Biomedical subjects

Klaus Qvortrup

Publications and source records attributed to Klaus Qvortrup.

11 recordsLinked to original sources

PubMed2007

Surgical induction of choroidal neovascularization in a porcine model.

PURPOSE: To develop a reproducible surgical technique for the induction of choroidal neovascularization (CNV) in the subretinal space of porcine eyes and to analyse the resulting CNV clinically and histologically. METHODS: Two different modifications of a surgical technique previously described were compared with the original method. In ten porcine eyes retinal pigment epithelial (RPE) cells were removed using a silicone tipped cannula, in ten porcine eyes Bruch's membrane was perforated once with a retinal perforator without prior RPE removal and in ten eyes RPE removal was followed by a single perforation of Bruch's membrane. Fifteen of the eyes, five from each group, were enucleated 30 minutes after surgery, while the remaining eyes were enucleated after 14 days. Prior to enucleation, at day 14, fundus photographs and fluorescein angiograms were obtained. Eyes were examined by light microscopy and by immunohistochemical staining. In addition to these 30 eyes, two eyes underwent surgery with the purpose of subsequent scanning electron microscopic (SEM) examination. RESULTS: In eyes enucleated immediately after surgery neuroretinas overlying the induced lesions were intact without apparent atrophy of cells regardless of the surgical technique applied. The process of RPE removal was found to induce breaks in Bruch's membrane and both the size and the number of breaks varied between eyes. CNV membranes were identified in 15 of 15 eyes enucleated after 14 days. CNV membranes induced by perforation of Bruch's membrane without prior RPE removal were significantly thicker than membranes from eyes undergoing both RPE removal and Bruch's perforation (p = 0.03) and also thicker than membranes from eyes with only RPE-removal (p < 0.01). CNV membranes from eyes with perforation of Bruch's membrane without prior RPE removal had a higher cellular content and were more richly vascularized and also exhibited the highest propensity to leak in fluorescense angiograms. CONCLUSION: All three surgical techniques were capable of inducing CNV, but the one applying perforation of Bruch's membrane without RPE removal was easier to reproduce and involved fewer variables than the techniques utilizing RPE removal. The presence of RPE cells seems to affect both the morphology and cellular composition of induced CNV.

Animals↗

PubMed2007

A potential portal flow in the inner ear.

OBJECTIVES/HYPOTHESIS: The aim of the present study was to visualize the flow direction of blood in the extraosseous part of the vein of the vestibular aqueduct (VVA) and to explore the effect of an induced obstruction in the distal part of the VVA before it merges with the sigmoid sinus. The endolymphatic sac has been implicated as a potential endocrine gland, which venules drain to the VVA. A reversal of the direction of flow in the VVA toward the inner ear could, through vestibular arteriovenous anastomosis, cause portal circulation in the inner ear. STUDY DESIGN: The authors conducted an experimental animal study using in vivo fluorescence microscopy. RESULTS: Obstructing the distal part of the VVA just before it empties into the sigmoid sinus immediately reverses the flow of blood in the VVA toward the inner ear. CONCLUSIONS: After an obstruction of the VVA, the drained venous blood from the endolymphatic sac may enter a portal circulation in the inner ear, which could cause disturbances in the endolymph homeostasis and potentially symptoms as seen in Meniere disease.

Animals↗

PubMed2006

Decrease in intramuscular lipid droplets and translocation of HSL in response to muscle contraction and epinephrine.

A better understanding of skeletal muscle lipid metabolism is needed to identify the molecular mechanisms relating intramuscular triglyceride (IMTG) to muscle metabolism and insulin sensitivity. An increasing number of proteins have been reported to be associated with intracellular triglyceride (TG), among them the PAT family members: perilipin, ADRP (for adipocyte differentiation-related protein), and TIP47 (for tail-interacting protein of 47 kDa). Hormone-sensitive lipase (HSL) is thought to be the major enzyme responsible for IMTG hydrolysis in skeletal muscle. In adipocytes, regulation of HSL by intracellular redistribution has been demonstrated. The existence of such regulatory mechanisms in skeletal muscle has long been hypothesized but has never been demonstrated. The aim of this study was to characterize the PAT family proteins associated with IMTG and to investigate the effect of epinephrine stimulation or muscle contraction on skeletal muscle TG content and HSL intracellular distribution. Rat soleus muscles were either incubated with epinephrine or electrically stimulated for 15 min. Single muscle fibers were used for morphological analysis by confocal and transmission electron microscopy. We show a decrease in IMTG in response to both lipolytic stimuli. Furthermore, we identify two PAT family proteins, ADRP and TIP47, associated with IMTG. Finally, we demonstrate HSL translocation to IMTG and ADRP after stimulation with epinephrine or contraction.

Animals↗

PubMed2005

MEK kinase 1 activity is required for definitive erythropoiesis in the mouse fetal liver.

Mitogen-activated protein kinase/extracellular signal to regulated kinase (MEK) kinase 1 (MEKK1) is a c-Jun N-terminal kinase (JNK) activating kinase known to be implicated in proinflammatory responses and cell motility. Using mice deficient for MEKK1 kinase activity (Mekk1(DeltaKD)) we show a role for MEKK1 in definitive mouse erythropoiesis. Although Mekk1(DeltaKD) mice are alive and fertile on a 129 x C57/BL6 background, the frequency of Mekk1(DeltaKD) embryos that develop past embryonic day (E) 14.5 is dramatically reduced when backcrossed into the C57/BL6 background. At E13.5, Mekk1(DeltaKD) embryos have normal morphology but are anemic due to failure of definitive erythropoiesis. When Mekk1(DeltaKD) fetal liver cells were transferred to lethally irradiated wild-type hosts, mature red blood cells were generated from the mutant cells, suggesting that MEKK1 functions in a non-cell-autonomous manner. Based on immunohistochemical and hemoglobin chain transcription analysis, we propose that the failure of definitive erythropoiesis is due to a deficiency in enucleation activity caused by insufficient macrophage-mediated nuclear DNA destruction.

Animals↗

PubMed2005

Phosphorylation-dependent translocation of glycogen synthase to a novel structure during glycogen resynthesis.

Glycogen metabolism has been the subject of extensive research, but the mechanisms by which it is regulated are still not fully understood. It is well accepted that the rate-limiting enzymes in glycogenesis and glycogenolysis are glycogen synthase (GS) and glycogen phosphorylase (GPh), respectively. Both enzymes are regulated by reversible phosphorylation and by allosteric effectors. However, evidence in the literature indicates that changes in muscle GS and GPh intracellular distribution may constitute a new regulatory mechanism of glycogen metabolism. Already in the 1960s, it was proposed that glycogen was present in dynamic cellular organelles that were termed glycosomas but no such cellular entities have ever been demonstrated. The aim of this study was to characterize muscle GS and GPh intracellular distribution and to identify possible translocation processes of both enzymes. Using in situ stimulation of rabbit tibialis anterior muscle, we show GS and GPh intracellular redistribution at the beginning of glycogen resynthesis after contraction-induced glycogen depletion. We identify a new "player," a new intracellular compartment involved in skeletal muscle glycogen metabolism. They are spherical structures that were not present in basal muscle, and we present evidence that indicate that they are products of actin cytoskeleton remodeling. Furthermore, for the first time, we show a phosphorylation-dependent intracellular distribution of GS. Here, we present evidence of a new regulatory mechanism of skeletal muscle glycogen metabolism based on glycogen enzyme intracellular compartmentalization.

Actins↗

PubMed2005

The antiprogesterone Org 31710 inhibits human blastocyst-endometrial interactions in vitro.

OBJECTIVE: To investigate the effect of the anti-P Org 31710 on human blastocyst attachment to cultured endometrial epithelial cells. DESIGN: Experimental in vitro study. SETTING: University hospital. PATIENT(S): Eleven fertile endometrial donors. INTERVENTION(S): Timed endometrial biopsy for cell cultures. MAIN OUTCOME MEASURE(S): Blastocyst attachment rate on endometrial cell cultures; secretion of glycodelin and leukemia inhibitory factor into the culture medium measured by RIA and ELISA techniques; and expression of progesterone receptors, interleukin-1 receptor type-1, and integrin subunit beta(3) on endometrial epithelial cells examined by immunohistochemistry. Endometrial pinopodes visualized by scanning electron microscopy. RESULT(S): Eleven of 16 human blastocysts attached to control cultures, whereas none of 10 blastocysts attached when Org 31710 was added to the culture medium (P=.0007). Immunohistochemical studies demonstrated no significant differences between groups. Biochemical analyses displayed a trend toward higher glycodelin secretions and, by scanning electron microscopy, a tendency toward less pinopode formation in the Org 31710 group, but the results did not reach statistical significance. The presence of swollen microvilli, precursors of endometrial pinopodes, was significantly reduced on cultures with Org 31710 (P=.03). CONCLUSION(S): The study presents a model for human blastocyst-endometrial interactions responding to an anti-P drug. The exact mechanism for the anti-attachment properties of Org 31710 on the cultured endometrial cells and the blastocysts needs further evaluations.

Blastocyst↗

PubMed2004

Abnormal bone collagen morphology and decreased bone strength in growth hormone-deficient rats.

Patients with growth hormone deficiency (GHD) have an increased risk of bone fractures. In these patients, the well-described decrease in bone mineral density (BMD) and content (BMC) may, however, not alone explain the increase in fracture rate. Accordingly, the aim of this study was to evaluate collagen morphology and bone mineralisation in cortical bone as well as bone strength in GHD rats to try to clarify the explanation for the increased fracture rate. The Dw-4 rat was used as a model for GHD. This strain of rats has an autosomal recessive disorder, reducing GH synthesis to approximately 10% and growth rate to approximately 40-50% when compared to normal control rats. Five male Dw-4 rats were examined at age 12 weeks and five healthy Lewis rats served as age-matched controls. The animals were examined for (1) bone mineral status by dual energy X-ray absorptometry (DXA) and ash weight/bone volume, (2) biomechanical properties, (3) serum insulin-like growth factor I (IGF-I) and IGF binding protein 3 (IGFBP-3), and (4) collagen morphology of cortical bone from the right femurs was examined by scanning and transmission electron microscopy. A significant decrease was found in serum IGF-I, IGFBP-3 and biomechanical properties in GHD rats compared to controls (P < 0.009). While DXA-derived BMD was decreased, no significant difference was found in ash weight/bone volume. Electron microscopy showed a significant decrease in the number and a significant increase in the diameter of collagen microfibrils in GHD rats as compared to their controls (P < 0.009). In conclusion, we report for the first time that collagen morphology in bone is markedly altered in rats with isolated GHD. Whether similar conditions are present in GHD patients need further investigations. The changes described, however, may provide a co-explanation for the increased fracture rate in GHD.

Absorptiometry, Photon↗

PubMed2004

Destructive, granulating lesion in the temporal bone after elevated plasma homocysteine.

OBJECTIVE: This is a presentation of a seemingly new otolaryngologic disease. SETTING: This study was conducted at a tertiary referral center. CASE REPORT: A 38-year-old healthy man developed left-sided sudden deafness with vertigo and temporary left facial palsy. A granulating and destructive lesion in the left temporal bone was discovered; repeated histologic examination only showed simple granulation tissue. After 6 months, a part of the bony cochlea was extruded. With approximately 8 months' delay and after the patient had had postoperative lung embolism, plasma homocysteine was found to be significantly elevated, a condition known as an independent risk factor for thromboembolic lesions. In the acquired form, it is most often caused by nutritional deficiency of vitamin B cofactors. Accordingly, the patient was treated with folic acid, which rapidly normalized plasma homocysteine. Subsequently, the granulation tissue in the temporal bone gradually disappeared, clinically and radiologically, and the lesion healed, obviously without cochlea function. CONCLUSIONS: Thromboembolic lesion in the left temporal bone, probably in the thin end artery a. labyrintina, i.e., an avascular osteonecrosis. During the latest years, an association between avascular osteonecrosis (most often in the hip) and conditions with increased risk of thrombosis such as hyperhomocystinemia has been established but, to the best of our knowledge, it is never with a lesion in the temporal bone.

Adult↗

PubMed2002

Baculovirus expression of erythrovirus V9 capsids and screening by ELISA: serologic cross-reactivity with erythrovirus B19.

Diagnosis of erythrovirus B19 (B19) relies on serology and the detection of viral DNA. Recently, a distinct erythrovirus isolate termed V9, markedly different from erythrovirus B19 (> 11% nucleotide disparity), was isolated. Standard B19 PCR assays were inconclusive and serologic tests failed to categorize V9 as an acute B19-like infection. Sequencing, combined with PCR studies, have since demonstrated the need for specific and differentiated techniques when examining samples for possible B19 or V9 viremia. The antigenic properties of the V9 capsid proteins have not been characterized previously. To address this question, V9 VP1 and VP2 open reading frames were cloned and expressed in insect cells using a baculovirus vector. Large quantities of purified recombinant V9 capsid protein were produced and electron micrographs revealed self-assembly of V9 VP1/VP2 and VP2 capsids into empty icosahedral erythrovirus-like particles with a diameter of approximately 23 nm. Screening of a panel of 270 clinical samples for the presence of V9 IgM and IgG antibodies in ELISA showed 100% serologic cross-reactivity between B19 and V9 when comparing V9 VP2 capsids to a commercial B19 VP2 assay. This suggests that both a V9 and a B19 antibody response may be diagnosed equally well by ELISA using either V9 or B19 recombinant capsids as antigen source. Retrospectively, translation of the V9 sequence indicates that despite a significant genetic variation on the DNA level, the majority of the discrepant DNA sequence represents silent mutations leading to an amino acid sequence very similar to the known B19 strains (96-97% homology).

Adolescent↗

PubMed2002

Sieve plugs in fenestrae of glomerular capillaries--site of the filtration barrier?

The exact location of the filtration barrier of the glomerular capillary wall, which consists of an endothelium, a basement membrane and a visceral epithelium, has not yet been determined. Apparent discrepancies between different investigators in the past could be explained if postmortem artifactual tissue changes, due to subnormal blood pressure or anoxia, have taken place in the endothelium before the tissue and tracers have been sufficiently fixed and immobilized by the fixative. To test this supposition, a new method of fixation, which includes a technique to maintain a physiological perfusion pressure and a fixative composed of an oxygen-carrying blood substitute fluid containing glutaraldehyde, was employed combined with contrast enhancement. New observations of the glomerular capillary wall revealed that filamentous plugs (about 90 nm in height) filled the capillary fenestrae and a filamentous surface coat about 60 nm thick covered the interfenestral domains of the endothelial cell. Based on these purely morphological data, we dare to suggest that the fenestral plugs are the primary site of the glomerular filtration barrier - albeit highly speculative, nevertheless a logical location - and consequently that the glomerular filtration process is a 'tangential-flow' as opposed to a 'dead-end' filtration process. A tangential-flow filtration would minimize 'clogging' and 'concentration polarization' in the 'filter'.

Animals↗

PubMedDate not supplied

The endolymphatic sac: a scanning and transmission electron microscopy study.

A recent investigation has suggested that the chief cells of the endolymphatic sac produce an endogenous inhibitor of sodium resorption in the kidneys, tentatively named saccin. In the current study, the ultrastructure of the endolymphatic sac and in particular the chief cells are described to demonstrate that this organ fulfils the morphological criteria of a potential endocrine gland. Accordingly, the chief cells are shown to exhibit all the organelles and characteristics of cells that simultaneously synthesize, secrete, absorb and digest proteins.

Acid Phosphatase↗