Cold: A risk factor for stroke?

A retrospective study was performed to investigate seasonal variation in stroke incidence and to evaluate the hypothesis that cold might be a risk factor. Data were obtained from the central registry of the Hospital de S. João, Porto, Portugal, concerning 4048 patients consecutively admitted for cerebrovascular disease during a period of 33 months. Monthly admissions for stroke and its subtypes were related to mean values of ambient temperature using linear correlation. There was a strong inverse correlation between average temperature and total admissions for cerebrovascular disease (r = –0.72,P < 0.00005), intracerebral haemorrhage (r = –0.66,P < 0.00005), ischaemic stroke (r = –0.46, P = 0.007) and transient ischaemic attack (r = –0.41,P = 0.017). These correlations were independent of any seasonal variation in the number of hospital admissions due to all causes. No relation was found between temperature and subarachnoid haemorrhage. The rhythmometric analysis showed the presence of a statistically significant rhythm with an acrophase in the coldest months. These results support the hypothesis of stroke being a chronorisk disease to which cold might represent a triggering factor.     

Quantitative correlation between tetanus-induced decreases in extracellular calcium and LTP

Decreases in the extracellular calcium concentration ([Ca2+]o), induced by tetanization of the Schaffer collaterals in rat hippocampal slices, were measured by means of Ca2+-sensitive microelectrodes. The amount of long term potentiation (LTP) of the evoked field potentials, induced by this tetanus, was determined. A positive correlation was found between the amplitude of the tetanus induced decrease in [Ca2+]o and the amount of LTP that was elicited. The N-methyl-D-aspartate (NMDA) receptor antagonist 2-amino-phosphonovalerate decreased both the tetanus-induced decreases in [Ca2+]o and the amount of LTP that was induced. We conclude that the amount of Ca2+ that enters the cell during a tetanus is of major importance in the induction process of LTP.     

Specific mechanics for abutment uprighting

ABSTRACT General practitioners can use adjunctive orthodontics in preparation for complex comprehensive dental restorative procedures. Two orthodontic educators from opposite sides of the world explain and illustrate the biomechanics of controlled abutment uprighting. Solutions to the common mechanical and clinical problems are discussed.     

Membrane phosphoproteins of rat hippocampus: Sensitivity to tetanic stimulation and enkephalin

Hippocampal slices are electrically stimulated in the perforant path with a pulse-train, which can lead to long-term potentiation (LTP). Of the thus stimulated slices, subcellular fractions are prepared and used in an endogenous protein phosphorylation assay. A phosphoprotein band which was reported earlier to be sensitive to electric stimulation as well as to methionine-enkephalin is now further analyzed: it consists of two phosphoproteins only slightly differing in molecular weight: 50,000 Mr (50 K) and 52,000 Mr (52 K), but having distinct biochemical properties and subcellular localization. Their IEP is dissimilar (3.5-4.3 and 5.3, respectively), they display different sensitivity towards calcium when tested in the phosphorylation assay, but are both cAMP-independently phosphorylated. Only one of them responds to tetanic stimulation with an increased phosphorylation post hoc. This protein, the 52 K component, is localized in synaptic membranes. Moreover, this protein also responds to incubation of slices with methionine-enkephalin. The phosphorylation of the 50 K component is not influenced by electric stimulation, nor by incubations with neuropeptides; its phosphorylation takes place in material sedimenting with the mitochondrial cell fractions and is strongly calcium- and calmodulin-dependent.     

Comparative multicentre trial of three IUDs inserted immediately following delivery of the placenta

A multinational comparative trial of three IUDs (Copper 7, Lippes loop size D and the Postpartum T) randomly inserted immediately following delivery of the placenta was conducted in six centres. A total of 841 women entered the study. As the predetermined termination indices for expulsions were exceeded at six months the trial was prematurely closed. An excess of expulsions during the first 48 hours following insertion was observed for the Lippes loop compared to the other devices. At six months the expulsion rate for the Lippes loop was significantly higher than that for the Copper 7. In addition, the discontinuation rate for the Lippes loop at 12 months was significantly higher than that for the Copper 7. There were no significant differences in either the expulsion rates or the discontinuation rate at six or twelve months between the postpartum T and the other devices. At 12 months the pregnancy rates with all three devices was high; there were no ectopic pregnancies. Considerable between-centre differences were observed, particularly for expulsion rates. Possible reasons for this are discussed and future research lines are suggested.     

Influence of axiopulpal line angle and proximal retention on fracture strength of amalgam restorations.

Proximal retentive grooves significantly increase the strength of amalgam restorations in Class II cavities. There were no remarkable differences that could have clinical significance between sharp or rounded axiopulpal line angles and rounded or rounded and sloped pulpal walls. Chromium-cobalt dies are effective for tests of fracture strength of amalgam restorations.