Biomedical subjects

M J Miller

Publications and source records attributed to M J Miller.

At least 109 records · Page 6Linked to original sources

PubMed1998

Cloning, characterization, and chromosomal localization of a gene frequently deleted in human liver cancer (DLC-1) homologous to rat RhoGAP.

The isolation of genes involved in cancer development is critical for uncovering the molecular basis of cancer. We report here the isolation of the full-length cDNA and chromosomal localization of a new gene frequently deleted in liver cancer (DLC-1) that was identified by representational difference analysis. Loss of heterozygosity was detected for DLC-1 in 7 of 16 primary hepatocellular carcinomas (HCCs) and in 10 of 11 HCC cell lines. Although mRNA for DLC-1 was expressed in all normal human tissues, it was not expressed in 4 of 14 HCC cell lines. Full-length cDNA for DLC-1 of 3800 bp encodes a protein of 1091 amino acids, has 86% homology with rat p122 RhoGAP gene, and was localized by fluorescence in situ hybridization on chromosome 8 at bands p21.3-22. Deletions on the short arm of chromosome 8 are recurrent in liver, breast, lung, and prostate cancers, suggesting the presence of tumor suppressor genes. DLC-1 may be a tumor suppressor gene in liver cancer as well as in other cancers.

Animals↗

PubMed1998

Accelerated reaction of nitric oxide with O2 within the hydrophobic interior of biological membranes.

We demonstrate herein dramatic acceleration of aqueous nitric oxide (NO) reaction with O2 within the hydrophobic region of either phospholipid or biological membranes or detergent micelles and demonstrate that the presence of a distinct hydrophobic phase is required. Per unit volume, at low amounts of hydrophobic phase, the reaction of NO with O2 within the membranes is approximately 300 times more rapid than in the surrounding aqueous medium. In tissue, even though the membrane represents only 3% of the total volume, we calculate that 90% of NO reaction with O2 will occur there. We conclude that biological membranes and other tissue hydrophobic compartments are important sites for disappearance of NO and for formation of NO-derived reactive species and that attenuation of these potentially damaging reactions is an important protective action of lipid-soluble antioxidants such as vitamin E.

Animals↗

PubMed1998

Polymer concepts in tissue engineering.

Traumatic injuries, cancer treatment, and congenital abnormalities are often associated with abnormal bone shape or segmental bone loss. Restoration of normal structure and function in these cases requires replacement of the missing bone that may be accomplished by surgical transfer of natural tissue from an uninjured location elsewhere in the body. However, this procedure is limited by availability, adequate blood supply, and secondary deformities at the donor site. One strategy to overcome these problems is to develop living tissue substitutes based on synthetic biodegradable polymers. Three methods of bone regeneration using biodegradable polymers are being studied in our laboratory: tissue induction, cell transplantation, and fabrication of vascularized bone flaps. Injectable polymers are used for filling skeletal defects and guiding bone tissue growth. Their main advantage is minimizing the surgical intervention or the severity of the surgery. Polymer-cell constructs also hold great promise in the field of tissue engineering. They provide a scaffold on which cells grow and organize themselves. As the cells begin to secrete their own extracellular matrix, the polymer degrades and is eventually eliminated from the body, resulting in completely natural tissue replacement. Bone flaps can be fabricated ectopically into precise shapes and sizes. With an attached vascular supply, these flaps can be transferred into areas deficient in vascularity. This article discusses polymer concepts regarding bone tissue engineering and reviews recent advances of our laboratory on guided bone regeneration using biodegradable polymer scaffolds.

Animals↗

PubMed1998

Localization of inducible nitric oxide synthase mRNA in inflamed gastrointestinal mucosa by in situ reverse transcriptase-polymerase chain reaction.

Immunohistochemistry has been critical in determining the tissue localization of inducible nitric oxide synthase (iNOS). However, this technique suffers from nonspecific staining which may lead to false-positive results and the failure of antisera to recognize iNOS from different species. We developed a technique to determine the localization of iNOS mRNA, as opposed to protein, in tissue sections using an in situ RT-PCR (IS RT-PCR) technique. Sections of inflamed gastrointestinal mucosa were used because they were known to be positive for iNOS. The IS RT-PCR technique localized iNOS mRNA to the same sites as immunoreactive iNOS in human gastritis associated with Helicobacter pylori infection, Crohn's disease, and experimental inflammatory bowel disease induced by the hapten TNBS, in rat colon and in guinea pig ileum. The detection of mRNA had an excellent signal-to-noise ratio. Preservation of tissue morphology was poorer than that with immunohistochemistry due the cycles of heating required in the PCR process. This method could be very useful in detecting iNOS gene expression in situations of excessive nonspecific staining with immunohistochemistry or of failure of antibodies to react because of species differences. This technique is also readily applicable to detect RNA and DNA markers of other disease processes.

Animals↗

PubMed1998

Alteration of Kupffer cell function and morphology by low melt point paraffin wax in female Fischer-344 but not Sprague-Dawley rats.

This study was conducted to compare the effects of 60-day dietary exposure (2%) to low melt point paraffin wax (LMPW) on both general liver morphology and Kupffer cell (KC) function and morphology in female F-344 and Sprague-Dawley (SD) rats. Livers from only F-344 rats fed LMPW had granuloma formation/lymphoid cell aggregates with small areas of necrosis. Significant increases in serum alanine and aspartate aminotransferase as well as gamma-glutamyltransferase activities were detected only in treated F-344 rats. Additionally, detectable amounts of LMPW were present only in livers of treated F-344 rats. Because KC can be involved in granuloma formation, their morphology and function were examined. Electron microscopy revealed the presence of large, irregularly shaped, membrane-associated vacuoles in cells isolated from F-344 rats exposed to LMPW. These vacuoles were not seen in KC from control rats and rarely detected in KC isolated from LMPW-exposed SD rats. Moreover, indices of KC function including phagocytic activity and nitric oxide and superoxide anion production were significantly increased by KC isolated from F-344 rats exposed to LMPW (1.6-, 36-, and 2.2-fold increases, respectively) over untreated controls. In contrast, LPS-stimulated production of TNF and LTB4 was significantly decreased only in KC of LMPW-fed F-344 rats. No significant changes in these functions were observed in KC isolated from SD rats exposed to LMPW or from KC isolated from control F-344 or SD rats. These data provide evidence that dietary LMPW alters the morphology and functional capacity of KC of F-344 but not SD rats and these changes may ultimately lead to granuloma formation.

Animals↗

PubMed1998

Soft tissue reconstruction following hemipelvectomy.

BACKGROUND: Resection of primary and metastatic pelvic bone disease may result in large soft tissue deficits. Guidelines for soft tissue reconstruction following pelvic bone resection were evaluated in a retrospective study. METHODS: Over a 5-year period 21 patients (31%) required soft tissue reconstruction following pelvic bone resection. Data on these patients were retrieved from case records. RESULTS: Twelve patients underwent immediate, planned reconstruction, 1 a two-stage reconstruction, and 8 patients required a delayed procedure for complications after bone resection and primary closure. Soft tissue reconstruction was usually accomplished with muscle-based flaps; (25 flaps in 20 patients: 20 pedicled, 5 free), or with skin grafts alone (1 patient). Specific postreconstruction complications occurred in 9 patients, 5 in flaps based on the ipsilateral rectus muscle. CONCLUSION: Flap closure is indicated to achieve primary closure and eliminate deadspace. The ipsilateral rectus muscle should be used with caution and contralateral-based rectus flaps considered. Indications for free flaps include the size and location of the defect and availability of tissue from an amputated limb.

Adult↗

PubMed1998

Persistence of the biphasic ventilatory response to hypoxia in preterm infants.

OBJECTIVE: To characterize postnatal maturation of the biphasic ventilatory response to hypoxia in order to determine whether it persists beyond the first weeks of life in preterm infants, and the contributions of respiratory frequency and tidal volume to this response. METHODS: Stable preterm infants were studied at two postnatal ages, 2 to 3 weeks (n = 12) and 4 to 8 weeks (n = 12), before hospital discharge at 35 weeks (range, 33 to 38 weeks) of postconceptional age. Infants were exposed to 5 minutes of 15% (or 13%) inspired oxygen; ventilation, oxygen saturation, end-tidal partial pressure of carbon dioxide, and heart rate were simultaneously recorded. RESULTS: Minute ventilation exhibited a characteristic biphasic response to hypoxia at both postnatal ages, regardless of the development of periodic breathing. At both ages there was a transient increase in tidal volume, which peaked at 1 minute, accompanied by a sustained decrease in respiratory frequency as a result of significant prolongation of expiratory time. CONCLUSION: The characteristic biphasic ventilatory response to hypoxia persists into the second month of postnatal life in preterm infants. We speculate that this finding is consistent with the prolonged vulnerability of such infants to neonatal apnea.

Apnea↗

PubMed1998

Regionalization of infection prevention and control services in a publicly funded health care system.

In 1994 health services in the Edmonton region were consolidated into an integrated network called Capital Health. Infection control professionals in the region met to develop a vision for the future of infection control; the tasks were to prepare a proposal for a regional program, develop indicators for outcome measurements, and standardize guidelines and products. Although regionalization of infection control is a complex process, we have had success with a proactive approach led by infection control professionals.

Alberta↗

PubMed1998

Transosseous transposition of a pedicled rectus abdominis flap to cover hip wounds.

Bone-marrow transplantation may be complicated by aseptic necrosis of the femoral head. Prolonged immunosuppression places the patient at increased risk of infection and is of particular concern if replacement arthroplasty is contemplated. Infection of a prosthesis usually requires thorough debridement and removal of the device. However, attention must also be paid to the resultant cavity and soft-tissue cover. Several flaps have been reported for this problem, though limitations of flap size may make it difficult to achieve both objectives. This report describes the use a pedicled rectus abdominis flap that was tunnelled through the acetabulum in order to gain direct access to the hip and allow adequate length both to fill the dead-space and to provide cover.

Adult↗

PubMed1998

Selective growth promotion and growth inhibition of gram-negative and gram-positive bacteria by synthetic siderophore-beta-lactam conjugates.

Conjugates of a carbacephalosporin with hydroxamate, spermexatol, N alpha,N epsilon-bis(2,3-dihydroxybenzoyl)-L-lysine, mixed catecholate/hydroxamate and cyanuric acid-based siderophores were investigated for their potential to promote growth of siderophore indicator strains of Gram-negative and Gram-positive bacteria under iron depleted conditions, for their antibacterial activity and for their ability to use iron transport pathways to penetrate the Gram-negative bacterial outer membrane. The selective growth promotion of enterobacterial and pseudomonas strains by hydroxamate, spermexatol and mixed catecholate-hydroxamate siderophore-based conjugates bearing a L- or D-amino acid spacer was correlated with TonB dependent uptake routes. The preferred outer membrane siderophore receptor used in Escherichia coli was found to be Fiu, followed by Cir. Antagonistic effects of siderophores administered with the conjugates to determine antibacterial activity confirmed the active transport of conjugates via siderophore receptors. All of the conjugates were still able to diffuse through the porin proteins OmpC and OmpF. Nevertheless, strong inhibition of E. coli and Pseudomones aeruginosa outer membrane mutants DC2 and K799/61 compared to the parent strains indicated inefficient penetrability of all types of conjugates tested. Mycobacterium smegmatis SG 987 was able to use all of the siderophore-cephalosporin conjugates as growth promotors. Consequently there was no growth inhibition of this strain.

Bacterial Outer Membrane Proteins↗

PubMed1998

Antiinflammatory actions of cat's claw: the role of NF-kappaB.

BACKGROUND: Uncaria tomentosa is a vine commonly known as cat's claw or 'uña de gato' (UG) and is used in traditional Peruvian medicine for the treatment of a wide range of health problems, particularly digestive complaints and arthritis. PURPOSE: The aim of this study was to determine the proposed anti-inflammatory properties of cat's claw. Specifically: (i) does a bark extract of cat's claw protect against oxidant-induced stress in vitro, and (ii) to determine if UG modifies transcriptionally regulated events. METHODS: Cell death was determined in two cell lines, RAW 264.7 and HT29 in response to peroxynitrite (PN, 300 microM). Gene expression of inducible nitric oxide synthase (iNOS) in HT29 cells, direct effects on nitric oxide and peroxynitrite levels, and activation of NF-kappaB in RAW 264.7 cells as influenced by UG were assessed. Chronic intestinal inflammation was induced in rats with indomethacin (7.5 mg/kg), with UG administered orally in the drinking water (5 mg/mL). RESULTS: The administration of UG (100 microg/mL) attenuated (P < 0.05) peroxynitrite-induced apoptosis in HT29 (epithelial) and RAW 264.7 cells (macrophage). Cat's claw inhibited lipopolysaccharide-induced iNOS gene expression, nitrite formation, cell death and inhibited the activation of NF-kappaB. Cat's claw markedly attenuated indomethacin-enteritis as evident by reduced myeloperoxidase activity, morphometric damage and liver metallothionein expression. CONCLUSIONS: Cat's claw protects cells against oxidative stress and negated the activation of NF-kappaB. These studies provide a mechanistic evidence for the widely held belief that cat's claw is an effective anti-inflammatory agent.

Animals↗

PubMed1998

Reconstruction of posterior mandibular defects with soft tissue using the rectus abdominis free flap.

Immediate reconstruction of posterior mandibular composite defects by replacement with vascularised bone is ideal in principle, but may have excessive morbidity for certain patients who, because of poor general health or a poor tumour prognosis, are not good candidates for a complex surgical procedure. Also, if the temporomandibular joint (TMJ) is missing, the continuity of the entire mandible cannot be restored without either reconstructing the TMJ or resorting to a prosthesis. For such patients, reconstruction of the posterior defect without bone using a rectus abdominis free flap or other soft-tissue flap may be a good alternative. A series of 21 patients with posterior mandibular defects underwent this type of reconstruction. The patients reconstructed only with soft tissue were found to have a reasonable cosmetic appearance, and speech and swallowing function were very acceptable. For posterior mandibular defects that include a missing condyle this approach is an acceptable alternative, especially for patients who are poor candidates for more complex surgical procedures.

Bone Transplantation↗

PubMed1998

Does prior irradiation increase the risk of total or partial free-flap loss?

Answers to the question, "Does previous irradiation of a recipient site interfere with reconstruction by free-tissue transfer?" have been elusive. In an attempt to address that question, all free-flap procedures performed for reconstruction of the breast or of head and neck defects at the University of Texas M. D. Anderson Cancer Center between May 1, 1988 and February 15, 1996 were reviewed. The effects of prior irradiation of the recipient site on the incidence of total flap loss, partial flap loss, and thrombosis were assessed. During the study period, 1384 eligible free-flap reconstructions were performed. Total flap loss and partial flap loss were more common in the 428 flaps transferred to previously irradiated sites than in the patients without previous irradiation, but multiple logistic regression analysis showed that these differences were due to confounding factors. The authors conclude that previous irradiation of flap recipient sites does not statistically significantly affect the rate of partial or total free-flap loss.

Adult↗

PubMed1998

Reconstruction of complex radiation-induced injuries using free-tissue transfer.

The purpose of this study was to evaluate the use of free-tissue transfers for the reconstruction of radiation-induced complex injuries. The case files for patients who underwent reconstruction for radiation-induced injuries between May 1988 and November 1995 at The University of Texas M.D. Anderson Cancer Center were retrospectively reviewed. Thirty patients in whom 33 free flaps were done were included. Radiation-induced defects were located in the head and neck (n=23), extremities (n=4), chest wall (n=2), and inguinal area (n=1) The mean period between irradiation and injury was 78 months (range: 4 months to 38 years). Free-tissue transfer was successful in 97 percent (32/33) of patients. The overall complication rate was 40 percent (12/30). Flap donor sites included the fibula (n=12), latissimus dorsi (n=6), rectus abdominis (n=6), iliac crest (n=4), scapula (n=3), and radial forearm (n=2). Large-caliber vessels in the cervical, axillary, or inguinal regions were most commonly used to revascularize flaps. Vein grafts were used in five cases for the artery (2/5) or vein (3/5). Pedicle thrombosis occurred in three cases in recipient vessels located within the irradiated field. Two flaps were salvaged; one was lost, and the patient required a second free-flap reconstruction The mean follow-up was 40 months (range: 2.5 to 83 months). The disease-free survival rate was 67 percent (20/30), local failures occurred in 10 percent (3/30) of patients, and 23.3 percent (7/30) of patients either died or were lost to follow-up. Healing of radiation-induced wounds may be achieved using free-tissue transfers, but complications are frequent. Large-caliber irradiated vessels may be used to revascularize flaps, but there may be an increased risk of pedicle thrombosis.

Adult↗

PubMed1998

Second free flaps in head and neck reconstruction.

Over the past decade, free-tissue transfer has greatly improved the quality of oncology-related head and neck reconstruction. As this technique has developed, second free flaps have been performed for aesthetic improvement of the reconstructed site. This study evaluated the indications for and the success of second free flaps. Medical files for patients who underwent second free flaps for head and neck reconstruction at the University of Texas M.D. Anderson Cancer Center, from May 1, 1988 to November 30, 1996, were reviewed. The flaps were classified as being either immediate (done within 72 hr) or delayed (done within 2 years) reconstructions. Indications, risk factors, recipient vessels, outcome, and complications were analyzed. Of the 28 patients included in this study, 12 had immediate (nine as salvage after primary free flap failure, and three for reconstruction of a soft-tissue defect), and 16 had delayed second free flaps (two for reconstruction of a defect resulting from excision of recurrent tumors, and 14 for aesthetic improvement). Reconstruction sites included the oral cavity in 18 patients; the midface in six; the skull base in two; and the scalp in two. The success rate for the second free flaps was 96 percent. Five patients had significant wound complications. In a substantial number of cases, identical recipient vessels were used for both the first and second free flaps. The authors conclude that second free flaps can play an important role in salvaging or improving head and neck reconstruction in selected patients. In many cases, the same recipient vessels can be used for both the first and second flaps.

Adolescent↗

PubMed1998

Expression, activity and cellular localization of inducible nitric oxide synthase in rat ileum and colon post-irradiation.

PURPOSE: Studies were conducted to determine the acute effect of exposure to ionizing radiation on inducible nitric oxide synthase (iNOS) activity and expression in the rat ileum and colon. MATERIALS AND METHODS: Rats received whole body exposure to 10 Gy gamma-radiation and were studied 0.5-48 h later. Segments of ileum and colon were taken from anaesthetized rats for determination of myeloperoxidase activity (a marker of acute inflammation), and iNOS mRNA expression, enzyme activity and localization. RESULTS: Myeloperoxidase activity in ileum was not increased compared with shams until 48 h post-irradiation. In colon, myeloperoxidase activity was lower than shams at 48 h post-irradiation. Irradiation resulted in a dexamethasone-sensitive expression of iNOS mRNA in both the ileum and colon within 2h. Inducible NOS activity was significantly elevated in the ileum, but not in the colon. The elevated ileal nitric oxide synthase activity was significantly reduced by pretreatment with the iNOS inhibitor, aminoguanidine. Immunoreactivity for iNOS protein was localized to the epithelium and was apparent at 2-6 h post-irradiation in the ileum, but not the colon. CONCLUSIONS: Exposure to ionizing radiation results in the expression of iNOS in ileum and colon, but only significantly increases iNOS activity in the ileum. Inducible NOS-derived NO may participate in acute, whole body radiation-induced ileal dysfunction, independently of the development of an inflammatory response.

Animals↗

PubMed1998

Carcinogenesis, apoptosis and cell proliferation.

Biological agents, especially viruses, have been linked to the carcinogenesis process in major human cancers, especially lymphomas (retroviruses), hepatocarcinomas (hepatitis viruses) and carcinomas of the female genital organs (papilloma viruses). Chronic infection and inflammation have long been suspected to play a role in human carcinogenesis. Helicobacter pylori is the first bacterial infection recognized as a human carcinogen, essentially on the basis of epidemiological evidence of causality. Contrary to most other recognized human carcinogens, experimental evidence of carcinogenesis is lacking. As a consequence, mechanistic explanations of H. pylori carcinogenesis at this point in time are hypothetical.

Apoptosis↗

PubMed1998

Interleukin-10 attenuates experimental fetal growth restriction and demise.

Premature labor, fetal demise, and fetal growth restriction are accompanied by indices of inflammation or infection of the uteroplacental unit. To understand whether these events are causally related, we established an animal model of fetal demise and growth restriction and evaluated the potential utility of the anti-inflammatory cytokine interleukin-10 (IL-10). We administered low-dose endotoxin (lipopolysaccharide, or LPS, 100 microg/kg, i.p.) to third trimester rats (gestational days 14-20). Control rats received normal saline. A third group received IL-10 (100 microg/kg; s.c.) concomitantly with LPS for 7 prenatal days. Cytokine gene expression (IL-10 and TNF-alpha) was evaluated by RT-PCR and tissue levels (TNF-alpha) were determined by ELISA. Apoptosis was evaluated by TdT-mediated dUTP nick end labeling immunohistochemistry, and nitric oxide (NO) levels were quantified by microelectrode electrochemical detection in explants in culture media. LPS exposure resulted in 43% fetal demise and reduced the size of the surviving fetuses. Placental weight was not altered by LPS. IL-10 attenuated the LPS-induced fetal death rate (to 22%) and growth restriction (P<0.05). In normal rats, IL-10 did not affect fetus size or the incidence of resorptions, although placental size was marginally smaller. Increased uterine TNF-alpha content and NO release and apoptosis of uterine epithelia and muscularis were hallmarks of the LPS model. All were normalized by IL-10. IL-10 may represent a new therapeutic option for the treatment of a variety of perinatal complications. Benefit may result from the suppression of TNF-alpha- and NO-mediated cell death.

Animals↗