Annoyance and performance during the experimental chemical challenge of subjects with multiple chemical sensitivity

OBJECTIVES: This study explored the subjective reactions and psychological test performance of smell-intolerant subjects during consecutive challenges to chemicals with contrasting neurotoxic properties. METHODS: Women with symptoms compatible with multiple chemical sensitivity (N=10) and healthy referents (N=20) were individually challenged in an exposure chamber. All the subjects attended two separate 2-hour sessions of exposure to n-butyl acetate and toluene, in counterbalanced sequence. After an initial phase without exposure, air concentrations were increased in steps ranging from 3.6 to 57 mg/m3 for n-butyl acetate and from 11 to 180 mg/m3 for toluene. The response measures comprised ratings of annoyance and smell intensity and also neurobehavioral test performance. RESULTS: Both groups showed an increase in annoyance ratings and a decrease in test performance in the initial unexposed chamber phase and also in the first phase of the chemical exposure, these results indicating slight immediate expectancy or "suggestion" effects. During the six chamber phases, the ratings of mucous membrane irritation and fatigue showed a steeper increase in the group with multiple chemical sensitivity than among the referents, while the ratings of smell intensity and smell annoyance were similar in the two groups. A reduction in test performance was observed during the chamber phases, particularly in the group with multiple chemical sensitivity. No relation was found between the ratings or performance and chemical substance. CONCLUSIONS: Stronger immediate expectancy or "suggestion" reactions than normal did not characterize the group with multiple chemical sensitivity. This group showed a stronger than normal gradual build-up of fatigue, mucous membrane irritation, and reduced performance during chemical exposure. The results offer the most support to an irritative basis for multiple chemical sensitivity.     

The glycaemic index: importance of dietary fibre and other food properties

An increasing body of evidence suggests that a low-glycaemic-index (GI) diet has a therapeutic as well as a preventive potential in relation to the insulin resistance syndrome. The implementation of a low-GI diet, however, will require an extended list of low-GI foods to be available on the market. The tailoring of low-GI bread products offers a particular challenge due to their generally high GI and abundance in the diet. Low-GI bread products can be tailored by, for example,enclosure of cereal kernels, sour dough fermentation and/or addition of organic acids, or use of cereal genotypes with elevated contents of amylose or f-glucans. Low-GI cereal foods appear to vary in effect on 'second-meal' glucose tolerance in healthy subjects. In addition to the slow-release properties of such foods, the content of dietary fibre appears to play a role. The low glycaemia to starch in a pasta breakfast (GI 54) promoted a higher glucose tolerance and lowered triacylglycerol levels at a standardized lunch ingested 4 h later, compared with a white-wheat-bread breakfast (GI 100). The metabolic benefits of the low GI properties per se have been demonstrated also in the longer term. Thus, a reduction in dietary GI improved glucose and lipid metabolism and normalized fibrinolytic activity in type 2 diabetics, while maintaining a similar amount and composition of dietary fibre. However, the higher dietary fibre content frequently associated with low-GI foods may add to the metabolic merits of a low-GI diet. Consequently, a low-GI barley meal rich in dietary fibre (GI 53) improved glucose tolerance from evening meal to breakfast, whereas an evening meal with pasta had no effect (GI 54). The exchange of common high-GI bread for low-GI high-fibre bread, as the only dietary modification, improved insulin economy in women at risk of type 2 diabetes. These results are in accordance with epidemiological evidence of a reduced risk of type 2 diabetes with a low-GI diet rich in cereal fibre. It is concluded that low-GI cereal foods developed should preferably be rich in dietary fibre.     

Polychlorinated biphenyls and organochlorine pesticides in Baltic and Atlantic gray seal (Halichoerus grypus) pups

Organochlorine pollutants (OCs), such as polychlorinated biphenyls (PCBs), DDT, chlordanes (CHLs), hexachlorobenzene (HCB) and hexachlorocyclohexanes (HCHs) were determined in blubber biopsies from free-ranging Baltic and Atlantic gray seal (Halichoerus grypus) pups. Well-fed pups from the Baltic Sea had concentrations of DDT, PCBs, and HCHs that were 2 to 10 times higher than in corresponding pups from populations in the Atlantic Ocean. The OC pattern in the Baltic seals differed significantly from that of their Atlantic relatives, reflecting the predominance of regional point source inputs into the Baltic Sea and long-range atmospheric inputs into the Atlantic Ocean. The differences in the pattern of the compounds also indicated an enhanced metabolism of the more metabolizable compounds in the more contaminated Baltic seals. Surprisingly, the proportions of the high chlorinated and low-volatile PCB congeners (> 6 Cl atoms) were comparable or lower in the Baltic pups as compared to the Atlantic pups. This difference might be due to Baltic seals occupying a lower trophic level than Atlantic seals and/or to the eutrophication situation in the Baltic Sea, which causes sedimentation of these PCB congeners. Significantly higher OC concentrations were found in starved and/or abandoned Baltic pups as compared to well-fed pups. The most contaminated Baltic seal pups in the present study had PCB concentrations that are comparable or higher than those reported to impair the immune systems and vitamin A dynamics in phocids.     

Polychlorinated biphenyls and reproductive hormones in female polar bears at Svalbard

High concentrations of polychlorinated biphenyls (PCBs) in polar bears from Svalbard have increased concern for that population's reproductive health. We examined whether there were associations between the plasma concentrations of PCBs and reproductive hormones [progesterone (P4)] and 17 beta-estradiol (E2)] in free-living female polar bears from Svalbard. Concentrations of P4 depended on reproductive status, and concentrations were lowest in females with offspring--females with cubs and females with yearlings. In these females, the P4 concentrations were positively correlated with plasma sigma PCBs (sum of all analyzed polychlorinated biphenyl congeners) concentrations. The sigma PCBs concentrations explained 27% of the variation in the P4 concentrations. There were no correlations between sigma PCBs and E2 and cortisol in any of the groups of polar bears, or between sigma PCBs and P4 in single polar bears. Although the sigma PCBs-P4 relationship in female polar bears with offspring is not evidence per se of a direct cause-effect association, the results indicate that PCBs may affect levels of P4 in polar bear females. There is a clear need to further assess the hormone balance and population health of polar bears at Svalbard.     

Lack of influence of omega-3 fatty acid-enriched lipids on apoptosis and secondary necrosis of cultured human lymphocytes

OBJECTIVE: The anti-inflammatory properties of parenteral nutrition might be improved by enrichment with omega-3 polyunsaturated fatty acids (PUFAs), which are responsible for the enhanced release of metabolites derived from eicosapentaenoic acid. Under physiologic conditions, lymphocyte populations are regulated by cellular mechanisms such as apoptosis. In contrast to cell death by necrosis, apoptosis does not induce an inflammatory response that might injure the host. METHODS: Apoptosis and necrosis of cultured human blood lymphocytes were investigated in vitro after incubation for 48 and 72 h with three lipid emulsions containing 50% medium-chain triacylglycerols. The lipid emulsions differed in the percentage of long-chain triacylglycerols, which were replaced in part by different amounts of omega-3 PUFA (8%, 20%, or 40%). Rates of apoptosis and necrosis of lymphocyte subpopulations were analyzed with a sensitive annexin V flow cytometric assay. RESULTS: After 48 and 72 h of incubation, time- and dose-dependent increases of apoptosis and necrosis, respectively, were found in all lymphocyte subsets regardless of the percentage of omega-3 PUFAs. CONCLUSIONS: Our results suggested that enrichment with omega-3 PUFAs in the tested lipid emulsions does not alter apoptosis and secondary necrosis of lymphocyte populations. Thus PUFAs may exert their functional effects through other mechanisms.     

Determination of the glycaemic index of foods: interlaboratory study

OBJECTIVE: Practical use of the glycaemic index (GI), as recommended by the FAO/WHO, requires an evaluation of the recommended method. Our purpose was to determine the magnitude and sources of variation of the GI values obtained by experienced investigators in different international centres. DESIGN: GI values of four centrally provided foods (instant potato, rice, spaghetti and barley) and locally obtained white bread were determined in 8-12 subjects in each of seven centres using the method recommended by FAO/WHO. Data analysis was performed centrally. SETTING: University departments of nutrition. SUBJECTS: Healthy subjects (28 male, 40 female) were studied. RESULTS: The GI values of the five foods did not vary significantly in different centres nor was there a significant centrexfood interaction. Within-subject variation from two centres using venous blood was twice that from five centres using capillary blood. The s.d. of centre mean GI values was reduced from 10.6 (range 6.8-12.8) to 9.0 (range 4.8-12.6) by excluding venous blood data. GI values were not significantly related to differences in method of glucose measurement or subject characteristics (age, sex, BMI, ethnicity or absolute glycaemic response). GI values for locally obtained bread were no more variable than those for centrally provided foods. CONCLUSIONS: The GI values of foods are more precisely determined using capillary than venous blood sampling, with mean between-laboratory s.d. of approximately 9.0. Finding ways to reduce within-subject variation of glycaemic responses may be the most effective strategy to improve the precision of measurement of GI values.     

Occupational and social variation in subjective health complaints

OBJECTIVES: Occupational and social factors are thought to be important determinants of health inequality. The aim of this study was to examine the relationships between occupation, lifestyle and subjective health complaints (SHC). METHODS: SHC and self-reported sickness absence were recorded in a cross-sectional study of 662 individuals aged between 16 and 67 from five occupational groups: blue-collar, school/education, health service, white-collar and service. Differences in SHC and sickness absence were investigated. A model of sociodemographic, lifestyle and work-related factors was tested to examine associations with SHC. RESULTS: Few differences in SHC and sickness absence were found when educational level, age and gender were controlled for. Female health service workers did, however, show significantly higher prevalence of pseudoneurological complaints compared with white-collar workers. Male blue-collar workers had significantly higher frequency of sickness absence than white-collar workers; otherwise, there were no significant differences in frequency and duration of sickness absence. The model explained very little of the variance of SHC (R(2)(adj) = 0.15) and occupational group was not significantly associated with health. Physical workload and sleep quality showed significant relationships with SHC for both genders. Education, however, was a significant factor for women only. CONCLUSIONS: The differences in health found between major occupational groups in this sample were mainly explained by gender differences. Sociodemographic, lifestyle and work-related factors explained little of the variance in SHC, suggesting that factors such as psychological demands, perceived job stress, coping and other psychological factors might be of stronger importance for SHC.     

An external fixation method and device to study fracture healing in rats

We wished to establish a reproducible model for fracture fixation to be used in fracture healing research and therefore developed an external fixation construct and surgical procedure adapted to Sprague-Dawley rats. We evaluated the mechanical properties of the construct in brass rods and rat bone, in an Instron test machine with axial and transverse loading, and the in vivo performance. We found that the mechanical properties of the construct in brass rods were predictable and could be repeated in rat femora. In all tests, the axial load was about 10 times the transverse for the same degree of deformation. The stiffness among fixators was uniform. 1 mm pins caused about 50% less stiffness than 1.2 mm pins in axial loading of rat bone (p < 0.001) and brass rods (p < 0.001) as well as in transverse loading of brass rods (p < 0.001). Loosening of 1 or 2 screws that lock the pins to the fixator reduced stiffness by about 50% in axial loading of rat bone (p = 0.009) and brass rods (p = 0.05). A change in the distance between the bone surface and the fixator was linearly related to the stiffness in axial loading of rat bone (p < 0.001) and brass rods (p < 0.001) and in transverse loading of brass rods (p < 0.001). If the bone ends touched each other, the axial stiffness of the construct increased almost 10 times (265 N/mm), as compared to a fracture gap size of 2 mm (31 N/mm). In vivo experiments had a complication rate of less than 10% when we used 1.2 mm pins, 6 mm offset and rats weighing 350-450 g. Our method and device for experimental external fixation of rat femora are reliable and the findings are reproducible. These can be used in bone repair and fracture healing research.     

The effects of isoflurane-induced electroencephalographic burst suppression on cerebral blood flow velocity and cerebral oxygen extraction during cardiopulmonary bypass

We investigated the effects of isoflurane-induced burst suppression, monitored with electroencephalography (EEG), on cerebral blood flow velocity (CBFV), cerebral oxygen extraction (COE), and autoregulation in 16 patients undergoing cardiac surgery. The experimental procedure was performed during nonpulsatile cardiopulmonary bypass (CPB) with mild hypothermia (32 degrees C) in fentanyl-anesthestized patients. Middle cerebral artery transcranial Doppler flow velocity, right jugular vein bulb oxygen saturation, and jugular venous pressure (JVP) were continuously measured. Autoregulation was tested during changes in mean arterial blood pressure (MAP) within a range of 40-80 mm Hg, induced by sodium nitroprusside and phenylephrine before (control) and during additional isoflurane administration to an EEG burst-suppression level of 6-9/min. Isoflurane induced a 27% decrease in CBFV (P < 0.05) and a 13% decrease in COE (P < 0.05) compared with control. The slope of the positive relationship between CBFV and cerebral perfusion pressure (CPP = MAP - JVP) was steeper with isoflurane (P < 0.05) compared with control, as was the slope of the negative relationship between CPP and COE (P < 0.05). We conclude that burst-suppression doses of isoflurane decrease CBFV and impair autoregulation of cerebral blood flow during mildly hypothermic CPB. Furthermore, during isoflurane administration, blood flow was in excess relative to oxygen demand, indicating a loss of metabolic autoregulation of flow. IMPLICATIONS: The effects of isoflurane on cerebral blood flow velocity (CBFV) and oxygen extraction (COE) as a function of perfusion pressure were studied. When added to fentanyl anesthesia, isoflurane induced a 27% and 13% decrease in CBFV and COE, respectively. CBFV became more pressure-dependent with isoflurane indicating an impaired autoregulation.