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Biomedical subjects

A G King

Publications and source records attributed to A G King.

At least 19 recordsLinked to original sources
PubMed1996

Structure-activity relationships of novel hematoregulatory peptides.

Hematopoiesis is a lifelong cell renewal process regulated by a family of lineage specific hematopoietic growth factors. Several hematopoietic growth factors such as G-CSF, GM-CSF, and M-CSF have been clinically evaluated for enhancement of host defense in normal and immunocompromised patients and for the treatment of infectious diseases. This paper reports the structure-activity relationships of low molecular weight hematoregulatory peptides based on a nonapeptide (1, SK&F 107647). Like the macromolecular growth factors, these peptides modulate host defense. A molecular target for this class of compounds has not yet been identified. However, the structure-activity relationships established by this study implicate a very specific molecular recognition event that is pivotal for the biological activities of 1 and its analogues.

Amino Acid Sequence↗
PubMed1995

Isolation and characterisation of a uniquely regulated threonine, tyrosine phosphatase (TYP 1) which inactivates ERK2 and p54jnk.

The recent discovery of the vaccinia virus protein phosphatase VH1, and its mammalian counterparts has highlighted a novel subfamily of protein tyrosine phosphatases that exhibit dual specificity toward phosphotyrosine- and phosphoserine/threonine-residues. We have identified further members of this subfamily. The characterisation of one clone in particular, which we have named threonine-tyrosine phosphatase 1 (TYP 1), encodes a protein homologous to CL100, but differs dramatically in its regulation. TYP 1 is not expressed in human fibroblasts unlike other CL100-like genes. Furthermore, northern analysis has demonstrated that following mitogenic stimulation of squamous cells, induction of TYP 1 mRNA reaches its maximal levels after four hours, in contrast to the immediate early CL100-like genes. Both TYP 1 and CL100 mRNAs are induced upon TGF-beta treatment of squamous cell lines sensitive to the growth factors antiproliferative effects. When TYP 1 is transfected into COS-1 cells, the gene product inhibits both ERK2 and p54 MAP kinase subfamilies. In addition, we show that purified TYP 1 protein efficiently inactivates recombinant ERK2 in vitro by the concomitant dephosphorylation of both its phosphothreonine and -tyrosine residues. TYP 1 encodes a nuclear protein, which when expressed in COS cells is stabilised by EGF treatment.

3T3 Cells↗
PubMed1994

Enhanced spino-pelvic fixation for segmental spinal instrumentation: a preliminary biomechanical evaluation.

A new method for spino-pelvic fixation of Luque rods was developed and biomechanically evaluated on cadaveric specimens. The technique is surgically simpler and faster than the Galveston technique because it does not require the complex three-dimensional bending of rods to conform to the medullary cavity of the iliac wings. Spines were tested in axial compression in both bilateral and unilateral ischial weight bearing in the intact condition, instrumented with the new technique, and instrumented with the Galveston technique. Compared to the intact spine, the technique increased bilateral average stiffness by 131% and unilateral average stiffness by 192%. Compared directly to the Galveston technique, the new method exhibited increased average stiffness of 15% in bilateral and 11% in unilateral ischial weight bearing. The new method combines the advantages of a simpler and faster surgical procedure than the Galveston technique with enhanced spino-pelvic fixation with the potential to decrease migration of rods relative to each other and the pelvis.

Aged↗
PubMed1994

In vivo modulation of hematopoiesis by a novel hematoregulatory peptide.

The hematoregulatory peptide dimer, HP5B, enhances myelopoiesis by stimulating stromal cell cytokine production. However, the disulfide bridge of this peptide is susceptible to reduction, leading to the formation of monomeric pentapeptide, HP5, a direct-acting inhibitor of myelopoiesis. We have replaced the disulfide (S-S) bond of HP5B dimer with an isosteric ethylene (CH2-CH2) group, creating a new, nonreducible, metabolically more stable peptide (SK&F 107647). This novel peptide was tested in vitro and in vivo for hematopoietic effects. In vitro, SK&F 107647 has no direct colony-stimulating activity (CSA). Stimulation of murine stromal cells with SK&F 107647 results in production and release of CSA at concentrations as low as 0.01 ng/mL, at least 10-fold lower than observed with HP5B dimer. Injection of SK&F 107647 in normal mice results in a two- to six-fold increase in serum CSA, which becomes maximal at 6 hours postinjection. Administration of peptide daily over 4 days (q.d. x 4) by both parenteral and oral routes results in significant increases in absolute numbers of granulocyte-macrophage (CFU-GM), erythroid (BFU-E), and multipotential (CFU-GEMM) progenitor cells, as well as stimulating their cell cycle rates. A doubling in day 8 CFU-S was also observed in SK&F 107647-treated mice. Continuous subcutaneous (s.c.) infusion of SK&F 107647 in femorally cannulated rats demonstrated modest but significant elevation of peripheral blood neutrophil and monocyte counts within 7 days. SK&F 107647 represents a novel synthetic hematoregulatory peptide that shares biological and/or modulatory activities with natural hematopoietic cytokines.

Administration, Oral↗
PubMed1993

Isolation and characterization of the genes encoding mouse and human type-5 acid phosphatase.

The gene (mT5AP) encoding murine type-5 acid phosphatase has been isolated and completely sequenced while the gene (hT5AP) encoding human T5AP has been partly sequenced. The murine gene spans 4 kb and contains five exons. Exon 1 is completely non-coding and exon 2 starts with the initiation codon in both mT5AP and hT5AP. The positions of the intron/exon boundaries are completely conserved between mT5AP and hT5AP, but are distinct from the gene encoding the related porcine protein, uteroferrin (Utf). There is strong homology at both the nucleotide (nt) and amino acid (aa) levels between the inferred mouse cDNA and the sequences of rat T5AP and hT5AP, and pig Utf. The mT5AP and hT5AP genes were found to have multiple transcription start points (tsp) by primer extension analysis, consistent with the absence of a consensus TATA box. The sequences for the 5'-flanking regions of mT5AP and hT5AP were determined to -1.6 and -1.0 kb, respectively, relative to the tsp. A 2-kb segment of the mT5AP 5' flanking region linked to a luciferase-encoding reporter gene (Luc) was sufficient to direct tissue-specific transcription in the mouse macrophage cell line, RAW264. Significant sequence similarity between the mT5AP and hT5AP promoters is restricted to the most proximal 200 bp, which also resembles the porcine Utf gene, and a 300-bp segment 700 bp upstream. A progesterone-response element is present only in the mouse promoter and the estrogen- and iron-response elements described previously in the pig gene are absent from both the mouse and human genes. These differences may result in distinctive regulation of T5AP and Utf expression.

Acid Phosphatase↗
PubMed1993

Cervical spondylolysis. Report of two cases.

Two cases of cervical spondylolysis are presented. Both cases were discovered during radiographic examination after incidental trauma. The first patient experienced transient quadriplegia that spontaneously resolved and the other experienced only neck pain. Further radiographic evaluation of the first patient revealed significant spinal cord compromise, ultimately requiring decompression and fusion. The second patient's cervical spine proved stable to dynamic studies and was without cord compromise.

Adult↗
PubMed1992

Transpedicular convex anterior hemiepiphysiodesis and posterior arthrodesis for progressive congenital scoliosis.

Nine children with progressive congenital scoliosis underwent bilateral posterior spinal fusion supplemented with transpedicular convex anterior hemiepiphysiodesis. The average preoperative curve was 52 degrees. The average age at surgery was 9 years and 1 month and the average follow-up period was 3 years and 6 months. Curve progression was arrested in all cases, and curve correction greater than 10 degrees was achieved in four patients.

Adolescent↗
PubMed1992

Regulation of colony-stimulating activity production from bone marrow stromal cells by the hematoregulatory peptide, HP-5.

It has been reported that the granulocyte-derived hematoregulatory pentapeptide, HP-5, and its dimer (HP-5b) have potent hematoregulatory properties. The proposed mechanism of action for HP-5b is synergy with colony-stimulating activity (CSA) resulting in enhanced myeloid colony formation in vitro. We now demonstrate that the effects of HP-5b on enhanced colony formation are indirect and mediated by an effect on CSA production by bone marrow stromal cells. Bone marrow stromal cell culture systems from mice, rats, and humans were used as target cells for the action of HP-5 monomer and dimer. Cell-free supernatants from these cultures were assayed for CSA in a murine granulocyte-macrophage colony-forming unit (CFU-GM) assay. Supernatants from stromal cell cultures pulsed for 1 h with HP-5b resulted in increased murine CFU-GM colony proliferation with an estimated half-maximal effective concentration (EC50) of 1-5 ng/ml. This increase in CFU-GM proliferation was neutralized by anti-macrophage colony-stimulating factor (anti-M-CSF) antibodies. The HP-5 monomer was without effect on constitutive CSA production by stromal cells, but it antagonized HP-5b-induced CSA production in a dose-responsive manner with an estimated half-maximal inhibitory concentration (IC50) of 0.2-0.4 ng/ml. The ability of HP-5 monomer to antagonize HP-5b induction of CSA appears specific in that HP-5 monomer failed to alter interleukin 1 (IL-1) or lipopolysaccharide (LPS)-induced stromal cell CSA production.

Animals↗
PubMed1991

Induction of non-specific suppressor cells and myeloregulatory effects of an immunomodulatory azaspirane, SK&F 105685.

Administration of the immunosuppressive agent, SK&F 105685, has demonstrated immunosuppressive activity in several animal models of autoimmunity such as adjuvant arthritis and experimental autoimmune encephalomyelitis. The mechanism of action of SK&F 105685 in these autoimmune disease models appears to be the induction of non-specific suppressor cells (SC) detected in the spleen and bone marrow of treated animals. In this study we have examined the kinetics of SC appearance in the spleen and bone marrow following treatment with 30 mg/kg/day, p.o., for 1-6 days. SC activity was apparent following a single dose and increased with successive treatments. Treatment with SK&F 105685 also resulted in significantly enhanced myelopoiesis as measured by a 128% increase in the frequency of bone marrow myeloid progenitors (CFU-GM). Mechanistic studies indicated that in vitro treatment of bone marrow stromal cell cultures with SK&F 105685 upregulated the production of colony stimulating activity (CSA) detectable in a rat CFU-GM assay. Further, in vitro studies revealed that the SC in the bone marrow or spleens of SK&F 105685-treated rats admixed with normal marrow cells inhibited CFU-GM formation at a six-fold less cell concentration than cells obtained from control rats. These in vitro results suggest that the SK&F 105685-induced myelopoiesis is regulated by the subsequent generation of SC.

Adjuvants, Immunologic↗
PubMed1991

Administration of an immunomodulatory azaspirane, SK&F 105685, or human recombinant interleukin 1 stimulates myelopoiesis and enhances survival from lethal irradiation in C57Bl/6 mice.

The immunomodulatory azaspirane SK&F 105685 has immunosuppressive activity in animal models of autoimmune disease such as adjuvant-induced arthritis and experimental autoimmune encephalomyelitis. The mechanism of SK&F 105685 appears to be the induction of nonspecific suppressor cell (SC) activity. SC appear to be "null cells," that is, cells that lack specific cell surface markers of mature B cells, T cells, natural killer (NK) cells, or macrophages. Because we hypothesized that the induction of SC was associated with enhanced hematopoiesis, we sought to determine the hematopoietic potential of SK&F 105685. Recombinant interleukin 1 alpha (rIL-1) was included as a positive control for hematopoietic stimulation in our studies. We demonstrate here that administration of SK&F 105685 increases the number of granulocyte-macrophage colony-forming units (CFU-GM) within the bone marrow 24 h after injection in a dose-dependent manner. In addition, the percentage of CFU-GM in S-phase of the cell cycle was significantly increased, as was colony-stimulating activity (CSA) present in the serum of treated animals. In our experiments IL-1 did not increase marrow CFU-GM; however, splenic CFU-GM, the proportion of CFU-GM in S-phase of the cell cycle, and serum CSA were all increased 24 h after a single treatment. Administration of SK&F 105685 24 h prior to lethal irradiation resulted in a dose-related increase in the number of surviving mice. These results demonstrate that SK&F 105685 and rIL-1 stimulate myelopoiesis in vivo and suggest a mechanism by which prophylactic treatment with these agents protects mice from otherwise lethal irradiation.

Adjuvants, Immunologic↗
PubMed1990

Induction of non-specific suppressor cells in normal Lewis rats by a novel azaspirane SK&F 105685.

SK&F 105685 (N,N-Dimethyl-8,8-dipropyl-2-azaspiro[4,5]decane-2- propanamine dihydrochloride) is a novel azaspirane which has therapeutic activity in rat models of autoimmune disease. In this study, we have demonstrated that SK&F 105685 is a potent inducer of non-specific suppressor cells (SC). Oral administration of 15-30 mg/kg/day results in the generation of SC in the spleen, lymph nodes and bone marrow, but not the thymus of Lewis rats. Splenic SC suppress Con-A-induced proliferation in co-culture assays at effector-responder ratios of 1:1 to 1:64. SC are radiation resistant (2000 R), non-T, non-B cells, partially adherent to plastic surfaces and are enriched in a 1.07 g/ml fraction of a Percoll density gradient. Their activity is increased, rather than ablated, by indomethacin. No definitive changes in Ig+, OX-19+, OX-8+, W3/25+ or asialo GM1+ cells could be detected in the spleens of treated rats compared to control untreated animals. Elevated levels of both radiation-sensitive and radiation-resistant suppressor cells were found in the bone marrow of treated rats in addition to the radiosensitive SC normally present in this tissue.

Adjuvants, Immunologic↗
PubMed1989

Measurement of effective pedicle diameter in the human spine.

Effective pedicle diameter (EPD), the maximal cancellous diameter of the spinal pedicle, demonstrates the maximal diameter available for transpedicular screw placement. The pedicles of 16 spines from T6 to L5 were measured directly with a graduated mean increase in the EPD ranging from 4.8 mm at T6 to 5.9 mm at L5. This direct pedicle measurement was significantly smaller than that of previously reported studies, which directly and radiographically measured pedicle outside width rather than inner diameter. Three specimens had little, if any, pedicular medullary cavity on direct measurement, although radiographic appearance of a medullary cavity existed. If EPD is significantly smaller than radiographic pedicle width measurements, safe transpedicular screw fixation may not be achieved. Preoperative planning must account for this so that transpedicular screws of correct diameter may be used and the complications of pedicular blowout fracture and neurologic impairment may be avoided.

Adult↗
PubMed1989

Bone marrow stromal cell regulation of B-lymphopoiesis. II. Mechanisms of hydroquinone inhibition of pre-B cell maturation.

Previous investigations from our laboratory have shown that the benzene metabolite, hydroquinone (HQ), inhibits B cell production by preventing the maturation of pre-B cells. Data presented in this paper demonstrate that HQ interrupts B-lymphopoiesis indirectly by inhibiting the production of interleukin-4 (IL-4) by fibroblastic stromal cells. HQ exposure of fibroblastic stromal cells (SCL-173 and SCL-160) did not affect IL-4 production by these cell lines at any dose tested. Addition of untreated bone marrow-derived macrophages to HQ-treated bone marrow stromal cells (heterogeneous population of fibroblastic cells and macrophages) reversed inhibition of IL-4 production. However, addition of HQ-treated macrophages was without effect. Our studies suggest that HQ inhibits macrophage production of IL-1, a potent inducer of IL-4 production by bone marrow fibroblastic stromal cells. Interruption of IL-1 release from macrophages mediates the observed inhibition of B lineage cell maturation.

Animals↗
PubMed1988

Bone marrow stromal cell regulation of B-lymphopoiesis. I. The role of macrophages, IL-1, and IL-4 in pre-B cell maturation.

Our experiments have addressed regulation of B lymphocyte formation by bone marrow stromal cells. Stromal cells appear to produce a regulatory factor that acts at the pre-B cell stage to induce the expression of Ig L chains and surface Ig. Bone marrow stromal cell conditioned medium was found to contain this factor and the active component was partially purified by HPLC. This stromal cell-derived factor had a m.w. between 16,000 and 20,000, was specifically neutralized by anti-IL-4 mAb, 11B11, and enhanced the proliferation of anti-mu-stimulated B cells. We also found that rIL-4 induced B cell formation in culture. In our studies, IL-1 had no direct effect on pre-B cell maturation, however, IL-1 was found to stimulate the production of IL-4 by both heterogeneous bone marrow stromal cells and a cloned stromal cell line, SCL-160. These effects of IL-1 on factor production by stromal cells were duplicated by the addition of bone marrow-derived macrophages to SCL-160 cells. We conclude that stromal cell-derived IL-4 is a physiologic stimulator for B cell generation. In addition, macrophages appear to play a role in B cell formation by regulating the production of IL-4 by stromal cells via the secretion of IL-1.

Animals↗
PubMed1987

Mechanical consequences of rod contouring and residual scoliosis in sublaminar segmental instrumentation.

The mechanical performance of contoured Luque rods in a neuromuscular model of spine deformity was examined to define an upper limit of deformity above which rod stresses would exceed the endurance limit for 316L stainless steel and therefore predict fatigue failure. Bovine constructs varying from 0-120 degrees scoliosis were loaded axially, with strain recordings obtained at the apex of the curve. Relatively low loads produced enough tensile stress to contemplate implant fatigue in all except the nondeformed (0 degrees) construct. Construct stiffness was found to decrease rapidly in spines with greater than 38 degrees deformity. In addition, data on patients who had suffered rod fracture from four different centers were found to compare favorably with experimental observations. We conclude that the vulnerability of Luque rod constructs to implant failure, from a mechanical standpoint, is greater than is generally assumed. Cross-linking of rods was found to increase stiffness. Methods to decrease tensile stresses in the implants and increase stiffness include external immobilization, larger diameter rods, and procedures to enhance correction.

Adolescent↗