The energy balance of leaves of the evergreen desert shrub Atriplex hymenelytra

Summary Atriplex hymenelytra is an evergreen shrub distributed in the hot deserts of parts of Mexico and the southwestern United States. The leaves of the species have a number of characteristics that are adaptive in a hot, dry environment, some of which change seasonally. Steeply angled leaves reduce midday solar interception, yet result in relatively high interception when solar angles are low and vapor pressure deficits are at a minimum. The leaves substantially reduce their absorptance of incident radiation during the hot periods of the year by changing their moisture and hence dissolved salt contents. At these times the light intensity required for saturation of photosynthesis is low and a reduction in the radiation absorbed by the leaves therefore results in a greater water-use efficiency.     

Mutations that eliminate the requirement for the vertex protein in bacteriophage T4 capsid assembly.

The capsid of bacteriophage T4 is composed of two essential structural proteins, gp23, the major constituent of the capsid, and gp24, a less prevalent protein that is located in the pentameric vertices of the capsid. gp24 is required both to stabilize the capsid and to allow it to be further matured. This requirement can be eliminated by bypass-24 (byp24) mutations within g23. We have isolated, cloned and sequenced several new byp24 mutations. These mutations are cold-sensitive in the absence of gp24, and are located in regions of g23 not known to contain any other mutations affecting capsid assembly. The cold-sensitivity of the byp24 mutations can be reduced by further mutations within g23 (trb mutations). Cloning and sequencing of these trb mutations has revealed that they lie in regions of g23 that contain clusters of mutations that cause the production of high levels of petite and giant phage (ptg mutations). Despite the proximity of the trb mutations to the ptg mutations, none of the ptg mutations has a Trb phenotype. The mutation ptE920g, which is also located near one of the ptg clusters, and which produces only petite and wild-type phage, has been shown to confer a Trb but not a Byp24 phenotype. The relevance of these observations to our understanding of capsid assembly is discussed.     

Further observations on the water relations ofProsopis tamarugo of the northern Atacama desert

Summary Prosopis tamarugo, a tree native to the Atacama desert of Chile apparently has unique water relations. It is proposed that in its native habitat, where there is essentially no precipitation, establishment occurs during the rare flooding periods, with water coming as runoff from the Andes. These plants subsequently exist as phreatophytes tapping the relatively shallow ground water. Although phreatophytic, the plants appears to come under increasing drought stress as the growing season progresses. Because of the very low water potentials of the salty surface soils, water evidently moves from the plant into the soil under certain conditions. This water may be reabsorbed subsequently and used by the plant as the water table capillary fringe is depleted toward the end of the leafy period.     

A System for Evaluating and Treating Chronic Back Disability

Five methods of personality assessment are evaluated to provide guidance for the psychological treatment of patients with chronic back pain. Patient pain drawings, pentothal pain studies, stress score index, psychological testing with the Minnesota Multiphasic Personality Inventory (MMPI) and response to treatment challenge are used as measurements for evaluation. This evaluation gives the treating staff guidelines for individual treatment programs utilizing operant conditioning techniques. Using this approach, three fourths of the severely disabled patients seen have been successfully treated.     

Volatile factor involved in the dimorphism of Mucor racemosus.

Both hyphal and yeastlike development of Mucor racemosus and M. rouxii were demonstrated under 100% N2. Under standardized conditions in yeast extract-peptone-glucose medium, the morphology depended on the N2 flow rate and not on the glucose concentration. The effect was related to the rate of flushing of the atmosphere over the culture medium. The results indicate that a volatile compound produced by Mucor is involved in morphogenesis.     

An Excess of Deleterious Variants in VEGF-A Pathway Genes in Down-Syndrome-Associated Atrioventricular Septal Defects

About half of people with trisomy 21 have a congenital heart defect (CHD), whereas the remainder have a structurally normal heart, demonstrating that trisomy 21 is a significant risk factor but is not causal for abnormal heart development. Atrioventricular septal defects (AVSD) are the most commonly occurring heart defects in Down syndrome (DS), and ∼65% of all AVSD is associated with DS. We used a candidate-gene approach among individuals with DS and complete AVSD (cases = 141) and DS with no CHD (controls = 141) to determine whether rare genetic variants in genes involved in atrioventricular valvuloseptal morphogenesis contribute to AVSD in this sensitized population. We found a significant excess (p < 0.0001) of variants predicted to be deleterious in cases compared to controls. At the most stringent level of filtering, we found potentially damaging variants in nearly 20% of cases but fewer than 3% of controls. The variants with the highest probability of being damaging in cases only were found in six genes: COL6A1, COL6A2, CRELD1, FBLN2, FRZB, and GATA5. Several of the case-specific variants were recurrent in unrelated individuals, occurring in 10% of cases studied. No variants with an equal probability of being damaging were found in controls, demonstrating a highly specific association with AVSD. Of note, all of these genes are in the VEGF-A pathway, even though the candidate genes analyzed in this study represented numerous biochemical and developmental pathways, suggesting that rare variants in the VEGF-A pathway might contribute to the genetic underpinnings of AVSD in humans.