A morphometric comparison of subcellular structures between primary breast tumors and their nodal metastases.

A morphometric study of subcellular structures in human primary breast tumors (of the ductal infiltrating type) and their synchronous lymph node metastases was carried out using planimetry and stereology. Each primary neoplasm was compared separately with its axillary metastatic growth in order to detect differences in the quantitative estimates of their subcellular components. A set of 24 morphometric parameters was used to quantitatively describe each neoplastic cell profile. Although some subcellular parameters showed significant differences between the cells of a primary tumor and its metastases, no parameter was found to be consistently altered in all cases. No consistent increase or decrease in the values of the affected parameters was observed in the metastases. More than being due to the expression of a biologically variant (more-or-less differentiated) metastatic phenotype, the differences in stereologic parameters detected in metastatic cells appear to reflect the existence of different functional states of the same cell type.     

Measurement of endogenous leucine enkephalin in canine caudate nuclei and hypothalami with high-performance liquid chromatography and field-desorption mass spectrometry

For the first time, endogenous amounts of Leu-enkephalin are measured in brain tissue with a technique preserving integrity of the entire molecular structure of the neuropeptide. Field-desorption mass spectrometry enables measurement of picomole amounts of endogenous, chemically underivatized Leu-enkephalin in canine caudate nuclei and hypothalami. The optimal sensitivity and resolution of high-performance liquid chromatography is coupled with maximal molecular specificity of field-desorption mass spectrometry to measure enkephalins in caudate nuclei and hypothalami from dog brains. This novel combination of two recent instrumental methodologies provides a firm molecular basis for calibrating the radioimmunoassay measurement of endogenous levels of biologically active brain neuropeptides.     

Mass spectrometry of acetylated,permethylated and reduced oligopeptides

The amino acid sequence of oligopeptides can be determined from the mass spectra of their volatile derivatives. New peptide derivatives are described which are prepared from permethylated peptides by reduction with borane-tetrahydrofuran. These derivatives have been found to be more volatile than the corresponding permethylated ones. The procedure is illustrated by application of this technique to representative oligopeptides. As little as 10–100 nmol of these peptides have been sequenced using this technique.     

Exosomes surf on filopodia to enter cells at endocytic hot spots,traffic within endosomes,and are targeted to the ER

Exosomes are nanovesicles released by virtually all cells, which act as intercellular messengers by transfer of protein, lipid, and RNA cargo. Their quantitative efficiency, routes of cell uptake, and subcellular fate within recipient cells remain elusive. We quantitatively characterize exosome cell uptake, which saturates with dose and time and reaches near 100% transduction efficiency at picomolar concentrations. Highly reminiscent of pathogenic bacteria and viruses, exosomes are recruited as single vesicles to the cell body by surfing on filopodia as well as filopodia grabbing and pulling motions to reach endocytic hot spots at the filopodial base. After internalization, exosomes shuttle within endocytic vesicles to scan the endoplasmic reticulum before being sorted into the lysosome as their final intracellular destination. Our data quantify and explain the efficiency of exosome internalization by recipient cells, establish a new parallel between exosome and virus host cell interaction, and suggest unanticipated routes of subcellular cargo delivery.     

Microphytobenthos and chironomid larvae attenuate nutrient recycling in shallow‐water sediments

相似文献   

β-Amyloid carrying the Dutch mutation has diverse effects on calpain-mediated toxicity in hippocampal neurons

Hereditary cerebral hemorrhage with amyloidosis-Dutch type is a disorder associated with a missense mutation (E693Q) in the β-amyloid (Aβ)-coding region of the amyloid precursor protein (APP). This familial disease is characterized by cognitive deficits secondary to intracerebral hemorrhage and, in some cases, progressive Alzheimer's disease (AD)-like dementia. Although this mutation was the first ever reported in the human APP gene, little is known about the molecular mechanisms underlying the direct toxic effects of this mutated Aβ on central neurons. In the present study, we assessed the role of calpain-mediated toxicity in such effects using an AD primary culture model system. Our results showed that Dutch mutant Aβ (E22Q) induced calpain-mediated cleavage of dynamin 1 and a significant decrease in synaptic contacts in mature hippocampal cultures. These synaptic deficits were similar to those induced by wild-type (WT) Aβ. In contrast, calpain-mediated tau cleavage leading to the generation of a 17-kDa neurotoxic fragment, as well as neuronal death, were significantly reduced in E22Q Aβ-treated neurons when compared with WT Aβ-treated ones. This complex regulation of the calpain-mediated toxicity pathway by E22Q Aβ could have some bearing in the pathobiology of this familial AD form.     

Chlamydomonas raudensis (UWO 241), Chlorophyceae,exhibits the capacity for rapid D1 repair in response to chronic photoinhibition at low temperature1

Maximum photosynthetic capacity indicates that the Antarctic psychrophile Chlamydomonas raudensis H. Ettl UWO 241 is photosynthetically adapted to low temperature. Despite this finding, C. raudensis UWO 241 exhibited greater sensitivity to low‐temperature photoinhibition of PSII than the mesophile Chlamydomonas reinhardtii P. A. Dang. However, in contrast with results for C. reinhardtii, the quantum requirement to induce 50% photoinhibition of PSII in C. raudensis UWO 241 (50 μmol photons) was comparable at either 8°C or 29°C. To our knowledge, this is the first report of a photoautotroph whose susceptibility to photoinhibition is temperature independent. In contrast, the capacity of the psychrophile to recover from photoinhibition of PSII was sensitive to temperature and inhibited at 29°C. The maximum rate of recovery from photoinhibition of the psychrophile at 8°C was comparable to the maximum rate of recovery of the mesophile at 29°C. We provide evidence that photoinhibition in C. raudensis UWO 241 is chronic rather than dynamic. The photoinhibition‐induced decrease in the D1 content in C. raudensis recovered within 30 min at 8°C. Both the recovery of the D1 content as well as the initial fast phase of the recovery of F_v/F_m at 8°C were inhibited by lincomycin, a chloroplast protein synthesis inhibitor. We conclude that the susceptibility of C. raudensis UWO 241 to low‐temperature photoinhibition reflects its adaptation to low growth irradiance, whereas the unusually rapid rate of recovery at low temperature exhibited by this psychrophile is due to a novel D1 repair cycle that is adapted to and is maximally operative at low temperature.     

Carbon isotope evidence for recent climate‐related enhancement of CO 2 assimilation and peat accumulation rates in Antarctica

Signy Island, maritime Antarctic, lies within the region of the Southern Hemisphere that is currently experiencing the most rapid rates of environmental change. In this study, peat cores up to 2 m in depth from four moss banks on Signy Island were used to reconstruct changes in moss growth and climatic characteristics over the late Holocene. Measurements included radiocarbon dating (to determine peat accumulation rates) and stable carbon isotope composition of moss cellulose (to estimate photosynthetic limitation by CO ₂ supply and model CO ₂ assimilation rate). For at least one intensively ¹⁴C‐dated Chorisodontium aciphyllum moss peat bank, the vertical accumulation rate of peat was 3.9 mm yr^?1 over the last 30 years. Before the industrial revolution, rates of peat accumulation in all cores were much lower, at around 0.6–1 mm yr^?1. Carbon‐13 discrimination (Δ), corrected for background and anthropogenic source inputs, was used to develop a predictive model for CO ₂ assimilation. Between 1680 and 1900, there had been a gradual increase in Δ, and hence assimilation rate. Since 1800, assimilation has also been stimulated by the changes in atmospheric CO ₂ concentration, but a recent decline in Δ (over the past 50–100 years) can perhaps be attributed to documented changes in temperature and/or precipitation. The overall increase in CO ₂ assimilation rate (¹³C proxy) and enhanced C accumulation (¹⁴C proxy) are consistent with warmer and wetter conditions currently generating higher growth rates than at any time in the past three millennia, with the decline in Δ perhaps compensated by a longer growing season.