Calmodulin antagonists induce changes in lens permeability and transparency

Calmodulin has been shown to perform several important functions in the lens including regulation of the plasma membrane Ca(2+)-ATPase. This study investigated the effects of a variety of different CaM antagonists on rat lens membrane potential, membrane resistance, intracellular Na+ and Ca2+ content and transparency, in order to examine the role of CaM in control of lens membrane permeability. W7, calmidazolium and trifluoperazine caused biphasic changes in lens membrane electrical characteristics. Phase 1 consisted of a depolarization of the membrane potential and an increase in resistance, indicating that K+ channels were being blocked. This was confirmed by application of the K+ channel antagonist, quinine, which inhibited Phase 1 changes. Phase 2 was a further depolarization coupled with a decrease in resistance, indicating the activation of a cation conductance. Application of W7 in low Na+ medium slowed the Phase 2 depolarization and decrease in resistance indicating that Na+ is the main charge carrier through the activated conductance. The CaM inhibitors also led to a large increase in the Na+ and Ca2+ contents of the lens. W5, a less potent analogue of W7, caused a depolarization and increase in membrane resistance, but no Phase 2 changes were observed. Na+ and Ca2+ contents were similar to control lenses after 4 hours incubation in 200 microM W5. In addition, exposure to W7, TFP and calmidazolium resulted in a loss of transparency, while W5 treated lenses remained clear. It appears, therefore, that CaM is involved in control of lens membrane permeability. Loss of control of these channels leads to catastrophic changes in the intracellular ionic environment and hence opacification of the lens.

pCMPS-induced changes in lens membrane permeability and transparency

PURPOSE

To investigate the role of externally facing membrane protein sulfhydryl groups in controlling lens permeability and transparency using the impermeant sulfhydryl complexing agent p-chloromercuriphenyl sulfonate (pCMPS).

METHODS

Membrane permeability changes were studied by measuring lens voltage and resistance. Ion movements were monitored by measuring 22Na+ and 45Ca2+ fluxes, and internal free calcium was monitored by ion-selective microelectrodes. Opacification was quantified by photographing and analyzing back-scattered light.

RESULTS

pCMPS, at concentrations above 1 microM, produced a depolarization of membrane potential and decrease in membrane resistance. These changes were accompanied by a marked stimulation in 22Na+ and 45Ca2+ influxes into the lens. There was a concomitant loss of lens transparency, mainly in the bow region. The pCMPS-induced electrical changes could be prevented by substituting N-methyl-D-glucamine for Na+ in the external medium. Na(+)-free solution alone increased 45Ca2+ influx, and the addition of pCMPS further stimulated the influx. Quinine (300 microM) was found to reduce the pCMPS-induced stimulation of 22Na+ and 45Ca2+ influxes and also to reduce opacification.

CONCLUSIONS

pCMPS at low concentrations induces many of the cation permeability changes previously found to occur with age and cataract in the lens. The fact that quinine can ameliorate pCMPS-induced changes in ion movements and opacification suggests a novel approach for membrane-based anticataract strategies.

Use of thrombolysis for acute myocardial infarction by general practitioners

The early administration of thrombolytic agents significantly reduces mortality following a myocardial infarct and ideally they could be given by general practitioners when the patient is first seen. However, the diagnosis of myocardial infarction in the early stages can be very difficult especially if an electrocardiogram is not available. This may limit the use of thrombolytic drugs by general practitioners. We assessed the accuracy of diagnosis in general practice by asking general practitioners referring patients with chest pain, the likelihood that the event was due to a myocardial infarction and if they would use thrombolysis if it were available. Diagnostic accuracy and appropriate use of thrombolysis was analysed retrospectively, comparing the general practitioner with the admitting hospital doctor. One hundred consecutive patients were studied. The general practitioners accurately diagnosed myocardial infarctions in approximately 45% of cases and would have given thrombolysis inappropriately on 67% of occasions mainly because the final diagnosis in most of these patients was unstable angina rather than infarction. The hospital doctors administered streptokinase inappropriately to 33% of the patients and four had complications during treatment. Of those patients receiving thrombolysis, the average time delay from the general practitioner referring the patient to hospital to the patient being treated was 107 minutes. This study confirms that the diagnosis of myocardial infarction in the early stages is difficult and that thrombolytic therapy may be given inappropriately (mainly to patients with unstable angina). We conclude that until the accuracy of diagnosis of myocardial infarction can be improved in general practice it would seem inappropriate for thrombolysis to be given in the community at the moment.

Molecular biology of Crohn's disease mycobacteria

A Glasgow surgeon, T.K. Dalziel, published a detailed description of chronic enteritis in humans in 1913. He proposed that the disease was caused by the same organisms as those responsible for chronic enteritis, Johne's disease, in animals described a few years earlier (1895). Dalziel's dilemma was that he could see acid-fast bacilli in the diseased animal tissues but not in the diseased human tissues. Little real progress in the medical understanding of the causes of chronic enteritis in humans occurred over the next half a century or more. From 1978, a decade of research in many laboratories using improved methods for the culture of environmental mycobacteria showed that these could be grown in bacillary form from about one in five cases of Crohn's disease, from the same proportion of cases of ulcerative colitis, and from about one in ten control tissues. Spheroplasts were grown from two in five cases of Crohn's disease, one in five cases of ulcerative colitis, and rarely from control tissues. The nature of these agents was often uncertain. We describe work which began in 1985 and led rapidly to the identification of IS900, a DNA repetitive element in an uncharacterized Crohn's disease mycobacterial isolate. With other isolates, these were then shown by DNA fingerprinting to be indistinguishable from Mycobacterium paratuberculosis, Johne's bacillus. Similar techniques also demonstrated the wood-pigeon strain of M. avium in some Crohn's disease cultures. This bacillus can also cause chronic enteritis in calves. IS900 is the first of a family of unusual DNA insertion sequences which extend widely throughout environmental mycobacteria. Use of assays based on PCR amplification of highly specific DNA sequences from these insertional elements, and recombinant and synthetic peptides from their predicted proteins, will revolutionize the detection and characterization of these agents. These methods, applied to animal, human and environmental samples, will indicate new ways for the prevention and treatment of chronic enteritis, as well as other disorders associated with infections by environmental mycobacteria.

Hypophosphataemic rickets and melorheostosis

Hypophosphataemic rickets/osteomalacia has been described in association with fibrous dysplasia and neurofibromatosis. This is the first reported case of melorheostosis associated with hypophosphataemic rickets. The literature is reviewed regarding the known association with the other bone dysplasias.

Recent clinical experience with the vena cava filter

In the past at our institution, insertion of the vena cava filter was recommended almost exclusively for recurrent pulmonary emboli in anticoagulated patients or in those with emboli and contraindications to anticoagulation. More recently, prophylaxis has become a frequent indication for patients with extensive deep vein thrombosis and contraindications to anticoagulation. Herein, we review a recent series of caval filter insertions to determine if increased utilization of this technique is justified in terms of morbidity and effectiveness. Twenty-one filters were inserted in 20 patients during a 1-year period. The operative mortality rate was 0 and satisfactory filter placement was achieved in 90 percent of patients. There were no documented instances of recurrent emboli or vena cava thrombosis. These data suggest that use of the filter is justified as prophylaxis for patients at high risk for an initial pulmonary embolus in a clinical setting where heparin therapy is not appropriate.

Previous ear, nose and throat surgery in children presenting with allergic perennial rhinitis

Children with allergic perennial rhinitis had a four-fold greater likelihood of having had an ear, nose and throat (ENT) operation than children with orthopaedic problems. Whilst the patients who had ENT operations had significantly lower serum IgA and IgE levels than the non-operated patients, there was no difference in clinical features of atopy or allergy skin-test responses between the two groups of rhinitic patients. Forty per cent of the perennial rhinitics had an improvement in symptoms following ENT operations, whereas 90% improved on medical therapy. Thus, patients with perennial rhinitis should have allergy investigations and the benefit of medical treatment prior to consideration for surgery.

Occupational mercury exposure and its consequences for behaviour

Mercury is a known neurotoxin. Evidence from animal studies show behavioural impairment which can be long-lasting, after low-level exposure to mercury. Human research, however, has not been conclusive. Chronic, high-level mercury exposure such as occurred in Japan, and the Middle East, Causes long-lasting and profound neurological damage. However the effects of low-level exposure, such as occurs in occupational exposure, are far from clear. This study used a comprehensive test battery based on an information processing framework to compare a group of twelve chronically mercury-exposed workers with a matched control group. The mercury-exposed group showed poorer psychomotor co-ordination and premature fatigue, although simple motor responses were not affected. General arousal levels also remained unaffected but mercury-exposed workers were superior in sustaining attention. In spite of this, the mercury-exposed group showed clear deficits in short-term memory.

Modified development to improve the performance of AR10 stripping emulsions for use with the more energetic isotopes

Gold latensification of the image to increase the efficiency of the more energetic isotopes, such as 14 carbon, has been used before for liquid emulsions, with mild developers, but never successfully with AR10 stripping emulsion. This paper describes the performance of different developers and assesses their ability to suppress background fog on Kodak AR10 emulsion. A 14 carbon source was used and the effect of gold latensification was examined. Kodak D19, an efficient Metol/hydroquinone developer, could be usefully modified by altering the sodium carbonate and sulphite contents (D19 A/S). This developer discriminated well against the background with AR10 emulsion, producing a far better signal:background ratio than Kodak D19. A pretreatment in aurous thiocyanate for 4 min before development in D19 A/S for 4 min at 291 K increased the signal:background ratio by 200% compared with ordinary development in Kodak D19. When gold latensification was used with D19 developer, the signal was increased, but not more than with D19 A/S, and the gain was offset by the intense background that resulted.

Gonadotrophin levels in women with Cushing's syndrome before and after treatment

Basal serum concentrations of LH and FSH and their response to LHRH were studied in twelve pre- and ten post-menopausal women with Cushing's syndrome before and after treatment. Subnormal basal concentrations of LH were found in twelve out of twenty-two, and of FSH in ten of the twenty untreated patients. There was a correlation between the urinary free cortisol (UFC) and basal LH values, r = -0.59 (P less than 0.05), and UFC and basal FSH values, r = -0.76 (P less than 0.02) in the premenopausal women. All seven patients with a UFC value greater than 1080 nmol/24 h (normal range less than 270) had both a subnormal basal gonadotrophin level and a subnormal response of at least one gonadotrophin to the releasing hormone. In those patients in whom successful remission was obtained and who did not require replacement therapy, subnormal basal gonadotrophins were usually restored towards or into the normal range. It is concluded that while gonadotrophin levels may be normal in women with Cushing's syndrome, they are subnormal in those with the highest cortisol values. This may be due to a direct suppressive effect of cortisol on the release of stored pituitary hormone, and/or on LHRH release from the hypothalamus.

Permeability studies on epidermal–hypodermal sleeves isolated from roots of Allium cepa (onion)

Suberized sleeves of epidermal–hypodermal cells have been isolated by enzymic digestion from roots of onion. The average permeability coefficients of the sleeves to calcium and phosphate ions were 1.8 × 10−3 mm s−1 and 1 × 10−3 mm s−1. respectively, while the diffusive permeability coefficient for tritiated water was 2.6 × 10−3 mm s−1. If the cell walls in vivo have properties similar to those in the isolated sleeves, then it is concluded that diffusion of small molecules in the apoplast is subject to less resistance than diffusion across plasma membranes. Using a range of compounds differing in lipid solubility and molecular weight (MW), it was found that permeability was inversely related to MW. It is concluded that the suberized walls of the sleeves are microporous, having hydrophilic channels traversing them. The results accord with some published information on onion roots in vivo but contrast with the very low permeability of the hypodermis found in some other situations.

Sites of absorption and translocation of iron in barley roots: tracer and microautoradiographic studies

Absorption and translocation of labeled Fe were measured at various locations along the length of intact seminal axes and lateral roots of iron-sufficient (+Fe) and iron-stressed (-Fe) barley (Hordeum vulgare) plants. In seminal axes of +Fe plants, rates of translocation were very much higher in a zone 1 to 4 cm from the root tip than elsewhere in the root. Lateral roots of high rates of translocation were also restricted to a narrow band of maturing or recently matured cells. In -Fe plants the patterns of uptake and translocation were essentially the same as in +Fe plants but the rates were 7- to 10-fold higher. The amount of labeled Fe bound to the root itself was not increased by Fe stress and its distribution along the root seemed inversely related to the ability to translocate Fe.Microautoradiographic studies showed that most of the iron bound to roots was held in an extracellular peripheral band in which iron seemed to be precipitated. This process may be assisted by microbial colonies but did not depend on them since it was seen, although to a lesser extent, in sterile roots. In zones from which iron was translocated there was evidence that internal root tissues became labeled readily, but as translocation declined with distance from the root tip, radial penetration of Fe appeared to become progressively less. The results are discussed in relation to possible changes in the pH or redox potential of the surface of the root.

Influence of phosphate-stress on phosphate absorption and translocation by various parts of the root system of Hordeum vulgare L. (barley)

Plants of Hordeum vulgare (barley) were grown initially in a solution containing 150 μM phosphate and then transferred on day 6 to solutions with (+P) and without (-P) phosphate supplied. After various times plants from these treatments were supplied with labelled phosphate. Analysis of plant growth and rates of labelled phosphate uptake showed that a general enhancement of uptake and translocation was found, in plants which had been in the-P solution, several days before the rate of dry matter accumulation was affected. Subsequently a detailed analysis of phosphate uptake by segments of intact root axes showed that the enhancement of phosphate uptake by P-stress occurred first in the old and mature parts of the seminal root axis and last in the young zones 1 cm from the root apex. During this transition period there were profound changes in the pattern of P absorption along the length of the root. Most of the additional P absorbed in response to P-stress was translocated to the shoot, particularly in older zones of the axis. Enhancement of phosphate uptake in young zones of nodal axes occurred at an earlier stage than in seminal axes. The results are related to the P-status of shoots and root zones and discussed in relation to the general control by the shoot of phosphate transport in the root.

Variation in the incidence of diverticular disease within the city of Edinburgh

An estimate of the incidence of diverticular disease of the colon was based on all the barium enema examinations in Edinburgh over four years (12 335 cases); using the census data for 1971, incidence rates for the city by age, sex, and electoral ward were calculated. The overall annual incidence rate was 1-55/1000, the rate rising sharply with increasing age. The incidence of diverticular disease varies from ward to ward (range 0-92-2-04/1000), adjacent wards have similar incidence rates and the six wards with the lowest rates are clustered together in the South East of the city. Ward incidence rates have a significant negative association with the percentage of owner occupiers living in that area.

Urinary mercury excretion and proteinuria in pathology laboratory staff

The use of mercuric chloride as an histological fixative was associated with high environmental atmospheric concentrations of mercury vapour (up to 0-5 nmol/l) as well as mercury compounds (total Hg to 1-0 nmol/l). Technicians exposed to this environment showed increased urinary mercury (median value 265 nmol/24h) and protein outputs (median value 117 mg protein/24h). Routine control measures, ventilation and careful handling of mercuric chloride solutions, reduced the level of atmospheric mercury vapour levels to within acceptable limits (threshold limit values 0-01 mg/m3 (0-05 nmol/l) alkul compounds and 0-05 mg/m3 (0-25 nmol/l) for all forms except alkyl). This reduction was associated with the disappearance of trace proteinuria from the technicians' urine. Contamination of histology laboratories by mercuric chloride should be minimised.

New techniques for the preparation of uniform layers of nuclear emulsions for use in micro-autoradiography

A procedure is described whereby liquid emulsion can be used to coat glass coverslips to produce films of emulsion suitable for quantitative evaluation of grain density in micro-autoradiographs. Any thickness of emulsion layer can be produced from 3 mum upwards, depending on the volume and dilution of the emulsion dispensed. The uniformity and reproducibility of the films have been tested by observing light transmission of undeveloped preparations using a microscope photometer.

The tertiary endodermis in barley roots: Fine structure in relation to radial transport of ions and water

The presence of numerous pits containing plasmodesmata in the inner tangential wall of the tertiary endodermis in barley roots is demonstrated by electron microscopy. The pit floor is covered by a thin layer of material which is continuous with and resembles the tertiary wall. The plasmodesmatal pore is constricted at its ends so that the plasmalemma lining the pore is appressed to the desmotubule. The frequency of plasmodesmata and their cross-sectional area is estimated, and phosphate and water fluxes through them are calculated on the assumption that they represent the only communication between the cortex and the vascular tissue. The pressure gradient across the ends of the plasmodesmata necessary to support the observed water flux is calculated for limiting cases of the pore radius and the viscosity of the fluid passing through the pore.

The absorption and translocation of sodium by maize seedlings

The absorption and subsequent distribution of sodium and potassium has been examined in maize seedlings in short-term experiments using sodium-22 and potassium-42. The absorption and translocation of sodium by different segments of intact seedlings was also investigated. Although absorption of potassium exceeded that of sodium by a factor of about 50, there was no evidence that the entry of sodium was confined to a small region of the root. Determinations of the relative quantities of sodium and potassium in the xylem exudate of detached roots showed that the ratio of sodium to potassium decreased with increasing length of the root. These results suggested that upward movement of sodium in the xylem vessels was progressively reduced towards the basal part of the root. This conclusion was supported by microautoradiographs, which showed that although the concentration of sodium within the endodermis was greater than that in the cortex, there was an apparent decrease in the sodium content of the major xylem vessels at the basal end of the root.

The uptake of a polyvalent cation and its distribution in the root apices of Allium cepa: Tracer and autoradiographic studies

Observations on the inhibition of root elongation and cell division in Allium cepa showed that the toxic effects of scandium and aluminium were very similar. Tracer uptake studies using (46)Sc indicated that the rate of uptake in the apical 3.0 mm of the axis was more rapid than elsewhere in the root and proceeded in two distinct phases; Phase 1, probably superficial adsorption, was characterised by a rapid initial rate which was little affected by low temperature, the rate of Phase 2 was slower but remained constant for 24 hours and was highly dependent on temperature.Autoradiographs from roots treated for 30 min with (46)Sc showed that most of the isotope in the root tip was concentrated in a peripheral belt corresponding with the mucigel layer of the root cap and it is suggested that this is the site of Phase 1 adsorption. The underlying root cap and epidermal cells retained little scandium but interior to them some isotope was associated with dividing cells; this increased steadily over 6 hour to an estimated concentration of 30 mM, and possibly represents Phase 2 uptake. Differentiation and secondary wall formation in the cortex restricted the rate of radial penetration of scandium. The primary endodermis restricted the entry of scandium into the stele at a very early stage in its development, which leads to the conclusion that migration of the ion across the root is primarily in the free space.Scandium enters the dividing cells in advance of observable effects on cell division, a situation compatible with the direct involvement of this ion in the inhibition of the mitotic cycle. Suggestions are made on the mechanisms by which polyvalent cations might disturb cell division and extension.