Severe hemodilutional anemia increases cerebral tissue injury following acute neurotrauma.

Anemia may worsen neurological outcomes following traumatic brain injury (TBI) by undefined mechanisms. We hypothesized that hemodilutional anemia accentuates hypoxic cerebral injury following TBI. Anesthetized rats underwent unilateral TBI or sham injury (n > or = 7). Target hemoglobin concentrations between 50 and 70 g/l were achieved by exchanging 40-50% of the blood volume (1:1) with pentastarch. The effect of TBI, anemia, and TBI-anemia was assessed by measuring brain tissue oxygen tension (Pbr(O(2))), regional cerebral blood flow (rCBF), jugular venous oxygen saturation (Sjv(O(2))), cerebral contusion area, and nuclear staining for programmed cell death. Baseline postinjury Pbr(O(2)) values in the TBI and TBI-anemia groups (9.3 +/- 1.3 and 11.3 +/- 4.1 Torr, respectively) were lower than the uninjured controls (18.2 +/- 5.2 Torr, P < 0.05 for both). Hemodilution caused a further reduction in Pbr(O(2)) in the TBI-anemia group relative to the TBI group without anemia (7.8 +/- 2.7 vs. 14.8 +/- 3.9 Torr, P < 0.05). The rCBF remained stable after TBI and increased comparably after hemodilution in both anemia and TBI-anemia groups. The Sjv(O(2)) was elevated after TBI (87.4 +/- 8.9%, P < 0.05) and increased further following hemodilution (95.0 +/- 1.6%, P < 0.05). Cerebral contusion area and nuclear counts for programmed cell death were increased following TBI-anemia (4.1 +/- 3.0 mm(2) and 686 +/- 192, respectively) relative to TBI alone (1.3 +/- 0.3 mm(2) and 404 +/- 133, respectively, P < 0.05 for both). Hemodilutional anemia reduced cerebral Pbr(O(2)) and oxygen extraction and increased cell death following TBI. These results support our hypothesis that acute anemia accentuated hypoxic cerebral injury after neurotrauma.

Hypoxia alters the expression of inhibitor of apoptosis proteins after brain trauma in the mouse.

Hypoxia worsens brain injury following trauma, but the mechanisms remain unclear. The purpose of this study was to determine the effect of traumatic brain injury (TBI) and secondary hypoxia (9% oxygen) on apoptosis-related protein expression, cell death, and behavior. Using a murine weight-drop model, TBI led to an early (6 h) increase followed by a later (24 h) decrease in neuronal apoptosis inhibitor protein (NAIP) expression in the olfactory and motor cortex; in contrast, TBI led to a sustained (6 h to 7 days) increase in NAIP in the striatum. The peak increase in the expression of NAIP (6-12 h) following TBI alone was delayed (1-7 days) when hypoxia was added to TBI. Hypoxia following TBI further depleted other apoptosis inhibitor proteins (IAPs) and activated caspases, as well as increased contusion size and worsened cell death. Hypoxia added to TBI also increased motor and feeding activity on days 2 and 4 compared to TBI alone. Hypoxia without TBI had no effect on the expression of IAPs or cell death. These findings show that IAPs have a potential role in the increased vulnerability of brain cells to hypoxia following TBI, and have implications for configuring future therapies for TBI.

The locus coding for the 3-nitrobenzoate dioxygenase of Comamonas sp. strain JS46 is flanked by IS1071 elements and is subject to deletion and inversion events.

In Comamonas sp. strain JS46, 3-nitrobenzoate (3Nba) is initially oxidized at the 3,4 position by a dioxygenase, which results in release of nitrite and production of protocatechuate. The locus coding for the 3Nba dioxygenase (designated mnb, for m-nitrobenzoate) was mobilized from strain JS46 using a plasmid capture method, cloned, and sequenced. The 3Nba dioxygenase (MnbA) is a member of the phthalate family of aromatic oxygenases. An open reading frame designated mnbB that codes for an NAD(P)H-dependent class IA aromatic oxidoreductase is downstream of mnbA. MnbB is tentatively identified as the oxidoreductase that transfers reducing equivalents to MnbA in strain JS46. The mnb locus is flanked by IS1071 elements. The upstream element is interrupted by a novel insertion sequence designated ISCsp1, and the transposase genes of the flanking insertion elements are transcribed in the direction opposite the direction of mnbA transcription. Spontaneous deletion of mnb occurs because of homologous recombination between the directly repeated flanking IS1071 elements. In addition, in approximately 0.007 to 0.2% of any population of JS46 cells growing on 3Nba, alternative orientations of mnb relative to the flanking IS1071 elements are detected. These alternative forms are the result of inversions of mnb and the flanking IS1071 elements. Inversions appear to occur because of homologous recombination between the inverted repeats that flank the IS1071 elements.

Transgenic expression of numb inhibits notch signaling in immature thymocytes but does not alter T cell fate specification.

The conserved adaptor protein Numb is an intrinsic cell fate determinant that functions by antagonizing Notch-mediated signal transduction. The Notch family of membrane receptors controls cell survival and cell fate determination in a variety of organ systems and species. Recent studies have identified a role for mammalian Notch-1 signals at multiple stages of T lymphocyte development. We have examined the role of mammalian Numb (mNumb) as a Notch regulator and cell fate determinant during T cell development. Transgenic overexpression of mNumb under the control of the Lck proximal promoter reduced expression of several Notch-1 target genes, indicating that mNumb antagonizes Notch-1 signaling in vivo. However, thymocyte development, cell cycle, and survival were unperturbed by mNumb overexpression, even though transgenic Numb was expressed at an early stage in thymocyte development (CD4(-)CD8(-)CD3(-) cells that were CD44(+)CD25(+) or CD44(-)CD25(+); double-negative 2/3). Moreover, bone marrow from mNumb transgenic mice showed no defects in thymopoiesis in competitive repopulation experiments. Our results suggest that mNumb functions as a Notch-1 antagonist in immature thymocytes, but that suppression of Notch-1 signaling at this stage does not alter gammadelta/alphabeta or CD4/CD8 T cell fate specification.