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Biomedical subjects

J P Barnes

Publications and source records attributed to J P Barnes.

At least 19 recordsLinked to original sources
PubMed1999

A multifrequency electron spin resonance study of T4 lysozyme dynamics.

Electron spin resonance (ESR) spectroscopy at 250 GHz and 9 GHz is utilized to study the dynamics and local structural ordering of a nitroxide-labeled enzyme, T4 lysozyme (EC 3.2.1.17), in aqueous solution from 10 degrees C to 35 degrees C. Two separate derivatives, labeled at sites 44 and 69, were analyzed. The 250-GHz ESR spectra are well described by a microscopic ordering with macroscopic disordering (MOMD) model, which includes the influence of the tether connecting the probe to the protein. In the faster "time scale" of the 250-GHz ESR experiment, the overall rotational diffusion rate of the enzyme is too slow to significantly affect the spectrum, whereas for the 9-GHz ESR spectra, the overall rotational diffusion must be accounted for in the analysis. This is accomplished by using a slowly relaxing local structure model (SRLS) for the dynamics, wherein the tether motion and the overall motion are both included. In this way a simultaneous fit is successfully obtained for both the 250-GHz and 9-GHz ESR spectra. Two distinct motional/ordering modes of the probe are found for both lysozyme derivatives, indicating that the tether exists in two distinct conformations on the ESR time scale. The probe diffuses more rapidly about an axis perpendicular to its tether, which may result from fluctuations of the peptide backbone at the point of attachment of the spin probe.

Bacteriophage T4↗
PubMed1998

Dynamics and ordering in mixed model membranes of dimyristoylphosphatidylcholine and dimyristoylphosphatidylserine: a 250-GHz electron spin resonance study using cholestane.

We report here on a 250-GHz electron spin resonance (ESR) study of macroscopically aligned model membranes composed of mixtures of dimyristoylphosphatidylcholine (DMPC) and dimyristoylphosphatidylserine (DMPS), utilizing the nixtroxide-labeled cholesterol analog cholestane (CSL). Two clearly resolved spectral components, distinct in both their ordering and dynamics, are resolved. The major component in membranes composed mostly of DMPC shows typical characteristics, with the long axis of CSL parallel to the bilayer normal with slow (10(6) </= R </= 10(7) s-1) rotational diffusion rates, as expected for cholesterol. The second component grows in as the mole fraction of DMPS increases. A detailed analysis shows that CSL senses a local, strongly biaxial environment. Our results imply that the inefficient packing between cholesterol and DMPS occurs probably because of the strong interactions between the PS headgroups, which provide the local biaxiality. Such a packing of the headgroups has been predicted by molecular dynamics simulations but had not been observed experimentally. The analysis of these spectral components was greatly aided by the excellent orientational resolution provided by the 250-GHz spectra. This enabled the key qualitative features of this interpretation to be "read" off the spectra before the detailed analysis.

Cholestanes↗
PubMed1995

The distribution of electron trapping in DNA: one-electron-reduced oligodeoxynucleotides of adenine and thymine.

A series of single- and double-stranded oligodeoxynucleotides of adenine and thymine, 8 to 12 nucleotides in length, were one-electron-reduced at 10 K in a > 8 M LiCl/H2O glass. The Q-band electron paramagnetic resonance (EPR) spectra of these radicals show that thymine is the dominant trapping site for mobile electrons in these oligomers. The spectra of the reduced oligomers in the series pd(AnT10-n).pd(A10-nTn) with n = 5-->10 showed a trend which is interpreted as either an increase in the probability of trapping at an adenine base in tracks of adenine > 7 base pairs in length, or the presence of different protonated states of the one-electron-reduced bases due to the adoption of a different conformational state for longer tracks of adenine, or a combination of these two possibilities. Analysis of the trends in the EPR spectra of the radicals as a function of sequence using multicomponent analysis is presented.

Adenine Nucleotides↗
PubMed1994

Distribution of targets for avian retrovirus DNA integration in vivo.

The targeting of DNA integration in retrovirus-infected cells is a central yet very poorly understood aspect of the biology of the virus. To investigate this problem, we have assessed the use of specific sites for integration targets of avian leukosis virus (ALV) DNA within defined regions of turkey embryo fibroblast (TEF) cellular DNA. For this purpose, we developed an assay of sufficient sensitivity and specificity to allow detection and location of single integration events in a population of 5 million cells. Targets selected for study were either regions cloned by virtue of a previous integration event or clones chosen at random from cellular DNA. By use of this approach, we found that all genomic regions tested contained integration targets, with a frequency that varied from approximately 0.2 to 4 times that expected for random integration. Within regions, the frequency of use of specific sites varied considerably, with some sites used up to 280 times random frequency. When one region was introduced into cells at moderately high copy number by transfection, it provided integration targets in a pattern very much like that seen with the same sequence in vitro. On the basis of our sampling, we conclude that most or all regions of the TEF genome are accessible to ALV retroviral integration. As with integration in vitro, integration specificity seems to be determined largely by local structural features rather than accessibility of specific regions.

Animals↗
PubMed1994

Metabolism of cycloate in radish leaf: metabolite identification by packed capillary flow fast atom bombardment tandem mass spectrometry.

The metabolism of cycloate, a thiocarbamate herbicide, was investigated in mature radish leaf. Twelve new metabolites were identified by liquid chromatographic/mass spectrometric analysis using fast atom bombardment and packed capillary liquid chromatography columns. Full-scan and tandem mass spectrometric methods were employed. Application of the on-column focusing technique resulted in identifications with injections of as little as 15 ng of metabolite (20 ppb in radish). This injection technique allows the practical use of packed capillary liquid chromatography/mass spectrometry in sample-limited applications. Cycloate is oxidized to several ring-hydroxylated isomers that are subsequently glucosylated and esterified with malonic acid. Cycloate is also conjugated with glutathione. Metabolic hydrolysis of the glutathione conjugate formed a cysteine conjugate that is further metabolized by amidation with either malonic or acetic acid. Transamination of the cysteine conjugate gave a thiolactic acid derivative. Metabolites were also identified that were the result of both ring-hydroxylation and conjugation with glutathione. One of these, an N-acetylcysteine conjugate, is the first report of a mercapturic acid in plants. The structures of two of the new metabolites were confirmed by chemical synthesis.

Biotransformation↗
PubMed1993

Leukocyte common antigen-related receptor-linked tyrosine phosphatase. Regulation of mRNA expression.

Receptor-linked tyrosine phosphatases regulate cell growth by dephosphorylating proteins involved in tyrosine kinase signal transduction. Within this gene family, the leukocyte common antigen-related (LAR) gene is of particular interest with respect to the nervous system because it has sequence similarity to the neural cell adhesion molecule N-CAM and is located in a chromosomal region (1p32-33) frequently deleted in neuroectodermal tumors. However, immunostaining has detected LAR in non-neural tissues, but not in the central nervous system, peripheral neurons, or adrenal medulla. In this study, rat brain cDNA library LAR clones corresponding to cytoplasmic and 3'-untranslated regions of human LAR were identified. Using probes derived from these clones, high stringency Northern blots revealed approximately 8 kilobase and variable length tissue- and cell-specific LAR transcripts in cortex, brainstem, cerebellum, spinal cord, peripheral tissues, and cultured neural, glial, and pheochromocytoma cells. In situ hybridization showed expression by brain and dorsal root ganglion neurons. LAR expression was developmentally regulated in a region-dependent manner. Changes in LAR expression were also found during nerve growth factor-induced PC12 pheochromocytoma cell differentiation and with contact-mediated inhibition of fibroblast growth. These observations and studies demonstrating neurotrophins functioning via tyrosine kinase receptors suggest that LAR represents an additional mechanism regulating neural development.

Animals↗
PubMed1993

Laparoscopic appendectomy: treatment of choice for suspected appendicitis.

Results and complications in 100 patients treated over a 3-year period with the laparoscopic approach for clinically diagnosed acute appendicitis are evaluated. They are compared with results and complications in 100 patients with the same diagnosis who had been treated with the open technique performed by the same surgeon during the same 3 years. The results suggest that laparoscopy provides excellent exposure of the appendix regardless of its position. In the absence of pathology of the appendix, laparoscopy allows for a thorough examination of the entire abdomen and pelvis and good exposure and definitive treatment of most surgical conditions encountered. In the event of appendicitis, regardless of its severity, laparoscopic appendectomy results in less postoperative pain, shorter hospital stays, faster return to normal activities, fewer postoperative complications, and superior cosmetic results. Our experience suggests that the laparoscopic approach is the best approach to diagnosis and treatment of the conditions encountered in patients with suspected appendicitis.

Abdominal Pain↗
PubMed1993

Current techniques in laparoscopic appendectomy.

An improved technique for laparoscopic appendectomy based on an experience of > 120 cases is presented. This method includes numerous additions to and modifications of previously described techniques and is effective for gangrenous and perforated appendicitis as well as for less severe cases. The most important elements are that (a) it is a safer procedure for attaining insertion of the Veress needle and the primary trocar; (b) it employs electrocautery to separate the appendix from the mesoappendix; (c) an Endosac can be used for removal of the appendix from the abdomen without contamination of the abdominal wall; (d) no laser is necessary; and (e) staples are rarely necessary.

Appendectomy↗
PubMed1990

Recurrent inguinal hernia in relation to ideal body weight.

The records of 686 patients who underwent herniorrhaphy for primary or initially recurrent inguinal hernia during the years 1975 through 1985 were reviewed. Patients were divided into groups according to percentage of ideal body weight. Analysis showed that, compared with the patients with primary hernia, a larger proportion of patients with recurrent hernia were near or below ideal body weight. A follow-up survey of 64 patients who underwent primary repair of hernia indicated that the percentage of ideal body weight of a patient had no apparent effect on the recurrence rate of inguinal hernia.

Adult↗
PubMed1987

Inguinal hernia repair with routine use of Marlex mesh.

An analysis of an 11 year experience with the routine use of Marlex (polypropylene) mesh reinforcement of the canal floor in both indirect and direct inguinal herniorraphy is presented. All patients in good general health were accepted regardless of their age or weight. Survey responses were obtained from a large and representative sample of this experience. The results of this series demonstrate that Marlex mesh is well tolerated in the inguinal canal and that the recurrence rates are low for both direct and indirect inguinal hernias. In particular, there were no recurrences in patients less than 60 years of age and no recurrence in patients weighing less than 185 kilograms. The average weight of patients with a recurrence was 92 kilograms and the average age was 72 years old. Several possible ways to improve the technique are discussed.

Adult↗
PubMed1975

Joining gut ends of unequal diameter.

A simple, safe and precise method for joining ends of unequal diameter is presented. Very little septum is created by either anterior or posterior rows. The figure-eight seems to crush the septum almost flat on the posterior row and the Halsted's create an absolutely minimal septum anteriorly where they are correctly placed. The posterior row used two layers of submucosa and the anterior one, four layers, and no reliance is placed on the serosa-muscularis layer. This technique is thought to have distinct advantages relative to strength, safety, and minimal septum formation.

Humans↗