Search PubMed⌕ Search

Biomedical subjects

J Pooley

Publications and source records attributed to J Pooley.

At least 19 recordsLinked to original sources
PubMed2001

MHC class II expression is regulated in dendritic cells independently of invariant chain degradation.

We have investigated the mechanisms that control MHC class II (MHC II) expression in immature and activated dendritic cells (DC) grown from spleen and bone marrow precursors. Degradation of the MHC II chaperone invariant chain (Ii), acquisition of peptide cargo by MHC II, and delivery of MHC II-peptide complexes to the cell surface proceeded similarly in both immature and activated DC. However, immature DC reendocytosed and then degraded the MHC II-peptide complexes much faster than the activated DC. MHC II expression in DC is therefore not controlled by the activity of the protease(s) that degrade Ii, but by the rate of endocytosis of peptide-loaded MHC II. Late after activation, DC downregulated MHC II synthesis both in vitro and in vivo.

Animals↗
PubMed2000

The development, maturation, and turnover rate of mouse spleen dendritic cell populations.

Three distinct subtypes of dendritic cells (DC) are present in mouse spleen, separable as CD4(-)8alpha(-), CD4(+)8alpha(-), and CD4(-)8alpha(+) DC. We have tested whether these represent stages of development or activation within one DC lineage, or whether they represent separate DC lineages. All three DC subtypes appear relatively mature by many criteria, but all retain a capacity to phagocytose particulate material in vivo. Although further maturation or activation could be induced by bacterially derived stimuli, phagocytic capacity was retained, and no DC subtype was converted to the other. Continuous elimination of CD4(+)8(-) DC by Ab depletion had no effect on the levels of the other DC subtypes. Bromodeoxyuridine labeling experiments indicated that all three DC subtypes have a rapid turnover (half-life, 1.5-2.9 days) in the spleen, with none being the precursor of another. The three DC subtypes showed different kinetics of development from bone marrow precursors. The CD8alpha(+) spleen DC, apparently the most mature, displayed an extremely rapid turnover based on bromodeoxyuridine uptake and the fastest generation from bone marrow precursors. In conclusion, the three splenic DC subtypes behave as rapidly turning over products of three independent developmental streams.

Adjuvants, Immunologic↗
PubMed2000

CD4 and CD8 expression by dendritic cell subtypes in mouse thymus and spleen.

The dendritic cells (DC) of mouse spleen and thymus were examined for expression of CD4 and CD8. Provided care was taken to avoid selective extraction or selective depletion of DC subpopulations, three main types of DC were detected in mouse spleen: a major new population of CD4+8- DEC-205low CD11bhigh DC, together with the previously described CD4-8- DEC-205low CD11bhigh DC and CD4-8alphaalpha+ DEC-205high CD11blow DC. The CD4 on the surface of the CD4+ splenic DC subpopulation was produced by the DC themselves, and CD4 RNA transcripts were present. Likewise, the CD8alpha on the surface of the splenic CD8+ DC was shown to be a product of the DC themselves, in agreement with earlier evidence. All three spleen DC types would be considered as mature, based on expression of CD80, CD86, and CD40 as well as on T cell stimulating function. Mouse thymuses appeared to contain two DC types; both were DEC-205highCD11blow, but they differed in the level of CD8alphaalpha expression. However, as well as this authenticated marker expression, immunofluorescent staining was also found to reflect a series of artifacts, due to the autofluorescence of contaminating cells and due to pickup of CD4 and CD8alphabeta. By constructing mice chimeric for the hemopoietic lineages using mixtures of wild-type bone marrow with CD4null or CD8alphanull bone marrow, a marked pickup by thymic DC of Ags derived from thymocytes was demonstrated.

Animals↗
PubMed1998

Age related somatic mitochondrial DNA deletions in bone.

BACKGROUND: It has been suggested that the accumulation of damage to mitochondrial DNA is a major cause of age related, degenerative disease. Aging is known to cause bone loss leading to a fall in bone mineral density and disruption of bone microarchitecture. However, despite the evidence of age related bone loss, no attempt has been made to detect specific deletions of mitochondrial DNA in the bone of aged individuals. AIMS: To detect bone specific, age related deletions in mitochondrial DNA. METHOD: Blood leucocytes and bone biopsies from patients who had undergone orthopaedic surgery were used as a source of mitochondrial DNA and screened for deletions using the polymerase chain reaction. RESULTS: Although no deletions were detected in the blood mitochondrial DNA, specific deletions in bone mitochondrial DNA were found in three of five elderly subjects. CONCLUSION: The findings of this study suggest that there could be a link between mitochondrial DNA deletions and free radical induced apoptosis of bone cells in the development of age related bone loss.

Adult↗
PubMed1995

Evolution of mouse hepatitis virus (MHV) during chronic infection: quasispecies nature of the persisting MHV RNA.

Coronavirus infection of mice has been used extensively as a model for the study of acute encephalitis and chronic demyelination. To examine the evolution of coronavirus RNA during chronic demyelinating infection, we isolated RNA from intracerebrally inoculated mice at 4, 6, 8, 13, 20, and 42 days postinfection and used reverse transcription-polymerase chain reaction amplification methods (RT-PCR) to detect viral sequences. RNA sequences from two viral structural genes, the spike gene and the nucleocapsid gene, were detected throughout the chronic infection. In contrast, infectious virus was not detectable from brain homongenates beyond 13 days postinfection. These results indicate that coronavirus RNA persists in the brain at times when infectious virus is not detected. To determine if genetic changes were occurring during viral replication in the host, we cloned and sequenced the RT-PCR products from the spike and nucleocapsid regions and analyzed the sequences for mutations. Sequencing of the cloned products revealed that a variety of mutant forms of viral RNA persisted in the CNS, including point mutants, deletion mutants, and termination mutants. The mutations accumulated during persistent infection in both the spike and the nucleocapsid sequences, with greater than 65% of the mutations encoding amino acid changes. These results show that a diverse population or quasispecies consisting of mutant and deletion variant viral RNAs (which may not be capable of producing infectious virus particles) persists in the central nervous system of mice during chronic demyelinating infection. The implications of these results for the role of persistent viral genetic information in the pathogenesis of chronic demyelination are discussed.

Amino Acid Sequence↗
PubMed1995

Mutations associated with viral sequences isolated from mice persistently infected with MHV-JHM.

Mouse hepatitis virus JHM (JHMV or MHV-4) induces subacute and chronic demyelination in rodents and has been studied as a model human demyelinating diseases, such a multiple sclerosis. However, despite intensive investigation, the state of JHMV during chronic disease is poorly understood. Using reverse transcription-polymerase chain reaction amplification (RT-PCR) to "rescue" viral RNA, we have found that JHMV-specific sequences persist for at least 787 days after intracerebral inoculation of experimental mice. Analysis of persisting viral RNA reveals that it is extensively mutated, and we hypothesize that the mutations observed reflect adaptation of the viral quasispecies to low-level intracellular replication during chronic disease.

Animals↗
PubMed1994

Characterization of a subtype of primary osteoclastoma: extracellular calcium but not calcitonin inhibits aggressive HLA-DR-positive osteoclastoma possessing 'functional' calcitonin receptors.

We report here a case of primary osteoclastoma that despite possessing HLA-DR-positive status and 'functional' calcitonin receptors, exhibited aggressive in vitro and in vivo bone resorptive activity. In the osteoclast bone slice assay employing scanning electron microscopy, the giant cell-mediated bone resorption was uninhibited by salmon calcitonin (10 nM) and significantly inhibited by raised extracellular calcium (20 mM). In Fura-2AM based microspectrofluorimetric assays, the presence of the 'functional' calcitonin receptors was ascertained by a rise in intracellular calcium induced by calcitonin and high extracellular calcium. These findings provide evidence for a hitherto unrecognized subtype of giant cells that have HLA-DR-positive status, exhibit avid bone resorptive activity, but remain insensitive to calcitonin despite possessing calcitonin receptors.

Adult↗
PubMed1994

Pseudoaneurysm of the superficial femoral artery. An unusual complication following rotationplasty.

A 21 year old man presented with pain and swelling around the right knee. Staging studies and open biopsy provided a diagnosis of malignant fibrous histiocytoma, stage II B. A wide local excision followed by prosthetic reconstruction was not possible because of extensive involvement of the quadriceps muscle with tumor. Therefore the patient underwent wide local excision of the tumor and rotationplasty, providing functionally a transtibial amputation. Postoperatively (Day 44) a critical ischaemia of the foot developed, and angiography revealed a pseudoaneurysm of the superficial femoral artery at the level of the tibial condyle. The patient underwent successful arterial reconstruction and the bones united. The etiology of this pseudoaneurysm appears to be related to the presence of the coiled superficial femoral artery abutting the medial tibial condyle flare. This complication may be prevented by ensuring that the condylar flare be contoured, and then an adequate cushion of soft tissue be interposed between artery and bone at this level.

Adult↗
PubMed1991

The venous anatomy of the scaphoid.

The intraosseous injection of coloured latex allows the venous drainage of a particular area of a bone to be studied. The extraosseous anatomy is visualised by chemical digestion of the soft tissues, the intraosseous anatomy by clearing the bone using the Spalteholz technique. When applied to the proximal pole of the scaphoid, this showed the venous drainage to be via the dorsal ridge into the venae comitantes of the radial artery.

Carpal Bones↗
PubMed1990

The effect of anaesthesia on the bone blood flow of the rabbit.

The effect of anaesthesia on the rate of bone blood flow in the rabbit was studied. Two estimates of bone blood flow were performed, using 15 microns radioactively labelled microspheres, in three groups of rabbits. The first group was anaesthetised and the interval between the two estimates was 5 min. The second group was also anaesthetised but the interval between estimates was 60 min. The third group of rabbits was conscious and the interval between the two estimates was 4 h. In the first group, small uniform falls in whole bone blood flow were observed (mean change = -5%). In the second group, larger and less predictable reductions were observed (mean change = -24%). In the third group (conscious), little change was observed in whole bone blood flow during the 4-h experiment (mean change = +7%). It is concluded that substantial falls can occur in bone blood flow in the rabbit during a 1-h anaesthetic. If bone blood flow is to be monitored under anaesthesia, then the effect of the anaesthetic on bone blood flow must be accurately defined. In conscious rabbits, estimates of whole bone blood flow performed at an interval of 4 h under control conditions will give reproducible results.

Anesthesia↗
PubMed1990

Effect of exposure to compressed air and elevated oxygen levels on bone blood flow in the rabbit.

As the pathogenesis of dysbaric osteonecrosis is not fully understood, we investigated the effects of compressed air, decompression, and elevated oxygen levels on bone blood flow. Bone blood flow was measured in 4 groups of rabbits using the radioactive-labeled microsphere technique. In the Control and Oxygen groups it was measured at normal pressure (1 ATA) at the end of 4-h exposures to air and 100% oxygen, respectively. In the Pressure group it was measured "at pressure" at the end of a 4-h exposure to compressed air (3 ATA) and in the Decompression group it was measured after decompression following a 3.5-h exposure to compressed air (3 ATA). Femoral head blood flow was significantly lower (P = 0.027) in both the Pressure (7.5 ml.100 g-1.min-1) and Decompression (7.1 ml.100 g-1.min-1) groups than in the Control group (13.0 ml.100 g-1.min-1). Moreover, the distribution of blood flow between the cortex and marrow of the humerus differed significantly (P = 0.044) between the Control and Pressure groups. No differences were found between the bone blood flow rates of the Control and Oxygen groups. It is concluded that femoral head blood flow is reduced by prolonged exposure to compressed air (without decompression) and that this is not solely an effect of the high partial pressure of oxygen.

Animals↗