Ultrastructural features of gametogenesis during the life cycle in Branchiura sowerbyi Beddard (Oligochaeta,Tubificidae)

An ultrastructural analysis of the gametogenetic phases in Branchiura sowerbyi, a tubificid oligochaete, has been accomplished. These phases mostly conform to the usual pattern for the family, however, some interesting peculiarities are pointed out. The regression of sexual apparatus after reproductive period and its regeneration up to a new period of sexual maturity, has been followed throughout the year.     

Effects of sulphuric acid exposure on the behaviour of largemouth bass,Micropterus salmoides

Synopsis Young-of-the-year largemouth bass,Micropterus salmoides, were exposed to four concentrations of sulphuric acid (pH levels 7.2, 6.1, 4.8, and 3.7) for 30 days, and the frequencies of feeding acts and activity bouts, and time budgets were recorded. Juveniles at pH 6.1 and at pH 4.8 performed the two feeding acts, bites and orientations, more often, and spent more time feeding than bass at pH 7.2. Bass at pH 3.7, however, reduced feeding, and spent a significantly larger portion of their time hovering in the water column. Frequencies of comfort and agonistic acts increased with a decline in pH. Alterations of behavioural repertoires of young-of-the-year largemouth bass were useful indicators of sulphuric acid exposure.     

The Putative Oncogene Pim-1 in the Mouse: Its Linkage and Variation among t Haplotypes

Pim-1, a putative oncogene involved in T-cell lymphomagenesis, was mapped between the pseudo-alpha globin gene Hba-4ps and the alpha-crystallin gene Crya-1 on mouse chromosome 17 and therefore within the t complex. Pim-1 restriction fragment variants were identified among t haplotypes. Analysis of restriction fragment sizes obtained with 12 endonucleases demonstrated that the Pim-1 genes in some t haplotypes were indistinguishable from the sizes for the Pim-1b allele in BALB/c inbred mice. There are now three genes, Pim-1, Crya-1 and H-2 I-E, that vary among independently derived t haplotypes and that have indistinguishable alleles in t haplotypes and inbred strains. These genes are closely linked within the distal inversion of the t complex. Because it is unlikely that these variants arose independently in t haplotypes and their wild-type homologues, we propose that an exchange of chromosomal segments, probably through double crossingover, was responsible for indistinguishable Pim-1 genes shared by certain t haplotypes and their wild-type homologues. There was, however, no apparent association between variant alleles of these three genes among t haplotypes as would be expected if a single exchange introduced these alleles into t haplotypes. If these variant alleles can be shown to be identical to the wild-type allele, then lack of association suggests that multiple exchanges have occurred during the evolution of the t complex.     

Initiation of primary cell cultures from human intracranial tumors on extracellular matrix from bovine corneal endothelial cells

Tissue specimens from 105 human gliomas and 57 human meningiomas were obtained at surgery, dissociated into single cells and small cell aggregates and then plated onto plain plastic tissue culture dishes and dishes which had been precoated with an extracellular matrix (ECM) derived from bovine corneal endothelium. In 80% of the glioma cases we observed a marked improvement in initial plating efficiency, colony formation and speed of attachment when cells were plated on ECM. In 5 cases cells attached only to the ECM-coated dishes but remained afloat in the untreated dishes. In addition it could be noted that over the first 2 days, those cells which had been initiated on ECM showed more signs of morphological differentiation, i.e., extension of cytoplasmic processes or formation of fiber networks between cell groups. If adaptation occurred and proliferation began in vitro, either immediately or after a several days' lag phase, both the ECM-cultured cells as well as those which slowly had adapted to culture on plastic could be passed on to untreated culture ware and perpetuated thereon. In the case of well-differentiated low-grade gliomas where no growth in culture took place, the cultures on ECM could at least be used for initial experiments in the primary cultures (P0). Meningiomas usually attached well to both, plastic or ECM. In 50% of our cases the plating efficiency was higher on ECM but after successful initial culture, the delay until the cells on plastic reached confluence in comparison with those on ECM was 1 or 2 days. Again there were 2 cases in which the cells would not plate on plastic. Here the cells which after 1 day were still afloat plated to more than 80% within the first 2 h after transfer to ECM. In all cases the cells from plastic and ECM cultures were indistinguishable and could be passed onto untreated dishes henceforth. In later culture stages ECM offers several advantages: It is easier to shift cells to serum-free defined culture conditions, the cells will grow at a faster rate on ECM when in higher passages and the maximal number of passages possible is higher on ECM.