Polar budding

Cyniclomyces (1) weak few sugars formerly Saccharomycopsis guttulata occurs in alimentary canal of rabbits grows in complex medium between 30 and 40° difficult to maintain oval or cylindrical cells with polar budding not filamentous 33,44... 

C. albicans CaRSRl required for polar bud site selection in yeast form, germ tube emergence during mycelial transition and hyphal elongation. 145... 

Yeasts exhibit several types of budding which may be of diagnostic value. Among those isolated from fermenting and aging wine, multilateral (characteristic of Saccharomyces sp.) and restricted polar budding (characteristic of apiculate yeasts) are most frequendy observed. Occassionally, fission yeasts Schizosaccharomyces pombe) may be isolated. These reproduce by the formation of cross-walls which is visually similar to bacterial fission. 

Taste-modality recognition is a function of the cells of the taste buds. Perception of the sensation is a result of complex processes in the brain. The biological events that are discussed are those that occur, or are suggested as occurring, in taste-receptor cells, beginning at the instant when the taste-stimulus molecule interacts with the cell, until the membrane of the receptor cell is polarized. These are peripheral events. However, our knowledge of the peripheral mechanisms in taste perception is not sufficiently complete to provide a detailed, biophysical explanation of this phenomenon. Nevertheless, several stages in this explanation have been hypothesized, and some are demonstrable. 

Fig. 2.3 The development of polarity and asymmetric division in Saccharomyces cerevisiae. The diagram is reproduced in a slightly simplified form from the work of Lew Reed (1995) with the permission of Current Opinion in Genetics and Development, (a) The F-actin cytoskeleton strands = actin cables ( ) cortical actin patches, (b) The polarity of growth is indicated by the direction of the arrows (arrows in many directions signifies isotropic growth), (c) 10-nm filaments which are assembled to form a ring at the neck between mother and bud. (d) Construction of the cap at the pre-bud site. Notice that the proteins of the cap become dispersed at the apical/isotropic switch, first over the whole surface of the bud, then more widely. Finally, secretion becomes refocussed at the neck in time for cytokinesis, (e) The status and distribution of the nucleus and microtubules of the spindle. Notice how the spindle pole body ( ) plays an important part in orientation of the mitotic spindle.

The taste bud is a polarized structure with a narrow apical opening, termed the taste pore, and basolateral synapses with afferent nerve fibers. Solutes in the oral cavity make contact with the apical membranes of the TRCs via the taste pore. There is a significant amount of lateral connectedness between taste cells within a bud both electrical synapses between TRCs and chemical synapses between TRCs and Merkel-like basal cells have been demonstrated to occur [39]. Furthermore, there are symmetrical synapses between TRCs and Merkel-like basal cells [39]. In addition, these basal cells synapse with the afferent nerve fiber, suggesting that they may function in effect as interneurons [39]. The extensive lateral interconnections... 

Kaouadji, M. and Ravanal, P., Further non-polar flavonols from Platanus acerifolia buds, Phytochemistry, 29, 1348, 1990. 

An important observation is that certain viruses preferentially bud at different poles of their host cells. In MDCK-cell monolayers, VSV buds exclusively from the basal, or lateral, plasma membranes, and contains sialylated glycoproteins, whereas influenza virus buds exclusively from the apical plasma-membrane, and lacks neuraminic acid. The question arises as to whether glycosylation of viral glycoproteins is needed in order to determine the site of budding. An electron-microscope study revealed that polarity in the maturation sites of these viruses was maintained under conditions of inhibition of glycosyla-... 

After synthesis on the smooth ER, the polar lipids, including the glycerophospholipids, sphingolipids, and glycolipids, are inserted into specific cellular membranes in specific proportions, by mechanisms not yet understood. Membrane lipids are insoluble in water, so they cannot simply diffuse from their point of synthesis (the ER) to their point of insertion. Instead, they are delivered in membrane vesicles that bud from the Golgi complex then move to and fuse with the target membrane (see Fig. 11-23). Cytosolic proteins also bind phospholipids and sterols and transport them between cellular membranes. These mechanisms contribute to the establishment of the characteristic lipid compositions of organelle membranes (see Fig. 11-2). 

Rodriguez Boulan, E. and Sabatini, D. D. 1978. Asymmetric budding of viruses in epithelial monolayers a model system for study of epithelial polarity. Proc. Natl. Acad. Sci, USA 75, 5071-5075. 

Tn its normal polar, downward movement, the auxin stimulates the cells below the tip to elongate and sometimes to divide. Specific tissues, notably the cambium, are caused to divide laterally by auxin coming from the developing buds, which accounts for the wave of cell division occurring in tree trunks in the spring. Stimulation of other stem cells to divide... 

Tickle, C., Alberts, B., Wolpert, L., Lee, J. (1982). Local application of retinoic acid to the limb bud mimics the action of the polarizing region. Nature (London) 296, 564-566. 

During limb formation, SHH-N is synthesized and secreted by a small cohort of inducer cells in the posterior margin of the limb bud, a region referred to as the zone of polarizing activity (ZPA) (Figure 34.1). Studies in mice indicate that the type of digit formed at the distal end of the limb is determined by both the concentration and duration of SHH-N exposure to the cells at the distal end of the... 

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