The ultrastructure of the lens capsule abnormalities in Alport''s syndrome

Chronic overexpression of the neurite growth-promoting factor S100beta has been implicated in the pathogenesis of neuritic plaques in Alzheimer's disease. Such plaques are virtually universal in middle-aged Down's syndrome, making Down's a natural model of Alzheimer's disease. We determined numbers of astrocytes overexpressing S100beta, and of neurons overexpressing beta-amyloid precursor protein (beta-APP), and assayed for neurofibrillary tangles in neocortex of 20 Down's syndrome patients (17 weeks gestation to 68 years). Compared to controls, there were twice as many S100beta-immunoreactive (S100beta+) astrocytes in Down's patients at all ages: fetal, young, and adult (p = 0.01, or better, in each age group). These were activated (i.e., enlarged), and intensely immunoreactive, even in the fetal group. There were no neurofibrillary changes in fetal or young Down's patients. The numbers of S100beta+ astrocytes in young and adult Down's patients correlated with the numbers of neurons overexpressing beta-APP (p < 0.05). Our findings are consistent with the idea that conditions--including Down's syndrome--that promote chronic overexpression of S100beta may confer increased risk for later development of Alzheimer's disease.     

Effects of packaging SrI2(Eu) scintillator crystals

Recent renewed emphasis placed on gamma-ray detectors for national security purposes has motivated researchers to identify and develop new scintillator materials capable of high energy resolution and growable to large sizes. We have discovered that SrI₂(Eu) has many desirable properties for gamma-ray detection and spectroscopy, including high light yield of ∼90,000 photons/MeV and excellent light yield proportionality. We have measured <2.7% FWHM at 662 keV with small detectors (<1 cm³) in direct contact with a photomultiplier tube, and ∼3% resolution at 662 keV is obtained for 1 in.³ crystals. Due to the hygroscopic nature of SrI₂(Eu), similar to NaI(Tl), proper packaging is required for field use. This work describes a systematic study performed to determine the key factors in the packaging process to optimize performance. These factors include proper polishing of the surface, the geometry of the crystal, reflector materials and windows. A technique based on use of a collimated ¹³⁷Cs source was developed to examine light collection uniformity. Employing this technique, we found that when the crystal is packaged properly, the variation in the pulse height at 662 keV from events near the bottom of the crystal compared to those near the top of the crystal could be reduced to <1%. This paper describes the design and engineering of our detector package in order to improve energy resolution of 1 in.³-scale SrI₂(Eu) crystals.     

Scintillation properties of Cs2LiLaBr6 (CLLB) crystals with varying Ce concentration

Investigations of Ce³⁺-doped Cs₂LiLaBr₆ (CLLB) crystals show a systematic trend in their scintillation properties with varying Ce concentrations. The concentration studies provide input in the optimization of growth of the CLLB crystals. Scintillation properties viz. radioluminescence, energy resolution, light yield, decay times, and non-proportionality are discussed for samples from 0% to 20% Ce concentration.     

Somatostatin inhibits pancreatic exocrine secretion centrally via sympathetic nerves in conscious rats

Somatostatin is known to be a potent inhibitor of pancreatic exocrine secretion, but the mechanism of its effect is not fully understood. The mechanism of the inhibition by centrally administered somatostatin was examined in conscious rats. Rats were prepared with cannulae draining bile and pancreatic juice separately, and with a duodenal cannula, an extrajugular vein cannula and a cerebroventricular cannula. Somatostatin was injected into the left lateral ventricle, and the inhibitory mechanism was examined using vagotomized rats and various drugs that affect sympathetic neurons. Intracerebroventricular administration of somatostatin significantly inhibited pancreatic exocrine secretion stimulated by bile-pancreatic juice diversion. The inhibitory effect was not abolished by vagotomy, pretreatment with propranolol, but was abolished by pretreatment with hexamethonium or phentolamine. The plasma level of somatostatin after its intracerebroventricular administration increased 3-fold, but its intravenous infusion at a rate giving a similar plasma somatostatin level to that produced by its intracerebroventricular injection, had no significant effect on pancreatic secretion. These results suggest that somatostatin inhibits pancreatic exocrine secretion centrally via sympathetic efferent nerves and that alpha-adrenergic receptors have an important role in its inhibitory action.     

Further discussion on magnetic vector potential finite-elementformulation for three-dimensional magnetostatic field analysis

A linear soft-iron and current model called the IEE Japan model using a novel vector potential finite-element formulation is examined. Calculated and measured results are in close agreement. For comparison, the same model was calculated by the conventional variational formulation. The divergence of magnetic vector potential equals zero at the boundary of different materials and the values themselves are small enough at the Gaussian quadratural points, which means that uniqueness of the solution is guaranteed. The gauge condition is determined by the formulation, not by the boundary conditions. The new formulation requires less computing time and memory than the conventional variational formulation     

Clinical engineering worldwide

An overview is given of clinical engineering (CE) activities in Europe, North and South America, and the Far East. The discussion covers what CE is, its economics, in-house service centers, certification, life-support devices, support services for CE, European Community CE activities and directives, and CE trends. Medical equipment and technology management, human factors and quality assurance, increased regulations, new technologies and training, and computerization are also addressed     

A case of foramen magnum meningioma in which case enhanced three-dimensional CT scan was valuable for preoperative evaluation of the surgical approach

We report a case of foramen magnum meningioma in which case enhanced three-dimensional CT scan was valuable for preoperative evaluation of the surgical approach. A 53-year-old woman had suffered from stiffness and pain in the left occipital region and numbness of the left side of the face for about 2 years before admission. She had also weakness and numbness of the left side of her body for about 2 months before admission, and dysphagia and pain in the occipital region and in the posterior region of the neck produced by straining for about 1 month before admission. Neurological examination revealed left hemiparesis, and hypalgesia and tactile hypesthesia of the left side of the body, including the face. Plain X-P was normal. Enhanced CT scan and gadolinium enhanced MRI revealed a well-enhanced mass attached to the left anterolateral part of the foramen magnum. The left occipital condyle was observed at the lateral side of the attachment part of this mass. Angiography revealed tumor feeders from the meningeal branches of the left vertebral artery and the left ascending pharyngeal artery. Enhanced three-dimensional CT scan clearly showed that the tumor was attached to the left anterolateral part of the foramen magnum, that the left occipital condyle was at the lateral side of the attachment part of this mass and that the jugular foramen and jugular tubercle were situated superolateral to the attachment part of this mass. Considering these factors, we decided that removal of the posterior part of the left occipital condyle was necessary, but removal of the left jugular tubercle was not necessary for a good operative view from the left posterior lateral direction. The tumor was totally removed successfully and good results were obtained by the transcondylar approach without removal of the jugular tubercle. Histology of the tumor revealed meningothelial meningioma. In this case, preoperative evaluation with enhanced three-dimensional CT scan was helpful for deciding the surgical approach. With enhanced three-dimensional CT scan, it is easy to judge whether removal of the posterior part of the occipital condyle and/or the jugular tubercle is necessary for a good operative view, and we can get good images revealing the relationships between the tumor and surrounding structures. Preoperative evaluation with enhanced three-dimensional CT scan is very useful especially in this kind of situation.     

Characteristics of a Nonstoichiometric Gd3+δ(Al,Ga)5−δO12:Ce Garnet Scintillator

We have developed a new nonstoichiometric Gd_3+δ(Al,Ga)_5−δO₁₂:Ce garnet scintillator for an X-ray CT scanner. For commercially used scintillators, reproducible luminescence properties are of great importance. We have found that the afterglow properties of the garnet change drastically in the vicinity of the stoichiometric compositions. The most suitable properties are obtained at slightly excess (Gd,Ce) compositions from the stoichiometry. In order to investigate the afterglow properties, crystallography arrangements, phase equilibrium relationship between crystal phases, and luminescence characteristics of host material doped with different valence ions have been examined. The luminescence properties are explained by isoelectronic traps based on the difference in the electronegativity of the dopant and host ions, which would act as electron trap centers and hole trap centers within the band gap.     

Transcutaneous Blood Flow Measurement by Electromagnetic Induction

A new induction flowmeter which can measure the blood flow from the skin surface is discussed theoretically and experimentally. A pair of electrodes placed on the skin detect the EMF induced by the interaction of the blood flow and a magnetic field applied from outside the skin. The relation between the EMF and the flow rate, which is obtained theoretically, is also confirmed experimentally within the error of 10 percent.