Peroxisomes in human and mouse testis: differential expression of peroxisomal proteins in germ cells and distinct somatic cell types of the testis

The vital importance of peroxisomal metabolism for regular function of the testis is stressed by the severe spermatogenesis defects induced by peroxisomal dysfunction. However, only sparse information is available on the role and enzyme composition of this organelle in distinct cell types of the testis. In the present study, we characterized the peroxisomal compartment in human and mouse testis in primary cultures of murine somatic cells (Sertoli, peritubular myoid, and Leydig cells) and in GFP-PTS1 transgenic mice with a variety of morphological and biochemical techniques. Formerly, peroxisomes were thought to be absent in late stages of spermatogenesis. However, our results obtained by detection of different peroxisomal marker proteins show the presence of these organelles in most cell types in the testis, except for mature spermatozoa. Furthermore, we demonstrate a strong heterogeneity of peroxisomal protein content in various cell types of the human and mouse testis and show marked differences in structure, abundance, and localization of these organelles in spermatids, depending on their maturation. Highest and selective enrichment of the peroxisomal lipid transporters (ABCD1 and ABCD3) as well as ACOX2, the key regulatory enzyme of the beta-oxidation pathway 2 for side chain oxidation of cholesterol, were found in Sertoli cells, whereas Leydig cells were enriched in catalase and ABCD2. Our results suggest a cell type-specific metabolic function of peroxisomes in the testis and point to an important role for peroxisomes in spermiogenesis and in the lipid metabolism of Sertoli cells.     

Spider odors induce stoichiometric changes in fruit fly Drosophila melanogaster

Animal senses and signals are amazingly diverse,and the major modalities by which animals acquire sensory input from their environments are sound,light,vibration,and chemical signals.Insects mainly rely on visual,nociceptive,and olfactory cues to discriminate between rewards and risks.It has been shown that the visual and olfactory cues of predators substantially affect the adult phenotype in Drosophila melanogaster(Krams et al.2016),a prominent animal model for biological research.     

Sequences translated by Balbiani ring 75S RNA in vitro are present in giant secretory protein from Chironomus tentans

The 75S RNA originating in the large Balbiani rings 1 and 2 (BR1 and 2) was isolated and used for in vitro translation in the mRNA dependent reticulocyte lysate. Conditions (K⁺-concentration, temperature, time etc), were optimized for obtaining translation products of maximal size. Polypeptide chains up to about 500,000 D were obtained but no complete translation products. Tryptic fingerprints were performed on the in vitro products as well as on the secretory protein components nos. I and II+III labelled with ³⁵S-methionine. There was a large degree of correspondence between the fingerprint of the in vitro product and that of component I but less to that of component II+III. The results suggest that 75S RNA with an origin in the BR1 and BR2 codes for the giant secretory protein component I.     

Oligomer formation of staphylococcal α-toxin analyzed by electron microscopy and image processing

Abstract The 12S oligomeric form of Staphylococcus aureus α-toxin has been studied with electron microscopy after incubation of the toxin with membrane preparations or liposomes. The target material originated from human platelet. Different electron microscopic preparation techniques were used including negative staining, freeze-fracture and vitrification in liquid ethane. Analysis of micrographs with image processing methods revealed two groups of ring-like structures corresponding to α-toxin oligomers. One form measured 75 Å in diameter and had a high stain density in the central protein deficient part while the other was larger with a diameter of 100 Å and less stain accumulation in the center. The conditions under which the latter were formed suggest that this corresponds to an inactive loosely-bound form of the toxin. The high stain density in the smaller particle is consistent with the presence of a penetrating pore in this structure.     

Influence of the g-force on the circumnutations of sunflower hypocotyls

Circumnutations of hypocotyls of sunflower ( Helianthus annuus L. cv. Californicus) were studied under 1 g and 3 g conditions. Root mean square values of the hypocotyl deviation from the plumbline and period of the movements were determined from Calculations of the autocorrelation functions of the movements. The amplitude and the period of the circumnutations increased under 3 g as compared to 1 g . A transition from 3 to 1 g or vice versa also caused changes in period and amplitude of the movoments. The results are interpreted as a support for the idea that gravity influences the circumnutation parameters in this sunflower variety. A comparison is made with published results on the dwarf sunflower ev. Teddy Bear where the force influence is very small or negligible. Simulations of a model for circumnutations show movements which are in qualitative agreement with the experimental results, provided adaptation to g -levels is included in the model. Finally, the results are discussed with the recent Spacelab-experiment (SLI) as a background.