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Biomedical subjects

Y J Lin

Publications and source records attributed to Y J Lin.

At least 91 records · Page 5Linked to original sources
PubMed1996

Influenza B virus infection associated with shock in a two-month-old infant.

Influenza B virus usually causes a mild and self-limiting illness. A 2-month-old infant presented with acute symptoms suggestive of septic shock but recovered after vigorous resuscitation 1 day later. Influenza B was isolated from a throat swab taken from the infant. Bacterial cultures of blood, urine and spinal fluid had no growth. This case illustrates that the clinical signs and symptoms of influenza in infants may be indistinguishable from bacterial sepsis.

Humans↗
PubMed1996

Heterochromatin (chromosome dots and chromocentres): key to planarian regeneration?

Regenerating planaria were treated with colchicine dissolved in planarian saline solution in order to harvest metaphase chromosomes. Slides containing such chromosomes were incubated in phosphate buffer at high temperature for 2h and stained with Giemsa solution in order to view heterochromatic dots in chromosomes. The chromosomes were found to contain massive regions of dense heterochromatin. In addition, most interphase cells exhibited numerous densely staining chromocentres. Heterochromatin has been postulated to reduce the duration and enhance the speed of the cell cycle, and previous work has implicated heterochromatin in cells undergoing rapid division. These findings imply that the profound regenerative potential of planarians may be due to their high cellular levels of heterochromatin.

Animals↗
PubMed1995

Effects of caffeine on Ca2+ fluxes and secretion in bovine chromaffin cells.

The effects of caffeine on Ca2+ fluxes and catecholamine secretion in bovine adrenal chromaffin cells were examined. Caffeine inhibited secretion. 45Ca2+ uptake and cytosolic Ca2+ concentration ([Ca2+]i) rise induced by the nicotinic receptor agonist 1.1-dimethyl- 4-phenylpiperazinium (DMPP) and the Na+ channel activator veratridine. The inhibitory effect of caffeine on high K(+)-induced secretion was smaller than that on DMPP- and veratridine-induced responses. Caffeine only slightly inhibited high K(+)-induced 45Ca2+ uptake and did not affect [Ca2+]i rise. Caffeine also inhibited muscarinic receptor-mediated inositol phosphate generation. Our results suggest that the inhibitory effects of caffeine on bovine chromaffin cells mainly occur at both muscarinic and nicotinic receptors as well as at the voltage-dependent Na+ channels and to a smaller extent at site(s) distal to Ca2+ entry. The effects of caffeine on nicotinic receptors but not on muscarinic receptors can be explained by its ability to raise intracellular cAMP.

1-Methyl-3-isobutylxanthine↗
PubMed1995

Mastoparan activation of dopamine-modulated K+ channels on rat striatal neurons.

Coupling mechanisms between a D2-like dopamine receptor and an 85 pS K+ channel on freshly dissociated rat caudate-putamen neurons were studied using cell-attached patch-clamp electrophysiology. Channel currents were observed in the absence of dopamine receptor agonists when mastoparan, an activator of certain guanyl nucleotide binding proteins (G-proteins), was applied via the patch pipette. Channel current-voltage relationships and open probabilities observed with mastoparan were indistinguishable from those obtained with dopaminergic agonists. Alamethicin, which mimics the membrane-perturbing but not the G-protein activating properties of mastoparan, did not activate the channel, suggesting that non-specific effects of mastoparan were unlikely to account for this effect. Our results indicate that coupling between the D2 dopamine receptor and this K+ channel may involve a mastoparan-sensitive G-protein.

Animals↗
PubMed1995

Thyroid hormone upregulates gene expression, synthesis and release of pro-epidermal growth factor in adult rat kidney.

Attempts were made to elucidate whether thyroid hormone upregulates renal pro-epidermal growth factor (pro-EGF) gene expression, biosynthesis and release in adult rats which were rendered hypothyroid. Predominantly pro-EGF was detected in renal cortex, whereas pro-EGF and its degraded species were found in urine. We demonstrated that T3 increased pro-EGF levels in renal cortex to 2.2 +/- 0.17, 2.37 +/- 0.19, 2.73 +/- 0.25, and 3.10 +/- 0.45 fold within day 1, 2, 4 and 8, respectively following treatment. Immunoreactive EGF, assessed by immunohistochemical methods, was confined in the distal convoluted tubule and thick ascending limb of Henle. T3 markedly enhanced the density of irEGF in these nephrons. T3 augmented the concentration of urinary irEGF to 2.1, 2.2, 2.8 and 3.6 fold within day 1, 2, 4 and 8 and the abundance of urine pro-EGF to 2.53 +/- 1.39, 3.8 +/- 0.70, 3.59 +/- 1.48 fold within day 1, 2, 4, respectively. Moreover, we employed reverse transcriptase/polymerase chain reaction method to analyze relative abundance of pro-EGF mRNA in kidneys of various thyroid states and found T3 markedly increased pro-EGF mRNA levels after treatment of 1, 2 and 4 days. These results indicated that thyroid hormone augmented the gene expression, biosynthesis and excretion of pro-EGF in adult rat kidney.

Animals↗
PubMed1995

Dopamine-modulated potassium channels on rat striatal neurons: specific activation and cellular expression.

We have used cell-attached patch-clamp electrophysiology to characterize the activation and distribution of an 85 pS K+ channel on freshly dissociated rat striatal (caudate-putamen) neurons. In recordings from 643 cells, openings of this channel showed an absolute dependence on the presence of dopamine or the D2-like dopamine receptor agonist quinpirole in the cell-attached patch pipette, but were never seen when the D2 antagonist domperidone was applied along with quinpirole, or in the absence of drug. This channel displayed inward rectification at depolarized membrane potentials, but its activation was otherwise voltage insensitive. It was largely restricted to a subset of dissociated cells with diameters > or = 10 microns, with channel openings seen in about 25% of patches. When present, there were typically multiple channels per patch. Cells of this size were immunocytochemically stained for neuron-specific enolase but not glial fibrillary acidic protein; about 40% were also labeled for gamma-amino butyric acid (GABA) and about 60% for NADPH diaphorase, with GABAergic cells displaying a shape most similar to that of cells expressing the channel. A large number of distinct types of other channels were also present, comprising inwardly rectifying channels of 5-35 pS conductance and voltage-activated channels of 100-250 pS, but the frequencies of occurrence and fractional open times of these channels were independent of the presence or absence of dopaminergic agonists. Thus, the 85 pS K+ channel uniquely requires activation by a D2-like dopamine receptor on rat striatal neurons, and is selectively expressed by a subset of these cells, which are most likely to be GABAergic neurons.

Animals↗
PubMed1995

Analysis of K-ras gene mutations in periampullary cancers, gallbladder cancers and cholangiocarcinomas from paraffin-embedded tissue sections.

Point mutations of the K-ras gene were analyzed in 25 periampullary cancers (21 ampulla vater cancers, two common bile duct cancers and two duodenal cancers), two gallbladder cancers and six cholangiocarcinomas. DNA extracted from the paraffin-embedded tissues was amplified with the polymerase chain reaction and subsequently analyzed by direct cycle sequencing at codons 12, 13 and 18 of the K-ras gene. Codon 61 was first screened with single strand conformation polymorphism and then sequenced by direct cycle sequencing. No point mutation was found in any of the 25 periampullary cancers or the two gallbladder cancers. These results are similar to previous reports. Mutation of the K-ras gene seems not to play an important role in tumorigenesis of periampullary cancer. In two of six (33%) cholangiocarcinoma patients, point mutations were found. Both mutations were transitions, GGT to GAT at codon 12. The incidence of mutation was greater than that in Thailand (about 8%) but less than that in Japan (about 60%). Mutation of the K-ras gene may play varied roles in the tumorigenesis of cholangiocarcinoma, depending on geographic area.

Adult↗
PubMed1994

Exponentially tapered t-tube model of systemic arterial system in dogs.

This study determines the role of an asymmetric T-tube model as a representation of arterial mechanical properties. The model consists of two non-uniform tubes connected in parallel. The non-uniform properties of each tube include geometric and elastic tapering and each tube terminates in a complex load. Pulsatile pressure and flow velocity of the ascending aorta were measured in 10 closed-chest, anaesthetized dogs. An exponentially tapered transmission line is used to describe the non-uniform properties of the vasculature. The phase constant is a function of position along the path length due to geometric and elastic tapers. This non-uniform T-tube model makes it possible to fit the measured pressure waveform in the ascending aorta. Model parameters could be estimated and used to interpret the physical properties of the arterial system. The mathematical and experimental model impedance spectra are similar. There is a close correspondence between the impedance parameters derived from the non-uniform T-tube model and values computed from measurements on dogs. The results suggest that inclusion of tube tapering improves the mathematical model so that it closely represents the experimentally derived arterial impedance in closed-chest dogs. We conclude that the non-uniform properties of wave-transmission paths may play an important role in governing the behaviour of an asymmetric T-tube for the description of the arterial system.

Animals↗
PubMed1994

Identification of the cis-acting signal for minus-strand RNA synthesis of a murine coronavirus: implications for the role of minus-strand RNA in RNA replication and transcription.

Minus-strand RNA is the first RNA species made by plus-strand RNA viruses, such as mouse hepatitis virus (MHV), and serves as a template for subsequent RNA replication and transcription. The regulation of minus-strand RNA synthesis has been difficult to study because of the paucity of minus-strand RNA. We have optimized a ribonuclease (RNase) protection assay which enabled the detection of minus-strand RNA synthesis from nonreplicating RNAs, thus clearly separating minus-strand from plus-strand RNA synthesis. We used an MHV defective interfering (DI) RNA containing a chloramphenicol acetyltransferase gene as a reporter to determine the cis-acting signal for MHV minus-strand RNA synthesis. It was found that minus-strand RNAs existed in double-stranded RNA form in the cell. By using various deletion clones, we demonstrated that the cis-acting signal for minus-strand RNA synthesis resides in the 55 nucleotides from the 3' end plus poly(A) tail of the MHV genome. This is much shorter than the 436 nucleotides previously reported for the 3'-end replication signal. No specific upstream MHV sequence was required for the initiation of minus-strand RNA synthesis. This finding suggests that the requirement for minus-strand RNA synthesis is much less stringent than that for genomic and subgenomic plus-strand RNA synthesis and that some of the minus-strand RNAs made may not be functional since they may lack the recognition signals for RNA replication or transcription. We further showed that the DI clones which actively transcribed a subgenomic mRNA from an internal intergenic sequence synthesized much less minus-strand RNA than those clones which did not transcribe subgenomic mRNAs, indicating that minus-strand RNA synthesis was inhibited by transcription from an internal promoter of the same DI RNA. This result also suggests that the regulation of the quantities of subgenomic mRNAs is not at the point of minus-strand RNA synthesis but rather at plus-strand RNA synthesis. Furthermore, the finding that the leader sequence was not required for minus-strand RNA synthesis suggests that the leader RNA regulates mRNA transcription during plus-strand RNA synthesis.

Animals↗
PubMed1994

Differential staining of Dugesia tigrina sister chromatids.

Planaria were cultured in a solution of bromodeoxyuridine (BrdU) for 24 h in an attempt to produce sister chromatid differential staining (SCD) and sister chromatid exchange (SCE). SCD was produced when planaria were cultured in planarian saline solution (PSS) containing 5 x 10(-5) M BrdU. Colchicine (0.02%) was added to the BrdU/PSS culture medium 8 to 10 h before sacrifice. Animals were then vigorously dissociated into cells, centrifuged, and fixed in Carnoy's solution. Slides were prepared using the air-drying method, allowed to age for at least 1 day, stained with the fluorochrome Hoechst 33258, exposed to high intensity incandescent light, stained with Giemsa solution, and mounted. This method is the first reported SCD/SCE investigation in the Platyhelminthes and consistently yielded second division metaphases exhibiting SCD and third division metaphases exhibiting non-reciprocal SCE's composed of unifilarly BrdU-labelled DNA.

Animals↗
PubMed1994

Gingival absorption of triclosan following topical mouthrinse application.

This study assessed the gingival uptake and urinary excretion of triclosan in dogs following topical applications of a mouthrinse containing 0.03% of triclosan. Five different phases were conducted to define the time course of plasma concentration. The effect of plaque on gingival absorption was also measured. Phase I: Animals' teeth were cleaned of plaque via scraping. Blood sampling time was 0-2 hours. Phase II: Plaque was not removed from the animals' teeth. Blood sampling time was 0-2 hours. Phase III: Plaque was not removed from the animals' teeth. Blood sampling time was 0-6 hours. Phase IV: Plaque was not removed from the animals' teeth. Blood sampling time was 0-12 hours. Phase V: Animals' teeth were cleaned of plaque via scraping. Blood sampling time was 0-12 hours. The test substance was administered to 1 male and 1 female dog in Phases I, II, IV and V, and to 1 male dog in Phase III. The same animals were used in each phase. On the first day of each phase, the animals were treated with distilled water for a 15-minute period. The animals were exposed daily to the test material for a 15-minute period during the remaining 7 days of each phase. The test material was administered using custom-made acrylic applicator trays to enclose the maxillar premolars and molars and gingiva of one-half of the upper jaw. A leak-proof seal along the mucogingival junction and palatal mucosa was established and maintained during the exposure period.(ABSTRACT TRUNCATED AT 250 WORDS)

Analysis of Variance↗
PubMed1993

Deletion mapping of a mouse hepatitis virus defective interfering RNA reveals the requirement of an internal and discontiguous sequence for replication.

All of the defective interfering (DI) RNAs of mouse hepatitis virus (MHV) contain both the 5' and 3' ends of the viral genomic RNA, which presumably include the cis sequences required for RNA replication. To define the replication signal of MHV RNA, we have used a vaccinia virus-T7 polymerase-transcribed MHV DI RNA to study the effects of sequence deletion on DI RNA replication. Following infection of susceptible cells with a recombinant vaccinia virus expressing T7 RNA polymerase, various cDNA clones derived from a DI RNA (DIssF) of the JHM strain of MHV, which is a 3.5-kb naturally occurring DI RNA, behind a T7 promoter were transfected. On superinfection with a helper MHV, the ability of various DI RNAs to replicate was determined. Serial deletions from the middle of the RNA toward both the 5' and 3' ends demonstrated that 859 nucleotides from the 5' end and 436 nucleotides from the 3' end of the MHV RNA genome were necessary for RNA replication. Surprisingly, an additional stretch of 135 nucleotides located at 3.1 to 3.3 kb from the 5' end of the genome was also required. This stretch is discontiguous from the 5'-end cis replication signal and is present in all of the naturally occurring DI RNAs studied so far. The requirement for a long stretch of 5'- and 3'-end sequences predicts that the subgenomic MHV mRNAs cannot replicate. The efficiency of RNA replication varied with different cDNA constructs, suggesting possible interaction between different regions of DI RNA. The identification of MHV RNA replication signals allowed the construction of an MHV DI-based expression vector, which can express foreign genes, such as the chloramphenicol acetyltransferase gene.

Animals↗
PubMed1993

Multiple sulfonylurea-sensitive potassium channels: a novel subtype modulated by dopamine.

In single channel patch-clamp recordings from freshly dissociated rat corpus striatum (caudate-putamen) neurons, the sulfonylurea drugs tolbutamide and glibenclamide caused a concentration-dependent blockade of a K+ channel that is activated by D2 dopamine receptor agonists. Tolbutamide was about 10-100 times more potent than glibenclamide, a rank-order potency opposite to that seen at previously described adenosine triphosphate-sensitive K+ channels. The channel also was poorly activated by diazoxide, which is a known opener of adenosine triphosphate-sensitive K+ channels. However, like adenosine triphosphate-sensitive channels, it opened in the absence of dopaminergic agonist when the cells were treated with the metabolic inhibitor rotenone, indicating that channel openings occur under energy-depleting conditions. This suggests the existence of a novel, pharmacologically distinct class of sulfonyl-urea-sensitive K+ channels, regulated metabolically and also mediating dopaminergic neurotransmission.

Animals↗
PubMed1993

The crystal and molecular structure of trichosanthin at 2.6 A resolution.

The crystallographic refinement of trichosanthin has been performed at 2.6 A resolution. The crystal and molecular structure of trichosanthin is described in detail in this paper. On summarizing the regularity of the amino acid sequences of eight kinds of ribosome inactivating proteins and combining with the crystal and molecular structure of trichosanthin, fifteen most conservative amino acid residues are analyzed. It is found that four most conservative polar amino acid residues Gln156, Glu160, Arg163 and Glu189 gather on the molecular surface on the boundary of the large and small domains, thus forming the active center of the protein molecule.

Amino Acid Sequence↗
PubMed1992

Detection of mutations in the p53 gene in human head and neck carcinomas by single strand conformation polymorphism analysis.

Using the polymerase chain reaction (PCR)-based single strand conformation polymorphism (SSCP) analysis, we have examined the highly conserved regions of the p53 gene in 58 biopsy samples of head and neck tumors. Mutations were found in 13/58 (23%) tumor specimens, but not in 6 normal tissues. Ten of 13 mutations were due to single base changes and the remaining 3 were 1- or 8-base deletion mutants. These mutations were clustered in exons 5 and 7 and resulted in amino acid changes. Our results seem to indicate that mutations in the p53 gene contribute to a significant number of cases of the head and neck tumors including 20% of nasopharyngeal carcinoma biopsies. The relationship of Epstein-Barr virus or human papillomavirus and p53 gene mutations in this group of cancers was also analyzed and discussed.

Base Sequence↗