Selection of homeotic proteins for binding to a human DNA replication origin

We have previously shown that a cell cycle-dependent nucleoprotein complex assembles in vivo on a 74 bp sequence within the human DNA replication origin associated to the Lamin B2 gene. Here, we report the identification, using a one-hybrid screen in yeast, of three proteins interacting with the 74 bp sequence. All of them, namely HOXA13, HOXC10 and HOXC13, are orthologues of the Abdominal-B gene of Drosophila melanogaster and are members of the homeogene family of developmental regulators. We describe the complete open reading frame sequence of HOXC10 and HOXC13 along with the structure of the HoxC13 gene. The specificity of binding of these two proteins to the Lamin B2 origin is confirmed by both band-shift and in vitro footprinting assays. In addition, the ability of HOXC10 and HOXC13 to increase the activity of a promoter containing the 74 bp sequence, as assayed by CAT-assay experiments, demonstrates a direct interaction of these homeoproteins with the origin sequence in mammalian cells. We also show that HOXC10 expression is cell-type-dependent and positively correlates with cell proliferation.     

Significant reduction in HIV-1 plasma viral load but not in proviral infected cells during sub-optimal antiretroviral therapy

Attempts to eradicate HIV infection through highly active antiretroviral therapy (HAART) in the very early stages of the infection have failed due to the resumption of viral replication from unknown reservoirs. It has been postulated that antiretroviral therapy capable of suppressing viral replication, as shown by reduction of HIV-RNA copies in plasma and lymph nodes, should have less effect on the number of HIV-DNA carrying cells in the same districts. To test this hypothesis, plasma viremia and the proportion of provirally infected cells in peripheral blood and in lymph nodes were measured in patients at 3 and 6 months of treatment with zidovudine plus lamivudine. All patients showed a significant decrease in plasma viremia at 3 months that was maintained at 6 months (mean values of 1.6 +/- 0.6 log10 from baseline). Conversely the proportion of HIV-DNA carrying cells slightly declined at 3 months but remained substantially stable thereafter both in peripheral blood and in lymph nodes. Taken together these data suggest that this therapeutic regimen, although sub-optimal, is effective in significantly reducing the virus production by productively infected cells but does not seem to substantially affect the load of provirally infected cells.     

Feeding biology of a guild of benthivorous fishes in a sandy shore on south-eastern Brazilian coast

The feeding biology of eight species of benthivorous fishes was studied in a sandy shore at Anchieta Island, south-eastern Brazilian coast. The fishes fed mainly on Amphipoda and Mysidacea crustaceans. The diet of the most abundant species, the drum Umbrina coroides, was analyzed in three standard length classes (20-55, 56-90 and 91-135 mm). This sciaenid showed an ontogenetic diet shift from Mysidacea to Amphipoda. The feeding behaviour of the sciaenid U. coroides and the gerreid Eucinostomus gula was recorded while snorkeling. During their foraging both species uncovered small organisms buried in the sand. Notwithstanding general similarities in diet, U. coroides and E. gula presented differences in feeding behaviour and morphology. Two carangid species of the genus Trachinotus differed in diet composition and consumed a larger array of food items than the remaining fish species. Differences in diet and feeding activity between the remaining benthivorous species were noted. These differences possibly reduce overlap in resource use and favour the coexistence of guilds of benthivorous fishes on sandy shores.     

Serum immunoglobulin type G concentrations in calves produced by IVF and delivered by elective cesarean section

Colostrum ingestion by neonatal calves is widely recognized to provide passive transfer of immunity. In this study immunoglobulin absorption from colostrum was evaluated in 54 IVF-produced calves. The IVF calves were delivered by Cesarean section on Days 275 to 277 of gestation, 24 h after the dams had been administered 30 mg dexamethasone. The calves suckled bottles or were force-fed 6 L of colostrum in the first 12 h of life. Colostrum was obtained from the first post-calving milking of recipient dams or from frozen storage reserves if dam secretion was not adequate. Immunoglobulin type G (IgG) content of both sources of colostrum was determined. Serum samples from the calves were collected at 0, 12 and 24 h of age and analyzed for IgG. Twenty dairy calves born vaginally served as the controls and were subjected to the same colostrum management protocol except that the colostrum was obtained only from frozen post-calving milk of dairy cows from the same farm. The control calves were also subjected to the same sampling protocol. The IVF group of calves ingested more IgG (P < 0.0001) and absorbed more IgG by 24 h of age (P < 0.0001) than their control group counterparts. Absorption of IgG was analyzed by comparing the g/kg body weight of IgG with serum IgG values at corresponding times after birth. Colostrum absorption efficiency was the same for both IVF and control groups of calves at 12 and 24 h of age. There was a maximum IgG dose above which additional increases in serum IgG were not realized. The slightly premature, Cesarean delivered IVF calves absorbed IgG from colostrum similarly to control calves delivered vaginally.     

Herbicide-resistant sugarcane (Saccharum officinarum L.) plants by Agrobacterium-mediated transformation

The presence of undesirable plants in sugarcane (Saccharum officinarum L.) plantations reduces crop yields. Using genetic engineering as a complement for traditional breeding methods it is possible to introduce herbicide-resistant traits into Saccharum germplasm. Transgenic sugarcane plants resistant to phosphinothricine (PPT), the active compound of the commercial herbicide BASTA were generated by Agrobacterium tumefaciens-mediated transformation. Meristematic sections of sugarcane were treated with anti-necrotic compounds to minimize oxidative bursts and used as explants. Four transformation protocols were assessed and the transformation frequencies reached 10–35%. The regeneration rate was high and did not appear to be affected by the transformation procedure. Southern blot analysis of several transformed plants indicated the integration per genome of one or two intact copies of the bar gene which encodes PPT acetyltransferase and confers resistance to BASTA. The levels of BASTA resistance were evaluated under greenhouse and small-plot conditions. Received: 8 November 1997 / Accepted: 22 November 1997