Biomedical subjects

K McCuaig

Publications and source records attributed to K McCuaig.

8 recordsLinked to original sources

PubMed1996

Differential effects and glucocorticoid potentiation of bone morphogenetic protein action during rat osteoblast differentiation in vitro.

Bone morphogenetic proteins (BMPs) induce cartilage and bone differentiation in vivo and promote osteoblast differentiation from calvarial and marrow stromal cell preparations. Functional differences between BMP-2, -4, and -6 are not well understood. Recent investigations find that these three closely related osteoinductive proteins may exert different effects in primary rat calvarial cell cultures, suggesting the possibility of unique functions in vivo. In this study, we use a fetal rat secondary calvarial cell culture system to examine the differential effects of BMP-2, -4, and -6 on early osteoblast differentiation. These cells do not spontaneously differentiate into osteoblasts, as do cells in primary calvarial cultures, but rather require exposure to a differentiation initiator such as glucocorticoid or BMP. We determined that BMP-6 is a 2- to 2.5-fold more potent inducer of osteoblast differentiation than BMP-2 or -4. BMP-6 induced the formation of more and larger bone nodules as well as increased osteocalcin secretion. The effects of all three of these BMPs were potentiated up to 10-fold by cotreatment or pretreatment with the glucocorticoid triamcinolone (Trm). The Trm effects were synergistic with those of BMP-2 or -4, suggesting that this glucocorticoid may increase the cell responsiveness to these BMPs. Finally, BMP-6 did not require either cotreatment or pretreatment with Trm to achieve greater amounts of osteoblast differentiation than seen with BMP-2 or BMP-4 treatment, suggesting that BMP-6 may act at an earlier stage of cell differentiation.

Animals↗

PubMed1994

Highly potent transcriptional activation by 16-ene derivatives of 1,25-dihydroxyvitamin D3. Lack of modulation by 9-cis-retinoic acid of response to 1,25-dihydroxyvitamin D3 or its derivatives.

Although several studies have been performed on the biological activities of analogs of 1,25-dihydroxyvitamin D3 (1,25-(OH)2 D3) at the whole animal and cellular levels, little work has been done to analyze their transcriptional activation properties. A highly inducible 1,25-(OH)2 D3-responsive promoter composed of three copies of the mouse osteopontin vitamin D3 response element (VDRE3) inserted upstream of a herpes simplex virus thymidine kinase promoter has been constructed, and its transcriptional properties have been analyzed by transient transfection into the monkey kidney cell line COS-7 and the rat osteoblast-like osteosarcoma line ROS 17/2.8. We have studied systematically transcriptional activation by a number of 1,25-(OH)2 D3 analogs, particularly those substituted at positions 16, 23, 26, and 27, sites that are targets for metabolism. Strikingly, except for derivatives that bind the 1,25-(OH)2 D3 receptor (VDR) very weakly, we find no parallel between the potency of action of a derivative as a transcriptional inducer and its affinity for the VDR. Derivatives substituted by multiple bonds at positions 16 and/or 23, although having varying affinities for the VDR, all stimulate transcription more potently than D3, in some cases at 100-fold lower concentrations. The peak transcriptional activity observed varies by only approximately 20% among different active analogs, indicating little difference in the activity of the VDR once bound to ligand. Gel retardation assays with ROS 17/2.8 nuclear extracts suggest that the VDR binds to the mouse osteopontin VDRE predominantly as a heterodimer with retinoid X receptor(s) (RXR(s)). We find that 9-cis-retinoic acid, the cognate ligand for RXRs, does not have a significant effect on the response of the VDRE3 promoter to 1,25-(OH)2 D3 or a number of its derivatives in ROS 17/2.8 or in COS-7 cells, under conditions in which promoters containing retinoid X response elements are activated. This suggests that 9-cis-retinoic acid may not act on the response to 1,25-(OH)2 D3 or its derivatives by directly influencing the transcriptional activity of VDR/RXR heterodimers. This promoter/reporter system should be useful for analyzing the tissue-specific transcriptional activity of 1,25-(OH)2 D3 and its derivatives in any cell type amenable to transient transfection.

Animals↗

PubMed1994

Surgical problems in space: an overview.

Terrestrial experience indicates that surgical emergencies may cause significant morbidity in space, and may present unique problems. Microgravity physiologic changes that may increase susceptibility to, and complications from, injury include fluid redistribution and diuresis, bone demineralization, and immune system alterations. Conventional diagnostic tests may be unavailable or unreliable--e.g. the radiologic finding of "air under the diaphragm", which conventionally indicates perforation of an air-containing hollow viscus, such as the stomach, with a gravity-dependent rising of gas in the abdominal cavity to collect under the diaphragm. Microgravity surgical experience is limited, but studies conducted in the U.S.S.R. and on KC-135 aircraft indicate that, although surgical procedures are possible, weight and volume constraints, lack of gravity, altered fluid mechanics, and risk of environmental contamination mandate considerable modifications of conventional equipment and technique.

Animals↗

PubMed1993

Expression of the Bgp gene and characterization of mouse colon biliary glycoprotein isoforms.

The biliary glycoprotein (BGP)-encoding gene is a member of the human carcinoembryonic antigen (CEA) gene family. We have now cloned several mouse Bgp cDNAs from an outbred CDR-1 mouse colon cDNA library, as well as by reverse transcription-PCR amplification of colon RNA. The distinguishing features of the deduced Bgp protein isoforms are found in the two divergent N-terminal domains, the highly conserved internal C2-set immunoglobulin domains, and an intracytoplasmic domain of either 10 or 73 amino acids (aa). The cDNA structures suggest that these mRNAs are produced through alternative splicing of a Bgp gene and the usage of multiple transcriptional terminators. The Bgp deduced aa sequences are highly homologous to several well characterized rat hepatocyte proteins such as the cell CAM105/ecto-ATPase/pp120/HA4 proteins. Oligodeoxyribonucleotide probes representing the various cDNA isoform domains revealed predominant transcripts of 1.8, 3.1 and 4.0 kb on Northern analyses of mouse colon RNA; some of these bands are actually composed of several co-migrating transcripts. The transcripts encoding the long intracytoplasmic-tailed Bgp proteins are expressed at one-tenth the relative abundance of the shorter-tailed species. We have previously demonstrated that several mouse Bgp cDNAs, when transfected into eukaryotic cells, express BGP proteins at the cell surface and function in vitro as cell adhesion molecules, much like their human and rat counterparts. The expression of the many Bgp isoforms at the surface of epithelial cells, such as colon, suggests that these proteins play a determinant role, through self- or heterologous contact, in renewal and/or differentiation of their epithelia.

Amino Acid Sequence↗

PubMed1993

Several members of the mouse carcinoembryonic antigen-related glycoprotein family are functional receptors for the coronavirus mouse hepatitis virus-A59.

Mouse hepatitis virus-A59 (MHV-A59), a murine coronavirus, can utilize as a cellular receptor MHVR, a murine glycoprotein in the biliary glycoprotein (BGP) subfamily of the carcinoembryonic antigen (CEA) family in the immunoglobulin superfamily (G.S. Dveksler, M. N. Pensiero, C. B. Cardellichio, R. K. Williams, G.-S. Jiang, K. V. Holmes, and C. W. Dieffenbach, J. Virol. 65:6881-6891, 1991). Several different BGP isoforms are expressed in tissues of different mouse strains, and we have explored which of these glycoproteins can serve as functional receptors for MHV-A59. cDNA cloning, RNA-mediated polymerase chain reaction analysis, and Western immunoblotting with a monoclonal antibody, CC1, specific for the N-terminal domain of MHVR showed that the inbred mouse strains BALB/c, C3H, and C57BL/6 expressed transcripts and proteins of the MHVR isoform and/or its splice variants but not the mmCGM2 isoform. In contrast, adult SJL/J mice, which are resistant to infection with MHV-A59, express transcripts and proteins only of the mmCGM2-related isoforms, not MHVR. These data are compatible with the hypothesis that the MHVR and mmCGM2 glycoproteins may be encoded by different alleles of the same gene. We studied binding of anti-MHVR antibodies or MHV-A59 virions to proteins encoded by transcripts of MHVR and mmCGM2 and two splice variants of MHVR, one containing two immunoglobulin-like domains [MHVR(2d)] and the other with four domains as in MHVR but with a longer cytoplasmic domain [MHVR(4d)L]. We found that the three isoforms tested could serve as functional receptors for MHV-A59, although only isoforms that include the N-terminal domain of MHVR were recognized by monoclonal antibody CC1 in immunoblots or by MHV-A59 virions in virus overlay protein blot assays. Thus, in addition to MHVR, both the two-domain isoforms, mmCGM2 and MHVR(2d), and the MHVR(4d)L isoform served as functional virus receptors for MHV-A59. This is the first report of multiple related glycoprotein isoforms that can serve as functional receptors for a single enveloped virus.

3T3 Cells↗

PubMed1992

Simulation of blood flow in microgravity.

Knowledge of venous, capillary, and arterial blood flow in microgravity is required to modify hemostatic techniques for control of bleeding in traumatic injuries or surgical procedures in space. To simulate human arterial, venous, and capillary bleeding, fresh whole bovine blood was injected by two operators at calculated flow rates (3.5, 7, and 14 mL for venous and 14 and 28 mL for arterial) in 10 seconds with empirical controls in a lucent glove box during zero gravity parabolic flight on NASA's KC-135 aircraft. A pig's foot was used to mimic capillary bleeding. Hemostasis with sponges and laerdal suction was evaluated by video and still photography. Evaluations of the arterial and venous bleeding were conducted at 3 rates x 3 parabolas, and capillary bleeding was evaluated with 5 parabolas x 2 methods (pig's foot and sponge). Influenced by surface tension, the slow venous bleeding coated syringe surfaces and formed a dome over the skin laceration bleeding site. Arterial and venous bleeders broke into uniform spheres with low-velocity spheres bouncing off an absorbent pad and suction tip. Conventional dabbing with gauze fragmented blood into small spheres. Capillary oozing was better controlled by "wicking" up blood with gauze. Repeated arterial bleeding opacified the glove box wall. This stimulation demonstrated unique characteristics of extracorporeal blood flow and inadequacies of common methods of hemostasis in microgravity.

Animals↗

PubMed1992

Aseptic technique in microgravity.

Within the next decade, the United States will launch a space station into low Earth orbit as a preliminary step toward a manned mission to Mars. Provision of asepsis in the unique microgravity environment, essential in operative and invasive procedures, is addressed. An assessment of conventional terrestrial aseptic methods and possible modifications for a microgravity environment was done during the microgravity portion of parabolic flight on NASA KC-135 aircraft. During 110 parabolas on three flight days, a "surgical team" (surgeon, scrub nurse and circulating nurse) using a life size mannequin fastened to a prototype surgical "work station" (operating table), evaluated open and closed gloving (ten parabolas), skin preparation (six parabolas), surgical scrub methods (24 parabolas), gowning (22 parabolas) and draping (48 parabolas). Evaluated were povidone iodine solution, 1 percent povidone iodine detergent, Chloroxylenol with detergent, wet prep soap sponge, a water insoluble iodophor polymer (DuraPrep, 3M), disposable towels, disposable and reusable gowns, large and small disposable drapes with and without adhesive edges, disposable latex surgeon's gloves with and without packaging modifications and restraint mechanisms (tether, swiss seat, waist and foot restraint devices, fairfield and wire clamps and clips). Ease of use, provision of restraint for supplies and personnel and waste disposal were assessed. The literature was reviewed and its relevance to the space environment discussed, including risk factors, environmental contamination, immune status and microbiology. The microgravity environment, limited water supply and restricted operating area mandated that modifications of fabrication and packaging of supplies and technique be made to create and preserve asepsis. Material must meet stringent flammability and off-gassing standards. Either a chlorhexidine or povidone iodine detergent prepackaged brush and sponge would provide an adequate scrub plus preliminary cleansing of a dirty wound. Choice may depend on ease of removal from the water supply as well as sensitivity to each compound of individual crew members. Rinsing was achieved with sterile water soaked gauze. Drying would be more efficient with two small hand towels, which would be easier to manipulate in microgravity and require less stowage volume. Skin preparation highlighted unexpected packaging problems, as centrifugal force was required to "shake" the solution out of the container on to the mannequin. To minimize contamination, a gown should be folded in an accordion manner and fastened to the base of its sterile wrapper, so that an assistant can compensate for the lack of gravity by applying constant tension.(ABSTRACT TRUNCATED AT 400 WORDS)

Aerospace Medicine↗

PubMed1992

mmCGM1a: a mouse carcinoembryonic antigen gene family member, generated by alternative splicing, functions as an adhesion molecule.

Carcinoembryonic antigen is a human tumor marker and the prototype of a large family of immunoglobulin-like proteins. We have been developing a mouse model for this large protein family and have cloned a complementary DNA (cDNA) for a mouse carcinoembryonic antigen gene family member (mmCGM1a). Two transcripts expressed in several different adult mouse tissues hybridize to this cDNA, a 1.8-kilobase and a 4.6-kilobase mRNA. Sequences of many related cDNA clones indicate that they are most likely encoded by a single gene which undergoes alternative splicing. The protein encoded by the mmCGM1a cDNA shares 69% of the amino acid residues in the NH2-terminal domain with a rat liver ecto-ATPase and with the human biliary glycoprotein. Mouse fibroblast transfectant cells expressing the mmCGM1a protein on their cell surface exhibit calcium- and temperature-independent adhesion in vitro which can be specifically inhibited by an antibody raised against a carcinoembryonic antigen-related 120 kilodalton protein.

Amino Acid Sequence↗