Search PubMed⌕ Search

Biomedical subjects

P Russell

Publications and source records attributed to P Russell.

At least 217 records · Page 12Linked to original sources
PubMed1993

Magnetic resonance spectroscopy detects cancer in draining lymph nodes.

The spread of cancer cells to draining lymph nodes is an important prognostic factor for many cancers and influences postoperative therapy in patients. Histopathology is used routinely to assess if lymph nodes contain metastases. There are, however, time and resource constraints on the volume of lymph node tissue that can be examined by the pathologist in a routine laboratory (less than 2% of each node), thus major sampling errors are possible. Conventional histopathology also relies on identifying aggregates of malignant cells for a positive diagnosis. Proton (1H) magnetic resonance (MR) spectroscopy can detect chemical changes, specifically increased levels of lactate, choline, fucose and amino acids, in lymph nodes infiltrated by cancer. Increase in lactate indicates the presence of anaerobically respiring cells, whereas choline reports that the cells are replicating. Since MR spectroscopy can identify early infiltration by malignant cells, before cell clusters are visible under the light microscope, it detects micrometastases in lymph nodes missed histopathologically. Furthermore, MR spectroscopy eliminates sampling errors since the entire lymph node is examined.

Adenocarcinoma↗
PubMed1992

Activation of MPF in fission yeast.

In fission yeast p34cdc2/cyclin is activated at the G2/M boundary by dephosphorylation of Tyr15 of the p34cdc2 subunit. Two protein phosphatases carry out this dephosphorylation event. The major activity is encoded by cdc25, which is a distantly related member of the protein tyrosine phosphatase family. A minor activity is provided by a newly identified fission yeast protein tyrosine phosphatase.

Amino Acid Sequence↗
PubMed1992

Dual functions of CDC6: a yeast protein required for DNA replication also inhibits nuclear division.

The Saccharomyces cerevisiae gene CDC6, whose protein product is required for DNA replication, is transcribed only in late G1 and S phases. We have discovered a critical reason why CDC6 expression is regulated in this fashion. Constitutive CDC6 transcription greatly delayed the initiation of M phase without effecting the G1-S transition or growth rate. This occurred in both fission and budding yeasts. The CDC6-induced M phase delay was dependent on the wee1/mik1 mitotic inhibitor kinases and was greatly accentuated in strains defective for the cdc25/MIH1 mitotic inducer phosphatases, indicating that CDC6 indirectly inhibits activation of the p34cdc2/CDC28 M phase kinase. Thus CDC6 appears to have an important and perhaps unique dual role in S phase, it is first required for the initiation of DNA replication and then actively participates in the suppression of nuclear division.

Base Sequence↗
PubMed1992

Pyp3 PTPase acts as a mitotic inducer in fission yeast.

The p34cdc2 M-phase kinase is regulated by inhibitory phosphorylation of Tyr15, largely through the actions of the p107wee1 tyrosine kinase and p80cdc25 protein tyrosine phosphatase (PTPase). In this study we demonstrate that a second PTPase, encoded by pyp3, also contributes to tyrosyl dephosphorylation of p34cdc2. Pyp3 was identified as a high copy suppressor of a cdc25- mutation. The pyp3 gene encodes a 33 kDa PTPase that is more closely related to human PTP1B and fission yeast pyp1 and pyp2 PTPases than to cdc25. Pyp3 does not share an essential overlapping function with pyp1 or pyp2. We demonstrate that disruption of pyp3 causes a mitotic delay that is greatly exacerbated in cells that are partially defective for cdc25 function and that pyp3 function is essential in cdc25-disruption wee1- strains. Pyp3 PTPase effectively dephosphorylates and activates the p34cdc2 kinase in vitro. We conclude that the pyp3 PTPase acts cooperatively with p80cdc25 to dephosphorylate Tyr15 of p34cdc2.

Alleles↗
PubMed1992

Negative regulation of mitosis by two functionally overlapping PTPases in fission yeast.

We have identified a third protein tyrosine phosphatase (PTPase) gene in fission yeast, pyp2, encoding an 85 kDa protein. Disruption of pyp2 has no impact on cell viability, but pyp2 is essential in strains lacking the 60 kDa pyp1 PTPase. The two pyp PTPases are approximately 42% identical in their C-terminal catalytic domains and share weak homology in their N-terminal regions. Both genes play a role in inhibiting the onset of mitosis. Disruption of either gene rescues the G2 arrest caused by mutation of the cdc25 mitotic inducer, though the effect of pyp1-disruption is more pronounced. Disruption of pyp1 advances mitosis, suppresses overexpression of the tyrosine kinase encoded by the wee1 mitotic inhibitor, and causes lethal mitotic catastrophe in cdc25 overproducer cells. Cells bearing inactive wee1 are unresponsive to disruption of pyp1. Overexpression of pyp1 or pyp2 delays the onset of mitosis by a wee1-dependent mechanism. These data reveal an unexpected second role for protein tyrosine phosphorylation in the mitotic control that acts by promoting the inhibitory wee1 pathway.

Amino Acid Sequence↗
PubMed1992

cdc25 is a nuclear protein expressed constitutively throughout the cell cycle in nontransformed mammalian cells.

A family of proteins homologous to the cdc25 gene product of the fission yeast bear specific protein tyrosine phosphatase activity involved in the activation of the p34cdc2-cyclin B kinase. Using affinity-purified antibodies raised against a synthetic peptide corresponding to the catalytic site of the cdc25 phosphatase, we show that cdc25 protein is constitutively expressed throughout the cell cycle of nontransformed mammalian fibroblasts and does not undergo major changes in protein level. By indirect immunofluorescence, cdc25 protein is found essentially localized in the nucleus throughout interphase and during early prophase. Just before the complete nuclear envelope breakdown at the prophase-prometaphase boundary, cdc25 proteins are redistributed throughout the cytoplasm. During metaphase and anaphase, cdc25 staining remains distributed throughout the cell and excludes the condensed chromosomes. The nuclear locale reappears during telophase. In light of the recent data describing the cytoplasmic localization of cyclin B protein (Pines, J., and T. Hunter. 1991. J. Cell Biol. 115:1-17), the data presented here suggest that separation in two distinct cellular compartments of the cdc25 phosphatase and its substrate p34cdc2-cyclin B may be of importance in the regulation of the cdc2 kinase activity.

Amino Acid Sequence↗
PubMed1992

Chromosome condensation caused by loss of RCC1 function requires the cdc25C protein that is located in the cytoplasm.

We cloned the hamster cdc25C cDNA by using the human cdc25C cDNA as a probe and prepared an antibody to Escherichia coli-produced hamster cdc25C protein that is specific to the human cdc25C protein. The microinjected antibody inhibited a chromosome condensation induced by tsBN2 mutation, indicating that the cdc25C protein is required for an activation of p34cdc2 kinase caused by loss of RCC1 function. The hamster cdc25C protein located in the cytoplasm, prominently in a periphery of the nuclei of cells arrested with hydroxyurea, and seemed to move into the nuclei by loss of RCC1 function. Also, we found a molecular shift of the cdc25C protein in cells showing premature chromosome condensation (PCC), in addition to normal mitotic cells. This molecular-shift appeared depending on an activation of p34cdc2 kinase.

Amino Acid Sequence↗
PubMed1992

Variation in lumbar spine mobility measured over a 24-hour period.

An electronic device for the measurement of three-dimensional movements, the Polhemus Navigation Sciences 3Space Isotrak system, was used to measure the range of movement in the lumbar spine of: (1) 10 young adults pre- and post-normal night-time sleep; (2) 10 young adults tested every 2 h over a 24-h period. The results obtained for the 10 subjects tested pre-/post-sleep showed there to be significant decreases in flexion, extension and lateral bend post-sleep. Axial rotation was not seen to alter significantly. The results obtained for the 10 subjects tested over a 24-h period showed movement during the day to be significantly more than at night. A decrease in the range of all movements except extension was observed when testing subjects in the early hours of the morning (after they had been supine for a minimum of 4 h) relative to the range observed from mid-afternoon to early evening.

Adult↗
PubMed1992

Bilateral fibroepithelial polypi of labium minus with atypical stromal cells.

A case of fibroepithelial polyp of labium minus with stromal atypia is described. This unusual tumor has only recently been reported occurring in the vulva. The tumor measured 12 cm in maximal diameter and its cut surface was soft and myxoid. After fixation the tumor was considerably smaller in size. The light microscopic findings were of a loose acellular myxoid stroma, traversed by thin walled dilated vascular spaces and covered by stratified squamous epithelium and with sparse fibroblast-like cells dispersed throughout. This case is unusual as fibroepithelial polyps with stromal atypia are an uncommon tumor of the vulva, are rarely bilateral and in this site no lesion previously has exceeded 4.0 cm in diameter.

Adult↗
PubMed1992

Protein analysis of monkey aqueous humor.

Aqueous humor from individual eyes of young monkeys (Macaca mulatta) was analyzed by gel exclusion chromatography, and one- and two-dimensional gel electrophoresis. The data indicated that in young normal monkey the main peak of protein eluting from gel exclusion columns was observed around 80,000 daltons. There was a small amount of heavy molecular weight material eluting from these columns with an apparent molecular size of greater than 500,000 daltons, but very little material smaller than 40,000 daltons. By one- and two-dimensional gel electrophoresis, the major polypeptide components in the monkey aqueous were similar to those reported for the human aqueous with polypeptides at around 170, 130, 110, 80, 67, 60, 42, 34, 28, 25, 22, 16, and 14 kilodaltons (kD). The monkey aqueous humor also contains the protease inhibitor cystatin.

Animals↗
PubMed1992

Two-dimensional gel electrophoretic analysis of human lens proteins.

Human lens proteins from clear lenses were separated and identified using two-dimensional polyacrylamide electrophoresis. Isoelectric focusing, both equilibrium and non-equilibrium, was performed in the first dimension and SDS electrophoresis in the second dimension. Proteins were identified by Western blotting and sequencing techniques and by comparison with patterns obtained with purified crystallin fractions. Analyses were performed on total urea soluble proteins of lenses varying in age from fetal to 73 yr. Several hundred protein spots representing crystallins, cytoskeletal proteins and enzymes were resolved in the fetal lens. In the older lenses there was a dramatic increase in the number of protein species in the molecular weight range of the crystallins and a reduced number of discrete protein species visible at molecular weights greater than 50,000. Conversely, a number of proteins below approximately 15 kDa were visible even in the fetal lens. The number and amount of polypeptides in this molecular weight range were increased in the older lenses. Many of these low molecular weight species could be assigned to either the alpha-, beta- or gamma-crystallin fractions. An age dependent increase in the number of acidic species of both crystallins and other proteins, such as, glyceraldehyde 3-phosphate dehydrogenase was observed as well as the loss or mobility change of gamma-crystallin. Two-dimensional gel electrophoresis provides a sensitive and practical technique for characterizing all of the proteins of the human lens.

Adult↗
PubMed1992

Carbonic anhydrase III is expressed in bovine lens.

A highly basic protein isolated from bovine lens has been shown to be carbonic anhydrase III by immunological and peptide sequencing techniques. This is the first demonstration of the presence of this isoenzyme, which is primarily found in skeletal muscle, in the lens or other ocular tissues. The physiological function of this enzyme in the lens is unknown.

Amino Acid Sequence↗
PubMed1992

Evaluation of an in vitro invasion assay for use on solid tissue samples and cultured cells.

An invasion assay, developed for monitoring the in vitro penetration of reconstituted basement membrane, matrigel, was modified and successfully applied to solid tumours, normal tissues as well as a variety of normal and tumour cell lines. However, we found that some normal fibroblasts were capable of in vitro invasion whilst some malignant cell lines with invasive capacity in vivo did not penetrate the matrigel. Nevertheless, this method can distinguish invasive capacity within a tumour model, and as a consequence may be used to elucidate some of the biochemical mechanisms in the invasion process comparing cells grown both in vitro and in vivo. Since the method does not always correlate with invasion in vivo the results must be interpreted with caution.

3T3 Cells↗
PubMed1991

p55CDC25 is a nuclear protein required for the initiation of mitosis in human cells.

The cdc25+ gene of fission yeast encodes a phosphotyrosine phosphatase that dephosphorylates tyrosine-15 of p34cdc2 and thereby activates p34cdc2/cyclin to bring about entry into M phase. We have recently cloned a human homolog, CDC25, which rescues the M-phase initiation defect of yeast cdc25 temperature-sensitive mutants. Antibodies raised against the CDC25 gene product specifically recognize human proteins of approximately 55 and approximately 52 kDa. Microinjection of affinity-purified anti-CDC25 antibodies into HeLa cells inhibits entry into mitosis. These observations suggest that the CDC25 gene products are essential for the initiation of mitosis in human cells, similar to their homologs in fission yeast and Drosophila. CDC25 gene products, like p34CDC2, are localized primarily in the nucleus during interphase, suggesting that activation of p34CDC2/cyclin by p52/p55CDC25 occurs within the nucleus.

Cell Cycle↗