Community structure of Pleistocene coral reefs of Curaçao, Netherlands Antilles

The Quaternary fossil record of living coral reefs is fundamental for understanding modern ecological patterns. Living reefs generally accumulate in place, so fossil reefs record a history of their former biological inhabitants and physical environments. Reef corals record their ecological history especially well because they form large, resistant skeletons, which can be identified to species. Thus, presence-absence and relative abundance data can be obtained with a high degree of confidence. Moreover, potential effects of humans on reef ecology were absent or insignificant on most reefs until the last few hundred years, so that it is possible to analyze "natural" distribution patterns before intense human disturbance began. We characterized Pleistocene reef coral assemblages from Curacao, Netherlands Antilles, Caribbean Sea, focusing on predictability in species abundance patterns from different reef environments over broad spatial scales. Our data set is composed of >2 km of surveyed Quaternary reef. Taxonomic composition showed consistent differences between environments and along secondary environmental gradients within environments. Within environments, taxonomic composition of communities was markedly similar indicating nonrandom species associations and communities composed of species occurring in characteristic abundances. This community similarity was maintained with little change over a 40-km distance. The nonrandom patterns in species abundances were similar to those found in the Caribbean before the effects of extensive anthropogenic degradation of reefs in the late 1970s and early 1980s. The high degree of order observed in species abundance patterns of fossil reef coral communities on a scale of tens of kilometers contrasts markedly with patterns observed in previous small-scale studies of modern reefs. Dominance of Acropora palmata in the reef crest zone and patterns of overlap and nonoverlap of species in the Montastraea ''annularis'' sibling species complex highlight the tendency for distribution and abundance patterns of Pleistocene corals to reflect environmental preferences at multiple spatial scales. Wave energy is probably the most important physical environmental variable structuring these coral communities. The strong similarity between ancient and pre-1980s Caribbean reefs and the nonrandom distribution of coral species in space and time indicate that recent variability noted at much smaller time scales may be due to either unprecedented anthropogenic influences on reefs or fundamentally different patterns at varying spatio-temporal scales

Induction of white cell proliferation due to haematopoietic growth factors is associated with an increase in multiple forms of dihydrofolate reductase in non-neutropenic cancer patients

Objective: Granulocyte-colony stimulating factor (G-CSF) and granulocyte macrophage-colony stimulating factor (GM-CSF) are frequently used in cancer patients to overcome the granulocytopenic effects of chemotherapy, and also to mobilize the stem cells. The mobilized stem cells are collected from the peripheral blood and used for transplantation following high doses of chemotherapy. However, the molecular mechanism by which these colony stimulating factors (CSFs) bring about proliferation of myeloid precursor cells is not clearly known. Dihydrofolate reductase (DHFR), which has an established role in DNA synthesis, could be a link between administration of CSF and stem cell proliferation. The purpose of this study was to investigate whether CSFs induce white cell proliferation by producing multiple forms of DHFR.Methods: Twelve patients with non-haematological malignancies were treated with either G-CSF or GM-CSF to mobilize stem cells. Nine healthy subjects were treated with placebo as controls. Blood samples were obtained before and after stimulation with CSFs or placebo. White blood cells were separated and concentrations of both active DHFR and immunoreactive nonfunctional form of DHFR were determined in their cytoplasm using methotrexate-binding assay and enzyme-linked immunosorbent assay, respectively. Total leucocytes count (TLC) was also monitored before and after stimulation with CSFs or placebo.Results: There was a significant (P \u3c 0.05) increase in concentration of immunoreactive nonfunctional form of DHFR and TLC following stimulation with CSFs. There was an increase in concentration of active DHFR as well, however, this did not reach statistical significance. In the placebo-treated subjects, no significant increase in active DHFR, immunoreactive nonfunctional form of enzyme or TLC was observed. However, it was noticed that the base-line values of active DHFR and immunoreactive nonfunctional form of enzyme in leucocytes of cancer patients were higher than the base-line values in leukocytes of normal healthy subjects.Conclusion: Our data suggest that colony stimulating factors induce white cell proliferation by increasing levels of multiple forms of DHFR

Bacterial isolates from neutropenic febrile pediatric patients and their sensitivity patterns to antibiotics

Patients on cytotoxic therapy often develop neutropenia and fever. Our interest was to identify the common pathogens isolated from such patients and to study the sensitivity patterns of these organisms to the antibiotics used in their treatment. Thus, guidelines can be established by hospitals to identify which antibiotics can be used in the treatment of these patients when the results of cultures and sensitivities are not available. We conducted a retrospective study of neutropenic pediatrics presenting to AKUH from July, 1990 to June, 1996. A total of 153 isolates in 35 different patients were studied. Samples for culture were taken from the sites at risk. The majority of samples consisted of blood, stool, pus and urine. Twenty stool samples were also sent for microscopy. Malignancies were both hematological and non-hematological. Gram negatives were isolated in 52.9%, gram positives in 33.9% and parasites in 13.2%. Salmonella paratyphi B was the most commonly isolated organism, followed by Pseudomonas aeroginosa, Giardia lamblia was the most common parasite. Sensitivity patterns of these organisms to antibiotics studied showed that Escheria coli had the lowest sensitivity rate being only 40% sensitive to Aztreonam and 64% sensitive to Ofloxacillin. A comparison was made between our findings and those reported in literature, as well as the risk factors for developing neutropenia. A guide to management is also discussed