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Biomedical subjects

B Ma

Publications and source records attributed to B Ma.

At least 73 records · Page 4Linked to original sources
PubMed1999

Fine needle aspiration cytology of basal cell carcinoma of the skin: a clinical and cytopathological appraisal.

This report describes the fine needle aspiration cytologic findings of 22 cases of basal cell carcinoma of the skin. The series consisted of 17 men and 5 women with a mean age of 60.7 years (range, 35-80). All the patients were from south of Xinjiang and were outdoor workers with histories of prolonged exposure to strong sunlight. Histopathologic study was performed in all cases. Using fine needle aspiration cytology (FNAC) in evaluating basal cell carcinoma, there were no false-positive cases, but one false-negative one giving a diagnostic accuracy of 95.65%. Cytologic features suggestive of basal cell carcinoma included increased numbers of small, uniform hyperchromatic, relatively little cytoplasmic cell clusters. The peripheral cells appeared in monolayer form as a papillated outline with very strong cellular cohesion. Scattered tumor cells were seldom seen. The differential diagnosis of basal cell carcinoma in FNAC includes poorly differentiated squamous cell carcinoma, eccrine gland carcinoma, and neuroendocrine carcinoma of the skin. FNAC diagnosis of basal cell carcinoma is essential in order to ensure proper treatment.

Adult↗
PubMed1999

Mechanisms of internalization of Staphylococcus aureus by cultured human osteoblasts.

Staphylococcus aureus is an important bone pathogen, and evidence shows that this organism is internalized by chick osteoblasts. Here we report that S. aureus is internalized by human osteoblasts. Internalization was inhibited by monodansylcadaverine and cytochalasin D and to a lesser extent by ouabain, monensin, colchicine, and nocodazole. We propose that internalization occurs via a receptor-mediated pathway, requiring the participation of cytoskeletal elements, principally actin.

Actins↗
PubMed1999

Effects of inhibitors of the tyrosine kinase signaling cascade on an in vitro model of allergic airways.

It has been shown that activation of protein tyrosine kinases (PTKs) is the earliest detectable signaling response to FcepsilonRI cross-linking on mast cells. Following tyrosine kinase activation, a family of mitogen-activated protein kinases (MAPKs) was found to be activated as well. Activation of this PTK signaling cascade will lead to mast cell degranulation. This review summarizes our recent studies on the role of PTK signaling cascade in an in vitro guinea pig model of allergic asthma using PTK inhibitors, genistein and tyrphostin 47, and MAPK kinase inhibitor, PD098059. Inhibitors of the PTK and MAPK signaling pathways significantly attenuated the ovalbumin (OVA)-induced bronchial anaphylactic contraction and enhanced relaxation of constricted airways, respectively, and substantially blocked the release of histamine and peptidoleukotrienes from chopped lung preparations induced by OVA. Based upon their substantial inhibitory effects on the Schultz-Dale reaction, further examination on the potential anti-asthmatic effects of PTK cascade inhibitors in an in vivo model of allergic asthma is recommended.

Animals↗
PubMed1999

[Rapid effects of hydrocortisone on the cholinergic synaptic transmission of B neurons in bullfrog sympathetic ganglia].

Rapid effects of hydrocortisone 21-hemisuccinate (F-suc) on cholinergic synaptic transmission of B neurons in bullfrog sympathetic ganglia (BFSG) were studied with intracellular recording technique in vitro. The main results are as follows: (1) F-suc blocked cholinergic synaptic transmission of 52 B neurons within 0.5-3 min, which was concentration-dependent and partially suppressed by the cytoplasm receptor antagonist of steroid hormones, RU38486; (2) after protein synthesis was suppressed by actidione, the above effect persisted; and (3) the effect of F-suc could be potentiated by atropine. All these results suggest that the F-suc induced rapid effects of cholinergic synaptic transmission of B neurons in BFSG may be mediated by non-genomic mechanisms.

Animals↗
PubMed1999

[Effect of L1ECD on mouse primarily cultured neurons and construction of transgenic mice specifically expressing L1ECD in brain].

Neural cell adhesion molecule L1 is an important molecule mediating cell-cell interactions during the development of nervous system. L1 can promote axonal outgrowth and is related with nerve cell migration, and therefore L1 plays an important role both in the development and maintaince of the nervous system. In humans, mutations in the L1 gene can lead to mental retardation, spastic paraplegia, hydrocephalus, and other developmental abnormalities. The molecular mechanisms of mutations in L1 gene to induce inherited neurological diseases are not clear. In present investigation, a transgenic DNA of mouse L1 extracellular domain (L1ECD) was constructed by adding a stop codon to the end of L1ECD cDNA and then putting it under the control of CAMK II promoter, which is active specifically in the brain. To verify this construct, L1ECD cDNA was subcloned into an expression vector pCEP4 and then transfected the C6 cells. The expression of L1ECD cDNA in C6 cells was confirmed by Northern blotting and the effects of L1ECD on the growth rate and morphology of C6 cells in vitro as well as primarily cultured neurons were observed. The L1ECD constructs were microinjected into the fertilized zygotes of C57BL/6 mice. The transgenic mice thus produced were identified by Southern and Northern hybridization analysis. The results demonstrated that the L1ECD was integrated in the genome of transgenic mice and expressed specifically in the brain.

Animals↗
PubMed1998

SNAP19 mediates the assembly of a functional core promoter complex (SNAPc) shared by RNA polymerases II and III.

The basal transcription factor SNAPc binds to the PSE, a core element in the RNA polymerase II and III human snRNA promoters. SNAPc contains at least four subunits, but it has not been possible to assemble a fully defined recombinant SNAPc. Here we reconstitute SNAPc from five recombinant subunits, SNAP43, SNAP45, SNAP50, SNAP190, and a newly identified subunit, SNAP19. This recombinant complex binds specifically to the PSE and directs both RNA polymerase II and III snRNA gene transcription. Thus, the same core SNAPc nucleates the assembly of two classes of initiation complexes.

Amino Acid Sequence↗
PubMed1998

Reverse transcription-PCR analysis of the regulation of the manganese peroxidase gene family.

Manganese peroxidase (MnP) gene expression in the lignin-degrading fungus Phanerochaete chrysosporium is regulated by nutrient nitrogen levels and by Mn(II), the substrate for the enzyme, as well as by heat shock and other factors. Reverse transcription-PCR (RT-PCR) of total RNA can distinguish the mRNAs of each of the three sequenced P. chrysosporium mnp genes, i.e., mnp1, mnp2, and mnp3. Quantitative RT-PCR demonstrates that each of the three transcripts is present at a similar low basal level in nitrogen-sufficient cultures, with or without Mn, and in nitrogen-limited cultures lacking Mn. However, in 5-day-old, nitrogen-limited, stationary cultures supplemented with 180 microM Mn, the levels of the mnp1 and mnp2 transcripts increased approximately 100- and 1,700-fold, respectively, over basal levels. In contrast, under these conditions, the level of the mnp3 transcript did not increase significantly over the basal level. Quantitative RT-PCR of total RNA extracted from nitrogen-deficient, Mn-supplemented cultures on days 2 through 7 demonstrates that whereas the mnp1 transcript was present at relatively low levels on days 3 through 7, the mnp2 transcript level peaked on day 5 and the mnp3 transcript level peaked on day 3. Comparison of total RNA extracted on day 5 from nitrogen-deficient, Mn-supplemented stationary and agitated cultures indicates that in stationary cultures, mnp2 was the major expressed mnp gene, whereas in large agitated cultures, mnp1 was the major expressed mnp gene.

Basidiomycota↗
PubMed1998

The large subunit of basal transcription factor SNAPc is a Myb domain protein that interacts with Oct-1.

The human RNA polymerase II and III snRNA promoters have similar enhancers, the distal sequence elements (DSEs), and similar basal promoter elements, the proximal sequence elements (PSEs). The DSE, which contains an octamer motif, binds broadly expressed activator Oct-1. The PSE binds a multiprotein complex referred to as SNAPc or PTF. On DNAs containing both an octamer site and a PSE, Oct-1 and SNAPc bind cooperatively. SNAPc consists of at least four stably associated subunits, SNAP43, SNAP45, SNAP50, and SNAP190. None of the three small subunits, which have all been cloned, can bind to the PSE on their own. Here we report the isolation of cDNAs corresponding to the largest subunit of SNAPc, SNAP190. SNAP190 contains an unusual Myb DNA binding domain consisting of four complete repeats (Ra to Rd) and a half repeat (Rh). A truncated protein consisting of the last two SNAP190 Myb repeats, Rc and Rd, can bind to the PSE, suggesting that the SNAP190 Myb domain contributes to recognition of the PSE by the SNAP complex. SNAP190 is required for snRNA gene transcription by both RNA polymerases II and III and interacts with SNAP45. In addition, SNAP190 interacts with Oct-1. Together, these results suggest that the largest subunit of the SNAP complex is involved in direct recognition of the PSE and is a target for the Oct-1 activator. They also provide an example of a basal transcription factor containing a Myb DNA binding domain.

Amino Acid Sequence↗
PubMed1998

CD 80(B7-1) expression on human tumor cell lines and its costimulatory signals for T cell proliferation and cytokine production.

OBJECTIVE: To investigate CD 80 expression on human tumor cell lines and establish stable CD 80 expression transfectants to illustrate CD 80 costimulation on the T cell proliferation and cytokine production. METHODS: Raji, MDA-453, MCF-7, Hela, 3AO, MKN-45 and EBV transformed B cell were detected for CD 80 expression by RT-PCR. CD 80 cDNA subcloned to retrovirus vector pLXSN, with them stable CD 80 transfectanants were established. With specific mAb BB1 and FACS assay, the expression of CD 80 were detected. Anti-CD3 induced T lymphocyte proliferation and IL-2, IFN-r production were performed to evaluate CD 80 costimulatory activity in the presence of calcium ionophore A23187 and phorbol ester PMA. RESULTS: CD 80 (B7-1) expression of MDA-453, MCF-7, Hela, 3AO, MKN-45 was negative, and that of Raji and EBV transformed B cell was positive by RT-PCR and FACS methods. Cocultured with CD 80 transfected human breast carcinoma cell line MDA-453, anti-CD3 induced T cells proliferation and cytokine production were significantly increased in the presence of A23187 and PMA, but not with parental MDA-453. CONCLUSIONS: CD 80 expression is absent on most human tumor cell line except for Raji and EBV transformed B cell. Full activation of T cell needs CD 80 costimulation. Influence of CD 80 costimulation on cytokine production is mainly regulated via IL-2 and IFN-r.

B7-1 Antigen↗
PubMed1998

[Analysis of the relations between Toynbee phenomenon and middle ear pressure].

This paper studied the relations between the middle ear pressure, the opening duration of eustachian tube (ET), and the duration of nasopharyngeal pressure phase during Toynbee maneuver by sonotubometry, tympanometry and nasopharynx manometry. The mucociliary clearance of ET in Toynbee maneuver was also studied by Saccharin method. The results showed that negative middle ear pressure induced by Toynbee maneuver was related to prolonged opening duration of ET and duration of negative pressure in nasopharynx and lower opening pressure of ET. This phenomenon was often shown on the patients with nasal obstruction, and reduced ET mucociliary clearance. The Toynbee phenomenon indicates a closing failure of the ET, clinically, this situation needs to be prevented and resolved in a timely manner.

Adolescent↗
PubMed1998

[Rapid effect of glucocorticoid on excitatory postsynaptic potential of B cells in bullfrog paravertebral ganglia].

In the present study, the rapid effect of hydrocortisone 21-hemisuccinate (F-suc) on the amplitude of f-EPSP of B cells in isolated bullfrog sympathetic ganglia was examined with the use of intracellular recording technique. It was found that the amplitude of f-EPSP of B cells was decreased by F-suc, with a latency less than 3 min after the beginning of perfusion of F-suc. The inhibition of F-suc was concentration-dependent and could be blocked by the antagonist of intracellular glucocorticoid receptor RU38486, but not by the protein synthesis inhibitor actidione. These findings suggest that the inhibition of f-EPSP of B cells by F-suc is probably mediated through a nongenomic mechanism.

Animals↗
PubMed1998

[Bone scintigraphy in evaluating revascularization of the heat-devitalised autografts in adult dogs].

OBJECTIVE: To establish an animal model of microwave hyperthermic devitalization of long bones and compare bone scintigraphy of the devitalised bone with pathologic examination. METHOD: 16 Mongrel adult dogs were used. Enght 8 cm of one femur of each dog was exposed and isolated by heat-proof material. Two microwave antennas were inserted into the medullary cavity at a distance of 2.5 cm, and the bone was heated intermittently to maintain a surface temperature of 50 degrees C to 60 degrees C for 30 minutes. Bone scintigraphy was carried out at different postoperative time, combined with tetracycline labeling, microangiography with Indian ink and HE staining. RESULT: About 5 cm - 6 cm of segmental femur was deprived of blood supply after devitalization which was confirmed by microangiography and negative labeling of tetracyclines. At two weeks, the devitalised bone demonstrated a cold region on the scintiscan and no revascularization in microangiography. 12 - 16 weeks after the operation, partial devitalised bone was revascularized and HE staining showed widel bone resorption and minimum formation of new bone. However, the radionuclide uptakes of the devitalised segments were greater than those of the normal femurs. At one year, the devitalised segment was well (not completely) revascularised and showed evident appositional new bone formation. The scintigraphic bone-imaging was slightly lower than that of the normal femur. CONCLUSION: A strong positive scintiscan in early stage might demonstrate a good potential of revascularization of the heat-devitalised cortical bone rather than its viability. And the scintiscans of long-term follow-up more than one year should be more informative.

Angiography↗
PubMed1998

In vitro and in vivo evaluations of intestinal barriers for the zwitterion L-767,679 and its carboxyl ester prodrug L-775,318. Roles of efflux and metabolism.

The barriers to oral delivery of the hydrophilic zwitterion L-767, 679 (I) and its carboxyl ester prodrug L-775,318 (II) were examined. In the Caco-2 cell model, transport of II, but not I, was strongly oriented in the secretory direction. The basal-to-apical transport of II displayed saturable kinetics and was markedly inhibited by verapamil and quinidine, known P-glycoprotein inhibitors. In Caco-2 cells, metabolism of I was not observed, whereas hydrolysis of II was modest (</=20%). In the in situ rat intestinal loop model, verapamil did not affect the absorption of I but significantly increased the absorption of II. I was resistant to intestinal metabolism, whereas II underwent hydrolysis partially in rat lumen but more extensively in rat intestinal tissue and blood. In vitro metabolism studies indicated that verapamil also inhibited the hydrolysis of II in rats. The inhibition was relatively specific for the intestinal and not the luminal esterases. These results suggested that the intestinal absorption of I was limited not by intestinal efflux or metabolism but more likely by the low lipophilicity of I. However, an efflux system, likely mediated by P-glycoprotein, played an important role in limiting the absorption of II. In rats, metabolism served as an additional barrier to the absorption of II. Verapamil increased the intestinal absorption of the prodrug by inhibiting the efflux system in the two models studied, as well as possibly inhibiting metabolism in rats. For the first time, secretory transport was identified as a cause of the failure to increase the absorption of a lipophilic and cationic prodrug developed to overcome the absorption problem.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1997

Muscle coordination of maximum-speed pedaling.

A simulation based on a forward dynamical musculoskeletal model was computed from an optimal control algorithm to understand uni- and bi-articular muscle coordination of maximum-speed startup pedaling. The muscle excitations, pedal reaction forces, and crank and pedal kinematics of the simulation agreed with measurements from subjects. Over the crank cycle, uniarticular hip and knee extensor muscles provide 55% of the propulsive energy, even though 27% of the amount they produce in the downstroke is absorbed in the upstroke. Only 44% of the energy produced by these muscles during downstroke is delivered to the crank directly. The other 56% is delivered to the limb segments, and then transferred to the crank by the ankle plantarflexors. The plantarflexors, especially soleus, also prevent knee hyperextension, by slowing the knee extension being produced during downstroke by the other muscles, including hamstrings. Hamstrings and rectus femoris make smooth pedaling possible by propelling the crank through the stroke transitions. Other simulations showed that pedaling can be performed well by partitioning all the muscles in a leg into two pairs of phase-controlled alternating functional groups, with each group also alternating with its contralateral counterpart. In this scheme, the uniarticular hip/knee extensor muscles (one group) are excited during downstroke, and the uniarticular hip/knee flexor muscles (the alternating group) during upstroke. The ankle dorsiflexor and rectus femoris muscles (one group of the other pair) are excited near the transition from upstroke to downstroke, and the ankle plantarflexors and hamstrings muscles (the alternating group) during the downstroke to upstroke transition. We conclude that these alternating functional muscle groups might represent a centrally generated primitive for not only pedaling but also other locomotor tasks as well.

Ankle↗
PubMed1997

Exponential heating in drug stability experiment and statistical evaluation of nonisothermal and isothermal prediction.

A new nonisothermal heating model (exponential heating model) for drug stability experiments, based on a theoretical study of simulated nonisothermal data, is presented. In the model, the heating rate dT/dt is increased by 2-4 times at every increase of 10 degrees C in temperature: dT/dt = a(T-T0)/10.(dT/dt)0 where a is the times by which the heating rate is increased at every increase of 10 degrees C. A computation method with optimization and Simpson integration for the experiment was also introduced. The estimates for the shelf-life and activation energy obtained by the exponential and other nonisothermal heating models were statistically evaluated and were compared with those obtained by the isothermal method under various conditions. The results indicated that under the same experimental conditions, the estimates obtained by the exponential heating model were significantly more accurate and precise than those obtained by the linear, reciprocal, and logarithmic heating models. The accuracy and precision of the estimates were independent of the shelf-life of drugs and experimental period. The estimates obtained by the isothermal method were somewhat more accurate and precise than those obtained by the exponential heating model. However, the experimental period needed by the isothermal method was about five times longer than that needed by the exponential heating model. The results also showed that in each of the heating models, the estimates are more accurate and precise by increasing the extent of drug degradation, changing temperature range or sampling frequency, or by having the mean temperature closer to room temperature. To demonstrate its applicability, the exponential heating model was used to study the stability of vitamin C tablets and predict their shelf-life.

Drug Stability↗
PubMed1997

Determination of rate order for degradation of drugs with nonisothermal stability experiment.

The inability of ordinary nonisothermal experiments to determine the rate order (n) of drug degradation is discussed on the basis of a theoretical study of simulated nonisothermal data. In ordinary nonisothermal experiments, using either r or sigma(C[experiment] C[compute])2 as the measure of goodness of fit, the rate order cannot be assessed because the same set of c-t data can be well fitted by different combinations of estimates for n and the activation energy (E). Hence, a new nonisothermal heating-and-cooling model is introduced as a revision, in which sigma(C[experiment] C[compute])2 changes significantly with various kinetic models. Therefore, all the kinetic parameters, including the rate order, can be obtained in one nonisothermal stability experiment. Furthermore, the ability to determine rate order is significantly affected by the extent of drug degradation and experimental error, though not by sampling frequency or temperature change. To demonstrate the applicability of the heating-and-cooling model, the stability and rate order of degradation of vitamin C tablets was studied by this method.

Ascorbic Acid↗
PubMed1997

Novel saponins hainaneosides A and B isolated from Marsdenia hainanensis.

Novel saponins possessing fertility-regulating activity, hainaneosides A (1) and B (2), have been isolated from the twigs and stems of Marsdenia hainanensis, and their structures have been elucidated unambiguously as 12-nicotinoyl sarcostin-3-O-beta-D-glucopyranosyl-(1-->4)-3-O-methyl-6-deoxy-bet a-D- allopyranosyl-(1-->4)-beta-D-oleandropyranosyl-(1-->4)-beta-D- cymaropyranosyl-(1-->4)-beta-D-cymaropyranoside and 12-nicotinoyl-20-cinnamoyl sarcostin-3-O-beta-D-glucopyranosyl-(1-->4)-3-O-methyl-6-deoxy-bet a-D- allopyranosyl-(1-->4)-beta-D-oleandropyranosyl-(1-->4)-beta-D-c ymaropyranoside using NMR spectroscopic techniques and chemical transformations.

Abortifacient Agents, Nonsteroidal↗