Priority effects transcend scales and disciplines in biology.

Although primarily studied through the lens of community ecology, phenomena consistent with priority effects appear to be widespread across many different scenarios spanning a broad range of spatial, temporal, and biological scales. However, communication between these research fields is inconsistent and has resulted in a fragmented co-citation landscape, likely due to the diversity of terms used to refer to priority effects across these fields. We review these related terms, and the biological contexts in which they are used, to facilitate greater cross-disciplinary cohesion in research on priority effects. In breaking down these semantic barriers, we aim to provide a framework to better understand the conditions and mechanisms of priority effects, and their consequences across spatial and temporal scales.

Neuropharmacology: a part for purines in pattern generation.

Purinergic transmission has been found to play a key role in the neural control of rhythmic swimming behaviour in Xenopus embryos: it may have similar importance in other vertebrate motor behaviours.

The pharmacological properties of K+ currents from rabbit isolated aortic smooth muscle cells.

1. Using the whole-cell patch-clamp technique, the effects of several K+ channel blocking drugs on K+ current recorded from rabbit isolated aortic smooth muscle cells were investigated. 2. Upon depolarization from -80 mV, outward K+ current composed of several distinct components were observed: a transient, 4-aminopyridine (4-AP)-sensitive component (I1) and a sustained component (Isus), comprising a 4-AP-sensitive delayed rectifier current (IK(V)), and a noisy current which was sensitive to tetraethylammonium (TEA), and probably due to Ca(2+)-activated K+ current (IK(Ca)). 3. Several drugs in clinical or experimental use have as part of their action an inhibitory effect on specific K+ channels. Because of their differential K+ channel blocking effects, these drugs were used in an attempt to characterize further the K+ channels in rabbit aortic smooth muscle cells. Imipramine, phencyclidine, sotalol and amitriptyline failed to block selectively any of the components of K+ current, and were thus of little value in isolating individual channel contributions. Clofilium showed selective block of IK(V) in the presence of TEA, but only at low stimulation frequencies (0.07 Hz). At higher frequencies (1 Hz) of depolarization, both I1 and IK(V) were suppressed to a similar extent. Thus, the blocking action of clofilium was use-dependent. 4. The voltage-dependent inactivation of I1 and the delayed rectifier were very similar although a brief (100 ms) pre-pulse to -30 mV could preferentially inactivate I1. Together with the non-selective blocking effects of the K+ channel blockers, similarities in the activation and inactivation of these two components suggest that they may not exist as separate ionic channels, but as distinct kinetic states within the same K+ channel population. 5. The effects of all of these drugs on tension were examined in strips of rabbit aorta. The non-specific K+ channel blockers caused only minor increases in basal tension. TEA and 4-AP by themselves caused significant increases in tension and were even more effective when applied together. There appeared to be no correlation between the effects of the drugs tested on tension and their actions on currents recorded from isolated myocytes. Thus tension studies are an inappropriate means of investigating the mechanism of action of these drugs, and studies on ionic currents in isolated myocytes cannot easily predict drug actions on intact tissues.

Carrier detection in X-linked retinitis pigmentosa.

X-linked retinitis pigmentosa (XLRP) is manifested in affected males in their first decade and results in blindness by the third or fourth decade. Carrier detection is difficult since most carrier females show no or only equivocal signs well into or beyond their reproductive years. The genes, or the mutations causing RP have not been identified but at least two have been localised to the short arm of the X chromosome provisionally named RP2 and RP3. Identifying inheritance of one or other of these genes must be done by linkage in families using close, informative DNA markers. Here we report the localisation of a highly informative polymerase chain reaction (PCR) detectable microsatellite marker DXS538 using a previously studied family with X-linked RP3 in which recombination had occurred in the region of importance. The DXS538 dinucleotide repeat locus was previously localised to Xp21.1-p11.21 to study RP3 in one XLRP family. Using published RFLP data we narrowed the localisation of DXS538 to the region Xp21.1-p11.23. Thus DXS538 is now a convenient diagnostic tool, aiding carrier detection of XLRP in females, as shown in the family presented here.

Ethanol kinetics: extent of error in back extrapolation procedures.

1. Plasma ethanol concentrations were measured in 24 male volunteers for 9 h after a single oral dose of 710 mg kg-1. 2. The rate of decline of the plasma ethanol concentration (k0; mean +/- s.d.), was 186 +/- 26 mg l-1 h-1. 3. In each individual, three elimination rates were used to back-extrapolate plasma ethanol concentrations over 3 and 5 h periods from observed values at 4 h and 6 h post-dosing assuming zero-order kinetics. The extrapolated values were then compared with the observed concentrations. 4. Using the mean k0 values for the subjects the mean error in back extrapolation was small but highly variable. The variability in the error increased with the length of the extrapolation period. 5. When a k0 value of 150 mg l-1 h-1 (a value often cited as a population mean) was used for back extrapolation this resulted in significant under-estimation of actual values whereas the use of a k0 value of 238 mg l-1 h-1 (the highest value observed in the present study) resulted in significant over-estimation of actual values. 6. These results indicate that because the kinetics of ethanol are associated with substantial inter-subject variability the use of a single slope value to back calculate blood concentrations can give rise to considerable error.

Linkage heterogeneity between X-linked retinitis pigmentosa and a map of 10 RFLP loci.

In nine families in which X-linked retinitis pigmentosa (XLRP) is segregating, the lod scores of XLRP in a map of 10 RFLP loci were obtained by multipoint linkage analysis. The XLRP locus was located telomeric to DXS7 in seven of the families and centromeric to DXS7 in two of the families. Under the hypothesis of two XLRP loci, a heterogeneity (admixture) test was performed, providing significant evidence of heterogeneity in XLRP (P less than .01). No correlation was detected between the clinical manifestations of XLRP and the two different disease loci.

Localization of the X-linked retinitis pigmentosa locus between DXS7 and DXS84 in a family showing tapetal reflex in heterozygotes.

The linkage relationships between the X-linked retinitis pigmentosa (XLRP) locus and seven Xp loci: DXS14, DXS7, OTC, DXS141, DXS148, DXS84 and DXS206 were analysed in one large family in which the heterozygotes exhibited the tapetal reflex. Evidence drawn from two-point and multipoint linkage analysis and a number of triply informative crossovers suggests that the XLRP locus in this family is between DXS7 and DXS84. The putative order of loci on the short arm of the X chromosome is: centromere - DXS14 - DXS7 - OTC - XLRP/DXS141 - DXS148 - DXS84 - DXS206 - telemere.

Carrier detection in X-pigmentary retinal dystrophy (X-linked retinitis pigmentosa) by DNA restriction fragment length polymorphism studies.

As part of a patient care and DNA research programme commenced in 1985, a number of DNA markers on the short arm of the X chromosome have been used to demonstrate restriction fragment length polymorphisms (RFLPs) segregating with the X-pigmentary retinal dystrophy (X-linked retinitis pigmentosa) gene. The analysis of the segregation of the RFLPs in 3 kindreds enables carrier detection, to a high degree of probability, in females at risk who are not manifesting symptoms and signs.

Two different genes for X-linked retinitis pigmentosa.

Linkage analysis was carried out in three large multigenerational kindreds with X-linked retinitis pigmentosa using DNA markers on Xp. About 10% recombination has been found between the retinitis pigmentosa locus (RP2) and the marker locus DXS7, assigned to band Xp11.3, which was reported earlier to be closely linked to RP2 in several independent families. In the kindreds described in this paper, however, RP2 shows close linkage and no recombination with the marker loci OTC and DXS148, both assigned to Xp21, indicating that, contrary to previous linkage studies, there is evidence of an RP locus distal to DXS7. This suggests that X-linked retinitis pigmentosa is genetically heterogeneous, i.e., caused by mutations at different loci.

Analysis of linkage relationships of X-linked retinitis pigmentosa with the following Xp loci: L1.28, OTC, 754, XJ-1.1, pERT87, and C7.

A number of variants of X-linked retinitis pigmentosa (XLRP) have been described. In one variant, listed in the McKusick (McK) catalogue (McKusick 1983) as entry no. 30320, the heterozygotes exhibit a golden metallic or tapetal reflex. Three large pedigrees segregating for XLRP with the characteristic tapetal reflex in the heterozygotes were examined, and the linkage between the XLRP locus and Xp loci, L1.28, OTC, 754, XJ-1.1, pERT87 and C7 was measured. The strongest linkage was found to be between the XLRP locus and OTC. In addition, recombinational evidence drawn from the three pedigrees suggests that the XLRP locus is distal to L1.28 and proximal to 754. This putative location of the XLRP gene between L1.28 and 754 taken together with the tight linkage to OTC, a locus already located between L1.28 and 754, leads us to propose a gene order of centromere-L1.28-OTC/XLRP-754-telomere.

Outline for a comprehensive classification of retinal dystrophy and its consequences.

Classification of all relevant factors is a prerequisite to the formulation of specific objectives to attain goals of prevention of retinal dystrophy (RD) and effective provision of services. National and international agreement on a classification is sought. This outline stresses the importance of a sound conceptual basis. The root meaning of dystrophy (difficult nourishment), and the concepts given in the World Organization's International Classification of Impairments, Disabilities and Handicaps are emphasized. The proposed classification is designed to be statistical as well as assisting diagnosis and case management. The scheme for RD entities takes into account special features, in contrast to most treatable eye diseases. Genetics is stressed because of the importance of genetic counseling and rapid research advances. Three appendices illustrate portions of a comprehensive classification already in operation at the Retinal Dystrophy Service of NSW.

[Manpower migrations in the Arab world: the reverse of the New Economic Order]. / Migrations de main-d'oeuvre dans le monde Arabe l'envers du Nouvel Ordre Economique.

PIP: Population and petroleum, 2 essential factors in the development of the Arab world, are unequally distributed in the 18 Arab countries. The abstract possibility of mutually beneficial cooperation between the countries with large populations and no oil and those with oil but small populations is far from being realized; on the contrary, growing inequality and deterioration of human and productive resources can be observed in the Arab world. The apparent economic progress of the oil producing states is illusory, because it has permitted them to defer development of their own internal resources such as agriculture, industry, professional training and education in favor of greater dependence on the temporary palliative of petroleum revenues. In 1980, over 3 million Arabs had emigrated toward other Arab countries, where they were joined by approximately 1.8 million non-Arabs. 4 types of Arab migration have been important: movement from the countryside to cities within countries, movement of Arab migrants to non-Arab countries, movement from 1 Arab state to another because of political factors and especially to earn high wages in the oil producing states, and immigration of non-Arabs and especially Asians to Arab countries. 6 of the principal manpower importing countries, Saudi Arabia, Kuwait, Libya, United Arab Emirates, Bahrain, and Qatar, had total labor forces of about 5.2 million in 1985, of which only 41% were nationals. There have been 4 main consequences for the states importing manpower: 1) petroleum production is very capital intensive and creates few jobs; the jobs filled by migrants are mostly in construction and services funded by oil revenues 2) the expansion is temporary because petroleum is a nonrenewable resource; the manpower transfers will therefore not be permanent 3) the migrants represent a large proportion of the labor force and populations of the Gulf oil-producing states, and 4) the migrants are systematically excluded from the political and social life of the countries in which they work, have no juridical protection or political rights, and are the objects of growing hostility in the countries where they work. The most important consequence may be the least visible: because of the petroleum income and the migratory flows the local populations are less and less motivated to work. The immigrants are almost all single or unaccompanied men who send most of their earnings to their home countries. Thus far there has been little apparent political activity or labor unrest among them in the host countries, but it is unclear how long the apparent calm can be sustained. The most obvious consequence of the migration for the sending countries is the massive flow of remittances. In 1980, such transfers between Arab countries were estimated to total around $3 billion, not counting income in kind. The remittances do not appear to be invested in productive enterprises with any frequency but rather to be used for purchases of mostly imported consumer goods and in speculation. Few migrants learn useful job skills, and some countries have lost large proportions of their skilled workers to migration. Migrant earnings have depressed local production by encouraging imports, especially of foodstuffs, and have fostered inflation by stimulating demand for land and wage increases.^ieng

Labour migration in the Arab world: the ugly face of the new economic order.

PIP: The migration of Arabs and non-Arabs to the oil-producing countries of the Middle East is examined for the period since the oil price rises of 1973. The consequences of this migration for labor-importing states and labor-exporting states are examined separately. The author concludes that the effects of this migration are proving largely negative for both groups of countries under the existing conditions of capitalist development and the unequal distribution of wealth. (summary in FRE)^ieng