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T M Seed

Publications and source records attributed to T M Seed.

At least 37 records · Page 2Linked to original sources
PubMed1990

Changing patterns of radiosensitivity of hematopoietic progenitors from chronically irradiated dogs prone either to aplastic anemia or to myeloproliferative disease.

Hematopoietic patterns have been assessed in chronic 60Co gamma irradiated dogs during preclinical phases of evolving aplastic anemia (AA) or myeloproliferative disease (MPD), principally myeloid leukemia. Within the AA-prone dog, a singular phase of progressive decline in blood levels of granulocytes and monocytes was noted along with a similar reduction in marrow progenitors committed to granulocyte/monocyte differentiation (CFU-GM). Measured radioresistance of the preAA CFU-GM in vitro, relative to control CFU-GM from nonirradiated animals, revealed only slightly increased resistance to gamma rays, but significantly increased resistance to fission neutrons. Within the MPD-prone dogs, four preclinical phases (i.e. suppression, partial recovery, accommodation, and preleukemic transition) preceding development of overt MPD were evidenced by the monitored change in blood granulocyte/monocyte counts and marrow progenitor levels. Analysis of radioresistance of preMPD CFU-GM revealed marked changes with time of exposure and, in turn, with preclinical phase transitions. Gamma ray resistance increased in the initial phases of exposure, with maximal levels occurring during the middle phase of exposure (accommodation, phase III) followed by a tailing off of resistance at later times. Resistance to fission neutrons by preMPD CFU-GM was observed as well, but somewhat later in the exposure course and at a much lower, more consistent level. These differential patterns of radioresistance expressed by marrow CFU-GM of chronically irradiated MPD-prone dogs to gamma rays and fission neutrons gave rise to preclinical phase-specific 'relative biological effectiveness' (RBE) values. From these observations, we conclude that: (i) CFU-GM of MPD-prone dogs acquire and maintain marked radioresistance to low linear energy transfer (LET) gamma rays, but only marginally elevated radioresistance to high-LET fission neutrons during the course of chronic gamma ray exposure; and (ii) CFU-GM of the AA-prone dog, in contrast, acquire little change in resistance to gamma rays, but, surprisingly, marked resistance to neutrons relative to progenitors from nonirradiated controls. These results support the concept that acquired radioresistance of vital granulocyte/monocyte lineage-committed hematopoietic progenitors is temporally, perhaps causally, linked to the processes mediating hematopoietic recovery and accommodation under chronic irradiation, and in turn to preclinical events of evolving MPD. In addition, the marked differential responses of progenitors to gamma and neutron irradiation in vitro might suggest differences in the nature of cellular lesions elicited by chronic gamma irradiation, in vivo.

Anemia, Aplastic↗
PubMed1990

Ultrastructural evidence for differentiation in a human glioblastoma cell line treated with inhibitors of eicosanoid metabolism.

Human glioblastoma cells incubated in the presence of inhibitors of eicosanoid biosynthesis show decreased cellular proliferation without cytotoxicity. We studied the ultrastructural morphology of a human glioblastoma cell line cultured with nordihydroguaiaretic acid (NDGA), a lipoxygenase inhibitor, or 5,8,11,14-eicosatetraynoic acid, a cyclooxygenase and lipoxygenase inhibitor. When glioblastoma cells were treated for 3 days with antiproliferative concentrations of either agent, they shared many morphological characteristics, including evidence for increased astrocytic differentiation with only limited signs of toxicity. The inhibited glioma cells demonstrated an increase in the number and length of astrocytic processes containing greater numbers of glial filaments, and the NDGA-treated cells also demonstrated extensive lateral pseudopod formation along the processes. The glioblastoma cell shape also became more elongated, losing the usual nuclear lobularity and nuclear inclusions, especially in NDGA-treated cells. Many cytoplasmic organelles packed the cytosol of the inhibited glioma cells, including prominent Golgi apparatus, dilated smooth endoplasmic reticulum evolving into dilated vesicles, cytoplasmic vacuoles, and numerous concentric laminations. There was limited evidence for toxicity, however, as the mitochondria were more pleomorphic with some mitochondrial distention and disruption of the cristae along with an increase in cytoplasmic vacuolization. We conclude that the inhibitors of eicosanoid biosynthesis, NDGA and 5,8,11,14-eicosatetraynoic acid, not only suppress glioblastoma cell proliferation, but also induce increased astrocytic differentiation.

5,8,11,14-Eicosatetraynoic Acid↗
PubMed1989

Blood responses under chronic low daily dose gamma irradiation: I. Differential preclinical responses of irradiated male dogs in progression to either aplastic anemia or myeloproliferative disease.

Male beagles chronically exposed to low daily doses of 60Co gamma rays (7.5 cGy/22h/day) show one of three hematopoietic patterns, which reflect three different distinctly responding subgroups: (1) low radioresistance with progressing aplastic anemia and shortened survival (-S-AA subgroup); (2) high radioresistance with a complex of progressing myeloproliferative disorders (+R-MPD group); or (3) high radioresistance with other nonMPD syndromes (+R-nonMPD group). Blood cell levels (granulocytes, monocytes, erythrocytes, lymphocytes, and platelets) were assessed and fitted to a flexible polynomial spline model, thus defining the (a) initial suppressive and (b) subsequent recovery phases for the subgroups. Results showed that relative to the overall magnitude of blood cell loss as well as to the maximum rate of suppression during the initial phase, the subgroups were generally ranked -S-AA much greater than +R-MPD greater than +R-nonMPD. Relative to the overall strength of the recovery response, the subgroups were generally ranked +R-MPD greater than +R-nonMPD much much greater than -S-AA. In terms of overall maintenance levels of circulating blood cells during the recovery phase, however, the +R-nonMPD subgroup consistently exhibited stronger responses than the +R-MPD subgroup. These results tend to support our contention that selected subgroups of dogs have strong propensities to specific hematopathologies (i.e. aplastic anemia and myeloid leukemia) under chronic irradiation and that these pathology-prone animals exhibit a series of marked differential hematopoietic responses during early preclinical phases, which serve effectively to prognosticate subsequent pathological progression.

Adaptation, Physiological↗
PubMed1988

SEM of canine chromosomes: normal structure and the effects of whole-body irradiation.

Canine chromosomes are not only numerous (38 autosomal pairs), but they are small (compared to human chromosomes) and morphologically similar as well. Analysis of the canine karyotype by light microscopy (LM) of banded chromosomes is, thus, difficult, and the literature on the canine karyotype is scanty. In this study, we describe examination of chromosomes from normal and chronically irradiated dogs with the scanning electron microscope (SEM). Metaphase chromosomes from bone marrow aspirates were Giemsa-banded with either 0.025% trypsin alone or 0.1% trypsin preceded by 10% H2O2 and prepared for SEM. Examination of chromosomes from normal dogs revealed cylindrical chromosome profiles with well-defined chromatids and centromeres. The chromosome arms were consistently marked by periodic grooves that had complementary structures on sister chromatids and may represent the trypsin-sensitive chromatic regions. The quality of the preservation varied from preparation to preparation and depended on the concentration and time of trypsin treatment. Chromosomes from irradiated dogs revealed translocations, deletions, and gaps. We conclude that SEM produces images superior to LM images of canine chromosomes; SEM images can be used not only to identify individual chromosomes, but also to identify genetic lesions in the chromosomes of chronically irradiated dogs. We further conclude that the two Giemsa-banding protocols used in the present study produced variable results, although 0.025% trypsin alone appeared to give better and more consistent results than 0.1% trypsin preceded by 10% H2O2.

Animals↗
PubMed1988

Developmental and radiobiologic characteristics of canine multinucleated, osteoclast-like cells generated in vitro from canine bone marrow.

We report here our initial observations on the growth and morphology, and developmental radiosensitivity of giant, multinucleated, osteoclast-like cells (MN-OS) generated through in vitro cultivation of hematopoietic progenitor-enriched canine bone marrow samples. Maximum cell densities of 5.5 x 10(3) to 6.5 x 10(3) MN-OS per cm2 of growth area were achieved following 10 to 14 days of culture at 37 degrees C. Acute gamma irradiation of the initial marrow inocula resulted in significant, dose-dependent perturbations of MN-OS formation, growth, and development. Attempts to estimate radiosensitivity of MN-OS progenitors from canine marrow yielded a range of Do values from a low of 212 cGy measured at six days of culture to higher values of 405 to 542 cGy following 10 to 22 days of culture. At the intermediate times of culture (10 to 14 days), the radiation-induced responses were clearly biphasic, reflecting either (a) the presence of multiple subpopulations of MN-OS progenitors with varying degrees of radiosensitivity or (b) the inherent biphasic nature of MN-OS development involving early progenitor cell proliferation followed by maturation and subsequent fusion. Morphologically, MN-OS generated from irradiated marrow inocula appeared only marginally altered, with alterations expressed largely in a biphasic, dose-dependent fashion in terms of smaller cell size, reduced number of nuclei, increased expression of both surface microprojections, and a unique set of crystalloid cytoplasmic inclusions. Functionally, MN-OS appeared to be impaired by irradiation of marrow progenitors, as evidenced by failure to initiate resorptive attachments to devitalized bone spicules in vitro.

Animals↗
PubMed1988

The ultrastructure of hematopoietic stroma on cellulose ester membranes implanted intraperitoneally into Sl/Sld and Sl+/Sl+ mice.

The structural features of hematopoietic stromal elements forming on cellulose ester membranes (CEM) implanted intraperitoneally into hematopoietically impaired, anemic Sl/Sld mice and their normal Sl+/Sl+ littermates were compared by combined light and electron microscopy. The generally thicker, multilayered stroma lining the Sl+/Sl+ CEM implants developed from a bed--a syncytium--of large, highly pleomorphic macrophage-type lining cells whose filopodial extensions exhibited extensive interactions (i.e., nurse cell interactions) with both stromal and hematopoietic elements. In contrast, the thinner stromal layers lining the CEM of Sl/Sld mice formed from a base of dysplastic lining elements. These CEM-lining macrophage-type cells had much reduced cytoplasmic volumes, less extensive interactive surface projections, and an absence of select types of cytoplasmic organelles (e.g., membrane-bound crystalline inclusions). These observations suggest that the reduction of cell layering and, in turn, hematopoietic support activity, is due to an impaired interactive capacity of these elemental lining cells, i.e., pleomorphic macrophagic cell types, in the hematopoietically impaired strain of Sl/Sld mice.

Anemia, Hemolytic, Congenital↗
PubMed1987

Chronic radiation leukemogenesis: postnatal hematopathologic effects resulting from in-utero irradiation.

Previous studies have shown that continuous whole-body exposure to low daily doses of gamma radiation is highly leukemogenic for beagles initially exposed during either young adulthood or fetal development. In contrast, terminated radiation-exposure regimens (continuous exposure terminated after accumulation of preset total radiation doses) markedly reduce leukemogenic potential. In this study, we examined leukemic incidences and postnatal hematopoietic function in three groups of dogs; continuously irradiated (7.5 cGy/day) during both fetal life and after birth, continuously irradiated during fetal life only, and nonirradiated. Results were compared to results from studies with similarly irradiated and nonirradiated groups of young adult dogs initially tested at 400 days of age. Hematopoietic function was assessed in terms of both circulating blood levels of red cells, platelets, granulocytes, and monocytes, and marrow concentrations and radiosensitivities of hematopoietic progenitors. Results indicated that under continuous fetal/postnatal irradiation, i.e. the high leukemogenic exposure regimen, a marked, progressive suppression in hematopoietic function occurred following birth. This suppression continued to 100-150 days of age and was followed by partial hematopoietic recovery that was associated with an acquired radioresistance by hematopoietic progenitors. In contrast, neonates that had been continuously irradiated during fetal life, but not postnatally, i.e. the low leukemogenic regimen, exhibited a similar initial suppression of hematopoietic function followed by partial recovery. However, no temporally linked acquisition of radioresistance by hematopoietic progenitors was demonstrated. These results support the hypothesis, developed from earlier studies with adult dogs, that the processes of acquired radioresistance and recovery in numbers of transformable hematopoietic progenitors are causally linked to early stages of the leukemogenic process under continuous ionizing irradiation.

Animals↗
PubMed1987

Structure-function relationships in radiation-induced cell and tissue lesions: special references to the contributions of scanning electron microscopy and hematopoietic tissue responses.

Contributions of scanning electron microscopy to the field of radiation biology are briefly reviewed and presented in terms of an overall goal to identify and characterize the structural features of radiation-induced lesions in vital cell and tissue targets. In the context of "lesion" production, the major radiation-elicited response sequences, the types and nature of measured end points, and governing temporal and radiobiological parameters are discussed and illustrated by using results derived from both in vitro cell systems and in vivo studies that measured tissue responses from various organ systems (respiratory, digestive, circulatory, and central nervous systems). Work in our laboratory on the nature of early and late hematopathologic tissue responses (aplastic anemia and myeloid leukemia) induced by protracted radiation exposure and the "bridging effect" of repair processes relative to the expression of these pathologies is highlighted.

Animals↗
PubMed1986

Hematopoiesis on cellulose ester membranes: VII. Ultrastructure of stroma of marrow-enriched membranes with trilineal hematopoiesis.

The ultrastructure of developing osseous and hematopoietic tissue and supporting stroma was examined within intraperitoneally implanted, marrow-coated cellulose ester membranes (CEMs). During initial periods of implantation (two weeks), coated CEMs were shallowly infiltrated and surface-lined with mainly two stromal cell types--primitive mesenchymal cells and large, pleomorphic, multinucleated monocytoid-like stromal cells--and, in addition, endothelial cells in early stages of vessel development. Selective proliferation, maturation, and orientation of these cell types along the CEM's surface (one month), resulted in the formation of primitive osseous and hematopoietic tissue sites. Osseous sites developed as undifferentiated mesenchymal cells transformed into well-differentiated secretory cells residing in an electron-dense, pre-mineralized extracellular matrix, that upon extended implantation (3-6 months) formed bone. Hematopoietic sites developed as mesenchymal cells, in intimate contact with the monocytoid-like stromal cells, extended elongated branches into the medullary cavity, and enveloped newly formed surface-associated vascular structures. With subsequent maturation of vascular sinuses and supporting adventitial stroma (3-6 months), the sites were colonized with either uni-, bi-, or trilineal hematopoietic elements. These observations provide evidence that common, marrow-derived precursor stromal cells, i.e., mesenchymal and multinucleated monocytoid-like cells, cooperate in the development of both osseous and hemic tissue sites.

Animals↗
PubMed1984

CFU-GM colony-enhancing activity in sera of dogs under acute and chronic gamma-irradiation regimens.

Dogs were chronically irradiated (10 R/day; 0-400 R) or acutely irradiated (20 R/min; 0-400 R) with 60Co gamma-rays. Sera were collected and assayed for colony-enhancing activity by a double-layer agar cloning technique. When test sera alone were incorporated in the feeder layers, no colony-forming units-granulocyte/macrophage formation occurred; the addition of peripheral blood leukocytes to such test sera-containing feeder layers resulted in formation of colonies, the number of which was directly related to the cumulative radiation dose. Serum-enhancing factor activity indirectly increased colony formation by stimulating feeder layer leukocytes to generate increased levels of colony-stimulating activity. Levels of serum-enhancing activity were higher at similar dose levels following acute gamma irradiation then following chronic irradiation.

Animals↗
PubMed1982

Phospholipid-nucleoside conjugates. The aggregational characteristics and morphological aspects of selected 1-beta-D-arabinofuranosylcytosine 5'-diphosphate-L-1,2-diacylglycerols.

1-beta-D-Arabinofuranosylcytosine 5'-diphosphate-1,2-diacylglycerols have previously been shown to be promising candidates as prodrugs of the clinically useful antileukemic agent 1-beta-D-arabinofuranosylcytosine. Because of the amphipathic nature of these liponucleotides and the potential that their morphological state may mediate their biological activity, it was necessary to undertake detailed studies of their aggregational and morphological characteristics. When samples of 1-beta-D-arabinofuranosylcytosine 5'-diphosphate-L-1,2-diacylglycerols (containing either dimyristoyl, dipalmitoyl or distearoyl fatty acid side chains) were prepared in buffered saline solutions using sonication methods, the morphological nature of the resulting aggregate was shown to be related to temperature and the length of the side chain. When sonicated at low temperatures all the above-mentioned derivatives gave turbid solutions containing large bilayer sheets. As the temperature was raised, a transition temperature was reached at which a stable three-dimensional cross-linked network of small interlocking bilayer stacks was formed. This turbidity transition temperature was directly related to the chain length of the fatty acid side chain. Sonication at temperatures close to this turbidity transition temperature produced small disc-shaped micellar structures. These micelles were shown to exist in another aggregational equilibrium consisting of a stacking-destacking process, the position within this equilibrium being dependent upon the concentration. In contrast, a sample of 1-beta-D-arabinofuranosylcytosine 5'-diphosphate-L-1,2-dioleoylglycerol (which contains an unsaturated carbon-carbon bond in each of the fatty acid side chains) was shown to give a multilamellar liposome structure when sonicated in buffered saline at temperatures above its turbidity transition temperature.

Antineoplastic Agents↗
PubMed1982

Aberrant megakaryocytopoiesis preceding radiation-induced leukemia in the dog.

Six of nine decedent beagles exposed continuously to 2.5 R*/22 hour day of whole-body 60Co gamma-radiation died with myeloproliferative diseases: three cases of myelogenous leukemia and one each of monocytic leukemia, erythroleukemia, and erythremic myelosis. The three dogs that died with myelogenous leukemia had micromegakaryocytes and megakaryoblasts in the peripheral blood during the preleukemic phase when myeloblasts were not observed in the peripheral blood or in increased numbers in the bone marrow. In this study we have examined the megakaryocytes during the preleukemic period by a combination of light, transmission, and scanning electron microscopy. Morphologic abnormalities seen by light microscopy included mononucleated and binucleated forms, many with cytoplasmic blebs. The small mononuclear forms in the bone marrow tended to form clusters. Ultrastructural features included a paucity of both specific alpha granules and dense granules. The micromegakaryocytes showed dysgenesis of the demarcation membrane system. This membrane system appeared disorganized with a few dilated round, oval, or rarely, elongated vesicles and showed no evidence of platelet formation. The cells also had a paucity of endoplasmic reticulum, few mitochrondria, and sparse glycogen accumulations. The scarcity of cytoplasmic organelles gave a pale immature appearance to the cytoplasm. By scanning electron microscopy, the sponge-like surface of large mature megakaryocytes from unirradiated marrow contrasted with the characteristically smooth, topographically featureless surfaces of the micromegakaryocytes from preleukemic dogs.

Animals↗
PubMed1982

The ultrastructure of radiation-induced endosteal myelofibrosis in the dog.

A rapidly developing, progressive form of endosteal myelofibrosis (MF) (with myeloid metaplasia) has been shown to occur at low frequency (approximately 4%) in dogs exposed continuously to low daily doses (10 R/day) of whole-body gamma irradiation. We report in this study the morphological details of the endosteal surface during both preclinical and clinical phases of developing MF by combination light microscopy and scanning/transmission electron microscopy. Pronounced alterations of the endosteum were observed and included: (1) during the early preclinical phases, a progressive time-dependent transition of the endosteal surface from predominantly resting to actively formative and resorptive states; and (2) during the late preclinical phase, aberrant autonomous osteogenic process(es) characterized by a marked reduction in the resorptive, osteoclast-associated endosteal areas occurring concomitantly with further increases in formative areas of the endosteum. Localized patches of overlapping, morphologically transformed endosteal cells (i.e., round-osteoblastic to branched-reticular shaped) were observed within the morphologically reactive, formative endosteum. Osteogenic-endosteal changes coincided with major restructuring of the hematopoietic parenchyma and supporting stromal network. We discuss the possibility that the early occurring endosteal changes are causally linked to normal reparative functions that operate during regenerative hematopoiesis following local and systemic injury. Based on morphological data collected during the late preclinical phase, we speculate that the mechanism of myelofibrosis induction involves the failure to terminate early osteogenic-dependent repair sequences.

Animals↗
PubMed1981

Antiviral properties of polyinosinic acids containing thio and methyl substitutions.

Polyinosinic acids containing methyl and sulphur substitutions are potent inhibitors of reverse transcriptase. Substitution of sulphur for oxygen at the 6 position produces significant effects on the properties of polyinosinic acid: the kinetics of inhibition change from competitive to mixed-type and the inhibition constant falls by three orders of magnitude. In contrast, 1-methyl substitution produces no such effects. Poly(1-methyl-6-thioinosinic acid) or poly(m1s6I) inhibits irreversibly, inhibiting all ten reverse transcriptases tested under a variety of assay conditions. In cell culture test systems, poly(m1s6I) is capable of blocking both infection by non-transforming viruses and transformation by a sarcoma virus. The presence of poly(m1s6I) in a preinfected culture results in the production of non-infectious virus particles lacking reverse transcriptase activity.

Avian Myeloblastosis Virus↗
PubMed1981

Sequential changes in bone marrow architecture during continuous low dose gamma irradiation.

Beagles continuously exposed to low daily doses (10 R) of whole-body 60Co gamma-radiation are prone to develop either early occurring aplastic anemia or late occurring myeloproliferative disorders (Seed et al., 1977). In this study, we have examined by a combination of light microscopy and scanning and transmission electron microscopy the sequential changes in the morphology of biopsied rib bone marrow of continuously irradiated dogs that developed either aplastic anemia, myelofibrosis, or myelogenous leukemia. Characteristic modification of key elements of marrow architecture have been observed during preclinical and clinical phases of these hemopathological conditions. The more prominent of these changes include the following. (i) In developing aplastic anemia: severe vascular sinus and parenchymal cord compression, and focally degenerate endosteal surfaces. (ii) In developing myelofibrosis: hyperplasia of endosteal and reticular stomal elements. (iii) In developing leukemia: hypertrophy of reticular and endothelial elements in the initial restructuring of the stromal matrix and the subsequent aberrant hemopoietic repopulation of the initially depleted stromal matrix. These architectural changes during preclinical phases appear to be related to the pathological progression to each of the radiation-induced hemopathological end points.

Animals↗