Biomedical subjects

A Keller

Publications and source records attributed to A Keller.

At least 19 recordsLinked to original sources

PubMed2006

Sustained peripheral arterial insufficiency durably impairs normal and regenerating skeletal muscle function.

Peripheral vascular occlusive diseases are frequently observed in humans, and studies with animal models have been largely used. However the effects of sustained lower limb ischemia on normal and regenerating hindlimb skeletal muscles are not well known in the mouse model. Therefore prolonged unilateral hindlimb ligation was generated by femoral artery ligation. Normal (myotoxic-untreated) and regenerating (myotoxic-reated) ischemic muscles were studied by analyses of the in situ contractile properties and histological parameters. Concerning normal mouse muscles, we found that femoral artery ligation reduced hindlimb perfusion and altered muscle structure and function. Thus 7 days after ligation, maximal tetanic force was reduced by about 70%, (p < 0.05). By 56 days after ligation, muscle weights and cross-section areas of muscle fibers were still reduced (p < 0.05). Concerning myotoxic treated muscles, we report that ligation reduced the recovery of muscle weight and maximal tetanic force and increased fatigue resistance at 56 days (p < 0.05). In conclusion, our results demonstrate that sustained peripheral arterial insufficiency in mice induces long-term as well as acute detrimental effects in both normal and regenerating muscles.

Animals↗

PubMed2006

Clinical and functional characteristics of the human Arg59Ter insulin-like growth factor i receptor (IGF1R) mutation: implications for a gene dosage effect of the human IGF1R.

CONTEXT: Signaling via the IGF-I receptor (IGF-IR) is crucial for normal prenatal and postnatal growth. The heterozygous IGF-IR mutation Arg59Ter resulted in reduced IGF-IR expression and represents haploinsufficiency of the human IGF1R gene. OBJECTIVE: We studied clinical and in vitro aspects of a human IGF1R gene dosage effect. We provide detailed clinical data on the two half-brothers and their mother with the Arg59Ter mutation. Arg59Ter and control fibroblasts were examined for functionality of IGF-I and insulin-stimulated receptor phosphorylation and signal transduction. RESULTS: The two brothers presented with primary microcephaly, mild mental retardation, and intrauterine as well as postnatal growth deficits. After GH therapy (30 microg/kg.d) for 24 months, the growth deficit in the propositus decreased by +1.0 sd. There was no clinical evidence for impaired glucose tolerance or hypoglycemia in all Arg59Ter subjects. In vitro, IGF-IR-deficient Arg59Ter cells expressed less IGF-IR and unchanged insulin receptor (IR) protein. Receptor autophosphorylation and phosphorylation of downstream protein kinase B/Akt exhibited resistance to IGF-I but showed an augmented response to insulin in Arg59Ter cells. Decreased IGF-IR content was accompanied by a reduction of IGF-IR/IR receptor hybrids, and therefore, increased levels of IR/IR homodimers probably explain increased insulin-stimulated receptor autophosphorylation and Akt phosphorylation. CONCLUSIONS: In vivo and in vitro IGF-I resistance in Arg59Ter subjects and fibroblasts indicates a human IGF1R gene dosage effect involving not only the IGF-IR, but also IGF-IR/IR hybrids. The abundance of both the IGF-IR protein and IGF-IR/IR hybrid receptors may have an impact on human growth, organ function, and glucose metabolism.

Body Weight↗

PubMed2006

An audit of imaging test utilization for the management of lymphoma in an oncology hospital: implications for resource planning?

The purpose of this study was to assist with resource planning by examining the pattern of physician utilization of imaging procedures for lymphoma patients in a dedicated oncology hospital. The proportion of imaging tests ordered for routine follow up with no specific clinical indication was quantified, with specific attention to CT scans. A 3-month audit was performed. The reasons for ordering all imaging procedures (X-rays, CT scans, ultrasound, nuclear scan and MRI) were determined through a retrospective chart review. 411 lymphoma patients had 686 assessments (sets of imaging tests) and 981 procedures (individual imaging tests). Most procedures were CT scans (52%) and chest radiographs (30%). The most common reasons for ordering imaging were assessing response (23%), and investigating new symptoms (19%). Routine follow up constituted 21% of the assessments (142/686), and of these, 82% were chest radiographs (116/142), while 24% (34/142) were CT scans. With analysis restricted to CT scans (296 assessments in 248 patients), the most common reason for ordering CT scans were response evaluation (40%), and suspicion of recurrence and/or new symptom (23%). Follow-up CT scans done with no clinical indication comprised 8% (25/296) of all CT assessments. Staging CT scans were under-represented at 6% of all assessments. Imaging with CT scans for follow up of asymptomatic patients is infrequent. However, scans done for staging new lymphoma patients were unexpectedly low in frequency, due to scans done elsewhere prior to referral. This analysis uncovered utilization patterns, helped resource planning and provided data to reduce unnecessary imaging procedures.

Adolescent↗

PubMed2005

Structural daily rhythms in GFP-labelled neurons in the visual system of Drosophila melanogaster.

In the visual system of Drosophila melanogaster, two classes of interneurons in the first optic neuropil, or lamina, the monopolar cells L1 and L2, show rhythmic circadian changes in the shape and size of their axons. In the present study we have used the GAL4-UAS system to target the GFP expression to the L2 cells in D. melanogaster and to examine morphological changes in the cell body, nucleus, axon and dendritic spines. Our results showed that in addition to changes in the caliber of its axon, L2 also shows daily changes in the morphology of its dendritic spines, differences which are most pronounced at the beginning of the night. There are also changes in the sizes of the cells' nuclei in the lamina cortex, which are largest at the beginning and in the middle of day, in females and males, respectively. In contrast to the axon and dendrites, L2's soma does not change size significantly during the day or night. The observed changes clearly indicate the cyclical modulation of the structure of the L2 interneurons. These changes seem to be regulated by a circadian clock, which exhibits certain differences between the sexes.

Animals↗

PubMed2005

[Influence of sacral fracture on the long-term outcome of pelvic ring injuries].

Initial treatment of pelvic ring fractures with involvement of the iliosacral complex is directed at bleeding control and fixation of the pelvic ring. However, long-term outcome is determined by persisting neurological deficits, malunion of the posterior pelvic ring with low back pain, and urological lesions. Between 1991 and 2000, 173 patients with sacral fractures were treated at our institution. Sacral fractures as part of type B2 ("lateral compression") or type C ("vertical shear") pelvic ring fractures were treated conservatively, if dislocation was less than 1 cm. Fractures with a dislocation of more than 1 cm were treated operatively (n=33, 19%). A total of 112 patients were examined after an average of 4.9 years. Of the 39 patients with primary neurological deficits (35%) only 4 showed complete neurological recovery. Chronic low back pain was rarely observed (n=8, 7%) and only in type C injuries. The low incidence of chronic low back pain justifies conservative treatment of minimally (<1 cm) displaced sacral fractures. Long-term outcome is largely determined by neurological deficits, which persist in 30% of all patients with sacral fractures.

Adolescent↗

PubMed2005

Nuclear imaging of an extraskeletal retroperitoneal osteosarcoma: respective contribution of 18FDG-PET and (99m)Tc oxidronate (2005:1b).

Extraskeletal osteosarcoma (ExOs) is a rare, usually highly aggressive malignancy, which affects individuals beyond the fifth decade of life. ExOs prinicipally occurs as a soft tissue mass in a limb or retroperitoneum. We present the case of a 58-year-old man with a huge abdominal mass who underwent a complete range of clinical imaging investigations including computed tomography (CT), skeletal scintigraphy (BS) and positron emission tomography (PET). These exams showed a central calcified and ossified, strongly metabolic retroperitoneal tumour suggestive of an ExOs. This diagnosis was later confirmed by histopathology. To our knowledge, such a case has not previously been documented fully using radiological imaging correlated to modern nuclear medicine techniques such as PET.

Fluorodeoxyglucose F18↗

PubMed2005

Parametric and quantitative analysis of MR renographic curves for assessing the functional behaviour of the kidney.

The aim of this study was to refine the description of the renal function based on MR images and through transit-time curve analysis on a normal population and on a population with renal failure, using the quantitative model of the up-slope. Thirty patients referred for a kidney MR exam were divided in a first population with well-functioning kidneys and in a second population with renal failure from ischaemic kidney disease. The perfusion sequence consisted of an intravenous injection of Gd-DTPA and of a fast GRE sequence T1-TFE with 90 degrees magnetisation preparation (Intera 1.5 T MR System, Philips Medical System). To convert the signal intensity into 1/T1, which is proportional to the contrast media concentration, a flow-corrected calibration procedure was used. Following segmentation of regions of interest in the cortex and medulla of the kidney and in the abdominal aorta, outflow curves were obtained and filtered to remove the high frequency fluctuations. The model of the up-slope method was then applied. Significant reduction of the cortical perfusion (Qc = 0.057+/-0.030 ml/(s 100 g) to Qc = 0.030 +/- 0.017 ml/(s 100 g), P < 0.013) of the medullary perfusion (Qm = 0.023 +/- 0.018 ml/(s 100 g) to Qm = 0.011 +/- 0.006 ml/(s 100 g), P < 0.046) and of the accumulation of contrast media in the medulla (Qa = 0.005 +/- 0.003 ml/(s 100 g) to Qa = 0.0009 +/- 0.0008 ml/(s 100 g), P < 0.001) were found in presence of renal failure. High correlations were found between the creatinine level and the accumulation Qa in the medulla (r2 = 0.72, P < 0.05), and between the perfusion ratio Qc/Qm and the accumulation Qa in the medulla (r2 = 0.81, P < 0.05). No significant difference was found in times to peak between both populations despite a trend showing Ta the time to the end of the increasing contrast accumulation period in the medulla, arriving later for renal failure. Advances in MR signal calibration with the building of quantitative model such as the up-slope allow to assess kinetic and haemodynamic and functional parameters of the diseased kidney.

Contrast Media↗

PubMed2005

Functional, cellular and molecular aspects of skeletal muscle recovery after injury induced by snake venom from Notechis scutatus scutatus.

We have analysed the rate and ultimate extent of muscle functional recovery after snake venom-induced myotoxicity, as well as the relationships between functional, biochemical and structural indices of recovery. We also compared the effects of various injuries leading to muscle necrosis, loss of innervation/vasculature and/or precursors of muscle cells (pmc). We found that several parameters of rat soleus muscle such as maximal isometric force, slow myosin heavy chain, and citrate synthase, were fully and rapidly restored within 6 weeks after treatment with snake Notechis scutatus venom (im, 2 microg/muscle). In contrast, some muscle contractile properties (degree of tetanic fusion, fatigue resistance...) were not fully recovered even by 12 weeks after venom treatment. However, when compared to other injuries, recovery 3 weeks after venom treatment, was better than that observed after severing the terminal nerve and accompanying vessels and after cryodamage known to kill pmc. In conclusion, our studies demonstrate that-contrary to what is commonly believed -- muscle treated by myotoxic agent does not recover rapidly and fully. However, the degree or rate of muscle recovery after snake venom treatment was much better when compared to other types of injury. In addition, histological and biochemical parameters cannot be used as such to easily predict functional recovery following injury.

Animals↗

PubMed2004

ZD9331 as second- or third-line therapy in patients with advanced colorectal cancer: a phase II multicenter trial.

This study investigated the efficacy and tolerability of ZD9331 as second- or third-line treatment for patients with advanced colorectal cancer (aCRC). One hundred patients were recruited to the study: 45 in group 1 (failed first-line 5-FU-based regimen) and 55 in group 2 (failed first-line 5-FU-based regimen and second-line irinotecan). Patients received ZD9331 as a 30-minute intravenous infusion on days 1 and 8 of a 3-week cycle, and treatment continued until disease progression (PD) or withdrawal. After a median of 4 cycles of treatment, there were no objective responses in group 1 (N = 37), 25 (67.6%) patients had a best overall response of stable disease (SD), and 12 (32.4%) had PD. After a median of 3 cycles of treatment, there were 2 (4.5%) partial responses in group 2 (N = 44), 21 (47.7%) patients had a best overall response of SD, 20 (45.4%) had PD, and 1 (2.3%) had clinical progression. At data cut-off, 59.5% and 77.3% of patients in groups 1 and 2, respectively, had PD. The main adverse events were neutropenia (69%), fatigue (53%), nausea (46%), and diarrhea (40%), and most (72.3%) were grade I/II. ZD9331 demonstrated minimal antitumor activity, and manageable toxicity, in the second- or third-line treatment of aCRC.

Adult↗

PubMed2004

Priming with testosterone enhances stimulated growth hormone secretion in boys with delayed puberty.

BACKGROUND AND OBJECTIVE: Tests for growth hormone (GH) deficiency are not always helpful in the differential diagnosis of physiological delay of growth and puberty and GH deficiency. PATIENTS AND METHODS: To enhance diagnostic specificity, we used a single dose testosterone priming before repeating the arginine stimulation test in 26 boys with short stature and only early signs of puberty who failed to show an adequate response of serum GH in the first test. RESULTS: 77% (20/26 patients) increased their serum GH peak to more than 10 ng/ml, whereas six patients were still below this concentration. CONCLUSION: We propose that testosterone priming is a useful tool to distinguish between physiological delay of growth and puberty and GH deficiency and should be included in the diagnostic procedure.

Adolescent↗

PubMed2003

Medical students' perceptions of sexual health issues prior to a curriculum enhancement.

The objectives were to compare first, second and third year medical students on self-perceived sexual health knowledge, comfort in addressing sexual health problems, and attitudes towards the importance of addressing sexual health issues with patients as part of a sexual health medical curriculum enhancement project. A paper-and-pencil questionnaire survey was designed and administered to first and second year medical students at the start of the fall semester, resulting in high participation rates for both years (98% and 86%, respectively). Third year students were surveyed through an on-line version of the questionnaire yielding a lower response rate (52%). Multivariate statistical analyses were used to compare knowledge, comfort and attitudes by year in medical school. Results were as follows: As might be expected, sexual health knowledge and comfort in addressing sexual health problems increased linearly from first to third year (P<0.01) for all questions. Unexpectedly, second year students had significantly higher scores on questions assessing attitudes towards the importance of addressing sexual health issues than either first or third year students (P<0.001). Female medical students reported that addressing sexual health issues with patients was significantly more important than did male medical students; however, male students reported higher levels of self-reported knowledge and comforting related to sexual health issues than did female students in a number of areas. In conclusion, knowledge gained from this survey was used to finalize the design of an enhanced, integrated curriculum on sexual health for medical students. Further investigation of gender differences related to training medical students in this area is suggested.

Attitude of Health Personnel↗

PubMed2003

Neurobehavioral and autonomic effects of hammock positioning in infants with very low birth weight.

PURPOSE: This study was designed to determine whether supine positioning of infants born preterm in a hammock instead of the prone position affects their neuromuscular maturity, growth, and autonomic stability. METHODS: Twenty healthy infants who were born premature with very low birth weight (VLBW) (<1500 g) were randomized into two groups. Subjects were pair-matched for weight (difference less than 100 g), gestational age (difference less than eight days), and postnatal age (difference less than eight days). Ten infants were placed supine in a hammock for three hours daily for ten consecutive days, and ten infants were maintained nested in the prone position. Neuromuscular maturity (based on three neurological parameters adopted from the Ballard examination), heart rate, respiratory rate, and weight gain (g/cal) were compared between the groups. RESULTS: Compared with nested prone positioning, supine positioning in a hammock was associated with a higher neuromuscular maturity score (p < 0.003) and a more relaxed condition, as expressed by lower heart rate and respiratory rate (p < 0.05 and p < 0.01, respectively). CONCLUSIONS: Maintaining infants who were born preterm with VLBW in the supine position in a hammock may positively affect their autonomic stability and neuromuscular maturity.

Journal Article↗

PubMed2002

Pelvic haemophilic pseudotumour: management of a patient with high level of inhibitors.

Haemophilic pseudotumour (HP) is a rare but very serious complication of haemophilia. HP affects mainly patients with severe haemophilia and those who have developed antibodies to factor VIII or factor IX. We report on a 45-year-old man with haemophilia A and high titres of inhibitors who developed an extensive HP with progressive destruction of the right ilium over a period of 12 years. The different therapeutic options (conservative management by replacement therapy, surgical approach, radiotherapy, percutaneous evacuation with secondary refilled cavity and transcatheter arterial embolization) are reviewed.

Bone Diseases↗

PubMed2002

Kindling-induced overexpression of Homer 1A and its functional implications for epileptogenesis.

Despite an extensive research on the molecular basis of epilepsy, the essential players in the epileptogenic process leading to epilepsy are not known. Gene expression analysis is one strategy to enhance our understanding of the genes contributing to the functional neuronal changes underlying epileptogenesis. In the present study, we used the novel MPSS (massively parallel signature sequencing) method for analysis of gene expression in the rat kindling model of temporal lobe epilepsy. Kindling by repeated electrical stimulation of the amygdala resulted in the differential expression of 264 genes in the hippocampus compared to sham controls. The most strongly induced gene was Homer 1A, an immediate early gene involved in the modulation of glutamate receptor function. The overexpression of Homer 1A in the hippocampus of kindled rats was confirmed by RT-PCR. In order to evaluate the functional implications of Homer 1A overexpression for kindling, we used transgenic mice that permanently overexpress Homer 1A. Immunohistochemical characterization of these mice showed a marked Homer 1A overexpression in glutamatergic neurons of the hippocampus. Kindling of Homer 1A overexpressing mice resulted in a retardation of seizure generalization compared to wild-type controls. The data demonstrate that kindling-induced epileptogenesis leads to a striking overexpression of Homer 1A in the hippocampus, which may represent an intrinsic antiepileptogenic and anticonvulsant mechanism in the course of epileptogenesis that counteracts progression of the disease.

Animals↗

PubMed2002

Short-term growth response to GH treatment and considerations upon the limits of short-term growth predictions.

OBJECTIVES: To investigate the impact of short-term growth measurements on predicting the individual growth response to GH treatment, and to elucidate the possible reasons for the limited accuracy of current growth prediction models for GH-treated children. METHODS: Short-term growth measurements by knemometry and stadiometer in 99 short, GH-treated children (27 girls, 72 boys), aged 10.3 +/- 2.3 years, from the Children's University Hospital, Leipzig, Germany. RESULTS: GH treatment significantly accelerated the mean height velocity (HV) from 4.3 +/- 1.0 to 8.1 +/- 1.8 cm/year during the first year of treatment, the average height standard deviation score (SDS) shifted by +0.52 SD. The variation in HV also increased, from S(2) = 1.0 before to S(2) = 3.4 cm(2)/year(2) during treatment. Lower leg length (LLL) velocity accelerated from 1.6 +/- 0.7 before treatment to 3.4 +/- 1.0 cm/year during the first 8 weeks of treatment. Four coefficients of correlation appeared clinically meaningful: (1) LLL velocity vs. body HV during the first year of GH treatment (r = 0.87), indicating that GH acts simultaneously on leg and rump growth; (2) early (first 8 weeks) LLL velocity vs. 1-year body HV during treatment, with r = 0.61 (R(2) = 0.38), indicating that 38% of the variation in HV during the first year of treatment is already predictable by an initial 8-week period of knemometry; (3) early (first 8 weeks) LLL velocity vs. 1-year LLL velocity during treatment, with r = 0.63 (R(2) = 0.39), and (4) early (first 8 weeks) LLL velocity vs. later LLL velocity, up to the end of the first year, with r = 0.53 (R(2) = 0.28) indicating that the early response on lower leg growth persists for at least 1 year of GH treatment. CONCLUSIONS: (1) Thirty-eight percent of the variation in HV during the first year of GH treatment is predictable by an initial 8-week period of knemometry. This parallels early changes in biochemical markers of bone turnover after GH treatment. (2) There is evidence for a baseline variability in HV both in healthy children and in children with growth disorders that make growth prediction difficult.

Anthropometry↗

PubMed2001

A central neural circuit for experience-independent olfactory and courtship behavior in Drosophila melanogaster.

We have studied the function of the major central olfactory pathway in fruit flies. Key elements of this pathway, the projection neurons (PNs), connect the antennal lobes with the lateral protocerebrum both directly and indirectly, the latter via the mushroom bodies (MBs). Transgenic expression of tetanus toxin in the majority of PNs and few MB neurons leads to defects in odor detection and male courtship. Considering behavioral data from flies lacking MBs, our results argue that the direct PN-to-lateral protocerebrum pathway is necessary and sufficient to process these experience-independent behaviors. Moreover, the involvement of an olfactory pathway in male courtship suggests a role of volatile attractive female pheromones in Drosophila.

Animals↗

PubMed2001

Ephaptic interactions in the mammalian olfactory system.

Ephaptic coupling refers to interactions between neurons mediated by current flow through the extracellular space. Ephaptic interactions between axons are considered negligible, because of the relatively large extracellular space and the layers of myelin that separate most axons. By contrast, olfactory nerve axons are unmyelinated and arranged in tightly packed bundles, features that may enhance ephaptic coupling. We tested the hypothesis that ephaptic interactions occur in the mammalian olfactory nerve with the use of a computational approach. Numerical solutions of models of axon fascicles show that significant ephaptic interactions occur for a range of physiologically relevant parameters. An action potential in a single axon can evoke action potentials in all other axons in the fascicle. Ephaptic interactions can also lead to synchronized firing of independently stimulated axons. Our findings suggest that ephaptic interactions may be significant determinants of the olfactory code and that such interactions may occur in other, similarly organized axonal or dendritic bundles.

Action Potentials↗

PubMed2001

Low-dose theophylline reduces eosinophilic inflammation but not exhaled nitric oxide in mild asthma.

Theophylline is well-established in the management of asthma, and there is some evidence of an antiinflammatory effect in asthma. It is not known whether theophylline affects inflammatory markers such as sputum eosinophils and exhaled nitric oxide (NO) in patients with mild asthma not receiving inhaled steroid therapy. In a double-blind, placebo-controlled, cross-over study of 15 patients with mild asthma, we assessed the effect of low-dose theophylline therapy (250 mg twice per day) on eosinophils in induced sputum, bronchoalveolar lavage (BAL) and airway biopsies at the end of both the treatment and placebo periods. Measurements of exhaled nitric oxide (NO) were made at the end of the active and placebo treatment periods of 5 wk each. Low-dose theophylline (mean serum level, 6.1 mg/L) led to a significant reduction in mean (95% confidence interval [CI]) sputum eosinophils from 11.3% (7.80-14.76%) to 8.0% (5.46-10.44%), BAL eosinophils from 3.4% (2.4-4.4%) to 1.7% (1.1-2.3%) and biopsy eosinophils from 1.83% (0.76-2.89%) to 1.20% (0.27-2.13%) compared with placebo (all p < 0.05). There was no significant change in levels of exhaled NO or improvement in lung function and bronchial responsiveness. Low-dose theophylline induced antiinflammatory effects in asthma, reflected by a fall in airway eosinophils with no change in exhaled NO or changes in lung function.

Adult↗