Inhibition of rat yolk sac tumour growth in vivo by a monoclonal antibody to the retroviral molecule P15E

Summary A monoclonal mouse IgG2b antibody 19F8, directed towards a determinant on the retroviral transmembranous molecule p15E, binds selectively to certain rat tumours, including all tested yolk sac tumours, one rat colon carcinoma, one spontaneous kidney carcinoma and an adenovirus-type-9-induced rat breast tumour, as tested by antibody-dependent cellular cytotoxicity (ADCC) and immunohistochemistry. Groups of rats receiving yolk sac tumour F56 isografts intraperitoneally (i.p.) or subperitoneally (s.p.) were treated with this monoclonal antibody (mAb), 19F8, inoculated twice a week in doses of 100 µg. Parallel control groups received analogous inoculations of an isotype-matched monoclonal antibody. A significant growth inhibitory effect was observed with 19F8. In 5/10 rats isografted i.p., tumour outgrowth was completely inhibited and in the other 5 rats the outgrowth was delayed compared to the 10 rats in the control group, which all developed tumours. All rats of the control group developed large volumes of ascites, whereas the 5 rats in the therapy group with eventual tumour outgrowth had little or no ascites. In two experiments with rats carrying subperitoneal isografts and treated with the 19F8 mAb, tumour grew out in 4/5 and 5/10 rats, though growth was delayed compared to the control groups, in which 5/5 and 9/9 rats developed tumours. The tumours grew significantly more slowly in the therapy groups compared to the controls. All rats that developed tumours in the therapy groups showed an anti-idiotypic response against mAb 19F8. The single tumour-free rat in the first experiment and 1/5 tumour-free rats in the other showed no such response. The draining lymph node cells from the tumour-free animals showed a specific proliferative response to yolk sac tumour F56 cells in a mixed lymphocyte tumour cell culture (MLTC), and the MLTC-induced cells were cytotoxic to F56 but not to the natural-killer-sensitive rat T cell lymphoma G1—Tc1. The cytotoxic cell population was more than 90% CD4⁺. It is concluded that the two test systems for identification of the epitope of p15E detected by mAb 19F8 correlated well in detection of the epitope in the cells (immunohistochemistry) and at the cell surface (ADCC). It is also concluded that mAb 19F8 has a growth-inhibitory effect on yolk sac tumour F56 and that, as a result of the treatment, T cells with specificity for F56 are appearing in draining lymph nodes of tumour-free animals.     

The malmö polymorphism of coagulation factor IX, an immunologic polymorphism due to dimorphism of residue 148 that is in linkage disequilibrium with two other F.IX polymorphisms

A mouse monoclonal antibody (MAB 9.9) to coagulation factor IX (F.IX) detects a polymorphism in the plasma of normal people. Its epitope has been narrowed down to <6 amino acids in the activation peptide of the X-linked F.IX protein. The activation peptide contains a dimorphism—Thr:Ala—at position 148 of the protein. Using synthetic oligonucleotides, we have demonstrated that (1) the F.IX which reacts with 9.9 has Thr at position 148 and (2) that which does not has Ala. Positive reactors (148^thr) are designated Malmö A, and negative reactors (148^ala) are designated Malmö B. The plasma levels of AA women are indistinguishable from those of A men, and both B men and BB women are null against MAB 9.9. The plasma level of Malmö A in AB women is approximately half that of AA women, and “lyonization” is clearly operating in the heterozygotes. The dimorphism is in strong linkage disequilibrium with two other intragenic RFLPs, TaqI and XmnI. Furthermore, intragenic crossing-over—including double crossing-over—appears to have occurred between the three sites. Seven of the eight possible haplotypes have been identified, five in men and two others in women. The immunoassay that identifies ～50% of the AB women in the pool of Malmö A females with 95% confidence identifies men unambiguously as A or B. The assay would be very useful for population-genetic studies of the Malmö epitope if the studies were limited to men.     

Human cellular retinol-binding protein gene organization and chromosomal location

The gene encoding the human cellular retinol-binding protein (CRBP) has been isolated from genomic libraries and its structure determined. Only one copy of the gene is present in the human genome. We have located the CRBP gene to segment 3p11-3qter on human chromosome 3 using hybridizations to mouse-human, rat-human and hamster-human cell hybrids. The gene harbors four exons encoding 24, 59, 33, and 16 amino acid residues respectively. The second intervening sequence alone occupies 19 kb of the 21 kb of the CRBP gene. The nucleotide sequence of the gene has been determined with the exception of the second intron. The positions of the introns agree with those in the rat CRBPII, the rat liver fatty-acid-binding protein and the mouse adipose P2 protein genes encoding molecules belonging to the same protein family as CRBP. In contrast to the other sequenced members of this family the promoter of the CRBP gene resembles those found in the 'housekeeping' genes in that it is (G + C)-rich, contains multiple copies of the CCGCCC sequence and lacks TATA box. A 9-bp homology containing the core sequence of the simian virus 40 enhancer repeat was found in the 5' upstream region. A genomic Southern blot probed with CRBP cDNA revealed hybridizing bands in restricted chicken and frog DNA.     

Microbially Mediated Mn(II) Oxidation in an Oligotrophic Arctic Lake

Rates of oxidation of Mn(II) were measured by an in situ incubation technique in the water column of Toolik Lake, Alaska. Measured rates were lower than those observed in other aquatic systems but were sufficient to oxidize all Mn(II) in the lake within a 3-month period. Measured rates compared favorably with rates estimated from a previous study of the geochemical cycling of Mn in Toolik Lake. The Mn(II) oxidation was largely microbially mediated, as indicated by inhibition of oxidation rates by sodium azide. Azide had been previously demonstrated to be a suitable microbial poison for studying Mn(II) oxidation in seawater. This study demonstrates that azide is also a suitable poison for freshwaters and that it inhibits microbial but not abiotic oxidation of Mn(II). Manganese(II) oxidation rates were similar during cold, under-ice conditions in early spring and during warmer summer conditions. This observation suggests that Mn(II) concentration, rather than temperature or oxygen concentration, is the most important factor regulating Mn(II) oxidation rates in Toolik Lake.     

Dual effect of glucose on cytoplasmic free Ca2+ concentration and insulin release reflects the beta-cell being deprived of fuel

Influence of basal glucose concentration on the response evoked by subsequent stimulation with the sugar, was evaluated by investigating changes in free cytoplasmic Ca2+ concentration, [Ca2+]i, and insulin release, using beta-cells isolated from obese hyperglycemic mice. When increasing the glucose concentration from 0 to either 11 or 20 mM, there was a transient decrease in both [Ca2+]i and insulin release. The decrease was followed by a pronounced increase in both of the parameters. When increasing the basal glucose concentration, the initial decrease gradually disappeared, being abolished already at 5 mM of the sugar and the subsequent increase appeared more rapidly. It is suggested that the observed decrease in [Ca2+]i and thereby insulin release reflects a phenomenon associated with fuel deprived beta-cells.     

Rapid stimulation of liver palmitoyl-CoA synthetase, carnitine palmitoyltransferase and glycerophosphate acyltransferase compared to peroxisomal beta-oxidation and palmitoyl-CoA hydrolase in rats fed high-fat diets

Key enzymes involved in oxidation and esterification of long-chain fatty acids were investigated in male rats fed different types and amounts of oil in their diet. A diet with 20% (w/w) fish oil, partially hydrogenated fish oil (PHFO) and partially hydrogenated soybean oil (PHSO) was shown to stimulate the mitochondrial and microsomal palmitoyl-CoA synthetase activity (EC 6.2.1.3) compared to soybean oil-fed animals after 1 week of feeding. Rapeseed oil had no effect. Partially hydrogenated oils in the diet resulted in significantly higher levels of mitochondrial glycerophosphate acyltransferase compared to unhydrogenated oils in the diet. Rats fed 20% (w/w) rapeseed oil had a decreased activity of this mitochondrial enzyme, whereas the microsomal glycerophosphate acyltransferase activity was stimulated to a comparable extent with 20% (w/w) rapeseed oil, fish oil or PHFO in the diet. Increasing the amount of PHFO (from 5 to 25% (w/w)) in the diet for 3 days led to increased mitochondrial and microsomal palmitoyl-CoA synthetase and microsomal glycerophosphate acyltransferase activities with 5% of this oil in the diet. The mitochondrial glycerophosphate acyltransferase was only marginally affected by increasing the oil dose. Administration of 20% (w/w) PHFO increased rapidly the mitochondrial and microsomal palmitoyl-CoA synthetase, carnitine palmitoyltransferase and microsomal glycerophosphate acyltransferase activities almost to their maximum value within 36 h. In contrast, the glycerophosphate acyltransferase and palmitoyl-CoA hydrolase (EC 3.1.2.2) activities of the mitochondrial fraction and the peroxisomal beta-oxidation reached their maximum activities after administration of the dietary oil for 6.5 days. This sequence of enzyme changes (a) is in accordance with the proposal that an increased cellular level of long-chain acyl-CoA species act as metabolic messages for induction of peroxisomal beta-oxidation and palmitoyl-CoA hydrolase, i.e., these enzymes are regulated by a substrate-induced mechanism, and (b) indicates that, with PHFO, a greater part of the activated fatty acids are directed from triacylglycerol esterification and hydrolysis towards oxidation in the mitochondria. It is also conceivable that the mitochondrial beta-oxidation is proceeding before the enhancement of peroxisomal beta-oxidation.     

Accumulation of cadmium in pancreatic beta cells is similar to that of calcium in being stimulated by both glucose and high potassium

The transport of Cd2+ and the effects of this ion on secretory activity and metabolism were investigated in beta cell-rich pancreatic islets isolated from obese-hyperglycemic mice. The endogenous cadmium content was 2.5 mumol/kg dry wt. After 60 min of incubation in a Ca2+-deficient medium containing 2.5 microM Cd2+ the islet cadmium content increased to 0.18 mmol/kg dry wt. This uptake was reduced by approx. 50% in the presence of 1.28 mM Ca2+. The incorporation of Cd2+ was stimulated either by raising the concentration of glucose to 20 mM or K+ to 30.9 mM. Whereas D-600 suppressed the stimulatory effect of glucose by 75%, it completely abolished that obtained with high K+. Only about 40% of the incorporated cadmium was mobilized during 60 min of incubation in a Cd2+-free medium containing 0.5 mM EGTA. It was possible to demonstrate a glucose-induced suppression of Cd2+ efflux into a Ca2+-deficient medium. Concentrations of Cd2+ up to 2.5 microM did not affect glucose oxidation, whereas, there was a progressive inhibition when the Cd2+ concentration was above 10 microM. Basal insulin release was stimulated by 5 microM Cd2+. At a concentration of 160 microM, Cd2+ did not affect basal insulin release but significantly inhibited the secretory response to glucose. It is concluded that the beta cell uptake of Cd2+ is facilitated by the activation of voltage-dependent Ca2+ channels. Apparently, the accumulation of Cd2+ mimics that of Ca2+ also involving a component of intracellular sequestration promoted by glucose.     

Binding specificity of monoclonal antibodies to ganglioside, Fuc-GM1

The binding specificity of thirteen mouse monoclonal antibodies reacting with Fuc-GM1, Fuc alpha 1-2Gal beta 1-3GalNAc beta 1-4(NeuAc alpha 2-3)-Gal beta 1-4Glc beta 1-1Cer, a ganglioside found to be associated with small cell lung carcinoma (O. Nilsson et al. (1984) Glycoconjugate J. 1, 43-49) was studied. The results are based upon radioimmunodetection of their binding to structurally related glycolipids adsorbed to microtiter plates or chromatographed on thin-layer plates. Four of thirteen antibodies reacted only with Fuc-GM1 and both the fucose and the sialic residues were necessary for binding. Optimal binding was obtained when the sialic acid was N-acetylneuraminic acid. When this sialic acid residue was substituted with N-glycoloylneuraminic acid the binding activity was reduced and up to 10-times more Fuc-GM1 was needed for detection. The ceramide composition did not influence the binding. The other nine monoclonal antibodies cross-reacted with glycolipids containing structures closely related to Fuc-GM1 and differed from the specific ones by recognizing a smaller portion of the carbohydrate moiety in Fuc-GM1. These results indicate that anticarbohydrate monoclonal antibodies, recognizing structures involving a large proportion of the sugar in the glycolipid, possess a high specificity and might be useful for detection of tumor-associated ganglioside antigen.     

Stimulation of insulin release by the phorbol ester 12-O-tetradecanoylphorbol 13-acetate in the clonal cell line RINm5F despite a lowering of the free cytoplasmic Ca2+ concentration

The effects of 12-O-tetradecanoylphorbol 13-acetate (TPA) on the handling of Ca2+ and insulin release were investigated in the clonal insulin-producing cell line RINm5F. The presence of the phorbol ester lowered the free cytoplasmic Ca2+ and suppressed the increase obtained by depolarization with high concentrations of K+. Despite the lowering in cytoplasmic Ca2+ by TPA, there was a concomitant stimulation of insulin release indicating that one feature of protein kinase C activation is to make the secretory system more sensitive to Ca2+. Furthermore, there was no interaction of TPA with the mechanisms responsible for inositol 1,4,5-tris(phosphate) induced Ca2+ release or Ca2+ uptake in permeabilized cells. Although TPA slightly depolarized the RINm5F cells there was no interference with K+-induced depolarization. It is suggested that an additional effect of protein kinase C activation in these cells, is to stimulate the extrusion of Ca2+ over the plasma membrane.