An experimental study on post-mortem dissolution and overgrowth processes affecting coccolith assemblages: A rapid and complex process

Coccolith dissolution together with post-mortem morphological features are immensely important phenomena that can affect assemblage compositions, complicate taxonomic identification as well as provide valuable palaeoenvironmental insights. This study summarizes the effects of pH oscillations on post-mortem coccolith morphologies and the abundances and compositions of calcareous nannoplankton assemblages in three distinct types of material—(i) Cretaceous chalk, (ii) Miocene marls, and (iii) late Holocene calcareous ooze. Two independent experimental runs within a semi-enclosed system setting were realized to observe assemblage alterations. One experiment was realized with the presence of bacteria and, in contrast, the second one inhibited their potential effect on the studied system. The pH was gradually decreased within the range of 8.3–6.4 using a reaction of CO₂ with H₂O forming weak carbonic acid (H₂CO₃), thereby affecting [${\mathrm{CO}}_3^{2-}$]. Further, a subsequent overgrowth study was carried out during spontaneous degassing accompanied by a gradual pH rise. The experiment revealed that the process and intensity of coccolith corrosion and subsequent overgrowth build-ups are influenced by a plethora of different factors such as (i) pH and associated seawater chemistry, (ii) mineral composition of the sediment, (iii) the presence of coccoliths within a protective substrate (faecal pellets, pores, pits), and (iv) the presence/absence of bacteria. Nannoplankton assemblages with corroded coccoliths or with coccoliths with overgrowth build-ups showed that the observed relative abundances of taxa experienced alteration from the original compositions. Additionally, extreme pH oscillations may result in enhanced morphological changes that make coccoliths unidentifiable structures, and might even evoke the absence of coccoliths in the fossil record.     

Computational identification of miRNAs,their targets and functions in three‐spined stickleback (Gasterosteus aculeatus)

An intriguing question in biology is how the evolution of gene regulation is shaped by natural selection in natural populations. Among the many known regulatory mechanisms, regulation of gene expression by microRNAs (miRNAs) is of critical importance. However, our understanding of their evolution in natural populations is limited. Studying the role of miRNAs in three‐spined stickleback, an important natural model for speciation research, may provide new insights into adaptive polymorphisms. However, lack of annotation of miRNA genes in its genome is a bottleneck. To fill this research gap, we used the genome of three‐spined stickleback to predict miRNAs and their targets. We predicted 1486 mature miRNAs using the homology‐based miRNA prediction approach. We then performed functional annotation and enrichment analysis of these targets, which identified over‐represented motifs. Further, a database resource (GAmiRdb) has been developed for dynamically searching miRNAs and their targets exclusively in three‐spined stickleback. Finally, the database was used in two case studies focusing on freshwater adaptation in natural populations. In the first study, we found 44 genomic regions overlapping with predicted miRNA targets. In the second study, we identified two SNPs altering the MRE seed site of sperm‐specific glyceraldehyde‐3‐phosphate gene. These findings highlight the importance of the GAmiRdb knowledge base in understanding adaptive evolution.     

Effect of adrenalectomy and corticosterone on cocaine-induced sensitization in rats.

Effects of adrenalectomy (ADX) and corticosterone (CORT) on the development and expression of sensitization to the locomotor effect of cocaine (COC) were studied in rats. Sensitization was evoked by 5 daily injections of COC (10 mg/kg) and measured after a challenge dose of the drug (10 mg/kg) after a 5-day withdrawal (on day 10 of the experiment). ADX, performed before the start of COC administration, completely blocked the manifestation of COC-induced sensitization. In contrast, ADX performed on animals already sensitized to COC did not affect the sensitized locomotor activity response to a challenge dose of COC (on day 18). Pretreatment with CORT, 10 mg/kg, but not 5 mg/kg, before each of the 5 daily COC injections facilitated the development of COC sensitization, tested after a 5-day withdrawal. When pretreated with CORT alone (10 mg/kg), the challenge dose of COC administered on day 10 induced cross-sensitization to CORT. CORT (10 mg/kg) injected acutely before COC on day 10, potentiated the expression of COC sensitization. When given alone, on day 10 CORT (5-10 mg/kg) induced an increase in the locomotor activity of rats pretreated daily (5 injections) with COC. No drug treatment induced conditioned locomotion, as measured after saline challenge on day 8. Our results indicate that CORT facilitates the development and expression of COC sensitization, while ADX blocks the initiation of the behavioral phenomenon only. Moreover, there takes place cross-sensitization between CORT and COC, which indicates a close relationship between the drug-related mechanism and behavioral sensitization.     

Noninvasive tumor volume measurement using magnetic resonance (MR) imaging and an open sided saddle coil

A magnetic resonance (MR) imaging scanner operated at 0.5 T with a specially constructed receiving coil was used to measure volumes of primary spontaneous tumors in rats and guinea pigs. The coil was used to improve the signal to noise ratio (S/N) of the MR images of tumors in these small animals. The tumor volume was determined by the summation of the volume of contiguous slices or ellipsoid approximation. The accuracy of the volume measurement was better when the numerical integration was used in calculating the slice volume. The open sided saddle (OSS) coil used as the receiving coil gave better S/N than that of the standard head coil.     

Cloning and expression of a Clostridium acetobutylicumα-amylase gene in Escherichia coli

A gene library of Clostridium acetobutylicum ATCC824 was constructed in the plasmid vector pEcoR251. The library was tested for the presence of starch hydrolyzing clones. One clone in which the recombinant plasmid, pVP101, conferred alpha-amylase activity to the Escherichia coli host cell, was detected. The gene is carried on a 3.45-kbp BglII restriction fragment. A detailed physical map of pVP101 is presented.     

Simmonds' disease following chronic sclerosing hypophysitis

A case of Simmonds' disease following chronic sclerosing hypophysitis is described in a moderately confused, 54-years-old woman in an extremely advanced cachexia. The patient died four days later in cardio-respiratory failure. The anterior lobe of the hypophysis showed dense, interlacing bands of fibrosis delineating small areas of atrophic pituitary cells. More than four-fifths of the anterior hypophyseal lobe was replaced by fibrosis or dense scarring. A scarce lymphocytic infiltrate between the fibrous bands was noted. The liver showed advanced fatty changes. An interesting finding was the presence of a chronic lymphocytic infiltrate in the adrenals. The association of chronic adrenalitis and sclerosing hypophysitis could be interpreted as an autoimmune endocrinopathy.     

Application of enzyme immunoassay for detection of the nitrogen-fixing bacteria of the genus <Emphasis Type="Italic">Azospirillum</Emphasis> in soil suspensions

The enzyme immunoassay of soil suspensions was performed using antibodies against the lipopolysaccharides of Azospirillum brasilense model strains in order to assess the monthly population dynamics of the A. brasilense Sp245 introduced into the soil samples in laboratory simulation experiments and to determine the abundance of azospirilla in the various soils of the Saratov oblast. In laboratory simulation experiments (a sample of southern chernozem was used), the maximum amount of the antigen in question was detected in soil suspensions on day 7 of the one-month experiment on the introduction of bacterial cells into soil samples. Analysis of the major soil types of the Saratov oblast (saline, alluvial, and grey forest soils, as well as typical and southern chernozem) revealed the predominance of azospirilla antigens of the Sp245 serotype; significant amounts of the serotype Sp7 antigens were detected in southern chernozem.