Biomedical subjects

L Yang

Publications and source records attributed to L Yang.

At least 505 records · Page 28Linked to original sources

PubMed1997

Retrograde cerebral perfusion provides limited distribution of blood to the brain: a study in pigs.

OBJECTIVE: The objective of this study was to investigate flow distribution during retrograde and antegrade cerebral perfusion with India ink as a marker. METHODS: Ten pigs received cerebral perfusion with a solution containing 50% filtered India ink for 5 minutes either antegradely through both internal carotid arteries at a flow of 180 to 200 ml/min (n = 5) or retrogradely via the superior vena cava at a flow of 300 to 500 ml/min (n = 5). The brains were then fixed for quantitative measurement of the density of ink-filled capillaries (reported as a percentage of the total selected area). The assessment was done with the use of an in-house software program. RESULTS: In the antegrade cerebral perfusion group, the intracranial arterial and venous systems were completely filled with ink. The gray matter was colored uniformly black, and light coloring was observed in the white matter. During retrograde cerebral perfusion, the majority of ink was returned to the inferior vena cava, and only a small amount of ink was found in the innominate artery draining from the brain. Massive ink filling was observed in the sagittal sinus and other venous sinuses in all the pigs. Vessels on the surface of the brain and large vessels in the brain were also well filled with ink. However, only 10% of capillaries were filled with ink during retrograde cerebral perfusion relative to the number observed with antegrade cerebral perfusion. CONCLUSIONS: Retrograde cerebral perfusion supplies a limited amount of blood to brain tissue, which flows mainly through superficial and large deep cerebral vessels.

Animals↗

PubMed1997

The monitoring biomarker for immune function of lymphocytes in the elderly.

In this paper, we determined the number of peripheral blood lymphocytes (PBL) in the elderly and their proliferative response to PHA (Phytohemagglutinin). The data showed that the PBL number decreased with age. For the young group: 1680.0 +/- 644.7/microliters; the 60-69 years old group: 1284.0 +/- 492.3/microliters; the 70-79 years old group: 987.5 +/- 309.1/microliters, P < 0.05. The OD (optical density) value measured by MTT method for proliferative response of PBL in the elderly was 0.15 +/- 0.08, which was lower than the young group 0.18 +/- 0.05. Also, an apparent decline of soluble IL-2 receptor (sIL-2R) release from activated PBL in old people was found. The results suggested that the changes of PBL number and sIL-2R level could be considered as an indication of immune function of lymphocytes in the elderly.

Adult↗

PubMed1997

The antiproliferative effects of calcitonin gene-related peptide in different passages of cultured vascular smooth muscle cells.

Previously our laboratory showed that calcitonin gene-related peptide (CGRP) is released from perivascular nerves exposed to endotoxin or inflammatory mediators bradykinin and prostaglandins. CGRP contributes significantly to the vasodilation of inflammation and septic shock. Another potential action of CGRP is inhibition of vascular smooth muscle cell (VSMC) growth, which could serve to counterbalance the stimulatory effects of IL-1 and TNF on VSMC proliferation. VSMCs from rabbit and rat aorta (in the second and fifth passages) were plated at 100,000 cells/well in 24-well trays in 10% fetal bovine serum (FBS) for 24 h, incubated for an additional 24 h without FBS, and then exposed to 2.5% FBS for 24 h in the presence or absence of CGRP. 3H-thymidine incorporation was used to measure DNA synthesis and proliferation. CGRP caused significant inhibition of 3H-thymidine incorporation, which correlated with elevations of cAMP in both rat and rabbit aortic VSMCs. Interestingly, the responses of both the elevation of cAMP and the inhibition of DNA synthesis became larger in VSMCs with an increasing number of passages. The data suggest that the CGRP, released during vascular inflammation, may serve to inhibit the proliferation of VSMCs, thus limiting the growth of atheromatous lesions.

Animals↗

PubMed1997

Repression of tumor necrosis factor-beta expression by the human immunodeficiency virus type-1 tat protein in central nervous system-derived glial cells.

HIV-1 Tat is a potent transactivator that stimulates expression from the HIV-1 LTR, from certain cellular gene promoters and from several heterologous viral promoters. Previous reports show that HIV-1 Tat transactivates tumor necrosis factor-beta (TNF-beta) promoter-directed gene expression in lymphocytic and monocytic cell lines and further demonstrate that a 'TAR-like structure' downstream of the TNF-beta promoter is essential for Tat activity. The ability of Tat to activate TNF-beta may have profound effects as TNF has been shown to be a potent activator of HIV-1 gene expression and an important immunomodulatory and growth regulatory factor. The studies presented herein demonstrate a novel finding where HIV-1 Tat specifically represses (> 10-fold) TNF-beta promoter-directed gene expression in central nervous system-derived glial cells. Amino acid residues 2 to 36 of HIV-1 Tat are required for TNF-beta repression. Tat repression of TNF-beta, a factor which upregulates HIV-1 gene expression, suggests a novel mechanism whereby HIV-1 is able to establish latent infection of glial cells that present no detectable virions and/or viral antigens.

Astrocytes↗

PubMed1997

Diffusion anisotropy in excised normal rat spinal cord measured by NMR microscopy.

A conventional spin-echo NMR imaging pulse sequence was used to obtain high-resolution images of excised normal rat spinal cord at 7 and 14 T. It was observed that the large pulsed-field gradients necessary for high-resolution imaging caused a diffusion weighting that dominated the image contrast and that could be used to infer microscopic structural organization beyond that defined by the resolution of the image matrix (i.e., fiber orientation could be assigned based on diffusion anisotropy). Anisotropic diffusion coefficients were therefore measured using apparent diffusion tensor (ADT) imaging to assess more accurately fiber orientations in the spinal cord; structural anisotropy information is portrayed in the six unique images of the complete ADT. To reduce the dimensionality of the data, a trace image was generated using a separate color scale for each of the three diagonal element images of the ADT. This new image retains much of the invariance of the trace to the relative orientations of laboratory and sample axes (inherent to a greyscale trace image) but provides, by the use of color, contrast reflecting diffusion anisotropy. The colored trace image yields a pseudo-three-dimensional view of the rat spinal cord, from which it is possible to deduce fiber orientations.

Animals↗

PubMed1997

Factors regulating production of alpha-galactosidase from Bacillus sp. JF2.

Certain factors affecting the production of cell-associated alpha-galactosidase by Bacillus sp. JF2 were investigated. The intention was to maximize alpha-galactosidase activity of potential commercial application, by consecutive optimization of growth media and conditions. The highest alpha-galactosidase activity was obtained when grown on melibiose, whereas sucrose inhibited the production of alpha-galactosidase, alpha-Galactosidase production was optimally active at pH 7.5 and 55 degrees C. It was identified that a soy effluent stream could be used as the best carbon source for alpha-galactosidase by Bacillus sp. JF2.

Bacillus↗

PubMed1997

Pathological manifestations in murine Lyme disease: association with tissue invasion and spirochete persistence.

The clinical manifestations of human Lyme disease present with a spectrum of tissue or organ involvement and severity of symptoms. The murine model of Lyme disease has proved to be an accurate reflection of many of the human symptoms of disease and has been particularly useful for studying development of subacute arthritis and tendonitis. Direct tissue invasion by Borrelia burgdorferi and persistence of high levels of spirochetes in tissues are important components of arthritis development. The outer-surface lipoproteins contain a biologically active lipid-modified moiety with potent ability to stimulate inflammatory cytokine production and other inflammatory mediators such as nitric oxide. Localized inflammation stimulated by these lipoproteins may be the trigger for neutrophil infiltration, synovial proliferation, and other events associated with this arthritis. Invasion of maternal uterine tissue, but not direct invasion of fetal tissue, is associated with low levels of pregnancy loss in mice infected during gestation, consistent with the detrimental effect of inflammatory cytokines on pregnancy.

Animals↗

PubMed1997

Antigenic phenotypes common to rat oval cells, primary hepatocellular carcinomas and developing bile ducts.

The shared expression of monoclonal antibody-defined antigens by oval cells and by bile ducts, neoplastic nodules and primary hepatocellular carcinomas (PHC) has provided support for the ability of oval cells to undergo differentiation along ductular or hepatocyte lineages and/or to progress to hepatocellular carcinoma. With the aim of obtaining additional insight into this process, we have combined serial section and double labeling immunofluorescence analysis to determine if phenotypes expressed in vitro by four rat oval cell lines and the H5D.61 hepatocellular carcinoma cell line and in situ by ethionine-induced primary hepatocellular carcinomas reproduce antigenic patterns occurring during normal liver development. Analysis using monoclonal antibodies specific for the oval cell antigens OV6 and OC.2 and hepatocyte markers HBD.1 and H.4 defined subpopulations in four oval cell lines and neoplastic hepatocytes in PHC and H5D.61 with OC.2-/OV6+ and OC.2+/OV6+ phenotypes. Cells with an OC2+/OV6- phenotype were rarely observed in cell lines or primary tumors. In contrast, areas composed of OV6+/H.4+ cells were frequently found in PHC. Examination of fetal and neonatal rat livers demonstrated the stage-specific appearance of three of these phenotypes during liver development. The OC.2+/OV6- phenotype appeared transiently prior to embryonic day (ED) 18 in a subpopulation of HBD.1+ hepatoblasts. OV6 expression was first detected at ED18 on developing bile ducts that were negative for OC.2. These newly formed ducts rapidly acquired OC.2, starting with ducts in the hilar region and spreading outward towards the periphery. This OC.2 expression gradient persisted in the newborn rat liver but became more skewed towards doubly positive cells, with OC.2-/OV6+ cells being found primarily in the periphery. Hepatocytes expressing both OV6 and H.4 were not observed in fetal liver but appeared in neonatal liver in close proximity to OV6+ interlobular ducts. From these findings, it was concluded that oval cells and PHC display phenotypes representing normal stages in liver development, suggesting that oval cells and cells within ethionine-induced PHC are capable of initiating but are unable to complete pathways of hepatocytic or biliary differentiation.

Animals↗

PubMed1997

Sphingosine 1-phosphate, a bioactive sphingolipid abundantly stored in platelets, is a normal constituent of human plasma and serum.

Although sphingosine 1-phosphate (Sph-1-P) is reportedly involved in diverse cellular processes and the physiological roles of this bioactive sphingolipid have been strongly suggested, few studies have revealed the presence of Sph-1-P in human samples, including body fluids and cells, under physiological conditions. In this study, we identified Sph-1-P as a normal constituent of human plasma and serum. The Sph-1-P levels in plasma and serum were 191+/-79 and 484+/-82 pmol/ml (mean+/-SD, n=8), respectively. Furthermore, when Sph-1-P was measured in paired plasma and serum samples obtained from 6 healthy adults, the serum Sph-1-P/plasma Sph-1-P ratio was found to be 2.65+/-1.26 (mean+/-SD). It is most likely that the source of discharged Sph-1-P during blood clotting is platelets, because platelets abundantly store Sph-1-P compared with other blood cells, and release part of their stored Sph-1-P extracellularly upon stimulation. We also studied Sph-1-P-related metabolism in plasma. [3H]Sph was stable and not metabolized at all in plasma, but was rapidly incorporated into platelets and metabolized mainly to Sph-1-P in platelet-rich plasma. [3H]Sph-1-P was found to be unchanged in plasma, revealing that plasma does not contain the enzymes needed for Sph-1-P degradation. In summary, platelets can convert Sph into Sph-1-P, and are storage sites for the latter in the blood. In view of the diverse biological effects of Sph-1-P, the release of Sph-1-P from activated platelets may be involved in a variety of physiological and pathophysiological processes, including thrombosis, hemostasis, atherosclerosis and wound healing.

Blood Cells↗

PubMed1997

Further development of hybrid functional electrical stimulation orthoses.

In this study two aspects of hybrid functional electrical stimulation (FES) orthoses were investigated: joint motion constraints and FES control strategies. First, the effects of joint motion constraints on the gait of normal subjects were investigated using modern motion analysis systems, including electromyogram (EMG) and heart rate measurements. An orthosis was developed to impose joint motion constraints; the knee and ankle could be fixed or free, and the hip joint could rotate independently or coupled, according to a preset flexion-extension coupling ratio (FECR). Compared with a 1:1 hip FECR, a 2:1 hip FECR was associated with a reduced energy cost and increased speed and step length. The knee flexion during swing significantly reduced energy cost and increased walking speed. Ankle plantar flexion reduced the knee flexing moment during the early stance phase. Second, trials on 3 paraplegic subjects were conducted to implement some of these findings. It appeared that the 2:1 FECR encouraged hip flexion and made leg swing easier. A simple FES strategy increased walking speed and step length and reduced crutch force impulse using fixed orthotic joints.

Ankle↗

PubMed1997

Expression of BMP-2 and TGF-beta 1 mRNA during healing of the rabbit mandible.

To identify the cell types which produce BMP and TGF-beta during fracture healing and to elucidate the interactions between BMP and TGF-beta in regulating cell proliferation and differentiation at various stages, an experimental model of fracture healing in the rabbit mandible was established and the expression of BMP-2 and TGF-beta 1 mRNA was studied at different healing stages by in situ hybridization. The results showed that undifferentiated mesenchymal cells, differentiating osteoblasts and chondroblasts, had higher levels of BMP-2 mRNA at the stage of intramembranous bone formation and early chondrogenesis, while the level of TGF-beta 1 mRNA was higher in chondrocytes and active differentiated osteoblasts during chondrogenesis and endochondral ossification, respectively. We conclude that BMP-2 expression was correlated with the differentiation of mesenchymal cells into osteoblasts and chondrocytes. TGF-beta 1 mRNA expression was closely associated with the active synthetic stage of osteoblasts and chondrocytes. These observations suggest that both BMP and TGF-beta are involved in the regulation of fracture healing. BMP may play an important role in bone induction and early chondrogenesis, while TGF-beta regulates the proliferation and active synthetic ability of chondrocytes and osteoblasts.

Animals↗

PubMed1997

Effects of oren-gedoku-to and unsei-in, Chinese traditional medicines, on interleukin-8 and superoxide dismutase in rats.

This study was conducted to elucidate the mechanisms of action of two Chinese traditional drugs, Oren-gedoku-to and Unsei-in, which have been used for many years in the treatment of inflammatory disorders. In rats with acetic acid-induced inflammation, both drugs reduced interleukin-8 concentrations in the serum. Neither drug significantly affected superoxide dismutase activity in the serum, although Unsei-in increased superoxide dismutase activity in liver after 1 month of administration. Oren-gedoku-to showed no significant effect on liver superoxide dismutase activity. It was considered that these medicines exert their anti-inflammatory effects mainly on the early stages of inflammation, wherein increased capillary permeability and migration of leucocytes occur.

Animals↗

PubMed1997

Cloning of adeno-associated virus type 4 (AAV4) and generation of recombinant AAV4 particles.

We have cloned and characterized the full-length genome of adeno-associated virus type 4 (AAV4). The genome of AAV4 is 4,767 nucleotides in length and contains an expanded p5 promoter region compared to AAV2 and AAV3. Within the inverted terminal repeat (ITR), several base changes were identified with respect to AAV2. However, these changes did not affect the ability of this region to fold into a hairpin structure. Within the ITR, the terminal resolution site and Rep binding sites were conserved; however, the Rep binding site was expanded from three GAGC repeats to four. The Rep gene product of AAV4 shows greater than 90% homology to the Rep products of serotypes 2 and 3, with none of the changes occurring in regions which had previously been shown to affect the known functions of Rep68 or Rep78. Most of the differences in the capsid proteins lie in regions which are thought to be on the exterior surface of the viral capsid. It is these unique regions which are most likely to be responsible for the lack of cross-reacting antibodies and the altered tissue tropism compared to AAV2. The results of our studies, performed with a recombinant version of AAV4 carrying a lacZ reporter gene, suggest that AAV4 can transduce human, monkey, and rat cells. Furthermore, comparison of transduction efficiencies in a number of cell lines, competition cotransduction experiments, and the effect of trypsin on transduction efficiency all suggest that the cellular receptor for AAV4 is distinct from that of AAV2.

3T3 Cells↗

PubMed1997

Differential response properties to amplitude modulated signals in the dorsal nucleus of the lateral lemniscus of the mustache bat and the roles of GABAergic inhibition.

We studied the phase-locking of 89 neurons in the dorsal nucleus of the lateral lemniscus (DNLL) of the mustache bat to sinusoidally amplitude modulated (SAM) signals and the influence that GABAergic inhibition had on their response properties. Response properties were determined with tone bursts at each neuron's best frequency and then with a series of SAM signals that had modulation frequencies ranging from 50-100 to 800 Hz in 100-Hz steps. DNLL neurons were divided into two principal types: sustained neurons (55%), which responded throughout the duration of the tone burst, and onset neurons (45%), which responded only at the beginning of the tone burst. Sustained and onset neurons responded differently to SAM signals. Sustained neurons responded with phase-locked discharges to modulation frequencies < or = 400-800 Hz. In contrast, 70% of the onset neurons phase-locked only to low modulation frequencies of 100-300 Hz, whereas 30% of the onset neurons did not phase-lock to any modulation frequency. Signal intensity differentially affected the phase-locking of sustained and onset neurons. Sustained neurons exhibited tight phase-locking only at low intensities, 10-30 dB above threshold. Onset neurons, in contrast, maintained strong phase-locking even at relatively high intensities. Blocking GABAergic inhibition with bicuculline had different effects on the phase-locking of sustained and onset neurons. In sustained neurons, there was an overall decline in phase-locking at all modulation frequencies. In contrast, 70% of the onset neurons phase-locked to much higher modulation frequencies than they did when inhibition was intact. The other 30% of onset neurons phase-locked to SAM signals, although they fired only with an onset response to the same signals before inhibition was blocked. In both cases, blocking GABAergic inhibition transformed their responses to SAM signals into patterns that were more like those of sustained neurons. We also propose mechanisms that could explain the differential effects of GABAergic inhibition on onset neurons that locked to low modulation frequencies and on onset neurons that did not lock to any SAM signals before inhibition was blocked. The key features of the proposed mechanisms are the absolute latencies and temporal synchrony of the excitatory and inhibitory inputs.

Acoustic Stimulation↗

PubMed1997

Epileptogenesis following neocortical trauma from two sources of disinhibition.

Epileptogenesis following neocortical trauma from two sources of disinhibition. J. Neurophysiol. 78: 2804-2810, 1997. Intracellular and field potential recordings were obtained from superficial and deep neurons from both intact coronal rat somatosensory slices, and from slices which had been acutely divided into a superficial strip of cortex ( approximately 450 micron from the pia) and a deep segment. Membrane properties for cells in the traumatized slices were similar to those of their counterparts in intact slices. However, synaptic hyperexcitability developed in the deep segments in which a majority of cells likely underwent dendrotomy. This hyperexcitability was manifested by epileptiform activity in 54% of traumatized slices. Measurements of fastGABAergic inhibitory strength showed these slices were disinhibited. Superficial delivery of tetrodotoxin to the upper 450 micron of intact slices led to disinhibition of fast GABAergic transmission as well as an attendant increase in excitatory postsynaptic potential strength but not epileptogenesis. Pharmacological maneuvers aimed at preventing glutamate-triggered increases in intracellular calcium [glutamate ionotropic antagonists, dantrolene, and bis-(o-aminophenoxy)-N,N,N', N'-tetraacetic acid (BAPTA)-AM] showed that a 1 h treatment in these agents conferred protection against epileptogenesis. These results demonstrate that the seizure-like activity developing in deep dendrotomized cortical segments resulted from two sources of GABAergic disinhibition: the physical removal of important superficial inhibitory circuits and glutamate-triggered increases in intracellular calcium.

6-Cyano-7-nitroquinoxaline-2,3-dione↗

PubMed1997

Craniofacial and TMJ effects after glutamate and TRH microsphere implantation in proximity to trigeminal motoneurons of growing rats.

The sequelae of sustained, in vivo delivery of two important neurotransmitter substances, glutamate and thyrotropin-releasing hormone (TRH), upon craniofacial growth and development have previously not been investigated. Our purpose was to document and compare the relative effects of glutamate and TRH microspheres stereotactically placed in proximity to trigeminal motoneurons within the trigeminal motor nucleus. The following null hypotheses were tested: (1) TRH microspheres in proximity to trigeminal motoneurons have no significant effect upon the craniofacial skeleton, and (2) there are no significant differences between the relative effects of chronic, long-term delivery of glutamate and TRH upon the neuromusculoskeletal system of growing rats. Forty male Sprague-Dawley rats were divided into 4 experimental groups (glutamate microspheres, TRH microspheres, blank microspheres, sham surgeries) and underwent stereotactic neurosurgery at 35 days; 5 rats of each group were killed at 14 and 21 days for data collection. Histology revealed that implants were clustered in the pontine reticular formation, close to the ventrolateral tegmental nucleus. Both glutamate and TRH rats had implant-side deviation of their facial skeleton and snout regions; 4 x 2 ANOVA and post hoc t-tests revealed significant (P < or = 0.05, 0.01) differences between groups and sides for motoneuron count, muscle weight, and osteometric data. TRH rats also demonstrated larger implant-side TMJ discs and mandibular fossae in comparison with the other groups. The stated null hypotheses were therefore rejected.

Analysis of Variance↗

PubMed1997

Crocidolite asbestos induces apoptosis of pleural mesothelial cells: role of reactive oxygen species and poly(ADP-ribosyl) polymerase.

Mesothelial cells, the progenitor cells of the asbestos-induced tumor mesothelioma, are particularly sensitive to the toxic effects of asbestos, although the molecular mechanisms by which asbestos induces injury in mesothelial cells are not known. We asked whether asbestos induced apoptosis in mesothelial cells and whether reactive oxygen species were important. Rabbit pleural mesothelial cells were exposed to crocidolite asbestos or control particles (1-10 micrograms/cm2) over 24 hr and evaluated for oligonucleosomal DNA fragmentation, loss of membrane phospholipid asymmetry, and nuclear condensation. Asbestos fibers, not control particles, induced apoptosis in mesothelial cells by all assays. Induction of apoptosis was dose dependent; crocidolite (5 micrograms/cm2) induced apoptosis (15.0 +/- 1.1%, mean +/- SE; n = 12) versus control particles (< 4%), as measured by appearance of nuclear condensation. Apoptosis induced by asbestos, but not by actinomycin D, was inhibited by extracellular catalase, superoxide dismutase in the presence of catalase, hypoxia (8% oxygen), deferoxamine, and 3-aminobenzamide (an inhibitor of the nuclear enzyme, poly(adenosine diphosphate-ribosyl) polymerase). We conclude that asbestos induces apoptosis in mesothelial cells via reactive oxygen species. We speculate that escape from this pathway could allow the abnormal survival of mesothelial cells with asbestos-induced mutations.

Animals↗

PubMed1997

[An experimental study on effect of atrial natriuretic peptide on intraocular pressure of white rabbits].

OBJECTIVE: To study the therapeutic effect of atrial natriuretic peptide (ANP) on glaucoma. METHODS: Various doses of ANP were injected subconjunctivally in albino rabbits, and their effects on intraocular pressures (IOPs) were observed. RESULTS: The IOPs were significantly decreased by the subconjunctival injection of 20, 30, 40 micrograms of ANP, and with a dose of 40 micrograms, the maximum effect of IOP lowering of 0.88-0.15 kPa maintaining for the longest time 7.5 hours was obtained. Generally, one hour after the injection, the maximum effect could be seen. A dose-effect relationship that is the degree of the reduction of IOP increasing with the dose increase of ANP could be observed. CONCLUSION: This study indicates that ANP might play an effective therapeutic role in glaucoma.

Animals↗