Structural characterisation of the photoisomers of reactive sulfonated azo dyes by NMR spectroscopy and DFT calculations

1H NMR spectroscopy coupled with in situ laser irradiation has been used together with density functional theory (DFT) computation to examine the structures of the photoisomers of a series of sulfonated reactive azo dyes. Assignment of 1H NMR spectra acquired at the photostationary state has allowed, for the first time, NMR characterisation of unstable cis isomers of commercially relevant water-soluble azo dyes. Structural features of the two isomeric forms predicted by DFT calculations are clearly reflected in the experimental NMR data. The trans-cis photoisomerisation process could be unambiguously identified in each case, based on the large chemical shift change observed for resonances associated with aromatic protons adjacent to the azo linkage.

Application of principal components analysis to 1H-NMR data obtained from propolis samples of different geographical origin

Propolis is a widely used natural remedy and a range of biological activities have been attributed to it. The chemical composition of propolis is highly variable and its quality is often controlled on the basis of one or two marker compounds. In order to progress towards a method for the quality control of this complex material, HPLC and 1H-NMR approaches as methods of quality control have been compared. HPLC analyses of 43 samples of propolis were carried out and six marker compounds were quantified in each sample. The same samples were analysed using 1H-NMR and the spectra were then converted into their first derivative forms and digitised using the software application MestRe-C. The digitised data were subjected to principal component analysis using the software application Simca-P. It was found that the chemical composition of propolis mapped well according to the geographical origins of the samples studied when the first three principal components were used to display them. In addition, each sample was assessed for anti-oxidant activity, and the results were then overlaid onto the sample groupings according to 1H-NMR data. It was observed that anti-oxidant properties also mapped quite well according to geographical origin.

In silico footprinting of ligands binding to the minor groove of DNA

The sequence selectivity of small molecules binding to the minor groove of DNA can be predicted by "in silico footprinting". Any potential ligand can be docked in the minor groove and then moved along it using simple simulation techniques. By applying a simple scoring function to the trajectory after energy minimization, the preferred binding site can be identified. We show application to all known noncovalent binding modes, namely 1:1 ligand:DNA binding (including hairpin ligands) and 2:1 side-by-side binding, with various DNA base pair sequences and show excellent agreement with experimental results from X-ray crystallography, NMR, and gel-based footprinting.

Autonomic arousal in an appetitive context in primates: a behavioural and neural analysis

Central to many emotional responses is the accompanying peripheral somatic and autonomic arousal, feedback from which has been hypothesized to enhance emotional memory and to contribute to appraisal processes and decision making, and dysfunction of which may contribute to antisocial behaviour. Whilst peripheral arousal may accompany both positive and negative emotional contexts, its relationship with the former is poorly understood, as are the neural mechanisms underlying such a relationship. The purpose of the present study was to determine the autonomic correlates of anticipation, as well as consumption, of high incentive food, in the freely moving common marmoset and to investigate the contribution of the amygdala to such effects. Blood pressure (BP) and heart rate (HR) were measured remotely by a telemetric device implanted into the descending aorta and behavioural responses were monitored whilst marmosets viewed preferred or non-preferred foods and were then allowed access to eat those foods. A marked rise in blood pressure in unrestrained marmosets was observed in response both to the sight of highly preferred foods (anticipatory period) as well as during the actual consumption of those foods (consummatory period). Excitotoxic lesions of the amygdala abolished the autonomic arousal in the anticipatory period, but spared both the behavioural arousal in the anticipatory period and the autonomic arousal in the consummatory period. Together these data serve as an important step towards understanding the role of autonomic arousal in emotion and its neural underpinnings.

Acquisition of instrumental conditioned reinforcement is resistant to the devaluation of the unconditioned stimulus

The associative mechanisms responsible for the efficacy of Pavlovian stimuli during first- and second-order conditioning have been extensively studied, but little is known about the representations underlying instrumental conditioned reinforcement. The present study investigated the associative structure underlying conditioned reinforcement, by employing an unconditioned stimulus (US) devaluation procedure on a commonly used instrumental task: the acquisition of a new response with conditioned reinforcement. Whilst US-directed behaviour was abolished following devaluation, the conditioned stimulus acting as a conditioned reinforcer supported the acquisition of instrumental responding. In this preparation then, the conditioned reinforcer appears to be impervious to devaluation of its associated US, suggesting that the underlying representation maintaining behaviour is independent of the current value of the US and may reflect the activation of a central appetitive motivational state.

Competitive reactions of a ruthenium arene anticancer complex with histidine, cytochrome c and an oligonucleotide

The ruthenium arene anticancer complex [(eta(6)-bip)Ru(en)Cl][PF(6)] (1) (bip is biphenyl, en is ethylenediamine) reacted slowly with the amino acid L-histidine (L-His) in aqueous solution at 310 K. Two L-His adducts of 1 were separated by high-performance liquid chromatography and identified by electrospray ionisation mass spectrometry and NMR: an imidazole N(delta)-bound complex [(eta(6)-bip)Ru(en)(N(delta)-L-His)](2+), and an N(epsilon)-bound complex [(eta(6)-bip)Ru(en)(N(epsilon)-L-His)](2+). At 310 K, after 24 h only about 22% of complex 1 (2 mM) reacted with L-His, and of the unreacted 1, 59% had hydrolysed. In the presence of 100 mM NaCl, approximately 90% of 1 remained unreacted. In aqueous solution or triethylammonium acetate (TEAA) buffer (pH 7.6), (15)N-labelled 1 reacted with cytochrome c to give two monoruthenated protein adducts. The reaction reached equilibrium within 2 h by which time approximately 50% of cytochrome c was ruthenated. On the basis of [(1)H, (15)N] NMR data, one adduct may have Ru bound to the N-terminus, and the other to a carboxylate group on the protein. In TEAA buffer and at 310 K, more than 90% of the 14-mer oligonucleotide d(TATGTACCATGTAT) reacted with 2 mol Eq of 1 to give rise to monoruthenated and diruthenated oligonucleotide adducts. The presence of cytochrome c (1 mol Eq) or L-His (4 mol Eq) had little effect on the course of the reaction with the oligonucleotide. In cells, DNA (or RNA) may be a favoured reaction site for this Ru anticancer complex.

Neural contributions to the motivational control of appetite in humans

The motivation to eat in humans is a complex process influenced by intrinsic mechanisms relating to the hunger and satiety cascade, and extrinsic mechanisms based on the appetitive incentive value of individual foods, which can themselves induce desire. This study was designed to investigate the neural basis of these two factors contributing to the control of motivation to eat within the same experimental design using positron emission tomography. Using a novel counterbalanced approach, participants were scanned in two separate sessions, once after fasting and once after food intake, in which they imagined themselves in a restaurant and considered a number of items on a menu, and were asked to choose their most preferred. All items were tailored to each individual and varied in their incentive value. No actual foods were presented. In response to a hungry state, increased activation was shown in the hypothalamus, amygdala and insula cortex as predicted, as well as the medulla, striatum and anterior cingulate cortex. Satiety, in contrast, was associated with increased activation in the lateral orbitofrontal and temporal cortex. Only activity in the vicinity of the amygdala and orbitofrontal cortex was observed in response to the processing of extrinsic appetitive incentive information. These results suggest that the contributions of intrinsic homeostatic influences, and extrinsic incentive factors to the motivation to eat, are somewhat dissociable neurally, with areas of convergence in the amygdala and orbitofrontal cortex. The findings of this study have implications for research into the underlying mechanisms of eating disorders.

Structure and dynamics of dinuclear zirconium(IV) complexes

We have determined by X-ray crystallography the structures of three dinuclear zirconium(IV) complexes containing the heptadentate ligand dhpta (where H(5)dhpta = 1,3-diamino-2-propanol-N,N,N',N'-tetraacetic acid, 1) and different countercations: K(2)[Zr(2)(dhpta)(2)].5H(2)O (2.5H(2)O), Na(2)[Zr(2)(dhpta)(2)].7H(2)O.C(2)H(5)OH (3.7H(2)O.C(2)H(5)OH), and Cs(2)[Zr(2)(dhpta)(2)].H(5)O(2).Cl.4H(2)O (4.H(5)O(2).Cl.4H(2)O). In the K(I) complex 2, crystallized from water, the two Zr(IV) ions are 3.5973(4) A apart and bridged via two alkoxo groups (average Zr-O 2.165 A). Each Zr(IV) is eight-coordinate and also bound to two N atoms (average Zr-N 2.448 A), and four carboxylate O atoms (average Zr-O 2.148 A). The two dhpta ligands in the dinuclear unit have different conformations. One face of the complex contains an array of 14 oxygen atoms and interacts strongly with the two K(I) ions, one of which is 6-coordinate, the other 8-coordinate, which are 3.922(4) A apart and bridged by a carboxylate O and by two water molecules. The structures of the dinuclear anion [Zr(2)(dhpta)(2)](2-) in the Na(I) complex 3 and in the Cs(I) complex 4 are essentially identical to that found in complex 2, although the alkali metal ions coordinate differently to the oxygen-rich face. All Zr(IV) ions have a distorted triangulated dodecahedral geometry. Although the crystal structure of complex 2 does not indicate the presence of acidic protons, in 4 an [H(5)O(2)](+) unit is strongly H-bonded to an oxygen atom of a coordinated carboxylate group. 1D and 2D (1)H and (13)C NMR spectroscopic and potentiometric studies reveal two deprotonations with pK(a) values of 9.0 and 10.0. At low pH, two carboxylate groups appear to undergo protonation accompanied by chelate ring-opening, and the complex exhibits dynamic fluxional behavior in which the two magnetically nonequivalent dhpta ligands exchange at a rate of 11 s(-1) at pH 3.30, 298 K, as determined from 2D EXSY NMR studies. Ligand interchange is not observed at high pH (>11). The same crystals of complex 2 were obtained from solutions at pH 3 or 12. The dynamic configurational change is therefore mediated by the aqueous solvent.

A Homologous Series of Regioselectively Tetradeprotonated Group 8 Metallocenes: New Inverse Crown Ring Compounds Synthesized via a Mixed Sodium−Magnesium Tris(diisopropylamide) Synergic Base

Subjecting ferrocene, ruthenocene, or osmocene to the synergic amide base sodium-magnesium tris(diisopropylamido) affords a unique homologous series of metallocene derivatives of general formula [(M(C(5)H(3))(2))Na(4)Mg(4)(i-Pr(2)N)(8)] (where M = Fe (1), Ru (2), or Os (3)). X-ray crystallographic studies of 1-3 reveal a common molecular "inverse crown" structure comprising a 16-membered [(NaNMgN)(4)](4+) "host" ring and a metallocenetetraide [M(C(5)H(3))(2)](4-) "guest" core, the cleaved protons of which are lost selectively from the 1, 1', 3, and 3'-positions. Variable-temperature NMR spectroscopic studies indicate that 1, 2, and 3 each exist as two distinct interconverting conformers in arene solution, the rates of exchange of which have been calculated using coalescence and EXSY NMR measurements.

Short Lexitropsin that Recognizes the DNA Minor Groove at 5‘-ACTAGT-3‘: Understanding the Role of Isopropyl-thiazole

Isopropyl-thiazole ((iPr)Th) represents a new addition to the building blocks of nucleic acid minor groove-binding molecules. The DNA decamer duplex d(CGACTAGTCG)(2) is bound by a short lexitropsin of sequence formyl-PyPy(iPr)Th-Dp (where Py represents N-methyl pyrrole, (iPr)Th represents thiazole with an isopropyl group attached, and Dp represents dimethylaminopropyl). NMR data indicate ligand binding in the minor groove of DNA to the sequence 5'-ACT(5)AG(7)T-3' at a 2:1 ratio of ligand to DNA duplex. Ligand binding, assisted by the enhanced hydrophobicity of the (iPr)Th group, occurs in a head-to-tail fashion, the formyl headgroups being located toward the 5'-ends of the DNA sequence. Sequence reading is augmented through hydrogen bond formation between the exocyclic amine protons of G(7) and the (iPr)Th nitrogen, which lies on the minor groove floor. The B(I)/B(II) DNA backbone equilibrium is altered at the T(5) 3'-phosphate position to accommodate a B(II) configuration. The ligands bind in a staggered mode with respect to one another creating a six base pair DNA reading frame. The introduction of a new DNA sequence-reading element into the recognition jigsaw, combined with an extended reading frame for a small lexitropsin with enhanced hydrophobicity, holds great promise in the development of new, potentially commercially viable drug lead candidates for gene targeting.

DNA binding of a short lexitropsin

Footprinting, capillary electrophoresis, molecular modelling and NMR studies have been used to examine the binding of a short polyamide to DNA. This molecule, which contains an isopropyl-substituted thiazole in place of one of the N-methylpyrroles, is selective for the sequence 5'-ACTAGT-3' to which it binds with high affinity. Two molecules bind side-by-side in the minor groove, but their binding is staggered so that the molecule reads six base pairs, unlike the related natural products, which tend to bind to four-base-pair sequences. The result suggests that high affinity and selectivity may be gained without resort to very large molecules, which may be difficult to deliver to the site of action.

Biochemical prognostic markers of outcome in non-paracetamol-induced fulminant hepatic failure

BACKGROUND

Fulminant hepatic failure (FHF) is associated with major metabolic disturbances, the onset and severity of which can predict clinical outcome. This study uses admission blood samples to identify early biochemical markers of clinical outcome in patients with non-paracetamol-induced FHF.

PATIENTS AND METHODS

Fifty-nine patients admitted to the Scottish Liver Transplant Unit with non-paracetamol-induced FHF were studied. Plasma samples were collected at a median of 5.4 hr after admission to our unit and analyzed using conventional laboratory tests and nuclear magnetic resonance spectroscopy.

RESULTS

A total of 19 patients underwent transplantation, 15 patients died without undergoing transplantation, and 25 patients survived with medical management alone. There were significantly lower levels of lactate, alanine, valine, and bilirubin and significantly higher levels of pyruvate and albumin in patients who survived spontaneously compared with the other two groups. By use of multiple logistic regression analysis, an equation was devised that best predicted clinical outcome: 0.5x(albumin [g/L])-2x(lactate [mmol/L])-36x(valine [mmol/L])-38x(pyruvate [mmol/L]). Values of less than 2 were associated with poor clinical outcome and had a positive predictive value of 91%, a negative predictive value of 86%, a sensitivity of 94%, and a specificity of 86% for death or transplantation. This algorithm can be applied on admission, thus expediting decision-making.

CONCLUSION

We identified biochemical markers that may be useful in predicting outcome in patients with non-paracetamol-induced FHF and should be evaluated further in a different patient population.

Lesions of the orbitofrontal but not medial prefrontal cortex disrupt conditioned reinforcement in primates

The ventromedial prefrontal cortex (PFC) is implicated in affective and motivated behaviors. Damage to this region, which includes the orbitofrontal cortex as well as ventral sectors of medial PFC, causes profound changes in emotional and social behavior, including impairments in certain aspects of decision making. One reinforcement mechanism that may well contribute to these behaviors is conditioned reinforcement, whereby previously neutral stimuli in the environment, by virtue of their association with primary rewards, take on reinforcing value and come to support instrumental action. Conditioned reinforcers are powerful determinants of behavior and can maintain responding over protracted periods of time in the absence of and potentially in conflict with primary reinforcers. It has already been shown that conditioned reinforcement is dependent on the amygdala, and because the amygdala projects to both the orbitofrontal cortex and the medial PFC, the present study determined whether conditioned reinforcement was also dependent on one or the other of these prefrontal regions. Comparison of the behavioral effects of selective excitotoxic lesions of the PFC in the common marmoset revealed that orbitofrontal but not medial PFC lesions disrupted two distinct measures of conditioned reinforcement: (1) acquisition of a new response and (2) sensitivity to conditioned stimulus omission on a second-order schedule. In contrast, the orbitofrontal lesion did not affect sensitivity to primary reinforcement as measured by responding on a progressive-ratio schedule and a home cage consumption test. Together, these findings demonstrate the critical and specific involvement of the orbitofrontal cortex but not the medial PFC in conditioned reinforcement.

Induced-fit recognition of DNA by organometallic complexes with dynamic stereogenic centers

Organometallic chemistry offers novel concepts in structural diversity and molecular recognition that can be used in drug design. Here, we consider DNA recognition by eta 6-arene Ru(II) anticancer complexes by an induced-fit mechanism. The stereochemistry of the dinuclear complex [((eta 6-biphenyl)RuCl(en))2-(CH2)6]2 + (3, en = ethylenediamine) was elucidated by studies of the half unit [(eta 6-biphenyl)RuCl(Et-en)]+ (2, where Et-en is Et(H)NCH2CH2NH2). The structures of the separated RRu*RN* and SRu*RN* diastereomers of 2 were determined by x-ray crystallography; their slow interconversion in water (t(1/2) approximately 2 h, 298 K, pH 6.2) was observed by NMR spectroscopy. For 2 and 3 the RRu*RN* configurations are more stable than SRu*RN* (73:27). X-ray and NMR studies showed that reactions of 2 and 3 with 9-ethylguanine gave rise selectively to SRu*RN* diastereomers. Dynamic chiral recognition of guanine can lead to high diastereoselectivity of DNA binding. The dinuclear complex 3 induced a large unwinding (31 degrees) of plasmid DNA, twice that of mononuclear 2 (14 degrees), and effectively inhibited DNA-directed RNA synthesis in vitro. This dinuclear complex gave rise to interstrand cross-links on a 213-bp plasmid fragment with efficiency similar to bifunctional cisplatin, and to 1,3-GG interstrand and 1,2-GG and 1,3-GTG intrastrand cross-links on site-specifically ruthenated 20-mers. Complex 3 blocked intercalation of ethidium considerably more than mononuclear 2. The concept of induced-fit recognition of DNA by organometallic complexes containing dynamic stereogenic centers via dynamic epimerization, intercalation, and cross-linking may be useful in the design of anticancer drugs.

Dissociable contributions of the human amygdala and orbitofrontal cortex to incentive motivation and goal selection

Theories of incentive motivation attempt to capture the way in which objects and events in the world can acquire high motivational value and drive behavior, even in the absence of a clear biological need. In addition, for an individual to select the most appropriate goal, the incentive values of competing desirable objects need to be defined and compared. The present study examined the neural substrates by which appetitive incentive value influences prospective goal selection, using positron emission tomographic neuroimaging in humans. Sated subjects were shown a series of restaurant menus that varied in incentive value, specifically tailored for each individual, and in half the trials, were asked to make a selection from the menu. The amygdala was activated by high-incentive menus regardless of whether a choice was required. Indeed, activity in this region varied as a function of individual subjective ratings of incentive value. In contrast, distinct regions of the orbitofrontal cortex were recruited both during incentive judgments and goal selection. Activity in the medial orbital cortex showed a greater response to high-incentive menus and when making a choice, with the latter activity also correlating with subjective ratings of difficulty. Lateral orbitofrontal activity was observed selectively when participants had to suppress responses to alternative desirable items to select their most preferred. Taken together, these data highlight the differential contribution of the amygdala and regions within the orbitofrontal cortex in a neural system underlying the selection of goals based on the prospective incentive value of stimuli, over and above homeostatic influences.

Selective Recognition of Configurational Substates of Zinc Cyclam by Carboxylates: Implications for the Design and Mechanism of Action of Anti-HIV Agents

The interaction of metal cyclams with carboxylate groups is thought to play an important role in their binding to the CXCR4 chemokine receptor and in their anti-HIV activity. Here we report the synthesis of acetate, phthalate, perchlorate and chloride complexes of Zn(II) cyclam (1,4,8,11-tetraazacyclotetradecane). The X-ray crystal structures of [Zn(cyclam)(phthalate)](n)(CH(3)OH)(2n) and [Zn(cyclam)(H(2)O)(2)](OAc)(2) contain octahedral Zn(II) centres. Phthalate acts as a bridging ligand in the former complex, binding through monodentate carboxylate groups, and giving rise to infinite chains in the lattice together with extensive hydrogen bonding between carboxylate donor oxygen atoms and amine and methanol acceptor atoms. The uncoordinated acetate groups and the aqua ligand in the acetate complex are also involved in a rich network of hydrogen bonds and this may account for the unusually long Zn[bond]O distance (2.27 A). In both crystalline complexes, the macrocycle adopts the trans-III (S,S,R,R) configuration. 1D (1)H NMR spectra of all four complexes have been fully assigned by a combination of 2D [(1)H, (1)H] COSY and TOCSY, and [(1)H, (13)C] and [(1 )H, (15)N] HSQC NMR data. In aqueous solution, the stable trans-III configuration found in the solid-state equilibrates slowly (hours at 298 K) with trans-I (R,S,R,S) and cis-V (R,R,R,R) configurations. The trans-III configuration is predominant in aqueous solution for both the chloride and perchlorate complexes, but for the acetate and phthalate complexes, the cis-V configuration dominates. Carboxylate groups appear to stabilize the cis-V configuration in solution through Zn(II) coordination and hydrogen bonding. Titration of the chloride Zn(II)-cyclam complex with acetate confirmed that carboxylates strongly induce formation of the cis-V configuration. This implies that carboxylates can exert a strong influence over configurational selectivity. Cyclam NH hydrogen bonding is prevalent both in the solid state and in solution, and is relevant to the anti-HIV activity of Zn(II) and other metal cyclam complexes and to their ability to recognize the CXCR4 transmembrane co-receptor.

Role of the anterior cingulate cortex in the control over behavior by Pavlovian conditioned stimuli in rats

To investigate the contribution of the anterior cingulate cortex (ACC) to stimulus-reward learning, rats with lesions of peri- and postgenual ACC were tested on a variety of Pavlovian conditioning tasks. Lesioned rats learned to approach a food alcove during a stimulus predicting food, and responded normally for conditioned reinforcement. They also exhibited normal conditioned freezing and Pavlovian-instrumental transfer, yet were impaired at autoshaping. To resolve this apparent discrepancy, a further task was developed in which approach to the food alcove was under the control of 2 stimuli, only 1 of which was followed by reward. Lesioned rats were impaired, approaching during both stimuli. It is suggested that the ACC is not critical for stimulus-reward learning per se, but is required to discriminate multiple stimuli on the basis of their association with reward.

Synthesis of the mixed lithium-potassium-(bis)magnesium N-metallated/N, C-dimetallated amide [Li2K2Mg4[But(Me3Si)N]4[But[Me2(H2C)Si]N]4]: an inverse crown molecule with an atomless cavity

Unlike previous members of the inverse crown family, which are heterobimetallic and have cationic rings surrounding anionic cores, the title compound is heterotrimetallic and its "guest" anion is intramolecularly stitched into the complex fused-ring structure of its cationic "host".

Sequence-selective metalation of double-helical oligodeoxyribonucleotides with PtII, MnII, and ZnII ions

Reactions of [PtCl(dien)](+) (dien=diethylenetriamine), Mn(2+) and Zn(2+) ions with three different double-helical oligodeoxyribonucleotides, which contain the central sequence GGXY (XY=AT, TA or CC) have been monitored by NMR spectroscopy. 2 D [(1)H, (15)N] HSQC/HMQC NMR spectroscopy using (15)N-labeled Pt(dien) shows that the rate of formation of 3'-G-N 7 and 5'-G-N 7 platinated adducts is highly sequence dependent. The relative rates of platination of 5'-G versus 3'-G are largest for the sequence -GGCC-, for which only a small fraction of the 3'-G adduct is formed; for -GGTA-, the rate of 5'-G platination is about eight times that of 3'-G, and for -GGAT- the ratio is 1.2. These values are in qualitative agreement with those obtained for G-N 7/Mn(2+) selectivity as determined by paramagnetic line broadening of the adjacent G-H 8, and also G-N 7/Zn(2+) selectivity as determined by G-H 8 chemical shift changes. Fluctuation in the nucleophilicity of G-N 7 may be explained by variation of the pi-stacking interaction between base residues along the double helix. The reaction mixtures containing platinated 3'-G and 5'-G fractions were separated by HPLC. Since the duplexes are self-complementary, the platinated single strands were readily annealed to duplexes with twofold symmetry and analyzed by 2 D [(1)H, (1)H] NOESY NMR spectroscopy. Unexpectedly, the 5'-G-H 8 resonance signals of both 5'-G and 3'-G platinated duplexes showed large downfield shifts in the range delta=0.3-0.6 ppm, while the 3'-G-H 8 resonance signals in both cases exhibited no, or only slight, upfield shifts. Resonance signals for several other protons in the central region undergo large chemical shift variations induced by platination, indicating that monofunctional binding to DNA leads to appreciable conformational changes.

Appetitive behavior: impact of amygdala-dependent mechanisms of emotional learning

In this chapter, we review data from studies involving appetitive conditioning using measures of pavlovian approach behavior and the effects of pavlovian conditioned stimuli on instrumental behavior, including the pavlovian-to-instrumental transfer effect and conditioned reinforcement. These studies consistently demonstrate double dissociations of function between the basolateral area and the central nucleus of the amygdala. Moreover, the data show marked parallels with data derived from aversive (fear) conditioning studies and are consistent with the idea that these subsystems of the amygdala mediate different kinds of associative representation formed during pavlovian conditioning. We hypothesize that the basolateral amygdala is required for a conditioned stimulus to gain access to the current affective value of its specific unconditioned stimulus, whereas the central nucleus mediates stimulus-response representations and conditioned motivational influences on behavior. Although these systems normally operate together, they can also modulate behavior in distinct ways. In many circumstances, then, emotional behavior can be seen as a coordinated combination of processing by these amygdaloid sub-nuclei, reflecting the superimposition of a phylogenetically recent basolateral amygdala subsystem that encodes and retrieves the affective value of environmental stimuli and thereby directs complex, adaptive behavioral responses onto a phylogenetically older central amygdala subsystem that enables cortical structures (including the basolateral amygdala) to recruit incentive motivational processes and thereby invigorate emotional responding.

The effect of hypothermia on primary porcine hepatocyte metabolism monitored by (1H) nuclear magnetic resonance spectroscopy

OBJECTIVE

The aim of our study was to use (1H) nuclear magnetic resonance (NMR) spectroscopy as a tool to assess metabolic functions of hepatocytes and to monitor major metabolic pathways of these cells during culture following hypothermic preservation.

METHODS

After isolation, 2 x 10(7) primary porcine hepatocytes were preserved at 4 degrees C in supplemented Leibovitz L-15 medium for 48 h. Viability was assessed at isolation, 24 and 48 h. At isolation and at 48 h cells were plated and cultured with serum free supplemented Williams E medium. 1H NMR spectroscopy was used to assess indices of glucose metabolism, ammonia clearance indices and ketone bodies precursors at 48 h post-plating. Peak integration was applied with sodium 3-(trimethylsilyl-2,2,3,3-2H4)-1-propionate as an internal standard to obtain quantitative results.

RESULTS

Results were obtained from six isolations. Viability was 78.1 +/- 1.2% at isolation, 69 +/- 3.4% at 24 h and 58.9 +/- 3.8% at 48 h of hypothermia. Plating efficiency was 87 +/- 4% for freshly isolated cells and 33.6 +/- 7.6% for hypothermically preserved cells. Glucose consumption was comparable in both groups. Hypothermically preserved cells consumed more threonine, produced more pyruvate and alanine but less lactate. They also produced less acetate and consumed less tyrosine. Glutamate and glutamine concentrations were similar under both conditions.

CONCLUSION

1H NMR spectroscopy is a valid method for assessing metabolic pathways of cultured primary porcine hepatocytes. Although hypothermically preserved cells had a reduced plating efficiency, they were still metabolically active. Thus, hypothermia can be used as a temporary preservation technique for primary porcine hepatocytes.