Is There a Role for the Apex in Shoot Geotropism?

Experiments with horizontal etiolated sunflower (Helianthus annuus L.) seedlings supported centrally such that both apical and basal ends are free to react to geostimulus, revealed that the apical end commences curvature 1 to 2 hours earlier than the basal end. The later curvature in the basal region is a consequence of the absence of growth in the initial period rather than merely slower growth. A comparison of zonal growth rates in a vertical and a horizontal seedling confirmed that geostimulus induces a renewal of growth in a region where growth had ceased. Removing the apical half of the hypocotyl showed that the curvature resulting from this growth initiation in the basal region is dependent on attachment to the apical region. Evidence that this dependence is unlikely to be due to energy deficiency is adduced. The prior response of the apical end to geostimulus and the apically dependent later initiation of new growth in the basal region are compatible with the delay inherent in message transport from apex to base and are considered as evidence for apical involvement in the totality of the seedling's georesponse.     

Studies in vitro of the nature and synthesis of the cell wall ofChlamydia trachomatis

The possibility thatChlamydia trachomatis contains peptidoglycan was examined by three methods. Preincubation of chlamydia with enzymes known to cleave peptidoglycan had no adverse effect on the subsequent development. Immunofluorescence studies with antistreptococcal peptidoglycan antisera failed to show any cross reactions with chlamydial antigens. The antichlamydial activity of anti-cell-wall antimicrobials was examined; lactams proved the most active, and cycloserine and bacitracin also showed antichlamydial activity. Alaphosphin, phosphomycin, and vancomycin showed no antichlamydial activity at the concentrations tested.     

Sodium-23 NMR studies of cation-DNA interactions

Sodium-23 NMR has been used to study the extent to which monovalent cations associate with double stranded DNA in aqueous solution (28°C, pH = 7.5). On the basis of the two site model for rapid exchange the ²³Na linewidth can be related to the fraction of sodium ions associated with DNA. To test the applicability to this system of the condensation model for the association of small counterions with polyelectrolytes, the concentration dependence of the sodium linewidth has been determined by making additions of NaCl to solutions of tetraethyl or tetrabutylammonium DNA. ([P], the DNA phosphate concentration was about 0.02M). The resulting titration curves extend over a wide range of the ratio [Na]/[P] (0.3–30). When [Na]/[P] ? 3 only sodium is associated, and the extent to which it compensates the charges on DNA does not vary with the addition of salt, at least until [Na]/[P] ≈ 30, the highest concentration examined. When [Na]/[P] ? 3 the tetraalkylammonium species is also associated with DNA; an equation has been derived to account for the effect on the ²³Na linewidth of the competition between sodium and another monovalent cation. Based on the assumption that the fraction of uncompensated charge remaining on DNA after the condensation of both species is constant, this equation fits all the linewidth data if the charge fraction is in the range 0.25 ± 0.10. The value required by the condensation model for DNA in the presence of monovalent counterions is ξ^?1 = 0.24. The reasonable agreement between experimental and theoretical values of the charge fraction and its invariance with respect to large variations in the concentration of added salt indicate that even in moderately concentrated solutions of DNA, the association of sodium can usefully be described in terms of the condensation model. If the theoretical value of the charge fraction is assumed, it follows from fitting the titration curves that the approximate relative affinities for DNA of Na⁺, Et₄N⁺, and Bu₄N⁺ are in the ratio 20:5:1, and the transverse relaxation rate of condensed sodium is 180 ± 10 s^?1.     

Purification of the protein employed in an immunodiffusion test to diagnose infectious bovine rhinotracheitis.

The antigen used in an immunodiffusion test to diagnose infectious bovine rhinotracheitis has been purified by affinity chromatography. The homogeneity of the antigen was indicated by sedimentation rate and sedimentation equilibrium experiments. A So20,w of 0.749 was determined and a molecular weight of 8900 was calculated from sedimentation equilibrium analysis. The purified antigen formed precipitin lines of identity with crude diagnostic antigen. Purified antigen remained serologically active in the immunodiffusion test after lyophilization and subsequent reconstitution.     

Glutamate oxaloacetate transaminase isozymes of the Triticinae: dissociation and recombination of subunits

Summary A simple procedure has been developed for the dissociation of active molecules of glutamate oxaloacetate transaminase (GOT: E.C. 2.6.1.1) into protomers and for the reassociation of the subunits into active enzymes. Results of experiments in which the protomers of genetically controlled electrophoretic variants of GOT of Triticum aestivum and of several related species were dissociated and recombined in crude tissue extracts and in partially purified preparations support the hypothesis that the enzyme exists functionally as a dimer in the Triticinae.This paper is Technical Article No. 13157 of the Texas Agricultural Experiment Station.     

Familial fragility on chromosome 16 (Fra 16q22) enhanced by both interferon and distamycin A

A family with a "fragile site" at 16q22, inducible by both interferon and Distamycin A, is reported. Immunological problems were found in the family. In a sibship of ten, eight children had died in infancy. Our study led to the conclusions that interferon and Distamycin A induce fragility at the same site, which has the same characteristics as the spontaneous fragile site; that a viral hypothesis for this fragility may be supported; and that immunoincompetence of one kind or another must be considered in families presenting a fragile site at 16q22.     

A review of the salt sensitivity of the Australian freshwater biota

In Victoria, Australia, both dryland salinity and salinity in irrigation regions are serious agricultural problems. One option to control the latter is to pump groundwater to maintain it below the surface. However, this leaves a saline wastewater for disposal, probably into local streams or wetlands. This review of the salt sensitivity of the biota of Australian streams and wetlands gives information of interest to those responsible for developing controls on these discharges. The review addresses the lethal and sub-lethal effects of salinity on microbes (mainly bacteria), macrophytes and micro-algae, riparian vegetation, invertebrates, fish, amphibians, reptiles, mammals, and birds. Data suggest that direct adverse biological effects are likely to occur in Australian river, stream and wetland ecosystems if salinity is increased to around 1 000 mg L⁻¹. The review highlights a general lack of data on the sensitivity of freshwater plants and animals to salinity increases.     

Crystallization of an endochitinase from Hordeum vulgar L. seeds.

Higher plants contain several constitutively expressed proteins for protection against infections by viruses, bacteria and fungi. Here we report the crystallization of a polypeptide with antifungal activity, a 26,000 dalton endochitinase from barley (Hordeum vulgare L.) seeds, in a form suitable for high-resolution X-ray analysis. Crystals were grown by vapor diffusion under several different conditions. The best crystals, obtained with ammonium sulfate as the precipitant, belong to the tetragonal space group P4(1)2(1)2 (P4(3)2(1)2), with cell dimensions a = b = 62.9 A and c = 96.0 A. The cell dimensions are consistent with one endochitinase molecule per asymmetric unit, and the crystals diffract to at least 2.0 A resolution.     

Effect of inorganic cations and metabolic inhibitors on putrescine transport in roots of intact maize seedlings

The specificity and regulation of putrescine transport was investigated in roots of intact maize (Zea mays L.) seedlings. In concentration-dependent transport studies, the kinetics for putrescine uptake could be resolved into a single saturable component that was noncompetitively inhibited by increasing concentrations of Ca²⁺ (50 micromolar to 5 millimolar). Similarly, other polyvalent cations, including Mg²⁺ (1.8 millimolar) and La³⁺ (200 micromolar), almost completely abolished the saturable component for putrescine uptake. This suggests that putrescine does not share a common transport system with other divalent or polyvalent inorganic cations. Further characterization of the putrescine transport system indicated that 0.3 millimolar N-ethyl-maleimide had no effect on putrescine uptake, and 2 millimolar p-chloromercuribenzene sulfonic acid only partially inhibited transport of the diamine (39% inhibition). Metabolic inhibitors, including carbonylcyanide-m-chlorphenylhydrazone (20 micromolar) and KCN (0.5 millimolar), also partially inhibited the saturable component for putrescine uptake (V_max reduced 48-60%). Increasing the time of exposure to carbonylcyanide-m-chlorphenylhydrazone from 30 minutes to 2 hours did not significantly increase the inhibition of putrescine uptake. Electrophysiological evidence indicates that the inhibitory effect on putrescine uptake by these inhibitors is correlated to a depolarization of the membrane potential, suggesting that the driving force for putrescine uptake is the transmembrane electrical potential across the plasmalemma.     

Twenty five years of case finding and audit in a socially deprived community.

OBJECTIVE--To evaluate audit and case finding (whole population care) in a community over 25 years. DESIGN--Contemporary screening for and audits of care of chronic disease and risk factors; retrospective review of computerised practice records; and comparisons of mortality and social indices with neighbouring communities. SETTING--One general practice in Glyncorrwg, West Glamorgan. SUBJECTS--1800 people registered with the practice in 1987 and 558 people who died from 1964 to 1987, whose records had been retained. MAIN OUTCOME MEASURES--Detection of high blood pressure, smoking, airways obstruction, obesity, diabetes, and alcohol problems in adults aged 20-79; prevalence of smoking in this population and in hypertensive and diabetic groups; age standardised mortality ratios in relation to indices of social deprivation. RESULTS--In the population aged 20-79 (1207 patients) 249 (21%) had peak expiratory flow rate less than 50% of expected value or which improved by 15% or more with an inhaled beta agonist, 207 (17%) had body mass index at or over 30 kg/m2, 118 (10%) had untreated mean arterial pressures greater than 159/104 mm Hg (three readings), 80 (7%) (65 (16%) men, 15 (4%) women) had recognised alcohol problems, and 35 (3%) had diabetes. The proportion of men aged 20-64 who said they smoked fell from 61% (290/476) in 1968-70 to 36% (162/456) in 1985 whereas that of women who smoked was unchanged (43%, 187/436 v 42%, 190/448 respectively). In 116 screened hypertensive patients group mean blood pressure fell from 186/110 mm Hg before treatment to 146/84 mm Hg at 1987 audit, as did the proportion of smokers (56% v 20%), but body mass index and total cholesterol concentration showed no significant change. In 34 diabetic patients mean blood pressure and the proportion of smokers fell (171/93 mm Hg v 155/81 mm Hg; 44% v 12%). The age standardised mortality ratio in 1981-6 was lower than in a neighbouring village without a developed case finding programme (actual to expected deaths less than 65 = 21 to 22 in Glyncorrwg, 48 to 30 in control village). CONCLUSIONS--Whole population care through organised case finding and audit is feasible but only with a labour intensive approach combining accessibility, flexibility, and continuity, as well as a planned and structured approach, which requires substantial expansion of staff numbers and assiduous recording. It may reduce risks for at least some high risk groups. Despite their shortcomings the available data are consistent with the hypothesis that whole population care helps reduce mortality. Incentives in the new contract, which encourage the uncritical development of structured process, may diminish health outputs.