Pharmacokinetics of the PDGF-antagonist trapidil in patients with and without renal impairment

BACKGROUND: From July 1989 to February 1996, 130 patients underwent stereotactic radiosurgery. We report the results of the first 50 patients eligible for a minimum of three years of follow-up. METHODS: Twenty women and 30 men, (mean age: 37.5 years) were treated by dynamic rotation on a 6 MV linear accelerator. Prior treatment was embolization in seventeen, surgery in three and embolization and surgery in six. All had DSA and enhanced CT scanning, while some had MRI. Forty-seven treatments used a single isodose. Restricting eloquent normal tissue to 15 Gy, margin doses (at 50-90% isodose) were 12 Gy (one patient); 15 Gy (sixteen patients); 20 Gy (31 patients); 25 Gy (two patients). Maximum diameters were: < 1.5 cm (12 patients); < 2.0 cm (nine patients); < 2.5 cm (twelve patients); < 3.0 cm (thirteen patients; 3.0 cm (four patients). RESULTS: Forty-five patients were evaluable at three years, with thirty-nine having angiography. Twenty-five had angiographically confirmed obliterations; two had parenchymal AVMs obliterated but with residual dural components; four had MRI evidence of obliteration (refused angiography). One patient acutely had a seizure; one patient (with hemorrhages, resection, and embolizations preceding two applications of radiosurgery, separated by 3.5 years) had worsening of memory. CONCLUSIONS: Our uncorrected (five patients unevaluable at three years) and corrected angiographically confirmed obliteration rates are 54% and 60% respectively. Our follow-up (98% accounting of cohort; 78% angiographic rate) and explicit derivation of denominators help delineate the efficacy of radiosurgery at these doses.     

Heat-mediated activation of affinity-immobilized Taq DNA polymerase

A novel strategy for heat-mediated activation of recombinant Taq DNA polymerase is described. A serum albumin binding protein tag is used to affinity-immobilize an E. coli-expressed Taq DNA polymerase fusion protein onto a solid support coated with human serum albumin (HSA). Analysis of heat-mediated elution showed that elevated temperatures (> 70 degrees C) were required to significantly release the fusion protein from the solid support. A primer-extension assay showed that immobilization of the fusion protein resulted in little or no extension product. In contrast, fusion protein released from the HSA ligand by heat showed high polymerase activity. Thus, a heat-mediated release and reactivation of the Taq DNA polymerase fusion protein from the solid support can be obtained to allow for hot-start PCR with improved amplification performance.     

Imaging of the knee. Current status

This article reviews the variety of imaging modalities that are currently being used to evaluate the knee. Nuclear scintigraphy is discussed with emphasis on prosthesis abnormalities. Sonography is discussed with regard to the evaluation of popliteal masses. The uses of computed tomography, especially in the evaluation of the tibial plateau fracture, are discussed, and the role of fluoroscopy, computed tomography, and sonography in image-guided needle procedures are reviewed. Emphasis is placed on the role of MR imaging in knee imaging, with attention to internal derangements, bursal and capsular pathology, and other assorted intra- and extra-articular disorders. The focus of this article is to review the wealth of information that may be obtained by using these imaging modalities.     

Inability of the activated partial thromboplastin time to predict heparin levels. Time to reassess guidelines for heparin assays

BACKGROUND: In treating venous thromboembolic disorders, patient outcomes appear to correlate with heparin levels. Due to pharmacokinetic and pharmacodynamic variations, a relationship between heparin dose and level cannot be reliably predicted in individual patients. Some patients have low heparin levels despite therapeutic activated partial thromboplastin times (aPTTs), which may increase their risk for recurrent thromboembolism. Patients with high heparin requirements appear to have fewer bleeding episodes with heparin level-guided therapy. The aPTT does not reliably correlate with heparin blood concentrations or antithrombotic effects. Consequently, heparin therapy monitored with heparin levels may be more effective and safer. OBJECTIVES: To prospectively determine whether (1) the aPTT therapeutic range adequately predicts heparin levels in 38 patients used to establish the therapeutic aPTT range as is currently recommended and (2) whether 3 paired sets of aPTT-antifactor Xa levels provide the basis for using aPTTs to predict subsequent heparin levels in individual patients (n = 27) receiving intravenous heparin for coronary artery disease or venous thromboembolic disease. RESULTS: In the therapeutic aPTT range established, the R2 value for the relationship was 0.4. Prediction intervals were wide. For an aPTT of 60 seconds, the 95% prediction interval estimates were heparin levels of 0.05 to 1.0 U/mL. In individual patients, the aPTT-antifactor Xa relationship had an average R2 value of 0.75. There was no consistent relationship between the aPTT and anti-factor Xa level in a significant number of patients. CONCLUSIONS: The aPTT does not appear to be a useful surrogate for heparin levels. These findings suggest that the current recommendations on the use of heparin levels should be expanded.     

Retinoid therapy for aging skin and acne

Primary care physicians should be familiar with the effects and appropriate uses of retinoids. Topical tretinoin (Retin-A) can reverse photoaging of the skin, although some transient, undesirable side effects usually occur. In patients with acne vulgaris, topical tretinoin and systemic isotretinoin (Accutane) are the only agents that act upon the apparent underlying causes. Recurrence is unlikely after successful results are achieved. Chronic hypervitaminosis A presents insidiously, and physicians must maintain a high index of suspicion. Complete history taking should always include questions about the patient's use of vitamin supplements.     

Vibrio cholerae Hcp, a secreted protein coregulated with HlyA

Hcp is a 28-kDa secreted protein of Vibrio cholerae regulated coordinately with the hemolysin, HlyA. Both proteins show a dependence on HlyU for expression, suggesting that Hcp may be secreted by V. cholerae in vivo. We have identified and sequenced two genes for Hcp, designated hcpA and hcpB (hemolysin-coregulated protein). The genes encode identical amino acid sequences. Both express a 28-kDa protein, despite open reading frames with only a 19-kDa capacity, suggesting that the Hcp protein runs aberrantly on polyacrylamide gel electrophoresis. There is no cleavage involved in secretion of Hcp from the cell, suggesting a novel mechanism of secretion. An hcp null mutant was constructed, and this strain displayed no deficiency in virulence or colonization in the infant mouse cholera model. From sequence data and primer extension analysis, we predict that the hcp promoter is the sigma 54 type, with a candidate integration host factor binding site upstream. Although hcp and hlyA are coregulated by HlyU, there are no obvious similarities between their promoters. We predict that an intermediate regulator may be involved in the activation of hcp by HlyU. This raises the possibility that HlyU is part of a regulatory cascade.     

Comparison of gene probe and conventional methods for the differentiation of ovine footrot isolates of Dichelobacter nodosus

In a collaborative study that involved four Australian veterinary diagnostic laboratories a gene probe test based on the recombinant plasmids pJIR318, pJIR314B, and pJIR313, which contain genomic vap or vrl regions, was compared with conventional tests used for the differential diagnosis of ovine footrot. A total of 771 clinical dichelobacter nodosus isolates were tested and designated as belonging to one of several gene probe categories. The results showed that 87% of the virulent isolates belonged to gene probe category 1, compared to only 6% of the benign isolates. It was concluded that there was good correlation between the gene probe test and the virulence designation of these isolates as well as the results of elastase, gelatin-gel and protease isoenzyme tests. Furthermore, the gene probe test was converted to a polymerase chain reaction (PCR)-based test. It is suggested that diagnostic laboratories consider carrying out both this PCR test and tests based on the extracellular proteases of D. nodosus.     

Partitioning of proteins in dextran/hydrophobically modified dextran aqueous two-phase systems

Partitioning of proteins was studied in aqueous two-phase systems composed of the polymers dextran and hydrophobically modified dextran. The modified dextrans were benzoyl dextran with a degree of substitution of 0.17 and valeryl dextran with a degree of substitution of 0.20. Phase diagrams for the systems of dextran/benzoyl dextran and dextran/valeryl dextran were determined at room temperature. The proteins studied were beta-galactosidase, bovine serum albumin, beta-lactoglobulin, lysozyme, myoglobin and cytochrome C. The partition coefficients of a series of salts were determined in dextran/benzoyl dextran two-phase systems. The addition of salts had strong effect on the partitioning of proteins. This effect was related to protein net charge and the position of the ions in the Hofmeister series. Cross partitioning of bovine serum albumin was studied in a dextran/benzoyl dextran aqueous two-phase system.     

Lens-specific expression of PDGF-A alters lens growth and development

The vertebrate lens provides an in vivo model to study the molecular mechanisms by which growth factors influence development decisions. In this study, we have investigated the expression patterns of platelet-derived growth factor (PDGF) and PDGF receptors during murine eye development by in situ hybridization. Postnatally, PDGF-A is highly expressed in the iris and ciliary body, the ocular tissues closest to the germinative zone of the lens, a region where most proliferation of lens epithelial cells occurs. PDGF-A is also present in the corneal endothelium anterior to the lens epithelium in embryonic and early postnatal eyes. PDGF-B is expressed in the iris and ciliary body as well as in the vascular cells which surround the lens during early eye development. In the lens, expression of PDGF-alpha receptor (PDGF-alphaR), a receptor that can bind both PDGF-A and PDGF-B, is restricted to the lens epithelium throughout life. The expression of PDGF-alphaR in the lens epithelial cells and PDGF (A- and B-chains) in the ocular tissues adjacent to the lens suggests that PDGF signaling may play a key role in regulating lens development. To further examine how PDGF affects lens development in vivo, we generated transgenic mice that express human PDGF-A in the lens under the control of the alphaA-crystallin promoter. The transgenic mice exhibit lenticular defects that result in cataracts. The percentage of surface epithelial cells in S-phase is increased in transgenic lenses compared to their nontransgenic littermates. Higher than normal levels of cyclin A and cyclin D2 expression were also detected in transgenic lens epithelium. These results together suggest that PDGF-A can induce a proliferative response in lens epithelial cells. The lens epithelial cells in the transgenic mice also exhibit characteristics of differentiating fiber cells. For example, the transgenic lens epithelial cells are slightly elongated, contain larger and less condensed nuclei, and express fiber-cell-specific beta-crystallins. Our results suggest that PDGF-A normally acts as a proliferative factor for the lens epithelial cells in vivo. Elevated levels of PDGF-A enhance proliferation, but also appear to induce some aspects of the fiber cell differentiation pathway.