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Biomedical subjects

S Mann

Publications and source records attributed to S Mann.

At least 127 records · Page 7Linked to original sources
PubMed1988

Ultrastructure, morphology and organization of biogenic magnetite from sockeye salmon, Oncorhynchus nerka: implications for magnetoreception.

Although ferromagnetic material has been detected in the tissues of a variety of animals that are known or suspected to respond to magnetic fields, in only a few cases has the material been identified and its suitability for use in magnetoreception been determined. Using high-resolution transmission electron microscopy (HRTEM), we have studied magnetic particles isolated from ethmoid tissue of the sockeye salmon, Oncorhynchus nerka. Low-magnification electron micrographs showed chains containing up to 58 (median = 21-25) electron-dense particles that were held together by intimately attached organic material. The particle size range was 25-60 nm with a mean of 48 nm and a standard deviation of 8.5 nm. Elemental analysis, by energy-dispersive X-ray analysis (EDXA), electron diffraction patterns and HRTEM lattice images, showed that many of the particles were structurally well-ordered and crystallographically single-domain magnetite. These results imply that the production of the biomineral is under precise biological control. The crystal morphology was cubo-octahedral with the (111) faces of adjacent crystals lying perpendicular to the chain axis. The magnetic moments of the particles will therefore be aligned along the chain axis and will sum to produce a total moment dependent on the number of particles present in each chain. In the presence of the geomagnetic field, the mean moment for the particles will give a magnetic to thermal energy ratio of about 0.2. The corresponding calculations for individual chains gave two clusters of ratios ranging between 2.7 and 5.3 and between 6.6 and 9.5. The implications of these results in the possible use of the particles in magnetoreception are discussed.

Animals↗
PubMed1988

Is inpatient medical alcohol detoxification justified: results of a randomized, controlled study.

The findings of this study revealed relatively few short-term outcome differences for patients meeting study criteria who were randomly assigned to either outpatient or inpatient medical detoxification. Given the higher costs of inpatient treatment, these findings suggest that outpatient detoxification be considered as a meaningful and cost-effective treatment for persons with mild to moderate alcohol withdrawal symptomatology.

Alcoholism↗
PubMed1987

Reconstituted and native iron-cores of bacterioferritin and ferritin.

The structural and magnetic properties of the iron-cores of reconstituted horse spleen ferritin and Azotobacter vinelandii bacterioferritin have been investigated by high-resolution transmission electron microscopy, electron diffraction and Mossbauer spectroscopy. The structural properties of native horse spleen ferritin, native Az. vinelandii, and native and reconstituted Pseudomonas aeruginosa bacterioferritins have also been determined. Reconstitution in the absence of inorganic phosphate at pH 7.0 showed sigmoidal behaviour in each protein but was approximately 30% faster in initial rate for the Az. vinelandii protein when compared with horse spleen apoferritin. The presence of Zn2+ reduced the initial rate of Fe(II) oxidation in Az. vinelandii to 22% of the control rate. The iron-cores of the reconstituted bacterioferritins adopt defect ferrihydrite structures and are more highly ordered than their native counterparts, which are both amorphous. However, the blocking temperature for reconstituted Az. vinelandii (22.2 K) is almost identical to that for the native protein (20 K). Particle size measurements indicate that the reconstituted Az. vinelandii cores are smaller in median diameter than the native cores and this reduction in particle volume (V) offsets the increased magnetocrystalline contribution to the magnetic anisotropy constant (K) in such a way that the magnetic anisotropy barrier (KV), and hence the blocking temperature, is similar for both proteins. Reconstituted horse spleen ferritin exhibits a similar blocking temperature (38 K) to that determined for the native protein, although it is structurally more disordered. The possibility of introducing structural and compositional modifications in both horse ferritin and bacterioferritins by in-vitro reconstitution suggests that these proteins do not function primarily as a crystallochemical-specific interface for core development in vivo.

Animals↗
PubMed1987

Carbohydrate taste preferences in rats: glucose, sucrose, maltose, fructose and polycose compared.

The taste preferences of adult female rats for solutions of five different carbohydrates were evaluated using brief (3-min) two-bottle preference tests. At the lowest concentration tested (0.03 molar) the order of preference was Polycose greater than maltose greater than sucrose greater than glucose = fructose. Whereas at the highest concentrations tested (0.5 or 1.0 molar) the preference order was sucrose greater than maltose greater than or equal to Polycose greater than glucose greater than fructose. Thus, at low concentrations starch-derived polysaccharides (Polycose) are more palatable to rats than are sugars. These findings are consistent with the hypothesis that rats have separate taste receptors for sugars and for starch-derived polysaccharides. The fact that maltose is the most preferred sugar at low concentrations is attributed to its stimulation of "polysaccharide" taste receptors.

Animals↗
PubMed1986

Structure and composition of ferritin cores isolated from human spleen, limpet (Patella vulgata) hemolymph and bacterial (Pseudomonas aeruginosa) cells.

Ferritin cores isolated from human spleen, limpet (Patella vulgata) hemolymph and bacterial (Pseudomonas aeruginosa) cells have been investigated by high resolution transmission electron microscopy, electron diffraction and chemical analysis. Hemosiderin particles isolated from thalassemic spleens also have been studied. The results show that there is a marked difference in structure and composition of the biomineral phases. Human ferritin and hemosiderin particles are single domain crystals of hydrated iron (III) oxide (ferrihydrite). Lattice fringes were low in contrast and often discontinuous within the central regions of the core. Heat treatment of human ferritins results in a 5 A shrinkage in particle size and an increase in the single crystalline nature of the core. In contrast, lattice images and electron diffraction of limpet and bacterial cores show no evidence of long-range crystallographic order. Chemical analysis indicates a high inorganic phosphate (Pi) (Fe/Pi = 1.71) content in bacterial ferritin compared with human ferritin (thalassemic) (Fe/Pi = 21.0). The high Pi content of bacterial ferritin suggests a hydrated amorphous iron (III) phosphate mineral core. Structural disorder within the limpet and bacterial cores may be associated with increased Pi content and increased oxidation in Fe(II), resulting in rapid mineral deposition. Growth of the iron (III) oxide cores in human ferritin is discussed on the basis of high resolution electron microscopy results.

Animals↗
PubMed1986

The child health clinic: results of a new strategy of community care in a deprived area.

Substantial changes were made in the organisation of a child health clinic serving an underprivileged population in Nottingham. A community paediatric team approach was adopted, routine medical checks were reduced, and referrals from elsewhere (including parents) were encouraged. The changes resulted in an older and more deprived population of preschool children being seen by the clinic doctors. More treatable medical disorders were detected with this approach.

Age Factors↗
PubMed1986

Mössbauer spectroscopic studies of the cores of human, limpet and bacterial ferritins.

Ferritin cores from human spleen, limpet (Patella vulgata) haemolymph and bacterial (Pseudomonas aeruginosa) cells have been investigated using 57Fe Mössbauer spectroscopy. The Mössbauer spectra were recorded over a range of temperatures from 1.3 to 78 K, all the spectra are quadrupole-split doublets with similar quadrupole splittings and isomer shifts, characteristic of iron(III), while at sufficiently low temperatures the spectra of all the samples show well-resolved magnetic splitting. At intermediate temperatures, the spectra from the human ferritin exhibit typical superparamagnetic behaviour, while those from the bacterial ferritin show behaviour corresponding to a transition from a magnetically ordered to a paramagnetic state. The spectra from the limpet ferritin show a complex combination of the two effects. The results are discussed in terms of the magnetic behaviour of small particles. The data are consistent with magnetic ordering temperatures of about 3 and 30 K for the bacterial and limpet ferritin cores, respectively, while the data indicate that the magnetic ordering temperature for the human ferritin cores must be above 50 K. These differences are interpreted as being related to different densities of iron in the cores and to variations in the composition of the cores. The human ferritin cores are observed to have a mean superparamagnetic blocking temperature of about 40 K, while that of the limpet ferritin cores is about 25 K. This difference is interpreted as being due not only to different mean numbers of iron atoms in the two types of core but also to the higher degree of crystallinity in the cores of the human ferritin.

Animals↗
PubMed1986

Structural aspects of biogenic silica.

The objectives of this paper are to discuss the characterization of biogenic silica in terms of structural properties, and to elucidate the mechanisms of structural organization within biological systems. The scale of organization is a critical factor in the characterization of biosilicification processes, and order at the nanometre, micrometre and macroscopic levels is described. Molecular order is discussed in the light of high-resolution transmission electron microscopy and solid-state NMR results obtained from samples of biogenic silica. Microscopic organization is expressed in a range of structural motifs, e.g. gels, sheets, fibres, tubes and globular assemblies, and reflects the infinitely adaptive morphology of biogenic silica. Macroscopic structures such as curved rods, spicules, perforated plates, teeth and reticular frameworks can be assembled from these microscopic motifs. The mechanisms of structural organization involve spatial (scalar and vectorial) constraints, ordered particle aggregation and chemical regulation. The possible importance of organic surfaces is discussed.

Eukaryota↗
PubMed1986

Differential alterations in striatal acetylcholine function in rats during 12 months' continuous administration of haloperidol, sulpiride, or clozapine.

Rats were treated continuously for 12 months with therapeutically equivalent doses of either haloperidol (1.4-1.6 mg/kg/day), sulpiride (102-109 mg/kg/day), or clozapine (24-27 mg/kg/day). After treatment for 3 and 12 months with haloperidol or clozapine but not sulpiride, striatal acetylcholine levels were increased. Striatal choline acetyltransferase activity was not altered by any drug treatment. Vmax for striatal acetylcholinesterase activity during the course of 12 months' treatment with haloperidol or clozapine, but not with sulpiride, tended to increase; Km was not altered by any drug treatment. Bmax for specific striatal [3H]quinuclidinyl benzilate binding was not altered by haloperidol or sulpiride treatment but was transiently elevated after 6 months of clozapine treatment, thereafter returning to control levels. Kd was not altered by any drug treatment. These findings indicate that alterations in striatal acetylcholine content caused by chronic treatment with some but not all neuroleptics are due to changes in cholinergic neuronal activity rather than neurotransmitter synthesis or destruction. The effects of haloperidol but not those of clozapine may be related to the emergence of functional striatal dopamine receptor supersensitivity. Since haloperidol (which is associated with a high prevalence of tardive dyskinesias) but not clozapine (which is not) had similar effects on striatal cholinergic function, the latter may not be related to the emergence of tardive dyskinesias during chronic therapy.

Acetylcholine↗
PubMed1986

The study of biominerals by high resolution transmission electron microscopy.

This paper presents an overview of the study of the ultrastructure of biogenic inorganic solids (biominerals) using high resolution transmission electron microscopy (HRTEM). A range of biominerals have been studied including iron oxides, calcium phosphates, calcium carbonates and silica. The studies have revealed information concerning the structural complexity of these materials and have identified crystallographic order and disorder at the nanometre level. In addition, the results have aided the elucidation of the mechanisms of nucleation and growth of biogenic minerals.

Animals↗
PubMed1985

Chronic treatment with clozapine, unlike haloperidol, does not induce changes in striatal D-2 receptor function in the rat.

Comparison has been made of the effects on brain dopamine function of chronic administration of haloperidol or clozapine to rats for up to 12 months. In rats treated for 1-12 months with haloperidol (1.4-1.6 mg/kg/day), purposeless chewing jaw movements emerged. These movements were only observed after 12 months' treatment with clozapine (24-27 mg/kg/day). Apomorphine-induced (0.125-0.25 mg/kg) stereotyped behaviour was inhibited during 12 months treatment with haloperidol. Clozapine treatment was without effect. After 12 months, stereotypy induced by higher doses of apomorphine (0.5-1.0 mg/kg) was enhanced in haloperidol, but not clozapine, treated rats. Bmax for striatal 3H-spiperone binding was elevated throughout 12 months of haloperidol administration, but was not altered by clozapine treatment. Bmax for striatal 3H-NPA binding was only elevated after 12 months of haloperidol treatment; clozapine treatment was without effect. Bmax for 3H-piflutixol binding was not altered by haloperidol treatment, but was increased after 9 and 12 months of clozapine treatment. Dopamine (50 microM)-stimulated adenylate cyclase activity was inhibited after 1 month's haloperidol treatment but normal thereafter. Adenylate cyclase activity was not altered by chronic clozapine treatment. Striatal acetylcholine content was increased after 3 and 12 months of haloperidol or clozapine intake. These findings indicate that the chronic administration of the atypical neuroleptic clozapine does not produce changes in brain dopamine function which mirror those of the typical neuroleptic haloperidol. In particular, chronic administration of clozapine, unlike haloperidol, does not appear to induce striatal D-2 receptor supersensitivity. Unexpectedly, clozapine treatment, unlike haloperidol, altered D-1 receptor function.

Acetylcholine↗
PubMed1985

Measured and predicted caloric expenditure in the acutely ill.

Predicted energy requirements calculated from the Harris-Benedict basal energy expenditure (BEE) formulas, and caloric allowances recommended by the Food and Nutrition Board National Research Council, were compared to metabolic expenditures measured by indirect calorimetry, using a feedback-controlled gas replenishment technique with a prototype device for the continuous determination of oxygen consumption (VO2) and carbon dioxide production (VCO2). In a group of 50 acutely ill surgical patients, predicted metabolic requirements based on ideal body weight (1.75 BEE) averaged 59% greater than metabolic expenditures measured by indirect calorimetry. Metabolic requirements based on actual body weight averaged 52% greater; recommended caloric allowances averaged 39% greater. Thus, accepted methods of predicting metabolic requirements significantly overestimated the caloric needs of these acutely ill patients. These results should encourage the development of new bedside equipment for measuring VO2 and VCO2, so that indirect calorimetry can be used to guide nutritional support in the clinical setting.

Acute Disease↗