Hexamerization and thermostability emerged very early during geranylgeranylglyceryl phosphate synthase evolution

A large number of archaea live in hyperthermophilic environments. In consequence, their proteins need to adopt to these harsh conditions, including the enzymes that catalyze the synthesis of their membrane ether lipids. The enzyme that catalyzes the formation of the first ether bond in these lipids, geranylgeranylglyceryl phosphate synthase (GGGPS), exists as a hexamer in many hyperthermophilic archaea, and a recent study suggested that hexamerization serves for a fine‐tuning of the flexibility – stability trade‐off under hyperthermophilic conditions. We have recently reconstructed the sequences of ancestral group II GGGPS enzymes and now present a detailed biochemical characterization of nine of these predecessors, which allowed us to trace back the evolution of hexameric GGGPS and to draw conclusions about the properties of extant GGGPS branches that were not accessible to experiments up to now. Almost all ancestral GGGPS proteins formed hexamers, which demonstrates that hexamerization is even more widespread among the GGGPS family than previously assumed. Furthermore, all experimentally studied ancestral proteins showed high thermostability. Our results indicate that the hexameric oligomerization state and thermostability were present very early during the evolution of group II GGGPS, while the fine tuning of the flexibility – stability trade‐off developed very late, independent of the emergence of hexamerization.     

Effects of Nigella sativa on apoptosis and GABAA receptor density in cerebral cortical and hippocampal neurons in pentylenetetrazol induced kindling in rats

We investigated the effects of Nigella sativa on apoptosis and gamma-aminobutyric acid (GABA_A) receptor density in cerebral cortical and hippocampal neurons in a pentylenetetrazol (PTZ)-induced kindling model in rats. The PTZ kindling model was produced by injecting PTZ in subconvulsive doses to rats on days 1, 3, 5, 8, 10, 12, 15, 17, 19, 22 and 24 of the study into animals of PTZ treated (PTZ) and PTZ + N. sativa treated (PTZ + NS) groups. Clonic and tonic seizures were induced by injecting a convulsive dose of PTZ on day 26 of the study. Rats in the PTZ + NS group were treated also with a 10 mg/kg methanolic extract of N. sativa 2 h before each PTZ injection. Rats in the control group were treated with 4 ml/kg saline. The number of neurons that expressed GABA_A receptors in the hippocampus and cerebral cortex of rats in the PTZ and PTZ + NS groups increased significantly. There was no significant difference in the number of GABA_A receptors between the PTZ and PTZ + NS groups. GABA_A receptor density of the neurons in the cerebral cortex, but not hippocampus, was increased in PTZ group compared to controls. We observed a significant increase in the number of apoptotic neurons in the cerebral cortex of rats of both the PTZ and PTZ + NS groups compared to controls. We observed a significant decrease in the number of the apoptotic neurons in the cerebral cortex of rats in the PTZ + NS group compared to the PTZ group. N. sativa treatment ameliorated the PTZ induced neurodegeneration in the cerebral cortex as reflected by neuronal apoptosis and neuronal GABA_A receptor frequency.     

Detrimental effects of albuterol on airway responsiveness requires airway inflammation and is independent of β-receptor affinity in murine models of asthma

Background

Inhaled short acting β2-agonists (SABA), e.g. albuterol, are used for quick reversal of bronchoconstriction in asthmatics. While SABA are not recommended for maintenance therapy, it is not uncommon to find patients who frequently use SABA over a long period of time and there is a suspicion that long term exposure to SABA could be detrimental to lung function. To test this hypothesis we studied the effect of long-term inhaled albuterol stereoisomers on immediate allergic response (IAR) and airway hyperresponsiveness (AHR) in mouse models of asthma.

Methods

Balb/C mice were sensitized and challenged with ovalbumin (OVA) and then we studied the IAR to inhaled allergen and the AHR to inhaled methacholine. The mice were pretreated with nebulizations of either racemic (RS)-albuterol or the single isomers (S)- and (R)-albuterol twice daily over 7 days prior to harvest.

Results

We found that all forms of albuterol produced a significant increase of IAR measured as respiratory elastance. Similarly, we found that AHR was elevated by albuterol. At the same time a mouse strain that is intrinsically hyperresponsive (A/J mouse) was not affected by the albuterol isomers nor was AHR induced by epithelial disruption with Poly-L-lysine affected by albuterol.

Conclusions

We conclude that long term inhalation treatment with either isomer of albuterol is capable of precipitating IAR and AHR in allergically inflamed airways but not in intrinsically hyperresponsive mice or immunologically naïve mice. Because (S)-albuterol, which lacks affinity for the β2-receptor, did not differ from (R)-albuterol, we speculate that isomer-independent properties of the albuterol molecule, other than β2-agonism, are responsible for the effect on AHR.     

Wound botulism: a life-threatening complication of hand injuries

Botulism is usually associated with the ingestion of food contaminated with Clostridium botulinum, and these organisms occasionally contaminate traumatic injuries. It is unusual for them to result in clinical infection, but when this occurs, it is a catastrophe completely out of proportion to the degree of wound injury. A case is presented in which typical manifestations of descending cranial nerve and generalized motor paralysis were noted. Prolonged respiratory and general supportive assistance was required, as is usually the case. Although mortality rates in this disease are high, recovery is usually complete in survivors and was true in this instance.