Stretch Activated Channels in Proprioceptive Organs of Crab and Crayfish Are Sensitive to Gadolinium but not Amiloride, Ruthenium Red or Low pH

The type of stretch activated receptors (SARs) in the chordotonal organs in the crab walking leg and of the muscle receptor organ (MRO) in the crayfish abdomen have not yet been classified as to their molecular or pharmacological profile. The purpose of this study is to examine the pharmacological profile of SARs in the proprioceptive neurons in the crab and crayfish models. Since many SARs share the pharmacological profile of displaying low pH or being proton sensitive (i.e. being more active) or blocked by the diuretic amiloride or ruthenium red as well as being blocked by the broad stretch activated channel blocker gadolinium (Gd3+), we used these agents to screen the receptors. Various displacement rates as well as static positions that activate the stretch activated receptors were used in examining their pharmacological profiles. Hour-long exposure to low pH decreased neural activity of the chordotonal organ of the crab more so than to amiloride or ruthenium red. The crayfish MRO did not show pH sensitivity or sensitivity to amiloride or ruthenium red. Gd3+ rapidly blocked neural activity in both the crab and crayfish. It appears these stretch activated receptors may not have a classification that is suited to the standard pharmacological profiles. The molecular makeup of the channels also awaits characterization. This could reveal a novel SAR subtype. Our neurophysiology course1 took this project on as a course-based undergraduate research experience (CURE) to address an authentic research question

The Effect of CO\u3csub\u3e2\u3c/sub\u3e, Intracellular pH and Extracellular pH on Mechanosensory Proprioceptor Responses in Crayfish and Crab

Proprioceptive neurons monitor the movements of limbs and joints to transduce the movements into electrical signals. These neurons function similarly in species from arthropods to humans. These neurons can be compromised in disease states and in adverse environmental conditions such as with changes in external and internal pH. We used two model preparations (the crayfish muscle receptor organ and a chordotonal organ in the limb of a crab) to characterize the responses of these proprioceptors to external and internal pH changes as well as raised CO2. The results demonstrate the proprioceptive organs are not highly sensitive to changes in extracellular pH, when reduced to 5.0 from 7.4. However, if intracellular pH is decreased by exposure to propionic acid or saline containing CO2, there is a rapid decrease in firing rate in response to joint movements. The responses recover quickly upon reintroduction of normal pH (7.4) or saline not tainted with CO2. These basic understandings may help to address the mechanistic properties of mechanosensitive receptors in other organisms, such as muscle spindles in skeletal muscles of mammals and tactile as well as pressure (i.e., blood pressure) sensory receptors

“We Live in a Very Toxic World”: Changing Environmental Landscapes and Indigenous Food Sovereignty

The purpose of this article is to understand how historical oppression has undermined health through environmental injustices that have given rise to food insecurity. Specifically, the article examines ways in which settler colonialism has transformed and contaminated the land itself, impacting the availability and quality of food and the overall health of Indigenous peoples. Food security and environmental justice for Gulf Coast, state-recognized tribes has been infrequently explored. These tribes lack federal recognition and have limited access to recourse and supplemental resources as a result. This research fills an important gap in the literature through exploring the intersection of environmental justice and food insecurity issues for this population. Partnering with a community-advisory board and using a qualitative descriptive methodology, 31 Gulf Coast Indigenous women participated in semi-structured interviews about their healthcare experiences and concerns. Through these interviews, participants expressed concerns about (a) the environmental impacts of pollution on the contamination of food and on the health of tribal members; and (b) the impact of these changes on the land, such as negatively impacting gardening practices. The authors of this study document how environmental changes have compounded these concerns and contribute to the overall pollution of food and water sources and unviability of subsistence practices, severely effecting tribal members’ health. In conclusion, we show how social and environmental justice issues such as pollution, industry exploitation, and climate change perpetuate the goals of settler colonialism through undermining cultural practices and the overall health of Indigenous peoples