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Physicians, hospitals, and other health care facilities will assume the responsibility for aiding individuals injured by a terrorist act involving radioactive material. Scenarios have been developed for such acts that include a range of exposures resulting in few to many casualties. This consensus document was developed by the Strategic National Stockpile Radiation Working Group to provide a framework for physicians in internal medicine and the medical subspecialties to evaluate and manage large-scale radiation injuries. Individual radiation dose is assessed by determining the time to onset and severity of nausea and vomiting, decline in absolute lymphocyte count over several hours or days after exposure, and appearance of chromosome aberrations (including dicentrics and ring forms) in peripheral blood lymphocytes. Documentation of clinical signs and symptoms (affecting the hematopoietic, gastrointestinal, cerebrovascular, and cutaneous systems) over time is essential for triage of victims, selection of therapy, and assignment of prognosis. Recommendations based on radiation dose and physiologic response are made for treatment of the hematopoietic syndrome. Therapy includes treatment with hematopoietic cytokines; blood transfusion; and, in selected cases, stem-cell transplantation. Additional medical management based on the evolution of clinical signs and symptoms includes the use of antimicrobial agents (quinoiones, antiviral therapy, and antifungal agents), antiemetic agents, and analgesic agents. Because of the strong psychological impact of a possible radiation exposure, psychosocial support will be required for those exposed, regardless of the dose, as well as for family and friends. Treatment of pregnant women must account for risk to the fetus. For terrorist or accidental events involving exposure to radioiodines, prophylaxis against malignant disease of the thyroid is also recommended, particularly for children and adolescents.

Bile acids (BAs) have been established as ubiquitous regulatory molecules implicated in a large variety of healthy and pathological processes. However, the scope of BA heterogeneity is often underrepresented in current literature. This is due in part to inadequate detection methods, which fail to distinguish the individual constituents of the BA pool. Thus, the primary aim of this study was to develop a method that would allow the simultaneous analysis of specific C24 BA species, and to apply that method to biological systems of interest. Herein, we describe the generation and validation of an LC-MS/MS assay for quantification of numerous BAs in a variety of cell systems and relevant biofluids and tissue. These studies included the first baseline level assessment for planar BAs, including allocholic acid, in cell lines, biofluids, and tissue in a nonhuman primate (NHP) laboratory animal, Macaca mulatta, in healthy conditions. These results indicate that immortalized cell lines make poor models for the study of BA synthesis and metabolism, whereas human primary hepatocytes represent a promising alternative model system. We also characterized the BA pool of M. mulattain detail. Our results support the use of NHP models for the study of BA metabolism and pathology in lieu of murine models. Moreover, the method developed here can be applied to the study of common and planar C24 BA species in other systems.

Introduction:Although significant scientific advances have been made over the past six decades in developing safe, nontoxic and effective radiation/medical countermeasures (MCMs) for acute radiation syndrome (ARS), no drug has been approved by the US FDA. The availability of adequate animal models is a prime requisite under the criteria established by the FDA ‘animal rule’ for the development of novel MCMs for ARS and the discovery of biomarkers for radiation exposure.Areas covered:This article reviews the developments of MCMs to combat ARS, with particular reference to the various animal models (rodents: mouse and rat; canine: beagle; minipigs and nonhuman primates [NHPs]) utilized for the in-depth evaluation. The objective, pathways and challenges of the FDA Animal Efficacy Rule are also discussed.Expert opinion:There are a number of well-defined animal models, the mouse, canine and NHP, that are being used for the development of MCMs. Additional animal models, such as the minipig, are under development to further assist in the identification, efficacy testing and approval of MCMs under the FDA Animal Efficacy Rule.

Since the terrorist attack of September 11, 2001, preparation by the health care system for an act of terrorism has been mandated by leaders of governments. Scenarios for terrorist acts involving radioactive material have been identified, and approaches to management (based on past experience from atomic weapons detonations and radiation accidents) have been developed. Because of their experience in managing patients with profound cytopenia and/or marrow aplasia, hematologists will be asked to play a significant role in evaluating and treating victims of mass accidental or deliberate exposure to radiation. This review provides a framework for understanding how radiation levels are quantified, how radiation alters the function of hematopoietic (and nonhematopoietic) cells and tissues, and how victims receiving a significant radiation dose can be identified and managed. In Section I, Dr. Nicholas Dainiak reviews four components of the Acute Radiation Syndrome: the hematopoietic, neurovascular, gastrointestinal and cutaneous subsyndromes. Clinical signs and symptoms are discussed for exposed individuals at the time of initial presentation (the prodromal phase) and during their course of disease (the manifest illness). In Section II, he presents clinical and laboratory methods to assess radiation doses, including time to onset and severity of vomiting, rate of decline in absolute blood lymphocyte count and the appearance of chromosome aberrations such as dicentrics and ring forms. Potential scenarios of a radiation terrorist event are reviewed, and methods for initial clinical assessment, triage, and early management of the acute radiation syndrome and its component subsyndromes are summarized. In Section III, Dr. Jamie Waselenko reviews the hematopoietic syndrome, and presents guidelines for the use of cytokine therapy, antibiotics, and supportive care that have been developed by the Strategic National Pharmaceutical Stockpile Working Group. Results of preclinical and clinical growth factor therapy studies with G-CSF, GM-CSF, pegylated G-CSF, SCF, and IL-3 are summarized. When and how potassium iodide should be used after exposure to radioiodines is also reviewed. In Section IV, Dr. James Armitage describes a narrow “window” of 7 to 10 Gy where therapy with stem cell transplantation may be appropriate. Victims who are candidates for allotransplantation should not have major trauma or significant injury to other (nonhematopoietic) tissues. Rarely, victims may have an identical sibling or autologous stored marrow or blood stem cells, in which case the threshold for transplantation is 4 Gy. In Section V, Dr. Thomas MacVittie describes new directions for therapy, using cytokines such as IL-7, keratinocyte growth factor, and FLT-3. The potential for combinations of cytokines to enhance hematopoietic recovery is also reviewed.

SB-251353 is an N-terminal truncated form of the human CXC chemokine GROβ. Recombinant SB-251353 was profiled in murine and rhesus monkey peripheral blood stem cell mobilization and transplantation models. SB-251353 rapidly and transiently mobilized hematopoietic stem cells and neutrophils into the peripheral blood after a single subcutaneous injection. Transplantation of equivalent numbers of hematopoietic stem cells mobilized by SB-251353 into lethally irradiated mice resulted in faster neutrophil and platelet recovery than stem cells mobilized by granulocyte colony-stimulating factor (G-CSF). A single injection of SB-251353 in combination with 4 days of G-CSF administration resulted in augmented stem and progenitor cell mobilization 5-fold greater than G-CSF alone. Augmented stem cell mobilization could also be demonstrated in mice when a single injection of SB-251353 was administered with only one-day treatment with G-CSF. In addition, SB-251353, when used as a single agent or in combination with G-CSF, mobilized long-term repopulating stem cells capable of hematopoietic reconstitution of lethally irradiated mice. In rhesus monkeys, a single injection of SB-251353 induced rapid increases in peripheral blood hematopoietic progenitor cells at a 50-fold lower dose than in mice, which indicates a shift in potency. These studies provide evidence that the use of SB-251353 alone or in combination with G-CSF mobilizes hematopoietic stem cells with long-term repopulating ability. In addition, this treatment may (1) reduce the number of apheresis sessions and/or amount of G-CSF required to collect adequate numbers of hematopoietic stem cells for successful peripheral blood cell transplantation and (2) improve hematopoietic recovery after transplantation.

Myelopoietins (MPOs) constitute a family of engineered, chimeric molecules that bind and activate the IL-3 and G-CSF receptors on hematopoietic cells. This study investigated the in vivo hematopoietic response of rhesus monkeys administered MPO after radiation-induced myelosuppression. Animals were total body irradiated (TBI) in 2 series, with biologically equivalent doses consisting of either a 700 cGy dose of Cobalt-60 (60Co) γ-radiation or 600 cGy, 250 kVp x-irradiation. First series: On day 1 after 700 cGy irradiation, cohorts of animals were subcutaneously (SC) administered MPO at 200 μg/kg/d (n = 4), or 50 μg/kg/d (n = 2), twice daily, or human serum albumin (HSA) (n = 10). Second series: The 600 cGy x-irradiated cohorts of animals were administered either MPO at 200 μg/kg/d, in a daily schedule (n = 4) or 0.1% autologous serum (AS) , daily, SC (n = 11) for 23 days. MPO regardless of administration schedule (twice a day or every day) significantly reduced the mean durations of neutropenia (absolute neutrophil count [ANC] < 500/μL) and thrombocytopenia (platelet < 20 000/μL) versus respective control-treated cohorts. Mean neutrophil and platelet nadirs were significantly improved and time to recovery for neutrophils (ANC to < 500/μL) and platelets (PLT < 20 000/μL) were significantly enhanced in the MPO-treated cohorts versus controls. Red cell recovery was further improved relative to control-treated cohorts that received whole blood transfusions. Significant increases in bone marrow-derived clonogenic activity was observed by day 14 after TBI in MPO-treated cohorts versus respective time-matched controls. Thus, MPO, administered daily was as effective as a twice daily schedule for multilineage recovery in nonhuman primates after high-dose, radiation-induced myelosuppression.

The therapeutic efficacy of recombinant human leukemia inhibitory factor (LIF) was examined in a nonhuman primate model of radiation-induced marrow aplasia. Rhesus monkeys received 450 cGy of total-body, 1:1 mixed neutron:gamma radiation. For 23 days thereafter, each monkey received a daily subcutaneous injection of LIF or human serum albumin (HSA) at a dose of 15 µg/kg body weight. Complete blood counts and white blood cell differentials were monitored for 60 days postirradiation. Administration of LIF significantly decreased (P ≤.05) the duration of thrombocytopenia (platelet count <30,000 or 20,000/µL), ie, 9.3 days or 6.3 days, respectively, versus the HSA-treated control monkeys, 12.2 days or 10.2 days, respectively. Treatment with LIF did not alter the duration of neutropenia (absolute neutrophil count <1,000/µL) as compared with the HSA-treated control monkeys. Cytokine administration did not exacerbate the radiation-induced anemia observed in the HSA-treated control monkeys.

Formylated peptides are potent stimulants of polymorphonuclear neutrophilic leukyocyte (PMN) migration from species such as humans and rabbits. Interestingly, PMNs from dogs, cats, pigs and cows have been reported as refractory toN-formyl-1-methionyl-1-leucyl-1-phenylalanine (FMLP) and generally are believed not to express formylpeptide receptors. Formylpeptides are a major component of conditioned media fromE. coli cultures and believed to be a significant element in inflammatory responses elicited byE. coli. Our studies have found thatE. coli filtrate was a potent stimulant of dog PMN migration. Inhibition of migration toE. coli filtrates by the antagonistt-botyloxycarbonyl-1-methionyl-1-leucyl-1-phenylalanine (t-boc-MLP) demonstrated that the migration was mediated through the formylated peptide receptor. Migration in response to peptides with higher affinity for the formylpeptide receptor than FMLP was further evidence for these receptors on the dog PMN. PMNs from dogs migrated in response to FMLP at high concentrations (100µM); however, pretreatment with phorbol myristate acetate resulted in increased migration of dog PMNs in response to concentrations of FMLP as low as 1 pM. These results demonstrate that dog PMNs are responsive to formylpeptides and that these responses can be up-regulated by PMA. Thus PMNs from a species previously thought incapable of responding to formylpeptides can respond to formylpeptide analogs with high affinity for the receptor as well as be primed for enhanced migration to FMLP by PMA.

Combination cytokine therapy continues to be evaluated in an effort to stimulate muftilineage hematopoietic reconsfrtu-tion after bone marrow myelosuppression. This study evaluated the efficacy of combination therapy with the synthetic interleukin-3 receptor agonist, Synthokine-SC55494, and recombinant methionyl human granulocyte colony-stimulating factor (rhG-CSF) on platelet and neutrophil recovery in nonhuman primates exposed to total body 700 cGy 60Co gamma radiation. After irradiation on day (d) 0, cohorts of animals subcutaneously received single-agent protocols of either human serum albumin (HSA; every day [QD], 15 jug/ kg/d, n = 10), Synthokine (twice daily [BID], 100 μg/kg/d, n = 5), rhG-CSF (QD, 10 μg/kg/d, n = 5), or a combination of Synthokine and rhG-CSF (BID, 100 and 10 μg/kg/d, respectively, n = 5) for 23 days beginning on d1. Complete blood counts were monitored for 60 days postirradiation and the durations of neutropenia (absolute neutrophil count <500/ μL) and thrombocytopenia (platelet count <20,000/μL) were assessed. Animals were provided clinical support in the form of antibiotics, fresh irradiated whole blood, and fluids. All cytokine protocols significantly (P< .05) reduced the duration of thrombocytopenia versus the HSA-treated animals. Only the combination protocol of Synthokine + rhG-CSF and rhG-CSF alone significantly shortened the period of neutropenia (P< .05). The combined Synthokine/rhG-CSF protocol significantly improved platelet nadir versus Synthokine alone and HSA controls and neutrophil nadir versus rhG-CSF alone and HSA controls. All cytokine protocols decreased the time to recovery to preirradiation neutrophil and platelet values. The Synthokine/rhG-CSF protocol also reduced the transfusion requirements per treatment group to 0 among 5 animals as compared with 2 among 5 animals for Synthokine alone, 8 among 5 animals for rhG-CSF, and 17 among 10 animals for HSA. These data showed that the combination of Synthokine, SC-55494, and rhG-CSF further decreased the cytopenic periods and nadirs for both platelets and neutrophils relative to Synthokine and rhG-CSF monotherapy and suggest that this combination therapy would be effective against both neutropenia and thrombocytopenia consequent to drug- or radiation-induced myelosuppression.

We investigated the effects of two different Gram-negative bacteria and radiation-induced leukopenia on endotoxemia, cardiovascular abnormalities, and mortality in a canine model of septic shock. Serial hemodynamics were measured in conscious dogs using radionuclide heart scans and thermodilution cardiac output catheters. Plasma endotoxin concentrations were determined with a chromogenic Limulus amebocyte lysate assay. Viable Pseudomonas aeruginosaor Escherichia coliimplanted intraperitoneally produced concordant hemodynamic patterns of septic shock (p<0.01). Endotoxin concentrations were more than tenfold lower in dogs infected with P aeruginosacompared with E coli(p<0.0001). Despite lower endotoxin levels, P aeruginosa-infected dogs had a higher mortality (p<0.01), more severe hypotension (p<0.05), and greater depression of the left ventricular ejection fraction (p<0.05) than dogs with E colisepsis. A nonlethal E colichallenge combined with leukopenia (induced by a nonlethal dose of radiation) resulted in a mortality of 60 percent (p<0.01) without greater cardiovascular dysfunction or higher endotoxin concentrations. These findings suggest that bacterial products other than endotoxin and host-related factors may be important contributors to the toxicity, cardiovascular instability, and mortality of Gram-negative septic shock. Quantitative determinations of plasma endotoxin are unlikely to correlate with the clinical severity of septicemia in heterogeneous patient populations infected with different Gram-negative organisms.

Megakaryocyte growth and development factor (MGDF) is a novel cytokine that binds to the c-mplreceptor and stimulates megakaryocyte development in vitro and in vivo. This report describes the ability of recombinant human (r-Hu) MGDF to affect megakaryocytopoiesis in normal nonhuman primates. r-HuMGDF was administered subcutaneously to normal, male rhesus monkeys once per day for 10 consecutive days at dosages of 2.5, 25, or 250 jug/kg of body weight. Bone marrow and peripheral blood were assayed for clonogenic activity and peripheral blood counts were monitored. Circulating platelet counts increased significantly (P< .05) for all doses within 6 days of r-HuMGDF administration and reached maximal levels between day 12 and day 14 postcy-tokine administration. The 2.5, 25.0, and 250.0 μg/kg/d doses elicited peak mean platelet counts that were 592%, 670%, and 449% of baseline, respectively. Bone marrow-derived clonogenic data showed significant increases in the concentration of megakaryocyte (MEG)-colony-forming unit (CFU) and granulocyte-erythroid-macrophage-megakaryo-cyte (GEMM)-CFU, whereas that of granulocyte-macrophage (GM)-CFU and burst-forming unit-erythroid (BFU-e) remained unchanged during the administration of r-HuMGDF. These data show that r-HuMGDF is a potent stimulator of thrombocytopoiesis in the normal nonhuman primate.

Graft-versus-host disease (GVHD) has been evaluated in partially inbred miniature swine in order to study this complication of allogeneic bone marrow transplantation (BMT) in a major histocompatibility complex (MHC) genetically defined large animal model. Bone marrow from MHC homozygous (“parental”) swine was injected into irradiated (900 rads total-body irradiation) MHC heterozygous (“F1”) swine that shared one haplo-type with the donor. All 18 animals successfully engrafted with donor bone marrow, and 17 of these devel-

Radiation with doses >7.5 Gy damages the canine intestinal mucosa, and pretreatment with WR2721 reduces this damage. However, the effects of radiation and of WR2721 onin vivo intestinal transport are unclear. Therefore, we determined canine survival, intestinal transport, and mucosal histology following unilateral abdominal irradiation. Isoperistaltic ileostomies were prepared in 23 dogs under general anesthesia and aseptic conditions. After a three-week recovery period, animals were given either placebo or WR2721, 150 mg/kg intravenously, 30 min prior to 10 Gy cobalt-60 abdominal irradiation. Ileal transport and histology were determined in both groups before exposure and one, four, and seven days after irradiation. Seven-day survival was significantly improved by pretreatment with WR2721 (91% vs 33%,P<0.02). On day 4, both mucosal integrity and net intestinal absorption were significantly better (P<0.05) after WR2721 than after placebo. Thus, radiation-induced damage to the ileal mucosa is accompanied by a reduction in net ileal absorption of water and electrolytesin vivo. In addition, pretreatment with WR2721 improves animal survival while reducing ileal damage and improving intestinal absorption.

In order to stusy the effct of defined genetic differences of one bone marrow transplantation in miniature swain, five different conninations of major histocompatibility complex (MHC)-matched adn mismatched bone marrow transplants were perfomed. Eight of nine fully MHC-mismatched allogeneic bone a marrow transplants faile to reconstitute, and one animal reconstituted briefly but then died quickly therafter. Five of six class I-matched/class II-mismatched (gc) bone marrow transplants engrafted, showed a skin rash trypical of graft-versus-host (GVH) reaction, and died 3 weeks after the marrow transplants into F1hosts engrafted and caused GVH skin rash, with survivals from 1 to 9 montsh (n=5). Serologica typint of the F1recipients of parental marrow showed only donor-type peripheral blood lymphocytes (PBL), suggesting complete marrow replacemetnt. Conversely, F1into parental marrow transplants showed no engraftment (n=6).These results indicate that resistance to MHC-mismatched allogeneic bone marrow engraftment donor class I MHC differences. This response appears to interfere with engraftment of donor bone marrow cells despionte host preparation with 900–1100 rads total-body irradiation. In the absebce of donor MHC class IO differences, engraftment was seen despite the existence of multiple non-MHC differences, and even in the presence of class II differeces. Such engraftment also led to GVH, varying in intensity according to the strength of genetic disparioty (i.e., worst in parentF1combination). Thses results suggest that miniature swaine should proviode adn effective model for study of both GVH elimination (in the parentF1combination) and problems of engraftment (in the F1parent combination), the two most important obstacles to clinical allogeneic transplantation.

Procedures for successful autologous and MHC-matched allogeneic bone marrow transplantation in partially inbred, MHC-defined miniature swine have been established. All marrow recipients were conditioned with single-dose total-body irradiation at the upper level of tolerance, and supported with antibiotics and irradiated blood products during aplasia. Surgical harvest of autologous and allogeneic marrow yielded sufficient numbers of cells to successfully reocnstitute recipients. Radiation control animals that reveived no marrow failed to show recovery of marrow function. Pigs transplanted with autologous marrow at dosed greater than108cells/kg/ routinely engrafted and recovered normal marrow function. The major clinical complications were acute and chronic infections and hemorrhage. T cell-depleted autologous marrow also engrafted, and there was no observed increase in clinical complications. In bone marrow transplantation across non-MHC allogeneic differences, engraftment and survival were similar

Murine spleen cells were separated on the basis of adherence to glass beads into distinct subpopulations that differ in their ability to produce acute graft-versus-host disease (GVHD). Nonadherent CBA spleen cells produce acute GVHD in 6–10 days in lethally irradiated (C57BL/6 × CBA) F1mice as do unfractionated spleen cells. Spleen cells which are adherent to glass beads, however, enable 71 of the mice to survive without symptomatology of acute GVHD. The low proliferative response of these cells to phytohemagglutinin (PHA) correlated with the mitigated GVHD seen in animals grafted with this fraction. Proliferative cells as determined by the spleen colony assay and the in vitro agar colony-forming assay are present in this fraction as are cells responsive to mitogenic stimulation with lipopolysaccharide (LPS). B6CBF1mice grafted with CBA adherent cells exhibit a gradual return over a period of 5 months to normal PHA and LPS stimulation levels as shown by splenic cell responses of these mice to mitogens. Surviving mice grafted with adherent cells were chimeric as determined by electrophoretic hemoglobin pattern analysis and serial bone marrow transplantation.

Mice exposed to 10 Gy cobalt-60 radiation were given intramuscular antimicrobial therapy of gentamicin, or metronidazole, or a combination of the two. Mortality in the mice treated with metronidazole alone or in combination with gentamicin occurred earlier than in the controls (P < 0·001). Microorganisms were recovered from the blood, spleen, and liver of the metronidazole-treated mice earlier than from other groups. The predominant organisms recovered from these animals were Enterobacteriaceae. Quantitative cultures of the ileal flora showed a decrease in the number of aerobic, facultative anaerobic and strict anaerobic bacteria after irradiation, and a subsequent increase only in the number of strict aerobic bacteria. As compared to untreated mice, a rapid decrease (by 8·8 logs) in the number of anaerobic flora occurred in the mice treated with metronidazole 5 days after irradiation. This was followed by a rapid increase in the number of aerobic organisms which coincided with the earlier mortality in this group. These data suggest that antimicrobial agents that decrease the number of the strict anaerobic component of the gut flora enhance systemic infection by aerobic or facultative anaerobic bacteria, and this facilitates mortality after irradiation.

The synthetic cytokine (Synthokine) SC-55494 is a high-affinity interleukin-3 (IL-3) receptor ligand that stimulates greater in vitro multilineage hematopoietic activity than native IL-3, while inducing no significant increase in inflammatory activity relative to native IL-3. The aim of this study was to investigate the in vivo hematopoietic response of rhesus monkeys receiving Synthokine after radiation-induced marrow aplasia. Administration schedule and dose of Synthokine were evaluated. All animals were total-body irradiated (TBI) with 700 cGy 60Co gamma radiation on day 0. Beginning on day 1, cohorts of animals (n = 5) received Synthokine subcutaneously (SO twice daily with 25 μg/kg/d or 100 μg/kg/d for 23 days or 100 μg/kg/d for 14 days. Control animals (n = 9) received human serum albumin SC once daily at 15 μg/kg/d for 23 days. Complete blood counts were monitored for 60 days postirradiation and the durations of neutropenia (NEUT; absolute neutrophil count [ANC] <500/μL) and thrombocytopenia (THROM; platelet count <20,000/μL) were assessed. Synthokine significantly (P< .05) reduced the duration of THROM versus the HSA-treated animals regardless of dose or protocol length. The most striking reduction was obtained in the animals receiving 100 μg/kg/d for 23 days (THROM = 3.5 v12.5 days in HSA control animals). Although the duration of NEUT was not significantly altered, the depth of the nadir was significantly lessened in all animal cohorts treated with Synthokine regardless of dose versus schedule length. Bone marrow progenitor cell cultures indicated a beneficial effect of Synthokine on the recovery of granulocyte-macrophage colony-forming units that was significantly higher at day 24 post-TBI in both cohorts treated at 25 and 100 μg/kg/d for 23 days relative to the control animals. Plasma pharmacokinetic parameters were evaluated in both normal and irradiated animals. Pharmacokinetic analysis performed in irradiated animals after 1 week of treatment suggests an effect of repetitive Synthokine schedule and/or TBI on distribution and/or elimination of Synthokine. These data show that the Synthokine, SC55494, administered therapeutically post-TBI, significantly enhanced platelet recovery and modulated neutrophil nadir and may be clinically useful in the treatment of the myeloablated host.

The influence of in utero low-dose ionizing radiation exposure on murine hemopoietic embryogenesis was investigated. In vitro assays such as micro plasma-clot cultures and double-layer soft agar cultures served as sensitive biodosimeters to determine erythropoietic and granulopoietic injuries. Day-10·5, HA/1CR, pregnant mice were irradiated with 0, 50, 100, 150,200, or 300 rads, and day-14·5 fetal livers were studied for colony-forming unit-erythroid (CFU-E), buist-forming unit-erythroid (BFU-E), granulocyte-macrophage colony-forming cell (GM-CFC), and macrophage-colony-forming cell (M-CFC) activity. Fetuses subjected to doses of 200 rads or higher on day 10-5 of gestation responded with a decrease in day-14·5 liver cellularity, reflecting injury to the developing organ and its inability to recover to the nonirradiated values. Difference in response between erythropoietin(EPO)-dependent and EPO-independent CFU-E strongly suggests existence of two populations of erythroid progenitor cells with different radiosensitivities. A dose of 200 rads markedly reduced CFU-E recovery, and a dose of 100 rads was sufficient to reduce BFU-E recovery to almost 10% of 0-rad values. Nonirradiated day-14·5 fetal liver had more GM-CFC compared to any of the irradiated fetuses, and a dramatically reduced M-CFC recovery occurred with each increase in dose following 150 rads. Our results showed that (1) fetal liver granulopoiesis is more sensitive to radiation injury compared to erythropoiesis, and (2) fetal liver has a greater potential for erythropoiesis recovery.

Three groups of dogs were given lipid X (0, 1, or 10 mg/kg) every 8 h for sevendoses, starting simultaneously with the intraperitoneal placement of Escherichia coli-containing fibrin clots. All animals developed bacteremia, hypotension, and a pattern of decreased left ventricular ejection fraction characteristic of septic shock (P = .01). Survival rates and survival times were not significantly differentbetweentreatment groups (P>.2). In a similar experiment, higher doses of lipid Xresulted in a significantlydecreased survivaltime compared with concurrent controls (P = .04). Animals receiving lipid X did not differ from controls in serial determinations of temperature, hemodynamic measurements, or laboratory parameters (except serum total protein). Although lipid X has antiendotoxin effects, no benefit could be demonstrated in this antibiotic treated, gram-negative bacillary-infected model of septic shock. These data do not support a therapeutic role for lipid X in the treatment of gram-negative sepsis.