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Biomedical subjects

M Englund

Publications and source records attributed to M Englund.

16 recordsLinked to original sources
PubMed2005

Multimode fiber devices with single-mode performance.

A taper transition can couple light between a multimode fiber and several single-mode fibers. If the number of single-mode fibers matches the number of spatial modes in the multimode fiber, the transition can have low loss in both directions. This enables the high performance of single-mode fiber devices to be attained in multimode fibers. We report an experimental proof of concept by using photonic crystal fiber techniques to make the transitions, demonstrating a multimode fiber filter with the transmission spectrum of a single-mode fiber grating.

Journal Article↗
PubMed2005

Patellofemoral osteoarthritis coexistent with tibiofemoral osteoarthritis in a meniscectomy population.

OBJECTIVES: To evaluate the frequency of patellofemoral osteoarthritis and its relevance to symptoms and function in a meniscectomy population. METHODS: 317 patients with no cruciate ligament injury were evaluated (mean (SD) age, 54 (11) years). They had undergone meniscal resection 15 to 22 years earlier (follow up rate 70%). Standing tibiofemoral and skyline patellofemoral radiographs were graded according to the OARSI atlas. The Knee Injury and Osteoarthritis Outcome Score (KOOS) was used to quantify symptoms and function. Controls were 68 unoperated subjects identified from national population records. RESULTS: Patellofemoral osteoarthritis (isolated or coexisting with tibiofemoral osteoarthritis) was present in 66 of 317 index knees (21%) and 21 of 263 unoperated contralateral knees (8%, p<0.001). In 57/66 (86%) of these index knees, tibiofemoral osteoarthritis was present (mixed osteoarthritis). In a model adjusted for age, sex, and body mass index, the odds ratio for patellofemoral osteoarthritis (alone or in combination with tibiofemoral osteoarthritis) was 2.6 (95% confidence interval, 1.1 to 6.6) after medial meniscectomy and 5.3 (1.9 to 15.0) after lateral meniscectomy, using controls as the reference. Individuals with a mixed knee osteoarthritis pattern had more symptoms, lower function in sports and recreation, and worse knee related quality of life than subjects with isolated tibiofemoral osteoarthritis. CONCLUSIONS: Mixed patellofemoral and tibiofemoral osteoarthritis is common in a meniscectomy population. Patellofemoral osteoarthritis is a contributing cause of knee symptoms and reduced knee related quality of life and is relevant to the management of knee complaints of this group of patients.

Adult↗
PubMed2004

Association of radiographic hand osteoarthritis with radiographic knee osteoarthritis after meniscectomy.

OBJECTIVE: To evaluate the association between radiographic hand osteoarthritis (OA), a disease with marked heredity, and radiographic knee OA in patients treated with meniscectomy. METHODS: We retrospectively identified 170 patients (mean age 54 years [range 33-87 years], 23% women) who had undergone isolated meniscectomy an average of 20 years earlier (range 17-22 years). Patients with cruciate ligament injury were excluded. All subjects were examined by standardized knee and hand radiography. Individual joints were considered to have OA when displaying radiographic features corresponding to a Kellgren/Lawrence (K/L) grade > or =2. Hand OA was considered present if at least 1 of the following criteria was fulfilled: the presence of radiographic OA (K/L grade > or =2) in at least 1 interphalangeal joint in each hand symmetrically, or in at least 2 distal or proximal interphalangeal joints in the same hand in a pattern consistent with primary OA (in the same row or ray), or in the first carpometacarpal joint bilaterally. The association between radiographic hand OA and radiographic knee OA was evaluated using logistic regression. RESULTS: Radiographic hand OA was present in 57 patients (34%) and radiographic knee OA was identified in 105 patients (62%), within 94 index knees (55%) and 47 contralateral knees (28%). In a multivariate model, radiographic hand OA was associated with an increased likelihood of radiographic OA in the index knee (odds ratio [OR] 3.0, 95% confidence interval [95% CI] 1.2-7.5) and in the nonoperated contralateral knee (OR 3.5, 95% CI 1.0-12.2). CONCLUSION: The presence of radiographic hand OA is associated with an increased frequency of radiographic knee OA after meniscectomy. This finding confirms and extends that of a single previous study showing an interaction between hereditary and environmental risk factors for OA, a common and genetically complex disease. Accordingly, the development of OA following a meniscal tear and the resulting meniscal surgery should not be regarded to be of secondary origin only.

Arthroscopy↗
PubMed2004

Risk factors for symptomatic knee osteoarthritis fifteen to twenty-two years after meniscectomy.

OBJECTIVE: To evaluate the influence of age, sex, body mass index (BMI), extent of meniscal resection, cartilage status, and knee load on the development of radiographically evident osteoarthritis (OA) of the knee and knee symptoms after meniscal resection. METHODS: We evaluated 317 patients with no cruciate ligament injury (mean +/- SD age 54 +/- 11 years) who had undergone meniscal resection 15-22 years earlier (followup rate 70%), with radiographic and clinical examination. The Knee injury and Osteoarthritis Outcome Score was used to quantify knee-related symptoms. Sixty-eight unoperated subjects identified from national population records were included as a reference group. RESULTS: Symptomatic radiographic OA (corresponding to Kellgren/Lawrence grade > or =2) was present in 83 of 305 operated knees (27%) and 7 of 68 control knees (10%) (relative risk 2.6, 95% confidence interval [95% CI] 1.3-6.1). Patients who had undergone total meniscectomy and subjects with obesity (BMI > or =30) had a greater likelihood of tibiofemoral radiographic OA than those who had undergone partial meniscal resection and those with a BMI <25, respectively. Furthermore, degenerative meniscal tear, intraoperative cartilage changes, and lateral meniscectomy were associated with radiographic OA more frequently than were longitudinal tear, absence of cartilage changes, and medial meniscectomy, respectively. Symptomatic tibiofemoral or patellofemoral radiographic OA was associated with obesity, female sex, and degenerative meniscal tear. CONCLUSION: Contributing risk factors for OA development after meniscal resection are similar to risk factors for common knee OA. Systemic factors and local biomechanical factors interact. Obesity, female sex, and preexisting early-stage OA are features associated with poor self-reported and radiographic outcome. Partial meniscal resection is associated with less radiographic OA over time than is total meniscectomy.

Aged↗
PubMed2004

High prevalence of knee osteoarthritis, pain, and functional limitations in female soccer players twelve years after anterior cruciate ligament injury.

OBJECTIVE: To determine the prevalence of radiographic knee osteoarthritis (OA) as well as knee-related symptoms and functional limitations in female soccer players 12 years after an anterior cruciate ligament (ACL) injury. METHODS: Female soccer players who sustained an ACL injury 12 years earlier were examined with standardized weight-bearing knee radiography and 2 self-administered patient questionnaires, the Knee Injury and Osteoarthritis Outcome Score questionnaire and the Short Form 36-item health survey. Joint space narrowing and osteophytes were graded according to the radiographic atlas of the Osteoarthritis Research Society International. The cutoff value to define radiographic knee OA approximated a Kellgren/Lawrence grade of 2. RESULTS: Of the available cohort of 103 female soccer players, 84 (82%) answered the questionnaires and 67 (65%) consented to undergo knee radiography. The mean age at assessment was 31 years (range 26-40 years) and mean body mass index was 23 kg/m2 (range 18-40 kg/m2). Fifty-five women (82%) had radiographic changes in their index knee, and 34 (51%) fulfilled the criterion for radiographic knee OA. Of the subjects answering the questionnaires, 63 (75%) reported having symptoms affecting their knee-related quality of life, and 28 (42%) were considered to have symptomatic radiographic knee OA. Slightly more than 60% of the players had undergone reconstructive surgery of the ACL. Using multivariate analyses, surgical reconstruction was found to have no significant influence on knee symptoms. CONCLUSION: A very high prevalence of radiographic knee OA, pain, and functional limitations was observed in young women who sustained an ACL tear during soccer play 12 years earlier. These findings constitute a strong rationale to direct increased efforts toward prevention and better treatment of knee injury.

Adult↗
PubMed2004

Hypoxic excitability changes and sodium currents in hippocampus CA1 neurons.

1. The objective of the present study was to distinguish if inhibition of neuronal activity by hypoxia is related to a block of voltage-gated Na+ channels. 2. The effect of chemical hypoxia induced by cyanide (0.5 mM, 10 min perfusion) was studied with patch-clamp technique in visualized intact CA1 pyramidal neurons in rat brain slices. Action potentials were elicited in whole cell current-clamp recordings and the threshold was estimated by current pulses of 50-ms duration and incremental amplitudes (n = 31). The effect of cyanide on the Na+ current and conductance was studied in voltage clamp recordings from cell-attached patches (n = 13). 3. Cyanide perfusion during 10 min increased the threshold for excitation by 73 +/- 79 pA (p = 0.001), which differed from the effect in control cells (11 +/- 41 pA, ns). The change in current threshold was correlated to a change in membrane potential (r = -0.88, p < 0.0001). Cyanide had no significant effect on the peak amplitude, duration, or rate of rise of the action potential. 4. Cyanide perfusion did not change the Na+ current size, but caused a small decrease in ENa (-17 +/- 22 mV, ns) and a slight increase in Na+ conductance (+14 +/- 26%, ns), which differed (p = 0.045) from controls (-19 +/- 23 %, ns). 5. In conclusion, chemical hypoxia does not cause a decrease in Na+ conductance. The decreased excitability during hypoxia can be explained by an increase in the current threshold, which is correlated with the effect on the membrane potential.

Action Potentials↗
PubMed2004

Venous gas embolism in chamber attendants after hyperbaric exposure.

An initial occupational survey (OS) was initiated to investigate the prevalence of venous gas embolism (VGE) in chamber attendants assisting hyperbaric oxygen (HBO2) treatments. Nine female subjects were exposed for three consecutive days to the routine hospital procedure of compressed air exposure to 240 kPa for approximately 115 min with 12 min of terminal oxygen (O2) breathing. VGE was monitored with ultrasound Doppler in 15 min intervals for 2h after the first and third exposure. A follow-up experimental study was completed to investigate whether changed breathing gases and decompression would affect the high incidence of VGE observed in the OS. Ten female subjects were randomly exposed to the routine or revised profile (12 and 24 min of terminal O2 breathing respectively), and a Nitrox profile (breathing gas 40.5% O2 in Nitrogen during 90 min of the isobaric phase). VGE was monitored with transthoracic ultrasound scanner and Doppler. In the OS precordial VGE grade III (Doppler) was observed in five subjects, but median resting precordial VGE was Grade 0 both days and VGE score at all sites were equal Days 1 and 3. In the experimental study, median resting precordial VGE was Grade 0 (Doppler) and Grade 1 (Scanner). VGE Grade III (Doppler) was observed in all series, but VGE scores were not significantly different between the series. We conclude that chamber attendants assisting HBO2 treatment at 240 kPa for approximately 115 min are exposed to a significant decompression stress using the profiles tested in the present study.

Adult↗
PubMed2003

Impact of type of meniscal tear on radiographic and symptomatic knee osteoarthritis: a sixteen-year followup of meniscectomy with matched controls.

OBJECTIVE: To investigate long-term radiographic and patient-relevant outcome of isolated limited meniscectomy with regard to type of meniscal tear and extent of surgical resection. METHODS: We studied 155 patients with intact cruciate ligaments (mean +/- SD age 54 +/- 12 years) who had undergone meniscectomy an average of 16 +/- 1 years earlier. The patients were examined using standardized radiography and validated self-administered questionnaires. The Knee Injury and Osteoarthritis Outcome Score (KOOS) was used to quantify knee-related symptoms, and the definition of a symptomatic knee was determined. We used 68 control subjects matched for age, sex, and body mass index to calculate the relative risks (RRs). RESULTS: Radiographic tibiofemoral osteoarthritis (OA) (Kellgren/Lawrence grade > or =2) was present in 66 index knees (43%), of which 39 (59%) were considered to be symptomatic according to the KOOS. In total, 77 patients (50%) had a symptomatic index knee. In a multivariate model, degenerative meniscal tears were associated with both radiographic OA (P = 0.030) and combined radiographic and symptomatic OA (P < or = 0.015). The RRs for combined radiographic and symptomatic OA after degenerative and traumatic types of meniscal tear were 7.0 (95% confidence interval [95% CI] 2.1-23.5) and 2.7 (95% CI 0.9-7.7), respectively, compared with matched controls. CONCLUSION: An isolated meniscal tear treated by limited meniscectomy is associated with a high risk of radiographic and symptomatic tibiofemoral OA at 16-year followup. Factors associated with worse outcome were degenerative meniscal lesions and extensive resections. We suggest that degenerative meniscal tears may be associated with incipient OA, and that the meniscal tear signals the first symptom of the disease.

Adult↗
PubMed2001

Chemical hypoxia in hippocampal pyramidal cells affects membrane potential differentially depending on resting potential.

The aim of the present study was to analyze the effect of chemical hypoxia (cyanide) on the membrane potential of hippocampal CA1 neurons and to elucidate the reason for previously found differences in the reaction to hypoxia in these cells. Recordings were performed in brain slices from 8-19-day-old rats with whole-cell patch clamp on cells identified with near-infrared video microscopy. Cyanide (0.1-2.0 mM) caused different responses depending on the resting potential of the cells: hyperpolarization (or an initial depolarization followed by hyperpolarization) was generally seen in cells with less negative resting potential (-56+/-6.1 mV), and depolarization in cells with more negative resting potential (-62+/-3.4 mV). After 10 min in cyanide the membrane potential in all cells had reached approximately the same level (-62+/-5.8 mV), the direction and size of the voltage response having an inverse linear relation to the resting potential (k=-0.98, r=0.71). The direction of the cyanide response was not reversed by current injection (depolarization by 12 mV) in cells with more negative resting potential (-60+/-2.8 mV). Wash out of cyanide caused hyperpolarization in 70% of the cells. Presence of ouabain (2 microM) resulted in pronounced depolarization during cyanide perfusion, and potentiated the hyperpolarization during wash out indicating that this part of the effect is not dependent on a reactivation of the Na/K pump. In conclusion, chemical hypoxia with cyanide changes the membrane potential in CA1 cells in size and direction depending on the original resting potential of the cells. The present findings suggested that cyanide activated not only K+ channels but in addition increased a Na+ current which has a more positive equilibrium potential.

Animals↗
PubMed2001

Patient-relevant outcomes fourteen years after meniscectomy: influence of type of meniscal tear and size of resection.

OBJECTIVES: To study long-term patient-relevant outcomes after meniscectomy, a surgical procedure associated with a high risk of knee osteoarthritis (OA). Principal objectives were to compare traumatic with degenerative meniscal tear and partial with subtotal meniscectomy. METHODS: We studied a well-defined cohort of 205 patients who had undergone isolated unilateral meniscectomy between 1983 and 1985. There was no previous knee surgery and all knees were stable. The type of meniscal tear and surgical resection was ascertained by review of medical records. Patients were followed up after 14 yr (range 12-15 yr) by self-administered questionnaires, one generic [Short Form 36 (SF-36)] and one disease-specific [Knee Injury and Osteoarthritis Outcome Score (KOOS)]. RESULTS: In a multivariate analysis, using the Sports and Recreation Function and knee-related Quality of Life subscales of the KOOS questionnaire as dependent variables, patients with a degenerative tear scored significantly worse than individuals with a traumatic tear (P < or = 0.001). When we analysed unmatched subgroups and age- and sex-matched patients with degenerative or traumatic lesions, the same result was found for the knee-specific outcome (P < or = 0.02) and SF-36 except for Social Functioning (P < or = 0.04). There was no difference in outcome for the total cohort according to the type of resection. However, subgroup analyses showed that patients who underwent subtotal meniscectomy for a degenerative tear scored significantly worse on the knee-specific outcome than individuals who had had a partial meniscectomy for the same type of tear (P < or = 0.02). CONCLUSIONS: The long-term outcome of meniscal injury and surgery appears to be determined largely by the type of meniscal tear. Furthermore, our findings support the use of minimal meniscal resection in the treatment of degenerative tears. We suggest that the disease processes associated with the development of OA of the joint cartilage may also be active in the meniscus, and that a tear in a meniscus with degenerative changes might be regarded as the first sign of OA of the joint.

Adult↗
PubMed2000

Renal response to a protein load persists during long-term follow-up of children after renal transplantation.

BACKGROUND: Kidney donors and transplant recipients may be at risk of complications from glomerular hyperfiltration of the single kidney. It has been assumed that tests of the existence of renal functional reserve [delta glomerular filtration rate (deltaGFR), delta effective renal plasma flow (deltaERPF)] can be used to demonstrate hyperfiltration. It would therefore be of interest to evaluate the response of the kidney graft to a protein load. i.e., testing the renal reserve and to find out whether a reduction in baseline GFR is preceded by a loss of deltaGFR. METHODS: We repeatedly studied the change in GFR and renal plasma flow (ERPF) after an oral protein load in 30 children after renal transplantation (Tx). Follow-up time was 1.0-8.0 years. Renal function was evaluated with the clearances of inulin and para-aminohippuric acid (PAH). Seven recipient/donor pairs were examined twice (median 0.3 and 4 years, after Tx). RESULTS: The baseline GFR and ERPF remained stable throughout the follow-up and the increase after stimulation (deltaGFR and deltaERPF) did not change in the whole group of Tx children over the years. However, a reduction in the baseline GFR from the first to the last investigation occurred in 23 of 30 children. In the 23 patients whose baseline GFR decreased, deltaGFR was still preserved. In the recipient/donor pairs, the baseline GFR and ERPF were the same, but on the second investigation, donors showed higher deltaGFR. CONCLUSION: Despite fairly low baseline GFR and ERPF values in the Tx children, no change occurs in the capacity to increase GFR and ERPF after a protein load during follow-up, which suggests that they are not maximally hyperfiltrating.

Child↗
PubMed1993

The significance of gender boundaries in preadolescence: contemporary correlates and antecedents of boundary violation and maintenance.

Previous research has established the importance of gender boundaries as a normative aspect of development in middle childhood. Here, the nature and importance of gender boundaries as an individual differences construct was explored. Ratings of gender boundary violation and gender boundary maintenance were made of 47 10-11-year-old children participating in a series of summer day camps. These ratings were supported by videotape-based behavior codings of gender boundary violating behaviors and by live observations of sheer number of associations with members of the opposite gender. In addition, considerable external validation of these individual differences was obtained. Children low on gender boundary violation and (especially) children high on boundary maintenance were independently judged by camp counselors to be socially competent. They also were found to be higher on a friendship variable, based on observation. Those who violated boundaries were especially unpopular with peers, based on a child interview. Finally, boundary violation and maintenance were related to attachment history and to early measures of parent-child generational boundary distortions.

Child↗
PubMed1990

Central nervous system complications in children treated with ciclosporin after renal transplantation.

Severe complications involving the central nervous system occurred in 7 of 36 children (19%) after renal transplantation. The children, aged 1.6-13.1 years at transplantation were treated with ciclosporin and prednisolone. Six of them had azathioprine as well. The neurological symptoms consisted of seizures, drowsiness, confusion, hallucinations, visual disturbances, and mental changes. In all cases electroencephalograms were severely pathological, showing diffuse abnormalities with or without focal abnormalities and epileptic activity. In all but one case the ciclosporin trough blood levels were within the therapeutic range. Blood glucose and electrolytes were normal. Several factors might contribute to the central nervous system complications: ciclosporin, corticosteroids, hypertension, rejection, and as yet unknown ones.

Adolescent↗