Glycoprotein Nature of Glycosidases from Leaves of Pisum sativum L

-Mannosidase, ß-N-acetylglucosaminidase, - and ß-galactosidaseand ß-glucosidase were partially purified from leavesof Pisum sativum by ammonium sulphate fractionation and columnchromatography on DEAE-Sephadex A-50 and hydroxylapatite. Atleast two molecular forms of each enzyme were resolved by thesetechniques except for ß-glucosidase of which onlyone form was resolved. Except for one form of -galactosidase,all of the glycosidases thus purified were completely boundby Sepharose-linked Concanavalin A. The binding was stronglyinhibited by cr-methyl-D-mannoside and no binding to Sepharose-6-Boccurred indicating that these glycosidases contain mannose-richoligosaccharides. The glycoprotein nature of -mannosidase, ß-galactosidaseand ß-glucosidase was further demonstrated by chromatographyon phenylboronate agarose columns. The differences in the concentrationof cr-methyl-D-mannoside and sorbitol required to elute thevarious glycosidases from Sepharose-linked Con A and phenylboronateagarose, respectively, suggested that these enzymes are glycosylatedto various degrees or that structural variation in their carbohydratemoieties occur. This is the first demonstration that glycosylationof several glycosidases present in a single plant species isapparently a generalized feature of these enzymes. Key words: Pisum sativum, Glycosidase, Glycoprotein     

Survey of Evidence for Neurosecretion in Gastropod Molluscs

In gastropods that have been studied, there is some indicationof the presence of neurons with specialized staining propertiesthat are possibly neurosecretory. However, there are no stainsspecific for neurosecretion, and certain cellular inclusionscan simulate secretory products. The presence of elementaryneurosecretory granules does not as such determine neurosecretorystatus since such granules may represent neurotransmitters. Evidence of cyclical secretory activity of so-called neurosecretoryneurons is most frequently related to reproductive phenomena,but there are also instances of control of water balance andhibernation. The existence of neurohemal organs within nerves and commissureshas been described in several species. So-called neuroglandularcomplexes have been reported in association with the nervoussystem. Vesicles incorporated in the central nervous systemmay be sensory rather than glandular. Some caution is neededin estimating secretory activity of these complexes. Possible non-neural endocrine glands adjacent to the centralganglia have been described. In pulmonates granule-laden fibersare associated with the mediodorsal bodies; however, the natureof the neurosecretomotor or neurosecretory-neuropil controlis still unclear, both morphologically and physiologically.     

GUSTATORY NEURAL RESPONSE OF THE CHORDA TYMPANI TO LICK-DURATION STIMULI

NaCl solutions were flowed over the anterolateral region ofthe tongue of laboratory albino rats to determine the effectsof stimulus flow duration upon muitiunit chorda tympani nerveresponses. Fifty-five msec flow duration ‘artificial licks’delivered 5µl, while 2000 msec flow duration stimuli delivered650µl. Resonses were summated, A/D converted, and averaged,with time to stimulus presentation onset, ± 1 msec, astrigger. It was found that the latency and slope of the initialsegment of the phasic response were independent of flow duration,but they changed systematically with NaCl concentration. Slopeof both premaximum and postmaximum response was insensitiveto flow duration. In contrast, the magnitude and duration ofall segments of the phasic response were dependent upon bothstimulus flow duration and concentration. The final rising slopeof the phasic response, and the maximum response magnitude attained,were smaller, and were reached sooner, for the shorter flow,lick-duration stimuli. All maximum magnitudes to lick-durationstimuli occurred 170 msec or less after stimulus on-set. Thisis similar to the interval between actual licks. The contributionto the observed response differences of total number of fungiformpapillae stimulated, total number of receptor sites available,and rate of stimulus spread, was estimated.     

NORTH AMERICAN GRASSLAND BIRDS: AN UNFOLDING CONSERVATION CRISIS?

Abstract: The widespread and ongoing declines of North American bird populations that have affinities for grassland and grass-shrub habitats (hereafter referred to as grassland birds) are on track to become a prominent wildlife conservation crisis of the 21st century. There is no single cause responsible for the declines of grassland birds. Rather, a cumulative set of factors such as afforestation in the eastern United States, fragmentation and replacement of prairie vegetation with a modern agricultural landscape, and large-scale deterioration of western U.S. rangelands are the major causes for these declines. The North American Bird Conservation Initiative (NABCI) is a set of comprehensive and coordinated strategic actions modeled on the Joint Venture initiatives that were used to successfully implement the North American Waterfowl Management Plan. The NABCI is emerging as a potential broad-scale solution for conserving populations of grassland birds. Coordinating grassland bird conservation efforts with initiatives to stabilize and increase upland game birds that have strong affinities for grassland habitats—such as quail and prairie grouse—presents additional opportunities to leverage funding and resources that will positively impact virtually all species of North American grassland birds.     

CARBOHYDRATE MOVEMENT FROM AUTOTROPHS TO HETEROTROPHS IN PARASITIC and MUTUALISTIC SYMBIOSIS

1. The bulk of the fixed carbon which moves from autotroph to heterotroph in most symbiotic associations is in a single compound, a carbohydrate. Techniques employing ¹⁴C have been most valuable for investigating this movement. 2. Most ‘zoochlorellae’ belong to the Chlorococcales, and they release carbohydrate to the animal tissue as either glucose or maltose. In some molluscs, the ‘zoochlorellae’ are actually chloroplasts, possibly derived from siphonaceous algae. Although it is known that these chloroplasts supply photosynthetically fixed carbon to the animal tissue, the form of the carbon compounds which move is not known. In Convoluta roscoffensis the ‘zoochlorellae’ belong to the Pyramimonadales, but carbohydrate movement has not yet been directly studied in this association. 3. Most ‘zooxanthellae’ belong to the Dinophyceae. In associations involving co-elenterates and molluscs, glycerol is the main carbohydrate moving to the animal. Homogenates of the host animal tissue stimulate excretion by isolated zooxanthellae. 4. In lichens, symbiotic blue-green algae release glucose to the fungus, but the various genera of green algae that have been studied all release polyols (either ery-thritol, ribitol or sorbitol). Lichen fungi rapidly synthesize mannitol from all these compounds. When lichen algae are isolated into pure culture, they soon lose the ability to excrete carbohydrate, and intracellular production of the carbohydrate that is excreted either becomes much reduced, or ceases altogether. 5. Mostly indirect evidence indicates that sucrose is the main carbohydrate moving from flowering plants to their associated symbiotic fungi. Diversion of the translocation stream towards the site of the association occurs. The fungi convert host sugars to their own carbohydrates, principally trehalose and polyols. 6. ‘Saprophytic’ higher plants are all obligately mycotrophic and receive carbohydrate from their associated fungi. In at least some associations, the fungus is simultaneously associated with an autotrophic higher plant, which is the ultimate source of carbohydrate for the association. 7. Some parasitic higher plants possess chlorophyll, but the extent to which they depend on their host for carbohydrate varies with different species. Green mistletoes evidently derive negligible carbon from their hosts, but other green parasites derive at least some. There is no evidence that any of the chlorophyll-containing parasites export carbohydrate back to their hosts. Parasitic higher plants which lack chlorophyll presumably derive all their carbohydrates from their hosts, but experimental investigations of this are scarce. 8. Comparison between different types of symbiotic association show that a number of common features emerge. 9. The algal symbionts of both invertebrates and lichens have, in comparison to free-living forms, reduced growth rates and greater incorporation of fixed carbon into soluble carbohydrates. They excrete a much greater proportion of their fixed carbon than free-living forms, and most of it is usually as a single carbohydrate. Particularly striking is the fact that the excreted carbohydrate is one which is either not the major intracellular carbohydrate, or one which ceases or nearly ceases to be produced in culture. 10. The translocation stream of autotrophic higher plants is diverted towards the site of association with either fungi or parasitic higher plants, but it is not known how this is achieved. 11. In all associations, the cell walls of the autotroph become reduced or modified at the site of contact with the heterotroph, but it seems likely that this is not directly connected with the mechanism of carbohydrate transfer between the symbionts. 12. In many associations, the heterotroph rapidly converts host sugars into other compounds (frequently into its own carbohydrates which are usually different from those of the host). This may serve to maintain a concentration gradient and so ensure a continued flow from the host. 13. Polyols feature prominently in symbiotic and parasitic associations, not only as the carbohydrates of many plant heterotrophs, but also as the form of carbohydrate released by both zooxanthellae and the green algae of lichens to their heterotrophic partners.     

STUDIES OF BEHAVIOR AND BEHAVIOR DEVELOPMENT BY LABORATORY MANIPULATION OF CONDITIONS

Book reviewed in this article:
Mother-Love. By H. F. HARLOW
Nature and Development of Affection. By H. R. HARLOW and R. ZIMMERMAN