Nuclear matrix involvement in sperm head structural organization

Summary— In the sperm nuclei the DNA is packaged into a highly condensed form and is not organized into nucleosome and solenoid but is bound and stabilized mainly by the protamines that arrange the DNA in an almost crystalline state. As demonstrated for somatic cells, the sperm DNA has been reported to be organized in loop domains attached to the nuclear matrix structures. However, the possible role of the sperm head matrix in maintaining the loop organization in absence of a typical nucleosomal structures has not been fully elucidated. By using in situ nick translation at confocal and electron microscope level, we analyzed the organization of the DNAprotamine complex and its association with the sperm nuclear matrix. The data obtained indicate that the chromatin organization in sperm nuclei is maintained during the sperm condensation by means of interactions with the nuclear matrix at fixed sites. The fine stucture of sperm nucleus and of sperm nuclear matrix, investigated on sections and replicas of freeze-fractured specimens, suggests that the lamellar array, observed by freeze-fracturing in the sperm nuclei, could depend on the inner matrix which presents a regular organization of globular structures possibly involved in the maintenance of chromatin domains in highly condensed sperm nuclei also.     

Tail-to-tail orientation of the Atlantic salmon alpha- and beta-globin genes

We report the cloning of a cDNA and two corresponding -globin genes of the Atlantic salmon (Salmo salar L.) as well as two genes for -globins. Nucleotide sequence analysis of the cDNA shows that the predicted -globin peptide comprises 148 amino acids with a calculated molecular mass of 16,127 Da and an overall amino acid similarity of 40–50% to higher vertebrates and 60–90% to fish sequences. The study of the genomic organization of - and -globin genes shows that, as is the case in Xenopus, the salmon genes are adjacent. Two sets of linked - and -globin genes were isolated and restriction-enzyme polymorphisms indicate that they belong to two distinct loci, possibly as a result of the salmon tetraploidy. In each locus the - and -globin genes are oriented 3 to 3 relative to each other with the RNA coding sequences located on opposite DNA strands. This is the first evidence for this type of arrangement found for globin genes. Moreover, while the linkage found in salmon and Xenopus supports the hypothesis of an initial tandem duplication of a globin ancestor gene, our results raise the question of the actual original orientation of the duplicated genes. Correspondence to: F. Gannon     

Do chimpanzees cooperate in a learning task?

The aim of this study was to assess the ability of chimpanzees (Pan troglodytes) to cooperate in an instrumental task. A specially constructed fruit distributor was presented to a group of six captive chimpanzees. A cooperative response required two chimpanzees: both had to pull a handle simultaneously to make a fruit fall into the cage. The dominant male of the group and an infant produced most of the operant responses, and the male got nearly all the fruits. Other conspecifics avoided the dominant male at the apparatus. Social influences appear to limit the possibility of co-operation between individuals because a certain level of interindividual tolerance is required. The results revealed a significant increase in the number of pulls each time both chimpanzees were together at the apparatus. Operant chimpanzees learn to coordinate their actions in time and space.     

Molecular analysis of two genes between let-653 and let-56 in the unc 22(IV) region of Caenorhabditis elegans

Summary A previous study of genomic organization described the identification of nine potential coding regions in 150 kb of genomic DNA from the unc-22(IV) region of Caenorhabditis elegans. In this study, we focus on the genomic organization of a small interval of 0.1 map unit bordered on the right by unc-22 and on the left by the left-hand breakpoints of the deficiencies sDf9, sDf19 and sDf65. This small interval at present contains a single mutagenically defined locus, the essential gene let-56. The cosmid C11F2 has previously been used to rescue let-56. Therefore, at least some of C11F2 must reside in the interval. In this paper, we report the characterization of two coding elements that reside on C11F2. Analysis of nucleotide sequence data obtained from cDNAs and cosmid subclones revealed that one of the coding elements closely resembles aromatic amino acid decarboxylases from several species. The other of these coding elements was found to closely resemble a human growth factor activatable Na⁺/H⁺ antiporter. Pairs of oligonucleotide primers, predicted from both coding elements, have been used in PCR experiments to position these coding elements between the left breakpoint of sDf19 and the left breakpoint of sDf65, between the essential genes let-653 and let-56.     

Age differences in spatial positioning of males in a chimpanzee unit-group at the mahale mountains National Park,Tanzania

Proximity partner choice by male chimpanzees of various age classes was analyzed in relation to their spatial positioning. Field work was carried out twice at the Mahale Mountains National Park, Tanzania. Proximity data were recorded at 3 and 10m from the focal animal. The data for the proximity between the focal male and other individuals allowed the males to be classified into two categories according to both criteria: early adolescence to young adult, and prime to old age. Between the males, the 3m proximity data permitted a classification into two categories as above, but those for 10m did not. These two spatial distances thus probably have different meanings for the males. The numbers of male proximity partners and proximity with the alpha male also allowed the males to be classified into two categories: early and late adolescence, and young adult to old age. Together, the above results support the classification of males into three age-graded categories: (1) early and late adolescence, (2) young adult, and (3) prime to old age. This does not arise because the males of each category form an age group. Prime or older males are most frequently in proximity, while their juniors consistently attempt to approach them. However, even prime or older males are not equally in proximity with one another. Their proximity partners change as time passes. Probably recognizing such changes, they form coalitions or are in rivalry. The sexual interest of adolescent males is probably a factor stimulating them to separate from their mothers, and to approach older males. Young adult males, even though physically mature, do not have equal proximity relations with older males. They are not yet sufficiently qualified to join the coalitions formed by their seniors.     

Cellular location,activity states,and macromolecular organization of glucoamylase in Clostridium thermosaccharolyticum

By application of immunocytochemical techniques at the electron microscope level, glucoamylase was localized to the cell periphery in Clostridium thermosaccharolyticum during and following growth on starch, sucrose or glucose. Levels of immunolabelling were found to be relatively independent of growth substrate and of phase of growth, whereas previous studies had demonstrated strong dependence of glucoamylase activity on growth conditions; previously high levels of glucoamylase activity had been detected after growth on starch (i.e. during the stationary phase after growth) and only very low activities detected during exponential growth and following growth on glucose. The results presented demonstrate that levels of the glucoamylase protein are independent of measurable enzyme activity, and imply that the protein is constitutive. This indicates that the protein can exist in active and inactive states in the cell. By analogy with similar systems, we consider it likely that maturation or activation of newly synthesized glucoamylase occurs during (or following) transport through the cytoplasmic membrane. Electron microscopy of individual protein molecules which had been subjected to negative staining revealed that the enzyme consists of two domains of approximately equal size which are linked by a hinge region.     

A new heterospecific foraging association between the puddingwife wrasse,Halichoeres radiatus,and the bar jack,Caranx Tuber: evaluation of the foraging consequences

Synopsis The bar jack,Caranx Tuber, was commonly observed to follow individual puddingwife wrasses,Halichoeres radiatus, that were foraging on the substrate. Individuals of both species actively pursued the other to maintain these heterospecific foraging teams, were sometimes attracted to feeding acts initiated by team partners, and the foraging rates of teamed jacks and wrasses were positively correlated. Pilfering of food items was rare, suggesting little, if any, competition cost of this foraging association. The ratio of bites to search in teamed jacks was over three times that when solitary, and jacks were sometimes aggressive to conspecifics attempting to join their team, suggesting that the association is beneficial to the jacks. Both bite and search rates were higher in puddingwifes when teamed with a jack, indicating that the association also benefits the wrasses. Benefits to puddingwifes may be derived directly from attendants because wrasses were sometimes attracted to jack foraging acts. However, increased foraging in wrasses may also be a consequence of heightened motivation to feed owing to heterospecific social facilitation.