Isolation of three MiDi19-4 genes from mango, the ectopic expression of which confers early flowering and enhances stress tolerance in transgenic Arabidopsis

MAIN CONCLUSION

Three Di19-4 genes were identified in mango. Overexpression of MiDi19-4B in A. thaliana promoted earlier flowering and enhanced drought, salt, and ABA resistance. Drought-induced protein 19 (Di19) is a drought-induced protein that is mainly involved in multiple stress responses. Here, three Di19-4 genes (MiDi19-4A/B/C) in mango (Mangifera indica L.) were identified, and the coding sequences (CDS) had lengths of 684, 666, and 672 bp and encoded proteins with 228, 222, and 224 amino acids, respectively. The promoters of the MiDi19-4 genes contained phytohormone-, light-, and abiotic stress-responsive elements. The MiDi19-4 genes were expressed in every tissue and highly expressed in leaves. Moreover, MiDi19-4 genes were highly correlated with the vegetative growth period and induced by polyethylene glycol (PEG) or salt stress. MiDi19-4B displayed the highest expression during the vegetative growth period and then showed decreased expression, and MiDi19-4B was highly expressed at both the late stage of the vegetative growth period and the initial stage of the flowering induction period. The 35S::GFP-MiDi19-4B fusion protein was located in the cell nucleus. The transgenic plants ectopically expressing MiDi19-4B exhibited earlier flowering and increased expression patterns of FRUITFULL (AtFUL), APETALA1 (AtAP1), and FLOWERING LOCUS T (AtFT). The drought and salt tolerance of MiDi19-4B transgenic plants was significantly increased, and these plants showed decreased sensitivity to abscisic acid (ABA) and considerably increased expression levels of drought- and salt-related genes and ABA signalling pathway genes. Additionally, bimolecular fluorescence complementation (BiFC) experiments revealed that the MiDi19-4B protein interacted with CAULIFLOWER (MiCAL1), MiCAL2, MiAP1-1, and MiAP1-2. Taken together, these results highlighted the important regulatory roles of MiDi19-4B in tolerance to multiple abiotic stresses and in flowering.

Clonal evolution of AML1-ETO coexisting with BCR-ABL and additional chromosome abnormalities in a blastic transformation of chronic myeloid leukemia

Blast crisis develops in a minority of patients with chronic myeloid leukemia even in the era of tyrosine kinase inhibitor (TKI) therapy. Reports suggest that we know little about the mechanism of BCR-ABL and AML1-ETO co-expression in blast crisis of chronic myeloid leukemia, and that other chromosomal abnormalities also coexist. Here, we document an unusual and interesting case of a 51-year-old female diagnosed in the chronic phase of chronic myeloid leukemia. After undergoing TKI treatment for 3 months, her bone marrow aspirates in the chronic phase had transformed to blast crisis. Molecular genetic testing indicated she was positive for p210 form of BCR-ABL (copy number decreased from 108.91% to 56.96%) and AML1-ETO fusion (copy number, 5.65%) genes and had additional chromosomal abnormalities of t(8; 21)(q22; q22)/t(9; 22)(q34; q11), t(2; 5)(p24; q13) and an additional +8 chromosome.

[An analysis of the characteristics of perioperative cardiac troponin elevation in orthopaedic surgical patients]

Objective: Perioperative myocardial infarction remains a severe complication in non-cardiac surgery and is one of the major causes of death. Cardiac troponin (cTn) I elevation is associated with short-term and long-term mortality. The aim of the study was to assess the proportion rate of cTnI elevation and its clinical characteristics among patients admitted for orthopaedic surgery with or without cardiovascular events. Methods: This is a retrospective study including 27 744 patients aged 50 years or older who admitted for orthopaedic surgery from 2009-2015 in Beijing Jishuitan Hospital. Results: Two hundred and sixty-five patients [age (71.7±9.9) years] had cTnI level> 0.04 μg/L with 66% (175 patients) of them being female. Among them, 59 patients were isolated troponin rise (ITR) (n=59), 13 were preoperative acute myocardial infarction (AMI), and 193 were postoperative AMI. The proportion of postoperative AMI was 0.69%. Those patients were more likely to have a history of coronary artery disease or hypertension. Non-ST-segment elevation myocardial infarction (NSTEMI) was more common (93.3%) than ST-segment elevation myocardial infarction in these patients. Most of them did not experience ischemic symptoms. Totally 76.7% of the AMI occurred within 3 days of surgery; and the in-hospital mortality rate was 10.4%. Conclusions: Perioperative elevation of troponin is common in patients undergoing orthopaedic surgery. Most postoperative AMI were NSTEMI and with absent or atypical ischemia symptoms. Monitoring troponin levels and electrocardiograph in at-risk patients is needed to find most of the AMI.

Reliability of the Sunnybrook Facial Grading System by novice users

OBJECTIVES

To evaluate the intrarater and inter-rater reliability of the Sunnybrook Facial Grading System (SFGS) by novice users.

DESIGN

Prospective interval study using one measurement instrument.

SETTING

Tertiary teaching hospital (Sunnybrook & Women's College Health Science Centre).

METHODS

Twenty-two patients with a wide spectrum of facial dysfunction recorded on videotapes were rated using the SFGS by eight novice observers independently in two different sittings separated by 3 weeks. The order of patients was randomized for the second sitting. Intraclass correlation coefficients were calculated for component scores and for total scores within and between raters.

RESULTS

The intrarater reliability coefficients for the eight raters ranged from .838 to .929. This largely overlaps with the data obtained in previous studies with expert raters. The inter-rater reliability for all eight raters at time 1 was .982 and for time 2 was .970. This is higher than what was previously obtained with expert raters.

CONCLUSION

The SFGS is as reliable when applied by novice users as by expert users.

KAI1/CD82 gene expression in benign prostatic hyperplasia and late-stage prostate cancer in Chinese

AIM

To evaluate KAI1/CD82 expression in Chinese patients with benign prostatic hyperplasia (BPH) and late-stage carcinoma of prostate (CaP).

METHODS

Thirty Chinese patients with benign prostatic hyperplasia and 34 with CaP (adenocarcinoma clinical stage C and D) were analyzed by means of immunohistochemical methods.

RESULTS

The KAI1/CD82 expression in BPH tissue was all positive, which was uniformly located on the glandular cell membrane at the cell-to-cell borders, but KAI1/CD82 expression in metastasis CaP tissues was either significantly lower than that of BPH or negative, and the immunostaining pattern was not continuous. In late-stage CaP KAI1/CD82 expression was correlated inversely to the pathological grade ( P < 0.05), but not to clinical stage ( P > 0.05).

CONCLUSION

The authors believe that decreased and negative KAI1/CD82 expression in late-stage CaP may be related to tumor progression and metastasis, and appears to be a prognostic marker.

Pediatric intracranial germinoma treated with chemotherapy alone

BACKGROUND

Pediatric intracranial germinoma treated with radiotherapy is considered a standard treatment, but may cause significant delayed damage to the central nervous system. Chemotherapy has been shown to be effective for the treatment of an intracranial germinoma. In the past 10 years, we treated 11 cases of primary intracranial germinoma with chemotherapy alone. The purpose of this retrospective study is to review the clinical outcome of these patients.

METHODS

Eleven children with newly diagnosed, previously untreated primary intracranial germinomas were treated with six courses of chemotherapy (vinblastine bleomycin, cisplatin and etoposide, VBPE). The response to chemotherapy, relapses and outcomes are reviewed and evaluated.

RESULTS

All 11 assessable children achieved a complete response and are alive, with a median follow-up of 61 months. Five patients with tumors located in the midline position of the brain, including pineal, sellar, suprasellar and hypothalamic areas, had no relapse. Six patients had relapses, and all of them achieved a second complete remission after salvage focal radiotherapy. The time of onset of relapse was from nine to 24 months after chemotherapy, with an average of 16.8 months.

CONCLUSIONS

VBPE chemotherapy was effective for treating newly diagnosed intracranial germinomas. Although a high rate of relapse (6/11) was observed, all of these patients survived with first or second complete remissions. It was beneficial for five children that focal radiation was eliminated and delayed post-irradiation neurologic sequelae were avoided.

Neonatal myocardial infarction: a case report

Neonatal myocardial infarction is a rare disorder. It occurs in association with congenital heart disease or coronary artery abnormalities. In the absence of structural heart disease, perinatal asphyxia and coronary artery thromboembolism have been reported as common etiologies. Whether the Coxsackie B viral group has a causal role in adult myocardial infarction remains controversial. We report herein a case of neonatal myocardial infarction without known congenital heart disease, in whom perinatal Coxsackie B viral infection was suspected to be the underlying cause. However, definite evidence indicating a causal relationship between neonatal myocardial infarction and Coxsackie B viral infection was lacking in this case.

Interaction of transferrin with rat alveolar macrophages

Binding of rat transferrin to isolated alveolar macrophages was investigated in the 0.125 nM to 2 microM range. Computer analysis of the data revealed two classes of binding sites, a small number (< 1000 exposed/cell) having high affinity (dissociation constant (Kd), 3.4 nM) and a large number (approximately 4 x 10(6)/cell) having low affinity (Kd 48 microM). Measurements with a monoclonal antibody to the rat transferrin (rTf) receptor yielded values in the same range as the high-affinity sites derived from studies of ligand binding. Binding to the low-affinity sites at pH 5.8 was nearly one order of magnitude stronger than that at pH 7.3. Bovine lactoferrin (12 microM), cationized bovine serum albumin (14 microM), L-arginine (50 mM), and L-lysine (50 mM) did not compete against rTf binding to the low-affinity sites. Removal of an average of 2.6 x 10(8) sialyl residues from each cell did not affect binding. Heparan sulphate proteoglycan purified from alveolar macrophages bound strongly to immobilized rTf, thus raising the possibility that the low-affinity interaction of transferrin with these cells may be mediated, at least in part, by this glycosaminoglycan.

Effect of transferrin on the degradation of glycoproteins bearing a hybrid or high-mannose glycan by alveolar macrophages

A subfraction of hen ovalbumin and a special form of rat transferrin, possessing a hybrid glycan, were studied with respect to their binding to, and degradation by macrophages isolated from the rat lung. Both ligands were found to be degraded partly through the mannose receptor pathway and partly by another mechanism, presumably adsorptive pinocytosis. Catabolism of both proteins was markedly increased by adding standard (i.e., normally glycosylated) transferrin from various species to the medium. This increase was not diminished, or even augmented, when Ca2+ was depleted in the medium, thus implying involvement of the pinocytic pathway rather than the mannose receptor. Binding to the cell surface of both ligands was altered in the presence of transferrin. A hypothesis is advanced to suggest that when transferrin is bound to a component of macrophage plasmalemma, thought to be the glycosaminoglycan of heparan sulfate, its conformation may change in such a way that it attracts other proteins. Protein molecules temporarily captured by adsorbed transferrin would then be taken up by a "piggyback" process and degraded.

Observations with a residualizing label in use to map the catabolic sites of plasma proteins

Rat albumin, immunoglobulin G, transferrin, and aglycotransferrin were prepared for the comparison of their sites of degradation in rats. Iodotyramine-cellobiose was used as the residualizing label and a tyrosine-iodinated portion of the corresponding protein was used as the marker of extracellular undegraded protein. Each protein yielded a distinct distribution (or map) of catabolic activity throughout the body when expressed as percent dose accumulated per gram of tissue. The maps for albumin and transferrin were broadly comparable, whereas those for immunoglobulin G and aglycotransferrin were markedly different. As a whole entity, the liver appeared to top the list of organs/tissues contributing to the degradation of albumin and transferrin. Additional experiments aimed at facilitating the interpretation of results with residualizing labels were carried out with denatured albumin, asialofetuin, and human asialotransferrin type 3. These showed that various types of cells retained the label for markedly different periods of time. We feel, therefore, that the technique is more suited for making comparative measurements than for obtaining degradation rates as absolute values in a given anatomical location.

Transport of lactoferrin from blood to bile in the rat

The bile contains small quantities of lactoferrin, the origin of which is uncertain. For this reason, we studied the liver's capability of transferring lactoferrin from the plasma to the bile by injecting a dose (10 to 20 micrograms/100 gm) of labeled bovine lactoferrin intravenously and following its appearance in bile over 3 hr. Whether diferric or iron free, lactoferrin peaked in the bile 35 min after administration (i.e., the same time as bovine lactoperoxidase and diferric rat transferrin). However, only a small portion of the lactoferrin dose (approximately 1%) was recovered with the bile in 3 hr. On the basis of autoradiographic evidence, the excreted lactoferrin appeared intact. The biliary excretion profile of albumin, a protein thought to reach the canaliculus by paracellular diffusion, was notably devoid of a peak. This, together with competition observed between lactoferrin and lactoperoxidase on one hand and 2Fe-transferrin and lactoferrin on the other for transfer to bile, suggests that lactoferrin is routed through the hepatocyte in vesicles. The process is initiated by binding to a plasma membrane component to which lactoperoxidase and 2Fe-transferrin can also bind. Most 59Fe bound to lactoferrin accompanied the protein carrier to the bile. We conclude that under normal circumstances (i.e., when concentration of lactoferrin in the plasma is very low), lactoferrin transferred from plasma by the liver is probably not the major source of this protein in bile.

Interaction of transferrin and its iron-binding fragments with heparin

The interaction of heparin with transferrin (Tf; bovine and rat) and the isolated iron-binding lobes of bovine Tf were investigated. Affinity chromatography of rat Tf on heparin-agarose showed that interaction depended on both the iron content of Tf and the pH of the medium. Both the iron-free and iron-saturated forms of Tf were strongly bound by the column at pH 5.6, but only the iron-free form revealed significant affinity at pH 7.4. Desialylation of Tf moderately promoted interaction, treatment with cyclohexanedione moderately reduced interaction, and succinylation abolished it altogether. In the presence of heparin, iron release from the N-terminal lobe of native bovine Tf was accelerated and from the C-terminal lobe it was slightly reduced. The heparin effect remained qualitatively the same on each lobe after their separation by tryptic digestion and DEAE-cellulose chromatography. The affinity of native bovine Tf for heparin was very close to that of its isolated N-terminal lobe, thus suggesting that it is this portion of the molecule that binds to the glycosaminoglycan. It is concluded that the consequences for iron-binding strength of the two transferrin lobes are diagonally opposite when Tf is bound to heparin as opposed to its natural cell-surface receptor.

[Effect of glycerol-induced acute renal failure in rabbit with Ligusticum wallichii on thromboxane B2, 6-keto-prostaglandin F1 alpha/thromboxane B2]

The effect in preventing and treating glycerol-induced acute renal failure (ARF) in rabbit with Ligusticum wallichii (LW) has been studied. 33 male and female rabbits weighing 2.0-3.0 Kg were divided into three groups randomly: (1) LW treated group. (2) pathological control group and (3) normal control group. The measurement of plasma 6-keto-PGF1 alpha, TXB2 concentration and 6-keto-PGF1 alpha/TXB2 ratio were carried out with radioimmunoassay after 24 hr, 48 hr and 72 hr of ARF. The results showed that plasma TXB2 concentration obviously increased (P < 0.01), 6-keto-PGF1 alpha concentration had no obvious changes (P > 0.05), 6-keto-PGF1 alpha/TXB2 ratio markedly decreased and LW could reduce plasma TXB2 concentration, slightly increase the plasma 6-keto-PGF1 alpha concentration, keep 6-keto-PGF1 alpha/TXB2 ratio in normal level after ARF. It showed that LW could inhibit effectively platelet activation, correct 6-keto-PGF1 alpha/TXB2 imbalance and have a preventing and treating effect for ARF.

Lactoferrin interferes with uptake of iron from transferrin and asialotransferrin by the rat liver

Intravenous injection of bovine or human lactoferrin (6.25 x 10(-2) mumol/100 g body wt) in rats resulted in marked reduction of hepatic iron uptake from transferrin and asialotransferrin. The effect was dose dependent, saturable at approximately 5 mg/100 g body wt, and independent of lactoferrin's iron content. At this dose level, iron uptake from transferrin was reduced by 28% and from asialotransferrin by 43% in experiments lasting 90 min. Bovine lactoperoxidase, another basic protein, was similarly effective. The clearance of asialofetuin and pinocytosis of polyvinylpyrrolidone remained unaffected. Perfusion of isolated rat livers at 4 degrees C showed a strong reduction in asialotransferrin binding in the presence of lactoferrin. Chromatography of hepatic heparan sulfate proteoglycan on immobilized lactoferrin, lactoperoxidase, asialotransferrin, and transferrin showed that it possessed affinity for each of these proteins, more for the first two than the latter two. Heparan sulfate proteoglycan binding and efficacy in reducing hepatic iron uptake were also studied after selective modifications of positively charged amino acids in these proteins. The data obtained are compatible with the hypothesis that lactoferrin and other proteins with similarly high affinity for hepatic heparan sulfate exert their negative effect on iron uptake by preventing transferrin binding to the proteoglycan. The possibility is thus raised that the large number of low-affinity transferrin binding sites reported by earlier investigators for the liver may be heparan sulfate molecules.

Variable alpha-tocopherol stimulation and protection of glutathione peroxidase activity in established and malignant fibroblasts

Studies on glutathione (GSH) metabolism in an established baby hamster kidney fibroblast cell line (BHK-21/C13) and in its polyoma virus-transformed counterpart (BHK-21/PyY) have revealed a significant stimulation of intracellular GSH peroxidase (GSHpx) activity (selenium-independent plus selenium-dependent) by alpha-tocopherol supplementation (14 microM). This stimulation was found to be much greater in the transformed cells. Other GSH-requiring enzyme activities (i.e. GSH reductase and GSH S-transferase) were unaltered by alpha-tocopherol treatment, suggesting a degree of specificity in its action on GSHpx. In unsupplemented growth media, the GSHpx activity in both cell lines was significantly decreased by oxidative stress. However, the same stress applied to the alpha-tocopherol-supplemented cells had no effect on the stimulated GSHpx activity, suggesting that some protection was afforded by the alpha-tocopherol.

The perfused liver is capable of producing all transferrin glycan variants found in the sera of intact rats

The single oligosaccharide attachment in rat transferrin exhibits marked structural microheterogeneity. In this study we examined whether all microheterogeneous forms of rat transferrin found in plasma are derived from a single organ, such as the liver. To this end we analyzed the glycans of rat transferrin synthesized by the isolated perfused rat liver by a method established earlier for rat transferrin isolated from rat plasma. Our observations provide evidence that the liver can and does produce all variant rat transferrin glycans present in plasma. However, this discovery does not preclude the possibility that extrahepatic sources with an active rat transferrin gene may contribute to the circulation rat transferrin molecules, which bear glycan variants identical to those made by the liver. The glycan spectra of rat transferrin in plasma and in liver perfusate compared closely with each other in a quantitative sense. Nevertheless, rat transferrin in the perfusate was sialylated to a lesser extent and fucosylated to a greater extent than rat transferrin in plasma. These differences could not be eliminated by supplementation of the medium with insulin, dexamethasone, pyruvate and adenine or adenosine either alone or in combinations, nor could it be eliminated by use of a fluorocarbon O2 carrier. In contrast, epidermal growth factor normalized both parameters. The pH of the perfusing medium also influenced sialylation and fucosylation in such a way that higher pH brought these parameters closer to their values in plasma rat transferrin. Lower pH, on the other hand, reduced sialylation and left the fucosylation index unchanged.

In vivo behaviour of rat transferrin bearing a hybrid glycan and its interaction with macrophages

Production of rat transferrin containing a single hybrid glycan was induced by treating rats with swainsonine, an inhibitor of alpha-mannosidase II. The principal component of this variant transferrin containing one sialic acid residue per mole of protein was separated from other forms of transferrin by anion-exchange chromatography, followed by lectin affinity chromatography. Transferrin bearing the hybrid glycan was degraded in vivo with a half-life of 14 h as compared with 40 h for transferrin containing a standard diantennary glycan. By using 125I-labelled tyramine-cellobiose, a label whose discharge from lysosomes is strongly retarded, organs rich in reticuloendothelial elements (liver, bone marrow, lungs, and spleen) were identified as the major sites of catabolism of the transferrin variant. The liver took up more 59Fe from the variant (26% of the dose in 90 min) than from control rat transferrin (12%). The excess iron uptake was reduced by the intravenous injection of either human transferrin or ovalbumin, and it was abolished by administering both. Macrophages from bone marrow and lungs degraded the transferrin variant in vitro. The degradation was significantly enhanced when transferrin receptors were blocked by human transferrin, and it was significantly reduced by ovalbumin and methyl glucopyranoside.

Hepatic heparan sulphate proteoglycan and the recycling of transferrin

Heparan sulphate proteoglycan, labelled with [35S]sulphate, was prepared from rat livers for studies of its interaction with purified rat transferrin. Affinity chromatography of the preparation on columns of immobilized differic transferrin and apotransferrin showed that the proteoglycan possessed affinity for both types of matrices at pH 7.3 and that this affinity significantly increased at pH 5.6. The glycosaminoglycan chains liberated from the proteoglycan by heparan sulphate lyase also bound to apotransferrin, albeit less strongly, whereas the deglycosylated core protein exhibited virtually no interaction with this matrix. In the presence of the proteoglycan at pH 5.6, the release of iron from the N-lobe of transferrin was accelerated. These observations suggest that heparan sulphate proteoglycan from the liver can mimick some of the known functions of bona fide transferrin receptors and, hence, interaction with the proteoglycan may provide an alternative nondegradative pathway for transferrin through hepatic cells.

Variable alpha-tocopherol stimulation and protection of glutathione peroxidase activity in non-transformed and transformed fibroblasts

Studies on glutathione metabolism in an established baby hamster kidney cell line (BHK-21/C13) and in its polyoma virus-transformed counterpart (BHK-21/PyY), have revealed a significant stimulation of intracellular glutathione peroxidase activity (Se-independent plus Se-dependent) by alpha-tocopherol supplementation (14 microM). This stimulation was found to be much greater in the transformed cells. Other GSH-requiring enzyme activities (namely glutathione reductase and glutathione transferase) were unaltered by alpha-tocopherol treatment, suggesting a degree of specificity in its action on GSHpx. In unsupplemented growth media, the GSHpx activity in both cell lines was significantly decreased by an oxidative stress. However, the same stress applied to the alpha-tocopherol-supplemented cells had no effect on the stimulated GSHpx activity, suggesting a protection afforded by the alpha-tocopherol.

Reduced hepatic iron uptake from rat aglycotransferrin

Rat aglycotransferrin (rAgTf) was produced from the disialosyl diantennary fraction of rat transferrin (rTf) by treatment with peptide: N-glycosidase F. Following removal of the enzyme by gel filtration and isolation of the deglycosylated protein by lectin chromatography, rAgTf was compared to rTf both in vitro and in vivo. No significant differences were found between the two proteins with respect to affinity for iron and kinetics of Fe release from the N-lobe and C-lobe. The fluorescence emission spectrum of apo-rTf was red-shifted by approximately 3 nm relative to diferric rTf; however, no spectral difference was detected between rTf and rAgTf when the analogous forms (apo or diferric) were compared. Plasma clearance of radioactive iron administered to rats as either rTf or rAgTf was comparable. Reticulocytes took up iron from rAgTf slightly faster than from rTf. In contrast, Fe acquisition by the liver from rAgTf was significantly reduced relative to rTf. This finding contrasts sharply with earlier observations with asialotransferrin (rAsTf) and provides a basis for discounting charge loss as the mechanism of enhanced hepatic Fe uptake from rAsTf. It is suggested that the glycan complement of rTf, while unimportant for interaction of the protein with specific receptors, probably plays a role in the interaction with low-affinity hepatic binding sites.

Isolation and partial characterization of a lactotransferrin receptor from mouse intestinal brush border

Several lines of evidence have recently suggested the occurrence of a specific lactotransferrin receptor in the small intestinal brush-border membrane in several animal species, which is thought to be involved in lactotransferrin-mediated intestinal iron absorption. We report here for the first time the isolation and partial characterization of this receptor from mouse intestinal brush border. The receptor has been purified to homogeneity by affinity chromatography on an immobilized human lactotransferrin column. The purified receptor was found to be active in that it binds iron-free and iron-saturated lactotransferrin with a Kd of 0.1 microM. Anti-receptor antibodies were prepared, and the receptor was further isolated by immunoaffinity chromatography in higher yield but in a denatured form. The purified receptor was revealed by sodium dodecyl sulfate-polyacrylamide electrophoresis to be a protein of about Mr = 130,000, consisting of a single polypeptide chain. The isoelectric point was determined to be 5.8. The receptor was further shown to bear concanavalin A and phytohemagglutinin L binding glycans. Digestion by N-glycanase and endo-N-acetyl-beta-D-glucosaminidase B led to a decrease of Mr = 25,000, while the endo-N-acetyl-beta-D-glucosaminidase H was uneffective, suggesting that the lactotransferrin receptor is mainly glycosylated by bi- and triantennary glycans. To gain further insight into the interaction of the receptor with lactotransferrin, namely, the number of ligand molecules bound per molecule of receptor, mouse lactotransferrin was cross-linked to its membrane-bound enterocyte receptor by use of radiolabeled sulfosuccinimidyl 3-[[2-(p-azidosalicylamido)ethyl]dithio]propionate (SASD).(ABSTRACT TRUNCATED AT 250 WORDS)

Indole Alkaloids from Alstonia angustifolia

From the stem bark of ALSTONIA ANGUSTIFOLIA, eleven alkaloids were isolated. Seven of them are known ones: echitamine ( 1), N(b)-demethylechitamine ( 2), pseudoakuammigine ( 3), tubotaiwine ( 5), akuammicine ( 6), N(b)-beta-methylantirhine ( 12), and N(b)-methylakuammidine ( 13). The four others, pseudoakuammigine N-oxide ( 4), akuammicine N-oxide ( 7), N(b)-demethylalstogustine ( 8), and N(b)-demethylalstogustine N-oxide ( 11), are new alkaloids. Their structures were determined by means of spectroscopic analysis and chemical correlation with known alkaloids.

Expression of human lactotransferrin receptors in phytohemagglutinin-stimulated human peripheral blood lymphocytes. Isolation of the receptors by antiligand-affinity chromatography

In the resting rate, the human peripheral blood lymphocytes did not show detectable surface and intracellular receptors for human lactotransferrin. However, both types of lactotransferrin receptors were expressed during stimulation of lymphocytes with phytohemagglutinin. The appearance of receptors was time-dependent and the number of receptors reached a plateau after at least two days of mitogen stimulation. These results suggest that the presence of surface receptors on mitogen-stimulated lymphocytes is not consecutive to a modification of subcellular distribution but to an induction of biosynthesis of the receptors. As measured by incorporation of [3H]thymidine into DNA, addition of human lactotransferrin in a serum-free medium increased the proliferative activity of phytohemagglutinin-stimulated lymphocytes. Optimal enhancement of [3H]thymidine incorporation was obtained by adding 30% iron-saturated lactotransferrin at a concentration of 0.17 microM. Therefore, the role of lactotransferrin in the response of lymphocytes to mitogen stimulation appears to be similar to that previously described for serotransferrin. The lactotransferrin receptor was visualized using 125I-labeled lactotransferrin on nitrocellulose paper after electroblotting of the Triton X-100 extract of the phytohemagglutinin-stimulated lymphocytes as two protein bands of 100 and 110 kDa molecular mass. Purification of the lactotransferrin receptor from the Triton-X-100-soluble extract of stimulated lymphocytes was performed by antiligand-affinity chromatography. The binding of lactotransferrin to the purified receptors was reversible and dependent on concentration and pH.

The Alkaloids of Melodinus acutiflorus. Rhyzicine N-Oxide

From the leaves of MELODINUS ACUTIFLORUS a new alkaloid, rhazicine N-oxide ( 2), and two known compounds, deacetylakuammiline ( 3) and 16- EPI-rhazinaline ( 4) were isolated. The structure of 2 was determined by spectral analysis and chemical correlation with rhazicine ( 1).

Lactotransferrin receptor of mouse small-intestinal brush border. Binding characteristics of membrane-bound and triton X-100-solubilized forms

A specific lactotransferrin receptor was identified in the mouse small-intestinal brush-border membrane and the binding features were investigated in homologous and heterologous systems. The receptor was found to be specific for lactotransferrins isolated from milk of various species, but the affinity was higher toward the homologous ligand (Ka = 3.5 x 10(6) M-1 compared with 2.6 x 10(6) M-1 for both human and bovine lactotransferrins). However, the number of binding sites (n) was the same for the three lactotransferrins, namely 0.53 x 10(12)/micrograms of membrane protein. The binding of mouse lactotransferrin to its receptor was found to be pH-dependent, with an optimal binding at pH 5.5, and seemed unlikely to be carbohydrate-mediated. The receptor was demonstrated to be devoid of any affinity for human and mouse serotransferrins or for a 'serotransferrin-like' protein isolated from mouse milk. The receptor was solubilized with 1% Triton X-100 with good yield. The solubilized receptor was found to retain lactotransferrin-binding activity and sensitivity to pH.