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Biomedical subjects

J A Hunt

Publications and source records attributed to J A Hunt.

At least 55 records · Page 3Linked to original sources
PubMed1998

Macrophage--polymer interactions.

One of the most notable and initial indications of the body's response to an implanted material is the inflammatory response, a process which is known to be largely influenced by the activation of macrophages and other cell types. Thus, the magnitude of the inflammatory response can be related to the level of activation of macrophages. As certain well defined morphological changes are known to accompany cell activation, we quantitatively evaluated the cell--substrate interactions, between a range of polymeric materials and isolated macrophages in vitro, using microscopy and image analysis. This enabled us to assess the morphology of the cells, and how the morphology of the macrophages was influenced by changes in time and substrate. This method provided detailed images which were used to evaluate cell-substrate interactions. It was found that, polyurethane (PU) and poly(dimethylsiloxane) (Si) samples displayed a similar pattern in cell behaviour, whilst macrophages placed in contact with polyvinylchloride (PVC) samples continually displayed a more activated morphology with increasing time throughout the test period. As well as providing a detailed analysis of cell-substrate interactions this study also highlighted the advantages of employing an image analysis program for a more comprehensive and reproducible form of assessment of cellular morphology.

Biocompatible Materials↗
PubMed1998

No relationship between carbohydrate intake and effect of acarbose on HbA1c or gastrointestinal symptoms in type 2 diabetic subjects consuming 30-60% of energy from carbohydrate.

OBJECTIVE: To determine the relationship between carbohydrate intake and the effect of acarbose on HbA1c in subjects with type 2 diabetes treated with acarbose alone, acarbose plus sulfonylurea, acarbose plus metformin, or acarbose plus insulin. RESEARCH DESIGN AND METHODS: We conducted a double-blind randomized placebo-controlled study in which subjects with diabetes in four treatment strata (77 on diet alone, 83 treated with metformin, 103 treated with sulfonylurea, and 91 treated with insulin) were randomized to treatment with placebo or acarbose for 12 months. Before randomization, and 3, 6, 9, and 12 months after randomization, fasting blood was obtained for HbA1c, and 3-day diet records were collected. Subjects who completed at least 6 months of acarbose therapy and provided at least three 3-day diet records were included. RESULTS: In the 114 subjects included in this analysis, carbohydrate intake varied from approximately 30-60% of energy There was no significant relationship between carbohydrate intake and change in HbA1c in any of the four treatment strata (diet: n=26, r=0.35, P=0.076; metformin: n=27, r=0.26, P=0.19; sulfonylurea: n=35, r=0.24, P=0.16; insulin: n=25, r=-0.27, P=0.19). In the 80 subjects consuming <50% of energy from carbohydrate, the fall in HbA1c (7.83 +/-0.17% at baseline to 6.72+/-0.13% on acarbose, P < 0.001) was no different from that of the 34 subjects consuming >50% of energy from carbohydrate (7.55+/-0.25% at baseline to 6.66+/-0.23% on acarbose, P < 0.001). There was no difference in carbohydrate intake between those who dropped out of the study because of gastrointestinal side effects and those who did not, and there was no relationship between severity of symptoms and the composition of the diet. CONCLUSIONS: In subjects with type 2 diabetes consuming 30-60% of energy from carbohydrate, the effect of acarbose on HbA1c and gastrointestinal symptoms was not related to carbohydrate intake. Because most people consume at least 30% of energy from carbohydrate, we conclude that no special diet is needed for acarbose to be effective in improving blood glucose control in the treatment of type 2 diabetes.

Acarbose↗
PubMed1998

Variation of postprandial plasma glucose, palatability, and symptoms associated with a standardized mixed test meal versus 75 g oral glucose.

OBJECTIVE: To compare within-subject variability of plasma glucose measured 2 h after a glucose tolerance test (GTT) with that of plasma glucose measured 2 h after administration of a standardized test meal (diabetes screening product [DSP], Ceapro, Edmonton, Alberta, Canada) and to determine the relationship between the two sets of plasma glucose measurements. RESEARCH DESIGN AND METHODS: Plasma glucose and insulin responses of 36 overnight-fasted subjects (10 lean normal, 9 obese normal, 9 with impaired glucose tolerance [IGT], and 8 with mild diabetes) were studied on eight different mornings after they consumed 75 g oral glucose or 50 g carbohydrate from the DSP. Each test meal was repeated four times by each subject. Within-subject coefficients of variation (CVs) (CV = 100 x SD/mean) of plasma glucose concentrations 2 h after administration of the GTT and DSP were compared by repeated measures ANOVA and linear regression analysis. RESULTS: Mean plasma glucose 2 h after administration of the DSP (D) was linearly related to that 2 h after the GTT (G): G = 1.5 x D - 1.6 (r = 0.97, P < 0.0001). The CV of 2-h plasma glucose was significantly lower after administration of the DSP, 10.5 +/- 1.0%, than after the GTT, 12.7 +/- 1.18% (P = 0.025). The effect of test meal on CV differed in different groups of subjects (P = 0.018), with the largest difference found in IGT subjects, in whom the CV after DSP administration was 47% less than after the GTT (P = 0.0005). The DSP was significantly more palatable and produced fewer adverse symptoms than the GTT. CONCLUSIONS: Plasma glucose concentrations measured 2 h after DSP administration are closely related to those measured 2 h after the GTT but are more consistent than the 2-h post-GTT concentrations within the critical IGT range. This finding suggests that measurement of plasma glucose 2 h after administration of the DSP may allow more precise discrimination among normal glucose levels, IGT, and diabetes than measurement of plasma glucose 2 h after the GTT.

Administration, Oral↗
PubMed1997

Macrophage subpopulation differentiation by stimulation with biomaterials.

Macrophages were elicited by the subcutaneous implantation of ultra high molecular weight polyethylene (UHMWPE) for periods of 2, 7, and 14 days in rats. Exudates of varying volumes were produced that was comprised of granulocytes, monocytes, immature and mature macrophages, and T-lymphocytes. No B-lymphocytes were observed at any time periods. Cell types were identified by their granularity and positivity to the following antibodies: leucocyte common antigen (LCA, pan leucocyte); CD11b/c (macrophage/monocyte); CD5 (T-lymphocyte); CD45RA (B-lymphocyte); HIS48 (granulocyte); ED2 (mature macrophage); and MCP-1 (monocyte chemoattractant protein 1). Monocytes isolated from control rat blood demonstrated a size slightly larger than that of granulocytes but with less granularity. Their size and granularity were followed over increasing time periods. The macrophages elicited by UHMWPE showed a similar pattern, with the exception of an apparently highly granular subpopulation with volumes similar to that of granulocytes but significantly more granular. The granular macrophage subset had a very high degree of ED2 and MCP-1 positivity, and their proportion, compared with other macrophages, was greatest at 2 days. The high MCP-1 expression was accounted for by MCP-1 molecules bound to the surface of a small proportion of macrophages that were activated. It is postulated that this subpopulation was responsible for the synthesis of the MCP-1 and could indicate a mechanism by which monocytes are attracted to the site of an implanted material.

Animals↗
PubMed1997

Hydrophilicity of polymers and soft tissue responses: a quantitative analysis.

This study investigates the effect of changing the hydrophilicity of polyurethane on the soft tissue inflammatory response after implantation into rats. A series of five polyurethanes were made from the macrodiols poly(ethylene oxide) (PEO), poly(tetramethylene oxide) (PTMO), poly (hexamethylene oxide) (PHMO), poly(octamethylene oxide) (POMO), and poly(decamethylene oxide) (PDMO). In the sequence the macrodiols become less polar and phase separation in the polymer increases, creating a range of hydrophilicity. These five polyurethanes were studied along with commercial Pellethane 2363-80A. The materials were implanted intramuscularly into rats for 7 days, 1 month, and 3 months. The inflammatory response was analyzed using a combination of immunohistochemistry, enzyme histochemistry, and image analysis to determine the specific cell types involved in the response and to quantify these cellular responses. The presence of three cytokines also was investigated. The cell types targeted were neutrophils, monocytes, macrophages, and T and B lymphocytes. The cytokines target were tumor necrosis factor alpha (TNF alpha), interleukin 6 (IL-6), and monocyte chemotactic protein 1 (MCP-1). All samples were positive for macrophages and activated macrophages, TNF alpha, and MCP-1, and negative for all other antibodies. The response was sustained throughout the implantation period with no significant difference among the samples except at the 7-day time point. The study demonstrated an absence of lymphocytes and neutrophils in a response that was sustained in terms of macrophages with the presence of TNF alpha and MCP-1 and the absence of IL-6. The position of subsets of macrophages with respect to increasing distance from the implants was demonstrated to be significant and consistent within this series of polyurethanes.

Animals↗
PubMed1997

Selection of carbonic anhydrase variants displayed on phage. Aromatic residues in zinc binding site enhance metal affinity and equilibration kinetics.

In all metalloenzymes, hydrophobic residues surround the metal binding site. In carbonic anhydrase II (CAII) residues Phe93, Phe95, and Trp97 flank two of the three histidines that coordinate zinc to form a hydrophobic cluster beneath the zinc binding site. A library of CAII variants differing in these hydrophobic amino acids was prepared using cassette mutagenesis, then displayed on filamentous phage, and screened for proteins retaining high zinc affinity. Wild-type CAII was enriched 20-fold by selection, and consensus residues at each position were identified from the enriched CAII variants (Ile, Phe, Leu, and Met at position 93; Ile, Leu, and Met at position 95; and Trp and Val at position 97). Highly selected variants have zinc affinity and catalytic activity nearly equal to that of wild-type CAII, indicating that the aromatic residues are not absolutely essential. However, the zinc dissociation rate constant and catalytic activity of the variants correlate with the volume of the amino acids at positions 93, 95, and 97. In summary, metalloenzyme variants displayed on phage can be selected on the basis of metal affinity; such methods will be useful for optimization of metal ion biosensors.

Bacteriophages↗
PubMed1997

Frequency and duration of remission after isolated limb perfusion for melanoma.

OBJECTIVE: To examine the frequency and duration of complete remission for locally recurrent and metastatic limb melanoma after isolated limb perfusion (ILP) with cytotoxic agents. DESIGN: A case series of 114 consecutive therapeutic ILPs performed between April 1984 and April 1994 and a review of previously published studies. SETTING: A tertiary referral center for melanoma treatment, located at a university teaching hospital. RESULTS: Of 111 assessable ILPs, 81 (73%) resulted in complete limb tumor remission and 14 (13%) resulted in partial remission (defined as a reduction in size of tumor deposits by > 50%). Complete remission was maintained in 37 (46%) of the 81 cases without any further treatment (median follow-up, 33 months; range, 8-112 months). Of the other 44 cases, disease subsequently recurred in the perfused limb (median time to recurrence, 9.5 months; range, 2-65 months). In 19 of these cases, however, the limb was again disease free at last follow-up after local surgery (12 cases) or a repeat ILP (7 cases). Overall, complete locoregional control was achieved after 50% of assessable ILPs, and a long-term disease-free state in the limb was achieved, with or without further treatment, in 56 (69%) of the 81 cases in which an initial complete remission occurred. For 743 therapeutic ILPs undertaken in 12 series previously reported in the literature, an initial complete remission was reported in 50% of these cases and partial remission in 32%. CONCLUSION: Therapeutic ILP is an effective form of treatment for patients with recurrent and metastatic limb melanoma, achieving short- and long-term results that are superior to those achievable by any other form of treatment currently used.

Adult↗
PubMed1997

Sequence diversity and molecular evolution of the merozoite surface antigen 2 of Plasmodium falciparum.

Eleven new alleles of the Plasmodium falciparum merozoite surface antigen 2 (MSA2) from Papua New Guinea were analyzed by direct sequencing of polymerase chain reaction (PCR) products. We have used the sequence information to trace the molecular evolution of MSA2. The repeats of ten alleles belonging to the 3D7 allelic family differed considerably in size, nucleotide sequence, and repeat copy number. In the repeat region of these new alleles, codon usage was extremely biased with an exclusive use of NNT codons. Another new allele sequenced belonged to the FC27 family and confirmed the family-specific conserved structure of 96 and 36 bp repeats. In order to assess sequence microheterogeneity within samples defined as the same genotype by restriction fragment length polymorphism (RFLP), we have analyzed single-strand conformation polymorphism (SSCP) of different samples of the most frequent allele (D10 of the FC27 family) in the study population. No sequence heterogeneity could be detected within the repeat region. Based on analysis of the repeat regions in both allelic families, we discuss the hypothesis of a different evolutionary strategy being represented by each of the allelic families. Kew words: Merozoite surface antigen 2 - Nucleotide sequence comparisons - Molecular evolution

Amino Acid Sequence↗
PubMed1997

Biogeographic analysis of the Uhu and LOA elements in the Hawaiian Drosophila.

Two transposable elements have been isolated from the Hawaiian Drosophila, the Uhu and LOA elements. The Uhu element has been shown to be present in a group of closely related species, the planitibia subgroup of the picture-winged Drosophila. This study examines the distribution of the Uhu element in several other subgroups of the picture-winged Drosophila, as well as the modified-mouthparts and antopocerus groups of the Hawaiian Drosophila. The LOA element has a much more limited distribution, having only been found in representatives of the planitibia and grimshawi subgroups of the picture-winged Drosophila. For both the Uhu and LOA elements there is an inverse correlation between the copy number of the element and the age of the island on which the species is endemic, i.e., species endemic to the Island of Hawaii, the youngest island, have the highest copy number, while species endemic to Kauai, the oldest island, have the lowest copy number of the element. The correlation suggests there is a relationship between speciation and the activity of transposable elements.

Animals↗
PubMed1997

Techniques to investigate cellular and molecular interactions in the host response to implanted biomaterials.

Evaluation of the host response to implanted materials requires systematic, objective investigations of responses at both the cellular and molecular levels. This article explains the basis behind two technologies: antibody and molecular techniques, which will give valuable information when applied to investigations of cells and molecules involved in the host biomaterial interaction. Such investigations are well underway, and a number of groups are now studying well characterised cell markers or molecules to evaluate the host response to biomaterials. Here we outline current technologies for the development of antibodies as tools to study cell markers or molecules, including those for which reagents are not yet available and DNA based technologies, whose continued application should prove an invaluable adjunct to existing approaches. These technologies may be particularly valuable to investigations focusing on newly characterised cytokines, receptors or cell adhesion molecules and subsequently provide a way forward for the production of advanced biomaterials.

Animals↗
PubMed1997

Amphiphilic peroxynitrite decomposition catalysts in liposomal assemblies.

BACKGROUND: Peroxynitrite (ONOO-), a toxic biological oxidant, has been implicated in many pathophysiological conditions. The water-soluble porphyrins 5,10,15,20-tetrakis(N-methyl-4'-pyridyl)porphinato iron(III) (FeTMPyP) and manganese(III) (MnTMPyP) have recently emerged as potential drugs for ONOO- detoxification, and FeTMPyP has demonstrated activity in models of ONOO- related disease states. We set out to develop amphiphilic analogs of FeTMPyP and MnTMPyP suitable for liposomal delivery in sterically stabilized liposomes (SLs). RESULTS: Three amphiphilic iron porphyrins (termed 1a-c.) and three manganese porphyrins (termed 2a-c.) bound to liposomes and catalyzed the decomposition of ONOO-. The polyethylene-glycol-linked metalloporphyrins 1b. and 2b. proved the most effective of these catalysts, rapidly decomposing ONOO- with second-order rate constants (kcat) of 2.9 x 10(5) M-1 s-1 and 5.0 x 10(5) M-1 s-1, respectively, in dimyristoylphosphatidylcholine liposomes. Catalysts 1b. and 2b. also bound to SLs, and these metalloporphyrin-SL constructs efficiently catalyzed ONOO- decomposition (kcat approximately 2 x 10(5) M-1 s-1). The analogous metalloporphyrins 1a. and 2a., which are not separated from the vesicle membrane surface by polyethylene glycol linkers, were significantly less effective (kcat approximately 3.5 x 10(4) M-1 s-1). CONCLUSIONS: For these amphiphilic analogs of FeTMPyP and MnTMPyP, the polarity of the environment of the metalloporphyrin headgroup is intimately related to the efficiency of the catalyst; a polar aqueous environment is essential for effective catalysis of ONOO- decomposition. Thus, catalysts 1b. and 2b. react rapidly with ONOO- and are potential therapeutic agents that, unlike their water-soluble TMPyP analogs, could be administered as liposomal formulations in SLs. These SL-bound amphiphilic metalloporphyrins may prove to be highly effective in the exploration and treatment of ONOO- related disease states.

Catalysis↗
PubMed1997

Small weight loss on long-term acarbose therapy with no change in dietary pattern or nutrient intake of individuals with non-insulin-dependent diabetes.

OBJECTIVES: To see if the long-term treatment of non-insulin dependent diabetes (NIDDM) with the alpha-glucosidase inhibitor acarbose affects food intake and body weight. DESIGN: Randomized, double-blind, placebo-controlled, parallel design clinical trial of 12 months duration. SUBJECTS: Subjects with NIDDM in four treatment strata: 77 on diet alone, 83 also treated with metformin, 103 also treated with sulfonylurea and 91 also treated with insulin. MEASUREMENTS: Two 3 day diet records were obtained before randomization to acarbose or placebo therapy, and additional 3 day diet records were obtained at 3, 6, 9 and 12 months after randomization. Body weight was also measured at these times. RESULTS: Of the 354 subjects randomized, 279 (79%) completed at least 9 months of therapy and, of these, 263 (94%) provided at least one diet record during the baseline period and two diet records during the treatment period. After one year, subjects on acarbose had lost 0.46 +/- 0.28 kg, which differed significantly from the 0.33 +/- 0.25 kg weight gain on placebo (P = 0.027). The difference in weight change between acarbose and placebo did not differ significantly in the different treatment strata. Being in the study had significant effects on diet, including a reduction in energy intake from 1760-1700 Kcal/d (P < 0.05), a reduction in simple sugars intake from 18.5-17.4% of energy (P < 0.001), and reductions in the number of different foods consumed (33-30, P < 0.001) and the number of meals eaten per day (4.7-4.3, P < 0.001). However, compared to placebo treatment, acarbose had no effect on energy intake, nutrient intakes, or dietary patterns. CONCLUSIONS: In subjects with NIDDM on weight-maintaining diets, long-term acarbose therapy results in a small weight loss, but has no effect on energy or nutrient intakes. The weight loss induced by acarbose may be due partly to reduced doses of concomitant oral agents and insulin and partly to energy loss due to increased colonic fermentation.

Acarbose↗
PubMed1997

Percutaneous microcoil embolization of intraperitoneal intrahepatic and extrahepatic biliary fistulas.

BACKGROUND: Persistent intraperitoneal biliary fistulas are associated with significant morbidity and mortality. Percutaneous drainage, stenting, and endoscopic sphincterotomy or embolization of biliary radicals have largely replaced the need for hepatic resection or biliary reconstruction in managing such fistulas. When endoscopy is contraindicated, a previously undescribed technique of percutaneous embolization of intrahepatic and extrahepatic biliary fistula following penetrating liver trauma, and orthotopic liver transplant and its application in three patients, will be discussed. METHODS: Embolization procedures were performed by an interventional radiologist. Percutaneous trans-hepatic cholangiography via a standard right-side approach or via tube cholangiography was initially performed and the fistula defined. Coaxial catheter systems were used (5 Fr angiography catheters and Tracker 18 infusion catheters), and were positioned within the biliary tree as close as possible to the origin of the fistula. Embolization was performed using vascular Embolization 28 coils (WA Cook) 2-3 mm x 2 cm coils, straight Hilal 18 embolization coils (WA Cook) 5-7 cm, as well as Gelfoam (Upjohn) 1 mm pellets, and Histoacryl (B. Braun) 0.25-1 mL. Occlusion of the duct was confirmed by a selective intrahepatic cholangiogram. In cases of multiple fistulas several embolizations were performed at subsequent procedures. Follow-up is over 13 months without adverse event. RESULTS: The technique was used in the three cases and was successful in all. A peripheral biliary fistula required embolization twice and two cystic leaks were cured after a single attempt. CONCLUSIONS: Percutaneous embolization of biliary fistulas provides a management option in cases where conservative treatment has failed and other techniques are relatively contraindicated. The technique is effective and safe in skilled hands, and avoids major surgery. The long-term effect of microcoils in the biliary tree is unknown.

Adult↗
PubMed1996

Effect of biomaterial surface charge on the inflammatory response: evaluation of cellular infiltration and TNF alpha production.

A rat model was used to investigate the effect of net surface charge on polymer biocompatibility and its potential to modify and stimulate the inflammatory response. Poly(ether)urethane was taken as the base material and the net charge altered by introducing sulphonate ionic groups to the polymer backbone. Three differently charged poly(ether)urethanes were made with 10, 20, and 30% sulphonate substitution, giving a range of negative charge, with unmodified poly(ether)urethane used as a control. The polymers were implanted intramuscularly into rats for 2 days, and for 1, 2, and 12 weeks. After explantation, the cellular infiltration in the tissue surrounding the implants was evaluated using immunohistochemistry to stain for specific cell types: macrophages, neutrophils, lymphocytes, and the cytokine TNF alpha. In situ hybridization was used to detect expression of mRNA encoding TNF alpha. Stained sections were analyzed and the cellular response quantified using image analysis. Initially macrophages and neutrophils were observed around all the materials, but neutrophils were absent in all samples at 12 weeks. The 2-day time point had significantly more macrophages than the later time points. By 2 weeks the 20%-charged polymer elicited significantly less neutrophil infiltration than the other three polymers. In all samples where macrophages were observed, cells staining positive fore TNF alpha protein and message also were observed. No T or B lymphocytes were observed in the infiltrates around the materials at any time point. The results indicate that surface charge can influence the early phase acute inflammatory response to an implanted material.

Animals↗
PubMed1996

Quantitative assessment of the tissue response to films of hyaluronan derivatives.

The aim of this study was to evaluate the in vivo response following implantation into a rat model of three innovative hyaluronan derivatives for clinical use: HYAFF 7, HYAFF 11 and HYAFF 11p75 (respectively, the 100% ethyl ester, 100% and 75% benzyl esters). The tissue reaction evoked by films of these new biomaterials implanted into the dorsolumbar musculature of rats was assessed quantitatively using a well established technique based upon an image analysis system. The number of inflammatory cells present and the patterns of cell distribution around the implant up to a distance of 642 microns were examined at different time periods after implantation. Since a well-delineated tissue-material interface was needed for this type of investigation, it was not possible to apply image analysis to sections once dissolution of the implanted materials had begun. Films of both the total esters, HYAFF 7 and HYAFF 11, were found to undergo a slow dissolution process and, after a month, films of these materials were still present at the site of implantation. Differences in response to the two materials were observed only during the first two weeks, particularly with respect to neutrophil distribution and total cellularity. HYAFF 7 was found to be more reactive, with higher numbers of neutrophils near the surface of the implant than HYAFF 11. Thereafter, the differences between the two materials were minimal and owing mainly to a faster dissolution of HYAFF 7 films. After 3 and 5 months, considerable degradation of films of both total esters had occurred. Significant quantities of material appeared inside numerous macrophages with an ED1-positive phenotype. Only a very thin layer of fibrous connective tissue, indicative of low reactivity, was found to surround the site of implantation, separating the dissolved material and the phagocytic cells from healthy muscular tissue. ED2-positive macrophages were primarily confined within the lining connective tissue. The partial benzyl ester, HYAFF 11p75, showed a different behaviour. In fact, evidence of film dissolution was already present a week after the implantation. After two weeks, the implanted films were completely dissolved and numerous ED1-positive macrophages phagocytosing the material were observed at the site of implantation. Therefore, in agreement with previous in vitro studies, which showed a greater susceptibility to degradation of hyaluronan derivatives with lower percentage of esterification, HYAFF 11p75 underwent resorption faster than the corresponding total ester.

Animals↗
PubMed1996

Secondary sternal repair following median sternotomy using interosseous absorbable sutures and pectoralis major myocutaneous advancement flaps.

A consecutive series of 19 patients were treated for median sternotomy dehiscence by secondary sternal closure with interosseous absorbable sutures and superimposed pectoralis major myocutaneous advancement flaps. These patients were selected for this treatment only on the basis of the quality and quantity of remaining bone stock after debridement. Using this technique there have been no failures of primary therapy with a zero 30-day mortality rate. All patients have achieved good functional and aesthetic results with mechanically stable sternums, wounds confined to the chest and elimination of sepsis. This technique has the advantages of being simple, safe and relatively quick and avoids many of the inherent complications and disadvantages of other techniques and flaps commonly used in the management of this complication.

Adult↗