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Biomedical subjects

Y Lee

Publications and source records attributed to Y Lee.

At least 361 records · Page 20Linked to original sources
PubMed1996

A primary acoustic startle pathway: obligatory role of cochlear root neurons and the nucleus reticularis pontis caudalis.

Davis et al. (1982) proposed a primary acoustic startle circuit in rats consisting of the auditory nerve, posteroventral cochlear nucleus, an area near the ventrolateral lemniscus (VLL), nucleus reticularis pontis caudalis (PnC), and spinal motoneurons. Using fiber-sparing lesions, the present study reevaluated these and other structures together with the role of neurons embedded in the auditory nerve [cochlear root neurons (CRNs)], recently hypothesized to be involved in acoustic startle. Small electrolytic lesions of the VLL of ventrolateral tegmental nucleus (VLTg) failed to eliminate startle. Large electrolytic lesions including the rostral ventral nucleus of the trapezoid body (rVNTB) and ventrolateral parts of PnC or lesions of the entire PnC blocked startle. However, small NMDA-induced lesions of the rVNTB failed to block startle, making it unlikely that the rVNTB itself is part of the startle pathway. In contrast, NMDA lesions of the full extension of the ventrolateral part of the PnC blocked startle completely, suggesting that the ventrolateral part of the PnC is critically involved. Bilateral kainic acid lesions of CRNs also blocked the startle reflex completely, providing the first direct evidence for an involvement of CRNs in startle. This blockade probably was not caused by damage to the auditory nerve, because the lesioned animals showed intact compound action potentials recorded from the ventral cochlear nucleus. Hence, a primary acoustic startle pathway may involve three synapses onto (1) CRNs, (2) neurons in PnC, and (3) spinal motoneurons.

Action Potentials↗
PubMed1996

Cue recognition and cue elaboration in learning from examples.

This paper describes the processes used by students to learn from worked-out examples and by working through problems. Evidence is derived from protocols of students learning secondary school mathematics and physics. The students acquired knowledge from the examples in the form of productions (condition-->action): first discovering conditions under which the actions are appropriate and then elaborating the conditions to enhance efficiency. Students devoted most of their attention to the condition side of the productions. Subsequently, they generalized the productions for broader application and acquired specialized productions for special problem classes.

Cognition↗
PubMed1996

Structure and expression of the tenecin 3 gene in Tenebrio molitor.

A genomic DNA fragment encoding tenecin 3, an antifungal protein was cloned from the genomic DNA library of Tenebrio molitor. The DNA sequence analysis showed that the coding region is divided into two exons by an intron of 49 bp in the middle of the putative leader peptide coding region. Southern blot analysis suggests that the gene is present as a single copy. The transcription initiation site was determined by primer extension analysis and S1 mapping. The TATA box and CCAAT box sequences were found at -30, and -121, respectively, from the transcription initiation site. Tenecin 3 mRNA is abundantly expressed in larvae and adults, while little was detected in RNAs from pupae, suggesting that the expression of the tenecin 3 gene is developmentally regulated.

Amino Acid Sequence↗
PubMed1996

Abnormally short serum half-lives of IgG in beta 2-microglobulin-deficient mice.

The MHC class I-related receptor, FcRn, mediates the transfer of maternal gamma globulin (IgG) to young rodents, primarily via intestinal transcytosis, and this provides humoral immunity for the first few weeks after birth. In a previous study, the site of mouse IgG1 (mIgG1) with which FcRn interacts has been mapped using recombinant wild-type and mutated Fc-hinge fragments. The site encompasses residues at the CH2-CH3 domain interface of Fc (Ile253, His310, Gln311, His433 and Asn434) and the same amino acids are involved in regulating the pharmacokinetics of the Fc-hinge fragments. This suggests that in addition to its known function, FcRn might also play a role in IgG homeostasis. Consistent with this hypothesis, in this study, we demonstrate that FcRn alpha-chain mRNA is present not only in neonatal brush border but also in other tissues of adult animals (liver, lung, spleen and endothelial cells). In addition, analysis of the pharmacokinetics of mouse Ig/Fc-hinge fragments in genetically manipulated mice that are deficient in the expression of FcRn demonstrates that the beta-phase half-lives are abnormally short. These findings suggest that FcRn is involved in IgG homeostasis.

Animals↗
PubMed1996

Lack of a temporal gradient of retrograde amnesia following NMDA-induced lesions of the basolateral amygdala assessed with the fear-potentiated startle paradigm.

M. Kim and M. Davis (1993b) previously reported that electrolytic lesions of the central nucleus of the amygdala, made 6 or 30 days after training, completely blocked the expression of fear-potentiated startle in rats. The present study shows that excitotoxic lesions of the basolateral amygdala also block fear-potentiated startle and do so whether the lesions are made soon (i.e., 6 days) or long (i.e., 30 days) after training. The relevance of these findings to various theories of amygdala function is discussed.

Amygdala↗
PubMed1996

Detection of evolving viruses.

The spread of viruses on a homogeneous lawn of receptive hosts provides an opportunity to detect the dynamics of their evolution. We have previously found that when repeated virus passages are confined to the expanding perimeter of a growing plaque, the appearance and outgrowth of genetically diverse strains (all descended from the same parent strain) can be traced along different radii of the plaque. As a plaque grows, the random mutation and selection of new fast-growing strains reduce the roundness or circularity of the growing plaque. Here we have quantified such changes in growing plaques of bacteriophage T7 using a digital imaging system. We find that T7 populations not adapted for fast growth exhibit a broader diversity of growth rates than populations adapted for fast growth. These results provide a foundation for understanding how viruses exploit mutation and selection processes to persist in nature.

Bacteriophage T7↗
PubMed1996

Cloning and characterization of cDNA for human adenylate kinase 2A.

We have isolated and characterized a cDNA clone encoding human adenylate kinase 2A (AK2A) from cDNA libraries of fetal liver origin. The complete nucleotide sequence of the cloned 889 nucleotide cDNA fragment indicated that the deduced gene product of human AK2A is composed of 239 amino acids with a molecular weight of 26 kD. Comparison of these nucleotide and amino acid sequences with the corresponding sequences of bovine AK2A and rat AK2 revealed a high degree of conservation. It showed 91% and 98% homologies in DNA and amino acid sequences, respectively, with bovine AK2A throughout the full open reading frame. RNA blot analysis revealed that three species of mRNA were present with approximate sizes of 3.4, 2.1, and 1.0 kb. This gene was expressed in E. coli cells and the recombinant protein was enzymatically active.

Adenylate Kinase↗
PubMed1996

Endoscopic sinus surgery with partial middle turbinate resection: effects on olfaction.

Few studies have investigated the effects of endoscopic sinus surgery (ESS) on olfaction. In particular, the effect of surgical manipulation of the middle turbinate on olfaction has not been established. Using the University of Pennsylvania Smell Identification Test (UPSIT) and patient questionnaires, the authors performed a prospective study of olfaction in 64 patients undergoing ESS. Thirty-eight patients (59%) underwent partial middle turbinate resection; in the remaining 26 patients (41%), the middle turbinate was preserved. All patients were reevaluated approximately 8 weeks after surgery by endoscopic examination, questionnaire, and the UPSIT. Patients who underwent no resection had a median decrease in UPSIT score of 1.4, and those who underwent resection had a median decrease of 0.5; this difference was not statistically significant. Further, no correlation was found between changes in UPSIT score and follow-up time, sex of the patient, or the patient's subjective assessment of postoperative olfaction. It is concluded that middle turbinate resection has no effect on olfaction.

Adolescent↗
PubMed1996

Purification and characterization of a fibrinolytic enzyme produced from Bacillus sp. strain CK 11-4 screened from Chungkook-Jang.

Bacillus sp. strain CK 11-4, which produces a strongly fibrinolytic enzyme, was screened from Chungkook-Jang, a traditional Korean fermented-soybean sauce. The fibrinolytic enzyme (CK) was purified from supernatant of Bacillus sp. strain CK 11-4 culture broth and showed thermophilic, hydrophilic, and strong fibrinolytic activity. The optimum temperature and pH were 70 degrees C and 10.5, respectively, and the molecular weight was 28,200 as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The first 14 amino acids of the N-terminal sequence of CK are Ala-Gin-Thr-Val-Pro-Tyr-Gly-Ile-Pro-Leu-Ile-Lys-Ala-Asp. This sequence is identical to that of subtilisin Carlsberg and different from that of nattokinase, but CK showed a level of fibrinolytic activity that was about eight times higher than that of subtilisin Carlsberg. The amidolytic activity of CK increased about twofold at the initial state of the reaction when CK enzyme was added to a mixture of plasminogen and substrate (H-D-Val-Leu-Lys-pNA). A similar result was also obtained from fibrin plate analysis.

Amino Acid Sequence↗
PubMed1996

Cytotoxic activities of solanum steroidal glycosides.

Cytotoxic activities of 20 steroidal glycosides obtained from Solanum genera plants were examined against various cell lines to provide new evidence as follows: 1) As regarding the sugar linkage, the glycosides possessing a beta-chacotriosyl moiety were the most effective and the presence of the terminal rhamnosyl residue was required for exhibiting strong activity. 2) As for the aglycone, the glycosides carrying a spirostanol aglycone showed the strongest activity and even an aglycone without a sugar linkage presented considerably strong activity.

Antineoplastic Agents↗
PubMed1996

Mutational analysis of Saccharomyces cerevisiae nuclear RNase P: randomization of universally conserved positions in the RNA subunit.

Three regions in the Saccharomyces cerevisiae RNase P RNA have been identified, at positions Sce 87-94, Sce 309-316, and Sce 339-349, that contain nucleotides that are invariant in identity and position among all the known RNase P RNAs. To study the importance of these conserved RPR1 RNA regions in enzyme function, three independent mutational libraries were created in which the positions of invariant nucleotides were randomized simultaneously. Screening in vivo was used to identify viable RPR1 variants when reconstituted into holoenzyme in cells. Despite the universal evolutionary conservation, most of these positions tolerate certain sequence changes without severely affecting function. Most changes, however, produced subtle defects in cell growth and RNase P function, supporting the importance of these conserved regions. Isolation of conditional growth mutants allowed the characterization of the effects of mutations on cell growth, RPR1 RNA maturation, and activity of the holoenzyme in vitro. Kinetic analysis showed that viable variants were usually more defective in catalytic rate (Kcat) than in substrate recognition (Km).

Base Sequence↗
PubMed1996

A conserved RNA motif involved in divalent cation utilization by nuclear RNase P.

Catalytic RNAs are metalloenzymes that require precise coordination of divalent cation cofactors. In RNase P RNA, a conserved structural subdomain that has been implicated in magnesium coordination contains the consensus sequence acAGaRA. Randomization mutagenesis of the analogous sequence in the Saccharomyces cerevisiae nuclear RNase P RNA gene, RPR1, gave viable sequence variants that confer magnesium-correctable growth defects and are defective in magnesium cofactor utilization by the RNase P holoenzyme in vitro. Kinetic analysis of the defective holoenzymes suggests that the primary effects were on catalytic rate, rather than substrate recognition. The possible involvement of this RNA subdomain in catalysis is discussed.

Base Sequence↗
PubMed1996

Panic attacks with psychotic features.

BACKGROUND: Anxiety disorders are among the most frequently diagnosed group of psychiatric disorders in the general population. Although anxiety disorders are often comorbid with depression and personality disorders, they rarely culminate in psychosis. METHOD: Having observed psychosis in the course of a severe panic attack, the authors prospectively identified four patients who experienced panic attacks with co-occurring psychosis. All met the DSM-IV criteria for panic disorder. Distinctive features of their clinical presentation, pharmacotherapy, and follow-up were recorded. RESULTS: Three patients had a history of panic disorder, and one had a history of generalized anxiety disorder. In all cases, psychosis (auditory hallucinations or delusions) originated in the course of a severe panic attack. Psychotic symptoms occurred only during panic attacks; however, these could occur up to 10 to 15 times a day. In all four patients, psychotic symptoms resolved after a brief time either spontaneously or with benzodiazepine/SSRI treatment. None of the patients required neuroleptic treatment. CONCLUSION: The cases suggest that psychosis may develop in the course of a severe panic attack in patients with panic disorder, as was reported previously for patients with obsessive-compulsive disorder and posttraumatic stress disorder. Distinguishing panic attacks with psychotic features from other psychotic disorders is clinically important since antipsychotic medication treatment for these psychotic symptoms is not indicated. Further research on the prevalence of psychotic symptoms in the anxiety disorders and the pathophysiology of this phenomenon is required to clarify the relationship between the anxiety disorders and psychosis.

Adult↗
PubMed1995

Suppression of gene expression on the simian virus 40 major late promoter by human TR4 orphan receptor. A member of the steroid receptor superfamily.

The key expression of the simian virus 40 (SV40) major late promoter could be repressed by the human TR4 orphan receptor via the +55 region of the SV40 major late promoter (nucleotide numbers 368-389, 5' -GTTA-AGGTTCGTAGGTCATGGA-3'). Using the coupled in vitro transcribed and translated TR4 orphan receptor with a molecular mass of 67.3 kilodaltons, electrophoretic mobility shift assay showed specific binding with a dissociation constant of 1.09 nM between the TR4 orphan receptor and the SV40 +55 oligonucleotides. In addition, chloramphenicol acetyltransferase assay demonstrated that this SV40 +55 region can function as a repressor via the TR4 orphan receptor, suppressing the transcriptional activities of both SV40 early and late promoters. Together, our data suggest that the TR4 orphan receptor may play an important role for the suppression of the SV40 gene expression.

Base Sequence↗
PubMed1995

Termination as a factor in "quality control" during ribosome biogenesis.

In eukaryotes, nascent rDNA and 5 S rRNA gene transcripts undergo 3'-end processing after termination. Mutations in which terminator sequences in these ribosomal RNA genes are deleted completely result in highly unstable transcripts, which are not properly processed and integrated into stable ribosome structure. Mutations that retard RNA processing by extending the 3' external transcribed spacer or by introducing additional secondary structure in the spacers have a similar effect on stable transcript integration. The results indicate that proper termination coupled with efficient rRNA processing acts as a "quality control" process, which helps to ensure that only normal rRNA precursors are effectively processed and assembled into active ribosomes.

Base Sequence↗
PubMed1995

Role of carbohydrates in oxidative modification of fibrinogen and other plasma proteins.

Oxidative stress is related to the mechanism of oncogenesis, cell death, and the pathogenesis of many human diseases. Proteins are important targets for oxidative modification, and a Western blot assay that can identify individual oxidized proteins in whole tissue extracts has been described. Using that assay, it was found that plasma proteins show different susceptibilities to oxidative modification. Here, we examine the possibility that the carbohydrate groups of glycoproteins may contribute to the assessment of protein oxidation by carbonyl assays. We used fibrinogen as a model because it is highly susceptible to oxidative modification and contains subunits that are differentially glycosylated. When oxidation-induced carbonyls were measured in fibrinogen subunits by Western blot immunoassay, it was found that the A alpha-chains, which contain no associated carbohydrate groups, were most highly oxidized while the B beta- and gamma-chains, which are glycosylated, were oxidized far less. However, no major difference in the oxidation pattern was obtained when fibrinogen was deglycosylated prior to or after exposure to oxidants. This argues against a possible protective role of the carbohydrate moieties in oxidation of the different fibrinogen subunits. Similar results were obtained with purified human immunoglobulin G and transferrin as well as whole plasma. The results show that carbohydrate moieties are not good targets for oxidative attack by metal-catalyzed oxidation systems. Oxidant-induced carbonyl formation in glycoproteins derives largely, if not entirely, from amino acid oxidation and not from oxidation of carbohydrate groups.

Blood Proteins↗