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Biomedical subjects

J W Armstrong

Publications and source records attributed to J W Armstrong.

At least 19 recordsLinked to original sources
PubMed2001

Quarantine security of bananas at harvest maturity against Mediterranean and Oriental fruit flies (Diptera: Tephritidae) in Hawaii.

Culled bananas (dwarf 'Brazilian', 'Grand Nain', 'Valery', and 'Williams') sampled from packing houses on the islands of Hawaii, Kauai, Maui, Molokai, and Oahu identified specific "faults" that were at risk from oriental fruit fly, Bactrocera dorsalis (Hendel), infestation. Faults at risk included bunches with precociously ripened bananas, or bananas with tip rot, fused fingers, or damage that compromised skin integrity to permit fruit fly oviposition into fruit flesh. No Mediterranean fruit fly, Ceratitis capitata (Wiedemann), or melon fly, B. cucurbitae (Coquillett), infestations were found in culled banana samples. Field infestation tests indicated that mature green bananas were not susceptible to fruit fly infestation for up to 1 wk past the scheduled harvest date when attached to the plant or within 24 h after harvest. Recommendations for exporting mature green bananas from Hawaii without risk of fruit fly infestation are provided. The research reported herein resulted in a USDA-APHIS protocol for exporting mature green bananas from Hawaii.

Animals↗
PubMed2001

Potential for areawide integrated management of Mediterranean fruit fly (Diptera: Tephritidae) with a braconid parasitoid and a novel bait spray.

The braconid wasp, Fopius arisanus (Sonan), a biological control agent for Mediterranean fruit fly, Ceratitis capitata (Wiedemann), was studied in coffee, Coffea arabica L. Fopius arisanus, comprised 79.3% of the total parasitoids (7,014) recovered from fruits collected at three small coffee farms. Data from seasonal host/parasitoid studies at a large coffee plantation also suggested that the most effective natural enemy of C. capitata in coffee may now reside in Hawaii. The original parasitoids introduced into Hawaii for C. capitata control (Diachasmimorpha tryoni (Cameron), Tetrastichus giffardianus Silvestri, and Dirhinus giffardii Silvestri) are now rare. Abundance of F. arisanus with respect to other parasitoids collected was influenced by elevation (274, 457, 610 m). Fopius arisanus was the dominant parasitoid at all three elevations, Diachasmimorpha longicaudata (Ashmead) occurred consistently, and T. giffardianus was abundant only at low elevation. The impacts on C. capitata and F. arisanus populations of bait sprays containing malathion, spinosad, or phloxine B applied to coffee were also evaluated. All three bait sprays suppressed C. capitata populations. Spinosad and phloxine B bait sprays appeared less harmful to the wasp than malathion. Fopius arisanus offers the potential for areawide management of C. capitata that includes biological control and integration with more environmentally safe chemical controls such as spinosad and phloxine B bait sprays.

Animals↗
PubMed1998

Macrophage cell lines derived from major histocompatibility complex II-negative mice.

Two bone-marrow-derived macrophage cell lines, C2D and C2Dt, were isolated from major histocompatibility class II negative knock-out mice. The C2D cell line was stabilized by continuous culture in colony-stimulating factor-1 and the C2Dt cell line was transformed with SV40 virus large T antigen. These cells exhibited phenotypic properties of macrophages including morphology and expression of Mac 1 and Mac 2 cell surface molecules. These cells also had comparable growth to the bone-marrow-derived macrophage cell line B6MP102. These new cell lines were not spontaneously cytotoxic and were only capable of modest killing of F5b tumor cells when stimulated with LPS and interferon-gamma, but not when stimulated with LPS alone or with staphylococcal exotoxin. C2D and C2Dt cells phagocytosed labeled Staphylococcus aureus similarly to B6MP102 cells but less well than C2D peritoneal macrophages. These cell lines secreted interleukin-6, but not tumor necrosis factor or nitric oxide in response to LPS or staphlococcal enterotoxins A or B C2D(t) cells were tumorigenic in C2D and C57BL/6J mice but C2D cells were not. These data suggest that macrophage cell lines can be established from bone marrow cells of major histocompatibility complex II-negative mice.

Animals↗
PubMed1995

The effect of space and parabolic flight on macrophage hematopoiesis and function.

We used weak electric fields to monitor macrophage spreading in microgravity. Using this technique, we demonstrated that bone marrow-derived macrophages responded to microgravity within 8 s. We also showed that microgravity differentially altered two processes associated with bone marrow-derived macrophage development. Spaceflight enhanced cellular proliferation and inhibited differentiation. These data indicate that the space/microgravity environment significantly affects macrophages.

Animals↗
PubMed1995

The effects of rM-CSF and rIL-6 therapy on immunosuppressed antiorthostatically suspended mice.

Antiorthostatically suspended mice had suppressed macrophage development in both unloaded and loaded bones, indicating a systemic effect. Bone marrow cells from those mice secreted less macrophage colony-stimulating factor (M-CSF) and interleukin-6 (IL-6) than did control mice. Because M-CSF and IL-6 are important to bone marrow macrophage maturation, we formulated the hypothesis that suppressed macrophage development occurred as a result of the depressed levels of either M-CSF or IL-6. To test the hypothesis, mice were administered recombinant M-CSF or IL-6 intraperitoneally. We showed that recombinant M-CSF therapy, but not recombinant IL-6 therapy, reversed the suppressive effects of antiorthostatic suspension on macrophage development. These data suggest that bone marrow cells that produce M-CSF are affected by antiorthostatic suspension and may contribute to the inhibited maturation of bone marrow macrophage progenitors.

Animals↗
PubMed1994

Effects of extracellular matrix proteins on macrophage differentiation, growth, and function: comparison of liquid and agar culture systems.

Both spaceflight and skeletal unloading suppress the haematopoietic differentiation of macrophages (Sonnenfeld et al., Aviat. Space Environ. Med., 61:648-653, 1990; Armstrong et al., J. Appl. Physiol., 75:2734-2739, 1993). The mechanism behind this reduction in haematopoiesis has yet to be elucidated. However, changes in bone marrow extracellular matrix (ECM) may be involved. To further understand the role of ECM products in macrophage differentiation, we have performed experiments evaluating the effects of fibronectin, laminin, collagen type I, and collagen type IV on macrophage development and function. Bone marrow-derived macrophages cultured on four different ECM substrates in liquid culture medium showed less growth than those cultured on plastic. Significant morphological differences were seen on each of the substrates used. Phenotypically and functionally, as measured by class II major histocompatibility molecule (MHCII) expression, MAC-2 expression, and the secretion of interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-alpha), these macrophages were similar. In contrast, bone marrow-derived macrophages cultured in suspension, using agar, showed no difference in growth when exposed to ECM proteins. However, IL-6 and TNF-alpha secretion was affected by fibronectin, laminin, collagen type I, and collagen type IV in a concentration-dependent manner. We conclude that the ECM products fibronectin, laminin, collagen type I, and collagen type IV have profound effects on macrophage development and function. Additionally, we suggest that an ECM-supplemented agar culture system provides an environment more analogous to in vivo bone marrow than does a traditional liquid culture system.

Agar↗
PubMed1994

Class I and class II major histocompatibility molecules play a role in bone marrow-derived macrophage development.

Class I and class II major histocompatibility complex (MHC) molecules play significant roles in T cell development and immune function. We show that MHCI- and MHCII-deficient mice have low numbers of macrophage precursors and circulating monocytes, as well as abnormal bone marrow cell colony-stimulating factor type 1 secretion and bone composition. We suggest that MHCI and MHCII molecules play a significant role in macrophage development.

Animals↗
PubMed1994

Thyroid epithelial morphogenesis in vitro: a role for bumetanide-sensitive Cl- secretion during follicular lumen development.

The structural and functional unit of the thyroid gland is the follicle, consisting of a closed lumen surrounded by a single layer of polarized epithelial cells. In this paper we have attempted to characterize the process of lumenal development when primary cultures of porcine thyroid cells reorganized to form follicles. Cells incubated with the loop diuretic, bumetanide, an inhibitor of NaK2Cl cotransport, aggregated but failed to form normal follicles. Laser scanning confocal microscopy combined with immunohistochemical markers of thyroid cell-surface proteins demonstrated that in the presence of bumetanide cells polarized and assembled ZO-1-containing tight junctions separating their apical and basolateral membrane domains. Cultures formed small lumena but their subsequent growth was inhibited by bumetanide. Electrophysiological studies confirmed that bumetanide-sensitive Cl- transport was the major contributor to the transepithelial electrical potential difference across the follicular wall after 48 h incubation. Other potential mechanisms did not contribute significantly to follicular lumenal growth. In particular, bumetanide did not affect cell proliferation and, in contrast to tissue follicles, thyroglobulin could not be detected within the lumena of cultured follicles. We conclude that thyroid follicular reorganization involves two distinct and separate phases of lumenal development: initial lumen formation which probably reflects the assembly of a specialized apical membrane domain; and subsequent lumenal growth which is mediated by the inward transport of Cl- by polarized epithelial cells.

Animals↗
PubMed1994

Binding and activation of major histocompatibility complex class II-deficient macrophages by staphylococcal exotoxins.

Macrophages from C2D transgenic mice deficient in the expression of major histocompatibility complex (MHC) class II proteins were used to identify binding sites for superantigens distinct from the MHC class II molecule. Iodinated staphylococcal enterotoxins A and B (SEA and SEB) and exfoliative toxins A and B (ETA and ETB) bound to C2D macrophages in a concentration-dependent and competitive manner. All four toxins increased F-actin concentration within 30 s of their addition to C2D macrophages, indicating that signal transduction occurred in response to toxin in the absence of class II MHC. Furthermore, ETA, ETB, SEA, and, to a lesser extent, SEB induced C2D macrophages to produce interleukin 6. Several molecular species on C2D macrophages with molecular masses of 140, 97, 61, 52, 43, and 37 kDa bound SEA in immunoprecipitation experiments. These data indicate the presence of novel, functionally active toxin binding sites on murine macrophages distinct from MHC class II molecules.

Actins↗
PubMed1994

Interleukin-2 therapy reverses some immunosuppressive effects of skeletal unloading.

Using antiorthostatic suspension, we characterized hematopoietic changes that may be responsible for the detrimental effect of skeletal unloading on macrophage development. Skeletally unloaded mice had suppressed macrophage development in unloaded and loaded bones, which indicated a systemic effect. Bone marrow cells from unloaded mice secreted less macrophage colony-stimulating factor and interleukin-6 than control mice. Additionally, T-lymphocyte proliferation was reduced after skeletal unloading. We show that polyethylene glycol-interleukin-2 therapy reversed the effects of skeletal unloading on macrophage development and cell proliferation.

Animals↗
PubMed1993

Staphylococcus-mediated T-cell activation and spontaneous natural killer cell activity in the absence of major histocompatibility complex class II molecules.

We used major histocompatibility complex class II antigen-deficient transgenic mice to show that in vitro natural killer cell cytotoxicity and T-cell activation by staphylococcal exotoxins (superantigens) are not dependent upon the presence of major histocompatibility complex class II molecules. T cells can be activated by exotoxins in the presence of exogenously added interleukin 1 or 2 or in the presence of specific antibody without exogenously added cytokines.

Animals↗
PubMed1993

Activation of sodium transport mediates regulation of thyroid follicle volume in response to hypotonic media.

The thyroid epithelium possesses a bidirectional fluid transport system capable of absorbing Na+ and secreting Cl-. In the present studies we have examined its possible role in the regulation of thyroid follicular size. When exposed to hypotonic media (200 mosM) cultured porcine thyroid follicles first swelled and then displayed a regulatory volume decrease (RVD) over 60 min. This was associated with a transient depolarization of the transepithelial potential difference (TEP) and subsequent hyperpolarization with a time course similar to RVD. Phenamil (1 microM), an antagonist of epithelial Na+ channels, did not affect initial swelling but prevented the subsequent follicular RVD. Phenamil abolished hyperpolarization of TEP, but the loop diuretic bumetanide, which inhibits Cl- secretion in thyroid cells, did not prevent it. Exposure to hypotonic medium produced a slow hyperpolarization of the intracellular potential (basolateral membrane potential) consistent with an increase in basolateral membrane K+ conductance. Ba2+ and quinidine, which are known to inhibit K+ channels in epithelia, prevented RVD. Addition of the K+ ionophore valinomycin (1 microM) caused follicle shrinkage that was prevented by phenamil (1 microM). We conclude that cultured follicles respond to hypotonically induced stretch by activating outwardly directed Na+ transport through a mechanism which involves change in the basolateral K+ conductance. This response would be characteristic of a system that controlled follicle volume. However, it is not clear from these studies whether the cells responded primarily to the increase in follicle volume or to the change in cell volume that is expected to accompany hypotonic challenge.

Amiloride↗
PubMed1993

Skeletal unloading causes organ-specific changes in immune cell responses.

The effects of skeletal unloading using antiorthostatic tail suspension on the mouse immune system are tissue specific. This phenomenon was demonstrated by analyzing cells from the lymph nodes, spleen, and bone marrow. Phytohemagglutinin-induced T-cell proliferation was depressed in lymph nodes after 11 days of antiorthostatic suspension. In contrast, splenic T-cell proliferation in response to phytohemagglutinin was enhanced. Splenic natural killer cell cytotoxicity was unchanged after suspension, which demonstrated the organ- and cell-specific effects of skeletal unloading. Whereas antiorthostatic suspension induced minimal changes in bone, there was a significant depression in the number of macrophage precursors in the bone marrow. Overall, skeletally unloaded animals had slightly higher blood corticosterone levels than did control animals; however, it did not appear to be responsible for the observed changes. In conclusion, skeletal unloading produces organ- and cell-specific changes in the murine immune system rather than a generalized immunosuppression.

Animals↗
PubMed1992

Autogenous conchal cartilage as a replacement after a diskectomy.

A surgical procedure to place autogenous conchal cartilage as an interpositional graft after a diskectomy is described. The apparent advantages of this procedure are as follows: (1) the form of the external ear corresponds to joint morphology; (2) a graft of adequate size can be harvested; (3) the form of the external ear remains unchanged after surgery; (4) the graft can be obtained adjacent to the surgical site; (5) biologically acceptable material is used; (6) the additional expense of allogeneic grafts is avoided; and (7) excellent results have been reported.

Cartilage, Articular↗
PubMed1992

Chloride conductance of apical membrane in cultured porcine thyroid cells activated by cyclic AMP.

The thyroid epithelium transports fluid bidirectionally using active transport of Na+ ions from apical to basal poles and active transport of Cl- in the reverse direction. In these studies we sought evidence for cyclic AMP activated Cl- channels on the apical membranes of thyroid cells in monolayer culture. A Cl(-)-dependent basal-positive short-circuit current (ISC) was demonstrated in bicameral chambers after blocking Na+ transport with phenamil, and responded to prostaglandin (PG) E2 with a spike of 5-10 min duration followed by a plateau. The onset of the spike coincided with an increase in the conductance of the epithelium. Application of an external Cl- concentration gradient, by replacing the medium in the apical compartment with Cl(-)-free medium, resulted in an increase in ISC after, but not before, addition of PGE2. Forskolin and thyroid-stimulating hormone (TSH), but not A23187, also stimulated Cl- transport. In conjunction with previous observations that Cl- transport was mediated by a bumetanide-sensitive NaKCl2 symporter on the basal membrane, these observations indicated the presence of a cyclic AMP activated Cl- conductance in the apical membrane of thyroid cells.

Animals↗
PubMed1991

Regulation of thyroid follicular volume by bidirectional transepithelial ion transport.

Previous studies have shown that thyroid cells in monolayer culture exhibit bidirectional ion transport comprising apical-to-basal amiloride-sensitive Na+ transport and oppositely directed bumetanide-sensitive Cl- transport. We have now investigated the role of ion transport in the regulation of thyroid follicular size using follicular primary porcine thyroid cell cultures. Bumetanide (10 microM) added at the beginning of culture inhibited the formation of follicular lumina and caused a fall in follicle height when added to 3-day-old cultures. In contrast, phenamil (1 microM; an amiloride analog) increased follicle size both in freshly isolated and 3-day-old cultures. The effect of bumetanide was prevented by the prior addition of phenamil. Micropuncture studies showed that follicles had a lumen-negative, basal-positive transepithelial potential difference which was progressively reduced in magnitude by the serial addition of bumetanide (10 microM) and phenamil (1 microM). We conclude that thyroid follicles possess a bidirectional ion transport system which transports Na+ in an apical-to-basal direction and Cl- in the opposite direction. The balance between these two processes determines net solute flux and hence follicular size. A physiological role of ion transport in the thyroid may be to regulate follicular volume suggesting that abnormalities of ion transport may be responsible for disorders of follicular size.

Animals↗