bluuebunny/crossref_metadata_2025 huggingface dataset:
The timing of initial neuropeptide expression by an identified insect neuron does not depend on interactions with its normal peripheral target
Authors: Wall John B. , Taghert Paul H.
Published: May 2005

To study the developmental regulation of a neuropeptide phenotype, we have analyzed the biochemical and morphological differentiation of two identifiable neurons in embryos of the moth, Manduca sexta. The central cell, CF, and the peripheral cell, L1, are both neuroendocrine neurons that express neuropeptides related to the molluscan tetrapeptide FMRFamide. Both neurons project axons to the transvers nerve in each thoracic segment. Within the CF and L1 cells, neuropeptide‐like immunoreactivity was localized to secretory granules that had cell specific morphologies and sizes. The onset of neuropeptide expression in the two cell types displayed a similar pattern: immunoreactivity was first detected in distal processes and soon after within cells bodies. However, the onsets occurred at different times: for the CF cell, neuropeptides were first seen at 60%‐63% of embryonic development, after the neuron had extended a long axon into the periphery, while L1 neuropeptide expression began at ∼42%, as it first extended its growth cone. These times were related in that they corresponded to the arrival times of the respective growth cones at a similar position in the developing peripheral nerve. Withinthis region of the nerve, the growth cones of both cell typesexhibited a transient and cell‐specific interaction with an identified mesodermal cell, called the Syncytium. Like the L1 and B neurons (Carr and Taghert, 1988b), the CF growth cones typically grew past this cell, yet remained attached to it by lamellipodial and filopodial processes of the axon. Ultrastructurally, the interaction involved filopodial adhesion to and insertion within the Syncytial cell. Two other nonneuroendocrine cell types grew axons past this same region, but showed no such tendencies. To test the hypothesis that the morphological and biochemical differentiation of these cells was somehow linked, central ganglia were isolated (as individuals or connected as ganglionic chains) in tissue culture, prior to the time when CF growth cones entered the periphery and prior to the development of CF neuropeptide expression. In the majority of cases, CF neurons nevertheless displayed their neuropeptide phenotype at a normal and cell‐specific stage. We conclude that the initiation of neuropeptide expression is highly correlated with schedules of morphological differentiation in these neurons, but that, in the case of the CF neuron, it is not regulated by interactions of the growth cone with peripheral structures.
Tamoxifen's effects on the zebra finch song system are estrogenic, not antiestrogenic
Authors: Mathews Greta A. , Arnold Arthur P.
Published: May 2005

Antiestrogens fail to block the masculine ontogeny of the zebra finch song system that is hypothesized to occur as a result of early estrogen action. Moreover, they hypermasculinize the male, and masculinize the female song systems. In experiment 1, we assessed whether these antiestrogenic effects might mimic estrogenic actions. Zebra finch chicks received one of two treatments. They were given estradiol benzoate (EB) or vehicle daily for the first 20 days after hatching and sacrificed at 60 days of age, or they received EB or vehicle for the first 25 days after hatching, at which time they were sacrificed. In the day 60 group, certain attributes of the song system were hypermasculinized in males and masculinized in females by EB, when compared with controls. In the day 25 group, males treated with EB were partially demasculinized, while the females were partially masculinized. In experiment 2, we assessed whether simultaneous treatment with tamoxifen was capable of antagonizing the effects of EB obtained in experiment 1 (day 60 group). Sixty‐day‐old females, previously treated with both EB and tamoxifen for the first 20 days after hatching, had more masculine song regions than females treated with either EB alone or tamoxifen alone. In males, the effects of the combined treatment of EB and tamoxifen over those produced by tamoxifen alone were not as dramatic as in the female. These results are similar to those obtained in systems where tamoxifen is purely estrogenic and suggest that in the song system, tamoxifen acts as an estrogen, not an antiestrogen.
Transient and permanent effects of androgen during synapse elimination in the levator ani muscle of the rat
Authors: Lubischer Jane L. , Jordan Cynthia L. , Arnold Arthur P.
Published: May 2005

Young male rats were castrated at 7 days of age, and treated with testosterone propionate daily from 7 to 34 days of age. At 13 months of age, motor axons and terminals innervating the levator ani (LA) muscle were stained with tetranitroblue tetrazolium (TNBT). The number of separate axons innervating individual muscle fibers was counted, and muscle fiber diameter was measured. Previous studies have shown that this androgen treatment increases muscle fiber diameter and delays synapse elimination, measured as (1) a greater percentage of muscle fibers innervated by multiple axons and (2) larger motor units. The present results indicate that the androgenic effect on synapse elimination is permanent, in that high levels of multiple innervation persisted for 12 months after the end of androgen treatment. In contrast, the effect on muscle fiber diameter was not maintained for this period. This dissociation of androgenic effects on the pattern of innervation from androgenic effects on muscle fiber diameter offers further evidence that the androgenic maintenance of multiple innervation is not dependent on muscle fiber size. In addition, circulating testosterone levels were measured at 50 and 60 days of age in animals similarly treated with androgen or oil from 7 to 34 days of age. By 60 days of age, testosterone levels in hormone‐treated animals had dropped below detectability, comparable to levels in oil‐treated controls. This provides additional evidence that androgen treatment during juvenile development can have permanent effects on the adult pattern of innervation in the LA muscle.
The relationship of intramuscular nerve branching and synaptogenesis to motoneuron survival
Authors: Landmesser Lynn
Published: May 2005

The target has been considered for some time to play a major role in allowing neurons to survive the period of naturally occurring cell death. For the motoneurons that innervate the chick limb, evidence is presented that suggests access to target‐derived trophic factor via intramuscular nerve branches and synapses may be important in regulating neuronal survival. Alterations in branching and synapse formation produced by activity blockade as well as by alteration of adhesion molecule function are shown to result in changes in motoneuron survival consistent with the proposed hypothesis. The relevance of these observations to the numerical‐matching hypothesis of vertebrate neuronal cell death is also considered. © 1992 John Wiley & Sons, Inc.
Cell death and the creation of regional differences in neuronal numbers
Authors: Finlay Barbara L.
Published: May 2005

Regional variations in cell death are ubiquitous in the nervous system. In the retina, cell death in retinal ganglion cells is elevated in the retinal periphery and may be important in setting up the initial conditions that produce central retinal specializations such as an area centralis or visual streak. In central visual system structures, pronounced spatial and spatiotemporal inhomogeneities in cell death are seen both in layers and regions of the lateral geniculate nucleus and superior colliculus; similar indications of inhomogeneities are seen in those nonvisual structures that have been examined. Cell death in the cortex is highly nonuniform, by layer and by cortical area. A variety of possible functions for these regional losses are proposed, in the context of a uniform mechanism for cell death that allows it to assume multiple functions. © 1992 John Wiley & Sons, Inc.
Matters of life and death in the songbird forebrain
Authors: Bottjer Sarah W. , Johnson Frank
Published: May 2005

Male zebra finches learn a specific vocal pattern during a restricted period of development. They produce that song in stereotyped form throughout adulthood, and are unable to learn new song patterns. Development of the neural substrate for song learning and behavior is delayed relative to other brain regions, and neural song‐control circuits undergo dramatic changes during the period of vocal learning due to both loss of neurons as well as incorporation of newly generated neurons. In contrast, canaries do learn new song patterns in adulthood and modify their vocal repertoires each breeding season. Adult canaries also maintain a large population of dividing cells in the ependymal zone of the telencephalon, and vast numbers of newly generated neurons migrate out to become incorporated into functional circuits and replace older neurons. We review the relationships between cellular and behavioral aspects of song learning in both zebra finches and canaries, as well as the role of gonadal hormones in regulating diverse aspects of the song‐control system. © 1992 John Wiley & Sons, Inc.
Mechanisms of neuronal death in brain aging and alzheimer's disease: Role of endocrine‐mediated calcium dyshomeostasis
Authors: Landfield Philip W. , Thibault Olivier , Mazzanti Mary L. , Porter Nada M. , Kerr D. Steven
Published: May 2005

This paper reviews evidence that brain aging and Alzheimer's disease (AD) are somehow closely related and that the hippocampus (CA1) is highly vulnerable to cell loss under both conditions. In addition, two current lines of evidence on the mechanisms of hippocampal cell loss with aging are considered, including studies of neuronal calcium dysregulation and studies of cumulative glucocorticoid (GC) neurotoxicity. Moreover, recent electro‐physiological studies have shown that excess glucocorticoid activation of hippocampal neurons increases the influx of calcium through voltage‐activated calcium channels. Second messenger systems may mediate the steroid modulation of calcium channels. Therefore, it is hypothesized that excess glucocorticoid activation and neuronal calcium dysregulation may be two phases of a single process that increases the susceptibility of neurons to neurodegeneration during aging and Alzheimer's disease. © 1992 John Wiley & Sons, Inc.
Development of anuran locomotion: Ethological and neurophysiological considerations
Authors: Stehouwer Donald J.
Published: May 2005

There are dramatic quantitative and qualitative differences in the locomotor behavior of larval and juvenile frogs. Larvae (tadpoles) are primarily herbivourous and rely heavily on locomotion via undulations to acquire food and avoid predation. After metamorphosis, juvenile frogs adopt a carnivorous lifestyle and capture prey and avoid predators by remaining motionless in a place of concealment. When they must move, frogs locomote by means of ballistic hops or by more conventional walking. However, locomotion of both tadpoles and frogs can be considered of two fundamental functional types: (a) startle and escape; and (b) sustained locomotion. Neural mechanisms underlying startle responses and sustained locomotion in larvae and juveniles are described and possible ontogenetic relationships those behaviors are proposed. The role of different parts of the nervous system in the ontogeny of locomotion, as well as nonneuronal factors, are described. Results show that the transition from tadpole‐like behavior to frog‐like behavior is not a simple function of maturation of central locomotor controls. Rather, it results from a complex interaction of central nervous system maturation, morphological change, and a change in habitat preference. Examples of similar multidimensional control of behavioral ontogeny in other species are described, and it is argued that to understand the ontogeny of behavior, one must investigate contributions made at all levels, from the neuronal to the environmental. © 1992 John Wiley & Sons, Inc.
Neuroethological approaches to the study of motor development in chicks: Achievements and challenges
Authors: Bekoff Anne
Published: May 2005

Chicks and chick embryos provide a useful model system for the study of related to the development of motor behaviors. EMG and kinematic analyses of leg movements have been used to provide new data on the organization of embryonic motility. These data suggest that the circuitry needed to produce a basic, coordinated motor pattern is available early in development. This circuitry then appears to be retained throughout life. Evidence from analysis of EMG patterns and leg deafferentation studies suggest that the output of this basic circuit can be modulated by sensory input to produce the motor patterns of later behaviors, such as hatching and walking. If the same circuitry is present throughout life, then mechanisms for initiation and termination of particular behaviors must be available to ensure that specific behaviors are turned on and off at appropriate times. For example, hatching can be turned on by a specific sensory signal: proprioceptive signals from the bent neck. In addition to reviewing current research on the development of chick motor behaviors, methodological considerations and suggestions for future research are presented. © 1992 John Wiley & Sons, Inc.
Developmental plasticity in neural circuits controlling birdsong: Sexual differentiation and the neural basis of learning
Authors: Arnold Arthur P.
Published: May 2005

In many species of passerine songbirds, males learn their song during defined periods of life. Female song in often reduced or absent, as are the brain regions controlling song. Sexual differences in the brain arise because of the action of sex steroids, which trigger the formation of some neural pathways (especially the pathway from the higher vocal center to the robust nucleus) and prevent the atrophy of others in males. These neural changes occur during periods of developmental song learning and can recur during periods of learning in adult birds. The process of learning is correlated with major increases or decreases in the number of neurons in specific neuronal populations, suggesting that the formation or loss of specific neural pathways regulates the ability to learn. Species differences in sexual differentiation and learning allow informative cross‐species comparisons of neural structure and behavior. © 1992 John Wiley & Sons, Inc.
Emergence of pattern in the development of mammalian movement sequences
Authors: Fentress John C.
Published: May 2005

The manner in which behavior is patterned in space and over time represents a fundamental problem in both ethology and neuroscience. Prior to the analysis of mechanism it is important to be sensitive to issues involved in the provision of descriptive taxonomies. Often alternative modes of description lead to different perspectives and research strategies. In both the development of behavioral patterns and their expression a major question is how underlying organizational systems become self‐organizing through the process of mutual interactions. It is clear that simple static dichotomies in both behavioral and developmental science must be replaced by more sophisticated models that emphasize the dynamics of pattern formation and control. Some of these perspectives are illustrated from our ongoing research on rodent movement patterns. © 1992 John Wiley & Sons, Inc.
A model of selective synapse formation in sympathetic ganglia
Authors: Liestøl Knut , Mæhlen Jan , Njå Arild
Published: May 2005

In the sympathetic system, neurons from several spinal segments are mapped onto targets in the periphery in a topographically ordered way by means of selective synaptic connections in the superior cervical ganglion. Experimental evidence points to a crucial role for chemoaffinity in establishing this topographic map. Furthermore, rearrangements of synapses after surgical manipulations indicate that this chemoaffinity is not based on rigid “key‐and‐lock” markers. Our model is used to study how such nonrigid markers may interact with other regulatory factors, including growth‐regulating signals and the growth potential of individual nerons. In the model, these latter factors are limiting, so that an increasing number of synaptic contacts decreases the likelihood of further synapse formation. These factors are combined with chemoaffinity using a linear threshold model. The model is robust to parameter changes and reproduces experimental observations with reasonable detail. Simulation results are used to discuss characteristic experimental results, such as the substantial plasticity of the connections seen after partial denervation. A surprisingly small effect of transient hyperinnervation in the model may help explain why final connectivities are similar in two real situations with high and low degrees of transient hyperinnervation (development and adult reinnervation). It is shown that spatial restrictions on post‐synaptic neurons (dendrites) may contribute significantly to the segmentally broad innervation of each ganglion cell. Finally, we discuss potential effects of presynaptic neuronal death in systems with a high degree of plasticity. © 1993 John Wiley & Sons, Inc.
Dendritic development in the dorsal lateral geniculate nucleus of ferrets in the postnatal absence of retinal input: A golgi study
Authors: Sutton J. Keith , Brunso‐Bechtold Judy K.
Published: May 2005

In order to determine the ongoing role of retinal fibers in the development of dorsal lateral geniculate nucleus (dLGN) neurons during postnatal development, the development of dLGN neurons in the postnatal absence of retinal input was studied in pigmented ferrets using the Golgi‐Hortega technique. The development of four dLGN cell classes, defined on the basis of somatic and dendritic morphology, was described previously in normal ferrets (Sutton and Brunso‐Bechtold, 1991, J. Comp. Neurol. 309: 71–85). The present results indicate that the morphological development of dLGN neurons is strikingly similar in normal and experimental ferrets. The exuberant dendritic appendages that appear after eye opening in normal ferrets are overproduced and eliminated in the postnatal absence of retinal input; however, the final reduction of these transient appendages is delayed. Because exuberant appendages develop in the absence of retinal input, their production cannot depend upon visual experience. Differences in cell body size between normal and experimental ferrets are apparent only after neurons can be classified at the end of the first postnatal month. Cell body size is markedly reduced for class 1 neurons; class 2 cells also are reduced in size but to a far lesser extent. As there is a general trend for class 1 neurons to have the functional properties of Y‐cells, it is likely that the dLGN neurons most affected by the absence of retinal input also are Y‐cells. © 1993 John Wiley & Sons, Inc.
Sensitivity of neurite outgrowth to microfilament disruption varies with adhesion molecule substrate
Authors: Abosch Aviva , Lagenaur Carl
Published: May 2005

Interactions between the cytoskeleton and cell adhesion molecules are presumed responsible for neurite extension. We have examined the role of microfilaments in neurite outgrowth on the cell adhesion molecules L1, P84, N‐CAM, and on laminin. Cerebellar neurons growing on each substrate exhibited differing growth cone morphologies and rates of neurite extension. Growth of neurites in the presence of cytochalasin B (CB) was not inhibited on substrates of L1 or P84 but was markedly inhibited on N‐CAM. Neurons on laminin were initially unable to extend neurites in the presence of CB but recovered this ability within 9 h. These studies suggest that neurite outgrowth mediated by different cell adhesion molecules proceeds via involvement of distinct cytoskeletal interactions. © 1993 John Wiley & Sons, Inc.
Hormone‐induced changes in identified cell populations of the higher vocal center in male canaries
Authors: Johnson Frank , Bottjer Sarah W.
Published: May 2005

Male canaries revise their vocal repertoire every year. Early work indicated that the volume and neuron number of the song‐control nucleus HVC (Higher Vocal Center) declined in late‐summer/fall as birds added and deleted syllables from their repertoire, and increased in spring as the set of song syllables stabilized to a fixed number. Seasonal variation in serum testosterone levels suggested that these changes in brain and behavior were regulated by testosterone (T). However, although initial studies describing growth and regression of HVC used Nissl‐staining to define its borders, recent experiments that have measured the distribution of identified populations of HVC cells (projection neurons, hormone target cells) suggest that there are no seasonal changes in HVC volume or neuron number. In order to clarify the role of T in the regulation of HVC morphology, we castrated male canaries, maintained them on short (fall‐like) days, and treated them with either T, antisteroid drugs, or nothing. After 1 month of treatment, we used a double‐labeling technique to characterize HVC projection neurons and androgen target cells. The results showed that hormonal manipulation influenced HVC volume, the density and size of HVC cells, and the absolute number and percentage of androgen target cells in HVC. Hormonal manipulation did not influence the absolute number of cells in HVC. Moreover, the distribution of projection neurons, androgen target cells, and the Nissl‐defined borders of HVC were closely aligned in all experimental groups, indicating that exposure to T and/or its metabolites (estradiol and dihydrotestosterone) regulates the overall size of HVC by affecting the distributions of both projection neurons and androgen target cells. Analysis of double‐labeling results suggests that T specifically influences both cell size and the ability to accumulate androgen among HVC neurons that project to the robust nucleus of the archistriatum (RA). The results of this study show that steroid hormones exert potent effects on HVC morphology in male canaries, but differences between our results and studies of seasonal males suggest there may be additional factors that can regulate HVC morphology. © 1993 John Wiley & Sons, Inc.
Induction of programmed cell death in a dorsal root ganglia × neuroblastoma cell line
Authors: Linnik Matthew D. , Hatfield Marsa D. , Swope Melissa D. , Ahmed Nahed K.
Published: May 2005

Growth factor‐dependent neurons die when they are deproved of their specific growth factor. This “programmed” cell death (PCD) requires macromolecular synthesis and is distinct from necrotic cell death. To investigate the mechanisms involved in neuronal PCD, we have studied the sequence of events that occur when a neuronal cell line (F‐11: Mouse neuroblastoma X rat dorsal root ganglia) is deprived of serum in a manner analogous to growth factor deprivation from neurons. Protein synthesis was inhibited within the first 8 h of serum deprivation, while DNA cleavage into nucleosome ladders was prominent by 24 h. The DNA cleavage could be inhibited by cycloheximide, consistent with a requirement for protein synthesis. In contrast, mitochondrial function was not compromised by serum deprivation. Rather, the cells appeared to be metabolically activated after serum removal as shown by an increased reduction of MTT by mitochondrial dehydrogenases and an increase in cellular autofluorescence, which is thought to be due to elevated levels of NADH and flavoproteins. Assessment of cell viability by propidium iodide staining showed no indication of cell death within 24 h. After 48 h of serum deprivation, cells decreased in size and increased propidium iodide uptake. Thus, serum deprivation activates PCD in F‐11 cells and may be a useful model to study the intracellular events responsible for PCD. © 1993 John Wiley & Sons, Inc.
Comparison of the physiology of the auditory receptor organs in Gryllus bimaculatus and Ephippiger ephippiger: CSD Recordings within the auditory neuropiles
Authors: Nebeling Bernd , RöUssler Wolfgang , Jatho Martin
Published: May 2005

The syllables of the song of the tettigoniid Ephippiger ephippiger consist of a series of short sound impulses with a broad‐banded frequency spectrum. Syllables of the song of the gryllid species Gryllus bimaculatus are nearly pure tones with sharply tuned frequency maxima. A comparison of the physiology of the audiotory receptor organs of both species was carried out by using acoustical stimuli with different carrier frequencies and time‐amplitude patterns. The neuronal ensemble activity of receptor cell groups of the tympanal organ was measured within the prothoracic ganglion using the CSD technique. In E. ephippiger, response maxima were found at carrier frequencies mirroring the broad frequency content of the conspecific song. The receptor cells of E. ephippiger are highly sensitive to transient sound impulses. In G. bimaculatus, the receptor cell population is more sharply tuned to the basic frequencies of the natural songs; pure tones represent more effective stimuli than transient sound signals. The causes for these speciesspecific differences are discussed with regard to probable adaptations of the receptor organs to the parameters of the conspecific songs. © 1993 John Wiley & Sons, Inc.
Calcium regulates neuronal differentiation both directly and via co‐cultured myocytes
Authors: Holliday Janet , Spitzer Nicholas C.
Published: May 2005

Control of neuronal development by cellular interactions can be regulated by both extracellular and intracellular calcium. Removal of extracellular calcium affects the differentiation of amphibian spinal neurons in vitro by preventing neuronal calcium influx during the production of calcium‐dependent action potentials (Holliday and Spitzer, Dev. Biol. 141:13‐23, 1990). However, this culture condition affects differentiation through other mechanisms as well. We have investigated the interaction between neurons and myocytes to distinguish direct effects of low extracellular calcium on neuronal differentiation and indirect effects due to interference with neuron‐myocyte interactions. We have examined the initiation of neurite outgrowth and the subsequent extension and orientation of processes. We find that (1) the number of neurons that initiate process outgrowth is reduced by the presence of myocytes in a standard medium containing calcium. Experiments with muscle‐conditioned medium indicate that the production and/or secretion of inhibitory cues is calcium dependent. (2) When neurite initiation occurs, neuronal architecture in the absence of myocytes is similar to that in their presence, either in standard or in calcium‐free medium, although neurite extension is enhanced by the absence of calcium. (3) Conditioned medium (CM) experiments additionally demonstrate that the orientation of neurite outgrowth to myocyte‐derived cues is calcium dependent, although the production of directional cues by myocytes is calcium independent. © 1993 John Wiley & Sons, Inc.
Retrograde signaling and the development of transmitter release properties in the invertebrate nervous system
Authors: Davis Graeme W. , Murphey R. K.
Published: May 2005

The dynamics of presynaptic transmitter release are oftern matched to the functional properties of the prostsynaptic cell. In organisms ranging from cats to crickets, evidence suggests that retrograde signaling is essential for matching these presynaptic release properties to individual postsynaptic partners. Retrograde interactions appear to control the development of presynaptic, short‐term facilitation and depression. 1994 John Wiley & Sons, Inc.
Adrenocorticotropic hormone activation of adenylate cyclase in raphe neurons: Multiple regulatory pathways control serotonergic neuronal differentiation
Authors: Eaton Mary J. , Whittemore Scott R.
Published: May 2005

The RN46A cell line was derived from embryonic day 13 rat medullary raphe cells by infection with a retrovirus encoding the temperature‐sensitive mutant of SV 40 large T antigen (tsT‐ag). The RN46A cell line is neuronally restricted and constitutively differentiates following a shift to nonpermissive temperature. Differentiated RN46A cells express low levels of tryptophan hydroxylase (TPH) but no detectable levels of serotonin (5‐HT). Treatment of cultures with the adrenocorticotrophic hormone peptide ACTH4–10 up‐regulates the expression of TPH immunoreactivity in differentiated RN46A cells, but 5‐HT synthesis requires initial treatment with ACTH4–10, followed by partial membrane depolarizing conditions. Up‐regulation of TPH by ACTH4–10 is apparently due to activation of adenylate cyclase, whereas the increased 5‐HT synthesis with membrane depolarization can be blocked with the voltage‐sensitive Ca2+ ‐channel blockers nifedipine and ω‐conotoxin. ACTH4–10 treatment also markedly up‐regulates the expression of the 5‐HT reuptake transporter, as do dibutyryl cyclic AMP and forskolin; chronic membrane depolarization has no effect on 5‐HT reuptake. The expression of the high‐affinity 5‐HT1A receptor is increased threefold by ACTH4–10 treatment during differentiation and fivefold by differentiation under partial membrane depolarizing conditions. Combining ACTH4–10 treatment and membrane depolarization does not increase expression of the 5‐HT1A receptor further. 5‐HT release is constitutive in ACTH‐treated RN46A cells and linked to spontaneous synaptic vesicle fusion in RN46A cells. Considered with previous results, these data indicate that multiple effectors, ACTH, brain‐derived neurotrophic factor, and membrane depolarization, have both distinct and overlapping effects that regulate specific elements of the serotonergic neuronal phenotype during differentiation and maturation. © 1995 John Wiley & Sons, Inc.
An application of the INEPT pulse sequence to the NMR assignment of halogenated marine natural products
Authors: Brownlee R. T. C. , Hall J. G. , Reiss J. A.
Published: May 2005

The routine use of the INEPT pulse sequence is shown to be the method of choice for the assignment of multiplicity from 13C NMR spectra where no prior information about the 1J(CH) coupling constants is available, or where these are expected to vary over a large range. This technique is illustrated using spectra obtained from polyhalogenated monoterpenes isolated from the red alga Plocamium angustum, which have 1J(CH) values varying from 127 to 203 Hz.
Mass spectrometry in structural and stereochemical problems—CLXVI. The electron impact promoted fragmentation of some aliphatic 1,2‐glycols
Authors: Kossanyi Jean , Morizur J. P. , Furth Bernard , Wiemann Joseph , Duffield A. M. , Djerassi Carl
Published: May 2005

The mass spectra of nineteen aliphatic 1,2‐glycols containing a variety of substituents have been recorded and mechanistic rationalizations are presented for the more important degradation processes observed. Fragmentation of the hydroxylated carbon‐carbon bond in these compounds occurred to an appreciable degree often accompanied by the transfer of a hydroxylic hydrogen atom.
Mass spectra of azetidines and 2‐azetidinones
Authors: Jackson M. B. , Spotswood T. M. , Bowie J. H.
Published: May 2005

The mass spectra of twenty three azetidines and seventeen 2‐azetidinones are reported and discussed. The majority of spectra contain molecular ions. Fragmentation modes are largely dependent upon the substitution pattern and involve specific cleavage of the four‐membered ring. Several hydrogen rearrangement reactions occur, and in some cases, cis and trans isomers may be distinguished by large differences in the relative abundances of certain fragment ions.
The oxygen rearrangement of aromatic and unsaturated esters under electron‐impact—I: General regularities of the rearrangement
Authors: Kadentsev V. I. , Zolotarev B. M. , Chizov O. S. , Shachidayatov Ch. , Yanovskaya L. A. , Kucherov V. F.
Published: May 2005

Some esters of γ, δ‐unsaturated or β‐arylsubstituted acids undergo a peculiar transformation under electron‐impact including an elimination of the alcohol residue as a radical R. with the following loss of the ketene molecule. One of the oxygen atoms of the carbonyl group enters an ion which is formed from an unsaturated part of the molecule. The possible mechanism of this reaction and the influence of structural modifications on the course of this process are discussed.
The mass spectra of some fluorine‐containing dimethyl esters
Authors: Cotter J. L.
Published: May 2005

The mass spectra of esters of the general formula MeO2C·[CF2]n·CO2Me, n = 6 to 9, are reported and briefly discussed. Common features of the mass spectra are prominent peaks at [M  CO2], [M  CO2  C2F4] and [M  CO2  2C2F4].
Mass spectrometry in structural and stereochemical problems—CLXXXV Effect of phenyl group in the mass spectra of trans‐10‐phenyl‐2‐decalone and trans‐10‐phenyldecalin
Authors: Gray Robin T. , Djerassi Carl
Published: May 2005

With the use of deuterium labeling and metastable ion measurements, the major fragmentation pathways of trans‐10‐phenyl‐2‐decalone (II) have been deduced. A comparison with trans‐10‐phenyldecalin (IV) demonstrated the almost complete domination of the phenyl group in directing the electron‐impact promoted decomposition of II. In fact, in contrast to the spectra of the methylated analogs, only one fragmentation pathway is uniquely associated with the carbonyl function. The substitution of a phenyl group at the ring junction in IV has permitted the recognition of definitive fragmentation pathways for this compound also. Such definition has not previously been possible for unsubstituted alicyclic hydrocarbons. The formation of an abundant tropylium ion from both II and IV has been examined, but its genesis is too complicated to be accurately defined from the labeling data at hand.
The mass spectral behavior of β‐bromoethyl benzoate and some of its ring substituted derivatives: Evidence for oxygen participation in the formation of [M  Br]+
Authors: Shapiro Robert H. , Tomer Kenneth B.
Published: May 2005

The expulsion of a bromine atom from the molecular ion of β‐bromoethyl benzoate displays a kinetic behavior which resembles that of a rearrangement reaction. The two oxygen atoms in the resulting [M  Br]+ ion become equivalent before or during the secondary decomposition of this ion, as shown by oxygen labeling. In addition, the primary ions generated from benzophenone ethylene ketal and acetophenone ethylene ketal by phenyl and methyl expulsion, respectively, undergo subsequent fragmentation in the same way as the [M  Br]+ from β‐bromoethyl benzoate. These results strongly indicate that the carbonyl‐oxygen atom participates in the expulsion of bromine. The effect of ring substituents on the competing loss of bromine and McLafferty rearrangement is also discussed.
Mass spectrometry differentiation of isomeric alkyl porphyrins. Fragmentation analysis of meso‐tetraoxoporphyrinogens
Authors: Boylan David B.
Published: May 2005

The mass spectra of lead dioxide oxidation products of three etiotype porphyrins and one meso‐substituted etiotype porphyrin have been analyzed. The meso‐tetraoxo products formed, fragment upon electron‐impact to give mono‐, di‐, and tri‐pyrrole fragments with the pyrrole substituents still intact. From this fragment information it is possible to differentiate many isomeric alkyl porphyrins. Due to the inability to assign exact positions to the substituents on each pyrrole unit, however, definite isomeric identification is impossible without further information. High resolution gas chromatography retension data of volatile (trimethylsiloxy) SiIV derivatives may eventually provide the necessary additional information to make absolute structural assignment possible.

The described method has been designed to prove detailed structural information about geoporphyrin materials. Geochemical conclusions from such data should help provide information about the origin of organic materials and thus help establish possible connections with early life processes.
The significance of hammett correlations in mass spectral decompositions
Authors: Bursey Maurice M. , Kissinger Peter T.
Published: May 2005

An unexpected correlation of ion intensities with sigma constants was observed for the loss of substituents from biphenyl molecular ions. The observation is more easily reconciled with an argument based upon energy distributions in molecular ions than on interpretation in terms of rates.
Zur Massenspektrometrie von Nitrophenylverbindungen—II. Nitrophenylhydrazone Aliphatischer Aldehyde und Ketone
Authors: Seibl J.
Published: May 2005

Als chemisch klassifizierende Derivate zur isolierung von Carbonylverbindungen aus Gemischen erlauben DNPH aliphatischer Aldehyde und Ketone wegen ihrer Molekülionenstabilität eine sichere massenspektrometrische Molekulargewichtsbestimmung und wegen ihrer unterschiedlichen Fragmentierungsmuster eine Gruppenzuordnung (Aldehyde, Ketone, minimale Kettenlänge). Reaktionsmechanistisch sind sie interessant als Beispiele für eine Reihe spezifischer Umlagerungsreaktionen beim monomolekularen Zerfall. Als Primärreaktion im Molekülion st eine Sauerstoffumlagerung aus der ortho‐nitrogruppe von wesentlicher bedutung, die die Fragmentierung zu einem guten Teil bestimmt.
The mass spectra of spiro‐alkanones with five‐ and six‐membered rings
Authors: Weringa W. D.
Published: May 2005

The mass spectral fragmentations of three spiro‐undecanones and four dispiro‐hexadecanones with six‐membered rings, and of two spiro‐nonanones with five‐membered rings are recorded and discussed. The fragmentation patterns for the spiro[4,4]nonanones and the spiro[5,5]undecanones have been determined by using specific deuterium labelling and in some cases the measurement of metastable transitions by the defocusing technique. The most important fragment ions in the spectra of four dispiro‐hexadecanones could be explained by assuming the same types of fragmentation as found for the monospiro‐ketones. The composition of the fragment ions has been checked by high resolution mass measurements.
Mass spectra of haloperidol and related neuroleptics (major tranquilisers)
Authors: Blessington B.
Published: May 2005

The mass spectra of ten, structurally related, neuroleptics (major tranquilisers) are presented and their fragmentation patterns are discussed. The relevance of these findings to current biochemical work is indicated.
The calculation of the 70 eV mass spectrum of thiacyclobutane
Authors: Gilbert J. R. , Stace A. J.
Published: May 2005

The mass spectrum of thiacyclobutane at 70 eV has been calculated using quasi‐equilibrium theory and an energy distribution given by f(E)= βE exp (‐ E2γ). The measured and calculated spectra are shown to be in reasonable agreement.
Metal‐metal chelate exchange reactions in the ion source of a mass spectrometer
Authors: Terlouw J. K. , De Ridder J. J.
Published: May 2005

In the mass spectra of several transition metal chelates with diethyldithiocarbamate as a ligand, intense peaks are present which could be assigned to extraneous metal (particularly nickel) containing ions. Using an Au‐Rh coated ion source, evidence was obtained for the occurrence of exchange reactions in the region of the filament assembly.
Mass spectrometry of benzylamines and benzylamine derivatives
Authors: Couch M. W. , Williams C. M.
Published: May 2005

The mass spectra of benzylamine, N‐ethylbenzylamine, N,N‐dimethylbenzylamine, p‐methoxybenzylamine and 4‐hydroxy‐3‐methoxybenzylamine, and their acetamide and trimethyl‐ silyl (TMS) derivatives have been recorded. Low and high resolution spectroscopy were employed in conjunction with ion kinetic energy (IKE) determinations to establish the empirical formulae of the fragment ions and their modes of fragmentation. In the case of the acetamide derivatives the acyl group is lost by acetoxy elimination giving rise to the [M — 1] ion of the parent amine which then undergoes fragmentation very similar to the original amine. The TMS derivatives present more complex fragmentation patterns which involve rearrangement of the TMS side chain during decomposition. Consequently the acetamide derivative of an unknown aromatic amine is preferred for diagnostic purposes.
Fragmentation and rearrangement processes in the mass spectra of perhalogeno‐aromatic compounds—VII. Pentafluorophenyl derivatives of nitrogen
Authors: Lanthier G. F. , Miller J. M.
Published: May 2005

The mass spectra of several perfluoroaromatic nitrogen compounds, including primary and secondary amines, diamines, nitriles, hydrazines, azines and azo compounds, are presented. Fragmentation patterns of these compounds are described and the data are discussed in terms of comparisons amongst perfluoroaromatic nitrogen compounds, and with reference to the hydrogen substituted analogs, or to oxygen and sulfur analogs of a particular compound.
Does photoelectron spectrometry give the energy distribution of molecular ions obtained by electron‐impact?
Authors: Innorta G. , Torroni S. , Pignataro S.
Published: May 2005

Photoelectron spectroscopy gives too crude an approximation to the energy distribution of molecular ions obtained by electron‐impact.
Mass spectrometric fragmentations of hexafluoroacetone ketals derived from N‐alkenes
Authors: Johnson Bruce M. , Taylor James W.
Published: May 2005

The mass spectrometric fragmentation behavior of the cyclic hexafluoroacetone ketals derived from eighteen n‐alkenes is discussed with emphasis on locating the original olefinic bond. The major analytically useful fragments result from loss of CF3, loss of an alkyl side chain or loss of an aldehyde moiety from the ring. Influences of geometric isomerism on the spectra are examined by intensity ratios and ratios of competing fragmentations.
The mass spectra of carboxylic acids—VI: Metastable dissociations of isomeric ions in the mass spectra of oxalic and formic acids, and malonic and acetic acids
Authors: Holmes J. L.
Published: May 2005

Metastable ion peak shapes and abundances have been studied for competing dissociations of the [H2CO2]+. ions produced in the mass spectra of formic and oxalic acids, and of [H4C2O2]+. ions produced from acetic and malonic acids. It is concluded that for each pair ions different with respect to structure and energy content are present; the difference is more apparent in the [H4C2O2]+. ions than in the smaller [H2CO2]+. species.
Spectrometrie de Masse—VIII: Elimination D'eau Induite par Impact Electronique Dans le Tetrahydro‐1,2,3,4 Naphtalenediol‐1,2
Authors: Perros P. , Morizur J. P. , Kossanyi J. , Duffield A. M.
Published: May 2005

La perte d'une molécule d'eau impact électronique est une voie de fragmentation importante du tétrahydro‐1,2,3,4 naphtalénediol‐1,2. A l'aide de composés marqués spécifiquement au deutérium, it a pu étre montré que les atomes d'hydrogéne hydroxyliques participent pour plus de 70% à cette élimination. Les autres d'hydrogéne impliques dans cette perte d'eau, sont principalement ceux de carbone C‐4. Une répartition statistique, à laquelle participeraient différents atomes d'hydrogéne a été envisagée sans pouvoir étre retenue définitivement.
High resolution mass spectrometry in molecular structure studies—VI: The fragmentation of amaryllis alkaloids in the crinine series. Compounds bearing a hydroxyl substituent at C‐11 (and some 11‐oxo derivatives)
Authors: Longevialle P. , Fales H. M. , Highet R. J. , Burlingame A. L.
Published: May 2005

High resolution mass spectral fragmentation patterns of Amaryllidaceae alkaloids in the crinine series bearing a substituent at C‐11 have been investigated, as well as certain isotopically labeled derivatives. The substituent at C‐11 governs almost entirely the fragmentation pattern of these bases due to the ability of the hydroxylic hydrogen atom to rearrange. In contrast to the bases lacking this hydrozyl substituent, stereochemistry exerts a profound influence on the fragmentation.
The effect of 2,3‐substituents upon the mass spectrometric fragmentation of quinoxalines
Authors: Kováčik V. , Fedoroňko M. , Ježo I.
Published: May 2005

The mass spectrometric fragmentation of quinoxalines substituted with alkyl and aryl groups in the C‐2 and C‐3 positions and with groups containing heteroatoms have been studied. Fragmentation mechanisms for the compounds under investigation are proposed and discussed.
Ring contraction upon electron‐impact as a function of ring size: The mass spectrometric fragmentation of 2,3,4,5‐tetrahydrobenzoxepin and lower homologues
Authors: Richter W. J. , Liehr J. G. , Burlingame A. L.
Published: May 2005

The origin of a prominent [M – CH3] ion in the mass spectrum of 2,3,4,5‐tetrahydrobenzoxepin is investigated with the aid of extensive deuterium labelling of the saturated heterocyclic portion of the molecule, identifying the C‐2 methylene group as the chief source of the methyl radical expelled. Ring contraction of the seven‐membered cyclic molecular ion to a six‐membered intermediate is proposed in accordance with interpretations of similar findings on related acylated cyclic amines.
A study of negative ions from substituted benzils
Authors: Dillard John G. , O'Toole J. Herb. , Ogliaruso Michael A.
Published: May 2005

The mass spectra and the appearance potentials for the negative ions from a number of 4‐substituted and 4,4′‐disubstituted benzils, containing CH3, CH3O, CH3S, (CH3)2N and NO2 substituents have been measured. Molecular anions were observed for all benzils. The negative ion mass spectra of the CH3O‐ and CH3S‐substituted compounds also exhibited ions resulting from loss of CH3 from the parent; Cl− was observed too in the spectra of the chlorine substituted benzils. Only for the nitrobenzils is more than one fragment ion observed in the spectra. A comparison of the negative ion spectra with the positive ion spectra previously reported is also presented and discussed.
Surface dependent hydrogen rearrangement reactions in field ionisation mass spectrometry
Authors: Röllgen F. W. , Levsen K. , Beckey H. D.
Published: May 2005

Surface dependent hydrogen rearrangement reactions under field ionisation conditions have been investigated. It was not possible to detect surface‐induced intramolecular hydrogen rearrangements in molecular ions, in accordance with theoretical expectations. The possibility of intramolecular hydrogen rearrangements exists only for radical ions chemically bound to the emitter surface, for example, the [M – H]+ ions of the alcohols. The great majority of surfacedependent hydrogen transfer reactions are intermolecular reactions between parts of different molecules or ions bound to the emitter surface. These reactions produce fragment ions, cluster ions and doubly charged ions.
Electron‐impact‐induced hydrogen migration in organic molecules. II—novel hydrogen migration in dihydro‐2‐stilbazole derivatives
Authors: Ramana D. V. , Sundaram N.
Published: May 2005

The mass spectra of 2′‐OH, 2′‐NH2 and 2′‐CH3‐dihydro‐2‐stilbazole derivatives show an interesting hydrogen migration. The hydrogen migration is shown to be taking place from the above mentioned substituents to the nitrogen of the pyridine ring followed by a β‐cleavage giving rise to a common ion e at m/e 93, perhaps through an 8‐membered transition state.