Cytogenetic effects on lymphocytes in osteoporotic patients on long-term fluoride therapy

The genotoxicity of fluoride in vivo in seven patients with osteoporosis was cytogenetically investigated. The patients were treated with fluoride-containing formulations (disodium monofluorophosphate and sodium fluoride) for a period of 15 months up to 49 months. Fluoride intake ranged from 22.6-33.9 mg F/day and serum fluoride concentrations were between 0.1 mg F/l and 0.2 mg F/l. Peripheral blood lymphocytes of these patients were cultured in vitro and examined for chromosomal aberrations, micronuclei in cytokinesis-blocked binucleated lymphocytes as well as cell cycle progression. When a comparison was made between patients' group and a matched control group, it was found that fluoride at the tested concentrations had no detectable genotoxic potential in human.     

Effects of cardiovascular disease on driving tasks

Heart disease, even in the elderly individual, need not preclude driving; however, safety for the patient and the public is dependent on close cooperation between the patient and the physician. The patient with ischemic heart disease must be in a stable condition wherein the risk of sudden incapacitation is acceptably low. The physician must take into consideration not only the symptom history, but also the potential impact of concomitant illnesses, devices (e.g., pacemakers), and medications. The patient with congestive heart failure must be assessed for functional ability. Where there is doubt about a subjective report, a practical road test may be advisable. Consideration also should be given to limited driving under preset conditions, such as daytime only, or local roads (excluding highways). Many elderly drivers already limit their driving in such a fashion. Finally, it should be realized that a driving permit is a means to independent mobility. Where heart disease precludes driving and personal transportation is not available, physicians should advise and support their patients to obtain paratransport services where communities offer such services for otherwise immobile citizens.     

A nonexchangeable apolipoprotein E peptide that mediates binding to the low density lipoprotein receptor

ApoE is a 34-kDa apoprotein that mediates lipoprotein binding to the low density lipoprotein (LDL) receptor and to the LDL receptor-related protein. Receptor binding is mediated by a highly basic, alpha-helical sequence of approximately 15 amino acids that interacts with cysteine-rich repeat regions of the receptor. To determine the relationship between the receptor binding and lipid associating properties of apoE, we have synthesized a series of apoE peptides containing all (residues 129-169) or part (residues 139-169, 144-169, and 148-169) of the receptor-binding domain. The lipophilicity of these peptides was increased by modification of their N termini by acylation with either palmitic acid (C16-apoE peptide) or the N,N-distearyl derivative of glycine (diC18-Gly-apoE peptide). The unmodified peptides demonstrated low affinity for lipid surfaces (Kd > 10(-5) M) and moderate alpha-helicity in the presence of lipid (40%) and had no effect on LDL uptake by fibroblasts. N-Palmitoyl peptides had increased affinity for lipid (Kd approximately 10(-6) M) and increased alpha-helicity (55%) in the presence of lipid. The addition of the C16-apoE-(129-169)-peptide to 125I-LDL enhanced its uptake and degradation by fibroblasts 8-10-fold; however, < 50% of the degradation was mediated by the LDL receptor. By contrast, the diC18-Gly-apoE-(129-169)-peptide was essentially nonexchangeable (Kd < or = 10(-9) M) and highly helical (78%) in the presence of lipid. The addition of the diC18-Gly-apoE-(129-169)-peptide to 125I-LDL enhanced the specific uptake and degradation of LDL by both LDL receptor-mediated and non-LDL receptor-mediated mechanisms. Uptake and degradation of methylated LDL containing diC18-Gly-apoE-(129-169) revealed that the lipoprotein-bound peptide is the active agent. In agreement with this finding, a mutant diC18-Gly-apoE peptide (Arg142-->Gln) was much less effective than the wild-type peptide in potentiating binding, uptake, and degradation of 125I-LDL. Complexes of diC18-Gly-apoE-(129-169), apoA-I, and 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine containing four to six copies of the peptide/particle displayed an affinity for the LDL receptor similar to that of apoE-L-alpha-dimyristoylphosphatidylcholine discs containing four copies of apoE.(ABSTRACT TRUNCATED AT 400 WORDS)     

Ultrastructural studies of platelet aggregates from human subjects receiving clopidogrel and from a patient with an inherited defect of an ADP-dependent pathway of platelet activation

Our study investigated the effect of the antithrombotic drug clopidogrel (75 mg/d for 7 days) on the ultrastructure of platelet aggregates induced by ADP or 2-methylthio-ADP (2-MeS-ADP) in citrated platelet-rich plasma and examined the activation state of the GP IIb/IIIa complexes. Results were compared with those obtained for patient M.L., who has a congenital disorder characterized by a reduced and reversible platelet response to ADP. When untreated normal platelets were stimulated with high-dose ADP, electron microscopy revealed large and stable aggregates often surrounded by a layer of what appeared to be degranulated platelets. The reversible aggregates of platelets from subjects receiving clopidogrel or from patient M.L. did not show this layer. Electron microscopy showed that in both situations, the aggregates were composed of loosely bound platelets with few contact points. Immunogold labeling of ultrathin sections of Lowicryl-embedded aggregates formed by ADP or 2-MeS-ADP showed a much decreased platelet surface staining by (1) a polyclonal anti-fibrinogen antibody and (2) AP-6, a murine anti-ligand-induced binding site monoclonal antibody specific for GP IIb/IIIa complexes occupied with fibrinogen. Similar findings were seen after disaggregation, when many single platelets were present that showed no signs of secretion. Flow cytometry confirmed that the number of ligand-occupied GP IIb/IIIa complexes was much lower on platelets stimulated with ADP or 2-MeS-ADP after clopidogrel treatment. As expected from previous studies, ADP-induced platelet shape change and Ca2+ influx were unaffected by clopidogrel. These results agree with the hypothesis that platelet activation by ADP is biphasic and highlight a receptor-induced activation pathway affected by clopidogrel (or congenitally impaired in patient M.L.) that is necessary for the full activation of GP IIb/IIIa and the formation of stable macroaggregates.     

Recombinant natural killer enhancing factor augments natural killer cytotoxicity

An 18-year-old schizophrenic female was recently treated after overdosing on trihexyphenidyl, thioridazine and an unknown antidepressant. On presentation to a local hospital, she was cyanotic with dilatated pupils and in acute respiratory failure. She was intubated prior to transfer. While in our Emergency Department, she exhibited occasional premature ventricular contractions which later became intermittent torsade de pointes. As this was an anticholinergic overdose we infused sodium bicarbonate in an attempt to increase protein binding, hoping to decrease the concentration of toxic metabolites. We also tried to suppress the dysrhythmia by infusing magnesium. The potassium level was borderline low so a supplemental infusion was initiated. Defibrillation was attempted. To try to shorten the action potential duration by activating the K+ channel, an isuprel infusion was also attempted. All methods failed. The patient fluctuated between an irregular sinus rhythm with prolonged QT interval and pulseless torsade de pointes for almost 24 hours. At all times, she responded appropriately to pain. Finally we attempted blockade of the calcium channel using verapamil with dramatic results. Each single bolus (0.1 mg/kg) successfully converted the patient back to sinus rhythm for some 15-20 minutes before the torsade recurred. After the initiation of a continuous verapamil infusion (0.005 mg/kg/hr), the patient remained in stable sinus rhythm. Verapamil proved highly effective in this patient with an anticholinergic overdose induced dysrhythmia.     

Activated oxazaphosphorines are transported predominantly by erythrocytes

PURPOSE: Oxazaphosphorines are metabolised by a variety of pathways, one of which leads to activation and the formation of alkylating compounds. However, the transport forms conveying activated oxazaphosphorines to the tumour cell have not been fully characterised. There is increasing recognition of the importance of the erythrocyte as a carrier of compounds in the circulation, and we have recently described higher concentrations of 4-hydroxycyclophosphamide within the erythrocyte compartment compared to plasma. We have now determined the concentrations of ifosfamide and seven of its metabolites in the plasma and erythrocytes of patients receiving a six-hour intravenous infusion of ifosfamide. PATIENTS AND METHODS: Red cells from five patients, receiving a total of eight cycles of ifosfamide, were separated from plasma using the MESED instrument, and analysis of red cells and plasma performed using Gas Chromatography-Mass Spectrometry (GC/MS). RESULTS: The concentration of all compounds in the erythrocyte compartment was higher than or equal to those in plasma, and isophosphoramide mustard and carboxyifosfamide showed a particular affinity for the erythrocyte. The red cell fraction can contain as much as 77% of the total blood concentration of isophosphoramide mustard. CONCLUSIONS: Erythrocyte associated isophosphoramide mustard is an important transport form of activated ifosfamide. Red cells may have a role in the delivery of activated oxazaphosphorines to tissues.