Nuclear heterogeneity is prevalent in high-quality fractionated human sperm cells typically used for assisted conception

STUDY QUESTION

What is the nuclear heterogeneity of high-density purified human spermatozoa typically used for IVF purposes.

SUMMARY ANSWER

The data show that while density gradient separation has improved the overall sperm population, there is still a large degree of nuclear heterogeneity within these cells.

WHAT IS KNOWN ALREADY

Chromomycin A3 (CMA3) is an important DNA binding fluorochrome for the assessment of male-factor fertility. It is typically used to predict IVF outcomes on entire sperm ejaculates with very high receiver operating characteristic. Here we used CMA3 to characterise typical populations of human spermatozoa that would be used for IVF purposes after density gradient separation.

STUDY DESIGN, SIZE, DURATION

We compared the intensity of CMA3 binding within high-dense sperm populations obtained from men. Binding heterogeneity was confirmed through fluorescence microscopy and FACS analysis independently. We also looked at CMA3 staining directly with head morphology in this sperm population. Finally, we looked at electron micrographs of nuclear heterogeneity (vacuoles, chromatin compaction) of spermatozoa following density gradient sorting of CMA3-stained cells.

PARTICIPANTS/MATERIALS, SETTING, METHODS

We used sperm donors who had fathered one or more children. Semen was collected after 2 days abstinence and purified over Percoll gradients. Only the high-quality spermatozoa, the same used for assisted conception, were then used. Cells were stained with CMA3 and sorted using FACS. Following this, electron micrographs were used to assess nuclear heterogeneity of CMA3-dependent sorted spermatozoa.

MAIN RESULTS AND THE ROLE OF CHANCE

CMA3 staining occurs within morphologically normal as well as abnormal spermatozoa. High-intensity CMA3-stained sperm possessed large vacuoles that were not seen in the low-CMA3 population. In addition, the high-CMA3 stained cells possess higher amounts of nuclear granulation.

LIMITATIONS, REASONS FOR CAUTION

The present study only describes the issues within the chromatin of these cells and does not suggest an alternate selection technique.

WIDER IMPLICATIONS OF THE FINDINGS

CMA3 is one of the better reported prognostic assays in predicting pregnancy outcomes, especially in cases where the male is at fault. However, it is clear that even in fractionated populations of human spermatozoa, there are sperm cells that are morphologically normal yet possess high levels of CMA3 staining and chromatin granulation. The implication of this is that the embryologist, whom selects on the basis of sperm morphology, may choose a cell with poor chromatin, which may lead to poor embryo outcomes.

STUDY FUNDING/COMPETING INTEREST(S)

The project was funded by the National Health and Medical Research council, APP1118943. The authors have no conflict of interest to declare.

TRIAL REGISTRATION NUMBER

N/A.

Head and neck target delineation using a novel PET automatic segmentation algorithm

PURPOSE

To evaluate the feasibility and impact of using a novel advanced PET auto-segmentation method in Head and Neck (H&N) radiotherapy treatment (RT) planning.

METHODS

ATLAAS, Automatic decision Tree-based Learning Algorithm for Advanced Segmentation, previously developed and validated on pre-clinical data, was applied to ¹⁸F-FDG-PET/CT scans of 20 H&N patients undergoing Intensity Modulated Radiation Therapy. Primary Gross Tumour Volumes (GTVs) manually delineated on CT/MRI scans (GTVp_CT/MRI), together with ATLAAS-generated contours (GTVp_ATLAAS) were used to derive the RT planning GTV (GTVp_final). ATLAAS outlines were compared to CT/MRI and final GTVs qualitatively and quantitatively using a conformity metric.

RESULTS

The ATLAAS contours were found to be reliable and useful. The volume of GTVp_ATLAAS was smaller than GTVp_CT/MRI in 70% of the cases, with an average conformity index of 0.70. The information provided by ATLAAS was used to grow the GTVp_CT/MRI in 10 cases (up to 10.6mL) and to shrink the GTVp_CT/MRI in 7 cases (up to 12.3mL). ATLAAS provided complementary information to CT/MRI and GTVp_ATLAAS contributed to up to 33% of the final GTV volume across the patient cohort.

CONCLUSIONS

ATLAAS can deliver operator independent PET segmentation to augment clinical outlining using CT and MRI and could have utility in future clinical studies.

The response to testosterone undecanoate in men with type 2 diabetes is dependent on achieving threshold serum levels (the BLAST study)

BACKGROUND

The association between testosterone deficiency and insulin resistance in men with type 2 diabetes is well established. Current Endocrine Society and European Association of Urology guidelines recommend the measurement of testosterone levels in all men with type 2 diabetes and in men suffering from erectile dysfunction. It is recognised that a range of physical symptoms appear as the testosterone level falls but few studies have addressed the threshold at which symptoms improve with physiological replacement. We report the first double-blind placebo-controlled study conducted exclusively in a male type 2 diabetes population to assess the metabolic changes with testosterone replacement.

METHODS

The type 2 diabetes registers of seven general practices were screened to establish the prevalence of low testosterone and the associations with diabetes control. Of 550 eligible patients approached, 488 men (mean age 62.6) consented to take part in screening with a morning testosterone level, assessed between 8 and 11 am. This identified 211 patients for a double-blind placebo-controlled study of long acting testosterone undecanoate (TU) 1000 mg lasting 30 weeks followed by 52 weeks of open label use. The population was divided into a SEVERE group with either total testosterone (TT) of 8 nmol/l or less or free testosterone (FT) 180 pmol/l or less or a MILD group with TT 8.1-12 nmol/l or FT 181-250 pmol/l.

RESULTS

Men in the SEVERE group increased mean through TT from 7.73 nmol/l at baseline to 9.93 at 30 weeks and the MILD group from 10.47 to 11.94. The SEVERE group showed marked improvement in sexual function, but no significant improvement in metabolic parameters. The MILD group showed no improvement in sexual function, but significant improvement in weight, body mass index, waist circumference and Hospital Anxiety and Depression Scale. Improvement was seen in all parameters during 52 weeks open label treatment where trough TT levels approached 15 nmol/l. Baseline prostate-specific antigen (PSA) was lower in the SEVERE group and increased with TU for 30 weeks and then stabilised. There was no increase in PSA with treatment in the MILD group.

CONCLUSIONS

Testosterone undecanoate significantly improves sexual parameters and Ageing Male Symptom Score, but not metabolic factors at 30 weeks in men with SEVERE testosterone deficiency syndrome (TDS). In men with MILD TDS, significant improvements in metabolic but not sexual parameters were seen, suggesting that there are threshold levels for response to testosterone replacement therapy and that trials of therapy need to achieve sustained therapeutic levels to be effective. PSA showed minor rises, but only for 30 weeks in the SEVERE group.

Dietary competition between the alien Asian Musk Shrew (Suncus murinus) and a re-introduced population of Telfair's Skink (Leiolopisma telfairii)

Re-introduction of rare species to parts of their historical range is becoming increasingly important as a conservation strategy. Telfair's Skinks (Leiolopisma telfairii), once widespread on Mauritius, were until recently found only on Round Island. There it is vulnerable to stochastic events, including the introduction of alien predators that may either prey upon it or compete for food resources. Consequently, skinks have been introduced to Ile aux Aigrettes, another small Mauritian island that has been cleared of rats. However, the island has been invaded by Asian Musk Shrews (Suncus murinus), a commensal species spread by man well beyond its natural Asian range. Our aim was to use next-generation sequencing to analyse the diets of the shrews and skinks to look for niche competition. DNA was extracted from skink faeces and from the stomach contents of shrews. Application of shrew- and skink-specific primers revealed no mutual predation. The DNA was then amplified using general invertebrate primers with tags to identify individual predators, and then sequenced by 454 pyrosequencing. 119 prey MOTUs (molecular taxonomic units) were isolated, although none could be identified to species. Seeding of cladograms with known sequences allowed higher taxonomic assignments in some cases. Although most MOTUs were not shared by shrews and skinks, Pianka's niche overlap test showed significant prey overlap, suggesting potentially strong competition where food resources are limited. These results suggest that removal of the shrews from the island should remain a priority.

Services for erectile dysfunction in the UK - a 12-month review of referrals to a west Midlands NHS clinic

INTRODUCTION

Few studies have addressed the health economics of the provision of services for sexual dysfunction within the National Health Service.

AIM

To evaluate the referral patterns, workload and prescribing costs in secondary care resulting from government guidance on erectile dysfunction (ED).

METHOD

A review of 324 consecutive referral letters to the Good Hope Hospital Erectile Dysfunction Clinic was conducted to assess the purpose of referral. Prescribing data and costs were assessed over the same 2-year period.

RESULTS

Severe distress was the main reason for referral in 54% of referrals. Long term prescribing according to government guidance doubled the cost of care and created an unsustainable increase in clinic and pharmacy workload.

CONCLUSIONS

Existing regulations designed to control costs of ED therapy have created health inequalities, waste of resources and have increased the overall cost of care.

Interaction of the antimicrobial peptide melimine with bacterial membranes

Melimine is a novel cationic peptide possessing broad-spectrum antimicrobial activity that is retained when attached to a surface, suggesting that interactions with bacterial membranes may be of primary importance to its activity. The effects of alterations in the environment on the conformation of melimine were investigated using circular dichroism and fluorescence spectra in membrane-mimetic solvents. Furthermore, the interactions of melimine with bacterial membranes of Pseudomonas aeruginosa and Staphylococcus aureus were examined using scanning electron and fluorescence microscopy, and perturbation of membrane integrity was tested by measurement of melimine-mediated diSC(3)-5 dye release from bacterial cells. Melimine has a predominantly random coil conformation that adopts a helical fold when exposed to organic solvents. However, when it is solubilised in micelles of sodium dodecyl sulphate, which are bacterial membrane-mimetic, the alpha-helical content increases to ca. 35-40%. A major effect of melimine was on the integrity of the cytoplasmic membrane both for P. aeruginosa and S. aureus. However, for P. aeruginosa the rapid loss of cytoplasmic membrane integrity correlated directly with loss of cell viability, whilst for S. aureus maximal dye release was obtained at concentrations where there was no significant loss of viability. There have been few studies to date investigating differences in the action of cationic peptides towards Gram-positive and Gram-negative bacteria. Consequently, further investigation of these mechanistic differences may allow more refined targeting of increasingly difficult-to-treat bacterial infections and/or further inform design of novel peptides with improved broad-spectrum activity.

Organisational infrastructures to promote evidence based nursing practice

BACKGROUND

The purpose of this systematic review is to determine to what extent organisational infrastructures are effective in promoting the implementation of high quality research evidence on the effectiveness of nursing interventions.

OBJECTIVES

To identify and summarize rigorous evaluations of organisational infrastructure developments aimed at promoting evidence based nursing practice.

SEARCH STRATEGY

We searched: The Cochrane Library, MEDLINE, EMBASE, CINAHL, SIGLE, HEALTHLINE, National Research Register, Nuffield Database of Health Outcomes, NIH Databases up to August 2002. We hand searched the Journal of Advanced Nursing, Applied Nursing Research and Journal of Nursing Administration (to 1999), and checked the reference lists of articles obtained. We contacted experts in the field and relevant Internet groups.

SELECTION CRITERIA

Randomized controlled trials, controlled clinical trials and interrupted times series studies of an entire or identified component of an organisational infrastructure development aimed at promoting effective nursing interventions. The participants were health care organisations comprising nurses, midwives and health visitors in hospital and community settings.

DATA COLLECTION AND ANALYSIS

All identified papers were screened independently for relevance, design and outcome by two reviewers.

MAIN RESULTS

No studies were sufficiently rigorous to be included in this systematic review. Seven case study evaluations were identified but excluded from the review because of poor design and lack of controls.

REVIEWER'S CONCLUSIONS

1. There are no clear implications for practice.2. Several conceptual models on organisational processes to promote evidence based practice have been described in published papers, and a number of organisational infrastructural interventions have been described in published papers. None have been evaluated properly. The next step in this field should be to conduct well planned evaluations of well planned interventions. 3. Interrupted and Complex Interrupted Times Series (ITS and CITS) designs should be adopted as a useful alternative to randomized controlled trials where such trials would be impractical. The health service cost of any infrastructure developments should be assessed in any evaluation. If possible, patient outcomes should be measured directly.

The gene encoding alsin, a protein with three guanine-nucleotide exchange factor domains, is mutated in a form of recessive amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) and primary lateral sclerosis (PLS) are neurodegenerative conditions that affect large motor neurons of the central nervous system. We have identified a familial juvenile PLS (JPLS) locus overlapping the previously identified ALS2 locus on chromosome 2q33. We report two deletion mutations in a new gene that are found both in individuals with ALS2 and those with JPLS, indicating that these conditions have a common genetic origin. The predicted sequence of the protein (alsin) may indicate a mechanism for motor-neuron degeneration, as it may include several cell-signaling motifs with known functions, including three associated with guanine-nucleotide exchange factors for GTPases (GEFs).

The gene encoding alsin, a protein with three guanine-nucleotide exchange factor domains, is mutated in a form of recessive amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) and primary lateral sclerosis (PLS) are neurodegenerative conditions that affect large motor neurons of the central nervous system. We have identified a familial juvenile PLS (JPLS) locus overlapping the previously identified ALS2 locus on chromosome 2q33. We report two deletion mutations in a new gene that are found both in individuals with ALS2 and those with JPLS, indicating that these conditions have a common genetic origin. The predicted sequence of the protein (alsin) may indicate a mechanism for motor-neuron degeneration, as it may include several cell-signaling motifs with known functions, including three associated with guanine-nucleotide exchange factors for GTPases (GEFs).

Effects of exogenous interleukin-6 during Pseudomonas aeruginosa corneal infection

Lack of interleukin-6 (IL-6) during Pseudomonas aeruginosa corneal infection leads to more severe disease with changes in neutrophil recruitment. Exogenous IL-6 leads to increased efficiency of neutrophil recruitment and reduced bacterial loads in corneal infection in both IL-6 gene knockout and wild-type mice. This may be mediated by IL-6 increasing the production of corneal macrophage inflammatory protein 2 and intercellular cell adhesion molecule 1. We conclude that effective recruitment of neutrophils into the cornea is dependent on the production of IL-6 and that early augmentation of IL-6 may be protective in corneal infection.

Differential interleukin-6 mRNA expression in Nippostrongylus brasiliensis infection of susceptible and resistant strains of mice

Intestinal parasitic infection is still a major problem in humans and animals, yet host immunity against gut parasitic infection remains partially understood. Eosinophilia and mastocytosis are features of such infection that have been shown to be genetically controlled. The expression of IL-6 is detected in eosinophils, mast cells and neutrophils and may be responsible for the regulation of leucocytes at infective sites. The relationships between IL-6 expression, eosinophilia, mastocytosis and host immunity remain unclear. In the present report, a close correlation between IL-6 mRNA+ cells, eosinophilia, mastocytosis and worm expulsion is demonstrated, which may indicate a role for IL-6 in regulation of host immunity against intestinal parasite infection.

Multiple transcripts of the human Cu,Zn superoxide dismutase gene

We have identified five alternatively spliced transcripts of the gene for human Cu,Zn superoxide dismutase (SOD1), a causative gene for autosomal dominant amyotrophic lateral sclerosis (ALS). The splice variants of wild-type or mutant SOD1 were expressed in a tissue-specific manner; therefore, their expression may be regulated to modify SOD1 function. In addition, the expression in the brain implies that variants may play a role in the nervous system, the region involved in ALS. Immunoblot study of HeLa cells transfected with two variants encoding C-terminal truncated proteins did not show the proteins of expected size. However, this observation is consistent with the previous study of C-terminal truncated mutant proteins that cause ALS, suggesting that both variant and mutant proteins may share certain properties, such as instability or insolubility in the cytosol. These findings suggest that the splice variants may contribute to a physiological function of SOD1 or to a pathological mechanism in ALS.

Protein microanalysis of animal tears

Sub-microlitre volumes of normal koala, mouse, dog, rat and cat tears were fractionated using size exclusion-high performance liquid chromatography (SE - HPLC), giving reproducible profiles which were different for each species. Microlitre volumes of tears were also fractionated using sodium dodecylsulphate-polyacrylamide gel electrophoresis (SDS - PAGE), resulting in good separation of individual tear proteins with a species specific distribution. Tears from koalas with conjunctivitis and mice with keratitis were similarly examined and showed mostly quantitative changes. These simple, rapid techniques gave reproducible results and, in contrast to conventional separation techniques, used easily obtainable volumes (as little as 0.75 microl) of tears. Their expansion could allow isola tion, identification and quantitation of individual tear components, enabling effective investigation of changes occurring in disease.

Genetic disorders of motor neurons

Disorders of the motor neuron are etiologically and clinically heterogeneous and cause serious disability and death. Whereas mendelian inheritance can be demonstrated in a subset of these disorders, the genetic contribution to the sporadic forms of motor neuron degeneration are not well understood. In families with spinal muscular atrophy, Kennedy disease and amyotrophic lateral sclerosis, genetic linkage analysis and positional cloning have proven to be extremely productive. The genetics of these neurodegenerative disorders are reviewed.

KC production in the cornea in response to Pseudomonas aeruginosa challenge

Pseudomonas aeruginosa can cause ulcerative bacterial keratitis. A feature of keratitis is the rapid infiltration of the avascular corneal stroma by neutrophils. KC is a potent neutrophil chemokine. The present study used a mouse model of ocular infection to assess the relationship between KC and inflammation in the cornea in response to challenge with a strain of P. aeruginosa causing keratitis. Low levels of KC mRNA and protein were detected by in situ hybridization and ELISA, respectively, in unchallenged corneas. Dramatically increased numbers of KC mRNA+ cells were present in P. aeruginosa strain 6294-challenged corneas. Expression of KC mRNA was found to be up-regulated in the corneal epithelium in response to wounding alone. The KC mRNA+ cells were located in the epithelium and corresponding to infiltrating neutrophils cells in the stroma. Quantification of KC protein at different time points showed peak levels at 8 h of bacterial challenge. These results suggest that KC may be involved with the regulation of leucocyte infiltration early during bacterial keratitis.

Van Gogh and lithium. Creativity and bipolar disorder: perspective of a lawyer/parliamentarian

Neil Cole has been the State Member for Melbourne since 1988 and was a Melbourne City Councillor for 3 years. He was the first Member of Parliament in Australia to confront the stigma of mental illness by publicly acknowledging his manic depression. Prior to entering parliament he was a Community Lawyer at Flemington Community Legal Service for 7 years. Neil was National Convenor of the Nuclear Free Zone Secretariat (1986-88), Chairperson Joint Parliamentary Economic and Budget Review Committee (1991-92) and Shadow Attorney General from 1992 to 1995. He is Deputy Chair of the Joint Parliamentary Law Reform Committee of the Victorian Parliament. Neil has written three plays with 'Alive at Williamstown Pier' being his first. He is currently employed as a consultant to the Mental Health Research Institute at Royal Park Melbourne.

Expression of interleukin-6 in the cornea in response to infection with different strains of Pseudomonas aeruginosa

Strains of Pseudomonas aeruginosa causing keratitis can be either cytotoxic (6206) or invasive (6294), while a strain (Paer1) causing contact lens-induced acute red eye has been shown to be neither. In situ hybridization was used to examine the location and identity of cells expressing interleukin-6 (IL-6) mRNA in the murine cornea and changes in expression in response to infection with different strains of P. aeruginosa. The number of IL-6-positive cells was determined by image analysis. IL-6 protein levels were measured by an enzyme-linked immunosorbent assay. BALB/c mice were challenged by use of the wounded-cornea model with P. aeruginosa 6294, 6206, or Paer1 (2 x 10(6) CFU). At time intervals up to 24 h, postchallenge corneal tissue was probed for IL-6 mRNA. IL-6 mRNA expression was rapidly elevated in the epithelium in response to strains 6294 and 6206. At the conclusion of the experiments, infiltrating inflammatory cells also stained positively for IL-6 mRNA. In contrast, corneas challenged with strain Paer1 showed significant upregulation of IL-6 mRNA only at 4 h postchallenge. Three distinct patterns of IL-6 mRNA expression in the mouse cornea occur in response to these three ocular isolates of P. aeruginosa. The data obtained for mRNA expression in the cornea for all three strains of P. aeruginosa correlated well with IL-6 protein analysis of whole-eye homogenates. Differences in the cytokine responses to these strains correlate with differences in the pathology associated with each strain and may offer an opportunity to develop strategies for the improved management of ocular inflammation.

TNF-alpha production in the cornea in response to Pseudomonas aeruginosa challenge

Pseudomonas aeruginosa can cause ulcerative bacterial keratitis or contact lens-induced acute red eye (CLARE) in humans. The present study used a mouse model of ocular infection and inflammation to examine the relationship between TNF-alpha and inflammation in the cornea in response to challenge with either a strain of P. aeruginosa causing keratitis or a CLARE strain. Constitutive TNF-alpha mRNA was detected in the epithelium, mainly towards the periphery. After infection with the keratitis-inducing strain (6294), TNF-alpha expression was elevated four-fold by 24 h post-challenge. No detectable induction of TNF-alpha mRNA was seen with CLARE strain (Paer1) challenge at any time point. The TNF-alpha protein production detected by ELISA showed a corresponding pattern to the mRNA expression, which also correlated with pathological changes. These results suggest that invasive strains of P. aeruginosa create greater pathological changes as a result of elevated TNF-alpha production, which contributes to inflammation during keratitis in vivo.

Different strains of Pseudomonas aeruginosa isolated from ocular infections or inflammation display distinct corneal pathologies in an animal model

PURPOSE

The present investigation sought to define the responses of mouse eyes to challenge with three different strains of P. aeruginosa isolated from human corneas or contact lenses: two different strains produced an ulcerative keratitis, and one strain produced contact lens-induced acute red eye (CLARE).

METHODS

The corneas of BALB/c mice were inoculated with three different strains of P aeruginosa. The strains were allowed to interact with the corneas for up to 24 h. In addition, strain Paerl, isolated from CLARE, was subjected to in vitro assays to measure its ability to invade corneal epithelial cells, or to produce cytotoxicity in these cells. Both these assays used cultured rabbit corneal epithelial cells.

RESULTS

Both MK isolates were able to infect the corneas of mice, but the CLARE isolate was non-infective. The predominant response to infection with the cytotoxic strain was severe corneal edema and infiltration of the corneal stroma with polymorphonuclear leukocytes (PMNs). The predominant response with the invasive MK isolate was corneal ulceration and infiltration with PMNs. The CLARE strain produced only low levels of PMN infiltration. In in vitro assays the CLARE strain was non-invasive and non-cytotoxic.

CONCLUSIONS

This study has identified that P. aeruginosa produces at least three different types of corneal pathology and that not all strains are able to infect mouse corneas.

Scaling of intrinsic contractile properties and myofibrillar protein composition of fast muscle in the fish myoxocephalus scorpius L

Contractile properties were determined for fast muscle fibres from short-horn sculpin (Myoxocephalus scorpius L.) ranging from 5 to 35 cm total body length (L) and from 2.0 to 758 g body mass. Maximum unloaded shortening velocity (V0) decreased with increasing body size, scaling as 19.5L-0.34, and isometric twitch activation and tetanus relaxation times became longer, scaling as 12.0L0.31 and 19. 5L0.42 respectively. Myofibrillar Mg2+/Ca2+-ATPase activity scaled as 2.51L-0.28. In order to investigate the mechanisms underlying the scaling of contractile properties, myofibrillar protein composition and I filament lengths were determined. One-dimensional SDS-PAGE and two-dimensional isoelectric focusing/non-equilibrium isoelectric focusing-PAGE revealed no differences in the myofibrillar protein isoforms of myosin light chains, actin, tropomyosin, troponin-T and troponin-C in fish of differing body size. Peptide maps of purified myosin heavy chains digested with eight different proteolytic enzymes were also similar in all fish examined. Three isoforms of troponin-I were present in fish less than 20 cm in total length with relative molecular masses of 17 (TnIf3), 22 (TnIf2) and 23 (TnIf1). The ratio of TnI isoforms varied with body length, and only TnIf3 was present in fish greater than 28 cm total length. The length of I filaments was independent of body length. Thus, although the expression of TnI isoforms changes during growth, the underlying mechanism responsible for increased shortening velocity with decreased body size remains unknown. <P>

Embryonic temperature modulates muscle growth characteristics in larval and juvenile herring

The influence of embryonic and larval temperature regime on muscle growth was investigated in Atlantic herring (Clupea harengus L.). Eggs of spring-spawning Clyde herring were incubated at 5 degrees C, 8 degrees C or 12 degrees C until hatching and then reared until after metamorphosis at rising temperatures to simulate a seasonal warming. Metamorphosis to the juvenile stage was complete at 37 mm total length (TL), after an estimated 177 days as a larva at 5 degrees C, 117 days at 8 degrees C and 101 days at 12 degrees C. Growth rate and the development of median fins were retarded in relation to body length at 5 degrees C compared with 8 degrees C and 12 degrees C. Between hatching (at 8-9 mm TL) and 16 mm TL, there was a threefold increase in total muscle cross-sectional area, largely due to the hypertrophy of the embryonic red and white muscle fibres. The recruitment of additional white muscle fibres started at approximately 15 mm TL at all temperatures, and by 37 mm was estimated to be 66 fibres day-1 at 5 degrees C and 103 fibres day-1 at 8 degrees C and 12 degrees C. Peptide mapping studies revealed a change in myosin heavy chain composition in white muscle fibres between 20 and 25 mm TL. Embryonic red muscle fibres expressed fast myosin light chains until 24-28 mm TL at 5 degrees C and 22 mm TL at 12 degrees C, and new red fibres were added at the horizontal septum starting at the same body lengths. Following metamorphosis, the total cross-sectional area of muscle was similar at different temperatures, although the number of red and white fibres per myotome was significantly greater at the warmest than at the coldest regime. For example, the mean number of white muscle fibres per myotome in 50 mm TL juveniles was calculated to be 23.4 % higher at 12 degrees C (12 065) than at 5 degrees C (9775). In other experiments, spring-spawning (Clyde) and autumn-spawning (Manx) herring were reared at different temperatures until first feeding and then transferred to ambient seawater temperature and fed ad libitum for constant periods. These experiments showed that, for both stocks, the temperature of embryonic development influenced the subsequent rate of muscle fibre recruitment and hypertrophy as well as the density of muscle nuclei. Labelling experiments with 5'-bromo-2-deoxyuridine showed that both the hypertrophy and recruitment of muscle fibres involved a rapidly proliferating population of myogenic precursor cells. The cellular mechanisms underlying the environmental modulation of muscle growth phenotype are discussed.

Unravelling Golgi membrane traffic with green fluorescent protein chimeras

An important new tool for investigating how the Golgi receives cargo and maintains its integrity in the face of ongoing secretory traffic has emerged with the advent of green fluorescent protein (GFP) chimeras. GFP chimeras, which can be visualized in the unperturbed environment of a living cell, are being used in a wide variety of applications to study Golgi dynamics. These include time-lapse imaging, double-label and photobleach experiments. These studies are helping to clarify the steps involved in the formation, translocation and fate of transport intermediates associated with the Golgi complex, including the roles of cytoskeletal elements. They are also providing insights into mechanisms of protein retention and localization within Golgi membranes.

Golgi tubule traffic and the effects of brefeldin A visualized in living cells

The Golgi complex is a dynamic organelle engaged in both secretory and retrograde membrane traffic. Here, we use green fluorescent protein-Golgi protein chimeras to study Golgi morphology in vivo. In untreated cells, membrane tubules were a ubiquitous, prominent feature of the Golgi complex, serving both to interconnect adjacent Golgi elements and to carry membrane outward along microtubules after detaching from stable Golgi structures. Brefeldin A treatment, which reversibly disassembles the Golgi complex, accentuated tubule formation without tubule detachment. A tubule network extending throughout the cytoplasm was quickly generated and persisted for 5-10 min until rapidly emptying Golgi contents into the ER within 15-30 s. Both lipid and protein emptied from the Golgi at similar rapid rates, leaving no Golgi structure behind, indicating that Golgi membranes do not simply mix but are absorbed into the ER in BFA-treated cells. The directionality of redistribution implied Golgi membranes are at a higher free energy state than ER membranes. Analysis of its kinetics suggested a mechanism that is analogous to wetting or adsorptive phenomena in which a tension-driven membrane flow supplements diffusive transfer of Golgi membrane into the ER. Such nonselective, flow-assisted transport of Golgi membranes into ER suggests that mechanisms that regulate retrograde tubule formation and detachment from the Golgi complex are integral to the existence and maintenance of this organelle.

Potassium intake and cardiovascular reactivity in children with risk factors for essential hypertension

OBJECTIVES

Our study objectives were as follows: (1) to determine whether urinary excretion of potassium is lower in black than in white children, (2) to determine whether cardiovascular reactivity (CVR) varies inversely with dietary intake of potassium, and (3) to confirm that CVR is greater in black than in white children, and in children with a family history of hypertension than in those without such a history.

STUDY DESIGN

Baseline measurements included 24-hour urinary sodium, potassium, and creatinine levels and food intake (by questionnaire). Resting and stress blood pressure were measured during blood sampling, cold water foot immersion, and a video game before and after 1 week each of supplementation with potassium citrate, 1.5 mmol/kg per day, and placebo administered in random order.

RESULTS

Thirty-nine children aged 7 to 15 years were studied. White subjects had higher baseline excretion of potassium than black subjects (p < 0.001) and higher vegetable intake (p < 0.01), which were positively correlated (r = 0.53, p < 0.001). At baseline, the 24-hour urinary potassium/creatinine ratio varied inversely with diastolic CVR to the video game stressor in white children (r = -0.55, p = 0.02). Cardiovascular reactivity was not attenuated measurably by potassium supplementation compared with placebo. The CVR was greater in children with a family history of hypertension than in those without, but was not greater in black children than in white children.

CONCLUSIONS

The urinary potassium/creatinine ratio is higher in white than black children because their intake of vegetables is greater; dietary potassium intake may modulate CVR, particularly in white children with a family history of hypertension, but may need to be supplemented for more than 1 week to demonstrate attenuation of CVR; and a family history of hypertension may be a stronger predictor of enhanced CVR than is race.

High-dose cytosine arabinoside in the treatment of acute myeloid leukaemia

Cytosine arabinoside (Ara-C) has earned its recognition as the most important antileukaemic drug currently available for the treatment of acute myeloid leukaemia. Approximately 60-80% of patients less than 60 years of age can be expected to enter complete remission if treated with standard-dose Ara-C (100-200 mg/m2) in combination with an anthracycline. The efficacy of Ara-C appears clinically to be dose and schedule dependent. A 15-30 fold dose escalation in Ara-C can elicit a therapeutic response in patients who have previously failed treatment with standard-dose Ara-C or other anti-leukaemic drugs. The use of high-dose cytosine arabinoside (HDAC 3 gm/m2) appears rational based on cytosine pharmacology. Drug-scheduling is used to exploit drug synergy when HDAC is given in combination with asparaginase or fludarabine (+/- G-CSF) in a schedule-dependent fashion. Toxicity following Ara-C is also dose- and schedule-dependent. Central nervous system toxicity--particularly cerebellar dysfunction--although rare, is particularly serious because it may preclude further use of the drug. Older patients are particularly susceptible. This article will describe the rationale for and the value of HDAC alone or in combination with other cytotoxics in the treatment of acute myeloid leukaemia.

Temperature and developmental plasticity of muscle phenotype in herring larvae

Myogenesis, the expression of myofibrillar protein isoforms and the development of muscle innervation were investigated in Clyde herring (Clupea harengus L.) in two successive spawning seasons at temperatures ranging from 5 &deg;C to 15 &deg;C. Myotube formation occurred in a rostral to caudal progression at similar somite stages at all temperatures. Superficial mononuclear muscle pioneer fibres were present at the horizontal septum. Myofibrillogenesis was retarded with respect to somite stage at low temperatures; for example, by the 50-somite stage, myofibrils were observed in the muscle pioneers of the first 31 somites at 12 &deg;C, but only the first 20 somites at 5 &deg;C. In the electron microscope, the earliest stages of myofibril assembly were observed in the muscle pioneer cells and in a proportion of the multinucleated myotubes within the same somite. By the end of somitogenesis, the density of myofibrils in the rostral myotomes was much higher at 15 &deg;C than at 5 &deg;C. Embryonic isoforms of myosin light chain 2 (LC2), troponin I and troponin T were identified in the presumptive white muscle using two-dimensional gel electrophoresis. Expression of the embryonic isoforms was gradually switched off during the larval stages. The size range over which embryonic isoforms were present was inversely related to rearing temperature. For example, the adult pattern of myosin LC2 expression was established at 11 mm total length (TL) at 15 &deg;C, but not until 15 mm TL at 5 &deg;C. Acetylcholinesterase staining was apparent at the myosepta in 31-somite stage embryos at 15 &deg;C, but not until approximately the 40-somite stage at 5 &deg;C. The red muscle fibres of larvae were initially innervated only at their myoseptal ends. The temperature at which the red muscle fibres became multiply innervated was inversely related to body size, occurring at 12&shy;14 mm at 12 &deg;C, but not until 16&shy;19 mm at 5 &deg;C. We conclude that the temperature during early development determines the relative timing and degree of expression of the myogenic programme, resulting in significant phenotypic variation in the swimming muscles of the larval stages. Our results highlight a potential mechanism whereby early thermal experience could influence survival and hence the strength of particular year classes of fish.

Quantitative assessment of the association of the alpha-I fragment of spectrin with oligomers of intact spectrin

The alpha-I fragment of human spectrin that carries the binding site on the alpha-chain of spectrin for the beta-chain has been purified from limited trypsin digests of spectrin by means of FPLC. The self-association of spectrin and the binding of the alpha-I fragment to spectrin heterodimers and to tetramers have been quantified through the use of gel electrophoresis, staining with Coomassie Blue, and quantification of the bound dye following elution with pyridine. The parameters of self-association were found to be consistent with those estimated from sedimentation equilibrium analysis. The data were consistent with a model in which both self-association and the binding of the alpha-I fragment are considered to occur through an intermediate in which the alpha-beta interface is initially dissociated. The alpha-beta interface in the heterodimer was found to be less stable than that of higher oligomers by approx. 3 kJ/mol.

Enhancement of self-association of human spectrin by polyethylene glycol

1. In the presence of polyethylene glycol, the self-association of human spectrin is enhanced in a manner that depends approx. exponentially on the mass concentration of polyethylene glycol. 2. For a given mass concentration, the enhancement is independent of the molecular weight of the polyethylene glycol. 3. These data are consistent with the operation of excluded volume effects, and support the contention that the association of spectrin is likely to be increased in the presence of the high concentration of hemoglobin within the erythrocyte in vivo.

The self-association of ovine erythrocyte spectrin

1. Spectrin extracted from ovine erythrocyte membranes at low temperature shows association behaviour similar to that reported for human and bovine erythrocytes. 2. The spectrin tetramer is the predominant oligomer, the dimer is well represented, and smaller amounts of hexamer and higher oligomers are present. 3. The estimates of parameters describing the self-association of purified ovine spectrin studied by sedimentation equilibrium analysis were found to be indistinguishable from those obtained for human spectrin under the same conditions, within the precision of the measurements. 4. The data suggest that the cooperative isodesmic model may be general for spectrin, and not a peculiarity of the human.

The effects of ionic strength on the self-association of human spectrin

The self-association of human spectrin has been studied by means of sedimentation equilibrium in the analytical ultracentrifuge at pH 7.5 and over a range of ionic strength from 0.009 to 1.0 M. Increasing ionic strength above 0.1 M reduces the equilibrium constants for all of the measurable steps in the self-association reaction. These results support the concept of charge-charge interactions stabilizing the tetramer and higher oligomers with respect to the heterodimer. In addition, increasing ionic strength brought about a dissociation of the heterodimer to component polypeptide chains. Dissociation to the heterodimers is also enhanced with a decrease in ionic strength below 0.05 M. This low ionic strength-dependent dissociation is consistent with generalised electrostatic repulsion; however, this effect also correlates with some loss of alpha-helical content as revealed by circular dichroism. The secondary, tertiary and quaternary structures may all be partially disrupted by electrostatic free energy at low ionic strength.

Inhibition of DOI-induced wet dog shakes in the guinea-pig by 5-HT2 receptor antagonists

The preferential 5-HT( 2)/5-HT(1C) receptor agonist DOI (0.1-4 mg/kg s.c.) caused an increase in locomotor activity, grooming and 'wet-dog' shakes (WDS) in the adult guinea-pig. The DOI-induced WDS behaviour was potently inhibited by several antagonists that have high affinity for the 5-HT(2) binding site. The WDS response is likely to be centrally-mediated since the effects of peripherally administered DOI were poorly antagonized by the peripherally-acting 5-HT(2) receptor antagonist BW501C67. Although these studies do not exclude an effect of DOI at 5-HT(1C) receptors, the high potency of ketanserin and spiperone in attenuating the effects of DOI would suggest an effect at the 5-HT(2) receptor. The present data suggest that antagonism of the directly-acting agonist DOI may be useful for assessing the selectivity and duration of action of centrally-acting 5-HT(2) receptor antagonists in the guinea-pig.