Monoclonal antibody uptake in B-cell lymphomas: Experimental studies in nude mouse xenografts

Accumulation of radiolabelled monoclonal antibodies (mAb) in human B-lymphoma xenografts was found to result in two distinct patterns. The basic elements leading to these patterns were elucidated by autoradiographic and immunohistological analysis applied to the nude mouse xenografts BJAB and OCI.LY1. With BJAB, accumulation occurred exclusively in peripheral cell layers of the lymphoma nodule, while central areas were not accessible irrespective of mAb dose. This feature was the consequence of an inefficient transport across intratumoral vessels together with peripheral mAb supply through a subcapsular pseudosinus. With OCI.LY1, intratumoral vessels showed generalized leakiness. Furthermore, interstitial transport was operative to a fair extent, such that in early images multiple sites of mAb extravasation were obvious, which coalesced during the course of prolonged uptake. The pattern of peripheral mAb uptake resulted in a low overall tumour uptake, while multifocal uptake yielded substantial accumulation values.     

Morphology of the Bony Labyrinth Supports the Affinities of Paradolichopithecus with the Papionina

International Journal of Primatology - Discoveries in recent decades indicate that the large papionin monkeys Paradolipopithecus and Procynocephalus are key members of the Late Pliocene –...     

Analysis of human V H gene repertoire expression in peripheral CD19+ B cells

Using CD19 B-cell selection and polymerase chain reaction-amplified cDNA libraries, we analyzed the peripheral immunoglobulin heavy chain variable repertoire of three healthy adult donors. Here we report that most of the CD19+ circulating B cells expressed unmutated V _H-D-J_H rearrangements. By specific V _H family hybridization, we show that V _H gene family utilization in the periphery roughly corresponds to the complexity of these families in the germline and appears to be relatively constant among the analyzed subjects. However, sequence data of clones picked at random from one IgM cDNA library reveals that in spite of this random utilization, the V _H gene expression in naive circulating B cells is highly biased towards the expression of a limited set of V _H genes. As previously reported by others, this restricted mechanism is also found for the D and J _H segments.The nucleotide sequence data reported in this paper have been submitted to the GenBank/EMBL nucleotide sequence database and have been assigned the accession numbers Z47213-Z47243 and Z47349     

Speculations on the origin of life and thermophily: Review of available information on reverse gyrase suggests that hyperthermophilic procaryotes are not so primitive

All present-day hyperthermophiles studied so far (eitherBacteria orArchaea) contain a unique DNA topoisomerase, reverse gyrase, which probably helps to stabilize genomic DNA at high temperature. Herein the data relating this enzyme is reviewed and discussed from the perspective of the nature of the last detectable common ancestor and the origin of life. The sequence of the gene encoding reverse gyrase from an archaeon,Sulfolobus acidocaldarius, suggests that this enzyme contains both a helicase and a topoisomerase domains (Confalonieriet al.,Proc. Natl. Acad. Sci., 1993, 90, 4735). Accordingly, it has been proposed that reverse gyrase originated by the fusion of DNA helicase and DNA topoisomerase genes. If reverse gyrase is essential for life at high temperature, its composite structure suggests that DNA helicases and topoisomerases appeared independently and first evolved in a mesophilic world. Such scenario contradicts the hypothesis that a direct link connects present day hyperthermophiles to a hot origin of life. We discuss different patterns for the early cellular evolution in which reverse gyrase appeared either before the emergence of the last common ancestor ofArchaea, Bacteria andEucarya, or in a lineage common to the two procaryotic domains. The latter scenario could explain why all today hyperthermophiles are procaryotes.     

Use of the Reverse Transcription-Polymerase Chain Reaction for the Detection of Pelargonium Flower Break Carmovirus

A polymerase chain reaction (PCR)-based assay was used to detect pelargonium flower break carmovirus (PFBV) in total RNA extractions made from infected Pelargonium plants. Extracts were reverse transcribed (RT) and the resultant cDNA was amplified by PCR, using oligonucleotide primers specific for 343, 510 and 832 base pair fragments of the RNA-dependent RNA polymerase gene of PFBV.
The specificity and sensitivity of RT-PCR were compared with the enzyme-linked immunosorbent assay (ELISA) for the detection of PFBV in Pelargonium tissues. The virus could be detected efficiently in high dilutions of sap from infected plants and at low concentrations of purified virus. Although ELISA is a powerful tool for virus detection, RT-PCR was over 1000 times more sensitive in detecting PFBV in leaf extracts of infected Pelargonium than was ELISA. The limit of detecting PFBV RNA by RT-PCR was 200 fg, compared with 200 pg of virus by ELISA.     

Modification of the erythrocyte membrane by a non-specific lipid transfer protein

The non-specific phospholipid transfer protein purified from bovine liver has been used to modify the phospholipid content and phospholipid composition of the membrane of intact human erythrocytes. Apart from an exchange of phosphatidylcholine between the red cell and PC-containing vesicles, the protein appeared to facilitate net transfer of phosphatidylcholine from the donor vesicles to the erythrocyte and sphingomyelin transfer in the opposite direction. Phosphatidylcholine transfer was accompanied by an equivalent transfer (on a molar basis) of cholesterol. An increase in phosphatidylcholine content in the erythrocyte membrane from 90 to 282 nmol per 100 microliters packed cells was observed. Phospholipase C treatment of modified cells showed that all of the phosphatidylcholine which was transferred to the erythrocyte was incorporated in the lipid bilayer. The nonspecific lipid transfer protein used here appeared to be a suitable tool to modify lipid content and composition of the erythrocyte membrane, and possible applications of this approach are discussed.     

Predominance of bacteriophage SP82 over bacteriophage SP01 in mixed infections of Bacillus subtilis

In mixed infections with Bacillus subtilis phages SP82 and SP01, the SP82 genotype is predominant among the progeny. This predominance is determined by a specific region of the genome, the pos region, which apparently is located near genes 29 to 32 (by the SP01 numbering system). Recombination between SP82 and SP01 yields phage which have both the SP82 pos region and an SP01 mutation. This mutation then behaves in mixed infection as if it were part of an SP82 genome.     

Onset of nucleolus organizer activity in early mouse embryogenesis and evidence for its regulation

Ovulated mouse oocytes and preimplantation embryos were examined for NOR activity by means of selective silver staining. Evidence of the first staining activity appeared in two cell embryos, which was later followed by an increase in nucleolar activity, whereas the ovulated oocytes and pronuclei showed no such activity whatsoever. The staining of chromosomes was restricted to the nucleolus organizing region. Our results agree with earlier observations that genes for ribosomal RNA (rRNA) are transcribed as early as in the 2-cell stage in mouse embryogenesis. In addition to the nuclear staining we also observed some silver staining within the cytoplasm, at least from 4-cell stages onwards. Cytoplasmic staining was resistant to incubation with cycloheximide and actinomycin D. Nuclear staining was depressed, or even totally blocked, after actinomycin D incubation but was not blocked by cycloheximide. The onset of silver staining depends not on a specific embryonic stage but on the time interval following ovulation. This appears to indicate that the initiation of ribosomal cistrons is regulated by molecules which are activated or synthesized within the oocyte soon after ovulation.