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Biomedical subjects

M J Miller

Publications and source records attributed to M J Miller.

At least 127 records · Page 7Linked to original sources
PubMed1998

Functional results of dental restoration with osseointegrated implants after mandible reconstruction.

We reviewed the cases of 20 cancer patients (mean age 47.4 years) in whom osseointegrated implants were used for dental restoration after mandibular reconstruction between January of 1988 and December of 1994. Seventy-one implants were placed into bone flaps (n = 60) or native mandible (n = 11), an average of 3.55 per patient (range, 2 to 5). Successful integration occurred in 91.5 percent (65 of 71); there were five early failures and one late failure, with no significant difference between the number lost in microvascular flaps (5 of 60) and native mandible (1 of 11) (as determined by Fisher's exact test). Functional evaluation included assessments of diet, speech, and cosmesis. Based on our review, we concluded that (1) implants enhance dental restoration in selected patients, and (2) microvascular bone flaps, including the fibula and iliac crest, are well suited for dental implant restoration.

Adult↗
PubMed1998

A comparison of resource costs of immediate and delayed breast reconstruction.

The resource cost (cost to our hospital) of providing mastectomy plus breast reconstruction was calculated for 276 patients who had received both mastectomy and breast reconstruction at our institution. All patients had completed the entire reconstructive process, including reconstruction of the nipple. The resource costs of providing mastectomy with immediate breast reconstruction were compared with those of mastectomy with subsequent delayed reconstruction. We found that the mean resource cost for the 57 patients who had separate mastectomy followed by delayed breast reconstruction ($28,843) was 62 percent higher than that of mastectomy with immediate reconstruction ($17,801; n = 219, p < 0.001). Similar differences were found when patients were subgrouped by type of reconstruction (TRAM versus tissue expansion and implants), by laterality (unilateral versus bilateral), and by history of preoperative irradiation. We conclude that mastectomy with immediate breast reconstruction is significantly less expensive than mastectomy followed by delayed reconstruction and can potentially conserve resources.

Breast Neoplasms↗
PubMed1998

Laparoscopic harvesting of jejunal free flaps for esophageal reconstruction.

Endoscopic harvest of the jejunum is indicated for the reconstruction of complex defects of the head and neck and specifically the reconstruction of circumferential defects of the esophagus. However, open laparotomies are associated with systemic and local morbidity and are often seen as prohibitively invasive procedures. Laparoscopy for intra-abdominal procedures is a proven technique that yields less morbidity and provides an anatomical exposure similar to that of the open approach. We report on 11 consecutive clinical cases of free jejunal flap harvesting with the laparoscopic technique and show that the procedure is feasible.

Adult↗
PubMed1998

Fat necrosis in free and pedicled TRAM flaps.

One purported advantage of the free transverse rectus abdominis musculocutaneous (TRAM) flap for breast reconstruction is that, compared with the conventional TRAM flap, it has a better blood supply and therefore a lower incidence of fat necrosis. We tested this claim by reviewing the incidence of fat necrosis, both clinically and mammographically, in a group of 110 patients with 116 TRAM flap breast reconstructions who had undergone mammography of their reconstructed breasts. Of the 49 breasts reconstructed with free TRAM flaps, 4 (8.2 percent) had clinically evident fat necrosis, and 1 (2.0 percent) had fat necrosis that was detectable by mammography. Of the 67 breasts reconstructed with conventional TRAM flaps, 18 (26.9 percent) had clinically detectable fat necrosis, and 9 (13.4 percent) had fat necrosis that was detectable mammographically. Both of these differences were statistically significant (p = 0.0113 for clinical fat necrosis; p = 0.031 for mammographic fat necrosis). Fat necrosis was more common in patients who were obese or had a history of smoking, but neither association was statistically significant. We conclude that the use of the free TRAM flap reduces the incidence of fat necrosis in the reconstructed breast.

Abdominal Muscles↗
PubMed1998

Muscarinic receptor binding sites of the M4 subtype in porcine lung parenchyma.

Muscarinic acetylcholine receptors regulate distal airway resistance and secretion. The subtype expressed in the lung in different species remains uncertain. It has recently become possible to identify the M4 subtype by careful comparison of antagonist affinities. We characterized the binding of [3H]quinuclidinyl benzilate ([3H]QNB) to muscarinic receptors in cell membranes from lung parenchyma of 2-8 week old pigs in comparison to cloned human M3 and M4 receptors expressed in COS cells, to M2 in rat atria and to M4 in bovine adrenal medulla. In porcine lung, [3H]QNB bound with high affinity (Kd = 95 +/- 9 pM) to a single homogeneous population of muscarinic receptor sites (Bmax = 340 +/- 10 fmol/mg protein). Competition studies showed that the affinity (expressed as pKi) of 3 selective blockers was in close agreement between pig lung and cloned human m4 (r = 0.996). A series of 10 blockers showed affinities closely matching reported values for M4 receptors of the adrenal medulla (r = 0.965). Conversely, affinity values in porcine lung differed significantly (P < 0.05, t-test) from those determined in parallel with either human cloned M3 or with rat atria expressing the M2 subtype. We conclude that pig lung muscarinic receptor binding sites most closely resemble the M4 subtype, in contrast to the M3 subtype typical of large airways in this species.

Adrenal Medulla↗
PubMed1998

Differential effects of protein kinase A on Ras effector pathways.

Ras mutants with the ability to interact with different effectors have played a critical role in the identification of Ras-dependent signaling pathways. We used two mutants, RasS35 and RasG37, which differ in their ability to bind Raf-1, to examine Ras-dependent signaling in thyroid epithelial cells. Wistar rat thyroid cells are dependent upon thyrotropin (TSH) for growth. Although TSH-stimulated mitogenesis requires Ras, TSH activates protein kinase A (PKA) and downregulates signaling through Raf and the mitogen-activated protein kinase (MAPK) cascade. Cells expressing RasS35, a mutant which binds Raf, or RasG37, a mutant which binds RalGDS, exhibited TSH-independent proliferation. RasS35 stimulated morphological transformation and anchorage-independent growth. RasG37 stimulated proliferation but not transformation as measured by these indices. TSH exerted markedly different effects on the Ras mutants and transiently repressed MAPK phosphorylation in RasS35-expressing cells. In contrast, TSH stimulated MAPK phosphorylation and growth in cells expressing RasG37. The Ras mutants, in turn, exerted differential effects on TSH signaling. RasS35 abolished TSH-stimulated changes in cell morphology and thyroglobulin expression, while RasG37 had no effect on these activities. Together, the data indicate that cross talk between Ras and PKA discriminates between distinct Ras effector pathways.

Animals↗
PubMed1998

Bacteria rapidly colonize and modulate healing of gastric ulcers in rats.

The stomach is generally regarded as an environment that is not conducive to bacterial colonization. In this study, we examined the possibility that this changes significantly when an ulcer has formed and that colonization of ulcers interferes with the normal healing process. Gastric ulcers were induced by serosal application of acetic acid. The relationship between ulcer healing and bacterial colonization was examined. The effects of antibiotics, induction of Lactobacillus colonization, and selective colonization with an antibiotic resistant strain of Escherichia coli on ulcer healing were examined. Within 6-12 h of their induction, gastric ulcers were colonized by a variety of bacteria, with gram-negative bacteria predominating. Suppression of colonization with antibiotics resulted in marked acceleration of healing. Induction of Lactobacillus colonization also accelerated ulcer healing. The beneficial effects of antibiotics were reversed through selective colonization with antibiotic-resistant E. coli. Bacterial colonization occurred irrespective of the method used to induce the ulcer. This study demonstrates that colonization of gastric ulcers in rats occurs rapidly and significantly impairs ulcer healing. This effect appeared to be primarily attributable to gram-negative bacteria.

Acetic Acid↗
PubMed1998

Genistein and gut inflammation: role of nitric oxide.

Genistein, a principal soy isoflavone, has been identified as a protein kinase inhibitor that possesses immunosuppressive and anti-inflammatory properties. The aim of the study was to determine if genistein modified chronic ileitis in guinea pigs induced by the hapten trinitrobenzene sulfonic acid (TNBS), and the activity index of cultured macrophages (RAW 264.7 cells) stimulated with lipopolysaccharide (LPS). Genistein at low doses (0.1 mg/kg, s.c.) had mild anti-inflammatory effects in TNBS ileitis. Therapeutic benefit included a reduction in nitric oxide production, granulocyte infiltration and improved mucosal architecture. Genistein, at low doses, also appeared to attenuate immunohistochemical staining for inducible nitric oxide synthase (iNOS) and nitrotyrosine. The beneficial effects of genistein were not apparent at doses above 0.1 mg/kg. We found that genistein also inhibited LPS-induced nitrite production by cultured macrophages and protected against LPS-induced necrosis despite its ability to cause apoptosis. These results indicate that genistein displayed mild anti-inflammatory properties which may, in part, involve an attenuation of nitric oxide release via inducible nitric oxide synthase, and the formation of peroxynitrite.

Animals↗
PubMed1998

A comparison of blood lead levels in bald eagles from two regions on the great plains of North America.

The connection between bald eagles (Haliaeetus leucocephalus) and the consumption of waterfowl, lead shotshell pellet ingestion, and subsequent lead exposure is well documented in the United States and is presumed also to be widespread in Canada. We compared blood lead concentrations in samples from bald eagles ranging in age from 0.5- to 1.5-yr-old at Galloway Bay, Saskatchewan, Canada (n = 97) during October-November, 1992-95 and Hauser Lake, Montana, USA (n = 81) during October-December, 1990-94, within the Great Plains region of North America. Abundant prey are available in the form of hunter-injured waterfowl in Saskatchewan and spawning salmon in Montana; both areas attract large numbers of mid-continent bald eagles during fall migration. Blood lead concentrations suggestive of recent lead exposure (> 0.201 microgram/ml) were found in 32% and 8% of eagles at Hauser Lake and Galloway Bay, respectively, when samples from each study area were analyzed independently at two laboratories. To determine if this difference was an artifact of interlaboratory variation, we determined a correction factor by reanalyzing 14 Saskatchewan blood samples at each laboratory and predicted blood lead concentrations from Hauser Lake had the samples been analyzed at the Canadian laboratory. Adjusted blood lead concentrations of samples from Hauser Lake indicated that 21% of eagles were recently exposed to lead, a proportion not significantly different from the proportion of the same exposure category at Galloway Bay. Our data do not support the supposition that a large proportion of bald eagles feeding on waterfowl in areas of high hunting pressure will be exposed to lead via consumption of lead shotshell pellets in waterfowl.

Animals↗
PubMed1998

Computer-assisted histometric analysis of tissue-engineered ovine bone.

OBJECTIVE: To develop a computer-assisted histometric technique that quantitatively determines the amount of regenerating bone, while excluding fibrovascular tissue and void spaces, in tissue-engineered bone constructs. To this end, a histometric technique was developed that couples digital tiling with adaptive, multiband color thresholding (AMBCT). STUDY DESIGN: To test the technique, a previously described model bone tissue-engineered construct filled with morcellized bone graft was employed. Histometric techniques were applied to quantify the amount of bone formed following eight weeks of implantation. RESULTS: The histometric technique was able to yield quantitative information regarding the amount of bone despite intrahistologic and interhistologic differences in staining. The technique is user friendly and highly automated. In addition to area fractions, the technique can provide bone ingrowth profiles as a function of geometry and implantation time. CONCLUSION: Digital tiling coupled with AMBCT offers an easy, fast and reproducible technique that aids in quantification of bone within histologic sections. In addition, the technique can be adapted to quantification of other tissues. Further studies are under way to investigate the potential of correlating the histometric technique with mechanical strength analyses of tissue-engineered bone specimens.

Animals↗
PubMed1998

Transferrin in normal and neoplastic endocervical tissues: distribution and receptor expression.

OBJECTIVE: Our recent studies showed that lactoferrin seems to be down-regulated in endocervical adenocarcinomas. We extended those studies to examine the expression of transferrin (Tf) and its receptor (TfR) in endocervical carcinogenesis and any relationship to the expression of lactoferrin, steroid receptors and the proliferative index. STUDY DESIGN: A retrospective study was performed using sections prepared from paraffin-embedded, formalin-fixed surgical specimens of normal endocervix, endocervical adenocarcinoma and cervical adenocarcinoma in situ. Standard immunohistochemical techniques were used to localize Tf and its receptor in the normal and malignant endocervix. In situ detection of mRNA for Tf and the TfR was also performed. The relative intensity of the immunoreaction was estimated using digital computer image analysis. Statistical significance was tested by Student's t test. RESULTS: No differences in the relative staining intensity for Tf and TfR proteins were noted between normal and neoplastic glands. However, quantitation revealed that a greater number of malignant glands stained positive for TfR than observed in the normal endocervix. Expression of Tf and TfR did not correlate with the expression of steroid receptors and lactoferrin or with the rate of proliferation. CONCLUSION: We have demonstrated the expression of Tf and its receptor by both normal and malignant endocervical glands. The increased number of malignant endocervical glands expressing TfR may indicate a special requirement for Tf and the iron that it carries. Our data provide evidence for the existence of a Tf, TfR autocrine or paracrine circuit involved in the regulation of normal and abnormal endocervical physiology.

Adenocarcinoma↗
PubMed1997

Chromosome localization and structure of the murine cyclin G1 gene promoter sequence.

Cyclins play an essential role in the control of the cell cycle. In this study the murine cyclin G1 gene expression, structure, and chromosomal localization were examined. Genes with high homology to murine cyclin G1 were detected in various mammals, including human, monkey, rat, dog, cow, and rabbit, but not in yeast or chicken. Cyclin G1 gene was expressed in all murine tissues examined, with the highest levels in cardiac and skeletal muscle. A 10,366-bp genomic DNA fragment encompassing the promoter region and the 5'-flanking region of the gene was cloned and sequenced. Three putative binding sites for the myocyte enhancer factor-2 family of transcription factors were revealed. Furthermore, an upstream p53-binding site was localized to nucleotides -252 to -233 and a new putative p53-binding site was identified in the first intronic region at nucleotides 275 to 294. By fluorescence in situ hybridization, the cyclin G1 gene was mapped to mouse chromosome 11B1.1. This region is homologous with human chromosome 5q31-q32, consistent with the recent mapping of the human cyclin G1 gene to chromosome 5q32-q34. Localization of murine cyclin G1 will facilitate determination of gene linkage and the identification of synteny groups in mammals and of DNA elements in or near this gene that mediate its tissue expression or development-specific pattern of expression.

Amino Acid Sequence↗
PubMed1997

Semiautomated resolution of overlapping stutter patterns in genomic microsatellite analysis.

Microsatellites are polymorphic, short nucleotide repeating units scattered more or less randomly throughout the genome. They are readily detectable by polymerase chain reaction (PCR) and often used as genomic markers. One problem in the analysis of microsatellite data is the appearance of secondary bands during PCR that result in extended banding patterns. These "stutter" patterns may overlap in heterozygous alleles and obscure the overall pattern, severely interfering with analysis. This paper develops a model that successfully predicts the general shape of stutter patterns. It then presents techniques for measuring the intensity of the individual contributing alleles. The model is based on the assumption that there is a certain probability of losing or gaining a microsatellite repeat unit during each PCR cycle. The effect is cumulative, with the chance of losing a repeat unit being much greater than that of gaining one, which leads to a gradual reduction in the mean length of the pattern with increased PCR cycles. This can be modeled quantitatively to predict the shape of the stutter pattern, a prediction borne out by experiment. Next, a least-squares technique is presented that is used to analyze the overlapping stutter patterns and determine the relative concentration of each microsatellite in heterozygous alleles. The technique is based on the observation that, at least for microsatellites of approximately the same length, the relative intensity of each band in the stutter pattern is approximately the same for each allele. The stutter shape is most easily determined from homozygous alleles. It can also be approximated from heterozygous samples if the difference between the lengths of the primary microsatellite bands can be determined.

Algorithms↗
PubMed1997

Protection of mice against Trypanosoma cruzi by immunization with paraflagellar rod proteins requires T cell, but not B cell, function.

Previous studies have shown that immunization of mice with the paraflagellar rod proteins (PAR) of Trypanosoma cruzi induces an immune response capable of protecting mice against an otherwise lethal challenge with this parasite. Herein, we define immunologic responses that do or do not play a critical role in PAR-mediated protection. Firstly, PAR-immunized Ab-deficient (muMT) strain mice survived an otherwise lethal T. cruzi challenge, indicating that a B cell response is not required for PAR-induced immunity. However, beta2m -/- mice, which are severely deficient in MHC class I and TCR alphabeta+ CD8+ CD4- T cells, did not survive challenge infection following PAR immunization, indicating that MHC class I/CD8+ T cell function is necessary for protection induced by PAR immunization. Surprisingly, PAR-immunized mice depleted of CD4+ T cells survived a T. cruzi challenge for >84 days postinfection while maintaining a parasitemia that is generally thought to be lethal (i.e., >10(6) trypomastigotes/ml), thus associating CD4+ T cell function with the process of parasite clearance. Consistent with this association, CD4+ T cells from PAR-immunized mice released INF-gamma and stimulated T. cruzi-infected macrophages to release nitric oxide. The importance of IFN-gamma in PAR-induced protective immunity is further indicated by the observation that PAR-immunized INF-gamma knockout mice developed an extremely high parasitemia and did not survive a challenge infection. Thus, while Ab-mediated immune mechanisms are not required for protection induced by PAR immunization, T cell responses are necessary for both elimination of bloodstream parasites and survival.

Animals↗
PubMed1997

Anti-inflammatory properties of interleukin-10 administration in hapten-induced colitis.

Therapeutic efficacy of interleukin-10 administration in colonic inflammation was assessed in rats. Following intracolonic instillation of 2,4,6-trinitrobenzene sulfonic acid (TNBS), subcutaneous administration of 1-1000 micrograms/kg per day interleukin-10, or a placebo (0.9% NaCl) was commenced and continued for 5 days. Interleukin-10 administered at 1, 10 and 100 micrograms/kg per day significantly reduced myeloperoxidase activity by 34, 57, and 28%, respectively, compared to the placebo-treated group, which was paralleled by an attenuation of colonic tumor necrosis factor alpha (TNF-alpha) content. In contrast, the severity of mucosal necrosis was not affected by interleukin-10 administration at the dose range used. In addition, the 10-fold elevation in nitric oxide release, 5-fold rise in colonic nitrite production and enhanced expression of inducible nitric oxide synthase, associated with TNBS colitis, was not suppressed by interleukin-10. Interleukin-10 gene expression was elevated during the first 14 days of TNBS colitis. We conclude that 5 days administration of interleukin-10 in TNBS colitis displays mild anti-inflammatory properties which were not mediated via a nitric oxide-dependent pathway, but may involve TNF-alpha.

Animals↗
PubMed1997

Inducible nitric oxide synthase expression and erythropoietin production in human hepatocellular carcinoma cells.

We have previously reported an interaction of nitric oxide (NO) and cyclic 3',5'-guanosine monophosphate (cGMP) in erythropoietin (Epo) production. Further studies have been carried out to clarify the role of NO in the hypoxic regulation of Epo production in Epo producing human hepatocellular carcinoma (Hep3B) cells, which produce Epo in response to physiological stimuli. Our reverse transcriptase-polymerase chain reaction (RT-PCR) technique revealed the expression of iNOS mRNA in Hep3B cells after incubation under hypoxic (1% O2) conditions for 6 hr. Hypoxia also significantly increased medium levels of nitrite in Hep3B cells. In order to investigate the role of NO in Epo production in Hep3B cells under normoxic (20% O2) conditions, we have studied the effects of interferon-gamma (IFN-gamma) on Epo production. IFN-gamma is known to induce iNOS and enhance the production of NO. IFN-gamma produced significant increases in medium levels of Epo and nitrite. IFN-gamma also significantly increased cGMP levels in Hep3B cells. Furthermore, NG-nitro-L-arginine methyl ester (L-NAME), an NO synthase inhibitor, significantly decreased IFN-gamma induced elevations in medium levels of Epo and nitrite as well as cGMP levels in Hep3B cells. These results provide further support for an important role of the NO/cGMP system in hypoxic regulation of Epo production in Hep3B cells.

Base Sequence↗
PubMed1997

RalGDS functions in Ras- and cAMP-mediated growth stimulation.

Thyroid-stimulating hormone stimulates proliferation through both the cAMP-dependent protein kinase and Ras but not through Raf-1 and mitogen-activated and extracellular signal-related kinase kinase. We now report that thyroid-stimulating hormone represses mitogen-activated protein kinase activity and that microinjection of an effector domain mutant Ha-Ras protein, Ras(12V,37G), defective in Raf-1 binding and mitogen-activated protein kinase activation, stimulates DNA synthesis in quiescent and thyroid-stimulating hormone-treated thyrocytes. A yeast two-hybrid screen identified RalGDS as a Ras(12V,37G) binding protein and therefore a potential effector of Ras in these cells. Associations between Ras and RalGDS were observed in extracts prepared from thyroid cells. Microinjection of a mutant RalA(28N) protein thought to sequester RalGDS family members reduced DNA synthesis stimulated by Ras as well as cAMP-mediated DNA synthesis in two cell lines which respond to cAMP with mitogenesis. These results support the idea that RalGDS may be an effector of Ras in cAMP-mediated growth stimulation.

Cyclic AMP↗