Insulin-mediated targeting of phosphatidylinositol 3-kinase to GLUT4-containing vesicles

Phosphatidylinositol (PI) 3-kinase is hypothesized to be a signaling element in the acute redistribution of intracellular GLUT4 glucose transporters to the plasma membrane in response to insulin. However, some receptors activate PI 3-kinase without causing GLUT4 translocation, suggesting specific cellular localization may be critical to this PI 3-kinase function. Consistent with this idea, complexes containing PI 3-kinase bound to insulin receptor substrate 1 (IRS-1) in 3T3-L1 adipocytes are associated with intracellular membranes (Heller-Harrison, R., Morin, M. and Czech, M. (1995) J. Biol. Chem. 270, 24442-24450). We report here that in response to insulin, activated complexes of IRS-1.PI 3-kinase can be immunoprecipitated with anti-IRS-1 antibody from detergent extracts of immunoadsorbed GLUT4-containing vesicles prepared from 3T3-L1 adipocytes. The targeting of PI 3-kinase to rat adipocyte GLUT4-containing vesicles using vesicles prepared by sucrose velocity gradient ultracentrifugation was also demonstrated. Insulin treatment caused a 2.3-fold increase in immunoreactive p85 protein in these GLUT4-containing vesicles while anti-p85 immunoprecipitates of PI 3-kinase activity in GLUT4-containing vesicle extracts increased to a similar extent. HPLC analysis of the GLUT4 vesicle-associated PI 3-kinase activity showed insulin-mediated increases in PI 3-P, PI 3,4-P2, and PI 3,4,5-P3 when PI, PI 4-P, and PI 4,5-P2 were used as substrates. Our data demonstrate that insulin directs the association of PI 3-kinase with GLUT4-containing vesicles in 3T3-L1 and rat adipocytes, consistent with the hypothesis that PI 3-kinase is involved in the insulin-regulated movement of GLUT4 to the plasma membrane.

Determinants of late allograft nephrectomy

When loss of graft function occurs more than six months after transplantation, allograft nephrectomy is not routinely performed at the time of graft failure. It is usually performed only on those patients who subsequently develop specific complications. However, little is known about the characteristics that make patients more likely to require allograft nephrectomy. The purpose of our study was to identify risk factors for the subsequent need for allograft nephrectomy in patients with graft failure occurring more than 6 months after transplantation. Forty-one patients were studied. Inclusion criteria were: loss of graft function > or = 6 months after transplantation, resumption of dialysis and initiation of weaning from immunosuppression. Thirty patients were treated with cyclosporine + prednisone +/- azathioprine and 11 with azathioprine + prednisone. Mean follow-up time was 17.8 months, ranging from 6 months to 6.1 years. Recipient age, sex and race, original renal disease, donor, donor source (cadaveric vs living related), HLA compatibility, levels of panel reactive antibodies, occurrence of initial delayed graft function, causes of graft failure and tapering of immunosuppression were similar in patients with and without allograft nephrectomy. Using univariate analysis, allograft nephrectomy was found to be significantly more frequent in patients with a history of 2 or more episodes of acute rejection than in patients with no rejection episode: 83% vs 30% (p = 0.03). In addition, allograft nephrectomy was found to be significantly more frequent if the immunosuppressive regimen included cyclosporine (62% vs 27.3%; p = 0.04). Using multivariate analysis however, the number of previous episodes of rejection was found to be the only significant predictor for allograft nephrectomy. None of the other variables considered in the multivariate analysis, including the type of immunosuppressive therapy, was identified as a significant predictor for the need to perform allograft nephrectomy. In summary, the need for late allograft nephrectomy was correlated with the number of previous episodes of acute rejection. Patients with a history of numerous rejection episodes should thus be considered more likely to require allograft nephrectomy once immunosuppression is withdrawn. Possible interventions to reduce or prevent the need for nephrectomy include more gradual tapering of immunosuppression at the time of graft failure or indefinite low-dose immunosuppressive therapy.

Waveguides formed by quasi-steady-state photorefractive spatial solitons

We show that a quasi-steady-state photorefractive spatial soliton forms a waveguide structure in the bulk of a photorefractive material. Although the optically induced waveguide is formed by a very low-power (microwatts) soliton beam, it can guide a powerful (watt) beam of a longer wavelength at which the medium is nonphotosensitive. Furthermore, the waveguide survives, either in the dark or when guiding the longerwavelength beam, for a long time after the soliton beam is turned off. We take advantage of the solitons' property of evolution from a relatively broad input beam into a narrow channel and show that the soliton induces a tapered waveguide (an optical funnel) that improves the coupling efficiency of light into the waveguiding structure.

Insulin regulation of membrane-associated insulin receptor substrate 1

Insulin stimulation of 3T3-L1 adipocytes results in rapid activation of the insulin receptor tyrosine kinase followed by autophosphorylation of the receptor and phosphorylation of insulin receptor substrate 1 (IRS-1), its major substrate. The insulin receptor resides mostly at the cell surface of 3T3-L1 adipocytes under basal conditions, while about two-thirds of IRS-1 fractionates with intracellular membranes and one-third fractionates with cytosol. To test whether insulin receptor internalization is required for optimal tyrosine phosphorylation of IRS-1, 3T3-L1 adipocytes and CHO-T cells were incubated at 4 degrees C which inhibits receptor endocytosis but not its tyrosine kinase activity. Under these conditions, tyrosine phosphorylation of IRS-1 in the low density microsome fraction in response to insulin was as intense as that observed at 37 degrees C, indicating that endocytosis of insulin receptors is not necessary for tyrosine phosphorylation of IRS-1 to occur. Surprisingly, at 37 degrees C, insulin action on 3T3-L1 adipocytes progressively decreased the amount of IRS-1 protein associated with the low density microsome fraction and increased that in the cytosol. This redistribution of IRS-1 from the low density microsome fraction to the cytosol in response to insulin was accompanied by decreased electrophoretic mobility of IRS-1 on SDS-polyacrylamide gel electrophoresis. Incubation of adipocytes at 4 degrees C blocked the appearance of tyrosine-phosphorylated IRS-1 in the cytosol. Taken together, these data indicate that insulin receptors phosphorylate IRS-1 at the cell surface, perhaps in coated pits which are included in the low density microsome fraction. The results also suggest a desensitization mechanism in which the tyrosine-phosphorylated membrane-bound IRS-1, associated with signaling molecules such as phosphatidylinositol 3-kinase, is released into the cytoplasm in concert with its serine/threonine phosphorylation.

Assessing vascular dementia

Vascular dementia is the most common cause of dementia in the elderly after Alzheimer's disease. Many forms of vascular dementia have been described: multi-infarct dementia, lacunar dementia, Binswanger's subcortical encephalopathy, cerebral amyloid angiopathy, white matter lesions associated with dementias, single infarct dementia, dementia linked to hypoperfusion and haemorrhagic dementia. The difficulty of diagnosing vascular dementia must not be underestimated and an international consensus is needed for epidemiological studies. The NINCDS-AIREN group has recently published diagnostic criteria. The State of California Alzheimer's Disease Diagnostic and Treatment Centers also proposed some which differ from the NINCDS-AIREN criteria in considering only ischaemic vascular dementia and not other mechanisms such as haemorrhagic or hypoxic lesions. Most studies stress hypertension as the most powerful risk factor for all forms of vascular dementia. The incidence rate ranges from 7 per 1000 person-years in normal volunteers to 16 per 1000 person-years in hypertensive patients. No therapeutic attempt has influenced the course of the disease once the dementing condition is established. The only effective approach is preventive treatment. The objective of the SYST-EUR Vascular Dementia project is to confirm that the treatment of isolated systolic hypertension is able to reduce its incidence.

Commitment, value conflicts and role strains among French GPs in care for HIV positive patients

A survey was carried out on a random sample of GPs in the city of Marseille. 18.5% had been involved during the past year in a regular follow-up of HIV patients. They were in charge with 79.8% of all ambulatory care of HIV+ patients. Those informally 'specialized' professionals were connected to health networks (not only hospital structures but also associations dealing with commitment in care). Socio-biographical factors, training and environmental opportunities and ideological orientations would positively relate with commitment in care. GPs who were not involved with care, would worry more about personal risk of contamination; would not believe that wearing gloves could be a sufficient protection when doing invasive procedures; would feel less at ease with HIV patients, would be more strongly in favor of coercive measures with IVDU's. Most GP's would agree to avoid drug users HIV+ patients. They would attribute to them more guilt and responsibility than to other patients. Uncertainty concerning relevant knowledge, negative attitudes towards some patients like IVDU's and anticipated difficulties to deal with ethical and relational dilemmas keep limiting GPs interest and positive motivation in care for HIV patients.

Moment definition of the pointing stability of a laser beam

A new definition of the pointing stability of a laser beam is proposed. It is derived from the superposition integral between the optical field and a misaligned version of itself. This approach permits the characterization of the pointing stability with a single number, while taking into account the intensity and phase features of the beam. This pointing stability criterion is invariant under propagation and can be related to the moment definitions of beam size, divergence, and quality. The definition is also suggestive of an experimental measurement procedure.

[Arterial risks in celiosurgery]

It is important to recognize exceptional vascular events in celiosurgery because of their gravity. Most occur during pneumoperitoneal manoeuvres using a Palmer needle and rarely at the insertion of the first trocar. We performed a tomodensitometric study in 200 subjects free of abdominal pathology in order to determine the distance from the umbilicus to the aortic bifurcation, their projection over the spine and the superficial relations of the large vessels to the cutaneous umbilical cover. Generally, the projections of the umbilicus, and also the aortic bifurcation, lie over L4. The distance between the skin and the large retroperitoneal vesses is generally equal to one-third of the antero-posterior abdominal diameter. In thin subjects with a flat abdomen however, this distance may be smaller, even less than 3 cm. These findings emphasize the importance of "safety" manoeuvres during celiosurgery, especially during the learning period.

[Relationship between irradiation and appearance of brain tumors in rats]

Sprague-Dawley rats were exposed to Co 60 irradiation (3 Gy) at different ages. Rats were distributed among sham-control (618 males and 120 females) and exposed groups: foetus (66 males and 65 females), 3 month-old (304 males), and 9 month-old (120 males and 60 females). The incidence of brain tumours was 5.3% in male control rats and nil in female control rats. Brain tumour incidence decreased in 9 month-old rats (3.3%), and increased from 6.6% in 3 month-old rats to 15.2% in male foetuses and 12.3% in female foetuses. Age at incidence of brain tumours decreased in irradiatiated animals. Astrocytomas were the more susceptible type of brain tumours to radiocarcinogenesis.

[Experimental study of different histologic types of pulmonary cancers induced by irradiation]

Recent epidemiologic studies suggested that some histologic types of carcinomas were preferentially induced in the lung by irradiation, whatever the mode of exposure and the radiation quality. Since smoking and other environmental airborne pollutants may be strong confounding factors in humans, we have investigated whether histological subtypes were dependent or not on the mode of exposure, in a large series of 9000 rats exposed to external and internal sources at high and low Linear Energy Transfer. Despite comparable overall risk coefficients in rats and humans, our results show that histological types are influenced not only by dose but also by radiation quality and heterogeneity of dose delivering. We suggest that extrapolation from one group to an other take this information in consideration.

Carcinogenic and cocarcinogenic effects of radon and radon daughters in rats

It has been previously established that lung cancer could be induced in rats by exposure to radon and radon daughters. Although the oat-cell carcinomas that are common in humans were not found in rats, other histological types of lung carcinomas, especially squamous cell carcinomas and primitive lung adenocarcinomas, were similar to those observed in humans. A dose-effect relationship was established for cumulative doses varying from 25 to 3000 working-level-months (WLM), which was similar for medium and high cumulative doses to that observed in uranium miners. This experimental protocol was also used to study the potential cocarcinogenic effects of other environmental or industrial airborne pollutants such as tobacco smoke, mineral fibers, diesel exhausts, or minerals from metallic mine ores that may act synergistically with radon exposure. In rats exposed to radon and tobacco smoke combined, the incidence of lung cancers was higher by a factor of 2-4 according to the cumulative radon exposure and the duration of tobacco smoke exposure. When mineral fibers were injected intrapleurally, an increased incidence of malignant thoracic tumors was observed in rats exposed to radon and fibers combined, but synergistic effects resulted in additivity. With diesel exhausts or minerals from metallic ores, a slight, nonsignificant increase in the incidence of lung carcinomas was observed compared with rats exposed to radon alone. These results demonstrated that it is possible to establish the potential cocarcinogenic action, showing either multiplicative, additive, or no effect of various environmental or industrial airborne pollutants combined with radon exposure. This radon model is valid for investigating possible interactions between two occupational exposures.

The chondroitin sulfate form of invariant chain can enhance stimulation of T cell responses through interaction with CD44

Invariant chain (Ii) is a nonpolymorphic glycoprotein that associates with major histocompatibility complex class II molecules and has been shown to mediate several functions in class II-restricted antigen presentation. A small proportion of Ii is modified by the addition of chondroitin sulfate (Ii-CS), and this form of Ii is associated with class II on the surface of antigen-presenting cells. In this report we show that expression of Ii-CS dramatically enhanced the ability of class II-positive EL4 transfectants to stimulate class II-dependent allogeneic and mitogenic T cell responses. Antibody blocking studies and the ability of CD44 to bind directly to Ii-CS suggest that Ii-CS can function as an accessory molecule during T cell responses through interactions with CD44.

[Serologic diagnosis of avian salmonelloses: adjustment of an ELISA test using antigens adsorbed with the aid of anti-colibacillary sera]

A serological ELISA test for diagnosis of avian salmonellosis infections with Salmonella typhimurium or enteritidis has been established. Plates were coated half with a negative antigen and half with a positive antigen. Both negative and positive antigens were adsorbed with a monovalent agglutinant anti Escherichia coli serum prior to being distributed into wells of the plates. Sera from SPF birds and from SPF birds vaccinated and/or inoculated with numerous viruses or bacteria, or sera from conventional birds bacteriologically free of any salmonellosis were tested and the percentage of false positive reactions was inferior than 1%. In groups of birds naturally infected or experimentally inoculated with Salmonella enteritidis or typhimurium the percentages of positive individuals were ranged from 15 to more than 90% according to the doses and routes of inoculation and the delay between contamination and sampling.

Open cholecystectomy: its morbidity and mortality as a reference standard

In a retrospective study of 10,471 cholecystectomies, performed between 1971 and 1990, the incidence and causes of death and morbidity of cholecystectomy were analysed. There were 47 postoperative deaths (0.4%); 6 deaths occurred in 5841 patients less than 50 years old, 23 in 3898 patients between 50 and 70 years old and 18 in 732 patients more than 70 years old. Death rates in each group were, respectively, 0.1%, 0.6% and 2.5% (p < 0.001). The death rate in 9339 patients who had cholecystectomy alone was 0.3% and the death rate in 1132 patients who had a concomitant common bile duct exploration (CBDE) was 1.6% (p < 0.001). Cardiovascular complications were the main cause of death, and biliary, pulmonary and wound complications were the most common. There were 614 complications in 529 patients; 176 of these patients were less than 50 years old, 252 were between 50 and 70 years old and 101 were more than 70 years old. Complication rates were, respectively, 3.0%, 6.5% and 13.8% (p < 0.001). For patients with cholecystectomy alone the morbidity was 3.6% and for patients who had a concomitant CBDE the morbidity was 17% (p < 0.001). The mortality and morbidity of cholecystectomy increase significantly with age and a concomitant CBDE. However, patients who underwent cholecystectomy electively or for acute cholecystitis had comparable mortality and morbidity.

A five-year experience with second-trimester induced abortions: no increase in complication rate as compared to the first trimester

OBJECTIVE

Our purpose was to compare the complication rate of first-trimester suction curettage with that of second-trimester dilation-and-evacuation abortions in the same clinical setting.

STUDY DESIGN

Retrospective analysis (chart review) of the 3772 induced abortions performed between 1986 and 1990 at the Family Planning Clinic of the Centre Hospitalier Universitaire de Sherbrooke, Quebec, Canada.

RESULTS

Among the 3355 cases with known follow-up (89%), the complication rate was 5.1% for the 2908 suction curettages at < 15 weeks' gestation compared with 2.9% for the 447 dilation-and-evacuation procedures at 15 to 20 weeks' gestation. Serious complications were few and not increased among patients undergoing dilation and evacuation.

CONCLUSION

A careful approach to second-trimester dilation-and-evacuation procedures can make them comparatively as safe as suction curettages, contrary to common belief derived from large surveys done in the late 1970s.

The design of an adjustable half block for nonasymmetric linear accelerators

Half-block techniques in radiotherapy may be used to junction two abutting radiation fields. Removable half blocks for linear accelerators not equipped with asymmetrical jaws can accomplish this technique providing the block edge is properly secured with respect to the beam central axis to achieve a smooth beam junction. Successive block edge cuts with a milling machine are, however, required to achieve an acceptable junction of the fields. The design of a half-block device that allows secure adjustment of the block edge on the linac thus alleviating the need for successive milling procedures is presented.

Diffractive analysis of annular resonators

The modal properties of annular resonators are investigated by using an approximate version of the Kirchhoff-Fresnel integral. It is shown that the radial diffraction of a thin annular beam with a large inside radius is similar to that of a cylindrical field distribution. This permits the formal demonstration of the equivalence that exists between large Fresnel number annular resonators and infinite strip resonators. The model explains the properties of annular resonators that have been observed either experimentally or numerically by others, such as the lack of azimuthal discrimination.

Sudden death in turkeys with perirenal hemorrhage: pathological observations and possible pathogenesis of the disease

A pathological study was conducted on 32 turkeys that died of sudden death with perirenal hemorrhage syndrome. Turkeys were selected from routine necropsy cases in a diagnostic laboratory. A higher incidence was observed in heavy tom turkeys. In addition to the characteristic gross lesions of perirenal hemorrhage, splenomegaly, and pulmonary congestion, turkeys in most cases had a hypertrophic cardiopathy. Microscopic lesions included moderate-to-marked acute passive congestion of all tissues examined (32/32), severe perirenal hemorrhage (32/32), and splenic lymphoid depletion (25/32). Changes in the thyroid follicular epithelium of most birds suggested an increased glandular activity. No lesions suggestive of arterial hypertension were observed. Adenoviral infection was detected in only four of 32 birds. Bacteriological cultures revealed no significant pathogen. Results suggest that sudden death in turkeys with perirenal hemorrhage is caused by an acute congestive heart failure consecutive to a hypertrophic cardiopathy. The perirenal hemorrhage would be a consequence of a severe passive congestion in kidneys.

[Isolation of an adenovirus responsible for a case of pancreatitis in guinea fowl]

Necrotizing pancreatitis is observed in 2 to 4 week-old guinea poult. Virus isolation was attempted from the pancreata of naturally affected birds. The isolate was identified as a type 1 adenovirus, and it reproduced the disease when inoculated to sensible guinea fowl.

Identification of atypical rotaviruses in outbreaks of preweaning and postweaning diarrhea in Québec swine herds

Intestinal contents of diarrheic pigs from 120 outbreaks of diarrhea were examined for the presence of atypical rotaviruses. Pigs involved in these outbreaks were aged two days to five weeks and samples collected over a period of one year originated from different regions of the province of Québec. Samples were analyzed by polyacrylamide gel electrophoresis (PAGE) for the presence of viral RNA and genome profiles were compared to those of porcine rotavirus A/OSU, B/Ohio and C/Cowden. Based on electropherotypes both typical (group A) and atypical (groups B and C) rotaviruses were identified. Rotaviruses could be demonstrated in 25.8% of outbreaks and together atypical rotaviruses accounted for 46.7% of rotavirus-positive outbreaks. Other common enteropathogens were often present in conjunction with rotaviruses in the preweaning and postweaning outbreaks studied.

[Evaluation studies of experimental carcinogenesis]

In many cases, epidemiological studies demonstrate carcinogenic risk of occupational exposures and industrial processes, but do not allow to assess carcinogenic potential of the various substances involved in exposures (speciation). Expert judgment combining human and animal data is needed for classifying and labelling of the pure substances. For decision aiding purpose, a method was established for reviewing critically experimental carcinogenesis: 1. Standardized toxicological profiles are established according to pure substances, species, strains and administration routes. 2. Methodological evaluation is made using a scheme based on 3 critical parameters: study duration which should extend to the life expectancy of the species under study; sample size, the statistical significance of negative experiments being ascertained depending on size of samples; survival rates of groups, since sufficient numbers of animals should be at risk during most of their life span. 3. Classification of the results for risk assessment, taking into account the relevance of the administration routes.

Picogram concentrations of endotoxin stimulate synthesis of IL-1 beta and TNF alpha by human peripheral blood mononuclear cells exposed to recombinant human C5a

Endotoxemia, complement activation, and the generation of C5a occur in the course of sepsis, trauma, and the adult respiratory distress syndrome, clinical situations in which TNF and IL-1 are thought to play an important role. In the present studies, we examined the effect of picogram concentrations of endotoxin (LPS) on the synthesis of IL-1 beta and TNF alpha by human PBMC exposed to recombinant human C5a (rhuC5a). rhuC5a induced the synthesis of IL-1 beta by PBMC made in response to otherwise substimulatory levels of LPS. In the presence of rhuC5a, LPS concentrations from 10 pg to 1000 pg/ml substantially amplified IL-1 beta synthesis by PBMC compared to LPS alone. Since rhuC5a can induce transcription of IL-1 beta with minimal translation to cytokine protein, these studies support the concept that fM concentrations of LPS can combine with rhuC5a to provide the "second signal" for optimal translation of IL-1 beta mRNA.

Severe proliferative and necrotizing pneumonia in pigs: A newly recognized disease

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Porcine group C rotavirus as a cause of neonatal diarrhea in a Quebec swine herd

A porcine group C rotavirus was found to be the unique cause of a problem of enzootic neonatal diarrhea in a minimal disease herd composed of 190 sows on a continuous farrowing program. During the outbreaks of diarrhea, 10 to 80% of the litters were affected with a morbidity rate of 100% and case fatality rates of 5 to 10%. Clinical signs began 24 to 48 h after birth and were characterized by a profuse yellow diarrhea lasting a few days. Piglets from different outbreaks of diarrhea were necropsied. They had multifocal villous atrophy in the small intestine, especially in the ileum. Group C rotavirus was demonstrated by direct immunofluorescent staining of frozen intestinal sections and by polyacrylamide gel electrophoresis of viral RNA extracted from the intestinal contents of diarrheic piglets. The infection with clinical illness and lesions was reproduced experimentally in newborn piglets by oral inoculation of a suspension prepared from a pool of intestinal contents from diarrheic piglets.

Standing views to differentiate gallbladder or bile leak from duodenal activity on cholescintigrams

Confusing a gallbladder or bile leak with duodenal activity is a common source of error in the interpretation of cholescintigrams. Techniques such as supplementary oblique views, delayed views, the "water test," dynamic display and combined cholescintigraphy and ultrasound have been used with varying degrees of success. As illustrated in two cases, supplementary standing views provide a simple alternative method to differentiate gallbladder from small bowel activity.

Rotaviral enteritis in a raccoon

A hand-reared raccoon (Procyon lotor) kit had severe diarrhea and died within 24 hr. Gross and histopathologic findings were compatible with a diagnosis of viral enteritis. The immunoperoxidase test revealed rotavirus group A antigen in the intestinal mucosa. This is the first record of rotaviral enteritis in a raccoon.

Postoperative myocardial infarction and cardiac death. Predictive value of dipyridamole-thallium imaging and five clinical scoring systems based on multifactorial analysis

Sixty-six patients unable to complete a standard preoperative exercise test because of physical limitations were studied to determine the predictive value of individual clinical parameters, of clinical scoring systems based on multifactorial analysis, and of dipyridamole-thallium imaging before major general and vascular surgery. Study endpoints were limited to postoperative myocardial infarction or cardiac death before hospital discharge. There were nine postoperative cardiac events (seven deaths and two nonfatal infarctions). There was no statistical correlation between cardiac events and preoperative clinical descriptors, including individual clinical parameters, the Dripps-American Surgical Association score, the Goldman Cardiac Risk Index score, the Detsky Modified Cardiac Risk Index score, Eagle's clinical markers of low surgical risk, and the probability of postoperative events as determined by Cooperman's equation. There were no cardiac events in 30 patients with normal dipyridamole-thallium scans or in nine patients with fixed myocardial perfusion defects. Of 21 patients with reversible perfusion defects who underwent surgery, nine had a postoperative cardiac event (sensitivity, 100%; specificity, 43%). In the six other patients with reversible defects, preoperative angiography showed severe coronary disease or cardiomyopathy. Thus in patients unable to complete a standard exercise stress test, postoperative outcome cannot be predicted clinically before major general and vascular surgery, whereas dipyridamole-thallium imaging successfully identified all patients who sustained a postoperative cardiac event.

Interferential mode locking: Gaussian pulse analysis

A simple analysis of the interference between two Gaussian pulses is presented. It is shown that the resulting pulse may be shorter than the initial ones if the interference phase is properly adjusted. The compression effect results from the difference of the durations of the interfering pulses and from their phase modulation. This mechanism may be implemented in mode-locked lasers, eitherby adjunction of a coupled cavity or use of a pulse-shaping Michelson interferometer as the outputcoupler. Gain-bandwidth-limited pulses may then be obtained. The model provides analytical expressions for pulse duration.

Characterization of French avian paramyxovirus type 1 (PMV 1) isolates with a Panel of monoclonal antibodies to the Ploufragan strain of Newcastle disease virus

Eight monoclonal antibodies against the Ploufragan strain of Newcastle disease virus were used to characterize 58 virus strains including 29 French isolates. By combining ELISA and haemagglutination inhibition tests, PMV 1 strains were differentiated from other avian PMV 1 and grouped into 7 classes.

High-order transverse modes of misaligned laser resonators with Gaussian reflectivity mirrors

Analytical expressions of high-order transverse modes of misaligned laser resonators with Gaussian reflectivity mirrors are presented. We found that modal discrimination is independent of the mirror tilt angle. The propagation laws of the beam parameters are also discussed.

Lung carcinomas in Sprague-Dawley rats after exposure to low doses of radon daughters, fission neutrons, or gamma rays

The effectiveness of radon-daughter inhalation and irradiation with fission neutrons and gamma rays in the induction of lung carcinomas in Sprague-Dawley rats at low doses is compared. Earlier reports which compared radon-daughter inhalations and neutron irradiations over a wider range of doses were based on dosimetry for the radon-daughter inhalations which has recently been found to be faulty. In the present analysis, low-dose experiments were designed to derive revised equivalence ratios between radon-daughter exposures, and fission neutron or gamma irradiations. The equivalence is approximately 15 working level months (WLM) of radon daughters to 10 mGy of neutrons (the earlier value was 30 WLM to 10 mGy). The relative biological effectiveness (RBE) of neutrons is 50 or more at a gamma-ray dose of 1 Gy. In these experiments with low doses and exposures, the lifetime incidences can be estimated from the raw incidences, while the derivation of the time dependence of the prevalence is essential for the estimation of RBE values and equivalence ratios.