Temperature dependence of electrocommunication signals and their underlying neural rhythms in the weakly electric fish, Apteronotus leptorhynchus

Weakly electric fish emit an electric communication signal that is controlled by a highly specialized neural circuit. In Apteronotus, the continuous electric organ discharge (EOD) is generated by electrotonically coupled neurons in the hindbrain pacemaker nucleus, and transient EOD modulations involve chemical synapses from descending midbrain and thalamic prepacemaker nuclei. We characterized the effects of temperature change (18-32 degrees C) on both the continuous EOD and EOD modulations, chirps, in A. leptorhynchus. EOD frequency was linearly related to temperature (Q(10)=1.62). By contrast, the temperature dependence of EOD amplitude changed with temperature. Amplitude increased steeply with temperature below 25 degrees C (Q(10)=2.0), but increased only gradually above 25 degrees C (Q(10)=1.15). EOD waveform, and consequently harmonic content, was also affected by temperature. The amplitude of the second harmonic was relatively high at both low and high temperature and relatively low at intermediate temperatures. The amplitude of the third harmonic increased monotonically with temperature. Thus, temperature has qualitative as well as quantitative effects on the production of the EOD. Chirp rate (Q(1)0=3.2) had a higher temperature dependence than that of the continuous EOD, which likely reflects its reliance on chemical rather than electrotonic synapses. In vitro pacemaker firing frequency had a similar, but slightly higher Q(10) (1.82) than that of the EOD frequency.

Pharmacological characterization of ionic currents that regulate the pacemaker rhythm in a weakly electric fish

Electric organ discharge (EOD) frequency in the brown ghost knifefish (Apteronotus leptorhynchus) is sexually dimorphic, steroid-regulated, and determined by the discharge rates of neurons in the medullary pacemaker nucleus (Pn). We pharmacologically characterized ionic currents that regulate the firing frequency of Pn neurons to determine which currents contribute to spontaneous oscillations of these neurons and to identify putative targets of steroid action in regulating sexually dimorphic EOD frequency. Tetrodotoxin (TTX) initially reduced spike frequency, and then reduced spike amplitude and stopped pacemaker activity. The sodium channel blocker muO-conotoxin MrVIA also reduced spike frequency, but did not affect spike amplitude or production. Two potassium channel blockers, 4-aminopyridine (4AP) and kappaA-conotoxin SIVA, increased pacemaker firing rates by approximately 20% and then stopped pacemaker firing. Other potassium channel blockers (tetraethylammonium, cesium, alpha-dendrotoxin, and agitoxin-2) did not affect the pacemaker rhythm. The nonspecific calcium channel blockers nickel and cadmium reduced pacemaker firing rates by approximately 15-20%. Specific blockers of L-, N-, P-, and Q-type calcium currents, however, were ineffective. These results indicate that at least three ionic currents-a TTX- and muO-conotoxin MrVIA-sensitive sodium current; a 4AP- and kappaA-conotoxin SIVA-sensitive potassium current; and a T- or R-type calcium current-contribute to the pacemaker rhythm. The pharmacological profiles of these currents are similar to those of currents that are known to regulate firing rates in other spontaneously oscillating neural circuits.

Clinical Utility of FDG-PET in Detecting Head and Neck Tumors. A Comparison of Diagnostic Methods and Modalities

Positron emission tomography (PET) using F-18-fluoro-2-deoxy-d-glucose(F-18-FDG) is gaining acceptance as a useful imaging method for head and neck tumors. Results of 59 PET scans done on 45 patients with head and neck tumors were evaluated retrospectively. Thirty-six patients had prior treatment consisting of surgery, radiation therapy, chemotherapy, or a combination of these modalities. PET results were compared to computed tomography and magnetic resonance imaging results and validated by histologic findings or survival. PET identified 36 out of 37 tumors (sensitivity 97%) and 18 of 22 benign processes (specificity 82%). Tumor was ruled out in 18 out of 19 patients. For CT, the sensitivity was 80% (20/25) and specificity was 31% (4/13). FDG-PET facilitates differentiation of recurrent head and neck tumors from treatment related changes sometimes difficult to characterize by CT or MRI and may have a significant impact on the management of patients reducing morbidity and costs.

Vitrectomy for phacolytic glaucoma in a patient with homocystinuria

PURPOSE

To determine the successful treatment of unilateral phacolytic glaucoma by vitrectomy and trabeculectomy in a patient with homocystinuria whose lens had dislocated into the vitreous at least 15 years earlier.

METHODS

In a 32-year-old woman with homocystinuria, bilateral dislocation of the lens into the vitreous, and phacolytic glaucoma in her left eye a three-port pars plana vitrectomy was performed with the patient under general anesthesia. The lens was removed and a trabeculectomy fashioned. Special precautions for general anesthesia included preoperative aspirin and compression stockings for thromboembolic prophylaxis and intraoperative dextrose infusion, 5%, to maintain intravascular volume and prevent hypoglycemia.

RESULTS

The intraocular pressure and uveitis resolved postoperatively with improvement in the visual acuity and intraocular pressure, which returned to normal without further treatment.

CONCLUSIONS

Phacolytic glaucoma is best resolved by removal of the exciting lens material. Pars plana vitrectomy with the patient under general anesthesia can be carried out safely despite the risks traditionally associated with homocystinuria.

Children's perceptions of parental drinking: the eye of the beholder

OBJECTIVE

Children learn about alcohol and about how to drink through modeling experience, in part. Modeling is typically studied by asking parents to describe their drinking behavior. However, children's perception of parents' drinking may differ from the way parents describe it. This study examined the degree to which children's perceptions and parents' reports agreed.

METHOD

A sample of 177 grade-school children and their parents was drawn from a public school in Kentucky. Children completed questionnaires inquiring about their perceptions of the quantity, frequency and the positive and negative consequences of their parents' drinking. Their parents completed similar questionnaires describing their own drinking and its consequences.

RESULTS

As hypothesized, first and second grade children's perceptions of parents' drinking were unrelated to parents' self-reports: Most of these children perceived their parents as nondrinkers even though parents reported drinking. Also as hypothesized, children's perceptions and parents' reports were significantly correlated for third through sixth grade students. However, there was a great deal of reliable, but unshared variance between these older children's perceptions and parents' reports. Children's perceptions and parents' reports were consistently quite different, even when both child and parent described the parent as a drinker.

CONCLUSIONS

Studies of modeling influences on children regarding drinking should assess children's perceptions of their parents' behavior rather than parents' self-reports.

Ionic currents that contribute to a sexually dimorphic communication signal in weakly electric fish

Weakly electric fish produce a communication signal, the electric organ discharge, that is species specific, and in many species, sexually dimorphic. Because the neural circuit that controls the electric organ discharge is relatively simple, it is an excellent model in which to study both the biophysical mechanisms underlying a rhythmic behavior and the neuroendocrine control of a sexually dimorphic behavior. By studying the effects of ion channel blockers on neurons in the medullary pacemaker nucleus, I pharmacologically characterized three ionic currents that influence the pacemaker rhythm, and thus electric organ discharge frequency, in the gymnotiform fish, Apteronotus leptorhynchus. These currents included a tetrodotoxin-sensitive sodium current; a potassium current that was sensitive to 4-aminopyridine; and a calcium current that was sensitive to nickel and cadmium, but resistant to specific blockers of L-, N-, P-, and Q-type calcium currents. The pharmacological profiles of the ionic currents in the pacemaker nucleus are similar to those of ionic currents involved in pacemaking in other neuronal oscillators. Because these ionic currents dramatically influence pacemaker firing frequency, which is directly related to electric organ discharge frequency, these ionic currents are likely targets of steroid hormone action in producing sexual dimorphisms in electric organ discharge frequency. Additional studies are needed to determine how these ionic currents interact to generate the electric organ discharge rhythm and to investigate the possibility that sexual dimorphism in the electric organ discharge results from the actions of gonadal steroids on these ionic currents.

Cell sensitivity to transplacental mutagenesis by N-ethyl-N-nitrosourea is greatest during early gestation in the Syrian hamster

The extremely high rate of cell division that occurs during early embryogenesis is hypothesized to predispose to high rates of mutation after chemical exposure. We tested this supposition experimentally. To probe the variation in susceptibility to mutation induction as a function of gestation stage, somatic cells of the developing Syrian hamster were isolated after transplacental treatment with N-ethyl-N-nitrosourea (ENU). Mutants were quantified using either 6-thioguanine (6-TG) or diphtheria toxin (DT) as selective agents. Several different approaches were used. In one, three litters were exposed on each gestation day and fetuses were removed on day 13. Maximum fetal sensitivity to ENU's genotoxic action was noted when treatment was at days 8 and 9, fewer mutants being obtained with earlier and later exposures. To compensate for the low numbers of target cells early in gestation, this experiment was repeated using larger numbers of litters exposed at the earlier time points, and the highest mutation frequency was now found to occur after treatment on gestation days 6 and 7. In the second approach, mutations were quantified in cells harvested 24 h after transplacental ENU exposure. Here again, embryos exposed at earlier times of gestation were more susceptible than those treated at later periods. Based on the total cell numbers in embryos and fetuses at each gestation day, we conclude that mutation frequency is maximal on day 6, corresponding to the primitive streak stage with extremely high rates of cell division.

Plasticity of the electric organ discharge: implications for the regulation of ionic currents

Weakly electric fish emit electric organ discharges (EODs) to locate objects around themselves and for communication. The EOD is generated by a simple hierarchically organized, neurophysiologically accessible circuit, the electromotor system. A number of forms of plasticity of the EOD waveform are initiated by social or environmental factors and mediated by hormones or neurotransmitters. Because the behavior itself is in the form of electric discharges, behavioral observations easily lead to testable hypotheses about the biophysical bases of these plasticities. This allows us to study ionic channels in their native cellular environments, where the regulation of various parameters of these currents have obvious functional consequences. In this review, we discuss three types of plasticity: a rapidly occurring, long-lasting, N-methyl-d-aspartate (NMDA)-receptor-dependent increase in baseline firing frequency of neurons in the pacemaker nucleus that underlies a readjustment of the baseline EOD frequency after long bouts of the jamming avoidance response; a rapidly occurring diurnal change in amplitude and duration of the EOD pulse that depends in part on modulation of the magnitude of the electrocyte Na+ current by a protein kinase; and a slowly occurring, hormonally modulated tandem change in pacemaker firing frequency and in the duration of the EOD pulse in which changes in EOD pulse duration are mediated by coordinated shifts in the activation and inactivation kinetics of the electrocyte Na+ and K+ currents.

Telemedicine for dermatology care in rural patients

BACKGROUND

Rural patients who develop dermatologic disorders often do not seek specialty care because of multiple logistical and economic factors.

OBJECTIVE

To assess the effect of teledermatology consultations on the cost of care for a given episode of illness.

METHODS

Telemedicine records were reviewed for 119 visits by 87 patients referred for teledermatology consultation over a 17-month period.

RESULTS

Seven patients (8%) required follow-up in the dermatologist office for extended care, while 20 patients (23%) (52 visits) underwent follow-up teledermatology evaluation. The average duration of the dermatologic condition for each patient prior to the telemedical consultation was 17 months. The average of care for the diagnosed dermatologic condition, for all patients during an average period of 8 months prior to teledermatology was $294, compared with $141 for the 6 months after diagnosis by teledermatology.

CONCLUSIONS

Telemedicine can be effective for dermatology consultation in new patients referred from rural communities. Our data indicate teledermatology can decrease the cost of care for the diagnosed condition.

Validation of deconvolutional analysis for the measurement of hepatic function in dogs with toxic-induced liver disease

The extraction of the hepatobiliary radiopharmaceutical 99mTc-mebrofenin (Choletec) by the liver can be used to evaluate the severity of hepatocellular disease. The hepatic parenchymal cells extract mebrofenin from the blood by the same active transport mechanism as bilirubin. The ability of the liver to extract 99mTc-mebrofenin is a measure of hepatic parenchymal cell function. In this study, we induced hepatocellular disease by administration of a hepatotoxic drug and compared a direct method of determining the hepatic extraction of 99mTc-mebrofenin to hepatic extraction fraction derived from deconvolutional analysis. We also compared both methods of calculating the hepatic extraction of 99mTc-mebrofenin to liver histopathology. Hepatic extraction fraction derived from deconvolutional analysis correlated very well to the direct measurement technique (R=0.922, p < 0.001). Both methods of determining hepatic extraction correlated well to quantitative histopathology, having the same correlation coefficient and p values. (R=-0.833, p=0.003). As the hepatic extraction 99mTc-mebrofenin decreased, the severity of the histopathologic lesions of the liver increased in a linear fashion. There was a significant correlation of the hepatic excretion T1/2 to quantitative histopathology (R=0.949, p < 0.001). The hepatic excretion T1/2 increased as the severity of the histopathologic lesions of the liver increased. Hepatic extraction (HEF) and excretion of 99mTc-mebrofenin are good predictors of the severity of hepatocellular damage in toxic induced liver disease. This study helps validate the premise that HEF derived from deconvolutional analysis is a good predictor of the actual first pass hepatic extraction of 99mTc-mebrofenin.

Hepatic extraction efficiency of technetium-99m-mebrofenin in the dog with toxic-induced acute liver disease

Extraction of the hepatobiliary radiopharmaceutical 99mTc-N-(3-bromo-2,4,6-trimethyacetanilide) iminodiacetic acid (mebrofenin; Choletec, Squibb Diagnostic, Princeton, NJ) by the liver may be used as an index of hepatocellular function. The hepatic parenchymal cells extract mebrofenin from the blood using the same active transport mechanism as bilirubin.

METHODS

In this study, we induced hepatocellular disease by administering a hepatotoxic drug and compared the hepatic extraction efficiency (HEE), measured directly from an afferent injection of 99mTc-mebrofenin, to quantitative histopathology and to serum biochemistry analysis.

RESULTS

The baseline HEE was 95.9% +/- 2.71% (mean +/- s.d.). Dogs that were affected by the hepatotoxic drug had reduced HEE. HEE correlated well to the severity of histologic lesions (r = -0.83, p = 0.003). HEE also correlated well to the increases in the activities of alanine aminotransferase (ALT; r = -0.85, p = 0.002) and aspartate aminotransferase (AST; r = -0.89, p = <0.001), the concentration of fasting bile acid (r = -0.97, p = <0.001), bilirubin (r = -0.92, p = <0.001) and, to a lesser degree, to the activities of alkaline phosphatase (Alk Phos; r = -0.73, p = 0.016). HEE had higher correlation coefficients to the serum biochemistry analysis than did the quantitative liver histopathology.

CONCLUSION

Hepatic extraction of 99mTc-mebrofenin is a good predictor of the severity of hepatocellular damage in toxic-induced liver disease.

Seasonal plasticity and sexual dimorphism in the avian song control system: stereological measurement of neuron density and number

Differences in neuron density and number are associated with seasonal plasticity and sexual dimorphism in the avian song control system. In previous studies, neuron density and number in this system have been quantified primarily through nonstereological approaches in thick tissue sections by using the nucleolus as the unit of count. The reported differences between seasons and sexes may be inaccurate due to biases introduced by neuron splitting during sectioning. We used the unbiased optical disector technique on tissue from three previous studies (two investigations of seasonal plasticity and one investigation of sexual dimorphism in avian song nuclei) to assess seasonal and sex differences in neuron density and number. In two song nuclei, HVc and the robust nucleus of the archistriatum (RA), the optical disector yielded intergroup differences in neuron density and number that coincided well with the three previous reports. We also estimated neuron number and density with a random, systematic, nonstereological counting protocol that used the neuronal nucleolus as the unit of count. We compared this method directly to the optical disector. In all cases, the two neuron-counting methods produced similar estimates of neuron number and density; the differences between treatment groups were equally discernible regardless of the counting method used. This study confirms previously reported seasonal and sex differences in the HVc and the RA by use of stereology and indicates that a random, systematic, nonstereological neuron-counting protocol is accurate and is well suited to the study of these phenomena in the avian song control system.

Evaluation of the direct genotoxic potential of cadmium in four different rodent cell lines

Cadmium is a toxic environmental contaminant that is carcinogenic in humans and laboratory animals. Although the mechanism underlying cadmium carcinogenesis has not yet been determined experimental evidence suggests that the stress-inducible, metal-binding proteins, metallothioneins, may mediate organ specificity. In the present study, four different rodent cell lines (Chinese hamster ovary cells, rat L6 myoblast cells, rat Clone 9 liver cells, and rat TRL 1215 liver cells) were exposed to 0, 1, 5, 10, 50, or 100 microM CdCl2 and monitored for evidence of direct DNA damage. A microfiltration assay was used to measure DNA strand breaks and a filter-binding assay was used to measure DNA-protein crosslinks, two lesions that have been associated with cadmium exposure and may mediate genotoxicity of the metal. Although variability in sensitivity to DNA damage was evident between the different cell lines, in all of the cell lines tested, increases in DNA damage were observed only at cadmium doses that completely arrested cell growth. In addition, in three of the four cell lines tested, induction of metallothionein had no substantial protective effect against cadmium-induced cytotoxicity or genotoxicty. While protection against cadmium-induced DNA strand breakage with metallothionein preinduction was observed in the TRL 1215 rat liver cells, metallothionein preinduction did not protect against cadmium-induced DNA-protein crosslinking in that cell line. Taken together, our results support the hypothesis that cadmium is not directly genotoxic.

Effect of cadmium exposure on background and anti-5 methylchrysene-1,2-dihydrodiol 3,4-epoxide-induced mutagenesis in the supF gene of pS189 in human Ad293 cells

Cadmium is a toxic environmental contaminant that is carcinogenic in humans and rodents. Although cadmium has proven to be mutagenic in a variety of assay systems, exactly how cadmium achieves gentoxicity is poorly understood. To define the mechanism(s) underlying the mutagenicity and comutagenicity of cadmium, human Ad293 cells were exposed to subtoxic doses of the metal and transfected with untreated or anti-5-methylchrysene-3,4-dihydrodiol 1,2-epoxide (5-MCDE)-treated pS189 shuttle vector. Alterations in the frequency, types, and distribution of mutations were subsequently assessed in the supF gene of pS189 that was replicated in Ad293 cells and screened in indicator bacteria. Doses of 0.5 and 1 microM CdCl2 increased the mutation frequency of untreated pS189 by approximately 4- and 8-fold, respectively, with no apparent effect on the types of mutations generated. In contrast, host-cell exposure to cadmium had little or no effect on the frequency, types, or distribution of mutations generated with 5-MCDE-treated pS189. These results indicate that cadmium increases mutagenesis of untreated pS189 by affecting a process that is not involved in mutagenesis of the 5-MCDE-treated vector. Although it is not clear exactly how host-cell exposure to cadmium increases background mutagenesis, presumably, the mutagenic effect does not involve cadmium interaction with the cellular machinery used to replicate past bulky DNA lesions.

Evaluation of fluorine-18-BPA-fructose for boron neutron capture treatment planning

Boron neutron capture therapy (BNCT) using 4-[10B]boronophenylalanine-fructose (BPA-Fr) is in Phase II clinical trials to validate BNCT as a treatment for glioblastoma multiforme and melanoma. Successful BNCT depends on knowledge of the distribution of boron-containing agents in both tumor and normal tissue as currently determined by chemical confirmation of boron deposition in surgically removed malignant tissue before BNCT.

METHODS

We used PET to noninvasively obtain in vivo information on the pharmacokinetics of the 18F-labeled analog of BPA-Fr in two patients with glioblastoma multiforme. Time-activity curves generated from the bolus injection of 18F-BPA-Fr were coinvolved to simulate a continuous infusion used for BNCT therapy.

RESULTS

Distribution of 18F-BPA-Fr by PET was found to be consistent with tumor as identified by MR imaging. The 18F-BPA-Fr tumor-to-normal brain uptake ratio was 1.9 in Patient 1 and 3.1 in Patient 2 at 52 min after injection. The 18F-BPA-Fr uptake ratio in glioblastoma paralleled that of nonlabeled BPA-Fr seen in patients as previously determined by boron analysis of human glioblastoma tissue obtained from pre-BNCT surgical biopsy.

CONCLUSION

Knowledge of the biodistribution of BPA-Fr enables pre-BNCT calculation of expected tissue dosimetry for a selected dose of BPA-Fr at a specific neutron exposure. Fluorine-18-BPA-Fr PET is capable of providing in vivo BPA-Fr biodistribution data that may prove valuable for patient selection and pre-BNCT treatment planning.

Seasonal changes in testosterone, neural attributes of song control nuclei, and song structure in wild songbirds

Seasonal changes in the neural attributes of brain nuclei that control song in songbirds are among the most pronounced examples of naturally occurring plasticity in the adult brain of any vertebrate. The behavioral correlates of this seasonal neural plasticity have not been well characterized, particularly in songbird species that lack adult song learning. To address this question, we investigated the relationship between seasonal changes in gonadal steroids, song nuclei, and song behavior in adult male song sparrows (Melospiza melodia). At four times of the year, we measured plasma concentrations of testosterone, neural attributes of song nuclei, and several aspects of song structure in wild song sparrows of a nonmigratory population. We found seasonal changes in the song nuclei that were temporally correlated with changes in testosterone concentrations and with changes in song stereotypy. Male song sparrows sang songs that were more variable in structure in the fall, when testosterone concentrations were low and song nuclei were small, than in the spring, when testosterone concentrations were higher and song nuclei were larger. Despite seasonal changes in the song nuclei, the song sparrows continued to sing the same number of different song types, indicating that changes in the song nuclei were not correlated with changes in song repertoire size. These results suggest that song stereotypy, but not repertoire size, is a potential behavioral correlate of seasonal plasticity in the avian song control system.

Seasonal changes in the size of the avian song control nucleus HVC defined by multiple histological markers

Bird song is controlled by a discrete network of brain nuclei. The size of several song control nuclei changes seasonally in many seasonally breeding songbird species. Reports of seasonal changes in the size of song nuclei have relied primarily on Nissl stains to define the borders of these regions. Recent studies found that the size of the song nucleus higher vocal center (HVC) in male canaries did not change seasonally when its borders were defined by histological markers other than Nissl staining. We used three labels to define the borders of the HVC in male Gambel's white-crowned sparrows (Zonotrichia leucophrys gambelii): Nissl staining, the distribution of acetylcholinesterase-positive neuropil, and the distribution of neurons projecting to another song nucleus, area X. The HVC was larger in males exposed to a breeding photoperiod and testosterone concentrations than in males exposed to a nonbreeding photoperiod and testosterone concentrations, regardless of which of these three methods was used to define the borders of the HVC. This result suggests that seasonal changes in the Nissl-defined borders of the HVC reflect changes in the distribution of physiologically relevant markers of the nucleus and are not merely artifacts of the Nissl-staining method.

Self-trephination of the skull with an electric power drill

There is extensive archaeological evidence of the practice of trephination of the skull in many ancient cultures in different parts of the world. We report a case of self-trephination of the skull by a patient using an electrical power drill subsequently requiring neurosurgical intervention.

Roles of photoperiod and testosterone in seasonal plasticity of the avian song control system

The song control nuclei of songbirds undergo pronounced seasonal changes in size and neuronal attributes. The mechanisms by which seasonal changes in environmental variables such as photoperiod mediate seasonal changes in these brain regions are not known. Manipulations of photoperiod and/or testosterone in captive songbirds induce seasonal changes in the size of song nuclei comparable to those observed in wild songbirds. It is unclear, however, whether the effects of photoperiod on the song nuclei are mediated by testosterone or by steroid-independent mechanisms. We independently manipulated photoperiod and testosterone in castrated male Gambel's white-crowned sparrows (Zonotrichia leucophrys gambelii) to determine the contributions of steroid-dependent and -independent actions of photoperiod to seasonal changes in the size and neuronal attributes of song nuclei. Testosterone implants increased the size of several song nuclei, regardless of photoperiod. Photoperiod exerted small but significant steroid-independent effects on the volume of the higher vocal center and the size of neurons in the robust nucleus of the archistriatum. Photoperiod also modulated the effect of testosterone on the size of area X; testosterone treatment had a more pronounced effect on the size of area X on short days than on long days. These results suggest that although testosterone is the primary factor mediating seasonal changes in neural attributes of the song nuclei, photoperiod may act via mechanisms that are independent of steroid levels to supplement or modulate the actions of testosterone.

Quantification of diazeniumdiolate mutagenicity in four different in vitro assays

Diazeniumdiolates are under investigation as possible prodrugs of the multifaceted bioregulatory agent nitric oxide. This study was undertaken to assess further the mutagenic potential of two diazeniumdiolates, DEA/NO (Et2N[N(O)NO]Na) and SPER/NO ([H2N(CH2)3NH(CH2)4N[N(O)NO-](CH2)3 NH3+]), which generate NO spontaneously with half-lives at 37 degrees C and pH 7.4 of 2 and 39 min, respectively. The genotoxic potential of these compounds was investigated with the Ames bacterial reverse mutation assay, two mammalian cell gene mutation assays (CHO/HGPRT and L5178Y TK+/-), and an assay for sister chromatid exchange (SCE) using Chinese hamster ovary (CHO) cells. Both diazeniumdiolates had previously been shown to be mutagenic in the Ames Salmonella plate assay. In the experiments reported here, Salmonella typhimurium strain TA1535 was exposed to the compounds in a liquid incubation assay for either 15 min or 48 h without an S-9 fraction. With the 15-min exposure, DEA/NO was mutagenic at concentrations of 0.625 mM (3.5 x control) and greater, while SPER/NO was mutagenic at 0.5 mM (2.7 x control) and above. In the CHO/HGPRT assay, DEA/NO was weakly mutagenic only at the highest concentration used, 20 mM, inducing a mutant frequency per survivor that was 2.5 x control, while SPER/NO was mutagenic at 0.5 mM with a mutant frequency of 2.5 x control. When the CHO cells were given 10 repetitive 20 mM DEA/NO exposures (3 min each), HGPRT mutant frequency was 4.1 x control. In the L5178Y mouse lymphoma cell TK+/- assay, DEA/NO doubled the mutation rate at 1.82 mM, while SPER/NO's mutation frequency was more than twice that of control at 0.63 mM. DEA/NO was positive in the SCE assay without metabolic activation, yielding significant SCE at 1.25, 2.5, and 5 mM that was 1.8, 2.2, and 2.6 times control, respectively. SPER/NO increased the SCE by 1.2, 1.4, and 1.3 times at 1.5, 2.0, and 2.5 mM. The results suggest that the two diazeniumdiolates, although mutagenic in the bacteria, are much weaker mutagens in mammalian cells.

Effects of eicosapentaenoic and gamma-linolenic acid on lung permeability and alveolar macrophage eicosanoid synthesis in endotoxic rats

OBJECTIVES

Proinflammatory eicosanoids (cyclooxgenase and lipoxygenase metabolites of arachidonic acid) released by alveolar macrophages play an important role in endotoxin-induced acute lung injury. We investigated the effect of prefeeding rats for 21 days with enteral diets that provided the anti-inflammatory fatty acids, eicosapentaenoic acid and gamma-linolenic acid (derived from fish oil and borage oil, respectively), as compared with an n-6 fatty acid-enriched diet (corn oil) on the following: a) lung microvascular protein permeability, arterial blood pressure, and platelet and white blood cells in a model of endotoxin-induced acute lung injury; b) alveolar macrophage prostaglandin and leukotriene synthesis; and c) liver and alveolar macrophage phospholipid fatty acid composition.

DESIGN

Prospective, randomized, controlled, double-blind study.

SETTING

Research laboratory at a university medical center.

SUBJECTS

Male Long-Evans rats, weighing 250 g.

INTERVENTIONS

Rats were randomized into four dietary treatment groups and fed nutritionally complete diets (300 kcal/kg/day), containing 55.2% of the total calories from fat with either 97% corn oil, 20% fish oil, 20% fish and 5% borage oil, or 20% fish and 20% borage oil for 21 days. On day 22, lung microvascular protein permeability, mean arterial pressure, and platelet and white blood cell counts were determined for 2 hrs after an intravenous injection of Salmonella enteritidis endotoxin (10 mg/kg). In a second group of prefed rats, the phospholipid fatty acid composition was determined in liver and alveolar macrophages. Alveolar macrophages were harvested by bronchoalveolar lavage and stimulated in vitro with a calcium ionophore (A23187), and the concentrations of leukotrienes B4 and B5, thromboxane A2, prostaglandin E2, and 6-keto-prostaglandin F1 alpha were measured in a third group of prefed rats.

MEASUREMENT AND MAIN RESULTS

Lung permeability was greatest with corn oil and was significantly attenuated with 20% fish oil and 20% fish and 5% borage oil, and this effect approached significance with 20% fish and 20% borage oil (p = .06). The early and late hypotensive effects of endotoxin were attenuated with 20% fish oil, 20% fish and 5% borage oil, and 20% fish and 20% borage oil, as compared with corn oil. Concentrations of leukotriene B4, prostaglandin E2, and thromboxane B2 released from A23187-stimulated alveolar macrophages were significantly lower with 20% fish oil and 20% fish and 20% borage oil, as compared with corn oil. The increase in lung microvascular protein permeability with 20% fish and 20% borage oil was not significantly different than the lung microvascular protein permeability that was found in animals receiving 20% fish oil (p = .20) and 20% fish and 5% borage oil (p = .31). Alveolar macrophage and liver phospholipid concentrations of arachidonic acid were lower, and the concentrations of eicosapentaenoic acid and docosahexaenic acid were higher, with 20% fish oil, and 5% borage oil, and 20% fish and 20% borage oil, as compared with corn oil. Dihomo-gamma-linolenic acid, the desaturated and elongated intermediate of gamma-linolenic acid, was increased with 20% fish and 20% borage oil, as compared with 20% fish oil and 20% fish and 5% borage oil.

CONCLUSIONS

The severity of pulmonary microvascular protein permeability and the degree of hypotension were reduced with fish or fish and borage oil diets, as compared with corn oil, in endotoxic rats. The reduced synthesis of the proinflammatory arachidonic acid-derived mediators, leukotriene B4, thromboxane B2, and prostaglandin E2 from stimulated alveolar macrophages was indicative of a decrease in arachidonic acid and an increase in eicosapentaenoic acid and docosahexaenoic acid in cell membrane phospholipids.