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Biomedical subjects

B Hudson

Publications and source records attributed to B Hudson.

At least 19 recordsLinked to original sources
PubMed1991

Corneal biopsy in microbial keratitis.

Presumed microbial keratitis in the absence of a specific microbiological diagnosis is a particularly difficult clinical problem. Corneal biopsy may provide the diagnosis when corneal scrapings have been negative. We present two cases in which corneal biopsy was helpful and discuss the role of corneal biopsy in the management of chronic keratitis.

Acanthamoeba Keratitis↗
PubMed1989

Pattern recognition display methods for the analysis of computed molecular properties.

Pattern recognition methods, particularly the 'unsupervised learning' techniques, are well suited for the preliminary analysis of the large data sets produced by computer chemistry. The use of linear and non-linear display methods for such exploratory analysis are exemplified with the aid of two data sets of biologically active molecules. Advantages and disadvantages of these techniques are discussed.

Computer Simulation↗
PubMed1989

Critical density fluctuations in lipid bilayers detected by fluorescence lifetime heterogeneity.

The heterogeneity of the decay of the fluorescence of transparinaric acid in single-component lipid bilayers at temperatures above their gel/liquid crystalline phase transition is shown to be due to the presence of regions of higher local density and higher acyl chain order than the predominant fluid regions. This conclusion is based on selective excitation behavior and the observation of time-resolved fluorescence anisotropies that increase at long times. The fractional amplitude of the long lifetime component of the fluorescence shows a temperature variation that conforms to conventional descriptions of critical behavior. The critical exponent extracted from this variation is 1.1, close to the value of 1.0 that describes ultrasonic data. We therefore conclude that liquid crystalline lipid bilayers exhibit critical behavior with significant density and order fluctuations. This behavior must be taken into account in the interpretation of fluorescence and other spectroscopic measurements of the properties of bilayers.

Kinetics↗
PubMed1989

Analysis of the anisotropy decay of trans-parinaric acid in lipid bilayers.

An analysis is presented of the complex anisotropy behavior of trans-parinaric acid in single component DEPC lipid bilayers. It is shown that a model involving two species with distinct lifetime and motional behavior is required, and is adequate, to explain the observed data. In particular, the observed increase in the anisotropy at long times demonstrates the presence of a species with a long fluorescence lifetime that has a high anisotropy. The time dependence of the anisotropy for these two environments is treated using both a purely mathematical sum of exponentials and a constrained fit based on an approximate solution of the anisotropic diffusion problem. In this latter model the anisotropy is described in terms of the second and fourth rank order parameters, (P2) and (P4), and a single dynamical parameter, D1, the perpendicular diffusion coefficient for this uniaxial probe. The parameters of both models are accurately determined from the fits to the data when two environments coexist and an association is made between lifetime components and distinct rotational sites. The values of the parameters obtained demonstrate the "solid-like" and "fluidlike" nature of these two coexisting environments.

Fatty Acids, Unsaturated↗
PubMed1989

Acetylator phenotype and short-course chemotherapy for tuberculosis in Papua New Guinea.

In Papua New Guinea the slow acetylator phenotype is unusual and peripheral neuropathy during isoniazid therapy is uncommon. Acetylator status and other factors influencing isoniazid-induced peripheral neuropathy are discussed, and statistics from Papua New Guinea are presented. The relevance of acetylator phenotype to other side-effects of isoniazid is less well defined. Prophylactic pyridoxine supplementation during short-course chemotherapy for tuberculosis is not generally necessary in the daily 'A' regimen, but should be maintained in the twice-weekly (high-dose isoniazid) 'B' regimen for adults and children over 20 kg.

Acetylation↗
PubMed1987

Time-resolved fluorescence anisotropy for systems with lifetime and dynamic heterogeneity.

The time dependence of the fluorescence anisotropy expected when a fluorophore exists in distinct environments having different fluorescence decay and motional behavior is illustrated by simulation calculations. A wide range of behavior is observed. The analysis of such decays in terms of the underlying physical parameters is also illustrated and discussed. In particular, the analysis of 'associated' heterogeneous behavior using a homogeneous environment model with complex motional behavior is evaluated. It is argued that anisotropy decays that exhibit a high initial anisotropy and that rise at long times must be due to a heterogeneous environment. Anisotropic rotor diffusion cannot give rise to behavior of this type. A similar conclusion is reached for anisotropies that exhibit downward curvature. On the other hand, anisotropy decays that are monotonically decreasing and have a positive second derivative at all times cannot be analyzed in a unique fashion and therefore an ambiguity exists in the interpretation of such data in terms of motional behavior.

Fluorescence Polarization↗
PubMed1987

Alpha-inhibin gene expression occurs in the ovine adrenal cortex, and is regulated by adrenocorticotropin.

Inhibin is a glycoprotein hormone composed of two nonidentical subunits. It is produced by the ovary and testis and plays a vital role in gonadal function by inhibiting the secretion of FSH. More recently, additional activities associated with inhibin peptides have been identified. Inhibin heterodimers (alpha-beta) are reported to act directly on ovarian granulosa cells and inhibit estrogen production induced by FSH. Furthermore, homodimers of beta-inhibin subunits stimulate the secretion of FSH, an activity that is directly opposite to that of inhibin. Each of these inhibin-related activities are concerned with the hypothalamic-pituitary-gonadal axis. We have investigated further the complexity of inhibin activity by determining whether inhibin genes are expressed in nongonadal tissue. RNA hybridization experiments demonstrate that the alpha-inhibin gene is expressed in the sheep adrenal cortex and hybridization histochemistry shows that this gene is expressed in each of the functional zones within the cortex. Dot blot analysis showed that the level of alpha mRNA within the adrenal is influenced by ACTH, one of the major regulators of adrenal cortex function. These observations imply that there are inhibin-related peptides not directly associated with the gonads. beta-inhibin gene expression was not clearly detected in the adrenal and we conclude that if expression occurs then it does so at extremely low levels.

Adrenal Cortex↗
PubMed1985

Testicular vein ligation and fertility in men with varicoceles.

Pregnancy rates in 651 subfertile couples in which the man had a varicocele were analysed by life table methods and were not found to be significantly different before and after testicular vein ligation performed in 283 patients. Estimated proportions of couples conceiving were roughly 30% by one year and 45% by two years in both groups. The operation was also not associated with improvement in results of semen analysis. These findings suggest that testicular vein ligation for varicoceles does not improve fertility.

Female↗
PubMed1985

Variability in the apparent molecular weight of inhibin.

An in vitro bioassay based on suppression of GnRH-stimulated FSH secretion by pituitary cells in culture was used to monitor inhibin activity after dialysis, gel filtration or polyacrylamide gel electrophoresis of protein preparations from a variety of gonadal secretions and extracts under native and dissociating conditions. The suggestion that inhibin is a peptide of molecular weight less than 5000 was not confirmed. Although some fractions of low molecular weight suppressed FSH secretion, the amount of activity was low and the dose response curves were not parallel with a standard preparation of inhibin. Under most conditions, inhibin eluted with an apparent molecular weight of about 90 000. However, gel filtration of rete testis fluid protein in 1 M acetic acid resulted in elution of inhibin activity with a lower apparent molecular weight and with polyacrylamide gel electrophoresis in 0.1% (w/v) sodium dodecylsulfate, the apparent molecular weight was 30 000. It is concluded that inhibin is a protein which tends to aggregate and coelute with larger molecules.

Animals↗
PubMed1985

Ultraviolet resonance Raman excitation profiles of nucleic acid bases with excitation from 200 to 300 nanometers.

Raman spectra are presented for dilute aqueous solutions of the four ribonucleotides AMP, GMP, UMP, and CMP obtained with laser excitation at 299, 266, 253, 240, 229, 218, 209, and 200 nm. Distinct evidence of strong, selective resonance enhancement is obtained. Low-resolution excitation profiles have been constructed for the strongest bands by using the phosphate band at 994 cm-1 as an internal reference. The excitation spectra for many of the vibrational bands are dominated by a peak corresponding to the lowest-energy electronic transition near 260 nm. Smaller peaks are seen for higher-energy electronic transitions. For some modes, the resonance enhancement is dominated by the higher-energy transitions. It is clear from these new data that a full description of the resonance Raman profiles of the nucleic acids will have to include several excited electronic states. Two examples are given of cases where ionic species can be distinguished easily by using far-UV excitation, but these species are indistinguishable with 266-nm excitation. This demonstrates the utility of far-UV resonance Raman spectroscopy for obtaining structural information.

Adenosine Monophosphate↗