Nutritional Ecology of the Western Cottonmouth (Agkistrodon piscivorus leucostoma)

Nutritional ecology aims to understand the factors that shape the diets of animals, how these ingested meals are processed, and how the assimilated nutrients are used to shape an organism’s interactions with its environment. As environmental parameters are altered due to anthropogenic changes, the availability and quality of prey may be altered. The alteration of the nutritional landscape can be devastating to nutritional specialists, yet generalist predators may be able to cope with these changes. The western cottonmouth (Agkistrodon piscivorus leucostoma) is a unique semiaquatic pitviper that can both forage along the land-water interface and in upland habitat when faced with drought conditions. Given the potentially wide diet breath of this species, how would it respond to shifts in prey base? Is there a relationship between prey preference and digestive performance of the cottonmouth? I explored this question using stable isotope dietary analysis, behavioral prey preference trials, and measurement of the metabolic response to feeding (specific dynamic action). The notoriously wide diet breath of the cottonmouth was verified through stable isotope analysis, where animals were consuming various fish and frog species, and potentially crayfish. Prey preference trials conducted using an X maze showed that these snakes would readily eat fish, frog, and mouse, yet they showed a very strong aversion to crayfish. Of the prey types that were readily eaten by cottonmouths, mouse meals generated the highest overall specific dynamic action response while fish and frog meals were comparable to one another

Nutritional Ecology of the Western Cottonmouth (Agkistrodon piscivorus leucostoma)

Nutritional ecology aims to understand the factors that shape the diets of animals, how these ingested meals are processed, and how the assimilated nutrients are used to shape an organism’s interactions with its environment. As environmental parameters are altered due to anthropogenic changes, the availability and quality of prey may be altered. The alteration of the nutritional landscape can be devastating to nutritional specialists, yet generalist predators may be able to cope with these changes. The western cottonmouth (Agkistrodon piscivorus leucostoma) is a unique semiaquatic pitviper that can both forage along the land-water interface and in upland habitat when faced with drought conditions. Given the potentially wide diet breath of this species, how would it respond to shifts in prey base? Is there a relationship between prey preference and digestive performance of the cottonmouth? I explored this question using stable isotope dietary analysis, behavioral prey preference trials, and measurement of the metabolic response to feeding (specific dynamic action). The notoriously wide diet breath of the cottonmouth was verified through stable isotope analysis, where animals were consuming various fish and frog species, and potentially crayfish. Prey preference trials conducted using an X maze showed that these snakes would readily eat fish, frog, and mouse, yet they showed a very strong aversion to crayfish. Of the prey types that were readily eaten by cottonmouths, mouse meals generated the highest overall specific dynamic action response while fish and frog meals were comparable to one another

Observations of flotsam entrapment in the northern Diamond-backed Watersnake (Nerodia R. Rhombifer)

—Small areas of protected land may act as islands of suitable habitat surrounded by human development. Although these areas receive protection, we have observed one way that the surrounding human population can still endanger the welfare of its inhabitants. During our observations of the Northern Diamond-backed Watersnake (Nerodia r. rhombifer) in a semi-protected nature park surrounded by human development, we encountered 13 individuals entangled with flotsam. Of the 220 juvenile through adult snakes that we captured, 12 were encircled by various types of objects (e.g., finger cots; latex sheaths that cover a single digit, dental elastics, and plastic bottle neck rings) within the first half of their body; a 13th individual was observed but was not captured. The injuries resulting from these rings ranged from superficial wounds to death. We conducted behavioral experiments to determine if entanglement was due to attraction or to incidental entrapment during activity, with the latter being more likely. Our observations show that becoming trapped in refuse may be an important source of impairment and mortality in limbless reptiles, as has been previously documented in other species

Stiff Mutant Genes of Phycomyces Affect Turgor Pressure and Wall Mechanical Properties to Regulate Elongation Growth Rate

Regulation of cell growth is paramount to all living organisms. In plants, algae and fungi, regulation of expansive growth of cells is required for development and morphogenesis. Also, many sensory responses of stage IVb sporangiophores of Phycomyces blakesleeanus are produced by regulating elongation growth rate (growth responses) and differential elongation growth rate (tropic responses). “Stiff” mutant sporangiophores exhibit diminished tropic responses and are found to be defective in at least five genes; madD, E, F, G, and J. Prior experimental research suggests that the defective genes affect growth regulation, but this was not verified. All the growth of the single-celled stalk of the stage IVb sporangiophore occurs in a short region termed the “growth zone.” Prior experimental and theoretical research indicates that elongation growth rate of the stage IVb sporangiophore can be regulated by controlling the cell wall mechanical properties within the growth zone and the magnitude of the turgor pressure. A quantitative biophysical model for elongation growth rate is required to elucidate the relationship between wall mechanical properties and turgor pressure during growth regulation. In this study, it is hypothesized that the mechanical properties of the wall within the growth zone of stiff mutant sporangiophores are different compared to wild type (WT). A biophysical equation for elongation growth rate is derived for fungal and plant cells with a growth zone. Two strains of stiff mutants are studied, C149 madD120 (−) and C216 geo- (−). Experimental results demonstrate that turgor pressure is larger but irreversible wall deformation rates within the growth zone and growth zone length are smaller for stiff mutant sporangiophores compared to WT. These findings can explain the diminished tropic responses of the stiff mutant sporangiophores. It is speculated that the defective genes affect the amount of wall-building material delivered to the inner cell wall

Karyotype analysis and sex determination in Australian Brush-turkeys (Alectura lathami)

Sexual differentiation across taxa may be due to genetic sex determination (GSD) and/or temperature sex determination (TSD). In many mammals, males are heterogametic (XY); whereas females are homogametic (XX). In most birds, the opposite is the case with females being heterogametic (ZW) and males the homogametic sex (ZZ). Many reptile spe- cies lack sex chromosomes, and instead, sexual differentiation is influenced by temperature with specific temperatures promoting males or females varying across species possessing this form of sexual differentiation, although TSD has recently been shown to override GSD in Australian central beaded dragons (Pogona vitticeps). There has been speculation that Australian Brush-turkeys (Alectura lathami) exhibit TSD alone and/or in combination with GSD. Thus, we sought to determine if this species possesses sex chromosomes. Blood was collected from one sexually mature female and two sexually mature males residing at Sylvan Heights Bird Park (SHBP) and shipped for karyotype analysis. Karyotype analysis revealed that contrary to speculation, Australian Brush-turkeys possess the classic avian ZW/ZZ sex chromosomes. It remains a possibility that a biased primary sex ratio of Austra- lian Brush-turkeys might be influenced by maternal condition prior to ovulation that result in her laying predominantly Z- or W-bearing eggs and/or sex-biased mortality due to higher sensitivity of one sex in environmental conditions. A better understanding of how maternal and extrinsic factors might differentially modulate ovulation of Z- or W-bearing eggs and hatching of developing chicks possessing ZW or ZZ sex chromosomes could be essential in conservation strategies used to save endangered members of Megapodiidae

Accuracy of pin placement in the canine thoracolumbar spine using a free-hand probing technique versus 3D-printed patient-specific drill guides: An ex-vivo study.

OBJECTIVE To compare pin placement accuracy, intraoperative technique deviations, and duration of pin placement for pins placed by free-hand probing (FHP) or 3D-printed drill guide (3DPG) technique. SAMPLE POPULATION Four greyhound cadavers. METHODS Computed tomography (CT) examinations from T6-sacrum were obtained for determination of optimal pin placement and 3DPG creation. Two 3.2/2.4-mm positive profile pins were inserted per vertebra, one left and one right from T7-L7 (FHP [n = 56]; 3DPG [n = 56]) by one surgeon and removed for repeat CT. Duration of pin placement and intraoperative deviations (unanticipated deviations from planned technique) were recorded. Pin tracts were graded by two blinded observers using modified Zdichavsky classification. Descriptive statistics were used. RESULTS A total of 54/56 pins placed with 3DPGs were assigned grade I (optimal placement) compared with 49/56 pins using the FHP technique. A total of 2/56 pins placed with 3DPGs and 3/56 pins using the FHP technique were assigned grade IIa (partial medial violation). A total of 4/56 pins placed using the FHP technique were assigned grade IIIa (partial lateral violation). No pins were assigned grade IIb (full medial violation). Intraoperative technique deviations occurred with 6/56 pins placed using the FHP technique and no pins with 3DPGs. Overall, pins were placed faster (mean ± SD 2.6 [1.3] vs. 4.5 [1.8] min) with 3DPGs. CONCLUSIONS Both techniques were accurate for placement of spinal fixation pins. The 3DPG technique may decrease intraoperative deviations and duration of pin placement. CLINICAL RELEVANCE Both techniques allow accurate pin placement in the canine thoracolumbar spine. The FHP technique requires specific training and has learning curve, whereas 3DPG technique requires specific software and 3D printers

Feasibility and accuracy of intraosseous endoscopy for inspection of thoracolumbar and lumbar pedicle drill tracts in a canine large-breed cadaveric model.

OBJECTIVE To evaluate the feasibility of endoscopic inspection of thoracolumbar and lumbar pedicle tracts in a canine large-breed model and its accuracy for the detection of breached versus nonbreached tracts. ANIMALS 2 greyhound cadavers. METHODS CT scans of 2 greyhound cadavers from the sixth thoracic vertebra to the sacrum were obtained. Fifty-six pedicles were randomized to have drill tracts with different modified Zdichavsky grades (nonbreached, partial/full medial breach, or partial/full lateral breach) using 3-D-printed guides. Endoscopy was performed on a single occasion from October 9 to 10, 2023, using a 1.9-mm 0-degree needle arthroscope in a randomized blinded fashion. The grading of drill tracts was performed on postoperative CT. Specificity, sensitivity, positive and negative predictive values, and time to assign endoscopic grade were investigated. RESULTS Postoperative CT confirmed 43 nonbreached tracts, 7 medial breaches (partial/full), and 5 lateral breaches (partial/full). One tract was excluded because of guide misplacement. Intraosseous endoscopy was successfully performed in the remaining 55 drill tracts. Sensitivity to detect medial and lateral breaches was 71.4% and 60.0%. Negative predictive value was 93.1%. Specificity was 94.2%. Positive predictive value for detection of medial and lateral breaches was 83.3% and 54.5%. Median (range) time to assign an endoscopic grade was 118 (30 to 486) seconds. CLINICAL RELEVANCE Intraosseous endoscopy of pedicle drill tracts may be a useful adjunct technique during pedicle screw/pin placement in dogs

Gastric Prolapse with Pseudocysts Following Laparoscopic Adjustable Gastric Banding

Nonpancreatic pseudocysts may be associated with gastric prolapse in patients who have undergone laparoscopic adjustable gastric banding

Solution NMR studies reveal the location of the second transmembrane domain of the human sigma-1 receptor

The sigma-1 receptor (S1R) is a ligand-regulated membrane chaperone protein associated with endoplasmic reticulum stress response, and modulation of ion channel activities at the plasma membrane. We report here a solution NMR study of a S1R construct (S1R(?35)) in which only the first transmembrane domain and the eight-residue N-terminus have been removed. The second transmembrane helix is found to be composed of residues 91–107, which corresponds to the first steroid binding domain-like region. The cytosolic domain is found to contain three helices, and the secondary structure and backbone dynamics of the chaperone domain are consistent with that determined previously for the chaperone domain alone. The position of TM2 provides a framework for ongoing studies of S1R ligand binding and oligomerisation