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Biomedical subjects

W Schrader

Publications and source records attributed to W Schrader.

At least 19 recordsLinked to original sources
PubMed2001

Development of a simple gradient LC-IR interface for the detection of terpenoids from the alpha-pinene-ozone reaction.

The development of a simple interface between liquid chromatography and infrared spectroscopy (LC-IR) using a coaxial sprayer is described for less volatile analytes. The system consists of a transfer capillary, in which the analytes are transported from the separation column of the gradient-LC to the outlet of the sprayer. This transfer capillary is coaxially surrounded at the outlet by a stainless steel sprayer capillary, which is resistively heated and flushed with nitrogen gas. The samples are sprayed in the manner that the eluent is vaporized by the heated nitrogen when exiting the capillary, while the analytes are deposited on a moving slide made of infrared transparent material (ZnSe or CaF2). Afterwards the deposited compounds are analyzed with an infrared microscope in transmission. First results from reaction products of the gas phase reaction of alpha-pinene with ozone are presented.

Bicyclic Monoterpenes↗
PubMed2001

Degradation of alpha-pinene on Tenax during sample storage: effects of daylight radiation and temperature.

The behavior of alpha-pinene sampled on adsorption cartridges filled with Tenax TA has been investigated in relation to different storage conditions, focusing on daylight radiation and temperature. After sampling, the respective cartridges containing the terpene were placed in sunlight on the windowsill for up to 1 month. Corresponding samples have been wrapped in aluminum foil to prevent the influence of daylight radiation. Additional sample cartridges with alpha-pinene were stored in the refrigerator at 4 degrees C and a freezer at -18 degrees C. All cartridges were analyzed using thermodesorption injection onto a gas chromatograph, and the compounds were detected using either a cryocondensation-interface to a Fourier transform infrared-spectrometer (GC/FT-IR) or the flame ionization detector (FID). In summary, 12 compounds were detected and identified, from which eight were products that were formed on Tenax through different mechanisms. Two compounds seemed to be formed under the influence of daylight radiation, while the others appear to be mainly autoxidation products. Estimates after 1 month of storage showed recoveries of over 99% for wrapped samples, while for unwrapped cartridges only about 88% of alpha-pinene was found. A pattern of up to five compounds was found that can be used as an indicator for storage reactions.

Adsorption↗
PubMed2001

A "hard/soft" mismatch enables catalytic Friedel-Crafts acylations.

[figure: see text] Cationic complexes of Pt(II) and other late transition metals efficiently catalyze Friedel-Crafts acylations of moderately activated arenes by carboxylic acid anhydrides. The nature of the catalytically relevant species formed from (PhCN)2PtCl2 and AgSbF6 and their interactions with the substrates are studied by NMR and ESI-MS.

Journal Article↗
PubMed2000

[Penetrating and perforating eye injuries in 343 patients due to auto accidents before and after compulsory seat belt legislation resulting in fines (1966-1998)].

BACKGROUND: Constructional improvements of passengers safety in cars alone did not result in a significant decline of open globe injuries in traffic accidents. Only after compulsory seat belt legislation was introduced in Germany and Great Britain, a 60%-75% reduction in ocular injuries was observed. We examined, how the characteristics of severe eye injuries in car accidents changed during the last 28 years. PATIENTS AND METHODS: The case records of 343 patients, who suffered from open globe injuries during car accidents between 1966 and 1993 and were primarily admitted in the University Eye Hospitals of Freiburg and Würzburg, have been analyzed retrospectively. Injuries were evaluated for their extent, time of injury (hour and season), age, sex and outcome of visual acuity after surgery. RESULTS: Between 1966 and 1984 wind-screen injuries declined slowly from 25/year to 16/year. Since the introduction of compulsory seat belt legislation in Germany in 1984 we observed a sudden reduction to 4 injuries/year, followed by an additional slow decline to 2.5 injuries/year. Male/female ratio changed from 2.1/1 before to 9/1 after 1984. Due to the seat belt legislation, injuries declined during summer season (april through september) by factor 7.6, during winter season (october through march) by factor 3.8. Injuries during daylight (6 a.m. to 6 p.m.) decreased more rapidly (by factor 14) than during nighttime (6 p.m. to 6 a.m.: factor 4). The decline of eye injuries was most pronounced among those with an age of less than 23 years (by factor 10.8) and those who were 31-50 years old (by factor 6.8), but least among those between 23 and 30 years of age (2.2). Since 1984, open globe injuries combined with mid-facial and cranial fractures increased resulting in a poorer visual outcome: 29% of eyes became blind before 1984 and 40% since then due to the higher survival probability of very severe accidents. A majority of injured persons still had not fastened their seat belt and about 50% were drunk. CONCLUSION: Compulsory seat belt legislation introduced in Germany in 1984 was most effective in preventing eye injuries among female passengers, during daytime or among persons younger than 23 years. However, 23-30 year old male drivers who had not fastened their seat belt, drove in darkness or during winter and had drunk alcohol, were still at highest risk for an open globe injury. The increase of victims with a combination of open globe injuries and midfacial injuries, polytrauma or cerebral trauma may be related to the airbag and other improved safety measures.

Accidents, Traffic↗
PubMed1999

Application of gas chromatography-cryocondensation-Fourier transform infrared spectroscopy and gas chromatography-mass spectrometry to the identification of gas phase reaction products from the alpha-pinene/ozone reaction.

The gas phase reaction of alpha-pinene with the atmospheric oxidant ozone was investigated by using the capabilities of both gas chromatography-cryocondensation-Fourier transform infrared spectroscopy (GC-FT-IR) and gas chromatography-mass spectrometry (GC-MS), for the identification of the reaction products formed. The reaction was carried out in a flow reaction chamber from where the compounds were sampled on Tenax-containing adsorption cartridges. The reaction mixture was injected onto the column after thermodesorption and analyzed using both GC-IR and GC-MS. Twenty compounds could be detected, including the reactant alpha-pinene and it's impurities tricyclene and camphene. Eleven compounds were identified by spectra comparison with either reference data or spectra obtained from commercial standards. Four compounds were tentatively identified from their IR and MS spectra, while from the remaining two compounds the nature of basic functional groups could be established.

Bicyclic Monoterpenes↗
PubMed1998

[Acute lymphatic leukemia of the T-cell line. Visual impairment as the initial symptom].

INTRODUCTION: Visual impairment as the initial symptom of leukemia is rare. Although retinal involvement during leukemia is frequent, a leukemic macular lesion is an exception. CASE REPORT: A 5 1/2-year-old female child, pale and with a general feeling of illness complained about bilateral reduced vision for 3 days. Binocular visual acuity in reading distance was 0.4. Anterior segment and optic disc were inconspicuous. The macula in both eyes displayed a preretinal hemorrhage in the form of a spot with red, yellow and clear layers lying on top of one another. After a hematological examination the illness was diagnosed as T-cell-type acute lymphocytic leukemia (ALL). Chemotherapy was given immediately and general improvement of ALL was observed. Eleven months after the first presentation visual acuity of the right eye was 0.7 and of the left eye 0.3. The central lesion was completely resorbed and revealed paramacular pigment clumping. CONCLUSION: Because of the differentiated and improved therapy schemata available now, e.g., the ALL-BFM 95 protocol, ALL can be cured more frequently. The prognosis, however, is essentially dependent on early diagnosis. By being familiar with the corresponding ocular findings, an ophthalmologist can contribute to this.

Child, Preschool↗
PubMed1997

Styrene oxide DNA adducts: in vitro reaction and sensitive detection of modified oligonucleotides using capillary zone electrophoresis interfaced to electrospray mass spectrometry.

Styrene is one of the most important synthetic chemicals in the world and is subject to investigations concerning carcinogenicity and mutagenicity due to the active metabolite, styrene-7,8-oxide. This epoxide shows a tendency to react, among others, with DNA and DNA constituents. The in vitro reaction of styrene oxide with DNA was investigated by cleaving incubated calf thymus DNA with two different enzymes, namely Benzonase and alkaline phosphatase, to obtain oligonucleotides of the type n-nucleotide-(n-1)-phosphate with chain length from 2 to 8 bases. Alkylated and nonalkylated nucleotides were separated in groups according to their chain length using capillary zone electrophoresis and were detected with electrospray mass spectrometry. This improvement in sensitivity made it possible to obtain new information about the reaction of styrene oxide with DNA, especially to detect unknown reaction products. The results indicate that primarily purine bases were alkylated by styrene oxide before pyrimidine bases, which react with higher concentrations of styrene oxide. This means that in addition to the already reported adducts in DNA at the N-7-, O6- and N2-position of guanine also adducts at the nucleophilic sites of adenine can be found using mass spectrometry. We anticipate for the future this procedure will allow us to investigate base sequence specific reactions as well as interactions from xenobiotics and cytostatic drugs, since reaction products would directly be detectable.

Adenine↗
PubMed1995

Determination of styrene oxide adducts in DNA and DNA components.

The reaction of styrene oxide with DNA components was studied using separation by capillary zone electrophoresis (CZE) and detection by negative-ion electrospray mass spectrometry (MS). The CZE-MS interface was built for a sector field mass spectrometer. The reaction of styrene oxide with mononucleotides (dGMP, dAMP) was used to optimize the relevant separation parameters and to gather the first information about the behaviour of the possible products. With these mixtures, sample stacking procedures were developed and the scope of collision-induced dissociations were studied. From the fragments recorded, information about the reaction sites in the nucleotides was obtained. Further, the reaction with intact calf thymus DNA was investigated. The DNA was digested into oligonucleotides using the previously described approach with Benzonase, an unspecific nuclease, and alkaline phosphatase. Styrene oxide mono-adducts in dinucleotides, trinucleotides and tetranucleotides were detected, whereas pentanucleotides exhibit mono- and discernible amounts of di-adducts. The hexanucleotides were generally modified twice. The alkylated species moved faster than the unmodified oligomers.

Animals↗
PubMed1994

A new mass spectrometric approach to detect modifications in DNA.

A new approach is described for the enzymatic digestion of DNA yielding oligonucleotides ranging from dinucleoside monophosphates to octanucleoside heptaphosphates. DNA was digested by means of the benzon nuclease, an unspecific nuclease, and alkaline phosphatase to remove the terminal phosphate. The mixture of oligonucleotides was separated using capillary-zone electrophoresis with a buffer system, yielding a rather strong electro-osmotic flow. The oligomers are separated into groups with nucleotides of the same chain length. The separation capillary was used as the innermost capillary of an electrospray spraying system. Negative molecular ions of the nucleotides were recorded using a home-built interface and ion source for a sector-field mass spectrometer. This approach allows the facile detection of DNA modifications since they lead not only to differences in mass, but also can possess altered electrophoretic mobility. For modifying reactions which exhibit sequence specificity, the information is retained in the oligomers. Thus, reactions of DNA with electrophiles can be evaluated at different levels, since in longer chains, even complex sequence specificity may be apparent. Results from calf thymus DNA digests and preliminary experiments with DNA adducts with styrene oxide are discussed.

Animals↗
PubMed1994

Progressive proliferative diabetic retinopathy after transplantation of the pancreas. A case and a review of the topic.

The unusual case history of the development of a progressive diabetic retinopathy despite normal blood glucose after transplantation of the pancreas and despite panretinal laser coagulations is described. A 26-year-old male with diabetic background retinopathy underwent a segmental transplantation of the pancreas in 1988. One year after surgery, a progressive proliferative retinopathy despite normoglycemia was found, which required an intensive panretinal photocoagulation during the following months. However, despite massive retinal coagulations, vitreous hemorrhages and retinal neovascularizations continuously occurred, thus requiring two vitrectomies. After these procedures, visual acuity recovered distinctly. It is suggested that the 'point of no return' for the development of proliferative changes in the retina had been passed at a time when a background retinopathy was still present. The effect of normoglycemia during follow-up of patients with diabetic retinopathy, described in the literature, is compared to this unusual case history.

Adult↗
PubMed1994

[Late complications and functional results at least 5 years following pars plana lentectomy for congenital cataract].

Pars plana or pars plicata lentectomy was introduced for congenital cataract at the University Eye Clinic of Freiburg 12 years ago. Records of 32 patients (48 eyes) who were operated on during a period of 7 years were retrospectively analyzed to determine the anatomical and functional results in comparison to previous methods of treatment for congenital cataract. The documented follow-up was at least 5 years long (maximum 11 years, mean 7.3 years). Seventeen patients had bilateral, 15 patients monolateral cataract operations. Thirteen eyes were operated on during the first 2 months of life, and 31 of the 48 eyes during the first year. Sixteen of the 48 eyes had additional malformations, like microphthalmus, different stages of persistent hyperplastic primary vitreous, or anterior chamber malformation. Visual acuity was at least 20/50 at the last visit in 3 of 15 eyes after monolateral lentectomy and in 19/33 eyes after bilateral lentectomy. Twenty-four children are now able to attend a regular school; only one child is attending a school for the visual handicapped; another child attends a school for deaf children. Postoperatively, secondary cataract or a retropupillary membrane was found in two eyes. Glaucoma developed in two eyes, requiring additional surgery. Postoperative retinal detachment caused by a giant tear complicated the postoperative course in one case. The anatomic results turned out to be better than after discission and aspiration with fewer postoperative complications like secondary cataract, glaucoma, or retinal detachment. The functional outcome is mainly dependent on good postoperative orthoptic and pleoptic management of the children.

Adolescent↗
PubMed1993

[Peripheral retinal correspondence after retinal detachment].

BACKGROUND: Occasionally, patients who underwent surgery for complicated retinal detachment report spatial distortions. This may be due to a translocation of photoreceptors when they become reattached to the pigment epithelium. We wanted to find out if, and to what extent, similar translocations occur after a simple buckling operation. METHODS: Binocular retinal correspondence was used as an indicator of photoreceptor translocation. Correspondence was measured in the peripheral visual field at eccentricities of 5, 10 and 20 degrees, using a mirror haploscope. We examined two normal observers, one patient having had surgery for complicated retinal detachment including retinotomy, and 23 patients who had simple radial buckling operations. RESULTS: The patient who had received complicated detachment surgery including retinotomy revealed a tremendous shift in correspondence. Of the 23 patients who had simple radial buckle operations, only 10 were able to sustain central fixation while being tested in the periphery. Of these 10 patients, 2 showed distortions of peripheral retinal correspondence in the area of previous retinal detachment. However, only one of them remembered some spatial distortion after surgery. CONCLUSION: As a rule, photoreceptors become correctly reattached after radial buckle operations for retinal detachment. Rarely, vertical or horizontal translocations of about 1 to 2 degrees occur, but this does not usually lead to metamorphopsia.

Adult↗
PubMed1993

Perforating injuries: causes and risks are changing. A retrospective study.

We reanalyzed all 384 records of perforating injuries primarily admitted to the University Eye Hospital of Freiburg during the years 1981-1983 and 1987-1989. Complete data could be obtained from 369 records. Injuries from 1987-1989 were compared with those from 1981-1983 with regard to the cause and extent of the perforation as well as sex, age, occupation, and activity of the patient at the time of injury. The following significant trends were observed. Seat-belt legislation in 1984 was extremely beneficial for the prevention of penetrating occular injuries, especially among women aged 16-25 years. Of 39 injuries to women, 17 (43%) were related to traffic accidents in 1981-1983 as opposed to only 1 of 16 injuries (6%) in 1987-1989. Therefore, the male/female ratio increased from 4.1 to 9.6 (P = 0.006). Perforations during traffic accidents declined from 26% (52/199) to 11% (19/170). The number of occupational injuries remained constant, although their proportion increased from 42.7% (85/199) in 1981-1983 to 50% (85/170) in 1987-1989. High-risk activities at work as well as during leisure time changed from hammering to work with rotating machines (drills, lathes) and wires. The incidence of agricultural injuries rose from 4% to 9% (from 8 to 15). Injuries during leisure activities remained constant (66 vs 62). Among this group, injuries related to a hobby increased, whereas perforations occurring during visits to pubs or festivities decreased. Pediatric injuries remained constant and were responsible for 15.6% and 14.7%, respectively, of all injuries (age, < or = 15 years).(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1992

Diagnosis and management of the acute retinal necrosis syndrome.

The acute retinal necrosis (ARN) syndrome is an increasingly occurring entity characterized by the triad of acute confluent peripheral retinitis with papillitis and anterior-chamber uveitis. We present case reports on four patients (age, 12-65 years) with an ARN syndrome caused by herpes simplex or varicella zoster virus and discuss diagnostic and therapeutic modalities. Immediate antiviral therapy in three patients exhibiting the typical clinical features reduced the intraocular inflammation. However, due to proliferative vitreoretinopathy with peripheral retinal necrosis, vitrectomy with encircling band and silicone oil instillation was necessary in all patients. The suspected diagnosis of an ARN syndrome induced by herpes simplex virus (HSV) was confirmed in one case during the early stage of the disease by the detection of increased levels of HSV-IgA in the vitreous and in another case by the measurement of increased titers of HSV-IgG in the vitreous. For the first time, we found intraocular HSV DNA sequences using the polymerase chain reaction (PCR) in one of these patients. In a fourth patient intraocular varicella zoster virus (VZV) infection was confirmed by the detection of elevated VZV-IgA levels and by positive PCR in the intraocular fluids. Two patients who were diagnosed and treated early retained a visual acuity of 0.4 and 0.5, respectively, whereas in the other two patients, whose diagnosis and therapy were delayed (> 6 weeks), visual acuity was reduced to light perception. We conclude that use of the PCR in the intraocular fluids together with detection of autochthonous antibodies in the vitreous seem to be the most important diagnostic laboratory tools.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1991

[Isovolemic hemodilution on non-arteritic anterior optic neuropathy. Initial results of a randomized study].

As there is no generally accepted treatment for non-inflammatory anterior ischemic optic neuropathy, we have started a randomized, controlled clinical trial on isovolemic hemodilution. In this study all patients received a basic treatment of 75 mg of acetylsalicyclic acid daily. Patients were then randomly assigned to either a group without additional therapy or a group with isovolemic hemodilution. Isovolemic hemodilution was carried out over 6 weeks by several blood-letting procedures and replacement of volume by infusion of hydroxyethyl starch solutions (PCV down to 35-32%). So far, 21 patients have fulfilled the inclusion criteria (symptoms less than or equal to 30 days, no medical contraindications, no giant-cell arteritis), and since they matched for age, duration of symptoms, cardiovascular risk factors, they could be observed for at least 3 months. Although only 1 of 10 control patients hat better visual acuity after 3 months; 6 out of 11 hemodiluted patients had better vision after treatment (p = 0.024). These results indicate that isovolemic hemodilution most likely has a beneficial effect on the visual prognosis of patients with anterior ischemic neuropathy.

Aged↗
PubMed1991

[Dosage errors and their prevention in intraocular SF6 injection for endotamponade in pneumatic retinopexy and after vitrectomy].

Sulfur hexafluoride (SF6) is used for internal tamponade during retinal detachment surgery. It is usually injected into the eye by a plastic syringe either with a sharp needle or by using the infusion system during pars plana vitrectomy. Although several suggestions exist for the appropriate application of intraocular SF6 and other perfluocarbons, a sudden postoperative rise in tension or hypotonia has been observed repeatedly. We simulated the preparation and application of mixtures of sulfur hexafluoride and air and analyzed possible mistakes. SF6 was quantitatively analyzed by infrared spectroscopy. SF6 does not rapidly diffuse out of capped plastic syringes made of polypropylene, as commonly employed in the Federal Republic of Germany. SF6 and air mix completely during aspiration. If the volume of microporefilters or tubes being used for preparation and instillation of mixtures of SF6 and air is ignored, this may result in a 20% deviation in SF6 concentration. Silicone tubes, which are widely used for the influsion during pars plana vitrectomy, are not recommended for the application of SF6. SF6 and fluorcarbones diffuse through silicone tubes and absorb and desorbe in the tube. Infusion lines made of polyethylene or polyvinylchloride, e.g. butterflies, should be preferred.

Dose-Response Relationship, Drug↗