Optimization of intrabone delivery of hematopoietic progenitor cells in a swine model using cell radiolabeling with [89]zirconium.

Intrabone (IB) hematopoietic cell transplantation (HCT) of umbilical cord blood in humans remains experimental and the technique has not been optimized. It is unknown whether hematopoietic progenitor cells (HPCs) injected IB are initially retained in the marrow or rapidly enter into the venous circulation before homing to the marrow. To develop an IB-injection technique that maximizes HPC marrow-retention, we tracked radiolabeled human HPCs following IB-injection into swine. We developed a method to radionuclide-label HPCs using a long-lived positron emitter (89) Zr and protamine sulfate that resulted in cellular-retention of low-dose radioactivity. This approach achieved radioactivity levels sufficient for detection by positron emission tomography with both high sensitivity and spatial resolution when fused with computed tomography. We found that conditions utilized in pilot IB-HCT clinical trials conducted by others led to both rapid drainage into the central venous circulation and cellular extravasation into surrounding muscle and soft tissues. By optimizing the needle design, using continuous real-time intra-marrow pressure monitoring, and by reducing the infusion-volume and infusion-rate, we overcame this limitation and achieved high retention of HPCs in the marrow. This method of IB cellular delivery is readily applicable in the clinic and could be utilized in future investigational IB-HCT trials aimed at maximizing marrow retention of HPCs.

MRI roadmap-guided transendocardial delivery of exon-skipping recombinant adeno-associated virus restores dystrophin expression in a canine model of Duchenne muscular dystrophy.

Duchenne muscular dystrophy (DMD) cardiomyopathy patients currently have no therapeutic options. We evaluated catheter-based transendocardial delivery of a recombinant adeno-associated virus (rAAV) expressing a small nuclear U7 RNA (U7smOPT) complementary to specific cis-acting splicing signals. Eliminating specific exons restores the open reading frame resulting in translation of truncated dystrophin protein. To test this approach in a clinically relevant DMD model, golden retriever muscular dystrophy (GRMD) dogs received serotype 6 rAAV-U7smOPT via the intracoronary or transendocardial route. Transendocardial injections were administered with an injection-tipped catheter and fluoroscopic guidance using X-ray fused with magnetic resonance imaging (XFM) roadmaps. Three months after treatment, tissues were analyzed for DNA, RNA, dystrophin protein, and histology. Whereas intracoronary delivery did not result in effective transduction, transendocardial injections, XFM guidance, enabled 30±10 non-overlapping injections per animal. Vector DNA was detectable in all samples tested and ranged from <1 to >3000 vector genome copies per cell. RNA analysis, western blot analysis, and immunohistology demonstrated extensive expression of skipped RNA and dystrophin protein in the treated myocardium. Left ventricular function remained unchanged over a 3-month follow-up. These results demonstrated that effective transendocardial delivery of rAAV-U7smOPT was achieved using XFM. This approach restores an open reading frame for dystrophin in affected dogs and has potential clinical utility.

B-cell depletion extends the survival of GTKO.hCD46Tg pig heart xenografts in baboons for up to 8 months.

Xenotransplantation of genetically modified pig organs offers great potential to address the shortage of human organs for allotransplantation. Rejection in Gal knockout (GTKO) pigs due to elicited non-Gal antibody response required further genetic modifications of donor pigs and better control of the B-cell response to xenoantigens. We report significant prolongation of heterotopic alpha Galactosyl transferase "knock-out" and human CD46 transgenic (GTKO.hCD46Tg) pig cardiac xenografts survival in specific pathogen free baboons. Peritransplant B-cell depletion using 4 weekly doses of anti-CD20 antibody in the context of an established ATG, anti-CD154 and MMF-based immunosuppressive regimen prolonged GTKO.hCD46Tg graft survival for up to 236 days (n = 9, median survival 71 days and mean survival 94 days). B-cell depletion persisted for over 2 months, and elicited anti-non-Gal antibody production remained suppressed for the duration of graft follow-up. This result identifies a critical role for B cells in the mechanisms of elicited anti-non-Gal antibody and delayed xenograft rejection. Model-related morbidity due to variety of causes was seen in these experiments, suggesting that further therapeutic interventions, including candidate genetic modifications of donor pigs, may be necessary to reduce late morbidity in this model to a clinically manageable level.

Left ventricular pressure measurement by telemetry is an effective means to evaluate transplanted heart function in experimental heterotopic cardiac xenotransplantation.

Evaluation of the function of heterotopic cardiac transplants has traditionally been accomplished by either manual palpation or serial biopsies. Both methods have drawbacks. Palpation can be difficult to differentiate a pulse from the graft versus a transmitted pulse from the native aorta. Serial biopsies, though accurate, require multiple laparotomies, leading to increased morbidity and possibly mortality rates. In this study we used an advanced telemetry system, consisting of an intra-abdominal implant, that was capable of continuously monitoring simultaneously several parameters of the transplanted heart and the status of the recipient. In a large animal model of heterotopic cardiac xenotransplantation (pig donor to baboon recipient), we implanted the device in 12 animals: 8 with and 4 without immunosuppression. We monitored and continuously recorded the left ventricular pressure (both peak-systolic and end-diastolic [LVEDP]), heart rate, and the electrocardiogram pattern of the transplanted heart as well as the temperature of the recipient. The left ventricular pressure proved to be the most valuable parameter to assess graft heart function. In the 4 nonimmunosuppressed cases, grafts were rejected acutely. In these cases, the end-diastolic pressure increased sharply and the heart stopped contracting when the difference between the systolic and the diastolic pressure decreased to <10 mm Hg. The earliest reproducible sign of rejection was an increased LVEDP. Among long-term survivors, the increase in diastolic pressure was gradual, indicating progressive thickening of the myocardium and decreased compliance of the ventricle. Six of 8 immunosuppressed animals died of other complications before rejecting the transplanted heart. The telemetry was also helpful to indicate early onset of fever in the recipients, thus allowing us to intervene early and prevent potentially lethal septic complications. Continuous monitoring of several parameters via telemetry allowed detection of changes associated with rejection as well as other complications at an early stage, allowing prompt intervention, treatment, and possibly reversal of rejection.

Surgical and nonsurgical complications of a pig to baboon heterotopic heart transplantation model.

A modified immunosuppressive regimen, developed at the National Institutes of Health, has been employed in a large animal model of heterotopic cardiac xenotransplantation. Graft survival has been prolonged, but despite this, our recipients have succumbed to various surgical or nonsurgical complications. Herein, we have described different complications and management strategies. The most common complication was hypercoagulability (HC) after transplantation, causing thrombosis of both small and large vasculature, ultimately leading to graft loss. While managing this complication we discovered that there was a delicate balance between HC and consumptive coagulopathy (CC). CC encountered in some recipient baboons was not able to be reversed by stopping anticoagulation and administering multiple blood transfusions. Some complications had iatrogenic components. To monitor the animals, a solid state left ventricular telemetry probe was placed directly into the transplanted heart via the apex. Induction of hypocoagulable states by continuous heparin infusion led to uncontrollable intra-abdominal bleeding in 1 baboon from this apical site. This occurrence necessitated securing the probe more tightly with multiple purse strings and 4-quadrant pledgeted stay sutures. One instance of cardiac rupture originated from a lateral wall infarction site. Earlier studies have shown infections to be uniformly fatal in this transplant model. However, owing to the telemetry placement, infections were identified early by temperature spikes that were treated promptly with antibiotics. We had several cases of wound dehiscence due to recipients disrupting the suture line. These complications were promptly resolved by either re-approximating the wound or finding distractions for the baboon. A few of the most common problems we faced in our earlier experiments were related to the jacket, tether, and infusion pumps. It was difficult to keep the jackets on some baboons and the tether had to be modified several times before we assured long-term success. Infusion catheter replacement resulted in transplant heart venous obstruction and thrombosis from a right common femoral venous line. Homeostatic perturbations such as HC and CC and baboon-induced wound complications comprised most complications. Major bleeding and death due to telemetry implantation and infarct rupture occurred in 2 baboons. Despite the variety of complications, we achieved significant graft prolongation in this model.

Introduction to microsurgery: an emerging discipline in biomedical research.

Using microsurgical techniques, biomedical researchers are able to perform procedures that would otherwise be impossible on small laboratory animals. The authors provide a primer on learning microsurgical technique, from correct posture and hand position, to understanding lenses and proper handling of surgical needles and suture material.

Microsurgical instrumentation and suture material.

Microsurgery requires specialized instruments and very fine suture material. The authors describe microsurgical instruments and suturing materials available for small animal microsurgery.

Manometric changes during retrograde biliary infusion in mice.

The manometric, ultrastructural, radiographic, and physiological consequences of retrograde biliary infusion were determined in normostatic and cholestatic mice. Intraluminal biliary pressure changed as a function of infusion volume, rate, and viscosity. Higher rates of constant infusion resulted in higher peak intraluminal biliary pressures. The pattern of pressure changes observed was consistent with biliary ductular and/or canalicular filling followed by leakage at a threshold pressure. Retrograde infusion with significant elevations in pressure led to paracellular leakage of lanthanum chloride, radiopaque dye, and [(14)C]sucrose with rapid systemic redistribution via sinusoidal and subsequent hepatic venous drainage. Chronic extrahepatic bile duct obstruction resulted in significantly smaller peak intrabiliary pressures and lower levels of paracellular leakage. These findings indicate that under both normostatic and cholestatic conditions elevated intrabiliary volumes/pressures result in an acute pressure-dependent physical opening of tight junctions, permitting the movement of infusate from the intrabiliary space into the subepithelial tissue compartment. Control of intraluminal pressure may potentially permit the selective delivery of macromolecules >18-20 A in diameter to specific histological compartments.

In vivo evidence for both lipolytic and nonlipolytic function of hepatic lipase in the metabolism of HDL.

To investigate the in vivo role that hepatic lipase (HL) plays in HDL metabolism independently of its lipolytic function, recombinant adenovirus (rAdV) expressing native HL, catalytically inactive HL (HL-145G), and luciferase control was injected in HL-deficient mice. At day 4 after infusion of 2 x 10(8) plaque-forming units of rHL-AdV and rHL-145G-AdV, similar plasma concentrations were detected in postheparin plasma (HL=8.4+/-0.8 microg/mL and HL-145G=8.3+/-0.8 microg/mL). Mice expressing HL had significant reductions of cholesterol (-76%), phospholipids (PL; -68%), HDL cholesterol (-79%), apolipoprotein (apo) A-I (-45%), and apoA-II (-59%; P<0.05 for all), whereas mice expressing HL-145G decreased their cholesterol (-49%), PL (-40%), HDL cholesterol (-42%), and apoA-II (-89%; P<0.005 for all) but had no changes in apoA-I. The plasma kinetics of (125)I-labeled apoA-I HDL, (131)I-labeled apoA-II HDL, and [(3)H]cholesteryl ester (CE) HDL revealed that compared with mice expressing luciferase control (fractional catabolic rate [FCR] in d(-1): apoA-I HDL=1.3+/-0.1; apoA-II HDL=2.1+/-0; CE HDL=4.1+/-0.7), both HL and HL-145G enhanced the plasma clearance of CEs and apoA-II present in HDL (apoA-II HDL=5.6+/-0.5 and 4.4+/-0.2; CE HDL=9.3+/-0. 0 and 8.3+/-1.1, respectively), whereas the clearance of apoA-I HDL was enhanced in mice expressing HL (FCR=4.6+/-0.3) but not HL-145G (FCR=1.4+/-0.4). These combined findings demonstrate that both lipolytic and nonlipolytic functions of HL are important for HDL metabolism in vivo. Our study provides, for the first time, in vivo evidence for a role of HL in HDL metabolism independent of lipolysis and provides new insights into the role of HL in facilitating distinct metabolic pathways involved in the catabolism of apoA-I- versus apoA-II-containing HDL.

Vascular effects following homozygous disruption of p47(phox) : An essential component of NADPH oxidase.

BACKGROUND: Evidence suggests that the vessel wall contains an oxidase similar, if not identical, to phagocytic NADPH oxidase. We tested the contribution of this specific oxidase to the progression of atherosclerosis and the regulation of blood pressure. METHODS AND RESULTS: An examination of aortic rings from wild-type mice and mice with homozygous targeted disruptions in p47(phox) revealed that p47(phox) knockout mice had a reduction in vascular superoxide production. However, analyses of apoE -/- p47(phox)+/+ and apoE -/- p47(phox) -/- strains of mice demonstrated no significant differences in atherosclerotic lesion sizes. Similarly, analyses of wild-type and p47(phox) knockout mice revealed no differences in either basal blood pressure or the rise in blood pressure seen after the pharmacological inhibition of nitric oxide synthase. CONCLUSIONS: NADPH oxidase contributes to basal vascular superoxide production. However, the absence of a functional oxidase does not significantly affect the progression of atherosclerosis in the standard mouse apoE -/- model, nor does it significantly influence basal blood pressure.

Cholesteryl ester transfer protein corrects dysfunctional high density lipoproteins and reduces aortic atherosclerosis in lecithin cholesterol acyltransferase transgenic mice.

Expression of human lecithin cholesterol acyltransferase (LCAT) in mice (LCAT-Tg) leads to increased high density lipoprotein (HDL) cholesterol levels but paradoxically, enhanced atherosclerosis. We have hypothesized that the absence of cholesteryl ester transfer protein (CETP) in LCAT-Tg mice facilitates the accumulation of dysfunctional HDL leading to impaired reverse cholesterol transport and the development of a pro-atherogenic state. To test this hypothesis we cross-bred LCAT-Tg with CETP-Tg mice. On both regular chow and high fat, high cholesterol diets, expression of CETP in LCAT-Tg mice reduced total cholesterol (-39% and -13%, respectively; p < 0.05), reflecting a decrease in HDL cholesterol levels. CETP normalized both the plasma clearance of [(3)H]cholesteryl esters ([(3)H]CE) from HDL (fractional catabolic rate in days(-1): LCAT-Tg = 3.7 +/- 0.34, LCATxCETP-Tg = 6.1 +/- 0.16, and controls = 6.4 +/- 0.16) as well as the liver uptake of [(3)H]CE from HDL (LCAT-Tg = 36%, LCATxCETP-Tg = 65%, and controls = 63%) in LCAT-Tg mice. On the pro-atherogenic diet the mean aortic lesion area was reduced by 41% in LCATxCETP-Tg (21.2 +/- 2.0 micrometer(2) x 10(3)) compared with LCAT-Tg mice (35.7 +/- 2.0 micrometer(2) x 10(3); p < 0.001). Adenovirus-mediated expression of scavenger receptor class B (SR-BI) failed to normalize the plasma clearance and liver uptake of [(3)H]CE from LCAT-Tg HDL. Thus, the ability of SR-BI to facilitate the selective uptake of CE from LCAT-Tg HDL is impaired, indicating a potential mechanism leading to impaired reverse cholesterol transport and atherosclerosis in these animals. We conclude that CETP expression reduces atherosclerosis in LCAT-Tg mice by restoring the functional properties of LCAT-Tg mouse HDL and promoting the hepatic uptake of HDL-CE. These findings provide definitive in vivo evidence supporting the proposed anti-atherogenic role of CETP in facilitating HDL-mediated reverse cholesterol transport and demonstrate that CETP expression is beneficial in pro-atherogenic states that result from impaired reverse cholesterol transport.

Hepatic lipase facilitates the selective uptake of cholesteryl esters from remnant lipoproteins in apoE-deficient mice.

We have investigated the role of hepatic lipase (HL) in remnant lipoprotein metabolism independent of lipolysis by using recombinant adenovirus to express native and catalytically inactive HL (HL-145G) in apolipoprotein (apo)E-deficient mice characterized by increased plasma concentrations of apoB-48-containing remnants. In the absence of apoE, the mechanisms by which apoB-48-containing remnants are taken up by either low density lipoprotein (LDL)-receptor or LDL-receptor-related protein (LRP) remain unclear. Overexpression of either native or catalytically inactive HL in apoE-deficient mice led to similar reductions (P > 0.5) in the plasma concentrations of cholesterol (41% and 53%) and non high density lipoprotein (HDL)-cholesterol (41% and 56%) indicating that even in the absence of lipolysis, HL can partially compensate for the absence of apoE in this animal model. Although the clearance of [3H]cholesteryl ether from VLDL was significantly increased (approximately 2-fold; P < 0. 02) in mice expressing native or inactive HL compared to luciferase controls, the fractional catabolic rates (FCR) of [125I-labeled] apoB- very low density lipoprotein (VLDL) in all three groups of mice were similar (P > 0.4, all) indicating selective cholesterol uptake. Hepatic uptake of [3H]cholesteryl ether from VLDL was greater in mice expressing either native HL (87%) or inactive HL-145G (72%) compared to luciferase controls (56%). Our combined findings are consistent with a role for HL in mediating the selective uptake of cholesterol from remnant lipoproteins in apoE-deficient mice, independent of lipolysis. These studies support the concept that hepatic lipase (HL) may serve as a ligand that mediates the interaction between remnant lipoproteins and cell surface receptors and/or proteoglycans. We hypothesize that one of these pathways may involve the interaction of HL with cell surface receptors, such as scavenger receptor (SR)-BI, that mediate the selective uptake of cholesteryl esters.

Altered compliance and residual strain precede angiographically detectable early atherosclerosis in low-density lipoprotein receptor deficiency.

BACKGROUND: This study was performed to detect changes in vascular biomechanical properties early in atherogenesis. METHODS AND RESULTS: Age- and weight-matched LDL-receptor deficient Watanabe hypercholesterolemic male rabbits (Group I: n = 11) and normal rabbits (Group II: n = 11) were studied. Fasting plasma lipoprotein concentrations, aortic angiography and intravascular ultrasound, in vivo aortic compliance evaluation, ex vivo aortic residual strain measurements, aortic lipid content and histopathology were determined. Plasma cholesterol was increased 9.8 fold and aortic cholesterol content was increased from 20 to 43 fold in Group I compared to Group II, respectively (P < .00005). Angiography revealed no stenoses in either group, whereas intravascular ultrasound and histological studies of Group I showed small circumferential plaques with < 10% cross-sectional area involvement. The residual strain in Group I was significantly increased in the ascending thoracic aorta (22.1 +/- 6.9% versus 10.4 +/- 3.2% in Group II, P < .0001), descending thoracic aorta (15.7 +/- 7.2% versus 4.8 +/- 1.3% in Group II, P < .0001), and abdominal aorta (18.0 +/- 4.8% versus 8.3 +/- 6.3% in Group II, P < .005). Changes in residual strain were inversely correlated with the aortic cholesterol content in the ascending thoracic aorta (r = -.72; P = -.001), descending thoracic aorta (r = -.95; P < .001), and abdominal aorta (r = -.51; P = .019). CONCLUSIONS: Early atherosclerosis in LDL-receptor deficient rabbits, undetectable by angiography yet observed by intravascular ultrasound imaging and histology, is associated with marked changes in ex vivo residual strain. Alterations in vascular biomechanical properties, associated with changes in cholesterol content, may have physiologic consequences and may be useful in detecting and quantitating early atherosclerosis.

High plasma HDL concentrations associated with enhanced atherosclerosis in transgenic mice overexpressing lecithin-cholesteryl acyltransferase.

A subset of patients with high plasma HDL concentrations have enhanced rather than reduced atherosclerosis. We have developed a new transgenic mouse model overexpressing human lecithin-cholesteryl acyltransferase (LCAT) that has elevated HDL and increased diet-induced atherosclerosis. LCAT transgenic mouse HDLs are abnormal in both composition and function. Liver uptake of [3H]cholesteryl ether incorporated in transgenic mouse HDL was reduced by 41% compared with control HDL, indicating ineffective transport of HDL-cholesterol to the liver and impaired reverse cholesterol transport. Analysis of this LCAT-transgenic mouse model provides in vivo evidence for dysfunctional HDL as a potential mechanism leading to increased atherosclerosis in the presence of high plasma HDL levels.

Factors influencing fetal macrophage development: III. Immunocytochemical localization of cytokines and time-resolved expression of differentiation markers in organ-cultured rat lungs.

BACKGROUND: Exogenous TNF alpha, IL-1 beta, M-CSF, and GM-CSF all stimulate growth of macrophages arising in explanted fetal rat lungs. The present study examines the intrinsic availability of these factors in intact and organ-cultured lungs and utilizes expression of cytokines and marker proteins to explore the differentiation pathway followed by phagocytes in vitro. METHODS: Factors and markers were localized immunocytochemically in paraffin sections of 14- and 15-day fetal rat lungs and lungs organ-cultured up to 7 days on serum-containing medium solidified with agar. Western analyses for the cytokines were performed on lysates of whole 15-day lungs, and in situ hybridization of M-CSF receptor mRNA was carried out in sections of 14 + 2 day cultured lung. RESULTS: IL-1 beta, M-CSF, and GM-CSF were demonstrated in the stroma of intact and cultured lungs by immunostaining, results confirmed by Western blotting. TNF alpha appeared to be absent. A few precursors (angular cells) expressed the macrophage lineage marker RM-1 as early as day 14, and immunostaining became stronger and more widespread as the population matured and expanded in cultures. The OX-6 antibody to Ia antigen first reacted with macrophages in 14 + 1 day explants, and within a week 50% of cells were positive. M-CSF and mRNA for its receptor were present at 14 + 2 days, as was PDGF, which had been demonstrated in the stroma and epithelium prior to explantation. Definite reactivity for IL-1 beta and GM-CSF followed at 14 + 4 and 14 + 5 days. CONCLUSIONS: M-CSF, GM-CSF, and IL-1 beta, but not TNF alpha, are available to replicating angular cells before and during their conversion to phagocytes. Fetal lungs thus qualify as a hematopoietic tissue supportive of macrophages. The path of differentiation pursued in organ cultures involves early expression of structural elements (RM-1, Ia antigen) followed by synthesis of cytokines of the TNF alpha cascade. Immunostaining for both RM-1 and OX-6 suggests that fetal lung macrophages share a common heritage with antigen-presenting pulmonary dendritic cells.

Ontogeny of neuroepithelial bodies: correlations with mitogenesis and innervation.

This paper summarizes current knowledge and advances speculation about the formation of the neuroendocrine system of mammalian lungs (comprising uninnervated solitary and clustered small-granule cells and innervated neuroepithelial bodies). It relates the initial appearance of neuroendocrine cells to regulation of mitotic activity in the epithelium during the development of the lung and pays special attention to the later in growth of nerves that converts some of them into neuroepithelial bodies, structures considered ideally adapted to function as chemoreceptors. A few original observations from ongoing immunohistochemical, electron microscopic, and analytical studies have been included here and there to point the discussion. The neuroendocrine cells are derived from undifferentiated precursors present in the endodermal pulmonary epithelium. At an early pseudoglandular stage of lung development these precursors begin to differentiate into neuroendocrine small-granule cells, commencing in the larynx and upper trachea, and expanding centrifugally into pulmonary airways almost as rapidly as these are laid down. Subsequently many of the intrapulmonary small-granule cell clusters become innervated. This event, the delayed appearance of small-granule cells synthesizing other than the dominant peptides and amines (calcitonin gene-related peptide and serotonin in rodents, gastrin-releasing peptide and serotonin in human beings), and other regional adjustments yield the population distribution present in the lungs of adults. Neuroendocrine cell precursors normally differentiate into typical serotonin- or peptide-synthesizing small-granule cells without requiring direct contact by nerves, and dissociated cells from a previously innervated population continue to exhibit physiological characteristics of oxygen sensors despite the loss of contact with nerves. Development of the innervation occurs in stages. Small-granule cell clusters are reached first by ganglion cells derived from pulmonary neuroblasts and later on by processes of extrinsic sensory nerves. The latter not only convey information to the central nervous system but also serve in a variety of ways to extend the neuroepithelial bodies' sphere of influence within the lung itself.

Targeted disruption of the mouse lecithin:cholesterol acyltransferase (LCAT) gene. Generation of a new animal model for human LCAT deficiency.

We have established a mouse model for human LCAT deficiency by performing targeted disruption of the LCAT gene in mouse embryonic stem cells. Homozygous LCAT-deficient mice were healthy at birth and fertile. Compared with age-matched wild-type littermates, the LCAT activity in heterozygous and homozygous knockout mice was reduced by 30 and 99%, respectively. LCAT deficiency resulted in significant reductions in the plasma concentrations of total cholesterol, HDL cholesterol, and apoA-I in both LCAT -/- mice (25, 7, and 12%; p < 0. 001 of normal) and LCAT +/- mice (65 and 59%; p < 0.001 and 81%; not significant, p = 0.17 of normal). In addition, plasma triglycerides were significantly higher (212% of normal; p < 0.01) in male homozygous knockout mice compared with wild-type animals but remained normal in female knockout LCAT mice. Analyses of plasma lipoproteins by fast protein liquid chromatography and two-dimensional gel electrophoresis demonstrated the presence of heterogenous prebeta-migrating HDL, as well as triglyceride-enriched very low density lipoprotein. After 3 weeks on a high-fat high-cholesterol diet, LCAT -/- mice had significantly lower plasma concentrations of total cholesterol, reflecting reduced levels of both proatherogenic apoB-containing lipoproteins as well as HDL, compared with controls. Thus, we demonstrate for the first time that the absence of LCAT attenuates the rise of apoB-containing lipoproteins in response to dietary cholesterol. No evidence of corneal opacities or renal insufficiency was detected in 4-month-old homozygous knockout mice. The availability of a homozygous animal model for human LCAT deficiency states will permit further evaluation of the role that LCAT plays in atherosclerosis as well as the feasibility of performing gene transfer in human LCAT deficiency states.

Effects of hydrogen and bicarbonate ions on endocrine cells in fetal rat lung organ cultures.

Concentrations of H+ and HCO3- rise in fluid lining hypercapnic airways. Effects of these ions on pulmonary endocrine cells were studied in 119 fetal rat lung organ cultures by semiquantitative staining for calcitonin gene-related peptide (CGRP)-like immunoreactive material. Intracellular CGRP was determined in cultures under "no-release" baseline conditions and after incubation in control or test media. After exposure to HCO3(-)-free medium at pH 7.4 (incubation control), CGRP fell moderately from no-release levels. Bombesin (1 ng/ml) promoted further significant loss of peptide, which was dependent on extracellular Ca2+ and inhibited by somatostatin and [D-Arg(1),D-Pro(2),D-Trp(7,9),Leu(11)]substance P, a bombesin receptor antagonist. CGRP staining of explants incubated with 24 mM HCO3- maintained no-release levels at and above pH 7.1 but decreased significantly at pH 6.8. The drop was blocked by somatostatin or exclusion of HCO3- and was not augmented by bombesin or 48 mM HCO3-. Results suggest that pulmonary endocrine cells may respond to hypercapnia by releasing bioactive peptides like CGRP, thus stimulating afferent nerves and altering patterns of ventilation and perfusion.

Factors influencing fetal macrophage development: I. Reactions of the tumor necrosis factor-alpha cascade and their inhibitors.

BACKGROUND: When fetal rat lungs are explanted to organ culture, precursor angular cells soon convert to nascent macrophages that multiply rapidly as they mature into efficient phagocytes. The present study examines the influence of proinflammatory early cytokines of the tumor necrosis factor-alpha (TNF alpha) cascade on this initial expression of the macrophage phenotype. METHODS: Fourteen- and 15-day fetal rat lungs were grown for varying periods on an agar-solidified medium with and without test factors added singly or in combination. Growth of the macrophage population was followed daily by light microscopy and quantified by measuring the area of coronas formed as cells emerged from explants. RESULTS: TNF alpha interleukin-1 beta (IL-1 beta) stimulated growth of the macrophage population, as had macrophage- and granulocyte-macrophage colony-stimulating factors (M- and GM-CSFs) in prior studies. Inhibition was obtained by exposure to IL-1 receptor antagonist and antibodies neutralizing the CSFs. Only the effects of TNF alpha were sufficiently delayed to discount possible influence on conversion and growth of nascent macrophages. Two transcription blockers, dexamethasone and pyrrolidine dithiocarbamate (PDTC), an inhibitor of nuclear factor NF-kappa B, both profoundly suppressed macrophage growth without preventing conversion of precursors. Effects of dexamethasone were significantly ameliorated by IL-1 beta alone and combined with GM-CSF; those of PDTC were mitigated by M-CSF and a combination of IL-1 beta and TNF alpha but not by GM-CSF. CONCLUSIONS: IL-1 beta, M-CSF, and GM-CSF all promote growth of the young macrophage population. TNF alpha is effective only later on, likely because early-stage cells lack its receptors which normally use intracellular signalling pathways similar to those for IL-1. The severity of PDTC inhibition to population growth indicates that NF-kappa B is important for transmitting proliferative signals in these cells.