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Biomedical subjects

K Kilpatrick

Publications and source records attributed to K Kilpatrick.

13 recordsLinked to original sources
PubMed2001

Dexras1/AGS-1, a steroid hormone-induced guanosine triphosphate-binding protein, inhibits 3',5'-cyclic adenosine monophosphate-stimulated secretion in AtT-20 corticotroph cells.

Dexras1 is a novel GTP-binding protein that shares structural similarity with the Ras family of small molecular weight GTPases and is strongly and rapidly induced during treatment with dexamethasone. The function of Dexras1 and its contribution to glucocorticoid-dependent signaling in the corticotroph cell are unknown. The present study was undertaken to examine the potential role of Dexras1 in the regulation of peptide hormone secretion in the AtT-20 corticotroph cell line. To determine the effects of Dexras1 expressed independently of glucocorticoid treatment, expression plasmids for wild-type and constitutively active mutant Dexras1 proteins were cotransfected with human GH (hGH), which provides an ectopic marker for the stimulus-coupled secretory pathway. GTP binding properties and the GTP to GDP ratio of wild-type and mutant Dexras1 proteins were examined in transiently transfected AtT-20 and COS-7 cells. Stimulated and constitutive components of secretion were assessed after 2-h incubations with 5 mM 8-Br-cAMP or control. cAMP treatment led to a 2-fold increase in hGH secretion relative to control. Cotransfection of wild-type Dexras1 had no effect on cAMP-stimulated hGH secretion, but a constitutively active mutant, Dexras[A178V], attenuated stimulated secretion by 86% (P < 0.01). A double-mutant containing a deletion of the carboxyl terminus isoprenylation site, Dexras[A178V/C277term], did not inhibit cAMP-stimulated hGH secretion, indicating that the effect is prenylation dependent. These findings suggest that activation of Dexras1 has important functional consequences leading to inhibition of stimulus-secretion coupling in corticotroph cells. Because Dexras1 messenger RNA is strongly and rapidly induced during glucocorticoid treatment, these results raise the possibility that Dexras1 may participate in the signal transduction pathways that govern the rapid regulatory effects of glucocorticoids on peptide hormone secretion in corticotroph cells.

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed2001

A longitudinal study of the effects of graduate medical education on hospital operating costs.

OBJECTIVE: To examine the effect of graduate medical education sponsorship on hospital operating costs over a seven-year period, to test for a longitudinal association between teaching intensity and cost, and to determine whether the indirect medical education (IME) payment adjustments made under Medicare's Prospective Payment System are appropriate. DATA SOURCES: Medicare cost and payment data from the Hospital Cost Report Information System and other related HCFA files, from FFY 1989 through 1995. The study population consists of all short-stay hospitals (approximately 5,000) participating in Medicare and receiving case payments by diagnosis-related groups. STUDY DESIGN: The original cost functions used to develop indirect medical education payment adjustments under PPS are re-estimated with panel data. Specification changes are included based on findings from critiques of the original hospital cost model. Additional variations on the model are explored to test for differences by hospital status, to control for the effect of additional disproportionate share and outlier payments, and to isolate the effects of improved case-mix measurement on model results. PRINCIPAL FINDINGS: Fixed effects regression produces no evidence of a significant within-hospital association between increased sponsorship of medical residents and increased cost per case. In models designed to capture a cross-sectional association, operating costs are positively related to teaching activity, but the association shows a decline in strength over time. In all years, the strength of the association is significantly greater among hospitals eligible for disproportionate share adjustments and among major teaching hospitals. Controlling for secular trends of increased teaching intensity results in a pattern of declining cross-sectional teaching coefficients that supports a theory that observed teaching effects are the result of unmeasured case severity. CONCLUSIONS: A significant but declining cost differential is observed between teaching and nonteaching hospitals. The association appears to be related to hospital and patient characteristics that cannot be controlled using currently available case-mix and wage indices. Longitudinal models do not provide evidence to support a payment adjustment formula that allows individual hospitals to recompute their IME adjustment rates as their teaching ratios rise or fall from year to year. Cross-sectional findings suggest that re-estimations of the teaching effect may be appropriate when significant improvements occur in Medicare case-mix measurement.

Centers for Medicare and Medicaid Services, U.S.↗
PubMed2000

Inter-organizational relationships of seven Veterans Affairs Medical Centers and their affiliated medical schools: results of a multiple-case-study investigation.

PURPOSE: This study describes the costs and and value added to Veterans Affairs Medical Centers (VAMCs) through their affiliations with medical schools. The study also creates a conceptual framework for evaluating the critical dimensions across which these affiliations vary. METHOD: Case studies of seven VAMCs' affiliations with medical schools, ranging from two highly affiliated VAMCs to one with only one funded residency position, were conducted in 1997 and 1998 using a survey and in-depth interviews with 78 key individuals at the institutions. The qualitative data were then used to develop a conceptual framework for evaluating these affiliations. RESULTS: The results are reported in two stages. In stage one, three organizing themes emerged from the data that formed the conceptual framework for evaluating affiliations: (1) the characteristics of each VAMC and its environment, (2) the characteristics of the relationships between each VAMC and its medical school affiliates, and (3) the costs and value that medical school affiliations add to VAMCs. The affiliations that were most beneficial to VAMCs were characterized by a relationship of trust, extensively shared education and research programs, and a high degree of physician interaction. The achievement of these characteristics is influenced by the distance between the VAMCs and their affiliated medical schools, the VAMCs' levels of organizational complexity, the degree of managed care penetration, and the continuity and academic orientation of leadership at the VAMCs. In stage two, study data were used to create a conceptual framework to evaluate the characteristics of VAMCs and their affiliations with medical schools. CONCLUSIONS: The study supplied data to construct a conceptual framework that describes many of the relationships among the different affiliations in the study. The framework offers a tool for evaluating the dimensions across which affiliations vary and how these differences influence the costs and value of medical school affiliations to VAMCs.

Costs and Cost Analysis↗
PubMed1998

Inhibition of establishment of primary and micrometastatic tumors by a urokinase plasminogen activator receptor antagonist.

Tumor establishment and metastasis are dependent on extracellular matrix proteolysis, tumor cell migration, and angiogenesis. Urokinase plasminogen activator (uPA) and its receptor are essential mediators of these processes. The purpose of this study was to investigate the effect of a recombinant human uPAR antagonist on growth, establishment, and metastasis of tumors derived from human cancer cell lines. A noncatalytic recombinant protein, consisting of amino acids 1-137 of human uPA and the CH2 and CH3 regions of mouse IgG1 (uPA-IgG), was expressed, purified, and shown to bind specifically to human uPAR and to saturate the surface of human tumor cells which express uPAR. Daily i.p. administration of uPA-IgG to nude mice extended latencies of unstaged tumors derived from Lox melanoma and SW48 colon carcinoma cells by 7.7 and 5.5 days, respectively. uPA-IgG treatment did not affect the growth of Lox or KB tumors staged to 200 mg before antagonist treatment commenced. The effect of uPA-IgG on the establishment of micrometastases was assessed in SCID mice. KB head/neck tumor cells were injected in the tail vein and allowed to seed for 48 h before initiation of daily i.p. injections of uPA-IgG for 24 days. The number of lung colonies ranged between 5 and 30% of vehicle-treated mice in two separate experiments. Furthermore, a single 800 microg dose of uPA-IgG administered 1 h prior to tail vein injection of KB cells reduced lung colony formation to just 3.5% of vehicle-treated SCID mice. These data demonstrate that antagonism of uPAR arrested metastasis and inhibited the establishment of primary tumors and micrometastases. Thus, small molecule uPAR antagonists may serve as useful adjuvant agents in combination with existing cancer chemotherapy.

Animals↗
PubMed1993

Transcriptional regulation of human corticotropin releasing factor gene expression by cyclic adenosine 3',5'-monophosphate: differential effects at proximal and distal promoter elements.

cAMP participates in the regulation of endogenous hypothalamic and placental CRF by increasing levels of both peptide secretion and mRNA expression. In previous studies we have shown that stimulation of the protein kinase A-dependent pathway by cAMP analogues or forskolin produced a dose-dependent increase in levels of CRF mRNA when the intact hCRF gene was stably transfected and expressed in the mouse corticotroph AtT20 cell line. In the present study, we explored the mechanism of the cAMP-dependent increase in CRF gene expression in the stably transfected AtT20 cell line using pharmacologic, slot-blot, and RNase mapping methodologies. Following incubation with cAMP, there was a rapid increase in CRF mRNA which was completely blocked by pre-treatment with actinomycin D, an inhibitor of transcription. Cycloheximide, an inhibitor of protein synthesis, produced an independent increase in CRF mRNA, but did not change the relative induction of CRF mRNA produced by cAMP. Solution hybridization studies using intron- and exon-specific hCRF probes demonstrated a rapid rise in nuclear CRF hnRNA, which was apparent within 15 min of cAMP incubation and preceded the rise in cytoplasmic CRF mRNA. RNase mapping studies demonstrated that CRF transcription was initiated at discrete promoter sites in CRF-AtT20 cells, and that this pattern of promoter utilization was similar to that observed in mRNA derived from sites of endogenous CRF expression, human placenta and human hepatoma NPLC cell line. Treatment with cAMP selectively increased CRF mRNA transcripts initiated at the proximal promoter site, but had little or no effect on transcripts initiated at the distal promoters. We conclude that cAMP effects on CRF gene expression occur rapidly, do not require new protein synthesis, and are initiated within the nuclear compartment, consistent with a direct effect on CRF gene transcription. This effect is mediated predominantly through the proximal promoter element, while more distal promoters are less sensitive to transcriptional activation by cAMP.

Animals↗
PubMed1993

Cultured keratinocyte allografts fail to induce sensitization in vivo.

BACKGROUND: The use of cultured keratinocyte (CK) allografts for burn wounds offers a potentially unlimited supply of skin. It is unknown, however, whether CK allografts induce rejection in vivo. This study investigated the induction of immune responsiveness to CK allografts as measured by mixed lymphocyte response and serum cytotoxic antibody. METHODS: Female CBA mice (n = 160) were randomized to four equal groups, each receiving a 3 cm2 flank graft of autologous CBA CK (Auto CK), allogeneic C57BL/6 CK (Allo CK), C57BL/6 full thickness skin (Allo FT), or Sham. Graft take was assessed by gross and histologic examinations. Unidirectional mixed lymphocyte response was measured with graft recipient and donor splenocytes by use of tritiated thymidine uptake. Stimulation indexes were calculated. Serum cytotoxic antibody was measured by coculturing graft recipient serum with donor splenocytes and rabbit complement and assessing resultant cell killing. RESULTS: Overall graft take was 50% for Allo CK and 74% for Auto CK, Allo FT, but not Allo CK, were associated with significantly increased stimulation indexes compared with Auto CK and Sham (p < 0.01). Allo FT, but not Allo CK, resulted in elevated titers of alloantibody, reaching significant levels 10 days after grafting (p < 0.05). CONCLUSIONS: CK allografts do not result in increased in vitro T cell responses or enhanced alloantibody formation, indicating that sensitization to major histocompatibility antigens by CK does not occur. These data suggest that CK allografts may provide a possible source of grafts for victims of large burn wounds.

Animals↗
PubMed1988

Kappa/lambda immunoglobulin distribution in Graves' thyroid-stimulating antibodies. Simultaneous analysis of C lambda gene polymorphisms.

From patients with untreated Graves' disease 11 sera showing high cAMP release in the FRTL-5 cell assay were studied for relative proportions of kappa or lambda Ig molecules showing cAMP releasing activity. Immunoabsorption of gamma-globulins was performed using monoclonal murine anti-kappa or anti-lambda antibodies linked to cyanogen bromide-activated sepharose. Specific kappa- or lambda-adsorbed fractions were also eluted from immunoabsorbents using chaotrophic thiocyanate buffers and equilibrated with pH 7.4 low salt buffer by dialysis. Immunoabsorption and elution experiments showed that five Graves' sera contained predominant cAMP-releasing activity within lambda Ig fractions, whereas two Graves' sera showed predominant cAMP-releasing activity in kappa Ig fractions. Four sera showed cAMP release approximately equally divided between kappa and lambda Ig both after immunoabsorption and specific anti-kappa or anti-lambda eluates were studied. C lambda genotypes were examined by Southern blotting and restriction fragment length polymorphism analysis of Eco RI-digested genomic DNA from 158 patients with Graves' disease in parallel with 112 normal controls and 29 patients with autoimmune hypothyroidism. Notable shifts in proportions of 8/8 and 18/18 genotypes were present when Graves' patients were compared with normal controls. Allelic frequencies and ratios of genotype 8 to 18 were significantly different (P less than 0.05) when Graves' patients were compared either to normal controls or to patients with autoimmune hypothyroidism.

Absorption↗
PubMed1985

Immunofluorescence studies of cardiac valves in infective endocarditis.

Mitral and aortic valves removed at emergency cardiac surgery from a patient with infective endocarditis caused by Streptococcus viridans were studied by immunofluorescence to ascertain the extent and pattern of various immune reactants within the large valvular vegetations. Heavy intravalvular deposits of IgG as well as bacterial antigen were present. Much more focal interstitial IgM and C3 deposits were noted within vegetations and valve substance. Diffuse endocardial and subendocardial deposition of C5b-C9 and C9 complement neoantigens was present. Direct staining of valvular tissues and vegetations for rheumatoid factor showed extensive interstitial tissue deposition. These findings emphasize the large amounts of immune reactants and constituents of immune complexes present in valves and vegetations of patients with infective endocarditis.

Adult↗
PubMed1981

T gamma subset specificity of lymphocyte reactive factors in juvenile rheumatoid arthritis and systemic lupus erythematosus sera.

Sera from 34 patients with juvenile rheumatoid arthritis (JRA), 31 patients with systemic lupus erythematosus (SLE), and 22 normal controls were studied for microcytotoxicity before and after clearing in the ultracentrifuge. Normal T cells as well as T gamma and non-T gamma subpopulations were used. Before ultracentrifugation all test sera showed apparent T gamma cell specificity in the microcytotoxicity assay where rabbit complement was added. JRA and SLE sera produced much higher proportions of cell killing than normal controls. Ultracentrifugal clearing resulted in marked diminution in microcytotoxicity of JRA and some SLE sera. However, a considerable proportion of lupus sera continued to show T cell subset cytotoxicity after ultracentrifugal clearing. No evidence for significant alteration of T gamma rosetting capacity was recorded when ultracentrifuge-cleared test sera were preincubated with T cells prior to T gamma EA rosette formation. Apparent T gamma cytotoxic specificity in some uncleared JRA and SLE sera may relate to high molecular weight materials (IgM and immune complexes) present in such samples, whereas in others it relates to lymphocyte reactive antibody with subset reactivity.

Adult↗