Effect of different levels of hyperoxia on breathing in healthy subjects

Becker, Heinrich F., Olli Polo, Stephen G. McNamara, MichaelBerthon-Jones, and Colin E. Sullivan. Effect of different levelsof hyperoxia on breathing in healthy subjects. J. Appl. Physiol. 81(4): 1683-1690, 1996.Wehave recently shown that breathing 50%O₂ markedly stimulates ventilationin healthy subjects if end-tidal PCO₂(PET_CO2) ismaintained. The aim of this study was to investigate apossible dose-dependent stimulation of ventilation byO₂ and to examine possiblemechanisms of hyperoxic hyperventilation. In eight normalsubjects ventilation was measured while they were breathing 30 and 75%O₂ for 30 min, withPET_CO2 being held constant.Acute hypercapnic ventilatory responses were also tested in thesesubjects. The 75% O₂ experimentwas repeated without controllingPET_CO2 in 14 subjects, andin 6 subjects arterial blood gases were taken at baseline and at theend of the hyperoxia period. Minute ventilation(I) increased by 21 and 115% with 30 and 75% isocapnic hyperoxia, respectively. The 75%O₂ without any control onPET_CO2 led toa 16% increase inI, butPET_CO2 decreased by3.6 Torr (9%). There was a linear correlation(r = 0.83) between the hypercapnic and the hyperoxic ventilatory response. In conclusion, isocapnic hyperoxia stimulates ventilation in a dose-dependent way, withI more than doubling after 30 min of75% O₂. If isocapnia is notmaintained, hyperventilation is attenuated by a decrease in arterialPCO₂. There is a correlation betweenhyperoxic and hypercapnic ventilatory responses. On the basis of datafrom the literature, we concluded that the Haldane effect seems to bethe major cause of hyperventilation duringboth isocapnic and poikilocapnichyperoxia.

     

Markers for the gene ob and serum leptin levels in human morbid obesity

Leptin, the product of the ob gene, reduces body fat in genetically obese animals and circulates in elevated concentrations in the blood of obese patients. Polymorphic markers situated in the proximity of the human ob gene have recently been suggested to be linked to morbid obesity. We have studied the possible association between the microsatellite markers near the ob gene and morbid obesity in 252 morbidly obese patients with a mean body mass index (BMI) of 43 ± 7 kg/m², and 151 lean controls with a mean BMI of 22 ± 2 kg/m², and searched for linkage of these gene markers to obesity in 76 affected sib-pairs (BMI ≥ 32). No significant association was observed between any of the eight microsatellite markers and morbid obesity, and affected-sib-pair analysis failed to show linkage of three selected ob gene markers to obesity in the sibships. There was a strong positive correlation between serum leptin levels and BMI in morbidly obese patients; a carrier status for either of the two most prevalent alleles of the microsatellite marker D7S530 in the vicinity of the ob gene was associated with serum leptin levels in the obese subjects. Two of the markers (D7S2519, D7S649) showed a significant relation to the weight-losing response to a 16-week very-low-calorie dietary intervention. We have thus been able to confirm a tight relationship between serum leptin and body mass but have found no evidence for genetic linkage of the ob gene markers to morbid obesity in a population considered to represent a genetic isolate and to be an ideal model for studies of complex disorders. Received: 25 October 1996 / Revised: 4 December 1996     

The gene encoding human low-molecular weight insulin-like growth-factor binding protein (IGF-BP25): regional localization to 7p12–p13 and description of a DNA polymorphism

The low-molecular weight insulin-like growth-factor binding protein (IGF-BP25) is synthesized by human liver, secretory endometrium and decidua, and is also present in human serum. It binds insulin-like growth factors IGF-I and IGF-II with high affinity, and is proposed to act as a paracrine regulator of cell growth. In situ hybridization studies with a cDNA encompassing the entire protein coding region of IGF-BP25 localized the gene to bands p12-p13 on chromosome 7. Southern blot analysis with the enzyme BglII revealed a common restriction fragment length polymorphism: the presence of the polymorphic BglII site results in the formation of two fragments 4.6 kb and 1.6 kb in size whereas its absence produces a single 6.2 kb fragment. The frequencies of the two alleles were 0.73 and 0.27, respectively. IGF-BP25 constitutes a useful genetic marker for the proximal short arm of chromosome 7.     

Ultrastructural changes in the rat carotid body in severe haemorrhagia

Summary Rat carotid bodies were studied electron microscopically after short-term severe hypovolaemia, which is known to induce a marked chemoreceptor activation in the carotid body. Altogether 84 nerve-endings in the hypovolaemic rats' carotid bodies and 91 nerve-endings in the control carotid bodies were investigated. An increased accumulation of the glomus cell granular vesicles near the synaptic specializations of the nerve-endings was observed after hypovolaemia. Moreover, a statistically significant increase in the contacts between the nerve-ending synaptic specializations and the glomus cell granular vesicles was observed after hypovolaemia. A suggestion was made that the glomus cells might act as modulating, probably inhibitory, interneurones, whose catecholamines are responsible for the inhibition.The authors are greatly indebted to lecturer Pekka Korkala Ph.L. from the Department of Psychology for his skilful statistical analysis of the results.     

Effect of temperature on the microbiological leaching of sulfide ore material in percolators containing chalcopyrite,pentlandite, sphalerite and pyrrhotite as main minerals

Summary Microbiological leaching of complex sulfide ore material was evaluated in percolators at 4, 10, and 20°C. The onset of leaching was associated with an increase in redox potential and a decrease in pH. Copper from chalcopyrite was leached at a slow rate at each test temperature compared with the leaching of zinc from sphalerite and nickel from pentlandite.     

Categorization of Natural Dynamic Audiovisual Scenes

This work analyzed the perceptual attributes of natural dynamic audiovisual scenes. We presented thirty participants with 19 natural scenes in a similarity categorization task, followed by a semi-structured interview. The scenes were reproduced with an immersive audiovisual display. Natural scene perception has been studied mainly with unimodal settings, which have identified motion as one of the most salient attributes related to visual scenes, and sound intensity along with pitch trajectories related to auditory scenes. However, controlled laboratory experiments with natural multimodal stimuli are still scarce. Our results show that humans pay attention to similar perceptual attributes in natural scenes, and a two-dimensional perceptual map of the stimulus scenes and perceptual attributes was obtained in this work. The exploratory results show the amount of movement, perceived noisiness, and eventfulness of the scene to be the most important perceptual attributes in naturalistically reproduced real-world urban environments. We found the scene gist properties openness and expansion to remain as important factors in scenes with no salient auditory or visual events. We propose that the study of scene perception should move forward to understand better the processes behind multimodal scene processing in real-world environments. We publish our stimulus scenes as spherical video recordings and sound field recordings in a publicly available database.     

Inhibitory effects of particulate materials in growing cultures of Thiobacillus ferrooxidans

Particulate materials (flowers of sulfur, fluorapatite, glass beads, and pyrite) inhibited the growth of Thiobacillus ferrooxidans on ferrous iron at pH 1.5. The degree of inhabitation varied with the type of the particulate and culture conditions. The inhibition caused by pyrite involved a soluble toxic component. The inhibition caused by sulfur particles and glass beads was alleviated by incubation under static culture conditions (i.e., no shaking) but oxidation rates declined because of lack of aeration an increase in the pH above 2 also relieved the inhibition. The nature of inhibition. The nature of inhibition by different particles varied from declined iron oxidation rates to prolonged lag periods depending on the concentration of the test material. Thus, the results indicate that the bacterial activity at the liquid-solid interface is different from that in the bulk liquid phase and is influenced by the proton concentration and by the physiochemical properties of the solids.     

Iodinated melatonin: preparation and characterization of the molecular structure by mass and 1H NMR spectroscopy

Synthetic melatonin was iodinated by treatment with potassium iodide in the presence of an oxidizing agent, Iodo-Gen. The iodination products of melatonin were extracted with chloroform and separated by HPLC. The fraction showing immunoreactivity with respect to melatonin antisera was characterized as iodomelatonin by mass spectrometry, so that the substitution of iodine had occurred at a ring carbon atom. 1H NMR spectra showed the iodine to be incorporated at the C-2 position of the indole moiety. The N-[2-(2-iodo-5-methoxy-1H-indol-3-yl)ethyl]acetamide (2-iodomelatonin) reported here is more useful than [3H]melatonin as a tracer in melatonin radioimmunoassay. This method offers also the possibility of preparing iodinated serotonin and other indoleamines for biological studies.