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Biomedical subjects

P F Davis

Publications and source records attributed to P F Davis.

At least 19 recordsLinked to original sources
PubMed2003

Effects of five commonly used glucocorticoids on haemangioma in vitro.

1. High-dose systemic or intralesional steroids are the first-line pharmacological treatments for haemangioma. However, the mechanism of action of steroids is unknown. Using the in vitro model developed by us, the present study examined some of the effects of five commonly used glucocorticoids on haemangioma biopsies taken from two patients. 2. At 12 micro mol/L, triamcinolone and dexamethasone consistently exhibited capillary growth inhibition, whereas methylprednisolone displayed an inhibitory effect during the first 7 days of culture. At this concentration, inhibition of capillary growth was observed in betamethasone-treated cultures derived from one patient but not in those derived from the other. However, hydrocortisone had a negligible effect on capillary growth. 3. Transcription of various factors considered important for haemangioma development were studied by reverse transcription-polymerase chain reaction. Neither vascular endothelial growth factor nor fibroblast growth factor-2 played a vital role in steroid-induced inhibition of capillary growth. All glucocorticoids induced a marked decrease of interleukin (IL)-6 transcripts. 4. Capillary growth inhibition in cultures treated with all glucocorticoids, except triamcinolone, was associated with an increased transcription of clusterin/apolipoprotein J (clust/apoJ), an apoptotic gene. There was increased transcription of mitochondrial cytochrome (cyt) b in the inhibited cultures resulting from triamcinolone, dexamethasone or methylprednisolone treatment that was associated with capillary growth inhibition, suggesting an important role of mitochondria in glucocorticoid-induced regression of haemangioma. 5. Our results indicate that glucocorticoids may modulate haemangiogenesis via an upregulation of cyt b, clust/apoJ and/or IL-6. The variable effects of different glucocorticoids on one or more of these factors may explain the interindividual variation in the in vivo response of haemangioma to the steroids.

Analysis of Variance↗
PubMed2001

Altered mitochondrial cytochrome b gene expression during the regression of hemangioma.

Hemangioma is a primary tumor of microvasculature. Its development typically exhibits a proliferative phase followed by an involuting phase that continues into the involuted phase. Although apoptosis has been reported, the mechanisms regulating the spontaneous regression of hemangioma are largely unknown. The authors recently demonstrated up-regulation of the mitochondrial cytochrome b gene in hemangioma associated with steroid-induced regression. The present study investigated whether a similar change occurred during spontaneous regression. Biopsy material was obtained from 11 patients with hemangiomas at different phases of development. In one of these patients, a biopsy was taken from the proliferative, involuting, and involuted areas of the hemangioma. In another patient, a biopsy was taken before and 5 weeks after the intralesional administration of steroids. From each tissue specimen, RNA was isolated and subjected to reverse transcriptase-polymerase chain reaction analysis by use of specific primers for the human mitochondrial cytochrome b gene. Semiquantitative reverse transcriptase-polymerase chain reaction analysis revealed that the strongest expression of the mitochondrial cytochrome b transcripts was in specimens taken from hemangiomas in the involuting phase compared with those from the proliferative and involuted phases. The authors concluded that mitochondrial cytochrome b is associated with both the spontaneous and the steroid-induced regression of hemangioma, probably by regulating apoptosis.

Apoptosis↗
PubMed2000

Interleukin-4 transgenic mice develop glomerulosclerosis independent of immunoglobulin deposition.

Mice with constitutive transgenic (tg) expression of IL-4 develop autoimmune-type disorders resembling human lupus nephritis. The kidneys show progressive glomerulosclerosis with immunoglobulin (Ig) and complement deposition. This study investigated the roles of renal IL-4 expression and glomerular Ig deposition in the pathogenesis of glomerulosclerosis in IL-4 tg mice. Treatment of these mice with IL-4 neutralizing antibody prevented renal disease. IL-4 tg mice treated with methylprednisolone (MP) showed increased mesangial collagen deposition with only trace amounts of glomerular Ig. To analyze the relevance of Ig deposition in the development of the renal lesions, IL-4 tg mice were cross-bred with mu chain-deficient mice (muMT-/-), which are unable to produce Ig. IL-4 tg/muMT-/- mice developed progressive glomerulosclerosis with mesangial accumulation of collagen types I, IV and V despite complete absence of glomerular Ig deposits. Renal IL-4 expression was observed in both anti-IL-4- and MP-treated IL-4 tg mice as well as in IL-4 tg/muMT-/- mice. No statistical difference in the number of glomerular T cells and macrophages between any of the groups was evident. Our data demonstrate that in this model glomerulosclerosis can develop independently of and prior to Ig deposition, and suggest that the initial accumulation of glomerular extracellular matrix is due to renal IL-4 expression. Our results point to a novel mechanism for the development of glomerulosclerosis which may have implications for human disease.

Animals↗
PubMed2000

The alpha1(VIII) and alpha2(VIII) collagen chains form two distinct homotrimeric proteins in vivo.

The short chain collagen variant, type VIII, is considered to be comprised of two distinct gene products, the alpha1 and alpha2 polypeptide chains. However, recent in vitro translation studies suggest that these chains can form homotrimers. We report here data from biochemical, immunohistochemical and molecular biological experiments, which together provide evidence that alpha1 and alpha2 polypeptides of type VIII collagen exist as homotrimers in cells and tissues. High-performance liquid chromatographic separation of type VIII collagen isolated from Descemet's membrane consistently demonstrated equimolar quantities of the two chains (alpha1:alpha2 1. 03+/-0.02 (S.E.M.); n=41). The availability of highly specific antibodies for the two polypeptides has assisted the in vivo characterisation of type VIII collagen. Immunoprecipitation of trimeric type VIII collagen from Descemet's membrane with purified anti-alpha1(VIII) and anti-alpha2(VIII) yielded fractions that contained only the alpha1(VIII) and alpha2(VIII) chains, respectively. Cultured human mesangial cells synthesised both polypeptides, but the alpha1(VIII) chain was found exclusively in the cell pellet, while the media contained only the alpha2(VIII) chain. The RNA from human mesangial cells and cornea showed message for both chains. However, in peritoneal fibroblast and mesothelial cell RNA, only alpha1(VIII) mRNA was detectable, demonstrating that the transcription of these two genes was not always co-ordinated. Immunohistochemistry showed that both polypeptides were present in cornea, optic nerve, aorta and umbilical cord but did not always co-localise. These results indicate the alpha1(VIII) and alpha2(VIII) chains preferentially form pepsin-resistant, homotrimeric molecules and so can exist as two distinct proteins.

Animals↗
PubMed2000

A novel in vitro human model of hemangioma.

Hemangioma, the most common tumor of infancy, is characterized by a proliferation of capillary endothelial cells with multilamination of the basement membrane and accumulation of cellular elements, including mast cells. The initial rapid growth is followed by an inevitable but slow involution. The currently available therapies are empirical and unsatisfactory because what is known of the cellular and molecular basis of hemangioma development is rudimentary. Advances in the understanding of its programmed biologic behavior has been hampered by the lack of a valid human model. We report here a novel in vitro culture system that is a useful human model of hemangioma. A small fragment of hemangioma biopsy is embedded in fibrin gel in a well of culture plates and incubated in a serum-free, buffered-salt, minimal medium. A complex network of microvessels grows out from the tissue fragments. Biopsies taken from all three phases of hemangioma development were cultured successfully; proliferative phase samples developed microvessels in 1 to 4 days, involuting phase in 5 to 7 days, and involuted phase in 7 to 12 days. The relative growth rates of the microvessels in the culture of biopsies taken from different stages of hemangioma development reflect the growth patterns seen clinically. This model has been validated using histochemistry, immunohistochemistry, and reverse transcriptase-polymerase chain reaction. Comparison of the number, localization, and phenotype of endothelial and mast cells and the distribution of basement membrane constituents (type IV collagen, perlecan, and laminins) and growth factors (basic fibroblast growth factor, vascular endothelial growth factor, transforming growth factor-betas) in the biopsy and the tissue after culture shows that many of the characteristics of the original tissues were retained in culture. This in vitro human model of hemangioma overcomes some of the deficiencies associated with earlier models. It offers an opportunity for studying the precise cellular, biochemical, and molecular basis of hemangioma It may also help to elucidate the mechanisms of action of existing therapies and may lead to the identification of novel treatments for hemangioma.

Biomarkers, Tumor↗
PubMed2000

Clusterin/apoJ expression during the development of hemangioma.

Hemangioma is the most common tumor of infancy. This vascular tumor is characterized by an initial rapid proliferation followed by an inevitable regression. The life cycle of hemangioma is divided into proliferative, involuting, and involuted phases. The cellular and molecular mechanisms responsible for controlling the biological behavior of hemangioma are largely unknown. Differential display analysis using mRNA isolated from biopsy specimens representative of the 3 different phases showed increased expression of clusterin/apoJ (clust/apoJ) in the involuting samples. Clust/apoJ is a multifunctional glycoprotein that has been associated with apoptosis. Reverse transcription-polymerase chain reaction (RT-PCR) and immunohistochemistry showed that both the transcription and protein expression of clust/apoJ were increased in hemangioma as the tumor progressed from the proliferative to the involuting and involuted phases. This suggests that clust/apoJ is involved in regulating apoptosis during the spontaneous regression of hemangioma. It has been suggested that mast cells (MC) play a role in the regression of hemangioma. The increase in the number and proportion of clust/ apoJ-positive MC with progression of hemangioma, along with the localization of clust/apoJ to MC granules, supports this hypothesis. We suggest that MC may be synthesizing/releasing this apoptotic modulator, leading to the regression of the tumor. Better understanding of the pathogenesis of hemangioma by identification of the relevant factors involved in its regression such as clust/apoJ will result in the development of novel therapies for this condition and tumors that do not undergo spontaneous regression.

Biopsy↗
PubMed2000

Cellular and extracellular markers of hemangioma.

Several cellular and extracellular markers that distinguish the phases of the hemangioma life cycle have been described previously. However, details of the phenotypic changes of; the various cellular elements during hemangioma development have not been fully reported, and the extracellular matrix composition, especially in the vicinity of the proliferating endothelial cells, is poorly described. This study examined the expression of cellular and extracellular molecules and cytokines in the proliferative, involuting, and involuted phases of hemangioma. Paraffin-embedded hemangioma specimens, four from each phase, were examined histochemically and immunohistochemically. Throughout the three phases, vascular endothelial cells stained positive for CD31 and von Willebrand factor, although in the involuted phase, not all vessels in the tissue expressed these endothelial markers. Proliferating cell nuclear antigen was expressed by the majority of endothelial cells and pericytes in the proliferative and early involuting phases, but its expression was negligible in the involuted phase. In addition to finding that the total number of mast cells was highest in the involuting phase, the authors observed that the proportion of chymase-positive mast cells decreased with the progression of hemangioma and that virtually all mast cells expressed the biogenic amine phenotype throughout the hemangioma life cycle. The localization of vascular endothelial growth factor predominantly to the pericytes and endothelial cells during the proliferative phase and of basic fibroblast growth factor to the endothelial cells in both the proliferative and early involuting phases is consistent with previous reports, although the latter growth factorwas also observed in mast cells. Type IV collagen and the beta chain of laminin and perlecan were detected in the basement membranes in all phases. Interestingly, collagen types I, III, and V were present in basal membranes throughout the phases and with increasing density in the stromal areas with involution, although type I collagen was less prominent during the proliferative phase. Short-chain collagen type VIII was localized extracellularly throughout the development of hemangioma but, during the early proliferative phase, it was also detected within mast cells. The expression of specific cytokines and cellular and extracellular markers may help distinguish the different clinical phases of the hemangioima life cycle. These results provide further insight into the biology of hemangioma.

Antigens, Nuclear↗
PubMed2000

Steroid therapy of a proliferating hemangioma: histochemical and molecular changes.

OBJECTIVES: Hemangioma is a primary tumor of the microvasculature in which angiogenesis is initially excessive, followed by regression of the newly formed vessels. Intervention is necessary in up to 20% of cases, high-dose systemic or intralesional steroids being the first-line treatment. As the mechanism of action of steroids is unknown, we undertook an investigation of the cellular and molecular effects of their action. STUDY DESIGN: A unique opportunity to study the effect of steroid treatment was presented when biopsy material was obtained from an infant with an ulcerated proliferating hemangioma before and after intralesional triamcinolone injection, which resulted in an accelerated regression of the lesion. Histochemical quantitation of mast cells, molecular analysis by reverse transcriptase-polymerase chain reaction (RT-PCR) for 7 growth factor transcripts and differential display RT-PCR (DD RT-PCR) were conducted. RESULTS: After steroid therapy, the mast cell number increased (untreated = 2.22 +/-.27 [standard error of the mean ¿SEM¿]; treated = 8.7 +/-.71 [SEM] mast cells per field, respectively; P <.0001; n = 40 fields for each group), and the transcriptional expression of cytokines: platelet-derived growth factor-A and -B; interleukin-6; transforming growth factor-beta1 and -beta3 decreased, while that of basic fibroblast growth factor (bFGF) and vascular endothelial cell growth factor remained unaltered. Elevated urinary bFGF levels noted in cases of proliferating hemangioma, persisted even after steroid treatment. Using DD RT-PCR an amplicon that shared 100% sequence homology with the human mitochondrial cytochrome b gene was detected in the hemangioma biopsy after steroid treatment. CONCLUSIONS: The regression of this hemangioma subsequent to steroid therapy was accompanied by a significant increase in mast cell density, reduced transcription of several cytokines, and an enhanced expression of the mitochondrial cytochrome b gene.

Anti-Inflammatory Agents↗
PubMed1999

Progression of renal disease in interleukin-4 transgenic mice: involvement of transforming growth factor-beta.

Recent reports have suggested the involvement of interleukin-4 (IL-4) in glomerular pathophysiology. Using immunohistochemistry and reverse transcriptase polymerase chain reaction we investigated the renal lesions in transgenic (tg) mice with widely distributed IL-4 expression including the kidney, and measured the serum levels of the cytokines transforming growth factor-beta (TGF-beta) and IL-4 by ELISA. Transgenic animals exhibited glomerular hypertrophy with progressive mesangial sclerosis leading to renal failure. Renal IL-4 transcript expression, mesangial accumulation of collagen types I, III, IV and V, and immune deposition accompanied by increased expression of TGF-beta1 protein and mRNA were observed. Seven day-old transgenic animals showed early renal fibrotic changes in the absence of immune deposits or TGF-beta1 upregulation. The sera of transgenic mice not only showed elevated levels of circulating IL-4 (tg: 76.6 pg/ml +/- 7.1 vs wildtype (wt): < 3 pg/ml), but significantly decreased TGF-beta1 levels (tg: 18.9 ng/ml +/- 4.1 vs wt: 38.7 ng/ml +/- 2.9; P < 0.005). The disease severity correlated with the serum IL-4/TGF-beta1 ratio rather than with the IL-4 concentration. These data suggest that renal IL-4 production results in matrix accumulation prior to any immunological insult, that increased circulating IL-4/TGF-beta1 ratios are associated with renal immunopathological manifestations and that upregulation of renal TGF-beta1 expression following glomerular Ig deposition accelerates the sclerosis and exacerbates disease development.

Animals↗
PubMed1996

Mast cells and type VIII collagen in human diabetic nephropathy.

Renal injury in diabetes mellitus is associated with progressive interstitial fibrosis and extracellular matrix accumulation. However, the phenotypes of cells forming the interstitial infiltrate in diabetic nephropathy have not been precisely defined. There is increasing evidence for the association of mast cells with angiogenesis, chronic inflammatory conditions and fibrosis. We have recently shown that human mast cells can produce the non-fibrillar short chain type VIII collagen in vivo. Using immunohistochemistry, in situ hybridisation and reverse transcriptase-polymerase chain reaction, we examined the contribution of mast cells and type VIII collagen to the fibrotic changes occurring in biopsy-proven diabetic nephropathy. We observed that the number of interstitial mast cells was significantly increased in diabetic nephropathy compared with normal kidney tissue. In specimens from diabetic subjects, intense immunohistochemical staining for type VIII collagen was detected in mast cells, on periglomerular fibres and in perivascular and interstitial sites. The expression of type VIII collagen in periglomerular and interstitial sites coincided with that of alpha smooth muscle actin, a marker for myofibroblastic differentiation mRNA for type VIII collagen was detected by reverse transcriptase-polymerase chain reaction in diabetic nephropathy and in a human mast cell line. By in situ hybridisation the transcripts for type VIII collagen were localised to renal mast cells. The increased number of mast cells and the elevated type VIII collagen deposition in human diabetic nephropathy provides a potential link between the extracellular matrix accumulation and the fibrosis observed in this condition.

Adult↗
PubMed1996

Clinical results of simultaneous adjacent interdigital neurectomy in the foot.

Fifteen patients (19 feet) who underwent simultaneous surgical excision of two primary interdigital neuromas in adjacent web spaces of the foot were studied retrospectively. There were 11 female patients (73%). The average age of the patients was 54.4 years. Other causes of multiple web space tenderness were excluded prior to surgical resection of both neuromas. At an average follow-up of 68.6 months (range, 32-113 months), 10 feet (53%) had complete resolution of symptoms and six feet (31%) had minimal residual symptoms. Three feet in two patients (16%) continued to have significant pain after surgery. One sequela of the procedure was dense sensory loss of the plantar aspect of the third metatarsal head to the tip of the third toe. There was also proximal dorsal sensory loss to the second, third, and fourth toes which was a function of the type of incision used. The sensory loss did not cause disability in the patients, but did cause some awkwardness with nail care. Resection of adjacent interdigital neuromas, although rarely indicated, can be expected to provide significant pain relief in 84% of patients, which is similar to results reported for resection of a single neuroma.

Female↗
PubMed1994

Painful heel syndrome: results of nonoperative treatment.

One hundred five patients (70% female and 30% male; average age, 48 years) with 132 symptomatic heels were treated according to a standard nonoperative protocol and then reviewed at an average follow-up of 29 months. The treatment protocol consisted of nonsteroidal anti-inflammatory medications, relative rest, viscoelastic polymer heel cushions, Achilles tendon stretching exercises, and, occasionally, injections. Obesity, lifestyle (athletic versus sedentary), sex, and presence or size of heel spur did not influence the treatment outcome. Ninety-four patients (89.5%) had resolution of heel pain within 10.9 months. Six patients (5.7%) continued to have significant pain, but did not elect to have operative treatment, and five patients (4.8%) elected to have surgical intervention. Despite attention to the outcome of surgical treatment for heel pain in the current literature, initial treatment for heel pain is nonoperative. The treatment protocol used in this study was successful for 89.5% of the patients.

Combined Modality Therapy↗
PubMed1992

Isolation and purification of extracellular matrix vesicles from blood vessels.

Extracellular membrane-bound vesicles (called matrix vesicles) which occur in abundance in atherosclerotic blood vessels are believed to be associated with lipid accumulation and calcification. A technique has been developed to isolate them from experimental aneurysms in sheep in which they are known to be plentiful. The matrix vesicles were isolated by differential centrifugation following extraction by hypotonic salt solution. Most of the vesicles were pelleted at 30,000g and fell within the size range of matrix vesicles in situ in the aneurysmal wall. Preliminary characterization of the enzymatic activities indicates that many of these vesicles are formed from cell membranes rather than being derived from lysosomes, mitochondria or endoplasmic reticulum. Morphologically they are similar to matrix vesicles of other mineralizing tissues.

Animals↗
PubMed1991

Salt-soluble collagen and elastin in the human aorta and pulmonary artery.

Collagen and elastin, the major structural components of blood vessels, have a very low turnover. In disease, this rate may be increased and an elevation of the tissue concentration of the soluble degradation fragments might be anticipated. In this preliminary study the concentration of extractable collagen and elastin in the aorta and pulmonary artery of eight human subjects postmortem was determined. The proportion of pulmonary artery collagen and elastin that was soluble was generally either equal to or greater than that in the abdominal aorta. The fraction of collagen that was salt extractable was larger than the soluble elastin fraction.

Adult↗