What do we mean when we talk about "structure/function" relationships?

To disrupt the traditional compartmentalized learning of nutrition functions, a proposition for integrative teaching at undergraduate level

Rather than an anatomy-centered study of the nutrition functions of the body (circulation, respiration, food digestion, and intestinal absorption of nutrients) as found in undergraduate physiology textbooks, a more integrative, mechanistic approach to teaching human physiology at the undergraduate level in science faculties is presented. Starting from the cell's needs for nutrients and oxygen, this proposal highlights the way in which each organ or apparatus ensures cell function. Then the fundamental physiological concepts of structure-function relationships and matter gradients can be constructed by considering the physicochemical mechanisms involved. The diversity of devices found in circulatory, ventilatory, and digestive systems is then examined through the prism of the mechanisms used to maintain gradients in nutrient concentration or gas partial pressure through exchange surfaces. Finally, the systems controlling nutrition functions are studied in fluctuating physiological contexts, such as during physical exercise or fasting. The presented pedagogical approach emphasizes the integration of functions on an organism-wide scale and focuses teaching on basic mechanisms rather than on the description of structures, while ensuring the transferability of physiological concepts. This pedagogical approach seems particularly relevant for the training of undergraduate students intending to teach biology in secondary education.NEW & NOTEWORTHY A proposal for teaching of human physiology at the undergraduate level in a science faculty outlines a pedagogical progression centered on cellular requirements for nutrients and oxygen. Rather than being taught independently, the three nutrition functions, circulation, respiration, and digestion, are interrelated and functional similarities are highlighted. The core concepts of physiology are thus more integrated at the organism level, with an emphasis on common mechanisms rather than specific structures.

Endocrine gland size is proportional to its target tissue size

Endocrine glands secrete hormones into the circulation to target distant tissues and regulate their functions. The qualitative relationship between hormone-secreting organs and their target tissues is well established, but a quantitative approach is currently limited. Quantification is important, as it could allow us to study the endocrine system using engineering concepts of optimality and tradeoffs. In this study, we collected literature data on 24 human hormones secreted from dedicated endocrine cells. We find that the number of endocrine cells secreting a hormone is proportional to the number of its target cells. A single endocrine cell serves approximately 2,000 target cells, a relationship that spans 6 orders of magnitude of cell numbers. This suggests an economic principle of cells working near their maximal capacity, and glands that are no bigger than they need to be.

Automated 3D cytoplasm segmentation in soft X-ray tomography

Cells' structure is key to understanding cellular function, diagnostics, and therapy development. Soft X-ray tomography (SXT) is a unique tool to image cellular structure without fixation or labeling at high spatial resolution and throughput. Fast acquisition times increase demand for accelerated image analysis, like segmentation. Currently, segmenting cellular structures is done manually and is a major bottleneck in the SXT data analysis. This paper introduces ACSeg, an automated 3D cytoplasm segmentation model. ACSeg is generated using semi-automated labels and 3D U-Net and is trained on 43 SXT tomograms of immune T cells, rapidly converging to high-accuracy segmentation, therefore reducing time and labor. Furthermore, adding only 6 SXT tomograms of other cell types diversifies the model, showing potential for optimal experimental design. ACSeg successfully segmented unseen tomograms and is published on Biomedisa, enabling high-throughput analysis of cell volume and structure of cytoplasm in diverse cell types.

Bioarchitectural Design of Bioactive Biopolymers: Structure-Function Paradigm for Diabetic Wound Healing

Chronic wounds such as diabetic ulcers are a major complication in diabetes caused by hyperglycemia, prolonged inflammation, high oxidative stress, and bacterial bioburden. Bioactive biopolymers have been found to have a biological response in wound tissue microenvironments and are used for developing advanced tissue engineering strategies to enhance wound healing. These biopolymers possess innate bioactivity and are biodegradable, with favourable mechanical properties. However, their bioactivity is highly dependent on their structural properties, which need to be carefully considered while developing wound healing strategies. Biopolymers such as alginate, chitosan, hyaluronic acid, and collagen have previously been used in wound healing solutions but the modulation of structural/physico-chemical properties for differential bioactivity have not been the prime focus. Factors such as molecular weight, degree of polymerization, amino acid sequences, and hierarchical structures can have a spectrum of immunomodulatory, anti-bacterial, and anti-oxidant properties that could determine the fate of the wound. The current narrative review addresses the structure-function relationship in bioactive biopolymers for promoting healing in chronic wounds with emphasis on diabetic ulcers. This review highlights the need for characterization of the biopolymers under research while designing biomaterials to maximize the inherent bioactive potency for better tissue regeneration outcomes, especially in the context of diabetic ulcers.

Teaching Systems and their Sub-Topics Under Competency-Based Medical Education (CBME) to Undergraduate Medical Students in a Stepwise Approach

Medical education in India is confronting a charismatic transformation from traditional curriculum to competency-based medical education (CBME). It is more clinically oriented; skill-based and claims to produce competent Indian medical graduates. CBME has divided subjects into competencies and related topics are scattered over different competencies. The intention behind teaching should not be merely students' learning, but contemplation should be towards concept building, imagination, creativity, self-motivated thinking, and the rightful application of knowledge in day-to-day life. Hence a well-formulated, organized, effective, and practically assessable design and an efficient approach are essential not only to link these spread-over pieces of the topic but to teach that topic in a certain flow and rhythm to a medical student also. Therefore, a stepwise approach has been proposed to teach a CBME-driven curriculum to medical students.

Which airways should we treat? Structure-function relationships and estimation of the singular input modes from the forward model alone

Structure-function relationships occur throughout the sciences. Motivated by optimization of such systems, we develop a framework for estimating the input modes from the singular value decomposition from the action of the forward operator alone. These can then be used to determine the input (structure) changes, which induce the largest output (function) changes. The accuracy of the estimate is determined by reference to the method of snapshots. The proposed method is demonstrated on several example problems, and finally used to approximate the optimal airway treatment set for a problem in respiratory physiology.

"Local control": another core concept of physiology

The maintenance of a more or less constant internal environment by homeostatic (negative feedback) mechanisms is well understood, and "homeostasis" is regarded as an important core concept for students to understand. However, there are critically important control mechanisms that operate at the local level and are more or less independent of homeostasis. Here we define a core concept of "local control," present examples of it in many different organ systems, and propose a conceptual framework for it. Local control, like all of the other core concepts, can provide students with a learning tool that can facilitate understanding physiology.NEW & NOTEWORTHY Local control of many physiological phenomena occurs to meet the needs of certain systems and to enable these systems to meet the episodic challenges that occur. The mechanisms by which local control is exerted include locally released chemical messengers, physical stimuli acting on the structures, and local neural networks. Examples of important local controls are present throughout the body.

Unpacking the renal system component of the "structure and function" core concept of physiology by an Australian team

An Australia-wide consensus was reached on seven core concepts of physiology, one of which was "structure and function" with the descriptor "Structure and function are intrinsically related to all levels of the organism. In all physiological systems, the structure from a microscopic level to an organ level dictates its function." As a framework for the structure and function core concept, the renal system was unpacked by a team of 5 Australian Physiology educators from different universities with extensive teaching experience into hierarchical levels, with 5 themes and 25 subthemes up to 3 levels deep. Within theme 1, the structures that comprise the renal system were unpacked. Within theme 2, the physiological processes within the nephron such as filtration, reabsorption, and secretion were unpacked. Within theme 3, the processes involved in micturition were unpacked. In theme 4, the structures and processes involved in regulating renal blood flow and glomerular filtration were unpacked; and within theme 5, the role of the kidney in red blood cell production was unpacked. Twenty-one academics rated the difficulty and importance of each theme/subtheme, and results were analyzed using a one-way ANOVA. All identified themes were validated as "essential" to "important"/"moderately important" and rated between "difficult" to "not difficult." A similar framework consisting of structure, physiological processes, physical processes, and regulation can be used to unpack other body systems. Unpacking of the body systems will provide a list of what students should be taught in curricula across Australian universities and inform assessment and learning activities.NEW & NOTEWORTHY This is the first attempt to unpack and validate the "structure and function" core concept in physiology with all Australian educators. We unpacked the renal system into themes with hierarchical levels, which were validated by an experienced team of Australian physiology educators. Our unpacking of the "structure and function" core concept provides a specific framework for educators to apply this important concept in physiology education.

Using Test Question Templates to teach physiology core concepts

The past ∼15 years have seen increasing interest in defining disciplinary core concepts. Within the field of physiology, Michael, McFarland, Modell, and colleagues have published studies that defined physiology core concepts and have elaborated many of these as detailed conceptual frameworks. With such helpful definitions now in place, attention is turning to the related issue of how to maximize student understanding of the core concepts by linking these "big ideas" to concrete student-facing resources for active learning and assessment. Our practitioner-based view begins with the recognition that in many if not most undergraduate physiology courses assessment drives learning. We have therefore linked published conceptual frameworks to Test Question Templates (TQTs), whose structure promotes transparent assessments as well as the active learning needed to prepare for such assessments. We provide examples of conceptual framework-linked TQTs for the physiology core concepts of Homeostasis, Flow Down Gradients, the Cell Membrane, and Cell-Cell Communication. We argue that this deployment of TQTs has at least two distinct benefits for the teaching and learning of core concepts. First, documenting the connections between conceptual frameworks and TQTs may clarify coverage and assessment of the core concepts for both instructors and students. Second, misconceptions about core concepts may be directly targeted and dispelled via thoughtful construction, arrangement, and iteration of TQTs. We propose that the TQT framework or similar approaches may be applied fruitfully to any sufficiently articulated physiology core concept for high school, undergraduate, or graduate students.NEW & NOTEWORTHY Our students often focus on the grades they need to advance through academic programs. How can instructors harness this understandable interest in grades to help students gain a true understanding of core concepts? The new framework of Test Question Templates (TQTs) shows promise in linking student priorities like test scores to instructor priorities like core concepts.

Skin ionocyte density of amphibious killifishes is shaped by phenotypic plasticity and constitutive interspecific differences

When amphibious fishes are on land, gill function is reduced or eliminated and the skin is hypothesized to act as a surrogate site of ionoregulation. Skin ionocytes are present in many fishes, particularly those with amphibious life histories. We used nine closely related killifishes spanning a range of amphibiousness to first test the hypothesis that amphibious killifishes have evolved constitutively increased skin ionocyte density to promote ionoregulation on land. We found that skin ionocyte densities were constitutively higher in five of seven amphibious species examined relative to exclusively water-breathing species when fish were prevented from leaving water, strongly supporting our hypothesis. Next, to examine the scope for plasticity, we tested the hypothesis that skin ionocyte density in amphibious fishes would respond plastically to air-exposure to promote ionoregulation in terrestrial environments. We found that air-exposure induced plasticity in skin ionocyte density only in the two species classified as highly amphibious, but not in moderately amphibious species. Specifically, skin ionocyte density significantly increased in Anablepsoides hartii (168%) and Kryptolebias marmoratus (37%) following a continuous air-exposure, and only in K. marmoratus (43%) following fluctuating air-exposure. Collectively, our data suggest that highly amphibious killifishes have evolved both increased skin ionocyte density as well as skin that is more responsive to air-exposure compared to exclusively water-breathing and less amphibious species. Our findings are consistent with the idea that gaining the capacity for cutaneous ionoregulation is a key evolutionary step that enables amphibious fishes to survive on land.