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Biomedical subjects

D B Jensen

Publications and source records attributed to D B Jensen.

At least 19 recordsLinked to original sources
PubMed2005

Abnormal hepatic vein Doppler waveform in patients without liver disease.

In patients with liver cirrhosis Doppler ultrasound often detects absence of the retrograde (hepatopetal) flow phase in the hepatic vein, suggestive of an increased stiffness of the liver parenchyma around the vein. This is rarely or never reported in healthy control persons. We examined the frequency of absent retrograde flow in a consecutive series of 139 patients referred for abdominal ultrasound. We used state-of-the-art ultrasound scanners, and placed the Doppler gate so that in non-forced end-expiration it would sample the right hepatic vein 4-6 cm from the vena cava. There was no association between the hepatic vein flow pattern and age, sex or body mass index. 43 of 139 studied patients showed absent retrograde flow. Review of the case records revealed liver disease in 26 patients and no sign of liver disease in 17 patients. We suggest that absent retrograde flow in the hepatic veins may be seen not only in patients with overt liver disease but also in apparently liver-healthy patients.

Adult↗
PubMed2002

Muscle reflexes during gait elicited by electrical stimulation of the posterior cruciate ligament in humans.

We investigated the influence of electrical stimulation of the posterior cruciate ligament (PCL) on the motoneuron pool of the thigh and calf muscle during gait. The study group comprised eight young men without any history of injury to the knee joints. Multistranded teflon-insulated stainless steel wires were inserted into the PCL guided by sonography and in four subjects also into the fat pad of the knee. The PCL was electrically stimulated during gait on a treadmill at heel strike and 100 ms after heel strike. Electromyographic signals were recorded with bipolar surface electrodes placed over the vastus medialis, rectus femoris, vastus lateralis, biceps femoris caput longum, and semitendinosus muscles. The stimuli consisted of four pulses delivered at 200 Hz; the stimulus amplitude was two to three times the sensory threshold. The electrical stimulation of the PCL inhibited the ongoing muscle activity in both the quadriceps and the hamstrings. The latency of the inhibition ranged between 78 and 148 ms in the quadriceps, between 88 and 110 ms in the hamstrings and between 189 and 258 ms in m. gastrocnemius. Stimulation of the fat pad of the knee did not influence the thigh and calf muscle motoneuron pool as evidenced by electromyography. The response elicited from the stimulation of the PCL was not limited to a specific muscle group but depended on ongoing muscle contraction, which suggests that the mechanoreceptors in the PCL are involved in the control of all muscles acting on the knee joint during gait.

Adult↗
PubMed2001

Inhibition of dynamic thigh muscle contraction by electrical stimulation of the posterior cruciate ligament in humans.

We investigated the influence of electrical stimulation of the posterior cruciate ligament (PCL) on the motoneuron pool of the thigh muscle during voluntary static and dynamic muscle contraction. The study group comprised nine young men with no history of injury to the knee joints. Multistranded Teflon-insulated stainless-steel wires were inserted into the PCL guided by ultrasound. In three subjects wires were also inserted into the fat pad of the knee. The PCL was electrically stimulated during static, concentric, or eccentric muscle contraction with a constant load of 20% of the maximal voluntary contraction of either the quadriceps or the hamstrings. Electromyographic signals were recorded with bipolar surface electrodes placed over the vastus medialis, rectus femoris, vastus lateralis, biceps femoris caput longum, and semitendinosus muscles. The stimuli consisted of four pulses delivered at 200 HZ; the stimulus amplitude was two to three times the sensory threshold. The electrical stimulation of the PCL inhibited the ongoing muscle activity in both the quadriceps and hamstrings with latencies of 114-150 ms and 99-130 ms, respectively. Stimulation of the fat pad of the knee did not influence the muscle activity. The study suggests that the mechanoreceptors in the PCL are involved in controlling muscle activity during both static and active muscle contractions. The relative long latency of the reflex makes it unlikely that it can serve as a directly protective reflex for the cruciate ligaments.

Adult↗
PubMed1999

Sonographic guided insertion of electrodes into the cruciate ligaments of the knee.

The present cadaver study examined the probability of accurate ultrasound guided insertion of electrodes into the anterior (ACL) and posterior (PCL) cruciate ligament with a fine needle. Visualisation of the structures appeared clearest from the posterior approach. From this approach 24 electrodes were inserted into the PCL and six into the ACL. From the anterior 16 were inserted into the ACL and six into the PCL. Twenty-one out of 24 electrodes were placed correctly into the PCL from the posterior view, and four out of six were placed correctly from the anterior view. From the posterior view four out of six were placed correctly in the ACL, and eight electrodes out of 16 were placed correctly from the anterior view. In conclusion, ultrasound guided insertion of electrodes from the posterior view can be performed with high accuracy into the PCL, whereas insertion into the ACL seems to be less accurate, probably because it is more difficult to visualise.

Aged↗
PubMed1993

In vitro functional characterization of overproduced Escherichia coli katF/rpoS gene product.

The katF/rpoS gene product (sigma s), a central regulator of stationary-phase gene expression in Escherichia coli, has been purified from an overproducing strain. sigma s was used as an immunogen for the production of monoclonal antibodies. Previous sequence analysis of sigma s strongly indicated homology to the sigma factor family. We show biochemically in this paper that sigma s is a sigma factor. This protein can bind to core RNA polymerase (E), and this binding can be competed effectively by the major E. coli transcription initiation factor, sigma 70. Immunopurified sigma s holoenzyme (E sigma s) transcribes the promoters of the bolAp1 gene and the xthA gene. Interestingly, both promoters can also be transcribed by sigma 70 holoenzyme (E sigma 70).

Bacterial Proteins↗
PubMed1993

Overproduction and purification of sigma 32, the Escherichia coli heat shock transcription factor.

This paper reports the overproduction and the details of a rapid method to purify active sigma 32 that is free of core RNA polymerase enzyme. Maximal overproduction of sigma 32 in a T7 RNA polymerase-based expression system is achieved only in the presence of rifampicin. This 2-day procedure involves solubilizing inclusion bodies in Sarkosyl, removal of Sarkosyl by dialysis, and a single S-Sepharose column chromatography step. The final yield of sigma 32 is about 4.1 mg of approximately 95% purity from 1 g of wet weight cells.

Chromatography, Agarose↗
PubMed1993

Synthesis of the stationary-phase sigma factor sigma s is positively regulated by ppGpp.

Strains of Escherichia coli which lack detectable guanosine 3',5'-bispyrophosphate (ppGpp) display a pleiotropic phenotype that in some respects resembles that of rpoS (katF) mutants. This led us to examine whether ppGpp is a positive regulator of sigma s synthesis. sigma s is a stationary-phase-specific sigma factor that is encoded by the rpoS gene. We found that a ppGpp-deficient strain is defective in sigma s synthesis as cells enter stationary phase in a rich medium, as judged by immunoblots. Under more-defined conditions we found that the stimulation of sigma s synthesis following glucose, phosphate, or amino acid starvation of wild-type strains is greatly reduced in a strain lacking ppGpp. The failure of ppGpp-deficient strains to synthesize sigma s in response to these starvation regimens could indicate a general defect in gene expression rather than a specific dependence of rpoS expression on ppGpp. We therefore tested the effect of artificially elevated ppGpp levels on sigma s synthesis either with mutations that impair ppGpp decay or by gratuitously inducing ppGpp synthesis with a Ptac::relA fusion. In both instances, we observed enhanced sigma s synthesis. Apparently, ppGpp can activate sigma s synthesis under conditions of nutrient sufficiency as well as during entry into stationary phase. This finding suggests that changes in ppGpp levels function both as a signal of imminent stationary phase and as a signal of perturbations in steady-state growth.

Amino Acids↗
PubMed1993

Interpretation of group behavior.

A Systematic Multiple Level Observation of Groups (SYMLOG) allows managers to graphically see how their perception of personal behavior compares with their colleagues' views of the same behavior. Through recognition and awareness, groups can change ineffective behavioral patterns.

Behavior↗
PubMed1992

[Ultrasonography of the rotator cuff of the shoulder].

Clinical examination for rotator cuff (RC) tear is rarely conclusive. Arthrography has been considered the standard diagnostic procedure for detection of rotator cuff tears. Ultrasonography (US) is less time-consuming and less expensive than arthrography and is, in addition, noninvasive. During recent years, many reports concerning US evaluation of RC tears have been published, but with different results about the diagnostic value of the examination. Recently, some authors have pointed out the ability of US in visualizing degenerative changes in the RC and that it is difficult to differentiate between tears and degenerative changes. By review of the English literature, we conclude that the experienced examiner with proper equipment can confidently differentiate between normal and pathological RC an that in quite a number of cases it is possible to differentiate tears from degenerative changes. In case of doubt, the examination should be supplemented by shoulder arthrography. In the hands of an experienced examiner with proper equipment US seems to be suitable as the initial imaging modality for evaluation of RC.

Humans↗
PubMed1991

[Epitheloid sarcoma--an overlooked diagnosis?].

Epitheloid sarcoma (ES) is a malignant soft-tissue tumour which occurs particularly on the hand and forearm in young adults. The tumour grows slowly and metastasizes relatively late but has, nevertheless, a considerable mortality and morbidity because it is frequently erroneously diagnosed, both clinically and pathologically, either as a benign tumour or as a reactive inflammatory process. Two typical cases with diagnostic delays of 12 and 15 years, respectively, which required amputations through the upper arm or forearm are described. Even although ES is a rare tumour form, clinicians and pathologists should be aware of this possibility as, in the early stages, the tumour can frequently be treated effectively and radically by wide local excision without amputation.

Adult↗
PubMed1990

Magnetic resonance imaging in the evaluation of sequelae after tibial plateau fractures.

Nine knees with persistent radiographic depression of the articular surface after tibial plateau fractures treated by traction and early knee motion were examined using magnetic resonance imaging (MRI). The MRI examinations demonstrated that the radiographic bone defects were filled up with different tissues, which we interpreted as cartilage, fibrous tissue and synovial plica. The type of tissue in the bone defect did not seem to affect the functional capabilities of the knee. However, a demonstrable thin cover of tissue, with the signal-intensity of cartilage, over the defect, seemed to be associated with an excellent functional result.

Adult↗
PubMed1990

Tibial plateau fractures. A comparison of conservative and surgical treatment.

We evaluated the long-term results of 109 tibial plateau fractures, 61 treated by skeletal traction and early knee movement and 48 treated by surgery, at an average follow-up of 70 months. The functional results were much the same, though meniscectomy had been performed in almost half of the surgical patients. Time in bed and duration of hospital stay were clearly shorter after surgery (p less than 0.0001). We concluded that conservative management is a valid alternative to surgery, but should probably be reserved for cases where operation is undesirable. Future studies should compare surgery without meniscectomy and conservative treatment using cast braces to reduce the time in traction.

Adolescent↗
PubMed1990

Epidemiology of meniscal lesions in the knee. 1,215 open operations in Copenhagen 1982-84.

In a suburban area of Copenhagen with approximately 620,000 inhabitants, all the openly operated on meniscal lesions of the knee joint between 1982 and 1984 inclusive were reviewed. The mean annual incidence of meniscal lesions per 10,000 inhabitants was 9.0 in males and 4.2 in females. The highest incidences were seen in the 3rd, 4th, and 5th decades of life. A higher frequency of trauma related to onset of symptoms was found among males (77 percent) than among females (64 percent). The bucket-handle lesion was the most frequent type of meniscal lesion in males (35 percent), whereas peripheral detachment was the most frequent in females (41 percent). A variable frequency of trauma inducing the lesions in males and females did not explain differences in type of meniscal lesion. Nineteen percent of our 1,215 patients had a partial meniscectomy, whereas 0.7 percent had meniscal repair.

Adolescent↗
PubMed1990

The natural history of chondromalacia patellae. A 12-year follow-up.

A series of 45 patients with chondromalacia patellae demonstrated clinically and by arthrotomy, but without demonstrable biomechanical misalignment, was investigated retrospectively. Thirty-one of the patients had only been treated conservatively while partial chondrectomy was performed in 14. All of the patients underwent an intensive rehabilitation program. After 12 years the patients were interviewed. Eighty-one percent of the patients who were treated conservatively and 57 percent of the patients in whom partial chondrectomy was performed had mild or no pain and no other knee complaints. The results were better for patients aged 20 years or younger. Two patients received disability pensions on account of poor knee function and 6 had changed to less strenuous occupations. Restraint is advised as regards operative treatment of chondromalacia patellae.

Adolescent↗
PubMed1989

[Metastasizing squamous cell carcinoma in patients with psoriasis treated with immunosuppressive agents].

Immunosuppressive agents are imployed increasingly frequently in treatment of nonfatal disorders. We report two cases of metastasizing squamous cell carcinoma after treatment for psoriasis with methotrexate. Additional cases must be reported, but we consider that: 1) methotrexate medication, when possible, should be withdrawn when a localized squamous cell carcinoma is diagnosed and 2) when this diagnosis is confirmed the patient should be referred for radical treatment.

Aged↗
PubMed1989

Patellectomy for chondromalacia.

Fifteen patients with 17 patellectomies for chondromalacia were evaluated after an average of 5.5 years. The average age was 38 years. No knees were rated as excellent, whereas 5 were rated as good, 9 as fair, and 3 as poor. However, 10 patients, including both bilateral patellectomies, were satisfied with the results.

Adult↗