Synapsis in grasshopper bivalents heterozygous for centric shifts.

Analysis of surface-spread synaptonemal complexes of zygotene and pachytene spermatocytes was carried out on centric-shift heterozygotes of grasshoppers. These rearrangements affected the M7 chromosome in Chorthippus vagans and the M6 and S8 chromosomes in Chorthippus apricarius. The shifts in the latter two chromosomes were also associated with C-heterochromatin variations between homologous chromosomes. Rearranged chromosomes proceeded directly to heterosynapsis without an apparent intervening homosynaptic phase in M7 bivalents of Ch. vagans and M6 bivalents of Ch. apricarius. In the latter case, axial equalization of the heterochromatin polymorphism was also achieved. On the other hand, asynapsis of the intercentromeric regions throughout pachytene was the rule in the centric shift involving the S8 chromosome of Ch. apricarius. In the three cases analysed, the production of unbalanced gametes in the heterozygotes is precluded either by the lack of chiasma formation in heterosynapsed rearranged segments or by the lack of pairing between such segments. Chiasmata were limited to the homologous regions of the heteromorphic bivalents.     

Parental care in the rocky intertidal: a case study of adaptation and exaptation in Mediterranean and Atlantic blennies

Summary The main features of the behavioural ecology of rocky intertidal species are compared both within families — though concentrated on blennies — and between habitats. It is suggested that, at the behavioural level, the reduction of vertical and swimming elements in the male sexual and agonistic displays of Blennioidei may constitute an adaptation to typical intertidal conditions, especially in those species that inhabit areas exposed to strong wave action. The other aspect which is discussed is the prevalence of parental care in rocky intertidal fishes. In these fishes parental care is much more frequent than for marine fishes as a whole. Taken alone, this could also suggest that guarding evolved as an adaptation during the process of colonization of these habitats. The hypothesis proposed in this paper is that guarding was already present in the ancestors of the resident species, at least in the majority of cases. Many differences in interhabitat studies may express the action of the environment, not as an agent of natural selection, but as a filter, which prevented some groups from invading a given habitat and, at the same time, made colonization easier for other groups. When a number of taxa that colonized a given habitat display clear similarities in their behaviour and their biology, adaptation is not necessarily demonstrated. There is evidence in the literature to support the hypothesis that those traits were already present in the ancestors of the rocky intertidal resident fishes, thus being best viewed as exaptations.     

The larval midgut of the cassava hornworm (Erinnyis ello)

Summary Columnar cells of the larval midgut of the cassava hornworm, Erinnyis ello, display microvilli with vesicles pinching off from their tips (anterior and middle midgut) or with a large number of double membrane spheres budding along their length (posterior midgut). Basal infoldings in columnar cells occur in a parallel array with many openings to the underlying space (posterior midgut) or are less organized with few openings (anterior and middle midgut). Goblet cells have a cavity, which is formed by invagination of the apical membrane and which occupies most of the cell (anterior and middle midgut) or only its upper part (posterior midgut). The infolded apical membrane shows modified microvilli, which sometimes (posterior midgut) or always (anterior and middle midgut) contain mitochondria. The cytoplasmic side of the membrane of the microvilli that contain mitochondria are studded with small particles. The results suggest that the anterior and middle region of the midgut absorbs water, whereas the posterior region secretes it. This results in a countercurrent flux of fluid, which is responsible for the enzyme recovery from undigested food before it is expelled. Intermediary and final digestion of food probably occur in the columnar cells under the action of plasma membrane-bound and glycocalix-associated enzymes.     

Bone marrow transplantation: current results in leukemia

Bone marrow transplantation offers two potential therapeutic advantages over more conventional therapy of leukemia. It allows more intensive treatment to be given without regard to marrow toxicity and allows in the case of allogeneic marrow an additional immunotherapeutic effect through graft-versus-host disease (GVHD). Initially, allogeneic transplants in HLA matched sibling donors were only employed in end-stage patients. Although there were encouraging results in terms of long-term therapeutic effects, the overall mortality was prohibitive. Subsequently, patients were transplanted in remission with a marked improvement in overall survival in both acute lymphocytic leukemia and acute non-lymphocytic leukemia. The major obstacles to further improvement in the therapeutic effects of this procedure have been identified (i.e., GVHD, viral infection, and relapse in ALL) and are subject to intensive investigations that already show encouraging results. Syngeneic marrow transplantation is limited for obvious reasons, but early results have shown significant therapeutic effects, in particular, in chronic myelogenous leukemia. These results have encouraged others to use autologous bone marrow. Marrow contamination with unseen tumor cells is being approached by pharmacologic and immunologic techniques designed to "purge" marrow of tumor cells. Animal and initial clinical studies have been encouraging.     

Peroxidases in Relation to Removal of Dormancy and Germination of Apple Embryos

The changes in germination, peroxidase activity and isoperoxidase spectrum have been studied in apple embryos at 5°C (stratification) and at 20°C in the presence or absence of seed coats. The embryo dormancy is progressively released at 5°C, but not at 20°C. The peroxidase activity in embryos covered with seed coats is very low at 5°C as well as at 20°C which corresponds to a restricted number of isoenzymes. In isolated embryos the peroxidase activity increases significantly. This is due to an increase in both the number and the activity of the isoperoxidases and it is more pronounced at 20°C than at 5°C. The obtained results suggest that the soluble peroxidases are not involved in the process of the release of embryo dormancy. The variations observed are attributed to the growth process following germination, which can occur even at low temperature.     

Dihydroisocoumarins and phthalide from wood samples infested by fungi

Wood samples, infested by fungi during storage, were shown to contain, besides the known 5-methyl-mellein, additional (3R)-8-hydroxy-3-methyl-3,4-dihydroisocoumarins substituted by 7-methyl, 5-formyl, 5-carboxy, 5-hydroxy, 5-methoxy, 6-methoxy-5-methyl and 6,7-dimethoxy-5-methyl groups, as well as 6-formyl-7-hydroxy-5-methoxy-4-methylphthalide. Several 2-methylchromanones were synthesized in order to show that this class of compounds can be distinguished from 3-methyl-3,4-dihydroisocoumarins by MS.     

The phosphorus efficiency of three annual legumes

Summary Trifolium subterraneum, Trifolium glomeratum andOrnithopus compressus were grown in soil and solution culture at varying P concentrations. Efficiency of P utilization was determined using the following criteria: (1) The ability to produce tops dry matter with a given amount of applied P, (2) Tops dry matter produced per unit of P taken up, (3) Tops dry matter produced at a constant plant P level and (4) Phosphorus uptake per unit root weight. The order of efficiency varied according to the crieteria used. Using the agronomic definition (1), Serradella was the most efficient species at 70 days. The need to clearly define what is meant by an efficient species is demonstrated.     

B-chromosome polymorphism and interchromosomal chiasma interference in Eyprepocnemis plorans (Acrididae; Orthoptera)

Using the C-banding technique, the morphology and meiotic behaviour of four different types of B-chromosomes present in several populations of Eyprepocnemis plorans have been studied. The possible relationship between these four types is discussed. The analysis of chiasma frequency in A and B-chromosomes suggests the existence of interchromosomal interference and demonstrates that the chiasma frequency of B-s depends on the genetic background of the individual carrying them.