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Biomedical subjects

B Conrad

Publications and source records attributed to B Conrad.

At least 91 records · Page 5Linked to original sources
PubMed1996

Lasting reduction of severe spasticity after ending chronic treatment with intrathecal baclofen.

OBJECTIVE: To investigate whether the dose of intrathecal baclofen necessary for a sufficient reduction of muscle tone and spasms changes during treatment of severe spasticity. METHODS: A group of 27 patients received intrathecal baclofen for 61 (SD 18) months. RESULTS: Spasticity remained absent or strongly reduced after stopping the intrathecal baclofen infusion in seven patients. The dose of baclofen could be reduced to 40% of that dose which was originally necessary in 10 patients. The dose remained the same or increased slightly in 10 patients. Possible reasons for the continuing reduction of spasticity after terminating long term intrathecal baclofen infusion in some patients could be: lasting morphological changes in spinal cord neurons by second messenger controlled modulation of gene expression, a toxic effect of baclofen on spinal neurons, muscular atrophy, inflammation due to the catheter, or progression of multiple sclerosis. CONCLUSIONS: A higher initial daily dose of intrathecal baclofen might lead to a faster, lasting suppression of spasticity and the development of spastic symptoms might even be prevented by pre-emptive treatment with baclofen in patients with newly acquired lesions of the spinal cord.

Adult↗
PubMed1996

Cerebrotendinous xanthomatosis without tendon xanthomas mimicking Marinesco-Sjoegren syndrome: a case report.

A 39 year old patient with cerebellar signs, juvenile cataracts, and dull normal intelligence had cerebrotendinous xanthomatosis without tendon xanthomas, diagnosed previously as Marinesco-Sjoegren syndrome. Cerebrotendinous xanthomatosis was proved by a greatly increased excretion of bile alcohols in the patient's urine. Cerebrotendinous xanthomatosis is a sterol storage disorder due to an autosomal recessive inherited defect of sterol 27-hydroxylase characterised by high cholestanol concentration in multiple tissues. If tendon xanthomas are not present, a diagnosis of cerebrotendinous xanthomatosis will often not be made, unless biochemical tests are performed. The clinical features of cerebrotendinous xanthomas strongly resembles Marinesco-Sjoegren syndrome. Marinesco-Sjoegren syndrome is a autosomal recessive disorder characterised by the triad cerebellar ataxia, congenital cataract, and mental retardation. Although a late onset after the first decade of life favours cerebrotendinous xanthomatosis as the underlying disease, a definite distinction between cerebrotendinous xanthomatosis without tendon xanthomas and Marinesco-Sjoegren syndrome based on clinical presentation may be difficult. It is considered that some patients with Marinesco-Sjoegren syndrome reported in the medical literature had cerebrotendinous xanthomatosis without tendon xanthomas. This is of crucial clinical relevance, because, by contrast with Marinesco-Sjoegren syndrome, treatment for cerebrotendinous xanthomatosis is already available.

Adult↗
PubMed1996

[Intracranial blood flow parameters in cerebral functional changes and cognitive cerebral performance].

Extensive studies have revealed a close relationship between neuronal activity and regional cerebral blood flow. However, SPECT and PET, the technologies most commonly used in these studies, are of limited value for assessment of the dynamics of cerebral blood flow changes at different states of functional brain activity. The introduction of transcranial Doppler sonography and the extended application of stimuli presentation and perception have now been added to the investigator's armamentarium. Simple sensory stimulation (visual, acoustic and tactile) and complex mental tasks (viewing of complex pictures, tactile differentiation of objects) changed the blood flow velocity in the basal intracranial arteries. These changes corresponded to the current concepts of functional cortical organization. The magnitude of the flow velocity increases upon visual stimulation was dependent on the complexity of the stimuli used, and was up to 38% in our studies. The introduction of continuous and bilateral simultaneous Doppler recordings, the calculation of mean flow velocity from cardiac cycle to cardiac cycle and a specially designed averaging method for data analysis allowed effective elimination of non-specific influences and made it possible to demonstrate rapid changes of perfusion in both middle cerebral artery territories in direct response to hemisphere-specific tasks. These changes were correlated with known functional cerebral asymmetries. A language task, for instance, was associated with a significantly larger flow velocity increase in the middle cerebral artery of the dominant hemisphere than in the corresponding artery of the non-dominant hemisphere (5.2 +/- 1,8% vs 3.0 +/- 1.8%, p < 0.001). The excellent time resolution of this technology made it possible to record hemodynamic changes taking place in response to modifications of neuronal activity within less than 1 s. The shortest time interval between stimulus presentation and the first significant increase in flow velocity was on average 717 +/- 191 ms. The latency of less than 1 s suggest that the coupling between alterations of neuronal activity and the regional cerebral blood flow response is mediated by an remarkably rapid mechanism.

Arousal↗
PubMed1996

[Isolation and cryopreservation of human islets of Langerhans].

Islet transplantation represents an alternative to whole pancreas transplantation for the treatment of patients suffering from diabetes type I. The transplantation of a sufficient number of islets is an essential condition for successful allograft. Islet cryopreservation allows the storage of islet preparations for subsequent pooling, at the time of transplantation, of cryopreserved islets with a fresh preparation in order to increase the mass of transplanted pancreatic endocrine tissue. From May 1994 to April 1995, islets were isolated from 22 human pancreases using a modified automated method, and 19 preparations were cryopreserved. The function of cryopreserved islets was tested in vitro (static incubation and perifusion). The results of static incubation experiments confirmed that the insulin secretion of cryopreserved human islets in response to glucose stimulation was comparable to the response of islets that have not been frozen. In static incubation experiments, the mean (+/- SEM) insulin secretion of islets, prior to cryopreservation, was 239.3 (+/- 58.9) and 479.5 (+/- 59.5) pg/islet/15 min at 2.8 mM glucose and 16.7 mM glucose respectively. The mean (+/- SEM) insulin secretion of cryopreserved islets was 274 (+/- 103.2) and 468.5 (+/- 191.9) pg/islet/15 min at 2.8 mM and 16.7 mM glucose respectively. The perifusion experiments also demonstrated a significant increase of insulin secretion from cryopreserved islets perifused with a stimulating glucose concentration. Our experiments allow us to envisage the use of cryopreserved islet preparations for allotransplantation in diabetic patients.

Adult↗
PubMed1996

Combined islet-lung transplantation in a cystic fibrosis patient.

The prevalence of insulin-dependent diabetes mellitus (IDDM) in cystic fibrosis patients ranges from 2 to 8% and glucose intolerance up to 15%. In recent years, lung transplantation has helped to prolong life expectancy of cystic fibrosis patients and represents 10 to 30% of all indications for lung transplantation. The postoperative need for immunosuppressive therapy using diabetogenic agents has decompensatory effects on glucose regulation and will probably increase the number of insulin-dependent cystic fibrosis patients. We report the case of an insulin-dependent cystic fibrosis patient transplanted with a combined islet-lung allograft. The pre-transplantation C-peptide level was below 0.04 nmol/l and preoperative insulin requirement was some 100 U per day. A sequential bipulmonary lung transplantation was performed and, using the pancreas of the same donor, we isolated and purified the islets of Langerhans by a modified automated method. We obtained 232,200 islets equivalent, which were injected into the liver by portal embolization. The postoperative course was uncomplicated, the insulin requirement decreased to 50% of the preoperative need and the C-peptide value increased to normal values and remained with the normal range during a follow-up period of 15 months. In conclusion, we believe that, besides type I diabetic patients, insulin-dependent cystic fibrosis patients with a negative C-peptide value could also be good candidates for combined islet-lung allotransplantation.

Adult↗
PubMed1995

Hybrid Bacillus amyloliquefaciens X Bacillus licheniformis alpha-amylases. Construction, properties and sequence determinants.

A series of 33 single and mosaic hybrid alpha-amylases was constructed from the genes amyBA or amyLI, encoding the alpha-amylases from Bacillus amyloliquefaciens (AmyBA) and Bacillus licheniformis (AmyLI). The hybrid proteins, consisting of the entire alpha-amylase sequence with a variable portion of AmyBA or AmyLI origin, were characterized in order to find enzymes with new properties (thermostability, temperature and pH optima, and substrate specificity), and to localize the amino acid sequence regions responsible for the changes. The thermostability of the AmyBA/AmyLI (AL-type) hybrid proteins correlated with the position and the length of the hybrid sequence. The hybrid enzymes fell into six groups retaining, in comparison to AmyBA, a certain value of the extra-thermostability of AmyLI or becoming more thermolabile than AmyBA. Four regions are proposed to contain thermostability determinants (TSDs). They map between amino acid residues 34-76, 112-142, 174-179 and 263-276 of the respective hybrid enzymes, indicating the dominance of the N-terminal half of AmyLI for these hybrid enzymes' resistance against irreversible inactivation. Two (TSD3 and TSD4) coincide with regions I and II that had already been suggested to stabilise AmyLI [Suzuki, Y., Ito, N., Yuuki, T., Yamagata, H. & Udake, S. (1989) J. Biol. Chem. 264, 18,933-18,938]. The temperature dependence of activity of the AL-type hybrid alpha-amylases was compared at pH 6.4 and pH 7.6 and the hybrid enzymes of one thermostability group were found to have similar temperature responses. A hybrid region between residues 34-76 is demonstrated to correlate with the alpha-amylases' substrate specificity, i.e. either hydrolysis or accumulation of maltohexaose. This region was therefore named the G6G5 region. The exchange of internal sequences between residues 17-201 of AmyBA by the AmyLI counterpart in ALA-type mosaic hybrid alpha-amylases, with one exception (ALA99-429), unexpectedly destabilized the respective ALA-type hybrids. Two of these hybrid alpha-amylases (ALA17-151 and ALA76-151) were less thermostable than AmyBA, while others (ALA112-151, ALA112-201) were enzymically inactive. These data support specific roles of the predicted A1-B domain portion between residues 17-201 of those Bacillus alpha-amylases probably for correct folding and enzymic activity.

Amino Acid Sequence↗
PubMed1995

Influence of baclofen upon the alpha-motoneuron in spasticity by means of F-wave analysis.

Intrathecal baclofen dramatically improves severe spastic syndromes. This improvement is likely related to reduced excitability of alpha-motoneurons. To investigate the influence of baclofen upon the alpha-motoneuron, we analyzed F-waves before and after intrathecal baclofen bolus injection (usually 50 micrograms) as well as after administration of different, constantly delivered doses (60-200 micrograms/day). Intrathecal baclofen bolus decreased the maximum F-wave amplitude (Fp) from an initial value of 9% of the maximum M amplitude (Mmax) (= F/M-ratio) to 2.4% of the Mmax after 130-180 min, reduced the mean F-wave amplitude 60% within 150 min, and shortened the mean duration by 40-60% after 130-180 min. Constantly delivered baclofen of 100 micrograms/day reduced the F/M-ratio from 5% to 2%, the mean F-wave amplitude by 40-80%, and the F-wave mean duration by 40-80%. The minimum F-wave latency did not change after bolus or during steady state administration. The findings indicate that the F-wave mean and maximum amplitude as well as the mean duration are altered in a quantifiable manner following intrathecal baclofen application.

Baclofen↗
PubMed1995

Dynamics of cerebral blood flow velocities during normal human sleep.

Bilateral flow patterns of the middle cerebral artery (MCA) were recorded continuously throughout the night in 18 healthy male subjects (mean age 27.4 years) by a computer-assisted pulsed Doppler (2 MHz) system together with simultaneous polysomnography. After inception of sleep, mean flow velocity (MFV) decreased steadily during deepening sleep stages reaching -15.0 +/- 3.6% (p < 0.001) in the right MCA and -16.2 +/- 3.4% in the left MCA (p < 0.001) in stage 4 of the first sleep cycle compared to the waking state. Lowest MFV values were found in stage 2 preceding the last REM period (right MCA: -19.2 +/- 4.1%: left MCA: -19.7 +/- 5.1%). Changing from non-REM into REM sleep, a sudden rise of MFV, which varied from 8.9% (first sleep cycle, left MCA) to 18% (last sleep cycle, right MCA), could be consistently detected indicating a coupling of cerebral electrical activity and cerebral perfusion in REM sleep. During non-REM sleep this concomitant change of MFV and EEG activity was only found in the first sleep cycle, whereas no parallel changes could be observed in later sleep cycles. These results indicate a decoupling of EEG measured cerebral electrical activity and perfusion and suggest that factors other than metabolic mechanisms contribute to the regulation of cerebral perfusion during human non-REM sleep.

Adult↗
PubMed1995

Comparison of various coils used for magnetic stimulation of peripheral motor nerves: physiological considerations and consequences for diagnostic use.

We compared the ability of 4 magnetic coils to activate peripheral nerves in healthy subjects. No differences in motor threshold intensities were found between the coils, but the intensities needed to elicit maximum compound muscle action potential (CMAP) amplitudes were different. For superficial nerves maximum CMAPs in comparison with electrical stimulation were usually but not always found. CMAPs were at their maximum only when the direction of induced current flowed from proximal to distal and when a certain part of the coil was over the nerve. Distal nerve stimulation was time consuming. Due to artifacts many stimuli were necessary and sometimes no maximum CMAP could be elicited. CMAPs were much less sensitive to position changes of the coil than to changes in an electrical stimulator. Small circular coils were superior to larger coils in terms of the lower intensities necessary to elicit maximum CMAPs, better focusing of the stimulus, and less artifacts. For deep nerves amplitudes were always submaximal. Coactivation of nearby nerves and underlying muscles was another main drawback especially at proximal sites and for coils of large diameter. Despite better focusing, double coils are less useful due to their great diameter. Magnetic stimulation cannot replace electrical neurography at the moment, even if different coils are used at different sites of stimulation.

Action Potentials↗
PubMed1995

Temperament in toddlerhood.

The purpose of this article is to describe how toddler temperament can affect parent-child relations using a goodness-of-fit framework. Nursing considerations for assessing toddler temperament with families and providing parental guidance for managing toddlers with difficult temperament styles are discussed. Emphasis is placed on helping parents to understand their toddler's temperament-based behavior and to devise strategies that maximize compatibility between the toddler's temperament and parental expectations.

Child, Preschool↗
PubMed1995

Cerebral perfusion during sleep-disordered breathing.

Snoring, a leading symptom of the sleep apnoea syndrome (SAS), has been reported to be one of the risk factors for sleep-related cerebral strokes. Episodes of apnoea are accompanied by hypoxaemia as well as hypercapnia. As CO2 constitute a major regulatory factor controlling cerebral blood flow, it is likely that changes in cerebral perfusion are to be found in patients with SAS, which may be related to nocturnal stroke. A computer-assisted pulsed (2 mHz) Doppler ultrasonography system has been modified for continuous long-term and on-line recording of cerebral haemodynamics together with simultaneous polysomnography, continuous blood pressure recordings, and measurement of the end-expiratory CO2. The dynamics of cerebral blood flow velocity (CBFV) during sleep were measured in the right middle cerebral artery in 10 SAS patients. CBFV showed a characteristic nocturnal pattern with decreases during non-rapid eye movement (NREM) sleep and increases during REM sleep. Changes in sleep stage patterns as well as awakenings from NREM sleep were not regularly accompanied by corresponding changes in CBFV. Dramatic increases in CBFV could be observed during apnoeic episodes, with maximum increases during REM sleep. CO2 reactivity and changes in CBFV related to apnoea duration were markedly increased during sleep compared with the waking state in SAS patients. The dynamic feature of CBFV in relation to sleep patterns reflects quantitative uncoupling between cerebral electrical activity and cerebral perfusion during sleep in SAS patients as has been previously reported for normal subjects (Hajak et al. 1994). It supports a dissociation in the activity of central regulatory mechanisms during human sleep which might cause abnormal cerebral perfusion under certain circumstances. The increased CO2 reactivity during sleep in SAS suggests a 'hypersensitivity' of intracranial vasoactive receptors and/or disturbances in the central autonomic control of cerebrovascular functions. It may be concluded that, under certain conditions, the interaction of decreased cerebral perfusion in SAS patients with sleep-related cerebral perfusion patterns and haemodynamic changes during apnoeic episodes might lead to a critical reduction in cerebral perfusion.

Journal Article↗
PubMed1995

Clinical phenotype associated with terminal 2q37 deletion.

Three children with deletions of the terminal portion of the long arm of chromosome 2 [del (2) (q37)] are described and their clinical findings compared to published cases of 2q terminal deletions. Common clinical findings include development delay, macrocephaly, frontal bossing, depressed nasal bridge and cardiac anomaly. Hypotonia and repetitive behavior are also seen during different times of development. The facial characteristics of children with 2q terminal deletions are not uniform, but development delay is a constant finding. Chromosomal analysis of such children using high resolution banding may uncover the diagnosis of a small chromosomal deletion.

Abnormalities, Multiple↗
PubMed1995

[Rockwood capsulorrhaphy in shoulder instability. A clinical follow-up study].

Rockwood described a capsulorrhaphy technique for operative treatment of multidirectional shoulder instability with anterior dislocation. We have used this technique mainly in patients with severe multidirectional instability and now have 8 years' experience with it, which is reported below. The surgical technique involves refixation of the Bankart lesion with transosseous suture and double breasting of the anterior capsule. No transposition of the subcapularis muscle was performed. A functional rehabilitation program without immobilization was used in all patients. The daily activity level, the degree of discomfort upon shoulder-related activities and the subjective assessment of outcome were recorded for each patient. General outcome was determined with reference to Rowe's score. A clinical examination was performed as well as radiography. Strength was evaluated by standardized bilateral dynamometry. Follow-up examination was possible in 73 out of 82 patients. The mean age at follow up was 32.7 +/- 4.1 years, and the mean follow-up time, 4.3 years. The reason for surgery was recurrent dislocation in 81% of patients, pain in 4% and both pain and dislocation in 15% of patients. In 8 patients (10.9%) multiple (up to 4) previous surgical attempts by various methods had been unsuccessful. Postoperatively 59% (n = 44) were able to take part in sports without restrictions, 27.4% could take part only in sports not involving the shoulder, and 13.5% (n = 10) did not engage in any sports postoperatively. The redislocation rate was 12.3% (n = 9), and there was 1 traumatic redislocation. A deficit in abduction/elevation by 10-60 degrees was found in 4 patients (5.4%) and by > 60 degrees in 2 patients (2.7%).(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1994

Evidence for superantigen involvement in insulin-dependent diabetes mellitus aetiology.

Insulin-dependent diabetes mellitus (IDDM) is a T-cell-mediated autoimmune disease whose onset is believed to be triggered by unknown environmental factors acting on a predisposing genetic background. Islet-infiltrating T (IIT) cells from two IDDM patients, who had died at the onset of the disease from brain swelling as a complication of ketoacidosis, were analysed. The results provided evidence for the involvement of a pancreatic islet cell membrane-bound superantigen as a diabetes aetiopathogenetic factor. There was a selective expansion of a T-cell receptor (TCR) variable segment of the beta-chain (V beta 7) in these IIT cells in association with unselected V alpha-chain segments; extensive junctional diversity of the TCR V beta 7 chains; and evidence of positive selection, after exposure to diabetic islet cell membrane preparations, of V beta 7+ T-cell clones among peripheral blood lymphocytes from non-diabetic individuals.

Amino Acid Sequence↗
PubMed1994

Magnetically induced muscle contraction is caused by motor nerve stimulation and not by direct muscle activation.

When magnetically stimulating peripheral nerves, a local cocontraction of muscle under the coil is observed. We assessed whether this contraction results from: (1) magnetic stimulation of motor nerves, or (2) direct depolarization of the muscle membrane. Wrist extensor muscles of normal subjects were magnetically stimulated with the coil placed directly above the muscle. Neuromuscular transmission was then blocked by atracurium using a technique of local curarization. As a reference, the radial nerve was stimulated electrically. Magnetic and electrical stimuli were applied alternatingly every 10 s. Twitch force of wrist extension was measured isometrically over a period of about 70 min including the phase of complete neuromuscular block. Twitch amplitudes elicited by magnetic and electrical stimuli were equivalent during the whole experiment. These results suggest that muscle cocontraction following magnetic stimulation results from depolarization of terminal motor nerve branches.

Action Potentials↗
PubMed1994

Dysfunctional activation of subcortical nuclei in palatal myoclonus detected by high-resolution MRI.

Magnetic resonance images that were sensitized to changes in cerebral blood oxygenation state demonstrated dysfunctional activation of the dentate nuclei, the left inferior olivary nucleus and the left red nucleus in a 56-year-old patient with palatal myoclonus. These findings represent the first demonstration of movement-related activation of cerebellar, brainstem and midbrain nuclei in a single subject and at a spatial resolution comparable to that of anatomic MR images.

Brain Stem↗
PubMed1994

A longitudinal model of maternal self-efficacy, depression, and difficult temperament during toddlerhood.

The purpose of this study was to test a model of maternal self-efficacy during toddlerhood using a longitudinal sequential design. Participants were 126 mothers of 1-year olds (Cohort 1) and 126 mothers of 2-year olds (Cohort 2) who completed questionnaires measuring maternal self-efficacy, depression, and perceived difficult toddler temperament three times over 1 year. Data were analyzed using structural equation modeling and maximum likelihood estimation. Findings support a model whereby (a) the more depressed the mother feels, the more likely she is to rate her toddler's temperament as difficult, (b) the more difficult the child's temperament is perceived to be, the lower the mother's estimates of her parenting self-efficacy, (c) the lower the mother's self-efficacy, the greater her depression, and (d) the more depressed the mother feels at one point in time, the more likely she is to remain depressed 6 months later. Implications of the findings are discussed as they relate to self-efficacy theory and nursing intervention with parents of difficult toddlers.

Adult↗