Dr. Rowland has over 14 years of experience in biomedical imaging and a further 6 years experience in instrumentation for physics experiments. He is the Principal Research Scientist at the Center for Molecular and Genomic Imaging (CMGI) at UC Davis. Since 2007, he has been responsible for collaborating with principal investigators in the design and implementation of imaging experiments on the full compliment of small animal in vivo imaging technologies at CMGI including MRI, microCT, Optical and microPET.
A magnetic resonance imaging study of early brain injury in a rat model of acute DFP intoxication.
Neurotoxicology. 2017 Nov 26;:
Authors: Hobson BA, Rowland DJ, Supasai S, Harvey DJ, Lein PJ, Garbow JR
Current treatments for seizures induced by organophosphates do not protect sufficiently against progressive neurodegeneration or delayed cognitive impairment. Developing more effective therapeutic approaches has been challenging because the pathogenesis of these delayed consequences is poorly defined. Using magnetic resonance imaging (MRI), we previously reported brain lesions that persist for months in a rat model of acute intoxication with the OP, diisopropylfluorophosphate (DFP). However, the early spatiotemporal progression of these lesions remains unknown. To address this data gap, we used in vivo MRI to longitudinally monitor brain lesions during the first 3 d following acute DFP intoxication. Adult male Sprague Dawley rats acutely intoxicated with DFP (4mg/kg, sc) were MR imaged at 6, 12, 18, 24, 48, 72h post-DFP, and their brains then taken for correlative histology to assess neurodegeneration using FluoroJade C (FJC) staining. Acute DFP intoxication elicited moderate-to-severe seizure activity. T2-weighted (T2w) anatomic imaging revealed prominent lesions within the thalamus, piriform cortex, cerebral cortex, hippocampus, corpus striatum, and substantia nigra that corresponded to neurodegeneration, evident as bands of FJC positive cells. Semi-quantitative assessment of lesion severity demonstrated significant regional variation in the onset and progression of injury, and suggested that lesion severity may be modulated by isoflurane anesthesia. These results imply that the timing of therapeutic intervention for attenuating brain injury following OP intoxication may be regionally dependent, and that longitudinal assessment of OP-induced damage by MRI may be a powerful tool for assessing therapeutic response.
PMID: 29183789 [PubMed - as supplied by publisher]
Pair bond formation leads to a sustained increase in global cerebral glucose metabolism in monogamous male titi monkeys (Callicebus cupreus).
Neuroscience. 2017 Apr 21;348:302-312
Authors: Maninger N, Hinde K, Mendoza SP, Mason WA, Larke RH, Ragen BJ, Jarcho MR, Cherry SR, Rowland DJ, Ferrer E, Bales KL
Social bonds, especially attachment relationships, are crucial to our health and happiness. However, what we know about the neural substrates of these bonds is almost exclusively limited to rodent models and correlational experiments in humans. Here, we used socially monogamous non-human primates, titi monkeys (Callicebus cupreus) to experimentally examine changes in regional and global cerebral glucose metabolism (GCGM) during the formation and maintenance of pair bonds. Baseline positron emission tomography (PET) scans were taken of thirteen unpaired male titi monkeys. Seven males were then experimentally paired with females, scanned and compared, after one week, to six age-matched control males. Five of the six control males were then also paired and scanned after one week. Scans were repeated on all males after four months of pairing. PET scans were coregistered with structural magnetic resonance imaging (MRI), and region of interest (ROI) analysis was carried out. A primary finding was that paired males showed a significant increase in [(18)F]-fluorodeoxyglucose (FDG) uptake in whole brain following one week of pairing, which is maintained out to four months. Dopaminergic, "motivational" areas and those involved in social behavior showed the greatest change in glucose uptake. In contrast, control areas changed only marginally more than GCGM. These findings confirm the large effects of social bonds on GCGM. They also suggest that more studies should examine how social manipulations affect whole-brain FDG uptake, as opposed to assuming that it does not change across condition.
PMID: 28242440 [PubMed - in process]
Persistent neuroinflammation and cognitive impairment in a rat model of acute diisopropylfluorophosphate intoxication.
J Neuroinflammation. 2016 Oct 12;13(1):267
Authors: Flannery BM, Bruun DA, Rowland DJ, Banks CN, Austin AT, Kukis DL, Li Y, Ford BD, Tancredi DJ, Silverman JL, Cherry SR, Lein PJ
BACKGROUND: Acute intoxication with organophosphorus (OP) cholinesterase inhibitors can trigger convulsions that progress to life-threatening status epilepticus. Survivors face long-term morbidity including mild-to-severe decline in memory. It is posited that neuroinflammation plays a key role in the pathogenesis of OP-induced neuropsychiatric deficits. Rigorous testing of this hypothesis requires preclinical models that recapitulate relevant phenotypic outcomes. Here, we describe a rat model of acute intoxication with the OP diisopropylfluorophosphate (DFP) that exhibits persistent neuroinflammation and cognitive impairment.
METHODS: Neuroinflammation, neurodegeneration, and cognitive function were compared in adult male Sprague Dawley rats injected with an acutely toxic dose of DFP vs. vehicle controls at multiple time points up to 36 days post-exposure. Neuroinflammation was quantified using immunohistochemical biomarkers of microglia (ionized calcium-binding adapter molecule 1, IBA1) and activated astrocytes (glial fibrillary acidic protein, GFAP) and positron emission tomography (PET) imaging of [(11)C]-(R)-PK11195, a ligand for the 18-kDa mitochondrial membrane translocator protein (TSPO). FluoroJade-B staining was used to assess neurodegeneration; Pavlovian conditioning, to assess cognitive function.
RESULTS: Animals exhibited moderate-to-severe seizures within minutes of DFP injection that continued for up to 6 h post-injection. As indicated by IBA1 and GFAP immunoreactivity and by PET imaging of TSPO, acute DFP intoxication triggered neuroinflammation in the hippocampus and cortex during the first 3 days that peaked at 7 days and persisted to 21 days post-exposure in most animals. Neurodegeneration was detected in multiple brain regions from 1 to 14 days post-exposure. All DFP-intoxicated animals exhibited significant deficits in contextual fear conditioning at 9 and 20 days post-exposure compared to vehicle controls. Whole-brain TSPO labeling positively correlated with seizure severity score, but did not correlate with performance in the contextual fear-conditioning task.
CONCLUSIONS: We describe a preclinical model in which acute DFP intoxication causes seizures, persistent neuroinflammation, neurodegeneration, and memory impairment. The extent of the neuroinflammatory response is influenced by seizure severity. However, the observation that a subset of animals with moderate seizures and minimal TSPO labeling exhibited cognitive deficits comparable to those of animals with severe seizures and significant TSPO labeling suggests that DFP may impair learning and memory circuitry via mechanisms independent of seizures or neuroinflammation.
PMID: 27733171 [PubMed - in process]
High-throughput discovery of novel developmental phenotypes.
Nature. 2016 Sep 22;537(7621):508-514
Authors: Dickinson ME, Flenniken AM, Ji X, Teboul L, Wong MD, White JK, Meehan TF, Weninger WJ, Westerberg H, Adissu H, Baker CN, Bower L, Brown JM, Caddle LB, Chiani F, Clary D, Cleak J, Daly MJ, Denegre JM, Doe B, Dolan ME, Edie SM, Fuchs H, Gailus-Durner V, Galli A, Gambadoro A, Gallegos J, Guo S, Horner NR, Hsu CW, Johnson SJ, Kalaga S, Keith LC, Lanoue L, Lawson TN, Lek M, Mark M, Marschall S, Mason J, McElwee ML, Newbigging S, Nutter LM, Peterson KA, Ramirez-Solis R, Rowland DJ, Ryder E, Samocha KE, Seavitt JR, Selloum M, Szoke-Kovacs Z, Tamura M, Trainor AG, Tudose I, Wakana S, Warren J, Wendling O, West DB, Wong L, Yoshiki A, International Mouse Phenotyping Consortium, Jackson Laboratory, Infrastructure Nationale PHENOMIN, Institut Clinique de la Souris (ICS), Charles River Laboratories, MRC Harwell, Toronto Centre for Phenogenomics, Wellcome Trust Sanger Institute, RIKEN BioResource Center, MacArthur DG, Tocchini-Valentini GP, Gao X, Flicek P, Bradley A, Skarnes WC, Justice MJ, Parkinson HE, Moore M, Wells S, Braun RE, Svenson KL, de Angelis MH, Herault Y, Mohun T, Mallon AM, Henkelman RM, Brown SD, Adams DJ, Lloyd KC, McKerlie C, Beaudet AL, Bućan M, Murray SA
Approximately one-third of all mammalian genes are essential for life. Phenotypes resulting from knockouts of these genes in mice have provided tremendous insight into gene function and congenital disorders. As part of the International Mouse Phenotyping Consortium effort to generate and phenotypically characterize 5,000 knockout mouse lines, here we identify 410 lethal genes during the production of the first 1,751 unique gene knockouts. Using a standardized phenotyping platform that incorporates high-resolution 3D imaging, we identify phenotypes at multiple time points for previously uncharacterized genes and additional phenotypes for genes with previously reported mutant phenotypes. Unexpectedly, our analysis reveals that incomplete penetrance and variable expressivity are common even on a defined genetic background. In addition, we show that human disease genes are enriched for essential genes, thus providing a dataset that facilitates the prioritization and validation of mutations identified in clinical sequencing efforts.
PMID: 27626380 [PubMed - in process]
Compact cold stage for micro-computerized tomography imaging of chilled or frozen samples.
Rev Sci Instrum. 2014 Apr;85(4):043708
Authors: Hullar T, Paige DF, Rowland DJ, Anastasio C
High resolution X-ray microCT (computerized tomography) can be used to image a variety of objects, including temperature-sensitive materials. In cases where the sample must be chilled or frozen to maintain sample integrity, either the microCT machine itself must be placed in a refrigerated chamber, or a relatively expensive commercial cold stage must be purchased. We describe here the design and construction of a low-cost custom cold stage suitable for use in a microCT imaging system. Our device uses a boron nitride sample holder, two-stage Peltier cooler, fan-cooled heat sink, and electronic controller to maintain sample temperatures as low as -25 °C ± 0.2 °C for the duration of a tomography acquisition. The design does not require modification to the microCT machine, and is easily installed and removed. Our custom cold stage represents a cost-effective solution for refrigerating CT samples for imaging, and is especially useful for shared equipment or machines unsuitable for cold room use.
PMID: 24784619 [PubMed - indexed for MEDLINE]
A LINE-1 insertion in DLX6 is responsible for cleft palate and mandibular abnormalities in a canine model of Pierre Robin sequence.
PLoS Genet. 2014 Apr;10(4):e1004257
Authors: Wolf ZT, Leslie EJ, Arzi B, Jayashankar K, Karmi N, Jia Z, Rowland DJ, Young A, Safra N, Sliskovic S, Murray JC, Wade CM, Bannasch DL
Cleft palate (CP) is one of the most commonly occurring craniofacial birth defects in humans. In order to study cleft palate in a naturally occurring model system, we utilized the Nova Scotia Duck Tolling Retriever (NSDTR) dog breed. Micro-computed tomography analysis of CP NSDTR craniofacial structures revealed that these dogs exhibit defects similar to those observed in a recognizable subgroup of humans with CP: Pierre Robin Sequence (PRS). We refer to this phenotype in NSDTRs as CP1. Individuals with PRS have a triad of birth defects: shortened mandible, posteriorly placed tongue, and cleft palate. A genome-wide association study in 14 CP NSDTRs and 72 unaffected NSDTRs identified a significantly associated region on canine chromosome 14 (24.2 Mb-29.3 Mb; p(raw )= 4.64 × 10(-15)). Sequencing of two regional candidate homeobox genes in NSDTRs, distal-less homeobox 5 (DLX5) and distal-less homeobox 6 (DLX6), identified a 2.1 kb LINE-1 insertion within DLX6 in CP1 NSDTRs. The LINE-1 insertion is predicted to insert a premature stop codon within the homeodomain of DLX6. This prompted the sequencing of DLX5 and DLX6 in a human cohort with CP, where a missense mutation within the highly conserved DLX5 homeobox of a patient with PRS was identified. This suggests the involvement of DLX5 in the development of PRS. These results demonstrate the power of the canine animal model as a genetically tractable approach to understanding naturally occurring craniofacial birth defects in humans.
PMID: 24699068 [PubMed - indexed for MEDLINE]
The temporal role of leptin within fracture healing and the effect of local application of recombinant leptin on fracture healing.
J Orthop Trauma. 2013 Nov;27(11):656-62
Authors: Khan SN, DuRaine G, Virk SS, Fung J, Rowland DJ, Reddi AH, Lee MA
OBJECTIVE: We hypothesized that leptin is expressed in a specific time sequence during fracture healing, and its deficiency leads to impaired healing.
METHODS: Control (C57BL/6) mice and leptin -/- obese (ob/ob) mice were used. ARM 1:: Fracture callus was harvested at 1, 3, 5, 7, 10, 14, and 21 days (n = 8/time point) after closed middiaphyseal femur fractures were created in 56 C57BL/6 mice, and reverse transcriptase polymerase chain reaction analysis was then performed. Levels of leptin were tracked at each time point listed. ARM 2:: Forty-two C57BL/6 controls and 42 ob/ob mice underwent open stabilized middiaphyseal femur fractures, and tissues were harvested at 14, 21, and 42 days and radiographic, histologic, and quantitative computerized tomography analyses were performed. ARM 3:: Murine recombinant leptin was applied directly at the newly created fracture site in 2 separate groups (10 or 100 μg of leptin) of 42 ob/ob mice. Two-factor analysis of variance and the Student t-test were used for statistical analysis.
RESULTS: The time course of Leptin mRNA expression within a fracture callus was detected. Delay in callus maturation was demonstrated radiographically and histologically in the ob/ob mice. ob/ob fractures had an increase in total callus volume by quantitative computerized tomography (P < 0.05). Application of local leptin at both doses reversed the delay in healing.
CONCLUSIONS: Leptin is expressed in a unique time course during fracture healing and leptin deficiency leads to impaired fracture healing that reverses by local application of leptin.
PMID: 23287761 [PubMed - indexed for MEDLINE]
Chelyabinsk airburst, damage assessment, meteorite recovery, and characterization.
Science. 2013 Nov 29;342(6162):1069-73
Authors: Popova OP, Jenniskens P, Emel'yanenko V, Kartashova A, Biryukov E, Khaibrakhmanov S, Shuvalov V, Rybnov Y, Dudorov A, Grokhovsky VI, Badyukov DD, Yin QZ, Gural PS, Albers J, Granvik M, Evers LG, Kuiper J, Kharlamov V, Solovyov A, Rusakov YS, Korotkiy S, Serdyuk I, Korochantsev AV, Larionov MY, Glazachev D, Mayer AE, Gisler G, Gladkovsky SV, Wimpenny J, Sanborn ME, Yamakawa A, Verosub KL, Rowland DJ, Roeske S, Botto NW, Friedrich JM, Zolensky ME, Le L, Ross D, Ziegler K, Nakamura T, Ahn I, Lee JI, Zhou Q, Li XH, Li QL, Liu Y, Tang GQ, Hiroi T, Sears D, Weinstein IA, Vokhmintsev AS, Ishchenko AV, Schmitt-Kopplin P, Hertkorn N, Nagao K, Haba MK, Komatsu M, Mikouchi T, Chelyabinsk Airburst Consortium
The asteroid impact near the Russian city of Chelyabinsk on 15 February 2013 was the largest airburst on Earth since the 1908 Tunguska event, causing a natural disaster in an area with a population exceeding one million. Because it occurred in an era with modern consumer electronics, field sensors, and laboratory techniques, unprecedented measurements were made of the impact event and the meteoroid that caused it. Here, we document the account of what happened, as understood now, using comprehensive data obtained from astronomy, planetary science, geophysics, meteorology, meteoritics, and cosmochemistry and from social science surveys. A good understanding of the Chelyabinsk incident provides an opportunity to calibrate the event, with implications for the study of near-Earth objects and developing hazard mitigation strategies for planetary protection.
PMID: 24200813 [PubMed - indexed for MEDLINE]