The effect of soil strength on the yield of wheat

Although it is well-known that high soil strength is a constraint to root and shoot growth, it is not clear to what extent soil strength is the main physical stress that limits crop growth and yield. This is partly because it is difficult to separate the effects of soil drying and high soil strength, which tend to occur together. The aim of this paper is to test the hypothesis that for two different soil types, yield is closely related to soil strength irrespective of difference in soil water status and soil structure. Winter (Triticum aestivum L., cv. Hereward) and spring wheat (cv. Paragon) were grown in the field on two soils, which had very different physical characteristics. One was loamy sand and the other sandy clay loam; compaction and loosening treatments were applied in a fully factorial design to both. Crop growth and yield, carbon isotope discrimination, soil strength, water status, soil structure and hydraulic properties were measured. The results showed that irrespective of differences in soil type, structure and water status, soil strength gave a good prediction of crop yield. Comparison with previous data led to the conclusion that, irrespective of whether it was due to drying or compaction (poor soil management), soil strength appeared to be an important stress that limits crop productivity.     

Partial mechanical impedance can increase the turgor of seedling pea roots

Roots of 3-d-old pea seedlings (Pisum sativum L.) were mechanically impeded using a sand core apparatus, which allowed mechanical impedance to be varied independently of aeration and water status. Turgor of root cortical cells was then measured using a pressure probe. In seedlings grown in sand cores for 1 d, impedance had little effect on turgor, but in seedlings grown in the sand cores for 2 d, impedance increased turgor by 0.18 MPa in the apical 6 mm.     

Metabolism-resistant bradykinin antagonists: development and applications

Bradykinin plays many roles in normal and pathological physiology, but rapid enzymatic degradation made elucidation of its functions extremely difficult. Development of effective degradation-resistant antagonists made it possible to delineate these roles and to open the way for development of new drugs to control pathology due to excess production of bradykinin. Presently available peptide bradykinin antagonists are extremely potent, are completely resistant to enzymatic degradation, and are orally available. Non-peptide bradykinin antagonists have also been discovered. Development of bradykinin antagonists as drugs for cancer, inflammation and trauma is anticipated.     

Childhood IQ of parents related to characteristics of their offspring: linking the Scottish Mental Survey 1932 to the Midspan Family Study

The objective of the study was to investigate the relationship between childhood IQ of parents and characteristics of their adult offspring. It was a prospective family cohort study linked to a mental ability survey of the parents and set in Renfrew and Paisley in Scotland. Participants were 1921-born men and women who took part in the Scottish Mental Survey in 1932 and the Renfrew/Paisley study in the 1970s, and whose offspring took part in the Midspan Family study in 1996. There were 286 offspring from 179 families. Parental IQ was related to some, but not all characteristics of offspring. Greater parental IQ was associated with taller offspring. Parental IQ was inversely related to number of cigarettes smoked by offspring. Higher parental IQ was associated with better education, offspring social class and offspring deprivation category. There were no significant relationships between parental IQ and offspring systolic blood pressure, diastolic blood pressure, cholesterol, glucose, lung function, weight, body mass index, waist hip ratio, housing, alcohol consumption, marital status, car use and exercise. Structural equation modelling showed parental IQ associated with offspring education directly and mediated via parental social class. Offspring education was associated with offspring smoking and social class. The smoking finding may have implications for targeting of health education.     

X-Y Exchange and the Coevolution of the X and Y Rdna Arrays in Drosophila melanogaster

The nucleolus organizers on the X and Y chromosomes of Drosophila melanogaster are the sites of 200-250 tandemly repeated genes for ribosomal RNA. As there is no meiotic crossing over in male Drosophila, the X and Y chromosomal rDNA arrays should be evolutionarily independent, and therefore divergent. The rRNAs produced by X and Y are, however, very similar, if not identical. Molecular, genetic and cytological analyses of a series of X chromosome rDNA deletions (bb alleles) showed that they arose by unequal exchange through the nucleolus organizers of the X and Y chromosomes. Three separate exchange events generated compound X·Y ^L chromosomes carrying mainly Y-specific rDNA. This led to the hypothesis that X-Y exchange is responsible for the coevolution of X and Y chromosomal rDNA. We have tested and confirmed several of the predictions of this hypothesis: First, X· Y^L chromosomes must be found in wild populations. We have found such a chromosome. Second, the X·Y^L chromosome must lose the Y^L arm, and/or be at a selective disadvantage to normal X⁺ chromosomes, to retain the normal morphology of the X chromosome. Six of seventeen sublines founded from homozygous X·Y^Lbb stocks have become fixed for chromosomes with spontaneous loss of part or all of the appended Y^L. Third, rDNA variants on the X chromosome are expected to be clustered within the X⁺ nucleolus organizer, recently donated (" Y") forms being proximal, and X-specific forms distal. We present evidence for clustering of rRNA genes containing Type 1 insertions. Consequently, X-Y exchange is probably responsible for the coevolution of X and Y rDNA arrays.     

Cerebrovascular effects of prostanoids: in-vitro studies in feline middle cerebral and basilar artery

The effect of prostaglandin (PG) E2, F2 alpha, the thromboxane-A2 mimetic U46619 (9,11-dideoxy-9 alpha,11 alpha-methanoepoxy-prostaglandin F2 alpha) and the prostacyclin mimetic iloprost was investigated in cat middle cerebral and basilar arteries in vitro precontracted with 5-hydroxytryptamine (5-HT) (50nM) in the absence and presence of the cyclooxygenase inhibitor indomethacin or the thromboxane receptor blocker AH23848B [1 alpha (z),2 beta,5 alpha]-(+)-7-[5-[1,1'-(biphenyl)-4-yl] methoxy]-2-(4-morpholinyl)-3-oxocyclopentyl]-4-heptenoic acid). PGF2 alpha and U46619 both produced further concentration-related contractions of basilar and middle cerebral artery, U46619 being approximately 1,000 times more potent than PGF2 alpha. Iloprost produced concentration-related relaxations of precontracted basilar and middle cerebral artery, the mean maximum relaxations produced at a concentration of 1.3 microM being 57.3% and 80.6%, respectively of the contraction produced by 50nM 5-HT. PGE2, 100nM relaxed the basilar and middle cerebral artery, 46.7% and 38.5% respectively. However, at 1 microM, PGE2 caused contraction. Indomethacin, 2.8 microM had no effect on contractile or relaxant responses to any of the prostanoids. Oxyhaemoglobin inhibited the relaxation of both arterial preparations but had no effect on responses to PGE2 or iloprost. The thromboxane-receptor blocker AH23848B antagonised the contractile responses to U46619, PGF2 alpha and PGE2 and had no effect against relaxant responses to PGE2 or iloprost. It is concluded that both contraction- and relaxation-inducing prostanoid receptors are present in the in vitro preparation of feline basilar and middle cerebral artery. Under sustained tension conditions, endothelial factors do not appear to be involved in the responses to dilating prostanoids.     

The influence of drugs on the kinin-forming system in relation to pregnancy and parturition in the rat.

The duration of normal gestation and parturition in the rat can be changed by treatment with drugs which alter the equilibrium of the kallikrein-kinin system. The kallikrein inhibitor, aprotinin, when given from Days 19-22 of pregnancy prolongs gestation. Treatment with aprotinin from Days 20-22 of pregnancy prolongs the parturient process, as does a single dose given on the morning of Day 22. Kallikrein, when administered from Days 19-22 of pregnancy, results in a prolongation of gestation and abolishes the pre-parturient behaviour ('labour'). Parturition is prolonged and many fetuses are stillborn. Soya bean trypsin inhibitor when given from Days 19-22 of pregnancy delays and prolongs parturition; maternal haemorrhage occurs during birth and many fetuses are born dead or are abandoned at birth. It is suggested that the kallikrein-kinin system plays a functional role in the normal process of parturition in the rat.     

Two major groups of neutralizing anti-gp120 antibodies exist in HIV-infected individuals. Evidence for epitope diversity around the CD4 attachment site.

The aim of this study was to dissect neutralizing anti-gp120 antibody populations in seropositive asymptomatic individuals. Murine anti-Id mAb were raised against polyclonal affinity-purified human anti-gp120 antibodies. These anti-Id mAb were used to fractionate anti-gp120 antibodies from a pool of HIV-positive sera into idiotypically distinct anti-gp120 antibody (Id+Ab) preparations. Immunochemical and neutralization studies indicated that all Id+Ab that neutralized HIV-1 in vitro interacted with either the V3 loop or the CD4 attachment site of gp120. The V3-specific Id+Ab neutralized HIV-1 in a strain-restricted manner. Id+Ab specific for the CD4 attachment site exhibited different spectra of neutralizing activities against multiple strains of HIV-1. This finding indicates that multiple, antigenically diverse epitopes reside around the CD4 attachment site of gp120. Significantly, depletion of the Id+Ab from affinity-purified total anti-gp120 antibodies abrogated most of the neutralizing activities of these antibodies, suggesting that neutralizing anti-gp120 antibodies consist of two major specificities, either to the V3 region or to the CD4 attachment site. The understanding of specificities and neutralizing activities of different anti-gp120 antibodies in seropositive healthy individuals will be helpful for designing effective vaccines and immunotherapeutic strategies for AIDS.     

Alpha-tocopherol consumption during low-density-lipoprotein oxidation.

1. The kinetics of the depletion of alpha-tocopherol in human low-density lipoprotein (LDL) were measured during macrophage-mediated and cell-free oxidation. The formation of oxidatively modified, high-uptake species of LDL in these systems was not detectable until all of the endogenous alpha-tocopherol had been consumed. 2. Supplementation of the alpha-tocopherol content of LDL by loading in vivo extended the duration of the lag period during which no detectable oxidative modification occurred. 3. The addition of a flavonoid (morin) prevented both alpha-tocopherol consumption and oxidative modification of LDL. 4. The alpha-tocopherol contents of LDLs from a range of individual donors could not be used to predict their relative resistance to oxidation, indicating that other endogenous antioxidants may also be present, and quantitatively significant, in human LDL.     

The effect of aprotinin on luteolytic and uterine contractile mechanisms in the pregnant rat at term.

The effect of the kallikrein inhibitor aprotinin on luteal function, uterine activity and parturition was studied in primigravid pregnant rats. Luteal function was monitored by the determination of serum progesterone levels. Aprotinin given daily from Day 19 to Day 22 of gestation had no effect on progesterone concentrations compared to saline-treated controls, but indomethacin delayed the decline in progesterone levels over the same time period. Aprotinin treatment had no effect on fetal and placental weights from Days 19 to 22 of gestation. Aprotinin infusion in Day-22 pregnant rats resulted in a reduction in uterine motility (studied by continuous recording in conscious rats by means of an intrauterine microballoon) in 10/12 rats. Continuous infusion of aprotinin into rats which had been allowed to deliver one young resulted in a significantly prolonged duration of parturition compared to that in saline-infused controls. In one rat the delivery process was completely arrested and recommended only when the infusion was stopped. Aprotonin had no effect on either the spontaneous or oxytocin-induced uterine contractions of the isolated Day-22 pregnant rat uterus. It is concluded that the kallikrein-kinin system in the late pregnant rat does not appear to be involved in the luteolytic process but may play a functional role in the control of uterine and/or cervical function before and during parturition.