Flow period influence on uranium and trace elements release in water from the waste rock pile of the former La Commanderie uranium mine (France)

Uranium mining activities expose uranium ore and mine tailings to the surface environment, where the release of radionuclides is facilitated by weathering at rates exceeding those typically found in nature. Therefore, close to former uranium mining sites, radionuclides and especially uranium concentrations in water may surpass local background levels. The methodology proposed herein, entails coupling, gamma-ray mapping, water sampling and chemical analyses including DGT (Diffusive Gradient in Thin Film) measurements, provides new insights into describing the environment of the La Commanderie site (France). Gamma-ray mapping allows identifying water seepage, output from a waste rock pile, as a potential pathway for radionuclides into the environment. Water seepage monitoring has shown: a low pH value (4.2), high sulfate content (179 mg.L^-1) and high uranium concentrations of up to 436 μg.L^-1. These recordings indicate that an acid mining drainage (AMD) process is occurring inside or under the oxidized parts of the waste rock pile. Monitoring data over three flow periods revealed the release of the highest uranium concentrations during a high-flow period downstream of the site, which is compliant with local regulations. The AMD process is also responsible for the release of significant amounts of Fe, Mn and As within the immediate environment in both dissolved and particulate forms. Changes in dissolved oxygen concentration and redox potential during low flow periods, modify the speciation of Fe (in AMD waters) which acts as a scavenger for other elements such as As, Mn and U. The use of DGT under environmental conditions, and specifically AMD waters, seems to be relevant in comparison to filtered spot water sampling strategies. Moreover, based on DGT measurements, the dissolved part of the released uranium is considered as labile with concentrations above the environmental standards for freshwater organisms.

Herschel survey and modelling of externally-illuminated photoevaporating protoplanetary disks

CONTEXT

Protoplanetary disks undergo substantial mass-loss by photoevaporation, a mechanism which is crucial to their dynamical evolution. However, the processes regulating the gas energetics have not been well constrained by observations so far.

AIMS

We aim at studying the processes involved in disk photoevaporation when it is driven by far-UV photons (i.e. 6 < E < 13.6 eV).

METHODS

We present a unique Herschel survey and new ALMA observations of four externally-illuminated photoevaporating disks (a.k.a. proplyds). For the analysis of these data, we developed a 1D model of the photodissociation region (PDR) of a proplyd, based on the Meudon PDR code and we computed the far infrared line emission.

RESULTS

With this model, we successfully reproduce most of the observations and derive key physical parameters, i.e. densities at the disk surface of about 106 cm-3 and local gas temperatures of about 1000 K. Our modelling suggests that all studied disks are found in a transitional regime resulting from the interplay between several heating and cooling processes that we identify. These differ from those dominating in classical PDRs i.e. grain photo-electric effect and cooling by [OI] and [CII] FIR lines. This specific energetic regime is associated to an equilibrium dynamical point of the photoevaporation flow: the mass-loss rate is self-regulated to keep the envelope column density at a value that maintains the temperature at the disk surface around 1000 K. From the physical parameters derived from our best-fit models, we estimate mass-loss rates - of the order of 10-7 M⊙/yr - that are in agreement with earlier spectroscopic observation of ionised gas tracers. This holds only if we assume photoevaporation in the supercritical regime where the evaporation flow is launched from the disk surface at sound speed.

CONCLUSIONS

We have identified the energetic regime regulating FUV-photoevaporation in proplyds. This regime could be implemented into models of the dynamical evolution of protoplanetary disks.

Attitudes of the dental team to the provision of care for people with learning disabilities

The aim of this study was to report on the evaluation of an attitude scale for General Dental Practitioners (GDPs) and Dental Auxiliaries/Professionals Complementary to Dentistry (PCDs), to determine the reliability of the scale with these two groups and to note any inter-group differences. Seventy-four GDPs and 89 PCDs completed the self-administered questionnaires. The main outcome measures were reliability statistics, attitude scores, and factor analysis statistics. Reliability was satisfactory for both groups. PCDs scored consistently higher than GDPs on this attitude scale. Six factors were found to underlie the responses of GDPs, accounting for 62% of the variance. Seven factors were found to underlie the responses of PCDs, accounting for 65% of the variance. PCDs expressed more positive views about provision of care for patients with learning disabilities than did GDPs. Factor analysis revealed that GDPs were concerned about effectiveness of treatment and the stress related with treating patients with disabilities. PCDs appeared to be more concerned with the human rights of people with learning disabilities and how they fit into society.

Oral health status of heroin users in a rehabilitation centre in Hubei province, China

OBJECTIVE

To report on the oral health of heroin users and to determine risk factors for oral health status.

DESIGN

All heroin users at one rehabilitation camp received an interview using a pre-tested questionnaire from one of three trained interviewers and a dental examination using World Health Organization recommended procedures from one of three calibrated dentists.

SETTING

Interviews and examinations were carried out at Hubei Province camp.

PARTICIPANTS

All 520 resident heroin users at the camp participated in the study.

OUTCOME MEASURES

Oral hygiene expressed using the Debris Index; caries status by DMFT; periodontal status by percentage with bleeding, pocketing and calculus; mucosal status using standard World Health Organization criteria.

RESULTS

One hundred (19%) of the heroin users were caries free; their mean DMFT was 4.2. The majority (92%) of the DMFT was decay and only a small proportion (8%) was treatment related. The proportion of heroin users with bleeding, calculus, shallow pocketing and deep pocketing was 42%, 95%, 42% and 8% respectively. The mean Debris Index score was 3.2. Mucosal lesions were present in 31 subjects (6%). Using multivariate analysis, duration of heroin use and education were risk factors for DMFT, route of drug administration was a risk factor for calculus and gender was a risk factor for deep pocketing.

CONCLUSIONS

There are indications of poorer periodontal health as well as higher caries experience in this group when compared to provincial dental epidemiological data. Mucosal lesions were not widely prevalent. Both social factors and characteristics of drug use were related to oral health in this group.

Caries patterns and their relationship to infant feeding and socio-economic status in 2-4-year-old Chinese children

AIMS

To describe the prevalence, severity and patterns of caries in 2-4-year-old children and to evaluate the association between caries experience of the children and their feeding patterns and socio-economic background in terms of mothers' education and family income.

DESIGN

Cross-sectional survey.

SETTING

Suburban area of Hanchuan in Hubei province, China.

PARTICIPANTS

A sample of 426 children (250 boys and 176 girls).

METHODS

Dental-examinations were undertaken in kindergartens using World Health Organization diagnostic criteria for dental caries. Mothers completed a short questionnaire.

OUTCOME MEASURES

Prevalence of caries; rampant caries; caries in incisors; caries in incisors and/or canines and molars; mean number of decayed, missing and filled teeth/surfaces (dmft/s).

RESULTS

36% of the children had caries, 7% had rampant caries. The more extensive pattern of caries involving primary molars as well as incisors and/or canines was seen in 12% of children. Children who had been wholly bottle-fed had five times the risk of having rampant caries compared to children who were breast-fed.

CONCLUSIONS

The results indicated that infant feeding practice might be a key risk factor for the development of caries at an early age in this country as elsewhere.

Dental care for children and young people who have a hearing impairment

AIM

The aim was to determine whether there are indications that hearing-impaired children experience difficulties in accessing dental care and/or in receiving dental treatment.

METHOD

The study was carried out by means of a questionnaire. Parents of 84 children contacted through the National Deaf Children's Society returned completed questionnaires.

RESULTS

Eighty-two children (98%) had visited a dentist. Nearly two-thirds (63%) were reported to have at least one problem in communication while receiving dental care, this increased significantly as the severity of the hearing impairment increased. Fifty-nine children (70%) reported having at least one problem in communication at the doctors'. Fifty-two (62%) reported that the dentist had worn a mask while communicating with the child and 48 (57%) that there had been background noise in the surgery during appointments.

CONCLUSIONS

Removing masks while talking, reducing background noise and learning to use simple signs may improve communication with hearing-impaired children.

Laser safety management

LASER is an acronym for Light Amplification by Stimulated Emission of Radiation. Since the first working laser was demonstrated in 1960 the laser has evolved from being viewed as a weapon, courtesy of the film industry, to its current position as a commonplace medical device within the healthcare industry. As perioperative staff we have become very familiar with the therapeutic use of this device. It is my experience however that, just occasionally, we are guilty of the old adage 'familiarity breeds contempt'. We must remember that the very same features which make lasers so useful in healthcare may also represent major health hazards to patients, staff and others.

Risk assessment. A five step process

Risk assessment is a process which involves identifying hazards in the workplace and assessing the risk of them causing harm (Croner's Health Service Risks 1997). This step by step approach to risk assessment should make the whole process seem less daunting and encourage active participation in this effective method of proactive risk management.

Fault slip rates in the modern new madrid seismic zone

Structural and geomorphic analysis of late Holocene sediments in the Lake County region of the New Madrid seismic zone indicates that they are deformed by fault-related folding above the blind Reelfoot thrust fault. The widths of narrow kink bands exposed in trenches were used to model the Reelfoot scarp as a forelimb on a fault-bend fold; this, coupled with the age of folded sediment, yields a slip rate on the blind thrust of 6.1 +/- 0.7 mm/year for the past 2300 +/- 100 years. An alternative method used structural relief across the scarp and the estimated dip of the underlying blind thrust to calculate a slip rate of 4.8 +/- 0.2 mm/year. Geometric relations suggest that the right lateral slip rate on the New Madrid seismic zone is 1.8 to 2.0 mm/year.

How are men with urethral discharge managed in general practice?

Chlamydia and gonorrhoea remain major causes of morbidity despite the availability of effective therapy. Because of the asymptomatic nature of many infections, particularly in women, active case finding is necessary to trace and offer screening and treatment to sexual contacts of those infected. Genitourinary medicine (GUM) clinics provide investigation and treatment for a variety of sexual health problems but the proportion of infections treated outside these clinics is unknown. A questionnaire survey of general practitioners (GPs) was used to examine the prevalence and management of male urethritis in Scotland. Responses were received from 277/347 (80%) of GPs. A median of one case/year of male urethritis was seen and screening for gonorrhoea and chlamydia was undertaken in 82% and 63% of cases not referred to a GUM clinic respectively. Six per cent of GPs attempted to trace sexual contacts. Twenty-nine per cent (60) of patients were not referred to a GUM clinic and increasing distance to the clinic was associated with non-referral. Eleven per cent (18) of patients objected to referral to a GUM clinic. There is scope to improve the management of male urethritis by providing greater support for GPs, encouraging clinic referral where possible and appropriate investigations and treatment when not.

In vitro stimulation of human endothelial cells by derivatized dextrans

Derivatized dextrans exert a stimulatory effect on the in vitro growth of human umbilical vein endothelial cells (HUVEC). Measurements of growth were monitored by [3H]thymidine uptake and cell numbers. Our results show that some derivatized dextrans at 4 micrograms/ml (88 nM) increase the [3H]thymidine incorporation, whereas starting dextran (40,000 Da), dextran sulfate, and carboxymethyl dextran have no effect. In addition, heparin under similar experimental conditions shows a slight inhibitory effect on the HUVEC growth. The stimulatory effect of derivatized dextrans was also found when HUVEC grew during 7 days in medium containing 2% fetal bovine serum. We also observed that derivatized dextrans had no effect on the mitogenic activity of acidic fibroblast growth factor, a mitogenic factor for several cell types including HUVEC. By assessment of [3H]thymidine uptake at 48 h without serum, we concluded that the exogenous growth factors were not involved in the proliferative activity of these components. The stimulatory effects are related to the chemical nature and the proportion of substituents on the synthetic polysaccharides. The data indicate that benzylamide sulfonated groups play a key role in the stimulation of HUVEC growth. Neither carboxyl nor sulfate groups alone exhibit this effect. Thus, the stimulatory capacity of dextran derivatives depends strongly on the respective ratios of the functional groups.

Delayed retinal effects of the frequency-doubled YAG laser (532 nm)

In order to compare the retinal effects of the frequency-doubled YAG laser (532 nm) with those of argon laser, rabbit eyes were exposed to green YAG laser irradiation and processed for light and electron microscopic study at 24 hr, 2 weeks and 4 weeks. Detailed analysis was conducted on tissue exposed to 7.3 and 7.6 millijoules (mj). Response of the photoreceptors and retinal pigmented epithelium to green YAG was very similar to that described for argon laser over the same time period. By 2 weeks post-exposure, there was histologic evidence of partial recovery with absence of damaged, pycnotic photoreceptor nuclei, increased numbers of typical photoreceptor outer segment lamellae and repair of retinal pigmented epithelium. Four weeks after irradiation, normal-appearing photoreceptor nuclei were present although inner photoreceptor segments still showed mitochondrial damage. Outer segments at 4 weeks showed regular lamellar structures. We conclude that the frequency-doubled YAG laser is equivalent to the argon laser with respect to the production of thermal lesions in the retina. Its additional advantages include increased efficiency, portability, reliability and lack of absorption by macular xanthophyll pigment.

Thoracotomy for pulmonary metastatic osteosarcoma. An analysis of prognostic indicators of survival

Removal of pulmonary metastases of osteosarcoma by thoracotomy is an accepted treatment; however, few investigators have analyzed the value of various prognostic factors in estimating survival. A review of all patients undergoing thoracotomy for recurrent osteosarcoma with pulmonary metastases treated at St. Jude Children's Research Hospital is reported. Since 1968, two thirds (39/59) of all patients who developed pulmonary metastases have had a total of 66 thoracotomies. Nine patients are alive with no evidence of disease, and six additional patients are alive with disease. Analyzed in 39 evaluable patients, the prognostic factors that correlate with survival by univariate analysis are: sex, number of nodules detected radiographically and resected, completeness of resection, and tumor location (bilateral versus unilateral). By Cox regression analysis, only sex and the number of nodules detected either radiographically or during surgery, and resected, had statistically significant correlation with survival. Thoracotomy is curative for some patients with pulmonary metastatic osteosarcoma and Prognostic factors predictive for survival are defined.

Relapsed Wilms' tumor. Factors affecting survival and cure

To identify factors contributing to extended survival among patients with relapsed Wilms' tumor, we assessed 10 clinical and biologic variables thought to have predictive value. With a median follow-up of 6 years, 32 (20%) of 156 patients who achieved complete remission have relapsed. Twenty-four have died with recurrent tumor, and eight are surviving for 2 to 12 years from diagnosis. Only time to relapse, or length of initial complete remission, had a significant influence on survival. Of 11 patients with complete remissions lasting longer than 12 months, six have died--compared with seven of 10 having remissions of 6 to 12 months and 11 of 11 with shorter remissions (p = 0.014). Surgery alone was the curative therapy in three of the eight surviving patients. Until more effective chemotherapy regimens are developed, an aggressive surgical approach may be indicated in selected patients with relapsed Wilms' tumor.

Childhood multifocal osteosarcoma. Clinicopathologic and radiologic correlates

The authors reviewed the clinical charts and pathologic and radiographic materials of nine pediatric patients (mean age, 11.0 years) presenting with multiple skeletal foci of osteosarcoma. Four patients presented with pulmonary metastases, and five had osseous disease only. All had densely sclerotic, predominantly osteoblastic tumors, usually in metaphyseal locations. Evidence of aggressive tumor cell behavior--such as vascular, articular, epiphyseal, or soft-tissue invasion--was usually present in surgical specimens. Despite intensive chemotherapy, all patients died from 6 to 37 months after diagnosis (median survival, 12 months). Comparison of clinical and pathologic features for patients presenting with or without pulmonary metastases failed to disclose any notable differences between the two groups, indicating a common pathogenesis and evolution for their multifocal disease. The authors conclude that this variant of osteosarcoma is a highly aggressive form of the disease that may be accompanied by pulmonary metastases.

Retinal effects of the frequency-doubled (532 nm) YAG laser: histopathological comparison with argon laser

Retinal lesions produced in Dutch Cross rabbits with a frequency-doubled (532 nm) YAG laser in single pulse mode (30-100 microJ) and in train of uniform pulses (2.6 and 7.5 mJ) underwent histopathological examination by light and electron microscopy. The results were compared to argon laser lesions (11 and 15 mJ) in the same animals. Low-energy single-pulse YAG lesions produced separation of the neural retina from the retinal pigmented epithelium (RPE), while higher energies caused severe disruption of retinal structures with moderate damage to the RPE. A striking and consistent finding of all the single-pulse lesions was the presence of red blood cells between the RPE and neural layers. The findings appear to support a process of mechanical disruption. In contrast, the lesions produced by a uniform train of pulses showed well-defined damage to RPE and photoreceptors with no red blood cells between these two layers, no choroidal damage, and relatively little disruption of the inner retina. The typical argon lesion evidenced cellular damage from the RPE through all retinal layers. Leukocytes in the choroid contained "holes" or vacuoles not seen in YAG lesions. Both the uniformly pulsed YAG laser burst and argon laser produced effects consistent with a thermal process. Some differences between argon and YAG burst were observed. The results suggest that there may be a clinical potential for the 532-nm burst YAG in treating retinopathies.

Effective cisplatin (DDP) based chemotherapy in the treatment of hepatoblastoma

Nine of 11 patients with hepatoblastoma treated with cisplatin (DDP) based chemotherapy had a complete (CR) or partial (PR) remission. Five of these patients had measurable pulmonary disease and four achieved a CR of pulmonary lesions. The average interval of disease control following DDP was three times that of Adriamycin (ADR). DDP is an effective agent in the treatment of hepatoblastoma.

Regulation by estrogen receptor of vitellogenin gene transcription in Xenopus hepatocyte cultures

We have used primary cell cultures of hepatocytes from male or female Xenopus laevis to study the mechanisms by which estrogen induces vitellogenin gene transcription and how primary exposure to estrogen renders cells more responsive to secondary stimulation. We have characterized the estrogen receptor in hormonally naïve cells and in hepatocytes treated with estrogen under a variety of conditions. Under all conditions the receptor has a Kd congruent to 4 X 10(-10) M. Hormonally naïve male cells contain 300 binding sites whereas female cells or male cells previously exposed to estradiol exhibit 6-7-fold higher levels. In parallel cultures, the absolute rate of vitellogenin gene transcription was determined by hybridization of newly synthesized RNA pulse-labelled with [3H]uridine to cloned Xenopus vitellogenin cDNA. Naïve male cells on primary stimulation with estradiol synthesized vitellogenin mRNA at an average rate of approximately 150 moles/cell/h compared to 1200 moles/cell/h for cells previously exposed to estrogen, thus bearing a close correlation with receptor number. Furthermore, we show that the kinetics of the induced up-regulation of receptor exactly parallel those of the increase in the rate of vitellogenin gene transcription upon secondary hormonal stimulation following various periods of primary exposure to estrogen. Addition of cycloheximide to cell cultures during primary estrogen treatment abolishes both receptor up-regulation and increased rate of vitellogenin gene transcription on secondary stimulation. In addition, primary treatment with the antiestrogen tamoxifen prevents both receptor up-regulation and an enhanced rate of transcription or accumulation of vitellogenin mRNA on secondary hormonal exposure. These results demonstrate that estrogen treatment of male Xenopus hepatocytes results in the rapid up-regulation of its own receptor to female levels via new receptor synthesis, and that receptor number is rate-limiting in vitellogenin gene transcription.

The value of computerized tomography as a routine follow-up procedure for patients with Wilms' tumor

We performed routine computerized tomography (CT) of the chest and abdomen on patients treated for Wilms' tumor and reviewed the records of all patients who relapsed (10 patients) and 43 additional patients followed for at least 1 year. Routine chest radiographs and abdominal ultrasounds were compared with 210 CT examinations (107 chest and 103 abdomen). CT examinations were obtained at 6 months for stage I (13 patients) and at 3, 8, and 15 months for stages II, III, and IV (40 patients). Of the 10 patients who relapsed, only 2 were documented by CT scan in the absence of clinical symptomatology and presence of normal radiographs and ultrasound. Eight relapses were diagnosed by physical examination, chest radiograph, or ultrasound and confirmed by CT scan. Questionably abnormal CT scans were obtained in 7 patients, only 1 of whom eventually relapsed. Since only 2 of 210 routine CT examinations were the the only indicator of relapse, we conclude that the routine use of CT for follow-up in Wilms' tumor is not warranted.

Signal sequences, secondary modification and the turnover of miscompartmentalized secretory proteins in Xenopus oocytes

The cytoplasm of the Xenopus oocyte can be altered by the microinjection of proteins and the regulatory responses to such perturbations can then be studied. We have investigated proteolytic systems within the oocyte which may be involved in the maintenance of the integrity of the different subcellular compartments. Thus primary translation products, made in the wheat germ system under the direction of frog liver, chicken oviduct, rat liver rapidly sedimenting endoplasmic reticulum, rat seminal vesicle, guinea pig mammary gland or honey been venom gland RNA, were injected into oocytes. Their stability in the frog cell cytosol was in general low compared to that of their processed counterparts. The latter were usually obtained by collecting the heterologous proteins exported by RNA-injected oocytes. Electrophoretic analysis of oocytes injected with particular primary and processed polypeptides permitted measurement of the stabilities of proteins differing only by the presence or absence of a detachable signal sequence, or by the presence of a specific secondary modification. The effect of the latter on protein stability appears slight. However, the presence of a detachable signal sequence destabilizes those miscompartmentalized secretory proteins which are otherwise stable. Indeed all other results are consistent with this concept for they show that primary translation products are in general much less and are never more stable than their processed counterparts. Thus we provide evidence that errors of compartmentation can be corrected in living cells and that this process is often facilitated by the properties conferred on a protein by a detachable signal sequence.

Intrarenal angiotensin I conversion at normal and reduced renal blood flow in the dog

Intrarenal conversion of angiotensin I (ANG I) to angiotensin II (ANG II) under conditions of normal and reduced renal blood flow (RBF) elicited by constriction of the renal artery was examined in pentobarbital-anesthetized dogs. In eight animals, tracer doses of 125I-ANG I (5-12 pmol) were injected into the renal artery and 125I-ANG I, 125I-ANG II, and 125I-labeled metabolites were measured in renal venous effluent by high-voltage paper electrophoresis. The mean conversion of ANG I to ANG II during a single passage through the kidney was 21.8 +/- 2.1% at control RBF. When RBF was decreased by 25 and 53%, percent ANG I conversion was not altered significantly. In six dogs percent conversion of 125I-[Sar1, Ile5]ANG I, an ANG I analogue refractory to hydrolysis by aminopeptidases, was 18.1 +/- 1.7% at control RBF and did not change significantly when the RBF was reduced by 55%. Although there were severalfold increases in renal renin secretion rate and net ANG I generation rate during reduced RBF, net renal ANG II formation rate did not change significantly. These data indicate that there is substantial conversion of ANG I in a single passage through the dog kidney and that intrarenal ANG I conversion is independent of RBF even under conditions in which renin secretion rate and ANG I generation rate are increased severalfold.

Antibody responses to Epstein-Barr virus-specific DNase in relation to the prognosis of juvenile patients with nasopharyngeal carcinoma

We have examined serial sera from 17 juvenile patients with nasopharyngeal carcinoma (NPC) for their capacity to neutralize the activity of Epstein-Barr virus (EBV)-specific DNase. The results revealed that NPC patients who became long-term survivors (LTS) without evidence of the disease either never possessed significant levels of antibodies to the enzyme or showed a gradual decline in the number of EBV DNase units neutralized from an elevated level at diagnosis to an insignificant figure several years later. All the 10 LTS neutralized less than 4, and some neutralized less than 2 units of the enzyme 3 or more years after the initial diagnosis. In contrast, serial sera from juvenile patients who died of NPC neutralized over 10 and as many as 25 units of EBV DNase either persistently until death occurred or with transient declines during unmaintained remissions. Rises and declines in the neutralizing activity were, with few exceptions, accompanied by corresponding changes in the titers of IgA and IgG antibodies to EB viral capsid antigen and to the diffuse component of the early antigens. Although the number of juvenile NPC cases available for study was small, the observations suggest that the EBV DNase neutralization test may serve to provide information on the prognosis of the patients.

Nasopharyngeal carcinoma in American Children: Epstein-Barr virus-specific antibody titers and prognosis

Seven American juvenile patients with undifferentiated or nonkeratinizing nasopharyngeal carcinoma (NPC) were examined serially for Epstein-Barr virus (EBV)-specific antibody spectra and titers in sera. At diagnosis, all showed antibody patterns characteristic of NPC: i.e., high titers of IgG antibodies to viral capsid antigen (VCA) and to the diffuse (D) component of the early antigen complex. Six patients had IgA antibodies to VCA, and four to the D component. In the patients who responded to therapy with complete and maintained remissions, the IgG antibodies to D and the IgA antibodies to VCA and D decreased to undetectable levels within 12 to 30 months. By contrast, of the four patients who responded only transiently to therapy, three showed substantial increases and one continuously high titers of IgG anti-D and IgA anti-VCA. The increases in antibody titers preceded clinical recognition of recurrent tumors by 1 to 6 months. Three of these patients have died and the fourth is alive with disease. These data indicate that American juvenile NPC does not differ from the adult disease observed anywhere in the World. They reaffirm the potential usefulness of EBV-specific serology in the diagnosis and prognosis of NPC and the monitoring of patients following therapy.

The sequestration, processing and retention of honey-bee promelittin made in amphibian oocytes

Messenger RNAs from one kind of secretory cell can be introduced into the cytoplasm of another: the heterologous proteins formed by the recipient cell are usually processed and topologically segregated in the manner characteristic of the donor cell. Xenopus oocytes injected with honey-bee venom gland RNA provide some support for this generalization, but also reveal important exceptions to it. Thus, the frog cell makes a small polypeptide whose partial sequence matches perfectly that of insect promelittin, except that the product formed in oocytes ends at the C terminus with a glycine as opposed to a glutamine amide residue. N-terminal heterogeneity is seen in protoxin made in oocytes and venom gland cells, and species shorter by two residues are seen in both tissues. We suggest that the oocyte contains a dipeptidylpeptidase. Promelittin made in oocytes is barely detectable in the cytosol but is found associated with a vesicle fraction which also contains some newly synthesized endogenous oocyte proteins. The association with vesicles is long-lasting; thus promelittin is retained slightly more efficiently than sequestered oocyte proteins, and an incubation period of about two weeks is required to reduce by half the amount of these endogenous vesicle proteins. Thus neither promelittin nor any products derived from it are secreted rapidly. Gel analysis fails to reveal promelittin in the medium surrounding the oocyte, although traces can be detected by assaying for a characteristic heptapeptide. Such small amounts could result from slow secretion or leakage. Melittin could not be detected by gel analysis or peptide assay. The retention of the honey-bee protein within the frog cell is discussed in terms of the specificity of the processing systems and secretory pathways of venom gland cells and oocytes. We suggest that whilst some export mechanisms function efficiently in a wide variety of cells, others do not, and may even be restricted to specific cell types.

The Xenopus oocyte as a surrogate secretory system. The specificity of protein export

Combining messenger RNA from one kind of secretory cell with the cytoplasm of another such cell can reveal the nature and specificity of protein export mechanisms. We show that messenger RNAs from secretory cells of chickens, rats, mice, frogs, guinea-pigs, locusts and barley plants, when injected into Xenopus oocytes, direct the synthesis and export of proteins. Chicken ovalbumin, Xenopus albumin, mouse thyroid-stimulating hormone, locust vitellin and guinea-pig milk proteins were identified using specific antibodies, whilst chicken lysozyme and ovomucoid, rat albumin, Xenopus vitellogenin and rat seminal vesicle basic proteins were identified provisionally from their molecular weights. Certain endogenous proteins are sequestered and secreted although most oocyte proteins are not exported. Similarly the major polyoma viral protein and the simian virus 40 and polyoma tumour antigens are retained within the oocyte. Radioactive proteins exported by oocytes programmed with chicken oviduct or Xenopus liver RNA are not re-exported in detectable amounts when injected into fresh oocytes, nor is there secretion of chicken oviduct or guinea-pig mammary gland primary translation products prepared using wheat germ extracts. Thus the export of secretory proteins from oocytes cannot be explained by leakage and may require a cotranslational event. The secretory system of the oocyte is neither cell-type nor species-specific yet is highly selective. We suggest that the oocyte can be used as a general surrogate system for the study of gene expression, from transcription through translation to the final subcellular or extracellular destination of the processed protein.