The nucleus: a highly organized but dynamic structure

The nucleus in plants and animals is a highly structured organelle containing several well-defined subregions or suborganelles. These include the nucleolus, interphase chromosome territories and coiled bodies. We have visualized transcription sites in plants at both light- and electron-microscopy level by the incorporation of BrUTP. In the nucleolus many dispersed foci are revealed within the dense fibrillar component, each of which probably corresponds to a single gene copy. In the nucleoplasm there are also many dispersed foci of transcription, but not enough to correspond to one site per transcribed gene. We have shown that in wheat, and probably many other plant species, interphase chromosome territories are organized in a very regular way, with all the chromosomes in the Rabl configuration, all the centromeres clustered at the nuclear membrane and all the telomeres located at the nuclear membrane on the opposite side of the nucleus. However, despite this regular, polarized structure, there is no sign of polarization of transcription sites, or of any preferred location for them with respect to chromosome territorial boundaries. The nucleus is also highly dynamic. As an example, we have shown by the use of a green fluorescent protein fusion to the spliceosomal protein U2B" that coiled bodies move and coalesce within the nucleus, and may act as transport structures within the nucleus and nucleolus.

Glucoamylase::green fluorescent protein fusions to monitor protein secretion in Aspergillus niger

A glucoamylase::green fluorescent protein fusion (GLA::sGFP) was constructed which allows the green fluorescent protein to be used as an in vivo reporter of protein secretion in Aspergillus niger. Two secretory fusions were designed for secretion of GLA::sGFP which employed slightly different lengths of the glucoamylase protein (GLA499 and GLA514). Expression of GLA::sGFP revealed that fluorescence was localized in the hyphal cell walls and septa, and that fluorescence was most intense at hyphal apices. Extracellular GLA::sGFP was detectable by Western blotting only in the supernatant of young cultures grown in soya milk medium. In older cultures, acidification of the medium and induction of proteases were probably responsible for the loss of extracellular and cell wall fluorescence and the inability to detect GLA::sGFP by Western analysis. A strain containing the GLA::sGFP construct was subjected to UV mutagenesis and survivors screened for mutations in the general secretory pathway. Three mutants were isolated that were unable to form a halo on either starch or gelatin medium. All three mutants grew poorly compared to the parental strain. Fluorescence microscopy revealed that for two of the mutants, GLA::sGFP accumulated intracellularly with no evidence of wall fluorescence, whereas for the third mutant, wall fluorescence was observed with no evidence of intracellular accumulation. These results indicate that the GLA::sGFP fusion constructs can be used as convenient fluorescent markers to study the dynamics of protein secretion in vivo and as a tool in the isolation of mutants in the general secretory pathway.

Nucleoside analogs plus ritonavir in stable antiretroviral therapy-experienced HIV-infected children: a randomized controlled trial. Pediatric AIDS Clinical Trials Group 338 Study Team

CONTEXT

Although protease inhibitors are used routinely in adults with human immunodeficiency virus (HIV) infection, the role of these drugs in the treatment of clinically stable HIV-infected children is not clear.

OBJECTIVE

To evaluate the safety, tolerance, and virologic response produced by a change in antiretroviral therapy in HIV-infected children who were clinically and immunologically stable while receiving previous therapy.

DESIGN

The Pediatric AIDS Clinical Trials Group 338, a multicenter, phase 2, randomized, open-label controlled trial conducted from February 6 to April 30, 1997 (patient entry period); patients were followed up for 48 weeks.

SETTING

Pediatric HIV research clinics in the United States and Puerto Rico.

PATIENTS

Two hundred ninety-seven antiretroviral-experienced, protease inhibitor-naive, clinically stable HIV-infected children aged 2 to 17 years.

INTERVENTIONS

Children were randomized to receive zidovudine, 160 mg/m2 3 times per day, plus lamivudine, 4 mg/kg 2 times per day (n = 100); the same regimen plus ritonavir, 350 mg/m2 2 times per day (n = 100); or ritonavir, 350 mg/m2 2 times per day, and stavudine, 4 mg/kg 2 times per day (n = 97).

MAIN OUTCOME MEASURE

Plasma HIV-1 RNA levels at study weeks 12 and 48, compared among the 3 treatment groups.

RESULTS

At study week 12, 12% of patients in the zidovudine-lamivudine group had undetectable plasma HIV RNA levels (<400 copies/mL) compared with 52% and 54% of patients in the 2- and 3-drug ritonavir-containing groups, respectively (P<.001). Through study week 48, 70% of children continued receiving their ritonavir-containing regimen. At study week 48, 42% of children receiving ritonavir plus 2 nucleosides compared with 27% of those receiving ritonavir and a single nucleoside had undetectable HIV RNA levels (P = .04); however, similar proportions in each group continuing initial therapy had HIV RNA levels of less than 10000 copies/mL (58% vs 48%, respectively; P = .19).

CONCLUSIONS

In our study, change in antiretroviral therapy to a ritonavir-containing regimen was associated with superior virologic response at study week 12 compared with change to a dual nucleoside analog regimen. More children receiving ritonavir in combination with 2 compared with 1 nucleoside analog had undetectable HIV RNA levels at study week 48.

The relationship of biochemical markers of bone turnover to bone density changes in postmenopausal women: results from the Postmenopausal Estrogen/Progestin Interventions (PEPI) trial

We assessed the associations of eight bone turnover markers (BTMs) with baseline and 1-year percentage changes in lumbar spine and hip bone mineral density (BMD) of 293 postmenopausal women undergoing treatment with hormone replacement therapy (HRT) or placebo using squared correlation coefficients (R2). In 239 women assigned to treatment with estrogen alone or with with estrogen plus progestins (active treatment), mean percentage changes for all markers decreased significantly and remained below baseline values through 3 years of study, whereas mean percentage changes for 54 women assigned to the placebo group showed no significant change from baseline in any marker. At baseline, age and body mass index (BMI) together accounted for 16% and 25% of the variance in spine and hip BMD, respectively. The telopeptide resorption marker, cross-linked N-telopeptide of type I collagen (NTX), alone accounted for 12% and 8% of variance, respectively. Another telopeptide, carboxy-terminal telopeptide of type I collagen (Crosslaps), accounted for 8% and 7% of variance, respectively. A bone-specific alkaline phosphatase (BALP-2) accounted for 8% of variance at the spine and 5% at the hip. No other marker accounted for more than 5% of total variance at either site; adding either baseline NTX, Crosslaps, or BAP-2 to regressions containing age and BMI increased R2 values at the spine and hip to about 22% and 28%, respectively. In the placebo group, baseline spine BMD accounted for 4% of the variance in 1-year spine BMD percentage change, whereas baseline values for age and BMI accounted for 1% and 0% of the variance, respectively; none of the three accounted for more than 0% of hip BMD percentage change; Crosslaps and NTX contributed 5% and 4% to the variance in 1-year spine BMD percentage change, but other markers accounted for < 2% of variance at the spine. At the hip, another BALP (BALP-1) accounted for 4% of variance, but no other baseline marker except NTX accounted for more than 1% of variance. In the active treatment group, baseline values for age, BMI, and spine BMD together accounted for 13% of the percentage change in spine BMD and for 4% of the BMD change at the hip. No individual or pair of baseline markers significantly enhanced these R2 values, but addition of 1-year percentage changes in some individual markers did significantly increase it. The largest R2 value was obtained by adding the percentage change in BALP-2, which increased the R2 in spine BMD percentage change to 20% and that at the hip to 8%. Adding baseline and change variables for all eight markers to the regression increased R2 to 28% at the spine and 12% at the hip. Restricting the set of analyses to individuals who suppressed marker activity beyond the precision error for the measurement did not improve R2s for the regressions. When baseline marker values were stratified into quartiles, only NTX and osteocalcin showed significant relationships between quartile and change in spine BMD, and these did not reach significance at the hip. When the 1-year change in markers was stratified into quartiles, significant relationships with percentage change in spine BMD were observed only for BALP phosphatases. We conclude that BTMs are not a surrogate for BMD to identify women with low bone mass and that they offer little useful information for predicting BMD changes for individual untreated or HRT-treated postmenopausal women.

Ribavirin and interferon alfa-2b in chronic hepatitis C: assessment of possible pharmacokinetic and pharmacodynamic interactions

AIMS

The primary objective of this study was to determine whether pharmacokinetic interactions occurred between interferon alpha-2b (IFN) and ribavirin in patients with chronic hepatitis C infections. Additionally this study assessed the single and multiple-dose pharmacokinetics of ribavirin and IFN, and compared the safety, tolerability and antiviral pharmacodynamics of IFN plus ribavirin compared with either drug alone.

METHODS

In this open label parallel group study, patients with chronic hepatitis C were randomized to receive IFN 3 million IU thrice weekly s.c. alone, ribavirin 600 mg twice daily p.o. alone or both drugs in combination over 6 weeks. Single and multiple dose pharmacokinetics and indices of antiviral pharmacodynamics were assessed during weeks 1 and 6, along with safety assessments during the study.

RESULTS

The range of mean ribavirin terminal phase half-lives after single doses was 44-49 h. Comparison of week 1 and week 6 AUC(0,12h) values showed accumulation in plasma of approximately 6-fold. The range of mean washout half-lives after week 6 was 274-298 h, reflecting release of ribavirin from deep compartment stores. The range of single and multiple dose IFN terminal phase half-lives was 5-7 h. IFN demonstrated an increase in bioavailability (approximately 2-fold) upon multiple dose administration. Ribavirin and IFN pharmacokinetic parameters for combined ribavirin and IFN were similar to those during monotherapy with either compound, although the power of this study to detect differences was low. Serum HCV-RNA titers and ALT concentrations were reduced by IFN alone, ribavirin alone reduced ALT concentrations only, and combined IFN plus ribavirin produced numerically greater falls in both measurements than either treatment alone. Serum concentrations of neopterin and activity of 2',5'-oligoadenylate synthetase (2'5'-OAS) were increased by IFN alone and in combination with ribavirin, whereas serum 2'5'-OAS activity was decreased and neopterin concentrations unaltered by ribavirin monotherapy. IFN and ribavirin monotherapy produced characteristic changes in safety laboratory tests (IFN--reductions in white cells, neutrophils and platelets; ribavirin--reduced haemoglobin) and characteristic adverse event profiles (IFN--headache, flu-like symptoms, fatigue, anorexia, nausea, myalgia, and insomnia; ribavirin--headache, fatigue, myalgia, and pruritus). There was no additive effect of combination therapy on safety laboratory tests or reported adverse events. All changes were fully reversible upon treatment cessation.

CONCLUSIONS

There was no evidence of pharmacokinetic interactions between IFN and ribavirin in this study. There were numerical trends indicating that the combination of IFN and ribavirin reduced titers of HCV-RNA to a greater extent than did either treatment alone, and the safety profile of combination therapy was similar to those of both monotherapy treatments.

Prosody as an interactional resource: turn-projection and overlap

One aim of current research into talk-in-interaction is to identify the resources that enable recipients to monitor the course of a turn in progress in order to project its upcoming completion. This issue is addressed through analysis of instances of overlapping talk, focusing on their design--that is, their particular prosodic and other linguistic characteristics; their placement--in other words, where precisely they occur in relation to the turn being overlapped; and the subsequent behavior of the coparticipants. Phonetic analysis is combined with interactional techniques developed within Conversation Analysis, to warrant the relevance of categories by reference to the behavior of the participants themselves. As French and Local (1983) found, for an incoming to be treated as turn-competitive, it has to be designed with relatively high pitch and loud volume. These turn-competitive incomings are positioned within the turn in progress, and before the final major accent. By contrast, overlapping incomings positioned after the major accent are not designed as or treated as turn-competitive. On the basis of this analysis, we can define transition relevance place (TRP) as the space between the TRP-projecting accent of the current turn and the onset of the next turn. TRP-projecting accents are identifiable on independent grounds, being phonetically distinct from non-TRP-projecting accents. They thus provide a robust resource for participants to monitor the upcoming completion of the turn.

The ROOT HAIRLESS 1 gene encodes a nuclear protein required for root hair initiation in Arabidopsis

The epidermis of Arabidopsis wild-type primary roots, in which some cells grow hairs and others remain hairless in a position-dependent manner, has become an established model system to study cell differentiation. Here we present a molecular analysis of the RHL1 (ROOT HAIRLESS 1) gene that, if mutated, prevents the formation of hairs on primary roots and causes a seedling lethal phenotype. We have cloned the RHL1 gene by use of a T-DNA-tagged mutant and found that it encodes a protein that appears to be plant specific. The predicted RHL1 gene product is a small hydrophilic protein (38.9 kD) containing putative nuclear localization signals and shows no significant homology to any known amino acid sequence. We demonstrate that a 78-amino-acid sequence at its amino terminus is capable of directing an RHL1-GFP fusion protein to the nucleus. The RHL1 transcript is present throughout the wild-type plant and in suspension culture cells, but in very low amounts, suggesting a regulatory function for the RHL1 protein. Structural evidence suggests a role for the RHL1 gene product in the nucleolus. We have examined the genetic relationship between RHL1 and GL2, an inhibitor of root hair initiation in non-hair cells. Our molecular and genetic data with double mutants, together with the expression analysis of a GL2 promoter-GUS reporter gene construct, indicate that the RHL1 gene acts independently of GL2.

Feasibility of prescribing injectable heroin and methadone to opiate-dependent drug users: associated health gains and harm reductions

OBJECTIVE

To assess the feasibility of offering the choice of prescribing injectable heroin (diamorphine) or injectable methadone to opiate-dependent injecting drug users and to assess whether there are health and social gains associated with prescribing injectable opiates.

DESIGN

A protocol-driven prospective observational study. Type of injectable opiate received was based on self-selection.

SETTING

A large west London drug clinic.

PATIENTS

Fifty-eight patients admitted to the clinic between 1 June 1995 and 31 December 1996, who were long term opiate-dependent injecting drug users, who had previously tried and failed oral methadone and who were apparently unable or unwilling to give up injecting.

MAIN OUTCOME MEASURES

Retention in treatment, illicit drug use, HIV risk behaviour, criminal activity, social functioning, health and psychological status as measured by self-report, urinalysis and doctor's ratings.

RESULTS

Thirty-seven patients (64%) chose heroin and 21 (36%) chose injectable methadone. Fifty (86%) were retained in treatment after three months, 40 (69%) after six months and 33 (57%) after 12 months. Among those in treatment at three months, there were significant reductions in illicit drug use, illicit drug-injecting risk behaviour, and criminal activity, and significant improvements in social functioning, health status and psychological adjustment. Generally, these gains were sustained between three, six and 12 months. Doctors' ratings of health and urinalysis results further supported these findings.

CONCLUSIONS

Injectable heroin is not always the drug of choice. This intervention retained most patients in treatment with substantial benefits to both patients and the community. Prescribing injectable opiates to long term injecting drug users is a feasible treatment option.

Children's comprehension of unfamiliar regional accents: a preliminary investigation

The effect of regional accent on children's processing of speech is a theoretically and practically important aspect of phonological development that has been little researched. 48 children from London, aged four and seven years old, were tested on their ability to repeat and define single words presented in their own accent and in a Glaswegian accent. Results showed that word comprehension was significantly reduced in the Glaswegian condition and that four-year-olds performed less successfully than seven-year-olds. Both groups made similar numbers of lexical misidentifications, but the younger children were more likely to fail to access any word at all. On the repetition task, the younger children showed a different pattern of errors to the older children, their productions being apparently more influenced by the phonetics of the Glaswegian stimuli. It is suggested that such phonetic responses are related to the younger children's failure to map the unfamiliar accent onto their own phonological representations. It is proposed that the lexical misidentifications, common to both age groups, are more likely to be induced by lack of context. The paper concludes with discussion of implications of these findings for our understanding of how children develop the ability to process unfamiliar regional accents.

Plant-adapted green fluorescent protein is a versatile vital reporter for gene expression, protein localization and mitosis in the filamentous fungus, Aspergillus nidulans

Green fluorescent protein (GFP) is a useful reporter to follow the in vivo behaviour of proteins, but the wild-type gfp gene does not function in many organisms, including many plants and filamentous fungi. We show that codon-modified forms of gfp, produced for use in plants, function effectively in Aspergillus nidulans both as gene expression reporters and as vital reporters for protein location. To demonstrate the use of these modified gfps as reporter genes we have used fluorescence to follow ethanol-induced GFP expression from the alcA promoter. Translational fusions with the modified gfp were used to follow protein location in living cells; plant ER-retention signals targeted GFP to the endoplasmic reticulum, whereas fusion to the GAL4 DNA-binding domain targeted it to the nucleus. Nuclear-targeted GFP allowed real-time observation of nuclear movement and division. These modified gfp genes should provide useful markers to follow gene expression, organelle behaviour and protein trafficking in real time.

Sites of rDNA transcription are widely dispersed through the nucleolus in Pisum sativum and can comprise single genes

Incorporation by RNA polymerases of BrUTP into both plant root tissue and isolated plant nuclei as a method for localization of the sites of transcription has been used. In this paper pea root tissue was used, and under the conditions employed, nearly all the incorporation occurs in the nucleolus, and thus must be catalysed by RNA polymerase I. Immunofluorescence and confocal microscopy shows that incorporation occurs in a pattern consisting of many small foci distributed widely through the dense fibrillar component of the nucleoli. Immunogold labelling using silver-enhanced Nanogold probe at the electron microscopic level confirms the sites of transcription as small foci approximately 200 nm in diameter. Simultaneous fluorescence in situ hybridization with a probe to the external transcribed spacer (ETS) region of the pre-rRNA shows that the structures revealed by this probe and the BrUTP immunofluorescence labelling are very similar. A probe to the transcribed portion of the rDNA (18S) also shows a good correlation to the sites of BrUTP incorporation within the nucleolus. On the other hand a probe to the non-transcribed intergenic spacer region (NTS) shows very little coincidence with the sites of BrUTP incorporation, and double fluorescence in situ labelling with both 18S and NTS probes confirms this difference in localization. These results suggest that most BrUTP foci correspond to single transcribed genes.

Structural and genetic analysis of epidermal cell differentiation in Arabidopsis primary roots

In a screen designed to identify genes in the specification of epidermal cell fate in Arabidopsis primary roots we have isolated 8 new mutants that fall into 6 complementation groups corresponding to the ‘root hairless’ genes RHL1, RHL2 and RHL3 and the ‘ectopic root hair’ genes ERH1, ERH2 and ERH3. The erh2 mutant is allelic to pom1, a conditional root expansion mutant, and reveals a possible link between epidermal root hair initiation and radial cell expansion. Apart from erh1 the mutants also show defects in shoot development, indicating a complex role for the affected genes. Mutant phenotypes in the patterning and shape of leaf trichomes in rhl1, rhl2, rhl3 and erh3 were particularly obvious. The root hairless mutants are only partly responsive to increased ethylene concentrations, while the ectopic root hair mutants are fully responsive to reduced concentrations of ethylene, a permissive regulator of root hair initiation. This result and the analysis of double mutants suggest a complex pathway leading to root hair initiation that requires the RHL and ERH genes for correct differentiation.

The context of ethics in the health care industry

Examines ethics in the health care industry from the perspectives of investors, employees, patients, competitors and the environment. Ethical behaviour in the health care industry is essential and desirable; however, determining which behavioural actions are ethical and which are unethical is difficult. Although never will everyone agree on specific ethical standards, everyone should agree that setting ethical standards is vital. Therefore, administrators of health care institutions and health care providers should work together to establish codes of ethics which define boundaries for ethical behaviours in the health care industry.

Methods of and attitudes toward screening obstetrics and gynecology patients for domestic violence

OBJECTIVE

Our purpose was to define screening behaviors of obstetrician-gynecologists and barriers to screening their patients for domestic violence.

STUDY DESIGN

A questionnaire was developed to collect information on current practices and attitudes regarding screening for domestic violence. A randomly selected sample of obstetrician-gynecologists was surveyed. Respondents were also asked to rank a series of 19 potential barriers that may affect screening.

RESULTS

Of 6568 physicians sampled, 962 (14.6%) returned questionnaires. Of the respondents, 77.6% were male and 22.4% were female. Male physicians were less likely to screen for domestic violence (25.9% vs. 18.9%). Thirty-four percent said that they had no training in abuse. Physicians indicating they had received training in abuse were more likely to screen for domestic violence. The lack of education was identified as the most common barrier physicians have to screening. The feeling that abuse was not a problem in their patients (46%), lack of time to deal with abuse (39.2%), and frustration that the physician cannot help the victim (34.2%) were other common barriers.

CONCLUSION

The majority of obstetrician-gynecologists do not screen their patients for current or past domestic violence. If universal screening is to become a reality, educational tools and training materials are needed to overcome physician barriers.

Chemical compatibility of inotropic and vasoactive agents delivered via a multiple line infusion system

OBJECTIVES

To determine the chemical compatibility of three different triple drug admixtures diluted with either 5% dextrose in water or 0.9% NaCl solution when administered via a multiple line infusion system (Omni-Flow 4000, Abbott Laboratories, Abbott Park, IL). The triple drug admixtures were: a) dobutamine, dopamine, and norepinephrine; b) nitroglycerin, sodium nitroprusside, and dobutamine; and c) nitroglycerin, dopamine, and dobutamine.

DESIGN

Two phase in vitro compatibility study.

SETTING

Pharmaceutical laboratory.

SUBJECTS

None.

INTERVENTIONS

Phase I assessed chemical stability when the triple drug admixture was placed in a single container. In phase II, individual drug components of the admixtures were infused via the multiple line infusion system. Samples were collected at time 0, 1 hr, 2 hrs, 4 hrs, 12 hrs, and 24 hrs. All samples were frozen and stored at -70 degrees C until assayed.

MEASUREMENTS AND MAIN RESULTS

Samples were assayed using stability-indicating high performance liquid chromatography. The triple drug admixtures were considered to be chemically stable if there was < or = 10% loss of stated potency over 24 hrs. In phase I, chemical stability was observed for all triple drug admixtures at 24 hrs. In phase II, dobutamine, dopamine, norepinephrine, and sodium nitroprusside showed chemical stability at 24 hrs. Nitroglycerin showed a two-fold increase in concentration at 24 hrs compared with the initial concentration through the test infusion system; however, this amount was still one third lower than originally anticipated.

CONCLUSIONS

All triple drug admixtures were chemically stable when placed in single containers. Dobutamine, norepinephrine, and sodium nitroprusside showed chemical stability when delivered via a multiple line infusion system. The reduced recovery of nitroglycerin from the test infusion system may result from adsorption of the nitroglycerin to the polyvinyl chloride plastic cassette and tubing during infusion.

Plasmodesmata of maize root tips: structure and composition

A procedure is described for obtaining clean maize cell wall preparations that contain embedded plasmodesmata. Negative staining and rotary shadowing have been used with transmission electron microscopy to visualise the plasmodesmata in these isolated walls, and to assess the effects of simple biochemical treatments on plasmodesmal components. Light protease treatment removes material from the exposed ends of plasmodesmata but does not extract the plasmodesmal core, which lies within the cell wall. However, heavy proteolysis occasionally removes the complete plasmodesma, including its enclosing collar structure, from the wall. Extraction with urea has a similar effect. The collar itself appears not to be proteinaceous in composition, although protein may bind it into the wall. Callose is localised in the wall around plasmodesmata, but does not appear to be a constituent of the collar. The membrane components of the plasmodesma (plasma membrane and desmotubule) can be extracted with membrane-solubilising detergents. This treatment releases from the wall a small number of proteins that are regarded as being potentially of plasmodesmal origin. These results show that plasmodesmata from maize can be dissected biochemically and suggest a strategy for the characterisation of individual molecular components.

Vanadium air pollution: a cause of malabsorption and immunosuppression in cattle

An epidemiological investigation into an "illthrift" problem occurring on a dairy farm adjacent to an alloy-processing unit, established that the probable cause of the problem was chronic vanadium poisoning. The disease manifested initially in animals 4-18 months old which showed emaciation, chronic diarrhoea and, in some cases, rhinitis, conjunctivitis and recumbency followed by death. Post-mortem (n = 17) and clinical-pathology findings (n = 60) indicated that malabsorption and immunosuppression were the basis of the pathogenesis in affected animals. Eight months after the commencement of the investigation, adult cows began showing evidence of emaciation, reduced milk production and an apparent increase in the number of abortions, stillbirths and dystocias. Over a 2-year period, 134 surface-soil samples, 134 subsoil samples and 134 grass samples from the farm were analysed for various fractions of vanadium. Thirty-four of each of these samples were collected at different time intervals (autumn 1990, summer 1991 and winter 1991) and at varying distances and directions from the processing unit, in order to gauge the magnitude of the problem, and the distribution pattern of vanadium, and to identify possible seasonal trends. The remaining 100 of each of these samples were taken at 100-m intervals over an area of approximately 1,140,000 m2 directly adjacent to the processing unit so that concentration isolines for vanadium could be drawn and the source more conclusively identified. The levels of vanadium were found to be highest closest to the mine, and surface-soil levels were consistently higher than subsoil levels, suggesting aerial pollution, which was confirmed by air sampling.(ABSTRACT TRUNCATED AT 250 WORDS)

Correlates of bone mineral density in the postmenopausal estrogen/progestin interventions trial

We assessed the cross-sectional relationship of age, menopausal years, body mass, previous estrogen use, and ethnic background to bone mineral status in a sample of 875 healthy postmenopausal women at the time they were recruited from the community to participate in a multicenter clinical trial. The women were 1-10 years postmenopause, 45-64 years of age, and had not received estrogen replacement therapy within 3 months of enrollment. Of the participants, 89% were white, 69% had a spontaneous menopause, and 53% had a history of previous estrogen replacement therapy. Bone mineral density (BMD) of the lumbar spine (L2-4) and proximal femur was measured by dual-energy x-ray absorptiometry. Results were consistent with a significant negative linear regression of BMD on age or years from menopause. Body mass index (BMI) correlated significantly with BMD at all sites (L 2-4 r = 0.28; femoral neck r = 0.34, p < 0.0001). BMD adjusted for age and BMI were higher at both sites in women who had taken estrogen versus those who had not (L2-4 0.976 +/- 0.009 versus 0.932 +/- 0.01; femoral neck 0.740 +/- 0.006 versus 0.708 +/- 0.008, p < 0.05). Adjusted BMD also increased with duration of ERT. Parity was negatively associated with L2-4 BMD (p = 0.03) but did not correlate significantly with BMD at the femoral neck. Black women had the highest L2-4 BMD, and Hispanic women had the highest femoral neck BMD, even when results were adjusted for age and BMI. When data were corrected for differences in bone size, these interethnic differences were no longer significant. We conclude that increased body mass is positively correlated with BMD, and this may confer a degree of skeletal protection to heavier postmenopausal women. Exposure for 5 years to exogenous estrogen is associated with significantly increased age- and BMI-adjusted BMD.

Treatment and services for drug users in Britain

The pattern of British drug service provision was transformed during the late 1980s. Policy makers and service providers recognised the need for a more flexible response to changing drug trends and client needs; consequently community-based services proliferated. HIV has had considerable impact on the working approach of many agencies, where harm minimisation is now the immediate goal. This article provides an overview of patterns of drug use and drug service provision in Britain.

Psycholinguistic assessment of developmental speech disorders

Although various psycholinguistic models of speech and language processing have been developed to account for levels of breakdown in developmental speech disorders, it is not obvious how they are to be applied in clinical practice. At the same time, speech and language therapists have routinely been using a wide range of procedures, including published tests, that tap different levels of phonological processing in the child. When analysed and classified appropriately, these procedures can form the basis for a comprehensive psycholinguistic investigation of developmental speech disorders. The aim of this paper is to present a clinically usable, needs-driven but theoretically motivated framework for investigation. The framework is organised in terms of a series of questions that the clinician can pose about the levels of deficit in processing that may be giving rise to the child's speech problems. It is illustrated by means of a case study of a child with a severe developmental speech disorder, which reveals a complex pattern of deficits within the speech processing chain. As the main purpose of the framework is to provide a useful clinical tool to facilitate the planning of appropriate therapy for the individual child, some therapy objectives deriving from the assessment are outlined.

The tobacco mosaic virus 30K movement protein in transgenic tobacco plants is localized to plasmodesmata

Transgenic tobacco plants expressing a gene encoding the tobacco mosaic virus (TMV) movement protein (30K) were studied using immunocytochemical techniques. The movement protein was shown to be localized within or on most of the plasmodesmata observed in the transformed plant. These results are consistent with the idea that the movement protein interacts with the plasmodesmata to facilitate the cell-to-cell spread of TMV.

Solid-phase extraction and liquid chromatography of torsemide and metabolites from plasma and urine

Torsemide is a new diuretic drug with a profile of action similar to that of furosemide. The high potency of torsemide results in low dose therapy and causes problems for the pharmacokinetic study of the drug due to low plasma levels. Described here are methods for the analysis of torsemide and two metabolites in plasma and urine using solid-phase extraction and liquid chromatography. The limits of quantitation are 10 ng/mL for plasma and 20 ng/mL for urine. The relative standard deviations for precision are less than 10% for most analytes at most concentrations in the calibration range. The recoveries from plasma were 94.3, 92.9, and 95.6%, and from urine were 77.5, 66.6, and 76.5% for torsemide and metabolites M1 and M5, respectively. The method was suitable for pharmacokinetic studies. Data from a normal volunteer are presented.

Immunoassay and ultrastructural localization of isopentenyladenine and related cytokinins using monoclonal antibodies

Two hybridoma cell lines, J40-IV-A1 and J40-IV-C4 were obtained from a fusion of spleen cells of Balb/c mice immunized against an isopentenyladenosine-bovine serum albumin conjugate with X63. Ag 8.653 myeloma cells. These hybrids secrete monoclonal antibodies of the immunoglobulin G (IgG) class and share high affinities and specificities to isopentenyladenine and isopentenyladenosine suitable for the detection of femtomole amounts of these cytokinins in plant extracts by enzyme-linked immunosorbent assay (ELISA). One of the monoclonal antibodies (J40-IV-C4) has been employed to localize isopentenyladenine immunoreactivity in a cytokinin-over-producing mutant of the moss, Physcomitrella patens. After fixation and embedding at low temperature, immunoreactivity was visualized in protonemal filaments of the moss mutant by the use of indirect immunogold labelling. In the mutant, the labelling was predominantly in the wall of the protonemal cells. Neither the wild-type nor control treatments showed any labelling. The signficance of these observations is discussed with respect to the applicability of immunocytochemical techniques for the localization of low-molecular-weight compounds in plant tissue.

Nodulation inhibition by Rhizobium leguminosarum multicopy nodABC genes and analysis of early stages of plant infection

During analysis of early events in the infection and nodulation of Vicia hirsuta roots inoculated with normal and mutant strains of Rhizobium leguminosarum and strains containing cloned nodulation (nod) genes, a number of novel observations were made. (i) Alternating zones of curled and straight root hairs were seen on roots of V. hirsuta inoculated with the wild-type strain of R. leguminosarum. This phasing of root hair curling was not seen if plants were grown under continuous light or continuous dark conditions. (ii) Reduced nodulation and delayed nodule initiation was observed with a strain carrying a Tn5 mutation in the nodE gene. In addition the phased root hair curling was absent, and root hair curling was observed along the length of the root. (iii) The nodABC genes cloned on a multicopy plasmid in a wild-type strain inhibited nodulation but induced a continuous root hair curling response. Those few nodules that eventually formed were found to contain bacteria which had lost the plasmid carrying the nodABC genes. (iv) With a strain of Rhizobium cured of its indigenous symbiotic plasmid, but containing the cloned nodABCDEF genes, continuous root hair curling on V. hirsuta was observed. However, no infection threads were observed, and surprisingly, it did appear that initial stages of nodule development occurred. Observations of thin sections of these early developing nodules indicated that early nodule meristematic divisions may have occurred but that no bacteria were found within the nodules and no infection threads were observed either within the nodule bumps or within any of the root hairs. It was concluded that for normal infections to occur, precise regulation of the nod genes is required and that overexpression of the root hair curling genes inhibits the normal infection process.

Microtubules are at the tips of root hairs and form helical patterns corresponding to inner wall fibrils

Root hairs have sometimes provided contradictory evidence for microtubule/microfibril parallelism. This tissue was re-examined using optimized conditions for the fixation, before immunofluorescence, of root hairs. In phosphate buffer, microtubules did not enter the apical tip of radish root hairs and were clearly fragmented. However, in an osmotically adjusted microtubule-stabilizing buffer, microtubules were observed within the apical dome and appeared unfragmented. Microtubules are not, therefore, absent from the region where new cell wall is presumed to be generated during tip growth. A spiralling of microtubules was seen at the apices of onion root hairs. Using shadow-cast preparations of macerated radish root hairs, it was confirmed that steeply helical microtubules matched the texture of the inner wall. In onion, the 45 degrees microtubular helices are accompanied by similarly wound inner wall fibrils. Results do not support the view that microtubules are not involved in the oriented deposition of fibrils in root hairs. Instead, they are interpreted in terms of a flexible helical cytoskeleton, which is capable of changing its pitch but is sensitive to fixation conditions.

Monoclonal antibodies to antigens in the peribacteroid membrane from Rhizobium-induced root nodules of pea cross-react with plasma membranes and Golgi bodies

Three rat hybridoma lines that produced monoclonal antibodies reacting with the peribacteroid membrane from Pisum sativum were isolated, and these all appeared to recognize the same antigenic structure. Using one of these monoclonal antibodies, AFRC MAC 64, electron microscopy of immunogold-stained thin sections of nodule tissue revealed that the antigen, present in the peribacteroid membrane, was also found in the plant plasma membranes and in the Golgi bodies, but not in the endoplasmic reticulum. When peribacteroid membrane proteins were separated by SDS-polyacrylamide gel electrophoresis and transferred to nitrocellulose by electro-blotting, it was found that MAC 64 bound to a series of protease-sensitive bands that migrated in the mol. wt. range 50-85 K. The epitope was sensitive to periodate oxidation and its structure may therefore involve the carbohydrate component of a membrane glycoprotein. We suggest that this structure originates in the Golgi apparatus and is subsequently transferred to the peribacteroid membranes and plasma membranes. The monoclonal antibody also reacted with peribacteroid membranes from nodules of Vicia and lupin, and with plasma membranes and Golgi membranes from uninfected plant cells, including root tip cells from onion (Allium cepa), indicating that the antigen is highly conserved in the plasma membranes of plant cells.

Rhizobium leguminosarum genes involved in early stages of nodulation

Nodulation genes from Rhizobium leguminosarum have been subcloned and transferred to a strain of R. phaseoli with its symbiotic plasmid deleted (and therefore its nodulation and nitrogen fixation genes). Normal infection and nodule development occurred when these strains were added to the roots of Pisum sativum (peas) and Vicia hirsuta. The pea nodules were examined by electron microscopy; bacteroid forms were seen surrounded by peribacteroid membranes and using immuno-gold labelling it was shown that the nodule cells contained leghaemoglobin within the cytoplasm. By subcloning and analysing the nodulation region it was found that a small (3.2 X 10(3) bases) fragment of DNA contained three genes involved in root hair curling, the first observed step in the interaction between R. leguminosarum and the root hair cells of these legumes.

The legume-Rhizobium symbiosis: a cell surface interaction

This review will examine the early stages of infection of legume roots by strains of Rhizobium that induce nitrogen-fixing nodules. The object is to show that, at least in terms of ultrastructure, the interactions between the plant and the rhizobia occur at the cell surface interface between these organisms. This situation exists at all stages, from the time the bacteria attach to the surface of the root hairs to the time they occur as the nitrogen-fixing form in the cytoplasm of the nodule cells, enclosed by peribacteroid membranes.

The cytoskeleton underlying side walls and cross walls in plants: molecules and macromolecular assemblies

Plant cells organize their growth by reinforcing side walls during interphase (causing them to elongate) and by positioning and orienting the cross wall at cytokinesis. In the first part of this presentation we review progress made in identifying different cytoskeletal components that underlie side walls and that are involved in the deposition of the cross wall. During interphase, the cortical microtubule arrays co-distribute with an antigen recognized by a 'universal' monoclonal antibody to intermediate filaments. Using rhodaminyl-lysine-phalloidin no F-actin could be detected at the cortex but endoplasmic, axial cables were found. The cytokinetic apparatus--the phragmoplast--contains microtubules and we find that F-actin and the intermediate filament antigen also co-distribute with this array. We describe the three-dimensional arrangement of microtubules forming the interphase array in cells enlarging by both tip-growth and intercalary growth. In root hairs of higher plants and in apical cells of the filamentous stage of moss Physcomitrella patens, microtubules (MT) are detected at the apices and it is suggested from this that fragmentation of microtubules and absence of MTs from the tip are preparation artefacts. Using human serum from a scleroderma patient, possible microtubule nucleating sites are detected in meristematic cells; these segregate with the broad spindle poles and they surround the nucleus during early interphase--implying a peri-nuclear origin for the cortical MT array. The interphase microtubule array is described in terms of a dynamic helical model, which proposes: that the MT array is an integral complex; that microtubules form helices; that helices can change their pitch--the array converting to the various conformations.

Differential dose-response effects of dexamphetamine sulphate on hunger, arousal and mood in human volunteers

The effect of dexamphetamine (d-Amp) and placebo on visual analogue scale (VAS) ratings of hunger, arousal and mood in nine male volunteers was observed. d-Amp (10 mg) significantly depressed hunger ratings but did not significantly affect arousal and mood ratings. d-Amp (20 mg) had a significant effect on all three ratings. There was a difference in the pattern of dose-response effects. Whereas 20 mg d-Amp produced greater changes than 10 mg in ratings of mood and arousal, there was no significant difference on ratings of hunger. These differences in dose-response relationships may reflect differences in the underlying neurochemical mechanisms mediating the stimulant and anorectic effects of d-Amp.