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Dennis M Heisey

Publications and source records attributed to Dennis M Heisey.

At least 19 recordsLinked to original sources
PubMed2006

A regional classification scheme for estimating reference water quality in streams using land-use-adjusted spatial regression-tree analysis.

Various approaches are used to subdivide large areas into regions containing streams that have similar reference or background water quality and that respond similarly to different factors. For many applications, such as establishing reference conditions, it is preferable to use physical characteristics that are not affected by human activities to delineate these regions. However, most approaches, such as ecoregion classifications, rely on land use to delineate regions or have difficulties compensating for the effects of land use. Land use not only directly affects water quality, but it is often correlated with the factors used to define the regions. In this article, we describe modifications to SPARTA (spatial regression-tree analysis), a relatively new approach applied to water-quality and environmental characteristic data to delineate zones with similar factors affecting water quality. In this modified approach, land-use-adjusted (residualized) water quality and environmental characteristics are computed for each site. Regression-tree analysis is applied to the residualized data to determine the most statistically important environmental characteristics describing the distribution of a specific water-quality constituent. Geographic information for small basins throughout the study area is then used to subdivide the area into relatively homogeneous environmental water-quality zones. For each zone, commonly used approaches are subsequently used to define its reference water quality and how its water quality responds to changes in land use. SPARTA is used to delineate zones of similar reference concentrations of total phosphorus and suspended sediment throughout the upper Midwestern part of the United States.

Environmental Monitoring↗
PubMed2006

Hemorrhage causes interalveolar perfusion maldistribution in the lungs of anesthetized rats.

BACKGROUND: Lung injury often occurs following hemorrhage and we hypothesized that this might be due to the effects of hemorrhage on perfusion distribution among alveoli. To test this, we measured interalveolar perfusion distribution in anesthetized, spontaneously breathing rats subjected to blood losses of 0%, 10%, 20%, or 30% of calculated blood volume. METHODS: We measured interalveolar perfusion distribution by analyzing trapping patterns of 4-mum diameter fluorescent latex particles infused into the pulmonary circulation. The particles (2 x 10) were infused 1 hour after each animal had been bled, and the lungs were then removed and air-dried. Using a confocal fluorescence microscope, we collected images of the particles in eight sections of each lung. Each image encompassed 3,360 x 3,360 x 100 microm (approximately 5,000 alveoli), and included 3-4,000 particles. Particle distributions in the images were measured using the method of dispersion index (DI) analysis. A DI value of zero corresponds to a statistically random distribution; the more DI exceeds zero, the more the distribution is clustered or inhomogenous. RESULTS: The largest DI values for the four groups were: 0%, 0.69 +/- 0.41; 10%, 0.57 +/- 0.58; 20%, 0.72 +/- 0.34; 30%, 1.38 +/- 0.41. The 30% blood loss group had a max DI value approximately twofold greater than those of the other three (p < 0.0001). CONCLUSIONS: Our results suggest that interalveolar perfusion distribution becomes markedly maldistributed at blood losses of 30%. This contributes to ventilation-perfusion mismatching, and may be a precipitating event for lung injury following hemorrhage.

Anesthesia↗
PubMed2006

The fitting of general force-of-infection models to wildlife disease prevalence data.

Researchers and wildlife managers increasingly find themselves in situations where they must deal with infectious wildlife diseases such as chronic wasting disease, brucellosis, tuberculosis, and West Nile virus. Managers are often charged with designing and implementing control strategies, and researchers often seek to determine factors that influence and control the disease process. All of these activities require the ability to measure some indication of a disease's foothold in a population and evaluate factors affecting that foothold. The most common type of data available to managers and researchers is apparent prevalence data. Apparent disease prevalence, the proportion of animals in a sample that are positive for the disease, might seem like a natural measure of disease's foothold, but several properties, in particular, its dependency on age structure and the biasing effects of disease-associated mortality, make it less than ideal. In quantitative epidemiology, the "force of infection," or infection hazard, is generally the preferred parameter for measuring a disease's foothold, and it can be viewed as the most appropriate way to "adjust" apparent prevalence for age structure. The typical ecology curriculum includes little exposure to quantitative epidemiological concepts such as cumulative incidence, apparent prevalence, and the force of infection. The goal of this paper is to present these basic epidemiological concepts and resulting models in an ecological context and to illustrate how they can be applied to understand and address basic epidemiological questions. We demonstrate a practical approach to solving the heretofore intractable problem of fitting general force-of-infection models to wildlife prevalence data using a generalized regression approach. We apply the procedures to Mycobacterium bovis (bovine tuberculosis) prevalence in bison (Bison bison) in Wood Buffalo National Park, Canada, and demonstrate strong age dependency in the force of infection as well as an increased mortality hazard in positive animals.

Age Factors↗
PubMed2005

Influence of kidney function to the impact of acute rejection on long-term kidney transplant survival.

In kidney transplantation, timing of an initial acute rejection (AR) is correlated with a variable risk of graft loss. However, it is unknown whether the increased risk for graft loss because of AR is conditioned by impaired graft function. A total of 730 cadaveric kidney transplant recipients were retrospectively evaluated from 1994 to 2001. When AR occurred, the risk ratio (RR) for graft loss was strongly time-dependent and increased, the later the rejection episode occurred. Compared with the reference group (no rejection) having an AR within 0-30, 31-365, or >365 days post-transplant conferred a 3.1-, 9.1- and 49.3-fold risk for subsequent graft loss (P < 0.001). By including serum creatinine as an indicator for graft function at the time of rejection RR decreased to 2.4-, 7.1- and 21.8-fold, but remained still significant (P = 0.023). In conclusion, the higher risk of graft loss after late AR is not fully explained by impaired graft function measured by serum creatinine.

Acute Disease↗
PubMed2004

Association of cytomegalovirus disease and acute rejection with graft loss in kidney transplantation.

BACKGROUND: Cytomegalovirus (CMV) and acute rejection (AR) alone have been associated with an increased risk of graft loss in kidney transplantation. However, little is known about their association with graft loss when both affect the transplant recipient. METHODS: By using the dynamic time-varying covariate approach to the Cox-proportional hazards model, we retrospectively analyzed the strength of association of AR and CMV disease on graft loss in a single-center kidney and simultaneous pancreas-kidney transplant population. RESULTS: Between January 1990 and December 2000, 2,740 kidney and simultaneous pancreas-kidney transplants were performed at the authors' center. The overall 5-year incidence of biopsy-proven AR and CMV disease was 45.8% (n=1,254) and 15.3% (n=420), respectively. The risk ratio (RR) for graft loss was increased by the presence of AR (RR=3.7; P<0.0001), CMV disease (RR=1.9; P=0.0007), AR following CMV disease (RR=6.6; P<0.0001), and CMV disease following AR (RR=3.3; P<0.0001). In patients with AR and CMV disease the average time until AR occurred was longer (441 days) when AR followed CMV disease in comparison with when AR preceded CMV disease (47 days). After adjusting for time-dependent risk of AR for kidney graft loss, the order of AR and CMV disease had no association with graft loss (RR=1.2; P=0.5055). CONCLUSIONS: These results demonstrate the strength of AR and CMV disease as prognosticators of impeding kidney graft loss in transplant recipients. Although AR usually precedes CMV disease, the order of AR and CMV disease has no impact on kidney graft loss in kidney and simultaneous pancreas-kidney transplant recipients.

Acute Disease↗
PubMed2004

Epidemiology of fractures in people with severe and profound developmental disabilities.

Fractures are more prevalent among people with severe and profound developmental disabilities than in the general population. In order to characterize the tendency of these people to fracture, and to identify features that may guide the development of preventive strategies, we analyzed fracture epidemiology in people with severe and profound developmental disabilities who lived in a stable environment. Data from a 23-year longitudinal cohort registry of 1434 people with severe and profound developmental disabilities were analyzed to determine the effects of age, gender, mobility, bone fractured, month of fracture, and fracture history upon fracture rates. Eighty-five percent of all fractures involved the extremities. The overall fracture rate increased as mobility increased. In contrast, femoral shaft fracture risk was substantially higher in the least mobile [relative risk (RR), 10.36; 95% confidence interval (CI), 3.29-32.66] compared with the most mobile group. Although the overall fracture rate was not associated with age, the femoral shaft fractures decreased but hand/foot fractures increased with age. Overall fracture risk declined in August and September (RR, 0.70; 95% CI, 0.55-0.89), being especially prominent for tibial/fibular fractures (RR, 0.31; 95% CI, 0.13-0.70). Gender was not a factor in fracture risk. Two primary fracture mechanisms are apparent: one, largely associated with lack of weight-bearing in people with the least mobility, is exemplified by femoral fractures during non-traumatic events as simple as diapering or transfers; the other, probably due to movement- or fall-related trauma, is exemplified by hand/foot fractures in people who ambulate. The fracture experience of people with severe and profound developmental disabilities is unique and, because it differs qualitatively from postmenopausal osteoporosis, may require population-specific methods for assessing risk, for improving bone integrity, and for reduction of falls and accidents.

Adolescent↗
PubMed2003

Ca transients from Ca channel activity in rat cardiac myocytes reveal dynamics of dyad cleft and troponin C Ca binding.

The properties of the dyad cleft can in principle significantly impact excitation-contraction coupling, but these properties are not easily amenable to experimental investigation. We simultaneously measured the time course of the rise in integrated Ca current (ICa) and the rise in concentration of fura 2 with Ca bound ([Ca-fura 2]) with high time resolution in rat myocytes for conditions under which Ca entry is only via L-type Ca channels and sarcoplasmic reticulum (SR) Ca release is blocked, and compared these measurements with predictions from a finite-element model of cellular Ca diffusion. We found that 1) the time course of the rise of [Ca-fura 2] follows the time course of integrated ICa plus a brief delay (1.36 +/- 0.43 ms, n = 6 cells); 2) from the model, high-affinity Ca binding sites in the dyad cleft at the level previously envisioned would result in a much greater delay (>/=3 ms) and are therefore unlikely to be present at that level; 3) including ATP in the model promoted Ca efflux from the dyad cleft by a factor of 1.57 when low-affinity cleft Ca binding sites were present; 4) the data could only be fit to the model if myofibrillar troponin C (TnC) Ca binding were low affinity (4.56 microM), like that of soluble troponin C, instead of the high-affinity value usually used (0.38 microM). In a "good model," the rate constants for Ca binding and dissociation were 0.375 times the values for soluble TnC; and 5) consequently, intracellular Ca buffering at the rise of the Ca transient is inferred to be low.

Adenosine Triphosphate↗
PubMed2003

Thromboxane receptor analog, U-46619, redistributes pulmonary microvascular perfusion in isolated rat lungs.

Effects of vasoconstriction on the distribution of perfusion among alveoli are not well understood. To address this, we used a new method we developed to determine how microvascular perfusion distribution was affected by a potent vasoconstrictor, the thromboxane receptor analog U-46619. Our method was to infuse 4-microm-diameter fluorescent latex microspheres into the circulation of isolated rat lungs vasoconstricted with U-46619. We used a confocal microscope to image trapping patterns of the particles in dried sections of the lungs and then used dispersion index analysis to quantify the particle patterns in the images, which encompassed approximately 2,000 alveoli. Dispersion indexes revealed significantly more particle clustering (inhomogeneous distribution) in vasoconstricted lungs than in normal flow controls or in controls in which flow was reduced by either lowering pulmonary arterial pressure or raising left atrial pressure. These results suggest that vasoconstriction occurred in the microvessels themselves, which are much smaller vessels than those previously thought to be capable of vasoconstriction.

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗
PubMed2003

Chronic allograft nephropathy uniformly affects recipients of cadaveric, nonidentical living-related, and living-unrelated grafts.

BACKGROUND: Chronic allograft nephropathy (CAN) remains a major barrier to long-term allograft survival. The authors retrospectively compared the development of CAN in recipients of cadaveric (CAD), living-related donor (LRD), and living-unrelated donor (LURD) transplants at their center. METHODS: The authors retrospectively examined the impact of various factors on the incidence of CAN using univariate and multivariate proportional hazards analysis in a single-center kidney transplant population. RESULTS: Between 1 January 1990 and 31 May 2000, 2,140 kidney-alone transplants were performed at the authors' center. The overall 5-year incidence of biopsy-proven CAN was 12.2% (n=203). Risk factors for CAN included the number of transplants (P=0.0001), acute rejection (P=0.0001), panel reactive antibody (P=0.0001), discharge creatinine (P=0.0001), 1-year creatinine (P=0.0015), delayed graft function (P=0.007), total human leukocyte antigen (HLA)-B and -DR mismatches (P=0.0005), recipient age (P=0.003), black donor race (P=0.001), black recipient race (0.0457), donor age (P=0.0053), cold storage time (P=0.019), and cytomegalovirus infections (P=0.002). Interestingly, although the LRD HLA-identical recipients had a significantly lower incidence of CAN (P=0.0015), the incidence of CAN in CAD and HLA-nonidentical LRD recipients did not differ. Graft survival was significantly worse in CAD recipients compared with all other groups (P<0.001). CONCLUSIONS: These results demonstrate the importance of immunologic and nonimmunologic factors on the development of CAN. The disparities in overall graft survival, despite the similarities in CAN rates, suggests that other factors, in addition to CAN, influence the increase in graft loss in CAD transplant recipients.

Adult↗
PubMed2003

Underutilization of pancreas donors.

BACKGROUND: Transplantation of the pancreas has become the treatment of choice for selected patients with type 1 diabetes mellitus. With the current shortage of cadaver donors and the increasing number of diabetic patients on the transplant waiting list, there is a critical need to optimally use all available pancreas grafts for transplantation. We have therefore explored the use of traditionally "less-than-ideal" pancreas donors, including pediatric (4-10 years), older (>or=45 years), obese (weight >or=200 lb), and non-heart-beating donors and donors with an elevated amylase (75% greater than normal values). METHODS: A total of 620 primary simultaneous pancreas-kidney transplantations were performed at our center. We analyzed the ratio of livers to pancreata transplanted at our center and compared this to the United Network for Organ Sharing database. Using univariate and multivariate analyses, we then assessed the impact of these less-than-ideal donors on patient survival, graft survival, and postsurgical complications after simultaneous pancreas-kidney transplantation. RESULTS: A substantial nationwide underutilization of pancreata from donor procurements is demonstrated in the United Network for Organ Sharing database. By using these less-than-ideal donors, the ratio of liver to pancreata procured can be reduced to 1.25:1. Graft survival was not significantly different in patients receiving transplants from obese, non-heart-beating, pediatric, or hyperamylasemic donors compared with grafts from ideal donors. However, grafts from donors 45 years of age or older had significantly lower 1- and 5-year graft survival rates (76% and 65% vs. 90% and 80%, P=0.006). CONCLUSIONS: This study demonstrates that utilization of pancreas grafts from selected, less-than-ideal donors results in good overall outcomes and could potentially expand the organ donor pool.

Adolescent↗
PubMed2003

Inheritance of susceptibility to induced Escherichia coli bladder and kidney infections in female C3H/HeJ mice.

In the present study, the inheritance of resistance and susceptibility to bladder and kidney infections in BALB/c, C3H/HeJ, F(1), and backcross mice was investigated, and the number of genes contributing to the phenotypes was estimated. Infections were induced in female mice by intravesical inoculation with Escherichia coli, and the number of bacteria in bladder and kidneys was quantified at 10 days. The (BALB/c x C3H/HeJ) F(1) mice had bladder and kidney infection intensities equivalent to those observed in the resistant BALB/c parents. Twelve percent of the (F(1) x C3H/HeJ) backcross mice had severe bladder infections, similar to the susceptible C3H/HeJ parents. Kidney infections ranging in intensity between those observed in BALB/c and C3H/HeJ parents were present in one-half of the backcross mice. Statistical analyses indicated that >/=1 gene is responsible for the increased susceptibility of C3H/HeJ mice and that the trait appears to be recessive.

Animals↗
PubMed2003

Comparing a mechanical device with medicinal leeches for treating venous congestion.

OBJECTIVE: To compare mechanical device therapy to medicinal leech therapy for treating venous congestion. STUDY DESIGN: Fasciocutaneous flaps of 9 x 7-cm (porcine model, n = 11) were elevated and the associated veins clamped for 15 hours. Device-treated flaps (n = 6) were treated with up to 3 devices/flap. Leech-treated flaps (n = 5) were treated with 75 leeches/flap (5 leeches/hour). Treatment evaluation parameters included: blood volume removed, skin color, surface perfusion, tissue oxygen tension, and endpoint histology. RESULTS: No significant differences were seen in blood volume removed, surface perfusion, and oxygen tension. However, significant differences were seen in skin color change over time. Histological assessment showed mild congestion in 5/5 leech-treated flaps and 2/6 device-treated flaps. CONCLUSION: Device therapy was comparable to leech therapy for decongesting a 9 x 7-cm flap over a 15-hour period. However, digital images and significant differences in skin color change over time demonstrate that device therapy promotes more global decongestion versus leech therapy.

Animals↗
PubMed2003

Process utility for imaging in cerebrovascular disease.

RATIONALE AND OBJECTIVES: The morbidity associated with a diagnostic test can influence its cost-effectiveness, but the quantification of that morbidity is controversial. Accounting for pain and invasiveness requires the measurement of "process utility" in addition to the expected value of testing. An original time trade-off variant was applied to the imaging evaluation of cerebrovascular disease, for which differences in morbidity are important to patients. MATERIALS AND METHODS: A "waiting trade-off" (WTO) was used to evaluate the preferences of 89 patients for magnetic resonance (MR) angiography and conventional x-ray angiography. Patients were experienced with both tests. A weighted difference was calculated between the period a patient was willing to wait for a test result and treatment after a hypothetical "ideal" test and the choice to undergo conventional angiography or MR angiography with immediate treatment. A rating scale was used to check the convergent validity of the WTO. RESULTS: Paired data showed a highly significant difference (P = .0001) between the mean preference for conventional and MR angiography, favoring the latter and translating into a difference of 5 quality-adjusted life days. The more negatively patients judged their conventional angiographic experience, the longer they were willing to wait for the ideal test result. CONCLUSION: The WTO provides a reasonable estimate of the relative morbidity of more invasive conventional angiographic procedures and provides a quality-adjustment term for economic analysis. Such an approach may enable more complete evaluation of the effects of other processes on medical care.

Adolescent↗
PubMed2002

Perfusion heterogeneity in rat lungs assessed from the distribution of 4-microm-diameter latex particles.

Pulmonary vascular perfusion has been shown to follow a fractal distribution down to a resolution of 0.5 cm(3) (5E11 microm(3)). We wanted to know whether this distribution continued down to tissue volumes equivalent to that of an alveolus (2E5 microm(3)). To investigate this, we used confocal microscopy to analyze the spatial distribution of 4-microm-diameter fluorescent latex particles trapped within rat lung microvessels. Particle distributions were analyzed in tissue volumes that ranged from 1.7E2 to 2.8E8 microm(3). The analysis resulted in fractal plots that consisted of two slopes. The left slope, encompassing tissue volumes less than 7E5 microm(3), had a fractal dimension of 1.50 +/- 0.03 (random distribution). The right slope, encompassing tissue volumes greater than 7E5 microm(3), had a fractal dimension of 1.29 +/- 0.04 (nonrandom distribution). The break point at 7E5 microm(3) corresponds closely to a tissue volume equivalent to that of one alveolus. We conclude that perfusion distribution is random at tissue volumes less than that of an alveolus and nonrandom at tissue volumes greater than that of an alveolus.

Animals↗
PubMed2002

Erythropoietin therapy may retard progression in chronic renal transplant dysfunction.

BACKGROUND: Recent data suggests that erythropoietin therapy may actually retard the progression of chronic kidney disease (CKD). Transplant recipients with evidence of chronic allograft dysfunction could respond in a similar manner to erythropoietin. METHODS: We evaluated 166 individuals who initiated erythropoietin therapy after at least 18 days of transplant function. One hundred and nine individuals received erythropoietin between days 18 and 294 of transplant function (group 1-early epoietin alfa) while 57 individuals received erythropoietin on or after day 294 of transplant function (group 2-late epoietin alfa). The slope of serum creatinine (Scr) (Deltaslope Scr) prior to and following the start of erythropoietin therapy and calculated glomerular filtration rates (GFR) were used to assess renal function over time. RESULTS: The average haematocrit rose 6.6% in group 1 patients and 2.1% in group 2 patients during the first 100 days of erythropoietin therapy. The Deltaslope Scr was not significantly altered in group 1 patients. However, for group 2 individuals who continued to have graft function (n=35), the Deltaslope Scr became negative during erythropoietin treatment. This indicated a deceleration in the rate of loss of renal function (day 200 Deltaslope Scr -0.0033, P=0.00091; day 300 Deltaslope Scr -0.0014, P=0.05; day 400 Deltaslope Scr -0.0066, N.S., P=0.066). GFR remained stable in both cohorts. Finally, group 2-late epoietin alfa patients treated with erythropoietin demonstrated a marked trend towards longer graft survival than a group of similar control patients (N.S., P=0.064). CONCLUSIONS: The data in a group of renal transplant recipients with chronic allograft dysfunction reinforce data from the CKD realm suggesting that erythropoietin may be of benefit in slowing the rate of loss of function over time. However, this renal response is not evident in all patients. Prospective studies of erythropoietin or erythropoietin-like medications are warranted in this population to better discriminate those who may respond well to administration of these drugs.

Adult↗
PubMed2002

Evaluation of performance characteristics of the medicinal leech (Hirudo medicinalis) for the treatment of venous congestion.

Medicinal leeches (Hirudo medicinalis) are a standard treatment for venous congestion, a complication that can occur after reconstructive surgery. If the cause of venous congestion cannot be surgically corrected, then medicinal leeches are used to temporarily increase perfusion levels and maintain physiologic requirements within the congested tissue. Leeches increase perfusion within congested tissue by actively drawing off blood as a bloodmeal. Furthermore, the leech bite continues to bleed and relieve congestion after detachment because of the anticoagulation effects of leech saliva left behind in the bite. In a porcine model, a 10 x 10 cm cutaneous flank flap was congested by clamping the venae comitantes. Four medicinal leeches were allowed to attach to the congested flap, and parameters of active feeding and passive bleeding after detachment were recorded. The average bloodmeal volume for the medicinal leeches was 2.45 ml. Average passive bleeding for the first 2 and 4 hours after leech detachment totaled 2.21 and 2.50 ml, respectively, with 90 percent of passive bleeding occurring within 5 hours after detachment. Laser Doppler imaging indicated that the spatial arrangement of surface perfusion increases were localized to a 1.6-cm-diameter circle around the leech head (bite) and corresponded well with the visual return of normal skin tones to the same area. This study provides a realistic and quantitative estimate of the spatial and volumetric characteristics of leech feeding and passive bleeding using a clinically relevant model of acute, severe congestion.

Animals↗
PubMed2002

Time-resolved three-dimensional contrast-enhanced MR angiography of the peripheral vessels.

PURPOSE: To compare the diagnostic accuracy of time-resolved three-dimensional contrast material-enhanced magnetic resonance (MR) angiography with that of conventional angiography for imaging the lower extremity vasculature. MATERIALS AND METHODS: Sixty-nine patients who were evaluated for possible surgical intervention underwent conventional angiography (ie, digital subtraction angiography [DSA]) and contrast-enhanced MR angiography (ie, time-resolved imaging of contrast kinetics [TRICKS]). Two independent, blinded readers evaluated vessel stenosis and occlusion at DSA and MR angiographic image readings. Sensitivity, specificity, positive and negative predictive values, and area under the receiver operating characteristic curve were analyzed with repeated-measures analysis of variance. The Cohen kappa test was performed to examine interreader variability. RESULTS: At pooled readings, contrast-enhanced MR angiography had a sensitivity of 78% and a specificity of 98% for detection of occlusion. For detection of significant stenosis (at least one > or = 50% stenosis), sensitivity and specificity were 77% and 91%, respectively. Interreader agreement was high for detection of both occlusion (kappa = 0.76) and significant stenosis (kappa = 0.68). Sensitivity increased as MR angiographic technical parameters were optimized. When improvements resulting from coil type and injection protocol were considered, the sensitivity and specificity of TRICKS MR angiography were 89% and 97%, respectively, for occlusion detection and 87% and 90%, respectively, for significant stenosis detection. CONCLUSION: Contrast-enhanced TRICKS MR angiography is a feasible and minimally invasive means of acquiring angiograms of the peripheral vasculature with high sensitivity and specificity.

Adult↗