Patterns of segregation of structural elements during cell division

Summary Adaptations of currently available autoradiographic electron microscopic methods to the study of organelle development in single Paramecium cells are described. Cells of known age were pulse-labeled with tritiated leucine and observed either as whole mounts, or as sections of specified age and cell-lineage. Labeled trichocysts appear as early as one hour after uptake and retain the label without dilution for at least 3 fission generations thereafter. Cells grown in unlabeled medium, but derived from labeled cells, show the bulk of the residual label to be conservatively associated with the stable structural organelles of the cell surface. These organelles include those trichocysts and ciliary corpuscles that had been synthesized in the ancestral progenitor cell during or shortly after administration of the isotopically labeled amino acid.Work supported by U. S. Atomic Energy Commission.Dedicated to Professor Friedrich Wassermann with admiration and affection on the occassion of his eightieth birthday.     

Soil organic carbon fractions in the Great Plains of the United States: an application of mid-infrared spectroscopy

Biogeochemistry - Spectroscopy is a powerful means of increasing the availability of soil data necessary for understanding carbon cycling in a changing world. Here, we develop a calibration...     

Stejneger's beaked whale strandings in Alaska, 1995–2020

Presented here is the first comprehensive and updated compilation of history, distribution, and findings of Stejneger's beaked whales (Mesoplodon stejnegeri) in Alaska. Stejneger's beaked whales are a poorly understood, elusive, deep-diving cetacean species found in the North Pacific Ocean. Since Stejneger's beaked whale strandings data in Alaska through 1994 were last published, 35 additional strandings have been documented. Twenty-seven animals stranded in the Aleutian Islands, seven stranded in Southcentral Alaska, and one animal stranded on St. Lawrence Island. Twenty-two carcasses were necropsied, but only four were fresh. Seventeen of the 22 died during mass stranding events and cause of death could not be definitively determined. Barotrauma was suspected in three cases and infectious disease possibly complicated by barotrauma occurred in two cases. We documented an expansion of strandings into the northern Bering Sea, characterized a sex bias, examined stomach contents that included macroplastic, and identified parasites not previously associated with Stejneger's beaked whales. Also included are data on the largest known mass stranding of Stejneger's beaked whales, which occurred on Adak Island in 2018. The history, distribution, and findings presented here are central to further our understanding of this species.     

Effects of Caregiver-Implemented Aggression Reduction Procedure on Problem Behavior of Dogs

Problem behavior of companion animals poses a threat to caregivers, other targets of problem behavior (e.g., strangers, other nonhuman animals), and those animals engaging in problem behavior. This study examined the effects of an aggression reduction procedure (ARP) on dog problem behavior. After a baseline condition showing caregivers were unsuccessful in reducing dog aggression and the behaviors preceding aggression, caregivers were trained to implement a procedure to address dog problem behavior in relatively simple contexts. Generalization programming then was used to target caregiver plan implementation and dog problem behavior in more complex contexts. The ARP effectively reduced dog aggression for all dogs. A slight reduction and increased variability in dog precursor behavior was observed when the ARP was implemented. In addition, caregivers and experts rated the goals, procedures, and effects as acceptable. Implications of these findings are discussed.     

A Versatile Composite Gel Column for the Electrophoretic Separation of Ribonucleic Acid Molecules

A composite gel column system containing 2.4% acry I amide, 0.14% N,n¹-methylene bisacrylamide, 0.6% agarose and 15% glycerol as a component has been developed for the electrophoretlc separation of all kinds of ribonucleic acid molecules extracted from eucaryotlc cells. The separations achieved In this composite gel are due to the sieving of RNA molecules of various sizes with similar charge. As a result of the addition of glycerol the polymerization time of the composite gel is extended and the gel has increased mechanical stability. These stable gels can be sliced at room temperature for such procedures as measuring radioactivity or extraction. Their suitability for staining and absorbance scanning is not altered.     

Long‐term changes in forest carbon under temperature and nitrogen amendments in a temperate northern hardwood forest

Currently, forests in the northeastern United States are net sinks of atmospheric carbon. Under future climate change scenarios, the combined effects of climate change and nitrogen deposition on soil decomposition, aboveground processes, and the forest carbon balance remain unclear. We applied carbon stock, flux, and isotope data from field studies at the Harvard forest, Massachusetts, to the ForCent model, which integrates above‐ and belowground processes. The model was able to represent decadal‐scale measurements in soil C stocks, mean residence times, fluxes, and responses to a warming and N addition experiment. The calibrated model then simulated the longer term impacts of warming and N deposition on the distribution of forest carbon stocks. For simulation to 2030, soil warming resulted in a loss of soil organic matter (SOM), decreased allocation to belowground biomass, and gain of aboveground carbon, primarily in large wood, with an overall small gain in total system carbon. Simulated nitrogen addition resulted in a small increase in belowground carbon pools, but a large increase in aboveground large wood pools, resulting in a substantial increase in total system carbon. Combined warming and nitrogen addition simulations showed a net gain in total system carbon, predominately in the aboveground carbon pools, but offset somewhat by losses in SOM. Hence, the impact of continuation of anthropogenic N deposition on the hardwood forests of the northeastern United States may exceed the impact of warming in terms of total ecosystem carbon stocks. However, it should be cautioned that these simulations do not include some climate‐related processes, different responses from changing tree species composition. Despite uncertainties, this effort is among the first to use decadal‐scale observations of soil carbon dynamics and results of multifactor manipulations to calibrate a model that can project integrated aboveground and belowground responses to nitrogen and climate changes for subsequent decades.     

Diel patterns of autotrophic and heterotrophic respiration among phenological stages

Improved understanding of the links between aboveground production and allocation of photosynthate to belowground processes and the temporal variation in those links is needed to interpret observations of belowground carbon cycling processes. Here, we show that combining a trenching manipulation with high‐frequency soil respiration measurements in a temperate hardwood forest permitted identification of the temporally variable influence of roots on diel and seasonal patterns of soil respiration. The presence of roots in an untrenched plot caused larger daily amplitude and a 2–3 h delay in peak soil CO₂ efflux relative to a root‐free trenched plot. These effects cannot be explained by differences in soil temperature, and they were significant only when a canopy was present during the growing season. This experiment demonstrated that canopy processes affect soil CO₂ efflux rates and patterns at hourly and seasonal time scales, and it provides evidence that root and microbial processes respond differently to environmental factors.     

Caloric restriction augments radiation efficacy in breast cancer

Dietary modification such as caloric restriction (CR) has been shown to decrease tumor initiation and progression. We sought to determine if nutrient restriction could be used as a novel therapeutic intervention to enhance cytotoxic therapies such as radiation (IR) and alter the molecular profile of triple-negative breast cancer (TNBC), which displays a poor prognosis. In two murine models of TNBC, significant tumor regression is noted with IR or diet modification, and a greater regression is observed combining diet modification with IR. Two methods of diet modification were compared, and it was found that a daily 30% reduction in total calories provided more significant tumor regression than alternate day feeding. At the molecular level, tumors treated with CR and IR showed less proliferation and more apoptosis. cDNA array analysis demonstrated the IGF-1R pathway plays a key role in achieving this physiologic response, and multiple members of the IGF-1R pathway including IGF-1R, IRS, PIK3ca and mTOR were found to be downregulated. The innovative use of CR as a novel therapeutic option has the potential to change the biology of tumors and enhance the opportunity for clinical benefit in the treatment of patients with TNBC.