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Biomedical subjects

Michael Schubert

Publications and source records attributed to Michael Schubert.

17 recordsLinked to original sources
PubMed2006

Transforaminal posterolateral endoscopic discectomy with or without the combination of a low-dose chymopapain: a prospective randomized study in 280 consecutive cases.

STUDY DESIGN: A prospective randomized study involving 280 consecutive cases of lumbar disc herniation managed either by an endoscopic discectomy alone or an endoscopic discectomy combined with an intradiscal injection of a low dose (1000 U) of chymopapain. OBJECTIVE: To compare outcome, complications, and reherniations of both techniques. SUMMARY OF BACKGROUND DATA: Despite a low complication rate, posterolateral endoscopic nucleotomy has made a lengthy evolution because of an assumed limited indication. Chemonucleolysis, however, proven to be safe and effective, has not continued to be accepted by the majority in the spinal community as microdiscectomy is considered to be more reliable. METHOD: A total of 280 consecutive patients with a primary herniated, including sequestrated, lumbar disc with predominant leg pain, was randomized. A clinical follow-up was performed at 3 months, and at 1 and 2 years after the index operation with an extensive questionnaire, including the visual analog scale for pain and the MacNab criteria. The cohort integrity at 3 months was 100%, at 1 year 96%, and at 2 years 92%. RESULTS: At the 3-month evaluation, only minor complications were registered. At 1-year postoperatively, group 1 (endoscopy alone) had a recurrence rate of 6.9% compared to group 2 (the combination therapy), with a recurrence rate of 1.6%, which was a statistically significant difference in favor of the combination therapy (P = 0045). At the 2-year follow-up, group 1 reported that 85.4% had an excellent or good result, 6.9% a fair result, and 7.7% were not satisfied. At the 2-year follow-up, group 2 reported that 93.3% had an excellent or good result, 2.5% a fair result, and 4.2% were not satisfied. This outcome was statistically significant in favor of the group including chymopapain. There were no infections or patients with any form of permanent iatrogenic nerve damage, and no patients had a major complication. CONCLUSIONS: A high percentage of patient satisfaction could be obtained with a posterior lateral endoscopic discectomy for lumbar disc herniation, and a statistically significant improvement of the results was obtained when an intradiscal injection of 1000 U of chymopapain was added. There was a low recurrence rate with no major complications. The method can be applied in any type of lumbar disc herniation, including the L5-S1 level.

Adult↗
PubMed2006

Radon as a naturally occurring tracer for the assessment of residual NAPL contamination of aquifers.

The noble gas radon has a strong affinity to non-aqueous phase-liquids (NAPLs). That property makes it applicable as naturally occurring partitioning tracer for assessing residual NAPL contamination of aquifers. In a NAPL contaminated aquifer, radon dissolved in the groundwater partitions preferably into the NAPL. The magnitude of the resulting radon deficit in the groundwater depends on the NAPL-specific radon partition coefficient and on the NAPL saturation of the pore space. Hence, if the partition coefficient is known, the NAPL saturation is attainable by determination of the radon deficit. After a concise discussion of theoretical aspects regarding radon partitioning into NAPL, related experimental data and results of a field investigation are presented. Aim of the laboratory experiments was the determination of radon partition coefficients of multi-component NAPLs of environmental concern. The on-site activities were carried out in order to confirm the applicability of the "radon method" under field conditions.

Environmental Pollutants↗
PubMed2006

A retinoic acid-Hox hierarchy controls both anterior/posterior patterning and neuronal specification in the developing central nervous system of the cephalochordate amphioxus.

Retinoic acid (RA) mediates both anterior/posterior patterning and neuronal specification in the vertebrate central nervous system (CNS). However, the molecular mechanisms downstream of RA are not well understood. To investigate these mechanisms, we used the invertebrate chordate amphioxus, in which the CNS, although containing only about 20,000 neurons in adults, like the vertebrate CNS, has a forebrain, midbrain, hindbrain, and spinal cord and is regionalized by RA-signaling. Here we show, first, that domains of genes with expression normally limited to diencephalon and midbrain are generally not affected by altered RA-signaling, second, that contrary to previous reports, not only Hox1, 3, and 4, but also Hox2 and Hox6 are collinearly expressed in the amphioxus CNS, and third, that collinear expression of all these Hox genes is controlled by RA-signaling. Finally, we show that Hox1 is involved in mediating both the role of RA-signaling in regionalization of the hindbrain and in specification of hindbrain motor neurons. Thus, morpholino knock-down of the single amphioxus Hox1 mimics the effects of treatments with an RA-antagonist. This analysis establishes RA-dependent regulation of collinear Hox expression as a feature common to the chordate CNS and indicates that the RA-Hox hierarchy functions both in proper anterior/posterior patterning of the developing CNS and in specification of neuronal identity.

Animals↗
PubMed2006

Retinoic acid signaling and the evolution of chordates.

In chordates, which comprise urochordates, cephalochordates and vertebrates, the vitamin A-derived morphogen retinoic acid (RA) has a pivotal role during development. Altering levels of endogenous RA signaling during early embryology leads to severe malformations, mainly due to incorrect positional codes specifying the embryonic anteroposterior body axis. In this review, we present our current understanding of the RA signaling pathway and its roles during chordate development. In particular, we focus on the conserved roles of RA and its downstream mediators, the Hox genes, in conveying positional patterning information to different embryonic tissues, such as the endoderm and the central nervous system. We find that some of the control mechanisms governing RA-mediated patterning are well conserved between vertebrates and invertebrate chordates, such as the cephalochordate amphioxus. In contrast, outside the chordates, evidence for roles of RA signaling is scarce and the evolutionary origin of the RA pathway itself thus remains elusive. In sum, to fully understand the evolutionary history of the RA pathway, future research should focus on identification and study of components of the RA signaling cascade in non-chordate deuterostomes (such as hemichordates and echinoderms) and other invertebrates, such as insects, mollusks and cnidarians.

Animals↗
PubMed2006

Amphioxus and tunicates as evolutionary model systems.

One important question in evolutionary biology concerns the origin of vertebrates from invertebrates. The current consensus is that the proximate ancestor of vertebrates was an invertebrate chordate. Today, the invertebrate chordates comprise cephalochordates (amphioxus) and tunicates (each a subphylum in the phylum Chordata, which also includes the vertebrate subphylum). It was widely accepted that, within the chordates, tunicates represent the sister group of a clade of cephalochordates plus vertebrates. However, recent studies suggest that the evolutionary positions of tunicates and cephalochordates should be reversed, the implications of which are considered here. We also review the two major groups of invertebrate chordates and compare relative advantages (and disadvantages) of each as model systems for elucidating the origin of the vertebrates.

Animals↗
PubMed2005

[A 90-year-old woman with acute abdomen].

Bowel strangulation is defined as mechanical obstruction associated with compromised blood circulation of the bowel wall. Delayed diagnosis and treatment are the main causes of the high mortality. A 90-year-old woman was admitted to our hospital with acute abdominal pain. Plain abdominal x-ray studies were inconclusive. However, bowel strangulation was suggested by computer tomography and the diagnosis was confirmed under the laparotomy. In the case of bowel strangulation, abdominal CT is a fast, reliable and useful diagnostic tool when imaging is considered necessary before a laparotomy.

Abdomen, Acute↗
PubMed2005

Nuclear beta-catenin promotes non-neural ectoderm and posterior cell fates in amphioxus embryos.

In vertebrate development, Wnt/beta-catenin signaling has an early role in specification of dorsal/anterior identity and a late one in posterior specification. To understand the evolution of these roles, we cloned beta-catenin from the invertebrate chordate amphioxus. The exon/intron organization of beta-catenin is highly conserved between amphioxus and other animals including a cnidarian, but not Drosophila. In development, amphioxus beta-catenin is concentrated in all nuclei from the 16-cell stage until the onset of gastrulation when it becomes undetectable in presumptive mesendoderm. Li(+), which up-regulates Wnt/beta-catenin signaling, had no detectable effect on axial patterning when applied before the late blastula stage, suggesting that a role for beta-catenin in specification of dorsal/anterior identity may be a vertebrate innovation. From the mid-gastrula through the neurula stage, the highest levels of nuclear beta-catenin are around the blastopore. In the early neurula, beta-catenin is down-regulated in the neural plate, but remains high in adjacent non-neural ectoderm. Embryos treated with Li(+) at the late blastula stage are markedly posteriorized and lack a neural plate. These results suggest that in amphioxus, as in vertebrates, down-regulation of Wnt/beta-catenin signaling in the neural plate is necessary for maintenance of the neuroectoderm and that a major evolutionarily conserved role of Wnt/beta-catenin signaling is to specify posterior identity and pattern the anterior/posterior axis.

Animals↗
PubMed2005

Endoscopic transforaminal nucleotomy with foraminoplasty for lumbar disk herniation.

OBJECTIVE: Removal of a sequestered lumbar disk; in instances of foraminal stenosis a decompression (foraminoplasty) can also be performed. The objective is to restore the best possible pain-free function of the spinal column. INDICATIONS: Prolapsed lumbar vertebral disk, sequestered caudally or cranially, that is no longer responding to nonoperative treatment. Cauda equina syndrome. CONTRAINDICATIONS: Sequestered herniated lumbar disk posterior to the dura mater. SURGICAL TECHNIQUE: Lateral decubitus on a radiolucent table allowing the use of an image intensifier. The usual access to a sequester at segments L5/S1 and L4/5 is approximately 12-14 cm lateral to the midline, at segments L3/4 and L2/3 approximately 10 cm lateral to the midline. In the case of sequestration in a cranial direction a somewhat smaller angle of access should be chosen, for caudal displacement the angle should be greater. Reaming of a lateral transforaminal approach to the spinal canal. The sequester is removed endoscopically through a working cannula. POSTOPERATIVE MANAGEMENT: The patient remains in the recovery room for approximately 2 h, is fitted with a brace and transferred to the ward. No medicinal thrombosis prophylaxis. Follow-up examination the next morning. Physiotherapy after 1 week. The brace is worn for approximately 2-6 weeks. MRI checkup and after 3 months evaluation of the development of strength and the state of the back musculature. RESULTS: Between January 1999 and January 2002, 611 patients underwent surgery, 32% women and 68% men, age between 18 and 65 years (average age 43.8 years). Clinical follow-up examinations were carried out after 3 months, follow-ups with questionnaire after 1 and 2 years. The evaluation criteria were based on an own questionnaire, and also on MacNab's score and the visual analog scale (VAS). After 2 years 558 patients (91.2%) responded to the questionnaires. Excellent or good results were achieved in 95.3% of the patients. 74.7% were very satisfied, 20.6% satisfied. The result was judged unsatisfactory by 4.7% of patients (less satisfied 3.9%, unsatisfied 0.8%). The numbness of the leg, present in 448 patients preoperatively, was either no longer present (63.9%) or had improved (30.3%). There were no serious complications, in particular no infections. The recurrence rate was 3.6%.

Adolescent↗
PubMed2004

Retinoic acid signaling acts via Hox1 to establish the posterior limit of the pharynx in the chordate amphioxus.

In the invertebrate chordate amphioxus, as in vertebrates, retinoic acid (RA) specifies position along the anterior/posterior axis with elevated RA signaling in the middle third of the endoderm setting the posterior limit of the pharynx. Here we show that AmphiHox1 is also expressed in the middle third of the developing amphioxus endoderm and is activated by RA signaling. Knockdown of AmphiHox1 function with an antisense morpholino oligonucleotide shows that AmphiHox1 mediates the role of RA signaling in setting the posterior limit of the pharynx by repressing expression of pharyngeal markers in the posterior foregut/midgut endoderm. The spatiotemporal expression of these endodermal genes in embryos treated with RA or the RA antagonist BMS009 indicates that Pax1/9, Pitx and Notch are probably more upstream than Otx and Nodal in the hierarchy of genes repressed by RA signaling. This work highlights the potential of amphioxus, a genomically simple, vertebrate-like invertebrate chordate, as a paradigm for understanding gene hierarchies similar to the more complex ones of vertebrates.

Animals↗
PubMed2004

Preliminary observations on the spawning conditions of the European amphioxus (Branchiostoma lanceolatum) in captivity.

Members of the subphylum Cephalochordata, which include the genus Branchiostoma (i.e. amphioxus), represent the closest living invertebrate relatives of the vertebrates. To date, developmental studies have been carried out on three amphioxus species (the European Branchiostoma lanceolatum, the East Asian B. belcheri, and Floridian-Caribbean B. floridae). In most instances, adult animals have been collected from the field during their ripe season and allowed (or stimulated) to spawn in the laboratory. In any given year, dates of laboratory pawning have been limited by two factors. First, natural populations of these three most studied species of amphioxus are ripe, at most, for only a couple of months each year and, second, even when apparently ripe, animals spawn only at unpredictable intervals of every several days. This limited supply of living material hinders the development of amphioxus as a model system because this limitation makes it more difficult to work out protocols for new laboratory techniques. Therefore we are developing laboratory methods for increasing the number of amphioxus spawning dates per year. The present study found that a Mediterranean population of B. lanceolatum living near the Franco-Spanish border spawned naturally at the end of May and again at the end of June in 2003. Re-feeding experiments in the laboratory demonstrated that the gonads emptied at the end of May refilled with gametes by the end of June. We also found that animals with large gonads (both, obtained from the field and kept and fed at the laboratory during several weeks) could be induced to spawn in the laboratory out of phase with the field population if they were temperature shocked (spawning occurred 36 hours after a sustained increase in water temperature from 19 degrees C to 25 degrees C).

Animal Husbandry↗
PubMed2004

Retinoic acid influences anteroposterior positioning of epidermal sensory neurons and their gene expression in a developing chordate (amphioxus).

In developing chordates, retinoic acid (RA) signaling patterns the rostrocaudal body axis globally and affects gene expression locally in some differentiating cell populations. Here we focus on development of epidermal sensory neurons in an invertebrate chordate (amphioxus) to determine how RA signaling influences their rostrocaudal distribution and gene expression (for AmphiCoe, a neural precursor gene; for amphioxus islet and AmphiERR, two neural differentiation genes; and for AmphiHox1, -3, -4, and -6). Treatments with RA or an RA antagonist (BMS009) shift the distribution of developing epidermal neurons anteriorly or posteriorly, respectively. These treatments also affect gene expression patterns in the epidermal neurons, suggesting that RA levels may influence specification of neuronal subtypes. Although colinear expression of Hox genes is well known for the amphioxus central nervous system, we find an unexpected comparable colinearity for AmphiHox1, -3, -4, and -6 in the developing epidermis; moreover, RA levels affect the anteroposterior extent of these Hox expression domains, suggesting that RA signaling controls a colinear Hox code for anteroposterior patterning of the amphioxus epidermis. Thus, in amphioxus, the developing peripheral nervous system appears to be structured by mechanisms parallel to those that structure the central nervous system. One can speculate that, during evolution, an ancestral deuterostome that structured its panepidermal nervous system with an RA-influenced Hox code gave rise to chordates in which this patterning mechanism persisted within the epidermal elements of the peripheral nervous system and was transferred to the neuroectoderm as the central nervous system condensed dorsally.

Animals↗
PubMed2004

New method for estimating bacterial cell abundances in natural samples by use of sublimation.

We have developed a new method based on the sublimation of adenine from Escherichia coli to estimate bacterial cell counts in natural samples. To demonstrate this technique, several types of natural samples, including beach sand, seawater, deep-sea sediment, and two soil samples from the Atacama Desert, were heated to a temperature of 500 degrees C for several seconds under reduced pressure. The sublimate was collected on a cold finger, and the amount of adenine released from the samples was then determined by high-performance liquid chromatography with UV absorbance detection. Based on the total amount of adenine recovered from DNA and RNA in these samples, we estimated bacterial cell counts ranging from approximately 10(5) to 10(9) E. coli cell equivalents per gram. For most of these samples, the sublimation-based cell counts were in agreement with total bacterial counts obtained by traditional DAPI (4,6-diamidino-2-phenylindole) staining.

Adenine↗
PubMed2003

Differential mesodermal expression of two amphioxus MyoD family members (AmphiMRF1 and AmphiMRF2).

To explore the evolution of myogenic regulatory factors in chordates, we isolated two MyoD family genes (AmphiMRF1 and AmphiMRF2) from amphioxus. AmphiMRF1 is first expressed at the late gastrula in the paraxial mesoderm. As the first somites form, expression is restricted to their myotomal region. In the early larva, expression is strongest in the most anterior and most posterior somites. AmphiMRF2 transcription begins at mid/late gastrula in the paraxial mesoderm, but never spreads into its most anterior region. Through much of the neurula stage, AmphiMRF2 expression is strong in the myotomal region of all somites except the most anterior pair; by late neurula expression is downregulated except in the most posterior somites forming just rostral to the tail bud. These two MRF genes of amphioxus have partly overlapping patterns of mesodermal expression and evidently duplicated independent of the diversification of the vertebrate MRF family.

Animals↗
PubMed2002

Direct isolation of purines and pyrimidines from nucleic acids using sublimation.

A sublimation technique was developed to isolate purines and pyrimidines directly from lambda-deoxyribonucleic acid (lambda-DNA) and Escherichia coli cells. The sublimation of adenine, cytosine, guanine, and thymine from lambda-DNA was tested under reduced pressure (approximately 0.5 Torr) at temperatures of >150 degrees C. With the exception of guanine, approximately 60-75% of each base was sublimed directly from the lambda-DNA and recovered on a coldfinger of the sublimation apparatus after heating to 450 degrees C. Several nucleobases including adenine, cytosine, thymine, and uracil were also recovered from E. coli bacteria after heating the cells to the same temperature, although some thermal decomposition of the bases also occurred. These results demonstrate the feasibility of using sublimation to isolate purines and pyrimidines from native E. coli DNA and RNA without any chemical treatment of the cells.

Chromatography, High Pressure Liquid↗
PubMed2002

Functional equivalency of amphioxus and vertebrate Pax258 transcription factors suggests that the activation of mid-hindbrain specific genes in vertebrates occurs via the recruitment of Pax regulatory elements.

Pax genes encode transcription factors that control key developmental decisions in various animal phyla. The Pax2/5/8 subfamily plays a key role in specification and/or maintenance of vertebrate mid-hindbrain boundary (MHB) region by directly regulating expression of other genes, most notably En2. In the invertebrate chordate amphioxus, expression of AmphiPax2/5/8 is found in many sites that are homologous to the regions of the vertebrate embryo expressing orthologous genes Pax2, Pax5 or Pax8. However, no co-expression of AmphiPax2/5/8 and AmphiEn is detected in the region of the neural tube that might correspond to the vertebrate MHB. Based on this observation and the absence of AmphiWnt expression in this region it appears that amphioxus does not have a MHB. Here we investigated the possibility that the AmphiPax2/5/8, as a key component of MHB development, has lost some of the properties of its vertebrate counterparts. We have analyzed both the DNA-binding and transactivation properties of AmphiPax2/5/8 as well as its ability to interact with the groucho co-repressor. In all these assays AmphiPax2/5/8 is indistinguishable from the human Pax5. In addition, we found two alternatively spliced AmphiPax2/5/8 isoforms that function similarly to the alternatively spliced isoforms of human Pax8. Analysis of the AmphiEn regulatory region provided no evidence for AmphiPax2/5/8 binding and transactivation. Therefore, in amphioxus, AmphiPax2/5/8, although capable of performing all the necessary functions has not been recruited for a developmental mechanism which usually sets up MHB development in vertebrates.

3T3 Cells↗
PubMedDate not supplied

Expression of estrogen-receptor related receptors in amphioxus and zebrafish: implications for the evolution of posterior brain segmentation at the invertebrate-to-vertebrate transition.

Summary The evolutionary origin of vertebrate hindbrain segmentation is unclear since the amphioxus, the closest living invertebrate relative to the vertebrates, possesses a hindbrain homolog that displays no gross morphological segmentation. Three of the estrogen-receptor related (ERR) receptors are segmentally expressed in the zebrafish hindbrain, suggesting that their common ancestor was expressed in a similar, reiterated manner. We have also cloned and determined the developmental expression of the single homolog of the vertebrate ERR genes in the amphioxus (AmphiERR). This gene is also expressed in a segmented manner in a region considered homologous to the vertebrate hindbrain. In contrast to the expression of amphioxus islet (a LIM-homeobox gene that also labels motoneurons), AmphiERR expression persists longer in the hindbrain homolog and does not later extend to additional posterior cells. In addition, AmphiERR and one of its vertebrate homologs (ERRalpha) are expressed in the developing somitic musculature of amphioxus and zebrafish, respectively. Altogether, our results are consistent with fine structural evidence suggesting that the amphioxus hindbrain is segmented, and indicate that chordate ERR gene expression is a marker for both hindbrain and muscle segmentation. Furthermore, our data support an evolution model of chordate brain segmentation: originally, the program for anterior segmentation in the protochordate ancestors of the vertebrates resided in the developing axial mesoderm which imposed reiterated patterning on the adjacent neural tube; during early vertebrate evolution, this segmentation program was transferred to and controlled by the neural tube.

Amino Acid Sequence↗