Leaf extension in the slender barley mutant: delineation of the zone of cell expansion and changes in translatable mRNA during leaf development

The slender mutant of barley (Hordeum vulgare L.) results from an alteration to a single nuclear gene. Plants homozygous for the mutant allele have long, attenuated leaves as a result of a greatly increased extension rate. Although the growth rate at any one position in the extension zone appears not to differ between slender and normal (wild-type) barley, in slender the length of the zone over which cells extend is approximately 50% greater than that in normal barley. Epidermal cells are both longer and narrower in slender, so the whole-plant phenotype is mirrored at the cell level. Translation in vitro of RNA extracted from successive sections of the young primary leaf, followed by one-dimensional SDS-PAGE separation, facilitated the alignment of equivalent developmental stages in the two genotypes, but failed to demonstrate major differences between the two genotypes. Two-dimensional separation of translation products from total leaf tissue revealed a few small differences between normal and slender. Growth of plants at 8°C compared with 20°C caused changes in some translation products, with one (unknown) product decreasing in abundance in cold-treated normal tissue but not in slender tissue.     

Mother-infant interactions in captive slow lorises (Nycticebus coucang)

Information is presented about mother-infant interactions and infant development in a rarely studied prosimian primate, the slow loris (Nycticebus coucang). Four dyads were observed, by means of closed circuit TV, in a semi-natural environment for 1 hour per day three times a week. Infants were inactive for the first 6–8 weeks. Although mothers carried infants, they also left them alone for substantial periods of time after the 1st week. Over the 20-week study period, there was a significant decline in ventral contact but not in sitting within 12 inches or engaging in active social interactions. By the end of the study, infants were not yet fully independent. Three of the 4 were primarily responsible for maintaining physical closeness to the mother; they made most of the approaches and mothers made most of the departures. However, only 2 of the 4 infants had assumed responsibility for the initiation and maintenance of social interactions with the mother. By comparison with other nocturnal prosimians of similar size, the rate of development is relatively slow. Unlike many anthropoids, mothers were not strongly protective or rejecting. They did not bring infants back to a fixed location or try to prevent infants from leaving them; and the decline in ventral contact was not accompanied by fights between the pair. The 3 group-living mothers were more protective than the single individually housed mother, and it would seem advisable to isolate mother-infant pairs in laboratory breeding colonies.     

Observations on the pyramidal tract of the slow loris

The pyramidal system of the slow loris was investigated physiologically and histologically. The cerebral response to medullary pyramid stimulation was mapped and found to distribute in two separate foci, rostral to the hand and foot somatosensory foci. The tract was found to contain about 204,000 fibers at the midolivary level on one side, with about 85% of the fibers less than 2 Μm and 1% greater than 4 Μm. Calculation of the amplitude and configuration of the true antidromic response, based on the histological findings, disagreed with the observed response. The latter was found to be analogous to the rwave of the American opossum, which appears to result from intracortical pyramidal tract collateral activation of the cerebral neurons. This response is not present in the macaque monkey.     

Primates in perspective. Review of “Order Primates,” pp. 352–450 in Walker's Mammals of the World, 4th Edition,by Ronald M. Nowak and John L. Paradiso. Baltimore and London,The Johns Hopkins University Press, 1983, 1362 pp., two-volume set, $65

This study examines the positional and activity behavior of a captive slow loris, Nycticebus coucang. The male individual was housed in a primate facility providing a seminatural environment and was subjected to a series of videotape recordings from which 1,878 point observations were taken. The enclosure was designed to allow maximum flexibility of substrate use. Quantitative information detailing activity, positional mode, and substrate geometry was collected using a checklist of 15 variables. Data were tabulated and compared as frequency distributions to describe activity budgets, the use of locomotor and postural modes, and the relation of posture to activity behavior and substrate geometry. The results indicated that almost 90% of the active day may be devoted to behaviors directly or indirectly related to dietary functions. For locomotor behavior, both climbing and walking were associated with the use of diagonal couplets. The loris devoted 52% of its positional behavior to postural modes, favoring the quadrupedal stand, triplets, and sitting. Suspension was found to be used more often in posture than locomotion. Overall, the loris's repertory of positional modes accommodated a wide range of substrate geometries.