Gradients in maize roots: local elongation and pH

The elongation rate, the gradient of the local elongation rate and the surface pH of maize roots were measured over 12 h. A data bank was constituted by storing these values. By sorting these results on the basis of different elongation rates, different classes of root were obtained. Two classes were chosen: the low-growth roots and the high-growth roots. The mean growth of these two root classes was stable with time and differed significantly from one another. The surface pH of the elongation zone was the same for the roots of these two classes, but the roots selected for their higher growth rate had a larger acid efflux in this zone.     

Values,Errors, and Precautions

In the environmental health literature, errors in interpreting studies or data are not infrequent. Many are of the Type II variety. Common solecisms of this type are: treating the criterion of p < 0.05 as a sacrament; demanding complete confounder control; arguing for the existence of phantom confounders; arguing that the effect size is trivial; building nonveridical models; arguing for no effect from inadequate sample size; demanding causal proof; arguing that causality is reversed; conducting a ballot of published studies. These are examined in this paper.     

Externally attached radio transmitters do not affect the parental care behaviour of rock bass

Turning, pectoral fin and caudal fin rates and time spent on the nest of male rock bass Ambloplites rupestris , engaged in parental care, were not affected after the attachment of external radio transmitters. Reproductive success was similar between treatment and control fish. Micro external radio transmitters can be used on small fishes for studying parental care duration and post-care movement without altering their behaviour.     

Radioiodinated surface proteins of rabbit trophectoderm cells

Summary We have previously used surface iodination to discriminate between the protein patterns of epithelial cell surfaces in uteri of rabbits receptive (Day 6.5) or nonreceptive (Day 4) to nidation (Ricketts et al. 1984). In this paper, we describe application of the same technique to the trophoblastic surface of rabbit blastocysts collected on the same days of pregnancy. Analysis of labelled proteins by polyacrylamide-gel electrophoresis under denaturing conditions did not reveal qualitative differences between the two days of pregnancy. Scanning densitometry was used to quantitate the area under each protein peak on an autoradiogram; these areas were used as variables in statistical analysis of the protein pattern of individual animals. Quantitative differences between the protein patterns of the two surfaces were detected by canonical variate analysis of the pattern of relative areas of labelled protein peaks. In proteins separated on 7.5% gels, this statistical analysis correctly assigned blastocysts from 8 out of 10 animals to one of two groups according to day of pregnancy. The discrimination was not statistically significant, however, in protein patterns on 12.5% gels, used to give better separation in the lower range of molecular weights. The same analysis in the uterus unequivocally separated the surface iodination patterns from these same days of pregnancy. Thus the changes detected by surface iodination appear to be less pronounced on the trophectoderm than on the uterine epithelium in relation to the time of ovoimplantation.     

Tuning cellular responses to BMP-2 with material surfaces

Bone morphogenetic protein 2 (BMP-2) has been known for decades as a strong osteoinductive factor and for clinical applications is combined solely with collagen as carrier material. The growing concerns regarding side effects and the importance of BMP-2 in several developmental and physiological processes have raised the need to improve the design of materials by controlling BMP-2 presentation. Inspired by the natural cell environment, new material surfaces have been engineered and tailored to provide both physical and chemical cues that regulate BMP-2 activity. Here we describe surfaces designed to present BMP-2 to cells in a spatially and temporally controlled manner. This is achieved by trapping BMP-2 using physicochemical interactions, either covalently grafted or combined with other extracellular matrix components. In the near future, we anticipate that material science and biology will integrate and further develop tools for in vitro studies and potentially bring some of them toward in vivo applications.     

Zosteric acid and salicylic acid bound to a low density polyethylene surface successfully control bacterial biofilm formation

The active moieties of the anti-biofilm natural compounds zosteric (ZA) and salicylic (SA) acids have been covalently immobilized on a low density polyethylene (LDPE) surface. The grafting procedure provided new non-toxic eco-friendly materials (LDPE-CA and LDPE-SA) with anti-biofilm properties superior to the conventional biocide-based approaches and with features suitable for applications in challenging fields where the use of antimicrobial agents is limited. Microbiological investigation proved that LDPE-CA and LDPE-SA: (1) reduced Escherichia coli biofilm biomass by up to 61% with a mechanism that did not affect bacterial viability; (2) significantly affected biofilm morphology, decreasing biofilm thickness, roughness, substratum coverage, cell and matrix polysaccharide bio-volumes by >80% and increasing the surface to bio-volume ratio; (3) made the biofilm more susceptible to ampicillin and ethanol. Since no molecules were leached from the surface, they remained constantly effective and below the lethal level; therefore, the risk of inducing resistance was minimized.     

Cardiovascular and respiratory responses associated with limb autotomy in the blue crab, Callinectes sapidus

Cardiovascular and respiratory variables were recorded in the blue crab, Callinectes sapidus, during injury and subsequent autotomy of a chela. Cardiac function and haemolymph flow rates were measured using a pulsed-Doppler flowmeter. Oxygen uptake was recorded using an intermittent flow respirometry system. Crabs reacted to the loss of a chela with a rapid increase in heart rate, which was sustained for 2 h. Stroke volume of the heart also increased after the chela was autotomized. A combined increase in heart rate and stroke volume led to an increase in cardiac output, which was maintained for an hour after the loss of a chela. There was also differential haemolymph perfusion of various structures. There was no change in perfusion of the anterolateral arteries or posterior and anterior aortae, during injury of the chela or subsequent autotomy. Haemolymph flow rates did increase significantly through the sternal artery during injury and immediately following autotomy of the chela. This was at the expense of blood flow to the digestive gland: a sustained decrease in haemolymph flow through the hepatic arteries occurred for 3 h following autotomy. Fine-scale cardiac changes associated with the act of autotomy included a bradycardia and/or associated cardiac pausing before the chela was shed, followed by a subsequent increase in cardiac parameters. Changes in the cardiovascular physiology were paralleled by an increase in oxygen uptake, which was driven by an increased ventilation of the branchial chambers. Although limb loss is a major event, it appears that only acute changes in physiology occur. These may benefit the individual, allowing rapid escape following autotomy with a subsequent return to normal activity.     

Testing for Validity and Reliability in Cross-Cultural Research

A set of procedures is offered for assessing interraler reliability and certain aspects of validity of codes in cross-cultural studies. The method assumes that at least two independent raters have coded more than one trait. Each trait coded by one rater is correlated with each trait coded by a second, and all the codings by a single rater are intercorrelated with each other. The results are presented in a multitrait-multi-rater matrix. From this matrix it is possible to determine the interrater reliability and discriminant validity of trails in addition to a higher order concept based on pairs of traits.     

Purification of Neuronal Cell Surface Proteins and Generation of Epitope-Specific Monoclonal Antibodies Against Cell Adhesion Molecules

To establish a procedure for the purification of a broad spectrum of cell surface proteins, three separate methods based on different principles were compared with the aid of four marker proteins. Membrane preparation by sedimentation-flotation centrifugation, temperature-induced phase separation with Triton X-114, and lectin affinity chromatography were used separately as well as in combination. The two-step procedure of membrane preparation and lectin affinity chromatography provided by far the best enrichment of cell surface marker proteins. This result was further substantiated by screening greater than 6,600 hybridoma cultures that originated from mice that had been immunized with protein fractions obtained by different purification protocols. In addition, it was found that solubilized glycoproteins used as immunogens led to many more cell surface-specific monoclonal antibodies than glycoproteins immobilized on lectin-agarose beads. Three monoclonal antibodies that recognize distinct epitopes of cell adhesion molecules (CAMs) were isolated. Monoclonal antibody C4 bound to a detergent-labile epitope of G4 (neuron-glia CAM). Monoclonal antibody D1 recognized specifically nonreduced neural CAM (N-CAM) with intact disulfide bridges, and monoclonal antibody D3 recognized only the 180-kilodalton isoform of N-CAM. Because of these specificities, these monoclonal antibodies promise to be useful tools for the elucidation of the structural organization of adhesion molecules.