Saturable Bragg reflector self-starting passive mode locking of a Cr(4+):YAG laser pumped with a diode-pumped Nd:YVO(4) laser

We demonstrate self-starting passive mode locking of a Cr (4+):YAG laser, using an intracavity nonlinear mirror as a saturable absorber. The pump source is a diode-pumped Nd:YVO(4) laser. Output pulses are centered at 1541 nm, with 26-nm spectral bandwidth and 110-fs pulse width. Output powers of 70 mW are obtained with 8 W of pump power. This mode locking technique is compared with Kerr-lens mode locking.

Series: current issues in mutagenesis and carcinogenesis, No. 65. The genotoxicity and carcinogenicity of paracetamol: a regulatory (re)view

The publication of several studies reporting genotoxic effects of paracetamol, one of the world's most popular over-the-counter drugs, has raised the question of regulatory action. Paracetamol does not cause gene mutations, either in bacteria or in mammalian cells. There are, however, published data giving clear evidence that paracetamol causes chromosomal damage in vitro in mammalian cells at high concentrations and indicating that similar effects occur in vivo at high dosages. Available data point to three possible mechanisms of paracetamol-induced genotoxicity: (1) inhibition of ribonucleotide reductase; (2) increase in cytosolic and intranuclear Ca2+ levels; (3) DNA damage caused by NAPQI after glutathione depletion. All mechanisms involve dose thresholds. Studies of the relationship between genotoxicity and toxic effects in the rat (induction of micronuclei in rat bone marrow including dose-response relationship, biotransformation of paracetamol at different dosages, concomitant toxicity and biochemical markers) have recently been completed. These studies, which employed doses ranging from the dose resulting in human therapeutic peak plasma levels to highly toxic doses, give convincing evidence that genotoxic effects of paracetamol appear only at dosages inducing pronounced liver and bone marrow toxicity and that the threshold level for genotoxicity is not reached at therapeutic dosage. Reliable studies on the ability of paracetamol to affect germ cell DNA are not available. However, based on the amount of drug likely to reach germ cells and the evidence of thresholds, paracetamol is not expected to cause heritable damage in man. Various old and poorly designed long-term studies of paracetamol in the mouse and rat have given equivocal results. A few of these studies showed increased incidence of liver and bladder tumours at hepatotoxic doses. National Toxicology Program (U.S.A.) feeding studies have shown that paracetamol is non-carcinogenic when given at non-hepatotoxic doses up to 300 mg/kg/d to the rat and up to 1000 mg/kg/d to the mouse. Taking into account the knowledge of the hepatotoxicity and metabolism of paracetamol and the existence of thresholds for its genotoxicity, the animal studies do not indicate a carcinogenic potential at non-hepatotoxic dose levels. Based on this updated assessment of the genotoxicity and carcinogenicity of paracetamol, it is concluded that there is no need for regulatory action.

Clinical and epidemiological investigations of Acinetobacter genomospecies 3 in a neonatal intensive care unit

A prospective study of Acinetobacter isolates from a neonatal intensive care unit was performed for 24 months. Fifty-six isolates were obtained from 21 patients, and another eight were obtained from environmental specimens. Infection due to Acinetobacter organisms was established for 16 patients, 6 with septicemia, 9 with pneumonia, and 1 with a wound infection. Further investigations were performed with 38 representative isolates. Twenty-nine isolates were identified as unnamed DNA-DNA hybridization group (genomospecies) 3, three were identified as genomospecies 2 (Acinetobacter baumannii), one was identified as genomospecies 5 (Acinetobacter junii), three were identified as genomospecies 14, and two were unclassified. Eight distinguishable protein profiles, coded I through VIII, were found by cell envelope protein electrophoresis. Profile V, a common profile, was observed for 17 isolates that had been recovered from 11 patients and 1 dust specimen. These isolates, all of which belonged to genomospecies 3, had similar antibiograms and biotypes. This study has revealed that genomospecies 3 can be associated with infection and be spread in hospitals.

Squeezing in a fiber interferometer with a gigahertz pump

We report 5.1 dB of squeezing from a fiber interferometer pumped with a 1-GHz pulse source that successfully eliminates guided-acoustic-wave Brillouin scattering in significant frequency regimes. The pulse source is a diode-pumped Nd:YLF laser actively mode locked at 1.314 microm. The squeezing results are consistent with the limits imposed by the Gaussian pulse shape and the detection quantum efficiency.

Toxicological studies of the false morel (Gyromitra esculenta): embryotoxicity of monomethylhydrazine in the rat

The embryotoxic and teratogenic potential of monomethylhydrazine (MMH), a toxic component of the widely consumed false morel (Gyromitra esculenta), was studied in rat. Groups of pregnant Sprague-Dawley rats received MMH as a constant i.v. infusion via implanted osmotic minipumps (1.2, 3.0, 4.2, 6.0, 9.0 or 13.2 mg MMH/kg bw/day) on days 6-13 of pregnancy, or as a single intragastric bolus (1 mg MMH/kg/bw or 5 mg MMH/kg/bw) on day 6 of pregnancy. Controls received corresponding amounts of saline. The average maternal serum concentrations, measured during the infusion treatment with a sensitive HPLC method, ranged from 0.072 micrograms MMH/ml (lowest dose) to 0.60 microgram MMH/ml (highest dose). The average serum levels measured 45 min after the intragastric application (peak levels) were 0.28 microgram MMH/ml and 1.6 microgram MMH/ml, respectively. Serum concentrations of MMH corresponding to those measured in the lower dose groups in this study were seen in pilot studies after a single mushroom meal in human volunteers. A dose-dependent, statistically significant increase in the number of resorptions was seen in all but the lowest dose group after the infusion of MMH. In addition, except for the two lowest doses, there was a dramatic, dose-dependent decrease in the pregnancy rate as compared to controls, with no pregnancies occurring at the two highest dose level groups. The decreased pregnancy rate was probably due to preimplantation loss which was shown to occur after a single intragastric bolus dose of MMH (5 mg/kg bw).(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of maternal dietary supplementation with selenite on the postnatal development of rat offspring exposed to methyl mercury in utero

Female Sprague-Dawley rats were fed a control standard diet or a selenite (Se) supplemented diet (1.3 p.p.m. Se) for 8 weeks before mating and during gestation and lactation. Blood glutathione peroxidase activity (GSH-Px) was measured as a biomarker of Se in dames. After mating, the females from two dietary groups were divided into three subgroups (6 groups with 10 animals in each) given 0 (vehicle), 2 or 6 mg/kg methyl mercury (MeHg) by gavage on days 6-9 of gestation. Day 2 post parturition all litters were standardized to 6 pups per litter and remaining pups were used for determination of blood and brain total Hg contents. Behavioural testing was performed at two months of age. The results of the study showed that supplementing the diet with Se partly antagonized some adverse effects of the MeHg such as hypoactivity especially in the high MeHg dose group. There were no changes in physical development or body weight except a tendency to decreased body weight in offspring of mothers exposed to 6 mg Hg/kg. The GSH-Px activity was significantly increased in animals fed on Se supplemented diet. The dietary Se supplementation resulted in considerably increased concentrations of mercury in the blood of the offspring despite milder signs of CNS toxicity and no increase in brain concentrations of mercury.

CT of blunt chest trauma in children

While trauma is still the leading cause of death in the pediatric age range, it is surprising how little the CT appearances of pediatric chest injury have been investigated in the literature. We have reviewed the CT findings of blunt chest trauma in 44 children for whom chest CT examinations were requested to investigate the extent of intrathoracic injury. We noted a propensity for pulmonary contusions to be located posteriorly or posteromedially, and for them to be anatomically nonsegmental and crescentic in shape. This is possibly attributable to the relatively compliant anterior chest wall in children. The CT appearances of other major thoracic injuries are described, including pulmonary lacerations, pneumothoraces, malpositioned chest tubes, mediastinal hematomas, aortic injury, tracheobronchial injury, hemopericardium, and spinal injuries with paraspinal fluid collections. Children demonstrating findings incidental to the actual injury yet important to the subsequent therapy are also presented. We conclude that, in the event of clinically significant blunt chest trauma, the single supine chest examination in the trauma room is insufficient to adequately identify the extent of intrathoracic injury. With the exception of concern for aortic injury for which aortography is indicated, a dynamically enhanced CT scan of the thorax should be performed as clinically significant findings may result in altered therapy.

Studies of embryotoxicity and the incidence of external malformations after continuous intravenous infusion of alpha-chaconine in pregnant rats

Embryotoxicity and effects on the incidence of external malformations of the major potato glycoalkaloid alpha-chaconine (alpha-cha) were studied in rats. Pregnant Sprague-Dawley rats (n = 17) were given a continuous intravenous infusion of alpha-cha via implanted osmotic minipumps (1.7 mg/kg/day), to maintain a stable blood concentration on days 6-13 of gestation. Control animals received physiological saline solution or were left untreated, respectively. Blood serum levels of alpha-cha were monitored at selected time intervals during the treatment using a specific HPLC method. The foetal body weights and the number of resorbed or dead foetuses per litter in the alpha-cha treated group were not significantly different from the control groups. No case of malformation was detected among 143 foetuses inspected in the treated group. The average maternal blood serum concentration of alpha-cha measured during the experiment was 340 ng/ml. This is more than 20 times the average peak serum level previously reported for human volunteers after intake of potatoes with a total glycoalkaloid content at the upper safe limit for acute adverse effects. The results support the view that potato glycoalkaloids, at levels normally found in potatoes, do not present a risk for teratogenicity in humans.

Functional benefit of an adaptive myoelectric prosthetic hand compared to a conventional myoelectric hand

Eight patients with a traumatic unilateral upper limb amputation, who used conventional myoelectric prostheses, were also fitted with a commercially available myoelectric prosthetic hand with an adaptive grip, in order to compare the functional benefit of the two types of prostheses. Comparisons were made regarding width of grip, force of grip, scores in a standardised grip function test and prosthesis preference. The conventional prosthesis showed significantly better results regarding these parameters. The adaptive hand does not appear to be fully developed for practical use in prosthetic rehabilitation.

Methylation of rat and mouse DNA by the mushroom poison gyromitrin and its metabolite monomethylhydrazine

Consumption of false morel (Gyromitra esculenta Fr.) has been associated not only with acute poisoning, but also with a carcinogenic risk. The hydrolysis of acetaldehyde-N-methyl-N-formylhydrazone (gyromitrin, the main toxic component of false morel) results in the formation of the methylating agents N-methyl-N-formylhydrazine (MFH) and N-methylhydrazine (MMH) (by further hydrolysis of MFH). This study reports traces of N-7-methylguanine (N7MeGu) in liver DNA from mice and a rat treated with gyromitrin. After repeated administration of MMH, N7MeGu was identified in rat liver DNA. In mice exposed to MMH according to a dosing scheme identical to that reported to induce tumours in this species, O6-methylguanine was present in liver and kidney DNA. The results indicate that a relatively low carcinogenic risk is associated with false morel consumption. The risk may be greater in individuals with a decreased detoxification rate (acetylation) of MFH, in whom larger amounts of MMH are formed from gyromitrin.

Mutations in the two flagellin genes of Rhizobium meliloti

The previously cloned DNA fragment which complements the behavioral defects of the che-1 and che-3 mutations of Rhizobium meliloti codes for two nearly identical (93%) flagellin genes. A wild-type copy of one of the two genes (flaA) but not the other (flaB) can complement the mutations. The behavior and flagellar morphology of newly isolated strains carrying insertion and deletion mutations or various combinations of these mutations demonstrated that either gene product alone can form functional flagellar filaments but when both gene products are present they interact in the formation of filaments. Both the nucleic acid sequences of the genes and the deduced amino acid sequences of the proteins from strain Rm1021 showed significant differences from the sequences determined previously for strain RU10406. (E. Pleier and R. Schmitt, J. Bacteriol. 171:1467-1475, 1989). The tandem arrangement of the two genes is stable, although in vitro recombination between them gave rise to a strain with wild-type behavior.

Squeezing in fibers with optical pulses

A novel method of squeezing with optical pulses in a fiber ring reflector is demonstrated experimentally. Squeezing of greater than 5 +/- 0.3 dB has been observed. The pump is separated from the squeezed radiation with a fiber ring reflector and can be reused, in principle fully, as the local oscillator. The detection is at low frequencies (35-85 kHz) and is unaffected by guided-acoustic-wave Brillouin scattering.

Demonstration of optical switching by means of solitary wave collisions in a fiber ring reflector

We have demonstrated the use of solitary wave collisions in optical pulse switching. Our apparatus consisted of a fiber ring with 11 sections of polarization-maintaining fiber, with successive sections fusion spliced with the axes rotated 90 deg. The configuration yielded enhanced transmission (autocorrelation contrast ratio 2.82:1), in agreement with expectation for this number of sections and the unoptimized fiber coupler that was used. Design criteria for complete switching are presented.

Milk transfer of inorganic mercury to suckling rats. Interaction with selenite

The transport of mercury into rat milk, and uptake in the suckling offspring was studied after peroral administration of inorganic mercury to lactating control rats, and to rats fed selenite in the diet. On day 8, 9, 10, or 11 of lactation, dams were administered a single oral dose of 0.1, 0.4, 0.7, 1.3, or 5.8 mg Hg/kg bw labeled with 203mercuric acetate. There was a linear relationship between mercury concentrations in dam's plasma and milk. The level of mercury in milk was approximately 25% of the level in plasma. After 3 d, milk levels were reduced to half the levels at 24 h. In the suckling offspring, exposed to mercury via milk during 3 d, the mercury level in blood was approximately 1% of the level in maternal blood. Mercury concentration in milk was linearly correlated to the levels in kidney, liver, and brain in the suckling offspring after 3 d exposure to mercury via milk. Selenite treatment of rats, 1.3 micrograms Se/g diet for 5 mo, resulted in increased transport of mercury to milk, probably because of increased plasma levels of mercury. However, selenite treatment of the dams did not cause any increased tissue levels of mercury in the suckling offspring.

Life events: the reliability of rating changes in routine and environment

Alterations in routine and environment can affect clinical state in patients suffering from cognitive impairment. A method for rating life events for changes in routine and environment is described and found to be highly reliable even when used by inexperienced raters after brief training.

Effects of dietary sodium selenite supplementation on salicylate-induced embryo- and fetotoxicity in the rat

The effects of dietary supplementation with sodium selenite (3.0 or 4.5 ppm Se) for 8 weeks prior to and throughout gestation on sodium salicylate induced embryo- and fetotoxicity (resorptions, fetal deaths, malformations, fetal weight reduction) have been studied in the rat. Salicylate was administered either as daily intragastric bolus doses of 250 mg/kg on gestation days 6-13 (maternal peak and trough salicylate levels of 222-120 micrograms/ml whole-blood) or via constant rate intravenous infusion of 150 mg/kg/day on the same gestation days via implanted osmotic minipumps (stable average maternal blood salicylate level of 120 micrograms/ml = human antirheumatic concentration). Both gavage and infusion of salicylate resulted in an increase of resorptions and fetal deaths as well as a decrease of fetal body weights. Gavage with salicylate also produced about 50% malformed fetuses. Selenite did not protect against the embryotoxic effects of salicylate administered as intragastric bolus doses. However, selenite was found to significantly increase fetal survival rate in the infusion experiment, although it did not counteract the decrease of fetal body weight. In animals fed selenite only, no negative effects on fetal body development were noted. The protective effect of selenite against salicylate induced embryotoxicity is difficult to explain, since very little is known about the mechanisms of salicylate embryotoxicity and the biological effects of selenium. However, an interaction between selenium, via glutathione peroxidase, and salicylate at the level of prostaglandin synthesis could be possible.

PET imaging in obsessive compulsive disorder with and without depression

Obsessive compulsive disorder (OCD) is a classic psychoneurosis which is frequently complicated by major depression. Recent positron emission tomography neuroimaging studies, when taken in the context of a variety of other data, implicate a brain dysfunction involving the orbital prefrontal cortex and the striatum in the mediation of OCD behaviors and those of the related Gilles de la Tourette's syndrome. The anterolateral prefrontal cortex is implicated in the secondary major depressions often complicating OCD.

Accumulation and turnover of metabolites of toluene and xylene in nasal mucosa and olfactory bulb in the mouse

Autoradiography of male mice following inhalation of the radioactively labelled solvents, toluene, xylene, and styrene, revealed an accumulation of non-volatile metabolites in the nasal mucosa and olfactory bulb of the brain. Since no accumulation occurred after benzene inhalation, it was assumed that the activity represented aromatic acids, which are known metabolites of these solvents. This was supported by the finding that also radioactive benzoic acid (main metabolite of toluene) and salicylic acid accumulated in the olfactory bulb. High-performance liquid chromatography revealed that after toluene inhalation (for 1 hr), nasal mucosa and olfactory bulb contained mainly benzoic acid, with a strong accumulation in relation to blood plasma, and considerably less of its glycine conjugate, hippuric acid. After xylene inhalation, on the other hand, methyl hippuric acid dominated over the non-conjugated metabolite, toluic acid. The results indicate a specific, possibly axonal flow-mediated transport of aromatic acids from the nasal mucosa to the olfactory lobe of the brain. The toxicological significance of these results remains to be studied.

Faculty and student perceptions of effective clinical teachers: an extension study

This extension study was conducted to (1) identify which characteristics of the effective clinical teacher are deemed most important by nursing students and faculty; (2) determine whether previous findings remain valid (are transferable); and (3) investigate whether the perception of effective teaching behavior shifts as students advance toward graduation. The research tool, a two-part questionnaire developed by Brown, was circulated among students and instructors at a university college of nursing in southwestern Ohio. The first section listed 20 characteristics of teachers to be rated, using a Likert-type scale, from "of most importance" to "of no importance." The second section required subjects to select and rank in order the five most important characteristics from the list of 20. Descriptive analysis was applied to the data, and findings were compared with those of Brown. The study suggests that both faculty and students favor articulate, knowledgeable clinical instructors who are "objective and fair" in student evaluation. There is a high degree of similarity between the responses of faculty and students, but differences emerge. Both value skills involving the student-faculty relationship over skills centering on the professional or personal attributes of the instructor. However, faculty respondents appear to place a higher value on instructor interest in patients, and students are more concerned with communication-related attributes. Faculty members place a greater value on showing interest in patients than do students. The results, when compared with Brown's findings, appear largely transferable, but significant differences appear. For example, faculty members ranked characteristics dealing with the clinical instructor's relationship with students to be more important than those dealing with professional competence--the opposite of Brown's results. This study shows the need for nursing institutions to implement programs to foster and to promote uniformly identified effective clinical teaching characteristics. Given the special challenges of clinical nursing education, graduate programs should also seek to teach the skills identified as most effective, and persons with the skills perceived as effective should be urged to enter clinical instruction and should be rewarded for success in this important area.