Ferricrocin functions as the main intracellular iron-storage compound in mycelia ofNeurospora crassa

Summary Neurospora crassa produces several structurally distinct siderophores: coprogen, ferricrocin, ferrichrome C and some minor unknown compounds. Under conditions of iron starvation, desferricoprogen is the major extracellular siderophore whereas desferriferricrocin and desferriferrichrome C are predominantly found intracellularly. Mössbauer spectroscopic analyses revealed that coprogen-bound iron is rapidly released after uptake in mycelia of the wild-typeN.crassa 74A. The major intracellular target of iron distribution is desferriferricrocin. No ferritin-like iron pools could be detected. Ferricrocin functions as the main intracellular iron-storage peptide in mycelia ofN. crassa. After uptake of ferricrocin in both the wild-typeN. crassa 74A and the siderophore-free mutantN. crassa arg-5 ota aga, surprisingly little metabolization (11%) could be observed. Since ferricrocin is the main iron-storage compound in spores ofN. crassa, we suggest that ferricrocin is stored in mycelia for inclusion into conidiospores.     

Vitamin A deficiency and inflammation: the pivotal role of secretory cells in the development of atrophic, hyperplastic and metaplastic change in the tracheal epithelium in vivo.

We showed previously that the proliferation of hamster airway secretory cells decreases during vitamin A deficiency (VAD) but later increases when submucosal inflammation develops (Virchows Arch [B] 59:231-242, 1990). This observation has important biological implications since two morphological extremes (atrophy and quiescence versus hyperplasia and hyperproliferation) are reported in the literature for VAD tracheal epithelium in vivo. In the present study, histological slides of tracheal rings from 35-day-old control and VAD hamsters (Virchows Arch [B] 45:197-219, 1984) were reviewed again. Rings from VAD hamsters were selected based on the absence or presence of a florid submucosal inflammation. Quantitative analyses were made on the cartilaginous part of rings from the anterior third of the trachea. When inflammation was absent, a mucociliary pseudostratified epithelium was, for the most part, maintained. The mitotic rate (MR, 6 h colchicine blockade) of secretory cells was markedly reduced (29-fold) but that of basal cells was not changed significantly. Moreover, cell density was not changed by VAD but ciliated cells and secretory cells were decreased and basal cells were increased, proportionally. We call this "minimal morphological change." Thinning (atrophy) of the minimally changed epithelium was associated with focal cell sloughing. Small scattered foci of epidermoid metaplasia (multiple layers of highly keratinized cells which were extremely flat, so that the epithelium was thin and attenuated) were also seen. We call this "atrophic epidermoid metaplasia." When inflammation was present, hyperplastic changes (stratification and epidermoid metaplasia) predominated and cells were in mitosis at all epithelial levels (low, middle, superficial) except in the most superficial (terminally differentiated) squames. The tracheal epithelium was thickened and hypercellular. The cells were piled up at the stratified lesions, and epithelial height, cell density and epithelial MR were significantly increased compared with the non-inflamed VAD epithelium. The effects of VAD and inflammation on cell proliferation were analyzed further by studying 7 h bromodeoxyuridine (BrdU) labelling patterns of cells in VAD tracheal epithelium, with and without submucosal inflammation. In addition, inflammation was induced in "minimally changed epithelium" by mild mechanical injury. The BrdU labelling patterns confirmed that DNA synthesis by secretory cells is reduced markedly by VAD. However, this suppression is overidden by the influx of inflammatory cells (the nature of the stimulus is unknown). The results indicate that the morphological contrasts (atrophy and hyperplasia) seen in the trachea during VAD in vivo are related to extremes in proliferation rates of tracheal secretory cells, regulated by VAD alone (minimal replication) and by inflammation (maximal replication).     

Assignment of genes encoding a unique cytokine (IL12) composed of two unrelated subunits to chromosomes 3 and 5.

IL12 (formerly NKSF or CLMF) is a unique cytokine composed of two unrelated disulfide-linked subunits. The larger 40-kDa subunit (p40) is a member of the cytokine receptor family, and the smaller 35-kDa subunit (p35) is related to IL6 and GCSF. The chromosomal localization of these two subunits was determined by PCR analysis of DNA from rodent-human hybrids. More refined mapping was obtained by PCR analysis of hybrids containing translocation chromosomes and for p40, by analysis of radiation hybrids. The subunits map to different chromosomes: p40 (IL12B) to 5q31-q33 and p35 (IL12A) to 3p12-3q13.2.     

Human dopamine transporter gene (DAT1) maps to chromosome 5p15.3 and displays a VNTR.

The human dopamine transporter (DAT1) gene is localized to chromosome 5p15.3 by in situ hybridization and PCR amplification of rodent somatic cell hybrid DNA. Analysis of a 40-bp repeat in the 3' untranslated region of the message revealed variable numbers of the repeat ranging from 3 to 11 copies. These results will aid in the investigation of a role for this gene in genetic disorders of the dopaminergic system in humans.     

Recombinational analysis of a natural noncytopathic human immunodeficiency virus type 1 (HIV-1) isolate: role of the vif gene in HIV-1 infection kinetics and cytopathicity.

Two molecularly cloned coisolates of human immunodeficiency virus type 1 (HIV-1) have been found to exhibit different phenotypes of viral expression, either rapid and cytopathic (N1T-A virus) or delayed and noncytopathic (N1T-E virus [X. Ma, K. Sakai, F. Sinangil, E. Golub, and D. J. Volsky, Virology 176:184-194, 1990]). To identify the viral genetic elements responsible for these phenotypes, we prepared reciprocal recombinants in different regions of N1T-A and N1T-E viral genomes. Infectivity experiments with the recombinant viruses revealed that the rapid/cytopathic (N1T-A-like) phenotype assorted cleanly with the V1f-coding region and Vif expression. The smallest HIV-1 DNA region that conferred the complete phenotypic switch was a 284-bp NdeI-StuI fragment within the vif open reading frame. Nucleotide sequence analysis revealed a 35-bp deletion starting at nucleotide 218 in the N1T-E vif gene. A 23-kDa Vif protein was detected by immunoblotting using Vif-specific antiserum in extracts of cells infected with N1T-A but not N1T-E virus. No detectable vif protein was found in association with sedimented particles of either virus. Cotransfection of a eucaryotic vif expression plasmid with N1T-E DNA complemented the N1T-E defect; rapid/cytopathic infection similar to that in N1T-A-transfected cells was observed. We conclude that Vif controls the rate, and consequently the cytopathic outcome, of HIV-1 infection.     

Plasma amino acids of lean and obese Zucker rats subjected to a cafeteria diet after weaning.

Plasma amino acids of Zucker obese (fa/fa) and lean (Fa/?) rats fed either a reference nonpurified pellet or a cafeteria diet have been studied from 30 to 60 days after birth. Obese rats showed higher plasma branched chain amino acid levels but similar total amino acids, urea and glucose concentrations. The ingestion of a cafeteria diet induced higher levels in many amino acids, as well as in the composite figure in lean rats, but failed to alter total 2-amino nitrogen concentrations in obese rats, despite high levels in several non-essential amino acids and lower values in essential amino acids; urea levels were much lower in rats fed the cafeteria diet. The results are consistent with an impairment of amino acid nitrogen elimination via urea cycle in cafeteria diet-fed rats. This is independent of the hyperinsulinemia-driven plasma accumulation of several essential amino acids induced by genetic obesity. The effects were, then additive.     

Nuclease hypersensitivity in the beta-globin gene region of K562 cells

We have investigated chromatin structure in the beta-globin gene region of the K562 human erythroleukemic cell line by using S1 and DNase I nuclease sensitivity assays. Despite the lack of beta-globin gene expression in these cells, we find nuclease-hypersensitive sites to these enzymes in its 5' and 3' flanking regions in K562 chromatin. This result is in contrast to previous reports in which no hypersensitive sites were found in the immediate vicinity of this gene. In the 3' region, one major hypersensitive site at 0.9 kpb 3' and three minor hypersensitive sites at 0.7 kbp, 0.5 kbp 3' and 0.2 kbp 5' of the polyadenylation site were observed; these sites are very similar to those found in fetal liver and adult bone marrow cells in which the beta-globin gene is expressed. We find hypersensitive sites to both enzymes in the 5' region of the beta-globin gene: a major site 0.8 kbp 5' to the cap site, and two minor sites 1.2 and 1.5 kbp 5' to the cap site. The -0.8 kbp site is also present in plasmids containing the beta-globin gene. Our results suggest that the lack of beta-globin gene expression may be related to the lack of hypersensitivity sites in the immediate (150 bp) 5' flanking region of the beta-globin gene, as occurs in other active globin genes.