1,25 dihydroxyvitamin D(3) activates sphingomyelin turnover in ROS17/2.8 osteosarcoma cells without sphingolipid-induced changes in cytosolic Ca(2+).

1,25-Dihydroxyvitamin D(3) [1,25(OH)(2)D(3)] initiates the hydrolysis of sphingomyelin in ROS 17/2.8 osteosarcoma cells with the resultant generation of cell-associated ceramide. Increases in ceramide levels were detectable at 15 min and maximal one hour after exposure of cells to 1,25(OH)(2)D(3). Neither 1,25(OH)(2)D(3) nor exogenous ceramide elicited a change in cytosolic free Ca(2+) ([Ca(2+)](i)). Transient elevations in [Ca(2+)](i) were observed when cells were exposed to exogenous sphingosine, but there was no detectable conversion of ceramide to sphingosine in 1, 25(OH)(2)D(3)-treated cells. Ceramide also did not stimulate Ca(2+) uptake across ROS 17/2.8 cell plasma membranes. Collectively, these results suggest that 1,25(OH)(2)D(3) activates sphingomyelin turnover in ROS 17/2.8 osteosarcoma cells but that the sphingolipid metabolite ceramide is not responsible for 1,25(OH)(2)D(3)-induced activation of plasma membrane Ca(2+) channels.

Redesigning nucleic acids.

A research program has applied the tools of synthetic organic chemistry to systematically modify the structure of DNA and RNA oligonucleotides to learn more about the chemical principles underlying their ability to store and transmit genetic information. Oligonucleotides (as opposed to nucleosides) have long been overlooked by synthetic organic chemists as targets for structural modification. Synthetic chemistry has now yielded oligonucleotides with 12 replicatable letters, modified backbones, and new insight into why Nature chose the oligonucleotide structures that she did.

Mineralization of bone-like extracellular matrix in the absence of functional osteoblasts.

When grown in medium containing ascorbic acid and beta-glycerol phosphate, mouse MC3T3-E1 cells express an osteoblast phenotype and produce a highly mineralized extracellular matrix. The purpose of this study was to independently examine the role of the collagenous matrix and functional osteoblasts on the mineralization process. Cultures with and without an extensive collagenous matrix were prepared by growing MC3T3-E1 cells in the presence and absence of ascorbic acid. Matrix-rich cultures mineralized at much lower calcium phosphate ion products than nonmatrix cultures. At higher ion products, spontaneous precipitation in the medium and cell layers of nonmatrix cultures were observed. In contrast, mineral in matrix-rich cultures was still exclusively associated with collagen fibrils and not with ectopic sites in the cell layer or medium. To examine the effect of cell viability on matrix mineralization, cells were grown 8 or 16 days in the presence of ascorbic acid, then killed and incubated in a mineralizing medium. Significant mineralization was not observed in the collagenous matrix of 8-day killed cultures or age-matched controls. At 16 days mineral was associated with collagen fibrils at specific foci in the matrix of both viable and killed cultures. This observation is consistent with the concept that collagenous matrices must undergo a maturation process before they can support a mineral induction and growth. It further shows that osteoblast-like cells are not required for mineralization of mature matrices, but are required for matrix maturation.

Hemodynamic effects of intermittent pneumatic compression of the lower limbs during laparoscopic cholecystectomy.

BACKGROUND: The effects of surgical pneumoperitoneum on lower-limb venous hemodynamics have already been studied; however, the effects of intermittent compression boots are not known in such venous-stasis conditions. METHODS: In 12 volunteers and 12 patients, the venous hemodynamic effects of intermittent leg compression were studied under external abdominal pressure or during laparoscopic cholecystectomy, respectively. Femoral venous diameter and velocity were measured. Venous pressure was monitored during the surgical procedures. RESULTS: External abdominal pressure of 50 mm Hg and pneumoperitoneum were found to increase the diameter (17% in the volunteers and 14% in the patients) and decrease peak velocity (49% and 32%, respectively) in the femoral vein. Femoral pressure was increased (106%) during pneumoperitoneum. In both venous-stasis circumstances, intermittent compression of the legs restored venous flow velocity, but had no effect on vessel diameter and pressure. CONCLUSIONS: The lower-limb venous hemodynamic changes were similar during external abdominal pressure or pneumoperitoneum, and the flow velocity decrease was intermittently reversed by pneumatic compression boots.

Thrombolytic therapy compared with mechanical recanalization in non-acute peripheral arterial occlusions: a randomized trial.

PURPOSE: To evaluate whether thrombolytic therapy followed by angioplasty has any added benefit compared with angioplasty alone for the treatment of chronic peripheral arterial occlusions. PATIENTS AND METHODS: Twenty patients with claudication or limb-threatening ischemia of at least 3 weeks duration due to iliac or femoropopliteal artery occlusions were randomized either to thrombolytic therapy with recombinant tissue-type plasminogen activator for up to 4 hours (n = 11) followed by angioplasty or to angioplasty alone (n = 9). Clinical follow-up was obtained for 1 year. RESULTS: Life-table analysis revealed a significant improvement in the cumulative primary patency rate for patients with claudication treated initially with thrombolysis followed by angioplasty (n = 7; 86% at 6 months; 51% at 1 year) compared with angioplasty alone (n = 9; 11% at 6 months and 1 year) (P < .02). All four patients with limb-threatening ischemia were randomized to thrombolytic therapy, and none exhibited continued patency at 1 year. The most common complication in the thrombolysis group was peripheral embolization; three of these four patients were among those who had limb-threatening ischemia as the indication for entry into this study. There was no increased incidence of bleeding with thrombolytic therapy. CONCLUSIONS: A short course of thrombolytic therapy prior to angioplasty appears to improve the 1-year patency rate for claudication due to iliac or femoropopliteal occlusions. However, patients with limb-threatening ischemia have a high prevalence of peripheral embolization and dismal patency rates with this form of therapy. A larger scale study is necessary to confirm these findings.

D-dimer plasma measurement in patients undergoing major hip surgery: use in the prediction and diagnosis of postoperative proximal vein thrombosis.

Plasma D-Dimer (DD), a highly sensitive marker of venous thromboembolism, was measured with an ELISA assay preoperatively and on the 12th postoperative day in 173 patients undergoing major hip surgery (78 elective arthroplasties and 95 operations for fractures). Proximal deep venous thrombosis (DVT) was detected by systematic compression venous ultrasonography on the 12th postoperative day in 12 (7%) patients. In one additional case, proximal DVT was diagnosed by venography. Preoperative DD level was significantly higher in patients with fracture than in patients undergoing elective arthroplasty. At a cutoff of 500 micrograms/L as determined by ROC curve analysis, the sensitivity, specificity, positive and negative predictive values of the pre-operative DD concentration for the development of subsequent proximal DVT were 93%, 23%, 36% and 96%, respectively. The diagnostic exclusion value of the DD measurement on the 12th postoperative day was similar but for a cutoff of 2000 micrograms/L. These data suggest that plasma DD measurement might be useful to predict and diagnose proximal DVT following major hip surgery.

Laboratory and clinical features in systemic lupus erythematosus patients with or without anticardiolipin antibodies.

The purpose of this study was to investigate whether the presence of anticardiolipin antibodies (aCL) in systemic lupus erythematosus (SLE) patients was associated with particular laboratory or clinical features. Anticardiolipin antibodies were determined in 63 unselected SLE patients: 32 (50.8%) were found to be aCL positive and this positivity was significantly associated with the presence of lupus anticoagulant (p less than 0.003) and false positive VDRL reaction (p less than 0.001), but not with other haematological or biological markers. Thrombin-antithrombin III (TAT) complexes were found to be increased with disease activity, but no relationship was found between TAT complexes and the presence or absence of aCL. In this study a statistically significant association was found between aCL positivity and arterial thromboembolic events, but not with venous thrombotic complications. In summary half of SLE patients had aCL and the presence of these antibodies was associated with other antiphospholipid antibodies and with arterial thromboembolic events.

Respirability, microstructure and filler content of composite dusts.

Dusts were generated from five composites, with two different shades each. Between 54 and 70 mass percent of the dust (60 to 92% of the particles) collected was respirable. The average particle size collected was 3.97 microns by mass (0.9 microns by number of particles). Between 14 and 22% of the dust generated was respirable. Filler content of the respirable dust particles was within 3 mass percent of the amount of filler in each cured composite. Powder x-ray diffraction revealed that respirable dust particles collected from composites reported to contain crystalline silica fillers contain the same crystalline silica. The results indicate that improperly protected dental personnel who are regularly exposed to composite dusts generated during high-speed finishing of composites containing quartz filler may be at risk for developing silicosis. Dental personnel should wear masks specifically designed to filter respirable silica when finishing composite restorations with high-speed instrumentation.

Anticardiolipin antibody determination: comparison of three ELISA assays.

The aim of this study was to compare two commercial kits (A and B) with our our own assay (C) for the determination of anticardiolipin antibodies (aCL). In 42 controls no subject was found to be aCL positive with kit A, seven were aCL positive with kit B and 1 with assay C. In 61 patients, the results were as follows: 50.8% aCL positivity for A, 57.4% for B and 50.8% for C. Only 57.3% of the patients were either positive (20 patients) or negative (15 patients) in the three tests. As for controls the concordance in patients was better between kit A and assay C than between kit B and assay C. Another group of patients with high IgM blank values in assay C were selected; when their blank values as measured with the kits were subtracted, 40% of the aCL positive patients with kit A became negative. In summary this comparison indicates that aCL positivity may vary according to the assay used and that non-specific binding may lead to false positive results.

Protein C deficiency and pregnancy: a case report.

Protein C is thought to play a key role in the regulation of hemostasis, and its deficiency has been associated with an increased risk of thromboembolism. Protein C-deficient women are at particular risk of developing thromboembolic complications during pregnancy and delivery. The incidence of thromboembolic events is estimated to be 500-1000 times higher than in normal women. We report the case of a 26-year-old woman with previous iliofemoral deep vein thrombosis who experienced a successful pregnancy and delivery despite severe congenital protein C deficiency (protein C antigen and activity 25%). She was anticoagulated with heparin during the second part of her pregnancy. Our observation suggests that ambulatory full-dose subcutaneous heparin therapy during pregnancy constitutes adequate prevention. However, definite guidelines will require more extensive studies.

[Prolonged anticoagulation following chlorophacinone poisoning]. / Anticoagulation prolongée lors d'une intoxication à la chlorphacinone.

In 1985 and 1986 the Swiss Toxicologic Information Center registered 152 cases of rodenticide poisoning. Among those substances chlorophacinone, an indanedione derivative, has a prolonged antivitamin K effect. We report here the case of an eighteen-year-old female hospitalized 3 days after deliberately ingesting some 100 mg chlorophacinone. Her Quick time at admission was less than 10% (Prothrombin time 79 sec., normal control 12 sec.). Under high dose vitamin K therapy the Quick was rapidly corrected but fell again on each vitamin K withdrawal. In a search for a relation between the variations of prothrombin time and chlorophacinone plasma levels, these were assessed by HPLC. Prothrombin time (and vitamin K dependent factors VII and X) finally normalized only 7 weeks after chlorophacinone ingestion. Clinical condition remained satisfactory throughout and other biological parameters unaffected. This case emphasizes the need for prolonged clinical and laboratory follow-up for rodenticide intoxications and for vitamin K administration for several weeks.

[Bernard-Soulier syndrome in a Swiss family]. / Syndrome de Bernard-Soulier dans une famille suisse.

We report the case of a 38-year-old woman with hemorrhagic diathesis. Since early childhood she has suffered from epistaxis, gingival bleeding, ecchymoses and, since puberty, very frequent menorrhagia. Prolongation of bleeding time and thrombocytopenia (100,000 platelets/microliter) with giant platelets were observed. Since idiopathic thrombopenic purpura was suspected, splenectomy was performed. Neither this nor steroid treatment caused any improvement. The patient was able to give birth to an unaffected child, but delivery was followed by a major hemorrhage. In 1986, hysterectomy was considered because of frequent menorrhagia and, therefore, the patient's hemostasis was reinvestigated. The aforementioned abnormalities were confirmed and complementary examinations by electron microscope revealed giant platelets without granular abnormalities. While von Willebrand factor was normal, ristocetin agglutination was defective and analysis of platelet membrane glycoproteins showed absence of glycoprotein Ib. - These observations prompted the diagnosis of Bernard-Soulier syndrome. The study of the family demonstrated that 6 family members were heterozygote. This is believed to be the first large Bernard-Soulier family reported in Switzerland.

Proteolipid and collagen calcification, in vitro.

Initiation of in vitro calcification with insoluble type I collagen appears to be a function of tightly-bound proteolipid. The collagen preparation calcified during incubation in a metastable calcium phosphate solution before but not after lipid extraction. Calcifiability of the extracted lipid, similarly incubated, was restricted to the proteolipid fraction.

Characterization of calcifiable proteolipid from Streptococcus mutans.

Proteolipid is known to initiate calcification in vitro. Apoprotein and phospholipid components of proteolipid from five of 14 calcifiable S. mutans specimens were characterized. The apoproteins contained 16 amino acids with calculated percent polarities ranging from 32.0 to 45.2. The acidic phospholipids were cardiolipin, mono- and diphosphoinositides, and phosphatidylserine. Neutral lipids, phosphatidylethanolamine and phosphatidylcholine, were also found. The latter were the most abundant in all isolates. Appropriate hydrophobic proteins and acidic phospholipids in the proteolipids accounted for S. mutans calcifiability.

Magnesium inhibition of apatite nucleation by proteolipid.

The effect of magnesium on apatite nucleation by Bacterionema matruchotii proteolipid was determined. The ion, in metastable calcium phosphate solution at a concentration that did not reduce proteolipid calcium binding, prevented apatite crystallization. The data were compared with those involving magnesium and homogenous nucleation of apatite in vitro.

Intracellular crystal formation in bacteria from human urines: a contributing factor in urinary calculi.

Understanding of the bacterial contribution to urinary calculi has been limited to those organisms capable of altering the urine through urease activity. Sterilized urines from stone forming and non-stone forming individuals were inoculated with bacteria having either strong, weak, or no urease activity. All organisms grown in unbuffered urines produced crystallization (calcite or apatite) as demonstrated by X-ray diffraction. Bacteria grown in conventional medium (Heart Infusion broth) did not demonstrate crystal formation. Unstained specimens revealed electron-dense deposits within bacteria grown in urine. Deposits were not present in organisms grown in conventional media. Analysis revealed increased levels of calcium within these deposits as compared to extracellular levels. These findings support the hypothesis that both urease producing an non-urease producing organisms may accumulate calcium crystals intracellularly and form nidi for calculus formation.