Construction and plasmid-borne complementation of strains lacking the epsilon subunit of the Escherichia coli F1F0 ATP synthase.

Two strains of Escherichia coli that lack the epsilon subunit of the F1F0 ATP synthase have been constructed. They are shown to be viable but with very low growth yields (28%). These strains can be complemented by plasmids carrying wild-type uncC, but not when epsilon is overproduced. These results indicate that epsilon is not essential for growth on minimal glucose medium and that the level of its expression affects the assembly of the ATP synthase.     

Structure of the murine complement factor H gene

Factor H is a regulatory protein of the alternative pathway of complement activation comprised of 20 tandem repeating units of 60 amino acids each. A factor H cDNA clone was used to identify 17 genomic clones from a cosmid library. Four clones were selected for analysis of intron/exon junctions and 5' and 3' regions of the gene and for mapping of the exons. The factor H gene was found to be comprised of 22 exons. Each repeating unit is encoded by one exon, except the second repeat, which is coded by two exons; the leader sequence is encoded by a separate exon. The exons range in size from 77 to 210 base pairs (bp) and average 178 bp. They span a region of approximately 100 kilobases (kb) on chromosome 1. The leader sequence exon is 26 kb upstream of the first repeat exon, representing the largest intron. The other introns range in size from 86 bp to 12.9 kb, and the average intron size is 4.7 kb. Analysis of the genomic organization of the factor H gene has provided insight into the protein structure and will enable the construction of deletion mutants for functional studies.     

Variations in lymphokine generation by individual lymph nodes draining human malignant tumors

Summary Individual lymph nodes draining tumors vary in their degree of immunological activity. Cell suspensions from tumor-free nodes located relatively near to tumors are spontaneously less reactive and respond poorly to exogenous stimulation by mitogens and lymphokines. Diminished spontaneous uptake of tritiated thymidine by lymph node cells not exposed to exogenous stimulation suggests that tumor-proximate immune suppression exists in vivo and is not purely a laboratory artefact. The present study was undertaken to explore that possibility further. Fluid in which cell suspensions from tumor-free nodes were prepared, and supernatants from short-term cultures of nodes located at different distances from tumors were compared for their capacity to inhibit the in vitro migration of the human lymphoblastoid cell line QIMR-WIL. Inhibitory activity of fluids from individual nodes was related to their position relative to the tumor and their immune competence, assessed by the responses to mitogens of cell suspensions prepared from them. Cell suspension fluids from 92/111 nodes (83%) significantly inhibited the migration of QIMR-WIL, at a level similar (44±14%) to that induced by the supernatants of mixed lymphocyte cultures (43±17%). Fluids from the nodes of melanoma patients were more inhibitory than those from breast cancer patients (49±12% and 37±13%, respectively,P = 0.003). The inhibitory activity of the different nodes of individual node groups varied significantly in 25 of 33 patients (76%), the node nearest the tumor generating least inhibitory activity (indexing the greatest immune suppression) in 20 of these 25 patients (80%). The strength of migration-inhibitory activity was concordant with the responsiveness to mitogen stimulation in up to 14 of 18 patients (78%). Studies of molecular size and heat stability indicated that the inhibitory factors had characteristics consistent with common migration-inhibitory lymphokines such as leukocyte-migration-inhibitory factor, macrophage-inhibitory factor and interleukin-2. Our findings further support the hypothesis that lymph nodes nearest to tumors are relatively immune-suppressed in vivo.Supported by grants CA 29938 and CA 43658, awarded by the National Cancer Institute, DHHS and a grant from the Candle Foundation, Los Angeles     

Effects of type beta transforming growth factor in combination with retinoic acid or tumor necrosis factor on proliferation of a human glioblastoma cell line and clonogenic cells from freshly resected human brain tumors

Summary Type beta transforming growth factor (-TGF) is a potent regulator of cell growth and differentiation. The human glioblastoma cell line, T-MGl, was growth inhibited by -TGF under anchorage independent conditions. The antiproliferative effect of -TGF was potentiated to nearly total arrest by low doses of retinoic acid (RA) or tumor necrosis factor (TNF), while epidermal growth factor, platelet-derived growth factor, interleukin-2, and gamma interferon did not have this potentiating effect. The potentiation of the -TGF effect by RA and TNF could not be explained by modulation of the epidermal growth factor receptor, the -TGF receptor, or the TNF receptor. -TGF alone and in combination with RA or TNF were further tested on primary cultures from freshly resected human glioma biopsies (n=13). There was great individual variation in sensitivity to -TGF, RA, or TNF. The astrocytoma and oligodendroglioma cells were inhibited to various degrees by -TGF or TNF, while most of the glioblastomas were not sensitive to these agents. Most of the biopsies were stimulated by RA. RA or TNF did not potentiate the growth inhibitory effect of -TGF on biopsy cells. We therefore think it unlikely that -TGF in combination with RA or TNF will be effective agents in the treatment of gliomas.     

Mapping of a retinoic acid-responsive element in the promoter region of the complement factor H gene.

Retinoic acid receptors are members of the steroid/thyroid hormone receptor superfamily. Pursuant to the discovery that dexamethasone increases complement factor H expression, we examined the effects of retinoic acid on this gene. Both H mRNA and protein levels are increased by retinoic acid in L cells. Using the luciferase reporter gene system we have identified a region of the H promoter required for the retinoic acid response. This region contains an imperfect palindrome of the TGACC motif, present in thyroid hormone and estrogen-responsive elements. We demonstrate specific binding of the retinoic acid receptor beta to this sequence of the H gene by DNA-protein gel retardation assay. Therefore, these studies extend the sphere of influence of the retinoids to complement, an intrinsic component of the humoral immune system.     

Comparison of multiplex ligation dependent probe amplification to immunohistochemistry for assessing HER-2/neu amplification in invasive breast cancer

The HER-2/neu transmembrane tyrosine kinase receptor is both a prognostic marker and a therapeutic target for breast cancer. Accurate determination of HER-2/neu status is a prerequisite for selecting breast tumors for HER-2/neu immunotherapy or for taxan based chemotherapy. Unfortunately, there is no consensus concerning how this determination should be reached. We compared assessment of HER-2/neu status using Multiplex ligation-dependent probe amplification (MLPA) and immunohistochemistry (IHC). The patient group comprised 60 Indonesian breast cancers patients. IHC was performed on paraffin sections using the CB11 antibody from Novocastra. Results were scored according to the Hercept test. For MLPA, DNA was extracted from frozen samples, PCR amplified with a probe set containing three hemi-primer sets for the HER-2 locus and another nine control probes spread over chromosome 17 and other chromosomes, and analyzed on a gene scanner. A ratio above two for at least two HER-2 locus probes compared to the control probes was regarded as amplification. IHC for HER-2/neu was negative in 36 cases, and 24 cases (40%) showed expression. Seven, eight and nine of the latter cases were 1+, 2+ and 3+ positive, respectively. Forty-seven cases showed no amplification by MLPA, and 13 cases (22%) were amplified. Comparison of IHC and MPLA showed that none of the 36 IHC-negative or seven IHC 1+ cases was amplified. Five of the eight (63%) 2+ cases were amplified, and eight of nine (89%) of the IHC 3+ tumors showed gene amplification by MLPA assay. For HER-2/neu, there is a good correlation between gene amplification detected by MLPA and overexpression by IHC in invasive breast cancer. It appears that MLPA can detect the HER-2 amplified cases in the IHC 2+ class. Because MLPA is quick and inexpensive, it is an attractive method for detecting HER-2/neu amplification in daily laboratory practice.     

Hair-loss epizootic in moose (Alces alces) associated with massive deer ked (Lipoptena cervi) infestation

Deer keds (Lipoptena cervi) are blood-sucking flies in the family Hippoboscidae; moose (Alces alces) are their main host in Scandinavia. There are no detailed reports of the negative impacts of deer keds on moose. In 2006 and 2007, hunters in southeastern Norway and midwestern Sweden found several moose cadavers with severe alopecia; numerous moose had extensive hair loss. Between February 2006 and June 2007, materials from 23 moose were submitted for laboratory examination and large numbers of deer keds were found in the coat of most animals. The body condition of the moose varied but was poor in animals with severe alopecia. The findings of enormous numbers of deer keds in the coat of the majority of the affected animals and a consistent histologic image (acute to chronic, multifocal to coalescing, eosinophilic to lymphocytic dermatitis), concurrent with the absence of any other lesions, trace element deficiencies, or dermal infections which are known to cause alopecia, suggest that the hair-loss epizootic was linked to massive infestations with deer keds. The emergence of this hair-loss syndrome implies that the dynamics between parasite and host have been disrupted by a currently unknown environmental or ecological factor. A high moose density, combined with extraordinarily mild weather June 2006-June 2007 and a particularly long period with the absence of night-frost in autumn of 2006, may have been ideal for deer ked development, survival, and optimal host acquisition.     

Type IV Pilus Assembly Proficiency and Dynamics Influence Pilin Subunit Phospho-Form Macro- and Microheterogeneity in Neisseria gonorrhoeae

The PilE pilin subunit protein of the gonococcal Type IV pilus (Tfp) colonization factor undergoes multisite, covalent modification with the zwitterionic phospho-form modification phosphoethanolamine (PE). In a mutant lacking the pilin-like PilV protein however, PilE is modified with a mixture of PE and phosphocholine (PC). Moreover, intrastrain variation of PilE PC modification levels have been observed in backgrounds that constitutively express PptA (the protein phospho-form transferase A) required for both PE and PC modification. The molecular basis underlying phospho-form microheterogeneity in these instances remains poorly defined. Here, we examined the effects of mutations at numerous loci that disrupt or perturb Tfp assembly and observed that these mutants phenocopy the pilV mutant vis a vis phospho-form modification status. Thus, PC modification appears to be directly or indirectly responsive to the efficacy of pilin subunit interactions. Despite the complexity of contributing factors identified here, the data favor a model in which increased retention in the inner membrane may act as a key signal in altering phospho-form modification. These results also provide an alternative explanation for the variation in PilE PC levels observed previously and that has been assumed to be due to phase variation of pptA. Moreover, mass spectrometry revealed evidence for mono- and di-methylated forms of PE attached to PilE in mutants deficient in pilus assembly, directly implicating a methyltransferase-based pathway for PC synthesis in N. gonorrhoeae.     

Parameters in dynamic models of complex traits are containers of missing heritability

Polymorphisms identified in genome-wide association studies of human traits rarely explain more than a small proportion of the heritable variation, and improving this situation within the current paradigm appears daunting. Given a well-validated dynamic model of a complex physiological trait, a substantial part of the underlying genetic variation must manifest as variation in model parameters. These parameters are themselves phenotypic traits. By linking whole-cell phenotypic variation to genetic variation in a computational model of a single heart cell, incorporating genotype-to-parameter maps, we show that genome-wide association studies on parameters reveal much more genetic variation than when using higher-level cellular phenotypes. The results suggest that letting such studies be guided by computational physiology may facilitate a causal understanding of the genotype-to-phenotype map of complex traits, with strong implications for the development of phenomics technology.     

The nature of the copper atoms of cytochrome c oxidase as studied by optical and x-ray absorption edge spectroscopy.

X-ray absorption edge spectroscopy has been used to study the copper of 1--2 mM cytochrome c oxidase in the resting oxidized, mixed-valence, and fully reduced states. A comparison was made of this protein with copper complexes and with natural and artificial copper proteins. Spectra were obtained with synchrotron radiation from the SPEAR storage ring using highly sensitive fluorescence detectors. Temperatures of -80 to -120 degrees C were employed further to improve the stability of the samples and to avoid the possibility of either auto- or photon-induced reduction of the materials, which might have occurred in previous studies. In order to characterize the valence states of the Cu and Fe components, the samples were monitored by infrared and visible spectroscopy before and after irradiation by the X-ray beam. The combination of the optical and X-ray absorption techniques has afforded a deconvolution of the four species of copper in the various states of cytochrome c oxidase and the tentative assignment of Cu alpha, the copper redox coupled to the heme alpha of cytochrome alpha, as a highly covalent type of copper and Cu alpha 3, the copper of cytochrome alpha 3, as a more ionic 'blue' type I copper. The implications of these findings upon the mechanism of action of cytochrome oxidase are briefly outlined.