The Energy Expenditure of Stair Climbing One Step and Two Steps at a Time: Estimations from Measures of Heart Rate

Stairway climbing provides a ubiquitous and inconspicuous method of burning calories. While typically two strategies are employed for climbing stairs, climbing one stair step per stride or two steps per stride, research to date has not clarified if there are any differences in energy expenditure between them. Fourteen participants took part in two stair climbing trials whereby measures of heart rate were used to estimate energy expenditure during stairway ascent at speeds chosen by the participants. The relationship between rate of oxygen consumption () and heart rate was calibrated for each participant using an inclined treadmill. The trials involved climbing up and down a 14.05 m high stairway, either ascending one step per stride or ascending two stair steps per stride. Single-step climbing used 8.5±0.1 kcal min⁻¹, whereas double step climbing used 9.2±0.1 kcal min⁻¹. These estimations are similar to equivalent measures in all previous studies, which have all directly measured The present study findings indicate that (1) treadmill-calibrated heart rate recordings can be used as a valid alternative to respirometry to ascertain rate of energy expenditure during stair climbing; (2) two step climbing invokes a higher rate of energy expenditure; however, one step climbing is energetically more expensive in total over the entirety of a stairway. Therefore to expend the maximum number of calories when climbing a set of stairs the single-step strategy is better.     

Effects of wheat germ agglutinin on tunicate egg activation and fertilization: Is there a plasma membrane sperm receptor system on Ascidia ceratodes eggs?

Little work has been carried out on the sperm recognition systems present on the egg plasma membrane. Here it is shown that wheat germ agglutinin (WGA) interferes with the sperm-interacting system on the plasma membrane of eggs of the ascidian, Ascidia ceratodes. The WGA activates the dechorionated egg, indicating that a plasma membrane sugar residue can be directly tied to egg activation. Low concentrations of this lectin do not activate the eggs, but reduce fertilizability. This observation suggests that the WGA binding site might be part of a sperm reception–activation complex in the plasma membrane. While WGA also affects sperm binding to the chorion, the mechanisms of sperm interaction at the plasma membrane and chorion show different sensitivities to lectins, sugars and enzymes.     

Genetic analysis of human B cell hybridomas expressing a cross-reactive idiotype

We have examined the genetic basis for the expression of a human cross-reactive idiotype (CRI) commonly found on monoclonal IgM rheumatoid factors. The CRI was identified with a monoclonal antibody (17.109) and has been localized previously to the kappa-variable region. By using the human lymphoblastoid cell line WI-L2-729-HF2, and mononuclear cells from several sources, a panel of hybridomas was generated that produced 17.109 CRI-positive Ig. A recently cloned human germ-line V kappa III gene, Humkv305, served as a probe to identify genes which were rearranged and expressed in 17.109 CRI-positive and -negative hybridomas. This probe, when hybridized to human genomic DNA under stringent conditions, identified only two to five germ-line bands. In 10 separate 17.109 CRI-positive hybridoma clones, an additional rearranged V kappa band was identified. The probe did not anneal to rearranged V kappa bands in hybridoma clones that produced kappa-chains lacking the CRI. RNA dot-blot studies provided evidence for expression of genes hybridizing to the Humkv305 probe. The results indicate that the 17.109 CRI is a serologic marker for a single V kappa gene, or a small family of closely related V kappa genes, which is identified by the Humkv305 probe.     

Beta 2 (Oriental) human liver alcohol dehydrogenases do not exhibit subunit interaction: oxidation of cyclohexanol by homo- and heterodimers

The steady-state kinetics of isozymes of human liver alcohol dehydrogenase (ADH) containing the beta 2 (Oriental) subunit were investigated in order to confirm the supposition [Fong, W.P., & Keung, W. M. (1987) Biochemistry (preceding paper in this issue)] that the subunits of such heterodimeric ADHs act independently and noncooperatively. The ADH isozymes alpha beta 2, beta 2 beta 2, beta 2 gamma 1, and beta 2 gamma 2 as well as gamma 1 gamma 1 were purified by chromatography on DEAE-cellulose, 4-[3-[N-(6-aminocaproyl)amino]propyl]pyrazole--Sepharose, and CM-cellulose. Their kinetics were studied at pH 9.0 with cyclohexanol since this substrate permits maximal differentiation between activities of the heterodimeric subunits. Oxidation of cyclohexanol by the homodimers beta 2 beta 2 and gamma 1 gamma 1 follows conventional Michaelis-Menten kinetics. The values of Km and kcat determined for beta 2 beta 2 and gamma 1 gamma 1 are 0.11 M and 260 min-1 and 79 microM and 45 min-1, respectively, indicating that beta 2 beta 2, like the previously studied beta 1 beta 1, has an unusually low binding affinity for cyclohexanol compared to that of the ADH isozymes formed by the combination of alpha, gamma 1, and gamma 2 chains. Cyclohexanol oxidation by the heterodimers alpha beta 2, beta 2 gamma 1, and beta 2 gamma 2 follows biphasic kinetics which can be fully accounted for by the individual subunits, one exhibiting a high and the other a low substrate-binding affinity. Eadie-Hofstee plots resolve the biphasic kinetics into two linear components, each of which yields a set of kinetic parameters.(ABSTRACT TRUNCATED AT 250 WORDS)