Molecular analysis of HLA-A2.4 functional variant KLO: close structural and evolutionary relatedness to the HLA-A2.2 subtype

The structure of an HLA-A2.4 functional variant (A2.4c) expressed on donor KLO has been examined by comparative peptide mapping with other HLA-A2 antigens of known structure and radiochemical sequencing. All the peptide differences between A2.4c and A2.1 could be accounted for by five amino acid changes at positions 9, 43, 66, 95, and 156. The nature of residues 9, 43, and 95 in A2.4c was determined by sequencing to be identical to those in A2.2Y. The nature of residue 156 in A2.4c was also assigned as identical to that in A2.2Y on the basis of the identity of the corresponding peptide in its chromatographic comparison with A2.2Y. Position 66 was unique to A2.4c. It was determined to be an Asn residue instead of the Lys present in all other HLA-A2 antigens of known structure. This was the only detected amino acid difference between A2.4c and A2.2Y. The results indicate that, from a structural point of view, A2.4c is most closely related to the A2.2 subtype antigens and not to other A2.4 antigens. The data are compatible with the assumption that A2.4c was derived from A2.2Y by a single point mutation event.     

An HLA-A2 population variant with structural polymorphism in the α3 region

The HLA-A2 antigen expressed by donor OZB can be distinguished from the main HLA-A2.1 subtype by isoelectric focusing - it is one charge unit more acidic — and by some alloreactive T-cell clones but not by cytolytic T lymphocyte lines. The structure of variant OZB has been examined by comparative peptide mapping with A2.1 and radiochemical sequence analysis. The two molecules were found to differ in a single tryptic peptide from the 0 region, spanning residues 220–243. The amino acid sequence of this peptide from variant OZB revealed that there was only one amino acid change of Glu instead of Ala at position 236, a hitherto invariant residue in class I HLA antigens. All previously characterized HLA or H-2 natural variants have structural changes restricted to the 1 and/or 2 domains. Thus, variant OZB is unique in that (1) it has one amino acid change in 3 and (2) it has no changes in l and 2. The only detected substitution of this variant may be accounted for by a single base change at the DNA level, suggesting that it might have resulted from a point mutation in the A2.1 gene. The structural features of variant OZB open a novel way to examine the influence of polymorphism in 3 on cytolytic T-cell recognition of naturally occurring class I antigens.Abbreviations CTL cytolytic T lymphocytes - HPLC high performance liquid chromatography - IEF isoelectric focusing - MHC major histocompatibility complex     

Chromium in plants

Chromium is an essential trace element and is associated with some biological pathways, especially with glucose tolerance. For these reasons, we decided to determine the concentration of chromium in two sets of Brazilian medicinal plants. The first group consisted of plants that are considered as antidiabetic, whereas the second included plants that do not have this therapeutic property. The concentration of chromium was determined by flameless atomic absorption. All the plants analyzed contain chromium in the normal range for this element, but the hypoglycemic plants contain more chromium than the others (1–4 μg/g compared to 0.5–1.5 μg/g).     

Transfer factor of131I from the fallout to human thyroid dose equivalent after the Chernobyl accident

Summary A similar pattern of variation with time in observed maxima of daily dose equivalent rates in human thyroids (TD - µSv·d^–1) and of daily fallout radioactivities (FR - kBq·m^–2) has been found after the Chernobyl accident. An estimate of the time-lag between the maxima in TD lines and the preceding FR peaks was made of about seven days for adult and nine days for juveniles. Applying this time-lag it was possible to estimate transfer factors from the fall-out to thyroid dose equivalent: the highest estimated values were 221 µSv/kBq·m^–2 for adult and 641 µSv/kBq·m^–2 for juvenile thyroids. These values differ from those published by UNSCEAR (United Nations 1988), which have been calculated for various regions of Czechoslovakia, from ingestion and inhalation intake estimates. A broad variation of transfer factor values could be expected to result from such transfer calculations using ingestion and inhalation estimates. The findings also support the concept of a need for prolonged iodine prophylaxy after emissions of radioiodine into the environment.Abbreviations TD dose equivalent rates in thyroids [µSv·d^–1] - FR fall-out radioactivity (-ies) [kBq·m^–2]     

Changes in invertase activities precede ovary growth induced by gibberellic acid in

Developing pods of pea ( Pisum sativum L. cv. Alaska no 7) were used to study the enzymes of sucrose metabolism. Acid and neutral invertase (EC 3.2.1.26). sucrose synthase (SS, EC 2.4.1.13) and sucrose phosphate synthase (SPS, EC 2.4.1.14) have been localized in the soluble fraction. Acid invertase activity was also present in the insoluble fraction and in pea ovary apoplast. In pea pods, sucrose breakdown was dominated by the invertase pathway. SS specific activity only increased at late stages of parthenocarpic pod development, while SPS did so in pods obtained by pollination. Changes in time course of invertase activities have been correlated with the growth rate of fruits induced to develop either by fertilization or by exogenous application of giberellic acid (GA), 2,4-dichloro-phenoxy acetic acid (2,4-D) or 6-benzylaminopurine (6-BAP). The soluble neutral activities might be associated with pod elongation, while the acid ones were rather related to assimilate import by the induced fruits. Application of gibberellic acid to non-pollinated ovaries significantly enhanced the soluble neutral invertase activity before any ovary outgrowth was detected (up to 2 h after treatment). Within the same period of time. GA-treated ovaries showed a decrease in the acid invertase activity of the soluble fraction and an increase of the acid invertase activity in the apopiast. preceding in time the increment of the acid invertase activity associated with the insoluble fraction. Our results suggest that the early GA response may be mediated through a promotion of processes of protein secretion.     

Lectin binding sites on head structures of the spermatid and spermatozoon of the mosquito Culex quinquefasciatus (Diptera,Culicidae)

The presence of intranuclear and acrosomal lectin binding sites in spermatids and spermatozoa of the mosquito Culex quinquefasciatus was analysed. Direct and indirect lectin-gold techniques were used on LR White-embedded cells. The nuclear compartment was the structure most intensely labelled. Early spermatid nucleus showed moderate labelling for peanut agglutinin (PNA), Griffonia simplicifolia IB4 (GS-IB4) and Ricinus communis agglutinin (RCA), and light labelling for the other lectins tested. The sperm nucleus was intensely labelled by all lectins. The acrosome, an enzyme-containing structure, was labelled by some lectins. The anterior acrosomal region was labelled by PNA, while the proximal acrosomal region was labelled by PNA and G. simplicifolia II (GS II) lectins, and showed the presence of fucose residues with the use of Ulex europaeus I (UEA-I) lectin. The spermatozoa stored in the spermatheca showed the same pattern of labelling as that observed in spermatozoa localized in testis and seminal vesicles for all lectins tested. Carbohydrate residues in the nuclear compartment may be involved with the process of chromatin condensation. In the acrosomal region these residues may play a role in the process of spermoocyte interaction.     

gltF, a member of the gltBDF operon of Escherichia coli, is involved in nitrogen-regulated gene expression

We report here the construction and analysis of insertional mutations in each of the three genes of the gltBDF operon and the nucleotide sequence of the region downstream from gltD. Two open reading frames were identified, the first of which corresponds to gltF. The gltB and gltD genes code for the large and small subunits, respectively, of the enzyme glutamate synthase (GOGAT). gltF codes for a protein, with a molecular mass of 26,350 Da, which is required for Ntr induction. Histidase synthesis was determined as a measure of Ntr function. First, insertions in gltB, gltD or gltF all prevent Ntr induction. Second, complementation analysis indicates that high-level expression of both the gltD and gltF genes is required for the induction of the Ntr enzymes under nitrogen-limiting conditions, indicating that the phenotype of the gltB insertion probably results from polarity on gltD and gltF. Third, glutamate-dependent repression of the glt operon appears to be mediated by the product of the gltF gene. Thus, the gltBDF operon of Escherichia coli is involved in induction of the so-called Ntr enzymes in response to nitrogen deprivation, as well as in glutamate biosynthesis.