A model of associative memory in the brain

A model of associative memory for time varying spatial patterns is proposed and simulated on a digital computer. This is a network composed of many neuron-like elements, and shows an ability for associative memory similar to that of the brain.Suppose a number of sequences of spatial patterns are presented to this network, for example, 12345, ABC, and so on. Then, these patterns are memorized in the network. After that, if any part of one of these sequences, say 23, is presented to the circuit, the rest of the sequence, 45, is recalled following to it. It resembles to such a situation — if we hear a part of a melody which we have memorized in the past, the rest of the melody is recalled even after it is stopped half-way. Although the recalled patterns are not always 100% correct, they are not completely destroyed even if the presented patterns are imperfect.     

On the sufficiency of the velocity field for perception of heading

All models of self-motion from optical flow assume the instantaneous velocity field as input. We tested this assumption for human observers using random-dot displays that simulated translational and circular paths of movement by manipulating the lifetime and displacement of individual dots. For translational movement, observers were equally accurate in judging direction of heading from a velocity field with a two-frame dot life and a direction field in which the magnitudes of displacement were randomized while the radial pattern of directions was preserved, but at chance with a speed field in which the directions were randomized, preserving only magnitude. Accuracy declined with increasing noise in vector directions, but remained below 2.6° with a 90° noise envelope. Thus, the visual system uses the radial morphology of vector directions to determine translational heading and can tolerate large amounts of noise in this pattern. For circular movement, observers were equally accurate with a 2-frame velocity field, 3-frame acceleration displays, and 2-frame and 3-frame direction fields, consistent with the use of the pattern of vector directions to locate the center of rotation. The results indicate that successive independent velocity fields are sufficient for perception of translational and circular heading.     

Electron microscopic and cytochemical study on the role of Golgi elements and plasma membrane of enterocytes in the intestinal lipid transport

Summary Intestinal lipid absorption and transport were investigated in albino rats. The observations point towards the existence of a continuity between plasma membrane invaginations and elements of the Golgi complex on its mature face. They also suggest a segregation of lipid droplets by paired Golgi membranes and plasma membrane invaginations. The following way for lipid transport is deduced: lipid droplets moving inside the smooth endoplasmic reticulum accumulate progressively and are condensed in Golgi cisternae of the forming face. Their limiting membrane ruptures and liberated lipid droplets are segregated by paired Golgi membranes of the mature face or by plasma membrane invaginations. Subsequently the inner of the two segregating membranes disappears while the lipid droplet is moved towards the intercellular space inside a canal communicating with this space. The suggestion is made that the Golgi apparatus is of double origin: one component representing a terminal plication of the endoplasmic reticulum; the second one—a terminal plication of the plasma membrane invagination. This concept explains the ultrastructural and histochemical differences between Golgi membranes of the forming and mature faces of the complex.     

The identification of a DNA polymorphism of the α fibrinogen gene,and the regional assignment of the human fibrinogen genes to 4q26-qter

Summary We have identified a common restriction fragment length polymorphism of the fibrinogen gene with the enzyme TaqI. This polymorphism is probably due to a single base change that creates or destroys a TaqI recognition site about 1000 basepairs from the 3 end of the fibrinogen géne. The frequency of the rare allele in 83 unrelated healthy individuals is 0.33. We have used in situ hybridisation of the fibrinogen cDNA to localise the gene on chromosome 4q29–31. We have confirmed this regional localisation by restriction fragment detection in a human x Chinese hamster somatic cell hybrid which contains a translocated human chromosome 4 with a breakpoint at 4q26. The , , and fibrinogen genes are all present on human chromosome 4q26-qter.     

Molecular characterization of HbH disease in the Cuban population

Summary Molecular characterization of the -thalassemia mutations present in nine HbH subjects from Cuba was achieved by digestion with Bam HI, Bgl II, and Apa I and hybridization with - and -specific probes. The results show that the molecular basis of the genetic defect is quite homogeneous, all the subjects carrying the –^3.7 type I/--^SEA genotype. Variations are observed in the size of the polymorphic fragments.     

Immobilized Lotus tetragonolobus agglutinin binds oligosaccharides containing the Lex determinant

A defined set of oligosaccharides and glycopeptides containing -linked fucose were used to examine the specificity of the immobilized fucose-binding lectin Lotus tetragonolobus agglutinin (LTA1), also known as lotus lectin. Glycans containing the Lewis x determinant (Lex) Gal1-4[Fuc1-3]GlcNAc1-3-R were significantly retarded in elution from high density LTA-Emphaze columns. The lectin also bound the fucosylated lacdiNAc trisaccharide GalNAc1-4[Fuc1-3]GlcNAc. The lectin did not bind glycans containing either sialylLex or VIM-2 determinants, nor did it bind the isomeric Lea, Gal1-3[Fuc1-4]GlcNAc-R. Although 2-fucosyllactose Fuc1-2Gal1-4Glc) was retarded in elution from the columns, larger glycans containing the H-antigen Fuc1-2Gal1-3(4)GlcNAc-R interacted poorly with immobilized LTA. Our results demonstrate that immobilized LTA is effective in isolating glycans containing the Lex antigen and is useful in analyzing specific fucosylation of glycoconjugates. Abbreviations: LTA, Lotus tetragonolobus agglutinin; UEA-1, Ulex europaeus agglutinin-I; LNT, AAL, Aleuria aurantia agglutinin; Gal1-3GlcNAc1-3Gal1-3Glc; LNnT, Gal1-4GlcNAc1-3Gal1-3Glc; Lex, Lewis x antigen; Lea, Lewis a antigen; GDPFuc, guanosine 5-diphosphate--L-fucose     

Primary structure of hemoglobin β-chain fromColumba livia (gray wild pigeon)

Primary structure of -chain of pigeon is presented. It was determined by amino acid sequence analysis of intact -chain and its peptides obtained by the enzymatic and chemical cleavage. Comparison of amino acid sequence of the chain with other available data shows 14 Ile, 61 Lys, and 113 Ile as residues specific to pigeon. One important replacement at ₁₁ contact is 55 MetSer.     

The spermatozoon of Oikopleura dioica Fol (Larvacea,Tunicata)

Summary The spermatozoon of Oikopleura dioica is about 30 m long, with a spherical head, about 1 m wide, a 3 m long and 1 m wide midpiece, and a 25 m long tail with a tapered end piece. The head contains a nucleus with the chromatin volume limited to about 0.1 m³. A small acrosome is found in an anterior inpocketing, and a flagellar basal body in a posterior inpocketing of the nucleus. The midpiece contains a single mitochondrion with the flagellar axoneme embedded in a groove along its medial surface. The flagellar axoneme has the typical 9 + 2 substructure, and the basal body the typical 9+0 substructure. A second centriole and special anchoring fibres are absent.     

Das eigenartige Kopulationsverhalten vonChloromonas saprophila,einer neuen Chlamydomonadacee

Zusammenfassung Chloromonas saprophila n. sp., die in H₂S-haltigem Milieu über verwesendem Laub auftrat, zeichnet sich durch ihr Kopulationsverhalten aus. Die Gameten gleichen jungen vegetativen Zellen und entstehen wie diese zu viert aus einer Mutterzelle. Die Kopulation beginnt bei höherer Individuenzahl unter Gruppenbildung, bei niederer unter Pärchenbildung, Die Geißeln der Gameten sind in den Pärchen zu zweit parallel aneinander gelegt und miteinander verklebt. In den Kopulationsgruppen sind zwei Bündel von Geißeln in entsprechender Zahl vorhanden.Die Gameten verschiedenen Geschlechts stimmen zunächst morphologisch überein, verhalten sich jedoch verschieden: während des Herumschwimmens der Pärchen wird stets der gleiche Gamet vorangetrieben; dieser streift vom Vorderende beginnend seine Membran ab und befestigt sich in der Regel mit seinem Vorderende an der Flanke des behäuteten Gameten; die Geißelpaare trennen sich unterdessen. An der Befestigungsstelle wird die Membran des behäuteten Gameten lokal aufgelöst und sein Protoplast tritt in den des unbehäuteten über.Die reifen Zygoten haben eine glatte, bräunliche Wand und einen kupferroten Inhalt.Der unbehäutete Gamet ist von einer zarten, hyalinen Spezialhülle unbekannter Natur umgeben. Sie zeigt sich auch am Protoplasten des behäuteten dort, wo er sich von der Wand abhebt, und außerdem an den jungen Zygoten und an vegetativen Zellen, bei denen die Membran ausnahmsweise an einzelnen Stellen etwas absteht.     

Variability and structure of natural populations of Elymus caninus (L.) L. based on morphology

Great variability involving 36 quantitative and 31 qualitative characters, as well as the habitats occupied has been shown in 18 populations of Elymus caninus from Poland, based on the detailed population and statistical analyses of morphological characters. The variability of these characters proves that the intraspecific units which have been distinguished on the basis of these characters do not have systematic significance. The two morphotypes of E. caninus (pauciflorum and caninus) described in this study will provide the basis for further genetic studies aimed at establishing their significance for considerations in the systematics of the species.It is the first paper from the series: Biodiversity of wild Triticeae (Poaceae) in Poland.     

Effects of lead and cadmium on chemical composition and total water content of the pupal parasitoid, Pimpla turionellae

The parasitoid Pimpla turionellae L. (Hymenoptera, Ichneumonidae) was fed on Cd, Pb and Cd+Pb-contaminated food (33g Cd, 82g Pb and 33g Cd+82g Pb per gram food fresh weight, respectively). Significant decrease in the total lipid and protein content was found along with an increase in the water content particularly in Cd-contaminated parasitoids.     

On the heterogeneity of the slow reassociating (“unique”) DNA

Summary The slow reassociating fraction of mouse DNA (unique DNA), when allowed to reassociate in 0.14 m sodium phosphate buffer at 50 °C showed a biphasic melting curve with a transition at 78–80 °C. On the basis of this feature, the slow reassociating DNA was separated preparatively into two fractions: unique DNA I and II. Their duplexes showed differences with respect to thermal stability, S1 nuclease resistance and rate of reassociation. About one third of the sequences in each fraction were fraction-specific. The conclusion was drawn that for unique DNA I these should be the low repetitive or single copy related sequences (multigene families) and for unique DNA II—the unrelated single copy sequences or recent families of low repetitive not yet diverged sequences.     

Reproductive Biology of Southwestern Atlantic Wreckfish, Polyprion americanus (Teleostei: Polyprionidae)

We report on the reproductive biology of southwestern Atlantic wreckfish. Females mature first at 77.9cm total length (TL) (10.4 years) and all are mature by 90cm TL (15.2 years). Males mature first at 74.9cm (9 years) and all are mature by 80cm TL (10.9 years). The wreckfish is a gonochoristic multiple spawner and the gonadal cycle is synchronized at the population level. Spawning occurs from late July to early October along the continental slope (<300m). Ovarian fecundity varies from 3 to 11.9 million (135–311 oocytes×g^–1) and increases exponentially with length. Spawning at western boundary current systems, maintained by homing of adults, is a basic requirement for self-sustaining populations of this species.     

Peptide insertions in β-galactosidase activating interface can improve binding in TPEG-Sepharose affinity chromatography

Summary Chimeric -galactosidase fusion proteins containing foreign peptides inserted either at the amino terminus or at inner sites have been studied regarding their purification properties. Whereas fusions at the amino terminal are retained less on TPEG-Sepharose columns than native -galactosidase, the insertion in a specific site of the activating interface increases the binding of the modified -galactosidase. This offers a way to construct more powerful -galactosidase purification tags.     

Characterization of carotene accumulation inUstilago violacea using high-performance liquid chromatography

Quantitative analysis of carotene accumulation in white, pink, pumpkin, orange, and yellow haploid strains ofUstilago violacea by high-performance liquid chromatography indicated that specific patterns of carotene accumulation are primarily responsible for the white, pumpkin, orange, and yellow phenotypes. The yellow strains accumulated primarily -zeacarotene and -carotene. The white strains accumulated primarily the colorless carotene, phytoene, or did not accumulate any carotene at all. Carotene accumulation in pink haploid strains followed the same patterns as for the white, pumpkin, orange, or yellow strains. Pink diploid and disomic strains ofU. violacea with various parental combinations of the color mutations accumulated either cis--zeacarotene and -carotene or only -carotene. The pattern of carotene accumulation in conjunction with the available genetic information for the carotene loci inU. violacea was used as a basis for the construction of a new genetic model for carotene biosynthesis inU. violacea. The model employs three dehydrogenases and one cyclase for the synthesis of -carotene from phytoene, and accounts for the carotene accumulation patterns of either cis--zeacarotene and -carotene or lycopene, -carotene, and -carotene.     

The adult α-globin locus of old world monkeys: An abrupt breakdown of sequence similarity to human is defined by an Alu family repeat insertion site

Summary The haploid genomes of all known primates have two or more adult -globin genes contained within tandemly arranged duplication units. Although the tandem duplication event generating these -globin loci is believed to occur prior to the divergence of primates, a number of length polymorphisms exist within the loci among different primate species. In order to understand the molecular basis of these length polymorphisms, we have cloned and determined the nucleotide sequence of a major portion of the rhesus monkey adult -globin locus. Sequence comparison to human suggests that the length difference between the adult -globin loci of human and Old World monkey is the result of one or more DNA recombination processes, all of which appeared to be related to the transposition of Alu family repeats. First, the finding of a monomeric Alu family repeat at the junction between nonhomology block I and homology block Y of the 2 genecontaining unit in rhesus macaque suggests that the dimeric Alu family repeat, Alu 3, at the orthologous position in human was generated by insertion of a monomeric Alu family repeat into the 3 end of another preexisting Alu family repeat. Second, two Alu family repeats, Alu 1 and Alu 2, exist in human at the 3 end of each of the two X homology blocks, respectively. However, this pair of paralogous Alu family repeats is absent at the corresponding positions in rhesus macaques. This raises interesting questions regarding the evolutionary origin of Alu 1 and Alu 2. Finally, DNA sequences immediately downstream from the insertion site of Alu 2 are completely different between human and rhesus macaque. This last event is similar to DNA rearrangements occurring nearby transposable element(s) in the chromosomes of bacteria, yeast, and plant cells. Its possible role in accelerating the genomic evolution of noncoding or spacer DNA is discussed.     

Modulation of natural killer activity by thymosin alpha 1 and interferon

Summary A single injection of -interferon (-IFN) (30 000 units/mouse), a major biological modifier of natural killer (NK) cytolytic activity, strongly stimulated NK activity in normal mice, as expected, while the same treatment did not statistically alter the NK response in cyclophosphamide (CY)-suppressed animals.We investigated the possibility of thymosin ₁ cooperating with -IFN in boosting NK activity in CY-suppressed animals.The results show that treatment with thymosin ₁ (200 g/kg) for 4 days, followed by a single injection of -IFN 24 h before testing, strongly restored NK activity in CY-suppressed mice. Thymosin ₁ was, moreover, able to accelerate the recovery rate of NK activity in bone marrow reconstituted murine chimeras.Taken together the data support the concept that the synergic effect between thymosin ₁ and -IFN could be the result of effects on differentiation of the NK lineage at different levels.     

Multivariate morphometric study of theCardamine pratensis group (Cruciferae) in the Carpathian and Pannonian area

A multivariate morphometric study of theCardamine pratensis group is presented, based on 84 population samples collected from the Carpathian and Pannonian area in the Czech Republic, Slovakia, Poland, Ukraine, Hungary, and Romania. Among the multivariate methods, principal component analysis, cluster analysis, and classificatory and canonical discriminant analysis were used. The analysis of chromosome numbers from all populations studied showed wide variation. The morphometric study showed that not all groups of populations characterised by their chromosome numbers and geographical criteria are morphologically, and thus taxonomically, distinguishable. Besides the morphologically well characterised speciesCardamine dentata andC. rivularis, the following species were recognised in the area studied:C. matthioli, C. majovskii andC. pratensis. Within the last species, besides the typical populations, two diploid types are provisionally recognised: type ucranica and type rivularis auct..     

Polarities in Mammalian Evolution Seen Through Homologs of the Inner Cell Mass

Embryogenetic pathways differ markedly among monotremes, marsupials, and placentals, and their analysis provides information of fundamental importance to recognition of mammalian evolutionary directions. The cap of cuboidal cells of the marsupial late unilaminar blastocyst, generally known as the embryonic area, probably is induced to form (prior to origin of Hensen's node) by signals from earliest hypoblastic cells (anterior visceral endoderm). The thickened cap is a medullary plate of sauropsid terminology because it includes epiblastic cells presumptive to neurectoderm (including neural crest), Hensen's node, primitive streak, and gut endoderm. The remainder of the definitive embryo (i.e., parts of epidermal origin, including ectodermal placodes) derives from squamous ectoderm (surrounding the medullary plate) of the blastocyst's ill-named trophoblastic area. Amniotic ectoderm develops farther distally within the trophoblastic area. The autapomorphic inner cell mass (ICM) of placental mammals is homologous to medullary plate of the marsupial blastocyst plus morphologically undefined, proximal parts of surrounding ectoderm (of the trophoblastic area). Considerations of early cell lineages in marsupials are greatly affected by recognition that the boundary between future embryonic and extra-embryonic tissues does not match the margin of the medullary plate (i.e., embryonic area). Marsupials and monotremes largely conform to sauropsid early embryogenesis, but placentals express, at earliest developmental stages, innovations unique within Amniota that are linked to early establishment of the brain. Neonatal marsupials and hatchling monotremes are extremely altricial and closely comparable anatomically/physiologically; they share a temporal pattern in combining early morphogenesis of craniofacial features (related to suckling) with deferral of telencephalic completion into postnatal/posthatching life. Placentals contrast greatly in establishing the central nervous system prior to rudiments of the cranial skeleton and associated musculature, and they complete essentials of forebrain development before birth. Comparative evidence from transitory periderm suggests that primordial eutherians had extremely altricial hatchlings or newborns, whichever was the mode of early development. Details remain unknown about the origin of the unique specialization of ICM plus encapsulating trophoblast from the more generalized blastula of ancestral synapsids.