Comparative energetics and thermal responses to feeding in allied Agkistrodon snakes with contrasting diet and habitat use.

Variation in animal responses to feeding can be attributed to a variety of ecological factors, including foraging mode and dietary specialization. Specialization often favors species that have traits for exploiting food resources that are rare and that are not commonly shared by dietary generalists. We investigated physiological and behavioral responses to feeding between two snake species with different degrees of mammal feeding specialization: Agkistrodon contortrix (copperheads; a terrestrial species in which adults feed almost exclusively on mammals) and Agkistrodon piscivorus (cottonmouths; a semi-aquatic species feeding less on mammals and primarily on ectothermic prey). We measured metabolic rates (at 20, 25, and 30 °C) and body temperature (Tb) selection of snakes both pre- and post-feeding. Following the consumption of rodent meals, post-feeding energy use was higher in A. piscivorus than A. contortrix at both 25 and 30 °C. After feeding, A. piscivorus maintained body temperatures that were 3-4 °C higher, whereas A. contortrix remained within 1 °C of their pre-feeding Tb. Our results support the contention that dietary specialization leads to potential energetic advantages and that generalist species may change their behavior to offset energy used to digest prey.

Using Mobile Monitoring to Develop Hourly Empirical Models of Particulate Air Pollution in a Rural Appalachian Community.

Most empirical air quality models (e.g., land use regression) focus on urban areas. Mobile monitoring for model development offers the opportunity to explore smaller, rural communities - an understudied population. We use mobile monitoring to systematically sample all daylight hours (7 am to 7 pm) to develop empirical models capable of estimating hourly concentrations in Blacksburg, VA, a small town in rural Appalachia (population: 182 635). We collected ∼120 h of mobile monitoring data for particle number (PN) and black carbon (BC). We developed (1) daytime (12-h average) models that approximate long-term concentrations and (2) spatiotemporal models for estimating hourly concentrations. Model performance for the daytime models is consistent with previous fixed-site and short-term sampling studies; adjusted R2 (10-fold CV R2) was 0.80 (0.69) for the PN model and 0.67 (0.58) for the BC model. The spatiotemporal models had comparable performance (10-fold CV R2 for the PN [BC] models: 0.42 [0.25]) to previous mobile monitoring studies that isolate specific time periods. Temporal and spatial model coefficients had similar magnitudes in the spatiotemporal models suggesting both factors are important for exposure. We observed similar spatial patterns in Blacksburg (e.g., roadway gradients) as in other studies in urban areas suggesting similar exposure disparities exist in small, rural communities.

Proposed clinical internal carotid artery classification system.

INTRODUCTION: Numerical classification systems for the internal carotid artery (ICA) are available, but modifications have added confusion to the numerical systems. Furthermore, previous classifications may not be applicable uniformly to microsurgical and endoscopic procedures. The purpose of this study was to develop a clinically useful classification system. MATERIALS AND METHODS: We performed cadaver dissections of the ICA in 5 heads (10 sides) and evaluated 648 internal carotid arteries with computed tomography angiography. We identified specific anatomic landmarks to define the beginning and end of each ICA segment. RESULTS: The ICA was classified into eight segments based on the cadaver and imaging findings: (1) Cervical segment; (2) cochlear segment (ascending segment of the ICA in the temporal bone) (relation of the start of this segment to the base of the styloid process: Above, 425 sides [80%]; below, 2 sides [0.4%]; at same level, 107 sides [20%]; P < 0.0001) (relation of cochlea to ICA: Posterior, 501 sides [85%]; posteromedial, 84 sides [14%]; P < 0.0001); (3) petrous segment (horizontal segment of ICA in the temporal bone) starting at the crossing of the eustachian tube superolateral to the ICA turn in all 10 samples; (4) Gasserian-Clival segment (ascending segment of ICA in the cavernous sinus) starting at the petrolingual ligament (PLL) (relation to vidian canal on imaging: At same level, 360 sides [63%]; below, 154 sides [27%]; above, 53 sides [9%]; P < 0.0001); in this segment, the ICA projected medially toward the clivus in 275 sides (52%) or parallel to the clivus with no deviation in 256 sides (48%; P < 0.0001); (5) sellar segment (medial loop of ICA in the cavernous sinus) starting at the takeoff of the meningeal hypophyseal trunk (ICA was medial into the sella in 271 cases [46%], lateral without touching the sella in 127 cases [23%], and abutting the sella in 182 cases [31%]; P < 0.0001); (6) sphenoid segment (lateral loop of ICA within the cavernous sinus) starting at the crossing of the fourth cranial nerve on the lateral aspect of the cavernous ICA and located directly lateral to the sphenoid sinus; (7) ring segment (ICA between the 2 dural rings) starting at the crossing of the third cranial nerve on the lateral aspect of the ICA; (8) cisternal segment starting at the distal dural ring. CONCLUSIONS: The classification may be applied uniformly to all skull base surgical approaches including lateral microsurgical and ventral endoscopic approaches, obviating the need for 2 separate classification systems. The classification allows extrapolation of relevant clinical information because each named segment may indicate potential surgical risk to specific structures.

Multifocal melanocytoma of the posterior fossa and subcutaneous scalp in the absence of neurocutaneous melanosis.

BACKGROUND: Primary leptomeningeal melanocytic neoplasms of the central nervous system are rare. Multifocal lesions typically occur in the setting of cutaneous melanosis. We present the first report of a posterior fossa melanocytoma and subcutaneous melanocytoma of intermediate grade in the absence of cutaneous melanosis. CASE DESCRIPTION: We present the case of a 22-year-old male with decreased hearing on the right side, ataxia, nausea, vomiting and a scalp mass. Magnetic resonance imaging (MRI) demonstrated occipital and cerebellopontine (CP) angle masses. The patient underwent gross total resection of the scalp mass and subtotal resection of the CP angle mass. Pathologic examination revealed melanocytoma with intermediate grade. The patient underwent stereotactic radiosurgery to the residual CP angle tumor. This case represents, to the author's knowledge, the first report associating a posterior fossa melanocytoma with a subcutaneous melanocytoma of intermediate grade in the absence of cutaneous melanosis. CONCLUSION: This case introduces the first report of a new variant of multifocal melanocytoma which is not confined to the central nervous system.

Analysis of Decompressive Craniectomies with Subsequent Cranioplasties in the Presence of Collagen Matrix Dural Substitute and Polytetrafluoroethylene as an Adhesion Preventative Material.

OBJECTIVE: Decompressive craniectomy is an established treatment for malignant intracranial hypertension. Cranioplasty is performed once cerebral swelling has resolved. Complications include infection, postoperative fluid collections, hematoma, reoperation, and seizures. Our experience using a double layer technique during craniectomy with a collagen matrix onlay dural substitute and expanded polytetrafluoroethylene for antiadhesive properties during cranioplasty was reviewed. METHODS: This is a retrospective chart review of 39 consecutive patients who underwent craniectomy with placement of collagen matrix dural onlay and expanded polytetrafluoroethylene and subsequent cranioplasty. Demographic data, size of craniectomy defect, estimated blood loss, operative time, time between operations, presence of dural tackups, and postoperative complications were analyzed. RESULTS: Mean operative time was 132 minutes and estimated blood loss was 112 mL. Overall complication rate was 25.6% and no mortality was encountered. Nine patients had postoperative fluid collections measuring ≥ 10 mm in thickness and/or 5 mm of midline shift. Two patients required reoperation for these collections. Two patients developed infections requiring bone flap removal. Three patients developed seizures after cranioplasty. Five patients required shunt placement for hydrocephalus. CONCLUSIONS: Our dual layer closure technique at time of decompressive craniectomy carries a similar reduction in operative time and estimated blood loss when compared with cranioplasty series with other antiadhesives present. The technique described enables easy dissection of the musculocutaneous flap from the dural plane during cranioplasty and increases the safety of the operation.