Effect of cardiac output on gravity-dependent and nondependent inequality in pulmonary blood flow

To examine the effect of cardiac output (CO) on the gravity-nondependent distribution of pulmonary blood flow, 2 X 10(6) 99mTc-labeled albumin microspheres (20 microns) were injected at end expiration into dogs (anesthetized, supine, and breathing room air spontaneously). Two animals were injected at their resting CO, two were injected during increased CO (arteriovenous fistulas induced), and two were injected at low CO (phlebotomy induced). The chest was opened and the lungs were removed, drained of blood, and dried while fully inflated. Single-photon emission-computed tomography was performed on the dry lungs to map the distribution of activity in transverse, coronal, and sagittal slices. The results confirmed the presence of a central-peripheral gravity-nondependent gradient and showed that increases in CO were associated with increases in absolute flow to both the central and peripheral regions of the lung with persistence of the central-peripheral gradient. These observations were further confirmed by direct imaging of midcoronal slices. Examination of the average flow in vertical and horizontal slices showed that, when zone 1 was not present, changes in CO affected all slices uniformly, such that when the CO doubled, the absolute flow in every slice in all three planes also doubled. We conclude that, with the exception of recruitment and derecruitment of vascular channels in the upper regions of the lung (zone 1), when CO changes, the blood flow everywhere in the lung changes uniformly and in proportion to the CO. This uniform increase in blood flow is consistent with the three-dimensional nature and resistive properties of the pulmonary vascular tree.     

The polymorphic marker DXS304 is within 5 centimorgans of the fragile X locus

The fragile X syndrome, which is the most common cause of inherited mental retardation, poses important diagnostic problems for genetic counseling. The development of diagnostic strategies based on DNA analysis has been impaired by the lack of polymorphic markers very close to the disease locus. Here we report that the polymorphic probe U6.2 (locus DXS304) is much closer to the fragile X locus than all the previously reported markers. A recombination fraction of 0.02 between DXS304 and the fragile X locus was estimated by multipoint linkage analysis (confidence interval 0.002 to 0.05). Our data suggest that DXS304 is distal to the fragile X locus. This marker thus represents a major improvement for carrier detection and prenatal diagnosis in fragile X families.     

Mycobacterial cell wall: Structure and role in natural resistance to antibiotics

Abstract Mycobacteria show a high degree of intrinsic resistance to most antibiotics and chemotherapeutic agents. The low permeability of the mycobacterial cell wall, with its unusual structure, is now known to be a major factor in this resistance. Thus hydrophilic agents cross the cell wall slowly because the myobacterial porin is inefficient in allowing the permeation of solutes and exists in low concentration. Lipophilic agents are presumably slowed down by the lipid bilayer which is of unusually low fluidity and abnormal thickness. Nevertheless, the cell wall barrier alone cannot produce significant levels of drug resistance, which requires synergistic contribution from a second factor, such as the enzymatic inactivation of drugs.     

Global mangrove root production,its controls and roles in the blue carbon budget of mangroves

Mangroves are among the most carbon-dense ecosystems worldwide. Most of the carbon in mangroves is found belowground, and root production might be an important control of carbon accumulation, but has been rarely quantified and understood at the global scale. Here, we determined the global mangrove root production rate and its controls using a systematic review and a recently formalised, spatially explicit mangrove typology framework based on geomorphological settings. We found that global mangrove root production averaged ~770 ± 202 g of dry biomass m⁻² year⁻¹ globally, which is much higher than previously reported and close to the root production of the most productive tropical forests. Geomorphological settings exerted marked control over root production together with air temperature and precipitation (r² ≈ 30%, p < .001). Our review shows that individual global changes (e.g. warming, eutrophication, drought) have antagonist effects on root production, but they have rarely been studied in combination. Based on this newly established root production rate, root-derived carbon might account for most of the total carbon buried in mangroves, and 19 Tg C lost in mangroves each year (e.g. as CO₂). Inclusion of root production measurements in understudied geomorphological settings (i.e. deltas), regions (Indonesia, South America and Africa) and soil depth (>40 cm), as well as the creation of a mangrove root trait database will push forward our understanding of the global mangrove carbon cycle for now and the future. Overall, this review presents a comprehensive analysis of root production in mangroves, and highlights the central role of root production in the global mangrove carbon budget.     

Developmental requirements for the ecdysoneless (ecd) locus in Drosophila melanogaster

The ecdysoneless locus in Drosophila melanogaster has been defined previously by a single conditional mutation, I(3)ecd¹, that causes an ecdysteroid deficit and larval death at the restrictive temperature, 29°C, although the primary role of the mutation in developmental processes has been unclear. Gene dosage and complementation studies reported here for ecd¹ and five nonconditional lethal alleles indicate that the ecd locus plays prezygotic and postzygotic roles essential for normal embryonic development, the successful completion of each larval molt, adult eclosion, and female fertility. The ecd locus is also required for normal macrochaete differentiation. For each observed phenotype, the severity of mutational effects was correlated with ecd mutant genotypes. In all cases, ecd¹ homozygotes were least affected. Mutants heteroallelic for ecd¹ and any one of four nonconditional recessive mutations were more severely affected than ecd¹ homozy-gotes, revealing these as hypomorphic alleles. For all phenotypic effects, mutants heteroallelic for ecd¹ and a dominant mutation (ecd^3D) were most severely affected. These individuals died during embryogenesis at 29°C and developed no macrochaetes on the dorsal thorax when transferred to 29°C during the white prepupal stage. The ecd^3D mutation also caused female semisterility in heterozygotes. Ecdysteroid regulation has been implicated previously in all the developmental processes disrupted by these ecd mutations except for macrochaete differentiation. © 1993 Wiley-Liss, Inc.     

Family and Community in Ireland.

Family and Community in Ireland. Conrad M. Arensberg and Solon T. Kimball. Third edition, with. new introduction by Anne Byrne, Ricca Edmondson, and Tony Varley. Ennis, Ireland: Clasp Press, 2001. 417 pp.