A modified,local sweat collector for warm and humid conditions

Summary The purpose of this study was to modify a previously described local sweat collector to facilitate the investigation of sweat rate and composition in a warm (30°C) and humid (relative humidity 80%) environment. The adherence of the collector to the skin was improved and a pouch was appended at the lower end of the collector. The limitations of the closed collector were examined by comparing the local sweat rate and the quantity of electrolyte excreted in sweat with those obtained using a second collector with a wide opening (to permit free evaporation) and by changes in the body mass. Eight subjects performed exercise on a cycle ergometer consisting of four equal periods of 15 min each, at 60% maximal oxygen consumption, with a rest of 5 min between each period. The sweat produced on a local skin area (85 cm², upper posterior thorax region) was collected at the end of each period, before measuring the body mass on a sensitive (±1 g) platform balance. The mean local sweat rate [2.61 (SEM 0.19) Mg-CM^–2. min^-1] was 2.4 times greater than the pro-rated whole body mass loss but the two were strongly correlated (r=0.82,P<0.01). Compared to the open collector, the greater quantity of electrolyte excreted into the closed collector would suggest that the conditions which prevailed in the closed collector, such as a higher local skin temperature, may have affected the function of the sweat gland. This method enabled the efficiency of local sweat evaporation to be assessed by measuring the difference between sweat volume collected in the open and in the closed collectors. Recovery of water volumes at rest indicated that no contamination and no apparent leakage occurred. This improved sweat collector is suitable for obtaining clean local sweat samples of up to 6 ml, and for measuring the sweat composition and also sweat rate during exercise in warm and humid conditions.     

An improved method for water vapor detection

We describe improvements in and details for the construction, calibration and use of a device using a thermal conductivity cell for the measurement of low-level rates of water evaporation (E) from a small surface area. E is measured from 0.0 to 1.0 mg·min^?1 with a correlation coefficient of 0.999 between measured and independently verified rates and amounts of water evaporation. Data are available as a recordable analog d.c. voltage as well as in digital display for E and for the amount of water evaporated during an operator defined time period. The device we describe is noninvasive and it is designed to be constructed of conventional components. It is useful not only for measuring transcutaneous water diffusion in normal and diseased skin, but also it is adequately sensitive and rapidly responding to follow thermoregulatory and psychogenic sweating in small (nom. 1.0 cm²) skin areas. It can also be used to measure accurately and precisely the rates at which water is adsorbed by and removed from inanimate materials, as well as to determine how much water they store.     

Calciuresis elicited by spontaneous rehydration in dehydrated sheep

Cardiovascular and renal responses to a step-up infusion of endothelin-1 (ET-1) (1, 5, and 15 ng kg^-1 min^-1) were investigated in conscious dogs. In addition, the disappearance of ET-l in arterial and central venous plasma after an infusion of 10 ng kg^-1 min^-1 was quantified, and the effects of vasopressin (AVP, 10 ng kg^-1 min^-1) and angiotensin II (AII, 2, 5, and 10 ng kg^-1 min^-1) on plasma ET-1 were investigated. The step-up infusion of ET-1 increased the plasma level from 3.6 ± 0.3 to 243 ± 23 pg ml^-1. Concomitantly, arterial blood pressure increased and heart rate (HR) decreased dose-dependently. Diuresis, sodium, and potassium excretion did not change significantly. However, free water clearance increased during the infusion. Clearance of creatinine and excretion of urea decreased (39 ± 4 to 29 ± 3 ml min^-1 and 87 ± 16 to 71 ± 14 μmol min^-1, respectively). Decay curves for ET-1 in venous and arterial plasma were identical, and initial t_½ was 1.1 ± 0.1 min. Vasopressin increased arterial blood pressure (107 ± 4 to 136 ± 3 mmHg) beyond the infusion period and increased plasma ET-1 (85%). An equipressor dose of AII tended to decrease plasma ET-1. It is concluded that the lung is apparently not important in the removal of ET-1, that the disappearance of ET-1 follows a complex pattern, and vasopressin – in contrast to angiotensin II – is able to increase the plasma concentration of ET-1. The latter may suggest that ET-1 is involved in the prolonged pressor action of AVP observed.     

Photo-oxidative degradation and stabilization of isotactic poly(1-butene) in solid state, 1

The kinetics of photo-oxidative degradation and stabilization of poly(1-butene), [poly(1-ethylethylene), PB-1] at 253, 7 nm and a constant intensity of 2,38·10^?9 Einstein.s^?1·cm^?2 (1,12·10^?3 J·mol^?1·s^?1·cm^?2) was studied in the absence and presence of 0,1 wt.-% 6-(2-hydroxyphenyl)-2,4-diphenyl-1,3,5-triazine ( 1 ) dispersed evenly in the matrix of polymer films in the temperature range of 267 to 313 K. The progress of the reaction was followed by measuring the rate of chain scission of the polymer. It has been confirmed by light scattering and potassium ferrioxalate actinometric measurements that random scission of the polymer chain occurs and 1 acts as a stabilizer to the photo-oxidative degradation processes. Irrespective of the variations in the values of ΔH^≠ and ΔS^≠ the values of ΔF^≠ remain almost constant around 159 kJ·mol^?1 indicating that the rate determining step is the same for both systems.     

Lactation affects pressor,volumetric and natriuretic responses to angiotensin II in goats

Demands on cardiovascular function and fluid turnover increase during lactation and pregnancy in the goat, but the hormonal status is different. This study is aimed at investigating the effects of hypertensive angiotensin II (ANGII) in lactating goats. The results were compared with those of pregnancy and control conditions. ANGII (0.5 pg min^-1) was infused intravenously for 60 min (n = 6). The rise in blood pressure in response to ANGII was attenuated during lactation as in pregnancy (P < 0.001 vs control period). ANGII caused reflex bradycardia. Plasma protein concentration decreased by 7.5% during infusions in lactating goats (pregnancy: 9%; control period: 4.5%). Renal Na excretion increased by 260% (lactation), by 400% (pregnancy; n.s. vs. lactation), and by 800% (control period; P < 0.01 vs. lactation). The glomerular filtration rate was unchanged during ANGII infusions in lactating animals, but increased in the other periods. Effective renal plasma flow decreased. ANGII raised aldosterone from < 34.5 pmol 1^--¹ to 539 ± 80 pmol l^-1 (lactation) and to 428 ± 41 pmol l^-1 (control; P < 0.05 vs. lactation), and from 72 ± 9 to 651 ± 103 pmol l^-1 (pregnancy; P < 0.01 vs. lactation). Plasma progesterone was undetectable during lactation, but varied from 0 to 17 nmol l^-1 during control conditions and was 16 ± 1 nmol l^-1 during pregnancy. Oestradiol 17β was 181± 22 pmol l^-1 in pregnant goats, and undetectable in lactating animals. In conclusion, lactation affects ANGII-induced changes in cardiovascular and fluid regulation, but in this period the effects were not related to progesterone or oestradiol 17 β.     

On the theoretical limits of detecting cyclic changes in cardiac high‐energy phosphates and creatine kinase reaction kinetics using in vivo 31P MRS

Adenosine triphosphate (ATP) is absolutely required to fuel normal cyclic contractions of the heart. The creatine kinase (CK) reaction is a major energy reserve reaction that rapidly converts creatine phosphate (PCr) to ATP during the cardiac cycle and at times of stress and ischemia, but is significantly impaired in conditions such as hypertrophy and heart failure. Because the magnitudes of possible in vivo cyclic changes in cardiac high‐energy phosphates (HEPs) during the cardiac cycle are not well known from previous work, this study uses mathematical modeling to assess whether, and to what extent, cyclic variations in HEPs and in the rate of ATP synthesis through CK (CK flux) could exist in the human heart, and whether they could be measured with current in vivo ³¹P MRS methods. Multi‐site exchange models incorporating enzymatic rate equations were used to study the cyclic dynamics of the CK reaction, and Bloch equations were used to simulate ³¹P MRS saturation transfer measurements of the CK reaction. The simulations show that short‐term buffering of ATP by CK requires temporal variations over the cardiac cycle in the CK reaction velocities modeled by enzymatic rate equations. The maximum variation in HEPs in the normal human heart beating at 60 min^–1 was approximately 0.4 m m and proportional to the velocity of ATP hydrolysis. Such HEP variations are at or below the current limits of detection by in vivo ³¹P MRS methods. Bloch equation simulations show that ³¹P MRS saturation transfer estimates the time‐averaged, pseudo‐first‐order forward rate constant, k_f,ap′, of the CK reaction, and that periodic short‐term fluctuations in k_f′ and CK flux are not likely to be detectable in human studies employing current in vivo ³¹P MRS methods. Copyright © 2015 John Wiley & Sons, Ltd.     

Rapid steady-state analysis of blood-brain glucose transfer in rat

A new kinetic analysis of blood-brain glucose transport is described, based on a steady-state model that takes account of cerebral blood flow, mean capillary glucose concentration, and cerebral metabolic rate. The maximal rate (T_max) and half-saturation constant (K_m) of glucose transport from blood to brain were determined in rats by measuring the rate of blood-to-brain glucose transfer at different blood glucose concentrations. Each determination lasted 20 seconds. For whole-brain, T_max and K_m averaged 258±33 (S.E.) μmol (100 g)^-1 min^-1 and 5.9±1.6 (S.E.) mmol 1^-1, respectively. The regional variations were insignificant. The new approach permits kinetic parameters to be measured locally in brain in rapidly changing functional states.     

A simplified procedure of direct calorimetry for bedside monitoring of the resting metabolic rate

A simplified procedure of direct calorimetry (SPDC) for determination of resting metabolic rate of respiratory uncompromised subjects in a supine position is presented. This procedure was based on computer-assisted measurements of heat losses due to evaporation, radiation, conduction, and convection. The subject's total loss of mass was recorded hydraulically with a beam scale and afterwards transformed into a digital electric signal. Differences between dry bulb temperature and mean skin temperature were measured by semiconductor thermistors and also transformed into digital signals. With special software an interfaced personal computer assisted in performing SPDC and in calculating heat losses due to evaporation, radiation, and conduction. In a thermoneutral environment,six healthy volunteers were investigated to determine the mean convective heat transfer coefficient (h _c) from the difference in an individual between the metabolic energy transformation (M) measured by indirect calorimetry (IC) and the sum of heat losses by radiation, conduction, and evaporation. The room-specific value of h _c of 2.12 (SD 0.22) W·m^–2·°C^–1 was in good agreement with data in the literature. Compared to the results of M from a second series of IC, the total heat loss (THL) measured by SPDC in a thermoneutral environment was calculated as 100.5 (SD 6.0) %. The THL by SPDC performed three times at 3-h intervals on ten other volunteers revealed a mean difference of 0.22 (SD 1.74) W·m^–2. Thus, SPDC would seem to be a valid and reproducible method under conditions of thermal neutrality.     

Impact of O-glycosylation on the molecular and cellular adhesion properties of the Escherichia coli autotransporter protein Ag43

Antigen 43 (Ag43) represents an entire family of closely related autotransporter proteins in Escherichia coli and has been described to confer aggregation and fluffing of cells, to promote biofilm formation, uptake and survival in macrophages as well as long-term persistence of uropathogenic E. coli in the murine urinary tract. Furthermore, it has been reported that glycosylation of the Ag43 passenger domain (α⁴³) stabilizes its conformation and increases adhesion to Hep-2 cells.We characterized the role of Ag43 as an adhesin and the impact of O-glycosylation on the function of Ag43. To analyze whether structural variations in the α⁴³ domain correlate with different functional properties, we cloned 5 different agn43 alleles from different E. coli subtypes and tested them for autoaggregation, biofilm formation, adhesion to different eukaryotic cell lines as well as to purified components of the extracellular matrix. These experiments were performed with nonglycosylated and O-glycosylated Ag43 variants. We show for the first time that Ag43 mediates bacterial adhesion in a cell line-specific manner and that structural variations of the α⁴³ domain correlate with increased adhesive properties to proteins of the extracellular matrix such as collagen and laminin. Whereas O-glycosylation of many α⁴³ domains led to impaired autoaggregation and a significantly reduced adhesion to eukaryotic cell lines, their interaction with collagen was significantly increased. These data demonstrate that O-glycosylation is not a prerequisite for Ag43 function and that the different traits mediated by Ag43, i.e., biofilm formation, autoaggregation, adhesion to eukaryotic cells and extracellular matrix proteins, rely on distinct mechanisms.     

Rate-responsive pacing using the atrio-ventricular conduction time: Design and test of a new algorithm

The cardio-circulatory system of chronotropic incompentent patients is unable to adapt heart rate adequately to the level of strain. A common therapy is the implantation of a pacemaker that stimulates the heart at a rate derived from a strain related sensor signal. The paper describes a new pacemaker concept that uses a well-defined time interval in the electrogram as a sensor parameter, the atrioventricular conduction time (AVCT). Identification experiments with patients delivered the stationary and dynamic behaviour of AVCT subject to variations in the exercise rate and the pacing frequency. Furthermore, it was demonstrated that AVCT is perturbed by respiratory activity. The new rate-responsive algorithm, which uses the internal model control principle, explicitly takes into account the closed-loop nature of the underlying system. The major design objectives were: extended range of the individual heart rate; effective attenuation of the respiratory-related disturbance; and stability. Seven patients undergoing incremental exercise were paced with this AVCT-based algorithm. The experiments confirmed the suitability of this concept with respect to the design goals. The patients' peak intrinsic heart rate at exercise was 100±20 min⁻¹. When paced with the AVCT algorithm, the paced heart rate was 126±12 min⁻¹. The increase was significant (26±13 min⁻¹; 15 to 53 min⁻¹), which clearly demonstrated the potential of this concept to restore chronotropic competence.     

The effect of hyperglycaemia on regional cerebral glucose oxidation in humans studied with [1–11C]-D-glucose

The effect of hyperglycaemia on regional cerebral glucose utilization was studied in five healthy males fasted over-night using positron emission tomography. Selectively labelled glucose, [1–¹¹C]-D -glucose, was used as a tracer. After correction for the small loss of [¹¹C]CO₂ from the tissue, this tracer measures the rate of glucose oxidation rather than the total rate of glucose metabolism. Each subject was investigated twice: during normoglycaemia (plasma glucose 5.3 ± 0.3 μmol mL^?1) and at the end of a 2-h period of hyperglycaemia (plasma glucose 13.8 ± 0.7 μmol mL^?1). Assuming unchanged rate constant for loss of labelled CO₂ at normo- and hyperglycaemia the oxidative metabolic rate of glucose was found to be slightly larger at combined hyperglycaemia and hypersulinemia (0.30 ± 0.01 mmol mL^?1 min^?1) than at normal glucose and insulin levels (0.25 ± 0.01 mmol mL^?1 min^?1). This suggests that the process of glucose phosphorylation might not be fully saturated in the human brain or, alternatively, that the glycogen deposition increases during short-term hyperglycaemia. The relative increase of oxidative metabolic rate was considerably larger (≈50%) in white matter than in the brain as a whole (20%). The brain glucose content was found to increase non-linearly with increasing plasma glucose. Together with data from previous studies these results suggest that the free glucose in the human brain is close to zero when the plasma glucose is below 2 μmol mL^?1.     

The damage of the hepatic mixed functional oxygenase system by CCl4: significance of incorporation of 14CCl4 metabolites in vivo

The relation between incorporation of ¹⁴C from ¹⁴CCl₄ into liver lipids and damage to the mixed functional oxygenase system of liver microsomes was investigated in rats of different sex or differently pretreated. Under the respective conditions of pretreatment the ¹⁴C incorporation rate and the relative decrease of the cytochrome P-450 level as the parameters most influenced by CCl₄ were compared with those for untreated female rats. Induction by 3-methylcholanthrene does not after both parameters. Induction by sodium phenobarbital enhances the ¹⁴C incorporation rate as well as the cytochrome P-450 decrease but the latter is more affected. In male rats only the ¹⁴C incorporation rate increased. Vitamin D₃-pretreated rats showed a smaller decrease of cytochrome P-450 but an enhanced ¹⁴C incorporation rate. Therefore, there is no correlation between the cytochrome P-450 decrease and ¹⁴C incorporation rate. Reasons for the lack of that correlation are discussed with regard to the mechanism of liver cell damage by carbon tetrachloride.     

Characterization of high-affinity antifluorescyl IgM antibodies

High-affinity IgM rabbit antibodies were elicited using the fluorescein hapten system. Purity and identification of IgM and IgG anti-fluorescyl antibodies was determined by immunoelectrophoresis and SDS-polyacrylamide gel electrophoresis. Ultracentrifugation studies verified that liganded antibodies were of a high mol. wt (901 kd).Comparative analyses of IgM and IgG anti-fluorescyl antibody active sites substantiated the observation that purified IgM preparations, similar to their IgG counterparts, possessed high-affinity antibody active sites. Dissociation rate data confirmed that some IgM molecules within the purified antibody populations possessed association constants at 10¹¹M^?1, comparable with values of 10¹¹M^?1 or greater obtained for some anti-fluorescein IgG populations studied in this laboratory. A diffusion-controlled association rate of 4.6 × 10⁸M^?1 sec^?1 (Levison et al., 1971) was assumed in dissociation rate calculations. This is the first report of purified IgM antibodies possessing exceptionally high affinities.     

Hypersensitivity pneumonitis induced by Penicillium species

An entomologist developed an illness with typical features of hypersensitivity pneumonitis. On-site investigations indicated that on the days of his attacks he was exposed to dust laden with several species of mold, especially Penicillium spp., as well as to mists generated by reservoir-type humidifiers, Serologic tests to more than 40 antigens prepared from organisms and sources known to cause hypersensitivity pneumonitis showed strong reactions to Penicillium and to antigens prepared from the scum of a large industrial humidifier and from his laboratory humidifier. PFTs revealed a significant reduction in DLCO. Following a 4-mo period without laboratory exposure, he experienced no further episodes, a return to his previous exercise tolerance, and a normal DLCO, BP studies with extracts of Penicillium casei and humidifier water from his laboratory (H¹) resulted in objective evidence, both clinically and by hematologic and pulmonary function testing, of hypersensitivity to Penicillium spp. and possibly also to the H¹ preparation.     

A novel hypothesis of lipofuscinogenesis and cellular aging based on interactions between oxidative stress and autophagocytosis

Based on a series of experiments, using cultured postmitotic neonatal rat cardiac myocytes as a model system, we present a novel hypothesis of lipofuscin formation. This hypothesis proposes that lipofuscin is formed within secondary lysosomes due to an interplay of two processes, the production of partially reduced oxygen species by mitochondria and the autophagocytotic degradation within secondary lysosomes. Specifically, it is proposed that H₂O₂ generated by mitochondria and other organelles permeates into the lumen of secondary lysosomes, which contain iron derived from cellular structures undergoing intralysosomal degradation. The interaction between reactive ferrous iron and H₂O₂ results, via Fenton-type mechanisms, in the generation of hydroxyl free radicals (OH), inducing lipid peroxidation and eventually leading to intermolecular cross-linking and lipofuscin formation. Additionally, mitochondria undergoing intralysosomal decomposition might continue for a certain period to produce superoxide anion radicals (O₂⁻) and thus also H₂O₂. This model of lipofuscinogenesis could satisfactorily explain the variations observed in the rates of lipofuscinogenesis among different postmitotic cell types in various species. Such variations might arise from a variety of factors including differences in the efficiency of the ‘anti-oxidative shield’, rate of H₂O₂ generation, amount of chain-breaking antioxidants, mode of intralysosomal iron chelation, rate of autophagocytosis as well as degree of efficiency of the intralysosomal hydrolytic enzymes.     

Kinetic effect of radiation intensity and thermal after-treatment in the photopolymerization of diallyl oxydiethylene dicarbonate

The influence of radiation intensity (from 1,08 · 10^?7 to 2,48 · 10^?4 einstein.s^?1 · 1^?1) on the photopolymerization of diallyl oxydiethylene dicarbonate was investigated systematically not only in the initial stages of reaction, but also at high monomer conversion (x), in order to detect possible variations in the polymerization mechanism. In some of the runs irradiation was stopped at x = 0,55–0,65 and thermal after-treatments were carried out both in the presence and absence of air by following kinetically x-values during the self-decelerating cross-linking. To rationalize experimental data a model is proposed which assumes two basically different mechanisms occurring simultaneously (bimolecular termination and radical trapping), but with different “weights” as a function of time. Long living radicals produced by irradiation continue to react in the dark. The rate of this reaction, which is enhanced in the presence of oxygen, is fitted by a relaxation model that considers double bonds, particularly of pendant groups, as traps, with increasing lifetimes, able to transfer to radical sites. The role of oxygen is also discussed.     

Bestimmung der geschwindigkeitskonstanten und der effektivitäten beim zerfall von 2,2′-azoisobutyronitril in styrol,N-vinyl-2-pyrrolidon und methylmethacrylat

The decomposition rate constants k_d of initiators can be determined by a new method directly in monomers as solvents. If a suitable inhibitor is added to a monomer mixture with the initiator the latter decomposes nearly without monomer conversion. The initiator concentration—after the inhibitor is consumed—can be found by means of the dilatometrically determined polymerization rate after the induction period. The functional connection between polymerization rate and initiator concentration found without inhibitor is used as a calibration curve for that purpose. The dilatometrical measurements were made in the monomers styrene and N-vinyl-2-pyrrolidone using 2,2′-azoisobutyronitrile (AIBN) as initiator and p-quinone as inhibitor. The following decomposition rate constants were found: k_d=1,52 · 10^?5 S^?1 (styrene) and k_d=1,62 · 10^?5 S^?1 (N-vinyl-2-pyrrolidone), which is in agreement with literature values. Initiator efficiencies f were calculated: f=0,46 (styrene), f=0,47 (N-vinyl-2-pyrrolidone). In methyl methacrylate (MMA) 2,2′-diphenyl-1-picrylhydrazyl (DPPH) was used as inhibitor. Under certain conditions the product k_df can be calculated from the consumption rate of DPPH. The value found in MMA (k_df=3,7 · 10^?6 s^?1) is lower than that reported in literature (6,45 · 10^?6 s^?1).     

Isolation and identification of virus-specific mRNAs in cells infected with mouse hepatitis virus (MHV-A59)

We have determined the kinetics of virus production and virus-specific RNA synthesis in Sac(?) cells infected with mouse hepatitis virus strain A59 (MHV-A59). Immunofluorescence showed that all cells became infected at a multiplicity of 10 PFU/cell. The virus was concentrated and purified to obtain the high titered stocks needed for these one-step growth experiments. Release of virus into the culture medium started 4 hr after infection (pi) and was complete at 10 hr pi. Synthesis of virus-specific RNA, measured by the incorporation of [³H]uridine in the presence of 1 μg/ml actinomycin D, also started at 4 hr pi and its maximum rate occurred between 6 and 8 hr pi. RNA labeled during this period was isolated from infected cells. About 50% of this RNA bound to oligo(dT)-cellulose; this material was denatured with glyoxal-dimethyl sulfoxide and analyzed by electrophoresis in 1% agarose gels. Seven RNA species with the following molecular weights were present: 5.6 × 10⁶ (RNA1), 4.0 × 10⁶ (RNA2), 3.0 × 10⁶ (RNA3), 1.4 × 10⁶ (RNA4), 1.2 × 10⁶ (RNA5), 0.9 × 10⁶ (RNA6), and 0.6 × 10⁶ (RNA7). RNA1 comigrated with the viral genome. Artifacts caused by defective interfering particles or breakdown of RNA were excluded. To determine whether these RNA species were functional as messengers in infected cells, virus-specific RNAs present in polyribosomes were analyzed. EDTA treatment was used to discriminate between RNA present in polyribosomes and in EDTA-resistant, presumably ribonucleoprotein, particles. Most (91%) of RNA1 was present in EDTA-resistant particles; the remainder and all other RNAs synthesized between 6 and 8 hr pi were present in polyribosomes. We conclude that MHV-A59 has six subgenomic mRNAs. Since the total molecular mass (11.1 × 10⁶ daltons) of these messengers is about twice that of the viral genome, sequence homologies must exist between the mRNAs. The position of these homologous regions and the translation products of each of the mRNAs remain to be determined.