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Biomedical subjects

D Chapman

Publications and source records attributed to D Chapman.

At least 217 records · Page 12Linked to original sources
PubMed1984

Biochemical and anatomical effects of antibodies against nerve growth factor on developing rat sensory ganglia.

The importance of nerve growth factor (NGF) for the development of sensory ganglia was investigated by injecting rat fetuses (16.50 days of gestation) with a single dose of anti-NGF antiserum. Four months later the treated animals showed a very large decrease in substance P- and somatostatin-like immunoreactivities in dorsal root ganglia and skin with a lesser decrease in trigeminal ganglia. Fluoride-resistant acid phosphatase, substance P-, and somatostatin-like immunoreactivities were greatly decreased in the dorsal horn of the spinal cord. No change in neurotensin- and [Met]enkephalin-like immunoreactivities was observed. The anti-NGF antiserum treatment produced a greater than 90% decrease in the number of unmyelinated dorsal root fibers and a 35% decrease in the total number of myelinated fibers. The loss in myelinated fibers was restricted to small-diameter fibers with no change in large-diameter fibers. No change in taste bud morphology was noted, thereby refuting the proposal that anti-NGF antiserum treatment may represent an animal model for familial dysautonomia. The present results indicate that NGF is a necessary requirement for the normal development of a significant population of prenatal rat dorsal root ganglion cells.

Aging↗
PubMed1984

The effects of ionizing radiation on the peroxide content of a pure polyunsaturated lipid dispersion and of lipids and membranes derived from Acholeplasma laidlawii.

Dispersions of a pure unsaturated phospholipid, dilinoleoylphosphatidyl choline, formed conjugated diene hydroperoxides when irradiated in air with 7 MeV electrons (150 Gy and 300 Gy). Peroxide formation was optimized when the dispersions were irradiated in air at 37 degrees C at a dose rate of 5 Gy/min. No significant loss of linoleic acid from the irradiated phospholipid dispersions was observed after doses of 150 or 300 Gy. Small amounts of thiobarbituric acid-reactive material were formed in irradiated unsaturated phospholipid dispersions. However, lipids or membranes isolated from 48 hour cultures of Acholeplasma laidlawii grown in media supplemented with either linoleic or linolenic acid did not appear to be peroxidized by irradiation under the same conditions.

Acholeplasma laidlawii↗
PubMed1983

Monitoring membrane protein rotational diffusion using time-averaged phosphorescence.

Rotational motions of membrane proteins have previously been measured using time-dependent phosphorescence techniques. This paper discusses a method of examining membrane protein mobility at temperatures relevant to biological systems, using a technique similar to steady-state fluorescence. The method is demonstrated using sarcoplasmic reticulum ATPase labelled with erythrosin isothiocyanate, both in its natural condition and crosslinked by incubation with glutaraldehyde. The experimentally-observed dependence of phosphorescence anisotropy on temperature is compared to a calculated anisotropy-temperature curve. Comparison is made between the anisotropy decay curves obtained by time-averaged phosphorescence and steady-state fluorescence.

Animals↗
PubMed1983

The biosynthetic incorporation of diacetylenic fatty acids into the biomembranes of Acholeplasma laidlawii A cells and polymerisation of the biomembranes by irradiation with ultraviolet light.

Acholeplasma laidlawii A has been grown in media containing synthetic, long chain C20- and C23-fatty acids possessing a diacetylene group in their acyl chains. Growth on the C23 diacetylenic acid was poor but was good on the C20 acid. Biosynthetic incorporation of the fatty acids occurs; as much as 90% of the membrane lipid fatty acyl chains consisting of the C20-diacetylenic fatty acid, the remainder being shorter chain, saturated fatty acids. The thermal phase transition of this biomembrane has been studied and a differential scanning calorimetry heating curve shows the presence of an endotherm corresponding to a membrane lipid phase transition occurring at about 26 degrees C. The lipid class composition of membranes containing the C20-diacetylene lipids was examined and found to be similar to membranes from cells grown on oleic acid-containing medium. (The ratio of monoglucosyl- to diglucosyldiacylglycerols was the same but the ratio of glycolipid to phosphatidylglycerol was higher in the cells grown with diacetylene fatty acids). Upon irradiation with ultraviolet light the cells and isolated biomembranes become coloured, either red or yellow depending upon their thermal history. The colour change indicates that extensive cross-linking of the lipids of the biomembranes of A. laidlawii has occurred and that a conjugated polymeric structure has been formed. Analysis of the extracted lipids from the biomembranes by GLC indicates that extensive cross-linking of the lipid chains within the biomembrane of a natural cell system has been achieved. The monoglucosyldiacylglycerols cross-link more readily that do the phosphatidylglycerol lipids. The effect of such lipid cross-linking or polymerisation on the activity at 35 degrees C of an intrinsic membrane-bound enzyme, NADH oxidase, and ribonuclease, an extrinsic membrane-bound enzyme, was studied. The NADH oxidase activity decreased rapidly upon cross-linking of the lipid environment whereas ribonuclease activity was unaffected. The potential for future studies of polymerised model and natural biomembranes is discussed.

Acholeplasma laidlawii↗
PubMed1983

Radiation studies of Acholeplasma laidlawii: the role of membrane composition.

Acholeplasma laidlawii, a mycoplasma, is unable to synthesize unsaturated fatty acids but it will incorporate them into its plasma membrane if they are supplied exogeneously. Thus the fatty acid composition of the cell membrane can be defined by growing the organism in media containing specific fatty acids. We obtained cells with predominantly one type of unsaturated fatty acid (either oleic, linoleic or linolenic acid) or cells with only saturated fatty acid in the cell membrane. The cells were irradiated with 7 MeV electrons and the effect of membrane fatty acid composition on cell survival was examined. At 200 Gy/min and 0.5 degrees C (melting ice) there was little difference in the radiation sensitivities of the cells grown in unsaturated fatty acids either in aerated or anoxic radiation conditions. However, the cells containing saturated fatty acids irradiated in anoxic conditions were markedly more sensitive than the cells containing unsaturated fatty acids. At 200 Gy/min and 37 degrees C the two types of cells were of similar sensitivity both in aerated and anoxic radiation conditions. At 5 Gy/min at 0.5 degrees C the cells containing linolenic acid (18:3) were less sensitive than those containing solely saturated fatty acids. However, at 5 Gy/min at 37 degrees C there was no difference in sensitivity between these two types of cell. Our results strongly argue against the involvement of lipid peroxidation as a molecular change leading to cell death.

Acholeplasma laidlawii↗
PubMed1983

Dose-dependent effects of capsaicin on primary sensory neurons in the neonatal rat.

The numbers of myelinated and unmyelinated fibers were counted in dorsal roots of adult rats treated neonatally with capsaicin in doses ranging from 5 to 100 mg/kg. Substance P and somatostatin levels in the spinal cord, dorsal roots, and sensory ganglia also were determined in control and treated animals. Capsaicin administration lead to the loss of both small myelinated and unmyelinated fibers from dorsal roots. However, whereas a near total loss, up to 94%, of unmyelinated fibers was achieved after high doses of capsaicin, the reduction of myelinated fibers, even of the smallest caliber, did not exceed 40%. The degree of fiber loss showed a clear dose dependency, with little detectable damage to myelinated fibers at doses of less than 50 mg/kg and with an ED50 for damage to unmyelinated fibers of 5 to 10 mg/kg. In all of the structures examined, particularly the dorsal roots, a roughly parallel decrease of substance P and somatostatin was found with capsaicin dose. The depletions of spinal cord substance P (55%) and somatostatin (20%) produced by neonatal capsaicin treatment were similar to those produced by dorsal rhizotomy. Capsaicin does not appear to be specific for primary afferents containing either substance P or somatostatin.

Animals↗
PubMed1982

The optical activity and circular dichroic spectra of diacetylenic phospholipid polymers.

Phospholipids (phosphatidylcholines) which contain a diacetylene group in a single acyl chain and within both acyl chains have been synthesized. Upon irradiation with ultraviolet light, both types of lipid crosslink via the diacetylene groups to produce coloured polymers. The colour arises from the conjugated double and triple bonds which make up the polymer backbone. These phospholipid polymers can exhibit optical activity, as shown by their circular dichroic spectra. The optical activity is thought to stem from asymmetric packing of the polydiacetylene chains, a packing of one particular screw sense being favoured by the chiral glycerol moiety of the lipid. The presence of an intrinsic membrane protein within the liposome structure affects the CD spectra of polymer produced by irradiation.

Calorimetry, Differential Scanning↗
PubMed1982

Stable biomembrane surfaces formed by phospholipid polymers.

Phospholipids (phosphatidylcholines) with diacetylene in each acyl chain have been deposited in Langmuir-Blodgett multilayers on a variety of substrates. Upon irradiation the diacetylene groups polymerise and link the phospholipid molecules together with a conjugated chain made up of alternating single, double and triple bonds. Advantage has been taken of this polymerisation process to increase the stability of these lipids layers and to produce stable biomembrane hydrophilic surface. These surfaces may be useful for studies of blood coagulation and protein adsorption. In addition they could also have medical application.

Biopolymers↗
PubMed1982

A statistical comparison of the emotional status of hospitalized versus nonhospitalized subjects: a pilot study.

It has been suggested that the health care system might be best assessed by the patient's own attitudes concerning the quality of service rendered (Wood, 1974). The purpose of this study is to analyze the psychosocial quality of the health service/hospital system in the greater Iowa City, Iowa area, and the relative emotional stability of hospitalized patients in several local hospitals. Specifically, a survey of 20 questions has been developed to assess (1) patient's attitudes and psychosocial outlook, (2) patient's self-perception. (3) situation generated feelings and (4) family/support group generated feelings. The comparative results of this experiment may indicate (1) the overall emotional status of hospitalized patients relative to non-hospitalized individuals and (2) the general psychosocial effectiveness of the hospital system (in the greater Iowa City. Iowa area). This information may be useful to both the medical/allied-health student and the inexperienced clinician, relative to various preconceived notions concerning the emotional state of hospitalized patients, in general.

Attitude↗
PubMed1981

Intrinsic proteins and their effect upon lipid hydrocarbon chain order.

We present evidence that at temperatures greater than their main transition temperature, phospholipid molecules that are trapped within clusters of intrinsic molecules such as polypeptides or proteins have the ends of their hydrocarbon chains more statically disordered than those of lipid molecules far from such intrinsic molecules. We have constructed a model in which the lipids are divided into three populations: (i) those that are not adjacent to any protein ("free" lipids), (ii) those that are adjacent to only one protein ("adjacent" lipids), and (iii) those that are "trapped" between two or three proteins. We applied this model to study deuterium nuclear magnetic resonance of dimyristoyl-3-sn-phosphatidylcholine (DMPC) bilayers containing gramicidin A' or cytochrome oxidase and found that while the methyl groups of adjacent lipids are slightly more statically ordered than those of free lipids, the methyl groups of trapped lipids are more statically disordered than those of free lipids. We propose a physical explanation for this and show that phosphorus-31 nuclear magnetic resonance data for DMPC-cytochrome oxidase bilayers can be understood as a consequence of changes in the polar region of only trapped lipids.

Dimyristoylphosphatidylcholine↗
PubMed1981

Raman scattering in bilayers of saturated phosphatidylcholines and cholesterol. Experiment and theory.

Raman spectroscopy has been applied to a model biomembrane structure in order to obtain information about the effect of cholesterol upon phospholipid hydrocarbon chain ordering. The intensity of the 1130-cm-1 Raman line obtained from a dipalmitoylphosphatidylcholine (DPPC) coarse aqueous dispersion was measured as a function of temperature for two concentrations, c, of cholesterol: c=0.15 and c = 0.35. The contribution of cholesterol to this line was deduced. Intensities of all lines were taken as peak areas. By use of a theory for assigning raman intensities to chain conformations as well as a model of lipid bilayers containing cholesterol, the temperature and concentration dependence of the 1130-cm-1 line was calculated. Good agreement with DPPC experimental data was obtained, and predictions are made for dimyristoylphosphatidylcholine. The experimental results are interpreted in terms of a DPPC-cholesterol phase diagram and the average number of gauche bonds per DPPC molecule.

Cholesterol↗
PubMed1981

Protein rotation, enzyme activity and photooxidation of SH groups in sarcoplasmic reticulum Ca2+-ATPase.

The binding of probe molecules such as fluorescein isothiocyanate, eosin isothiocyanate and erythrosin isothiocyanate to the Ca2+-ATPase of sarcoplasmic reticulum followed by illumination of the labelled protein causes substantial reductions of ATPase activity over a 1-h period. The degree of light-sensitivity induced by these probes is related to the triplet yield of these probe molecules. Consistent with this, the greatest effect is seen with erythrosin isothiocyanate and the least effect with fluorescein isothiocyanate. These reductions of ATPase activity associated with illumination are also associated with an aggregation of the protein molecules. This is indicated by laser flash photolysis measurements and also by polyacrylamide gel electrophoresis. A reduction in the number of thiol groups present on the ATPase molecule parallels the reduction of enzyme activity and changes in the protein mobility. The results are discussed in relation to the use of these probe molecules to study biological systems and also in terms of oxidative processes which may affect protein function in vivo.

Animals↗
PubMed1981

Intrinsic molecules in fluid phospholipid bilayers. Fluorescence probe studies.

Fluorescence probe data using 1,6-diphenyl-1,3,5-hexatriene for various concentrations of intrinsic molecules (cholesterol, gramicidin A amd cytochrome oxidase) within fluid lipid bilayers have been examined. The polarization value increases with increasing concentration of intrinsic molecule and then approaches a limiting value. Empirical curve-fitting of the experimental data, change of polarization with concentration, shows that each system can be fitted approximately by an exponential curve. A theory has been constructed based upon the assumption that only one intrinsic molecule need be adjacent to a fluorescent probe molecule to affect its motion drastically. The change in probe motion then depends upon the probability p of all positions next to a lipid chain being free of intrinsic molecules. The value of the probability p has been calculated and it is shown that (formula: see text) depending on whether the intrinsic molecule spans the lipid bilayer or not. The approximation p = e-Mx gives a good fit to the data for all x, thereby explaining the observed phenomenological fit. The fluorescent probe data is interpreted to show that protein-protein contacts increase as the intrinsic protein concentration increases within the lipid bilayer. An apparent dichotomy between the results from the fluorescence probe and from the deuterium magnetic resonance is explained in terms of a dominant affect on the probe being its hindrance to motion by interaction with the intrinsic molecule (protein) whilst individual C2H2 groups of the chain may exhibit greater disorder.

Cholesterol↗