Biomedical subjects

S Cai

Publications and source records attributed to S Cai.

At least 127 records · Page 7Linked to original sources

PubMed1999

[Studies on the infrared spectra of mico2-OR or micro2-SR-bridged double-cubane-like clusters containing MoFe3S4 cores].

The IR spectra of micro2-OR or micro2-SR- bridged double-cubane-like clusters containing MoFe3S4 cores (Et4N)3 [Mo2Fe6S8Cl6 (OMe)3] (1), (Et4N) [Mo2Fe6S8 (SPh)6 (OMe)3 (2), (Bu4N)3 Mo2Fe6S (SPh)6 (OMe)3] (3), (Et4N)3 [Mo2Fe6S8 (SBu(t))6(OMe)3](4), (Et4N)3[Mo2Fe6S8 (SPh)9](5) have been investigated. Their characteristic frequencies (v)Mo-micro2O(R), (v)Mo-micro2S(R), (v)Mo-S, (v)Fe-S*, (v)Fe-SR, (v)Fe-Cl were assigned by comparing their vibrational frequencies with their structural parameters and by comparing the IR spectra of them with that of the linear clusters. The electrophilic induced effects in different way and the relationship between deltav (i.e. (v)Mo-S* (v)Fe-S*) and Fe --> Mo charge transfer have been discussed. Finaly, the sameness and difference between the double-cubane-like and linear Mo-Fe-S clusters were demonstrated.

English Abstract↗

PubMed1998

Single-channel characterization of the pharmacological properties of the K(Ca2+) channel of intermediate conductance in bovine aortic endothelial cells.

The pharmacological profile of a voltage-independent Ca2+-activated potassium channel of intermediate conductance (IK(Ca2+)) present in bovine aortic endothelial cells (BAEC) was investigated in a series of inside-out and outside-out patch-clamp experiments. Channel inhibition was observed in response to external application of ChTX with a half inhibition concentration of 3.3 +/- 0.3 nm (n = 4). This channel was insensitive to IbTX, but channel block was detected following external application of MgTX and StK leading to the rank order toxin potency ChTX > StK > MgTX >>IbTX. A reduction of the channel unitary current amplitude was also measured in the presence of external TEA, with half reduction occurring at 23 +/- 3 mm TEA (n = 3). The effect of TEA was voltage insensitive, an indication that TEA may bind to a site located on external side of the pore region of this channel. Similarly, the addition of d-TC to the external medium caused a reduction of the channel unitary current amplitude with half reduction at 4.4 +/- 0.3 mm (n = 4). In contrast, application of d-TC to the bathing medium in inside-out experiments led to the appearance of long silent periods, typical of a slow blocking process. Finally, the IK(Ca2+) in BAEC was found to be inhibited by NS1619, an activator of the Ca2+-activated potassium channel of large conductance (Maxi K(Ca2+)), with a half inhibition value of 11 +/- 0.8 micron (n = 4). These results provide evidence for a pharmacological profile distinct from that reported for the Maxi K(Ca2+) channel, with some features attributed to the voltage-gated KV1.2 potassium channel.

Animals↗

PubMed1998

The genomic sequences bound to special AT-rich sequence-binding protein 1 (SATB1) in vivo in Jurkat T cells are tightly associated with the nuclear matrix at the bases of the chromatin loops.

Special AT-rich sequence-binding protein 1 (SATB1), a DNA-binding protein expressed predominantly in thymocytes, recognizes an ATC sequence context that consists of a cluster of sequence stretches with well-mixed A's, T's, and C's without G's on one strand. Such regions confer a high propensity for stable base unpairing. Using an in vivo cross-linking strategy, specialized genomic sequences (0.1-1. 1 kbp) that bind to SATB1 in human lymphoblastic cell line Jurkat cells were individually isolated and characterized. All in vivo SATB1-binding sequences examined contained typical ATC sequence contexts, with some exhibiting homology to autonomously replicating sequences from the yeast Saccharomyces cerevisiae that function as replication origins in yeast cells. In addition, LINE 1 elements, satellite 2 sequences, and CpG island-containing DNA were identified. To examine the higher-order packaging of these in vivo SATB1-binding sequences, high-resolution in situ fluorescence hybridization was performed with both nuclear "halos" with distended loops and the nuclear matrix after the majority of DNA had been removed by nuclease digestion. In vivo SATB1-binding sequences hybridized to genomic DNA as single spots within the residual nucleus circumscribed by the halo of DNA and remained as single spots in the nuclear matrix, indicating that these sequences are localized at the base of chromatin loops. In human breast cancer SK-BR-3 cells that do not express SATB1, at least one such sequence was found not anchored onto the nuclear matrix. These findings provide the first evidence that a cell type-specific factor such as SATB1 binds to the base of chromatin loops in vivo and suggests that a specific chromatin loop domain structure is involved in T cell-specific gene regulation.

Base Composition↗

PubMed1998

Role of zinc in the structure and toxic activity of botulinum neurotoxin.

Zn2+-protease activity of botulinum neurotoxin causes the blockage of neurotransmitter release resulting in botulism disease. We have investigated the role of Zn2+ in the biological activity of type A botulinum neurotoxin by removing the bound Zn2+ by EDTA treatment, followed by monitoring its structure in terms of secondary and tertiary folding (second derivative UV, FT-IR, and circular dichroism spectroscopy) and function in terms of its effect on the release of norepinephrine from PC12 cells. The single Zn2+ bound to each neurotoxin molecule was reversibly removed by EDTA treatment, whereas the biological activity of the neurotoxin was irreversibly lost. Based on the Amide III IR spectral analysis, the alpha-helical content of neurotoxin increased from 29% to 42% upon removal of Zn2+, which reverted to 31% upon treatment with 1:5 molar excess of exogenous Zn2+. Second derivative UV spectroscopy revealed no change in surface topography of Tyr residues with removal of Zn2+. However, near-UV circular dichroism signals suggested significant alterations in the topography of Phe and Tyr residues that could be buried in the protein matrix. Thermal unfolding experiments suggested that removal of Zn2+ results in the formation of the molten globule-like structure of type A botulinum neurotoxin. Tertiary structural changes introduced by Zn2+ removal were irreversible, which correlated well with the irreversibility of the biological activity of the neurotoxin. On the basis of these results, we suggest that Zn2+ plays a significant structural role in addition to its catalytic role in Zn2+-protease activity of type A botulinum neurotoxin.

Animals↗

PubMed1998

Localization and characterization of nitric oxide synthase at the frog neuromuscular junction.

The frog neuromuscular junction is sensitive to nitric oxide (NO), since exogenously applied NO reduces the release of transmitter b presynaptic terminals and the size of ATP-induced Caoffresponses in perisynaptic Schwann cells. This study aimed at determining whether an NO synthase (NOS) is present at the neuromuscular junction, notably in perisynaptic Schwann cells, the glial cells at this synapse. The NADPH-diaphorase (NADPH-d) histochemical technique revealed the presence of NOS in cell bodies and presumed processes of perisynaptic Schwann cells. Incubation with NOS inhibitors, NG-nitro-L-arginine methyl ester or NG-nitro-L-arginine-acetate abolished the NADPH-d staining. Moreover, L-arginine, the precursor of NO, impeded the blockade by NOS inhibitors, establishing the NOS specificity of NADPH-d staining in frog tissue. The pattern of labelling with a polyclonal antibody against the neuronal form of NOS was similar to the NADPH-d staining, also suggesting the presence of a neuronal NOS in perisynaptic Schwann cells. Using electron microscopy the NOS immunostaining was found at the membrane and occasionally in the cytoplasm of perisynaptic Schwann cells and was not detected in the nerve terminal or muscle. There was no enzymatic or immunocytochemical labelling of NOS 6 days after denervation. It is concluded that NOS is present in frog perisynaptic Schwann cells. The presence of this endogenous NOS suggests that NO may act as a diffusible glial messenger to modulate synaptic activity and synapse formation at the neuromuscular junction.

Acetylcholinesterase↗

PubMed1998

The role of neutralizing antibody and T-helper subtypes in protection and pathogenesis of vaccinated mice following ocular HSV-1 challenge.

In order to determine the possible correlation of specific immune responses with protection against mortality and ocular disease following ocular herpes simplex virus type 1 (HSV-1) challenge, BALB/c mice were vaccinated with different doses and regimens of baculovirus-expressed gD. Neutralizing antibody, virus titres in the eyes, corneal scarring, and survival were measured. In addition, infiltration into the cornea of CD4+ T cells and cells containing the lymphokines interleukin-2 (IL-2), IL-4, IL-6 and tumour necrosis factor-alpha (TNF-alpha) were monitored on days 3, 7, 10, 14 and 21 post-challenge by immunocytochemistry. The vaccination regimens used induced varying degrees of immune responses and protection upon ocular challenge with HSV-1. Our results suggest that neutralizing antibody was the most important immune response in protecting mice against lethal ocular challenge and corneal scarring. TNF-alpha and IL-2 were not crucial in terms of survival and corneal scarring, since gD1 (one vaccination with 1 microg of gD) and gD0.1 (one vaccination with 0.1 microg of gD), both of which provided high levels of protection, showed no TNF-alpha or IL-2 expression. However, TNF-alpha and IL-2 were crucial in terms of virus clearance from the eyes, since gD3 (three vaccinations with 1 microg of gD), which had less virus in their eyes, had high numbers of TNF-alpha and IL-2 infiltrates. Finally, mock-vaccinated mice were not protected from death and corneal disease following HSV-1 challenge. Eyes of mock-vaccinated mice had little or no TNF-alpha or IL-2 responses and the strongest IL-4 and IL-6 responses.

Animals↗

PubMed1998

Regulation of cytoskeletal mechanics and cell growth by myosin light chain phosphorylation.

The role of myosin light chain phosphorylation in regulating the mechanical properties of the cytoskeleton was studied in NIH/3T3 fibroblasts expressing a truncated, constitutively active form of smooth muscle myosin light chain kinase (tMK). Cytoskeletal stiffness determined by quantifying the force required to indent the apical surface of adherent cells showed that stiffness was increased twofold in tMK cells compared with control cells expressing the empty plasmid (Neo cells). Cytoskeletal stiffness quantified using magnetic twisting cytometry showed an approximately 1.5-fold increase in stiffness in tMK cells compared with Neo cells. Electronic volume measurements on cells in suspension revealed that tMK cells had a smaller volume and are more resistant to osmotic swelling than Neo cells. tMK cells also have smaller nuclei, and activation of mitogen-activated protein kinase (MAP kinase) and translocation of MAP kinase to the nucleus are slower in tMK cells than in control cells. In tMK cells, there is also less bromodeoxyuridine incorporation, and the doubling time is increased. These data demonstrate that increased myosin light chain phosphorylation correlates with increased cytoskeletal stiffness and suggest that changing the mechanical characteristics of the cytoskeleton alters the intracellular signaling pathways that regulate cell growth and division.

3T3 Cells↗

PubMed1998

The US5 open reading frame of herpes simplex virus type 1 does encode a glycoprotein (gJ).

Based on sequence analysis, the protein encoded by the US5 open reading frame (ORF) of herpes simplex virus type 1 (HSV-1) was predicted to contain an N-glycosylation site and was given the designation of glycoprotein J (gJ). However, the US5 gene product has not been identified and the identity of gJ as a glycoprotein has not been confirmed. We have cloned and expressed the DNA encoding the complete sequence of the US5 ORF, using a baculovirus expression system. Western blotting, using polyclonal antibody raised against synthetic US5 peptides, revealed two major baculovirus-US5-expressed protein bands with apparent molecular weights of 16-17 and 10 kD. The recombinant US5 was found on the membrane of Spodoptera frugiperda cells and was susceptible to tunicamycin, endoglycosidase H, glycosidase F and partially resistant to endoglycosidase F. Vaccination of mice with baculovirus-expressed US5 did not induce a neutralizing antibody to HSV-1 or provide protection against lethal HSV-1 challenge. However, serum from these vaccinated mice was able to recognize US5 in purified HSV-1 virions by Western blot analyses and on the surface of HSV-1-infected cells by immunofluorescence. These findings establish that US5 does encode a glycoprotein and confirm the appropriateness of naming the US5 gene product gJ.

Amino Acid Sequence↗

PubMed1998

T-lymphocyte chemotaxis to IL-8 in patients with psoriasis in vitro.

OBJECTIVE: The critical role of infiltrating T cells in the pathogenesis of psoriasis is now well established. In order to determine whether circulating T cells from patients with psoriasis were also involved in the disease process, the authors investigated the biological behavior as studied by chemotactic activity of T cells in patients with psoriasis. METHODS: A 48 microchemotaxis chamber was employed to determine T-cell chemotaxis activity. In addition, the expression of T cell activation markers such as HLA-DR and interleukin 2 receptor were analysed with fluorescence activated cell sorting technique and serum IL-8 level was measured with ELISA methods. Forty-five patients with psoriasis (23 patients with severe psoriasis and 22 with mild psoriasis) and 21 patients with atopic dermatitis were investigated. For comparison, T-lymphocytes from 20 healthy controls were tested equally. RESULTS: T-cell chemotactic responses were significantly decreased in patients with severe psoriasis and atopic dermatitis as compared to healthy controls. Increased expression of activation markers such as HLA-DR and interleukin 2 receptor were demonstrated in circulating T cells from psoriatic patients and atopic dermatitis patients in comparison to healthy controls. Serum IL-8 level was significantly increased in patients with psoriasis and atopic dermatitis. CONCLUSIONS: Circulating T cells in patients with severe psoriasis show abnormal in vitro chemotactic response to IL-8. Furthermore, the in vivo activation state of T lymphocytes in these patients and increased level of serum IL-8 seemed to be associated to their decreased in vitro T-cell chemotactic responses.

Chemotaxis, Leukocyte↗

PubMed1998

[Repair of cartilage defect in joint with transplantation of cryopreserved homologous embryonic periosfeum of rabbits].

In order to repair cartilage defect in joint with transplantation of cryopreserved homologous embryonic periosteum, 30 rabbits were used and divided into two groups. A 4 mm x 7 mm whole thickness cartilage defect was made in the patellar groove of femur of each rabbit. The homologous embryonic rabbit skull periosteum (ERSP), preserved in two-step freezing schedule, was transplanted onto the cartilage defect of joints of one group and autogenous periosteal graft was done in the joint defect of the other group. The knees were not immobilized, following operation and 16 weeks later, the newly formed tissue in the defects were assessed by gross observation, histochemical examination and biochemical analysis. The results showed that new hyaline-like cartilage was formed in the cryopreserved ERSP grafted knee, and had no significant difference from that of the knee receiving autogenous periosteal graft, but had significant difference from that of the fresh ERSP grafted knee and the non-grafted knee. Furthermore, the new hyaline-like cartilage had the biochemical characteristics of a fibrous cartilage. The conclusion was that this method might be feasible to repair articular cartilage defects.

Animals↗

PubMed1998

[The comparison of radiosensitivity between uterine cervical squamous carcinoma and adenocarcinoma].

OBJECTIVE: To compare the radiosensitivity of uterine cervical squamous carcinoma and adenocarcinoma. METHODS: The shrinkage of tumor and the radiation-induced damage were compared between cervical squamous carcinoma and adenocarcinoma after twice afterloading radiotherapy. Proliferating cell nuclear antigen index (PI), detected immunohistochemically, was compared before and after radiotherapy between the two tumors. RESULTS: Patients of squamous carcinoma with tumor shrinkage 50% or more accounted for 70% (21/30) and patients of adenocarcinoma accounted for 27% (4/15), which was statistically significant (P < 0.01). The radiation-induced damage grade II b-III accounted for 60% (18/30) in squamous carcinoma and for 20% (3/15) in adenocarcinoma, which was statistically significant (P < 0.05); PI decreased from 53.50% +/- 4.34% to 39.30% +/- 4.02% after radiotherapy in squamous carcinoma (P < 0.001), while PI decreased from 35.47% +/- 3.83% to 31.80% +/- 3.06% in adenocarcinoma (P > 0.05). CONCLUSIONS: The radiosensitivity of cervical squamous carcinoma is higher than that of adenocarcinoma. The decrease of PI after radiotherapy may be a biological basis of radiosensitivity for uterine cervical squamous carcinoma.

Adenocarcinoma↗

PubMed1998

[Proliferating cell nuclear antigen (PCNA) in ovarian carcinoma and its relation to lymph node metastasis and prognosis].

OBJECTIVE: To investigate expression of proliferating cell nuclear antigen (PCNA) in ovarian epithelial cancer and its relation to lymph node metastasis, second-look laparotomy (SLL) and prognosis. METHODS: Monoclonal antibody PC10 was used to stain PCNA in archival paraffin-embedded tissues. RESULTS: PC10 immunostaining was performed successfully in all 74 primary and 31 intraperitoneal metastatic tumors. The expression of PCNA was significantly elevated in 31 metastatic tumors compared with their primary tumor from the same patient (7.94 vs 6.89, P = 0.042). The expression was more marked in bilateral than in unilateral ovarian cancer but it was not associated with lymph node metastasis, clinical stage, histologic grade and subtype. In 28 patients with stage III ovarian cancer undergone SLL, the mean immunoreactive score (IRS) of PCNA of the primary tumor was significantly higher in patients with negative SLL than in those with positive SLL (7.59 vs 6.10, P = 0.03). Since chemotherapy was performed following surgical debulking, negative SLL more frequently seen in patients with high PCNA expression might suggest better chemotherapeutic sensitivity due to higher proliferation fraction of tumor cells. Univariate analysis of survival indicated that the overall survival was inversely associated with the level of PCNA expression, while multivariate analysis with Cox's model showed that independent prognostic factors were the residual tumor after primary debulking (P < 0.001) and clinical stage (P < 0.05), followed by PCNA expression (P = 0.09). CONCLUSION: The expression of PCNA may be useful in predicting prognosis, but is not correlated with lymph node metastasis.

Adult↗

PubMed1998

[Identification of Tougucao derived from Clematis species].

Comparative studies were carried out on the morphology and histology of 5 Clematis species, namely, C. intricata, C. aethusifolia, C. glauca, C. tangutica and C. hexapetala, allegedly used as "Tougucao". New characteristics, a sclerenchymatous ring composed of primary phloem fibers and lignified parenchyma cells, and a parenchymatous tertiary ring were discovered. A parameter representing the ratio of the diameter of cambium ring to the diameter of the stem (RCR) is created. A key for identification of the stems of the above five species is made according to the presence or absence of the sclerenchymatous ring, the diameter and numbers of hair cells, the thickness of fiber wall and the value of RCR, etc.

Magnoliopsida↗

PubMed1998

[Chemical constituents of Taraxacum sinicum Kitag].

Five compounds were separated from Taraxacum sinicum by means of solvent extraction and rechromatography on silical gel. Their structures were established as caffeic acid, ferulic acid, chlorogenic acid, luteolin and diosmetin by spectral analysis and chemical evidence. All the compounds were isolated from this plant for the first time. Chlorogenic acid and diosmetin have not been discovered from Taraxacum genus previously.

Asteraceae↗

PubMed1998

[Studies on flavonoids from Fenugreek (Trigonella foenumgraecum L.)].

OBJECTIVE: To study the flavonoids in fenugreek (Trigonella foenumgraecum) produced in China. METHOD: The flavonoids were isolated with silica gel, polyamide and Sephadex LH-20 chromatography, and their structures were identified by physical, chemical properties and spectral analysis. RESULT: Five flavonoid compounds were isolated from fenugreek seeds and identified as vitexin, tricin, naringenin, quercetin and tricin-7-O-beta-D-glucopyranoside. CONCLUSION: Three flavonoids, tricin, naringenin and tricin-7-O-beta-D-glucopyranoside, were isolated from fenugreek as well as from the plants of Trigonella for the first time.

Apigenin↗

PubMed1998

[Analysis of amino acids in Trigonella foenumgraecum seeds].

Seventeen amino acids in Trigonella foenumgraecum seeds are analyzed by means of HITACHI Model 835-50 High Speed Amino Acid Analyzer. Seven of them are essential amino acid for human body. The results provide references for evaluating the usefulness of T. foenumgraecum seeds in medicine and food.

Amino Acids↗

PubMed1998

[The relation of diabetic retinopathy with blood-fat and lipid peroxidation].

PURPOSE: To observe and inquire into the relation of diabetic retinopathy with lipid metabolism, and lipid peroxidation. METHODS: The contents of triglyceride (TG), total cholesterol (TC), high density lipoprotein-cholesterol (HDL-C), low density lipoprotein-cholesterol (LDL-C), superoxide dismutase (SOD) and lipid peroxide (LPO) of serum were examined and determined both in thirty patients with diabetes in early stage suffering from retinopathy and twenty four healthy people. RESULTS: TG, TC, LDL-C and LPO in patients group were obviously higher than those in the control group, while HDL-C and SOD were lower than those in healthy control group. CONCLUSION: The disorder of lipid metabolism and the growing intensity of lipid peroxidation caused by diabetes may be one of the dangerous factors to bring about the retinopathy.

Aged↗

PubMed1998

Renal dysfunction from cadmium contamination of irrigation water: dose-response analysis in a Chinese population.

In a cadmium-contaminated area in China and a nearby non-contaminated area, 342 persons were selected for studies of a possible relationship between cadmium dose (i.e. total cadmium intake) and response in terms of renal dysfunction. An increase in urinary excretion of beta-2-microglobulin (UB2M), adjusted for age and sex, was used as an indicator of the response. A statistically significant relationship was found between measured cadmium concentrations in whole blood (range; < 3.5 to > 15 micrograms/l) and UB2M, and there was a statistically significant linear trend. Also, cadmium in urine (< 4 to > 16 micrograms/g creatinine) and UB2M displayed a statistically significant positive relationship when the total data set was analysed for males and females. The relationship between a dose index (obtained from calculated cumulative absorbed doses over a lifetime) and UB2M was statistically significant. The results of this first study on dose-response relationships in a Chinese population are similar to those observed in other populations.

Adult↗