Absence of functional and structural homology of natural and recombinant human leukocyte interferon (IFN-α) with human α-ACTH and β-endorphin

A comparison of the amino acid sequence of one human recombinant IFN-α (IFLrA) with either human β-endorphin or ACTH reveals only a minimal and insignificant degree of homology. Also, synthetic ACTH, β-endorphin and β-endorphin-(1–15) have no antiviral protective effects on human fibroblasts and cannot inhibit the neutralization of the antiviral effects of natural IFN-α by an antiserum directed against the interferon. Anti ACTH and Anti β-endorphin do not neutralize the antiviral effects of IFLrA, and radioimmunoassays of partially purified natural IFN-α and pure IFLrA do not reveal any evidence of α-MSH or β-endorphin-like material in the interferons. These results demonstrate an absence of functional and structural homology of natural and recombinant IFN-α with ACTH and β-endorphin.     

Distribution of indicator bacteria and Vibrio parahaemolyticus in sewage-polluted intertidal sediments

The impact of a sewage point source on the bacterial densities in an intertidal mud flat in Boston Harbor, Mass., was investigated. The area, Savin Hill Cove, acts as a receiving basin for a combined storm and sewage outlet (CSO). Preliminary examination of sediments and overlying water at high tide demonstrated that fecal coliforms were present in sediments at abundances 2 to 4 orders of magnitude higher than in the overlying water column. The following bacterial counts were determined from sediments along a sampling transect extending 460 m from the CSO: total bacteria by epifluorescent microscopy, heterotrophic bacteria by plate counts on nutrient-rich and nutrient-poor media, fecal coliforms and enterococci by membrane filtration, and Vibrio parahaemolyticus by a most-probable-number technique with a resuscitation step. Median sediment grain size, average tidal exposure, carbon/nitrogen ratio, and total organic carbon were also measured. All bacterial indices, except for V. parahaemolyticus, declined significantly with distance from the outfall. Multiple regression analysis indicated that tidal exposure (low tides) may affect densities of total bacteria. Fecal coliforms and enterococci were still present in appreciable numbers in sediments as far as 460 m away from the CSO. In contrast, V. parahaemolyticus densities did not correlate with the other bacterial counts nor with any of the environmental parameters examined. These results indicate that intertidal sediments which adjoin point sources of pollution are severely contaminated and should be considered as potentially hazardous reservoirs of sewage-borne diseases.     

Lake-watershed acidification in the North Branch of the Moose River: Introduction

An integrated analysis of a terrestrial-aquatic ecosystem, the North Branch of the Moose River in the Adirondack region of New York, was conducted. This basin contains a large number of interconnected surface waters that exhibit marked gradients in pH and acid neutralizing capacity (ANC). As a result, the basin has been the focus of research activity, including the Regional Integrated Lake-Watershed Acidification Study (RILWAS). The objective of the current analysis was to use the North Branch of the Moose River as a case study to:

1. Evaluate processes regulating the acid-base chemistry of surface waters.
2. To assess the effects of surface water acidification on fish populations.

The observations of this study were consistent with the model of surface water acidification developed during the Integrated Lake-Watershed Acidification Study (ILWAS). The processes depicted in the original ILWAS simulation model were adequate to describe the acid-base chemistry of surface waters in the North Branch of the Moose River. However, the reduction of SO ₄ ^2? in lake sediments, a process not represented in the original model, proved to be a significant source of acid neutralizing capacity (ANC) for some of these waters. As a result, reduction processes were added to the model. Analysis of in-situ bioassay and survey data indicate that acid-sensitive fish species have disappeared from the more acidic areas of the basin over the last half century. Paleoecological analyses indicate that pH has decreased from the high 5's to about 5 in Big Moose Lake during this period. ILWAS model simulations indicate that the pH of Big Moose Lake would increase by at least 0.1 to 0.5 pH units (depending on the season) in response to a 50% reduction in total atmospheric S deposition. Considerable variability in processes regulating acid/base chemistry was evident in the North Branch of the Moose River. Therefore, regional assessments of past or possible future effects of acidic deposition require widespread application of ILWAS theory within the Adirondack region and other potentially acid-sensitive areas.     

Properties of the reaction center of the thermophilic purple photosynthetic bacterium Chromatium tepidum

Reaction centers were purified from the thermophilic purple sulfur photosynthetic bacterium Chromatium tepidum. The reaction center consists of four polypeptides L, M, H and C, whose apparent molecular masses were determined to be 25, 30, 34 and 44 kDa, respectively, by polyacrylamide gel electrophoresis. The heaviest peptide corresponds to tightly bound cytochrome. The tightly bound cytochrome c contains two types of heme, high-potential c-556 and low-potential c-553. The low-potential heme is able to be photooxidized at 77 K. The reaction center exhibits laser-flash-induced absorption changes and circular dichroism spectra similar to those observed in other purple photosynthetic bacteria. Whole cells contain both ubiquinone and menaquinone. Reaction centers contain only a single active quinone; chemical analysis showed this to be menaquinone. Reaction center complexes without the tightly bound cytochrome were also prepared. The near-infrared pigment absorption bands are red-shifted in reaction centers with cytochrome compared to those without cytochrome.     

TGF-Beta inhibits the in vitro induction of lymphokine-activated killing activity

Summary Employing serum-free media, human peripheral blood mononuclear cells, and purified recombinant interleukin-2 (IL-2), conditions were observed in which the development of IL-2-driven cytotoxic activity was suppressed. The cytotoxic activity of such IL-2-generated lymphokine activated killing (LAK) was tested against natural killer-resistant cultured tumor cells (Daudi, Raji, and a glioma). LAK generation was inhibited by addition of some normal sera, normal platelets, or some tumor cells. Because recent reports have indicated that transforming growth factor-beta (TGF-beta)-like factors are often secreted by tumors and the acidic alpha granules of platelets and can be present in sera, we tested the effect of purified human TGF-beta on the activation of LAK. Our results indicated that TGF-beta is very suppressive for LAK induction, and can completely prevent both the IL-2-driven proliferation and cytotoxicity at concentrations as low as 5 ng/ml. Titrations of IL-2 and of TGF-beta indicated that the suppression is dose-dependent and can be avoided by employing higher levels of IL-2. It was also found that the suppressive effect of TGF-beta can be overcome by washing suppressed cell populations and further culture in low levels of IL-2. Collectively, these data indicate that TGF-beta can be a potent inhibitor of LAK generation under standard activation conditions, but that this effect is regulated by the relative level of IL-2 and may be overcome and/or reversed in vitro.     

Platelet-activating factor in the rabbit uterus during early pregnancy

Platelet-activating factor (PAF) concentrations were low in the non-pregnant, oestrous uterus (mean +/- s.e.m.: 2.2 +/- 1.2 pmol/g, n = 3). However, uterine PAF increased dramatically during pregnancy to a maximum of 37.8 +/- 4.90 pmol/g (n = 7) on Day 5. By Day 7, PAF concentrations in the uteri of pregnant rabbits had returned to levels similar to those found at oestrus. In contrast, uterine PAF in pseudopregnant rabbits peaked at 30.6 +/- 2.8 pmol/g (n = 8) on Day 4, declined to 20.5 +/- 2.4 pmol/g (n = 8) on Day 5 and then remained at that concentration through Day 7. Uterine PAF co-migrated with synthetic PAF (1-O-hexadecyl-2-acetyl-sn-glycero-phosphocholine) in both thin-layer and normal-phase high-performance liquid chromatography. PAF activity in the uterus during pregnancy and pseudopregnancy was found almost exclusively in the endometrium; little or no PAF was found in myometrium, uterine flushings or blastocysts. While no PAF was detected in blastocysts on Days 5 and 6 of pregnancy, the presence of the embryo appears to modulate biosynthesis and/or degradation of PAF by the uterus, since PAF decreased significantly in uterine tissue apposed to the implanting embryo (but not in similar areas between such attachment sites). Increased concentrations of PAF in the preimplantation rabbit uterus followed by a dramatic decrease on the day of blastocyst attachment suggest that this potent inflammatory autacoid may play a vital role in implantation.     

Donnan potentials from striated muscle liquid crystals. Sarcomere length dependence.

Donnan potentials from A-bands and I-bands were measured as a function of sarcomere length in skinned long-tonic muscle fibers of the crayfish. These measurements were made using standard electrophysiological technique. Simultaneously, the relative cross-sectional area of the fibers was determined. Lattice plane spacings and hence unit-cell volumes were determined by low-angle x-ray diffraction. At a sarcomere length at which the myosin filaments and actin filaments nominally do not overlap, measurements of potential, relative cross-sectional area, and unit-cell volume were used in conjunction with Donnan equilibrium theory to calculate the effective linear charge densities along the myosin filament (6.6 X 10(4) e-/mu) and actin filament (6.8 X 10(3) e-/mu). Using these linear charge densities, unit-cell volumes and Donnan equilibrium theory, an algorithm was developed to predict A-band and I-band potentials at any sarcomere length. Over the range of sarcomere lengths investigated, the predicted values coincide with the experimental data. The ability of the model to predict the data demonstrates the applicability of Donnan equilibrium theory to measurements of electrochemical potential from liquid-crystalline systems.     

Effect of norepinephrine on swelling-induced potassium transport in duck red cells. Evidence against a volume-regulatory decrease under physiological conditions

Duck red cells exhibit specific volume-sensitive ion transport processes that are inhibited by furosemide, but not by ouabain. Swelling cells in a hypotonic synthetic medium activates a chloride-dependent, but sodium-independent, potassium transport. Shrinking cells in a hypertonic synthetic medium stimulates an electrically neutral co-transport of [Na + K + 2 Cl] with an associated 1:1 K/K (or K/Rb) exchange. These shrinkage-induced modes can also be activated in both hypo- and hypertonic solutions by beta-adrenergic catecholamines (e.g., norepinephrine). Freshly drawn cells spontaneously shrink approximately 4-5% when removed from the influence of endogenous plasma catecholamines, either by incubation in a catecholamine-free, plasma-like synthetic medium, or in plasma to which a beta-receptor blocking dose of propranolol has been added. This spontaneous shrinkage resembles the response of hypotonically swollen cells in that it is due to a net loss of KCl with no change in cell sodium. Norepinephrine abolishes the net potassium transport seen in both fresh and hypotonically swollen cells. Moreover, cells swollen in diluted plasma, at physiological pH and extracellular potassium, show no net loss of KCl and water ("volume-regulatory decrease") unless propranolol is added. Examination of the individual cation fluxes in the presence of catecholamines demonstrates that activation of [Na + K + 2Cl] co-transport with its associated K/Rb exchange prevents, or overrides, swelling-induced [K + Cl] co-transport. These results, therefore, cast doubt on whether the swelling-induced [K + Cl] system can serve a volume-regulatory function under in vivo conditions.     

Contrasting roles of tau and microtubule-associated protein 2 in the vinblastine-induced aggregation of brain tubulin

Two different proteins, tau and microtubule-associated protein 2 (MAP 2), are able to stimulate tubulin polymerization into microtubules in vitro, but it is not certain if both proteins act by the same mechanism. We have examined the effects of tau and MAP 2 on the vinblastine-induced polymerization of tubulin into spiral filaments. In the presence of tau, vinblastine induced extensive aggregation of tubulin as shown by a large increase in turbidity. The increase in turbidity was accompanied by the formation of large numbers of spirals composed of a filament 40-60 A in diameter. The rate and extent of this aggregation into spirals were dependent on the concentrations of tubulin, tau, and vinblastine. Unlike normal microtubule assembly, this type of aggregation was not inhibited by colchicine or podophyllotoxin. In contrast, MAP 2, even at high concentrations, was less effective than tau at promoting the vinblastine-induced increase in turbidity of tubulin. In fact, MAP 2 strongly inhibited the effect of tau. These results indicate that tau and MAP 2 interact differently with the tubulin molecule in the presence of vinblastine and suggest that the two proteins may play different roles in regulating or promoting microtubule assembly. Vinblastine may thus be a useful probe in analyzing the modes of interactions of tau and MAP 2 with tubulin.