The Ti-B-N system: nanocomposite nc-TiN/a-(TiB2, BN) and nano-multilayer nc-TiN/a-TiBN thin films

The nanostructures and mechanical properties of nanocomposite nc-TiN/a-(TiB2, BN) and nanostructured multilayers nc-TiN/a-TiBN were investigated using X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), microindentation, and stress measurements. It was found that the monolayer Ti-B-N thin films consisted of nanometer-sized crystalline (nc-) Ti(N, B) embedded into amorphous (a-) (TiB2, BN) matrix. When B content was below approximately 16 at.%, two different-sized nanocrystallites with mean grain sizes of approximately 3 and 9 nm respectively were embedded in a-TiB2. With increasing B incorporation (> approximately 27 at.%), more uniform nanograins was embedded a-(TiB2, BN). Incorporation of B not only decreased the size of nanocrystallites, but also gave rise to twinning deformation in nanocrystallites. A maximum hardness of approximately 44 GPa was achieved at B content of 19 at.%. It was also found that the nanostructure and mechanical behaviors of nc-TiN/a-TiBN multilayers was dependent on the modulation length (bilayer thickness A). Decrease of Lambda made the preferred orientation of nc-TiN gradually transform from (200) to (111). A maximum hardness of approximately 30 GPa was achieved at Lambda = 1.8 nm. Deflection from this Lambda value decreased hardness. By contrast, the residual compressive stress value monotonically increased with decrease of A. The enhancement of the hardness was due to the coherent stresses and the structural barriers to dislocation motion in the interface.

A viable mouse model of factor X deficiency provides evidence for maternal transfer of factor X

BACKGROUND

Activated factor X (FXa) is a vitamin K-dependent serine protease that plays a pivotal role in blood coagulation by converting prothrombin to thrombin. There are no reports of humans with complete deficiency of FX, and knockout of murine F10 is embryonic or perinatal lethal.

OBJECTIVE

We sought to generate a viable mouse model of FX deficiency.

METHODS

We used a socket-targeting construct to generate F10-knockout mice by eliminating F10 exon 8 (knockout allele termed F10(tm1Ccmt), abbreviated as '-'; wild-type '+'), and a plug-targeting construct to generate mice expressing a FX variant with normal antigen levels but low levels of FX activity [4-9% normal in humans carrying the defect, Pro343-->Ser, termed FX Friuli (mutant allele termed F10(tm2Ccmt), abbreviated as F)].

RESULTS

F10 knockout mice exhibited embryonic or perinatal lethality. In contrast, homozygous Friuli mice [F10 (F/F)] had FX activity levels of approximately 5.5% (sufficient to rescue both embryonic and perinatal lethality), but developed age-dependent iron deposition and cardiac fibrosis. Interestingly, F10 (-/F) mice with FX activity levels of 1-3% also showed complete rescue of lethality. Further study of this model provides evidence supporting a role of maternal FX transfer in the embryonic survival.

CONCLUSIONS

We demonstrate that, while complete absence of FX is incompatible with murine survival, minimal FX activity as low as 1-3% is sufficient to rescue the lethal phenotype. This viable low-FX mouse model will facilitate the development of FX-directed therapies as well as investigation of the FX role in embryonic development.

Structures of potent selective peptide mimetics bound to carboxypeptidase B

This article reports the crystal structures of inhibitors of the functional form of thrombin-activatable fibrinolysis inhibitor (TAFIa). In vivo experiments indicate that selective inhibitors of TAFIa would be useful in the treatment of heart attacks. Since TAFIa rapidly degrades in solution, the homologous protein porcine pancreatic carboxypeptidase B (pp-CpB) was used in these crystallography studies. Both TAFIa and pp-CpB are zinc-based exopeptidases that are specific for basic residues. The final development candidate, BX 528, is a potent inhibitor of TAFIa (2 nM) and has almost no measurable effect on the major selectivity target, carboxypeptidase N. BX 528 was designed to mimic the tripeptide Phe-Val-Lys. A sulfonamide replaces the Phe-Val amide bond and a phosphinate connects the Val and Lys groups. The phosphinate also chelates the active-site zinc. The electrostatic interactions with the protein mimic those of the natural substrate. The primary amine in BX 528 forms a salt bridge to Asp255 at the base of the S1' pocket. The carboxylic acid interacts with Arg145 and the sulfonamide is hydrogen bonded to Arg71. Isopropyl and phenyl groups replace the side chains of Val and Phe, respectively. A series of structures are presented here that illustrate the evolution of BX 528 from thiol-based inhibitors that mimic a free C-terminal arginine. The first step in development was the replacement of the thiol with a phosphinate. This caused a precipitous drop in binding affinity. Potency was reclaimed by extending the inhibitors into the downstream binding sites for the natural substrate.

A viable mouse model of factor X deficiency provides evidence for maternal transfer of factor X

BACKGROUND

Activated factor X (FXa) is a vitamin K-dependent serine protease that plays a pivotal role in blood coagulation by converting prothrombin to thrombin. There are no reports of humans with complete deficiency of FX, and knockout of murine F10 is embryonic or perinatal lethal.

OBJECTIVE

We sought to generate a viable mouse model of FX deficiency.

METHODS

We used a socket-targeting construct to generate F10-knockout mice by eliminating F10 exon 8 (knockout allele termed F10(tm1Ccmt), abbreviated as '-'; wild-type '+'), and a plug-targeting construct to generate mice expressing a FX variant with normal antigen levels but low levels of FX activity [4-9% normal in humans carrying the defect, Pro343-->Ser, termed FX Friuli (mutant allele termed F10(tm2Ccmt), abbreviated as F)].

RESULTS

F10 knockout mice exhibited embryonic or perinatal lethality. In contrast, homozygous Friuli mice [F10 (F/F)] had FX activity levels of approximately 5.5% (sufficient to rescue both embryonic and perinatal lethality), but developed age-dependent iron deposition and cardiac fibrosis. Interestingly, F10 (-/F) mice with FX activity levels of 1-3% also showed complete rescue of lethality. Further study of this model provides evidence supporting a role of maternal FX transfer in the embryonic survival.

CONCLUSIONS

We demonstrate that, while complete absence of FX is incompatible with murine survival, minimal FX activity as low as 1-3% is sufficient to rescue the lethal phenotype. This viable low-FX mouse model will facilitate the development of FX-directed therapies as well as investigation of the FX role in embryonic development.

Increased response to morphine in mice lacking protein kinase C epsilon

The protein kinase C (PKC) family of serine-threonine kinases has been implicated in behavioral responses to opiates, but little is known about the individual PKC isozymes involved. Here, we show that mice lacking PKCepsilon have increased sensitivity to the rewarding effects of morphine, revealed as the expression of place preference and intravenous self-administration at very low doses of morphine that do not evoke place preference or self-administration in wild-type mice. The PKCepsilon null mice also show prolonged maintenance of morphine place preference in response to repeated testing when compared with wild-type mice. The supraspinal analgesic effects of morphine are enhanced in PKCepsilon null mice, and the development of tolerance to the spinal analgesic effects of morphine is delayed. The density of mu-opioid receptors and their coupling to G-proteins are normal. These studies identify PKCepsilon as a key regulator of opiate sensitivity in mice.

Paresthesia as a favorable predictor of migraine prophylaxis using topiramate

Migraineurs treated with topiramate often experience adverse effects, such as paresthesia, fatigue, memory difficulty, or taste perversion. To investigate correlations between side effects and drug efficacy, we analyzed for these in 133 migraineurs treated with topiramate (100 mg/day). A 4-week baseline screening phase preceded a 4-week titration period and a 20-week maintenance phase. A total of 118 patients were evaluated at 3 months and 89 patients at 6 months. Patients who developed paresthesia (n = 73) showed lower headache days than those who did not (n = 60) (P = 0.026 at 3 months, P = 0.002 at 6 months), and had a higher responder rate (3 months, 57.5% and 6 months, 65.8%) than those who did not develop paresthesia (3 months, 38.3% and 6 months, 41.7%). Moreover, retrospective analysis of patients that dropped out showed no survival bias between paresthesia and headache improvement. Other adverse effects were not found to correlate with drug efficacy. This study suggests that the development of paresthesia predicts a favorable response to topiramate in migraine prophylaxis.

Gemcitabine, docetaxel, and capecitabine (GTX) in the treatment of metastatic pancreatic cancer (PC): A prospective phase II study

14024

Background: We have found that the combination of gemcitabine, docetaxel, and capecitabine (GTX), when administered in a specific sequence, will induce a p53 independent pathway of cell death through the MAP kinase pathway. The sequence overcomes drug resistance in PC cells in vitro. We have begun a prospective, phase II trial of GTX in patients with metastatic PC as first-line therapy. Methods: 23 patients with metastatic PC, ECOG 0–2 were enrolled at either Columbia or a community practice. Each cycle was administered over a 21 days. Capecitabine was administered at 750 mg/m2 twice daily for 14 days. Gemcitabine (750 mg/m2 over 75 minutes) and docetaxel (30 mg/m2) were administered on days 4 and 11. Responses were measured by CT (RECIST) and PET after every three cycles. A response by PET was defined as a 50% reduction in SUV while a CR was an absence of uptake. Results: Median age was 61, including 8 men and 15 women. Metastatic sites included liver (87%), abdomen (65%), and lung (17%). 70% of liver positive patients had at least five metastases. 22% had malignant ascites. 16 patients remain alive and 7 have progressive disease. Median survival has not yet been reached. Progression occurred at a median of 5.1 months. By CT, the response rate at metastatic sites was 39% (17% CR / 22% PR). Stable disease was observed in 48% at metastatic sites. PET showed a 53% response rate at metastatic sites. At the primary site, CT showed a 30% response rate including 17% complete responses. By PET criteria, there was a 31% response rate and a 26% CR rate at the primary site. In three patients, a PET response heralded a CT response by three cycles. In one patient, progressive disease on PET preceded progression on CT by two months. Toxicity: Grade 3 leukopenia and thrombocytopenia were 13% and 9%, respectively. There was no grade four hematologic toxicity. One patient experienced lung disease related to gemcitabine and withdrew from the study. A second patient experienced grade 4 mucositis, thrush, and sepsis which was presumed due to DPD deficiency. Grade 3–4 toxicities: HFS: 9%. There was no grade 3–4 diarrhea. Conclusions: GTX, elicits a promising response rate when used in metastatic P.C. PET detects a response and failure of chemotherapy earlier than CT scans.

[Table: see text]