Aluminium maltol–induced neurocytoskeletal changes in fetal rabbit midbrain in matrix culture

We have developed a neuronal culture system to evaluate the neurotoxic effects of aluminium maltol on fetal rabbit midbrain sections containing the oculomotor nucleus. Cultures were treated with 5, 7, 9, 11, 13 and 15 mumol/l aluminium maltol or 39 and 45 mumol/l maltol (molal equivalents to 13 and 15 mumol/l aluminium maltol). Control cultures were maintained in nutrient medium alone. Silver-positive neuritic swellings and occasional perikaryal neurofibrillary tangles were observed in cultures treated with 11, 13 and 15 mumol/l aluminium maltol. The number of tangles (involved neurons) produced in aluminium maltol treated cultures were counted and compared to (untreated) controls. We observed a total of 3, 7 and 7% of involved neurons following treatment with 11, 13 and 15 mumol/l aluminium maltol respectively, and none in the control group. By immunohistochemistry, neurofibrillary tangles were immunoreactive with MAbs to phosphorylated (SMI-31), non-phosphorylated, phosphorylation dependent (SMI-32) and phosphorylation independent (SMI-33) epitopes of the high (-H) and middle (-M) molecular weight neurofilament subunits (NF-H/M). By contrast these lesions were nonreactive with MAbs recognizing tau, MAP2 or different beta-tubulin isotypes. The perikaryal tangles consisted of focal accumulations of 10 nm straight filaments by electron microscopy. These findings are in agreement with previous data from rabbit in vivo studies after the administration of aluminium maltol intravenously (Bertholf et al., 1989) or intraventricularly (Katsetos et al., 1990). Using this in vitro system, aluminium-induced neurofibrillary tangles can be consistently produced, and changes in the distribution of neurofilament proteins evaluated. These studies may aid in the assessment of the possible role of aluminium in the aetiology of human neurodegenerative disorders.     

Peripheral Leukocyte Kinetic Studies of Acute Leukemia in Relapse and Remission and Chronic Myelocytic Leukemia in Blastic Crisis

Peripheral blood leukocyte dynamics were investigated in a group of patientswith acute leukemia both in relapse and remission and in chronic granulocyticleukemia in blastic crisis. In acute leukemia in relapse and in chronic granulocytic leukemia in blastic crisis, labeled blast cells appeared promptly with apeak at one to two days. Secondary peaks occurred 40-70 hours following thefirst peaks with labeled blasts usually the predominant labeled cell in bothpeaks. The time interval between these successive waves of labeled blastscould represent a generation time. The leukocyte specific activity patterns obtained in patients in blastic crisis resembled some of the patterns of patientswith acute leukemia.

The leukocyte kinetic patterns in patients with acute leukemia consideredto be in complete remission were usually normal. However, in some patientsin bone marrow remission only, an abnormal early peak was present usuallycomposed of labeled abnormal cells released early into the peripheral circulation. In the presence of a known leukemic infiltrate, alteration of the normalleukocyte kinetic curve apparently depended upon release of these leukemiccells into the circulating blood.

Submitted on August 29, 1967 Accepted on November 8, 1967     

Chemical synthesis of phosphoseryl-phosphoserine,a partial analogue of human salivary statherin,a protein inhibitor of calcium phosphate precipitation in human saliva

Human salivary secretions are supersaturated with respect to basic calcium phosphates but spontaneous precipitation of these salts from saliva, or surface-induced precipitation of calcium phosphates onto dental enamel, does not normally occur. This unexpected stability has been attributed to the inhibitory activities of two kinds of salivary phosphoproteins: statherin and the acidic, proline-rich phosphoproteins (PRP). Investigation of the structure-function relationships of statherin, the most potent inhibitor of primary (spontaneous) and secondary (seeded) precipitation of calcium phosphate salts in human saliva has been limited to studies of peptide segments obtained from the native peptide by specific proteolysis. Solid phase peptide synthesis (SPPS) is a useful and potentially more flexible alternative. Phosphoserine residues (positions 2 & 3) play critically important roles in the precipitation-inhibition activities of statherin, but SPP synthesis of these phosphorylated peptides is precluded because of the instability of phosphoserine residues in the presence of HF. Thus, this peptide was synthesized by solution-phase methods. The dipeptide possessed substantial inhibitory activity in assays for inhibition of both primary and secondary precipitation of calcium phosphate salts, but was not as active as either N-terminal tryptic hexapeptide of statherin or intact statherin. Syntheses of other model phosphorylated peptides are underway to expand the structure-function relationships.     

The Use of the Balloon-Tipped Floating Catheter in Temporary Transvenous Cardiac Pacing

The effectiveness and safety of balloon-tipped, flow guided, electrodes for ventricular pacing as opposed to the fluoroscopy-guided semi-rigid bipolar electrodes have never been compared in a controlled study. A prospective study was therefore undertaken to compare both techniques in semi-elective and emergency procedures. Flow guided electrodes were inserted in 67 patients (group A) and semi-rigid electrodes in 44 patients (group B). The results of group A were judged to be superior to those of group B in four aspects: a) shorter time (6'45" vs. 13'30", p less than 0.0005); b) lower incidence of catheter displacement (13.4 vs. 32.0 percent, p less than 0.05); c) longer interval of time between implantation and catheter displacement (4.4 vs. 1.9 days, p less than 0.0005); d) lower incidence of serious ventricular arrhythmias during insertion (1.5 vs. 20.4 percent, p less than 0.005). Threshold at insertion was not significantly different (0.6 +/- 0.3 vs 0.7 +/- 0.2 milliampere). The superiority of flow-guided electrodes over fluoroscopy-guided electrodes persisted in the comparison of semielective insertions in groups A and B. We conclude that the flow-guided insertion technique is safer, more expeditious and more stable than the fluoroscopy-guided technique in semi-elective as well as in emergency insertions.     

Disposition of diazepam in young and elderly subjects after acute and chronic dosing

1. The pharmacokinetics of diazepam were examined in seven young (20–30 years) and six elderly (60–75 years) males prior to and also after chronic oral dosing of diazepam.
2. Following intravenous administration, the half-life and volume of distribution of ¹⁴C-labelled diazepam in the elderly were approximately twofold greater than corresponding estimates in younger subjects (mean ±s.d., 71.5±27.6 vs 44.5±16.5 h and 1.39±0.32 vs 0.88±0.30 1 kg⁻¹, respectively). Clearance did not differ between the two groups (0.26±0.09 vs 0.29±0.09 ml min⁻¹ kg⁻¹).
3. The accumulation of diazepam and its major metabolite, desmethyldiazepam, were extensive during chronic administration. A radioreceptor assay that measured total benzodiazepine activity, including diazepam and its active metabolites, indicated that the accumulation of ‘benzodiazepine equivalents’ was similar to the sum of the accumulated diazepam and desmethyldiazepam concentration levels. However, the level of ‘benzodiazepine equivalents’ on multiple-dosing was about double that of the predicted steady-state ‘equivalent’ concentration from single-dose studies. This was due to the insensitivity of the radioreceptor assay for desmethyldiazepam following single-dose diazepam administration.
4. There were no age- or dosing-related differences in diazepam clearance (0.37±0.22 vs 0.32±0.18 ml min⁻¹ kg⁻¹, young vs elderly, single-dose; 0.37± 0.11 vs 0.27±0.12 ml min⁻¹ kg⁻¹, young vs elderly, multiple-dose) and no age-related differences in the levels of accumulated ‘benzodiazepine equivalents’ (243.7±60.1 vs 288.0±125.8 ng ml⁻¹, young vs elderly).