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Biomedical subjects

M Gu

Publications and source records attributed to M Gu.

At least 73 records · Page 4Linked to original sources
PubMed1998

Mitochondrial function, GSH and iron in neurodegeneration and Lewy body diseases.

The cause of neuronal loss in patients with idiopathic Parkinson's disease is unknown. Oxidative stress and complex I deficiency have both been identified in the substantia nigra in Parkinson's disease but their place in the sequence of events resulting in dopaminergic cell death is uncertain. We have analysed respiratory chain activity, iron and reduced glutathione concentrations in Parkinson's disease substantia innominata and in the cingulate cortex of patients with Parkinson's disease, Alzheimer's disease and dementia with Lewy bodies to investigate their association with neuronal death and Lewy body formation. No abnormalities of mitochondrial function, iron or reduced glutathione levels were identified in Parkinson's disease substantia innominata or cingulate cortex. Mitochondrial function also appeared to be unchanged in cingulate cortex from patients with Alzheimer's disease and from patients with dementia with Lewy bodies, however, iron concentrations were mildly increased in both, and reduced glutathione decreased only in Alzheimer's disease. These results confirm the anatomic specificity of the complex I deficiency and decreased levels of reduced glutathione within the Parkinson's disease brain and suggest that these parameters are not associated with cholinergic cell loss in Parkinson's disease nor with Lewy body formation in this or other diseases. We propose that our data support a 'two-hit' hypothesis for the cause of neuronal death in Parkinson's disease.

Aged↗
PubMed1998

Contribution of cells at the site of DNA vaccination to the generation of antigen-specific immunity and memory.

Gene gun-mediated DNA vaccination stimulates an immune response characterized by the activation of IgG-secreting B cells and IFN-gamma-secreting T cells. To monitor the contribution of cells at the site of vaccination to this process, transfected skin was periodically removed and grafted onto naive recipients. Immediate removal of vaccinated skin abrogated the development of an immune response. Low-level IgG production was stimulated when the vaccination site was left in place for > or = 5 h, with the strength of this response increasing the longer the site remained intact (for up to 2 wk). Measurable primary T cell responses were observed in animals whose vaccination site remained in place for > or = 1 day. Skin grafts transferred 0 to 24 h postvaccination stimulated a primary immune response in naive recipients. Memory B and T cells were generated in animals whose site of vaccination remained intact for 5 to 12 h. Skin transferred within 12 h of vaccination triggered memory B and T cell development in graft recipients, while the removal of skin >12 h postvaccination did not reduce memory in vaccinated mice. These findings suggest that 1) primary immunity is induced by cells that migrate rapidly from the site of immunization, 2) nonmigratory cells influence the magnitude of this primary response, and 3) migratory cells alone are responsible for the induction of immunologic memory.

Animals↗
PubMed1998

Uncoupling protein-3: a muscle-specific gene upregulated by leptin in ob/ob mice.

We identified and partially characterized another member of the uncoupling protein termed UCP3. Human and mouse UCP3 protein sequences are 86% identical to each other, and 73% and 59% identical to UCP2 and UCP1, respectively. Expression of human UCP3 in yeast resulted in a drastic decrease of mitochondria membrane potential. Northern analysis showed that UCP3 was highly expressed in skeletal muscle in human, rat, and mouse. Mapping of UCP3 placed it to the same chromosomal region of UCP2 in both human and mouse, a region that is linked to obesity and hyperinsulinemia. Furthermore, adenovirus-mediated leptin expression in obese ob/ob mice led to increased expression of UCP3 in skeletal muscle. The data indicate that UCP3 encodes a muscle-specific uncoupling protein that may play an important role in the regulation of energy expenditure and development of obesity.

Adenoviridae↗
PubMed1998

Mitochondrial DNA transmission of the mitochondrial defect in Parkinson's disease.

Several groups have identified mitochondrial complex I deficiency in Parkinson's disease (PD) substantia nigra and in platelets. A search for any mitochondrial DNA (mtDNA) mutation underlying this defect has not yet produced any consistent result. We have made use of a mtDNA-less (p0) cell line to determine if the complex I deficiency follows the genomic transplantation of platelet mtDNA. From a preselected group of PD patients with low platelet complex I activity, 7 patients were used for detailed study. All 7 patients were used for mixed cybrid analysis and demonstrated a selective 25% deficiency of complex I activity. Individual clonal analysis of A549 p0/PD platelet fusion cybrids from 1 of the patients expressed combined complex I and IV deficiencies with 25% and 20% decreased activities in the PD clones, respectively. Histocytochemical, immunocytochemical, and cellular functional imaging studies of these clones showed the cells within the clones were heterogeneous with respect to cytochrome c oxidase (COX) function, COX I content, and mitochondrial respiratory chain activity. These results are in agreement with a previous study and support the proposition that an mtDNA abnormality may underlie the mitochondrial defect in at least a proportion of PD patients. This p0 technology may serve as a means to identify the subgroup of PD patients in whom an mtDNA defect may contribute to development of the disease.

Benzimidazoles↗
PubMed1998

Mitochondria in the etiology and pathogenesis of Parkinson's disease.

Mitochondria play a critical role in cellular energy metabolism. The identification of a respiratory chain defect in Parkinson's disease (PD) provides not only a direct link with toxin models of parkinsonism but also insight into the mechanisms involved in etiology and pathogenesis. The presence of the complex I deficiency in PD substantia nigra and platelets suggests the involvement of a systemic cause. Genomic transplantation studies have been undertaken that involve the transfer to a novel nuclear background of mitochondrial DNA (mtDNA) from PD patients with a complex I defect, followed by both mixed and clonal expansion of the resulting cybrids. The mixed cybrids with the PD mtDNA expressed the complex I defect present in the original PD donor platelets. Clonal expansion of one such mixed cybrid culture produced a spectrum of clones with complex I and complex IV activities, ranging from severe deficiency to normal range, a pattern typical of a heteroplasmic mtDNA mutation. Histochemical, immunohistochemical, and functional assessments of delta psi(m) all showed a pattern in the PD clones typical of that produced by a mtDNA mutation. Patients with focal dystonia and a platelet complex I defect were used as disease controls for the cybrid studies. The mitochondrial abnormality was eradicated by transfer of dystonia mtDNA to a control nuclear background in both mixed and clonal cybrids, with no evidence of clonal heterogeneity. These results help to validate our findings in the PD patients and suggest that the complex I deficiency in dystonia is not due to an abnormality of mtDNA. We hypothesize that the mtDNA defect alone may be the cause of PD in a proportion of patients and may contribute to pathogenesis in others. Identification of the mtDNA genotype responsible for PD may allow the testing of neuroprotective strategies in appropriate patients.

DNA, Mitochondrial↗
PubMed1998

Electrophoresis combined with novel mass spectrometry techniques: powerful tools for the analysis of proteins and proteomes.

Analytical and preparative electrophoresis separation techniques have been essential tools in protein biochemistry and the biological sciences in general. The combination of high resolution electrophoresis techniques with high performance analytical procedures has dramatically enhanced analytical protein biochemistry. In this report we describe the combination of electrophoretic separation techniques with electrospray ionization (ESI) tandem mass spectrometry (MS/MS). A series of different techniques, consisting of automated high performance liquid chromatography (HPLC)-MS/MS, capillary-HPLC-MS/MS, and solid phase extraction (SPE)-capillary zone electrophoresis (CZE)-MS/MS, are described in the context of the identification of high pmol to the low fmol amounts of proteins. Application of these powerful new tools for the analysis of proteins on a large proteome-wide scale is presented. Furthermore, the combination of orthogonal separation techniques, such as immobilized metal affinity chromatography (IMAC) with SPE-CZE-MS/MS, and IMAC followed by HPLC, and by SPE-CZE-MS/MS, are presented for the detailed investigation of post-translational modifications of specific proteins.

Amino Acid Sequence↗
PubMed1998

Tumour necrosis factor-alpha, but not septic plasma depresses cardiac myofilament contraction.

PURPOSE: In sepsis, myocardial depression may be caused by mediators released as part of the inflammatory reaction, lumour necrosis factor alpha (TNF alpha) is one mediator that may contribute to this depression. In the present study, we contrasted the effects of TNF alpha and septic plasma fraction (SP) obtained from an E. coli model on contractile tension in intact and skinned canine ventricular trabecular (VT) preparations. The objectives were to determine whether SP or TNF alpha could impair contractile tension at the level of the myofilaments, and to determine the extent to which TNF alpha may account for myocardial depression found in E. coli sepsis. METHODS: Measurements of isometric tensions were made after TNF alpha and SP (10,000 to 30,000 MW fraction) were added to respective intact or skinned canine VT preparations. In the skinned preparation, trabeculae were chemically skinned with Triton X-100. RESULTS: Septic plasma caused a decrease in contraction in the intact preparation compared with preseptic plasma (50 +/- 7 vs 33 +/- 7%, P < 0.05), but had no effect in the skinned preparation. On the other hand, TNF alpha (30 ng.ml-1) caused an approximately 50% reduction in tension (29 +/- 2 mg vs 16 +/- 5 mg) in the skinned preparation (P < 0.05), but had no effect in the intact preparation. CONCLUSION: These results suggest that TNF alpha and SP act through different mechanisms. While SP requires an intact membrane, TNF alpha impairs function by a direct effect on the myofilaments.

Actin Cytoskeleton↗
PubMed1998

Effects of Erkang, a modified formulation of Chinese folk medicine Shi-Quan-Da-Bu-Tang, on mice.

Shi-Quan-Da-Bu-Tang is a traditional Chinese herbal medicine formula used to increase vital energy, and strengthen health and immunity. Data from previous studies demonstrated that this formula also has the ability to attack tumor tissue. The Erkang capsule is a modified formula of Shi-Quan-Da-Bu-Tang, with the addition of four other herbs to increase the adaptogen effects and ergogenic properties. Results from this study in mice indicated that the Erkang treated group had significant differences in mortality, body weight change, fatigue, cold temperature endurance, and immune function related organ weight change, compared to the control animals.

Animals↗
PubMed1998

Image Formation in Femtosecond Confocal Interference Microscopy

: Three-dimensional image formation in an interference confocal scanning microscope under ultrashort pulsed beam illumination is investigated in this study. The novelty of this new image system is that it keeps advantages in femtosecond interferometry but also provides a femtosecond-resolved three-dimensional image without necessarily using an ultrafast detector. For a 5-fs pulsed beam illumination, spatial resolution in the axial and transverse directions in this system is improved by approximately 45% and 15%, respectively, compared with that in the case of continuous wave illumination. However, strong chromatic aberration caused by an ultrashort pulsed beam can result in a degradation of spatial and temporal resolution, whereas weak chromatic aberration may lead to an improvement in transverse resolution.

Journal Article↗
PubMed1998

Image Enhancement in a Reflection Optical Microscope by Suppression of Diffusing Photons Using Polarizing Annular Objectives.

: In this report, we describe the implementation of an angle-gating mechanism into a reflection optical microscope for imaging through a turbid medium. A significant improvement in image resolution and contrast is obtained when a polarizing annular objective is used to image a reflective test bar through various turbid media. The experimental results confirm that the improvement is caused by the efficient suppression of diffused photons scattered from the turbid medium when a polarized annular objective is employed as an angular gate.

Journal Article↗
PubMed1998

Gut and brain effects of American ginseng root on brainstem neuronal activities in rats.

Brainstem neurons receiving subdiaphragmatic vagal inputs were recorded in an in vitro neonatal rat brainstem-gastric preparation. Aqueous extracts of American ginseng root (Panax quinquefolium L.) were applied to the gastric compartment or the brainstem compartment of the bath chamber to evaluate the peripheral gut and central brain effects of the extracts on brainstem unitary activity. After Panax quinquefolium L. application to the gastric or brainstem compartment, a concentration-related inhibition in neuronal discharge frequency in the brainstem unitary activity was observed, suggesting that Panax quinquefolium L. may play an important role in regulating the digestive process and modulating brain function. In this study, pharmacological effects of American-cultivated Panax quinquefolium L. and Chinese-cultivated Panax quinquefolium L. were also compared. Our results suggest that American-cultivated Panax quinquefolium L. possesses a significantly stronger gastric modulating effect on brain neuronal activity.

Animals↗
PubMed1998

Characterization of the testis and epididymis in mouse models of human Tay Sachs and Sandhoff diseases and partial determination of accumulated gangliosides.

Beta-hexosaminidase (Hex) is an essential lysosomal enzyme whose activity is higher in the epididymis than in other tissues. The enzyme is also present in sperm and has been postulated to be required for fertilization. To better understand the role of Hex in reproduction, we have examined the testes and epididymides of mouse models of human Tay Sachs and Sandhoff diseases, produced by targeted disruption of the Hexa (alpha-subunit) or Hexb (beta-subunit) genes, respectively, encoding the enzymes Hex A (structure, alphabeta) and Hex B (betabeta). Testis weight, morphology, and sperm counts were unaffected in Hex-deficient mice. In the epididymis of the Hex A-deficient Hexa-/- mice, there was a large increase in the size and number of lysosomes in the initial segment/intermediate zone. In Hexb-/- mice (Hex A and B-deficient), the epididymal defects were much more extensive and the cytoplasm of all cell types throughout the efferent ducts and epididymis was filled with pale, uncondensed, enlarged lysosomes. In contrast to the brain where GM2 ganglioside accumulates, both mutant mice accumulated two non-GM2 gangliosides in the epididymis. The major accumulated species was characterized by electrospray ionization tandem mass spectrometry. The Hexa-/- male mice were fertile; however, litter sizes were reduced. The Hexb-/- males were able to sire normal sized litters up to nine weeks of age and remained healthy until 16-20 weeks of age. The extensive abnormalities in the Hexb-/- mice, in contrast to region-specific effects in the Hexa-/-mice, indicate an important and novel role for the Hex B isozyme in the epididymis and a region-specific role for Hex A in the initial segment/intermediate zone. In contrast to other reports, our results indicate that Hex is not essential for fertilization in young adult male mice. To explain the extensive epididymal abnormalities in the Hexb-/- mice, we propose that substrates for Hex, such as testis-derived glycolipids, cannot be catabolized and accumulate in lysosomes, leading to epididymal dysfunction and abnormalities in the epididymal luminal environment that supports sperm maturation.

Animals↗
PubMed1998

[A clinical control study on the treatment of uterine leiomyoma with gonadotrophin releasing hormone agonist or mifepristone].

OBJECTIVE: To compare the results and side effects in treating uterine leiomyoma with gonadotrophin releasing hormone agonist (GnRH-a) or mifepristone. METHODS: 75 patients with uterine leiomyoma who had clinical symptoms and diagnosed by Bcan were divided into two groups. The GnRH-a group (30 patients) was treated by injection of GnRH-a 150 micrograms/day subcutaneously for three months, and the mifepristone group (45 patients) was treated by mifepristone 12.5 mg/day po for three months. RESULTS: The clinical symptoms improved obviously in both groups. The volume of leiomyoma reduced 20.0% or more in 90.0% (27/30) of the patients in GnRH-a group, while it was 91.1% (41/45) in mifepristone group. However, the recurrent rates were 40.0% and 17.8% in the 2 groups. CONCLUSION: It suggested that mifepristone is a more practical and hopeful drug in treating uterine leiomyoma.

Adult↗
PubMed1997

The alpha7beta1 integrin mediates adhesion and migration of skeletal myoblasts on laminin.

Many aspects of myogenesis are believed to be regulated by myoblast interactions with specific components of the extracellular matrix. For example, laminin has been found to promote adhesion, migration, and proliferation of mammalian myoblasts. Based on affinity chromatography, the alpha7beta1 integrin has been presumed to be the major receptor mediating myoblast interactions with laminin. We have prepared a monoclonal antibody, O26, that specifically reacts with both the X1 and the X2 extracellular splice variants of the alpha7 integrin chain. This antibody completely and selectively blocks adhesion and migration of rat L8E63 myoblasts on laminin-1, but not on fibronectin. In contrast, a polyclonal antibody to the fibronectin receptor, alpha5beta1 integrin, blocks myoblast adhesion on fibronectin, but not on laminin-1. The alpha7beta1 integrin also binds to a mixture of laminin-2 and laminin-4, the major laminin isoforms in developing and adult skeletal muscle, but O26 is a much less potent inhibitor of myoblast adhesion on the laminin-2/4 mixture than on laminin-1. Based on affinity chromatography, we suggest that this may be due to higher affinity binding of alpha7X1 to laminin-2/4 than to laminin-1.

Alternative Splicing↗
PubMed1997

Fas-induced apoptosis of T cells occurs independently of ceramide generation.

The Fas receptor is one of a number of important physiological inducers of programmed cell death (apoptosis). Current models for regulation of this process involve rapid conversion of sphingomyelin to ceramide by cellular sphingomyelinases. Induced changes in cellular levels of such sphingosine-based ceramides are normally extrapolated from measurements of sphingomyelinase activity or following their conversion to ceramide phosphate by treatment of cellular lipid extracts with bacterial diacylglycerol kinase (DAGK). To allow direct study of cellular sphingosine- and sphinganine-based ceramide levels, we developed a mass spectrometric technique capable of determining inducible changes in both overall ceramide levels and species distribution in cellular lipid preparations. Contrary to current models, we detected no changes in cellular ceramide levels up to 2 hr poststimulation of Jurkat T cells with an anti-Fas IgM, although this treatment did induce apoptosis. We also determined in the same system that, when utilizing the DAGK assay, increased phosphorylation of substrates that comigrated with ceramide standards was apparent but that this effect was due to an enhancement of DAGK activity rather than increases in levels of cellular ceramides as substrates per se. Thus, the first direct measurement of ceramides present in cells undergoing apoptosis indicates that, insofar as it can be measured, the induction of apoptosis does not involve the generation of sphingosine-based ceramides, contrary to many published accounts.

Apoptosis↗
PubMed1997

Ceramide profiling of complex lipid mixtures by electrospray ionization mass spectrometry.

Ceramides and sphingoid bases are important intracellular second messengers that play a role in the regulation of cell growth, differentiation, and programmed cell death. Until now, quantitative and qualitative analysis of ceramide second messengers has been limited by a lack of analytical methods capable of detecting endogenous levels of, and differentiating between, individual ceramide species. Here we report the use of electrospray ionization tandem mass spectrometry for the qualitative and quantitative analysis of ceramides. Collision-induced fragmentation resulted in characteristic product ions for the sphingosine and dihydrosphingosine (sphinganine) head groups at m/z 264 and 282 and m/z 266 and 284, respectively, regardless of the length of the fatty acyl chains, with spectra being reproducible at concentrations as low as 25 nM (25 fmol/microliter). These reporter ions were used to detect both sphingosine- and sphinganine-based ceramides in complex mixtures using precursor ion scan analysis. We demonstrated the application of this method for profiling the composition of ceramides in a commercial preparation of bovine brain ceramides and, following minimal chromatographic separation, a lipid extract of cultured T cells. Furthermore, we easily detected relative differences in individual ceramide species levels by comparing the profiles of three related lymphocyte cell lines, Jurkat, U937, and WEHI 231. Finally, by the addition of a nonnaturally occurring internal standard, we show that the technique can be used to measure quantitative changes in ceramide levels in such biologically derived lipid preparations.

Animals↗