bluuebunny/crossref_metadata_2025 huggingface dataset:
Long‐Term Effects of Ciliary Neurotrophic Factor on the Survival of Vasopressin Magnocellular Neurones in the Rat Supraoptic Nucleus In Vitro
Authors: Rusnak M. , House S. B. , Gainer H.
Published: September 2003

The use of hypothalamic organotypic cultures for the long‐term study of mechanisms in magnocellular neurones (MCNs) of the hypothalamic‐neurohypophysial system has been limited by the relatively poor maintenance of the vasopressin MCNs in vitro. Recent studies have shown that addition of ciliary neurotrophic factor (CNTF) to the media significantly reduced the apoptosis of both oxytocin and vasopressin MCNs. Here, we studied various temporal factors in the CNTF treatment that can influence the efficacy of MCN survival. Immunohistochemistry was used to identify and count surviving vasopressin and oxytocin MCNs in the supraoptic nucleus (SON) in hypothalamic slices cultured in the presence of CNTF (10 ng/ml media) for various time intervals, and in situ hybridization for vasopressin mRNA was used to evaluate the vasopressin mRNA gene expression in the SON under the same conditions. The presence of CNTF in the medium for 10 days produced a maximal increase in the survival of vasopressin MCNs (by 11‐fold) and in the survival of oxytocin‐MCNs (by approximately four‐fold) over controls. These effects persisted for an additional 7–10 days even in the absence of CNTF. The ability of CNTF to increase survival of the MCNs or increase vasopressin mRNA levels in the SON required that the CNTF be present during the initial 7–10 days of culture. CNTF failed to rescue vasopressin or oxytocin MCNs when added to the media only for the last 7 days of a total of 14 days in vitro. Similar results were observed when SON vasopressin mRNA levels were measured. These results indicate that the presence of CNTF is required at the outset to rescue the vasopressin and oxytocin MCN from axotomy induced apoptosis, and that, after 10 days in CNTF, the MCNs no longer require the CNTF for survival.
Kinase‐Dependent Regulation of the Secretion of Thyrotrophin and Luteinizing Hormone By Glucocorticoids and Annexin 1 Peptides
Authors: John C. D. , Christian H. C. , Morris J. F. , Flower R. J. , Solito E. , Buckingham J. C.
Published: September 2003

Our previous studies have identified a role for annexin 1 (ANXA1), a protein produced by the pituitary folliculostellate cells, as a paracrine/juxtacrine mediator of the acute regulatory effects of glucocorticoids on the release of adrenocorticotropic hormone and other pituitary hormones. In the present study, we focused on the secretion of thyroid stimulating hormone (TSH) and luteinizing hormone (LH) and used a battery of ANXA1‐derived peptides to identify the key domains in the ANXA1 molecule that are critical to the inhibition of peptide release. In addition, as ANXA1 is a substrate for protein kinase C (PKC) and tyrosine kinase, we examined the roles of these kinases in the manifestation of the ANXA1‐dependent inhibitory actions of dexamethasone on TSH and LH release. Dexamethasone suppressed the forskolin‐induced release of TSH and LH from rat anterior pituitary tissue in vitro. Its effects were mimicked by human recombinant ANXA1 (hrANXA1) and a truncated protein, ANXA11‐188. ANXA1Ac2−26, also suppressed stimulated peptide release but it lacked both the potency and the efficacy of the parent protein. Shorter N‐terminal ANXA1 sequences were without effect. The PKC inhibitor PKC19‐36 abolished the inhibitory actions of dexamethasone on the forskolin‐evoked release of TSH and LH; it also attenuated the inhibitory actions of ANXA1Ac2−26. Similar effects were produced by annexin 5 (ANXA5) which sequesters PKC in other systems. By contrast, the tyrosine kinase inhibitors, p60v‐src (137–157) and genistein, had no effect on the secretion of TSH or LH alone or in the presence of forskolin and/or dexamethasone. Dexamethasone caused the translocation of a tyrosine‐phosphorylated species of ANXA1 to the surface of pituitary cells. The total amount of ANXA1 exported from the cells in response to the steroid was unaffected by tyrosine kinase blockade. However, the degree of tyrosine‐phosphorylation of the exported protein was markedly reduced by genistein. These results suggest that (i) the ANXA1‐dependent inhibitory actions of dexamethasone on the release of TSH and LH require PKC and sequences in the N‐terminal domain of ANXA1, but are independent of tyrosine kinase, and (ii) while dexamethasone induces the cellular exportation of a tyrosine‐phosphorylated species of ANXA1, tyrosine phosphorylation per se is not critical to the steroid‐induced passage of ANXA1 across the membrane.
DNA Microarray Analyses of Circadian Timing: The Genomic Basis of Biological Time
Authors: Duffield G. E.
Published: September 2003

Many aspects of physiology and behaviour are organized around a daily rhythm, driven by an endogenous circadian clock. Studies across numerous taxa have identified interlocked autoregulatory molecular feedback loops which underlie circadian organization in single cells. Until recently, little was known of (i) how the core clock mechanism regulates circadian output and (ii) what proportion of the cellular transcriptome is clock regulated. Studies using DNA microarray technology have addressed these questions in a global fashion and identified rhythmically expressed genes in numerous tissues in the rodent (suprachiasmatic nucleus, pineal gland, liver, heart, kidney) and immortalized fibroblasts, in the head and body ofDrosophila, in the fungusNeurosporaand the higher plantArabidopsis. These clock controlled genes represent 0.5–9% of probed genes, with functional groups covering a broad spectrum of cellular pathways. There is considerable tissue specificity, with only approximately 10% rhythmic genes common to at least one other tissue, principally consisting of known clock genes. The remaining common genes may constitute genes operating close to the clock mechanism or novel core clock components. Microarray technology has also been applied to understand input pathways to the clock, identifying potential signalling components for clock resetting in fibroblasts, and elucidating the temperature entrainment mechanism inNeurospora. This review explores some of the common themes found between tissues and organisms, and focuses on some of the striking connections between the molecular core oscillator and aspects of circadian physiology and behaviour. It also addresses the limitations of the microarray technology and analyses, and suggests directions for future studies.
Photoperiod Alters the Time Course of Brain Cyclooxygenase‐2 Expression in Siberian Hamsters
Authors: Bilbo S. D. , Quan N. , Prendergast B. J. , Bowers S. L. , Nelson R. J.
Published: September 2003

Fever is initiated by activation of the arachidonic acid cascade and the biosynthesis of prostaglandins within the brain. Inducible cyclooxygenase (COX‐2) is a rate‐limiting enzyme in prostaglandin synthesis, and the number of blood vessels expressing COX‐2 correlates with elevated body temperature following peripheral lipopolysaccharide (LPS). Despite its importance in host defense, fever is energetically expensive and we hypothesized that fever may be limited by available metabolic resources. During winter, when competing metabolic demands are constrained by low temperatures and food availability, it was predicted that fever duration would be reduced in seasonally breeding Siberian hamsters (Phodopus sungorus). We measured LPS‐induced COX‐2 expression in blood vessels of hamsters to test whether photoperiodic alterations in fever duration are centrally mediated, or whether they reflect changes in peripheral modulation of body temperature. Hamsters housed in long, ‘summer‐like’ or short, ‘winter‐like’ day lengths for 10 weeks were injected with LPS, and brains were collected 2, 4, or 8 h later. COX‐2 expression was comparably increased in long‐ and short‐day hamsters by 2 h and 4 h post‐LPS; however, short‐day hamsters exhibited significantly fewer COX‐2‐positive cells and blood vessels by 8 h post‐LPS compared to long‐day hamsters, corresponding with reduced fever duration in short‐day hamsters. Cortisol concentrations increased more than two‐fold in short‐day compared to long‐day hamsters by 4 h; this increase may have contributed to the decrease in COX‐2 expression observed by 8 h in short days. We conclude that short photoperiods significantly altered the time course of central COX‐2 protein expression in hamsters in a manner consistent with reduced fever duration.
Central Nervous System Receptors Involved in Mediating the Inhibitory Action of Neuropeptide Y on Luteinizing Hormone Secretion in the Male Rhesus Monkey (Macaca mulatta)
Authors: Shahab M. , Balasubramaniam A. , Sahu A. , Plant T. M.
Published: September 2003

An earlier finding that gonadotropin‐releasing hormone (GnRH) secretion may be triggered prematurely in the juvenile male monkey by central administration of 1229U91, a Y1 receptor antagonist, contributed to our current hypothesis that neuropeptide Y (NPY) is a major component of the brake that holds pulsatile GnRH release in check during prepubertal development in primates. However, 1229U91 is also a Y4 receptor agonist, and the present study was conducted to further examine the role of the Y1 receptor in mediating the putative inhibitory action of NPY on GnRH release. Agonadal juvenile and postpubertal male monkeys were implanted with i.v. and i.c.v. cannulae to gain continuous access to the venous and cerebroventricular circulations without sedation. Luteinizing hormone (LH) secretion was measured to provide an indirect index of GnRH release. The specific Y1 antagonists, VD‐11 (476 µg; n = 4) and isopropyl 3‐chloro‐5‐[1‐({6‐[2‐(5‐ethyl‐4‐methyl‐1,3‐thiazol‐2‐yl)ethyl]‐4‐morpholin‐4‐ylpyridin‐2‐yl}amino)ethyl]phenylcarbamate (Compound A, 300 µg; n = 4), did not mimic the stimulatory action of 1229U91 on GnRH secretion in the juvenile male monkey. Additionally, neither NPY (200 µg; n = 2), a general Y receptor agonist, nor rPP (100 µg; n = 4), a Y4 agonist, mimicked the action of 1229U91 in stimulating GnRH release. Moreover, previous exposure of the hypothalamus of juvenile monkeys (n = 5) to NPY (660 µg) failed to block 1229U91‐induced (200 µg) GnRH release. However, the action of NPY (364 µg) in inhibiting GnRH release postpubertally was attenuated by 1229U91 (300 µg). We conclude that, although the action of exogenous NPY to suppress GnRH release from the postpubertal hypothalamus appears to be mediated, at least in part, by the Y1 receptor, the existence of a Y1 receptor pathway inhibitory to GnRH release in the prepubertal hypothalamus remains to be substantiated.
Short‐Photoperiod Exposure Reduces Vasopressin (V1a) Receptor Binding But Not Arginine‐Vasopressin‐Induced Flank Marking in Male Syrian Hamsters
Authors: Caldwell H. K. , Albers H. E.
Published: September 2003

In Syrian hamsters, socially relevant information is communicated with a form of scent marking known as flank marking. There is substantial evidence that arginine‐vasopressin acting on V1a vasopressin receptors (V1aR) in the medial preoptic‐anterior hypothalamic continuum (MPOA‐AH) regulates the expression of flank marking. Previous studies have shown that the expression of flank marking is also influenced by the circulating concentrations of gonadal hormones. In hamsters housed in long ‘summer‐like’ photoperiods (i.e. >12.5 h of light/day), castration reduces flank marking and administration of testosterone restores precastration levels of flank marking. When exposed to short ‘winter‐like’ photoperiods (i.e. <12.5 h of light/day), hamsters undergo gonadal regression and the circulating levels of testosterone decline. Surprisingly, flank marking induced during social encounters is not reduced in hamsters exposed to short photoperiods despite the low circulating concentrations of testosterone. In the present study, it was hypothesized that reductions in testosterone, caused by exposure to short photoperiod, would not reduce the ability of vasopressin to stimulate flank marking by its actions in the MPOA‐AH. The amount of flank marking induced by vasopressin injected into the MPOA‐AH did not significantly differ between hamsters housed in long and short photoperiods; however, short photoperiod‐exposed males had significantly less V1aR binding in the MPOA than long photoperiod‐exposed males. These results support the hypothesis that the sensitivity of the MPOA‐AH to vasopressin is not reduced in short photoperiod‐exposed males, despite decreases in serum testosterone. However, by contrast to our predictions, short photoperiod‐exposed males have significantly reduced V1aR binding in the MPOA‐AH compared to long photoperiod‐exposed males.
Changes in Progesterone Receptor Isoforms Content in the Rat Brain During the Oestrous Cycle and After Oestradiol and Progesterone Treatments
Authors: Guerra‐Araiza C. , Villamar‐Cruz O. , González‐Arenas A. , Chavira R. , Camacho‐Arroyo I.
Published: September 2003

We studied the effects of oestradiol and progesterone on progesterone receptor (PR) isoform content in the brain of ovariectomized rats and in intact rats during the oestrous cycle by Western blot analysis. In the hypothalamus and the preoptic area of ovariectomized rats, PR‐A and PR‐B content was increased by oestradiol, whereas progesterone significantly diminished the content of both PR isoforms after 3 h of treatment in the hypothalamus, but not in the preoptic area. In the hippocampus, only PR‐A content was significantly increased by oestradiol while progesterone significantly diminished it after 12 h of treatment. In the frontal cortex, no treatment significantly modified PR isoform content. During the oestrous cycle, the lowest content of PR isoforms in the hypothalamus was observed on diestrus day and, by contrast, in the preoptic area, the highest content of both PR isoforms was observed on diestrus day. We observed no changes in PR isoform content in the hippocampus during the oestrous cycle. These results indicate that the expression of PR isoforms is differentially regulated by sex steroid hormones in a regionally specific manner.
Double Oestrogen Receptor α and β Knockout Mice Reveal Differences in Neural Oestrogen‐Mediated Progestin Receptor Induction and Female Sexual Behaviour
Authors: Kudwa A. E. , Rissman E. F.
Published: September 2003

To test the hypothesis that oestrogen receptor α (ERα) and ERβ act together to mediate the actions of oestrogen in the ventromedial hypothalamus (VMH), we used mice with single or double knockout mutations of the ERα and ERβ genes. Ovariectomized mice were implanted with 17β‐oestradiol and killed 5 days later. Oestradiol treatment promoted progestin receptor (PR)‐immunoreactivity (‐ir) in the VMH of all genotypes, but was maximal in brains of wild‐type and ERβKO females. Analysis of specific VMH subregions revealed that PR‐ir induction was limited to the caudal VMH in ERαKO and ERαβKO mice. In the rostral VMH, oestradiol only induced PR‐ir in wild‐type and ERβKO mice, and the number of PR‐ir neurones in this region was greater in ERβKO than wild‐type females. Next, we tested the ability of a dopamine agonist and progesterone to facilitate sexual behaviour in females lacking functional ERα, ERβ, or both receptors. Ovariectomized mice were implanted with oestradiol, and tested for sexual behaviour three times after administration of the dopamine agonist, apomorphine, followed by two tests concurrent with progesterone treatment and a final test with just apomorphine treatment. ERαKO and ERαβKO females failed to display lordosis under any testing conditions, while ERβKO females exhibited lordosis behaviour equal to that of wild‐type females. Our data show that a subpopulation of PR‐ir neurones is induced by oestradiol in the caudal VMH of female mice lacking both ERα and ERβ genes. We hypothesize that this action of oestradiol is either mediated by a novel ER or by the mutant portion of the AF2 subregion of the ERα gene present in ERαKO brain. However, despite the presence of PR in VMH, females lacking a functional ERα gene do not display sexual behaviour, via either ligand‐dependent or ‐independent activation.
A comparison of the methods used to determine chewing preference
Authors: Varela J. M. F. , Castro N. B. , Biedma B. M. , Da Silva Domínguez J. L. , Quintanilla J. S. , Muñoz F. M. , Penín U. S. , Bahillo J. G.
Published: September 2003

summary  For much human activity there exists a ‘lateral preference’, that is a tendency to use one side of the body or the other; with respect to the hands for example, the vast majority of individuals have a preference for either the right or left hand. Most experts agree that mastication is no exception in that there is a ‘preferred chewing side’ but the determination of this preference is somewhat complex. This research analyses the mastication of 60 healthy subjects by means of preferred chewing side or ‘PCS’ tests, the Kazazoglu test, and kinesiography (KGF). While some authors consider the PCS to be the side which first comes into contact with the food we prefer to define it as the side on which the majority of the cycles analysed and registered take place. The objective of this research was to analyse the relationship that might exist between the two different methods used for determining a lateral chewing preference. Although there was no statistically significant agreement between the two techniques, both reflected the fact that there was a marked preference for the right hand side.
Masticatory laterality – evaluation and influence of food texture
Authors: Mizumori T. , Tsubakimoto T. , Iwasaki M. , Nakamura T.
Published: September 2003

summary  The purpose of this study is the objective and quantitative evaluation of masticatory laterality and its daily variability. Various foods with different textures were used to investigate whether food texture influenced masticatory laterality. Ten healthy subjects and seven foods were used. Recordings of chewing movements were repeated three times at intervals of 1 week. Masticatory laterality was assessed with an Asymmetry Index [AI: (number of right side strokes – number of left side strokes)/number of total strokes]. Medians and ranges of the three recordings were calculated. The observed AI ranges in the three trials were limited with the exception of two subjects. Among the other subjects, averages of the absolute values of the medians were from 32·5 to 73·4%. Statistically significant differences between the hardest food and softer foods were observed in absolute value of AI medians. Masticatory laterality could be evaluated by an AI. Eight of 10 subjects showed limited ranges of AI in three recordings. It should be noted that a few people actually chew on either side but might chew on one side only on a particular day. Hard food evoked more masticatory laterality, and seemed more appropriate for laterality examinations.
The effects of masseter muscle pain on biting performance
Authors: Shiau Y. Y. , Peng C. C. , Wen S. C. , Lin L. D. , Wang J. S. , Lou K. L.
Published: September 2003

summary  The present study applied a standardized test food of known hardness to evaluate the biting performance of 20 female patients who had pain mainly in the masseter muscle during palpation. Another 20 women of a similar age group who were pain‐free during examination served as controls. Electromyograms (EMG) of the masseter and sternocleidomastoid (SCM) muscles and the jaw position were recorded and measured when the subjects were biting through two types of test foods with known hardness (hard type, 20 kg hardness and extra‐hard type, 60 kg hardness). Pressure‐pain‐threshold (PPT) values of both the patients and the normal subjects were obtained with an algometer. It was found that the PPT of the patients with pain was significantly lower and that the extra‐hard food took more masseter muscle activity and more working side jaw movement in both the pain and the normal groups. During both hard and extra‐hard food biting, a significantly longer duration of masseter muscle activity was found in pain patients while the total muscle activity was not significantly stronger. Strong correlation existed between SCM and masseter muscle activity during both hard and extra‐hard food biting in the patient group, while such correlation was very weak in the normal group. In conclusion, painful masseter muscles required longer masseter and SCM muscle contraction time for breaking through a hard food of 20 kg and more, and co‐activation of SCM and masseter muscles existed and was more evident when the food was harder or the pain was more severe.
A retrospective study of pre‐fabricated carbon fibre root canal posts
Authors: Hedlund S.‐O. , Johansson N. G. , Sjögren G.
Published: September 2003

summary 

Although pre‐fabricated carbon fibre posts have been used during the past decade clinical evaluations of the technique are still few. Using dental records and radiographs the clinical performance of 65 pre‐fabricated carbon fibre posts (Composipost and Endopost) placed in 48 patients who regularly visited a general practice were evaluated in the present study. After an average time of 2.3 ± 0·8 years (median 2·1 years, range 1–4·9 years) of clinical service the failure rate was 3%. Failure occurred in one tooth with a single crown restoration and in one tooth that was part of a cantilever fixed partial denture. Although the failure rate is lower than those mostly reported for metallic posts and cores more clinical studies are necessary to assess the suitability of pre‐fabricated carbon fibre posts for routine use as an alternative to individually cast posts.
Developing a career in the mental health services: guidance for student nurses
Authors: Robinson  , Murrells
Published: September 2003

Current concern about a shortage of nurses has led to attention focusing on the provision of career guidance as a strategy to facilitate retention in the workforce. This paper presents findings on career guidance provided for psychiatric nursing students, and thus adds to the very small volume of research that exists on guidance in nursing generally. Questionnaires were sent to 556 Registered Mental Nurses shortly after qualification; 80% responded. This represented the first phase of a longitudinal study of these nurses' careers. Participants were asked whether they had received information about career pathways that might be pursued, educational opportunities available and work experience outside the NHS. If not they were asked whether they had wanted such information. They were also asked whether they had been given advice about planning their own career. Only a minority of respondents had received information or advice, but the majority would have liked to have done so. The findings are discussed in the context of whether there is a need for career guidance and, if so, by whom it should be provided.
Effects of habitat fragmentation and changes of dispersal behaviour after a recent population decline on the genetic variability of noncoding and coding DNA of a monogamous Malagasy rodent
Authors: Sommer S.
Published: September 2003

While interactions among demography, behaviour and genetic structure are well‐documented for neutral genetic markers, the role of these parameters and the effects of genetic drift and selection are considerably less well understood in functional genes, such as the major histocompatibility complex (MHC). In this study, the consequences of habitat fragmentation and the effects of a current population decline on noncoding (mitochondrial DNA) and two coding MHC loci (DQA, DRB) with different functional importance were investigated in the small remnant subdivided population of the endangered Malagasy giant jumping rat (Hypogeomys antimena). Both neutral and selective markers revealed a significant genetic differentiation between the two remnant subpopulations. The FST values were much lower in the MHC DQA and DRB genes than in the mitochondrial data. The MHC DRB loci display the effects of both balancing selection (high sequence diversity, four times higher nonsynonymous than synonymous substitutions in the functionally important antigen‐binding site positions, twice the average heterozygosity of individual amino acids at the positions identified as part of the antigen‐binding site (ABS) than those outside the ABS and nonselective forces including genetic drift. Simultaneously with a current population decline offspring reduced their dispersal distances. No substantial effects were detected within the first 6 years of reduced gene flow in either mitochondrial or MHC markers.
Huge populations and old species of Costa Rican and Panamanian dirt frogs inferred from mitochondrial and nuclear gene sequences
Authors: Crawford A. J.
Published: September 2003

Molecular genetic data were used to investigate population sizes and ages of Eleutherodactylus (Anura: Leptodactylidae), a species‐rich group of small leaf‐litter frogs endemic to Central America. Population genetic structure and divergence was investigated for four closely related species surveyed across nine localities in Costa Rica and Panama. DNA sequence data were collected from a mitochondrial gene (ND2) and a nuclear gene (c‐myc). Phylogenetic analyses yielded concordant results between loci, with reciprocal monophyly of mitochondrial DNA haplotypes for all species and of c‐myc haplotypes for three of the four species. Estimates of genetic differentiation among populations (FST) based upon mitochondrial data were always higher than nuclear‐based FST estimates, even after correcting for the expected fourfold lower effective population size (Ne) of the mitochondrial genome. Comparing within‐population variation and the relative mutation rates of the two genes revealed that the Ne of the mitochondrial genome was 15‐fold lower than the estimate of the nuclear genome based on c‐myc. Nuclear FST estimates were ≈ 0 for the most proximal pairs of populations, but ranged from 0.5 to 1.0 for all other pairs, even within the same nominal species. The nuclear locus yielded estimates of Ne within localities on the order of 105. This value is two to three orders of magnitude larger than any previous Ne estimate from frogs, but is nonetheless consistent with published demographic data. Applying a molecular clock model suggested that morphologically indistinguishable populations within one species may be 107 years old. These results demonstrate that even a geologically young and dynamic region of the tropics can support very old lineages that harbour great levels of genetic diversity within populations. The association of high nucleotide diversity within populations, large divergence between populations, and high species diversity is also discussed in light of neutral community models.
Evidence for the existence of some dissociation in an otherwise strong linkage disequilibrium between mitochondrial and chloroplastic genomes in Cyclobalanopsis glauca
Authors: Lin T.‐P. , Chuang W.‐J. , Huang S. S. F. , Hwang S.‐Y.
Published: September 2003

Variations in mitochondrial DNA in Cyclobalanopsis glauca (Thunb. ex Murray) Oerst. were studied in 140 trees from 32 populations collected from within the tree's natural range. By sequencing two mitochondrial DNA intron fragments (nad4/3‐nad4/4r and nad7/2‐nad7/3r), we revealed a total of 1788 bp and five polymorphic sites which allowed us to distinguish six mitotypes. The mitochondrial DNA markers provided replicated data to support population phylogeographical scenarios suggested previously using chloroplastic DNA markers. The gene genealogical tree of mitochondrial DNA was partially congruent with the chloroplastic DNA tree owing to the slower mutation rate and different mutational direction. Significant linkage disequilibrium existed between the two organellar genomes. Further paring analyses between fragments synthesized using different primers, accompanied by exclusion of polymorphic sites, showed that the random association could be attributed specifically to one of the polymorphic sites of the petG‐trnP fragment of the chloroplastic genome, and the three polymorphic sites of the nad4/3‐nad4/4r fragment of the mitochondrial genome. The former was inferred to derive from paternal leakage, and the latter from recurrent mutation. These polymorphic sites were also responsible for uncoupling of the combined gene tree of mitotype and chlorotype. In conclusion, specific fragments found in this study contribute to the incomplete congruence of the two organellar lineages that otherwise associate well phylogeographically.
Phylogeography of the harlequin beetle‐riding pseudoscorpion and the rise of the Isthmus of Panamá
Authors: Zeh J. A. , Zeh D. W. , Bonilla M. M.
Published: September 2003

Molecular and geological evidence indicates that the emergence of the Isthmus of Panamá influenced the historical biogeography of the Neotropics in a complex, staggered manner dating back at least 9 Myr bp. To assess the influence of Isthmus formation on the biogeography of the harlequin beetle‐riding pseudoscorpion, Cordylochernes scorpioides, we analysed mitochondrial COI sequence data from 71 individuals from 13 locations in Panamá and northern South America. Parsimony and likelihood‐based phylogenies identified deep divergence between South American and Panamanian clades. In contrast to low haplotype diversity in South America, the Panamanian Cordylochernes clade is comprised of three highly divergent lineages: one clade consisting predominantly of individuals from central Panamá (PAN A), and two sister clades (PAN B1 and PAN B2) of western Panamanian pseudoscorpions. Breeding experiments demonstrated a strictly maternal mode of inheritance, indicating that our analyses were not confounded by nuclear‐mitochondrial pseudogenes. Haplotype diversity is striking in western Atlantic Panamá, where all three Panamanian clades can occur in a single host tree. This sympatry points to the existence of a cryptic species hybrid zone in western Panamá, a conclusion supported by interclade crosses and coalescence‐based migration rates. Molecular clock estimates yield a divergence time of ≈ 3 Myr between the central and western Panamanian clades. Taken together, these results are consistent with a recent model in which a transitory proto‐Isthmus enabled an early wave of colonization out of South America at the close of the Miocene, followed by sea level rise, inundation of the terrestrial corridor and then a second wave of colonization that occurred when the Isthmus was completed ≈ 3 Myr bp.
Low genetic differentiation among seasonal cohorts inSenecio vulgarisas revealed by amplified fragment length polymorphism analysis
Authors: Haldimann P. , Steinger T. , Müller‐Schärer H.
Published: September 2003

Common groundsel,Senecio vulgaris(Asteraceae), is a highly selfing semelparous ephemeral weed that belongs to the few plant species in central Europe capable of growing, flowering and fruiting all year round. In temperate climates, floweringS. vulgariscohorts were found to appear up to three times per year. Using amplified fragment length polymorphism (AFLP) molecular markers we examined temporal genetic differentiation among spring, summer and autumn cohorts at each of seven sites located in two regions in Switzerland. Strong genetic differentiation among cohorts may indicate the existence of seasonal races ofS. vulgaris, reproductively isolated by nonoverlapping flowering phenologies. Analysis of molecular variance (amova) revealed that < 2.5% of the AFLP variation resided among cohorts within sites, whereas there was significant genetic differentiation among plants from different sites (15.6%) and among individuals within cohorts (81.9%). Significant genetic differentiation was also observed between the two regions. Isolation‐by‐distance was found on a regional scale, but not on a local scale. Gene flow was estimated to be ≈ 15‐fold higher among cohorts within sites than among sites. We further found, on average, similar levels of genetic diversity within the three seasonal cohorts. The results of this study demonstrate that season of growth represents a weak barrier for genetic exchange amongS. vulgarispopulations and does not affect molecular variance. Therefore, there is no evidence for the existence of seasonally specialized races ofS. vulgaris. We discuss some implications of the results for the biological control ofS. vulgarisusing a native rust fungus.
Evidence for gene flow in parasitic nematodes between two host species of shrews
Authors: Brant Sara V. , Ortí Guillermo
Published: September 2003

We describe the genetic structure of populations of the intestinal nematode Longistriata caudabullata (Trichostrongyloidea: Heligmosomidae), a common parasite of short‐tailed shrews (genus Blarina, Insectivora: Soricidae). Parasites and hosts were collected from a transect across a contact zone between two species of hosts, Blarina brevicauda and B. hylophaga, in central North America. An 800‐base pairs (bp) fragment of the ND4 mitochondrial DNA (mtDNA) gene was sequenced for 28 worms and a 783‐bp fragment of the mtDNA control region was analysed for 16 shrews. Phylogenetic analyses of mtDNA sequences revealed reciprocal monophyly for the shrew species, concordant with morphological diagnosis, and supported the idea that the transect cuts through a secondary contact zone between well‐differentiated B. brevicauda and B. hylophaga. In contrast to this pattern, the parasitic nematode mtDNA phylogeny was not subdivided according to host affiliation. Genealogical discordance between parasite and host phylogenies suggests extensive gene flow among parasites across the host species boundary.
Methods of parentage analysis in natural populations
Authors: Jones Adam G. , Ardren William R.
Published: September 2003

The recent proliferation of hypervariable molecular markers has ushered in a surge of techniques for the analysis of parentage in natural and experimental populations. Consequently, the potential for meaningful studies of paternity and maternity is at an all‐time high. However, the details and implementation of the multifarious techniques often differ in subtle ways that can influence the results of parentage analyses. Now is a good time to reflect on the available techniques and to consider their strengths and weaknesses. Here, we review the leading techniques in parentage analysis, with a particular emphasis on those that have been implemented in readily useable software packages. Our survey leads to some important insights with respect to the utility of the different approaches. This review should serve as a useful guide to anyone who wishes to embark on the study of parentage.
Global patterns in peatmoss biodiversity
Authors: Shaw A. Jonathan , Cox Cymon J. , Boles Sandra B.
Published: September 2003

DNA sequence data from the nuclear ribosomal internal transcribed spacers (ITS) and thetrnL‐trnFchloroplast DNA regions were used to quantify geographical partitioning of global biodiversity in peatmosses (Sphagnum), and to compare patterns of molecular diversity with patterns of species richness. Molecular diversity was estimated for boreal, tropical, Neotropical, nonboreal (tropical plus Southern Hemisphere), Old World and New World partitions, based on a total of 436 accessions. Diversity was partitioned among geographical regions in terms of combined nuclear and chloroplast sequence data and separately for theITSandtrnL‐trnFdata sets. Levels of variation were estimated using phylogenetic diversity (PD), which incorporates branch lengths from a phylogenetic tree, and the number of polymorphic nucleotide sites. Estimates of species richness suggest that peatmoss diversity is higher in New World than Old World regions, and that the Neotropics constitute a ‘hotspot’ of diversity. Molecular estimates, in contrast, indicate that peatmoss biodiversity is almost evenly divided between New and Old World regions, and that the Neotropics account for only 20–35% of global peatmoss diversity. In general, levels of tropical and boreal peatmoss molecular diversity were comparable. Two species,S. sericeumfrom the Old World tropics andS. lapazensefrom Bolivia, are remarkably divergent in nucleotide sequences from all other Sphagna and together account for almost 20% of all peatmoss diversity, although they are represented by only three of the 436 accessions (0.7%). These species clearly demonstrate the nonequivalence of species biodiversity value.
Plastid DNA variation in theDactylorhiza incarnata/maculatapolyploid complex and the origin of allotetraploidD. sphagnicola(Orchidaceae)
Authors: Hedrén M.
Published: September 2003

To obtain further information on the polyploid dynamics of the theDactylorhiza incarnata/maculatapolyploid complex and the origin of the allotetraploidD. sphagnicola(Orchidaceae), plastid DNA variation was studied in 400 plants from from Sweden and elsewhere in Europe and Asia Minor by means of polymerase chain reaction–restriction fragment length polymorphisms (PCR‐RFLPs) and sequencing. Allotetraploid taxa in Europe are known have evolved by multiple independent polyploidization events following hybridization between the same set of two distinct ancestral lineages. Most allotetraploids have inherited the plastid genome from parents similar toD. maculata sensu lato, which includes, e.g. the diploidD. fuchsiiand the autotetraploidD. maculata sensu stricto.D. sphagnicolacarries a separate plastid haplotype different from the one found in other allotetraploid taxa, which is in agreement with an independent origin from the parental lineages. Some of the remaining allotetraploids have local distributions and appear to be of postglacial origin, whereas still other allotetraploids may be of higher age, carrying plastid haplotypes that have not been encountered in present day representatives of the parental lineages. Introgression and hybridization between diploids and allotetraploids, and between different independently derived allotetraploids may further have contributed to genetic diversity at the tetraploid level. Overall, theDactylorhizapolyploid complex illustrates how taxon diversity and genetic diversity may be replenished rapidly in a recently glaciated area.
Inter‐island movements and population differentiation in a pelagic seabird
Authors: Dearborn Donald C. , Anders Angela D. , Schreiber E. A. , Adams Rachelle M. M. , Mueller Ulrich G.
Published: September 2003

We used mark–resight data and amplified fragment length polymorphism (AFLP) markers to assess movements and gene flow between Central Pacific breeding colonies of the great frigatebird, Fregata minor. Of 715 adult frigatebirds marked on Tern Island and Johnston Atoll, 21.3% were resighted at other frigatebird colonies at least 582 km away. Mark–resight data indicated regular movement of males and females between Tern Island and Johnston Atoll (873 km apart), and less frequent movements to other islands; no birds marked on Tern or Johnston were seen on Christmas Island, but one was seen in the Philippines, 7627 km from where it was marked. Despite the regular occurrence of interisland movements, Bayesian analyses of AFLP data showed significant genetic differentiation between Tern Island and Johnston Atoll, and more pronounced differentiation between these two islands and the more distant Christmas Island. The AFLP profiles of three birds breeding on Tern Island fell within the profile‐cluster typical for Christmas Island birds, both in a nonmetric multidimensional scaling analysis and in a population assignment test, suggesting dispersal events from Christmas Island to Tern Island. Several factors could explain the persistence of genetic structure despite frequent movements between colonies: many movements occurred during the nonbreeding season, many breeding‐season movements did not involve mate‐acquisition behaviours and individuals that do disperse may be selected against, as suggested by morphometric differences between colonies. The persistence of genetic structure among breeding colonies despite significant interisland movements suggests limits to the effectiveness of migration as a homogenizing force in this broadly distributed, extremely mobile species.
Census vs. effective population size in chinook salmon: large‐ and small‐scale environmental perturbation effects
Authors: Shrimpton J. Mark , Heath Daniel D.
Published: September 2003

Population viability has often been assessed by census of reproducing adults. Recently this method has been called into question and estimation of the effective population size (Ne) proposed as a complementary method to determine population health. We examined genetic diversity in five populations of chinook salmon (Oncorhynchus tshawytscha) from the upper Fraser River watershed (British Columbia, Canada) at 11 microsatellite loci over 20 years using DNA extracted from archived scale samples. We tested for changes in genetic diversity, calculated the ratio of the number of alleles to the range in allele size to give the statistic M, calculated Ne from the temporal change in allele frequency, used the maximum likelihood method to calculate effective population size (NeM), calculated the harmonic mean of population size, and compared these statistics to annual census estimates. Over the last two decades population size has increased in all five populations of chinook examined; however, Ne calculated for each population was low (81–691) and decreasing over the time interval measured. Values of NeM were low, but substantially higher than Ne calculated using the temporal method. The calculated values for M were generally low (M < 0.70), indicating recent population reductions for all five populations. Large‐scale historic barriers to migration and development activities do not appear to account for the low values of Ne; however, available spawning area is positively correlated with Ne. Both Ne and M estimates indicate that these populations are potentially susceptible to inbreeding effects and may lack the ability to respond adaptively to stochastic events. Our findings question the practice of relying exclusively on census estimates for interpreting population health and show the importance of determining genetic diversity within populations.
Genetic variation among interconnected populations of Catostomus occidentalis: implications for distinguishing impacts of contaminants from biogeographical structuring
Authors: Whitehead Andrew , Anderson Susan L. , Kuivila Kathryn M. , L. Roach Jennifer , May Bernie
Published: September 2003

Exposure to contaminants can affect survivorship, recruitment, reproductive success, mutation rates and migration, and may play a significant role in the partitioning of genetic variation among exposed and nonexposed populations. However, the application of molecular population genetic data to evaluate such influences has been uncommon and often flawed. We tested whether patterns of genetic variation among native fish populations (Sacramento sucker, Catostomus occidentalis) in the Central Valley of California were consistent with long‐term pesticide exposure history, or primarily with expectations based on biogeography. Field sampling was designed to rigorously test for both geographical and contamination influences. Fine‐scale structure of these interconnected populations was detected with both amplified fragment length polymorphisms (AFLP) and microsatellite markers, and patterns of variation elucidated by the two marker systems were highly concordant. Analyses indicated that biogeographical hypotheses described the data set better than hypotheses relating to common historical pesticide exposure. Downstream populations had higher genetic diversity than upstream populations, regardless of exposure history, and genetic distances showed that populations from the same river system tended to cluster together. Relatedness among populations reflected primarily directions of gene flow, rather than convergence among contaminant‐exposed populations. Watershed geography accounted for significant partitioning of genetic variation among populations, whereas contaminant exposure history did not. Genetic patterns indicating contaminant‐induced selection, increased mutation rates or recent bottlenecks were weak or absent. We stress the importance of testing contaminant‐induced genetic change hypotheses within a biogeographical context. Strategic application of molecular markers for analysis of fine‐scale structure, and for evaluating contaminant impacts on gene pools, is discussed.
Chloroplast DNA diversity of the dioecious European tree Ilex aquifolium L. (English holly)
Authors: Rendell S. , Ennos R. A.
Published: September 2003

Variation in the chloroplast genome of Ilex aquifolium (English holly), a dioecious evergreen tree native to south, west and central Europe, was analysed using polymerase chain reaction–restriction fragment length polymorphisms (PCR‐RFLPs) and microsatellites. Differentiation between populations was high (GST = 0.595) and evidence for phylogeographical structure was detected (NST = 0.697, significantly higher than GST). Two chloroplast lineages were inferred originating from putative glacial refugia in southern Europe (Iberia, Italy and possibly the Balkans). The GST value was higher than reported for endozoochorous hermaphrodite species and for anemochorous dioecious species investigated over a similar geographical scale. It appears that dioecy has contributed to strong differentiation between refugia and that this has been maintained following postglacial recolonization as a result of limited seed flow. Palynological records for I. aquifolium are poor, thus these results give an important insight into patterns of glacial isolation and postglacial recolonization of this species.
Postglacial population growth of Cunninghamia konishii (Cupressaceae) inferred from phylogeographical and mismatch analysis of chloroplast DNA variation
Authors: Hwang Shih‐Ying , Lin Tsan‐Piao , Ma Chiu‐Shun , Lin Chung‐Ling , Jeng‐Der Chung  , Yang Jenq‐Chuan
Published: September 2003

Phylogeographical and mismatch analysis of chloroplast DNA (cpDNA) variation were used to infer the temporal dynamics of distributional and demographic history of Taiwan fir (Cunninghamia konishii). We examined 64 and 52 trees from 17 populations of C. konishii and 14 provenances of C. lanceolata, respectively, by sequencing three intergenic spacers and one intron using cpDNA universal primers. Of the aligned 1888 base pairs (bp) sequence, 30 varied among 28 haplotypes, which consisted of three transitions, 14 transversions and 13 indels. One ancestral haplotype was found in 86 individuals across the surveyed range of both species, C. konishii and C. lanceolata, which was distributed in all populations and provenances. The 28 haplotypes also included 15 C. konishii specific and 12 C. lanceolata‐specific haplotypes. Ancestral haplotype was found fixed in five populations of C. konishii and five provenances of C. lanceolata. Other haplotypes occurred mainly as singletons. The levels of population differentiation studied are relatively low in both Cunninghamia species. The nucleotide diversity (θ) of chloroplast DNA sequences within C. konishii was slightly higher than that of C. lanceolata. Excess in singletons as well as star‐like phylogeny of haplotypes suggested no clearcut migration patterns of C. konishii after glacial maximum. One probable demographic history of C. konishii is the postglacial population growth of C. konishii after a glacial bottleneck event. This inference is supported by the combined results of fossil pollen record, low nucleotide diversity, significant Tajima's d‐value, phylogeographical analysis and unimodal mismatch distribution. Similarities and discrepancies between our results and those of Lu et al. (2001) are discussed.