Neonatal nephrotoxic medication exposure and early acute kidney injury: results from the AWAKEN study

BACKGROUND

We aimed to describe nephrotoxic medication exposure and investigate associations between exposure and acute kidney injury (AKI) in the neonatal intensive care unit during the first postnatal week.

DESIGN/METHODS

Secondary analysis of the AWAKEN cohort. We evaluated nephrotoxic medication exposure during the first postnatal week and associations with AKI using time-varying Cox proportional hazard regressions models. Nephrotoxic medication exposure categories were defined as: no nephrotoxic medication, nephrotoxic medications excluding aminoglycosides, aminoglycoside alone, and aminoglycoside and another nephrotoxic medication.

RESULTS

Of 2162 neonates, 1616 (74.7%) received ≥1 nephrotoxic medication. Aminoglycoside receipt was most common (72%). AKI developed in 211(9.8%) neonates and was associated with a nephrotoxic medication exposure (p < 0.01). Nephrotoxic medication exposures including a nephrotoxic medication excluding aminoglycoside (aHR 3.14, 95% CI 1.31-7.55) and aminoglycoside and  another nephrotoxic medication (aHR 4.79, 95% CI 2.19-10.50) were independently associated with AKI and severe AKI (stage 2/3), respectively.

CONCLUSIONS

Nephrotoxic medication exposure in critically ill infants is common during the first postnatal week. Specific nephrotoxic medication exposure, principally aminoglycosides with another nephrotoxic medication, are independently associated with early AKI.

Documentation of acute kidney injury at discharge from the neonatal intensive care unit and role of nephrology consultation

OBJECTIVE

To investigate whether NICU discharge summaries documented neonatal AKI and estimate if nephrology consultation mediated this association.

STUDY DESIGN

Secondary analysis of AWAKEN multicenter retrospective cohort.

EXPOSURES

AKI severity and diagnostic criteria.

OUTCOME

AKI documentation on NICU discharge summaries using multivariable logistic regression to estimate associations and test for causal mediation.

RESULTS

Among 605 neonates with AKI, 13% had documented AKI. Those with documented AKI were more likely to have severe AKI (70.5% vs. 51%, p < 0.001) and SCr-only AKI (76.9% vs. 50.1%, p = 0.04). Nephrology consultation mediated 78.0% (95% CL 46.5-109.4%) of the total effect of AKI severity and 82.8% (95% CL 70.3-95.3%) of the total effect of AKI diagnostic criteria on documentation.

CONCLUSION

We report a low prevalence of AKI documentation at NICU discharge. AKI severity and SCr-only AKI increased odds of AKI documentation. Nephrology consultation mediated the associations of AKI severity and diagnostic criteria with documentation.

The nephrologist of tomorrow: towards a kidney-omic future

Omics refers to the collective technologies used to explore the roles and relationships of the various types of molecules that make up the phenotype of an organism. Systems biology is a scientific discipline that endeavours to quantify all of the molecular elements of a biological system. Therefore, it reflects the knowledge acquired by omics in a meaningful manner by providing insights into functional pathways and regulatory networks underlying different diseases. The recent advances in biotechnological platforms and statistical tools to analyse such complex data have enabled scientists to connect the experimentally observed correlations to the underlying biochemical and pathological processes. We discuss in this review the current knowledge of different omics technologies in kidney diseases, specifically in the field of pediatric nephrology, including biomarker discovery, defining as yet unrecognized biologic therapeutic targets and linking omics to relevant standard indices and clinical outcomes. We also provide here a unique perspective on the field, taking advantage of the experience gained by the large-scale European research initiative called "Systems Biology towards Novel Chronic Kidney Disease Diagnosis and Treatment" (SysKid). Based on the integrative framework of Systems biology, SysKid demonstrated how omics are powerful yet complex tools to unravel the consequences of diabetes and hypertension on kidney function.

Drug-induced acute kidney injury in neonates

PURPOSE OF REVIEW

Acute kidney injury (AKI) is an independent risk factor for morbidity and mortality in critically ill neonates. Nephrotoxic medication exposure is common in neonates. Nephrotoxicity represents the most potentially avoidable cause of AKI in this population.

RECENT FINDINGS

Recent studies in critically ill children revealed the importance of recognizing AKI and potentially modifiable risk factors for the development of AKI such as nephrotoxic medication exposures. Data from critically ill children who have AKI suggest that survivors are at risk for the development of chronic kidney disease. Premature infants are born with incomplete nephrogenesis and are at risk for chronic kidney disease. The use of nephrotoxic medications in the neonatal intensive care unit is very common; yet the effects of medication nephrotoxicity on the short and long-term outcomes remains highly understudied.

SUMMARY

The neonatal kidney is predisposed to nephrotoxic AKI. Our ability to improve outcomes for this vulnerable group depends on a heightened awareness of this issue. It is important for clinicians to develop methods to minimize and prevent nephrotoxic AKI in neonates through a multidisciplinary approach aiming at earlier recognition and close monitoring of nephrotoxin-induced AKI.

Minimally invasive right colectomy: challenges and clinical practice

AIM

Since the introduction of laparoscopic and robotic technology in surgical practice, there have been multiple reports and a few clinical trials on their use in colorectal surgery. Although the application of laparoscopy to right colectomy has been increasingly adopted in many institutions around the world, there are still several open issues regarding the effective role of robotics and single incision surgery. This is a review of the relevant surgical literature evaluating the risks, benefits, and costs of minimally invasive approaches to right colectomy (RC) surgery.

METHODS

Retrospective and prospective articles spanning the past 20 years were reviewed to identify the current application of minimally invasive surgery in RC. A review of the most relevant papers comparing open vs. laparoscopic vs. robotic approaches will illustrate the role of minimally invasive surgery in current clinical practice in terms of surgical outcomes, technical advantages and oncological outcomes. We then pooled the evidence for and against the application of laparoscopy and robotics in intracorporeal vs. extracorporeal anastomosis creation, single incision and natural orifice surgery.

RESULTS

Evidence shows that compared to open surgery, laparoscopic RC provides lower postoperative morbidity, faster return to normal bowel function and a shorter length of hospital stay, with a similar oncological outcome. The application of robotics to RC procedure has proven to be safe and feasible, however the intraoperative and postoperative outcomes are similar with the laparoscopic technique and no clear advantages have been demonstrated. When adopted in a single incision technique and natural orifice surgery, robotics can help to overcome the limitations of laparoscopy, enabling the surgeon to perform scar-less surgery.

CONCLUSION

Laparoscopy surgery, whenever performed by adequately trained surgeons, can be safely applied to right colectomy and should be considered as the gold standard procedure. In terms of robotic surgery, to date, this technology needs more evidence from multicenter randomized clinical trials. New tools and instruments are needed to expand the field of single incision and natural orifice surgery, and make it available in current clinical practice.

Metabolomics in pediatric nephrology: emerging concepts

Metabolomics, the latest of the "omics" sciences, refers to the systematic study of metabolites and their changes in biological samples due to physiological stimuli and/or genetic modification. Because metabolites represent the downstream expression of genome, transcriptome, and proteome, they can closely reflect the phenotype of an organism at a specific time. As an emerging field in analytical biochemistry, metabolomics has the potential to play a major role in monitoring real-time kidney function and detecting adverse renal events. Additionally, small molecule metabolites can provide mechanistic insights into novel biomarkers of kidney diseases, given the limitations of the current traditional markers. The clinical utility of metabolomics in the field of pediatric nephrology includes biomarker discovery, defining as yet unrecognized biological therapeutic targets, linking of metabolites to relevant standard indices and clinical outcomes, and providing a window of opportunity to investigate the intricacies of environment/genetic interplay in specific disease states.

Repair of complex parastomal hernias

Development of parastomal hernias (PH) is very common after stoma formation and carries a risk of subsequent bowel incarceration, obstruction and strangulation. The management of PH remains a challenge for the colorectal surgeon, and there are currently no standardized guidelines for the treatment of PH. Even more difficult is the management of complex parastomal hernias (CPH). We conducted a review of the literature to identify recent developments in the treatment of CPH, including analysis of the use of synthetic and biologic mesh prostheses, method of mesh placement and surgical approach.

Urinary metabolomic markers of aminoglycoside nephrotoxicity in newborn rats

BACKGROUND

Aminoglycoside exposure is a common cause of acute kidney injury (AKI). Delay in the diagnosis of AKI using conventional biomarkers has been one of the important obstacles in applying early effective interventions. We tested the hypothesis that urinary metabolomics could identify novel early biomarkers for toxic renal injury.

METHODS

Three-day-old rats were divided into three groups; they received a single daily injection of vehicle (0.9% NaCl solution) or gentamicin at a dose of 10 or 20 mg/kg/d for 7 d. Urine and blood were collected after 3 and 7 d of injections. Urinary metabolites were evaluated using high-performance liquid chromatography and gas chromatography/mass spectrometry.

RESULTS

A distinct urinary metabolic profile characterized by glucosuria, phosphaturia, and aminoaciduria was identified preceding changes in serum creatinine. At both the gentamicin doses, urinary tryptophan was significantly (P < 0.05) increased (fold change: 1.91 and 2.31 after 3 d; 1.81 and 1.93 after 7 d). Similarly, kynurenic acid, a tryptophan metabolite, showed a significant (P < 0.05) decrease (fold change: 0.26 and 0.24 after 3 d; 0.21 and 0.52 after 7 d), suggesting an interruption of the normal tryptophan metabolism pathway.

CONCLUSION

We conclude that urinary metabolomic profiling provides a robust approach for identifying early and novel markers of gentamicin-induced AKI.

Necrotizing enterocolitis after recurrent supraventricular tachycardia

Necrotizing enterocolitis (NEC) is the most common gastrointestinal (GI) emergency that primarily affects premature infants. In the last decade, there have been significant advances to our understanding of neonatal NEC. The exact etiology of NEC remains unclear, but it is widely considered a multifactorial disease; prematurity, enteral feeding, intestinal hypoxia-ischemia, and bacterial colonization are considered major risk factors. We report a case of a 35 week preterm infant with recurrent episodes of supraventricular tachycardia who developed NEC in the second week of life. This case underscores the importance of being appropriately cautious in the feeding of these high-risk premature infants.

Comparative study of analgesic efficacy and morphine-sparing effect of intramuscular dexketoprofen trometamol with ketoprofen or placebo after major orthopaedic surgery

AIMS

Multimodal analgesia is thought to produce balanced and effective postoperative pain control. A combined therapy with nonsteroidal anti-inflammatory drugs (NSAIDs) and opiates could result in synergistic analgesia by acting through different mechanisms. Currently there are very few parenterally administered NSAIDs suitable for the immediate postoperative period. Therefore, this study was undertaken to assess the analgesic efficacy, relative potency, and safety of parenteral dexketoprofen trometamol following major orthopaedic surgery.

METHODS

One hundred and seventy-two patients elected for prosthetic surgery, were randomized to receive two intramuscular injections (12 hourly) of either dexketoprofen 50 mg, ketoprofen 100 mg or placebo in a double-blind fashion. Postoperatively, the patient's pain was stabilized, then they were connected to a patient- controlled analgesia system (PCA) of morphine for 24 h (1 mg with 5 min lockout).

RESULTS

The mean cumulative amount of morphine (CAM) used was of 39 mg in the dexketoprofen group and 45 mg in the ketoprofen group vs 64 mg in the placebo group. (Reduction in morphine use was approximately one-third between the active compounds compared with placebo (adjusted mean difference of -25 mg between dexketoprofen and placebo and -23 mg between ketoprofen and placebo. These differences were statistically significant: P </= 0.0003; 95% CI -35, -14. Pain-intensity scores were consistently lower with the active compounds, the lowest corresponded to the dexketoprofen-treated patients. Regarding sedation, there were statistically significant differences between the two active compounds and placebo only at the 2nd and 13th hours. Wound bleeding was specifically measured with no statistically significant differences found between all the groups.

CONCLUSIONS

Intramuscular administration of dexketoprofen trometamol 50 mg has good analgesic efficacy both in terms of opioid-sparing effect and control of pain after major orthopaedic surgery.

A comparative study of patient-controlled epidural diamorphine, subcutaneous diamorphine and an epidural diamorphine/bupivacaine combination for postoperative pain

This randomized double blind study investigates the relative efficacies of controlled analgesia (PCA) regimens in three different patient groups: epidural diamorphine 2.5 mg followed by PCA bolus 1 mg with a 20-min lockout (Gp1), subcutaneous diamorphine 2.5 mg followed by PCA bolus with a 10-min lockout period (Gp2) and epidural diamorphine 2.5 mg in 4 mL of 0.125% (w/v) bupivacaine followed by a PCA bolus of 1 mg diamorphine in 4 mL 0.125% (w/v) bupivacaine with a 20-min lockout (Gp3). Patients were evaluated at 0, 1, 2, 3, 4, 8, 12, 16, 20, 24 and 48 h. Patients in Gp2 consumed significantly more diamorphine than those in Gp1 or Gp3 (P < 0.05), but their pain scores were higher only at 1, 2 and 3 h (P < 0.05) with respect to Gp3 and at 1 h with respect to Gp1. Fewer side effects (sedation, pruritus and nausea as assessed by anti-emetic requirements) occurred in Gp2 compared to Gp1 (P < 0.05). Fewer patients in Gp2 required catheterization than in Gp3 (P < 0.05). This study indicates that the use of PCA epidural diamorphine, either alone or in combination with bupivacaine, reduces the dose requirement for analgesia but offers little clinical advantage over subcutaneous PCA diamorphine.

Lumbar plexus block: an anatomical study

The anatomy of the lumbar plexus and the various approaches used to perform lumbar plexus blockade are reviewed. A single needle technique for a posterior approach to the plexus at the L2-3 interspace is described. This technique was used bilaterally in six intact cadavers, and the extent of spread of an injected dye was documented photographically during a subsequent detailed dissection of the region. In all cases, dye was confined to the posterior part of the psoas muscle, and tracked down the nerves of the lumbar plexus. No dye was seen anterior to the psoas, around the sympathetic chain, on the sacral plexus or in the extradural or subarachnoid spaces. Further studies in patients with needle position and drug disposition being confirmed using computerised tomography and X ray scanning were in agreement with the results observed in the cadavers. This technique represents a simple approach to the lumbar plexus which does not require needle localisation by X ray screening.

Morphine-6-glucuronide disposition in renal impairment

Twelve patients with chronic renal failure (dialysis-dependent) and six with good renal function after renal transplantation received i.v. morphine-6-glucuronide (M6G) 30 micrograms kg-1 as part of a standardized anaesthetic technique for minor surgery. Continuous peritoneal dialysis was commenced 6 h after M6G administration in six of the dialysis-dependent patients. Serum was sampled for up to 12 h and analysed for morphine and M6G by high pressure liquid chromatography. Morphine was not detected. Mean (SD) derived pharmacokinetic variables for the three groups (transplant, renally impaired non-dialysed and renally impaired dialysed, respectively) were: elimination half-life 2.14 (0.69) h, 27.10 (15.8) h, 17.33 (4.6) h; clearance 96.0 (34.9) ml min-1, 10.57 (5.57) ml min-1, 14.3 (6.2) ml min-1; volume of distribution 0.19 (0.03) litre kg-1, 0.25 (0.06) litre kg-1, 0.27 (0.06) litre kg-1. The elimination half-life was shorter (P < 0.01) and the clearance greater (P < 0.01) for the transplanted group compared with the dialysed and non-dialysed groups. Peritoneal dialysis for the second 6 h after drug administration had little effect on M6G disposition as assessed by comparison with data obtained from the non-dialysed group.

Audit of neural blockade for palliative care patients in an acute unit

During the period from September 1990 to March 1992, 155 nerve blocks were performed for 125 patients as part of the clinical management of pain due to malignant disease. The efficacy, in terms of pain score reduction, and spontaneously reported side effects secondary to these procedures were prospectively audited. Neural blockade was undertaken in accordance with strict clinical criteria, and medication was optimized with the aim of achieving maximum analgesia with minimum side effects at all times. Pain was assessed before the block, 24 hours after the block and at follow-up (two to six weeks) using visual analogue scores or verbal rating scales. All patients were audited. The total (all patients, all blocks) median (lower-upper quartile) pain score dropped from 8 (6-10) cm before the block to 2 (0-4) cm at 24 hours after the block (p < 0.05) and to 1 (0-4) cm at follow-up (p < 0.005). A concomitant reduction in analgesic requirements was observed. The incidence of serious side effects was low (two patients in this series). The results indicate the usefulness of these techniques for patients in the palliative care setting.

Morphine-6-glucuronide: effects on ventilation in normal volunteers

The respiratory responses to intravenous morphine sulphate (0.12 mg/kg), morphine-6-glucuronide (M6G: 0.03 mg/kg) and placebo were assessed in 6 healthy volunteers, using a single blind randomised crossover design. Five of these subjects underwent an additional study of M6G at 0.06 mg/kg. Respiratory rate, minute volume and end-tidal CO2 were continuously measured using a low resistance non-rebreathing circuit, a mass spectrometer and a dry gas meter. The ventilatory responses to CO2 exposures (5.5% for 4 min) were assessed 40 and 20 min before, and 20, 40 and 80 min after drug administration. Following placebo and M6G (at both doses) no change in end-tidal CO2 occurred whilst the subjects were breathing air, whereas following morphine a significant rise was seen (P less than 0.05). Morphine reduced the ventilatory response to 5.5% CO2 at all times tested (P less than 0.05) and M6G (at both doses) reduced the response to CO2 at 20 and 40 min after administration, but to a lesser degree than did morphine (P less than 0.05).

Disposition of morphine-6-glucuronide and morphine in healthy volunteers

The pharmacokinetics and subjective side effects of i.v. morphine sulphate 120 micrograms kg-1 and morphine-6-glucuronide (M6G) 30 micrograms kg-1 were determined in six healthy volunteers, using a placebo-controlled, single-blind randomized crossover design. Five of these volunteers underwent an additional (non-randomized) study of M6G 60 micrograms kg-1. Subjective side effects were similar following both drugs, but of shorter duration following M6G. Morphine was not detected after administration of M6G. For M6G 30 micrograms kg-1 the mean (SD) volume of distribution, elimination half-life and clearance were 29.38 (18.36) litre, 2.05 (1.2) h and 187.81 (37.41) litre h-1, respectively. These values were not significantly different from those obtained for M6G 60 micrograms kg-1. In all subjects the volumes of distribution and clearances were significantly smaller for M6G than for morphine, but the elimination half-lives were similar.

Analgesic efficacy and CSF pharmacokinetics of intrathecal morphine-6-glucuronide: comparison with morphine

The analgesic efficacy and CSF pharmacokinetics of intrathecal morphine sulphate and morphine-6-glucuronide (M6G) were compared in a single-blind crossover study. Lumbar intrathecal catheters were sited in three patients with chronic cancer pain, and morphine sulphate 500 micrograms or M6G 500 micrograms given via the catheter on separate days. CSF was sampled for 24 h following drug administration and analysed for morphine and M6G by high pressure liquid chromatography. The mean (SD) requirement for patient controlled analgesia with pethidine was 393.3 (227.4) mg/24 h during the morphine limb of the trial and 226.7 (113.6) mg/24 h during the M6G limb. M6G was not detected in CSF following administration of morphine. Fitting of CSF concentrations to triexponential curves revealed mean (SD) alpha, beta and gamma half-lives of 13.2 (7.4), 54.9 (31.5) and 222.5 (100) min for morphine and 11.2 (2.4), 67.3 (49.9) and 619.3 (629.7) min for M6G.

Ketanserin in reflex sympathetic dystrophy. A double-blind placebo controlled cross-over trial

Ketanserin, a selective S2 serotonergic antagonist, was assessed against placebo in a double-blind cross-over study of 16 patients with chronic peripheral burning pain. Nine of these had signs of reflex sympathetic dystrophy (RSD). All patients underwent 4 intravenous regional treatments, 2 with ketanserin (10 mg for upper limb pain, 20 mg for lower limb pain) and 2 with placebo. In those patients with RSD ketanserin and not placebo provided significant (P less than 0.05) sustained pain relief as assessed by linear analogue scales. In patients who did not fulfil the criteria for RSD no significant relief was seen with placebo or ketanserin. Following tourniquet release, drowsiness, shakiness and faintness were reported at a higher (P less than 0.05) frequency after ketanserin than after placebo. All side effects were mild and transient, and no changes occurred in heart rate or blood pressure following ketanserin that were significantly different from those seen following placebo. A role for serotonin in the pathogenesis of RSD is proposed.

A double-blind comparison of epidural ketamine and diamorphine for postoperative analgesia

Twenty patients who had abdominal hysterectomy under general anaesthesia were randomly assigned to receive either epidural ketamine (30 mg), or epidural diamorphine (5 mg) peri-operatively and on first request for analgesia. Failure to obtain satisfactory analgesia with one of the agents was treated by epidural administration of the other. Pain was assessed by an independent observer, and by the patient using a visual analogue scale. The mean (SD) pain score on recovery from general anaesthesia, on a scale of 0-4, was 2.9 (1.2) for the ketamine group and 1.0 (1.0) for the diamorphine group (p less than 0.01). The mean (SD) time to first request for analgesia was 272 (206) and 72 (41) minutes in the diamorphine and ketamine groups respectively (p less than 0.01). All patients in the diamorphine group obtained adequate analgesia, but all patients in the ketamine group were changed to epidural diamorphine. Epidural ketamine does not appear to be a sufficiently effective alternative to epidural diamorphine for routine use in postoperative pain.

Paraplegia after coeliac plexus block

A case is described in which paraplegia followed a coeliac plexus block performed using 90% alcohol under X ray screening. The likely cause was an ischaemic injury to the cord secondary to damage to the artery of Adamkiewicz. This rare complication seems difficult to avoid.

Thalamic pain--the effect of electroconvulsive therapy (ECT)

An open study of the effect of a standard course of unilateral ECT applied to 4 patients with intractable thalamic pain. There was no significant change in pain, personality or affective profiles after treatment. Venous plasma endorphins were measured during the ECT course and there were no significant correlations with treatment.

Purification, characterization, and partial structure of D factor from Polysphondylium violaceum

The A component of D factor (DfA) was overproduced during development of wild type Polyspondylium violaceum strain China after starvation in liquid medium. Crude DfA excreted by strain China was partially purified by ultrafiltration using Amicon YM10 and YM2 filters with DfA extracted from the filtrate by absorption onto a preparative grade C-18 resin. The concentrated material was further purified on a C-18 analytical column using both acetonitrile:water and methanol:water gradients. This highly purified fraction was a single component with a final specific activity of greater than 10(6) units per mg dry weight. Purified DfA is red having a broad visible absorbance at 500 nm and a ultraviolet (uv) absorbance at 290-300 nm. The red chromophore is sensitive to pH and to oxidation-reduction. 1H and 13C nmr studies with purified DfA indicate that it is a C11 compound with both polar and non-polar regions. The non-polar region has been identified as a hexanone and is the same as the side chain of DIF from Dictyostelium discoideum. Purified DfA has been used in studies with the D factor non-producing mutant, tsg-119 cyc-1 aggA586 (A586), to show that neither production of glorin nor chemotactic sensitivity to glorin are affected by D factor. However, founder cells develop in A586 mutant populations only after addition of D factor. These data suggest that DfA may be necessary for induction of aggregate formation by aggregation-competent amoebae.

Analysis of developmentally defective chemical signaling mutants of Polysphondylium violaceum

Six aggregation-defective mutants of Polysphondylium violaceum dependent on external addition of the pheromone D factor for aggregation were isolated after nitrosoguanidine mutagenesis. With a screening technique based on synergistic development, D-factor-dependent mutants can be separated from other kinds of aggregateless mutants. Genetic complementation analyses of the newly isolated mutants showed them to be mutant at the aggA locus. Individual mutants exhibited different sensitivities to D factor(s), responding maximally over a 300-fold range of concentrations.

Developmental regulation of production of an aggregation-stimulating factor from the cellular slime mold Polysphondylium violaceum

An excreted, dialyzable component(s) produced during development of wild-type Polysphondylium violaceum has been previously shown to stimulate aggregation of aggregateless mutants in the complementation group aggA. Production of this aggregation-stimulating factor, called D factor, is greater during development in liquid culture than during development on a surface. after partial purification of crude D factor using high performance liquid chromatography, multiple species are found that retain the ability to stimulate aggregation of the aggA mutants. The three major components (DfA, DfB, and DfC) show decreasing polarity based on purification using reverse-phase chromatography. The proportion of each component secreted varies, depending on the developmental conditions (surface versus liquid) and the time after starvation when the factors are isolated. Preliminary physical and chemical characterization of the three D factor components suggests that they are related.

Extracellular cyclic AMP during development of the cellular slime mold Polysphondylium violaceum: comparison of accumulation in the wild type and an aggregation-defective mutant

Cyclic AMP was synthesized by Polysphondylium violaceum after starvation and during the preaggregation stage of development. Most of the newly synthesized cyclic AMP accumulated in the extracellular medium, with very little change in the intracellular cyclic AMP concentration. The addition of 10(-3) to 10(-6) M exogenous cyclic AMP to starved amoebae caused a 20 to 50% decrease in the number of aggregation centers formed compared with untreated controls. An aggregation-defective mutant of P. violaceum (strain aggA586) excreted or accumulated very little cyclic AMP. Strain aggA586 aggregated normally in the presence of a dialyzable, excreted product (D factor) produced by wild-type amoebae. When the mutant was incubated with D factor, cyclic AMP accumulated in the medium, and the amount accumulated depended on the amount of D factor added to the mutant amoebae.

Cardiac dysrhythmia associated with general anaesthesia for oral surgery. Its prevention by the prophylactic use of an oral beta-adrenergic blocker

Ninety patients, divided randomly into three groups, received either no metoprolol, 50 mg or 100 mg metoprolol as an oral premedication. The electrocardiogram was monitored throughout the procedure. It was found that both doses of metoprolol significantly reduced the incidence of cardiac dysrhythmia.

Reinitiation of deoxyribonucleic acid synthesis by deoxyribonucleic acid initiation mutants of Escherichia coli: role of ribonucleic acid synthesis, protein synthesis, and cell division

The dnaA and dnaC genes are thought to code for two proteins required for the initiation of chromosomal deoxyribonucleic acid replication in Escherichia coli. When a strain carrying a mutation in either of these genes is shifted from a permissive to a restrictive temperature, chromosome replication ceases after a period of residual synthesis. When the strains are reincubated at the permissive temperature, replication again resumes after a short lag. This reinitiation does not require either protein synthesis (as measured by resistance to chloramphenicol) or ribonucleic acid synthesis (as measured by resistance to rifampin). Thus, if there is a requirement for the synthesis of a specific ribonucleic acid to initiate deoxyribonucleic acid replication, this ribonucleic acid can be synthesized prior to the time of initiation and is relatively stable. Furthermore, the synthesis of this hypothetical ribonucleic acid does not require either the dnaA of dnaC gene products. The buildup at the restrictive temperature of the potential to reinitiate deoxyribonucleic acid synthesis at the permissive temperature shows rather complex kinetics the buildup roughly parallels the rate of mass increase of the culture for at least the first mass doubling at the restrictive temperature. At later times there appears to be a gradual loss of initiation potential despite a continued increase in mass. Under optimal conditions the increase in initiation potential can equal, but not exceed, the increase in cell division at the restrictive temperature. These results are most easily interpreted according to models that postulate a relationship between the initiation of deoxyribonucleic acid synthesis and the processes leading to cell division.