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1.
Diabet Med ; 38(1): e14374, 2021 01.
Article in English | MEDLINE | ID: mdl-32740984

ABSTRACT

AIM: To describe the effect of the stringent lockdown measures, introduced in the UK on 23 March 2020 to curtail the transmission of COVID-19, on glycaemic control in people with type 1 diabetes using flash glucose monitoring. METHODS: We undertook an observational study of 572 individuals with type 1 diabetes for whom paired flash glucose monitoring data were available between early March and May 2020. The primary outcome was change in flash glucose monitoring variables. We also assessed clinical variables associated with change in glycaemic control. RESULTS: Percentage of time in range increased between March and May 2020 [median (interquartile range) 53 (41-64)% vs 56 (45-68)%; P < 0.001], with associated improvements in standard deviation of glucose (P <0.001) and estimated HbA1c (P <0.001). There was a small reduction in the number of individuals meeting the hypoglycaemia target of <5% per day (64% vs 58%; P = 0.004). Comparing changes in flash glucose monitoring data from March to May in 2019 with the same period in 2020 confirmed that these differences were confined to 2020. Socio-economic deprivation was an independent predictor of a ≥5% reduction in time in range during lockdown (odds ratio 0.45 for people in the two most affluent Scottish Index of Multiple Deprivation quintiles; P <0.001). CONCLUSIONS: Lockdown was not associated with a significant deterioration in glycaemic control in people with type 1 diabetes using flash glucose monitoring. However, socio-economic deprivation appeared to increase the risk of decline in glycaemic control, which has implications for how support is focused in challenging times.


Subject(s)
Blood Glucose Self-Monitoring/methods , COVID-19/prevention & control , Diabetes Mellitus, Type 1/blood , Glycemic Control/statistics & numerical data , Quarantine/statistics & numerical data , SARS-CoV-2 , Adult , Blood Glucose/analysis , Female , Glycated Hemoglobin/analysis , Humans , Male , Middle Aged , Scotland , Socioeconomic Factors
2.
Psychoneuroendocrinology ; 66: 214-20, 2016 Apr.
Article in English | MEDLINE | ID: mdl-26849203

ABSTRACT

AIMS: This study assess differences in clinical variables in diabetes patients prescribed antipsychotic medication and determines relative schizophrenia prevalence in the diabetes population. METHODS: This population-based case-control study utilizing Scotland's national diabetes registry (SCI-diabetes) and linked psychiatric hospital discharge data (SMR04) established diabetes phenotypes in a patient cohort prescribed long term antipsychotic medication (n=2362) (cases). Cases were matched 1:10 to diabetes patients not prescribed antipsychotic medication (controls) for BMI, gender; diabetes type; birth year; diagnosis date; smoking status. Sub-groups with defined schizophrenia (n=196) or bipolar disorder (n=190) were further examined. Schizophrenia prevalence in the diabetes versus general population was compared. RESULTS: During follow up, antipsychotic prescription was associated with lower HbA1c (55.1 (95% CI 54.5-55.8) or 7.2 (95% CI 7.1-7.3)% vs 58.2 (58.0-58.4) mmol or 7.5 (95% CI 7.5-7.5)% p<0.001) lower serum total cholesterol, 4.2 (4.1-4.2) vs 4.3 (4.2-4.3) mmol/l, p<0.001, lower blood pressure (systolic 130 (130.17-131.29) vs 134 (134.3-134.7) mmHg, p<0.001), higher prescription of oral hypoglycaemic medication (42% (40-45) vs 38% (37-39) p<0.001), similar statin prescriptions (85% (81-89) vs 85% (84-86), p=0.55), and lower retinopathy rates (28% (25.6-30.5) vs 32% (31.5-33.1), p<0.001). HbA1c at diagnosis was similar (p=0.27). Schizophrenia prevalence was higher in the diabetes versus general population with differences across age groups (Scottish population versus diabetic population rate of 522.2 (522.1-522.3) versus 717.4 (703.4-731.9) per 100,000). CONCLUSIONS: We confirm higher diabetes rates in schizophrenia up to age 70, similar attendance rates and clinical measurements that are not worse in a large well-matched population-based Scottish sample prescribed antipsychotic medication versus matched general diabetes patients.


Subject(s)
Antipsychotic Agents/therapeutic use , Diabetes Complications/epidemiology , Diabetes Mellitus/epidemiology , Metabolic Diseases/epidemiology , Adult , Aged , Bipolar Disorder/drug therapy , Bipolar Disorder/epidemiology , Case-Control Studies , Diabetes Complications/metabolism , Diabetes Complications/psychology , Female , Humans , Male , Middle Aged , Prevalence , Risk Factors , Schizophrenia/drug therapy , Schizophrenia/epidemiology
3.
Qual Prim Care ; 22(1): 43-51, 2014.
Article in English | MEDLINE | ID: mdl-24589150

ABSTRACT

BACKGROUND: The rising prevalence of obesity and diabetes in Kuwait represents a significant challenge for the country's healthcare system. Diabetes care in Scotland has improved by adopting a system of managed clinical networks supported by a national informatics platform. In 2010, a Kuwait-Dundee collaboration was established with a view to transforming diabetes care in Kuwait. This paper describes the significant progress that has been made to date. METHODS: The Kuwait-Scotland eHealth Innovation Network (KSeHIN) is a partnership among health, education, industry and government. KSeHIN aims to deliver a package of clinical service development, education (including a formal postgraduate programme and continuing professional development) and research underpinned by a comprehensive informatics system. RESULTS: The informatics system includes a disease registry for children and adults with diabetes. At the patient level, the system provides an overview of clinical and operational data. At the population level, users view key performance indicators based on national standards of diabetes care established by KSeHIN. The national childhood registry (CODeR) accumulates approximately 300 children a year. The adult registry (KHN), implemented in four primary healthcare centres in 2013, has approximately 4000 registered patients, most of whom are not yet meeting national clinical targets. A credit-bearing postgraduate educational programme provides module-based teaching and workplace-based projects. In addition, a new clinical skills centre provides simulator-based training. Over 150 masters students from throughout Kuwait are enrolled and over 400 work-based projects have been completed to date. CONCLUSION: KSeHIN represents a successful collaboration between multiple stakeholders working across traditional boundaries. It is targeting patient outcomes, system performance and professional development to provide a sustainable transformation in the quality of diabetes healthcare for the growing population of Kuwaitis with diabetes in Kuwait.


Subject(s)
Diabetes Mellitus/epidemiology , Health Personnel/education , Medical Informatics/organization & administration , Obesity/epidemiology , Patient Education as Topic/methods , Quality Assurance, Health Care/organization & administration , Adult , Child , Diabetes Mellitus/prevention & control , Diabetes Mellitus/therapy , Education, Graduate , Health Care Coalitions/organization & administration , Health Care Coalitions/standards , Humans , Interinstitutional Relations , International Cooperation , Kuwait/epidemiology , Medical Informatics/standards , Medical Informatics/trends , Obesity/complications , Obesity/therapy , Prevalence , Quality Assurance, Health Care/methods , Quality Assurance, Health Care/standards , Quality Improvement/organization & administration , Quality Improvement/standards , Registries , Scotland/epidemiology
4.
Clin Endocrinol (Oxf) ; 65(1): 81-7, 2006 Jul.
Article in English | MEDLINE | ID: mdl-16817824

ABSTRACT

OBJECTIVE: Glucocorticoid hyperactivity in adipose tissue, due to up-regulation of local glucocorticoid reactivation by 11beta-hydroxysteroid dehydrogenase-1 (11HSD1) or of glucocorticoid receptors (GR), may underpin susceptibility to the metabolic syndrome. This hypothesis has been tested extensively in subcutaneous adipose tissue (SAT) but inadequately in visceral adipose tissue (VAT). The aim of the study was therefore to examine expression of 11HSD1, GRalpha and hexose-6-phosphate dehydrogenase (H6PDH), which supplies cofactor for 11HSD1, in abdominal adipose tissue compartments and to characterize their relation to metabolic syndrome parameters. DESIGN AND SUBJECTS: A cross-sectional study including 26 premenopausal South African women. MEASUREMENTS: Biopsies were taken for measurement of mRNA levels by real-time polymerase chain reaction (RT-PCR) and 11HSD1 activity from VAT, and deep and superficial SAT compartments during elective surgery. Prior to surgery, blood pressure, blood lipid profile, body composition [by dual X-ray absorptiometry (DEXA) scan], body fat distribution [by computed tomography (CT) scan], and glucose tolerance were determined. RESULTS: 11HSD1 activity (P < 0.01) was higher in VAT than SAT, but 11HSD1 and GRalpha mRNA levels were not statistically different between compartments. 11HSD1 mRNA levels in superficial SAT correlated with VAT volume (R = 0.57, P < 0.01), insulin sensitivity calculated from the oral glucose tolerance test (OGTT) (R = -0.52, P < 0.016) and blood pressure (R = 0.48, P < 0.016). Apart from a correlation between deep SAT 11HSD1 activity and blood pressure (R = 0.72, P < 0.01), glucocorticoid action in deep SAT and VAT depots was not significantly associated with any metabolic syndrome parameters. CONCLUSION: Increased capacity for glucocorticoid regeneration in superficial SAT but not VAT is associated with visceral adiposity and other features of the metabolic syndrome in women.


Subject(s)
Glucocorticoids/metabolism , Metabolic Syndrome/metabolism , Premenopause/metabolism , Subcutaneous Fat/metabolism , 11-beta-Hydroxysteroid Dehydrogenases/genetics , 11-beta-Hydroxysteroid Dehydrogenases/metabolism , Adult , Body Composition , Carbohydrate Dehydrogenases/genetics , Carbohydrate Dehydrogenases/metabolism , Cross-Sectional Studies , Female , Glucose Tolerance Test , Humans , Hydrocortisone/urine , Intra-Abdominal Fat/metabolism , Middle Aged , RNA, Messenger/analysis , Receptors, Glucocorticoid/genetics , Receptors, Glucocorticoid/metabolism , Regression Analysis , Reverse Transcriptase Polymerase Chain Reaction , South Africa
5.
Nature ; 435(7038): 87-90, 2005 May 05.
Article in English | MEDLINE | ID: mdl-15875021

ABSTRACT

Nearly 70% of the 535 species of salamanders in the world are members of a single family, the Plethodontidae, or lungless salamanders. The centre of diversity for this clade is North and Middle America, where the vast majority (99%) of species are found. We report the discovery of the first Asian plethodontid salamander, from montane woodlands in southwestern Korea. The new species superficially resembles members of North American genera, in particular the morphologically conservative genus Plethodon. However, phylogenetic analysis of the nuclear encoded gene Rag-1 shows the new taxon to be widely divergent from Plethodon. The new salamander differs osteologically from putative relatives, especially with respect to the tongue (attached protrusible) and the derived tarsus. We place the species in a new genus on the basis of the morphological and molecular data. The distribution of the new salamander adds to the enigma of Old World plethodontids, which are otherwise restricted to the western Mediterranean region, suggesting a more extensive past distribution of the family.


Subject(s)
Phylogeny , Urodela/anatomy & histology , Urodela/classification , Animals , Bayes Theorem , Bone and Bones/anatomy & histology , Extremities/anatomy & histology , Female , Korea , Male , Trees , Urodela/genetics
6.
Diabetologia ; 47(10): 1668-71, 2004 Oct.
Article in English | MEDLINE | ID: mdl-15455200

ABSTRACT

AIMS/HYPOTHESIS: Highly active antiretroviral therapy (HAART) in patients infected with human immunodeficiency virus (HIV) is associated with a poorly understood lipodystrophic and hypertriglyceridaemic syndrome, which resembles Cushing's syndrome, but in which plasma cortisol is not elevated. We tested the hypothesis that this HAART-associated lipodystrophy is explained by increased local regeneration of cortisol from inactive cortisone within adipose tissue, catalysed by the enzyme 11beta-hydroxysteroid dehydrogenase type 1 (11beta-HSD1). METHODS: In this cross-sectional study, a previously described cohort of 30 HIV-infected patients with lipodystrophy were compared with 13 HIV-infected patients without lipodystrophy. Intra-abdominal and subcutaneous adipose tissue were quantified using magnetic resonance imaging. Gene expression in subcutaneous fat was measured using real-time PCR. Urine cortisol and its metabolites were analysed by gas chromatography/mass spectrometry. RESULTS: Patients with lipodystrophy had significantly higher 11beta-HSD1 mRNA concentrations (relative to beta2-microglobulin mRNA) in subcutaneous adipose tissue than non-lipodystrophic patients (0.29+/-0.20 vs 0.09+/-0.07, p=0.0004) and higher ratios of urinary cortisol : cortisone metabolites. Adipose tissue 11beta-HSD1 mRNA correlated with multiple features of insulin resistance and with mRNA concentrations for glucocorticoid receptor and angiotensinogen. CONCLUSIONS/INTERPRETATION: In adipose tissue of patients with HAART-associated lipodystrophy, 11beta-HSD1 mRNA is increased and its concentration is correlated with features of insulin resistance. We suggest that increased adipose tissue 11beta-HSD1 may explain the pseudo-Cushing's features in patients with HAART-associated lipodystrophy, and is a potential therapeutic target.


Subject(s)
11-beta-Hydroxysteroid Dehydrogenase Type 1/genetics , Adipose Tissue/enzymology , Antiretroviral Therapy, Highly Active/adverse effects , Cushing Syndrome/etiology , HIV Infections/drug therapy , Lipodystrophy/chemically induced , Adult , Female , Humans , Hydrocortisone/urine , Male , RNA, Messenger/genetics
7.
Evolution ; 57(1): 129-43, 2003 Jan.
Article in English | MEDLINE | ID: mdl-12643573

ABSTRACT

We used partial sequences of the cytochrome b mitochondrial DNA (mtDNA) gene, obtained from 76 individuals representing 45 populations of Iberian Salamandra salamandra plus 15 sequences of additional species of Salamandra and related genera, to investigate contact zones. These zones, identified by earlier allozymic and morphological analyses, are between populations of viviparous (S. s. bernardezi and S. s. fastuosa) and ovoviviparous (S. s. gallaica and S. s. terrestris) salamanders. The distribution of mtDNA and nuclear markers is mostly concordant at one contact zone (between S. s. gallaica and S. s. bernardezi), but at another (between S. s. fastuosa and S. s. terrestris) the markers are offset by about 250 km. The observed geographic variation fits a model of mtDNA capture. Among the potential mechanisms responsible for such discordance we favor a combination of range shifts due to climatic fluctuations and biased genetic admixture across moving contact zones. We apply our findings to the issue of possible homoplasy in the evolution of viviparity and conclude that viviparity likely arose only once within S. salamandra.


Subject(s)
Urodela/physiology , Animals , DNA, Mitochondrial/genetics , Genetic Markers , Genetic Variation , Phylogeny , Species Specificity , Urodela/classification , Urodela/genetics
8.
Proc Natl Acad Sci U S A ; 98(14): 7888-91, 2001 Jul 03.
Article in English | MEDLINE | ID: mdl-11427707

ABSTRACT

Fossorial salamanders typically have elongate and attenuated heads and bodies, diminutive limbs, hands and feet, and extremely elongate tails. Batrachoseps from California, Lineatriton from eastern México, and Oedipina from southern México to Ecuador, all members of the family Plethodontidae, tribe Bolitoglossini, resemble one another in external morphology, which has evolved independently. Whereas Oedipina and Batrachoseps are elongate because there are more trunk vertebrae, a widespread homoplasy (parallelism) in salamanders, the genus Lineatriton is unique in having evolved convergently by an alternate "giraffe-neck" developmental program. Lineatriton has the same number of trunk vertebrae as related, nonelongated taxa, but individual trunk vertebrae are elongated. A robust phylogenetic hypothesis, based on sequences of three mtDNA genes, finds Lineatriton to be deeply nested within a clade characterized by generalized ecology and morphology. Lineatriton lineolus, the only currently recognized taxon in the genus, shows unanticipated genetic diversity. Surprisingly, geographically separated populations of L. lineolus are not monophyletic, but are sister taxa of different species of the morphologically generalized genus Pseudoeurycea. Lineatriton, long thought to be a unique monospecific lineage, is polyphyletic. Accordingly, the specialized morphology of Lineatriton displays homoplasy at two hierarchical levels: (i) with respect to other elongate lineages in the family (convergence), and (ii) within what is currently recognized as a single taxon (parallelism). These evolutionary events are of adaptive significance because to invade the lowland tropics salamanders must be either arboreal or fossorial; the repeated evolution of elongation and attenuation has led to multiple lowland invasions.


Subject(s)
Ecology , Urodela , Animals , Molecular Sequence Data , Phylogeny , Tropical Climate , Urodela/anatomy & histology , Urodela/physiology
10.
Proc Natl Acad Sci U S A ; 97(4): 1640-7, 2000 Feb 15.
Article in English | MEDLINE | ID: mdl-10677512

ABSTRACT

Although salamanders are characteristic amphibians in Holarctic temperate habitats, in tropical regions they have diversified evolutionarily only in tropical America. An adaptive radiation centered in Middle America occurred late in the history of a single clade, the supergenus Bolitoglossa (Plethodontidae), and large numbers of species now occur in diverse habitats. Sublineages within this clade decrease in number from the northern to southern parts of Middle America, and in Costa Rica, there are but three. Despite this phylogenetic constraint, Costa Rica has many species; the number of salamander species on one local elevational transect in the Cordillera de Talamanca may be the largest for any such transect in the world. Extraordinary variation in sequences of the mitochondrial gene cytochrome b within a clade of the genus Bolitoglossa in Costa Rica reveals strong phylogeographic structure within a single species, Bolitoglossa pesrubra. Allozymic variation in 19 proteins reveals a pattern largely concordant with the mitochondrial DNA phylogeography. More species exist than are currently recognized. Diversification occurs in restricted geographic areas and involves sharp geographic and elevational differentiation and zonation. In their degree of genetic differentiation at a local scale, these species of the deep tropics exceed the known variation of extratropical salamanders, which also differ in being less restricted in elevational range. Salamanders display "tropicality" in that although speciose, they are usually local in distribution and rare. They display strong ecological and physiological differentiation that may contribute importantly to morphological divergence and species formation.


Subject(s)
Genetic Variation , Urodela/genetics , Altitude , Animals , Biological Evolution , Costa Rica , Cytochrome c Group/genetics , DNA, Mitochondrial/genetics , Ecology , Geography , Molecular Sequence Data , Phylogeny
12.
Novartis Found Symp ; 222: 24-33; discussion 33-46, 1999.
Article in English | MEDLINE | ID: mdl-10332751

ABSTRACT

The reality of evolution requires some concept of 'sameness'. That which evolves changes its state to some degree, however minute or grand, although parts remain 'the same'. Yet homology, our word for sameness, while universal in the sense of being necessarily true, can only ever be partial with respect to features that change. Determining what is equivalent to what among taxa, and from what something has evolved, remain real problems, but the word homology is not helpful in these problematic contexts. Henning saw this clearly when he coined new terms with technical meanings for phylogenetic studies. Analysis in phylogenetic systematics remains contentious and relatively subjective, especially as new information accumulates or as one changes one's mind about characters. This pragmatic decision making should not be called homology assessment. Homology as a concept anticipated evolution. Homology dates to pre-evolutionary times and represents late 18th and early 19th century idealism. Our attempts to recycle words in science leads to difficulty, and we should eschew giving precise modern definitions to terms that originally arose in entirely different contexts. Rather than continue to refine our homology concept we should focus on issues that have high relevance to modern evolutionary biology, in particular homoplasy--derived similarity--whose biological bases require elucidation.


Subject(s)
Adaptation, Biological , Biological Evolution , Anatomy, Comparative , Animals , Models, Biological
13.
Nature ; 393(6686): 632, 1998 Jun 18.
Article in English | MEDLINE | ID: mdl-9641674
14.
Trop Doct ; 28(1): 4-8, 1998 Jan.
Article in English | MEDLINE | ID: mdl-9481189

ABSTRACT

The acute medical services could not exist without blood transfusions--life-savers in many situations. But transfusions can also be a quick and easy route for the transmission of infectious agents such as HIV, HBV, HCV and malaria. Infection through blood supply is a major issue in all countries but particularly in those with economic constraints which limit safety. This study was carried out in India (March-May 1997) and involved centres in Delhi, Calcutta and Vellore. It examined many aspects of blood transfusion including donor screening, use of professional donors, blood testing and criteria for blood use. The many problems in Indian blood transfusion services are mirrored in other countries. Here we examine the problems, priorities and practicalities of blood transfusion particularly in developing countries.


PIP: HIV and hepatitis transmission through blood transfusion is a major concern in developing countries where economic constraints limit blood supply safety. Blood transfusion may account for up to 15% of HIV transmission in developing countries. Only 66% of developing and 46% of the least developed countries screen blood for HIV since such testing can double the basic cost of a unit of blood. Blood banks in the private sector tend to be driven by commercial interests, and both public and private programs rely on high-risk professional donors given a shortage of voluntary donors. The following measures are recommended to improve blood transfusion services in India and other developing countries: 1) thorough donor screening to eliminate high-risk donors; 2) the availability of cheaper, more sensitive HIV tests; 3) assumption of responsibility for blood safety by physicians giving the transfusions; 4) adaptation of guidelines for blood administration to local needs; 5) avoidance of unnecessary transfusions; 6) more widespread use of autologous transfusions and intra- and postoperative blood salvage; 7) cost-benefit analyses of blood safety procedures; 8) monitoring of implementation of blood safety legislation; 9) use of an independent authority for blood bank licensing and monitoring; and 10) promotion of voluntary donation as a public responsibility.


Subject(s)
Blood Banks , Blood Transfusion , Communicable Disease Control , Blood Donors , Blood Substitutes , Blood Transfusion/economics , Blood Transfusion/statistics & numerical data , Developing Countries , Humans , India , Practice Guidelines as Topic , Transfusion Reaction
15.
Trends Ecol Evol ; 13(10): 379-80, 1998 Oct 01.
Article in English | MEDLINE | ID: mdl-21238352
16.
Mol Biol Evol ; 14(8): 883-91, 1997 Aug.
Article in English | MEDLINE | ID: mdl-9254927

ABSTRACT

We analyzed sequence data for 555 bp of the mitochondrial gene cytochrome b in plethodontid salamanders, taken from 18 ingroup (tribe Bolitoglossini) and 4 outgroup (tribe Plethodontini) taxa. There were 257 variable sites, of which 219 were phylogenetically informative. Sequence differences among taxa exceeded 20%, and there were up to 15% amino acid differences among the sequences. We also analyzed 37 morphological (including karyological) characters, taken from the literature. Data were analyzed separately and then combined using parsimony and likelihood approaches. There is little conflict between the morphological and DNA data, and that which occurs is at nodes that are weakly supported by one or both of the data sets. Treated separately, the morphological and DNA data provide strong support for some nodes but not for others. The combined data act synergistically so that good support is obtained for nearly all of the nodes in the tree. Recent divergences are supported by silent transitions, and older divergences are supported by a combination of morphological, karyological, DNA transversion, and amino acid changes. Eliminating silent changes from the DNA data improves the consistency index and improves some bootstrap and decay index values for several deeper branches in the tree. However, the combined data set with all characters included provides a better supported tree overall. Maximum likelihood and parsimony with all of the data give not only the same topology but also remarkably similar branch lengths. Results of this analysis support the monopoly of the supergenera Hydromantes and Batrachoseps, and of a sister group relationship of Batrachoseps and the supergenus Bolitoglossa (represented in this study one species of the genus Bolitoglossa).


Subject(s)
Evolution, Molecular , Phylogeny , Urodela/genetics , Animals , Cytochrome b Group/genetics , DNA, Mitochondrial/genetics , Genes , Likelihood Functions , Molecular Sequence Data , Sequence Homology, Nucleic Acid , Species Specificity , Urodela/anatomy & histology , Urodela/classification
17.
Proc Natl Acad Sci U S A ; 94(15): 7761-7, 1997 Jul 22.
Article in English | MEDLINE | ID: mdl-9223261

ABSTRACT

The Ensatina eschscholtzii complex of plethodontid salamanders, a well-known "ring species," is thought to illustrate stages in the speciation process. Early research, based on morphology and coloration, has been extended by the incorporation of studies of protein variation and mitochondrial DNA sequences. The new data show that the complex includes a number of geographically and genetically distinct components that are at or near the species level. The complex is old and apparently has undergone instances of range contraction, isolation, differentiation, and then expansion and secondary contact. While the hypothesis that speciation is retarded by gene flow around the ring is not supported by molecular data, the general biogeographical hypothesis is supported. There is evidence of a north to south range expansion along two axes, with secondary contact and completion of the ring in southern California. Current research targets regions once thought to show primary intergradation, but which molecular markers reveal to be zones of secondary contact. Here emphasis is on the subspecies E. e. xanthoptica, which is involved in four distinct secondary contacts in central California. There is evidence of renewed genetic interactions upon recontact, with greater genetic differentiation within xanthoptica than between it and some of the interacting populations. The complex presents a full array of intermediate conditions between well-marked species and geographically variable populations. Geographically differentiated segments represent a diversity of depths of time of isolation and admixture, reflecting the complicated geomorphological history of California. Ensatina illustrates the continuing difficulty in making taxonomic assignments in complexes studied during species formation.


Subject(s)
Urodela/genetics , Animals , Genetics, Population , Hybridization, Genetic , Species Specificity , Urodela/classification
18.
Brain Behav Evol ; 50(1): 50-9, 1997 Jul.
Article in English | MEDLINE | ID: mdl-9209766

ABSTRACT

Compared to other vertebrates, even including lampreys and hagfishes in some respects, salamanders exhibit a relatively simple organization of brain and sense organs which is illustrated here using the visual system as an example. The greatest simplicity is found in the bolitoglossine salamanders, yet all bolitoglossines possess highly projectile tongues and rely on vision for survival; furthermore, some species are agile and acrobatic. The unusual features of the visual system of salamanders include small numbers of large neurons, a low degree of morphological differentiation among neurons, a small proportion of myelinated axons in the optic nerve, and an optic tectum consisting essentially of a periventricular cellular layer and a superficial fiber layer. Similar features are found throughout the central nervous system of salamanders and in the lateral line, auditory and olfactory systems as well. Phylogenetic analysis shows that the most parsimonious interpretation of these data is that the simple organization of the brain and sense organs of salamanders was derived secondarily from a more complex ancestral state. We hypothesize that increased genome size has led to simplification of the nervous system in salamanders. Increased genome size appears to have had profound effects on neural development in salamanders, leading to paedomorphosis, the retention of juvenile or even embryonic characteristics into adulthood. In particular, large genome size is associated with large cell size and reduced rates of cell proliferation, migration and differentiation. Secondary simplification has constrained the function of the salamanders' visual system, primarily by increasing cell size and decreasing cell numbers. However, it also has provided an opportunity for the evolution of compensating mechanisms, which have helped to restore or even enhance visual function. Most apparent among the compensatory mechanisms of bolitoglossine salamanders is the presence of well developed ipsilateral retinotectal projections, which apparently enhance depth perception. It is difficult to explain the unusual history of the nervous system in salamanders solely in terms of natural selection and adaptation. Increasing genome size through selfish replication appears to have played a major role in the evolution of salamander brains by imposing functional constraints as well as creating opportunities for overcoming them.


Subject(s)
Biological Evolution , Brain/anatomy & histology , Phylogeny , Urodela/anatomy & histology , Animals , Cell Differentiation/physiology , Cell Division/physiology , Cell Size , Genome , Neurons/cytology , Selection, Genetic , Superior Colliculi/anatomy & histology , Urodela/genetics
19.
Analyst ; 121(9): 1241-6, 1996 Sep.
Article in English | MEDLINE | ID: mdl-8831282

ABSTRACT

Passive samplers are light, convenient and cheap. However, the sample size tends to be small and a correlation exercise between the results of a passive sampler and a conventional sampler must be carried out. The design principles and mode of action of an electret-based passive dust sampler are described. The device captures dust particles at a rate independent of the velocity of air except when this is very low but dependent on the electrical properties of the dust being sampled. Experimental results are presented of measurements made in bakeries, pig farms, a dairy farm, an arable farm and a rubber-manufacturing plant. Correlation between measurements made with the passive sampler and measurements of inhalable dust performed by other means are reasonable. The results are interpreted in terms of the physical properties of the dust being sampled.


Subject(s)
Air Pollutants, Occupational/analysis , Dust/analysis , Hydrocarbons/analysis , Occupational Exposure , Agriculture , Chemical Phenomena , Chemistry, Physical , Static Electricity
20.
Int J Dev Biol ; 40(4): 859-69, 1996 Aug.
Article in English | MEDLINE | ID: mdl-8877460

ABSTRACT

Direct development is a widespread alternate reproductive mode in living amphibians that is characterized by evolutionary loss of the free-living, aquatic larval stage. Courtship, mating, and oviposition occur on land, and the terrestrial egg hatches as a fully formed, miniature adult. While it is the most common reproductive mode in urodeles, development outside the reproductive tract of the female that proceeds directly to a terrestrial hatchling occurs in only a single lineage, the lungless salamanders of the family Plethodontidae. Evolution of direct development in plethodontids has contributed importantly to the extraordinary evolutionary success of this speciose, geographically widespread, and morphologically and ecologically diverse taxon. Developmental consequences and correlates include increased egg size and embryonic development time, loss of larval structures and ontogenetic repatterning, and altered pattern formation in organogenesis. Evolutionary and phylogenetic consequences and correlates include the loss of larval constraints and origin of morphological novelty, and frequent homoplasy. Analysis of direct development in an evolutionary context illustrates the complex interplay between processes of phylogenetic divergence and developmental biology, and substantiates the prominent role of developmental processes in both constraining phenotypic variation and promoting phenotypic diversity. Despite the proven suitability of direct-developing plethodontid salamanders for laboratory and field study, knowledge of basic features of their developmental biology remains far below that available for many other urodeles. Examination of such features of these "non-model" organisms is an appropriate and deserving goal of future research.


Subject(s)
Developmental Biology/methods , Phylogeny , Salamandridae/growth & development , Animals , Biological Evolution , Body Patterning/genetics , Body Patterning/physiology , Female , Ovum/growth & development , Ovum/physiology
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