Effects of sequential acute stress exposure on stress-induced pituitary luteinizing hormone and prolactin secretion

The present study was carried out to determine the effects of repetitive acute stress exposure on pituitary secretion of both luteinizing hormone (LH) and prolactin (PRL). Adult male rats were exposed to sequential episodes of acute novel environment stress separated by intervals of either 60 or 120 minutes. Serial blood samples were obtained from animals before, during and after each stress episode via indwelling intra-cardiac cannulas. The imposition of 10 minute episodes of novel environment stress on an hourly basis eventually rendered the hypothalamic-hypophyseal LH axis refractory to the stimulatory effect of stress. If sequential stress was imposed at 120 minute intervals, LH release was significantly enhanced during each exposure. A different pattern of PRL release was observed during the same sequential stress schedule. After an initial increase in hormone release in response to the first hourly stress episode, PRL levels were unaltered during the second and third hourly stress exposures. Thereafter, plasma PRL levels showed a trend toward a progressive increase in release during each successive episode, and were significantly elevated above preceding baseline levels during the fourth and fifth hourly stress exposures. In rats exposed to stress every two hours, a significant increase in PRL levels occurred following the first, but not the second stress episode. Hormone release was again enhanced in response to the third exposure to novel environment. The present results demonstrate that the repetitive exposure to acute novel environment stress results in differential alterations in pituitary LH and PRL secretion over time, and that the timing of repeated episodes is an important determinant of continued responsiveness to stress, particularly with regard to LH release. These findings suggest that the LH and PRL hormonal responses to at least this specific stressor are mediated by independent neural mechanisms.     

Population attenuation in zooplankton communities during transoceanic transfer in ballast water

Successful biological invasion requires introduction of a viable population of a nonindigenous species (NIS). Rarely have ecologists assessed changes in populations while entrained in invasion pathways. Here, we investigate how zooplankton communities resident in ballast water change during transoceanic voyages. We used next‐generation sequencing technology to sequence a nuclear small subunit ribosomal DNA fragment of zooplankton from ballast water during initial, middle, and final segments as a vessel transited between Canada and Brazil. Operational taxonomic unit (OTU) diversity decreased as voyage duration increased, indicating loss of community‐based genetic diversity and development of bottlenecks for zooplankton taxa prior to discharge of ballast water. On average, we observed 47, 26, and 24 OTUs in initial, middle, and final samples, respectively. Moreover, a comparison of genetic diversity within taxa indicated likely attenuation of OTUs in final relative to initial samples. Abundance of the most common taxa (copepods) declined in all final relative to initial samples. Some taxa (e.g., Copepoda) were represented by a high number of OTUs throughout the voyage, and thus had a high level of intraspecific genetic variation. It is not clear whether genotypes that were most successful in surviving transit in ballast water will be the most successful upon introduction to novel environments. This study highlights that population bottlenecks may be common prior to introduction of NIS to new ecosystems.     

Antiproliferative and apoptotic effects of tocopherols and tocotrienols on preneoplastic and neoplastic mouse mammary epithelial cells

Studies were conducted to determine the comparative effects of tocopherols and tocotrienols on preneoplastic (CL-S1), neoplastic (-SA), and highly malignant (+SA) mouse mammary epithelial cell growth and viability in vitro. Over a 5-day culture period, treatment with 0-120 microM alpha- and gamma-tocopherol had no effect on cell proliferation, whereas growth was inhibited 50% (IC50) as compared with controls by treatment with the following: 13, 7, and 6 microM tocotrienol-rich-fraction of palm oil (TRF); 55, 47, and 23 microM delta-tocopherol; 12, 7, and 5 microM alpha-tocotrienol; 8, 5, and 4 microM gamma-tocotrienol; or 7, 4, and 3 microM delta-tocotrienol in CL-S1, -SA and +SA cells, respectively. Acute 24-hr exposure to 0-250 microM alpha- or gamma-tocopherol (CL-S1, -SA, and +SA) or 0-250 microM delta-tocopherol (CL-S1) had no effect on cell viability, whereas cell viability was reduced 50% (LD50) as compared with controls by treatment with 166 or 125 microM delta-tocopherol in -SA and +SA cells, respectively. Additional LD50 doses were determined as the following: 50, 43, and 38 microM TRF; 27, 28, and 23 microM alpha-tocotrienol; 19, 17, and 14 microM gamma-tocotrienol; or 16, 15, or 12 microM delta-tocotrienol in CL-S1, -SA, and +SA cells, respectively. Treatment-induced cell death resulted from activation of apoptosis, as indicated by DNA fragmentation. Results also showed that CL-S1, -SA, and +SA cells preferentially accumulate tocotrienols as compared with tocopherols, and this may partially explain why tocotrienols display greater biopotency than tocopherols. These data also showed that highly malignant +SA cells were the most sensitive, whereas the preneoplastic CL-S1 cells were the least sensitive to the antiproliferative and apoptotic effects of tocotrienols, and suggest that tocotrienols may have potential health benefits in preventing and/or reducing the risk of breast cancer in women.     

Relationship between propagule pressure and colonization pressure in invasion ecology: a test with ships' ballast

Increasing empirical evidence indicates the number of released individuals (i.e. propagule pressure) and number of released species (i.e. colonization pressure) are key determinants of the number of species that successfully invade new habitats. In view of these relationships, and the possibility that ships transport whole communities of organisms, we collected 333 ballast water and sediment samples to investigate the relationship between propagule and colonization pressure for a variety of diverse taxonomic groups (diatoms, dinoflagellates and invertebrates). We also reviewed the scientific literature to compare the number of species transported by ships to those reported in nature. Here, we show that even though ships transport nearly entire local communities, a strong relationship between propagule and colonization pressure exists only for dinoflagellates. Our study provides evidence that colonization pressure of invertebrates and diatoms may fluctuate widely irrespective of propagule pressure. We suggest that the lack of correspondence is explained by reduced uptake of invertebrates into the transport vector and the sensitivity of invertebrates and diatoms to selective pressures during transportation. Selection during transportation is initially evident through decreases in propagule pressure, followed by decreased colonization pressure in the most sensitive taxa.     

The journey of a sandwich: computer-based laboratory experiments about the human digestive system in high school biology teaching

Teaching high school students about the digestive system can be a challenge for a teacher when s/he wants to overcome rote learning of facts without a deeper understanding of the physiological processes inside the alimentary tract. A series of model experiments illustrating the journey of a sandwich was introduced into teaching high school biology. Using a computer equipped with a commercially available data-acquisition system and a couple of sensors, it was possible to illustrate the basic underlying physical and chemical principles of digestion to the students. Students were able to investigate, through hands-on activities, the chewing force of the jaws, importance of the mechanical breakdown of food, enzymatic activity of pepsin and amylase, antibacterial activity of hydrochloric acid, and importance of the villi for absorption. Students found the experiments interesting and helpful for understanding the digestive process. Furthermore, the results from testing indicated that the students had a deeper understanding of the physiological processes.     

Are genetic databases sufficiently populated to detect non-indigenous species?

Correct species identifications are of tremendous importance for invasion ecology, as mistakes could lead to misdirecting limited resources against harmless species or inaction against problematic ones. DNA barcoding is becoming a promising and reliable tool for species identifications, however the efficacy of such molecular taxonomy depends on gene region(s) that provide a unique sequence to differentiate among species and on availability of reference sequences in existing genetic databases. Here, we assembled a list of aquatic and terrestrial non-indigenous species (NIS) and checked two leading genetic databases for corresponding sequences of six genome regions used for DNA barcoding. The genetic databases were checked in 2010, 2012, and 2016. All four aquatic kingdoms (Animalia, Chromista, Plantae and Protozoa) were initially equally represented in the genetic databases, with 64, 65, 69, and 61 % of NIS included, respectively. Sequences for terrestrial NIS were present at rates of 58 and 78 % for Animalia and Plantae, respectively. Six years later, the number of sequences for aquatic NIS increased to 75, 75, 74, and 63 % respectively, while those for terrestrial NIS increased to 74 and 88 % respectively. Genetic databases are marginally better populated with sequences of terrestrial NIS of plants compared to aquatic NIS and terrestrial NIS of animals. The rate at which sequences are added to databases is not equal among taxa. Though some groups of NIS are not detectable at all based on available data—mostly aquatic ones—encouragingly, current availability of sequences of taxa with environmental and/or economic impact is relatively good and continues to increase with time.     

Assessing introduction risk using species’ rank-abundance distributions

Mixed-species assemblages are often unintentionally introduced into new ecosystems. Analysing how assemblage structure varies during transport may provide insights into how introduction risk changes before propagules are released. Characterization of introduction risk is typically based on assessments of colonization pressure (CP, the number of species transported) and total propagule pressure (total PP, the total abundance of propagules released) associated with an invasion vector. Generally, invasion potential following introduction increases with greater CP or total PP. Here, we extend these assessments using rank-abundance distributions to examine how CP : total PP relationships change temporally in ballast water of ocean-going ships. Rank-abundance distributions and CP : total PP patterns varied widely between trans-Atlantic and trans-Pacific voyages, with the latter appearing to pose a much lower risk than the former. Responses also differed by taxonomic group, with invertebrates experiencing losses mainly in total PP, while diatoms and dinoflagellates sustained losses mainly in CP. In certain cases, open-ocean ballast water exchange appeared to increase introduction risk by uptake of new species or supplementation of existing ones. Our study demonstrates that rank-abundance distributions provide new insights into the utility of CP and PP in characterizing introduction risk.     

Sex-dimorphic moderate hypoglycemia preconditioning effects on Hippocampal CA1 neuron bio-energetic and anti-oxidant function

Molecular and Cellular Biochemistry - Hypoglycemia is a detrimental complication of rigorous management of type 1 diabetes mellitus. Moderate hypoglycemia (MH) preconditioning of male rats...