The potato mitochondrial initiator methionine tRNA gene and its flanking regions: an illustration of the diversity of mitochondrial genome rearrangements among plant species

The initiator methionine transfer RNA (tRNAf ^Met) gene was identified on a 347 bpEco RI-Hind III DNA fragment of the potato mitochondrial (mt) genome. The sequence of this gene shows 1 to 7 nucleotide differences with the other plant mt tRNAsf ^Met or tRNAf ^Met genes studied so far. Whereas the tRNAf ^Met gene is present as a single copy in the potato mt genome, a tRNA pseudogene corresponding to 60% of a complete tRNA (from the 5 end to the variable region) and located at 105 nucleotides upstream of the tRNAf ^Met gene on the opposite strand was shown to be repeated at least three times. Furthermore, the physical environment of the tRNAf ^Met gene in the mt genome is very different among plants, which suggests that the tRNAf ^Met gene region has often been implicated in recombination events of plant mt genomes leading to important rearrangements in gene order.     

Splicing of Arabidopsis tRNAMet precursors in tobacco cell and wheat germ extracts

Intron-containing tRNA genes are exceptional within nuclear plant genomes. It appears that merely two tRNA gene families coding for tRNA^Tyr _{G A} and elongator tRNA^Met _CmAU contain intervening sequences. We have previously investigated the features required by wheat germ splicing endonuclease for efficient and accurate intron excision from Arabidopsis pre-tRNA^Tyr. Here we have studied the expression of an Arabidopsis elongator tRNA^Met gene in two plant extracts of different origin. This gene was first transcribed either in HeLa or in tobacco cell nuclear extract and splicing of intron-containing tRNA^Met precursors was then examined in wheat germ S23 extract and in the tobacco system. The results show that conversion of pre-tRNA^Met to mature tRNA proceeds very efficiently in both plant extracts. In order to elucidate the potential role of specific nucleotides at the 3 and 5 splice sites and of a structured intron for pre-tRNA^Met splicing in either extract, we have performed a systematic survey by mutational analyses. The results show that cytidine residues at intron-exon boundaries impair pre-tRNA^Met splicing and that a highly structured intron is indispensable for pre-tRNA^Met splicing. tRNA precursors with an extended anticodon stem of three to four base pairs are readily accepted as substrates by wheat and tobacco splicing endonuclease, whereas pre-tRNA molecules that can form an extended anticodon stem of only two putative base pairs are not spliced at all. An amber suppressor, generated from the intron-containing elongator tRNA^Met gene, is efficiently processed and spliced in both plant extracts.     

Macronutrient input from pollen in two regenerating pine stands in southeast Korea

This study examined macronutrient input from pollen in two naturally regenerating pine stands in southeast Korea. Durham gravity pollen collectors were used to measure pine pollen deposition and the macronutrients in the collected pine pollen were analyzed. In 1998, pine pollen deposition began just before 18 April and lasted for approximately 2weeks. Total pine pollen deposition differed between the two sampling sites; 27.5kgha^–1 was collected from the mature stand and 17.7kgha^–1 was collected from the young stand. The values for nutrient deposition from pine pollen are 549gha^–1 N, 78gha^–1 P, 240gha^–1 K, 45gha^–1 S and 22gha^–1 Mg at the mature stand and 353gha^–1 N, 51gha^–1 P, 151gha^–1 K, 27gha^–1 S and 14gha^–1 Mg at the young stand, suggesting that nutrients from pine pollen contribute to forest nutrient cycling. The pine pollen deposition values obtained from our study (17.7–27.5kg^–1ha^–1year^–1) are approximately 1/115–180-fold that of pine litterfall in Korea. If we take pollen nutrients into account, the contribution rate of pollen to the annual nutrient input is very high in our study (N 1/30, P 1/5, K 1/9 that of litterfall). Macronutrient deposition from pine pollen is concentrated temporally in spring. Although the annual contribution of nutrient mass by pollen is small compared to that of litterfall, the rapid turnover rate of pollen nutrients combined with episodic deposition suggests that pollen may play a disproportionate role in temperate pine forest nutrient cycling.     

Laboratory culture studies of Trichodesmium isolated from the Great Barrier Reef Lagoon, Australia

Cultures of Trichodesmium from the Northern and Southern Great Barrier Reef Lagoon (GBRL) have been established in enriched seawater and artificial seawater media. Some cultures have been maintained with active growth for over 6years. Actively growing cultures in an artificial seawater medium containing organic phosphorus (glycerophosphate) as the principal source of phosphorus have also been established. Key factors that contributed to the successful establishment of cultures were firstly, the seed samples were collected from depth, secondly, samples were thoroughly washed and thirdly, incubations were conducted under relatively low light intensities (PAR 40–50molquantam^–2s^–1). N₂ fixation rates of the cultured Trichodesmium were found to be similar to those measured in the GBRL. Specific growth rates of the cultures during the exponential growth phase in all enriched media were in the range 0.2–0.3day^–1 and growth during this phase was characterised by individual trichomes (filaments) or small aggregations of two to three trichomes. Characteristic bundle formation tended to occur following the exponential growth phase, which suggests that the bundle formation was induced by a lack of a necessary nutrient e.g. Fe. Results from some exploratory studies showed that filament-dominated cultures of Trichodesmium grew over a range of relatively low irradiances (PAR 5–120molquantam^–2s^–1) with the maximum growth occurring at 40–50molquantam^–2s^–1. These results suggest that filaments of the tested strain are well adapted for growth at depth in marine waters. Other studies showed that growth yields were dependent on salinity, with maximum growth occurring between 30 and 37psu. Also the cell yields decreased by an order of magnitude with the reduction of Fe additions from 450 to 45nM. No active growth was observed with the 4.5nM Fe addition.     

On T-tubule openings at the sarcolemma of white fast-twitch muscle fibres in fish and frog

Summary In white muscle fibres of a teleost fish T-tubule openings may occur regularly at all Z-disc levels between adjacent peripheral myofibrils, the T-tubule openings thus occurring at a density of ca. 0.9 m^-2.In frog white fibres, T-tubule openings are infrequently seen in material fixed like the fish material. In material prepared according to the albumin method of Gray (1975, 1976 a, b) which renders the muscle fibres swollen, straight tubules or sometimes chains of vesicles instead are seen opening at the sarcolemmal surface. Such tubules occur at a higher density than expected from experiments with local activation of contraction. Lability and dynamics within the T-system normally and during fixation are discussed.     

Genetic analysis of brown planthopper resistance in twenty varieties of rice,Oryza saliva L.

Summary The inheritance of resistance to brown planthopper, Nilaparvata lugens (Stol.), of 20 rice cultivars was studied. Single dominant genes that are allelic to Bph 3 condition the resistance in cultivars Ptb 19, Gangala (Acc. 7733), Gangala (Acc. 15207), Horana Mawee, Kuruhondarwala, Mudu Kiriyal and Muthumanikam. Single recessive genes that are allelic to bph 4 govern the resistance in cultivars Gambada Samba, Heenhoranamawee, Hotel Samba, Kahata Samba, Kalukuruwee, Lekam Samba, Senawee, Sulai, Thirissa and Vellai Illankali. The resistance in Ptb 33, Sudu Hondarwala, and Sinna Sivappu is governed by one dominant and one recessive gene which segregate independently of each other. The dominant resistance genes in these cultivars appear allelic to either Bph 1 or Bph 3. Similarly, the recessive genes in these cultivars seem allelic to either bph 2 or bph 4. Further investigations are needed to conclusively determine the allelic relationships of resistance genes in Ptb 33, Sudu Hondarwala and Sinna Sivappu.     

Gamma carbonic anhydrase like complex interact with plant mitochondrial complex I

We report the identification by two hybrid screens of two novel similar proteins, called Arabidopsis thaliana gamma carbonic anhydrase like1 and 2 (AtCAL1 and AtCAL2), that interact specifically with putative Arabidopsis thaliana gamma Carbonic Anhydrase (AtCA) proteins in plant mitochondria. The interaction region that was located in the N-terminal 150 amino acids of mature AtCA and AtCA like proteins represents a new interaction domain. In vitro experiments indicate that these proteins are imported into mitochondria and are associated with mitochondrial complex I as AtCAs. All plant species analyzed contain both AtCA and AtCAL sequences indicating that these genes were conserved throughout plant evolution. Structural modeling of AtCAL sequences show a deviation of functionally important active site residues with respect to CAs but could form active interfaces in the interaction with AtCAs. We postulate a CA complex tightly associated to plant mitochondrial complex.     

Edge preference of retinal and tectal neurons in common toads (Bufo bufo) in response to worm-like moving stripes: the question of behaviorally relevant ‘position indicators’

Summary Previous experiments have shown that during prey-catching behavior (orienting, snapping) in response to a worm-like moving stripe common toads.Bufo bufo (L.) exhibit a contrast-and direction-dependent edge preference. To a black (b) stripe moving against a white (w) background (b/w), they respond (R^*) preferably toward the leading (l) rather the trailing (t) edge (R _l ^* > R _t ^* ), thus displaying head preference. If the contrastdirection is reversed (w/b), the stripe's trailing edge is preferred (R _l ^* < R _t ^* ), hence showing tail preference. In the present study, neuronal activities of retinal classes R2 and R3 and tectal classes T5(2) and T7 have been extracellularly recorded in response to leading and trailing edges of a 3 ° × 30 ° stripe simulating a worm and traversing the centers of their excitatory receptive fields (ERF) horizontally at a constant angular velocity in variable movement direction (temporo-nasal or naso-temporal).The behavioral contrast-direction dependent edge preferences are best resembled by the responses (R) of prey-selective class T5(2) neurons (R_l R_t=101 for b/w, 0.31 for w/b) and T7 neurons (R_lR_t=61 for b/w, 0.41 for w/b); the T7 responses may be dendritic spikes. This property can be traced back to off-responses dominated retinal class R3 neurons (R_lR_t=61 for b/w, 0.51 for w/b), but not to class R2 (R_lR_t =1.21 for b/w and 0.91 for w/b). The respective edge preference phenomena are independent of the direction of movement.When stimuli were moved against a stationary black-white structured background, the head preference to the black stripe and the tail preference to the white stripe were maintained in class R3, T5(2), and T7 neurons. If the stripe traversed the ERF together with the structured background in the same direction at the same velocity, the responses of tectal class T5(2) and T7 neurons were strongly inhibited, particularly in the former. Responses of retinal R2 neurons in comparable situations could be reduced by about 50%, while class R3 neurons responded to both the stimulus and the moving background structure.The results support the concept that the prey feature analyzing system in toads applies principles of (i) parallel and (ii) hierarchial information processing. These are (i) divergence of retinal R3 neuronal output contributes to stimulus edge positioning and (in combination with R2 output) area evaluation intectal neurons and to stimulus area evaluation and (in combination with R4 output) sensitivity for moving background structures inpre tectal neurons; (ii) convergence of tectal excitatory and pretectal inhibitory inputs specify the property of prey-selective tectal T5(2) neurons which are known to project to bulbar/spinal motor systems.Abbreviations ERF excitatory receptive field - IRF inhibitory receptive field - N nasal - T temporal - R _w response to a worm-like stripe moving in the direction of its longer axis - R _A response to an antiworm-like stripe whose longer axis is oriented perpendicular to the direction of movement - R _l response to the leading edge of a worm-like moving stripe - R _t response to the trailing edge of a worm-like moving stripe - b/w black stimulus against a white background - w/b white stimulus against a black background - sm structured moving background - ss structured stationary background - u minimal structure width of a structured background consisting of rectangular black and white patches in random distribution - HRP horseradish peroxidase     

Ethnocentricity and the social construction of ‘mass hysteria’

This study provides a critical historical review and analysis of the variety of human expressions which have been erroneously labeled under the grandiose category mass hysteria. It is argued that Western science reductionist approaches to the classification of mass hysteria treat it as an entity to be discovered transculturally, and in their self-fulfilling search for universals systematically exclude what does not fit within the autonomous parameters of its Western-biased culture model, exemplifying what Kleinman (1977) terms a category fallacy. As a result of objectivist methodologies, the etiology of actions labeled as mass hysteria is typically viewed as deviant, irrational or abnormal behavior resulting from a malfunctioning proper social order. However, what constitutes the correct social order is a function of a researcher's historical sociocultural and/or scientific milieu. This study reviews the problem, advocating Geertz's (1973) culturally relativistic approach to understanding various cross-cultural behavior that is sensitive to and tolerant of the unique context and milieu of participants. Mass or epidemic hysteria is viewed as an invention of Western psychiatry and should be abandoned and replaced with the term collective exaggerated emotions. Instead of attempting to discover a neatly packaged, unitary external disease entity, the focus of a meaning-oriented approach emphasizes the deciphering of foreign realities, semantic networks and symbol systems.     

Detection and characterization of new mutations in the human angiotensinogen gene (AGT)

As part of the multicenter project entitled Pathobiological Determinants of Atherosclerosis in Youth (PDAY), we are testing polymorphisms in candidate genes of atherosclerosis and hypertension for associations with arterial lesions in autopsied young persons. In this study, we used temperature gradient gel electrophoresis (TGGE) to type the Met²³⁵Thr polymorphism in exon 2 of the angiotensinogen gene (AGT) that is associated with essential hypertension in some human populations. In addition to Met²³⁵Thr, we detected and sequenced four other TGGE variants in exon 2 of AGT. These included two new amino acid substitutions (Thr²⁰⁹ Ile and Leu²¹¹Arg) that were found only among black PDAY cases. The frequency of the Ile²⁰⁹ mutation was 0.002 and the frequency of the Arg²¹¹ was 0.006 in 260 black PDAY cases. The other two TGGE variants were Tyr²⁴⁸Cys and a TC substitution at nucleotide position 171 that had been identified in previous studies. We also developed restriction isotyping for rapid typing of each AGT variant using PCR amplification and digestion with diagnostic restriction enzymes.     

Characterisation and transferability of apple SSRs to two European pear F<Subscript>1</Subscript> populations

European pear (Pyrus communis L.) is among the important fruit species for which only few genetic studies have been carried out. Available evidence indicates that simple sequence repeats (SSR) are very useful as molecular markers because they are codominant, highly polymorphic, abundant and reproducible. The present paper reports more than 100 apple SSR markers in two populations of European pear; a total of 41 SSR markers were then positioned on a genetic linkage map of the cross Passe Crassane × Harrow Sweet and 31 in the map Abbè Fétel × Max Red Bartlett. Syntenic relationships between pear and apple maps have been considered for the chromosomes carrying two or more SSR markers. The alignment among the two maps supports the colinearity of the two genomes with respect both to identification and to orientation of the linkage groups.     

Ein Verfahren zur näherungsweisen Berechnung des Fruchtvolumens bei Äpfeln

Zusammenfassung Unter Berücksichtigung des Fruchtformindexes h/Ø der einzelnen Frucht kann man den Volumzuwachs beliebig zusammengesetzter Gruppen von Früchten an verschiedenen Bäumen vergleichen. Bei der Berechnung der Zuwachsraten des Fruchtvolumens braucht man nur Durchmesser und Höhe der Früchte zu kennen, um das tatsächliche Volumen in guter Annäherung zu berechnen. Die Daten der Regression des Korrekturfaktors für das Volumen (K ) auf den Fruchtformindex werden für vier Sorten stark unterschiedlicher Fruchtform angegeben. Das Volumen der Frucht wird nach folgender Formel berechnet: V = 4/3 · · r ³ · K . Vergleichende Untersuchungen über die Zuwachsrate verschiedener Sorten können bei Verwendung der sortentypischen Regressionen durchgeführt werden.

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A method for approximate calculation of fruit volume in apples

Summary Growth rates of fruit volume can be determined more precisely by using the index h/Ø (length of fruit/diameter) than by simply calculating the volume of a sphere based on the measured diameter. Fruit volume is to be calculated by: V = 4/3 · · r ³ · K K is the factor of deviation of fruit shape from a sphere. K is given for 4 different varieties with varying shape of fruits (Echter Winterglockenapfel, Golden Delicious, Cox Orange Pippin and Ingrid Marie). The increase in volume of any group of apples within one variety or of different varieties can be compared by means of the specific regression of h/Ø to K .

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Obstbauversuchsanstalt des Alten Landes in Jork     

Drosophila mitochondrial DNA: Conserved sequences in the A+T-rich region and supporting evidence for a secondary structure model of the small ribosomal RNA

Summary The sequence of a segment of theDrosophila virilis mitochondrial DNA (mtDNA) molecule that contains the A+T-rich region, the small rRNA gene, the tRNA^f-met, tRNA^gln, and tRNA^ile genes, and portions of the ND2 and tRNA^val genes is presented and compared with the corresponding segment of theD. yakuba mtDNA molecule. The A+T-rich regions ofD. virilis andD. yakuba contain two correspondingly located sequences of 49 and 276/274 nucleotides that appear to have been conserved during evolution. In each species the replication origin of the mtDNA molecule is calculated to lie within a region that overlaps the larger conserved sequence, and within this overlap is found a potential hairpin structure. Substitutions between the larger conserved sequences of the A+T-rich regions, the small mt-rRNA genes, and the ND2 genes are biased in favor of transversions, 71–97% of which are AT changes. There is a 13.8 times higher frequency of nucleotide differences between the 5 halves than between the 3 halves of theD. virilis andD. yakuba small mt-rRNA genes. Considerations of the effects of observed substitutions and deletion/insertions on possible nucleotide pairing within the small mt-rRNA genes ofD. virilis andD. yakuba strongly support the secondary structure model for theDrosophila small mt-rRNA that we previously proposed.     

Quaternary uplifted coral reef terraces on Alor Island,East Indonesia

A flight of six major coral reef terraces, up to 700 m in altitude, occurs along the eastern and northern sides of Kabola Peninsula, Alor Island, Indonesia. Some radiometric dates have been obtained from unrecrystallized coral samples collected in growth position by three different methods (¹⁴C, ²³⁰Th/²³⁴U, ESR). This enabled the identification of the terraces corresponding to the Holocene and to oxygen-isotope stages 5c, 5e and 7. According to the present elevation of the dated terraces, a 1.0–1.2 mm/y mean rate of uplift can be discerned. Extrapolation of this trend to the whole sequence of terraces reveals a good correlation between the development of major terraces and interglacial or interstadial stages corresponding to astronomically calibrated oxygen isotope records, up to stage 13. The relatively rapid uplift rate in this region minimized the possibility of polycyclic sea-level stands at the same levels and contributed to the good preservation of some morphological reef features. Two superimposed marine notches are visible near the present shoreline, with retreat points at about 5.0 m and 8.6 m respectively above the present MLWST level. They can be interpreted as corresponding to a glacial interstadial (the upper notch) and to the Holocene sea-level peak (the lower one). As Holocene emergence has been less than what could be expected from a 1 mm/y rate of uplift, a major coseismic vertical displacement may occur in the future.This work is a contribution to the IGCP Project 367 Late Quaternary coastal records of rapid change and to the activities of the INQUA Commissions Neotectonics and Shorelines, the task group Paleoseismicity of the Late Holocene of the Inter-Union Commission on the Lithosphere, and the UNESCO-IUGS cooperative programme Earth Processes in Global Change (CLIP Pilot Project)     

Genetic polymorphism of human plasma α1-B-glycoprotein: phenotyping by immunoblotting or by a simple method of 2-D electrophoresis

Summary Genetic polymorphism of human plasma (serum) ₁B-glycoprotein (₁B) was observed using one-dimensional horizontal polyacrylamide gel electrophoresis (PAGE) pH 9.0 of plasma samples followed by Western blotting with specific antiserum to ₁B. A simple method of two-dimensional agarose gel electrophoresis (pH 5.4) — horizontal PAGE (pH 9.0) of plasma samples, followed by general protein staining, was reported as an alternative method for ₁B typing. The there different phenotypes of ₁B observed (designated 1-1, 1-2, and 2-2) were apparently identical to those reported by Altland et al. (1983), who used double one-dimensional electrophoresis. Family data supported the hypothesis that the three ₁B phenotypes are determined by two codominant alleles at an autosomal locus, designated A1B. Allele frequencies in a Swedish population were: A1B ^*1, 0.937; A1B ^*2, 0.063; PIC, 0.111. For clues on linkage relationships of human A/B, the previously known linkages of A1B in pigs and horses, including the one between A1B and the gene that determines susceptibility to malignant hyperthermia in pigs were discussed.     

Inheritance of heading date,plant height,ear length and spikelets per spike in an intervarietal cross of wheat

Summary A study to obtain information on early segregating generations of an intervarietal cross WG 357 X Tobari 66 in spring wheat on the genetics of days to heading, plant height, ear length and spikelets per spike was conducted. WG 357 has amber, hard and lustrous grains and is a well adapted high yielding variety of North India whereas Tobari 66 is red grained introduction from CIMMYT.The parental F₁, F₂, B₁, B₂, biparentals, F₃ (parents of biparentals), F₃ bulk and F₄ bulk generations were studied in order to provide analysis of generations means (Mather 1949; Hayman 1958) and variance component analysis (Kearsay 1965; Perkins and Jinks 1970).There were highly significant differences among the generations for all the characters studied. There were significant differences among the F₃ lines as well as among the biparental progenies. Only in case of ear length was the contrast between the two also significant. The mean value of most of the generations arising from the cross fell between the parental range.The three-parameter model failed to account for the variation in generation means in the case of days to heading. This character was concluded to be influenced by linkage and higher order interactions. For the other characters the three parameter model was adequate. For all characters, additive gene effects were most important as compared to dominance gene effects.The analysis of gene action as provided by the generation variance indicated that additive variance was much more pronounced as compared to dominance variance. The heritability was high for days to heading (71 per cent for narrow sense and 80 per cent in broad sense) and plant height (62 and 93 per cent in narrow and broad sense respectively.The implications of the results in breeding programmes have been discussed.     

Conformational dynamics of the anticodon loop in yeast tRNAPhe as sensed by the fluorescence of wybutine

Conformational and dynamic properties of the anticodon loop of yeast tRNA^Phe were investigated by analyzing the time resolved fluorescence of wybutine serving as a local structural probe adjacent to the anticodon GmAA on its 3 side. The influence of Mg²⁺, important for stabilizing the tertiary structure of tRNA, and of the complementary anticodon s²UUC of E. coli tRNA ₂ ^Glu were investigated.Fluorescence lifetimes and anisotropies were measured with ps time resolution using time correlated single photon counting and a mode locked synchronously pumped and frequency doubled dye laser as excitation source. From the analysis of lifetimes () and rotational relaxation times ( _R ) we conclude that wybutine occurs in various structural states: (i) one stacked conformation where the base has no free mobility and the only rotational motion reflects the mobility of the whole tRNA molecule (=6 ns, _R =19 ns), (ii) an unstacked conformation where the base can freely rotate (=100 ps, _R = 370 ps) and (iii) an intermediary state (=2 ns, _R = 1.6 ns).Under biological conditions, i. e. in the presence of Mg²⁺ and neutral salts, wybutine is found in a stacked and immobile state which is consistent with the crystallographic picture. In the presence of the complementary codon however, as exemplified by the E. coli-tRNA ₂ ^Glu anticodon, our analysis indicates that the codon-anticodon complex exists in an equilibrium of structural states with different rotational mobility of wybutine. The conformation with wybutine freely mobile is the predominant one and suggests that this conformation of the codon-anticodon structure differs from the canonical 3–5 stack.     

Ongoing ultradian activity rhythms in the common vole,Microtus arvalis,during deprivations of food,water and rest

Summary The timing mechanism underlying ultradian (2–3 h) activity patterns in the common vole, Microtus arvalis, was studied using behavioural deprivation experiments. These were aimed at distinguishing between a homeostatic control mechanism, in which the rhythmic behaviour itself is part of the causal loop, and a clock mechanism, independent of the behaviour.In 175 experiments, deprivation of food during 3 ultradian cycles in (subjective) daytime did not result in significant changes in the ultradian periodicity of attempts to obtain the food, compared with ad lib. access to food and water. A minor, but significant increase in ultradian activity time () occurred in the course of the deprivation, but this was compensated by a shorter ultradian rest (). These results were obtained both in intact animals (n = 24), which showed ultradian and circadian rhythmicity in behaviour, and in animals (n = 21) with electrolytic lesions aimed at the suprachiasmatic nuclei (SCN), which lacked the circadian modulation of behaviour. Simultaneous deprivation of water and food in 8 voles without circadian rhythmicity during 40 experiments also did not lead to any change in the ultradian periodicity of feeding attempts.Rest deprivation was studied in 5 SCN lesioned voles, by forcing running wheel activity to continue following spontaneous running. Thus, the experimental activity bout was artificially lengthened to 2–9 h in 67 experiments. The onset of the subsequent rest episodes occurred independent of the duration of the preceding . The duration of was dependent on the preceding, experimental in a periodic fashion. The interval experimental (=lengthened +following ) was equal to one, two or three times the control (obtained on nonexperimental days). This result fits the prediction of a clock model and is in conflict with a monotonicincrease of with , as expected in a homeostatic, restorative process.It is concluded that the ultradian timing of activity in the common vole can be explained neither by homeostatic hunger or thirst mechanisms nor by homeostatic rest/activity regulation. The results strongly suggest an independent clock system generating ultradian feeding rhythms in the common vole.Abbreviations DD continuous darkness - LD light-dark regime - LL continuous light - RCA retrochiasmatic area - ARC arcuate nucleus - SCN suprachiasmatic nuclei - ultradian period - ultradian activity time - ultradian rest time     

Extended haplotype analysis of cystic fibrosis mutations and its implications for the selective advantage hypothesis

The major cystic fibrosis (CF) mutation, F508, is associated with one haplotype (B) determined by the two polymorphic markers, XV2C and KM19. This haplotype is rare (15%) among non-F chromosomes. Its frequency among non-F508 CF chromosomes is 50% with variation between populations. One hypothesis for the high frequency of CF haplotype B chromosomes suggests that there was a selective advantage for CF mutations on this specific background as a result of epistatic selection at other closely linked loci. Since the XV2C and KM19 markers are located 200kb 5 to the CF gene and span only 60 kb, an extended haplotype analysis was needed to test this hypothesis. Haplotypes were determined for 183 CF and 120 non-CF Israeli chromosomes at the XV2C and KM19 loci and at three intragenic polymorphic sites (GATT in intron 6A, TUB18 in intron 19, and 24M in exon 24). Among the studied chromosomes the frequency of non-F508 CF chromosomes associated with haplotype B was 70% (88% among Ashkenazi CF chromosomes). Nine mutations (F508, W1282X, G542X, N1303K, 3849+10 kb CT, Q359K/T360K, S549I, S549R, and 1717-1GA) were identified among the studied chromosomes. These mutations accounted for 96% of CF chromosomes of Ashkenazi origin. Haplotype B was associated with seven of these (F508, W1282X, G542X, N1303K, Q359K/ T360K, S549R, and 1717-1GA). The extended haplotype analysis revealed that in five of the seven mutations associated with the haplotype B, 97% of the chromosomes shared the same intragenic haplotype, 212. The variation found in 3% of the chromosomes was only in the GATT repeat. Two mutations, W1282X and 1717-1GA, were associated with a completely different intragenic haplotype, 121. The results of this study indicate that grouping of CF chromosome by haplotype analysis spanning a small extragenic region might not be sufficient. In addition, the results of the extended haplotype analysis indicate that all the studied CF chromosomes that carry the same mutation derived from the same origin. Furthermore, the results indicate that the majority of the CF mutations are associated with the same extended haplotype, supporting the selective advantage hypothesis.     

Structural relationship between tRNA2 Lys and tRNA4 Lys from mouse lymphoma cells

Summary Mouse lymphoma cells have three major isoaccepting lysine tRNAs. Two of these isoacceptors, tRNA₂ ^Lys and tRNA₄ ^Lys, were sequenced by rapid gel or chromatogram readout methods. They have the same primary sequence but differ in two modified nucleotides. tRNA₄ ^Lys has an unmodified uridine replacing one dihydrouridine and an unidentified nucleotide, t⁶A^*, replacing t⁶A. This unidentified nucleotide is not a hypomodified form of t⁶A. Thus, tRNA4ys is not a simple precursor of tRNA₂ ^Lys. Both tRNAs have an unidentified nucleotide, U^**, in the third position of the anticodon. Also, partial sequences of minor homologs of tRNA₂ ^Lys and tRNA₄ ^Lys were obtained. The distinctions between tRNA₂ ^Lys and tRNA₄ ^Lys may be part of significant cellular roles as illustrated by the differential effects of these isoacceptors on the synthesis by lysyl-tRNA synthetase of diadenosine-5,5-P₁,P₄-tetraphosphate, a putative signal in DNA replication.