Onset of photosynthesis in spring speeds up monoterpene synthesis and leads to emission bursts.

Emissions of biogenic volatile organic compounds (BVOC) by boreal evergreen trees have strong seasonality, with low emission rates during photosynthetically inactive winter and increasing rates towards summer. Yet, the regulation of this seasonality remains unclear. We measured in situ monoterpene emissions from Scots pine shoots during several spring periods and analysed their dynamics in connection with the spring recovery of photosynthesis. We found high emission peaks caused by enhanced monoterpene synthesis consistently during every spring period (monoterpene emission bursts, MEB). The timing of the MEBs varied relatively little between the spring periods. The timing of the MEBs showed good agreement with the photosynthetic spring recovery, which was studied with simultaneous measurements of chlorophyll fluorescence, CO2 exchange and a simple, temperature history-based proxy for state of photosynthetic acclimation, S. We conclude that the MEBs were related to the early stages of photosynthetic recovery, when the efficiency of photosynthetic carbon reactions is still low whereas the light harvesting machinery actively absorbs light energy. This suggests that the MEBs may serve a protective functional role for the foliage during this critical transitory state and that these high emission peaks may contribute to atmospheric chemistry in the boreal forest in springtime.

Bursts of CO2 released during freezing offer a new perspective on avoidance of winter embolism in trees.

BACKGROUND AND AIMS: Woody plants can suffer from winter embolism as gas bubbles are formed in the water-conducting conduits when freezing occurs: gases are not soluble in ice, and the bubbles may expand and fill the conduits with air during thawing. A major assumption usually made in studies of winter embolism formation is that all of the gas dissolved in the xylem sap is trapped within the conduits and forms bubbles during freezing. The current study tested whether this assumption is actually valid, or whether efflux of gases from the stem during freezing reduces the occurrence of embolism. METHODS: CO2 efflux measurements were conducted during freezing experiments for saplings of three Scots pine (Pinus sylvestris) and three Norway spruce (Picea abies) trees under laboratory conditions, and the magnitudes of the freezing-related bursts of CO2 released from the stems were analysed using a previously published mechanistic model of CO2 production, storage, diffusion and efflux from a tree stem. The freezing-related bursts of CO2 released from a mature Scots pine tree growing in field conditions were also measured and analysed. KEY RESULTS: Substantial freezing-related bursts of CO2 released from the stem were found to occur during both the laboratory experiments and under field conditions. In the laboratory, the fraction of CO2 released from the stem ranged between 27 and 96 % of the total CO2 content within the stem. CONCLUSIONS: All gases dissolved in the xylem sap are not trapped within the ice in the stem during freezing, as has previously been assumed, thus adding a new dimension to the understanding of winter embolism formation. The conduit water volume not only determines the volume of bubbles formed during freezing, but also the efficiency of gas efflux out of the conduit during the freezing process.

Contributions of climate, leaf area index and leaf physiology to variation in gross primary production of six coniferous forests across Europe: a model-based analysis.

Gross primary production (GPP) is the primary source of all carbon fluxes in the ecosystem. Understanding variation in this flux is vital to understanding variation in the carbon sink of forest ecosystems, and this would serve as input to forest production models. Using GPP derived from eddy-covariance (EC) measurements, it is now possible to determine the most important factor to scale GPP across sites. We use long-term EC measurements for six coniferous forest stands in Europe, for a total of 25 site-years, located on a gradient between southern France and northern Finland. Eddy-derived GPP varied threefold across the six sites, peak ecosystem leaf area index (LAI) (all-sided) varied from 4 to 22 m(2) m(-2) and mean annual temperature varied from -1 to 13 degrees C. A process-based model operating at a half-hourly time-step was parameterized with available information for each site, and explained 71-96% in variation between daily totals of GPP within site-years and 62% of annual total GPP across site-years. Using the parameterized model, we performed two simulation experiments: weather datasets were interchanged between sites, so that the model was used to predict GPP at some site using data from either a different year or a different site. The resulting bias in GPP prediction was related to several aggregated weather variables and was found to be closely related to the change in the effective temperature sum or mean annual temperature. High R(2)s resulted even when using weather datasets from unrelated sites, providing a cautionary note on the interpretation of R(2) in model comparisons. A second experiment interchanged stand-structure information between sites, and the resulting bias was strongly related to the difference in LAI, or the difference in integrated absorbed light. Across the six sites, variation in mean annual temperature had more effect on simulated GPP than the variation in LAI, but both were important determinants of GPP. A sensitivity analysis of leaf physiology parameters showed that the quantum yield was the most influential parameter on annual GPP, followed by a parameter controlling the seasonality of photosynthesis and photosynthetic capacity. Overall, the results are promising for the development of a parsimonious model of GPP.

Predicting the decline in daily maximum transpiration rate of two pine stands during drought based on constant minimum leaf water potential and plant hydraulic conductance.

The effect of drought on forest water use is often estimated with models, but comprehensive models require many parameters, and simple models may not be sufficiently flexible. Many tree species, Pinus species in particular, have been shown to maintain a constant minimum leaf water potential above the critical threshold for xylem embolism during drought. In such cases, prediction of the relative decline in daily maximum transpiration rate with decreasing soil water content is relatively straightforward. We constructed a soil-plant water flow model assuming constant plant conductance and daily minimum leaf water potential, but variable conductance from soil to root. We tested this model against independent data from two sites: automatic shoot chamber data and sap flow measurements from a boreal Scots pine (Pinus sylvestris L.) stand; and sap flow measurements from a maritime pine (Pinus pinaster Ait.) stand. To focus on soil limitations to water uptake, we expressed daily maximum transpiration rate relative to the rate that would be obtained in wet soil with similar environmental variables. The comparison was successful, although the maritime pine stand showed carry-over effects of the drought that we could not explain. For the boreal Scots pine stand, daily maximum transpiration was best predicted by water content of soil deeper than 5 cm. A sensitivity analysis revealed that model predictions were relatively insensitive to the minimum leaf water potential, which can be accounted for by the importance of soil resistance of drying soil. We conclude that a model with constant plant conductance and minimum leaf water potential can accurately predict the decline in daily maximum transpiration rate during drought for these two pine stands, and that including further detail about plant compartments would add little predictive power, except in predicting recovery from severe drought.

Transcutaneous oxygen tension in patients with post-thrombotic leg ulcers: treatment with intermittent pneumatic compression.

Transcutaneous oxygen tension (TcPO2) and the effect of intermittent pneumatic compression on tissue oxygenation were studied in 10 patients with post-thrombotic leg ulcers. Oxygen tension was measured near the edge of the leg ulcer before and after 60 min of intermittent compression at 50 mmHg. The control group consisted of nine subjects with no evidence of peripheral vascular disease. The mean TcPO2 for the controls was 59.7 (SEM2.9) mmHg and for the study group 26.2 (SEM7.0) mmHg before treatment and 42.7 (SEM6.4) mmHg after treatment (p less than 0.005). Oxygen tension increased in nine patients in the study group. The change in TcPO2 correlated highly significantly (r = 0.912, p less than 0.002) with the reduction of oedema and the inverse change of skin temperature. The results suggest that intermittent pneumatic compression decreases interstitial fluid volume and venous stasis, both of which may lead to increased tissue oxygenation.

A non-invasive method for testing neural circulatory control in man.

Exaggerated cardiovascular responsiveness is common in young men and may cause non-specific symptoms and poor performance. Conventional autonomic function tests are not clinically useful. We have therefore designed a thermal entrainment method to evaluate sympathetic and parasympathetic cardiovascular function in subjects with dystonic symptoms and orthostatic intolerance. Oscillations of thermal gradient in the skin were produced by standardised periodic stimulation of the lower part of the arm with warm and cool water. Vasomotor activity of the skin induced oscillations of arterial blood pressure which were thought to be regulated by sympathetic and parasympathetic heart rate control and by oscillation of the sympathetically controlled peripheral vascular resistance. We tested the method in subjects with cardiovascular symptoms (n = 7) and controls (n = 7). At supine rest, the frequency response of the heart rate variability to the thermal stimulation at frequencies of 0.01, 0.02, 0.03 and 0.1 Hz was significantly different (p = 0.008) between symptomatic subjects and controls. The gain of the heart rate control was increased to 0.03 Hz [-1.3(SEM 0.5) dB v -3.8(0.8) dB, p = 0.068] and decreased at 0.1 Hz [-3.9(1.1) dB v -1.5(0.6) dB, p = 0.076] in the test group compared to the control group. At stimulus frequencies of less than 0.03 Hz the individual overall heart rate variability of the subjects with symptoms stayed below the mean control value, at 60(6) ms v 79(15) ms, p = 0.16. The cutaneous temperature oscillations at the site of stimulation, frequency response of the oscillations of the skin blood flow and respiration to the thermal stimulation, and mean heart rate were similar in the both groups. The results show that this thermal entrainment method quantifies the increased sympathetic and decreased parasympathetic cardiac control of subjects with dystonic symptoms.

Cleansing of hands with emulsion--a solution to skin problems of hospital staff?

In this study of hand cleansing, nursing staff with skin problems used emulsion followed by rinsing with water, while control groups, with or without skin problems, used liquid soap and water. Clinical evaluation of the without skin problems, used liquid soap and water. Clinical evaluation of the skin by a dermatologist, as well as by self-assessment, suggested that when the staff with skin problems used emulsion their skin was in better condition than that of controls with similar skin problems. This favourable effect on skin was later confirmed in extended use of emulsion for hand cleansing in other hospital wards. Objective evaluation of skin condition with biophysical measurements was unsuccessful. Emulsion cleansing of the hands seems to offer a favourable alternative to washing with soap and water, especially for persons with skin problems.

Effect of cohort definition and follow-up length on occupational mortality rates.

The purpose of this study was to clarify the effects of cohort formation, period of entry, and period of follow-up on occupational mortality figures. The study material comprised three cohorts of metal industry workers (6 415 iron foundry workers, 3 901 metal product workers, and 5 398 workers manufacturing electrical devices). The men, hired between 1950 and 1976, were followed until the end of 1978. The number of person-years was approximately 215 800. Different cohort formation criteria and variations in the follow-up modify the results of occupational mortality studies. A cross-sectionally based cohort (workers employed in a certain year or years) produces results different from those for an open cohort (new workers hired during a certain period of time) although the cohorts are formed from the same workplaces. The cohorts for retrospective cohort studies usually contain various periods of entry, periods of follow-up, and age structures. Increased or decreased mortality in a cohort depends on this internal structure. The structure of the cohort becomes especially important when a certain cause of death is concentrated in certain age classes and/or when a period of latency is required, as for tumors. In an attempt to reveal this internal structure the three cohorts were analyzed in five-year calendar periods and stratified according to the length of follow-up. The mortality pattern remained nearly unchanged when the number of periods of entry increased, and it was also comparable with the mortality pattern of the general male population.(ABSTRACT TRUNCATED AT 250 WORDS)

Completeness of occupational history and occurrences of work-related diseases.

The lack of complete occupational histories causes underestimates or overestimates of occupational mortality and morbidity. The problem is emphasized in cohorts with high turnover and in cross-sectional study designs. In the study of the effect of selective turnover on occupational mortality and morbidity complete occupational histories were acquired via questionnaire. The sample comprised 1 200 current and 1 800 alive former workers and the closest relatives of 450 deceased workers and was formed from three exposure-level cohorts (defined primarily according to the physical demands of the work) of 15 714 metal workers hired in 1950-1976. The occupational histories reported in the questionnaires were compared with those collected from employers' personnel records. The coverage of occupational histories was the most accurate for current and former workers with the longest duration of exposure and the least accurate for dead workers and the oldest age groups. The use of complete occupational histories and the combining of the similar levels of exposure through the lifetime produced clear differences in the occurrences of musculoskeletal, respiratory, and cardiovascular diseases between the three levels of exposure. The errors in person-years were smaller than the errors in the duration of exposure; the coverage varied from 51 to 94%. However, misclassification clearly caused cancer cases to be located in classes with too short a period of latency. About 30% of the deceased workers had reportedly entered the industry before the first follow-up year.

Mortality and disability among granite workers.

The objective of the present study was to investigate the mortality, disability, and long-term morbidity of granite workers. The study included 1,026 workers hired between 1940 and 1971 and followed until the end of 1981. The total number of deaths was 235, and the expected number was 229.7. Excess mortality rates were observed for respiratory diseases (observed/expected = 28/13.9). The number of tumor deaths was 46 (expected 44.9). Excess lung cancer mortality was evident at 15 to 35 years of latency; the observed number of lung cancer deaths for the follow-up period of 25 to 29 years was 8, while 2.1 were expected. Mortality from cardiovascular diseases and violent deaths was slightly less than expected. The results for disability and long-term morbidity showed elevated incidence and prevalence rates for respiratory diseases and rheumatoid arthritis. The observed number of disability pensions due to rheumatoid arthritis in 1981 was 10 observed versus 1.8 expected, and the observed number of patients granted free medication was 19 versus 8.1 expected. The results indicate that granite dust exposure per se may be an etiologic and pathogenetic factor for lung cancer, cancer of the gastrointestinal tract, and some extrapulmonary nonmalignant chronic diseases.

Vasomotor oscillation in vibration-induced white finger.

Vasomotor oscillation at different ambient temperatures, with and without anesthesia of the finger nerves, was studied in six persons with vibration-induced white finger (VWF) and in 10 referents. The power spectral density (PSD) of the Fourier transform of the laser-Doppler flowmeter signal from the finger pad vessels was analyzed. In both groups, the PSD of the vasomotor oscillation in the frequency range of 0.05-0.25 Hz was more pronounced in a cold than in a hot environment. Without finger nerve anesthesia, the oscillations of the referents were significantly greater (p less than 0.01) than those of the VWF subjects (PSD -34.4 dB and -41.6 dB, respectively). With anesthesia of the finger vasomotor nerves, the PSD was reduced in both groups. In the anesthetized finger there was no statistically significant group difference. Thus the myogenic component of the vasomotor activity was the same in the referents as in the VWF subjects. The results show that the autonomic neural influence on vasomotor oscillation in skin of the finger pad is weaker in persons with VWF. This weakness may be a sign of peripheral neuropathy, which may lead to a denervation syndrome causing hypersensitivity of the adrenoceptors to cold.

Cancer mortality of granite workers.

A retrospective cohort study was undertaken to investigate the cancer mortality of granite workers. The study comprised 1,026 workers hired between 1940 and 1971. The number of person-years was 20,165, and the number of deaths 235. During the total follow-up 46 tumors were observed and 44.9 were expected. An excess mortality from tumors was observed for the workers followed for 20 years or more, the greatest excess occurring during the follow-up period of 25-29 years (observed 11, expected 5.2). Of the 46 tumors, 22 were lung cancers (expected 17.1) and 15 were gastrointestinal cancers (expected 9.7), nine of which were cancers of the stomach (expected 6.0). Mortality from lung cancer was excessive for workers with at least 15 years since entry into granite work (latency) (21 observed and 9.5 expected), being highest during the follow-up period of 25-29 years (observed 8, expected 2.1). The results indicate that granite exposure per se may be an etiologic factor in the initiation or promotion of malignant neoplasms.

Finger peripheral resistance during local cold provocation in vasospastic disease.

Finger systolic blood pressure (FSBP), finger arterial inflow (FAI), finger venous opening pressure (FVOP), and finger peripheral resistance (FPR) were evaluated in 56 workers exposed to chain-saw vibration. Twenty-one of the workers were free from vibration-induced white finger (VWF). In 17 subjects VWF had ceased; 12 of the subjects had active VWF; 6 subjects had Raynaud's disease. The subjects were examined in a supine position under thermoneutral conditions with strain-gauge plethysmography. Cold provocation of the finger caused a significant reduction in FSBP in the groups with Raynaud's disease and active VWF. The finger circulation of the subjects with active VWF and that of those with Raynaud's disease showed a significantly reduced FAI when compared with that of the symptom-free referents. Finger cooling produced a gradual reduction in the FVOP and a significantly increased FPR of the subjects with active VWF and in those with Raynaud's disease. FPR was already increased in the Raynaud's disease group at the beginning of the test, whereas it increased in the VWF group as the temperature fell. The results suggest that in Raynaud's disease the fault is in the level of activity of the sympathetic outflow and in VWF it is peripheral mechanisms controlling the vessel tone.

Different stages of disease, changes in heaviness of work and life cycle.

The aim of this study was to determine which age and exposure categories are the most prone to health selection. Mortality and morbidity were studied on three different exposure levels defined primarily according to the physical demands of the work, heavy (iron foundries), medium (manufacture of metal products), and light (manufacture of electrical devices). The population comprised 15 714 men hired in 1950-1976 to work in the three branches of the metal industry. A questionnaire on occupational history, morbidity, and the causes of turnover was sent to 3 450 current and former workers. The occupational histories of current and former workers were compared for changes in heaviness throughout their complete occupational histories. Occupations during a lifetime were also classified into three levels of exposure on the basis of physical demand (heavy, medium, and light). The three levels of exposure showed different patterns of changes in heaviness of the work according to age throughout the workers' complete occupational histories. Selection into and out of jobs within and between different levels of exposure seemed to be some kind of continuous process, a chain of selection. Similarly as changes in the heaviness of the work formed a chain of selection during lifetime, the workers' health also changed to form a chain through their life cycle. Hard and soft measures formed a continuum (dissatisfaction - death), and they followed each other as explanations for termination of employment. The points of inflection in age, where the measures of different stages of disease turned from soft to hard, varied according to the level of exposure. The life-table technique was used to show the turning of the measures.

Evaluation of a decision-support system for inoperable non-small cell lung cancer.

The purpose of this study was to find out whether a decision-support system is able to assist a clinician in predicting patient outcome and in selecting optimal treatment in oncology. The domain of the evaluated decision-support prototype was primary therapeutic decision making in inoperable non-small cell lung cancer. The performance of the prototype was tested on retrospective material consisting of 112 patients treated by radiotherapy. Survival was the endpoint for examining whether the treatment decision proposed by the system was more accurate than the decision actually made by the clinician. Certain prognostic variables were used by the system to classify patients into two treatment groups, radical or palliative radiotherapy. The median survival times of these groups were 15 and 7 months, respectively, compared with 9 and 8 months in the corresponding groups classified by the clinician. Our results indicate that clinicians need support in treatment selection and that decision-support systems could be a potential answer.

Venoarteriolar response to experimental venous hypertension in legs with chronic venous insufficiency and in healthy legs, measured using a double-wavelength laser Doppler technique.

The venoarteriolar response (VAR) of the skin in legs caused by experimental venous hypertension was measured using a new, double-wavelength laser Doppler probe technique (543 nm and 780 nm). This enables the measurement of the laser Doppler flux in the superficial and deep layers of the skin simultaneously. The recordings were obtained from the leg with the patient in a recumbent position with a sphygmomanometer cuff around the thigh. The VAR was recorded at the cuff pressures of 30 mmHg and 60 mmHg. Ten patients with chronic venous insufficiency (CVI) and 20 control subjects with healthy legs were investigated. The VAR increased in relation to the increase of cuff pressure at both wavelengths. There were no significant differences in the VAR between the cuff pressures within or between the legs with CVI and healthy legs. The VAR measured at 780 nm was very significantly greater than the VAR measured at 543 nm in legs with CVI (p<0.005), as well as in healthy legs (p<0.001). The VAR depends both on the wavelength of the laser Doppler light used and on the degree of venous hypertension. The VAR is not impaired in legs with CVI compared with healthy legs.

Blood flux and venoarteriolar response of the skin in legs with chronic venous insufficiency measured at two different depths by using a double-wavelength laser Doppler technique.

The laser Doppler flux (LDF) and the venoarteriolar response (VAR) of the skin in legs with chronic venous insufficiency (CVI) was measured by using a new double-wavelength probe technique (543 nm and 780 nm). The recordings were taken in a recumbent and in a sitting position. Ten patients with CVI and 20 control subjects with healthy legs were investigated. The LDF was found to be significantly enhanced in a recumbent position at 543 nm and in a sitting position at 780 nm in legs with CVI compared with healthy legs (P<0.05 and P=0.02, respectively). The authors could not find the VAR to be impaired in either wavelength in legs with CVI compared with healthy legs. The double-wavelength probe technique makes it possible to record simultaneously the LDF in the superficial and deep layers of the skin on the same place in the leg.

Continuous mean arterial pressure measurement in the fingers: the influence of local arm cooling.

Two different methods were studied for non-invasive beat-to-beat finger mean arterial pressure (MAP) measurement in 14 healthy volunteers during local arm cooling to 17 degrees C. Fingertip skin blood flow was recorded by a laser Doppler instrument. The difference between the oscillometric beat-to-beat blood pressure measurement device (UT9201) and volume clamp monitor (Finapres) before cooling was -1.5+/-1.1 mmHg, and, although statistically significant, (p< 0.01), this difference cannot be considered clinically meaningful. The results obtained using the two devices during arm cooling showed a systematic disagreement in the continuously recorded MAP. After a 30s period of cooling, the group-averaged difference of UT9201 minus Finapres, calculated as change from the baseline, reached (mean +/- SD) 8.8+/-6.3 mmHg (statistically significant, p< 0.01).

Laser Doppler vasomotion among patients with post-thrombotic venous insufficiency: effect of intermittent pneumatic compression.

Laser Doppler fluxmetry (LDF) was used to measure skin blood flux and its vasomotion, i.e. rhythmical variations in nineteen patients with post-thrombotic venous insufficiency, and in eight healthy control subjects before and after a single intermittent pneumatic compression treatment session. Following the compression treatment session skin blood flux increased and vasomotion was seen in all the patients. The transcutaneous oxygen tension also increased slightly, but significantly, from 25.4 (range 3-56) mmHg to 30.8 (range 7-61) mmHg (p less than 0.01). It is suggested that IPC treatment decreases venous distention and venous pressure thereby decreasing vasocontrictor stimulus. This seems to restore normal skin blood flow including vasomotion.

Poor penetration of infra-red and helium neon low power laser light into the dermal tissue.

The skin transmittance for low power laser light was studied in vitro. The penetration of both He-Ne and infra-red lasers was observed for only a few millimeters. The most important absorption was observed at the depth level of 0.4 and 0.5 mm. These results suggested that the dermal vascular plexus barrier seemed to decrease the penetration at that level. This finding should mean that the laser therapy did not have really direct effects on the deep tissues. However, the effects can be mediated by many different pathways.