Generation of three different fragments of bound C3 with purified factor I or serum. II. Location of binding sites in the C3 fragments for factors B and H, complement receptors, and bovine conglutinin.

The many different recognized functions of C3 are dependent upon the ability of the activated C3 molecule both to bind covalently to protein and carbohydrate surfaces and to provide binding sites for as many as eleven different proteins. The location of the binding sites for six of these different proteins (factors B and H, complement receptors CR(1), CR(2) and CR(3) and conglutinin) was examined in the naturally occurring C3-fragments generated by C3 activation (C3b) and degradation by Factor I (iC3b, C3c, C3d,g) and trypsin (C3d). Evidence was obtained for at least four distinct binding sites in C3 for these six different C3 ligands. One binding site for B was detectable only in C3b, whereas a second binding site for H and CR(1) was detectable in both C3b and iC3b. The affinity of the binding site for H and CR(1) was charge dependent and considerably reduced in iC3b as compared to C3b. H binding to iC3b-coated sheep erythrocytes (EC3bi) was measurable only in low ionic strength buffer (4 mS). The finding that C3c-coated microspheres bound to CR(1), indicated that this second binding site was still intact in the C3c fragment. However, H binding to C3c was not examined. A third binding site in C3 for CR(2) was exposed in the d region by factor I cleavage of C3b into iC3b, and the activity of this site was unaffected by the further I cleavage of iC3b into C3d,g. Removal of the 8,000-dalton C3g fragment from C3d,g with trypsin forming C3d, resulted in reduced CR2 activity. However, because saturating amounts of monoclonal anti-C3g did not block the CR(2)-binding activity of EC3d,g, it appears unlikely that the g region of C3d,g or iC3b forms a part of the CR(2)-binding site. In addition, detergent-solubilized EC3d (C3d-OR) inhibited the CR(2)-binding activity of EC3d,g. Monocytes and neutrophils, that had been previously thought to lack CR(2) because of their inability to form EC3d rosettes, did bind EC3d,g containing greater than 5 x 10(4) C3d,g molecules per E. The finding that monocyte and neutrophil rosettes with EC3d,g were inhibited by C3d-OR, suggested that these phagocytic cells might indeed express very low numbers of CR(2), and that these CR(2) were detectable with EC3d,g and not with EC3d because C3d,g had a higher affinity for CR2 than did C3d. A fourth C3 binding site for CR(3) and conglutinin (K) was restricted to the iC3b fragment. Because of simultaneous attachment of iC3b to phagocyte CR3 and CR(3), the characteristics of iC3b binding to CR3 could only be examined with phagocytes on which the CR(1) had been blocked with anti-CR(1). Inhibition studies with EDTA and N-acetyl-D-glucosamine demonstrated a requirement for both calcium cations and carbohydrate in the binding of EC3bi to CR3 and to K. However, CR(3) differed from K in that magnesium cations were required in addition to calcium for maximum CR(3) binding activity, and NADG produced less inhibition of CR(3) activity than of K activity.

Regeneration of ischemic cardiac muscle and vascular endothelium by adult stem cells.

Myocyte loss in the ischemically injured mammalian heart often leads to irreversible deficits in cardiac function. To identify a source of stem cells capable of restoring damaged cardiac tissue, we transplanted highly enriched hematopoietic stem cells, the so-called side population (SP) cells, into lethally irradiated mice subsequently rendered ischemic by coronary artery occlusion for 60 minutes followed by reperfusion. The engrafted SP cells (CD34(-)/low, c-Kit(+), Sca-1(+)) or their progeny migrated into ischemic cardiac muscle and blood vessels, differentiated to cardiomyocytes and endothelial cells, and contributed to the formation of functional tissue. SP cells were purified from Rosa26 transgenic mice, which express lacZ widely. Donor-derived cardiomyocytes were found primarily in the peri-infarct region at a prevalence of around 0.02% and were identified by expression of lacZ and alpha-actinin, and lack of expression of CD45. Donor-derived endothelial cells were identified by expression of lacZ and Flt-1, an endothelial marker shown to be absent on SP cells. Endothelial engraftment was found at a prevalence of around 3.3%, primarily in small vessels adjacent to the infarct. Our results demonstrate the cardiomyogenic potential of hematopoietic stem cells and suggest a therapeutic strategy that eventually could benefit patients with myocardial infarction.

Lipoxygenase inhibitor nafazatrom fails to attenuate postischaemic ventricular dysfunction.

The role of lipoxygenase activation in the genesis of postischaemic myocardial dysfunction was investigated in open chest dogs undergoing a 15 min occlusion of the left anterior descending artery followed by 4 h of reperfusion. Treated animals (n = 9) received nafazatrom, a potent lipoxygenase inhibitor, 10 mg.kg-1 orally 4 h before occlusion followed by intravenous boluses of 1.5 mg.kg-1 and 0.5 mg.kg-1 5 min before occlusion and 1 min before reperfusion respectively. Control animals (n = 10) received saline. No discernible haemodynamic effects were produced by the drug. Collateral flow to the ischaemic zone (radioactive microspheres) was 0.14(0.02) ml.min-1.g-1 in the control group and 0.16(0.05) ml.min-1.g-1 in the treated group. The size of the occluded bed as determined by postmortem perfusion was 25.5(0.8)% of the left ventricle in the control and 24.3(1.3)% in the treated group. Histological examination showed a decrease in neutrophil infiltration of the non-ischaemic myocardium and, to a lesser extent, of the reperfused myocardium in nafazatrom treated animals, suggesting lipoxygenase inhibition. Systolic wall thickening (an index of regional function) was assessed using an epicardial pulsed Doppler probe. The two groups exhibited comparable systolic thickening under baseline conditions. Though treated animals showed less dyskinesis during coronary occlusion (p less than 0.05), recovery of function was not enhanced over controls and in both groups the reperfused myocardium was still dyskinetic at 4 h. Thus nafazatrom failed to improve postischaemic ventricular dysfunction, suggesting that leukotrienes do not contribute importantly to this phenomenon.

Stem cell plasticity in muscle and bone marrow.

Recent discoveries have demonstrated the extraordinary plasticity of tissue-derived stem cells, raising fundamental questions about cell lineage relationships and suggesting the potential for novel cell-based therapies. We have examined this phenomenon in a potential reciprocal relationship between stem cells derived from the skeletal muscle and from the bone marrow. We have discovered that cells derived from the skeletal muscle of adult mice contain a remarkable capacity for hematopoietic differentiation. Cells prepared from muscle by enzymatic digestion and 5 day in vitro culture were harvested and introduced into each of six lethally irradiated recipients together with distinguishable whole bone marrow cells. Six and twelve weeks later, all recipients showed high-level engraftment of muscle-derived cells representing all major adult blood lineages. The mean total contribution of muscle cell progeny to peripheral blood was 56%, indicating that the cultured muscle cells generated approximately 10- to 14-fold more hematopoietic activity than whole bone marrow. Although the identity of the muscle-derived hematopoietic stem cells is still unknown, they may be identical to muscle satellite cells, some of which lack myogenic regulators and could respond to hematopoietic signals. We have also found that stem cells in the bone marrow can contribute to cardiac muscle repair and neovascularization after ischemic injury. We transplanted highly purified bone marrow stem cells into lethally irradiated mice that subsequently were rendered ischemic by coronary artery occlusion and reperfusion. The engrafted stem cells or their progeny differentiated into cardiomyocytes and endothelial cells and contributed to the formation of functional tissue.

Scalable Yb-MOPA-driven carrier-envelope phase-stable few-cycle parametric amplifier at 1.5 microm.

Carrier-envelope phase-stable 4 microJ pulses at approximately 1.5 microm are obtained from a femtosecond Yb:KGW-MOPA-pumped two-stage optical parametric amplifier. This novel technology represents a highly attractive alternative to traditional Ti:sapphire front-ends for seeding multimillijoule-level optical parametric chirped-pulse amplifiers. For this task, we demonstrate stretching of the OPA output to approximately 40 ps and recompression to 33 fs pulse duration. As a stand-alone system, our tunable two-stage OPA might find numerous applications in time-resolved spectroscopy and micromachining.

Age and previous lactations as factors in the amount of bovine colostral immunoglobulins.

Blood and colostrum samples were obtained from 87 dairy cows in five lactation groups and analyzed for immunoglobulins G1, G2, M, and A. The five groups ranged from cows in first lactation, about 30 mo of age, to cows in fifth or more lactation, about 84 mo of age. Compared to older groups, blood serum of cows in first lactation contained less G1. Cows in first lactation also produced less total colostrum containing less total G1, G2, and M. Immunoglobulin G1 comprised over two-thirds of the immunoglobulins in the colostrum of all groups. Older cows had more immunoglobulin G1 in their colostrum with a tendency toward a higher ratio of G1 to G2. Amount of immunoglobulin A was constant through all lactations. After a rise in the second lactation, total amount of immunoglobulins G2 and M tended to level off. Total immunoglobulin G1 tended to reach a maximum in the third or fourth lactation, almost doubling in amount compared to the first lactation. Age and number of lactations are factors correlated with amounts of these immunoglobulins in colostrum.

Techniques for preparation of bovine mammary smooth membranes.

Most procedures for fractionation of lactating mammary tissue membranes have utilized centrifuge tubes of small volume. We report a method for large-scale fractionation of bovine mammary membranes by a zonal rotor. Because of the large volume of the zonal rotor (1350 ml), greater amounts of starting material can be fractionated to obtain greater yields of desired fractions. We report results of linear sucrose gradients to fractionate mammary tissue homogenates and step gradient adaptations to accelerate membrane separations. Assay of membrane fractions for marker enzyme activities demonstrated that zonal fractionation and derived techniques were applicable for large scale preparation with higher yields of selected bovine mammary membranes. Application of this technique to small volumes is discussed for laboratories without a zonal rotor.

Phagocytosis by human monocyte-derived macrophages. Independent function of receptors for C3b (CR1) and iC3b (CR3).

Human monocytes and monocyte-derived macrophages were examined for their ability to bind and ingest C3-coated sheep erythrocytes (E). Greater than 90% of monocytes and macrophages formed rosettes with EC3b and EC3bi prepared with 15,000-20,000 molecules of C3 per E. Binding of EC3b to the monocyte or macrophage surface was inhibited by rabbit anti-C3b receptor (CR1), but was not inhibited by two different monoclonal anti-C3bi receptor (CR3) antibodies. EC3bi rosette formation was inhibited by monoclonal anti-CR3, but not by anti-CR1. Monocytes and macrophages did not form rosettes with similarly prepared EC3d,g or EC3d. Macrophages cultured for 7 days, but not freshly isolated monocytes, phagocytosed both EC3b and EC3bi. This ability was a consequence of macrophage maturation, as no external stimuli were present during in vitro culture. Experiments directed to determine if EC3b was converted to EC3bi before ingestion suggested that macrophage CR1 and CR3 mediated phagocytosis independently. No evidence was obtained that during the phagocytosis assay, macrophage factor I converted EC3b to EC3bi. The number of E bound or ingested by monocytes and macrophages was dependent on the number of molecules of C3b or iC3b bound per E. Monocytes and macrophages did not require the presence of either Ca++ or Mg++ for rosette formation with EC3b, whereas both divalent cations were required for optimum rosette formation with EC3bi. The presence of divalent cations was required for macrophage phagocytosis of EC3b and EC3bi. For ingestion of EC3b, Mg++ alone was sufficient, and the addition of Ca++ did not increase the number of EC3b ingested. For ingestion of EC3bi, both Ca++ and Mg++ were required for optimal phagocytosis, and their effect was concentration dependent and additive.

Myocardial infarction and remodeling in mice: effect of reperfusion.

Anatomic and functional changes after either a permanent left anterior descending coronary artery occlusion (PO) or 2 h of occlusion followed by reperfusion (OR) in C57BL/6 mice were examined and compared with those in sham-operated mice. Both interventions generated infarcts comprising 30% of the left ventricle (LV) measured at 24 h and equivalent suppression of LV ejection velocity and filling velocity measured by Doppler ultrasound at 1 wk. Serial follow-up revealed that the ventricular ejection velocity and filling velocity returned to the levels of the sham-operated controls in the OR group at 2 wk and remained there; in contrast, PO animals continued to display suppression of both systolic and diastolic function. In contrast, ejection fractions of PO and OR animals were depressed equivalently (50% from sham-operated controls). Anatomic reconstruction of serial cross sections revealed that the percentage of the LV endocardial area overlying the ventricular scar (expansion ratio) was significantly larger in the PO group vs. the OR group (18 +/- 1.7% vs. 12 +/- 0.9%, P < 0.05). The septum that was never involved in the infarction had a significantly (P < 0.002) increased mass in PO animals (22.5 +/- 1.08 mg) vs. OR (17.8 +/- 1.10 mg) or sham control (14.8 +/- 0.99 mg) animals. Regression analysis demonstrated that the extent of septal hypertrophy correlated with LV expansion ratio. Thus late reperfusion appears to reduce the degree of infarct expansion even under circumstances in which it no longer can alter infarct size. We suggest that reperfusion promoted more effective ventricular repair, less infarct expansion, and significant recovery or preservation of ventricular function.