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Biomedical subjects

D Burkhardt

Publications and source records attributed to D Burkhardt.

At least 37 records · Page 2Linked to original sources
PubMed1994

[Dyskeratosis congenita in monozygous twins].

Dyskeratosis congenita (DC) is a very rare form of genodermatosis with variable manifestations, which mainly affects male patients. The main clinical symptoms are poikilodermia, nail dystrophy and leucoplakia; there are many other cutaneous and systemic symptoms. To avoid complications and improve the prognosis early diagnosis and regular close surveillance of the patients are important. We report on 13-year-old monozygotic twin brothers who, in addition to the typical symptoms, had increased vulnerability of the skin, scarring of the hands and atrophy of the oral mucosa as well as splenomegaly, pancytopenia with severe aplasia of bone marrow and aseptic necrosis of the hip. The two brothers had nearly synchronous clinical manifestation and progression. This paper reviews the clinical symptoms, pathogenesis, differential diagnosis and genetic aspects of DC.

Adolescent↗
PubMed1994

Biological aspects of bird colouration and avian colour vision including ultraviolet range.

Many diurnal birds possess a set of four spectrally different types of cone photoreceptor. The spectral range of vision is extended into the UV by a UV receptor. We have investigated the spectral properties of plumage colours including the UV by reflection spectroscopy. Some basic general principles of colour vision indicate that plumage colours are tuned to avian colour vision.

Animals↗
PubMed1994

Short-term and long-term effects of serial bronchoalveolar lavages in a nonhuman primate model.

Bronchoalveolar lavage (BAL) has gained widespread use as a tool for investigating human lung diseases. In certain cases, it can be useful to obtain BAL material in a serial manner. There is convincing evidence from experimental and clinical studies that BAL can cause influx of neutrophils into the bronchoalveolar space. However, conflicting data have been reported on whether this side effect of BAL also affects previously nonlavaged lung areas. In addition, there is little information available on whether multiple repetitive BAL procedures cause damage to lung tissue. To reexamine the short-term effects of serial BAL procedures, the left lung of 10 cynomolgus monkeys was lavaged with five 20-ml aliquots of saline four times at 24-h intervals (Group A). 72 h after the initial BAL, the right lung was lavaged as a control. The percentage of neutrophils increased significantly (p < 0.05), with the greatest effect seen at 48 h (30.7 +/- 5.8 versus 0.8 +/- 0.3%, mean +/- SEM). No significant changes were observed in the control BAL of the right lung at 72 h. A multidisciplinary approach was used to assess the long-term effects of multiple BAL procedures. BAL was performed 14 times over 26 mo at 2-mo intervals (Group B, n = 5). The right lung was lavaged as a control 25 mo after the initial BAL. In addition to standard cellular BAL parameters, the concentrations of fibronectin, procollagen III amino-terminal peptide-related antigen, total phospholipids, and lactate dehydrogenase activity were measured.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

[Incontinentia pigmenti in a male patient].

Incontinentia pigmenti (Bloch-Sulzberger syndrome) is a rare genetic disorder usually affecting females. Familial cases show an X-linked dominant inheritance with male lethality. The typical skin manifestations occur in several stages and can be associated with various extracutaneous anomalies. We report on a 10-month-old male patient with incontinentia pigmenti (IP) and a normal male karyotype. Besides the typical cutaneous lesions no other signs have been found so far. IP in male patients can be explained by the presence of Klinefelter syndrome, by the half-chromatid mutation model, or by an early somatic mutation. On the basis of this case report we discuss the clinical findings in and the genetics of IP.

Biopsy↗
PubMed1992

The chondroprotective drugs, Arteparon and sodium pentosan polysulphate, increase collagenase activity and inhibit stromelysin activity in vitro.

The effects of the chondroprotective drugs, sodium pentosan polysulphate (SP54) and Arteparon (glycosaminoglycan polysulphate), on the in vitro activities of the purified matrix metalloproteinases interstitial collagenase (matrix metalloproteinase 1, MMP1) and stromelysin (MMP3) were examined. Both drugs produced concentration-dependent enhancement of the degradation of type I collagen fibrils by purified human fibroblast collagenase and rat tumour collagenase. Rat collagenase activity was increased by drug concentrations above 0.5 microgram/mL, whereas human collagenase activity was only increased by higher drug concentrations, above 5 micrograms/mL. The concentration dependence of the increase in rat collagenase activity was similar for both drugs, with a maximal 3-fold increase at 50 micrograms/mL. In contrast, human collagenase activity was increased to a greater extent by SP 54 compared to Arteparon, with maximal increases at 5000 micrograms/mL of 6-fold and 2-4-fold, respectively. Both drugs produced concentration-dependent inhibition of the proteoglycan-degrading activity of both human fibroblast stromelysin and rat tumour stromelysin. Rat and human stromelysin activities were inhibited at drug concentrations above 0.005 microgram/mL, with a similar concentration dependence for both drugs. Fifty percent inhibition of rat stromelysin was produced by concentrations of each drug in the 0.5-5 microgram/mL range. The pattern of inhibition of human stromelysin was similar, except that drug concentrations in the 500-5000 micrograms/mL range produced 50% inhibition. The possible modes of action for these drug effects and their possible pharmacological significance are discussed.

Animals↗
PubMed1992

IgA producing primary intracerebral lymphoma.

The first case of a primary and solitary IgA (lambda) producing tumour (possibly a non-Hodgkin's lymphoma) in the CNS is reported. Clinical and neuroimaging findings are described. Early diagnosis without brain biopsy and successful therapy were possible by CSF and serum immunoglobulin analysis which proved local paraprotein production restricted to the CNS.

Adrenal Cortex Hormones↗
PubMed1991

[Sense organs: selective projections and control of behaviors].

Some aspects of comparative sensory physiology are reviewed in the context of the historical development. Emphasis is placed on the concepts how spatial and temporal stimulus patterns are processed into nervous excitation patterns and projected in the brain: Both receptor organs and neuron networks may act as selective filters for certain features of the stimulus situation. Neural projections represent not only the spatial distribution of the stimulus pattern but also other parameters. Excitation patterns resulting from the stimulus situation are compared in the neuronal networks with patterns inherited, learned, or inherited and modified by learning. The result of this comparison may then trigger the behavior necessary under the conditions present.

Animals↗
PubMed1991

Recent advances in animal models for evaluating chondroprotective drugs.

While a variety of animal models have been described to evaluate the effects of antiarthritic and chondroprotective drugs on cartilage metabolism, most cannot be said to truly reproduce the temporal changes that occur in human osteoarthritis (OA). Total meniscectomy is a common orthopedic procedure in humans and frequently leads to OA in later years. We investigated the effects of unilateral medial meniscectomy in sheep knee joints subjected to moderate regular exercise. Morphological and biochemical studies of joint cartilage after 6 months revealed slowly progressive changes similar to those seen in early OA, characterized by cartilage fibrillation, chondrocyte hypertrophy, matrix proliferation and marginal osteophyte formation. The proteoglycans synthesized contained more chondroitin-4-sulphate than chondroitin-6-sulfate.

Animals↗
PubMed1985

The proteoglycans of the canine intervertebral disc.

The high-buoyant-density proteoglycans of the nucleus pulposus and annulus fibrosus of the beagle intervertebral disc have been isolated by CsCl density gradient ultracentrifugation. The sulphated proteoglycans were labelled in vivo with 35SO4, 24 h and 60 days prior to killing. The hydrodynamic size and aggregation of the 24 h, 60 day and resident (from hexuronic acid and hexosamine analysis) proteoglycan subunit populations were determined by Sepharose CL-2B chromatography in the presence or absence of excess hyaluronic acid. The hydrodynamic size of the keratan sulphate-proteoglycan core protein complexes were also determined by Sepharose CL-2B chromatography after chondroitinase ABC digestion of proteoglycans. When initially synthesised (24 h) or after 60 days, the percentage aggregation and hydrodynamic size of the proteoglycans derived from the annulus fibrosus were larger than those present in the nucleus pulposus. Hexosamine, hexuronic and protein determination of the high-buoyant-density fractions showed that the proteoglycans of the nucleus pulposus were richer in chondroitin sulphate than those in the annulus. However there was no difference in Mr of the chondroitin sulphate and keratan sulphate attached to the proteoglycans of the two disc regions, nor were differences detected by HPLC between the proportions of chondroitin 4-sulphate and chondroitin 6-sulphate present in these high-density fractions. In contrast, the low-buoyant-density (1.54 greater than p greater than 1.45) proteoglycan fractions and tissue residues remaining after 4 M GuHCl extraction were found to contain dermatan sulphate, suggesting the presence of a third proteoglycan species possibly associated with the collagen of the fibrocartilagenous matrix.

Animals↗
PubMed1985

Effects of spinal fusion on the proteoglycans of the canine intervertebral disc.

Posterior lumbar two-level spinal fusion was undertaken in 10 mature beagles. The animals were sacrificed 6 and 12 months later. Two months before sacrifice control and experimental animals received intravenously Na2(35)SO4 (1 mCi/kg). Discs encompassed by the fusion and those adjacent to it were dissected into the nucleus pulposus and annulus fibrosus (AF), which were analysed separately. Proteoglycans (PGs) were extracted with 4.0 M guanidine HCl and purified by CsCl density gradient ultracentrifugation. The hydrodynamic size and ability of the PG subunits to aggregate in the presence of hyaluronic acid were investigated by Sepharose CL-2B chromatography. The PG subunits were analysed for their galactosamine (galN), glucosamine (glcN), hexuronic acid, and protein content or were subjected to digestion with papain or chondroitin-ABC-lyase to establish the size of the chondroitin (CS) and keratan (KS) sulphate chains and the KS-PG core protein complex. Decreased ability to aggregate of PGs isolated from discs 6 and 12 months after surgery was demonstrated. While their hydrodynamic size after 6 months was generally the same or smaller than those in control tissues, the PG population present after 12 months was larger, particularly in the AF. Analysis of PG subunits from fusion discs afforded galN/glcN, galN/protein, and hexuronic acid/protein ratios that were compatible with the presence in these tissues of PGs in which the proportion of CS attached to core protein was greater than in control tissues. These studies provide the first experimental evidence that a metabolic response of discs in a fused segment may be accompanied by the biosynthesis of a new PG population whose structure is similar to that present in immature tissues.

Animals↗
PubMed1982

Birds, berries and UV. A note on some consequences of UV vision in birds.

The problem of UV vision in vertebrates is briefly discussed in its historical context. For example, UV vision has been demonstrated in some birds by several authors. Hence the reflectances of plumage, petals of bird-pollinated flowers and of berries in the near UV may play an important rôle within the visual environment of birds. Some data obtained by means of UV photography are presented, and it is shown, that the waxlayer of glaucous fruits is highly reflective in the UV.

Animals↗
PubMed1982

Effects of 4-nitro- and 4-sulpho-7-substituted benzofurazans on nucleic acid and protein synthesis of a malignant fibrosarcoma cell line in combination with mild hyperthermia.

The inhibitory effects of substituted nitro- and sulphobenzofurazans on DNA, RNA and protein synthesis were compared in a new malignant fibrosarcoma cell line at 37 degrees C and 41 degrees C. The effects of these drugs with and without mild hyperthermia were evaluated by determining the % inhibition of incorporation of 3H-precursors into DNA, RNA and protein. None of the sulphobenzofurazan derivatives (Sbf) were effective inhibitors of nucleic acid and protein synthesis at 37 degrees C nor did they enhance the inhibitory effect of hyperthermia alone. The nitrobenzofurazan derivatives (Nbf) at concentrations 10% that used for the Sbf derivatives strongly inhibited biopolymer synthesis in a dose related manner; 4-chloro-7-nitrobenzofurazan (Nbf-Cl) being the most potent inhibitor. Hyperthermia amplified the effect of all the Nbf compounds tested on RNA and protein synthesis but did not further affect DNA synthesis. This selective synergistic effect was most pronounced when the lowest concentrations of Nbf compounds were studied. The synergism however, did not follow a uniform pattern. 6-Mercaptopurine and 6-(1-methyl-4-nitro-5-imidazoyl)thiopurine (Azathioprine) (100 microM) had marginal effects on nucleic acid and protein synthesis when the cells were exposed to these two thiopurines for 1 h at both 37 degrees C and 41 degrees C and they had only a moderate inhibitory effect after exposure for 15 h.

Animals↗
PubMed1981

Fine structure of the ommatidia and the occurrence of rhabdomeric twist in the dorsal eye of male Bibio marci (Diptera, Nematocera, Bibionidae).

The ommatidia in the dorsal eye of male Bibio marci (March flies) are comprised of eight retinula cells (R 1--8). In the distal region, the open rhabdomeres of retinula cells 1--6 are arranged in a symmetrically circular pattern with their microvilli directed radially. Immediately beneath the crystalline cone, cell 7 forms a rhabdomere that is about 1 micrometer long and lies in the center of the circle formed by the rhabdomeres of cells 1--6. For the remaining length of an ommatidium it is replaced by the rhabdomere of retinula cell 8. The cell body of this retinula cell almost encloses its own rhabdomere by forming a deep invagination. Consequently, no ommatidial cavity is present. In the left eye rhabdomeres R 3, 5 and 6 first twist clockwise along their longitudinal axes, while rhabdomeres R 1, 2, 4 and 8 twist counterclockwise. Opposite twisting is observed in the right eye. The twist rate varies along the length of the rhabdomeres. In a middle region of 60 micrometers, within which the direction of twist does not change, the maximal twist rates are approximately 2 degrees--5 degrees/micrometers in R 1--6 and even higher in R 8. In a proximal region, the direction of twist is reversed, but the initial orientation of the microvilli not reestablished. Both the cross-sectional shape of the rhabdomeres and their geometric arrangement in the retinula change along with the twisting. It is substantiated that the rhabdomeric twist is not due to artifactual deformation.

Animals↗
PubMed1977

Hyperthermia and cancer.

The effects of heat and its possible significance in cance therapy have been documented for more than a century. Hyperthermia has been widely investigated as an alternative or adjuvant to conventional therapies such as surgery, radiation, and chemotherapy. The clinical reports are interesting, notwithstanding some harmful side effects and other complications which, however, may be attributable to an advanced stage of the disease at the time of treatment. In view of the extreme difficulty in matching suitable controls for cancer patients undertaking such therapy, it is essential to extend knowledge of the effects of hyperthermia on normal and neoplastic tissue by experimental studies. Further, the different methods of utilizing heat therapy have need for substantial technological improvements. To stimulate interest in this area, we have gathered together in this review some of the more pertinent reports on the application of hyperthermia to neoplastic and normal tissues as observed clinically and in the laboratory.

Animals↗