Identification of macrophages in sections of rabbit lung using acetoacetylated lipoproteins

Macrophages were labeled in sections of rabbit lung with acetoacetylated low density lipoprotein (LDL), a marker internalized by cultured macrophages but not by other connective tissue cells. Using a modified technique, thin slices of fresh rabbit lung were incubated in 3,3'-dioctadecylindocarbocyanine (DiI)-labeled, acetoacetylated LDL, fixed in paraformaldehyde, and sectioned. Alveolar macrophages incorporated the fluorescently labeled, modified LDL, but surrounding stroma and parenchyma did not stain. Our results indicate that DiI-labeled, acetoacetylated LDL may be used to identify mononuclear phagocytes in tissue sections.     

Construction and characterization of an active factor VIII variant lacking the central one-third of the molecule

The primary structure of factor VIII consists of 2332 amino acids that exhibit 3 distinct structural domains, including a triplicated region (A domains), a unique region of 909 amino acids (B domain), and a carboxy-terminal duplicated region (C domains), that are arranged in the order A1-A2-B-A3-C1-C2. The B domain (residues 741-1648) of factor VIII is lost when factor VIII is activated by thrombin, which proteolytically processes factor VIII to active subunits of Mr 50,000 (domain A1), 43,000 (domain A2), and 73,000 (domains A3-C1-C2). To determine if the B domain is required for factor VIII coagulant activity, a variant was constructed by using recombinant DNA techniques in which residues 797-1562 were eliminated. This shortened the B domain from 909 to 142 amino acids. This variant factor VIIIdes-797-1652 was expressed in mammalian cells and was found to be functional. The factor VIIIdes-797-1562 protein was purified and shown to be processed by thrombin in the same manner as full-length factor VIII. The factor VIIIdes-797-1562 variant also bound to von Willebrand factor (vWF) immobilized on Sepharose. These results indicate that most of the highly glycosylated B domain of factor VIII is not required for the expression of factor VIII coagulant activity and its interaction with vWF.     

Effect of denervation on the glycolytic metabolism of the main electric organ of Electrophorus electricus (L.)

Biochemical modifications of the glycolytic metabolism of the electric organ of Electrophorus electricus (L.) have been studied as a function of denervation. The activities of LDH, MDH and the concentrations of ATP, lactic and pyruvic acids were measured at intervals of zero, 15, 30 and 60 days following denervation. In parallel, CPK activity was also measured. All of these biochemical characteristics were substantially altered by denervation. The results obtained point to a change, after 15 days of denervation, from the normal anaerobic to an aerobic metabolism which remains after 30 days and reverts to anaerobic at 60 days.     

T-cell-antigen positive, E-rosette negative acute lymphoblastic leukaemia (author's transl)]

The lymphoblasts from 100 patients with acute lymphocytic leukaemia were investigated for the expression of receptors for sheep erythrocytes (E) and of a specific heterologous T cell antigen (T). In 17 cases, both T cell markers were expressed simultaneously on the leukaemic cells. In 13 cases only T antigens could be demonstrated on the lymphoblasts. A quantitative analysis of T antigens by immunoautoradiography revealed that the T expression of E-T+ -lymphoblasts was in general like that of E+T+-lymphocytes in the blood of normal persons, in several cases even higher. Therefore, the failure of E-rosette formation cannot be correlated to a decrease of the other T cell differentiation marker. In 7 out of 9 tested cases, a strong acid phosphatase reaction product located paranuclearly could be demonstrated. Complement-receptors were expressed in 3 of 5 cases which were also demonstrated in some cases of the E+T+-ALL group. The latter group was characterized by a T antigen expression like that of thymocytes. 4 cases of the E-T+ALL group were adults. Since the leukaemia cells of 2 cases were negative for acid phosphatase, PAS and all surface markers including cALL antigen, the T antigen can classify undifferentiated and otherwise unclassificable leukaemias. The clinical signigicance of the E-T+-ALL seems to be important since 5 out of 9 children with this type of ALL died soon after diagnosis.     

Identification of the major metabolite of 4,4'-thio-bis-(6-t-butyl-m-cresol)

Metabolism of 4,4'-thio-bis-(2-t-butyl-5-methylphenol)(TBBC) in rats resulted in the formation of a glucuronide conjugate of TBBC. This conjugate was identified by a combination of high-performance liquid chromatography (HPLC) and mass spectrometry and a tandem mass spectrometric method employing a fast particle ionization technique. A comparison of mass spectral data from the in-vivo metabolite of TBBC and an enzymically synthesized glucuronide conjugate of TBBC showed the metabolite to be the monoglucuronide.     

Sodium and potassium currents recorded during an action potential

A simple method was used to measure directly sodium and potassium currents underlying the action potential in single nerve fibres of Xenopus laevis. A short rectangular stimulus under current-clamp conditions elicited an action potential which was digitally stored and later used as command when voltageclamping the same fibre. The currents thus obtained nearly reproduced the original rectangular stimulus. Adding first 100 nM TTX and subsequently 100 nM TTX plus 10 mM TEA to the extracellular Ringer solution revealed the sodium and the potassium currents during an action potential. They were converted to permeabilities by use of the constant-field equation and are in good agreement with the curves which had been calculated from conventional voltage-clamp data. Thus experimentally determined currents and permeabilities are shown as they are changing during an action potential.     

Persistence of Four Heterorhabditis spp. Isolates in Soil: Role of Lipid Reserves

Infective juveniles of four Heterorhabditis isolates (H. bacteriophora HI, H. megidis UK211 and HF85, and H. downesi M245) were stored in moist (pF 1.7) and dry (pF 3.3) loam soil at 20°C for up to 141 days. Survival, assessed by the number of nematodes extracted by centrifugal flotation, declined over time, reaching fewer than 18% alive by day 141 for all but one treatment (H. bacteriophora HI in dry soil). The infectivity of nematodes in soil for Tenebrio molitor also declined over time, roughly in accordance with the decline in numbers of nematodes. Energy reserves of extracted nematodes were assessed by image analysis densitometry. There were differences among isolates both in survival and in the depletion of reserves, and there was a significant correlation between these two parameters, suggesting that the extent to which energy reserves are depleted affects survival or that a common factor influences both. However, significant nematode mortality occurred while levels of reserves remained high, and the maximum reduction in utilizable body content for any treatment was 51%, well above starvation level. Therefore, the decline in numbers of living nematodes and the reduced nematode infectivity in soil cannot directly result from starvation of the nematodes. Survival and infectivity declined more rapidly in moist than in dry soil; one isolate, H. downesi M245, was less affected by soil moisture content than the other three isolates.