Isolation and regional localization of a large collection (2,000) of single-copy DNA fragments on human chromosome 3 for mapping and cloning tumor suppressor genes

Summary A collection of 2,000 lambda phage-carrying human single-copy inserts (> 700 bp) were isolated from two chromosome-3 flow-sorted libraries. The single-copy DNA fragments were first sorted into 3p and 3q locations and about 700 3p fragments were regionally mapped using a deletion mapping panel comprised of two humanhamster and two-human-mouse cell hybrids, each containing a chromosome 3 with different deletions in the short arm. The hybrids were extensively mapped with a set of standard 3p markers physically localized or ordered by linkage. The deletion mapping panel divided the short arm into five distinct subregions (A-E). The 3p fragments were distributed on 3p regions as follows: region A, 26%; B, 31%; C, 4%; D, 4% and E, 35%. We screened 300 single-copy DNA fragments from the distal part of 3p (regions A and B) with ten restriction endonucleases for their ability to detect restriction fragment length polymorphisms (RFLPs). Of these fragments 110 (36%) were found to detect useful RFLPs: 35% detected polymorphisms with frequency of heterozygosity of 40% or higher, and 25% with frequency of 30% or higher. All polymorphisms originated from single loci and most of them were of the base pair substitution type. These RFLP markers make it possible to construct a fine linkage map that will span the distal part of chromosome 3p and encompasses the von Hippel-Lindau disease locus. The large number of single-copy fragments (2,000) spaced every 100–150 kb on chromosome 3 will make a significant contribution to mapping and sequencing the entire chromosome 3. The 300 conserved chromosome 3 probes will increase the existing knowledge of man-mouse homologies.     

Pulmonary vascular compliance and viscoelasticity

When dog lung lobes were perfused at constant arterial inflow rate, occlusion of the venous outflow (VO) produced a rapid jump in venous pressure (Pv) followed by a slower rise in both arterial pressure (Pa) and Pv. During the slow rise Pa(t) and Pv(t) tended to converge and become concave upward as the volume of blood in the lungs increased. We compared the dynamic vascular volume vs. pressure curves obtained after VO with the static volume vs. pressure curves obtained by dye dilution. The slope of the static curve (the static compliance, Cst) was always larger than the slope of the dynamic curve (the dynamic compliance, Cdyn). In addition, the Cdyn decreased with increasing blood flow rate. When venous occlusion (VO) was followed after a short time interval by arterial occlusion (AO) such that the lobe was isovolumic, both Pa and Pv fell with time to a level that was below either pressure at the instant of AO. In an attempt to explain these observations a compartmental model was constructed in which the hemodynamic resistance and vascular compliance were volume dependent and the vessel walls were viscoelastic. These features of the model could account for the convergence and upward concavity of the Pa and Pv curves after VO and the pressure relaxation in the isovolumic state after AO, respectively. According to the model analysis, the difference between Cst and Cdyn and the flow dependence of Cdyn are due to wall viscosity and volume dependence of compliance, respectively. Model analysis also suggested ways of evaluating changes in the viscoelasticity of the lobar vascular bed. Hypoxic vasoconstriction that increased total vascular resistance also decreased Cst and Cdyn and appeared to increase the vessel wall viscosity.     

Cat lung hemodynamics: comparison of experimental results and model predictions

Commonly, attempts have been made to learn about the structure and function of the pulmonary vascular bed from measurements of arterial and venous pressures and blood flow rate under steady-state conditions (e.g., from pressure vs. flow data) or dynamic conditions (e.g., from vascular occlusion data). Zhuang et al. (J. Appl. Physiol. 55: 1341-1348, 1983) have presented a detailed model of steady-state cat lung hemodynamics based on direct measurements of anatomical and elasticity data. This model provides an opportunity to better understand the information content of the hemodynamic data. Therefore, in the present study we carried out a series of steady-state and dynamic experiments on isolated cat lungs. We then compared the results with those predicted by the model. We found that the model provided a good fit to the steady-state data. However, to fit the dynamic data, some modifications were necessary to account for the viscous behavior of the vessel walls and to move the first moment of the distribution of vascular resistance toward the arterial end of the vascular bed relative to that of the distribution of vascular compliance. Due to the sensitivity of the vascular resistance to small changes in vessel diameters and branching ratio, the modifications in morphometry represent small changes in morphometric data and are probably within the range of uncertainty in such data. The modifications had little effect on the steady-state model simulations but substantially improved the dynamic model simulations, suggesting that the dynamic data are quite sensitive to small changes in the relative distributions of vessel diameters and elasticity.     

Plasma protein binding and endothelial enzyme interactions in the lung

The influence of plasma albumin binding of the synthetic angiotensin-converting enzyme (ACE) substrate [3H]benzoyl-phenylalanyl-alanyl-proline (BPAP) on BPAP hydrolysis by pulmonary endothelial ACE was studied in isolated rabbit lungs perfused with a salt solution containing either 5% bovine serum albumin (BSA) or 5% dextran. The single-pass indicator-dilution method was used to measure the fraction (M) of [3H]BPAP hydrolyzed. Lung M was greater with albumin-free perfusate than when BSA was present. M decreased as the time (ti) that the BPAP was in contact with the BSA before reaching the lung was increased, suggesting that some BSA binding sites for BPAP were not in equilibrium during bolus transit through the lungs. The M vs. ti data were correlated using a model incorporating both rapid and slow binding kinetics of BPAP and BSA. For the slow BPAP-BSA interaction, the dissociation rate constant was approximately 0.015 s-1, and the fraction of the BPAP bound to these slowly equilibrating sites at equilibrium was approximately 22%. The results indicate that transient plasma protein binding kinetics can affect lung BPAP hydrolysis.     

The uptake by plants of polymaleic acid: A polycarboxylic acid structurally related to those of soils

Summary The uptake of¹⁴C labelled polymaleic acid (PMA) by tomato and wheat plants cultured under axenic conditions was estimated during 48 d growth for tomato and 17 d for wheat seedlings. The concentrations of PMA, calculated from¹⁴C data, reached values of over 1 mg g⁻¹ FW for root tissue and over 0.2 mg g⁻¹ FW for shoots. Freeze-dried roots were shown to take up a substantial amount of PMA over short periods demonstrating a major non-metabolic adsorption. PMA was adsorbed by carboxymethyl cellulose, used as a model system for plant roots, in amounts comparable with freeze-dried roots. The adsorptive capacity of carboxymethyl cellulose was increased by treatment with solutions of metal ions. Especially effective in this respect were Cu, Fe and Al. It is suggested that at least two mechanisms are involved in the adsorption of PMA by polysaccharides and by plant roots. One, possibly hydrogen bonding, being independent of the presence of metal ions and another depending on the presence of multivalent cations.     

A method for analysis of pulmonary arterial and venous occlusion data.

Recently, we presented a compartmental model of the pulmonary vascular resistance (R) and compliance (C) distribution with the configuration C1R1C2R2C3 (J. Appl. Physiol. 70: 2126-2136, 1991). This model was used to interpret the pressure vs. time data obtained after the sudden occlusion of the arterial inflow (AO), venous outflow (VO), or both inflow and outflow (DO) from an isolated dog lung lobe. In the present study, we present a new approach to the data analysis in terms of this model that is relatively simple to carry out and more robust. The data used to estimate the R's and C's are the steady-state arterial [Pa(0)] and venous [Pv(0)] pressures, the flow rate (Q), the area (A2) encompassed by Pa(t) after AO and the equilibrium pressure (Pd) after DO, and the average slope (m) of the Pa(t) and Pv(t) curves after VO. The following formulas can then be used to calculate the 2 R's and 3 C's: [Pa(0) - Pv(0)]/Q = R1 + R2 = RT, R1C1 congruent to to A2/[Pa(0) - Pd], R1 congruent to [Pa(0) - Pd]/Q, Q/m = C1 + C2 + C3 = CT, and C2 = CT - (RTC1/R2).