Entrapment of Cultured Pancreas Islets in Three-Dimensional Collagen Matrices

In vitro culture of islets of Langerhans decreases their immunogenecity, presumably by eliminating passenger leukocytes and other Ia+ presenting cells within the islets. Islets cultivated in petri dishes either at 37°C or at 25°C gradually disintegrate during culture in a time-dependent manner which is related to the free-floating condition of the islets. Also, a fraction of the islets disperse as single cells and beta-cell aggregates or adhere to the bottom of the culture dishes. Thus, the retrieval rate of transplantable islets is dampened due to their disintegration and spontaneous dispersion in conventional petri dish cultures.

Entrapment of freshly harvested islets of Langerhans in a three-dimensional collagen matrix was studied as an alternative method for islet cultivation. The contraction of collagen fibrils during in vitro culture counteracts the dispersion of islets and helps in maintaining their integrity while in culture. It was observed that the entrapped islets maintain satisfactory morphology, viability, and capability of glucose-dependent insulin secretion for over 2 wk. The oxygen consumption rate and glucose metabolism of these islets was not deranged when entrapped in collagen. Also, the retrieval of islets is easier and more efficient than that observed in conventional culture systems.

Our results indicate that culture of islets in three-dimensional collagen gels can potentially develop into an ideal system applicable to clinical transplantation of cultured islets or beta-cell aggregates.

Relationship between chlorine consumption and chlorination by-products formation for model compounds

The objective of this research is to investigate the relationship between chlorine decay and the formations of disinfection by-products (DBP), including trichloromethane (TCM) and chloroacetic acid (CAA) in the presence of four model compounds, i.e., resorcinol, phloroglucinol, p-hydroxybenzoic acid, and m-hydroxybenzoic acid. The chlorine degradation in model compounds with OH and/or COOH functional groups were rapid after chlorination. The TCM yields of carboxylic group substituted compounds (3-hydroxybenzoic acid [3-HBA], 4-hydroxybenzoic acid [4-HBA]) were found to be lower than that of the m-dihydroxy substituted compounds. Phloroglucinol, with one more OH substitution group than resorcinol, tends to form significant amounts of CAA after chlorination. However, it was observed that with the COOH substitution of 3-HBA and 4-HBA tend to exhibit more CAA formation potential than resorcinol. The developed parallel second and first-order reaction model for chlorine demand has been successfully utilized for TCM, CAA and DBP formation modeling. A high correlation between CAA and TCM was observed for the model compounds.

Flavopiridol inactivates P-TEFb and blocks most RNA polymerase II transcription in vivo

Flavopiridol (L86-8275, HMR1275) is a cyclin-dependent kinase (Cdk) inhibitor in clinical trials as a cancer therapy that has been recently shown to block human immunodeficiency virus Tat transactivation and viral replication through inhibition of positive transcription elongation factor b (P-TEFb). Flavopiridol is the most potent P-TEFb inhibitor reported and the first Cdk inhibitor that is not competitive with ATP. We examined the ability of flavopiridol to inhibit P-TEFb (Cdk9/cyclin T1) phosphorylation of both RNA polymerase II and the large subunit of the 5, 6-dichloro-1-beta-D-ribofuranosylbenzimidazole (DRB) sensitivity-inducing factor and found that the IC(50) determined was directly related to the concentration of the enzyme. We concluded that the flavonoid associates with P-TEFb with 1:1 stoichiometry even at concentrations of enzyme in the low nanomolar range. These results indicate that the apparent lack of competition with ATP could be caused by a very tight binding of the drug. We developed a novel immobilized P-TEFb assay and demonstrated that the drug remains bound for minutes even in the presence of high salt. Flavopiridol remained bound in the presence of a 1000-fold excess of the commonly used inhibitor DRB, suggesting that the immobilized P-TEFb could be used in a simple screening assay that would allow the discovery or characterization of compounds with binding properties similar to flavopiridol. Finally, we compared the ability of flavopiridol and DRB to inhibit transcription in vivo using nuclear run-on assays and concluded that P-TEFb is required for transcription of most RNA polymerase II molecules in vivo.

Juglone, an inhibitor of the peptidyl-prolyl isomerase Pin1, also directly blocks transcription

The C-terminal domain (CTD) of the large subunit of RNA polymerase II plays a role in transcription and RNA processing. Yeast ESS1, a peptidyl-prolyl cis/trans isomerase, is involved in RNA processing and can associate with the CTD. Using several types of assays we could not find any evidence of an effect of Pin1, the human homolog of ESS1, on transcription by RNA polymerase II in vitro or on the expression of a reporter gene in vivo. However, an inhibitor of Pin1, 5-hydroxy-1,4-naphthoquinone (juglone), blocked transcription by RNA polymerase II. Unlike N-ethylmaleimide, which inhibited all phases of transcription by RNA polymerase II, juglone disrupted the formation of functional preinitiation complexes by modifying sulfhydryl groups but did not have any significant effect on either initiation or elongation. Both RNA polymerases I and III, but not T7 RNA polymerase, were inhibited by juglone. The primary target of juglone has not been unambiguously identified, although a site on the polymerase itself is suggested by inhibition of RNA polymerase II during factor-independent transcription of single-stranded DNA. Because of its unique inhibitory properties juglone should prove useful in studying transcription in vitro.

Flavopiridol inhibits P-TEFb and blocks HIV-1 replication

Flavopiridol (L86-8275, HMR1275) is a cyclin-dependent kinase (Cdk) inhibitor that is in clinical trials as a cancer treatment because of its antiproliferative properties. We found that the flavonoid potently inhibited transcription by RNA polymerase II in vitro by blocking the transition into productive elongation, a step controlled by P-TEFb. The ability of P-TEFb to phosphorylate the carboxyl-terminal domain of the large subunit of RNA polymerase II was inhibited by flavopiridol with a K(i) of 3 nm. Interestingly, the drug was not competitive with ATP. P-TEFb composed of Cdk9 and cyclin T1 is a required cellular cofactor for the human immunodeficiency virus (HIV-1) transactivator, Tat. Consistent with its ability to inhibit P-TEFb, flavopiridol blocked Tat transactivation of the viral promoter in vitro. Furthermore, flavopiridol blocked HIV-1 replication in both single-round and viral spread assays with an IC(50) of less than 10 nm.

The Bloch equations in high-gradient magnetic resonance force microscopy: theory and experiment

We report theory and observations of paramagnetic resonance in a measured field gradient of 44,000 T per meter by the technique of magnetic resonance force microscopy (MRFM). Resonance was induced in a dilute solid solution of diphenylpicrylhydrazyl in polystyrene at 77 and 10 K by an amplitude-modulated microwave field. This modulated the force between resonant sample spins and a micrometer-scale SmCo magnetic tip on a force microscope cantilever. The force signals were typically of order 10 fN, and were detected above a thermal noise floor of 80 aN per root hertz at 10 K, equivalent to a magnetic moment noise of 200 micro(B) per root hertz of bandwidth. Resonance saturation was readily observed. Starting with the Bloch equations, we derived simple analytic expressions for the predicted cantilever signal amplitudes and T(1)-dependent phase lags, valid at low microwave power levels. For power levels below saturation, the data were in good agreement with the Bloch equation predictions, while above saturation the measured force increased more slowly with power than predicted. Several ESR mechanisms which might lead to non-Bloch dynamics in the MRFM environment are reviewed. Spin-relaxation mechanisms are also reviewed. A detailed description of the experimental apparatus is offered.

Effects of polydiallyldimethyl ammonium chloride coagulant on formation of chlorinated by products in drinking water

The objectives of this research work was to evaluate the reduction of THM precursors by cationic p-DADMAC and determine the correlations between the chlorine demand and trihalomethane formation in the presence of electrolyte solutions and ambient light. The chlorine demand was found to be significantly reduced provided that the H2SO4 electrolyte was fed to the sample solutions. The amount of CHCl3 formation was also decreased when the Na2SO4 electrolyte was introduced in spite of the levels of light intensity. The p-DADMAC can not only effectively remove the turbidity but also reduce the formation of CHCl3. The optimum dosage of p-DADMAC for reducing the turbidity, TOC and CHCl3 in the humic acid and source water samples was determined and depended upon the nature of organics.

Surgical management of refractory exit-site/tunnel infection of Tenckhoff catheter: technical innovations of partial replantation

OBJECTIVE

Catheter-related infection has been the major cause of catheter removal for peritoneal dialysis (PD) patients. A salvage technique--partial replantation of the infected catheter--was developed in our hospital to rescue catheters with refractory exit-site or tunnel infection.

PATIENTS

We performed 26 partial replantations of Tenckhoff catheters for 23 patients with refractory exit-site or tunnel infection and 2 patients with near-cuff perforation of the catheter. Their problems were all resolved successfully without interruption of PD.

INTERVENTIONS

We removed the infected portion of the catheter and preserved the still-functioning internal conduit, connecting it to a divided new catheter. All of the patients resumed PD immediately after the advancement of the new catheter through a new subcutaneous tunnel and exit site on the opposite side.

RESULTS

No technical complications such as disconnection of the catheter or leakage of dialysate were noted. Repeated partial replantation of the catheter was done for 1 patient with a new refractory exit-site infection. Tunnel infection was not an absolute contraindication for this procedure. About one third (34.6%) of our patients had preoperative tunnel infection.

CONCLUSION

Partial replantation of a Tenckhoff catheter is a simple and effective procedure for patients with refractory exit-site/tunnel infection and patients with near-cuff perforation of the catheter. Repeated partial replantation is also feasible for repeat exit-site infections.

Immunocytochemical localization of ribonuclease in yolk granules of adult Rana catesbeiana oocytes

To determine the localization of the pyrimidine-guanine sequence-specific ribonuclease in Rana catesbeiana (bullfrog) oocytes, the RNase was first isolated and used to prepare a specific rabbit antiserum. Only one protein of similar molecular size to the RNase was immunoprecipitated from ovary homogenate by the antiserum, but two bands were observed by Western blotting analysis. These two proteins were shown by further purification of antibody and Western blotting analysis to have similar antigenicity. Immunoprecipitation and Western blotting of tissue homogenates showed that the RNase was found predominantly in the ovary, but not in other tissues. The specific localization of the RNase was determined by immuno-electron microscopy of oocyte sections incubated with the specific antiserum; the yolk granules, but not other organelles, were found to contain the RNase. Most of the RNase was evenly distributed in the lateral amorphous area of the yolk granule but not in the central yolk crystal area which contains stored vitellogenin proteins. Our results indicate that the RNase is compartmentalized in the yolk granules of oocytes, which might prevent damage to cellular RNAs.

Stimulation of myosin light-chain kinase by Cd2+ and Pb2+

The effect of Cd2+ on myosin light chain kinase (MLCK) reported in the literature is controversial, apparently because the level of Ca2+ contaminating the reaction mixture could not be accurately controlled by the addition of a metal chelator when Cd2+ was also present. In the present study, we have reduced the contaminating Ca2+ to a trace level that did not interfere with the enzyme activity; thus the use of a metal chelator was not necessary. We showed that Cd2+, or Pb2+ had a biphasic effect on MLCK isolated from chicken gizzard: stimulation at low and inhibition at high concentrations. (The stimulatory effect of on the enzyme activity isolated from chicken gizzard: stimulation at low and inhibition at high concentrations). The stimulatory effect of Cd2+ or Pb2+ on MLCK activity was not seen in the absence of calmodulin, and was abolished by trifluoperazine, a calmodulin antagonist, indicating that the heavy metals exert their activation via calmodulin. The inhibition of the enzyme activity by Cd2+ or Pb2+ at higher concentrations was also seen with the calmodulin-independent catalytic fragment of MLCK, suggesting that the inhibition is probably through their binding to sulfhydryl groups that are essential for catalytic activity. Pb2+ was more effective than Cd2+ in stimulating the enzyme activity, but less potent in inhibition. The extent of stimulation by heavy metals most likely resulted from a combination of the biphasic effects. Dithiothreitol and N,N,N',N'-tetrakis (2-pyridylmethyl) ethylenediamine selectively chelated Cd2+ and Pb2+ over Ca2+, and reversed their stimulatory or inhibitory effect on MLCK.(ABSTRACT TRUNCATED AT 250 WORDS)

In vivo antithrombotic effect of triflavin, an Arg-Gly-Asp containing peptide on platelet plug formation in mesenteric microvessels of mice

Triflavin, an Arg-Gly-Asp-containing snake venom peptide, inhibits platelet aggregation through the blockade of fibrinogen binding to the activated platelets. In this study, platelet thrombus formation was induced by irradiation of the mesenteric venules with filtered light in mice pretreated intravenously with fluorescein sodium. Electron microscopy reveals moderately damaged endothelial cells, as well as aggregates consisting almost exclusively of platelets with pseudopod formation, and degranulated appearance. Triflavin (10-20 micrograms/g) significantly prolonged the lag period of inducing platelet plug formation in mesenteric venules when it was intravenously infused. Triflavin (20 micrograms/g) prolonged the occlusion time about 2-fold (from control 112 +/- 23 to 240 +/- 47 s). Furthermore, PGE1 briefly prolonged the occlusion time about 1.5-fold (from 105 +/- 21 to 168 +/- 20 s) when it was given by continuous infusion (40 micrograms/kg/min). On the other hand, triflavin was also effective in reducing the mortality of ADP-induced acute pulmonary thromboembolism in mice when administered intravenously at dose of 2-4 micrograms/g. Heparin (1.5 U/g) and indomethacin (200 micrograms/g) had no significant effect in prolonging the occlusion time or in reducing ADP-induced pulmonary embolism in mice. Therefore, triflavin is an effective antithrombotic agent in preventing the thromboembolism in these two in vivo models.

Transmural suture technique for trocar-site bleeding following laparoscopic cholecystectomy

Laparoscopic cholecystectomy was performed in a cirrhotic patient who had cholelithiasis. Despite the existence of coagulopathy, excessive bleeding from the gallbladder and nodular liver was avoidable. Dissection and extraction of the gallbladder went smoothly. However, serious bleeding from the trocar site occurred following the withdrawal of the trocar/cannula. The bleeding was not controllable by electrocauterization. A novel attempt using a transmural suture technique was tried, and hemostasis was achieved satisfactorily. Our patient enjoyed an uneventful postoperative recovery and was discharged 2 days after surgery.

Embolization of a renal transplant pseudoaneurysm following angiolipoma resection. A case report

The development of a pseudoaneurysm in renal allografts is a well-known complication of percutaneous biopsy. However, the authors report a case of pseudoaneurysm formation in a renal cadaver allograft, following documented angiolipoma resection prior to transplantation. Treatment required superselective embolization with multiple platinum coils.

Laparoscopic assisted gastrostomy tube placement

Gastrostomy commonly is performed for patients who have esophageal stenosis or difficulty in swallowing. The fact that most patients who require a gastrostomy are malnourished or debilitated urges surgeons to seek a safe and simple procedure. Percutaneous endoscopic gastrostomy (PEG) was introduced into clinical use and recommended as the procedure of choice in the 1980s. However, for patients with obstruction of the oroesophageal canal, PEG was not possible, and only traditional open gastrostomy could be considered. We describe a technique for placement of a gastrostomy tube under laparoscopic guidance. The technique is simple and easily mastered, requires equipment routinely used in laparoscopic surgery, and can be used by surgeons without gastroendoscopic experience. When performed properly, the method is simple, economical, and reliable.

Laparoscopic-guided gastrostomy

Gastrostomy is commonly performed in patients who have esophageal stenosis or difficulty in swallowing. The fact that most patients who require a gastrostoma are usually malnourished or debilitated urges surgeons to seek a convenient and reliable method for performing the operation. Percutaneous endoscopic gastrostomy (PEG) was introduced into clinical practice and recommended as the procedure of choice in the 1980s. However, PEG was not indicated and only traditional open gastrostomy was considered for those who had obstruction in their oroesophageal canal. We describe a technique for placement of a gastrostomy tube under laparoscopic control. The technique is easily mastered, requires equipment routinely used in laparoscopic control. The technique is easily mastered, requires equipment routinely used in laparoscopic surgery, and can be used by surgeons untrained in gastroendoscopy. When performed properly, the method is accurate, economic and reliable.

Revision of dysfunctional Tenckhoff catheters by laparoscopic technique in continuous ambulatory peritoneal dialysis patients

A laparoscopic technique was used to rescue dysfunctional Tenckhoff catheters in five continuous ambulatory peritoneal dialysis (CAPD) patients. This method proved to be effective in recovering the function of the catheters, whose malfunction was found to be due to catheter entrapment or endoluminal tamponing by the omentum. The videoscope-assisted laparoscopic technique provides access and allows identification and eradication of the specific etiology leading to catheter drainage failure. It also provides an alternative for treating patients with a dysfunctional Tenckhoff catheter. This method avoids the need to remove the original catheter or to reimplant a new catheter.

Epilogue: health care reform and productivity

Only a health care system that balances the best interests of consumers with those of employers and government payers will ultimately provide quality care at manageable costs. These need not be opposing interests.

Serum interleukin-2 and soluble interleukin-2 receptor in renal transplant recipients

Interleukin-2 (IL-2) and soluble interleukin-2 receptor (sIL-2R), released during T-lymphocyte activation, were measured in serial samples of serum from 32 patients with renal allografts and other uremic patients. Patients undergoing chronic hemodialysis had elevated sIL-2R levels (1,801.93 +/- 753.23 U/mL) which dropped after stable renal transplantation (822 +/- 438 u/mL). However, these values were higher than those of a normal control group (397.3 +/- 84.5 u/mL, p < 0.01). Marked elevation of sIL-2R (1,503.78 +/- 640 u/mL) was noted in patients with acute rejection episodes compared to those in a stable allograft condition (p < 0.02) and those with cyclosporine nephrotoxicity (793.2 +/- 245.2 u/mL, p < 0.01), but returned to a stable level after successful anti-rejection treatment (745.91 +/- 345.8 u/mL, p < 0.01). Acute tubular necrosis and infection also showed a comparable rise in the sIL-2R level. The increase in sIL-2R with rejection was found one to four days earlier than the clinical diagnosis of acute rejection. There was a marked rise in the serum IL-2 level of uremic and post-transplant patients when compared to normal subjects (34.76 +/- 32.16 u/mL and 9.3 +/- 12.7 u/mL vs 4.38 +/- 3.38 u/mL, p < 0.001), but no significant differences were found between the IL-2 level of patients with acute rejection and cyclosporine nephrotoxicity or acute tubular necrosis (3.74 +/- 4.51 u/mL, 1.57 +/- 1.25 u/mL and 6.73 +/- 6.3 u/mL, p > 0.05). The diagnostic value of sIL-2R assay was more meaningful than that of IL-2.(ABSTRACT TRUNCATED AT 250 WORDS)

An analysis of traffic injuries in Taiwan in relation to alcohol use and economic loss

Breath alcohol analysis of 449 patients with motor vehicle injuries attending the emergency department of a Taiwan urban general hospital during a 10-week period showed that 19.2 per cent had breath alcohol concentration (BAC greater than 0.002 per cent and 8.5 per cent greater than or equal to 0.05 per cent). Injured males were more likely to have BAC greater than or equal to 0.05 per cent than women (11 per cent vs 0 per cent). Injuries resulting from alcohol-associated collisions were about 6.7 times more likely to occur between 1800 and 0600 than at other time periods. A telephone survey after hospital discharge showed that the risk factors of alcohol use, speed at time of collision and type and site of collision were significantly associated with degree of economic loss resulting from the accidents. Logistic regression analysis showed that the odds of high economic loss associated with BAC greater than 0.002 per cent were three times greater than for persons in whom no alcohol was detected. This is the first study in Taiwan to use breath alcohol analysis in assessing the effect of alcohol consumption on motor vehicle injuries. The results show that alcohol use is an important cause of motor vehicle injuries. Preventive measures such as strict legal control of drunk driving and limitation of the hours that drinking places can stay open at night are recommended to reduce the damage caused by this severe public health problem.

Aortomesenteric bypass using autogenous saphenous vein graft for superior mensenteric artery aneurysm: report of a case

We report a 62-year-old man who had symptoms of abdominal angina and was diagnosed preoperatively with a superior mesenteric artery (SMA) aneurysm. The findings of the CT scan and angiography revealed a 3 X 4 cm saccular aneurysm at the proximal site of the SMA. During abdominal exploration, a weak pulsation of the SMA branches distal to the aneurysm was felt. The aneurysmal cavity was full of old thrombi. Brisk retrograde bleeding from the orifices of the connecting collaterals was seen after removal of the thrombi. Our operative procedures included endoaneurysmorrhaphy, proximal ligation, and distal interruption of the aneurysm. Vascular reconstruction by an aortomesenteric bypass using a segment of autogenous saphenous vein graft was also done. After creating the vein graft bypass, the weak pulsation of the distal SMA branches became normalized. The patient enjoyed an uneventful postoperative course and did not complain of abdominal pain on clinical follow up. Four months later, he received an evaluation including angiography and CT scan, which confirmed that the vein graft was patent and without deformity.

Activation of troponin C by Cd2+ and Pb2+

Certain heavy metal actions such as Cd2+ and Pb2+ mimic Ca2+ effectively in stimulating calmodulin (CaM). We now show that these cations also activate skeletal muscle troponin C (TnC), a Ca2(+)-binding protein highly homologous to CaM. Like Ca2+, these cations allow TnC to alter its electrophoretic mobility on polyacrylamide gels, and to bind to phenyl-Sepharose. Moreover, they activate TnC to stimulate myofibrillar ATPase. When TnC was removed from the skeletal myofibrils by treatment with trans-1,2-cyclohexanediamine-N,N,N',N'-tetraacetic acid (CDTA), the ATPase activity was no longer stimulated by the cations. However, after reconstitution of CDTA-treated skeletal myofibril with TnC, the response of ATPase to Ca2+, Cd2+ or Pb2+ was restored. These findings suggest that the activation of myofibrillar ATPase by Cd2+ and Pb2+ is mediated through TnC. The ability of the heavy metals to stimulate TnC-supported ATPase activity correlated quite well with the ability to increase the extent of the myofibrillar superprecipitation. The activation of TnC by Cd2+ or Pb2+ could constitute a possible molecular basis for their toxicity.

A technique using V-shaped transmural suture fixation in percutaneous endoscopic gastrostomy

A new method of percutaneous endoscopic gastrostomy (PEG) using V-shaped transmural suture fixation was performed on 2 patients with advanced carcinoma. This method secures the gastrostoma in a way superior to the conventional technique. It facilitates exchange of the catheter and avoids potential morbidity caused by peritoneal leakage even when tube feeding has been initiated in the early post-insertion stage. Inadvertent complications of hematoma formation and necrotizing fasciitis can also be prevented.

An extracorporeal perfusion system to bridge pediatric liver transplant candidates

An extracorporeal liver perfusion system was designed to maintain cadaver livers in an oxygenated, normothermic state for bridging procedures for hepatic transplantation. Nonpulsatile high flow and pulsatile low flow blood are supplied to the portal venous (PV) and hepatic arterial (HA) circulations. Controlled low blood flow (5-10 cc/kg [patient]/min) is exchanged between the high flow extracorporeal perfusion circuit (1 cc/g [liver]/min) and the patient. The system was evaluated in perfusions of fresh, excised pig livers (n = 5). The average oxygen consumption was 9 +/- 3 microliters/g/min, and bile production averaged 4.7 microliters/g/hr. Perfusion pressures and flows were normal in both the HA and PV circulations for about 4 hr. Pressures then gradually rose, especially in the HA circulation, causing flow to decrease, with subsequent mottling and discoloration of the liver. Red blood cell, platelet, and white blood cell counts fell continuously. Maintenance of liver function was assessed by clearance of an 80 mg taurocholic acid challenge. An average of 56% of injected acid was cleared from the perfused livers (n = 5) in the first half hour, compared with 90% and 25% for the in situ (n = 3) and unperfused (n = 3) control livers, respectively. The system consistently maintained livers in a moderately well functioning state through the first 4 hr of perfusion. Adequate support of animals with induced hepatic failure must now be demonstrated.

Preoperative evaluation of rectal carcinoma invasion using transrectal ultrasonography: preliminary experience of 30 patients

Transrectal ultrasonography was used to examine and to preoperatively evaluate rectal carcinoma invasion in 30 patients. Satisfactory sonography pictures were obtained in 23 patients. Four stages of tumor invasion were identified in our study. The sensitivity of preoperative evaluation in this study was 91%. In order to verify the correspondence between the ultrasonographic findings and the actual histo-anatomic condition of rectum, 10 resected rectal specimens were studied by in vitro ultrasonography. We conclude that the appearance of the muscularis propria layer of rectum as a homogeneous hypoechogenic band can be stably defined with transrectal ultrasonography and is crucial for accurate evaluation of cancer invasion. Although lymph node enlargement was shown as hypoechogenic nodules on the sonographic pictures, the existence of cancer metastasis could not be differentiated in this study.

Theoretical analysis of stable and unstable aspherical laser cavities

The low- order resonant modes of the stable and unstable aspherical resonators are studied by the Fox- Li method. An integral equation is given with which the effect of varying the aspherical cavity surface parameters on the field distribution, the energy loss and the intensity profile have been studied.

Stimulation of calmodulin by cadmium ion

Cd2+, a serious environmental pollutant in certain industrial regions, accumulates in mammalian tissues with a very slow turnover. Using various criteria, we studied the ability of Cd2+ to substitute for Ca2+ in calmodulin (CaM), a ubiquitous Ca2+-binding protein that mediates many of the Ca2+ effects. CaM bound Cd2+ with a Kd of 4.5 microM, presumably to the Ca2+-binding sites. Binding of Cd2+ allowed CaM to bind 2 moles chlorpromazine, or to form a complex with skeletal muscle troponin-I, troponin-T, or phosphodiesterase. Complex formation with phosphodiesterase led to its activation, which was observed even in the presence of glutathione or cysteine, agents known to chelate Cd2+. This raises the possibility that one manifestation of Cd2+ toxicity may be through its activation of CaM, thus upsetting its normal regulation by a cellular flux of Ca2+.

Activation of calmodulin by various metal cations as a function of ionic radius

The active form of calmodulin is a Ca2+ . calmodulin complex. The purpose of this investigation was to determine whether other metal cations substitute for Ca2+ to activate calmodulin. Binding of Ca2+ resulted in an altered conformation of calmodulin with an increased quantum yield in its tyrosine fluorescence. Qualitatively similar results were obtained with Zn2+, Mn2+, Cd2+, Hg2+, Sr2+, Pb2+, Tb3+, Sm3+, and La3+. The relative extents of fluorescence enhancement by these cations were related to their ionic radii: all cations with ionic radii close to Ca2+ (0.99 A) increased tyrosine fluorescence, whereas those with different ionic radii were not effective, or much less so. The change in calmodulin conformation by the cations was confirmed by its altered electrophoretic mobility on polyacrylamide gels. Cations that change the conformation of calmodulin allow it to stimulate phosphodiesterase. The relative extents of stimulation of phosphodiesterase by cations were also related to their ionic radii. Finally, the ability of metal cations to inhibit Ca2+ binding was similarly related to their ionic radii. In general, the closer the radius of a metal cation was to that of Ca2+, the more effective was the cation to substitute for Ca2+. The range of effective ionic radii was approximately 1 +/- 0.2 A. Calmodulin-stimulated phosphodiesterase activity by the cations was reversed by trifluoperazine, an antagonist of calmodulin.

Fecal Salmonella carriers in the Chinese army recruits in Taiwan

A survey for Salmonella carriers in the Chinese army recruits was made. Each isolated strain was identified by conventional biochemical tests, rapid Inolex plates, and for identification serological methods. The rapid Inolex plates could save approximately 24-48 hours for identification. Salmonella was detected in 1.83% of the rectal swabs collected from 1,150 recruits and 50 cooks. Among the 22 isolates 5, 1, 5, and 6 strains were identified as Salmonella groups: B, C1, D and E1 respectively and 5 strains were ungroupable. Salmonella isolates were found to be susceptible to chloramphenicol, kanamycin, ampicillin and tetracycline. Chloramphenicol or kanamycin is still the drug of choice for treatment of Salmonella infections, but the former should be used with caution.

Salmonellae in Tan-Shui River (author's transl)

A total of 61 water samples collected from 10 stations along the Chilung River, Hsintien Chi, Ta-han River were examined for salmonellae from Sep. 1978 to July 1979. There were 227 Salmonella strains isolated. After biochemical test and serological identification, 31 serotypes were verified. They were classified into 12 groups: B, C1, C2, C3, D1, E1, E2, E4, F, G2, H and R. S. derby was isolated in the highest rate (27.75%) and was followed by S. kuru (11.89%), S. worthington (7.93%), S. cambridge (5.73%), S. panama (4.41%). Twenty-three serotypes were firstly recovered from Taiwan area.