Internal dissection

Studies of the stereochemical course of rmcleophilic substitution reactions are a powerful tool for investigation of the mechanisms of these reactions. Bimolecular direct displacement reactions by the limSj.j2 meohanism are expected to result in 100% inversion of configuration. The stereochemical outcome of the lirnSj l ionization mechanism is less predictable because it depends on whether reaction occurs via one of the ion-pair intermediates or through a completely dissociated ion. Borderline mechanisms may also show variable stereochemistry, depending upon the lifetime of the intermediates and the extent of internal return. It is important to dissect the overall stereochemical outcome into the various steps of such reactions. 

Dissection of the internal carotid and vertebral arteries is a common cause of stroke, particularly in young patients. Although many occur due to trauma, it is estimated that over half occur spontaneously. The mechanism of stroke following arterial dissection is either by artery-to-artery embolism, by thrombosis in situ, or by dissection-induced lumenal stenosis with secondary cerebral hypoperfusion and low-flow watershed infarction. Occasionally, dissection may lead to the formation of a pseudoaneurysm as a source of thrombus formation. Vertebrobasilar dissections that extend intracranially have a higher risk of rupture leading to subarachnoid hemorrhage (SAH). ° ... 

Lucas C, Moulin T, Deplanque D, Tatu L, Chavot D. Stroke patterns of internal carotid artery dissection in 40 patients. Stroke 1998 29 2646-2648. 

Engelter S, Lyrer P, Kirsch E, Steck AJ. Long-term follow-up after extracranial internal carotid artery dissection. Eur Neurol 2000 44 199-204. 

Pestova, T. V., Shatsky, I. N., and Hellen, C. U. (1996b). Functional dissection of eukaryotic initiation factor 4F The 4 A subunit and the central domain of the 4G subunit are sufficient to mediate internal entry of 43S preinitiation complexes. Mol. Cell Biol. 16, 6870-6878. 

Absolute contraindications to fibrinolytic therapy include (1) active internal bleeding (2) previous ICH at anytime (3) ischemic stroke within 3 months (4) known intracranial neoplasm (5) known structural vascular lesion (6) suspected aortic dissection and (7) significant closed head or facial trauma within 3 months. Primary PCI is preferred in these situations. 

All frequencies in cm HF/6-31G(d,p) calculations. Each normal mode is dissected into internal parameter associated vibrations according to Reference 162. Compare with Figure 20. 

Chemical carcass analysis is considered the gold standard for accurate whole body composition analysis (13). It is, however, terminal and time consuming. The adiposity index can also be measured by dissecting and weighing of fat depots in individual animals (14). This method is also terminal and less accurate. The collection of visceral fat required can be particularly challenging as it is often spread throughout internal organs. 

Spontaneous dissection of the internal carotid or the vertebral artery is an important cause of ischemic stroke in young adults (Fig. 1.3). In the late 1970s Fisher et al. (1978) and Mokri et al. (1979) described dissections of carotid and vertebral arteries as detected by modern diagnostic techniques rather than by post-mortem examination. This may occur... 

Mokri B, Sundt TM Jr, Houser OW (1979) Spontaneous internal carotid dissection, hemicrania, and Horner s syndrome. Arch Neurol 36 677-680... 

Mokri B, Silbert PL, Schievink WI et al (1996) Cranial nerve palsy in spontaneous dissection of the extracranial internal carotid artery. Neurology 46 356-359 Molina CA, Montaner J, Abilleira S et al (2001) Timing of Spontaneous Recanalization and Risk of Hemorrhagic Transformation in Acute Cardioembolic Stroke. Stroke 32 1079-1084 Molina CA, Alvarez-Sabin J, Montaner J et al (2002) Thrombolysis-related hemorrhagic infarction a marker of early reperfusion, reduced infarct size, and improved outcome in patients with proximal middle cerebral artery occlusion. Stroke 33 1551-1556... 

Guillon B, Levy C, Bousser MG (1998) Internal carotid artery dissection an update. J Neurol Sci 153 146-158 Hacke W, Brott T, Caplan L et al. (1999) Thrombolysis in acute ischemic stroke controlled trials and clinical experience. Neurology 53 S3-14... 

MCA infarcts are mainly caused by cardioembolism, internal carotid artery (ICA) thrombosis, dissection or embolism and rarely (in Caucasians) by intrinsic MCA disease. MCA atherothrombotic territory infarctions related to intrinsic MCA disease often cause concomitant small cortical (territorial or borderzone) and subcortical infarcts (Min et al. 2000). 

Gass A, Gaa J, Schwartz A (1997) Cerebral infarction due to internal carotid artery dissection. J Neurol Neurosurg Psychiatry 63 420... 

Because of the increased internal pressure ( Hydroskelett ), dissected mawworms emit malodorous compounds, which are present in both perienteric fluid and tissues of these nematodes. During dissection, these volatiles may evoke pruritus, inflammation of the eye, and vomiting in humans. In Ascaris lumbricoides, and also in other species such as Parascaris equorum, formic, acetic, propionic, -butyric, 2-methylbutanoic, and caproic acids (C5- and C6-acids main compounds) were found along with unidentified C5-a,/3 unsaturated acids.53 These acids are probably derived from mawworm metabolism and are not formed by microbial activity. 

Eagle KA, Isselbacher EM, DeSanctis RW International Registry for Aortic Dissection (IRAD) Investigators. Cocaine related aortic dissection in perspective. Circulation 2002 105 1529-30. 

The presence of cranial neuropathy may result in a misdiagnosis of brainstem stroke. Cranial nerve palsies may result from local pressure from the false internal carotid artery lumen, thromboembolism or hemodynamic compromise to the blood supply of the nerve. Cranial nerve III receives its blood supply from the ophthalmic artery, branches of the internal carotid or the posterior cerebral artery and, consequently, may rarely become ischemic after carotid dissection. 

The incidence of diagnosed internal carotid artery dissection is approximately 1-4 per 100000 per year. Vertebral dissection is a little less common. The actual incidence of dissections is likely to be considerably higher, but the diagnosis is often missed, particularly in older patients. Usually only one artery is involved but in about 10%, multiple arteries... 

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