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Biomedical subjects

K Lin

Publications and source records attributed to K Lin.

At least 73 records · Page 4Linked to original sources
PubMed1999

[Investigation of Y chromosome and polymorphism of 5 Chinese ethnic groups in Yunnan Province, China].

OBJECTIVE: To investigate the polymorphism of DYS287 in the Han, Dai, Lahu, Wa and Tibetan groups living in Yunnan Province, China. METHODS: YAP element was detected by PCR amplification and agarose gel electrophoresis. RESULTS: With 150bp product in all Han,Dai, Lahu and Wa individuals, YAP element is absent. In 11 Tibetan individuals out of 30, YAP element is present and the PCR product is 455bp. CONCLUSION: As an important and stable genetic marker, DYS287 can provide reliable evidence in evolution study.

China↗
PubMed1998

Cleavage planes in frog eggs are altered by strong magnetic fields.

Early cleavages of Xenopus embryos were oriented in strong, static magnetic fields. Third-cleavage planes, normally horizontal, were seen to orient to a vertical plane parallel with a vertical magnetic field. Second cleavages, normally vertical, could also be oriented by applying a horizontal magnetic field. We argue that these changes in cleavage-furrow geometries result from changes in the orientation of the mitotic apparatus. We hypothesize that the magnetic field acts directly on the microtubules of the mitotic apparatus. Considerations of the length of the astral microtubules, their diamagnetic anisotropy, and flexural rigidity predict the required field strength for an effect that agrees with the data. This observation provides a clear example of a static magnetic-field effect on a fundamental cellular process, cell division.

Animals↗
PubMed1998

The 41-kDa protein of human herpesvirus 6 specifically binds to viral DNA polymerase and greatly increases DNA synthesis.

We previously isolated a 41-kDa early antigen of human herpesvirus 6 (HHV-6), which exhibited nuclear localization and DNA-binding activity (Agulnick et al., 1993). In this study, we observed that a 110-kDa protein was coimmunoprecipitated with p41 from HHV-6-infected cells by an anti-p41 antibody. This 110-kDa protein was identified as the HHV-6 DNA polymerase (Pol-6) by an antibody raised against the N terminus of Pol-6. Reciprocal immunoprecipitation and Western blot analyses confirmed that p41 complexes with Pol-6 in HHV-6-infected cells. In addition, both p41 and Pol-6 were expressed in vitro and shown to form a specific complex. An in vitro DNA synthesis assay using primed M13 single-stranded DNA template demonstrated that p41 not only increased the DNA synthesis activity of Pol-6 but also allowed Pol-6 to synthesize DNA products corresponding to full-length M13 template (7249 nucleotides). By contrast, Pol-6 alone could only synthesize DNA of <100 nucleotides. The functional interaction between Pol-6 and p41 appears to be specific because they could not be physically or functionally substituted in vitro by their herpes simplex virus 1 homologues. Moreover, as revealed by mutational analysis, both the N and C termini of Pol-6 contribute to its binding to p41. In the case of p41, the N terminus is required for increasing DNA synthesis but not binding to Pol-6, whereas the C terminus is totally dispensable.

Cell Line↗
PubMed1998

FTIR study of the thermal denaturation of alpha-actinin in its lipid-free and dioleoylphosphatidylglycerol-bound states and the central and N-terminal domains of alpha-actinin in D2O.

Fourier transform infrared (FTIR) spectroscopy has been carried out to investigate the thermal denaturation of alpha-actinin and its complexes with dioleoylphosphatidylglycerol (DOPG) vesicles. The amide I regions in the deconvolved spectra of alpha-actinin in the lipid-free and DOPG-bound states are both consistent with predominantly alpha-helical secondary structure below the denaturation temperatures. Studies of the temperature dependence of the spectra revealed that for alpha-actinin alone the secondary structure was unaltered up to 40 degrees C. But, in the presence of DOPG vesicles, the thermal stability of the secondary structure of alpha-actinin increased to 55 degrees C. The thermal denaturation mechanisms of the lipid-free and DOPG-bound states of alpha-actinin also vary. The secondary structure of the lipid-free alpha-actinin changed to be predominantly unordered upon heating to 65 degrees C and above. Whereas, the original alpha-helical structure in the DOPG-bound alpha-actinin retained even at 70 degrees C, the highest temperature we examined. Analysis of the reduction in amide II intensities, which is due to peptide H-D exchange upon heating alpha-actinin in D2O, showed that partially unfolded states with increased solvent accessibility but substantial secondary structures could be observed from 35 to 40 degrees C only if DOPG vesicles were present. A so-called "protamine precipitation" method has been developed to purify the N-terminal domain of alpha-actinin by use of the fact that the central domain of alpha-actinin is negatively charged but the N-terminal domain is positively charged. Thermal denaturation of the central and N-terminal domains of alpha-actinin were then investigated with FTIR. The secondary structure of the N-terminal domain of alpha-actinin was found to be thermally sensitive below 35 degrees C, which is characterized as the increase of the alpha-helical structure at the expense of the random coil upon heating the N-terminal domain from 4 to 35 degrees C. The membrane-binding ability of the N-terminal domain of alpha-actinin was proposed in terms of the analysis of the local electrostatic properties of alpha-actinin and the assignment of the amide II bands in the FTIR spctra of alpha-actinin.

Actinin↗
PubMed1998

Two- and three-dimensional computer graphic evaluation of the subacute spinal cord injury.

We have evaluated three-week-old compression lesions of the rat spinal cord using two-dimensional and three-dimensional morphometry, reconstruction, and visualization techniques. We offer a new computer assisted method to determine the number and density of macrophages within the spinal lesion using the macrophage specific monoclonal label ED1. We also provide quantitative information on pathological cyst formation and cavitation. This technique does not require: (1) subjective identification of the cell type, (2) human interaction with the data during the phase of quantification, and (3) can be applied to any sampling paradigm based on immunocytochemical labeling. Using novel algorithms based on solutions to 'correspondence' and 'branching' problems inherent in cross-sectional histological data, we provide three-dimensional reconstructions and visualizations of the macrophagic lesions and cysts imbedded within it. Our three-dimensional surface reconstructions can be interrogated to determine volumes and surface areas of structures within the data set. Using these methods we have learned that macrophage numbers approach the maximum density possible for such isodiametric cells (approximately 12 microm diameter) in the central lesion ranging from 4000-7000 cells per mm2 of lesion. At the time point studied, macrophage numbers would have peaked following the initial insult, and would not be expected to decline for several months. While the density of macrophages is highest in the region of most tissue damage, we show that the central regions of cavitated and cystic spinal parenchyma is not. We discuss how this density of cells may effect the secondary pathological responses of the spinal cord to injury.

Algorithms↗
PubMed1998

Selective inhibition of muscle gene expression by oxidative stress in cardiac cells.

Reactive oxygen species have been suggested to play an important role in damage to cardiac tissue following ischemia and reperfusion. Oxygen radicals may also contribute to the cardiotoxicity of the anthracycline antibiotics, such as doxorubicin. We tested whether a selective inhibition of muscle gene expression, previously observed in cardiocytes treated with doxorubicin, might be reflective of a more generalized response evoked by oxidative stress in cardiac tissue. Cardiocytes in culture were exposed to hydrogen peroxide or glucose oxidase, and the effects on muscle gene expression were measured. Exposure to these agents led to a reduction in the levels of mRNA for the muscle-specific genes cardiac alpha-actin, troponin I, myosin light chain 2 (slow), and M isoform of creatine kinase, without affecting levels of the non-muscle genes pyruvate kinase and beta-actin. The magnitude of this effect was similar to that observed with doxorubicin. Although the hydrogen peroxide scavenging enzyme catalase and the intracellular radical scavengers N-acetylcysteine and 1,3-dimethyl-2-thiourea were without effect on doxorubicin-dependent reduction in gene expression, they inhibited the reduction in muscle gene expression mediated by hydrogen peroxide. These observations suggest that oxygen free radicals modulate muscle gene expression in cardiocytes by a pathway distinct from that utilized by doxorubicin.

Animals↗
PubMed1998

Indium-111 capromab pendetide (ProstaScint) imaging to detect recurrent and metastatic prostate cancer.

This study evaluated the utility of In-111 capromab pendetide imaging to detect prostate cancer metastases or local recurrence. The specific goal was to identify clinical factors such as prostate-specific antigen, pathologic stage, and Gleason score that were most predictive of a positive scan outcome. In addition, a new concept of a weighted Gleason score was defined and correlated with the scan outcome. Fifty-one patients with an elevated prostate-specific antigen level and otherwise negative workup were studied. Forty-eight patients had been treated by radical prostatectomy, two by radiation therapy, and one patient was studied before prostatectomy. Each patient received an intravenous injection of approximately 5 mCi of In-111 containing 0.5 mg of CYT 356, a conjugated site-specific monoclonal antibody against prostate specific membrane antigen. Tomographic blood pool images were obtained the day of injection. Four days later planar images and tomographic images of the abdomen and pelvis were obtained. Scans were interpreted by two experienced nuclear medicine physicians. Differences in the scan interpretation were settled by consensus. Scan outcomes were correlated with prostate-specific antigen levels, pathologic stage, Gleason score, weighted Gleason score, and clinical data. Of 51 scans, 70.6% (36 of 51) were positive. Eight patients had abnormal activity in the prostatic fossa, 12 patients had abnormal activity in the abdominal or pelvic lymph nodes, and 16 patients demonstrated abnormal activity in both areas. One patient with a positive scan underwent lymphadenectomy and was confirmed to be a true positive. Patients with a prostate-specific antigen level greater than 10 ng/ml, a weighted Gleason score higher than 4.5, or prostate-specific antigen levels greater than 2 ng/ml plus a weighted score higher than 4.5 showed positive rates of 100% (6 of 6), 88.2% (14 of 16), and 100% (6 of 6), respectively. In-111 capromab pendetide imaging was useful to detect metastases or local recurrence. Serum prostate-specific antigen levels and weighted Gleason scores are good predictive factors of the likelihood of a positive scan outcome.

Abdominal Neoplasms↗
PubMed1998

A conformation-specific monoclonal antibody reacting with fusion-active gp41 from the human immunodeficiency virus type 1 envelope glycoprotein.

The gp41 subunit of the human immunodeficiency virus type 1 (HIV-1) envelope glycoprotein plays a major role in the membrane fusion step of viral infection. The ectodomain of gp41 contains a six-helix structural domain that likely represents the core of the fusion-active conformation of the molecule. A monoclonal antibody (MAb), designated NC-1, was generated and cloned from a mouse immunized with the model polypeptide N36(L6)C34, which folds into a stable six-helix bundle. NC-1 binds specifically to both the alpha-helical core domain and the oligomeric forms of gp41. This conformation-dependent reactivity is dramatically reduced by point mutations within the N-terminal coiled-coil region of gp41 which impede formation of the gp41 core. NC-1 binds to the surfaces of HIV-1-infected cells only in the presence of soluble CD4. These results indicate that NC-1 is capable of reacting with fusion-active gp41 in a conformation-specific manner and can be used as a valuable biological reagent for studying the receptor-induced conformational changes in gp41 required for membrane fusion and HIV-1 infection.

Amino Acid Sequence↗
PubMed1998

Cloning and functional analysis of Kaposi's sarcoma-associated herpesvirus DNA polymerase and its processivity factor.

Kaposi's sarcoma-associated herpesvirus (KSHV), or human herpesvirus 8, is a newly identified virus with tumorigenic potential. Here, we cloned and expressed the DNA polymerase (Pol-8) of KSHV and its processivity factor (PF-8). Pol-8 bound specifically to PF-8 in vitro. Moreover, the DNA synthesis activity of Pol-8 was shown in vitro to be strongly dependent on PF-8. Addition of PF-8 to Pol-8 allowed efficient synthesis of fully extended DNA products corresponding to the full-length M13 template (7,249 nucleotides), whereas Pol-8 alone could incorporate only several nucleotides. The specificity of PF-8 and Pol-8 for each other was demonstrated by their inability to be functionally replaced by the DNA polymerases and processivity factors of herpes simplex virus 1 and human herpesvirus 6.

Amino Acid Sequence↗
PubMed1998

Combined surfactant therapy and inhaled nitric oxide in rabbits with oleic acid-induced acute respiratory distress syndrome.

Intratracheal administration of surfactant and inhaled nitric oxide (INO) have had variable effects in clinical trials on patients with acute respiratory distress syndrome (ARDS). We hypothesized that combined treatment with exogenous surfactant and INO may have effects in experimental ARDS. After intravenous infusion of oleic acid in adult rabbits and 4-6 h of ventilation, there was more than a 40% reduction in both dynamic compliance (Cdyn) of the respiratory system and functional residual capacity (FRC), a 50% increment of respiratory resistance (Rrs), a 70% reduction in PaO2 /FIO2, and an increase in intrapulmonary shunting (Q S/Q T) from 4.4 to 33.5%. The animals were then allocated to groups receiving (1) neither surfactant nor INO (control), (2) 100 mg/kg of surfactant (S) administered intratracheally, (3) 20 ppm INO (NO), or (4) 100 mg/kg of surfactant and 20 ppm INO (SNO), and subsequently ventilated for 6 h. After the period of ventilation, the animal lungs were used for analysis of disaturated phosphatidylcholine (DSPC) and total proteins (TP) in bronchoalveolar lavage fluid (BALF), and for determination of alveolar volume density (VV). The animals in the control group had the lowest survival rate, and no improvement in lung mechanics and blood oxygenation, whereas those in the S group had a modest but statistically significant improvement in Cdyn, Rrs, PaO2 and FRC, reduced Q S/Q T, lowered minimum surface tension (gammamin) of BALF, and increased DSPC/ TP and alveolar VV. The NO group had increased PaO2 and reduced Q S/Q T. The SNO group showed improved Cdyn, Rrs, FRC, DSPC/TP, alveolar VV, and gammamin of BALF comparable to the S group, but there was a further increase in survival rate and PaO2, and additional reduction in Q S/Q T and TP in BALF. These results indicate that, in this animal model of ARDS, a combination of surfactant therapy and INO is more effective than either treatment alone.

Administration, Inhalation↗
PubMed1998

Effects of object affordances on reaching performance in persons with and without cerebrovascular accident.

OBJECTIVE: This study investigated whether affording objects with different levels of functional support would have an impact on reaching performance in patients after cerebrovascular accident (CVA) and in adults who were neurologically intact. Reaching performance was quantitatively analyzed, using several kinematic variables. METHOD: Two groups, 14 participants after CVA and 24 age-matched adults who were neurologically intact, performed a food chopping task under two conditions: enriched affordances and impoverished affordances. Enriched affordances involved reaching forward to a chopper and pushing down on the handle to chop a fresh mushroom. Impoverished affordances involved reaching forward to a simulated chopper (i.e., a chopper covered with cardboard) without anything in it and then pushing the handle down. Reaching movement was measured by a three-dimensional motion analysis system. RESULTS: For the CVA group, the enriched condition of reaching to chop the mushroom resulted in more efficient, direct, smooth, and preplanned movement than the impoverished condition of reaching to push on the chopper handle. The neurologically intact group responded similarly except that the participants' movement was equally smooth, as measured by movement unit, between the two testing conditions. Force generation, as characterized by peak velocity, was similar for both conditions for both groups. CONCLUSION: The finding that enriched affordances had a positive effect on movement kinematics in both CVA and neurologically intact groups suggests that providing natural objects for completing a task and providing functional information on the objects may enhance the functional performance of persons who have had a CVA. These findings should be replicated and extended to confirm the validity of these effects and allow for generalization.

Adult↗
PubMed1998

Hunting TPR Domains Using Kleisli.

We have two objectives. First, we want to build a system for detecting tetratricopeptide repeats in protein sequences. Second, we want to demonstrate how the general bioinformatics database integration system called Kleisli can help build such a system easily. We achieve these two objectives by showing that short and clear programs can be written in Kleisli, using its high-level query language CPL, to build a TPR domain hunter by integrating WU-BLAST2.0, HMMER, Entrez, and PFAM.

Journal Article↗
PubMed1998

Methylglyoxal-derived modifications in lens aging and cataract formation.

PURPOSE: To determine whether the Maillard reaction of methylglyoxal is associated with human lens aging and cataractogenesis and to investigate how glutathione depletion affects methylglyoxal-derived modifications in organ-cultured lenses. METHODS: Antibodies against methylglyoxal-derived modifications were developed in rabbits and purified by immunoaffinity chromatography. A competitive enzyme-linked immunosorbent assay (ELISA) measured methylglyoxal-derived products in human lens proteins. Lenses of galactosemic rats grown in organ culture were used to assess the role of glutathione-dependent pathways in methylglyoxal metabolism and Maillard reactions. RESULTS: Methylglyoxal-derived modifications in the human lens were age dependent, and brunescent lenses had the highest levels of these modifications. Immunofluorescence staining identified antigens distributed throughout the lens, with higher levels in old lenses than in younger ones. Experiments with normal or galactosemic rat lenses grown in organ culture showed that lens proteins do not have an increase in methylglyoxal-modified proteins when cultured in medium containing 500 microM methylglyoxal alone, but they accumulate modified proteins when cultured with DL-glyceraldehyde. Inclusion of 30 mM glucose in the medium marginally increased methylglyoxal-derived products, but there was no correlation between lens glutathione content and methylglyoxal-derived modifications. CONCLUSIONS: Methylglyoxal-mediated Maillard reactions that occur in the human lens may play a role in lens aging and cataract formation. Methylglyoxal is probably derived from metabolic pathways within the lens. Decreased glutathione in organ-cultured rat lenses does not significantly influence methylglyoxal-mediated Maillard reactions.

Adolescent↗
PubMed1997

Distinct phosphorylation signals converge at the catalytic center in glycogen phosphorylases.

BACKGROUND: Glycogen phosphorylases (GPs) catalyze the conversion of the storage form of carbohydrate (glycogen) to the readily usable form (glucose-1-phosphate) to provide cellular energy. Members of this enzyme family have evolved diverse regulatory mechanisms that control a conserved catalytic function. The mammalian and yeast GPs are expressed as inactive forms requiring phosphorylation for activation. Phosphorylation of yeast GP occurs at a distinct site from that of mammalian GP. This work addresses the structural basis by which distinct activation signals relay to the conserved catalytic site in yeast and mammalian GPs. Such knowledge may help understand the principles by which diverse biological regulation evolves. RESULTS: We have compared the crystal structures of the unphosphorylated and phosphorylated forms of yeast GP and propose a relay which links phosphorylation to enzyme activation. Structural components along the activation relay becomes more conserved within the GP family downstream along the relay, towards the catalytic center. Despite distinct upstream activation signals, a response element downstream of the relay leading to the catalytic center is conserved in all GPs. The response element consists of ten hydrophobic residues dispersed over two subunits of the homodimer. Phosphorylation induces hydrophobic condensation of these residues via structural rearrangement, which triggers conformation change of the active site GATE loop, leading to enzyme activation. CONCLUSIONS: Members of the GP family with diverse activation mechanisms have evolved from a constitutively active ancestral enzyme which has the TOWER hydrophobic response element in the active position. Diverse regulation evolved as a result of evolutionary constraint on the downstream response element in the active state, coupled with flexibility and variability in elements of the upstream relays.

Amino Acid Sequence↗
PubMed1997

daf-16: An HNF-3/forkhead family member that can function to double the life-span of Caenorhabditis elegans.

The wild-type Caenorhabditis elegans nematode ages rapidly, undergoing development, senescence, and death in less than 3 weeks. In contrast, mutants with reduced activity of the gene daf-2, a homolog of the insulin and insulin-like growth factor receptors, age more slowly than normal and live more than twice as long. These mutants are active and fully fertile and have normal metabolic rates. The life-span extension caused by daf-2 mutations requires the activity of the gene daf-16. daf-16 appears to play a unique role in life-span regulation and encodes a member of the hepatocyte nuclear factor 3 (HNF-3)/forkhead family of transcriptional regulators. In humans, insulin down-regulates the expression of certain genes by antagonizing the activity of HNF-3, raising the possibility that aspects of this regulatory system have been conserved.

Aging↗