Bicarbonate buffering of lactic acid generated during exercise

The pattern of decrease in arterial bicarbonate concentration ([HCO3-]) during progressive incremental exercise was compared with that of the rise in arterial lactate ([La-]) to determine the degree of buffering of lactic acid by bicarbonate. A mathematical model was derived for the change in [HCO3-] beyond the lactate threshold. This was based on a log-log transformation of the data, a model previously found to provide a very good fit to the [La-]-O2 consumption (VO2) relationship. The results of the analysis of incremental exercise data from 10 subjects show that the decrease in [HCO3-] very nearly matches the increase in [La-]. However, it was found by comparing regression models that the correspondence between [HCO3-] and [La-] could be improved by assuming that the [HCO3-] decrease was delayed until the arterial lactate level had increased by approximately 0.4 meq/l. This result is compatible with the existence of buffering mechanisms in the cell which buffer the initial increase of lactic acid. Beyond this initial buffering, lactic acid appears to be buffered almost entirely by the bicarbonate buffer system.     

A Functional Polymorphism in a Serotonin Transporter Gene (5-HTTLPR) Interacts with 9/11 to Predict Gun-Carrying Behavior

On September 11, 2001, one of the deadliest terrorist attacks in US history took place on American soil and people around the world were impacted in myriad ways. Building on prior literature which suggests individuals are more likely to purchase a gun for self-protection if they are fearful of being victimized, the authors hypothesized that the terrorist attacks of 9/11 would lead to an increase in gun carrying among US residents. At the same time, a line of research has shown that a polymorphism in the 5-HTT gene (i.e., 5-HTTLPR) interacts with environmental stressors to predict a range of psychopathologies and behaviors. Thus, it was hypothesized that 9/11 and 5-HTTLPR would interact to predict gun carrying. The results supported both hypotheses by revealing a positive association between 9/11 and gun carrying (b = .426, odds ratio = 1.531, standard error for b = .194, z = 2.196, p = .028) in the full sample of respondents (n = 15,052) and a statistically significant interaction between 9/11 and 5-HTTLPR in the prediction of gun carrying (b = −1.519, odds ratio = .219, standard error for b = .703, z = −2.161, p = .031) in the genetic subsample of respondents (n = 2,350). This is one of the first studies to find an association between 9/11 and gun carrying and, more importantly, is the first study to report a gene-environment interaction (GxE) between a measured gene and a terrorist attack.     

The anti-inflammatory actions of tilorone hydrochloride.

Tilorone suppressed inflammation induced by immune (direct passive Arthus reaction) as well as by non-immune agents (carrageenam-induced paw edema and abscess formation), if the compound is given 24 hr prior to the proinflammatory agonists. The non-immune anti-inflammatory effect is independent of the adrenals. A surprising findings was that total serum hemolytic complement is markedly elevated 24 hr after a single dose of tilorone.     

Stranger with a Camera

Stranger with. Camera. 2000. 60 minutes, color. video by Elizabeth Barret For more information, contact Appalshop Film Studios, 91 Madison Avenue, Whitesburg, KY 41858.     

Ectomycorrhizas of <Emphasis Type="Italic">Coltricia</Emphasis> and <Emphasis Type="Italic">Coltriciella</Emphasis> (Hymenochaetales,Basidiomycota) on Caesalpiniaceae,Dipterocarpaceae and Myrtaceae in Seychelles

Ectomycorrhizal fungi, especially basidiomycetes, have repeatedly evolved from saprotrophic ancestors. Using rDNA internal transcribed spacer and large subunit sequences, we demonstrate that four species of Coltricia and Coltriciella form ectomycorrhiza with the native Vateriopsis seychellarum (Dipterocarpaceae) and Intsia bijuga (Caesalpiniaceae) as well as the introduced Eucalyptus robusta (Myrtaceae) in Seychelles. Coltricia and Coltriciella species share a thin, orange-brown to dark brown mantle and extremely thick, clampless hyphae. Phylogenetic analyses placed Coltriciella monophyletic within Coltricia. This study provides further evidence that fruiting habit on dead wood does not indicate saprotrophic lifestyle.     

Zooplankton response to extreme drought in a large subtropical lake

Plankton data from 1997 to 2005 were used to examine impacts of a managed draw-down, subsequent drought and resulting historic low water levels (during 2000 and 2001) on the zooplankton of Lake Okeechobee, Florida. Prior to the drought the lake supported less than 150 ha of submerged vegetation. Following the drought, over 15,000 ha of submerged vegetation developed around the lake shore and conditions favored greater survival of age 0 fish. The zooplankton changed significantly from the pre- to post-drought period, including: (a) a near-complete loss of all dominant species of cladocerans and rotifers; and (b) an abrupt transition to a community with over 80% of total biomass comprised of Arctodiaptomus dorsalis, a calanoid copepod previously described as being resistant to fish predation. These changes persisted over a 5 year post-drought sampling period. In contrast, there were no systematic changes in biomass of bacteria, phytoplankton, inedible cyanobacteria, algal cell size, suspended solids, or any other physical or chemical attributes known to affect zooplankton in shallow lakes. Evidence points towards increased predation by fish, and perhaps invertebrates, as factors responsible for loss of cladocerans and rotifers following the drought, and indicates a need for future research to link changes in water level to shifts in predation pressure in this and other shallow lakes. Handling editor: S.I. Dodson     

A microfilaria of exceptional size from the ixodid tick, Ixodes dammini, from Shelter Island, New York

Thirty or more microfilariae 0.70-1.32 mm in length were recovered from the hemocele of an unengorged adult tick, Ixodes dammini, that was collected from vegetation on Shelter Island, New York. Among approximately 500 I. dammini collected from the same area only 1 other was similarly infected. Outstanding features, in addition to size, were absence of a cephalic space and the presence of nuclei in 2 or 3 irregular rows extending to the end of a bluntly rounded tail. The microfilariae apparently were ingested in a blood meal that was taken when the ticks were larvae or nymphs, and had persisted alive without development.     

A new method for detecting anaerobic threshold by gas exchange

Excess CO2 is generated when lactate is increased during exercise because its [H+] is buffered primarily by HCO-3 (22 ml for each meq of lactic acid). We developed a method to detect the anaerobic threshold (AT), using computerized regression analysis of the slopes of the CO2 uptake (VCO2) vs. O2 uptake (VO2) plot, which detects the beginning of the excess CO2 output generated from the buffering of [H+], termed the V-slope method. From incremental exercise tests on 10 subjects, the point of excess CO2 output (AT) predicted closely the lactate and HCO-3 thresholds. The mean gas exchange AT was found to correspond to a small increment of lactate above the mathematically defined lactate threshold [0.50 +/- 0.34 (SD) meq/l] and not to differ significantly from the estimated HCO-3 threshold. The mean VO2 at AT computed by the V-slope analysis did not differ significantly from the mean value determined by a panel of six experienced reviewers using traditional visual methods, but the AT could be more reliably determined by the V-slope method. The respiratory compensation point, detected separately by examining the minute ventilation vs. VCO2 plot, was consistently higher than the AT (2.51 +/- 0.42 vs. 1.83 +/- 0.30 l/min of VO2). This method for determining the AT has significant advantages over others that depend on regular breathing pattern and respiratory chemosensitivity.     

Lakewide odours in Ontario and New Hampshire caused by Chrysochromulina breviturrita Nich. (Prymnesiophyceae)

At densities of 500–9 000 cells/ml, the planktonic alga Chrysochromulina breviturrita Nich. produced obnoxious lake-wide odours in five lakes between 1978 and 1980. In one case, CuSO₄ was used to kill the organism and control the odour, but in the other four lakes, the species persisted for 4–6 weeks before populations declined and odours disappeared. This is the first recorded instance of odour production by any member of the Prymnesiophyceae.