虾壳虾青素酯皂化工艺研究

为了提高虾青素产品的纯度和得率,研究了KOH-C2H5OH将不同的虾青素酯皂化成游离虾青素的皂化工艺,如碱的种类、助溶剂、碱浓度、皂化时间和温度对皂化的影响.以碱浓度、反应温度、反应时间为因素,选用U12(122×31)混合水平均匀设计表进行试验,确定了皂化的最佳工艺条件为KOH-C2H5OH 40.3 g/L(mKOH/VC2H2OH),温度16.0℃,时间37.0 min.在上述条件下得到的游离虾青素含量从未皂化前的8.1%提高到85.7%.     

Dynamic characterization of thin-walled laminated channel beams with warping

The dynamic characteristics of a round cornered C-channel beam made of laminated composite material are studied. The sharp corners are rounded for manufacturing considerations. Thin-walled beam theory is used to formulate the coupled vibration of a rounded C-channel beam with fixed-free end conditions. It is shown that cross-sectional properties used for isotropic case are applicable for laminated composites and the material properties needed for the formulation can be obtained using the law of average. A comparative study is conducted to show the advantage of using composites. The effect of radius of corner and warping on the natural frequency is investigated. The functional of the equations of motion is formed using the variational method. The Ritz method has been used to formulate an eigenvalue problem and its frequency equation. The method proposed is systematic. The computerized procedure can be used as a fast design tool in the design of composite channel beam structures.     

PTR3, a novel gene mediating amino acid-inducible regulation of peptide transport in Saccharomyces cerevisiae

We have isolated and characterized the Saccharomyces cerevisiae PTR3 gene by functional complementation of a mutant deficient for amino acid-inducible peptide transport. PTR3 is predicted to encode a protein of 678 amino acids that exhibits no similarity to any other protein in the database. Deletion of the PTR3 open reading frame pleiotropically reduced the sensitivity to toxic peptides and amino acid analogues. Initial rates of radiolabelled dipeptide uptake demonstrated that elimination of PTR3 resulted in the loss of amino acid-induced levels of peptide transport. PTR3 was required for amino acid-induced expression of PTR2, the gene encoding the dipeptide/tripeptide transport protein, but was not necessary for nitrogen catabolite repression of peptide import or PTR2 expression. It was determined that PTR3 also modulates expression of BAP2, the gene encoding the branched-amino acid permease. Furthermore, we present genetic evidence that suggests that PTR3 functions within a novel regulatory pathway that facilitates amino acid induction of the PTR system.     

Selective inhibition of [D-Ala2, Glu4]deltorphin antinociception by supraspinal, but not spinal, administration of an antisense oligodeoxynucleotide to an opioid delta receptor

Evidence in vivo has suggested the existence of subtypes of the delta opioid receptor (DOR), which have been termed delta 1 and delta 2. These proposed DOR subtypes are thought to be activated by [D-Pen2, D-Pen5]enkephalin (DPDPE, delta 1) and [D-Ala2, Glu4]deltorphin (delta 2). Recent work in which an antisense oligodeoxynucleotide (oligo) to a cloned DOR was administered by the intrathecal (i.th.) route has demonstrated a reduction in the antinociceptive actions of both i.th. DPDPE and [D-Ala2, Glu4]deltorphin, but not of [D-Ala2, NMPhe4, Gly-ol]enkephalin (DAMGO, mu agonist) in mice. The present investigation has extended these observations by administering the same DOR antisense oligo sequence by the intracerebroventricular (i.c.v.) route and evaluating the antinociceptive actions of i.c.v. agonists selective for delta, mu and kappa receptors. I.th. treatment with DOR antisense oligo, but not mismatch oligo, significantly inhibited the antinociceptive actions of both i.th. DPDPE and [D-Ala2, Glu4]deltorphin but not of i.th. DAMGO or U69,593 (kappa agonist), confirming previous data. In contrast, i.c.v. DOR antisense oligo, but not mismatch oligo, selectively inhibited the antinociceptive response to i.c.v. [D-Ala2, Glu4]deltorphin without altering the antinociceptive actions of i.c.v. DPDPE, DAMGO or U69,593. The data suggest that the cloned DOR corresponds to that pharmacologically classified as delta 2 and further, suggest that this delta receptor subtype may play a major role in eliciting spinal delta-mediated antinociception.     

Sphingosylphosphocholine reduces the calcium ion requirement for activating tissue transglutaminase

Tissue transglutaminase (tTG) catalyzes a Ca2+-dependent transglutaminase reaction resulting in the formation of gamma-glutamyl-epsilon-lysine bonds and is activated during apoptosis to catalyze the formation of apoptotic body. We investigate whether lipids that are membrane components and involved in cell signaling could modify the Ca2+-dependent activation of tTG. We found that sphingosylphosphocholine (lyso-SM) was the only lipid to activate transglutaminase at low Ca2+ concentrations. In the presence of lyso-SM (125 microM), transglutaminase was detectable at 10 microM Ca2+, whereas in the absence of lyso-SM, similar activity was obtained at 160 microM Ca2+. Furthermore, in the presence of lipid vesicles lyso-SM retained the ability to enhance the Ca2+-dependent activation of tTG. Lyso-SM did not significantly change the Km for the glutamyl and primary amine substrates. However, the Kact for Ca2+ was reduced from 300 microM to 90 microM. Structure-function studies of lyso-SM analogs indicate that phosphocholine group on C1, the free amino group at C2 and a C4-C5 double bond are critical for the activation of transglutaminase activity. This is the first demonstration that a specific sphingolipid could enhance the activity of tTG and could play a role in vivo in activation of the tTG at physiologic Ca2+ levels.     

Colorectal surgery using a biofragmentable anastomotic ring

To compare the efficacy of the biofragmentable anastomotic ring (Valtrac-BAR, Davis and Geck, Medical Device Division, Danbury, CT, USA) with conventional anastomotic techniques, 30 patients who underwent colorectal surgery from August 1993 to March 1995 were retrospectively studied. The use of the BAR was also compared with conventional techniques including hand-sewn sutures in 30 patients and an end-to-end anastomosis (EEA) stapler in 24 patients. There were 17 men and 13 women in the BAR group with ages ranging from 37 to 80 years, 18 men and 12 women in the hand-sewn group with ages ranging from 41 to 82 years and 14 men and 10 women in the EEA group with ages ranging from 38 to 72 years. Surgical indications included: 25 colon cancers and five rectal cancers in the BAR group; 27 colon cancers and three rectal cancers in the hand-sewn group; and six colon cancers and 18 rectal cancers in the EEA group. There was no conversion to other anastomotic methods. Most of the patients tolerated a low-residual diet from the fifth post-operative day. No clinical leakage or stricture was noted. Only seven patients were aware of the passage of BAR fragments. The mean hospital stay was 14.1 days. There were no significant differences among these techniques in the return of bowel function, the incidence of surgical complications, including anastomotic leakage, or the length of hospitalization. BAR anastomosis was more time efficient than conventional techniques. Our results confirmed that BAR was an ideal sutureless alternative for anastomosis in colorectal surgery.     

Fuzzy logic controller design for spacecraft proximity operations

A Genetic Algorithms (GAs) based method is presented in this paper for concurrent design of rule sets and membership functions for a fuzzy logic controllers to be used in spacecraft proximity operations. The heuristic nature of fuzzy logic makes GAs a natural candidate for logic design in which both rule sets and membership functions are optimized simultaneously. The employment of GAs natural genetic operations provides a means to search in a complex system space that is difficult to described mathematically. A one-dimensional controller for spacecraft proximity operations is implemented for examination in detail. The expension of the algorithm for a 6 DOP controller is discussed.     

Neuregulin receptors, erbB3 and erbB4, are localized at neuromuscular synapses

Neuregulin (NRG) is concentrated at synaptic sites and stimulates expression of acetylcholine receptor (AChR) genes in muscle cells grown in cell culture. These results raise the possibility that NRG is a synaptic signal that activates AChR gene expression in synaptic nuclei. Stimulation of NRG receptors, erbB3 and erbB4 initiates oligomerization between these receptors or between these receptors and other members of the epidermal growth factor (EGF) receptor family, resulting in stimulation of their associated tyrosine kinase activities. To determine which erbBs might mediate synapse-specific gene expression, we used antibodies against each erbB to study their expression in rodent skeletal muscle by immunohistochemistry. We show that erbB2, erbB3 and erbB4 are concentrated at synaptic sites in adult skeletal muscle. ErbB3 and erbB4 remain concentrated at synaptic sites following denervation, indicating that erbB3 and erbB4 are expressed in the postsynaptic membrane. In addition, we show that expression of NRG and erbBs, like AChR gene expression, increases at synaptic sites during postnatal development. The localization of erbB3 and erbB4 at synaptic sites is consistent with the idea that a NRG-stimulated signaling pathway is important for synapse-specific gene expression.