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Biomedical subjects

S Hodson

Publications and source records attributed to S Hodson.

At least 19 recordsLinked to original sources
PubMed2004

Intergenerational transmission of somatization behaviour: 2. Observations of joint attention and bids for attention.

BACKGROUND: Somatoform disorders may have their roots in childhood through processes that involve an enhanced parental focus on health. The aim of this study was to test the hypothesis that somatizing mothers will show less joint involvement than other mothers during play but greater responsiveness when this play involves a 'medical' theme. METHOD: Cross-sectional observational study of 42 chronic somatizers, 44 organically ill and 50 healthy mothers and their 4-8 year-old children during structured play and a meal. Tasks comprised boxes containing tea-set items, 'medical' items and a light snack. RESULTS: Somatizing mothers were emotionally flatter and showed lower rates of joint attention than other mothers during both play tasks. While the three groups had similar rate of bids for attention, somatizing mothers were more responsive to their child's bids during play with the medical box than at other times. In contrast, the children of somatizing mothers ignored a greater proportion of their mother's bids during play with the medical box than did children of other mothers or during play with a non-medical theme. CONCLUSION: The study has demonstrated tentative evidence in support of the hypothesis.

Affect↗
PubMed2000

Homeless youth in London: II. Accommodation, employment and health outcomes at 1 year.

BACKGROUND: While there is considerable evidence of a high prevalence of psychiatric disorder among homeless youth, much less is known about its long-term course or the impact it may have on accommodation outcomes. METHOD: A random sample of 161 homeless people 16-21 years of age were recruited from consecutive attendees at two of London's largest facilities for homeless young people. These young people were traced and re-interviewed a year later to examine accommodation, occupation and health outcomes. RESULTS: A total of 107 (67%) people were successfully re-interviewed. Psychiatric disorder was identified in 55% at follow up. Two thirds of those with a psychiatric disorder at index interview remained symptomatic at follow-up. Persistence of psychiatric disorder was associated with adverse childhood experiences and rough sleeping. Satisfactory accommodation outcomes were achieved by 45 subjects (42%). Better accommodation outcomes were associated with three variables measured at the index assessment: ethnic minority status; educational achievement; and, the presence of accommodation plans negotiated through a resettlement agency. While psychiatric disorder at index interview was not associated with accommodation outcome, persistent substance use in the follow-up year was associated with poor accommodation outcome. Over half of the young people had been involved in petty crime and just under a third had been convicted for more serious criminal activity. Offending and antisocial behaviour in the follow-up year were related to a history of conduct disorder, persistent substance abuse and poor accommodation outcomes. CONCLUSIONS: Young homeless people are characterized by multiple social and medical needs. Successful resettlement of this population may depend upon integrated services that address problems of persisting substance use and mental illness as well as the immediate housing need.

Adolescent↗
PubMed1998

Homeless youth in London: I. Childhood antecedents and psychiatric disorder.

BACKGROUND: There has been an increase in the numbers of homeless young people in Britain. Little is known of the health and social welfare needs of this population. METHOD: This case-control study compares a random sample of homeless people aged under 22 years recruited from consecutive attenders at two of London's largest facilities for homeless young people with a contemporaneous sample of domiciled young people recruited through general practice registration lists. The homeless and domiciled groups were compared on measures of childhood care, education and psychiatric disorder. RESULTS: One hundred and sixty-one homeless people (88% of those approached) and 107 domiciled subjects (60% of those approached) were interviewed. Sixty-nine per cent of homeless and a third of the domiciled subjects reported a childhood lacking in affection, with indifferent and often violent carers. Psychiatric disorder was identified in 62% of homeless respondents and a quarter of the domiciled population. A fifth of homeless and 5 domiciled respondents had attempted suicide in the previous year. Multivariate analysis suggest that childhood adversity, low educational attainment and the prior presence of psychiatric disorder all independently increase the likelihood of homelessness in a youthful population. CONCLUSIONS: The evidence presented in this paper supports the hypotheses that characterize the young homeless population as experiencing higher rates of childhood adversity and psychiatric disorder than their domiciled contemporaries. A tentative model is suggested whereby childhood experiences, educational attainment and the prior presence of psychiatric disorder all independently increase the likelihood of homelessness in a youthful population.

Adolescent↗
PubMed1998

In vitro bovine ciliary body/epithelium in a small continuously perfused Ussing type chamber.

Our goal is to assess the viability of an in vitro preparation of bovine ciliary body/epithelium (CBE) in a small volume Ussing-type chamber. A new small volume Ussing-type chamber with continuous perfusion was developed for bovine CBE. The trans-CBE electrical parameters were monitored and the electrical responses of the CBE to ouabain (1 and 0.01 mM) were recorded. The trans-CBE fluxes of [14C]-L-ascorbate and [3H]-L-glucose were also studied. The bovine CBE preparation was stable inside the chamber in terms of its potential difference (PD), short circuit current (SCC) and trans-CBE resistance. They were -0.51+/-0.05 mV (aqueous side negative), -5.43+/-0.04 microAcm-2 and 94+/-2 Q.cm2 (mean s.e.m., n=35), respectively. The preparation hyperpolarised when 0.01 mM ouabain was administered to the aqueous side, depolarised when ouabain was applied to the stromal side. [3H]-L-glucose diffusion was about 74 nEq h(-1)cm(-2) in either direction (n=12). Taking the area magnification factor of the CBE into consideration, the diffusional L-glucose flux across the bovine CBE was comparable to other tight epithelia. A significant net ascorbate flux (0.26+/-0.05 nEq h(-1)cm(-2), n=4, p<0.01) was found in the stroma to aqueous direction. We have developed a viable in vitro bovine CBE preparation which was (1) electrically stable, (2) responsive to ouabain, (3) tight to L-glucose diffusion, and (4) capable of actively secreting ascorbate. A net trans-CBE chloride transport (0.81+/-0.30 microEq h(-1)cm(-2), n=12, p=0.01) from stromal to aqueous side was found in the present in vitro model under short-circuited conditions.

Animals↗
PubMed1994

Of an extracellular matrix in human pre-corneal tear film.

A theory relating viscosity to fluid flow rates in human tear film was developed and from that theory arises a relationship between viscosity, tear-film thickness and vertical drainage rates at the air-tear interface. Human tears were collected in capillary tubes at rates, on average, of less than 1 microliter min-1. Protein concentration was slightly higher than values reported in the literature and electrophoretic distributions of tear-film proteins were normal. Viscosity of the tear films were measured at 35 degrees C (physiological temperature). Vertical flow rates of tear film were measured in the inter-blink period either by observing the movement of lipid plaques at the air-tear interface or by observing naturally occurring contaminant specs (size around 1 micron). Tear film vertical flow rates were at least an order of magnitude lower than those predicted from collected tear-fluid viscosity measurements. It was concluded that collected tears are not representative of the whole pre-corneal tear film and that the tear film includes a fluid flow-inhibiting matrix whose structural components have a longer time-constant of exchange than the soluble proteins of the collected tear fluid.

Adult↗
PubMed1994

Regulation of the retinal interphotoreceptor matrix Na by the retinal pigment epithelium during the light response.

We examined the rabbit retinal pigment epithelium (RPE) for Na transport properties which would allow it to buffer undesirable changes in Na concentrations in the interphotoreceptor matrix (IPM) during light and dark cycles. The RPE is selectivity permeable to sodium. Open and short circuit transport studies with RPE indicate a circulating (choroid to retina and back) Na current which does not compromise the electrical integrity of the blood brain barrier but together with the Na permselectivity is of sufficient magnitude to buffer both upwards and downwards movements of IPM [Na] during light or dark responses.

Animals↗
PubMed1993

The incorporation of gel pressure into the irreversible thermodynamic equation of fluid flow in order to explain biological tissue swelling.

After the Donnan osmotic potential derived theory of corneal stromal swelling was suggested (Hodson, 1971) it later was proposed, and verified experimentally, (Elliott et al., 1980) that the theory could be applied even in situations where there were no bounding cellular membranes attached to the corneal stroma. This was a paradox. The central problem with swelling in the absence of membranes (i.e. with a gel boundary whose reflexion coefficient is essentially zero) is that the driving force is not readily understandable as osmotic (but see Oster & Peskin, 1992) and yet the magnitude of the swelling fitted quantitatively with Donnan theory. We believe that we have resolved this paradox with a new and expanded irreversible thermodynamic relationship for fluid flows into and across biological tissues. In the course of the derivation, fresh concepts arise: for example the relationship of salt disparity is described which forbids diffusible salt-generated chemical and osmotic potentials to be simultaneously at equilibrium in the presence of ionised macromolecules and this relationship is developed to generate a new intrinsic thermodynamic property which is termed gel pressure and which drives fluid flow. Gel pressure provides a theoretical basis for biological tissue swelling. Microscopically, gel pressure is identified as the electrostatic potential developed by the mutual repulsion of the fixed matrix charges.

Animals↗
PubMed1993

Rabbit corneal endothelial cell membrane potential.

Membrane potential of rabbit corneal endothelial cells measured using microelectrodes was -29.3 +/- 0.8 mV, n = 45, (mean +/- SEM). Histological location of Lucifer Yellow dye iontophoresed out of the microelectrode confirmed that the microelectrode was located intracellularly. The Lucifer Yellow diffused five to six cell diameters away from the impaled cell indicating endothelial cell coupling. Depolarization by ouabain (10(-4) M) and high extracellular potassium (potassium for sodium substitution) showed the cells to be responsive to changes in the bathing solution whilst impaled, that the cell membrane is more permeable to potassium than sodium and that membrane bound Na(+)-K(+)-ATPase activity generates the transmembrane electrolyte gradients.

Animals↗
PubMed1992

Regulation of the respiratory burst by cyclic 3',5'-AMP, an association with inhibition of arachidonic acid release.

The mechanism of cAMP regulation of the respiratory burst was studied with HL-60 cells that had been DMSO-differentiated to a neutrophil-like cell. To evaluate the effects of known cAMP concentrations, cells were permeabilized with streptolysin-O. Chemotactic peptide (FMLP)-stimulated NADPH oxidase activity was inhibited by cAMP at concentrations higher than 3 microM. Because intracellular calcium was buffered, inhibitory actions of cAMP were not mediated by modulation of calcium concentration. Effects of cAMP on chemotactic peptide signal transduction mediated by phospholipase C, phospholipase D, and phospholipase A2 were then determined. Neither inositol phosphate generation (phospholipase C) nor phosphatidylethanol generation (phospholipase D activity in presence of 1.6% ethanol) induced by FMLP were significantly affected by cAMP. In contrast, cAMP potently inhibited FMLP-induced arachidonic acid mobilization (phospholipase A2). NADPH oxidase activity induced by exogenous arachidonic acid was not inhibited by cAMP. These results indicate that cAMP-mediated inhibition of arachidonic acid mobilization may be important in regulation of the respiratory burst.

Acridines↗
PubMed1992

Transient chloride binding as a contributory factor to corneal stromal swelling in the ox.

1. Investigations were made of the cation exchange capacity of fresh isolated ox corneal stroma (Q, units: mequiv fixed stromal charge/kg stromal fluid) at pH 7.4 over a variety of stomal hydrations (H, units: kg stromal fluid/kg dry tissue) both above and below the physiological hydration of 3.2, whilst the stromas were immersed in a variety of sodium chloride solutions (range 5-1000 mM). 2. At any particular salt concentration, the product QH (dry tissue exchange capacity, units: mequiv/kg dry tissue) appeared constant, over all the hydrations investigated. 3. Dry tissue exchange capacity (QH) varied, however, when the bathing salt concentration was altered. It varied between 55 mequiv/kg dry tissue (e.g. Q = 17 mequiv at H = 3.2) in 5 mM-NaCl to 240 mequiv/kg dry tissue (e.g. Q = 75 mequiv/l at H = 3.2) in 1000 mM-NaCl. 4. The variation of stromal exchange capacity in NaCl solutions of different concentrations was similar when detected by three independent procedures: stromal gel pressure measurements, intrastromal sodium ion distributions, and intrastromal electrical potentials. 5. Intrastromal chloride ion distributions were anomalous. Total chloride (measured by radio-isotopes) was consistently higher than that predicted by Donnan theory. 6. The data were consistent with Elliott's hypothesis that a fraction of intrastromal chloride ions bind to the corneal stromal matrix and in so doing contribute to the fixed negative charge of the stroma. 7. Our observations may be explained by a model of the cation exchange capacity of ox cornea which has two types of components. On is (at constant pH) invariant, and has a dry tissue exchange capacity of about 50 mequiv/kg dry tissue, and is probably generated by the sulphonic and carboxylic acid groups of the glycosaminoglycans. The other is explained by supposing it to consist of a chloride binding ligand which exhibits first order binding, is half occupied at ambient chloride concentrations of 300 mM, and has a total capacity of 240 mequiv/kg dry tissue. 8. Partial stromal extraction with 4 M-guanidine HCl indicated that the chloride binding ligand is not associated with the collagen molecules in the corneal stromal fibrils. 9. It is suggested that such a stromal chloride ion binding ligand would help to stabilize the hydration and transparency of the living cornea when it is exposed to environments of varying tonicity (such as in river or sea bathing).

Animals↗
PubMed1992

Plasma concentrations of endogenous heparinoids in portal hypertension.

Bleeding as a complication of liver disease can occur in the absence of recognised haemostatic defects. It is now possible to measure the concentration of endogenous heparinoid substances in the blood using a competitive binding assay. One such substance, heparan sulphate (normal range < 600 ng/ml) was assayed in the plasma of 49 patients admitted because of oesophageal varices. In 27 patients with recent upper gastrointestinal bleeding the median plasma heparan sulphate value was 1700 ng/ml (interquartile (IQ) range 900-3900) compared with 390 ng/ml (IQ range 256-800) in 22 patients with no recent bleed (p < 0.01). As heparan sulphate is metabolised by the same route as exogenous heparin, an attempt to establish a cause for the raised heparan concentrations was made by measuring the clearance of exogenous heparin in 10 portal hypertensive patients and 10 controls. The median half life of heparin in plasma in the portal hypertensive patients (25.5 minutes; IQ range 22-34) was significantly longer (p < 0.007) than the median half life in the controls (18.7 minutes; IQ range 17-21.5). Thus, there is evidence of raised concentrations of endogenous heparin like substances in portal hypertensive patients after gastrointestinal bleeding. These high concentrations may result from reduced hepatic clearance.

Esophageal and Gastric Varices↗
PubMed1991

No transplacental passage of standard heparin or an enzymatically depolymerized low molecular weight heparin.

In 21 women who had an abortion by hysterotomy between the 15th and 23rd week of pregnancy, the possibility that unfragmented heparin or low molecular weight heparin (LMWH) passed the placental barrier to the foetus was studied. Laboratory analyses included amidolytic assays of factor Xa inhibitory activity (XaI), antithrombin III (ATIII) and a direct measurement of heparin-like substances in plasma with a competitive binding assay. The ATIII concentration in foetal plasma was about 20% of that in normal human plasma and varied considerably between individuals (2-27%). The XaI activity did not differ between the two treated groups, but the mean XaI activity of the combined groups differed from zero (P less than 0.05). If the XaI activity was corrected for the ATIII concentration, the heparin activities no longer differed significantly from zero. As the concentration of heparin-like substances were above the detection limit (0.35 microgram/ml) in 6/16 analysable samples of foetal plasma, a further 15 women who had not received any heparin were included as controls. In 12/14 analysable foetal plasmas heparin-like substances in concentrations above 0.35 micrograms/ml could be detected. Determination of heparin activity in foetal plasma is thus difficult due to the influence of endogenous ATIII on heparin assays. In conclusion, this study did not demonstrate any evidence for the passage of heparin or LMWH across the placental barrier. No differences were detected whether unfragmented heparin or LMWH had been given to the mothers. Our results also indicate the presence of an endogenous glycosaminoglycan in foetal plasma.

Adolescent↗
PubMed1991

The measurement of ox corneal swelling pressure by osmometry.

1. Ox corneal stromal swelling pressure (gel pressure) may be measured by osmometry: polyethylene glycol of nominal molecular mass 10,000 Da (PEG 10K) is a suitable non-penetrating solute. 2. Corneal hydrations equilibrate within 4 h of exposure to 154 mM-NaCl including various concentrations (2-8%) of PEG 10K, providing that the epithelium covers the anterior surface and Descemet's membrane covers the posterior surface. At equilibrium hydration, corneal gel pressure equals the external osmotic pressure contributed by PEG 10K. 3. The osmotic pressure of PEG 10K may be calibrated using Descemet's membrane as the semi-permeable membrane. 4. Corneal gel pressure decreases with increasing hydration. 5. The relationship may be adequately explained by the Donnan theory of corneal swelling with a fixed negative matrix charge of 39.5 +/- 0.8 mequiv l-1 at physiological hydration of 3.2 at this salt concentration (154 mM-NaCl).

Animals↗
PubMed1989

A near-zero membrane potential in transporting corneal endothelial cells of rabbit.

1. When rabbit corneal endothelial cells are impaled with 3 M-KCl-filled microelectrodes (Rt = 20-70 M omega) a stable membrane potential of -28.7 +/- 4.8 mV (mean +/- S.D., n = 400) is measured. 2. Varying the [KCl] of the filling solution causes a change in measured membrane potential; 154 mM gives typically -2 mV, 10 mM typically +37 mV. 3. Variation in membrane potential with different [KCl] cannot be ascribed to tip potential. Double-barrelled microelectrodes containing a different [KCl] in each barrel both give the same membrane potential when inserted into a cell. 4. Microelectrodes filled with a reference liquid ion exchanger (RLIE) give a membrane potential of +2 mV. 5. Impaling a cell with a double-barrelled microelectrode, one barrel containing KCl and the other RLIE, showed that the ion exchanger is not having a toxic effect on the cell and does not affect membrane potential measured by the KCl-filled barrel. 6. We suggest that microelectrodes containing non-isotonic concentrations of KCl generate a significant and artifactual change in membrane potential of corneal endothelial cells caused by the movement of excess KCl (originating from the microelectrode tip) across the plasma membrane where a liquid-junction potential is generated. 7. We further suggest that the physiological membrane potential of corneal endothelial cells is around zero. This could result from a solution of the constant field equation where: 0.9 PNa congruent to PK congruent to 3.2 PCl.

Animals↗
PubMed1988

The absence of bicarbonate-stimulated ATPase activity in the plasma membranes of the bicarbonate secreting ox corneal endothelial cells.

Membranes of ox corneal endothelial cells were studied for their surface area by electron microscopical stereology and then separated from homogenates on self forming Percoll gradients. Enzymic analysis of the plasma membrane-enriched fraction failed to demonstrate an ATPase activity which was stimulated by the presence of bicarbonate ions. It is proposed that the well-established bicarbonate secretion of these cells may be coupled to the plasma membrane (Na+ + K+)-ATPase activity by the stoichiometry of Na+/HCO3- close to 1:1.

Adenosine Triphosphatases↗