Cell interactions in skin

1. The literature concerning the growth and differentiation of skin cells is reviewed. The interaction between the dermis and epidermis of postembryonic skin is compared with other forms of mesodermal-epithelial interaction, and the possible involvement of gap junction-mediated transfer of molecules between the two tissue layers is discussed. 2. Cultures of epidermal keratinocytes and dermal fibroblasts were established from newborn mouse skin and adult guinea pig ear skin. The ability of these cells to form gap junctions with one another in vitro was examined by auto- radiographic analysis of 3H-uridine nucleotide transfer between prelabelled donor cells and unlabelled recipient cells. 3. A novel statistical approach was used to analyse the transfer of radiolabelled molecules between cells in culture. Comparison of the autoradiographic grain counts of recipient cells in contact with prelabelled donor cells and recipient cells not in contact with donor cells was used to generate a probability value which was used as a measure of cell-cell communication. 4. This method was used to demonstrate gap junction formation between epidermal keratinocytes and dermal fibroblasts in culture. 5. Junction formation between skin cells is in contradiction to published proposals of epithelial-fibroblastic specificity To determine whether this is an unusual situation, two other mouse primary cell types, epidermal melanocytes and renal epithelial cells, and cells of several established cell lines, were examined for gap junction formation in vitro. It was shown that epidermal keratinocytes, dermal fibroblasts renal epithelial cells and epidermal melanocytes communicate non-specifically with cells of the fibroblast line C13 and the epithelial cell line BRL. However, cells of the canine kidney epithelial line MDCK form gap junctions with one another but do not communicate with cells of the junction-competent C13 and BRL lines. From these results it was proposed that specificity in cell communication may be a more general property of established cell lines. 6. The epidermal structural protein prekeratin was used as a biochemical marker for epidermal cell differentiation in culture. Prekeratin from newborn mouse skin was purified by citrate buffer extraction, and shown to consist of polypeptide chains of 61,000MW and 69,000MW in a 2:1 stoichiometry. 7. A further method for the study of keratinocyte differentiation in vitro was developed, based on the relative uptake of the amino acids histidine and leucine. Using these techniques it was demonstrated that epidermal keratinocytes undergo only limited differentiation in dispersed cell culture. 8. The dermal-epidermal interaction was also studied using a transfilter organ culture system. Direct contact between dermis and epidermis was shown to result in stimulation of epidermal protein synthesis. This stimulation does not occur when the two tissues are separated by porous filters with a mean particle retention size of 0. 8um. However, no de novo prekeratin synthesis was detected by labelling of skin organ cultures with 35S-methionine and 3H-leucine. 9. The implications of these observations for the normal growth and differentiation of skin in vivo are discussed

Searching speeds and the energetic feasibility of an obligate whale-scavenging fish

Two recently published models reach opposite conclusions on the energetic feasibility of a scavenging fish that specialises oil whale carcasses. We argue that the key difference between these models lies in their estimate of the likely searching speed of such a hypothetical scavenger. Neither of the previous models considers that although faster searching will allow food sites to be found more quickly, it will also reduce the time between meals that the fish can survive on its reserves. Hence, we present a novel model that encapsulates this trade-off, and use this model to predict the optimal searching speed for Such a hypothetical scavenger. The model predicts that the optimal speed should increase with mass and be in the range 0.1-0.2 m s(-1) for fish of the range of sizes found for the ubiquitous grenadier Coryphaenoides armatus. These values accord with most estimates of the swimming speeds for this species. Hence, we conclude that rejection of a whale-carcass feeding specialist fish on energetic grounds is premature. Although, we see no reason to dismiss Such a specialist oil energetic grounds, we argue that such a fish will be unlikely oil ecological grounds, although a deep-sea fish that gathered much of its energy from scavenging at relatively large food packages oil the ocean floor should be feasible

Disubstituted cobalt (III) triethylenetetramine complexes : their stereochemistry and kinetics of aquation

[xiv, 229 l.] : illusWhereas some work has been done on triethylenetetramine (trien) complexes by relating magnetism (1,2,3,10) and spectra (4,5,6,7) to stereochemistry in the solid state, little is known about the precise configurations of the few compounds isolated, Even less structural information on complexes obtained only in solution has been provided by studies of complex formation by carious methods (1,2,11,21,23,26) and measurements of formation constants (20,21,22,24). (First paragraph of chapter one.

Generic Utilization Rates, Real Pharmaceutical Prices, and Research and Development Expenditures

Generic utilization rates have risen substantially since the enactment of The Drug Price Competition and Patent Term Restoration Act (Hatch-Waxman) in 1984. In the year Hatch-Waxman was enacted, generic utilization rates were 19 percent; in contrast, today, the generic utilization rate is approximately 70 percent. Striking a balance between access to existing medicines and access to yet-to-be-discovered (and developed) drugs, through research incentives, was the principal objective of this landmark legislation. However, given the current rate of generic utilization, it seems plausible, if not likely, that any balance achieved by the 1984 Act has since shifted away from research incentives and towards improved access, ceteris paribus. Among other factors, recent mandatory substitution laws in most states have driven up generic utilization rates. In the current paper, we employ semi-annual data from 1992 to 2008 to examine the link between generic utilization rates and real U.S. prescription drug prices. This link is important because previous research has identified a causal relationship between real drug prices in the U.S. and industry-level R&D investment intensity. We identify a statistically significant, positive relationship between generic utilization rates in the U.S. and real U.S. prescription drug prices. Specifically, we estimate an elasticity of real drug prices to generic utilization rates of -0.15. This finding, when coupled with previous empirical work on the determinants of pharmaceutical R&D intensity, suggests an elasticity of R&D to generic utilization rates of about 0.090. While the magnitude of this elasticity is modest, as theory would predict—the effect of greater generic erosion of brand sales at patent expiration is heavily discounted due to the long time horizon to generic erosion when an R&D project is in clinical development. However, because there has been a very substantial increase in generic utilization rates since 1984, the impact on R&D is nevertheless quite large. We explore this and other issues in the current paper.

An electromyographic assessment pilot study on the reliability of the forearm muscles during multi-planar maximum voluntary contraction grip and wrist articulation in young males

BACKGROUND: Electromyographic systems are widely used in scientific and clinical practice. The reproducibility and reliability of these measures are crucial when conducting scientific research and collecting experimental data.OBJECTIVE: To test the reliability of surface electromyography signals from both the Flexor Digitorum Superficialis (FDS) and Extensor Carpi Radialis Brevis (ECRB) muscles of both the left and right arms during an individual, static multi-planar maximum voluntary contraction handgrip task using the Myon 320 system (Myon AG, Switzerland).METHODS: Eight right-handed male participants performed two maximal handgrip tests in five separate wrist positions using both hands. Muscle activity was recorded from both forearms. Reliability was measured using the Standard Error of Measurement (SEM), Coefficient of Variation (CV)and Intra-class correlation coefficients. Wrist joint position correlations within and between theFDS and ECRB muscle activities were also analysed.RESULTS: Absolute reliability was shown across all positions for both hands with CV and SEM recorded at below 10%. The output measures indicate that the Myon 320 system (Myon AG, Switzerland) produces good to fair reliability when assessing forearm muscle activity. Correlations in the left FDS muscles were negative. Correlations between the left ECRB and left FDS muscles were variable but positive between the right ECRB and right FDS muscles.CONCLUSIONS: The data sets retrieved from all participants were reliably evaluated. Wrist position correlations within and between the FDS and ECRB muscles may have been influenced by hand dominance. The findings demonstrate that the methods and systems outlined in this study can be used reliably in future research

An evaluation of temporal and club angle parameters during golf swings using low cost video analyses packages

The purpose of this study was to compare swing time and golf club angle parameters during golf swings using three, two dimensional (2D) low cost, Augmented-Video-based-Portable-Systems (AVPS) (Kinovea, SiliconCoach Pro, SiliconCoach Live). Twelve right-handed golfers performed three golf swings whilst being recorded by a high-speed 2D video camera. Footage was then analysed using AVPS-software and the results compared using both descriptive and inferential statistics. There were no significant differences for swing time and the golf phase measurements between the 2D and 3D software comparisons. In general, the results showed a high Intra class Correlation Coefficient (ICC > 0.929) and Cronbach’s Coefficient Alpha (CCA > 0.924) reliability for both the kinematic and temporal parameters. The inter-rater reliability test for the swing time and kinematic golf phase measurements on average were strong. Irrespective of the AVPS software investigated, the cost effective AVPS can produce reliable output measures that benefit golf analyses