Closed-loop locking of an optical frequency comb to a large ring laser

We report on the frequency locking of a 16  m2 ring laser to a single tooth of an optical frequency comb referenced to a hydrogen maser, obtaining a frequency stability of 1 kHz over several days. In common mode operation, where the counterpropagating laser beams run on the same longitudinal mode index, a sensitivity to rotation of 3×10(-9) relative to Earth's rotation is obtained. To test a proposal to bypass time-varying backscatter-induced readout errors in large ring laser gyroscopes, we have operated the laser on adjacent longitudinal cavity modes. The Sagnac frequency due to Earth's rotation obtained in this fashion was strongly influenced by atmospheric pressure changes because the counterpropagating beams within the cavity are affected differently by geometric cavity fluctuations.

Long-term frequency stabilization of a 16 m(2) ring laser gyroscope

A 16 m(2) helium-neon-based ring laser gyroscope has been frequency stabilized to within 60 kHz over a period of three months. This is achieved using the beat frequency of the ring laser and an iodine-stabilized reference laser as a feedback signal on a pressure vessel enclosing the entire laser, under servo control. We demonstrate that we can compensate for, and thereby negate the influence of, atmospheric pressure variations, which are considerable sources of long-term instability.

How to detect the Chandler and the annual wobble of the Earth with a large ring laser gyroscope

We demonstrate a 16 m(2) helium-neon ring laser gyroscope with sufficient sensitivity and stability to directly detect the Chandler wobble of the rotating Earth. The successful detection of both the Chandler and the annual wobble is verified by comparing the time series of the ring laser measurements against the "C04 series" of Earth rotation data from the International Earth Rotation and Reference System Service.

Course of platelet counts in cirrhotic patients after implantation of a transjugular intrahepatic portosystemic shunt--a prospective, controlled study

BACKGROUND/AIMS

The pathogenesis of thrombocytopenia associated with advanced liver disease is still controversial. To study the impact of portal decompression on this hematologic complication, we conducted a prospective, controlled study to compare the course of platelet counts in patients after implantation of a transjugular intrahepatic portosystemic shunt (TIPS) with matched controls without shunts.

METHODS

Fifty-five TIPS patients and 110 controls matched for age, sex, Child-Pugh class, etiology of liver disease and baseline platelet count were included, and followed for 1 year. Follow-up visits were scheduled after 1 month, after 3 months, and at 3-month intervals thereafter.

RESULTS

Nonparametric Mann-Whitney U-tests revealed significantly higher platelet counts for TIPS patients as compared to controls from the 1st through the 12th month (p<0.01). During the study period, the median platelet count of TIPS patients increased by 19.7%, from 104.0/nl (IR: 68.0) to 124.5/nl (IR: 41.0). In contrast, during the same period the median platelet count of controls decreased by 17.1%, from 102.5/nl (IR: 66.0) to 85.0/nl (IR: 67.5). In the group of cases with baseline platelet counts < or =100/nl, platelet counts had increased by at least 25% at month 12 in 65% of TIPS patients, but in only 5% of controls (p<0.001). However, normalization of platelet counts, i.e. > or =150/nl, was not achieved in any case. Neither the portosystemic pressure gradient after TIPS implantation, nor the percentage of portosystemic pressure gradient reduction during the procedure was predictive of platelet response.

CONCLUSIONS

TIPS implantation increases platelet counts significantly. However, portal hypertension is clearly not the only mechanism contributing to thrombocytopenia in advanced liver disease.

Acute and chronic complications after implantation of a transjugular intrahepatic portosystemic shunt--a prospective study in 53 patients

Implantation of a transjugular intrahepatic portosystemic shunt (TIPS) is associated with a broad spectrum of acute and chronic complications. Data concerning incidence and prognosis of these complications are conflicting but of great importance toward defining the role of TIPS relative to other therapeutic options. We conducted a prospective, uncontrolled cohort study in 53 patients to assess incidence, management and clinical outcome of complications occurring after TIPS procedure. Mean follow-up was 21.1 +/- 9.0 months. Technique-related mortality was 2%; 9% of patients died within 30 days after TIPS procedure. The overall survival rate after 18 months was 74%. The overall incidence of primary hepatic encephalopathy (HE) within the first year was 25%, and 77% of episodes could be managed successfully by medical treatment or implantation of a reducing stent. The rate of patients without rebleeding after 18 months was 84%. Rebleeding was associated with shunt abnormalities, and the bleeding was controlled by revision of the stent. Two patients died of variceal hemorrhage. The cumulative incidence of shunt stenosis or occlusion was 47% after 18 months. The technical success rate of shunt revision was 97%. TIPS implantation is associated with a considerable risk of HE and shunt stenosis or occlusion. Nevertheless most episodes of HE can be managed by medical treatment or implantation of a reducing stent. Angiographic revision of the stent is successful in nearly all cases of stenosis or occlusion. We therefore conclude that TIPS implantation in combination with careful follow-up examinations constitutes effective medium-term treatment of portal hypertension in a considerable proportion of patients.

Clinical outcome two years after implantation of a transjugular intrahepatic portosystemic shunt for recurrent variceal bleeding

OBJECTIVE

Implantation of a transjugular intrahepatic portosystemic shunt (TIPS) is a relatively new therapy for variceal bleeding. The aim of this study was to assess clinical course 2 years after TIPS procedure.

DESIGN

The study was designed as a prospective, uncontrolled cohort study.

METHODS

Forty-six patients who underwent successful TIPS implantation were followed prospectively by clinical examinations, duplex sonography and portal venography. Mean follow-up in surviving patients was 24.1 +/- 9.0 months.

RESULTS

The cumulative rate of survival was 80.4% at 1 year and 70.2% at 2 years. The cumulative rebleeding rate was 12.4% at 1 year and 21.3% at 2 years. The mortality rate of episodes of variceal rebleeding was 22.2%. Variceal rebleeding was associated with shunt abnormalities, and successful shunt revision resulted in control of the bleeding. The cumulative incidence of shunt stenosis or occlusion was 41.2% at 1 year and 54.9% at 2 years. Of those patients without shunt abnormalities after 1 year, 23.3% developed shunt stenosis or occlusion during the second year after TIPS procedure. Shunt revision was successful in 96.6% of cases. Secondary patency rate was 88.1% after 2 years.

CONCLUSION

Successful TIPS implantation results in a low rate of morbidity and mortality from variceal rebleeding over 2 years. TIPS creation in combination with careful follow-up examinations represents an effective long-term treatment of recurrent variceal bleeding. Even in patients in whom no shunt abnormality is detected during the first year, routine duplex follow-up examinations should be continued at 3-month intervals.

Severe microbial keratitis in temperate and tropical Western Australia

To determine the patterns of severe microbial keratitis in Western Australia, all acute admissions over a 2 year period to the Department of Ophthalmology, Royal Perth Hospital were assessed. Fifty-three cases (n = 53) of severe, presumed microbial keratitis were identified. Seventy per cent of these eyes had a visual acuity of 6/60 or less on admission and only 38.8% had 6/12 or better corrected acuity following resolution of the keratitis. The most commonly identified predisposing factors were: prior ocular surgery with or without exposed monofilament sutures (43.4%); contact lens wear (22.6%); lid malposition (17.0%); history of ocular trauma (15.1%); and history of previous herpes simplex keratitis (13.2%). It is notable that 26.4% of the subjects had been applying topical ophthalmic corticosteroids prior to admission. Following corneal scrape or biopsy a positive microbial diagnosis was made in 71% of samples, with Gram-negative and Gram-positive bacterial isolates being equally frequent. Five cases of Acanthamoeba keratitis were identified following corneal biopsy. Where antibiotic sensitivities were available, it was noted that 61.5% of Gram-positive and 46.1% of Gram-negative bacteria were susceptible to chloramphenicol, with 84.6% of Gram-negative bacteria being sensitive to gentamicin. Many of these severe cases of microbial keratitis might have been avoided, or their severity lessened, by earlier identification of predisposing risk factors, more intensive and appropriate antibiotic administration, and improved patient education following ocular surgery.

Benzimidazolones and renzapride facilitate acetylcholine release from guinea-pig myenteric plexus via 5-HT4 receptors

The effects of the 5-HT4 receptor agonists BIMU 8, BIMU 1, renzapride and of the 5-HT1p receptor agonist 5-hydroxyindalpine on basal and electrically evoked outflow of tritium were studied in guinea-pig longitudinal muscle myenteric plexus preparations preincubated with [3H]choline. Muscle contractions were recorded simultaneously. BIMU 8 caused a calcium dependent and tetrodotoxin sensitive increase in basal [3H]outflow that was assumed to represent release of [3H]acetylcholine. In addition, BIMU 8 enhanced the release of [3H]acetylcholine and twitch contractions evoked by submaximal electrical stimulation. Ondansetron (1 mumol/l) did not change the effects of BIMU 8, but DAU 6285 and tropisetron (each 1 mumol/l) competitively antagonized the various facilitatory effects of BIMU 8 with pA2 values of 7.0-7.2 (DAU 6285) and 7.0-7.3 (tropisetron). The phosphodiesterase inhibitors IBMX and rolipram did not increase the effects of BIMU 8. BIMU 1 and renzapride also concentration-dependently increased basal release of acetylcholine, and release and contractions caused by submaximal stimulation. The effects of BIMU 1 and renzapride were competitively antagonized by 1 mumol/l tropisetron (pA2 6.6-7.1). The EC50 values for the increase in the evoked [3H]acetylcholine release and contractions were closely similar. 5-Hydroxyindalpine did not change basal release and slightly inhibited the evoked release of [3H]acetylcholine. Release of acetylcholine and contractions elicited by submaximal stimulation were strongly inhibited by (+)-tubocurarine which indicates that nicotine ganglionic transmission is involved in this kind of release. The results suggest that BIMU 8, BIMU 1 and renzapride stimulate 5-HT4 receptors at cholinergic interneurones and thereby facilitate nicotinic ganglionic transmission in the myenteric plexus.(ABSTRACT TRUNCATED AT 250 WORDS)

[Ultrasound-guided fine-needle biopsy with an automatic full-incision system: the initial experiences and comparison with a conventional biopsy gun]

The purpose of this study was to evaluate the efficacy of a new automatic biopsy device (Autovac, Angiomed, Karlsruhe, Germany) in ultrasound (US) guided biopsies of focal abdominal lesions. 50 consecutive patients with focal abdominal lesions underwent US guided biopsies. In the first 24 patients, needle passes were performed with the Autovac system (outer diameter 0.95 mm) as well as with the Biopty gun (outer diameter 0.9 mm) (Bard Covington, USA). The size and the quality of the histologic and the cytologic material obtained by both systems were evaluated by histopathologists blinded to the system used. Autovac yielded significantly more material (defined as the area of the obtained tissue cores) and a significantly higher quality score than did the Biopty system. 96% of the histologic specimen and 100% of the cytologic smears obtained with Autovac were diagnostic, compared to 70 and 81% with Biopty, respectively. With the exception of a short-time elevation of the blood pressure in one patient, no complications occurred. The results indicate an advantage of the automatic full-cut type system Autovac over the tru-cut type Biopty gun in US-guided biopsies of focal abdominal lesions.

Modulation by 5-HT3 and 5-HT4 receptors of the release of 5-hydroxytryptamine from the guinea-pig small intestine

The effects of agonists and antagonists of 5-hydroxytryptamine (5-HT) receptors on the release of endogenous 5-HT from enterochromaffin cells were studied in the vascularly perfused isolated guinea-pig small intestine. The experiments were done in the presence of tetrodotoxin in order to exclude a neuronally mediated influence on 5-HT release. The 5-HT3 receptor agonist 2-methyl-5-HT increased 5-HT release, and this effect was antagonized by 1 nmol/l tropisetron. Nanomolar concentrations of tropisetron, MDL 72,222 and granisetron decreased 5-HT release. Ondansetron (0.1 and 1 mumol/l) did not modify 5-HT release. 5-Methoxytryptamine, BIMU8 and cisapride concentration-dependently inhibited 5-HT release. BIMU8 was more potent than 5-methoxytryptamine. Micromolar concentrations of tropisetron (1 and 10 mumol/l) enhanced the release, whilst methiothepine (0.1 mumol/l) did not affect the release of 5-HT. The results suggest that enterochromaffin cells of the guinea-pig ileum do not contain 5-HT1 and 5-HT2 receptors, but are endowed with 5-HT3 and 5-HT4 autoreceptors. Activation of the 5-HT3 receptors triggers a positive feedback mechanism leading to an increase of 5-HT release. The 5-HT3 receptors on the enterochromaffin cell differ from neuronal 5-HT3 receptors on guinea-pig myenteric plexus by their high affinity for tropisetron and MDL 72,222, and their very low affinity for ondansetron. Stimulation of 5-HT4 receptors causes inhibition of release; the inhibitory 5-HT4 receptor mechanism appears to predominate.

[The percutaneous catheter drainage of pancreatic pseudocysts]

The results of CT/US-guided percutaneous drainage in 35 patients with pancreatic pseudocysts are reported. 27 patients recovered without surgery and no further treatment was required. 8 patients required a subsequent surgery due to recurrence. The role of CT/US-guided percutaneous drainage in pancreatic pseudocysts as well as an analysis of the technical aspects associated with a successful procedure are discussed. Although US may be used, we believe CT is safer and allows more precise localisation and guidance in the treatment of pseudocysts.

[The percutaneous ultrasonic-guided fluoroscopy-controlled drainage of pericardial fluids]

The results of 25 ultrasonographically guided percutaneous pericardial drainage procedures and of one pericardiocentesis performed in 25 patients with pericardial fluid collections are reported. After initial puncture of the pericardial cavity under sonographic guidance, dilatation and placement of 5F to 8.3F catheters in Seldinger technique was controlled fluoroscopically in 22 procedures. Clinical indications were emergency treatment of tamponade (n = 6) or urgent treatment of large (n = 14) pericardial effusions. The remaining 6 procedures were performed to establish specific diagnoses of small effusions. Puncture sites were subxiphoid in 23 and left parasternal in 3 cases. The volume of aspirated fluid ranged from 20 to 1710 ml (median: 615 ml). Median duration of pericardial drainage was 3 days (range less than 1 day to 21 days). A specific diagnosis was obtained in 48% of patients. 4 patients had subsequent elective surgical intervention for recurrent effusion or for pericardial biopsy. Three minor complications included one vasovagal reaction and two asymptomatic pneumothoraces. Percutaneous ultrasonically guided and fluoroscopically controlled placement of a pericardial catheter is safe and effective for treatment and diagnosis of pericardial effusions.

Therapeutic transrenal occlusion of the ureter: solution of plug migration problem

Vesicovaginal fistulas in three patients and a vesicocutaneous fistula in one patient were treated by percutaneous transrenal occlusion of the ureter with a commercially available silicone occluder (Angiomed, Karlsruhe, Germany) which was secured by means of histoacryl placed on top. Urinary flow was diverted by a permanent nephrostomy tube. We observed no complications (e.g., urinary tract infection, occluder migration, or recurrence of urine discharge) at an average follow-up period of 9.1 months.

[A posttraumatic pseudoaneurysm of the hepatic artery. Duplex sonographic diagnosis and follow-up in spontaneous thrombosis]

Guided percutaneous biopsy represents a standard procedure in establishing specific diagnosis of focal liver lesions. We report a case of left hepatic artery pseudoaneurysm diagnosed by means of Duplex Doppler sonography (DS) immediately before percutaneous biopsy should be performed. Selective hepatic artery embolization was planned, but spontaneous thrombosis of the pseudoaneurysm was documented by DS and angiography, respectively. DS is able to identify the vascular nature of a lesion and is helpful to avoid puncture of an aneurysm.

[Vascular kidney transplant rejection--is a duplex sonographic diagnosis possible?]

The diagnostic value of quantitative Duplex Doppler sonography (DS) in renal allograft evaluation is being viewed increasingly critically. We undertook a retrospective analysis of DS in 51 consecutive patients to assess the capability of DS in the diagnosis of vascular rejection. At the time of renal allograft biopsy, a mean resistive index (RI) was calculated from Doppler measurements within main, segmental, interlobar and arcuate arteries and correlated with histological diagnosis. Our results indicate a low specificity (36% for RI greater than 0.7), low sensitivity (35% for RI greater than 0.9) as well as a low positive predictive value (54% for RI greater than 0.7) for the diagnosis of vascular rejection. Therefore, elevation of the RI is an unspecific finding in different causes of allograft dysfunction. Thus, renal biopsy to establish specific histologic diagnosis of allograft dysfunction remains mandatory.

"False positive" immunoscintigraphic diagnosis of liver abscesses in a patient with a necrotic liver tumour

The following report describes the scintigraphic findings in a patient who underwent immunoscintigraphy with anti granulocyte Mab because of septic fever. Focal tracer accumulation in the liver corresponding with hypoechoic and hypodense areas documented by sonography and computed tomography was believed to represent liver abscesses, yet surgery and autopsy revealed a large necrotic cholangiocellular liver carcinoma. The possible mechanisms, which had led to the false positive immunoscintigraphic image are discussed and we conclude that a necrotic neoplasm has to be a major differential diagnosis in any case of positive liver uptake in an anti granulocyte scan.

[Aneurysm of the superior mesenteric artery. Its diagnosis and clinical significance]

This is a report about 4 patients with aneurysms of the superior mesenteric artery of arteriosclerotic, mycotic and probably congenital etiology together with a review of the literature as to the etiology, diagnostic possibilities and therapy. Arteriography is the method of choice even though a diagnosis may be possible by sonography or CT in special cases. Even though an aneurysm of the superior mesenteric artery is rare, it has to be considered in the differential diagnosis of persisting abdominal problems of unknown origin. This is especially true for patients with a predisposing history such as previous or existing endocarditis, sepsis, arteriosclerosis and hypertension. Because of the possibility of rupture followed by life threatening bleeding an adequate diagnostic step such as arteriography has to be considered finally.

[2-dimensional echoencephalography or cranial CT in premature or newborn infants with suspected intracranial hemorrhages]

65 newborns or low-birthweight infants with suspicion of intracranial hemorrhage were examined with B-mode small part scanners. In 12 cases the diagnosis made by ultrasound could be compared with CT. There was a similar accuracy of both methods in case of intraventricular (IVH) and subependymal (SEH) hemorrhage. SEH seems to be easier detected by US. On the other hand there are problems in diagnosing subdural (SDH) and intracerebral (IHC) hemorrhages by US. These problems are caused by the adjacent skull, but does not exist for CT. B-mode-Echoencephalography is the method of choice for examination of high risk infants and for the follow up, because US is a cribside method and of high diagnostic accuracy. CT-studies should be done in case of hemorrhage adjacent to the skull and if the US-diagnosis seems not to be reliable.

[Percutaneous transluminal removal of embolised catheter fragments (author's transl)]

Seven patients had a percutaneous transluminal removal of catheter fragments using a Dormier stone-basket within the last 14 months. An immediate intervention should be performed because serious complications are expected from catheter embolization. The percutaneous transluminal catheter retrieval as a method of low risk and of little discomfort to the patient should always precede surgical procedures. The Dormier-basket proved to be a successful and easy handling catheter instrument in all our cases.

[Radionuclide angiography (RNA) with 99mTc-DTPA to follow palliative embolization of renal cell carcinoma (author's transl)]

In 14 patients with renal cell carcinoma, not to be treated by nephrectomy, radionuclide angiography with 99mTc-DTPA (RNA) was employed before and after palliative tumor embolization. If RNA revealed remaining perfusion of the tumor, functional scintigraphy with 131J-hippurate was performed to detect and quantify residual function. Up to 16 months after embolization, 7 patients (50%) revealed neither residual perfusion nor function. In 5 patients (36%) remaining perfusion without functioning renal parenchyma and in 2 patients (14%) residual perfusion with additional function were found. In 4 cases (28%) a nuclear "tumor-halo" was imaged, describing a stripe of high radioactivity caused by capsular arteries surrounding the avascular tumor. RNA has proven to be a suitable non-invasive procedure for to blow-up of embolized renal cell carcinomas.

[Angiographic and isotopic studies following pole resection of kidneys in dogs and hemostasis performed by infrared-contact-coagulation (author's transl)]

It has been shown in an animal experiment that alterations of the renal vasculature and parenchyma after hemostasis performed by Infrared-Contact-Coagulation are best shown by intravital magnification angiography (magnification factor 2.22). Following pole resection and hemostasis the final morphologic state is reached 6 weeks postoperatively. The resulting scar penetrates into the parenchyma up to 1 cm. The loss of function corresponds to the parenchymal defect. There was no additional loss of renal function or damage to the parenchyma on nuclear medicine or histologic examinations.

[Significance of ultrasonography in diagnosing complications following renal transplantations (author's transl)]

Routine follow-up examinations by ultrasonography after renal transplantation were performed in 72 patients from December 1978 until March 1980. The aim of these controls was to recognize local complications in the area or surgery in order to differentiate from a rejection reaction in patients with unclear clinical symptoms. 22 out of 72 patients had local complications. 15 out of those 22 were detected by ultrasound in a state without clinical symptoms, which then could be treated by surgical or urological intervention. We therefore believe that routine follow-up examinations after renal transplantation by ultrasound are indicated in order to recognize local complications. Nuclear procedures should be employed if alteration of blood flow or disturbed function of the transplanted kidney are considered.

[Computed tomography and densitometric pattern of pulmonary lesions (author's transl)]

Fifty-five peripheral pulmonary lesions in 46 patients were examined by computed tomography. The results were correlated with histologic diagnoses. The series comprised 26 bronchial carcinomas, 17 metastases, 4 chondromas, 5 tuberculomas and 3 echinacoccal cysts. The high resolution capacity of CT in the evaluation of macro pathologic pattern specially with the electronic image processing, with densitometry in regional interest is emphasised. Therefore cysts, fatty and other solid masses in the lung can be distinguished. Further more one can gain information of the underlying tissue on the basis of absorption profile.