Perialveolar interstitial resistance and compliance in isolated rat lung

We have developed a method to characterize fluid transport through the perialveolar interstitium using micropuncture techniques. In 10 experiments we established isolated perfused rat lung preparations. The lungs were initially isogravimetric at 10 cmH2O arterial pressure, 2 cmH2O venous pressure, and 5 cmH2O alveolar pressure. Perialveolar interstitial pressure was determined by micropuncture at alveolar junctions by use of the servo-null technique. Simultaneously a second micropipette was placed in an alveolar junction 20-40 microns away, and a bolus of albumin solution (3.5 g/100 ml) was injected. The resulting pressure transient was recorded for injection durations of 1 and 4 s in nonedematous lungs. The measurements were repeated after gross edema formation induced by elevated perfusion pressure. We model the interstitium as a homogeneous linearly poroelastic material and assume the initial pressure distribution due to the injection to be Gaussian. The pressure decay is inversely proportional to time, with time constant T, where T is a measure of the ratio of interstitial tissue stiffness to interstitial resistance to fluid flow. A linear regression was performed on the reciprocal of the pressure for the decaying portion of the transients to determine T. Comparing pressure transients in nonedematous and edematous lungs, we found that T was 4.0 +/- 1.4 and 1.4 +/- 0.6 s, respectively. We have shown that fluid transport through the pulmonary interstitium on a local level is sensitive to changes in interstitial stiffness and resistance. These results are consistent with the decreased stiffness and resistance in the perialveolar interstitium that accompany increased hydration.     

Rapid extraction of high purity chromosomal DNA from Serratia marcescens

Rapid non-specific degradation of Serratia marcescens DNA extracted with guanidium thiocyanate, occurred within 10 min of incubation with restriction endo-nuclease enzymes. The described modified method based on chemical and enzymatic deproteinization produced preparations of Ser. marcescens DNA of high yield and quality which did not autodegrade when incubated with restriction endonucleases.     

Epigenetic and pharmacological control of pigmentation via Bromodomain Protein 9 (BRD9)

Lineage-specific differentiation programs are activated by epigenetic changes in chromatin structure. Melanin-producing melanocytes maintain a gene expression program ensuring appropriate enzymatic conversion of metabolites into the pigment, melanin, and transfer to surrounding cells. During neuroectodermal development, SMARCA4 (BRG1), the catalytic subunit of SWItch/Sucrose Non-Fermentable (SWI/SNF) chromatin remodeling complexes, is essential for lineage specification. SMARCA4 is also required for development of multipotent neural crest precursors into melanoblasts, which differentiate into pigment-producing melanocytes. In addition to the catalytic domain, SMARCA4 and several SWI/SNF subunits contain bromodomains which are amenable to pharmacological inhibition. We investigated the effects of pharmacological inhibitors of SWI/SNF bromodomains on melanocyte differentiation. Strikingly, treatment of murine melanoblasts and human neonatal epidermal melanocytes with selected bromodomain inhibitors abrogated melanin synthesis and visible pigmentation. Using functional genomics, iBRD9, a small molecule selective for the bromodomain of BRD9 was found to repress pigmentation-specific gene expression. Depletion of BRD9 confirmed a requirement for expression of pigmentation genes in the differentiation program from melanoblasts into pigmented melanocytes and in melanoma cells. Chromatin immunoprecipitation assays showed that iBRD9 disrupts the occupancy of BRD9 and the catalytic subunit SMARCA4 at melanocyte-specific loci. These data indicate that BRD9 promotes melanocyte pigmentation whereas pharmacological inhibition of BRD9 is repressive.     

Projected structure of unstained, frozen-hydrated T-layer of Bacillus brevis.

This paper presents the projected structure of the T-layer of Bacillus brevis, obtained from electron microscopic studies of the unstained protein layer in the frozen-hydrated state. Computer image processing is used to correct for the effects of the contrast transfer function, and to increase the signal-to-noise ratio by lattice averaging. The results obtained show a good agreement with those previously obtained using negatively stained specimens. It is shown that the contrast of T-layer embedded in ice can be approximated to pure phase contrast.     

Pseudomonas aeruginosa colonisation in an intensive therapy unit: role of cross infection and host factors.

Despite the sparsity of Pseudomonas aeruginosa in the environment colonisation and infection with this organism was found at several sites by selective culture in 20 out of 46 patients in an intensive therapy unit. Three patients developed Ps aeruginosa pneumonia. Serial serogrouping and phage typing identified multiple strains in the unit and in the same patient. Rectal carriage occurred in 16 patients but rectal strains did not subsequently appear in tracheal aspirates; strains varied in their affinity for the upper respiratory tract. Colonisation was not directly related to length of stay and was detected in 16 of those colonised within 24 hours of admission. In intubated patients, who were colonised more frequently than those not intubated, upper respiratory tract colonisation correlated strongly with low initial arterial pH values. Personnel were probably responsible for cross infection among patients when the unit was busy. Strain differences and the susceptibility of patients also influenced colonisation and infection. Elimination of major reservoirs of Ps aeruginosa and compliance with procedures to control cross infection remain essential if patients in hospital are to escape colonisation by the organism.     

An improved medium for the detection of Aspergillus flavus and A. parasiticus

An effective selective medium for the enumeration of Aspergillus flavus and Aspergillus parasiticus has been developed by modification of Bothast and Fennell's Aspergillus Differential Medium. Results can be obtained with the new medium, Aspergillus flavus and parasiticus Agar (AFPA), after 42 h incubation at 30°C. The medium is thus suitable for use in quality control as a guide to the presence of A. flavus and, potentially, of aflatoxins. AFPA has been extensively tested on peanuts and soils. Results were reproducible and comparable with those on standard fungal enumeration media incubated for much longer periods. A very low percentage of false positives or negatives was found.     

Using dBASE to write PENNAME, a computer key to common Penicillium species

dBASE III Plus™ computer software includes a high level computer language as well as a database management program. dBASE possesses advantages for key construction, including simple entry of raw data, effective user interaction in the selection of outputs, and ready comparison of included species with unknowns. This paper describes the use of dBASE in the construction of PENNAME, a new computer key to common Penicillium species.