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Biomedical subjects

H Stevens

Publications and source records attributed to H Stevens.

At least 37 records · Page 2Linked to original sources
PubMed1998

60Co and 45Ca autoradiography in cerebral ischemia in the rat.

Radioisotopes of divalent Co (57Co in single photon emission tomography (SPECT)and 55Co in positron emission tomography (PET) have clinically been applied to visualize Ca related brain damage. The cerebral uptake of 45Ca and 60Co in a unilateral stroke model in the rat was compared; 100 microCi 45CaCl2 or 60 microCi 60CoCl2 was intravenously given at day 2 or 9 and the rats were killed 24 h later for autoradiography. Similarly increased uptake of 45Ca and 60Co was observed at both time points in unilaterally affected areas such as the cerebral cortex, dentate gyrus, caudate putamen of the striatum, substantia nigra pars reticulatum and corpus geniculatum. More Ca-uptake was found in the hippocampus CA1 region (at day 10) and the thalamus (ventral part at both time points). Radioactive Co but not Ca accumulated in the choroid plexus. Although the present investigation supports the idea that divalent Co-isotopes are useful to visualize stroke induced damage and choroid plexus function, these radionuclides do, however, not allow to detect excessive Ca-influx in degenerating neurones.

Animals↗
PubMed1998

Cobalt-57 as a SPET tracer in the visualization of ischaemic brain damage in patients with middle cerebral artery stroke.

In PET studies we have shown the usefulness of cobalt radionuclides for the visualization and quantification of ischaemic damage in stroke. In the present study, we explored 57Co2+ as a SPET tracer. Uptake of radioactivity was estimated by using a cobalt enhancement ratio defined as the ratio of cobalt uptake in the affected region versus a similar volume in the non-affected contralateral side. Clinical status was assessed with the Orgogozo stroke score at the time of scanning and at least 60 days after admission. Nineteen patients (11 men, 8 women) with a middle cerebral artery stroke were examined with 57Co2+ SPET 0-30 days after stroke onset. Our investigations show enhanced cobalt uptake in the infarcted brain tissue in patients with a major stroke and little clinical improvement. There was a significant correlation between the cobalt enhancement ratio and the Orgogozo score at the time of scanning and discharge. Our results suggest that 57Co2+ SPET is suitable for determining the extent of (possibly calcium-mediated) damage in stroke and in the assessment of potential therapeutic interventions.

Adult↗
PubMed1998

AIDS, Not Hearing Aids: Exploring the Link Between the Deaf Community and HIV/AIDS.

This article will address the reasons that the messages brought by massive HIV/AIDS prevention campaigns in several countries literally fell on deaf ears within the Deaf community, and how this in turn made it possible for Deaf people's health and human rights to be violated. Then it will show how the Deaf community has gradually geared up to protect itself against the spread of the HIV virus. Attention is given to the importance and meaning of "effective communication" and the role of Sign Language interpreters. Finally, recommendations are offered towards better protection of Deaf people's health and human rights.

Journal Article↗
PubMed1998

Cobalt-57 and technetium-99m-HMPAO-labeled leukocytes for visualization of ischemic infarcts.

UNLABELLED: Previous studies have shown the usefulness of divalent cobalt isotopes to visualize cerebral damage after stroke. The site of accumulation of cobalt ion is unknown but may be explained by neuronal influx, analogous to that of calcium ion. Additionally, uptake may be due to infiltrating leukocytes or protein-bound cobalt. The aims of this study were to compare 57Co-SPECT with leukocyte SPECT and to compare the SPECT findings with clinical outcome as scored by the Orgogozo scale. MATERIALS: Ten patients with a CT scan positive for middle cerebral artery infarcts were included in the study (7 men, 3 women; mean age 70 yr). Technetium-99m leukocyte and cobalt-SPECT (interval 2-4 days) were made with a double-headed gamma camera, after the injection of 10-15 mCi 99mTc-HMPAO-labeled leukocytes and 0.4 mCi 57Co, respectively. Scans were performed within 5-30 days after onset of the first symptoms. Regions of interest (ROI) containing the area of infarction in the slices displaying enhanced radioactivity or the middle cerebral artery (MCA) region in four successive slices were defined for calculating enhancement ratios. The 99mTc leukocyte enhancement ratio (LER) and cobalt enhancement ratio (CER) were defined as the quotient of radioactivity in the ROI and an identical contralateral ROI. The MCA stroke-scale according to Orgogozo was used to assess neurological deficits at the time of scanning and discharge. RESULTS: Cobalt-57 and 99mTc-HMPAO showed uptake in the infarcted brain area in five patients; the quantitative uptake in the infarcted brain area of the two tracers correlated significantly (p < 0.05). Both the LER and the CER correlated significantly (p < 0.05) with the Orgogozo score at the time of scanning. Only the LER correlated significantly (p < 0.05) with the Orgogozo score at discharge. CONCLUSION: Uptake of cobalt and leukocytes in the peri-infarct tissue suggests that 57Co may visualize a component of the inflammatory response. Divalent 57Co may be convenient to predict clinical prognosis after stroke.

Aged↗
PubMed1997

Identification of apoptotic changes in osteocytes in normal and pathological human bone.

Previous work on bone growth and biomechanics suggests that osteocytes might sense the requirement for bone remodeling and signal to cells in the basic multicellular unit that undertake this function. The present study looked for evidence of apoptosis in human osteocytes in adult, pediatric, and pathological bone to compare these situations of differing levels of turnover and considered the possibility of a functional role for this death mechanism in bone modeling and remodeling. Apoptosis was identified in bone tissue by agarose gel electrophoresis of DNA (to demonstrate DNA ladders). In cryostat sections it was possible to visualize individual cells with fragmented DNA in situ using a modified nick translation technique (NT). In addition, visualization of apoptotic morphology was undertaken using light and electron microscopy. Adult femoral head and iliac crest bone showed no evidence of DNA ladders and very small numbers of osteocytes with DNA fragmentation using NT. In contrast, samples of pediatric calvaria, adult heterotopic bone, and osteophytes all displayed characteristic laddering of extracted DNA and showed evidence of potentially apoptotic osteocytes in situ using NT. In agreement with these findings, transmission electron microscopy showed numbers of osteocytes in infant calvaria with advanced chromatin condensation and cell shrinkage indicative of apoptosis. Since all three types of positive bone are involved in rapid matrix turnover, apoptotic changes in human osteocytes in vivo might be related in general terms to the modeling and remodeling activity level of the bone sampled. It was further found that the distribution of potentially apoptotic cells in the infant and pathological bone was anatomically nonuniform, raising the intriguing possibility of a functional relationship between bone turnover and the controlled cell death of osteocytes.

Adult↗
PubMed1997

55Co-PET in stroke: relation to bloodflow, oxygen metabolism and gadolinium-MRI.

BACKGROUND: Several studies have shown the feasibility of Co-isotopes (55Co and 57Co) in imaging of neuronal damage in stroke, multiple sclerosis, cerebral tumors and trauma. These studies indicate that Co-isotopes allow visualization of brain pathology related to inflammatory processes, reactive gliosis and cell death. Until now, it is not clear if 55Co accumulation occurs in the core of infarction or in the penumbra. Therefore, in the present study, we compared 55Co-PET with functional parameters such as cerebral bloodflow (rCBF) using C15O2, oxygen metabolism (rCMRO2) using 15O2 and cerebral bloodvolume (CBV) using C15O in PET and with the anatomical parameter Gd-MRI. PATIENTS AND METHODS: Seventeen patients (11 male; 6 female) age 43 to 84 (mean 69) with middle cerebral artery (mca) stroke, as proven by CT or MRI, were examined with 55Co-PET (0.5-1.0 mCi 55CoCl2), C15O2-, 15O2- and C15O-PET in one session 0-30 days after stroke-onset. Regions of infarction were defined by rCMRO2 being smaller than 65% or rCBF below 45% of the contralateral value and were subsequently superimposed on the cobalt scan. To compare the Cobalt uptake with the Gd-MRI, a realignment program was used that matches the MRI with the bloodflow images. Clinical status was established using the Orgogozo stroke scale at admission and at discharge (at least 6 weeks after admission) and the Barthel index. RESULTS: Eight patients showed a positive Co-PET scan and were used for further analysis. It appeared that Co accumulates in areas with a diminished oxygen metabolism and with a preserved bloodflow. We found Co-uptake in only a part of the Gd enhanced brain tissue with a tendency to be located peripherally or outside the Gd demarcated brain tissue. CONCLUSION: The results of the present study suggest that Co accumulates into infarcted brain tissue with a rather preserved flow independently of blood-brain barrier breakdown.

Adult↗
PubMed1995

Follow-up of adult patients with atopic eczema treated with Chinese herbal therapy for 1 year.

Adult patients with severe atopic eczema who had completed a double-blind placebo-controlled crossover trial of a specific formulation of Chinese herbal therapy were offered continued therapy for 1 year. Of 31 patients who completed the original placebo-controlled study and after a washout period and 2 months of further treatment, 17 continued treatment (group 1), 11 chose not to continue treatment (group 2), one was lost to follow-up and two patients originally in group 1 decided to stop treatment and became pregnant. At the end of the year, 12 of the patients in group 1 had greater than 90% reduction and the remaining five had greater than 60% reduction in clinical scores compared with baseline values. Clinical scores of patients in group 2 gradually deteriorated so that by the end of the year the difference between groups 1 and 2 was highly significant (P = 0.005 and P = 0.002 for erythema and surface damage, respectively). At the end of the year no patient in group 1 felt able to discontinue treatment permanently, but eight patients were on an alternate-day regimen by 6 months and remained on this regimen until the end of the year, and seven were able to control their eczema with a 1 in every 3 day treatment by the end of the year. The remaining two patients continued on daily treatments. Toxicology screening revealed no abnormalities in either full blood counts or biochemical parameters in any patient on continued treatment. Improvement in disease was not associated with any significant change in serum IgE level or peripheral blood lymphocyte subsets.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1995

Distribution of a second dose of exogenous surfactant in rabbits with severe respiratory failure.

Newborn infants with respiratory distress who fail to respond to surfactant treatment receive a second dose of surfactant. The effect of this strategy on the distribution of surfactant to the lung is unknown. We therefore investigated the distribution of the first (100 mg/kg body weight) and second dose (50 mg/kg body weight) of surfactant (Alveofact) in lung-lavaged rabbits (n = 6). We used 141Ce- and 103Rn-labeled microspheres that were mixed with the first and second dose of surfactant, respectively. Arterial PO2 increased from 5.7 +/- 1.1 to 10.6 +/- 2.0 kPa (p < 0.05) (mean +/- SD) after the first and from 20.1 +/- 3.8 to 30.1 +/- 2.5 kPa (p < 0.05) after the second dose. Thereafter the rabbits were killed, and the lungs were cut into 200 pieces. The radioactivity of Ce and Rn microspheres was measured and distribution histograms were obtained. Histograms of the first, second, and the total dose of surfactant showed similar nonuniform distribution. Correlation coefficients of the Ce and Rn radioactivity in the different lung lobes widely ranged per lung lobe per rabbit. In addition, the percentage of the number of lung pieces that received an amount of surfactant that was less than the calculated endogenous surfactant pool decreased from 12.5 +/- 3.2% to 8.5 +/- 3.0% (p < 0.05) after the first and second dose, respectively. This indicates that the second dose was directed both to areas that initially received surfactant and to areas that were still surfactant-deficient. The surfactant-deficient areas were aerated after this second dose, resulting in a further rise in PO2.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Heart rate variation during fetal behavioural states 1 and 2.

Fetal heart rate (FHR) variation was numerically assessed in relation to behavioural states in 34 normal near term fetuses, in order to study the normal ranges of FHR variation during state 1F and 2F and to determine possible factors influencing variation in these states. In all individuals 2-h recordings were made of fetal heart rate, and body and eye movements. FHR variation was quantified using the Sonicaid System 8000. During both 1F and 2F there was a large range in variation, with a wide overlap in variation between both states (mean 1-min range in pulse intervals 16-53 ms and 36-97 ms, respectively). In all fetuses variation was higher during 2F than during 1F. The large ranges in variation were mainly caused by differences in basal heart rate and the correlation coefficients between rate (beats/min) and variation were -0.68 and -0.49 for 1F and 2F, respectively. Other reasons for a relatively high FHR variation during 1F included 'pseudo' sinusoidal patterns related to fetal sucking or mouth movements and relatively flat periods sporadically interrupted by an acceleration. With the System 8000, periods of low and high variation are identified using fixed criteria. Because of the large overlap in variation between both states, these episodes poorly correlated with the underlying behavioural states. Objective identification of the heart rate patterns during states 1F and 2F requires incorporation of heart rate itself in the analysis. As yet, 'global' visual identification of heart rate patterns is superior to computer analysis in identifying the underlying fetal behavioural states.

Behavior↗
PubMed1993

Bullous pemphigoid in infancy--a case report including new immunoblotting observations.

A 1-year-old boy developed bullous pemphigoid. Immunoblotting, which has not been previously reported in childhood pemphigoid, showed the serum reacted to a 190 kDa band only. Bullous pemphigoid is rare in infancy and childhood with only 40 cases previously reported. A brief review of the literature is given and treatment of childhood bullous pemphigoid is discussed.

Humans↗
PubMed1992

Leuconostoc lactis beta-galactosidase is encoded by two overlapping genes.

A 16-kb BamHI fragment of the lactose plasmid pNZ63 from Leuconostoc lactis NZ6009 was cloned in Escherichia coli MC1061 by using pACYC184 and was found to express a functional beta-galactosidase. Deletion and complementation analysis showed that the coding region for beta-galactosidase was located on a 5.8-kb SalI-BamHI fragment. Nucleotide sequence analysis demonstrated that this fragment contained two partially overlapping genes, lacL (1,878 bp) and lacM (963 bp), that could encode proteins with calculated sizes of 72,113 and 35,389 Da, respectively. The L. lactis beta-galactosidase was overproduced in E. coli by using a lambda pL expression system. Two new proteins with M(r)s of 75,000 and 36,000 appeared upon induction of PL. The N-terminal sequences of these proteins corresponded to those deduced from the lacL and lacM gene sequences. Mutation and deletion analysis showed that lacL expression is essential for LacM production and that both the lacL and lacM genes are required for the production of a functional beta-galactosidase in E. coli. The deduced amino acid sequences of the LacL and LacM proteins showed considerable identity with the sequences of the N- and C-terminal parts, respectively, of beta-galactosidases from other lactic acid bacteria or E. coli. DNA and protein sequence alignments suggest that the L. lactis lacL and lacM genes have been generated by an internal deletion in an ancestral beta-galactosidase gene.

Amino Acid Sequence↗
PubMed1987

Biphasic fluence-response curves for phytochrome-mediated kalanchoë seed germination : sensitization by gibberellic Acid.

The fluence-response curves for the effect of two red pulses separated by 24 hours on the germination of Kalanchoe blossfeldiana Poelln. cv Vesuv seeds, incubated on gibberellic acid (GA(3)) are biphasic for suboptimal concentrations. The response in the low fluence range corresponds with a classical red/far-red reversible phytochrome mediated reaction. GA(3) induces an additional response in the very low fluence range, which is also phytochrome mediated. The sensitivity to phytochrome-far-red absorbing form (Pfr), however, is increased about 20,000-fold, so that even far-red fluences become saturating. Both in the very low and low fluence response range, the maximal responses induced by saturating fluences are modulated by the GA(3) concentration. GA(3) having no direct influence on the phytochrome phototransformations, alters the Pfr requirement and determines the responding seed population fraction in the very low and low fluence range. The effet of GA(3) appears to be on the transduction chain of the phytochrome signal.

Journal Article↗
PubMed1986

Is it organic or is it functional. Is it hysteria or malingering?

Conversion hysteria, a common affliction, requires prompt diagnosis and treatment to prevent fixation of the incapacity and secondary contractures, and to protect the patient from unnecessary surgery. Diagnostic and therapeutic principles are outlined.

Adolescent↗