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Biomedical subjects

R Hoffmann

Publications and source records attributed to R Hoffmann.

At least 325 records · Page 18Linked to original sources
PubMed1992

Expression, purification and biochemical characterisation of the human immunodeficiency virus 1 nef gene product.

The human immunodeficiency virus 1 (HIV-1) nef gene encoded by the HIV-1 isolate lymphadenopathy-associated virus type 1 was expressed in Escherichia coli under the control of the tac promoter. The protein is found mainly in the soluble part of the bacterial lysate; a simple two-column purification scheme has been developed allowing isolation of the recombinant protein without using denaturing agents. Analysis of the circular dichroism spectra reveals that the purified protein is folded and has a helix content of 16% and a beta-pleated sheet content of 31%. GTPase activity and binding of guanine nucleotides were measured for Nef and compared with the results obtained under identical experimental conditions for p21rasC, which represents a typical, well-characterized guanine-nucleotide-binding (GNB) protein. Within the limits of error, native Nef does not show GTPase activity and does not bind guanine nucleotides strongly (association constant, Kass less than 5 x 10(3) M-1). An upper limit for the association constant of Nef for ATP was determined by equilibrium dialysis as 5 x 10(3) M-1. Nef can be autophosphorylated by ATP; under the experimental conditions used, 1-2% of the protein become phosphorylated. Correspondingly, our Nef preparation shows a low, but significant, ATPase activity. In conclusion, Nef is not a member of the GNB protein family, but a possible role as a protein kinase cannot be excluded.

Adenine Nucleotides↗
PubMed1992

[Perioperative prevention of thromboembolism with standard heparin and low molecular weight heparin, evaluation of postoperative hemorrhage. A double-blind, prospective, randomized and mono-center study].

From October 1987 through June 1988 594 patients admitted to the department of visceral surgery, were included in a prospective, randomized double-blind study dealing with postoperative thromboembolic complications. 5000 I.U. heparin were administered twice daily to one group, the other group received a single dose of low molecular heparin (3000 I.U. anti-Xa) daily. In each group more than 290 patients were included. Diagnostic screening was done using LCCT (Liquid Crystal Contact Thermography) and phlebography. 130 patients had to be excluded from the study. 66 patients because of contra-indication, 54 patients because of administrative failing and 10 patients were excluded by the surgeon himself. There was no significant difference between the two groups concerning thromboembolic complications. However analysis of the patients who were excluded from the study shows an increase of thromboembolic complications. Looking at cases of postoperative haemorrhage we found that there was no significant difference between both groups. Interestingly, even compared to the excluded group, there was no difference. In our study postoperative haemorrhagic complications did not depend on the method of prophylaxis but on the surgeon performing the operation. Should a patient have a contra-indication for administration of thromboembolic prophylaxis, he has to take a certain risk of thrombosis. The fact that prophylaxis was not initiated because of neglect or fear of haemorrhagic complications is not only unforgiveable, but dangerous as well.

Adolescent↗
PubMed1992

Association of a heat-stable inhibitor protein with cyclic-3',5'-AMP-dependent protein kinase from the nematode Ascaris suum: purification and characterization of the inhibitor.

An inhibitor protein of the catalytic subunit of the cyclic 3',5'-AMP-dependent protein kinase from the nematode Ascaris suum was isolated and characterized. The molecular weight of the inhibitor was estimated as 28,000 by electrophoresis under denaturing conditions and as 30,000 by gel permeation chromatography on Superose 12. The Trypsin-labile inhibitor was resistant to short incubations (less than or equal to 5 min) at temperatures up to 95 degrees C and at pH 3. It affected the protein kinase from Ascaris and bovine heart with almost the same affinity, and inhibition was not relieved by the presence of cAMP and cGMP. However, the inhibition was antagonized by low concentrations of heparin. Unlike in mammalian tissues, the concentration of the inhibitor was sufficiently high to exert at least 90% inhibition of the protein kinase activity in Ascaris muscle. Therefore, the inhibitor may play a role in cellular regulation in the nematode.

Animals↗
PubMed1992

[The imaging diagnosis of sclerosing peritonitis (SP) following continuous ambulatory peritoneal dialysis (CAPD)].

Sclerosing peritonitis is a serious complication of CAPD characterised by thickened peritoneal membranes which lead to decreased ultrafiltration and intestinal obstruction. The roentgenographic signs of SP were analysed in 11 patients who underwent plain x-ray of the abdomen, follow-through examinations of the small bowel, ultrasonography and computed tomography. Results were correlated with the histological degree of SP. Besides the non-specific findings of intestinal obstruction, patients with histologically marked SP had loculated fluid collections, thickening of the bowel wall and/or peritoneum, peritoneal calcifications and thickened peritoneal membranes. Due to the fact that postoperative complications often occur in patients with SP, detection of the radiological signs should lead to cautious surgical interventions and changeover to haemodialysis.

Acute Disease↗
PubMed1992

Transoesophageal stress echocardiography for pre-operative detection of patients at risk of intra-operative myocardial ischaemia.

Patients with coronary artery disease have an increased risk of developing intra-operative myocardial ischaemia and peri-operative myocardial infarction. Pre-operative identification of patients at risk of developing peri-operative myocardial ischaemia is often difficult or even impossible due to the inability of the patient to perform an exercise test. For those unable to perform physical exercise a system has recently been described combining transoesophageal echocardiography with simultaneous transoesophageal atrial pacing via the same probe to detect pacing-induced wall motion abnormalities, a sign of coronary artery disease. In a prospective study, 20 patients with clinically suspected coronary artery disease undergoing hip replacement were examined pre-operatively by transoesophageal stress echocardiography. During the subsequent operation the incidence of intra-operative ischaemia was evaluated again in all 20 patients by transoesophageal echocardiography. In eight of the 20 patients (40%) wall motion abnormalities could be induced by transoesophageal stress echocardiography pre-operatively. Intra-operative wall motion abnormalities occurred in six of these eight patients. In two patients with wall motion abnormalities induced by transoesophageal stress echocardiography no abnormalities occurred during surgery. However, in those in whom wall motion abnormalities did occur during operation they occurred in the same left ventricular segment as those initiated by stress echocardiography. None of the patients without pre-operatively inducible wall motion abnormality developed them during surgery. No patient developed a myocardial infarction intra- or post-operatively. Thus, preoperative transoesophageal stress echocardiography is a valuable technique for the detection of patients who may develop ischaemic wall motion abnormalities during surgery.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1992

Transoesophageal echocardiography in the diagnosis of cor triatriatum; incremental value of colour Doppler.

Cor triatriatum sinistrum is a rare congenital cardiac abnormality often accompanied by other malformations. Transthoracic echocardiography does not always define the membrane and associated abnormalities; so, transoesophageal colour Doppler echocardiography was used to visualize intra-atrial blood flow through the intra-atrial membrane in a patient in whom the membranous orifice could not be seen by precordial echocardiography. There was no anomalous pulmonary venous drainage or associated atrial septal defect.

Adult↗
PubMed1992

Initial experience with a multiplane transoesophageal echo-transducer: assessment of diagnostic potential.

BACKGROUND: the prototype of a transoesophageal echocardiographic transducer with a rotatable cross-sectional scanning plane underwent initial evaluation. METHODS: the 5 MHz, phased array, 64 element transducer is incorporated into a 16 by 11 by 40 mm echoscope tip. The instrument also has pulsed wave and colour flow Doppler capabilities. Exterior controls allow continuous mechanical rotation of the scanning plane from 0 degree, corresponding to the conventional transverse plane, through 180 degrees, thereby encompassing all possible planes. RESULTS: 103 patients underwent examination without complications; two additional patients were excluded because of difficulty in swallowing the probe. Advantages include precise alignment of aortic valve long- and short-axis views, long-axis views of the ascending aorta (mean visualized length: 6 cm), and full scanning of the entire circumference of the mitral valve and the left ventricle. Separation of paravalvular and transvalvular leakage in prosthetic valves is distinctly improved. CONCLUSION: multiplanar transoesophageal imaging is feasible and increases the diagnostic yield, especially in mitral and aortic pathology and in the assessment of left ventricular wall motion. Three-dimensional reconstruction is an attractive potential application.

Adult↗
PubMed1992

Blunt abdominal trauma in cases of multiple trauma evaluated by ultrasonography: a prospective analysis of 291 patients.

Early recognition of blunt abdominal trauma in patients with multiple injuries and in shock is of utmost importance and calls for a rapid screening method. The reliability of diagnostic ultrasonography in detecting hemoperitoneum in patients with multiple trauma was evaluated prospectively. From 1986 to 1990, 291 patients with severe multiple injuries (ISS greater than 20, mean ISS 31.2) were included in the study. Laparotomy was performed on 117 patients (40%). Initial ultrasound (US) findings showed a sensitivity, specificity, and accuracy of 89%, 97%, and 94%, respectively, in detecting intra-abdominal injuries requiring surgical repair. The positive and negative predictive values were 94% and 95%, respectively. A standardized management of frequent repeat US studies can even improve on these numbers. In our department ultrasonography has replaced diagnostic peritoneal lavage (DPL) as the diagnostic study of first choice. Diagnostic peritoneal lavage is reserved for selected cases only.

Abdominal Injuries↗
PubMed1992

The use of ultrasonography in the foot and ankle.

Ultrasonography of the soft tissue has achieved an increasing importance in the last years. Since sonography of the shoulder, knee, muscles, and tendons has become a routine method, there is less application of ultrasound in foot and ankle pathology. Since 1985, ultrasonography has been the routine examination technique in the Trauma Department of Hannover Medical School, Hannover, Germany. We now have a series of more than 4000 sonographic examinations. This paper gives a comprehensive overview of the possibilities in application and technique of ultrasonography in foot and ankle disorders. The sonographic patterns of the pathological changes of the main structures are described.

Ankle Joint↗
PubMed1992

[Osteosynthesis of distal radius fractures with biodegradable fracture rods. Results of two years follow-up].

Forty distal fractures of the radius were stabilized with biodegradable polyglycolic acid rods (Biofix). A forearm plaster cast was fit for 4 weeks. Nine patients developed late (4 to 16 weeks) aseptic inflammatory reactions at the pin site, which were treated by débridement. The histological specimens showed giant-cell phagocytosing fragmented polyermic debris. In two cases a bacterial wound infection occurred secondary to débridement. All local reactions healed within 4 weeks. A classification system and treatment regimen for these inflammatory reactions are proposed. Thirty-four patients (including those with local foreign body reaction) were available for the 2-year follow-up. The anatomical results of fracture reduction on the postoperative and follow-up radiograms were the same, confirming good mechanical fracture stabilization. According to the Sarmiento score, the overall results were excellent and good in 31 cases. In one of the three fair cases, the result was clearly due to the initial local foreign-body reaction. Because of the high incidence of local inflammatory reaction, for now clinical application of biodegradable implants seems problematic despite the good overall 2-year results. This should only be advocated for well-controlled prospective studies using implants with improved biocompatibility.

Adult↗
PubMed1992

[Initial clinical trial of a multi-planar transesophageal echoscope].

The prototype of a multiplanar transesophageal echocardiographic transducer was evaluated clinically. This 5 MHz, phased array, 64-element transducer allows to continuously rotate the imaging plane from the transverse (0 degree) position to a maximal 180 degrees position, thus encompassing transverse, longitudinal, and every intermediate position. The transducer is incorporated in the echoscope tip measuring 16 by 11 by 40 mm. The shaft of the instrument is 110-cm long and has a 9-mm diameter. The instrument has pulsed wave, continuous wave, and color Doppler capabilities. 176 clinical patients were examined with the multiplane transducer. No complications occurred. Advantages of this transducer included: 1) comprehensive scanning of the whole mitral circumference and mitral valve; 2) quick and precise alignment of aortic valve long and short axis views, including long axis views of the ascending aorta, with a mean visualized length of 6 cm; 3) improved imaging and evaluation of transvalvular and paravalvular regurgitant jets in mitral and aortic valve prostheses; 4) complete evaluation of all left ventricular segments using multiple planes from transgastric and transesophageal transducer positions. An important potential application is three-dimensional reconstruction of cardiac structures and color Doppler jets.

Adult↗
PubMed1992

[Severe necrotizing fasciitis].

The pathophysiology of necrotizing fasciitis remains unclear in patients with no apparent immunologic disorders. Between 1987 and 1990 we treated six patients with necrotizing fascitis and septic-toxic multiple organ failure, three patients survived. The mean age was 38 years (25-62). In all patients the primary bacteriological examination revealed streptococcus. Between the first symptoms and an adequate therapy were 4 days in surviving patients and 7 days in patients who died. Four patients showed spread of the gangrene into the adjacent tissue: muscles (n = 3), bowel (n = 2), mediastinum (n = 1). Adequate débridement was not possible or not performed in patients with spread into the abdominal cavity or the mediastinum. These patients did not survive. The duration of intensive care treatment in surviving patients were 14 to 78 days. We conclude that survival of patients with severe necrotizing fasciitis is influenced by the delay before adequate treatment, the localisation of the gangrene and intensive care facilities.

Adult↗
PubMed1992

[Technique of intraoperative laparoscopic cholangiography].

Since laparoscopic cholecystectomy has been established at our institution, the routine use of intraoperative cholangiography was abandoned but preoperative intravenous cholangiography and sonography are mandatory. However, these investigations are not always conclusive and in some cases not applicable. We have therefore started to use selective intraoperative laparoscopic cholangiography for laparoscopic cholecystectomy. Our technique and the materials required for this peroperative investigation are described in the present article.

Cholangiography↗
PubMed1992

[Prevention of venous thromboembolism in surgery].

Incidence of postoperative deep venous thrombosis extends from 7% (transurethral prostatectomy) to more than 50% (hip surgery) depending on the magnitude of trauma and due to the corresponding surgical procedure. Although more common with higher age, younger patients suffer from postoperative thromboembolic complications as well. This insight leads to the conclusion that all immobilized adult patients or those needing an operation are to receive thromboembolic prophylaxis should there be no contraindication. As 50% of all postoperative thromboses develop sometime during the operative procedure, thromboembolic prophylaxis has to be effective intraoperatively as well. The first dose must therefore be preoperative. Duration of prophylaxis depends on the ambulation of the individual patient and should be maintained for at least seven days. Physiotherapeutic measures and drug therapy should complement each other. Low molecular heparins have been very successful lately. Their effect on thrombosis in visceral surgery has been equal when compared with unfractioned heparin whereas the effect in hip surgery compared to unfractioned heparin has been even more promising. Due to the longer half-life of low molecular heparin when compared with unfractioned heparin and its better bioavailability, one dose of low molecular heparin a day is sufficient. This is certainly a benefit for the patient and the nursing staff. To our current knowledge the tendency toward bleeding does not differ basically if low molecular heparins or standard heparin is being used. In patients with spinal anaesthesia, as with low molecular heparins, the first dose has to be administered preoperatively. Different ways of application are possible.

Anticoagulants↗
PubMed1992

[Primary sonographic diagnosis and follow-up of muscular and tendon injuries of the lower extremity].

Ultrasound examination has become an important diagnostic method in muscle and tendon injuries. In addition dynamic ultrasound examination allows evaluation of the course of healing from various aspects. Starting with the sonoanatomy, the pathologic ultrasound patterns typical for injuries to muscle and to Achilles, patellar and quadriceps tendons are demonstrated. As complement to clinical examination, ultrasonography enables appropriate adaptation of the therapy concept to the course of healing. In the hands of experienced operators, ultrasound examination has reached a high level of sensitivity and specificity in these injuries and can justifiably be routinely performed.

Achilles Tendon↗
PubMed1992

[Initial experiences with the bio-fragmentable Valtrac anastomosis ring].

The biofragmentable ring (Valtrac) to perform a sutureless bowel anastomosis was used in a short period until complications rate became to big. There were six ileo-colostomies with the 28 mm ring and 7 colo-colostomies with the 31 mm ring. In 4 patients additional sutures were placed because the ring was shining through the tissue. Thirteen patients (4 women, 9 men) with a mean age of 63 years (36-78) were included. Complications occurred in 3 men (71, 36 and 63 years old). Two of them had an additional suturing. One demonstrated insufficiency at day four with many small gabs in the anastomotic line according to the ring design. Histology demonstrated perfect microcirculation. The second patient developed a fistula three weeks after operation. Both had an ileo-colostomy. The third operated because of a gastrocolic fistula with cachexia reentered hospital seven weeks postoperatively with a new gastrocolic fistula on X-ray. He died with a cardiac arrest. Postmortem was refused. We conclude from our results that the Valtrac ring should be used only by experienced surgeons, there is no reduction in operation time, and ileo-colostomy needs special care. We believe that surgeons using an extramucosal monofilament running suture for colonic anastomosis are more unlikely to switch to the Valtrac ring than those using other technics.

Adult↗