Point mutations in the conserved box 1 region inactivate the human granulocyte colony-stimulating factor receptor for growth signal transduction and tyrosine phosphorylation of p75c-rel

The human granulocyte colony-stimulating factor receptor (hG-CSFR) belongs to the cytokine receptor superfamily. As with other members of this family, the cytoplasmic domain of hG-CSFR lacks intrinsic tyrosine kinase activity. To identify critical regions mediating growth signal transduction by hG-CSFR, deletions or site-directed amino acid substitutions were introduced into the cytoplasmic domain of hG-CSFR, and the mutant cDNAs were transfected into the murine interleukin-3 (IL- 3)-dependent Ba/F3 and FDCP cell lines. Truncation of the carboxy- terminal end of the receptor to the membrane-proximal 53 amino acids of the cytoplasmic domain, which retained the conserved Box 1 and Box 2 sequence motifs, decreased the ability of hG-CSFR to transduce G-CSF- mediated growth signals without an associated loss in receptor binding affinity. Substitution of proline by alanine at amino acid positions 639 and 641 within Box 1 completely abolished the G-CSF-mediated growth signal. Rapid induction of tyrosine phosphorylation of several cellular proteins, including a 75-kD protein (p75) identified as c-rel, was an early event associated with transduction of proliferative signals by hG- CSFR in Ba/F3 transfectants. Mutant receptors containing Pro-to-Ala substitutions that inactivated the receptor for mitogenic activity also inactivated the receptor for tyrosine-specific phosphorylation of p75. These results show that the conserved Box 1 sequence motif (amino acids 634 to 641) is critical for mitogenesis and activation of cellular tyrosine kinases by hG-CSFR.     

Immunolocalization of beta 1 integrins in platelets and platelet- derived microvesicles

Human platelets contain several adhesion receptors belonging to the integrin superfamily. At least three beta 1 integrins are present on platelets and have been shown to mediate platelet adhesion to collagen, fibronectin, and laminin. To study the cellular localization of the beta 1 integrins in platelets, we produced a polyclonal antibody by immunization of goat 172 with purified beta 1 subunit from HPB-ALL cells. Antibody 172 (Ab172) specifically immunoblotted a 135-Kd protein in a lysate of whole platelets. The reactivity of Ab172 with platelet membrane proteins was further determined by immunoprecipitation of lysates of surface-radioiodinated platelets. Ab172 immunoprecipitates, resolved by nonreducing/reducing two-dimensional sodium dodecyl sulfate- polyacrylamide gel electrophoresis consisted of three labeled proteins with migrational properties of platelet glycoprotein (GP)Ia, GPIc and GPIIa. Neither GPIIb/IIIa nor the vitronectin receptor were immunoprecipitated by Ab172, confirming a lack of cross-reactivity with the beta 3 integrins in platelets. Immunofluorescence studies using Ab172 were performed to investigate the cellular distribution of beta 1 integrins in platelets. Fluorescent labeling of intact cells demonstrated the presence of beta 1 antigen on the surface of resting cells. Permeabilization of platelets with Triton X-100 showed the presence of an intracellular pool of beta 1 antigen. Double-label experiments using Ab172 and AP-2 (anti-GPIIb/IIIa) showed identical labeling patterns, suggesting a similar subcellular distribution for these integrins. Following thrombin stimulation, permeabilized cells showed a centralized clearing of both beta 1 antigen and GPIIb/IIIa as well as an intensification of surface labeling for beta 1 antigen. These findings suggest the translocation of intracellular beta 1 antigen to the platelet surface as a result of thrombin stimulation. Because platelet-derived microvesicles have been reported to contain GPIIb/IIIa, we investigated the possible distribution of beta 1 integrins in these structures. Microvesicles, produced as a result of platelet activation, were labeled with Ab172, suggesting the distribution of beta 1 integrins in these structures as well as in intact cells.     

Fractures in the Maxillofacial Region: A Four Year Retrospective Study

Introduction

The incidence of maxillofacial injuries is on the rise due to motor vehicle accidents and increased incidence of violence in recent times. The aim of this retrospective study was to determine the incidence, aetiology, the pattern of fractures, their management with open reduction and internal fixation (ORIF) and complications, if any.

Methods

A retrospective analysis of 621 fractures in 361 patients managed by ORIF over a four year period was carried out.

Result

The average age of patients was 24.3 years with a male to female ratio of 21.2:1. Panfacial fractures comprised 4.7%, frontal bone fractures 8.9%, orbital fractures 0.7%, naso-orbito-ethmoid complex (NOE) fractures 0.7%, zygomatic complex fractures 23.5%, fracture maxilla 11.5% and mandibular fractures 52.2% of all facial fractures. All the cases were successfully managed by ORIF under general anaesthesia (GA). Complications were noticed in 6.8% of cases in the form of reactive implants in 3.6%, deranged occlusion in 1% and infection at operated site in 1% cases which were managed satisfactorily.

Conclusion

The findings of this study reveal sharp annual increase in the number of cases of maxillofacial trauma. Road traffic accidents (RTA) were the commonest cause and the age group most affected was between 20-25 years. ORIF of these fractures was chosen for its obvious advantages of direct anatomical reduction, early return to function and minimal complications.Key Words: Road traffic accidents (RTA), Inter maxillary fixation (IMF), Open reduction and internal fixation (ORIF)     

银杏叶提取物对体外循环细胞因子的干预作用

目的：探讨体外循环脑损伤的发生机制及银杏叶提取物的干预作用．方法：选择44例心脏病需体外循环手术的风湿性心脏瓣膜病患者,随机分为观察组和对照组,每组22例．观察组在体外循环予充液中加入银杏叶提取物2mg／kg体质量,对照组应用常规予充液．分别在术前、主动脉阻断后1h,术后6,12,24和48h抽取静脉血标本,检测血清IL-1β,IL-18和S100蛋白水平．结果：对照组自CPB结束即刻开始,血清IL-1β显著升高,观察组血清IL-1β自主动脉阻断1h开始升高,持续至术后48h,自主动脉阻断1h开始,对照组显著低于观察组．对照组自术后6h开始,血清IL-18持续升高至术后48h,观察组血清IL-18主动脉阻断1h开始,血清IL-18持续升高至术后48h,主动脉阻断1h,对照组血清IL-18低于观察组,但术后6,12,24,48h显著高于观察组．对照组S100蛋白自CPB结束开始升高,持续至实验结束,自主动脉阻断1h开始至术后48h血清S100蛋白水平对照组均显著高于观察组．结论：体外循环心脏直视手术细胞因子IL-18参与脑组织损伤过程,GBE可调节细胞因子,使血清S100蛋白显著降低．