Localization of secreted protein acidic and rich in cysteine (SPARC) expression in the rat eye

Secreted protein acidic and rich in cysteine (SPARC) is a secreted glycoprotein protein which modulates cell shape and cell-matrix interactions and has been implicated in the regulation of angiogenesis, vascular permeability and cataract formation. In situ hybridization and immunohistochemical studies for SPARC were performed to determine the cell and tissue distribution of SPARC in rat eye. Studies demonstrated SPARC mRNA and protein co-localization at all sites. In the retina SPARC mRNA and protein were localized predominantly to the Müller and ganglion cells. Within the choroid, SPARC was found in vascular endothelial cells and fibroblasts; in the sclera SPARC was present in blood vessels and fibroblasts. SPARC was also present in the non-pigmented epithelial cells of the ciliary body, and in the epithelium of the lens capsule and cornea. The demonstrated anatomical distribution of SPARC in the rat eye is consistent with several of the biological functions ascribed to this matricellular protein and provides a rational basis for its examination in pathological conditions.

Mutational analysis of the cystathionine beta-synthase gene: a splicing mutation, two missense mutations and an insertion in patients with homocystinuria. Mutations in brief no. 120. Online

RT-PCR and direct sequence analyses were used to define mutations in the cystathionine beta-synthase (CBS) gene in two unrelated male patients with vitamin B6 nonresponsive homocystinuria. Both patients were compound heterozygotes for CBS alleles containing point mutations. One patient had a maternally derived G->A transition in the splice-donor site of intron 1, resulting in aberrant splicing of CBS mRNA. The other allele contained a missense mutation resulting in the previously reported E144K mutant CBS protein. The second patient had a maternally derived 4 bp insertion in exon 17, predicted to cause a CBS peptide of altered amino acid sequence. A 494G->A transition was found in exon 4 of the other allele, predicting a C165Y substitution. Expression of recombinant CBS protein, containing the C165Y mutation, had no detectable catalytic activity. Each mutation was confirmed in genomic DNA.

Effects of endothelin or angiotensin II receptor blockade on diabetes in the transgenic (mRen-2)27 rat

BACKGROUND

Endothelin (ET) and angiotensin II (Ang II) are vasoactive/trophic peptides that may contribute to the progression of diabetic nephropathy. The transgenic (mRen-2)27 rat exhibits overexpression of Ang II at sites of normal physiological expression. Unlike other rat strains, the streptozotocin-induced diabetic Ren-2 rat develops progressive renal pathology associated with a declining glomerular filtration rate (GFR) and provides a convenient model to evaluate the role of these vasoactive peptides in the nephropathic process.

METHODS AND RESULTS

Oral administration of either the endothelin A (ETA) and ETB receptor antagonist bosentan or the angiotensin type 1 (AT1) receptor antagonist valsartan for 12 weeks reduced systolic blood pressure (SBP) of nondiabetic and diabetic Ren-2 rats to normotensive levels. Diabetic renal pathology was associated with intense renin mRNA and protein in the proximal tubules and juxtaglomerular cells along with overexpression of transforming growth factor-beta1 (TGF-beta1) and collagen IV mRNA in glomeruli and tubules. With valsartan but not bosentan, renin mRNA and protein in the proximal tubules were not detected. Valsartan but not bosentan reduced TGF-beta1 and collagen IV mRNA and the severity of diabetic renal pathology. A declining GFR with diabetes was attenuated by both treatments. Albuminuria in diabetic rats rose further with bosentan but was reduced with valsartan.

CONCLUSIONS

Despite producing normotension, severe diabetic renal pathology was not prevented by bosentan, suggesting dissociation of ET, albuminuria, and hypertension from the structural injury in this diabetic model. The beneficial effects afforded by valsartan therapy strengthen the importance of the local renin-angiotensin system in mediating progressive diabetic renal injury.

Cloning and characterisation of the Pasteurella multocida ahpA gene responsible for a haemolytic phenotype in Escherichia coli

Haemolysins are membrane-damaging agents which have been described as bacterial virulence factors due to their ability to lyse erythrocytes and other host cells, and therefore inducing a greater inflammatory response (Elliott et al., 1998). Pasteurella multocida was found to be haemolytic under anaerobic conditions. In this study, we cloned and characterised a P. multocida gene, designated ahpA, which conferred a haemolytic phenotype on Escherichia coli when incubated under anaerobic conditions. A deletion was introduced into the ahpA open reading frame which abolished the haemolytic phenotype. The clone containing ahpA showed erythrocyte specificity, causing haemolysis of bovine and equine erythrocytes, and demonstrated weak haemolysis on ovine erythrocytes. Upon further investigation, AhpA was found to affect the expression of the E. coli K-12 latent haemolysin, SheA, under anaerobic conditions.

Endothelin receptor antagonism ameliorates mast cell infiltration, vascular hypertrophy, and epidermal growth factor expression in experimental diabetes

Vascular hypertrophy, a feature of experimental and human diabetes, has been implicated in the pathogenesis of the microvascular and macrovascular complications of the disease. In the present study, we sought to examine the role of endogenous endothelin and its relation to vascular growth factors in the mediation of vascular hypertrophy in experimental diabetes and to examine the contribution of mast cells to this process. Vessel morphology, endothelin, growth factor gene expression, and matrix deposition were studied in the mesenteric arteries of control and streptozotocin-induced diabetic Sprague-Dawley rats treated with or without the dual endothelin(A/B) receptor antagonist bosentan (100 mg x kg(-1) x d(-1)) during a 3-week period. Compared with control animals, diabetic animals had significant increases in vessel weight, wall-to-lumen ratio, mast cell infiltration, extracellular matrix deposition, and gene expression of epidermal growth factor (EGF) and transforming growth factor-beta(1). In diabetic, but not control, vessels, not only were EGF mRNA and endothelin present in endothelial cells, but also their expression was observed in adventitial mast cells. Immunoreactive endothelin was present in the media of mesenteric vessels of diabetic, but not control, animals. Bosentan treatment significantly reduced mesenteric weight, wall-to-lumen ratio, mast cell infiltration, matrix deposition, and EGF mRNA but did not prevent the overexpression of transforming growth factor-beta(1) mRNA in diabetic rats. These findings suggest that endogenous endothelin and EGF may play a role in diabetes-induced vascular hypertrophy and that mast cells may be pathogenetically involved in this process.

Acellular dermal allograft for sellar reconstruction after transsphenoidal hypophysectomy

Obliteration of the sphenoid sinus using fat is often used after transsphenoidal hypophysectomy. The morbidity of this approach includes donor site complications, fat necrosis, and delayed mucocele formation. As obliteration with fat is intended to prevent cerebrospinal fluid (CSF) leakage, an alternative for this technique would be techniques used for CSF rhinorrhea repair. Instead of sinus obliteration, these defects are repaired with fascial autografts, which are unfortunately associated with donor site complications. To avoid sinus obliteration and donor site complications, we have reconstructed the sella with acellular dermal allograft in lieu of sinus obliteration. Transsphenoidal hypophysectomy was performed under combined microscopic and endoscopic visualization. For closure, the sellar anterior wall was reconstructed with acellular dermal allograft, septal cartilage/bone autograft, and fibrin glue. The sinus mucosa was then draped over the reconstruction and held in place with microfibrillar collagen hemostat slurry. The sphenoid sinus was not obliterated. Postoperatively, all patients underwent serial nasal endoscopy. Thirteen patients underwent the procedure as described for removal of pituitary adenoma. Postoperative discomfort and pain were minimal. Intraoperative CSF leaks were identified in five patients; none of these patients experienced a postoperative CSF leak. The microfibrillar collagen hemostat was cleared by sphenoid mucociliary clearance. One patient developed acute sphenoid sinusitis several weeks after surgery; this patient did not develop meningitis. One postoperative CSF leak occurred in an obese patient, in whom an intraoperative CSF leak was not identified; this leak resolved with bedrest and delayed lumbar drainage alone. Sellar reconstruction with acellular dermal allograft may eliminate the need for sphenoid sinus obliteration after transsphenoidal hypophysectomy. Acellular dermal allograft sellar reconstruction ultimately provides for an aerated, functioning sphenoid sinus without increased CSF leak risk or potential donor site morbidity.

Decreased splatter in dermabrasion

OBJECTIVE

To compare a new dermabrasion instrument equipped with a metal shield and hydration-suction apparatus with the standard instrument, with specific attention to the exposure of operating room personnel to potentially hazardous particles.

DESIGN

A surgical trial with each of the instruments was performed with a skin model. The splatter caused by the 2 instruments was evaluated and compared statistically and graphically.

SUBJECTS

Female hairless guinea pigs (450 g) were used as a skin model.

INTERVENTIONS

Ten guinea pigs were treated with the standard dermabrading instrument, and 10 were treated with a shielded suction-irrigating dermabrader. The splatter was analyzed by counting the number of particles landing on strategically placed glass slides. Evaluations of histologic cross-sections of the dermabraded skin were compared in a blinded fashion.

RESULTS

Statistical and graphic analysis showed the number of potentially hazardous particles generated by the suction dermabrader to be significantly less than that generated by the standard dermabrader. Histologic sections showed no difference between the 2 subsets.

CONCLUSION

The new shielded suction-irrigating dermabrader provides comparable surgical results while significantly decreasing exposure to potentially hazardous splatter particles. Arch Facial Plast Surg. 2000;2:23-26

SPARC gene expression is increased in diabetes-related mesenteric vascular hypertrophy

The anti-adhesive extracellular matrix protein SPARC (secreted protein and rich in cysteine; osteonectin or BM-40) has been implicated in the regulation of matrix turnover, cell migration, and proliferation. The present study sought to examine whether modulation in the expression of this protein may play a role in diabetes-associated vascular remodeling. SPARC mRNA and protein were measured in mesenteric vessels of diabetic rats and controls. Hypertrophy of mesenteric vessels was noted after 3 and 32 weeks of diabetes as revealed by the increase in mesenteric vessel wet weight and an increased wall/lumen ratio. SPARC mRNA was sparsely present in intima and adventitia of control vessels. There was a marked increase in SPARC gene expression in the intima and adventitia of mesenteric vessels after 1, 3, and 32 weeks of diabetes. SPARC protein was demonstrated in the vessel wall in control animals and was increased in the mesenteric vessels of diabetic rats after 1 and 32 weeks of diabetes. Administration of the inhibitor of advanced glycation end-product formation, aminoguanidine, to diabetic rats attenuated both the hypertrophic response in mesenteric vessels and the overexpression of SPARC mRNA and protein without affecting glycemic control or food intake. In summary, diabetes-related mesenteric vascular hypertrophy is associated with an increase in SPARC expression in the vessel wall. The modulation of SPARC expression in mesenteric vessels of diabetic rats might be of pathogenetic significance in the development of vascular remodeling in diabetes.

Increased renal expression of vascular endothelial growth factor (VEGF) and its receptor VEGFR-2 in experimental diabetes

It has been suggested that the cytokine vascular endothelial growth factor (VEGF) has an important role in the pathogenesis of diabetic retinopathy, but its role in nephropathy has not been clearly demonstrated. Assessment of VEGF, 125I-VEGF binding, and vascular endothelial growth factor receptor-2 (VEGFR-2) in the kidney was performed after 3 and 32 weeks of streptozotocin-induced diabetes. Gene expression of both VEGF and VEGFR-2 was assessed by Northern blot analysis and the localization of the ligand and receptor was examined by in situ hybridization. VEGF and VEGFR-2 protein were also evaluated by immunohistochemistry. Binding of the radioligand 125I-VEGF was evaluated by in vitro and in vivo autoradiography. Diabetes was associated with increased renal VEGF gene expression. VEGF mRNA and protein were localized to the visceral epithelial cells of the glomerulus and to distal tubules and collecting ducts in both diabetic and nondiabetic rats. Renal VEGFR-2 mRNA was increased after 3 weeks of diabetes but not in long-term diabetes. In situ hybridization and immunohistochemical studies revealed that glomerular endothelial cells were the major site of VEGFR-2 expression. In addition, VEGFR-2 gene expression was detected in cortical and renomedullary interstitial cells and on endothelial cells of peritubular capillaries. There was an increase in 125I-VEGF binding sites after 3 but not 32 weeks of diabetes. The major VEGF binding sites were in the glomeruli. 125I-VEGF binding was also observed in medullary rays and in the renal papillae. These studies indicate an early and persistent increase in renal VEGF gene expression in association with experimental diabetes. In addition, an early and transient increase in renal VEGF receptors was also observed in diabetic rats. These findings are consistent with a role for VEGF in mediating some of the changes observed in the diabetic kidney.

Role of hyperlipidemia in progressive renal disease: focus on diabetic nephropathy

BACKGROUND

It has been suggested that lipids promote renal injury and that 3-hydroxy-3-methylglutaryl coenzyme A (HMG CoA) reductase inhibitors confer renoprotection in certain renal diseases, including diabetic nephropathy.

METHODS

Sprague-Dawley rats were randomized to sham, subtotal nephrectomy (STNx) or STNx + atorvastatin groups. After 12 weeks, proteinuria, renal function, glomerular injury, renal transforming growth factor-beta (TGF-beta) gene expression and macrophage (ED1-positive cells) accumulation were assessed. In addition, the effects of HMG CoA reductase in human diabetic nephropathy were reviewed.

RESULTS

Atorvastatin therapy was associated with a modest reduction in proteinuria and glomerulosclerosis without influencing lipid levels or renal function in STNx rats. These effects were associated with decreased renal TGF-beta 1 gene expression and less glomerular and tubulointerstitial macrophage accumulation. The renoprotective effects of HMG CoA reductase inhibitors in both insulin- and non-insulin-dependent diabetic subjects with either incipient or overt nephropathy appear to be highly variable.

CONCLUSIONS

HMG CoA reductase inhibition appears to confer renoprotection via effects on prosclerotic cytokines such as TGF-beta and macrophage accumulation, independent of their lipid-lowering properties. The role of lipid-lowering agents in early or overt diabetic nephropathy remains to be fully ascertained.

Closure of a scalp defect

In repairing cutaneous defects, the facial plastic and reconstructive surgeon is faced with many specialized areas of tissue. Reconstruction of thin eyelid skin and thick, sebaceous nasal skin requires different methods. The unique characteristics of the scalp make it one of the greatest repair challenges in the head and neck region, sometimes requiring multiple different reconstructive techniques for the same defect.

Sudden sensorineural hearing loss following nonotologic, noncardiopulmonary bypass surgery

OBJECTIVES

To report 3 cases of sudden sensorineural hearing loss (SSHL) following nonotologic surgery in which cardiopulmonary bypass (CPB) surgery was not involved and to review reports in the literature of similar cases.

DATA SOURCES

Clinical records and MEDLINE and Healthstar databases.

STUDY SELECTION

Reports in the world literature of cases of SSHL following nonotologic, non-CPB surgery.

DATA SYNTHESIS

While said to be more common after CPB surgery, fewer than 20 cases of SSHL following non-otologic, non-CPB surgery have been reported. A number of proposed causes of SSHL temporally related to non-otologic, non-CPB surgery have been theorized; however, the true cause is unknown. This report presents 3 cases of SSHL following nonotologic, non-CPB surgery. Two patients had profound unilateral loss; 1 had moderate bilateral loss. None of the patients demonstrated recovery despite diuretic and prednisone therapy; in approximately 30% of the cases reported to date, the patients experienced significant improvement.

CONCLUSIONS

Sudden sensorineural hearing loss following nonotologic, non-CPB surgery is rare, and its cause remains unknown. The scarcity of reports of SSHL following nonotologic, non-CPB surgery raises the possibility that the apparent association may be spurious.

Ingestion of caustic hair relaxer: is endoscopy necessary?

Hair relaxer, a commercially available alkaline product, is commonly the offending agent in caustic ingestion. These patients often experience oral cavity and facial burns; however, no clinically significant esophageal injuries have been reported. Therefore, we questioned the therapeutic and economic efficacy of the "standard treatment protocol" that includes hospitalization and endoscopic evaluation. Twenty-six patients over a 7-year period presented to our institution having ingested hair relaxer. Presenting signs and symptoms, esophageal findings, and cost of the standard treatment protocol were reviewed. Also, we analyzed the caustic potential and current packaging of hair relaxer. Our findings support modifications in the standard treatment protocol for hair relaxer ingestion including elimination of hospitalization and endoscopy in most patients. We also question compliance with childproof packaging laws and suggest avenues for prevention of hair relaxer ingestion.

Clinical and histologic response of subcutaneous expanded polytetrafluoroethylene (Gore-Tex) and porous high-density polyethylene (Medpor) implants to acute and early infection

OBJECTIVE

To examine the responses of subcutaneously implanted expanded polytetrafluoroethylene (e-PTFE, Gore-Tex) and porous high-density polyethylene (PHDPE, Medpor) to experimentally induced infection.

DESIGN

Sprague-Dawley rats were implanted subcutaneously with either e-PTFE or PHDPE implants. Inocula of Staphylococcus aureus were injected directly over the implants and the wounds were observed for clinical signs of infection. After the animals were killed, the implants were harvested and underwent Histologic examination.

SUBJECTS

Twenty-eight adult male Sprague-Dawley rats weighing 200 to 250 g.

INTERVENTION

A 8-mm diameter, 1-mm-thick implant of either e-PTFE or PHDPE was placed in a subcutaneous pocket over each animal's dorsum. Either at the time of implantation or 14 days afterward, an inoculum of 10(9) colony-forming units of S aureus was injected transcutaneously directly over each implant. The animals were observed for 7 days before being killed. The implants were harvested and examined by both conventional light and scanning electron microscopy, and the degree of capsule reaction, infection, inflammation, and implant degradation was evaluated.

RESULTS

Implants inoculated at the time of implantation were more likely to become clinically infected. Results for e-PTFE and PHDPE implants were similar in this group (5 of 5 e-PTFE and 5 of 5 PHDPE implants infected). The PHDPE implants inoculated 14 days after implantation were less likely to become infected (1 of 4 infected) than e-PTFE implants (3 of 4 infected), and were statistically less likely to become infected than PHDPE implants inoculated immediately after implantation (25% vs 100%; P < .02). Histologically, this resistance to infection correlated with increasing fibrovascular ingrowth into the PHDPE implants. The infected PHDPE implant had little to no ingrowth compared with PHDPE control implants. The uninfected e-PTFE implant had evidence of early fibrovascular ingrowth into the peripheral pores of the implant.

CONCLUSIONS

Because of differences in pore size, PHDPE promotes faster fibrovascular ingrowth. The presence of vascularized host tissue in and around the implant lends stability and resistance to experimentally induced infection. Conservative management of clinical implant infections should be considered if bacterial seeding occurs after substantial fibrovascular ingrowth is present. Future alloplast designs should include pore sizes that will encourage invasion of the implant by host tissue.

Characterisation of five missense mutations in the cystathionine beta-synthase gene from three patients with B6-nonresponsive homocystinuria

Homocystinuria, due to a deficiency of the enzyme cystathionine beta-synthase (CBS), is an inborn error of sulphur-amino acid metabolism. This is an autosomal recessive disease which results in hyperhomocysteinaemia and a wide range of clinical features, including optic lens dislocation, mental retardation, skeletal abnormalities and premature thrombotic events. We report the identification of 5 missense mutations in the protein-coding region of the CBS gene from 3 patients with pyridoxine-nonresponsive homocystinuria. Reverse-transcription PCR was used to amplify CBS cDNA from each patient and the coding region was analysed by direct sequencing. The mutations detected included 3 novel (1058C-->T, 992C-->A and 1316G-->A) and 2 previously identified (430G-->A and 833C-->T) base alterations in the CBS cDNA. Each of these mutations predicts a single amino acid substitution in the CBS polypeptide. Appropriate cassettes of patient CBS cDNA, containing each of the above defined mutations, were used to replace the corresponding cassettes of normal CBS cDNA sequence within the bacterial expression vector pT7-7. These recombinant mutant and normal CBS constructs were expressed in Escherichia coli cells and the catalytic activities of the mutant proteins were compared with normal. All of the mutant proteins exhibited decreased catalytic activity in vitro, which confirmed the association between the individual mutation and CBS dysfunction in each patient.

Metabotropic glutamate receptors regulate APP processing in hippocampal neurons and cortical astrocytes derived from fetal rats

It has previously been shown that stimulation of muscarinic m1 or m3 receptors can, by generating diacylglycerol (DAG) and activating protein kinase C (PKC), accelerate the breakdown of the amyloid precursor protein (APP) to form soluble, non-amyloidogenic peptides (APPs). This relationship has been demonstrated in human glioma and neuroblastoma cells as well as in transfected human embryonic kidney (HEK) cells and PC12 cells. We now provide evidence that stimulation of metabotropic glutamate receptors (mGluRs), which also are coupled to DAG and PKC, similarly accelerates processing of APP into non-amyloidogenic APPs in hippocampal neurons and cortical astrocytes derived from normal fetal rats. The mGluR antagonist, L(+)-2-amino-3-phosphonopropionic acid (L-AP3), and GF 109203X, an inhibitor of PKC, both blocked the release of APPs from hippocampal neurons and astrocytes evoked by glutamate receptor stimulation. Inasmuch as glutamatergic neurons in cortex and hippocampus are known to be damaged in Alzheimer's disease, our findings suggest that amyloid formation may be enhanced by the resulting glutamate deficiency and that selective mGluR agonists may be useful in facilitating synaptic efficacy and treating the disease.

Amyloid precursor protein processing is stimulated by metabotropic glutamate receptors

Stimulation of muscarinic m1 or m3 receptors can, by generating diacylglycerol and activating protein kinase C, accelerate the breakdown of the amyloid precursor protein (APP) to form soluble, nonamyloidogenic derivatives (APPs), as previously shown. This relationship has been demonstrated in human glioma and neuroblastoma cells, as well as in transfected human embryonic kidney 293 cells and PC-12 cells. We now provide evidence that stimulation of metabotropic glutamate receptors (mGluRs), which also are coupled to phosphatidylinositol 4,5-bisphosphate hydrolysis, similarly accelerates processing of APP into nonamyloidogenic APPs. This process is demonstrated both in hippocampal neurons derived from fetal rats and in human embryonic kidney 293 cells transfected with cDNA expression constructs encoding the mGluR 1 alpha subtype. In hippocampal neurons, both an mGluR antagonist, L-(+)-2-amino-3-phosphonopropionic acid, and an inhibitor of protein kinase C, GF 109203X, blocked the APPs release evoked by glutamate receptor stimulation. Ionotropic glutamate agonists, N-methyl-D-aspartate or S(-)-5-fluorowillardiine, failed to affect APPs release. These data show that selective mGluR agonists that initiate signal-transduction events can regulate APP processing in bona fide primary neurons and transfected cells. As glutamatergic neurons in the cortex and hippocampus are damaged in Alzheimer disease, amyloid production in these regions may be enhanced by deficits in glutamatergic neurotransmission.