Showing papers by "University of Hertfordshire published in 1986"

SDS Polyacrylamide Gel Electrophoresis of Proteins

Abstract: Crosslinked polyacrylamide gels are formed from the polymerization of acrylamide monomer in the presence of smaller amounts of N,N'-methylene-bis-acrylamide (normally referred to as “bis-acrylamide”) (Fig. 1). Note that bis-acrylamide is essentially two acrylamide molecules linked by a methylene group and is used as a crosslinking agent. Acrylamide monomer is polymerized in a head-to-tail fashion into long chains, and occasionally a bis-acrylamide molecule is built into the growing chain, thus introducing a second site for chain extension. Proceeding in this way, a crosslinked matrix of fairly well-defined structure is formed (Fig. 1). The polymerization of acrylamide is an example of free-radical catalysis, and is initiated by the addition of ammonium persulfate and the base N,N,N',N'-tetramethylenediamine (TEMED). TEMED catalyzes the decomposition of the persulfate ion to give a free radical (i.e., a molecule with an unpaired electron): S2O8 + e– → SO4 + SO4 • (1)

The growth and activity of winter wheat roots in the field: nutrient inflows of high-yielding crops.

Abstract: Root and shoot growth and nutrient uptake have been monitored for several winter wheat crops which gave a mean grain yield of 9·5 t/ha (85% D.M.) when grown on three soil types in 1980 and 1981. Averaged over all crops, maximum growth rates were 170 kg/ha/day for shoots and 14 kg/ha/day for roots; maximum nutrient uptake rates for N, P, K, Ca and Mg were 2·75, 0·47, 341, 0·60 and 0·18 kg/ha/day respectively. Maximum uptake of K and Ca occurred at anthesis with values of 239 and 38 kg/ha respectively, whilst for the other nutrients maximum uptake was at final harvest with values of 200, 39 and 14 kg/ha for N, P and Mg respectively. The grain contained 141 kg N, 27 kg P, 41 kg K, 3·2 kg Ca and 7·1 kg Mg/ha.The quantity of nutrients arriving at root surfaces by mass flow was calculated for one of the crops from measurements of soil solution concentration and potential evapotranspiration data. The potential supply of nutrients by mass flow, as a percentage of that actually taken up between 19 March and 29 June, was 25% for N, 4% for K, 800% for Ca and 32% for Mg.

Effect of polysaccharide stabilizers on the rate of growth of ice

Abstract: Measurements of the linear rate of advance of ice into undercooled aqueous solutions and gels have been made. The solutes consisted of sucrose with smaller quantities of other substances, mostly polysaccharides. The linear crystallization velocity in sucrose solutions is mainly governed by the rate of diffusion of sucrose molecules, and the addition of soluble polysaccharides causes only a small extra retardation. However, the growth of ice into undercooled sucrose solutions is drastically retarded and altered in morphology by the presence of a gel network. This effect is discussed qualitatively in terms of the interaction of the ice front with the gel fibres, which reduces the equilibrium freezing point and may lead to rupture of the fibres.

The detection of acute paralysis virus in Varroa jacobsoni by the use of a simple indirect ELISA.

Abstract: SummaryA simple indirect enzyme-linked immunosorbent assay (ELISA) was used to detect and quantify acute paralysis virus (APV) in individual female Varroa jacobsoni collected from naturally infested honeybee (Apis mellifera) colonies in the Netherlands and Germany. The assay was very specific and sensitive, detecting the virus in concentrations as low as 3 ng/ml. Mites collected from both adult honeybees and sealed brood cells contained APV but virus concentrations varied widely between individuals. The possible role of V. jacobsoni as a vector of honeybee virus diseases is discussed.

Accumulation and subcellular distribution of cations in relation to the growth of potassium-deficient barley

Abstract: Growth of barley (Hordeum vulgare L., cv. Georgie) was insensitive to soil K content above about 150 mg kg−1, but at lower levels it declined. The reduction in yield was greater in soils containing approximately 10 mg Na kg−1 than in soils with about 90 mg kg−1 of Na. Growth was unaffected by changes in shoot K concentration above 75 mol m−3, but declined at lower concentrations, and the decrease was less in plants grown in soils with high Na. Growth responses were not simply related to tissue K concentrations because plants grown in soils with extra Na had higher yields but lower K concentrations. When soil Na was low, plants accumulated Ca as tissue K declined, but when Na was provided this ion was accumulated. Plant Mg concentrations were generally low but increased as K decreased. The Ca and Mg were osmotically active. There were highly significant inverse linear relationships between yield and either the Ca or Mg concentrations in the shoots. X-ray microanalysis was used to examine the compartmentation of cations in leaves from barley plants (cv. Clipper) grown in nutrient solutions with high and low K concentrations. In plants grown with 2.5 mol m−3 K, this was the major cation in both the cytoplasm and vacuole of mesophyll cells. However, in plants grown with 0.02 mol m−3 K it declined to undetectable levels in the vacuole, although it was still detectable in the cytoplasm. In all plants, Ca was mainly located in epidermal cells. The implication of the results for explaining responses to K. in terms of compartmentation of solutes is discussed.

The pollination requirements of oil-seed rape ( Brassica napus L.)

Abstract: The pollination requirements of three cultivars of winter and one of spring swede rape (Brassica napus), grown in a glasshouse, were compared. All cultivars yielded more when hand-pollinated than when auto-pollinated but were self-fertile and yielded equally well whether self- or cross-pollinated. In most cultivars plants that were shaken to simulate movement of plants by wind yielded more than autopollinated plants and not significantly differently from hand-pollinated plants. Handpollinating and shaking plants also increased the set of early flowers.

Identification of vesicular‐arbuscular mycorrhizal fungi in roots of leek (allium porrum l.) and maize (zea mays l.) on the basis of enzyme mobility during polyacrylamide gel electrophoresis

Abstract: Summary The mobilities of three enzymes, esterase (EST), glutamate oxaloacetate transaminase (GOT) and peptidase (PEP), during polyacrylamide gel electrophoresis have been used to identify individual species of vesicular–arbuscular mycorrhizal fungi in roots. The enzyme banding patterns obtained from mycorrhizal root extracts were compared with those of uninfected roots. Chlamydospores, external mycelium and internal mycelium (obtained by enzymic digestion of host root tissue) were used as controls to confirm the position of the fungal specific enzyme bands on the gels. Glomus caledonium (Nicol. and Gerd.) Trappe and Gerd. and Glomus mosseae (Nicol. and Gerd.) Gerd. and Trappe could be detected in leek (Allium porrum L.) roots against the host background by the mobility of bands of EST, GOT and PEP activity and it was possible to detect both G. caledonium and G. mosseae in leek roots which had been grown in the presence of a mixed inoculum, by staining for any of these three enzymes. Glomus mosseae could be identified in maize (Zea mays L.) roots by location of GOT and PEP activity but the major bands of EST, GOT and PEP activity in G. caledonium had the same mobility as those of maize and so this fungus could not be easily identified in this host using these experimental conditions. Glomus fasciculatum (Thaxter sensu Gerd.) Gerd. and Trappe type E3 had a characteristic PEP band which was separable from leek and maize host bands and this fungus could also be identified in maize roots by the position on the gel of fungal GOT activity.

Neuropeptides and dopamine in the marmoset. Effect of treatment with 1-methyl-4-phenyl-1, 2, 3, 6 tetrahydropyridine (MPTP): an animal model for Parkinson's disease?

Abstract: Neurochemical studies of post-mortem human parkinsonian brains have demonstrated specific alterations in neuropeptide concentrations within the substantia nigra and striatal structures The drug, 1-methyl-4-phenyl-1, 2, 3, 6 tetrahydropydine (MPTP) has been reported to act as a selective toxin to nigrostriatal dopamine neurons, and induces a parkinsonian-like syndrome in primates In this study, marmosets developed features typical of Parkinson' disease following treatment with MPTP for four days. The effects of MPTP treatment on the concentrations of dopamine and neuropeptides were determined and changes compared with those reported for Parkinson' disease It was found that within the substantia nigra, substance P concentrations doubled following treatment with MPTP, in contrast, concentrations of vasoactive intestinal peptide and neuropeptide Y were significantly reduced. No changes were observed in the concentrations of six other neuropeptides measured in this region, notably cholecystokinin. Despite marked depletion of dopamine within the caudate nucleus and putamen, concentrations of all neuropeptides within these structures remained unchanged with the exception of an isolated reduction of neuropeptide Y within the putamen. Somatostatin concentrations within the frontal cortex and hippocampus were significantly elevated in the marmosets treated with MPTP. These neuropeptide changes in the CNS contrast with those reported for Parkinson' disease In view of the autonomic dysfunction associated with Parkinson' disease, peripheral concentrations of neuropeptides were determined. Significant depletion of neuropeptide Y was identified in the ureter, adrenal and cardiovascular tissue. Thus the neurochemical changes induced by MPTP may not be as selective as previously reported.

A comparison of the regional depesition in a model nose of a drug discharged from metered serosel and metered-pump nasal delivery systems

Abstract: The morphology and airflow behavior in the nose are considered briefly in relationship to the various ways that are often used to evaluate the spray or aerosol discharged from inhalation delivery systems. A glass-model nose of a design based on published anatomic measurements is described. Its use is described for examining the major sites of drug deposition from nasal delivery systems. That no significant differences are detected between the regional deposition from a metered aerosol and a metered-pump product confirm what might be expected from the nasal anatomy. Most of the drug in each case is deposited in the anterior region of the nose by inertial impaction, and there is little nasal penetration of the drug. Inhaled airflow at 10 L/min through one side of the nose has little effect on regional deposition. The anteriorly deposited drug can be spread backward by mucociliary flow and general surface flow, factors that are essentially independent of the presentation used.

On the paper chase

Abstract: Elements of the Scientific Paper: A Step-by-Step Guide for Students and Professionals. ByMichael J. Katz. Yale University Press: 1986. Pp.130. Hbk 25, 18; pbk 8.50, 5.95.

Protein concentration of grain in relation to some weather and soil factors during 17 years of english winter‐wheat experiments

Abstract: Results from a long term study of wheat experiments on Rothamsted farm were examined by multiple regression analysis to estimate the size of the contributions made by four weather factors to the year-to-year variance of grain protein. Whether considered singly or in either of two chosen models, air temperature during the early part of the grain-filling period had a positive effect, incident radiation during the early or middle part a smaller negative effect. Both models accounted for 25% of the total variance or 60% of the year-to-year variance. After fitting either model winter leaching and maximum potential soil-moisture deficit were not significant. Closely matching results were obtained by including 15 nearby farms. Some soil factors were investigated in a similar manner. A soil N index accounted for 30% of the total variance, with grain N% of 1.95 corresponding to Index 0 and 2.23 to the average of 1 and 2. In models combining the best weather and best soil variables (N Index and wetness class), the variance accounted for was 46%, with all effects significant. There were significant interactions of radiation, winter leaching and soil wetness class with the response to fertiliser nitrogen. As the yield data are less well based than those for grain N% their relationships were examined only in parallel to the main study.

Helmet with auxiliary, electrically operated service

Abstract: A helmet comprises a headshell, visor and a harness within which the head of the user is engagable. An auxiliary electrically operated service is provided, such as a lamp or air supply, operated by a switch actuated as the helmet is engaged or disengaged from the user's head. When the service is an air supply, the switch operates a fan motor which draws air into the helmet through a filter.

Infrared spectropolarimetry of the Galactic Centre: magnetic alignment in the discrete sources

Abstract: On presente les resultats d'observations spectropolarimetriques 8−13 μm des sources du centre galactique. Toutes les sources presentent une polarisation interstellaire due a l'absoption par des grains de silicate alignes et ces grains semblent etre spatialement separes sur la ligne de visee de ceux qui provoquent la polarisation aux plus courtes longueurs d'onde. On discute de l'origine de l'alignement des grains

Some fluorine‐containing pheromone analogues

Abstract: Two analogues of the aphid alarm pheromone (E)-β-farnesene, a trifluorofarnesene and a difluoro-1-norfarnesene, were found to be highly active and were more readily detectable than the parent compound. For (Z)-hexadec-11-enal, a component of some lepidopteran sex attractant pheromones, replacement of the carbonyl oxygen with a difluoromethyl group to give a difluoroheptadecadiene resulted in loss of activity. A trifluoroacetoxyhexadecanolide was a more volatile analogue of the mosquito oviposition pheromone (−)-(5R,6S)-6-acetoxy-5-hexadecanolide and was highly active.

Reversal by β‐funaltrexamine of the antinociceptive effect of opioid agonists in the rat

Abstract: The effect of the irreversible opioid receptor antagonist, beta-funaltrexamine (beta-FNA), on antinociception produced by mu- and kappa-receptor agonists was studied in the rat. beta-FNA, 20 to 80 mg kg-1, s.c., given 24 h before testing, produced a dose-related antagonism of the effects of morphine in the paw pressure, hotplate and tail-flick tests. Following the 80 mg kg-1 dose, the degree of antagonism of morphine was stable for up to 48 h after dosing, but was reduced by 5 days and had disappeared by 8 days. In the paw pressure test, beta-FNA, 40 mg kg-1, s.c., antagonized the effects of fentanyl, buprenorphine, tifluadom, ethylketocyclazocine and proxorphan; it was without effect against the highly selective kappa-agonist, U-50,488. In light of these results, the possible opioid receptor selectivities of both the agonists and beta-FNA are reassessed.

Differential gene-expression in the developing barley endosperm

Abstract: Barley prolamin storage proteins account for 50% of the seed proteins. They are encoded by small multigene families that are only expressed in the developing endosperm. Previous work has shown that the major prolamins in barley are characterized by the presence of two or more unrelated structural domains, one of which contains repeated sequences. The non-repetitive domain is homologous with sequences present in other seed proteins found in the seed of mono- and dicotyledonous plants. Comparison of the 5 flanking region of a B1 hordein storage protein gene of barley with those of other prolamin genes (zeins and $\alpha$ -gliadins) reveals short sequences within 600 base pairs (bp) of the translation initiation codon that are strongly conserved. A short sequence at -300 bp seems to be unique to the prolamin genes and is possibly involved in the control of gene expression in the developing cereal endosperm. Six DNA-binding proteins have been identified that might recognize and interact with the putative regulatory sequences identified in the B1 hordein gene. Protease inhibitors account for a large proportion of the salt-soluble proteins of the barley seed, and contain up to 10% lysine. Cloned cDNAs for chymotrypsin inhibitors 1 and 2 have been isolated and characterized. All contain ochre stop condons in the sequences encoding a putative signal peptide. The two inhibitors are encoded by small multigene families that specify several subfamilies of mRNAs. The accumulation of chymotrypsin inhibitors in normal and mutant endosperms of barley is related to the abundances of their mRNAs.

Effect of temperature on potato virus X infection in potato cultivars carrying different combinations of hypersensitivity genes

Abstract: In potato cultivars reacting non-hypersensitively, systemic mosaic symptoms were obvious at 10-20°C for potato virus X (PVX) isolate DX, and at 10 and 15°C for PVX isolate B: systemic movement was slowest at 10°C especially with DX. Viral antigen accumulation in non-inoculated leaves was greatest at 15 and 20°C with B. but with DX accumulation was as great at 25°C, The highest viral antigen concentrations reached were less with B than with DX. No PVX was detected in plants grown at 30°C. In potato cultivars carrying gene Nx, necrotic local lesions appeared at 10-25°C in DX-inoculated lea ves within 8 days; systemic necrosis developed soon after at 15 and 20°C, but was very slow to appear or failed to develop at 10 and 25°C, Necrosis was more conspicuous when gene Nb was also present. Except at 10°C in the Nx:nb cultivar used, presence of Nx decreased accumulation of DX antigen. Although numerous necrotic lesions developed in B-inoculated leaves at 10°C in the presence of gene Nb, very few formed at 15 and 20°C, and none at 25°C. In B-inoculated leaves from plants at 15-25°C, no new lesions were induced by temperature shock treatments and no starch lesion formation was detected. Gene Nb completely prevented movement of isolate B out of inoculated leaves at all temperatures regardless of whether infection was symptomless or necrotic local lesions developed, The concentration of B-antigen was considerably decreased by Nb. It was possible to quantify the general effects of genes Nx and Nb on accumulation of DX- and B-antigens: in the combination Nx:Nb the ineffective gene interacted with the effective gene to cause a greater depression of viral antigen accumulation than expected. Unlike hypersensitivity genes for tobacco mosaic virus in tomato and tobacco, Nx and Nb in potato did not lose their effectiveness with increasing temperature. Differences in virus accumulation and in temperature optima for multiplication between PVX strain groups may account for the lack of competitiveness shown by those belonging to group two.

The applicability of a laser triangulation probe to non-contacting inspection

Abstract: SUMMARY This paper highlights the main advantages of non-contacting inspection and discusses the methods adaptable for the dimensional inspection of engineering components by using a compact solid-state laser triangulation sensor on a computer-assisted co-ordinate measuring machine (CMM). The machine used is the bridge-type Granite 80 model of the LK Tools Company. The methods described are equally applicable for similar inspection work by using industrial robots. The motivation for looking at non-contacting inspection methods is also discussed.

A double-blind controlled study of chlormethiazole and triazolam as hypnotics in the elderly

Abstract: This study compared the hypnotic efficacy and the psychometric effects of treatment with either chlormethiazole or triazolam for 9 weeks in elderly patients with sleep disturbance. Chlormethiazole and triazolam were found to be similarly effective in short-term use. However, evidence of sustained hypnotic efficacy throughout the 9 weeks of treatment was obtained for chlormethiazole but not for triazolam. There were daytime withdrawal effects with triazolam, but none with chlormethiazole.

Genetic factors in Rhizobium affecting the symbiotic carbon costs of N2 fixation and host plant biomass production

Abstract: The effect of genetic factors in Rhizobium on host plant biomass production and on the carbon costs of N2 fixation in pea root nodules was studied. Nine strains of Rhizobium leguminosarum were constructed, each containing one of three symbiotic plasmids in combination with one of three different genomic backgrounds. The resulting strains were tested in symbiosis with plants of Pisum sativum using a flow-through apparatus in which nodule nitrogenase activity and respiration were measured simultaneously under steady state conditions. Nodules formed by strains containing the background of JI6015 had the lowest carbon costs of N2 fixation (7.10–8.10 μmol C/μmol N2), but shoot dry weight of those plants was also smaller than that of plants nodulated by strains with the background of B151 or JI8400. Nodules formed by these two strain types had carbon costs of N2 fixation varying between 11.26 and 13.95 μmol C/μmol N2. The effect of symbiotic plasmids on the carbon costs was relatively small. A time-course experiment demonstrated that nodules formed by a strain derived from JI6015 were delayed in the onset of nitrogenase activity and had a lower rate of activity compared to nodules induced by a strain with the background of B151. The relationship between nitrogenase activity, carbon costs of N2 fixation and host plant biomass production is discussed.

Atmospheric deposition at Rothamsted, Saxmundham, and Woburn experimental stations, England, 1969-1984

Abstract: The pH of precipitation, and the concentrations in precipitation and depositions by precipitation of H+, major cations, N, S, and chloride were measured in bulk collectors at three sites in Eastern England. The Rothamsted site is 100 km from the coast in a semi-urban environment. The Saxmundham site is 13 km and the Woburn site 120 km from the coast; both are in rural environments. Precipitation is acidic at all three sites, with a pH of 4.3 at Rothamsted and 5.0 at Saxmundham and Woburn at present, but the pH has been increasing. Precipitation chemistry is chiefly controlled by sea-salts (Na, Mg, Cl) and earth salts (K, Ca, Mg, NH4, N03). Sea-salts dominate near the coast at Saxmundham, but earth salts become much more important inland at Rothamsted and at Woburn. The concentration and deposition of non-sea Cl are increasing at Rothamsted and Saxmundham, those of non-sea SO4-S are increasing at Woburn, and those of NO3-N are increasing at all of the sites. Precipitation acidity is associated chiefly with non-sea SO4, and only a little with NO3 and non-sea Cl, at Rothamsted and Woburn. At Saxmundham, no correlation between acidity and anions is observed, presumably because of the overwhelming effect of sea-salts.

Estimating and mapping grass cover and biomass from low-level photographic sampling†

Abstract: A method of estimating the quantity of biomass in the ground layer of semi-arid rangeland is described and applied to a region of 700 km2 in Botswana. Vertical true colour diapositives, each covering approximately 60 × 90 m, were taken at 1 km intervals from a light aircraft flying at about 120 m above the ground along transects 1·6 km apart. The results of four seasonal surveys are presented. The ground layer cover, as a percentage, was estimated on each diapositive. It ranged mainly from 10 to 60 percent. A set of sampling plots on which the cover and biomass were measured on the ground provided standards for the air photograph estimates and a calibration equation of exponential form from which to convert estimates of cover to those of biomass. The values obtained were analysed spatially. Sample semi-variograms were computed and modelled as anisotropic power functions to lags of 10 km by least squares approximation, and validated by kriging. The grass cover and biomass were mapped from the samp...