Use of the Microdialysis Technique in the Monitoring of Subcutaneous Tissue Glucose Concentration

For some time the subcutaneous (s.c.) tissue has been the target for continuous glucose measurement. The microdialysis technique permits an extracellular region approach, which has been used for about two decades for measuring various metabolites in dialysates obtained from different body regions. By connecting a s.c. implanted microdialysis probe to a flow chamber of an amperometric glucose sensor, the procedure of glucose sensing was transferred to ex vivo. Using this device it was possible to obtain, for up to 24 hours, s.c. tissue glucose profiles of healthy and diabetic people. The microdialysis theory, the calibration process and other microdialysis technique applications are discussed in this paper. Although the combination of the microdialysis technique and amperometric glucose sensing requires certain technical equipment, the combination of microdialysis and glucose sensor seems to be a promising approach to a continuously functioning glucose sensing system.

First use of flat-panel computed tomography during cochlear implant surgery : Perspectives for the use of advanced therapies in cochlear implantation

BACKGROUND

Cochlear implantation in routine cases with normal anatomy is commonly performed without intraoperative image guidance. Revision cochlear implantation as well as surgery in malformations require not only a precise understanding of the underlying complex anatomy, but surgeons need to transform two-dimensional computed tomography (2D CT) scans into the surgical field and use this information for intraoperative surgical navigation. So far, information about the exact position of the electrode during insertion cannot be provided to the surgeon. Here, we present our first operative experience with cochlear implant surgery supported by intraoperative Dyna-CT technology, providing the surgeon with detailed views of the electrode location.

METHODS

To prove the feasibility of the procedure, two cases of cochlear implantation were performed with intraoperative application of cone-beam CT acquired by a C-arm Dyna-CT system (Artis Zeego, Siemens Healthcare, Erlangen, Germany). Image reconstruction was performed intraoperatively in order to assess the correct positioning of the electrodes.

RESULTS

Intraoperative Dyna-CT enabled clear visualization of the surgical anatomy and intracochlear electrode position. Dyna-CT technology can be applied with acceptable additional time requirements without adding too much complexity to the surgical procedure.

CONCLUSION

Intraoperative data acquisition by Dyna-CT represents a suitable option for online surgical navigation during cochlear implant surgery. This imaging technology will push further advances in cochlear implant surgery and lateral skull base surgery, particularly if linked to intraoperative navigation.

Zoomed EPI DWI of Acute Spinal Ischemia Using a Parallel Transmission System

PURPOSE

A new method for diffusion-weighted imaging (DWI) using independent parallel transmission technique resulting in zoomed DWI was applied in four patients suffering from acute spinal cord ischemia.

METHODS

Four patients with clinical symptoms of acute spinal cord ischemia were examined on a 3 T MR-system equipped with a two-channel transmit array. Scans included T2-weighted turbo spin echo, conventional DWI, and zoomed DWI. Image evaluation was performed with regard to overall image quality, anatomic delineation of the spinal cord, and the level of confidence to establish the diagnosis of spinal cord ischemia.

RESULTS

Through spatially selective excitation, zoomed DWI allows for acquisition of high-resolution images with reduced scan time due to a reduced field of view in phase-encoding direction, resulting in zoomed images. In all cases the ischemia was demonstrated in conventional DWI as well as zoomed DWI.

CONCLUSIONS

Compared to conventional DWI, zoomed DWI enables a faster image acquisition and allowed a more detailed analysis of the spinal lesion which may be critical to attribute the lesion to a particular vessel territory.

Feasibility of Noninvasive Diagnosis and Treatment Planning in a Case Series with Carotid-Cavernous Fistula using High-Resolution Time-Resolved MR-Angiography with Stochastic Trajectories (TWIST) and Extended Parallel Acquisition Technique (ePAT 6) at 3 T

PURPOSE

The evaluation of carotid-cavernous fistulas (CCFs) and the intracranial vasculature has been predominantly carried out using conventional digital subtraction angiography (DSA). Recent developments in time-resolved magnetic resonance angiography (MRA) provide the opportunity to assess both multiple arterial and venous phases with high temporal and spatial resolution. Here, we investigated the feasibility of this technique to functionally assess CCF prior to intervention.

METHODS

Six consecutive patients with clinical symptoms of a CCF were scheduled for clinically indicated MRA and underwent a protocol that comprised conventional imaging sequences and high resolution time-resolved MRA with interleaved stochastic trajectories (TWIST). The location of the fistulous communication, the flow pattern, and venous drainage were determined by time-resolved MRA and compared with DSA which was available in five out of six patients.

RESULTS

Typical morphological findings (including enlargement of the superior ophthalmic vein, exophthalmos) were found in all cases in both conventional MRI and time-resolved MRA source data. The temporal resolution of time-resolved MRA enabled a good separation of the early filling of the cavernous sinus during the arterial phase. Direct fistulous communication was assessed in three patients with good correlation to DSA, whereas indirect CCF could not definitely be visualized. The time-resolved MRA provided information about the flow pattern and the venous drainage of the fistula in all patients, which is essential for therapy planning.

CONCLUSION

Time-resolved MRA provides important morphological and functional information in patients with CCF. Although DSA remains the gold standard for diagnosis and exact classification of fistulas, time-resolved MRA can provide the relevant hemodynamic information to plan interventional treatment as a one-step procedure with a focused diagnostic workup.

[Total hip arthroplasty with shortening subtrochanteric osteotomy and custom-made prosthesis in Crowe type IV developmental dysplasia]

AIM

Total hip arthroplasty in patients with a Crowe type IV developmental dysplasia is a technically demanding procedure with a higher complication rate compared to a standard total hip replacement. Specific anatomic features and the necessity of a femoral shortening osteotomy are the reasons for more complications. In this retrospective study we intended to find out whether the use of a custom-made stem based on a CT scan will lead to a better outcome including a lower complication rate. MATERIAL UND METHOD: From 2003 to 2010 we implanted a cementless CTX® individual stem in combination with a subtrochanteric Z-shaped shortening osteotomy in 25 patients with a high hip dislocation, four of them were men (one bilateral) and 16 women (four bilateral). Mean age of the patients was 44.6 years. In all cases the cup was implanted at the level of the anatomic hip centre. Patients were followed with a clinical and radiographic assessment. The morphology of the femur was analysed by CT scans.

RESULTS

The average amount of femoral shortening was 3.4 cm (max. 4.2/min. 2.6 cm). Lengthening of the leg was achieved with an average of 3.8 cm (max. 4.4/min. 3.2 cm). The remaining leg length discrepancy was 0.8 cm (max. 1.2/min. 0.4 cm). In none of the cases did an intraoperative fracture of the femur occur, either in the proximal or in the distal part of the femur. Enlargement of the intramedullary canal was not necessary in any case. The planned depth of the prosthesis could be achieved in all patients. We did not observe any problems with wound healing in our patients. The average Harris hip score was 90 (83 up to 100). Additional cerclage wires are not necessary with this technique when the osteotomy is well adapted. After complete healing the osteotomy can just be noticed by a certain hypertrophy of the cortical bone. In our cases we had a complication rate of 16 %, significantly lower in comparison to literature values.

CONCLUSIONS

Total hip arthroplasty in type IV developmental dysplasia with a custom-made stem based on a CT scan is a procedure that respects the special anatomic features preoperatively und is able to correct the deformity with the individually manufactured prosthesis. High femoral anteversion is corrected at the level of the neck of the stem. There is no necessity for a derotation at the level of the osteotomy. The osteotomy is stabilised by the Z-shape and through a perfect intramedullary fit of the stem. The anatomic shape of the subtrochanteric region is perfectly suitable to perform a femoral shortening.

Pilot-scale anaerobic submerged membrane bioreactor (AnSMBR) treating municipal wastewater: the fouling phenomenon and long-term operation

An anaerobic submerged membrane bioreactor (AnSMBR) on pilot-scale treating a mixture composed of municipal wastewater and glucose under mesophilic temperature conditions was operated for 206 days. The performance of the AnSMBR was evaluated at different fluxes, biomass concentrations and gas sparging velocities (GSV). GSV was used to control fouling. In addition, the AnSMBR was operated in cycles that included relaxation and backwashing phases. The increase in the transmembrane pressure (fouling rate) was measured under different operational conditions and was used to evaluate the stability of the process. The fouling rate could be controlled for a long period of time at a flux of 7 l m(-2) h(-1) with a GSV of 62 m/h and an average biomass concentration of 14.8 g TSS/L. The membrane was physically cleaned after 156 days of operation. The cleaning efficiency was almost 100% indicating that no irreversible fouling was developed inside the pores of the membrane. The COD removal efficiency was close to 90%. As in anaerobic processes, nutrients were not exposed to degradation and almost no pathogens were found in the effluent, hence the effluent could be used for irrigation in agriculture.

[Electromagnetic fields of mobile telephone systems--thresholds, effects and risks for cochlear implant patients and healthy people]

Every day life is detectably affected by manifold natural sources of electromagnetic fields (EMF), e. g. infrared radiation, light and the terrestrial magnetic field. However, there is still uncertainty about the consequences or hazards of artificial EMF, which emerge from mobile phone or wireless network (wireless local area network [WLAN]) services, for instance. Following recommendations of the International Commission on Non-Ionizing Radiation Protection (ICNIRP) the German Commission on Radiation Protection (SSK) defined corresponding thresholds for high frequency electromagnetic fields (HF-EMF) in 2003. By observing those thresholds HF-EMF is thought to be innocent so far. However, there is still controversial discussion about induction of cancer or neurovegetative symptoms due to inconsistent study results. Patients with cochlea implants are of particular interest within the speciality of otorhinolaryngology due to specific hazards, which arise during mobile telephone use from the distance between brain and inductive metal implants (electrode) on the one hand and the electronic system of the cochlear implant and the source of HF-EMF on the other hand. Besides many studies about the impact of HF-EMF on common welfare, there are only very few surveys (n = 6) covering the effects on patients with cochlear implants. The purpose of this paper is to overview sources, thresholds and subsequently harmful or harmless effects of HFEMF. Due to the current state of knowledge about the impact of mobile phone use on health, we assume, that HF-EMF are harmless both for healthy people and patients with cochlea implants, provided that legal thresholds are observed.

Thermophilic anaerobic digestion in compact systems: investigations by modern microbiological techniques and mathematical simulation

Thermophilic anaerobic digestion in compact systems can be an economical and ecological reasonable decentralised process technique, especially for rural areas. Thermophilic process conditions are important for a sufficient removal of pathogens. The high energy demand, however, can make such systems unfavourable in terms of energy costs. This is the case when low concentrated wastewater is treated or the system is operated at low ambient temperatures. In this paper we present experimental results of a compact thermophilic anaerobic system obtained with fluorescent in situ hybridisation (FISH) analysis and mathematical simulation. The system was operated with faecal sludge for a period of 135 days and with a model substrate consisting of forage and cellulose for a period of 60 days. The change in the microbial community due to the two different substrates treated could be well observed by the FISH analysis. The Anaerobic Digestion Model no. 1 (ADM1) was used to evaluate system performance at different temperature conditions. The model was extended to contribute to decreased methanogenic activity at lower temperatures and was used to calculate energy production. A model was developed to calculate the major parts of energy consumed by the digester itself at different temperature conditions. It was demonstrated by the simulation study that a reduction of the process temperature can lead to higher net energy yield. The simulation study additionally showed that the effect of temperature on the energy yield is higher when a substrate is treated with high protein content.

Development of an empirical mathematical model for describing and optimizing the hygiene potential of a thermophilic anaerobic bioreactor treating faeces

Poor sanitation and insufficient disposal of sewage and faeces are primarily responsible for water associated health problems in developing countries. Domestic sewage and faeces are prevalently discharged into surface waters which are used by the inhabitants as a source for drinking water. This paper presents a decentralized anaerobic process technique for handling of such domestic organic waste. Such an efficient and compact system for treating faeces and food waste may be of great benefit for developing countries. Besides a stable biogas production for energy generation, the reduction of bacterial pathogens is of particular importance. In our research we investigated the removal capacity of the reactor concerning pathogens, which has been operated under thermophilic conditions. Faecal coliforms and intestinal enterococci have been detected as indicator organisms for bacterial pathogens. By the multiple regression analysis technique an empirical mathematical model has been developed. The model shows a high correlation between removal efficiency and both, hydraulic retention time (HRT) and temperature. By this model an optimized HRT for defined bacterial pathogens effluent standards can be easily calculated. Thus, hygiene potential can be evaluated along with economic aspects. In this paper not only results for describing the hygiene potential of a thermophilic anaerobic bioreactor are presented, but also an exemplary method to draw the right conclusions out of biological tests with the aid of mathematical tools.

Pathological long-bone fractures in residents with cerebral palsy in a long-term care facility in South Africa

A high incidence of long-bone fractures has been observed in children and young adults with quadriplegic cerebral palsy in residential care. This study aimed to determine factors that contribute to these fractures and to institute preventive treatment. Twenty individuals (12 males, eight females) of a cohort of 88 residents with spastic quadriplegia in residential care in Gauteng, South Africa who had sustained fractures were compared with a random sample of age-matched control participants (10 males, 10 females) from the same facility. Participants ranged in age from 6 to 29 years (median 17.5 years). The majority of fractures were in the upper extremities. There was radiological and biochemical evidence of rickets and osteomalacia in both groups. However, the severity of the disease was more pronounced in the group with fractures. There was a significant relation (p=0.002) between the number of fractures and the use of anticonvulsant therapy (ACT). Three months of vitamin D administration (calciferol 5000 iu/day) resulted in a marked clinical improvement. There were no fractures during this period in either group. In addition, the mean serum calcium (Ca) and phosphate (Pi) levels increased (Ca from 2.17 to 2.35 mmol/L and Pi from 1.13 to 1.66 mmol/L) and mean total alkaline phosphatase level decreased (from 1123 to 423 U/L). We concluded that vitamin D deficiency was the major factor contributing to the occurrence of fractures in this population. Unless sunlight exposure can be guaranteed, vitamin D supplementation should be considered for children and adults in residential care, especially if they are on ACT, even in areas with year-round sunshine.

Specific treatment of autoimmunity with recombinant invariant chains in which CLIP is replaced by self-epitopes

The invariant chain (Ii) binds to newly synthesized MHC class II molecules with the CLIP region of Ii occupying the peptide-binding groove. Here we demonstrate that recombinant Ii proteins with the CLIP region replaced by antigenic self-epitopes are highly efficient in activating and silencing specific T cells in vitro and in vivo. The Ii proteins require endogenous processing by antigen-presenting cells for efficient T cell activation. An Ii protein encompassing the epitope myelin basic protein amino acids 84-96 (Ii-MBP84-96) induced the model autoimmune disease experimental allergic encephalomyelitis (EAE) with a higher severity and earlier onset than the peptide. When applied in a tolerogenic manner, Ii-MBP84-96 abolished antigen-specific T cell proliferation and suppressed peptide-induced EAE more effectively than peptide alone. Importantly, i.v. administration of Ii proteins after EAE induction completely abrogated the disease, whereas peptides only marginally suppressed disease symptoms. Ii fusion proteins are thus more efficient than peptide in modulating CD4(+) T cell-mediated autoimmunity, documenting their superior qualities for therapeutic antigen delivery in vivo.

Aerobic thermophilic treatment of sewage sludge contaminated with 4-nonylphenol

4-Nonylphenol (4-NP) occurs in sewage sludge as a result of the breakdown of detergents which contains nonylphenol ethoxylates (NPEs). 4-NP is of environmental concern because of its toxicity to biological systems. The present paper reports results of aerobic treatment under thermophilic conditions of sewage sludge artificially contaminated with 4-NP. Experiments were carried out using three parallel laboratory-scale batch reactors operating with blank, 50 and 100 mg/l of 4-NP concentration. For the two studied concentrations up to 66% 4-NP reduction was achieved at a specific air flow rate of 16 l/(l.h) and a thermophilic temperature of 60 degrees C, within 10 days of operation. The presence of 4-NP has minor effect on the rate of sludge oxidation and the nitrogen and phosphorous content in the sludge.

[Individual cement-free total hip endoprosthesis in a patient with a rare form of dwarfism (Fuhrmann syndrome)]

We present a single case study of a 47-year-old female patient with a rare form of primary dysostotic dwarfism. This syndrome was first described by Fuhrmann in 1972. Seven years ago, this patient underwent bilateral cementless total hip arthroplasties for severe osteoarthritis about her hips. Custom-made components were used. While achondroplastic patients present with wide femoral medullary canals, it is clinically relevant that Fuhrmann Syndrome features narrow femoral medullary canals. This complicating anatomical factor in Fuhrmann syndrome as well as the increased anteversion angles were overcome by the use of CAD stems. We conclude that the custom-made stems, although in our case measuring half the size of the smallest commercially available design, have proved to be durable and able to withstand physiological loads at follow-up period of 72 months.

Arthroscopic labrum refixation for post-traumatic anterior shoulder instability: suture anchor versus transglenoid fixation technique

SUMMARY

The aim of this retrospective study was to compare recurrence rates following transglenoid labrum refixation or fixation using the suture anchor (FASTak, Arthrex, Naples, FL) technique. Additionally, parameters that apparently influence the rate of redislocation were investigated. There were 163 patients with post-traumatic anterior shoulder instability treated with an arthroscopic labrum refixation; 108 patients (66.3%) were stabilized with the transglenoid suture technique (group I) and 55 patients (33. 7%) with the suture anchor (FASTak) technique (group II). The average follow-up was 4.5 years (range, 2.0 to 7.9 years) in group I and 3.2 years (range, 2.0 to 5.0 years) in group II. The Rowe score increased from a preoperative average of 35.0 points in group I and 35.4 points in group II to a postoperative average of 68.3 points in group I and 84.6 points in group II (P <.01). There was recurrence in 35 patients (32.4%) in group I and 9 patients (16.4%) in group II (P <.05). All incidents of redislocation occurred during the first 21 postoperative months; 58.4% of the patients (n = 63) in group I and 16.4% of the patients in group II (n = 9) had to reduce their sporting activity (P <.001). Independent of the type of surgery, there was a significant correlation of the postoperative rate of redislocation and age (P <.001), number of preoperative dislocations (P <.01), and degree of labrum lesion (P <.001). No correlation with the rate of redislocation was shown for gender, handedness, dislocation-operation interval, degree of Hill-Sachs lesion, or number of transglenoid sutures or anchors. Concerning post-traumatic anterior shoulder instability, the arthroscopic labrum reconstruction with the suture anchor (FASTak) technique was superior to the transglenoid technique but has not yet achieved the level of success obtained by open surgery. With fewer than 5 preoperative redislocations after a first traumatic shoulder dislocation, the arthroscopic treatment is recommended. In cases of more frequent preoperative dislocations, open surgery in combination with a capsular shift should be performed.

Thermal hydrolysis (TDH) as a pretreatment method for the digestion of organic waste

The recycling concept under consideration is based on the process of Thermal Hydrolysis (TDH) followed by an anaerobic digestion. By increasing pressure and temperature the organic part of the waste is split up in a first step into short-chain fragments that are biologically well suited for microorganisms. The following fermentation runs much faster and more complete than in conventional digestion processes and the biogas yield is increased. Left is just a small amount of a solid residue that can be easily dewatered and utilized as surrogate fuel for incineration or as compost additive. The thermal hydrolysis process allows a complete energy recovery from organic waste. During the total procedure more energy sources are produced than are needed for running the plant. The procedure is especially suited for wet organic waste and biosolids that are difficult to compost, such as food scraps, biological waste from compact residential areas and sewage sludge. As a complete disinfection is granted due to the process temperatures the procedure is also suited for carcasses.

Experimental assessment of bio-reduction of di-2-thylhexyl phthalate (DEHP) under aerobic thermophilic conditions

The reduction of organic contaminants in sewage sludge is of great importance for a further sludge disposal or agricultural utilization. Laboratory scale batch experiments were performed to assess the potential use of the aerobic thermophilic treatment technique to reduce the concentration of difficult to degrade organic chemicals. Di-2-ethylhexyl phthalate (DEHP) was chosen as a model representative of these chemicals. The effect of the sludge temperature and aeration rate on the reduction of DEHP concentration as well as on the reduction of the organic dry solid (oDS) was investigated. With a specific air flow rate of 16 m3/m3.h and a thermophilic temperature of 63 degrees C it was possible to achieve up to 70% reduction of the DEHP concentration and 61% of oDS within 96 hours. The maximum degradation of the oDS matter occurred within the first 24 hours of operation whereby only little oDS was degraded afterward. During the experiments the reactor content was routinely monitored for pH, COD, along with the ammonia nitrogen and orthophosphate concentrations.

Cerebral vein thrombosis in a case with thromboangiitis obliterans

Thromboangiitis obliterans is a chronic inflammatory vessel disease that involves predominantly the small and medium-sized arteries and veins of the distal extremities. Appearance and cessation of symptoms are closely related to patterns of tobacco consumption. That cerebral arteries can also be involved is shown by reports of rare cases in which cerebral artery occlusion led to infarction. We report on a 28-year-old man with thromboangiitis obliterans who developed extensive cerebral vein thrombosis after a single episode of cigarette smoking following several years of nonsmoking. Despite extensive evaluation, no other known cause or predisposition of cerebral vein thrombosis could be found. This case suggests that cerebral veins can be involved in thromboangiitis obliterans and patients with thromboangiitis obliterans might be at risk for cerebral vein thrombosis.

Persistent cerebellar deterioration in a patient with lobar pneumonia under lithium, carbamazepine, and trifluperidol treatment

We report on a patient with schizoaffective disorder who was on combination therapy of lithium, carbamazepine, and the neuroleptic trifluperidol. He experienced a lobar pneumonia and developed an acute and persistent cerebellar deterioration which was most likely due to lithium toxicity, while the serum lithium level was within the therapeutic range. The combination of lithium, carbamazepine, and neuroleptics is common, and is generally considered to be safe. The reported case suggests that this regimen might increase the risk of intoxication with potentially disabling side-effects.

[Arthroscopic labral reconstruction for anterior shoulder instability. Failure analysis in 187 patients]

Comparing open with arthroscopic labral reconstruction for anterior shoulder instability we found a higher recurrence rate after arthroscopic capsulolabral repair. The aim of this study was, to analyse the reasons for recurrent instability after arthroscopic labral repair.

MATERIALS AND METHODS

Between 1989 and 1995 we performed a arthroscopic labral reconstruction on 187 patients with anterior shoulder instability. 118 patients (63%) were treated with a transglenoid suture technique and 69 patient (37%) with a suture anchor technique. The average age at the time of the operation was 26.4 +/- 6.3 years (14-52 years). There were 41 women (21.9%) and 146 men (78.1%).

RESULTS

The minimum follow-up was 18 months. The average follow-up was 3.7 +/- 1.1 years. The average Rowe Score increased from 34.7 points (0-75) preoperatively to 75.3 points (15-100) postoperatively. There were 47 (25.1%) excellent. 76 (40.6%) good, 21 (11.3%) fair, and 43 (23.0%) poor results. 105 patients (56.1%) regained their preoperative level of activity. 50 patients (26.7%) had recurrent subluxations or dislocations postoperatively. All failures occurred within two years (0.5-21 months) after the operation. Failure rates were associated with the patients age (p < 0.001), the level of activity (p < 0.05), the number of the preoperative dislocations (p < 0.01), the degree of the labral lesion (p < 0.001), and the operation method (p < 0.05). No correlation was found for the parameters sex, handiness, time between luxation and operation, size of Hill-Sachs-lesion and numbers of used sutures or anchors.

CONCLUSION

We prefer the arthroscopic suture anchor technique if there are less than 5 preoperative dislocation and a type 1 or 2 labral lesion. If there are more than 5 preoperative dislocations and a degenerative labrum defect we favor the open Bankart repair technique.

Glucocorticoids inhibit CD40 ligand expression of peripheral CD4+ lymphocytes

The ligand for CD40 (CD40L) is a type II transmembrane glycoprotein that belongs to the tumor necrosis factor superfamily. CD40L expression on peripheral CD4+ cells is increased upon activation and delivers signals to B lymphocytes which constitutively express CD40. We show that dexamethasone in vitro inhibits CD40L expression in a dose-dependent manner in concentrations ranging from 0.1 to 1 mg/mL. Semiquantitative analysis of CD40L mRNA by RT-PCR revealed that this effect was due to inhibition of CD40L transcription. The inhibitory effect of dexamethasone on CD40L expression was reversible and not due to affection of cell viability. Lymphocytes which have been exposed to dexamethasone in vitro retained the ability to express CD40L after incubation in medium alone for 48 h. Dexamethasone also inhibited PMA/ionomycin induced IL-2 and IFN-gamma production but not CD25 and CD69 expression. Glucocorticoids may exert their immunosuppressive effect in part by suppression of CD40L. Regulation of CD40L expression is steroid sensitive and may be similar or in part identical with IL-2 and IFN-gamma regulation.

Investigations on the point mutations at nt 5460 of the mtDNA in different neurodegenerative and neuromuscular diseases

Point mutations of the mitochondrial genome are often considered to be the cause of certain neurodegenerative disorders and mitochondrial myopathies. Recently, there has been a report on Alzheimer's disease (AD) point mutations at position 5460 of the mitochondrial genome located within the ND2 gene. Using allele-specific PCR with a sensitivity of detection of less than 1% mutated mtDNA, we investigated postmortem brain samples from 48 patients with AD and blood samples of 15 patients with clinically diagnosed AD. In addition, we investigated tissue samples of patients with different neuromuscular disorders and patients with Downs syndrome. Independent of the tissue analysed very few of all the tested samples of patients showed a point mutation at nt 5460 with a base substitution from G to A. Two out of 19 brain and 48 blood samples from controls carried this mutation. The G to T transversion was not found in any of the so far tested samples. Our results do not support the previously reported significant high frequency of these mutations in AD.A polymorphism seems more likely.

Subcutaneous glucose concentration in humans. Real estimation and continuous monitoring

OBJECTIVE

To determine the real subcutaneous glucose concentration in healthy volunteers to help in the development of new calibration methods for subcutaneous glucosensors.

RESEARCH DESIGN AND METHODS

We developed a new method to estimate the real subcutaneous glucose concentration based on the recirculation of phosphate-buffered saline (PBS) in a microdialysis probe inserted into the subcutaneous tissue. Tissue glucose diffuses into the probe until complete equilibration between the glucose concentration outside and inside the microdialysis probe is achieved. Later, the glucose content of the recirculated PBS is assessed in vitro. We applied the method in 10 healthy volunteers under fasting state and during a hyperglycemic clamp. In addition, we monitored the subcutaneous glucose with an enzymatic-amperometric glucosensor combined with a microdialysis probe.

RESULTS

The subcutaneous glucose concentration measured by the recirculation method was 72 +/- 6 and 78 +/- 6% of the blood glucose measured in the fasting state and during the hyperglycemic clamps, respectively. On the other hand, the glucosensor's signal correlated significantly with the blood glucose.

CONCLUSION

The recirculation method estimated the real subcutaneous glucose concentration, opening the way to develop new calibration procedures for subcutaneous glucosensors. However, a suitable calibration procedure is still lacking.

3.1-kb deletion of mitochondrial DNA in a patient with Kearns-Sayre syndrome

Mitochondrial DNA (mtDNA) deletions have been found in the majority of patients with chronic progressive external ophthalmoplegia and Kearns-Sayre syndrome. A large number of different mtDNA deletions have been identified. They generally spare the two origins of replication and are frequently flanked by direct or indirect repeats. We have found a 3.1-kb deletion of mtDNA in a patient with Kearns-Sayre syndrome that has some unusual features. First, it encompasses nucleotides 11259 to 14368, a localization that was not described before. Second, the deletion is not flanked by direct or indirect repeats, supporting the view that homologous recombination and slip-replication do not account for all mtDNA deletions.

Quality control of intensified insulin therapy: HbA1 versus blood glucose

Since the measurement of HbA1 has become available to the diabetologists, the physicians and patients tend to rely exclusively on this parameter for the assessment of metabolic control. Therefore, in this study, 24 hour glucose profiles of 8 selected patients (4 under intensified conventional therapy, ICT, and 4 under continuous subcutaneous insulin infusion, CSII) with HbA1 values indicating good metabolic control were taken three times at four week intervals and were compared to mean blood glucose (MBG), mean average of glucose excursions (MAGE) and Schlichtkrull's M-value. MBG of the 24 profiles was 114 +/- 21 mg/dl. The patients under CSII were somewhat lower than the patients under ICT. In 16 of the 24 profiles, there was at least one period of hypoglycemia of 50 mg/dl and below. Only in one patient, M-value and MAGE showed stable metabolic control. In conclusion, hyperglycemic excursions in patients under intensified conventional therapy or treated by continuous subcutaneous insulin infusion do escape their reflection in the HbA1 values because of low blood sugar periods following hyperglycemic swings. Undoubtedly, the partial failure of ICT and CSII to prevent diabetic complications might be ascribed to the incomplete assessment of the metabolic control based on HbA1 values exclusively.

Calibration problems of subcutaneous glucosensors when applied "in-situ" in man

Continuous glucose monitoring is the conditio sine qua non to achieve total automation in glucose-controlled insulin-delivery. Several types of glucosensors have been designed according to the enzyme-amperometric method to measure the glucose in different human compartments. However, problems such as long-term stability and calibration prevent this technique being put into practice. A feasible method is needed to calibrate the glucosensor and at the same time should be accepted by the patients. To achieve calibration we determined the absolute tissue glucose, as well as the microdialysis recovery in-vivo, in healthy subjects under normal conditions and during a hyperglycaemic clamp by applying a device based on the recirculation of phosphate buffer saline in a microdialysis probe implanted in the s.c. adipose tissue. The first experiments carried out were promising and encouraging, but further investigations are still needed to favour an ideal "before implantation, all in-vitro" method to calibrate a s.c. glucosensor.

Combination of microdialysis and glucose sensor for continuous on line measurement of the subcutaneous glucose concentration: theory and practical application

The microdialysis technique can be used to get dialysates of the subcutaneous tissue, which can be continuously measured by an amperometric glucose sensor. In order to get further insight into the microdialysis procedure, we used a steady-state theory for microdialysis to predict the recovery of glucose in the dialysate and compared the results to experimental data obtained by a combination of the microdialysis technique with continuous amperometric glucose sensing. The recovery of glucose obtained in vitro for two different microdialysis probes was close to the theoretical predictions. When quantifying the predictions of the model with regard to the spatial concentration profile in the subcutaneous tissue, it appeared, that the presence of the microdialysis probe depressed the concentration of glucose for 0.2 mm from the probe surface. In a 24 hour in vivo experiment, there were less fluctuations in the sensor signal when the patient was lying in bed compared to the time, when the patient could move freely. In conclusion, the combination of microdialysis and glucose sensor seems to be a promising approach to a continuously functioning glucose sensing system. However, the microdialysis procedure itself disturbs the surrounding of the probe leading to a concentration gradient of glucose. This might explain some differences between the course of blood glucose and the course of subcutaneous glucose, measured by the combination of microdialysis and an amperometric glucose sensor. Further developments of such systems should aim at implanting microdialysis devices which have a minimal influence upon the tissue metabolism.

Long-term experiences with a computerized diabetes management and glucose monitoring system in insulin-dependent diabetic patients

Only a minority of patients use diabetes management systems. In our study, 24 patients were given a memory based blood glucometer (ROMEO, Diva Medical Systems), which additionally allowed the input of insulin doses, food intake and exercise for up to four years. Eight patients returned ROMEO within one month (group I), 8 used the system as long it was available as a loan (group II) and 8 patients bought the system (group III). The patients of group III had a significantly better diabetic control (HbA1 = 7.8% +/- 0.7 (S.D.) vs. 11.7 +/- 3.6 (group I) and 10.7 +/- 2.6 (group II)) and were more reliable in their input of the data. After 3 years, however, only five patients of group III continued to use the system, but as a glucose meter only. One patient used the options of the system. These data show that glycemic control is not a question of the equipment. After a certain period, even the well-motivated patients do not use the system options routinely. Obviously, the advantages of the system are only used by a minority of patients characterized by good metabolic control and good compliance, and even these patients do not persistingly use all the options of the system after a certain period of time.

Multiple symmetric lipomatosis: abnormalities in complex IV and multiple deletions in mitochondrial DNA

Multiple symmetric lipomatosis (MSL) is a rare disorder of middle life characterized by large nonencapsulated lipomas distributed around the neck, shoulders, and other axial regions. Neurologic involvement, particularly peripheral neuropathy, is frequent. The pathogenesis of the syndrome is still unknown, but ragged-red fibers are occasionally present in muscle of affected patients, suggesting a mitochondrial abnormality. We studied 11 unrelated patients with MSL by means of neurophysiology, muscle morphology, muscle biochemistry, Southern blot, and PCR analysis of mitochondrial DNA. All patients were men aged 41 to 63 years. Clinical or electrophysiologic signs of a sensorimotor polyneuropathy were present in nine patients, eight of whom had a history of alcoholism. In muscle biopsy specimens, the most prominent feature was pathologic subsarcolemmal aggregates of mitochondria. Biochemical analysis of respiratory chain enzymes revealed a moderate but significant decrease of cytochrome c oxidase activity as compared with age-matched controls. In one patient, Southern blot analysis showed multiple deletions of mitochondrial DNA. We conclude that mitochondrial dysfunction is common in MSL and may be based on identifiable defects in the mitochondrial genome.

Unaltered respiratory chain enzyme activity and mitochondrial DNA in skeletal muscle from patients with idiopathic Parkinson's syndrome

There is good evidence that patients with Parkinson's disease have respiratory chain dysfunction in their substantia nigra. Since mitochondrial cytopathies due to enzyme defects in the respiratory chain are predominantly manifested in tissues with a high oxidative metabolism we analyzed oxidative energy metabolism in skeletal muscle from 6 patients with Parkinson's disease. Control muscles were from subjects of the same age group. Histological and histochemical analyses showed no morphological abnormalities found in mitochondrial myopathies. Biochemical analyses of the various complexes of the respiratory chain were normal. Since 13 subunits of complexes I, III, IV and V of the respiratory chain are encoded by the mitochondrial genome we performed Southern blot and PCR analyses in skeletal muscle from patients and controls and found no disease-specific increase in deletions or insertions of the mitochondrial genome. Therefore, we do not think that skeletal muscle reflects the mitochondrial disturbance in Parkinson's disease found in the substantia nigra.

Use of the microdialysis technique in the monitoring of subcutaneous tissue glucose concentration

For some time the subcutaneous (s.c.) tissue has been the target for continuous glucose measurement. The microdialysis technique permits an extracellular region approach, which has been used for about two decades for measuring various metabolites in dialysates obtained from different body regions. By connecting a s.c. implanted microdialysis probe to a flow chamber of an amperometric glucose sensor, the procedure of glucose sensing was transferred to ex vivo. Using this device it was possible to obtain, for up to 24 hours, s.c. tissue glucose profiles of healthy and diabetic people. The microdialysis theory, the calibration process and other microdialysis technique applications are discussed in this paper. Although the combination of the microdialysis technique and amperometric glucose sensing requires certain technical equipment, the combination of microdialysis and glucose sensor seems to be a promising approach to a continuously functioning glucose sensing system.

On line continuous monitoring of subcutaneous tissue glucose is feasible by combining portable glucosensor with microdialysis

A new method for continuous measurement of subcutaneous tissue glucose content is introduced: by combining the microdialysis technique with a wearable amperometric glucose sensor, a device for continuous glucose measurement in the subcutaneous tissue was obtained. This device was applied to healthy volunteers (n = 10) over the period of an oral glucose load and to type I diabetic patients (n = 10) under the conditions of daily life. Glucose profiles in both healthy and diabetic persons were followed in the subcutaneous tissue up to 27 hours. This technique will certainly open new perspectives of monitoring and treating diabetic patients.

On line continuous monitoring of blood lactate in men by a wearable device based upon an enzymatic amperometric lactate sensor

A wearable device for the continuous measurement of lactate in the blood was constructed by the combination of continuous blood sampling employing a double lumen catheter with an amperometric lactate sensor. In vitro, the lactate sensor turned out to have a linear concentration range between 0 and 15 mmol/l. The response time of the sensor itself amounted to 100 sec, whereas the lag time for blood sampling amounted to 2.2 min. In vivo, the lactate sensor was successfully used for the detection of changes of the blood lactate concentration following strenuous exercise in 7 healthy volunteers, in two cases up to 22 h. In conclusion, the technique of continuous blood sampling by the use of a double lumen catheter in combination with the amperometric lactate sensor is feasible and simplifies frequent blood lactate estimations.

On line continuous monitoring of subcutaneous tissue glucose in men by combining portable glucosensor with microdialysis

For the normalisation of blood glucose levels in diabetic patients by feedback controlled insulin delivery, a self-manageable and reliable method for continuous glucose estimation is still not available. By combining a commercially available needle type dialysis probe (molecular cutoff 20,000 Da) with a sensitive glucose sensor, we obtained a device for continuous glucose measurement in dialysate. This device was tested in healthy volunteers during a 75-g oral glucose tolerance test and in Type 2 (non-insulin-dependent) diabetic patients. Venous glucose and subcutaneous sensor signal were followed for 300 min (ten healthy subjects), 21 h (three healthy subjects) or 9 h (seven Type 2 diabetic patients). The recovery of the microdialysis was interindividually different, but after calibration, glucose levels in the dialysate and subcutaneous glucose sensor signal correlated well (r = 0.84-0.95). Under the assumption of a physiologic and technical delay between intravenous and subcutaneous glucose, correlation coefficient between intravenous glucose and subcutaneous sensor signal ranged from 0.60 to 0.93. We conclude that changes in blood glucose could be monitored in the subcutaneous tissue by the microdialysis technique in a continuous on line manner.