The specific involvement of coat protein in tobacco mosaic virus cross protection

Nicotiana sylvestris infected by strains of tobacco mosaic virus (TMV) causing mosaic can be superinfected in the dark green leaf tissue, but not light green tissue, by necrotizing strains of TMV. The dark green tissue, however, is much less susceptible than healthy tissue, to some extent, even to unrelated viruses. The RNA of necrotizing strains of TMV was relatively more infectious than intact virus on mosaic than on healthy leaves and caused lesions in both light and dark green tissues. The same relationship was found in Nicotiana longiflora and, when the protecting strain in N. sylvestris could be used as a challenge, in Capsicum baccatum. The efficiency of superinfection by RNA was not found with viruses unrelated to TMV. When bentonite at 1 mg/ml, which is known to strip protein from TMV, was included in the inoculum of intact TMV it superinfected in the same manner as RNA. RNA of a necrotizing strain of TMV, encapsidated in brome mosaic virus protein and used as a challenge, superinfected in the same manner as RNA. When encapsidated in common TMV protein, however, it behaved as native virus. Cross protection apparently results from the prevention of uncoating of related challenge virus in light green tissue of N. sylvestris. Locally inoculated N. sylvestris leaves were insusceptible to challenge RNA or intact virus when the protecting virus was increasing. After increase ceased, RNA was more infectious than intact virus.     

Use of 3D reconstruction to correct for patient motion in SPECT

Patient motion occurring during data acquisition in single photon emission computed tomography (SPET) can cause serious reconstruction artefacts. We have developed a new approach to correct for head motion in brain SPECT. Prior to motion, projections are assigned to conventional projections. When head motion occurs, it is measured by a motion monitoring system, and subsequent projection data are mapped to 'virtual' projections. The appropriate position of each virtual projection is determined by applying the converse of the patient's accumulated motion to the actual camera projection. Conventional and virtual projections, taken together, form a consistent set that can be reconstructed using a three-dimensional (3D) algorithm. The technique has been tested on a range of simulated rotational movements, both within and out of the transaxial plane. For all simulated movements, the motion corrected images exhibited better agreement with a motion free reconstruction than did the uncorrected images. This technique may help to overcome one of the major remaining limitations on image quality and quantitative accuracy in SPECT.     

Ligand binding and platelet uptake studies of loxapine, amoxapine and their 8-hydroxylated derivatives

Loxapine, amoxapine and their 8-hydroxylated derivatives were studied by means of [3H]imipramine binding to rat cortical membranes, [3H]spiperone binding to rat striatal membranes, and the inhibition of serotonin uptake by human platelets. As inhibitors of [3H]imipramine binding: amoxapine greater than hydroxyamoxapine greater than loxapine = hydroxyloxapine; as inhibitors of platelet serotonin uptake: hydroxyamoxapine greater than amoxapine greater than hydroxyloxapine greater than loxapine; and as inhibitors of [3H]spiperone binding: loxapine greater than amoxapine greater than hydroxyamoxapine greater than hydroxyloxapine. The antipsychotic properties of loxapine and amoxapine were supported by the binding results, which also indicated the probable antipsychotic activities of the metabolites. All 4 compounds may possess dual action of antidepressant effect as well as antipsychotic effect.     

"Self-screening" of rhodopsin in rod outer segments

Microspectrophotometry (MSP) shows rhodopsin highly concentrated (about 3.0 mmol/l) in rod outer segments (ROS). Calculation of the in vivo absorption spectrum of human rhodopsin from such data reveals a striking failure to agree with the action spectrum of human rod vision. Agreement is good between the spectral distribution of absorption coefficients and the action spectrum, but the "concentration-broadening" (or "self-screening") introduced by the high end on absorbance at this concentration results in a misfit among the largest in the 93 years comparisons of this kind have been made! To deal with this anomaly, it has been suggested that "concentration-broadening" is inappropriate for rhodopsin in rod vision. This proposal was tested by comparing rod action spectra of 15-day-old and adult rats, since the lengths of ROS increase by a factor of about two in maturation. Three lines of evidence are inconsistent with it. Although the conundrum remains unexplained, it cannot be dismissed by supposing "self-screening" inappropriate for night vision.     

The course of maturation of rod-mediated visual thresholds in infants.

PURPOSE: To measure the developmental course of infants' rod-mediated thresholds. METHODS: Thresholds for detecting stimuli (2 degrees diameter, 50 msec duration) presented at 10 degrees (parafoveal site) or 30 degrees (peripheral site) from a central fixation target were estimated using a preferential-looking method. Nine infants were tested at both stimulus positions at ages 10, 18, and 26 weeks. RESULTS: At 10 weeks, infants' thresholds at both sites were significantly higher than those of adults. The infants' average threshold at 10 degrees was 0.5 log unit higher than the infants' average threshold at 30 degrees. Adults' thresholds at the two sites were equal. Thresholds of all infants decreased with age until by age 26 weeks the parafoveal and peripheral thresholds were equal and were the same as those of adults. The rate of change of parafoveal thresholds was significantly faster than the rate of change of peripheral thresholds. CONCLUSIONS: Although postreceptoral factors cannot be ruled out, the results suggest that developmental increases in rod outer segment length and rhodopsin density account for most of the threshold changes during infancy.     

Propofol. A pharmacoeconomic appraisal of its use in day case surgery

Propofol is an intravenous anaesthetic agent that has become widely used in day case surgery. It induces anaesthesia rapidly and 'smoothly', is associated with a quick recovery and has a lower incidence of postoperative nausea and vomiting (PONV) than other agents. In studies comparing propofol with other intravenous anaesthetics (most commonly thiopental sodium) in day case surgery, the use of propofol as induction and/or maintenance anaesthesia was associated with a shorter time to intermediate recovery (street fitness or time to discharge), although the mean time difference was generally less than 1 hour. However, when compared with volatile anaesthetics (particularly desflurane), the differences in time to discharge were smaller. Propofol is also associated with less PONV than barbiturates, volatile anaesthetics or barbiturate/volatile anaesthetic combinations in the immediate postoperative period. The faster recovery time and the decreased incidence of PONV have potential pharmacoeconomic implications. Delayed recovery can increase the use of hospital resources and decrease patient throughput and PONV can incur costs due to an increase in adjunctive medications usage (e.g. antiemetics), nursing time or unintended admissions. The pharmacoeconomic significance of these properties of propofol requires formal evaluation. Pharmacoeconomic investigations, such as cost-effectiveness, cost-benefit and cost-minimisation studies, which include clinical outcome parameters are difficult to conduct in anaesthesia since there are no objective measures of equipotency between anaesthetic agents and because there is no specific health outcome associated with the delivery of anaesthesia. At present, cost-utility studies are not possible because there are no validated instruments for measuring utility in the provision of anaesthesia. To date, pharmacoeconomic analyses of propofol (and other anaesthetic agents) in day case surgery have been restricted to partial cost analyses. Only 2 of these have included the cost of drug wastage, an important consideration since propofol contains no preservative. With 1 exception, these studies have only included drug acquisition costs and propofol was reported to be approximately 1- to 3-fold as costly as other intravenous/inhalational agents. However, these limited analyses have little applicability since they do not include all relevant costs. In addition to drug acquisition costs, pharmacoeconomic studies should also include other direct costs such as the cost of adjunctive medications (including treatment necessary for adverse events), equipment and staff time, indirect costs such as loss of productivity and/or wages and intangible costs such as patient satisfaction and quality of life. A few studies have attempted to quantify some of these factors. Based on differences in recovery time, 2 studies have estimated a decreased demand for nursing staff time associated with the use of propofol compared with thiopental sodium/isoflurane. In addition, informal patient satisfaction assessments show propofol to be equal to or better than other anaesthetic agents. With these broader considerations, it thus remains for future studies to quantify the intangible and indirect costs associated with propofol anaesthesia, to determine whether differences in recovery between propofol and other agents (especially the newer inhalational anaesthetics) are of economic importance, and to identify those instances where propofol use provides the greatest value for available funds.     

Successful placement and re-expansion of a new balloon expandable stent to maintain patency of the ductus arteriosus in a newborn animal model

Objective: We performed this study in order to evaluate the usefulness of a new balloon expandable stent for maintaining ductal patency in a neonatal piglet model and to evaluate the ability to re-expand the stent weeks following initial implantation. Background: Maintaining patency of the ductus arteriosus without administration of Prostaglandin E has been reported previously using balloon dilation and stent implantation techniques. However, the experience is limited and the currently available stents are not modified for neonates. Methods: 14 newborn piglets all at age 12 days and median weight 3.6 Kg (range 2.7-4.3 Kg), underwent initial balloon dilation of the ductus arteriosus. Angiography after dilation demonstrated no significant left to right shunt. All piglets underwent successful stent (3.5 mm x 17 mm) placement in the ductus arteriosus. Results: Percutaneous ductal stent implantation via the arterial route was successful in all piglets with angiographic demonstration of a significant left to right shunt. Follow-up studies at weekly intervals with color flow Doppler were used to confirm patency of the stents. In 3 piglets the stent was not patent at initial follow-up and autopsy revealed sub-optimal stent placement. In two animals the stent was later re-expanded to 4 mm at 22 days, in one to 4 mm at 30 days and in one to 6 mm at 15 days, maintaining flow for an additional period of 15 to 34 days.(ABSTRACT TRUNCATED AT 250 WORDS)     

Congenital pulmonary atresia with ventricular septal defect: angiographic and surgical correlates

Of 181 patients with severe congenital pulmonary atresia and ventricular septal defect or "type IV truncus" (an obsolete term), all but 11% had true central pulmonary arteries. These arteries were demonstrable by large serial biplane angiograms using multiple selective injections into collateral vessels, frequent photographic subtraction, and occasional pulmonary vein-wedge angiograms. These techniques are extremely important for accurate diagnosis and in planning corrective or palliative surgery, which was done in 77% of patients with pulmonary arteries.     

Abbreviated course of radiation therapy in older patients with glioblastoma multiforme: a prospective randomized clinical trial.

PURPOSE: To prospectively compare standard radiation therapy (RT) with an abbreviated course of RT in older patients with glioblastoma multiforme (GBM). PATIENTS AND METHODS: One hundred patients with GBM, age 60 years or older, were randomly assigned after surgery to receive either standard RT (60 Gy in 30 fractions over 6 weeks) or a shorter course of RT (40 Gy in 15 fractions over 3 weeks). The primary end point was overall survival. The secondary end points were proportionate survival at 6 months, health-related quality of life (HRQoL), and corticosteroid requirement. HRQoL was assessed using the Karnofsky performance status (KPS) and Functional Assessment of Cancer Therapy-Brain (FACT-Br). RESULTS: All patients had died at the time of analysis. Overall survival times measured from randomization were similar at 5.1 months for standard RT versus 5.6 months for the shorter course (log-rank test, P =.57). The survival probabilities at 6 months were also similar at 44.7% for standard RT versus 41.7% for the shorter course (lower-bound 95% CI, -13.7). KPS scores varied markedly but were not significantly different between the two groups (Wilcoxon test, P =.63). Low completion rates of the FACT-Br (45%) precluded meaningful comparisons between the two groups. Of patients completing RT as planned, 49% of patients (standard RT) versus 23% required an increase in posttreatment corticosteroid dosage (chi(2) test, P =.02). CONCLUSION: There is no difference in survival between patients receiving standard RT or short-course RT. In view of the similar KPS scores, decreased increment in corticosteroid requirement, and reduced treatment time, the abbreviated course of RT seems to be a reasonable treatment option for older patients with GBM.     

妥卡尼对豚鼠心室肌细胞钙电流和钾电流的抑制作用

利用酶分散的成年豚鼠心室肌细胞和全细胞电压钳技术,研究了妥卡尼(tocainide)对心室肌细胞钙电流(I_ca)、延迟整流钾电流(I_k)和ATP敏感性钾电流(Ik,ATP)的作用。结果表明,妥卡尼对I_ca和I_k均显示浓度相关的抑制作用,妥卡尼50umol·L^-1对I_ca和I_k的抑制率分别为16%和3%。这可能是妥卡尼有效抑制室上性心动过速和缩短心肌动作电位平台期的重要机制。