Preliminary results from a field study of wild Guizhou snub-nosed monkeys (Rhinopithecus brelichi).

The Guizhou snub-nosed monkey, Rhinopithecus brelichi, is a large-bodied colobine confined to the subtropical semi-deciduous forests of Fanjing Mountain Reserve in Guizhou province, southwest China. Field work beginning in 1979 and including 10 months of intensive study in 1991 has revealed several aspects of the behavior and ecology of this species that are distinct from other colobines, including the closely related species R. roxellana and R. bieti. The Guizhou snub-nosed monkey is arboreal, traveling through the trees by quadrupedal walking, climbing, leaping, semibrachiation and (occasionally) by full brachiation. Terrestrial locomotion is use occasionally. Social organization centers around family groups of 5-10 individuals with a single adult male. Many family groups range and rest together in large, semicohesive bands. These bands may split up or coalesce temporarily to form large aggregations of over 400 animals and perhaps more. All-male groups of 2-5 adult or subadult males are found on the periphery of the bands.

Neural cell adhesion molecule (N-CAM) is elevated in adult avian slow muscle fibers with multiple terminals.

Many adult avian muscles contain two types of muscle fiber: those that receive innervation at single focal terminals and those with multiple terminals. The muscles of the syrinx, the vocal organ of birds, are such mixed muscles. To study this heterogeneity of fiber type and innervation, we combined immunocytochemistry to classify muscle fibers with techniques to visualize neuromuscular junctions. One monoclonal antibody, S58, directed against a slow class of myosin, labels only fibers that have multiple terminals. We also examined the distribution of immunoreactivity for neural cell adhesion molecule (N-CAM), which has been suggested to play a role in innervation of muscle and formation of neuromuscular junctions. S58-positive fibers have elevated N-CAM staining, indicating that multiple innervation of a fiber is correlated with the fiber's expression of high levels of N-CAM immunoreactivity. Most, and perhaps all, fibers that have multiple terminals also contain abundant N-CAM immunoreactivity. This suggests that N-CAM may play a role in the maintenance of multiterminal innervation in adult innervated muscle.

Androgens modulate endplate size and ACh receptor density at synapses in rat levator ani muscle.

The dorsal bulbocavernosus or "levator ani" muscle of the rat is highly responsive to androgens. Both the muscle and the motoneurons which innervate it contain high concentrations of androgen receptors. The neuromuscular synapses in this muscle are also affected by changing androgen levels. In particular, the total number of ACh receptors (AChRs) in the muscle is lower in males that have been castrated, and it increases after treatment with the androgens, testosterone and 5 alpha-dihydrotestosterone. An examination of individual endplates using histochemistry and quantitative autoradiography suggested that the reduction in AChR number following castration is caused by reductions in both the size of endplates and in the density of AChRs at each synapse.

Modification of synapses in androgen-sensitive muscle. I. Hormonal regulation of acetylcholine receptor number in the songbird syrinx.

The songbird syrinx is sexually dimorphic and responds to changes in blood testosterone levels with changes in muscle size and in activity of cholinergic enzymes (Luine, V., F. Nottebohm, C. Harding, and B.S. McEwen (1980) Brain Res. 192: 89-107). Here, we demonstrate that there is a sex difference in the number of acetylcholine receptors (AChRs) in the syrinx and that alterations in the levels of circulating testosterone can cause changes in AChR number in syringeal muscles. These results suggest that the size or number of endplates in the syringeal muscles may be increased by circulating testosterone. The time course of these effects was examined after increases in blood testosterone in females and decreases in males. We also examined the effect of increased testosterone in syrinx isolated from neural influences by denervation and found that denervated muscle responded to testosterone with an increase in acetylcholinesterase activity but not with increases in protein content or AChR number.

Specificity of gonadal hormone modulation of cholinergic enzymes in the avian syrinx.

The effectiveness of testosterone (T) and metabolites to increase activity of cholinergic enzymes in the androgen-sensitive syrinx of male zebra finches was assessed. Administration of aromatizable (T and androstenedione) or non-aromatizable (androsterone) androgens to castrates increased total activity of acetylcholinesterase (AChE) in the syrinx. Estradiol was ineffective in altering AChE activity. Results, when compared with behavioral data from the birds, support the hypothesis that expression of male reproductive behaviors requires peripheral target organ activation by androgens and central target area activation by both androgens and estrogens.

Molecular forms of acetylcholinesterase: regulation in a testosterone-sensitive nerve-muscle axis.

We measured the distribution of molecular forms of acetylcholinesterase (AChE) in muscles of a song bird, the zebra finch, and found a pattern similar to those reported in other vertebrates. As in other species, the most rapidly sedimenting form of the enzyme decreases to barely detectable levels following denervation. In the muscles of the syrinx, castration causes a large decrease in AChE activity, but has little or no effect on the relative abundance of AChE forms. This suggests that the number of AChE catalytic sites is changing without affecting the distribution of catalytic sites among the molecular forms. This is in marked contrast with the effect of denervation in the syrinx, which causes changes in the distribution of activity, as well as in total activity.

Minireview: quantitative autoradiography of neurochemicals.

Several new methods have been developed that apply quantitative autoradiography to neurochemistry. These methods are derived from the 2-deoxyglucose (2DG) technique of Sokoloff (1), which uses quantitative autoradiography to measure the rate of glucose utilization in brain structures. The new methods allow the measurement of the rate of cerebral protein synthesis and the levels of particular neurotransmitter receptors by quantitative autoradiography. As with the 2DG method, the new techniques can measure molecular levels in micron-sized brain structures; and can be used in conjunction with computerized systems of image processing. It is possible that many neurochemical measurements could be made by computerized analysis of quantitative autoradiograms.

Testosterone increases acetylcholine receptor number in the "levator ani" muscle of the rat.

The "levator ani" muscle of male rats provides a neuromuscular system in which both the muscle and its motoneurons have high levels of androgen receptors. Two weeks of castration caused a 48% loss of acetylcholine receptors in this muscle. One week of testosterone propionate injections initiated on week after castration increased receptor number by 27% over untreated castrate levels. These changes paralleled changes in muscle protein content. In contrast, castration and testosterone treatments of castrates had no effect on total. Triton X-100-extractable acetylcholinesterase activity. This system may provide a useful model of synaptic plasticity.

Quantitative densitometry of neurotransmitter receptors.

An autoradiographic procedure is described that allows the quantitative measurement of neurotransmitter receptors by optical density readings. This procedure is a modification of the method of Young and Kuhar (1979a). Frozen brain sections are labeled in vitro with [3H]ligands under conditions that maximize specific binding to neurotransmitter receptors. The labeled sections are then placed against the 3H-sensitive LKB Ultrofilm to produce the autoradiograms. These autoradiograms resemble those produced by [14C]deoxyglucose autoradiography (Sokoloff, 1977) and are suitable for quantitative analysis with a densitometer. Muscarinic cholinergic receptors in rat and zebra finch brain and 5-HT receptors in rat brain were visualized by this method. When the proper combination of ligand concentration and exposure time are used, the method provides quantitative information about the amount and affinity of neurotransmitter receptors in brain sections. This was established by comparisons of densitometric readings with parallel measurements made by scintillation counting of sections.