Osteoarthritis associated with mild chondrodysplasia in transgenic mice expressing alpha 1(IX) collagen chains with a central deletion

Type IX collagen, containing molecules of the three distinct polypeptides alpha 1(IX), alpha 2(IX), and alpha 3(IX), is an interesting hybrid extracellular matrix component in cartilage and eye tissues, with the properties of both a proteoglycan and a collagen. The alpha 1 (IX) chain has two forms, as a result of the tissue-specific utilization of two alternative promoters; the alpha 2(IX) chain carries a covalently attached glycosaminoglycan side chain. We have introduced a gene construct controlled by a tissue-specific promoter/enhancer and expressing a truncated alpha 1(IX) chain into mice. Examination of the offspring of two different founders revealed pathological changes similar to osteoarthritis in the articular cartilage of knee joints. In addition, mice homozygous for the transgene developed mild chondrodysplasia (i.e., mild dwarfism, anterior tonguing in the vertebral bodies, and ophthalmopathy). The relative ratio of transgene product to the endogenous alpha 1(IX) chain was approximately one in homozygotes and less than one in heterozygotes. Therefore, the phenotypic severity correlated well with the level of transgene expression. These findings suggest that mutations in type IX collagen genes may cause certain forms of osteoarthritis and chondrodysplasia in humans.     

Reharvest of iliac crest donor site cancellous bone

Patients requiring cancellous bone grafting of an extensive deficit or multiple bone grafting procedures often lack a sufficient quantity of autogenous cancellous bone. Canine studies have indicated that a potential exists for reharvesting autogenous cancellous bone from an iliac crest donor site using a trapdoor harvesting technique. However, significant human experience with this procedure has been lacking. This report describes four patients who underwent successful reharvesting of an iliac crest donor site that provided clinically sufficient autogenous cancellous bone graft material to treat an ongoing or a new skeletal problem. These patients all met specific criteria regarding use of the trapdoor method of bone graft harvest and a minimum 24-month interval between bone grafting procedures. Preoperative computed tomography scanning of the iliac crest was useful in documenting that sufficient cancellous bone was available for reharvest. It appears that iliac crest donor site reharvesting is a specific advantage of the trapdoor technique and is a possible alternative to multiple site grafting or the use of allograft or bone substitute materials.     

The cenpB gene is not essential in mice

Centromere protein B (CENP-B) is a centromeric DNA-binding protein that binds to alpha-satellite DNA at the 17 bp CENP-B box sequence. The binding of CENP-B, along with other proteins, to alpha-satellite DNA sequences at the centromere, is thought to package the DNA into heterochromatin subjacent to the kinetochore of mitotic chromosomes. To determine the importance of CENP-B to kinetochore assembly and function, we generated a mouse null for the cenpB gene. The deletion removed part of the promoter and the entire coding sequence except for the carboxyl-terminal 35 amino acids of the CENP-B polypeptide. Mice heterozygous or homozygous for the cenpB null mutation are viable and healthy, with no apparent defect in growth and morphology. We have established mouse embryo fibroblasts from heterozygous and homozygous cenpB null littermates. Microscopic analysis, using immunofluorescence and electron microscopy of the cultured cells, indicated that the centromere-kinetochore complex was intact and identical to control cells. Mitosis was identical in fibroblasts derived from cenpB wild-type, heterozygous and null animals. Our studies demonstrate that CENP-B is not required for the assembly of heterochromatin or the kinetochore, or for completion of mitosis.     

Dihydropteroate synthase polymorphisms in Pneumocystis carinii

Sulfa drugs are widely used in the treatment and prophylaxis of Pneumocystis carinii pneumonia. The nucleotide sequences of the sulfa target enzyme, dihydropteroate synthase (DHPS), differed substantially in human-, rat-, and mouse-derived P. carinii. Sequence variation also existed in the DHPSs from human-derived isolates. Six nucleotide changes were found in 6 human isolates; each was nonsynonymous and resulted in an amino acid change. Several of these changes were in highly conserved regions and are similar to those that cause sulfa resistance in other organisms. These data suggest that the human-derived P. carinii DHPS may be evolving under positive selective pressure from sulfa drugs.     

Absence of human herpesvirus 8 and Epstein-Barr virus genome sequences in cutaneous epithelial neoplasms arising in immunosuppressed organ-transplant patients

Recent studies have implicated herpesvirus 8 and Epstein-Barr virus in the development of cutaneous malignancies in immunosuppressed patients. In order to examine the strength of this association, we examined 37 malignant, pre-malignant and benign cutaneous epithelial neoplasms removed from immunosuppressed organ recipients for the presence of human herpesvirus 8 and Epstein-Barr viral genome sequences using polymerase chain reaction (PCR) and in situ hybridization. We examined 2 actinic keratoses, 1 benign keratosis, 11 invasive squamous cell carcinomas, 17 squamous cell carcinomas in situ and 6 basal cell carcinomas. We also examined 4 basal cell carcinomas, 1 invasive squamous cell carcinoma and 3 squamous cell carcinomas in immunocompetent hosts. In contrast to findings reported by other investigators, we were unable to detect viral genome sequences in any of the biopsies examined. Our findings suggest that human herpesvirus 8 and Epstein-Barr virus likely do not play an etiologic role in cutaneous epithelial oncogenesis in immunocompromised patients.     

TP-9201, a glycoprotein IIb/IIIa platelet receptor antagonist, prevents rethrombosis after successful arterial thrombolysis in the dog

BACKGROUND AND PURPOSE: We examined the ability of TP-9201, a platelet glycoprotein IIb/IIIa receptor antagonist, to prevent carotid artery rethrombosis in the anesthetized dog. METHODS: Occlusive thrombosis was induced by electrolytic injury of the left carotid artery. Thirty minutes later, 0.05 U/kg of anisoylated plasminogen streptokinase activator complex (APSAC) was infused locally to achieve clot lysis. Carotid artery recanalization was followed immediately by the infusion of either saline (10 mL/h, 240 minutes; n = 9), low-dose TP-9201 (120 micrograms/kg plus 3 micrograms.kg-1.min-1, 240 minutes; n = 7), or high-dose TP-9201 (185 micrograms/kg plus 5 micrograms.kg-1.min-1, 240 minutes; n = 7). Ex vivo platelet aggregation responses to ADP or arachidonic acid were determined. RESULTS: TP-9201 produced complete inhibition of platelet aggregation in citrated platelet-rich plasma but a partial and dose-dependent inhibition in heparinized platelet-rich plasma. A twofold and eightfold increase in the template bleeding time was associated with the infusion of low-dose and high-dose TP-9201, respectively. There were frequent cyclic flow reductions in both the saline and low-dose TP-9201-treated groups after thrombolysis. However, the high-dose TP-9201-treated group exhibited a sustained flow with minimal evidence of cyclic flow reductions. At the conclusion of the protocol, patent vessels were found more frequently in the high-dose TP-9201 (5/7; P = .0048) than in the low-dose TP-9201 treatment group (2/7; P = .17) when compared with the saline group (0/9). Infusion of high-dose TP-9201 was associated with a significant reduction in the thrombus mass as compared with the control vessels. CONCLUSIONS: Administration of TP-9201 in conjunction with successful thrombolysis inhibited ex vivo platelet aggregation and prevented rethrombosis of the canine carotid artery. This study demonstrates that TP-9201, an inhibitor of the platelet GPIIb/IIIa receptor, can inhibit platelet-vessel wall interaction and thus prevent rethrombosis.