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Biomedical subjects

M Li

Publications and source records attributed to M Li.

At least 1,117 records · Page 62Linked to original sources
PubMed1989

[Study on the biological nature of ginseng pearl knot].

Pearl knots of the root system of cultivated ginseng in different ages and different development stages were studied and compared with wild ginseng. It has been found that the biological nature of pearl knots is the foundation of seasonal absorbing root of ginseng. It is pointed out that to remove the cold-proof matter later and keep suitable soil water in spring are important to prevent cold injury and promote growth of root system of ginseng. Key words ginseng; pearl knot; seasonal absorbing root

Panax↗
PubMed1989

[Protective effect of extracts from Aloe vera L. var. chinensis (Haw.) Berg. on experimental hepatic lesions and a primary clinical study on the injection of in patients with hepatitis].

The injection(10-15 ml/kg/d, ip x 4), total glycoside (125-225 mg/kg/d, ip x (3-4); 600 mg/kg/d, ig x 3) and crystal III (120 mg/kg/d, ip x 4) of Aloe vera var. chinensis were found to be effective in lowering the elevated sGPT induced by CCl4, thioacetamide and D-aminogalactose in mice or rats. It was also observed that these agents could protect hepatic cells from the CCl4-induced injury. When dogs were given in with Aloe injection of 0.1 ml/kg/d x 180, no toxicity was noted. The total effective sGPT-lowering rate of Aloe injection on 38 patients of chronic hepatitis with positive HBsAg was 86.8%.

Alanine Transaminase↗
PubMed1989

[Effect of murine malarial circulating immune complexes on the production of reactive oxygen species by peritoneal exudate cells of normal mice].

Circulating immune complexes (CIC) isolated from sera of mice infected with Plasmodium berghei by precipitation with polyethylene glycol were examined for their ability to stimulate the production of reactive oxygen species by peritoneal exudate (PEC) of normal mice, using luminol-aided chemiluminescence (CL). CIC were found to be capable of stimulating the production of CL by normal mouse PEC. Weaker CL responses were observed when PEC were incubated with P. berghei soluble antigens. Normal mouse IgG and IgG1, IgG2b subclasses showed no effect on the stimulation of the production of CL. When normal mouse PEC were preincubated with CIC, their CL responses to opsonized zymosan were significantly depressed to 34% of the control level. The data suggest that CIC are capable of stimulating phagocytes to release reactive oxygen species and mediating pathological tissue damage.

Animals↗
PubMed1989

Crystal structure determination of 4-zinc bovine insulin at 1.9 A resolution.

With the isomorphous difference Fourier method and the restrained least-squares refinement technique, the crystal structure of 4-zinc bovine insulin in space group R3 was determined. The final crystallographic residual is 0.19 at 1.9 A resolution. Based on the refined model, the structural mechanism for prolonged action of 4-zinc insulin is discussed.

Animals↗
PubMed1989

Pediatric emergency medicine: a developing subspecialty.

Questionnaires were sent to 245 North American institutions with pediatric residency programs. There was a 69% response rate. Pediatric emergency care is provided in three types of facilities: emergency departments in pediatric hospitals, separate pediatric emergency departments or combined pediatric and adult emergency departments, in multidisciplinary hospitals. There are at least 262 pediatricians practicing full-time pediatric emergency medicine. The majority work in pediatric emergency departments, an average of 30.7 clinical hours per week. There are 27 pediatric emergency medicine programs with 46 fellows in training and 117 full-time positions available for emergency pediatricians throughout North America. Varying qualifications for these positions include board eligibility in pediatrics, certification in Basic Life Support or Advanced Trauma Life Support, and a fellowship in pediatric emergency medicine. The demonstrated need for pediatricians, preferably trained in emergency care, clearly indicates that pediatric emergency medicine is a rapidly developing subspecialty of Pediatrics that will be an attractive career choice for future pediatricians.

Adult↗
PubMed1988

Cyclic AMP-dependent protein kinase opens chloride channels in normal but not cystic fibrosis airway epithelium.

Chloride (Cl-) secretion by the airway epithelium regulates, in part, the quantity and composition of the respiratory tract fluid, thereby facilitating mucociliary clearance. The rate of Cl- secretion is controlled by apical membrane Cl- channels. Apical Cl- channels are opened and Cl- secretion is stimulated by a variety of hormones and neurotransmitters that increase intracellular levels of cyclic AMP (cAMP). In cystic fibrosis (CF), a common lethal genetic disease of Caucasians, airway, sweat-gland duct, secretory-coil and possibly other epithelia are anion impermeable. This abnormality may explain several of the clinical manifestations of the disease. The Cl- impermeability in CF-airway epithelia has been localized to the apical cell membrane, where regulation of Cl- channels is abnormal: hormonal secretagogues stimulate cAMP accumulation appropriately but Cl- channels fail to open. Here we report that the purified catalytic subunit of cAMP-dependent protein kinase plus ATP opens Cl- channels in excised, cell-free patches of membrane from normal cells, but fails to open Cl- channels in CF cells. These results indicate that in normal cells, the cAMP-dependent protein kinase phosphorylates the Cl- channel or an associated regulatory protein, causing the channel to open. The failure of CF Cl- channels to open suggests a defect either in the channel or in such an associated regulatory protein.

Adenosine Triphosphate↗
PubMed1988

Evaluation of the binding of Acanthamoeba profilin to pyrene-labeled actin by fluorescence enhancement.

We have used a fluorescence assay to measure the binding of Acanthamoeba profilin to monomeric Acanthamoeba and rabbit skeletal muscle actin labeled on cysteine-374 with pyrene iodoacetamide. The wavelengths of the pyrene excitation and emission maxima are constant at 346 and 386 nm, but the fluorescence is enhanced up to 50% by profilin. The higher fluorescence is largely due to higher absorbance in the presence of profilin. The fluorescence enhancement has a hyperbolic dependence on the concentration of profilin, suggesting a single class of binding sites. Linear Scatchard plots yield an estimate of the dissociation constant, Kd, of the complex of profilin with pyrenyl-actin. In low-ionic-strength buffers with 2 to 6 mM imidazole (pH 7.0) and 0.1 mM CaCl2 the Kd is 9 microM for both muscle and Acanthamoeba actin. In 50 mM KCl the Kd for the complex with Acanthamoeba actin is 16 microM, while the Kd for the complex with muscle actin is greater than 50 microM.

Acanthamoeba↗
PubMed1988

Characterization of human tracheal epithelial cells transformed by an origin-defective simian virus 40.

To facilitate understanding of the mechanisms underlying pulmonary diseases, including lung cancer and cystic fibrosis, we have transformed and characterized cultures of human tracheal epithelial cells. Cells were transfected by calcium phosphate precipitation with a plasmid containing a replication-defective simian virus 40 (SV40) genome. Colonies of cells with enhanced growth potential were isolated and analyzed for transformation- and epithelial-specific characteristics. Precrisis cells were observed to express the SV40 large tumor antigen, produce cytokeratins, have microvilli, and form tight junctions. After crisis, cells continued to express the SV40 large tumor antigen as well as epithelial-specific cytokeratins and to display the apical membrane microvilli. Apical membrane Cl channels were opened in postcrisis cells exposed to 50 microM forskolin. These channels showed electrical properties similar to those observed in primary cultures. The postcrisis cells have been in culture for greater than 250 generations and are potentially "immortal." In addition to providing a useful in vitro model for the study of ion transport by human airway epithelial cells, the cells can be used to examine stages of neoplastic progression.

Cell Line, Transformed↗
PubMed1988

Gonadotropic regulation of prostaglandin production by ovarian follicular cells of the pig.

Prepubertal gilts were treated with 750 IU pregnant mare's serum gonadotropin (PMSG) and 72 h later with 500 IU human chorionic gonadotropin (hCG) to induce follicular growth and ovulation. Dispersed granulosa cells (GC) and theca interna cells (TC) from follicles of gilts 72 h (GC-72 and TC-72, respectively) and 108 h (GC-108 and TC-108 h, respectively) after PMSG treatment were cultured for 0, 12, 24, and 36 h in medium with or without luteinizing hormone (LH), dibutyryl cyclic adenosine 3',5'-monophosphate [Bu)2cAMP), calcium ionophore (A23187), and/or arachidonic acid (AA), and the production of prostaglandin E2 (PGE) and prostaglandin F2 alpha (PGF) was measured by radioimmunoassay. TC-72 was the principal source of PGs 72 h after PMSG. At 108 h, the production of PGE and PGF by GC was increased 10- and 30-fold, respectively, whereas corresponding increases by TC were 2-fold. LH and A23187 significantly stimulated PGE and PGF production by both GC-72 and TC-72, but only thecal PG production was stimulated by (Bu)2cAMP. LH had minimal or no effect on PG production by GC-108 and TC-108, but A23187 (GC-108, TC-108) and (Bu)2cAMP (TC-108) were stimulatory. Basal PG production by GC-72, GC-108, and TC-108 was stimulated by AA. However, production by GC and TC cultured in medium containing AA and LH, A23187, or (Bu)2cAMP was not different from that produced by AA alone. These findings suggested that GC and TC can synthesize PGs in vitro, but AA availability is rate-limiting in GC. After exposure to hCG in vivo, the capacity of both cell types to produce PGs is increased but is limited by AA availability.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

Wounding properties of steel pellets with different velocities and quality on soft tissue of dogs.

The characteristics of the soft-tissue wounds of the hind legs of 155 dogs produced by stainless steel spheres with four different masses and at various impact velocities were observed. It was found that when the mass of the spheres was identical, the velocity became the main factor to determine the severity of the damage; when the mass of the spheres was different but their kinetic energy was similar, then a smaller but faster sphere produced more severe damage than a larger but slower one. Shallow but wide and severe wounds usually resulted. The rate of disability of extremities with such wounds was very high. These wounding properties of steel spheres have caused some new problems in the treatment of war injuries.

Animals↗
PubMed1988

The characteristics of the pressure waves generated in the soft target by impact and its contribution to indirect bone fractures.

When a high-velocity spherical fragment impacts a biological body, it will initiate strong pressure waves spreading throughout the body. A pressure wave, especially a shock wave with a steep front, generated by impact, may cause blood vessel injuries, viscera injuries, and indirect bone fractures. This paper reports research on pressure waves near the wound tracks, generated by spherical fragments, and calculates the zones of indirect bone fractures generated by pressure waves of impact.

Animals↗
PubMed1988

An analysis of the wounding factors of four different shapes of fragments.

The wounding characteristics to a biological target of four typical shapes of fragments (square, triangular, cylindrical, and spherical) with masses of less than 1 gram and velocities between 460 and 1,500 m/s are studied in this paper. The following conclusions about the effects of the wounding factors, such as energy transfer, velocity, mass, and shape of fragment are presented: 1) For given target characteristics, the important wounding factors of fragments are impact velocity, mass, and shape, and of these velocity is the most important. 2) Besides direct effects, the fragment velocity has great influence on far-reaching, indirect wounding effects. When velocity increases, it not only increases the size of direct wound, but also the rate of indirect bone fracture. 3) The rate of energy transfer is affected by fragment shape, and it is also a decreasing function of mass. 4) Under the same conditions there are differences in wounding effectiveness among the four fragment shapes, the triangular with a comparatively high wounding effectiveness, followed by the square, cylindrical, and spherical. The types of wound channels are also different, the cylindrical and spherical making a "through" type, the square and triangular making a "blind-tube" type.

Animals↗
PubMed1988

Hemorrhagic shock induces bacterial translocation from the gut.

Sepsis and multiple organ failure are common after hemorrhagic shock. The goal of the current experiments was to determine whether hemorrhagic shock would promote the translocation of bacteria from the gut to visceral organs. Twenty-four hours after being subjected to sham shock, or 30, 60, or 90 minutes of shock (30 mm Hg), rats were sacrificed and their organs quantitatively cultured for translocating bacteria. There was a direct relationship between the duration of hemorrhagic shock and the 24-hour mortality rate (p = 0.02). Bacteria did not translocate from the gut in the sham-shock rats, but did translocate to the mesenteric lymph nodes, livers, and spleens of the rats subjected to hemorrhagic shock (p less than 0.01). Rats subjected to 90 minutes of shock shock exhibited a greater degree of bacterial translocation than rats receiving 30 or 60 minutes of shock (p less than 0.05). The most common translocating bacteria were Escherichia coli and Enterococcus. Hemorrhagic shock injured the gut mucosa and caused subepithelial edema and focal areas of necrosis. Thus hemorrhagic shock followed by reinfusion of shed blood disrupts the gut barrier and allows indigenous bacteria normally contained within the gut to cause systemic infections.

Animals↗
PubMed1988

Effect of calcium ionophore A23187 on pregnenolone metabolism to progesterone in rat granulosa cells.

The effect of calcium ionophore A23187 on the metabolism of pregnenolone to progesterone was examined in rat granulosa cells during a 24-h culture period. Granulosa cells harvested from pregnant mare's serum gonadotropin treated immature rats were incubated in the presence and absence of the divalent cation ionophore A23187. The ionophore induced progesterone synthesis from both endogenous sterol substrate and exogenous pregnenolone in a time- and concentration-dependent manner. Pregnenolone metabolism was examined in the presence of aminoglutethimide phosphate, an inhibitor of endogenous pregnenolone production. Steroid secretion resulting from metabolism of endogenous substrate was more sensitive to A23187 in that a lower concentration of the ionophore was required to induce a significant increase than that noted for exogenous pregnenolone metabolism. In addition, progesterone production from endogenous sterol occurred 6 h earlier than the observed increase in the conversion of pregnenolone to progesterone. These results indicate that A23187 and therefore possibly enhanced calcium influx may play a significant role in the regulation of pregnenolone metabolism in granulosa cells depending on the duration of incubation. The earlier steroidogenic response from endogenous substrate may be a reflection of an acute effect of A23187 on certain steroidogenic steps proximal to pregnenolone production.

Animals↗
PubMed1988

Microfilaments and FSH stimulation of rat granulosa cell steroidogenesis in vitro.

The secretion of progesterone and 20 alpha-hydroxypregn-4-en-3-one (20 alpha-dihydroprogesterone) by granulosa cells from 30-day-old rats pretreated with PMSG (4 i.u.; i.p.) was significantly increased in a time- and concentration-dependent manner by FSH or cytochalasin B. Whereas FSH markedly stimulated progestagen secretion during 3 h of incubation, a significant enhancement of the steroidogenic response was not noted until 12 h of exposure to the inhibitor in vitro. Although cytochalasin B also enhanced the submaximal stimulation of progestagen production by FSH (15 ng/ml), it was ineffective in the presence of maximal stimulatory concentration of the gonadotrophin (150 ng/nl). With increasing concentrations of cytochalasin B, the ability of FSH to further stimulate progestagen secretion was progressively reduced. Granulosa cells cultured in medium alone contained a prominent cytoplasmic array of microfilaments which was markedly reduced by FSH or cytochalasin B. FSH and, to a greater extent, cytochalasin B elicited concentration-dependent reductions in the mean area occupied by the cells on the culture surface, the contour index (a size-independent representation of cell profile irregularity) and cell perimeter, indicating that the cells underwent less spreading and were more spherical and regular in outline in the presence of either agent. The FSH-induced reductions in the three shape-related parameters were augmented by cytochalasin B although the influence of the FSH on the mean area and perimeter was progressively reduced in the presence of higher concentrations of cytochalasin B.(ABSTRACT TRUNCATED AT 250 WORDS)

Actin Cytoskeleton↗