Growth of bone marrow CFU-GM in a case of cyclical neutropenia. Preliminary report

We studied bone marrow CFU-GM growth behaviour of a 9-year-old male child with cyclic neutropenia. The cultures were performed on day 0 and on day 13 of cyclic oscillation, in order to study some correspondences between CFU-GM culture parameters and the phases of a whole cyclic oscillation "in vivo". We explored the CFU-GM growth under three different conditions of GM-CSA production: a) standard source of CSA; b) endogenous GM-CSA assay; c) GM-CSA-gamma-globulin assay. At both observation times the endogenous GM-CSA assay produced more aggregates than the baseline culture. The GM-CSA-gamma-globulin assay partly corrected the growth increase, produced by endogenous assay. At time 0, at the nadir of peripheral blood neutrophils, there was a balance between the number of aggregates, appeared early in culture and early degenerated, and those appeared late. From progenitor cells culture performed on day 13 of cycle, a week before the zenith of neutrophils in vivo, we obtained an increase in aggregates, which appeared late. The values of CFU-GM grown from the culture performed on day 13 reached higher levels than the ones performed on day 0. The CFU-GM growth behaviour shows that in our case with cyclic neutropenia there is no defect in progenitor cells, while on the contrary there is an increase in CSA production.     

Isolation of Corynebacterium diphtheriae from sperm fluid

The isolation of toxigenic Corynebacterium diphtheriae from sperm is reported. The organism was identified through the investigation of fluorescence under the UV light, the presence of pirazinecarboxilamidase enzyme (Pyz), in vitro and in vivo and virulence methods (single radial immunodiffusion, cell culture, guinea pig intradermic test). The strain was initially considered nontoxinogenic by single radial immunodiffusion, but its virulence was observed afterwards, when we applied the tests already mentioned. The strain could be considered a "Diphtheroid" without adequate specification.     

The association of H-2Ld with human beta-2 microglobulin induces localized conformational changes in the alpha-1 and- 2 superdomain

We have analyzed changes in the antigenicity of major histocompatibility complex class I molecules resulting from the association of human beta-2 micro-globulin (B2m) with the mouse class I heavy chain. In particular, the H-2L^d molecule exhibited enhanced crossreactivity for the 34-1-2 monoclonal antibody. In order to assess the nature of this structural alteration induced by human B2m, we utilized H-2 class I hybrid molecules in the mapping of the 34-1-2 determinant to the helical region of the alpha-1 domain. H-2L^d class I hybrid molecules were then used to establish the importance of the alpha-2 and- 3 domains in the observed increase of 34-1-2 cross-reactivity following exchange with human B2m. The H-2L^d hybrids suggest that alterations in interdomain contact are responsible for enhanced 34-1-2 cross-reactivity on the H-2L^d molecule. It is likely that this alteration arises through changes in class I conformation at regions of the molecule distant from points of contact between B2m and the class I molecule. This suggests that perturbations induced by association of human B2m with H-2L^d can affect the conformation of the alpha-1 and- 2 superdomain. That class I antigenic determinants are altered by the association of human B2m with mouse class I further suggests that the class I molecule is structurally flexible and may reflect the ability of the class I molecule to bind and present a vast array of disparate peptides to the T-cell receptor.     

Partial characterization of cell wall from a flocculent strain ofKluyveromyces marxianus

Summary Cell walls from aKluyveromyces marxianus either non flocculent or flocculent strain were isolated and analysed for protein, carbohydrates and phosphate content. Alkaline extract of proteins were analysed by SDS-PAGE. The results revealed a higher protein content in the cell walls from the flocculent strain. Electrophoresis of the cell wall proteins of the flocculent strain showed an extra peptide with an apparent molecular weight of 37 KDa which is absent fom non-flocculent cells. The involvement of this protein in cell adhesion during flocculation is discussed.     

Hydrolysis of sunflower oil by means of hydrophobic membrane with lipolytic activity

Polytetrafluoroethylene (PTFE) membranes of different porosity were used for lipase from Rhizopus immobilization. The immobilized enzyme applied to sunflower oil hydrolysis achieved the activity of 1228 U/m² of the membrane area and the half-life time was calculated to be 7 days.     

Home range use and the exploitation of gum in the marmosetCallithrix jacchus jacchus

Three wild groups of common marmoset, Callithrix jacchus jacchus,in north-east Brazil, of approximately similar size, had home ranges between 2.5 and 6.5 ha. But their core areas were similar in size between 1.0 and 1.5 ha, with a monthly area of heavy use between 1.1 and 1.6 ha. The groups were selective in the use of their home ranges, even though they were small: they used some areas heavily and others lightly. The core areas had higher densities of trees that produced gum exudates than did other parts of the home ranges. Our data suggest that a group of marmosets in this habitat may require a minimum of about 50 gum trees in its home range at a minimum density of about 50 trees/ha. In addition, the animals require suitable trees in which to sleep. We suggest that patches of forest with these desirable properties remain relatively fixed in size and location over the years and that individual animals are constantly in flux between them.     

Photosynthetic properties of leaves of a yellow green mutant of wheat compared to its wild type

We investigated several photosynthetic parameters of a virescent mutant of durum wheat and of its wild-type. Electron transport rate to ferricyanide was the same in the two genotypes when expressed on leaf area basis while O₂ evolution of the leaf tissue in saturating light and CO₂ was slightly higher in the yellow genotype. RuBPCase was also slightly higher. Quantum yield per absorbed light was similar in the two genotypes. P700 and Cyt f were less concentrated in the mutant while PS II was only marginally lower. The light response curve of CO₂ assimilation indicated higher level of photosynthesis of the mutant in high light, which corresponded to a lower non-photochemical quenching compared to the wild-type. It is concluded that the reaction centres, cyt f and chlorophyll are not limiting factors of electron transport in wheat seedlings and that electron transport capacity is in excess with respect to that needed for driving photosynthesis. Since the differences in photosynthesis reflect differences in RuBPCase activity, it is suggested that this enzyme limits photosynthesis in wheat seedlings also at high light intensities.Abbreviations cyt f cytochrome f - chl chlorophyll - PS II photosystem II - Pn_max maximum photosynthesis - RuBCase Ribulose, 1-5,bisphosphate carboxylase     

Replacement of potassium ions by ammonium ions in different micro-organisms grown in potassium-limited chemostat culture

The biomass concentration extant in potassiumlimited cultures of either Klebsiella pneumoniae or Bacillus stearothermophilus (when growing at a fixed temperature and dilution rate in a glucose/ammonium salts medium) increased progressively as the medium pH value was raised step-wise from 7.0 to 8.5. Because the macromolecular composition of the organisms did not vary significantly, this increase in biomass could not be attributed to an accumulation of storage-type polymers but appeared to reflect a pH-dependent decrease in the cells' minimum K⁺ requirement. Significantly, this effect of pH was not eviden with cultures in which no ammonium salts were present and in which either glutamate or nitrate was added as the sole nitrogen source; however, it was again manifest when various concentrations of NH₄Cl were added to the glutamate-containing medium. This suggested a functional replacement of K⁺ by NH ₄ ⁺ , a proposition consistent with the close similarity of the ionic radii of the potassium ion (1.33 Å) and the ammonium ion (1.43 Å). At pH 8.0, and with a medium containing both glutamate (30 mM) and NH₄Cl (100 mM), cultures of B. stearothermophilus would grow without added potassium at a maximum rate of 0.7 h^-1. Under these conditions the cells contained maximally 0.1% (w/w) potassium (derived from contaminating amounts of this element in the medium constituents), a value which should be compared with one of 1.4% (w/w) for cells growing in a potassiumlimited medium containing initially 0.5 mM K⁺. Qualitatively similar findings were made with cultures of K. pneumoniae; and whereas one may not conclude that NH ₄ ⁺ can totally replace K⁺ in the growth of these bacteria, it can clearly do so very extensively.     

Evidence for chromosomal replicons as units of sister chromatid exchanges

Chromosomal replicons have been described as the cytological counterpart of DNA replicon clusters and have previously been studied in vitro using premature chromosome condensation-sister chromatid differentiation (PCC-SCD) techniques. Chromosomal replicons are visualized as small SCD segments in S-phase cells, and measurement of these segments can provide estimates of relative chromosomal replicon size corresponding to DNA replicon clusters functioning coordinately in S-phase. Current hypotheses of sister chromatid exchange (SCE) formation postulate that sites of SCE induction are associated with active replicons or replicon clusters. We have applied the PCC-SCD technique to in vivo studies of mouse bone marrow cells that have been treated with cyclophosphamide (CP) for two cell cycles. We have been able to visualize chromosomal replicons, as well as SCEs which have been induced in vivo by CP treatment, simultaneously in the same cells. Chromosomal replicons visualized as small SCD segments were measured in PCC cells classified at early or late S-phase based on SCD segment size prevalence. Early S-phase (E/S) PCC cells contained 90% of the SCD segments measured clustered in a segment size range of 0.1 to 0.8 m with a peak value around 0.3 to 0.6 m regardless of CP treatment. As the cells progressed through S-phase, late S-phase (L/S) PCC cells were characterized by the appearance of larger SCD segments and even whole SCD chromosomes in addition to small SCD segments. A concentration of units around 0.4 to 1.0 m was found for L/S SCD segment size distributions regardless of CP treatment with an apparent bimodal profile. Our in vivo data support the existence of a subunit organization of chromosomal replication with a basic functional unit being 0.3 to 0.6 m in size. In addition, we have found that this chromosomal unit of replication or chromosomal replicon does not seem to be functionally perturbed by the mutagen CP. We also found that small SCD segments of 0.4 to 0.7 m in length were involved in the formation of an SCE, suggesting that both spontaneous and CP-induced SCEs occur between chromosomal replicons. These findings provide direct cytogenetic evidence to support a replicon cluster/chromosomal replicon model for SCE formation.