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Biomedical subjects

E Meyer

Publications and source records attributed to E Meyer.

At least 235 records · Page 13Linked to original sources
PubMed1987

Time-dependent changes of lumped and rate constants in the deoxyglucose method in experimental cerebral ischemia.

Time-dependent changes in the lumped and rate constants in a bilateral middle cerebral artery (MCA) occlusion in cats were evaluated. These variables were measured in 11 cats after a sham operation, in five after a 1-h occlusion, in two after a 2-h occlusion, in five after a 4-h occlusion, and in four after a 16-h occlusion. The time course of the cerebral tissue radioactivity [Ci* (t)] was monitored by external coincidence counting during a programmed infusion of [18F]2-fluorodeoxyglucose (FDG). Arterial plasma concentration [Cp* (t)] of tracer was kept constant during the first 45 min. Comparison of k2* and k3* in the sham-operated group, estimated by external coincidence counting, and by the ratio of extraction fractions of glucose and [18F]2-FDG, demonstrated no significant difference between these rate constants in these two groups of animals. The rate and lumped constants were also estimated from Ci* (t) and Cp* (t), as well as from the ratio of extraction fractions of glucose and [18F]2-FDG, respectively, in the MCA occlusion group. Significant decrease in k3* was observed after 1 h of occlusion (20% lower than in the sham operation, p less than 0.05); in k1* decrease occurred within 4 h of occlusion (21% lower than in the sham operation, p less than 0.05). However, decrease in k2* was observed only after 16 h of occlusion (26% lower than in the sham operation, p less than 0.05). Namely, decrease of rate constants occurred first in k3* then in k1* and k2*.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1987

Estimation of cerebral oxygen utilization rate by single-bolus 15O2 inhalation and dynamic positron emission tomography.

This study shows that regional CMRO2 can be estimated by means of nonlinear regression using dynamic positron emission tomographic data acquired during 1 min following single-bolus inhalation of 15O2. The feasibility of simultaneous estimation of CBF, cerebral blood volume (CBV), oxygen extraction ratio (OER), and CMRO2 was assessed by simulations using the model of Mintun et al. Four oxygen metabolic measurements, each consisting of a CBF, CBV, and 15O2 bolus study, were carried out on three volunteers. Regional values for CBF, CBV, OER, and CMRO2 were derived in two ways: from the fits of the time-activity curves of the dynamic 15O2 bolus study alone [CMRO2(fit)] and from the three separate studies [CMRO2 (control)]. For the 56 regions of interest analyzed, using a fit interval of 60 s, CMRO2(fit) was 93.4 +/- 7.8% of CMRO2(control) (mean +/- SD) with a correlation coefficient of r = 0.95. CMRO2(control) ranged from 87 to 290 mumol/min/100 g. Individual simultaneous estimates of CBF, CBV, and OER were not reliable. Finally, we found that the validity of the model was limited in practice to the first minute after tracer inhalation.

Administration, Inhalation↗
PubMed1987

Cerebral blood volume is increased in dogs during administration of nitrous oxide or isoflurane.

Positron emission tomography was used to study the effects of nitrous oxide (N2O) and isoflurane on regional cerebral blood volume (rCBV) in dogs during normocapnia and hypocapnia. Regional cerebral blood volume was measured serially during the addition of 50% N2O to a background anesthetic of fentanyl in normocapnic (group 1) and hypocapnic (PaCO2 25 mmHg, group 2) dogs. In each group, after 15 min of N2O administration accompanied by rCBV measurement, elimination of N2O with 100% O2 was continued for 15 min. This was followed by introduction of 2% isoflurane (no N2O), again accompanied by serial measurements of rCBV. In the normocapnic animals, the addition of 50% N2O caused an 11% increase in rCBV (6.1 +/- 1.4 to 6.8 +/- 1.0 ml/100 g, P less than 0.02) while 2% isoflurane caused a 36% increase (6.1 +/- 1.3 to 8.0 +/- 1.7 ml/100 g, P less than 0.02). The initial induction of hypocapnia during infusion of fentanyl in group 2 animals was associated with a 17% decrease in rCBV. In the hypocapnic dogs, there was no change in rCBV when N2O was introduced; however, an increase of 15% occurred following the addition of isoflurane (3.9 +/- 0.6 to 4.5 +/- 0.7 ml/100 g, P less than 0.02). Isoflurane, even during hypocapnia, may increase cerebral blood volume which in some circumstances may lead to an increase in ICP.

Animals↗
PubMed1987

Efficacy of antiprostaglandin therapy in vernal conjunctivitis.

Twenty-seven patients with vernal conjunctivitis who remained symptomatic following treatment with corticosteroid drops and/or Opticrom drops (sodium cromoglycate 2%, benzalkonium chloride 0.01%) were treated with aspirin. Aspirin produced marked improvement in all patients apart from three. The possible mechanism of the efficacy of aspirin in vernal conjunctivitis is discussed.

Administration, Topical↗
PubMed1987

Hemodynamic and metabolic effects of cerebral revascularization.

Pre- and postoperative positron emission tomography (PET) was performed in six patients undergoing extracranial to intracranial bypass procedures for the treatment of symptomatic extracranial carotid occlusion. The six patients were all men, aged 52 to 68 years. Their symptoms included transient ischemic attacks (five cases), amaurosis fugax (two cases), and completed stroke with good recovery (one case). Positron emission tomography was performed within 4 weeks prior to surgery and between 3 to 6 months postoperatively, using oxygen-15-labeled CO, O2, and CO2 and fluorine-18-labeled fluorodeoxyglucose. Cerebral blood flow (CBF), cerebral blood volume (CBV), cerebral metabolic rates for oxygen and glucose (CMRO2 and CMRGlu), and the oxygen extraction fraction (OEF) were measured in both hemispheres. Preoperatively, compared to five elderly control subjects, patients had increased CBV, a decreased CBF/CBV ratio, and decreased CMRO2, indicating reduced cerebral perfusion pressure and depressed oxygen metabolism. The CBF was decreased in only one patient who had bilateral carotid occlusions; the OEF, CMRGlu, and CMRO2/CMRGlu and CMRGlu/CBF ratios were not significantly different from control measurements. All bypasses were patent and all patients were asymptomatic following surgery. Postoperative PET revealed decreased CBV and an increased CBF/CBV ratio, indicating improved hemodynamic function and oxygen hypometabolism. This was associated with increased CMRO2 in two patients in whom the postoperative OEF was also increased. The CMRGlu and CMRGlu/CBF ratio were increased in five patients. Changes in CBF and the CMRO2/CMRGlu ratio were variable. One patient with preoperative progressive mental deterioration, documented by serial neuropsychological testing and decreasing CBF and CMRO2, had improved postoperative CBF and CMRO2 concomitant with improved neuropsychological functioning. It is concluded that symptomatic carotid occlusion is associated with altered hemodynamic function and oxygen hypometabolism. Cerebral revascularization results in decreased CBV, indicating improved hemodynamic reserve, but does not consistently improve oxygen metabolism.

Aged↗
PubMed1987

Radiation dose to upper airways from inhaled oxygen-15 carbon dioxide.

According to Powell et al., significant retention of 15O in the tracheal mucosa results in a radiation absorbed dose of 75 to 200 rad upon breathing of 15O-CO2 for one hour at 1 mCi/liter. Such a high dose would seriously compromise the 15O-CO2 inhalation method for positron emission tomographic (PET) measurement of cerebral blood flow (CBF). In order to verify these results, we have assayed 15O activity in the tracheal region of three volunteers by PET during inhalation of 15O-CO2 and 15O-O2. Using methods similar to those of the above authors for estimating absorbed dose in the tracheal mucosa, we have obtained a value of 14-38 rad, which is more in keeping with 3-5 rad found by Bigler et al. from direct assay of mucus and saliva. We conclude that the 15O-CO2 inhalation method is a safe and practical means of measuring CBF by PET.

Carbon Dioxide↗
PubMed1987

[Bone marrow aplasia: a rare complication in virus-induced hepatitis].

Bone marrow aplasia associated with acute viral hepatitis is a rare, in the rule late complication. A prognostic relation between the latency of acute hepatitis and the development of aplastic anemia is described. We report a case of nearly symptomless hepatitis in a 25 year old women with a fatal course of aplastic anemia. First clinical symptoms were caused by aplastic anemia. The pathogenesis of aplastic anemia associated to viral hepatitis is obscure. Genetic and immunological causes are discussed. A direct viral action is possible. Because the main part of the described cases is caused by non-A, non-B hepatitis, it seems apparent that at least a non-A, non-B virus strain could have an affinity to bone marrow cells. Ensuring this, relations will be impossible up to the identification of the virus.

Adult↗
PubMed1987

[Unusual, tumor-like calcinosis in scleroderma. Thibièrge-Weissenbach syndrome].

In patients with progressive scleroderma, interstitial calcifications are present to a varying extent. They are mostly located in the soft tissues of the fingers, resembling points, commas or dashes. They may also appear as "calcinosis universalis" and reach a considerable size. Thus they mimic proliferative tumors. Scintigraphy, proving the existence of further calcifications can be helpful. We report the case of a female patient who presented with such a "pseudotumor" of unusual size, site and extent in the lumbar region.

Bone and Bones↗
PubMed1987

Metabolic and hemodynamic evaluation of gliomas using positron emission tomography.

Positron emission tomography (PET) was used on 16 patients with untreated cerebral gliomas to measure cerebral glucose and oxygen metabolism, oxygen extraction, blood flow, and blood volume. In addition, pH values were obtained for seven cases. Gliomas were later proven by biopsy; two patients had tumors with degrees of malignancy of grade II, two patients had grade III, and 12 patients had grade IV tumors. Compared with homologous gray matter regions in the opposite hemisphere, tumor tissue showed increased blood volume, but decreased oxygen extraction and oxygen metabolism. Compared with grade II tumors, grade IV tumors demonstrated higher blood volumes, but lower relative oxygen extraction and utilization. Tumor blood flow was variable, but was lower in the higher grade tumors. Rates of glucose utilization in tumor, calculated by using individually determined rate constants, were variable, and did not correlate with tumor size or tumor grade. Parietal tumors (n = 6) tended to have higher relative glucose utilization and blood flow, and lower relative oxygen extraction, when compared with frontal tumors (n = 4). Tumor pH differed significantly from the pH in contralateral brain (p less than 0.005); alkalotic pH values were consistently seen. These findings in and around cerebral gliomas studied before intervention differ from the results found in gliomas after exposure to radiation or chemotherapy.

Blood Volume↗
PubMed1987

Electron microscopic study of Bitot's spots.

The histological and structural features of Bitot's spots are described. Light microscopy revealed squamous metaplasia with keratinization. Electron microscopy showed severe loss and attenuation in height of microvilli as well as widening of the intercellular spaces. The amorphous material overlying the conjunctiva was composed of cellular debris containing edemetous endoplasmic reticular membranes and lysozomes.

Adolescent↗
PubMed1987

Alternative approach to estimate lumped constant in the deoxyglucose model: simulation and validation.

An alternative method of estimating the lumped constant (LC) in the deoxyglucose model was developed. The LC was estimated using data obtained during the first 10 min after injection of the tracer by a nonlinear least-squares (NLSQ) method. The method does not require a constant plasma concentration. This approach was evaluated in a computer simulation by adding different levels of noise and considering various input functions. Errors in the estimated LC in this and Sokoloff et al.'s conventional method were compared. We found that the approach proposed here results in more reliable estimates of LC. The study in completed in a shorter experimental period, and any shape of the input function can be used. The new technique was then applied to measure whole brain LC and rate constants in cat brain for 2-[18F]fluoro-2-deoxy-D-glucose (2-[18F]FDG). Measured mean value (+/-s.e.m.) for the whole brain LC = 0.443 +/- 0.012 (N = 7), for the whole brain k2* = 0.124 +/- 0.009 and k3* = 0.024 +/- 0.001 (N = 7).

Animals↗
PubMed1987

Recovery of the electroretinogram in rabbits after argon laser photocoagulation.

Argon laser is widely used to coagulate the diabetic retina in order to inhibit the proliferative stage of diabetic retinopathy. Ten pigmented rabbits underwent retinal photocoagulation with argon laser. Retinal function was assessed electroretinographically before treatment and at different time intervals after treatment. The ERG responses measured 4-7 days after treatment were reduced in amplitude by a degree which was proportional to the number of laser applications. In five eyes that were treated with at least 1000 applications the ERG responses were very small when measured 4 days post-treatment. However, a gradual recovery was observed and within 2 months the ERG responses approached the normal pretreatment amplitudes. Histological findings from light and electron-microscopy suggested that the ERG recovery could not be solely explained by healing of the coagulated areas. Structural differences were seen in the pigment epithelial layer between a retina obtained immediately after treatment and one studied after ERG recovery. It is suggested that changes in the electrical resistance of the pigment epithelium may contribute to the ERG reduction seen immediately after laser treatment in the rabbit and to the increase in the ERG amplitude observed during the apparent functional recovery of the retina.

Animals↗
PubMed1987

The role of carcinoembryonic antigen in surveillance of patients with choroidal malignant melanoma: a prospective study.

Serum carcinoembryonic antigen levels were measured in nine patients with choroidal malignant melanoma prior to enucleation and at three-month intervals thereafter for three years. Raised levels were found preoperatively in four of the nine patients. One of these patients had persistent and progressive elevation of serum carcinoembryonic antigen levels postoperatively, and clinical evidence of metastases subsequently became apparent. In the remaining eight patients, carcinoembryonic antigen levels remained at or returned to normal values and no clinical evidence of progression of the disease was detected. These results suggest that although serum carcinoembryonic antigen estimation is not a reliable diagnostic screening test for choroidal malignant melanoma, it may be useful for follow-up and monitoring of recurrences of the disease.

Carcinoembryonic Antigen↗
PubMed1986

Nucleotide sequence of the Paramecium primaurelia G surface protein. A huge protein with a highly periodic structure.

The complete DNA sequence of the G surface protein of Paramecium primaurelia has been determined. It contains an open reading frame of 8145 nucleotides devoid of introns and coding for a protein of 329,000 Mr. Analysis of the deduced amino acid sequence reveals remarkable features such as important internal homologies and a periodic structure, which could be dictated in part by the rigid scaffolding of cysteine residues. The predicted secondary structure shows a quasi absence of alpha-helix and an abundance of beta-pleated sheets and random coils. The monotony of the amino acid sequence is in favour of a structural role for the protein. Interestingly, homologies with other proteins are limited to surface antigens of trypanosomes. Finally, our data are consistent with a genetic code for paramecium which differs from the "universal" code by the assignment of TAA and TAG codons to glutamine.

Amino Acid Sequence↗