Rab is a newly identified family of small G-proteins that share 35-70% homology with the yeast Sec4p and Yptlp involved in the regulation of the secretory pathway. Mature phagocytes display functions requiring organized intracellular traffic and, for this reason, we questioned whether phagocyte differentiation could correlate with the increased expression of rab proteins. Rabbit antisera raised against the recombinant proteins rablAp, 2p, 4p, and 6p were able to detect the corresponding proteins in the human monoblast leukemic cell line U937. When these cells were induced to differentiate into monocyte/ macrophage-like cells displaying functional characteristics of a normal phagocyte, rablAp, 2p, 4p, and 6p were increased and this correlated with an increase in the rab transcripts. Using a rab5 probe, we also observed an increased expression of the rab5 gene in differentiated cells. Similarly, differentiation of the human leukemic myeloblast HL60 cell line along either monocyte or granulocyte pathways induced an increased expression of the rab proteins. Rab proteins were also detected in human neutrophils and in guinea pig alveolar macrophages. As degranulation is one of the phagocyte functions acquired in the late stage of differentiation, we investigated whether rab proteins would be involved in this process. Although rab proteins were tightly membrane bound, none of them was detected in the specific or azurophil granules purified from human neutrophils. The increased expression of rab proteins in mature phagocytes suggests that they may promote functions highly developed in these cells. (J. Clin. Invest. 1991. 87:901-907.)

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Polysaccharides from Auricularia polytricha (APPS) were extracted using Ultrasonic/Microwave Assisted Extraction (UMAE) technology. UMAE conditions of APPS were optimized with Response Surface Methodology (RSM). Rheological properties of APPS were investigated. The results suggested that the optimal UMAE conditions for APPS were ratio of water to raw material 22 (mL/g), extraction time 15.3 min and microwave power 59W. APPS solution exhibited Newtonian flow behavior at low concentration, formed entanglement network at lower concentration and established weak gel structures with solid-like properties at higher concentration. The viscosity of APPS solutions decreased when temperature increased. The viscosity, storage (G') and loss (G") modulus of APPS solution increased when sucrose concentration increased. Heating time and freeze-thaw changes had no significant effect on rheological properties of APPS. The results suggested that UMAE was a suitable and efficient method for APPS extraction and APPS had potential as a novel food additive hydrocolloid in food industry.

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