DNA content of spermatozoa in different genetic lines of turkeys

The variability of DNA content in turkey spermatozoa of four different lines and its correlation with body weight and sperm concentration were studied. In lines selected for lower body weight the DNA content was 2.034 and 2.036 pg per spermatozoon. In lines selected for higher body weight the DNA content was 2.267 and 2.370 pg per spermatozoon. Sperm concentration in 1 mm³ of semen, however, was higher in lines with a lower body weight (6.08–6.21 million) in comparison with lines selected for higher body weight (5.46–5.67 million). The correlations between the DNA content and sperm concentration were negative (r ranged from ?.457 to ?.860).     

Mutational analysis of the Bradyrhizobium japonicum common nod genes and further nod box-linked genomic DNA regions

Summary By insertional and deletional marker replacement mutagenesis the common nod region of Bradyrhizobium japonicum was examined for the presence of additional, essential nodulation genes. An open reading frame located in the 800 bp large intergenic region between nodD1 and nodA did not appear to be essential for nodulation of soybean. Furthermore, a strain with a deletion of the nodI- and nodJ-like genes downstream of nodC had a Nod⁺ phenotype. A mutant with a 1.7 kb deletion immediately downstream of nodD1 considerably delayed the onset of nodulation. This region carried a second copy of nodD (nodD2). A nodD1-nodD2 double mutant had a similar phenotype to the nodD2 mutant. Using a 22-mer oligonucleotide probe partially identical to the nod box sequence, a total of six hybridizing regions were identified in B. japonicum genomic DNA and isolated from a cosmid library. Sequencing of the hybridizing regions revealed that at least three of them represented true nod box sequences whereas the others showed considerable deviations from the consensus sequence. One of the three nod box sequences was the one known to be associated with nodA, whereas the other two were located 60 to 70 kb away from nif cluster I. A deletion of one of these two sequences plus adjacent DNA material mmutant 308) led to a reduced nodulation on Vigna radiata but not on soybean. Thus, this region is probably involved in the determination of host specificity.Dedicated to Prof. Giorgio Semenza on the occasion of his 60th birthday     

Endoparasitic flies,pollen-collection by bumblebees and a potential host-parasite conflict

Summary Conopid flies (Conopidae, Diptera) are common larval parasites of bumblebees. The larva develops inside the abdomen of workers, queens and males. Development is completed within 10–12 days after oviposition when the host is killed and the parasite pupates in situ. Development results in parasitised bees becoming unable to carry large loads of nectar, as the conopid larvae reside where the honey crop is normally located. Furthermore, an addition to the bee's unloaden body mass is likely (average larval weight reached at pupation by the common parasite species Sicus ferrugineus: ±SD 36.3±12.3 mg, n=59; by Physocephala rufipes: 55.8±16.9 mg, n=108). We here asked whether the propensity of workers of the bumblebee Bombus pascuorum to collect nectar rather than pollen is related to the presence of conopid larvae. For samples of bees (n=2254 workers) collected over 3 years of field studies in northwestern Switzerland, there was no difference in the frequency of bees caught as pollen collectors among parasitised (38.1% of cases, n=210) as compared to non-parastised bees (43.9%, n=360) ( ²=1.83, n.s.). However, compared to the non-parasitised bees (n=360), those hosts containing a third (last) instar larva (n=9) were less likely to collect pollen than expected by chance ²=6.91, P=0.003. Similarly, hosts with short survival time between capture and being killed by the developing larva (which hence must have harboured a late instar parasite at time of capture) were less likely to collect pollen (8%, n=25) than those found not parasitised (37.6%, n=891 ²=9.16, P<0.001). Late instar larvae grow so big that they fill the entire abdomen. Although there was also a tendency for presumably older bees to collect less pollen, this is unlikely to explain the observations. We also discuss whether these changes in foraging behaviour of bumblebees may reflect a host-parasite conflict over the type of resource to be collected.     

Differential expression and localization of brain-type and mitochondrial creatine kinase isoenzymes during development of the chicken retina: Mi-CK as a marker for differentiation of photoreceptor cells

The expression and the cellular- as well as subcellular-distribution of brain-type B-CK and mitochondrial Mi-CK during development of the chicken retina was studied by immunoblotting, immunofluorescence and immunogold methods. B-CK expression and accumulation in retina was high from early stages of embryonic development on, decreased slightly around hatching and remained high again during adulthood. At early stages of development (days 2-5), B-CK was more or less evenly distributed over the entire retina with the exception of ganglion cells, which were stained more strongly for B-CK than other retinal precursor cells. Then, at around day 10, the beginning of stratified immunostaining by anti-B-CK antibody was noted concomitant with progressing differentiation. Finally, a dramatic increase in staining of the differentiating photoreceptor cells was seen before hatching (day 18) with weaker staining of other cell types. At hatching, as in the adult state, most of the B-CK was localized within rods and cones. Thus, during retinal development marked changes in the immunostaining pattern for B-CK were evident. By contrast, Mi-CK expression was low during development in ovo and rose just before hatching with a predominant accumulation of this isoenzyme within the ellipsoid portion of the inner photoreceptor cell segments. Mi-CK accumulation in the retina coincided with functional maturation of photoreceptors and therefore represents a good marker for terminal differentiation of these cells. B-CK, present from early stages of retina development, seems to be relevant for the energetics of retinal cell proliferation, migration and differentiation, whereas the simultaneous expression of both B- and Mi-CK around the time of hatching indicates a coordinated function of the two CK isoforms as constituents of a PCr-circuit involved in the energetics of vision, which, in autophagous birds, has to be operational at this point in time.     

Glycosaminoglycan synthesis is depressed during mitosis and elevated during early G1

[35S]Sulfate incorporation was measured in populations of Chinese hamster ovary cells enriched for mitotics, early G1 cells, and interphase monolayers or suspensions. Incorporation was determined by biochemical analysis of extracts and quantitative autoradiography of thick sections. 90% of [35S]sulfate was incorporated into glycosaminoglycan (GAG). Incorporation was depressed fourfold in mitotics and stimulated by from two- to three-fold in early G1 cells relative to mixed interphase cells. GAG synthesis was maintained into late G2. Thus, the rate of GAG biosynthesis was correlated temporally with the detachment and reattachment of cells to substrate. Inhibitors of protein synthesis brought about the rapid arrest of GAG biosynthesis. However, xylosides, which bypass the requirement for core protein, did not bring oligosaccharide sulfation in mitotics to interphase levels. These observations indicate an inhibition of Golgi processing and are consistent with a generalized defect of membrane vesicle-mediated transport during mitosis.     

Structure of the segmentation gene paired and the Drosophila PRD gene set as part of a gene network

The sequence of paired, a pair-rule gene required for segmentation in Drosophila, is presented. A search for genes with domains homologous to the paired gene was initiated and three homologues from a set of 12 were characterized with respect to temporal or spatial expression and sequence homologies. All four are transcribed in early development, one in the oocyte and during cleavage stages in the form of a gradient. In addition to the prd-specific his-pro repeat, some of the 12 genes contain M-repeats and two new types of homeo boxes not detectable by hybridization with the two known classes of homeo boxes. The observed linking of gene sets through combinations of homologies coding for protein domains is consistent with a general network concept of gene action.     

Mechanisms of blood flow during pneumatic vest cardiopulmonary resuscitation

Mechanisms of blood flow during cardiopulmonary resuscitation (CPR) were studied in a canine model with implanted mitral and aortic flow probes and by use of cineangiography. Intrathoracic pressure (ITP) fluctuations were induced by a circumferential pneumatic vest, with and without simultaneous ventilation, and by use of positive-pressure ventilation alone. Vascular volume and compression rate were altered with each CPR mode. Antegrade mitral flow was interpreted as left ventricular (LV) inflow, and antegrade aortic flow was interpreted as LV outflow. The pneumatic vest was expected to elevate ITP uniformly and thus produce simultaneous LV inflow and LV outflow throughout compression. This pattern, the passive conduit of "thoracic pump" physiology, was unequivocally demonstrated only during ITP elevation with positive-pressure ventilation alone at slow rates. During vest CPR, LV outflow started promptly with the onset of compression, whereas LV inflow was delayed. At compression rates of 50 times/min and normal vascular filling pressures, the delay was sufficiently long that all LV filling occurred with release of compression. This is the pattern that would be expected with direct LV compression or "cardiac pump" physiology. During the early part of the compression phase, catheter tip transducer LV and left atrial pressure measurements demonstrated gradients necessitating mitral valve closure, while cineangiography showed dye droplets moving from the large pulmonary veins retrograde to the small pulmonary veins. When the compression rate was reduced and/or when intravascular pressures were raised with volume infusion, LV inflow was observed at some point during the compressive phase. Thus, under these conditions, features of both thoracic pump and cardiac pump physiology occurred within the same compression. Our findings are not explained by the conventional conceptions of either thoracic pump or cardiac compression CPR mechanisms alone.     

AgTHR4, a new selection marker for transformation of the filamentous fungusAshbya gossypii, maps in a four-gene cluster that is conserved betweenA. gossypii andSaccharomyces cerevisiae

Single-read sequence analysis of the termini of eight randomly picked clones ofAshbya gossypii genomic DNA revealed seven sequences with homology toSaccharomyces cerevisiae genes (15% to 69% on the amino acid level). One of these sequences appeared to code for the carboxy-terminus of threonine synthase, the product of theS. cerevisiae THR4 gene (52.4% identity over 82 amino acids). We cloned and sequenced the complete putativeAgTHR4 gene ofA. gossypii. It comprises 512 codons, two less than theS. cerevisiae THR4 gene. Overall identity at the amino acid sequence level is 67.4%. A continuous stretch of 32 amino acids displaying complete identity between these two fungal threonine synthases presumably contains the pyridoxal phosphate attachment site. Disruption of theA. gossypii gene led to threonine auxotrophy, which could be complemented by transformation with replicating plasmids carrying theAgTHR4 gene and variousS. cerevisiae ARS elements. Using these plasmids only very weak complementation of aS. cerevisiae thr4 mutation was observed. Investigation of sequences adjacent to theAgTHR4 gene identified three additional ORFs. Surprisingly, the order and orientation of these four ORFs is conserved inA. gossypii andS. cerevisiae.