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Biomedical subjects

H C Andersen

Publications and source records attributed to H C Andersen.

At least 19 recordsLinked to original sources
PubMed1988

Acute phase reactants in the elderly.

The erythrocyte sedimentation rate (ESR), plasma fibrinogen, serum orosomucoid, serum alpha 1-antitrypsin and serum haptoglobin were measured in 267 apparently healthy elderly subjects (median age 79 years, range 60-93), and compared to the values in 58 healthy younger subjects (median age 27 years, range 18-50). The acute phase reactants displayed no sex differences, but were significantly higher in elderly than in younger persons (mean +/- SD): ESR 13 +/- 10 mm/h vs 4 +/- 3 mm/h (p less than 0.001); fibrinogen 4.35 +/- 0.95 g/l vs 3.33 +/- 0.54 g/l (p less than 0.001); orosomucoid 0.68 +/- 0.20 g/l vs 0.60 +/- 0.16 g/l (p less than 0.01); alpha 1-antitrypsin 2.16 +/- 0.38 g/l vs 1.84 +/- 0.43 g/l (p less than 0.001); haptoglobin 1.30 +/- 0.50 g/l vs 1.00 +/- 0.30 g/l (p less than 0.001). Correlations existed between the acute phase reactants, being highest between ESR and fibrinogen (r = 0.53, p less than 0.001).

Acute-Phase Proteins↗
PubMed1986

Serum ferritin and iron status in 'healthy' elderly individuals.

Iron status, including S-ferritin, S-iron, S-transferrin, transferrin saturation and haemoglobin, was assessed in 267 selected elderly subjects (128 male, 139 female) with a median age of 79 years (range 60-93 years) not suffering from diseases connected with inappropriately high S-ferritin. In both sexes, S-ferritin levels were practically constant over the examined age range. Males had a geometric mean ferritin of 75 micrograms/l and females a value of 60 micrograms/l (p less than 0.001). Levels of S-ferritin less than 15 micrograms/l (i.e. depleted iron stores) were found in 7.8% of males and in 10.1% of females. An S-ferritin level less than 15 micrograms/l and transferrin saturation less than 15% (i.e. latent iron deficiency) was observed in 2.3% of males and in 2.2% of females. None had iron deficiency anaemia. In subjects (n = 232) without iron deficiency [i.e. S-ferritin greater than or equal to 15 micrograms/l, mean red cell volume greater than or equal to 79 fl and haemoglobin greater than or equal to 121 g/l (7.5 mmol/l)], the arithmetic mean of S-iron was 18 mumol/l. S-transferrin 28 mumol/l and transferrin saturation 33%. The levels of S-iron, S-transferrin and transferrin saturation were not significantly different in males and females.

Aged↗
PubMed1982

A theory of effect of protons and divalent cations on phase equilibria in charged bilayer membranes: comparison with experiment.

We summarize the concepts in the recently developed statistical mechanical theory of the effects of proton binding and divalent cation binding on phase equilibria in bilayer membrane composed of acidic phospholipids. The theory is used to calculate membrane phase transition temperatures for different aqueous concentrations of protons, divalent cations and monovalent salt. We discuss methods for calculating transition temperatures even for systems in which there is not an excess of protons or divalent cations relative to lipids. The results are compared with existing experimental data for a number of lipids. There is good agreement between calculated transition temperature vs. pH curves and experimental data for dimyristoylmethylphosphatidic acid, dimyristoylphosphatidylglycerol, dipalmitoylphosphatidylglycerol, dipalmitoylphosphatidylserine, and dimyristoylphosphatidic acid. General thermodynamic considerations are used to derive in Clapeyron-like equation for the rate of variation in membrane transition temperature with divalent cation concentration. This equation and some available experimental data are used to argue that the large increase in solid to fluid phase transition temperature that is observed experimentally as the divalent cation concentration is increased is the result of the metastable solid phase that exists at low but not high divalent cation concentration. A calculated coexistence diagram is compared with existing experimental data for transition temperatures of dimyristoylphosphatidylglycerol membranes at different total calcium concentrations. Good agreement is obtained when the existence of a metastable solid phase is assumed.

Cations, Divalent↗
PubMed1980

A theory of the effects of head-group structure and chain unsaturation on the chain melting transition of phospholipid dispersions.

We have developed statistical mechanical descriptions of the effects of head-group structure and acyl chain unsaturation on the chain melting phase transition of aqueous dispersions of bilayers containing glycerophosphocholines and glycerophosphoethanolamines. The theoretical framework is an extension of the model of Jacobs et al. [Jacobs, R. E., Hudson, B. S., & Andersen, H. C. (1975) Proc. Natl. Acad. Sci. U.S.A. 72, 3993]. There are several systematic trends in the experimental transition data for various types of phospholipids. Assumptions about the physical origins of these trends were incorporated into statistical mechanical models, which were used to calculate transition temperatures and enthalpies. The extent to which the calculated results of a model reproduce the experimental trends is taken as a measure of the validity of the assumptions on which the model is based. We found that the gross differences among the transition temperatures of phospholipids with two saturated chains, two trans-unsaturated chains, two cis-unsaturated chains, and one cis-unsaturated and one saturated chain can all be explained in terms of the effect of the double bonds on molecular shape and the subsequent effect of shape on the ability of molecules to pack together into a low-energy state at high density. The dependence of transition temperature on the location of the double bond in cis-unsaturated molecules can be understood on the same basis. The differences between the transition temperatures of glycerophosphocholines and glycerophosphoethanolamines with the same hydrocarbon chains can be explained in terms of a larger intermolecular attraction (or smaller repulsion) for the latter than for the former. These differences depend on the presence or absence of unsaturation in the hydrocarbon chains in a way that is consistent with the postulate that hydrogen bonding between glycerophosphoethanolamines is responsible for the differences.

Chemical Phenomena↗
PubMed1977

A theory of phase transitions and phase diagrams for one- and two-component phospholipid bilayers.

A statistical mechanical partition function for phospholipid bilayers is constructed to obtain a theoretical description of the chain melting phase transition in lipid bilayer membranes and of the phase diagrams for two-component bilayers. In addition to providing an accurate representation of the transition temperatures and enthalpies of one-component bilayers composed of 1,2-diacylphosphatidylcholines, the theory can also account for the shapes of the phase diagrams observed for bilayers which are binary mixtures of these compounds with two different hydrocarbon chain lenghts.

Kinetics↗
PubMed1977

Nasal cancers, symptoms and upper airway function in woodworkers.

In 186 cases of nasal cancer diagnosed over the decade 1965-74, in a population of 2-0 million, 114 of 157 ectodermal tumours were found in men. Adenocarcinoma was found in 17 patients, two women and 15 men; 12 of these had a history of occupational exposure to wood dust in the furniture industry. The period of latency was from 28 to 57 years. Among the remaining 99 tumours in men there was occupational exposure to wood dust in 10 cases. Wood dust concentrations in the breathing zone, respiratory symptoms and upper airway function were studied in 68 workers in the furniture industry. The dust concentrations affecting 63% of the workers were higher than 5 mg/m3 (TLV). Middle ear inflammation and common colds were more frequent at high dust concentrations, and the number of workers with nasal mucostasis was directly proportional to the wood dust concentration.

Adenocarcinoma↗
PubMed1975

A theory of the chain melting phase transition of aqueous phospholipid dispersions.

A model for the chain melting phase transition in dilute aqueous phospholipid bilayer dispersions is presented. This model includes interactions between head groups, between hydrocarbon chains, and within the chains. The head groups are modeled as hard disks which are constrained to lie on a two-dimensional surface separating the aqueous and hydrocarbon regions. The chain statistics problem is treated in an approximate manner using an approach motivated by scaled particle theory to describe the inter-chain steric repulsions in a mathematically tractable way. In this approach the whole system interacts with any given chain through an average lateral pressure which is proportional to the hard disk pressure. Following Nagle, we assume that the steric repulsions between chains and between head groups and the trans-gauche rotation energies are the dominant interactions in determining the transition and we describe the effect of the other interactions with a mean field approximation. Using the known transition temperature of a series of 1,2-diacyl phosphatidyl cholines to adjust two parameters in the theory, the model gives enthalpy and area changes that are in quite reasonable agreement with experiment. Moreover, the curvature observed in the plot of the transition temperature against acyl chain length is reproduced.

Binding Sites↗