Biomedical subjects
J Cai
Publications and source records attributed to J Cai.
Reduction of ribonucleotides by the obligate intracytoplasmic bacterium Rickettsia prowazekii.
Rickettsia prowazekii, an obligate intracellular parasitic bacterium, was shown to have a ribonucleotide reductase that would allow the rickettsiae to obtain the deoxyribonucleotides needed for DNA synthesis from rickettsial ribonucleotides rather than from transport. In the presence of hydroxyurea, R. prowazekii failed to grow in mouse L929 cells or SC2 cells (a hydroxyurea-resistant cell line), which suggested that R. prowazekii contains a functional ribonucleotide reductase. This enzymatic activity was demonstrated by the conversion of ADP to dADP and CDP to dCDP, using (i) a crude extract of Renografin-purified R. prowazekii that had been harvested from infected yolk sacs and (ii) high-performance liquid chromatographic analysis. The rickettsial ribonucleotide reductase utilized ribonucleoside diphosphates as substrates, required magnesium and a reducing agent, and was inhibited by hydroxyurea. ADP reduction was stimulated by dGTP and inhibited by dATP. CDP reduction was stimulated by ATP and adenylylimido-diphosphate and inhibited by dATP and dGTP. These characteristics provided strong evidence that the rickettsial enzyme is a nonheme iron-containing enzyme similar to those found in mammalian cells and aerobic Escherichia coli.
Plasma membrane phospholipid translocation in the mouse peritoneal macrophage: differential response to stimulation of eicosanoid production.
The metabolism and translocation of exogenously introduced plasma membrane phosphatidylcholine (PC) having the fluorescent fatty acid analog aminocaproyl NBD (N-nitrobenzo-2-oxa-1,3 diazole) (NBD-PC), in the sn2 position was studied in cultured murine peritoneal macrophages using biochemical and morphological techniques. Following labeling of the cell plasma membrane at 2 degrees C by vesicle lipid exchange, macrophages were warmed in the presence or absence of pharmacological stimuli of eicosanoid production and release. Fluorescence microscopy indicated that the phospholipid was translocated to an internal cellular pool upon stimulation with zymosan. In contrast, the membrane PC analog was primarily metabolized and released after being found diffusely associated with the cytoplasm in macrophages stimulated with the calcium ionophore A23187. Evidence obtained by double labeling zymosan-treated macrophages with NBD-PC and a monoclonal antibody directed against a lysosomal membrane protein demonstrated that the fluorescent lipid is internalized in association with the zymosan particles and both are found in lysosomes. The results suggest that multiple pathways exist in peritoneal macrophages which target plasma membrane PC into different cellular compartments for hydrolysis and conversion to eicosanoid products and release from cells.
[Studies on the quality of fructus Cnidii--comparison of antibacterial action].
Comparative studies on antibacterial and antifungal action of the fruits of C. monnieri from four habitats and two other species of Cnidium showed they had inhibitory potency to some bacterial and fungi in vitro. C. monnieri and C. salium were more effective than C. dahuricum in antibacterial activities. C. monnieri had higher antifungal effect than C. salium and C. dahuricum.
Lattice model of defect-plane wetting.
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Investigation of the electric-field effect on weak localization using the balance-equation approach.
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[Effect of a decoction of six ingredients with rehmannia on the periodontal tissues of animals with kidney diseases].
In this paper, Kidney Yin and Yang deficiency animal models were made by the medicine (hydrocortisone, thyroxin). At the same time the occlusal trauma was accompanied. It was caused by means of corprophagy (microorganism) fed and artificial damage. The authors observed the injuries and effects of the local and systemic factors caused on the periodontal tissues of rats. From the experiment the authors found the injuries of the periodontal tissues in Kidney deficiency models were severer than those of the models without Kidney deficiency. The results showed that the function of the traditional medicine was a matter of protection, regeneration and repairing to the periodontal tissues of Kidney Yin deficiency models. In addition, the weights and activities of the experimental animals fed by Decoction of Six Ingredients with Rehmannia were higher than those without taking the traditional medicine.
Vertex correction to the Eliashberg equation for the superconducting critical temperature.
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A rapid method for detection of flavivirus antigens: staphylococcal co-agglutination test using monoclonal antibodies to Japanese encephalitis virus.
Staphylococcus aureus rich in protein A when coated with monoclonal antibodies (MoAb) to Japanese encephalitis virus (JEV) gave a highly specific reaction with flavivirus antigens. The bacteria coated with JEV species-specific MoAb gave a strong co-agglutination with fifty-six JEV isolates from various parts of China, but no co-agglutination with Murray Valley encephalitis (MVE) and Kunjin (Kun) virus antigens. The flavivirus- and subgroup-specific MoAbs were reactive with MVE and Kun, as well as with the majority of the JEV strains. Blocking test with homologous MoAbs abolished co-agglutination further confirming its specificity. Numerous virus particles were observed on the surface of MoAb-coated staphylococci under the electron microscope after co-agglutination. The test appeared rapid, specific, simple to perform, and useful for rapid detection and identification of flaviviruses.
[Comparison of endoscopy and the milk 99mTc-EHIDA test in assessing duodenogastric reflux].
Duodenogastric reflux was estimated in 101 patients with chronic gastritis by means of endoscopy and milk 99mTc-EHIDA test. 61 patients (60.4%) were deemed to be duodenogastric reflux positive by endoscopy, as compared to 40 patients (39.6%) by milk 99mTc-EHIDA test. These differences are statistically significant (P less than 0.005). The discrepancy arises largely from the error in endoscopic estimation of duodenogastric reflux. In a group of 58 patients who were mild to moderate reflux positive by endoscopy, the assessment made by the milk 99mTc-EHIDA test was reflux positive in only 33 (57%). In other words more than 40% of the endoscopically reflux positive patients did not show reflux with 99mTc activity in the stomach. Measurement of the ratio of 99mTc activity in gastric aspirates to the total 99mTc activity injected intravenously was carried out in 13 patients. A perfect correlation was found between the ratio and the grading of duodenogastric reflux estimated by the milk 99mTc-EHIDA test. This finding suggests that by using the milk 99mTc-EHIDA test, duodenogastric reflux may be monitored semiquantitatively without recourse to a nasogastric tube. Furthermore, 10 patients were evaluated twice by the milk 99mTc-EHIDA test at intervals ranging from 3-14 days. In 8 patients the results were identical. This indicates the good reproducibility of the test. This study demonstrates that milk 99mTc-EHIDA test is a more physiological and more accurate method of studying duodenal contents in the stomach, than endoscopy.
[Clinical characteristics of bile reflux gastritis].
Thirty patients with bile reflux gastritis, proven by gastroscopy and Milk 99mTc-EHIDA Test, were studied and their clinical features were compared with those of patients with non-bile reflux gastritis. The symptoms were similar in both groups of patients, whereas histologically in bile reflux gastritis there were more hyperemia of mucosa, more obvious edema in lamina propria and more polymorphonuclear infiltration. Furthermore, in bile reflux gastritis the histological changes were more severe in the antrum and decreased in severity toward the cardia. Acid secretion was significantly lower in patients with bile reflux gastritis than in patients with non-bile reflux gastritis while the serum gastrin level was significantly higher in the former than in the latter group. The authors suggest that there may be a vicious cycle among duodenogastric reflux, low level of gastric acidity and high level of serum gastrin. When duodenogastric reflux occurs, not only the bile salts damage the gastric mucosa and subsequently cause the back diffusion of hydrogen ion but also the alkaline duodenal juice neutralizes the gastric acid, resulting in decrease of gastric acidity. The bile salts and low acidity can stimulate the release of serum gastrin which antagonizes the effects of cholecystokinin and secretin on pyloric tone and aggravates the duodenogastric reflux.
High-field balance equations for electronic transport in weakly nonuniform systems.
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High-temperature superconductivity in the presence of O 2p-Cu 3d holes: A spectroscopic study.
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Immunological and biochemical characterization of an epitope of the transferrin receptor involved in the production of interferon-gamma and B-cell growth factor.
We have investigated the effect of a newly developed monoclonal antibody, MoAb NDA9, on human lymphocyte function. This MoAb inhibits the capacity of peripheral blood lymphocytes to display blastogenic responses and to produce immunoglobulins when stimulated in vitro with PWM or with soluble antigens. The inhibitory effect seems to result from the decreased ability of T lymphocytes to produce B cell growth factors (BCGF) in the presence of MoAb NDA9. This antibody also blocks the capacity of polyclonal or monoclonal populations of activated human T cells to produce immune interferon (gamma) but has no direct effect on B cell activation and growth in T-cell-independent systems. Immunochemical studies of the antigen recognized by MoAb NDA9 showed that it is an epitope of the transferrin receptor molecule which is distinct from that recognized by the MoAb OKT9.
Coinduction of glucose-regulated proteins and doxorubicin resistance in Chinese hamster cells.
The glucose-regulated protein (GRP) system in mammalian cells is induced by glucose deprivation, anoxia, the calcium ionophore A23187, and 2-deoxyglucose. In Chinese hamster ovary cells the major GRPs are approximately equal to 76, 97, and 170 kDa. Removal of each of these four GRP-inducing stresses leads to the coordinate repression of GRPs and induction of the major heat shock proteins at 70 and 89 kDa. The application of each of these four GRP-inducing conditions leads to a significant induction of resistance to the drug doxorubicin. Removal of each GRP-inducing condition results in the rapid disappearance of this resistance in a manner that correlates with the repression of the GRPs. The retention of doxorubicin by GRP-induced cells does not explain the induced drug resistance. When the RIF in vitro/in vivo tumor system is probed with an antibody against the 76-kDa GRP, a significant increase in this GRP is observed in cells obtained from the central regions of tumors. Since hypoxia and/or nutrient deprivation can occur during tumor development, a GRP-induced state in the tumor may confer resistance to doxorubicin treatment.
Differentiation antigens associated with the function of alloreactive T lymphocytes.
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Functional modifications of alloreactive T cell clones infected with HTLV-I.
Two alloreactive T cell clones with anti-HLA-DR1 specificity showed significant alterations of cognitive and functional characteristics after infection with human T cell leukemia virus (HTLV-I). Similar to HTLV-I-infected lines derived from immunologically uncommitted lymphocytes, the transformed clones displayed blastogenic mixed lymphocyte culture (MLC) responses to cells carrying any of the allelic variants of human HLA-D/DR antigens, including self. Although these two clones were originally able to provide allospecific help only to B cells expressing the DR1 antigen, after infection with HTLV-I they stimulated B cells of any HLA-D/DR phenotype to produce immunoglobulin in cultures. The helper inducer activity of the transformed clones remained susceptible to the effect of monoclonal antibody anti-LDA1 that inhibits the helper function of normal human T cells. One of these clones (207TK), which before infection specifically killed DR1-positive target cells, lost its killing ability. The other clone (19TK) although originally noncytotoxic, acquired natural killer-like function after transformation. Study of the rearrangement of the genes coding for the beta-chain of the T cell antigen receptor revealed no differences between the wild (noninfected) and mutant (infected) clones. There was, however, an increased level of this message, as well as of the message encoded by the beta-chain gene of HLA-DR in the mutant clones. Such changes may be related to transacting transcriptional effects induced by the human T cell lymphotropic virus HTLV-I.
Total cross sections for electrons scattered by 3(2)P3/2 sodium atoms.
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