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Biomedical subjects

H Lee

Publications and source records attributed to H Lee.

At least 577 records · Page 32Linked to original sources
PubMed1995

Vasculature and morphometry of the optic canal and intracanalicular optic nerve.

OBJECTIVES: To study the bony structure of the optic canal and the vasculature of the intracanalicular optic nerve in human cadavers. MATERIALS AND METHODS: Gross and microscopic examinations were performed in 25 optic canals from 13 cadavers to study the pattern of vascular supply of the intracanalicular optic nerve. Neoprene latex was injected through the most proximal part of the ophthalmic artery in seven optic canals. The intracanalicular branches from the ophthalmic artery were carefully identified and quantified. Quantitative measurements of the canal length, canal thickness, canal transverse area, optic nerve transverse area, and subdural space were done for the other 18 canals by means of semiautomated morphometric analysis system. Each canal was divided into anterior, middle, and posterior parts for better visualization and measurement. RESULTS: The ophthalmic artery gives off three branches that supply the intracanalicular optic nerve: medial collateral branch, lateral collateral branch, and ventral branch. Each branch pierces the dura and then supplies the nerve through the pia mater. The middle medial wall was the thinnest bony part of the canal (0.31 +/- 0.06 mm). The optic canal, optic nerve, and subdural space transverse area varied at different transection levels. The narrowest space was in the middle part of the optic canal. The mean subdural cross-sectional space was only 1.84 mm2. This, multiplied by the average canal length (11.79 mm), can be considered the potential space for hemorrhage, optic nerve edema, or hematoma. CONCLUSIONS: The vasculature within the bony canal is extremely delicate. Due to the limitation of this space, even a tiny amount of blood or swelling of the nerve (21.69 mm3) may cause optic nerve compression. It appears that these vessels could easily be disrupted in closed head injury by a shearing or concussive force, leading to ischemic infarction of the optic nerve. Since the narrowest portion of the canal is in the middle portion, it is the middle part of the optic canal that is most critical in doing an optic canal decompression.

Anthropometry↗
PubMed1994

Bis-catechol-substituted redox-reactive analogues of hexamethonium and decamethonium: stimulated affinity-dependent reactivity through iron peroxide catalysis.

Symmetrically bis-catechol-substituted analogues (1 and 2, respectively) of hexamethonium and decamethonium were synthesized and investigated as redox-activated affinity reagents toward the neurotoxin-binding sites of the nicotinic acetylcholine receptor (nAcChR), purified from Torpedo californica electroplax. These reagents bound to nAcChR with Kd = 1.8 x 10(-8) and 2.3 x 10(-7) M for 1 and 2, respectively. In the presence of a metal, Fe(II)/Fe(III), and peroxide, both reagents produced a rapid and efficient half-of-sites inactivation of neurotoxin-binding sites in the nAcChR in a concentration-dependent manner, which paralleled the extent of receptor binding of the reagents. In the absence of Fe(II)/Fe(III) peroxide, redox-dependent inactivation occurred for both 1 and 2 more slowly and only at concentrations much higher (10(3)-10(4) times) than those necessary to produce significant binding to nAcChR. However, receptor inactivation in the absence of added metal peroxide was still more efficient for 1 and 2 than observed previously for [(trimethylammonio)methyl]catechol (3), the prototypic redox-dependent affinity reagent after which 1 and 2 were patterned. Thus, the new reagents reported are expected to provide more efficient and selective conditions for redox-dependent inactivation at nAcChR and other macromolecular sites to which such reagents may be directed.

Animals↗
PubMed1994

Identification of an antennapedia-like homeobox gene in the ascidians Styela clava and S. plicata.

Homeobox genes from the urochordates Styela clava (AHox2) and S. plicata (AHox3) were cloned and analyzed. The two genes are homologous and Antennapedia-like. The homeobox regions have 87% identity at the nucleotide level and are identical at the amino-acid level. No introns are present in the homeobox region of AHox3, and AHox3 is represented at a low copy number per haploid genome. AHox2 and AHox3 represent the second type of homeobox gene found in this evolutionarily and developmentally important group of organisms.

Amino Acid Sequence↗
PubMed1994

Gene therapy targeted by radiation preferentially radiosensitizes tumor cells.

Transcriptional regulation of the promoter/enhancer region of the Egr-1 gene is activated by ionizing radiation. We linked DNA sequences from the promotor region of Egr-1 to a complementary DNA sequence which encodes human tumor necrosis factor (TNF) alpha, a radiosensitizing cytokine. The Egr-TNF construct was transfected into a human cell line of hematopoietic origin, HL525, which was used in an experimental animal system. HL525 (clone 2) cells containing the Egr-TNF construct which exhibits radiation induction of TNF-alpha were injected into human xenografts of the radioresistant human squamous cell carcinoma cell line SQ-20B. Animals treated with radiation and clone 2 demonstrated an increase in tumor cures compared with animals treated with radiation alone or unirradiated animals given injections of clone 2 alone. No increase in local or systemic toxicity was observed in the combined treatment group. The combination of gene therapy and radiation therapy enhances tumor cures without increasing normal tissue toxicity and is a new paradigm for cancer treatment.

Animals↗
PubMed1994

Mechanism of action of the redox affinity reagent [(trimethylammonio)methyl]catechol.

The synthesis of 4- and 5-hydroxy-3-[(trimethylammonio)methyl]catechol (4- and 5-HTMC) was carried out to examine their proposed involvement as intermediates in the spontaneous redox-dependent half-of-sites inactivation of neurotoxin binding sites in the nicotinic acetylcholine receptor (nAcChR) mediated by the parent compound 3-[(trimethylammonio)methyl]catechol (TMC) [Nickoloff et al. (1985) Biochemistry 24, 999-1007]. Oxidation of 4- and 5-HTMC occurred with sodium periodate with facile conversion to the corresponding p-quinones which were intercepted with thiols and cyclopentadiene. Both 4- and 5-HTMC inactivated neurotoxin binding in the nAcChR in a time course and over a concentration range consistent with their involvement as intermediates in the TMC redox-dependent inactivation of neurotoxin ([125I]-alpha-bungarotoxin) binding sites. Rapid concentration-dependent inactivation of neurotoxin sites occurred over a 10-1000 microM range and was resistant to further inactivation after 50% loss of available toxin binding sites on the nAcChR. Both 4- and 5-HTMC inactivated nAcChR neurotoxin sites much more rapidly and efficiently than was observed previously with TMC. The apparent binding constants for 4- and 5-HTMC with the nAcChR, calculated from their concentration-dependent inactivation behavior toward toxin binding sites, were Kd = 224 +/- 98 and 39 +/- 17 microM, respectively. The observed results and the redox potentials (vs Ag/AgCl reference electrode) measured by cyclic voltammetry at pH 1.8 for TMC (719 mV) and the 4- and 5-HTMC derivatives (519 and 443 mV, respectively) supported the previously proposed mechanism for inactivation of the nAcChR by TMC.(ABSTRACT TRUNCATED AT 250 WORDS)

Benzalkonium Compounds↗
PubMed1994

Structure and organization of a stable extrachromosomal element in human cells.

We have determined the structure and organization of a 630-kb extrachromosomal element (amplisome) containing the dihydrofolate reductase-encoding gene (DHFR) in a methotrexate (MTX)-resistant human cell line, HeLa-Bu25-10B3. The size and copy number of amplisomes have previously been found to remain remarkably stable with or without selection. Both linear and open circular 630-kb amplisomes are present in these cells. We have been able to isolate the linear amplisomes after pulsed-field gel electrophoresis (PFGE), and transfect the amplisomes into MTX-sensitive recipient cells by electroporation, thus demonstrating that DNA as large as 630 kb can be transfected into mammalian cells. The NotI restriction site immediately upstream from DHFR on the circular amplisome is devoid of methylation, suggesting that it is transcriptionally active. Restriction mapping by PFGE reveals that there is only one copy of DHFR per amplisome and no repetitive structure is observed. The small size of the amplisomes, their stability and our ability to transfect large DNA molecules provide the necessary ingredients for the development of mammalian cloning vectors for large DNA fragments.

Azacitidine↗
PubMed1994

Formation and identification of carcinogenic heterocyclic aromatic amines in boiled pork juice.

Bacterial frameshift mutagens have been found in boiled pork juice. The mutagenic compounds of boiled pork juice were purified and analyzed by HPLC. The mutagenic fractions corresponding to the peaks of the standard mutagens 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx), 2-amino-3-methylimidazo[4,5-f]quinoline (IQ), and 2-amino-3,4-dimethylimidazo[4,5-f]quinoline (MeIQ) were confirmed by comparison of UV and mass spectra. One gram equivalent of original lean ground pork was estimated to contain 4.1 ng of MeIQx, 3.7 ng of IQ, and 1.2 ng of MeIQ, which accounted for 21.0%, 30.4%, and 38.1%, respectively, of the total mutagenicity. The remaining mutagenic fractions might be diMeIQx isomers. This will be further confirmed by mass spectrometry in future studies. The amount of IQ-type mutagens in boiled pork juice was about 4-fold higher than in broiled beef. Furthermore, we investigated the effects of 20 amino acids, three monosaccharides, and creatinine on mutagen formation when added to the pork juice to elucidate possible precursors leading to the formation of mutagens. Results showed that five amino acids (glutamine, tyrosine, glycine, alanine, and threonine) and two monosaccharides (ribose and glucose) might participate in mutagen formation in boiled pork juice.

Amines↗
PubMed1994

FTIR analysis of the interaction of azide with horse heart myoglobin variants.

The interaction of azide with variants of horse heart myoglobin (Mb) has been characterized by Fourier transform infrared (FTIR), electron paramagnetic resonance (EPR), and UV-VIS absorption spectroscopy and by molecular modeling calculations. Distal histidine variants (His64Thr, His64Ile, His64Lys) and charged surface variants (Val67Arg, Lys45Glu, Lys45Glu/Lys63Glu) were included in this study. All variants, with the exception of Val67Arg, have a lower azide affinity than the wild-type protein. Analysis of the temperature dependence of the FTIR spectra (277-313 K) revealed that the wild-type protein and all variants exhibit a high-spin/low-spin equilibrium. Introduction of positively charged amino acid residues shifts nu max for the low-spin form to higher energy while negatively charged residues shifted this maximum to lower energy. The low azide binding affinity exhibited by the His64Thr and His64Ile variants is accompanied by a shift of the nu max for the low-spin infrared band to lower energy and by a significant increase in the corresponding half-bandwidths. This observation indicates greater mobility of the bound azide ligand in these variants. The His64Lys variant exhibits two infrared bands attributable to low-spin forms that are assigned to two different conformations of the lysyl residue. In one conformation, the lysine is proposed to form a hydrogen bond with the bound azide similar to that proposed to occur between the distal histidine and bound azide, and in the other conformation no interaction occurs.

Animals↗
PubMed1994

Suppression of a temperature-sensitive cdc33 mutation of yeast by a multicopy plasmid expressing a Drosophila ribosomal protein.

The Saccharomyces cerevisiae cdc33ts4-2 mutant produces a temperature-sensitive allele of the cap-binding subunit of eukaryotic initiation factor-4F (also termed eIF-4E). From a Drosophila cDNA library constructed in a multicopy yeast shuttle vector, a clone was isolated which restored the ability to grow at elevated temperature to cdc33ts4-2 cells. The rescuing Drosophila clone encodes a small ribosomal subunit protein, which we name S15a based on its molecular weight and similarity with the Brassica napus S15a ribosomal protein. Transcription of the Drosophila gene, RpS15a, occurs at all developmental stages and is enhanced during oogenesis. The ribosomal protein gene is capable of suppressing other alleles of cdc33 but not an inactivation mutation, suggesting that suppression is dependent upon the presence of the temperature-sensitive eIF-4E protein. Supporting this, Western blot analysis shows that far more eIF-4E protein is present in cdc33 yeast cells expressing the RpS15a gene than lacking it. Levels of other unrelated proteins are unaffected. We propose therefore that the expression of high levels of the Drosophila S15a ribosomal protein in the cdc33 yeast cells leads to a selective stabilization of the temperature-sensitive eIF-4E protein, which accounts for the suppression phenomenon.

Amino Acid Sequence↗
PubMed1994

Comparison of the sites of reaction of three polycyclic aromatic hydrocarbons in the supF gene.

The distribution of hydrocarbon-DNA adducts through the supF gene in plasmid pS189 was examined using the polymerase arrest assay. For three hydrocarbon dihydrodiol epoxides, derived from 5-methylchrysene, 7-methylbenz[a]anthracene, and benzo[a]pyrene, that exhibit a preference for reaction with guanine residues in DNA, polymerase arrest spectra were similar but not identical. For each agent, guanines in different sequence contexts exhibited varying reactivities and each specific guanine did not necessarily respond to each agent in the same fashion. Thus, sequence context together with the individual dihydrodiol epoxide's chemical and physical properties all play a role in determining sites and extents of reaction within a specific gene. The polymerase arrest data were not predictive of the known sites of mutation hotspots for these dihydrodiol epoxides in the supF gene indicating that further action upon the adducted DNA by repair systems is probably necessary to determine which specific chemical adducts will ultimately give rise to mutation.

Base Sequence↗
PubMed1994

D-ribose stabilizes precursor and mature ribose-binding proteins of Escherichia coli.

Heat- and guanidine hydrochloride-induced unfolding and refolding of precursor as well as mature ribose-binding proteins of Escherichia coli were studied in the presence of D-ribose using intrinsic tyrosine fluorescence and circular dichroism. The precursor and mature proteins have shown virtually identical unfolding-folding behavior. It was observed that D-ribose refolds partially unfolded precursor and mature ribose binding proteins into native structure and decreases the unfolding rate of the these proteins. The conformational stabilities of these proteins were found to increase with increasing D-ribose concentration.

Carrier Proteins↗
PubMed1994

Correlation between meteorological conditions and mutagenicity of airborne particulate samples in a tropical monsoon climate area from Kaohsiung City, Taiwan.

Kaohsiung is a city of 1.5 million located in the southern part of Taiwan. It has a serious air pollution problem mainly attributable to much industrial and commercial activity. In order to estimate the effects of traffic, season, and meteorological conditions on the mutagenicity of Kaohsiung City's urban ambient particulate matter, 624 airborne particulate samples were collected on a weekly basis from 12 locations for an entire year. The mutagenic potential of acetone extracts of air samples was evaluated by the Salmonella/microsomal test with S. typhimurium TA98 in the presence and absence of S9 mixtures. The air samples from November 1990 showed the highest direct and indirect mutagenicity among the 12 months, whereas those from June and July 1991 had the lowest direct and indirect mutagenic activity, respectively. The mutagenicity showed a good correlation with amounts of the acetone extractable matter of airborne particulates. The meteorological conditions, monthly mean precipitation, and wind speed also showed a good correspondence with mutagenicity. Wind direction and temperature had a moderate relationship. The major mutagenic fractions of air samples that had the highest mutagenic activity in a month were purified using Sephadex LH-20 column chromatography, and the contents of PAHs, 1-NP, and DNPs were analyzed by HPLC. The characteristic concentration ratios of PAHs indicated that, for the main pollution sources of airborne particulates from Kaohsiung city, the mobile sources were more important than the stationary ones. The total amounts of 1-NP and DNPs in airborne particulates seemed to correspond to their mutagenicity. Although the total amounts of 1-NP and DNPs in the air samples correlated with their mutagenicity, the major mutagenic chemicals in the airborne particulate samples from Kaohsiung City need further investigation.

Air Pollutants↗
PubMed1994

Bacterial mutagenicity, metabolism, and DNA adduct formation by binary mixtures of benzo[a]pyrene and 1-nitropyrene.

Air pollutants are a complex mixture containing polycyclic organic compounds. Among these are 1-NP and B[a]P, which are important contributors to the mutagenicity of diesel exhaust and airborne particulate matters. To investigate the interaction of a complex mixture of airborne mutagens, the mutagenicity of 1-NP was examined with S. typhimurium TA98 and TA98NR in the presence and absence of B[aP. B[a]P exhibited a more antagonistic effect on the mutagenicity of 1-NP in strain TA98 than in strain TA98NR. Also studied were (1) the inhibitory effects of B[a]P on the nitroreductive metabolism of 1-NP and (2) DNA adduct formation by 1-NP. Nitroreductase was associated with the metabolism of 1-NP, and was reduced in a dose-dependent manner in a binary mixture of 1-NP and B[a]P. HPLC analysis showed that the amounts of 1-AP and NAAP, the metabolites of 1-NP, were significantly decreased by the addition of B[a]P in mixtures. The results indicate that the antagonistic effect of B[a]P on the mutagenicity of 1-NP is mediated through altering its nitroreductive metabolism.

Air Pollutants↗
PubMed1994

Multidisciplinary treatment of biliary tract cancers.

Ninety-six patients referred for radiation therapy to Washington University affiliated institutions with tumors of the extrahepatic biliary tree form the basis of this report. Patients were examined with regard to demographic factors, tumor primary site, presenting symptoms, methods of diagnosis, and methods of management. The median survival of all 96 patients in this series was 11 months. There was no significant difference between patients with gallbladder cancer and patients with cancer of the biliary ductal system. There was a statistically significant improvement in survival in those patients undergoing resection as management or as a component of the management of their tumors (P = 0.02). Patients receiving > 4,000 cGy of radiation therapy had an improved survival compared to those patients receiving < or = 4,000 cGy of radiation therapy (P = 0.003). While surgical resection improved survival for those patients undergoing removal of all gross tumor, this effect was noted especially in patients with gallbladder cancer.

Adult↗
PubMed1994

Adequacy of lymphadenectomy in laparoscopic-assisted colectomy for colorectal cancer: a preliminary report.

The hypothesis that the length of bowel and amount of mesentery resected with laparoscopically assisted colectomy are comparable to traditional open techniques was tested by means of a chart review of prospectively collected data of 22 laparoscopically assisted colectomies, 35 open colectomies performed by the same surgeon, and 39 other open colectomies performed at the same institution by other community surgeons. The average length of bowel resected in the laparoscopically assisted group was 21.7 cm, for the traditionally resected group, 31.4 cm, and for the other group, 26.7 cm. No statistically significant differences existed between the three evaluable groups. Although there was a trend toward greater length of bowel resected with the open technique, there was no statistically significant difference in this study. Follow-up at a mean of 24 months after resections shows no abdominal wall recurrences or any unusual patterns of recurrence. It is concluded that laparoscopically assisted colectomy can be performed in select groups to obtain adequate surgical resection for colorectal carcinoma. Further studies to generate larger numbers of patients with longer follow-up to determine the adequacy of resection as well as the comparability of cure rate will be necessary to confirm the findings of this preliminary study.

Aged↗
PubMed1994

Ion fragmentation activated by matrix-assisted laser desorption/ionization in an ion-trap/reflectron time-of-flight device.

An ion-trap storage/reflectron time-of-flight mass spectrometer has been used to study the decay of large ions following activation by matrix-assisted laser desorption/ionization (MALDI). It is shown that large ions may undergo fragmentation over long periods of time, extending even to milliseconds in some cases. These fragments are stored in the trap and detected as stable ions in the reflectron device, rather than as metastable ions due to decay during the flight time to the detector. The ion decay is found to depend strongly on the laser intensity, while a smaller effect may be due to the matrix used in the MALDI process. The fragmentation observed was found to also depend strongly on the RF voltage applied to the ring electrode; higher RF voltage produced enhanced fragmentation. A gated RF experiment further demonstrated the importance of the level of the RF voltage, during the initial activation event, in producing fragmentation. A study of the effects of buffer gas composition and pressure showed that increased pressure may result in reduced fragmentation due to collisional cooling in the trap. However, the use of argon or nitrogen buffer gas at increased pressure in the trap may result in fragmentation upon extraction from the trap, producing metastable ions in the flight tube. The implications of the use of the time variable for obtaining fragmentation in the trap for rapid sequencing are discussed.

Amino Acid Sequence↗