Compartmentalization and actin binding properties of ABP-50: the elongation factor-1 alpha of Dictyostelium

ABP-50 is the elongation factor-1 alpha (EF-1 alpha) of Dictyostelium discoideum (Yang et al.: Nature 347:494-496, 1990). ABP-50 is also an actin filament binding and bundling protein (Demma et al.: J. Biol. Chem. 265:2286-2291, 1990). In the present study we have investigated the compartmentalization of ABP-50 in both resting and stimulated cells. Immunofluorescence microscopy shows that in addition to being colocalized with F-actin in surface extensions in unstimulated cells, ABP-50 exhibits a diffuse distribution throughout the cytosol. Upon addition of cAMP, a chemoattractant, ABP-50 becomes localized in the filopodia that are extended as a response to stimulation. Quantification of ABP-50 in Triton-insoluble and -soluble fractions of resting cells indicates that 10% of the total ABP-50 is recovered in the Triton cytoskeleton, while the remainder is in the soluble cytosolic fraction. Stimulation with cAMP increases the incorporation of ABP-50 into the Triton cytoskeleton. The peak of incorporation of ABP-50 at 90 sec is concomitant with filopod extension. Immunoprecipitation of the cytosolic ABP-50 from unstimulated cells using affinity-purified polyclonal anti ABP-50 results in the coprecipitation of non-filamentous actin with ABP-50. Purified ABP-50 binds to G-actin with a Kd of approximately 0.09 microM. The interaction between ABP-50 and G-actin is inhibited by GTP but not by GDP, while the bundling of F-actin by ABP-50 is unaffected by guanine nucleotides. We conclude that a significant amount of ABP-50 is bound to either G- or F-actin in vivo and that the interaction between ABP-50 and F-actin in the cytoskeleton is regulated by chemotactic stimulation.

The chromosomes of tufted deer (Elaphodus cephalophus)

Mitotic and meiotic chromosome preparations of the tufted deer (Elaphodus cephalophus) were studied to elucidate the sex-chromosomal polymorphism evidenced by this species. Females had 2n = 46 or 47 chromosomes, whereas males had 2n = 47 or 48 chromosomes. An X;autosome translocation was identified by synaptonemal complex analysis of spermatocytes at pachytene and confirmed by the presence of a trivalent at diakinesis/metaphase I. The present work, in combination with earlier observations by others, indicates that E. cephalophus possesses a varied X-chromosome morphology involving an X;autosome translocation and addition of varying amounts of heterochromatin. It is speculated that sex-chromosome polymorphism may be responsible for the observed differences in diploid chromosome number of tufted deer.

Alpha 2-HS-glycoprotein: expression in chondrocytes and augmentation of alkaline phosphatase and phospholipase A2 activity

The alpha 2-HS-glycoprotein is a plasma protein synthesized in liver and enriched in bone. The concentration of alpha 2-HS-glycoprotein dynamically changes in various physiological conditions and is highest in bone during growth, suggesting that it is involved in regulation of endochondral ossification. Northern blot analysis demonstrated that mRNA transcripts from growth zone and resting zone costochondral chondrocyte cultures hybridized with alpha 2-HS-glycoprotein cDNA. However, a difference of mRNA transcript size was observed, with chondrocyte mRNA transcripts being 2.2 kb, while mRNA isolated from liver was 1.6 kb. Presence of alpha 2-HS-glycoprotein in cartilage cells was found by immunohistochemical staining of human fetal epiphyses using anti-human alpha 2-HS-glycoprotein antibody. To understand the role of alpha 2-HS-glycoprotein in cartilage growth, the effects of exogenous alpha 2-HS-glycoprotein were correlated with alkaline phosphatase (ALPase) and phospholipase A2 (PA2) activity in the chondrocyte cultures. Alkaline phosphatase specific activity was stimulated by alpha 2-HS-glycoprotein at concentrations between 0.25 and 1.25 micrograms/mL in the growth zone and resting zone cultures 2.7 and 2.0-fold, respectively. Matrix vesicle PA2 activity was increased only in the growth zone chondrocyte cultures. These results suggested that alpha 2-HS-glycoprotein may contribute to the regulation of the expression of the chondrocyte phenotype. Steady state mRNA levels of ALPase were analyzed in chondrocytes after additions of alpha 2-HS-glycoprotein. The ALPase mRNA levels remained stationary during the stimulation of enzymatic activity, indicating that the effect of alpha 2-HS-glycoprotein upon alkaline phosphatase activity is not at the transcriptional level.

Effect of nitrendipine on cardiac and renal lesions and arterial hypertrophy. Protective effect of a low dose of calcium antagonist in deoxycorticosterone-induced hypertensive rats

A low dose of nitrendipine (1 mg/kg twice daily) ameliorated the percent incidence and severity of vascular lesions in the kidney and heart induced by deoxycorticosterone (DOC). Less protection was offered by administration of 1 mg/kg of the calcium antagonist once daily. A lower dose of the antagonist (0.5 mg/kg) administered twice daily produced almost no protection against myocardial scars, but the percent incidence and severity of renal tubular casts and glomerular changes were similar to those following injection of 1 mg/kg of the antagonist twice daily. DOC induced hypertrophy of the media in aorta, coronary artery and renal interlobular artery and renal arteriole. Neither 1 mg/kg once or twice daily nor 0.5 mg twice daily of calcium antagonist modified the hypertrophy of the arterial vasculature in the hypertensive DOC group. We conclude that a low dose of the calcium antagonist dissociates at least in part lesions but not hypertrophy from the increased systolic blood pressure, because the antagonist protects against vascular lesions induced by the hypertension. The antagonist likely acts on the endothelial cell of the vessels alone or combined with an effect on the vascular smooth muscle cells.

Identification of an actin-binding protein from Dictyostelium as elongation factor 1a

Indirect evidence has implicated an interaction between the cytoskeleton and the protein synthetic machinery. Two recent reports have linked the elongation factor 1a (EF-1a) which is involved in protein synthesis, with the microtubular cytoskeleton. In situ hybridization has, however, revealed that the messages for certain cytoskeletal proteins are preferentially associated with actin filaments. ABP-50 is an abundant actin filament bundling protein of native relative molecular mass 50,000 (50K) isolated from Dictyostelium discoideum. Immunofluorescence studies show that ABP-50 is present in filopodia and other cortical regions that contain actin filament bundles. In addition, ABP-50 binds to monomeric actin in the cytosol of unstimulated cells and the association of ABP-50 with the actin cytoskeleton is regulated during chemotaxis. Through complementary DNA sequencing and subsequent functional analysis, we have identified ABP-50 as D. discoideum EF-1a. The ability of EF-1a to bind reversibly to the actin cytoskeleton upon stimulation could provide a mechanism for spatially and temporally regulated protein synthesis in eukaryotic cells.

[Inhibiting effect of mitoxantrone on cell cycle progression of Chinese hamster ovary cells]

The effect of Mitoxantrone, a Potential anticancer chemotherapeutic agent, on the cell cycle progression of Chinese Hamster ovary (CHO) cells was investigated by microspectrophotometry. CHO cells incubated with the agent for either 30 min or 24 h were inhibited, to various degrees, from proliferation. The inhibition appeared in dose dependent fashion. A 10-fold dose of the drug was required for the 30 min group, as compared to the 24h group, to develop an equivalent inhibiting effect. When exponentially growing cells were treated with Mitoxantrone for 30 min, washed free of drug, and cultured in fresh medium for another 23.5 h a dose of 0.01 micrograms/ml had little or no effect on the distribution of CHO cells throughout the cell cycle at any point. However, a dose of 0.10-1.00 micrograms/ml was sufficient to cause a decrease of cells in G1 and an accumulation of cells in G2. Block cells had abnormally large nucleus.

Mapping and conservation of the group-specific component gene in mouse

The group-specific component (GC), also known as the vitamin D-binding protein, transports vitamin D and its metabolites in plasma to target tissues throughout the body. The GC gene shares an evolutionary origin with genes encoding albumin (ALB) and alpha-fetoprotein (AFP). All three genes are descendants of an evolutionary ancestor that arose from an intragenic triplication. As a result, each gene is composed of three homologous domains. The study described here characterizes and compares mouse GC to the corresponding nucleotide and amino acid sequences of GC from human and rat. The deduced amino acid sequence of mouse GC was 78% identical to human and 91% identical to rat GC. The results suggest that, unlike the corresponding sequences in the ALB and AFP genes, chromosomal sequences encoding the first domain and the leader sequence of the GC gene have specifically been conserved throughout vertebrate evolution. Protection of domain I during evolution may correlate with an important functional aspect of its sequence. The mouse GC gene was mapped to chromosome 5, where the ALB and AFP genes are also located, demonstrating conservation of the three genes in vertebrate species.

Expression of human plasma protein genes in ageing transgenic mice

Introduction of human plasma protein genes into the mouse genome to produce transgenic mice furnishes an in vivo model for correlating chromosomal DNA sequences with developmental and tissue-specific expression. The liver produces an array of plasma proteins that circulate throughout the body contributing to homeostasis. Non-hepatic tissue sites of synthesis have been identified where a local provision of plasma proteins is needed. Analysis of expression of human plasma protein genes in ageing transgenic mice appears especially promising in identifying DNA sequences that respond to environmental adversities such as inflammatory factors, hormonal changes and metal toxicity. The results indicate that human genes encoding and controlling liver plasma proteins serve as useful models for studying genetic regulation in the background of development and ageing.

Effect of nitrendipine, a calcium antagonist, on the distribution of calcium in aortic smooth muscle cells of deoxycorticosterone-hypertensive rats. A quantitative ultracytochemical study

Rats were made hypertensive by implantation of a pellet of deoxycorticosterone (DOC). A low dose (1 mg/kg twice daily) of the calcium antagonist nitrendipine protects against the increase in total and ionic levels of calcium in the aorta produced by the elevated blood pressure, dissociating at least in part the hypertension from the rise in aortic calcium. Ionic (free) calcium was demonstrated in aortic smooth muscle cells by the pyroantimonate ultra-cytochemical method and the electron opaque reaction product quantitated by stereological techniques. As compared to the control group, nitrendipine did not increase the number of vesicles/micron with precipitate located adjacent to the sarcolemma. DOC however increased the number of subsarcolemmal vesicles with electron opaque precipitate and sarcoplasmic calcium. Nitrendipine administration to DOC-treated rats decreased the number of vesicles to that found in the control or nitrendipine-treated group while ionic calcium in the nitrendipine + DOC group was intermediate between the control or nitrendipine group and the DOC group. The total content of calcium measured by atomic absorption correlates with the observations of ionic calcium levels demonstrated ultracytochemically. Aortic dry weights of the DOC and DOC + nitrendipine groups were comparable and significantly greater than those in the control or nitrendipine groups.

Effects of high-frequency chest wall oscillation on respiratory control in humans

We studied the spontaneous breathing patterns of 10 normal adult volunteers during high-frequency chest wall oscillation (HFCWO), accomplished by inflating and deflating a vest worn around each subject's thorax at 2.5 Hz. Tidal volumes generated by HFCWO averaged 100 ml. Mean vest pressure was maintained at approximately 35 cm H2O throughout each experiment, even when HFCWO was not applied. During HFCWO, subjects were instructed occasionally to exhale deeply to obtain end-tidal samples representative of PACO2. HFCWO increased the breath-to-breath variability of spontaneous respiration in all subjects, prolonging expiratory pauses and producing short apneas in some cases. PACO2 decreased significantly (p less than 0.05). The effects on minute ventilation, tidal volume, and inspiratory and expiratory durations remained variable across subjects, even when differences in PACO2 between control and HFCWO states were reduced through inhalation of a low CO2 mixture. None of the changes were statistically significant, although average expiratory duration increased by 29%. Ventilatory responses to CO2 with and without HFCWO were also measured. Normocapnic (PACO2 = 40 mm Hg) ventilatory drive increased significantly (p less than 0.05) in six subjects (Type 1 response) and decreased substantially in the others (Type 2 response); with hypercapnia, the changes in drive were attenuated in both groups. Consequently, CO2 sensitivity decreased in Type 1 subjects and increased in Type 2 subjects. A simple analysis based on this result shows that with HFCWO, Type 2 subjects breathing air will tend to have a lower spontaneous minute ventilation and become hypercapnic. Type 1 subjects will become hypocapnic, but minute ventilation may be higher or lower than control.(ABSTRACT TRUNCATED AT 250 WORDS)

The pharmacological and pathological studies on several hepatic protective crude drugs from Taiwan (II)

Four crude drug extracts of Solanum incanum (entire plant), Ixeris chinensis (entire plant), Gardenia jasminoides (wild and cultivated, fructus) were administered to rats as dose of 1.0 g/kg, I.P. injection to screen the liver protective effect on CC14 induced hepatotoxicity. The acute increase of transaminase SGOT and SGPT levels that was caused by CC14 (1.0 ml/kg) S.C. injection can be significantly improved when treated with Solanum incanum (p less than 0.005), Ixeris chinensis (p less than 0.001), Gardenia jasminoides (cultivated) (p less than 0.005) but only a moderate change was shown by means of wild Gardenia jasminoides (p less than 0.05). As our results indicated, the extraction of these drugs has been found to possess a marked hepatic protective effect. The hepatic fatty metamorphosis and necrosis of central lobule were obviously improved by S. incanum and I. chinensis, administration, while the effect of treatment with G. jasminoides (cultivated) demonstrated a moderate protective action and little histopathological change by G. jasminoides (wild). In contrast to B. chinese, which has been reported previously as a treatment criteria, the S. incanum (p less than 0.01) and I. chinensis (p less than 0.01) in the present study have indicated that a significantly different hepatic protective effect on CC14 induced hepatic injury.

Direct correlation between calcium content and blood pressure: a study of aortic coarctation in rats

The calcium content of aorta was measured by atomic absorption after coarctation in the rat. At 7 and 14 days, the calcium content was elevated on the proximal side of the coarctation, where pressure was increased significantly. On the distal, low pressure side of the aortic coarctation, calcium was reduced significantly. There is a direct correlation between the blood pressure and the content of calcium (r = 0.69, P less than 0.001). The width of the aortic media on the high pressure side was increased significantly at 7 and 14 days after coarctation, whereas no significant changes in width were present on the low pressure side of the constriction. We conclude that pressure regulates the aortic calcium content, likely acting through a local effect.

Effect of parathyroidectomy on arterial hypertrophy, vascular lesions, and aortic calcium content in deoxycorticosterone-induced hypertension

Parathyroidectomy (Px) did not prevent the development of deoxycorticosterone (DOC)-induced hypertension inasmuch as the systolic blood pressure at 4 weeks did not differ from that of parathyroid intact, DOC-treated rats. Px, however, ameliorated the percent incidence and severity index of hypertension-induced vascular lesions in the heart and kidney. There was less hyaline change in the coronary artery and renal arteriole and fewer scars in the myocardium of Px + DOC rats than in DOC-treated animals. Arterial hypertrophy in aorta, coronary artery, renal interlobular artery, and renal arteriole in hypertensive animals was not affected by Px. The aortic content of total calcium in the Px-hypertensive rats was reduced significantly as compared to parathyroid-intact hypertensive rats. The abdominal aorta in the Px + DOC group showed a greater reduction in calcium than the thoracic aorta. We conclude that calcium may not be essential in mediating hypertension-induced vascular hypertrophy. Parathyroidectomy permitted a separation of high blood pressure-hypertrophy from hyaline vascular lesions in DOC-induced hypertensive rats, likely acting upon endothelial cells to prevent movement of plasma proteins (hyaline change) from the vascular lumen into the media-subendothelial space of blood vessels.

Calcium distribution in aortic smooth muscle cells of deoxycorticosterone-hypertensive rats. A quantitative cytochemical study

The effect of deoxycorticosterone (DOC)-induced hypertension on the calcium content within the aorta was studied before the increase in pressure (one week) and after the pressure had reached hypertensive levels (4 weeks). The volume density of free calcium detected ultrastructurally by pyroantimonate precipitation was quantitated by stereological techniques in aortic smooth muscle cells. An increase in the volume density of electron opaque precipitate was observed in the cytoplasm at one week of DOC treatment when neither the systolic blood pressure, the thickness of the media nor volume fraction of medial smooth muscle as compared to the extracellular space was increased significantly. The total aortic calcium as measured by atomic absorption spectroscopy was not increased at one week. By 4 weeks when the rats were hypertensive, the cytoplasmic free calcium in the smooth muscle cells and the number of peripherally-located cytoplasmic vesicles with precipitate was increased significantly. Total aortic calcium was also increased significantly in the DOC-saline group but not in the DOC group drinking tap water or in the saline drinking controls. An elevation of calcium within the cytoplasm of vascular smooth muscle cells may precede the development of hypertension and play a role in the pathogenesis of the increased blood pressure, increased medial thickness and hypertrophy of the vascular smooth muscle cells.

The pharmacological and pathological studies on several hepatic protective crude drugs from Taiwan (I)

This study is to investigate the hepatic protective effect of several Taiwan crude drug extractions on the carbon tetrachloride (CCl4)-induced hepatotoxicity in rats. The pharmacological and pathological effects of Bupleurum chinense, Phellodendron wilsonii, Clematis chinensis and Hedyotis corymbosa were analyzed by liver enzyme function test and pathological studies. However, the results of amine transferase SGOT and SGPT have shown a significant hepatic protective effect after treatment with Bupleurum chinense (P less than 0.005), Phellodendron wilsonii (P less than 0.001), Clematis chinensis (P less than 0.005) and Hedyotis corymbosa (P less than 0.005, SGPT only). The fatty degeneration around the central vein area and necrosis of the central lobule can be significantly improved by P. wilsonii and moderately changed by B. chinense or C. chinensis. Although fatty metamorphosis has been affected by H. corymbosa, various inflammatory cell infiltrations in the cytoplasm were noted.

Human alpha 2-HS-glycoprotein localized to 3q27----q29 by in situ hybridization

Human plasma protein alpha 2-HS-glycoprotein (AHSG) is composed of two polypeptide chains, A and B, encoded by a single mRNA. Southern blot analysis of mouse x human somatic cell hybrids has mapped the AHSG gene to human chromosome 3 in the region 3q21----qter (Lee et al., 1987). Using a recombinant plasmid containing a 1,538 bp insert spanning the entire AHSG coding region, AHSG was localized to chromosomal bands 3q27----q29 by in situ hybridization.

The vitamin D-binding protein gene contains conserved nucleotide sequences that respond to heavy metal, adipocyte and mitotic signals

Characterization of the 5'-flanking region of the DBP genomic sequence is reported. Nucleotide sequences that serve as cis-regulatory elements for transcription in other genes have been found and include metal regulatory elements, viral enhancers, adipocyte and mitotic signals. The promoter region of DBP is not homologous to the 5'-flanking region of the albumin and alpha-fetoprotein genes despite the strong protein homology and evolutionary relationship among the three proteins.

Long-range surface modes of metal-clad four-layer waveguides

The surface modes of metal-clad four-layer waveguides were theoretically analyzed. We showed that the long-range surface modes can be excited in such waveguides. The long-range surface modes were experimentally studied with the angle scanning attenuated-total-reflection method; the dependence of wave vector and loss of these modes on the waveguide parameters were measured. Experimental results were in good agreement with theoretical calculations.