Scenarios for modeling solar radiation modification.

Making informed future decisions about solar radiation modification (SRM; also known as solar geoengineering)-approaches such as stratospheric aerosol injection (SAI) that would cool the climate by reflecting sunlight-requires projections of the climate response and associated human and ecosystem impacts. These projections, in turn, will rely on simulations with global climate models. As with climate-change projections, these simulations need to adequately span a range of possible futures, describing different choices, such as start date and temperature target, as well as risks, such as termination or interruptions. SRM modeling simulations to date typically consider only a single scenario, often with some unrealistic or arbitrarily chosen elements (such as starting deployment in 2020), and have often been chosen based on scientific rather than policy-relevant considerations (e.g., choosing quite substantial cooling specifically to achieve a bigger response). This limits the ability to compare risks both between SRM and non-SRM scenarios and between different SRM scenarios. To address this gap, we begin by outlining some general considerations on scenario design for SRM. We then describe a specific set of scenarios to capture a range of possible policy choices and uncertainties and present corresponding SAI simulations intended for broad community use.

Endovascular Repair of Ruptured Popliteal Artery Aneurysms: A Case Report and Review of the Literature.

OBJECTIVE/BACKGROUND: The objectives were to report the management and outcomes of a 96-year-old man who presented with an acutely swollen right leg due to a ruptured popliteal aneurysm, and to review the relevant literature. METHODS: A ruptured popliteal artery aneurysm is a rare diagnosis and is one that is often missed at time of presentation. Previous case reports have documented successful outcomes following surgical repair, and a smaller number following endovascular repair. This is a case report of a 96-year-old man who eventually underwent endovascular repair of a ruptured popliteal artery aneurysm after a delay in diagnosis. A literature review was performed to analyse published data in this field. RESULTS: The patient underwent an uncomplicated endovascular repair with a GORE® VIABAHN® stent. A 15-week follow-up ultrasound demonstrated biphasic flow in a patent stent-graft with an unchanged aneurysm sac size and no evidence of an endoleak. A review of the literature demonstrated nine cases of ruptured non-mycotic popliteal artery aneurysms treated endovascularly. Seven cases survived the postoperative period, three had no follow-up recorded, and four cases had patent stent-grafts at time of follow-up. CONCLUSION: Safe and effective endovascular repair of a ruptured popliteal artery aneurysm with endograft patency seen at the 15-week follow-up is reported. Review of the literature suggests that open repair remains the first-line management choice; however, endovascular repair is a valuable alternative. There is a further need for longer-term monitoring of endograft patency following endovascular repair.

Bupivacaine inhibits baroreflex control of heart rate in conscious rats.

BACKGROUND: Because exposure to intravenously administered bupivacaine may alter cardiovascular reflexes, the authors examined bupivacaine actions on baroreflex control of heart rate in conscious rats. METHODS: Baroreflex sensitivity (pulse interval vs. systolic blood pressure in ms/mmHg) was determined before, and 1.5 and 15.0 min after rapid intravenous administration of bupivacaine (0.5, 1.0, and 2.0 mg/kg) using heart rate changes evoked by intravenously administered phenylephrine or nitroprusside. The actions on the sympathetic and parasympathetic autonomic divisions of the baroreflex were tested in the presence of a muscarinic antagonist methyl atropine and a beta-adrenergic antagonist atenolol. RESULTS: Within seconds of injection of bupivacaine, mean arterial pressure increased and heart rate decreased in a dose-dependent manner. Baroreflex sensitivity was unaltered after administration of 0.5 mg/kg bupivacaine. In addition, 1 mg/kg bupivacaine at 1.5 min depressed phenylephrine-evoked reflex bradycardia (0.776 +/- 0.325 vs. 0.543 +/- 0.282 ms/mmHg, P < 0.05) but had no effect on nitroprusside-induced tachycardia. Bupivacaine (2 mg/kg), however, depressed reflex bradycardia and tachycardia (phenylephrine, 0.751 +/- 0.318 vs. 0.451 +/- 0.265; nitroprusside, 0.839 +/- 0.256 vs. 0.564 +/- 0.19 ms/mmHg, P < 0.05). Baroreflex sensitivity returned to prebupivacaine levels by 15 min. Bupivacaine (2 mg/kg), in the presence of atenolol, depressed baroreflex sensitivity (phenylephrine, 0.633 +/- 0.204 vs. 0.277 +/- 0.282; nitroprusside, 0.653 +/- 0.142 vs. 0.320 +/- 0.299 ms/mmHg, P < 0.05). In contrast, bupivacaine did not alter baroreflex sensitivity in the presence of methyl atropine. CONCLUSIONS: Bupivacaine, in clinically relevant concentrations, inhibits baroreflex control of heart rate in conscious rats. This inhibition appears to involve primarily vagal components of the baroreflex-heart rate pathways.

Differential regenerative growth of CNS axons into tibial and peroneal nerve grafts in the thalamus of adult rats.

Segments of peripheral nerve were autografted into the thalamus of adult rats. The peroneal nerve was used in one group, the tibial nerve (which has approximately twice the cross-sectional area of the peroneal nerve) in a second group, and two lengths of peroneal nerve side by side in a third group. Between 1 and 4 months later HRP was applied to the distal end of each graft to label neurons which had regenerated their axons into the graft. Serial coronal sections of each brain were reacted to reveal retrogradely transported HRP, and the positions of all labeled neurons were recorded in camera lucida drawings. In all three groups a few labeled neurons resembling thalamocortical projection cells were found in the dorsal thalamus close to the graft tip (mean number, 29 in the single peroneal group; 22 in the tibial group; and 14 in the double-peroneal group). However, neurons in the thalamic reticular nucleus (TRN) regenerated much more successfully into the larger nerve grafts; many more retrogradely labeled cells were found in animals with tibial or double-peroneal nerve grafts (mean number, 1.1 in the single-peroneal group; 272 in the tibial group; and 163 in the double-peroneal group). These neurons were concentrated in the sector of TRN known to project to the part of the dorsal thalamus containing the graft tip. The largest numbers of labeled neurons were found when the graft tip encroached upon the TRN. These results suggest that both graft size and graft position are critical determinants of the extent of axonal regeneration from the TRN. Larger grafts may be more copiously invaded by regenerating axons because such grafts damage larger numbers of TRN axons when implanted and/or because they stimulate regeneration by releasing critical quantities of neurotrophic factors.