Lipolysis in Adipocytes Isolated from Deep and Superficial Subcutaneous Adipose Tissue

Objective: Abdominal subcutaneous adipose tissue (SAT) occurs in two depots separated by a fascial plane: deep SAT and superficial SAT. In a recent study it was demonstrated that the amount of deep SAT has a much stronger relationship to insulin resistance than does superficial SAT. Because insulin resistance may be related to fatty acid release from adipose tissue, we hypothesized that the two SAT depots may have a different lipolytic activity. Research Methods and Procedures: To test this hypothesis, we obtained samples of deep and superficial SAT from patients undergoing elective abdominal surgery. The rate of lipolysis was determined in the collagenase‐digested adipocytes obtained from the two fat depots by measuring glycerol release in the presence and absence of isoproterenol. In addition, the relative concentration of hormone‐sensitive lipase was determined in both SAT depots by Western blot analysis. Results: Our results showed that the rate of isoproterenol‐stimulated lipolysis was ～20% higher in cells from deep SAT compared with those from superficial SAT, indicating that the deep SAT is more lipolytically active. The concentration of hormone‐sensitive lipase did not differ between the two adipose tissue depots. Discussion: These findings suggest that the higher lipolytic activity of deep SAT may account for its stronger association with insulin resistance. The mechanism seems to be independent of differences in hormone‐sensitive lipase concentration.     

Human neuromuscular fatigue is associated with altered Na+-K+-ATPase activity following isometric exercise.

The purpose of this study was to investigate the hypothesis that reductions in Na+-K+- ATPase activity are associated with neuromuscular fatigue following isometric exercise. In control (Con) and exercised (Ex) legs, force and electromyogram were measured in 14 volunteers [age, 23.4 +/- 0.7 (SE) yr] before and immediately after (PST0), 1 h after (PST1), and 4 h after (PST4) isometric, single-leg extension exercise at ~60% of maximal voluntary contraction for 30 min using a 0.5 duty cycle (5-s contraction, 5-s rest). Tissue was obtained from vastus lateralis muscle before exercise in Con and after exercise in both the Con (PST0) and Ex legs (PST0, PST1, PST4), for the measurements of Na+-K+-ATPase activity, as determined by the 3-O-methylfluorescein phosphatase (3-O-MFPase) assay. Voluntary (maximal voluntary contraction) and elicited (10, 20, 50, 100 Hz) force was reduced 30-55% (P < 0.05) at PST0 and did not recover by PST4. Muscle action potential (M-wave) amplitude and area (measured in the vastus medialis) and 3-O-MFPase activity at PST0-Ex were less than that at PST0-Con (P < 0.05) by 37, 25, and 38%, respectively. M-wave area at PST1-Ex was also less than that at PST1-Con (P < 0.05). Changes in 3-O-MFPase activity correlated to changes in M-wave area across all time points (r = 0.38, P < 0.05, n = 45). These results demonstrate that Na+-K+- ATPase activity is reduced by sustained isometric exercise in humans from that in a matched Con leg and that this reduction in Na+-K+-ATPase activity is associated with loss of excitability as indicated by M-wave alterations.     

cost-effective method of preparing larval fish otoliths for reading using enzyme digestion and staining

A fast and cost-effective method for examining otoliths in fish larvae was developed whereby the otolith remains in situ . Whole fish of the clownfish Amphiprion melanopus were enzymecleared using a laundry pre-soak and then stained using the Von Kossa silver staining method for calcium. The otolith nucleus, daily rings and the otolith edge were all clearly visible and were suitable for a variety of age and growth analyses. The total 'hands on' time required to process these otoliths was c . 3 min, and multiple samples could be processed simultaneously. The reduction in labour of this method to produce clear daily rings in the otolith lends itself to broad use in fish biology where large quantities of otoliths need to be examined in a cost- and time-efficient manner.     

The photobiont determines the pattern of photosynthetic activity within a single lichen thallus containing cyanobacterial and green algal sectors (photosymbiodeme)

Photosystem activity status of the green algal (Pseudocyphellaria lividofusca) and cyanobacterial (P. knightii) components of a photosymbiodeme were continuously monitored in the field over a period of 35 days. The photosymbiodeme grew on a Nothofagus menziesii tree at Lake Waikaremoana, Urewera National Park, North Island, New Zealand. Two Mini-PAM fluorometers were placed so that the chlorophyll a fluorescence, temperature and PPFD (photosynthetically active photon flux density) could be recorded every 30 min for green algal and cyanobacterial parts of the thallus. Microclimate conditions were also recorded with a datalogger. The study confirmed the already known ability of green algal lichens to reactivate from high humidity alone whilst cyanobacterial species need liquid water, here obtained from rainfall. The photosystems of P. lividofusca were activated on every day and positive ETR (relative electron transport rate) occurred on all but 3 days. Activation level depended on the overnight relative humidity. P. knightii was activated and had positive ETR on only 13 days when rainfall had occurred. Both species were mostly inactive above 12°C but differed at low temperatures. P. knightii showed no activation at very low temperatures, -2 to 0°C, since these only occurred on clear, rain-free nights. PPFD was always very low, mostly below 80 µmol m^-2 s^-1, and both species were inactive at higher PPFD. The three-dimensional structure of the thallus seemed to contribute to the hydration. The cyanobacterial sectors were more appressed to the trunk and needed substantial rainfall to rewet whereas the green algal lobes were more distant from the trunk and this probably caused more rapid desiccation as well as lower temperatures. It is suggested that the longer active periods for photosynthesis by P. lividofusca are balanced by several factors: first, depressed net photosynthesis at high thallus water contents after rainfall, a feature not shown by P. knightii; second, possible lower maximal net photosynthetic rates; and third, the possibility of greater respiratory rates when thalli have been hydrated by high relative humidity. There is little evidence for high PPFD differently affecting the photosymbiodeme components since sustained, high PPFD did not occur. It has been reported that the photosystems of cyanobacterial species from photosymbiodemes can reactivate at high relative humidity but the results obtained here suggest that it is not ecologically significant.     

In vitro propagation of Spilanthes mauritiana DC., an endangered medicinal herb, through axillary bud cultures

Summary Spilanthes mauritiana DC., (Compositae), a East African medicinal herb containing pharmaceutically promising secondary metabolites, has successfully been raised in vitro. We have developed a clonal propagation protocol that uses juvenile plants as starting material. The addition of benzylaminopurine (BA) (1.0 μM) and naphthaleneacetic acid (NAA) (0.1 μM) to the culture medium resulted in maximum shooting response with minimal callusing. Shoots rooted best in vitro in MS medium supplemented with indole-3-acetic acid (IAA; 0.2 μM), and plants that had already developed roots showed better growth, with maximum survival rate, in the greenhouse after an initial hardening.     

When repair meets chromatin: First in series on chromatin dynamics

In eukaryotic cells, the inheritance of both the DNA sequence and its organization into chromatin is critical to maintain genome stability. This maintenance is challenged by DNA damage. To fully understand how the cell can tolerate genotoxic stress, it is necessary to integrate knowledge of the nature of DNA damage, its detection and its repair within the chromatin environment of a eukaryotic nucleus. The multiplicity of the DNA damage and repair processes, as well as the complex nature of chromatin, have made this issue difficult to tackle. Recent progress in each of these areas enables us to address, both at a molecular and a cellular level, the importance of inter-relationships between them. In this review we revisit the ‘access, repair, restore’ model, which was proposed to explain how the conserved process of nucleotide excision repair operates within chromatin. Recent studies have identified factors potentially involved in this process and permit refinement of the basic model. Drawing on this model, the chromatin alterations likely to be required during other processes of DNA damage repair, particularly double-strand break repair, are discussed and recently identified candidates that might perform such alterations are highlighted.