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Biomedical subjects

G R Johnson

Publications and source records attributed to G R Johnson.

At least 127 records · Page 7Linked to original sources
PubMed1990

Resting and activated subsets of mouse multipotent hematopoietic stem cells.

The fluorescent vital dye rhodamine 123 (Rh-123), which preferentially accumulates in mitochondrial membranes, can be used as a probe to indicate mitochondrial and hence cellular activity. In this study, mouse bone marrow hematopoietic stem cells were subdivided into Rh-123lo, Rh-123med, and Rh-123hi populations. The Rh-123lo (resting) population was significantly enriched in cells with a higher proliferative potential compared to the Rh-123hi (activated) population. The resting population exhibited a 20-fold greater ability to differentiate into splenic colony-forming units (CFU-S) relative to the activated population, whereas the activated population contained about 4-fold more day 13 CFU-S on primary transfer relative to the resting population. The two populations produced morphologically distinct splenic colonies; however, the frequency and morphology of in vitro colonies were very similar. Only the resting population provided sufficient stem cells to transfer long-term hematopoietic repopulation to secondary recipient animals after lethal irradiation. On a single cell level, the resting and activated populations exhibited an equivalent ability to differentiate into lymphoid and myeloid progeny. These observations provide further insight into the heterogeneous nature of CFU-S and directly demonstrate that multipotent hematopoietic stem cells are heterogeneous with regard to their clonogenic capacities.

Animals↗
PubMed1990

In vivo expression of interleukin 5 induces an eosinophilia and expanded Ly-1B lineage populations.

In vitro, murine interleukin 5 (IL-5) acts as a colony-stimulating factor for eosinophils and induces B cells to proliferate and secrete antibody. In order to assess the biological effects of IL-5 in vivo, we transplanted lethally irradiated mice with bone marrow cells infected with a recombinant retrovirus bearing the IL-5 coding sequence. Within 2 weeks the peripheral blood of recipient mice exhibited a marked eosinophilia which persisted for at least 12 months, and an excess number of eosinophils was also evident in the bone marrow, spleen, liver, lung, and gut. Although no changes could be detected in the conventional B lymphocyte population, the peritoneum was replete with B cells characteristic of the Ly-1 lineage. Despite these expanded cell populations, mice remained healthy for 12 months after transplantation. These results suggest that IL-5 acts primarily on eosinophils and B cells of the Ly-1 lineage and that persistent overproduction of these cell types is not pathogenic.

Animals↗
PubMed1990

Value of the cutaneous basophil hypersensitivity (CBH) response for distinguishing weak contact sensitization from irritation reactions in the guinea pig.

Numerous studies of the histology of allergic contact dermatitis reactions to potent allergens in guinea pigs and humans have indicated that there is significant tissue infiltration with basophilic leukocytes. In this study we determined whether this histologic finding could be of value in distinguishing weak sensitization reactions from primary irritation, thereby aiding in the predictive identification of weak or moderate contact allergens. Guinea pigs were sensitized by the Buehler test method. Skin reactions were graded 24, 48, and 72 h post-challenge with duplicate patch sites biopsied at the 24- or 72-h grading timepoints. The biopsies were fixed, embedded in glycol methacrylate, thin sectioned, and Giemsa stained. The number of basophils per 400 leukocytes were counted along the upper dermis just below the dermal/epidermal junction. Challenge patch sites from animals sensitized to a relatively low dose of the strong contact allergen, oxazolone, were compared with patch sites from animals challenged only with a strong irritant, sodium lauryl sulfate (SLS). Compared to normal skin (7.5 +/- 1.0 basophils/400 leukocytes +/- SEM) only the oxazolone patch sites showed significant basophil infiltration (36.8 +/- 6.5), despite the fact that the skin reactions to the low oxazolone challenge dose were relatively weak. SLS patch sites showed no basophil infiltration above normal skin levels (4.8 +/- 0.9). Subsequent blinded studies compared weak/moderate presumptive sensitization reactions (as defined by accepted visual skin grading criteria) to various chemicals (citronellal, vanillin, cinnamic aldehyde, and ethylenediamine) to primary irritation reactions to the same chemicals. In each case, low-challenge-dose sensitization sites on previously treated (induced) animals showed mean basophil infiltration (range, 11.9-69.2 basophils/400 leukocytes) significantly greater than higher-dose irritant reactions (range, 1.6-13.3). The range for normal skin was 0.2-10.2 and the range for strong patch reactions to higher concentrations of oxazolone was 59.8-209.3. These data strongly indicate that light-microscopic quantitation of the CBH response can be used to distinguish relatively weak to moderate contact sensitization reactions from primary irritation reactions to the same chemicals.

Animals↗
PubMed1990

Effect of tube ovalling on pressure wave propagation speed.

For physiological and other flows it is often assumed that the pressure pulse wave speed is given by the classic Moens-Korteweg expression and this may be used, for example, to assist in the determination of in vivo blood vessel wall incremental Young's modulus. A number of physical factors affecting the value of this wave speed have been reviewed in the literature, but the effect of slight ovalling of the tube cross-section is rarely mentioned. The analysis for a tube of elliptic cross-section shows that even a very small degree of ovalling can cause quite substantial reductions in Young mode wave propagation velocities compared with the classic Moens-Korteweg expression. Bending-induced changes in cross-section shape with internal pressure increase the apparent elasticity of the tube wall. Experimental confirmation is provided by waterhammer wave speed measurements in a copper tube that has been ovalled by coiling. Even though the Young mode is not dominant in this case, as it would be for a physiological case, the measured wave speed is quite clearly less than the Moens-Korteweg theory and it can be shown that the small degree of measured tube ovality explains this.

Blood Flow Velocity↗
PubMed1990

Insulin-like growth factors promote DNA synthesis and support cell viability in fetal hemopoietic tissue by paracrine mechanisms.

There is significant evidence that the insulin-like growth factors (IGF) play a role in both murine and human hemopoiesis. In order to better define the nature and mechanisms of these effects, we have used a serum-free system to examine DNA synthesis and cell replication in murine hemopoietic cells. Cell preparations from 13-day fetal mice livers were incubated in serum-free DMEM alone or with erythropoietin (Epo) 0.5 U/ml, recombinant human IGF-I, purified IGF-II, or recombinant human growth hormone (GH) in various doses, and [3H]thymidine added for the last 3 hr of 21-hr incubation. Cell distribution was over 80% erythroid or erythroblasts. IGF-I and IGF-II promoted thymidine incorporation into cells at a half-maximal dose of 3 and 1 nM respectively, IGF-II with a maximum potency 65% of IGF-I; insulin stimulated at a half-maximum dose of 100 nM, with similar maximum effect to IGF-I, and their effects were not additive. GH was stimulatory at 1 microM. Epo was 2-9 times as effective as IGF-I and their effects were not additive. A monoclonal antibody to IGF-I reduced the effect of IGF-I by 50-80%, had no effect on Epo, and abolished the GH effect. Separation of erythroid cells and precursors from accessory and other liver cells did not alter the response to IGF-I. Cell counts increased in response to IGF-I or Epo, and cell viability was maintained by IGF-I compared to control medium.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

Mussel culture and the accumulation of domoic acid.

The cultured mussel industry of Prince Edward Island had never experienced a toxic disease problem until November of 1987. With the successful use of the long-line culture system, the yearly production of fresh mussels to the gourmet food market had risen to close to 3.2 million pounds (1.46 million kg) of product. The physiology of this sessile bivalve and its method of feeding and location in the estuary leave it prone to the accumulation of a widely distributed biotoxin. Eastern Prince Edward Island became the epicentre of domoic acid-intoxicated mussels as early as 10 November 1987 (retrospective samples) during an intense bloom of the diatom Nitzschia. Mussels were able to accumulate large amounts of the domoic acid with little effect on their own well-being. Despite being in low water temperatures (below 4 degrees C) and under thick ice cover, the levels of the toxin decreased and were undetectable in about 6 weeks. The following year the toxin was detected in much smaller amounts, and the levels of toxin accumulation demonstrated a variable lag time with the increase in concentration of Nitzschia available in the water column. The sales of Prince Edward Island cultured mussels have rebounded to about 140% of the pre-domoic acid crisis.

Animals↗
PubMed1989

Metabolism of 125I-atrial natriuretic factor by vascular smooth muscle cells. Evidence for a peptidase that specifically removes the COOH-terminal tripeptide.

The addition of 200 pM monoiodinated human atrial natriuretic factor-(99-126) (125I-hANF) to cultured bovine aortic smooth muscle cells at 37 degrees C resulted in a rapid clearance from the medium (t1/2 approximately 7.5 min). Within 5 min, [125I]iodotyrosine126 (125I-Y), Arg125-[125I]iodotyrosine126 (125I-RY) and Phe124-Arg-[125]iodotyrosine126 (125I-FRY) appeared in the medium. The identities of these degradation products were confirmed by 1) retention time on high performance liquid chromatography (HPLC) relative to standards, 2) products generated by digestion with aminopeptidase M, and 3) the absence of the Met110. Preincubation of the cells with ammonium chloride or chloroquine resulted in a significant increase in the intracellular accumulation of radiolabel, indicative of endocytosis and rapid delivery of 125I-hANF to an acidic intracellular compartment (endosome and/or lysosome). Neither ammonium chloride, chloroquine, nor excess unlabeled hANF blocked the rapid appearance in the medium of 125I-RY or 125I-FRY. Bestatin inhibited the generation of 125I-RY, with a concomitant increase in 125I-FRY, suggesting that the 125I-RY is produced by aminopeptidase action on 125I-FRY. The endopeptidase 24.11 (enkephalinase) inhibitor, SCH 39370, did not inhibit the formation of 125I-FRY. These results provide evidence of a peptidase capable of specifically removing the COOH-terminal tripeptide from 125I-hANF. The COOH-terminal tripeptide, Phe124-Arg-Tyr126, was also isolated from cell digests of hANF by HPLC and its identity confirmed by amino acid analysis. Since it is generally believed that the COOH-terminal tripeptide is critical to many of atrial natriuretic factor-(99-126)'s bioactivities, this enzyme may be involved in the inactivation of atrial natriuretic factor-(99-126) in target tissues.

Amino Acids↗
PubMed1989

Nonneoplastic hematopoietic myeloproliferative syndrome induced by dysregulated multi-CSF (IL-3) expression.

Post 5-fluorouracil-treated murine marrow cells were infected with a retroviral vector (MPZen) bearing a multi-potential colony stimulating factor (Multi-CSF) cDNA insert and then transplanted into lethally irradiated syngeneic recipients to study the effects of autocrine production of Multi-CSF in normal hematopoietic cells. Extremely high levels (14,000 U/mL) of Multi-CSF were detected in the sera and in media conditioned by various hematopoietic tissues of the transplanted animals. While spleen, peritoneal, and peripheral blood cellularity increased approximately 10-fold, 10-fold, and 50-fold, respectively, bone marrow cellularity decreased twofold. Progenitor numbers were depressed twofold in the bone marrow but elevated more than 100-fold in the spleen and peritoneum. The majority (80%) of transplanted mice died within 5 weeks of transplantation and showed extensive neutrophilic infiltration of the spleen, lung, liver, and muscle, often with mast cell foci; a phenomenon also seen in the skin and intestine. Neither the infected cells from hematopoietic tissues of the primary mice, nor autonomous mast cell-lines that grew from these cells in liquid culture produced any overt disease when transplanted into normal or sublethally irradiated secondary recipients. In contrast, injection into mice of autonomous FDC-P1 cells transformed by the same retroviral construct led to tumor formation in vivo within 4 weeks. Thus, dysregulated Multi-CSF expression by normal hematopoietic cells produces a fatal but nonneoplastic myeloproliferative syndrome.

Animals↗
PubMed1989

A lethal myeloproliferative syndrome in mice transplanted with bone marrow cells infected with a retrovirus expressing granulocyte-macrophage colony stimulating factor.

Murine bone marrow cells infected with a novel recombinant retrovirus, MPZen(GM-CSF), were engrafted into lethally irradiated recipients. The transplanted animals developed extremely high circulating levels of GM-CSF (up to 3 x 10(5) units/ml), and greatly elevated peripheral nucleated cell counts (up to 110 x 10(6) per ml). Their haemopoietic tissues contained GM-CSF proviral DNA and produced substantial levels of GM-CSF. The mice died within 4 weeks of transplantation with extensive neutrophil and macrophage infiltration of the spleen, lung, liver and peritoneal cavity and significant infiltration of both heart and skeletal muscle by neutrophils, macrophages and eosinophils. The thymus and lymph nodes were deficient in lymphoid cells. No disease occurred when infected cells from haemopoietic tissues of the primary transplanted animals were injected into normal or sub-lethally irradiated mice. Dysregulated GM-CSF expression by haemopoietic cells thus produces a fatal albeit non-neoplastic myeloproliferative syndrome.

Animals↗
PubMed1989

Murine myeloid cell lines derived by in vitro infection with recombinant c-myb retroviruses express myb from rearranged vector proviruses.

To date, cellular transformation in vitro by the myb oncogene has been described for avian haemopoietic cells only. In order to exploit the well-characterized murine haemopoietic system to study transformation by myb, we have infected fetal liver cells with retroviral vectors carrying cDNAs that encode either complete or carboxy-terminally truncated c-myb proteins. We describe four cell lines which, despite our ability to efficiently infect haemopoietic target cells, were generated at low frequency. This was due, as least in part, to the requirement for a rearrangement within the vector that allowed expression of myb sequences. Three of the lines express a truncated myb protein while the fourth apparently expresses a normal c-myb protein, and thus constitutes an exception to the general association of truncation with transformation by myb. All four cell lines resemble immature cells of the myelomonocytic lineage and are dependent on colony-stimulating factors (CSFs) for their growth in vitro. One representative line could be converted to CSF-independence by infection with either Abelson murine leukaemia virus or a recombinant granulocyte-macrophage-CSF-encoding retrovirus; unlike the parental line, the resultant sublines were highly tumorigenic when injected into syngeneic mice.

Amino Acid Sequence↗
PubMed1989

Gene transfer into hemopoietic stem cells using retroviral vectors.

Gene transfer to hemopoietic cells offers a variety of new approaches to the experimental hematologist as well as potentially providing a means for correcting a number of genetic disorders of humans. From the experimental viewpoint, gene transfer utilizing retroviral vectors introduces new methods for analyzing hemopoietic cell lineages, and the effects of over-expression of genes affecting hemopoietic cell proliferation and differentiation. The unique properties of retroviral vectors and the optimized methods currently in use to infect hemopoietic cells are represented as a brief review of a rapidly expanding new field of experimental hematology.

Animals↗
PubMed1989

Biomechanical aspects of the repair of intertrochanteric fractures.

A two-dimensional model of a repaired intertrochanteric fracture has been proposed in order to estimate the forces transmitted by a sliding screw implant and at the fracture site. These forces have been estimated from the radiographs of 55 repairs which were previously graded as satisfactory or unsatisfactory. The unsuccessful group was found to have significantly higher fracture angles as well as increased forces and moments transmitted by the implant. The results support the view that increased loading of implant and therefore high stresses in the surrounding cancellous bone contribute to the failure of repairs.

Aged↗
PubMed1989

Erythropoietin.

Erythropoietin mRNA is detected primarily in kidney peritubular cells in response to hypoxia, and this tissue is the major adult source of the hormone. Erythropoietin can be assayed by in vivo or in vitro biological methods, or by radioimmunoassay, but only the in vivo assay can distinguish the most biologically active forms. The mature hormone consists of 166 amino acids and approximately 50% of the mature molecule (Mr 39,000) consists of carbohydrate. The gene is highly conserved among species studied, and is located on human chromosome 7, region q11-q22. Recombinant erythropoietin has been administered to haemodialysis patients and shown to increase haemoglobin levels, reticulocyte numbers and haematocrit. In transfusion-dependent patients, the need for regular transfusions was abrogated. Problems with hypertension have been noted in previously hypertensive patients, but the results of clinical trials with erythropoietin suggest that it will provide a valuable alternative therapy, for correcting some disorders of erythropoiesis.

Anemia, Hemolytic↗
PubMed1989

Long-term exposure to retrovirally expressed granulocyte-colony-stimulating factor induces a nonneoplastic granulocytic and progenitor cell hyperplasia without tissue damage in mice.

Murine marrow cells infected with a retroviral vector (MPZen) bearing a granulocyte-colony-stimulating factor (G-CSF) cDNA insert were transplanted into lethally irradiated recipients to study the effects of autocrine production of G-CSF in normal hemopoietic cells. Most animals remained healthy with no evidence of tissue damage throughout the observation period (4-30 wk) despite high circulating G-CSF levels (range 2,000-26,000,000 U/ml). A dramatic neutrophilic granulocytosis was observed in all hemopoietic tissues with neutrophilic infiltration occurring in the lung and liver. Spleen, peritoneal, and peripheral blood cellularity increased approximately three-, two-, and eightfold, respectively, but total bone marrow cell counts remained unchanged. Progenitor cell numbers granulocyte-macrophage colony-forming cell (GM-CFC), granulocyte colony-forming cell (G-CFC), burst-forming unit-erythroid (BFU-E), colony-forming unit-erythroid (CFU-E) and mixed colony-forming cells (Mix-CFC) were elevated between 10-100-fold in the spleen, peritoneal cavity, and peripheral blood, but were unaffected or slightly depressed in the marrow. No tumors developed in syngeneic recipients transplanted with bone marrow or spleen cells from such mice, confirming the nonneoplastic nature of the hyperplasia induced by chronic G-CSF stimulation. These experiments also indicated the stable integration of MPZen vectors in infected cells, as evident from the continuous expression of the inserted gene for at least 6 mo, and from the ability of infected stem cells from the primary recipients to express the gene in lethally irradiated secondary recipients.

Animals↗
PubMed1989

Twisting of the human back in forward flexion.

This paper addresses the role of torsion in the production of spinal injury and in particular the possibility of injury resulting from torsion combined with flexion. The back movement of 16 normal male subjects was measured using a non-invasive, three-dimensional measurement system for assessing spinal mobility, the opto-electronic CODA-3 scanner. Measurements were made of the ability to twist the back while standing upright and in two flexed postures. Rotational ability was shown, in general, to be increased in a flexed posture, presumed to be due to an opening of the lumbar zygapophysial joints. This suggests that twisting in a flexed posture could be a mechanism for intervertebral disc injury.

Adult↗