On the subtle tuneability of cellulose hydrogels: implications for binding of biomolecules demonstrated for CBM 1

Choice of molecular probe for determining porosity, surface area, or binding in never-dried cellulose hydrogels is critical to discern differences in structure.

Aminopiperidine based complexes for lactide polymerisation

A series of new ligands based on a 2-(aminomethyl)piperidine motif have been prepared. An interesting diversity in structure is observed, all complexes have been trialled for the polymerisation of rac-lactide.

MRS reveals additional hexose N-acetyl resonances in the brain of a mouse model for Sandhoff disease

Sandhoff disease, one of several related lysosomal storage disorders, results from the build up of N-acetyl-containing glycosphingolipids in the brain and is caused by mutations in the genes encoding the hexosaminidase beta-subunit. Affected individuals undergo progressive neurodegeneration in response to the glycosphingolipid storage. (1)H magnetic resonance spectra of perchloric acid extracts of Sandhoff mouse brain exhibited several resonances ca 2.07 ppm that were not present in the corresponding spectra from extracts of wild-type mouse brain. High-performance liquid chromatography and mass spectrometry of the Sandhoff extracts post-MRS identified the presence of N-acetylhexosamine-containing oligosaccharides, which are the likely cause of the additional MRS resonances. MRS of intact brain tissue with magic angle spinning also showed additional resonances at ca 2.07 ppm in the Sandhoff case. These resonances appeared to increase with disease progression and probably arise, for the most part, from the stored glycosphingolipids, which are absent in the aqueous extracts. Hence in vivo MRS may be a useful tool for detecting early-stage Sandhoff disease and response to treatment.

Detection of the inhibitory neurotransmitter GABA in macrophages by magnetic resonance spectroscopy

Macrophages are key components of the inflammatory response to tissue injury, but their activities can exacerbate neuropathology. High-resolution magnetic resonance spectroscopy was used to identify metabolite levels in perchloric acid extracts of cultured cells of the RAW 264.7 murine macrophage line under resting and lipopolysaccharide-activated conditions. Over 25 metabolites were identified including gamma-aminobutyric acid (GABA), an inhibitory neurotransmitter not previously reported to be present in macrophages. The presence of GABA was also demonstrated in extracts of human peripheral blood monocyte-derived macrophages. This finding suggests that there may be communication between damaged central nervous system (CNS) tissue and recruited macrophages and resident microglia, which could help orchestrate the immune response. On activation, lactate, glutamine, glutamate, and taurine levels were elevated significantly, and GABA and alanine were reduced significantly. Strong resonances from glutathione, evident in the macrophage two-dimensional 1H spectrum, suggest that this may have potential as a noninvasive marker of macrophages recruited to the CNS, as it is only present at low levels in normal brain. Alternatively, a specific combination of spectroscopic changes, such as lactate, alanine, glutathione, and polyamines, may prove to be the most accurate means of detecting macrophage recruitment to the CNS.

Critical incident stress intervention after loss of an air ambulance: two-year follow up

OBJECTIVE

Following an air ambulance crash with five fatalities, critical incident stress debriefing (CISD) was provided for involved paramedics, physicians, and nurses. A study was conducted to evaluate the long-term effects of a critical incident with critical incident stress debriefing according to the Mitchell model.

METHODS

Six months following the incident, empirically designed questionnaires were mailed to all transport paramedics and directly involved medical staff, and a random sample of both nurses from the dispatch/receiving institution and paramedics from around the province. Twenty-four months post-incident, all members of the transport paramedics completed the Impact of Events Scale and the General Health Questionnaires.

RESULTS

There were no differences between groups on any scores, except for disturbed sleep patterns, bad dreams, and the need for personal counseling being greater among transport paramedics at one day. There was no correlation between how well the deceased individuals were known, amount of debriefing, and symptom severity. A trend was seen for those with pre-existing stress management routines to have less severe symptoms at six months (p = 0.07). At two years, 16% of transport paramedics still had significant abnormal behavior.

CONCLUSIONS

CISD did not appear to affect the severity of stress symptoms, whereas having pre-existing stress management strategies may. These findings give justification for proceeding to a randomized, controlled trial of different levels of critical incident stress intervention.

Calculated reactivities of potentially carcinogenic intermediates of the cyclopenta-fused isomers of benz[a]anthracene

Delocalization energies have been calculated for carbocations formed from several epoxide intermediates of the cyclopenta-fused isomers of benz[a]anthracene. Except for the epoxides of benz[l]aceanthrylene, the largest calculated delocalization energies associated with the other benzaceanthrylenes result from ring-opening of the epoxide on the cyclopenta-ring yielding an alpha' type carbocation. Benz[l]aceanthrylene exhibits special behavior resulting from steric crowding in the bay-region of the molecule. For this molecule the calculated ease of epoxide ring opening is essentially the same for the bay-region epoxide and for the epoxide on the five-membered ring. Relative values of delocalization energy should provide an important index for ranking the reactivity of metabolites of the benzaceanthrylenes and benzacephenanthrylene that are potentially involved in the initiation of mutagenesis/carcinogenesis.

Benzofluoranthenes: calculated diol epoxide reactivities

The benzo- and dibenzofluoranthenes, widespread environmental contaminants, have been subjects of continued interest. Calculations of the reactivity of potential ultimate carcinogenic metabolites of the benzofluoranthenes predict unexpected behavior for these non-alternant hydrocarbons.

Heteroatom effects in chemical carcinogenesis: effects of ring heteroatoms on ease of carbocation formation

The presence of a heteroatom can influence the ease with which a PAH diol-epoxide forms a triol carbocation. The influence of the heteroatom should be greatest when it is located where the PAH undergoes maximum charge change upon ionization. Extended Hückel, INDO and Gaussian 70 calculations on nitrogen substituted benz[a]anthracene verify this reasoning. The sites of maximum effect are easily predicted using a simple Hückel method which does not require use of a computer. The greater carcinogenic activity of methylated benz[c]acridines over benz[a]acridines is an immediate result of these considerations. Methylated benzo[c]phenarsazines are implicated as likely carcinogens.

The Barrier to Internal Rotation in Ethane

The internal rotation barrier in ethane appears susceptible to "explanation" at a qualitative, intuitively useful, reasonably correct level. At this level, localized and delocalized MO's each produce a description. For a rigid rotation, the delocalized description is basically the "orbital control" type familiar from Woodward-Hoffmann rules (30), Walsh's rules (31), and the formation of diatomic molecules (32). This description indicates that long-range eclipsed H---H antibonding is responsible for the barrier. The equivalent localized-bond description invokes destructive interference or repulsion between eclipsed C-H bonds. The extension of this kind of description to other molecules requires care. Subsequent to rigid rotation, the relaxation of ethane into its optimum eclipsed geometry produces almost no energy change but produces an unknown degree of energy "redistribution." I have emphasized that the theoretical distinction between "orbital control" and "steric interaction" is not precise and that a clarification in terminology may be desirable in this connection. The discussion of barriers given here applies only to a limited class of molecules, exemplified by ethane. No doubt, additional factors enter into a proper description of barriers in molecules having lower symmetry or more polar bonds, or both (33). Finally, I should point out that approaches other than those in categories 1 to 3 have been made in efforts to rationalize or predict barriers to internal rotation (34). The Hellmann-Feynman theorem has been applied to find the torque on ethane at conformations between staggered and eclipsed (35). The integral Hellmann-Feynman theorem has served as a basis for discussing barriers in terms of transition densities (36) and has led to an electrostatic model for barriers which has given some remarkably successful barrier predictions (37). These approaches are mathematically valid, and it is perfectly legitimate to try to extract physical explanations from them also. Thus, several valid explanations for the barrier to internal rotation in ethane are possible. However, I feel that the explanations proposed above in terms of delocalized or localized orbitals are preferable at present inasmuch as they are couched in terms and concepts currently in the mainstream of chemical thinking.

The cardiovascular complications of intravenous regional anaesthesia

In view of the uncertainty over the safety of intravenous regional anaesthesia the heart-rate, blood-pressure, and electrocardiogram were recorded seriany in 100 Bantu gold-miners in whom this form of anaesthesia was used for minor surgical procedures on the extremities. Changes in blood-pressure were infrequent and mild. In 31 patients the heart slowed by more than 10 beats per minute after release of the tourniquet, falling to less than 60 beats per minute in 27. One patient with sinus bradycardia developed sino-atrial block with cardiac standstill of short duration, a second developed an intermittent idioatrial tachycardia and premature atrial beats, and in 3 others sinus bradycardia was complicated by atrial escape beats, nodal rhythm, and premature ventricular beats respectively. These toxic effects were thought to be due either to direct myocardial depression or to increased vagal or decreased sympathetic tone, or to both of these mechanis. It is suggested that the cardiovascular depression caused by large doses of lignocaine may be aggravated by coexisting ischaemic heart disease. The importance of monitoring the patients carefully after release of the tourniquet and having facilities available for resuscitation is stressed.