Douglas Hardesty - Academia.edu (original) (raw)

Papers by Douglas Hardesty

Environmental Toxicology and Chemistry, 2021

The US Environmental Protection Agency's short‐term freshwater effluent test methods include ... more The US Environmental Protection Agency's short‐term freshwater effluent test methods include a fish (Pimephales promelas), a cladoceran (Ceriodaphnia dubia), and a green alga (Raphidocelis subcapitata). There is a recognized need for additional taxa to accompany the three standard species for effluent testing. An appropriate additional taxon is unionid mussels because mussels are widely distributed, live burrowed in sediment and filter particles from the water column for food, and exhibit high sensitivity to a variety of contaminants. Multiple studies were conducted to develop a relevant and robust short‐term test method for mussels. We first evaluated the comparative sensitivity of two mussel species (Villosa constricta and Lampsilis siliquoidea) and two standard species (P. promelas and C. dubia) using two mock effluents prepared by mixing ammonia and five metals (cadmium, copper, nickel, lead, and zinc) or a field‐collected effluent in 7‐day exposures. Both mussel species were equally or more sensitive (more than two‐fold) to effluents compared with the standard species. Next, we refined the mussel test method by first determining the best feeding rate of a commercial algal mixture for three age groups (1, 2, and 3 weeks old) of L. siliquoidea in a 7‐day feeding experiment, and then used the derived optimal feeding rates to assess the sensitivity of the three ages of juveniles in a 7‐day reference toxicant (sodium chloride [NaCl]) test. Juvenile mussels grew substantially (30%–52% length increase) when the 1‐ or 2‐week‐old mussels were fed 2 ml twice daily and the 3‐week‐old mussels were fed 3 ml twice daily. The 25% inhibition concentrations (IC25s) for NaCl were similar (314–520 mg Cl/L) among the three age groups, indicating that an age range of 1‐ to 3‐week‐old mussels can be used for a 7‐day test. Finally, using the refined test method, we conducted an interlaboratory study among 13 laboratories to evaluate the performance of a 7‐day NaCl test with L. siliquoidea. Eleven laboratories successfully completed the test, with more than 80% control survival and reliable growth data. The IC25s ranged from 296 to 1076 mg Cl/L, with a low (34%) coefficient of variation, indicating that the proposed method for L. siliquoidea has acceptable precision. Environ Toxicol Chem 2021;40:3392–3409. © 2021 SETAC

Journal of Neurological Surgery Part B: Skull Base, 2016

Archives of Environmental Contamination and Toxicology, 2016

We performed toxicity tests with two species of pulmonate snails (Lymnaea stagnalis and Physa gyr... more We performed toxicity tests with two species of pulmonate snails (Lymnaea stagnalis and Physa gyrina) and four taxa of nonpulmonate snails in the family Hydrobiidae (Pyrgulopsis robusta, Taylorconcha serpenticola, Fluminicola sp., and Fontigens aldrichi). Snails were maintained in static-renewal or recirculating culture systems with adults removed periodically to isolate cohorts of offspring for toxicity testing. This method successfully produced offspring for both species of pulmonate snails and for two hydrobiid species, P. robusta and Fluminicola sp. Toxicity tests were performed for 28 days with copper, ammonia, and pentachlorophenol in hard reconstituted water with endpoints of survival and growth. Tests were started with 1-week-old L. stagnalis, 2-week-old P. gyrina, 5- to 13-week-old P. robusta and Fluminicola sp., and older juveniles and adults of several hydrobiid species. For all three chemicals, chronic toxicity values for pulmonate snails were consistently greater than those for hydrobiid snails, and hydrobiids were among the most sensitive taxa in species sensitivity distributions for all three chemicals. These results suggest that the toxicant sensitivity of nonpulmonate snails in the family Hydrobiidae would not be adequately represented by results of toxicity testing with pulmonate snails.

Biological Science Report, 2001

Journal of Pediatric Surgery Case Reports, 2014

Spinal arachnoid cysts are rare entities that often present with progressive myelopathy and are t... more Spinal arachnoid cysts are rare entities that often present with progressive myelopathy and are treated via surgical excision and fenestration. The acute onset of symptoms from these lesions is not well described in the literature. We report an 18-month-old child with acute onset of paraplegia following a mild trauma, who was found to have a compressive dorsal thoracic intradural spinal arachnoid cyst and emergently treated via surgical decompression and cyst resection. After several months of physical therapy the child achieved meaningful neurologic recovery. Spinal arachnoid cysts can cause acute decompensation in children with serious neurological injury following mild trauma, this risk should be weighed when managing asymptomatic lesions.

Journal of Neurosurgery: Pediatrics, 2008

Schizencephaly is a rare congenital cortical brain malformation defined by unilateral or bilatera... more Schizencephaly is a rare congenital cortical brain malformation defined by unilateral or bilateral clefts of the cerebral hemispheres. These malformations are often associated with medically intractable epilepsy. Surgical solutions include lesionectomy, lobectomy, or hemispherectomy. The authors describe the case of an anatomic hemispherectomy for medically intractable epilepsy in an 8-year-old boy with a large schizencephalic cleft. Seven years prior to his epilepsy surgery, the patient underwent placement of a ventriculoperitoneal shunt for communicating hydrocephalus that resulted in severe left-to-right shift. Subsequently, medically refractory epilepsy developed and the patient underwent an anatomic hemispherectomy for seizure control. The preoperative brain shift remained after the surgery, although the patient tolerated the procedure well and was seizure free postoperatively. Anatomic hemispherectomy is a viable option for treating medically intractable epilepsy in a schizencephalic pediatric patient-even one with considerable brain shift.

World Neurosurgery, 2014

To report a minimally invasive, nontubular endoscopic technique to resect intraparenchymal brain ... more To report a minimally invasive, nontubular endoscopic technique to resect intraparenchymal brain tumors and assess the feasibility, safety, and surgical resection margins achievable by this novel technique. Over a 21-month period, 48 patients underwent 50 consecutive endoscopic intraparenchymal tumor resections. Data on surgical morbidity and mortality and length of stay were collected prospectively. The percentage of surgical resection and residual tumor volumes were calculated using preoperative and postoperative volume computed tomography or magnetic resonance imaging. All tumors were resected through a 2-cm minicraniotomy using a high-definition rigid endoscope with a 30-degree viewing angle. Bimanual resection was performed using standard microsurgical technique. Mean patient age was 53 years. There were 42 supratentorial (19 frontal, 17 temporal, 3 occipital, 1 parietal, and 2 parafalcine) tumors and 8 infratentorial tumors. Mean tumor volume was 41 cm(3). There were 12 metastases, 24 glioblastomas, 4 World Health Organization grade III gliomas, 5 World Health Organization grade I-II gliomas, 3 meningiomas, and 2 hemangioblastomas. On volumetric analysis, the overall mean percent resection was 96%. In 70% of cases, &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;gt;95% resection was achieved; total resection was achieved in 48% of cases. At 30 days postoperatively, there was 1 new postoperative neurologic deficit; there were no deaths during this period. Our experience demonstrates that resection of intraparenchymal tumors using a minimally invasive endoscopic technique is technically feasible and safe, achieves good tumor resection margins, and has some potential advantages over a traditional microscopic technique.

Neurosurgery, Jan 19, 2015

Microscopic and endoscopic transsphenoidal approaches to the sellar are well established. Surgica... more Microscopic and endoscopic transsphenoidal approaches to the sellar are well established. Surgical freedom is an important skull base principle that can be measured objectively and used to compare approaches. To compare the surgical freedom of 4 transsphenoidal approaches to the sella turcica to aid in surgical approach selection. Four transsphenoidal approaches to the sella were performed on 8 silicon-injected cadaveric heads. Surgical freedom was determined with stereotactic image guidance using previously established techniques. The results are presented as the area of surgical freedom and angular surgical freedom (angle of attack) in the axial and sagittal planes. Mean total exposed area surgical freedom for the microscopic sublabial, endoscopic binostril, endoscopic uninostril, and microscopic endonasal approaches were 102 ± 13, 89 ± 6, 81 ± 4, and 69 ± 10 cm, respectively. The endoscopic binostril approach had the greatest surgical freedom at the pituitary gland and ipsilatera...

Journal of Neurosurgery, 2015

OBJECT The successful treatment of an intracranial dural arteriovenous fistula (dAVF) requires co... more OBJECT The successful treatment of an intracranial dural arteriovenous fistula (dAVF) requires complete obliteration of blood flow through the fistulous point. Surgical ligation is often used along with endovascular techniques. Digital subtraction angiography (DSA) can be used to confirm fistula obliteration; however, this technique can be cumbersome intraoperatively and difficult to correlate anatomically with the surgical field. Near-infrared indocyanine green (ICG) videoangiography has been described as a complementary tool for this purpose. METHODS The authors examined intracranial dAVF cases in which microscope-integrated intraoperative ICG videoangiography was used to identify and/or confirm obliteration of the dAVF during surgery. Retrospective evaluation of all intracranial dAVF cases treated with surgical ligation over a 10-year period at the Barrow Neurological Institute (n = 47) revealed 28 cases in which ICG videoangiography was used. The results were compared with findings on preoperative and intraoperative or postoperative DSA. RESULTS ICG videoangiography successfully confirmed the fistulous point intraoperatively in 96% (22/23) of the cases. It also revealed complete obliteration of fistulas, comparable to intraoperative or postoperative DSA, in 91% (21/23) of the cases. The false-negative rate of ICG was 8.7% (2/23), which is similar to the false-negative rate of intraoperative DSA alone (10.5% [2/19]). CONCLUSIONS Microscope-based ICG videoangiography provides real-time information about the intraoperative anatomy of dAVFs. In addition, it can confirm complete obliteration of a fistula. This technique may be useful during dAVF surgery as an independent form of angiography or as an adjunct to intraoperative or postoperative DSA.

Journal of neurosurgery, 2014

Coccidioidomycosis is a common fungal infection in the southwestern US. Hydrocephalus is a seriou... more Coccidioidomycosis is a common fungal infection in the southwestern US. Hydrocephalus is a serious complication of cranial coccidioidomycosis, and the surgical management of coccidioidomycosis-related hydrocephalus has unique challenges. The authors reviewed their institutional experience with hydrocephalus in the setting of coccidioidomycosis. The authors retrospectively identified 44 patients diagnosed with coccidioidomycosis-related hydrocephalus at their institution since 1990, who underwent a total of 99 shunting procedures. The authors examined patient demographics, type of shunt and valve used, pressure settings, failure rates, medical treatment, ventricular response to shunting, and other variables. The majority of patients were young (average age 37 years) men (male/female ratio 28:16) with a mean follow-up of 63 months. Patients of Asian and African descent were overrepresented in the cohort compared with regional demographic data. The overall shunt failure rate during fol...

The objective of the present study was to determine acute toxicity of copper, ammonia, or chlorin... more The objective of the present study was to determine acute toxicity of copper, ammonia, or chlorine to larval (glochidia) and juvenile mussels using the recently published American Society for Testing and Materials (ASTM) Standard guide for conducting laboratory toxicity tests with freshwater mussels. Toxicity tests were conducted with glochidia (24-to 48-h exposures) and juveniles (96-h exposures) of up to 11 mussel species in reconstituted ASTM hard water using copper, ammonia, or chlorine as a toxicant. Copper and ammonia tests also were conducted with five commonly tested species, including cladocerans (Daphnia magna and Ceriodaphnia dubia; 48-h exposures), amphipod (Hyalella azteca; 48-h exposures), rainbow trout (Oncorhynchus mykiss; 96-h exposures), and fathead minnow (Pimephales promelas; 96-h exposures). Median effective concentrations (EC50s) for commonly tested species were Ͼ58 g Cu/L (except 15 g Cu/L for C. dubia) and Ͼ13 mg total ammonia N/L, whereas the EC50s for mussels in most cases were Ͻ45 g Cu/L or Ͻ12 mg N/L and were often at or below the final acute values (FAVs) used to derive the U.S. Environmental Protection Agency 1996 acute water quality criterion (WQC) for copper and 1999 acute WQC for ammonia. However, the chlorine EC50s for mussels generally were Ͼ40 g/L and above the FAV in the WQC for chlorine. The results indicate that the early life stages of mussels generally were more sensitive to copper and ammonia than other organisms and that, including mussel toxicity data in a revision to the WQC, would lower the WQC for copper or ammonia. Furthermore, including additional mussel data in 2007 WQC for copper based on biotic ligand model would further lower the WQC.

Proceedings of the National Academy of Sciences, 2011

The second messenger phosphatidylinositol (3,4,5)-trisphosphate (PIP 3 ), formed by the p110 fami... more The second messenger phosphatidylinositol (3,4,5)-trisphosphate (PIP 3 ), formed by the p110 family of PI3-kinases, promotes cellular growth, proliferation, and survival, in large part by activating the protein kinase Akt/PKB. We show that inositol polyphosphate multikinase (IPMK) physiologically generates PIP 3 as well as water soluble inositol phosphates. IPMK deletion reduces growth factor-elicited Akt signaling and cell proliferation caused uniquely by loss of its PI3-kinase activity. Inhibition of p110 PI3-kinases by wortmannin prevents IPMK phosphorylation and activation. Thus, growth factor stimulation of Akt signaling involves PIP 3 generation through the sequential activations of the p110 PI3-kinases and IPMK. As inositol phosphates inhibit Akt signaling, IPMK appears to act as a molecular switch, inhibiting or stimulating Akt via its inositol phosphate kinase or PI3-kinase activities, respectively. Drugs regulating IPMK may have therapeutic relevance in influencing cell proliferation.

North American Journal of Aquaculture, 2013

Neurosurgery, 2014

Background: One challenge performing endoscopic endonasal approaches is the surgical conflict tha... more Background: One challenge performing endoscopic endonasal approaches is the surgical conflict that occurs between the surgical instruments and endoscope in the crowded nasal corridor. This conflict decreases surgical freedom, increases surgeon frustration, and lengthens the learning curve for trainees.

Journal of Clinical Neuroscience, 2014

Intraoperative angiography in cerebrovascular neurosurgery can drive the repositioning or additio... more Intraoperative angiography in cerebrovascular neurosurgery can drive the repositioning or addition of aneurysm clips. Our institution has switched from a strategy of intraoperative digital subtraction angiography (DSA) universally, to a strategy of indocyanine green (ICG) videoangiography with DSA on an as-needed basis. We retrospectively evaluated whether the rates of perioperative stroke, unexpected postoperative aneurysm residual, or parent vessel stenosis differed in 100 patients from each era (2002, ''DSA era''; 2007, ''ICG era''). The clip repositioning rate for neck residual or parent vessel stenosis did not differ significantly between the two eras. There were no differences in the rate of perioperative stroke or rate of false-negative studies. The per-patient cost of intraoperative imaging within the DSA era was significantly higher than in the ICG era. The replacement of routine intraoperative DSA with ICG videoangiography and selective intraoperative DSA in cerebrovascular aneurysm surgery is safe and effective.

European Spine Journal, 2009

There are several treatment options for rigid fixation at C1-C2 including Brooks and Gallie type ... more There are several treatment options for rigid fixation at C1-C2 including Brooks and Gallie type wired fusions and C1-2 transarticular screws. The use of a Goel-Harms type fusion, a construct with C1 lateral mass screws and C2 pedicle screws, has not been extensively described in pediatric patients. Here, we describe its relatively safe and effective use for treating pediatric patients by retrospective chart review of patients treated by the senior author for atlantoaxial instability with a Goel-Harms-type constructs during a 3-year period (2005)(2006)(2007). Six patients were treated using Goel-Harms-type constructs. Five patients were treated utilizing a construct containing C1 lateral mass screws and C2 pedicle screws; one patient was treated using construct containing C1 lateral mass screws and C2 trans-laminar screws. The patients ranged in age from 7 to 17 years old (mean 12.7). All patients had findings of an os odontoideum on CT scans and three of the six patients had T2 hyperintensity on MRI. Three of the six patients presented with transient neurologic deficits: quadraplegia in two patients and paresthesias in two patients. In each patient C1 lateral mass and C2 screws were placed and the subluxation was reduced to attain an anatomical alignment. No bone grafts were harvested from the iliac crest or rib. Local morsalized bone and sub-occipital skull graft was used. All patients tolerated the procedure well and were discharged home on post-operative day 3-4. The patients wore a hard cervical collar and no halo-vests were needed. All patients had solid fusion constructs and normal alignment on post-operative imaging studies performed on average 14 months post-operatively (range: 7-29). The results demonstrated that Goel-Harms fusions are a relatively safe and effective method of treating pediatric patients with atlantoaxial instability and are not dependent on vertebral anatomy or an intact ring of C1. Follow-up visits and studies in this limited series of patients demonstrated solid fusion constructs and anatomical alignment in all patients treated.

Environmental Toxicology and Chemistry, 2012

Carbon nanotubes (CNTs) are hydrophobic in nature and thus tend to accumulate in sediments if rel... more Carbon nanotubes (CNTs) are hydrophobic in nature and thus tend to accumulate in sediments if released into aquatic environments. As part of our overall effort to examine the toxicity of carbon-based nanomaterials to sediment-dwelling invertebrates, we have evaluated the toxicity of different types of CNTs in 14-d water-only exposures to an amphipod (Hyalella azteca), a midge (Chironomus dilutus), an oligochaete (Lumbriculus variegatus), and a mussel (Villosa iris) in advance of conducting whole-sediment toxicity tests with CNTs. The results of these toxicity tests conducted with CNTs added to water showed that 1.00 g/L (dry wt) of commercial sources of CNTs significantly reduced the survival or growth of the invertebrates. Toxicity was influenced by the type and source of the CNTs, by whether the materials were precleaned by acid, by whether sonication was used to disperse the materials, and by species of the test organisms. Light and electron microscope imaging of the surviving test organisms showed the presence of CNTs in the gut as well as on the outer surface of the test organisms, although no evidence was observed to show penetration of CNTs through cell membranes. The present study demonstrated that both the metals solubilized from CNTs such as nickel and the ''metal-free'' CNTs contributed to the toxicity. Environ. Toxicol. Chem.# 2012 SETAC