Pulsed magnetization transfer contrast for MR imaging with application to breast

The relative populations and transverse relaxation times of the solid-like hydrogen pool (PB and T2B) and the magnetization transfer (MT) rates between the solid-like and liquid-like hydrogen pools (kappa) have been determined for three different agar gel concentrations (2%, 4%, and 8% by weight) as well as excised fibroglandular breast tissue specimens. PB was determined to be .003(.001), .01(.002), .02(.01), and .06(.01); T2B was determined to be 13.0(.2), 14.0(.1), 14.5(.1) and 15.2(1.3) microseconds; and kappa was determined to be 0.78(.01), 1.15(.02), 2.00(.02), and 3.55(1.5) sec-1 for the 2%, 4%, and 8% agar gels and the fibroglandular tissue, respectively. The image signal intensities of a pulsed MTC-prepared gradient-echo imaging technique are predicted using these MT parameters and are shown to agree well with experimental data obtained from a clinical MR imaging system. This technique is shown to suppress signal intensity of fibroglandular breast tissue by 40%-50% without exceeding SAR limits (< or = 8 W/kg) and is helpful for visualizing lesions and silicone implants.     

一种精准数控STC设计方法

介绍了雷达接收机中STC控制的产生背景、原理及方法,采用MATLAB语言进行仿真,重点介绍了一种基于电控衰减器作为受控部件的数字STC控制曲线的精确设计方法,并提出了雷达STC的设计和使用原则。     

Geographic epidemiology of gonorrhea in Baltimore, Maryland, using a geographic information system

Ws/Ws rats are deficient in both mucosal- and connective tissue-type mast cells. To study the role of mast cells in active anaphylaxis, changes in vascular permeability in the trachea upon intravenous antigen challenge with Evans blue dye were examined in Ws/Ws, heterogenic Ws/+, and normal +/ + rats sensitized with the nematode Nippostrongylus brasiliensis. Antigen challenge resulted in fatal anaphylactic shock in some +/+ and Ws/+ rats, but not in Ws/Ws rats. Marked dye leakage developed within 30 min in the trachea of +/+ and Ws/+ rats, while Ws/Ws rats showed no substantial increases in the levels of vascular permeability. Ex vivo stimulation of sensitized lung fragments from +/+ animals with specific antigen induced significant releases of histamine and leukotriene (LT) C4, while sensitized Ws/Ws rat-lung fragments did not. In Ws/Ws rats, levels of nematode-specific IgE, IgG1 and IgG2a antibodies as well as levels of lung eosinophilia were not significantly different from those in +/+ rats. These results show that mast cell-deficient Ws/Ws rats fail to develop active anaphylaxis, and this is mediated probably by the lack of mast cell-derived mediators required for initiation of the reaction.     

Tay-Sachs disease in persons of French-Canadian heritage in northern New England

This study sought to determine whether persons of French-Canadian heritage in northern New England are at high risk for the lethal infantile form of Tay-Sachs disease. In order to accomplish this, death records and laboratory diagnostic records were surveyed to ascertain Tay-Sachs deaths in a cohort of 372,000 live births between 1977-1986. The proportion of the total population with French-Canadian or Jewish heritage was determined from census and birth records, and the ethnic background of Tay-Sachs cases was determined from the corresponding birth records. In 1,860 births, both parents were of Ashkenazi Jewish heritage. One of those children was diagnosed with Tay-Sachs disease. In 41,000 births, both parents were of French-Canadian heritage, and in an additional 93,000 births, one parent was of French-Canadian heritage. No cases of Tay-Sachs disease were identified in the offspring of those individuals. Approximately 14 cases (95% confidence interval 8-20) would be expected, if the gene frequency approximated that reported for individuals of Ashkenazi Jewish heritage. Based on the results of this study, routine testing for Tay-Sachs disease heterozygosity is not indicated for persons of French-Canadian heritage in northern New England. This conclusion may not necessarily be valid for persons of French-Canadian heritage residing in other states. Further studies of Tay-Sachs disease mutations and prevalence among persons of French-Canadian heritage will be important to determine possible regional variations in gene frequencies.     

OPS和OPC系列稠油乳化降黏剂的研制

以工业品烷基酚聚氧乙烯醚OP-n（n=4,6,8,10,15）为起始原料,合成了烷基酚聚氧乙烯醚乙酸盐OPC-n和磺酸盐OPS-n两个系列的阴-非离子表面活性剂。以酸值和黏度不同的胜利单家寺和陈庄稠油为实验油样。将OPC-n和OPS-n溶于矿化度5811 mg/kg的胜利标准盐水和NaCl、CaCl2盐水中作为水相,按油、水质量比7∶3在50℃用玻棒搅拌混合,观察是否形成水包油乳状液并测黏度进行确认。在胜利标准盐水溶液中,OPC-n和OPS-n乳化稠油所需的最低质量分数,随稠油、表面活性剂类型及氧乙烯链节数n而变,一般而言,OPC-n系列中的OPC-8和OPS-n系列中的OPS-4乳化稠油的性能最好,该最低质量分数值分别为0.05%或0.025%和0.025%。在NaCl盐水溶液中,OPC-n的该最低质量分数值与稠油和n有关,均随盐含量增加而增大,在盐含量≤15%时,抗盐性最好的OPC-8和OPC-10的该值≤0.05%;OPS-n的抗盐性好于OPC-n。OPC-n的抗钙性良好,钙盐含量为2%时该最低质量分数≤0.1%;OPS-n的抗钙性更好,钙盐含量为2%和3%时该最低质量分数仅为0.025%或0.05%。表6参5。     

Clinical effects of longitudinal division of the corpus callosum in normal dogs

Longitudinal division of the corpus callosum was performed in six normal beagles to determine surgical morbidity. The corpus callosum was divided sagittally on the midline and the effect on neurological function was determined. Five of six dogs were clinically normal within 14 days or less after surgery. One dog had persistent but improving clinical signs consistent with a forebrain disturbance at 30 days after surgery. Overall, minimal morbidity and no mortality was associated with this surgical procedure. Further study is indicated to determine the efficacy of this surgical treatment for seizure control in dogs with idiopathic epilepsy.     

Molecular and immunologic characterization of group A bovine rotavirus field isolates with P8[11] spike protein

Bovine rotavirus strain B223 is the North American prototype for group A P8[11] serotype/genotype rotaviruses. Rotaviruses with this serotype/genotype are a prevalent cause of neonatal calf diarrhea and have also been isolated from asymptomatic human infants. On the basis of deduced amino acid sequence of the outer capsid viral protein 4 (VP4), strain B223 lacks a cysteine at position 318 that is conserved among all other rotavirus strains. It has been speculated that this may result in the loss of disulfide bond and a change in the structure of the VP4 that may affect the infectivity and antigenicity of the virus. This paper describes partial sequences of the VP4 gene (nucleotides 613 to 1016 coding for amino acid positions 202 to 335) of 16 bovine rotavirus field isolates with P8[11] that were obtained from calves in Nebraska and Indiana. All the isolates lack a cystein at position 203 and had a conserved valine residue at position 318, thus indicating that the prototype strain B223 is representative of group A rotaviruses with P8[11] serotype/genotype.     

Membrane topology and glycosylation of the human multidrug resistance-associated protein

The membrane topology of the human multidrug resistance-associated protein (MRP) was examined by flow cytometry phenotyping, immunoblotting, and limited proteolysis in drug-resistant human and baculovirus-infected insect cells, expressing either the glycosylated or the underglycosylated forms of this protein. Inhibition of N-linked glycosylation in human cells by tunicamycin did not inhibit the transport function or the antibody recognition of MRP, although its apparent molecular mass was reduced from 180 kDa to 150 kDa. Extracellular addition of trypsin or chymotrypsin had no effect either on the function or on the molecular mass of MRP, while in isolated membranes limited proteolysis produced three large membrane-bound fragments. These experiments and the alignment of the MRP sequence with the human cystic fibrosis transmembrane conductance regulator (CFTR) suggest that human MRP, similarly to CFTR, contains a tandem repeat of six transmembrane helices, each followed by a nucleotide binding domain, and that the C-terminal membrane-bound region is glycosylated. However, the N-terminal region of MRP contains an additional membrane-bound, glycosylated area with four or five transmembrane helices, which seems to be a characteristic feature of MRP-like ATP-binding cassette transporters.     

Convergence properties of solitary tract neurons responsive to cardiac receptor stimulation in the anesthetized cat

The convergence pattern of cardiac receptors, pulmonary C-fibers, carotid chemoreceptor, and baroreceptor afferents onto neurons within the nucleus of the solitary tract (NTS) was studied in the anesthetized (pentobarbitone sodium, 40 mg/kg,) paralyzed and artificially ventilated cat. Extra- and intracellular recordings were made from NTS neurons while stimulating both cardiac receptors by aortic root injections of veratridine (1-3 micrograms/kg) and pulmonary C-fibers by a right atrial injection of phenylbiguanide (10-20 micrograms/kg). The ipsilateral carotid body was stimulated by using arterial injection of CO2-saturated bicarbonate solution, whereas inflation of the ipsilateral carotid sinus was used to activate baroreceptors. The ipsilateral cardiac vagal branch, cervical vagus, and carotid sinus nerves were stimulated electrically (1 Hz, 0.2-1 ms, 1-35 V). In 78 NTS neurons recorded either extracellularly (n = 47) or intracellularly (n = 31), electrical stimulation of the cardiac branch of the vagus nerve evoked synaptic potentials (spikes and/or excitatory postsynaptic potentials) with an onset latency between 4 and 220 ms. Some neurons displayed both short and long latency inputs(15.5 +/- 1.8 and 160.0 +/- 8.5 ms; n = 14). Of these 78 neurons, 24 responded to veratridine stimulation of cardiac receptors (i.e., cardioreceptive neurons) by exhibiting an augmenting-decrementing discharge of 37 +/- 4 s in duration with a peak frequency of 30 +/- 5 Hz. Convergence from other cardiorespiratory receptors was noted involving either carotid chemoreceptors (n = 7) or pulmonary C-fibers (n = 4) or from both carotid chemoreceptors and pulmonary C-fibers (n = 6). In contrast, only one cardioreceptive NTS neuron was activated by distension of the carotid sinus. Recording sites recovered were confined to the medial NTS at the level of the area postrema and extended caudally into the commissural subnucleus. Our results indicate a convergence of carotid chemoreceptor and pulmonary C-fiber afferent inputs to cardioreceptive NTS neurons. With the paucity of baroreceptor inputs to these neurons it is suggested that sensory integration within the NTS may reflect regulatory versus defensive or protective reflex control.     

Cerebrovascular ischemic events with high positive anticardiolipin antibodies

BACKGROUND AND PURPOSE: The aim of our study was to characterize the patient profile and prognostic value associated with high positive IgG (>100 GPL) anticardiolipin antibodies (aCL). METHODS: We studied the clinical, laboratory, radiological, and prospective historical features of ischemic cerebrovascular disease in patients with >100 GPL titers. From our neurology department, 27 consecutive patients were prospectively identified and followed up (mean follow-up time, 34 months). RESULTS: The mean age of our cohort was 41 years. Lupuslike illness occurred in 3; 23 had primary antiphospholipid syndrome, including 3 who met criteria for Sneddon's syndrome; 1 patient had progressive systemic sclerosis. Cerebral infarcts occurred in 74% and were recurrent in 37%. Systemic ischemic events, most commonly deep vein thrombosis, occurred in 37%. Tobacco use was documented in 85%, hyperlipidemia in 74%, hypertension in 44%, and diabetes mellitus in 7% of patients. A prominent headache history was present in 67%. Lupus anticoagulant (LA) was present in 72%, approximately one half had positive antinuclear antibodies and thrombocytopenia, and one quarter had a false-positive VDRL. We compared mean GPL levels in patients testing positive for specific laboratory features of antiphospholipid syndrome with those testing negative for these parameters. Only the LA(+) group had a significantly higher mean GPL than the LA(-) group (P=0.006). Brain imaging showed nonlacunar infarcts in 73% and lacunes in 12%. Of 19 cerebral angiograms, 5 (26%) showed large-vessel occlusive disease and 6 (32%) branch obstruction. Echocardiograms were abnormal in 75%: thickened left-sided valves in 33% and vegetations in 12%. Recurrent cerebrovascular ischemic events were observed in 96%, with transient events (mean rate, 25%/y) occurring 5 times more frequently than strokes (mean rate, 5%/y). Using a standardized disability scale blinded to aCL titer, neurological impairment was severe in 7%, moderate in 30%, and mild or nonexistent in 63%, and unrelated to mean GPL value (P=0.567). Titers fluctuated greatly for individual patients, and most did not consistently test as highly positive. An analysis of fluctuation in symptom severity with concurrent GPL values did not show a statistically significant correlation. Compared with historical controls having a wide range of positive titers, the presence of high IgG aCL titers did not confer a worse prognosis for disability and recurrent ischemic events. CONCLUSIONS: Our data suggest that cerebrovascular events associated with high positive GPL are frequently multiple and minor (with no disability-titer correlation), present in relatively young patients, and often associated with tobacco abuse, hyperlipidemia, LA, systemic ischemic events, and occult cardiac disease.