SEARCH · PubMed Health

Results for “AI”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 469 records · Page 26Linked to original sources

PubMed1985

Structure of layer II in cat primary auditory cortex (AI).

The cytoarchitecture, myeloarchitecture, neuronal architecture, and intrinsic and laminar organization of layer II were studied in the primary auditory cortex (AI) of adult cats. The chief goal was to describe the different types of cells and axons to provide a framework for experimental studies of corticocortical connections or of neurons accumulating putative neurotransmitters. A further goal was to differentiate layer II from layer III. Layer II extends from 150-200 micron to about 400 micron beneath the pia and has two subparts. The superficial stratum, layer IIa, has many small, chiefly non-pyramidal neurons, primarily with round or oval perikarya, and a sparse, fine, and irregularly arranged axonal plexus. Layer IIb somata are larger and more densely packed and there is a more developed vertical and lateral axonal plexus. The border with layer III was marked by numerous large pyramidal cells with a thicker apical dendrite with more developed basal dendritic arbors than those of layer II pyramidal cells. Eight varieties of neurons were recognized in Golgi-impregnated material. These included small and medium-sized pyramidal cells, whose apical dendrites often ramified in layer I; bipolar and bitufted cells with polarized, sparse dendritic arbors; small smooth or sparsely spinous multipolar cells with radiating dendrites and small dendritic fields; spinous multipolar cells, whose large dendritic fields had more extensive apical than basal arbors; large sparsely spinous multipolar cells with smooth, robust apical dendrites; tufted multipolar cells with highly developed apical dendrites and some dendritic appendages; and extraverted multipolar cells with a broad, candelabra-shaped dendritic configuration, and with most dendrites oriented at right angles to the pia. The axons of the different cell types had the following general dispositions: those arising from the pyramidal cells could often be traced into the white matter but had many local branches as well; those of the other neurons had more or less extensive local axonal collateral systems and fewer branches which appeared to be corticofugal. However, the complete trajectory of the axons was not always impregnated in the adult material.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

PubMed2006

cAMP cascade (PKA, Epac, adenylyl cyclase, Gi, and phosphodiesterases) regulates myelin phagocytosis mediated by complement receptor-3 and scavenger receptor-AI/II in microglia and macrophages.

The removal by phagocytosis of degenerated myelin is central for repair in Wallerian degeneration that follows traumatic injury to axons and in autoimmune demyelinating diseases (e.g., multiple sclerosis). We tested for roles played by the cAMP cascade in the regulation of myelin phagocytosis mediated by complement receptor-3 (CR3/MAC-1) and scavenger receptor-AI/II (SRAI/II) separately and combined in mouse microglia and macrophages. Components of the cAMP cascade tested are cAMP, adenylyl cyclase (AC), Gi, protein kinase A (PKA), exchange protein directly activated by cAMP (Epac), and phosphodiesterases (PDE). PKA inhibitors H-89 and PKI(14-22) amide inhibited phagocytosis at normal operating cAMP levels (i.e., those occurring in the absence of reagents that alter cAMP levels), suggesting activation of phagocytosis through PKA at normal cAMP levels. Phagocytosis was inhibited by reagents that elevate endogenous cAMP levels to above normal: Gi-inhibitor Pertussis toxin (PTX), AC activator Forskolin, and PDE inhibitors IBMX and Rolipram. Phagocytosis was inhibited also by cAMP analogues whose addition mimics abnormal elevations in endogenous cAMP levels: nonselective 8-bromo-cAMP, PKA-specific 6-Benz-cAMP, and Epac-specific 8-CPT-2'-O-Me-cAMP, suggesting that abnormal high cAMP levels inhibit phagocytosis through PKA and Epac. Altogether, observations suggest a dual role for cAMP and PKA in phagocytosis: activation at normal cAMP levels and inhibition at higher. Furthermore, a balance between Gi-controlled cAMP production by AC and cAMP degradation by PDE maintains normal operating cAMP levels that enable efficient phagocytosis.

Acetylcysteine↗

PubMed2006

Non-PKC DAG/phorbol-ester receptor(s) inhibit complement receptor-3 and nPKC inhibit scavenger receptor-AI/II-mediated myelin phagocytosis but cPKC, PI3k, and PLCgamma activate myelin phagocytosis by both.

Complement-receptor-3 (CR3/MAC-1), scavenger-receptor-AI/II (SRAI/II), and Fcgamma-receptor (FcgammaR) can mediate myelin phagocytosis in macrophages and microglia. Paradoxically, after injury to CNS axons these receptors are expressed but myelin is not phagocytosed, suggesting that phagocytosis is subject to regulation between efficient and inefficient states. In the present work, we focus on CR3/MAC-1 and SRAI/II-mediated myelin phagocytosis. Phagocytosis by CR3/MAC-1 and SRAI/II was inhibited by cPKC inhibitor Go-6976, general-PKC inhibitors Ro-318220 and calphostin-C, and BAPTA/AM, which chelates intracellular Ca2+ required for cPKC activation. Signaling/activation by cPKC are thus suggested. PMA, which mimics diacylglycerol (DAG) as an activator of cPKC, novel-PKC (nPKC), and non-PKC DAG-driven molecule(s), produced a dose-dependent dual effect on phagocytosis by CR3/MAC-1 and SRAI/II, i.e., augmentation at low concentrations and inhibition at high concentrations. Inhibition of phagocytosis by CR3/MAC-1 was enhanced by combining inhibiting concentrations of PMA with PKC inhibitors Go-6976 or Ro-318220, suggesting inhibition by PMA/DAG-driven non-PKC molecule(s). In contrast, inhibition of phagocytosis by SRAI/II was enhanced by combining inhibiting concentrations of PMA with cPKC inhibitor Go-6976 but not with general-PKC inhibitor Ro-318220, suggesting inhibition by nPKC. Phagocytosis by CR3/MAC-1 and SRAI/II was further inhibited by PI3K inhibitors wortmannin and LY-294002 and PLCgamma inhibitor U-73122. Altogether, our observations suggest that CR3/MAC-1 and SRAI/II-mediated myelin phagocytosis share activation by PI3K, PLCgamma and cPKC. The two differ, however, in that non-PKC DAG-driven molecule(s) inhibit CR3/MAC-1-mediated phagocytosis, whereas nPKC inhibit SRAI/II-mediated phagocytosis. Each of these signaling steps may be targeted for regulating CR3/MAC-1 and/or SRAI/II-mediated phagocytosis between efficient and inefficient states.

Animals↗

PubMed1999

Hepatocyte nuclear factor 4-mediated activation of rat CYP3A1 gene and its modes of modulation by apolipoprotein AI regulatory protein I and v-ErbA-related protein 3.

CYP3A1 gene (P450/6betaB) encodes testosterone 6beta-hydroxylase (EC 1.14.14.1) in rats. The promoter region of CYP3A1 gene contains three binding sites for nuclear factors: 6betaB-A (-105 to -86), 6betaB-B (-139 to -118), and 6betaB-C (-164 to -145). The 6betaB-A site shows a high degree of similarity to a consensus sequence of the binding site of hepatocyte nuclear factor 4 (HNF-4) and also to the 6betaA-A site on the rat CYP3A2 gene promoter region. Our previous study suggested an involvement of the 6betaA-A site in the basal transactivation of CYP3A2 gene using HepG2 cells. In the present study, transactivation through the 6betaB-A and 6betaA-A sites of CYP3A1 and CYP3A2 genes has directly been shown by coexpression of HNF-4 and CYP3A1 or CYP3A2 promoter-reporter fused genes. Similar experiments further showed that nuclear factor binding at the 6betaB-B site hampered HNF-4-mediated transactivation of CYP3A1 gene. Recombinant apolipoprotein AI regulatory protein I (ARP-1) and v-ErbA-related protein 3 (EAR-3) are shown to suppress HNF-4-mediated activation at the 6betaB-B site without competition of HNF-4.

Animals↗

PubMed2000

Cholesterol flux between lipid vesicles and apolipoprotein AI discs of variable size and composition.

Reconstituted discoidal high-density lipoproteins (rHDLs) of apolipoprotein AI are able to induce leakage of the internal aqueous space of lipid vesicles (A. Tricerri et al., 1998, Biochim. Biophys. Acta 1391, 67-78) and such interaction depends on the cholesterol content of vesicles and rHDL as well as the rHDL size. With the aim of knowing if this rHDL/vesicle interaction plays some role in the cholesterol exchange, the time course for bidirectional radiolabeled cholesterol transfer between 1-palmitoyl-2-oleoylphosphatidylcholine (POPC) vesicles and different sized rHDLs was measured. The results show that size increase in the rHDL decreases the rate constant for cholesterol transfer from POPC/cholesterol vesicles and that the initial presence of cholesterol in the vesicles results in an increased rate constant for cholesterol transfer from the rHDLs. This cannot be explained by a simple aqueous diffusion mechanism. The existing correlation between rHDL/vesicle interaction and cholesterol transfer rate suggests that besides the aqueous diffusion, another mechanism involving the binding or interaction between donor and acceptor may occur. This fact may be of physiological relevance since the relative high affinity of small cholesterol-poor discs for cell membranes could facilitate the cholesterol efflux, while the decreased membrane affinity as a consequence of cholesterol enrichment and increase in size would decrease the rate of transfer in the opposite direction.

Apolipoprotein A-I↗

PubMed1994

Vitamin A regulates the expression of apolipoprotein AI and CIII genes in the rat.

The effect of vitamin A on the expression of apoAI and CIII genes in intact rats was studied. In vitamin A-deficient rats, the hepatic level of apoAI mRNA was increased and enhanced by an oral administration of excess retinoic acid(RA). A similar administration to normal rats caused an increase in the apoAI mRNA level in the intestine without affecting that of hepatic mRNA. Though the hepatic level of apo CIII mRNA was not affected by the vitamin A status, the intestinal level was positively regulated by vitamin A. These findings show that vitamin A regulates the expression of apolipoprotein AI and CIII genes in a tissue-specific and complex fashion.

Animals↗

PubMed1999

Prediction of blood glucose levels in diabetic patients using a hybrid AI technique.

One of the problems in the management of the diabetic patient is to balance the dose of insulin without exactly knowing how the patient's blood glucose concentration will respond. Being able to predict the blood glucose level would simplify the management. This paper describes an attempt to predict blood glucose levels using a hybrid AI technique combining the principal component method and neural networks. With this approach, no complicated models or algorithms need be considered. The results obtained from this fairly simple model show a correlation coefficient of 0.76 between the observed and the predicted values during the first 15 days of prediction. By using this technique, all the factors affecting this patient's blood glucose level are considered, since they are integrated in the data collected during this time period. It must be emphasized that the present method results in an individual model, valid for that particular patient under a limited period of time. However, the method itself has general validity, since the blood glucose variations over time have similar properties in any diabetic patient.

Algorithms↗

PubMed1997

Rapid movement of newly synthesized chicken apolipoprotein AI to trans-Golgi network and its secretion in Madin-Darby canine kidney cells.

MDCK cells were utilized to study the biosynthesis and secretion of chicken apolipoprotein AI (apoAI). A full-length apoAI cDNA in an eukaryotic expression vector was transfected into a MDCK-TGG cell line, expressing a trans-Golgi network (TGN) marker (TGG), and stable clones expressing apoAI were selected. Pulse-chase and cell fractionation studies showed that, compared to gp 80 (an endogenous secretory protein), apoAI was rapidly transported from RER to Golgi complex within 5 min and released from the Golgi complex to the cell exterior by 30 min. Immunofluorescence and three-dimensional laser scanning confocal microscopy revealed that at steady state apoAI was predominantly localized in the TGN. Transferrin uptake experiments showed that apoAI, localized in the TGN, was derived primarily from biosynthetic and not from endocytic routes. ApoAI was secreted in a nonpolarized manner. We suggest that apoAI stays transiently in the TGN prior to its secretion and that the major events of apoAI biosynthesis in vivo and in MDCK cells are conserved. Possible mechanisms of rapid ER to Golgi transport and TGN localization of apoAI are discussed.

Animals↗

PubMed1998

Common genetic variants of lipoprotein lipase and apolipoproteins AI-CIII that relate to coronary artery disease: a study in Chinese and European subjects.

The large ethnic differences in prevalence of coronary artery disease between China and Europe may relate to both genetic and environmental differences. To assess possible genetic factors we have therefore studied the frequencies of disease-related variants of genes involved in lipid transport in 69 hypertriglyceridemic Chinese subjects and 74 healthy Chinese controls. The loci studied include lipoprotein lipase (Asp9Asn, Asn291Ser, Ser447Ter, and Thr361Thr); apolipoprotein A1 (restriction sites at MspI, XmnI, and PstI); and apolipoprotein (apo) CIII (G3175C). All these variants have been shown in previous literature publications to relate to either dyslipidemia and/or premature coronary heart disease in Caucasians. Two disease-related genetic variants in Europeans (Asp9Asn and Asn291Ser) were not found in the Chinese sample. The apo CIII G3175C variant was found more frequently in the upper tertile distributions for apolipoprotein CIII, apolipoprotein E, and plasma triglyceride/HDL ratios (P < 0.05). The rare allele of the apo AI MspI restriction site polymorphic variant was also found more frequently in the upper tertiles for apo CIII, apo E, and plasma triglyceride/HDL ratios (P < 0.04). Eleven of the most lipaemic Chinese subjects (with fasting plasma triglycerides >700 mg/dl) were analyzed for DNA sequence variation. One novel mutation was observed C1338A (which is a silent mutation at Thr361) and two others that are also found in European subjects (Ala261Thr and Ser447Ter). We conclude that genetic differences between Chinese and Europeans may have an effect on the prevalence of coronary artery risk factors involved in lipid transport, and further extended study is warranted.

Alleles↗

PubMed1993

Several neuronal and axonal types form long intrinsic connections in the cat primary auditory cortical field (AI).

Intrinsic connections in the cat primary auditory field (AI) as revealed by injections of Phaseolus vulgaris leucoagglutinin (PHA-L) or biocytin, had an anisotropic and patchy distribution. Neurons, labelled retrogradely with PHA-L were concentrated along a dorsoventral stripe through the injection site and rostral to it; the spread of rostrally located neurons was greater after injections into regions of low rather than high characteristic frequencies. The intensity of retrograde labelling varied from weak and granular to very strong and Golgi-like. Out of 313 Golgi like retrogradely labelled neurons 79.6% were pyramidal, 17.2% multipolar, 2.6% bipolar, and 0.6% bitufted; 13.4% were putatively inhibitory, i.e. aspiny or sparsely spiny multipolar, or bitufted. Individual anterogradely labelled intrinsic axons were reconstructed for distances of 2 to 7 mm. Five main types were distinguished on the basis of the branching pattern and the location of synaptic specialisations. Type 1 axons travelled horizontally within layers II to VI and sent collaterals at regular intervals; boutons were only present in the terminal arborizations of these collaterals. Type 2 axons also travelled horizontally within layers II to VI and had rather short and thin collateral branches; boutons or spine-like protrusions occurred in most parts of the axon. Type 3 axons travelled obliquely through the cortex and formed a single terminal arborization, the only site where boutons were found. Type 4 axons travelled for some distance in layer I; they formed a heterogeneous group as to their collaterals and synaptic specializations. Type 5 axons travelled at the interface between layer VI and the white matter; boutons en passant, spine-like protrusions, and thin short branches with boutons en passant were frequent all along their trajectory. Thus, only some axonal types sustain the patchy pattern of intrinsic connectivity, whereas others are involved in a more diffuse connectivity.

Animals↗

PubMed1995

C to T and/or G to A transitions are responsible for loss of a MspI restriction site at the 5'-end of the human apolipoprotein AI gene.

We detected the loss of a MspI restriction site by a C to T transition at +83 bp and a G to A transition at +84 bp of the 5'-end non-coding region of the human apolipoprotein AI gene. This base change occurred at the "hot spot" (CCGG) for methylation, which may be important in the regulation of gene expression. The population frequency for the loss of the MspI site is 6.1%.

Alleles↗

PubMed1986

Confirmation of the close linkage between the loci for human apolipoproteins AI and AIV by the use of a cloned cDNA probe and two restriction site polymorphisms.

We have isolated a cDNA probe for human apolipoprotein AI (apoAI) and used two DNA polymorphisms detected by this probe to analyse the inheritance of the apoAI gene in families informative for apoAIV protein variants. We have thereby increased the lod score for this linkage from 3.01 to 6.32 at a recombination fraction of zero.

Alleles↗

PubMed1986

Haplotypes of the human apoprotein AI-CIII-AIV gene cluster in coronary atherosclerosis.

Restriction fragment length polymorphisms of the apoprotein AI-CIII-AIV gene cluster (on the long arm of chromosome 11) were investigated in a group of Caucasian survivors of myocardial infarction, using genomic hybridisation analysis. Four common haplotypes were identified at this locus, M1P1S1, M2P1S1, M1P2S1, and M2P1S2; where M1 and M2 are the common and uncommon alleles defined using the restriction enzyme MspI, P1 and P2 are the common and uncommon alleles defined by the enzyme PstI, and S1 and S2 are the common and uncommon alleles defined by the enzyme SstI. Seven genotype combinations were observed of approximate frequencies; a/a 0.70 (33/47), a/d 0.15 (7/47), a/b 0.04 (2/47), d/d 0.04 (2/47), a/c 0.02 (1/47), b/c 0.02 (1/47), and c/d 0.02 (1/47). In contrast the corresponding values for normotriglyceridaemic Caucasian controls, without a personal or family history of atherosclerotic heart disease were; 0.83 (40/48), 0.02 (1/48), 0.06 (3/48), 0, 0.04 (2/48), 0.04 (2/48), and 0. The relative incidence of the d haplotype, characterised by the presence of a cleavage site for the enzyme SstI in the fourth exon of the ApoCIII gene, was significantly higher in the patient group (P less than 0.01). However, because of the tight linkage between the polymorphic loci studied, it was not possible to identify haplotypes associated with any greater risk of premature atherosclerosis than when the SstI polymorphism was considered in isolation.

Adult↗

PubMed1983

The resolution of brief interaural time-difference changes: recordings from primary auditory cortical projection field AI of the cat.

The ability of the auditory organ to resolve brief changes in an acoustic signal presented either monaurally or binaurally is not only of great importance in the processing of speech, it is also involved in the localization of sound stimuli and in selective listening. In the latter context, the electric activity of the primary auditory cortical projection field AI of the cat has been studied with the aim of evaluating specific response patterns evoked by brief changes in interaural time difference. The differences in response of the neuron populations sampled by two recording electrodes indicate that, within this area, there are significant differences in temporal resolution ability. Whereas click stimuli elicit distinct potential patterns at the two sites, with a brief change in interaural time difference, a marked response is recorded by only one of the electrodes. This response is characterized by a decrease in amplitude as the interaural time difference is reduced and as the duration of the time-shift stimulus decreases.

Animals↗

PubMed1995

Odontological identification of the victims of flight AI. IT 5148 air disaster Lyon-Strasbourg 20.01.1992.

The authors report on the contribution of odontological identification of the flight AI. IT 5148 air disaster victims, which occurred on 20th January 1992. The identification procedure was difficult due to large numbers of bodies and mutilations and required the involvement of multidisciplinary teams composed of odontologists, forensic pathologists, radiologists and biologists. The authors set up a simple, discriminant classification which was easy to handle by a multidisciplinary team. Four groups were defined according to the matching characteristics between ante and post mortem data. Perfect matching characteristics between ante and post mortem data were achieved in only 44 cases (Group A). Partial matching characteristics between ante and post mortem data were achieved in 12 cases (Group B). In 29 cases, the insufficiency or absence of odontological data (Group C and D) did not enable the victim to be identified. The results of the investigations showed that the dental examination alone enabled 17 victims to be identified and by including a morphological examination the figure reached 33. By the end of the investigations, 85 of the 87 victims were positively identified. Odontological identification is an essential, accurate and rapid method with allows a body to be identified from its dental characteristics. This anthropometrical method of identification is included with the descriptive and the biological methods. The authors present their experience in performing a formal identification of 44 victims in less than 15 days.

Accidents, Aviation↗

PubMed1981

Analysis of short-term changes in reversibly and irreversibly glycosylated haemoglobin AI: relevance to diabetes mellitus.

We have determined the stable (irreversibly glycosylated) fraction of haemoglobin AI (HbAI) on Bio-Rex 70 after incubation of red blood cells in 0.9 % saline solution for 6 h at 37 degrees C. The total (reversibly + irreversibly glycosylated fractions) HbAI was determined before each incubation. Labile (reversibly glycosylated) HbAI represented the difference between total and stable HbAI fractions. Total and stable HbAI fractions were determined during insulin- or meal-induced blood glucose fluctuations in 24 insulin-dependent diabetics and in seven subjects with impaired glucose tolerance. In the diabetics, the maximal fluctuation of total HbAI was 1.47% over 2-12 h, while the simultaneous plasma glucose variation was 21.5 mmol/l. The stable HbAI fraction did not change significantly. In diabetics the differences between the maximal and minimal values of plasma glucose and total HbAI were significantly correlated. Plasma glucose correlated with simultaneously determined total and labile HbAI fractions, but not with stable HbAI. In subjects with impaired glucose tolerance, similar changes in total but not in stable HbAI were observed during an oral glucose tolerance test. We conclude that, although rapid changes in chromatographically determined HbAI are relatively small, the determination of stable HbAI should be performed to circumvent this problem and to ensure a more accurate index of blood glucose control.

Blood Glucose↗

PubMed1990

Studies on the formation, separation, and characterization of cyanogen bromide fragments of human AI apolipoprotein.

We have sought to obtain conditions for cyanogen bromide (CNBr) cleavage of apolipoprotein AI which would preserve, as far as possible, the biological activity of the resulting fragments. We found that the choice of solvent is an important consideration since modification of amino acids in different proteins varies with cleavage conditions. Initially, an analytical technique employing reversed-phase (RP)-HPLC which separates the four CNBr fragments in a single chromatographic step was established to monitor the products and extent of cleavage. In developing this technique, spectral data indicated damage to tyrosine and tryptophan residues during CNBr digestion. This problem was resolved by using 70% trifluoroacetic acid instead of 70% formic acid as the solvent, which had the added benefit of increasing the extent of cleavage of the Met86-Ser87 bond by 50%. We applied the information derived from the analytical RP-HPLC method to achieve the preparative isolation of CNBr fragments. This procedure included a gel permeation chromatography step using a citrate/urea buffer before RP-HPLC to isolate pure fragments in volatile buffers. Finally, we discuss aspects of structural integrity with an emphasis on modification of aromatic amino acids and deamidation of asparagine and glutamine residues.

Amino Acid Sequence↗

PubMed1985

Sensitivity of cat primary auditory cortex (AI) neurons to the direction and rate of frequency modulation.

Responses of 65 single auditory cortex (AI) neurons to frequency-modulated (FM) sweeps with different rates and direction of frequency change were examined quantitatively. Most units responded differentially depending on the characteristics of the FM sweep stimulus. Sixty-five percent of the units encountered responded at least twice as well for one direction of the FM sweep as for the other direction. Of these direction selective neurons, 67% preferred downward-directed FM sweeps (i.e. changing from high to low frequencies) while only 33% preferred upward-directed FM sweeps. The preference for downward-directed FM sweeps was especially clear in EI cells. In addition, cortical neurons often displayed sensitivity to the rate of frequency modulation (speed sensitivity).

Acoustic Stimulation↗