Estrogen accelerates immune complex glomerulonephritis but ameliorates T cell-mediated vasculitis and sialadenitis in autoimmune MRL lpr/lpr mice.

Estrogen is known to influence immune responses in healthy subjects in a dichotomous fashion. Thus, in number of previous studies we and others have demonstrated that B cell activities are augmented after exposure to estrogen whereas T cell reactivity is suppressed. Furthermore, it has been shown that this hormone has significant impact on the course of certain human and experimental autoimmune diseases. In this study we report that treatment with physiological doses of estradiol exerts dichotomous effects on different manifestations of the lupus disease in MRL/l mice. On one hand immune complex-mediated glomerulonephritis was significantly accelerated. This outcome was due to polyclonal B cell activation with increased production of antibodies to double-stranded DNA and formation of circulating immune complexes. In contrast, T cell-mediated lesions such as focal sialadenitis, renal vasculitis, and periarticular inflammation were all significantly ameliorated in MRL/l mice exposed to estrogen. Thus, we were able to demonstrate that, within one subject and even within one organ, administration of estrogen leads to differential outcome of SLE morbidity. We propose that the differential effect of estrogen on the manifestations of the autoimmune disease of MRL/l mice is due to its dichotomous effects on B and T cell-mediated immune responses.     

A genetic study of the human low-voltage electroencephalogram

Summary The studied phenotype, the low-voltage electroencephalogram (LVEEG), is characterized by the absence of an alpha rhythm from the resting EEG. In previous studies, evidence was found for a simple autosomal-dominant mode of inheritance of the LVEEG. Such a polymorphism in brain function can be used as a research model for the stepwise elucidation of the molecular mechanism involved in those aspects of neuronal activity that are reflected in the EEG. Linkage with the variable number of tandem repeats (VNTR) marker CMM6 (D20S19) and localization of an LVEEG (EEGV1) gene on 20q have previously been reported, and genetic heterogeneity has been demonstrated. This latter result has been corroborated by studing new marker (MS214). The phenotype of the LVEEG is described here in greater detail. Its main characteristic is the absence of rhythmic alpha activity, especially in occipital leads, whereas other wave forms such as beta or theta waves may be present. Analysis of 17 new families (some of them large), together with 60 previously described nuclear families, supports the genetic hypothesis of an autosomal-dominant mode of inheritance. Problems connected with the analysis of linkage heterogeneity, exclusion mapping, and the study of multipoint linkage are discussed. A possible explanation of the localization of LVEEG in the close vicinity of another gene influencing synchronization of the normal EEG, the gene for benign neonatal epilepsie, is given.     

Transformation of sperm nuclei into male pronuclei in nucleate and anucleate fragments of parthenogenetic mouse eggs

Our objective was to examine the ability of nucleate and anucleate fragments of artificially activated mouse eggs to transform sperm nucleus into male pronucleus. To this end, zona-free oocytes in metaphase II were activated by ethanol and bisected into halves (one with the spindle, the other anucleate) either within 10 to 20 min (series A) or 3 or 5 hr later (series B). In series A, the fragments were inseminated 3,5, and 8 h after activation, and in series B. 3 and 5 h after activation. Both nucleate and anucleate fragments lose the capability of transforming sperm nucleus into fully formed pronucleus sometime between 3 and 5 h after activation. In 8 h old parthenogenetic fragments, the majority of sperm nuclei remain unchanged or begin decondensation but never reach the stage of an early pronucleus. In over 1/3 of anucleate fragments of this age group, sperm nuclei develop defectively: chromatin decondenses inside the persisting nuclear envelope. In other experimental groups, the incidence of these abnormal sperm nuclei varies between 0 and 10%. In general, the anuclcate fragments retain the capability to transform sperm nuclei (fully or partially) longer than their nuclear counterparts. This difference may be accounted for by a different level of substances required for pronuclcar growth (extrachromosomal constituents of the germinal vesicle and nuclear lamins): high and constant in the cytoplasm of anucleate egg halves and low and progressively decreasing in the nucleate halves because of their putative uptake by the female pronucleus. However, the cytoplasmic factors responsible for the initial stages of transformation (nuclear envelope breakdown, chromatin decondensation) become eventually inactivated both in the presence and in the absence of a female pronucleus.     

Restriction endonucleases from Selenomonas ruminantium which recognize and cleave 5′-AT/TAAT-3′

Two natural isolates from fallow-deer rumen identified as Selenomonas ruminantium were found to produce a restriction endonuclease which we called Sru4DI. This enzyme was isolated from cell extracts by phosphocellulose chromatography. Analysis of the Sru4DI recognition site showed that Sru4DI recognizes the hexanucleotide sequence 5-AT/TAAT-3 generating 5 dinucleotide protruding ends upon cleavage and thus is a true isoschizomer of VspI, a restriction enzyme isolated from Vibrio sp.     

Optimization of the electrostatic interactions in proteins of different functional and folding type

The 3-dimensional optimization of the electrostatic interactions between the charged amino acid residues was studied by Monte Carlo simulations on an extended representative set of 141 protein structures with known atomic coordinates. The proteins were classified by different functional and structural criteria, and the optimization of the electrostatic interactions was analyzed. The optimization parameters were obtained by comparison of the contribution of charge-charge interactions to the free energy of the native protein structures and for a large number of randomly distributed charge constellations obtained by the Monte Carlo technique. On the basis of the results obtained, one can conclude that the charge-charge interactions are better optimized in the enzymes than in the proteins without enzymatic functions. Proteins that belong to the mixed αβ folding type are electrostatically better optimized than pure α-helical or β-strand structures. Proteins that are stabilized by disulfide bonds show a lower degree of electrostatic optimization. The electrostatic interactions in a native protein are effectively optimized by rejection of the conformers that lead to repulsive charge-charge interactions. Particularly, the rejection of the repulsive contacts seems to be a major goal in the protein folding process. The dependence of the optimization parameters on the choice of the potential function was tested. The majority of the potential functions gave practically identical results.     

The responses of auditory ventral-cord neurons ofLocusta migratoria to vibration stimuli

Summary Most of the auditory neurons in the ventral nerve cord ofLocusta migratoria carry information not only from the tympanal organs but also from the subgenual organs (vibration sensors). Six of the eight neuron types studied electrophysiologically respond to at least these two modalities. Artificial sounds (white noise and pure tones varying in frequency and intensity) and sinusoidal vibration (200 Hz with an acceleration of 15.8 cm/s₂ or 2000 Hz and 87 cm/s₂) were used as stimuli.Complex excitatory and/or inhibitory interactions of the signals from both tympanal organs form the discharge patterns of auditory ventral-cord neurons in response to stimulation with air-borne sound. Normally the input of the ipsilateral sense organ dominates. The response patterns of these same neurons elicited by vibration stimuli are formed differently, as follows: (1) the sensory inputs of all subgenual organs are integrated in the responses of the ventral-cord neurons; in a single neuron they have either excitatory or inhibitory effects, but not both. (2) The more legs vibrated, the larger is the response. (3) The subgenual organs in the middle legs are most effective, those in the hind legs least so. (4) Ipsilateral vibration has more effect than contralateral.The six auditory neurons react to vibration combined with air-borne sound in different ways. The B neuron is the only one inhibited by vibration stimuli. The G neuron has been studied more intensively; because its anatomical arrangement and the location of the endings of the subgenual receptor fibers are known, it could be inferred from effects of transection of the connectives that interneurons are interposed between receptor cells and the G neuron.Part of the program Sonderforschungsbereich 114 (Bionach) Bochum, under the auspices of the Deutsche Forschungsgemeinschaft, with the support of the Slovenic Research Society (RSS)     

Electron microscopy holdings of the Protein Data Bank: the impact of the resolution revolution,new validation tools,and implications for the future

As a discipline, structural biology has been transformed by the three-dimensional electron microscopy (3DEM) “Resolution Revolution” made possible by convergence of robust cryo-preservation of vitrified biological materials, sample handling systems, and measurement stages operating a liquid nitrogen temperature, improvements in electron optics that preserve phase information at the atomic level, direct electron detectors (DEDs), high-speed computing with graphics processing units, and rapid advances in data acquisition and processing software. 3DEM structure information (atomic coordinates and related metadata) are archived in the open-access Protein Data Bank (PDB), which currently holds more than 11,000 3DEM structures of proteins and nucleic acids, and their complexes with one another and small-molecule ligands (~ 6% of the archive). Underlying experimental data (3DEM density maps and related metadata) are stored in the Electron Microscopy Data Bank (EMDB), which currently holds more than 21,000 3DEM density maps. After describing the history of the PDB and the Worldwide Protein Data Bank (wwPDB) partnership, which jointly manages both the PDB and EMDB archives, this review examines the origins of the resolution revolution and analyzes its impact on structural biology viewed through the lens of PDB holdings. Six areas of focus exemplifying the impact of 3DEM across the biosciences are discussed in detail (icosahedral viruses, ribosomes, integral membrane proteins, SARS-CoV-2 spike proteins, cryogenic electron tomography, and integrative structure determination combining 3DEM with complementary biophysical measurement techniques), followed by a review of 3DEM structure validation by the wwPDB that underscores the importance of community engagement.     

Effect of H. pylori on the expression of TRAIL, FasL and their receptor subtypes in human gastric epithelial cells and their role in apoptosis

BACKGROUND AND AIMS: In the human stomach expression of TNF-related apoptosis inducing ligand (TRAIL) and its receptors and the modulatory role of Helicobacter pylori are not well described. Therefore, we investigated the effect of H. pylori on the expression of TRAIL, FasL and their receptors (TRAIL-R1-R4, Fas) in gastric epithelial cells and examined their role in apoptosis. MATERIALS AND METHODS: mRNA and protein expression of TRAIL, FasL and their receptors were analyzed in human gastric epithelial cells using RT-PCR, Western blot, and immunohistochemistry. Gastric epithelial cells were incubated with FasL, TRAIL and/or H. pylori, and effects on expression, cell viability and epithelial apoptosis were monitored. Apoptosis was analyzed by histone ELISA, DAPI staining and immunohistochemistry. RESULTS: TRAIL, FasL and their receptor subtypes were expressed in human gastric mucosa, gastric epithelial cell primary cultures and gastric cancer cells. TRAIL, FasL and H. pylori caused a time- and concentration-dependent induction of DNA fragmentation in gastric cancer cells with synergistic effects. In addition, H. pylori caused a selective up-regulation of TRAIL, TRAIL-R1 and Fas mRNA and protein expression in gastric cancer cells. CONCLUSIONS: Next to FasL and Fas, TRAIL and all of its receptor subtypes are expressed in the human stomach and differentially modulated by H. pylori. TRAIL, FasL and H. pylori show complex interaction mediating apoptosis in human gastric epithelial cells. These findings might be important for the understanding of gastric epithelial cell kinetics in patients with H. pylori infection.     

Lipoproteins in Drosophila melanogaster-Assembly, Function, and Influence on Tissue Lipid Composition

Interorgan lipid transport occurs via lipoproteins, and altered lipoprotein levels correlate with metabolic disease. However, precisely how lipoproteins affect tissue lipid composition has not been comprehensively analyzed. Here, we identify the major lipoproteins of Drosophila melanogaster and use genetics and mass spectrometry to study their assembly, interorgan trafficking, and influence on tissue lipids. The apoB-family lipoprotein Lipophorin (Lpp) is the major hemolymph lipid carrier. It is produced as a phospholipid-rich particle by the fat body, and its secretion requires Microsomal Triglyceride Transfer Protein (MTP). Lpp acquires sterols and most diacylglycerol (DAG) at the gut via Lipid Transfer Particle (LTP), another fat body-derived apoB-family lipoprotein. The gut, like the fat body, is a lipogenic organ, incorporating both de novo-synthesized and dietary fatty acids into DAG for export. We identify distinct requirements for LTP and Lpp-dependent lipid mobilization in contributing to the neutral and polar lipid composition of the brain and wing imaginal disc. These studies define major routes of interorgan lipid transport in Drosophila and uncover surprising tissue-specific differences in lipoprotein lipid utilization.