Behavioral dynamics and neural grounding of a dynamic field theory of multi-object tracking

The ability to dynamically track moving objects in the environment is crucial for efficient interaction with the local surrounds. Here, we examined this ability in the context of the multi-object tracking (MOT) task. Several theories have been proposed to explain how people track moving objects; however, only one of these previous theories is implemented in a real-time process model, and there has been no direct contact between theories of object tracking and the growing neural literature using ERPs and fMRI. Here, we present a neural process model of object tracking that builds from a Dynamic Field Theory of spatial cognition. Simulations reveal that our dynamic field model captures recent behavioral data examining the impact of speed and tracking duration on MOT performance. Moreover, we show that the same model with the same trajectories and parameters can shed light on recent ERP results probing how people distribute attentional resources to targets vs. distractors. We conclude by comparing this new theory of object tracking to other recent accounts, and discuss how the neural grounding of the theory might be effectively explored in future work.

Transgenic mice over-expressing human beta-amyloid have functional nicotinic alpha 7 receptors

A potentially major factor in the development of Alzheimer's disease is the enhanced production of soluble beta-amyloid peptide fragments amyloid beta peptide(1-40) and amyloid beta peptide(1-42). These amyloid peptides are generated by cleavage of the amyloid-precursor protein and aggregate spontaneously to form amyloid plaques, which are a classical pathological hallmark in Alzheimer's disease. Although the precise mechanisms are unknown, it is widely believed that amyloid peptides initiate the degenerative process, resulting in subsequent cognitive decline. One interaction of amyloid beta peptide that may contribute to an impairment of cognition is its high affinity binding to the alpha 7 nicotinic receptor; a receptor shown to be important for cognition in a number of studies. There is some controversy, however, whether amyloid beta peptide inhibits or activates this receptor. We have cloned and stably expressed the human alpha 7 receptor and investigated its interaction with amyloid beta peptide using patch clamp electrophysiology. Human alpha 7 was activated in a concentration-dependent fashion by nicotine, acetylcholine and choline and potently inhibited by methyllycaconitine citrate. The responses were inwardly rectifying and exhibited rapid activation, desensitization and deactivation. Amyloid beta peptide(1-42) antagonized human alpha7 responses in a partially reversible fashion; no agonist effects of amyloid beta peptide(1-42) were detected. A similar inhibition of mouse alpha 7 was also observed. In addition, we have assessed the function of native alpha 7 receptors in hippocampal slices prepared from transgenic mice that over-express human amyloid. Despite this clear inhibition of recombinant receptors, hippocampal GABAergic interneurones in slices from beta-amyloid over-expressing mice still possess alpha 7 receptor-mediated currents.

Modulation of hippocampal excitability by 5-HT4 receptor agonists persists in a transgenic model of Alzheimer's disease

5-HT(4) receptors are widely distributed in both peripheral and central nervous systems where they couple, via a G-protein, to the activation of adenylate cyclase. In the brain, the highest 5-HT(4) receptor densities are found in the limbic system, including the hippocampus and frontal cortex. It has been suggested that activation of these receptors may be of therapeutic benefit in diseases that produce cognitive deficits such as Alzheimer's disease (AD). Previous electrophysiological studies have shown that the 5-HT(4) agonist, Zacopride, can increase population spike amplitude recorded in region CA1 of rat hippocampal slices in a cyclic AMP (cAMP)/cAMP-dependent protein kinase A-dependent manner. We report here that the 5-HT(4) agonist, Prucalopride, and the 5-HT(4) partial agonist, SL65.0155, produce a similar effect in rat hippocampal slices and that the specific 5-HT(4) antagonist, GR113808, blocks these effects. To investigate the potential use of 5-HT(4) agonists in the treatment of AD, Prucalopride was applied to hippocampal slices from a transgenic mouse line that overexpresses the Abeta peptide. Despite the deficit in synaptic transmission present in these mice, the percentage increase of the CA1 population spike induced by Prucalopride was the same as that observed in wild-type mice. These data support 5-HT(4) receptors as a target for cognitive enhancement and suggest that a partial agonist would be sufficient to produce benefits, while reducing potential peripheral side effects. In addition, we show that 5-HT(4) receptors remain functional in the presence of excess Abeta peptide and may therefore be a useful target in AD.

Bioavailability of flavan-3-ols and procyanidins: gastrointestinal tract influences and their relevance to bioactive forms in vivo

There is considerable interest in the bioavailability of flavan-3-ols such as tea catechins and cocoa-derived procyanidin components of the diet and their bioactivity in vivo. Their hydrogen-donating abilities and their propensity for nitration make these compounds powerful scavengers of reactive oxygen and nitrogen species. In addition, recent evidence has suggested that these compounds may interact with redox-sensitive cell signaling pathways. However, their bioactivity in vivo will be dependent on the absorption and metabolism of these compounds after ingestion and the reducing properties of resulting metabolites. Many cell, animal, and human studies have shown that flavanol monomers, such as epicatechin, are extensively metabolised to O-methylated forms and/or conjugated to glucuronides and sulphates during absorption into the circulation. The cleavage of higher procyanidin oligomers to mixtures of monomer and dimer in the stomach may act to enhance the potential for their absorption in the small intestine as higher oligomers have very limited absorption. Studies suggest that the major bioactive forms of flavanol monomers and procyanidins in vivo are likely to be metabolites and/or conjugates of epicatechin. One such metabolite, 3'-O-methylepicatechin, has been shown to exert protective effects against oxidative stress-induced cell death. Future studies will continue to concentrate on the exact mechanism of action of the bioactive forms of flavan-3-ols in vivo.

Contrasting influences of glucuronidation and O-methylation of epicatechin on hydrogen peroxide-induced cell death in neurons and fibroblasts

The purpose of this study was to examine the comparative mechanisms by which the dietary form of the flavonoid epicatechin and its predominant in vivo metabolite, epicatechin glucuronide, influence oxidative stress-induced cell death in fibroblasts and neurons. The results demonstrate the contrasting influences of in vivo glucuronidation and methylation on the bioactivity of epicatechin.

Flavonoids protect neurons from oxidized low-density-lipoprotein-induced apoptosis involving c-Jun N-terminal kinase (JNK), c-Jun and caspase-3

Oxidative stress has been associated with neuronal loss in neurodegenerative diseases and during age-associated cognitive decline. Flavonoids have been proposed to play a useful role in protecting the central nervous system against oxidative and excitotoxic stress, although the mechanism of action is unknown. Using oxidized low-density lipoprotein (oxLDL) as the oxidative insult we investigated the mechanism of neurotoxicity and attempted to identify possible sites of action of two of the most potent protective flavonoids, epicatechin and kaempferol, in cultured primary neurons. Using cultured striatal neurons and selective phosphospecific antibodies we addressed the potential role of extracellular signal-regulated kinases 1/2 (ERK1/2) and c-Jun N-terminal kinase (JNK). OxLDL stimulated a Ca(2+)-dependent activation of both ERK1/2 and JNK that was strongly inhibited by pre-treatment with low micromolar concentrations of epicatechin. Neurotoxicity induced by oxLDL, however, was neither reduced nor enhanced by inhibiting ERK1/2 activation with mitogen-activated protein kinase kinase (MEK) inhibitors, suggesting that this cascade is unlikely to be involved in either oxLDL toxicity or the protective effects of flavonoids. oxLDL caused a sustained activation of JNK that resulted in the phosphorylation of the transcription factor c-Jun, which was abolished in neurons pre-treated with flavonoids. Furthermore, oxLDL induced the cleavage of procaspase-3 and increased caspase-3-like protease activity in neurons, an effect which was strongly inhibited by pre-exposure to either epicatechin or kaempferol. In addition, a caspase-3 inhibitor reduced oxLDL-induced neuronal death, implicating an apoptotic mechanism. A major in vivo metabolite of epicatechin, 3'-O-methyl-epicatechin was as effective as epicatechin in protecting neurons. Thus dietary flavonoids might have potential as protective agents against neuronal apoptosis through selective actions within stress-activated cellular responses, including protein kinase signalling cascades.

Tests of a dynamic systems account of the A-not-B error: the influence of prior experience on the spatial memory abilities of two-year-olds

Recently, Smith, Thelen, and colleagues proposed a dynamic systems account of the Piagetian "A-not-B" error in which infants' errors result from general processes that make goal-directed actions to remembered locations. Based on this account, the A-not-B error should be a general phenomenon, observable in different tasks and at different points in development. Smith, Thelen, et al.'s proposal was tested using an A-not-B version of a sandbox task. During three training trials and three "A" trials, 2-year-olds watched as a toy was buried in a sandbox at Location A. Following a 10-s delay, children searched for the object. Across five experiments, children's (total N = 92) performance on the A trials was accurate. After the A trials, children watched as a toy was hidden at Location B, 8 to 10 inches from Location A. In all experiments, children's searches after a 10-s delay were significantly biased in the direction of Location A. Furthermore, this bias toward Location A decreased with repeated trials to Location B, as well as when children completed fewer trials to Location A. Together, these data suggest that A-not-B-type errors are pervasive across tasks and development.

Epicatechin is the primary bioavailable form of the procyanidin dimers B2 and B5 after transfer across the small intestine

Perfusion of isolated small intestine with the procyanidin dimers B2 and B5 extracted from cocoa indicated that both forms of dimer are transferred to the serosal side of enterocytes but only to a very small extent (<1% of the total transferred flavanol-like compounds). However, perfusion of dimer mainly resulted in large amounts of unmetabolised/unconjugated epicatechin monomer being detected on the serosal side (95.8%). The cleavage of dimer during transfer seemed to be energy-dependent, requiring an intact cell system, as incubation with jejunal homogenates failed to yield epicatechin. Low levels methylated dimer were also detected (3.2%), but no conjugates and metabolites of epicatechin indicating that metabolism of monomer and dimer is limited during dimer cleavage/translocation. The methylation of dimer may be by catechol-O-methyltransferase, however, at high concentrations of dimer COMT activity is reduced leading to an inhibition of both monomer and dimer O-methylation.

Medications in the breast-feeding mother

Prescribing medications for a breast-feeding mother requires weighing the benefits of medication use for the mother against the risk of not breast-feeding the infant or the potential risk of exposing the infant to medications. A drug that is safe for use during pregnancy may not be safe for the nursing infant. The transfer of medications into breast milk depends on a concentration gradient that allows passive diffusion of nonionized, non-protein-bound drugs. The infant's medication exposure can be limited by prescribing medications to the breast-feeding mother that are poorly absorbed orally, by avoiding breast-feeding during times of peak maternal serum drug concentration and by prescribing topical therapy when possible. Mothers of premature or otherwise compromised infants may require altered dosing to avoid drug accumulation and toxicity in these infants. The most accurate and up-to-date sources of information, including Internet resources and telephone consultations, should be used.

Novel biomarkers of the metabolism of caffeic acid derivatives in vivo

The purpose of this study was to investigate biomarkers of the bioavailability and metabolism of hydroxycinnamate derivatives through the determination of the pharmacokinetics of their urinary elimination and identification of the metabolites excreted. Coffee was used as a rich source of caffeic acid derivatives and human supplementation was undertaken. The results show a highly significant increase in the excretion of ferulic, isoferulic, dihydroferulic acid (3-(4-hydroxy-3-methoxyphenyl)-propionic acid), and vanillic acid postsupplementation relative to the levels presupplementation. Thus, ferulic, isoferulic, and dihydroferulic acids are specific biomarkers for the bioavailability and metabolism of dietary caffeic acid esters. Isoferulic acid is a unique biomarker as it is not a dietary component, however, dihydroferulic acid may well derive from other flavonoids with a structurally related B-ring. 3-Hydroxyhippuric acid has also been identified as an indicator for bioavailability and metabolism of phenolic compounds, and shows a highly significant excretion increase postsupplementation. The results reveal isoferulic acid (and possibly dihydroferulic acid) as novel markers of caffeoyl quinic acid metabolism.

Epicatechin and its in vivo metabolite, 3'-O-methyl epicatechin, protect human fibroblasts from oxidative-stress-induced cell death involving caspase-3 activation

There is considerable current interest in the cytoprotective effects of natural antioxidants against oxidative stress. In particular, epicatechin, a major member of the flavanol family of polyphenols with powerful antioxidant properties in vitro, has been investigated to determine its ability to attenuate oxidative-stress-induced cell damage and to understand the mechanism of its protective action. We have induced oxidative stress in cultured human fibroblasts using hydrogen peroxide and examined the cellular responses in the form of mitochondrial function, cell-membrane damage, annexin-V binding and caspase-3 activation. Since one of the major metabolites of epicatechin in vivo is 3'-O-methyl epicatechin, we have compared its protective effects with that of epicatechin. The results provide the first evidence that 3'-O-methyl epicatechin inhibits cell death induced by hydrogen peroxide and that the mechanism involves suppression of caspase-3 activity as a marker for apoptosis. Furthermore, the protection elicited by 3'-O-methyl epicatechin is not significantly different from that of epicatechin, suggesting that hydrogen-donating antioxidant activity is not the primary mechanism of protection.

Bioavailability of flavonoids and potential bioactive forms in vivo

Flavonoids are powerful antioxidants in vitro, but their overall functions in vivo have yet to be clarified, whether antioxidant, anti-inflammatory, enzyme inhibitor or inducer, or some other role. The reducing properties of flavonoids might also contribute to redox regulation in cells independently of their antioxidant properties. However, in order to understand their bioactivity in vivo, it is necessary to understand the factors influencing the absorption of flavonoids by the gastrointestinal tract, the nature of the conjugates and metabolites in the circulation and how this influences their antioxidant activities.

An internal ribosome entry segment in the 5' untranslated region of the mnt gene

Mnt is a transcriptional repressor related to the Myc/Mad family of transcription factors. It is expressed in proliferating, resting and differentiating cells and is believed to antagonize the function of Myc. Here we have characterized the major transcription initiation site of the mnt gene. In doing so we noted a remarkable level of sequence conservation between the murine and human 5' untranslated regions. Our experiments revealed that this sequence contains an internal ribosome entry segment (IRES). In addition, we show that sequences at both the 5' and 3' end of the IRES are essential for its function. These findings indicate that mnt can be translated by internal initiation. Such a mechanism may allow efficient Mnt synthesis when cap-dependent translation initiation is reduced.

Bi-directional changes in synaptic plasticity induced at corticostriatal synapses in vitro

Long-term changes in the synaptic efficacy of corticostriatal synapses are believed to be important for regulating the excitatory input to the basal ganglia, and hence for motor learning and certain forms of cognition. Previous reports have suggested that long-term depression (LTD) is the predominant form of plasticity at corticostriatal synapses. However, we report here that tetanic stimulation of the white matter can readily induce long-term potentiation (LTP) at corticostriatal synapses in a sagittal slice preparation. Furthermore, we find that corticostriatal LTP is obtained in the absence of pharmacological manipulation, and is dependent on NMDA receptor activation. In contrast, LTD is rarely observed following tetanic stimulation of the white matter, but in fact requires direct stimulation within the striatum. This striatally induced depression is blocked by both D1 and D2 dopamine receptor antagonists and by NMDA receptor blockade. Pairing of striatal stimulation with tetanic stimulation of the white matter does not prevent the induction, but significantly enhances the magnitude of LTP at corticostriatal synapses. We suggest that the corticostriatal depression reported here most likely involves the recruitment of local striatal circuits and dopaminergic inputs, and thus might explain the predominance of LTD previously reported. Our observation that it is indeed possible to induce LTP at corticostriatal synapses under physiological conditions in vitro has implications for the normal function and control of the basal ganglia in motor learning and cognition.

Epicatechin and catechin are O-methylated and glucuronidated in the small intestine

There is considerable interest in the bioavailability of polyphenols and their bioactivity in vivo. We have studied the absorption and metabolism of catechin and epicatechin in the small intestine and the comparative transfer across the jejunum and ileum. Perfusion of isolated jejunum with the flavanols resulted in glucuronidation ( approximately 45%), O-methylation: 3'-O-Methyl- and 4'-O-methyl- ( approximately 30%), and O-methyl-glucuronidation ( approximately 20% of total flavanols identified) during transfer across the enterocytes to the serosal side. This demonstrates the activity of catechol-O-methyl transferases in the metabolism of flavanols and suggests that these metabolites and conjugates are likely to enter the portal vein. In contrast, in the case of the ileum, the majority of the flavanols appeared on the serosal side unmetabolised and the total percentage of flavanols transferred was higher than that in the jejunum ( approximately fivefold).

Assisted vaginal delivery using the vacuum extractor

Vacuum extractors have replaced forceps for many situations in which assistance is required to achieve vaginal delivery. Compared with metal-cup vacuum extractors, soft-cup devices are easier to use and cause fewer neonatal scalp injuries; however, they detach more frequently. Vacuum extractors can cause neonatal injury. These devices should be employed when indicated, usually for a nonreassuring fetal heart tracing or failure to progress in the second stage of labor. Complications may be minimized if the physician recognizes contraindications to the use of vacuum extraction. Complete documentation is essential.

Decomposition of cocoa procyanidins in the gastric milieu

There is considerable interest in the bioavailability of flavonoids and phenolic components of the diet and their bioactivity in vivo. However, little is known of pre-absorption events in the gastric lumen. The effects of the acidic environment, as found in the gastric milieu, on procyanidin oligomers of catechin polyphenols has been investigated. The results show that under these conditions the procyanidin oligomers (trimer to hexamer) are hydrolysed to mixtures of epicatechin monomer and dimer, thus enhancing the potential for their absorption in the small intestine.

Resveratrol is absorbed in the small intestine as resveratrol glucuronide

We have studied the absorption and metabolism of resveratrol in the jejunum in an isolated rat small intestine model. Only small amounts of resveratrol were absorbed across the enterocytes of the jejunum and ileum unmetabolised. The major compound detected on the serosal side was the glucuronide conjugate of resveratrol (96.5% +/- 4.6 of the amount absorbed) indicating the susceptibility of resveratrol to glucuronidation during transfer across the rat jejunum. The presence of the glucuronide was confirmed using HPLC-PDA and nanoES-MS/MS techniques. These findings suggest that resveratrol is most likely to be in the form of a glucuronide conjugate after crossing the small intestine and entering the blood circulation. This will have important implications for the biological functions of resveratrol in vivo.

Nitrite-induced deamination and hypochlorite-induced oxidation of DNA in intact human respiratory tract epithelial cells

No modification of purine or pyrimidine bases was observed when isolated DNA was incubated with 1 mM nitrite at pH 7.4. However, exposure of human bronchial epithelial cells in culture medium at pH 7.4 to nitrite at concentrations of 100 microM or greater led to deamination of purine bases in cellular DNA. Deamination was more extensive in cells exposed to lower extracellular pH values and higher nitrite concentrations. Significant increases in the levels of xanthine and hypoxanthine, putative deamination products of guanine and adenine, respectively, were observed in DNA from nitrite-treated cells but no rise in any base oxidation products such as 8-hydroxyguanine. This pattern of damage suggests that exposure of cells to nitrite (even at pH 7.4) leads to intracellular generation of "reactive nitrogen species" capable of deaminating purines in DNA. In addition, significant DNA strand breakage occurred in nitrite-treated cells. The time course of base damage suggested that the repair of deaminated purine lesions in these cells is slow. By contrast, DNA isolated from cells exposed to hypochlorous acid (HOCl) has significant oxidation of pyrimidine bases and chlorination of cytosine but little oxidation of purines. Exposure of cells to both species (NO(2)(-) plus HOCl) potentiated the oxidative DNA base damage observed but decreased the extent of deamination. We hypothesize that this is due to the formation of nitryl chloride (NO(2)Cl) from reaction of HOCl with *NO(2)(-). The relevance of our observations to events in the stomach and respiratory tract, at sites of inflammation, and in ischemic tissues is discussed.

Protection against oxidative damage and cell death by the natural antioxidant ergothioneine

The natural antioxidant ergothioneine (EGT) was tested for its ability to inhibit cell death caused by hydrogen peroxide (H2O2) and to inhibit DNA oxidation by peroxynitrite (ONOO-) in human neuronal hybridoma cell line (N-18-RE-105). High concentrations of EGT (5 mM) were tolerated by the N-18-RE-105 cells. N-acetylcysteine (NAC) was not well tolerated by the cells at concentrations greater than 3 mM (cell viability averaged 50%). Increasing concentrations of EGT increases cell viability in the presence of NAC. EGT at concentrations up to 2 mM weakly improved cell viability in the presence of H2O2. NAC at concentrations up to 2 mM weakly decreased, but not significantly, the viability of the cells. At a higher concentration of 5 mM, NAC weakly protected the neuronal cells against the H2O2-induced cell death. The protection was significantly enhanced by preincubation with EGT. Ergothioneine inhibited ONOO(-)-induced oxidative damage in isolated calf thymus DNA and DNA in N-18-RE-105 cells. The concentration of EGT in human and mammalian tissue has been estimated to be 1-2 mM, which suggests that EGT may serve as a non-toxic thiol buffering antioxidant in vivo and may find applications in pharmaceutical preparations where oxidative stability is desired.

A multimuscle state analysis of adult motor learning

We introduce a new EMG state analysis to test two competing hypotheses about the role of muscle coactivity in learning a complex, multijoint reaching movement. Following Bernstein, one hypothesis is that as a task is learned, coactivity should decrease as degrees of freedom are released and limb stiffness is reduced. An alternative hypothesis is that as movement speed increases with learning, muscle coactivity should increase, possibly to stabilize joints against high inertial forces. Three participants performed a vertical reaching movement identical to that used by Schneider et al. We monitored the activity of four arm and shoulder muscles as participants completed 100 practice trials. Each frame of EMG activity was assigned to one of 16 possible combinations of the four monitored muscles based on an on-off activation threshold. This analysis yielded a time-based summary of muscle coactivity during the movement and across practice trials. Results of the state analysis supported the second hypothesis. As participants decreased their movement times over practice, coactivity increased - participants used more three- and four-muscle coactivity states. Changes were especially dramatic during the braking phase of the Up and Down portion of the vertical movement. When participants performed deliberately slow movements after speeded practice, three- and four-muscle coactivity was suppressed. We suggest that increased use of muscle coactivity may serve to counteract unwanted rotational forces generated during fast movements.

The small intestine can both absorb and glucuronidate luminal flavonoids

We have studied the perfusion of the jejunum and ileum in an isolated rat intestine model with flavonoids and hydroxycinnamates and the influence of glycosylation on the subsequent metabolism. Flavone and flavonol glucosides and their corresponding aglycones are glucuronidated during transfer across the rat jejunum and ileum and this glucuronidation occurs without the need for gut microflora. Furthermore, this suggests the presence of glycosidases as well as UDP-glucuronyl transferase in the jejunum. In contrast, quercetin-3-glucoside and rutin are mainly absorbed unmetabolised. The results suggest that the more highly reducing phenolics are absorbed predominantly as glucuronides (96.5%+/-4.6) of the amount absorbed, whereas monophenolic hydroxycinnamates and monophenolic B-ring flavonoids are less predisposed to glucuronidation and higher levels of aglycone (88.1%+/-10.1) are detected on absorption through both the jejunum and ileum.

Hypochlorous acid-induced DNA base modification: potentiation by nitrite: biomarkers of DNA damage by reactive oxygen species

Chronic inflammation results in increased nitric oxide formation and nitrite (NO-2) accumulation. Activated phagocytes release myeloperoxidase generating the cytotoxic agent hypochlorous acid (HOCl). Reaction of HOCl with NO-2 results in the formation of nitryl chloride (NO2Cl), a potent oxidising, nitrating and chlorinating species. Exposure of DNA to NO-2 alone (up to 250 microM) at pH 7.4 did not induce oxidative DNA base damage. However, incubation of DNA with NO-2 in the presence of HOCl led to increases in thymine glycol, 5-hydroxyhydantoin, 8-hydroxyadenine and 5-chlorouracil to levels higher than those achieved by HOCl alone. No significant increases in 8-hydroxyguanine, xanthine, hypoxanthine, 2-hydroxyadenine, FAPy guanine, FAPy adenine and 8-chloroadenine were observed. HOCl-induced depletion of FAPy guanine and 8-hydroxyguanine was reduced in the presence of NO-2. Modification of DNA by HOCl/NO-2 (presumably generating NO2Cl) produces a pattern of DNA base damage products in isolated DNA that is similar to the pattern produced by HOCl but not other reactive species.

Inhibition of peroxynitrite dependent DNA base modification and tyrosine nitration by the extra virgin olive oil-derived antioxidant hydroxytyrosol

Hydroxytyrosol is one of the o-diphenolic compounds in extra virgin olive oil and has been suggested to be a potent antioxidant. The superoxide radical (O2*-) and nitric oxide (NO*) can react very rapidly to form peroxynitrite (ONOO ), a reactive tissue damaging species thought to be involved in the pathology of several chronic diseases. Hydroxytyrosol was highly protective against the peroxynitrite-dependent nitration of tyrosine and DNA damage by peroxynitrite in vitro. Given that extra virgin olive oil is consumed daily by many humans, hydroxytyrosol derived from this diet could conceivably provide a defense against damage by oxidants in vivo. The biological activity of hydroxytyrosol in vivo will depend on its intake, uptake and access to cellular compartments.

Hydrogen peroxide induces oxidative DNA damage in rat type II pulmonary epithelial cells

Type II epithelial cells, which line the alveolar surface of the lung, are exposed to a variety of potentially mutagenic and carcinogenic insults. The purpose of this study was to determine if type II cells are susceptible to oxidative DNA damage in vitro. Treatment of cultured rat type II lung epithelial cells with hydrogen peroxide led to increased concentrations (nmol/mg DNA) of 12 of 14 monitored DNA base modifications, suggesting oxidative damage by the hydroxyl radical. These base modifications are typically associated with oxidative stress, and elevated levels have been correlated with mutagenesis and carcinogenesis. These data demonstrate that type II cells are indeed vulnerable to oxidative DNA damage.

Aminoglycosides: a practical review

Aminoglycosides are potent bactericidal antibiotics that act by creating fissures in the outer membrane of the bacterial cell. They are particularly active against aerobic, gram-negative bacteria and act synergistically against certain gram-positive organisms. Gentamicin is the most commonly used aminoglycoside, but amikacin may be particularly effective against resistant organisms. Aminoglycosides are used in the treatment of severe infections of the abdomen and urinary tract, as well as bacteremia and endocarditis. They are also used for prophylaxis, especially against endocarditis. Resistance is rare but increasing in frequency. Avoiding prolonged use, volume depletion and concomitant administration of other potentially nephrotoxic agents decreases the risk of toxicity. Single daily dosing of aminoglycosides is possible because of their rapid concentration-dependent killing and post-antibiotic effect and has the potential for decreased toxicity. Single daily dosing of aminoglycosides appears to be safe, efficacious and cost effective. In certain clinical situations, such as patients with endocarditis or pediatric patients, traditional multiple dosing is still usually recommended.

Conjugates of catecholamines with cysteine and GSH in Parkinson's disease: possible mechanisms of formation involving reactive oxygen species

Oxidation of L-3,4-dihydroxyphenylalanine (L-DOPA) and dopamine (DA) to generate semiquinones/quinones, oxygen radicals, and other reactive oxygen species may play a role in neuronal cell death in Parkinson's disease (PD). In particular, semiquinones/quinones can form conjugates with thiol compounds such as GSH and cysteine. Exposure of L-DOPA, DA, and other catecholamines to a system generating O2.- radical led to O2(.-)-dependent depletion of added GSH (or cysteine), accompanied by the formation of thiol-DA or -DOPA adducts as detected by HPLC. Superoxide could additionally cause destruction of these adducts. Iron or copper ions could also promote conjugate formation between GSH or cysteine and DA and L-DOPA, especially if H2O2 was present. We applied HPLC to measure glutathionyl and cysteinyl conjugates of L-DOPA, DA, and 3,4-dihydroxyphenylacetic acid (DOPAC) in postmortem brain samples from PD patients and normal control subjects. Conjugates were detected in most brain areas examined, but levels were highest in the substantia nigra and putamen. In most regions, adduct levels were lower in PD, but there were significant increases in cysteinyl adducts of L-DOPA, DA, and DOPAC in PD substantia nigra, suggesting that acceleration of L-DOPA/DA oxidation occurs in PD, although we cannot say if this is a primary feature of the disease or if it is related to therapy with L-DOPA. In vitro, conjugate formation could be inhibited by the dithiol dihydrolipoate but not by its oxidised form, lipoic acid.

Postural control during reaching in young infants: a dynamic systems approach

We conceptualize the coordinated development of posture and reaching within Schöner's (Ecological Psychology, 7:291-314, 1995) dynamic model of coupled levels of control: load, timing, and goal. In particular, the goal of postural stability must be maintained during a reach. Using longitudinal data from four infants followed from 3 weeks to 1 year, we show that coordination of the head with upper and lower arm activity is critical for successful reaching. First, infants acquire stable head control several weeks before reaching onset. Furthermore, reaching onset is characterized by a reorganization of muscle patterns to include more trapezius and deltoid activity, serving to stabilize the head and shoulder and provide a stable base from which to reach. We argue that initially, the system is working on postural stability and reaching as goals. Infants secondarily select appropriate muscle patterns to achieve those goals depending, in part, on their individual body sizes, body proportions and energy levels. Motor development proceeds as a continual dialogue between the nervous system, body, and environment.

Development of reaching during the first year: role of movement speed

When infants first learn to reach at about 4 months, their hand paths are jerky and tortuous, but their reaches become smoother and straighter over the first year. Here the authors consider the role of the underlying limb dynamics, which scale with movement speed, on the development of trajectory control. The authors observed 4 infants weekly and then biweekly from reach onset to 1 year. Improvements in trajectories were not linear, but showed plateaus and regressions in straightness and smoothness. When infants' nonreaching movements were fast, their reaches were also fast, and faster reaches were also less straight. This is consistent with an equilibrium trajectory form of control, where development involves the increasing ability to stabilize the trajectory against self-generated movement perturbations.

Base modification and strand breakage in isolated calf thymus DNA and in DNA from human skin epidermal keratinocytes exposed to peroxynitrite or 3-morpholinosydnonimine

Exposure of isolated calf thymus DNA and human skin epidermal keratinocytes to peroxynitrite or the peroxynitrite generator, 3-morpholinosydnonimine (SIN-1), led to extensive DNA base modification. Large increases in xanthine and hypoxanthine, possible deamination products of guanine and adenine, respectively, and in 8-nitroguanine were observed, but only small changes in some oxidized base products were seen. This pattern of damage suggests that hydroxyl radicals were not major contributors to base modification caused by peroxynitrite, as OH is known to cause multiple oxidative modifications to all four DNA bases. Instead, it seems that reactive nitrogen species play a much greater role in the mechanism of base damage, producing both nitration and deamination of purine bases when DNA or whole cells are exposed to peroxynitrite. If this pattern of damage is unique to peroxynitrite, it might act as a marker of cellular damage by this species in vivo.

Development of reaching during the first year: role of movement speed

When infants first learn to reach at about 4 months, their hand paths are jerky and tortuous, but their reaches become smoother and straighter over the first year. Here the authors consider the role of the underlying limb dynamics, which scale with movement speed, on the development of trajectory control. The authors observed 4 infants weekly and then biweekly from reach onset to 1 year. Improvements in trajectories were not linear, but showed plateaus and regressions in straightness and smoothness. When infants' nonreaching movements were fast, their reaches were also fast, and faster reaches were also less straight. This is consistent with an equilibrium trajectory form of control, where development involves the increasing ability to stabilize the trajectory against self-generated movement perturbations.

Oxidative DNA damage in human respiratory tract epithelial cells. Time course in relation to DNA strand breakage

When human respiratory tract epithelial cells were exposed to 100 microM H2O2, there was rapid induction of DNA strand breakage and chemical modifications to all 4 DNA bases suggestive of attack by OH.. The major products were FAPy-adenine, FAPy-guanine, and 8-OH-guanine. Some of the base modifications were removed very quickly from the DNA (e.g., 8-OH-guanine), whereas others persisted for longer (e.g., thymine glycol), probably due to differential activity of different repair enzymes. By contrast, strand breaks continued to increase over the time course of the experiment, perhaps because strand breakage is also implicated in the repair process. One should therefore be cautious in using strand breakage as a sole measure of oxidative DNA damage, and when drawing conclusions about the pattern and biological significance of oxidative DNA damage in cells the relative persistence of different lesions must be considered.

Practical nutrition for the healthy term infant

Breast milk is universally recommended as the preferred source of infant nutrition, in part because of its superior nutrient and immunologic properties. Successful breast feeding requires nursing on demand, prevention of sore nipples and convenient access to medical advice. For mothers relying on bottle feeding, cow's-milk-based formula is the preferred choice. Because soy-based formulas are lactose-free, they may be tolerated by infants who are allergic to cow's-milk protein. Protein hydrolysate formulas should be used only in infants who cannot tolerate cow's-milk-based or soy-based formulas. Low-Iron formulas and whole cow's milk should not be used during the first year. Breast-fed infants rarely require vitamin supplementation. Fluoride supplementation is no longer recommended for infants less than six months of age.

An evaluation of the antioxidant and antiviral action of extracts of rosemary and Provençal herbs

Extracts of herbs and spices are increasingly of interest in the food industry because they retard oxidative degradation of lipids. There is also increasing interest in the antiviral activity of plant products. A liquid, deodorized rosemary extract and an oily extract of a mixture of Provençal herbs were tested for antioxidant and antiviral action in vitro. The rosemary extract (Herbor 025) and the extract of Provençal herbs (Spice Cocktail) inhibited peroxidation of phospholipid liposomes with 50% inhibition concentration values of 0.0009% (v/v) and 0.0035% (v/v), respectively. Herbor 025 and the spice cocktail (at 0.2%, v/v) reacted with trichloromethylperoxyl radical with calculated rates of 2.7 x 10(4) s-1 and 1.5 x 10(3) s-1, respectively. The main active components in the herbal preparations, carnosol and carnosic acid, at 0.05% (v/v) react with rate constants of (1-3) x 10(6) M-1 sec-1 and 2.7 x 10(7) M-1 sec-1, respectively. Both extracts show good antioxidant activity in the Rancimat test, especially in lard. Herbor 025 and the spice cocktail inhibited human immunodeficiency virus (HIV) infection at very low concentrations which were also cytotoxic. However, purified carnosol exhibited definite anti-HIV activity at a concentration (8 microM) which was not cytotoxic. Both preparations promoted some DNA damage in the copper-phenanthroline and the bleomycin-iron systems. The two herbal preparations possess antioxidant properties that may make them useful in the food matrix.

Evaluation of the pro-oxidant and antioxidant actions of L-DOPA and dopamine in vitro: implications for Parkinson's disease

The antioxidant and pro-oxidant properties of L-DOPA and dopamine were investigated in vitro. Both compounds inhibited the peroxidation of ox-brain phospholipids, with IC50 values of 8.5 microM for dopamine and 450 microM for L-DOPA. Dopamine and L-DOPA reacted with trichloromethyl peroxyl radicals (CCl3O2.) with rate constants of 2.1 x 10(7)M-1s-1 and 1.3 x 10(7)M-1s-1 respectively. The effects of dopamine and L-DOPA on iron ion-dependent hydroxyl radical generation from H2O2 were complex. In general, low concentrations stimulated OH. formation in the presence of ferric-EDTA and, in the case of L-DOPA, ferric-ADP and ferric citrate chelates. Both compounds also reacted with superoxide radical and hypochlorous acid. The products of the reaction with HOCl could still inhibit alpha 1-antiproteinase and appear to be 'long lived' chloramine-type oxidizing species. Our results suggest that L-DOPA and dopamine might have a complex mixture of pro- and anti- oxidant effects, which could contribute to tissue damage due to oxidative stress in Parkinson's disease and other neurological disorders.

DNA damage in human respiratory tract epithelial cells: damage by gas phase cigarette smoke apparently involves attack by reactive nitrogen species in addition to oxygen radicals

Treatment of human respiratory tract tracheobronchial epithelial cells with gas-phase cigarette smoke led to dose-dependent DNA strand breakage that was highly correlated with multiple chemical modifications of all four DNA bases. The pattern of base damage suggests attack by hydroxyl radicals (OH.). However, by far the most important base damage in quantitative terms was formation of xanthine and hypoxanthine, presumably resulting from deamination of guanine and adenine respectively. Hence, DNA damage by cigarette smoke may involve reactive nitrogen species as well as reactive oxygen species.

DNA strand breakage and base modification induced by hydrogen peroxide treatment of human respiratory tract epithelial cells

Treatment of human respiratory tract epithelial cells with H2O2 led to concentration-dependent DNA strand breakage that was highly-correlated with multiple chemical modifications of all four DNA bases, suggesting that damage is due to hydroxyl radical, OH. However, the major base damage occurred to adenine. Hence, conclusions made about the occurrence and the extent of oxidative DNA damage on the basis only of changes in 8-hydroxyguanine should be approached with caution.

Superoxide-dependent depletion of reduced glutathione by L-DOPA and dopamine. Relevance to Parkinson's disease

The mechanism of nigral cell death in Parkinson's disease (PD) remains unknown, but it is increasingly proposed that free radical reactions are important in the disease pathology. One of the most striking features of PD is an approximate 40% decrease in the levels of reduced glutathione (GSH) which occurs early in the development of the disease. We describe a possible mechanism of GSH depletion which results from the reaction of L-DOPA and dopamine with the superoxide free radical (O2.-) and leads to a very rapid loss of GSH.

Intense oxidative DNA damage promoted by L-dopa and its metabolites. Implications for neurodegenerative disease

Oxidative DNA damage can cause mutation and cell death. We show that L-DOPA, dopamine and 3-O-methyl-DOPA cause extensive oxidative DNA damage in the presence of H2O2 and traces of copper ions. 8-Hydroxyguanine is the major product. Iron ions were much less effective and manganese ions did not catalyse DNA damage. We propose that copper ion release, in the presence of L-DOPA and its metabolites, may be an important mechanism of neurotoxicity, e.g. in Parkinson's disease and amyotrophic lateral sclerosis.

'CO2-ligated' cytochrome c oxidase: characterization and comparison with the Cl- -ligated enzyme

A form of fully oxidized bovine heart cytochrome c oxidase that is induced by CO2/HCO3- is described. The ligand-binding properties of this form are similar to those of Cl(-)-ligated oxidase [Moody, Cooper and Rich (1991) Biochim. Biophys. Acta 1059, 189-207]. Both bind cyanide at a rate (0.2 M-1.s-1 at pH 6.5) intermediate between the rate of binding to the fast and slow forms of the enzyme, and binding of formate to both is almost undetectable. They are also similar in showing poor reactivity with H2O2, or with CO in the presence of O2, which, with fast oxidase, induce the formation of the 'ferryl' and 'peroxy' states respectively. However, there is a clear difference in the near-u.v./visible absorption spectra of the two forms; that induced by CO2/HCO3- has a Soret maximum at 427 nm whereas Cl(-)-ligated oxidase has a Soret maximum similar to that of fast oxidase at about 424 nm. It appears that both CO2/HCO3- and Cl- are members of a class of ligands that lowers the reactivity of the binuclear centre but does not impede intramolecular electron transfer from haem a to the binuclear centre, unlike the putative endogenous ligand responsible for slow oxidase.

The transition to reaching: mapping intention and intrinsic dynamics

The onset of directed reaching demarks the emergence of a qualitatively new skill. In this study we asked how intentional reaching arises from infants' ongoing, intrinsic movement dynamics, and how first reaches become successively adapted to the task. We observed 4 infants weekly in a standard reaching task and identified the week of first arm-extended reach, and the 2 weeks before and after onset. The infants first reached at ages ranging from 12 to 22 weeks, and they used different strategies to get the toy. 2 infants, whose spontaneous movements were large and vigorous, damped down their fast, forceful movements. The 2 quieter infants generated faster and more energetic movements to lift their arms. The infants modulated reaches in task-appropriate ways in the weeks following onset. Reaching emerges when infants can intentionally adjust the force and compliance of the arm, often using muscle coactivation. These results suggest that the infant central nervous system does not contain programs that detail hand trajectory, joint coordination, and muscle activation patterns. Rather, these patterns are the consequences of the natural dynamics of the system and the active exploration of the match between those dynamics and the task.

Mice lacking major histocompatibility complex class I and class II molecules

Mice lacking major histocompatibility complex (MHC) antigens were generated by mating beta 2-microglobulin-deficient, and therefore class I-deficient, animals with MHC class II-deficient animals. When housed under sterile conditions, the resulting MHC-deficient mice appear healthy, survive for many months, and breed successfully. Phenotypically, MHC-deficient mice are depleted of CD4+ and CD8+ T cells in peripheral lymphoid organs due to a lack of appropriate restricting elements. In contrast, the B-cell compartment of these animals appears intact, and MHC-deficient mice can mount specific antibody responses when challenged with a T-independent antigen. Spleen cells from MHC-deficient animals are poor stimulators and responders in a mixed lymphocyte reaction. Despite their relatively weak cellular immune responses in vitro, MHC-deficient mice reject allogeneic skin grafts with little delay, and grafts from MHC-deficient animals are rapidly rejected by normal allogeneic recipients. Taken together, these results emphasize the plasticity of the immune system and suggest that MHC-deficient mice may be useful for examining compensatory mechanisms in severely immunocompromised animals.

Transfer of mannose from GDP-mannose to lipid-linked oligosaccharide by soluble mannosyl transferase

A solubilized mannosyl transferase(s) was obtained by treatment of the pig aorta particulate enzyme with the nonionic detergent Nonidet P-40 followed by centrifugation at 100,000 X g for 60 min. This enzyme preparation catalyzed the transfer of mannose from GDP-[14C]mannose (but not from [14C]mannosylphosphoryldolichol) to form a heptasaccharide-lipid. The synthesis of this heptasaccharide-lipid required the addition of an acceptor lipid that was isolated from pig liver. The oligosaccharide portion of the acceptor lipid appeared to be a mixture of trisaccharide and pentasaccharide. The formation of heptasaccharide-lipid did not require divalent cation, was not inhibited by EDTA, and was not inhibited by the antibiotic amphomycin. The heptasaccharide portion of the heptasaccharide-lipid had the same migration properties on paper chromatograms in two different solvent systems as a previously characterized Man5GlcNAc2 oligosaccharide [Li, E. & Kornfeld, S. (1979) J. Biol. Chem. 254, 2754-2758]. It also had the same migration properties as the oligosaccharide that accumulates in the presence of amphomycin. All three of these oligosaccharides emerged from a Bio-Gel P-4 column in the same position. Radioactive mannose was released from the heptasaccharide by digestion with alpha-mannosidase. These data demonstrate that at least some of the alpha-linked mannose residues in the heptasaccharide-lipid are donated directly from GDP-mannose.