Method for estimating the intensity of scattered radiation using a scatter generation model

An analytical formula for estimating the intensity of scattered radiation in an x-ray image under various exposure conditions has been developed. The formula was derived using measured data of scatter and primary intensity for various exposure conditions. To simplify the formula, a scatter generation model was constructed mathematically which assumes that the scattered fluence in a material depends on three processes: (1) scattering of the primary photons; (2) scattering of previously scattered photons; and (3) attenuation of the scattered photons. Using this model, the dependence of scatter-to-primary ratio on phantom thickness and the tube voltage was expressed by a simple equation. Parameters included in the model were determined from the analysis of measured data. Based on empirical data, it was assumed that the dependence of scatter-to-primary ratio on air gap and field size is not affected by variations of phantom thickness and tube voltage. The final formula, which does not include the term of phantom thickness, gives an estimate of the intensity of the scattered radiation from exposure conditions. The scatter intensity estimated using the formula was compared with measured data for various phantom thicknesses, tube voltages, air gaps, and field sizes; the results show that the intensity of scattered radiation can be estimated within about +/- 10% using predetermined parameters.     

Age-dependent changes in noradrenergic innervations of the frontal cortex in F344 rats

Noradrenergic innervations of the frontal cortex with advancing age (9, 13 and 25 months) in male F344 rats were quantified by immunohistochemistry for dopamine-beta-hydroxylase (DBH), which is a marker enzyme for noradrenergic axons. The density of DBH-positive axons, varicosities (swellings along an axon from which noradrenaline is released), and the number of varicosities per unit length of axon were measured in the frontal cortex. We found that the density of axons and varicosities significantly decreased at an earlier stage of aging (9-13 months), but not at a later stage (13-25 months). On the other hand, the number of varicosities per unit length of axon did not change with age. The result shows that the density of varicosities, which represent the synapses of noradrenergic neurons, decrease in the frontal cortex in the early aging process.     

Enamel mineralization and an initial crystalline phase

In this communication, we summarized our recent experimental approaches to an unsettled issue, i.e., the nature and role of an acidic precursor in enamel mineralization. The objectives we specially focused our attention on are: the composition, structure and high resolution images of enamel crystals at various developmental stages, thermodynamic and kinetic consideration of octacalcium phosphate (OCP) vs hydroxyapatite (HA) precipitation in physiological media simulating the enamel fluid, reversible changes in the composition and structure of OCP, effects of fluoride at low concentrations and enamel proteins on OCP hydrolysis, and adsorption of enamel proteins onto OCP and fluoridated hydrolysates at neutral pH and room temperature. On the basis of all experimental evidence, we propose that enamel crystal growth comprises two events: the two-dimensional growth of an OCP-like precursor in a narrow outermost zone adjacent to the ameloblasts and the subsequent overgrowth of apatite units on the template under discrete fluid environment in the underlying region distant from the cell layer. The experimental data also support the concept that the whole process of enamel mineralization is modulated substantially through interaction between enamel proteins and crystals including the acidic precursor.     

Eye movement-related activities in cells of the lateral suprasylvian cortex of the cat

Investigation of eye movement-related activities and photic responsiveness using behaving cats demonstrated distinctive representations of eye movement signals in different areas of the lateral suprasylvian cortex: visual reafference in the medial bank of the middle suprasylvian sulcus and non-visual signals (proprioceptive reafference or efference copy) in the lateral bank.     

Muscle spindle supply to the masticatory muscles in the Japane ermine (Carnivora).

Histological examination of the jaw muscles of the Japanese ermine showed that 4 jaw-closing muscles have 13 muscle spindles on one side of the face. The temporal muscle has 99 muscle spindles, 68 being in the anterior vertical and 31 in the posterior horizontal belly. The masseter muscle has 33 muscle spindles, 23 being in the profound and 10 in the superficial belly. The medial pterygoid muscle has 7 muscle spindles and the zygomaticomandibular muscle contains 4 muscle spindles. The lateral pterygoid and the jaw-opening muscles have no spindles.     

High Frequency of Antibiotic-Associated Diarrhea due to Toxin A-Negative, Toxin B-Positive Clostridium difficile in a Hospital in Japan and Risk Factors for Infection

Patients hospitalized in a hospital with a high incidence of antibiotic-associated diarrhea due to toxin A-negative, toxin B-positive (A–/B+) Clostridium difficile were retrospectively investigated to determine the clinical manifestations and risk factors for infection. Of 77 Clostridium difficile isolates obtained from 77 patients during the 1-year investigation period, 30 were A–/B+ and 47 were toxin A-positive, toxin B-positive (A+/B+). By pulsed-field gel electrophoresis analysis, 23 of the 30 A–/B+ strains were outbreak-related, suggesting nosocomial spread of a single type of bacterium, which mainly affected patients in the wards of respiratory medicine, hematology and neurology. Using regression analysis, three factors were found to be associated with infection by A–/B+ isolates: (i) exposure to antineoplastic agents (P=0.01, odds ratio [OR]=5.1), (ii) the use of nasal feeding tubes (P=0.008, OR=5.2), and (iii) assignment to a certain internal medicine ward (P=0.05, OR=3.0). Between patients with Clostridium difficile-associated diarrhea caused by A–/B+ strains and those with A+/B+ strains, no statistically significant difference was found in body temperature, serum concentration of C-reactive protein, leukocyte count in whole blood, frequency of diarrhea, or type of underlying disease. These results indicate that A–/B+ strains of Clostridium difficile can cause intestinal infection in humans and they spread nosocomially in the same manner as A+/B+ strains.     

TT病毒对干扰素的敏感性及其临床意义分析

目的 :探讨各种肝病 TTV- DNA阳性的临床意义 ,并对丙型慢性肝炎的干扰素疗效及 TT病毒对干扰素敏感性进行研究。方法 :利用半套式 PCR方法检测 TTV- DNA。结果 :TTV- DNA阳性者非甲～丙型急性肝病 4 0 .9%、乙型急性肝病 30 %、非甲～丙型慢性肝病 2 5 %、乙型慢性肝病 37.5 %、丙型慢性肝病 39.6 %。对丙型慢性肝炎进行干扰素治疗的 TTV- DNA阳性 10 1例病例和阴性 15 4例间的年龄、性别、AL T、肝组织学及 HCV- RNA量差异无显著性 ,干扰素治疗后的 AL T变化和 HCV- RNA的消长是一致的 ,和 TT病毒无关。结论 :TT病毒和丙型肝炎病毒重复感染的慢性肝炎患者 ,肝损伤的主要原因是丙型肝炎病毒 ,与 TT病毒关系不大     

A case of "interval" form of acute carbon monoxide poisoning--brain MRI and therapeutic effect of hyperbaric oxygenation

A 43-year-old female who had suffered from paranoid reaction attempted suicide with city gas. She was admitted to an emergency hospital in a comatose state, regained consciousness the next day and was discharged 12 days after. However, on the 21st day after the poisoning, behavioral anomalies and staggering appeared. She was readmitted into another emergency hospital with the diagnosis of an "interval" form of acute carbon monoxide poisoning. She was performed hyperbaric oxygen therapy 42 times until the 53rd day after the accident. Nevertheless, her symptoms did not improve and remained in a state like an apallic syndrome. With little promise of improvement, she was moved to our hospital, and hyperbaric oxygen therapy further continued for 40 times which resulted in a remarkable recovery. Repeat EEGs were performed. On the 32nd day, EEG showed an abnormality consisting of generalized delta waves. On the 56th day, the abnormal EEG improved slightly with more alpha activity. EEG was normalized 126 days after. The X-ray CT scan on the 32nd day revealed low densities in the bilateral globus pallidus and the deep white matters adjacent to the frontal horns of the lateral ventricle and in the semioval centers. On the 57th day, these low density areas were depicted more clearly by the X-ray CT scan, which became less marked on the 73rd day. MRI was performed 3 times.(ABSTRACT TRUNCATED AT 250 WORDS)     

The N-Methyl-D-aspartate (NMDA) receptor antagonist dizocilpine (MK-801) suppresses enfturane-induced opisthotonus in mice

We determined whether enflurane-induced opisthotonus in ddN mice is mediated by N-methyl-D-aspartate (NMDA) receptor using NMDA receptor antagonists dizocilpine (MK-801) and ketamine. Animals were given intraperitoneal injections of 0.2ml saline (control), 2.5 or 5.0mg·kg^–1 dizocilpine in saline, or 20 or 40mg·kg^–1 ketamine is saline 20min prior to exposure to 2.0% enflurane. Incidence of opisthotonus measured during exposure to enflurane for 20min was 49% (n = 51) in saline (control) group, 6.7 (P 0.01 vs control, n = 30) and 15.0% (P 0.01, n = 40) in 2.5 and 5.0mg·kg^–1 dizocilpine group, respectively, and 43.9 (NS, n = 41) and 40.0% (NS, n = 40) in 20 and 40mg·kg^–1 ketamine group, respectively. These results strongly suggest that enflurane-induced opisthotonus is mediated by NMDA receptor. Ketamine failed to suppress significantly due to possibly small dosages. Further, dizocilpine itself produced severe seizures during preenflurane period (30.0 and 40.0% in 2.5 and 5.0mg·kg^–1, respectively), which may be a novel finding.(Komatsu H, Nogaya J, Anabuki D, et al.: The N-methyl-D-aspartate (NMDA) receptor antagonist dizocilpine (MK-801) suppresses enflurane-induced opisthotonus in mice. J Anesth 7: 519–522, 1993)