Achievement of Target Gain Larger than Unity in an Inertial Fusion Experiment

On December 5, 2022, an indirect drive fusion implosion on the National Ignition Facility (NIF) achieved a target gain G_{target} of 1.5. This is the first laboratory demonstration of exceeding "scientific breakeven" (or G_{target}>1) where 2.05 MJ of 351 nm laser light produced 3.1 MJ of total fusion yield, a result which significantly exceeds the Lawson criterion for fusion ignition as reported in a previous NIF implosion [H. Abu-Shawareb et al. (Indirect Drive ICF Collaboration), Phys. Rev. Lett. 129, 075001 (2022)PRLTAO0031-900710.1103/PhysRevLett.129.075001]. This achievement is the culmination of more than five decades of research and gives proof that laboratory fusion, based on fundamental physics principles, is possible. This Letter reports on the target, laser, design, and experimental advancements that led to this result.

Lawson Criterion for Ignition Exceeded in an Inertial Fusion Experiment

For more than half a century, researchers around the world have been engaged in attempts to achieve fusion ignition as a proof of principle of various fusion concepts. Following the Lawson criterion, an ignited plasma is one where the fusion heating power is high enough to overcome all the physical processes that cool the fusion plasma, creating a positive thermodynamic feedback loop with rapidly increasing temperature. In inertially confined fusion, ignition is a state where the fusion plasma can begin "burn propagation" into surrounding cold fuel, enabling the possibility of high energy gain. While "scientific breakeven" (i.e., unity target gain) has not yet been achieved (here target gain is 0.72, 1.37 MJ of fusion for 1.92 MJ of laser energy), this Letter reports the first controlled fusion experiment, using laser indirect drive, on the National Ignition Facility to produce capsule gain (here 5.8) and reach ignition by nine different formulations of the Lawson criterion.

Maternal education and cognitive development in 15 European very-preterm birth cohorts from the RECAP Preterm platform

BACKGROUND

Studies are sparse and inconclusive about the association between maternal education and cognitive development among children born very preterm (VPT). Although this association is well established in the general population, questions remain about its magnitude among children born VPT whose risks of medical and developmental complications are high. We investigated the association of maternal education with cognitive outcomes in European VPT birth cohorts.

METHODS

We used harmonized aggregated data from 15 population-based cohorts of children born at <32 weeks of gestational age (GA) or <1500 g from 1985 to 2013 in 13 countries with information on maternal education and assessments of general development at 2-3 years and/or intelligence quotients between 4 and 15 years. Term-born controls (≥37 weeks of GA) were available in eight cohorts. Maternal education was classified as: low (primary/lower secondary); medium (upper secondary/short tertiary); high (bachelor's/higher). Pooled standardized mean differences (SMDs) in cognitive scores were estimated (reference: high educational level) for children assessed at ages 2-3, 4-7 and 8-15 years.

RESULTS

The study included 10 145 VPT children from 12 cohorts at 2-3 years, 8829 from 12 cohorts at 4-7 years and 1865 children from 6 cohorts at 8-15 years. Children whose mothers had low, compared with high, educational attainment scored lower on cognitive measures [pooled unadjusted SMDs: 2-3 years = -0.32 (95% confidence intervals: -0.43 to -0.21); 4-7 years = -0.57 (-0.67; -0.47); 8-15 years = -0.54 (-0.72; -0.37)]. Analyses by GA subgroups (<27 vs ≥27 weeks) in children without severe neonatal morbidity and term controls yielded similar results.

CONCLUSIONS

Across diverse settings and regardless of the degree of prematurity, low maternal education was associated with lower cognition.

Critical role of methionine-722 in the stimulation of human brain G-proteins and neurotoxicity induced by London familial Alzheimer's disease (FAD) mutated V717G-APP(714-723)

We have demonstrated earlier that V717G-APP(714-723), the membrane fragment of the V717G ("London") familial Alzheimer's disease (FAD) mutant of amyloid precursor protein (APP), is a potent stimulator of G-proteins in human brain membranes. In this study, we tested the hypothesis that Met-722 in the V717G-APP(714-723) peptide (P2) plays a critical role in the P2-induced oxidative stimulation of G-proteins in the human temporal cortex membranes and in the neurotoxicity of the peptide in differentiated PC12 and cerebellar granular cells. We found that 10 microM P3, the Met-722 sulfoxide analog of P2, produced a twofold lower stimulation of G-proteins ([(35)S]-GTPgammaS binding) in control temporal cortex membranes compared with 10 microM P2. The stimulatory effect of 10 microM P4, the Met-722 sulfone analog of P2, was 2.5-fold lower than the effect of P2. In Alzheimer's disease (AD) temporal cortex, the P3 and P4 stimulation of G-proteins was slightly weaker than the P2 stimulation. Substitution of the Met-722 S-atom in P2 by -CH(2)- group (P5) led to the disappearance of P2 stimulatory effect on G-proteins. Glutathione (GSH), melatonin (Mel), desferrioxamine (DFO) and 17-beta-estradiol (17betaE) significantly reduced P2 stimulatory effect on G-proteins in human brain. Only DFO and Mel were able to reduce the moderate stimulation of G-proteins by P3, whereas none of the tested antioxidants influenced the weak stimulation by P4. P2 at 100 microM induced a 40% decrease in PC12 cell viability as revealed by MTT assay, the effect being significantly higher than that of P3 or P4, whereas P1 (wild-type APP(714-723)) did not affect cell viability. Trypan Blue exclusion assay demonstrated that 10 microM P2 and P3 induced 3.8- and 3.5-fold death in the cerebellar granular cells as compared with the respective control values. P1 and P4 at 10 microM induced 1.7- and 2.3-fold increase in cell death, respectively. Treatment of the cerebellar granular cells with pertussis toxin decreased the high neurotoxicity of P2 and P3, whereas the low toxicity of P1 and P4 was not influenced. These results support the hypothesis that the G-protein stimulatory effect and neurotoxicity of "London"-mutated V717G-APP(714-723) (P2) and its Met-722 oxidized analogs involve oxidative-dependent and oxidative-independent mechanisms and the oxidation state of Met-722 plays a critical role in determining the mechanism.

PNA oligomers as tools for specific modulation of gene expression

Small synthetic molecules that can specifically inhibit translation and/or transcription have shown great promise as potential antisense/antigene drugs. Peptide nucleic acid (PNA), an oligonucleotide mimic, has a non-charged achiral polyamide backbone to which the nucleobases are attached. PNA oligomers are extremely stable in biological fluids and they specifically hybridise to DNA or RNA in a complementary manner, forming very strong heteroduplexes. Some of the mRNAs have yet undetermined and possibly long half-lives, successful down regulation of gene expression by antisense oligonucleotides (ON) requires that the antisense agent is long lived. PNA fulfils this requirement better than phosphodiester or phosphorothioate ONs. PNA can inhibit transcription and translation of respective genes by tight binding to DNA or mRNA. First in vitro experiments to specifically down regulate protein expression by PNA have been followed by successful antisense and antigene application of PNA oligomers in vivo. This review discusses the principles of the in vitro and in vivo use of PNA oligonucleotides.

Intrathecal administration of PNA targeting galanin receptor reduces galanin-mediated inhibitory effect in the rat spinal cord

Peptide nucleic acids (PNA) are nucleic acid analogues containing neutral amide backbone, forming stable and tight complexes with complementary DNA/RNA. However, it is unclear whether unmodified PNA can efficiently penetrate neuronal tissue in order to act as antisense reagent. Here we show that intrathecal (i.t.) injection of an unmodified antisense PNA complementary to the rat galanin receptor type 1 (GalR1) mRNA is able to block the inhibitory effect of i.t. administered galanin on spinal nociceptive transmission. Autoradiographic ligand binding studies using [125I]galanin show that the unmodified PNA is able to reduce the density of galanin binding sites in the dorsal horn. Thus, unmodified PNA applied i.t. appears to function as an effective antisense reagent in rat spinal cord in vivo.

What patients think of dental services

In 1998, research on 'What the general public wants from the general dental service' was carried out by the Centre for Dental Services Studies (CDSS) at the University of York and was commissioned by the British Dental Association (BDA). The research culminated in the report: 'User Priorities for General Dental Services'. This article outlines the main message from the research and contains the researcher's personal observations.

Targeting of a human iron-sulfur cluster assembly enzyme, nifs, to different subcellular compartments is regulated through alternative AUG utilization

Iron-sulfur clusters are prosthetic groups that are required for the function of numerous enzymes in the cell, including enzymes important in respiration, photosynthesis, and nitrogen fixation. Here we report cloning of the human homolog of NifS, a cysteine desulfurase that is proposed to supply the inorganic sulfur in iron-sulfur clusters. In human cells, different forms of NifS that localize either to mitochondria or to the cytosol and nucleus are synthesized from a single transcript through initiation at alternative inframe AUGs, and initiation site selection varies according to the pH of the medium or cytosol. Thus, a novel form of translational regulation permits rapid redistribution of NifS proteins into different compartments of the cell in response to changes in metabolic status.

Novel galanin receptor ligands

Galanin is a neuroendocrine peptide which is 29/30 amino acids in length and is recognised by G-protein-coupled central nervous system receptors via its N-terminus. We synthesised several galanin receptor ligands and fragments around C-terminal extensions of galanin(1-13) to yield chimeric peptides with C-terminals corresponding to bioactive peptides like bradykinin(2-9), mastoparan, neuropeptide Y(25-36) or substance P(5-11), respectively. We also synthesised short galanin analogs in which galanin(1-13) was C-terminally elongated with Lys14; different pharmacologically active small molecules were then attached to the epsilon-amino group of Lys14. Several cysteine-substituted linear and ring closed analogs of galanin(1-9) and galanin(1-16) were also synthesised. The equilibrium binding constants for these peptides at hypothalamic galanin receptors were determined and found in the subnanomolar to micromolar range. The large number of peptides and their binding affinities presented here permit structure-activity relationship analysis of peptide-type ligands to galanin receptors.

cDNA sequence, ligand biding, and regulation of galanin/GMAP in mouse brain

The cDNA encoding the 29 amino acid-long neuropeptide galanin and its flanking peptide galanin message associated peptide (GMAP), has been cloned and sequenced from mouse hypothalamic cDNA. The primary sequence of mouse galanin is GWTLNSAGYLLGPHAIDNHRSFSDKHGLT, followed by an amidation signal GKR. There are now 12 galanin sequences known: human, porcine, dog, rat, bovine, chicken, sheep, alligator, bowfin, dogfish, trout and mouse. The N-terminal 14 amino acids are identical in all of these species and the whole primary sequence of mouse galanin is identical to that of rate galanin. The mouse C-terminal flanking peptide, the GMAP, which is encoded on the same mRNA as galanin, shows a high degree of homology with all other known GMAP sequences but is not identical to any of them and it is more charged than the other GMAP sequences. Synthetic mouse galanin was found to displace [125I]mono-iodo-Tyr26 galanin (porcine) from receptors in the mouse hypothalamic membranes with high affinity (KD = 0.9 nM). Estrogen treatment of mice (0.1 mg/kg i.p.) for 6 h, which elevates the rat pituitary galanin mRNA levels, does not affect the galanin mRNA levels in mouse hypothalamus and pituitary. Neither does a subchronic glucocorticoid treatment (dexamethasone, 0.5 mg/kg i.p. for 7 days) affect these mRNA levels.

Galanin-receptor ligand M40 peptide distinguishes between putative galanin-receptor subtypes

The galanin-receptor ligand M40 [galanin-(1-12)-Pro3-(Ala-Leu)2-Ala amide] binds with high affinity to [mono[125I]iodo-Tyr26]galanin-binding sites in hippocampal, hypothalamic, and spinal cord membranes and in membranes from Rin m5F rat insulinoma cells (IC50 = 3-15 nM). Receptor autoradiographic studies show that M40 (1 microM) displaces [mono[125I]iodo-Tyr26]galanin from binding sites in the hippocampus, hypothalamus, and spinal cord. In the brain, M40 acts as a potent galanin-receptor antagonist: M40, in doses comparable to that of galanin, antagonizes the stimulatory effects of galanin on feeding, and it blocks the galaninergic inhibition of the scopolamine-induced acetylcholine release in the ventral hippocampus in vivo. In contrast, M40 completely fails to antagonize both the galanin-mediated inhibition of the glucose-induced insulin release in isolated mouse pancreatic islets and the inhibitory effects of galanin on the forskolin-stimulated accumulation of 3',5'-cAMP in Rin m5F cells; instead M40 is a weak agonist at the galanin receptors in these two systems. M40 acts as a weak antagonist of galanin in the spinal flexor reflex model. These results suggest that at least two subtypes of the galanin receptor may exist. Hypothalamic and hippocampal galanin receptors represent a putative central galanin-receptor subtype (GL-1-receptor) that is blocked by M40. The pancreatic galanin receptor may represent another subtype (GL-2-receptor) that recognizes M40, but as a weak agonist. The galanin receptors in the spinal cord occupy an intermediate position between these two putative subtypes.

Galanin receptors from human pituitary tumors assayed with human galanin as ligand

Galanin (i.v.) elevates circulating growth hormone levels in humans, and human growth hormone producing tumors show galanin-like immunoreactivity. We have therefore investigated the presence of galanin receptors in sixteen human pituitary tumors. Specific binding of [125I]monoiodo-[Tyr26]-porcine galanin was found in membranes from four clinically inactive and three growth hormone producing tumors. The affinity of human, rat and porcine galanin to these receptor sites was identical (Kd = 0.9 nM). The rank order of potency of galanin receptor ligands was the same in the human pituitary tissue as in the rat and porcine pituitary, hypothalamus, pancreas and hippocampus. GTP (1 mM) or GMPP(NH)P (0.5 mM) lowered the apparent specific binding of [125I]galanin (0.2 nM), suggesting that the human pituitary galanin receptor is coupled via a G-protein similarly to galanin receptors in mouse, rat and pig. The possible significance of galanin receptors in pituitary tumors is discussed.

Differential effects of the putative galanin receptor antagonists M15 and M35 on striatal acetylcholine release

The putative galanin receptor antagonists M15 and M35 were examined for their effects on the basal and the galanin-evoked release of acetylcholine in the striatum. Extracellular concentrations of acetylcholine were measured in male rats using in vivo microdialysis and high pressure liquid chromatography techniques. Galanin (300 microM or 3 nmol/10 microliters), perfused through the microdialysis membrane into the striatum, enhanced (100% increase) basal acetylcholine release. M35 (300 microM or 3 nmol/10 microliters) also stimulated the basal acetylcholine release to some extent (about 50%) while M15 at the same concentration failed to do so. When M15 and M35 were coinfused with galanin, the galanin-evoked acetylcholine release was blocked completely by M15 (300 microM or 3 nmol/10 microliters) but only partially by M35 (300 microM or 3 nmol/10 microliters). The increase in acetylcholine release induced by M35 (300 microM) was blocked by M15 (300 microM). It is concluded that M15 is a full galanin receptor antagonist while M35 behaves as a mixed agonist-antagonist in vivo in the rat striatum. Both M15 and M35 fully displaced 0.2 nM [125I]galanin from its binding sites in the striatal membranes. The Hill coefficient of these [125I]galanin displacement curves with M15 and M35 was 0.4-0.5 compared to unity in the case of galanin. Analysis of the displacement curves suggested that both M15 and M35 recognized two classes of galanin binding sites in striatal membranes of the rat. To explain the difference between M15 and M35 it is suggested that there may exist a putative subtype of galanin receptor in the striatum, which is differentially affected by M15 and M35.

Solution structure by 2D 1H-NMR of a chimeric peptide recognized by galanin and neuropeptide Y receptors

The 25 amino acid residue chimeric peptide M32, galanin(1-13)-neuropeptide Y(25-36)-amide, was synthesized. The peptide was found to be recognized by both galanin and NPY receptors. The solution structure in 30% (v/v) 1,1,1,3,3,3-hexafluoro-2-propanol was examined by 2-D 1H-NMR and by CD. Proton resonance assignments were made, and structures were calculated using DIANA and refined by restrained energy minimization and molecular dynamics. The obtained structures contain an alpha-helical part in the NPY portion of the peptide including residues 13-20, and in some structures it continues to the C-terminal Tyr25. The more flexible N-terminal portion of the peptide has the freedom to approach the C-terminal alpha-helix, via a reverse turn or a nascent alpha-helix, which permits the N-terminus with Trp2 to come into close contact with the C-terminus with Tyr25. Among the ten NMR structures with lowest energy, there are structures reminiscent of the horseshoe shape of aPP, a close relative of NPY with known crystal structure. It appears that the strong alpha-helical character of the NPY (25-36) amide fragment of M32 helps to stabilize structural features in the galanin-derived part of the peptide. It is noteworthy that this rigid NPY portion of M32 does not prevent the recognition of the peptide by galanin receptors; rather, the peptide has unusually high affinity: IC50 = 0.1 nM at galanin receptors. The chimeric peptide M32 is also recognized by NPY receptors with submicromolar affinity (IC50 = 0.25 microM). The availability of a solution structure for peptide M32, which is recognized by two peptide receptors that are both members of the family of G-protein-coupled receptors, may be useful in understanding peptide receptor-ligand interactions and in designing new galanin and NPY receptor ligands.

N-terminal galanin fragments inhibit the hippocampal release of acetylcholine in vivo

Using synthetic N-terminal fragments of galanin, galanin (1-7), galanin (1-9), galanin (1-12) and galanin (1-16), we have shown that the minimal sequence required for inhibition of acetylcholine release in vivo from rat ventral hippocampus corresponds to galanin (1-12). The fragment (1-9) displays activity in vivo but only at a very high concentration of 6.23 nmol while galanin (1-7) and C-terminal fragment (17-29) are without effect. Binding studies showed that galanin (1-16) and galanin (1-12) bind with submicromolar IC50 values to rat hippocampal galanin receptors. Galanin (1-9) has substantially lower affinity towards rat ventral hippocampal galanin receptor.

Blockade of galanin-induced inhibition of insulin secretion from isolated mouse islets by the non-methionine containing antagonist M35

The neuropeptide galanin occurs in pancreatic adrenergic nerves and has been suggested to be the adrenergic mediator of the stress-induced inhibition of insulin release. To study its physiological function, we recently synthesized a galanin-like galanin receptor antagonist, galantide. However, this antagonist contains a methionine moiety, and is therefore easily oxidized. We have now synthesized another galanin antagonist which does not contain methionine. This peptide, M35, is a chimeric 21 amino acid peptide in which galanin-(1-13) is coupled to bradykinin-(2-9). M35 (10 microM to 1 pM) had no effect by itself on glucose (11.1 mM)-stimulated insulin secretion in isolated mouse islets, but potently counteracted the inhibitory action of galanin (100 nM). The lowest effective dose of M35 was 10 nM. M35 did not counteract the inhibitory action of clonidine (1 microM) or somatostatin (1 microM) on insulin secretion. Furthermore, M35 displaced 125I-monoiodo-[Tyr26]galanin from membranes of insulin producing RINm5F cells. The displacement curve fitted to a two-site model in which 60% of label bound with a K1 of 0.1 +/- 0.01 nM and 40% with a K2 of 3 +/- 0.5 nM. In conclusion, M35 is a specific, non-methionine-containing galanin receptor antagonist on insulin-producing cells.

Design of chimeric peptide ligands to galanin receptors and substance P receptors

Several chimeric peptides were synthesized and found to be high-affinity ligands for both galanin and substance P receptors in membranes from the rat hypothalamus. The peptide galantide, composed of the N-terminal part of galanin and C-terminal part of substance P (SP), galanin-(1-12)-Pro-SP-(5-11) amide, which is the first galanin antagonist to be reported, recognizes two classes of galanin binding sites (KD(1) less than 0.1 nM and KD(2) approximately 6 nM) in the rat hypothalamus, while it appears to bind to a single population of SP receptors (KD approximately 40 nM). The chimeric peptide has higher affinity towards galanin receptors than the endogenous peptide galanin-(1-29) (KD approximately 1 nM) or its N-terminal fragment galanin-(1-13) (KD approximately 1 microM), which constitutes the N-terminus of the chimeric peptide. Galantide has also higher affinity for the SP receptors than the C-terminal SP fragment-(4-11) amide (KD = 0.4 microM), which constitutes its C-terminal portion. Substitution of amino acid residues, which is of importance for recognition of galanin by galanin receptors, such as [Trp2], in the galanin portion of the chimeric peptide or substitution of ([Phe7] or [Met11]-amide) in the SP portion of chimeric peptide both cause significant loss in affinity of the analogs of galantide for both the galanin- and the SP-receptors. These results suggest that the high affinity of the chimeric peptide, galantide, may in part be accounted for by simultaneous recognition/binding to both receptors.(ABSTRACT TRUNCATED AT 250 WORDS)

The novel high-affinity antagonist, galantide, blocks the galanin-mediated inhibition of glucose-induced insulin secretion

This study describes the synthesis and effects of the first antagonist to the widely distributed neuropeptide, galanin, which inhibits the secretion of insulin. The first galanin antagonist is a 20-amino acid-long chimeric peptide of the composition galanin-(1-12)-Pro-substance P-(5-11) amide: Gly-Trp-Thr-Leu-Asn-Ser-Ala-Gly-Tyr-Leu-Leu-Gly-Pro-Gln-Gln-Phe-Phe-Gly- Leu-Met amide. The peptide dose dependently (IC50 = 1.0 nM) antagonizes the galanin-mediated inhibition of the glucose-induced insulin secretion from mouse pancreatic islets. The antagonist was also found to displace 125I-monoiodo-[Tyr26]galanin from membranes of the insulin producing Rin m 5F cells with an IC50 value of less than 0.1 nM. The antagonist is named galantide.

M-15: high-affinity chimeric peptide that blocks the neuronal actions of galanin in the hippocampus, locus coeruleus, and spinal cord

The 20-amino acid peptide M-15 binds with high affinity (IC50 approximately 0.1 nM) to 125I-labeled galanin (125I-GAL) binding sites in membranes from the ventral hippocampus, midbrain, and rat spinal cord. Receptor autoradiographic studies show that M-15 can displace 125I-GAL from all labeled sites. M-15 acts as a reversible high-affinity antagonist in blocking the inhibitory effects of GAL on the evoked release of acetylcholine in vivo in the hippocampus and on the GAL-induced hyperpolarization of locus coeruleus neurons in slices. M-15 also blocks the facilitatory effects of GAL on the spinal flexor reflex. Thus, the chimeric peptide M-15 [GAL-(1-13)-substance P-(5-11)amide] represents the first antagonist to the neuronal actions of GAL.

Second-order conditioning of the rabbit's nictitating membrane response. Interstimulus interval and frequency of CS-CS pairings

Second-order conditioning of the rabbit's nictitating membrane response (NMR) was investigated when second-order trials (CS1-CS2) were intermixed with first-order trials (CS2-US) from the outset of training. Experiment 1 showed that CR acquisition to CS1 was inversely related to the CS1-CS2 interval but nevertheless extended to an interval of 8,400 ms. Experiment 2 revealed that CR acquisition of CS1 was an inverted-U function of the number of CS1-CS2 trials relative to a fixed number of CS2-US trials. Experiment 3 directly contrasted second-order conditioning with a reinforced serial compound procedure (CS1-CS2-US) and a mixed procedure in which second-order trials were intermixed with the reinforced serial compound. Second-order conditioning was about half the strength of either the reinforced serial compound or the mixed procedure, which were similar. The present results are discussed with respect to the relative strength of excitatory and inhibitory processes in second-order conditioning.

Hypothalamic degradation of galanin(1-29) and galanin(1-16): identification and characterization of the peptidolytic products

The degradation of the neuropeptide galanin(1-29) and its fully active synthetic N-terminal fragment galanin(1-16) in hypothalamic tissue, where these peptides potently affect feeding behaviour, is studied. Galanin(1-29) had a half-life of 100 min while galanin(1-16) had a half-life of 28 min when incubated with a hypothalamic membrane preparation. The putative sites of peptidolytic cleavage of the active N-terminal fragment galanin(1-16) were determined as being between amino acids Leu4 and Asn5, between Asn5 and Ser6, and between His14 and Ala15, respectively. The synthetic analogs of galanin(1-16) where Leu4, Asn5 or Ser6 was substituted by Ala were all more stable to peptidolysis; [Ala4]galanin(1-16) had a half-life of 55 min. Cleavage of the galanin(1-16) between His14-Ala15 yields a ligand-galanin(1-14) which binds to the receptor with high affinity (KD approximately 10(7) M), while cleavage at amino acid residues Leu4, Asn5 and Ser6 results in inactive peptide fragments with affinities for the galanin receptor below 10(-4) M. The enzyme(s) responsible for degradation of galanin were identified as endopeptidase(s), which were partially inhibited by bacitracin (1 mg/ml) by up to 50%, but not significantly by EDTA (1 mM), phosphoramidon (1 microM), phenylmethylsulfonyl fluoride, (100 microM) or aprotinin (10 micrograms/ml).

Linear and cyclic N-terminal galanin fragments and analogs as ligands at the hypothalamic galanin receptor

The neuropeptide galanin (1-29) binds with high affinity to hypothalamic receptors (KD approximately 0.9 nM) and regulates feeding behavior. The N-terminal fragments (1-16), (1-16)NH2 are high affinity (KD approximately 6 nM) full agonists in vivo and in vitro. L-Ala substitutions show that amino acid residues Gly1, Trp2, Asn5, Tyr9, and Gly12 are important for the high affinity binding of galanin (1-16). Shortening the fragment (1-16) to galanin (1-7) causes a gradual drop of affinity: galanin (1-15), (1-14), and (1-13) have submicromolar KD values and galanin (1-12) has KD approximately 3 microM. Cyclic analogs of galanin (1-12) of different ring size were synthesized by condensing Gly1 and Gly12 without or with spacer groups. These analogs, independent of ring size, had a lower affinity than the linear galanin (1-12). Derivatization of the N-terminus of galanin (1-29), (1-16), and (1-12) all resulted in a large drop of affinity for the receptors, suggesting again the importance of the free N-terminal Gly.

Anatomical study of the rabbit's corneal-VIth nerve reflex: connections between cornea, trigeminal sensory complex, and the abducens and accessory abducens nuclei

The corneal-VIth nerve reflex of the rabbit, involving retraction of the eyeball by the retractor bulbi muscle and the correlated extension of the nictitating membrane, has been suggested to be mediated by retractor bulbi motoneurons in the accessory abducens-(ACC) nucleus but not by those in the abducens (ABD) nucleus, and to consist of both a fast, disynaptic, component and a slower component mediated by the reticular formation (RF). We, therefore, employed the anterograde and retrograde transport of horseradish peroxidase (HRP) to examine the neural connections between anatomical structures proposed to be involved in the afferent limb of the corneal VIth nerve reflex. The transganglionic transport of HRP from cornea indicated a primary projection to the ventral half of pars oralis of the trigeminal sensory complex. The retrograde transport of HRP infused into ACC resulted in a bilateral labeling of cells in ventral pars oralis with 75% of the labeled cells being ipsilateral to the side of infusion. In contrast, there was no retrograde labeling of cells in the trigeminal sensory complex after HRP infusions into ABD. Infusion of HRP into ACC and ABD also revealed retrogradely labeled cells in the RF caudal to these two nuclei and infusion of HRP into this area of the RF resulted in both the retrograde labeling of cells in ventral pars oralis and anterograde-like labeling in both ACC and ABD. These data provide anatomical support for a direct relationship of the ACC, but not ABD, to the trigeminal sensory system and for the suggested existence of two components of the corneal-VIth nerve reflex: a disynaptic component from cornea to ventral pars oralis which in turn projects only to the ACC nucleus; and a multisynaptic component consisting of projections from the ventral pars oralis to RF cells which, in turn, are premotor to the ACC and ABD nuclei.

Classical conditioning of the rabbit (Oryctolagus cuniculus) nictitating membrane response, with electrical brain stimulation as the unconditioned stimulus

Rabbits were given classical conditioning training by using paired tone CS (conditioned stimulus) and brain-shock UCS (unconditioned stimulus), with the stimulating electrode localized in the vicinity of the abducens (6th nerve) nucleus such that the electrical stimulus elicited a low-threshold nictitating membrane (NM) extension response as the unconditioned response. Eight of the 27 animals developed clear conditioned NM responses to the tone CS. Control procedures, e.g., subsequent explicity unpaired training, argue against sensitization, pseudoconditioning, and "kindling" as possible explanations. There was no clear-cut anatomical differentiation of electrode-tip locations between learners and nonlearners. Both learners and nonlearners were subsequently trained with paired tone-corneal air puff, and neuronal unit activity was recorded from the stimulating electrode. Animals that had learned with the prior brain-shock UCS exhibited substantially greater increases in neuronal unit activity during air-puff training, which suggests the existence of a differentially effective anatomical-physiological substrate for conditionability.