title: The decrease in mature myostatin protein in male skeletal muscle is developmentally regulated by growth hormone

authors: Oldham, Jenny M.

subjects: myostatin

abstract: Myostatin inhibits myogenesis and there is reduced abundance of the mature protein in skeletal muscles of adult male compared with female mice. This reduction probably occurs after translation, which suggests that it is a regulated mechanism to reduce the availability of myostatin in males. Reduced myostatin may, thereby, contribute to the development of sexually dimorphic growth of skeletal muscle. Our first objective was to determine if the decrease in mature myostatin protein occurs before the linear growth phase to aid growth, or afterwards to maintain the mass of adult muscle. Mice were killed from 2 to 32 weeks and the gastrocnemius muscle was excised. Myostatin mRNA increased from 2 to 32 weeks and was higher in males than females (P < 0.001). In contrast, mature protein decreased in males after 6 weeks (P < 0.001). Our second objective was to determine if growth hormone (GH) induces the decrease in mature myostatin protein. GH increased myostatin mRNA and decreased the abundance of mature protein in hypophysectomised mice (P < 0.05). Our final objective was to determine if the decrease in mature protein occurs in skeletal muscles of male Stat5b−/− mice (Stat5b mediates the actions of GH). As expected, mature myostatin protein was not reduced in Stat5b−/− males compared with females. However, myostatin mRNA remained higher in males than females irrespective of genotype. These data suggest that: (1) the decrease in mature myostatin protein is developmentally regulated, (2) GH acting via Stat5b regulates the abundance of mature myostatin and (3) GH acts via a non-Stat5b pathway to regulate myostatin mRNA.

text: The decrease in mature myostatin protein in male skeletal muscle is developmentally regulated by growth hormone Myostatin inhibits myogenesis and there is reduced abundance of the mature protein in skeletal muscles of adult male compared with female mice. This reduction probably occurs after translation, which suggests that it is a regulated mechanism to reduce the availability of myostatin in males. Reduced myostatin may, thereby, contribute to the development of sexually dimorphic growth of skeletal muscle. Our first objective was to determine if the decrease in mature myostatin protein occurs before the linear growth phase to aid growth, or afterwards to maintain the mass of adult muscle. Mice were killed from 2 to 32 weeks and the gastrocnemius muscle was excised. Myostatin mRNA increased from 2 to 32 weeks and was higher in males than females (P < 0.001). In contrast, mature protein decreased in males after 6 weeks (P < 0.001). Our second objective was to determine if growth hormone (GH) induces the decrease in mature myostatin protein. GH increased myostatin mRNA and decreased the abundance of mature protein in hypophysectomised mice (P < 0.05). Our final objective was to determine if the decrease in mature protein occurs in skeletal muscles of male Stat5b−/− mice (Stat5b mediates the actions of GH). As expected, mature myostatin protein was not reduced in Stat5b−/− males compared with females. However, myostatin mRNA remained higher in males than females irrespective of genotype. These data suggest that: (1) the decrease in mature myostatin protein is developmentally regulated, (2) GH acting via Stat5b regulates the abundance of mature myostatin and (3) GH acts via a non-Stat5b pathway to regulate myostatin mRNA.

year: 2009

title: Busting myths on water weeds

authors: de Winton, Mary

abstract: Troublesome aquatic weeds have been an issue for the Rotorua Te Arawa Lakes for decades, but what do we really know about what drives water weed problems? Some common held beliefs about water weeds are ‘one weed is as bad as another’, ‘waterfowl move water weeds around’ and ’nutrient enrichment drives weed invasion’. However, these assumptions are incorrect or represent an oversimplified view of the problem. Exploring these popular misconceptions on water weeds will help us get a better understanding of weed problems, the role of humans and what we can do about it. This talk will draw evidence from New Zealand and international research findings and
information specific to the Rotorua Te Arawa Lakes.
Weed issues for the Rotorua Te Arawa Lakes involve just a few species of alien plant species that share characteristics including a high ‘standing crop’ (bulk biomass present at any one time), dense canopy at, or close to the water surface and generation of numerous fragments that can accumulate onshore. Nevertheless, these few species can be further distinguished and ranked in terms of ‘weediness’ and impact. Recognition that some weeds are worse than others allows for more effective and proactive management of
weed threats.
Water fowl are often implicated in spreading the most problematic water weeds that we have in New Zealand and yet there little real evidence that this is the case. Instead there is ample evidence that human activities are primarily responsible for the spread of water weeds between lake catchments. This means that it should be possible to intercept the routes and mechanisms (pathways and vectors) by which these water weeds can enter lakes.
Weed invasions in freshwater systems are suggested to be linked with nutrient enrichment. However, the presence of our worst water weeds and the development of weed-related problems are not limited to eutrophied lakes, but can be equally problematic in oligotrophic New Zealand lakes. Indeed, the most enriched lake systems have very limited submerged vegetation development. Therefore improving water quality does not necessarily flow on to the anticipated improvements in weed problems and there may even be increased weed development as lakes become less enriched.

text: Busting myths on water weeds Troublesome aquatic weeds have been an issue for the Rotorua Te Arawa Lakes for decades, but what do we really know about what drives water weed problems? Some common held beliefs about water weeds are ‘one weed is as bad as another’, ‘waterfowl move water weeds around’ and ’nutrient enrichment drives weed invasion’. However, these assumptions are incorrect or represent an oversimplified view of the problem. Exploring these popular misconceptions on water weeds will help us get a better understanding of weed problems, the role of humans and what we can do about it. This talk will draw evidence from New Zealand and international research findings and
information specific to the Rotorua Te Arawa Lakes.
Weed issues for the Rotorua Te Arawa Lakes involve just a few species of alien plant species that share characteristics including a high ‘standing crop’ (bulk biomass present at any one time), dense canopy at, or close to the water surface and generation of numerous fragments that can accumulate onshore. Nevertheless, these few species can be further distinguished and ranked in terms of ‘weediness’ and impact. Recognition that some weeds are worse than others allows for more effective and proactive management of
weed threats.
Water fowl are often implicated in spreading the most problematic water weeds that we have in New Zealand and yet there little real evidence that this is the case. Instead there is ample evidence that human activities are primarily responsible for the spread of water weeds between lake catchments. This means that it should be possible to intercept the routes and mechanisms (pathways and vectors) by which these water weeds can enter lakes.
Weed invasions in freshwater systems are suggested to be linked with nutrient enrichment. However, the presence of our worst water weeds and the development of weed-related problems are not limited to eutrophied lakes, but can be equally problematic in oligotrophic New Zealand lakes. Indeed, the most enriched lake systems have very limited submerged vegetation development. Therefore improving water quality does not necessarily flow on to the anticipated improvements in weed problems and there may even be increased weed development as lakes become less enriched.

year: 2015

title: Recognising the negative impacts of aquatic weed management: Okawa Bay, Lake Rotoiti case study

authors: Scholes, Paul

abstract: The Te Arawa Rotorua Lakes Programme continues to implement measures to maintain and restore lake water quality in line with trophic level indices (TLI’s) for respective lakes. In Lakes Rotorua and Rotoiti this has also meant not only reducing nutrients to and in the lakes but also managing periodic cyano-bacterial (blue-green) algal blooms.
Restoration measures in the Rotorua and Rotoiti catchments have included land use management efforts to arrest nutrient inputs; diversion of Lake Rotorua waters from entering Rotoiti; sewage reticulation of lakeside communities; and treatment of inflows
with aluminium sulphate (alum). While restoration efforts have produced water quality gains in both lakes, in recent years, cyano-bacterial blooms have occurred in the shallow embayment of Lake Rotoiti, known as Okawa Bay.
These water quality gains have not come without a cost. Submerged aquatic weeds such as Hornwort are an increasing problem in the Rotorua Te Arawa Lakes and significant resources are needed to manage infestations primarily for aesthetic and recreational
amenity. Control of exotic aquatic weed is mostly with application of herbicide. Herbicide treatment leaves a decomposing biomass in the waterbody, potentially increasing the nutrient status.
We examine the impact aquatic weed decomposition has had on Okawa Bay’s nutrient status and the cyano-bacterial blooms over recent summers, and Bay of Plenty Regional Council’s response to reduce localised bloom development.

text: Recognising the negative impacts of aquatic weed management: Okawa Bay, Lake Rotoiti case study The Te Arawa Rotorua Lakes Programme continues to implement measures to maintain and restore lake water quality in line with trophic level indices (TLI’s) for respective lakes. In Lakes Rotorua and Rotoiti this has also meant not only reducing nutrients to and in the lakes but also managing periodic cyano-bacterial (blue-green) algal blooms.
Restoration measures in the Rotorua and Rotoiti catchments have included land use management efforts to arrest nutrient inputs; diversion of Lake Rotorua waters from entering Rotoiti; sewage reticulation of lakeside communities; and treatment of inflows
with aluminium sulphate (alum). While restoration efforts have produced water quality gains in both lakes, in recent years, cyano-bacterial blooms have occurred in the shallow embayment of Lake Rotoiti, known as Okawa Bay.
These water quality gains have not come without a cost. Submerged aquatic weeds such as Hornwort are an increasing problem in the Rotorua Te Arawa Lakes and significant resources are needed to manage infestations primarily for aesthetic and recreational
amenity. Control of exotic aquatic weed is mostly with application of herbicide. Herbicide treatment leaves a decomposing biomass in the waterbody, potentially increasing the nutrient status.
We examine the impact aquatic weed decomposition has had on Okawa Bay’s nutrient status and the cyano-bacterial blooms over recent summers, and Bay of Plenty Regional Council’s response to reduce localised bloom development.

year: 2015