Modulation of responses and frequency tuning of thalamic and collicular neurons by cortical activation in mustached bats

In the Jamaican mustached bat, Pteronotus parnellii parnellii, one of the subdivisions of the primary auditory cortex is disproportionately large and over-represents sound at approximately 61 kHz. This area, called the Doppler-shifted constant frequency (DSCF) processing area, consists of neurons extremely sharply tuned to a sound at approximately 61 kHz. We found that a focal activation of the DSCF area evokes highly specific corticofugal modulation in the inferior colliculus and medial geniculate body. Namely a focal activation of cortical DSCF neurons tuned to, say, 61. 2 kHz with 0.2-ms-long, 100-nA electric pulses drastically increases the excitatory responses of thalamic and collicular neurons tuned to 61.2 kHz without shifting their best frequencies (BFs). However, it decreases the excitatory responses of subcortical neurons tuned to frequencies slightly higher or lower than 61.2 kHz and shifts their BFs away from 61.2 kHz. The BF shifts are symmetrical and centrifugal around 61.2 kHz. These corticofugal effects are larger on thalamic neurons than on collicular neurons. The cortical electrical stimulation sharpens the frequency-tuning curves of subcortical neurons. These corticofugal effects named "egocentric selection" last 相似文献   

Studies on function of the upper urinary tract. XXIX. Canine ureteral electromyogram isolated from "so-called Pacemaker"

Many workers have reported that ureteral peristaltic movement is controlled by the "so-called Pacemaker". But, in our recent studies, it was revealed that the existence of pacemaker is not always necessary for the peristaltic movement. In this study, we made isolated and non-isolated prototype models, using 18 mongrel dogs, to explore the influential factors on ureteral peristaltic discharge. Bilateral kidney and ureter were exposed transperitoneally. Unilateral upper urinary tract was prepared to preserve the pacemaker without renal blood supply, and contralateral one was prepared not to preserve the pacemaker by cutting at the proximal portion of the ureter. Vesico-ureteral reflux (VUR) was caused on these two models. A luminal pressure and ureteral electromyogram was recorded. In the result, there is spontaneous peristaltic discharges of the ureter which had the tendency to increase peristaltic frequency according to the increase of the luminal pressure. It was suggested that adequate expanding stimulation is the factor of peristaltic discharge to increase, and the peristaltic discharge under this condition propagates from upper to lower portion of the ureter.     

Cytotoxic effects of 2,6-di-tert-butyl-4-methylphenyl N-methylcarbamate (terbutol) herbicide on hepatocytes and mitochondria isolated from male rats

The cytotoxic effects of 2,6-di-tert-butyl-4-methylphenyl N-methylcarbamate (terbutol) and its major metabolites were investigated in freshly isolated rat hepatocytes. Terbutol and its metabolite, especially 2,6-di-tert-butyl-4-methylphenyl carbamate (N-demethylterbutol), at a concentration of 1.0 mM resulted in a time dependent cell killing accompanied by losses of intracellular ATP, protein thiols, and glutathione (GSH) and the accumulation of oxidized GSH. Supplementation of the hepatocyte suspension with 5 mM N-acetylcysteine, a precursor of intracellular GSH, inhibited the cytotoxicity of N-demethylterbutol. In mitochondria isolated from rat liver, terbutol and its metabolites impaired respiration related to oxidative phosphorylation and the potency of their toxicity is associated with impairment of mitochondrial respiration. These results indicate that N-demethylterbutol is the most cytotoxic followed by terbutol and other metabolites, and that both the mitochondrial respiratory system and protein thiols are important targets for these compounds.     

Stoichiometry of the Reaction Catalyzed by Skin Sulfhydryl Oxidase

The stoichiometry of the reaction catalyzed by skin sulfhydryl oxidase was investigated. Dithiothreitol (DTT) was used as the substrate for skin sulfhydryl oxidase. The consumption of DTT, consumption of oxygen, and production of hydrogen peroxide were measured during the enzyme reaction. The molar ratio of DTT:O₂:H₂O₂ in the enzyme reaction was 1:1.02:0.89. Correspondingly, the stoichiometry of the enzyme reaction was calculated to be R(SH)₂ + O₂ → + H₂O₂.     

Heterogeneity of rice ragged stunt oryzavirus genome segment 9 and its segregation by insect vector transmission

Summary Genomic heterogeneity of genome segment 9 (S9) of rice ragged stunt virus (RRSV) was investigated and a point mutation was found to be responsible for an electrophoretic mobility shift of S9 on polyacrylamide gel electrophoresis (PAGE). A new form of S9 (S9L) which migrated slightly faster than natural S9 (S9U) had the same length with AC transversion at nt 843. Synthetic S9 with a C:G pair at nt 843 migrated slightly faster than that with an A:U pair. Therefore, we conclude that the single point mutation shifts the electrophoretic mobility. Using polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP), we could detect S9U and S9L alone or mixture in insect vectors after acquisition as well as in infected rice plants.     

Tc-99m colloid and Ga-67 imaging of splenic inflammatory pseudotumor correlation with ultrasound, CT, and MRI

Splenic inflammatory pseudotumor is extremely rare and may mimic splenic neoplasms, such as lymphomas or hamartomas, clinically and radiologically. A case of a surgically proved splenic inflammatory pseudotumor is presented in which Tc-99m colloid SPECT and Ga-67 scintigraphy characterized the changes in the spleen, but the findings of ultrasound and unenhanced CT and MRI were nonspecific. This report indicates the utility of radionuclide imaging for diagnosing splenic inflammatory pseudotumor.     

Imaging features of pancreatoblastoma: a case report

We present a patient with pancreatoblastoma along with a discussion of various cross-sectional imaging features. The tumor was a large multilocular cystic mass with solid components in the left retroperitoneal space. There were fine internal echoes on ultrasonography, and the signal intensity was high on both T1- and T2-weighted MR images in most of the locules, suggesting the presence of hemorrhagic debris. Among the various retroperitoneal organs displaced by the tumor, only the pancreatic tail was inseparable from the mass, suggesting that the pancreatic tail was the origin of the tumor. Pancreatoblastoma should be included in the differential diagnosis when a large left upper quadrant mass with these imaging features is seen in infants and young children.     

Keyhole method for high-speed human cardiac cine MR imaging.

Although electrocardiographic (ECG)-gated magnetic resonance (MR) imaging is widely used for cardiac imaging, it has several disadvantages, such as long imaging time, respiratory artifacts, and motion artifacts induced by arrhythmia. An MR image can be acquired within about 0.3 seconds by using a fast gradient-echo imaging method. When this method is continuously applied, only two to three images can be obtained during a single cardiac cycle. The goal of this study is to obtain cine MR images in a single cardiac cycle using fast gradient-echo imaging combined with the "keyhole" method. The optimal conditions for the keyhole method for cardiac cine imaging were obtained by computer simulation based on a simplified cardiac model. When the read-out direction was set parallel to the cardiac short axis, left ventricular motion was almost correctly reproduced by the keyhole method with acquisition time reduced to one-fourth. J. Magn. Reson. Imaging 1999;10:778-783.     

Adhesions from flexor tendon surgery: an animal study comparing surgical techniques

Intraoperative and postoperative hemorrhage has long been considered a cause of tendon adhesion and, thus, scarring and poor surgical results. To prevent such problems bipolar coagulators are commonly used during surgery to help achieve hemostasis. Surgical lasers also have been reported to help limit bleeding and scar formation. Very little is known regarding the relationship between hemorrhage and/or direct tendon tissue effects and tendon adhesions with the use of these modalities. We compared 3 different surgical techniques (meticulous sharp scalpel dissection, scalpel dissection plus bipolar coagulation, and CO(2) laser dissection) and used chicken flexor tendons to biomechanically and histologically assess the amount of adhesion formation after each procedure. Our findings show that bipolar coagulation and CO(2) laser application are both associated with significantly increased adhesion formation in tendon surgery compared with sharp dissection alone and that the meticulous, conventional sharp dissection technique is the best method to control adhesion formation. These conclusions have relevance to clinical tendon surgery.