In vitro selection and molecular characterization of human immunodeficiency virus type 1 with reduced sensitivity to 9-[2-(phosphonomethoxy)ethyl]adenine (PMEA)

9-[2-(Phosphonomethoxy)ethyl]adenine (PMEA) is an acyclic nucleotide with potent in vitro activity against human immunodeficiency virus type 1 (HIV-1). The present study was undertaken to determine whether HIV-1 resistance to PMEA could be generated by in vitro selection and if so, to determine which mutations in reverse transcriptase (RT) were responsible. HIV-1LAI was serially passaged for 10 months in the presence of increasing concentrations of PMEA up to a maximum of 40 microM. After 40 passages, the 50% inhibitory concentration (IC50) of PMEA had increased almost 7-fold from 4.45 to 30.5 microM. Some cross-resistance to 2',3'-dideoxycytidine (ddC, zalcitabine), 2',3-dideoxyinosine (ddI, didanosine), and 3'-thiacytidine (3TC, lamivudine) was also observed, but no cross-reactive resistance to 3'-azido-3'-thymidine (AZT, zidovudine). Sequencing of the RT encoding region of each of eight pol clones from resistant isolates revealed a Lys-65-->Arg (K65R) substitution. HIV with the K65R mutation inserted by site-directed mutagenesis also had decreased sensitivity to PMEA in H9 cells and a similar cross-resistance profile. Thus, HIV can develop decreased sensitivity to PMEA after long-term in vitro exposure and this change is associated with a K65R substitution. Additional studies will be needed to determine whether a similar mutation in HIV RT develops in patients receiving PMEA or its orally bioavailable prodrug adefovir dipivoxil (bis-POM PMEA).

Comparison of virus burden in blood and sequential lymph node biopsy specimens from children infected with human immunodeficiency virus

BACKGROUND

Lymph nodes serve as reservoirs for the replication of human immunodeficiency virus (HIV) type 1. Comparison of serial measurements of virus burden in lymph nodes and peripheral blood after a change in antiretroviral therapy may provide insights into pathogenic mechanisms and permit a more accurate assessment of a therapeutic response.

STUDY DESIGN

Nevirapine was added to the drug regiment of eight children with HIV infection treated with the combination of zidovudine and didanosine who had increasing levels of serum p24 antigen. Lymph node biopsies were performed at entry and after 12 weeks of therapy.

RESULTS

Neither CD4 counts nor p24 antigen level correlated with the degree of viremia as measured by ribonucleic acid copy numbers in plasma. Correlations were found between HIV DNA copy number in peripheral blood mononuclear cells and HIV DNA copy number in lymph nodes (p = 0.02), as well as between peripheral blood CD4 counts and lymph node architecture. The HIV signals in the lymph nodes conformed to the anatomic organization of apical light zones in the germinal centers; however, in more advanced disease stages, organized germinal centers disappeared as evidence by a decline in the extent of the follicular dendritic network.

CONCLUSIONS

Lymph node biopsies in this small number of HIV-infected children revealed a progressive loss of an organized architecture, especially of the follicular dendritic network. This correlated with a progressive loss of CD4+ cells but not with other measures of disease stage, including viral load, as measured by ribonucleic acid copy numbers.

Analysis of sertraline-only overdoses

Sertraline is an antidepressant for which preliminary data suggest a low inherent toxicity. Previously reported case series have included coingestants or had small numbers of patients. This study was undertaken to determine the toxicity of overdoses of sertraline alone. A 2-year retrospective and 6-month prospective study was conducted at a regional poison center. There were 52 patients with a mean age of 19.3 +/- 13.8 years and a mean dose of 727 +/- 686 mg. There were no symptoms in 34 cases. Symptomatic patients experienced mild central nervous system, cardiovascular, and gastrointestinal effects. Two patients developed bradycardia which resolved without therapy. While all but 3 of 38 adolescents and adults were treated in a health care facility, 10 of 14 children were managed at home. Gastrointestinal decontamination was performed in 37 cases. No other specific therapy was required. Serious toxicity would not be expected following sertraline-only overdoses.

Usefulness of tumor volumetry by magnetic resonance imaging in assessing response to radiation therapy in carcinoma of the uterine cervix

PURPOSE

Clinical evaluation of tumor size in cervical cancer is often difficult, and clinical signs of radiation therapy failure may not be present until well after completion of treatment. The purpose of this study is to investigate early indicators of treatment response using magnetic resonance (MR) imaging for quantitative assessment of tumor volume and tumor regression rate before, during, and after radiation therapy.

METHODS AND MATERIALS

Thirty-four patients with cervical cancer Stages IB [5], IIB [8], IIIA [1], IIIB [14], IVA [3], IVB [1], and recurrent [2] were studied prospectively with four serial MR examinations obtained at the start of radiation therapy, at 2-2.5 weeks (20-24 Gy), at 4-5 weeks (40-50 Gy), and 1-2 months after treatment completion. Tumor volume was assessed by three-dimensional volumetric measurements using T2-weighted images of each MR examination. The volume regression rate was generated based on the four sequential MR studies. These findings were correlated with local control, metastasis rate, and disease-free survival. Median follow-up was 18 months (range: 9-43 months).

RESULTS

The tumor regression rate after a dose of 40-50 Gy correlated significantly with treatment outcome. The actuarial 2-year disease-free survival was 88.4% in patients with tumors regressing to < 20% of the initial volume compared with 45.4% in those with > or = 20% residual (p = 0.007). The incidence of local recurrence was 9.5% (2 out of 21) and 76.9% (10 out of 13), respectively (p < 0.001). Analysis by initial tumor volume showed that this observation was valid in patients with initial volumes between 40 and 100 cm3. Analysis by FIGO stage confirmed this observation in all patients except those with Stage IB.

CONCLUSION

Sequential tumor volumetry using MR imaging appears to be a sensitive measure of the responsiveness of cervical cancer to irradiation. Treatment response can be assessed as early as during the course of radiation therapy by measurement of initial tumor volume and regression rate at 40-50 Gy. In patients with large (> 40 cm3) and advanced (Stage > or = IIIA) tumors, this technique may be helpful in supplementing the clinical examination for response assessment. The identification of patients at high risk for treatment failure may ultimately lead to improved clinical outcome.

Alterations in cortical thickness and neuronal density in the frontal cortex of Albert Einstein

Neuronal density, neuron size, and the number of neurons under 1 mm2 of cerebral cortical surface area were measured in the right pre-frontal cortex of Albert Einstein and five elderly control subjects. Measurement of neuronal density used the optical dissector technique on celloidin-embedded cresyl violet-stained sections. The neurons counted provided a systematic random sample for the measurement of cell body cross-sectional area. Einstein's cortex did not differ from the control subjects in the number of neurons under 1 mm2 of cerebral cortex or in mean neuronal size. Because Einstein's cortex was thinner than the controls he had a greater neuronal density.

Treatment outcome of squamous cell carcinoma of the oral tongue

Treatment outcome was retrospectively assessed in 106 patients with squamous cell carcinoma of the oral tongue registered in the population-based Manitoba Cancer Registry between January 1979 and December 1992. Twenty-six percent were diagnosed with stage I lesions, while 33%, 16%, and 24% were stage II, III, and IV, respectively. Most patients with stage I and II disease were treated with either surgery alone (57%) or in combination with radiotherapy (29%). Advanced lesions were generally treated with radiotherapy alone (37%) or in combination with surgery (35%). Actuarial survival at 5 years was 44% for all patients, and 64%, 46%, 42%, and 16% for stages I to IV, respectively. Over 90% of the 35 treatment failures occurred within 24 months. The initial sites of recurrence were the neck in 22 patients, the primary site in 16 patients, and distant metastases in 5 patients. At the time of death, disease was present above the clavicles in 62%, and metastases were identified in 22%. Locoregional control remains a significant problem in oral cancer. Elective treatment of the neck, resection of the primary with negative surgical margins, and the use of combined modality treatment in advanced stages of disease may help reduce treatment failure.

A mathematical model of line bisection behaviour in neglect

Subjects with left hemispatial neglect frequently demonstrate an array of abnormal behaviours on line bisection tasks. They misbisect long horizontal lines to the right of true midline. They bisect short lines to the left of true midline. They exaggerate the left-sided length of lines when placing the endpoints for 'invisible' lines, and they underestimate the length of the left side of long lines that are shown to them bisected accurately. No current theory of neglect explains all these features of line bisection behaviour. A mathematical model of line bisection behaviour in neglect is presented that proposes that subjects bisect lines at the point where they perceive the 'salience' of the two line segments created by their bisection mark to be equal. Salience is determined by the brain's attentional systems which map salience amplitude to spatial position following a bell shaped distribution. Right hemisphere strokes simulated by decreasing the 'height' and "breadth' of the right hemisphere salience to position function produced all of the above features of clinical neglect subjects' line bisection behaviour. Neglect may be conceived of as damage to brain systems performing mappings between stimulus characteristics (such as spatial location) and salience.

Effects of positive and negative life events on time to depression onset: an analysis of additivity and timing

While the relationship of life events to depression onset has occupied researchers for almost a quarter of a century, few studies have attempted to account for either the temporal patterning of events relative to episode onset, or, the effect of multiple events in a study period. In this report, we attempt to address the issues of timing of events, multiple events (both positive and negative) and multiple aspects (both positivity and negativity) of single events on latency time to depression onset, while simultaneously accounting for possible decay in the effects of events over time. We use the proportional hazards approach to model the effects of life events and consider modelling the change in impact of events with the passage of time. After interviewing 142 recurrent unipolar patients using the Life Events and Difficulties Schedule, we rated severity and positivity of life events reported during the 6-month period prior to onset. As we hypothesized, additional life events occurring after an initial provoking agent level event significantly alter the risk of illness onset. Additional severely threatening events decrease the time to onset, but positive events do not appear to delay onset. Interestingly, seemingly neutral events had a highly significant effect in shortening the time to onset. We note the many limitations imposed on the interpretation of these findings related to the selected group of subjects studied and encourage those who have more generalizable data to apply these methods of analysis.

p53 allelotypes and enhanced detection of allelic loss in ovarian cancer: lack of correlation with familial and clinical factors

To develop a mapping strategy for improved detection of p53 allelic loss associated with ovarian carcinoma, we utilized multiple intragenic polymorphisms and single-strand conformation polymorphism (SSCP) analysis. p53 allelotype distributions were defined for 80 ovarian cancer patients from germ-line DNA. All polymorphic sites studied had polymorphism information content (PIC) rates of greater than 0.25. Tumor loss of heterozygosity (LOH) was determined from informative polymorphisms and migratory shifts on SSCP screening of exons 5-9. Of the four polymorphisms analyzed, the intron 1 (alu) was the most informative (PIC = 0.66). A novel allele of 110 base pairs was found in 4.4% of our ovarian cancer cohort at this site. The intron 3 (16-base pair repeat) and intron 6 (MSP1) polymorphisms were in relative equilibrium; thus, we chose to use only the intron 3 polymorphic site in the mapping strategy. Family cancer history did not influence the allelotype distribution frequencies. Overall, 56 of 61 tumors (91.8%) were informative for allelic loss, and LOH was observed in 66.1 %. A reduction to homozygosity at the p53 locus did not correlate with familial or clinical factors. These observations are consistent with the multiple mechanisms by which p53 dysfunction can occur.

Management of severe bronchiolitis: indications for ventilator support

AIM

Bronchiolitis is a common respiratory illness in children. We reviewed our experience of children under one year presenting to an intensive care unit with a clinical diagnosis of bronchiolitis in order to determine if ethnicity, prematurity, arterial carbon dioxide tension or nasopharyngeal aspirates positive for respiratory syncytial virus were related to the need for ventilator assistance.

METHOD

A review of the charts of all infants with bronchiolitis admitted to the paediatric intensive care unit from December 1991 to February 1994 was undertaken.

RESULTS

There were 94 infants. Ventilator assistance was given to 24 children--nine children had nasopharyngeal continuous positive airway pressure and 15 children required intermittent positive pressure ventilation. There was no difference in ethnic mix between the respiratory support group (Maori 45%, Pacific Islands 30%, other 25%) and those children managed conservatively (Maori 40%, Pacific Islands 36%, other 24%). Fifteen of the 24 infants who needed ventilator support were born prematurely. The mean (corrected) age of infants who required respiratory support was 1.79 (SD2.98) months compared to 3.32 (SD2.58) months for those infants who did not (p < 0.01). We were able to match 19 of the 24 infants who required ventilator support by age, sex and ethnicity with a nonventilated child. There was no significant difference in admission PaCO2 between groups (7.7 SD 1.5 vs 8.1 SD 1.5 kPa) or highest PaCO2 in the first 24 hours for nonventilated children and preintubation PaCO2 in ventilated children (8.6 SD1.3 vs 8.9 SD 1.9kPa). Nasopharyngeal aspirates were positive for respiratory syncytial virus in 39 patients. Respiratory support was required for 13 children who had positive RSV aspirates and for nine children who were not RSV positive (NS).

CONCLUSION

Infants with bronchiolitis that were premature were not likely to need respiratory support. Ethnicity, arterial PaCO2 and positivity for RSV were not related to the need for ventilator assistance.

Substance-use and psychiatric disorders among American Indian veterans

Native American (NA) veterans have rarely been the focus of investigational efforts. We review studies relevant to an assessment of NA substance-use disorders, and discuss findings of the Drug Abuse Treatment Services Evaluation Project pertaining specifically to NA veterans. A larger proportion of NA veterans discharged from VA inpatient care in FY93 were diagnosed with a substance-use disorder compared to the total population of veterans discharged that year. Substance-dependent NAs were more likely to be diagnosed with alcohol-use disorders and posttraumatic stress disorder, and less likely to be diagnosed with drug-use disorders and other psychiatric disorders than substance-dependent veterans generally.

Obesity and prognosis in endometrial cancer

OBJECTIVE

We tested the null hypothesis that morbid obesity as measured by the Quetelet index has no influence on survival in endometrial cancer.

STUDY DESIGN

A retrospective study of 492 women with endometrial carcinoma was performed. Age, height, weight, Quetelet index, stage, cell type, grade, node status, peritoneal cytologic findings, and depth of myometrial invasion were analyzed for influence on survival.

RESULTS

Mean Quetelet index was 34 (range 16 to 89). Quetelet index was < 30 in 45% of patients, 30 to 40 in 33%, and > 40 in 22%. Five percent of those with a Quetelet index > 40 had positive nodes, but 64% of patients with a Quetelet index > 40 did not have lymph node sampling done. Lack of sampling of lymph nodes in the entire group had no adverse effect on survival. In a proportional hazards regression model for time from diagnosis to death from disease, grade, node status, myometrial invasion, and stage had highly significant effects. When Quetelet index was analyzed as a continuous variable, as Quetelet index increased, time to recurrence was significantly increased (p = 0.0136), and significance was approached for survival (p = 0.0645). Quetelet index was strongly related to grade (p = 0.013), depth of myometrial invasion (p = 0.031), negative cytologic findings (p = 0.004), and stage (p = 0.011) with obese patients having better differentiated, less invasive tumors of lower stage with negative washings.

CONCLUSIONS

Morbid obesity positively affects survival in endometrial carcinoma. This effect is accounted for by the association of obesity with less aggressive disease. Morbid obesity is not associated with increased death from other causes. Lack of sampling of negative lymph nodes does not adversely affect survival.

Isolation and characterization of rice R genes: evidence for distinct evolutionary paths in rice and maize

R and B genes and their homologues encode basic helix-loop-helix (bHLH) transcriptional activators that regulate the anthocyanin biosynthetic pathway in flowering plants. In maize, R/B genes comprise a very small gene family whose organization reflects the unique evolutionary history and genome architecture of maize. To know whether the organization of the R gene family could provide information about the origins of the distantly related grass rice, we characterized members of the R gene family from rice Oryza saliva. Despite being a true diploid, O. sativa has at least two R genes. An active homologue (Ra) with extensive homology with other R genes is located at a position on chromosome 4 previously shown to be in synteny with regions of maize chromosomes 2 and 10 that contain the B and R loci, respectively. A second rice R gene (Rb) of undetermined function was identified on chromosome 1 and found to be present only in rice species with AA genomes. All non-AA species have but one R gene that is Ra-like. These data suggest that the common ancestor shared by maize and rice had a single R gene and that the small R gene families of grasses have arisen recently and independently.

G explained

This paper presents the hypothesis that the general factor, g, which emerges from psychometric batteries and which has been equated with general intelligence, is the result of a physical brain feature which enhances neural network efficiency and is determined for the brain in general. This conception of intelligence provides a resolution of the unity-versus-modularity debate in the intelligence field and yields specific predictions as to the nature and kind of brain features that will be found to provide a physical explanation for g. To avoid nosological confusion, it is suggested that 'n' be used to represent the neurological concept of general intelligence while 'g' should continue to denote the general factor emerging from mathematical analyses of mental test batteries.

Stage I squamous cell cervical carcinoma in pregnancy: planned delay in therapy awaiting fetal maturity

PURPOSE

It is not known whether intentional delay to allow fetal maturity in patients with Stage I cervical carcinoma diagnosed during pregnancy will affect the survival of these patients. The purpose of this study is to report our experience with invasive squamous cervical carcinoma after planned delay in therapy for fetal indications, to assess maternal morbidity due to treatment delay, and to report maternal and fetal survival.

METHODS

Between 1989 and 1994, eight pregnant women with Stage I squamous cervical carcinoma, who declined immediate therapy in order to improve fetal outcome, were prospectively followed until the late third trimester. Serial MRIs were used to follow the lesion in two patients.

RESULTS

Stage IB cervical cancer was diagnosed in seven pregnant women. All lesions were less than 2.5 cm. The mean diagnosis-to-treatment interval was 109 days (range, 21-201; median, 112). One woman conceived in the cycle after diagnosis and had a diagnosis-to-treatment interval of 282 days. All were delivered by cesarean section-radical hysterectomy late in the third trimester. There was no clinical progression of disease detected during any of the pregnancies. Serial MRI examination confirmed stable disease in one patient and suggested an increase in tumor volume in one patient that was not pathologically confirmed. All are alive and disease free after a mean follow-up of 37 months (range, 13-68; median, 33). Neonatal morbidity was encountered in one infant (spontaneous pneumothorax).

CONCLUSIONS

With a median follow-up of 33 months, patient-requested delays in therapy between 3 and 40 weeks (mean, 19) did not affect progression.