Bone growth in biomimetic apatite coated porous Polyactive 1000PEGT70PBT30 implants

We recently, developed a simple one-day one-step incubation method to obtain bone-like apatite coating on flexible and biodegradable Polyactive 1000PEGT70PBT30. The present study reports a preliminary biological evaluation on the coated polymer after implantation in rabbit femurs. The porous cylindrical implants were produced from a block fabricated by injection molding and salt leaching. This technique provided the block necessary mechanical integrity to make small cylinders (diameter 3.5 x 5 mm2) that were suitable for implantation in rabbits. The coating continuously covered the surface of the polymer, preserving the porous architecture of outer contour of the cylinders. Two defects with a diameter of 3.5 or 4 mm were drilled in the proximal and distal part of femur diaphysis. The implants were inserted as press-fit or undersized into the cortex as well as in the marrow cavity. The polymer swelled after implantation due to hydration, leading to a tight contact with the surrounding bone in both defects. The adherence of the coating on the polymer proved to be sufficient to endure a steam sterilization process as well as the 15% swelling of the polymer in vivo. The coated Polyactive 1000PEGT70PBT30 has a good osteoconductive property, as manifested by abundant bone growth into marrow cavity along the implant surface during 4-week implantation. A favorable bioactive effect of the coating with an intimate bone contact and extensive bone bonding with this polymer was qualitatively confirmed. Concerning the bone ingrowth into the porous implant in the defect of 4 mm diameter, only marginal bone formation was observed up to 8 weeks with a maximal penetration depth of about 1 mm. The pore interconnectivity is important not only for producing a coating inside the porous structure but also for bone ingrowth into this biodegradable material. This preliminary study provided promising evidence for a further study using a bigger animal model.

Biomimetic calcium phosphate coatings on Polyactive 1000/70/30

Precalcification of Polyactive 1000/70/30 with a biomimetic calcium phosphate coating is expected to enhance the bioactivity of this biodegradable polymer for the application as bone filler or scaffold of bone tissue engineering. This study presents a 1-day one-step incubation method to obtain either amorphous or bone-like apatitic calcium phosphate coating on Polyactive 1000/70/30. Either dense plates or three-dimensional porous blocks of the polymer were incubated in a simplified but concentrated simulated body fluid-derived solution at 37 degrees C. By bubbling CO2 gas, a solution was prepared with calcium and phosphate ion concentrations five times of that of regular simulated body fluid. With controlled stirring, the CO2 was released out of the solution and exchanged by air. The pH of the solution increased to induce coating formation. Adjusting stirring rate and CO2/air exchange rate controlled the process kinetics. The reaction kinetics had little influence on the crystallographic structure of the final coating mineral for a given solution composition as shown by Fourier transform infrared spectroscopy and X-ray diffraction. However, the interface structure between the coating and substrate was kinetics-dependent. A fast precipitation condition resulted in a uniform but superficial calcification pattern at the surface of polymer. A slow process by selecting either a slow stirring or a slow CO2/air exchange, on the contrary, induced a localized but deep inside calcification pattern. A tensile test showed no statistically significant difference in the mechanical properties among uncoated and coated polymers. The cracking behavior of coatings from different kinetics, however, exhibited different manners, as can be attributed to different interface structures and interfacial strengths.

Natural killer T cell activation protects mice against experimental autoimmune encephalomyelitis

Experimental autoimmune encephalomyelitis (EAE) serves as a prototypic model for T cell-mediated autoimmunity. V(alpha)14 natural killer T (NKT) cells are a subset of T lymphocytes that recognize glycolipid antigens presented by the nonpolymorphic major histocompatibility complex (MHC) class I-like protein CD1d. Here, we show that activation of V(alpha)14 NKT cells by the glycosphingolipid alpha-galactosylceramide (alpha-GalCer) protects susceptible mice against EAE. beta-GalCer, which binds CD1d but is not recognized by NKT cells, failed to protect mice against EAE. Furthermore, alpha-GalCer was unable to protect CD1d knockout (KO) mice against EAE, indicating the requirement for an intact CD1d antigen presentation pathway. Protection of disease conferred by alpha-GalCer correlated with its ability to suppress myelin antigen-specific Th1 responses and/or to promote myelin antigen-specific Th2 cell responses. alpha-GalCer was unable to protect IL-4 KO and IL-10 KO mice against EAE, indicating a critical role for both of these cytokines. Because recognition of alpha-GalCer by NKT cells is phylogenetically conserved, our findings have identified NKT cells as novel target cells for treatment of inflammatory diseases of the central nervous system.

Administration of dehydroepiandrosterone suppresses experimental allergic encephalomyelitis in SJL/J mice

Experimental allergic encephalomyelitis (EAE) is a Th1-mediated inflammatory demyelinating disease in the CNS, an animal model of multiple sclerosis. We have examined the effect of dehydroepiandrosterone (DHEA) on the development of EAE in mice. The addition of DHEA to cultures of myelin basic protein-primed splenocytes resulted in a significant decrease in T cell proliferation and secretion of (pro)inflammatory cytokines (IFN-gamma, IL-12 p40, and TNF-alpha) and NO in response to myelin basic protein. These effects were associated with a decrease in activation and translocation of NF-kappaB. In vivo administration of DHEA significantly reduced the severity and incidence of acute EAE, along with a decrease in demyelination/inflammation and expressions of (pro)inflammatory cytokines in the CNS. These studies suggest that DHEA has potent anti-inflammatory properties, which at least are in part mediated by its inhibition of NF-kappaB activation.

The Phe-X-Glu DNA binding motif of MutS. The role of hydrogen bonding in mismatch recognition

The crystal structures of MutS protein from Thermus aquaticus and Escherichia coli in a complex with a mismatch-containing DNA duplex reveal that the Glu residue in a conserved Phe-X-Glu motif participates in a hydrogen-bonded contact with either an unpaired thymidine or the thymidine of a G-T base-base mismatch. Here, the role of hydrogen bonding in mismatch recognition by MutS is assessed. The relative affinities of MutS for DNA duplexes containing nonpolar shape mimics of A and T, 4-methylbenzimidazole (Z), and difluorotoluene (F), respectively, that lack hydrogen bonding donors and acceptors, are determined in gel mobility shift assays. The results provide support for an induced fit mode of mismatch binding in which duplexes destabilized by mismatches are preferred substrates for kinking by MutS. Hydrogen bonding between the O epsilon 2 group of Glu and the mismatched base contributes only marginally to mismatch recognition and is significantly less important than the aromatic ring stack with the conserved Phe residue. A MutS protein in which Ala is substituted for Glu(38) is shown to be defective for mismatch repair in vivo. DNA binding studies reveal a novel role for the conserved Glu residue in the establishment of mismatch discrimination by MutS.

Stimulation of Th2 response by high doses of dehydroepiandrosterone in KLH-primed splenocytes

Although dehydroepiandrosterone (DHEA) has long been considered as a precursor for steroid hormones, it has also been shown to have regulatory effects in immune homeostasis. We have examined the effect of high DHEA doses on T cell proliferation, differentiation, and cytokine secretion patterns following stimulation with mitogens and soluble antigens. DHEA profoundly inhibited T cell receptor-mediated T cell proliferation in the upstream of IL-2R signaling. Addition of DHEA to KLH-primed splenocytes stimulated Th2 response, indicated by an increase of IL-4 or a decrease of IFN-gamma production in the cultures. Further studies showed that DHEA enhanced IL-4, but inhibited IL-12-mediated T cell proliferation and IL-12 production in antigen-presenting cells (APCs). Our data demonstrated that supraphysiologic levels of DHEA favored Th2 immune responses in vitro by inhibition of IL-12 production from APCs and/or stimulation of Th2 proliferation during the interactions of T cells with APCs.

Compensatory changes in Ca(2+) and myocardial O(2) consumption in beta-tropomyosin transgenic hearts

Transgenic mice overexpressing beta-tropomyosin have increased myofilament Ca(2+) sensitivity that we hypothesized would result in altered relationships among pressure and heart rates, intracellular Ca(2+), and myocardial O(2) consumption. In perfused hearts from transgenic mice there was a marked negative force-frequency response between 6 and 10 Hz with a 30 +/- 3% reduction in peak-positive first derivative of pressure development over time (dP/dt) compared with 14 +/- 2% in wild-type mice (P < 0.001). At 8 Hz systolic pressures were normal, though peak systolic intracellular Ca(2+) was significantly reduced in transgenic mice versus wild type (726 +/- 61 vs. 936 +/- 67 nM, P < 0.05) indicating an alteration in the pressure-Ca(2+) relationship. Over a wide range of positive and negative inotropic interventions there were normal developed pressures, though marked elevations in myocardial O(2) consumption (15-54%). Because pressures are normal and intracellular Ca(2+) decreased and myocardial O(2) consumption increased, this suggests that these abnormalities are at least in part compensatory mechanisms to the altered myofilament function.

Cycloheximide reduces infarct volume when administered up to 6 h after mild focal ischemia in rats

We have previously described a rodent model of brief (30 min) middle cerebral artery occlusion followed by reperfusion, in which infarction develops gradually, reaching completion more than 3 days after ischemia, accompanied by morphological, biochemical, and pharmacological evidence of apoptosis. In the present study, we tested the hypotheses that delayed administration of a protein synthesis inhibitor would be effective in reducing tissue injury in this slowly evolving ischemic infarction, and that efficacy of this treatment would wane with more prolonged ischemia. Focal cerebral ischemia was induced in Long-Evans rats by occlusion of the right middle cerebral artery. Infarction volume was analyzed using triphenyl tetrazolium chloride staining, and morphology was studied using hematoxylin and eosin stained sections. Following 30 min middle cerebral artery occlusion and reperfusion, the core ischemic region exhibited vacuolization in the neuropil by 36 h after ischemia, and infarction reached full size by 7 days after ischemia. Cycloheximide reduced infarct volume when given up to 6 h after ischemia. If the duration of ischemic insult was increased to 90 min, the therapeutic window for delayed cycloheximide was only 30 min. In permanent middle cerebral artery occlusion, cycloheximide was ineffective even when given prior to ischemia onset. After mild, but not severe, ischemic insults, cerebral infarction develops slowly and may be treatable with protein synthesis inhibitors, even when treatment is delayed for up to 6 h after the onset of ischemia.

The elongation domain of ELL is dispensable but its ELL-associated factor 1 interaction domain is essential for MLL-ELL-induced leukemogenesis

The MLL-ELL chimeric gene is the product of the (11;19)(q23p13.1) translocation associated with de novo and therapy-related acute myeloid leukemias (AML). ELL is an RNA polymerase II elongation factor that interacts with the recently identified EAF1 (ELL associated factor 1) protein. EAF1 contains a limited region of homology with the transcriptional activation domains of three other genes fused to MLL in leukemias, AF4, LAF4, and AF5q31. Using an in vitro transformation assay of retrovirally transduced myeloid progenitors, we conducted a structure-function analysis of MLL-ELL. Whereas the elongation domain of ELL was dispensable, the EAF1 interaction domain of ELL was critical to the immortalizing properties of MLL-ELL in vitro. To confirm these results in vivo, we transplanted mice with bone marrow transduced with MLL fused to the minimal EAF1 interaction domain of ELL. These mice all developed AML, with a longer latency than mice transplanted with the wild-type MLL-ELL fusion. Based on these results, we generated a heterologous MLL-EAF1 fusion gene and analyzed its transforming potential. Strikingly, we found that MLL-EAF1 immortalized myeloid progenitors in the same manner as that of MLL-ELL. Furthermore, transplantation of bone marrow transduced with MLL-EAF1 induced AML with a shorter latency than mice transplanted with the MLL-ELL fusion. Taken together, these results indicate that the leukemic activity of MLL-ELL requires the EAF1 interaction domain of ELL, suggesting that the recruitment by MLL of a transactivation domain similar to that in EAF1 or the AF4/LAF4/AF5q31 family may be a critical common feature of multiple 11q23 translocations. In addition, these studies support a critical role for MLL partner genes and their protein-protein interactions in 11q23 leukemogenesis.

Effect of dietary oils enriched with n-3 fatty acids on survival of mice

Female mice were fed a conventional diet, shifted at 119 days of age to a diet supplemented with 10 wt % lard (Lar), high-linoleic (n-6) safflower oil (Saf), rapeseed oil (low-erucic, Rap), high-alpha-linolenic (n-3) perilla oil (Per) or a mixture (1:9) of ethyl docosahexaenoate (n-3) and soybean oil (DHA/Soy). Weight gain was less in the Per group than in the other groups at 497 days of age. In the Rap group, proteinuria was more severe than in the Saf, Per and DHA/Soy group, and hepatic triacylglycerol accumulation was greater than in the other groups. The mean survival time of the DHA/Soy group (753 days) was significantly longer than in the Lar group (672 days) and Saf group (689 days); the differences among other groups (e.g., 701 days in the Per group and 712 days in the Rap group) were not statistically significant. Although DHA is more susceptible to auto-oxidation than other major fatty acids in the air, an oil containing DHA was found to increase the survival of mice. Rapeseed oil that decreases the survival time of SHRSP rats was found to be safe in the mouse strain used in this study when survival was an end point.

Interaction of Escherichia coli MutS and MutL at a DNA Mismatch

MutS and MutL are both required to activate downstream events in DNA mismatch repair. We examined the rate of dissociation of MutS from a mismatch using linear heteroduplex DNAs or heteroduplexes blocked at one or both ends by four-way DNA junctions in the presence and absence of MutL. In the presence of ATP, dissociation of MutS from linear heteroduplexes or heteroduplexes blocked at only one end occurs within 15 s. When both duplex ends are blocked, MutS remains associated with the DNA in complexes with half-lives of 30 min. DNase I footprinting of MutS complexes is consistent with migration of MutS throughout the DNA duplex region. When MutL is present, it associates with MutS and prevents ATP-dependent migration away from the mismatch in a manner that is dependent on the length of the heteroduplex. The rate and extent of mismatch-provoked cleavage at hemimethylated GATC sites by MutH in the presence of MutS, MutL, and ATP are the same whether the mismatch and GATC sites are in cis or in trans. These results suggest that a MutS-MutL complex in the vicinity of a mismatch is involved in activating MutH.

Differential modulation of nicotinic acetylcholine receptor subtypes and synaptic transmission in chick sympathetic ganglia by PGE(2)

The diversity of neuronal nicotinic acetylcholine receptors (nAChRs) is likely an important factor in the modulation of synaptic transmission by acetylcholine and nicotine. We have tested whether postsynaptic nAChRs are modulated in a subtype-specific manner by prostaglandin E(2) (PGE(2)), a regulator of neuronal excitability in both the central and peripheral nervous systems, and examined the effects of PGE(2) on nicotinic transmission. Somatodendritic nAChRs in chick lumbar sympathetic ganglia include four nAChR subtypes distinguished on the basis of conductance and kinetic profile. Nanomolar PGE(2) applied to the extrapatch membrane differentially regulates opening probability (Po), frequency and the opening duration of each nAChR channel subtype in cell-attached patches. PGE(2) decreases the Po of the predominant nAChR subtype (36 pS) and significantly increases Po and open duration of the 23 pS subtype. The 23 pS subtype is gated by the alpha 7-selective agonist choline, and choline-gated currents are inhibited by alpha-bungarotoxin. To examine whether PGE(2) modulates nAChRs at synaptic sites, we studied the effects of PGE(2) on amplitude and decay of synaptic currents in visceral motoneuron-sympathetic neuron co-cultures. PGE(2) significantly decreases the amplitude of miniature excitatory postsynaptic currents (mEPSCs), consistent with the predominant inhibition by PGE(2) of all but the 23 pS subtype. The time constant of mEPSCs at PGE(2)-treated synapses is prolonged, which is also consistent with an increased contribution of the longer open duration of the 23 pS nAChR subtype with PGE(2) treatment. To examine the presynaptic effect of PGE(2), nanomolar nicotine was used. Nicotine induces facilitation of synaptic transmission by increasing mEPSC frequency, an action thought to involve presynaptic, alpha 7-containing nAChRs. In the presence of PGE(2), nicotine-induced synaptic facilitation persists. Thus the net effect of PGE(2) is to alter the profile of nAChRs contributing to synaptic transmission from larger conductance, briefer opening channels to smaller conductance, longer opening events. This subtype-specific modulation of nAChRs by PGE(2) may provide a mechanism for selective activation and suppression of synaptic pathways mediated by different nAChR subtype(s) at both pre- and postsynaptic sites.

[Study on the dynamic changes of retinoblastoma gene of SO-Rb50 cell line]

PURPOSE

To study the dynamic changes of Retinoblastoma Gene of SO-Rb50 cell line.

METHODS

1) Southern blot hybridization was used to analyse the tumor cell DNA of 327th passage of SO-Rb50 cell line. 2) A promoter and 27 exons of Rb gene were screened exon-by-exon by using PCR-SSCP at 415th and 713th passages of SO-Rb50 cell line. 3) Three cell cloning strains named as MC2, MC3 and MC4 were isolated by single cell cloning technique from the SO-Rb50-775, and mutation of Rb gene were also screened exon-by-exon by using PCR-SSCP-HA in MC2-11, MC3-11, MC4-11 and MC3-138.

RESULTS

The 3.5 Kb, 2.9 Kb and 1.0 Kb bands were deleted in the DNA of SO-Rb50-327 tumor cells, showing the deletion of Rb gene in SO-Rb50 cell line. Exon23 of 451th passage cells decreased one band; but exon 25 of 713th passage cells decreased two bands, indicating that exon 25 had new mutation. PCR-SSCP-HA analysis of exon24 showed that MC4-11 and MC3-138 had abnormal bands, but MC2-11 and MC3-11 weren't found mutation of Rb gene. This result suggested that new mutation occurred to exon24 of MC3 during a long-term culture in vitro.

CONCLUSION

Retinoblastoma gene mutation of SO-Rb50 cell line had dynamic changes during a long-term culture.

Calibration of the calcium dissociation constant of Rhod(2)in the perfused mouse heart using manganese quenching

Both theoretical and experimental results are presented for in vivo calibration of the dissociation constant K(Ca)(d)of the calcium-sensitive fluorescent dye Rhod(2)in the perfused mouse heart, using manganese quenching of fluorescence transients. An analytical model is derived, based on the biochemical equilibrium of manganese competition with calcium for Rhod(2)binding. Expressing the differential of the changes between systole and diastole in fluorescence transient (delta Delta F(sys-dia)). delta DeltaF(sys-dia)in a beating heart as a function of the perfusate manganese concentration [Mn(2+)](p)allows correlation of the measured differential transient changes delta Delta F(sys-dia)with the calcium dissociation constant K(Ca)(d)of Rhod(2)and the calcium concentration in the heart. Numerical modeling indicates that the K(Ca)(d)predominantly affects the asymptotic slope of the delta Delta F(sys-dia)versus [Mn(2+)](p)curve at certain manganese concentrations, which suggests that the K(Ca)(d)can be inversely calculated by partially fitting the delta Delta F(sys-dia)distribution as a function of the perfusate manganese concentration. The feasibility of this approach is confirmed by quenching of calcium transients by manganese infusion into isolated perfused beating mouse hearts. The resulting calculated dissociation constant K(Ca)(d)of Rhod(2)is 720nM. Using the same approach, we are able to also estimate intracellular calcium concentrations of 700nM at peak systole and 300nM in diastole. This is in good agreement with values obtained by calibration of fluorescence values with a calcium saturation tetanization procedure in the same perfused mouse heart model.

A novel mis-sense mutation (G1381A) in the G6PD gene identified in a Chinese man

OBJECTIVE

To detect new mutations among 29 glucose-6-phosphate dehydrogenase (G6PD) deficient individuals from Yunnan province.

METHODS

The nitroblue tetrazolium (NBT) method was used to screen G6PD deficient individuals. Mutation was identified by single strand conformation polymorphism (SSCP), amplification created restriction site (ACRS), amplification refractory mutation system (ARMS) and DNA sequencing.

RESULTS

Among 29 cases, 18 cases of G1388A, 1 case of C1004A, and 1 case of G1381A were identified. Nine cases remained to be defined. The G1381A mutation is a novel mis-sense mutation, with a substitution of threonine for alanine (A461T). The resultant G6PD had reduced enzymatic activity. In addition, G1381A caused a restriction site of Stu I to disappear, providing a rapid method for the detection of this mutation.

CONCLUSION

A novel mis-sense mutation G1381A was found. This mutation results in a substitution of threonine for alanine, producing enzyme with reduced activity. The loss of the Stu I restriction site offers a rapid method for the detection of this mutation.

Inhibition of CD40 signaling pathway by tyrphostin A1 reduces secretion of IL-12 in macrophage, Th1 cell development and experimental allergic encephalomyelitis in SJL/J mice

Activation of antigen presenting cells through the interaction of CD40 with its ligand is a critical co-stimulatory signal for IL-12 production and Th1 differentiation. Tyrphostins are organic molecules that inhibit the phosphorylation of protein tyrosine kinases. We show that tyrphostin A1 inhibits CD40L-stimulated IL-12 production in macrophage cultures and antigen-induced generation of Th1 cells. Our data also show that tyrphostin A1 blocks CD40L-induced translocation of NF-kappaB to the nucleus, and reduces the activation of IL-12 p40 gene. In vivo therapy with A1 leads to decrease in generation of myelin basic protein (MBP) specific encephalitogenic T cells. In addition, treatment of SJL/J mice with A1 results in attenuation of experimental allergic encephalomyelitis (EAE).

Ischemic dysfunction in transgenic mice expressing troponin I lacking protein kinase C phosphorylation sites

To determine the in vivo functional significance of troponin I (TnI) protein kinase C (PKC) phosphorylation sites, we created a transgenic mouse expressing mutant TnI, in which PKC phosphorylation sites at serines-43 and -45 were replaced by alanine. When we used high-perfusate calcium as a PKC activator, developed pressures in transgenic (TG) perfused hearts were similar to wild-type (WT) hearts (P = not significant, NS), though there was a 35% and 32% decrease in peak-systolic intracellular calcium (P < 0.01) and diastolic calcium (P < 0.005), respectively. The calcium transient duration was prolonged in the TG mice also (12-27%, ANOVA, P < 0.01). During global ischemia, TG hearts developed ischemic contracture to a greater extent than WT hearts (41 +/- 18 vs. 69 +/- 10 mmHg, perfusate calcium 3.5 mM, P < 0.01). In conclusion, expression of mutant TnI lacking PKC phosphorylation sites results in a marked alteration in the calcium-pressure relationship, and thus susceptibility to ischemic contracture. The reduced intracellular calcium and prolonged calcium transients suggests that a potent feedback mechanism exists between the myofilament and the processes controlling calcium homeostasis.

Calcium measurements in perfused mouse heart: quantitating fluorescence and absorbance of Rhod-2 by application of photon migration theory

Both theoretical and experimental results are presented for the quantitative detection of calcium transients in the perfused mouse heart loaded with the calcium-sensitive fluorescent dye Rhod-2. Analytical models are proposed to calculate both the reflected absorbance and fluorescence spectra detected from the mouse heart. These models allow correlation of the measured spectral intensities with the relative quantity of Rhod-2 in the heart and measurement of the changes in quantum yield of Rhod-2 upon binding calcium in the heart in which multiple scattering effects are predominant. Theoretical modeling and experimental results demonstrate that both reflected absorbance and fluorescence emission are attenuated linearly with Rhod-2 washout. According to this relation, a ratiometric method using fluorescence and absorbance is validated as a measure of the quantum yield of calcium-dependent fluorescence, enabling determination of the dynamics of cytosolic calcium in the perfused mouse heart. The feasibility of this approach is confirmed by experiments quantifying calcium transients in the perfused mouse heart stimulated at 8 Hz. The calculated cytosolic calcium concentrations are 368 +/- 68 nM and 654 +/- 164 nM in diastole and systole, respectively. Spectral distortions induced by tissue scattering and absorption and errors induced by the geometry of the detection optics in the calcium quantification are shown to be eliminated by using the ratio method. Methods to effectively minimize motion-induced artifacts and to monitor the oxygenation status of the whole perfused heart are also discussed.

Rhod-2 based measurements of intracellular calcium in the perfused mouse heart: cellular and subcellular localization and response to positive inotropy

We have demonstrated a method of measuring intracellular calcium in the perfused mouse heart with the red fluorescent dye rhod-2. In Langendorff perfused isolated mouse hearts, rhod-2 is bolused through the perfusate, resulting in a 6.2+/-1.9-fold increase in fluorescence over background, and calcium transients with a transient amplitude to diastolic fluorescence ratio of 33+/-9%. Quantification of the relative amount of rhod-2 in the heart was done by taking the ratio of absorbance at 524 nm (rhod-2 sensitive) to 589 nm (rhod-2 insensitive). Maximal calcium saturated fluorescence was measured during tetanization of the heart with calcium chloride (20 mM) and cyclopiazonic acid (10 microM). Electron microscopy was used to determine the subcellular localization of rhod-2, by fixing rhod-2 in the heart with a carbodiimide compound, and then using a double antibody technique to stain rhod-2. These images demonstrated prominent cytosolic rhod-2 localization. Fluorescence and confocal fluorescence microscopy were consistent with the electron microscopy data. Endothelial cell uptake of rhod-2 was shown with fluorescence microscopy, though functional studies with bradykinin infusion (3 microM), which increases endothelial cell calcium, had no effects on mean fluorescence (N=4, p=NS), suggesting that endothelial uptake was small relative to total fluorescence. Calculated values of intracellular calcium were 686+/-237 nM at peak systole, and 360+/-101 nM in diastole, and with high perfusate calcium (3.5 mM) were 1199+/-215 and 544+/-53 nM, respectively. Thus, this appears a valid method of measuring cytosolic calcium in the perfused mouse heart, which will help determine the mechanisms of altered contractility in genetically engineered mice.

Structural basis of IAP recognition by Smac/DIABLO

Apoptosis is an essential process in the development and homeostasis of all metazoans. The inhibitor-of-apoptosis (IAP) proteins suppress cell death by inhibiting the activity of caspases; this inhibition is performed by the zinc-binding BIR domains of the IAP proteins. The mitochondrial protein Smac/DIABLO promotes apoptosis by eliminating the inhibitory effect of IAPs through physical interactions. Amino-terminal sequences in Smac/DIABLO are required for this function, as mutation of the very first amino acid leads to loss of interaction with IAPs and concomitant loss of Smac/DIABLO function. Here we report the high-resolution crystal structure of Smac/DIABLO complexed with the third BIR domain (BIR3) of XIAP. Our results show that the N-terminal four residues (Ala-Val-Pro-Ile) in Smac/DIABLO recognize a surface groove on BIR3, with the first residue Ala binding a hydrophobic pocket and making five hydrogen bonds to neighbouring residues on BIR3. These observations provide a structural explanation for the roles of the Smac N terminus as well as the conserved N-terminal sequences in the Drosophila proteins Hid/Grim/Reaper. In conjunction with other observations, our results reveal how Smac may relieve IAP inhibition of caspase-9 activity. In addition to explaining a number of biological observations, our structural analysis identifies potential targets for drug screening.

Amelioration of CR-EAE with lisofylline: effects on mRNA levels of IL-12 and IFN-gamma in the CNS

CR-EAE is a Th1-mediated inflammatory autoimmune demyelinating disease of the CNS and serves as a model of human multiple sclerosis. Our previous studies have shown the protective effect of orally administered lisofylline in the prevention of active and passively induced acute EAE. In our present studies we have examined the efficacy and mechanism of action of lisofylline on CR-EAE. Lisofylline decreased the number and severity of paralytic attacks in mice with relapsing EAE. The reduction of clinical disease correlated with decreased levels of mRNA levels of IFN-gamma but not of mRNA levels of IL-12. These studies suggest that lisofylline may be an effective therapeutic for established Th1 mediated autoimmune disease and that it acts by blocking IL-12R signaling and not IL-12 production in vivo.

Retrovirus-mediated gene transfer of MLL-ELL transforms primary myeloid progenitors and causes acute myeloid leukemias in mice

The MLL-ELL fusion gene results from the translocation t(11;19)(q23;p13.1) that is associated with de novo and therapy-related acute myeloid leukemia. To study its transforming properties, we retrovirally transduced primary murine hematopoietic progenitors and assessed their growth properties both in vitro and in vivo. MLL-ELL increased the proliferation of myeloid colony-forming cells in methylcellulose cultures upon serial replating, whereas overexpression of ELL alone had no effect. We reconstituted lethally irradiated congenic mice with bone marrow progenitors transduced with MLL-ELL or the control MIE vector encoding the enhanced green fluorescent protein. When the peripheral blood of the mice was analyzed 11-13 weeks postreconstitution, we found that the engraftment of the MLL-ELL-transduced cells was superior to that of the MIE controls. At this time point, the contribution of the donor cells was normally distributed among the myeloid and nonmyeloid compartments. Although all of the MIE animals (n = 10) remained healthy for more than a year, all of the MLL-ELL mice (n = 20) succumbed to monoclonal or pauciclonal acute myeloid leukemias within 100-200 days. The leukemic cells were readily transplantable to secondary recipients and could be established as immortalized cell lines in liquid cultures. These studies demonstrate the enhancing effect of MLL-ELL on the proliferative potential of myeloid progenitors as well as its causal role in the genesis of acute myeloid leukemias.

Chromatin-related properties of CBP fused to MLL generate a myelodysplastic-like syndrome that evolves into myeloid leukemia

As a result of the recurring translocation t(11;16) (q23;p13.3), MLL (mixed-lineage leukemia) is fused in frame to CBP (CREB binding protein). This translocation has been documented almost exclusively in cases of acute leukemia or myelodysplasia secondary to therapy with drugs that target DNA topo isomerase II. The minimal chimeric protein that is produced fuses MLL to the bromodomain, histone acetyltransferase (HAT) domain, EIA-binding domain and steroid-receptor coactivator binding domains of CBP. We show that transplantation of bone marrow retrovirally transduced with MLL-CBP induces myeloid leukemias in mice that are preceded by a long preleukemic phase similar to the myelodysplastic syndrome (MDS) seen in many t(11;16) patients but unusual for other MLL translocations. Structure-function analysis demonstrated that fusion of both the bromodomain and HAT domain of CBP to the amino portion of MLL is required for full in vitro transformation and is sufficient to induce the leukemic phenotype in vivo. This suggests that the leukemic effect of MLL-CBP results from the fusion of the chromatin association and modifying activities of CBP with the DNA binding activities of MLL.

Structural and biochemical basis of apoptotic activation by Smac/DIABLO

Apoptosis (programmed cell death), an essential process in the development and homeostasis of metazoans, is carried out by caspases. The mitochondrial protein Smac/DIABLO performs a critical function in apoptosis by eliminating the inhibitory effect of IAPs (inhibitor of apoptosis proteins) on caspases. Here we show that Smac/DIABLO promotes not only the proteolytic activation of procaspase-3 but also the enzymatic activity of mature caspase-3, both of which depend upon its ability to interact physically with IAPs. The crystal structure of Smac/DIABLO at 2.2 A resolution reveals that it homodimerizes through an extensive hydrophobic interface. Missense mutations inactivating this dimeric interface significantly compromise the function of Smac/DIABLO. As in the Drosophila proteins Reaper, Grim and Hid, the amino-terminal amino acids of Smac/DIABLO are indispensable for its function, and a seven-residue peptide derived from the amino terminus promotes procaspase-3 activation in vitro. These results establish an evolutionarily conserved structural and biochemical basis for the activation of apoptosis by Smac/DIABLO.

Infection of immunosuppressed C57BL/6N adult mice with a single oocyst of Cryptosporidium parvum

The present study was designed to determine the minimum number of Cryptosporidium parvum oocysts capable of producing patent infections in immunosuppressed C57BL/6N adult mice. Sixty-four female mice were divided into 6 groups of 8 mice each, except group 1 that contained 24 mice. Mice in groups 1-3 were immunosuppressed with dexamethasone and inoculated with 1, 5, and 10 oocysts per mouse, respectively. The accuracy of the inoculum size was microscopically confirmed. Mice in groups 4-6 served as controls: they received either only oocyst inoculation (group 4), or immunosuppression (group 5), or no treatments (group 6). Fecal oocyst shedding was monitored daily for each mouse using an indirect immunofluorescent assay. Parasite colonization in the terminal ileum of each mouse was evaluated histologically. Four of 24 mice in group 1 developed patent infections, with a prepatent period of approximately 6 days. All mice in groups 2 and 3 developed patent infections, with prepatent periods ranging from 4 to 7 days. Mice in groups 4-6 remained uninfected. Parasite colonization was observed in the terminal ilea of all mice in groups 1-3 that shed fecal oocysts. The present study experimentally demonstrates that a single viable oocyst can induce patent C. parvum infections in immunosuppressed C57BL/6N adult mice and indicates that this mouse model could be used for the parasite genotype or isolate cloning.