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T P Yu

Publications and source records attributed to T P Yu.

13 recordsLinked to original sources
PubMed2005

Genetic complementation to identify DNA elements that influence complement resistance in Leishmania chagasi.

Past studies showed that Leishmania spp. promastigotes exhibit differential sensitivity to complement mediated lysis (CML) during development in vitro and in vivo. Leishmania chagasi promastigotes in cultures during logarithmic and stationary growth phases are CML-sensitive or CML-resistant when exposed to human serum, respectively, but only in cultures recently initiated with parasites from infected animals; serially passaged cultures become constitutively CML-sensitive regardless of growth phase. Building on these observations, a genetic screen was conducted to identify novel complement resistance factors of L. chagasi. A cosmid library containing genomic DNA was transfected into a promastigote line previously subjected to >50 serial passages. Selection with human serum for CML resistance yielded 12 transfectant clones. Cosmids isolated from 7 of these clones conferred CML resistance when transfected into an independent, high-passage promastigote culture; at 12% human serum, the mean survival of transfectants was 37% (+/- 11.6%), and that of control transfectants was about 1%. Inserts within the 7 cosmids were unique. Determination of the complete DNA sequence for 1 cosmid indicated that its 32-kilobase insert was 89% identical (overall) to a 31-kilobase region of Leishmania major chromosome 36, which is predicted to encode 6 genes, all of which encode hypothetical proteins.

Animals↗
PubMed2001

Gamma-aminobutyric acid type A receptors modulate cAMP-mediated long-term potentiation and long-term depression at monosynaptic CA3-CA1 synapses.

cAMP induces a protein-synthesis-dependent late phase of long-term potentiation (LTP) at CA3-CA1 synapses in acute hippocampal slices. Herein we report cAMP-mediated LTP and long-term depression (LTD) at monosynaptic CA3-CA1 cell pairs in organotypic hippocampal slice cultures. After bath application of the membrane-permeable cAMP analog adenosine 3',5'-cyclic monophosphorothioate, Sp isomer (Sp-cAMPS), synaptic transmission was enhanced for at least 2 h. Consistent with previous findings, the late phase of LTP requires activation of cAMP-dependent protein kinase A and protein synthesis. There is also an early phase of LTP induced by cAMP; the early phase depends on protein kinase A but, in contrast to the later phase, does not require protein synthesis. In addition, the cAMP-induced LTP is associated with a reduction of paired-pulse facilitation, suggesting that presynaptic modification may be involved. Furthermore, we found that Sp-cAMPS induced LTD in slices pretreated with picrotoxin, a gamma-aminobutyric acid type A (GABA(A)) receptor antagonist. This form of LTD depends on protein synthesis and protein phosphatase(s) and is accompanied by an increased ratio of failed synaptic transmission. These results suggest that GABA(A) receptors can modulate the effect of cAMP on synaptic transmission and thus determine the direction of synaptic plasticity.

Animals↗
PubMed2001

Cloning of the full length pig PIT1 (POU1F1) CDNA and a novel alternative PIT1 transcript, and functional studies of their encoded proteins.

PIT1 is an essential regulatory gene of growth hormone (GH), prolactin (PRL) and thyrotropin beta subunit (TSHbeta). Previously, a partial pig PIT1 cDNA and a genomic clone of the entire 3' end of the PIT1 gene was isolated, and polymorphisms at PIT1 were associated with several performance traits in the pig. In order to understand the biological function of the pig PIT1 gene and its possible application in swine genetics, reverse transcriptase-polymerase chain reaction (RT-PCR) was used to complete the cloning of the full length cDNA for pig PIT1. The pig PIT1 cDNA and its deduced protein sequence have approximately 90% and 95% identity, respectively, with the PIT1 cDNA and protein of other mammals (human, bovine, sheep and rodents). Surprisingly, sequence comparison to other pig PIT1 sequences indicated only approximately 93% identity. Additional sequencing confirmed our sequence, and identified a new polymorphism in exon 4. Phylogenetic analysis of several mammalian PIT1 sequences indicates sequencing errors may account for the discrepancies observed in the other pig sequences reported. Several PIT1 alternative spliced forms were also identified by RT-PCR. They were the delta3PIT1 (missing entire exon 3), delta4PIT1 (missing entire exon 4) and PIT1beta (additional 26 amino acids inserted in front of exon 2) transcripts. The delta4PIT1 and PIT1beta transcripts have been found to encode functionally different proteins in rodents. The delta3PIT1 transcript is a novel isoform of PIT1. Potentially different functions between pig delta3PIT1 and PIT1 were analyzed by expressing these proteins in bacteria. The E. coli-expressed PIT1 and delta3PIT1 proteins were used with rat growth hormone (rGH) and rat prolactin (rPRL) promoter DNA in DNA mobility shift assays. The results showed that pig PIT1 can specifically bind rGH and rPRL promoter regions, but that the pig delta3PIT1 cannot, even at very high protein concentrations. Possible protein-protein interactions between delta3PIT1 and PIT1 were tested by mixing protein extracts before the gel shift assay, and the results showed that delta3PIT1 protein did not affect PIT1 binding to its target DNA. These data demonstrate the functionality of the PIT1 cDNA cloned in this study, and identify a novel delta3PIT1 transcript which encodes a protein that cannot bind rGH/rPRL target sequences.

Amino Acid Sequence↗
PubMed1998

Orphanin FQ/nociceptin inhibits synaptic transmission and long-term potentiation in rat dentate gyrus through postsynaptic mechanisms.

Orphanin FQ/nociceptin (OFQ), a recently characterized natural ligand for the opioid receptor-like 1 (ORL1) receptor, shares structural similarity to the endogenous opioids. Our previous study found that OFQ, like classical opioids, modulated synaptic transmission and long-term potentiation (LTP) in the hippocampal CA1 region, suggesting a modulatory role for OFQ in synaptic plasticity involved in learning and memory. In the present study we investigated the action of OFQ in the dentate gyrus and explored possible underlying cellular mechanisms. Field potential recordings showed that OFQ significantly inhibited excitatory synaptic transmission and LTP induction in the dentate lateral perforant path. In the presence of OFQ, the excitatory postsynaptic potential (EPSP) slope-population spike (E-S) curve was shifted to the right, and no significant change was found in paired-pulse facilitation, suggesting a postsynaptic mechanism responsible for the inhibition of synaptic transmission. Under whole cell voltage-clamp conditions, bath application of OFQ activated K+ currents in most granule cells tested at a holding potential of -50 mV, suggesting that OFQ could reduce the excitability of dentate granule cells by hyperpolarizing cell membranes. OFQ also inhibited the amplitude of N-methyl-D-aspartate (NMDA) receptor-mediated excitatory postsynaptic currents (EPSCs) without affecting alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor-mediated EPSCs. This inhibition was not blocked by opioid receptor antagonists. Furthermore, the inward currents evoked by focal application of NMDA to granule cells were suppressed by OFQ in a dose-dependent manner, suggesting that OFQ may suppress LTP by inhibiting the function of postsynaptic NMDA receptors. These results demonstrate that OFQ may negatively modulate synaptic transmission and plasticity in the dentate gyrus through postsynaptic mechanisms, including hyperpolarization of granule cells as well as inhibition of the function of postsynaptic NMDA receptors/channels in dentate granule cells.

Action Potentials↗
PubMed1998

A directed search for quantitative trait loci on chromosomes 4 and 7 in pigs.

Improvements in the porcine genetic map and availability of resource families to study performance traits in pigs have made it possible to re-examine previous findings that linked certain traits to genes or chromosomal regions. Previous studies suggested that chromosomes 4 and 7 may be associated with growth and performance traits. To confirm these previous results, an interval mapping-regression approach was used to determine whether quantitative trait loci (QTL) exist in the Iowa State University reference/resource families. Traits measured were birth weight; body weight at 21 d; weaning weight (weight at 42 d); average daily gain; backfat at the first, 10th, lumbar, and last ribs and average backfat thickness; loin eye area; meat color; marbling; and firmness. The total number of F2 pigs used ranged from 241 to 330 and came from five Chinese x American resource families. Five markers (S0001, SW871, S0175, S0214, and SW445) were genotyped and mapped on chromosome 4, and so were 10 markers (S0064, tumor necrosis factor alpha [TNFalpha], S0102, S0078, S0158, S0066, SW304, SW1083, S0101, and S0212) on chromosome 7. Data were analyzed for each family (breed cross) separately and were also pooled. Experiment-wise thresholds were used to determine significance. Suggestive evidence of QTL on chromosomes 4 and 7 was observed for several traits in pooled and individual family analyses. Suggestive evidence of a QTL with a relatively large effect for average daily gain was detected on chromosome 4 in the pooled analysis. Significant (P < .05) evidence for QTL was seen on chromosome 7 for 10th-rib, last-rib, and average backfat thickness in the pooled data set in a region of the chromosome that was near TNFalpha. These results verify in part that chromosomes 4 and 7 contain QTL for growth and carcass traits.

Animals↗
PubMed1997

Orphanin FQ inhibits synaptic transmission and long-term potentiation in rat hippocampus.

It is known that opioid peptides acting on opioid receptors can modulate hippocampal synaptic functions. Although a novel member of the opioid receptor family, ORL1 receptors, that displays high-sequence homology with classical opioid receptors is abundant in the hippocampus, little is known regarding its role in synaptic function. The present study was designed to investigate whether activation of the ORL1 receptor by its natural ligand, orphanin FQ, could modulate synaptic transmission and synaptic plasticity in the hippocampus. The actions of orphanin FQ in the CA1 and dentate gyrus were examined by field potential recordings in response to stimulation of Schaffer collaterals and perforant path, respectively. Our results showed that orphanin FQ, but not the inactive analog des-Phe1-orphanin FQ, reduced both the slope of the excitatory postsynaptic potentials and population spike amplitude. The inhibitory effect of orphanin FQ is dose dependent and probably involves a presynaptic mechanism, as suggested by the significantly increased paired-pulse facilitation evoked in the presence of orphanin FQ. In addition, orphanin FQ was found to inhibit the induction of long-term potentiation at the Schaffer collateral-CA1 synapse. These results demonstrate that orphanin FQ can function as an inhibitory modulator regulating synaptic transmission and synaptic plasticity in the hippocampus, suggesting that activation of ORL1 receptors may play an important role in synaptic plasticity involved in learning and memory.

Amino Acid Sequence↗
PubMed1995

Association of PIT1 polymorphisms with growth and carcass traits in pigs.

PIT1, a member of the POU-domain family of genes, is a positive regulatory factor of growth hormone, prolactin, and thyrotroph-stimulating hormone beta in several mammals. Therefore, PIT1 was chosen as a candidate gene to investigate its association with growth and carcass traits in pigs. The five Iowa State University reference/resource three-generation families consisting of crosses of Meishan x Duroc, Meishan x Hampshire, Meishan x Landrace, Minzhu x Hampshire, and Minzhu x Landrace were used. The three PIT1 polymorphisms were based on two RFLP using a PIT1 POU-domain cDNA probe and the restriction enzymes BamHI and MspI and a PCR/RFLP using RsaI. Birth, 21-d, and 42-d weights, average daily gain, several backfat measurements, longissimus muscle area, muscle color, marbling, and firmness scores were evaluated for their association with the three PIT1 polymorphisms. Mixed-animal-model analyses were used with the informative family data in which the PIT1 polymorphisms were segregating. Results from mixed-model analyses revealed that pigs with the MspI CC genotype (P < .01) were associated with heavier birth weight (.12 kg) than DD genotype pigs. The MspI CC genotype pigs were also significantly associated with greater average backfat (.41 cm, P < .01), greater first-rib backfat (.45 cm, P < .01), greater last-rib backfat (.32 cm, P < .07), and greater last lumbar backfat (.46 cm, P < .10) than the DD genotype pigs. The CC genotype represents primarily Chinese alleles and may be useful for future genetic improvement in synthetic lines involving Chinese and American pigs.(ABSTRACT TRUNCATED AT 250 WORDS)

Alleles↗
PubMed1994

Three-dimensional quantification of mossy-fiber presynaptic boutons in living hippocampal slices using confocal microscopy.

Confocal laser scanning microscopy (CLSM) was used to visualize presynaptic elements of mossy-fiber synapses in living rat hippocampal slices. Mossy fiber (mf) axons and their boutons were labeled in transverse hippocampal slices by injecting one of three fluorescent dyes (diI, diA, or fast diI) into stratum granulosum of the dentate gyrus and/or stratum lucidum of CA3. Three-dimensional (3D) images of the mf boutons were obtained from serial optical sections in stratum lucidum. The 3D data were used to quantify and characterize the size and shape of the boutons based on their volumes (V) and surface areas (A), and the latter were compared with conventional 2D analyses. Various geometric models were fitted to the V-A relationship, one of which provided a reasonable approximation to the data. The results demonstrate that this approach is useful for quantifying and characterizing the size and shape of mf expansions and raise the possibility of detecting and analyzing in real time activity-dependent modifications in presynaptic structure.

Animals↗
PubMed1994

Expression pattern, genomic cloning and RFLP analyses of the swine PIT-1 gene.

The swine PIT-1 POU domain cDNA was used to study PIT-1 expression and to clone the PIT-1 genomic region to identify additional PIT-1 polymorphisms. PIT-1 was expressed only in the pituitary, confirming the swine cDNA identity. To study the PIT-1 genomic region, a clone containing 13.7 kb DNA was isolated. EcoRI fragments hybridizing to PIT-1 were sequenced, and the 3' portion of PIT-1 gene identified. Primers for polymerase chain reaction (PCR)-restriction fragment length polymorphism (RFLP) analysis were then designed. Restriction analysis of PCR products identified a RsaI RFLP. In contrast to other PIT-1 RFLPs, the RsaI PCR-RFLP was widely distributed in American breeds. Thus, the RsaI RFLP and the previously reported PIT-1 RFLPs allow detection of PIT-1 alleles in most, if not all, breeds currently used in the US and European reference/resource pig mapping families.

Animals↗
PubMed1993

Cloning and restriction fragment length polymorphism analysis of a cDNA for swine PIT-1, a gene controlling growth hormone expression.

A partial swine cDNA which encodes the functional domain of PIT-1 was isolated by the polymerase chain reaction (PCR). The swine PIT-1 cDNA clone is 95% identical at the protein level to the rat Pit-1 gene. Thus, Pit-1's known function in control of rat growth hormone and prolactin expression is likely to be conserved in swine. This swine cDNA clone was used to investigate genetic variability at PIT-1 in several American and Chinese breeds. Polymorphic BamHI fragments were found in pure-bred Meishan animals (n = 13), but only monomorphic fragments in five American breeds (n = 36).

Amino Acid Sequence↗