Adoptions expérimentales de larves entre des fourmis de genres différents (II):Myrmica laevinodis Nylander etAnergates atratulus Schenck

Résumé Nous avons fait élever des larves d'Anergates atratulus par des ouvrières deMyrmica laevinodis à 22°C. Pour y parvenir, il n'est pas utile de faire hivernerensemble les larves d'Anergates et les ouvrières deMyrmica. La présence de larves autochtones n'empêche pas lesMyrmica d'élever des larves d'Anergates. Dans toutes les expériences lesMyrmica ont été soumises au fridavant de recevoir des larves d'Anergates. Aucune reine deMyrmica n'a été utilisée dans ces expériences.Sur les 64 larves d'Anergates que nous avons utilisées, 38 se sont transformées en imagos. C'est au début de l'adoption et au moment des métamorphoses que périrent la plupart des 26Anergates perdus. Les femelles vécurent en général 2 ou 3 jours et cherchèrent très tôt à quitter le nid natal. Les mâles vécurent 2 à 3 semaines.

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Summary Larvae ofAnergates atratulus were experimentally reared by workers ofMyrmica laevinodis, at 22°C. An overwintering of both larvae ofAnergates and workers ofMyrmica is not necessary for the success of that experiment. The presence of larvae ofMyrmica does not keep theMyrmica from rearing larvae ofAnergates. The workers ofMyrmica have been cooled, in all the experiments, before receiving larvae ofAnergates. No queen ofMyrmica have been used in that experiments.38 of the 64 larvae ofAnergates used became imagos. Most of the 26 lostAnergates died at the beginning of the adoption and during the metamorphosis. The females lived generally 2 or 3 days and tried, very early, to leave their native nest. The males lived 2 or 3 weeks.

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Anergates atratulus Myrmica laevinodis, 22 . bmecme Anergates Myrmica. Myrmica Anergates. Myrmica Anergates. Myrmica . 64 Anergates , 38 . 26 Anergates 2 3 . 2 3 .

     

Localization of adenosine 5′-phosphosulfate sulfotransferase in spinach leaves

Roots of spinach (Spinacia oleracea L.) seedlings contained only a very low activity of adenosine 5-phosphosulfate sulfotransferase compared to the cotyledons. Adenosine 5-phosphosulfate sulfotransferase activity increased about tenfold in cotyledons during greening. Preparation of organelle fractions from spinach leaves by a combination of differential and isopycnic density gradient centrifugation showed that adenosine 5-phosphosulfate sulfotransferase banded with NADP-glyceraldehyde-3-phosphate dehydrogenase, a marker enzyme for intact chloroplasts. In the fractions of peroxisomes, mitochondria and broken chloroplasts virtually no adenosine 5-phosphosulfate sulfotransferase activity was measured. Comparison with the chloroplast enzyme NADP-glyceraldehyde-3-phosphate dehydrogenase indicates that in spinach, adenosine 5-phosphosulfate sulfotransferase is localized almost exclusively in the chloroplasts.Abbreviations APS Adenosine 5-phosphosulfate - APSSTase Adenosine 5-phosphosulfate sulfotransferase - BSA Bovine serum albumin - BRIJ58 Polyethylene glycolmonostearylether - DTE Dithioerythritol - DTT Dithiothreitol - EDTA Ethylenediaminetetraacetic acid - ME 2-Mercaptoethanol - NADP-GPD NADP-linked glyceraldehyde-3-phosphate dehydrogenase - PAPS Adenosine 3-phosphate 5-phosphate 5-phosphosulfate - POPOP 1,4 Di [2-(5-phenyloxazolyl)]-benzene - PPO 2,5-Diphenyloxazol The results presented in this paper are taken from the Ph. D. thesis of H.F.     

Hexahydroindanone derivatives of steroids formed by Rhodococcus equi

Summary A mutant strain of Rhodococcus equi accumulates three metabolites from the androst-4-ene-3,17-dione or from its degradation intermediate, 3a-H-4(3'-propionic acid)-7a-methylhexahydro-1,5-indanedione (MEPHIP). These three metabolites are: 3a-H-4a(3'-propionic acid)-5-hydroxy-7a-methylhexahydro-1-indanone--lactone (HIL); 3a-H-4(3'-trans acrylic acid)-5-hydroxy-7a-methylhexahydro-1-indanone (^2'-5-hydroxy-MEPHIP); and 3a-H-4(3'-hydroxy-3'-propionic acid)-5-hydroxy-7a-methylhexahydro-1-indanone (3'-hydroxy-HIL). The behaviour of this mutant allows us to propose a pathway for degradation of the intermediates, methylperhydroindanone propionates. However, during this degradation, the side-chain propionate was eliminated by a-oxidation mechanism. Offprint requests to: A. Miclo     

The ability of acidic pH,growth inhibitors,and glucose to increase the proton motive force and energy spilling of amino acid-fermenting <Emphasis Type="Italic">Clostridium sporogenes</Emphasis> MD1 cultures

Clostridium sporogenes MD1 grew rapidly with peptides and amino acids as an energy source at pH 6.7. However, the proton motive force (p) was only –25 mV, and protonophores did not inhibit growth. When extracellular pH was decreased with HCl, the chemical gradient of protons (ZpH) and the electrical membrane potential () increased. The p was –125 mV at pH 4.7, even though growth was not observed. At pH 6.7, glucose addition did not cause an increase in growth rate, but increased to –70 mV. Protein synthesis inhibitors also significantly increased . Non-growing, arginine-energized cells had a of –80 mV at pH 6.7 or pH 4.7, but was not detected if the F₁F₀ ATPase was inhibited. Arginine-energized cells initiated growth if other amino acids were added at pH 6.7, and and ATP declined. At pH 4.7, ATP production remained high. However, growth could not be initiated, and neither nor the intracellular ATP concentration declined. Based on these results, it appears that C. sporogenes MD1 does not need a large p to grow, and p appears to serve as a mechanism of ATP dissipation or energy spilling.Mandatory disclaimer: Proprietary or brand names are necessary to report factually on available data; however, the USDA neither guarantees nor warrants the standard of the product, and the use of the name by the USDA implies no approval of the product, and exclusion of others that may be suitable.     

A Simple Method for Preparation of 18α-Glycyrrhetinic Acid and Its Derivatives

Treatment of 18-glycyrrhizic acid with a methanolic solution of HCl resulted in 1 : 1 mixture of methyl esters of 18- and 18-glycyrrhetinic acids. Benzoylation of the mixture led to methyl esters of 3-benzoyl-18-glycyrrhetinic acid and 3-benzoyl-18-glycyrrhetinic acid, which were separated by chromatography on silica gel. 18-Glycyrrhetinic acid was prepared by alkaline hydrolysis of methyl 3-benzoyl-18-glycyrrhetinate and was further used for the syntheses of 3-keto-18-glycyrrhetinic acid and methyl esters of 18-glycyrrhetinic acid and 3-keto-18-glycyrrhetinic acid.     

Heritable variation in the phaseolin protein of nondomesticated common bean,Phaseolus vulgaris L.

Summary Crude protein extracts from single seeds of nondomesticated Mexican bean accessions were analysed by SDS polyacrylamide gel electrophoresis for variability in phaseolin protein. Six new phaseolin types; M1, M2, M3, M4, M5, M6, which contained polypeptides within the same range of molecular weights (51,000 to 45,000 daltons) as occur in the S, T and C phaseolin types of cultivated beans were identified. No T and C types were found among the non-domesticated Mexican accessions, and the S type occurred in less than 7% of the seeds screened. Genetic analyses of F₂ progenies from crosses between Sanilac (S), and five of the M types showed that each M phaseolin phenotype was allelic to the S type and expressed codominantly.     

Mutation spectra of N-ethyl-N''-nitro-N-nitrosoguanidine and 1-(2-hydroxyethyl)-1-nitrosourea in Escherichia coli

Summary DNA sequencing was used to determine the specific types of DNA base changes induced following in vivo exposure of Escherichia coli to the ethylating agent N-ethyl-N-nitro-N-nitrosoguanidine (ENNG) and the hydroxyethylating agent 1-(2-hydroxyethyl)-1-nitrosourea (HENU) using the xanthine guanine phosphoribosyltransferase (gpt) gene as the genetic target. We observed that 22/30 of the ENNG-induced mutations were GCAT transitions, 4/30 were ATGC transitions, 3/30 were ATTA transversions, and 1/30 was an ATCG transversion. We observed that 37/40 HENU-induced mutations were GCAT transitions and that the remaining 3/40 were ATGC transitions. A majority of the GCAT transitions induced by ENNG and HENU (68% and 73%, respectively) occurred at the second guanine of the sequence 5-GG(A or T)-3; this sequence specificity was similar to that previously seen with the alkylating agents N-methyl- and N-ethyl-N-nitrosourea (MNU and ENU) and N-methyl-N-nitro-N-nitrosoguanidine (MNNG). A DNA strand preference for the GA changes (antisense strand), previously noted for MNU, ENU, and MNNG, was observed following exposure to HENU and ENNG. The ATGC transitions induced by ENNG, HENU, and ENU also exhibit a sequence specificity with 13/13 mutations occurring at the T of the sequence 5-NTC-3. A strand preference was not apparent for these mutations.     

Effect of Gamma Irradiation on Embryogenic Avocado Cultures and Somatic Embryo Development

Embryogenic avocado cultures were exposed to ionizing irradiation in order to determine its effect on proliferation and subsequent somatic embryo development. The approximate PD₅₀ as determined by linear regression is 35 Gy 2 weeks after irradiation for Fuerte 2.11.1 and 4 weeks after irradiation for T362 2.11.1. Irradiation of embryogenic cultures did not significantly affect the number of early stage Fuerte 2.11.1 somatic embryos that developed directly from irradiated cultures; however, 10–50 Gy inhibited somatic embryo development. Irradiation of T362 2.11.1 embryogenic cultures at 25–50 Gy inhibited the number of intermediate and mature stages of somatic embryos that developed directly from irradiated cultures, and 50 Gy inhibited somatic embryo maturation. Inhibition of somatic embryo development could be partially offset by proliferation of irradiated embryogenic cultures as suspensions. Irradiation up to 10 Gy significantly increased the number of mature Fuerte 2.11.1 somatic embryos that developed from suspension cultures. Irradiation with doses up to 25 Gy stimulated development of heart stage T362 2.11.1 somatic embryos; however, mature somatic embryo development was suppressed at dosages of 10 Gy and greater.     

Ganglioside-cholera toxin interactions: a binding and lipid monolayer study

Summary On t.l.c. plates ¹²⁵I-cholera toxin binds to a disialoganglioside tentatively identified as GD_lb with about 10 times less capacity than to ganglioside GM₁. Binding of labeled toxin to both gangliosides was abolished in presence of excess amounts of unlabeled B subunit. Ganglioside extracts from human or pig intestinal mucosa showed toxin binding to gangliosides GM₁ and GD_1b. In ganglioside-containing lipid monolayers the penetration of the toxin was independent of the ganglioside binding capacity.Abbreviations GM₂ Gal-NAc14Gal(3-2NeuAc)14G1c1Cer - GM₁ Gal3Ga1-NAc14Gal(32NeuAc)14G1c11Cer - GD_1a NeuAc23Ga113Gal-NAc14Gal(32NeuAc)14G1c11Cer - GD1b Gall3Gal-NAcl4Gal(32NeuAc82NeuAc)14Glc11Cer - GT_1b NeuAc23Ga113Ga1-NAcal4Gal(3-2NeuAc82NeuAc)14G1c11Cer - dpPC 1,2-hexadecanoyl-sn-glycero-3-phosphocholine - dpPE 1,2-hexadecanoyl-sn-glycero-3-phosphoethanolamine     

Rooting apple cultivars in vitro: Interactions among light,temperature, phloroglucinol and auxin

Delicious apple (Malus domestica Borkh.) and several of its strains, which have been difficult to root in vitro, were successfully propagated with rooting percentages up to 100%. The combination of treatments used to achieve this result included placing the shoots on rooting medium in the dark at 30°C for the first week of the rooting stage, then moving them to a regime of 16 hr light-8 hr dark at 25°C. The rooting medium contained half strength Murashige and Skoog salts plus 1.2 M thiamine HCl, 0.56 mM myo-inositol, 1 mM phloroglucinol (PG), 1.4 M indolebutyric acid (IBA), 1.3 M gibberellic acid (GA₃), 87.6 mM sucrose, and 7 g l^–1 Difco Bacto agar. Dark treatment applied during the proliferation stage (etiolation) was less effective than one applied at the beginning of the rooting stage. The optimum length of dark treatment during rooting was 4 to 7 days. Increasing the temperature from 25°C to 30°C improved rooting of Delicious, Royal Red Delicious, and Vermont Spur Delicious in the absence of PG but generally had less effect in the presence of PG. Further increase in temperature to 35°C stimulated rooting of Royal Red Delicious but reduced rooting of Vermont Spur Delicious. Transfer of the cuttings to auxin-free medium after 1 week had no effect on percentage rooting and increased the number of roots per cutting for only 1 of 4 cultivars tested and then only in the presence of PG. In general PG stimulated rooting of Delicious and its strains, but had no effect on Golden Delicious.     

Identification of a high-molecular-weight subunit of glutenin whose presence correlates with bread-making quality in wheats of related pedigree

Summary The subunit composition of glutenin was analysed by SDS-polyacrylamide-gel electrophoresis using two varieties of contrasting pedigrees. Maris Widgeon, a variety of good bread-making quality, was shown to contain 2 glutenin subunits not present in Maris Ranger, a much higher yielding variety that is unsuitable for making bread. A third subunit was only found in Maris Ranger glutenin. To determine if any of these subunits are directly related to bread-making quality, 60 randomly-derived F₂ progeny from a Maris Widgeon x Maris Ranger cross were analysed for bread-making quality and for glutenin subunit composition. A strong correlation was demonstrated between the presence of one of the two subunits inherited from Maris Widgeon, and quality. This subunit (termed subunit 1 glutenin) had an approx. mol. wt. of 145,000. It was also found in Maris Freeman, a bread-making variety selected from the same cross previously made in 1962. In further crosses involving Maris Widgeon or its descendants, more bread-making varieties have been produced in the last decade at the Plant Breeding Institute, Cambridge and all but one have inherited glutenin subunit 1. The subunit has been traced back through Holdfast to White Fife, a Canadian hard spring wheat of excellent breadmaking quality. Some 67 varieties were screened for the presence of glutenin subunit 1 and it was found in 31% of them. Several unrelated varieties of good bread-making quality did not contain subunit 1 glutenin.     

DNA markers tightly linked to a gall midge resistance gene (Gm2) are potentially useful for marker-aided selection in rice breeding

We have developed a polymerase chain reaction (PCR)-based assay that could effectively reduce the time period required to screen and select for Gall Midgeresistant rice lines under field conditions. The primers for the assay were designed on the basis of sequence information of two phenotype specific random amplified polymorphic DNA fragments which were found to be tightly linked to Gall Midge biotype-1 resistance gene (Gm2). The two RAPD fragments, F8₁₇₀₀ in the susceptible parent ARC6650 and F10₆₀₀ in the resistant parent Phalguna, were identified after screening 5450 loci using 520 random primers on genomic DNAs of ARC6650 and Phalguna. These primers, when used in a multiplexed PCR, amplified specifically a 1.7-kb and 0.6-kb fragment in the susceptible and resistant parents, respectively. When this assay was performed on genomic DNAs of 44 recombinant inbred lines derived from ARC6650 x Phalguna and 5 lines derived from other crosses where one of the parents was Phalguna, ARC6650 or their derivatives, the primers amplified a 1.7-kb fragment in all of the susceptible lines or a 0.6-kb fragment in all of the resistant ones. These markers can be of potential use in the marker-aided selection of Gall Midge biotype-1 resistant phenotypes. As screening for resistance can now be conducted independent of the availability of insects, the breeding of resistant varieties can be hastened.     

An elongated segment of DNA observed between two human α globin genes

Summary Detailed restriction enzyme analysis of the DNA from a Chinese female showed that one of her chromosomes had a >17.5 kb deletion of DNA, including the , 2, and 1 globin genes, which is present in many Southeast Asians with an -thalassemia-1 chromosome. Her normal chromosome had the expected cluster of -like globin genes (5----2-1-3), but the segment of DNA between the two globin genes was elongated by some 0.5–0.7 kb. Analyses of various restriction sites suggested that this normal variant of the human globin gene complex is due to a crossover between a normal chromosome with () and a chromosome with an -thalassemia-2 (–^3.7) and an -21-hybrid gene.     

Parameters involved in the enhancement of monoclonal antibody targeting in vivo with recombinant interferon

Summary The effects of recombinant human leukocyte (clone A) interferon (rHu-IFN-A) were investigated on the expression of monoclonal antibody (MAb)-defined tumor antigens expressed on human mammary and colon carcinomas. The rHu-IFN-A treatment substantially increased the localization of radiolabeled MAb B6.2-F(ab)₂ to the transplantable Clouser human mammary carcinoma, as well as to the moderately differentiated human colon xenograft WiDr, when grown as s.c. tumors in athymic mice. In contrast, human tumor cell lines (i.e., LS174T, A375, etc.) that were unresponsive to the antigen-augmenting ability of rHu-IFN-A in vitro were also unresponsive in vivo, indicating a possible method of screening carcinoma cell populations for subsequent rHu-IFN-A adjuvant therapy prior to MAb administration. The method of delivery of rHu-IFN-A was also studied. The i.m. route resulted in a 3–4 h plasma half-life for rHu-IFN-A. The administration of rHu-IFN-A via an osmotic pump resulted in a stable circulating plasma titer of 400–800 antiviral units/ml for 7 days. Utilizing delivery of rHu-IFN-A by the constant infusion route, it was found that the increase in localization of ¹²⁵I-B6.2-F(ab)₂ was dependent on (1) the length of time of treatment and (2) the circulating plasma rHu-IFN-A levels. These results thus provide information useful for subsequent studies to determine the potential efficacy of adjuvant rHu-IFN-A treatment for MAb-targeted tumor diagnosis and treatment.     

Hypoxia Tolerance of Two Haplochromine Cichlids: Swamp Leakage and Potential for Interlacustrine Dispersal

The ability to tolerate hypoxia in some haplochromine cichlid fishes contributes to the richness of habitats occupied by the lineage and may be important in interlacustrine dispersal through swampy channels. Lacustrine members of the genus Astatotilapia tend to be ecologically plastic but are rarely encountered in the interior of dense swamps. A notable exception is seen in the swamp corridor that joins Lake Kabaleka with Lake George, Uganda, where one species (Astatotilapia wrought-iron) is abundant, and a second species, A. aeneocolor, is rare. Both species are abundant in the open waters of the main lake. In this paper, we compare physiological (oxygen consumption) and behavioral indicators of hypoxia tolerance between A. wrought-iron from swamp and open-water habitats and between the two species of Astatotilapia. When exposed to progressive hypoxia, all fish used aquatic surface respiration (ASR); however, swamp-dwelling A. wrought-iron showed lower gill ventilation rates prior to the initiation of ASR, higher pre-ASR aggression rates, higher swimming speed during ASR, and a higher rate of bubble exchange than both the open-water group of A. wrought-iron and A. aeneocolor. These differences may reflect interpopulational variation in selection pressure for low-oxygen tolerance between swamp and open-water habitats. Several lines of evidence suggest that A. wrought-iron was in general more hypoxia tolerant than A. aeneocolor. These include a lower ASR₉₀ threshold, a drop in gill ventilation rate with the onset of ASR, and lower rate of equilibrium loss under extreme hypoxia in A. wrought-iron. The routine metabolic rate and critical oxygen tension did not differ between swamp-dwelling and open-water A. wrought-iron, or between A. wrought-iron and A. aeneocolor. Comparative data on the ASR thresholds and critical oxygen tensions of the Astatotilapia species from Lake Kabaleka and other East African cichlids suggest intermediate hypoxia tolerance. Nevertheless, our study suggests that some generalized lacustrine haplochromines may leak through swamp corridors even under relatively extreme conditions.     

A simple mathematical modeling of the growth of microorganism colonies

The growth rates of aspergillus, fusarium, and penicillium microorganism colonies in Czapex Dox Agar as a feed material, under room conditions, are observed to be linear. This phenomenon is mathematically modeled and exactly predicted on the basis of the exponential growth assumption of a single microorganism. The approach allows an easy determination of the multiplication constant of a had microorganisms been allowed to grow freely microorganism, in given conditions.     

Harzkonservierte fossile Vogelfedern aus der untersten Kreide

Zusammenfassung Harzkonservierte Fossilien ermöglichen bei Anwendung adäquater Methoden die morphologische Analyse der Feinmerkmale bis zur Auflösungsgrenze des Lichtmikroskops, Beobachtung in verschiedenen Ebenen und Richtungen, und somit konkrete Rückschlüsse auf die Wirkung und Bedeutung der Einzelelemente und des Gesamtgefüges.Eine so eingehende funktionsmorphologische Analyse mit Berücksichtigung der Positionsvariation (graduell verschiedene Gestaltung in gesetzmäßiger Abhängigkeit von der Lage innerhalb der Gesamtfeder) der Einzelelemente wie Abzweigungs-, Knick-, Neigungswinkel, Krümmung, Länge, Dicke, Querschnitt, Dichte, Differenzierungsgrad der verschiedenen Abschnitte von Rhachis, Rami, Radii inklusive Häkchen und Cirren wird erstmals für fossile Vogelfedern geliefert (hier als Abriß zu einer dokumentarisch und thematisch ausführlicheren Darstellung in Stuttgarter Beiträge zur Naturkunde).Diese Federn entstammen der untersten Unterkreide und sind damit nur relativ wenig jünger alsArchaeopteryx. Sie weisen extrem differenzierten Aufbau auf, der auf hohe flugtechnische und wärmeisolierende Leistungsfähigkeit schließen läßt.Die hier vorgelegten funktionsmorphologischen Ermittlungen an fossilen Körperkonturfedern mögen auch zu einer intensiveren Analyse der bis jetzt stark vernachlässigten Untersuchung ganz normaler Körperfedern rezenter Vögel anregen. Erst dann, nach umfassender Kenntnis ihrer Ausgestaltung innerhalb der verschiedensten rezenten Vogelgruppen, läßt sich überzeugend begründen, ob und wieweit die hier vorgelegten Federn dieses Unterkreide-Vogels noch ursprüngliche Elemente (Plesiomorphien) oder ihnen eigene Sonderbildungen (Autapomorphien) aufweisen; das gilt sowohl für morphologische wie für funktionelle Elemente der Gesamtstruktur.

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Resin-preserved fossil bird's feathers from the Lowermost Cretaceous

Summary Parts of some feathers, originating from a single bird, were discovered in our collections of Lower Cretaceous amber from the Lebanon mountains — which, in general, contains the oldest terrestrial microfossils preserved with all morphological details.These contour feathers of the trunk, which are nearly as old as Archaeopteryx (Lowermost Cretaceous: Neocomian/Uppermost Jurassic: Kimmeridigian) were studied with magnifications of 500–900 in several levels by a special technique. (In normal fossils, i.e., impressions, the granulation of the sediment and the fossil's bulky carbon remainders cause a blurred image even at a magnification of merely 100).Special emphasis was laid on the study of the individual elements' gradual variation, depending on the respective position within the total feather (position variation). Where appropriate, an analysis of lengths, quantity, degree of differentiation, angle of inclination, break, and branching, cross-sectional view, curvature, etc. of the rhachis, rami, distal and proximal radii, barbicles, hooklets, etc. were undertaken. [Through measurements of the depth of details the effects caused by a sloping position (apparent variation) may be precisely separated from the real variation.]On the basis of such a detailed knowledge of structure and relative position a thorough functional analysis of the single elements as well as the total system is given.Principal features: The production of plain stability in the feather's center, and of flexibility in its apical and lateral rims; dispersion of forces in case of pressure or a pulling load; function of the hooklets (which donot serve as an interlocking mechanism while the feather is in the normal resting position, but function with increasing braking action only when a neighboring ramus diverges to a precisely defined extent from its resting position) including the mechanism of their unhooking; devices for the avoidance of harmful hooking into contacted parts of other feathers; production of maximal stability by minimal air resistance, and of minute chambers (<0,00001 mm³) with still air for optimal heat isolation.Apart from this abstract, further information, accompanied by numerous figures, will be given in a later paper in Stuttgarter Beiträge zur Naturkunde.

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Veränderte Fassung eines am 11. 10. 1971 gehaltenen Vortrages auf der 83. Jahresversammlung der Deutschen Ornithologengesellschaft in Bonn.     

Kinetic studies of peptide bond formation. Effect of chloramphenicol

There might be an undetermined order in the interaction of the substrates with the ribosomes in the reaction of CACCA-Leu-Ac with puromycin to form Ac-Leu-puromycin and CACCA (fragment reaction). Km 0°=6×10^-4 M for the puromycin · ribosome interaction. Chloramphenicol totally blocks the fragment reaction as a consequence of a single interaction with the ribosome of Kd 0°=2.2×10^-6 M. The inhibition by chloramphenicol of the fragment reaction is mixed competitive for puromycin.     

Genomic organization of human complement protein C8α and further examination of its linkage to C8β

Human C8 is one of five complement components (C5b, C6, C7, C8, C9) that interact to form the cytolytic C5b-9 complex on target membranes. It is composed of three nonidentical subunits (C8, C8, C8) encoded by separate genes. C8 and C8 are linked on chromosome 1p32, whereas C8 is located on 9q22.3-q32. In this study, overlapping genomic clones were isolated and used to decipher the organization of the human C8 gene. The gene contains at least 11 exons spanning 70kb of DNA. When compared to C6, C8 and C9, there is a remarkable similarity in genomic organization, consistent with amino acid sequence comparisons that suggest these proteins are ancestrally related. Regions of each protein that are structurally similar are encoded in exons of correspondingly similar lengths with highly conserved boundaries and phases. Availability of genomic sequence also facilitated a more detailed analysis of C8 and C8 linkage. Based on analysis of genomic digests with cDNA probes, the loci were previously reported to be physically linked (< 2.5kb) and in a 5- 3 orientation. In the present study, results obtained using exon-specific probes indicate the loci are not as closely linked as initially believed. Furthermore, they suggest that cDNA probes used earlier yielded misleading information because they encode exons that are distributed across large segments of genomic DNA.     

Average phase difference theory and 1∶1 phase entrainment in interlimb coordination

The dynamics of coupled biological oscillators can be modeled by averaging the effects of coupling over each oscillatory cycle so that the coupling depends on the phase difference between the two oscillators and not on their specific states. Average phase difference theory claims that mode locking phenomena can be predicted by the average effects of the coupling influences. As a starting point for both empirical and theoretical investigations, Rand et al. (1988) have proposed d/dt= — K sin ), with phase-locked solutions =arcsin( /K), where is the difference between the uncoupled frequencies and K is the coupling strength. Phase-locking was evaluated in three experiments using an interlimb coordination paradigm in which a person oscillates hand-held pendulums. was controlled through length differences in the left and right pendulums. The coupled frequency _c was varied by a metronome, and scaled to the eigenfrequency _v of the coupled system K was assumed to vary inversely with _c. The results indicate that: (1) and K contribute multiplicatively to (2) =0 or = regardless of K when =0; (3) 0 or regardless of when K is large (relative to ); (4) results (1) to (3) hold identically for both in phase and antiphase coordination. The results also indicate that the relevant frequency is _c/_v rather than _c. Discussion high-lighted the significance of confirming =arcsin(/K) for more general treatments of phase-locking, such as circle map dynamics, and for the 11 phase-entrainment which characterizes biological movement systems.