Regulation of eukaryotic abasic endonucleases and their role in genetic stability

Abasic (AP) sites in DNA arise from spontaneous reactions or the action of DNA glycosylases and represent a loss of genetic information. The AP sites can be mutagenic or cytotoxic, and their repair is initiated by class II AP endonucleases, which incise immediately 5' to AP sites. The main enzyme of S. cerevisiae. Apn1, provides cellular resistance to oxidants (e.g., H2O2) or alkylating agents, and limits the spontaneous mutation rate. AP endonucleases from other species can replace Apn1 function in yeast to different extents. We studied the main human enzyme, Ape, with respect to its incision specificity in vitro and the expression of the APE gene in vivo. The results suggest that Ape evolved to act preferentially on AP sites compared to deoxyribose fragments located at oxidative strand breaks and that the incision modes of Ape and Apn1 may be fundamentally different. We also defined the functional APE promoter, and showed that APE expression is transiently downregulated during the regeneration of epidermis after wounding. This latter effect may lead to a window of vulnerability for DNA damage and perhaps mutagenesis during the healing of epidermal and other wounds. Such unexpected effects on the expression of DNA repair enzymes need to be taken into account in analyzing the susceptibility of different tissues to carcinogens.

The interaction of dopamine, cocaine, and cocaethylene with ethanol on central nervous system depression in mice

The interactions between dopamine, cocaine, cocaethylene, and ethanol were studied in Swiss-Webster mice. The loss of the righting reflex (LORR) was used as a measure of CNS depression. Animals were injected intraperitoneally (IP) with ethanol (4.0 g/kg). which caused a LORR. Immediately upon regaining of the righting reflex, mice were injected intracerebroventricularly (ICV) with saline, dopamine (0.1, 0.5, or 1.0 mumol/kg), cocaine (1, 15, or 25 mumol/kg), or cocaethylene (1, 15, or 25 mumol/kg). In the presence of systemic ethanol, all three compounds produced CNS depression in a dose-dependent manner. The dopamine D2-receptor antagonist sulpiride and the D1-receptor antagonist fluphenazine were given acutely ICV with dopamine in the presence of systemic ethanol to examine whether these antagonists could block the return to the LORR produced by dopamine. Sulpiride, however, actually enhanced the interaction between ethanol and dopamine in a dose-dependent manner as measured by the LORR; fluphenazine neither blocked nor enhanced the effect of dopamine in the presence of systemic ethanol. In addition, these antagonists had no effect on cocaine- and cocaethylene-induced CNS depression in the presence of systemic ethanol. The results of this study showed that the neurotransmitter dopamine and both cocaine and cocaethylene can promote further CNS depression in the presence of systemic ethanol, and that dopamine was significantly more potent than cocaine and cocaethylene as measured by the return to the LORR.

Folliculotropic mycosis fungoides with large-cell transformation presenting as dissecting cellulitis of the scalp

Follicular mycosis fungoides (MF) is a rare variant of cutaneous T-cell lymphoma (CTCL) in which malignant lymphocytes preferentially infiltrate hair follicles. This report describes a patient with follicular mycosis fungoides presenting in a manner similar to dissecting cellulitis of the scalp with nonhealing, draining nodular lesions. Follicular mucinosis associated with folliculotropic mycosis fungoides resulted in follicular disruption and deep dissecting cellulitis. Large-cell transformation of CTCL was present in the initial diagnostic scalp and axillary lymph node specimens. The patient died from progressive CTCL 9 months following initial diagnosis despite electron beam radiation, topical mechlorethamine, interferon-alpha, and systemic chemotherapy. This case indicates that large-cell transformation of folliculotropic mycosis fungoides is an aggressive form of CTCL, and that folliculotropic mycosis fungoides can give rise to lesions which resemble dissecting cellulitis of the scalp. Upregulation of intercellular adhesion molecule-1 (ICAM-1) on follicular epithelium adjacent to lymphocyte function-associated antigen-1 (LFA-1)-positive folliculotropic lymphoma cells in this report provides insight into lymphocyte homing mechanisms in folliculotropic MF.

Abasic site binding by the human apurinic endonuclease, Ape, and determination of the DNA contact sites

The mutagenic and lethal effects of abasic sites in DNA are averted by repair initiated by 'class II' apurinic (AP) endonucleases, which cleave immediately 5'to abasic sites. We examined substrate binding by the human AP endonuclease, Ape protein (also called Hap1, Apex or Ref-1). In electrophoretic mobility-shift experiments, Ape bound synthetic DNA substrates containing single AP sites or tetrahydrofuran (F) residues. No complexes were detected with single-stranded substrates or unmodified duplex DNA. In EDTA, the concentration of Ape required to shift 50% of duplex F-DNA was approximately 50 nM, while the addition of 10 mM MgCl2 nearly eliminated detectable F-DNA@Ape complexes. Filter-binding studies demonstrated a half-life of approximately 50 s at 0 degrees C for F-DNA@Ape complexes in the presence of EDTA, and <15 s after the addition of Mg2+. The DNA recovered from F-DNA@Ape complexes was intact but was rapidly cleaved upon addition of Mg2+, which suggests that these protein-DNA complexes are on the catalytic pathway for incision. Methylation and ethylation interference experiments identified DNA contacts critical for Ape binding, and Cu-1, 10-phenanthroline footprinting suggested an Ape-induced structural distortion at the abasic site prior to cleavage.

Psychiatric risk associated with early puberty in adolescent girls

OBJECTIVE

This study prospectively evaluated the relationship between early puberty and the onset of internalizing symptoms and disorders in adolescent girls.

METHOD

The sample was drawn from 1,463 sixth-, seventh-, and eighth-grade girls who participated in a longitudinal school-based study of growth and development. Pubertal stage was determined by self-assessment of Tanner stage. Psychiatric assessments included self-report instruments and structured diagnostic interviews. Survival methods were utilized for data analysis.

RESULTS

Girls with onset of internalizing symptoms were on average 5 months earlier in pubertal development than those who were asymptomatic (p < .001). In addition, girls with earlier maturation (earliest quartile) were more likely to develop internalizing symptoms than were nonearly matures (hazard ratio = 1.8, confidence interval = 1.2, 2.7). In a subsample of girls followed into high school, early-maturing girls were at marginally higher risk (p < .10) for developing internalizing disorders by the study's end. The highest risk for internalizing disorders was for those girls with both early puberty and prior internalizing symptoms (odds ratio = 3.3).

CONCLUSION

Early puberty increases the risk of internalizing symptoms and perhaps internalizing disorders in adolescent girls.

Weight concerns influence the development of eating disorders: a 4-year prospective study

The authors examined factors prospectively associated with age of onset of partial syndrome eating disorders over a 4-year interval in a community sample (N = 877) of high school-age adolescent girls. Four percent developed a partial syndrome eating disorder over the interval. A measure of weight concerns was significantly associated with onset in a multivariate Cox proportional hazard analysis (p < .001). Girls scoring in the highest quartile on the measure of weight concerns had the highest incidence (10%) of partial syndrome onset, whereas none of the girls in the lowest quartile developed eating disorder symptoms. This finding is consistent with both theoretical and clinical perspectives and may represent a useful step toward the establishment of a rational basis for the choice of a prevention intervention target.

Educational video game for juvenile diabetes: results of a controlled trial

Packy & Marlon, an interactive video game designed to improve self-care among children and adolescents with diabetes, was evaluated in a six-month randomized controlled trial. In the game, players take the role of animated characters who manage their diabetes by monitoring blood glucose, taking insulin injections, and choosing foods, while setting out to save a diabetes summer camp from marauding rats and mice who have stolen the diabetes supplies. Study participants were patients aged 8 to 16 from two separate diabetes clinics. Each participant received a Super Nintendo video game system at an initial clinic visit and was randomly assigned to receive either Packy & Marlon (treatment group, N = 31) or an entertainment video game containing no diabetes-related content (control group, N = 28). Participants were interviewed and a parent filled out a questionnaire at baseline, three months, and six months. The findings in this study indicate that well-designed, educational video games can be effective interventions. There was improvement in the treatment group relative to the control group in terms of diabetes-related self-efficacy (p = 0.07), communication with parents about diabetes (p = 0.025), and self-care behaviours (p = 0.003), and a decrease in unscheduled urgent doctor visits (p = 0.08). There were no significant differences between the groups in knowledge about diabetes or in glycated haemoglobin (HbA1c) levels. Since participants in the study were in general well-controlled patients who were receiving excellent medical care, future research is contemplated involving youngsters who are not under good glycaemic control.

Ethnicity and body dissatisfaction: are Hispanic and Asian girls at increased risk for eating disorders?

PURPOSE

To compare prevalences and correlates of body dissatisfaction among white, Hispanic, and Asian girls.

METHODS

A total of 939 6th and 7th grade girls (mean age 12.4 years) attending four middle schools in northern California completed self-administered assessments of age, ethnicity, desired body shape, parent education levels, mother's and father's body shapes, pubertal stage, and body dissatisfaction. Body dissatisfaction was assessed with the Body Dissatisfaction scale of the Eating Disorder Inventory. Height, weight, triceps skinfold thickness, and waist and hip circumferences were measured by trained examiners.

RESULTS

Hispanic girls reported significantly greater body dissatisfaction than white girls, with Asian girls in-between. After adjustment for body mass index (weight/height), normal and overweight white, Hispanic, and Asian girls reported similar levels of body dissatisfaction. However, among the leanest 25% of girls, Hispanics and Asians reported significantly more body dissatisfaction than white girls. Body mass index was the strongest independent predictor of increased body dissatisfaction in all three ethnic groups. Shorter height among white girls and taller height among Asian girls also made significant independent contributions. Parent education level, a measure of socioeconomic status, was not significantly associated with body dissatisfaction.

CONCLUSIONS

Body dissatisfaction is not limited to white girls in middle and upper socioeconomic strata. These findings suggest Hispanic and Asian girls may be at greater risk for adopting eating disorder behaviors than previously recognized.

Weight concerns influence the development of eating disorders: a 4-year prospective study

The authors examined factors prospectively associated with age of onset of partial syndrome eating disorders over a 4-year interval in a community sample (N = 877) of high school-age adolescent girls. Four percent developed a partial syndrome eating disorder over the interval. A measure of weight concerns was significantly associated with onset in a multivariate Cox proportional hazard analysis (p < .001). Girls scoring in the highest quartile on the measure of weight concerns had the highest incidence (10%) of partial syndrome onset, whereas none of the girls in the lowest quartile developed eating disorder symptoms. This finding is consistent with both theoretical and clinical perspectives and may represent a useful step toward the establishment of a rational basis for the choice of a prevention intervention target.

Predicting onset of drinking in a community sample of adolescents: the role of expectancy and temperament

We report results of a prospective examination of the influence of outcome expectancy variables and inherited temperaments on the onset of drinking over a 12-month period in a sample of 1,164 high school students. While univariate prospective analysis indicated that drinkers and nondrinkers were different both on measures of outcome expectancy and temperament, multivariate analysis supported, most strongly, a social learning account of the processes influencing the onset and maintenance of drinking behavior in this sample. The multivariate analysis revealed that only expectancies for enhanced social behavior were consistently associated with the onset of drinking from baseline to 12-month follow-up (p < .001). Among all nondrinkers at baseline, those entertaining higher expectancies about the positive effects of alcohol on social interaction were more likely to begin drinking between baseline and follow-up. At present, few, if any, alcohol abuse prevention studies with adolescents have explicitly attempted to alter alcohol expectancies or to establish a link between expectancy and behavior change. Our results suggest that it may be useful to do so.

In vivo activities of U-100592 and U-100766, novel oxazolidinone antimicrobial agents, against experimental bacterial infections

The Upjohn oxazolidinones, U-100592 and U-100766, are orally bioavailable synthetic antimicrobial agents with spectra of activity against antibiotic-susceptible and -resistant gram-positive pathogens. In several mouse models of methicillin-resistant Staphylococcus aureus infection, U-100592 and U-100766 yielded oral 50% effective doses (ED50) ranging from 1.9 to 8.0 mg/kg of body weight, which compared favorably with vancomycin subcutaneous ED50 values of 1.1 to 4.4 mg/kg. Similarly, both compounds were active versus a Staphylococcus epidermidis experimental systemic infection. U-100592 and U-100766 effectively cured an Enterococcus faecalis systemic infection, with ED50 values of 1.3 and 10.0 mg/kg, and versus a vancomycin-resistant Enterococcus faecium infection in immunocompromised mice, both drugs effected cures at 12.5 and 24.0 mg/kg. Both compounds were exceptionally active in vivo against penicillin- and cephalosporin-resistant Streptococcus pneumoniae, with ED50 values ranging from 1.2 to 11.7 mg/kg in systemic infection models. In soft tissue infection models with S. aureus and E. faecalis, both compounds exhibited acceptable curative activities in the range of 11.0 to 39.0 mg/kg. U-100766 was also very active versus the Bacteroides fragilis soft tissue infection model (ED50 = 46.3 mg/kg). In combination-therapy studies, both U-100592 and U-100766 were indifferent or additive in vivo against a monomicrobic S. aureus infection in combination with other antibiotics active against gram-positive bacteria and combined as readily as vancomycin with gentamicin in the treatment of a polymicrobic S. aureus-Escherichia coli infection. U-100592 and U-100766 are potent oxazolidinones active against antibiotic-susceptible and -resistant gram-positive pathogens in experimental systemic and soft tissue infections.

A single-sample, subcutaneous gonadotropin-releasing hormone test for central precocious puberty

OBJECTIVE

We compared a rapid, subcutaneous (SQ), single-sample gonadotropin-releasing hormone (GnRH) stimulation test with the standard multiple-sample, intravenous (IV) GnRH stimulation test used in the evaluation of central precocious puberty (CPP).

METHODS

We evaluated 22 patients presenting with evidence of precocious puberty. GnRH (100 microg) was administered subcutaneously in the clinic setting with single serum luteinizing hormone (LH) measured 40 minutes after injection. A standard IV GnRH stimulation test was performed within 2 weeks, with serum LH obtained at 0, 20, 40, and 60 minutes. LH was assayed by immunochemiluminometric assay.

RESULTS

The mean peak LH levels after IV and SQ testing were identical. A significant correlation (r = .88) was found between the LH determined by SQ stimulations and the peak LH determined by IV GnRH testing. CPP was diagnosed (LH, >/- 8 IU/L) by both SQ and IV testing in 7 of 22 patients and was excluded by both tests in 14 of 22 patients. A diagnostic discrepancy between peak IV and SQ results was seen in 1 patient.

CONCLUSIONS

We conclude that mean GnRH-stimulated LH levels from rapid SQ and standard IV testing are indistinguishable and that individual LH levels by each method are strongly correlated. A rapid SQ GnRH test is a valid tool for laboratory confirmation of CPP.

Thrombus imaging using technetium-99m-labeled high-potency GPIIb/IIIa receptor antagonists. Chemistry and initial biological studies

Platelet-specific compounds which are radiolabeled with gamma-emitting radionuclides may be particularly useful for the noninvasive in vivo detection of thrombi. The synthesis of peptides which are potent inhibitors of platelet aggregation and which contain a chelator for the radionuclide technetium-99m are described. The target compounds were designed such that stable, oxotechnetium(V) species could be prepared where the site of metal coordination was well defined. A strategy was employed where the pharmacophore-Arg-Gly-Asp-(RGD), or RGD mimetic, was constrained in a ring which was formed by the S-alkylation of a cysteine residue with an N-terminal chloroacetyl group. Binding affinities were enhanced by the replacement of arginine with the arginine mimetics S-(3-aminopropyl)cysteine and 4-amidinophenylalanine. Further enhancements could be obtained by the synthesis of oligomers which contained two or more rings containing receptor binding regions. The increase in binding affinity seen was more than that expected from a simple stoichiometric increase of pharmacophore. The most potent compounds described had IC50s of approximately 0.03 microM for the inhibition of human platelet aggregation. Two of the more potent peptides (P280 and P748) were labeled with technetium-99m and assessed in a canine thrombosis model. The 99m Tc complexes of the peptides prepared in this work hold promise as thrombus imaging agents due to their high receptor binding affinity, ease of preparation, and expected rapid pharmacokinetics.

Somatostatin receptor-binding peptides labeled with technetium-99m: chemistry and initial biological studies

The synthesis of peptides which possess a high affinity for the somatostatin receptor and contain a chelator for the radionuclide technetium-99m is described. The target compounds were designed such that they would form stable, oxotechnetium(V) chelate complexes in which the Oxorhenium(V) chelate complexes of these peptides were prepared as nonradioactive surrogates for the technetium complexes. Peptide oxorhenium complexes and Tc-99m complexes eluted closely upon HPLC analysis. The receptor-binding affinities of both the free and rhenium-coordinated species were measured in vitro. The binding affinities of the free peptides (Ki's in the 0.25 - 10 nM range) compared favorably with [DTPA]octreotide (Ki = 1.6 nM), which, as the indium-111 complex, is already approved for somatostatin receptor (SSTR)-expressing tumor imaging in the United States and Europe. Furthermore, the rhenium-coordinated peptides had binding affinities which, in many cases, were higher than those of the corresponding free peptides, with several complexes having a Ki's of 0.1 nM. Some of the more potent SSTR-binding peptides were labeled with technetium-99m and assessed in an in vivo study with tumor-bearing rats. The 99m Tc-labeled peptides prepared in this study should be useful as SSTR-expressing tumor-imaging agents due to their high SSTR-binding affinities, ease of preparation, and, because they are low molecular weight peptides, expected pharmacokinetics characterized by rapid tracer excretion from the body resulting in high-contrast images.

Chondrocytes from osteoarthritic cartilage have increased expression of insulin-like growth factor I (IGF-I) and IGF-binding protein-3 (IGFBP-3) and -5, but not IGF-II or IGFBP-4

Osteoarthritis is a disease in which articular cartilage metabolism is altered, leading to cartilage destruction. As insulin-like growth factor-I (IGF-I) is the major anabolic mediator for articular cartilage, and the IGF-binding proteins (IGFBPs) are an integral part of the IGF axis, they may play a role in the pathophysiology of osteoarthritis. Chondrocytes isolated from fibrillated and normal appearing areas of osteoarthritic human cartilage and from normal cartilage were studied for IGF and IGFBP expression. IGF and IGFBP messenger ribonucleic acids were analyzed by a RT-quantitative PCR technique and Northern blotting. In osteoarthritic chondrocytes, IGF-I message was increased 3.5-fold, IGFBP-3 was increased 24-fold, and IGFBP-5 was increased 16-fold over normal chondrocytes. Chondrocytes from normal appearing areas of cartilage from osteoarthritic joints had intermediate levels. Message levels for beta-actin, IGF-II, and IGFBP-4 were unchanged between the cartilage types. IGF and IGFBP production were analyzed by Western ligand blots and RIAs of conditioned medium from cartilage cultured in serum-free conditions. IGF-I was undetectable in conditioned medium from normal cartilage and increased in that from osteoarthritic cartilage. Osteoarthritic cartilage samples produced IGFBP-2, -3, and -4; glycosylated IGFBP-4; and IGFBP-5. IGFBP-2, -3, and -5 production was increased in osteoarthritic cartilage. Proteases with activity against IGFBP-3 and -5 were also produced by osteoarthritic cartilage. The observation that IGFBP-3 and -5 expression and production are elevated in osteoarthritic cartilage suggests that they may be acting as a competitor for IGF-I in osteoarthritic cartilage, thus reducing the anabolic stimulation of this tissue and contributing to the net loss of cartilage in this disease.

Values and Canadian health care: an Alberta exploration

In March 1994, a health care conference was held in Edmonton, Alberta, at which the values of conference participants towards health care were systematically recorded and analysed. This exploration is significant because the values that underpin the structure of the current publicly-funded and administered Canadian health care system rarely enter current discussions regarding health care system reform. Rather, economic and other sociopolitical forces now seem to be having a major impact on plans and actual changes within the health care system. Thus, the underlying attitudes and beliefs of Canadians towards health care have not been articulated or given due credence. The conference participants identified three dominant values: (1) the dignity of the human person as an individual and social being; (2) respect for pluralism and difference; and (3) accountability. These values were found to be robust, in that they sustain a focus on the 'common good'. The common good is the core of the Canadian health care system, and is enshrined in the 1984 Canada Health Act. Conceptually, these values could also lead to significant changes in health care, in keeping with the common good, particularly those changes focusing on the current deficiencies of the Canadian health care system.

Development of greenhouse screening for resistance to Aspergillus parasiticus infection and preharvest aflatoxin contamination in peanut

Aspergillus flavus Link ex Fries and A. parasiticus Speare can invade peanut kernels and under certain environmental conditions produce unacceptable levels of the mycotoxin aflatoxin. A concerted effort is underway to reduce aflatoxin contamination in peanut and peanut products. A potentially effective method of control in peanut is the discovery and use of genes for resistance to either fungal invasion or aflatoxin formation. The objective of the present experimental study was to develop an effective and efficient procedure for screening individual plants or pods of single plants for resistance to invasion by the aflatoxigenic fungi and subsequent aflatoxin production. Methods of obtaining adequate drought-stress and fungal infection were developed through this series of experiments. By completely isolating the pods from the root zone and imposing drought-stress only on pegs and pods, high levels of fungal infection were observed. High amounts of preharvest aflatoxin accumulation were also produced by completely isolating the pods from the root zone. Mid-bloom inoculation with A. parasiticus-contaminated cracked corn and drought-stress periods of 40 to 60 days were the most effective procedures. This technique was used to assess peanut genotypes previously identified as being partially resistant to A. parasiticus infection or aflatoxin contamination, and segregating populations from four crosses. Variability in aflatoxin contamination was found among the 11 genotypes evaluated, however, none were significantly lower than the standard cultivars. Broad-sense heritability of four crosses was estimated through evaluation of seed from individual plants in the F2 generation. The heritability estimates of crosses GFA-2 x NC-V11 and Tifton-8 X NC-V11 were 0.46 and 0.29, respectively, but mean aflatoxin contamination levels were high (73,295 and 27,305 ppb). This greenhouse screening method could be an effective tool when genes for superior aflatoxin resistance are identified.

Is testing for growth hormone release necessary?

The question of if testing for growth hormone release is necessary in patients with chronic renal failure (CRF) is part of a greater debate. The question of what constitutes growth hormone deficiency (GHD) has become more controversial over the past few years. In some ways, the question has been replaced by the question, "Who will have a meaningful response to growth hormone (GH) therapy?" Since children with CRF generally respond to GH therapy, the question should be recast as, "When is testing for growth hormone release necessary in patients with CRF?" Why is the diagnosis of GHD important? A clear diagnosis of class GHD has many important implications for a patient. GHD is an easily treated cause of neonatal hypoglycemia. The diagnosis alerts the clinician to search for etiologies of GHD such as intracranial tumors and should stimulate a search for other pituitary deficiencies. Another important claim is that patients with classic GHD have a better long-term response to GH therapy. Children in other diagnostic categories, such as renal failure and Turner syndrome, also respond to GH therapy. Do diagnostic studies use to determine the function of the growth hormone-insulin-like growth factor (GH-IGF) axis help in the management of these children? Recently, experts have become increasingly interested in what constitutes a useful diagnostic test. To be a "good" diagnostic test, a procedure should have the following properties: (1.) have a rational connection to the disorder; (2.) good concordance with the diagnosis/outcome; (3.) accurate; and (4.) reproducible. Among tests that share these properties, the best test is generally the easiest and/or the least expensive. Many different tests can be used to evaluate the GH-IGF axis. These include GH stimulation tests, 24-hour GH profiles, IGF-I, and insulin-like growth factor binding protein 3 (IGFBP-3). High quality determinations of IGF-I and IGFBP-3 can be used to evaluate the GH-IGF axis.

Trans-complementation by human apurinic endonuclease (Ape) of hypersensitivity to DNA damage and spontaneous mutator phenotype in apn1-yeast

Abasic (AP) sites in DNA are potentially lethal and mutagenic. 'Class II' AP endonucleases initiate the repair of these and other DNA lesions. In yeast, the predominant enzyme of this type is Apn1, and its elimination sensitizes the cells to killing by simple alkylating agents or oxidants, and raises the rate of spontaneous mutation. We investigated the ability of the major human class II AP endonuclease, Ape, which is structurally unrelated to Apn1, to replace the yeast enzyme in vivo. Confocal immunomicroscopy studies indicate that approximately 25% of the Ape expressed in yeast is present in the nucleus. High-level Ape expression corresponding to approximately 7000 molecules per nucleus, equal to the normal Apn1 copy number, restored resistance to methyl methanesulfonate to near wild-type levels in Apn1-deficient (apn1-) yeast. Ape expression in apn1- yeast provided little protection against H2O2 challenges, consistent with the weak 3'-repair diesterase activity of the human enzyme. Ape expression at approximately 2000 molecules per nucleus reduced the spontaneous mutation rate of apn1- yeast to that seen for wild-type cells. Because Ape has a powerful AP endonuclease but weak 3'-diesterase activity, these findings indicate that endogenously generated AP sites can drive spontaneous mutagenesis.

Mechanism of renal calcium conservation with estrogen replacement therapy in women in early postmenopause--a clinical research center study

To assess the mechanism by which estrogen replacement therapy (ERT) enhances renal calcium conservation in perimenopausal women, we studied 18 normal women in early postmenopause before and after 6 months of ERT (cyclic treatment with transdermal estradiol at 100 micrograms/day and medroxyprogesterone acetate at 10 mg/day for the first 12 days of each cycle). The changes after ERT were: serum ionized calcium and ultrafiltrable calcium, no change; serum intact PTH, 38.2% increase (P < 0.0001); serum 1,25-dihydroxyvitamin D, 23.8% increase (P < 0.0001); urinary calcium excretion, 33.3% decrease (P < 0.001); and deoxypyridinoline (a marker for bone resorption), 19.5% decrease (P < 0.0001). Also, ERT increased tubular reabsorption of calcium (TRCa; 97.6% +/- 0.2% to 98.7% +/- 0.1%; P < 0.0001), and this increase correlated with that in serum PTH (r = 0.49; P < 0.05). After the infusion of human PTH-(1-34), the TRCa maximum was greater after ERT than at baseline (99.4% +/- 0.1% vs. 99.0% +/- 0.1%; P < 0.0001), resulting in decreased calcium excretion (0.9 +/- 0.20 vs. 1.43 +/- 0.20 mumol/dL glomerular filtrate; P < 0.001). Thus, in early postmenopause, the major mechanism of increased renal calcium conservation after ERT is an increase in TRCa due to an increase in serum PTH because of estrogen-induced inhibition of bone resorption. However, ERT also may directly increase the TRCa maximum in response to PTH.

Oxandrolone therapy in constitutionally delayed growth and puberty. Bio-Technology General Corporation Cooperative Study Group

BACKGROUND

Male adolescents with constitutional delay of growth and puberty may have significant psychosocial difficulties related to their sexual immaturity and short stature. The purpose of this study was to test the hypothesis that 1 year of oxandrolone therapy would increase growth velocity and thereby improve psychosocial functioning in boys with constitutional delay of growth and pubertal development.

METHODS

Forty boys (ages 11 to 14.7 years) with delayed pubertal development and short stature were recruited from the pediatric endocrine clinics of 14 medical centers. The boys were randomized using a block design stratified for age to receive either oxandrolone (0.1 mg/kg daily for 1 year) or an identical-appearing placebo tablet, using a double-masked design.

RESULTS

Growth velocity in the oxandrolone-treated boys was significantly greater than in the control boys (9.5 vs 6.8 cm/y). Likewise, the mean height SD score increased 0.41 in the oxandrolone group, whereas it decreased 0.03 in the control group. Those in the oxandrolone group gained 2.4 kg more than those in the placebo group. Mean predicted adult heights did not change in either group. The mean rates of pubertal progression were equivalent in both groups. Self-image (Piers-Harris Self Concept Scale) and social competence (Child Behavior Profile) were normal at baseline in both groups and did not change significantly over the course of the study in either group. No complications of oxandrolone therapy were identified.

CONCLUSIONS

This randomized, placebo-controlled trial demonstrates that low-dose oxandrolone can increase both height and weight velocity in boys with delayed puberty safely. Under the conditions of this study, however, the increased growth velocity in the oxandrolone-treated boys was not associated with a greater improvement in psychosocial status compared with the control boys.

Polymerization of microtubule-associated protein tau under near-physiological conditions

Neurofibrillary tangles, which form in certain degenerating neurons in the brains of patients with Alzheimer's disease, are amassed from filaments having a straight or paired helical morphology. Solubilization of these filaments reveals that they are composed of the microtubule-associated protein tau. It has not previously been shown, however, that tau will assemble to form filaments of similar morphology under conditions representative of the intracellular environment. We have succeeded in forming such filaments using tau purified from porcine or rat microtubules. The filaments are relatively straight with narrowing at irregular intervals, and are about 10 nm wide, a morphology similar to that of straight filaments seen in Alzheimer's disease neurofibrillary tangles. At tau concentrations of 1-10 microM, in vitro assembly occurs at physiological pH, ionic strength, temperature, and reducing potential, and each one of these factors modulates the reaction. Assembly is judged to be only slowly reversible by the exponential rather than normal distribution of filament lengths, and by the limited disassembly observed under conditions which inhibit polymerization. Tau purified directly from whole brain tissue rather than from microtubules does not polymerize under conditions described in this report.

Osteomalacia associated with adult Fanconi's syndrome: clinical and diagnostic features

OBJECTIVE

Osteomalacia associated with adult acquired Fanconi's syndrome is thought to result from hypophosphataemia and relative 1,25-dihydroxyvitamin D deficiency. We have followed the clinical and diagnostic features of patients with osteomalacia associated with adult Fanconi's syndrome, with particular emphasis on their responses to treatment with calcium, phosphate and vitamin D.

DESIGN

Retrospective Mayo Clinic case-note review from 1975 to 1994 and prospective follow-up study, combined with literature review.

PATIENTS

Eleven patients (7 male, 4 female) were identified who satisfied criteria for diagnosis of osteomalacia and adult Fanconi's syndrome. Twenty-five additional patients were identified in a literature review from 1954 to the present.

METHODS

Clinical history and physical examination, serum and urine bone and mineral parameter, X-ray radiography and iliac crest bone histomorphometry.

RESULTS

All patients presented with typical symptoms of osteomalacia, including lower extremity or low back bone pain, and all had fractures, pseudofractures, and/or bone demineralization on X-ray radiography. Osteomalacia and Fanconi's syndrome were diagnosed concurrently in 10 patients, whereas osteomalacia preceded diagnosis of Fanconi's syndrome by 5 years in one patient. Pre-treatment bone biopsies in 9 of the 11 patients demonstrated increased osteoid surface, volume and width. In the one patient labelled with tetracycline prior to biopsy, mineralization lag time was prolonged at 111 days (normal 19.2 +/- 1.0 days). Hypophosphataemia, inappropriately low 1,25-dihydroxyvitamin D levels, renal insufficiency, and chronic acidosis due to bicarbonate leak and uraemia, contributed to the osteomalacia in these patients. Secondary hyperparathyroidism was present in two patients. Eight of the 11 patients with osteomalacia associated with Fanconi's syndrome had monoclonal disorders, including multiple myeloma or lymphoma, many of them manifest by light-chain proteinuria. Over a mean patient follow-up period of 46 months (range 1-239 months), patients responded symptomatically to calcium, phosphate, and vitamin D replacement typically within 1-6 months. In 8 patients in whom follow-up data were available, post-treatment serum phosphate and 1,25-dihydroxyvitamin D levels improved in the setting of stable mild renal insufficiency; only one patient developed end-stage renal failure after 20 years, suggesting that these patients do not invariably progress rapidly to renal failure.

CONCLUSIONS

Regardless of the underlying cause, osteomalacia associated with adult acquired Fanconi's syndrome appears to respond well to calcium, phosphate, and vitamin D replacement. These patients do not appear to necessarily require 1,25-dihydroxyvitamin D replacement.

Interleukin-1 and tumor necrosis factor-alpha increase insulin-like growth factor-binding protein-3 (IGFBP-3) production and IGFBP-3 protease activity in human articular chondrocytes

IGF-I is the major anabolic factor for cartilage matrix production. Chondrocytes and cartilage treated with interleukin-1 alpha (IL-1 alpha), and chondrocytes from several models of inflammatory joint disease, exhibit reduced responsiveness to IGF-I. Since the IGF-binding proteins (IGFBPs) modulate the effects of IGF-I, we examined the effect of IL-1 alpha and tumor necrosis factor-alpha (TNF-alpha) on IGFBP production by normal human articular chondrocytes in primary culture. Western ligand blots and immunoprecipitation of conditioned medium samples showed that articular chondrocytes produced IGFBPs-2, -3 and -4 and glycosylated IGFBP-4. Both IL-1 alpha and TNF-alpha increased chondrocyte production of IGFBP-3, but did not alter IGFBP-4 production. The activity of a neutral metalloprotease with the ability to cleave IGFBP-3 was also increased by IL-1 alpha. These data suggest that the cytokines IL-1 alpha and TNF-alpha may act to reduce IGF-I access to chondrocytes by increasing production of IGFBP-3. This may be a factor in the decreased matrix production in the inflammatory arthritides.