Hepatic and intestinal manganese excretion are both required to regulate brain manganese during elevated manganese exposure

Manganese (Mn) is essential but neurotoxic at elevated levels. Under physiological conditions, Mn is primarily excreted by the liver, with the intestines playing a secondary role. Recent analyses of tissue-specific Slc30a10 or Slc39a14 knockout mice (SLC30A10 and SLC39A14 are Mn transporters) revealed that, under physiological conditions: 1) excretion of Mn by the liver and intestines is a major pathway that regulates brain Mn; and surprisingly, 2) the intestines compensate for loss of hepatic Mn excretion in controlling brain Mn. The unexpected importance of the intestines in controlling physiological brain Mn led us to determine the role of hepatic and intestinal Mn excretion in regulating brain Mn during elevated Mn exposure. We used liver- or intestine-specific Slc30a10 knockout mice as models to inhibit hepatic or intestinal Mn excretion. Compared with littermates, both knockout strains exhibited similar increases in brain Mn after elevated Mn exposure in early or later life. Thus, unlike physiological conditions, both hepatic and intestinal Mn excretion are required to control brain Mn during elevated Mn exposure. However, brain Mn levels of littermates and both knockout strains exposed to elevated Mn only in early life were normalized in later life. Thus, hepatic and intestinal Mn excretion play compensatory roles in clearing brain Mn accumulated by early life Mn exposure. Finally, neuromotor assays provided evidence consistent with a role for hepatic and intestinal Mn excretion in functionally modulating Mn neurotoxicity during Mn exposure. Put together, these findings substantially enhance understanding of the regulation of brain Mn by excretion.NEW & NOTEWORTHY This article shows that, in contrast with expectations from prior studies and physiological conditions, excretion of manganese by the intestines and liver is equally important in controlling brain manganese during human-relevant manganese exposure. The results provide foundational insights about the interorgan mechanisms that control brain manganese homeostasis at the organism level and have important implications for the development of therapeutics to treat manganese-induced neurological disease.

SLC30A10 manganese transporter in the brain protects against deficits in motor function and dopaminergic neurotransmission under physiological conditions

Loss-of-function mutations in SLC30A10 induce hereditary manganese (Mn)-induced neuromotor disease in humans. We previously identified SLC30A10 to be a critical Mn efflux transporter that controls physiological brain Mn levels by mediating hepatic and intestinal Mn excretion in adolescence/adulthood. Our studies also revealed that in adulthood, SLC30A10 in the brain regulates brain Mn levels when Mn excretion capacity is overwhelmed (e.g. after Mn exposure). But, the functional role of brain SLC30A10 under physiological conditions is unknown. We hypothesized that, under physiological conditions, brain SLC30A10 may modulate brain Mn levels and Mn neurotoxicity in early postnatal life because body Mn excretion capacity is reduced in this developmental stage. We discovered that Mn levels of pan-neuronal/glial Slc30a10 knockout mice were elevated in specific brain regions (thalamus) during specific stages of early postnatal development (postnatal day 21), but not in adulthood. Furthermore, adolescent or adult pan-neuronal/glial Slc30a10 knockouts exhibited neuromotor deficits. The neuromotor dysfunction of adult pan-neuronal/glial Slc30a10 knockouts was associated with a profound reduction in evoked striatal dopamine release without dopaminergic neurodegeneration or changes in striatal tissue dopamine levels. Put together, our results identify a critical physiological function of brain SLC30A10-SLC30A10 in the brain regulates Mn levels in specific brain regions and periods of early postnatal life, which protects against lasting deficits in neuromotor function and dopaminergic neurotransmission. These findings further suggest that a deficit in dopamine release may be a likely cause of early-life Mn-induced motor disease.

Bile Acid Signaling in Neurodegenerative and Neurological Disorders

Bile acids are commonly known as digestive agents for lipids. The mechanisms of bile acids in the gastrointestinal track during normal physiological conditions as well as hepatic and cholestatic diseases have been well studied. Bile acids additionally serve as ligands for signaling molecules such as nuclear receptor Farnesoid X receptor and membrane-bound receptors, Takeda G-protein-coupled bile acid receptor and sphingosine-1-phosphate receptor 2. Recent studies have shown that bile acid signaling may also have a prevalent role in the central nervous system. Some bile acids, such as tauroursodeoxycholic acid and ursodeoxycholic acid, have shown neuroprotective potential in experimental animal models and clinical studies of many neurological conditions. Alterations in bile acid metabolism have been discovered as potential biomarkers for prognosis tools as well as the expression of various bile acid receptors in multiple neurological ailments. This review explores the findings of recent studies highlighting bile acid-mediated therapies and bile acid-mediated signaling and the roles they play in neurodegenerative and neurological diseases.

Understanding the structure and functioning of polar pelagic ecosystems to predict the impacts of change

The determinants of the structure, functioning and resilience of pelagic ecosystems across most of the polar regions are not well known. Improved understanding is essential for assessing the value of biodiversity and predicting the effects of change (including in biodiversity) on these ecosystems and the services they maintain. Here we focus on the trophic interactions that underpin ecosystem structure, developing comparative analyses of how polar pelagic food webs vary in relation to the environment. We highlight that there is not a singular, generic Arctic or Antarctic pelagic food web, and, although there are characteristic pathways of energy flow dominated by a small number of species, alternative routes are important for maintaining energy transfer and resilience. These more complex routes cannot, however, provide the same rate of energy flow to highest trophic-level species. Food-web structure may be similar in different regions, but the individual species that dominate mid-trophic levels vary across polar regions. The characteristics (traits) of these species are also different and these differences influence a range of food-web processes. Low functional redundancy at key trophic levels makes these ecosystems particularly sensitive to change. To develop models for projecting responses of polar ecosystems to future environmental change, we propose a conceptual framework that links the life histories of pelagic species and the structure of polar food webs.

New Zealand dentists' views on community water fluoridation

OBJECTIVE

To determine whether New Zealand general dental practitioners support community water fluoridation (CWF), and to gauge their opinions on its possible systemic side-effects.

METHODS

An online survey was conducted in 2010, involving the 1174 general dental practitioners who had email addresses on the Dental Register and were contactable in New Zealand. A total of 465 dentists (39.6%) participated.

RESULTS

Most practitioners (93.5%) reported supporting community water fluoridation; the other 6.5% either were unsure or did not support it. Higher proportions of more recent graduates supported CWF. Some 85.6% of practitioners thought that drinking fluoridated water was a harmless way to prevent dental caries, but 6.2% felt that fluoridated water may cause other health problems. There were no systematic differences by sociodemographic and practice characteristics, except that a higher proportion of males and more experienced practitioners reported being confident in discussing CWF-related issues.

CONCLUSIONS

Most New Zealand dental practitioners support community water fluoridation, although a very small proportion believe that it is harmful and/or does not prevent caries.

Bayesian inference of a historical bottleneck in a heavily exploited marine mammal

Emerging Bayesian analytical approaches offer increasingly sophisticated means of reconstructing historical population dynamics from genetic data, but have been little applied to scenarios involving demographic bottlenecks. Consequently, we analysed a large mitochondrial and microsatellite dataset from the Antarctic fur seal Arctocephalus gazella, a species subjected to one of the most extreme examples of uncontrolled exploitation in history when it was reduced to the brink of extinction by the sealing industry during the late eighteenth and nineteenth centuries. Classical bottleneck tests, which exploit the fact that rare alleles are rapidly lost during demographic reduction, yielded ambiguous results. In contrast, a strong signal of recent demographic decline was detected using both Bayesian skyline plots and Approximate Bayesian Computation, the latter also allowing derivation of posterior parameter estimates that were remarkably consistent with historical observations. This was achieved using only contemporary samples, further emphasizing the potential of Bayesian approaches to address important problems in conservation and evolutionary biology.

Altered mitogen-activated protein kinase signaling, tau hyperphosphorylation and mild spatial learning dysfunction in transgenic rats expressing the β-amyloid peptide intracellularly in hippocampal and cortical neurons

The pathological significance of intracellular Abeta accumulation in vivo is not yet fully understood. To address this, we have studied transgenic rats expressing Alzheimer's-related transgenes that accumulate Abeta intraneuronally in the cerebral and hippocampal cortices but do not develop extracellular amyloid plaques. In these rats, the presence of intraneuronal Abeta is sufficient to provoke up-regulation of the phosphorylated form of extracellular-regulated kinase (ERK) 2 and its enzymatic activity in the hippocampus while no changes were observed in the activity or phosphorylation status of other putative tau kinases such as p38, glycogen synthase kinase 3, and cycline-dependent kinase 5. The increase in active phospho-ERK2 was accompanied by increased levels of tau phosphorylation at S396 and S404 ERK2 sites and a decrease in the phosphorylation of the CREB kinase p90RSK. In a water maze paradigm, male transgenic rats displayed a mild spatial learning deficit relative to control littermates. Our results suggest that in the absence of plaques, intraneuronal accumulation of Abeta peptide correlates with the initial steps in the tau-phosphorylation cascade, alterations in ERK2 signaling and impairment of higher CNS functions in male rats.

Substrate turnover and oxidation during moderate-intensity exercise following acute plasma volume expansion

In previous work using prolonged, light cycle exercise, we were unable to demonstrate an effect of acute plasma volume (PV) expansion on glucose kinetics or substrate oxidation, despite a decline in whole-body lipolysis (Phillips et al., 1997). However, PV is known to decrease arterial O2 content. The purpose of this study was to examine whether substrate turnover and oxidation would be altered with heavier exercise where the challenge to O2 delivery is increased. Eight untrained males (VO2max = 3.52 +/- 0.12 l/min) twice performed 90 min of cycle ergometry at 62 % VO2peak, both prior to (CON) and following induced plasma volume expansion (Dextran [6 %] or Pentaspan [10 %]) (6.7 ml/kg) (PVX). Glucose and glycerol kinetics were determined with primed constant infusions of [6.6-(2)H2] glucose and [(2)H5] glycerol, respectively. PVX resulted in a 15.8 +/- 2.2 % increase (p < 0.05) in PV. Glucose and glycerol appearance (Ra) and utilization (Rd), although increasing progressively (p < 0.05) with exercise, were not different between conditions. Similarly, no differences in substrate oxidation, either fat or carbohydrate, were observed between the two conditions. Prolonged exercise resulted in an increase (p < 0.05) in plasma glucagon and a decrease (p < 0.05) in plasma insulin during both conditions. With PVX, the exercise-induced increase in glucagon was diminished (p < 0.05). We conclude that impairment in O2 content mediated by an elevated PV does not alter glucose, and glycerol kinetics or substrate oxidation even at moderate exercise intensity.

Out-of-hours emergency dental services--development of one possible local solution

This paper describes the development of a local solution to the problem of the provision of out-of-hours dental care in Newcastle and North Tyneside in the north east of England. Focus groups were used to review the current provision of, and problems with, dental out-of-hours emergency provision. A consensus conference involving both general dental and medical practitioners, was subsequently used to develop possible alternative methods for the provision of out-of-hours emergency dental services. A centralised service delivered from a secure location in conjunction with general medical practitioners was developed which was dependent on a nurse-led triage. The linkage with NHS Direct may be an opportunity, in some locations, to integrate dental services more fully with other out-of-hours primary care services. The method described allowed a solution to be generated by practitioners themselves, thus giving ownership and acceptance to the chosen option.

Acute plasma volume expansion in the untrained alters the hormonal response to prolonged moderate-intensity exercise

To investigate the role of an increase in plasma volume (PV), characteristically observed with short-term endurance training, on the endocrine response to prolonged moderate intensity exercise, eight untrained males (VO2 peak = 3.52 +/- 0.12 l x min(-1)) performed 90 min of cycle ergometry at approximately 60% VO2peak both before (CON) and following (PVX) PV expansion. Acute PV expansion, which was accomplished using a solution of Dextran (6%) or Pentispan (10%) (6.7 ml kg(-1)), resulted in a calculated 15.8+/-2.2% increase (p<0.05) in PV. The prolonged exercise resulted in increases (p<0.05) in plasma vasopressin (AVP), plasma rennin activity (PRA), aldosterone (ALD), atrial naturetic peptide (alpha-ANP), and the catecholamines norepinephrine (NE) and epinephrine (EPI). PVX blunted the increases (p<0.05) in AVP, PRA, ALD, NE and EPI, during the exercise itself. The concentration of alpha-ANP was also lower (p<0.05) during exercise following PVX, an effect that could be attributed to the lower resting levels. No differences in osmolality was observed between conditions. These results demonstrate that PVX alters the fluid regulatory hormonal response in untrained subjects to moderate intensity dynamic exercise in a manner similar to that observed following short-term training induced alterations in PV. The specific mechanisms responsible for these alterations remain unclear, but appear to be related directly to the increase in PV.

Abeta immunoreactive material is present in several intracellular compartments in transfected, neuronally differentiated, P19 cells expressing the human amyloid beta-protein precursor

Processing of the amyloid beta-protein precursor is believed to play a critical role in the development of Alzheimer's disease neuropathology. The localization of the human Abeta epitope within mature neuroectodermally differentiated embryonal carcinoma (P19) cells, stably transfected with the cDNA coding for a wild form human amyloid beta-protein precursor (AbetaPP 751) was investigated. For this, we applied high resolution electron microscopy and immunocytochemistry with a newly developed, highly specfic monoclonal antibody (McSA1). We observed immunoreactive signals in a number of subcellular organelles such as early endosomes, the trans-Golgi network and in the dilated rough endoplasmic reticulum, but not in lysosomes. Occasionally Abeta immunoreactivity was associated with microtubules and filaments, with the outer mitochondrial membrane, and with the nuclear envelope. These observations expand on current data regarding intracellular trafficking of AbetaPP fragments and provoke further questions regarding the role of intracellular Abeta peptides in basal conditions and pathological states.

Acute plasma volume expansion alters cardiovascular but not thermal function during moderate intensity prolonged exercise

To investigate the hypothesis that the increase in plasma volume (PV) that typically occurs with training results in improved cardiovascular and thermal regulation during prolonged exercise, eight untrained males (Vo2peak = 3.52 ± 0.12 L·min-1) performed 90 min of cycle ergometry at 62% Vo2peak before and after acute PV expansion. Subjects were infused with a PV-expanding solution (dextran (6%) or Pentaspan (10%)) equivalent to 6.7 mL·kg-1 body mass (PVX) or acted as their own control (CON) in a randomized order. PVX resulted in a calculated 15.8% increase in resting PV, which relative to CON, was maintained throughout the exercise (P < 0.05). During PVX, heart rate was lower (P < 0.05) and stroke volume and cardiac output were higher (P < 0.05) during the exercise. Mean arterial pressure and total peripheral resistance, although altered by exercise (P < 0.05), were not different between the two conditions. Core temperature, which was progressively increased by the exercise (P < 0.01), was not affected by PVX. A similar decrease in body weight was observed between the conditions as a result of the exercise (P < 0.01). These results indicate that acute PVX alters cardiovascular performance without affecting the thermoregulatory response to prolonged cycle exercise.Key words: cardiovascular, prolonged exercise, acute plasma volume expansion, thermoregulation, hypervolemia.

Acute plasma volume expansion alters cardiovascular but not thermal function during moderate intensity prolonged exercise

To investigate the hypothesis that the increase in plasma volume (PV) that typically occurs with training results in improved cardiovascular and thermal regulation during prolonged exercise, eight untrained males (V(O2)peak = 3.52 +/- 0.12 L x min(-1)) performed 90 min of cycle ergometry at 62% V(O2)peak before and after acute PV expansion. Subjects were infused with a PV-expanding solution (dextran (6%) or Pentaspan (10%)) equivalent to 6.7 mL x kg(-1) body mass (PVX) or acted as their own control (CON) in a randomized order. PVX resulted in a calculated 15.8% increase in resting PV, which relative to CON, was maintained throughout the exercise (P < 0.05). During PVX, heart rate was lower (P < 0.05) and stroke volume and cardiac output were higher (P < 0.05) during the exercise. Mean arterial pressure and total peripheral resistance, although altered by exercise (P < 0.05), were not different between the two conditions. Core temperature, which was progressively increased by the exercise (P < 0.01), was not affected by PVX. A similar decrease in body weight was observed between the conditions as a result of the exercise (P < 0.01). These results indicate that acute PVX alters cardiovascular performance without affecting the thermoregulatory response to prolonged cycle exercise.

Phosphorylation of mitogen-activated protein kinase is altered in neuroectodermal cells overexpressing the human amyloid precursor protein 751 isoform

The aberrant expression or processing of the amyloid precursor protein (APP) is the only known genetic basis for presenile familial Alzheimer's disease, and the molecular connection between APP and tau has been perplexing. Attention has focused on proline-directed serine/threonine kinases as mediating the cytoskeletal modifications of Alzheimer's disease, and we show that overexpression of APP can influence the activation of a candidate kinase, the mitogen-activated protein kinase (MAPK). In murine embryonal carcinoma cells stably transfected with the human 751 isoform of APP, we observed steady-state hyperactivation of p42(MAPK) concomitant with APP overexpression 3 days after neuroectodermal differentiation. In more mature differentiated cells, immunocytochemical analysis revealed enhanced basal somatic and nuclear immunoreactivity for phosphorylated MAPK coupled with an attenuated phosphorylation response to growth factor stimulation. Our results suggest that APP can influence the MAPK signaling pathway in such a way that the absolute and time-dependent activation required for discrimination of the appropriate downstream response are compromised. Such an effect would have important consequences for the functioning of cells coincidentally expressing both proteins, a situation that occurs in neuronal populations vulnerable to Alzheimer's disease pathology.

Mitochondrial abnormalities in neuroectodermal cells stably expressing human amyloid precursor protein (hAPP751)

Metabolic hypofunction is a common finding in a number of neurodegenerative diseases, including Alzheimer's disease (AD). The strong linkage between the amyloid precursor protein (APP) and AD led us to examine whether over-expression of this protein in CNS-type cells had an effect on mitochondria. We found abnormal morphology in mitochondria of the neuroectodermal progeny of P19 cells stably transfected with human APP751. In addition, the mitochondria of APP-transfected clones had a decreased mitochondrial membrane potential. These changes were independent of Abeta toxicity and distinct from complex I inhibition. Our results have important implications for the earliest events in the pathophysiology of AD and, by extrapolation, for intervention therapies.

Trends in exodontia under general anaesthesia at a dental teaching hospital

AIMS

To survey the use of simple exodontia for children under general anaesthesia on an out-patient basis at a Northern Dental Hospital. To monitor any effects resulting from the introduction of the Poswillo guidelines on the referral for and treatment of patients under general anaesthesia.

DESIGN

A retrospective longitudinal analysis.

SETTING

A Northern Dental Hospital in England.

MATERIALS

Information was recorded from original case records of children undergoing exodontia under general anaesthesia on an out-patient basis during October between 1989 and 1997.

RESULTS

The mean and modal age of the children decreased from 7.7 years to 6.0 years respectively in 1989 to 5.7 years and 4.0 years in 1997. The proportion receiving a general anaesthetic for orthodontic extractions substantially decreased from 18.0% in 1989 to 0.7% in 1997 and the need for repeat dental general anaesthetics within 18 months was eliminated with the introduction of a pre-general anaesthetic screening service.

CONCLUSION

Dental treatment under general anaesthesia should continue to be available where it is justified. A separate assessment appointment reduces the prescription of general anaesthesia and minimises its usage for orthodontic extractions and the necessity for repeat general anaesthesia.

Diver's mouth syndrome: a report of two cases and construction of custom-made regulator mouthpieces

Scuba diving is becoming more and more popular and dentists are increasingly likely to encounter patients with diving-related problems. Protruded mandibular positions and the biting forces exercised on the anterior occlusion during diving can cause pain and dysfunction, particularly where a predisposing factor such as bruxism exists. In this article, two cases are reported of patients with diving-exacerbated pain dysfunction syndrome, which improved following the construction of custom-made mouthpieces which distributed the forces more evenly. Laboratory procedures are described for construction of a custom-made scuba regulator mouthpiece that allows more comfortable diving.

Cellular immune responses to four doses of percutaneous bacille Calmette-Guérin in healthy adults

To explore the hypothesis that low-dose immunization might induce preferential Th1 cell immunity, 76 adults were vaccinated with one of four doses of bacille Calmette-Guérin (BCG): The doses contained very low (1.6 x 10(5) cfu), low (3.2 x 10(6) cfu), standard (1.6 x 10(8) cfu), or high (3.2 x 10(8) cfu) levels of BCG. Delayed-type hypersensitivity responses occurred 8 weeks after vaccination in 10% of persons given very low or low doses of BCG, compared with 95% and 100% of persons given standard or high doses, respectively. Lymphoproliferative responses, which were increased only for high-dose vaccinees, peaked 2 weeks after vaccination and were directed chiefly against Mycobacterium tuberculosis-secreted proteins, particularly the antigen 85 complex. Significant increases in mycobacteria-specific interferon-gamma expression were present 16 weeks after vaccination only for persons given standard or high doses of BCG. Percutaneous BCG appears capable of inducing a temporary Th1-like immune response, but standard or higher dosages are required.

Effects of acute expansion of plasma volume on cardiovascular and thermal function during prolonged exercise

To investigate the hypothesis that an increase in plasma volume (PV) is obligatory in reducing the cardiovascular drift that is associated with prolonged exercise following training, a plasma expander (Macrodex) was used to acutely elevate PV. Eight untrained volunteers [maximal oxygen consumption; VO2max 45.2 (2.2) ml x kg(-1) x min(-1), mean (SE)] cycled for 2 h [at 46 (4)% VO2max] in ambient conditions either with no PV expansion (CON) or following PV expansions of either 14% (LOW) or 21% (HIGH). During CON, heart rate (HR) increased (P < 0.05) from 147 (2.4) beats x min(-1) to 173 (3.6) beats x min(-1) from 15 to 120 min of exercise. Both LOW and HIGH conditions depressed (P < 0.05) HR, an effect that was manifested following 15 min of exercise. In contrast, stroke volume (SV) was elevated following PV expansion, with values (ml) of 89.6 (6.8), 97.8 (5.9) and 104 (4.6) noted by 15 min of exercise for CON, LOW and HIGH conditions, respectively. Acute PV expansion, regardless of magnitude, also resulted in elevations in cardiac output (Qc). These differences between conditions persisted throughout the exercise, as did the elevation in Qc that was noted with LOW and HIGH conditions. No difference between Qc, HR or SV was found between LOW and HIGH. In addition, neither LOW nor HIGH conditions altered the change in rectal temperature that was observed during exercise. These results demonstrate that, at least for moderate exercise performed in ambient conditions, PV expansion serves only to alter cardiac function (Qc, HR, SV) early in exercise, and not to attenuate the drift that occurs as the exercise is prolonged.

Reduced muscle lactate during prolonged exercise following induced plasma volume expansion

To examine the effects of a dilutional mediated decrease in arterial O2 content on muscle metabolic and substrate behaviour during exercise, plasma volume was acutely expanded by either 14% (LOW) or 21% (HIGH) using a 6% dextran solution dissolved in saline (Macrodex) and compared with a control (CON) condition. The exercise protocol, performed by eight untrained males (VO2max = 45.2 +/- 2.2 mL.kg-1.min-1, X +/- SE) and with the conditions randomized, was conducted for 120 min at 46 +/- 4% VO2max. The content of inosine monophosphate determined on muscle tissue extracted from the vastus lateralis increased (p < 0.05) by 120 min of exercise (0.119 +/- 0.02 vs 0.493 +/- 0.19 mmol/kg dry weight) in CON. No effect of either LOW or HIGH expansion of plasma volume was found. Similarly, phosphocreatine content (mmol/kg dry weight), although reduced (p < 0.05) with exercise, was not different between the conditions at either 3 min (61.9 +/- 3.5, 66.2 +/- 3.5, 64.3 +/- 2.1) or 120 min (52.5 +/- 6.3, 53.8 +/- 5.8, 59.4 +/- 5.5) of exercise. In contrast, both pyruvate and lactate were reduced (p < 0.05) by 3 min of exercise in both LOW and HIGH compared with CON. The reduction in these metabolites with plasma volume expansion was not accompanied by an alteration in glycogen depletion rates. Steady-state VO2 was unaffected by acute hypervolemia. These results suggest that moderate exercise following an approximate 10% reduction in arterial O2 content can be performed without increasing the imbalance between ATP production and utilization rates. Since high energy phosphate transfer and glycolysis appeared not to be increased, mitochondrial respiration was apparently preserved by mechanisms as yet undetermined.

Effect of acute plasma volume expansion on substrate turnover during prolonged low-intensity exercise

We investigated the effect of acute, graded increases in plasma volume (PV) by use of dextran on substrate turnover and oxidation during exercise. Eight untrained males [peak aerobic power (VO2peak) = 45.2 +/- 2.2 (SE) ml.kg-1.min-1] performed 2 h of cycle ergometry at 46 +/- 4% of VO2peak on three occasions in a randomized order: 0% PV expansion (CON) and after 14% (LOW) and 21% (HIGH) PV expansion. Glucose and glycerol turnover were measured using primed continuous infusions of [6,6-2H2]glucose and [2H5]glycerol, respectively. Glycerol rate of appearance (Ra) was taken as a relative index of whole body lipolysis. Increases in PV had no effect on glucose Ra or disappearance (Rd) either at rest or during exercise. At the onset of exercise, both glucose Ra and Rd increased approximately 100% (P < 0.01). Glucose Ra and Rd continued to increase with exercise duration (P < 0.05) so that, at 120 min of exercise, they were > 330% higher than at rest (P < 0.01). Glycerol Ra also increased with exercise duration (P < 0.05). Total lipolysis during exercise, calculated as the area under the glycerol Ra vs. time curve, was reduced during LOW vs. CON (P < 0.01). Further expansion of PV (HIGH) had no additional effect on whole body lipolysis. No effect of hypervolemia was observed on whole body fat or carbohydrate oxidation. These results indicate that acute PV expansion can alter whole body lipolysis, possibly via a reduction in catecholamine secretion.

Two-step tuberculin skin testing of injection drug users recruited from community-based settings

SETTING

Cross-sectional study of drug users recruited from street-based settings in four US cities: Denver, Portland, Oakland and San Francisco.

OBJECTIVE

To evaluate responses to two-step tuberculin skin testing among HIV-positive and HIV-negative injection drug users.

DESIGN

Subjects were recruited from existing studies of HIV and risk behaviors for tuberculin skin testing. Those with a negative initial tuberculin test were referred for a second skin test 1-3 weeks later. A positive tuberculin test was defined as > or = 10 mm, or > or = 5 mm if the subject was HIV-positive.

RESULTS

Of 997 persons receiving an initial tuberculin test, 13% had a positive response. Of 644 persons receiving a second tuberculin test, 8% had a positive response, with rates as high as 14% among those from Oakland and 12% among African Americans. HIV-positive subjects were less likely to have skin test responses > or = 10 mm on the initial test (P = 0.03), or increases between the initial and second test of > or = 10 mm (P = 0.06).

CONCLUSION

Boosting occurred in both HIV-positive and HIV-negative injection drug users. Two-step testing should be considered for this population, particularly those on whom repeat tuberculin testing will be performed.

Psychological evaluations, referrals, and follow-up of adolescents after their exposure to Hurricane Hugo

PROBLEM

There is little understanding of adolescent appraisal of stress and crisis intervention for adolescents who are exposed to major stress such as that of a natural disaster.

METHODS

A description of the psychological evaluations, referrals, and follow-up assessments made by nurse practitioners (NPs) and a nurse psychotherapist (NPT) of adolescents (N = 507) in two South Carolina high schools who experienced Hurricane Hugo.

FINDINGS

The NPs' evaluations concluded that 63 adolescents (12%) exhibited symptoms of psychological distress. The NPs referred 36 of these adolescents to high school counselors for minor distress or school-related problems and 27 for more intensive clinical evaluation by an NPT. Of the 27 adolescents who were referred to the NPT, 10 had symptoms associated with adolescent adjustment reaction, 8 showed symptoms of depression, 5 revealed symptoms of posttraumatic stress disorder, and 4 complained of serious family problems.

CONCLUSIONS

Based on these data and the mental processes described by these adolescents, the authors propose a model and suggest adolescent appraisal of stress and crisis is a critical issue to consider when intervening with adolescents who are exposed to major stressors, including those associated with a disaster.

Fluid and electrolyte hormonal responses to exercise and acute plasma volume expansion

To investigate the effect of acute graded increases in plasma volume (PV) on fluid and regulatory hormone levels, eight untrained men (peak aerobic power 45.2 +/- 2.2 ml.kg-1.min-1) performed prolonged cycle exercise (46 +/- 4% maximal aerobic power on three occasions, namely, with no PV expansion (Con) and after 14% (Low) and 21% (High) expansions, respectively. The exercise plasma levels of aldosterone (Aldo), arginine vasopressin (AVP), and atrial natriuretic peptide (ANP) were all altered by acute PV increases. A pronounced blunting (P < 0.05) of the Aldo response during exercise was observed, the magnitude of which was directly related to the amount of hypervolemia (Con < Low < High). At 120 min of exercise, Aldo concentrations were 660 +/- 71, 490 +/- 85, and 365 +/- 78 pg/ml for Con, Low, and High conditions, respectively. In contrast, the lower AVP and the higher ANP observed during exercise appeared to be due to the effect of PV expansion on resting concentrations. Because osmolality did not vary among conditions, the results indicate that PV represents an important primary stimulus in the response of Aldo to exercise. The lower exercise blood concentrations of both epinephrine and norepinephrine observed with PV expansion would suggest that a lower sympathetic drive may be implicated at least in the lower Aldo responses.

Effects of training duration on substrate turnover and oxidation during exercise

Adaptations in fat and carbohydrates metabolism after a prolonged endurance training program were examined using stable isotope tracers of glucose ([6,6-2H2]glucose), glycerol ([2H5]glycerol), and palmitate ([2H2]palmitate). Active, but untrained, males exercised on a cycle for 2 h/day [60% pretraining peak O2 consumption (VO2peak) = 44.3 +/- 2.4 ml.kg-1.min-1] for a total of 31 days. Three cycle tests (90 min at 60% pretraining VO2peak) were administered before training (PRE) and after 5 (5D) and 31 (31D) days of training. Exercise increased the rate of glucose production (Ra) and utilization (Rd) as well as the rate of lipolysis (glycerol Ra) and free fatty acid turnover (FFARa/Rd). At 5D, training induced a 10% (P < 0.05) increase in total fat oxidation because of an increase in intramuscular triglyceride oxidation (+63%, P < 0.05) and a decreased glycogen oxidation (-16%, P < 0.05). At 31D, total fat oxidation during exercise increased a further 58% (P < 0.01). The pattern of fat utilization during exercise at 31D showed a reduced reliance on plasma FFA oxidation (FFA Rd) and a greater dependence on oxidation of intramuscular triglyceride, which increased more than twofold (P < 0.001). In addition, glucose Ra and Rd were reduced at all time points during exercise at 31D compared with PRE and 5D. We conclude that long-term training induces a progressive increase in fat utilization mediated by a greater oxidation of fats from intramuscular sources and a reduction in glucose oxidation. Initial changes are present as early as 5D and occur before increases in muscle maximal mitochondrial enzyme activity.

Progressive effect of endurance training on metabolic adaptations in working skeletal muscle

We investigated the hypothesis that a program of prolonged endurance training, previously shown to decrease metabolic perturbations to acute exercise within 5 days of training, would result in greater metabolic adaptations after a longer training duration. Seven healthy male volunteers [O2 consumption = 3.52 +/- 0.20 (SE) l/min] engaged in a training program consisting of 2 h of cycle exercise at 59% of pretraining peak O2 consumption (VO2peak) 5-6 times/wk. Responses to a 90-min submaximal exercise challenge were assessed pretraining (PRE) and after 5 and 31 days of training. On the basis of biopsies obtained from the vastus lateralis muscle, it was found that, after 5 days of training, muscle lactate concentration, phosphocreatine (PCr) hydrolysis, and glycogen depletion were reduced vs. PRE (all P < 0.01). Further training (26 days) showed that, at 31 days, the reduction in PCr and the accumulation of muscle lactate was even less than at 5 days (P < 0.01). Muscle oxidative potential, estimated from the maximal activity of succinate dehydrogenase, was increased only after 31 days of training (+41%; P < 0.01). In addition, VO2peak was only increased (10%) by 31 days (P < 0.05). The results show that a period of short-term training results in many characteristic training adaptations but that these adaptations occurred before increases in mitochondrial potential. However, a further period of training resulted in further adaptations in muscle metabolism and muscle phosphorylation potential, which were linked to the increase in muscle mitochondrial capacity.

Increased clearance of lactate after short-term training in men

A short-term training model previously shown to result in a tighter metabolic control in working muscle in the absence of an increase in mitochondrial potential was used to examine changes in lactate turnover. Lactate flux was studied before and after 10 days of cycle training [2 h/day at 59% maximal oxygen consumption (VO2max)] in untrained men [VO2max = 45.5 +/- 2.4 (SE) ml.kg-1.min-1). A primed constant infusion of L-[1-13C]lactate was used to examine lactate kinetics during a prolonged exercise protocol (90 min at 59% VO2max). Rate of appearance of lactate increased with exercise (P < 0.01), both pretraining (rest = 30.3 +/- 4.9 ml.kg-1.min-1, exercise = 115 +/- 14 ml.kg-1.min-1) and posttraining (rest = 28.4 +/- 4.7 ml.kg-1.min-1, exercise = 112 +/- 13 ml.kg-1.min-1). Despite a lower blood lactate concentration (P < 0.05) during exercise after training, there was no difference in the rate of appearance of lactate. Training increased (P < 0.05) the metabolic clearance rate of lactate during exercise from 36.8 +/- 4.8 to 51.4 +/- 6.8 ml.kg-1.min-1. These findings indicate that at least part of the lower exercising blood lactate observed after training is due to an increase in metabolic clearance rate. In addition, the lower intramuscular lactate levels suggest a decreased recruitment of glycolysis particularly early in exercise.

Decreased glucose turnover after short-term training is unaccompanied by changes in muscle oxidative potential

This study investigated the hypothesis that training-induced reductions in exercise blood glucose utilization can occur independently of increases in muscle mitochondrial potential. To induce a training adaptation, eight active participants (23 +/- 1 yr, 80.6 +/- 3.7 kg, mean +/- SE) with a maximal oxygen consumption (VO2max) of 45.5 +/- 2.4 ml.kg-1.min-1, cycled at 59% VO2max for 2 h per day for 10 consecutive days. Measurements of blood glucose appearance (Ra) and disappearance (Rd), using a primed continuous infusion of [6,6-2H2]glucose, were made during 90 min of cycle exercise (59% VO2max) performance before and after training. Training resulted in a 25% decrease (P < 0.01) in mean glucose Ra during exercise (43.0 +/- 3.7 to 34.4 +/- 2.8 mumol.kg-1.min-1). Since blood glucose concentration was not different between training conditions, glucose metabolic clearance rate was also depressed (P < 0.05). Exercise-induced glycogen depletion in vastus lateralis muscle was reduced (P < 0.05) with training. Calculation of carbohydrate and fat oxidation based on the respiratory exchange ratio supported a shift toward greater preference for fat. Because training did not elicit changes in the maximal activities of citrate synthase and malate dehydrogenase, two enzymes of the citric acid cycle, it would appear that increases in mitochondrial potential are not necessary for the adaptations that occurred.

Case study: the painful os trigonum syndrome

The painful os trigonum syndrome is one cause of posterolateral ankle pain. This syndrome is most prevalent in athletes who perform frequent and/or forceful plantar flexion. The painful os trigonum may be misdiagnosed as Achilles and/or peroneal tendinitis. In this case, the patient was misdiagnosed for 15 months and treated for tendinitis. The appropriate clinical tests to evaluate the os trigonum as a source of posterolateral ankle pain are outlined. The surgical and postoperative management for the patient are discussed. Clinicians should be aware of the painful os trigonum syndrome as a possible source of posterolateral ankle pain.

An unusual cause of burning mouth sensation

A case of burning mouth and disturbed taste following accidental exposure to pyrethroid in an insecticide is reported. The symptoms were more prolonged than have been previously reported following cutaneous exposure.

Iloprost. A review of its pharmacodynamic and pharmacokinetic properties, and therapeutic potential in peripheral vascular disease, myocardial ischaemia and extracorporeal circulation procedures

Iloprost is an analogue of epoprostenol (prostacyclin; PGI2; a potent but short-lived prostanoid mainly produced in the vascular endothelium) and mimics the pharmacodynamic properties of this compound, namely: inhibition of platelet aggregation, vasodilatation and, as yet ill-defined, cytoprotection. Improved metabolic and, in particular, chemical stability enhance the clinical utility of iloprost. When administered as an intermittent intravenous infusion at less than or equal to 2 ng/kg/min for 2 to 4 weeks, iloprost reduced rest pain and improved ulcer healing in 40 to 60% of patients with critical leg ischaemia, including diabetic patients, and delayed amputation in the majority of responding individuals. Similar benefits have been seen in thromboangiitis obliterans and, in patients with severe Raynaud's phenomenon, shorter courses of therapy reduced the frequency, intensity and duration of ischaemic episodes for at least 6 weeks. The very few comparative trials reported to date (i.e. vs nifedipine in Raynaud's phenomenon; vs low-dose aspirin in thromboangiitis obliterans) have favoured iloprost, but comparisons with more established agents are needed to assess this drug's value in less severe forms of peripheral ischaemia, such as intermittent claudication. At present, iloprost is administered intravenously and this is a limitation to treatment. The potent, rapidly reversible antiplatelet activity of iloprost suits it for use in extracorporeal circulation and for the intraoperative management of heparin-induced platelet activation. Although results in animal models of ischaemic myocardial injury are encouraging, preliminary clinical experience in patients with myocardial ischaemia or infarction has been disappointing. Most patients tolerate iloprost infusion rates of up to 2 ng/kg/min. Headache and flushing are extremely common and are the suggested end-point of dose titration, as higher doses are associated with a significant incidence of gastrointestinal distress and, ultimately, hypotension. Thus, iloprost provides a pharmacotherapeutic option for patients with severe peripheral vascular disease, a condition for which few alternative drug therapies exist. Its potent but short-lived effects make it well-suited to certain therapeutic niches such as the management of intraoperative platelet activation. Prostanoid analogues have far-reaching therapeutic potential and further experience with iloprost will no doubt help to define its clinical applications.

Oxcarbazepine. A review of its pharmacology and therapeutic potential in epilepsy, trigeminal neuralgia and affective disorders

Oxcarbazepine is the 10-keto analogue of carbamazepine but has a distinct pharmacokinetic profile. In contrast to the oxidative metabolism of carbamazepine, oxcarbazepine is rapidly reduced to its active metabolite, 10,11-dihydro-10-hydroxy-carbamazepine. With the possible exception of the P450IIIA isozyme of the cytochrome P450 family, neither oxcarbazepine nor its monohydroxy derivative induce hepatic oxidative metabolism. Direct comparison of oxcarbazepine and carbamazepine has shown no difference in efficacy between these 2 agents in terms of reducing seizure frequency in patients with partial epilepsy with or without secondary generalisation, or with tonic-clonic seizures. Substitution of oxcarbazepine for carbamazepine in multiple antiepileptic drug regimens improved seizure control in some patients with refractory epilepsy; however, the rise in serum concentrations of concurrent antiepileptic agents secondary to elimination of carbamazepine-associated hepatic enzyme induction may have also played a role. Substitution of oxcarbazepine for carbamazepine was associated with improved cognition and alertness in some patients with epilepsy. Limited data indicate that oxcarbazepine may be a useful alternative to carbamazepine in the management of trigeminal neuralgia. Experience in patients with acute mania is promising, but the value of oxcarbazepine in managing affective disorders, particularly as a prophylactic agent, is not established. Oxcarbazepine may be better tolerated than carbamazepine; however, the current published database is small and the potential for oxcarbazepine to induce the type of serious idiosyncratic reactions occasionally associated with carbamazepine is unknown. Hyponatraemia has been reported in patients treated with oxcarbazepine. Although apparently asymptomatic, fluid restriction may be deemed necessary in some patients to reduce the risk of precipitating seizures secondary to low serum sodium. Thus, oxcarbazepine appears to be an effective substitute for carbamazepine in those patients intolerant of this agent, or experiencing significant drug interactions. Wider clinical experience should help clarify the long term efficacy and tolerability of oxcarbazepine. Pharmacokinetic advantages over current antiepileptic drugs, carbamazepine in particular, may then favour oxcarbazepine for consideration as a first-line agent in the management of partial and tonic-clonic epilepsy.

Recombinant granulocyte-macrophage colony-stimulating factor (rGM-CSF). A review of its pharmacological properties and prospective role in the management of myelosuppression

Recombinant granulocyte-macrophage colony-stimulating factor (rGM-CSF) is a polypeptide hormone produced through recombinant DNA technologies in glycosylated (yeast or mammalian expression systems) or nonglycosylated (Escherichia coli expression system) form. It is a multilineage haematopoietin which stimulates proliferation and differentiation of bone marrow myeloid progenitors and increases peripheral white blood cell counts when administered systemically. Treatment is generally well tolerated, although mild to moderate flu-like symptoms are common and rGM-CSF-induced fever and fluid retention may be problematic in occasional patients. rGM-CSF accelerates recovery of peripheral neutrophil counts after bone marrow transplantation, and results of a placebo-controlled randomised trial correlate this with reduced infectious episodes and shortened length of hospitalisation in patients with lymphoid malignancies. A substantial number of patients with graft failure after bone marrow transplantation also respond to rGM-CSF. The duration of myelosuppression secondary to cancer chemotherapy can be significantly reduced by rGM-CSF which has permitted investigation of antineoplastic dose-intensity escalation. In some haematopoietic disorders (e.g. aplastic anaemia, myelodysplasia and neutropenia secondary to HIV infection and antiviral therapy), rGM-CSF produces clinically useful increases in peripheral blood granulocyte counts, although the effect is generally not sustained after drug withdrawal. The potential for rGM-CSF to stimulate proliferation of the abnormal clone in myelodysplasia and in acute myelogenous leukaemia following induction therapy is of concern. Available data suggest, however, that with appropriate monitoring and exclusion of high-risk patients this serious potential risk can be avoided, and that myelopoiesis is enhanced in such patients by rGM-CSF treatment. Recombinant colony-stimulating factors are a new therapeutic modality; hence many aspects of their use remain to be clarified. Nonetheless, as one of a small group of novel agents rGM-CSF has major potential in the management of myelosuppression secondary to cytoreductive therapy with or without bone marrow transplantation, and in amelioration of disturbed myelopoiesis. It represents an important application of biotechnology to a difficult area of therapeutics.

Vigabatrin. A review of its pharmacodynamic and pharmacokinetic properties, and therapeutic potential in epilepsy and disorders of motor control

Vigabatrin was specifically designed to enhance gamma-aminobutyric acid (GABA) function in the CNS. By increasing brain concentrations of this inhibitory neurotransmitter the drug appears to decrease propagation of abnormal hypersynchronous discharges, thereby reducing seizure activity. At this stage in its development, clinical experience with vigabatrin is limited primarily to patients with refractory seizure disorders. In this difficult-to-treat population, 'add-on' therapy with vigabatrin greater than or equal to 2 g/day has shown impressive efficacy, reducing seizure frequency by greater than or equal to 50% in approximately half of patients. Clinical efficacy does seem to vary with seizure type with the best response reported in adults with complex partial seizures with or without generalisation and in children with cryptogenic partial epilepsy or symptomatic infantile spasm. Vigabatrin appears to have a negative effect on absences and myoclonic seizures. Some disorders of motor control may also be amenable to enhanced GABAergic function. In the small number of patients with tardive dyskinesia treated to date, vigabatrin produced mild to moderate improvement in hyperkinetic symptom scores but Parkinsonism or schizophrenic symptoms occasionally worsened. The best response was reported in a study of patients who had been withdrawn from neuroleptic therapy. In a small but well-controlled comparative trial, vigabatrin was as effective as baclofen in reducing spasm and improving some parameters of spasticity in patients with spinal cord lesions or multiple sclerosis. Most adverse reactions to vigabatrin are mild and transient with central nervous system (CNS) changes being reported most frequently. Of particular note, serial evoked potential studies and the few available histology reports have not found evidence of intramyelinic oedema during therapeutic use, as was reported in rats and dogs on chronic high-dose treatment. Thus, vigabatrin is a promising new anticonvulsant drug. Current evidence supports a trial of this agent as adjunctive therapy in patients with refractory seizure disorders, and future investigation of vigabatrin monotherapy and its efficacy relative to established agents is awaited with interest. Wider experience should help to clarify which patients - by seizure type and concurrent CNS pathology - are likely to benefit from vigabatrin and ongoing monitoring should further clarify the potential detrimental effects, if any, of long term use. In the meantime, it is a welcome addition in the difficult setting of resistant epilepsy.

Ketotifen. A review of its pharmacodynamic and pharmacokinetic properties, and therapeutic use in asthma and allergic disorders

Ketotifen is an orally active prophylactic agent for the management of bronchial asthma and allergic disorders. Accumulated evidence indicates that after 6 to 12 weeks of administration, ketotifen significantly reduces respiratory symptoms and the need for concomitant antiasthmatic drugs in about 70% and 50%, respectively, of patients with mild to moderate bronchial asthma. However, absolute improvement in lung function is generally slight. Ketotifen also has pronounced antihistaminic and antianaphylactic properties which result in moderate to marked symptom improvement in the majority of patients with atopic dermatitis, seasonal or perennial rhinitis, allergic conjunctivitis, chronic or acute urticaria or food allergy. Comparative trials with established agents--notably sodium cromoglycate (cromolyn sodium) in asthma and histamine H1-antagonists in allergic disorders--indicate that ketotifen has comparable clinical utility. Unlike inhaled sodium cromoglycate, ketotifen ameliorates the symptoms of asthma, rhinitis and dermatitis when present together in atopic patients. Patient acceptance of ketotifen is good, although sedation can be troublesome in older children and adults for the initial 2 weeks of treatment. Weight gain is another notable effect in a small percentage of patients. Thus, ketotifen appears to be a useful agent for the management of allergic disorders and bronchial asthma, particularly in patients for whom oral therapy is preferred. Although a lengthy run-in period is needed in the treatment of asthma, in those patients who respond, continued reduction in the frequency and severity of symptoms and in the use of additional antiasthmatic drugs can be anticipated.

Fluconazole. A review of its pharmacodynamic and pharmacokinetic properties, and therapeutic potential in superficial and systemic mycoses

Fluconazole is a bis-triazole antifungal drug with novel pharmacokinetic properties (metabolic stability, relatively high water solubility) which contribute to its therapeutic activity. Clinical experience is limited to a relatively small number of mycoses and, as might be expected at this early stage of development, optimal dosage and duration of treatment for some serious mycoses is not yet established. Further study to evaluate higher dosages and to establish the efficacy of fluconazole relative to more established antifungal agents is required. In patients with oropharyngeal or oesophageal candidiasis, fluconazole produces rapid relief and eradicates the yeast in 50 to 90% of patients. Relapse of oral infection is common in chronically immunocompromised patients regardless of the antifungal used, and adequate primary therapy plus long term prophylaxis appears necessary in patients with AIDS. A single oral dose of fluconazole was comparable to standard topical azole therapy in women with acute vaginal candidiasis. Preliminary reports of success against deep-seated candidiasis are encouraging; moreover, experience in noncomparative clinical trials suggests that fluconazole 200 to 400mg once daily resolves infection in the majority of seriously ill patients. Clinical improvement has been reported in a few cases of pulmonary Aspergillus infection but the overall efficacy of conventional dosages of fluconazole in this mycosis has not been as impressive. Early experience in coccidioidosis, predominantly meningitis, suggests a beneficial clinical effect with oral fluconazole in this difficult to treat mycosis but relapse remains a problem. Fluconazole is a promising treatment of cryptococcal meningitis. The rate of clinical resolution and eradication of Cryptococcus neoformans from cerebrospinal fluid has been similar between fluconazole and amphotericin B treatment groups in comparative trials. Comparative trials of maintenance therapy indicate a similar low rate of relapse among patients given oral fluconazole once daily and intravenous amphotericin B once weekly. However, these results are preliminary and further study is required. Fluconazole has been well tolerated to date but wider clinical experience is needed, especially with regard to the rate occurrence of hepatotoxicity and exfoliative skin reactions. The promising clinical response of patients with various forms of candidiasis or cryptococcosis--together with convenient administration regimens--recommends fluconazole as a useful addition to currently available systemic antifungal therapies, in particular for the treatment of mycoses in patients with AIDS.

Diltiazem. A reappraisal of its pharmacological properties and therapeutic use

Diltiazem is a calcium antagonist effective in the treatment of stable, variant and unstable angina pectoris and mild to moderate systemic hypertension, with a generally favourable adverse effect profile. It is also effective in terminating supraventricular tachycardia and in controlling the ventricular response to atrial fibrillation/flutter. Atrioventricular block, the risk of which may be exacerbated by concomitant beta-adrenoceptor antagonist therapy, occurs rarely as an adverse effect of diltiazem treatment. Diltiazem appears to exert complex cardioprotective effects which have been of benefit after intracoronary administration to patients undergoing coronary angiography and bypass procedures. In addition, long term diltiazem treatment has produced a significant reduction in subsequent cardiac events in patients with non-Q wave myocardial infarction. Thus, diltiazem is an effective and well-tolerated first-line or alternative treatment of patients with ischaemic heart disease, systemic hypertension, and supraventricular arrhythmias, with possible potential in limiting ischaemia-induced myocardial damage.

Famotidine. An updated review of its pharmacodynamic and pharmacokinetic properties, and therapeutic use in peptic ulcer disease and other allied diseases

Famotidine is a highly selective histamine H2-receptor antagonist. In healthy volunteers and patients with acid hypersecretory disease it is approximately 20 to 50 times more potent at inhibiting gastric acid secretion than cimetidine and 8 times more potent than ranitidine on a weight basis. As shown in placebo-controlled trials, famotidine is effective in healing both duodenal and gastric ulcers. Famotidine 20mg twice daily or 40mg at bedtime achieves healing rates and symptom relief similar or superior to those achieved by cimetidine 800mg daily or ranitidine 300mg daily in patients with peptic ulcer disease. Results of 1 placebo-controlled study suggest that famotidine prevents recurrence of duodenal ulcer, but comparative trials are needed to establish its relative efficacy in maintenance therapy. The few non-comparative trials conducted to date also suggest that famotidine 10 to 20mg twice daily may be effective in the treatment of gastritis and reflux gastro-oesophagitis. In comparative trials, famotidine was similar in efficacy to cimetidine in the treatment of upper gastrointestinal bleeding and to ranitidine in the prevention of pulmonary aspiration of acid. In patients with Zollinger-Ellison syndrome, the potency and long duration of action of famotidine may confer an advantage over other H2-receptor antagonists--in individualised doses (mean 0.33 g/day) famotidine successfully controlled acid secretion for up to 72 months in 1 study of such patients. Accumulated clinical evidence confirms that famotidine is very well tolerated and is free of the antiandrogenic effects infrequently reported with cimetidine. Moreover, famotidine is not associated with altered hepatic metabolism of drugs. Thus, famotidine is an effective, well-tolerated alternative to cimetidine and ranitidine. Famotidine is also promising as maintenance therapy for preventing recurrence of duodenal ulcer and as initial or maintenance treatment of gastric hypersecretory disorders, but further clinical experience, particularly in the long term, is needed to define the relative efficacy and tolerability of famotidine in these indications.

Ranitidine. An updated review of its pharmacodynamic and pharmacokinetic properties and therapeutic use in peptic ulcer disease and other allied diseases

Ranitidine, a histamine H2-receptor antagonist, is now well established as a potent inhibitor of gastric acid secretion effective in the treatment and prophylaxis of gastrointestinal lesions aggravated by gastric acid secretion. Therapeutic trials involving several thousands of patients with peptic ulcer disease confirm that ranitidine 300mg daily administered orally in single or divided doses is at least as effective as cimetidine 800 to 1000mg daily in increasing the rate of healing of duodenal and gastric ulcers. Similar dosages of ranitidine have been shown to relieve the symptoms of reflux oesophagitis and heal or prevent gastrointestinal damage caused by ulcerogenic drugs. Ranitidine 150mg orally at night maintains ulcer healing in the long term. Ranitidine has also demonstrated good results in the treatment of Zollinger-Ellison syndrome and in the prevention of aspiration pneumonitis when given prior to surgery and to pregnant women at full term. It may also have a place in the management of acute upper gastrointestinal bleeding and in the prevention of stress ulcers in the intensive care setting, although these areas require further investigation. Ranitidine has been used safely in obstetric patients during labour, in children, the elderly, and in patients with renal impairment when given in appropriate dosages. The drug is very well tolerated and is only infrequently associated with serious adverse reactions or clinically significant drug interactions. Even at high dosages, ranitidine appears devoid of antiandrogenic effects. Ranitidine is clearly comparable or superior to most other antiulcer agents in the treatment and prevention of a variety of gastrointestinal disorders associated with gastric acid secretion. With its favourable efficacy and tolerability profiles, ranitidine must be considered a first-line agent when suppression of gastric acid secretion is indicated.

Ultrasound physiotherapy treatment and calibration measurements in simulated tissue

The absorption, heating and relative intensities of ultrasonic beams used for physiotherapy are studied in water and in simulated tissue as a function of position in relation to the transducer head. It is found that the heating effects are significantly different from the beam profile shape. The effective area and depth of ultrasonic physiotherapy treatment is established for various situations, and tissue temperature rise curves are obtained. The results are appropriate for treatment planning. As an example, the typical volume of tissue effectively treated by ultrasound is a cylinder 6 to 8 cm in diameter and 1 cm deep.

Itraconazole. A review of its pharmacodynamic and pharmacokinetic properties, and therapeutic use in superficial and systemic mycoses

Itraconazole is an orally active triazole antifungal drug which has demonstrated a broad spectrum of activity and a favourable pharmacokinetic profile. It is a potent inhibitor of most human fungal pathogens including Aspergillus sp. In non-comparative clinical trials itraconazole was shown to be extremely effective in a wide range of superficial and more serious 'deep' fungal infections when administered once or twice daily. Generally, greater than 80% of patients with superficial dermatophyte or yeast infections are cured by itraconazole. Similarly, good to excellent response rates (clinical cure or marked improvement) are achieved in paracoccidioidomycosis, histoplasmosis, sporotrichosis, blastomycosis, systemic candidiasis, coccidioidomycosis, chromomycosis, aspergillosis and cryptococcosis. Understandably, given the rare nature of some of these diseases, clinical experience is relatively limited and further evaluation, preferably controlled trials with amphotericin B and ketoconazole, would help clarify the ultimate role itraconazole will have in their management. Preliminary findings also indicate that itraconazole may hold promise for the prophylaxis of opportunistic fungal infections in patients at risk, for example women with chronic recurrent vaginal candidiasis, immunodeficient patients with chronic mucocutaneous candidiasis, AIDS patients and patients receiving immunosuppressant drugs. In studies to date itraconazole has been very well tolerated. Transient changes in indices of liver function occurred in 1 to 2% of patients; however, symptomatic liver dysfunction (as occurs infrequently with ketoconazole) has not been reported. Wider clinical experience is needed to permit clear conclusions as to whether liver dysfunction can result from itraconazole administration. Thus, while several aspects of the drug's profile require further investigation, itraconazole is a promising new oral treatment of fungal disease. The extent to which itraconazole will be employed in preference to ketoconazole will be clarified by wider clinical experience.

Homozygous hypobetalipoproteinemia: a disease distinct from abetalipoproproteinemia at the molecular level

apoB DNA, RNA, and protein from two patients with homozygous hypobetalipoproteinemia (HBL) were evaluated and compared with normal individuals. Southern blot analysis with 10 different cDNA probes revealed a normal gene without major insertions, deletions, or rearrangements. Northern and slot blot analyses of total liver mRNA from HBL patients documented a normal size apoB mRNA that was present in greatly reduced quantities. ApoB protein was detected within HBL hepatocytes utilizing immunohistochemical techniques; however, it was markedly reduced in quantity when compared with control samples. No apoB was detectable in the plasma of HBL individuals with an ELISA assay. These data are most consistent with a mutation in the coding portion of the apoB gene in HBL patients, leading to an abnormal apoB protein and apoB mRNA instability. These results are distinct from those previously noted in abetalipoproteinemia, which was characterized by an elevated level of hepatic apoB mRNA and accumulation of intracellular hepatic apoB protein.

Human liver apolipoprotein B-100 cDNA: complete nucleic acid and derived amino acid sequence

Human apolipoprotein B-100 (apoB-100), the ligand on low density lipoproteins that interacts with the low density lipoprotein receptor and initiates receptor-mediated endocytosis and low density lipoprotein catabolism, has been cloned, and the complete nucleic acid and derived amino acid sequences have been determined. ApoB-100 cDNAs were isolated from normal human liver cDNA libraries utilizing immunoscreening as well as filter hybridization with radiolabeled apoB-100 oligodeoxynucleotides. The apoB-100 mRNA is 14.1 kilobases long encoding a mature apoB-100 protein of 4536 amino acids with a calculated amino acid molecular weight of 512,723. ApoB-100 contains 20 potential glycosylation sites, and 12 of a total of 25 cysteine residues are located in the amino-terminal region of the apolipoprotein providing a potential globular structure of the amino terminus of the protein. ApoB-100 contains relatively few regions of amphipathic helices, but compared to other human apolipoproteins it is enriched in beta-structure. The delineation of the entire human apoB-100 sequence will now permit a detailed analysis of the conformation of the protein, the low density lipoprotein receptor binding domain(s), and the structural relationship between apoB-100 and apoB-48 and will provide the basis for the study of genetic defects in apoB-100 in patients with dyslipoproteinemias.