Meiofauna associated with a Pacific coral reef in Costa Rica

The meiofauna of two coral reef habitats at Isla del Naño, Costa Rica was studied over a one year period. The dominant groups were: Foraminifera (21.2%), Copepoda (19.7%), Nematoda (19.1%), Gastropoda (16.5%), Polychaeta (7.2%) and Bivalvia (6.6%). The highest diversity was found in coarse, heterogeneous sands with the highest percentage of carbonates. The meiofauna showed a high degree of horizontal aggregation, which is a characteristic pattern for macro- and meiofauna in sediments of variable composition. No vertical variation in distribution was evident, probably due to the deep location of the Redox Potential Discontinuity layer. The total densities of organisms found in this study (99 to 575 ind/10 cm²) are low compared with densities in similar non-reefal sands (7 to 6116), and from fine sediments (80 to 17 000), but are comparable to densities found in other reef areas (39 to 609.5 ind/10 cm²). This is the first report on meiofauna from the eastern Pacific, and the first time that foraminiferans are the dominant group.     

The zygosity in the human HL-A transplantation system

Summary If by serological methods of tissue typing one antigen only is detected in one or both of the loci LA and 4 of the histocompatibility system HL-A, the question arises whether it is homozygous or heterozygous. The probability thereof is calculated. It depends on the frequency of the known and unknown genes in the HL-A-system. If e.g. the HL-A type of an examinee is 1,3,8 this subject could be homozygous 1,3,8,8 or heterozygous (with an unknown antigen X) 1,3,8,X. The frequencies of homozygous and heterozygous individuals are calculated in all possible combinations of the LA and 4 loci. The results justify always for both the LA-and 4 locus the assumption of heterozygosity, with the one exception that the gene HL-A 2 is under consideration. There the calculations result in a value of 49% for homozygosity (2,2) and 51% for heterozygosity (2,X). Neither alternative is in this case essentially more probable.For transplantations generally heterozygosity can be assumed — with the exception of HL-A 2 — and therefore the minor grade of histocompatibility.National Blood Group Reference Laboratory — WHO (Director: Prof. Dr. P. Speiser)     

Time-Dependent Increase in Protein Phosphorylation Following One-Trial Enhancement in Hermissenda

Abstract: One-trial conditioning of the nudibranch mollusk Hermissenda produces short- and long-term changes in excitability (enhancement) of identified sensory neurons. To investigate the biochemical mechanisms underlying this example of plasticity, we have examined changes in protein phosphorylation at different times following the in vitro conditioning trial. Changes in the incorporation of ³²PO₄ into proteins were determined using two-dimensional polyacrylamide gel electrophoresis, autoradiography, and densitometry. Conditioning resulted in increases in levels of several phosphoproteins, five of which, ranging in apparent molecular mass from 22 to 55 kDa, were chosen for analysis. The increased phosphorylation of the 46- and 55-kDa phosphoproteins detected 2 h postconditioning was significantly greater than the level of phosphorylation detected in an unpaired control group, indicating that long-term enhancement is pairing specific. Statistically significant increases in phosphorylation as compared with the control group that received only light were detected immediately after conditioning (5 min) for the 55-, 46-, and 22-kDa phosphoproteins, at 1 h for the 55- and 46-kDa phosphoproteins, and at 2 h for the 55-, 46-, and 22-kDa phosphoproteins. The 46- and 55-kDa phosphoproteins are putative structural proteins, and the 22-kDa phosphoprotein is proposed to be a protein kinase C substrate previously identified in Hermissenda following multitrial classical conditioning. Time-dependent increases in protein phosphorylation may contribute to the induction and maintenance of different memory stages expressed in sensory neurons after one-trial conditioning.     

The Surface Exclusion System of RP1: Investigation of the Roles of trbJ and trbK in the Surface Exclusion, Transfer, and Slow-Growth Phenotypes

The contiguous trbJ and trbK genes of RP1 were cloned individually to study their effects. Surface exclusion was conferred only by trbK and only when gene dosage was high or when trbJ was also present in cis or in trans. This suggests that in the low-copy-number RP1, surface exclusion is due to a two-gene interaction in which trbK is the dominant partner. Among surface exclusion genes, trbJ is novel in yielding a periplasmic product that is also essential for conjugal transfer. This cellular location and the disturbed membrane function that accompanies TrbJ-processing probably accounts for the retarded growth caused by trbJ⁺ clones in Pseudomonas aeruginosa strain PAO.     

Isolation and characterisation of deletion mutants involving the transfer genes of P-group plasmids in Pseudomonas aeruginosa

Summary The P-group plasmids RP1 and R26 are recovered at low frequency following conjugal transfer to B3-lysogens of P. aeruginosa PAO. The rare carbenicillin-resistant transcipients that do arise are usually transfer-defective (Tra^-) and may show the loss of other plasmid borne functions, namely kanamycin-resistance (Km^r) and reduced plating of phage GlOl (Spp⁺). The four phenotypic classes that occur among the Tra^- derivatives are respectively, Tra^- (69–81%), Tra^- Spp^- (12–30%), Tra^- Km^s and Tra^- Km^s Spp^- (0.2–1%), of which the latter three are due to plasmid deletions. This is seen from the sizes of the plasmids carried by these bacteria and from the transductional analysis of the R26-derivatives. Thus, although R26 (MW=52×10⁶ daltons) is too large to be transduced by phage F116L (MW=40×10⁶), this is possible for its Tra^- Km^s and Tra^- Km^s Spp^- derivatives. The phenotypes and frequencies of the various transcipient classes suggests that the gene order Km..Tra..Spp occurs in both RP1 and R26, and that Spp is more closely linked to Tra than is Km. These conclusions are supported by the sizes of the plasmid mutants since deletions spanning the loci Km Tra Spp, Km Tra, and Tra Spp involve the loss of DNA of MW 8-17×10⁶, 5-13×10⁶ and 1-9×10⁶ daltons respectively.Whilst all the transcipients displayed the incompatibility properties of the parent plasmids (Inc⁺), only some retained plasmid surface exclusion (Sfx⁺). Moreover, a strict correlation existed between the Sfx and Spp phenotypes such that the transcipients were either wild type, Sfx^- Spp^-, or displayed an intermediate phenotype for both characters. This suggests that these phenotypes are controlled by closely linked genes or are different manifestations of the same gene function. The deletion map of these various markers in both RP1 and R26 therefore seems to be Km..Tra..Sfx/Spp..Inc.     

Studies of insulin release and rat pancreatic islet metabolism with diastereomers of D-glucose

Studies of insulin release with diastereomers and other analogues of D-glucose demonstrated that only sugars which undergo oxidation to CO₂ stimulate insulin release by the pancreatic islet. None of the non-metabolizable diastereomers of glucose stimulated insulin release in the presence of a substimulatory concentration of glucose for fuel. Although 5.5 mM glucose formed 77% as much CO₂ as 16.7 mM mannose and twice that of 16.7 mM fructose, 5.5 mM glucose did not stimulate insulin release whereas 16.7 mM mannose and fructose did stimulate insulin release. These results indicate that the important stimulus for glucose-induced insulin release involves metabolism of glucose, but that the stimulus does not involve solely a fuel function of glucose.     

Impact of Simulated Microgravity on Oligodendrocyte Development: Implications for Central Nervous System Repair

We have recently established a culture system to study the impact of simulated microgravity on oligodendrocyte progenitor cells (OPCs) development. We subjected mouse and human OPCs to a short exposure of simulated microgravity produced by a 3D-Clinostat robot. Our results demonstrate that rodent and human OPCs display enhanced and sustained proliferation when exposed to simulated microgravity as assessed by several parameters, including a decrease in the cell cycle time. Additionally, OPC migration was examined in vitro using time-lapse imaging of cultured OPCs. Our results indicated that OPCs migrate to a greater extent after stimulated microgravity than in normal conditions, and this enhanced motility was associated with OPC morphological changes. The lack of normal gravity resulted in a significant increase in the migration speed of mouse and human OPCs and we found that the average leading process in migrating bipolar OPCs was significantly longer in microgravity treated cells than in controls, demonstrating that during OPC migration the lack of gravity promotes leading process extension, an essential step in the process of OPC migration. Finally, we tested the effect of simulated microgravity on OPC differentiation. Our data showed that the expression of mature oligodendrocyte markers was significantly delayed in microgravity treated OPCs. Under conditions where OPCs were allowed to progress in the lineage, simulated microgravity decreased the proportion of cells that expressed mature markers, such as CC1 and MBP, with a concomitant increased number of cells that retained immature oligodendrocyte markers such as Sox2 and NG2. Development of methodologies aimed at enhancing the number of OPCs and their ability to progress on the oligodendrocyte lineage is of great value for treatment of demyelinating disorders. To our knowledge, this is the first report on the gravitational modulation of oligodendrocyte intrinsic plasticity to increase their progenies.     

The roles of carbonic anhydrases IX and XII in cancer cell adhesion,migration, invasion and metastasis

The main function of carbonic anhydrases (CAs) in cancer cells is the pH regulation through a conversion of H₂O and CO₂ to H⁺ and HCO₃⁻. However, the data of in vitro and in vivo studies have demonstrated that transmembrane isoforms of CA IX and CA XII are involved in various steps of cancer cell migration, invasion and metastasis. According to literature, inhibition of these CAs can affect the expression of multiple proteins. Some scientific groups have reported the possible interactions between CA IX and E-cadherin–catenin system, CA IX and integrins, CA IX, CA XII and ion transporters, which all are highly involved in cell-to-cell adhesion, the formation of membrane protrusions and focal adhesions. Nevertheless, CA IX and CA XII have a high impact on tumour growth and metastases formation. The data discussed in this review are quite recent. It highly support the role of CA IX and CA XII in various cancer metastasis processes through their interactions to other invasion proteins. Nevertheless, all findings show the great potential of these CAs in the context of research and application in clinical use.