Establishment of reference panel for human platelet antigen genotyping.

BACKGROUND AND OBJECTIVES: Human platelet antigens (HPAs) are platelet-specific alloantigens associated with polymorphisms of platelet surface glycoproteins (GPs), and they can induce alloantibodies when individuals lacking a particular polymorphism are exposed to them via pregnancy or transfusion. Immune responses to HPAs are involved in the pathogenesis of several clinical syndromes. HPA genotyping is therefore important for clinical diagnosis and laboratory research. This study aims to establish a reference panel for HPA genotyping. MATERIALS AND METHODS: Genomic DNA extracted from human blood was used as the template for amplifying HPA (1a-5a and 15a) gene fragments using specific primers. The amplified products were cloned into pGM-T vectors, which were transformed into competent TOP10 cells. After clone screening and amplification, the plasmids were extracted and sequenced. Next, the gene fragments HPA-1b-5b and 15b were obtained by site-directed mutagenesis using the corresponding HPA-1a-5a and 15a plasmids as template DNA. RESULTS: We successfully constructed reference plasmids for HPA genotyping with HPA-1a-5a, 15a, HPA-1b-5b and 15b. The DNA sequences were consistent with those published in GenBank. CONCLUSION: Obtaining reference DNA for low-frequency HPAs is very difficult, and the successful construction of reference plasmids for the six HPA systems may solve this problem. Establishment of this panel has laid the foundation for future research on HPA genotyping.

[Changes of cardiac function during 21 d head-down tilt bed rest and the effect of lower body negative pressure in the last week].

OBJECTIVE: To investigate the change of cardiac function during 21 d head-down tilt (HDT) bed rest and the effect of lower body negative pressure (LBNP) in the last week in human. METHOD: 12 healthy male served as subjects which were randomly divided into control and LBNP groups, with 6 in each group. All of them were exposed to -6 degrees HDT for 21 d. The LBNP group received -4.0 kPa LBNP training 1 h/d in the last week of the test. The cardiac pump function and cardiac systole function were measured before, during and after HDT. RESULT: Cardiac output, cardiac index and stroke volume decreased significantly, whereas total peripheral resistance, pre-ejection period (PEP), isovolumetric contraction time/left ventricular ejection time (LVET) and PEP/LVET increased significantly during HDT in both control and LBNP groups, compared to pre-HDT values, and they returned to normal level on day 2 post HDT. PEP and PEP/LVET in LBNP group were significantly higher than those in control group on day 21 of HDT and day 2 post HDT. CONCLUSION: The reduction of cardiac pump function and cardiac systole function induced by 21 d HDT could not be prevented by LBNP training in the last week of 21 d HDT.

[Changes of cerebral blood flow during 21 d head-down tilt bed rest and the effect of lower body negative pressure during the last week].

Objective. To investigate the changes of cerebral blood flow (CBF) during 21 d head-down tilt (HDT) bed rest and the effect of lower body negative pressure (LBNP) in the last week. Method. Twelve healthy male subjects were randomly divided into control and LBNP groups, with 6 in each group. All of them were exposed to -6 degrees HDT for 21 d. The LBNP group received -4.0 kPa LBNP training 1 h/d in the last week of HDT while the control group did not. CBF and cerebral vascular resistance were measured by rheoencephalogram in pre-HDT, day 3, 10 and 21 of HDT. Result. In control group, left cerebral I quadrant area and inrush velocity decreased significantly during HDT, and left cerebral delta Gy wave crest height decreased significantly, whereas left cerebral resistance index increased significantly on day 3 and 21 of HDT as compared to those of pre-HDT. In LBNP group, left cerebral I quadrant area decreased significantly, and left cerebral delta Gy wave crest height and inrush velocity tended to decrease on day 3 and 21 of HDT, whereas left cerebral resistance index increased significantly during HDT as compared to those of pre-HDT. There were no significant differences between above indexes in control group and LBNP group. Conclusion. It is suggested that 21 d HDT may increase cerebral vascular resistance and decrease CBF, which can not be prevented by LBNP training in the last week of 21 d HDT.

[Countermeasuring effect of lower body negative pressure against orthostatic intolerance induced by 21 d -6 degrees head down tilt in humans].

Objective. To investigate whether LBNP during 21 d -6 degrees head-down tilt (HDT) would modify orthostatic tolerance. Method. 12 healthy males, age 23.7 +/- 5.0, were exposed to -6 degrees HDT for 21 d. 6 of them received -4.0 kPa LBNP sessions for 1 h/d from 15th day to 21st day of HDT. The other 6 served as control. HUT + 75 degrees, 20 min orthostatic tolerance test were done before, on day 10 and on day 21 of HDT. Result. During HUT + 75 degrees, 20 min orthostatic tolerance test on day 10 of HDT, 5 subjects of the control group and 4 of the LBNP group presented presyncopal or syncopal signs and symptoms, the average standing time of both groups were shorter than those of the pre-HDT (p<0.05). During HUT + 75 degrees, 20 min orthostatic tolerance test on day 21 of HDT, 5 subjects of the control group and one subject of the LBNP group presented presyncopal or syncopal signs and symptoms, the average standing time of control group reduced significantly as compared with those of pre-HDT(P<0.05), also significantly shorter than those of LBNP group (P<0.05). Conclusion. The present study clearly shows that the use of LBNP could alleviate the bed rest-induced orthostatic intolerance.