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Biomedical subjects

S Kan

Publications and source records attributed to S Kan.

At least 73 records · Page 4Linked to original sources
PubMed1996

Localization of endothelin ETB receptors on the myenteric plexus of guinea-pig ileum and the receptor-mediated release of acetylcholine.

1. The type of endothelin (ET) receptor located on the myenteric neurones of guinea-pig ileum was determined by receptor autoradiography and function of the receptor was examined by release experiments of acetylcholine (ACh) from the longitudinal muscle myenteric plexus (LM-MP) preparations. 2. Specific [125I]-ET-1 binding sites were distributed in muscle layers, myenteric and submucous plexuses, and mucosa layers. High-grain densities were detected in both myenteric and submucous plexuses. 3. Binding in the myenteric plexus was abolished by incubation with either IRL 1620 (endothelin ETB receptor agonist) or BQ 788 (endothelin ETB receptor antagonist), but not with BQ 123 (endothelin ETA receptor antagonist). The [125I]-IRL 1620 binding sites were evident in the myenteric plexus. Thus, the endothelin receptor located on the myenteric neurones is of the ETB type. 4. ET-1 (10(-10)-3 x 10(-8) M) and ET-3 (10(-10)-3 x 10(-8) M) evoked 3H outflow from LM-MP preparations of ileum preloaded with [3H]-choline, in a concentration-dependent manner. There was no significant difference between maximum amounts of ET-1-evoked and ET-3-evoked 3H outflow. 5. ET-1 and ET-3 evoked outflow of 3H was BQ 788-sensitive, but BQ 123-insensitive. Both evoked outflows of 3H were Ca(2+)-dependent and tetrodotoxin-sensitive. 6. These results indicate that the endothelin ETB receptor is located on the enteric cholinergic neurones and that stimulation evokes the release of ACh.

Acetylcholine↗
PubMed1996

[Study on the stability of Japanese encephalitis vaccine--development of freeze-dry dosage form].

In order to prolong shelf-life and improve the quality of the vaccine product, not only an effective stabilizer but also a more proper dosage form has been sought. The stability of a Japanese encephalitis (JE) vaccine produced from mouse brain along with a variety of stabilizers and lyophilization protocols was evaluated. Without any stabilizers added, almost 90% of the antigenicity would vanish after freeze-drying process. Comparative studies of various compounds, including carbohydrates, amino acids, peptides and medium 199, on both antigenicity preservation and thermostability of the vaccine were carried out. The results indicated that the best reconstituted vaccines were prepared with two stabilizer formulations, sucrose and sucrose/gelatin. They were further examined by accelerated stability test at room and higher temperatures. The sucrose-added lyophilized vaccine can retain its original antigenicity for more than 60 days both at 37 degrees C and 45 degrees C. We conclude the thermostability efficiency of each of the stabilizers tested is as that follows: sucrose > sucrose/gelatin > gelatin/medium > gelatin.

Animals↗
PubMed1995

Detection of deiminated proteins in rat skin: probing with a monospecific antibody after modification of citrulline residues.

We performed a systematic study on deiminated proteins present in rat epidermis. Proteins extracted from various epidermal samples were resolved by either one- or two-dimensional gel electrophoresis and Western blotted to nitrocellulose membranes. Deiminated proteins were detected by modification of citrulline residues followed by probing with an anti-modified citrulline monospecific antibody. The cornified layer of adult plantar skin gave multiple series of isoelectric variants, most of which were found to be differentially deiminated type II keratins (60 kDa, and 67 kDa or above). The whole epidermis of 5-day-old rat back skin showed isoelectric variants of 60-kDa keratin as major deiminated components, and deiminated 55-kDa keratin and deiminated filaggrin as minor spots. In addition, we found highly deiminated proteins (200-220 kDa) thought to be derived from trichohyalin. The immunoreactivity of deiminated proteins was mainly localized in the granular and cornified layers of epidermis. Co-localization of deiminated filaggrin and keratins in the granular layer suggests the possible role of protein deimination during the terminal stage of epidermal differentiation.

Animals↗
PubMed1994

Specific receptor for vasoactive intestinal contractor in myenteric cholinergic neurones.

The receptor for vasoactive intestinal contractor (VIC) involved in acetylcholine release was examined in the guinea-pig ileum. VIC (10(-9) to 10(-7) M) evoked tritium outflow from ileal strips preloaded with [3H]choline, in a concentration-dependent manner. The evoked tritium outflow was Ca(2+)-dependent and tetrodotoxin-sensitive, suggesting that VIC acts on somato-dendritic regions of the cholinergic neurones to stimulate acetylcholine release. The response to VIC did not change after desensitization to either endothelin-1, endothelin-2 or endothelin-3, hence there is probably no cross-desensitization in evoked tritium outflow between VIC and endothelins. VIC-induced contractions consisted of tetrodotoxin-sensitive and -resistant contractions, and the tetrodotoxin-resistant contraction was abolished after desensitization to either endothelin-1, endothelin-2 or endothelin-3. These results indicate that the VIC-specific receptor is located on cholinergic neurones, but not on the smooth muscle cells of guinea-pig ileum.

Acetylcholine↗
PubMed1994

Anomaly of venous system in congenital occipital dermal sinus.

We report two cases of congenital occipital dermal sinus in which elongation of the vein of Galen, elevation of the straight sinus, division of the superior sagittal sinus, elevation of the confluence of sinuses, elevation of transverse sinus and narrowing of the torcular angle were observed in the venous phase of cerebral angiography. Enhanced computed tomography (CT) revealed enlargement of the supracerebellar cistern, elevation of the straight sinus and of the confluence of sinuses, but no evidence of intracranial lesions. In order to study the relationship between anomalies in the dural venous sinuses and congenital occipital dermal sinus, we examined both cases from an embryological viewpoint.

Arteriovenous Malformations↗
PubMed1994

Molecular epidemiologic analysis of Vibrio cholerae O1 isolates by pulsed-field gel electrophoresis.

Isolates of Vibrio cholerae O1 El Tor from two well-defined cholera outbreaks in Malaysia were analyzed by using pulsed-field gel electrophoresis (PFGE). Isolates from sporadic cases occurring during the same time period were also studied. Digestion of chromosomal DNA from these isolates of V. cholerae O1 with restriction endonucleases NotI (5'-GCGGCCGC-3') and SfiI (5'-GGCCNNNN-3'), followed by PFGE, produced restriction endonuclease analysis (REA) patterns consisting of 13 to 24 bands (ranging in size from 46 to 398 kbp). Analysis of the REA patterns generated by PFGE after digestion with NotI and SfiI suggested the clonal nature and close genetic identity of the isolates obtained during each of the two outbreaks (Dice coefficient, 0.93 to 1.0). Although they had very similar REA patterns, the two outbreak clones were not identical. Isolates of V. cholerae O1 from sporadic cases, on the other hand, appeared to be much more heterogeneous (five different REA patterns detected in the five isolates tested; Dice coefficient, 0.31 to 0.81) than those obtained during the two outbreaks. We conclude that PFGE of V. cholerae O1 chromosomal DNA digested with infrequently cutting restriction endonucleases is a useful method for molecular typing of V. cholerae isolates for epidemiological purposes.

Bacterial Typing Techniques↗
PubMed1994

Aneurysmography for visualizing large aneurysms.

We report a case of a large cavernous sinus aneurysm, in which conventional angiography did not clearly demonstrate the exact form and the position of the neck. Superselective angiography performed with the catheter tip in the lumen of the aneurysm and with the internal carotid artery occluded just proximal to its neck is a new technique that demonstrates the morphological details of an entire aneurysm. With the use of cineangiography, the exact volume of the aneurysm was defined. The valuable aneurysmographic information obtained was useful in achieving occlusion of the aneurysm, while preserving the parent artery.

Carotid Artery, Internal↗
PubMed1994

Radiological study of symptomatic Rathke's cleft cysts.

We investigated the relationship between radiological findings and the nature of the cyst fluid and histological findings of six Rathke's cleft cysts. The results show that the majority (five of six cases) of symptomatic Rathke's cleft cysts exhibit no enlargement of the sella turcica on plain x-rays, which may be helpful in differentiating cystic pituitary adenoma in the radiological diagnostic process. Three cases with large cysts showing high-intensity T1-weighted magnetic resonance images harbored abundances of cholesterol crystal and hemosiderin pigment in the cyst walls. The high signal intensity in magnetic resonance images of Rathke's cleft cysts may be explained by hemorrhage and a deposition of cholesterol crystal and may be considered in certain cases of Rathke's cleft cyst, especially when they are large.

Adult↗
PubMed1994

Dural arteriovenous malformation involving the inferior petrosal sinus--case report.

A 59-year-old male presented with a dural arteriovenous malformation involving the inferior petrosal sinus manifesting as false-localizing ocular symptoms. Occlusion between the right inferior petrosal sinus and the right jugular bulb caused an unusual retrograde venous outflow from the inferior petrosal sinus to the cavernous sinus, thought to have been responsible for the chemosis, abducens nerve paresis, and orbital bruit. He was treated successfully with transarterial embolization and radiotherapy.

Cerebral Angiography↗
PubMed1994

Venous ischemia caused by dural arteriovenous malformation. Case report.

A case is presented of tentorial dural arteriovenous malformation (AVM) associated with visual hallucinations and quadrant hemianopsia. Computerized tomography (CT) and magnetic resonance imaging showed an ischemic region, mainly affecting the white matter of the right occipital lobe, that was defined as an area of increased blood volume on dynamic CT scans and as a decrease in cerebral blood flow on N-isopropyl-p-123I-iodoamphetamine single-photon emission CT scans. Angiography demonstrated venous congestion, probably because the retrograde arterial inflow from the dural AVM into the corticomedullary vein was direct and not via the sinuses. The symptoms and radiological findings improved immediately after endovascular treatment. The origin of these symptoms was fully evaluated and confirmed to be a reversible ischemic change caused by disturbance of the volume of venous return over an extensive area.

Aged↗
PubMed1994

[Completely thrombosed large aneurysm of the distal middle cerebral artery: a case report].

A 19 year old male was admitted for evaluation after a seizure. Physical and neurological examination was normal. CT demonstrated an enlarged, high density mass in the right parietal lobe. MRI showed a homogeneous high intensity T1 weighted mass, surrounded by a low intensity T2 weighted rim in the right parietal lobe. Angiography did not show any abnormal findings. A diagnosis of cavernous angioma with primary bleeding in the subcortical region of the right parietal lobe was made after radiological examination. Histological examination showed a completely thrombosed aneurysm. The mechanism of the complete thrombosis and the growth of this large aneurysm and the shortcomings of radiological examination are discussed.

Adult↗
PubMed1993

Involvement of cholinergic neurons in intestinal contraction caused by vasoactive intestinal contractor.

The mechanism of the contractile response to vasoactive intestinal contractor (VIC) was examined in the isolated guinea-pig small intestine. VIC at 10(-9) to 10(-7) M produced a transient relaxation followed by a contraction, and this contraction was partially inhibited, to the same degree, by either atropine or tetrodotoxin. VIC (10(-8) M) induced an increase in the release of [3H]acetylcholine from the ileum preloaded with [3H]choline. The VIC-induced acetylcholine release was dependent on external Ca2+. Thus, the VIC-induced contractions may relate to stimulation of cholinergic neurons and smooth muscle cells.

Acetylcholine↗
PubMed1993

Multi-turn, printed surface coil inductance, and Q optimization.

Wheeler's empirical inductance formula for a multi-turn, close-wound flat coil shows that the maximum inductance for a given length of wire occurs when the outer to inner radius ratios is equal to 15/7. A similar expression is proposed for a flat, printed spiral for surface coil antenna design by modifying one of the coefficients in Wheeler's formula. Measured inductance is in good agreement with this new formula and the optimum radius ratio for maximum inductance or Q is now of the order of 9/5.

Electric Conductivity↗
PubMed1993

Subcortical cerebral hemorrhage with reference to vascular malformations and hypertension as causes of hemorrhage.

The authors have reviewed 80 cases of subcortical cerebral hemorrhage, in all of which intraoperative examinations during craniotomy or autopsies were performed. Cases involving trauma and aneurysm were excluded from the study. The diagnosis of subcortical hemorrhage was made by plain computed tomography in all cases. The most common cause of hemorrhage was vascular malformation (68%; 56 cases), in 20 (36%) of which angiographically occult vascular malformations were noted. Hypertension was present in 23 (29%) of 80 cases but was the cause of hemorrhage in only 9 cases (11%). Hypertension was present in 6 (30%) of 20 angiographically occult vascular malformations, all of which were in patients under 65 years. In 12 (75%) of 16 cases of angiographically occult vascular malformations, prolonged high-dose delayed-contrast computed tomography and magnetic resonance imaging were able to provide definite diagnostic information. We recommend that patients with subcortical cerebral hemorrhage, especially those under age 65, with or without hypertension, be carefully examined by prolonged high-dose delayed contrast computed tomography and magnetic resonance imaging for the presence of angiographically occult vascular malformations causing hemorrhage.

Adolescent↗
PubMed1993

[Clinical study in patients with perimesencephalic subarachnoid hemorrhage of unknown etiology].

We have recognized a characteristic distribution of cisternal blood in 10 (43%) of 23 patients with subarachnoid hemorrhage (SAH) of unknown etiology. On the initial CT examination undertaken within 48 hours of the onset, blood from 10 patients was found to be more densely distributed in the cisterns around the brainstem. In this study, clinical characteristics and CT findings in those 10 cases were carefully evaluated and the CT findings were compared to those of 416 patients with aneurysmal SAH (anterior circulation aneurysm 368 cases, posterior circulation aneurysm 48 cases). There were seven men and three women, with an age ranging from 39 to 64 years (average age, 50.6 years). The follow-up period ranged from 4 to 45 months (average follow-up period, 23 months). Neurological grade (WFNS) on admission was I in 9 cases and III in one case. None of the patients suffered symptomatic vasospasm, hydrocephalus or rebleeding. All the patients had favourable outcome and were categorized as good recovery according to the Glasgow Outcome Scale. In comparison with the cases of aneurysmal SAH, especially in comparison with 48 cases with SAH caused by posterior circulation aneurysm, 43 cases could be easily distinguished on CT. The other 5 cases showed almost the same pattern of SAH on CT, but 4 cases could be differentiated by either the extension of SAH to the interhemispheric fissure or the presence of intraventricular hemorrhage. Only one case could not be differentiated on CT. Thus SAH located only around the brainstem differs from aneurysmal SAH in its clinical course, and in distribution and severity of bleeding on CT. This could be recognized as a new clinical entity and could be called benign SAH.

Adult↗
PubMed1992

Q optimization of RF inductors for use in NMR probes.

Radiofrequency inductors are important components of many NMR probe circuits, and a high quality factor Q of these inductors is necessary to achieve good signal-to-noise ratios. We have designed high Q inductors using an optimum coil diameter to coil length ratio of the order of 2.54. The latter was calculated from Lorenz's inductance formula for a solenoid and checked experimentally using a series of inductors of various diameters and lengths. The results show good agreement between theory and practice.

Humans↗
PubMed1992

Single-input double-tuned Foster-type probe circuit.

Synthesizing two different values of inductance from a given sample coil for use in a single-input double-tuned circuit is possible by means of three extra LC elements. A detailed analysis with derived equations shows how to calculate the circuit component values and what to expect from this kind of probe. It also derives the upper limit of the trap coil/sample coil inductance ratio beyond which no solution exists to double-tune the 31P-1H probe. The general expression for the channel efficiency shows that the latter is a function not only of the inductance of the coils, but also of their quality factor and of the operating frequencies. A numerical example is given illustrating good agreement between experiment and theory provided high quality rf capacitors are used.

Humans↗