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Biomedical subjects

K Köster

Publications and source records attributed to K Köster.

14 recordsLinked to original sources
PubMed2001

A Doppler ultrasonographic study of cyclic changes of ovarian perfusion in the Beagle bitch.

Changes in intraovarian arterial blood flow were monitored by means of colour-coded and pulsed Doppler ultrasonography in Beagle bitches during the normal oestrous cycle (n = 11) and pregnancy (n = 3), and at PGF(2alpha)-induced luteolysis (n = 4). The ultrasonographic findings were related to the reproductive stage of the bitch, as determined by vaginoscopical and cytological criteria, and by the concentrations of oestradiol, LH and progesterone in peripheral blood plasma. Colour-coded Doppler ultrasonography was used to visualize and estimate intraovarian vascularization, and pulsed Doppler ultrasonography was used to measure the arterial blood flow. The systolic and diastolic peak velocities, the end-diastolic velocity, and the pulsatility index and resistance index were calculated for quantitative analysis of the Doppler waveforms. Intraovarian perfusion increased gradually during pro-oestrus. A marked enhancement of intraovarian colouring and blood flow velocities, and a decline in the indices for pulsatility and resistance were observed in the preovulatory period. Maximum perfusion was observed at ovulation and during the early luteal phase. Significant differences (P < 0.05) were detected for the values of all calculated Doppler parameters 2 days before and 2 days after ovulation. Intraovarian blood flow decreased gradually in accordance with luteal regression. Treatment with PGF(2alpha) caused a distinct decline in luteal activity and a concomitant reduction in intraovarian perfusion. The values of blood flow parameters found during the luteal phase of pregnant bitches were comparable to those of the normocyclic bitches. Doppler ultrasonography of the intraovarian arteries in bitches provides complementary information about cyclic changes of ovarian function.

Animals↗
PubMed1992

Normal auditory brain stem evoked responses in infants of diabetic mothers.

Auditory brain stem responses potentials were recorded from 71 newborns within the first 2 weeks after birth; conceptional age ranged from 37 to 41 weeks. Thirty-nine newborns were infants of diabetic mothers (IDMs) (17 White A, 22 White B-D) and 32 healthy term newborns served as control group. IDMs with additional high risk for cochlear or brain stem integrity were excluded. Birthweight for gestational age was significantly higher for IDMs. No differences in auditory brain stem responses wave latencies or amplitudes were observed between healthy infants of the control group and IDMs.

Birth Weight↗
PubMed1992

Narcotic and nicotine effects on the neonatal auditory system.

To evaluate narcotic and nicotine effects on the neonatal auditory system, brain stem auditory evoked responses were recorded in 15 infants prenatally exposed to both narcotics and nicotine (median gestational age 38.4 weeks, median birth weight 2820 g), in 15 nicotine exposed infants (gestational age 40.0 weeks, birth weight 3000 g) and in 24 healthy term infants (gestational age 40.1 weeks, birth weight 3310 g) who served as controls. Whereas nicotine-exposed and control infants were similar in all brain stem auditory evoked response measurements, narcotic/nicotine infants had bilaterally increased wave V latencies (left: p = 0.005; right: p = 0.04) and I-V intervals (left: p = 0.02; right: p = 0.01) when compared to controls. Our findings suggest that prenatal narcotic but not nicotine exposure negatively affects maturation or integrity of the neonatal auditory brain stem tract and that neither narcotic nor nicotine exposure is associated with hearing loss in the neonate.

Brain Stem↗
PubMed1983

Regeneration of hemofiltrate by anodic oxidation of urea.

Urea can be oxidized electrochemically in a chloride solution to carbon dioxide, water, and nitrogen. The microkinetics of this hypochlorite-mediated urea oxidation are elucidated. Based on this kinetic information, the optimal conditions and construction principles for an electrochemical reactor are deduced. The construction of a cheap, disposable oxidation cell and necessary auxiliary equipment are described. In vitro data are reported for urea removal. A 36-L volume was used to simulate a 60-kg patient; 18 L was recirculated through a 0.12-m2 oxidation cell. Within 3 h, 35 g urea could be removed from the system. The technical and economic possibilities as well as safety requirements for hemofiltrate regeneration to a reinfusable substitution solution by anodic urea oxidation are discussed critically. Although the process does not appear to be economically practical for discontinuous hemofiltration, it might be desirable for continuous (24 h/day) treatment.

Blood↗
PubMed1980

[Regeneration in bony defects after implantation of resorbable calcium phosphate ceramics. A comparative clinical study].

After experimental demonstration of the excellent tissue tolerance with ceramics-bone contact without connective tissue in animals and because of the good resorbability of tri-calcium phosphate ceramics (TPC), TPC ceramics was used in a clinical study to fill the bony defects resulting from apicectomies and cystectomies. The patients were controlled for a period of up to six months. After an initially normal healing phase, an unusually high rate of late complications with fistula formation and rejection of the TPC ceramics was observed around the tenth postoperative week. Possible causes for these late complications were discussed.

Apicoectomy↗
PubMed1979

[Experimental application of calcium phosphate granulate for the substitution of conventional bone transplants (author's transl)].

Autologous spongiosa, a calcium phosphate ceramic and Kiel bone chips were implanted in the tibiae of dogs and compared with respect to tissue compatibility and osteogenetic effect. After the ceramic implants and the autologous spongiosa had been left in the tibial fat marrow for six weeks, bone tissue and bone marrow had formed to the same extent around both materials. Their stimulating effect on osteogenesis was comparable. In contrast to the ceramic material, together with which they had been implanted in active bone marrow, the Kiel bone chips were surrounded by fibrous tissue in addition to bone tissue. All of the three types of implant proved to be tissue compatible. On the whole, the calcium phosphate ceramic was found to be equal to autologous and superior to heterologous spongiosa from a biological point of view. In technical terms the ceramic implant was superior also to the autologous graft.

Animals↗
PubMed1977

[Resorbable calcium phosphate ceramics under load (author's transl)].

Cylindrical implants with 45% by volume continuous open tubular pores were prepared from ceramic materials based on tricalcium and tetracalcium phosphate and used to replace 7 mm thick bone segments in the tibiae of dogs. The treated limbs of the experimental animals were fixed for 12 weeks, after which time the dogs were allowed to move freely so that the limbs were physiologically loaded. The histological examination showed that primary bone healing had taken place between the bone and the ceramic material. After 10 months the tricalcium-phosphate-based ceramic material was resorbed and replaced by bone tissue to a large extent. The ceramic material on the bases of tetracalcium phosphate on the other hand, had remained completely unchanged, and its pores were filled with lamellar bone tissue which was in direct contact with the implant without connective tissue. The bond between natural bone and implant was mechanically stable. The ceramic materials investigated were found to be tissue-compatible, and in our opinion they can be substituted for part of the bone transplants used today. Considering its varying strength properties, the tricalcium phosphate ceramic material can be used only in cases where no high stress is expected; the tetracalciumphosphate-based ceramic material, however, has a higher mechanical strength and can therefore be used also for larger permanent implants which have to bear high mechanical stress.

Animals↗
PubMed1976

[Experimental bone replacement with resorbable calcium phosphate ceramic (author's transl)].

Compact cylindrical implants (5 x 15.5 mm) of seven calcium phosphate ceramics of different formulations that had been implanted for 6 weeks without fixation in the tibia of dogs were examined histologically. The tissue compatibility of the implant turned out to be dependent on the mineralogical and chemical composition of the material: the ceramic material was biocompatible at a CaO/P2O5 ratio between 2:1 and 4:1, the optimum ratio being about 3:1 (tricalcium phosphate). In addition, cylindrical tetracalcium phosphate implatns with an entirely porous structure were implanted in the same manner. After 6 months, they were resorbed to a minor extent. Implants of different calcium phosphate mixtures, on the other hand, were resorbed to a large extend after the same time. The ceramic material was replaced by mineralised bone tissue which had formed directly on the ceramic implant as well as within the pores. There were no foreign body reactions. Investigations with segment-shaped implants which were implanted in the tibia of dogs and fixed with AO-plates or splints extra-cutaneously for about 8-10 weeks, provided information abouth the maximum stress that can be borne by the implants. While implants with a porosity of 75 percent did not sustain the stress after the fixation had been removed, those with a porosity of 45 percent could be subjected to physiological stress after removal of the splints.

Animals↗
PubMedDate not supplied

[Growth and growth hormone in children with congenital lip and palatal clefts].

In order to investigate the correlation supposed between cleft lip and palate of children and growth hormone deficiency we determined the amount of growth hormone in the blood serum of 199 children with cleft lip and palate and partly with other additional diseases. In contrast to a previous result we could not find a significant relation between the cleft-syndrome and growth hormone deficiency. All patients had a normal and sufficient concentration of the hormone. As result of our work we propose to determine the hormone concentration only in those cases in which less growth is observed too.

Body Height↗