Keratinocyte growth-promoting activity from human placenta

Extracts of term human placenta were tested for enhancement of proliferative growth of primary cultures of human keratinocytes. Saline extracts or supernatants from homogenates were dialyzed extensively, lyophilized, and tested in subcultures of keratinocytes in MCDB 153 medium with 0.1 mM Ca++ containing only defined supplements (insulin, hydrocortisone, transferrin, ethanolamine, phosphoethanolamine). Cells plated in the absence of EGF at moderately high densities (1000-3000 cells per cm2) formed colonies and grew in the presence of placental extract at 25-500 micrograms/ml. Extracts of cord serum or maternal serum were inactive, suggesting that the activity is derived from placental tissue. The activity is not EGF, since the activity in the placental extract, unlike EGF, did not promote growth at low cell density, was synergistic with EGF under some conditions, and did not produce changes in colonial morphology which occurred in the presence of EGF. Unlike keratinocyte growth-promoting activity in bovine hypothalamic extract, the activity is non-dialyzable and is destroyed at 100 degrees C. Placental extract could not replace any of the defined components of the medium and is therefore distinct from them. The presence of activity in the placenta with distinctive properties suggests that this is a previously undescribed material with growth-promoting properties for epithelium.     

Estimation of population parameters and their application to the development of fishery management models in two African rivers

The dynamics of fish populations in two African rivers are being investigated with a view to developing fishery management models for tropical non-floodplain rivers. Preliminary work was carried out in the Rufiji River, East Africa, to establish growth and mortality rates along with L _∞ and K for six species in a river where fishing mortality is zero. These parameters, derived from scale-reading and length frequency analysis, also allowed the development of phased management plans for the fishery resulting from impoundment.
A subsequent investigation has begun on a West African river, the Taia in Sierra Leone, to pursue observations over four seasons, two of which are now complete. A systematic daily sampling programme is being carried out of the whole community, to accumulate similar but more extensive data to those obtained previously. In the Taia, however, fishing mortality must also be estimated from catch surveys, and analysis is carried out using the recently developed ELEFAN programs which can be compared with results obtained by other methods such as scale-reading.     

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.