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Biomedical subjects

D Köster

Publications and source records attributed to D Köster.

At least 19 recordsLinked to original sources
PubMed2002

Scale-up of dialysis fermentation for high cell density cultivation of Escherichia coli.

In dialysis fermentations inhibiting metabolites can be removed from cell suspensions resulting in a prolonged exponential growth phase and higher production yields. Because of successful high cell density cultivations of Escherichia coli in a laboratory dialysis reactor, a scale-up of the process was investigated. To provide sufficient membrane area for dialysis in a technical scale fermenter, an external membrane module was used, that was also applied for oxygen supply to the culture in the external loop. Cultivations with recombinant E. coli K12, with and without induction, in 2- and 300-l reactors were carried out using external modules. Cell densities exceeding 190 g l(-1), previously obtained in laboratory dialysis fermentation, were also produced with external dialysis modules. Protein concentration in a 300-l reactor was increased to the 3.8-fold of industrial fed-batch-fermentations.

Culture Media↗
PubMed2002

In-situ-fluorescence-probes: a useful tool for non-invasive bioprocess monitoring.

Optical sensors appear to be very promising for different applications in modern biotechnology. They offer the possibility to interface all the well known optical analysis techniques to bioprocesses via fiber optical cables. Thus, high sophisticated and sensitive optical analysis techniques can be coupled to a bioprocess via these light signal transporting fibers. A wide variety of sensor types for application in biotechnology has been described. Normally these sensors are non-invasive and the response times are nearly instantaneous. In particular, the use of glass fiber technology makes these sensors small, robust and reduces their costs.

Biomass↗
PubMed2001

Metabolic effects of HAY's diet.

The aim of the study was, to evaluate the metabolic effect of HAY's diet on protein turnover, fat oxidation, respiratory quotient, body fat and weight loss. Twelve healthy adults received an individually regular diet and thereafter a corresponding isocaloric and isonitrogenous 10-day HAY-diet. Protein turnover and 13C-fat oxidation were investigated after administration of [15N]glycine and an [U-13C]algae lipid mixture. The 15N and 13C enrichment in urine and breath were measured by isotope ratio mass spectrometry. The respiratory quotient was measured by indirect calorimetry. Body fat, total body water and lean body mass were estimated by bio-electric impedance analysis. HAY's diet led to a significantly higher 13C-fat oxidation (15.4 vs. 22.0% P < 0.01), corresponding to a lower respiratory quotient (0.88 vs. 0.81; P < 0.01), whereas the protein turnover remained constant in both diets (3.06 vs. 3.05 g/kg/day). HAY's diet did not reduce total body water, lean body mass, body fat and body weight (72.2 vs. 71.4 kg).

Adult↗
PubMed1992

Hepatitis A as an occupational hazard.

Few studies have been carried out to evaluate the role of hepatitis A virus (HAV) as an occupational hazard. Our analysis of data on occupational diseases in Germany showed that hepatitis A ranks as third among infectious occupational diseases. Morbidity based on the frequency of compensation (15.2%) was in the same range as that observed for hepatitis B (19.7%). In another study, data were collected on anti-HAV prevalence among 2293 hospital workers in southwest Germany. Anti-HAV prevalence of hospital staff responsible for patient care and that of the general population were comparable, while food-handlers under the age of 30 years had a higher degree of anti-HAV prevalence. When an evaluation of anti-HAV prevalence data was carried out on persons younger than 30 years who comprised subsets of the medical staff, the relative risk was: charwomen 4.2, food-handlers 2.49, and paediatric nurses 1.84, showing that they had higher prevalence rates than nurses 1.25, physicians 1.09 and laboratory assistants 0.93. Vaccinations for the prevention of hepatitis A should therefore reach individuals that have an increased occupational risk: food-handlers, health care workers in infectious diseases and paediatrics, medical staff in laboratories handling stool samples, medical charwomen and, according to previously published work, staff of day care centres and sewerage workers.

Food Handling↗
PubMed1988

[Craniofacial growth under the influence of blood supply. 13. Local biomechanical aspects of bone morphogenesis].

The origin of formative forces is to be sought in genetically controlled growth processes. The forces generated by various system components are analyzed. The forces acting in mutual opposition can be illustrated by considering the brain as an intracranial force factor and the temporalis muscle as an external force factor. Apposition and resorption of bone is governed by the interaction between the stresses. The skull's primary growth centres such as the basicranial synchondroses must, like epiphyses of tubular bones, exert growth forces to overcome the restraining forces stemming from surrounding tissues. Growth can be suppressed by excessive counter-pressure, diverted by asymmetrically acting forces, and encouraged by the removal of suppressive forces.

Biomechanical Phenomena↗
PubMed1988

[Craniofacial growth under the influence of the blood supply. 14. Theoretical deductions and clinical conclusion].

After eliminating the masticatory muscles as a growth factor in our animal model is was possible to analyze the blood supply to the skull in sufficient detail. The animal organism and its parts may be regarded as self-regulating, self-optimizing and self-adapting systems. Open systems exchange energy and material with their surroundings. This is typical of all organisms and, since growth is one of their properties, to growth. The processes of ossification and growth of the rat skull are therefore comparable in principle with those taking place in the human. The specific features of the chewing mechanism, in contrast, are not comparable. The clinical conclusions drawn from our model studies illustrate the importance of the blood supply for craniofacial growth while simultaneously demonstrating the compensation ability and adaptability of arteries and bones.

Animals↗
PubMed1988

[Craniofacial growth under the influence of the blood supply. II. Skull scoliosis].

After unilateral ligature of the common carotid artery in young rats, the rostrum was observed to shift towards the ligated side. The scoliosis was combined with arthropathic changes in the temporomandibular joint. The deflection of the rostrum is situated in the region of the right premaxillar bone. It is assumed that the scoliosis is caused by reduction of the blood flow to the frontonasal sutures because the terminal branches of the infraorbital artery have no collaterals. Moreover, the reduction in the blood supply also leads to disturbance of the muscular function and thus to a reduction in growth stimuli to the frontonasal sutures.

Animals↗
PubMed1988

[Craniofacial growth under the influence of the blood supply. 12. Regulation of bone remodeling].

Growth is controlled by phylogenetic and ontogenetic factors. Regulation of bone growth can be regarded as taking place at 3 levels, a high, general level at which genetics and hormones represent the main regulators, a middle, regional level where the vascular influence predominates, and a low, local level dominated by mechanical factors. Stresses within the bone, which under physiological conditions are in a state of dynamic equilibrium, play a significant role in the shaping of bony structures. The apposition or resorption of bony material is accelerated if such stresses exceed or drop below certain limits. Biophysically, bone is comparable to technical materials consisting mainly of hydroxyl apatite and collagen. Deformation of the hydroxyl apatite is associated with piezoelectric effects which induce changes in bone structure.

Animals↗
PubMed1987

[Craniofacial growth under the influence of blood supply. 9. Skull and mandibular growth after carotid ligation].

Unilateral ligature of the common carotid artery leads to a reduction in the size of the zygomatic arch complex in rats aged 8 and 12 months. Skull growth is accelerated during the 4th and 12th month in operated animals, so that these animals have large skulls than the controls at maturity. Comparison with the literature suggests that this is a result of over-compensation of the blood supply after the ligature. Increased availability of arterial blood also leads to greater axial growth of tubular bones. The lack of skull growth during the 8th month is discussed. The biomathematical methods of analysis used for these studies are of only limited validity for the observation of skull growth.

Animals↗
PubMed1987

[Craniofacial growth under the influence of blood supply. 10. Arthrosis of the temporomandibular joint].

Unilateral and bilateral deformation of the temporomandibular joint was observed in young rats after unilateral ligature of the common carotid artery. They involved both the mandibular condyle and the mandibular fossa and were usually associated with a reduction in the dry weight of the masticatory muscles on the ligated side. This leads to the assumption that muscular atrophy is causally related to arthropathy of the temporomandibular joint. The methodological approach to induce changes in the temporomandibular joint may be used as a model of arthrosis of that joint.

Age Factors↗
PubMed1987

[Craniofacial growth modified by blood supply. 3. Adaptation of the cranial arteries following unilateral ligation of the common carotid artery. Discussion of findings of the 1st and 2d communication].

Ligature of the right common carotid artery induces compensatory dilatation of the arteries of the head and neck, and particularly of the left common carotid artery. Functional mechanisms also caused dilatation of the arterioles. The enlargement of previously formed anastomoses and collaterals was also observed. Angiophysical effects and histochemical phenomena are implicated in the modification of previously existing anastomoses. The transport capacity of the collaterals increases as the area of the summated lumena increases and as the length of the vascular pathways decreases. The time factor, finally, also plays an important in role the formation of anastomoses, which continues even after an observation period of 12 months in the rat.

Animals↗
PubMed1987

[The influence of blood supply on craniofacial growth. 4. Reactions of the jaw musculature].

The dry weight of the chewing muscles differ distinctly between male and female. In rats aged 8 to 12 months the dry weight of the chewing muscles after ligature of the carotid artery was lower on the side of the ligature. Necrotic fibres were occasionally found in the masseter muscle on the ligature side. Morphometric investigation of the masseter muscle fibres revealed no significant differences between the 2 sides in the operated rats. Since the rats were relatively young when the commune carotid artery was ligatured unilaterally, the consequences of the initially reduced blood supply to the chewing muscles on the right side could be compensated for rather well, mainly by the enlargement of previously existing anastomoses. Our quantitative and histological studies nevertheless show that muscular dysbalance of the masticatory apparatus was severe.

Animals↗