Altered biodistribution of indium-111-labeled monoclonal antibody 96.5 to tumors and normal tissues of nude mice bearing human melanoma xenografts in visceral organs

Summary Human melanoma xenografts were produced in the subcutis, kidney, cecum and liver of different nude mice. An¹¹¹In-labeled anti-(human melanoma) monoclonal antibody (96.5) or an¹¹¹In-labeled nonspecific control monoclonal antibody (ZCE-025) was injected intravenously in separate groups of mice. Radioactive antibody accumulation was measured in tumor, blood, viscera, and carcasses. mAb 96.5 targeted specifically to tumor tissue regardless of site of growth. Tumors in the liver exhibited significantly (P <0.05) higher tumor-to-blood ratios (45±6, mean ±SEM) than xenografts at other visceral organs, the lowest value being found for subcutaneous melanoma (2.6±0.5). The differences in tumor-to-blood ratio were due to significant alterations of antibody biodistribution, since the actual antibody concentration in the different tumor sites was similar. The percentage of recovered anti-melanoma antibody per milliliter of blood in mice with visceral lesions (4.6±1.1%/ml) was significantly lower than that found in mice with subcutaneous tumors (9.5±1.4%/ml,P <0.05). Moreover, significantly higher levels (18.2±3.2%/g, 31.0±5.1%/g, respectively) of the melanoma mAb 96.5 were found in normal liver and spleen tissue recovered from mice with visceral tumors as compared to tissue from mice with subcutaneous tumors (9.2±0.9%/g, 13.5±1.9%/g, respectively;P <0.05). These results demonstrate that the presence of visceral tumor can significantly affect tumor-to-blood ratios, blood levels, and biodistribution of¹¹¹In-labeled mAb 96.5.This work was supported in part by funds from the National Institutes of Health, National Cancer Institute, Grant R35-CA42107 and Core Grant CA16672     

Synthesis of single-stranded plasmid pT181 DNA in vitro. Initiation and termination of DNA replication

The origin of replication of plasmid pT181 is nicked by the plasmid-encoded RepC protein. The free 3'-hydroxyl end at the nick is presumably used as primer for leading strand DNA synthesis. In vitro replication of pT181 was found to generate single-stranded DNA in addition to the supercoiled, double-stranded DNA. The single-stranded DNA was circular and corresponded to the pT181 leading strand. Recombinant plasmids were constructed that contain two pT181 origins of replication in either direct or inverted orientation. In vitro replication of the plasmid carrying two origins in direct orientation was shown to generate circular, single-stranded DNA that corresponded to initiation of replication at one origin sequence and termination at the other origin. These results demonstrate that the origin of pT181 leading strand DNA replication also serves as the site for termination of replication. Interestingly, the presence of two origins in inverted orientation resulted in initiation of replication at one origin and stalling of the replisome at the other origin. These results suggest that RepC can reinitiate replication at the second origin by nicking partially replicated, relaxed DNA. These data are consistent with the replication of pT181 by a rolling circle mechanism and indicate that single-stranded DNA is an intermediate in pT181 replication.     

Size-dependent pigmentation-pattern formation in embryos of Alligator mississippiensis: time of initiation of pattern generation mechanism

The pigmentation pattern of Alligator mississippiensis was examined. The number of white stripes on the dorsal side of embryos (stages 21-28) and hatchlings from eggs incubated at 30 degrees C (100% females) and 33 degrees C (100% males) was recorded. Total length, nape-rump length and tail length were recorded for each embryo and hatchling. The number of white stripes was affected by incubation temperature but not sex; hatchlings incubated at 33 degrees C had two more white stripes than those at 30 degrees C, despite being the same length. Five female hatchlings produced at 33 degrees C by manipulation of the temperature, had the same number of stripes as males that developed under the same incubation temperatures. The appearance of the pigmentation was accelerated in embryos incubated at 33 degrees C, occurring eight days earlier than at 30 degrees C. At the time just before the first signs of pigment deposition, embryos from 33 degrees C were longer than those at 30 degrees C. If the stripe formation is size dependent this explains why hatchlings at 33 degrees C have more stripes than hatchlings from 30 degrees C. The mechanism that produces the stripe patterns is unknown. We describe key elements a pattern formation mechanism must possess to produce such stripes and suggest a possible mechanism, based on cell movement driven by chemotaxis. We apply the mathematical model to dorsal patterning on A. mississippiensis. We show how length at pattern formation is the prime factor in determining stripe number and how the pattern can be formed in the observed anterior-posterior sequence. We present numerical simulations and show that the qualitative behaviour is consistent with the experimental results.     

Effect of 6-Phosphogluconate on Phosphoglucose Isomerase in Rat Brain In Vitro and In Vivo

The activity of phosphoglucose isomerase, its kinetic properties, and the effect of 6-phosphogluconate on its activity in the forward (glucose 6-phosphate----fructose 6-phosphate) and the reverse (fructose 6-phosphate----glucose 6-phosphate) reactions were determined in adult rat brain in vitro. The activity of phosphoglucose isomerase (in nmol/min/mg of whole brain protein) was 1,865 +/- 20 in the forward reaction and 1,756 +/- 32 in the reverse reaction at pH 7.5. It was 1,992 +/- 28 and 2,620 +/- 46, respectively, at pH 8.5. The apparent Km and Vmax of phosphoglucose isomerase were 0.593 +/- 0.031 mM and 2,291 +/- 61 nmol/min/mg of protein, respectively, for glucose 6-phosphate and 0.095 +/- 0.013 mM and 2,035 +/- 98 nmol/min/mg of protein, respectively, for fructose 6-phosphate. The activity of phosphoglucose isomerase was inhibited intensely and competitively by 6-phosphogluconate, with an apparent Ki of 0.048 +/- 0.005 mM for glucose 6-phosphate and 0.042 +/- 0.004 mM for fructose 6-phosphate as the substrate. With glucose 6-phosphate as the substrate, at concentrations from 0.05 to 0.5 mM, the activity of the enzyme was inhibited completely in the presence of 0.5-2.0 mM 6-phosphogluconate. With 0.05-0.2 mM fructose 6-phosphate as the substrate, it was inhibited greater than or equal to 85% at the same concentrations of the inhibitor. No significant changes were observed in the values of Km, Vmax, and Ki for phosphoglucose isomerase in the brain of 6-aminonicotinamide-treated rats.(ABSTRACT TRUNCATED AT 250 WORDS)     

Development of solid-phase enzyme-linked immunosorbent assays for the determination of epidermal growth factor receptor and pp60c-src tyrosine protein kinase activity.

Solid-phase ELISAs for the determination of EGF receptor (EGF-R) and pp60c-src tyrosine protein kinase activity are described. The methods were developed and optimized using purified recombinant EGF-R intracellular domain (ICD) and pp60c-src tyrosine protein kinases. A standardized assay that utilizes poly (GluNa-Tyr)4:1 as substrate and a monoclonal antiphosphotyrosine antibody for detection is described. Assay conditions for both enzymes were optimized with respect to substrate and ELISA plate-coating condition, divalent metal ion preferences, enzyme concentration, apparent kinetic constants for ATP, and reaction linearity. Following standardization, a number of reference tyrosine protein kinase inhibitors were tested in the ELISAs and compared to results obtained using solution-phase radioactive tyrosine protein kinase assays, which are based on the transfer of 32P from [gamma-32P]ATP to synthetic substrate. To enable a comprehensive comparison, IC50 values obtained in the ELISA were compared with values obtained in radioactive assays using both the holo-EGF-R and EGF-R ICD kinases. No substantial qualitative differences between these assays were seen. For many routine tyrosine protein kinase assays, semiquantitative or qualitative measurement of TPK activity is adequate. For such purposes, the ELISAs would be an attractive alternative to radioactive assays.     

Dentin phosphoprotein gene locus is not associated with dentinogenesis imperfecta types II and III.

Dentinogenesis imperfecta (DGI) is an autosomal dominant inherited dental disease which affects dentin production and mineralization. Genetic linkage studies have been performed on several multigeneration informative kindreds. These studies determined linkage between DGI type II and III and group-specific component (vitamin D-binding protein). This gene locus has been localized to the long arm of human chromosome 4 in the region 4q11-q21. Although this disease has been mapped to chromosome 4, the defective gene product is yet to be determined. Biochemical studies have suggested abnormal levels of dentin phosphoprotein (DPP) associated with DGI type II. This highly acidic protein is the major noncollagenous component of dentin, being solely expressed by the ectomesenchymal derived odontoblast cells of the tooth. The purpose of the present study was to establish whether DPP is associated with DGI types II and III, by using molecular biology techniques. The strategy was to use a synthetic degenerative DPP oligonucleotide probe to map this sequence to the long arm of human chromosome 4, 4q13-q21, by using somatic cell hybrids. Our results indicated that DPP is not localized to any region of human chromosome 4, thus suggesting that the DPP gene is not directly associated with DGI type II or DGI type III. Our data do not exclude the possibility that other proteins associated with DPP posttranslational modifications might be responsible for this genetic disease.