Ventilatory response to helium-oxygen breathing during exercise: effect of airway anesthesia

Krishnan, Bharath S., Ron E. Clemens, Trevor A. Zintel,Martin J. Stockwell, and Charles G. Gallagher. Ventilatory response to helium-oxygen breathing during exercise: effect of airwayanesthesia. J. Appl. Physiol. 83(1):82-88, 1997.The substitution of a normoxic helium mixture(HeO₂) for room air (Air) during exercise results in a sustained hyperventilation, which is present evenin the first breath. We hypothesized that this response is dependent onintact airway afferents; if so, airway anesthesia (Anesthesia) shouldaffect this response. Anesthesia was administered to the upper airwaysby topical application and to lower central airways by aerosolinhalation and was confirmed to be effective for over 15 min. Subjectsperformed constant work-rate exercise (CWE) at 69 ± 2 (SE) % maximal work rate on a cycle ergometer on three separate days: twiceafter saline inhalation (days 1 and3) and once after Anesthesia(day 2). CWE commenced after a briefwarm-up, with subjects breathing Air for the first 5 min (Air-1),HeO₂ for the next 3 min, and Airagain until the end of CWE (Air-2). The resistance of the breathingcircuit was matched for Air andHeO₂. BreathingHeO₂ resulted in a small butsignificant increase in minute ventilation(I) anddecrease in alveolar PCO₂ in both theSaline (average of 2 saline tests; not significant) and Anesthesiatests. Although Anesthesia had no effect on the sustainedhyperventilatory response to HeO₂breathing, theI transientswithin the first six breaths ofHeO₂ were significantly attenuatedwith Anesthesia. We conclude that theI response to HeO₂ is not simply due to areduction in external tubing resistance and that, in humans, airwayafferents mediate the transient but not the sustained hyperventilatoryresponse to HeO₂ breathing duringexercise.

     

Effects of bovine parathyroid hormone and 1,25-dihydroxyvitamin D3 on the production of prostaglandins by cells derived from human bone

Local production of prostaglandins by osteoblasts may be important in controlling the bone resorbing activity of some hormones which have receptors on osteoblasts. We have demonstrated that osteoblast-like cells derived from human bone can incorporate [14C]arachidonic acid into phospholipids and synthesise immunoreactive PGE. Parathyroid hormone increases both the release of incorporated arachidonic acid and the synthesis of PGE. This is the first demonstration of modulation of bone cell prostaglandin synthesis by a bone resorbing hormone.     

Further purification and characterization of human 3-methyladenine-DNA glycosylase Evidence for broad specificity

Further purification of a human placental 3-methyladenine-DNA glycosylase by phosphocellulose column chromatography yielded a 6000-fold increase in specific activity with greater than 5% recovery. Although 3-methyladenine was the predominant base released from double-stranded methylated DNA by this enzyme, minor releasing activities for 7-methylguanine and 3-methylguanine were also observed. During purification, the three DNA glycosylase activities consistently copurified with constant ratios of specific activity. Moreover, all the activities were heat-inactivated at 50°C at the same rate, required double-stranded methylated DNA as substrate, were inhibited by spermine and spermidine, and were not subject to product inhibition. These data strengthen the likelihood that the three activities are associated with a single DNA glycosylase.     

Pigmentation and skin reaction to sun as risk factors for cutaneous melanoma: Western Canada Melanoma Study.

Between 1 April 1979 and 31 March 1981, 904 residents of the four western provinces of Canada (population 6.5 million), were diagnosed as suffering from primary cutaneous malignant melanoma. Of 801 patients aged 20-79 years, 665 (83%) were interviewed along with control subjects chosen at random from the general population and matched for age, sex, and province. After exclusion of 70 subjects with lentigo maligna or acral lentiginous melanoma, comparisons of the 595 case-control pairs showed that light hair, skin, and eye colour, a history of heavy freckling in adolescence, and a tendency to burn readily and tan poorly in the sun were significant risk factors for melanoma. The strongest primary associations were with blond hair (relative risk 7.1 compared with black hair), light colour of unexposed skin (relative risk 2.4), and severe freckling (relative risk 2.1). These associations were independent of ethnic origin and of recorded amount of exposure to the sun and were somewhat stronger for superficial spreading than for nodular melanoma. This study is the largest and most detailed of an incident series of melanomas to be published to date. The results were consistent with other studies reporting associations between melanoma and poor tanning ability, a tendency to burn easily, and a history of sunburn and showed that light hair colour was the strongest risk factor for the disease.     

Calcium content and distribution as a function of growth and transformation in the mouse 3T3 cell

Total Ca content and that fraction of Ca sensitive to removal by the chelator ethylene glycol-bis(β-aminoethyl ether)N,N,N',N'-tetraacetate (EGTA) have been investigated in the mouse 3T3 cell as a function of growth stage, transformation with SV40 virus, and serum levels of the media. Cells were allowed to grow through several doublings in media containing (45)Ca. The cellular content of (45)Ca was used to access total cell Ca. That fraction of (45)Ca removed by EGTA was presumed to represent primarily surface-localized Ca. The data are expressed on a per cell volume basis to compensate for size differences as a function of growth stage and transformation. During exponential growth phase, the 3T3 cell contains 525pmol Ca/μl cell volume. Of this, approx. 457 pmol/μl is not removable by EGTA and, presumably, is cytoplasmically located. This value is in close agreement with previous studies on the HeLa cell (470 pmol Ca/μl cell water after the removal of the surface Ca). The low level of EGTA- removable Ca present in the 3T3 cell during early exponential growth (68 pmol Ca/μl cell volume) increases progressively with increasing cell density, and upon quiescence it is sevenfold greater. In contrast, SV40- transformed 3T3 cells growing exponentially possess total levels of Ca which are approximately two-thirds the levels of the normal 3T3 cell. However, their EGTA-sensitive Ca is not significantly different from that of exponentially growing, normal 3T3 cells. As the transformed cells continue to grow at high density, their total ca and their sensitivity to EGTA do not change, in contrast to the normal 3T3 cell. Thus, an increase in Ca associated with the cell surface appears to be correlated with growth inhibition. This has been investigated further by regulating growth of the normal and transformed cell with alterations in the serum level of the media. In 4 percent calf serum the normal cell is stopped from continued proliferation. Growth stoppage under these conditions is characterized by a nearly fourfold increase in EGTA-removable Ca, similar to the increase observed upon quiescence in depleted 10 percent serum. Similar treatment of the transformed cell does not reduce its growth rate, nor does it significantly alter Ca distribution. However, at 0.5 percent medium serum levels, the SV40 3T3 growth rate is substantially reduced and, under these conditions, EGTA-removable Ca increases twofold.     

Production of the Tremorgenic Mycotoxins Verruculogen and Fumitremorgin B by Penicillium piscarium Westling

The tremorgenic mycotoxins verruculogen and fumitremorgin B were isolated from Penicillium piscarium Westling. The coexistence of these tremorgens in culture has previously been reported for one other unrelated fungal species, Aspergillus caespitosus Raper and Thom, and lends further support to the suggestion that the tremorgens have a common biosynthetic origin.     

Differences in the distribution of O-sulphate groups of cell-surface and secreted heparan sulphate produced by human neuroblastoma cells in culture

Confluent cultures of a human neuroblastoma cell line (CHP100) were incubated for 48 h with d-[1-³H]glucosamine and sodium [³⁵S]sulphate. Radioactive glycosaminoglycans were analysed in the growth medium, rapid trypsin digest of the cell monolayer and a 1% (w/v) Triton/0.5 M NaOH extract of the final cell pellet. Sulphated glycosaminoglycans co-chromatographed when eluted by NaCL gradient from DEAE-cellulose. The medium contained mainly chondroitin sulphates, whereas the cell surface was enriched in heparan sulphate. Heparan sulphate was isolated as chondroitinase ABC-resistant material and treated with nitrous acid. Analysis of the scission products on Bio-Gel P-10 yielded fragments varying in size from single disaccharides to glycans consisting of nine disaccharide units. Cell-surface and medium heparan sulphate had respectively 52% and 54% N-sulphated glucosamine residues distributed in similar patterns along the polymer chain. The N:O-sulphate ratio of neuroblastoma heparan sulphate was 1.1:1. Analysis by high-voltage electrophoresis of di- and tetrasaccharide products produced by nitrous acid treatment showed that the distribution of $\text{‘O’-}\text{sulphate}$ groups differed strikingly between heparan sulphates from the medium and cell-surface compartments. A di-O-sulphated tetrasaccharide was identified in both heparan sulphate species. The absence of detectable amounts of ³⁵[S]sulphate associated with fragments larger than tetrasaccharide supports the close topographical association of N-sulphate and O-sulphate groups.