Physical studies on the mechanical stability of columns of calcium alginate gel pellets containing entrapped microbial cells

Constant strain rate and stress relaxation tests on columns of spherical alginate pellets containing entrapped microbial cells demonstrated non-linear viscoelastic behaviour, the columns being relatively resistant to compression over long periods. Compressibility rose with decreases in the alginate concentration used to form the pellets and the soluble sucrose concentration therein, and with increases in temperature and the concentration of cells or other particulate materials; but appeared to be unaffected by the relative dimensions of the column. Pellets were not fractured unless very high pressures were used and deformation was only partially reversible. Over long time periods large creep effects were observed, the rate of compression decreasing exponentially with time. The creep rate increased with the pressure applied, but could be decreased by pumping fluid up the column. Thus the compression of large columns operated continuously for long periods could be modelled by pumping fluid at high flow rates up small columns while applying large pressures to the top of the column. Abbreviation: the ratio of wet weight: dry weight for the yeast cells used in this study is 4:1; weights of cells are always quoted as wet weights.     

每搏量变异度在围手术期容量治疗监测中的应用

每搏量变异度是动态的容量监测指标.机械通气患者心肺的相互作用是每搏量变异度的产生基础,通过动脉压力波形分析技术可以进行连续监测.每搏量变异度能够准确预测容量治疗反应,与静态的血流动力学参数相比,对于优化心输出量和组织氧供更有优势,但也存在一定的局限性.每搏量变异度受多种因素影响且不能用于自主呼吸和心律失常的患者.临床应用时应该综合考虑其影响因素,结合其他的指标和方法指导容量治疗.     

Interaction of the human DnaJ homologue, HSJ1b with the 90 kDa heat shock protein, Hsp90

The 90 kDa heat shock protein (Hsp90) is a major cytoplasmic molecular chaperone associating with numerous other proteins. Both genetic and in vitro refolding experiments using reticulocyte lysate have suggested a functional interaction of Hsp90 with yeast human homologues of E. coli DnaJ. Here we present direct evidence using surface plasmon resonance that Hsp90 and the human DnaJ homologue, HSJ1b, bind to each other. We also show that Hsp90 and HSJ1b transfer alpha-lactalbumin to each other in an ATP-dependent manner. The two chaperones have additive effects in preventing rhodanese aggregation.     

The Aspergillus nidulans xprF gene encodes a hexokinase-like protein involved in the regulation of extracellular proteases

The extracellular proteases of Aspergillus nidulans are produced in response to limitation of carbon, nitrogen, or sulfur, even in the absence of exogenous protein. Mutations in the A. nidulans xprF and xprG genes have been shown to result in elevated levels of extracellular protease in response to carbon limitation. The xprF gene was isolated and sequence analysis indicates that it encodes a 615-amino-acid protein, which represents a new type of fungal hexokinase or hexokinase-like protein. In addition to their catalytic role, hexokinases are thought to be involved in triggering carbon catabolite repression. Sequence analysis of the xprF1 and xprF2 alleles showed that both alleles contain nonsense mutations. No loss of glucose or fructose phosphorylating activity was detected in xprF1 or xprF2 mutants. There are two possible explanations for this observation: (1) the xprF gene may encode a minor hexokinase or (2) the xprF gene may encode a protein with no hexose phosphorylating activity. Genetic evidence suggests that the xprF and xprG genes are involved in the same regulatory pathway. Support for this hypothesis was provided by the identification of a new class of xprG(-) mutation that suppresses the xprF1 mutation and results in a protease-deficient phenotype.     

Macroorchidism in two unrelated prepubertal boys with a normal FSH receptor

BACKGROUND: Macroorchidism in prepuberty is an uncommon condition which we hypothesised might reflect constitutive activation of the FSH receptor (FSHR). PATIENTS AND METHODS: Patient 1 was found to have macroorchidism (15 ml testicular volume) at the time of orchidopexy when 3.7 years of age. A gonadal biopsy was obtained at the time of surgery. Patient 2 developed macroorchidism (5 ml) when 8.8 years old. Despite a testicular volume >4 ml, morning testosterone levels were unrecordable with no measurable gonadotrophin production in either patient. Patient 2 had prepubertal gonadotrophin levels 3 years later despite a testicular volume that was 8 ml bilaterally. Inhibin B was measured and the FSHR sequenced in both patients. RESULTS: Inhibin B levels were age and pubertal stage appropriate. Gonadal biopsy (patient 1) demonstrated areas of Sertoli cell hyperplasia. Sequence analysis of all 10 exons of the FSHR was normal. There was significant, presumed gonadotrophin-dependent testosterone production in both boys by 15 years of age. CONCLUSIONS: The cause of prepubertal macroorchidism in our patients is unclear but the pronounced difference in phenotype suggests that there may be more than one underlying mechanism. This mechanism was not constitutive activation of a mutated FSHR.