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Biomedical subjects

H M Brown

Publications and source records attributed to H M Brown.

At least 19 recordsLinked to original sources
PubMed1979

Photoelectric properties and detection of the aromatic carcinogens benza[a]pyrene and dimethylbenzanthracene.

The absolute photoelectron quantum yield spectra for benzo[a]pyrene and dimethylbenzanthracene are presented in the wavelength range 180--230 nm. These polycyclic aromatic carcinogens have photoelectron quantum yields of approximately 2 x 10(-3) electrons per incident photon at 180 nm. The quantum yields fall off quickly and monotonically at wavelengths longer than 210 nm (5.9 eV). Threshold values for benzo[a]pyrene and dimethylbenzanthracene are 5.25 +/- 0.06 cV and 5.27 +/- 0.04 eV, respectively. The photoelectron quantum yields of benzo[a]pyrene and dimethylbenzanthracene are several orders of magnitude greater than typical components of biological membranes (amino acids, phospholipids, and polysaccharides). Preliminary micrographs of benzo[a]pyrene and dimethylbenzanthracene sublimed onto poly(L-lysine) and onto dimyristoyl phosphatidylcholine demonstrate the high contrast of small crystallites of carcinogens against a background of membrane components. These results and calculations involving relative contrast factors suggest that the distribution of these carcinogens in biological membranes can be determined by using photoelectron microscopy.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1979

Species specific grass pollen sensitivity: diagnosis and treatment with single grass species Allpyral vaccines.

Skin test titrations and nasal provocation tests in sixty patients with hay fever showed specific reactions to extracts of individual grass species. There was, however, no correlation between skin and nasal sensitivity. Repeat testing after treatment with Allpyral vaccines consisting of only the grass species to which the nasal reaction was most severe, or only one of several pollens to which reactions were equally severe, showed marked diminution of skin and nasal sensitivity not only to the single pollen used for immuno-therapy but to all five common pollens used in the Allpyral grass mix. Clinical results seemed much improved as compared with results in the same year for Allpyral five grass mix vaccines, especially in the case of patients treated with Timothy, rye, or cocksfoot. It was concluded that these three grassees were to be preferred for treatment in England, and that these grasses contain common allergens.

Dose-Response Relationship, Immunologic↗
PubMed1979

Light induced changes of internal pH in a barnacle photoreceptor and the effect of internal pH on the receptor potential.

1. Intracellular pH (pH1) was measured in Balanus photoreceptors using pH-sensitive glass micro-electrodes. The average pH1 of twelve photoreceptors which had been dark adapted for at least 30 min was 7.3 +/- 0.07 (S.D.). 2. Illumination reduced the recorded pH1 by as much as 0.2 pH unit. The change in pH1 was graded with light intensity. 3. When the cells were exposed to CO2 in the dark, pH1 declined monophasically. Saline equilibrated with 2% CO2; 98% O2 produced a steady reduction in pH1 of about 0.25 unit in 2--3 min. The buffering capacity of the receptor cell cytoplasm calculated from such experiments is approximately 15 slykes. 4. In the presence of HCO3-1, CO2 saline produced smaller, biphasic changes in pH1. 5. The membrane depolarization produced by a bright flash (depolarizing receptor potential) was reversibly reduced in the presence of external CO2 or by injection of H+. Iontophoretic injection of HCO2- increased the amplitude of the receptor potential. 6. In individual cells there was a close correlation between the amplitude of the receptor potential and pH1. 7. Saline equilibrated with CO2 reduced the light induced current (recorded under voltage-clamp) by 40--50% without affecting its reversal potential. 8. Exposure of the receptor to 95% CO2 saline for several minutes (pH0 5.5) not only abolished the receptor potential but also reversibly decreased the K conductance of the membrane in the dark. These effects were not reproduced by pH0 5.5 buffered saline or by a 5 min exposure to saline equilibrated with N2. 9. It is suggested that changes in pH1 induced by light modulate the sensitivity of the receptor under physiological conditions.

Animals↗
PubMed1978

Aerobiological studies based in Derby. I. A simplified automatic volumetric spore trap.

A simplified version of the Hirst automatic volumetric spore trap has been developed in Derby for aerobiological studies. In comparative trials, the number of spores retained by the Morrow Brown trap were similar in the case of larger spores such as Alternaria (102%), rather higher in the case of grass pollen (136%) and considerably higher (166--201%) for very small spores such as Sporobolomyces and Tilletiopsis. Impaction efficiency has been improved by using a narrower slit. The trap designed in Derby is simple to produce and presents advantages in design over the Hirst version.

Air Microbiology↗
PubMed1978

Aerobiological studies based in Derby. II. Simultaneous pollen and spore sampling at eight sites within a 60 km radius.

In order to determine whether a sampling site in the centre of Derby, where air sampling had been carried out for five summers, really provided valid aerobiological data for the surrounding area, eight identical volumetric spore traps were operated simultaneously during the summer of 1969 at various sites up to 56 km from Derby. For most pollen and spore types, total numbers and seasonal pattern at all the sampling sites were found to be similar, although a few extreme and unexpected variations were noted. Figures varied somewhat in different types of site, and local effects are emphasized.

Air Microbiology↗
PubMed1978

Aerobiological studies based in Derby. III. A comparison of simultaneous pollen and spore counts from the east coast, Midlands and west coast of England and Wales.

The air spora of two sites on the east coast of Britain and one on the west coast were compared with each other and with the regular sampling site in Derby by the simultaneous operation of volumetric spore traps. Concentrations of airborne spores and pollen were found to be usually less at the coastal sites than in Derby. The effect of wind direction was shown to be important at coastal sites because daily counts often showed rises and falls corresponding to off- and on-shore winds respectively. Counts at the west coast site were nearly always lower than those on the east. These findings, together with the prevalence of westerly winds over Britain and the different land use in the east and west, suggest that fewer airborne allergens may be encountered on the west coast.

Air Microbiology↗
PubMed1978

Crayfish stretch receptor: an investigation with voltage-clamp and ion-sensitive electrodes.

1. The membrane characteristics of the slowly adapting stretch receptor from the crayfish, Astacus fluviatilis, were examined with electrophysiological techniques consisting of membrane potential recording, voltage clamp and ion-sensitive microelectrodes. 2. The passive membrane current (Ip) following step changes of the membrane potential to levels above 0 mV required more than a minute to decay to a steady-state level. 3. The stretch-induced current (SIC, where SIC = Itotal--Ipassive) was not fully developed until the Ip had decayed to a steady state. 4. With Ip at the steady state and the stretch-induced current at the O-current potential, a slow stretch-induced inward current was isolated. The latter reaches a maximum after 1 sec of stretch and declines even more slowly after stretch. The I-V relation of the slow current had a negative slope and reversed sign near the resting potential. It is suggested that this current is due to a Cl- conductance change. 5. The stretch-induced current, consisting of a rapid transient phase and a steady component can be isolated from the slow stretch-induced current at a holding potential corresponding to the resting potential. 6. The SIC-Em relation is non-linear and reverses sign at about +15 mV. 7. In a given cell, the reversal potential of the stretch-induced potential change obtained with current clamp coincided with the 0-current potential of the stretch-induced current obtained by voltage clamp. The average value from twenty-six cells was +13 +/- 6.5 mV; cell to cell variability seemed to be correlated with dendrite length. 8. Tris (mol. wt. 121) or arginine (mol. wt. 174) susbstituted for Na+ reduces but does not abolish the stretch-induced current. 9. The permeability ratios of Tris:Na and arginine:Na were estimated from changes in the 0-current potential as these cations replaced Na+ in the external medium. The PTris:PNa was somewhat higher (0.31) than the Parginine:PNa ratio (0.25). 10. Changes in the external Ca2+ concentration had no effect on the 0-current potential in Na or Tris saline. However, reducing Ca2+ did augment the stretch-induced current in either saline. A tenfold reduction of Ca2+ increased the conductance (at the 0-current level) about twofold. 11. Intracellular K+ and Cl- activities were obtained with ion sensitive electrodes. The average values from six cells were aiK = 133 +/- 34 mM and aiCl = 15.2 +/- 1.8 mM S.D.). EK was about 20 mV more negative than Em and ECl was about 10 mV more positive than Em. 12. aik and resting Em undergo large changes in K+-free solutions. After 60 min, ak was reduced eightfold and Em was reduced from -67 to -40 mV. Reduced Ca2+ in K+-free augments the rate of these changes. Receptor potential amplitude was also reduced in K+-free solution but could be restored upon polarizing the membrane to the pre-existing resting level.

Animals↗
PubMed1977

Liquid and solid-state Cl- -sensitive microelectrodes. Characteristics and application to intracellular Cl- activity in Balanus photoreceptor.

When intracellular chloride activity (aiCl) was monitored with chloride-sensitive liquid ion exchanges (CLIX) microelectrodes in Balanus photoreceptors, replacement of extracellular chloride (Cl0) by methanesulfonate or glutamate was followed by a rapid but incomplete loss of aiCl. When propionate was used as the extracellular anion substitute, CLIX electrodes detected an apparent gain in aiCl, while a newly designed Ag-AgCl wire-in glass microelectrode showed a loss of aiCl under the same conditions. This discrepancy in Cl- washout when propionate replaced Cl0 is explained by the differences in selectivity of CLIX and Ag-AgCl electrodes for native intracellular anions and for the extracellular anion substitute which also replaces Cli and interferes in the determination of aiCl. Both electrodes indicate that ECl approximately Em when the cells are bathed in normal barnacle saline, and both electrodes showed the rate of Cl washout (tau approximately 5 min) to be independent of Cli when Cl0 was replaced by glutamate. Details of Ag-AgCl microelectrode construction are presented. These electrodes were tested and found to be insensitive to the organic anion substitutes used in this study. Selectivity data of CLIX electrodes for several anions of biological interest are described.

Animals↗
PubMed1977

Cation and anion sequences in dark-adapted Balanus photoreceptor.

Anion and cation permeabilities in dark-adapted Balanus photoreceptors were determined by comparing changes in the membrane potential in response to replacement of the dominant anion (Cl-) or cation (Na+) by test anions or cations in the superfusing solution. The anion permeability sequence obtained was PI greater than PSO4 greater than PBr greater than PCl greater than Pisethionate greater than Pmethanesulfonate. Gluconate, glucuronate, and glutamate generally appeared more permeable and propionate less permeable than Cl-. The alkali-metal cation permeability sequence obtained was PK greater than PRb greater than PCx greater than PNa approximately PLi. This corresponds to Eisenman's IV which is the same sequencethat has been obtained for other classes of nerve cells in the resting state. The values obtained for the permeability ratios of the alkali-metal cations are considered to be minimal. The membrane conductance measured by passing inward current pulses in the different test cations followed the sequence, GK greater than GRb greater than GCs greater than GNa greater than GLi. The conductance ratios obtained for a full substitution of the test cation agreed quite well with permeability ratios for all the alkali-metal cations except K+ which was generally higher.

Alkalies↗
PubMed1977

Beclomethasone dipropionate aerosol in treatment of perennial and seasonal rhinitis: a review of five years' experience.

1. Five years' experience in the use of beclomethasone dipropionate aerosol (BDA) in the treatment of 315 patients with upper respiratory tract allergy is reviewed. 2. A total of 223 patients with perennial rhinitis was treated. In 23, where the nasal allergy had recurred after oral corticosteroid therapy for asthma was withdrawn, BDA was effective in 69% of cases. A similar success rate (68%) was recorded in 169 patients suffering from perennial allergic rhinitis alone, but a satisfactory response was observed in only 45% of 31 patients with nasal polypi. 3. In 92 patients with seasonal allergic rhinitis freedom from symptoms was achieved in 80%. 4. A total of approximately 534 patient-years of treatment has been recorded without any evidence of side-effects either clinically or on nasal biopsy.

Aerosols↗
PubMed1977

Immunotherapy for grass pollenosis with allpyral allergen extracts. Improved results by objective control of treatment requirements.

Nasal provocation testing using a measured dose of dry grass pollen has been used as a method of controlling the amount of injection treatment required to achieve decreased sensitivity to grass pollen. This could seldom be shown at the usual top dose of 10,000 P.N.U., but by repeating the top dose until the reaction was negative, complete freedom from pollenosis was achieved in most cases. Strict criteria for assessment of results were used. Conventional dosage regimens produced only 27 percent excellent results, but 94 percent of those patients who became demonstrably nasal test-negative were completely or almost completely free from symptoms in the pollen season.

Adolescent↗
PubMed1976

Isolation and characterization of indole-3-acetaldehyde reductases from Cucumis sativus.

In a continuing study of the biosynthetic pathway and regulatory mechanisms governing indole-3-acetic acid (auxin) formation, we report the isolation and initial characterization of three distinct indole-3-acetaldehyde reductases from cucumber seedlings. These enzymes catalyze the reduction of indole-3-acetaldehyde to indole-3-ethanol with the concomitant oxidation of NAD(P)H to NAD(P)+. Two of the reductases are specific for NADPH as second substrate, while the third is specific for NADH. The enzymes show a strong specificity for indoleacetaldehyde, with apparent Km values of 73mum, 130mum, and 400mum being calculated for the two NADPH-specific reductases and the NADH-specific reductase, respectively. Under no conditions of substrate concentration, incubation time, or assay method could the reverse reaction be observed. Chromatography on a calibrated Sephadex gel column led to estimated molecualr weights of 52,000 and 17,000 for the NADPH-specific reductases, while a value of 33,000 was obtained for the NADH-specific reductase. Both NADPH-specific reductases showed a pH optimum of 5.2 with a secondary optimum at 7.0, and both enzymes were activated by increasing ionic strength. The NADH-specific reductase showed a pH optimum of 7.0 with a secondary optimum at 6.1 and was slightly inhibited by increasing ionic strength.

Aldehyde Oxidoreductases↗
PubMed1976

Intracellular Na+, K+, and C1- activities in Balanus photoreceptors.

Ion-sensitive microelectrodes were used to measure intracellular activities (aix) of Na+, K+, and C-1 in Balanus photoreceptors. Average values of aiNa, aiK, and aiCl were 28 mM, 120 mM, and 65 mM, respectively. Equilibrium potentials calculated from these average values were: Na+ +64 mV, K+ - 77 mV, and and Cl- -42 mV; ther average value of the resting potential for all cells examined was -41 mV. Long exposure to intense illumination produced measurable increases in aiNa. Classical Na+ - K+ reciprocal dilution experiments were analyzed with and without observed changes in aiK. As aoK was increased, the membrane depolarized, and aiK increased. Better agreement was found between the membrane potential and the directly determined EK than expected from the standard relation between Em and aoK. The latter produced pNa:pK estimates of the resting photoreceptor membrane that were higher than estimates based on data from the ion electrodes. Generally, Em was more negative than EK as aoK was increased. This is consistent with a significant chloride permeability in the dark-adapted photoreceptor.

Animals↗