Calcium localization and ultrastructure of clear and pCMPS-treated rat lenses

PURPOSE

The sulfhydryl complexing agent p-chloromercuri-phenylsulfonate (pCMPS) has been shown to increase lens membrane permeability, Na+ and Ca2+ content, and light scatter in the rat lens in vitro. This study aimed to investigate the ultrastructural changes accompanying the increase in light scatter. In addition, high-resolution histochemistry was used to study the cellular distribution of Ca2+ in normal and cataractous lenses.

METHODS

Rat lenses were incubated for 4 hours in normal (1 mM) and high (5 mM) Ca2+ containing media supplemented with 40 microM pCMPS. Control lenses were incubated in 1 mM Ca2+ containing medium. They were prepared for scanning and transmission electron microscopy and for Ca2+ localization using the oxalate-pyroantimonate procedure.

RESULTS

Control lenses incubated for 4 hours had normal morphology and showed no evidence of light scatter. Calcium distribution as observed with the oxalate-pyroantimonate precipitation method was low in superficial fibers, high in the membranes of intermediate fibers, and declined again toward the nucleus. In the deeper cortex, there also were small vacuoles of calcium accumulation. pCMPS treatment (in 1 and 5 mM Ca2+) induced a significant influx of calcium into the lens cytoplasm. Calcium-containing extracellular vacuoles also were seen in the intermediate cortex in both cases. The presence of these vacuoles appeared to correlate with the major areas of light scatter in the lens. In 5 mM Ca2+, intracellular vacuoles were observed throughout the superficial cortex.

CONCLUSIONS

Most of the calcium observed by oxalate-pyroantimonate in the normal lens is located at the membrane, and the staining appears strongest in the intermediate cortex. In pCMPS treatment, large extracellular vacuoles are present in this intermediate zone and appear to be the major source of light scatter. This zone may be the initiation site of many different types of cataract, including some described in human lenses.

Public education and depth of primary malignant melanoma, Hutt Hospital, 1985-92

AIMS

To document the depth of primary malignant melanoma treated at the Wellington regional plastic and maxillo-facial surgical unit, Hutt Hospital, from 1985-92. To determine the effects of public education campaigns commenced in 1987, on the presentation of melanoma at Hutt Hospital, and to ascertain whether the Department of Health, Health Goals for 1995 were attained in relation to Hutt Hospital.

METHODS

A surgical audit was established in 1985 to record all cases of melanoma treated at the plastic surgical unit, Hutt Hospital. Data relating to the depth (Breslow index) of each primary melanoma was extracted from this audit, and reviewed. Metastatic or recurrent disease was excluded.

RESULTS

The number of cases of primary melanoma treated at this unit increased greatly following the Cancer Society initiated Spotcheck programme in 1987. There was a significant increase (p < 0.001) in the number and proportion of thin (less than 0.76mm) invasive melanomas treated, from 30% of the total in 1985, through to 70% in 1992. There was no increase in the actual number of thick (> 0.75mm) invasive melanoma, with the total number of cases being treated remaining relatively constant from 1989 onwards.

CONCLUSIONS

Significantly more patients are presenting with thin melanoma. This may be due to the nature of the disease itself, alterations in referral patterns, or due to earlier identification of malignant lesions due to greater public education. The education campaigns appear to be responsible for the observed increase in cases of melanoma presenting to our unit. The Department of Health goals for 1995 have already been achieved with > 60% of primary malignant melanoma being < 0.76 mm in depth at time of presentation.

Histamine and ATP mobilize calcium by activation of H1 and P2u receptors in human lens epithelial cells

1. Cytoplasmic calcium concentration ([Ca2+]1) of single superfused tissue-cultured human lens epithelial cells (HLEC) was monitored using the fluorescent dye fura-2; the resting values were low and stable for several hours ([Ca2+]i = 96 +/- 20 nM; mean +/- S.D., n = 16). 2. Continuous superfusion with either ATP or histamine (0.1-10 microM) produced regular oscillations in [Ca2+]i that could be maintained for a short time in the absence of external calcium. 3. Short (30 s) pulses of histamine (0.1-100 microM) induced a transient rise in [Ca2+]i, the time course of which was insensitive to the removal of external calcium. The rate of rise and the amplitude of the response were very sensitive to agonist concentration, whereas the rate of recovery was relatively constant. 4. The responses to long pulses of histamine (> 100 s) consisted of an initial transient followed by a maintained [Ca2+]i which returned to baseline on removal of external calcium. 5. The kinetics of the responses to short and long pulses of ATP (0.1-100 microM) were very similar to those of histamine and showed a similar sensitivity to the presence or absence of external calcium. 6. The histamine responses were abolished by triprolidine (1 microM), but unaffected by ranitidine (1 microM), indicating that an Hi receptor subtype is activated by histamine. 7. The ATP responses were reversibly inhibited by suramin and the potency sequence for a range of agonists was ATP = UTP = ATP gamma S > ADP = GTP >> AMP = adenosine, indicating that activation of a P2u receptor subtype was responsible for the increase in [Ca2+]i. 8. Both histamine and ATP responses were abolished by thapsigargin (100 nM), confirming that calcium release from intracellular stores was responsible for the initial peak of the response. Application of either agonist during the plateau phase of the thapsigargin response often led to a marked, but reversible, decline in [Ca2+]i, indicating the presence of a further, normally hidden, calcium regulatory factor associated with the presence of the agonist. 9. Maximal concentrations of either histamine or ATP totally emptied the calcium store as a subsequent application of the other agonist (or thapsigargin), in the absence of external calcium, failed to induce a further increase in the calcium signal.

Acute stroke in South Ayrshire: comparative study of pre and post stroke units

In September 1993 arrangements for managing acute stroke victims in South Ayrshire changed with the opening of a six bedded Acute Stroke Unit and a fifteen bedded Rehabilitation Stroke Unit. Previously all such patients were managed within general medical wards with a few being managed in geriatric assessment and rehabilitation facilities. This study compares the management and outcome from acute stroke before and after the establishment of these new Units. Fifty-eight patients' medical, nursing and paramedical records were studied for the period of investigation in 1992 and 68 for the same period in 1993. There was no significant difference in the age of the patients admitted or in the degree of neurological or functional impairment at the time of admission. There was a reduction in mortality from 37.9% in 1992 to 22.0% in 1993. This was not accomplished by an increase in the number of survivors requiring long term institutional care and there was no significant difference in the degree neurological or functional impairment at the time of discharge. A variety of specific management issues were also addressed by the study and in all areas there were improvements in the quality of care received by this group of patients in 1993. This study supports the view that management of acute stroke victims in specifically designated Stroke Units has a beneficial effect on outcome and quality of care.

Validation of the doubly labeled water method in growing pigs

The CO2 production (rCO2) of eight growing pigs was determined by continuous collection of CO2 over 21 days and simultaneously estimated using the doubly labeled water (DLW) method. The aim was to assess the accuracy of the method before and after correction for known sources of error and to test for any residual discrepancy arising from as yet unidentified sources of error. Mass spectrometer accuracy was verified by analyzing serial dilutions of the dose material in the form of an artificial decay curve; no significant bias was detected. The physiological errors were linearly dependent on weight gain. DLW-derived rCO2 (corrected only for fractionated water loss) underestimated the true value by 0.270 l CO2/g wt gain or -8% in the restricted (group R) and -16% in the ad libitum-fed (group AL) groups. Known sources of error accounted for -0.006 (methane), -0.032 (fecal 2H losses), -0.108 (fat synthesis), and -0.146 (changing pool size) l CO2/g wt gain. After correction for these sources of error the DLW-derived rCO2 differed from the true value by -2 +/- 3% in group R and 0 +/- 3% in group AL. Thus there was no significant bias in the DLW method after correction for known sources of error, even during rapid weight gain or at weight stability with or without correction. The precision estimates include both dose and background errors and uncertainty in the correction factors used. Strategies for optimizing precision are presented.

The influence of exercise on the energy requirements of adult males in the UK

Energy expenditure was measured over 10 d using the doubly-labelled water (DLW) and activity diary methods in summer and winter in subjects with 'light' occupations but leisure activities which ranged from 'non-active' to 'very active'. The basal metabolic rate (BMR) and the energy cost of activities were determined by indirect calorimetry. The Department of Health (1991) predicted BMR for the group (6.89 (SD 0.30) MJ/d; n 18) was not significantly different from the measured value (7.17 (SD 0.70) MJ/d; n 18). The range of DLW-derived expenditure values within the group was BMR x 1.41 to 2.41. The largest seasonal change within individuals was BMR x 0.5. The energy expenditure of the group as a whole was lower in winter (BMR x 1.88; SD 0.33; n 9) than summer (BMR x 2.01; SD 0.30; n 9) though the difference was not statistically significant. The average summer and winter DLW-derived expenditure was BMR x 1.96 (SD 0.31; n 17). The activity diary estimate of expenditure was BMR x 1.79 (SD 0.32; n 17). In a subset of the group who were representative of the most active 26% of all adult males in the UK, the DLW-derived expenditure was BMR x 2.08 (SD 0.24; n 11). This is higher than the highest Department of Health (1991) estimate of BMR x 1.6 for individuals in light occupations. The measured energy costs of low-intensity activities were similar to those presented in the Department of Health (1991) report but the value determined for running (BMR x 13.08; SD 2.4; n 6) was higher than the highest value in the report (BMR x 6 to 8). The results indicate that the recent Department of Health (1991) reference values for energy may underestimate the expenditure of a significant proportion of the UK population largely because the energy costs of activity used in the report to calculate expenditure do not accurately reflect those achieved during active leisure in individuals who take regular exercise.

cAMP regulates morphogenesis in the fungal pathogen Ustilago maydis

The fungal pathogen Ustilago maydis exhibits a dimorphic switch from budding to filamentous growth in response to mating interactions and environmental conditions. We have found that disruption of the uac1 gene, encoding adenylate cyclase, results in a constitutively filamentous phenotype. Budding is restored to the uac1 mutant upon growth in the presence of cAMP or by extragenic suppression because of a mutation in the ubc1 gene. The ubc1 gene encodes a type II regulatory subunit of cAMP-dependent protein kinase (PKA); defects in this gene attenuate the filamentous growth that normally occurs in response to mating and exposure to air. Growth of wild-type cells in cAMP and mutation of the ubc1 gene also cause defects in the separation of mother and daughter cells (cytokinesis) and alter bud site selection. These results indicate a key role for cAMP and PKA in morphogenesis in U. maydis; this role may be common among dimorphic fungal pathogens.

Living wills: would sick people change their minds?

Patients admitted acutely to a geriatric medical unit were interviewed on admission about their opinions on cardiopulmonary resuscitation (CPR). They underwent a general examination and their mental health was documented by completing the geriatric depression scale. Those who did not wish CPR in the event of a cardiac arrest were questioned again on recovery. Of 216 patients admitted, only three objected to answering the questions and after the other exclusion criteria were applied, 100 patients were included in the study. A total of 92% of patients wished CPR in the event of a cardiac arrest. The 8% who did not wish CPR contained more people scoring high on the geriatric depression scale. After recovery, three of that eight had changed their minds and wished CPR if required. Patients who are acutely unwell may make decisions that are influenced by their condition at this point in time and it is important to recognize that these decisions may not be maintained. In this study, consultant geriatricians did not reflect their patients' desires in making decisions about who should receive CPR if required.

A correlated study of metabolic cell communication and gap junction distribution in the adult frog lens

By using low molecular weight dye injection and laser scanning confocal microscopy it has been possible to assess the degree of dye communication in several regions (intraepithelial, epithelium-fibre cell, fibre-epithelium and fibre-fibre) of the adult frog lens. These same areas of the lens have also been examined by freeze fracture electron microscopy for the presence and organisation of gap junctions. Epithelial cell lateral membranes have numerous gap junctions which efficiently transmitted dye to their neighbours though none was detectable in the underlying fibre cells. This was correlated with an apparent absence of gap junctions at the epithelium/fibre cell interface. Dye spread between cortical fibre cells was only observed in a subset of fibres in the bow region of the lens. Neither mature cortical fibres nor immature bow fibres appeared to be dye-coupled and we detected no dye passed from fibre cells to adjacent epithelial cells at their anterior ends. This pattern of dye communication was also correlated with the apparent absence of recognisable gap junctions on the lateral membranes of either the recently differentiated bow fibres or the mature cortical fibres. Classical gap junctions were only found on the membranes of fibres between five and ten cells in from the lens bow, i.e. the subset of fibres which were dye-coupled. No gap junctions were found between deeper cortical fibres or nuclear fibres, although they were characterised by a number of square arrays. Though electrically well coupled the adult frog lens may be relatively poorly dye coupled and this could depend on the age and differentiation stage of the cells concerned. The model of a freely communicating lens clearly requires re-examination by correlated physiological and morphological studies.

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.

Calcium regulation in tissue-cultured human and bovine lens epithelial cells

PURPOSE

To study calcium regulatory mechanisms in lens cells with particular reference to the relative contributions from the calcium adenosine triphosphatase of plasma and endoplasmic reticulum membranes, respectively.

METHODS

The calcium-sensitive fluorescent dye, Fura 2, was incorporated into tissue-cultured human and bovine epithelial cells and internal calcium was calibrated using the ionomycin (1 microM) method. The dynamics of calcium release from the endoplasmic reticulum were also studied in digitonin-permeabilized bovine cells.

RESULTS

Tissue-cultured bovine and human lens cells have very similar resting calcium levels (235 +/- 22 nM and 216 +/- 12 nM, respectively). Thapsigargin caused an increase in cytoplasmic calcium both in the presence and absence of external calcium, but the calmodulin antagonist W7 only initiated an increase in the presence of external Ca2+. The effects of thapsigargin and W7 were additive. Exposing lens cells to Na(+)-free perfusing solutions caused a transient increase in internal Ca2+. Bovine lens cells permeabilized by digitonin-released Ca2+ when exposed to inositol (1,4,5) triphosphate and the effect was maximal at 1 microM.

CONCLUSIONS

Lens cytoplasmic calcium is controlled by calcium adenosine triphosphatases at the plasma and endoplasmic reticulum membranes. The former is inhibited by W7 and insensitive to thapsigargin whereas the latter is inhibited by thapsigargin, but insensitive to W7. The lens endoplasmic reticulum store is also controlled by an inositol (1,4,5) trisphosphate calcium-release mechanism. Na+/Ca2+ exchange plays a relatively minor role in calcium regulation, at least at resting calcium levels.

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.

Patterns of palliative radiotherapy in Canada

A questionnaire study was performed to determine patterns of radiotherapy practice across Canada and the relationship of age, work-load, resources, intent and aims of therapy on departmental policy; 99 returns were analysed. Three case scenarios were given: Brain metastases were treated typically without a simulation as a parallel pair with palliative intent to 2000 cGy in 5 fractions; for locally advanced lung cancer most patients were simulated, but 40% we deemed 'radical' and there was a bimodal pattern of dose fractionation (the age of the radiation oncologist appeared to influence this and geographical differences were also notable); bony metastases from breast cancer were typically simulated as a single field using 2000-2500 cGy in 5 fractions and always considered palliative. Work-load and resources are likely to influence patterns of care. For example, over 20% felt that treatment choice was suboptimal, largely due to lack of radiation technologists and megavoltage equipment. The implications of these determinants on palliative care are discussed. Objective criteria and definitions are required to allow satisfactory workload measurements and comparisons to be made.

Evaluation of DNA probe removal from nylon membrane

Genetic fingerprinting is one of the most challenging applications of any hybridization membranes. Forensic DNA fingerprinting typically uses samples in the range of 100-400 ng of genomic DNA. To ensure the ability to successfully reprobe the samples, it is imperative that repeated stripping of sample DNA be minimized while stripping of the probe DNA be maximized. By using standard dilutions of K562 cell line, we compared the following three stripping techniques: NaOH at 25 degrees C, formamide (HCONH2) at 65 degrees C and 0.1 x standard saline citrate and 0.1% sodium dodecyl sulfate at 95 degrees C (high-temperature stripping). The largest amount of genomic DNA was stripped from the membrane with NaOH, with the other two techniques removing less. Formamide and high-temperature procedures resulted in a loss of approximately 5-10 ng of DNA per strip. In contrast, the NaOH resulted in a loss of approximately 10-20 ng per strip.

The prognosis of adenosquamous carcinomas of the uterine cervix

OBJECTIVES

Firstly, to identify a cohort of women with invasive adenosquamous carcinomas of the uterine cervix, including mucin-producing squamous cell carcinomas. Secondly, to compare the biological characteristics and behaviour of a cohort of adenosquamous carcinomas with a cohort of non-mucin-producing squamous cell carcinomas.

DESIGN

Histological review, retrospective survival analysis.

SETTING

Regional multidisciplinary gynaecological oncology service.

SUBJECTS

161 cases of stage 1B and above invasive cervical carcinoma presenting between 1 January 1980 and 31 July 1987. Thirty nine women with adenosquamous carcinomas were compared with 103 women with non-mucin-producing squamous cell tumours.

RESULTS

Inclusion of routine stains for mucin in the assessment of histological material resulted in the reclassification of 38 (24%) of the cases, including the identification of 31 mucin-producing squamous cell carcinomas. The survival with adenosquamous tumours was significantly worse than with squamous cell cancers (P = 0.006), 5-year survival rates being 52% and 75% respectively. Multivariate analysis showed that this effect was explained by differences in clinical stage, pelvic lymph node metastasis and vascular invasion by tumour.

CONCLUSIONS

The application of routine mucin stains to cervical tumours identifies a group of previously unrecognized adenosquamous cancers. Tumours so identified are likely to pursue a more aggressive clinical course associated with a poorer survival when compared to non-mucin-producing squamous carcinomas.