5-HT and 5-HT-SO4, but not tryptophan or 5-HIAA levels in single feeding neurons track animal hunger state.

Serotonin (5-HT) is an intrinsic modulator of neural network excitation states in gastropod molluscs. 5-HT and related indole metabolites were measured in single, well-characterized serotonergic neurons of the feeding motor network of the predatory sea-slug Pleurobranchaea californica. Indole amounts were compared between paired hungry and satiated animals. Levels of 5-HT and its metabolite 5-HT-SO4 in the metacerebral giant neurons were observed in amounts approximately four-fold and two-fold, respectively, below unfed partners 24 h after a satiating meal. Intracellular levels of 5-hydroxyindole acetic acid and of free tryptophan did not differ significantly with hunger state. These data demonstrate that neurotransmitter levels and their metabolites can vary in goal-directed neural networks in a manner that follows internal state.

Mass spectrometric imaging of the nervous system.

Mass spectrometric imaging (MSI) integrates multiple fields of analytical and biomedical research with the goal of generating chemical maps that present the identity and location of the elements, molecules, and molecular complexes that comprise biological structures. Rapid advances in the development of MSI, which include a broad range of sampling and mass spectrometry strategies, allow the increasingly information-rich creation of chemical images of structurally complex tissues, individual cells, and even single chromosomes. Here we describe a variety of MSI techniques available to investigate the nervous system, with particular focus on the capability of MSI to examine both normal and diseased brain function. An important investigative tool, MSI offers tremendous potential in fundamental studies of brain chemistry, localization of pharmaceutical compounds, and the discovery of biomarkers for different neuropathologies.

Cost-benefit analysis potential in feeding behavior of a predatory snail by integration of hunger, taste, and pain.

Hunger/satiation state interacts with appetitive and noxious stimuli to determine feeding and avoidance responses. In the predatory marine snail Pleurobranchaea californica, food chemostimuli induced proboscis extension and biting at concentration thresholds that varied directly with satiation state. However, food stimuli also tended to elicit avoidance behavior (withdrawal and avoidance turns) at concentration thresholds that were relatively low and fixed. When the feeding threshold for active feeding (proboscis extension with biting) was exceeded, ongoing avoidance and locomotion were interrupted and suppressed. Noxious chemostimuli usually stimulated avoidance, but, in animals with lower feeding thresholds for food stimuli, they often elicited feeding behavior. Thus, sensory pathways mediating appetitive and noxious stimuli may have dual access to neural networks of feeding and avoidance behavior, but their final effects are regulated by satiation state. These observations suggest that a simple cost-benefit computation regulates behavioral switching in the animal's foraging behavior, where food stimuli above or below the incentive level for feeding tend to induce feeding or avoidance, respectively. This decision mechanism can weigh the animal's need for nutrients against the potential risk from other predators and the cost of relative energy outlay in an attack on prey. Stimulation of orienting and attack by low-level noxious stimuli in the hungriest animals may reflect risk-taking that can enhance prey capture success. A simple, hedonically structured neural network model captures this computation.

Decreased HLA heterogeneity in parents of children with Down syndrome.

HLA-A and B antigens were determined in a study of 37 couples and their children with trisomy 21 Down syndrome (DS), using a standard microlymphocytotoxicity test. The comparison groups included 76 couples and their healthy children. All individuals were Caucasians from the same geographical area, and there was no history of consanguinity. The parents of children with DS did not show an association with a specific HLA antigen or haplotype. Sixteen of the 37 couples (43.24%) having children with DS share two or more antigens at the A and/or B locus. This was significantly higher than the proportion in the control group (6/76, or 7.88%). Of the 16 couples having children with DS and sharing two or more antigens, eight had a haplotype in common, in contrast with only two couples in the control group. The data suggest that sharing of parental HLA-A and B antigens may be related either to the occurrence of trisomy 21 zygotes or to prenatal survival of affected embryos and fetuses.

Somatic chromosome breakage in low birth weight newborns.

To detect any association between birth weight and frequency of aberration or cell damage and to investigate possible postnatal environmental effects on chromosomes, we studied controlled groups of newborn low and high birth weight infants and screened for chromosome breakage and rearrangement in cord blood and postnatal peripheral blood. No evidence of a correlation of neonatal chromosome damage and birth weight was found. A significant increase of chromosome damage in postnatal blood of intrauterine-growth-retarded infants is interpreted as a reflection of postnatal environmental factors.

Sister chromatid exchange in newborns.

Sister chromatid exchanges (SCE) were analyzed in the cord and postnatal blood of controlled groups of low and high birth weight infants to detect possible associations between abnormal birth weight and SCE frequency. Structural chromosome aberration rates had previously been evaluated for all infants, and possible correlations between aberration and SCE rates were sought. No correlation was found between neonatal or postnatal SCE frequency and birthweight, nor was there evidence of association of chromosome aberration rates with SCE frequency. In all groups of infants, however, mean postnatal SCE frequencies were significantly lower than mean neonatal SCE frequencies.

Chromosome breakage in low birth weight newborns.

The frequency of chromosome aberrations in cells cultured from umbilical cord blood was determined for 50 low birth weight (LBW) and 50 normal birth weight (NBW) euploid newborns matched for sex, race, and maternal age. The metaphase spreads had been prepared in the course of an earlier study of frequency of aneuploidy and results are from 72-h cultures, i.e., presumably, at the second division in vitro. There were no significant differences between the two groups in the frequency of cells with chromosome breakage, chromosome gaps, or hyperdiploid cells. There was, however, a significantly higher frequency of hypodiploid cells in the LBW group. The present findings differ from those of others who have reported an increase in chromosome breakage in premature newborns.

Apparent "in situ" clone of cytogenetically marked ataxia-telangiectasia lymphocytes.

Six adjacent metaphases, each with the same cytogenetic aberration of a group D chromosome, most probably a No. 14, were observed in a field of a slide from a 96-hour culture of lymphocytes from an individual with ataxia-telangiectasia (AT). None of the 304 other metaphases examined from this or other simultaneous cultures of this individual showed such an aberration. It seems most likely that an "in situ" marked clone has been observed and this supports interpretation of consistent cytogenetic abnormalities in those with AT as having clonal origin. The method of slide preparation employed which involves placing, rather than dropping, the cell suspension on the slide may facilitate detection of "in situ" clones.