Muscle channelopathies: does the predicted channel gating pore offer new treatment insights for hypokalaemic periodic paralysis?

Hypokalaemic periodic paralysis (hypoPP) is the archetypal skeletal muscle channelopathy caused by dysfunction of one of two sarcolemmal ion channels, either the sodium channel Nav1.4 or the calcium channel Cav1.1. Clinically, hypoPP is characterised by episodes of often severe flaccid muscle paralysis, in which the muscle fibre membrane becomes electrically inexcitable, and which may be precipitated by low serum potassium levels. Initial functional characterisation of hypoPP mutations failed to adequately explain the pathomechanism of the disease. Recently, as more pathogenic mutations involving loss of positive charge have been identified in the S4 segments of either channel, the hypothesis that an abnormal gating pore current may be important has emerged. Such an aberrant gating pore current has been identified in mutant Nav1.4 channels and has prompted potentially significant advances in this area. The carbonic anhydrase inhibitor acetazolamide has been used as a treatment for hypokalaemic periodic paralysis for over 40 years but its precise therapeutic mechanism of action is unclear. In this review we summarise the recent advances in the understanding of the molecular pathophysiology of hypoPP and consider how these may relate to the reported beneficial effects of acetazolamide. We also consider potential areas for future therapeutic development.

The non-dystrophic myotonias: molecular pathogenesis, diagnosis and treatment

The non-dystrophic myotonias are an important group of skeletal muscle channelopathies electrophysiologically characterized by altered membrane excitability. Many distinct clinical phenotypes are now recognized and range in severity from severe neonatal myotonia with respiratory compromise through to milder late-onset myotonic muscle stiffness. Specific genetic mutations in the major skeletal muscle voltage gated chloride channel gene and in the voltage gated sodium channel gene are causative in most patients. Recent work has allowed more precise correlations between the genotype and the electrophysiological and clinical phenotype. The majority of patients with myotonia have either a primary or secondary loss of membrane chloride conductance predicted to result in reduction of the resting membrane potential. Causative mutations in the sodium channel gene result in an abnormal gain of sodium channel function that may show marked temperature dependence. Despite significant advances in the clinical, genetic and molecular pathophysiological understanding of these disorders, which we review here, there are important unresolved issues we address: (i) recent work suggests that specialized clinical neurophysiology can identify channel specific patterns and aid genetic diagnosis in many cases however, it is not yet clear if such techniques can be refined to predict the causative gene in all cases or even predict the precise genotype; (ii) although clinical experience indicates these patients can have significant progressive morbidity, the detailed natural history and determinants of morbidity have not been specifically studied in a prospective fashion; (iii) some patients develop myopathy, but its frequency, severity and possible response to treatment remains undetermined, furthermore, the pathophysiogical link between ion channel dysfunction and muscle degeneration is unknown; (iv) there is currently insufficient clinical trial evidence to recommend a standard treatment. Limited data suggest that sodium channel blocking agents have some efficacy. However, establishing the effectiveness of a therapy requires completion of multi-centre randomized controlled trials employing accurate outcome measures including reliable quantitation of myotonia. More specific pharmacological approaches are required and could include those which might preferentially reduce persistent muscle sodium currents or enhance the conductance of mutant chloride channels. Alternative strategies may be directed at preventing premature mutant channel degradation or correcting the mis-targeting of the mutant channels.

Voltage sensor charge loss accounts for most cases of hypokalemic periodic paralysis

BACKGROUND

Several missense mutations of CACNA1S and SCN4A genes occur in hypokalemic periodic paralysis. These mutations affect arginine residues in the S4 voltage sensors of the channel. Approximately 20% of cases remain genetically undefined.

METHODS

We undertook direct automated DNA sequencing of the S4 regions of CACNA1S and SCN4A in 83 cases of hypokalemic periodic paralysis.

RESULTS

We identified reported CACNA1S mutations in 64 cases. In the remaining 19 cases, mutations in SCN4A or other CACNA1S S4 segments were found in 10, including three novel changes and the first mutations in channel domains I (SCN4A) and III (CACNA1S).

CONCLUSIONS

All mutations affected arginine residues, consistent with the gating pore cation leak hypothesis of hypokalemic periodic paralysis. Arginine mutations in S4 segments underlie 90% of hypokalemic periodic paralysis cases.

What causes paramyotonia in the United Kingdom? Common and new SCN4A mutations revealed

OBJECTIVE

To study the clinical and genetic features in a large cohort of UK patients with sodium channel paramyotonia congenita.

METHODS

We conducted a UK-wide clinical and molecular genetic study of patients presenting with a phenotype suggestive of paramyotonia congenita.

RESULTS

We identified 42 affected individuals (28 kindreds). All cases met our core criteria for a clinical diagnosis of paramyotonia congenita. Seventy-five percent of patients (32 patients/20 kindreds) had SCN4A mutations. Twenty-nine subjects from 18 kindreds had exon 22 and 24 mutations, confirming these exons to be hot spots. Unexpectedly, 3 of these subjects harbored mutations previously described with potassium-aggravated myotonia (G1306A, G1306E). We identified two new mutations (R1448L and L1436P). Ten cases (8 kindreds) without mutations exhibited paramyotonia congenita with prominent pain and weakness.

CONCLUSIONS

This study identifies two new mutations, confirms SCN4A as a common cause of paramyotonia congenita in the UK, and suggests further allelic and possibly genetic heterogeneity.

INTERACTION OF EIMERIA TENELLA WITH INTESTINAL MUCIN IN VITRO

The mucus gel layer overlying the gastrointestinal epithelium plays an important role in host-pathogen interactions. The initial interaction between the coccidian parasite Eimeria tenella and host cells of the intestinal epithelium must occur across this mucus interface. In this study, we examined the relationship between E. tenella and avian mucin, in particular the effect of purified intestinal regional mucin on parasite adherence and invasion in vitro. Secreted mucin from the chicken duodenum and cecum was purified by density gradient centrifugation and gel chromatography. Parasite invasion studies were performed in the Madin-Darby bovine kidney cell model. Eimeria tenella adherence to chicken duodenal mucin was detected, whereas adherence to cecal or bovine mucin was not shown. Parasite invasion into epithelial cells was not influenced by bovine mucin, whereas chicken mucin purified from the duodenum and cecum significantly inhibited invasion. Inhibition of E. tenella invasion into cells by mucin from the duodenum was marginally greater than that of the cecum, but this was not significant. This study demonstrated E. tenella interaction with native chicken intestinal mucin, which in turn inhibited parasite invasion into epithelial cells in vitro.

Glycosidase activity in the excretory-secretory products of the liver fluke, Fasciola hepatica

Fasciola hepatica secretes proteolytic enzymes and other molecules that are essential for host penetration and migration. This mixture may include enzymes required for the degradation of supramucosal gels, which defend epithelial surfaces against pathogen entry. These contain hydrated mucins that are heavily glycosylated. Excretory-secretory products (ES) from F. hepatica were examined for a range of glycosidase activities, using synthetic 4-methylumbelliferyl glycosides as substrates. The ES product contained at least 8 different glycosidase activities, the most abundant of which were beta-N-acetylhexosaminidase, beta-galactosidase and beta-glucosidase. Alpha-fucosidase, beta-glucuronidase, alpha-galactosidase, alpha-mannosidase and neuraminidase were also present. Beta-N-acetylhexosaminidase and beta-galactosidase were present in multiple isoforms (at least 4), whereas beta-glucosidase appeared to exist as one isoenzyme with a pI < 3.8. All three enzymes had acidic pH optima (4.5-5.0). Ovine small intestinal mucin was degraded by ES at pH 4.5 or 7.0, with or without active cathepsin L, the major protease found in F. hepatica ES. The ability of F. hepatica ES to degrade mucin in the presence or absence of active cathepsin L suggests that cathepsin L is not essential for mucin degradation. The abundance of beta-galactosidase and beta-hexosaminidase in ES supports a role for these enzymes in mucin degradation.

To tell or not to tell: barriers and facilitators in family communication about genetic risk

Communication about genetic risk in families is an important issue for genetic counsellors. The objective of this study was to explore the barriers and facilitators in family communication about genetic risk. Semi-structured interviews were undertaken with patients in the Northeast of Scotland who had attended genetic counselling for risk of hereditary breast and ovarian cancer and Huntington's disease, and with some spouses/partners. The interviews confirmed that the issue of disclosure was a problem for some, and that there were generic communication issues common to both groups. Telling family members about genetic risk was generally seen as a family responsibility and family structures, dynamics and 'rules' influenced disclosure decisions. A sense of responsibility towards younger generations was also important. The level of certainty felt by a person in relation to his or her own risk estimate also influenced what he or she could tell other family members. Communication within a family about genetic risk is a complex issue and is influenced by both pre-existing familial and cultural factors and individuals' responses to risk information. If genetic counsellors understood how these factors operate in individual families they might be able to identify effective strategies to promote considered decisions and prevent unnecessary emotional distress.

Preventing accidental falls among older people in long stay units

A fall prevention programme for older long-stay patients in a 95 bedded District Hospital was undertaken. Data on falls and resulting injuries for the year prior to the intervention were compared with equivalent data after one year (Year 1) and after two years (Year 2) of the intervention. In the pre-intervention year 25% of patients had at least one fall compared with 20.9% and 17.4% in Year 1 and Year 2 respectively. This difference was not statistically significant. However, there were 21% fewer falls in Year 1 and 49.3% fewer in Year 2 than in the pre-intervention year. This difference was significant in Year 2. In both intervention years there was a significant reduction in the incidence of fracture from 20.5% of falls (pre-intervention) to 2.8% in Year 1 and no fractures occurred in Year 2. Significant reductions in soft tissue injuries occurred in Year 2 but not in Year 1, dropping from 38.5% (pre-intervention) to 36.1% and 15.4% respectively. The percentage of patients uninjured after a fall increased from 41% to 61.1% to 84.6%. This intervention reduced falls and their adverse consequences for older people living in the long stay unit. The effect of the intervention escalated in Year 2. The intervention cost IR4,800 pounds. Fall prevention should be part of the routine care of older people in all types of long stay care.

Presenting risk information--a review of the effects of "framing" and other manipulations on patient outcomes

Discussing risks and benefits of treatments or care options is becoming an increasingly important part of modern health care. This paper reviews the literature about manipulations of risk and benefit information in the clinical setting. There is a paucity of evidence in this field, particularly when examining specific manipulations. Only three categories of manipulation had three or more studies. The available evidence shows that the way information is presented can have significant effects on decisions made. The largest effects are evident when relative risk information is presented, as compared with absolute risk data. In addition, "loss framing" is more effective in influencing screening uptake behaviors than "gain framing" (odds ratio 1.18 [95% confidence interval 1.01-1.38]). There is also a pattern of evidence from studies comparing simpler with more complex information, more data with less, and those comparing numerical with verbal descriptions of risks. These studies suggest that providing more information, and which is more understandable to the patient, is associated with improved patient knowledge and a greater wariness to take treatments or participate in trials. These findings can contribute to efforts to improve communication between professionals and patients.

Down-regulation of TGF-beta1 production restores immunogenicity in prostate cancer cells

The objective of this study is to determine if a non-immunogenic Dunning's rat prostate cancer cell line, MATLyLu, can become immunogenic by reducing the endogenous production of TGF-beta1. An expression construct containing a DNA sequence in an antisense orientation to TGF-beta1 (TGF-beta1 antisense) was stably transfected into MATLyLu cells. Following transfection, cellular content of TGF-beta1 reduced from 70 to 10 pg per 2x10(4) cells and the rate of in vitro 3H-thymidine incorporation increased 3-5-fold. After subcutaneous injection of tumour cells into syngeneic male hosts (Copenhagen rats), the tumour incidence was 100% (15/15) for the wild type MATLyLu cells and cells transfected with the control construct, but only 43% (9/21, P< or =0.05) for cells transfected with TGF-beta1 antisense. However, when cells were injected into immunodeficient hosts (athymic nude rats), the incidence of tumour development was 100% (10/10) for both the wild type MATLyLu cells and cells transfected with the control construct and 90% (9/10) for cells transfected with TGF-beta1 antisense. These observations support the concept that MATLyLu cells are immunogenic, when the endogenous production of TGF-beta1 is down-regulated.

The effectiveness of one-to-one risk communication interventions in health care: a systematic review

OBJECTIVES

To assess whether risk-communication interventions are associated with changes in patient knowledge, attitudes, and behaviors, and to identify aspects of these interventions that modify these effects.

DESIGN

Systematic review.

DATA SOURCES

96 studies from the period 1985-1996 retrieved by electronic searching of eight databases, hand searching of four journals, contacting key authors, and reference list searching.

MAIN OUTCOME MEASURES

The effect size of the principal outcome was identified from each study. Outcomes measuring behavioral change were preferred; if these were not available, knowledge, anxiety, or risk perceptions were used, according to the focus of the study. Data were available to calculate the principal effect sizes for 82 of the studies.

ANALYSIS

Meta-regression.

RESULTS

The methodologic qualities of the studies varied. Nevertheless, risk-communication interventions generally had positive (beneficial) effects. Interventions addressing treatment choices were associated with larger effects than were those in other contexts, such as prevention or screening. Interventions using individual risk estimates were associated with larger effects than were those using more general risk information. Two design variables were identified as effect modifiers: randomized controlled trials were associated with smaller effects than other designs, and dichotomous outcomes were associated with larger effects than continuous outcomes.

CONCLUSIONS

Risk communication interventions may be most productive if they include individual risk estimates in the discussion between professional and patient. Patient decisions about treatment appear more amenable to change by these interventions than attendance for screening or modification of risky behavior.

Enlargement of the receptive field size to low intensity mechanical stimulation in the rat spinal nerve ligation model of neuropathy

One characteristic of plasticity after peripheral tissue or nerve damage is receptive field reorganization, and enlargement of receptive field size has been suggested to occur in certain models of neuropathic pain. The aim of the present study was to explore whether enlargement of neuronal receptive fields could contribute to the mechanical allodynia found on the ipsilateral paw in the spinal nerve ligation model of neuropathy. After ligation of L(5)-L(6) spinal nerves, all rats developed behavioral signs of mechanical allodynia, while the sham-operated control group displayed no such changes. The characteristics of the evoked responses of the neurones recorded in the dorsal horn of the rats were similar between the spinal nerve ligation, the sham operated control group, and the nonoperated control group, except for spontaneous activity, which was significantly increased in the spinal nerve ligation group. The mean size of the receptive field on the ipsilateral hindpaw, mapped using low-intensity stimulation with 9-g von Frey hair, was significantly increased in the spinal nerve ligation group, as compared to the sham-operated group. No significant difference was seen with 15- or 75-g von Frey hairs. The distribution of the receptive fields over the plantar surface of the paw was similar between the study groups. The enlargement of receptive field for non-noxious touch could be an indication of central sensitization in this model.

Autonomy and the psychiatric patient

The aim of this paper is to consider possible justifications for the denial of the right to refuse treatment in the case of certain kinds of psychiatric patients. The basis of this right in general is first considered: arguments based on Kantian conceptions of autonomy are rejected as confused, and preference is given to Millian arguments based on the right to make decisions about one's own life, however irrational, as long as they do not harm others. In light of this discussion, it is argued that mentally disordered people cannot be denied this right on grounds of their 'irrationality', which is anyway a vague concept with several meanings. In conclusion, it is argued that there may be a case for such a denial in those sorts of mental disorder which involve a 'disturbance of personal identity'.

Climate forcings in the industrial era

The forcings that drive long-term climate change are not known with an accuracy sufficient to define future climate change. Anthropogenic greenhouse gases (GHGs), which are well measured, cause a strong positive (warming) forcing. But other, poorly measured, anthropogenic forcings, especially changes of atmospheric aerosols, clouds, and land-use patterns, cause a negative forcing that tends to offset greenhouse warming. One consequence of this partial balance is that the natural forcing due to solar irradiance changes may play a larger role in long-term climate change than inferred from comparison with GHGs alone. Current trends in GHG climate forcings are smaller than in popular "business as usual" or 1% per year CO2 growth scenarios. The summary implication is a paradigm change for long-term climate projections: uncertainties in climate forcings have supplanted global climate sensitivity as the predominant issue.

Communication about risk: diversity among primary care professionals

OBJECTIVE

We aimed to identify the important clinical topics and to report current practice of communication about risk in primary care.

METHODS

We carried out a qualitative study using six semi-structured focus group discussions with primary care professionals. The subjects were 36 primary care professionals from general practice, practice nurse, district nurse, community psychiatric nurse and health visitor disciplines.

RESULTS

All clinical topics were felt to raise issues of effective risk communication. Participants expressed concern about the lack of accessible up-to-date information and the problems of conveying information to patients. They described the circumstances and contexts in which communication varies and is difficult, and identified media and medico-legal influences and professional uncertainty as also contributing to the problems of risk communication. Specific training in risk communication was identified as an important need.

CONCLUSIONS

The complexity of risk communication and diversity of influences on it will require wide-ranging interventions in order to address them. Standardized communication may be a difficult goal to attain.

Communication about risk: the responses of primary care professionals to standardizing the 'language of risk' and communication tools

OBJECTIVE

We aimed to gauge responses of primary care professionals to standardization of the 'language of risk' and risk communication tools.

METHODS

We carried out a qualitative study using six semi-structured focus group discussions. The subjects were 36 primary care professionals from general practice, practice nurse, district nurse, community psychiatric nurse and health visitor disciplines.

RESULTS

Between professionals, the standardization of the language of risk was felt to have potential benefit in making professionals consistent in their appreciation of risks and communication with each other. Between professionals and patients, standardized language was thought inappropriate or insufficient because of contextual variation in communication and interpretation of risk information by patients. The use of more-detailed comparisons of risks was felt to be a potentially effective development of risk communication in practice.

CONCLUSIONS

A standard language of risk communication was perceived as being potentially helpful for communication between professionals, but many respondents were sceptical about its usefulness in communication with patients.

Activation of coagulation and angiogenesis in cancer: immunohistochemical localization in situ of clotting proteins and vascular endothelial growth factor in human cancer

Thrombin-catalyzed, cross-linked fibrin (XLF) formation is a characteristic histopathological finding in many human and experimental tumors and is thought to be of importance in the local host defense response. Although the pathogenesis of tumor-associated fibrin deposition is not entirely clear, several tumor procoagulants have been described as likely primary stimuli for the generation of thrombin (and XLF) in the tumor microenvironment (TME). In a previous study of a variety of human tumors we have shown that tissue factor (TF) is the major procoagulant. However, the relative contribution to fibrin deposition in the TME of tumor cell TF and host cell TF (eg, macrophage-derived) was not established. In addition, recent evidence has implicated TF in the regulation of the synthesis of the pro-angiogenic factor vascular endothelial growth factor (VEGF) by tumor cells. In the current study we used in situ techniques to determine the cellular localization of XLF, TF, VEGF, and an alternative tumor procoagulant, so-called cancer procoagulant (CP), a cysteine protease that activates clotting factor X. In lung cancer we have found XLF localized predominantly to the surface of tumor-associated macrophages, as well as to some endothelial cells and perivascular fibroblasts in the stromal area of the tumors co-distributed with TF at the interface of the tumor and host cells. Cancer pro-coagulant was localized to tumor cells in several cases but not in conjunction with the deposition of XLF. TF and VEGF were co-localized in both lung cancer and breast cancer cells by in situ hybridization and immunohistochemical staining. Furthermore, a strong relationship was found between the synthesis of TF and VEGF levels in human breast cancer cell lines (r2 = 0.84; P < 0.0001). Taken together, these data are consistent with a highly complex interaction between tumor cells, macrophages, and endothelial cells in the TME leading to fibrin formation and tumor angiogenesis.

Is health care a need?

This paper aims to provide an argument for saying that a publicly funded health care system, available to all free at the point of delivery, is morally superior to a market system, and to provide a framework for deciding questions about which forms of health care should be included in such a public system. The argument presents health care as a 'head', in the sense of something to which human beings are morally entitled as a necessary condition for a life worthy of human dignity. Alternative arguments for similar conclusions, proposed by Daniels and Buchanan, are critically examined and rejected.

Changes in regional cerebral blood flow following light treatment for seasonal affective disorder: responders versus nonresponders

BACKGROUND

Several brain imaging studies of antidepressant pharmacologic treatment utilizing single photon emission computed tomography (SPECT) have reported a normalization of deficits in cerebral blood flow (CBF) associated with recovery; other studies report no change, or a reduction in CBF following successful treatment. There have been no published SPECT studies of seasonal affective disorder (SAD) assessing response to light treatment in relation to changes in regional CBF (rCBF). In this study, we sought to test the hypothesis that increases in rCBF would be observed in SAD patients who responded to light treatment.

METHODS

Ten depressed patients with SAD underwent functional brain imaging studies with 99mTc-hexamethylpropyleneamine oxime SPECT before and after light treatment.

RESULTS

Relative increases in rCBF were observed in all brain regions compared to cerebellum in treatment responders, whereas nonresponders showed no change or decreases in rCBF relative to cerebellum. Significant differences in mean percentage change in rCBF between responders (n = 5) and nonresponders (n = 5) were detected in frontal and cingulate cortex, and thalamus.

CONCLUSIONS

These findings provide preliminary support for the hypothesis that an increase in rCBF is associated with recovery from depression in SAD.

Economic considerations for device design and development

The importance of the design and development process is often underestimated in the rush to get products to market. Studies have shown that sensible investment in this process will lead to manageable risk levels, consumer confidence and high levels of return. This article recommends procedures that manufacturers should follow to improve the quality and efficiency of their development endeavours, and thus maximize their product performance and market presence.

Isolation of InsP4 and InsP6 binding proteins from human platelets: InsP4 promotes Ca2+ efflux from inside-out plasma membrane vesicles containing 104 kDa GAP1IP4BP protein

A low-density membrane fraction from human platelets contained the plasma membrane marker glycoprotein Ib (GpIb) and selective binding sites for InsP4 and InsP6. It was separated from the bulk of InsP3-receptor-containing membranes, but was heterogeneous, probably also containing surface-connected canalicular system and some lighter elements of the internal dense tubule system. After loading with calcium oxalate and re-centrifugation on Percoll gradients, this mixed fraction was subfractionated into light membranes containing all of the GpIb, high-affinity InsP4 binding sites (KD = 18 nM) and phosphate-stimulated Ca2+ transport activity. InsP4 (EC50 0.6 microM), but not InsP3 or InsP6, released up to 35% of the accumulated Ca2+ from these vesicles, which were shown to be inside-out plasma membrane vesicles by a biotinylation labelling technique and selective removal of right-side-out plasma membrane vesicles with streptavidin-agarose. Most of the InsP4, and all of the InsP6, binding was present in the much denser calcium oxalate-loaded subfractions, which were free of GpIb. InsP6 binding activity was chromatographically purified as a 116 kDa protein (KD for InsP6 = 5.9 nM), with an amino acid content and two internal peptide sequences identical to those of 116 kDa vinculin. A 104 kDa InsP4 binding protein (KD for InsP4 = 12 nM), probably identical to GAP1IP4BP described by Cullen, Hsuan, Truong, Letcher, Jackson, Dawson and Irvine [(1995) Nature (London) 376, 527-530], was also isolated. This InsP4 receptor may mediate Ca2+ influx in platelets that occurs subsequent to receptor-stimulated production of InsP3 and unloading of internal Ca2+ stores.

Purification and characterization of the human type 1 Ins(1,4,5)P3 receptor from platelets and comparison with receptor subtypes in other normal and transformed blood cells

We report the first purification of a native human form of the Ins(1,4,5)P3 (InsP3) receptor. This receptor, isolated from platelets, has an apparent molecular mass on SDS/PAGE of 252 kDa and is chromatographed by gel filtration as an oligomer of about 1 x 10(6) kDa. [3H]InsP3 bound to a single class of sites on the purified receptor protein with a Kd of 27 nM and a Bmax. of 2.2 nmol/mg of protein. The platelet InsP3 receptor, like the rodent cerebellar receptors, was identified immunochemically as a type 1 receptor, but unlike its brain counterparts bound poorly to concanavalin A and other lectins and was not significantly phosphorylated by protein kinase A. All cultured megakaryocytic leukaemia cell lines (e.g. Dami, CHRF-288 and Meg-01) and HEL cells were also immunopositive for type 1 receptor, which was substantially increased in some cases by DMSO or phorbol 12-myristate 13-acetate (PMA) which induce further megakaryocytic differentiation. Normal mixed lymphocyte and granulocyte fractions and an enriched T-cell fraction from human blood had measurable InsP3-binding activity, but no detectable type 1 protein. In contrast, Jurkat E6-1 (T-cell lymphoma) cells and the transformed B-cell line RPMI 8392 were immunopositive for type 1 receptor. HL-60 (human promyelocytic leukaemia) cells had no detectable type 1 receptor unless they were stimulated to differentiate along monocyte/macrophage lines by PMA. We conclude that: (1) of the major normal blood cells only platelets contain type 1 InsP3 receptors; (2) some neoplastic transformed blood cell lines also express type 1 receptors, in contrast to their normal counterparts; and (3) increased levels of type 1 InsP3 receptor are induced in some transformed cells under conditions that favour their further terminal differentiation.

Ca2+ release by inositol 1,4,5-trisphosphate is blocked by the K(+)-channel blockers apamin and tetrapentylammonium ion, and a monoclonal antibody to a 63 kDa membrane protein: reversal of blockade by K+ ionophores nigericin and valinomycin and purification of the 63 kDa antibody-binding protein

Ins(1,4,5)P3-induced Ca2+ release from platelet membrane vesicles was blocked by apamin, a selective inhibitor of low-conductance Ca(2+)-activated K+ channels, and by tetrapentylammonium ion, and was weakly inhibited by tetraethylammonium ion. Other K(+)-channel blockers, i.e. charybdotoxin, 4-aminopyridine and glybenclamide were ineffective. A monoclonal antibody (mAb 213-21) obtained by immunizing mice with the InsP3-sensitive membrane fraction from platelets also blocked Ca2+ release by InsP3 from membrane vesicles obtained from platelets, cerebellum, aortic smooth muscle, HEL cells and sea-urchin eggs. ATP-dependent Ca2+ uptake and binding of [3H]InsP3 to platelet membranes was unaffected by either K(+)-channel blockers or mAb 213-21. Blockade of Ca2+ release by apamin, tetrapentylammonium and mAb 213-21 was not affected by the Na+/H+ carrier monensin or the protonophore carbonyl cyanide p-trifluoromethoxyphenylhydrazone (FCCP), but could be completely reversed by the K+/H+ ionophore nigericin and partially reversed by the K+ carrier valinomycin. The antibody-binding protein (ABP) solubilized from platelets, cerebellum, and smooth muscle chromatographed identically on gel filtration, anion-exchange and heparin-TSK h.p.l.c. ABP was purified to apparent homogeneity from platelets and aortic smooth muscle as a 63 kDa protein by immunoaffinity chromatography on mAb 213-21-agarose. These results suggest that optimal Ca2+ release by InsP3 from platelet membrane vesicles may require the tandem function of a K+ channel. A counterflow of K+ ions could prevent the build-up of a membrane potential (inside negative) that would tend to oppose Ca2+ release. The 63 kDa protein may function to regulate K+ permeability that is coupled to the Ca2+ efflux via the InsP3 receptor.

Recollected in tranquillity. A profile of Ernest Matthews. Interview by Colin Davis

Emeritus Professor Ernest Matthews, living in happy retirement in a delightful, small nineteenth century house in Petersfield, looks about 70 years old, and is in fact 17 years older. He has made many contributions to the advancement of dentistry, and we asked him, as he looked back over the years, how he saw the dental world today compared with 60 years ago when he qualified.

Heparin abolishes the chemotherapy-induced increase in plasma fibrinopeptide A levels

PURPOSE, PATIENTS, AND METHODS

Blood coagulation abnormalities are common in patients with cancer, particularly after treatment with chemotherapeutic agents. Chemotherapy has been associated with an increased incidence of thromboembolic events, and patients treated with chemotherapy often develop evidence of local phlebitis, which may lead to loss of venous access. We have utilized the radioimmunoassay for plasma fibrinopeptide A (FPA) and in vitro FPA generation to assess the rate of in vivo blood coagulation and the level of plasma thrombin activity in 16 cancer patients treated with chemotherapy. Eight patients were treated twice, once with chemotherapy alone and once with chemotherapy after an intravenous infusion of heparin (5,000 U).

RESULTS

Our results confirm that FPA levels are elevated in most cancer patients. Following chemotherapy, FPA levels were further increased within 45 minutes (mean FPA = 5.2 ng/mL before chemotherapy versus 8.3 ng/mL after chemotherapy, p less than 0.01) and were accompanied by an increase in the FPA generation rate. Infusion of heparin prior to chemotherapy significantly lowered plasma FPA levels and abolished post-chemotherapy FPA generation.

CONCLUSION

These data suggest that patients receiving chemotherapy express thrombin-like activity in plasma and, therefore, may be at risk for clinically significant intravascular activation of coagulation. Heparin diminished the laboratory evidence of this chemotherapy-related coagulopathy and may have a role in the prevention of thromboembolic disorders in some cancer patients undergoing cytotoxic therapy.

Influence of an insect growth regulator on the larval development of an estuarine shrimp

The influence of methoprene, an insect growth regulator used in mosquito control, on larval development of the estuarine grass shrimp (Palaemonetes pugio) was examined in the laboratory. No grass shrimp larvae successfully completed metamorphosis when continuously exposed to 1000 microg methoprene litre(-1). Completion of larval metamorphosis was significantly reduced by exposure to 100 microg litre(-1) of the isomeric mixture (R,S)-methoprene but not the single isomer formulation (S)-methoprene. No statistically significant difference was revealed, however, in ability to inhibit metamorphosis between these two isomeric types across the broad range of exposure concentrations from 0.1 to 1000.0 microg litre(-1). The first two larval stages and the final premetamorphic larval stage were more sensitive to methoprene toxicity than intermediate larval stages. Methoprene exposure did not alter either the duration of total larval development or the total number of larval stages prior to metamorphosis.

Pharmacological profile of MDL 26,024GO: a novel antiasthmatic agent

MDL 26,024GO was shown to be an orally absorbed mediator release inhibitor in the rat PCA and PPA tests. In addition, the compound was shown to both elicit and inhibit elicitation of the Bezold-Jarisch reflex in the dog. MDL 26,024GO also significantly reduced Ascaris-induced changes in pulmonary mechanics in cynomolgus monkeys. The compound inhibited both early and late phase antigen induced-changes in Ascaris-sensitive sheep, as well as the increased airway hyperreactivity which normally follows antigen challenge. These results suggest the compound may have therapeutic potential in the treatment of asthma.

Fibrinopeptide A during normal pregnancy

Fibrinopeptide A (FPA) is the first peptide released from fibrinogen upon thrombin action. Plasma FPA is cleared rapidly with a first order kinetics and therefore its level reflects the rate of thrombin cleavage of fibrinogen. A prospective study was undertaken to establish normal values of FPA during pregnancy. The mean FPA for the pregnant group (n = 136) was 2.8 ng/ml (SD = 3.3) while it was 1.24 ng/ml (SD = 0.4) for a nonpregnant control group of healthy women (n = 30). The median FPA for the pregnant group was 2.2 ng/ml and 1.4 ng/ml for the nonpregnant group (Wilcoxon test P less than 0.0001). Plasma FPA levels increased with gestational age. The median value was 1.5 ng/ml in the first trimester (n = 18), 1.8 ng/ml in the second trimester (n = 40), and 2.5 ng/ml in the third trimester (n = 78). Plasma FPA concentrations in the third trimester were significantly higher than in the first and second trimester. These findings suggest increased thrombin activity and fibrin generation during the course of normal pregnancy.

Can paternalism be modernised?

The contention that paternalism can be modernised in such a way as to avoid the usual criticisms is examined and dismissed. The alleged 'modernisation' consists simply in going through the motions of achieving the patient's free consent, while leaving the ultimate decision to the physician. Paternalism in this form is no better than the more old-fashioned variety, since it still takes away from patients the fundamental human right to make decisions about their own fate.

The H-2 complex regulates both the susceptibility to mouse viral lymphomagenesis and the phenotype of the virus-induced lymphomas

Neonatal infection of C57BL/10 mice with cloned ecotropic and/or dualtropic mink cell focus-inducing (MCF) mouse leukaemia viruses (MuLV), induces a wide spectrum of different lymphomas of T, B, and non-T/non-B cell types. The H-2 complex has a marked influence on both the development of lymphoma incidence and lymphoma type. A study using the oncogenic MCF 1233 virus and a series of B10 congenic mice enabled the mapping of the following: Resistance to the early development of T cell lymphoma is controlled by the H-2I-A locus. Susceptibility to early T cell lymphomagenesis is associated with an I-A-regulated low anti-MCF 1233 envelope antibody response and persistent infection of the thymus. B10 (H-2b) mice, which are resistant to early T cell lymphomagenesis induced by MCF 1233 or other MuLV isolates, have high anti-MuLV envelope antibody responses which are I-A-regulated. These mice develop more B cell lymphomas late in life in contrast to the early development of T cell lymphoma in B10.A (H-2a) mice. The possible response mechanisms which underlie these observations, including: I-A-regulated immunoselection against MuLV antigens expressed by (pre) leukaemic T cells, aberrant expression of class II MHC antigens on some B cell lymphomas and I-A-regulated chronic immunostimulation of MuLV-expressing (pre) leukaemic B cells, are discussed.

Two-dimensional echocardiographic diagnosis of intracardiac masses in infancy

Intracardiac masses in infancy are uncommon. Tumors, thrombi and vegetations of bacterial endocarditis are exceedingly rare in this age group. These masses are seldom diagnosed before the infant's death. In a review of two-dimensional echocardiograms performed from May 1979 to January 1981 on 741 infants less than 2 years of age, intracardiac masses were prospectively identified in 6 patients. All six patients presented with unexplained murmurs associated with either hemodynamic instability, arrhythmias or systemic emboli. One patient had a vegetation from bacterial endocarditis, one had an intracardiac thrombus associated with myocarditis, three had rhabdomyomas (two patients with tuberous sclerosis) and one had a fibro-fatty nodule attached to the eustachian valve. Two-dimensional echocardiography not only was important in the diagnosis, but also provided guidance in the medical and surgical treatment of these patients.