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Biomedical subjects

A Li

Publications and source records attributed to A Li.

At least 19 recordsLinked to original sources
PubMed1992

Neurotrophic activity of interphotoreceptor matrix on human Y79 retinoblastoma cells.

A neurotrophic activity of adult monkey and bovine interphotoreceptor matrix (IPM) was examined by using cultured human Y79 retinoblastoma cells as a model system. The cells were stimulated for 7 days in suspension culture with soluble IPM components and then attached to poly-D-lysine substratum. IPMs from both species induced greater than 80% neuronal differentiation of Y79 cell aggregates after 11 days of attachment as adjudged morphologically by the extension of lengthy, neurite-like processes. Immunocytochemical studies indicate that differentiated Y79 cells had an increased level of expression of neuron-specific enolase and a concomitant decreased expression of glial fibrillary acidic protein. This neurotrophic activity cannot be ascribed to nerve growth factor, platelet-derived growth factor, fibroblast growth factor, epidermal growth factor, or transforming growth factor beta. Although the nature of the factor and its cellular source have yet to be characterized, it may be related to a recently described neurotrophic protein secreted by human fetal retinal pigment epithelial cells in culture. Our findings provide evidence supporting the neuroblastic potential of the Y79 cell line and indicate that the IPM contains a potent neurotrophic activity. Such factors may be important to normal differentiation and maintenance of function of the neural retina.

Animals↗
PubMed1992

Excitotoxin induction of ornithine decarboxylase in cerebral cortex is reduced by phospholipase A2 inhibition.

The enzyme ornithine decarboxylase (ODC) has been shown to be induced by a number of conditions such as cold-injury, kindling, ischaemia and excitotoxin injection. In previous studies we have characterised the cortical response to kainate injection into the nucleus basalis and shown a substantial increase in both ODC mRNA and enzyme activity which reaches a maximum at 8h. This response is completely prevented by treatment with MK-801, indicating the involvement of NMDA receptors in mediating this response. Whilst NMDA receptors are known to gate a cation channel leading to increased calcium entry, an additional effect on the release of arachidonic acid has been reported. The possibility that NMDA receptor mediated activation of phospholipase A2 and release of arachidonic acid might mediate this ODC response was investigated in this study by treatment with the phospholipase inhibitors quinacrine and dexamethasone. Treatment of animals with quinacrine (100 mg/kg) at the time of injection of kainate into the nucleus basalis caused a significant attenuation of the induction of ODC in cerebral cortex of 43%. No further attenuation was seen at higher doses. A similar reduction in ODC induction was seen after treatment with dexamethasone (1 mg/kg) but a greater effect could be obtained (65% attenuation) at higher doses. The possible involvement of arachidonic acid derivatives in mediating ODC induction was further investigated by treatment with the cyclo-oxygenase inhibitor indomethacin and the lipoxygenase inhibitor nordihydroguaiaretic acid (NDGA). Indomethacin was able to significantly attenuate the induction of ODC (greater than 60%) whilst NDGA (30 mg/kg) was ineffective. These results indicate the possible role of arachidonic acid derivatives in the regulation of the expression of ODC in cerebral cortex after excitotoxin injection.

Animals↗
PubMed1992

Safety and immunogenicity of the live oral auxotrophic Shigella flexneri SFL124 in volunteers.

The live, aromatic dependent Shigella flexneri Y vaccine strain SFL124, with a deleted aroD gene, was tested for safety and immunogenicity in 21 healthy adult volunteers. A single dose of 2 x 10(9) live bacteria was given orally to ten volunteers, whereas 11 received three doses every other day. The vaccine was excreted for 4.2 days and was well tolerated by 90.5% of the vaccinees. Only 2 of 21 (9.5%) after the first dose had a self-limiting diarrhoea lasting 1 day; of volunteers given one dose only 3 of 10 showed anti-lipopolysaccharide (LPS) and anti-invasion plasmid coded antigen (Ipa) responses in serum. A faecal antibody response to LPS and Ipa was seen in six and three persons, respectively. Volunteers given three doses reacted with serum anti-LPS (9/11) and anti-Ipa (5/11) antibody responses. In stool, anti-LPS and anti-Ipa responses were detected in nine and eight volunteers, respectively. A booster dose of 2 x 10(9) bacteria given to six volunteers in the three-dose group 9-10 months later elicited high stool sIgA responses, indicating a strong mucosal memory, and was accompanied by a short excretion period of SFL124 (1.8 versus 4.2 days, p less than 0.05). The vaccination also elicited antibody-secreting cell (ASC) responses against LPS in peripheral blood: the three doses of the vaccine resulted in a stronger response than did the single dose, while the booster dose elicited only a limited ASC response. Volunteers previously exposed to shigellae exhibited stronger anti-Ipa responses in serum and stool suggestive of an immunological memory to the Ipa. The results indicate that SFL124 is a safe live vaccine strain inducing specific immune responses against LPS and Ipa with a mucosal immune memory lasting for at least 9 months.

Administration, Oral↗
PubMed1992

Dynamic balance changes between elastase and antiprotease in the early stages after smoke inhalation injury.

Following the use of a rabbit smoke inhalation injury model established in this institute, there were marked reductions in elastase activities in neutrophils and alveolar macrophages; rapid increases in elastase activity in broncho-alveolar lavage fluid (BALF); reductions of serum trypsin inhibitory capacity; a decrease of Pao2 and an increase of PaCO2, and marked increases of lung water volume. Significant correlations were found between the increased extravascular lung water content and the rising elastase activity in BALF. It seems probable that the imbalance between elastase and antiprotease played an important role in the development of acute lung injury after smoke inhalation.

Animals↗
PubMed1992

Clinical observations and methods for identifying the existence of cultured epidermal allografts.

Thirty-two burned or plastic surgery patients were grafted with allogeneic cultured epidermis on autograft donor sites. Two techniques, the indirect enzyme conjugated Staphylococcus Protein A assay with monoclonal antibodies against A or B blood group antigens and the polymerase chain reaction to detect a Y chromosome-specific DNA sequence, were employed to identify the presence of cultured epidermal allograft based on different ABO blood grouping or sex between donor and recipient. The methods have the advantage of high sensitivity and specificity in identifying the existence of allogeneic skin cells in grafts. The results indicated that the survival time of cultured epidermal allograft was prolonged up to 35 days. In addition, the intact coverage on some grafting sites may be composed of both host and donor origin cells, after about 3 weeks postgrafting.

Adolescent↗
PubMed1992

Clinical studies on postburn multiple organ failure: its aetiological factors and monitoring.

This study demonstrated that multiple organ failure (MOF) developed in 16 of 57 severely burned patients (28.1 per cent). When expressed as a percentage of the 590 patients admitted during the same period, the incidence became 2.7 per cent. Fifteen of the 16 MOF cases died, with a mortality of 93.8 per cent. In those patients with TBSA over 80 per cent with inhalation injury, severe shock and systemic infection, the incidence of MOF was significantly higher. Systemic infection and severe shock were the most important complications. These results indicated that the severity of the burn is the prime prerequisite of MOF, while severe shock and systemic infection are secondary but very important factors in the genesis and development of postburn MOF. The circulatory platelet aggregate ratio (CPAR) started to decrease significantly at 12 h postburn, remaining at low levels and declining further at 5-7 days postburn. However the values of the myocardial enzyme spectrum (MES) remained at significantly higher levels, indicating significant and continuous increases of microaggregate formation and the continuous existence of visceral and tissue ischaemia and cellular destruction. Changes of CPAR and MES in MOF patients were directly related to the development of MOF. It is advisable to use CPAR and MES to monitor the possible development of postburn MOF.

Adult↗
PubMed1992

The effect of tolbutamide on burn hypermetabolism.

The effect of tolbutamide on improving burn hypermetabolism was studied prospectively in 31 burn adults with total body surface area burned > 40 per cent and 18 burned rabbits immediately after burn injury to postburn day 10. The results showed that burn hypermetabolism could be reduced using tolbutamide, which may be the result of the correction of relative insulin insufficiency, tissue insulin resistance and improving glucose utilization.

Adult↗
PubMed1992

Roles of thromboxane and prostacyclin in the pathogenesis of acute respiratory failure in burn patients combined with inhalation injury.

Forty-one severely burned patients were divided into inhalation injury and non-inhalation injury groups. It was found that in the inhalation injury group, TXB2 level and TXB2/6-keto-PGF1 alpha ratio in both plasma and lung tissues were significantly elevated, circulatory platelet aggregate ratio markedly decreased, and blood viscosity greatly increased. Histopathologically, congestion, oedema, haemorrhage and thrombosis were observed in lung tissues taken from patients succumbing to respiratory failure. The changes in TXB2 and TXB2/6 keto-PGF1 alpha ratio accorded with the clinical course of the development of respiratory failure in burn patients with inhalation injury. It is proposed that the imbalance of TXA2/PGI2 plays an important role in the pathogenesis of respiratory failure in severely burnt patients complicated with inhalation injury.

Acute Disease↗
PubMed1992

Homozygous pyruvate kinase deficiency in Hong Kong ethnic minorities.

Three cases of pyruvate kinase (PK) deficiency resulting in congenital haemolytic anaemia with transfusion dependency are described. These cases resulted from consanguineous marriages in non-Han Chinese and include a pair of twins. We believe this to be the first documentation of homozygous PK deficiency in the Hong Kong population. The diagnosis was masked due to transfusion dependency in each case stressing the need to take a sample of pretransfusion blood for PK enzyme assay, and for family studies, when this disorder is suspected.

Anemia, Hemolytic↗
PubMed1992

Answering MCQs: a study of confidence amongst medical students.

Medical students at the beginning of their obstetrics and gynaecology module were asked to complete a multiple choice question paper from an earlier module. Half the students were asked to answer only those questions where they were certain of the answers. The other half were asked to answer all questions. The mean mark in the second group was 86% higher than that in the first group. A computer programme was written where multiple choice questions were asked in a standard true/false format but instead of a don't know alternative the students were asked to rate their degree of certainty in having answered correctly on a scale of 0 to 100. Five students completed a total of 45 multiple choice question papers (each with 20, 5-part questions) both before and towards the end of their obstetrics and gynaecology module. The mean mark increased by 68.5% over the course of the module reflecting the students' increased knowledge. Their mean certainty level only increased by 50%, suggesting that the students underestimated their newly acquired knowledge.

Educational Measurement↗
PubMed1992

Retrofacial lesions: effects on CO2-sensitive phrenic and sympathetic nerve activity.

We made unilateral chemical (10- or 50-nl microinjections; 4.7 mM kainic acid) or electrolytic (5-15 mA; 15 s) lesions in a region of the rostral ventrolateral medulla (VLM) caudal to the retrotrapezoid nucleus in 10 decerebrate, paralyzed, vagotomized, and servo-ventilated cats. The lesions were 3.0-4.2 mm lateral to the midline, within 2 mm caudal to the facial nucleus, and within 2.5 mm of the VLM surface. Four control injections (mock cerebrospinal fluid and fluorescent beads alone) produced small and inconsistent effects over 3-5 h. The predominant effect of the lesions was a significant decrease in baseline integrated phrenic nerve amplitude (PNA) (apnea in 2 cases), total respiratory cycle duration, and the response to increased CO2 (slope < 15% of control in 3 cases). The respiratory-related peak amplitude of the integrated sympathetic signal, blood pressure, and the sympathetic nerve activity response to CO2 were also decreased after the majority of lesions. Not all lesions produced all effects, and some lesions resulted in increased PNA and respiratory cycle duration. The lesioned region appears functionally to represent a caudal extension of the retrotrapezoid nucleus containing neurons necessary for normal baseline PNA and CO2 sensitivity. In addition, it contains neurons involved in the determination of resting respiratory frequency and normal sympathetic activity and blood pressure. The pattern of mixed responses among animals suggests that a heterogeneity of function is present within a relatively small VLM region.

Animals↗
PubMed1992

[Isolation of HAV from sea clam].

Three strains of HAV were isolated directly from clams (Arca Subcrensta Lisckke) collected from sea with cell culture and identified by electron microscopy, immunofluorescent test, ELISA, HAV-cDNA hybridization and neutralization test. The strains were stably passed in 2BS cells with the titer of 4.0-5.0 TCID50/ml. Results indicated that the clams were contaminated by HAV and may cause an outbreak of hepatitis A.

Animals↗
PubMed1992

[An urease negative Cryptococcus neoformans].

We report an urease negative Cryptococcus neoformans derived from pigeon dropping. This isolate produced brown pigmented colonies on cornmeal Tween-80 agar with 300 micrograms/ml caffeic acid, but was failure to hydrolyze urea. More identification tests were performed for this isolate, such as assimilation and fermentation of carbohydrates, nitrate assimilation, production of starch like compound, growth on GCP medium, germ tube formation and inoculation of mice, ect. Most of the results showed that the microbiological characteristics of the isolate were typical of C. neoformans except for negative urease test. Even though there has been a report about an urease negative C. neoformans derived from an AIDS patient, but we have never found any report about isolation from pigeon dropping or nature environment. We should pay attention to the exist of this atypical strain of C. neoformans in nature environment and the possibility of infection to human being. Additionally, we also be aware of the possibility of neglect when this urease negative C. neoformans is identified with urease test.

Animals↗
PubMed1992

[Farm irrigation index for culturing Panax ginseng C.A. Meyer].

The growth and yield of annual and perennial Panax ginseng were observed by applying methods of mini-irrigation and irrigation under different negative pressures of soil humidometer. After four experiments optimum values of negative pressure were found to assist timely irrigation, thus providing scientific criteria of rational irrigation and automated mini-irrigation for culturing Panax ginseng.

Humidity↗
PubMed1991

Sulfation and glucuronidation of acetaminophen by cultured hepatocytes reproducing in vivo sex-differences in conjugation on Matrigel and type 1 collagen.

The sulfate and glucuronide conjugation of acetaminophen (APAP) by hepatocytes cultured on Matrigel or type 1 collagen was compared to APAP metabolism in vivo. The metabolic fate of low (15 mg/kg), medium (125 mg/kg), and high (300 mg/kg) doses of APAP injected intraperitoneally were determined in male and female rats. Males excreted more APAP as the sulfate conjugate than females, which correlated with the twofold greater APAP sulfotransferase activity in the male vs. females (301 +/- 24 vs. 156 +/- 18 pmol.mg-1 protein.min-1). Also, as sulfate conjugation became saturated, there was a dose-related shift in APAP metabolism from sulfate to glucuronide conjugation in both sexes. After death, the livers of the same animals were perfused with collagenase and the hepatocytes cultured in modified Waymouth's medium on either Matrigel or rat-tail collagen, with various doses of APAP (0, 0.125, 0.25, 0.5, and 1.0 mM). Sex differences in APAP sulfation and glucuronidation persisted in culture for up to 4 days, with sulfation predominating in the male similar to in vivo. With increasing APAP concentration (dose), there was a saturation of sulfate conjugation and a shift to glucuronidation as observed in vivo. Sex differences in APAP sulfation and glucuronidation were no longer significant by Day 4 in culture. Sulfation, and to a lesser extent, glucuronidation, were more stable on Matrigel than collagen. We concluded that APAP metabolism of freshly isolated hepatocytes could replicate in vivo sex differences in conjugation, and that Matrigel was superior to collagen as substrate.

Acetaminophen↗
PubMed1991

Further explorations of abnormalities in serum proteins following burns.

This report extends our earlier studies of the abnormal protein bands found in burn sera by use of Western blotting and ion exchange chromatography. The current studies indicated that some of the protein bands contained materials with immunosuppressive activity. One of these materials cross reacted with anti human haptoglobin antibody. Many of the other proteins in the bands were found to be acute phase reactant proteins without immunosuppressive activity. Some proteins in these bands have not yet been characterized or tested for immunosuppressive activity.

Adult↗
PubMed1991

Application of sulcated half-ring external fixator for treating bone and joint injuries of burned lower extremities: a report of four cases.

Four patients with burned lower extremities complicated with severe bone and joint injuries were treated with sulcated half-ring external fixators. The results were satisfactory. This apparatus is simple, easy to handle and effective. Using this fixator, the burn wounds as well as the bone and joint injuries could be managed at the same time, without mutual interference. As it seems a desirable method for the management of such compound injuries, the advantages and disadvantages of this apparatus are discussed.

Adult↗