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Biomedical subjects

B Bertram

Publications and source records attributed to B Bertram.

At least 37 records · Page 2Linked to original sources
PubMed1997

Malformations in cochlear implant patients.

OBJECTIVE: To report on cochlear implantation in children with bony inner ear malformations. PATIENTS: 30 children with bony inner ear malformations who have received cochlear implants. INTERVENTIONS: High-resolution spiral computed tomography is used to identify malformations. Magnetic resonance imaging is used to detect the presence of an acoustic nerve and determine the integrity of the auditory pathway and central nervous system structures. Both imaging techniques may be used intraoperatively, as well as facial nerve monitoring and electrical auditory brainstem response monitoring. Three-dimensional reconstructions are helpful in preoperative planning. Large vestibular aqueducts and vestibular malformations can be successfully managed. RESULTS: Postoperative results have been encouraging, although children with malformations tend to occupy the lower third of rehabilitation results of all children with implants.

Child↗
PubMed1997

Stress experienced by parents of children with cochlear implants compared with parents of deaf children and hearing children.

OBJECTIVE: To compare the stress experienced by parents of children with cochlear implants with that experienced by parents of deaf children and hearing children. STUDY DESIGN: The Parenting Stress Index and problem-oriented interviews were used with the parents of these three groups of children. RESULTS: Parents of deaf children were found to experience greater levels of stress than parents in the other two groups. CONCLUSION: Parents of children with cochlear implants experience about the same level of stress as parents of hearing children.

Child↗
PubMed1997

Preliminary conversation with the parents before cochlear implantation.

OBJECTIVE: To provide parents of hearing-impaired children about to undergo cochlear implantation with an opportunity to discuss their expectations and the pedagogical implications of surgery. SETTING: Parents and children participate in discussions at the medical center where the cochlear implantation will take place. PATIENTS: More than 700 children and their parents have participated. OUTCOMES: Parents of congenitally deaf children differ somewhat in their expectations and behavior from the parents of postlingually deafened children.

Child, Preschool↗
PubMed1996

Mixed disulfides from disulfiram inhibit the benzo[a]pyrene induced mutagenesis.

Some mixed disulfides derived from disulfiram and endogenous thiol compounds have been synthesized, biochemically characterized and their potential antigenotoxic effects have been proposed. The present study evaluated the mutagenic and antimutagenic specificities of two mixed disulfides using S. typhimurium reversion assay, namely S-(N,N-diethyldithiocarbamoyl)-N-acetylcysteine (AC-DDTC) and-L-glutathione (GS-DDTC). The two mixed disulfides were not mutagenic to Salmonella strains TA98 and TA100 in the presence or absence of S9 mixture. The increased number of revertants by benzo[a]pyrene (B(a)P) has been reduced to the control level by the preincubation with AC-DDTC or GS-DDTC. It was not due to the killing effect of B(a)P, mixed disulfides or B(a)P-disulfide mixture. The antimutagenic effect of AC-DDTC was more potent than that of GS-DDTC. These results indicate that AC-DDTC and GS-DDTC may have a role to play in reducing the risk of mutagenic effects of B(a)P.

Animals↗
PubMed1996

Pharmacokinetics and whole-body distribution of the new chemotherapeutic agent beta-D-glucosylisophosphoramide mustard and its effects on the incorporation of [methyl-3H]-thymidine in various tissues of the rat.

beta-D-Glucosylisophosphoramide mustard (beta-D-Glc-IPM) is a new, potential chemotherapeutic agent currently under investigation. Its pharmacokinetics in plasma and elimination of the parent drug and its metabolites via urine, bile, and exhaled air were studied in female Sprague-Dawley rats after bolus injection of 315 mg/kg. Typically, the drug's disposition from plasma follows a linear two-compartment model with half-lives (t1/2) of 1.8 (t1/2 alpha) and 32 min (t1/2 beta). The rate of clearance is 0.0046 (range 0.0030-0.0071) 1 min-1 kg-1, and the steady-state volume of distribution (Vss) is 0.18 (0.08-0.042) 1/kg (mean +/- inter-individual standard deviation). In human plasma, 28.1 +/- 2.6% (mean +/- SD) of the drug (concentration range 0.5-5 mg/ml) is bound to plasma proteins (predominantly to albumin). Biliary excretion of the parent drug accounts for 2.9 +/- 1.7% of the dose; its elimination in the form of 14CO2 via exhaled air is less than 1%. Within 24 h, 63.5 +/- 4.9% of the 14C-labeled drug is excreted unchanged in the urine, whereas 17.5 +/- 5.1% is excreted in the urine as metabolites. In addition, beta-D-Glc-[14C]-IPM was given as a bolus injection to female Sprague-Dawley rats at dose levels of 315 and 56.2 mg/kg. The distribution of radioactivity into tissue was examined qualitatively by whole-body autoradiography (WBA). Parallel experiments were carried out using the high dose of the L-derivative. After dosing with the D-compound, the highest levels of radioactivity were found in the liver, kidneys, thymus, thyroid gland, and central nervous system, including the brain. A similar distribution pattern was observed for the L-compound, except in the brain, which contained negligible levels of radioactivity. The distribution of the D-compound (high dose) was also investigated in male Copenhagen rats bearing a Dunning prostate tumor. The results were similar to those obtained in healthy Sprague-Dawley rats. Additionally, radioactivity was found in the tumor at 1 h after dosing with the drug and remained there even after 24 h. The effects of beta-D-Glc-IPM on the incorporation of [methyl-3H]-thymidine into the DNA of the liver, kidneys, thymus, spleen, esophagus, and bone marrow of the rat were examined following tissue excision and liquid scintillation counting at 2, 8, and 24 h after administration of the drug. beta-D-Glc-IPM showed no effect on the incorporation of [methyl-3H]-thymidine in the liver and an insignificant reduction in kidney DNA (maximal reduction: -27.3%). However, after 8 h there was a marked reduction in the incorporation rate in the thymus (-83.7%), spleen (-74.6%), and esophagus (-87.2%), with a tendency toward recovery within 24 h. In bone marrow cells a reduction of -75.5% (8 h) and -73.3% (24 h) was observed.

Animals↗
PubMed1996

[Catheterization of the nasolacrimal duct].

A technique is described for passing a guide wire through the lacrimal duct into the nose following catheterisation of the duct. The wire is passed into the pharynx, a 7 F feeding tube is passed through the nose into the pharynx and these are then pulled out of the mouth with a Magill forceps. The tip of the feeding tube is then cut off and the guide wire introduced into a side hole of the catheter. By removing the catheter, the tip of the guide wire is pulled along and can be removed from the nose.

Catheterization↗
PubMed1996

[Cochlear implant management of young children].

INTRODUCTION: Since 1988, more than 450 children have received cochlear implants at the Department of Otolaryngology of the Medizinische Hochschule Hannover. Among them are 38 children who underwent surgery before the age of two. Due to increasing experience with this technique, the mean age at implantation has decreased over time so that most children nowadays receive implants between the ages of two and five. In terms of the critical periods of both development of the auditory system and the acquisition of language, it is advantageous for even younger children to receive implants soon after detection of deafness. However, the present diagnostic tools do not allow proper estimation of residual hearing and additional handicaps. Therefore longer periods of hearing aid use and audioverbal training are mandatory before implantation. Additional objections against early implantation are biosafety problems such as head growth, the high incidence of otitis media, and the specific surgical anatomy. This paper outlines criteria for patient selection, the surgical concept, postoperative rehabilitation, and complications. PATIENTS: Twenty-six children suffered from postmeningitic deafness and beginning obliteration of the cochlea as shown by repeated high resolution CT scans. Nine children had congenital deafness which was detected early in life and showed no improvement after proper hearing aid fitting and audioverbal training for speech development. Three children had severe inner ear malformations detected by CT scans. All children had no ABR or CAP responses in ECoG. Their developmental, language, and neuropaediatric status was examined. SURGERY: Thirty-five children received the Nucleus Mini 22 cochlear implant; three children received the Clarion 1.2 device. The surgery was not different from adult surgery. Special care was given to proper fixation and placement of the electrode in the drilled out mastoid to compensate for head growth. POSTOPERATIVE RESULTS: All children wear the speech processor regularly. They are able to detect everyday sounds and suprasegmental features of speech after a few months. After one year, the child begins to understand and produce speech; after two years speech understanding has been achieved and normal language development starts with small sentences. The complication rate was not higher than in other age groups of patients. Fitting and tune-up of the speech processor required a broad range of experience and a specialized team working at the children's implant center. CONCLUSION: Early implantation in children is both possible and effective in selected cases. Due to an improved early detection of deafness, it should be possible to increase the percentage of children with early cochlear implantation.

Child↗
PubMed1996

[Risk factors in patients with amaurosis fugax].

BACKGROUND: In the diagnosis of retinal and cerebral vascular occlusion and migraine amaurosis fugax may be an important symptom. To evaluate the relation between cardiovascular diseases and amaurosis fugax we investigated the risk factors in patients with amaurosis fugax. MATERIALS AND METHODS: Twenty-four patients (14 m, 10 f; aged 22 to 84 years; mean: 55 +/- 19 years) with amaurosis fugax were included in this study. All patients underwent a detailed clinical and ophthalmological examination, including video fluorescein angiography shortly after the event. RESULTS: The duration of symptoms ranged from 30 seconds to 30 minutes (median: 3 minutes). Additional acute symptoms were headache in eight patients and tinnitus in one patient. Visual acuity showed no difference between the effected and the fellow eye. Intraocular pressure was normal in all eyes. Video fluorescein angiography revealed normal retinal perfusion times in all cases (arm-retina-time: 12.9 +/- 3.8 s; arteriovenous passage time: 1.8 +/- 0.7 s). Cardiovascular risk factors were present in all patients: 58% of the patients suffered from arterial hypertension, 8% of the patients from diabetes mellitus. Hyperlipidaemia was diagnosed in 17% of the patients, 46% of the patients were smokers. A history of cardiovascular disease (e.g. myocardial infarction, vitium, arrhythmia) was found in 58% of the patients. Cerebrovascular disease was diagnosed in 54% of the patients (migraine: 33%). CONCLUSIONS: The ophthalmologic examination especially the fluorescein angiography revealed no pathologic findings in patients with amaurosis fugax. The risk factor distribution corresponded to data found in patients with retinal artery occlusion.

Adult↗
PubMed1996

[Retinal hemodynamics in diabetic retinopathy before and after laser coagulation].

PATIENTS AND METHODS: By means of video-fluoresce in angiography arm-retina-time (ART) and retinal arteriovenous passage time (AVP) were measured in order to determine the effect of panretinal laser-coagulation on retinal circulation in patients with diabetic retinopathy. 55 patients with either preproliferative (n = 29) or proliferative (n = 26) retinopathy we reexamined before, 3-9 weeks after panretinal laser-coagulation (mean: 848 burns, 0.5 mm diameter), and 0.5-3 years later. RESULTS: The ART of the diabetic patients was in the normal range and showed no differences among the three measuring times. The retinal AVP was significantly prolonged in the three measuring times (nasal and temporal) when compared to normals. Laser-coagulation showed no significant effect on AVP in the temporal branches, whereas in the nasal branches AVP decreased from 2.38 +/- 0.69 s (before laser-coagulation) to 2.11 +/- 0.68 s (3-9 weeks after treatment) and 2.06 +/- 0.67 s (0.5-3 years after treatment) (p < 0.01). In branches with neovascularisation (n = 24) a pronounced decrease of AVP from 2.60 +/- 0.70 s to 1.96 +/- 0.61 s and 2.09 +/- 0.64 s (p < 0.01) was detected. CONCLUSIONS: Thus, laser-coagulation leads to a faster circulation in areas with laser burns within 3-9 weeks post-treatment.

Adult↗
PubMed1996

[Quantification of cystoid changes in diabetic macular edema].

BACKGROUND: Cystoid changes in diabetic macular oedema can result in severe visual consequences and were previously difficult to quantify. This study was performed to introduce reliable measurements of the area covered by cysts, of their quantification and relation to visual acuity. PATIENTS AND METHODS: 58 diabetic patients suffering from cystoid macular oedema were examined by means of a scanning laser ophthalmoscope. Fluorescein angiography provides a detailed recognition of well demarcated cystoid formations in the early transit. In three different sampling areas from the center of the fovea (1.2 deg, 2.5 deg and 5 deg) and in the foveal avascular zone (FAZ) itself the area covered by cystoid changes was quantified as well as the number of cysts and their shortest distance from the center of the FAZ. RESULTS: The mean area covered by cystoid formations in the 2.5 degrees area was 0.128 +/- 0.08 micron2, the number of cysts ranged from 1 to 7. In all sampling areas there was a significant correlation between area of cysts and visual acuity. Their number and distance from the center of the FAZ did not show a significant correlation to vision. Measurements within the 2.5 degrees area seem to have the highest predictability concerning visual function. CONCLUSION: Fluorescein angiography allows the quantification of number and area covered by cystoid formations in patients with diabetic macular oedema. There is a significant correlation of visual acuity to the area covered by these cystoid changes. The distance of cysts from the center of the FAZ does not correlate significantly to visual acuity. These measurements can prove useful in following cystoid changes and in monitoring the effect of currently used therapy regimen.

Adult↗
PubMed1995

D-19575--a sugar-linked isophosphoramide mustard derivative exploiting transmembrane glucose transport.

D-19575 is a glucose derivative of ifosfamide mustard with a broad spectrum of antitumor activity in animal models. In comparison with ifosfamide, D-19575 is less toxic and is better tolerated by tumor-bearing animals, achieving a better therapeutic efficacy. D-19575 is directly cytotoxic in vitro--in contrast to ifosfamide--and it is possible to modulate this cytotoxicity by inhibition of transmembrane glucose transporters. Correspondingly, renal reabsorption of filtered D-19575 could be blocked by pre- and cotreatment with phlorizin, resulting in a higher urinary excretion of the unchanged drug. The toxicity to white blood cells, colony-forming units (CFU-C), and spleen-cell colony-forming units (CFU-S) is considerably lower for D-19575 as compared with ifosfamide. In conclusion, D-19575 is a new alkylating cytotoxic agent with increased antitumor selectivity, probably caused by an active transmembrane transport mechanism.

Absorption↗
PubMed1995

[Therapeutic hydrophilic bandage lenses after perforating keratoplasty in severe eye chemical burns].

BACKGROUND: The prognosis of penetrating keratoplasty after severe eye burns is uncertain. Beside of immune reactions the outcome is determined by surface problems. PATIENTS AND METHODS: Between July 1991 and October 1993 in 15 patients (16 eyes) with grade IV eye burns penetrating keratoplasties with large diameters (11-16 mm) were carried out. Cultured corneas were used with an intact epithelium. In 9 eyes hydrophilic bandage lenses (Geaflex 70, Fa. Wöhlk, Kiel) were applied initially, in the remainder 7 eyes within 7 days postoperatively. RESULTS: The lens radius best suited was found out by trial, because corneal topography was not possible for many weeks. In 12 (75%) eyes the lens had to be fitted steep, with a radius from < or = 8.7. A change in lens radius during the healing course was rare. The frequent use of artificial tear drops was important, because many eyes showed clinical manifestations of dry eye syndrome. Complications during soft contact lens wearing were rare. In 5 eyes microbiological examination was positive, but successfully treated. Under the protection of soft contact lenses 9 eyes maintained an intact epithelium. In the remainder eyes severe vascularisation with large persistent epithelial defects occurred mostly as a consequence of immune reactions. These keratoplasties developed on growth of inflammatory pannus or progressive ulceration. The average of the follow-up time was 22 months. CONCLUSION: The use of large diameter keratoplasties in combination with hydrophilic bandage lenses proved to be successful to maintain the integrity of the epithelium in these high-risk keratoplasties. The prognosis of these transplants is, however, determined by immune reactions.

Adolescent↗
PubMed1995

[Bilateral posterior ischemic optic neuritis in an adolescent with diabetes mellitus with decompensated blood glucose homeostasis].

BACKGROUND: Diabetogenic loss of visual acuity is very rare in juvenile onset diabetics. PATIENT: A 14-year-old adolescent with type-I diabetes mellitus since 7 years is reported. She experienced an episode of ketoacidotic diabetic coma after one year of very bad glycemic control. Even two weeks before onset of the diabetic coma her visual acuity decreased to 8/200 in both eyes. The perimetry revealed central and paracentral socotomas, the examination of the fundi showed only some microaneurysms and a normal optic disc. Electrophysiological results (normal ERG and EOG, pathologic pattern-VECP) proved irreversible damage of optic nerve or optic tract. RESULTS: Neuritis of optic nerve may not be existent but ischemic damage: the pattern-VECP showed no reproducible answers and the flash-VECP showed normal latency and borderline normal amplitude. There were no pathological findings in neurological and serological tests (like CT, NMR, EEG, cerebrospinal fluid, auto-antibodies or parasites). In the two years after visual loss the visual acuity increased only slightly to 13/200 in the right eye and 20/200 in the left. The optic disc showed temporal pallor in both eyes as sign of descending atrophy of the optic nerve. CONCLUSIONS: The clinical signs in this unusual case of diabetes mellitus point towards the diagnosis of a posterior ischemic optic neuropathy in both eyes caused by the extremely bad diabetic condition.

Adolescent↗
PubMed1995

Macular microcirculation in cystoid maculopathy of diabetic patients.

BACKGROUND: In patients with diabetic macular oedema and central cysts ischaemia of the retina appears to be an important contributing factor in the pathogenesis of cysts. This study was performed to further elucidate the role of the inner retinal microcirculation in diabetic cystoid macular oedema (CMO). METHODS: Video fluorescein angiography allows visualisation of the macular microvasculature and measurements of the capillary blood velocity (CBV), foveal avascular zone (FAZ), and perifoveal intercapillary area (PIA, characterising capillary density). RESULTS: Twenty three diabetic subjects with CMO, matched diabetic patients without macular oedema (n = 23), and healthy subjects (n = 23) were included. CBV, PIA, and FAZ did not differ significantly among diabetic groups regardless of presence of cystoid changes. CBV was significantly reduced (p < 0.0001) and PIA was more than doubled in both diabetic groups (p < 0.0001) when compared with healthy subjects. Furthermore, FAZ showed a nearly doubled size in diabetic patients without macular oedema (p < 0.01) and a less pronounced enlargement (by 29%) in diabetics with CMO (p < 0.05). CONCLUSION: The results indicate that the retinal microcirculation in diabetic patients is markedly altered when compared with healthy subjects, regardless of CMO presence. In CMO patients the microcirculatory changes are similar to those of diabetic patients without macular oedema. Thus inner retinal perfusion does not contribute to tissue ischaemia leading to cystoid formations in diabetic maculopathy.

Adult↗
PubMed1995

Inhibitory effects of mixed disulfides from disulfiram on the metabolism and genotoxicity of N-nitrosodiethylamine.

Disulfiram (CAS 97-77-8, DSF), a potent anticarcinogenic compound, is known to form mixed disulfides with sulfhydryl group containing amino acids or proteins in vivo. In the present study the stabilities of two mixed disulfides which may arise in the metabolism of disulfiram, i.e. S-(N,N-diethyldithiocarbamoyl)-N-acetyl-L-cysteine (AC-DDTC) and S-(N,N-diethyldithiocarbamoyl)-L-glutathione (GS-DDTC) in phosphate buffer (pH 7.2) and in rat liver subcellular fractions were investigated as well as their influences on the glutathione (GSH)-related detoxifying system, on the metabolism of [14C] N-nitrosodiethylamine (NDEA) and on the genotoxic activity of NDEA in rats. Both substances were stable in buffer and in microsomes but were degraded in cytosol showing a half life of 4.7 h (AC-DDTC) and 3.2 h (GS-DDTC). Addition of GSH to the incubation media accelerated the degradation of mixed disulfides in cytosol. In vivo administration of AC-DDTC and GS-DDTC (1.7 mmol/kg i.p.) led to an increase in hepatic GSH content and to an inhibition of the activity of NDEA deethylase. Both mixed disulfides inhibited the metabolism of NDEA. After a 28 mg/kg i.p. dose of [14C] NDEA only 0.4% was excreted unchanged in the urine. Pretreatment with AC-DDTC and GS-DDTC caused a 10 to 20 fold increase in the amount of NDEA excreted in the urine. The occurrence of DNA single strand breaks in rat liver cells induced by NDEA was completely neutralized by the pretreatment with AC-DDTC.

Animals↗