The Interval-Strength Relationship in Mammalian Atrium: A Calcium Exchange Model: I. Theory

A model is developed for predicting the interval-strength relationship in mammalian atrium. The postulates underlying the model relate the intracellular and transmembrane calcium fluxes to changes in contractility. The predictions of the model agree qualitatively with the behavior of atrium for the following patterns of stimulation: (a) constant interval between stimuli, (b) a rest, or period with no stimuli, after the attainment of a steady-state force level, (c) a sudden change in the interval between stimuli, and (d) paired pulse stimulation. The effects of varying several parameters of the model on both the contraction staircases, after a rested-state contraction, and the steady-state interval-strength relationship are examined. Additional considerations are made: (a) estimates are made of the tissue calcium content available for contraction; (b) the physical meaning of the rested-state contraction is discussed; and (c) estimates are made of the proportionality constant between the maximum value of the contractile tension and the amount of calcium released before a contraction.     

Collecting cultivated and wild Cucurbits in Mexico

The authors spent approximately 5 weeks in Mexico (October 13–November 15, 1979) collecting Cucurbitaceae in 5 areas: 1) Tampico- Valles- Ocampo; 2) San Luis Potosi; 3) Celaya- Queretaro; 4) Veracruz; 5) Zacatecas- Durango- Mazatlan. A few supplemental collections were made in the vicinity of Tapachula, Chiapas. A grand total of 183Cucurbita collections was made, distributed as follows:C. pepo-49;C. moschata-47;C. mixta- 41;C. ficifolia-11;C. foetidissima-13;Cucurbita sp. wild, unidentified- 22. A few collections were made in the following genera:Sechium-4;Lagenaria-2;Sicana-1;Momordica-4;Sicyos-2;Cucumis melo-2;C. anguria-1. The ecological distribution of the 4 cultivated species is reported and discussed. Seed of these materials was divided equally between the participating countries, and will be made available to interested plant breeders.     

Synthesis of internal re-initiation fragments of beta-galactosidase in vitro and in vivo.

Internal re-initiation polypeptides which are products of the lacZ gene of Escherichia coli have been synthesized in a DNA-directed cell-free protein synthesis system. Some of the properties of these protein fragments have been characterized. The de novo synthesized re-initiation proteins, unlike both in vitro synthesized wild-type β-galactosidase and nonsense termination fragments, are insoluble when synthesized at 37 °C, but soluble if synthesis takes place at 25 °C. The same re-initiation proteins which are made in vivo have been detected in vitro. Unlike their in vivo counterparts, which are degraded rapidly, the in vitro synthesized restart proteins are completely stable for at least one hour following their synthesis. Both in vivo and in vitro, the re-initiation proteins are not synthesized from DNA containing a wild-type Z gene, but require a specific nonsense mutation in order to be expressed. Furthermore, the location of the mutation within the Z gene is very important in determining whether or not re-initiation will occur at a given site.Several nonsense mutations which do not result in the synthesis of detectable amounts of restart protein in vivo produce specific re-initiation polypeptides in vitro. These restart proteins display many of the same properties as do those which are made both in vivo and in vitro: they are not made from wild-type DNA, and they are only made from DNA containing a specific nonsense mutation. One of these mutations is 118, which is an extreme polar mutation in vivo. Another is 545, which synthesizes a restart protein in vivo if, and only if, it is coupled with a secondary mutation, π(1). π(1) thus appears to be necessary for the synthesis of a particular re-initiation protein in vivo but unnecessary for the synthesis of the same protein in vitro. The efficiencies of re-initiation vary at the different sites, but in all cases are less than the initiation frequency at the start of the gene. The experiments thus show that when complicating factors, such as polarity and protein degradation, are eliminated, translational re-initiation can be detected at many sites in the lacZ gene.     

Structure and role in symbiosis of the exoB gene of Rhizobium leguminosarum bv trifolii

The Rhizobium leguminosarum bv trifolii exoB gene has been isolated by heterologous complementation of an exoB mutant of R. meliloti. We have cloned a chromosomal DNA fragment from the R. leguminosarum bv trifolii genome that contains an open reading frame of 981 bp showing 80% identity at the amino acid level to the UDP-glucose 4-epimerase of R. meliloti. This enzyme produces UDP-galactose, the donor of galactosyl residues for the lipid-linked oligosaccharide repeat units of various heteropolysaccharides of rhizobia. An R. leguminosarum bv trifoliiexoB disruption mutant differed from the wild type in the structure of both the acidic exopolysaccharide and the lipopolysaccharide. The acidic exopolysaccharide made by our wild-type strain is similar to the Type 2 exopolysaccharide made by other R. leguminosarum bv trifolii wild types. The exopolysaccharide made by the exoB mutant lacked the galactose residue and the substitutions attached to it. The exoB mutant induced the development of abnormal root nodules and was almost completely unable to invade plant cells. Our results stress the importance of exoB in the Rhizobium-plant interaction.     

A NEW CRUSTOSESTEREOCAULONFROM THE MOUNTAINS OF SCOTLAND AND WALES

The new combinationStereocaulon plicatile(Leight.) Fryday & Coppins is made for a previously enigmatic crustose lichen with submuriform ascospores; the basionym,Lecidea plicatilisLeight., was previously misapplied to a norstictic-acid containing species ofRhizocarpon. The systematic position of the crustoseStereocaulon leucophaeopsisgroup is discussed.     

On testing hypotheses concerning standardized mortality ratios

This paper describes tests of hypotheses concerning the equality of any k standardized mortality ratios (or, equivalently, of any k indirect adjusted rates) from p(≥k) populations. The distinction is made between the situation where the standard population is chosen independently of the p populations and one where the standard is formed by pooling all p populations. Different test procedures are required for these two situations. When the pooled standard is used, the appropriate test procedure is applicable only when k = p. Experimental evidence is given showing that when the pooled standard is used both test procedures lead to the same conclusion concerning the hypothesis for the case k = p. The recommendation is made, therefore, to use the “incorrect” test procedure when the standard is a pooled one even when k < p.     

Energy balance in the interaction of intense high-temperature plasma flows with solid targets

The energy balance in the interaction of intense (W≈7 MW/cm², Q≈130 J/cm²) flows of a high-temperature (T _e+T _i≈0.7 keV deuterium plasma with targets made of different materials (graphite, tungsten, copper, etc.) is studied experimentally. It is shown that radiation plays a decisive role in the interaction energy balance: a plasma layer arising near the surface of the eroded target reemits most of the plasma-flow energy into the surrounding space. No more than 50 J/cm² reaches the surface. Then, this energy is expended primarily on the target heating and only a small fraction (less than 3 J/cm²) is spent on the evaporation of the target surface layer. It is shown that, for targets made of high-Z materials, the energy reaching the surface is transferred predominantly by radiation.     

Messinian Lago-Mare deposits near the Strait of Gibraltar (Malaga Basin,S Spain)

A new stratigraphic unit (named LM unit) located at the base of the Pliocene marine succession in the eastern sector of the Malaga Basin has been distinguished. This unit is composed of two fining-upward sequences bounded by a discontinuity related to synsedimentary tectonic activity. Both sequences are made up of basal alluvial deposits overlain by subaquatic deposits. The lower sequence contains rich mollusc faunas characterized by bivalves Lymnocardiinae and Dreissenidae of Paratethyan origin, and non-marine gastropods, typical of oligo-low mesohaline shallow waters, and low diversified ostracod faunas of Paratethyan origin (Loxocorniculina djafarovi, Tyrrhenocythere pontica, Euxinocythere (Maeotocythere) praebaquana and Amnicythere propinqua) typical of low mesohaline waters. Alternances of monospecific ostracod assemblages made of Cyprideis agrigentina or oligotypic assemblages made of C. agrigentina and Loxoconcha spp. and richer assemblages made of L. djafarovi accompanied by several Amnicythere spp. and Camptocypria sp.1 characterize the upper sequence, pointing to more unstable environment affected by salinity and depth changes. Some samples collected from this upper sequence yielded rare, planktonic and benthic foraminifera, which could suggest the sporadic establishment of quasi-normal marine conditions in the westernmost Mediterranean during the deposition of this sequence. The palaeontological data and the palaeomagnetic results obtained in both the LM unit and the overlying Pliocene marine sediments restrict the age of the former to the post-evaporitic late Messinian. The age and the environmental conditions correlate these deposits with the Lago-Mare event occurring throughout the Mediterranean before the quick and widespread marine flooding of the Mediterranean at the beginning of the Pliocene.     

ELECTRIC IMPEDANCE OF SINGLE MARINE EGGS

Alternating current impedance measurements have been made on several single marine eggs over the frequency range from 1 to 2500 kilocycles per second. The eggs were placed in the center of a short capillary made by heating the end of a 2 mm. thin walled glass tube until it nearly closed, and electrodes were placed in the sea water on each side of the egg. When it is assumed that the membrane conductance is negligible, the membrane capacity and internal resistances of unfertilized and fertilized Arbacia eggs agree with the values obtained from suspensions. Preliminary data on centrifugally separated half Arbacia eggs, and whole Cumingia and Chaetopterus eggs are given.     

Biochemical research on oogenesis. The storage particles of the teleost fish Tinca tinca

Oocytes ofTinca tinca and other Teleosts accumulate small and large molecules of RNA in noncoordinate fashion. Previtellogenic oocytes synthesize far less 28 S and 18 S RNA than tRNA and 5 S RNA, so that the latter molecules make up 50 to 90% of total RNA in these cells. As inXenopus laevis, tRNA and 5 S RNA made in excess by small oocytes ofT. tinca are stored in two kinds of nucleoprotein particles, sedimenting at 7 S and 42 S. In this paper we describe the biochemical and physical properties of the storage particles ofT. tinca. The 7 S particles are made up of one 5 S RNA and one 32,000 M_r protein (c). The molecular weight of this protein is lower by 8,000 than itsX. laevis counterpart. In contrast, the 42 S particles have the same size and composition inT. tinca andX. laevis. The 42 S particles of both species are made up of four subunits, each of which contains three molecules of tRNA, one molecule of 5 S RNA, two molecules of a 50,000-M_r protein (a), and one molecule of a 40,000-M_r protein (b). We present evidence showing that in the 42 S particles protein a is associated with tRNA, whereas protein b is associated with 5 S RNA, and suggesting that protein c is a cleavage product of protein b.     

Changes in microflora and biochemical composition during the Baceman stage of traditional indonesian Kecap (soy sauce) production

Indonesian soy sauce (kecap) is made from black soybeans in a traditional way which involves two microbiological stages: a solid-state fermentation and a brine fermentation. This study is concerned with the brine fermentation, called baceman. Samples from different kecap producers were analyzed for (bio)chemical content and micro-organisms. It was found that the final composition of the baceman differed from manufacturer to manufacturer, and even within companies large differences were found in microflora and the amounts of fermentation products, formol nitrogen and salt concentration. The main fermentation products were lactate, acetate, glycerol and ethanol. Pediococcus halophilus, staphylococci, a coryneform bacterium and yeasts belonging to Candida, Debaromyces and Sterigmatomyces were isolated from the brines. Compared to Japanese soy sauce production, fermentation by yeasts does not play an important role in Indonesian kecap production. This is due to the fact that kecap is made from whole soybeans only, which are poor in sugars. After fermentation by P. halophilus no substrates are left for growth and ethanol production by yeasts. The presence of film forming yeasts can even lead to spoilage of the product.     

Morphological comparison ofSqualus blainvillei andS. megalops in the Eastern Atlantic,with notes on the genus

Morphological comparisons are made from the study of 64 specimens belonging to the following species:Squalus acanihias, S. blainvillei, S. megalops andS. acutirostris. The results suggest conspecificity betweenS. acutipinnis andS. megalops. The differences betweenS. blainvillei andS. megalops in the E-Atlantic are stressed. The Indo-Pacific species calledS. blainvillei by Chen et al. (1979) is regarded in this paper as probably an undescribed species. Some consideration on the status of several nominal species and the species grouping withinSqualus are also made.     

Tubulin from Mimosa pudica and its involvement in leaf movement

The sensitive plant Mimosa pudica is made insensitive by a brief treatment with colchicine. A high concentration of colchicine binding protein is present in the fresh actively moving leaves of M. pudica. This protein was partially characterized and compared with the animal brain tubulin. This colchicine binding activity is very low in the insensitive variety of Mimosa, namely Mimosa rubricaulis.     

Perilla frutescens seed agar, a new medium for identification of the Cryptococcus species complex: evaluation for all major molecular types

Here we present a new and simple medium made by Perilla frutescens seed as a tool for identification of the Cryptococcus species complex, namely Cryptococcus neoformans and Cryptococcus gattii. Its usefulness was evaluated for all major molecular types within the Cryptococcus species complex. As a result, this medium is better for identification of the species complex compared with Guizotia abyssinica or Helianthus annuus seed medium.     

The establishment ofRhyzobius forestieri [Col.: Coccinellidae] in greece and its efficiency as an auxiliary control agent against a heavy infestation ofSaissetia oleae [Hom.: Coccidae]

Introduction releases of the exotic coccinellid predatorRhyzobius forestieri Mulsant were made in 22 localities throughout Greece. The releases were made on olive, citrus, fig and almond trees infested with differentCoccidae scales. In 9 of these localities,R. forestieri was recovered 2–5 months later. The most important factor for the successful establishment ofR. forestieri seems to be an abundance of scales on the trees. To study the ability ofR. forestieri to enhance overall predation, 3 releases were made in an olive grove heavily infested withSaissetia oleae Olivier on Chios island during 1982 and 1983. The experiment began in June 1982. By April 1983, theS. oleae infestation was clearly in the process of being controlled by the coccinellid. A native coccinellid,Exochomus quadripustulatus L., contributed little during this period because of its obligatory estival diapause. The other main coccinellid,Chilocorus bipustulatus L., made an appreciable contribution toward achieving control during the summers of 1982 and 1983, but it was affected from July onward by increasing parasitism of its larvae. Both species are quiescent during the winter months. The introduced speciesR. forestieri was readily established in the olive grove and multiplied quickly. One month after the initial release,R. forestieri larvae made up most of the coccinellid larval population in the field. Thereafter until April 1983,R. forestieri larvae and adults comprised the dominant coccinellid population in the olive grove. During the winter months,R. forestieri remains active as long as temperature exceeds 8 °C. The important increase inR. forestieri's population size between July 1982 and April 1983 coincided with the increased rate of predation onS. oleae. This suggests thatS. forestieri played a key role in bringing theS. oleae infestation under control during this period. After April 1983, however, theR. forestieri population diminished rapidly andC. bipustulatus became the dominant coccinellid in the olive grove. It is believed that scarcity of prey was the cause of this reversal: by April 1983, the density ofS. oleae in the olive grove had already been reduced by about 100 times.