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Biomedical subjects

K Wilson

Publications and source records attributed to K Wilson.

At least 199 records · Page 11Linked to original sources
PubMed1994

Amplification of the inosinate dehydrogenase gene in Trypanosoma brucei gambiense due to an increase in chromosome copy number.

Drug resistance is a significant impediment to the therapy of African sleeping sickness in humans. To evaluate molecular mechanisms that contribute to drug resistance in African trypanosomes, a clonal strain of Trypanosoma brucei gambiense, MPA10, was selected in medium containing mycophenolic acid (MPA), an inhibitor of IMP dehydrogenase (IMPDH) activity. IMPDH activity in MPA10 cells was approximately 6-fold higher than that of wild type parental cells, although the enzymes in both strains were equally sensitive to inhibition by MPA. To evaluate the mechanism of IMPDH overexpression in MPA10 cells, the gene encoding IMPDH (impdh) was isolated from a T.b. brucei library by cross-hybridization to the Leishmania donovani impdh. Sequence analysis indicated that the T. brucei IMPDH was 76% identical with the L. donovani IMPDH. The T. brucei impdh hybridized to a 2.7-kb transcript that was expressed at approximately 10-fold greater levels in the MPA10 cells, and this impdh overexpression could be ascribed to an approximately 10-fold amplification of the impdh copy number. Pulsed field gel electrophoresis revealed that the extra impdh copies in MPA10 cells were localized to an approximately 6.0-Mb chromosome that comigrated with the wild type chromosome encompassing impdh. The amplification of impdh could be ascribed to an increased copy number of this 6.0-Mb chromosome, and a predicted augmented DNA content in MPA10 cells was confirmed by flow cytometry. This is the first demonstration that DNA amplification can serve as a molecular mechanism by which T. brucei become resistant to cytotoxic drugs, and the amplification of the 6.0-Mb chromosome represents a novel mechanism of drug resistance in parasitic protozoa.

Animals↗
PubMed1994

2.2 A resolution structure of the amino-terminal half of HIV-1 reverse transcriptase (fingers and palm subdomains).

BACKGROUND: HIV-1 reverse transcriptase (RT) catalyzes the transformation of single-stranded viral RNA into double-stranded DNA, which is integrated into host cell chromosomes. The molecule is a heterodimer of two subunits, p51 and p66. The amino acid sequence of p51 is identical to the sequence of the amino-terminal subdomains of p66. Earlier crystallographic studies indicate that the RT molecule is flexible, which may explain the difficulty in obtaining high-resolution data for the intact protein. We have therefore determined the structure of a fragment of RT (RT216), which contains only the amino-terminal half of the RT molecule ('finger' and 'palm' subdomains). RESULTS: The crystal structure of RT216 has been refined at 2.2 A resolution to a crystallographic R-value of 20.8%. The structure is very similar to that of the corresponding part of the p66 subunit in the p66/p51 heterodimer, although there is a small difference in the relative orientation of the two subdomains compared with the structure of an RT-DNA-antibody fragment complex. There are a large number of stabilizing contacts (mainly hydrogen bonds and hydrophobic interactions) between the subdomains. The locations of conserved amino acids and the position of some important drug-resistant mutations are described. CONCLUSIONS: The RT216 structure provides detailed three-dimensional information of one important part of HIV-1 RT (including the critical active site residues). We propose a model to explain the inhibitory effect of non-nucleoside inhibitors, which partially accounts for their effect in terms of conformational changes of active site residues.

Binding Sites↗
PubMed1994

Cloning and sequence analysis of a Drosophila melanogaster cDNA encoding IMP dehydrogenase.

A cDNA encoding the entire Drosophila melanogaster IMP dehydrogenase (IMPDH) protein was isolated and sequenced. Translation of the impdh cDNA nucleotide sequence indicated that the Drosophila IMPDH exhibited 48% and 65% amino acid identity to the Leishmania donovani and human isoform II counterparts, respectively. Northern analysis revealed that expression of the 2.4 kb impdh transcript was equivalent in adult Drosophila head and body and that impdh expression was developmentally regulated. In situ hybridization of the cloned impdh cDNA probe to Drosophila salivary gland chromosomes indicated that the impdh gene is located at position 9E1-4 on the X chromosome.

Amino Acid Sequence↗
PubMed1994

Identification, characterization, and physical mapping of 14 polymorphic simple sequence repeat markers on human chromosome 21.

Fourteen new dinucleotide repeat polymorphisms specific for human chromosome 21 have been identified, mapped, and characterized. The average heterozygosity of all markers was 0.66. The average PIC value was 0.61. The markers were mapped by STS content mapping of YACs previously assigned to chromosome 21. The correlation of polymorphic genetic markers with substantially complete physical maps should facilitate the identification of loci of interest on chromosome 21.

Base Sequence↗
PubMed1994

Metastatic implantation of an oral squamous-cell carcinoma at a percutaneous endoscopic gastrostomy site.

Percutaneous endoscopic gastrostomy (PEG) has become an important adjunct in the care of the head-and-neck cancer patient. When resection will likely affect swallowing, PEG can be performed just prior to cancer resection. However, it is unclear whether PEG should be the procedure of choice for establishing enteral access in head-and-neck cancer patients. In this report we describe a man with advanced oral squamous cell carcinoma who had a One-Step PEG button inserted immediately prior to his cancer resection. Six months later, the patient developed metastatic squamous-cell carcinoma at the PEG site. Although the mechanism of spread cannot be confirmed, direct seeding from passage through the cancer-filled oral cavity seems likely. Methods of establishing enteral access which avoid tumor-contaminated fields, such as use of an overtube during conventional PEG, open gastrostomy, or laparoscopic gastrostomy, may be more appropriate in head-and-neck cancer patients.

Abdominal Muscles↗
PubMed1994

Practical detection of epileptiform discharges (EDs) in the EEG using an artificial neural network: a comparison of raw and parameterized EEG data.

We have developed and tested "off-line" an artificial neural network (ANN) that successfully detects epileptiform discharges (EDs) when trained on EEG records marked by an electroencephalographer (EEGer). The system was trained on both parameterized and raw EEG data and can process 49 channels of EEG data in real time on an 80486/33 MHz personal computer, making it capable of processing EEG on-line in long-term monitoring units. Our detector consists of 2 stages: (1) a threshold detector identifies candidate EDs in 4-channel bipolar chains within the recording montage, parameterizes them and then passes these data to the second stage; (2) a 3-layer feed-forward ANN decides if a candidate wave form is an ED. The intersection of detector sensitivity and selectivity curves, or crossover threshold, for 10 patients from our Epilepsy Monitoring Unit occurred at 73% for parameterized EEG data and at 46% for "raw" EEG data. The ANN could be adapted to different EEGers' styles by changing the ANN output threshold for accepting candidate wave forms as EDs. In this "proof of principle" study the detector was trained on EEGs from 10 Johns Hopkins Hospital Epilepsy Monitoring Unit (JHH EMU) patients. We used different EEGs from the same patients for testing. Current testing should demonstrate that the ANN detector can generalize to previously "unseen" patients. This study shows that ANNs offer a practical solution for automated, real time ED detection that uses, standard, inexpensive computers, is easily adjustable to individual EEGer style and can produce sensitivities and selectivities similar to those of EEGers.

Brain↗
PubMed1994

Cyclopenta[cd]pyrene-induced tumorigenicity, Ki-ras codon 12 mutations and DNA adducts in strain A/J mouse lung.

Cyclopenta[cd]pyrene (CPP) is a ubiquitous cyclopenta-fused polycyclic aromatic hydrocarbon. CPP is highly genotoxic in bacterial and mammalian systems inducing gene mutations, sister chromatid exchanges and morphological transformation. CPP is a mouse skin carcinogen, a mouse skin tumor initiator and induces pulmonary tumors in newborn mice. We have examined the tumorigenic activity of CPP in strain A/J mice, have determined the formation and persistence of CPP-induced DNA adducts in lung tissue, and analyzed the mutational spectrum in the Ki-ras oncogene from CPP-induced tumors. CPP dissolved in tricaprylin was administered by i.p. injection to male A/J mice (20 mice/dose) at 0, 10, 50, 100 and 200 mg/kg. Animals were killed 8 months later and the lungs removed, fixed, and surface adenomas enumerated. CPP proved to be highly tumorigenic in A/J mice in terms of inducing lung adenomas. The observed tumor multiplicities (lung adenomas/mouse) were: 97.7 +/- 28.7 at 200 mg/kg, 32.8 +/- 15.4 at 100 mg/kg, 4.63 +/- 2.11 at 50 mg/kg and 0.58 +/- 0.82 at 10 mg/kg. Tricaprylin-treated controls produced 0.60 +/- 0.58 lung adenomas/mouse. Groups of mice treated under the same dosing conditions as those in the tumor studies were killed 1, 3, 7, 14 and 21 days after treatment. The lungs were removed, and the DNA was subjected to DNA adduct analysis by the 32P-postlabeling method. Total CPP-DNA adducts in mouse lung peaked at day 3 with 5870 amol CPP adducts/micrograms DNA after a single dose of 200 mg/kg. DNA adduct levels decreased to 1800 amol CPP adducts/micrograms DNA at day 21. Qualitative DNA adduct analysis revealed four major adducts and one minor adduct. Co-chromatography of the lung DNA from CPP-treated mice with calf thymus DNA treated with CPP-3,4-oxide indicated that all DNA adducts were oxide derived and comparison with CPP-3,4-oxide-treated polydeoxyguanylic acid suggests that almost all of these adducts are CPP-3,4-oxide-2'-deoxyguanosine adducts. Ki-ras codon 12 mutation analysis of the DNA from tumors taken from the 100 and 200 mg/kg CPP dose groups demonstrated the following patterns: GGT-->CGT (50%); GGT-->GTT (15%); GGT-->TGT (25%); GGT-->GAT (10%). We conclude that CPP is highly tumorigenic in the A/J mouse lung adenoma model, being five times more active than benzo[a]pyrene. This is unlike the result of CPP as a mouse skin tumorigen or tumor initiator in which CPP is considerably less potent than benzo[a]pyrene.(ABSTRACT TRUNCATED AT 400 WORDS)

Adenoma↗
PubMed1994

Maternal hypoxia as a model for intrauterine growth retardation: effects on insulin-like growth factors and their binding proteins.

Evidence suggests that IGF and their binding proteins play a role in fetal growth, but more knowledge concerning their regulation is essential. We examined the expression of IGF and their binding proteins in experimental intrauterine growth-retarded (IUGR) rat fetuses of hypoxic dams (13-14% oxygen, d 14-21 of gestation). The mean body weight of the fetuses (d 21 of gestation, n = 72) of the six hypoxic dams was 24% lower (p < 0.0001) than the mean weight of the fetuses of six control dams (n = 82). Wet liver weights demonstrated a 20% decrease (p < 0.0001) and placentas a 10% decrease (p < 0.01) compared with control fetuses. The mean serum concentrations of immunoreactive IGF-I in both groups were low but did not differ significantly. The mean serum concentrations of immunoreactive IGF-II, however, were higher in IUGR fetuses. As assessed by Northern blot analysis, there was a 4-fold increase in insulin-like growth factor binding protein-1 (IGFBP-1) mRNA expression in the livers of the IUGR fetuses compared with controls. IGFBP-2 mRNA expression was 6-fold increased in IUGR fetal livers. No difference was found in IGFBP-4 mRNA. An increase in IGFBP-1, -2, and -4 concentrations could be seen by Western ligand blotting in the serum of growth-retarded fetuses compared with control fetuses. This finding was verified by immunoprecipitation with specific antibodies, which demonstrated increases in IGFBP-1 and IGFBP-2. Our results validate the use of maternal hypoxia as an experimental model of intrauterine growth retardation and indicate that increased IGFBP-1 and -2 expression may be of importance in the etiology of fetal growth retardation caused by maternal hypoxia.

Animals↗
PubMed1994

Racial differences in rural adults' attitudes toward issues of adolescent sexuality.

This study, based on a random sample of adults in a rural North Carolina county, demonstrates racial differences in rural adults' attitudes relating to adolescent sexual issues. Blacks were 50% more likely than Whites to indicate that public schools should provide general health care services, including pregnancy testing and treatment of sexually transmitted diseases, to teenagers; however, they were only half as likely as Whites to approve of sexual experimentation by adolescents. The local community's attitudes must be considered in the implementation of rural adolescent health programs, including acquired immunodeficiency syndrome education.

Abortion, Induced↗
PubMed1994

7-Ethoxycoumarin O-deethylase kinetics in isolated rat, dog and human hepatocyte suspensions.

1. A comparative study of the kinetics of the O-deethylation of 7-ethoxycoumarin has been carried out in freshly isolated rat, dog and human hepatocytes. 2. Biphasic kinetics were observed for all three species with apparent Km and Vmax values of 11.5, 2.2 and 3.9 microM and 0.30, 0.21, 0.007 nmol/min/10(6) cells from rat, dog and man, respectively, for the high affinity-low capacity component, and 560, 40, 470 microM and 1.52, 0.74, 0.057 nmol/min/10(6) cells, respectively, for the low affinity-high capacity component. 3. These observed kinetic parameters in hepatocytes from rat and man were similar to published values for microsomes for the same two species. 4. Values for intrinsic clearance of 7-ethoxycoumarin for the three species calculated from the Km and Vmax data were 152, 631 and 6 ml/min/kg for rat, dog and human hepatocytes, respectively. These intrinsic clearance values predict that 7-ethoxycoumarin would be subject to a high hepatic clearance in rat and dog, and low hepatic clearance in man. These values are supported by published data on rat which show that 7-ethoxycoumarin is subject to high clearance.

7-Alkoxycoumarin O-Dealkylase↗
PubMed1994

A 2 year, open ended trial of methotrexate in systemic lupus erythematosus.

OBJECTIVE: To investigate a possible role for methotrexate (MTX) in the treatment of patients with systemic lupus erythematosus (SLE) who require unacceptably high doses of glucocorticosteroids (GCS) for control of their disease. METHODS: Twelve patients with SLE participated in this open ended prospective study. Patients with active renal or central nervous system (CNS) disease were excluded as were patients with liver disease. Serological variables, SLE disease activity index, joint count, and prednisone dose were serially evaluated. Data were analyzed using paired t test and contingency table analysis. RESULTS: Arthritis was the major persistent problem in 7 patients: 1 patient had recurrent pleuropericarditis, 2 patients had refractory cutaneous lupus rashes and 2 had vasculitis. Three patients discontinued MTX because of side effects. The remaining 9 patients have been treated from 7-26 months. In 6 patients the GCS dose was reduced by an average of 42%. In 1 patient symptoms subsided and joint count was reduced without change in the GCS dose. GCS dosage was increased in 2 patients: 1 with recurrent serositis, 1 with persistent vasculitis. No apparent effect on anti-dsDNA antibodies, complement or erythrocyte sedimentation rate (ESR) was noted. CONCLUSION: MTX appears to be useful in selected patients with SLE, especially those with persistent synovitis.

Adult↗
PubMed1994

Glucocorticoid-induced formation of cross-linked actin networks in cultured human trabecular meshwork cells.

PURPOSE: To determine the effects of glucocorticoid treatment on the microfilament structure of cultured human trabecular meshwork cells. Topical or systemic administration of glucocorticoids can lead to the development of ocular hypertension and to the development of vision loss, which is clinically similar to primary open angle glaucoma. However, the mechanism(s) by which glucocorticoids cause ocular hypertension is not well defined. Alterations in the trabecular meshwork, the site of drainage of aqueous humor from the eye, have been linked to the development of ocular hypertension. METHODS: Human trabecular meshwork cells were cultured in the presence and absence of glucocorticoids for 0 to 21 days. The microfilament organization of the cultured trabecular meshwork cells was examined by epifluorescent and transmission electron microscopy. RESULTS: Glucocorticoids caused a progressive change in the organization of microfilaments in the trabecular meshwork cells, but not in other cultured ocular cells. By fluorescence microscopic analysis, the actin stress fibers found in control trabecular meshwork cells were reorganized on treatment with glucocorticoids into cross-linked actin networks that resembled geodesic-dome-like polygonal lattices. The cross-linked actin networks were reversible on withdrawal of the glucocorticoid treatment. Dose-response data for dexamethasone, relative ranking of activity with glucocorticoid potency, and partial inhibition with glucocorticoid antagonists all suggest the involvement of the trabecular meshwork glucocorticoid receptor in cross-linked actin network formation. The reorganization of the trabecular meshwork cytoskeleton alters cell function because glucocorticoid treatment of cultured trabecular meshwork cells also inhibited trabecular meshwork cell migration and proliferation. CONCLUSION: The steroid-induced alteration in trabecular meshwork cytoskeleton may be an important factor in the development of steroid-induced ocular hypertension and may play a role in the ocular hypertension associated with primary open angle glaucoma.

Actin Cytoskeleton↗
PubMed1994

The use of a polymerase chain reaction as a diagnostic test for Rocky Mountain spotted fever.

A polymerase chain reaction (PCR) for amplifying ribosomal DNA of Rickettsia rickettsii was performed on blood clots and urine samples from 10 patients with suspected Rocky Mountain spotted fever (RMSF) and five controls with nonrickettsial diseases. The results of this PCR-based procedure were positive in four of the five patients with probable RMSF, but reamplification was required in three patients. Rickettsia rickettsii was grown from the blood of two of these four patients. The urine from one patient was also PCR-positive. These results confirm earlier findings that the PCR can detect R. rickettsii, but the need for reamplification indicates that the lack of sensitivity is a serious limitation in the usefulness of the PCR as a clinical diagnostic test.

Bacteremia↗
PubMed1993

Legislative issues related to breast cancer.

Cancer is a political issue. Legislative decision-making as it relates to breast cancer must be driven by reliable scientific data and analysis. Carefully directed advocacy and responsible leadership can provide focus, resources, and enhancements for a beneficial impact on lives of breast cancer patients and potential patients.

American Cancer Society↗
PubMed1993

The inhibitory effects of Ro 31-6930 and BRL 38227 on cholinergically-mediated bronchoconstriction in the guinea-pig.

This study compares the effects of two K(+0-channel openers, Ro 31-6930 and BRL 38227, on cholinergically-evoked contraction of guinea-pig airways to examine whether either compound acts through prejunctional inhibition of the release of acetylcholine. In the isolated trachea, Ro 31-6930 and BRL 38227 evoked concentration-dependent inhibition of tone generated by electrical field stimulation with pD2 values of 7.03 (6.77-7.29) and 6.26 (5.91-6.61) respectively and of that elicited by acetylcholine with pD2 values of 7.38 (6.52-8.24) and 6.65 (6.16-7.13). Neither compound was more potent against responses to electrical field stimulation than against acetylcholine. In the anaesthetised guinea-pig, Ro 31-6930 inhibited the bronchoconstriction evoked by bilateral vagus nerve stimulation and intravenous acetylcholine with ID50 values of 12.9 +/- 3.9 and 3.6 +/- 1.3 micrograms/kg i.v. respectively. The corresponding values for BRL 38227 were 356 +/- 157 and 37.9 +/- 13.4 micrograms/kg i.v. respectively. Thus, in vivo, both compounds were more potent against acetylcholine than against vagal stimulation. These results provide indirect evidence that K(+)-channel openers do not inhibit the release of acetylcholine from parasympathetic nerves in guinea-pig airway smooth muscle.

Acetylcholine↗
PubMed1993

Crystal structure of apo-neocarzinostatin at 0.15-nm resolution.

The three-dimensional structure of apo-neocarzinostatin, an antitumour antibiotic protein isolated from Streptomyces carzinostaticus, has been determined by X-ray diffraction at 0.15-nm resolution and refined to R = 17.2%. The crystal structure of neocarzinostatin is similar to that of the related proteins actinoxanthin and macromomycin. It is also in good agreement with the solution structure determined by NMR spectroscopy. The protein molecule consists of a seven-stranded antiparallel beta-sandwich and a smaller lobe formed by two beta-ribbons. A deep cleft between the two lobes is a putative chromophore binding site. Side chains of Trp39, Leu45, Phe52, Phe78 and the disulphide Cys37-Cys47 aligning the binding cleft in neocarzinostatin suggest the importance of hydrophobic interactions in stabilizing the chromophore molecule. Comparison of the atomic models of neocarzinostatin, actinoxanthin and macromomycin reveals functional residues which might determine specificity towards different chromophores.

Amino Acid Sequence↗