Foraminiferal isotope evidence of reduced nitrogen fixation in the ice age Atlantic Ocean.

Fixed nitrogen (N) is a limiting nutrient for algae in the low-latitude ocean, and its oceanic inventory may have been higher during ice ages, thus helping to lower atmospheric CO2 during those intervals. In organic matter within planktonic foraminifera shells in Caribbean Sea sediments, we found that the 15N/14N ratio from the last ice age is higher than that from the current interglacial, indicating a higher nitrate 15N/14N ratio in the Caribbean thermocline. This change and other species-specific differences are best explained by less N fixation in the Atlantic during the last ice age. The fixation decrease was most likely a response to a known ice age reduction in ocean N loss, and it would have worked to balance the ocean N budget and to curb ice age-interglacial change in the N inventory.

The global carbon cycle: a test of our knowledge of earth as a system.

Motivated by the rapid increase in atmospheric CO2 due to human activities since the Industrial Revolution, several international scientific research programs have analyzed the role of individual components of the Earth system in the global carbon cycle. Our knowledge of the carbon cycle within the oceans, terrestrial ecosystems, and the atmosphere is sufficiently extensive to permit us to conclude that although natural processes can potentially slow the rate of increase in atmospheric CO2, there is no natural "savior" waiting to assimilate all the anthropogenically produced CO2 in the coming century. Our knowledge is insufficient to describe the interactions between the components of the Earth system and the relationship between the carbon cycle and other biogeochemical and climatological processes. Overcoming this limitation requires a systems approach.

Linomide downregulates autoimmunity through induction of TH2 cytokine production by lymphocytes.

Linomide is a synthetic immunomodulator that has been shown to protect animals against a wide range of spontaneously developing or induced autoimmune diseases. We have previously reported that Linomide blocks both the clinical and the histopathological manifestations of experimental autoimmune encephalomyelitis (EAE) in various animal models. In this study, in an effort to elucidate the mechanisms by which Linomide suppresses EAE, and autoimmunity in general, we investigated the in vivo effects of this drug on the TH1/TH2 lymphocyte balance, which is important for the induction or inhibition of autoireactivity. Naive SJL/J mice were treated orally for 15 days with Linomide (80 mg/kg/day). Spleen cells were obtained at various time points during the treatment period and were stimulated in vitro with concanavalin A. Interleukins IL-4, IL-10 and IL-12, transforming growth factor-beta (TGFbeta) and interferon-gamma (IFNgamma) cytokine production was evaluated both by means of detection of the cytokines in the medium (by ELISA technique) and by detection of the cytokine mRNA production, using a semiquantitative reverse transcriptase polymerase chain reaction method. A significant upregulation of IL-4, IL-10 and TGFbeta was observed following treatment with Linomide, which peaked at day 10 (IL-10) or day 15 (IL-4). On the other hand, IL-12 and IFNgamma production were either unchanged or decreased. It seems therefore that Linomide induces in vivo a shift towards TH2 lymphocytes which may be one of the mechanisms of downregulation of the autoimmune reactivity in EAE. Our observations indicate that downregulation of TH1 cytokines (especially IL-12) and enhancement of TH2 cytokine production may play an important role in the control of T-cell-mediated autoimmunity. These data may contribute to the design of new immunomodulating treatments for a group of autoimmune diseases.

Precise determination of element/calcium ratios in calcareous samples using sector field inductively coupled plasma mass spectrometry.

A new method was developed for rapid and precise simultaneous determination of Mg/Ca, Sr/Ca, Mn/Ca, Cd/Ca, Ba/Ca and U/Ca ratios in foraminiferal shells using sector field inductively coupled plasma mass spectrometry (ICPMS). Element/calcium ratios were determined directly from intensity ratios using external, matrix-matched standard to correct for instrumental mass discrimination. Because of large differences in the abundance of chemical constituents of the foraminiferal shell, major elemental ratios were determined in analog mode (using (24)Mg, (43)Ca, (44)Ca, (55)Mn, and (88)Sr) whereas trace elemental ratios were determined in pulse-counting mode (using (111)Cd, (138)Ba, (238)U, and the low-abundance (46)Ca isotope). Matrix-induced variations in mass discrimination over a calcium concentration range of 2.0-24.5 mM were observed only for Mg/Ca and Cd/Ca ratios. However, these effects are negligible if the samples and standard calcium concentration are within a factor of 2-3. Multiratio method reproducibility was better than previously reported for other ICPMS methods yielding precision (1σ) of Sr/Ca = 0.45%; Mg/Ca = 0.45%, Mn/Ca = 0.8%, Cd/Ca = 1.7%, Ba/Ca = 0.7%, and U/Ca = 1.4% for foraminifera samples as small as 25 µg. Using this approach for a single-ratio analysis, Sr/Ca ratios were determined with precision of 0.06% (1σ) on carbonate samples as small as a single foraminifera shell (<10 µg). The new method is more sensitive, more precise, and simpler to use than previously available ICPMS techniques. It provides an efficient tool for simultaneous determination of several elemental ratios of paleoceanographic interest in a single foraminiferal sample, thereby reducing overall sample size requirement and analysis time.

Nursing management of adults in the hospital.

This chapter has provided an overview of the nursing process from the initial assessment to discharge planning in the care of the adult AIDS patient. The psychosocial aspects have not been addressed since they are discussed in the article by Govoni. The emotional support required by the patient may be as great as the physical nursing care needed. The AIDS patient may be experiencing social isolation related to discrimination, rejection or isolation by employers, society, family, friends, and even health care workers. It is important not to isolate the patient but to establish a therapeutic relationship. This may be accomplished by being professional, knowledgeable about the issues, nonjudgmental, understanding, and, lastly, sensitive to the patient's needs, fears, and concerns. Patients may be going through the stages of grieving as they try to come to terms with their prognosis. Caring for the adult AIDS patient is both complex and challenging for the nurse as the primary care provider. The nurse can help the patient to cope through the very difficult periods of the disease, even if it means to help the patient have a peaceful and dignified death.

Specific modulation of sodium channels in mammalian nerve by monoclonal antibodies.

Monoclonal antibodies (mAbs) were generated against the sodium channels in the intact membrane of the eel electroplax. These antibodies bind to nodes of Ranvier, as indicated by immunofluorescence. When externally applied to rat nerve fibers one of these mAbs blocks impulse conduction. In voltage-clamp experiments, this mAb was found to attenuate sodium current amplitude without affecting the time course. The dose-response curve was very steep and had an ED50 of 133 nM. About half of the mAb effect was shown to be due to a shift, in the hyperpolarizing direction, of the steady-state sodium inactivation versus membrane potential curve. The remaining effect was voltage- and time-independent. This mAb had no effect on the potassium or leakage currents. The results indicate that on the external surface of the sodium channel, there are a number of antigenically similar determinants, which are functionally linked to specific elements of the sodium conductance system. These functionally related determinants were preserved through the course of evolution.

Dopamine turnover in rat retina: a 24-hour light-dependent rhythm.

To examine the pattern of retinal dopamine (DA) turnover during 24 h, DA and 3,4-dihydroxyphenylacetic acid (DOPAC) were measured at 2-h intervals in rats kept in a regular 12-h light-dark cycle. DA and DOPAC were higher during the light and lower during the dark hours. These rhythmic variations were abolished and DA and DOPAC remained low during 24 h of light deprivation. Findings indicate that DA turnover in the retina is accelerated during the light and suppressed during the dark phases of the diurnal light-dark cycle. These fluctuations in retinal DA neuronal activity are not truly circadian but are dependent on environmental lighting as an external stimulator.