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Ultrastructural observations on the transvascular route of protein removal in vasogenic brain edema
Insights
This study investigated micro-blood vessel changes in cat brains after cold injury, revealing blood-brain barrier permeability issues and edema spread. Findings highlight early microvascular alterations in brain edema following injury.
Area of Science:
- Neuroscience
- Pathology
- Vascular Biology
Background:
- Brain edema is a critical consequence of neurological injury.
- Understanding micro-blood vessel (MBV) dynamics is crucial for treating brain edema.
- The blood-brain barrier (BBB) integrity is often compromised in edematous brain tissue.
Purpose of the Study:
- To investigate the ultrastructural changes in cat brain micro-blood vessels during edema formation after cold injury.
- To assess blood-brain barrier permeability to horseradish peroxidase (HRP) at various time points post-injury.
- To evaluate the distribution of edema fluid and identify specific microvascular sites of leakage.
Main Methods:
- Induction of cold-lesion injury in cat brains.
- Intravenous injection of horseradish peroxidase (HRP) and Evans blue (EB) as tracers.
- Ultrastructural examination of micro-blood vessels, including localization of alkaline phosphatase (AP) and cationized ferritin (CF).
- Analysis of brain tissue at 1 hour, 24 hours, and 7 days post-injury.
Main Results:
- Edema fluid, traced by EB, spread through white matter into adjacent gyri 24 hours post-injury.
- Micro-blood vessels in edematous white matter showed HRP accumulation in basement membranes, abluminal pits, and endothelial cell vesicles.
- HRP extravasation was observed near the cold injury lesion but not in more distant edematous areas within 40 minutes of circulation time.
Conclusions:
- Cold injury induces significant alterations in micro-blood vessel permeability and structure.
- Early microvascular leakage, particularly in larger MBVs, contributes to edema formation and spread.
- The BBB exhibits differential permeability responses in proximity to the primary injury site versus surrounding edematous regions.
Abstract:
Micro-blood vessels (MBVs), located in the area of edema, were studied in cat brain at various time intervals (1 h, 24 h, 7 days) after cold-lesion injury. Both cold-injured and adjacent gyri were examined for blood-brain barrier (BBB) permeability to i. v. injected horseradish peroxidase (HRP) with circulation times of 40 min and 24 h. Evans blue (EB) was used as a tracer for gross evaluation of the extension of brain edema. Localization of alkaline phosphatase (AP) and binding of cationized ferritin (CF), considered as a marker of anionic sites, were also studied ultrastructurally. Twenty-four hours after cold injury, the extravasated edema fluid, outlined by EB tracer, was observed to be spreading through the white matter (WM) into the adjacent gyrus. At this time, numerous, larger than capillary MBVs, presumably arterioles and venules located in the edematous WM, showed accumulations of HRP injected at the time of the operation, in the basement membrane, in abluminal pits, and in numerous pinocytotic vesicles and vacuoles of endothelial cells (ECs). The animals killed after 24 h with 40 min HRP circulation showed extravasation of HRP tracer in a zone underlying the necrotic cold injury lesion. On the other hand, there was no evidence of an abnormal HRP leakage in the further removed areas of edema in the WM, particularly in the adjacent gyrus.(ABSTRACT TRUNCATED AT 250 WORDS)