L-homocysteic acid (HCA) and other amino acids were conjugated to rat brain material (extracted rat brain protein) with glutaraldehyde to form HCA- and amino acids-brain material conjugates. The specificity of monoclonal antibody (McAb) was tested on serialdilution test and absorption test on enzyme-linked immunosorbent assay (ELISA) using these conjugates as antigens instead of amino acids-BSA (bovine serum albumin) conjugates used previously. The characterized McAb was applied for immunohistochemical staining using PAP (peroxidase antiperoxidase) technique in combination with silver enhancement of diamino-benzene (DAB) products. The results indicated that McAb to L-HCA reacted with L-HCA-brain material conjugates, but not with other amino acids-brain material conjugates so far tested. McAb absorbed with L-HCA-brain material abolished or decreased immunoreactivity of L-HCA-brain material with McAb. The antibody selectively stained subpopulation of cells and processes in the hippocampus fixed with glutaradehyde. Absorption of McAb with L-HCA-brain material abolished immunohistochemical staining. These results suggested that McAb was specific for L-HCA-brain materials and could be used for imunohistocytochemistry. This would provide a new tool for immunohistochemical visualization and localization of L-HCA in the nervous system.

In the present study, we examined the regulation of the expression and function of ABCA1 by modified LDL (ox-LDL)in vitro. After incubation with apoA-I for 24 h, RAW264. 7 cells effluxed 37.65% cholesterol loaded by acetyl LDL (ac-LDL), and 9.78% cholesterol in ox-LDL group. The level of ABCA1 mRNA increased about three times either when cells were incubated with 100 μg/mL ac-LDL or with 100 μg/mL ox-LDL. However, the level of ABCA1 protein rose by 1.57 times in ac-LDL group and 1.26 times in ox-LDL group. These results demonstrated that ox-LDL had different effect on the expression and function of ABCA1, ox-LDL might decrease the cholesterol efflux mediated by ABCA1 through other unknown mechanisms.

To explore the functions of very low density lipoprotein receptor (VLDL-R) subtype II in lipoprotein metabolism and foam cells formation, the recombinant plasmid with the two subtypes cDNA was constructed respectively, the ldl-A7 cell lines were transfected and two cell lines expressing VLDL-R were obtained: one stably expressing the VLDLR with the O-linked sugar region (type I VLDLR) and the other without the O-linked sugar region (type II VLDLR). In the study on binding of VLDLR to their nuclein labeled natural ligands (VLDL and β-VLDL), it was found that surface binding of¹²⁵I-VLDL or¹²⁵I-β-VLDL of ldl-A7 cells transfected with type II VLDLR recombinant (ldl-A7-VRII). After being incubated with VLDL for different time, the contents of triglyceride and total cholesterol in cells were mensurated, and the formation of foam cells and accumulation of lipid in cells was observed by oil-red O staining. The results showed that the contents of triglyceride and total cholesterol in ldl-A7-VR I were much higher than those in ldl-A7-VR II, and ldl-A7-VR I could transform into foam cells notably. It was suggested that type I VLDLR binds with relative higher affinity to VLDL and β-VLDL, and internalizes much mor elipoprotein into cells. As a result, we can conclude that type I VLDLR plays a more important role in lipoprotein metabolism and foam cells formation than type II VLDLR.

The P2X₇ receptor mRNA and proteins in guinea-pig dorsal root ganglia (DRG) were studied by using RT-PCR and immunohistochemistry. The co-localization of P2X₇ receptor with four cytochemical markers, the neurofilament protein NF200, S100, substance P and isolectin B4 (IB4) binding glyco-conjugates, were also examined. It was found that P2X₇ receptor immunoreactivity (P2X₇R-IR) was present mostly in large- and medium-sized DRG neurons (62%±9% and 36%±6% respectively in all P2X₇R-IR neurons). All the P2X₇R-IR neurons were also NF200 and S100 immunopositive. However, in a small number of NF200 or S100 immunopositive neurons no P2X₇R-IR was detectable. All the IB4-positive or substance P-immunopositive neurons had no P2X₇R-IR. These results demonstrate that P2X₇ receptors are expressed in a large subpopulation of DRG neurons and they may play a role in the transduction of specific peripheral sensory signals.