Biomedical subjects
Publications and source records attributed to Q Yu.
New megastigmane (1) and tetraketide (2) were isolated from the leaves of Euscaphis japonica and the structures were elucidated by means of spectroscopic and chemical evidence.
OBJECTIVE: To determine clinical manifestation and pathological changes in autoimmune hepatitis (AIH) by liver biopsy. METHODS: The clinical manifestation and pathological changes by liver biopsy in 14 AIH patients were investigated retrospectively. RESULTS: Clinically, AIH affects females with a females/male ratio of 13/1, the age range was 28-66 year; there was extended elevation of ALT and AST, hyperglobulinemia, hypergammaglobulinemia with predominant elevation of IgG and different kinds of antibodies. Patients usually had autoimmune diseases with pathological change of typical chronic hepatitis. The levels of globulin (33 approximately 60 g/L), gammaglobulin (23.9% approximately 60.5%), IgG (8.2 approximately 39. 0 g/L), ds-DNA (1.5 approximately 58.0 g/L) in AIH were significantly higher than those of normal (t=9.7, 9.3, 6.2, 3.5, P<0.01). CONCLUSION: AIH has severe liver impairment with many other symptoms due to multi-systemic damage out of liver. AIH is a distinct autoimmune disease.
New types of X-ray computed tomography (CT), fluorescent X-ray CT and phase-contrast X-ray CT are being developed for biomedical research. While fluorescent scanning X-ray CT (FXCT) can detect specific contrast elements, or endogenous iodine, at very low content (less than 400 pg iodine of tissue in a volume of 8 x 10(-6) ml), the phase-contrast X-ray CT (PCCT) is a highly sensitive imaging technique to differentiate between different biological tissue types (based on their specific gravity variation) without the use of a contrast agent. Therefore, we can expect functional diagnosis with FXCT, and high contrast, high resolution biological imaging with PCCT. In this paper, a human thyroid gland imaged by FXCT, and a metastatic human cancerous lesion depicted using PCCT are presented. The latter method used a newly manufactured, large, monolithic, X-ray interferometer, which is described in this paper in detail.
OBJECTIVE: To investigate mitochondrial DNA (mt-DNA) mutations in optic neuritis of unknown cause (ONUC) and to assess the practical value of mt-DNA mutation detection in etiologically and differentially diagnosing ONUC. METHODS: Thirty patients with ONUC were screened for mt-DNA mutations of nt11778, nt3460 and nt15257 by using SSCP, mutation-specific primer PCR and sequencing. RESULTS: mt-DNA mutations were found in twelve of thirty ONUC patients. All of the mutations were at nt11778 position, but no one at nt3460 and nt15257. CONCLUSIONS: Forty percent (12/30) of ONUC patients were caused by an mt-DNA mutation. Combined with other routine measures, screening for mt-DNA mutations in ONUC patients is of great significance in diagnosing ONUC etiologically and differentially.
This study sought to better understand the effects of human fetal liver cells(FLC) on immunity. FLC were injected into BALB/c mice intraperitoneally. The design included four groups: negative control and three dose (125 x 10(5), 25 x 10(5), 5 x 10(5) FLC/day) groups. The results showed that FLC increased the thymus visceral coefficient, numbers of T-lymphocytes(TLC) and lymphocytes(LC) in blood, total number of spleen cells, the number of plaque forming cells(PFC) of spleen, the rate(%) of transformation and stimulus index of TLC of spleen, and the function of macrophages. FLC also effected the function of natural killer cells(NK cells) of BALB/c mice. The findings suggest that human FLC can strengthen the nonspecific immunity, humoral immunity and cellular immunity in mice. In this study, however, no effect of FLC on spleen visceral coefficient was noticed, and no sign of delayed type allergy was observed.
PTEN/MMAC1/TEP1 is a tumor suppressor gene. Its mutation has been found in several different types of human cancers. 34 primary human hepatocellular carcinomas have been examined for mutations in exon 5 and exon 8 of the PTEN gene. Exon 5 and exon 8 were amplified by polymerase chain reaction (PCR) with intronic primers and subjected to single strand conformation polymorphism (SSCP) analysis. SSCPs were found in 4 of the 34 hepatocellular carcinomas analyzed. Direct sequencing of the PCR products identified single base-pair substitutions in the four tumor DNA samples, two in intron 4 and two in exon 8. One of the base-pair substitution in exon 8 is a missense mutation, which changed codon 304 of PTEN protein from Cys to Gly. These data suggest that PTEN may be involved in the carcinogenesis and development of hepatocellular carcinoma.
The mass of the central black holes in Seyfert galaxies and QSOs can be determined from the broad emission lines and the reverberation method. Using the measured black hole mass and the bolometric or ionizing luminosity, the accretion rate can be estimated. Compiling a sample of Seyfert 1 galaxies and QSOs with reliable central masses, estimated ionizing luminosities, and X-ray spectral slopes, we find that the X-ray spectral slope strongly correlates with the accretion rate. The objects in the sample are found to be distributed in two distinct classes in the spectral index versus log&parl0;Lion&solm0;LEdd&parr0;-plane. We argue that these two classes may correspond to advection-dominated accretion flow (ADAF) and thin disk accretion. The observations of a "two-state" Seyfert 1 galaxy, 1H 0419-577, confirm our results. Detailed fitting of the spectra of individual Seyfert 1 galaxies and QSOs using ADAF and/or thin disk models should further clarify the two-class classification.
The glycolytic enzyme glyceraldehyde-3-phosphate dehydrogenase (GAPDH) is induced by hypoxia in endothelial cells (EC). Upregulation occurs primarily at the level of transcription and occurs to a much greater extent in EC than in other cell types. To characterize EC specific hypoxia response elements within the GAPDH gene, we performed transient transfection studies in EC, fibroblasts and smooth muscle cells using portions of the GAPDH promoter linked to a CAT reporter gene. These initial studies identified an EC specific hypoxia responsive region that was further characterized (using SV40-promoter-CAT reporter constructs) as a 19-nucleotide sequence (-130 to -112) containing both an hypoxia inducible factor-1 (HIF-1)-binding site and a novel flanking sequence. Electrophoretic mobility shift assays confirmed inducible EC protein binding to this fragment. Mutation of either the HIF-1-binding site or the flanking sequence resulted in complete loss of function and loss of inducible protein binding. Thus, a single HIF-1-binding site is necessary, but not sufficient, for hypoxic regulation of GAPDH in EC. Furthermore, the novel HIF-1 flanking sequence required for GAPDH upregulation and the protein(s) that bind to it may be EC specific.
Dendritic cells (DCs) are professional Ag-presenting cells that are being considered as potential immunotherapeutic agents to promote host immune responses against tumor Ags. In this study, recombinant adenovirus (Ad) vectors encoding melanoma-associated Ags were used to transduce murine DCs, which were then tested for their ability to activate CTL and induce protective immunity against B16 melanoma tumor cells. Immunization of C57BL/6 mice with DCs transduced with Ad vector encoding the hugp100 melanoma Ag (Ad2/hugp100) elicited the development of gp100-specific CTLs capable of lysing syngeneic fibroblasts transduced with Ad2/hugp100, as well as B16 cells expressing endogenous murine gp100. The induction of gp100-specific CTLs was associated with long term protection against lethal s.c. challenge with B16 cells. It was also possible to induce effective immunity against a murine melanoma self Ag, tyrosinase-related protein-2, using DCs transduced with Ad vector encoding the Ag. The level of antitumor protection achieved was dependent on the dose of DCs and required CD4+ T cell activity. Importantly, immunization with Ad vector-transduced DCs was not impaired in mice that had been preimmunized against Ad to mimic the immune status of the general human population. Finally, DC-based immunization also afforded partial protection against established B16 tumor cells, and the inhibition of tumor growth was improved by simultaneous immunization against two melanoma-associated Ags as opposed to either one alone. Taken together, these results support the concept of cancer immunotherapy using DCs transduced with Ad vectors encoding tumor-associated Ags.
Blood group polymorphisms have been used as tools to study the architecture of the red blood cell (RBC) membrane. Some blood group variants have reduced antigen expression at the cell surface. Understanding the underlying mechanism for this reduced expression can potentially provide structural information and help to elucidate protein trafficking pathways of membrane proteins. The Kp(a+) phenotype is a variant in the Kell blood group system that is associated with a single amino acid substitution (R281W) in the Kell glycoprotein and serologically associated with a weakened expression of other Kell system antigens by an unknown mechanism. We found by immunoblotting of RBCs that the weakening of Kell antigens in this variant is due to a reduced amount of total Kell glycoprotein at the cell surface rather than to the inaccessibility of the antigens to Kell antibodies. Using a heterologous expression system, we demonstrate that the Kpa mutation causes retention of most of the Kell glycoprotein in a pre-Golgi compartment due to differential processing, thereby suggesting aberrant transport of the Kell protein to the cell surface. Furthermore, we demonstrated that single nucleotide substitutions into the coding region of the common KEL allele, as predicted by the molecular genotyping studies, was sufficient to encode three clinically significant low incidence antigens. We found that two low incidence antigens can be expressed on a single Kell protein, thus showing that the historical failure to detect such a variant is not due to structural constraints in the Kell protein. These studies demonstrate the power of studying the molecular mechanisms of blood group variants for elucidating the intracellular transport pathways of membrane proteins and the requirements for cell surface expression.
Four novel analogues (8-11) of cymserine (2) were synthesized by methods similar to those recently developed for the total syntheses of N8-norphenserine (Yu, Q. S.; et al. J. Med. Chem. 1997, 40, 2895-2901) and N1,N8-bisnorphenserine (Yu, Q. S.; et al. J. Med. Chem. 1998, 41, 2371-2379). As our structure-activity studies predicted, these compounds are highly potent and selective inhibitors of human butyrylcholinesterase (BChE) and will test the novel hypothesis that BChE inhibitors are useful in the treatment of Alzheimer's disease. In a similar manner, the same modifications that provided BChE selectivity were applied to the acetylcholinesterase (AChE)-selective inhibitor, tolserine (5), to provide the novel tolserine analogues 12-15. As predicted, these modifications altered the AChE-selective action of tolserine (5) to favor a lack of cholinesterase enzyme subtype selectivity.
The initiation of reverse transcription of human immunodeficiency virus type 1 (HIV-1) exclusively utilizes tRNALys,3 as a primer. Previous studies have shown that HIV-1 could use alternative tRNAs, such as tRNAIle or tRNAHis, to initiate reverse transcription only if the primer binding site (PBS) was made complementary to the 3' terminal 18 nucleotides of the cognate tRNA. However, upon in vitro culture, the viruses with a PBS complementary to the alternative tRNAs rapidly reverted to generate a PBS complementary to tRNALys,3. To investigate the process of reversion, we have constructed defective proviral genomes that contain a PBS complementary to tRNAIle or tRNAHis. The genomes contain the gene for xanthine-guanosine phosphoribosyl transferase (gpt) in place of env. Cotransfection of these proviral genomes with a plasmid-encoding vesicular stomatitis virus G protein (VSV-G) results in viruses that undergo a single round of HIV-1 infection; successful infections are scored as cells resistant to the drug mycophenolic acid. Using this single-round infection system, we demonstrated that HIV-1 with a PBS complementary to tRNAIle or tRNAHis is three- to fivefold less efficient in replication as measured by production of drug-resistant cell colonies compared to the wild-type virus. These viruses predominantly used the cognate tRNA as primer in their initial round of replication, although we did obtain a single cell colony in which the PBS was complementary to tRNALys,3. Using an HIV-1 provirus with a PBS complementary to yeast tRNAPhe, we established a single-round infection system in which the infectivity of this mutant HIV-1 relies on transfected yeast tRNAPhe. The results of our studies suggest that the mechanism for selection of the tRNA primer for initiation of reverse transcription relies primarily on the complementarity between the tRNA primerthe PBS.
The cell surface hyaluronan receptor CD44 promotes tumor growth and metastasis by mechanisms that remain poorly understood. We show here that CD44 associates with a proteolytic form of the matrix metalloproteinase-9 (MMP-9) on the surface of mouse mammary carcinoma and human melanoma cells. CD44-associated cell surface MMP-9 promotes cell-mediated collagen IV degradation in vitro and mediates tumor cell invasion of G8 myoblast monolayers. Several distinct CD44 isoforms coprecipitate with MMP-9 and CD44/MMP-9 coclustering is observed to be dependent on the ability of CD44 to form hyaluronan-induced aggregates. Disruption of CD44/MMP-9 cluster formation, by overexpression of soluble or truncated cell surface CD44, is shown to inhibit tumor invasiveness in vivo. Our observations indicate that CD44 serves to anchor MMP-9 on the cell surface and define a mechanism for CD44-mediated tumor invasion.
BACKGROUND: The central factor influencing therapeutic decisions in essential tremor (ET) is the functional impact of the tremor. Neither the neurological examination nor computerized tremor analysis measures function. Questionnaires may assess function, but data are highly subjective. Performance-based tests of functional impairment provide an alternative means with which to assess the functional impact of ET. OBJECTIVE: To determine the internal consistency and validity of a performance-based measure of functional impairment in ET. METHODS: Subjects with ET from a community in northern Manhattan, NY, and from a clinic and control subjects each underwent a 2 1/2-hour evaluation including 12 screening questions for ET, a 31-item Tremor Disability Questionnaire to assess the functional impact of tremor, a 26-item Videotaped Tremor Examination that was rated by a neurologist, a 15-item, 10-minute Performance-Based Test, and Quantitative Computerized Tremor Analysis. Internal consistency was assessed with Cronbach alpha. The correlation between the Performance-Based Test and these other measures of tremor was assessed by means of correlation coefficients (r). RESULTS: There were 50 ET cases and 51 normal control subjects. The Performance-Based Test was internally consistent (Cronbach alpha = .92). It also demonstrated validity among cases; the total score correlated with the total number of screening questions answered yes (r = 0.44; P = .001), the total score on the Tremor Disability Questionnaire (r=0.55; P<.001), the total score on the Videotaped Tremor Examination (r=0.71; P<.001), and multiple physiological measures recorded during Quantitative Computerized Tremor Analysis. CONCLUSIONS: A valid performance-based test was developed to objectively assess functional capacity in patients with ET. This test would be useful in therapeutic trials, where it would provide an objective means to quantify the functional impact of tremor.
This review focuses on the concept, criteria, and methods of an orthogonal amide ligating strategy suitable for syntheses of peptides, peptide mimetics, and proteins. Utilizing unprotected peptides or proteins derived from chemical or biosynthetic sources, this ligation strategy has been shown to be general and exceptionally mild. Its orthogonality in ligating two unprotected segments with free N-terminal (NT)-amines at a specific NT-amine is achieved through a chemoselective capture step and then an intramolecular acyl transfer reaction. Both coupling reagents for enthalpic activation and protection schemes therefore become unnecessary. More than a dozen orthogonal ligation methods based on either imine or thioester captures have been developed to afford native and unusual amino acids at ligation sites of linear, branched, or cyclic peptides. Because unprotected peptides and proteins of different sizes and forms can be obtained from either chemical or recombinant sources, orthogonal ligation removes the size limitation imposed on the chemical synthesis of a protein with a native or non-native structure. Furthermore, by using building blocks from biosynthetic sources, orthogonal ligation provides a unifying operational concept for both total and semisynthesis of peptides and proteins.
Twenty consecutive patients with idiopathic Parkinson's disease underwent stereotactic posteroventral pallidotomy. Schwab and England ADL scores in the "off" state were improved by 18% and in the "on" state the scores declined by 2%. Three patients also reported marked improvement in "off" state dystonia. One-year data are available on 12 patients who underwent evaluations according to the Core Assessment Program for Intracerebral Transplantation protocol preoperatively and at 3, 6, and 12 months after surgery. Significant improvements in Unified Parkinson's Disease Rating Scale sections II and III scores in the "off" state, composite "off" state scores of bradykinesia and rigidity, contralateral tremor in the "off" state, and contralateral dyskinesias were observed. Although there was reduction in the daily levodopa dose, this did not reach statistical significance. Major complications (15%) included hemiparesis (one of 20) and visual field cuts (two of 20); minor complications (45%) included mild cognitive dysfunction (four of 20), reading difficulty not related to visual disturbance (one of 20), and 5-10 lb weight gain (four of 20).
The internal lethal concentration (ILC) can be an effective approach in describing the toxicity of a chemical to aquatic organisms that can complement the use of the external toxic concentration characteristic of the LC50. The ILC is an estimate of the toxicant concentration close to the target site and can be estimated from bioconcentration relationships and acute toxicity data. The observed ILC values were found to be consistent for organic compounds exerting the same mode of toxic action. The nonspecific toxicants have the lowest toxicity and the highest ILC values, whereas the chemicals exhibiting specific modes of action have lower concentrations and higher toxicity. There are some reports that the ILC value decreases with increasing exposure periods for various organic chemicals with aquatic organisms. The nonspecific toxicants possibly exhibit their toxic action at the target site by at least two different mechanisms depending on the toxicant concentrations. First, the toxicants bind directly to membrane proteins at relatively low concentrations, resulting in reversible toxic effect. Second, the toxicants inhibit the membrane proteins, and alterations in the lipid bilayers occur at toxicant concentrations sufficient to produce mortality of the organisms. The nonspecific toxicity expressed as acute and chronic toxicity measures are found to correlate well with log Kow. However, the relationship between the ILC and log Kow is less satisfactory because the values of ILC are relatively consistent compared to those of LC50.
Experimental data have shown that the internal lethal concentrations of halobenzenes for aquatic organisms decreased with exposure time. In this paper, a model based on the concept of life expectancy reduction was developed to describe this relationship. The model was verified with experimental data for fish (Gambusia affinis) and juvenile crab (Porturius pelagicus(L)). It is proposed that long term non-specific toxicity can be measured as the reduction of the life expectancy of the exposed organism per unit internal concentration (or volume fraction) of the toxic compound. The model can be used to estimate internal lethal concentration at any given exposure period and vice versa. The model can also be used to estimate chronic values of the internal concentration, of the toxicants. It provides a useful tool for assessment of environmental risk of organic compounds in aquatic ecosystems.