Abstract T P400: Subarachnoid Hemorrhage-Induced Reactive Astrogliosis Is Correlated With Inversion of Neurovascular Coupling

Poor patient outcome following aneurysmal subarachnoid hemorrhage (SAH) has been linked to delayed cerebral ischemia (DCI), presenting several days following aneurysm rupture. Enhanced constriction of the brain vasculature, including intracerebral (parenchymal) arterioles contribute to SAH-induced DCI. Activity-dependent blood flow through parenchymal arterioles is controlled by local neuronal and astrocytic activity, a process known as neurovascular coupling. In response to numerous types of brain insults (e.g. tumors, trauma, and strokes), astrocytes undergo a transformation to a reactive phenotype, reactive astrogliosis, characterized by hypertrophy and hyperplasia. Here, we examined the hypothesis that SAH-induced reactive gliosis of perivascular astrocytes contribute to enhanced parenchymal arteriolar constriction. Astrocyte and vascular changes were assessed in a mouse endovascular perforation SAH model. Glial fibrillary acidic protein (GFAP), an astrocyte-specific intermediate filament that is upregulated during reactive astrogliosis, was assessed by immunohistochemistry in brain cortex of the middle cerebral artery territory. We observed increased GFAP staining at Day 2 and Day 4 following induction of SAH when compared to brain sections from control and sham-operated animals (all p values <.05). In separate animals, neurovascular coupling was examined using two-photon and infrared-differential interference contrast microscopy. In brain slices from control and sham-operated animals, neuronal activation caused the anticipated neurovascular response-an increase in astrocyte endfoot Ca2+ followed by parenchymal arteriole dilation. In marked contrast, brain slices from SAH animals exhibited an inverted neurovascular response (i.e. vasoconstriction rather than vasodilation) in ≈ 80% of brain slices from day 1 and day 2 SAH mice and ≈ 60% of slices from SAH day 4 mice. In conclusion, we demonstrate changes in astrocyte structure, the development of reactive astrogliosis, correlate to a polarity shift in neurovascular coupling after SAH. These data indicates that SAH-induced reactive astrogliosis may play an important role in DCI development.

Cerebral vasospasm following subarachnoid hemorrhage: time for a new world of thought

OBJECTIVE

Delayed cerebral vasospasm has long been recognized as an important cause of poor outcome after an otherwise successful treatment of a ruptured intracranial aneurysm, but it remains a pathophysiological enigma despite intensive research for more than half a century.

METHOD

Summarized in this review are highlights of research from North America, Europe and Asia reflecting recent advances in the understanding of delayed ischemic deficit.

RESULT

It will focus on current accepted mechanisms and on new frontiers in vasospasm research.

CONCLUSION

A key issue is the recognition of events other than arterial narrowing such as early brain injury and cortical spreading depression and of their contribution to overall mortality and morbidity.

Applying principles of pharmacoeconomic evaluation to perflenapent emulsion, a new echocardiographic contrast agent for use in cardiac function testing

A pharmacoeconomic evaluation was performed to determine the cost-effectiveness of perflenapent emulsion, a new contrast agent for use in echocardiography. A decision tree analysis was performed on data from the charts of 108 patients who had undergone stress echocardiography without contrast enhancement as part of a cardiac function or wall-motion study. An analysis of a theoretical cohort of patients was conducted to determine shifts in cost associated with enhancement of stress echocardiography with perflenapent emulsion. Outcome was determined by the point at which the clinician was able to determine a treatment course for the patient based on the diagnostic information given. Stress echocardiography without contrast was identified as the most cost-effective path in terms of a conclusive test. Perflenapent emulsion shows a positive cost impact in patients who have had an inconclusive stress echocardiogram without the use of a contrast agent. These results are supported by a sensitivity analysis across a wide range of pricing for perflenapent emulsion, a wide range of cost for a stress echocardiogram, and up to 99% efficacy of contrast-enhanced stress echocardiography.

A novel comprehensive DUE program--five years of experience

A comprehensive program has been developed to evaluate prescribing practices in diverse drug therapy categories and in all areas of the institution. Input for topic selection comes not only from the pharmacy department, but also from QA, medical staff, and nursing. The development of monitoring criteria and review of the results by the P&T Committee, Medical Executive Committee, and other key medical staff members, promotes ownership of the program by the medical staff. The benefit of this ownership is active support for the program and participation in peer review. Overall, the results of this cost-effective program include limited use of broad spectrum antibiotics, select prescribing of high-risk drugs, and focused educational efforts to improve quality of patient care. The primary goal for the future of the program is to develop criteria and documentation mechanisms for reporting measurable clinical outcomes. In making the transition, it is important to use the success and impact of the current program as the foundation. This is particularly true for the concurrent monitoring program and its immediate feedback mechanism. The major challenge will be evaluating negative clinical outcomes and developing corrective actions as well as documenting the positive outcomes and the avoidance of negative outcomes of the current program. To meet this challenge, the DUE program must be integrated with all other institutional QA programs. Although a difficult task, this is a significant yet necessary step in the right direction for assuring optimal patient care.

The aminoglycoside antibiotics.IV. Synthesis of aminodeoxy analogs of neamine

An efficient synthesis of the key 3',4'-galacto epoxide intermediate 4 obtained from the known 5,6-O,O'-cyclohexylidene-N,N'-bis-(methoxycarbonyl)-4-O-[2,6-bis(methoxycarbony lamino)-alpha-D-glucopyranosyl]-2-deoxystreptamine (5) is described. Treatment of this epoxide with sodium azide, followed by reduction and acetylation, yielded the protected4'-amino-4'-deoxyneamine 18 (3',4'-diequatorial), whereas treatment with ammonia followed by acetylation yielded the protected 3'-amino-3'-deoxyneamine analog 19 with a diaxial configuration of its 3' and 4' positions. Reaction of the previously described protected 3',4'-allo epoxide 3 with sodium azide yielded separable mixtures of the protected 3'-amino-3'-deoxyneamine 14 and the protected diaxial 4'-amino-4'-deoxyneamine isomer 13, the ratios of products depending on the solvent temperature. Structural assignments for 13, 14, 18 and 19 were based on their PMR spectra. An additional 4'-amino-4'-deoxyneamine analog (24) with an axial configuration as its 4' position was also prepared by azide displacement of an approximately protected 4'-methanesulfonyl neamine intermediate 10. The five protected isomers were deblocked to yield a series of aminodeoxyneamine analogs (15, 16, 20, 21 and 25), all of which were less active in vitro than neamine against a group of Gram-positive and Gram-negative bacteria.