Isoglobotetraosylceramide is a marker for highly metastatic cells in rat mammary adenocarcinomas

We have previously identified a neutral glycolipid antigen which appears to be a surface antigenic marker for the metastatic subpopulation in the R3230AC rat mammary adenocarcinoma (S.A. Carlsen, M. Barry, and K. Newton, Clin. Exp. Metastasis, 8: 141-151, 1990). In this article we describe the structural characterization of this glycolipid antigen. The sequence of the sugars in the saccharide portion of the molecule was determined by specific glycosidase cleavage and further confirmed by mass spectroscopic analysis. The nature of the linkages between the monosaccharide units was determined by methylation analysis. The final structure was confirmed by NMR analysis and found to be isoglobotetraosylceramide (GalNAc beta 1-3Gal alpha 1-3Gal beta 1-4Gle beta 1-O-ceramide). We also present evidence that the cells marked by this antigen have a higher metastatic potential than the cells lacking this glycolipid as measured by the formation of lung colonies after i.v. injection of the cells into the tail vein of the rat. Furthermore, isoglobotetraosylceramide seems to play a direct role in the metastatic process since the blocking of exposed antigen with monoclonal antibodies, or their Fab fragments, results in a highly significant decrease in lung colony formation.

Molecular cloning and adhesive properties of murine platelet/endothelial cell adhesion molecule 1

We describe the isolation and characterization of a functional murine platelet/endothelial cell adhesion molecule (PECAM) 1 cDNA clone from a mouse lung library. At the nucleotide level, the coding sequence of murine PECAM-1 is 73% identical to human PECAM-1, and at the amino acid level, the sequence is 79% homologous to its human counterpart. Southern hybridization reveals that one copy of the gene exists in the mouse genome; Northern hybridization reveals a single mRNA species in mouse lung tissue. COS-7 and mouse L cells transfected with murine PECAM-1 expressed a 130-kDa glycoprotein on their surfaces that reacted with anti-murine PECAM-1 monoclonal antibody and comigrated on SDS/PAGE with human PECAM-1. Stable L-cell transfectants aggregate with each other in a PECAM-dependent, homophilic manner.

Nereistoxin: a naturally occurring toxin with redox effects on neuronal nicotinic acetylcholine receptors in chick retina

Nereistoxin (NTX; 4-N,N-dimethylamino-1,2-dithiolane) is previously reported to block both muscle and neuronal nicotinic acetylcholine receptors, and reversibly inhibit radioligand binding to Torpedo nicotinic receptors. Here, we studied redox effects of NTX on neuronal nicotinic receptors in chick retinas by electrophysiological recordings and by [125I]neuronal bungarotoxin binding. NTX blocked retinal responses to the nicotinic agonist dimethylphenylpiperazinium (300 microM, 2 sec) with an IC50 of 3.5 microM. NTX inhibition was selective for nicotinic receptors, long lasting and not reversible upon washing. The nonselective oxidizing compound dithiobis(nitrobenzoic acid) (1 mM) transiently and repetitively reversed NTX (100 microM) inhibition (85% recovery). After application of the alkylating agent bromoacetylcholine (2 or 100 microM, with 2 microM neostigmine), dithiobis(nitrobenzoic acid) could no longer restore nicotinic function. d-Tubocurarine (300 microM) equally protected against alkylation with bromoacetylcholine (2 microM) after dithiothreitol (2 mM) or NTX treatment. The action of NTX differs from that of dithiothreitol because the agonist dimethylphenylpiperazinium (30 microM) protects against inactivation by dithiothreitol, but not by NTX. NTX reversibly inhibited [125I]neuronal bungarotoxin binding to chick retinal homogenates (IC50 = 16 microM). The present study suggests that nereistoxin or a metabolite is a potent antagonist as well as a selective reducing agent for nicotinic receptors in chick retina. As a dithiolane, this latter action by nereistoxin remains to be explained.

The indirect pathway of hepatic glycogen synthesis and reduction of food intake by metabolic inhibitors

The increasingly recognized role of the indirect pathway (glycolysis followed by hepatic gluconeogenesis) for glucose utilization and glycogen synthesis by the liver led us to administer 3-mercaptopicolinate (3MP), an inhibitor of phosphoenolpyruvate-carboxykinase, in an attempt to assess the role of liver glycogen or hexose-phosphates in the food-intake reducing effects of (-)hydroxy-citrate. Administration of (-)hydroxy-citrate increased hepatic glycogen content in i.v. glucose refed rats. Using the glucuronide probe technique, the mechanism of increased glycogen deposition was shown to be prolongation of indirect pathway (recycled) input. Daily (-)hydroxy-citrate significantly reduced food intake (from 12.0 +/- 2.3 to 6.4 +/- 3.6 g/day, p < 0.05) and had no chronic effect on hepatic glycogen content in rats trained to a single daily meal (meal-fed). Administration of 3MP completely suppressed hepatic glycogen synthesis (< 0.5 mg/g) when given alone or with (-)hydroxy-citrate. Isotopic studies confirmed inhibition of the indirect pathway of UDP-glucose synthesis. 3MP accentuated rather than prevented the (-)hydroxy-citrate reduction in food intake in meal-fed rats (intake 2.7 +/- 2.4 g/day). When given alone, 3MP also reduced intake (6.1 +/- 3.6 g/day). Severe hypoglycemia was observed (glucose < 20 mg/dl) in several meal-fed rats given repeated daily doses of 3MP, yet food intake did not occur despite food availability. Neither 3MP nor (-)hydroxy-citrate had any effects when given after the daily meal. We conclude that the role of the indirect glycogen synthesis pathway must be considered in any theory of regulation of food intake by hepatic metabolites and that, if the effects of these metabolic inhibitors can be shown not to be toxic or non-specific, neither hepatic glycogen nor hexose-phosphates are involved in the food-intake suppressive effects of (-)hydroxycitrate.

Age patterns of marital fertility: revising the Coale-Trussell method

"This article revises the Coale-Trussell method for analyzing data from the World Fertility Survey by proposing and testing alternative log-linear and log-multiplicative models. The models, in one form or another, represent the structural constraint underlying the Coale-Trussell method on the variation in the age pattern of human fertility. With a Poisson distribution assumption for the number of births, several parameters of the models are simultaneously estimated via maximum likelihood. It is shown that the new approach can be adopted whenever fertility limitation is compared across multiple populations or subpopulations."

[Clinical anti-caries effect of dentifrice containing two fluorides]

Anti-caries effect of dentifrice containing sodium monofluorophophate and sodium fluoride was studied among 2-3 years OLD nursery children.After one year,both mean dft and dfs were very significantly lower than those of control groups.

The importance of methionine residues for the catalysis of the biotin enzyme, transcarboxylase. Analysis by site-directed mutagenesis

Almost all biotin enzymes contain the conserved tetrapeptide Ala-Met-Bct-Met (Bct, N epsilon-biotinyl-L-lysine). In the 1.3 S biotinyl subunit of transcarboxylase (TC), this sequence is present between positions 87 and 90. The conserved nature of these amino acids implies a critical role in the function of biotin enzymes. In order to examine the role of these conserved amino acids, point mutations in the gene encoding the 1.3 S subunit have been made by site-directed mutagenesis to generate A87G, M88L, M90L, M88T, M88C, M88A, and a double mutant A87M, M88A in the 1.3 S subunit. TC, a multisubunit enzyme containing 12 S, 5 S, and 1.3 S subunits, catalyzes the transfer of a carboxyl group from methylmalonyl-CoA to pyruvate (overall reaction). TC can be dissociated into individual subunits and also reconstituted by assembling isolated subunits to a fully active form. The mutants of the 1.3 S subunit have been reconstituted with native 5 S and 12 S subunits from Propionibacterium shermanii. The effects of mutations on the activity of TC were compared with that of TC-1.3 S wild type (WT) prepared in a similar manner. The results show that any substitution of a residue in the conserved tetrapeptide causes impairment of the rate of TC activity. Comparison of gel filtration profiles, sodium dodecyl sulfate-polyacrylamide gel electrophoresis and electron micrographs of the TC assembled with mutant 1.3 S and with wild type 1.3 S subunits showed that the impairment of the overall activity was not due to a failure of the subunits to assemble into complexes. Steady state kinetic analysis using the mutant 1.3 S subunits indicated that the Km for methylmalonyl-CoA or pyruvate did not change significantly indicating that the binding of substrates is not altered. However, the kcat values were significantly lower for mutants at positions 87 and 88 than for those at position 90. The replacement of methionine at position 88 either by hydrophobic or hydrophilic residues significantly altered the activity in the overall reaction, while similar substitution at position 90 did not dramatically alter the kcat. These results suggest that Ala-87 and Met-88 are catalytically critical in the conserved tetrapeptide.

[Effects of adrenergic agonist on population spike in CA1 region of hippocampal slices from partial and full kindled rats]

Effects of adrenergic agonist on population spike (PS) amplitude were studied extracellularly at CA1 region of hippocampal slices from partial and full kindled rats with coriaria lactone (1-1.25 mg/kg, two days a time, i.m.) and compared with those from control rats. 5 mumol/L norepinephrine (NE) increased PS; 50 mumol/L NE decreased it slightly. 5 mumol/L isoproterenol (ISO) increased PS. 100 mumol/L phenylephrine (PE) decreased it. The effects of increasing and decreasing PS could be antagonised by beta and alpha adrenergic antagonists, respectively. The effects of NE and PE on PS amplitude showed no significant difference between the control and kindled rats. The effect of beta-adrenergic agonist ISO on PS amplitude in hippocampal slices from partial kindled rats was less than that of control (P < 0.01). The effect of ISO on PS of full kindled rats was partially recovered.

[Effects of calcium channel blocker verapamil on hippocampal kindled seizures induced by coriaria lactone in rabbits]

Eighteen fully kindled rabbits, whose epilepsy had been produced by intrahippocampal (i.h.) injections of 2 microliters of diluted solution containing 0.32 or 0.55 micrograms of coriaria lactone (CL), were separated into three groups. One of them was used as the control group. For seizure, all animals were given CL (0.6-1 micrograms/2 microliter i.h.). Ten minutes later, the verapamil (VR) group of six rabbits was treated with VR (1.5 or 2 mg/kg i.m. 2.5 or 5 micrograms/2 microliters i.h.); the normal saline (NS) group (six rabbits) received 0.8 ml/kg (i.m., in the same volume as that of the VR 2 mg/kg injection) or 2 microliters (i.h.) of NS; the control group of six received neither VR nor NS. The experiments were made once every eight days. Hippocampal EEGs of all animals were recorded by telemetric method and their behavior after injection was observed continuously in 4-7 hours. The results of the experiment indicated that the i.h. administration of 2.5 or 5 micrograms/2 microliters of VR is effective on hippocampal kindled seizures induced by CL in rabbits, but the curative effects of the i.m. administration of 1.5 or 2 mg/kg of VR were less notable than those of the i.h. administration.

[Observation of paired-pulse depression in CA1 region of hippocampal slices from coriaria lactone-kindled rats]

Paired-pulse depression (PPD) technique was used to investigate the potency of recurrent synaptic inhibition mediated by GABA in area CA1 of 54 hippocampal slices from coriaria lactone (CL)-kindled and control rats. When paired stimuli were sent to the axon of CA1 pyramidal cell and Schaffer collaterals, the effect of population spike PPD lasted about 40-60ms; no significant change was observed on PPD potency between kindled and control groups (P = 0.06, 2-way ANOVA). The results indicate that the GABA-ergic synaptic inhibition seemed not to play a key role in the maintenance of the chemical kindling induced by CL.

Effects of oxidizing and reducing analogs of acetylcholine on neuronal nicotinic receptors

The synthesis and pharmacological characterization of dithiobisacetylcholine and dithiobis-N,N-dimethyl-4-acetylpiperazinium (two oxidizing analogs of acetylcholine), as well as those of their reduced counterparts, are described. Both the oxidizing and reducing analogs stimulate nicotinic receptors in the chick retina and block the binding of 125I-labeled neuronal bungarotoxin to retinal homogenates (IC50 values of 2 x 10(-6) to 6 x 10(-5) M). Both oxidizing compounds reverse the physiological effects of reduction by dithiothreitol on nicotinic function in intact chick retina, when applied for 2 sec (EC50 values of about 10(-5) M). This effect is selective, insofar as neither agent alters the effects of dithiothreitol treatment on receptors for N-methyl-D-aspartate. Reoxidation takes place at the disulfide located near the nicotinic receptor agonist binding site, inasmuch as reoxidation by these agents prevents affinity alkylation by bromoacetylcholine, and occupation by the competitive antagonist d-tubocurarine prevents reoxidation. Unlike thiocholine, a weak agonist with a free sulfhydryl that, paradoxically, is reported to oxidize nicotinic receptors in electroplax, the reduced forms, mercaptoacetylcholine and N,N-dimethylamino-4-mercaptoacetylpiperazinium, have no direct redox effects on retinal receptors, but they do protect the receptors against reduction by dithiothreitol.

Endothelin-1 stimulates contraction and ion transport in the rat colon: different mechanisms of action

Endothelin-like immunoreactivity has been detected in all regions of the rat gastrointestinal tract. In the present study, we studied the effect of endothelin-1 (ET-1) on muscle contraction and ion transport in the rat colon. Isometric tension was recorded in colonic muscle strips oriented along their longitudinal axis. The effect of ET-1 on ion transport was investigated by assessing changes in short-circuit current in segments of muscle-stripped rat colon in Ussing chambers. ET-1 induced concentration-dependent contraction of the colon (EC50, 3 nM). The concentration-response curve to ET-1 was not modified by the neuronal blocker tetrodotoxin (0.1 microM) or by atropine (1 microM). Pretreatment of colon muscle strips with the calcium channel blockers diltiazem (0.1 microM) or nicardipine (1 microM) had no effect on the contractile response to ET-1. Furthermore, the response was not affected by removal of extracellular calcium. In the ion transport studies, serosal addition of ET-1 produced a transient, bumetanide (chloride secretion inhibitor) -sensitive, increase in transepithelial short-circuit current. The maximal increase was 107 +/- 13 microA/sq. cm, with an EC50 of 2.5 nM. The increase in short-circuit current evoked by ET-1 was not significantly affected by 1 microM atropine, but was reduced by 50% (P less than .05) by 1 microM tetrodotoxin, or removal of extracellular calcium. We conclude that ET-1 stimulates smooth muscle directly, whereas its effect on epithelial chloride secretion is mediated in part via the enteric nerves. Moreover, the effect of ET-1 in these two systems can be differentiated on the basis of sensitivity to extracellular calcium.

Phosphorylation regulates RNA binding by the human T-cell leukemia virus Rex protein

The Rex protein of human T-cell leukemia virus types I (HTLV-I) and II (HTLV-II) regulates the expression of the viral structural genes and is critical for viral replication. Rex acts by specifically binding to RNAs containing sequences of the R region of the 5' long terminal repeat. Two forms of Rex detected in HTLV-II-infected cells, p26rex and p24rex, differ in the extent of serine phosphorylation. Two-dimensional phosphopeptide analysis indicates that p26rex is extensively phosphorylated at multiple sites. Using a sensitive immunobinding assay, we show that the phosphorylation state of Rex determines the efficiency of binding of Rex to HTLV-II target RNAs. Thus, the phosphorylation state of Rex in the infected cell may be a switch that determines whether virus exists in a latent or productive state. These studies also suggest that phosphorylation of RNA-binding regulatory proteins is a more general mechanism of gene regulation.

[Ultrastructural observation of SC1001-sodium on brain neurons kindled seizures by coriaria lactone in rabbits]

The ultrastructural changes of hippocampus and cerebral cortex neurons were derived from the rabbits kindled by coriaria lactone and from the kindled rabbits after treatment with SC1001 Na. The results of experiment showed that the hippocampus and cerebral cortex neurons in the kindled group had some degenerative changes, such as the swelling mitochondria, dilated rough endoplasmic reticulum and Golgi complexes when the injuries of neurons were not serious, but the seriously injured neurons were subjected to rupture of the cell membrane and solution of most organella, with only a small amount of degenerative organella. In the group treated with SC1001 Na, the ultrastructure of brain neurons demonstrated a tendency of recreation to normal which showed that SC1001 Na had cured many of the degenerative brain cells. This suggested that active treatment is very important for the epileptic patients.

[Correlation among electrocardiogram, important risk factors of coronary artery diseases and coronary lesion in patients with chest pain]

Clinical and angiographic data from 103 patients with chest pain were evaluated to determine their correlation with ST-T abnormality in resting electrocardiogram. Univariate analysis suggested that male sex, hypertension, old myocardial infarction, severe coronary lesion, multiple vessel lesion and left ventricular wall motion abnormality significantly increase the likelihood of ST-T abnormality. Multivariate analysis suggested that male sex, hypertension and left ventricular wall motion abnormality were significant independent predictors of abnormal ST-T. It is essential to improve the electrocardiographic accuracy of diagnosing CAD so as to help clinical doctors in preventing and treating this disease.

Zeeman laser interferometer errors for high-precision measurements

We present a theoretical analysis of the errors of a Zeeman laser interferometer due to the nonorthogonally elliptic polarizations of laser modes. The polarizations make the measured Doppler frequency-shift signal become a modulated and nonharmonic signal and make the phase shift unstable and nonrepeatable when the signal is measured by a phasemeter. If the orthogonality error between two major axes of the laser polarizations is 6 degrees , the relative errors of the phasemeter output will exceed 200% when the measured phase shift is changed from -16.2 degrees to +3.5 degrees . We also introduce a way to eliminate the errors.

Pathophysiology of elevated ascites fluid cholesterol in malignant ascites. Increased ascites to serum relation of proteins and lipoproteins in patients with peritoneal carcinomatosis as compared to patients with cirrhosis of the liver

The existence of marked elevations of ascitic fluid cholesterol has been observed in patients with peritoneal carcinomatosis compared to patients with cirrhosis and has been found useful in differential diagnosis. This finding could be caused by an enhanced movement of plasma lipoproteins into the peritoneal cavity. To test this hypothesis we determined the fasting concentrations of total, high density lipoprotein (HDL)- and low density lipoprotein (LDL)-cholesterol, apolipoprotein-A1 (apo-A1) and apolipoprotein-B (apo-B) in serum and ascites of 17 patients with cirrhosis and 16 patients with peritoneal carcinomatosis. The movement of proteins from plasma to ascites was calculated from the ascites/serum concentration ratios of six different sized proteins with a molecular mass ranging from 54 kDa to 971 kDa. Mean values (mg/dl) for total cholesterol (92.6 vs. 21.0), HDL-cholesterol (15.6 vs. 1.8), LDL-cholesterol (63.4 vs. 16.1), apo-A1 (50.2 vs. 13.6) and apo-B (41.2 vs. 12.9) in ascites were significantly higher in peritoneal carcinomatosis than in cirrhosis. These differences could only partially be explained by the higher serum concentrations of these parameters in peritoneal carcinomatosis, but were mainly due to a lower selectivity for the movement of plasma proteins and lipoproteins into ascites (mean ascites/serum (A/S) ratio: 0.30-0.77) in peritoneal carcinomatosis as compared to cirrhosis (mean ascites/serum ratio: 0.11-0.21). In both groups about 85% of the total cholesterol in serum and ascites consisted of HDL- and LDL-cholesterol. These findings support the hypothesis that elevations in ascitic cholesterol in peritoneal carcinomatosis compared to cirrhosis are mainly caused by the increased movement of plasma HDL and LDL into the peritoneal cavity.

Expression of a partial synthetic human TNF cDNA in E. coli

A recombinant human tumour necrosis factor (rhTNF) cDNA was constructed. The TNF gene was isolated from a human genomic gene library. There are four exons in the TNF gene. The fourth exon codes for 140 amino acids of the TNF matured protein which is composed of 157 amino acids. A major portion of the fourth exon was isolated and then ligated to a synthesized DNA fragment coding for the remaining amino acids. The partial synthetic hTNF (rhTNF) cDNA thus generated was subcloned into a vector and successfully expressed in E. coli. 5-1 fermentator was used to produce rhTNF. About 20 g (wet weight) of bacterial pellet per liter medium and 10(6)-10(7) units of cytotoxicity to L929 cells per milliliter medium were obtained. rhTNF was purified by HPLC and dried with a freeze dryer. rhTNF with a purity of about 95% in the form of white powder was obtained. The sequence of ten amino acids at the amino terminus of the rhTNF was determined. The result showed that it was identical with that of the natural human TNF.

Observations of synaptic efficacy and paired-pulse facilitation in area CA1 of hippocampal slices from coriaria lactone-kindled rats

The changes of population spike(PS)/population excitatory postsynaptic potential (EPSP) slope relationship and paired-pulse facilitation (PPF) were primarily investigated with extracellular recording in stratum pyramidale to stimulation of Schaffer collaterals in CA1 region of hippocampal slices from coriaria lactone (CL)-kindled and control rats. The results were as follows: (1) neither spontaneous nor evoked epileptiform bursts were found in all hippocampal slices from CL-kindled and control rats; (2) the synaptic efficacy, expressed by the ratio of PS/EPSP slope, at low stimulation intensity ranging from 10-30% of its maximum was significantly increased on CL-kindled rats (P less than 0.05); and (3) although PPF was found in all slices, the PPF strength only at stimulation intensity of 10 and 20% of maximum was augmented remarkably in CL-kindled rats (P less than 0.002 and 0.024, respectively). According to the results from our previous work, we suggested that the increment of PS/EPSP slope ratio and PPF strength at low stimulation intensity may result from the potentiation of excitatory synaptic activity or/and the change of intrinsic excitability of pyramidal neurons.

[Ca2+ channels and the abnormal electrical activity of demyelinated nerve]

Peripheral nerve demyelination was produced in adult rats by placing loosely-constrictive ligatures around the common sciatic nerve. The postoperative behavior of these rats indicated that hyperalgesia, allodynia and possible spontaneous pain were produced. In the meantime, abnormal spontaneous afferent activities (ectopic firings)originating from the demyelinated region were recorded. Evidence showed that the application of Ca2+ and Ca2+ channel blockers modulated the abnormal activity of the injured nerve. Ca2+ facilitation was dependent on its concentration (in the range of 10-20 mol/L), while 40mol/L Ca2+ always abolished firing. Verapamil, as well as La3+, applied locally or i. v. (for verapamil) not only strongly inhibited the spontaneous ectopic firings, but also blocked discharges elicited by tetraethylammonium. It is suggested that newly formed Ca2+ channels on the naked axolemma are largely responsible for the abnormal afferent activities following demyelination of the nerve.