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Biomedical subjects

B Schwab

Publications and source records attributed to B Schwab.

At least 37 records · Page 2Linked to original sources
PubMed2001

Image-guided surgery of the anterior skull base.

Minimally invasive surgical procedures have revolutionized surgery of the paranasal sinuses. The endonasal procedure has become standard practice due to a better understanding of pathological physiology. However, malformations, previous operations and bleeding can interfere greatly with intraoperative orientation. Together with microscopy and endoscopy, image-guided surgery has the potential to be of significant assistance to the surgeon. We evaluated the electromagnetic navigation system InstaTrak 2000 (Visualization Technologies Inc., Lawrence, MA) in 168 patients with various disorders of the paranasal sinuses who underwent endonasal surgery. The system consists of a headset attached to an electronic transmitter which is fitted on the dorsum of the nose and in the external auditory canal. With the aid of low-frequency magnetic fields the position of the instrument equipped with an electromagnetic receiver is calculated on the basis of the reaction of ferromagnetic components in the magnetic field; the location is displayed in orthogonal sections on a high resolution screen. The intraoperative accuracy of the system was estimated to be 1.2-2.8 mm. The preparation time amounted to < 10 min. No system failures were observed. The InstaTrak 2000 navigation system is only suitable for endonasal surgery. The placement of the electromagnetic transmitter and receiver allows flexible head positioning through the use of a headset. This system is a valuable aid for the surgeon under anatomically complex conditions. The technology also lends itself well to training purposes, as visualization in different sectional planes augments the understanding of anatomy and pathological anatomy.

Adult↗
PubMed2000

Trichome morphogenesis in Arabidopsis.

Trichomes (plant hairs) in Arabidopsis thaliana are large non-secreting epidermal cells with a characteristic three-dimensional architecture. Because trichomes are easily accessible to a combination of genetic, cell biological and molecular methods they have become an ideal model system to study various aspects of plant cell morphogenesis. In this review we will summarize recent progress in the understanding of trichome morphogenesis.

Arabidopsis↗
PubMed2000

Magnesium sulfate potentiates morphine antinociception at the spinal level.

UNLABELLED: Intrathecal magnesium sulfate coinfusion with morphine increases antinociception in normal rats; however, because magnesium also delays the onset of tolerance, it is not clear whether this additional antinociception is a result of potentiated analgesia or tolerance abatement. We examined the antinociceptive interaction of intrathecal (IT) bolus magnesium sulfate and morphine in morphine naive rats and those with mechanical allodynia after a surgical incision. After intrathecal catheter implantation, rats were given preinjections of magnesium or saline, followed by injections of morphine or saline. In morphine naïve rats, IT bolus magnesium sulfate 281 and 375 microg followed by IT morphine 0.25 or 0.5 nmol enhanced peak antinociception and area under the response versus time curve two-to-three-fold in the tail-flick test as compared with morphine alone. Likewise, in rats with incisional pain, IT bolus magnesium sulfate 188 and 375 microg followed by morphine 0.5 nmol reduced mechanical allodynia, whereas morphine 0.5 nmol alone did not. This study suggests that IT magnesium sulfate potentiates morphine at a spinal site of action. IMPLICATIONS: Magnesium sulfate potentiates morphine analgesia when coadministered intrathecally in normal rats, and in an animal model of mechanical allodynia after a surgical incision. These results suggest that intrathecal administration of magnesium sulfate may be a useful adjunct to spinal morphine analgesia.

Analgesics, Opioid↗
PubMed1999

Isolation of ethyl methanesulfonate-induced gametophytic mutants in Arabidopsis thaliana by a segregation distortion assay using the multimarker chromosome 1.

The life cycle of plants comprises two alternating generations, the diploid sporophyte (spore-bearing plant) and the haploid gametophyte (gamete-bearing plant). In contrast to animals, the postmeiotic cells give rise to haploid organisms whose function is to produce the gametes and to mediate fertilization. Analysis of gametophyte development and function has been hampered by the difficulty of identifying haplo-phase-specific mutants in conventional mutagenesis screens. Here we use a genetic strategy that is based on segregation distortion of nearby visible markers to screen for EMS-induced gametophytic mutants in Arabidopsis thaliana. Using the multiple marker chromosome mm1 we have isolated seven lines that displayed an altered segregation of markers. Reciprocal backcrosses of these lines showed a marked reduction of the transmission of the male and/or female gametes. Phenotypic analysis revealed that different aspects of either gametophytic development or function were affected. Three male gametophytic lines showed specific arrests during pollen development. One male gametophytic line was specifically defective in pollen tube elongation. Three gametophytic lines showed variable defects in both male and female gametophytic development.

Arabidopsis↗
PubMed1999

Generation of a spacing pattern: the role of triptychon in trichome patterning in Arabidopsis.

Trichomes in Arabidopsis are single-celled hairs that exhibit a regular spacing pattern. Here, the role of TRIPTYCHON (TRY) in the generation of this spacing pattern is studied. By using genetic mosaics, we demonstrate that the formation of trichome clusters in try mutants is not correlated with cell lineage, indicating that TRY is required to single out trichome cells in a process involving cellular interactions. The genetic interactions of TRY, GLABRA1 (GL1), and TRANSPARENT TESTA GLABRA (T TG) in trichome patterning are assessed by determining the cluster frequency in various genetic combinations. It is shown that TRY acts as a negative regulator of GL1- and TTG-dependent pathways. Furthermore, it is demonstrated that trichome initiation in ttg-1, a strong ttg allele, is rescued almost to wild-type levels in a try background in which GL1 is expressed under the control of the cauliflower mosaic virus 35S promoter, indicating that T TG acts upstream of GL1 and TRY. These findings are incorporated into a model to explain the generation of a trichome spacing pattern from a homogeneous population of epidermal cells.

Arabidopsis↗
PubMed1998

[Myoclonus].

Explore the source record for details and available documents.

Diagnosis, Differential↗
PubMed1996

Statistical analysis of possible bias of clinical judgements due to observing an on-therapy marker variable.

In certain double-blind clinical trials there is the possibility that certain 'marker variables' observable during the trial may in part unblind the trial, even at a subliminal level. At issue is whether or not this potential unblinding biases the investigators' clinical efficacy assessments. This issue arose after the completion of three clinical trials that compared tretinoin emollient cream (TEC) 0.05 per cent to its vehicle in patients with photodamaged skin. The question raised was whether or not possible 'subliminal unblinding' of the investigators and patients, due to the cutaneous irritation associated with topical tretinoin, might have caused a treatment bias in the study. To address this issue, we undertook a reanalysis of these three clinical trials. In doing so, we develop in this paper a statistical modelling approach to address issues of possible bias introduced by the ability to observe such marker variables. The approach utilizes a linear discriminant analysis to introduce an auxiliary categorical variable for the efficacy analysis. A suitable categorical data model permits the estimation of relevant bias effects. We illustrate this approach with data from the three TEC 0.05 per cent trials.

Bias↗
PubMed1996

The role of self-help programs in the rehabilitation of persons with severe mental illness and substance use disorders.

Substance abuse treatment programs in the United States frequently incorporate self-help approaches, but little is known about the use of self-help groups by individuals with dual disorders. This paper brings together several current studies on the role of self-help programs in treating substance use disorders among individuals with severe mental illness. These studies indicate that only a minority of individuals with dual disorders become closely linked to self-help. Psychiatric diagnosis and possibly social skills are correlates of participation. Dually disorders consumers often experience the use of 12-step philosophy and jargon by mental health professionals as alienating and unempathic. The authors propose suggestions for incorporating self-help approaches into the comprehensive community care of individuals with dual disorders.

Alcoholism↗
PubMed1996

Histologic evaluation of the long term effects of tretinoin on photodamaged skin.

Sustained improvement with prolonged topical tretinoin for photodamaged skin has been well documented for up to 22 months of continuous treatment. We now report long-term (4 years) histologic effects of topical tretinoin in photodamaged skin of 27 patients, the longest study to date. The observed decreases in dermal elastin content and perivascular inflammation and increase in epidermal mucin in facial biopsies obtained after up to 4 years of treatment may be partly responsible for the continued clinical improvement. Furthermore, the study shows that there are no untoward effects on keratinocytes or melanocytes during long-term use of topical tretinoin.

Double-Blind Method↗
PubMed1995

A new system for fallopian tube sperm perfusion leads to pregnancy rates twice as high as standard intrauterine insemination.

OBJECTIVE: To evaluate the relative efficacy of a new system for fallopian tube sperm perfusion in comparison with standard IUI in controlled ovarian hyperstimulation (COH) cycles. DESIGN: Prospective randomized trial. SETTING: Ovulation induction program of a tertiary outpatient care center, Hôpital Antoine Béclère, Clamart, France. PATIENTS: We studied 74 infertile women aged 20 to 38 years undergoing 100 cycles of COH from December 1993 to May 1994 only excluding cases of age > 38 years, obstructed or severely damaged fallopian tubes, E2 levels per mature follicle < 250 pg/mL (conversion factor to SI unit, 3.671) on the day of hCG administration, spontaneous LH surge, and cases of marked sperm abnormalities. INTERVENTIONS: Controlled ovarian hyperstimulation was achieved using three types of ovarian stimulation protocols: clomiphene citrate (CC) and hMG (n = 35). hMG alone (n = 35) or GnRH agonist and FSH and hMG (n = 30). Thirty-six hours after hCG administration, patients were assigned randomly to either IUI (group A, n = 50) or fallopian tube sperm perfusion (group B, n = 50). Intrauterine insemination was performed with 0.2 mL of sperm suspension according to a standard technique. Fallopian tube sperm perfusion was performed using a simple and reliable system that ensures a good cervical seal and allows to a pressurized injection of 4 mL of sperm suspension. MAIN OUTCOME MEASURES: Feasibility of the fallopian tube sperm perfusion method, clinical pregnancy (presence of gestational sac with heart beats at 6 weeks of amenorrhea), and ongoing pregnancy rates (PRs) (> 12 weeks of amenorrhea), incidence of complications (multiple pregnancies and ovarian hyperstimulation syndrome [OHSS]). RESULTS: Overall, the new fallopian tube sperm perfusion system was simple to handle and well tolerated by patients. In group A, we observed 10 clinical pregnancies (20% per cycle) of which 7 were ongoing (14%). In group B, 20 clinical pregnancies (40% per cycle) of which 17 ongoing pregnancies (34%) were obtained. These differences were statistically significant. The prevalence of twin and three or more sac pregnancies was similar in the two groups (3/10 and 0/10, respectively, in group A, and 5/20 and 2/20, respectively, in group B). No case of moderate or severe OHSS was observed in this series. CONCLUSIONS: Our results indicate that the new system for fallopian tube sperm perfusion is not only simple and reliable but also may lead to PRs twice as high as standard IUI in COH cycles.

Adult↗
PubMed1995

Nasotracheal airway-oropharyngeal alimentary canal: a microvascular technique for reconstruction of the upper airway after total laryngectomy.

Every patient who has to be laryngectomized because of a carcinoma is concerned with the loss of his or her voice and the presence of a permanent tracheostoma in his or her neck. While various methods for producing a substitute voice are available (esophageal voice, voice devices, voice-shunt operations with or without voice prosthesis), it is usually impossible after laryngectomy to reconstruct a complete upper airway so that the tracheostoma can be closed. One potential method for reconstruction of the airway is its division into a nasotracheal airway and an oropharyngeal alimentary canal. Ten Alsatian dogs were laryngectomized, and a microvascularly anastomosed jejunal autograft was inserted as a junction between the tracheal stump and the circularly exposed nasopharynx, while the pharynx was reconstructed separately. One week postoperatively, oral feeding could be started again; at the same time breathing was possible via the reconstructed nasotracheal airway, which was kept open by insertion of a silicone tube. By means of this microvascular technique, a complete nasal airway could be reconstructed surgically after laryngectomy.

Anastomosis, Surgical↗
PubMed1994

Lipolysaccharide-induced monocyte retention in the lung. Role of monocyte stiffness, actin assembly, and CD18-dependent adherence.

Blood monocytes and monocyte-derived macrophages accumulate in the lungs and can modulate pulmonary inflammatory and reparative processes through their elaboration of cytokines and growth factors. Endotoxemia, often a prelude to acute lung injury, induces a monocytopenia, likely resulting from monocyte accumulation in the lung. We hypothesized that LPS would induce monocyte lung retention by increasing monocyte stiffness and thereby diminishing the cell's ability to deform and transit the narrow pulmonary capillary network, and that LPS would induce CD18-dependent adhesion of monocytes to endothelium, prolonging their retention. LPS induced a rapid and concentration-dependent increase in human monocyte stiffness, net filamentous actin assembly, and retention in a filtration model of pulmonary capillaries. These LPS-induced responses were dependent on the integrity of actin filaments in that cytochalasin D, an agent that disrupts filamentous actin assembly, attenuated each of these processes. LPS induced CD18-dependent and -independent human monocyte adhesion to unstimulated human endothelial cell monolayers. In vivo, rabbit monocytes were retained in the lungs of animals rendered endotoxemic. Pretreatment of monocytes ex vivo with LPS enhanced their lung retention suggesting that LPS was acting directly on monocytes. Initial lung retention during endotoxemia was attenuated by inhibiting monocyte F-actin assembly with cytochalasin D. Anti-CD18 Abs caused a slight decrease in initial retention of monocytes, but led to a 90% inhibition of retention by 2 h. Control IgG had no effect. These data suggest that the initial retention of monocytes in the lung during endotoxemia is dependent on alterations in their stiffness and assembly/organization of F-actin, and that CD18-dependent adhesive mechanisms prolong monocyte retention in the lung during this process.

Actins↗
PubMed1994

Juvenile nasopharyngeal fibroma: androgen receptors and their significance for tumor growth.

Since the publications of Martin, et al. (1948) and Schiff (1959), who were the first to report on the administration of sex hormones to juvenile nasopharyngeal fibroma (JNF) patients, several authors have described the different clinical effects and histologic changes after androgen and estrogen application. Since the mechanism of action of sex steroids in juvenile nasopharyngeal fibroma is almost unknown, the authors have studied androgen receptor binding in cultured tumor fibroblasts from three patients with JNF. Maximum androgen binding (Bmax) of the tumor fibroblasts approximated to that of genital skin fibroblasts, which served as a control androgen target tissue with high receptor density. Furthermore, in vitro experiments showed that the growth rate of tumor fibroblasts increased when testosterone was added to the culture medium, while the addition of two antiandrogens, cyproterone and flutamide, caused a reduction in growth rate. It is concluded from these results that JNF is a hormone-dependent tumor stimulated by testosterone whose growth rate may, at least in vitro, be reduced by antiandrogens such as cyproterone and flutamide.

Cell Division↗
PubMed1993

Acute and long-term effects of adrenocorticotropin and dexamethasone on the auditory brainstem response in multiple sclerosis patients.

Auditory brain-stem responses (ABRs) were compared in two groups of multiple sclerosis (MS) patients receiving standard treatment with adrenocorticotropin (ACTH) and with dexamethasone (DEX). ABRs were recorded prior to treatment, on the 1st and 8th day of therapy, and 21 days after the hormonal treatment had been discontinued. ABRs in MS patients were within the normal range of variability. Latencies of ABR components increased with increasing rate of presentation, and with decreasing intensity of the click stimuli. Changes in ABRs displayed a consistent pattern in patients treated with ACTH, but showed less coherence after DEX. In ACTH treated patients' latencies of the late ABR waves V and Vn were prolonged after clicks of high intensity, and reduced following clicks of low intensity resulting in a decreased slope of the latency-intensity function of these ABR waves. This pattern became most prominent in the recordings after the treatment had been discontinued, and could reflect an improved transmission across both afferent excitatory and recurrent inhibitory synapses in the auditory pathways. The findings indicate that--besides a common anti-inflammatory action--therapies with ACTH and DEX differ with regard to their influence on central nervous functioning.

Adolescent↗