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.     

Immunochemical and amino-terminal sequence comparison of two cytoadhesins indicates they contain similar or identical beta subunits and distinct alpha subunits

Platelet membrane glycoprotein (GP) IIb-IIIa is functionally and antigenically related to proteins present on many cell types, suggesting that it is a member of the proposed cytoadhesin family of membrane proteins. We have compared the purified tissue vitronectin receptor (VnR) with GP IIb-IIIa. Anti-VnR immunoprecipitated GP IIb-IIIa and a related endothelial cell protein. In immunoblots, GP IIIa reacted with anti-VnR and the beta subunit of the VnR reacted with poly and monoclonal anti-GP IIIa. In contrast, the alpha subunit of the VnR failed to react either with a polyclonal anti-GP IIb or with monoclonal anti-GP IIb. Furthermore, the amino-terminal sequence of GP IIIa and the beta subunit of VnR were identical at determined residues while the alpha subunit and the GP IIb were different, but showed 33% identity. These data indicate the identity or close homology of GP IIIa and the beta subunit of the VnR. In contrast, the alpha subunit and GP IIb are distinct polypeptides which may be homologous. Since GP IIb-IIIa and the VnR differ in ligand recognition specificity, the data also suggest that this specificity may be governed by the alpha subunit of cytoadhesins.     

Ultrastructure of the tube foot sensory-secretory complex in Ophiocomina nigra (Echinodermata,Ophiuridea)

Summary The ultrastructure of the epidermal layer of both the oral and arm podia of the brittle star Ophiocomina nigra is described. Despite external differences, little variation occurs in their internal structure. The podial epidermis, which is overlain by a three-layered cuticle, consists of five cell types: support, mucous, sensory, adhesive secretory and monociliated neurosecretory-like cells. Areas of specialisation are superimposed on this basic plan. These comprise four cells forming cohesive units, made up of two adhesive secretory, one sensory and one monociliated neurosecretory-like cells. The two adhesive secretory cells may be identical or vary in the structure of their secretory packets. The sensory cells are of the normal type bearing a short cilium with a 9+2 microtubular arrangement. The monociliated neurosecretory-like cells contain many small dense vesicles and a short sub-cuticular cilium of irregular microtubular structure. Together, they appear to form a sensory-secretory complex which functions in adhesion both for feeding and locomotion. A system in which the secretion of the monociliated neurosecretory-like cell may control adhesive secretion is proposed.