The impact of melaphene on the expression of chloroplastic chaperone protein HSP70B and photosynthetic pigments in cells of <Emphasis Type="Italic">Chlamydomonas reinhardtii</Emphasis>

The effects of growth regulator of the new generation—melamine salt of bis(oxymethyl)phosphine acid (melaphene)—on culture growth, pigment and protein content, and the induction of protective chloroplastic chaperone HSP70B in Chlamydomonas reinhardtii CW15 cells were studied. Melaphene exhibited 10–30% growth inhibition at 10⁻⁹–10⁻²% concentration. At 10⁻⁹–10⁻⁴% of melaphene electrophoretic concentration, the pattern of cellular proteins was similar to the control. The alterations in protein content of algae cells were detected only at 10⁻²% concentration. The content of chlorophyll and carotenoids in melaphene-treated cells was 17–40% lower than in the control. Melaphene at 10⁻⁹–10⁻²% concentration inhibited HSP70B induction by 39–43% compared to untreated cells. The potential mechanism of melaphene effect might involve its influence on nuclear gene expression.     

The dynamic expression of tenascin-C and tenascin-X during early heart development in the mouse

One of a family of extracellular matrix proteins, tenascin-C (TNC) is expressed in a spatiotemporally restricted pattern associated with tissue remodeling during embryonic development, wound healing, cancer invasion and tissue regeneration. Another form, tenascin-X (TNX), is found in most tissues but most predominantly in heart and muscle, often complementarily to TNC. The present analysis demonstrated their expression during early heart development, using mouse lines containing the lacZ gene targeted to the TNC locus, by RT-PCR, immunohistochemistry, and in situ hybridization. TNC was transiently expressed at important steps during heart development: (1) precardiac mesodermal cells differentiating to cardiomyocytes and endocardial cells at E 7.5 - 8.5; (2) cardiomyocytes in the outflow tract at E 8.5 - 12; (3) endocardial cells forming cushion tissue at E 9.5 - 13; and (4) mesenchymal cells in the proepicardial organ (PEO), the precursors of coronary vessels, at E 9.5. When PEO cells were transferred onto the heart surface, the expression of TNC was downregulated, while TNX was upregulated at E 11. Initially, epicardial cells around the AV groove and atrium started to express TNX. TNX-positive cells then gradually spread all over the entire surface of the heart and invaded and formed primitive vascular channels in the myocardium. Despite restricted expression at important sites and steps during cardiogenesis, the hearts of TNC deficient mice developed normally. No difference in the expression pattern of TNX were observed in TNC knockout and wild mice. These results suggest; (1) TNC could play important roles in the differentiation of cardiomyocytes and the early morphogenesis of the heart; (2) TNX could be involved in coronary vasculogenesis; (3) TNX does not compensate for the loss of TNC.     

Hyaluronan recognition mode of CD44 revealed by cross-saturation and chemical shift perturbation experiments

CD44 is the main cell surface receptor for hyaluronic acid (HA) and contains a functional HA-binding domain (HABD) composed of a Link module with N- and C-terminal extensions. The contact residues of human CD44 HABD for HA have been determined by cross-saturation experiments and mapped on the topology of CD44 HABD, which we elucidated by NMR. The contact residues are distributed in both the consensus fold for the Link module superfamily and the additional structural elements consisting of the flanking regions. Interestingly, the contact residues exhibit small changes in chemical shift upon HA binding. In contrast, the residues with large chemical shift changes are localized in the C-terminal extension and the first alpha-helix and are generally inconsistent with the contact residues. These results suggest that, upon ligand binding, the C-terminal extension and the first alpha-helix undergo significant conformational changes, which may account for the broad ligand specificity of CD44 HABD.     

Isolation and Partial Characterization of DNA Topoisomerase I from the Nucleoids of White Mustard Chloroplasts

DNA topoisomerase was isolated for the first time from nucleoids of white mustard (Sinapis alba L.) chloroplasts. The enzyme had a molecular weight of 70 kDa; was ATP-independent, required the presence of mono- (K⁺) and bivalent (Mg²⁺) cations, and was capable of relaxing both negatively and positively supercoiled DNA. These results suggest that the enzyme isolated belongs to the type IB DNA topoisomerases.     

EEG of striate cortex in blind monkeys: effects of eye movements and sleep.

After control studies, using electrodes permanently implanted in the central visual system, squirrel monkeys and macaques were in most instances blinded by acute glaucoma. This permitted subsequent observation of eye movements. Ocular nystagmus developed in all cases. Beginning immediately upon recovery from anesthesia, and persisting for at least 1 year, the EEG of the striate cortex was characterized by totally flat periods up to several seconds in duration which were ended abruptly by a sharp "spike" trailed in turn by a ragged high voltage, slow pattern for another second or two. The great majority of these "spikes" from the blind striate cortex occurred within 60-200 msec after a saccadic eye movement, made either in nystagmus or attempted fixation. They were not dependent upon proprioception from the extraocular muscles. It is suggested that they represent a "corollary discharge" for movement of the eyes. The blind striate cortex was judged to be hyperexcitable on the basis of these saccade-associated "spikes", not often observable in intact monkeys, and from the increase both in response evoked by electrical stimulation of optic radiation and amplitude of the EEG in sleep.     

Dual origin of mesenchymal tissues participating in mouse mammary gland embryogenesis

By the 14th day of gestation, two different mesenchymes can be identified which affect mouse mammary gland embryogenesis: the fibroblastic mammary mesenchyme (MM) closely surrounding the epithelial rudiment, and a condensed mesenchymal tissue (FP) appearing separately, posterior to the mammary rudiment, the precursor tissue of the fat pad. Late on the 16th day, the mammary epithelium (ME), surrounded by MM, starts to elongate, puts out branches, and penetrates the FP. A fatty substance appears in the FP at this stage. Interaction between ME and FP is necessary for typical mammary morphogenesis. When 17-day ME is combined with 14- or 17-day FP, the resulting mammary gland has the normal mammary pattern, but when 17-day ME is combined with 12- to 17-day MM, a ductal hyperplasia is formed by frequent branching, without the “stretching out” of these ducts. All the glands formed by combining ME with either FP or MM will lactate, if the mice carrying the grafts are allowed to mate and give birth. Adult ME also shows a different response to MM and FP.     

Appearance and distribution of dendritic cells and macrophages in dental pulp during early postnatal morphogenesis of mouse mandibular first molars

Dendritic cells and macrophages were examined in dental pulp during the postnatal development of mouse mandibular first molars, by immuno- and enzyme histochemistry. F4/80 antibody against dendritic cells and macrophages demonstrated labeled cells predominantly in and around the odontoblastic layer during tooth development from postnatal day 0 (PN0) to PN5. Labeling with Mac-1, Mac-2, and MOMA-2 antibodies against macrophages showed varied distribution patterns. Mac-1-positive cells were not detected in the dental pulp. Mac-2-positive cells appeared in the dental pulp at PN0, but not in or around the odontoblastic layer, and disappeared by PN3. A few MOMA-2-positive cells were detected in the dental pulp during the period examined. The F4/80-positive cells in and around the odontoblastic layer did not exhibit acid phosphatase or non-specific esterase activities. In addition, the F4/80-positive cells showed continued expression of Fcγ receptor, but not class II major histocompatibility complex (MHC). Other antibodies against dendritic cells (NLDC-145, MIDC-8, and 33D1) did not label the F4/80-positive cells. We concluded that the F4/80-positive and class II MHC-negative cells in and around the odontoblastic layer may be immature dendritic cells in the early stages before eruption, weaning, and crucial exposure to antigenic stimuli. They may not only act primarily as immunosurveillance cells, but also play a role in a regulatory function and differentiation of odontoblasts. Accepted: 8 June 1999     

The carboxy-terminal region of SMAP2 directs subcellular localization as well as Arf protein specificity

Small G proteins play a central role in the organization of secretory and endocytotic pathways. The recruitment of some effectors, including vesicle coat proteins, is mediated by the ADP-ribosylation factor (Arf) family. Arf proteins have distinct subcellular localizations. ArfGAPs (Arf GTPase-activating proteins) regulate Arf GTPase activity. Thus, each ArfGAP is distinctly localized to allow it to maintain a specific interaction with its target Arf(s). However, the domains that regulate the subcellular localization of ArfGAPs and the way in which these subcellular localizations affect the target specificities of ArfGAPs remain unclear. Recently, we identified two novel ArfGAPs, SMAP1 (Small ArfGAP protein 1) and SMAP2. In the current study, we identified sequences in the carboxy-terminal region of SMAP2 that are critical for its specific subcellular localization and its specificity for Arf proteins.