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Biomedical subjects

A G Harris

Publications and source records attributed to A G Harris.

At least 19 recordsLinked to original sources
PubMed2002

Orthogonal polarisation spectral imaging as a new tool for the assessment of antivascular tumour treatment in vivo: a validation study.

Tumour angiogenesis plays a key role in tumour growth, formation of metastasis, detection and treatment of malignant tumours. Recent investigations provided increasing evidence that quantitative analysis of tumour angiogenesis is an indispensable prerequisite for developing novel treatment strategies such as anti-angiogenic and antivascular treatment options. Therefore, it was our aim to establish and validate a new and versatile imaging technique, that is orthogonal polarisation spectral imaging, allowing for non-invasive quantitative imaging of tumour angiogenesis in vivo. Experiments were performed in amelanotic melanoma A-MEL 3 implanted in a transparent dorsal skinfold chamber of the hamster. Starting at day 0 after tumour cell implantation, animals were treated daily with the anti-angiogenic compound SU5416 (25 mg kg x bw(-1)) or vehicle (control) only. Functional vessel density, diameter of microvessels and red blood cell velocity were visualised by both orthogonal polarisation spectral imaging and fluorescence microscopy and analysed using a digital image system. The morphological and functional properties of the tumour microvasculature could be clearly identified by orthogonal polarisation spectral imaging. Data for functional vessel density correlated excellently with data obtained by fluorescence microscopy (y=0.99x+0.48, r2=0.97, R(S)=0.98, precision: 8.22 cm(-1) and bias: -0.32 cm(-1)). Correlation parameters for diameter of microvessels and red blood cell velocity were similar (r2=0.97, R(S)=0.99 and r2=0.93, R(S)=0.94 for diameter of microvessels and red blood cell velocity, respectively). Treatment with SU5416 reduced tumour angiogenesis. At day 3 and 6 after tumour cell implantation, respectively, functional vessel density was 4.8+/-2.1 and 87.2+/-10.2 cm(-1) compared to values of control animals of 66.6+/-10.1 and 147.4+/-13.2 cm(-1), respectively. In addition to the inhibition of tumour angiogenesis, tumour growth and the development of metastasis was strongly reduced in SU5416 treated animals. This new approach enables non-invasive, repeated and quantitative assessment of tumour vascular network and the effects of antiangiogenic treatment on tumour vasculature in vivo. Thus, quantification of tumour angiogenesis can be used to more accurately classify and monitor tumour biologic characteristics, and to explore aggressiveness of tumours.

Angiogenesis Inhibitors↗
PubMed2002

[Orthogonal polarization spectral imaging--a new clinical method for monitoring of microcirculation].

The orthogonal polarization spectral (OPS) imaging technology is a new non-invasive method to directly visualize multiple conditions of the microcirculation which has several clinical applications in humans. Quantitative measurement of the diameter of vessels, the velocity of red blood cells and functional capillary density (FCD) can be made. Activation of leukocytes can be monitored and also quantified. A transdermal approach can be used in premature babies and neonates to view the microcirculation and has also been used experimentally to determine haemoglobin levels. The application to various surfaces and solid organs allows a variety of pathophysiologies and phases to be examined.

Blood Flow Velocity↗
PubMed2002

Validation of OPS imaging for microvascular measurements during isovolumic hemodilution and low hematocrits.

Orthogonal polarization spectral (OPS) imaging is a new technique that can be used to visualize the microcirculation with reflected light. It uses hemoglobin absorption to visualize the red blood cells (RBCs). Thus the method could fail at low hematocrit (Hct). The aim of this study was to validate OPS imaging for quantitative measurements of diameter and functional capillary density (FCD) under conditions of hemodilution of varying degrees to achieve a wide range of Hcts. The validation was performed in the dorsal skinfold chamber of nine awake Syrian golden hamsters. Measurements of vessel diameter and FCD were performed off-line using Cap-Image on video sequences captured using OPS imaging and standard intravital fluorescence microscopy at baseline, 85, 70, 55, and 40% of the initial Hct. For hemodilution, isovolumic exchange of blood for 6% Dextran 60 was performed. Bland-Altman plots for the vessel diameter and FCD show good agreement between the two methods for both parameters at all studied Hcts. As expected, there was a systematic bias of approximately 4 microm in the diameter measurements since the RBC column was measured and not the intravascular diameter. In conclusion, OPS imaging can be used to measure diameter and FCD at a wide range of Hcts.

Animals↗
PubMed2001

Assessing the microcirculation in a burn wound by use of OPS imaging.

We report on the use of OPS imaging to visualize the microcirculation in a burn wound. This novel technique produces high quality images of the microcirculation and quantitative analysis of functional capillary density (FCD) was possible. FCD measured at day 3 following the injury was 11.2 +/- 4.6 (n/mm superset2; mean +/- SEM). During the initial phase of healing microcirculatory changes were characterized by a moderate but steady increase of FCD, which showed marked increase beginning from day 12 following the burn (16.6 +/- 6.9). Maximal FCD measured at day 23 (48.2 +/- 19.7) decreased from this point in time to finally reach 25.2 +/- 10.3 n/mm superset2 at the end of observation. OPS imaging allows for direct in vivo visualization and quantification of the microcirculation in burned skin. Our results of the use of OPS imaging in assessing the microcirculation in a burn wound appear promising, and we hope that this novel technique will allow to improve the knowledge of the dynamics of the microcirculation in the pathophysiology of thermal injury.

Adult↗
PubMed2001

Orthogonal polarization spectral imaging as a tool for the assessment of hepatic microcirculation: a validation study.

BACKGROUND: Quantitative analysis of liver microcirculation using intravital fluorescence microscopy in animals has increased our knowledge about ischemia-reperfusion injury. However, because of the size of the instrumentation and the necessity of fluochromes for contrast enhancement, human liver microcirculation cannot be observed. Orthogonal Polarization Spectral (OPS) imaging is a recently introduced technique that can be used to visualize the microcirculation without the need for fluorescent dyes. It is a small, hand-held device and could potentially be used to study the microcirculation of the human liver in a clinical setting. However, before implementation into clinical use its ability to quantitatively measure microcirculatory parameters must be validated. METHODS: The livers of Spraque-Dawley rats (n=9) were exteriorized, and images were obtained using OPS imaging and intravital fluorescence microscopy of the identical microvascular regions before and after the induction of a 20-min warm lobar ischemia. Images were videotaped for later computer-assisted off-line analysis. RESULTS: OPS imaging can be used to accurately quantify the sinusoidal perfusion rate, vessel diameter, and venular red blood cell velocity. Correlation parameters were significant and Bland-Altman analyses showed good agreement for data obtained from the two methods at baseline as well as during reperfusion. CONCLUSION: OPS imaging can be used to quantitatively measure microcirculatory parameters in the rat liver under both physiological and pathophysiological conditions. Thus, OPS imaging has the potential to be used to make quantitative measurements of the microcirculation in the human liver.

Animals↗
PubMed2001

In vivo monitoring of microvessels in skin flaps: introduction of a novel technique.

Orthogonal polarization spectral (OPS) imaging was validated against intravital fluorescence microscopy (IFM) for microvascular measurements in skin flaps of hairless mice. Examinations were performed 1, 6, and 24 hours after elevation (n = 8) with both OPS imaging and IFM. A fluorescent dye was a prerequisite for IFM measurements but not for OPS imaging. Our findings show that OPS imaging can visualize the skin flap microcirculation independent from the application of fluorescent tracers. From these images, quantitative analysis of functional capillary density (FCD) was feasible. As expected, FCD was significantly lower in the distal part of the flap compared with its base (171.8 +/- 34.7 versus 62.0 +/- 25.6, mean +/- SD; 1 hour data). Comparison of OPS imaging and IFM revealed a significant correlation of FCD values (P < 0.001) at all time points. Given the success of this validation study on mouse skin flaps, clinical investigations will have to prove that OPS imaging can also successfully be used to monitor flaps in humans.

Animals↗
PubMed2000

Characterization and prevention of phototoxic effects in intravital fluorescence microscopy in the hamster dorsal skinfold model.

Intravital microscopy is widely used to study the microcirculation. However, the use of fluorescent dyes can induce phototoxic effects which may affect the measurements, particularly in tissue exposed to oxidative stress. The aim of the study was to determine the threshold light dose at which fluorescent microscopy is associated with phototoxic effects in the hamster dorsal skinfold chamber under normal and pathological conditions. The extent of phototoxicity in the microcirculation in the hamster skinfold chamber was investigated using intravital fluorescent microscopy during 60 min of illumination (1048 mW/cm2) applying two different concentrations of fluorescein isothiocyanate dextran under baseline conditions (groups A and B) and following 4 h of ischemia (groups C and D). In the second part of the study the microvasculature was analyzed regarding phototoxic effects during a standardized intravital microscopic examination after 4 h of pressure induced ischemia. Groups I and II (n=7) were studied using epiillumination after injection of fluorescein isothiocyanate dextran plus rhodamine 6G or rhodamine 6G only. In group III (n=7) only transillumination was used. Arteriolar vasospasm, microvascular perfusion failure, thrombus formation, and enhanced leukocyte endothelium interaction were observed as signs of a phototoxic effect in normal tissue. However, the light doses needed to induce these effects clearly exceeded those during standard examinations. The induction of a 4-h ischemia and reperfusion further enhanced these effects. Despite the predamage by ischemia/reperfusion the comparison of epiillumination and transillumination microscopy using a standard protocol showed no differences regarding the parameters analyzed at any time. This indicates that epiillumination and the fluorescent dyes per se did not affect the experimental results. These results show that ischemia/reperfusion studies in the dorsal skinfold chamber of the Syrian golden hamster can be carried out safely without the risk of inducing phototoxic effects by fluorescent microscopy. Nevertheless every laboratory using epiillumination and fluorescent dyes should take precautions to avoid these effects by the use of sensitive cameras to lower the light dose.

Animals↗
PubMed2000

Efficacy and tolerability of loratadine versus fexofenadine in the treatment of seasonal allergic rhinitis: a double-blind comparison with crossover treatment of nonresponders.

BACKGROUND: Nonsedating antihistamines are well-established treatment for seasonal allergic rhinitis (SAR), but patients do not always respond to the first antihistamine prescribed. OBJECTIVE: This double-blind, double-dummy, randomized, 2-phase, multicenter study was designed primarily to compare the therapeutic responses to loratadine and fexofenadine in patients who failed initial therapy with the other drug. METHODS: Male and female patients aged 12 to 60 years received loratadine 10 mg once daily (n = 331) or fexofenadine 60 mg twice daily (n = 328) for 14 days (phase 1); nonresponders (ie, those who had <25% reduction in the sum of 5 SAR symptoms rated by the investigator on a 4-point scale) subsequently received the alternate medication for 14 days (phase 2). The investigator's rating of relief (complete, marked, moderate, or slight relief of symptoms or treatment failure) at the end of phase 2 was the primary efficacy measure; changes in total symptom severity (TSS) assessed by the investigator (4-point scale) and the patient (11-point visual analog scale) were secondary measures. RESULTS: Mean decreases in TSS were significantly greater with loratadine than with fexofenadine for the 659 patients who completed phase 1 (-12.7 vs -10.2, respectively; P = 0.019; patient assessment) and for the 389 patients who responded to initial therapy (-6.6 vs -6.1, respectively; P = 0.037; investigator assessment). Of the 389 patients who responded to initial therapy, 61.0% had received loratadine and 57.0% had received fexofenadine. More nonresponders to initial therapy had moderate, marked, or complete relief of symptoms after switching to loratadine than after switching to fexofenadine (62.4% vs 51.2%, respectively; P = 0.005) and treatment failure in 10.6% vs 21.7%, respectively (P = 0.011). CONCLUSION: Overall, ioratadine provided significantly better therapeutic response than fexofenadine in patients who failed to respond to initial therapy with the other drug.

Adolescent↗
PubMed2000

Automation of the use of fluorescent microspheres for the determination of blood flow.

Fluorescent-labeled microspheres (FM) are a new tool for the determination of organ blood flow. However, the FM-method is labor intensive, because of the necessity to recover the microspheres from the tissue samples. The aim of this study was to automate the FM-method. A Zymate-Robotic System (Zymark, Idstein, Germany) was modified to handle a novel filtration device. The robot is surrounded by 12 different stations which are necessary to process the samples. It performs the sequential steps which are needed to recover the microspheres from the samples. The dyes are finally released from the FM with a solvent and their fluorescent intensity is measured online using a spectrophotometer (Perkin Elmer, Uberlingen, Germany). The robotic system is able to recover the FM through digestion and filtration of the tissue samples using the new filter, to dissolve the FM and to release the dyes so that their fluorescent intensities can be measured for the calculation of organ blood flow.

Animals↗
PubMed2000

Use of digoxigenin-labelled ampicillin in the identification of penicillin-binding proteins in Helicobacter pylori.

Amoxycillin is used in current therapeutic regimens to treat the infection caused by the human gastric pathogen, Helicobacter pylori. The penicillin-binding proteins (PBPs) are the primary targets for the beta-lactam antibiotics, such as amoxycillin, and are involved in the terminal stages of peptidoglycan synthesis. They also play active roles in the determination and maintenance of cellular morphology. It was believed that an organism with a complex morphology, such as H. pylori, would have more than the three PBPs previously suggested. Using digoxigenin-labelled ampicillin (DIG-ampicillin), we report the identification of eight PBPs in H. pylori with masses of 72, 62, 54, 50, 44, 33.5, 30.5 and 28 kDa. A smaller (21 kDa) ninth band was also detected, which may represent another PBP. However, the relatively small size of this apparent PBP raises questions as to whether this is a true PBP. In an attempt to identify the PBPs to which amoxycillin preferentially binds, amoxycillin was used in competition assays with DIG-ampicillin. It appeared that amoxycillin inhibited the binding of DIG-ampicillin to only the 72 kDa PBP. The experimental data were also compared with the seven putative PBPs identified in the two published H. pylori genomes, most of which correlate with the experimental data. To investigate further the properties of these PBPs, the seven putative PBP genes identified in the H. pylori genomes were examined. The derived amino acid sequences of the putative PBPs were examined for the three characteristic motifs found in all conventional PBPs, SXXK, SXN and KTG. We were able to determine that all of the putative PBPs had at least one of these motifs, but none possessed all three motifs with the characteristics of conventional PBPs. These findings suggest that the PBPs of H. pylori are unique.

Ampicillin↗
PubMed1999

Implementation of the microdialysis method in the hamster dorsal skinfold chamber.

The aim of this study was to implement the microdialysis method, a well-established technique for measuring the local concentration of neurotransmitters and metabolites in the brain, in the dorsal skinfold chamber of the awake hamster. First, the effects of implanted, nonperfused microdialysis probes on the microcirculation were examined. Skinfold chambers were prepared with and without probes. Two and 3 days later, the following parameters were assessed: diameter, red blood cell (RBC) velocity, macromolecular leakage, leukocyte rolling fraction, and adherent leukocytes in venules, diameter and macromolecular leakage in arterioles, and functional capillary density (FCD). No significant differences between the animals of the two groups were observed in any of the parameters on either day. Second, the interstitial lactate concentration was measured at two perfusion rates in groups with and without a 4-h tourniquet ischemia. The induction of ischemia resulted in a significant increase in lactate concentration over the control values in the tissue within 1 h to 8000 +/- 860 microM, where it remained until the reperfusion, at which point the concentration returned to control values within 1 h. The microdialysis method provides the opportunity to measure the concentration of metabolites in the extravascular space of the hamster dorsal skinfold chamber.

Animals↗
PubMed1999

Comparison between nasal provocation tests and skin tests in patients treated with loratadine and cetirizine.

BACKGROUND: The effect of H1-blockers may differ depending on the target organ. OBJECTIVE: A double-blind, placebo-controlled study was carried out to compare the effect of a 7-day treatment with loratadine (10 mg daily) or cetirizine (10 mg daily) on nasal challenge with grass pollen grains and skin tests with allergen or histamine. METHODS: Twenty-four patients were enrolled, but the analysis was carried out on 23. Nasal challenge was carried out by using 5-fold increasing numbers of pollen grains. Skin prick tests were done with serial concentrations of allergens and 1 concentration of histamine. Patients were tested in a cross-over design, with each treatment being administered for the previous 7 days and with a 2-week washout period. RESULTS: By comparison with placebo, loratadine and cetirizine increased significantly the threshold number of pollen grains required to induce a positive nasal challenge (P <.001). There was no difference between loratadine and cetirizine. Skin test responses to allergen were significantly reduced by loratadine and cetirizine by comparison with placebo. Skin test responses to histamine were significantly decreased by the 2 H1-blockers, but they were more profoundly decreased by cetirizine than by loratadine. CONCLUSIONS: Both H1-blockers reduced similarly allergen-induced skin test and nasal challenge responses. Cetirizine was more effective on histamine skin test responses.

Adult↗
PubMed1999

Allergic rhinitis in Rochester, Minnesota residents with asthma: frequency and impact on health care charges.

BACKGROUND: Asthma is a common and costly condition. Concomitant asthma and allergic rhinitis (AR) have been shown to increase the medication costs for people with asthma. No studies have compared medical care costs of those with and without concomitant AR. OBJECTIVES: We sought to determine the prevalence and incremental medical care costs of concomitant AR. METHODS: For each member of a population-based asthma cohort, we used all their medical charts within Olmsted County to record age at first diagnosis of asthma; the presence and age of any diagnosis of AR; and the total, ambulatory, and respiratory care-related costs of medical care. Costs were compared for age- and sex-specific strata of people with asthma who did and did not have AR. RESULTS: AR was most commonly diagnosed in people whose asthma was diagnosed before age 25 (prevalence of 59%) and uncommonly diagnosed in anyone after age 40 (prevalence <15%). Yearly medical care charges were on average 46% higher for those with asthma and concomitant AR than for persons with asthma alone, controlling for age and sex. We were unable to assess the impact of treatment of AR on medical care charges. CONCLUSIONS: Physicians should consider the diagnosis of AR (prevalence >50%) in all symptomatic children and young adults with asthma. Further evaluation is necessary to evaluate the ability of treatment to decrease the incremental costs of AR in persons with asthma.

Adolescent↗
PubMed1999

Loratadine: a non-sedating antihistamine. Review of its effects on cognition, psychomotor performance, mood and sedation.

Although equally potent at blocking the H1 receptor, first- and second-generation antihistamines can be distinguished with respect to their different effects on the central nervous system (CNS). First-generation antihistamines readily cross the blood-brain barrier leading to significant drowsiness, altered mood, reduced wakefulness, and impaired cognitive and psychomotor performance. This paper reviews of studies CNS functioning conducted with loratadine, a second-generation H1-receptor antagonist, at its therapeutic dose of 10 mg per day. Studies employing self-report measures, such as diary cards, visual analogue scales, rating scales, and mood inventories have shown that the effect of loratadine on somnolence, fatigue, and mood was comparable to those found with placebo. In studies exploring physiological indices of CNS functioning, such as EEG-evoked potentials, and sleep latency tests, loratadine has been shown to be free of CNS effects. In addition, studies have investigated the effects of loratadine on actual driving performance, and on tests of cognitive and psychomotor functioning. On all of these performance measures, loratadine has been shown to have effects comparable to placebo. In contrast, diphenhydramine, a common first-generation antihistamine, usually available without a doctor's prescription, has significant adverse effects on vigilance, divided attention, working memory and psychomotor performance. Impairment has been shown to occur even in the absence of self-reported sleepiness.

Affect↗
PubMed1999

A new sample-processing unit for the fluorescent microsphere method.

The use of fluorescent-labeled microspheres (FM) for measurement of regional blood flow is an attractive alternative to the use of radioactive-labeled microspheres. In the FM method the FM have to be completely recovered from the tissue samples in a time- and labor-intensive process. For this reason, a considerable loss of FM is possible. The aim of this study was to develop a filtration device that allows the tissue sample to remain in a single container throughout the procedure to make the process easier and to avoid the loss of FM. The core of the sample-processing unit (SPU) is a single-tube filtration device with a polyamide wire mesh. The protocol for processing tissue from different organs (heart, kidney, liver, spleen, intestine, muscle, bone, lung, brain) was modified and thus shortened significantly. Furthermore, the SPU allows direct filtration of the blood reference sample without previous digestion. Different experiments showed that the SPU in combination with the new protocol excludes the loss of 15-micrometers FM. The modifications of the whole procedure render it faster and highly standardized.

Animals↗
PubMed1999

Mast cell degranulation and parenchymal cell injury in the rat mesentery.

OBJECTIVE: The objective of this study was to explore the degree of parenchymal cell injury after mast cell degranulation by application of compound 48/80 (CMP 48/80) in the absence of adherent leukocytes in the rat mesentery. METHODS: Rats were rendered leukopenic by injection of an antibody against leukocytes, and the mesentery was superfused with CMP 48/80 during intravital microscopy. The extent of cell injury was determined using a fluorescent cell-viability indicator, propidium iodide (PI). In an additional group, mast cell degranulation with CMP 48/80 was prevented by using the mast cell stabilizer Ketotifen. RESULTS: After a reduction in the number of circulating leukocytes, mast cell degranulation produced a mild increase in parenchymal cell injury. The injury levels significantly increased when individual regions of the mesentery were compared. Stabilization of the mast cells with Ketotifen reduced the injury to below baseline values. CONCLUSIONS: In the absence of leukocyte adhesion to the endothelium, mast cell degranulation contributes to parenchymal cell injury in the mesentery.

Animals↗
PubMed1999

In vivo assessment of synovial microcirculation and leukocyte-endothelial cell interaction in mouse antigen-induced arthritis.

OBJECTIVE: The microcirculation and leukocyte-endothelial cell interaction in synovial tissue of an inflamed joint are known to play a crucial role in the pathogenesis of rheumatoid arthritis. The aim of this study was to characterize the in vivo changes in the microvasculature and in leukocyte-endothelial cell interactions in the mouse synovial tissue using intravital fluorescence microscopy in three stages of antigen-induced arthritis. The expression of E- and P-selectin and ICAM-1 were also studied using immunohistochemistry. METHODS: Antigen-induced arthritis (AiA) was produced in Balb/c mice. The severity of arthritis at three different phases was quantified using a clinical and histological score. For the intravital fluorescence microscopy measurements, the patella tendon was partially resected for visualization of the intraarticular synovial tissue of the knee joint. The number of rolling and adherent leukocytes, functional capillary density (FCD) and RBC velocity were quantitatively measured in synovial microvessels. Expression of ICAM-1, E- and P-selectin was assessed by immunohistochemistry. RESULTS: There was a significant increase in the leukocyte rolling fraction in postcapillary venules in the acute phase of AiA (from 0.26 +/- 0.05 in controls to 0.45 +/- 0.04 8 d after AiA induction). The number of leukocytes adherent to the endothelium was significantly elevated in all phases of arthritis (from 121 +/- 27 in controls to 376 +/- 62 mm2 63 d after AiA-induction). Functional capillary density was significantly enhanced in the acute (332 +/- 15 cm/cm2) and intermediate phases (320 +/- 15 cm/cm2) compared to control values (227 +/- 15 cm/cm2). Arthritis resulted in a distinct increase in the expression of ICAM-1 on the synovial endothelium in all phases of AiA. E- and P-selectin expression were detected only in the acute phase. CONCLUSION: Our model provides new insights into the microcirculatory changes which occur in the synovial tissue of an arthritic joint.

Animals↗