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At least 343 records · Page 19Linked to original sources
PubMed2005

New insight into the mechanism of cardiovascular dysfunction in the elderly: transfer function analysis.

This study sought to test the hypothesis that alterations in the relationships between (i) mean arterial pressure (MAP) and heart rate (HR), (ii) cardiac output (CO) and MAP, and (iii) total peripheral resistance (TPR) and MAP variability contribute to the diminished dynamic control of cardiovascular function with advanced age. Six-minute hemodynamic data were continuously recorded in 11 elderly (70 +/- 2 years) and 11 young (26 +/- 1 year) healthy volunteers under supine resting condition and during lower body negative pressure-induced orthostatic challenge. The data were converted using fast Fourier transform, and the ratio of cross-spectra to auto-spectra between two signals (i.e., MAP-HR, CO-MAP, TPR-MAP) was computed for transfer function analysis. In the low-frequency ranges (LF; 0.04-0.14 Hz) and high-frequency ranges (0.15-0.30 Hz), the gain and coherence of the transfer function describing the relationship between MAP-HR signals were significantly greater in younger than in older adults. The phase degree was significantly >0 in both groups under all conditions, suggesting that the MAP variability preceded the HR variability. In contrast, the coherence between CO-MAP signals in both age groups was <0.5, indicating that the beat-to-beat MAP variability was not significantly related to the CO signals. However, the transfer function gain and coherence of TPR-MAP signals were significantly greater in the young group (coherence >/=0.5 in the LF range), suggesting a more effective dynamic vasomotor control. In conclusion, the oscillations in CO-MAP signals are not significantly synchronized or not related in a simply linear fashion in both age groups. The MAP variability is more related to the oscillation of TPR signals in the young group only. Advanced age not only diminishes MAP-HR transfer function gain, but also weakens its coherence. Thus, alterations in the relationship between MAP-HR variability and TPR-MAP variability may significantly contribute to the diminished dynamic control of cardiovascular function manifest in the elderly.

Adult↗
PubMed2002

Transfer function analysis of positron-emitting tracer imaging system (PETIS) data.

Quantitative analysis of the two-dimensional image data obtained with the positron-emitting tracer imaging system (PETIS) for plant physiology has been carried out using a transfer function analysis method. While a cut leaf base of Chinese chive (Allium tuberosum Rottler) or a cut stem of soybean (Glycine max L.) was immersed in an aqueous solution containing the [18F] F- ion or [13N]NO3- ion, tracer images of the leaf of Chinese chive and the trifoliate of soybean were recorded with PETIS. From the time sequence of images, the tracer transfer function was estimated from which the speed of tracer transport and the fraction moved between specified image positions were deduced.

Allium↗
PubMed2004

Loss-of-function analysis of EphA receptors in retinotectal mapping.

EphA tyrosine kinases are thought to act as topographically specific receptors in the well-characterized projection map from the retina to the tectum. Here, we describe a loss-of-function analysis of EphA receptors in retinotectal mapping. Expressing patches of a cytoplasmically truncated EphA3 receptor in chick retina caused temporal axons to have reduced responsiveness to posterior tectal repellent activity in vitro and to shift more posteriorly within the map in vivo. A gene disruption of mouse EphA5, replacing the intracellular domain with beta-galactosidase, reduced in vitro responsiveness of temporal axons to posterior target membranes. It also caused map abnormalities in vivo, with temporal axons shifted posteriorly and nasal axons anteriorly, but with the entire target still filled by retinal axons. The anterior shift of nasal axons was not accompanied by increased responsiveness to tectal repellent activity, in contrast to the comparable anterior shift in ephrin-A knock-outs, helping to resolve a previous ambiguity in interpreting the ephrin gene knock-outs. The results show the functional requirement for endogenous EphA receptors in retinotectal mapping, show that the receptor intracellular domain is required for a forward signaling response to topographic cues, and provide new evidence for a role of axon competition in topographic mapping.

Animals↗
PubMed2001

Kinetic linked-function analysis of the multiligand interactions on Mg(2+)-activated yeast pyruvate kinase.

The multiligand interactions governing the allosteric response of Mg(2+)-activated yeast pyruvate kinase (YPK) during steady-state turnover were quantitated by kinetic linked-function analysis. The substrate, PEP, the enzyme-bound divalent metal, Mg(2+), and the allosteric effector, FBP, positively influence each other's interaction with the enzyme in the presence of saturating concentrations of the second substrate, MgADP. The presence of Mg(2+) enhances the interaction of PEP and of FBP with YPK by -2.0 and -1.0 kcal/mol, respectively. The simultaneous interaction of PEP, Mg(2+), and FBP with YPK is favored by -4.1 kcal/mol over the sum of their independent binding free energies. The coupling free energies measured for Mg(2+)-activated YPK are weaker than the corresponding coupling free energies measured for Mn(2+)-activated YPK [Mesecar, A., and Nowak, T. (1997) Biochemistry 36, 6792, 6803], but are consistent with results of thermodynamic measurements with the Mg(2+)-YPK complex [Bollenbach, T. J., and Nowak, T. (2001) Biochemistry 36, 13088-13096]. A comparison of ligand binding data measured by kinetic and thermodynamic linked-function analyses reveals that the MgADP complex modulates both the binding of the other three ligands and the two- and three-ligand coupling interactions between the other three ligands. Enzyme-bound Mg(2+) does not influence the homotropic cooperativity in PEP binding to YPK. It is the MgADP complex that induces homotropic cooperativity in PEP binding. It is the enzyme-bound Mn(2+) that induces homotropic binding of PEP with Mn(2+)-activated YPK. These results lend support to the hypothesis that divalent metals modulate the interactions of ligands on YPK and that divalent metals play a role in regulation of the glycolytic pathway.

Adenosine Diphosphate↗
PubMedDate not supplied

Feasibility of ventricular function analysis by digital subtraction angiography.

Continuous or cine mode of digital subtraction angiography (DSA) following intravenous injection of contrast media was evaluated in regard to feasibility of obtaining physiologic data in cardiac abnormalities. Computer programs for cardiac function analysis including stroke volume, ejection fraction and display of left ventricular wall motion in end-diastole and end-systole have been developed with use of automatic contour plotting and densitometry for depth information. Experiments with contrast-filled balloons demonstrated good correlation between the true volumes and the calculated volumes. Clinical study also demonstrated good correlation between the values obtained from conventional left ventriculography and DSA.

Angiography↗
PubMed1993

Functional analysis of matrix proteins expressed from cloned genes of measles virus variants that cause subacute sclerosing panencephalitis reveals a common defect in nucleocapsid binding.

We have developed an in vitro nucleocapsid-binding assay for studying the function of the matrix (M) protein of measles virus (MV) (A. Hirano, A. H. Wang, A. F. Gombart, and T. C. Wong, Proc. Natl. Acad. Sci. USA, 89:8745-8749, 1992). In this communication we show that the M proteins of three MV strains that cause acute infection (Nagahata, Edmonston, and YN) bind efficiently to the viral nucleocapsids whereas the M proteins of four MV strains isolated from patients with subacute sclerosing panencephalitis (SSPE) (Biken, IP-3, Niigata, and Yamagata) fail to bind to the viral nucleocapsids. MV Biken (an SSPE-related virus) produces variant M sequences which encode two antigenically distinct forms of M protein. A serine-versus-leucine difference is responsible for the antigenic variation. MV IP-3 (an SSPE-related virus) also produces variant M sequences, some of which have been postulated to encode a functional M protein responsible for the production of an infectious revertant virus. However, the variant M proteins of Biken and IP-3 strains show no nucleocapsid-binding activity. These results demonstrate that the nucleocapsid-binding function is conserved in the M proteins of MV strains that cause acute infection and that the M proteins of MV strains that cause SSPE exhibit a common defect in this function. Analysis of chimeric M proteins indicates that mutations in the amino-terminal, carboxy-proximal, or carboxy-terminal region of the M protein all abrogate nucleocapsid binding, suggesting that the M protein conformation is important for interaction with the viral nucleocapsid.

Antigens, Viral↗
PubMed1993

A discriminant function analysis of various interferon parameters among alcoholics and heavy smokers.

A three-group design of alcoholics, heavy smokers and controls was used to investigate the status of the interferon system, including natural killer cell activity. Group differences were indicated via discriminant function analysis which correctly classified 86% of subjects. Test-retest relations were investigated for 14 subjects following a 30-day alcoholic inpatient program. Whereas significant immune suppression was indicated at the time of detoxification, recovery was evident at the 30-day follow-up. Results are discussed in terms of the significance of alcohol abuse on immune system functioning with consequences for susceptibility to viruses, bacteria and medical illnesses.

Adult↗
PubMed1997

Structural and functional analysis of the Pig-a protein that is mutated in paroxysmal nocturnal hemoglobinuria.

There is now convincing evidence that the Pig-a gene is mutated in patients with paroxysmal nocturnal hemoglobinuria (PNH), a disease in which one or more clones of hematopoietic cells have incomplete assembly of glycosylphosphatidylinositol (GPI) anchors and absence of GPI-linked protein expression on the cell surface. Little is known, however, about the Pig-a protein product that is necessary for GPI anchor bioassembly. Relatively few substitution (missense) Pig-a gene mutations have been identified, but we noted two apparent clusters at codons 128-129 and 151-156 and hypothesized that these might represent critical regions of the Pig-a protein. We therefore used site-directed mutagenesis to create conservative mutations in the Pig-a protein, then performed structural and functional analysis. Each Pig-a mutation generated a Pig-a protein of normal size and stability, but certain mutations had substantial deleterious effects on protein function. Conservative mutation of codons histidine 128 (H128), serine 129 (S129), and serine 155 (S155) had greatly diminished function, while mutations of flanking residues had no effect on function. Our results represent the first structure/function analysis of the Pig-a protein, and suggest that codons H128, S129, and S155 represent critical regions of the Pig-a protein. Our results also suggest a means by which transgenic mice with a "partial knock-out" of Pig-a function could be generated, which would allow investigation of PNH in an animal model.

Amino Acid Substitution↗
PubMed1999

Functional analysis of acid and neutral sphingomyelinases in vitro and in vivo.

The molecular cloning and the elucidation of the gene structures of the acid (aSMase) and a neutral sphingomyelinases (nSMase) of mouse and human facilitated the structural and functional analysis of these enzymes responsible for the catabolism of sphingomyelin present ubiquitously in the membrane lipid bilayer of mammalian cells. The protein and enzymic properties of the glycoprotein aSMase and of a non-glycosylated nSMase residing in the membranes of the endoplasmic reticulum have been analysed in the native as well as in the recombinant shingomyelinases. Important insight was gained from gene targeting experiments in which an aSMase deficient mouse line was generated which mimics the neurovisceral form of the human Niemann-Pick disease. The availability of the cloned aSMase and nSMases discovered so far led to a genetic approach to the verification of the concept that these enzymes in the 'sphingomelin cycle' are responsible for the generation of ceramide regarded as a lipophilic second messenger in the intracellular signal cascades activated by e.g. TNF-alpha, Fas ligand or cellular stress. All the available evidence derived from the aSMase deficient mouse line and several cell lines overexpressing aSMase and nSMase questions a role of ceramide released by the mammalian sphingomyelinases known so far in intracellular signal transduction.

Amino Acid Sequence↗
PubMed2003

Use of functional analysis methodology in the evaluation of medication effects.

The atypical antipsychotic medication risperidone was evaluated using a double-blind, placebo-controlled design in the treatment of destructive behavior in two individuals with autism. Pre-medication functional analyses indicated that destructive behavior was maintained by escape from demands, attention, or access to tangible items. For both individuals, destructive behavior during the demand condition was significantly reduced during the medication phases, whereas destructive behavior continued to occur to obtain tangible items (Reggie) and attention (Sean). In addition, there appeared to be a differential effect of the medication on self-injurious behavior (SIB) versus aggression for Sean. Results of the study demonstrate how functional analysis may provide information on those conditions and behaviors that are most likely to be affected by a specific medication.

Adult↗
PubMed1992

Functional analysis of the rat insulin-like growth factor I gene and identification of an IGF-I gene promoter.

Insulin-like growth factor I (IGF-I) mediates many of the systemic growth-promoting effects of growth hormone and also functions as a locally acting growth stimulator. In mammals, IGF-I gene expression is complicated, as the gene is transcribed and processed into multiple mRNAs (ranging in length from less than 1 to nearly 7.5 kb) that encode at least two protein precursors. As a step toward understanding the regulation of IGF-I, we report the complete organization of the rat IGF-I gene, including identification of the structural determinants for all IGF-I mRNA species, and an initial functional analysis of its promoters. The gene is composed of 6 exons distributed over nearly 80 kb of chromosomal DNA and is structurally heterogeneous. Several transcription start sites were identified within IGF-I exons 1 and 2, adjacent to presumptive promoters 1 and 2, respectively, and at least three polyadenylation sites were mapped to exon 6. To test promoter function, fusion genes were constructed linking fragments of IGF-I DNA to a reporter plasmid. Chimeric genes containing at least 395 bp of DNA from the 5'-flanking region of exon 1 enhanced luciferase activity after transfection into the IGF-I-producing SK-N-MC cell line, while fusion plasmids containing up to 1,300 bp of DNA from the 5'-flanking region of exon 2 were inactive. Relative levels of IGF-I mRNAs containing exons 1 or 2 varied among different rat tissues, although in response to acute or chronic growth hormone treatment both classes of transcripts were induced coordinately in rat liver. These observations represent the first thorough characterization of a mammalian IGF-I gene, and provide a starting point for defining the mechanisms by which growth hormone and other trophic factors regulate IGF-I gene expression.

Amino Acid Sequence↗
PubMed1989

Disturbed endocrine function in the psychoses. II: Discriminant function analysis of multihormone data.

Discriminant function analyses were performed on plasma concentrations of prolactin, growth hormone, cortisol, TSH, and the neurophysins measured over 17 hours in 70 newly admitted drug-free psychiatric patients and 35 control subjects. The hormone data distinguished between patients with different classes of drug-free psychosis (26 schizophrenic, 12 with manic disorder, 10 with major depressive disorder, psychotic subtype, 9 with schizoaffective mania (SAM]. Higher plasma cortisol and lower TSH concentrations separated eight of nine SAM patients from all others.

Bipolar Disorder↗
PubMed2004

Transcriptional regulation of the mouse deoxycytidine kinase: identification and functional analysis of nuclear protein binding sites at the proximal promoter.

Deoxycytidine kinase (EC 2.7.1.74, dCK) catalyzes the phosphorylation of deoxynucleosides and several nucleoside analogues that are important in antiviral and cancer chemotherapy. The enzyme is predominantly expressed in lymphoid tissue by as yet poorly defined mechanisms. In this work, we have studied the mouse dCK regulatory region to understand the molecular details of the tissue specific expression of the enzyme. DNase I footprinting and electrophoretic mobility shift assays using nuclear extracts from mouse lymphocytes (EL-4, T cells; J558, B cells) and non-lymphoid cells (L929, fibroblasts) demonstrated the existence of at least six cis-acting elements (FP-1-FP-6) within the proximal promoter region. Functional analysis revealed that all the elements necessary to promote high level transcription of the mdCK gene are located downstream the transcription start site. 5'-Deletion and site-directed mutagenesis assays demonstrated the importance of four GC-rich regions, which bind Sp-1 and Sp-3 transcription factors. In addition, we identified a site (FP-3) located at the -282 to -310 nucleotide region of the promoter, which binds NF-1, only in B cells. Analysis of point mutations introduced at the different regions revealed functional differences in their role in mdCK transcription in the cell lines used.

5' Flanking Region↗
PubMed1999

The reliability of in vivo structure-function analysis of tRNA aminoacylation.

The G.U wobble base-pair in the acceptor helix of Escherichia coli tRNAAlais critical for aminoacylation by the alanine synthetase. Previous work by several groups probed the mechanism of enzyme recognition of G.U by a structure-function analysis of mutant tRNAs using either a cell assay (amber suppressor tRNA) or a test tube assay (phage T7 tRNA substrate and purified enzyme). However, the aminoacylation capacity of particular mutant tRNAs was about 10(4)-fold higher in the cell assay. This led us to scrutinize the cell assay to determine if any parameter exaggerates the extent of aminoacylation in mutants forming substantial amounts of alanyl-tRNAAla. In doing so, we have refined and developed experimental designs to analyze tRNA function. We examined the level of aminoacylation of amber suppressor tRNAAlawith respect to the method of isolating aminoacyl-tRNA, the rate of cell growth, the cellular levels of alanine synthetase and elongation factor TU (EF-Tu), the amount of tRNA and the characteristics of EF-Tu binding. Within the precision of our measurements, none of these parameters varied in a way that could significantly amplify cellular alanyl-tRNAAla. A key observation is that the extent of aminoacylation of tRNAAlawas independent of tRNAAlaconcentration over a 75-fold range. Therefore, the cellular assay of tRNAAlareflects the substrate quality of the molecule for formation of alanyl-tRNAAla. These experiments support the authenticity of the cellular assay and imply that a condition or factor present in the cell assay may be absent in the test tube assay.

Acylation↗
PubMed1997

Primary structure and functional analysis of the soluble transducer protein HtrXI in the archaeon Halobacterium salinarium.

Signal transduction in the archaeon Halobacterium salinarium is mediated by a family of 13 soluble and membrane-bound transducers. Here, we report the primary structure and functional analysis of one of the smallest halobacterial putative transducers, HtrXI. Hydropathy plot analysis of the primary structure predicts no membrane-spanning segments in HtrXI. The fractionation of the H. salinarium proteins confirmed that HtrXI is a soluble protein. Capillary assay with an HtrXI deletion mutant and a complemented strain revealed that this soluble transducer is involved in Asp and Glu taxis. In vivo analysis of the methylesterase activity of the htrXI-1 deletion mutant suggests that HtrXI plays an important role in the adaptation of the chemotactic responses to His, Asp, and Glu, which are attractants for halobacteria. Stimulation by Asp and Glu causes demethylation of HtrXI and of another putative transducer, HtrVII. But addition of His to halobacterial cells increases HtrXI methylation together with that of other putative transducers. In the absence of HtrXI, stimulation by either Glu or His does not decrease or increase the methylation of any putative transducers. Therefire, the HtrXI transducer appears to have a complex role in chemotaxis signal transduction.

Amino Acid Sequence↗
PubMed2005

Lysinuric protein intolerance: identification and functional analysis of mutations of the SLC7A7 gene.

Lysinuric protein intolerance (LPI) is an inherited hyperdibasic aminoaciduria caused by defective cationic amino acid (CAA) transport at the basolateral membrane of epithelial cells in the intestine and kidney. LPI is relatively common in Finland and a few clusters of patients are known in Italy and Japan. The SLC7A7 gene, mutated in LPI patients, encodes the y+LAT-1 protein which is the light subunit of a heterodimeric CAA transporter. We performed the mutation analysis in seven probands from five unrelated LPI families and identified five novel SLC7A7 mutations (p.M50K, p.T188I, p.R333M, p.Y457X, and c.499+?_629-?). By expression studies in X. laevis oocytes or patient's renal tubular cells, the functional analysis of altogether eight SLC7A7 mutations is here reported. Noteworthy, the p.R333M mutation, caused by a G to T transversion of the last nucleotide at 3' end of exon 7, disrupts a functional splicing motif generating misspliced transcripts. Three of the novel mutations were found in patients originating from Greece and Pakistan thus increasing the list of ethnic backgrounds where LPI mutant alleles are present. This reinforces the view that the rarity of LPI outside Finland might be ascribed to misdiagnosis of this disease.

Alleles↗
PubMed2004

KIAA0008 gene is associated with invasive phenotype of human hepatocellular carcinoma--a functional analysis.

PURPOSE: To investigate the function of the KIAA0008 gene, one of the leading genes in the signature associated with hepatocellular carcinoma (HCC) metastasis selected by cDNA microarray, and especially its possible roles in invasion and metastasis of hepatocellular carcinoma. METHODS: Expression levels of KIAA0008 in 27 primary tumors and 23 matched non-tumor liver tissues from HCC patients, and four HCC cell lines with different metastatic potentials were detected by semi-quantitative RT-PCR and real-time RT-PCR. Recombinant expression plasmid vectors of the KIAA0008 gene were constructed and transfected into HCC cells. The subcellular localization of the KIAA0008 gene product and in vitro effects of KIAA0008 overexpression on proliferation and invasion of HCC cell line were also investigated. RESULTS: Expression levels of KIAA0008 in HCC tissues were statistically higher than those of paired non-tumorous liver tissues (P < 0.001, paired Wilcoxon test), and in HCCs with high invasiveness these were statistically higher than those with low invasiveness (P = 0.002, Mann-Whitney test). In the four HCC cell lines with an identical genetic background and stepwise higher invasiveness potentials, its expression was consistent with their invasiveness potential. The KIAA0008 gene product was concentrated on the nucleus and cell membrane of HCC cells, without any distribution in the cytoplasm. Overexpression of KIAA0008 in the MHCC97L cell line resulted in increased cell proliferation, colony formation, and invasion. CONCLUSIONS: KIAA0008 expression is associated with invasiveness of HCC; overexpression of KIAA0008 leads to a more invasive phenotype of HCC cell lines.

Adult↗
PubMed2004

Approach for functional analysis of glycan using RNA interference.

The elucidation of the biological role of glycan is one of the most important issues to be resolved following the genome project. RNA interference is becoming an efficient reverse genetic tool for studying gene function in model organisms, including C.elegans and Drosophila melanogaster. Our molecular evolutionary study has shown that a prototype of glycosyltransferases, which synthesize a variety of glycan structures in the Golgi apparatus, was conserved between mammals and Drosophila. For analyses of the basic physiological functions of glycans, we established the Drosophila inducible RNAi knockdown system and applied it to one glycosyltransferase and one transporter, proteoglycan UDP-galactose: beta-xylose beta1,4galactosyltransferase I and the PAPS-transporter, respectively. If on the silencing of each gene induced ubiquitously under the control of a cytoplasmic actin promoter, the RNAi knockdown fly died, then the protein was indispensable for life. The expression of the target gene was disrupted specifically and the degree of interference was well correlated with the phenotype. The inducible RNAi knockdown fly obtained using the GAL4-UAS system will pave the way for the functional analysis of glycans.

Actins↗