Optimum fiber spacing in a hollow fiber bioreactor

A high surface area hollow fiber reactor was developed for mammalian cell culture. The reactor employs an interfiber gel matrix of agar or collagen for cell support. A model was developed to predict cell density as a function of fiber spacing. Optimum spacings are calculated for two sizes of Celgard hollow fibers. Ehrlich Ascites Tumor (EAT) cells were grown to an estimated density of 1.1 x 10(8) viable cells/mL in the extracapillary space-corresponding to an overall reactor density of 7 x 10(7) cells/mL. On the basis of available kinetic and diffusivity data, the model predicts that lactate accumulation may limit cell growth in the early stage of medium utilization, while oxygen delivery becomes limiting at later stages.     

Dietary fiber

Dietary fiber is plant-derived material that is resistant to digestion by human alimentary enzymes. Fiber may be divided into two broad chemical classes: 1) non-alpha-glucan polysaccharides (cellulose, hemicelluloses, and pectins) and 2) lignins. Dietary fiber behaves within the gastrointestinal tract as a polymer matrix with variable physicochemical properties including susceptibility to bacterial fermentation, water-holding capacity, cation-exchange, and adsorptive functions. These properties determine physiological actions of fiber and are dependent on the physical and chemical composition of the fiber. Fiber undergoes compositional changes as a consequence of bacterial enzymatic action in the colon. Dietary fiber is of clinical significance in certain disorders of colonic function and in glucose and lipid metabolism. Dietary fiber increases stool bulk by acting as a vehicle for fecal water and by increasing fecal bacterial volume. Use of fiber in the treatment of constipation and uncomplicated diverticular disease is well established. By increasing stool bulk, fiber also reduces the fecal concentration of bile acids and other substances. Certain types of fiber decrease the rate of glucose absorption and attenuate postprandial rises in blood glucose and insulin. Plasma cholesterol levels are reduced by mucilaginous forms of fiber. This effect appears to be mediated in part by an increase in fecal acidic sterol excretion.     

Minor fiber industries

In which Spanish moss, Palmetto palm, Spartina grass and Teasel bur each plays its role by contributing to the manufacture of particular commodities.     

Bidirectional parallel fiber plasticity in the cerebellum under climbing fiber control

Cerebellar parallel fiber (PF)-Purkinje cell (PC) synapses can undergo postsynaptically expressed long-term depression (LTD) or long-term potentiation (LTP) depending on whether or not the climbing fiber (CF) input is coactivated during tetanization. Here, we show that modifications of the postsynaptic calcium load using the calcium chelator BAPTA or photolytic calcium uncaging result in a reversal of the expected polarity of synaptic gain change. At higher concentrations, BAPTA blocks PF-LTP. These data indicate that PF-LTD requires a higher calcium threshold amplitude than PF-LTP induction and suggest that CF activity acts as a polarity switch by providing dendritic calcium transients. Moreover, previous CF-LTD induction changes the relative PF-LTD versus -LTP induction probability. These findings suggest that bidirectional cerebellar learning is governed by a calcium threshold rule operating "inverse" to the mechanism previously described at other glutamatergic synapses (BCM rule) and that the LTD/LTP induction probability is under heterosynaptic climbing fiber control.     

Strong growth polarity of yeast prion fiber revealed by single fiber imaging

Using the yeast prion as a model, we have developed a novel system to observe the growth of individual prion fibers directly. NM fragments, the prion-determining region of the yeast protein Sup35p, were labeled by either red or green fluorescent dyes, and the fiber growth was observed under a fluorescence microscope. When green-Sup35NM was added to the preformed fibers made of red-Sup35NM, 70-97% of green fibers grew unidirectionally, from only one end of individual red fibers, whereas the remainder grew from both ends. Similarly, the majority of red fibers grew from only one end of green fibers when the order of addition was reversed. Sonication of preformed fibers to expose fresh ends did not change the results, excluding a possibility of occasional deformation of one end as the reason of the apparent unidirectional growth. These results indicate the polarity of Sup35 prion fibers and impose constraints on the models of fiber growth.     

Hollow fiber enzyme reactors

Recently there have been some exciting developments in techniques to encapsulate enzymes into hollow fiber membranes. This entrapment protects enzymes from proteolytic and immunochemical attacks and makes possible industrial and medical applications of the immobilized enzymes.     

Chitosan hollow fiber membranes

Chitosan hollow fibers were produced by wet spinning, taking advantage of the unique rheological properties of highly viscous chitosan solutions in acetic acid. The mechanical and separation properties of hollow fibers were tested. The mechanical properties were determined by measuring tensile force, tensile stress, elongation, and initial elasticity module. The separation properties were specified by determining retention coefficients of particular blood components and determining cut-off of the membrane by the analysis of dextran molecular weight distribution in the feed and permeate using a technique of gel chromatography (GPC)-Shimadzu gel chromatograph.     

试管棉纤维与天然棉纤维超微结构的差异（简报）

Native cotton fiber and in vitro cotton fiber that was induced from cotton ovule callus by suspension culture were observed using transmission electron microscope and scanning electron microscope. The ovule surface on the first day preanthesis was quite smooth. On the anthesis, it had a lot of protuberances. Two kinds of callus, smooth and rough were found. The microfibrils of callus was vertical to the cell long axis and they changed their orientations with the development of the in vitro cotton fiber: from the vertical to shallow spiral and then to parallel to the cell long axis. So was the native cotton fiber. It suggests that in vitro cotton fiber and native cotton fiber have similar development process. Compared with the ovule surface cell, most callus cells had smaller nuclear. During the development of the fiber, the plasm of native cotton fiber was denser than that of in vitro fiber, and it has more cellular organ than in vitro fiber. The cell wall of native cotton fiber was thicker and denser than that of the in vitro cotton fiber too. It suggests that the physiological activity of in vitro cotton fiber was less active than native cotton fiber.