One-dimensional double-quantum magic-angle-spinning NMR of deuterated solids

An approach to double-quantum magic-angle spinning (2Q-MAS) of spin I = 1 with a time-share irradiation, resulting in a one-dimensional (1D) MQ spectrum, is demonstrated in this paper. The experiment was carried out with perdeuterated dimethoxybenzene and showed that the 2Q transitions were insensitive to the spinning axis deviation from the magic angle. The 1D-2Q-MAS scheme may also be applied to nitrogen-containing solids.

Corrections to the cross-polarization dynamics in solids. The effect of nonsecular terms of heteronuclear dipolar interaction on cross-relaxation

The dynamic theory of cross-polarization in solids is modified by considering the contribution of the nonsecular terms of the heteronuclear dipolar interaction Hamiltonian in the laboratory frame to cross-relaxation. This contribution is evaluated numerically and confirmed experimentally. It is shown that these nonsecular terms may play a considerable role in cross-relaxation in many systems, especially in those with fast internal molecular motion. The complication in the cross-polarization process is further revealed.

Increased pulmonary artery elastolytic activity in adult rats with monocrotaline-induced progressive hypertensive pulmonary vascular disease compared with infant rats with nonprogressive disease

In a rat model of pulmonary hypertension induced by monocrotaline, medial hypertrophy of the pulmonary arteries is associated with enhanced production (synthesis) of insoluble elastin relative to accumulation and an increased number of elastin fragments, features suggestive of an elastolytic process. In the present study, we measured and characterized pulmonary artery (PA) elastolytic activity at time points before as well as coincident with the progression of medial hypertrophy in monocrotaline-injected adult male Sprague-Dawley rats. We also determined whether medial hypertrophy is preceded by ultrastructural changes in elastin. Since medial hypertrophy develops but fails to progress in rats injected with monocrotaline at 8 days of age, we assessed whether, compared with adult rats, there were also structural and biochemical differences in elastin and elastolytic activity. A twofold increase in elastolytic activity per milligram tissue was observed 2 days after monocrotaline injection in adult rats (p less than 0.01), and there was an increased number of breaks in the internal elastic lamina (IEL) at 4 days (p less than 0.05) (i.e., before the development of medial hypertrophy). Associated with the progression of medial hypertrophy between 16 and 28 days after monocrotaline injection, there was a further threefold increase in elastolytic activity per milligram tissue by 28 days (p less than 0.01). Susceptibility of the elastolytic activity to specific inhibitors suggested that one or more serine elastases is involved. In infant rats in which medial and right ventricular hypertrophy fail to progress in severity between 16 and 28 days after monocrotaline injection, we did not measure an increase in elastolytic activity, nor was there evidence of an increase in the number of breaks in the IEL at 4 days, suggesting a lack of increased elastolytic activity at an earlier time point. The total content of PA elastin in infant rats, although increased compared with control rats (p less than 0.01), was not associated with heightened production and appeared ultrastructurally as thicker laminae (p less than 0.05) rather than as fragments previously reported in adult rats.

New developments in the pulmonary circulation in children

This article reviews new advances in the diagnosis, treatment, and pathophysiology of pulmonary hypertension. In diagnosis, Doppler echocardiography has been refined and its accuracy increased, and magnetic resonance imaging is being developed as a new tool. Prostacyclin and calcium channel blockers remain mainstays of short-term therapy, and single-lung transplantation has become a new therapeutic option. Newer pharmacotherapeutics are largely directed at reversing acute vasoconstriction and include approaches related to ATP and endothelial-derived relaxing factor. In pathophysiology, recent studies have shown the role of elastase in mediating the initiation and progression of pulmonary hypertension, the regulation of gene expression of collagen, elastin, endothelin, and growth factors including transforming growth factor-B and insulinlike growth factor-I, and mechanisms of signal transduction of smooth muscle cell proliferation. The migratory smooth muscle cell phenotype has been studied in terms of altered expression of endothelial and smooth muscle extracellular matrix components, including hyaluronan and fibronectin, respectively.

[Pharmacological study on an irreversible ligand of opioid receptors, A-alpha-CAM, and its reaction with the sulfhydryl group]

A-alpha-CAM is an irreversible partial agonist of opiate receptors. Its binding to opioid receptors from P2 membrane preparations of rat brain and its effect on isolated tissues (GPI, MVD, RVD and RbVD) could not be washed away, indicating the irreversible nature of its binding. A-alpha-CAM inhibited the electrically elicited contraction of GPI, a pure agonist, with an IC50 of 2.6 mumol/L, and this effect could not be antagonized by Nx. A-alpha-CAM acted as a partial agonist on MVD with an IC50 of 0.153 mumol/L. With RVD and RbVD, A-alpha-CAM acted as an antagonist with PA2 values of 7.4 and 7.7 respectively. Possibly, covalent binding of A-alpha-CAM with the sulfhydryl groups of opioid receptors is the biochemical mechanisms responsible for its irreversible action.

Long-term starvation-induced loss of antibiotic resistance in bacteria

Escherichia coli, Pseudomonas fluorescens, and aPseudomonas sp. strain 133B containing the pSa plasmid were starved in well water for up to 523 days. There were two patterns of apparent antibiotic resistance loss observed. InPseudomonas sp. strain 133B, there was no apparent loss of antibiotic resistance even after starvation for 340 days. InE. coli, by day 49 there was a ten-fold difference between the number of cells that would grow on antibiotic- and nonantibiotic-containing plates. However, over 76% of the cells that apparently lost their antibiotic resistance were able to express antibiotic resistance after first being resuscitated on non-selective media. By day 523, only 12% of these cells were able to express their antibiotic resistance after being resuscitated. After starvation for 49 days, cells that could not grow on antibiotic medium even after resuscitation, showed a permanent loss of chloramphenicol (Cm) resistance but retained resistance to kanamycin (Km) and streptomycin (Sm). Restriction enzyme digests show that a 2.5 to 3.0 Kb region from map location 12.5 to 15.5 Kb was deleted. This coincides with the 2.5 Kb reduction in plasmid size observed in 3 isolates that had lost antibiotic resistance after starvation for 49 days.

Plasmid expression and maintenance during long-term starvation-survival of bacteria in well water

Strains of enteric bacteria and pseudomonads containing plasmid R388::Tnl721 (Tpr, Tcr) or pRO101 (Hgr, Tcr) were starved for over 250 days in sterile well water to evaluate effects of starvation-survival on plasmid expression and maintenance. Viable populations dropped to between approximately 0.1 and 1% of the initial populations. Escherichia coli(pRO101) and Pseudomonas cepacia(pRO101) lost both viability and plasmid expression at a lower rate than strains containing R388::Tnl721. Three patterns of host-plasmid interaction were detected: (i) no apparent loss of plasmid expression, (ii) loss of plasmid expression on initial recovery with subsequent expression upon resuscitation, and (iii) loss of capability to produce functional plasmid resistance.