Tropical Atlantic multidecadal variability is dominated by external forcing

The tropical Atlantic climate is characterized by prominent and correlated multidecadal variability in Atlantic sea surface temperatures (SSTs), Sahel rainfall and hurricane activity1-4. Owing to uncertainties in both the models and the observations, the origin of the physical relationships among these systems has remained controversial3-7. Here we show that the cross-equatorial gradient in tropical Atlantic SSTs-largely driven by radiative perturbations associated with anthropogenic emissions and volcanic aerosols since 19503,7-is a key determinant of Atlantic hurricane formation and Sahel rainfall. The relationship is obscured in a large ensemble of CMIP6 Earth system models, because the models overestimate long-term trends for warming in the Northern Hemisphere relative to the Southern Hemisphere from around 1950 as well as associated changes in atmospheric circulation and rainfall. When the overestimated trends are removed, correlations between SSTs and Atlantic hurricane formation and Sahel rainfall emerge as a response to radiative forcing, especially since 1950 when anthropogenic aerosol forcing has been high. Our findings establish that the tropical Atlantic SST gradient is a stronger determinant of tropical impacts than SSTs across the entire North Atlantic, because the gradient is more physically connected to tropical impacts via local atmospheric circulations8. Our findings highlight that Atlantic hurricane activity and Sahel rainfall variations can be predicted from radiative forcing driven by anthropogenic emissions and volcanism, but firmer predictions are limited by the signal-to-noise paradox9-11 and uncertainty in future climate forcings.

Effect of IFN-gamma on the killing of S. aureus in human whole blood. Assessment of bacterial viability by CFU determination and by a new method using alamarBlue

Given the increasing incidence of methicillin resistant Staphylococcus aureus (MRSA) and the recent emergence of MRSA with a reduced susceptibility to vancomycin, alternative approaches to the treatment of infection are of increasing relevance. The purpose of these studies was to evaluate the effect of IFN-gamma on the ability of white blood cells to kill S. aureus and to develop a simpler, higher throughput bacterial killing assay. Using a methicillin sensitive clinical isolate of S. aureus, a clinical isolate of MRSA, and a commercially available strain of MRSA, studies were conducted using a killing assay in which the bacteria were added directly into whole blood. The viability of the bacteria in samples harvested at various time points was then evaluated both by the classic CFU assay and by a new assay using alamarBlue. In the latter method, serially diluted samples and a standard curve containing known concentrations of bacteria were placed on 96-well plates, and alamarBlue was added. Fluorescence readings were taken, and the viability of the bacteria in the samples was calculated using the standard curve. The results of these studies demonstrated that the CFU and alamarBlue methods yielded equivalent detection of bacteria diluted in buffer. For samples incubated in whole blood, however, the alamarBlue method tended to yield lower viabilities than the CFU method due to the emergence of a slower growing subpopulation of S. aureus upon incubation in the blood matrix. A significant increase in bacterial killing was observed upon pretreatment of whole blood for 24 h with 5 or 25 ng/ml IFN-gamma. This increase in killing was detected equivalently by the CFU and alamarBlue methods. In summary, these studies describe a method that allows for the higher throughput analysis of the effects of immunomodulators on bacterial killing.

Interferon gamma administration increases monocyte HLA-DR antigen expression but not endogenous interferon production

OBJECTIVE

To determine the effect of the adjuvant administration of interferon gamma on monocyte HLA-DR antigen expression and mitogen-stimulated interferon gamma production following injury.

DESIGN

Double-blind, randomized, placebo-controlled trial.

SETTING

University Hospital, Newark, NJ, a level I trauma center.

PATIENTS

Persons older than 16 years with an Injury Severity Score greater than 20 and documented bacterial contamination at the time of injury (N = 98).

INTERVENTIONS

Recombinant human interferon gamma (n = 46; 0.1 mg subcutaneously) or placebo (n = 52) was given for 10 days following injury.

OUTCOMES

Incidence of major infection, monocyte and lymphocyte cell surface antigen expression, and interferon gamma production at multiple time points following injury.

RESULTS

Peripheral monocyte HLA-DR was measured as percent of cells staining positive and as mean channel fluorescence. Both values were significantly increased in the interferon gamma group compared with the placebo group on days 3, 5, 8, and 11. The incidence of major infection was unaffected by interferon gamma administration. Infection decreased percent of HLA-DR-positive monocytes and mean channel fluorescence as compared with noninfected patients on postinjury days 8 and 11 in the placebo group but not in the interferon gamma group. Interferon gamma production improved from 3 +/- 3 U/mL on day 1 to 15 +/- 10 U/mL by day 30 but was always significantly lower than normal (25 +/- 3 [mean +/- SD] U/mL). Interferon gamma production was unaffected by either infection or interferon gamma administration.

CONCLUSIONS

Interferon gamma administration after injury stimulated monocyte HLA-DR antigen expression and density but failed to improve interferon gamma production, a T-cell-mediated function. The incidence of infection was not decreased by the administration of interferon gamma for 10 days. Improvement in monocyte HLA-DR antigen expression did not correlate with a global restoration of immune function, and other interventions will be necessary to decrease infection after injury.

Modulation of leukocyte cyclic AMP phosphodiesterase activity by recombinant interferon-gamma: evidence for a differential effect on atopic monocytes

Mechanisms of interferon-gamma (IFN-gamma) effects on monocytes are poorly defined. Evidence for altered IFN-gamma responses and increased monocyte cyclic AMP phosphodiesterase (PDE) activity in atopic dermatitis (AD) suggested a possible relationship. PDE activity in response to IFN-gamma was assessed in normal and atopic monocytes to evaluate the IFN-gamma regulatory role in cell function. Adherence-isolated peripheral blood monocytes were exposed to recombinant human IFN-gamma at 0.1-300 U/ml in Gey's balanced salt solution for varying time periods. Anti-IFN-gamma was used as control. PDE activity was measured by radioenzyme assay using 1 microM cyclic AMP as final substrate concentration. IFN-gamma caused a dose-dependent increase in PDE activity of normal monocytes and the effect was neutralized by anti-IFN-gamma. By contrast, in atopic monocytes, PDE activity was not affected by IFN-gamma at low dose, while at concentrations greater than 200 U/ml, it significantly reduced phosphodiesterase activity. IFN-gamma of PDE activity may alter normal monocyte functions by decreasing cyclic AMP levels. Paradoxical PDE unresponsiveness probably reflects maximal PDE activation in atopic monocytes. This elevated PDE activity is inhibited by high IFN-gamma levels. Reduction of atopic monocyte PDE activity may help to normalize immune function and could account for recent reports of therapeutic efficacy of IFN-gamma in AD.

A rapid in vitro cytotoxicity assay for the detection of tumor necrosis factor on human BT-20 cells

This report describes a rapid, reproducible in vitro bioassay to quantitate the cytotoxic activity of human tumor necrosis factor-alpha using a human rather than murine cell line in the absence of metabolic inhibitors. The target cells are BT-20 (breast carcinoma) cultured at 39 degrees C in the presence of recombinant human tumor necrosis factor-alpha (rHuTNF-alpha) in 96-well microtiter plates for 2 days. Cytotoxicity is measured by the crystal violet dye uptake of the remaining viable cells. This bioassay is sensitive to 1.5 ng/ml of rHuTNF-alpha, with an assay range to 130 ng/ml. Samples spiked into human plasma are measurable from 0.5 to 150 ng/ml. The specificity of this cytotoxic effect on the BT-20 cell line was demonstrated using rHuTNF-alpha neutralizing antibodies. A panel of cytokines including interferons, interleukins, and tumor necrosis factors was also analyzed using this assay system. Of the cytokines assayed, only recombinant murine tumor necrosis factor-alpha and recombinant human tumor necrosis factor-beta demonstrated measurable cytotoxic activity when assayed independently, while recombinant human interferon-gamma was the only cytokine to demonstrate greater than additive activity in combination with rHuTNF-alpha. The simplicity and reproducibility of this assay on a human cell line makes it useful for the routine determination of the biological activity of human tumor necrosis factor-alpha.

Increase in cyclic AMP levels by relaxin in newborn rhesus monkey uterus cell culture

A novel relaxin sensitive cell line of apparent smooth muscle origin has been established from a newborn rhesus monkey uterus (NRMU). NRMU cells respond to relaxin, in the presence of 1 microM forskolin, by producing intracellular adenosine 3', 5'-cyclic monophosphate (cAMP). The increase in cAMP levels is dose, time and cell density dependent, reaching peak levels at 10 min when cells are seeded at 1 X 10(5) cells/well. Specificity was demonstrated by neutralization of the relaxin activity with anti-relaxin monoclonal and polyclonal antibodies, degradation of cAMP in the presence of phosphodiesterase, and confirmation of the absence of cGMP. Three synthetic analogs of human relaxin generated a dose-related cAMP response as did synthetic native human relaxin. Natural relaxin purified from human corpora lutea tissue also generated a response similar to synthetic human relaxin. Porcine and rat relaxins also increased levels of cAMP. Insulin, but not IGF I or IGF II, was capable of increasing cAMP levels in NRMU cells, however, 200 ng/mL were required to achieve cAMP levels comparable to 6.25 ng/ml relaxin. Combinations of relaxin with insulin, IGF I or IGF II did not increase cAMP levels above levels obtained with relaxin alone. The effect on NRMU cells of other hormones, growth factors and drugs potentially present in cell culture systems or serum samples was evaluated. In combination with relaxin, oxytocin significantly decreased the cAMP production below the levels induced by relaxin alone, whereas progesterone and prostaglandin E2 resulted in additive increases in cAMP. These data suggest that the NRMU cell line is an appropriate target tissue for studying relaxin-mediated biological responses in vitro as well as functioning as the primary component of a relaxin in vitro bioassay.

Enzyme-linked bio-immunoassay for IFN-gamma by HLA-DR induction

A novel enzyme-linked bio-immunoassay (bio-ELISA) has been developed to detect interferon-gamma (IFN-gamma) induced HLA-DR antigen on the surface of human tumor cells. Cells are cultured at 37 degrees C in 96-well microtiter plates in the presence of IFN-gamma for 2 days. After fixation with reagent alcohol the HLA-DR antigen is detected using a monoclonal antibody, followed by goat anti-mouse IgG-HRP conjugate. Four human cell lines were evaluated and all expressed HLA-DR in response to IFN-gamma in a dose-related fashion. Based on sensitivity, reproducibility and absence of antiproliferative effect by IFN-gamma, the COLO 205 cells (colon adenocarcinoma) were determined to be optimal. The bioassay is sensitive to 0.3 ng/ml IFN-gamma with a range to 10 ng/ml. The specificity of HLA-DR induction by IFN-gamma was demonstrated using an isotype specific monoclonal antibody as well as IFN-gamma neutralizing monoclonal and polyclonal antibodies. The effect of other cytokines on HLA-DR induction with COLO 205 cells was also investigated in this bioassay and only IFN-beta and interleukin-1 (IL-1) showed slight induction of HLA-DR. IFN-alpha had no effect at the concentration tested. Evaluation of assay parameters including reproducibility, sensitivity, simplicity, speed, cost and ability to standardize support the conclusion that this bioassay is a substantial improvement over the routinely used viral inhibition assay as a measure of IFN-gamma biological activity. The bio-ELISA technique also has potential applications for the quantitation of other cellular surface antigens induced by cytokines.

Characterization of the in vitro and in vivo species preference of human and murine tumor necrosis factor-alpha

The species preference of human and murine tumor necrosis factor-alpha (TNF-alpha) was evaluated in human and murine systems for cytotoxic/cytostatic effects and receptor binding in vitro and murine systems for toxicity and antitumor activity in vivo. The in vitro cytotoxic/cytostatic effects of both species TNF-alpha on human and murine cell lines as well as the receptor binding studies using 125I-labeled recombinant human TNF-alpha demonstrated homologous species preferences. Species preference of TNF-alpha was also apparent in toxicity studies with BALB/c nu/nu and CB6F1 mice, and antitumor responses of CB6F1 mice to s.c. Meth A sarcoma implants. Moreover the growth of Meth A sarcoma implanted i.p. was not inhibited by either human or murine TNF-alpha. These results are discussed in view of the potential for underestimation of the biological potency of TNF-alpha from heterologous sources.

Characteristics of wide-band planar ultrasonic transducers using plane and edge wave contributions

The transient pressure fields of ideal planar ultrasonic transducers may be described in terms of plane and edge wave contributions. Based on this concept, a technique is developed which allows characterization of wideband unfocused transducers by a single measurement close to the transducer face. This method is examined experimentally for both polyvinylidene difluoride and commercial PZT transducers. Also investigated is the effective radiated frequency of these devices.

Characterization of the antitumor activities of human tumor necrosis factor-alpha and the comparison with other cytokines: induction of tumor-specific immunity

We have investigated the in vitro and in vivo antitumor activities of recombinant human tumor necrosis factor-alpha (rHuTNF-alpha) against Meth A sarcoma. Meth A sarcoma cells were found to a) be relatively insensitive in vitro to rHuTNF-alpha, and b) express low numbers of TNF-alpha receptors. Intraperitoneally implanted Meth A sarcoma was insensitive to the antitumor effects of rHuTNF-alpha. In contrast, rHuTNF-alpha was highly efficacious against subcutaneously implanted Meth A sarcoma. Biodistribution studies with 125I- or 3H-labeled rHuTNF-alpha demonstrated that, after intravenous administration, the majority of the labeled rHuTNF-alpha localized in the kidney, lungs, and liver. Only low levels of radiolabel were found in subcutaneous Meth A implants. These results support the in vitro data on the low number of TNF-alpha receptors on Meth A sarcoma cells. The ability of rHuTNF-alpha to induce regression of established (7 days) subcutaneous Meth A implants, positively correlated with the degree of both macroscopic and microscopic tumor necrosis. In addition, recombinant human tumor necrosis factor-beta (lymphotoxin) and recombinant murine tumor necrosis factor-alpha induced similar levels of necrosis. Other lymphokines with known antitumor activities, recombinant human interferon-gamma, murine interferon-gamma, and human interleukin 1 alpha, failed to induce detectable necrosis of Meth A sarcoma. Mice which had rejected subcutaneous Meth A sarcoma implants after rHuTNF-alpha treatment and which were later challenged subcutaneously with Meth A sarcoma or other noncross-reacting chemically induced sarcomas were found to be specifically immune to Meth A sarcoma. In addition, low levels of cytotoxic antibodies reactive to Meth A sarcoma were detected in the sera of 21 of 30 Meth A immune mice. Histological evaluation of the hemorrhagic tumor necrosis induced by rHuTNF-alpha suggests that the primary lesion is vascular, possibly directly on the endothelial cells. The mechanisms involved in the generation of specific cell-mediated antitumor immunity in this model are at present unknown.

Characterization of the antitumor activities of human tumor necrosis factor-alpha and the comparison with other cytokines: induction of tumor-specific immunity

We have investigated the in vitro and in vivo antitumor activities of recombinant human tumor necrosis factor-alpha (rHuTNF-alpha) against Meth A sarcoma. Meth A sarcoma cells were found to a) be relatively insensitive in vitro to rHuTNF-alpha, and b) express low numbers of TNF-alpha receptors. Intraperitoneally implanted Meth A sarcoma was insensitive to the antitumor effects of rHuTNF-alpha. In contrast, rHuTNF-alpha was highly efficacious against subcutaneously implanted Meth A sarcoma. Biodistribution studies with 125I- or 3H-labeled rHuTNF-alpha demonstrated that, after intravenous administration, the majority of the labeled rHuTNF-alpha localized in the kidney, lungs, and liver. Only low levels of radiolabel were found in subcutaneous Meth A implants. These results support the in vitro data on the low number of TNF-alpha receptors on Meth A sarcoma cells. The ability of rHuTNF-alpha to induce regression of established (7 days) subcutaneous Meth A implants, positively correlated with the degree of both macroscopic and microscopic tumor necrosis. In addition, recombinant human tumor necrosis factor-beta (lymphotoxin) and recombinant murine tumor necrosis factor-alpha induced similar levels of necrosis. Other lymphokines with known antitumor activities, recombinant human interferon-gamma, murine interferon-gamma, and human interleukin 1 alpha, failed to induce detectable necrosis of Meth A sarcoma. Mice which had rejected subcutaneous Meth A sarcoma implants after rHuTNF-alpha treatment and which were later challenged subcutaneously with Meth A sarcoma or other noncross-reacting chemically induced sarcomas were found to be specifically immune to Meth A sarcoma. In addition, low levels of cytotoxic antibodies reactive to Meth A sarcoma were detected in the sera of 21 of 30 Meth A immune mice. Histological evaluation of the hemorrhagic tumor necrosis induced by rHuTNF-alpha suggests that the primary lesion is vascular, possibly directly on the endothelial cells. The mechanisms involved in the generation of specific cell-mediated antitumor immunity in this model are at present unknown.

Serum-free in vitro bioassay for the detection of tumor necrosis factor

A sensitive, reproducible in vitro bioassay is described for quantitating the cytolytic activity of tumor necrosis factor (TNF). The assay target cells, murine connective tissue L-M, are propagated and the assay performed under serum-free conditions. The quantitation of cytolytic activity is based on the ability of TNF to lyse L-M cells in the presence of actinomycin D, as measured by crystal violet dye uptake of residual viable cells. The assay is sensitive to 88 pg/ml TNF-alpha. The simplicity of the culture medium combined with high sensitivity and low variability make this a particularly well-suited bioassay for routine detection of TNF cytolytic activity.

Isolation of lymphocytopathic retroviruses from San Francisco patients with AIDS

Infectious retroviruses have been detected in 22 of 45 randomly selected patients with acquired immune deficiency syndrome (AIDS) and in other individuals from San Francisco. The AIDS-associated retroviruses (ARV) studied in detail had a type D morphology, Mg2+-dependent reverse transcriptase, and cytopathic effects on lymphocytes. The viruses can be propagated in an established adult human T cell line, HUT-78. They cross-react with antiserum to the lymphadenopathy-associated retrovirus isolated from AIDS patients in France. Antibodies to ARV were found in all 86 AIDS patients and in a high percentage of 88 other homosexual men in San Francisco. This observation indicates the widespread presence of these lymphocytopathic retroviruses and their close association with AIDS.

Detection of IgG antibodies to measles virus using monoclonal antibodies for antigen-capture in enzyme immunoassay

An enzyme immunoassay (EIA) for the detection of IgG antibodies to measles viral hemagglutinin (H) has been developed. Monoclonal antibodies were employed as antigen-capture reagents on a polystyrene ball solid phase. The antigen-capture EIA was significantly more sensitive than hemagglutination inhibition (HAI) and somewhat more sensitive than indirect immunofluorescence and indirect EIA for the detection of antibodies to measles virus. The importance of selecting a monoclonal antibody with a high binding affinity, and controlling for non-specific adherence of antigen or antibodies to the solid phase were demonstrated. This method offers not only greater sensitivity than HAI, but also the practicality of reagents capable of standardization and long term storage.

Biological activity of a monoclonal antibody to a measles virus haemagglutinin epitope detected late in infection

A hybrid cell line secreting monoclonal antibody 2H9c (mAb 2H9c) with measles virus haemagglutinin (HA) specificity was produced. The mAb 2H9c was non-reactive in haemagglutination inhibition and neutralization assays. A protein of apparent mol. wt. 79000 was immune-precipitated using a Triton X-100/SDS/sodium deoxycholate detergent buffer and two proteins with mol. wt. of 79000 and 69000 were immune-precipitated using 1% Nonidet P40/sodium deoxycholate buffer in SDS-PAGE assays. Similar results were obtained with other anti-HA monoclonal antibodies, supporting the assumption that mAb 2H9c was directed against the HA polypeptide. The indirect immunofluorescence (IFA) staining pattern of acetone-fixed infected cells with mAb 2H9c differed substantially from that with other HA-specific monoclonal antibodies. Kinetic studies revealed that the reactivity of mAb 2H9c lagged behind other HA-specific monoclonal antibodies by 18 to 36 h post-infection in IFA assays. This suggests that mAb 2H9c may be directed against a binding site that arises late in infection, possibly as a result of a conformational alteration of the HA polypeptide.

Aging and the thyroid. Decreased requirement for thyroid hormone in older hypothyroid patients

In 84 patients, aged 23 to 84, with primary hypothyroidism, the daily dose of thyroxine needed to lower the serum thyrotropin level into the normal range was significantly less in older patients than in younger ones (p less than 0.01). Most of the difference between middle-aged (40 to 60 years) and older patients (greater than 60 years) was due to a decrease in the required dose in men; there was no difference in the dose needed by women in these age groups. Previous hyperthyroidism did not affect the dose of thyroxine required; it is unlikely that residual autonomous thyroid tissue affected the dose. Although the wide range of doses needed precludes use of these data in calculating a dose of thyroxine for an individual patient, doses of 100 micrograms per day or less were common in patients over age 40, and a few patients over age 60 needed 50 micrograms per day or less. Thus, (1) there is a sound physiologic basis for the common practice of using low doses of thyroxine, e.g., 25 micrograms per day, as initial therapy in older hypothyroid patients and (2) it may be reasonable to reassess the dose of thyroxine after several years in older patients.

Discriminant analysis of data in enzyme immunoassay

A critical step in the development of both qualitative and quantitative enzyme immunoassays is establishing the positive/negative discrimination, or cut-off, value. Data derived from an indirect immunofluorescence assay, hemagglutination inhibition, and enzyme immunoassay to detect IgG antibodies to measles virus were applied to a discriminant analysis program to determine the positive/negative cut-off value. Application of the discriminant analysis demonstrated a greater utilization of the sensitivity of the enzyme immunoassay than the most commonly used methods. This method also illustrates the importance of examining both antibody positive and negative sera, rather than negative sera alone, in determining the cut-off value. In addition, probability of membership in the antibody positive or negative group is included in the determination. This increases the information base for risk assessment and clinical evaluation.