Increased Expression of Apolipoprotein D Following Experimental Traumatic Brain Injury

Increasing evidence suggests that apolipoprotein D (apoD) could play a major role in mediating neuronal degeneration and regeneration in the CNS and the PNS. To investigate further the temporal pattern of apoD expression after experimental traumatic brain injury in the rat, male Sprague-Dawley rats were subjected to unilateral cortical impact injury. The animals were killed and examined for apoD mRNA and protein expression and for immunohistological analysis at intervals from 15 min to 14 days after injury. Increased apoD mRNA and protein levels were seen in the cortex and hippocampus ipsilateral to the injury site from 48 h to 14 days after the trauma. Immunohistological investigation demonstrated a differential pattern of apoD expression in the cortex and hippocampus, respectively: Increased apoD immunoreactivity in glial cells was detected from 2 to 3 days after the injury in cortex and hippocampus. In contrast, increased expression of apoD was seen in cortical and hippocampal neurons at later time points following impact injury. Concurrent histopathological examination using hematoxylin and eosin demonstrated dark, shrunken neurons in the cortex ipsilateral to the injury site. In contrast, no evidence of cell death was observed in the hippocampus ipsilateral to the injury site up to 14 days after the trauma. No evidence of increased apoD mRNA or protein expression or neuronal pathology by hematoxylin and eosin staining was detected in the contralateral cortex and hippocampus. Our results reveal induction of apoD expression in the cortex and hippocampus following traumatic brain injury in the rat. Our data also suggest that increased apoD expression may play an important role in cortical neuronal degeneration after brain injury in vivo. However, increased expression of apoD in the hippocampus may not necessarily be indicative of neuronal death.     

Low degree of ubiquitination of histone 2A in the dipteran Chironomus tentans

A polyclonal antibody to ubiquitin has been prepared and shown to react with both ubiquitin and ubiquitinated histone 2A (uH2A). Applying this antibody in Western blotting experiments, we have observed that the salivary glands of Chironomus tentans contain an unusually low amount of uH2A (1% of histone 2A), while the amount of free ubiquitin is as abundant as in other animal cells, e.g. HeLa cells. The same low content of uH2A was also found in diploid epidermal cells of Chironomus origin suggesting that the low amount is not a characteristic of the polytene state of chromatin in salivary gland cells but rather a property of C. tentans as a species. The significance of the low degree of ubiquitination is discussed in relation to the information available on the organization of Chironomus chromatin into unusually large chromomeric entities.     

Intragroup serotyping of meningococci

The method for obtaining antisera to meningococci of different serotypes are described and the scheme for the preparation of serotyping is presented, as well as the method for the preparation of the determinate fraction of serotype 2. Antisera to typing antigens 1, 2, 2-7, 2-10, 4, 5, 6, 8 (1) have been obtained, their specificity tested in parallel experiments with American and French typing sera. When typing meningococci, the use of antisera to purified protein antigen 2 is recommended.     

Effect of substrate and pH on the oxidative half-reaction of phenol hydroxylase

The oxidative half-reaction of phenol hydroxylase has been studied by stopped-flow spectrophotometry. Three flavin-oxygen intermediates can be detected when the substrate is thiophenol, or m-NH2, m-OH, m-CH3, m-Cl, or p-OH phenol. Intermediate I, the flavin C(4a)-hydroperoxide, has an absorbance maximum at 380-390 nm and an extinction coefficient approximately 10,000 M-1 cm-1. Intermediate III, the flavin C(4a)-hydroxide, has an absorbance maximum at 365-375 nm and an extinction coefficient approximately 10,000 M-1 cm-1. Intermediate II has absorbance maxima of 350-390 nm and extinction coefficients of 10,000-16,000 M-1 cm-1 depending on the substrate. A Hammett plot of the logarithm of the rates of the oxygen transfer step, the conversion of intermediate I to intermediate II, gives a straight line with a slope -0.5. Fluoride ion is a product of the enzymatic reaction when 2,3,5,6-tetrafluorophenol is the substrate. These results are consistent with an electrophilic substitution mechanism for oxygen transfer. The conversions of I to II and II to III are acid-catalyzed. A kinetic isotope effect of 8 was measured for the conversion of II to III using deuterated resorcinol as substrate. The conversion of III to oxidized enzyme is base-catalyzed, suggesting that the reaction depends on the removal of the flavin N(5) proton. Product release occurs at the same time as the formation of intermediate III, or rapidly thereafter. The results are interpreted according to the ring-opened model of Entsch et al. (Entsch, B., Ballou, D. P., and Massey, V. (1976) J. Biol. Chem. 251, 2550-2563).     

Properties and serum levels of pregnancy-associated variant of human transcortin

The amino acid composition, N- and C-terminal amino acid sequences, and the basic physicochemical and immunochemical properties of the recently discovered pregnancy-associated molecular variant of human transcortin (Strel'chyonok, O.A., Avvakumov, G.V. and Akhrem, A.A. (1984) Carbohydr. Res. 134, 133-140) have been found to be identical to those of transcortin from normal donor serum. This suggests the identity of polypeptide moieties of the two glycoproteins. The transcortin variant has a lower isoelectric point (3.5-4.1) than normal transcortin (3.6-4.2), and different electrophoretic mobility in low-porosity polyacrylamide gel (one band versus two for normal transcortin). These differences can be reasonably explained by different organization of the carbohydrate moieties of these glycoproteins due to diverse post-translational modification of a single polypeptide chain. The levels of transcortin variant in the maternal venous serum throughout normal gestation (447 donors in all) and on the fifth day after delivery, as well as in umbilical cord serum and extracts of term placenta, have been measured by a radioimmune assay. Analysis of the data obtained allowed us to conclude that the biosynthesis of pregnancy-associated transcortin variant occurs in some organ of the maternal organism rather than in the feto-placental system, and it is a characteristic of pregnancy as a unique physiological state of the female organism rather than a phenomenon caused by individual features of certain women. We assume that the transcortin variant takes part in the guided transport of corticosteroids and/or progestins into some tissues that develop in the course of gestation.     

Relationship between cell density and prolidase activity in human skin fibroblasts: effects of ascorbate and fructose

To evaluate the influence of cell density on the activity of fibroblast prolidase (EC 3.4.13.9), we determined this activity in sparse and dense cultures. We also investigated, the effects of different concentrations of β-d(?) fructose and l(+) ascorbate, which both increased cell density at confluency. For a fructose concentration of 25 mM, we observed that in the absence of glucose, intracellular total proteins increased 1.5-fold and prolidase specific activity, 1.8-fold. For ascorbate, a broad optimum concentration was found (range 0.01 – 0.50 mM). Addition to cultures of 0.1 mM ascorbate increased total proteins 1.4-fold, and doubled prolidase activity. This investigation was prompted by our previous results [J. Metab. Dis. 1983, 6, 27–31], confirmed here, and suggesting that increased prolidase activity at confluency was due to a rise in cell density.     

Possible involvement of DNA breaks in epigenetic regulation of cell differentiation

The review summarizes the authors’ and literature data on accumulation of DNA breaks in differentiating cells. Large 50-kb free DNA fragments were observed by several research teams in non-apoptotic insect, mammal, and plant cells. More intense DNA breakage was observed during maturation of spermatides, embryo development, and differentiation of myotubes, epidermal cells, lymphocytes, and neutrophils. In general, accumulation of DNA breaks in differentiating cells cannot be attributed to a decrease in the DNA repair efficiency. Poly(ADP)ribose synthesis often follows the DNA breakage in differentiating cells. We hypothesize that DNA fragmentation is an epigenetic tool for regulating the differentiation process. Scarce data on localization of the differentiation-associated DNA breaks indicate their preferable accumulation in specific DNA sequences including the nuclear matrix attachment sites. The same sites are degraded at early stages of apoptosis. Recent data on non-apoptotic function of caspases provide more evidence for possible existence of a DNA breakage mechanism in differentiating cells, resembling the initial stage of apoptosis. Excision of methylated cytosine and recombination are other possible explanations of the phenomenon. Elucidation of mechanisms of differentiation-induced DNA breaks appears to be a prospective research direction.