Molecular evolutionary trends and feeding ecology diversification in the Hemiptera, anchored by the milkweed bug genome

BACKGROUND

The Hemiptera (aphids, cicadas, and true bugs) are a key insect order, with high diversity for feeding ecology and excellent experimental tractability for molecular genetics. Building upon recent sequencing of hemipteran pests such as phloem-feeding aphids and blood-feeding bed bugs, we present the genome sequence and comparative analyses centered on the milkweed bug Oncopeltus fasciatus, a seed feeder of the family Lygaeidae.

RESULTS

The 926-Mb Oncopeltus genome is well represented by the current assembly and official gene set. We use our genomic and RNA-seq data not only to characterize the protein-coding gene repertoire and perform isoform-specific RNAi, but also to elucidate patterns of molecular evolution and physiology. We find ongoing, lineage-specific expansion and diversification of repressive C2H2 zinc finger proteins. The discovery of intron gain and turnover specific to the Hemiptera also prompted the evaluation of lineage and genome size as predictors of gene structure evolution. Furthermore, we identify enzymatic gains and losses that correlate with feeding biology, particularly for reductions associated with derived, fluid nutrition feeding.

CONCLUSIONS

With the milkweed bug, we now have a critical mass of sequenced species for a hemimetabolous insect order and close outgroup to the Holometabola, substantially improving the diversity of insect genomics. We thereby define commonalities among the Hemiptera and delve into how hemipteran genomes reflect distinct feeding ecologies. Given Oncopeltus's strength as an experimental model, these new sequence resources bolster the foundation for molecular research and highlight technical considerations for the analysis of medium-sized invertebrate genomes.

Molecular evolutionary trends and feeding ecology diversification in the Hemiptera, anchored by the milkweed bug genome

BACKGROUND

The Hemiptera (aphids, cicadas, and true bugs) are a key insect order, with high diversity for feeding ecology and excellent experimental tractability for molecular genetics. Building upon recent sequencing of hemipteran pests such as phloem-feeding aphids and blood-feeding bed bugs, we present the genome sequence and comparative analyses centered on the milkweed bug Oncopeltus fasciatus, a seed feeder of the family Lygaeidae.

RESULTS

The 926-Mb Oncopeltus genome is well represented by the current assembly and official gene set. We use our genomic and RNA-seq data not only to characterize the protein-coding gene repertoire and perform isoform-specific RNAi, but also to elucidate patterns of molecular evolution and physiology. We find ongoing, lineage-specific expansion and diversification of repressive C2H2 zinc finger proteins. The discovery of intron gain and turnover specific to the Hemiptera also prompted the evaluation of lineage and genome size as predictors of gene structure evolution. Furthermore, we identify enzymatic gains and losses that correlate with feeding biology, particularly for reductions associated with derived, fluid nutrition feeding.

CONCLUSIONS

With the milkweed bug, we now have a critical mass of sequenced species for a hemimetabolous insect order and close outgroup to the Holometabola, substantially improving the diversity of insect genomics. We thereby define commonalities among the Hemiptera and delve into how hemipteran genomes reflect distinct feeding ecologies. Given Oncopeltus's strength as an experimental model, these new sequence resources bolster the foundation for molecular research and highlight technical considerations for the analysis of medium-sized invertebrate genomes.

Expression and function of spineless orthologs correlate with distal deutocerebral appendage morphology across Arthropoda

The deutocerebral (second) head segment is putatively homologous across Arthropoda, in spite of remarkable disparity of form and function of deutocerebral appendages. In Mandibulata this segment bears a pair of sensory antennae, whereas in Chelicerata the same segment bears a pair of feeding appendages called chelicerae. Part of the evidence for the homology of deutocerebral appendages is the conserved function of homothorax (hth), which has been shown to specify antennal or cheliceral fate in the absence of Hox signaling, in both mandibulate and chelicerate exemplars. However, the genetic basis for the morphological disparity of antenna and chelicera is not understood. To test whether downstream targets of hth have diverged in a lineage-specific manner, we examined the evolution of the function and expression of spineless (ss), which in two holometabolous insects is known to act as a hth target and distal antennal determinant. Toward expanding phylogenetic representation of gene expression data, here we show that strong expression of ss is observed in developing antennae of a hemimetabolous insect, a centipede, and an amphipod crustacean. By contrast, ss orthologs are not expressed throughout the cheliceral limb buds of spiders or harvestmen during developmental stages when appendage fate is specified. RNA interference-mediated knockdown of ss in Oncopeltus fasciatus, which bears a simple plesiomorphic antenna, resulted in homeotic distal antenna-to-leg transformation, comparable to data from holometabolous insect counterparts. Knockdown of hth in Oncopeltus fasciatus abrogated ss expression, suggesting conservation of upstream regulation. These data suggest that ss may be a flagellar (distal antennal) determinant more broadly, and that this function was acquired at the base of Mandibulata.

The electronic structure of iridium oxide electrodes active in water splitting

Iridium oxide based electrodes are among the most promising candidates for electrocatalyzing the oxygen evolution reaction, making it imperative to understand their chemical/electronic structure. However, the complexity of iridium oxide's electronic structure makes it particularly difficult to experimentally determine the chemical state of the active surface species. To achieve an accurate understanding of the electronic structure of iridium oxide surfaces, we have combined synchrotron-based X-ray photoemission and absorption spectroscopies with ab initio calculations. Our investigation reveals a pre-edge feature in the O K-edge of highly catalytically active X-ray amorphous iridium oxides that we have identified as O 2p hole states forming in conjunction with Ir(III). These electronic defects in the near-surface region of the anionic and cationic framework are likely critical for the enhanced activity of amorphous iridium oxides relative to their crystalline counterparts.

The first myriapod genome sequence reveals conservative arthropod gene content and genome organisation in the centipede Strigamia maritima

Myriapods (e.g., centipedes and millipedes) display a simple homonomous body plan relative to other arthropods. All members of the class are terrestrial, but they attained terrestriality independently of insects. Myriapoda is the only arthropod class not represented by a sequenced genome. We present an analysis of the genome of the centipede Strigamia maritima. It retains a compact genome that has undergone less gene loss and shuffling than previously sequenced arthropods, and many orthologues of genes conserved from the bilaterian ancestor that have been lost in insects. Our analysis locates many genes in conserved macro-synteny contexts, and many small-scale examples of gene clustering. We describe several examples where S. maritima shows different solutions from insects to similar problems. The insect olfactory receptor gene family is absent from S. maritima, and olfaction in air is likely effected by expansion of other receptor gene families. For some genes S. maritima has evolved paralogues to generate coding sequence diversity, where insects use alternate splicing. This is most striking for the Dscam gene, which in Drosophila generates more than 100,000 alternate splice forms, but in S. maritima is encoded by over 100 paralogues. We see an intriguing linkage between the absence of any known photosensory proteins in a blind organism and the additional absence of canonical circadian clock genes. The phylogenetic position of myriapods allows us to identify where in arthropod phylogeny several particular molecular mechanisms and traits emerged. For example, we conclude that juvenile hormone signalling evolved with the emergence of the exoskeleton in the arthropods and that RR-1 containing cuticle proteins evolved in the lineage leading to Mandibulata. We also identify when various gene expansions and losses occurred. The genome of S. maritima offers us a unique glimpse into the ancestral arthropod genome, while also displaying many adaptations to its specific life history.

Arthropods are the most abundant animals on earth. Among them, insects clearly dominate on land, whereas crustaceans hold the title for the most diverse invertebrates in the oceans. Much is known about the biology of these groups, not least because of genomic studies of the fruit fly Drosophila, the water flea Daphnia, and other species used in research. Here we report the first genome sequence from a species belonging to a lineage that has previously received very little attention—the myriapods. Myriapods were among the first arthropods to invade the land over 400 million years ago, and survive today as the herbivorous millipedes and venomous centipedes, one of which—Strigamia maritima—we have sequenced here. We find that the genome of this centipede retains more characteristics of the presumed arthropod ancestor than other sequenced insect genomes. The genome provides access to many aspects of myriapod biology that have not been studied before, suggesting, for example, that they have diversified receptors for smell that are quite different from those used by insects. In addition, it shows specific consequences of the largely subterranean life of this particular species, which seems to have lost the genes for all known light-sensing molecules, even though it still avoids light.

Smoking cessation post-discharge following nicotine replacement therapy use during an inpatient admission

BACKGROUND

Cigarette smoking remains a health issue despite declining prevalence in Australia. The burden of tobacco-related morbidity affects hospitals, particularly those in lower socioeconomic areas where prevalence is highest.

AIM

We have shown that nicotine replacement therapy (NRT) use during hospitalization increases motivation to quit post-discharge. We postulated that subjects using the nicotine patch post-discharge, in comparison to the inhaler, would have higher rates of abstinence at 12 months after discharge. The aim was to compare the efficacy of the nicotine patch or inhaler formulation for cessation post-discharge, following use during admission.

METHODS

Post-discharge, subjects chose their preferred formulation (patch or inhaler) based on their experience with NRT during admission. Tailored, medium-intensity support was provided with subsidized NRT during outpatient visits. Subjects were followed for 12 months. Exhaled breath CO confirmed non-smoking.

RESULTS

Of 123 subjects enrolled, 37 elected to use the inhaler, 50 the patch and 36 no NRT. At 12 months continuous abstinence rates were 38%, 38% and 25% respectively.

DISCUSSION

This study built upon the 'teachable moment' provided by hospitalization and the inpatient use of NRT, encouraging cessation post-discharge. Both NRT formulations provided similar 12 month cessation rates, and were superior to those achieved by subjects electing not to use NRT. Although the patch was the most popular formulation, the inhaler provided an equally efficacious alternative which addressed other facets of cigarette addiction. Subjects electing not to use NRT were less successful. Continuous abstinence rates were equivalent to community-based studies using NRT. We recommend a similar programme to other hospitals.

Smoking prevalence and perspectives on smoking on campus by employees in Australian teaching hospitals

BACKGROUND

Cigarette smoking prevalence has been declining over decades in Western countries especially in higher socioeconomic groups. Employees of Australian hospitals span the socioeconomic spectrum, but there are few data on smoking prevalence from these workplaces. Because smoking is a health hazard, some argue that it should be banned on hospital premises, but employees' opinions appear not to have been widely canvassed. Cigarette smoking is a particular problem in hospitals because of the need for prolonged abstinence by immobile patients and the stressors that accompany life-and-death events for patients and/or relatives. The Queen Elizabeth Hospital has had a Stop Smoking Service for >10 years, but how smoking prevalence has changed and how it compares with similar hospitals is unknown.

AIMS

The aims of this study were (i) to determine smoking prevalence by employees of The Queen Elizabeth Hospital and to compare this with employees of other hospitals and (ii) to ascertain employees' perspectives regarding smoking on hospital grounds.

METHODS

Single page questionnaires were forwarded to employees of four South Australian/Northern Territory hospitals enquiring about smoking status, employment category, views about smoking on hospital premises, etc. Responses were voluntary.

RESULTS

Response rates were 39-59%. Smoking prevalence has steadily declined at The Queen Elizabeth Hospital and is now 8.4%. Prevalence at comparator hospitals was approximately double this value. Most staff thought the visibility of smoking was problematic, but support for providing smoking area/s was greater than for a hospital-wide ban.

CONCLUSIONS

The ongoing decline in smoking prevalence at The Queen Elizabeth Hospital is probably the result of the Staff Stop Smoking Service.

Craving control using nicotine replacement therapy in a teaching hospital

BACKGROUND

A period of hospitalisation is perhaps the longest period of enforced 'temporary abstinence' smokers have to endure and hence many crave during their admission. Cravings may result in patients' smoking on hospital premises. Nicotine replacement may reduce cravings, decrease smoking on hospital grounds and increase interest in quitting post-discharge.

AIM

The aim of this study was to compare the efficacy of two nicotine formulations in controlling inpatient cravings and enthusiasm for quitting post-discharge.

METHODS

Inpatients who were smokers were randomised to nicotine patch or inhaler on alternating days. Patients selected their preferred formulation, which was then used for the duration of the hospital stay. Craving control and formulation preference were assessed by visual analogue scales (VAS), and interest in quitting on a 3-point scale. Abstinence was confirmed by exhaled breath CO monitoring.

RESULTS

Patches were preferred by 64% of the 367 subjects. Fewer patients went outside to smoke after either formulation (37% before, 5% after enrolment). Cravings were reduced by both nicotine formulations (mean VAS score fell from 7.5 to 1.7). Interest in quitting post-discharge increased. Estimated mean exposure to nicotine was 5 mg/day (inhaler), 15 mg/day (transdermal patch) compared with 30 mg/day (cigarettes) before hospitalisation.

CONCLUSIONS

Many smokers crave and some smoke outside during a hospital admission. While the patch was the preferred formulation of nicotine replacement therapy, both were effective in reducing cravings, increasing motivation for quitting post-discharge and improving Hospital 'image' by reducing smoking on campus. Nicotine replacement therapy should be made available to inpatients in all hospitals and other places of enforced prolonged abstinence.

The effects of gold and Co-adsorbed carbon on the adsorption and thermal decomposition of acetic acid on Pd{111}

The growth and annealing behavior of ultrathin Au films on Pd{111} were monitored with scanning tunneling microscopy (STM) and medium energy ion scattering (MEIS). The adsorption of acetic acid on both clean and deliberately carbon-contaminated bimetallic surfaces was investigated with reflection absorption infrared spectroscopy (RAIRS) and temperature-programmed desorption (TPD). We report that the surface chemistry of acetic acid is strongly modified by the presence of Au in the bimetallic surface which acts both to stabilize adsorbed acetate and to decrease the tendency of acetic acid to decompose on adsorption to produce adsorbed carbon. The adsorption of acetic acid at 300 K is found to cause measurable segregation of Pd to the surface for all surface compositions tested.

Investigating the mechanism of chiral surface reactions: the interaction of methylacetoacetate with (S)-glutamic Acid modified Ni{111}

The enantioselective hydrogenation of beta ketoesters over Ni-based catalysts is a rare example of a heterogeneously catalyzed chiral reaction. The key step in catalyst preparation is the adsorption from solution of chiral molecules (modifiers). One particularly interesting modifier is (S)-glutamic acid because the dominant enantiomeric product in the catalytic reaction depends upon the modification temperature. We report a reflection absorption infrared spectroscopy (RAIRS) study of the adsorption of methylacetoacetate (the simplest beta ketoester) onto (S)-glutamic acid modified Ni{111} surfaces as functions of the modifier coverage and modification temperature. We show that the sticking probability of methylacetoacetate is close to 0 on saturated (S)-glutamic acid covered surfaces. At lower modifier coverage, methylacetoacetate adsorption can occur. Adsorption of methylacetoacetate onto a Ni{111} surface modified by (S)-glutamic acid at 300 K results in the diketo tautomeric form, with evidence being observed for a 1:1 interaction between zwitterionic (S)-glutamate and methylacetoacetate. In contrast, adsorption of methylacetoacetate onto a Ni{111} surface modified by (S)-glutamic acid at 350 K occurs exclusively in the enol tautomeric form. The implications for the heterogeneous catalytic reaction are discussed.

Molecular ordering and adsorbate induced faceting in the Ag{110}-(S)-glutamic acid system

The adsorption of the amino acid, (S)-glutamic acid, was investigated on Ag{110} as a function of coverage and adsorption temperature using the techniques of scanning tunneling microscopy, low energy electron diffraction, and reflection absorption infrared spectroscopy. In the monolayer, (S)-glutamic acid was found to adsorb predominantly in the anionic glutamate form. Several discrete ordered adlayer structures were observed depending on preparation conditions. In addition, (S)-glutamic acid was found to induce both one- and two-dimensional faceting of the Ag{110} surface. In some cases, evidence was found that the 2-D faceting involved the creation of a chiral facet distribution. A comparison is made of the Ag/(S)-glutamic acid system with analogous studies of amino acids on Cu.

Effects of doxorubicin on human dental pulp cells in vitro

There is substantial information concerning the effects of continuous exposure to supratherapeutic or therapeutic concentrations of doxorubicin on human molar pulpal cells; the effects of continuous exposure to subtherapeutic concentrations of this agent are undetermined. To this end, we studied the proliferation of human fibroblasts and pulpal cells and their pattern of mineralized nodule deposition in vitro. Cell proliferation was assessed at 1, 3, 5, and 7 days from populations with either no exposure (control) or exposure to 10(-6)-10(-9) mol/L doxorubicin. Mineralized nodule deposition and calcium-45 incorporation were assessed at 7 and 21 days of culture. Data were compared by factorial ANOVA and a post-hoc Tukey test. 10(-6) and 10(-7) mol/L doxorubicin significantly reduced the total number of viable pulpal cells in cultures from days 1 to 3 (p < 0.05); doxorubicin 10(-6)-10(-9) mol/L significantly inhibited cell proliferation (p < 0.05) and DNA synthesis 5 days after plating (p < 0.001). After 21 days, doxorubicin 10(-6)-10(-8) mol/L significantly decreased calcium-45 incorporation into pulpal cultures (p < 0.001); all dilutions significantly reduced the number of mineralized nodules within the 21-day pulpal cultures (p < 0.05). In addition, all dilutions of doxorubicin significantly inhibited fibroblast cell proliferation and incorporation of [(3)H]thymidine. In contrast, the fibroblast cultures did not produce mineralized nodules, suggesting that the mineralized nodules within the pulpal cell cultures did not result from dystrophic calcification. Thus, exposure to subtheraputic doxorubicin concentrations has potential adverse effects on mineralized tissue formation within the pulp, which could affect the rates of reparative dentin deposition within the tooth pulps of patients receiving this chemotherapeutic agent.

The nucleotide-binding site of the sarcoplasmic reticulum Ca-ATPase is conformationally altered in aged skeletal muscle

Cellular conditions in senescent skeletal muscle have been shown to result in the loss of conformational stability of the sarcoplasmic reticulum (SR) Ca-ATPase. To identify underlying structural features of age-modified Ca-ATPase, we have utilized the fluorescence properties of protein-bound probes to assess both local and global structure. We find conformational changes that include an age-related decrease in the apparent binding affinity to high affinity calcium sites detected by fluorescence signals in both tryptophans within nearby membrane-spanning helices and fluorescein isothiocyanate (FITC) bound distally to Lys(515) within the nucleotide-binding site. In addition, a substantial (80%) age-related increase in the accessibility to soluble quenchers of fluorescence of FITC is observed without concomitant changes in bimolecular quenching constants (k(q)) for protein-bound IAEDANS, also within the nucleotide-binding domain, and tryptophans within the membrane. Using fluorescence resonance energy transfer to measure distances between IAEDANS and FITC across the nucleotide-binding domain, we find no significant age-related change in the mean donor-acceptor distance; however, significant increases are observed in the conformational heterogeneity of this domain, as assessed by the width at half-maximum (HW) of the distance distribution, increasing with age from 29.4 +/- 0.8 A to 42.5 +/- 1. 1 A. Circular dichroism indicates that the average secondary structure is unaltered with age. Thus, these data suggest tertiary structural alterations in specific regions around the nucleotide-binding site rather than global conformational changes.

Mechanisms of drug-induced diarrhoea in the elderly

In the rapidly increasing elderly population, diarrhoea as a result of drug therapy is an important consideration. The elderly consume a disproportionately large number of drugs for multiple acute and chronic diseases. Drugs can compromise both immune and nonimmune responses. Aging decreases the quality and proportion of T cells which in turn reduces the production of secretory IgA, the primary immune response of the gut. Acid production in the stomach decreases with increasing age and this compromise its vital 'self-sterilising' function, thus increasing the risk of diarrhoea due to viral, bacterial and protozoal pathogens. Other nonimmune defence mechanisms include the motility of the small intestine and the host-protective commensal bacteria of the colon. Drug induced hypomotility may result in bacterial overgrowth, deconjugation of bile salts and diarrhoea. Less commonly, diarrhoea may occur due to hypermotility because of a cholinergic-like syndrome. In the colon the host-protective commensal bacteria provide a powerful defence against pathogens. Disruption of this commensal population by antibiotic therapy may result in Clostridium difficile supra-infection which causes diarrhoea through toxin production. This is especially important in the elderly patient on chemotherapy for malignancy and those with multiple diseases. The organism responds to vancomycin, metronidazole and bacitracin. Metronidazole is the suggested drug of choice, with vancomycin reserved for relapses. Drugs also cause diarrhoea by interfering with normal physiological processes. Drugs impair fluid absorption by activating adenylate cyclase within the small intestinal enterocyte which increases the level of cyclic AMP. This causes active secretion of Cl- and HCO3-, passive efflux of Na+, K+ and water and inhibition of Na+ and Cl- into the enterocyte. Examples of these drugs (secretagogues) are bisacodyl, misoprostol and chenodeoxycholic acid (used to dissolve cholesterol gallstones). Drugs may also affect a second mechanism that regulates water and electrolyte transport, the Na+, K+ exchange pump. The energy for this pump is provided by the ATPase mediated breakdown of ATP. ATPase may be inhibited by digoxin, auranofin, colchicine and olsalazine. A number of drugs cause osmotic diarrhoea including antacids containing magnesium trisilicate or hydroxide. Lactulose is being used increasingly in compensated liver disease to increase protein tolerance and prevent hepatic encephalopathy. Sorbitol, an osmotic laxative agent also used in some liquid pharmaceutical preparations, induces diarrhoea by virtue of its osmotic potential. Another mechanism by which drugs cause diarrhoea is by mucosal damage of the small and large bowel. In the small intestine mucosal damage causes diarrhoea and fat malabsorption, as may occur with neomycin and colchicine. In the colon, for example, gold salts and penicillamine cause colitis of varying severity. Though the causes of diarrhoea are diverse, a drug-associated aetiology should always be considered and actively sought and addressed to prevent the complications of dehydration, electrolyte imbalance and undernutrition.

Smoking habits and cessation programme in an Australian teaching hospital

BACKGROUND

Data on prevalence of cigarette smoking by hospital employees are limited in Australia, but anecdotal evidence suggests that many health sector employees continue to smoke despite abundant evidence regarding the harmful effects of this habit. Nicotine is an addictive drug and arguably this should be known better in the health industry than in any other industry. Despite having this knowledge at their disposal, health sector employers rarely provide assistance to employees, relying instead on restrictive policies to reduce smoking in the workplace.

METHODS

To assist employees to quit smoking, we instituted a medium intensity Stop Smoking Programme, run by a clinical pharmacist offering nicotine patches and support on a weekly basis. A principal aim of the service was to redress the imbalance between the availability of cigarettes and the most effective nicotine replacement therapy, the trandermal nicotine patch. Following 18 months operation of this service, we surveyed hospital employees to ascertain smoking rates and views on smoking cessation in this South Australian teaching hospital.

RESULTS

In the first 18 months of operation, 111 staff members availed themselves of the service. At the first follow up period (three months), 21 were not contactable, 29 were successful in not smoking and 61 were still smoking. Six of the 29 who were not smoking at three months resumed smoking by six months, and a further four resumed smoking by 12 months. At the time of this report, 12 of the remaining 19 non smokers had completed two years since quitting and a further three of these had resumed regular smoking by this time. The cost of providing the service was modest at approximately $180.00 per known successful quitter. Results from the survey showed that 12.4% of hospital employees were regular smokers. Smoking prevalence was not equally distributed with female employees being twice as likely to smoke as their male counterparts and employees in the catering department having the highest smoking prevalence (23.8%).

CONCLUSIONS

Although the prevalence of cigarette smoking by employees of this teaching hospital is lower than for the general community, health sector employers can reduce smoking prevalence further by providing assistance to their employees to quit smoking. The Stop Smoking Programme we describe is effective and could be replicated by other hospitals and similar organisations.

Diltiazem disposition and metabolism in recipients of renal transplants

Diltiazem is widely prescribed in Australasia as a cyclosporine-sparing agent. On seven separate occasions at 2-week intervals, the authors studied eight patients who had undergone renal transplantation, were treated with cyclosporin A, and were in stable condition. The patients were administered escalating doses of conventional-release diltiazem, and (in an extension study) controlled-diffusion diltiazem, to consider the disposition and metabolism of diltiazem. Blood samples were drawn during a 24-hour period, and the AUC(0)(24) of diltiazem and three major metabolites was determined. Results demonstrated that seven patients had comparable diltiazem metabolite AUC(0)(24) profiles, despite considerable variability in parent diltiazem areas under the curve (AUCs), with DM-DTZ > DA-DTZ > DMDA-DTZ. The eighth patient displayed a different metabolite profile. The controlled-diffusion formulation reduced the interpatient variability in diltiazem AUC(0)(24) from 46-fold to <3-fold, but it did not appear to have release characteristics consistent with the manufacturer's specifications. The apparent bioavailability of the conventional-release diltiazem formulation appeared to be highly variable, and this has implications for its use in recipients of organ transplants. The dosage escalation demonstrated a linear relationship between dose and AUC for diltiazem and for each of the metabolites. There may be a subset of patients who display a different diltiazem metabolite profile.

Decreased conformational stability of the sarcoplasmic reticulum Ca-ATPase in aged skeletal muscle

Sarcoplasmic reticulum (SR) membranes purified from young adult (4-6 months) and aged (26-28 months) Fischer 344 male rat skeletal muscle were compared with respect to the functional and structural properties of the Ca-ATPase and its associated lipids. While we find no age-related alterations in (1) expression levels of Ca-ATPase protein, and (2) calcium transport and ATPase activities, the Ca-ATPase isolated from aged muscle exhibits more rapid inactivation during mild (37 degrees C) heat treatment relative to that from young muscle. Saturation-transfer EPR measurements of maleimide spin-labeled Ca-ATPase and parallel measurements of fatty acyl chain dynamics demonstrate that, accompanying heat inactivation, the Ca-ATPase from aged skeletal muscle more readily undergoes self-association to form inactive oligomeric species without initial age-related differences in association state of the protein. Neither age nor heat inactivation results in differences in acyl chain dynamics of the bilayer including those lipids at the lipid-protein interface. Initial rates of tryptic digestion associated with the Ca-ATPase in SR isolated from aged muscle are 16(+/- 2)% higher relative to that from young muscle. indicating more solvent exposure of a portion of the cytoplasmic domain. During heat inactivation these structural differences are amplified as a result of immediate and rapid further unfolding of the Ca-ATPase isolated from aged muscle relative to the delayed unfolding of the Ca-ATPase isolated from young muscle. Thus age-related alterations in the solvent exposure of cytoplasmic peptides of the Ca-ATPase are likely to be critical to the loss of conformational and functional stability.

Survey of cyclosporine therapeutic ranges, assay methodology, and use of 'sparing agents' in Australasian transplant centers

Since its introduction in the 1980s, cyclosporine has become the major immunosuppressive drug used in organ transplantation. Despite widespread experience with this expensive agent, a number of controversial issues remain. These include the use of sparing agents to allow a lower dose of cyclosporine to be prescribed, specificity of assay method, and values quoted as therapeutic ranges. The authors surveyed organ transplant centers in Australia and New Zealand to ascertain local practices and found considerable variability in the use and dosage of sparing agents, cyclosporine assay method, and therapeutic ranges. The implications of these differences are discussed.

Diltiazem-cyclosporin pharmacokinetic interaction--dose-response relationship

AIMS

To study the dose-response relationship of the pharmacokinetic interaction between diltiazem and cyclosporin in kidney transplant recipients.

METHODS

Eight stable kidney transplant recipients maintained on cyclosporin but not taking diltiazem, were given increasing doses of diltiazem to a maximum dose of 180 mg day(-1). Following a 2 week period on each dose of diltiazem, thirteen blood samples were taken over a 24 h period to allow morning and evening AUCs to be determined for cyclosporin, diltiazem and three metabolites of diltiazem.

RESULTS

Mean cyclosporin AUC(0, 24 h) increased sharply following the lowest dose of diltiazem used (10 mg day(-1)), the rate of increase slowed after 30-60 mg day(-1) but continued to increase up to the maximum dose tested. The effect of a single morning dose of DTZ was evident over both morning (0-12 h) and evening (12-24 h) cyclosporin AUCs. There was considerable interpatient variation in response to DTZ.

CONCLUSIONS

The dose of diltiazem required to increase cyclosporin AUC (and hence allow significant reduction in cyclosporin dose) is less than that currently used for many patients. Lower doses of diltiazem should result in fewer adverse effects and may allow its use in situations where it was hitherto contraindicated. Because of the significant interpatient variation in response, we recommend individual patient blood cyclosporin concentration monitoring both before and after the introduction of diltiazem.

The use of other drugs to allow a lower dosage of cyclosporin to be used. Therapeutic and pharmacoeconomic considerations

Since its discovery in 1970, and introduction into clinical practice in 1978, cyclosporin has become the most important immunosuppressive drug used to prevent organ transplant rejection. This has been achieved by virtue of the improved graft survival rates and adverse effect profiles in patients when compared with that of the older agents. Cyclosporin is substantially more expensive (both to provide and to monitor) however, and the magnitude of these costs may preclude its use, particularly where the transplant recipient is required to pay. Cyclosporin has a complex pharmacokinetic profile with poor absorption, extensive metabolism to more than 30 metabolites and considerable inter- and intrapatient variability. Many transplant centres routinely use drugs ("cyclosporin-sparing agents') to allow a reduction in the dosage of cyclosporin while maintaining therapeutic blood cyclosporin concentrations. The use of a second drug to affect the pharmacokinetic profile of a primary drug is not new, but the use of cyclosporin-sparing agents is a departure from previous practices in that this coprescription is primarily for economic reasons. The decision to use these agents (and the choice of agent) is based upon economic and other factors including the extent of the cyclosporin-sparing effect, the potential for additional therapeutic benefit and/or adverse effects. The coprescription of cyclosporin-sparing agents is ethically more acceptable where the transplant recipient is the economic beneficiary but where the savings accrue to a third party it is more difficult. Benefits to the community at large must be balanced against the risk of adverse effects to the patient. The use of cyclosporin-sparing agents may reduce compliance and hence, jeopardise transplant and/or recipient outcomes. The transplant recipient must be informed about the reasons for their use and advised to consult an experienced physician or pharmacist before altering the established drug regimen.

Formulation of diltiazem affects cyclosporin-sparing activity

OBJECTIVE

To consider the effect of changing from a conventional release formulation of diltiazem to the controlled diffusion diltiazem formulation on the cyclosporin-sparing effect in kidney transplant recipients.

METHODS

Seven stable renal transplant recipients were studied on two separate occasions following at least 2 weeks stabilisation on either formulation. The order of administration of the two formulations was not randomised as all patients were already prescribed lower dosages of diltiazem before entering this phase of a larger study. The doses of diltiazem used were 90 mg (conventional release diltiazem) taken twice daily and 180 mg controlled diffusion diltiazem taken in the morning.

RESULTS

Whilst there were no overall significant differences between the two formulations, the study demonstrated considerable interpatient variability when changing to the controlled diffusion formulation, particularly following the morning cyclosporin dose, with three patients showing a reduced cyclosporin AUC (30-60%) and one an increased cyclosporin AUC of 36%.

CONCLUSION

A change in formulation of the cyclosporin-sparing agent may result in unpredictable alterations in cyclosporin concentrations and resultant clinical sequelae.

Survey of cyclosporin-sparing agent use in Australasian transplant centres

BACKGROUND

The co-prescription of drugs which elevate cyclosporin blood concentration has been advocated to reduce the costs associated with use of this expensive immunosuppressive drug. This is the first time that drugs have been widely prescribed for an economic purpose and while it is thought to be widespread, there are little published data on the extent of this practice in Australia and New Zealand.

AIMS

To determine the extent to which cyclosporin sparing agents are used by Australian and New Zealand organ transplant centres, to determine which agents are used and why these agents are used by some but not all centres.

METHODS

Organ transplant centres were surveyed via a questionnaire.

RESULTS

Considerable variation in use of cyclosporin sparing agents exists both within and across organ transplant types by Australian and New Zealand transplant centres. Diltiazem use is more widespread than ketoconazole.

CONCLUSIONS

Little of the variability in use of cyclosporin sparing agents can be explained by scientific considerations. While the central government benefits from the significant cost savings achieved by the use of cyclosporin sparing agents, individual transplant units may not. Transplant units may however be the major target in the event of litigation arising as a result of adverse effects. The availability of generic brands and improved formulations of cyclosporin may affect the viability of using cyclosporin sparing agents.

Diltiazem does not always increase blood cyclosporin concentration

The pharmacokinetic interaction between the calcium channel blocking drug, diltiazem (DTZ), the antifungal agent itraconazole (ICZ) and the immunosuppressive drug cyclosporin (CsA) was studied in a patient with a single lung transplant. The CsA area under curve estimations demonstrated a significant increase when ICZ was co-prescribed (5836 micrograms l-1 h vs 8159 micrograms l-1 h) but no increase when DTZ was co-prescribed with CsA (5836 micrograms l-1 h vs 5069 micrograms l-1 h). Despite widespread use as a CsA-sparing agent, DTZ does not always increase CsA concentrations.

Dextromoramide pharmacokinetics following sublingual administration

The extent of absorption and other pharmacokinetic parameters of dextromoramide following sublingual administration were assessed in five patients receiving chronic opioid analgesia. The use of the standard 5 mg tablet formulation was associated with negligible absorption in two patients, a prolonged time to peak concentration in the other three and substantial variability in clearance. The study concluded that the standard tablet formulation cannot be recommended for sublingual use where reliable, rapid onset analgesia is required.

Membrane depolarization induces calcium-dependent secretion of tissue plasminogen activator

Tissue plasminogen activator (tPA), a serine protease that converts inactive plasminogen to active plasmin, is produced in the rat and mouse hippocampus and participates in neuronal plasticity. To help define the role of tPA in the nervous system, we have analyzed the regulation of its expression in the neuronal cell line PC12. In control cultures, tPA activity is exclusively cell-associated, and no activity is measurable in the culture medium. When the cells are treated with depolarizing agents, such as KCI, tPA activity becomes detectable in the medium. The increased secreted tPA activity is not accompanied by an increase in tPA mRNA levels, and it is not blocked by protein synthesis inhibitors. In contrast, tPA release is abolished by Ca2+ channel blockers, suggesting that chemically induced membrane depolarization stimulates the secretion of preformed enzyme. Moreover, KCI has a similar effect in vivo when administered to the murine brain via an osmotic pump: tPA activity increases along the CA2-CA3 regions and dentate gyrus of the hippocampal formation. These results demonstrate a neuronal activity-dependent secretory mechanism that can rapidly increase the amount of tPA in neuronal tissue.

Hydration assessment during cold-weather military field training exercises

To quantify the magnitude of dehydration and to identify predictors of dehydration by utilizing changes in total body water (TBW), 24 male Marines were studied during an 8d moderately cold-weather (1-3 degrees C) training exercise. Training consisted of approximately 12 h/d of moderately intense activity. Variables examined included body composition, TBW, and various blood and urinary parameters indicative of hydration. Dietary food and fluid records were also maintained. Body composition changes were consistently with the high energy expenditure and insufficient energy intake. Despite a decrease in TBW, significant dehydration as assessed by blood and urinary parameters did not occur over the 8d period, therefore no relationships were found between TBW and any of the clinical indicators of dehydration. The change in TBW was reflective of a decrease in lean body mass. These data suggest that during cold-weather military field exercise, despite high activity levels and a negative energy balance, body fluid balance can be maintained when particular attention is paid to fluid intake.

Relationship between resistance of salmonids to furunculosis and recovery of Aeromonas salmonicida from external mucus

Fish were sampled at the Ed Weed State Fish Hatchery (South Hero, Vermont, USA) in September 1992. Aeromonas salmonicida was common, with concentrations as high as 10(5) to 10(7) colony-forming units per gram of mucus, and readily recovered from most mucus samples obtained from furunculosis-sensitive populations of brook trout (Salvelinus fontinalis), lake trout (Salvelinus namaycush), and Atlantic salmon (Salmo salar). The pathogen was the predominant microorganism and accounted for greater than 85% of the total number of bacteria isolated from the mucus of these fish. By comparison, A. salmonicida was recovered only from two rainbow trout (Oncorhynchus mykiss), and bacterial frequencies did not exceed 10(3) colony-forming units per gram of mucus. The pathogen was not recovered from the mucus of steelhead (O. mykiss) or Rome brown trout (Salmo trutta) selectively bred for resistance to furunculosis, even though there was widespread contagion throughout the hatchery and fish were cultured on a common, unprotected water supply.

Doubly labeled water measurement of human energy expenditure during exercise at high altitude

Estimates of total daily energy expenditure (TDEE) by the doubly labeled water (DLW, 2H(2)18O) and intake balance (I-B) methods were compared in six male soldiers studied over 6 days that included 5 days of strenuous winter exercise at 2,500- to 3,100-m elevation. Use of body energy stores [-9.54 +/- 1.54 (SD) MJ/day or -2,280 +/- 368 kcal/day] was estimated from changes in body weight, body density (hydrodensitometry), and total body water (H(2)18O dilution). The subjects wore computerized activity monitors and kept daily records of ration consumption (9.87 +/- 3.60 MJ/day or 2,359 +/- 860 kcal/day). Accuracy of individual DLW and I-B TDEE values was estimated from the correlations of TDEE with fat-free mass (FFM) or total weight (body wt + load). The DLW and I-B estimates of TDEE differed by -12.0 to 15.2% but provided comparable estimates of group mean TDEE (DLW = 19.07 +/- 2.37 MJ/day or 4,558 +/- 566 kcal/day; I-B = 19.41 +/- 3.72 MJ/day or 4,639 +/- 889 kcal/day; P > 0.05). The DLW TDEE was correlated with both FFM (r2 = 0.89, P < 0.01, power = 0.95) and total weight (r2 = 0.95, P < 0.01, power = 0.99), whereas I-B TDEE was correlated only with total weight (r2 = 0.75, P < 0.03, power = 0.81). Under adverse field conditions the DLW method provided individual TDEE estimates that were probably more accurate than those provided by the I-B method.

Novel nematocidal agents from Curcuma comosa

Curcuma comosa is a member of the economically important plant family, Zingiberaceae. A methanolic extract of C. comosa was shown to be nematocidal when tested against the free-living nematode Caenorhabditis elegans. Five diphenylheptanoids [1-5], one new and four known, have been isolated and shown to be responsible for the activity. This is the first report of three of these compounds [1, 2, 4] being isolated from a natural source.

Dopamine receptor antagonists increase markedly the quantity of retrograde transport of HRP in the rat masseteric motoneuron

Horseradish peroxidase (HRP) was injected, bilaterally, into the rat masseter muscle, subsequent to an intramuscular or intraperitoneal injection of one of five dopamine antagonists (chlorpromazine and haloperidol as the D1 and D2 receptor antagonist, SCH 23390 as the specific D1 receptor antagonist, sulpiride and domperidone as the specific D2 receptor antagonist). Control rats received an injection of a corresponding vehicle solution. After a survival period of 16 h, the brainstem was cut into 60 microns cryosections and processed with the TMB technique. The amount of retrogradely transported HRP was quantitatively measured in terms of the amount of HRP reaction product present in the motoneuron by the method which we have developed using an image processing system combined with a light microscope and a TV camera. Chlorpromazine, haloperidol, SCH 23390 and sulpiride significantly raised the quantity of retrograde transport of HRP. On the contrary, domperidone which can not penetrate the blood-brain barrier showed no significant change in the amount of the retrograde transport. In addition, an intravenous injection of chlorpromazine (8 mg/kg) was found to increase the amplitude of monosynaptic masseteric reflex EMG activity evoked by stimulations of the mesencephalic trigeminal nucleus. These results suggest that a possible regulatory system involving the dopamine receptor in the uptake and retrograde transport of HRP from axon terminals to cell bodies of the masseteric motoneuron exists in higher order neurons which make synaptic contact with the motoneuron.

The differentiation of the skin and its appendages. I. Normal development of papillary ridges

In the present study, the normal development of papillary ridges was studied in the volar pads of both fore and hindpaws of the opossum, Monodelphis domesticus. At birth, the developmental state of the opossum's paws is equivalent to that of a six-week human embryo. The development of papillary ridges in the opossum occurs entirely postnatally and the hindpaw lags behind the forepaw by at least four days in most developmental parameters. Papillary ridge formation is preceded by four events: skin innervation, Merkel cell differentiation, mesenchymal condensation, and epidermal proliferation. The apical pads at the tips of the digits and the interdigital pads between the heads of the metacarpals (or metatarsals) have a unique pattern of innervation and mesenchymal content as compared to the non-pad skin. Each pad is innervated by a prominent nerve trunk and axons ascend towards the epidermis providing a density of innervation that exceeds that in the non-pad epidermis. Merkel cells are absent in non-pad epidermis but present in the pads prior to the onset of formation of papillary ridges. A loose aggregation of mesenchyme forms the core of the pads and the superficial dermis is more cellular in the pads as compared to the equivalent dermis in surrounding non-pad skin. Developing papillary ridges always contained Merkel cell-axon complexes. Merkel cell axon complexes serve as the anatomical substrate of slowly adapting (SA) mechanoreceptors. The presence of these complexes during early skin differentiation is consistent with the use of the opossum's forepaw in climbing to the nipple, but also suggests other possible functions. We hypothesize that the nervous system might play a role in the timing or patterning of the formation of papillary ridges.

The differentiation of the skin and its appendages. II. Altered development of papillary ridges following neuralectomy

In order to test the hypothesis that the nervous system is an important determinant of skin differentiation, deletions of the left lumbosacral dorsal root ganglia (DRGs), the sources of cutaneous afferents to the left hindpaw, were performed on opossum pups at day 1 when hindpaws have just begun to be innervated. At birth, each lumbosacral DRG measures about 200 microns rostrocaudally and a deletion measuring 1 mm would span 4-5 DRGs. Following survival periods of 5-24 days, serial sections through the trunk documented partial left lumbosacral DRG deletion and a variable degree of spinal cord destruction. The blood supply to the trunk and hindpaws was preserved. Bilateral enlargement of residual DRGs was observed and regenerating skin at the site of the deletion was hyperplastic and hyperinnervated. The skin of the plantar pads of the hindpaws was studied following the neuralectomies. Statistically significant differences were observed between the left (experimental) and right (control) hindpaws. The density of innervation of the left hindpaw was reduced compared to the right hindpaw, development of papillary ridges was retarded by 3-4 days, and non-innervated Merkel cells were hypogranulated. This period of delay in ridge development is probably a reflection of the expansion of residual DRGs into the peripheral domains of deleted DRGs. The present study confirms a role for afferent nerves in the timing of cutaneous differentiation and a mutual trophic dependence between cutaneous nerves and Merkel cells in the epidermis.

Doubly labeled water measurement of human energy expenditure during strenuous exercise

The energy expenditures (EE) of 23 adult male Marines were measured during a strenuous 11-day cold-weather field exercise at 2,200- to 2,550-m elevation by both doubly labeled water (2H2 18O, DLW) and intake balance methods. The DLW EE calculations were corrected for changes in baseline isotopic abundances in a control group that did not receive 2H2 18O. Intake balance EE was estimated from the change in body energy stores and food intake. Body energy-store changes were calculated from anthropometric [-1,574 +/- 144 (SE) kcal/day] and isotope dilution (-1,872 +/- 293 kcal/day) measurements made before and after the field exercise. The subjects kept daily logbook records of ration consumption (3,132 +/- 165 kcal/day). Mean DLW EE (4,919 +/- 190 kcal/day) did not differ significantly from intake balance EE estimated from food intake and either anthropometric (4,705 +/- 181 kcal/day) or isotope dilution (5,004 +/- 240 kcal/day) estimates of the change in body energy stores. The DLW method can be used with at least the same degree of confidence as the intake balance method to measure the EE of active free-living humans.

Immunization against learned helplessness in the cockroach (Periplaneta americana)

Cockroaches exposed to one day of escapable shock prior to three days of inescapable shock did not become helpless on a shuttlebox-escape task. Like dogs and rats, cockroaches are immunized against learned helplessness by prior experience with escapable shock.

Yield loss assessments for cultivars of broccoli, lettuce, and onion exposed to ozone

The effects of the photochemical oxidant air pollutant ozone (O(3)) on growth and yield of three garden crops, broccoli (Brassica oleracea L.), lettuce (Lactuca sativa L.), and onion (Allium cepa L.) were studied in an open-top chamber experiment conducted in the field in southern California. Four cultivars each of leaf lettuce, broccoli, and globe onion were exposed to charcoal-filtered air (CF), non-filtered (NF) air, or NF plus 1.5 times ambient O(3) concentration from 4 weeks after germination in January or February until harvest. Exposures lasted 31 days for lettuce, 55 to 78 days for broccoli, and 105 days for onion. Results showed that despite severe O(3) injury to outer leaves, lettuce yields were not affected by O(3). Broccoli also was resistant to O(3) and no growth reduction was observed at ambient O(3) concentrations. Onions were more susceptible to O(3), but only one cv. 'Rio Bravo' had significant yield losses (ca. 5%) at ambient O(3) levels. These results suggest that, in general, concentrations of O(3) in the winter and spring may be below the threshold for adverse effects on yields of broccoli, lettuce and onion.

Innervation of the tooth pulp by the mesencephalic trigeminal nucleus in the cat: a retrograde horseradish peroxidase study

HRP was applied to the tooth pulp of 8 cats. Six were subjected to postoperative administration of the anti-inflammatory drug, prednisolone, whereas the remaining two were not. In all prednisolone-treated cats, labeled neurons were found in both the mesencephalic trigeminal nucleus and trigeminal ganglion, ipsilaterally. On the other hand, no labeled neurons were observed in the mesencephalic nucleus in cats receiving no steroid.

The morphogenesis of the posterior neural tube and tail in Monodelphis domesticus

The process of secondary neuralation has been studied in the Brazilian opossum, Monodelphis domesticus. Secondary neuralation in this mammal was found to have qualities of secondary neuralation that were present in both the chick and the mouse. In this study, four stages of secondary neuralation were found beginning with the medullary cord stage. Other stages in the differentiation of the secondary neural tube were: differentiation of the neuroepithelium, cavitation of the medullary cord, and proliferation of the neural tube. The process of secondary neuralation proceeded in a rostral-to-caudal direction and was found to be independent of age. Diastematomyelia (doubling of the tube) was found in several animals. The process of cavitation was completed by the joining of several small, focal cavities in a rostral-to-caudal direction. The most distinctive feature of secondary neuralation in this animal was the finding of axons within the secondary neural tube, a feature not characteristic of either the chick or the mouse.

Neural modulation of cutaneous differentiation: epidermal hyperplasia and precocious hair development following partial neuralectomy in opossum pups

The original intent of the present study was to evaluate the compensatory response of the nervous system to areas of denervation. A portion of the spinal cord in the lumbosacral region of one-day opossum pups (Monodelphis domesticus) was removed by cauterization. This partial neuralectomy produced an expected compensatory response of neurons in the dorsal root ganglia, but in addition produced unexpected abnormalities of cutaneous differentiation. At 4-6 days following surgery, an increase in the thickness of the epidermis resembling glabrous palmar or plantar skin was seen. This hyperplastic epidermis appeared to be associated with an abnormally dense innervation of the dermis and epidermis. Eight days following partial neuralectomy most animals showed areas of precocious hair development. Nerve fibers were always seen in the dermis associated with these precocious hairs and were seen to penetrate the basal lamina in the region of the epidermal-hair shaft boundary. These results imply a critical role for afferent nerves in the normal development of the skin and its appendages.

Moxalactam kinetics during continuous ambulatory peritoneal dialysis after intraperitoneal administration

Moxalactam kinetics during continuous ambulatory peritoneal dialysis (CAPD) was followed in eight patients after a single intraperitoneal dose of 1 g. Approximately 60% of the dose was absorbed after a dwell time of 4 h. Dialysis solutions were exchanged at 4-h intervals with an overnight dwell of 8 h. The mean (+/- standard deviation) elimination half-life was 13.2 +/- 2.9 h, and the mean apparent volume of distribution was 0.22 +/- 0.08 liters/kg. Mean total clearance was 11.5 +/- 2.4 ml/min, with a mean dialysis clearance of 2.3 +/- 0.5 ml/min. The maximum concentration in plasma ranged from 24.5 to 54.1 micrograms/ml. Moxalactam concentrations in the peritoneal dialysis fluid were above 80 micrograms/ml during the first exchange and above 2 micrograms/ml for a further three exchanges. A suggested intraperitoneal dose regimen for patients undergoing CAPD is 1 g initially, followed by 15 to 25% of the recommended dose for normal patients given at the same time intervals, or 30 to 50% of the recommended dose at twice the usual intervals. Moxalactam is suggested for initial treatment of peritonitis in CAPD patients who do not have ready access to the antibiotic of choice.

Herpes simplex type 1 ribonucleotide reductase. Mechanism studies with inhibitors

Several known inhibitors of mammalian ribonucleotide reductase were studied for their interactions with herpes simplex virus type 1 (HSV-1) ribonucleotide reductase. MAIQ (4-methyl-5-amino-1-formylisoquinoline thiosemicarbazone) produced apparent inactivation of HSV-1 ribonucleotide reductase. Only catalytically cycling, not resting, enzyme could be inactivated. Double reciprocal replots of the rates of inactivation versus the concentration of MAIQ indicated that a reversible complex with the enzyme was formed prior to inactivation. In the presence of 10 microM CDP, the maximum rate of inactivation was 20 per h (t1/2 = 3 min). The half-maximum rate was achieved at about 15 microM MAIQ. INOX (periodate-oxidized inosine) also appeared to inactivate HSV-1 ribonucleotide reductase. In contrast to MAIQ, it readily inactivated resting as well as cycling enzyme. CDP retarded the rates of inactivation by INOX. An initial reversible complex between INOX and enzyme was not detectable under the conditions used. IMPY (2,3-dihydro-1H-pyrazolo(2,3-a)imidazole) and guanazole (3,5-diamino-1,2,4-triazole) produced reversible inhibition. Although the data with both inhibitors were most consistent with the noncompetitive inhibition model (versus CDP), the data with guanazole were also marginally consistent with the uncompetitive model.

Early differentiation of the afferent nervous system in glabrous snout skin of the opossum (Monodelphis domesticus)

Early differentiation of afferent fibers innervating the snout skin of Monodelphis domesticus was studied by electron microscopy and by light-microscopic silver staining techniques. This study was undertaken to investigate the relationship between dermal and epidermal innervation in the neonate opossum while correlating these findings with behavioral responses. The advantage of using this species is that the neonate is born in a very immature stage and has a rostrocaudal development of the peripheral nervous system. Glabrous snout skin from young opossums was studied at birth (0 day) and postnatal days 1, 3, and 5. Neurite bundles were seen within the dermis, with axons and growth cones approaching the epidermis. Some axons penetrated the dermal-epidermal junction in newborn pups. Merkel cells were consistently numerous during the time spanned by this study. Mature Merkel cells had granules polarized toward an associated neurite and were often located in the base of the rete pegs. Immature Merkel cells were characterized by a lack of polarization of granules and absence of an apposed neurite, suggesting that these cells can differentiate without an associated neurite. Contiguous Merkel cells had junctional complexes in 0- and 1-day animals. Schwann cells, identified by their contact with neurite bundles, were present in large numbers, especially in the superficial dermis. Melanocytes could be identified in the epidermis in 5-day pups only. Developing rete pegs could be recognized in 0-day animals and became prominent in 5-day pups. These observations suggest that afferent fibers are present at a very early age and that some of these fibers are anatomically mature. These findings support the concept that the ability of the neonate to locate a teat and suckle requires only the presence of mature epidermal innervation, while dermal receptors appear later during postpartum development.

Simultaneous demonstration of neuronal somata that innervate the tooth pulp and adjacent periodontal tissues, using two retrogradely transported anatomic markers

Two axonally transported substances were used to demonstrate the spatial relationships between trigeminal ganglion cells innervating the tooth pulp and adjacent periodontal tissues of the mandibular canine teeth in cats. 4',6-Diamidino-2-phenylindole (DAPI) and horseradish peroxidase (HRP) were applied in the periodontal tissues and in the tooth pulp, respectively. The trigeminal ganglion and brain stem were then examined for the presence of fluorescent DAPI-labeled cells, HRP-labeled cells, and cells containing both labels. Cells containing either DAPI or HRP were observed in the mandibular portion of the ganglion; DAPI-labeled cells were observed in the pontine portion of the mesencephalic nucleus of the trigeminal nerve. Examples of double labeling, indicative of collateralization of single neurons to innervate both the tooth pulp and adjacent tissues, were not commonly observed. Finally, there was no indication of a mesencephalic nucleus contribution to the tooth pulp innervation.

Monophosphates of formycin B and allopurinol riboside. Interactions with leishmanial and mammalian succino-AMP synthetase and GMP reductase

Formycin B 5'-monophosphate (Form B-MP) and allopurinol riboside 5'-monophosphate ( HPPR -MP) are isomers of IMP that are metabolically produced when Leishmania spp. are incubated with the antileishmanial agents formycin B and allopurinol or allopurinol riboside. The interactions of Form B-MP with succino -AMP synthetase and GMP reductase from both leishmanial and mammalian sources were compared with the data of earlier studies with HPPR -MP. Both analogs could substitute for IMP as a substrate for succino -AMP synthetase isolated from Leishmania donovani. The V'max values of Form B-MP and HPPR -MP were about 1% of the V'max of IMP. Only Form B-MP (and not HPPR -MP) could serve as an alternative substrate for mammalian succino -AMP synthetase. The V'max of Form B-MP was 40% that of IMP. The corresponding analogs of AMP, ADP and ATP were produced when Formycin B was incubated with mouse L cells. The Formycin A residue was incorporated into the cellular RNA. The amount of Formycin A-TP produced (relative to ATP) in mouse L cells was considerably less than that produced in Leishmania spp. Both Form B-MP and HPPR -MP were inhibitors of partially purified GMP reductase from L. donovani. The binding of Form B-MP and HPPR -MP to human GMP reductase was 40- and 100-fold weaker, respectively, than the binding to leishmanial GMP reductase. Pretreatment of promastigotes of L. donovani with either allopurinol or Formycin B resulted in greater than 95% reduction of the incorporation of the radiolabel from [14C]xanthine into ATP and greater than 80% reduction of the incorporation of the label into GTP. The HPPR -MP and Form B-MP present in these cells may have inhibited the leishmanial succino -AMP synthetase and GMP reductase. The analogs had little or no effect on the pool sizes of ATP and GTP of either mouse L cells or L. donovani.