bluuebunny/crossref_metadata_2025 huggingface dataset:
Ion gradients and contractility in skeletal muscle: the role of active Na+, K+ transport
Authors: NIELSEN O. B. , OVERGAARD K.
Published: November 2003

Intensive contractile activity is associated with a significant net loss of K+ and a comparable gain of Na+ in the working muscle fibres. This leads to an increase in the interstitial and T‐tubular K+ concentration and to a decrease in the T‐tubular Na+ concentration. It is well established that the exposure of muscles to high extracellular K+ or low extracellular Na+ inhibits contractile performance. More importantly, the combination of high extracellular K+ and low extracellular Na+ has a much more pronounced inhibitory effect on force than the sum of the individual effects of the two ions.

The inhibitory effects of high extracellular K+ or low extracellular Na+ can be alleviated within 5–10 min by acute hormonal stimulation of the Na+, K+ pump. In contrast, reductions in the capacity for active Na+, K+ transport by pre‐incubation of isolated muscles with ouabain or by prior K+ depletion of the animals significantly decreases contractile endurance during high‐frequency electrical stimulation. Thus, muscles from K+‐depleted rats exhibiting a 54% reduction in Na+, K+ pump concentration showed a 110% increase in force decline during 30 s of 60 Hz stimulation. Reducing the Na+, K+ pump capacity to a similar extent by pre‐incubation with ouabain led to a comparable decrease in endurance. Moreover, reductions in the Na+, K+ pump capacity were associated with an increased intracellular accumulation of Na+ during electrical stimulation. These observations support the notion that excitation‐induced decreases in Na+, K+ gradients contribute to fatigue during intensive exercise and suggest that the capacity for active Na+, K+ transport is a determining factor for contractile endurance.
Lactate/proton co‐transport in skeletal muscle: regulation and importance for pH homeostasis
Authors: JUEL C.
Published: November 2003

In skeletal muscle, intracellular pH is more alkaline than would be predicted if H+ were passively distributed across the sarcolemma. Therefore, the passive influx of H+ must be counteracted by transport processes mediating H+ efflux. In resting skeletal muscle, these transport processes are Na+/H+ exchange and bicarbonate‐dependent systems. During periods of high energy demand, skeletal muscle produces large amounts of lactic acid. The internal accumulation of lactic acid reduces pH, which may cause fatigue. It is therefore important for muscle cells to be able to regulate pH during and after activity. A part of the accumulated lactate and H+ is metabolized, but a considerable fraction is released from the cell. The efflux of H+ and lactate might be mediated by the lactate/proton co‐transport system found in almost all cell types in the body. The role of lactate/proton co‐transport in pH regulation has been studied both with intact cells and with sarcolemmal vesicles. In intact cells, inhibitors of lactate/proton transport have been shown to accelerate the development of fatigue, and to delay the recovery after activity. A comparison with vesicles has demonstrated that, at low pH, and with a high lactate concentration, the capacity for H+ removal is higher via the lactate/proton co‐transport system than via the sum of the Na+/H+ exchange and bicarbonate‐dependent exchange systems. Therefore, the carrier‐mediated lactate/proton efflux is of major importance for pH regulation in connection with muscle activity. The lactate/proton transport system has been shown to undergo long‐term changes depending on the level of physical activity. The capacity of the system was enhanced after intense training or chronic stimulation, and reduced after denervation. It is concluded that the lactate/proton transport system is of major importance for pH regulation in skeletal muscle, and that changes in the amount of transporters are one of the many adaptations to physical activity.
Effects of K+, Mg2+ deficiency and adrenal steroids on Na+, K+‐pump concentration in skeletal muscle
Authors: DØRUP I.
Published: November 2003

Animal studies have shown that deficiency of K+ is associated with a reduction in the concentration of Na+, K+ pumps in skeletal muscle, and that this reduction is closely correlated with the reduction in the muscle K+ concentration. Furthermore, animals deficient in Mg+ show a downregulation of the Na+, K+‐pump concentration, but this seems to be secondary to the concomitant K+ deficiency, which often accompanies Mg2+ deficiency. Measurements on skeletal muscle biopsies from patients who had been in long‐term treatment with diuretics showed that 55% had reduced concentrations of both K+ and Mg2+, and that this was associated with a reduction in the concentration of Na+, K+ pumps. Furthermore, the Na+, K+‐pump concentration correlated significantly with both muscle K+ and Mg2+, suggesting that the downregulation of the Na+, K+ pumps was related to the loss of K+, as predicted from the animal experiments. In accordance with this, normalization of muscle K+ and Mg2+ in response to oral Mg2+ supplementation, resulted in a restoration of the Na+, K+ pumps.

Apart from thyroid hormone, which is another major regulator for the Na+, K+‐pump concentration, other hormones may be of importance. It is well known that adrenal steroids control the synthesis of Na+, K+ pumps in the kidney and heart. Recently, treatment with dexamethasone was found to increase the Na+, K+‐pump concentration in rat skeletal muscle. The increase was found in EDL, soleus, gastrocnemius and diaphragm muscles, and amounted to 23–52%. In contrast, treatment with aldosterone induced a decrease in the Na+, K+‐pump concentration, which was closely correlated to the reduced K+ content of the muscles. The results indicate that in skeletal muscle, high doses of glucocorticoids upregulate the concentration of Na+, K+ pumps, whereas mineralocorticoids induce a downregulation which is secondary to the concomitant K+ deficiency.
Ischaemia‐reperfusion induced alterations of mitochondrial function in hypertrophied rat heart
Authors: LEICHTWEIS S. B. , LEEUWENBURGH C. , CHANDWANEY R. , PARMELEE D. J. , JI L. L.
Published: November 2003

The impact of in vivo ischaemia and ischaemia‐reperfusion (I‐R) on mitochondrial respiratory function was investigated in hypertrophied (HP) hearts with aortic constriction compared with control hearts using an open‐chest rat surgical model. Moreover, mitochondrial susceptibility to superoxide radicals (O2P‐) in vitro was examined in HP and control hearts with or without I‐R. With the site I substrates pyruvate‐malate, mitochondrial state 4 (basal) respiration and the respiratory control index (RCI) were not affected by either ischaemia alone or I‐R in both HP and control hearts. State 3 (ADP‐stimulated) respiration was increased with I‐R in control hearts, but showed a reduction after I‐R in the HP hearts. Exposure of mitochondria to O2P‐ (20 nm hypoxanthine in the presence of 0.13 unit mL‐1 xanthine oxidase) significantly increased state 4 respiration, whereas state 3 respiration and RCI were decreased in all treatment groups. I‐R hearts in both HP and control showed greater increases in state 4 respiration with O2P‐ than either sham or ischaemic hearts. HP hearts exhibited a significantly lesser extent of inhibition in state 3 respiration and RCI by O2P‐ compared with control hearts. These changes in mitochondrial respiratory properties were not observed with the site II substrate succinate. Myocardial reduced vs. oxidized glutathione ratio was significantly decreased after I‐R in both control and HP hearts. Malondialdehyde content showed an increase with I‐R, but the increase was significant only in control hearts. These data indicate that short‐term in vivo I‐R does not impair heart mitochondrial respiratory function, but renders the organelles more vulnerable to imposed oxidative stress. Mitochondria from the HP hearts are more resistant to free radical damage under normal and ischaemic conditions; however, this advantage is severely compromised after reperfusion.
Extract of the marine alga Prymnesium patelliferum induces release of acetylcholine from cholinergic nerves in the rat bronchial smooth muscle
Authors: MELDAHL A. S. , AAS P. , FONNUM F.
Published: November 2003

An extract of the marine algal flagellate Prymnesium patelliferum enhanced the spontaneous as well as the K+ evoked (51 mm K+) release of [3H]acetylcholine and endogenous acetylcholine from autonomic cholinergic nerves of rat bronchial smooth muscle. The effects were concentration‐dependent and reversible. The enhancement of the K+ evoked release by the algal extract was partly dependent on extracellular Ca2+ and was significantly suppressed by the organic Ca2+ blockers ω‐conotoxin GVIA (1 μm), diltiazem (100 μm), nifedipine (100 μm) and flunarizine (100 μm). The enhancement of the spontaneous release seemed Ca2+ independent and not sensitive to the Na+ channel blocker tetrodotoxin. Sphingosine (20 μm), a protein kinase C inhibitor, strongly potentiated the enhancement of spontaneous release of [3H]acetylcholine induced by the algal extract whereas another protein kinase C inhibitor, 1‐(5‐quinolinesulphonyl)‐2‐methylpiperazine (H‐7) (20 μm), was without effect. A similar potentiation as seen with sphingosine was observed with procaine (100 μm) and flunarizine (100 μm). The results indicate that the enhancement of the K+ evoked release of [3H]acetylcholine by the toxic extract of P. patelliferum was partly caused by activation of voltage‐dependent Ca2+ channels. The increase in the spontaneous release of [3H]acetylcholine and endogenous acetylcholine induced by the algal extract alone may be caused by an ionophore‐like property of the algal extract. This effect of the algal extract may be enhanced by compounds that facilitate the interaction of the algal toxin with the plasma membrane such as the lipophilic compounds flunarizine, procaine and sphingosine.
Shortening induced deactivation in the guinea‐pig urinary bladder
Authors: GROEN J. , VAN MASTRIGT R. , BOSCH R.
Published: November 2003

Shortening induced deactivation, the depressant effect of active muscle shortening on the subsequently measured isometric force, has been shown in smooth muscle strips and rings. The guinea‐pig bladder permits the investigation of this phenomenon in a whole organ preparation. Previous work in our laboratory showed that shortening of the in vitro guinea‐pig detrusor muscle had a depressant effect on the isovolumetric pressure that could be generated immediately afterwards. To test the hypothesis that this was caused by deactivation, the effects of active and passive detrusor shortening on the subsequently measured isovolumetric pressure were compared. The isovolumetric pressures measured after 5 min periods of recovery were taken as control values. It was found that the isovolumetric pressure after passive shortening was 7% smaller than the isovolumetric pressure without preceding shortening. This difference was ascribed to viscoelastic relaxation during shortening. Active shortening had an additional 8% depressant effect on isovolumetric pressure compared with passive shortening. The effects of active and passive shortening differed significantly. It was concluded that shortening induced deactivation in the guinea‐pig urinary bladder smooth muscle in toto can be considered proven. The fact that deactivation is shown both by striated and smooth muscle preparations is in line with the assumption that it is caused by reduced actin‐myosin interaction. The hypothesis that (in striated muscle) the latter is effected by a decrease in troponin–calcium binding, however, needs reconsideration.
Pleomorphic adenoma and adenoid‐cystic carcinoma of salivary glands: immunohistochemical assessment of proliferative activity in comparison with flow‐cytometric study
Authors: Daniele E. , Tralongo V. , Morello V. , Nagar C. , Russo A. , Bazan V. , Dardanoni G. , Ciotta S. , Nuara R. , Tomasino R. M.
Published: November 2003

In this study, 32 pleomorphic adenomas (PAs) and seven adenoid cystic carcinomas (ACCs) were analysed for the evaluation of proliferating cell nuclear antigen (PCNA) indices and flow cytometric variables. Our aim was to assess any possible relationship between these parameters and the clinico‐pathological variables and to clarify their histogenesis and reasons for their biological differences. The tumours were divided into three groups, mainly epithelial (E), myxoid (M) and chondroid (C); PCNA labelling index (LI) and weighted mean index (WI) and the WI/LI ratio were analysed in the predominant components; a single PCNA index, weighted by the percentage of each component, was also calculated. Only WI/LI was found to be significantly different in the three components, while PCNA single index did not show either significant differences by sex, age, site and size, or any correlation with the S phase fraction. A significant difference was found between PAs and ACCs by site (P <0.01) and DNA ploidy (P <0.05); furthermore, all PCNA indices (single index) were significantly lower in PAs than in ACCs.
Sodium butyrate is a potent modulator of smooth muscle cell proliferation and gene expression
Authors: Feng P. , Ge L. , Akyhani N. , Liau G.
Published: November 2003

Sodium butyrate is a small, naturally occurring molecule with demonstrated activity on cell growth and differentiation. However, its effect on smooth muscle cells had not been examined. We have found that sodium butyrate and its more stable in vivo analogue tributyrin are potent DNA synthesis and cell proliferation inhibitors. The inhibitory activity of sodium butyrate was not mediated by an elevation of endogenous cAMP levels, a known pathway involved in SMC growth‐arrest and maintenance of the contractile phenotype. Consistent with the concept that its activity is mediated by a cAMP‐independent pathway, butyrate was able to augment the maximum DNA synthesis inhibitory effect of various agents that elevated intracellular cAMP levels. Additionally, butyrate present for just the initial 8 h or present as late as 16 h after serum addition was able to inhibit DNA synthesis. By contrast, the cAMP analogue, 8Br‐cAMP had to be present throughout the entire G0 to S phase of the cell cycle to effectively inhibit DNA synthesis. These results indicated that sodium butyrate inhibited SMC growth through a cAMP‐independent mechanism. We also found that sodium butyrate was unable to abrogate the expression of the serum‐inducible genes c‐fos, c‐myc, Ki‐Ras and PS4, but was able to directly stimulate the expression of PS4 and thrombospondin. These results indicate that a number of important early G1 events initiated by serum growth factors are unaltered by sodium butyrate and that this compound is able to directly stimulate the expression of certain genes normally associated with SMC proliferation.
Child protection and family support: a practical approach
Authors: Duxbury Peter
Published: November 2003

This paper provides a practical response to the critical appraisal provided by Nigel Parton of the Department of Health research studies in child protection. Parton argues that the research is flawed because, whilst acknowledging that abuse is socially defined, it also claims that certain types of abuse are undoubtedly serious. This is refuted. The central focus of the research is upon the child protection process. The research does not simply suggest a re‐labelling of child protection work, but a more considered approach to the assessment of family circumstances. The research does not ignore the centrality of social work itself; indeed its emphasis is upon comprehensive and consistent assessment. The document provides useful practical assistance to social workers and professionals in other organizations and is a helpful framework for strategic development.
Reduced expression and normal nucleotide sequence of androgen receptor gene coding and promoter regions in a family with partial androgen insensitivity syndrome
Authors: Choong Catherine S. , Sturm Marian J. , Strophair Julie A. , McCulloch Ross K. , Hurley David M.
Published: November 2003

BACKGROUND AND OBJECTIVES Androgen insensitivity syndrome (AIS) is an X‐linked disorder of XY males characterized by varying degrees of impaired masculinization. In many AIS cases, mutations have been identified in the coding sequence of the human androgen receptor (AR) gene which impair receptor function. Cases have also been reported in which reduced AR mRNA expression may contribute to AIS in association with AR gene mutations. The purpose of this study was to define the molecular basis of AIS in members of a family with clinical and laboratory features of partial androgen insensitivity (PAIS).

DESIGN Genital skin fibroblast (GSF) cultures were established from foreskin tissue for androgen receptor binding analysis. Genomic DNA was obtained from blood leucocytes for AR gene nucleotide sequence analysis. AR mRNA levels were determined in total RNA extracted from GSF cultures.

PATIENTS  Three related subjects with perineo‐scrotal hypospadias, bifid scrotum and microphallus were studied. The family pedigree of these subjects suggested an X‐linked pattern of inheritance. Hormone assay results were consistent with AIS.

MEASUREMENTS AR binding capacity and affinity were determined in three subjects and compared with unaffected male controls. The coding sequence and 1.4 kb of promoter region of the AR gene were amplified in overlapping fragments by polymerase chain reaction from genomic DNA and sequenced. GSF AR mRNA was measured by a competitive PCR technique.

RESULTS In the PAIS subjects, AR affinity in cultured GSF was normal (Kd = 0.24, 0.30, 0.48 vs 0.27 ±0.07 (SD) nmol/l) but binding capacity was reduced (Bmax =0.31, 0.36, 0.27 vs 1.26 ±0.37 (SD) fmol/μg DNA). Sequence analysis of the CAG repeat polymorphism within exon 1 of the AR gene showed that both mothers were heterozygous at this locus, and that the three subjects had inherited the same allele. GSF AR mRNA levels were reduced in all three patients compared with controls (0.25, 0.74 and 0.74 vs 3.8 ±0.9 (SEM), range 1.8–7.3 amol/μg total RNA). The nucleotide sequences of the entire AR coding region and of a 1.4 kb segment containing the promoter region were normal.

CONCLUSION Members of this family with clinical and biochemical evidence of X‐linked partial androgen insensitivity syndrome demonstrated normal androgen receptor binding affinity and androgen receptor gene nucleotide sequence but reduced androgen receptor binding capacity and reduced androgen receptor mRNA. These results suggest that partial androgen insensitivity syndrome in this family may be caused by reduced expression of a normal androgen receptor gene.
In vivoin vitro effects of somatostatin and insulin on glucagon release in a human glucagonoma
Authors: Waeber Gérard , Gomez Fulgencio , Chaubert Pascal , Temler Evelyne , Chapuis Germain , Boulat Olivier , Nicod Pascal , Haefliger Jacques‐Antoine
Published: November 2003

Inhibition of pancreatic glucagon secretion has been reported to be mediated by glucose, insulin and somatostatin. As no human pancreatic α‐cell lines are available to study in vitro the relative importance of insulin and glucose in the control of pancreatic glucagon release, we investigated a patient presenting with a malignant glucagonoma who underwent surgical resection of the tumour. Functional somatostatin receptors were present as octreotide administration decreased basal glucagon and insulin secretion by 52 and 74%, respectively. The removed tumour was immunohistochemically positive for glucagon, chromogranin A and pancreatic polypeptide but negative for insulin, gastrin and somatostatin. The glucagonoma cells were also isolated and cultured in vitro. Incubation experiments revealed that change from high (10 mm) to low (1 mm) glucose concentration was unable to stimulate glucagon secretion. A dose‐dependent inhibition of glucagon release by insulin was however, observed at low glucose concentration. These findings demonstrate that insulin could inhibit glucagon secretion in vitro in the absence of elevated glucose concentrations. These data suggest, as observed in vivoin vitro in several animal studies, that glucopenia‐induced glucagon secretion in humans is not mediated by a direct effect of low glucose on α‐cells but possibly by a reduction of insulin‐mediated α‐cell suppression and/or an indirect neuronal stimulation of glucagon release.
Pituitary size and function in children and adolescents with shunted hydrocephalus
Authors: Löppönen Tuija , Pääkkö Eija , Laitinen Juhani , Saukkonen Anna‐Liisa , Serlo Willy , Tapanainen Päivi , Ruokonen Aimo , Pirttiniemi Pertti , Poikela Aila , Knip Mikael
Published: November 2003

OBJECTIVE

Most previous reports of endocrine disorders in children with shunted hydrocephalus have been case reports and there is a lack of systematic information on pituitary anatomy and function among these children. We have obtained these data in a large group of individuals with shunted hydrocephalus.

DESIGN

A controlled cross‐sectional study.

PATIENTS

Fifty‐four children and adolescents with shunted hydrocephalus were studied for pituitary anatomy and function. They had 54 age‐ and sex‐matched controls (group I). The mean age of the patients and controls was 12.6 years and the mean shunting period 10.6 years. There was a second control group (II) for the magnetic resonance imaging (MRI) and a third control group (III) for the radiography of the sella turcica.

MEASUREMENTS

The anatomy was visualized by MRI of the pituitary gland and by radiography of the sella turcica. The functional evaluation included an arginine–insulin test and a combined stimulation test with corticotrophin releasing factor (CRF), GnRH and TRH.

RESULTS

The patients were shorter (height 148.4 cm vs 153.7 cm, P < 0.05 and relative height −0.5 SDS vs 0.4 SDS, P < 0.05) and had a higher BMI than the control group I (20.6 kg/m2 vs 18.0 kg/m2, P < 0.001). They had also a greater pituitary height than the control group II (5.8 mm vs 5.1 mm, P < 0.01). The patients had significantly lower basal GH levels (P < 0.001) than controls I. Sixteen patients (30%) had a poor GH response (< 20 mU/l) in the arginine–insulin test. Pituitary height was significantly lower among these patients than in those with a normal response (4.7 mm vs 6.3 mm, P < 0.01), who had an increased pituitary height compared to controls II (5.1 mm, P < 0.01). The area under the curve (AUC) for GH correlated with the pituitary volume (r = 0.50, P < 0.001). The patients had higher basal FSH and LH concentrations than controls I (P < 0.001). The peak to basal ratios of FSH and LH were increased in the prepubertal patients and that of LH at Tanner pubertal stage II in the females. The basal FSH and LH levels correlated with the pituitary volume (r = 0.50 and r = 0.54, P < 0.001 for), as did FSH AUC and LH AUC (r = 0.48 and r = 0.75, P < 0.001 for both).

CONCLUSIONS

These observations indicate that children with shunted hydrocephalus have an increased pituitary size on average. About one‐third of these patients had signs of reduced GH secretion and significantly lower pituitary height, which probably contributes to their poor linear growth. Increased pituitary size was associated with enhanced gonadotrophin secretion, which may result in early puberty in children with shunted hydrocephalus.
Expression of the putative inhibitor of the insulin receptor tyrosine kinase PC‐1 in dermal fibroblasts from patients with syndromes of severe insulin resistance
Authors: Whitehead Jonathan P. , Humphreys Phillippa J. , Dib Karim , Goding James W. , O'Rahilly Stephen
Published: November 2003

OBJECTIVE

To date, mutations in the insulin receptor gene are the only clearly defined cause of extreme insulin resistance in man. Recently, however, some patients with severe insulin resistance have been reported to have marked over‐expression of the transmembrane glycoprotein PC‐1 in their cultured fibroblasts. This protein appears to act as an endogenous inhibitor of the insulin receptor tyrosine kinase which suggests that primary over‐expression of PC‐1 may play an aetiological role in some forms of insulin resistance. One sub‐type of extreme insulin resistance in which the insulin receptor gene has been reported to be normal is pseudo‐acromegalic insulin resistance. The main aim of this study was to determine whether overexpression of PC‐1 might contribute to the severe insulin resistance exhibited by some patients with pseudo‐acromegaly.

DESIGN AND PATIENTS

PC‐1 phosphodiesterase activity and PC‐1 protein and mRNA content were measured in cultured dermal fibroblasts from three severely insulin resistant pseudo‐acromegalic patients. These were compared with fibroblasts from normoinsulinaemic normoglycaemic controls and from subjects with known genetic defects in the insulin receptor or IRS‐1.

RESULTS

In the fibroblasts from pseudo‐acromegalic insulin resistant subjects PC‐1 activity and PC‐1 protein and mRNA levels were indistinguishable from the normoinsulinaemic controls. Consistent with this observation, insulin receptor tyrosine kinase activity was similar in extracts from fibroblasts of pseudo‐acromegalic subjects and normal controls. Surprisingly, subjects with insulin receptor or IRS‐1 mutations had a profound reduction in PC‐1 activity (p ≤ 0.005), protein (p ≤ 0.05) and mRNA levels (P ≤ 0.005).

CONCLUSIONS

The results indicate that PC‐1 overexpression does not appear to contribute to the insulin resistant state of pseudo‐acromegalic patients. The finding of normal insulin receptor tyrosine kinase activity in these subjects suggests that the site of defective insulin signalling is likely to be distal to the receptor. The unexpected finding that PC‐1 activity, protein and mRNA were all dramatically reduced in patients with lesions early in the insulin signalling cascade provides further evidence for a link, albeit as yet poorly understood, between cellular insulin action and the expression of PC‐1.
Growth hormone therapy may benefit protein metabolism in mitochondrial encephalomyopathy
Authors: Carroll P. V. , Umpleby A. M. , Albany E. , Jackson N. C. , Morgan‐Hughes J. A. , Sonksen P. H. , Russell‐Jones D. L.
Published: November 2003

Mitochondrial encephalomyopathy is a genetic disorder for which there is at present no cure. Conventional treatment regimes may not be effective in preventing weight loss and muscle wasting in many patients. Recombinant human GH has been shown to have anabolic effects on protein metabolism and to reduce muscle wasting in various diseases. We have treated a patient known to have myoclonus, epilepsy with ragged red fibres (MERRF) with a high protein diet for 1 month followed by a high protein diet and GH therapy for 1 month. To assess the benefit of these treatments the patient underwent whole body protein turnover, myometric and body composition studies at baseline, following the high protein diet (100 g/day) and following GH therapy. Whole body protein synthesis (and protein breakdown) increased following a high protein intake and was further enhanced by treatment with GH and a high protein diet. Body composition did not change significantly following treatment with either the high protein diet or GH but there was an improvement in muscle performance following GH treatment. Mitochondrial encephalomyopathy, a wasting disorder, may be a disease in which the known protein anabolic effect of GH may have a therapeutic benefit.
Inhaled beclomethasone dipropionate suppresses the hypothalamo–pituitary–adrenal axis in a dose dependent manner
Authors: Grebe Stefan K. G. , Feek Colin M. , Durham John A. , Kljakovic Marjan , Cooke Russell R.
Published: November 2003

OBJECTIVE

Little is known about the dose–response relationship of potential, unwanted, effects of inhaled beclomethasone (BDP) on the hypothalamo–pituitary–adrenal (HPA) axis, particularly in non‐specialist clinic settings. The purpose of our study was to investigate the dose–response relationship of inhaled BDP on the HPA axis in a general practice patient population. We also explored the optimal testing strategy in this population and correlated effects of inhaled BDP on the HPA axis with other systemic corticosteroid side effects.

PATIENTS AND DESIGN

Controlled observational study employing 21 patients on inhaled BDP recruited from general practice, with minimal past and no present exposure to other corticosteroids, and 21 age and gender‐matched controls.

MEASUREMENTS

Twenty‐four‐hour urinary free cortisol excretion (UFC), serum cortisol before and 30 minutes after injection of 1 μg and 250 μg of tetracosactrin, serum IGF‐I and serum osteocalcin were measured. BDP use was estimated by inhaler weighing and prescription count.

RESULTS

In subjects on inhaled BDP, 24‐hour UFC (P < 0.008), serum cortisol 30 minutes after 250 μg tetracosactrin (P < 0.05) and the serum cortisol rise after 250 μg tetracosactrin (P < 0.04) were significantly lower when compared with controls. Measurements of HPA function correlated inversely with BDP dose estimated by inhaler weighing (all P < 0.03). Serum IGF‐I and osteocalcin levels did not differ.

CONCLUSIONS

We have demonstrated hypothalamo–pituitary–adrenal axis suppression in non‐specialist‐clinic asthma patients on moderate to large doses of inhaled beclomethasone dipropionate. When accurate measurements of inhaled steroid dose are used, there is an exponential relationship between dose and hypothalamo–pituitary–adrenal axis suppression. There appears to be no ‘safe’ threshold, and around 15% of patients may have clinically significant suppression. However, the significance of hypothalamo–pituitary–adrenal axis suppression as a marker for concomitant corticosteroid effects on other organ systems remains uncertain.
Anisomycin and verapamil influence the action of progesterone on regulation of term human myometrial contractile activity
Authors: Fu Xin , Moberg Christian , Bäckström Torbjörn , Ulmsten Ulf , Gylfe Erik
Published: November 2003

OBJECTIVE

Progesterone has been shown to have both stimulatory and inhibitory effects on term human myometrial contractile activity. The mechanisms involved in this action of progesterone are still poorly understood.

DESIGN

Myometrial tissues were obtained from the lower uterine segment at elective Caesarean section of 30 term pregnant women. The contractile activity of muscle strips was measured by a superfusion technique and protein synthesis evaluated by [3H]‐leucine incorporation.

RESULTS

[3H]‐leucine incorporation into term myometrial strips was not affected by progesterone (10 μmol/l), but was markedly reduced by the protein synthesis inhibitor anisomycin (P  <  0.05). However, progesterone increased frequency and tonus of contractions and reduced the activity‐area of contractions (P  <  0.01). Anisomycin (100 μmol/l) did not change these effects or the spontaneous contractile activity. Removal or extracellular Ca2+ or addition of the L‐type calcium channel blocker verapamil prevented the spontaneous as well as the progesterone‐induced contractions, but had less pronounced effects on contractions initiated by oxytocin.

CONCLUSION

The results indicate that the actions of progesterone on term myometrial contractile activity occur without protein synthesis and that increased Ca2+ influx or decreased outward transport of Ca2+ may play a possible role.
Suspected hypoglycaemia in out patient practice: accuracy of dried blood spot analysis
Authors: Parker David R. , Bargiota Alexandra , Cowan Fiona J. , Corrall Roger J. M.
Published: November 2003

OBJECTIVE

The assay of dried blood spots on filter paper to determine blood glucose concentration has been used to detect hypoglycaemia in out patients. We assessed the accuracy of this approach in assaying blood glucose concentrations in the hypoglycaemic range.

DESIGN

Volunteers were rendered hypoglycaemic by intravenous infusion of insulin. The glucose concentration in simultaneously taken blood samples was measured either fresh or after drying on filter paper.

PATIENTS

Twenty‐four healthy young volunteers and 9 patients with insulin‐dependent diabetes were studied.

MEASUREMENTS

Plasma glucose concentrations were measured using a standard auto analyser glucose oxidase method. Whole blood taken simultaneously was placed on prepared filter paper and allowed to dry; glucose concentration was then measured using a well‐established technique. A correction factor was applied to convert the glucose concentration of plasma to that of whole blood. The relationship between glucose concentrations measured by the two methods was determined by regression coefficient.

RESULTS

In the unequivocally hypoglycaemic range (plasma 2.5 mmol/l), corrected dried blood spot glucose concentrations significantly correlated with standard plasma glucose concentrations (r = 0.81; P < 0.001). The dried blood spot method had a sensitivity of 91%. In the range designated probable hypoglycaemia (plasma 3.3 mmol/l), there was also significant correlation (r = 0.90; P < 0.001) and the sensitivity was 96%. The specificity of the dried blood spot method was 100% in both ranges.

CONCLUSIONS

Measurement of glucose concentrations in dried blood spots is specific and sensitive in the hypoglycaemic range. The present study indicates that hypoglycaemia may be excluded or confirmed respectively when levels in excess of 3.7 or below 2.8 mmol/l are found in uncorrected dried blood spot analysis.
L‐hydroxytryptophan amplifies pulsatile secretion of LH in the follicular phase of normal women
Authors: Lado‐Abeal J. , Rey C. , Cabezas‐Agrícola J. M. , Rodriguez A. , Camarero E. , Cabezas‐Cerrato J.
Published: November 2003

OBJECTIVES

The hypothalamus possesses serotoninergic fibres which arise from neuronal cell bodies located in the raphe nuclei and have synapse on GnRH‐secreting neurones. Hitherto, no firm evidence has been produced to support a role for serotoninergic control of LH in humans. Our first objective was to investigate whether pulsatile administration of L‐5‐hydroxytryptophan—the immediate precursor of serotonin—affects pulsatile LH secretion in the medium–late follicular phase of normal women. Since the results of the first experiment suggest that L‐5‐hydroxytryptophan amplifies LH release, our second objective was to investigate whether, in the absence of GnRH, L‐5‐hydroxytryptophan can release LH. This was done by studying LH response in patients with hypogonadotrophic hypogonadism of hypothalamic origin.

PATIENTS

Twenty‐two normal women (18–25 years old) and 8 patients with hypogonadotrophic hypogonadism (2 men with Kallmann's syndrome and 6 women with anorexia nervosa).

DESIGN

Serum LH levels in the 22 subjects (reference population) were monitored at 10‐minute intervals over an 8‐hour period (1000–1800 h) during medium–late follicular phase. In 7 of these subjects, serum LH levels were monitored in their next medium–late follicular phase while L‐5‐hydroxytryptophan was administered at hourly intervals from 1000 to 1800 h; the peripheral conversion of L‐5‐hydroxytryptophan to serotonin was inhibited by 150 mg of benserazide at 0930 and 1430 h. To investigate whether, in the absence of GnRH, L‐5‐hydroxytryptophan can release LH, two patients with Kallmann's syndrome were monitored over a 7‐hour period and 6 patients with anorexia nervosa over a 9‐hour period. After a 2.5 hour control period the subjects received 150 mg of benserazide, and pulsatile L‐5‐hydroxytryptophan (every 30 minutes in the Kallmann's patients and every 45 minutes in the subjects with anorexia nervosa).

MEASUREMENTS

LH pulses were identified and analysed according to number, amplitude, interpulse interval and pulse duration.

RESULTS

In the normal women, L‐5‐hydroxytryptophan increased pulse amplitude (mean ± SD: 3.02 ± 1.42 IU/l vs. 1.75 ± 0.98 IU/l before L‐5‐hydroxytryptophan and 1.90 ± 1.04 IU/l in the reference population; P < 0.01 in both cases), but had no significant effects on pulse duration, interpulse interval or number of pulses. L‐5‐hydroxytryptophan had no effect on LH in patients with Kallmann's syndrome. In the anorexia nervosa group, the mean serum LH level increased significantly after L‐5‐hydroxytryptophan (3.90 ± 2.46 IU/l vs. 3.06 ± 1.23 IU/l, P < 0.001) but, as in Kallmann's patients, the three women in this group without residual LH pulsatility did not respond to L‐5‐hydroxytryptophan.

CONCLUSION

Pulsatile administration of L‐5‐hydroxytryptophan increases LH pulse amplitude in the follicular phase of normal women. In the absence of GnRH, L‐5‐hydroxytryptophan does not stimulate pituitary LH secretion.
Effects of prolonged bisphosphonate therapy and its discontinuation on bone mineral density in post‐menopausal osteoporosis
Authors: Orr‐Walker Brandon , Wattie Diana J. , Evans Margaret C. , Reid Ian R.
Published: November 2003

OBJECTIVE The bisphosphonates have proven efficacy in the management of post‐menopausal osteoporosis. However, the benefits of prolonged (<2 years) administration and the effects of discontinuation of bisphosphonate treatment are not clear.

DESIGN We have previously reported a 2‐year, randomized, double‐blind, placebo‐controlled trial of pamidronate therapy (150mg/day) in women with established post‐menopausal osteoporosis. We now report the bone mineral density (BMD) changes in those women who continued for a third year of active treatment and were then observed off therapy for a further 12 months.

PATIENTS Twenty‐two women (mean age 66 years) continued on pamidronate in year 3, and in 16 of these the effects of subsequent discontinuation of therapy for 12 months were studied.

MEASUREMENTS BMD was measured in the total body, lumbar spine and proximal femur using a Lunar DPX‐L dual‐energy, X‐ray absorptiometer.

RESULTS The third year of therapy with pamidronate was associated with a significant further gain in BMD only at the lumbar spine (2.1±0.8%, P=0.003), resulting in a total gain of 9.5±1.0% at that site over 3 years of treatment. In the total body, BMD tended to decline (−0.6±0.3%) in year 3. One year after discontinuation of pamidronate, there were significant losses of BMD in the total body (−1.9±0.3%, P<0.0001) and femoral trochanter (−2.7±0.9%, P=0.01), and non‐significant changes at the lumbar spine (−0.9±0.8%), femoral neck (−0.5±1.6%), and Ward's triangle (−2.9±3.7%). By the end of one year off therapy, BMD was greater than baseline only in the lumbar spine (71±1.1%, P<0.0001) and femoral trochanter (4.5±1.88%, P<0.03). In the total body, BMD was 0.3±0.7% below the values at the trial’s inception (P=0.7).

CONCLUSIONS These data demonstrate that the rate of bone gain associated with bisphosphonate use slows over time, and that significant bone loss follows withdrawal of these agents. These findings have important implications for the duration of use of these novel drugs in the therapy of osteoporosis and suggest a need for close observation following their discontinuation.
Increased cerebrovascular mortality in patients with hypopituitarism
Authors: Bülow Birgitta , Hagmar Lars , Mikoczy Zoli , Nordström Carl‐Henrik , Erfurth Eva Marie
Published: November 2003

OBJECTIVE An increased prevalence of atherosclerosis has been shown among patients with hypopituitarism. The aim of the present study was to assess whether patients with hypopituitarism experience increased cardiovascular, in particular cerebrovascular, mortality.

DESIGN AND PATIENTS Retrospective cohort study of mortality, 1952–1992, in 344 patients, of whom 130 were female, receiving conventional hormone replacement for hypopituitarism following neurosurgery for pituitary tumours. The general population in the catchment area of southern Sweden from which the patients were recruited constituted the reference population. Expected mortality was obtained from cause, sex, calendar year, and 5‐year age‐specific death rates for the area.

RESULTS Increased mortality from cerebrovascular disease (standardized mortality ratio (SMR) 3.39; 95% CI 2.27–4.99) was the main contributor to the increased overall cardiovascular mortality (SMR 1.75; 95% CI 1.40–2.19). The increase in mortality from cardiac diseases was much smaller (SMR 1.41; 95% CI 1.04–1.88). The risk for cerebrovascular death was higher in women (SMR 4.91) than in men (SMR 2.64). The relative risk for cerebrovascular death was independent of the time interval since diagnosis of pituitary insufficiency, but was greater in subjects diagnosed at an earlier age (<55 years). No increased mortality in malignant tumours was observed (SMR 0.95; 95% CI 0.60–1.48).

CONCLUSION The increased cerebrovascular mortality may be due to GH deficiency, or to long‐term lack or inadequacy of substitution for other pituitary hormones. The observations that an early onset of pituitary insufficiency and female sex are predictors for a high risk for cerebrovascular mortality merit particular attention when treating this group of patients.
Time domain ultrasonography – a reliable method of percutaneousvolume flow measurement in large arteries
Authors: Länne T. , Solvig J. , Eriksson A. , Olofsson P. Å. , Marsal K. , Hansen F.
Published: November 2003

The estimation of blood flow inarteries is important in the study of the (patho)physiology of the circulatory system. However,non‐invasive techniques using pulsed Doppler ultrasound have so far shown potentially largeerrors. The aim of this study was to evaluate the precision and variability of a newly developednon‐invasive ultrasonic system based on time domain processing, CVI (Philips). In vitro measurement of blood flow was conducted on a phantom with an elastic silicon tube.Both constant and pulsatile flow were tested at increasing flow levels, and pulsatile flowmeasurements were performed at three different pulse rates at each flow level. Furthermore,fixed and hand‐held probes were compared. In vivo measurements of blood flowwere conducted on the common carotid artery of seven volunteers. The intra‐ and inter‐observer variability was evaluated. In vitro measurements with fixed transducer andcontinuous flow showed an inaccuracy of 3·5%. Pulsatile flow showed nodifference between measurements at the three different pulse rates (P=0·69), and the overall inaccuracy of pulsatile measurements was2·5%. Pulsatile flow was more accurately measured than continuous flow (P<0·01). No difference was seen between fixed and hand‐heldtransducers (P=0·26). In vivo, the intra‐observervariability was 25 ml min−1 (CV 7·8%), and theinterobserver variability was 35 ml min−1 (CV 10·9%).CVI is a promising non‐invasive new technique for flow measurements in arteries that givescorrect data with good reproducibility in vitro, as well as in healthy common carotidarteries in vivo.
The static pressure–volume relationship of the respiratory systemdetermined with a computer‐controlled ventilator
Authors: Svantesson C. , Drefeldt B. , Jonson B.
Published: November 2003

The pressure–volume relationship of the respiratorysystem offers a guide‐line for setting of ventilators. The occlusion method for determination of thestatic elastic pressure–volume (Pelst/V) relationship isused as a reference and the aim of the study was to improve it with respect to time consumptionand precision of recording and analysis. The inspiratory Pelst/Vcurve was determined with a computer‐controlled ventilator using its pressure and flow sensors.During an automated procedure, an operator‐defined volume history preceded each of a numberof study breaths. These were interrupted at different volumes evenly distributed over a predefinedvolume interval. Total positive end‐expiratory pressure (PEEP) was measured and could beseparated into its components, external PEEP and auto‐PEEP. The volume relationship betweenthe curve and the current tidal volume was defined. An analytical method for definition of a linearsegment of the Pelst/V curve and determination of itscompliance is presented. In eight healthy human anaesthetized subjects duplicate Pelst/V curves were studied with respect to compliance and the position alongthe volume axis of the linear segment. The difference in compliance between measurements was1·6±1·3 ml cmH2O−1 or1·2±0·9%. The position of the curve differed betweenmeasurements by 15±10 ml or by 1·1±0·9%. In a patientwith acute lung injury the feasibility of applying a numerical method for a more detaileddescription of the Pelst/V curve was illustrated.
Costs and benefits of cervical screening. I. The costs of the cervical screening programme
Authors: WAUGH N. , SMITH I. , ROBERTSON A. , REID G. S. , HALKERSTON R. , GRANT A.
Published: November 2003

In 1991, the average total Health Service cost of a cervical smear, including follow up at the colposcopy clinic, was almost £22.70 in the Perth and Kinross district of Scotland. The average cost per colposcopy clinic visit was £30. The main cost elements were in general practice (55% of total) and the laboratory (33%), and most of the cost was for staff time.
Regulation of platelet‐activating factor production in gastric epithelial cells
Authors: SOBHANI I. , DENIZOT Y. , MOIZO L. , LAIGNEAU J. P. , BADO A. , LABOISSE C. , BENVENISTE J. , LEWIN M. J. M.
Published: November 2003

The authors have previously reported that platelet‐activating factor (PAF), a phospholipid mediator with potent proinflammatory activities, is produced in the gastric mucosa and stimulates gastric acid secretion in humans and animals. In the present study they used the human gastric tumour cells HGT1 (clone 6) to examine whether PAF production is regulated by neuromediators. PAF was extracted by ethanol and assayed by the washed platelet aggregation test. HGT1 cells produced PAF spontaneously (110 ± 20 pg 106 cells). The addition of vasoactive intestinal peptide (VIP; 10−9 to 10−7 mol L−1) or of histamine (10−5 to 10−3 mol L−1) increased PAF production by three‐ to fivefold, while the addition of carbachol (10−7 to 10−4 mol L−1) increased PAF production up to sevenfold. PAF production was also increased up to 10‐ to 13‐fold, in a dose‐ and time‐dependent manner, by the addition of calcium and two‐ to threefold by the addition of phorbol myristate acetate (PMA; 10−7 to 10−5 mol L−1). However, the addition of dibutyryl cyclic AMP (dBcAMP; 10−6 to 10−4 mol L−1) was without any effect. This is the first report showing PAF production by gastric epithelial cells in response to histamine, VIP and carbachol. Furthermore, the findings are consistent with a central role of calcium in this production. The results of this study, together with those of previous studies from the authors’ laboratory, support the hypothesis that PAF is a physiological mediator of gastric acid secretion.
Objective determination of pH thresholds in the analysis of 24 h ambulatory oesophageal pH monitoring
Authors: WEUSTEN B. L. A. M. , ROELOFS J. M. M. , AKKERMANS L. M. A. , VANBERGE‐HENEGOUWEN G. P. , SMOUT A. J. P. M.
Published: November 2003

In 24 h oesophageal pH monitoring, pH 4 is widely but arbitrarily used as the threshold between reflux and non‐reflux pH values. The aim of the study was to define pH thresholds objectively, based on Gaussian curve fitting of pH frequency distributions. Single‐channel 24 h oesophageal pH monitoring was performed in 26 healthy volunteers and 26 patients with pathological gastro‐oesophageal reflux, and five‐channel pH‐metry was performed in 14 healthy volunteers and 14 patients. The calculated pH thresholds varied between healthy volunteers from 5.0 to 6.4 in the upright position and from 4.5 to 5.7 in the supine position, but were constant between different oesophageal recording sites. In 15 and nine patients (single‐channel and five‐channel pH‐metry respectively), pH thresholds could not be determined at the distal oesophageal sites. However, the calculated pH thresholds in the proximal oesophagus were in the same range as in the control subjects. The authors conclude that the use of the conventional threshold of pH 4 leads to underestimation of the extent of gastro‐oesophageal reflux, but are reluctant to advocate the use of higher thresholds in clinical practice.