Revisions to the derivation of the Australian and New Zealand guidelines for toxicants in fresh and marine waters

The Australian and New Zealand Guidelines for Fresh and Marine Water Quality are a key document in the Australian National Water Quality Management Strategy. These guidelines released in 2000 are currently being reviewed and updated. The revision is being co-ordinated by the Australian Department of Sustainability, Environment, Water, Population and Communities, while technical matters are dealt with by a series of Working Groups. The revision will be evolutionary in nature reflecting the latest scientific developments and a range of stakeholder desires. Key changes will be: increasing the types and sources of data that can be used; working collaboratively with industry to permit the use of commercial-in-confidence data; increasing the minimum data requirements; including a measure of the uncertainty of the trigger value; improving the software used to calculate trigger values; increasing the rigour of site-specific trigger values; improving the method for assessing the reliability of the trigger values; and providing guidance of measures of toxicity and toxicological endpoints that may, in the near future, be appropriate for trigger value derivation. These changes will markedly improve the number and quality of the trigger values that can be derived and will increase end-users’ ability to understand and implement the guidelines in a scientifically rigorous manner.

A comparison of mixture toxicity assessment: examining the chronic toxicity of atrazine, permethrin and chlorothalonil in mixtures to Ceriodaphnia cf. dubia

Pesticides predominantly occur in aquatic ecosystems as mixtures of varying complexity, yet relatively few studies have examined the toxicity of pesticide mixtures. Atrazine, chlorothalonil and permethrin are widely used pesticides that have different modes of action. This study examined the chronic toxicities (7-d reproductive impairment) of these pesticides in binary and ternary mixtures to the freshwater cladoceran Ceriodaphnia cf. dubia. The toxicity of the mixtures was compared to that predicted by the independent action (IA) model for mixtures, as this is the most appropriate model for chemicals with different modes of action. Following this they were compared to the toxicity predicted by the concentration addition (CA) model for mixtures. According to the IA model, the toxicity of the chlorothalonil plus atrazine mixture conformed to antagonism, while that of chlorothalonil and permethrin conformed to synergism. The toxicity of the atrazine and permethrin mixture as well as the ternary mixture conformed to IA implying there was either no interaction between the components of these mixtures and/or in the case of the ternary mixture the interactions cancelled each other out to result in IA. The synergistic and antagonistic mixtures deviated from IA by factors greater than 3 and less than 2.5, respectively. When the toxicity of the mixtures was compared to the predictions of the CA model, the binary mixture of chlorothalonil plus atrazine, permethrin plus atrazine and the ternary mixture all conformed to antagonism, while the binary mixture of chlorothalonil plus permethrin conformed to CA. Using the CA model provided estimates of mixture toxicity that did not markedly underestimate the measured toxicity, unlike the IA model, and therefore the CA model is the most suitable to use in ecological risk assessments of these pesticides.

Response and recovery of acetylcholinesterase activity in freshwater shrimp, Paratya australiensis (Decapoda: Atyidae) exposed to selected anti-cholinesterase insecticides

The toxicity of carbaryl, chlorpyrifos, dimethoate and profenofos to the freshwater shrimp, Paratya australiensis was assessed by measuring acetylcholinesterase (AChE) inhibition after 96h exposures. Shrimp exposed to these pesticides exhibited significant AChE inhibition, with mortality in shrimp corresponding to 70-90% AChE inhibition. The sensitivity of P. australiensis to the four pesticides based on AChE inhibition can be given as chlorpyrifos > profenofos > carbaryl > dimethoate. Recovery of AChE activity was followed in shrimp after 96 h exposures to carbaryl, chlorpyrifos and dimethoate. Recovery after exposure to the carbamate pesticide carbaryl was more rapid than for the two organophosphorus pesticides, chlorpyrifos and dimethoate. The slow recovery of depressed AChE activity may mean that affected organisms in the natural system are unable to sustain physical activities such as searching for food or eluding predators. To investigate the ecological significance of AChE inhibition, chemotaxis behaviour was assessed in shrimp exposed to profenofos for 24h. Abnormal chemotaxis behaviour in the exposed shrimp was observed at concentrations representing 30-50% AChE inhibition. A clear relationship existed between the depression of AChE activity and observed chemotaxis responses, such as approaching and grasping the chemoattractant source. These results suggest that in vivo toxicity tests based on this specific biomarker are sensitive and present advantages over conventional acute tests based on mortality. Behavioural studies of test organisms conducted in conjunction with measurement of AChE inhibition will provide data to clarify the toxic effects caused by sublethal chemical concentrations of anti-cholinesterase compounds.

The DNA sequence and biological annotation of human chromosome 1

The reference sequence for each human chromosome provides the framework for understanding genome function, variation and evolution. Here we report the finished sequence and biological annotation of human chromosome 1. Chromosome 1 is gene-dense, with 3,141 genes and 991 pseudogenes, and many coding sequences overlap. Rearrangements and mutations of chromosome 1 are prevalent in cancer and many other diseases. Patterns of sequence variation reveal signals of recent selection in specific genes that may contribute to human fitness, and also in regions where no function is evident. Fine-scale recombination occurs in hotspots of varying intensity along the sequence, and is enriched near genes. These and other studies of human biology and disease encoded within chromosome 1 are made possible with the highly accurate annotated sequence, as part of the completed set of chromosome sequences that comprise the reference human genome.

DNA sequence and analysis of human chromosome 9

Chromosome 9 is highly structurally polymorphic. It contains the largest autosomal block of heterochromatin, which is heteromorphic in 6-8% of humans, whereas pericentric inversions occur in more than 1% of the population. The finished euchromatic sequence of chromosome 9 comprises 109,044,351 base pairs and represents >99.6% of the region. Analysis of the sequence reveals many intra- and interchromosomal duplications, including segmental duplications adjacent to both the centromere and the large heterochromatic block. We have annotated 1,149 genes, including genes implicated in male-to-female sex reversal, cancer and neurodegenerative disease, and 426 pseudogenes. The chromosome contains the largest interferon gene cluster in the human genome. There is also a region of exceptionally high gene and G + C content including genes paralogous to those in the major histocompatibility complex. We have also detected recently duplicated genes that exhibit different rates of sequence divergence, presumably reflecting natural selection.

The DNA sequence and comparative analysis of human chromosome 10

The finished sequence of human chromosome 10 comprises a total of 131,666,441 base pairs. It represents 99.4% of the euchromatic DNA and includes one megabase of heterochromatic sequence within the pericentromeric region of the short and long arm of the chromosome. Sequence annotation revealed 1,357 genes, of which 816 are protein coding, and 430 are pseudogenes. We observed widespread occurrence of overlapping coding genes (either strand) and identified 67 antisense transcripts. Our analysis suggests that both inter- and intrachromosomal segmental duplications have impacted on the gene count on chromosome 10. Multispecies comparative analysis indicated that we can readily annotate the protein-coding genes with current resources. We estimate that over 95% of all coding exons were identified in this study. Assessment of single base changes between the human chromosome 10 and chimpanzee sequence revealed nonsense mutations in only 21 coding genes with respect to the human sequence.

The DNA sequence and analysis of human chromosome 13

Chromosome 13 is the largest acrocentric human chromosome. It carries genes involved in cancer including the breast cancer type 2 (BRCA2) and retinoblastoma (RB1) genes, is frequently rearranged in B-cell chronic lymphocytic leukaemia, and contains the DAOA locus associated with bipolar disorder and schizophrenia. We describe completion and analysis of 95.5 megabases (Mb) of sequence from chromosome 13, which contains 633 genes and 296 pseudogenes. We estimate that more than 95.4% of the protein-coding genes of this chromosome have been identified, on the basis of comparison with other vertebrate genome sequences. Additionally, 105 putative non-coding RNA genes were found. Chromosome 13 has one of the lowest gene densities (6.5 genes per Mb) among human chromosomes, and contains a central region of 38 Mb where the gene density drops to only 3.1 genes per Mb.

The DNA sequence and analysis of human chromosome 6

Chromosome 6 is a metacentric chromosome that constitutes about 6% of the human genome. The finished sequence comprises 166,880,988 base pairs, representing the largest chromosome sequenced so far. The entire sequence has been subjected to high-quality manual annotation, resulting in the evidence-supported identification of 1,557 genes and 633 pseudogenes. Here we report that at least 96% of the protein-coding genes have been identified, as assessed by multi-species comparative sequence analysis, and provide evidence for the presence of further, otherwise unsupported exons/genes. Among these are genes directly implicated in cancer, schizophrenia, autoimmunity and many other diseases. Chromosome 6 harbours the largest transfer RNA gene cluster in the genome; we show that this cluster co-localizes with a region of high transcriptional activity. Within the essential immune loci of the major histocompatibility complex, we find HLA-B to be the most polymorphic gene on chromosome 6 and in the human genome.

Uncontrolled insulin secretion from a childhood pancreatic beta-cell adenoma is not due to the functional loss of ATP-sensitive potassium channels

We report the case of an 8-year-old child who presented with severe hyperinsulinaemic hypoglycaemia due to a pancreatic islet cell adenoma. In vivo, there was no beneficial response to the hyperglycaemia-inducing agent diazoxide and as a consequence the child underwent a subtotal pancreatectomy. In vitro studies of adenomatous beta-cells revealed no operational defects in ATP-sensitive potassium channel activity and appropriate responses to diazoxide. In comparison with patients with focal adenomatous hyperplasia, genetic analysis of the isolated adenoma showed no loss of heterozygosity for chromosome 11p15 and expression of the cyclin-dependent kinase inhibitor p57(kip2). This case illustrates that the excess insulin secretion from an infantile adenoma has an aetiology different from that observed in hyperinsulinism in infancy.

The DNA sequence and comparative analysis of human chromosome 20

The finished sequence of human chromosome 20 comprises 59,187,298 base pairs (bp) and represents 99.4% of the euchromatic DNA. A single contig of 26 megabases (Mb) spans the entire short arm, and five contigs separated by gaps totalling 320 kb span the long arm of this metacentric chromosome. An additional 234,339 bp of sequence has been determined within the pericentromeric region of the long arm. We annotated 727 genes and 168 pseudogenes in the sequence. About 64% of these genes have a 5' and a 3' untranslated region and a complete open reading frame. Comparative analysis of the sequence of chromosome 20 to whole-genome shotgun-sequence data of two other vertebrates, the mouse Mus musculus and the puffer fish Tetraodon nigroviridis, provides an independent measure of the efficiency of gene annotation, and indicates that this analysis may account for more than 95% of all coding exons and almost all genes.

The differential effect of injecting estradiol-17beta, testosterone, and hydrocortisone during the immune adaptive period on the fertility of female mice

PROBLEM

Female mice injected with estradiol-17beta (E2) and testosterone during the immune adaptive period are infertile as adults. Study 1 examined the effect of the day of injection of E2 and testosterone on the incidence of infertility in two strains of mice. Study 2 examined the effect of hydrocortisone on E2-induced infertility.

METHOD OF STUDY

Study 1: Neonatal (C57BL/6J x A/J)F1 B6A and (C3H/HeJ x 129J)F1 C31 female mice were injected from 0 to 3 and from 3 to 6 days of age with either 20 microg E2 or 20 microg testosterone. Animals were tested for fertility by mating with fertile males. Study 2: Neonatal B6A females were injected with 20 microg E2 with/without 1000 microg hydrocortisone on days 1, 3, 5, 7, and 10. At adulthood, ovaries were examined for the presence of corpora lutea (CLs).

RESULTS

Study 1: The incidence of E2-induced infertility in adult B6A and C31 females decreased over three consecutive matings. In contrast, the incidence of testosterone-induced infertility in adult B6A and C31 females increased. E2 caused the highest incidence of infertility in C31 females when injected prior to 3 days of age. In B6A mice, E2 caused the highest incidence of infertility when injected after 3 days of age. Study 2: When hydrocortisone was injected with E2, 90% of the B6A females had ovaries with CLs at 100 days of age. Without hydrocortisone, only 16% of the B6A females injected with E2 had ovaries with CLs.

CONCLUSION

Study 1: The incidence of infertility caused by injections of E2 is dependent on the strain of mice and the day(s) injected. The incidence of infertility caused by injections of testosterone is independent of the strain of mice. Study 2: Hydrocortisone prevents E2-induced infertility. It is proposed that injections of E2 during the immune adaptive period alter T-cell maturation, which contributes to E2-induced infertility.

Profenofos residues in wild fish from cotton-growing areas of New South Wales, Australia

The organophosphorus (OP) pesticide profenofos (O-4-bromo-2-chlorophenyl O-ethyl S-propyl phosphorothioate) is used heavily in cotton-growing areas of eastern Australia toward the end of the growing season. European carp (Cyprinus carpio), bony bream (Nematalosa erebi), and mosquitofish (Gambusia holbrooki) were collected from the cotton-growing areas around Wee Waa, New South Wales, to determine the relationship between profenofos residues and acetyl-cholinesterase (AChE) activity in wild fish. Profenofos concentrations in water, sediment, and fish tissue reflected its general level of use; levels in March 1994 were significantly higher than in 1993 and generally decreased in May, 6 wk after cessation of spraying. Residues in carp and bony bream generally correlated with concentrations in water and sediment, although residues in fish tend to persist longer at some sites. Acetylcholinesterase inhibition was a useful indicator of profenofos exposure within a season, particularly if linked with residue measurements. Bony bream and gravid female mosquitofish recovered AChE levels more slowly than carp or nongravid mosquitofish. Recovery in creeks was generally more rapid than in lagoons.

Hyperinsulinism of infancy: the regulated release of insulin by KATP channel-independent pathways

Hyperinsulinism of infancy (HI) is a congenital defect in the regulated release of insulin from pancreatic beta-cells. Here we describe stimulus-secretion coupling mechanisms in beta-cells and intact islets of Langerhans isolated from three patients with a novel SUR1 gene defect. 2154+3 A to G SUR1 (GenBank accession number L78207) is the first report of familial HI among nonconsanguineous Caucasians identified in the U.K. Using patch-clamp methodologies, we have shown that this mutation is associated with both a decrease in the number of operational ATP-sensitive K+ channels (KATP channels) in beta-cells and impaired ADP-dependent regulation. There were no apparent defects in the regulation of Ca2+- and voltage-gated K+ channels or delayed rectifier K+ channels. Intact HI beta-cells were spontaneously electrically active and generating Ca2+ action currents that were largely insensitive to diazoxide and somatostatin. As a consequence, when intact HI islets were challenged with glucose and tolbutamide, there was no rise in intracellular free calcium ion concentration ([Ca2+]i) over basal values. Capacitance measurements used to monitor exocytosis in control and HI beta-cells revealed that there were no defects in Ca2+-dependent exocytotic events. Finally, insulin release studies documented that whereas tolbutamide failed to cause insulin secretion as a consequence of impaired [Ca2+]i signaling, glucose readily promoted insulin release. Glucose was also found to augment the actions of protein kinase C- and protein kinase A-dependent agonists in the absence of extracellular Ca2+. These findings document the relationship between SUR1 gene defects and insulin secretion in vivo and in vitro and describe for the first time KATP channel-independent pathways of regulated insulin secretion in diseased human beta-cells.

Female house mice develop a unique ovarian lesion in colonies that are at maximum population density

Colonies of house mice reach maximum population density in 120-180 days, irrespective of cage size and initial number of colonizing animals. Reproduction ceases because the females become aggressive and unreceptive to mating. The aggressive behavior is correlated with elevated levels of testosterone (T) and corticosterone (B) (Chapman et al., Phys Behav 64:529-533, 1998). In two of seven strains of mice, females developed ovarian lesions. The occurrence of the lesion in one strain was correlated with the age of the animal and duration of the study. In the second strain, cage size was the determining factor. Lesioned ovaries weighed significantly more than nonlesioned ovaries. The lesion consisted of accumulations of luteal membrane and organelle fragments, and other cellular debris, suggestive of incomplete and prolonged luteolysis. Electron microscopic (EM) analyses revealed the presence of deposits of permanganate-resistant congophilic amyloid fibrils in the intima and smooth muscle cells of luteal thecal arteries. Population females had thymus glands and uteri that weighed significantly less than the same organs from females housed in the breeding colony, whereas the adrenal glands from the population females weighed significantly more. It is proposed that the female aggression is due to high levels of T. It is also proposed that the high levels of B suppress the immune cells involved in normal luteolysis and contribute to the incomplete and prolonged luteolysis.

Alteration of cytokine production in follicular cystic ovaries induced in mice by neonatal estradiol injection

PROBLEM

Neonatal estradiol injections in mice lead to follicular cystic ovaries that are similar to ovaries in patients with polycystic ovarian syndrome (PCOS). The present study examined ovarian cytokine production following neonatal estradiol injection.

METHOD OF STUDY

Female (C3H,HeJ x 129/HeJ)F1 mice were injected daily with 20 microg 17beta-estradiol from 0-3 days postpartum. At intervals, animals were sacrificed to determine ovarian architecture, circulating levels of estradiol, ovarian and peritoneal macrophage cytokine production, and ovarian P450 aromatase enzyme mRNA levels.

RESULTS

Similar to PCOS, our results show that neonatally estradiol-injected mice have lower levels of circulating estrogen that are correlated with decreased mRNA levels of P450 aromatase enzyme. Our data also show that follicular cystic ovaries have increased tumor necrosis factor (TNF)-alpha and interleukin (IL)-6 production. This increase in TNF-alpha and IL-6 production is also observed in peritoneal macrophages of estradiol-injected mice.

CONCLUSION

The present study showed that neonatal estrogen injection in mice has an overall systemic effect on cytokine production. We speculate that increased cytokine production may alter certain important steps in follicular maturation, ultimately contributing to ovarian dysfunction.

Ulceration of the urethral meatus after simultaneous pancreas-kidney transplantation

A 39-year-old male developed painful ulceration of the glans penis following simultaneous pancreas and kidney transplantation for end-stage renal failure complicating insulin-dependent diabetes mellitus. Infection was excluded. Diversion of the pancreatic secretions away from the urinary bladder into the bowel resulted in healing.

ATP-sensitive potassium channels and efaroxan-induced insulin release in the electrofusion-derived BRIN-BD11 beta-cell line

The properties of ATP-sensitive K+ (K(ATP)) channels were explored in the electrofusion-derived, glucose-responsive, insulin-secreting cell line BRIN-BD11 using patch-clamp techniques. In intact cells, K(ATP) channels were inhibited by glucose, the sulfonylurea tolbutamide, and the imidazoline compounds efaroxan and phentolamine. Each of these agents initiated insulin secretion and potentiated the actions of glucose. K(ATP) channels were blocked by ATP in a concentration-dependent manner and activated by ADP in the presence of ATP. In both intact cells and excised inside-out patches, the K(ATP) channel agonists diazoxide and pinacidil activated channels, and both compounds inhibited insulin secretion evoked by glucose, tolbutamide, and imidazolines. The mechanisms of action of imidazolines were examined in more detail. Pre-exposure of BRIN-BD11 cells to either efaroxan or phentolamine selectively inhibited imidazoline-induced insulin secretion but not the secretory responses of cells to glucose, tolbutamide, or a depolarizing concentration of KCl. These conditions did not result in the loss of depolarization-dependent rises in intracellular Ca2+ ([Ca2+]i), K(ATP) channel operation, or the actions of either ATP or efaroxan on K(ATP) channels. Desensitization of the imidazoline receptor following exposure to high concentrations of efaroxan, however, was found to result in an increase in SUR1 protein expression and, as a consequence, an upregulation of K(ATP) channel density. Our data provide 1) the first characterization of K(ATP) channels in BRIN-BD11 cells, a novel insulin-secreting cell line produced by electrofusion techniques, and 2) a further analysis of the role of imidazolines in the control of insulin release.

Engineering a glucose-responsive human insulin-secreting cell line from islets of Langerhans isolated from a patient with persistent hyperinsulinemic hypoglycemia of infancy

Persistent hyperinsulinemic hypoglycemia of infancy (PHHI) is a neonatal disease characterized by dysregulation of insulin secretion accompanied by profound hypoglycemia. We have discovered that islet cells, isolated from the pancreas of a PHHI patient, proliferate in culture while maintaining a beta cell-like phenotype. The PHHI-derived cell line (NES2Y) exhibits insulin secretory characteristics typical of islet cells derived from these patients, i.e. they have no K(ATP) channel activity and as a consequence secrete insulin at constitutively high levels in the absence of glucose. In addition, they exhibit impaired expression of the homeodomain transcription factor PDX1, which is a key component of the signaling pathway linking nutrient metabolism to the regulation of insulin gene expression. To repair these defects NES2Y cells were triple-transfected with cDNAs encoding the two components of the K(ATP) channel (SUR1 and Kir6.2) and PDX1. One selected clonal cell line (NISK9) had normal K(ATP) channel activity, and as a result of changes in intracellular Ca(2+) homeostasis ([Ca(2+)](i)) secreted insulin within the physiological range of glucose concentrations. This approach to engineering PHHI-derived islet cells may be of use in gene therapy for PHHI and in cell engineering techniques for administering insulin for the treatment of diabetes mellitus.

Genetic variants showing apparent hot-spots in the human serum albumin gene

The molecular defects of three different slow-migrating genetic variants of human serum albumin, albumins Kamloops (formerly RIH), Stirling and Amsterdam, previously characterized only by electrophoretic and dye-binding studies, are now reported. Two of them are proalbumin variants: sequential analysis of the purified whole proteins has established the mutation responsible for albumin Kamloops as -1Arg-->Gln, and for albumin Stirling as -2Arg-->His. A Glu-->Lys substitution in position 570 of the mature albumin molecule was determined in albumin Amsterdam by sequential analysis of two abnormal tryptic fragments. The three alloalbumins are caused by single-base changes all of which seem to represent hot-spots in the albumin gene. The possible functional consequences of the presence of a circulating alloalbumin are discussed.

Effect of endosulfan runoff from cotton fields on macroinvertebrates in the Namoi river

Of the several pesticides used in the pest management strategy for cotton, endosulfan is ranked as having the greatest impact on the riverine ecosystem. A survey of changes in the densities of six abundant macroinvertebrate taxa (ephemeropteran nymphs Jappa kutera, Atalophlebia australis, Tasmanocoenis sp., and Baetis sp. and two trichopteran larvae, Cheumatopsyche sp. and Ecnomus sp.) between upstream and downstream zones of the cotton-growing region in the Namoi River was conducted between November 1995 and February 1996. In November and December 1995, there were few differences in population densities between all sites. In January and February 1996, population densities of the study taxa increased 7- to 10-fold higher at the two reference sites, with low concentrations of endosulfan in sediment and in passive samplers placed in the water column. In contrast, densities of these taxa at sites with exposure to 25-fold higher concentrations of endosulfan remained static and were between one and two orders of magnitude lower than densities at the reference sites in January and February. Population densities of Baetis sp., a mobile ephemeropteran, did not indicate any inverse relationship with endosulfan concentrations. Multivariate redundancy analysis indicated that endosulfan concentrations were the leading environmental predictor of changes in density of the five benethic taxa. Laboratory 48-h LC50 values of technical endosulfan in river water were 0.6, 1.3, and 0.4 ppb for early-instar nymphs of A. australis and J. kutera, and larvae of Cheumatopsyche sp., respectively. Endosulfan sulfate formed a large proportion of the total endosulfan concentrations measured from in situ passive samplers, indicating that its main route of entry into the river is through surface runoff during storm events.

Characterisation of new efaroxan derivatives for use in purification of imidazoline-binding sites

The insulin secretagogue activity of certain imidazoline compounds is mediated by a binding site associated with ATP-sensitive K+ (K(ATP)) channels in the pancreatic beta-cell. We describe the effects of a series of structural modifications to efaroxan on its activity at this site. Substitution of amino-, nitro- or azide- groups onto the 5-position of the benzene ring of efaroxan did not significantly affect the functional interaction of the ligand with the islet imidazoline binding site. Modification of the imidazoline ring to an imidazole to generate 2-(2-ethyl-2,3-dihydrobenzo[b]furan-2-yl)-1H-imidazole (KU14R) resulted in loss of secretagogue activity. Indeed, this reagent appeared to act as an imidazoline antagonist since it blocked the secretory responses to imidazoline compounds and also inhibited the blockade of beta-cell K(ATP) channels by efaroxan in patch clamp experiments. Application of KU14R alone resulted in a modest reduction in K(ATP) channel opening, suggesting that it may display weak partial agonism, at least in patch-clamp experiments.

Analysis of steroid hormone levels in female mice at high population density

Populations of predominantly female house mice (Mus musculus) were created by placing virgin female mice in cages (0.045 m2 to 0.48 m2) with a single stud male, and removing all ensuing male offspring at weaning. At maximum population size, the females in these all-female/one-male populations exhibited male-like aggressive behavior. Termination of the populations and subsequent measurement of steroid hormone levels indicated that the aggressive females had high circulating level of testosterone and corticosterone, and elevated baseline levels of progesterone. The high levels of corticosterone could be lowered by dexamethasone, but not the high levels of testosterone.

Characterization of ion channels in stimulus-secretion coupling in pancreatic islets

The regulation of insulin secretion from beta-cells of the pancreatic islets of Langerhans is a highly integrated process involving several plasma membrane ion channels. The key to our understanding of the normal process is the hypothesis that glucose-induced closure of K+ channels leads to a depolarization of the cell membrane potential and the opening of voltage-gated Ca2+ channels. Support for this is provided by direct electrophysiological recordings of ion channel activity, and by recent data that have revealed how gene defects in ion channel subunits leads to the loss of regulated insulin secretion. Here, we review the general features of stimulus-response coupling in beta-cells, and how novel initiatives are providing key insights into beta-cell pathogenesis.

The anovulation in female mice resulting from postnatal injections of estrogen is correlated with altered levels of CD8+ lymphocytes

PROBLEM

Injections of estradiol-17 beta (E2) are known to both induce anovulation and alter lymphocyte maturation in female mice. The current study examined whether the two events are related.

METHOD OF STUDY

Female (C3H/HeJ x 129J)F1 (C31) mice were injected with 20 micrograms of E2 from 0-3 days, or from 3-6 days, postpartum. At 8, 12, 20, 32, or 40 weeks of age, the animals were killed, T lymphocytes were characterized, and ovaries were histologically examined for the presence of corpora lutea.

RESULTS

Animals injected with E2 from 0-3 days postpartum had percentages of CD8+ thymocytes and CD8+ splenocytes that were always lower than in noninjected females, and the E2-injected animals never ovulated, even by 40 weeks of age. In contrast, animals injected with E2 from 3-6 days of age had percentages of CD8+ thymocytes and CD8+ splenocytes that, although initially lower than in control females, attained control values by 32 weeks of age. In addition, at 32 weeks of age a number of the 3-6-day E2-injected females ovulated, whereas at earlier ages none had. Further, injections of E2 had little effect on the percentages of CD4+ thymocytes and splenocytes in these animals.

CONCLUSIONS

The results suggest that E2-induced anovulation in C31 female mice is correlated with decreased levels of CD8+ lymphocytes, and an increased CD4+/CD8+ lymphocyte ratio.

The ovarian dysgenesis normally induced by neonatal thymectomy is prevented by the prior administration of estrogen

PROBLEM

Neonatal thymectomy (Tx) and estrogen (E2) administration disrupt the reproductive and immune systems of female mice. The current experiment examined the combined effects of the two procedures on ovarian function, performed in sequence, and in reverse sequence.

METHOD

Groups of (C57BL/6J x A/J)F1 (B6A) female mice were given four daily injections of 20 micrograms estradiol-17 beta, either from 0 days to 3 days, or from 3 days to 6 days postpartum. In some groups this regimen was combined with thymectomy performed either prior to steroid injection (TX-3), or after steroid treatment (TX-4). Animals were sacrificed between 100 and 110 days of age then ovaries evaluated via light microscopy for dysgenesis and follicular cysts.

RESULTS

When E2 treatment followed Tx, the incidence of ovarian dysgenesis was unchanged (study 1, Tx + E2 = 60% ovarian dysgenesis; Tx = 63% ovarian dysgenesis) (study 2, Tx + E2 = 46% ovarian dysgenesis; Tx = 45% ovarian dysgenesis). In contrast, when E2 was given before Tx, ovarian dysgenesis did not occur (study 2, E2 + Tx = 0% ovarian dysgenesis; Tx = 46% ovarian dysgenesis). Ovaries from E2 + Tx animals were characteristic of ovaries from E2-injected animals without Tx.

CONCLUSION

The results indicate that E2 injection prevents Tx-induced ovarian dysgenesis, suggesting E2-activation of an extrathymic pathway for thymus function.

Declining incidence of paediatric burns in Scotland: a review of 1114 children with burns treated as inpatients and outpatients in a regional centre

This retrospective study of paediatric burns in the Lothian region involved a review of 1114 case notes of children up to the age of 12 years, treated for burns as inpatients and outpatients, during a 3-year period between 1988 and 1990. There were more boys than girls and 79 per cent were below 5 years of age. 71.5 per cent were treated as outpatients only, whereas 28.5 per cent were admitted. The Lothian region had the highest incidence of burns of children in Scotland. There has been a statistically significant downward linear trend in burn rates and admissions in Scotland during the 20 years but in this hospital burns admissions have significantly diminished only since 1987. The number of flame burns has declined and a high proportion of the victims were scalded. Efforts need to be made to reduce the large number of scalds by educational and legislative measures.

Topology of 3 beta-hydroxy-5-ene-steroid dehydrogenase/delta 5-delta 4-isomerase in adrenal cortex mitochondria and microsomes

3 beta-Hydroxy-5-ene-steroid dehydrogenase/delta 5-delta 4-isomerase (3 beta HSD) is a NAD(+)-dependent membrane-bound enzyme that catalyzes the oxidation of delta 5-3 beta-hydroxysteroids to delta 4-3-keto structures during adrenal, gonadal, and placental steroidogenesis. Enzyme activity is located in both microsomes and mitochondria. In these experiments we examined the membrane topologies of 3 beta HSD in rat and calf adrenal microsomes and mitochondria by comparing access to the active sites of coenzyme and the inhibitor mersalyl, a nonpenetrant organic mercurial anion. Microsomal activity required exogenous NAD+ and was inhibited by mersalyl, indicating that the active site faced the medium in vitro and the cytoplasm in vivo. In contrast, mitochondrial 3 beta HSD used matrix space NAD+, was inhibited by reduction of intramitochondrial NAD(P)+, and was insensitive to mersalyl. Mitochondrial activity was decreased by exogenous NADH (apparent Ki, 2.8 microM) and increased by added NAD+ (apparent Ka, 2.4 microM). However, mersalyl blocked the effects of exogenous NADH and NAD+ and returned the activity to that observed before coenzyme addition. The membrane-sidedness of the NAD+ activation was examined further in submitochondrial particles prepared by sonication of pyridine nucleotide-depleted calf adrenal cortex mitochondria. Particles were prepared in the absence or presence of 10 mM NAD+ and contained none or 2.9-7.3 nmol NAD+/mg protein, respectively. Both groups of submitochondrial particles required exogenous NAD+ for 3 beta HSD activity, indicating that the active site faced the medium (the particles were everted), and the contained NAD+ was inside the particles. However, 3 beta HSD activity was increased 12-140% in particles that contained NAD+. The results suggest that mitochondrial 3 beta HSD is an integral inner membrane protein, that the active site faces the matrix space and is influenced by coenzyme availability, and that a regulatory site(s) faces the intermembrane space. Binding of NAD+ or NADH to this external site increases or decreases, respectively, the rate of catalysis at the active site. Mitochondrial 3 beta HSD activity may be enhanced by oxidation of intermembrane space NADH via an active rotenone- and antimycin-a-insensitive NADH oxidase.

Radioligand exchange binding cannot directly determine the dissociation constant (Kd) of the rat ventral prostate nuclear androgen receptor: valid Kd determinations require additional uptake binding data

Radioligand exchange was examined for its ability to derive the dissociation constant (Kd) of the rat ventral prostate nuclear androgen receptor. In one 24-h, 12 degrees C incubation, Scatchard plot analysis of [3H]dihydrotestosterone ([3H]DHT) exchange binding produced a Kd of 6.9 x 10(-9) M. Specific binding of [3H]DHT ranged from 114 to 758 pM, and the extrapolated value for the total number of binding sites (n) was 1320 pM. When aliquots from the same receptor pool were incubated with unlabeled DHT, and bound androgen was measured by radioimmunoassay, each titration point held a concentration of specifically bound unlabeled DHT little different from the preincubation value of bound endogenous ligand (1338 pM), suggesting that few, if any, unoccupied sites were created during the incubation. In a second radioligand exchange assay, unoccupied receptor sites were measured at the end of incubation. Virtually no unoccupied sites were found, though the range of predicted values was 124 to 383 pM (n = 425 pM). The data, in toto, suggest that although radioactive ligand exchanges with bound unlabeled ligand, the dynamics of the process do not include the creation of unoccupied sites. Since the Kd is determined by measuring the concentrations of unoccupied sites, free ligand, and receptor sites bound to ligand, the absence of unoccupied sites suggests that radioligand exchange cannot be used to directly determine the Kd of the prostate nuclear androgen receptor. The numerical value obtained from radioligand exchange, therefore, instead of being a Kd, is very likely the result of a graphic plot of the increase in specific activity of bound radioligand as [3H]DHT is titrated to higher levels. In the last phase of the study a technique was developed which allows for the correct determination of the Kd of the rat ventral prostate nuclear androgen receptor. For the determination, data from an experiment measuring uptake binding into unoccupied sites were combined with data obtained from radioligand exchange binding. From this, the Kd of the receptor was calculated to be 1 x 10(-12) M.

Changes in mitochondrial and microsomal 3 beta-hydroxysteroid dehydrogenase activity in mouse ovary over the course of the estrous cycle

3 beta-Hydroxysteroid dehydrogenase (HSD) is located in the endoplasmic reticulum and mitochondria. To determine whether the separate enzymes play different roles in steroidogenesis, the specific activity (SA) of both were measured at four different stages of the mouse estrous cycle. Microsomal HSD activity changed little throughout, averaging 8.7 +/- 0.7 nmol progesterone/min/mg protein. In contrast, mitochondrial HSD activity changed dramatically at diestrus, increasing to 14.4 nmol progesterone/min/mg protein. When measured at proestrus, estrus, and metestrus, mitochondrial HSD activity was 5.5, 7.4, and 4.5 nmol progesterone/min/mg protein, respectively. To ascertain whether the increase in mitochondrial HSD activity at diestrus could be due to a preferential induction of enzyme, its SA and the SA of a mitochondrial inner membrane enzyme, cytochrome C oxidase, were compared to the SA of a mitochondrial outer membrane enzyme, rotenone-insensitive NADH cytochrome C reductase. The SA of all three enzymes changed proportionally at diestrus, suggesting that the increase in mitochondrial HSD activity was not due to its preferential induction. Rather, we believe that the HSD activity in the mitochondrial fraction, as measured at the four stages of the estrous cycle, is a reflection of the combined contributions from an ever changing population of ovarian cells. Mitochondria from luteal cells have the highest HSD activity, and are very likely responsible for the major synthesis of progesterone during the luteal phase.

Labyrinthine enhancement on gadolinium-enhanced magnetic resonance imaging in sudden deafness and vertigo: correlation with audiologic and electronystagmographic studies

Sudden deafness with or without vertigo presents a difficult diagnostic problem. This article describes 12 patients with enhancement of the cochlea and/or vestibule on gadolinium-diethylenetriamine pentaacetic acid-enhanced magnetic resonance imaging (MRI), correlating the enhancement with the auditory and vestibular function. All patients were studied with T2-weighted axial images taken through the whole brain, enhanced 3-mm axial T1-weighted images taken through the temporal bone, and enhanced T1-weighted sagittal images taken through the whole brain. Cochlear enhancement on the side of hearing loss was found in all the patients. The vestibular enhancement correlated with both subjective vestibular symptoms and objective measures of vestibular function on electronystagmography. In 2 patients, the resolution of symptoms 4 to 6 months later correlated with resolution of the enhancement on MRI. No labyrinthine enhancement was seen in a series of 30 control patients studied with the same MRI protocol. Labyrinthine enhancement in patients with auditory and vestibular symptoms is a new finding and is indicative of labyrinthine disease. While abnormalities on electronystagmograms and audiograms are nonspecific and only indicate a sensorineural problem, enhanced MRI may separate patients with retrocochlear lesions, such as acoustic neuromas, from those in whom the abnormal process is in the labyrinth or the brain.

The effects of sewage on alpine streams in Kosciusko National Park, NSW

The impact of resort developments in three alpine streams of Kosciusko National Park was examined by the State Pollution Control Commission of NSW over 1981 and 1982. Physico-chemical measurements such as nutrient concentrations, stream flow and temperature were correlated with measures of periphyton growth using artificial substrates and the Thomas (1978) method for estimation of in-stream biomass.Stream flow was the major physical parameter controlling in-stream periphyton growth, far outweighing seasonal temperature variations. Nutrients emanating from resort developments were also a major influence on biomass and taxa. Natural accumulations occurred upstream of resort developments under low flow conditions and were associated with taxa typical of clean water conditions. The relationships between periphyton biomass and nutrient loads could be quantified.

Use of Australian cladocerans to generate life-cycle toxicity data

Cladocerans (or water-fleas) are important animals in freshwater exosystems. They are widely used in toxicity tests because of their small size, ease of culture, and sensitivity to chemicals. They are particularly suited to life-cycle tests because newly-hatched young can produce offspring in less than one week. Most data are available for European and North American species, and may be not be appropriate to Australian conditions. In the present study, eight Australian cladocerans were evaluated in three-brood life-cycle tests over ten days or less. Species were evaluated by duration of life cycle, ease of handling, numbers of young produced in three broods, and stability in laboratory culture.Ceriodaphnia cfdubia was the best test species. The greatest number of young, the highest survival rate and the shortest time to produce three broods were achieved in filtered Sydney mains water, aged in the presence of fish, using blended trout pellets and alfalfa as food.

Testes are asymmetric in the testicular hemicastration response of the male rat

An enquiry was made into variability in the testicular hemicastration response of the mature rat (doubling of testicular vein testosterone concentration from the remaining testis 24 h after hemicastration). The response was shown to be asymmetric, being more reliable and more robust when the left testis was removed first. Apparently the testicular hemicastration response, which has been shown to be neurally controlled, shares the asymmetry which has been reported recently in the neural regulation of unilateral ovariectomy.

The equivocal presence of nuclear androgen binding proteins in mammalian spermatids and spermatozoa

The presence of nuclear androgen binding proteins measured by nuclear androgen exchange in rat spermatids and spermatozoa was re-examined. Specific binding was observed to be related to less dense contaminating particles when sonicated testes were fractionated by isopcynic centrifugation through a 40-61% Nycodenz linear gradient. No specific binding was observed in a pure preparation of epididymal spermatozoa collected by retrograde perfusion of the cauda epididymidis, even when a nuclear exchange assay of superior sensitivity was used. Contamination could easily be induced by adding prostatic tissue to epididymal spermatozoa prior to sonication. Despite this strong evidence that the measure of nuclear androgen receptors by nuclear exchange in germ cells is artefactual, the persistence of high endogenous concentrations of 5 alpha-dihydrotestosterone and 5 alpha-diols (but not testosterone) in spermatozoa of castrated rats argues for the opposite conclusion.

The testicular response to hemicastration in the male rat cannot be maintained in vitro

The testicular response to hemicastration (in which testicular vein testosterone from the remaining testis doubles in concentration) was studied in vitro in order to establish whether the response is maintained after testicular tissue is removed from the animal. Decapsulated testes and collagenase-dispersed cells from decapsulated testes of rats were incubated for 24 h after hemicastration and testosterone production was compared with that in tissue collected at the time of surgery. Testosterone concentration in the remaining testis 24 h after hemicastration was significantly (P less than 0.05) higher than in the testis removed at the time of hemicastration, but testosterone production in vitro was similar in both tissues. Apparently the single testis remaining in a hemicastrated rat requires extratesticular support in order to maintain its stimulated state.

Medical image management

Medical image management is becoming increasingly complex as additional data are produced by equipment using digital techniques. As the requirements to store and display these images increase, the following questions become important: (a) What methods can be used to ensure that information given to the physician represents the originally acquired data? (b) What technology and methods are needed to guarantee that information is presented in a timely fashion when requested? (c) How can an image archiving and transmission system be designed to protect the patient's rights of confidentiality? The authors discuss the legal implications of digital archiving of image information and propose some approaches to designing systems that provide the most information to the physician and yet attempt to minimize infringement of the patient's rights.

Medical image management: practical, legal and ethical considerations

The data acquired by the new medical imaging techniques, in many ways, exceeded our ability to properly store, transmit and use the images produced. As diagnostic imaging procedures become progressively less invasive and traumatic, they are being applied to a much larger patient population. The decrease in memory and other instrumentation costs, along with expanded technological capability of computer systems, has provided medicine an opportunity to create network systems for the storage, processing, recall, and remote location of these diagnostic images. Therefore, problems of access and confidentiality have become increasingly important. This communication will consider certain medical, legal, and ethical aspects of these technologies of data acquisition, storage, manipulation and retrieval.

Nuclear androgen binding sites in the male rat. III. Late spermatids and spermatozoa in the testis, with an introduction to epididymal spermatozoa

Nuclear androgen binding sites were examined in late spermatids (stages 12-19) which resisted sonication of homogenized testes of mature male rats. The measurement of unoccupied binding sites in salt extract of purified spermatid heads by nuclear exchange at -10 degrees C was developed and validated. As in the prostate, unoccupied nuclear androgen binding sites in sonicated testes were in low concentration, were not artefactual, and could be occupied both in vivo and in vitro by exogenous androgens, and uniquely in hemicastrated rats by endogenously compensated androgens in the remaining testis. The properties of occupied binding sites in salt extract of purified spermatid heads (measured by nuclear exchange at 4 degrees C for 48 or more hours with 5 nM [3H]dihydrotestosterone) were almost identical to those of occupied binding sites in nuclei of the ventral prostate, except for their concentration. However, levels of specific binding activity approaching 50 fmol/mg DNA could be expected in salt extract of spermatid pellets, by use of a sulfhydryl reducing agent (dithiothreitol) prior to salt extraction, a protease inhibitor (phenylmethylsulfonyl fluoride) in all buffers, and optimization of the sonication protocol. Nuclear androgen binding sites of sonicated epididymal spermatozoa, collected by retrograde perfusion of the cauda epididymidis, were found to be completely salt-resistant. These binding proteins could be extracted by 0.4 M KCl if dithiothreitol and dihydrotestosterone were incorporated into the sonication buffer, if phenylmethylsulfonyl fluoride was added to all buffers, and if the purified epididymal sperm pellet was treated with sarkosyl, a non-ionic detergent, just before salt extraction. The salt extract of epididymal spermatozoa which were treated as described above contained two binding components: a soluble form which was eluted from hydroxylapatite by increasing concentrations of phosphate buffers, and a non-soluble form, free of DNA, which remained in the hydroxylapatite column, and which contained most of the androgen binding sites. Affinity (Kd) of dihydrotestosterone to the soluble and insoluble fractions of the steroid-binding protein complex was determined to be 0.7 and 0.1 nM, respectively. Salt-resistance of binding proteins in germ cells was shown to develop significantly in the last stages of spermiogenesis.

Nuclear androgen binding sites in the male rat. I. Unoccupied sites in the prostate

A study was made of unoccupied androgen binding sites in the nuclei of ventral prostate glands of male rats. They were measured at 0 degrees C by comparing specific binding of 1 nM [3H]DHT to salt extract of purified nuclei during the first hour with specific binding during both hours. This method was dependent upon demonstrated completion of uptake into unoccupied binding sites within the first hour and linearity of exchange with occupied binding sites during both hours. Unoccupied binding sites were not artefactual. They did not increase if tissue concentration was diluted prior to homogenization, while they decreased if homogenization was delayed after the tissue was minced. They could be occupied, both in vitro (if precharged with at least 1 nM unlabeled DHT) or in vivo, by administering testosterone propionate subcutaneously or by infusing testosterone into the jugular vein. Exposure to a high concentration of unoccupied prostatic cytosolic binding sites (608.4 fmol from castrated rats) as compared to low concentration (29.3 fmol from intact rats) during homogenization had little effect upon nuclear unoccupied binding site concentrations (2.16 fmol/mg DNA vs 2.41 fmol/mg DNA, respectively). In individual rats, concentration of unoccupied nuclear androgen binding sites was 4.61 +/- 1.05 fmol/mg DNA, while total binding site concentration (measured with 10 nM [3H]DHT for 24h at 12 degrees C) was 866 +/- 103 fmol/mg DNA. Unoccupied nuclear binding sites reached their highest concentration in animals 4 months old (15.09 fmol/mg DNA) when animals 21 days through 720 days of age were studied. By use of association and dissociation rates of binding, it was determined that the apparent Kd of nuclear binding sites was 1.11 X 10(-12) M. There were no observed differences between unoccupied and occupied binding sites in steroid specificity or in sedimentation rate in an 8-24% glycerol density gradient. Although no physiological importance can be attributed as yet to unoccupied nuclear androgen binding sites in the prostate, they do provide a convenient comparison with putative androgen binding sites in the nuclei of testicular and epididymal germ cells.

Hypophysectomy and hemivasectomy can inhibit the testicular hemicastration response of the mature rat

Three questions were asked in an attempt to understand how testosterone (T) concentration in the veins of the remaining testis can double within 24 h after hemicastration in the mature rat without a change in plasma luteinizing hormone (LH) levels. These three questions (and their answers) were: 1) Can the testicular hemicastration response occur in hypophysectomized rats? Answer, No. 2) Does LH binding to the testis increase after hemicastration? Answer, No. 3) Is there a neural route to the testis alternate to the superior spermatic plexi? Answer, Yes, apparently there is, since hemivasectomy contralateral to the excised testis partially suppressed the testicular hemicastration response (150.4 +/- 13.2 ng/ml in hemicastrated, sham- hemivasectomized rats [n = 18] vs. 109.4 +/- 11.6 ng/ml in hemicastrated, hemivasectomized rats [n = 18], P less than 0.026). It was concluded that LH was probably necessary to the testicular hemicastration response but that its presence did not provide a mechanism. The response was mediated at least partly through the inferior spermatic nerves associated with the vas deferens. A possible reason, although highly speculative, for failure to previously block the testicular hemicastration response by bilateral denervation of the superior spermatic plexi (Mock and Frankel , 1982) was that during the 12-wk interval between denervation and hemicastration, testicular innervation functionally transferred from the superior spermatic to the inferior spermatic nerves.

Stereochemistry of olefinic bond formation in defensive steroids of Acilius sulcatus (Dytiscidae)

The defensive secretion of Acilius sulcatus contains a number of pregnane derivates: cortexone, 20alpha-hydroxy-4-pregnen-3-one, together with the unusual delta4,6 dienes, 6,7-dehydrocortexone, 20alpha-hydroxy-4,6-pregnadien-3-one and 4,6-pregnadien-3,20-dione. The synthesis of all these steroids except cortexone is described. Complete separation of the steroids of Acilius can be achieved by high-performance liquid chromatography on the reversed-phase column system. During biosynthesis of the Acilius steroids from cholesterol, introduction of the delta4 and delta6 bonds involves elimination of the 4beta and 7beta hydrogens, respectively. Possible mechanisms of formation of the delta4,6 steroids are discussed.

Lupus erythematosus latex tests compared with the immunofluorescence method for antinuclear factor

Two commercially available lupus erythematosus (LE) latex tests were compared against positive antinuclear antibody (ANF) sera of known titers. The Lederle SLE Latex Test Kit was found to be more specific and relatively more sensitive, particulary with high ANF titers, than the Hyland LE Test Kit. The latex test is a rapid, simple method which, when positive, can be suggestive of systemic lupus erythematosus (SLE) or other collagen disease. However, at present this test cannot replace the immunofluorescence method for detecting ANF. Where there is any clinical suggestion of SLE or a related condition, all negative results should be tested by immunofluorescence methods.

Routes to 18-nor and 19-nor steroids

17-Oxo-18-nor-5α,13β-androstan-3β-yl acetate (6) and the 13α-epimer (7) have been synthesized by two routes, both of which involve initially an ?abnormal? Beckmann rearrangement of the oxime of 17-oxo-5α-androstan- 3β-yl acetate to the 13,17-seco nitrile (4). In the shorter but lower- yielding sequence, the mixture of epimeric epoxides obtained from (4) was converted into a mixture of (6) and (7) in 25% yield with boron trifluoride in refluxing toluene. A higher yield was achieved by a Dieckmann condensation of the nitrile esters (9) and (10), readily prepared from the above epoxides via the aldehydes. ��� The latter method was also found to be useful for the synthesis of 1-oxo-19-nor-5α,10β-androstan-17β-yl acetate (22) from 1-oxo-5α- androstan-17β-yl acetate.