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PubMed2004

The 5-HT1A receptor and behavioral stimulation in the rat: effects of 8-OHDPAT on spontaneous and cocaine-induced behavior.

RATIONALE: The contribution of the 5-HT(1A) somato-dendritic autoreceptor populations to spontaneous and cocaine-induced locomotion is unclear. OBJECTIVES: To use a low dose range of +/-8-hydroxy-2-(di- n-propylamino)tetralin (8-OHDPAT) to preferentially stimulate 5-HT(1A) autoreceptors and a medium 8-OHDPAT dose range to stimulate both 5-HT(1A) autoreceptors and postsynaptic receptors as pretreatments prior to either saline or cocaine. METHODS: In experiment 1, either a medium dose of 8-OHDPAT (0.4 mg/kg) or a low dose (0.05 mg/kg) was given as pretreatments 20 min before five separate 20-min open-field tests. In experiment 2, the pretreatments were changed to a low dose range of 8-OHDPAT (0.01-0.05 mg/kg), with or without WAY 100635 (0.01-0.05 mg/kg). In experiment 3, the 8-OHDPAT pretreatments (0.01, 0.025 or 0.05 mg/kg) were administered 20 min prior to saline or cocaine (10 mg/kg) tests. In experiment 4, a medium dose range (0.2-0.3 mg/kg) was given 20 min prior to saline or cocaine (10 mg/kg) tests. RESULTS: Experiment 1 showed that 8-OHDPAT (0.4 mg/kg) tended to increase locomotor activity but that pretreatment with 0.05 mg/kg severely suppressed locomotor activity. In experiment 2, 8-OHDPAT in the low dose range inhibited locomotor activity and this effect was reversed by co-administration of WAY 100635. Experiment 3 showed that the low-dose 8-OHDPAT pretreatment reduced locomotor activity in saline but not cocaine tests. In experiment 4, 8-OHDPAT in the medium dose range enhanced locomotor activity in cocaine tests. CONCLUSIONS: It is suggested that the facilitatory effect of 8-OHDPAT on cocaine-induced locomotor stimulation is mediated by inhibition of 5-HT(1A) somato-dendritic autoreceptors.

8-Hydroxy-2-(di-n-propylamino)tetralin↗
PubMed1987

Spontaneous asymmetric circling behavior in hemi-parkinsonism; a human equivalent of the lesioned-circling rodent behavior.

When induced experimentally in rodents, hemispheric asymmetry in basal ganglia dopamine results in spontaneous asymmetric circling toward the hemisphere with the lower level of dopamine. A similar asymmetry has long been thought to exist in the brains of hemi-Parkinsonian patients. Using an electronic turn counter, we demonstrated that, like unilaterally lesioned rats, and without being aware of it, five ambulating outpatients with hemi-Parkinson's disease exhibit spontaneous rotation toward the hemisphere containing less striatal dopaminergic activity.

Aged↗
PubMed2005

Behavior differences in drivers with attention deficit hyperactivity disorder: the driving behavior questionnaire.

Attention deficit hyperactivity disorder (ADHD) has been linked to an increased number of driving citations, especially for speeding and a four-fold increase in accident risk. Using three factors--errors, lapses and violations--found in prior work, we ran regression analyses to explore the impact of ADHD status, gender and age on error, lapse and violation report scores. The results indicate that ADHD status is positively and significantly related to error, lapse and violation scores. In the cases of errors and violations, however, interactions between ADHD status and age are significant such that older participants with ADHD do not differ statistically from controls. There were no significant effects of age on error, lapse or violation scores for control participants. Consistent with earlier work, gender was significantly related to violation scores, but not to errors or lapses, such that men were more likely than women to report higher violation scores, controlling for ADHD status and age. We consider possible explanations for these findings and discuss the implications of these results for the accident risk of individuals with ADHD as they age.

Adult↗
PubMed1991

Equilibrium muscle cross-bridge behavior. Theoretical considerations. II. Model describing the behavior of strongly-binding cross-bridges when both heads of myosin bind to the actin filament.

A model has been developed for characterizing the interaction between strongly-binding myosin cross-bridges and actin in muscle fibers under equilibrium conditions where both heads of the myosin cross-bridge bind to actin. The model, that of Anderson and Schoenberg (1987. Biophys. J. 52:1077-1082) is quite similar to that of Schoenberg (1985. Biophys. J. 48:467-475), except that explicit account is taken of the fact that each crossbridge has two heads which can bind to actin. The key assumption that allows this model to explain a large body of data unexplained by the Schoenberg (1985) model is that the two crossbridge heads are not totally independent of one another after attachment. After the first head attaches, the second head is then free to attach only to an actin site distal to the first head. This means that when the more distally attached head subsequently detaches and reattaches (as the heads continually do), it will not reattach in a position of lesser strain and reduce the force it supports, but instead will remain attached in its strained position until the proximally attached head also detaches. This model gives an explanation for two important and otherwise unexplained observations made previously: it explains why at ionic strengths in the range of 50-120 mM, (a) the rate constant of force decay after a small stretch is a sigmoidal function of nucleotide analogue concentration, and (b) why in the presence of analogues or in rigor the rate constant of force decay after a small stretch is significantly slower than the rate constant for myosin subfragment-1 detachment from actin in solution.

Actins↗
PubMed1995

Characterizing the secondary hydration shell on hydrated myoglobin, hemoglobin, and lysozyme powders by its vitrification behavior on cooling and its calorimetric glass-->liquid transition and crystallization behavior on reheating.

For hydrated metmyoglobin, methemoglobin, and lysozyme powders, the freezable water fraction of between approximately 0.3-0.4 g water/g protein up to approximately 0.7-0.8 g water/g protein has been fully vitrified by cooling at rates up to approximately 1500 K min-1 and the influence of cooling rate characterized by x-ray diffractograms. This vitreous but freezable water fraction started to crystallize at approximately 210 K to cubic ice and at approximately 240 K to hexagonal ice. Measurements by differential scanning calorimetry have shown that this vitreous but freezable water fraction undergoes, on reheating at a rate of 30 K min-1, a glass-->liquid transition with an onset temperature of between approximately 164 and approximately 174 K, with a width of between approximately 9 and approximately 16 degrees and an increase in heat capacity of between approximately 20 and approximately 40 J K-1 (mol of freezable water)-1 but that the glass transition disappears upon crystallization of the freezable water. These calorimetric features are similar to those of water imbibed in the pores of a synthetic hydrogel but very different from those of glassy bulk water. The difference to glassy bulk water's properties is attributed to hydrophilic interaction and H-bonding of the macromolecules' segments with the freezable water fraction, which thereby becomes dynamically modified. Abrupt increase in minimal or critical cooling rate necessary for complete vitrification is observed at approximately 0.7-0.8 g water/g protein, which is attributed to an abrupt increase of water's mobility, and it is remarkably close to the threshold value of water's mobility on a hydrated protein reported by Kimmich et al. (1990, Biophys. J. 58:1183). The hydration level of approximately 0.7-0.8 g water/g protein is approximately that necessary for completing the secondary hydration shell.

Calorimetry, Differential Scanning↗
PubMed1995

Exploring the energy surface of protein folding by structure-reactivity relationships and engineered proteins: observation of Hammond behavior for the gross structure of the transition state and anti-Hammond behavior for structural elements for unfolding/folding of barnase.

The structure of alpha-helix 1 (residues 6-18) in the transition state for the unfolding of barnase has been previously characterized by comparing the kinetics and thermodynamics of folding of wild-type protein with those of mutants whose side chains have been cut back, in the main, to that of alanine. The structure of the transition state has now been explored further by comparing the kinetics and thermodynamics of folding of glycine mutants with those of the alanine mutants at solvent-exposed positions in the alpha-helices of barnase. Such "Ala-->Gly scanning" provides a general procedure for examining the structure of solvent-exposed regions in the transition state. A gradual change of structure of the transition state was detected as helix 1 becomes increasingly destabilized on mutation. The extent of change of structure of helix 1 in the transition state for the mutant proteins was probed by a further round of Ala-->Gly scanning of those mutants. Destabilization of the helix 1 was found to cause the overall transition state for unfolding to become closer in structure to that of the folded protein. This is analogous to the conventional Hammond effect in physical-organic chemistry whereby the transition state moves parallel to the reaction coordinate with change in structure. But, paradoxically, the structure of helix 1 itself becomes less folded in the transition state as helix 1 becomes destabilized. This is analogous, however, to the rarer anti-Hammond effect in which there is movement perpendicular to the reaction coordinate. These observations are rationalized by plotting correlation diagrams of degree of formation of individual elements of structure against the degree of formation of overall structure in the transition state. There is a relatively smooth movement of the degree of compactness in the transition state against changes in activation energy on mutation that suggests a smooth movement of the transition state along the energy surface on mutation rather than a switch between two different parallel pathways. The results are consistent with the transition state having closely spaced energy levels. Helix 1, which appears to be an initiation point and forms early in the folding of wild-type protein, may be radically destabilized to the extent that it forms late in the folding of mutants. The order of events in folding may thus not be crucial.

Alanine↗
PubMed1990

Physical-chemical behavior of dietary and biliary lipids during intestinal digestion and absorption. 1. Phase behavior and aggregation states of model lipid systems patterned after aqueous duodenal contents of healthy adult human beings.

We developed equilibrium phase diagrams corresponding to aqueous lipid compositions of upper small intestinal contents during lipid digestion and absorption in adult human beings. Ternary lipid systems were composed of a physiological mixture of bile salts (BS), mixed intestinal lipids (MIL), principally partially ionized fatty (oleic) acid (FA) plus racemic monooleylglycerol (MG), and cholesterol (Ch), all at fixed aqueous-electrolyte concentrations, pH, temperature, and pressure. The condensed phase diagram for typical physiological conditions (1 g/dL total lipids, FA:MG molar ratio of 5:1, pH 6.5, 0.15 M Na+ at 37 degrees C) was similar to that of a dilute model bile [BS/lecithin (PL)/Ch] system [Carey, M. C., & Small, D. M. (1978) J. Clin. Invest. 61, 998-1026]. We identified two one-phase zones composed of mixed micelles and lamellar liquid crystals, respectively, and two two-phase zones, one composed of Ch monohydrate crystals and Ch-saturated micelles and the other of physiologic relevance composed of Ch- and MIL-saturated mixed micelles and unilamellar vesicles. A single large three-phase zone in the system was composed of Ch-saturated micelles, Ch monohydrate crystals, and liquid crystals. Micellar phase boundaries for otherwise typical physiological conditions were expanded by increases in total lipid concentration (0.25-5 g/dL), pH (5.5-7.5), and FA:MG molar ratio (5-20:1), resulting in a reduction of the size of the physiological two-phase zone. Mean particle hydrodynamic radii (Rh), measured by quasielastic light scattering (QLS), demonstrated an abrupt increase from micellar (less than 40 A) to micelle plus vesicle sizes (400-700 A) as this two-phase zone was entered. With relative lipid compositions within this zone, unilamellar vesicles formed spontaneously following coprecipitation, and their sizes changed markedly as functions of time, reaching equilibrium values only after 4 days. Further, vesicle Rh values were influenced appreciably by MIL:mixed bile salt (MBS) ratio, pH, total lipid concentration, and FA:MG ratio, but not by Ch content. In comparison, micellar systems equilibrated rapidly, and their Rh values only slightly influenced by physical-chemical variables of physiological importance. In contrast to the BS-PL-Ch system [Mazer, N. A., & Carey, M. C. (1983) Biochemistry 22, 426-442], no divergence in micellar sizes occurred as the micellar phase boundary was approached. The ionization state of FA at simulated "intestinal" pH values (5.5-7.5) in the micellar and physiologic two-phase zones was principally that of 1:1 sodium hydrogen dioleate, an insoluble swelling "acid soap" compound. By phase separation and analysis, tie-lines for the constituent phase in the two-phase zone demonstrated that the mixed micelles were saturated with MIL and Ch and the coexisting vesicles were saturated with MBS, but not with Ch.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗