Effects of Sterol-Like Additives on Phase Transition Behavior of Ion-Pair Amphiphile Bilayers.

The incorporation of additive in lipid bilayers is one of the ordinary approaches for modulating their properties. Additive effect on phase transition of ion-pair amphiphile (IPA) bilayers, however, is not known. In this work, four double-chained IPAs with different hydrocarbon chain lengths and symmetry were designed and synthesized from single-chained cationic and anionic surfactants by the precipitation method. By using differential scanning calorimetry (DSC), the thermotropic transition behavior from gel phase (Lß) through rippled phase (Pß') if any to liquid-crystalline phase (Lα) was studied for bilayers of these lipid-like IPAs in excess water. The effects of three sterol-like additives (cholesterol, α-tocopherol, and α-tocopheryl acetate) in IPA bilayers on thermal phase behavior were then systematically investigated. The experimental results revealed that with increasing concentration of additive, the phase transition temperatures were unaffected on the one hand and the enthalpies of phase transition were decreased on the other hand. When the addition of additive exceeded a specific amount, the phase transition disappeared. More hasty disappearance of phase transition was found for IPAs with lower total number of carbon atoms in the hydrocarbon chains. For IPAs with the same total number of carbon atoms in the hydrocarbon chains, the disappearance of phase transition is more hasty for the asymmetric one than for the symmetric one. Similar effects on thermal phase behavior of four IPA bilayers were exhibited by the three additives with similar chemical structures. Possible mechanism of additive effects on phase transition of IPA bilayers was then proposed in line with that of lipid bilayers.

Assessment of Anteroposterior Subpedicular Approach and Oblique Scotty Dog Subpedicular Approach for Selective Nerve Root Block

BACKGROUND: The technique used to administer a selective nerve root block (SNRB) varies depending on individual expertise. Both the anteroposterior (AP) subpedicular approach and oblique Scotty dog subpedicular approach are widely practiced. However, the literature does not provide a clear consensus regarding which approach is more suitable. Hence, we decided to analyse the procedural parameters and clinical outcomes following SNRBs using these two approaches. METHODS: Patients diagnosed with a single lumbar herniated intervertebral disc (HIVD) refractory to conservative management but not willing for immediate surgery were selected for a prospective nonrandomized comparative study. An SNRB was administered as a therapeutic alternative using the AP subpedicular approach in one group (n = 25; mean age, 45 ± 5.4 years) and the oblique Scotty dog subpedicular approach in the other group (n = 22; mean age, 43.8 ± 4.7 years). Results were compared in terms of the duration of the procedure, the number of C-arm exposures, accuracy, pain relief, functional outcome and the duration of relief. RESULTS: Our results suggest that the oblique Scotty dog subpedicular approach took a significantly longer duration (p = 0.02) and a greater number of C-arm exposures (p = 0.001). But, its accuracy of needle placement was 95.5% compared to only 72% using the AP subpedicular approach (p = 0.03). There was no significant difference in terms of clinical outcomes between these approaches. CONCLUSIONS: The AP subpedicular approach was simple and facile, but the oblique Scotty dog subpedicular approach was more accurate. However, a brief window period of pain relief was achieved irrespective of the approaching technique used.