Biomedical subjects

J Lin

Publications and source records attributed to J Lin.

At least 109 records · Page 6Linked to original sources

PubMed2001

A TRP homolog in Saccharomyces cerevisiae forms an intracellular Ca(2+)-permeable channel in the yeast vacuolar membrane.

The molecular identification of ion channels in internal membranes has made scant progress compared with the study of plasma membrane ion channels. We investigated a prominent voltage-dependent, cation-selective, and calcium-activated vacuolar ion conductance of 320 pS (yeast vacuolar conductance, YVC1) in Saccharomyces cerevisiae. Here we report on a gene, the deduced product of which possesses significant homology to the ion channel of the transient receptor potential (TRP) family. By using a combination of gene deletion and re-expression with direct patch clamping of the yeast vacuolar membrane, we show that this yeast TRP-like gene is necessary for the YVC1 conductance. In physiological conditions, tens of micromolar cytoplasmic Ca(2+) activates the YVC1 current carried by cations including Ca(2+) across the vacuolar membrane. Immunodetection of a tagged YVC1 gene product indicates that YVC1 is primarily localized in the vacuole and not other intracellular membranes. Thus we have identified the YVC1 vacuolar/lysosomal cation-channel gene. This report has implications for the function of TRP channels in other organisms and the possible molecular identification of vacuolar/lysosomal ion channels in other eukaryotes.

Amino Acid Sequence↗

PubMed2001

Combined angiotensin II receptor antagonism and angiotensin-converting enzyme inhibition further attenuates postinfarction left ventricular remodeling.

BACKGROUND: ACE inhibition (ACEI) attenuates post-myocardial infarction (MI) LV remodeling, but the effects of angiotensin II type 1 receptor (AT(1)) antagonism alone or in combination with ACEI are unclear. Accordingly, we investigated the effects of AT(1) antagonism, ACEI, and their combination in a well-characterized ovine postinfarction model. METHODS AND RESULTS: Beginning 2 days after transmural anteroapical MI, 62 sheep were treated with 1 of 5 treatment regimens: no therapy (control, n=12), standard-dose ACEI (sACEI; ramipril 10 mg/d, n=14), high-dose ACEI (hACEI; ramipril 20 mg/d, n=8), AT(1) blockade (losartan 50 mg/d, n=13), and combination therapy with sACEI+AT(1) blockade (CT; ramipril 10 mg/d+losartan 50 mg/d, n=15). MRI was performed before and 8 weeks after MI to quantify changes in LV end-diastolic and end-systolic volume indices (DeltaEDVI, DeltaESVI) and ejection fraction (DeltaEF). Change in regional percent intramyocardial circumferential shortening in noninfarcted segments adjacent to the infarct (Adj Delta%S) was measured by tagged MRI. CT resulted in the most marked blunting of LV remodeling: DeltaESVI (+1.0+/-0.4, +0.7+/-0.4, +0.6+/-0.3, +0.9+/-0.5, and +0.4+/-0.2* mL/kg); DeltaEDVI (+0.9+/-0.4, +0.7+/-0.5, +0.6+/-0.5, +0.9+/-0.5, and +0.4+/-0.3 mL/kg); DeltaEF (-24+/-7, -18+/-6, -14+/-7, -18+/-10, and -11+/-9* %); and Adj Delta%S (-8+/-4, -7+/-3, -5+/-3, -5+/-3, and -2+/-3* %) for Control, sACEI, hACEI, AT(1) blockade, and CT, respectively (*P<0.04 versus sACEI, AT(1) blockade, and control; P<0.05 versus control; P<0.002 versus AT(1) blockade and control). EDVI and ESVI at 8 weeks after MI were smallest with CT (P<0.02 versus all). CONCLUSIONS: Combination therapy with sACEI+AT(1) blockade shows promise in attenuating postinfarction LV remodeling but was not clearly superior to hACEI in the present study.

Angiotensin Receptor Antagonists↗

PubMed2001

Identification of the minimal tyrosine residues required for linker for activation of T cell function.

The linker for activation of T cells (LAT) is essential for signaling through the T cell receptor (TCR). Following TCR stimulation, LAT becomes tyrosine-phosphorylated, creating docking sites for other signaling proteins such as phospholipase C-gamma(1) (PLC-gamma(1)), Grb2, and Gads. In this study, we have attempted to identify the critical tyrosine residues in LAT that mediate TCR activation-induced mobilization of intracellular Ca(2+) and activation of the MAP kinase Erk2. By using the LAT-deficient Jurkat derivative, J.CaM2, stable cell lines were established expressing various tyrosine mutants of LAT. We show that three specific tyrosine residues (Tyr(132), Tyr(171), and Tyr(191)) are necessary and sufficient to achieve a Ca(2+) flux following TCR stimulation. These tyrosine residues function by reconstituting PLC-gamma(1) phosphorylation and recruitment to LAT. However, these same tyrosines can only partially reconstitute Erk activation. Full reconstitution of Erk requires two additional tyrosine residues (Tyr(110) and Tyr(226)), both of which have the Grb2-binding motif YXN. This reconstitution of Erk activation requires that the critical tyrosine residues be on the same molecule of LAT, suggesting that a single LAT molecule nucleates multiple protein-protein interactions required for optimal signal transduction.

Adaptor Proteins, Signal Transducing↗

PubMed2001

Oncogenic cell cycle start control.

The ability to proliferate in the absence of anchorage is a fundamental attribute of cancer cells, yet how it is acquired is one central problem in cancer biology. By utilizing growth factor-transformable NRK cells and its insensitive mutants, we recently found that oncogenic stimulation invokes Cdk6 to participate in a critical step of the cell cycle start, but not via the regulation of its catalytic activity and that Cdk6 participation closely correlates with the anchorage-independent growth ability. Since many hematopoietic cells employ predominantly Cdk6 for the cell cycle start and perform anchorage-independent growth by nature, this finding raises the possibility that the mechanism by which oncogenic stimulation invokes anchorage-independent growth of NRK cells is similar to the one used for hematopoietic cell proliferation. We discuss this novel mechanism and its implication.

Animals↗

PubMed2001

Delayed triggering of the 1999 Hector Mine earthquake by viscoelastic stress transfer.

Stress changes in the crust due to an earthquake can hasten the failure of neighbouring faults and induce earthquake sequences in some cases. The 1999 Hector Mine earthquake in southern California (magnitude 7.1) occurred only 20 km from, and 7 years after, the 1992 Landers earthquake (magnitude 7.3). This suggests that the Hector Mine earthquake was triggered in some fashion by the earlier event. But uncertainties in the slip distribution and rock friction properties associated with the Landers earthquake have led to widely varying estimates of both the magnitude and sign of the resulting stress change that would be induced at the location of the Hector Mine hypocentre-with estimates varying from -1.4 bar (ref. 6) to +0.5 bar (ref. 7). More importantly, coseismic stress changes alone cannot satisfactorily explain the delay of 7 years between the two events. Here we present the results of a three-dimensional viscoelastic model that simulates stress transfer from the ductile lower crust and upper mantle to the brittle upper crust in the 7 years following the Landers earthquake. Using viscoelastic parameters that can reproduce the observed horizontal surface deformation following the Landers earthquake, our calculations suggest that lower-crustal or upper-mantle flow can lead to postseismic stress increases of up to 1-2 bar at the location of the Hector Mine hypocentre during this time period, contributing to the eventual occurrence of the 1999 Hector Mine earthquake. These results attest to the importance of considering viscoelastic processes in the assessment of seismic hazard.

Journal Article↗

PubMed2001

Removal of ethylacetate vapor from waste gases by a trickle-bed air biofilter.

Biofilter system is a relatively new process that has been proven to be more cost-effective than traditional technologies such as carbon adsorption, liquid scrubbing, condensation, thermal incineration, and catalytic incineration for removing low-strength volatile organic compounds from waste gases. The trickle-bed air biofilter (TBAB) performance for ethylacetate (EA) removal was evaluated under different influent loadings. In the pseudo-steady states, the elimination capacity increased, but the removal efficiency decreased with increased influent loading. More than 95 and 90% removal efficiencies could be achieved for EA loadings below 490 and 810 g m(-3) h(-1), respectively. The TBAB appears to be very effective for controlling EA emission under low to high loading conditions, and the effectiveness could be maintained over 190 days of laboratory operation.

Acetates↗

PubMed2001

BAG-1 is a novel cytoplasmic binding partner of the membrane form of heparin-binding EGF-like growth factor: a unique role for proHB-EGF in cell survival regulation.

Several cell functions related to growth and survival regulation have been attributed specifically to the membrane form of heparin-binding EGF-like growth factor (proHB-EGF), rather than to the diffusible, processed HB-EGF isoform. These findings suggest the existence of a functional binding partner specifically for the membrane form of the growth factor. In this study we have identified the prosurvival cochaperone, BAG-1, as a protein that interacts with the cytoplasmic tail domain of proHB-EGF. Interaction between BAG-1 and the 24-amino acid proHB-EGF cytoplasmic tail was initially identified in a yeast two-hybrid screen and was confirmed in mammalian cells. The proHB-EGF tail bound BAG-1 in an hsp70-independent manner and within a 97-amino acid segment that includes the ubiquitin homology domain in BAG-1 but does not include the hsp70 binding site. Effects of BAG-1 and proHB-EGF co-expression were demonstrated in cell adhesion and cell survival assays and in quantitative assays of regulated secretion of soluble HB-EGF. Because the BAG-1 binding site is not present on the mature, diffusible form of the growth factor, these findings suggest a new mechanism by which proHB-EGF, in isolation from the diffusible form, can mediate cell signaling events. In addition, because effects of BAG-1 on regulated secretion of soluble HB-EGF were also identified, this interaction has the potential to alter the signaling capabilities of both the membrane-anchored and the diffusible forms of the growth factor.

Animals↗

PubMed2001

Removal of styrene vapor from waste gases by a trickle-bed air biofilter.

The trickle-bed air biofilter (TBAB) performance for the removal of high-strength styrene was evaluated under different gas flow rates and influent concentrations. Under pseudo-steady-state conditions, the elimination capacity increased but the removal efficiency decreased with the increase of styrene loading. More than 90 and 80% removal efficiencies were achieved for influent styrene loadings below 32 and 55g/m(3)/h, respectively. The TBAB appears to be an effective treatment process for controlling high-strength styrene emission under low-to-medium loading conditions, and the effectiveness could be maintained over 140 days of laboratory operation.

Air Movements↗

PubMed2001

PartsList: a web-based system for dynamically ranking protein folds based on disparate attributes, including whole-genome expression and interaction information.

As the number of protein folds is quite limited, a mode of analysis that will be increasingly common in the future, especially with the advent of structural genomics, is to survey and re-survey the finite parts list of folds from an expanding number of perspectives. We have developed a new resource, called PartsList, that lets one dynamically perform these comparative fold surveys. It is available on the web at http://bioinfo.mbb.yale.edu/partslist and http://www.partslist.org. The system is based on the existing fold classifications and functions as a form of companion annotation for them, providing 'global views' of many already completed fold surveys. The central idea in the system is that of comparison through ranking; PartsList will rank the approximately 420 folds based on more than 180 attributes. These include: (i) occurrence in a number of completely sequenced genomes (e.g. it will show the most common folds in the worm versus yeast); (ii) occurrence in the structure databank (e.g. most common folds in the PDB); (iii) both absolute and relative gene expression information (e.g. most changing folds in expression over the cell cycle); (iv) protein-protein interactions, based on experimental data in yeast and comprehensive PDB surveys (e.g. most interacting fold); (v) sensitivity to inserted transposons; (vi) the number of functions associated with the fold (e.g. most multi-functional folds); (vii) amino acid composition (e.g. most Cys-rich folds); (viii) protein motions (e.g. most mobile folds); and (ix) the level of similarity based on a comprehensive set of structural alignments (e.g. most structurally variable folds). The integration of whole-genome expression and protein-protein interaction data with structural information is a particularly novel feature of our system. We provide three ways of visualizing the rankings: a profiler emphasizing the progression of high and low ranks across many pre-selected attributes, a dynamic comparer for custom comparisons and a numerical rankings correlator. These allow one to directly compare very different attributes of a fold (e.g. expression level, genome occurrence and maximum motion) in the uniform numerical format of ranks. This uniform framework, in turn, highlights the way that the frequency of many of the attributes falls off with approximate power-law behavior (i.e. according to V(-b), for attribute value V and constant exponent b), with a few folds having large values and most having small values.

Cysteine↗

PubMed2001

Cdk6-cyclin D3 complex evades inhibition by inhibitor proteins and uniquely controls cell's proliferation competence.

Mammalian cells require a cyclin D-dependent kinase for the cell cycle start, yet many mesenchymal cells express three seemingly redundant D cyclins and similarly, seemingly redundant Cdk4 and Cdk6 as their kinase partners. We have found that the Cdk6-cyclin D3 complex is unique among the D cyclin and kinase combinations in the ability to promote the cell cycle start. In an anchorage-minus G(1)-arrested rat fibroblast, only Cdk6-D3 retains kinase activity due mainly to its ability to evade inhibition by p27(KIP1) and p21(CIP1) with a resemblance to viral cyclin-bound Cdk6. Rodent fibroblasts engineered to overexpress both Cdk6 and cyclin D3 highly resist serum starvation- or cell-cell contact-imposed G(1)-arrest. In BALB/c 3T3 cells, D3 is constitutively expressed, but Cdk6 is markedly induced with concomitant activation upon stimulation with a growth-promoting factor. These results suggest a role for the Cdk6-D3 complex in regulating cell's proliferation ability in response to external stimuli.

3T3 Cells↗

PubMed2001

Novel 3',5'-cyclic nucleotide analogue: adenosine 3',5'-cyclic boranomonophosphate.

A general procedure for the first synthesis of a 3',5'-cyclic boranomonophosphate was established. Specifically, adenosine 3',5'-cyclic boranomonophosphosphate (cyclic AMPB, 4c), a P-borane (BH(3)) analogue of adenosine 3',5'-cyclic monophosphate (cAMP), was synthesized via a phosphite approach in good yield. The method is also applicable for syntheses of natural cAMP and its phosphorothioate analogue. The two diasteromers of cyclic AMPB 4c were separated, and their chemical structures were established via spectroscopic methods.

Boron Compounds↗

PubMed2001

Trimethylolpropane phosphate induces epileptiform discharges in the CA1 region of the rat hippocampus.

The actions of trimethylolpropane phosphate (TMPP), an ethyl bicyclophosphate convulsant produced during the partial pyrolysis of some phosphate ester-based lubricants, were tested on CA1 neurons of rat hippocampal slices using intracellular recording techniques. Bath application of TMPP (0.1-100 microM) induced spontaneous paroxysmal depolarizing shifts and the associated spontaneous epileptiform bursts followed by after-hyperpolarizations in 63% of neurons tested. The TMPP-induced epileptiform bursts were blocked by muscimol, a gamma-aminobutyric acid A (GABA(A)) receptor agonist, diazepam (DZP), a GABA(A)-benzodiazepine ionophore complex agonist, or baclofen, a GABA(B) receptor agonist. While bath application of muscimol, DZP, or baclofen suppressed spontaneous activity in CA1 neurons not previously exposed to TMPP, subsequent application of TMPP (10 microM) reversed the actions of muscimol and diazepam, but not baclofen. TMPP (0.1-100 microM) also induced membrane hyperpolarization associated with an increase in peak input resistance and inward rectification in 33% of neurons tested or membrane depolarization associated with an increase in input resistance in 17% of neurons tested. In summary, TMPP induced epileptiform activities in hippocampal CA1 neurons. The epileptogenic effects of TMPP are consistent with its interaction with GABA(A)-benzodiazepine receptors.

Action Potentials↗

PubMed2001

Correlation of low-barrier hydrogen bonding and oxyanion binding in transition state analogue complexes of chymotrypsin.

The structures of the hemiketal adducts of Ser 195 in chymotrypsin with N-acetyl-L-leucyl-L-phenylalanyl trifluoromethyl ketone (AcLF-CF3) and N-acetyl-L-phenylalanyl trifluoromethyl ketone (AcF-CF3) were determined to 1.4-1.5 A by X-ray crystallography. The structures confirm those previously reported at 1.8-2.1 A [Brady, K., Wei, A., Ringe, D., and Abeles, R. H. (1990) Biochemistry 29, 7600-7607]. The 2.6 A spacings between Ndelta1 of His 57 and Odelta1 of Asp 102 are confirmed at 1.3 A resolution, consistent with the low-barrier hydrogen bonds (LBHBs) between His 57 and Asp 102 postulated on the basis of spectroscopy and deuterium isotope effects. The X-ray crystal structure of the hemiacetal adduct between Ser 195 of chymotrypsin and N-acetyl-L-leucyl-L-phenylalanal (AcLF-CHO) has also been determined at pH 7.0. The structure is similar to the AcLF-CF3 adduct, except for the presence of two epimeric adducts in the R- and S-configurations at the hemiacetal carbons. In the (R)-hemiacetal, oxygen is hydrogen bonded to His 57, not the oxyanion site. On the basis of the downfield 1H NMR spectrum in solution, His 57 is not protonated at Nepsilon2, and there is no LBHB at pH >7.0. Because addition of AcLF-CHO to chymotrypsin neither releases nor takes up a proton from solution, it is concluded that the hemiacetal oxygen of the chymotrypsin-AcLF-CHO complex is a hydroxyl group and not attracted to the oxyanion site. The protonation states of the hemiacetal and His 57 are explained by the high basicity of the hemiacetal oxygen (pK(a) > 13.5) relative to that of His 57. The 13C NMR signal for the adduct of AcLF-13CHO with chymotrypsin is consistent with a neutral hemiacetal between pH 7 and 13. At pH <7.0, His 57 in the AcLF-CHO-hemiacetal complex of chymotrypsin undergoes protonation at Nepsilon2 of His 57, leading to a transition of the 15.1 ppm downfield signal to 17.8 ppm. The pK(a)s in the active sites of the AcLF-CF3 and AcLF-CHO adducts suggest an energy barrier of 6-7 kcal x mol(-1) against ionizations that change the electrostatic charge at the active site. However, ionizations of neutral His 57 in the AcLF-CHO-chymotrypsin adduct, or in free chymotrypsin, proceed with no apparent barrier. Protonation of His 57 is accompanied by LBHB formation, suggesting that stabilization by the LBHB overcomes the barrier to ionization. On the basis of the hydration constant for AcLF-13CHO and its inhibition constant, its K(d) is 16 microM, 8000-fold larger than the comparable value for AcLF-CF3.

Acetals↗

PubMed2001

Genome sequence of enterohaemorrhagic Escherichia coli O157:H7.

The bacterium Escherichia coli O157:H7 is a worldwide threat to public health and has been implicated in many outbreaks of haemorrhagic colitis, some of which included fatalities caused by haemolytic uraemic syndrome. Close to 75,000 cases of O157:H7 infection are now estimated to occur annually in the United States. The severity of disease, the lack of effective treatment and the potential for large-scale outbreaks from contaminated food supplies have propelled intensive research on the pathogenesis and detection of E. coli O157:H7 (ref. 4). Here we have sequenced the genome of E. coli O157:H7 to identify candidate genes responsible for pathogenesis, to develop better methods of strain detection and to advance our understanding of the evolution of E. coli, through comparison with the genome of the non-pathogenic laboratory strain E. coli K-12 (ref. 5). We find that lateral gene transfer is far more extensive than previously anticipated. In fact, 1,387 new genes encoded in strain-specific clusters of diverse sizes were found in O157:H7. These include candidate virulence factors, alternative metabolic capacities, several prophages and other new functions--all of which could be targets for surveillance.

Base Sequence↗

PubMed2001

Secular trend in tooth size in urban Chinese assessed from two-generation family data.

Environmental improvements can lead to greater size of skeletodental structures as the population comes closer to expressing its genetic growth potential. Such secular trends have been documented in many human settings, especially for increased stature and faster tempos of growth. The present study is based on 185 same-sex parent-offspring pairs of data for maximum buccolingual crown diameters of the permanent teeth from a cohort in Beijing, China, where parents experienced much of their development during and after World War II with the deprivations of the changing regime. Their offspring enjoyed the relative stability of the established Communist system, where nutrition and stability were much improved. There were significant increases in buccolingual diameters of the premolars and molars in the offspring. Increase for premolars and molars was about 1%, but larger in females than males (1.6% vs. 0.5%). Opposite changes occurred in the incisors and canines (i.e., larger parental dimensions), but we contend that these are an age-related artifact brought on by greater passive eruption of older individuals' teeth that exposes a broader portion of the crown at the gingival margin. The secular trend in crown size coincides with other research in contemporary China, disclosing increases in body size and faster tempos of growth as health and nutrition continue to improve.

Adolescent↗

PubMed2001

A kinship analysis of asthma among the Hutterites.

A formal kinship analysis of asthma in a large Hutterite kindred indicates that cases are significantly more related to one another than are age matched controls. The higher kinship coefficient is shown to be due to an increased probability of the condensed identity state delta 8 which, in turn, is shown to be due to an increased probability of detailed identity state delta 10.

Adult↗

PubMed2001

Exploiting linkage disequilibrium in population isolates.

A comparison of haplotype frequencies between unrelated cases and controls from population isolates identifies a strong signal for the presence/absence of the discrete phenotype in an interval on chromosome 6 bounded by markers 34 and 35. We define a dissimilarity index, D, which is sensitive to differences in allele distributions and differences in the patterns of linkage disequilibrium between cases and controls. We describe two statistical methods to utilize D: a method appropriate for a single moderately sized sample and a sequential approach appropriate for multiple small independent samples.

Alleles↗

PubMed2001

GM3 as a novel growth regulator for human gliomas.

The simple ganglioside GM3 inhibits proliferation and induces apoptosis in proliferating immature rodent CNS cells. To determine whether GM3 influenced the expansion of human neural tumors the effects of GM3 treatment on primary human brain tumors were assayed. Here we demonstrate that GM3 treatment dramatically reduces cell numbers in primary cultures of high-grade human glioblastoma multiforme (GBM) tumors and the rat 9L cell gliosarcoma cell line. By contrast, GM3 treatment had little effect on cell number in cultures of normal human brain. A single injection of GM3 3 days after intracranial implantation of 9L tumor cells in a murine xenograft model system resulted in a significant increase in the symptom-free survival period of host animals. The effects of GM3 were not restricted to GBMs and 9L cells. Cultures of high-grade ependymomas, mixed gliomas, astrocytomas, oligodendrogliomas, and gangliogliomas were all susceptible to GM3 treatment. These results suggest that GM3 may have considerable value as a selectively toxic chemotherapeutic agent for human high-grade gliomas.

Animals↗