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Biomedical subjects

M Arnold

Publications and source records attributed to M Arnold.

At least 109 records · Page 6Linked to original sources
PubMed1997

Contrast-enhanced transcranial color-coded duplex sonography in ischemic cerebrovascular disease.

BACKGROUND AND PURPOSE: Echo contrast agents have been shown to provide conclusive examinations in most patients with insufficient ultrasound penetration through the temporal bone. We investigated the diagnostic value of contrast-enhanced (CE) transcranial color-coded duplex sonography (TCCD) in patients with ischemic cerebrovascular disease and insufficient temporal windows and evaluated TCCD criteria that predict whether CE-TCCD studies may become conclusive. METHODS: Thirty-three patients presenting with ischemic strokes (n = 21) and transient ischemic attacks (n = 12) were investigated. Extracranial color duplex imaging showed normal findings in 24 patients, eight > or = 70% stenoses and one occlusion of the carotid arteries in 8 patients, and severe occlusive disease of both vertebral arteries in 1 patient. Seven carotid stenoses and vertebral artery obstructions were confirmed by angiography. The galactose/palmitic acid-based echo contrast agent was injected intravenously as bolus of 200, 300, or 400 mg/mL in a dosage of 10, 5, and 5 mL, respectively. RESULTS: Thirty-two of the 33 patients were completely examined because 1 patient who felt pain at the injection site declined further investigations. Twenty-one (66%) of 32 CE studies were conclusive and showed cross-flow through three anterior and two posterior communicating arteries, but no stenoses and occlusions. Precontrast identification of any cerebral artery provided an overall accuracy of 97% in predicting a conclusive CE investigation. Precontrast TCCD identified no arterial Doppler signals in patients with inconclusive CE studies. CONCLUSIONS: CE-TCCD provided conclusive examinations in two thirds of patients with ischemic cerebrovascular disease and ultrasound-refractory temporal windows. Precontrast detection of any cerebral artery reliably predicted a conclusive CE investigation.

Adult↗
PubMed1997

Continuous intraoperative monitoring of middle cerebral artery blood flow velocities and electroencephalography during carotid endarterectomy. A comparison of the two methods to detect cerebral ischemia.

BACKGROUND AND PURPOSE: Intraoperative monitoring of brain function may influence the outcome of carotid endarterectomy (CEA). METHODS: We performed transcranial Doppler (TCD) monitoring of middle cerebral artery blood flow velocities (VMCAs) and eight-channel electroencephalographic (EEG) recording simultaneously in 82 patients undergoing CEA. Thiopental narcosis limited EEG interpretation in 11 patients, thus allowing direct comparison of both methods in 71 patients. RESULTS: There was a significant correlation between VMCA decrease and the frequency of EEG changes after carotid clamping (P < .001). Eight patients (11%) showed a VMCA decrease exceeding 60%, accompanied by EEG changes in 7 patients. Altogether, 16 patients (22%) showed severe or moderate EEG changes. Stenosis or occlusion of the contralateral carotid artery led to an increase of abnormal findings with both monitoring methods, which was, however, significant only for TCD (P < .05). Four patients (4.8%) suffered intraoperative transient ischemic attacks. In 3 of these patients, there were no abnormal findings with either of the methods. The events were thus unpredictable and probably of embolic origin. The fourth patient showed VMCA decrease to 0 and severe EEG changes. Nine patients had severe or moderate EEG changes without significant VMCA decrease and without complications. EEG monitoring alone in these would have led to unnecessary use of a shunt with the increased risk of embolism. CONCLUSION: EEG and TCD monitoring are complementary techniques. Their results showed a good overall correlation but with marked differences in the individual patient. TCD monitoring alone was sensitive enough to prevent ischemic intraoperative complications. EEG findings are of limited value when barbiturates are used.

Aged↗
PubMed1997

Well done.

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Complementary Therapies↗
PubMed1997

Transtemporal power- and frequency-based color-coded duplex sonography of cerebral veins and sinuses.

PURPOSE: To determine the ability of transtemporal power- and frequency-based transcranial color-coded duplex sonography to aid in the assessment of cerebral veins and sinuses, as well as to provide reference data for flow direction and velocity. METHODS: Using a color duplex device equipped with a 2.0/2.5-MHz sector scan, we insonated 120 healthy volunteers and three patients with cerebral venous thrombosis. RESULTS: In subjects 20 to 59 years old, deep middle cerebral veins were identified in 88%, basal veins in 97%, straight sinuses in 60%, and transverse sinuses in 42%. The corresponding values for subjects 60 to 79 years old were 53%, 86%, 23%, and 20%, respectively. Velocities were highest in transverse and straight sinuses, slower in basal veins, and slowest in deep middle cerebral veins. Flow was directed lateromedially in the deep middle cerebral vein, rostrocaudally in the basal vein and straight sinus, and mediolaterally in the transverse sinus. Two patients with straight sinus thromboses showed reversed flow direction in the basal veins, and one patient with superior sagittal sinus thrombosis showed elevated velocities in a deep middle cerebral vein. CONCLUSION: Transtemporal power- and frequency-based color-coded duplex sonography enabled imaging and velocity measurements in deep cerebral veins in subjects 20 to 59 years old, but detection of the straight and transverse sinuses was low. In older subjects, only the basal vein was regularly assessed.

Adult↗
PubMed1996

Dynamic coherence analysis of vasomotion and flow motion in skeletal muscle microcirculation.

The aim of our study was to determine the cause of fluctuations in microvascular blood flow measured by laser Doppler perfusion monitoring (LDPM) in microvessels of the hamster skin fold preparation. LDPM flow fluctuations (flow motion) were compared to simultaneous records of diameter changes obtained from arterioles and venules. Time-varying coherence analysis was used to quantify the frequency of flow and diameter changes in awake hamsters in control conditions and during sodium nitroprusside-induced vasodilation. Power spectrum analysis of LDPM signals of order 4 and 3 arterioles indicated frequencies of 0.06 +/- 0.01 and 0.08 +/- 0.02 Hz, respectively. Order 3 arterioles exhibited significant temporal coherence between flow motion and vasomotion signals at a frequency of the order of 0.1 Hz. There was lack of coherence when vasomotion was absent in arterioles. Order 4 arterioles had several coherent frequencies in addition to that around 0.1 Hz. In conclusion, time-variant coherence analysis indicated that spontaneous fluctuations in flow are caused by vasomotion of order 3 arterioles with frequency around 0.1 Hz that appears to coordinate local control processes in the microcirculation. Additional frequency components present in LDPM signals are unrelated to vasomotion.

Animals↗
PubMed1996

Effects of L-carnitine supplementation on physical performance and energy metabolism of endurance-trained athletes: a double-blind crossover field study.

A double-blind crossover field study was performed to investigate the effects of acute L-carnitine supplementation on metabolism and performance of endurance-trained athletes during and after a marathon run. Seven male subjects were given supplements of 2 g L-carnitine 2 h before the start of a marathon run and again after 20 km of the run. The plasma concentration of metabolites and hormones was analysed 1 h before, immediately after and 1 h after the run, as well as the next morning after the run. In addition, the respiratory exchange ratio (R) was determined before and at the end of the run, and a submaximal performance test was completed on a treadmill the morning after the run. The administration of L-carnitine was associated with a significant increase in the plasma concentration of all analysed carnitine fractions (i.e. free carnitine, short-chain acylcarnitine, long-chain acylcarnitine, total acid soluble carnitine, total carnitine) but caused no significant change in marathon running time, in R, in the plasma concentrations of carbohydrate metabolites (glucose, lactate, pyruvate), of fat metabolites (free fatty acids, glycerol, beta-hydroxybutyrate), of hormones (insulin, glucagon, cortisol), and of enzyme activities (creatine kinase, lactate dehydrogenase). Moreover, there was no difference in the result of the submaximal performance test the morning after the run. In conclusion, acute administration of L-carnitine did not affect the metabolism or improve the physical performance of the endurance-trained athletes during the run and did not alter their recovery.

Adult↗
PubMed1996

Use of adaptive Hilbert transformation for EEG segmentation and calculation of instantaneous respiration rate in neonates.

Broad, as well as narrow, band Hilbert transform filters (HTFs) were used as preprocessing units in the analysis of electroencephalogram (EEG) and respiratory movements in neonates. For these applications, new algorithms for the adaptation of the resonance frequency of a narrow-band-pass filter to the actual signal properties on the basis of an analytic filter design were developed. For the segmentation of the discontinuous EEG, the location of the resonance frequency was imbedded into the learning algorithm of a neural network (NN). In such automatic EEG pattern recognition, the detection of spike activity was taken into consideration. The spike detection scheme introduced uses broad-band HTFs as basis units. Additionally, the algorithm for the continuous control of the resonance frequency was applied to achieve the adaptation of the processing unit that performed the calculation of the instantaneous respiration rate, in this framework, a new on-line method for adaptive frequency estimation that is less sensitive to low signal-to-noise ratios (SNRs) was obtained. The new approaches introduced were tested in comparison with processing methods that have been established for the analysis of experimental and clinical data.

Algorithms↗
PubMed1996

Characterisation of the acute phase response of heifers to a prolonged low dose infusion of lipopolysaccharide.

The effect of a prolonged low dose infusion of bacterial lipopolysaccharide (LPS) on acute phase-like reactions was examined in heifers. LPS (2 micrograms kg-1 dissolved in 100 ml water), or saline was infused (at 1 ml min-1) intravenously for 100 minutes and blood samples were taken at various times before, during and after the infusion. The serum concentrations of tumour necrosis factor-alpha (TNF alpha), interleukin-1 beta (IL-1 beta), interleukin-6 (IL-6) and serum amyloid A (SAA) and the rectal temperature increased in response to the LPS infusion. Serum TNF alpha increased before the increases in IL-1 beta and IL-6 and remained high from 20 minutes after the onset of the infusion until the end of the sampling period (six hours). The LPS-induced increases in serum IL-1 beta and IL-6 were biphasic. Plasma cortisol and lactate concentrations also increased, and plasma glucose and beta-hydroxybutyrate concentrations decreased in response to the LPS infusion. The similarity of these reactions to changes observed in response to bacterial infections shows that the prolonged infusion of low doses of LPS is a good model for studying the acute phase response to Gram-negative bacterial infection in heifers.

Acute-Phase Proteins↗
PubMed1995

A quantitative electrophoretic migration shift assay for analyzing the specific binding of proteins to lipid ligands in vesicles or micelles.

We present a new assay for analyzing the specific binding of proteins to lipid ligands contained within vesicles or micelles. This assay, referred to as the electrophoretic migration shift assay, was developed using a model system composed of cholera toxin and of its physiological receptor, monosialoganglioside GM1. Using polyacrylamide gel electrophoresis in non-denaturing conditions, the migration of toxin components known to interact with GM1 was retarded when GM1 was present in either lipid vesicles or micelles. This effect was specific, as the migration of proteins not interacting with GM1 was not modified. The localization of retarded proteins and of lipids on gels was further determined by autoradiography. The stoichiometry of binding between cholera toxin and GM1 was determined, giving a value of five GM1 per one pentameric assembly of cholera toxin B-subunits, in agreement with previous studies. The general applicability of this assay was further established using both streptavidin and annexin V together with specific lipid ligands. This assay is fast, simple, quantitative, and requires only microgram quantities of protein.

Annexin A5↗
PubMed1995

Medical and health care needs of families providing in-home care for relatives with developmental disabilities.

The purpose of this investigation was to attempt to describe the health care needs of families providing in-home care to members with developmental disabilities as well as the characteristics and demographics of families providing in-home care. The survey included 761 families who participated in a federal demonstration project in rural southern Georgia. The results indicated that impoverished families need increased assistance to provide adequate medical and health care when providing in-home care to relatives experiencing developmental disabilities. Implications for administration of programs and development of policies are discussed.

Caregivers↗
PubMed1995

Radiation-induced impairment of osseous healing: quantitative studies using a standard drilling defect in rat femur.

The femora of adult Wistar rats were locally irradiated with single doses of X rays and 1 day later were wounded by a standardized drilling defect that extended through the diaphyseal cortex into the marrow cavity. Healing of the lesion was followed over 30 weeks to assess the time course of osseous closure. In unirradiated bones healing was complete by week 7. Irradiation with doses up to 15 Gy imparted a dose-dependent delay in the formation of primary callus and its subsequent replacement by more mature bone, while after higher doses healing remained permanently compromised or even suppressed. Using histomorphometry, osseous closure was also measured quantitatively for healing periods of 7, 10, 16 and 30 weeks and the data were expressed as the percentage of responders with < or = 40% fractional closure. The resulting dose-response curves were steep, displaying a large threshold dose and ED50 values between 16.8 to 17.5 Gy (7 to 16 weeks) and 19.4 Gy (30 weeks), respectively.

Animals↗
PubMed1994

Trial of a topically administered local anesthetic (EMLA cream) for pain relief during central venous port accesses in children with cancer.

Procedure-related pain is a significant problem for many children receiving cytotoxic chemotherapy. In an effort to lessen this toxicity, we studied the efficacy and safety of administering topical local anesthesia using EMLA cream in 47 evaluable children with cancer undergoing implanted central venous port injections. Children (< 21 years old) scheduled to undergo repeated venous access procedures were selected for study. A placebo-controlled, randomized, double-blind, crossover study design was utilized. Statistically significant decreases in pain intensity scores (P < 0.002) were recorded by both children and investigators during the use of EMLA cream as compared with placebo. There was a good correlation between pain scores recorded by both patients and health care providers using both visual analog scales and categorized pain measurement tools. The topical application of EMLA cream 5% provides highly effective superficial anesthesia, and promises to be extremely useful for pain relief during percutaneous access procedures in cancer patients.

Administration, Cutaneous↗
PubMed1994

Laparoscopic Excision of Ovarian Endometriomas: Does Post-Operative Medical Treatment Prevent Recurrence?

Of 103 women undergoing laparoscopic excision of ovarian endometriomas, 41 patients were prescribed to 3 to 6 months therapy with GnRH analogs or danazol postoperatively and 62 received no additional treatment. No significant difference in extent of disease was present between the two groups at the time of surgery. Follow-up longer than 3 months, including a sonogram, was available for 40 patients of the treatment group and for 42 patients of the group receiving no additional treatment. Four recurrences (10%) at 3, 12, 16 and 21 months occurred in the treatment group, and 3 recurrences (7%) at 5, 6 and 6 months occurred in the no-treatment group (p=NS). Postoperative medical treatment does not prevent recurrence of laparoscopically excised ovarian endometriomas.

Journal Article↗