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Biomedical subjects

A Li

Publications and source records attributed to A Li.

At least 217 records · Page 12Linked to original sources
PubMed1997

[Vertical transmission of hepatitis C virus].

To study the transmission of hepatitis C virus (HCV) from infected mother to their infants, out of 1047 mothers studied, 8 were anti-HCV antibody and 6 were HCV RNA positive as well as 2 mothers who were anti-HCV antibody and HCV RNA positive. 12 mothers and their 12 babies were followed up for 12 months. Only one of 12 infants showed persistently positive for anti-HCV antibody and HCV RNA at 1, 6 and 12 months of age. His HCV type was identical to his mother. These results suggest that vertical transmission is present but not an important route for HCV infection.

Adult↗
PubMed1997

aFGF, endogenous satiety substance, facilitates learning, memory and immune function in aging.

aFGF injection s.c. once a week into SAMP8 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 group were enhanced significantly, while those of the saline group deteriorated. 1. The number of cholinergic neurons was decreased by less than 20% and ChAT activity in individual neurons in the medial septum which send monosyonaptic terminals to the hippocampus was significantly decreased in the saline group, but not so much in the aFGF group. 2. The respective densities of muscarinic and aFGF receptors, on the hippocampal neurons were significantly higher in the aFGF group than in the saline group. 3. The LTP in hippocampal slice preparations was significantly facilitated in the aFGF group, but not in the saline group. 4. The DTH, (T cell immune response) measured at the end of the 2nd and 7th months were reduced in the 7th month as compared with the 2nd month in the saline group, but aFGF group protected against this reduction. 5. These results show that aFGF provides protection against impairment of not only learning and memory but also the DTH immunoreactivity in SAMP8.

Aging↗
PubMed1997

Functional analysis of histamine release from basophils and mast cells in subjects with the Ile-181-->Leu variant of Fc epsilon RI-beta.

1. Atopy is a genetically heterogeneous disorder, but there is now strong evidence that one important locus is on chromosome 11q13. Fc epsilon RI-beta at that location has been identified as a candidate gene and variants have been associated with atopy in population studies. 2. No information is available on the functional consequences of any of these variants, and defining this may prove difficult because of the complexity of the atopy phenotype and because Fc epsilon RI beta is expressed on a range of cells with different functions, including basophils, mast cells, eosinophils and antigen-presenting Langerhan's cells. 3. We have conducted a qualitative study of mast cell and basophil histamine release in nine atopic individuals with Ile-181-->Leu mutation of Fc epsilon RI beta, and ten unrelated similarly atopic individuals without Ile-181-->Leu mutation. There were non-significant trends for Ile-181-->Leu-positive atopic subjects to produce wheal responses at lower allergen challenge in skin prick tests, and to release more histamine from basophils following in vitro allergen challenge. 4. The data do not provide decisive evidence of functional differences between atopic subjects with Ile-181-->Leu and other atopic individuals; more discriminating functional experiments are required.

Adult↗
PubMed1997

[An experimental study of the endothelin-1 change in rat kidney after severe burn].

OBJECTIVE: To observe the changes of endothelin-1 (ET-1) concentration, immunohistochemical distribution, mRNA expression and localization in kidney of severe burn rat. METHODS: Wistar rats sustained with 30% TBSA III degree burn were divided randomly into 6 groups: normal control, 1, 3, 6, 12, and 24 postburn hour (PBH). The items studied were: the level of ET-1 in renal vein plasma and kidney tissue (cortex, outer medulla and inter medulla respectively), immunocytochemical distribution of ET-1 in kidney tissue by light and electron microscopy, mRNA expression of ET-1 in kidney by northern blot hybridization, localization and enumeration of mRNA expressiong cells of ET-1 by in situ hybridization. RESULTS: The rat kidney secretion and mRNA expression of ET-1 more evidently increased at 1, 3 PBH respectively than in normal control (P < 0.01), They distributed primarily on endothelial cells, glomerular mesangial cells. Tubular epithelial cells reached maximal mRNA expression and immunoreactivity at 3, 6 PBH respectively. Immune electron microscopic study demonstrated that ET-1 (gold particles) localized on the intracellular lumen surface of endothelium but on both apical and basal surfaces of epithelium. CONCLUSION: Secretion and mRNA expression of ET-1 increased obviously in kidney in early stage after severe burn.

Animals↗
PubMed1996

Neutralizing and infection-enhancing antibody responses do not correlate with the differential pathogenicity of SIVmac239delta3 in adult and infant rhesus monkeys.

Variants of SIV containing a deletion in the nef gene are attenuated in adult macaques, where they provide protection from challenge with pathogenic SIV, but the mechanism of protection remains unknown. One of these attenuated variants carrying deletions in nef, vpr, and NRE (SIVmac239delta3) was recently found to be pathogenic in infant macaques exposed to the virus at birth. We investigated whether inadequate or inappropriate antiviral humoral immune responses could explain why this virus causes disease in infant macaques. Plasma samples from four infants infected with SIVmac251 and five infants and two adults infected with SIVmac239delta3 were evaluated for neutralizing Abs to a laboratory-passaged stock of SIVmac251, an animal challenge stock of SIVmac239/nef-open, and a stock of SIVmac239delta3 to which animals were exposed. Plasma samples were evaluated further for complement-mediated Ab-dependent enhancement (C'-ADE) of SIVmac239/nef-open in vitro. High-titer neutralizing Abs to SIVmac251 were detected in plasma samples from adults and most infants within 3 to 5 wk of infection with either virus. Neutralizing Abs to SIVmac239/nef-open and SIVmac239delta3 developed more slowly, being undetectable before 23 to 63 wk of infection. Timing, magnitude, and breadth of neutralizing Ab responses did not correlate with progression to disease or lack thereof and gave no indication of an impaired humoral immune response in infants. Furthermore, C'-ADE was detected equally in plasma samples from adults and infants. The results indicate that infection with SIVmac239delta3 causes disease in infant macaques despite their mounting of antiviral humoral immune responses comparable to those of adults.

Age Factors↗
PubMed1996

Protection against impairment of memory and immunoreactivity in senescence-accelerated mice by acidic fibroblast growth factor.

Subcutaneous injection of aFGF once 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 group were enhanced significantly, while those of the saline group deteriorated. 1. The number of cholinergic neurons was decreased by less than 20% and choline acetyltransferase activity in individual neurons in the medical septum which send monosynaptic terminals to the hippocampus was significantly decreased in the saline group, but not so much in the aFGF group. 2. The respective densities of muscarinic and NMDA receptors and the aFGF receptor, i.e., FGFR-1 on the hippocampal neurons were also significantly higher in the aFGF group than in the saline group. 3. The long-term potentiation in the hippocampal slice preparations after a brief tetanic stimulation at the Schaffer collateral/commissural afferents was significantly facilitated in the aFGF group, but not in the saline group. 4. These data indicate the normalization caused by aFGF of the medial septohippocampal circuit, which is necessary for learning and memory. 5. 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 saline group, but the aFGF group was protected against this reduction in accordance with age. 6. These results show that aFGF provides protection against impairment of not only learning and memory but also DTH immunoreactivity in SAMP8. They also indicate a close relationship between learning and memory and T cell immune function.

Aging↗
PubMed1996

Identification and characterization of the unfolding transition state of chymotrypsin inhibitor 2 by molecular dynamics simulations.

Temperature-induced unfolding of chymotrypsin inhibitor 2 (CI2) in water has been investigated using molecular dynamics simulations. One simulation (2.2 ns) has been analyzed in detail and three additional simulations (each > or = 1 ns) were performed to check the generality of the results. Concurrent loss of secondary and tertiary structure during unfolding was observed in all the simulations. For each simulation, the major transition state of unfolding was identified based on conformational analysis of protein structures along the unfolding trajectory. The transition state has a considerably weakened hydrophobic core and disrupted secondary structure. Nevertheless, the overall structure of the transition state is closer to the native state than to the unfolded state. The disruption of the hydrophobic core appears to be rate limiting. However, other energy barriers have to be overcome before reaching the major transition state. A method is described to quantitatively compare the structure of the simulated transition state with that characterized by protein engineering experiments. Good agreement with the experimental data is obtained for all four transition state models (the correlation coefficient R = 0.80 to 0.93) and the average over all four models gives the best correlation (R = 0.94). These simulations provide the first comprehensive atomic-level view of what the unfolding transition state of C12 may look like.

Chymotrypsin↗
PubMed1996

Structure of the transition state for folding of a protein derived from experiment and simulation.

Independent experimental and theoretical studies of the unfolding of barley chymotrypsin inhibitor 2 (CI2) are compared in an attempt to derive plausible three-dimensional structural models of the transition states. A very simple structure index is calculated along the sequence for the molecular dynamics-generated transition state models to facilitate comparison with the phi F values. The two are in good agreement overall (correlation coefficient = 0.87), which suggests that the theoretical models should provide a structural framework for interpretation of the phi F values. Both experiment and simulation indicate that the transition state is a distorted form of the native state in which the alpha-helix is weakened but partially intact and the beta-sheet is quite disrupted. As inferred from the phi f values and observed directly in the simulations, the unfolding of CI2 is cooperative and there is a "folding core" comprising a patch on the alpha-helix and a portion of the beta-sheet, nucleated by interactions between Ala16, Ile49 and other neighbouring residues. The protein becomes less structured radiating away from this core. Overall the data indicate that CI2 folds by a nucleation-collapse mechanism. In the absence of experimental information, we have little confidence that the molecular dynamics simulations are correct, especially when only one or a few simulations are performed. On the other hand, even though the experimentally derived phi values may reflect the extent of overall structure formation, they do not provide an actual atomic-resolution three dimensional structure of the transition state. By combining the two approaches, however, we have a framework for interpreting phi F values and can hopefully arrive at a more trustworthy model of the transition state. The process is in some ways similar to the combination of molecular dynamics and NMR data to solve the tertiary structure of proteins.

Amino Acid Sequence↗
PubMed1996

Control of beta1 integrin function. Localization of stimulatory epitopes.

The beta1 integrins can be expressed on the surface of cells in a latent form, which is activated by a variety of stimuli. As an approach to examining the transition to an active receptor, a panel of stimulatory antibodies to beta1 were produced and characterized. These antibodies induced adherence of the T-leukemic cell line Jurkat to collagen and fibronectin. Competitive antibody binding assays indicated the existence of at least three distinct epitope clusters A (B3B11, JB1B, 21C8), B (B44, 13B9), and C(N29) defined by the indicated antibodies. Two antibodies to the A site, JB1B and B3B11, were shown to localize to positions 671-703 and 657-670, respectively, of the beta1. This region is located in an area encompassing a predicted disulfide bond between linearly distant cysteines in beta1 (Cys415-Cys671). The homologous region of the beta3 integrin (490 690 and 602 690) has been shown to be one of the sites recognized by stimulatory antibodies to ligand-induced binding sites. The present results indicate the existence of multiple stimulatory regions and suggest considerable homology between the locations of beta1 and beta3 regulatory sites.

Amino Acid Sequence↗
PubMed1996

Comparison of the capacity of rhTNF-alpha and Escherichia coli to induce procoagulant activity by baboon mononuclear cells in vivo and in vitro.

The procoagulant activity of mononuclear cells (MNCs) may play an important role in the disseminated intravascular coagulation seen in septic shock. This study compares the capacity of Escherichia coli (E. coli) and recombinant human TNF-alpha (rhTNF-alpha) to induce procoagulant activity by baboon MNCs. In vivo studies showed that MNC procoagulant activity was significantly increased at T + 120 min after LD100 E. coli infusion into baboons. Most of this procoagulant activity was attributable to tissue factor. In contrast, a bolus infusion of rhTNF-alpha (150 micrograms/kg) and a monoclonal antibody to activated protein C (2 mg/kg) did not induce any increase of MNC procoagulant activity at T + 120 min even though the plasma TNF-alpha level was 10 times higher than that seen following infusion of E. coli. In vitro studies showed that E. coli at concentrations comparable to that observed in the vivo study and LPS at a concentration of 2.5 ng/mL induced more intense tissue factor expression by both human and baboon monocytes than rhTNF-alpha in the concentrations ranging from 10 to 1,000 ng/mL. These results suggest that TNF-alpha alone is not sufficient to induced noticeable MNC procoagulant activity, at least, in the early stage of this septic shock model.

Animals↗
PubMed1996

Evidence for central chemoreception in the midline raphé.

We injected acetazolamide (AZ; 5 x 10(-6) M; 1 nl; n = 14), its inactive analogue 2-acetylamino-1,3,4-thiadiazole-5-sulfon-t-butylamide (5 x 10(-5) M; n = 6), or mock cerebrospinal fluid (n = 5) into the caudal raphé in the midline brain stem of anesthetized paralyzed ventilated rats. These AZ injections have been shown to produce a focal region of tissue acidosis with a radius < 350 microns and are used as a probe for sites of central chemosensitivity. Compared with control injections, AZ injection into the raphé, as demonstrated by anatomic analysis of injection location, significantly increased the amplitude of the integrated phrenic neurogram over 10-40 min. Not all raphé injections produced such a response. AZ injections identified as responders (n = 8 of 14) increased integrated phrenic amplitude 43.3 +/- 10.7% (SE) of baseline 20 min after the injection. We conclude that the midline caudal raphé contains sites of ventilatory chemoreception.

Acetazolamide↗
PubMed1996

Central chemoreception in the region of the ventral respiratory group in the rat.

We injected acetazolamide (AZ; 5 x 10(-6) M, 1 nl) into the region of the ventral respiratory group (VRG) of anesthetized paralyzed ventilated rats. Control injections (mock cerebrospinal fluid, n = 6, or the inactive AZ analogue 2-acetylamino-1,3, 4-thiadiazole-5-sulfon-t-butylamide, n = 6) did not increase the integrated phrenic neurogram [phrenic nerve amplitude (PNA)]. The AZ injections produced a focal region of tissue acidosis with a radius < 300-400 microns and are used as a probe for sites of central chemosensitivity. Injection location is determined by anatomic analysis. Of 22 VRG injections of AZ, 14 increased the amplitude of the PNA over 15-90 min; 8 had no effect. In 17 cases, we measured medullary tissue pH at the injection center and/or at a distant site and reaffirmed the size of the acidotic region produced by such small AZ injections. Of injections with pH electrodes within 300-400 microns of the injection center, all responders showed an acid pH; three nonresponders showed an acid pH, and one an alkaline pH. In a subgroup of five rats, at VRG sites with known respiratory effects identified by prior glutamate injection (10 nl, 100 mM), all subsequent AZ injections produced a PNA response. Simultaneous measurement of PNA and tissue pH responses at the injection center of eight rats did not show a uniform correlation in time; initially, both changed with a similar time course, but PNA recovered more quickly. We conclude that 1) the region of the VRG contains sites of ventilatory chemoreception, 2) ineffective AZ injections do produce a tissue acidosis but at sites with minimal impact on breathing, and 3) tissue pH does not uniquely represent the chemoreceptor stimulus.

Acetazolamide↗
PubMed1996

[A brief history of osteo-traumatology of the pre-Qin period].

Historical materials from oracle inscriptions to Mawangdui Ancient Books are summarized. Research is made on four aspects, including recognition on bone, wounds to bone, and bone diseases, osteological treatment by drugs, acu-moxibustion, massage and Daoyin, traumatological medical jurisprudence and prevention of such diseases. This fills the gap left out in the developmental history of osteo-traumatology.

China↗
PubMed1996

Ipsilateral hemisphere activation during motor and sensory tasks.

PURPOSE: To compare activation of the ipsilateral cerebral hemisphere during tactile sensory and motor tasks involving the right and left hands. METHODS: Eight volunteers had functional MR imaging to measure the extent of cerebral hemisphere activation during a motor task and sensory task involving each hand. Hemispheric indexes (left hemisphere activation minus right hemisphere activation)/(left hemisphere activation plus right hemisphere activation) were computed for each hand and each task. The indexes for two tasks and the two hands were compared. RESULTS: The left-hand motor tasks activated the ipsilateral hemisphere in right handers significantly more than did the right-hand tasks. Motor tasks produced a greater activation of the ipsilateral hemisphere than did the sensory tasks. No significant differences were found between the hemispheric indexes for the right-hand and left-hand sensory tasks. CONCLUSION: This study confirms findings of a previous study, showing that the left hemisphere is active in left-hand motor tasks. Activation of the ipsilateral hemisphere is significantly less pronounced during sensory tasks than during motor tasks.

Adolescent↗
PubMed1996

[A comparison of the changes of the nasal deformities after cleft lip repair between rotation advancement and triangular flap repair].

126 patients with the secondary nasal deformities of cleft lip were chosen at random, whose primary correction of cleft lip were performed by the same surgon. Of them, 68 patients were treated by triangular flap method, other 58 by rotation advancement method. On their photographs, two methods were compared by measurement of the distance between alar bases and median saggittal plane, the width of nostril floor, the height of the columella, the sizes of nostrils on both sides, and tilt of columella. The nasal deformities were improved in the rotation advancement group, but this method trend to result in a small nostril to make correction of secondary nasal deformities more difficult. On the other hand, the nasal defects were little improved in triangular flap group, whereas there were much less tendency to result in a small nostril.

Abnormalities, Multiple↗