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Biomedical subjects

A Li

Publications and source records attributed to A Li.

At least 253 records · Page 14Linked to original sources
PubMed1995

[The phenoloxidase test and its application to identify Cryptococcus neoformans with various biological characteristics].

Cryptococcus neoformans strains with various biological characteristics were examinated the phenoloxidase activity on the caffeic acid cornmeal agar (CACA). Other medically important yeasts were also included in this research. Firstly, thirteen reference strains of Cryptococcus neoformans were confirmly found positive phenoloxidase production on the CACA medium. Then, in total 150 isolates of yeasts, forty three Cryptococcus neoformans strains were phenoloxidase positive, other than that 107 other yeast strains were all negative. It is suggested that Cryptococcus neoformans strains with different biological features specifically and uniquely produce phenoloxidase, thus the phenoloxidase test can be applied as a useful tool to identify this pathogenic yeast. Our results also show that the culture on the CACA medium is an effective method to test the phenoloxidase activity within 72 hours. It is further approved that the urease test will not be able to be a screening test for Cryptococcus neoformans in the clinical laboratory, but it is still valuable to identify urease negative Cryptococcus neoformans when the test is used in combination with the phenoloxidase test.

Candida↗
PubMed1995

[Analysis of factors causing visual disability and its preventive measures in China].

Analysis of sampling data from Chinese people in 1987 showed prevalence of visual disability was 10.08/1000. Major factors causing visual disability were congenital or hereditary defects, ametropia, amblyopia and corneal disease in children aged 0-14 years; senile cataract, trachoma and corneal disease in the elderly people aged 60 and over; and ametropia, amblyopia, cataract and corneal disease in the other people. Glaucoma and eye trauma were two major causes leading to severe visual disability. Suggestion of three-level prevention for visual disability in the country was put forward by the authors with focus on primary prevention, including genetic counselling and health care in pregnancy, preventing from eye infection and trauma, and active treatment of primary diseases, such as diabetes.

Adolescent↗
PubMed1995

A study of biological function of retinoblastoma gene (Rb gene).

The human wild-type Rb gene cDNA has been cis- or trans inserted into the retrovirus vector DOL, resulting in a sense-expression vector DOLRB and an antisense-expression vector DOLRBAS of Rb gene. By eletroporation transfection techniques, the vector DOLRB has been introduced into the human breast carcinoma cell line MDAMB468 and human hepatocellular carcinoma cell line SMMC7721 both of which have an inactivated Rb gene and the vector DOLBAS, into normal human embryonic lung fibroblasts HEL cells. With the expression of Rb protein, the growth rate of the MDAMB468 cells is decreased by about 50%, their colony formation ability in soft agar is repressed completely, and their tumorigenicity in nude mice is repressed partially. Meanwhile, the cell population of G1 phase of Rb+ MDAMB468 cells is increased markedly. About 75% of transfected SMMC7721 cells have been killed by Rb gene product. For HEL cells, with the transient expression of antisense Rb gene, the Rb protein synthesis is reduced and the growth rate of those cells increased, but no colonies of HEL cells are formed in soft agar.

Animals↗
PubMed1995

Laryngotracheal flap for reconstruction of hypopharynx and upper esophagus after resection of advanced pyriform sinus cancer.

Reconstruction of the hypopharynx and upper esophagus after resection of advanced pyriform sinus cancer, is usually complicated and time-consuming. Laryngotracheal flap was used in hypopharyngoesophageal reconstruction for 26 elderly patients with advanced pyriform sinus cancer Pharyngocutaneous fistula developed in 5 patients and healed spontaneously without further surgery. Full diet was resumed in all the patients. The surgical technique and its advantages and disadvantages are discussed. The laryngotracheal flap in the reconstruction of hypopharyngoesophageal defect for elderly patients is a procedure of choice.

Aged↗
PubMed1995

Neuron-specific enolase: a neuronal survival factor in the retinal extracellular matrix?

To identify soluble proteins of the retinal interphotoreceptor matrix (IPM), we isolated IPM from the bovine eye by gentle lavage and subjected it to SDS-PAGE. In the resultant gel, a 46 kDa band was particularly prominent and appeared to be a single protein. This protein was electroblotted to nitrocellulose membrane, digested with trypsin, and selected peptides were isolated by HPLC and subjected to Edman microsequencing. The amino acid sequences of the peptides were found to be virtually identical to that of human neuron-specific enolase (NSE). A monoclonal antibody specific for human NSE confirmed the presence of this enzyme in the bovine IPM by both Western blotting and immunocytochemical analysis. Immunofluorescence microscopy demonstrated that NSE is mainly localized to the basal domain of the IPM surrounding photoreceptor cells but is also prominent in the inner segments of the cone photoreceptor neurons. When NSE was added to cultures of human retinoblastoma cells, no effect on morphology was observed. However, a positive effect on cell growth and/or survival was readily apparent. It thus seems that not only is NSE a significant component of the retinal extracellular matrix, but that it could function as a survival (neuronotrophic) factor for photoreceptor neurons.

Amino Acid Sequence↗
PubMed1995

Acidic fibroblast growth factor protects memory and immunoreactivity impairment in senescence accelerated mice.

Subcutaneous injection of aFGF once per a week into senescence accelerated mice (SAM)P8 was begun at 3 weeks after birth and continued for 10 months. Saline was injected as a control. Learning and memory and cellular immunological functions in the aFGF (F) group were enhanced significantly and while those of the saline (S) group deteriorated. The number of cholinergic neurons was decreased slightly and choline acetyltransferase activity in individual neurons in the medial septum which send monosynaptic terminals to the hippocampus was significantly decreased in the S group, but were more spared in the F group. The MAO-B activity was significantly lower in the F group than in the S group. The respective densities of muscarinic and NMDA receptors and the aFGF receptor, i.e. FGFR-1 in the hippocampus were also significantly higher in the F group than in the S group. The delayed type hypersensitivity reactions (DTH) in the footpad caused by challenge with trinitrophenyl or sheep red blood cells as measured at the end of the 2nd and 7th months, indicated the T cell immune response. Both types of DTHs were reduced in the 7th month as compared with the 2nd month in the S group. However, aFGF administration protected against this reduction in response with age. These results show that aFGF provides protection against impairment of not only learning and memory but also the DTH immunoreactivity in SAMP8, indicating thereby a close relationship between learning-memory and T cell immune function.

Aging↗
PubMed1995

[Late bladder complications following radiotherapy of carcinoma of the uterine cervix].

OBJECTIVE: To analyse the causes, clinical features, treatment and prevention of late bladder complications following radiotherapy of carcinoma of the uterine cervix. METHOD: This clinical retrospective study included 378 cases of irradiation cystitis following radiotherapy for carcinoma of the uterine cervix from February, 1958 to October, 1987. RESULTS: The incidence of irradiation cystitis was 3.2% and was not related to age, FIGO staging and the methods of intracavitary irradiation (conventional or afterloading). It was related to the external appearance of the local lesion; 66.5% of the tumors of patients with late bladder complications was of the exophytic type prior to radiotherapy. 51.1% of the patients developed late bladder complications in a period of 2-5 years after radiotherapy; 16.7% in 5-10 years and only 3.4% within the first years. The patients with irradiation cystitis had received a 10% higher dosage than that routine delivered, as found either in intracavitary irradiation of 39.4% of patients or in external irradiation of 31.6% of patients. Based on the clinical features and cystoscopic findings, late bladder complications can be divided into three types: (1) sudden and temporary hematuria (35.7%); (2) persistent hematuria (63.2%); and (3) vesico-vaginal fistula (1.1%). The 5-year survival rate of patients with irradiation cystitis was 90.4% which was higher than the survival rates of all patients treated by conventional intracavitary irradiation (65.7%) and all patients treated by afterloading intracavitary irradiation (70.4%). 3.7% of patients died of late bladder complications. CONCLUSIONS: To decrease the occurrence of late bladder complications and to obtain long term survival: (1) Dosage to the bladder should be adequate, and over dose to the bladder should by all means be avoided; (2) Patients are to be taught to observe indicated personal care during radiotherapy as well as in the follow-up period; (3) Early institution of proper conservative treatment of cystitis is beneficial.

Adult↗
PubMed1995

[An analysis of burn cases in the last decade].

The clinical data of 3,911 burn patients admitted to our institute from January, 1983 to December, 1992 were analyzed mainly on the distribution of age, causes of burns, burn area, combined injuries, common complications, incidence of burn shock, mortality and cause of death. Results showed that 91.7 per cent of deceased had suffered from inhalation injury, internal organ complications and systemic infection, suggesting that inhalation injury, visceral complication and systemic infection still remain to be the three major causes of death in burn patients.

Adolescent↗
PubMed1994

Characterization of the transition state of protein unfolding by use of molecular dynamics: chymotrypsin inhibitor 2.

Temperature-induced unfolding of chymotrypsin inhibitor 2 in water was investigated by molecular dynamics simulations. The major transition state of unfolding was identified on the basis of structural and conformational changes in the protein during the unfolding reaction. The native tertiary contacts in the hydrophobic core were considerably disrupted in the transition state, whereas the secondary structure was partially intact. The extent of structural change of the protein around a particular residue was represented quantitatively by the ratio of the number of contacts the residue makes in the transition state relative to the native state, phi MD, which allows quantitative comparison with the experimentally determined phi F values. For the region of the unfolding trajectory that is identified as the transition state, the phi MD and phi F values are in good agreement, suggesting that the transition state identified in the unfolding simulation corresponds to that probed with protein engineering methods. Although speculative, the transition state identified in the simulation is consistent with available experimental data and provides an in-depth view of what the transition state of unfolding may look like.

Amino Acid Sequence↗
PubMed1994

Molecular characterization of the mouse ribosomal protein S24 multigene family: a uniquely expressed intron-containing gene with cell-specific expression of three alternatively spliced mRNAs.

A family of 16 genes encoding the mouse ribosomal protein S24 was identified, and four members from this family were cloned. A single expressed intron-containing S24 gene (termed mrpS24) and one pseudogene (mrpS24p) were completely sequenced and characterized. The mrpS24 gene has seven exons and six introns spanning over 5.1 x 10(3) nucleotides (nt). The cap site of S24 was mapped to a G residue four nt upstream of a polypyrimidine tract and 15 nt downstream of a TATA-like (TATGA) element. The 5' region (-325 to +33) of the mrpS24 gene has a functional promoter that was able to express the fused chloramphenicol acetyltransferase (CAT) reporter gene. Two different forms of mouse S24 cDNA clones were previously isolated. Sequence analysis showed that one of these cDNA clones (termed S24a) lacks the entire exon V sequence (18 nt), and the deduced amino acid sequence is missing a C-terminal lysine residue encoded by the other cDNA (S24b). The pseudogene mrpS24p is flanked by an 11-bp direct repeat, and its sequence is almost identical to the S24 cDNA sequence, but it lacks two mini-exons, V and VI (20 nt), as in the cases of the human and rat S24 cDNAs. RT-PCR experiments demonstrated the existence of a third form (S24c) that similarly lacks both of the mini-exons, and suggested that different species of S24 mRNA might arise from alternative splicing of the mini-exons V and VI. Northern blot analysis showed that S24 expression is down- and up-regulated during adipocyte differentiation and in cellular transformation, respectively. RNase protection assays and RT-PCR experiments suggested that these cell-specific changes of S24 mRNA levels are mainly due to fluctuations in S24c mRNA level. Our results provide the first indication that a ribosomal protein gene is regulated by alternative usage of two mini-exons in a cell-specific manner.

Alternative Splicing↗
PubMed1994

Solubility of organic solutes in ethanol/water mixtures.

The log-linear solubilization model was applied to the experimental solubility data of 109 organic compounds in ethanol/water mixtures. It is found that the extent of solubilization strongly depends on the solute hydrophobicity and the ethanol concentration in the solvent mixture. Patterns of deviation from the log-linear model are related to the structure and hydrophobicity of the solutes. Predictive equations were obtained by regression of the experimental data with solute octanol/water partition coefficient (log Kow). The logarithms of the solubilization and the solute log Kow range over 11 orders of magnitude. The solubilities of chrysene, perylene, benzo[a]pyrene, pentachlorobenzene, and hexachlorobenzene in ethanol/water mixtures were experimentally determined, and the results fit well into the model.

Chemical Phenomena↗
PubMed1994

Retrotrapezoid nucleus lesions decrease phrenic activity and CO2 sensitivity in rats.

In chloralose-urethane anesthetized, paralyzed, and ventilated rats, we measured the effects of unilateral lesions in the region ventral and ventromedial to the facial nucleus, the retrotrapezoid nucleus (RTN), on eucapnic phrenic activity and the response to increased end-tidal CO2. Chemical (kainic acid injections; 4.7 mM; 10-100 nl) and electrolytic (5-15 mA; 5-15 sec) lesions, anatomically demonstrated to be in the RTN, resulted in a progressive decrease in the amplitude of the integrated phrenic nerve activity from baseline levels of 49-59% of maximum to values of 21-32% of maximum over 30 to 120 min. There were no consistent effects on frequency or on blood pressure. The initial slope of the response to hypercapnia was decreased by 86-92%. Bilateral carotid body ablation did not alter the general pattern of the responses. As in the cat, unilateral RTN lesions decrease baseline phrenic amplitude and virtually abolish the response to hypercapnia. We hypothesize that the RTN region provides; (1) a source of tonic activity which maintains eucapnic ventilatory output, and (2) allows expression of the response to hypercapnia.

Animals↗
PubMed1994

Retrotrapezoid nucleus muscarinic receptor subtypes localized by autoradiography.

Microinjection of muscarinic receptor subtype antagonists into the region of the cat retrotrapezoid nucleus (RTN) decreases blood pressure (greatest efficacy; M2 subtype) and both baseline phrenic activity and CO2 sensitivity (greatest efficacy; M3/M1 subtype). Here we examine, in cat medullary sections at the level of the RTN, the effects of the same antagonists on binding of the high affinity muscarinic agonist quinuclidinyl benzilate (QNB). 3H-QNB binding was saturated and highly specific at 1 nM concentration and stable over 30 to 120 min (Kd, 0.49 nM; Bmax, 136 fm/mg protein). Studied biochemically, we found IC50 values for whole sections of 4.9 x 10(-6) M (M1 antagonist pirenzepine); 1.0 x 10(-6) M (M2 antagonist AFDX); and 0.64 x 10(-7) M (M3 antagonist DAMP; P < 0.03 vs PZ). Densitometric analysis of whole medullary cross section autoradiograms resulted in similar IC50 values as in the biochemical approach. Specific analysis of the RTN region demonstrated the presence of 3H-QNB binding and similar competition by the antagonists. Average IC50 values determined by densitometry were 14 x 10(-6) M (pirenzepine); 1.3 x 10(-6) M (AFDX; P < 0.01 vs PZ); and 0.53 x 10(-7) M (DAMP; P < 0.01 vs PZ). All three subtypes of muscarinic receptors identifiable via pharmacological antagonists appear to be present in the RTN region but we could not distinguish a subtype-specific pattern of receptor distribution.

Adamantane↗
PubMed1994

Clinical significance of the change of blood monocytic interleukin-1 production in vitro in severely burned patients.

Biological methods were employed to measure the dynamic changes in the in vitro IL-1 production by blood monocytes in 24 severely burned patients. The serum myocardial and hepatic enzymes (C-reactive protein) (CRP), plasma lactic acid (LA), etc. were simultaneously measured. The results showed an obvious decrease in blood monocyte IL-1 production in vitro and increases in CRP, LA and serum enzymes. These changes were more evident in patients complicated with organ injury, multiorgan failure and systemic infection. It is suggested that blood monocytes are superstimulated postburn in vivo and produced large amounts of IL-1 leading to exhaustion of monocyte function. These changes might promote the development of severe systemic infection and internal organ injury even multiple organ failure.

Adolescent↗
PubMed1994

Horizontal cells in the rabbit retina: differentiation of subtypes at neonatal and postnatal stages.

We are investigating the differentiation of the major subtypes of horizontal cell in the rabbit retina in order to learn more about developmental controls responsible for the variety of neuronal phenotypes. Immunohistochemistry with anti-neurofilament and anti-calbindin-D antibodies, followed by epoxy resin embedding, has facilitated study of these neurons. In the mature rabbit retina, axonless (A-type) horizontal cells reacted strongly in procedures using either antibody; short axon (B-type) somas did not show a reaction with anti-neurofilament antibodies and stained moderately using anti-calbindin antibodies. In the immature neonatal retina the somas of all the horizontal cells seemed to be similar with regard to general morphology, but two populations could be distinguished on the basis of immunostaining. Some, identified as A-type horizontal cells (by comparison with mature retina), were stained using either antibody. Interspersed among these were similar cells with no detectable immunoreactivity, identified as B-type horizontal cells. By the end of the first postnatal week, faint reactivity to anti-calbindin-D was present in the somas of B-type horizontal cells; they stained moderately throughout the rest of the period studied. Thus differences in immunostaining indicate that the two horizontal cell subpopulations are established early in the rabbit, though some other distinguishing characteristics emerge only gradually as the retina matures. These results suggest that in mammals the determination of phenotypic subtype occurs early, possibly at the time that the cell is specified as a horizontal neuron, or shortly thereafter.

Animals↗
PubMed1994

Immune responses in Vietnamese children after a single dose of the auxotrophic, live Shigella flexneri Y vaccine strain SFL124.

The live, auxotrophic Shigella flexneri vaccine strain SFL124 was given in a single dose of 10(7), 10(8) or 10(9) colony forming units (cfu), respectively, to each of three groups of 10 Vietnamese children aged 9-14 years. The vaccine was well tolerated by all the children without any severe side effects such as diarrhoea or fever being observed. Mild symptoms were reported by five children. Only five children were found by culture to excrete SFL124 but, by PCR, 28 of 30 children were found to excrete the vaccine strain for up to 5 days (mean 2.8 days) with insignificant differences among the groups. Local mucosal immune responses and antibody secreting cell (ASC) responses to S. flexneri lipopolysaccharide (LPS) and invasion plasmid-coded antigens (Ipa) were elicited in the children in a dose-dependent manner. Doses of 10(9) cfu induced most prominent responses, followed by those of 10(8) and 10(7) cfu. The sIgA responses were the highest whereas the ASC were modest. High titres of serum antibodies to Shigella LPS and Ipa were found in all the children before ingestion of the vaccine which elicited increases in serum antibody titres in only a few of them. The immune response patterns seen indicate a booster rather than a primary response and may be a consequence of the endemic nature of shigellosis in Vietnam.

Adolescent↗