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Biomedical subjects

G G Miller

Publications and source records attributed to G G Miller.

At least 55 records · Page 3Linked to original sources
PubMed1997

Preclinical assessment of hypocrellin B and hypocrellin B derivatives as sensitizers for photodynamic therapy of cancer: progress update.

Hypocrellins are perylenequinone pigments with substantial absorption in the red spectral region and high singlet oxygen yield. They are available in pure monomeric form and may be derivatized to optimize properties of red light absorption, tissue biodistribution and toxicity. In vitro screening of synthetic derivatives of the naturally occurring compound, hypocrellin B (HB), for optimal properties of cyto-(dark) toxicity and phototoxicity resulted in selection of three compounds for preclinical evaluation: HBEA-R1 (ethanolaminated HB), HBBA-R2 (butylaminated HB) and HBDP-R1 [2-(N,N-dimethylamino)-propylamine-HB]. Extinction coefficients at 630 nm (epsilon 630) are 6230, 6190 and 4800, respectively; and 1O2 quantum yields, phi, 0.60, 0.32 and 0.42. Intracellular uptake is essentially complete within 2 h (HBEA-R1, HBBA-R2) and 20 h (HBDP-R1). Greatest uptake is associated with lysosomes and Golgi. The HBEA-R1 and HBBA-R2 elicit phototoxicity in vitro primarily via the type II mechanism, with some type I activity under stringently hypoxic conditions. Transcutaneous phototherapy with HBEA-R1 permanently ablates EMT6/Ed tumors growing in the flanks of Balb/c mice, with minimal cutaneous effects. The HBBA-R2 does not elicit mutagenic activity in strains TA98 and TA100 of Salmonella typhimurium. Further development of selected hypocrellin derivatives as photosensitizers for photodynamic therapy is warranted.

Animals↗
PubMed1997

T-cell, antibody, and cytokine responses to homologs of the 60-kilodalton heat shock protein in Helicobacter pylori infection.

For Helicobacter pylori, the hsp60 heat shock protein encoded by hspB is being considered as a potential candidate for subunit vaccines. We investigated the humoral and cellular responses to H. pylori hsp60 and its cross-reactivity with the homologous Mycobacterium bovis p65 protein and autologous human hsp60 protein. H. pylori-infected persons had significantly higher levels than uninfected persons of serum immunoglobulin G antibodies recognizing H. pylori hsp60, but not M. bovis p65 or human hsp60, as determined by enzyme-linked immunosorbent assay. In contrast, immunoblotting demonstrated cross-reactivity of H. pylori hsp60 with human hsp60. T-cell recognition of H. pylori hsp60 was found in both infected and uninfected subjects, and there was no recognition of human hsp60. T cells from infected and uninfected subjects that had been activated in response to H. pylori hsp60 or M. bovis p65 were phenotypically similar but appeared to secrete different levels of gamma interferon and interleukin-10. These results demonstrate an apparent difference in the epitopes recognized by the T and B cells responding to H. pylori hsp60 in H. pylori-infected persons. In contrast to the T-cell responses, which were highly variable in all subjects and showed no recognition of autologous proteins, a specific B-cell response that may have cross-reactivity to human hsp60 is evident in some infected subjects.

Adult↗
PubMed1997

The Helicobacter pylori genome is modified at CATG by the product of hpyIM.

To understand mechanisms of DNA methylation in Helicobacter pylori, a human pathogen associated with peptic ulcer disease and gastric adenocarcinoma, we cloned a putative DNA methyltransferase gene, hpyIM. This gene contains a 990-bp open reading frame encoding a 329-amino-acid protein, M.HpyI. Sequence analysis revealed that M.HpyI was closely related to CATG-recognizing adenine DNA methyltransferases, including M.NlaIII in N. lactamica. hpyIM was present in all H. pylori strains tested. DNA from wild-type H. pylori strains was resistant to digestion by SphI and NlaIII, which recognize DNA at sites containing CATG, whereas their isogenic hpyIM mutants were susceptible, indicating lack of modification. Overexpression of hpyIM in Escherichia coli rendered DNA from these cells resistant to NlaIII digestion, confirming the role of hpyIM in modifying CATG sites. We conclude that hpyIM encodes a DNA methyltransferase, M.HpyI, that is well conserved among diverse H. pylori strains and that modifies H. pylori genomes at CATG sites.

Amino Acid Sequence↗
PubMed1997

Enediyne-lexitropsin DNA-targeted anticancer agents. Physicochemical and cytotoxic properties in human neoplastic cells in vitro, and intracellular distribution.

Two series of hybrids of a dynemicin A model and DNA minor groove binding lexitropsins were synthesized and their cytotoxic activities were investigated in a panel of human normal and malignant cell lines using a colorimetric assay. Adriamycin was used as a control. Several of the agents demonstrated cytotoxic activity, the extent of which varied with tumor type. IC50s of the hybrids ranged from approximately 14-48 microM following 96 h incubation in the presence of test compound. Intracellular distribution studies were facilitated through endogenous fluorescence of the compounds. Evidence of nuclear uptake of the hybrid agents was demonstrated by confocal laser scanning microscopy. The results warrant further development of DNA-targeted enediyne-lexitropsin hybrids as potential anticancer agents.

Antibiotics, Antineoplastic↗
PubMed1997

Sporadic ampullary hamartoma simulating cancer.

Ampullary tumours are uncommon. They may occur with familial polyposis syndromes or neurofibromatosis. It can be difficult to distinguish them from their periampullary counterparts on clinical, radiologic or histologic grounds. Because most ampullary and periampullary tumours are malignant, they tend to be treated by radical surgery. A 67-year-old man was seen with a sporadic ampullary hamartoma that simulated cancer. It was successfully treated by local excision through a transverse duodenotomy.

Aged↗
PubMed1997

[New nucleoside conjugates with phospholipids: synthesis of anti-HIV activity of rac-1-hexadecyl-2-acyl-sn-glycero-3-phosphonucleosides].

New nucleoside-phospholipid conjugates were synthesized based on 1,2-disubstituted glycerides and nucleosides. These contain rac-1-hexadecyl-2-palmitoyl(or 2-methylcarbamoyl)-sn-glycero-3-phosphate as the phospholipid component and 2',3'-didehydro-3'-deoxythymidine, 1-(Z-5-hydroxypentene-2-yl)thymine, or 2',3'-isopropylideneuridine as a nucleoside component. The conjugates were synthesized by three different ways: from rac-1-hexadecyl-2-acyl-sn-glycero-3-phospodichlorides, -3-phosphatidic acids, or -3-H-phosphonates. When subjected to mild alkaline hydrolysis, conjugates containing a 2-palmitoyl group formed conjugates with the lysophospholipid component that had not yet been described. All the conjugates obtained were amorphous compounds stable at room temperature. Their hemolytic and anti-HIV activities were determined. Some conjugates were found to completely inhibit in vitro HIV-1 reproduction in lower doses than the corresponding nucleosides.

Anti-HIV Agents↗
PubMed1996

CD11b+CD28-CD4+ human T cells: activation requirements and association with HLA-DR alleles.

Engagement of CD28 induces a major costimulatory pathway required by many CD4+ T cells in addition to activation via the TCR. In the absence of signals provided by CD28, ligation of the TCR alone can induce anergy or apoptosis in CD28+ cells. However, we report here characterization of a distinct subset of CD4+ T cells that are CD28-. Three autoreactive CD4+ human T cell clones that could be activated to produce IL-2 and proliferate by anti-CD3 alone were found to lack expression of CD28. CD28- clones that were activated with anti-CD3 alone were not anergic to restimulation via CD3. The presence of CD28-CD4+ T cells was verified in peripheral blood, and their frequency ranged from 0% to >22% of CD4+ T cells in different individuals. The percentage of CD28-CD4+ T cells in the peripheral blood of 57 individuals was significantly correlated with specific class II MHC alleles. Persons with HLA-DRB1*0401 and DR1 alleles had significantly higher numbers of CD28- T cells, while individuals with HLA-DR2(15) had significantly fewer CD28-CD4+ T cells than the mean. Like the CD28- clones, CD28-CD4+ T cells isolated from peripheral blood proliferated upon CD3 cross-linking in the absence of costimulation. The finding that CD28-CD4+ T cells resist induction of anergy following engagement of the TCR in the absence of conventional costimulation demonstrates one mechanism by which autoreactive T cells can escape processes that censor self-reactivity. The MHC associations observed suggest a relationship with autoimmunity and loss of self-tolerance.

Alleles↗
PubMed1996

Anisotropy of radiance in tissue phantoms and Dunning R3327 rat tumors: radiance measurements with flat cleaved fiber probes.

BACKGROUND AND OBJECTIVE: The goal of this study is to determine if flat cleaved fiber probes are appropriate for interstitial measurements of radiance in tissue. Flat cleaved probes have the advantage of high responsivity, and they are easy to insert into tissue. Owing to the non-isotropic response of flat cleaved probes, a calibration function is required, taking the anisotropy in the radiance in tissue into account. STUDY DESIGN, MATERIALS AND METHODS: The method used to determine this function consists of radiance measurements in tissue, performed with a flat cleaved fiber probe mounted on a stereotactic stage for insertion into the tissue from different directions. Interstitial irradiation at 630 nm was delivered by a spherical source. RESULTS: We found that the degree of anisotropy in the radiance decreases with increasing distance from the interstitially implanted source in two different tissue phantoms and in the Dunning R3327-AT and R3327-H rat tumor models. CONCLUSION: A position-dependent calibration function is required for interstitially implanted flat cleaved fiber probes. An anisotropy function is presented, which modifies the measurements of radiance with a flat cleaved probe, to account for the change in anisotropy in the radiance. The anisotropy functions for the two tumor models differ substantially.

Animals↗
PubMed1996

Expression and functional expansion of fibroblast growth factor receptor T cells in rheumatoid synovium and peripheral blood of patients with rheumatoid arthritis.

OBJECTIVE: Rheumatoid arthritis (RA) is an inflammatory disorder of the diarthroidial joints, characterized by fibroblast proliferation, angiogenesis, and perivascular CD4+ T cell infiltration. The present study examined the interactions between fibroblast growth factor-1 (FGF-1) and T cells. METHODS: Synovial tissues from patients with RA or noninflammatory arthritis were examined for the expression of FGF-1 and its receptor, FGFR-1, by immunohistology and reverse transcriptase-polymerase chain reaction. Functional assays were used to detect enrichment of FGF-1-responsive peripheral CD4+ T cells in RA. RESULTS: FGF-1 is abundantly expressed by rheumatoid synovium. Enhanced expression of its receptor, FGFR-1, was found in perivascular CD4+ T cells. In addition, T cells that are activated by FGF-1 are increased in the peripheral blood of patients with RA, as compared with other inflammatory conditions. CONCLUSION: The increased frequency of peripheral T cells that respond to FGF-1 in RA is consistent with expansion of FGFR-1-expressing T cells in the rheumatoid synovium.

Arthritis, Rheumatoid↗
PubMed1996

Hypocrellins as photosensitizers for photodynamic therapy: a screening evaluation and pharmacokinetic study.

Hypocrellin compounds were selected as potential photosensitizers for photodynamic therapy (PDT) owing to their high quantum yields of singlet oxygen (1O2), and facility for site-directed chemical modification to enhance phototoxicity, pharmacokinetics, solubility, and light absorption in the red spectral region, among other properties. Parent hypocrellins A and B share an absorption peak at 658 nm. These molecules may therefore be considered useful progenitors of derivatives which absorb more strongly in the red, considering that the ideal sensitizer should absorb in the 650-800 nm range, beyond the absorption range of hemoglobin and melanin, and where light penetration in tissues is maximized through reduced scattering. A series of pure, monomeric hypocrellin derivatives was tested for properties of dark cytotoxicity and photosensitizing potential by clonogenic assay in monolayer cultures of EMT6/Ed murine tumor cells. Their respective toxicities are reported on a molar basis. The in vitro screening assay has, to date, resulted in the selection of four hypocrellin derivatives for further development as photosensitizers for PDT. Cellular uptake for photosensitizing doses of selected compounds was determined by fluorimetry. Dose escalation studies in rodents indicate that potentially photosensitizing doses promote no demonstrable systemic toxicity.

Animals↗
PubMed1996

Photosensitization by anticancer agents 21: new perylene- and aminonaphthoquinones.

Hypocrellins are under intensive investigation as photosensitizing agents for photodynamic therapy (PDT). A recent advance in the synthesis of hypocrellin congeners resulted in the production of an amino-substituted hypocrellin-B, and its "half chromophore." Both compounds exhibit stronger red light absorption than previously reported hypocrellins, and, therefore, merit investigation as photosensitizers.

Animals↗
PubMed1996

Diagnostic laparoscopy in childhood Crohn's disease.

In some children, contrast radiography and endoscopy fail to confirm suspected Crohn's disease, or fail to evaluate the extent of disease. This report documents seven cases in which laparoscopy was used to look for creeping mesenteric fat involving the small intestine, a pathological finding reported only for Crohn's disease. One child had extensive Crohn's colitis and possible terminal ileitis that remained clinically disabling despite intensive immunosuppression therapy. The lack of creeping fat in the small intestine was used to justify colon resection and forego further aggressive medical therapy. The patient had complete resolution of her symptoms after the colectomy. Six children had suspected Crohn's disease and underwent diagnostic laparoscopy after other studies were inconclusive. In three, creeping mesenteric fat of the small intestine was found, and all three responded to treatment for Crohn's disease, with resolution of symptoms. The other three children had Crohn's disease excluded based on the absence of creeping mesenteric fat, and subsequently other pathological conditions were identified. The usual radiographic and endoscopic studies will diagnose most cases of Crohn's disease, but this report emphasizes that, in select cases in which other investigations are inconclusive, laparoscopy can be useful to search for creeping mesenteric fat, a finding characteristic of Crohn's disease.

Adolescent↗
PubMed1995

Costimulation of human CD4+ T cells by fibroblast growth factor-1 (acidic fibroblast growth factor).

T cell infiltration is prevalent in wound healing, atherosclerosis, vascular lesions in chronic allograft rejection, and autoimmune diseases. Whether T cells play a role in the migration and proliferation of vascular smooth muscle cells and endothelial cells in these lesions is not known. We previously reported that some human T cells express FGF-1, a potent growth factor for vascular smooth muscle cells and endothelial cells. In this study, we extend this observation and examine the expression and function of FGF receptors on human T cells. Using reverse transcription-PCR, Northern analysis, and immunohistochemistry, we found that some human T cells also express high affinity FGF receptor 1 (FGFR-1) respond to FGF-1. In the presence of anti-CD3, exogenous FGF-1 functions as a costimulator for these T cells, while FGF-1 alone does not induce T cell proliferation. [3H]Thymidine incorporation is sevenfold higher in T cells costimulated with FGF-1 compared with stimulation with anti-CD3 alone. Using limiting dilution, we demonstrate that FGF-responsive T cells are present in normal peripheral blood at a mean frequency of 1:19780 (95% confidence limits, 1:15100-1:23000), and similar T cells are increased in the peripheral blood of heart transplant recipients (mean frequency, 1:4210; 95% confidence limits, 1:3420-1:6781). In addition, a subline of Jurkat, a human T cell tumor, expresses FGFR-1 receptor. The function of FGFR-1 receptor in Jurkat T cells is demonstrated by the production of IL-2 after stimulation with FGF-1 and anti-CD3. IL-2 levels are sevenfold higher in Jurkat T cells costimulated with FGF-1 compared with those stimulated with anti-CD3 alone. FGF-1 alone has no effect on Jurkat T cells. These findings thus provide evidence that a subset of human T cells expresses a receptor for vascular cell growth factors, and this receptor functions to increase IL-2 production consistent with costimulation. The potential role of FGF-responsive T cells in a variety of vascular and inflammatory lesions is discussed.

CD4-Positive T-Lymphocytes↗
PubMed1995

Association of acidic fibroblast growth factor and untreated low grade rejection with cardiac allograft vasculopathy.

Acidic fibroblast growth factor (aFGF) is a potent growth factor for vascular smooth muscle cells and may mediate vasculopathy in cardiac allografts subjected to chronic immunological injury. Therefore, we examined cardiac expression of aFGF, the number of rejection episodes, and other potential risk factors in 32 heart transplant patients who underwent intravascular ultrasound (IVUS) for detection of cardiac allograft vasculopathy (CAV). As defined by IVUS, CAV was present in 21 patients and absent in 11 patients (follow-up time: 52 +/- 21 vs. 51 +/- 12 months, respectively, P = NS). The level of aFGF in myocardial biopsies obtained at the time of IVUS was measured by semiquantitative reverse transcriptase polymerase chain reaction and expressed as the aFGF:GAPDH ratio. Higher level of aFGF were associated with CAV (mean aFGF:GAPDH ratio was 1.45 +/- 0.99 in patients with vs. 0.18 +/- 0.12 in patients without CAV [P < 0.001]). A strong association was found between high levels of cardiac aFGF and CAV, as 18 of 19 patients (95%) with high levels of aFGF (aFGF:GAPDH > 1) but only 3 of 13 patients with low levels of aFGF had CAV (P < 0.001). The relative risk of high level of aFGF for CAV was 4.1. Untreated low grade rejection (ISHLT I), but not treated high grade rejection (ISHLT > 2), was also associated with CAV (average number of untreated low grade rejection episodes was 3.5 +/- 1.8 in patients with vs. 2.1 +/- 1.0 in patients without CAV [P = 0.04]). Among other risk factors examined (age, sex, serum cholesterol, blood pressure, CMV infection, dose of immunosuppressants, and ischemic time), only triglycerides were higher in patients with than those without CAV (P = 0.003). We conclude that increased cardiac production of aFGF is significantly associated with CAV, which suggests that aFGF may serve as an important mediator in CAV. Untreated low grade rejection also poses an increased risk for CAV.

Adult↗
PubMed1995

Confirmation of alternatively spliced platelet-derived growth factor-A chain and correlation with expression of PDGF receptor-alpha in human cardiac allografts.

PDGF is a potent mitogen for vascular smooth muscle cells (SMC) and may play an important role in the pathogenesis of cardiac allograft vasculopathy (CAV). Two isoforms of PDGF-A chain exist as a result of alternative mRNA splicing that either includes (long-form) or excludes (short-form) exon 6. Short-form PDGF-A is expressed in both resting and activated cells, while the long-form is present predominantly in activated cells. Using RT/PCR, we have found previously that long-form PDGF-A chain was expressed in human cardiac allografts but not in normal human hearts. In the experiments reported here, we studied the cellular distribution of PDGF-A chain isoforms and expression of PDGF receptor-alpha in cardiac allografts. In situ hybridization and immunohistochemistry confirmed the PCR data and demonstrated that expression of long-form PDGF-A chain was diffusely increased in cardiac allografts, predominantly in myocytes and vascular structures. Expression of PDGF receptor alpha also was induced in cardiac allografts and was not detected in any of the normal hearts. Induction of PDGF receptor alpha in cardiac allografts was associated with the presence of long-form PDGF-A chain. In vitro experiments with human endothelial cells demonstrated that aFGF, IL-6, and TGF-beta, which are produced in cardiac allografts in vivo, induced expression of long-form PDGF-A chain. Expression of long-form PDGF-A chain and its receptor was markedly increased in cardiac allografts, predominantly in vascular structures and myocytes. Alterative splicing of PDGF-A chain variants may be mediated by growth factors and cytokines produced in vivo.

Adult↗