Utility of radioisotopic filtration markers in chronic renal insufficiency: simultaneous comparison of 125I-iothalamate, 169Yb-DTPA, 99mTc-DTPA, and inulin. The Modification of Diet in Renal Disease Study

Assessment of glomerular filtration rate (GFR) with inulin is cumbersome and time-consuming. Radioisotopic filtration markers have been studied as filtration markers because they can be used without continuous intravenous (IV) infusion and because analysis is relatively simple. Although the clearances of 99mTc-diethylenetriamine-pentaacetic acid (DTPA), 169Yb-DTPA, and 125I-iothalamate have each been compared with inulin, rarely has the comparability of radioisotopic filtration markers been directly evaluated in the same subject. To this purpose, we determined the renal clearance of inulin administered by continuous infusion and the above radioisotopic filtration markers administered as bolus injections, simultaneously in four subjects with normal renal function and 16 subjects with renal insufficiency. Subjects were studied twice in order to assess within-study and between-study variability. Unlabeled iothalamate was infused during the second half of each study to assess its effect on clearances. We found that renal clearance of 125I-iothalamate and 169Yb-DTPA significantly exceeded clearance of inulin in patients with renal insufficiency, but only by several mL.min-1.1.73m-2. Overestimation of inulin clearance by radioisotopic filtration markers was found in all normal subjects. No differences between markers were found in the coefficient of variation of clearances either between periods on a given study day (within-day variability) or between the two study days (between-day variability). The true test variability between days did not correlate with within-test variability. We conclude that the renal clearance of 99mTc-DTPA, 169Yb-DTPA, or 125I-iothalamate administered as a single IV or subcutaneous injection can be used to accurately measure GFR in subjects with renal insufficiency; use of the single injection technique may overestimate GFR in normal subjects.     

Administered radiopharmaceutical doses in children: a survey of 13 pediatric hospitals in North America.

Universally applied standards for administering radiopharmaceutical doses in children do not presently exist. Hence, pediatric radiopharmaceutical dosimetry varies considerably from institution to institution and is generally based on the recommended adult dose adjusted for body mass. METHODS: We surveyed 13 pediatric hospitals in North America to obtain objective data on dosimetry practices for 16 pediatric nuclear medicine examinations, including the minimum total radiopharmaceutical administered dose per examination, the total administered dose based on body mass, and maximum total doses in children. RESULTS: The reported administered doses of radiopharmaceuticals to children vary over a relatively large range, especially with respect to minimum total administered doses. CONCLUSION: This survey has identified a broad range of administered doses directly leading to variability in radiation-absorbed doses to patients. The nuclear medicine community should develop pediatric standards for radiopharmaceutical administered doses and reduce radiation exposure in children, such as through the use of modern software reconstruction techniques.     

Blinded clinical evaluation of positron emission tomography for diagnosis of probable Alzheimer's disease.

We evaluated the sensitivity and specificity of positron emission tomography for diagnosis of probable Alzheimer's disease under conditions similar to those encountered in the routine clinical practice of nuclear medicine. We obtained tomographic images of regional cerebral blood flow from three groups of subjects: (1) 13 subjects, ages 69 to 84, who had probable Alzheimer's disease diagnosed by validated clinical criteria; (2) 15 subjects, ages 57 to 77, who had Parkinson's disease without dementia; and (3) 11 subjects, ages 65 to 83, who were normal. Three blinded reviewers, who had not previously seen the images, categorized them as normal, bilateral temporoparietal flow defects typical of Alzheimer's disease, or other abnormality. Consensus interpretation demonstrated sensitivity of 0.38 (5/13) and specificity of 0.88 (23/26) for identifying patients with probable Alzheimer's disease. Thus, the criterion of bilateral temporoparietal reduction in cerebral blood flow used in this study did not have sufficient sensitivity to be of clinical value. While other criteria may be developed to improve diagnostic accuracy, clinical utility can be established only by testing for validity in patients with a full spectrum of complicating neurologic and psychiatric conditions for whom diagnosis is uncertain and who are then followed longitudinally to determine clinical outcome or pathologic findings.     

Entry of genital Chlamydia trachomatis into polarized human epithelial cells.

To study the initial invasion process(es) of genital chlamydiae, a model system consisting of hormonally maintained primary cultures of human endometrial gland epithelial cells (HEGEC), grown in a polarized orientation on collagen-coated filters, was utilized. After Chlamydia trachomatis inoculation of the apical surface of polarized HEGEC, chlamydiae were readily visualized, by transmission electron microscopy, in coated pits and coated vesicles. This was true for HEGEC maintained in physiologic concentrations of estrogen (proliferative phase) and of estrogen plus progesterone (secretory phase), despite the finding that association of chlamydiae with secretory-phase HEGEC is significantly reduced (P = 0.025; A.S. Maslow, C.H. Davis, J. Choong, and P.B. Wyrick, Am. J. Obstet. Gynecol. 159:1006-1014, 1988). In contrast, chlamydiae were rarely observed in the clathrin-associated structures if the HEGEC were cultured on plastic surfaces. The same pattern of coated pit versus noncoated pit entry was reproducible in HeLa cells. The quantity of coated pits associated with isolated membrane sheets derived from HeLa cells, grown on poly-L-lysine-coated cover slips in medium containing the female hormones, was not significantly different as monitored by radiolabeling studies and by laser scanning microscopy. These data suggest that culture conditions which mimic in vivo cellular organization may enhance entry into coated pits for some obligate intracellular pathogens.     

Granulocytic sarcoma with an indolent course and destructive skeletal disease. Tumor characterization with immunologic markers, electron microscopy, cytochemistry, and cytogenetic studies

A 6-year-old girl with a granulocytic sarcoma (GS) of the left maxillary sinus that followed a uniquely indolent clinical course (3.5 years) and was associated with highly destructive skeletal disease is described. The tumor cells demonstrated an unusual hematogenous "homing" preference for bone and soft tissue sites. Tumor cell characterization with immunologic markers, electron microscopy, cytochemistry, and cytogenetic studies revealed that the tumor cells expressed OKM1 and MMA (Leu-M1), but not HLA-DR, B-, or T-cell markers. The cells were nonspecific esterase- and myeloperoxidase-positive, had ultrastructural features of promyelocytes, and were clonal. The laboratory characterization of the tumor cells in this clinically unusual case of GS illustrates the utility of monoclonal antibodies, applied in conjunction with cytochemistry and ultrastructural analysis, in establishing the specific diagnosis, cell lineage, and maturational stage of this tumor.     

Reproducibility of lumbar paraspinal surface electromyogram power spectra

OBJECTIVE: To establish the reproducibility of surface recordings of electromyograms from lumbar erector spinae muscles. DESIGN: Repeated measurements in 10 male volunteers under controlled conditions. METHODS: While isometric load was held constant at (2/3) and (1/3) of maximum voluntary contraction, surface electromyograms were recorded from the 4th/5th lumbar interspace on three occasions separated by at least a day. Fresh surface electrodes were applied on each test occasion. The raw electromyographic signal was filtered and digitized and the signal processed by fast Fourier transformation to give median frequency and total amplitude spectra. Linear regression lines of median frequency and amplitude against time were calculated. The 'spectral halfwidth" was defined as the full width at half maximum of the composite amplitude spectrum. Reproducibility was assessed by calculation of the intraclass correlation coefficient. RESULTS: Reproducibility of initial median frequency and spectral halfwidth were found to be excellent at both (2/3) (ICCC 0.91 and 0.88) and (1/3) (ICCC 0.84 and 0.83) maximum voluntary contraction. Initial power and regression slopes of power and median frequency were not reproducible. CONCLUSIONS: The reproducibility of two electromyographic variables, the initial median frequency and the spectral halfwidth, were found to be satisfactory.     

Neurologic disease in injection drug users: therapeutic issues

Illicit drug use may cause nervous system impairment as a result of direct and indirect effects on the integrity and function of nervous system tissue and, potentially, through immune effects. HIV-1 infection poses an additional risk of impairment, and this risk may be decreased as a result of antiretroviral drug treatment. Obviously, the goal of such therapy is to improve the potential clinical course of infection. However, interactions between antiretroviral drugs, abused drugs, and hepatic metabolic enzyme systems may result in impaired or more efficient drug clearance and, consequently, antiretroviral or substance abuse treatment failure. The clinical outcome of this interaction may potentially include drug-related neurotoxicity or neurologic disease induced by HIV infection. The actual impact of these interactions on the occurrence of neurologic impairment and disease are unknown at this time, and, therefore, require study.     

Inequalities in cycle helmet use: cross sectional survey in schools in deprived areas of Nottingham.

AIMS: To describe cycle helmet owning and wearing among children in a deprived area and to investigate the association between helmet ownership and wearing and socioeconomic deprivation. METHODS: Cross sectional survey in 28 primary schools in deprived areas of Nottingham; 1061 year 5 schoolchildren were studied. RESULTS: All year 5 children attending school on the day of the survey completed the questionnaire (87% of children registered at participating schools). Children residing in a deprived area were less likely to own a bike and more likely to ride it four days a week or more. Half the children owned a helmet (52%), but only 29% of these always wore their helmet. Children in deprived areas were less likely to own a helmet, but those that owned a helmet were not less likely to always wear one. Family encouragement and parental warning of dangers of not wearing a helmet were associated with increased helmet ownership rates. Family encouragement and best friends wearing a helmet were associated with higher rates of helmet wearing. CONCLUSIONS: Programmes aimed at preventing head injury among child cyclists will need to address the inequality in helmet ownership that exists between children residing in deprived and non-deprived areas. Strategies to increase family encouragement to wear a helmet may be useful, as may those recognising the importance of the attitudes and behaviours of peers, such as peer education programmes. Further work is required to assess how exposure to risk of cycling injury varies with deprivation.