Abnormal regulation of thirst and vasopressin secretion following surgery for craniopharyngioma

OBJECTIVE

In this study we aimed to establish the frequency of postoperative diabetes insipidus and the incidence and characteristics of abnormalities of thirst in a cohort of patients with craniopharyngioma, in whom neurosurgery had been performed.

DESIGN

Diabetes insipidus was determined by either standard criteria for diagnosis in the immediate postoperative period, or by water deprivation test, in all craniopharyngioma and pituitary tumour patients who underwent surgery in Beaumont Hospital between the years 1986 and 1998. Osmoregulated thirst and vasopressin release were studied during a 2-h infusion of hypertonic (5%) saline followed by a 30-min period of free access to water.

PATIENTS

Data on the incidence of postoperative diabetes insipidus was collected in 26 patients with craniopharyngioma and 154 patients with pituitary adenomata. We recruited 16 healthy control patients, 16 patients with cranial diabetes insipidus following pituitary tumour surgery and 16 patients with cranial diabetes insipidus following craniopharyngioma resection for the hypertonic saline infusion study.

RESULTS

Twenty-five patients out of 26 (96%) patients developed diabetes insipidus after surgery for craniopharyngioma, a much higher incidence than after surgery for suprasellar (26/88, 30%, P < 0.001) or intrasellar pituitary tumours (9/66, 14%, P < 0.001). Hypertonic saline infusion identified abnormal thirst responses in five of the 16 craniopharygioma patients studied; all of the pituitary tumour patients had a normal thirst response. Three of the craniopharyngioma patients had adipsic diabetes insipidus whilst two had polydipsic diabetes insipidus.

CONCLUSION

This study demonstrates following surgery for craniopharyngioma there is a high incidence of cranial diabetes insipidus and a significant incidence of abnormal thirst responses to osmotic stimuli.

Improved patient survival in recipients of simultaneous pancreas-kidney transplant compared with kidney transplant alone in patients with type 1 diabetes mellitus and end-stage renal disease

BACKGROUND

There are emerging data that simultaneous pancreas-kidney transplant (SPK) prolongs life compared with kidney transplant alone (KTA) in type 1 diabetics with end-stage renal disease. This study was a retrospective comparison of SPK with KTA in patients with type 1 diabetes.

METHODS

Between 1 January 1992 and 30 April 2002, 101 patients with type 1 diabetes were transplanted. Fifty-one of these patients received a KTA and 50 had a SPK. All patients underwent coronary angiography with surgical correction of any coronary artery disease before being listed. All patients who underwent SPK received quadruple immunosuppressive therapy consisting of antilymphocyte globulin, calcineurin inhibitor (tacrolimus or cyclosporin), azathioprine and steroids. Those who underwent KTA received calcineurin inhibitor (tacrolimus or cyclosporin), azathioprine and steroids.

RESULTS

Patient survival at 1, 3, 5 and 8 years was 96, 93, 89 and 77 per cent respectively after SPK, and 93, 75, 57 and 47 per cent respectively after KTA (P = 0.018 at 8 years).

CONCLUSION

The addition of pancreatic transplantation prolongs life in type 1 diabetic patients with renal failure compared with renal transplantation alone.

The albuminuric action of atrial natriuretic peptide is not modified by ACE-inhibition with perindopril in Type 2 diabetes

AIMS

Atrial natriuretic peptide (ANP) increases urine albumin excretion (UAER) in humans with Type 1 diabetes. The aim of this study was to establish if ANP increases UAER in microalbuminuric subjects with Type 2 diabetes and to examine whether the albuminuric action of ANP was inhibited by pre-treatment with the ACE-inhibitor perindopril.

METHODS

Seven microalbuminuric, normotensive males with Type 2 diabetes were entered into a randomised, double-blind, three-armed study of (i) intravenous infusion of ANP (0.25 microg/kg/min in 0.9% NaCl) after 3 weeks' pre-treatment with placebo, (ii) intravenous infusion of vehicle (0.9% NaCl only) after 3 weeks' pre-treatment with placebo, or (3) intravenous infusion of ANP (0.25 microg/kg/min in 0.9% NaCl) after 3 weeks' pre-treatment with perindopril, 4 mg daily.

RESULTS

Baseline parameters were similar on all three study days. During the placebo/vehicle arm there was no change in urine flow rate (UFR, P=0.61), urine cyclic guanosine monophosphate (UcGMP P=0.48) or UAER (P=0.99). During the placebo/ANP arm there was a rise in UFR [13.7+/-2.8 (mean+/-sd) to 25.7+/-7.7 mL/min, P<0.001], UcGMP (60.0+/-36.6 to 160.8+/-118.5 micromol/mmolCr, P=0.045) and UAER [5.13 [2.4-11.6][median (range)] to 71.6 [21.6-175.1] mg/mmolCr, P<0.001]. Pre-treatment with perindopril did not alter the changes in UFR (P=0.63), UcGMP (P=0.46) or UAER (P=0.99) to infusion of ANP, compared with the placebo/ANP arm.

CONCLUSION

ANP increases UAER in microalbuminuric patients with Type 2 diabetes and the albuminuric action of ANP is not inhibited by pre-treatment with the ACE inhibitor perindopril.

Twelve-year experience in the investigation and treatment of paragangliomas

We report a 12-year laboratory experience in the diagnosis of 37 patients with phaeochromocytoma, one with malignant paraganglioma and one with ganglioneuroblastoma. Surgery was performed in eight different hospitals, which underlines the difficulty of ensuring uniformity of investigations. Of the 37 with phaeochromocytoma, 15 were in the right adrenal gland, 12 were on the left, seven were bilateral and three were extra adrenal. Twenty-three were male and 15 were female; the median age was 36 years. Four of five patients with von Hippel-Lindau disease had bilateral adrenal tumours and four had neurofibromatosis. None had multiple endocrine neoplasia. Using essential hypertensive patients as a reference population, diagnostic sensitivity was 80% for noradrenaline, 54.4% for adrenaline, 19.1% for dopamine, 93.3% for total normetanephrine, 33.3% for total metanephrine, 78.7% for 3-methoxy-4-hydroxymandelic acid (HMMA) and 23.5% for homovanillic acid (HVA). However, if each patient's results were taken as a package, the sensitivities were 100% for noradrenaline, 63.6% for adrenaline, 30.3% for dopamine and 89% for HMMA. Seven recent patients had gene analysis. There were six (15.4%) deaths due directly or indirectly to the paraganglioma. Postoperative blood pressures were normal in 74%. The decrement in catecholamine values post-surgery is shown. Urinary noradrenaline values fell by a mean of 94.5% and the use of urinary noradrenaline as a tumour marker is also demonstrated.

Baroregulation of vasopressin release in adipsic diabetes insipidus

Adipsic diabetes insipidus (ADI) occurs in association with a heterogeneous group of conditions. We report vasopressin (AVP) responses to hypotension in nine patients with ADI and nine controls. Hypertonic saline infusion produced absent thirst (1.7 +/- 1.7 to 1.5 +/- 1.7 cm, P = 0.99) and AVP responses (0.3 +/- 0.1 to 0.4 +/- 0.1 pmol/liter, P = 0.99) in the ADI group, who also drank less than the control group (258 +/- 200 ml vs. 1544 +/- 306 ml, P < 0.001). Intravenous infusion of trimetaphan camsylate produced a fall in mean arterial pressure of 31.6% +/- 8.9% in patients and 29.4% +/- 6.1% in controls. Plasma AVP concentrations rose from 1.4 +/- 0.8 to 340.3 +/- 497.4 pmol/liter (P < 0.001) in the control group. In three patients with craniopharyngioma, there was no rise in plasma AVP concentrations (0.3 +/- 0.1 to 0.3 +/- 0.1 pmol/liter, P = 0.96), but plasma AVP rose significantly in response to hypotension in the other six patients (0.4 +/- 0.2 to 204.5 +/- 223.2 pmol/liter, P < 0.001). We concluded that the AVP responses to hypotension in ADI are heterogeneous and reflect the site of the lesion causing the diabetes insipidus.

Brain natriuretic peptide increases urinary albumin and alpha-1 microglobulin excretion in Type 1 diabetes mellitus

Atrial natriuretic peptide (ANP) increases urinary albumin excretion in Type 1 diabetes mellitus (DM). Brain natriuretic peptide (BNP) is structurally and functionally related to ANP, but its effect on urine albumin excretion rate (UAER) is unknown.

AIMS

To compare the albuminuric effects of intravenous infusion of ANP and BNP, and to assess the effect of both peptides on tubular protein excretion.

METHODS

Eight subjects with Type 1 DM were randomised to a three leg, double blind, and placebo controlled study. On each study day, subjects were euglycaemic clamped and subsequently water loaded (20 mL/kg orally, plus urine losses) to steady state diuresis. When in steady state, creatinine clearance was estimated in three separate 1 hour periods. At the end of the first period, a 1 hour intravenous infusion of either placebo, ANP 0.025 microg/kg/min, or BNP 0.025 microg/kg/min was administered. There followed a 1 hour recovery period. Urine was collected at 15 min intervals for estimation of urine albumin (ACR) and alpha1 microglobulin creatinine ratio (MCR). Results were analysed by anova.

RESULTS

Creatinine clearance was similar on the three study days, and was unaltered by any infusion. ACR was unaltered by placebo (1.3 +/- 0.5-1.2 +/- 0.4 mg/mmol, mean +/- SD, p = 0.81), but increased compared to placebo with infusion of both ANP (1.2 +/- 0.4-9.8 +/- 8.4 mg/mmol, P = 0.0004), and BNP (1.1 +/- 0.4-13.4 +/- 8.6 mg/mmol, P = 0.0001). The MCR was unaltered by placebo infusion (P = 0.89), but increased compared with placebo after infusion of ANP (5.4 +/- 0.9-12.3 +/- 4.2 mg/mmol, P < 0.0001), and BNP (5.4 +/- 0.8-12.1 +/- 2.5 mg/mmol, P < 0.0001).

CONCLUSIONS

Intravenous infusion of BNP and ANP both increase the urine excretion of albumin and the tubular protein alpha1 microglobulin, independent of creatinine clearance.

The meaning of research utilization. A preliminary typology

The preliminary findings of the meaning of research utilization as perceived by the bedside nurse provide some clues for promoting research utilization. Nurses must believe in the importance of nursing research to the profession, the individual clinician, and the patient. Nurse researchers should present their findings to the bedside nurse in a way that can be easily applied to the practice setting. Shaping a positive research mindset is important to the goal of a research-based practice. Infusing research findings throughout nursing courses, in addition to having a research course to learn basic critiquing skills, emphasizes the importance of nursing research to the individual student and encourages a seamless transition to clinical practice. The institutional setting wields a great deal of power when it comes to mandating practice changes. The institution must value research and embrace a continuing state of change by empowering the nursing staff to question the status quo. Research-focused university settings provide excellent opportunities to learn about the research process and share research findings. Policies and procedures should be updated regularly to reflect changes in the scientific base of nursing practice. Institutional support of research utilization fosters an environment that expects excellence in practice. Encouraging nurses to be more involved in nursing research activities and to value their role as data collectors has been shown to increase research awareness and utilization of findings. Nurses must believe they have the personal and professional power to change practice according to the evidence. This preliminary report has presented data that begin to describe what research utilization means to the bedside RN. The typology presented is grounded in the reality of the practicing nurse and provides important insights for those who wish to foster a research and evidence base for professional nursing practice. As further qualitative and quantitative information about the phenomenon of research utilization is collected, an integrated approach to concept clarification can occur.

Pleiotropic functions of a Streptomyces pristinaespiralis autoregulator receptor in development, antibiotic biosynthesis, and expression of a superoxide dismutase

In Streptomyces, a family of related butyrolactones and their corresponding receptor proteins serve as quorum-sensing systems that can activate morphological development and antibiotic biosynthesis. Streptomyces pristinaespiralis contains a gene cluster encoding enzymes and regulatory proteins for the biosynthesis of pristinamycin, a clinically important streptogramin antibiotic complex. One of these proteins, PapR1, belongs to a well known family of Streptomyces antibiotic regulatory proteins. Gel shift assays using crude cytoplasmic extracts detected SpbR, a developmentally regulated protein that bound to the papR1 promoter. SpbR was purified, and its gene was cloned using reverse genetics. spbR encoded a 25-kDa protein similar to Streptomyces autoregulatory proteins of the butyrolactone receptor family, including scbR from Streptomyces coelicolor. In Escherichia coli, purified SpbR and ScbR produced bound sequences immediately upstream of papR1, spbR, and scbR. SpbR DNA-binding activity was inhibited by an extracellular metabolite with chromatographic properties similar to those of the well known gamma-butyrolactone signaling compounds. DNase I protection assays mapped the SpbR-binding site in the papR1 promoter to a sequence homologous to other known butyrolactone autoregulatory elements. A nucleotide data base search showed that these binding motifs were primarily located upstream of genes encoding Streptomyces antibiotic regulatory proteins and butyrolactone receptors in various Streptomyces species. Disruption of the spbR gene in S. pristinaespiralis resulted in severe defects in growth, morphological differentiation, pristinamycin biosynthesis, and expression of a secreted superoxide dismutase.

Ligand-induced changes in the Streptomyces lividans TipAL protein imply an alternative mechanism of transcriptional activation for MerR-like proteins

TipAL is a Streptomyces transcriptional activator assigned to the MerR/SoxR family based both on homology within its putative DNA recognition domain and the fact that its operator binding sites lie within a region of its promoter normally occupied by RNA polymerase. The tipA gene is also independently translated as the C-terminal ligand-binding domain of TipAL (TipAS; residues 111-254). Both TipAS and TipAL share broad recognition specificity for cyclic thiopeptide antibiotics. The molecular mechanism by which TipAL catalyzes prokaryotic transcriptional activation at the tipA promoter (ptipA) in response to thiostrepton was studied using a combination of analytical ultracentrifugation (AU), circular dichroism (CD), optical waveguide lightmode spectroscopy (OWLS; a sensitive in situ binding assay), and mutational analyses. AU showed that TipAL, but not TipAS, was a dimer in solution in the presence or absence of thiostrepton. This indicated that activation of TipAL by thiostrepton was not mediated by changes in multimerization and mapped the dimerization domain to its N-terminal 110 amino acids, presumably within amino acids predicted to form a coil-coil domain (residues 77-109). CD spectra showed that TipAL had more alpha-helical content than TipAS, probably because of the presence of the additional N-terminal region. The helicity of TipAL and TipAS both increased slightly after binding thiostrepton demonstrating conformation changes upon thiostrepton binding. OWLS experiments determined the overall binding constants via measurements of association and dissociation rates for both TipA proteins and RNA polymerase with ptipA. Thiostrepton slightly enhanced the rate of specific association of TipAL with ptipA, but drastically lowered the rate of dissociation from the binding site. TipAL-thiostrepton increased the affinity of RNA polymerase for ptipA more than 10-fold. In conjunction with genetic experiments, we propose that, while there are some similarities, the mechanism by which TipAL activates transcription is distinctly different from the established MerR/SoxR paradigm.

Smoke alarm ownership and installation: a comparison of a rural and a suburban community in Georgia

As part of a smoke alarm giveaway and installation program (The Get-Alarmed Campaign), a total of 454 households were surveyed in two counties in Georgia, one metropolitan and one nonmetropolitan. The targeted communities in these counties had a high prevalence of low-income and minority populations and thus were at high risk of house fire-related morbidity and mortality. The objectives of the program were to determine the prevalence of and predictors for installed, functioning smoke alarms, and to install at least one smoke alarm and/or smoke alarm batteries in 100% of participating homes in need. Characteristics associated with smoke alarm ownership included home ownership, having a higher income, and having a central heating source, factors which should be considered in targeting future intervention strategies. At onset, 159/454 households (35.0%) had no smoke alarms installed and 56/275 households with existing smoke alarms (20.4%) had none that were functional. Regardless of ownership status, a free smoke alarm was installed in the household of 93.8% of participants and new batteries were installed in existing smoke alarms for 31.7% of participants. This project illustrates the usefulness of a door-to-door campaign in increasing smoke alarm ownership in both a rural and a suburban community with a high concentration of residents at high risk of house fire-related morbidity and mortality.

Artificial aging of phenanthrene in porous silicas using supercritical carbon dioxide

Expedited artificial aging is described and demonstrated using a novel system that circulates a solution of supercritical carbon dioxide and a hydrophobic organic sorbate (phenanthrene) through a closed loop containing a porous substrate. Unlike traditional methods used to simulate the natural aging process, our approach allows for real-time monitoring of sorption equilibria, and the process is highly accelerated due to the unique physical properties of supercritcal carbon dioxide. The effectiveness of the system to simulate aging was demonstrated with a series of experiments in which three silicas with varying particle and pore sizes were loaded with phenanthrene. Batch aqueous desorption experiments were used to evaluate the extent of the aging process. For the two types of particles containing the largest pores (i.e., mean diameters of 202 and 66 A), 95% and 86%, respectively, of the phenanthrene was released to the aqueous fraction within 3 h. In contrast, only 16% of the phenanthrene was released from particles having a mean pore diameter of 21 A after 24 h. These results were confirmed by the results from an aqueous column desorption experiment. Confounding factors that might contribute to slow aqueous desorption such as the hydration state of the particles' surfaces, the chemical form of the loaded phenanthrene, and the organic carbon content were investigated and/or normalized for all three particle types. Consequently, we were able to attribute the slow desorption behavior and the presence of the resistant fraction in the 21 A silica to pore effects. With properly designed experiments, the results of this study suggest that the supercritical fluid system could be extended to the study of contaminant aging and bioavailability in natural soils and sediments.

Extreme altitude mountaineering and Type 1 diabetes; the Diabetes Federation of Ireland Kilimanjaro Expedition

AIMS

To examine the effects of extreme altitude mountaineering on glycaemic control in Type 1 diabetes, and to establish whether diabetes predisposes to acute mountain sickness (AMS).

METHODS

Fifteen people with Type 1 diabetes and 22 nondiabetic controls were studied during the Diabetes Federation of Ireland Expedition to Kilimanjaro. Daily insulin requirements, blood glucose estimations and hypoglycaemic attacks were recorded in diaries by the people with diabetes. The performance of blood glucose meters at altitude was assessed using standard glucose solutions. Symptoms of acute mountain sickness were recorded daily by people with diabetes and by the nondiabetic controls using the Lake Louise Scoring Charts. The expedition medical team recorded the incidence of complications of altitude and of diabetes. The final height attained for each individual was recorded by the expedition medical team and verified by the expedition guides.

RESULTS

The final altitude ascended was lower in the diabetic than the nondiabetic group (5187 +/- 514 vs. 5654 +/- 307 m, P = 0.001). The mean daily insulin dose was reduced from 67.1 +/- 28.3-32.9 +/- 11.8 units (P < 0.001), but only 50% of recorded blood glucose readings were within the target range of 6-14 mmol/L. There were few hypoglycaemic attacks after the first two days of climbing. Both blood glucose meters tested showed readings as low as 60% of standard glucose concentrations at high altitude and low temperatures. The Lake Louise questionnaires showed that symptoms of AMS occurred equally in the diabetic and nondiabetic groups. There were two episodes of mild diabetic ketoacidosis; two of the diabetic group and three of the nondiabetic group developed retinal haemorrhages.

CONCLUSIONS

People with Type 1 diabetes can participate in extreme altitude mountaineering. However, there are significant risks associated with this activity, including hypoglycaemia, ketoacidosis and retinal haemorrhage, with the additional difficulties in assessing glycaemic control due to meter inaccuracy at high altitude. People with Type 1 diabetes must be carefully counselled before attempting extreme altitude mountaineering.

Using collaborative research to facilitate student learning

Developing research partnerships between academia and the service sector is an innovative way to meet the demand for high-quality, cost-effective, and clinically oriented research. Undergraduate student participation in clinical research is an educational strategy to facilitate positive mindsets toward research. This article outlines the methodological steps in recruiting and training undergraduate students for clinical research teams to benefit nurse educators, nurse researchers, students, and institutional partners. Student volunteers collected data for a study examining patient satisfaction with pain management practices. The research proposal was used to demonstrate principles of the research process and to familiarize the students with the study. A detailed study protocol guided the entire team through the project. Student sensitivity to pain assessment and management was enhanced. Learning the research process and the students' appreciation for the rigors of research were reinforced using this experiential model. Student evaluation of the research experience is presented.

Novel pristinamycin-responsive expression systems for plant cells

Novel gene regulation systems were designed for plant cells responsive to the streptogramin antibiotic pristinamycin. The pristinamycin-repressible plant gene regulation concept (PIPpOFF) is based on a transcriptional activator (PIT) which consists of the Pip protein, the repressor of the pristinamycin resistance operon of Streptomyces coelicolor, fused to the VP16 transactivation domain of the Herpes simplex virus. PIT mediates pristinamycin-repressible activation of a synthetic plant promoter (P(pPIR)) in tobacco cells consisting of a nine Pip-binding site-containing artificial operator (PIR3) placed upstream of a TATA-box derived from the cauliflower mosaic virus 35S promoter (P(CaMV35S)). Pristinamycin interferes with induction by negatively regulating the DNA-binding capacity of the Pip moiety of PIT. A second, streptogramin-inducible plant gene regulation system (PIPpON) was constructed by combining Pip expression with a plant-specific pristinamycin-inducible promoter (P(pPIRON)). P(pPIRON) consists of a PIR3 module cloned downstream of the strong constitutive plant promoter P(CaMV35S). As in the native Streptomyces configuration, Pip binds to its cognate sequence within P(pPIRON) in the absence of regulating antibiotic and silences the chimeric plant promoter. Upon addition of pristinamycin, Pip is released from the PIR3 operator and full P(CaMV35S)-driven expression of desired plant genes is induced. The PIPpOFF and PIPpON systems performed well in Nicotiana tabacum suspension cultures and promise to provide an attractive extension of existing plant gene regulation technology for basic plant research or biopharmaceutical manufacturing using plant tissue culture.

A fluorescence spectroscopic study of phenanthrene sorption on porous silica

Fluorescence spectroscopic characteristics of sorbed phenanthrene in porous silica provide information about its chemical state such as monomer vs dimer or higher aggregates, as well as a basis for high sensitivity detection. In this study, the chemical state and distribution of phenanthrene sorbed in two types of porous silica particles, mesoporous silica (365 microns particle diameter, 150 A average pore diameter) and microporous silica (custom synthethized, 1 micron particle diameter, 20 A pore diameter), is determined by fluorescence spectroscopy, fluorescence lifetime measurements, and scanning two-photon excitation fluorescence profiling. From the characteristic fluorescence emission spectra, it is found that at loading levels of < or = 4.7 mg/g (phenanthrene/silica) phenanthrene exists as monomers in both meso- and microporous silica particles for phenanthrene loaded from super critical CO2 (SCF). Two-photon excitation fluorescence intensity distribution profiles indicate that for the mesoporous silica particles phenanthrene is adsorbed throughout the entire silica particle. Introduction of water into phenanthrene-loaded mesoporous silica particles causes instantaneous conversion of phenanthrene from monomer to crystalline form at phenantherene loading levels > or = 4.7 micrograms/g due to hydration of the silica surface. In this process, sorption of water molecules expels phenanthrene from the surface sorption sites and causes localized phenanthrene concentration beyond its solubility limit, resulting in crystallization. In comparison this fast conversion is not observed for phenanthrene-loaded microporous silica particles that show extremely slow conversion even for phenanthrene loading levels as high as 4.7 mg/g. This difference is interpreted as reflecting hindered diffusion of phenanthrene in the nearly monodispersed micropores with pore sizes close to the molecular diameter of phenanthrene.

Roles of aconitase in growth, metabolism, and morphological differentiation of Streptomyces coelicolor

The studies of aconitase presented here, along with those of citrate synthase (P. H. Viollier, W. Minas, G. E. Dale, M. Folcher, and C. J. Thompson, J. Bacteriol. 183:3184-3192, 2001), were undertaken to investigate the role of the tricarboxylic acid (TCA) cycle in Streptomyces coelicolor development. A single aconitase activity (AcoA) was detected in protein extracts of cultures during column purification. The deduced amino acid sequence of the cloned acoA gene constituted the N-terminal sequence of semipurified AcoA and was homologous to bacterial A-type aconitases and bifunctional eukaryotic aconitases (iron regulatory proteins). The fact that an acoA disruption mutant (BZ4) did not grow on minimal glucose media in the absence of glutamate confirmed that this gene encoded the primary vegetative aconitase catalyzing flux through the TCA cycle. On glucose-based complete medium, BZ4 had defects in growth, antibiotic biosynthesis, and aerial hypha formation, partially due to medium acidification and accumulation of citrate. The inhibitory effects of acids and citrate on BZ4 were partly suppressed by buffer or by introducing a citrate synthase mutation. However, the fact that growth of an acoA citA mutant remained impaired, even on a nonacidogenic carbon source, suggested alternative functions of AcoA. Immunoblots revealed that AcoA was present primarily during substrate mycelial growth on solid medium. Transcription of acoA was limited to the early growth phase in liquid cultures from a start site mapped in vitro and in vivo.

Role of acid metabolism in Streptomyces coelicolor morphological differentiation and antibiotic biosynthesis

Studies of citrate synthase (CitA) were carried out to investigate its role in morphological development and biosynthesis of antibiotics in Streptomyces coelicolor. Purification of CitA, the major vegetative enzyme activity, allowed characterization of its kinetic properties. The apparent K(m) values of CitA for acetyl coenzyme A (acetyl-CoA) (32 microM) and oxaloacetate (17 microM) were similar to those of citrate synthases from other gram-positive bacteria and eukaryotes. CitA was not strongly inhibited by various allosteric feedback inhibitors (NAD(+), NADH, ATP, ADP, isocitrate, or alpha-ketoglutarate). The corresponding gene (citA) was cloned and sequenced, allowing construction of a citA mutant (BZ2). BZ2 was a glutamate auxotroph, indicating that citA encoded the major citrate synthase allowing flow of acetyl-CoA into the tricarboxylic acid (TCA) cycle. Interruption of aerobic TCA cycle-based metabolism resulted in acidification of the medium and defects in morphological differentiation and antibiotic biosynthesis. These developmental defects of the citA mutant were in part due to a glucose-dependent medium acidification that was also exhibited by some other bald mutants. Unlike other acidogenic bald strains, citA and bldJ mutants were able to produce aerial mycelia and pigments when the medium was buffered sufficiently to maintain neutrality. Extracellular complementation studies suggested that citA defines a new stage of the Streptomyces developmental cascade.

A connection between stress and development in the multicellular prokaryote Streptomyces coelicolor A3(2)

Morphological changes leading to aerial mycelium formation and sporulation in the mycelial bacterium Streptomyces coelicolor rely on establishing distinct patterns of gene expression in separate regions of the colony. sigmaH was identified previously as one of three paralogous sigma factors associated with stress responses in S. coelicolor. Here, we show that sigH and the upstream gene prsH (encoding a putative antisigma factor of sigmaH) form an operon transcribed from two developmentally regulated promoters, sigHp1 and sigHp2. While sigHp1 activity is confined to the early phase of growth, transcription of sigHp2 is dramatically induced at the time of aerial hyphae formation. Localization of sigHp2 activity using a transcriptional fusion to the green fluorescent protein reporter gene (sigHp2-egfp) showed that sigHp2 transcription is spatially restricted to sporulating aerial hyphae in wild-type S. coelicolor. However, analysis of mutants unable to form aerial hyphae (bld mutants) showed that sigHp2 transcription and sigmaH protein levels are dramatically upregulated in a bldD mutant, and that the sigHp2-egfp fusion was expressed ectopically in the substrate mycelium in the bldD background. Finally, a protein possessing sigHp2 promoter-binding activity was purified to homogeneity from crude mycelial extracts of S. coelicolor and shown to be BldD. The BldD binding site in the sigHp2 promoter was defined by DNase I footprinting. These data show that expression of sigmaH is subject to temporal and spatial regulation during colony development, that this tissue-specific regulation is mediated directly by the developmental transcription factor BldD and suggest that stress and developmental programmes may be intimately connected in Streptomyces morphogenesis.

Does breastfeeding protect children from asthma? Analysis of NHANES III survey data

We sought to determine whether breastfeeding (yes/no) or its duration protects against the development of childhood asthma, its severity or age of onset. We conducted a secondary analysis of youth files of the National Health and Nutrition Examination Survey III (1988-94), and reviewed data from 6,783 children age 2 months to 6 years (3,316 breastfed), excluding children with a history of low birth weight or treatment in a neonatal intensive care unit. Study participants were breastfed an average of 157 days. The average age at onset of asthma was 14.3 months. In the logistic regression model, "ever breast-fed" was not a significant protective factor for developing asthma. Significant predictive factors were the mother's age at child's birth (beta = -0.08, p < 0.01), and a parent having asthma or hayfever (beta = 0.46, p < 0.01). In the linear regression model, the duration of breastfeeding was not a predictor for age at onset of asthma (beta = 0.01, p = 0.53). Only maternal smoking during pregnancy was a significant predictor of age at onset of asthma (beta = -7.59, p < 0.01). Breastfeeding does not appear to prevent asthma, delay its onset, or reduce its severity. However, breastfeeding is still recommended for its many other benefits.

Review of the diagnosis and management of acquired nasolacrimal duct obstruction

BACKGROUND

Acquired nasolacrimal duct obstruction is a common cause of epiphora. The absolute or partial blockage of the nasolacrimal duct occurs most frequently in middle-aged and elderly women. In addition to the troublesome symptom of epiphora, acquired nasolacrimal duct obstruction is predominantly the underlying cause of both acute and chronic dacryocystitis.

METHODS

The primary eye care provider plays an essential role in the diagnosis and management of the patient with epiphora. The potentially serious ramifications of acquired nasolacrimal duct obstruction demand a thorough understanding of the clinical presentation of this disorder. In addition, it is essential the optometrist be well-acquainted with the surgical treatments often necessary for optimal management.

CONCLUSION

Whether treatment is provided or an appropriate referral is made, the optometrist is instrumental in providing care for the patient who experiences an acquired nasolacrimal duct obstruction.