A novel preclinical rodent model of collagenase-induced germinal matrix/intraventricular hemorrhage.

Germinal matrix/intraventricular hemorrhage (GMH/IVH) is a complication that arises in premature infants associated with neurological sequelae. Greater understanding of GMH/IVH is needed to develop therapies, a goal that depends on the existence of appropriate animal models. Towards this goal, we aimed to develop a rodent model of GMH/IVH based on collagenase-induced hemorrhage that exhibits histological and neurological consequences similar to that seen in patients. Male 6-day-old rats were placed on a warming pad and anesthetized with halothane/nitrous oxide delivered by face mask. Uni- or bilateral periventricular injections of 2-µl collagenase (2.0 U) were performed freehand with a needle inserted percutaneously. Sham rats were infused with saline. Early neonatal development, long-term motor and cognitive performances and alterations in brain volume were assessed. Collagenase-based GMH/IVH negatively affected ambulation, surface righting and negative geotaxis outcomes more evidently in bilaterally infused rats, which also presented an early decrease in brain volume, as assessed by the Cavalieri method. In adult animals, a unilateral collagenase infusion produced no significant alteration on forepaw preference. Only bilaterally infused rats presented an impairment of object recognition memory and locomotor deficit. Nevertheless, histological evaluation also demonstrated a persistent brain volume reduction in bilaterally infused rats. Our study provides a pioneering animal model of collagenase-based GMH/IVH, which can be used to evaluate preventive strategies and potential therapeutic interventions for this disorder.

Differential degradation of amyloid beta genetic variants associated with hereditary dementia or stroke by insulin-degrading enzyme.

Inherited amino acid substitutions at position 21, 22, or 23 of amyloid beta (Abeta) lead to presenile dementia or stroke. Insulin-degrading enzyme (IDE) can hydrolyze Abeta wild type, yet whether IDE is capable of degrading Abeta bearing pathogenic substitutions is not known. We studied the degradation of all of the published Abeta genetic variants by recombinant rat IDE (rIDE). Monomeric Abeta wild type, Flemish (A21G), Italian (E22K), and Iowa (D23N) variants were readily degraded by rIDE with a similar efficiency. However, proteolysis of Abeta Dutch (E22Q) and Arctic (E22G) was significantly lower as compared with Abeta wild type and the rest of the mutant peptides. In the case of Abeta Dutch, inefficient proteolysis was related to a high content of beta structure as assessed by circular dichroism. All of the Abeta variants were cleaved at Glu3-Phe4 and Phe4-Arg5 in addition to the previously described major sites within positions 13-15 and 18-21. SDS-stable Abeta dimers were highly resistant to proteolysis by rIDE regardless of the variant, suggesting that IDE recognizes a conformation that is available for interaction only in monomeric Abeta. These results raise the possibility that upregulation of IDE may promote the clearance of soluble Abeta in hereditary forms of Abeta diseases.

Serum CK-BB isoenzyme in preterm infants with periventricular hemorrhage.

Periventricular hemorrhage in the preterm infant kills or injuries thousands annually. Because of the relatively recent emergencies of PVH as a major problem, the pathophysiology of this disorder is not yet known. This study was performed to examine the relationship between brain origin creatine kinase and the occurrence of PVH, both prior to the time of the hemorrhage and after. Twenty-six preterm infants were studied. Serum CK-BB levels were obtained at birth, if possible, and twice daily thereafter for four to seven days. The PVH was proven by either CT scan or autopsy. Infants with PVH had significantly higher average serum levels of CK-BB when compared to infants without, both immediately after birth and during the follow-up period.