Biotin determination by three different methods: specificity and application to urine and plasma ultrafiltrates of patients with and without disorders in biotin metabolism

A microbiological, an avidin-binding and a streptavidin-binding method for biotin determination were compared. All three methods detected biotin equally well but they exhibit different specificities for derivatives of biotin. The microbiological assay has the highest specificity and is the method of choice for biotin determination in biotinidase-deficient patients. The specificity of streptavidin-binding has not been investigated so far. Application of the three methods to urine samples of patients with and without biotin therapy indicated that only 50% of biotin equivalents measured with the avidin method correspond to authentic biotin as previously shown. The other 50% comprise mainly bisnorbiotin and biotin-d-sulfoxide. HPLC-separation of urine samples prior to assay confirmed this finding and revealed a bisnorbiotin oxidation product and an unknown compound as further biotin metabolites. The latter was measurable by all three methods and not detectable in plasma ultrafiltrate. This was the only metabolite which was able to restore deficient 3-methylcrotonyl-CoA carboxylase activity in biotin-deficient fibroblasts. The combination of the three methods together with HPLC-separation proved to be a valuable analytical tool for the identification of the main biotin metabolites in biological fluids.     

RANTES-induced T cell activation correlates with CD3 expression

The chemokine RANTES induces a unique biphasic cytoplasmic Ca2+ signal in T cells. The first phase of this signal, similar to that of other chemokines, is G-protein mediated and chemotaxis associated. The second phase of this signal, unique to RANTES and evident at concentrations greater than 100 nM, is tyrosine kinase linked and results in a spectrum of responses similar to those seen with antigenic stimulation of T cells. We show here that certain jurkat T cells responded to RANTES solely through this latter pathway. A direct correlation between the RANTES-induced second phase response and CD3 expression was demonstrated in these cells. Sorting the Jurkat cells into CD3(high) and CD3(low) populations revealed that only the CD3(high) cells were responsive to RANTES. Furthermore, stimulation of these Jurkat cells with anti-CD3 mAb significantly depresses their subsequent response to RANTES. While a RANTES-specific chemokine receptor is expressed at a low level on these Jurkat cells, the RANTES-induced activation is dependent on the presence of the TCR. Thus, stimulation through TCR may partially account for RANTES' unique pattern of signaling in T cells.     

Stiffness of trabecular bone of the tibial plateau in patients with rheumatoid arthritis of the knee

Stiffness of subchondral proximal tibial trabecular bone is a factor in the stability of prostheses implanted into that bone. The stiffness of trabecular bone in osteoarthritis (OA) has been documented. Trabecular bone in rheumatoid arthritis (RA) is osteopenic in numerous sites and morphologically abnormal in the proximal tibia. Reliable data on proximal tibial bone in RA are lacking, although 1 study failed to identify abnormalities. The purposes of this study were (1) to document the stiffness of the proximal tibial cancellous bone in patients with RA, (2) to determine the effect of angular deformity on bone stiffness in rheumatoid patients, and (3) to compare RA stiffness values with those in published reports for OA. Fifteen tibial plateau were obtained from patients with RA during surgery. Each plateau was horizontally seated in a mold and covered with cement. The plateau was divided into 6 regions, which were used to facilitate comparison between specimens and the existing literature. Indentation tests were conducted with a 4-mm-diameter cylindrical indentor controlled by an MTS machine. The indentor descended at a rate of 2 mm/min to a maximum depth of 1.0 mm; load and displacement data were digitally recorded. Stiffness was calculated from the slope of the linear region of the curve using best-fit linear regression. Where varus deformity was present, stiffness in the medial plateau was higher overall than for the other compartment; whereas in the case of valgus deformity, stiffness of the lateral side was significantly higher (P < .05 for each observation). In comparison to older normal specimens, both the medial compartment of the varus RA specimens (P < .01) and the posterolateral compartment of the valgus RA specimens (P < .01) had significantly lower stiffness. Comparison with OA specimens showed that in varus RA, the posteromedial region had significantly lower stiffness than in varus OA at the same site (P < .01). In valgus RA, the lateral region had significantly lower stiffness than in valgus OA at the same site (P < .01). The mean stiffness ratio of the valgus RA was significantly (P < .01) altered from normal, and for the varus RA, it was significantly (P < .01) different from normal posteriorly. The stiffness ratios for the varus RA were significantly (P < .01) different from those for varus OA; there was no difference between valgus RA and valgus OA. It is concluded that RA affected bone has significantly lower stiffness than normal and osteoarthritic bone. The loaded plateau is stiffer than the unloaded plateau in angular deformity, but is still less stiff than normal bone and osteoarthritic plateaus with corresponding deformities.     

The Dübendorf Study: a population-based investigation on normal values of blood pressure self-measurement

In a retrospective study of 50 consecutive children with posterior fossa tumors treated at Texas Children's Hospital, Houston, Tex., in 1989-1992, we evaluated perioperative factors which might influence the development of postoperative cerebrospinal fluid leaks. Factors analyzed included the presence of preoperative hydrocephalus, the institution of cerebrospinal fluid diversion, and the method of dural closure. No statistically significant impact on subsequent cerebrospinal fluid leakage was demonstrated.     

云中基于蚁群算法改进的负载均衡策略

针对云计算虚拟化资源中,提高资源利用率、负载均衡度的问题,在蚁群算法的基础上,提出云中节点间负载均衡的改进算法。前向蚂蚁检测节点的类型、记录节点信息,遇到负载节点时留下觅食信息素;后向蚂蚁依据循迹信息素追溯回负载节点,合理分配超载节点任务。所有蚂蚁不再更新自己的结果集,而是致力于更新单个结果集,在搜索过程中依据节点类型动态地修改路径信息素。在Cloudsim平台下进行的仿真实验验证了改进算法的有效性。     

Natural ligands of the B cell adhesion molecule CD22 beta can be masked by 9-O-acetylation of sialic acids

CD22 beta is a B cell-restricted phosphoprotein expressed on the surface of mature resting B cells. It mediates interactions with other cells partly or exclusively via recognition of alpha 2-6-linked sialic acids on glycoconjugates. The sialylated N-linked oligosaccharides recognized best by CD22 beta are common to many glycoproteins, suggesting that additional regulatory mechanisms may exist. Since the exocyclic side chain of sialic acid is required for recognition, we explored the effects of a naturally occurring modification of the side chain, 9-O-acetylation. Semisynthetic N-linked oligosaccharides terminating with 9-O-acetylated, alpha 2-6-linked sialic acids showed markedly reduced binding to CD22 beta relative to their non-O-acetylated counterparts. Murine lymphoid cells were probed for natural CD22 beta ligands that might be O-acetylated using recombinant soluble forms of CD22 beta (CD22 beta Rg) and influenza C esterase (CHE-Fc, which specifically removes 9-O-acetyl esters from sialic acids). By flow cytometry analysis, CD22 beta Rg binding to splenic B cells and a subset of T cells was increased by pretreatment with CHE-Fc, indicating that some potential CD22 beta ligands are naturally "masked" by 9-O-acetylation. Unmasking of these CD22 beta ligands by removal of 9-O-acetyl esters from intact splenocytes substantially increases their CD22 beta-dependent adhesion in an in vitro adhesion assay. Probing of murine lymphoid tissue sections by CD22 beta Rg and CHE-Fc treatment demonstrates regionally restricted and differentially expressed patterns of distribution between masked and unmasked ligands. For example, lymph node-associated follicular B cells express high levels of CD22 beta ligands, none of which are masked by 9-O-acetylation. In contrast, the ligands on lymph node-associated dendritic cells are almost completely masked by 9-O-acetylation, suggesting that masking may regulate interactions between CD22 beta-positive B cells and dendritic cells. In the thymus, only medullary cells express CD22 beta ligands, and a significant portion of these are masked by 9-O-acetylation, particularly at the cortical-medullary junction. Thus, 9-O-acetylation of sialic acids on immune cells is in a position to negatively regulate CD22 beta adhesion events in a manner depending on both cell type and tissue localization.     

Experimental studies of electro-optic polymer modulators and waveguides

The results of an experimental study of electro-optic modulators and waveguides based on polymeric materials are presented. Included are the design, fabrication, and testing of integrated Mach-Zehnder modulators, which are based on polymer films that contain a novel, nonlinear electro-optic chromophore. Studies also show the efficacy of photolithography or photobleaching by the use of this chromophore to form passive, branching waveguides, which are operated at the 1300-nm wavelength.