The effects of activin on pituitary FSH biosynthesis have been previously characterized using primary rat pituitary cultures; however, little is known of the effects of activin on FSH biosynthesis and secretion in human pituitary tissue. Production of intact glycoprotein hormones and free subunits is increasingly recognized in pituitary tumors; however, the regulation of gonadotropins in such tumors has not been addressed. We have investigated the effects of human recombinant activin on glycoprotein hormone biosynthesis and secretion in primary cultures of 12 human glycoprotein hormone-producing pituitary adenomas and compared this with the effects of activin in normal rat anterior pituitary cells. In 33% of the human pituitary tumors studied, significant (P less than 0.05) increases in FSH beta secretion occurred in response to incubation with 20 ng/mL activin for 24 h (19-287% stimulation), without changes in the production of intact FSH. A Northern analysis performed on cells derived from one tumor indicated that FSH beta mRNA levels increased 350% after activin treatments; however, FSH secretion did not parallel the mRNA changes. None of the human glycoprotein hormone-producing tumors significantly increased FSH secretion in response to activin. To validate the biological activity of recombinant human activin-A and to confirm time and dose conditions for the human tumor cultures, we also examined its ability to stimulate FSH production in rat pituitary cultures. Activin (20 ng/mL) added to the culture medium significantly increased FSH secretion and steady state levels of FSH beta mRNA after 24 h. These data indicate that some glycoprotein hormone-producing pituitary tumors treated with purified activin have discordant responses of intact gonadotropins and free subunit responses. In contrast to responses in normal rat gonadotrophs, FSH beta biosynthetic pathways may be uncoupled from intact FSH secretion in a subset of glycoprotein hormone-producing pituitary adenomas.
Climate change and other global change drivers threaten plant diversity
in mountains worldwide. A widely documented response to such
environmental modifications is for plant species to change their
elevational ranges. Range shifts are often idiosyncratic and difficult
to generalize, partly due to variation in sampling methods. There is
thus a need for a standardized monitoring strategy that can be applied
across mountain regions to assess distribution changes and community
turnover of native and non-native plant species over space and time.
Here, we present a conceptually intuitive and standardized protocol
developed by the Mountain Invasion Research Network (MIREN) to
systematically quantify global patterns of native and non-native species
distributions along elevation gradients and shifts arising from
interactive effects of climate change and human disturbance. Usually
repeated every five years, surveys consist of 20 sample sites located at
equal elevation increments along three replicate roads per sampling
region. At each site, three plots extend from the side of a mountain
road into surrounding natural vegetation. The protocol has been
successfully used in 18 regions worldwide from 2007 to present. Analyses
of one point in time already generated some salient results, and
revealed region-specific elevational patterns of native plant species
richness, but a globally consistent elevational decline in non-native
species richness. Non-native plants were also more abundant directly
adjacent to road edges, suggesting that disturbed roadsides serve as a
vector for invasions into mountains. From the upcoming analyses of time
series even more exciting results especially about range shifts can be
expected. Implementing the protocol in more mountain regions globally
would help to generate a more complete picture of how global change
alters species distributions. This would inform conservation policy in
mountain ecosystems, where some conservation policies remain poorly
implemented.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.