Binge ethanol-induced brain damage in rats: effect of inhibitors of nitric oxide synthase

Testing the possible role of endogenous nitric oxide (NO) in the neurotoxicity of ethanol, we examined how two different NO synthase (NOS) inhibitors affected the extent cerebrocortical and olfactory neuronal damage in a modified "binge intoxication" rat model (Collins et al., Alcohol Clin. Exp. Res. 20:284-292, 1996). Male rats intragastrically fed ethanol (6.5 to 12 g/kg/day) in nutrient solution three times daily for 4 days also received NG-nitro-L-arginine methyl ester by chronic intracerebroventricular infusion or 7-nitro-indazole by daily intraperitoneal injection; control rats were given nutrient solution only and/or vehicles. Blood ethanol levels did not differ among the ethanol-treated groups. The amount of ethanol-dependent neuronal degeneration in the entorihinal cortex, dentate gyrus, and olfactory bulb glomeruli--visualized with the de Olmos cupric silver stain and quantitatively assessed in the binge-intoxicated rats--was either unchanged or significantly increased by the NOS inhibitors. Although the efficacies of the inhibitors cannot be directly compared because of various NOS forms were probably inhibited to differing extents, the results do not support the idea that endogenous NO is a neurotoxic mediator of ethanol's effects. Rather NO may have a modest neuroprotectant role in this model of early brain damage induced by ethanol. In addition, the NOS that is localized histochemically as NADPH diaphorase was present primarily in regions and/or cells not damaged by binge ethanol treatment. Assuming that NADPH diaphorase represents most of the NO forming enzyme(s) this suggests a transcellular mechanism for NO. A further observation was that hippocampal CA pyramidal neuron degeneration was extensive in rats infused centrally with NG-nitro-L-arginine methyl ester.

On fighting versus accepting stressful circumstances: primary and secondary control among HIV-positive men in prison

The primacy of primary control over secondary control and ethnic differences in control processes were tested in HIV-positive male state prison inmates. They rated their perceptions of control and psychological distress at an initial interview (N = 95) and 3 months later (N = 78). Regression analyses revealed that primary control had primacy as it had greater adaptive value. However, secondary control did not function as a backup to primary control, and temporal differences in control were not found. No mean differences due to ethnicity (African American vs. White) were found, but there was a strong ethnic difference in the effects of primary control. White participants showed the expected negative relationship between distress and primary control, but African American participants did not. The idea that the benefits of primary control would be the same across various subcultures was not supported.

Metabolism and disposition of difluoromethane (HFC32) in the mouse

1. Difluoromethane (HFC32) is under development as a replacement for chlorofluorocarbons (CFCs) in some refrigeration applications. 2. The metabolism and disposition of [14C]-difluoromethane ([14C]-HFC32) was determined in male Swiss mice as a consequence of a single 6 h inhalation exposure to atmospheres of 10 000 p.p.m. 3. Of the inhaled dose, about 1-2% was recovered in expired air, urine, faeces and carcass suggesting that systemic absorption of this hydrofluorocarbon from the alveolar air space of the lung into blood is poor. Upon cessation of exposure the majority of the systemically absorbed HFC32 was exhaled within 1 h. 4. Carbon dioxide was a major metabolite of HFC32. Carbon dioxide measured post-exposure accounted for about 0.3% of the inhaled dose. Urinary and faecal excretion of non-volatile metabolites accounted for about 0.34% and 0.07% of the inhaled dose, respectively. 5. Carbon monoxide could not be detected. 6. Total metabolism, measured as the sum of the radioactivity recovered in urine, faeces, as carbon dioxide and that retained in the carcass, amounted to about 0.8% of the inhaled dose, equivalent to 64% of the total radioactivity recovered. 7. Analysis of a range of tissues at 4 days post-exposure showed a relatively uniform distribution of radioactivity with the highest concentration in the lung, liver and kidney. There was no evidence of a specific retention in any organ or tissue.

On fighting versus accepting stressful circumstances: primary and secondary control among HIV-positive men in prison

The primacy of primary control over secondary control and ethnic differences in control processes were tested in HIV-positive male state prison inmates. They rated their perceptions of control and psychological distress at an initial interview (N = 95) and 3 months later (N = 78). Regression analyses revealed that primary control had primacy as it had greater adaptive value. However, secondary control did not function as a backup to primary control, and temporal differences in control were not found. No mean differences due to ethnicity (African American vs. White) were found, but there was a strong ethnic difference in the effects of primary control. White participants showed the expected negative relationship between distress and primary control, but African American participants did not. The idea that the benefits of primary control would be the same across various subcultures was not supported.

The inhalation toxicology, genetic toxicology, and metabolism of difluoromethane in the rat

Difluoromethane (HFC32) is under development as a replacement for chlorofluorocarbons (CFCs) in some refrigeration applications. It has been evaluated by standard studies of toxicity, developmental toxicity, and genotoxicity. In addition, the metabolism and disposition of HFC32 was investigated and a physiologically based pharmacokinetic (PB-PK) model constructed. Inhalation of HFC32 (up to 50,000 ppm) caused no organ-specific effects, but resulted in slight maternal toxicity to the pregnant rat and rabbit and some fetotoxicity to the rat. HFC32 did not sensitize the heart to adrenaline. The pharmacokinetics of [14C]difluoromethane (10,000 to 50,000 ppm/6 hr) revealed that about 2.1% of the inhaled HFC32 was absorbed and that steady state blood levels were achieved within 2 hr and were proportional to dose. Carbon dioxide was the major metabolite of HFC32 at all exposure levels. Carbon monoxide was not detected. The in vivo data were used to validate a PB-PK model to describe the uptake and metabolism of HFC32. Absorption and distribution are adequately described using rat blood:air and tissue:air partition coefficients. Metabolism, which was linear across the dose range, was described by a first order rate constant (Kf = 8.98 hr-1). Of the absorbed HFC32, about 63% was metabolized at all doses; however, when metabolism was expressed as a percentage of the inhaled dose it was much lower, being about 1.4% of the HFC32 entering the airways. Overall, the results indicate that HFC32 is of very low toxicity and should be an acceptable alternative to CFCs.

Quality of decision making by registered nurses

This study investigated quality of decision making in a convenience sample of 26 registered nurses. Instruments used were the Joseph Decision Making Tool, Actual Decision Making instrument, and computer-assisted clinical simulations. Results were correlated with educational preparation, age, experience, practice area, and specialty certification. No differences among basic educational preparation with frequency of actual decision-making practices and willingness to make decisions were found. A positive correlation was found between practice area and frequency of actual decision making (r = 0.639, P < 0.001), and practice area and communication (r = 0.439, P < 0.05).

Neuronal degeneration in rat cerebrocortical and olfactory regions during subchronic "binge" intoxication with ethanol: possible explanation for olfactory deficits in alcoholics

Severe, repetitive ("binge") ethanol intoxication in adult rats (intragastric delivery 3 times daily for 4 days in a modification of the Majchrowicz method) precipitates neuronal degeneration in selected cerebral cortical regions involved in memory and olfaction, confirming the results of Switzer and colleagues (Anat. Rec. 202: 186a, 1982). Neuronal damage was visualized with the de Olmos cupric silver technique for degenerating neurons and processes (argyrophilia), and was quantitated by total counts and densities of argyrophilic cells/fields. The specificity of the degeneration provides a neuropathological basis for the olfactory memory deficits in chronic alcoholics. In highly intoxicated rats, argyrophilia was most extensive among hippocampal dentate gyrus granule cells, pyramidal neurons in layer 3 of the entorhinal cortex, and olfactory nerve terminals in the olfactory bulb. Degenerating pyramidal neurons were also consistently seen in the insular cortex and olfactory cortical regions, such as the piriform and perirhinal cortices. There were few argyrophilic neurons in the CA regions of the hippocampus and none in the cerebellum--regions generally shown to have cell loss in long-term ethanol feeding models--but degenerating mossy fibers in the CA2 region were observed. Degeneration was maximal before the peak period of abstinence symptoms in this model, because argyrophilic densities were no greater 36 hr, compared with 8 hr after the last ethanol dose. High blood ethanol levels were required, because argyrophilia, absent from isocaloric controls, also was only evident in ethanol-intoxicated rats with mean blood ethanol levels for days 2 to 4 above 300 mg/dl; however, it increased substantially between 350 and 550 mg/dl. The resemblance of the argyrophilic distribution to the regional neuropathology that occurs in experimental seizures indicates that the ethanol-induced degeneration may have an excitotoxic basis. Progressive reductions in the seizure threshold (e.g., kindling phenomena that have been documented during binge ethanol intoxication) might be associated with excitotoxic hyperactivity during the repetitive nadirs between high blood and brain ethanol peaks. However, direct toxic actions of ethanol or its metabolites could also be involved. Overall, the model should be useful for studying mechanisms of ethanol-induced selective cortical and olfactory brain damage.

Characterization of a proteinaceous antimicrobial produced by Lactobacillus helveticus CNRZ450

An antimicrobial substance which resembles a bacteriocin was identified in culture supernatant fluids of Lactobacillus helveticus strain CNRZ450. The bacteriocin was active against a narrow range of strains from closely related species of homofermentative lactobacilli. Its mode of action appeared to be bacteriostatic. Partial purification of the bacteriocin suggested that it was a complex protein with a mol. wt of between 30 and 50 kDa, although there is some evidence that the polypeptide monomer has a mol. wt of around 17 kDa. There was no evidence indicating an extrachromosomal location for its genetic determinant. PCR generated an amplicon from total DNA from strain CNRZ450 using primers based on the helJ gene sequence. A fragment showing homology to this amplicon was located in an EcoRI digest of total DNA from strain CNRZ450. The pattern obtained was different from that obtained with the helveticin J producer strain NCFB481. It is possible, therefore, that the antimicrobial from strain CNRZ450 is related to helveticin J at the DNA sequence level although the physical properties of the two antimicrobials reveal several differences.

The relation of work stress, hardiness, and burnout among full-time hospital staff nurses

In this descriptive study, the author examined the relation of work stress, hardiness, and burnout among 113 full-time hospital staff nurses. It was hypothesized that among hospital staff nurses: 1) the greater personality hardiness, the less job stress; and 2) the greater personality hardiness, the less burnout. Instruments used were Personal Views Survey, Nursing Stress Scale, and Tedium Burnout Scale. Promoting hardiness through nursing staff development programs may help manage stress and reduce burnout in the healthcare setting.

Computed tomography manifestations of tricuspid regurgitation

Six patients undergoing dynamic contrast enhanced abdominal computed tomography (CT) for upper abdominal symptoms and signs are described. Each patient demonstrated early, intense opacification of the inferior vena cava (IVC) and hepatic veins, exceeding that in the aorta on scans through the upper abdomen. Opacification of the IVC returned to normal on more caudal slices. All six patients were found to have echocardiographically proven tricuspid regurgitation (TR). It is suggested that this sign occurs in patients with TR due to direct reflux of contrast from the right atrium into the IVC during protracted bolus injection. Additional CT findings included patchy parenchymal liver enhancement in four patients and ascites in five. Recognition of this simple sign may direct the clinician to a cardiac aetiology for upper abdominal symptoms and signs.

(1S,2S)-1-(4-hydroxyphenyl)-2-(4-hydroxy-4-phenylpiperidino)-1-propanol: a potent new neuroprotectant which blocks N-methyl-D-aspartate responses

(1S,2S)-1-(4-Hydroxyphenyl)-2-(4-hydroxy-4-phenylpiperidino)-1-propanol (20, CP-101,606) has been identified as a potent and selective N-methyl-D-aspartate (NMDA) antagonist through a structure activity relation (SAR) program based on ifenprodil, a known antihypertensive agent with NMDA antagonist activity. Sites on the threo-ifenprodil skeleton explored in this report include the pendent methyl group (H, methyl, and ethyl nearly equipotent; propyl much weaker), the spacer group connecting the C-4 phenyl group to the piperidine ring (an alternating potency pattern with 0 and 2 carbon atoms yielding the greatest potency), and simple phenyl substitution (little effect). While potent NMDA antagonists were obtained with a two atom spacer, this arrangement also increased alpha 1 adrenergic affinity. Introduction of a hydroxyl group into the C-4 position on these piperidine ring resulted in substantial reduction in alpha 1 adrenergic affinity. The combination of these observations was instrumental in the discovery of 20. This compound potently protects cultured hippocampal neurons from glutamate toxicity (IC50 = 10 nM) while possessing little of the undesired alpha 1 adrenergic affinity (IC50 approximately 20 microM) of ifenprodil. Furthermore, 20 appears to lack the psychomotor stimulant effects of nonselective competitive and channel-blocking NMDA antagonists. Thus, 20 shows great promise as a neuroprotective agent and may lack the side effects of compounds currently in clinical trials.

1,1,1,2-Tetrafluoroethane: repeat exposure inhalation toxicity in the rat, developmental toxicity in the rabbit, and genotoxicity in vitro and in vivo

Subchronic and chronic studies were carried out in the rat and a developmental toxicity study in the rabbit with exposures to 1,1,1,2-tetrafluoroethane (HFC 134a) by inhalation. In the rat repeated exposure to 50,000 ppm HFC 134a for 13, 52, and 104 weeks elicited no effect on clinical condition, growth, and survival, or on a variety of hematological, clinical chemistry, and urinary parameters. Treatment-related pathological changes were seen only at study termination at 2 years and were confined to increased incidence of Leydig cell hyperplasia and adenoma in male rats exposed to 50,000 ppm. The tumors, which were also seen in control animals, were benign and not life-threatening. A battery of in vitro and in vivo tests gave no evidence of genotoxic activity. With exposure to pregnant rabbits, the only treatment-related effects were of minimal maternal toxicity at high exposure concentrations; there were no effects on fetal development. It is concluded that HFC 134a is of very low toxicity and should be an acceptable alternative to CFCs.

Methyl-beta-carbolinium analogs of MPP+ cause nigrostriatal toxicity after substantia nigra injections in rats

Eleven beta-carbolinium compounds (beta C+s) and MPP+ were stereotaxically injected (40-200 nmol in 5 microliter of vehicle) unilaterally into the substantia nigra of anesthetized adult male Sprague-Dawley rats. The rats were sacrificed after three weeks. The ipsilateral striatum was analyzed for dopamine and DOPAC levels with HPLC. The brainstem injection site was fixed and cut coronally. The largest lesion area in each animal was measured using NIH IMAGE. Three beta C+s produced lesions whose mean areas were nearly as large as that produced by MPP+ (defined as 100%): 2,9-Me2-harman (94%), 2-Me-harmol (74%), and 2,9-Me2-norharman (57%). Three other compounds produced somewhat smaller lesions: 2-Me-harmaline (34%), 6-MeO-2-Me-harman (29%), and 2-Me-harmine (25%). The remaining compounds were ineffective (< or = 12%): norharman, 2-Me-norharman, 2-Me-harman, harmine, and 2-Me-6-MeO-harmalan. A 40 nmol dose of MPP+ reduced ipsilateral striatal dopamine to 0.6% of control. None of the beta C+s approached this, although several did significantly reduce striatal dopamine at doses of either 40 nmol (2,9-Me2-harman (37%), 2,9-Me2-norharman (42%), and 2-Me-harman (63%)) or 200 nmol (2-Me-harmaline (23%), norharman (63%), and 2-Me-norharman (64%)). There was a moderate negative correlation between lesion size and dopamine level (r = -0.65). There were also moderately strong correlation between lesion size and dopamine level (r = -0.65). There were also moderately strong correlations (r = 0.39-0.78) between the beta C+ nigral lesion area or striatal dopamine level potencies and their previously described IC50 values for inhibiting mitochondrial respiration or their toxicity to PC12 cells in culture. Interestingly, our correlation analysis revealed a remarkably strong correlation between beta C+ Ki MAO-A values and their toxicity to PC12 LDH release (r = -0.84) or PC12 protein loss (r = 0.79). Although beta C+s appear to be less specific toxins than MPP+, their levels in human substantia nigra are 8-20-fold higher than in cortex, making their role as relatively selective nigral toxins in Parkinson's disease plausible.

Identification and quantification of fluorine-containing metabolites of 1-chloro-2,2,2-trifluoroethane (HCFC133A) in the rat by 19F-NMR spectroscopy

1-Chloro-2,2,2-trifluorethane (HCFC133a) causes a reduction in testis weight and germinal epithelial cell atrophy in the rat following exposure by inhalation at concentrations of 10,000 ppm and above. Following administration by gavage, an increased incidence of Leydig cell tumors of the testis was seen. The metabolism of HCFC133a has been investigated in respect to the known toxicity of this compound. Male rats were exposed by inhalation to an atmosphere of 50,000 ppm HCFC133a for a period of 6 hr. Analysis of urine, collected during the exposure period and up to 48 hr following exposure, by 19F-NMR spectroscopy identified 2,2,2-trifluoroethanol (TFE; and its beta-glucuronide), trifluoroacetaldehyde (TFAA; as its hydrate and urea adduct), and trifluoroacetic acid (TFA) as fluorine-containing metabolites of HCFC133a. Of the total amount of metabolite eliminated in urine, 83% was excreted within 24 hr postdose, establishing a rapid elimination of metabolites by this route. TFAA, an established testicular toxicant, was the major metabolite accounting for 57% of the total fluorinated metabolites eliminated in urine, whereas TFA and TFE accounted for 29% and 14%, respectively. The presence of these metabolites in urine is consistent with an oxidative route of metabolism of this fluorocarbon.

Differential cytotoxicities of N-methyl-beta-carbolinium analogues of MPP+ in PC12 cells: insights into potential neurotoxicants in Parkinson's disease

N-Methylated beta-carbolinium cations that can form in vivo from environmental or endogenous beta-carbolines are putative neurotoxic factors in Parkinson's disease. The cytotoxicities of 11 N-methylated beta-carbolinium cations and N-methyl-4-phenylpyridinium cation (MPP+), the experimental parkinsonian neurotoxicant which the carbolinium cations structurally resemble, were examined using rat pheochromocytoma (PC12) cells cultured in "low energy" N-5 medium; cell death was estimated by released lactate dehydrogenase activity and viable cell protein. Of the eight N2-monomethylated beta-carbolinium cations utilized, only 2-methyl-harmalinium (harmaline-2-methiodide) was as cytotoxic as MPP+. Also, three N2(beta), N9(indole)-dimethylated beta-carbolinium cations displayed cytotoxic effects, with the simplest, 2,9-dimethylnorharmanium, approaching the effectiveness of MPP+ in PC12 cells cultured in N-5 medium. However, when PC12 cells grown in higher energy Dulbecco's modified Eagle's medium were utilized with selected effective cations, it was observed that the cultures were relatively resistant to MPP+ and 2,9-dimethylnorharmanium, but remained vulnerable to 2-methylharmalinium. The results are interpreted to mean that different cytotoxic mechanisms exist for the two most potent beta-carbolinium cations--namely, a mechanism for the 2,9-dimethyl-beta-carbolinium species that, as with MPP+, is conditional on mitochondrial ATP depletion, but a different (or additional) mechanism for 2-methylharmalinium that is independent of mitochondrial inhibition. The possible accumulation of these cytotoxic cations in Parkinson's disease is discussed in the context of these findings.

Are adaptations to combined endurance and strength training affected by the sequence of training?

The purpose of this study was to determine whether the sequence of strength training before endurance training (ST/ET) is more or less effective than endurance training followed by strength training (ET/ST). Twenty-three females and 11 males were assigned to one of three groups: ST/ET (n = 15), ET/ST (n = 15) or control (n = 4). The 7-week training programme consisted of strength training using 10 exercises for two sets of 3-12 repetitions and running for 20-25 min at 60-90% of heart rate reserve. Maximal oxygen uptake (VO2 max) was measured during a graded treadmill test, and muscular strength was assessed using one-repetition maximum tests for the bench press (BP), shoulder press (SP), arm curl (AC) and leg press (LP). The VO2 max significantly (P < 0.05) increased 6.7 and 6.2% for the ST/ET and ET/ST groups, respectively. There was no significant (P > 0.05) difference between the two experimental groups. Muscular strength significantly (P < 0.05) improved by 15.2% (BP), 16.6% (SP), 17.2% (AC) and 11.9% (LP) for the ST/ET group and 19.9% (BP), 24.1% (SP), 20.9% (AC) and 14.0% (LP) for the ET/ST group. There were no significant (P > 0.05) differences between the two experimental groups for the BP, AC and LP; however, the ET/ST group increased (P < 0.05) SP strength more than the ST/ET group. In conclusion, adaptations to a combination of short-term endurance and strength training as assessed by VO2 max and BP, AC and LP strength appear to be independent of whether endurance training occurs prior to or following strength training.

Mast cell and myofibroblast in wound healing

Growing evidence in the literature indicates that mast cells are integrally involved in the process of dermal wound repair. They are resident cells of the normal dermis and have several cytokines stored in their granules that are stimulatory to fibroblasts. They also contain serine proteases that may be involved in remodeling of the extracellular matrix during healing. Mast cells are found in increased numbers in acute wounds and in certain chronic fibrotic diseases. Their influence on fibroblast growth and collagen production may be an important element in fibrosis. The effects of mast cell mediators on dermal fibroblasts are currently being explored by our laboratory and others. Myofibroblasts are implicated in the phenomenon of wound contraction. These phenotypically altered fibroblasts express some features of smooth muscle cells, notably actin filaments, and are abundant in granulation tissue. It has been proposed that they are responsible for wound contraction and possibly certain types of contracture. However, this hypothesis has been challenged by studies demonstrating the presence of myofibroblasts in wounds that do not contract, or the process of contraction in vitro in the absence of myofibroblasts. At this time the issue remains open to debate and further research.

Potential bioactivated neurotoxicants, N-methylated beta-carbolinium ions, are present in human brain

Potential bioactivated neurotoxicants, 2-N-methyl-beta-carbolinium and 2,9-N,N'-dimethyl-beta-carbolinium ions, as well as N-methylation activities which form these charged species, were analyzed for the first time in the parietal association cortex and the substantia nigra of human brain using GC/MS and HPLC. The brains were taken during forensic autopsies from corpses without obvious degeneration of substantia nigra. In the cortex, 2-methyl-norharmanium ion (2-MeNH) and 2,9-dimethyl-norharmanium ion (2,9-Me2NH) were detected in almost all samples. 2-Methyl-harmanium ions (2-MeHA) and 2,9-dimethyl-harmanium ions (2,9-Me2HA) were detectable in only two samples. In substantia nigra samples pooled from 3 or 4 brains for analysis, 2-MeNH and 2,9-Me2NH levels were higher than those in the cortex, whereas 2-MeHA and 2,9-Me2HA were below detection limits. Their precursors, norharman (NH) and harman (HA), were also measured using HPLC/fluorescence detection. In both regions, NH and HA were present in almost all samples; levels of NH and HA were also significantly higher in the nigra than in the cortex. Using 9-methyl-NH and 2-MeNH as substrates, in vitro N-methylation of the 2[beta] and 9[indole] nitrogens toward beta-carbolines was measured both in the cortex and in the nigra. 2[beta]-N-Methylation activity was significantly higher than 9[indole]-N-methylation activity in both regions. Recent studies show that beta-carbolinium ions resemble the synthetic parkinsonian toxicant, MPP+, with respect to structure and neurotoxic activity. Such 'bioactivated' carbolinium ions could be endogenous causative factors in Parkinson's disease.

The histology and development of hepatic nodules and carcinoma in C3H/He and C57BL/6 mice following chronic phenobarbitone administration

Male C3H/He and C57BL/6 mice were given diets containing sodium phenobarbitone (PB) to allow a daily intake of 85 mg/kg. Control and treated animals were killed at 5, 30, 40, 60, and 80 wk. Other mice were killed in extremis or at the end of the respective experiments: 91 wk for C3H/He and 100 wk for the C57BL/6 animals. A basophilic nodule was found in 1/5 control C3H/He mice at 30 wk; these nodules increased in number with time so that nodules of this type were found in approximately 70% of animals by 91 wk. Nodules were not found in control C57BL/6 mice until 80 wk, when they were found in 4% of mice. PB treatment markedly increased the number of hepatic nodules in both strains of mice. The additional nodule burden was due to the development of a second nodule type formed of large cells with a predominantly eosinophilic cytoplasm. C3H/He animals given PB for 60 wk and then returned to a control diet bore fewer nodules at 91 wk than treated mice killed at 60 or 91 wk. The cumulative incidence of carcinoma in control C3H/He and C57BL/6 mice was 28 and 4%, respectively. The incidence of carcinoma was not increased by PB treatment in either strain. It is concluded that both strains of mice behave in a qualitively similar way to PB administration, although they show considerable quantitative differences in terms of the time and number of nodules that develop. Furthermore, the increased nodule numbers associated with PB treatment were not accompanied by an increase in the number of carcinomas.

Novel S-adenosylmethionine-dependent indole-N-methylation of beta-carbolines in brain particulate fractions

Guinea pig brain S-adenosylmethionine (SAM)-dependent N-methyltransferase activity toward physiologically relevant beta-carboline (BC) substrates was examined with reverse-phase HPLC and radiochemical detection. Representative BCs, norharman and harmine, were enzymatically methylated on the 2[beta]-nitrogen by [3H]CH3-SAM in undialyzed homogenates to yield 2[beta]-methylated BCs and subsequently on the 9[indole]-nitrogen to generate 2,9-dimethylated BC products. This may be the first account of mammalian indole N-methyl transfer. There was no HPLC evidence for 9-methyl BC or (from carbon methylation) 2,6-dimethyl BC products. Capillary gas chromatography-mass spectrometry analysis confirmed the structures of the 2,9-dimethyl and 2-methyl products of norharman. The 2[beta]- and 9[indole]-N-methylation activities were mainly in the nuclear fractions and were negligible in undialyzed cytosol. This differs from the cytosolic SAM-dependent N-methylations reported with other azaheterocyclics, including 1,2,3,4-tetrahydro-BCs. The involvement of a single enzyme was suggested because the two N-methyl transfers with BC substrate had similar subcellular activity patterns, regional brain distributions, and Km and Vmax values. Sequential N-methylation of various BCs that have been observed in vivo may be a unique route to centrally retained N2,N9-dimethylated beta-carbolinium ions. Because they resemble the synthetic parkinsonian toxicant, N-methyl-4-phenylpyridinium, with respect to structure and neurotoxic activity, such "bioactivated" carbolinium ions could be endogenous causative factors in Parkinson's disease.

Mono-N-methylation of 1,2,3,4-tetrahydro-beta-carbolines in brain cytosol: absence of indole methylation

In an accompanying report we demonstrated enzyme activity in guinea pig brain cell nuclei that catalyzes S-adenosylmethionine (SAM)-dependent N-methylations of heteroaromatic beta-carbolines (BCs) on the 2[beta]-nitrogen and subsequently on the 9[indole]-nitrogen, ultimately yielding N2,N9-dimethylated BCs. Presented here are the results of a parallel study of the N-methylation of 1,2,3,4-tetrahydro-BCs (THBCs), which form endogenously via condensations of tryptophan and its derived indoles with carbonyl compounds or, like their BC oxidation products, are environmental constituents and plant alkaloids. THBCs were enzymatically methylated on the 2[beta]-nitrogen by [3H]-SAM in undialyzed homogenates of rat or guinea pig brain, but [3H]methyl transfer to the 9[indole]-nitrogen was not observed. The structure of the 2[beta]-methyl THBC product was verified with capillary gas chromatography-mass spectrometry. Furthermore, whereas BC N-methylation was largely particulate and displayed micromolar Km values for BC substrate, THBC 2[beta]-N-methylation activity was cytosolic and displayed a relatively high (millimolar) Km for THBC substrate. The N-methylation of THBCs may be due to cytosolic N-methyltransferases that others have studied using different azaheterocyclics. Our overall studies indicate that N2,N9-dimethylated BCs could be unique neurotoxic factors that are bioactivated within brain by sequential N-methylations of BCs. These results suggest the possibility of an additional route to the putative 2,9-dimethylated toxins involving, as a first step, 2[beta]-N-methylation of environmental or endogenously derived THBCs in the brain and perhaps other organs.

Effect of musculoskeletal development on the prediction of body density in females

The purpose of this study was to determine if musculoskeletal development had a significant effect on the prediction of body density in females. Subjects consisted of 156 females aged 17 to 44 years. Subjects were divided into three groups on the basis of musculoskeletal development as determined by the Heath-Carter Anthropometric Somatotype mesomorphy rating. Anthropometric measurements included eight skinfold measures (tricep, subscapula, chest, midaxillary, abdomen, suprailiac, thigh, and calf), body diameters of the humerus and femur, and circumferences at five locations (waist, forearm, upper arm, calf, and gluteal). Residual lung volume was determined by the closed circuit oxygen dilution method prior to the measurement of body density by hydrostatic weighing. A regression equation was developed to predict body density from the sum of seven skinfolds, sum of seven skinfolds squared, age, and mesomorphy rating. A similar regression equation was developed using the sum of three skinfolds, sum of three skinfolds squared, and the other variables. Results indicated that mesomorphy rating did not contribute significantly to the prediction of body density in females. It was concluded that musculoskeletal development did not have a significant effect on the prediction of body density in females.

Inhibition of mitochondrial succinate oxidation--similarities and differences between N-methylated beta-carbolines and MPP+

N-Methylated beta-carbolinium compounds (N-Me-BCs), including 2-N-methyl and 2,9-N,N-dimethyl analogs, structural analogs of 1-methyl-4-phenylpyridinium (MPP+), may be endogenously bioactivated, MPP(+)-like toxins, capable of inducing parkinsonism. Both MPP+ and selected N-Me-BCs inhibit NADH-linked mitochondrial respiration (Complex I). We now show that both also inhibit succinate-supported (Complex II) respiration, the greatest inhibition (80%) being seen for 2,9-dimethylharmanium. Complex I inhibition occurs at MPP+ concentrations (IC50 = 0.17 mM) about one order of magnitude lower than Complex II inhibition (greater than 1.2 mM). In contrast, Complex I and Complex II inhibition by the N-Me-BCs tested occurred at similar concentrations (I, 0.1 mM; II, 0.25 mM) and concentrations similar to Complex I inhibition by MPP+. 2,9-N,N-Dimethyl-BCs, which are the permanently charged BC analogs of MPP+, show inhibitory characteristics similar to MPP+: slow onset of inhibition, potentiation by TPB, and reversal by DNP. The fact that succinate oxidation cannot bypass the Complex II inhibition by N-Me-BCs could enhance any chronic neurotoxicity of N-Me-BCs.

Simulation of coherent energy transfer in an alpha-helical peptide by Fermi resonance

A mechanism by which NH stretching quanta are coherently transported along a chain of hydrogen bonded peptide groups is demonstrated by classical simulation of a section of the alpha-helical peptide poly(L-alanine). Vibrational motion takes place on a complex energy surface constructed from earlier ab initio and empirical surfaces. A speculative hypothesis of the biological role of this mechanism is presented, and the critical parameters governing the dynamics are identified and discussed.