Lacunarity

The modern period in the history of stroke began in the 1960s when C. Miller Fisher described detailed clinical and pathological observations on the features of lacunar strokes, carotid artery disease, transient ischemic attacks, and intracerebral hemorrhage. His student Louis Caplan established one of the first stroke registry... 

The reasons for the observed differences in mortality between aspirin-treated patients in 1ST and CAST are unclear. The findings may relate to baseline differences between the treated groups. CAST had a younger age profile (72% under 70 compared to 38% in 1ST), excluded some patients with severe stroke, and likely included more subjects with lacunar stroke, an etiology associated with lower mortality and less disability. 

Lacunar stroke is characterized by occlusion of a small penetrating artery creating a small deep infarct. Lacunar strokes have the lowest early recurrence risk and best survival rates, but may still cause significant functional morbidity. Although subgroup analyses are available from secondary prevention trials in lacunar stroke, few clinical trial data are available regarding nonthrombolytic antithrombotic therapy for lacunar stroke in the acute setting. 

Cardioembolic strokes may also have poor outcome, especially with large emboli as in AF. In the Rochester population, patients with cardioembolic stroke were the most impaired during the hospitalization only 14% were independent as compared to 38% with lacunar stroke, 24% with atherosclerotic stroke, and 27% with ischemic stroke of unknown cause. " The latter group probably included patients with emboli of unknown origin. As evidence of the proportion of patients with devastating strokes, patients classified as cardioembolic subtype were also least likely to be independent at 1 year (27%). 

Small vessel/lacunar strokes have better short- and long-term (1-year) survival as compared to other stroke subtypes. In the NINDS trial of rt-PA within 3 hours of onset, patients classified as small vessel stroke on the basis of their clinical syndrome had a 50% chance of a normal NIHSS score at 3 months if they received placebo, increasing to 70% in the treatment group. In the Lausanne cohort, 95% were independent after their first event, as opposed to only 65% of the cardioembolic strokes and 49% with large vessel atherothrombotic infarctions. Eighty-two percent of patients with small vessel stroke were independent at 1 year. Even at the time of maximal deficit, between 38% and 64% of small vessel/lacunar patients were independent, with motor impairment and extent of white matter disease adversely affecting outcomes. " In TOAST, small vessel/lacunar stroke was the only subtype associated with a favorable outcome, independent of the NIHSS score. ... 

It may be especially difficult to confidently establish the diagnosis of the most benign subtype of stroke, small vessel/lacunar stroke, accounting for 10-29% of all... 

Cardioembolism Cardioembolism accounts for approximately 30% of all stroke and 25-30% of strokes in the young (age <45 years)." AF accounts for a large proportion of these strokes (15-25%). Symptoms may be suggestive, but they are not diagnostic. Repetitive, stereotyped, transient ischemic attacks (TIAs) are unusual in embolic stroke. The classic presentation for cardioembolism is the sudden onset of maximal symptoms. The size of the embolic material determines, in part, the course of the embolic material. Small emboli can cause retinal ischemic or lacunar symptoms. Posterior cerebral artery territory infarcts, in particular, are often due to cardiac embolism. This predilection is not completely consistent across the various cardiac structural abnormalities that predispose to stroke, and may be due to patterns of blood flow associated with specific cardiac pathologies. 

Nadeau SE, Jordan JE, Mishra SK, Haerer AE. Stroke rates in patients with lacunar and large vessel cerebral infarction. J Neurol Sci 1993 114 128-137. 

Sacco SE, Whisnant JP, Broderick JP, Phillips SJ, O Eallon WM. Epidemiological characteristics of lacunar infarcts on a population. Stroke 1991 22(10) 1236-1241. 

Salgado AV, Eerro J M, Gouveia-Oliveira A. Long-term prognosis of first-ever lacunar strokes a hospital-based study. Stroke 1996 27(4) 661-666. 

Clavier I, Hommel M, Besson G, Noelle B, Perret JE. Long-term prognosis of symptomatic lacunar infarcts a hospital-based study. Stroke 1994 25 2005-2009. 

Lodder J, Boiten J. Incidence, natural history, and risk factors in lacunar infarction. Adv Neurol 1993 62 213-227. 

Toni D, Del Duca R, FiorelU M, Sacchetti ML, Bastianello S, Giubilei F, Martinazzo C, Argentino C. Pure motor hemiparesis and sensorimotor stroke accuracy of very early clinical diagnosis of lacunar strokes. Stroke 1994 25(l) 92-96. 

Gan R, Sacco RL, Kargman DE, Roberts JK, Boden-Albala B, Gu Q. Testing the validity of the lacunar h3fpothesis the Northern Manhattan Stroke Study experience. Neurology 1997 48 1204-1211. 

The penis consists of three components, two dorsolateral corpora cavernosa and a ventral corpus spongiosum that surrounds the penile urethra and distally forms the glans penis. The corpora cavernosa consist of blood-filled sinusoidal or lacunar spaces, which are lined with endothelial cells, supported by trabecular smooth muscle, and surrounded by a thick fibrous sheath called the tunica albuginea. The caver-nosal arteries, which are branches of the penile artery, penetrate the tunica albuginea and supply blood flow to the penis. 

Daturi, M., Bion, N., Saussey, J. et al. (2001) Evidences of a lacunar mechanism for deNO, activity in ceria-based catalysts, Phys. Chem. Chem. Phys., 3, 252. 

A number of model studies of the second type have also been investigated. In these, the iron complex provides a hydrophobic cavity so positioned that it surrounds the bound 02 molecule. These include the lacunar complexes mentioned in Chapter 3 (Goldsby, Beato Busch, 1986) particular complexes of which are quite efficient reversible carriers. A further (early) example of this type was (312) which encloses the dioxygen in a rudimentary cavity. However, this species only binds dioxygen reversibly at low temperatures (Baldwin Huff, 1973). 

Detailed kinetic studies of the reaction of Fe(II) in cyclophane hemes with 02 and with CO probed polarity and steric effects the effects of deformation of the porphyrin skeleton from planarity were assessed for one compound (121). Volume profiles have been established for reactions of a lacunar Fe(II) complex with CO (122 for myoglobin with 02 and with CO and for hemerythrin with 02 (123). 

In another study the binding of CO to lacunar Fe(II) complexes was studied in detail as a function of temperature and pressure (112, 113). In these systems the high-spin Fe(II) center is five coordinate and has a vacant pocket available for the binding of CO. These systems can... 

Lacunarity Analysis of TEM Images of Heat-Treated Hybrid Organosiliea Materials... 

This calculation is repeated over a range of box sizes, and a double - logarithmic plot of the lacunarity versns the size of the shding box is then produced. FracLac then outputs a text file containing the valnes of r and A for each image. 

When the samples were visnally inspected. Samples C and D are more clumped together as compared to Samples A and B. As seen in Fig. 47.5, the lacunarity for Samples C and D are relatively higher compared to the lacnnarity for Samples A and B. Also, the pores in Samples C and D are also more coimected than those of Samples A and B Samples C and D have more clnmping than Samples A and B. These observations correlated with the plotted lacnnarities. 

The same trend ean be seen when comparing Samples B and D, which have the same amonnt of snrfactant bnt treated differently (Sample B was heat - treated while Sample D was not). Evidently, the lacunarity is decreased by heat treatment. This indicates that, with heat treatment, the material becomes more homogeneous, and the holes tend to become evenly distributed throughout the material. 

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