Rapid immunofluorescent determination of cells in the S phase in pea root meristems: An alternative to autoradiography

Photosystem II (PS II) activity and the localization of ribulose-l,5-bisphosphate (RuBP) carboxylase (EC 4.1.1.39) were studied in primary leaves of young maize plants ( Zea mays L. cv. Fronica) by tetra-nitro-blue-tetrazoliumchloride reduction and immunolocalization, respectively. In tissue of 3-day-old plants all chloroplasts were structurally identical. From day 4 they developed into their typical appearance of mesophyll and bundle sheath chloroplasts. First PS II-activity was present in both types of chloroplasts. From day 4 it disappeared in bundle sheath chloroplasts concomitant with the loss of grana. RuBP carboxylase on the other hand was only present in bundle sheath chloroplasts at all stages of development. Thus, the control of the development of the photosystems and the Calvin cycle enzymes seem to differ.     

Properties of carboxymethylated cross-linked hemoglobin A

The selective carboxymethylation of the N-terminal amino groups of hemoglobin A with glyoxylic acid and sodium cyanoborohydride has been studied as a function of the state of ligation of hemoglobin. The N-terminal residues have been established as the primary sites of reaction by peptide mapping of the tryptic digest of each chain and subsequent amino acid analysis of the modified peptides. With oxyhemoglobin, the desired derivatives with a carboxymethyl group at the N-terminal of either or both chains amounted to 55% [Di Donato, A., Fantl, W. J., Acharya, A. S., & Manning, J. M. (1983) J. Biol. Chem. 258, 11890-11895]. In the present study it is shown that with deoxyhemoglobin the amount of the desired derivative is increased to 75%. The oxygen equilibrium curve of hemoglobin A carboxymethylated on its four N-terminal residues [0.5 mM as tetramer in 50 mM [bis(2-hydroxyethyl)amino]tris(hydroxymethyl)methane (Bis-Tris), pH 7.5, 37 degrees C] had a P50 value of 30 mmHg (Hill coefficient n = 2.8, alkaline Bohr value = 0.4) compared to a P50 of 9 mmHg for unmodified hemoglobin under the same conditions (n = 2.5, alkaline Bohr value = 0.5). In carboxymethylated oxyhemoglobin A, cross-linked with the mild agent glycolaldehyde for 3.5 h, there was 85% of Mr 64,000 species and 15% of Mr 128,000 or higher species. For the former, the extent of cross-linking between two subunits was 19%. For the latter, there was 29% of two cross-linked subunits and 13% of three cross-linked subunits. Termination of cross-linking, which may be desirable in some circumstances, can be successfully achieved with isonicotinic acid hydrazide.(ABSTRACT TRUNCATED AT 250 WORDS)     

Identification of S-100 proteins and S-100-binding proteins in a detergent-resistant EDTA/KCl-extractable fraction from bovine brain membranes

The Triton X-100-resistant residue of brain membranes contains appreciable amounts of S-100 proteins. This fraction of S-100 can be solubilized by high concentrations of EDTA plus or minus high concentrations of KCl. Whereas KCl (0.6 M) extracts the detergent-resistant S-100, NaCl (1 M) does not. Endogenous Ca2+ is required and is sufficient for S-100 to remain associated with the detergent-resistant residue. However, 0.6 M KCl extracts a further fraction of Triton X-100-resistant S-100. In contrast, the Triton X-100-extractable fraction of S-100 resists the action of EDTA. These data suggest that Ca2+ regulates the extent of association of S-100 with Triton X-100-resistant components in brain membranes, whereas the association of S-100 with the lipid bilayer of brain membranes and/or with some intrinsic membrane proteins is less Ca2+-regulated. Several S-100-binding proteins are identified in the detergent-resistant residue of brain membranes by an overlay procedure.     

Interaction of S-100b protein with cardiolipin vesicles as monitored by electron spin resonance, pyrene fluorescence and circular dichroism

The interaction of S-100b protein with cardiolipin (CL) vesicles has been studied by electron spin resonance, pyrene fluorescence, and circular dichroism. Electron spin resonance and pyrene fluorescence data indicate that S-100b binds to the polar surface of vesicles Ca2+-independently. In the presence of Ca2+, S-100b potentiates the Ca2+-induced clustering of the polar headgroups of CL molecules and causes a further reduction in the Ca2+-dependent decrease in the lateral mobility of the pyrene inserted into the lipid bilayer, which points to an effect of the protein on the hydrophobic core of the lipid bilayer through a larger perturbation of its polar surface. Circular dichroism analyses indicate that CL vesicles cause a decrease in the alpha-helical content of S-100b, analogous to that produced by Ca2+ and that the effects of CL vesicles and of Ca2+ on the secondary structure of the protein are supra-additive. By this technique, we found that the affinity of Ca2+ for S-100b increases substantially in the presence of CL vesicles, even in the presence of physiologic concentrations of KCl, suggesting that once S-100b had interacted with CL vesicles it assumes a new conformation in which its Ca2+-binding properties are greatly enhanced. These results are discussed in relation to binding of S-100b proteins to natural membranes, and to a possible involvement of S-100b in the regulation of membrane structural organization.     

tert–butylhydroperoxide—Induced toxicity in isolated hepatocytes: Contribution of thiol oxidation and lipid peroxidation

Incubation of isolated rat hepatocytes with tert-butylhydroperoxide resulted in marked cytotoxicity preceded by intracellular glutathione depletion and extensive lipid peroxidation. Addition of antioxidants delayed, but did not prevent, this toxicity. A significant decrease in protein-free sulfhydryl groups also, occurred in the presence of tert-butylhydroperoxide; direct oxidation of protein thiols and mixed disulfide formation with glutathione were responsible for this decrease. The involvement of protein thiol depletion in tert-butylhydroperoxide–induced cytotoxicity is suggested by our observation that administration of dithiothreitol, which caused re-reduction of the oxidized sulfhydryl groups and mixed disulfides, efficiently protected the cells from toxicity. Moreover, depletion of intracellular glutathione by pretreatment of the hepatocytes with diethyl maleate accelerated and enhanced the depletion of protein thiols induced by tert-butylhydroperoxide and potentiated cell toxicity even in the absence of lipid peroxidation.     

Non-linear filtering with discontinuous observations and applications to life sciences

In various applications one faces the problem of estimating a signal from discontinuous observations. For example, in biomedical applications the signal may be the ‘state’ of a given organ and one observes through an external counter the amount of radioactivity sequestered by the organ after injection of a radioactive tracer. Here the problem is studied in the context of nonlinear filtering when the signal can be modelled as either a random variable or a diffusion process, and the observations have a continuous and a purely discontinuous component; both components may be affected by the signal. When the signal is a random variable an explicitly computable solution is obtained; for the diffusion case the solution is given as a sequence of approximating filters that can be computed recursively.     

Timemresolved fluorescence of S-100a protein: effect of Ca, Mg and unilamellar vesicles of egg phosphatidylcholine

Phase-modulation fluorescence lifetime measurements were used to study the single Trp residue of the Ca²⁺-binding protein S-100a both in the absence and in the presence of Ca²⁺ and/or Mg²⁺. Trp fluorescence decay for the protein was satisfactorily described by Lorentzian lifetime distributions centered around two components (approximately 4 ns and 0.5 ns). Lifetime values were unchanged by 2 mM Ca²⁺, but the fractional intensity associated with longer lifetime increased up to 75%. In the presence of Mg²⁺, the Ca²⁺ induced increase of the fractional intensity associated with longer lifetime was only 57%. For the protein in buffer, about the 85% of the recovered anisotropy was associated to a rotational correlation time of 6.7 ns. After the addition of Ca²⁺, this value was increased to 16.08 ns. In the presence of Mg²⁺, Ca⁺² increased the rotational correlation time to 33.75 ns. Similar studies were performed with S-100a interacting with egg phosphatidylcholine vesicles (SUV). Our data suggest that the conformation of the protein may be influenced by structural features of the lipidic membrane. Moreover, data obtained in the presence of Mg²⁺ indicate some interaction between lipids and S-100, likely mediated by this ion.     

Transfer factor in chronic mucocutaneous candidiasis

Fifteen patients suffering from chronic mucocutaneous candidiasis were treated with an in vitro produced TF specific for Candida albicans antigens and/or with TF extracted from pooled buffy coats of blood donors. CMI of the patients was assessed using the LMT and the LST in presence of candidine. The aim of the study was the clinical evaluation of TF treatment and the incidence of positive tests before, during, and after therapy. Immunological data were matched using the Chi square test. 87 LMT were performed for each antigen dose and at the dilution of 1/50, 58.9% (33/56) tests were positive during non-treatment or non-specific TF treatment. On the contrary 83.9% (26/31) were positive during specific TF treatment (P<0.05). In the LST, a significant decrease of thymidine uptake in the control cultures in presence of autologous or AB serum was observed when patients were matched according to non-treatment, and both non specific (P<0.05) and specific TF treatment (P<0.01). Only during specific TF treatment was a significant increase of reactivity against the Candida antigen at the highest concentration noticed, when compared with the period of non specific treatment (P<0.01). Clinical observations were encouraging: all but one patient experienced significant improvement during treatment with specific TF. These data confirm that orally administered specific TF, extracted from induced lymphoblastoid cell-lines, increases the incidence of reactivity against Candida antigens in the LMT. LST reactivity appeared not significantly increased with respect to the periods of non treatment, but was significantly increased when it was compared to the non-specific TF treatment periods. At the same time, a clinical improvement was noticed.