ABSTRACT
Epidemiological and experimental data suggest that obesity exacerbates the health effects of air pollutants such as ozone (O3). Maternal inactivity and calorically rich diets lead to offspring that show signs of obesity. Exacerbated O3 susceptibility of offspring could thus be manifested by maternal obesity. Thirty-day-old female Long-Evans rats were fed a control (CD) or high-fat (HF) (60% calories) diet for 6 wks and then bred. GD1 rats were then housed with a running wheel (RW) or without a wheel (SED) until parturition, creating four groups of offspring: CD-SED, CD-RW, HF-SED and HF-RW. HF diet was terminated at PND 35 and all offspring were placed on CD. Body weight and %fat of dams were greatest in order; HF-SED > HF-RW > CD-SED > CD-RW. Adult offspring were exposed to O3 for two consecutive days (0.8 ppm, 4 h/day). Glucose tolerance tests (GTT), ventilatory parameters (plethysmography), and bronchoalveolar fluid (BALF) cell counts and protein biomarkers were performed to assess response to O3. Exercise and diet altered body weight and %fat of young offspring. GTT, ventilation and BALF cell counts were exacerbated by O3 with responses markedly exacerbated in males. HF diet and O3 led to significant exacerbation of several BALF parameters: total cell count, neutrophils and lymphocytes were increased in male HF-SED versus CD-SED. Males were hyperglycemic after O3 exposure and exhibited exacerbated GTT responses. Ventilatory dysfunction was also exacerbated in males. Maternal exercise had minimal effects on O3 response. The results of this exploratory study suggest a link between maternal obesity and susceptibility to O3 in their adult offspring in a sex-specific manner.
Subject(s)
Air Pollutants/toxicity , Diet, High-Fat , Obesity , Ozone/toxicity , Prenatal Exposure Delayed Effects , Sedentary Behavior , Animals , Blood Glucose/drug effects , Bronchoalveolar Lavage Fluid/chemistry , Bronchoalveolar Lavage Fluid/cytology , Cell Count , Female , Male , Pregnancy , Pulmonary Ventilation/drug effects , Rats , Rats, Long-Evans , Sex CharacteristicsABSTRACT
The hippocampus maintains a capacity for neurogenesis throughout life, a capacity that is reduced in models of adult onset hypothyroidism. The effects of developmental thyroid hormone (TH) insufficiency on neurogenesis in the adult hippocampus, however, has not been examined. Graded degrees of TH insufficiency were induced in pregnant rat dams by administration of 0, 3 or 10ppm of 6-propylthiouracil (PTU) in drinking water from gestational day (GD) 6 until weaning. Body, brain, and hippocampal weight were reduced on postnatal day (PN) 14, 21, 78 and hippocampal volume was smaller at the 10 but not 3ppm dose level. A second experiment examined adult hippocampal neurogenesis following developmental or adult onset hypothyroidism. Two male offspring from 0 and 3ppm exposed dams were either maintained on control water or exposed to 3ppm PTU to create 4 distinct treatment conditions (Control-Control; Control-PTU, PTU-Control, PTU-PTU) based on developmental and adult exposures. Beginning on the 28th day of adult exposure to 0 or 3ppm PTU, bromodeoxyuridine (BrdU, 50mg/kg, ip) was administered twice daily for 5days, and one male from each treatment was sacrificed 24h and 28days after the last BrdU dose and brains processed for immunohistochemistry. Although no volume changes were seen in the hippocampus of the neonate at 3ppm, thinning of the granule cell layer emerged in adulthood. Developmental TH insufficiency produced a reduction in newly born cells, reducing BrdU+ve cells at 1 with no further reduction at 28-days post-BrdU. Similar findings were obtained using the proliferative cell marker Ki67. Neuronal differentiations was also altered with fewer doublecortin (Dcx) expressing cells and a higher proportion of immature Dcx phenotypes seen after developmental but not adult TH insufficiency. An impaired capacity for neurogenesis may contribute to impairments in synaptic plasticity and cognitive deficits previously reported by our laboratory and others following moderate degrees of developmental TH insufficiency induced by this PTU model.
Subject(s)
Hippocampus/pathology , Hypothyroidism/pathology , Neurogenesis/drug effects , Prenatal Exposure Delayed Effects/physiopathology , Analysis of Variance , Animals , Animals, Newborn , Antimetabolites/toxicity , Bromodeoxyuridine/metabolism , Cell Count , Cell Differentiation/drug effects , Disease Models, Animal , Dose-Response Relationship, Drug , Doublecortin Domain Proteins , Doublecortin Protein , Female , Hippocampus/embryology , Hippocampus/growth & development , Hypothyroidism/blood , Hypothyroidism/chemically induced , Ki-67 Antigen/metabolism , Microtubule-Associated Proteins/metabolism , Neuropeptides/metabolism , Pregnancy , Prenatal Exposure Delayed Effects/chemically induced , Propylthiouracil/toxicity , Rats , Rats, Long-Evans , Thyroid Hormones/bloodABSTRACT
The prevalence of a sedentary (SED) life style combined with calorically rich diets has spurred the rise in childhood obesity, which, in turn, translates to adverse health effects in adulthood. Obesity and lack of active (ACT) lifestyle may increase susceptibility to air pollutants. We housed 22-day-old female Long-Evans rats in a cage without (SED) or with a running wheel (ACT). After 10 wk the rats ran 310 ± 16.3 km. Responses of SED and ACT rats to whole-body O3 (0, 0.25, 0.5, or 1.0 ppm; 5 h/day for 2 days) was assessed. Glucose tolerance testing (GTT) was performed following the first day of O3 ACT rats had less body fat and an improved glucose GTT. Ventilatory function (plethysmography) of SED and ACT groups was similarly impaired by O3 Bronchoalveolar lavage fluid (BALF) was collected after the second O3 exposure. SED and ACT rats were hyperglycemic following 1.0 ppm O3 GTT was impaired by O3 in both groups; however, ACT rats exhibited improved recovery to 0.25 and 1.0 ppm O3 BALF cell neutrophils and total cells were similarly increased in ACT and SED groups exposed to 1.0 ppm O3 O3-induced increase in eosinophils was exacerbated in SED rats. Chronic exercise from postweaning to adulthood improved some of the metabolic and pulmonary responses to O3 (GTT and eosinophils) but several other parameters were unaffected. The reduction in O3-induced rise in BALF eosinophils in ACT rats suggests a possible link between a SED lifestyle and incidence of asthma-related symptoms from O3.
Subject(s)
Aging/physiology , Ozone/pharmacology , Physical Conditioning, Animal , Weaning , Animals , Biomarkers/blood , Body Composition/drug effects , Bronchoalveolar Lavage Fluid/cytology , Cell Count , Disease Susceptibility , Female , Plethysmography , Rats, Long-Evans , Time FactorsABSTRACT
Body fat serves as a storage compartment for lipophilic pollutants and affects the pharmacokinetics of many toxic chemicals. Understanding how body fat varies with gender, strain, and age may be essential for development of experimental models to study mechanisms of toxicity. Nuclear magnetic resonance (NMR)-based analysis serves as a noninvasive means of assessing proportions of fat, lean, and fluid in rodents over their lifetime. The aim of this study was to track changes in body composition of male and female Long-Evans (LE), Sprague-Dawley (SD), Fischer (F334), and Brown Norway (BN) rats from postweaning over a >2-yr period. Percent fat of preweaned LE and SD rats was markedly higher compared to the other strains. LE and SD strains displayed marked increases in body fat from weaning to 8 mo of age. Postweaned F344 male and females showed relatively low levels of percent fat; however, at 2 yr of age percent fat of females was equal to that of SD and LE in females. BN rats showed the highest levels of lean tissue and lowest levels of fat. Percent fat of the BN strain rose at the slowest rate as they aged. Percent fluid was consistently higher in males for all strains. Females tended to have higher percent fat than males in LE, SD, and F344 strains. Assessing changes in body fat as well as lean and fluid of various strains of male and female rats over their lifetime may prove useful in many research endeavors, including pharmacokinetics of lipophilic toxicants, mechanisms underlying obesity, and metabolic disorders.
Subject(s)
Body Composition/genetics , Rats/physiology , Age Factors , Animals , Female , Longitudinal Studies , Male , Rats/genetics , Rats, Inbred BN/genetics , Rats, Inbred BN/physiology , Rats, Inbred F344/genetics , Rats, Inbred F344/physiology , Rats, Long-Evans/genetics , Rats, Long-Evans/physiology , Rats, Sprague-Dawley/genetics , Rats, Sprague-Dawley/physiology , Sex Factors , Species SpecificityABSTRACT
Diet-induced obesity has been suggested to lead to increased susceptibility to air pollutants such as ozone (O3); however, there is little experimental evidence. Thirty day old male and female Brown Norway rats were fed a normal, high-fructose or high-fat diet for 12 weeks and then exposed to O3 (acute - air or 0.8 ppm O3 for 5 h, or subacute - air or 0.8 ppm O3 for 5 h/d 1 d/week for 4 weeks). Body composition was measured non-invasively using NMR. Ventilatory parameters and exploratory behavior were measured after the third week of subacute exposure. Bronchoalveolar lavage fluid (BALF) and blood chemistry data were collected 18 h after acute O3 and 18 h after the fourth week of subacute O3. The diets led to increased body fat in male but not female rats. O3-induced changes in ventilatory function were either unaffected or improved with the fructose and fat diets. O3-induced reduction in exploratory behavior was attenuated with fructose and fat diets in males and partially in females. O3 led to a significant decrease in body fat of males fed control diet but not the fructose or fat diet. O3 led to significant increases in BALF eosinophils, increase in albumin, and reductions in macrophages. Female rats appeared to be more affected than males to O3 regardless of diet. Overall, treatment with high-fructose and high-fat diets attenuated some O3 induced effects on pulmonary function, behavior, and metabolism. Exacerbation of toxicity was observed less frequently.
Subject(s)
Air Pollutants/toxicity , Diet, High-Fat , Fructose/pharmacology , Oxidants, Photochemical/toxicity , Ozone/toxicity , Albumins/metabolism , Animals , Blood Cell Count , Body Composition/drug effects , Body Weight/drug effects , Bronchoalveolar Lavage Fluid/cytology , Eating/drug effects , Eosinophils/cytology , Female , Lung/drug effects , Lung/physiology , Macrophages/cytology , Male , Motor Activity/drug effects , Pulmonary Ventilation/drug effects , RatsABSTRACT
Chronic exercise is considered as one of the most effective means of countering symptoms of the metabolic syndrome (MS) such as obesity and hyperglycemia. Rodent models of forced or voluntary exercise are often used to study the mechanisms of MS and type 2 diabetes. However, there is little known on the impact of genetic strain on the metabolic response to exercise. We studied the effects of housing rats with running wheels (RW) for 65 days compared to sedentary (SED) housing in five female rat strains: Sprague-Dawley (SD), Long-Evans (LE), Wistar (WIS), spontaneously hypertensive (SHR), and Wistar-Kyoto (WKY). Key parameters measured were total distance run, body composition, food consumption, motor activity, ventilatory responses by plethysmography, and resting metabolic rate (MR). WKY and SHR ran significantly more than the WIS, LE, and SD strains. Running-induced reduction in body fat was affected by strain but not by distance run. LE's lost 6% fat after 21 d of running whereas WKY's lost 2% fat but ran 40% more than LE's. LE and WIS lost body weight while the SHR and WKY strains gained weight during running. Food intake with RW was markedly increased in SHR, WIS, and WKY while LE and SD showed modest increases. Exploratory motor activity was reduced sharply by RW in all but the SD strain. Ventilatory parameters were primarily altered by RW in the SHR, WKY, and WIS strains. MR was unaffected by RW. In an overall ranking of physiological and behavioral responses to RW, the SD strain was considered the least responsive whereas the WIS was scored as most responsive. In terms of RW-induced fat loss, the LE strain appears to be the most ideal. These results should be useful in the future selection of rat models to study benefits of volitional exercise.
Subject(s)
Adipose Tissue/metabolism , Basal Metabolism/genetics , Eating/genetics , Motor Activity/genetics , Pulmonary Ventilation/genetics , Weight Loss/genetics , Animals , Body Composition , Drinking , Exploratory Behavior , Female , Rats , Rats, Inbred StrainsABSTRACT
Setting exposure standards for environmental pollutants may consider the aged as a susceptible population but the few published studies assessing susceptibility of the aged to air pollutants are inconsistent. Episodic ozone (O3) is more reflective of potential exposures occurring in human populations and could be more harmful to the aged. This study used radiotelemetry to monitor heart rate (HR), core temperature (T(c)) and motor activity (MA) in adult (9-12 months) and senescent (20-24 months) male, Brown Norway rats exposed to episodic O3 (6 h/day of 1 ppm O3 for 2 consecutive days/week for 13 weeks). Acute O3 initially led to marked drops in HR and T(c). As exposures progressed each week, there was diminution in the hypothermic and bradycardic effects of O3. Senescent rats were less affected than adults. Acute responses were exacerbated on the second day of O3 exposure with adults exhibiting greater sensitivity. During recovery following 2 d of O3, adult and senescent rats exhibited an elevated T(c) and HR during the day but not at night, an effect that persisted for at least 48 h after O3 exposure. MA was elevated in adults but not senescent rats during recovery from O3. Overall, acute effects of O3, including reductions in HR and T(c), were attenuated in senescent rats. Autonomic responses during recovery, included an elevation in T(c) with a pattern akin to that of a fever and rise in HR that were independent of age. An attenuated inflammatory response to O3 in senescent rats may explain the relatively heightened physiological response to O3 in younger rats.
Subject(s)
Aging , Air Pollutants/toxicity , Bradycardia/chemically induced , Hypothermia/chemically induced , Inhalation Exposure/adverse effects , Neurotoxicity Syndromes/physiopathology , Ozone/toxicity , Animals , Behavior, Animal/drug effects , Body Temperature Regulation/drug effects , Heart Rate/drug effects , Male , Motor Activity/drug effects , Oxidants, Photochemical/toxicity , Rats, Inbred BN , Severity of Illness Index , Tachyphylaxis , Toxicity Tests, Acute , Toxicity Tests, Subchronic , ToxicokineticsABSTRACT
Neuronal assemblies within the nervous system produce electrical activity that can be recorded in terms of action potential patterns. Such patterns provide a sensitive endpoint to detect effects of a variety of chemical and physical perturbations. They are a function of synaptic changes and do not necessarily involve structural alterations. In vitro neuronal networks (NNs) grown on micro-electrode arrays (MEAs) respond to neuroactive substances as well as the in vivo brain. As such, they constitute a valuable tool for investigating changes in the electrophysiological activity of the neurons in response to chemical exposures. However, the reproducibility of NN responses to chemical exposure has not been systematically documented. To this purpose six independent laboratories (in Europe and in USA) evaluated the response to the same pharmacological compounds (Fluoxetine, Muscimol, and Verapamil) in primary neuronal cultures. Common standardization principles and acceptance criteria for the quality of the cultures have been established to compare the obtained results. These studies involved more than 100 experiments before the final conclusions have been drawn that MEA technology has a potential for standard in vitro neurotoxicity/neuropharmacology evaluation. The obtained results show good intra- and inter-laboratory reproducibility of the responses. The consistent inhibitory effects of the compounds were observed in all the laboratories with the 50% Inhibiting Concentrations (IC(50)s) ranging from: (mean ± SEM, in µM) 1.53 ± 0.17 to 5.4 ± 0.7 (n = 35) for Fluoxetine, 0.16 ± 0.03 to 0.38 ± 0.16 µM (n = 35) for Muscimol, and 2.68 ± 0.32 to 5.23 ± 1.7 (n = 32) for Verapamil. The outcome of this study indicates that the MEA approach is a robust tool leading to reproducible results. The future direction will be to extend the set of testing compounds and to propose the MEA approach as a standard screen for identification and prioritization of chemicals with neurotoxicity potential.
ABSTRACT
The release of transmitter at neuromuscular junctions (NMJ) of the opener muscle in crayfish is quantal in nature. This NMJ offers the advantage of being able to record quantal events at specific visually identified release sites, thus allowing measurement of the physiological parameters of vesicle release and its response to be directly correlated with synaptic structure. These experiments take advantage of areas between the varicosities on the nerve terminal that we define as "stems." Stems were chosen as the region to study because of their low synaptic output due to fewer synaptic sites. Through 3D reconstruction from hundreds of serial sections, obtained by transmission electron microscopy (TEM), at a site in which focal macropatch recordings were obtained, the number of synapses and AZs are revealed. Thus, physiological profiles with various stimulation conditions can be assessed in regards to direct synaptic structure. Here, we used the properties of the quantal shape to determine if distinct subsets of quantal signatures existed and if differences in the distributions are present depending on the frequency of stimulation. Such a quantal signature could come about by parameters of area, rise time, peak amplitude, latency, and tau decay. In this study, it is shown that even at defined sites on the stem, with few active zones, synaptic transmission is still complex and the quantal responses appear to be variable even for a given synapse over time. In this study, we could not identify a quantal signature for the conditions utilized.
Subject(s)
Motor Neurons/physiology , Motor Neurons/ultrastructure , Presynaptic Terminals/physiology , Presynaptic Terminals/ultrastructure , Synaptic Transmission/physiology , Action Potentials/physiology , Animals , Astacoidea , Microscopy, Electron, Transmission , Synapses/physiology , Synapses/ultrastructureABSTRACT
We provide both theoretical and computational improvements to the analysis of synaptic transmission data. Theoretically, we demonstrate the correlation structure of observations within evoked postsynaptic potentials (EPSP) are consistent with multiple random draws from a common autoregressive moving-average (ARMA) process of order (2, 2). We use this observation and standard time series results to construct a statistical hypothesis testing procedure for determining whether a given trace is an EPSP. Computationally, we implement this method in R, a freeware statistical language, which reduces the amount of time required for the investigator to classify traces into EPSPs or non-EPSPs and eliminates investigator subjectivity from this classification. In addition, we provide a computational method for calculating common functionals of EPSPs (peak amplitude, decay rate, etc.). The methodology is freely available over the internet. The automated procedure to index the quantal characteristics greatly facilitates determining if any one or multiple parameters are changing due to experimental conditions. In our experience, the software reduces the time required to perform these analyses from hours to minutes.
Subject(s)
Electrophysiology/methods , Evoked Potentials/physiology , Excitatory Postsynaptic Potentials/physiology , Models, Neurological , Synaptic Transmission/physiology , Animals , Area Under Curve , Artifacts , Astacoidea , Classification , Computational Biology , Presynaptic Terminals/physiologyABSTRACT
The reserve pool (RP) and readily releasable pool (RRP) of synaptic vesicles within presynaptic nerve terminals were physiologically differentiated into distinctly separate functional groups. This was accomplished in glutamatergic nerve terminals by blocking the glutamate transporter with dl-threo-beta-benzyloxyaspartate (TBOA; 10 microM) during electrical stimulation with either 40 Hz of 10 pulses within a train or 20- or 50-Hz continuous stimulation. The 50-Hz continuous stimulation decreased the excitatory postsynaptic potential amplitude 60 min faster than for the 20-Hz continuous stimulation in the presence of TBOA (P < 0.05). There was no significant difference between the train stimulation and 20-Hz continuous stimulation in the run-down time in the presence of TBOA. After TBOA-induced synaptic depression, the excitatory postsynaptic potentials were rapidly (<1 min) revitalized by exposure to serotonin (5-HT, 1 microM) in every preparation tested (P < 0.05). At this glutamatergic nerve terminal, 5-HT promotes an increase probability of vesicular docking and fusion. Quantal recordings made directly at nerve terminals revealed smaller quantal sizes with TBOA exposure with a marked increase in quantal size as well as a continual appearance of smaller quanta upon 5-HT treatment after TBOA-induced depression. Thus 5-HT was able to recruit vesicles from the RP that were not rapidly depleted by acute TBOA treatment and electrical stimulation. The results support the notion that the RRP is selectively activated during rapid electrical stimulation sparing the RP; however, the RP can be recruited by the neuromodulator 5-HT. This suggests at least two separate kinetic and distinct regulatory paths for vesicle recycling within the presynaptic nerve terminal.
Subject(s)
Presynaptic Terminals/metabolism , Synaptic Vesicles/metabolism , Amino Acid Transport System X-AG/antagonists & inhibitors , Amino Acid Transport System X-AG/metabolism , Animals , Aspartic Acid/pharmacology , Astacoidea , Electric Stimulation , Excitatory Amino Acids/metabolism , Excitatory Postsynaptic Potentials , Kinetics , Membrane Fusion , Motor Neurons/drug effects , Motor Neurons/metabolism , Muscles/innervation , Presynaptic Terminals/drug effects , Presynaptic Terminals/ultrastructure , Serotonin/pharmacology , Synaptic Transmission/drug effects , Synaptic Vesicles/drug effects , Synaptic Vesicles/ultrastructureABSTRACT
Forty-four adults with aspirin poisoning were treated with oral fluids only, standard forced alkaline diuresis, forced diuresis alone, or sodium bicarbonate (alkali) alone. Alkali alone was at least as effective and possibly more effective than forced alkaline diuresis in enhancing salicylate removal. Unlike the diuresis regimens it did not cause fluid retention or biochemical disturbances. The renal excretion of salicylate depends much more on urine pH than flow rate, and forced diuresis alone had little useful effect. In overdosage aspirin causes sodium and fluid retention and may impair renal function. Attempts to force a diuresis are potentially hazardous and the spurious fall in plasma salicylate concentration caused by haemodilution gives a false impression of efficacy. Further studies are required to determine the optimum treatment for salicylate poisoning.