The effect of gibberellins on the storage life of plantains

Dipping plantain fruits in gibberellins (GA_4/7 or GA₃) delayed the ripening of individual fruits by approximately 50%, the two treatments being equally effective. Measurement of the preclimacteric period (PCP) by increased respiration showed that plantain fruits vacuum infiltrated with GA_4/7 (10^-5 M) gave an extension of 37% in the PCP under high humidity. No effect was observed at low humidity. The use of gibberellins on plantain storage is discussed.     

The effect of spray volume on spray partitioning between plant and soil

Summary Applications of chlorsulfuron (11.25 g ai ha⁻¹) were made to wheat, flax, canola and lentils at spray volumes of 48, 108 and 2171 ha⁻¹, and with metsulfuron methyl (6.00 g ai ha⁻¹) at spray volumes of 48 and 2171 ha⁻¹. Applications were made to the shoot only, the soil only and to the plant plus soil. Spectrofluorometric analysis was used to determine spray partitioning within the plant-soil system and foliar retention was related to efficacy. Fresh and dry weights of shoot material were determined 3 weeks after treatment. Flax and wheat were more tolerant of restricted-foliar applications than those made to the soil, the converse being true to canola and lentils. Applications made to the plant and soil were always the most deleterious. Foliar retention and efficacy did not correlate directly. Applications in 2171 ha⁻¹ were generally more efficacious than those at 481 ha⁻¹.     

Pulmonary metabolic function in the awake lamb: effect of development and hypoxia

The effect of postnatal development and acute alveolar hypoxia on pulmonary metabolic function was studied in conscious newborn lambs. Measurements of the ability of the lungs of these animals to metabolize [3H]benzoyl-L-phenyl-alanyl-L-alanyl-L-proline ([3H]BPAP; a synthetic substrate for angiotensin-converting enzyme, ACE) and to remove 5-hydroxy-[14C]tryptamine (5-[14C]HT) were made by modified indicator-dilution techniques during normoxic and hypoxic (fraction of inspired O2 = 0.10) conditions at 1 day, 1 wk, and 1 mo of age. Six additional sheep (8-23 wk old) were studied acutely as "adult" controls. BPAP metabolism in the 1-day-old group was 48 +/- 3% and increased slowly to 57 +/- 1% (P less than 0.05) at 1 mo of age and to 79 +/- 3% (P less than 0.01) by 23 wk of age. Pulmonary 5-[14C]HT removal was adultlike at birth (69 +/- 2%). Alveolar hypoxia significantly decreased BPAP only in the 1-day-old group (41 +/- 3%; P less than 0.05) and had no significant effect on 5-[14C]HT removal over the range of ages studied. These data demonstrate a selective and gradual postnatal development of pulmonary ACE which could be due to alterations in either the affinity or maximal capacity of pulmonary ACE, or increased endothelial cell surface area secondary to rapid growth of small blood vessels in this period. Alveolar hypoxia does not appear to closely regulate either ACE activity or 5-HT removal in conscious lambs greater than 1 day old when trace amounts of substrate are used.     

Behavioural development in the neonatal lamb: effect of maternal and birth-related factors

The survival of the neonate relies on the integrated expression of appropriate behaviours from both the mother and young. In precocious species, like the sheep, the speed with which the lamb stands and seeks the udder is related to lamb survival. In this study the effects of birth difficulty, lamb birth weight, ewe loss or gain in backfat from conception to delivery, ewe parity, litter size, and lamb sex on neonatal lamb behavioural development were investigated in over 500 lambs of two breeds (Scottish Blackface and Suffolk). Lambs that required assistance to be delivered were significantly slower to perform all neonatal behaviours than unassisted lambs (P<0.001), and were less active over the first 3 days after delivery (P<0.05). There were no effects of lamb birthweight that were not accounted for by the increased likelihood of requiring assistance in heavier birth weight lambs. Ewes that mobilised less body fat during their pregnancy produced lambs that stood and sucked quickly (P<0.001), and were more active over the first 3 days of life. Lambs born to first parity ewes were slower to stand and suck than lambs born to experienced ewes (P<0.001). There was an improvement in time taken by lambs to stand, seek the udder and to suck with each increase in ewe parity. Litter size had an additional retarding influence on the behaviour of multiple-born lambs that could not be accounted for by birthweight. In the Suffolk breed male lambs were slower to stand and suck than female lambs, this effect was not seen in Blackface lambs. These data demonstrate that lambs that require assistance at birth, even if they survive the birth process, lambs born to ewes that lose a lot of condition over pregnancy or first parity ewes, triplet lambs and, at least in some breeds, male lambs are slower to progress through the sequence of neonatal behaviours. These lambs are, therefore, at greater risk of not surviving to weaning.     

The effect of tetronasin and monensin on fermentation, microbial numbers and the development of ionophore-resistant bacteria in the rumen

The Gram-negative rumen bacteria Fibrobacter succinogenes S85, Prevotella ruminicola M384 and Veillonella parvula L59 were grown in media containing successively increasing concentrations of the ionophores, monensin and tetronasin. All three species became more resistant to the ionophore with which they were grown. Increased resistance to one ionophore caused increased resistance to the other, and cross-resistance to another ionophore—lasalocid—and an antibiotic—avoparcin. Recovery of tetronasin-resistant bacteria from the rumen of monensin-fed sheep increased and vice versa, indicating that similar cross-resistance occurred in vivo.     

The effect of chronic and acute haemorrhage on erythropoietin in the neonatal lamb.

In all mammalian species studied the haematocrit (hct) declines after birth in the absence of any known nutritional deficiencies. The glycoprotein hormone, erythropoietin (Epo), is essential for normal red blood cell production. The aims of this study were 1) to investigate the changes in plasma Epo during the normal post-natal decrease in hct in lambs; 2) to compare the effects of chronic and acute haemorrhage in neonatal lambs; and 3) to test the hypothesis that the Epo response to haemorrhage is blunted in the neonatal period. Twenty-one lambs (0-9 weeks of age) were studied; group I (n = 8) were used to document normal post-natal changes (98 samples); group II (n = 7) lambs were haemorrhaged repetitively during weeks 3-6 (95 samples); group III (n = 6) lambs were bled once in the first 3-week period. In the group I (control lambs) the hct decreased from 30.6 +/- 1.3 (weeks 1 & 2) to a nadir of 23.2 +/- 0.8 (75.8% of initial value) in the 6th week, and the plasma Epo declined from 25.7 +/- 4.9 (week 1) to 12.3 +/- 1.0 mU/ml (week 6). In group II, the lambs were bled repetitively, a total of 510 +/- 32 ml blood being removed during weeks 3-6, the hct was 18.7 +/- 0.8 (81% of hct at nadir in controls) in week 6, and Epo was 26.9 +/- 13.3 in week 3, 23.4 +/- 3.6 mU/ml in week 6.(ABSTRACT TRUNCATED AT 250 WORDS)     

Improving protein array performance: focus on washing and storage conditions

For protein microarrays, maintaining protein stability during the slide processing steps of washing, drying, and storage is of major concern. Although several studies have focused on the stability of immobilized antibodies in antibody microarrays, studies on protein-protein interaction arrays and enzyme arrays are lacking. In this paper we used five bait-prey protein interaction pairs and three enzymes to optimize the washing, drying, and storage conditions for protein arrays. The protein arrays for the study were fabricated by combining HaloTag technology and cell-free protein expression. The HaloTag technology, in combination with cell-free expression, allowed rapid expression and immobilization of fusion proteins on hydrogel-coated glass slides directly from cell extracts without any prior purification. Experimental results indicate enzyme captured on glass slides undergoes significant loss of activity when washed and spin-dried using only phosphate buffer, as is typically done with antibody arrays. The impact of washing and spin-drying in phosphate buffer on protein-protein interaction arrays was minimal. However, addition of 5% glycerol to the wash buffer helps retain enzyme activity during washing and drying. We observed significant loss of enzyme activity when slides were stored dry at 4 degrees C, however immobilized enzymes remained active for 30 days when stored at -20 degrees C in 50% glycerol. We also found that cell-free extract containing HaloTag-fused enzymes could undergo multiple freeze/thaw cycles without any adverse impact on enzyme activity. The findings indicate that for large ongoing studies, proteins of interest expressed in cell-free extract can be stored at -70 degrees C and repeatedly used to print small batches of protein array slides to be used over a few weeks.     

Effect of ozone on the postnatal development of lamb mucociliary apparatus

We determined whether exposure to O3 early in the postnatal period impairs the normal development of the mucociliary apparatus in lambs and whether such changes lead to prolonged abnormalities in mucociliary function. Lambs were exposed to air (controls) or to 1 ppm O3 for 4 h/day for 5 days during the 1st wk of life. Tracheal mucus velocity (TMV), a marker of lung mucociliary clearance, was measured in vivo at birth (0 wk) and up to 24 wk later, and tracheal secretory function was measured (in vitro) and the morphology of the tracheal mucosa was determined at 0 and 2 wk in both groups. In the control group, TMV increased 94% from 0 to 2 wk (P less than 0.05), continued to increase until reaching a plateau at 8 wk, and then remained constant from 8 to 24 wk. In contrast, O3-exposed lambs showed a 24% decrease in TMV from 0 to 2 wk (P less than 0.05 vs. control), and throughout the remaining time TMV remained below (P less than 0.05) that observed in control lambs. O3 exposure partially prevented the age-dependent decrease in basal secretion of tracheal macromolecules normally observed between 0 and 2 wk. These changes in secretory function were associated with a significant increase in tissue conductance (37%, P less than 0.05 vs. 0 wk), predominantly the result of active chloride secretion. The functional changes induced by O3 were associated with a retardation of the normal morphological development of the tracheal epithelium.(ABSTRACT TRUNCATED AT 250 WORDS)     

The effect of air support on droplet characteristics and spray drift

Air assistance on field sprayers creates a forced airstream under the spray boom which blows the spray droplets into the crop. The advantages of this relative new technique are less drift of spray droplets and the possibility to reduce the amount of pesticides and spray Liquid. The purpose of this work was to investigate the effect of air assistance on the characteristics of spray droplets and their driftability. Based on air velocity measurements on an air assisted field sprayer, a system of air assistance was developed in addition to a laser-based measuring set-up for the characterisation of spray droplets. With this set-up, the effect of air support on the droplet characteristics was investigated for different settings of the air assistance. The effect on spray drift was quantified based on field drift measurements. A reducing effect on the total amount of spray drift was demonstrated for the Hardi ISO F 110 02, F 110 03 and LD 110 02 nozzles with drift reduction factors a(d) of, respectively, 2.08, 1.77 and 1.53. The use of air support had no significant effect for the LD 110 03 nozzles on the total amount of spray drift. Comparing droplet size and drift results, it was found that air support has the highest impact on the amount of spray drift for the finer sprays by increasing droplet velocities. The effect of air support on droplet sizes is rather limited.     

Root morphogenesis in legumes and cereals and the effect of bacterial inoculation on root development

Root morphology is both genetically programmed and environmentally determined. We have begun an analysis into the components of root development by: (a) constructing a range of transgenic clover plants to assess some of the genetic programs involved as both roots and nodules are initiated and develop. These transgenic plants report on auxin activity, flavonoid synthesis and chitinase expression and suggest a role for flavonoids as regulators of auxin levels; and (b) determining in cereals the effect of both added auxin and specific microorganisms on the initiation and development of modified root outgrowths and lateral roots. Appropriate combinations of auxin, the nitrogen fixing Acetobacter diazotrophicus, and rice variety did give rise to some plants which grew slowly for over 12 months in a nitrogen-free medium.     

The effect of anabiosis autoinducers on the bacterial genome

The mutagenic activity of chemical analogues of microbial anabiosis autoinducers (the autoregulatory d1 factors of cell differentiation), which act to inhibit cell proliferation, to enhance cell tolerance, and to induce the transition of cells to anabiotic state, was studied using the Ames test. In the range of concentrations studied (0.1 to 100 micrograms/ml), alkyl-substituted hydroxybenzenes (AHBs) differing in hydrophobicity, i.e., methylresorcinol (C1-AHB) and hexylresorcinol (C6-AHB), as well as unsubstituted resorcinol, showed different growth-inhibiting and mutagenic effects. C6-AHB was found to inhibit the growth of Salmonella typhimurium TA100 and to induce its mutagenesis at a rate of 1.8 revertants/nmol. C1-AHB taken at low concentrations not only failed to inhibit bacterial growth but even stimulated it and exerted an antimutagenic effect. Unsubstituted resorcinol virtually did not influence bacterial growth and showed weak mutagenic activity. The growth-inhibiting effect of elevated C6-AHB concentrations correlated with the degree of the transition of the original phenotype producing S-type colonies to a phenotype producing R-type colonies. The role of AHB homologues, as microbial autoregulators with mutagenic activity, in the regulation and correlation of two processes (the phenotypic dissociation of microbial populations and the formation of resting microbial forms) is discussed. The accumulation of AHBs in senescent microbial cultures may induce adaptive mutations, change the expression of genes, and promote the development of minor cell subpopulations (phenotypes), thus providing for the adaptation of these cultures to varying environmental conditions.