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Biomedical subjects

B Smeets

Publications and source records attributed to B Smeets.

14 recordsLinked to original sources
PubMed2006

Proliferating cells in HIV and pamidronate-associated collapsing focal segmental glomerulosclerosis are parietal epithelial cells.

Collapsing focal segmental glomerulosclerosis (cFSGS) is characterized by hyperplasia of glomerular epithelial cells. In a mouse model of FSGS and in a patient with recurrent idiopathic FSGS, we identified the proliferating cells as parietal epithelial cells (PECs). In the present study, we have evaluated the origin of the proliferating cells in cFSGS associated with human immunodeficiency virus (HIV) and pamidronate. We performed a detailed study of glomerular lesions in biopsies of two patients with HIV-associated cFSGS and a nephrectomy specimen of a patient with pamidronate-associated cFSGS. Glomeruli were studied by serial sectioning using light and electron microscopy and immunohistochemistry to determine the epithelial cell phenotype. We used Synaptopodin, vascular endothelial growth factor, and CD10 as podocyte markers, CK8 and PAX2 as PEC markers and Ki-67 as marker of cell proliferation. The newly deposited extracellular matrix was characterized using antiheparan sulfate single-chain antibodies. The proliferating cells were negative for the podocyte markers, but stained positive for the PEC markers and the cell proliferation marker Ki-67. The proliferating PAX-2 and CK8 positive cells that covered the capillary tuft were always in continuity with PAX-2/CK8 positive cells lining Bowman's capsule. The matrix deposited by these proliferating cells stained identically to Bowman's capsule. Our study demonstrates that PECs proliferate in HIV and pamidronate-associated cFSGS. Our data do not support the concept of the proliferating, dedifferentiated podocyte.

AIDS-Associated Nephropathy↗
PubMed2006

Blue five-level frequency-upconversion system in rubidium.

We demonstrate production of continuous coherent blue laser light by using a five-level system in rubidium vapor. Two low-power lasers, at 780 and 776 nm, induce strong atomic coherence in the 5S-5P-5D states. The atoms decay to the 6P excited state, from which stimulated emission produces a coherent blue (420 nm) beam. We have coupled both ground-state hyperfine levels, effecting coherence between four levels. The coherent blue output is enhanced by several mechanisms, including stronger coupling to a larger fraction of the atomic population, operation at a detuning such that the vapor is nominally transparent to the 780 nm pump field, reduced losses owing to optical pumping, and optimal phase matching. We report experimental findings and compare them with results from a semiclassical Maxwell-Bloch model.

Journal Article↗
PubMed2006

Lessons from studies on focal segmental glomerulosclerosis: an important role for parietal epithelial cells?

Glomerular diseases are caused by multiple mechanisms. Progressive glomerular injury is characterized by the development of segmental or global glomerulosclerosis independent of the nature of the underlying renal disease. Most studies on glomerular disease focus on the constituents of the filtration barrier (podocytes, glomerular basement membrane (GBM), endothelial cells) or the mesangial cells. Little attention is given to the epithelial cells lining Bowman's capsule, the so called parietal epithelial cells (PECs). This 'lack of attention' is partly explained by the presumed 'passive' function of PECs, which are large, flattened cells that cover Bowman's capsule in a single cell layer and form a barrier between the ultrafiltrate and the periglomerular interstitium, in normal glomerular physiology. A more important reason has been the lack of an established primary role for the parietal epithelium in glomerular diseases. However, in recent years, several studies have demonstrated that PECs are involved in extracapillary proliferation. In addition, PECs can become highly active, proliferating cells, expressing many growth factors, chemokines, cytokines, and their receptors. It was recently demonstrated that PECs also play a part in the development of focal segmental glomerulosclerosis (FSGS). This review summarises current knowledge of the PEC, with emphasis on the role of PECs in the development of FSGS.

Animals↗
PubMed2002

Magnetic nanodots from atomic Fe: can it be done?

Laser focusing of Fe atoms offers the possibility of creating separate magnetic structures on a scale of 10 nm with exact periodicity. This can be done by using the parabolic minima of the potential generated by a standing light wave as focusing lenses. To achieve the desired 10-nm resolution, we need to suppress chromatic and spherical aberrations, as well as prevent structure broadening caused by the divergence of the incoming beam. Chromatic aberrations are suppressed by the development of a supersonic Fe beam source with speed ratio S = 11 +/- 1. This beam has an intensity of 3 x 10(15) atoms sr(-1) s(-1). The spherical aberrations of the standing light wave will be suppressed by aperturing with beam masks containing 100-nm slits at 744-nm intervals. The beam divergence can be reduced by application of laser cooling to reduce the transverse velocity. We have constructed a laser system capable of delivering over 500 mW of laser light at 372 nm, the wavelength of the (5)D(4) --> (5)F(5) atomic transition of (56)Fe we intend to use for laser cooling. Application of polarization spectroscopy to a hollow cathode discharge results in a locking system holding the laser continuously within 2 MHz of the desired frequency.

Journal Article↗
PubMed2001

Changes in mRNA expression profile underlie phenotypic adaptations in creatine kinase-deficient muscles.

We have studied the mechanisms that regulate the remodeling of the glycolytic, mitochondrial and structural network of muscles of creatine kinase M (M-CK)/sarcomeric mitochondrial creatine kinase (ScCKmit) knockout mice by comparison of wild-type and mutant mRNA profiles on cDNA arrays. The magnitudes of changes in mRNA levels were most prominent in M-CK/ScCKmit (CK(-/-)) double mutants but did never exceed those of previously observed changes in protein level for any protein examined. In gastrocnemius of CK(-/-) mice we measured a 2.5-fold increase in mRNA level for mitochondrial encoded cytochrome c oxidase (COX)-III which corresponds to the increase in protein content. The level of the nuclear encoded mRNAs for COX-IV, H(+)-ATP synthase-C, adenine nucleotide translocator-1 and insulin-regulatable glucose transporter-4 showed a 1.5-fold increase, also in agreement with protein data. In contrast, no concomitant up-regulation in mRNA and protein content was detected for the mitochondrial inorganic phosphate-carrier, voltage-dependent anion channel and certain glycolytic enzymes. Our results reveal that regulation of transcript level plays an important role, but it is not the only principle involved in the remodeling of mitochondrial and cytosolic design of CK(-/-) muscles.

Adaptation, Physiological↗
PubMed1997

Nd:YAG laser posterior hyaloidotomy for the treatment of a premacular vitreous floater.

A 63-year old man, with a large central vitreous floater, underwent a Nd:YAG laser posterior hyaloidotomy. Although the vitreous floater disappeared from the central optical axis, visual acuity did not improve. Microperimetry performed with the SLO revealed an absolute scotoma, which corresponded well in shape and dimension with the original vitreous floater. This finding suggests that a fragment of the neurosensory retina became detached together with the internal limiting membrane in the process of the vitreous collapse.

Aluminum Silicates↗
PubMed1996

[Use of the computer in dentistry: video superimposition and facial reproduction using the expedience of the computer interface].

Both video superimposition and computer facial reproduction play a useful role in the process of identification, particularly in the early stages of an investigation or when other more definitive methods may not be available. Video superimposition combined with a computer overlay technique can be used to establish whether a skull outline matches an image of a missing person, being a photograph, slide or videoimage. A computer driven robot can be used to simplify the alignment of the skull with the position of the head on the image. Craniofacial or facial reproduction are used in both 2D or 3D to produce an image which can be used for identification purposes.

Computer Graphics↗
PubMed1994

Learning phacoemulsification: the surgeon-in-training.

With the increasing trend towards phacoemulsification a perceived increased complication rate during the learning curve gives rise to a dilemma as to the best stage at which a surgeon-in-training can safely learn the technique. We prospectively analysed the complications and visual outcome of the first 160 phacoemulsification procedures performed by three surgeons-in-training. The main outcome measures included posterior capsule tear, vitreous and nuclear loss, surgical re-intervention rate and visual outcome. Posterior capsule tear occurred in 7 eyes (4.4%) and vitreous loss in 6 (3.8%). No nucleus was lost in the vitreous. Surgical re-intervention was required in 1 eye. Best corrected visual acuity was 6/12 or better in 88% of eyes. These results compare favourably with reports of surgeons-in-training learning extracapsular surgery and also with recently reported phacoemulsification series. This study indicates that with careful case selection and supervision phacoemulsification can be a safe procedure.

Aged↗
PubMed1993

Learning phaco in a teaching environment.

We prospectively analysed the complications and visual outcome of the first 160 phacoemulsification procedures performed by three surgeons in training under supervision. The main complications were posterior capsular tear (4,35%), vitreous loss (3,3%), nuclear loss (none) and surgical reintervention (one). Postoperative visual acuity was 0,7 or better in 94% of eyes without pre-existing pathology. Only one eye did not have a posterior chamber lens implanted.

Cataract Extraction↗
PubMed1991

ABO bloodgrouping on tooth material.

The ABO bloodgroup was determined on the pulp, dentin and enamel of 35 teeth using the adsorption-elution technique. A bloodstained compress from the extraction wound was used as the reference sample. Twenty teeth were examined within 6 weeks after extraction and fifteen teeth were examined 6-10 months after extraction. It was found, that bloodgrouping on pulp gives fairly good results, whereas the possibilities for correct bloodgrouping seem to be limited for dentin and debatable for enamel. Similar results were found in both groups of teeth.

ABO Blood-Group System↗
PubMed1989

Definition of subchromosomal intervals around the myotonic dystrophy gene region at 19q.

The localization to 19q of the gene causing myotonic dystrophy (DM) has been defined more precisely by refinement of the physical location of several linked markers. A somatic cell hybrid mapping panel from cells with t(1;19), t(12;19), and t(X;19) translocation products was constructed to define five different intervals across 19q. In addition, we have derived a series of cell hybrids by irradiation of a der(19)-only hybrid to further subdivide the cen-q13.1 region. Using an array of 36 cloned genes, anonymous DNAs, and enzyme markers, we have tested the location of the panel breakpoints and refined the regional assignment of several of these markers. All markers tightly linked to DM are localized mainly within 19q13.2, thus suggesting that the DM gene is also close to this region.

Animals↗
PubMed1988

Tight linkage between myotonic dystrophy and apolipoprotein E genes revealed with allele-specific oligonucleotides.

In 16 families with myotonic dystrophy (DM) a novel approach based on use of allele-specific oligonucleotides has been employed to study the linkage relationship between the apolipoprotein E (APOE) gene and DM. Synthetic oligonucleotides, designed to discriminate between APOE alleles epsilon 3 and epsilon 4, enabled us to distinguish heterozygous carriers in a hybridization assay. In a subset of families, the relevant segment of the APOE gene was enzymatically amplified to increase the sensitivity of the method. For DM and APOE, a maximum lod score (zmax of 7.47 was obtained at a recombination frequency (theta) of 0.047 (male theta = female theta). No recombination (maximum lod score of 5.61 at theta = 0.0) was found between APOE and the apolipoprotein CII (APOC2) gene. These results suggest that, in addition to APOC2, APOE is a useful marker for presymptomatic DM diagnosis.

Alleles↗