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Biomedical subjects

T Benter

Publications and source records attributed to T Benter.

36 records · Page 2Linked to original sources
PubMed1997

[Duplex ultrasound characterization of hepatic vein blood flow in healthy probands].

PURPOSE: To characterise and standardise hepatic venous flow during the respiratory cycle in all three hepatic veins and to determine the most adequate measurement area within the vessel. METHOD: In 25 healthy subjects duplex Doppler measurements were performed of the right (RHV), middle (MHV) and left (LHV) hepatic vein. In full inspiration, mid-inspiration and expiration the maximum flow velocities of all three hepatic venous flow components (phase 1 to 3) were measured and a systolic to diastolic (S/D) ratio was determined. RESULTS: In full inspiration there was a decrease of the maximum flow velocities compared to mid-inspiration (p = 0.0001). In expiration there was an increase of the maximum flow velocities (p = 0.0005). The maximum flow velocities of the MHV in mid-inspiration were -0.21 +/- 0.019 m/s (phase 1), -0.16 +/- 0.016 m/s (phase 2) and 0.08 +/- 0.011 m/s (phase 3). The S/D ratio decreases on inspiration and increases on expiration. The maximum flow velocities of the LHV differed significantly from those of the RHV and MHV. The measurements of the RHV and MHV were both reliable. Measurements from central to peripheral within the hepatic veins showed a decrease in maximum flow velocities. CONCLUSION: For standardisation of hepatic venous flow measurements the respiratory state must be determined. The most adequate area for duplex Doppler ultrasound measurements is situated about one or two centimetres from the orifice of the vena cava.

Adult↗
PubMed1997

A sonographically guided technique for central venous access.

OBJECTIVE: The internal jugular vein (IJV) is an important access to the central venous system. We compared sonographically guided technique with the traditional anatomic landmark technique for IJV catheterization. SUBJECTS AND METHODS: In a prospective randomized trial, 100 patients underwent routine catheterization of the IJV (50 patients in the sonography group and 50 patients in the anatomic landmark group). Access time, failure rates, and complication rates were evaluated. In addition, the physicians' number of years of experience with catheter insertion was recorded. RESULTS: Access time was markedly shorter with the sonographically guided technique (mean, 15.2 sec; range, 8-76 sec) than with the anatomic landmark technique (mean, 51.4 sec; range, 3-820 sec) (p = .001). The failure rate was significantly lower with the sonographically guided technique (p = .002). Complications were fewer with the sonographically guided technique (neck hematoma, 2% versus 10%; plexus irritation, 4% versus 6%; carotid artery puncture, 0% versus 12%). We found that the number of years of postgraduate clinical training was greater in the group of physicians using the anatomic landmark technique. CONCLUSION: The sonographically guided technique is associated with less risk and less inconvenience for patients, especially critically ill patients, for whom the technique provides fast, safe, and easy IJV catheterization.

Catheterization, Central Venous↗
PubMed1997

Effect of respiration, exercise, and food intake on hepatic vein circulation.

Since the effects of respiration, nutrition, and exercise on blood flow in the hepatic vein are not well understood, the objective of this study was to determine the hemodynamic influence of these factors on hepatic venous circulation using Doppler ultrasonographic tracings. The venous blood flow of the middle hepatic vein was determined during arrested full inspiration, midinspiration, and expiration in 25 healthy subjects. The maximum velocity and the systolic-to-diastolic ratio of the blood flow were measured. The portal vein blood flow velocity was measured in 20 volunteers before and after food intake. The portal vein blood flow and the hepatic vein flow velocity were examined in eight volunteers after exercise. During inspiration, maximum blood flow velocity of the hepatic veins decreased compared to midinspiration (P < 0.001). With expiration the maximum velocity increased (P < 0.001). After food consumption, there was no change in the velocity of the hepatic veins, but the portal vein blood flow increased (P = 0.041). After physical exercises, the maximum velocity of the hepatic venous flow increased, on average, about 148% (P = 0.01), and the portal vein blood flow decreased about 44% (P = 0.027). To achieve standard measurements of hepatic venous blood flow, the state of respiration and physical exertion should be established. The nutritional status had only a minor influence on hepatic vein measurements.

Adult↗
PubMed1996

[Importance of duplex velocity histograms in the diagnosis of liver cirrhosis].

PURPOSE: A prospective study was carried out to determine the diagnostic value of velocity histograms of hepatic veins in patients with liver cirrhosis and healthy subjects. METHODS: The hepatic veins of ten healthy subjects and ten patients with liver cirrhosis were examined by the Doppler method. The velocity histogram measures the velocity variation at a defined area in the duplex tracing. Within this tracing, the peak, mean, mode and velocity range were measured. RESULTS: A velocity range of 0.02 +/- 0.015 m/s was examined in healthy subjects, and a range of 0.06 +/- 0.013 was examined in liver cirrhosis patients (p < 0.001). The other measurement options showed no significant changes between the healthy subjects and the liver cirrhosis patients (p < 0.05). CONCLUSIONS: Until now, differentiation of the hepatic vein tracings was possible only on a qualitative basis. With the assessment of the velocity range it is possible to obtain a more objective differentiation between the duplex tracing in hepatic veins of liver cirrhosis patients and healthy subjects.

Adult↗
PubMed1995

Optimization and reproducibility of random amplified polymorphic DNA in human.

In this work, we have optimized random amplified polymorphic DNA (RAPD) for the use of human DNA in altering the concentration of the reaction components and the steps of the thermal profile in the polymerase chain reaction. By using two primers in every reaction and 2.5 U Taq DNA polymerase, we found that DNA concentrations between 50 and 500 ng gave reproducible banding patterns. The tested DNA was extracted in seven different ways giving the same amplification results in six of them. We have also observed that reactions consisting of 35 cycles gave sufficient product yields. A slow heating/ramping from the annealing to the extension temperature increased the number of amplified bands and enhanced reproducibility. We conclude that RAPD is a robust and, under the mentioned conditions, reproducible method that could prove very useful for scientists and physicians.

Base Sequence↗
PubMed1993

Analysis of a non-ras 21-kDa protein in patients with metastatic testicular germ-cell tumors.

A novel protein of 21 kDa (p21) has been detected in the sera of patients with different solid tumors. The serum levels of this p21 protein were measured in seven patients with metastatic testicular germ-cell tumors before and after chemotherapy using an enzyme-linked immunosorbent assay. In five out of six patients who responded to chemotherapy a concomitant decrease of p21 serum levels was found. The decrease of p21 was in accordance with the decline of the established tumor markers alpha-fetoprotein, human chorionic gonadotropin beta-subunit and lactate dehydrogenase in three patients with non-seminomatous tumors and with the decline of lactate dehydrogenase and the clinical response in two patients with seminoma. In one patient the predicted decline of p21 did not occur despite the patient's clinical response to chemotherapy. In the seventh patient, who relapsed directly after chemotherapy, no decline of either p21 levels or tumor markers was observed. The absolute amount of the p21 protein prior to chemotherapy did not correlate with the patients' tumor burden. Elevated levels of p21 were found in patients with seminomatous and non-seminomatous germ-cell tumors. Since seminoma patients do not secrete tumor markers like alpha-fetoprotein or human chorionic gonadotropin beta, the determination of p21 levels may help to evaluate the efficacy of chemotherapy in patients with seminomatous as well as in patients with marker-negative non-seminomatous germ-cell tumors. The biological role of p21 and its clinical significance will be further investigated.

Adult↗
PubMed1992

Regulation of the proto-oncogenes c-sis, c-fos, c-myc and c-myb in acute myeloid leukemias.

RNA transcriptional levels of the proto-oncogenes c-sis, c-fos, c-myb and c-myc were measured in peripheral blood leukemic blast cells of 16 patients with acute myeloid leukemia (AML) of different FAB subtypes, 8 being at diagnosis and 8 upon relapse. The studied proto-oncogenes were found to be regulated but varied considerably within morphologically identical subtypes. This is consistent with the clinically observable diverse behavior of seemingly identical AMLs as to the course and outcome of the individual disease. Overexpression of c-sis and c-myc was found more often in AML upon relapse than at diagnosis and in two cases overexpression not found at diagnosis was present at relapse. This implies alterations of biological behavior in the course of antileukemic drug therapy. A decline of c-myb expression was observed in one patient studied throughout therapy which was found to be associated with a complete but transient hematological remission after chemotherapy.

Acute Disease↗
PubMed1990

Transcriptional activation from the long-terminal repeat of human immunodeficiency virus in vitro.

The mechanism of trans-acting regulation of transcription from the long terminal repeat (LTR) of human immunodeficiency virus (HIV) has been investigated. The roles of the cis-acting elements within HIV LTR, as well as the trans-acting factors present in HIV-infected cells, have been evaluated by an in vitro transcription system. Our observations indicate that both the sequence downstream from the CAP site of HIV LTR (located at nucleotide positions +1 to +56; called the TAR element) and the GC boxes (-77 to -45) are required for full transcriptional stimulation and that both the virus-encoded tat protein and one or more cellular factors might be involved. These results demonstrate the presence of a combinatorial regulation of HIV transcription by multiple factors, which may confer the provirus with greater flexibility in regulated viral gene expression.

Binding, Competitive↗
PubMed1988

Site-directed mutagenesis of two trans-regulatory genes (tat-III,trs) of HIV-1.

Point mutations were introduced into the overlapping trans-regulatory genes (tat-III and trs) of human immunodeficiency virus type 1 (HIV-1), and the mutants were evaluated for virus expression. The results showed that tat-III has a positive transacting role and is required for transcriptional activation. A chain terminating mutation early in the trs gene resulted in an increase in transcription of viral messenger RNA as measured by nuclear transcription experiments, but only one major species of viral messenger RNA (1.8 kilobases) was detected, and little or no viral structural proteins were made. Thus, the trs gene product is essential for expression of virus structural proteins but, at the same time, may have a negative trans-regulatory role in transcription. Cotransfection of the point mutant proviruses defective in tat or trs with each other or with a complementary DNA clone containing tat and trs sequences restored the normal transcription pattern and subsequent virus production.

Acetyltransferases↗
PubMed1988

Missense mutations in an infectious human immunodeficiency viral genome: functional mapping of tat and identification of the rev splice acceptor.

Single nucleotide alterations were introduced into an infectious clone of human immunodeficiency virus type 1 to create a series of missense mutants in the tat coding region. Although mutations in a proline-rich region and a basic lysine-arginine-rich region resulted in wild-type phenotypes, five of six mutations in a cysteine-rich domain completely abolished tat activity and virus replication. One cysteine mutant retained tat activity but was negative for virus expression. Surprisingly, this mutant could not be complemented by tat, and virus expression was restored only by cotransfection with a plasmid expressing the rev gene. Another mutant with an alteration toward the C-terminal region showed significantly reduced tat activity and required complementation by a combination of tat and rev for virus replication. Further analysis revealed that a previously unrecognized splice acceptor site within this region, apparently used to generate the rev mRNA, had been altered. We provide evidence suggesting that tat and rev proteins are encoded by distinct mRNA species.

Amino Acid Sequence↗
PubMed1987

Interaction of viral and cellular factors with the HTLV-III LTR target sequences in vitro.

The location of cis-acting regulatory sequences within the long terminal repeat (LTR) of the human T-cell lymphotropic virus type III was determined by eukaryotic cell transfection and chloramphenicol acetyltransferase (CAT) assay or in vitro cell-free transcription. A 160 base pair (bp) region of the LTR at position - 104 to 56 is required for trans-activation (cap site 1). A 24 bp enhancer element (EHE) capable of increasing the rate of transcription, irrespective of orientation, is located between nucleotides -105 to -80. It contains two 10 bp repeats. Three Sp1 binding sites (Sp1 III-I) are located between -78 and -45. A deletion of Sp1 III allowed for limited TATIII response while the presence of a functional enhancer restored the activity in HTLV-III infected cells. Complete loss of transcriptional activity and CAT gene expression could be attributed to the absence of EHE and Sp1 III-I at position -48. However, reinsertion of the enhancer restored accurate initiation but at a decreased level suggesting that the presence of a Sp1 binding site is not a prerequisite for the accurate initiation of transcription but is required for transcriptional activation independent of a promoter. The presence of a negative regulatory element (NRE) has been demonstrated by removal of the 5' part of U3 to position -117. Nucleotide sequences around the cap site and poly (A) site contain a trans-activator response element (TRE) and could be arranged into a unique secondary structure. A deletion of four nucleotides TCTGAGCCTGGGAGCTC causes a loss of three dimer linkage sequence binding. The CAT gene enzyme expression is completely abolished but transcriptional activity remains at reduced level.

Acetyltransferases↗
PubMed1985

Isolation and characterization of the human cellular myc gene product.

Antibodies against the product of the human cellular myc gene (c-myc) were prepared against a bacterially expressed human c-myc protein by inserting the ClaI/BclI fragment of the human c-myc DNA clone in an expression vector derived from pPLc24. These antibodies cross-react with viral-coded myc (v-myc) proteins from MC29 and OK10 viruses. Furthermore, IgGs specific for synthetic peptides, corresponding to the 12 carboxy-terminal amino acids of the human c-myc gene and 16 internal amino acids, were isolated. By use of the various myc-specific antisera or IgGs, a protein of Mr 64 000 was detected in several human tumor cell lines including Colo320, small cell cancer of the lung (417d), HL60, Raji, and HeLa. This protein is larger than the corresponding v-myc or chicken c-myc proteins from avian virus transformed cells or avian bursa lymphoma cells (RP9), both of which are proteins of Mr 55 000. The human c-myc protein is located in the nucleus of Colo320 cells, exhibits a half-life of about 15 min, and is expressed at significantly lower levels than the viral protein. The human c-myc protein was enriched about 3000-fold from Colo320 cells using c-myc-specific IgG coupled to Sepharose beads. The protein binds to double-stranded DNA in vitro, a reaction that can be inhibited to more than 90% by c-myc specific IgG.

Antibodies↗
PubMedDate not supplied

Central venous access catheters: radiological management of complications.

A great variety of central venous access devices such as tunneled and non-tunneled central venous catheters (CVC) as well as port systems are implanted by interventional radiologists at an increasing rate. There are some possible immediate, early, and late complications related to the implantation technique, care, and maintenance of CVCs. This review will illustrate possible complications of CVCs and will discuss risk factors. Different strategies will be shown regarding the prevention and treatment of complications.

Blood Vessels↗