATED AT 400 WORDS)

Germinal cell ectopism in the strepsirhine prosimian Galago crassicaudatus crassicaudatus

The presence of germinal cells outside of the embryonal and fetal gonads of the strepsirhine prosimian Galago crassicaudatus crassicaudatus is described. Forty-three embryos and fetuses from day 26 or 27 of gestational age to near term were studied: more than 90% possessed germinal cells in ectopic sites situated either far from (extragonadal ectopism) or close to the gonads (perigonadal ectopism). The first sites were the walls of the aorta and mesenteric artery, the stroma between the aorta and the cardinal vein, and the retroperitoneal neuroganglia. The second were the mesenchyme dorsal to the gonads and around the vestigia of the mesonephric glomeruli and tubules, and the rete ovarii and testis. The ectopic cells were generally present in conscpicuous numbers, in some animals being more numerous than in the gonads. Those situated far from the gonads underwent degeneration and decreased significantly in numbers during post-embryonal stages of development, while the others remained numerous and functionally active up to near term. While the differentiation of the extragonadal germinal cells after day 60 of gestational age could not be studied due to technical difficulties, the XX and XY cells in perigonadal sites appeared to follow patterns of differentiation identical to those of their entopic counterparts.

Clustering and subfamily relationships of the Alu family in the human genome.

Thirteen and 10 sequences of the Alu family of repeated DNA elements found within the human thymidine kinase and beta-tubulin genes, respectively, were compared. These genes have approximately five times the expected density of Alu family members. The consensus sequence that could be drawn from these 23 Alu family members would differ slightly from others drawn from random Alu family sequences but only at very heterogeneous positions. The different Alu family members do show different pairwise percentage identities, with approximately 15% (7 of 48 Alu family members analyzed) of them clearly representing a separate subfamily of sequences. This analysis also confirms the species-specific differences between human and the prosimian Galago crassicaudatus Alu family members. These data are consistent with both the origin of these sequences in primates less than 65-70 Myr ago and amplification since that time to their present 500,000 copies. The data do not show any special relationships among densely clustered Alu family members.

Cortical and subcortical projections of the middle temporal area (MT) and adjacent cortex in galagos.

Projections of the middle temporal visual area, MT, and of visual cortex adjoining MT were investigated with autoradiographic methods in the prosimian primate, Galago senegalensis. Ipsilateral cortical targets of MT included area 17, area 18, cortex caudal to MT, cortex ventral to MT, and parietal-occipital cortex dorsal to MT. This pattern of projections suggests that extrastriate cortex contains a number of visual subdivisions in addition to MT. Contralateral projections were to MT and parietal-occipital cortex. Projections from MT to areas 17 and 18 connected regions representing similar parts of the visual hemifield while the location of callosal projections in MT matched the location of the injection site in the other hemisphere. Label in area 17 was concentrated in layers I, III, and VI whereas other cortical areas were most densely labeled in the granular and supragranular layers. Subcortical projections of MT included the reticular nucleus of the thalamus, the lateral posterior nucleus, the superior pulvinar, the inferior pulvinar, the superior colliculus, and the pontine nuclei. The projection pattern to the superior and inferior pulvinar nuclei suggests that MT projects in a topographic manner to two subdivisions within each of these structures. Injections in cortex just outside of MT labeled area 18, inferotemporal cortex, parietal-occipital cortex, and, to a lesser extent, MT. The projections to inferotemporal cortex clearly distinguish the bordering cortex from MT. Contralateral cortical terminations were in locations corresponding to the injection site. Subcortical targets were generally similar to those seen after MT injections, although additional projections were observed depending on the location of the injection. Comparison of these results from the prosimian galago with studies in New and Old World monkeys indicates there are substantial similarities in projections. Thus, some of the cortical and thalamic subdivisions described for monkeys appear to exist in prosimians.

Projection pattern of functional components of thalamic ventrobasal complex on monkey somatosensory cortex

Projection pattern of functional components of thalamic ventrobasal complex on monkey somatosensory cortex

The distribution of lateral funicular and cortical fibers to the dorsal column, Z and X nuclei in the prosimian Galago

The distribution of lateral funicular and cerebral corticofugal fibers to the dorsal column, Z and X nuclei were studied in the prosimian primate Galago senegalensis. Lesions of the lateral funiculus resulted in a differential distribution pattern of preterminal degeneration within the nuclei studied. In the nucleus gracilis, spinal lesions produced moderate amounts of debris in ventral cell nest and rostral areas. Diffuse degeneration was present in both the dorsal cell nest area of the nucleus gracilis and the rostral nucleus cuneatus. Extremely dense debris was present within both ipsilateral Z and X nuclei. Cortical ablations of predominantly hind-limb motor-sensory areas resulted in degeneration throughout most of the longitudinal and transverse extent of the contralateral dorsal column nuclei. Degeneration appeared to be more concentrated in ventral nuclear areas. The distribution of cortical fibers to the rostral gracile and Z nuclei was essentially the inverse of that observed for lateral funicular fibers. The contralateral nucleus Z received only a sparse corticobulbar input while the rostral gracile contained more moderate amounts of preterminal degeneration. The results are in agreement with previous reports on the morphology and fiber connections of the dorsal column, Z and X nuclei in Galago and other animals. They support the concept that the Z and X nuclei are functional components of the dorsal column nuclear system.

Some aspects of the organization of the lateral geniculate nucleus in Galago senegalensis revealed by using horseradish peroxidase to label relay neurons

Following injection of horseradish peroxidase into area 17 of the prosimian Galago senegalensis, columns of labeled neurons are seen in the dorsal lateral geniculate nucleus extending through all cell layers. Individual counts of the number of labeled and unlabeled neurons reveal that from 91 to 98% of all neurons within these densely labeled columns are labeled. These results indicate that most of the neurons within the LGN of the bushbaby project to striate cortex. Average diameter measurements of labeled and unlabeled cells within the labeled columns were used to determine whether cell layers could be separated into two types (parvocellular and magnocellular) or three types (small, medium, and large) on the basis of cell body size. These measurements indicate that the LGN of the bushbaby is composed of two layers each of small (layers 4 and 5), medium (layers 3 and 6), and large (layers 1 and 2) relay neurons. These observations are consistent with the conclusion that layers 1 and 2 in the LGN of Galago are homologous with the magnocellular layers, and layers 3 and 6 homologous with the parvocellular layers, identified in the LGN of New and Old World monkeys.

On the relationship between chitin particle size and digestibility in the primate Galago senegalensis

AbstractExperiments were performed to examine the relationship between the particle size of chitin and its digestibility in the small insectivorous prosimian Galago senegalensis. In the first set of experiments, four animals were fed a 25% chitin diet with the chitin particles less than or equal to 60‐mesh (0.250 mm maximum diameter). On average, the animals digested 22.5 ± 2.2 percent of the ingested chitin. In the second set of experiments, the four animals were fed a 25% chitin diet with the chitin particles ground to ≤ 40‐ and ≥ 45‐mesh (between 0.425 and 0.325 mm). On average, the animals digested 2.75 ± 1.38 percent of the ingested chitin. There was no significant variation between the performance of any of the animals on either the 60‐ or 40–45‐mesh trials. In all instances, however, each animal digested significantly more of the 60‐mesh chitin and the 40–45‐mesh chitin.These experiments demonstrate the importance of masticatory efficiency among small mammals for improving the digestibility of foods such as insects which contain high proportions of chitin. They also suggest why insectivorous and folivorous primates have certain convergent dental specializations for finely grinding their foods. Both leaves and insects contain relatively indigestible structural carbohydrates. These substances are much more completely digested when the surface area to volume ratio of the swallowed material is increased. The masticatory efficiency of frugivorous primates is much lower since the constituents of these foods are relatively completely digested irrespective of the fineness of grinding.

Sex Ratio and Local Resource Competition in a Prosimian Primate

Competition between female kin for local limiting resources may explain a male-biased secondary sex ratio in the prosimian Galago crassicaudatus. Data demonstrating the skewed sex ratio, a brief summary of field observations on the species, and a simple mathematical statement of the hypothesis are presented. Local resource competition may influence sex ratio in other mammals.

Glucose preferences in the greater galago (Galago crassicaudatus) and slow loris (Nycticebus coucang).

The glucose preferences of two prosimian primate species, slow loris and greater galago, were determined by the paired comparison method. Stimuli were solutions of the following concentrations: 5, 10, 20, 30, and 40%. Both species preferred solutions of intermediate concentration, but they differed significantly in that lorises showed a greater preference than galagos for sweet solutions. Lorises preferred the 20% concentration while galagos preferred the 10% concentration, and lorises consumed significantly more at all concentrations. Lorises also showed a greater tendency to discriminate between solutions in the middle range.

The cortico-thalamic projections from the sensorimotor cortex of Galago crassicaudatus.

AbstractThe cortico‐thalamic pathways from the sensorimotor cortex of the prosimian Galago crassicaudatus were studied after cortical lesions. The Glees method and several modifications of the Nauta technique were used. A short description of the thalamic nuclei in Galago is given. The motor cortex was found to project to the following nuclei: reticularis thalami, lateralis anterior, lateralis ventralis oralis, lateralis dorsalis intermedius, the pars paralamellaris of the nucleus lateralis ventralis posterior, the intralaminar nuclei, parafascicularis‐centrum medianum complex, lateral third of the mediodorsalis, praetectalis, zona incerta, H fields of Forel and the subthalamic nucleus. The cortical projections to nucleus centrum medianum was found to be topically organized.The sensory cortex was found to project to the following nuclei: reticularis thalami, lateralis dorsalis intermedius, paracentralis, parafascicularis, pars lateralis and pars medialis of the nucleus lateralis ventralis posterior, praetectalis, posterior, zona incerta, and the H fields of Forel. The topical organization of the cortical projection to the lateral complex and posterior nucleus is discussed.

VI.—The Heart and Great Vessels in the Strepsirhini

SynopsisDetails of the anatomy of the heart and the great vessels are recorded in the following genera of prosimian Primates,Loris, Arctocebus, Perodicticus, Galago, Galagoides, Hapalemur, Lemur, LepilemurandPropithecus, and comparison made with previously published data onNycticebus. Special attention is drawn to the proportions, shape and mode of branching of the systemic aorta, which is of typical lemurine pattern in all butLorisandPropithecus. In the heart, attention is paid particularly to the valvular arrangements in the right atrium, where much variation has been found; to the number of pulmonary veins entering the left atrium, also a variable feature; to the internal and external morphology of the ventricles and the valvular arrangements therein. The presence of an os cordis is recorded for the first time in any Primate (viz. inLoris), and the occurrence is mentioned of “brown” (glandular) fat sub-epicardially inLoris. The significance is discussed of the principal anatomical features.