Expression of complement receptors 1 and 2 on follicular dendritic cells is necessary for the generation of a strong antigen-specific IgG response

Two mechanisms could account for the impaired humoral immune response found in Cr2-/- mice. The absence of complement receptors 1 and 2 (CR1, CR2) on B cells could affect their activation. Alternatively, impaired Ag trapping by follicular dendritic cells (FDC) could affect B cell maturation into Ig-secreting or memory B cells. To compare the roles of CR1 and CR2 on B cells vs FDC in this abnormal response, bone marrow (BM) chimeric mice were generated and immunized with specific T-dependent Ags. The primary and secondary Ab response was measured. Cr2+/+ animals reconstituted with a Cr2-/- BM generated a diminished but detectable humoral immune response compared with controls. When injected with preformed immune complexes (IC), these mice maintained follicular IC localization. Cr2-/- animals reconstituted with a Cr2+/+ BM had an initial rise in the Ab titer, but were unable to maintain it as shown by a pronounced decrease in the IgG titer. This defect persisted during the secondary immune response. Follicular IC trapping was also impaired. Despite the abnormal Ab response, germinal center formation was retained in all of the chimeric animals. These experiments are the first to demonstrate an absolute requirement for CR1 and CR2 expression on FDC in the generation of a normal humoral immune response.     

Survival of Taenia solium cysticerci in carcasses of pigs kept at 4 C

In the present study, the survival of cysticerci of Taenia solium in carcasses of 1 Small-Ear-Miniature and 2 Landrace Small-Ear-Miniature pigs kept in a refrigerator at 4 C was determined. The viability of the cysticerci was determined by observing evagination and active movement of the scolex under a fluorescent light after digestion in pig bile. Although no viable cysticerci were found after day 30, 58.8% cysticerci survived between day 26 and day 30. Moreover, more than 80% of the cysticerci were viable between day 1 and day 25. These findings indicate that taeniasis solium can be transmitted through eating raw or undercooked pork or viscera of pigs following refrigeration at 4 C for less than 30 days.     

Hypervariability generated by natural selection in an extracellular complement-inhibiting protein of serotype M1 strains of group A Streptococcus

In many countries, M1 strains of the human pathogenic bacterium group A Streptococcus are the most common serotype recovered from patients with invasive disease episodes. Strains of this serotype express an extracellular protein that inhibits complement [streptococcal inhibitor of complement (Sic)] and is therefore believed to be a virulence factor. Comparative sequence analysis of the 915-bp sic gene in 165 M1 organisms recovered from diverse localities and infection types identified 62 alleles. Inasmuch as multilocus enzyme electrophoresis and pulsed-field gel electrophoresis previously showed that most M1 organisms represent a distinct streptococcal clone, the extent of sic gene polymorphism was unexpected. The level of polymorphism greatly exceeds that recorded for all other genes examined in serotype M1 strains. All insertions and deletions are in frame, and virtually all nucleotide substitutions alter the amino acid sequence of the Sic protein. These molecular features indicate that structural change in Sic is mediated by natural selection. Study of 70 strains recovered from two temporally distinct epidemics of streptococcal infections in the former East Germany found little sharing of Sic variants among strains recovered in the different time periods. Taken together, the data indicate that sic is a uniquely variable gene and provide insight into a potential molecular mechanism contributing to fluctuations in streptococcal disease frequency and severity.     

Inactivation and conformational changes of aminoacyclase in trifluoroethanol solutions

The inactivation and unfolding of aminoacyclase (EC 3.5.1.14) during denaturation by different concentrations of trifluoroethanol (TFE) have been studied. A marked decrease in enzyme activity was observed at low TFE concentrations. The kinetic theory of the substrate reaction during irreversible inhibition of enzyme activity described previously by Tsou [Tsou (1988), Adv. Enzymol. Related Areas Mol. Biol. 61, 381-436] was applied to study the kinetics of the inactivation course of aminoacyclase during denaturation by TFE. The inactivation rate constants for the free enzyme and substrate-enzyme complex were determined by Tsou's method. The inactivation reaction was a monophasic first-order reaction. The kinetics of the unfolding course were a biphasic process consisting of two first-order reactions. At 2% TFE concentration, the inactivation rate of the enzyme was much faster than the unfolding rate. At a higher concentration of TFE (10%), the inactivation rate was too fast to be determined by conventional methods, whereas the unfolding course remained as a biphasic process with fast and slow reactions occurring at measurable rates. The results suggest that the aminoacyclase active site containing Zn2+ ions is situated in a limited and flexible region of the enzyme molecule that is more fragile to the denaturant than the protein as a whole.     

玻璃钢——钢混合抽油杆柱系统设计方法

在前人工作的基础上，提出了一种新的玻璃钢－－钢混合抽油杆柱的设计方法－－系统设计法。     

Prolonged immunodepression after trauma and hemorrhagic shock

OBJECTIVE: To define and discuss the cytologic findings in six cases of nodular pseudoangiomatous stromal hyperplasia (PASH) of the breast. STUDY DESIGN: Retrospective evaluation of the medical records, cytologic and histologic material from six patients with palpable mammary PASH. Cases in which PASH was associated with other predominant mammary lesions were not included in the study. RESULTS: A total of six patients with histologically proven PASH underwent aspiration in nine occasions (three patients studied twice). Clinically, five patients were diagnosed as having fibroadenoma or another benign lesion, and in one patient carcinoma was suspected. In two patients, mammography disclosed rapid growth of the lesion. Seven aspirations, performed on five patients, were diagnosed as fibroadenoma (n = 5) or fibroadenomatous lesion (n = 2). An eighth aspiration was cystic and reported as fibrocystic disease. The last case was erroneously diagnosed as suspicious for carcinoma. Even after revision, the cytologic similarities of PASH with fibroadenoma were remarkable. Most smears were less cellular than those of conventional fibroadenomas. Epithelial clusters showed variable size, with a predominance of medium to small groups. Stromal elements were minimal or absent. Background cellularity was composed of round to oval naked nuclei and others with spindle shapes. Occasional epithelial clusters showed cellular dissociation and slight atypia. CONCLUSION: Due to the absence of specific cytologic features and similarities to fibroadenoma, a precise diagnosis of PASH cannot be made on cytologic material. However, the majority of cases can be diagnosed correctly as benign, allowing appropiate treatment.     

Effects of inhibitor of protein kinase C on brain edema formation evoked by experimental cerebral ischemia in gerbils and rats

Recent studies have suggested that protein kinase C (PKC) may be involved in the formation of brain edema. In this paper, the effects of two kinds of PKC inhibitors, H-7 and matrine, were examined on the brain edema formation in experimental models. The results showed that pretreatment with H-7 6.25 and 12.5 mg.kg-1 prevented the accumulation of water and certain electrolytes in the unilateral hemisphere of the brain evoked by ligation of a single common carotid artery in Mongolian gerbil; pretreatment with matrine 25 and 50 mg.kg-1 reduced the extent of cerebral edema formation evoked by ligation of a single common carotid artery in gerbil and by middle cerebral artery occlusion in Sprague-Dawley rats. These results present new evidence for the involvement of PKC in the formation of brain edema.