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Biomedical subjects

R J Johnson

Publications and source records attributed to R J Johnson.

At least 109 records · Page 6Linked to original sources
PubMed1998

TGF-beta in glomerular disease.

Transforming growth factor-beta (TGF-beta) is an important cytokine in glomerular disease. Its major role may be to mediate extracellular matrix deposition, by both increasing the synthesis of matrix components and by reducing their degradation. Strong evidence supports the functional role for TGF-beta in mesangial matrix expansion. However, TGF-beta may also have other important functions in the glomerulus, including the regulation of cell proliferation, hypertrophy, and survival (apoptosis), as well as modulation of the local and systemic immune response.

Animals↗
PubMed1998

Predictive value of clinical examination, transrectal ultrasound and magnetic resonance imaging prior to radiotherapy in carcinoma of the cervix.

The objectives of this study were to compare tumour staging and volume assessment by examination under anaesthesia (EUA), transrectal ultrasound (TRU) and magnetic resonance imaging (MRI) in patients with invasive carcinoma of the cervix, and to correlate findings with long-term outcome following treatment by radiotherapy. Tumour staging was performed on 60 patients immediately before starting radiotherapy. Clinicians and radiologists performing EUA, TRU or MRI were blinded to the results of other investigations. Tumour stage and dimensions were recorded prospectively for each technique, and analysed for concordance. The relationship between pre-treatment stage, size of tumour and patient outcome after radiotherapy was assessed, using clinical status 5 years after treatment as the truth measure. EUA, TRU and MRI assigned the same tumour stage in only 30% of patients and EUA and MRI agreed tumour stage in a further 27%. In cases of disagreement, the MRI stage correlated better with outcome than the TRU or EUA stage. There was a significant difference between tumour volume obtained from measurements made on MRI and those from TRU. 62% of patients with enlarged lymph nodes on pre-treatment MRI either died, or developed tumour recurrence or metastases. The ability of MRI to assess the full extent of bulky tumours and the presence of lymph node enlargement was an advantage over both EUA and TRU in identifying patients with a poor prognosis.

Female↗
PubMed1998

Tubulointerstitial disease in aging: evidence for underlying peritubular capillary damage, a potential role for renal ischemia.

Aging is associated with a progressive decline in renal function and the development of glomerulosclerosis and interstitial fibrosis. Although many studies have addressed the cellular mechanisms of age-related glomerulosclerosis, less is known about the tubulointerstitial fibrosis. In this study, aging (24 mo) rats develop tubulointerstitial fibrosis characterized by tubular injury and focal tubular cell proliferation, myofibroblast activation, macrophage infiltration with increased immunostaining for the adhesive proteins osteopontin and intercellular adhesion molecule-1, and collagen IV deposition. Aging rats demonstrated immunostaining for endothelial nitric oxide synthase (eNOSIII) in renal tubular epithelial cells and infiltrating mononuclear cells in areas of tubulointerstitial injury, with a relative loss of staining of the peritubular capillaries compared with young rats. The aging rats also displayed focal loss of peritubular capillaries (as noted by focally decreased RECA-1 and OX-2 staining) in areas of tubulointerstitial injury. The areas of fibrosis and hypocellularity were associated with increased apoptosis of tubular and interstitial cells compared with young (3 mo) rats (25.4 +/- 5.3 versus 3.5 +/- 2.5 TUNEL-positive cells/0.25 mm2 in old versus young rats, P = 0.0001). It is concluded that tubulointerstitial fibrosis in aging is an active process associated with interstitial inflammation and fibroblast activation. The progressive loss of cells in areas of fibrosis may be due to accelerated apoptosis. Furthermore, the tubulointerstitial injury may be the consequence of ischemia secondary to peritubular capillary injury and altered eNOS expression.

Actins↗
PubMed1998

CD59 protects glomerular endothelial cells from immune-mediated thrombotic microangiopathy in rats.

CD59 is a cell membrane-bound complement regulatory protein on glomerular cells that inhibits C5b-9 assembly and insertion. This report describes a recently developed model of immune thrombotic microangiopathy (TMA) induced by the renal artery perfusion of anti-glomerular endothelial cell (anti-GEN) antibody. To examine the role of CD59 in protecting the GEN from immune-mediated injury, rats underwent selective renal artery perfusion with F(ab')2 fragments of anti-CD59 monoclonal antibody to block CD59 activity or control mouse IgG followed by anti-GEN antibody or control goat IgG. Neutralization of CD59 in normal rats did not result in any significant functional or histologic changes. Perfusion with anti-CD59 did not change deposition of the pathogenic anti-GEN IgG used to induce the TMA model. However, neutralization of CD59 in the TMA model resulted in more C5b-9 formation in glomeruli, accompanied by increased platelet and fibrin deposition, more severe endothelial injury, and reduced renal function compared with the animals perfused with control F(ab')2 fragments. These results demonstrate directly that CD59 serves a protective role for GEN in this TMA model of rats, and confirm that C5b-9 formation has a critical pathogenic role in the mediation of the disease. CD59 may play an important role in protecting glomerular endothelium from other complement-mediated types of injury.

Animals↗
PubMed1998

Endogenous fibroblast growth factor-2 mediates cytotoxicity in experimental mesangioproliferative glomerulonephritis.

Fibroblast growth factor-2 (FGF-2) is released from mesangial cells in experimental mesangioproliferative glomerulonephritis induced with anti-Thy 1.1 antibody. To investigate the functional role of released FGF-2, rats received either neutralizing anti-FGF-2 IgG or a functional peptide antagonist of FGF-2 (FGF119-126) before or shortly after induction of anti-Thy 1.1 nephritis. In additional experiments, rats were treated with bolus injections of FGF-2 from 2 to 6 h after disease induction. The data showed that anti-FGF-2 therapy led to significant reductions of early mesangial cell injury (mesangiolysis, microaneurysm formation) and the subsequent mesangioproliferative changes (glomerular de novo expression of alpha-smooth muscle actin, mesangial cell proliferation, matrix accumulation, and platelet influx). Conversely, injections of FGF-2 augmented both mesangial injury and the subsequent mesangioproliferative changes. Studies on the mechanisms underlying the amplification of mesangial cell injury by FGF-2 showed that anti-FGF-2 therapy reduced cell death at 2 and 8 h after disease induction by 58 and 54%, respectively. This was associated with significant reductions in the number of glomerular H2O2- and OH -producing cells, as well as reduced glomerular production of nitric oxide. These data suggest that release of constitutively expressed FGF-2 after immune-mediated cell injury contributes to glomerular cell damage and thus identify FGF-2 as a novel mediator of cytotoxicity.

Animals↗
PubMed1998

The potential for Ontario region's health information system to facilitate case management, program planning, and evaluation and to promote enhanced First Nations' control of health services.

The Ontario Region of Medical Services Branch, Health Canada, comprises approximately 63,000 First Nations people living on-reserve in four geographical areas: Sioux Lookout, Moose Factory, Thunder Bay, and Southern Ontario. As of April 1996, 35% of the 126 First Nations communities in Ontario Region have either assumed control of the delivery of health services or are in the process of transfer negotiations with the federal government. Another 14% have entered into Integrated Community-based Health Services Agreements with the federal government, which is an intermediate step that could culminate in a complete transfer agreement. In order to provide First Nations with an epidemiological database for effective program planning and evaluation, Medical Services Branch, Ontario Region, has worked in partnership with First Nations during the past two and one-half years to develop a comprehensive, computerized Health Information System (HIS). HIS will provide First Nations with a significant degree of autonomy from the Medical Services Branch structure, with regard to access to health information for case management, program planning and evaluation, and the establishment of their own program priorities at the community level. With access to the HIS, First Nations will eventually be able to re-profile available resource in response to their own identified community health priorities.

Case Management↗
PubMed1998

A new national allocation scheme for adult kidneys in the United Kingdom. United Kingdom Transplant Support Service Authority (UKTSSA) Users' Kidney Advisory Group and its Task Forces.

A new allocation scheme for kidneys from adult cadaver donors was introduced in the UK on July 1st, 1998. The new scheme is based on data from an analysis of factors influencing transplant survival instigated by the Kidney Advisory Group (KAG) of the UKTSSA. A cohort of 6,363 first cadaver allografts performed in the UK between 1986-1993 was used for the analysis with 99.6% one-year follow-up and 97.8% 5-year follow-up. HLA matching was one of a number of factors that were found to influence transplant survival, thus supporting the policy of exchange of kidneys based on matching. The new allocation scheme is based on 3 tiers in which cadaver organs are offered first in Tier 1 to patients with zero HLA antigen mismatches (000 matchgrade), in Tier 2 to favorably matched patients, (matched for HLA-DR and mismatched for a maximum of one HLA-A and one-B locus antigen -100, 010, 110 matchgrades) and remaining kidneys in Tier 3 to non-favorably matched patients. A points score devised by a subgroup of the KAG to reflect natural justice and common sense is used as a discriminator between equally matched patients. The points are based on recipient age, donor-recipient age difference, waiting time, matchability for HLA antigens, sensitization to HLA antigens and the transplant unit balance of organ exchange. The performance of the scheme will be closely monitored, but computer simulations predict that there will be an overall improvement in transplant survival as a result of an increase in well matched transplants.

Adolescent↗
PubMed1998

Evidence for a role of osteopontin in macrophage infiltration in response to pathological stimuli in vivo.

Previous studies have suggested that osteopontin, an arginine-glycine-aspartate-containing secreted protein, might be important in macrophage accumulation during interstitial nephritis and wound healing. The current study investigated the role of osteopontin in intradermal macrophage infiltration using immunohistochemistry and neutralizing antibodies. Purified osteopontin induced macrophage accumulation after injection in rat dermis and facilitated adhesion and migration of cultured macrophage-like cells in vitro. Intradermal injection of N-formyl-met-leu-phe (FMLP), a potent macrophage chemotactic peptide, induced a macrophage-rich infiltrate at the site of injection. Most of these macrophages expressed high levels of osteopontin as shown by immunochemical analysis. To determine whether osteopontin expressed by macrophages was required for their infiltration, we treated rats with either anti-osteopontin neutralizing antibody (OP199) or nonimmune antibody. We found that FMLP-induced macrophage accumulation was largely inhibited (>60%) by anti-osteopontin antibody treatment compared with rats receiving nonimmune antibody. These data support the hypothesis that osteopontin may be a critical mediator of inflammation in specific disease and injury states, potentially by promoting macrophage adhesion and migration.

Animals↗
PubMed1998

Skiing injuries in children, adolescents, and adults.

We prospectively gathered data on skiing injuries that had been sustained at the Sugarbush North ski area since 1972 and at the Sugarbush South ski area since 1981. The purpose of the current study was to document the overall rates of injury in children, adolescents, and adults participating in alpine skiing. We also sought to determine the ten most common injuries in each age-group. Finally, we analyzed short-term and long-term trends to determine if changes in equipment had had an effect on the frequency or pattern of injury. From the 1981-1982 to the 1993-1994 season, there were 2.79 injuries per 1000 skier days: 4.27 injuries in children, 2.93 in adolescents, and 2.69 in adults. During the last eight years of the study, the most common injuries were a contusion of the knee in children, a sprain of the ulnar collateral ligament of the thumb in adolescents, and a grade-III sprain of the anterior cruciate ligament in adults. The short-term trends revealed that, in children, the frequency of tibial fractures decreased 10 per cent while that of fractures of the upper extremity increased 8 per cent. The long-term trends showed that, in adults, the rate of tibial fractures decreased 89 per cent while that of injuries of the anterior cruciate ligament increased 280 per cent. The overall rate of injury decreased 43 per cent from the beginning of the study in 1972 to the end of the study in 1994; the decrease was 58 per cent in children, 45 per cent in adolescents, and 42 per cent in adults. Data on the types of equipment and the binding-release values were collected prospectively from injured skiers and from 2083 non-injured skiers. Of the fifty-nine skiers who sustained a spiral fracture of the tibia, forty-two (71 per cent) had binding-release values that were higher than the average for the uninjured group. We believe that the use of properly functioning modern equipment will decrease the rate of injury, particularly in children.

Adolescent↗
PubMed1997

Retinal Muller glia secrete apolipoproteins E and J which are efficiently assembled into lipoprotein particles.

We have shown that apolipoprotein E (ApoE) is synthesized by Muller cells, the major glial cell of the rabbit retina, and secreted into the vitreous after which it is taken up by retinal ganglion cells and rapidly transported into the optic nerve [Amaratunga et al., J. Biol. Chem. 271 (1996) 5628-5632]. In this report we demonstrate that the ApoE secreted by Muller cells in vivo and in culture is efficiently assembled into lipoprotein particles. Apolipoprotein J (ApoJ) is also synthesized by these cells and assembled into lipoprotein particles. The lipoproteins are triglyceride-rich and contain cholesterol esters and free cholesterol. They are heterogeneous, with densities between 1.006 and 1.18 and diameters between 14 and 45 nm. We discuss the possible role of these lipoproteins in supplying the needs of neurons for lipids, especially long axonal projection neurons such as retinal ganglion cells, which are vulnerable to age-related neurodegenerative diseases including Alzheimer's disease.

Animals↗
PubMed1997

Extraglomerular origin of the mesangial cell after injury. A new role of the juxtaglomerular apparatus.

We investigated the origin of the glomerular mesangial cell, a smooth muscle-like cell that provides structural support in the glomerulus. Injection of anti-Thy 1 antibody that binds the Thy 1 antigen on rat mesangial cells eliminated (> 95%) the mesangial population at 20-28 h, while Thy 1-positive cells in the juxtaglomerular apparatus (JGA) were sequestered from the circulation and survived. Single pulse labeling with [3H]thymidine at 36 h labeled Thy 1-positive cells in the JGA and hilus. Serial biopsies demonstrated the progressive migration (5-15 micron/d) and proliferation of these mesangial reserve cells until the entire glomerulus was repopulated. The regenerating mesangial population expressed contractile and migratory proteins preferentially at the leading edge of the migratory front. Single as well as multiple pulse labeling with [3H]thymidine confirmed that the entire mesangial cell repopulation originated from only a few mesangial reserve cells. These reserve cells resided in the extraglomerular mesangium in the JGA and were not renin-secreting cells, macrophages, smooth muscle cells, or endothelial cells. These studies document mesangial cell migration in the anti-Thy 1 model of mesangial proliferative glomerulonephritis and provide evidence for a new role for the juxtaglomerular apparatus in the maintenance of the mesangial cell population.

Animals↗
PubMed1997

Cloning of a new human gene with short consensus repeats using the EST database.

The complement system, which provides many of the effector functions of humoral immunity and inflammation, is tightly regulated by various complement regulatory proteins. The most common structural feature of these proteins is a motif called short consensus repeat (SCR). In order to identify a new human complement regulatory protein, we performed a similarity search using SCR on the expressed sequence tag (EST) database and found a partial sequence of a new human gene. Using a probe containing this partial sequence, we obtained a full-length cDNA of this gene from a human umbilical vein endothelial cell (HUVEC) library. The sequencing reaction demonstrated an open reading frame of 1383 nucleotides coding for a 461 amino acid polypeptide with a deduced relative molecular mass of 51 000. Structural analysis showed that the protein has three SCRs with one transmembrane domain. A characteristic feature of these SCR was that they have six conserved cysteines per repeat instead of the usual four. Therefore, we named this cDNA THECY (three hexa-cysteine motifs). A six cysteine motif is a characteristic feature of selectins. We used northern blot analysis to show that a 2.0 kilobase (kb) transcript was ubiquitously present in most organs studied, and the mRNA was most abundant in the heart. In conclusion, we discovered a member of a new class of membrane-bound SCR-containing molecules using the EST database. Utilization of the EST database may be useful in the search for other new immunological proteins. The function of this gene remains to be elucidated.

Amino Acid Sequence↗
PubMed1997

Have we ignored the role of oncotic pressure in the pathogenesis of glomerulosclerosis?

Focal and segmental glomerulosclerosis (FSGS) develops in a number of renal conditions, especially those associated with severe nephrotic syndrome or a reduction in renal mass. Strong evidence suggests that in diseases associated with reduced renal mass that FSGS develops as a consequence of elevated glomerular hydrostatic pressure (P(GC)) resulting from single nephron hyperfiltration. In nephrotic syndrome, the contribution of an elevated P(GC) is less certain. We hypothesize that in both conditions there is an elevation in net ultrafiltration pressure (P(UF)), which in nephrotic syndrome is secondary to a reduction in glomerular plasma oncotic pressure (piGC) and in conditions with reduced renal mass is secondary to an elevated P(GC). The elevated P(UF) would result in increased convective forces with trafficking and deposition of macromolecules in the mesangium, a process that could trigger local cytokine release with the stimulation of cell proliferation and matrix synthesis. In addition to explaining why FSGS develops in both nephrotic syndrome and with reduced renal mass, the hypothesis explains why the lesion in FSGS is segmental and preferentially involves the hilar area. This is because P(UF) varies along the glomerular capillary, being highest at the proximal (afferent arteriolar) end. In contrast, an elevated P(GC) alone does not readily explain the segmental nature of FSGS, because P(GC) remains relatively constant within the glomerulus. Thus, the hypothesis suggests an important role for the plasma oncotic pressure in the pathogenesis of FSGS. Future studies examining the role of P(UF) and piGC in FSGS would be of interest.

Animals↗
PubMed1997

Mesangial cell proliferation mediated by PDGF and bFGF is determined by levels of the cyclin kinase inhibitor p27Kip1.

Mesangial cell proliferation in vitro is regulated by many cytokines. Platelet-derived growth factor (PDGF) and basic fibroblast growth factor (bFGF) are potent mesangial cell mitogens, whereas transforming growth factor-beta1 (TGF-beta1) reduces their effects. We examined how these cytokines regulate rat mesangial cell proliferation at the level of the cell-cycle. Quiescent mesangial cells in vitro express the cyclin kinase inhibitor, p27Kip1 (p27), and PDGF- and bFGF-induced mesangial cell proliferation is associated with a substantial decrease in p27 levels. Consequently there is a marked increase in expression (Western blot analysis, immunostaining) of cyclin A and CDK2. The decline in p27 levels was prevented by TGF-beta1 during inhibition of PDGF- and bFGF-induced mesangial cell proliferation. To determine the functional role of p27 during cytokine-mediated mesangial cell proliferation, the expression of p27 was reduced with specific p27Kip1 antisense oligodeoxynucleotides. Reducing the levels of p27 resulted in an increased magnitude of mesangial cell proliferation (BrdU and 3H-thymidine incorporation) induced by PDGF and bFGF compared to non-transfected mesangial cells and mesangial cells transfected with control mismatch oligodeoxynucleotides. Furthermore, the onset of maximal proliferation occurred earlier in mesangial cells transfected with antisense compared to control. The reduction in proliferation by TGF-beta1 were not altered by decreased p27 expression. Reducing p27 expression in the absence of mitogens was not associated with entry into the cell-cycle. These results suggest cytokine mediated mesangial cell proliferation is associated with specific cell-cycle proteins, and that the levels of p27 may be important in determining the mesangial cell's proliferative response to PDGF and bFGF in vitro.

Animals↗
PubMed1997

Osteopontin regulation in cultured rat renal epithelial cells.

Osteopontin is a secreted, arginine-glycine-aspartate (RGD)-containing phosphoprotein that is up-regulated in kidney cortical tubular epithelial cells in many experimental models of tubulointerstitial fibrosis. Its close association with infiltrating macrophage in this disease and its ability to directly stimulate macrophage migration has made it a key target as a molecule likely to be important in mediating renal inflammation. The mechanism responsible for osteopontin up-regulation in kidney disease is unknown, but may involve induction by specific cytokines released by damaged glomeruli or other parts of the kidney, prior to the onset of interstitial disease. We have investigated this hypothesis by testing the effects of angiotensin II, bFGF, TGF beta 1, EGF, and IGF, important renal cytokines, on osteopontin regulation in cultured NRK52E cells, a rat renal epithelial cell line. Using Northern blot, Western blot, and ELISA analyses, we find that NRK52E cells constitutively express low levels of osteopontin mRNA and protein. TGF beta 1 and EGF are potent inducers of osteopontin mRNA and protein in those cells. mRNA stability and nuclear run on assays suggest that induction of osteopontin expression by TGF beta 1 and EGF is via increased transcription of the osteopontin gene. In contrast, IGF-1, angiotensin II, and PDGF BB did not significantly modulate osteopontin expression in NRK52E cells. These studies are consistent with the hypothesis that release of potent cytokines by the injured kidney might be one mechanism whereby elevated levels of osteopontin are synthesized by cortical tubular epithelial cells early in tubulointerstitial disease.

Animals↗