Search PubMed⌕ Search

Biomedical subjects

J Karlsson

Publications and source records attributed to J Karlsson.

At least 91 records · Page 5Linked to original sources
PubMed1999

Subacute versus delayed reconstruction of the anterior cruciate ligament in the competitive athlete.

The objective of this study was to compare the function and activity level in patients with anterior cruciate ligament injuries, who participated in competitive sports (Tegner activity level > or = 7) and underwent a reconstruction of the anterior cruciate ligament, either subacute (2-12 weeks, group I) or late (12-24 months, group II) after the injury. The patients in group I (n = 97) were comparable with those in group II (n = 103) in terms of gender, age, preinjury activity level, and the reconstruction technique. At the final follow-up (2-5.5 years after the operation), the Lysholm score, the IKDC evaluation system and the one-leg-hop test revealed no differences between the groups. There were also no differences between the groups in terms of the patients' subjective evaluation or expectations. The Tegner activity level at follow-up was 8 (range 2-10) in group I and 6 (range 2-9) in group II (P = 0.0001). The same thing was found in terms of the desired Tegner activity level, which was 9 (range 4-9) in group I and 7 (range 3-10) in group II (P = 0.0002). The KT-1000 laxity meter revealed a total side-to-side difference of 1.5 mm (-3.5-8.5) in group I and 1.5 mm (-3.5-7) in group II (NS). Associated meniscal surgery between the index injury and the reconstruction, or during the reconstruction, was performed in 37/97 (38%) of the patients in group I and 59/103 (57%) of the patients in group II (P < 0.01). This study revealed that competitive athletes who underwent reconstruction at a subacute stage after the anterior cruciate ligament injury had a higher activity level 2-5.5 years after the index operation, as well as a higher desired level of activity compared to athletes who had the reconstruction delayed by 12-24 months. Furthermore, meniscal injuries were significantly more frequent if the reconstruction was delayed.

Adolescent↗
PubMed1999

Analysis of subjective, objective and functional examination tests after anterior cruciate ligament reconstruction. A follow-up of 527 patients.

This study included 527 patients (178 female and 349 male) with unilateral anterior cruciate ligament (ACL) rupture who underwent arthroscopic ACL reconstruction using bone-patellar tendon-bone autograft and interference screw fixation. The follow-up examination was performed by independent observers at a median of 38 (21-68) months after the index operation. At the follow-up, the Lysholm score was 86 (14-100) points, the Lysholm instability subscore was 22 (0-25) points and the Lysholm pain subscore was 19 (0-25) points. The Tegner activity level was 6 (1-10). The one-leg-hop test was 91 (0-167)% of the non-injured knee. The difference in the anterior side-to-side laxity as measured with the KT-1000 arthrometer at 89 Newton (N) was 1.5 (-5-13) mm and the total KT-1000 side-to-side difference at 89 N was 2 (-7-11) mm. Using the International Knee Documentation Committee (IKDC) evaluation system, 177 (33.6%) patients were classified as normal (group A), 211 (40%) as nearly normal (group B), 109 (20.7%) as abnormal (group C) and 30 (5.7%) as severely abnormal (group D). The highest correlation coefficients were recorded between the IKDC evaluation system and the Lysholm score (p = 0.66), the patients' subjective evaluation (p = 0.53), the Tegner activity level (p = 0.34), all the laxity tests (p > or = 0.34) and the one-leg-hop test (p = 0.28). The resumption of sporting activities and work as evaluated by the Tegner activity level correlated with the patients' subjective evaluation (p = 0.34) but did not correlate with the laxity tests, i.e., the manual Lachman test (p = -0.06) and the total and anterior KT-1000 tests (p = -0.06). Furthermore, none of the laxity tests correlated with the functional tests or the patients' subjective evaluation. We conclude that the IKDC evaluation system is a reliable and useful tool for evaluating the post-operative outcome after an ACL reconstruction.

Adolescent↗
PubMed1999

Paracellular drug transport across intestinal epithelia: influence of charge and induced water flux.

The influence of drug charge and transepithelial water flux on passive paracellular drug transport was investigated in Caco-2 cell monolayers and rat ileal mucosa in vitro. Three small hydrophilic compounds with different net charges (creatinine, erythritol and foscarnet) were used as model drugs. A hypotonic glucose-rich solution was applied apically to induce epithelial absorption of water. In the Caco-2 monolayers, permeability to creatinine (positively charged) was 25-fold greater than to foscarnet (negatively charged), indicating a pronounced cation selective paracellular permeability. During apical exposure to the hypotonic glucose-rich solution, transport of all model drugs increased in both the absorptive and secretory directions. This enhanced transport coincided with a decrease in transepithelial resistance. Further, fluorescence and transmission electron microscopy indicated dilatations of the paracellular spaces but no damage to the cell membranes. These findings suggested that the enhancement in drug transport was attributable to increased paracellular tight junction permeability rather than to "solvent drag". In the ileal segments, mucosal exposure to the hypotonic glucose-rich solution had no effect on transepithelial resistance and only a marginal increase in drug transport was observed. Taken together, the modest absorption enhancement demonstrated in the in vitro models agrees with results obtained in vivo, supporting the conclusion that a more pronounced disruption of the tight junction barrier than that obtained through stimulation of epithelial absorption of water is required for efficient enhancement of paracellular intestinal drug absorption.

Animals↗
PubMed1999

The localization of the infrapatellar nerves in the anterior knee region with special emphasis on central third patellar tendon harvest: a dissection study on cadaver and amputated specimens.

The aim of this dissection study on cadaver and amputated specimens was to determine the position of the infrapatellar nerves in the anterior knee region, and to investigate whether it would be possible to harvest the patellar tendon through two small vertical incisions, leaving the infrapatellar nerves undamaged and the major part of the paratenon intact. The infrapatellar nerve did not pass through the area between the apex of the patella and the tibial tubercle in 1 of 60 specimens. The nerve passed through this area as one branch in 15 of 60 specimens, as two branches in 37 of 60, as three in 6 of 60, and as four in 1 of 60 specimens. The distance from the apex of the patella to the infrapatellar nerve or the uppermost branch of the nerve was 30 mm (+/- 27 mm [2 SD]). The distance from the tibial tubercle to the infrapatellar nerve or the lowermost branch of the nerve was 27 mm (+/- 27 mm [2 SD]). In one specimen, the infrapatellar nerve passed 10 mm distal to the tibial tubercle. In 4 of 60 specimens, a branch of the infrapatellar nerve passed just above the tibial tubercle, and in 2 of 60 a branch passed just above the apex of the patella. In 19 of 20 specimens in which the harvesting procedure was performed, the infrapatellar nerve or the nerve branches were undamaged. The length of the undamaged paratenon was 27 mm (+/- 23 mm [2 SD]). This study showed that it was possible to harvest consistent bone-patellar tendon-bone autografts through two vertical 25-mm incisions, leaving the infrapatellar nerve undamaged and the paratenon partially intact in the majority of the cadaver and amputated specimens.

Aged↗
PubMed1999

Magnetic resonance imaging of the patellar tendon after harvesting its central third: a comparison between traditional and subcutaneous harvesting techniques.

The aim of this study was to compare the 2-year results after anterior cruciate ligament reconstruction using patellar tendon autografts harvested through a paratenon-splitting, traditional technique (group A) with the results of a subcutaneous technique aiming at protecting the infrapatellar nerves and the paratenon (group B). Special emphasis was placed on evaluating the donor site. Magnetic resonance imaging (MRI) of the patellar tendon was performed to evaluate the reconstitution after harvesting its central third. Examinations of knee-walking ability and assessments of anterior knee sensitivity were made in order to evaluate donor-site discomfort and the function of infrapatellar nerves. Seventy-two consecutive patients were included in the study; group A comprised 35 patients and group B, 37 patients. At the 2-year follow-up, the Tegner activity level, the Lysholm score, and the IKDC evaluation system showed no significant differences between groups A and B. The median loss of normal anterior knee sensitivity was 16 cm2 (range, 0 to 200 cm2) in group A and 0 cm2 (range, 0 to 285 cm2) in group B (P = .20). In group A 20% of the patients and in group B 58% had normal sensitivity (P < .01). MRI showed that the donor-site gap (area corresponding to non-tendinous-like tissue signal) was 5 mm (range, 0 to 9 mm) in group A and 2 mm (range, 0 to 5 mm) in group B (P < .0001). At 2-year follow-up, the subcutaneous graft-harvesting technique resulted in less disturbance of anterior knee sensitivity and a smaller donor-site gap than the traditional technique.

Adolescent↗
PubMed1999

Comparison of arthroscopic one-incision and two-incision techniques for reconstruction of the anterior cruciate ligament.

The purpose of this study was to assess the outcome of arthroscopic anterior cruciate ligament reconstruction performed using either the 'one-incision' technique or the rear-entry 'two-incision' technique. A series of 221 consecutive patients who underwent anterior cruciate ligament reconstruction was reviewed retrospectively. In the study population, two subgroups were defined. Group A consisted of 118 patients who underwent reconstruction using the one-incision transtibial endoscopic technique and Group B consisted of 103 patients who underwent reconstruction using the two-incision technique. The groups were comparable in terms of age, sex and activity level. The follow-up was performed after 47 (40-68) months in Group A and 55 (40-68) months in Group B. The Lysholm score at the final follow-up was significantly lower in Group A (90, 38-100) than in Group B (94, 34-100) (P = 0.002). The median KT-1000 total side-to-side difference was 1.5 (-6 to 7.5) mm in Group A, and 2.0 (-3.5 to 9) mm in Group B (n.s.). No significant difference between the groups was found when the IKDC evaluation system was used. Four intra-operative complications were registered in Group A and none in Group B (P = 0.06). No significant difference was found in terms of anterior knee pain, the one-leg-hop quotient or the activity level at the final follow-up. In this study the two methods gave similar and satisfactory results. Serious intraoperative complications were, however, recorded in four cases when the one-incision technique was used.

Adolescent↗
PubMed1999

A comparison of results after arthroscopic anterior cruciate ligament reconstruction in female and male competitive athletes. A two- to five-year follow-up of 429 patients.

The aim of this study was to compare the results after arthroscopic anterior cruciate ligament reconstruction in female and male competitive athletes who had a pre-injury Tegner activity level of > or =7 and a non-injured contralateral anterior cruciate ligament. One hundred and thirty-three female and 296 male patients were followed at 38 (21-68) months after the index operation. All the patients were operated on by experienced knee surgeons using patellar tendon autografts and interference screw fixation. At the index operation the median age of the female patients was 23 (1645) years and the median age of the male patients was 26 (16-47) years. The reconstruction was performed a median of 10 (0-141) and 10 (0-203) months after the injury in women and men respectively. The patients were re-examined by independent observers. At the follow-up, the median Lysholm score was 89 (38-100) points in the female group and 90 (22-100) points in the male group (P=0.015). The IKDC evaluation system, subjective anterior knee pain, subjective evaluation of the results, the knee-walking test and the KT-1000 tests revealed no differences between the groups. The mean (+/-2 SD) pre-injury Tegner activity level was 8.1 (+/-1.9) (median 8 (7-10)) in the female group and 8.4 (+/-1.8) (median 9 (7-10)) in the male group (P=0.003). At the follow-up, the Tegner activity level was 6.2 (+/-3.8) in the female group and 6.8 (+/-3.6) in the male group (P=0.012). At the follow-up, the Tegner activity level had decreased by 1.9 (+/-3.8) for the women and 1.6 (+/-3.3) for the men, as compared with the pre-injury level (n.s.). The difference between the performed and the desired activity level at the follow-up was 1.1 (+/-3.2) in the female group and 0.9 (+/-3.0) in the male group (n.s.). In the female group 53/133 (40%) and in the male group 115/296 (39%) returned to the pre-injury activity level (n.s.). The median one-leg-hop quotient was 93 (0-116)% in the female group and 96 (0-130)% in the male group (P=0.006). Concomitant meniscal injuries prior to the index operation, at the index operation or during the follow-up period were found in 64/133 (48%) women and in 185/ 296 (62%) men (P<0.01). The main conclusion was that the overall results in female and male athletes were comparable two to five years after the anterior cruciate ligament reconstruction. However, concomitant meniscal injuries were more common in male than females athletes after anterior cruciate ligament injuries.

Adolescent↗
PubMed1999

Early mobilization versus immobilization after ankle ligament stabilization.

Functional outcome, stability at radiographic investigation and ankle joint torque after anatomical reconstruction of the lateral ankle ligaments were evaluated in patients with early postoperative mobilization versus those with cast immobilization. Thirty patients with chronic lateral ligament instability of the ankle underwent anatomical reconstruction of the ligaments. Postoperatively the patients were randomly allocated to two groups: Group A (n=15) were immobilized in a below-knee plaster for 6 weeks and Group B (n=15) underwent early controlled range of motion training using an Air-Cast ankle brace. The functional results were evaluated using a scoring scale and objective results using standardized stress radiographs. Also eccentric and concentric muscle torque at 60 degrees/s was measured in plantar flexion and dorsiflexion, respectively. The functional results were satisfactory in 12/15 ankles in Group A and 14/15 in Group B (n.s.). All the patients with satisfactory results regained normal range of motion. Patients with unsatisfactory results had either residual pain or recurrent instability. In Group B, the strength measurements revealed significantly higher peak torque values after three months in plantar flexion at 60 degrees/s. Six months postoperatively, the torque values did not differ significantly between the groups. Also, there was no group difference in the laxity of the ankle joint, including both anterior talar translation test and talar tilt test, at the two-year follow-up. One patient had a superficial wound infection. We conclude that after the reconstruction of chronic lateral ligament instability of the ankle the functional and stability results were equally good with early postoperative mobilization and 6-week immobilization. However, using early mobilization plantar flexion strength was regained earlier than with cast immobilization, without any risk of short- or medium-term complications, such as increased ankle laxity. We recommend early mobilization after anatomical reconstruction of the lateral ankle ligaments.

Adolescent↗
PubMed1999

Reconstruction of the anterior cruciate ligament: comparison of outside-in and all-inside techniques.

The aim of this prospective study was to compare two arthroscopic techniques for reconstructing the anterior cruciate ligament, the "outside-in" (two incisions) and the "all-inside" (one incision) techniques. The results obtained for 30 patients operated on using the "outside-in" technique (group I) were compared with those for 29 patients operated on using the "all-inside" technique (group II). Before surgery, there were no significant differences between the groups in terms of Lysholm score, Tegner activity level, patellofemoral pain score, or knee laxity. Both groups displayed significant improvements in Lysholm score after 24 months, from 69 (16) to 91 (9) in group I and from 70 (17) to 90 (15) in group II (means (SD)). There were also significant improvements in patellofemoral pain scores in both groups, from 13 (6) to 18 (5) in group I and from 14 (6) to 18 (4) in group II after 24 months. No difference was found between the groups in knee stability at the 24 month follow up. The IKDC score was identical in both groups at follow up. The operation took significantly longer for patients in group I (mean 94 (15)) than for those in group II (mean 86 (20)) (p = 0.03). The mean sick leave was 7.7 (6.2) weeks in group I and 12.3 (9.7) weeks in group II (p = 0.026), indicating that there may be a higher morbidity associated with the "all-inside" technique. It can be concluded that there were no significant differences between the two different techniques in terms of functional results, knee laxity, or postoperative complications. The results were satisfactory and the outcome was similar in both treatment groups.

Adolescent↗
PubMed1999

Adsorption and activity of Trichoderma reesei cellobiohydrolase I, endoglucanase II, and the corresponding core proteins on steam pretreated willow.

The adsorption and the hydrolytic action of purified cellulases of Trichoderma reesei, namely, cellobiohydrolase I (CBH I), endoglucanase II (EG II), and their core proteins, on steam-pretreated willow were compared. The two enzymes differed clearly in their adsorption and hydrolytic behavior. CBH I required the cellulose-binding domain (CBD) for efficient adsorption and hydrolysis, whereas EG II was able to adsorb to steam pretreated willow without its CBD. Absence of the CBD decreased the hydrolysis of cellulose by EG II, but the decrease was less pronounced than with CBH I. A linear relationship was observed between the amount of enzyme adsorbed and the degree of hydrolysis of cellulose only for CBH I. EG II and EG II core appeared to be able to hydrolyze only 1 to 2% of the substrate regardless of the amount of protein adsorbed.

Adsorption↗
PubMed1999

Hydrolysis of steam-pretreated lignocellulose: synergism and adsorption for cellobiohydrolase I and endoglucanase II of Trichoderma reesei.

The mechanism of hydrolysis of cellulose is important for improving the enzymatic conversion in bioprocesses based on lignocellulose. Adsorption and hydrolysis experiments were performed with cellobiohydrolase I (CBH I) and endoglucanase II (EG II) from Trichoderma reesei on a realistic lignocellulose substrates: steam-pretreated willow. The enzymes were studied both alone and in equimolar mixtures. Adsorption isotherms were determined at 4 and 40 degrees C during 90-min reaction times. Both CBH I and EG II adsorbed stronger at 40 than at 4 degrees C. The time course of adsorption and hydrolysis, 3 min to 48 h, was studied at 40 degrees C. About 90% of the cellulases were adsorbed within 2 h. The hydrolysis rate was high in the beginning but decreased during the time course. Based on adsorption data, the hydrolysis and synergism were analyzed as function of adsorbed enzyme. CBH I showed a linear correlation between hydrolysis and adsorbed enzyme, whereas for EG II the corresponding curve leveled off at both 4 and 40 degrees C. At low conversion, below 1%, EG II produced as much soluble sugars as CBH I. At higher conversion, CBH I was more efficient than EG II. The synergism as function of adsorbed enzyme increased with bound enzyme before reaching a stable value of about 2. The effect of varying the ratio of CBH I:EG II was studied at fixed total enzyme loading and by changing the ratio between the enzymes. Only a small addition (5%) of EG II to a CBH I solution was shown to be sufficient for nearly maximal synergism. The ratio between EG II and CBH I was not critical. The ratio 40% EG II:60% CBH I showed similar conversion to 5% EG II:95% CBH I. Modifications of the conventional endo-exo synergism model are proposed.

Journal Article↗
PubMed1999

Patellofemoral pain syndrome: a review of current issues.

There is no clear consensus in the literature concerning the terminology, aetiology and treatment for pain in the anterior part of the knee. The term 'anterior knee pain' is suggested to encompass all pain-related problems. By excluding anterior knee pain due to intra-articular pathology, peripatellar tendinitis or bursitis, plica syndromes, Sinding Larsen's disease, Osgood Schlatter's disease, neuromas and other rarely occurring pathologies, it is suggested that remaining patients with a clinical presentation of anterior knee pain could be diagnosed with patello-femoral pain syndrome (PFPS). Three major contributing factors of PFPS are discussed: (i) malalignment of the lower extremity and/or the patella; (ii) muscular imbalance of the lower extremity; and (iii) overactivity. The significance of lower extremity alignment factors and pathological limits needs further investigation. It is possible that the definitions used for malalignment should be re-evaluated, as the scientific support is very weak for determining when alignment is normal and when there is malalignment. Consequently, pathological limits must be clarified, along with evaluation of risk factors for acquiring PFPS. Muscle tightness and muscular imbalance of the lower extremity muscles with decreased strength due to hypotrophy or inhibition have been suggested, but remain unclear as potential causes of PFPS. Decreased knee extensor strength is a common finding in patients with PFPS. Various patterns of weaknesses have been reported, with selective weakness in eccentric muscle strength, within the quadriceps muscle and in terminal knee extension. The significance of muscle function in a closed versus open kinetic chain has been discussed, but is far from well investigated. It is clear that further studies are necessary in order to establish the significance of various strength deficits and muscular imbalances, and to clarify whether a specific disturbance in muscular activation is a cause or an effect (or both) of PFPS. The most common symptoms in patients with PFPS are pain during and after physical activity, during bodyweight loading of the lower extremities in walking up/down stairs and squatting, and in sitting with the knees flexed. However, the source of patellofemoral pain in patients with PFPS cannot be sufficiently explained. There are several types of clinical manifestation of pain, and therefore a differentiated documentation of the patient's pain symptoms is necessary. The connection between strength, pain and inhibition, as well as between personality and pain, needs further investigation. Many different treatment protocols are described in the literature and recent studies advocate a comprehensive treatment approach allowing for an individual and specifically designed treatment. Surgical treatment is rarely indicated. It is strongly suggested that, when presenting studies on PFPS, a detailed description should be provided of the diagnosis, inclusion and exclusion criteria of the patients should be specified along with a detailed methodology, and the conclusions drawn should be compared with those of other studies in the published literature. As this is not the case in most studies on PFPS found in the literature, it is only possible to make general comparisons. In order to further develop treatment models for PFPS we advocate prospective, randomised, controlled, long term studies using validated outcome measures. However, there is a strong need for basic research on the nature and aetiology of PFPS in order to better understand this mysterious syndrome.

Arthralgia↗
PubMed1998

Gene discovery in the wood-forming tissues of poplar: analysis of 5, 692 expressed sequence tags.

A rapidly growing area of genome research is the generation of expressed sequence tags (ESTs) in which large numbers of randomly selected cDNA clones are partially sequenced. The collection of ESTs reflects the level and complexity of gene expression in the sampled tissue. To date, the majority of plant ESTs are from nonwoody plants such as Arabidopsis, Brassica, maize, and rice. Here, we present a large-scale production of ESTs from the wood-forming tissues of two poplars, Populus tremula L. x tremuloides Michx. and Populus trichocarpa 'Trichobel.' The 5,692 ESTs analyzed represented a total of 3,719 unique transcripts for the two cDNA libraries. Putative functions could be assigned to 2,245 of these transcripts that corresponded to 820 protein functions. Of specific interest to forest biotechnology are the 4% of ESTs involved in various processes of cell wall formation, such as lignin and cellulose synthesis, 5% similar to developmental regulators and members of known signal transduction pathways, and 2% involved in hormone biosynthesis. An additional 12% of the ESTs showed no significant similarity to any other DNA or protein sequences in existing databases. The absence of these sequences from public databases may indicate a specific role for these proteins in wood formation. The cDNA libraries and the accompanying database are valuable resources for forest research directed toward understanding the genetic control of wood formation and future endeavors to modify wood and fiber properties for industrial use.

Arabidopsis↗
PubMed1998

[Common overuse knee-to-toes injuries in recreational exercise. Most cases are treatable in primary health care].

Although overuse injuries are common among recreational exercise-takers, in most cases they are treatable in primary care. It is important to evaluate both intrinsic and extrinsic aetiological factors underlying the development of overuse injuries. Treatment should always be focused on the aetiological factors, rather than solely on the symptoms. After an initial period of rest, a supervised rehabilitation programme, combined with correction of intrinsic and extrinsic factors, is the optimal treatment for most overuse syndromes. Surgery is only rarely necessary.

Athletic Injuries↗
PubMed1998

[Ligament injuries of the ankle--what happens later? Non-surgical treatment is effective in 80-90 per cent of cases].

Ligament injuries of the ankle joint are the most common sports-related injuries. In more than 90 per cent of all cases, it is a question of lateral ligament injury. The recommended acute treatment is always non-surgical, with range of motion training, followed by strengthening and co-ordination exercises. Approximately 80-90 per cent of all ligament injury patients regain normal ankle function after this form of treatment. Early active treatment can reduce time off from sports and the duration of sick leave. Residual problems, mainly pain or recurrent or chronic instability are seen in approximately 10-20 per cent of cases. In cases of chronic instability, ligament reconstruction is recommended. In patients with anterior or anterolateral ankle pain, arthroscopic resection of bone spurs or loose bodies may be beneficial.

Acute Disease↗
PubMed1998

Treatment with the spin-trap agent alpha-phenyl-N-tert-butyl nitrone does not enhance the survival of embryonic or adult dopamine neurons.

Reactive oxygen species are thought to be involved in the death of dopaminergic neurons in Parkinson's disease as well as in transplanted embryonic dopaminergic neurons. The spin-trap agent alpha-phenyl-N-tert-butyl nitrone (PBN) reacts directly with radical species and may thereby prevent them from damaging important cellular molecules such as membrane lipids. We found that PBN does not increase the survival of cultured embryonic dopaminergic neurons subjected to serum deprivation, whereas the antioxidant and lipid peroxidation inhibitor lazaroid U-83836E does. Moreover, PBN does not increase the survival of grafted embryonic dopaminergic neurons or graft efficacy (monitored as changes in drug-induced motor asymmetry in hemiparkinsonian rats) when the spin-trap agent is given intraperitoneally to the graft recipient or is added to the solutions used when preparing tissue for transplantation. Another spin-trap agent, alpha-(4-pyridyl-1-oxide)-N-tert-butyl nitrone (POBN) also failed to protect neurons when given to graft recipients in the same experimental paradigm. Finally, we found that adult nigral neurons subjected to a progressive retrograde 6-OHDA lesion are not protected by systemic treatment with PBN. Even though reduction of oxidative stress by overexpression of superoxide dismutase or addition of lazaroids have previously been shown to enhance the survival of cultured and grafted dopaminergic neurons, spin-trap agents PBN and POBN do not provide protection in these experimental paradigms. This may be due to antioxidants and spin-trap agents interfering in different steps of free radical-induced cell damage.

Aging↗
PubMed1998

Hydrolysis of microcrystalline cellulose by cellobiohydrolase I and endoglucanase II from Trichoderma reesei: adsorption, sugar production pattern, and synergism of the enzymes.

Microcrystalline cellulose (10 g/L Avicel) was hydrolysed by two major cellulases, cellobiohydrolase I (CBH I) and endoglucanase II (EG II), of Trichoderma reesei. Two types of experiments were performed, and in both cases the enzymes were added alone and together, in equimolar mixtures. In time course studies the reaction time was varied between 3 min and 48 h at constant temperature (40 degrees C) and enzyme loading (0.16 micromol/g Avicel). In isotherm studies the enzyme loading was varied in the range of 0.08-2.56 micromol/g at 4 degrees C and 90 min. Adsorption of the enzymes and production of soluble sugars were followed by FPLC and HPLC, respectively. Adsorption started quickly (50% of maximum achieved after 3 min) but was not completed before 60-90 min. For CBH I a linear relationship was observed between the production of soluble sugars and adsorption, showing that the average activity of the bound CBH I molecules does not change with increasing saturation. For EG II the corresponding curve levelled off which is explained by initial hydrolysis of loose ends on Avicel. The enzymes competed for binding sites, binding of EG II was considerably affected by CBH I, especially at high concentration. CBH I produced more soluble sugars than EG II, except at conversions below 1%. At 40 degrees C when the enzymes were added together they produced 27-45% more soluble sugars than the sum of what they produced alone, i.e. synergistic action was observed (the final conversion after 48 h of hydrolysis was 3, 6, and 13% for EG II, CBH I, and their mixture, respectively). At 4 degrees C, on the other hand, when the conversion was below 2.5%, almost no synergism could be observed. Molar proportions of the produced sugars were rather stable for CBH I (11-15%, 82-89%, and <6% for glucose, cellobiose, and cellotriose, respectively), while it varied considerably with both time and enzyme concentration for EG II. The observed stable but high glucose to cellobiose ratio for CBH I indicates that the processivity for this enzyme is not perfect. EG II produced significant amounts of glucose, cellobiose, and cellotriose, which are not the expected products of a typical endoglucanase activity on a solid substrate. We explain this by hypothesizing that EG II may show processivity due to its extended substrate binding site and the presence of its cellulose binding domain.

Adsorption↗