Cumulative Indices Research Articles

Non-linear relationship between food resource exploitation and population density of stored-product pests

The main current strategies (IPM, HACCP) to control pests in stored food products are based on critical thresholds derived from pest population density. These thresholds usually do not consider cumulative effects of earlier pest infestation although injuries caused by biotic pest organisms to stored food commodities are irreversible. We present conceptual and illustrative models showing that population size indices, in contrast to cumulative (population history) indices, could (i) underestimate critical thresholds if pest population can grow exponentially and (ii) provide incorrect information about the level of stored food damage if pest population density can fluctuate. The importance of entomological food microanalysis and continual “cumulative monitoring” based on trapping is discussed with respect to HACCP and IPM programmes in stored food products.

Case-cohort analysis of brain cancer and leukemia in electric utility workers using a refined magnetic field job-exposure matrix.

The potential association between occupational electric and magnetic field exposure and cancer is well documented in the literature, but there is uncertainty regarding a causal relation. Using data from a completed cohort study, we sought to refine the job-exposure matrix in a case-cohort analysis by regrouping jobs into more homogeneous groups, but without making additional measurements. From the original cohort, we selected the 164 men who died of leukemia, 145 men who died of brain cancer, and a random subcohort of 800 men (0.6% of the cohort). Erroneous job assignments were corrected and job groups were subdivided based on differences in work environments or tasks performed. Magnetic field exposure remained unrelated to leukemia mortality and positively associated with brain cancer mortality based on both cumulative and average magnetic field indices. Although not monotonic across the middle intervals, increased risk of brain cancer was found in relation to career exposure, with risk ratios of 1.8 (95% CI = 0.7-4.7) and 2.5 (95% CI = 1.0-6.3) in the uppermost categories for cumulative and average exposure, stronger for exposure 2-10 years past. Improvements in exposure assignment based only on reassignment of job titles to occupational categories had little impact on the measured associations of magnetic fields with leukemia or brain cancer.

Comparison of Cell Kinetics between the Boundary and the Interboundary Areas during Hindbrain Segmentation in the Chick Embryo.

It has been proposed that a difference between the length of the cell cycle and the S−phase in cells in the rhombomere boundary and those in the center of each rhombomere (interboundary) produces a driving force for hindbrain segmentation. To assess the validity of this hypothesis, we examined the cell kinetics of rhombomeric cells in the chick embryo using two kinds of labeling procedures. Cumulative labeling indices with bromodeoxyuridine (BrdU) revealed that the ratio of the number of S−phase nuclei in the boundary tended to be greater than in the interboundary area, whereas the time intervals required for reaching the plateau phase of labeling indices were similar (6hr) in the two areas through all stages examined with the exception of r4 at stage 15. By employing a double labeling method using BrdU and iododeoxyuridine that enables the comparison of the length of the S−phase in cells in the boundary and interboundary areas, we demonstrated that the ratio of the number of double−labeled nuclei in the two areas was not significantly different at stage 15. The present studies have indicated that the cell kinetic parameters of the cell populations in the boundary are not significantly different from those in the interboundary during hindbrain segmentation and suggest that molecular and cellular interactions other than the differential growth rate may play more crucial roles in hindbrain segmentation.

Mapping and monitoring net primary productivity with AVHRR NDVI time-series: statistical equivalence of cumulative vegetation indices

In the last two decades, numerous investigators have proposed cumulative vegetation indices (i.e., functions which encode the cumulative effect of NDVI maximum value composite time-series into a single variable) for net primary productivity (NPP) mapping and monitoring on a regional to continental basis. In this paper, we investigate the relationships among three of the most commonly used cumulative vegetation indices, expanding on the definition of equivalence of remotely sensed vegetation indices for decision making. We consider two cumulative vegetation indices as equivalent, if the value of one index is statistically predictable from the value of the other index. Using an annual time-series of broad-scale AVHRR NDVI monthly maximum value composites of the island of Corsica (France), we show that the pairwise linear association among the analysed cumulative vegetation indices shows coefficients of determination ( R 2) higher than 0.99. That is, knowing the value of one index is statistically equivalent to knowing the value of the other indices for application purposes.

Assessing processes of intraspecific competition within spatially heterogeneous black spruce stands

The objective of this study was to develop and subsequently apply an individual-tree analytical approach for assessing resource competition processes within monospecific, even-aged, and spatially heterogeneous black spruce (Picea mariana (Mill.) BSP) stands. The approach consisted of five basic steps: (1) ranking competitors with respect to subject tree size using a relative scale, (2) stratifying competitors into competition strata based on their relative size differential with respect to a subject tree, (3) quantifying the intensity of competition within each stratum using spatially explicit local competition indices and subsequently formulating directional-specific cumulative indices, (4) regressing relative measures of stem growth against each directional-specific index, and (5) graphically and statistically assessing differences in resultant standardized regression coefficients as competition accumulated upward from below and downward from above. This analytical framework was used with stem growth data derived from 401 subject trees situated within 18 monospecific, even-aged, density-stressed, and spatially heterogeneous black spruce stands. The results indicated directional-specific asymmetrical relationships between subject trees and their neighbours in which increasing competition from above resulted in declines in stem production. Consequently, these results were in accord with those expected when competition is dominated by a resource preemption process.

Relationships of ozone exposure to pine injury in the Sierra Nevada and San Bernardino Mountains of California, USA

Hourly ambient ozone exposure data and crown injury measurements were gathered in the Sierra Nevada and San Bernardino Mountains of California to develop relationships between the Ozone Injury Index (OII), the Forest Pest Management Index (FPM), chlorotic mottle, fascicle retention (OII index components) and cumulative ambient ozone indices for Pinus ponderosa Dougl. ex Laws and Pinus jeffreyi Grev. and Balf. Eleven sites located in the mixed conifer forest near ambient ozone monitoring sites were evaluated annually for 4 years. Four other sites in the San Bernardino Mountains were evaluated for 1 year. Analyses showed OII to be functionally equivalent ( r 2 = 0.96) to the FPM, and to depend only on fascicle retention and chlorotic mottle ( R 2 = 0.95) of the fourth whorl (or if four whorls are not present at the site, then the last whorl present for the majority of trees). Significant associations were found between OII and 4-year 24-h. summer SUM0, SUM06, W126 and HRS80 ozone indices. Three sites had higher levels of cumulative chlorotic mottle for individual whorls and larger numbers of trees with visible crown injury than other sites with similar cumulative ambient ozone levels. Including an indicator variable to discriminate between these two groups of sites increased R 2 and decreased root mean square (RMSE) for all indices, especially SUM0 ( R 2 = 0.93, RMSE reduced by 46%).

An evaluation of indices that describe the impact of ozone on the yield of spring wheat ( Triticum aestivum L.)

A comparison of the performance of different ozone indices in exposure-response functions was made using crop yield and ozone monitoring data from spring wheat studies carried out within the framework of the European open-top chamber programme. Indices were calculated for a twelve-hour period (0900–2100 h, local time). An attempt was made to incorporate a measure of absorbed dose into current indices by weighting with simultaneous sunshine hour values. Both linear and Weibull models were fitted to the exposure-response data in order to evaluate index performance. Cumulative indices which employed continuous weighting functions (allometric or sigmoid) or which censored concentrations above threshold values performed best as they attributed increasing weight to higher concentrations. Indices which simply summed concentrations greater than or equal to a threshold value did not perform as well as equal weight was given to all concentrations greater than the threshold value. Model selection was found to be very important in determining the indices that best describe the relationship between exposure and response. In general weighting hourly ozone concentrations with the corresponding sunshine hour values in an attempt to incorporate this proposed measure of plant activity into current indices did not improve index performance. Ozone exposure indices accounted for a large proportion of the variability in data (91%) and it is suggested that a strong link exists between exposure and dose.

Serial Ultrasound-Guided Percutaneous Liver Biopsy in a Partial Hepatectomy Porcine Model: A New Technique in the Study of Liver Regeneration

Studies on liver regeneration are often carried out on small animal models such as the rat. The use of large animal models however has many advantages. Repeated biopsies of the liver may be carried out and the animal can thus serve as its own control. Sequential changes in the regenerative response to various putative hepatotrophic factors can therefore be studied. Ultrasound-guided percutaneous biopsy (USGPB) of the liver, a technique widely used in clinical practice to obtain liver samples, offers a means for repeated liver biopsies. This study was carried out to validate the use of serial USGPB of the liver as a research technique in the study of liver regeneration in a porcine hepatectomy model. Material and method: Left hepatectomy was carried out in nine Yorkshire pigs (20–30 kg). Bromodeoxyuridine (BrdU) at 50 mg/kg BW was administered daily for the first 5 days after surgery. USGPB was carried out 1 hr later using 16F biopsy needles in a Biopty device. Ultrasonography was carried out using an Acuson XP10 color doppler ultrasound machine. Immunoperoxidase staining of the biopsy specimens was performed using mouse monoclonal antibody to BrdU. Regenerating cells were identified and labeling indices constructed for each day after hepatectomy. All animals were sacrificed at the end of the study and postmortem was performed. Results and conclusion: USGPB was successful at every attempt and no animal suffered complications following the procedure. Median cumulative labeling indices increased rapidly after hepatectomy and the steepest rise occurred between the third and fourth day after surgery when it increased from 2.25 to 3.40% before leveling off. These results are consistent with those obtained by other reported techniques. USGPB of the liver overcomes the need for repeated laparotomies to obtain biopsy samples in a large animal model and has no morbidity and mortality that could lead to animal wastage.

Relationships between ozone resistance and climate in European populations of Plantago major.

The relative ozone resistance of 20 European and two American populations of Plant ago major was examined, and relationships with climatic factors at the source of the plant material were explored using data provided by participants in the ICP-Crops initiative (International Co-operative Programme to Investigate the Effects of Air Pollutants and Other Stresses on Agricultural and Semi-Natural Vegetation). Plants grown from seed were exposed to either charcoal/Purafil® filtered air (CF < 5 nmol mol-1 O3 ) or CF + ozone (70 nmol mol-1 O3 7 h d-1 ) over a 2-wk period in controlled environment chambers, and effects on mean plant relative growth rate (R) and allometric root/shoot growth (K) determined. Ozone resistance (R%) was calculated from (R03 /RCF ) × 100. Populations exhibited contrasting sensitivities to ozone, without the development of typical visible symptoms of injury. A positive relationship was found between relative ozone resistance and descriptors of the ozone-climate at the site of seed collection for the year of, and the 2 yr before, seed collection. The best predictors of inherent ozone resistance were shown to be cumulative ozone exposure indices calculated according to current United Nations Economic Commission for Europe (UN-ECE) critical level guidelines for the pollutant (i.e. the accumulated hourly average ozone exposure over a threshold level of 40 nmol mol-1 (AOT40) or 30 nmol mol-1 (AOT30) calculated during daylight hours for the consecutive 3-month period of the year experiencing the highest ozone concentrations). No relationships were found between ozone resistance and climatic factors (temperature, precipitation, sunshine hours, humidity) or the concentrations of other air pollutants (SO2 , NO2 , NO). These findings support the view that current ambient levels of ozone in many regions of Europe are high enough to promote evolution of resistance to the pollutant in native plant populations. The significance of these findings to the debate over the establishment of separate critical levels for the protection of natural and semi-natural vegetation is discussed.

Skin tolerance of adapalene 0.1% gel in combination with other topical antiacne treatments

Background: Adapalene (Differin® gel) is a new naphthoic acid derivative developed for the topical treatment of acne vulgaris. Objective: We assessed, in healthy volunteers, the skin irritancy potential of three combinations, each including adapalene 0.1% gel and one topical marketed antiacne product. Methods: Twenty-five healthy volunteers were enrolled in a 21-day cumulative irritancy study performed in a double-blind, randomized, controlled, intraindividual design. Five days a week, the three materials (benzoyl peroxide, clindamycin phosphate, and erythromycin) were applied in a nonocclusive manner either alone or in combination with adapalene gel on seven cutaneous sites on the upper back. Adapalene was applied in the evening whereas the three other materials were applied in the morning. Irritation was evaluated and scored daily except on weekends. Results: All materials were well-tolerated when tested alone. The combinations of adapalene 0.1% gel and either benzoyl peroxide, clindamycin phosphate, or erythromycin were also well-tolerated. The mean cumulative irritancy indices indicated that all three combinations were nonirritating. Conclusion: Under the conditions of the study, all tested treatments alone or in combination appeared nonirritating. (J Am Acad Dermatol 1997;36:S113-5.)

Lung cancer in relation to employment in the electrical utility industry and exposure to magnetic fields.

OBJECTIVES: A recent study found that lung cancer may be associated with exposures encountered in the electrical utility industry. To further evaluate this possibility, data were collected and analysed from...

Differential contribution of current and cumulative indices of lead dose to neuropsychological performance by age

We examined measures of lead dose that reflect intensity of exposure and cumulative exposure for differential association with neuropsychological functional domains and with neuropsychological performance by age. Eighty active lead smelter workers assessed for verbal memory and visuomotoric skills had a mean (range) age of 44 (24-64) years, duration of employment of 20 (4-26) years, education of 8 (0-13) grades, current blood lead (B-Pb) of 26 microgPb dl(-1) (13-43), working lifetime weighted average blood lead (TWA) of 42 microgPb dl(-1) (17-57), working lifetime integrated blood lead (IBL) of 903 microgPb-yr dl(-1) (81-1,436) and bone lead (bone-Pb) of 41 microgPb (g bone mineral)(-1) (-12-90). Multiple linear regression after adjusting for age and education showed a significant amount of variance in verbal memory (Rey Auditory Verbal Learning Test and Verbal Paired Associates) explained only by measures of lead dose intensity, B-Pb, and TWA. Visuomotoric ability (Grooved Pegboard [GP] and Digit Symbol) had significant variance accounted for by measures of both lead dose intensity, TWA, and of cumulative lead dose, IBL, and bone-Pb. The relationship between bone-Pb and GP was curvilinear in older workers, with increasingly slower performance above a bone-Pb threshold of 20 microgPb (g bone mineral)(-1). Examination of age-related change in GP with exposure using IBL, a surrogate for cumulative lead dose in the brain, showed enhanced age-related change in older workers with high IBL. These findings suggest that the older nervous system provides a substrate more susceptible to the effects of chronic lead exposure.

Correlation between cumulative labeling indices measured in the terminal bronchioles and in the centriacinar region in the lungs of rats exposed to oxidant air pollutants

Male Sprague-Dawley rats were exposed on 7 consecutive days for 8 h a night to 0.6 ppm ozone, 10.8 ppm NO 2 or a mixture of the two gases. Cumulative labeling indices were measured in the epithelium of the terminal bronchioles and the adjacent centriacinar region. An excellent correlation in labeling indices between the two sites was found. It is concluded that the labeling index in the terminal bronchioles represents a sensitive measurement for ozone-induced lung injury.

Six-Month Exposure of Strain A/J Mice to Cigarette Sidestream Smoke: Cell Kinetics and Lung Tumor Data

Six-Month Exposure of Strain A/J Mice to Cigarette Sidestream Smoke: Cell Kinetics and Lung Tumor Data. Witschi, H. P., Oreffo, V. I. C., and Pinkerton, K. E. (1995). Fundam. Appl. Toxicol. 26, 32-40.Male strain A/J mice were exposed to sidestream smoke (SS) generated from burning Kentucky 1R4F reference cigarettes. Chamber concentrations were 4 mg/m3 of total suspended respirable particulate matter (TSP). Animals were exposed 6 hr a day, 5 days a week. One-week cumulative labeling indices were significantly increased in the large intrapulmonary airways during the 1st week and in the respiratory epithelium of the nasal and maxillar turbinates during the first 3 weeks of exposure and then returned to control values. Subsequently, signs of increased cell proliferation were again found in the nasal and maxillar turbinates during the 9th and 16th exposure weeks. The experiment was terminated after 6 months. The number of animals bearing lung tumors was the same in smoke-exposed as in filtered air-exposed animals as was the average number of tumors per lung. Analysis of the DNA of individual tumors obtained from exposed and control mice for K-ras mutations suggested that exon 2 might be a specific target for SS. It was concluded that (1) duration of exposure was too short or (2) concentration or TSP was too low to reveal a possible carcinogenic potential of SS in strain A/J mice or that (3) SS is not carcinogenic in strain A mice.

Six-Month Exposure of Strain A/J Mice to Cigarette Sidestream Smoke: Cell Kinetics and Lung Tumor Data

Male strain A/J mice were exposed to sidestream smoke (SS) generated from burning Kentucky 1R4F reference cigarettes. Chamber concentrations were 4 mg/m3 of total suspended respirable particulate matter (TSP). Animals were exposed 6 hr a day, 5 days a week. One-week cumulative labeling indices were significantly increased in the large intrapulmonary airways during the 1st week and in the respiratory epithelium of the nasal and maxillar turbinates during the first 3 weeks of exposure and then returned to control values. Subsequently, signs of increased cell proliferation were again found in the nasal and maxillar turbinates during the 9th and 16th exposure weeks. The experiment was terminated after 6 months. The number of animals bearing lung tumors was the same in smoke-exposed as in filtered airexposed animals as was the average number of tumors per lung. Analysis of the DNA of individual tumors obtained from exposed and control mice for K-ras mutations suggested that exon 2 might be a specific target for SS. It was concluded that (1) duration of exposure was too short or (2) concentration of TSP was too low to reveal a possible carcinogenic potential of SS in strain A/J mice or that (3) SS is not carcinogenic in strain A mice.

Occupational exposure to chlorinated aliphatic hydrocarbons and risk of astrocytic brain cancer

Chlorinated aliphatic hydrocarbons (CAHs) were evaluated as potential risk factors for astrocytic brain tumors. Job-exposure matrices for six individual CAHs and for the general class of organic solvents were applied to data from a case-control study of brain cancer among white men. The matrices indicated whether the CAHs were likely to have been used in each industry and occupation by decade (1920-1980), and provided estimates of probability and intensity of exposure for "exposed" industries and occupations. Cumulative exposure indices were calculated for each subject. Associations of astrocytic brain cancer were observed with likely exposure to carbon tetrachloride, methylene chloride, tetrachloroethylene, and trichloroethylene, but were strongest for methylene chloride. Exposure to chloroform or methyl chloroform showed little indication of an association with brain cancer. Risk of astrocytic brain tumors increased with probability and average intensity of exposure, and with duration of employment in jobs considered exposed to methylene chloride, but not with a cumulative exposure score. These trends could not be explained by exposures to the other solvents.

Retrospective assessment of exposure through modeling in a study on cancer risks among workers exposed to phenoxy herbicides, chlorophenols and dioxins.

The study aimed at developing a model for the retrospective assessment of exposures in epidemiologic studies when little or no data on past exposures are available. A deterministic model was developed for the level of exposure by industrial hygienists involved in an international study on cancer risks among phenoxy herbicide or chlorophenol manufacturing workers and pesticide sprayers. The general source-receptor model was used as the conceptual framework for the model. The model included variables related to job, the emission of chemicals, contact with chemicals, personal protection, and other relevant determinants of exposure. Cumulative dose indices were calculated from the duration of exposure (from the work histories) and the level of exposure (from the model). Deterministic modeling in complex exposure situations may provide more valid and reliable results than its conventional alternative, subjective assessment by an expert.

Short-Term Effects of Sidestream Smoke on Respiratory Epithelium in Mice: Cell Kinetics

Short-Term Effects of Sidestream Smoke on Respiratory Epithelium in Mice: Cell Kinetics. Rajini, P., and Witschi, H. P. (1994). Fundam. Appl. Toxicol. 22, 405-410.Male strain A/J and C57BL/6 mice were exposed on five consecutive days, for 6 hr a day, to sidestream smoke generated from Kentucky 1R4F reference cigarettes. Chamber concentrations were 1 mg/m3 of total suspended particulate matter and 528 to 549 μg/m3 of nicotine. Cumulative labeling indices in the airways and in the pulmonary parenchyma were measured following 1, 3, or 5 days exposure to unfiltered or filtered sidestream smoke. A significantly increased labeling index was found in A/J mice in the epithelium lining large intrapulmonary airways and terminal bronchioles after 3 and 5 days exposure to unfiltered smoke, whereas following exposure to filtered smoke labeling indices remained normal. The alveolar labeling index was not increased following smoke exposure. In C57BL/6 mice, sidestream smoke did not produce signs of increased cell proliferation in the respiratory tract. It is concluded that the response to sidestream smoke inhalation in mice may depend upon the strain of mice examined.

Cell Kinetics in the Respiratory Tract of Hamsters Exposed to Cigarette Sidestream Smoke

AbstractMale Syrian golden hamsters were exposed for 6 h/day, 7 days/wk for up to 3 wk to side-stream smoke generated from Kentucky 1R4F reference cigarettes. Monitoring showed that the chamber atmosphere contained 1 mg/m3 of total suspended particulate, 385 μg/m3 of nicotine, and 4 ppm carbon monoxide. Cumulative labeling indices were measured in the pulmonary parenchyma, intrapulmonary airways, trachea, and nasal passages with the bromodeoxyuridine osmotic minipump technique. Cells were labeled during wk 1, 2, and 3 of smoke exposure and for a 1-wk recovery period in air after 1, 2, or 3 wk of smoke exposure. In the airway epithelia, exposure to sidestream smoke did not increase cell proliferation as long as the animals were inhaling smoke, but did so upon removal of the animals from the chamber. In the nasal respiratory epithelium, cell proliferation was initially increased, but then, after removal of the animals into air, was inhibited relative to clean air controls. No changes in labeling index were ...

Cell Proliferation in the Respiratory Tract of Hamsters Continuously Exposed During 4 Weeks to 0.8 PPM Ozone

Male Syrian golden hamsters were exposed to 0.8 ppm ozone, 24 h/day for 4 wk. Cumulative labeling indices were measured during each week of exposure in the lung, the intrapulmonary airways, the trachea, and the nasal passages. In the alveolar zone, ozone did not affect labeling indices beyond the centriacinar region. In the terminal bronchioles and large intrapulmonary airways, labeling indices were significantly higher than in controls throughout exposure to ozone. The largest increase was seen during wk I. In the trachea and the nasal passages, a significant increase in cell labeling was only seen during wk I; thereafter the values returned to control levels. It was concluded that exposure to 0.8 ppm ozone produces signs of proliferative activity during a 4-wk continuous exposure in the epithelium of the intrapulmonary airways, but not in other sites.