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Biomedical subjects

S Lindahl

Publications and source records attributed to S Lindahl.

63 records · Page 4Linked to original sources
PubMed1977

On the mechanism of sodium- and potassium-activated adenosine triphosphatase. Time course of intermediary steps examined by computer simulation of transient kinetics.

In order to learn whether the kinetics of transient phosphorylation of sodium plus potassium ion transport adenosine triphosphatase was compatible with the hydrolysis of ATP, computer simulation of experimental data was studied. The enzyme mechanism was described in terms of first order and pseudo-first order reactions. The resulting system of linear first order differential equations was solved by a Runge-Kutta method. Phosphorylation kinetics was studied by means of a rapid mixing apparatus at 21 degrees in the presence of 100 micron ATP, 3 mM MgCl2, 120 mM NaCl, and 10 mM KCl. Computer simulation gave a close fit to experimental data with a model of the reaction mechanism which included a sequence of two dephospho forms and two phospho forms of the enzyme. With this model, rate constants obtained by computer simulation were in agreement with constants which had been determined in separate phosphorylation and dephosphorylation experiments. Within experimental limits, the net flux of reaction in each partial step was compatible with the (Na+,K+)-stimulated hydrolysis of ATP (about 324 and 300 nmol-mg-1-min-1, respectively).

Adenosine Triphosphatases↗
PubMed1975

Human renal carbonic anhydrase. Purification and properties.

Carbonic ahyndrase was isolated from fresh human donor kidneys which had been thoroughly perfused free from blood. The isolation procedure involved biospecific affinity chromatography on a sulfanilamide-agarose column and yielded one soluble form of the enzyme, which was homogenous with respect to sedimentation in the ultracentrifuge, electrophoresis, isoelectric focusing and immunodiffusion. The renal enzyme had an amino acid composition and beahved chromatographically, electrophoretically, and immunochemically like the erythrocyte form human carbonic anhydrase C, isolated by the same technique. The kinetic behaviour of the renal enzyme was similar to that of human carbonic anhydrase C when compared by the stopped-flow pH-indicator technique. The results therefore suggest that the cytoplasmic carbonic anhydrase of the human kidney is very similar, if not identical, to the high-activity erythrocyte form of human carbonic anhydrase C.

Amino Acids↗
PubMedDate not supplied

Unstable thoracolumbar fractures. A comparative radiologic study of conservative treatment and Harrington instrumentation.

Two comparable groups with unstable thoracolumbar fractures have been studied: one consisting of 23 patients treated conservatively and one consisting of 20 patients treated surgically with Harrington instrumentation. The vertebral injuries have been analysed radiologically at the time of injury as well as after completion of conservative and surgical treatment and at follow-up on average 6 years and 3 months after injury in the conservatively treated group and 2 years and 2 months after injury in the operated group. The vertebral fractures were often solitary at the L1 level with a characteristic radiologic appearance and mainly caused by flexion-rotation injuries. There were indirect signs of associated ligament injuries in most cases. Indirect signs of associated disc injury were found in 77 per cent of the cases, most of them related to the superior disc. The signs of disc injury were accentuated at the two follow-up examinations. In the operated group, the radiologic appearance of the vertebral body normalised after Harrington instrumentation. A preoperative gibbus angle of 19.4 degrees was reduced to 6.8 degrees on average postoperatively. In 13 of the operated cases the rods were removed. Among these patients the gibbus angle increased to 17.6 degrees at the final follow-up examination, compared with 11.9 degrees in the patients who had their rods retained. This difference in gibbus angle was significant. In the conservatively treated group, the initial gibbus angle of 19.5 degrees continuously increased to 27.6 degrees at the follow-up examination. All vertebral fractures had healed at the follow-up examination.

Adult↗
PubMedDate not supplied

Computed tomography of lipomatous and myxoid tumors.

Thirty-two lipomatous and myxoid tumors were examined by computed tomography (CT). An attempt was made to correlate the radiographic appearance of the tumor to different histologic types of these tumors. It was found that a well delineated lipomatous lesion with uniform radiographic density, an attenuation value below -73 Hounsfield units (HU) and absence of contrast enhancement can be considered strongly suggestive of a benign lipoma. Atypical lipomas, myxoma and well differentiated liposarcomas have good delineation against the surrounding tissue with no peripheral hypervascularity in the majority of cases. The attenuation values varied between -83 and +38 HU. Liposarcomas of myxoid type, mixed myxoid and round-cell type, round-cell type, and pleomorphic type were all poorly delineated with attenuation values between +12 and +38 HU and with varying contrast enhancement. Thus CT can be considered to play an important role in the preoperative evaluation of lipomatous and myxoid tumors of the soft tissues. Besides valuable topographic information CT helps, to some extent, to differentiate between various types of lipomatous tumors.

Adult↗
PubMedDate not supplied

Computed tomography of retinoblastoma.

Retinoblastoma is the most common primary malignant intraocular tumor in children. The clinical features are leucocoria and/or strabismus. The ophthalmic diagnosis is straight forward in clear eye media with a white gray mass in the fundus. With opaque ocular media, other diagnostic procedures such as CT and ultrasonography are important. In the present study the results of CT examinations of 23 patients with histologically proven retinoblastomas are presented. The mean age of the patients was two years. The characteristic CT finding is a partly calcified intravitreous mass lesion mostly confined within the eyeball. Two cases showed retrobulbar extension and two intracranial tumor extension. No metastasis was found in the brain, liver, spleen, long bones, chest or skull. The radiologic screening procedures for retinoblastoma metastasis are discussed. In patients suspected to have a retinoblastoma, it is recommended to perform CT of the orbits and brain in order to detect the tumor and its possible retrobulbar and intracranial extension.

Child, Preschool↗
PubMedDate not supplied

A radiographic and histologic evaluation of the patellar tendon after harvesting its central third.

Nineteen consecutive patients undergoing anterior cruciate ligament reconstruction using the central third of the ipsilateral patellar tendon were included in the study. Serial magnetic resonance images revealed that the donor-site gap in the tendon decreased with time (mean follow-up, 26 months). The thickness was significantly increased compared with the intact contralateral patellar tendon, regardless of when the magnetic resonance imaging was performed. Ultrasonography showed the same findings at a mean follow-up of 26 months. Histologic evaluation of the repair tissue in the central part of the tendon, as well as the tissue in the peripheral part of the patellar tendon at the donor site, revealed a significant increase in cellularity and vascularity as compared with normal control tendons. Thus, 2 years after the harvesting procedure, the patellar tendon displayed significant radiographic and histologic abnormalities. On the basis of these findings, reharvest of the patellar tendon, at least up to 2 years after primary harvest, cannot be recommended.

Adolescent↗
PubMedDate not supplied

Ipsi- or contralateral patellar tendon graft in anterior cruciate ligament revision surgery. A comparison of two methods.

Twenty-four patients who underwent anterior cruciate ligament revision surgery were studied postoperatively (12 with reharvested ipsilateral patellar tendon grafts and 12 with contralateral patellar tendon grafts). For comparison purposes, 12 matched patients with primary anterior cruciate ligament reconstruction, who had been operated on using the same technique by the same surgeons, were chosen. The median time since the first reconstruction was 57 months (range, 15 to 132) in the ipsilateral tendon group and 54 months (range, 20 to 108) in the contralateral tendon group. Follow-up examination showed that there were no significant differences in total KT-1000 arthrometer side-to-side measurements between the groups, but the Lysholm score was higher for patients with contralateral tendon grafts than for patients with ipsilateral grafts. Only two patients with ipsilateral grafts were classified as having excellent or good results. Functional testing outcomes were similar for all groups, and magnetic resonance imaging screening showed no differences between the reharvest and primary harvest groups in terms of length, width, thickness, or donor site gap of the patellar tendon. However, there were two major complications in the group with revision surgery with the ipsilateral reharvested patellar tendon. Reharvesting the ipsilateral patellar tendon resulted in lower functional scores and a higher rate of complications than revision with the contralateral patellar tendon or primary anterior cruciate ligament reconstruction.

Adult↗
PubMedDate not supplied

Computed tomography of intraorbital foreign bodies.

Computed tomography (CT) has been shown to be an important diagnostic tool in the evaluation of intraorbital foreign bodies (IOFB). In order to further analyze the capacity and limitations of CT in this respect, 55 cases with IOFB (intraocular and extraocular) detected at CT were retrospectively analyzed. It was shown that CT was an excellent diagnostic modality in detecting and localizing IOFB of different material and superior to ultrasonography in this respect. Still, even with high resolution CT, there are some limitations of this modality that are discussed. CT is recommended as the primary diagnostic tool in the detection and localization of intraocular and extraocular foreign bodies.

Adolescent↗