Imaging of small-scale features on 433 Eros from NEAR: evidence for a complex regolith.

On 25 October 2000, the Near Earth Asteroid Rendevous (NEAR)-Shoemaker spacecraft executed a low-altitude flyover of asteroid 433 Eros, making it possible to image the surface at a resolution of about 1 meter per pixel. The images reveal an evolved surface distinguished by an abundance of ejecta blocks, a dearth of small craters, and smooth material infilling some topographic lows. The subdued appearance of craters of different diameters and the variety of blocks and different degrees of their burial suggest that ejecta from several impact events blanketed the region imaged at closest approach and led to the building up of a substantial and complex regolith consisting of fine materials and abundant meter-sized blocks.

Metabolic activation of dacarbazine by human cytochromes P450: the role of CYP1A1, CYP1A2, and CYP2E1.

Dacarbazine (DTIC), a widely used anticancer agent, is inactive until metabolized in the liver by cytochromes P450 to form the reactive N-demethylated species 5-[3-hydroxymethyl-3-methyl-triazen-1-yl]-imidazole-4-carboxamide (HMMTIC) and 5-[3-methyl-triazen-1-yl]-imidazole-4-carboxamide (MTIC). The modest activity of DTIC in the treatment of cancer patients has been attributed in part to lower activity of cytochromes P450 (P450) in humans when compared with rodents. Importantly, the particular P450 isoforms involved in the activation pathway have not been reported. We now report that the DTIC N-demethylation involved in MTIC formation by human liver microsomes is catalyzed by CYP1A1, CYP1A2, and CYP2E1. The most potent inhibitors of DTIC N-demethylation were alpha-naphthoflavone (CYP1A1 and CYP1A2), quercetin (CYP1A2), chlorzoxazone (CYP1A2 and CYP2E1), and di-sulfiram (CYP2E1). Antihuman CYP1A2 antiserum also inhibited DTIC N-demethylation. DTIC N-demethylation in a panel of 10 human liver microsome preparations was correlated with the catalytic activities for CYP1A2 (ethoxyresorufin O-deethylation and caffeine N3-demethylation) in the absence of alpha-naphthoflavone and with the catalytic activities for CYP2E1 (chlorzoxazone 6-hydroxylations) in the presence of alpha-naphthoflavone. DTIC metabolism was catalyzed by recombinant human CYP1A1, CYP1A2, and CYP2E1. The Km (Vmax) values for metabolism of DTIC by recombinant human CYP1A1 and CYP1A2 were 595 microM (0.684 nmol/min/mg protein) and 659 microM (1.74 nmol/min/mg protein), respectively. The CYP2E1 Km value exceeded 2.8 mM. Thus, we conclude that (a) CYP1A2 is the predominant P450 that catalyzes DTIC hepatic metabolism; (b) CYP2E1 contributes to hepatic DTIC metabolism at higher substrate concentrations; and (c) CYP1A1 catalyzes extrahepatic metabolism of DTIC.

The effect of beta-blockers on mental performance on older hypertensive patients.

This double-blind, three-way crossover study measured the influence of beta-blocker treatment on drowsiness and mental test performance in older hypertensive patients and determined if lipophilicity was a determinant of these effects. Twenty-seven hypertensive patients (mean age, 63 +/- 3 years) were studied. Patients received two weeks each of daily treatment with placebo, 100 mg of atenolol, or 150 mg of metoprolol tartrate and were evaluated on the 14th day of each treatment period, after which their next treatment period began. Mental performance was measured using Trails-A maze testing. Drowsiness was measured subjectively using a visual analogue scale, and objectively using critical fusion-frequency threshold testing. Blood pressure control was equivalent and clinically adequate in all subjects. Steady-state levels of metoprolol tartrate (235.7 +/- 46 ng/mL) and atenolol (453.6 +/- 56 ng/nL) achieved were those expected to produce similar beta-blockade. Mental performance as measured by Trials-A testing showed better scores during beta-blocker treatment compared with placebo. Trails-A scores improved as patients went from placebo to metoprolol treatment, but did not change as patients went from placebo to atenolol treatment. Critical fusion-frequency threshold measurements were lower following administration of both drugs than following that of placebo, but subjectively there was no difference in feelings of lethargy between either beta-blocker and placebo. These data show greater improvement in mental testing performance to be associated with metoprolol treatment, but neither produced more lethargy than placebo in elderly patients.

The pharmacodynamics of diphenhydramine-induced drowsiness and changes in mental performance.

The time course of diphenhydramine concentrations and effects on both mental performance and subjective feelings of drowsiness were assessed in 15 healthy men. Subjects received single oral doses of diphenhydramine, 50 mg, and placebo in this double-blind crossover study. Diphenhydramine plasma concentrations and central nervous system actions were assessed for 24 hours after each treatment. Cognitive impairment was assessed with an automobile driving simulator and digit symbol substitution scores, whereas drowsiness was self-assessed on a visual analog scale. Diphenhydramine produced significant feelings of drowsiness for up to 6 hours after the dose, whereas significant mental impairment was apparent for only 2 hours. Despite the difference in duration of these effects, drowsiness and mental impairment have parallel slopes when effects are related to diphenhydramine concentrations. These data suggest that although the apparent diphenhydramine concentration thresholds to produce drowsiness are lower (30.4 to 41.5 ng/ml) than those needed to produce mental impairment (58.2 to 74.4 ng/ml), these effects have profiles consistent with their being manifestations of the same pharmacologic effect.

The relative antihistaminic and psychomotor effects of hydroxyzine and cetirizine.

Twelve healthy subjects with atopy received single doses of hydroxyzine, 25 mg, its metabolite cetirizine, 10 and 20 mg, and placebo in a four-way crossover study randomized by Latin square design. Skin wheal response to histamine, psychomotor effects, and serum concentrations of each drug were measured for 36 hours after each dose. Central nervous system (CNS) effects were measured with critical flicker frequency, Stroop word testing, and visual analog scales. All three active treatments (cetirizine, 10 mg, cetirizine, 20 mg, and hydroxyzine) produced an equivalent suppression of skin wheal response to histamine that was significantly greater than placebo (P less than 0.01). Hydroxyzine produced a significant change compared with placebo in all three CNS parameters. Neither cetirizine, 10 mg, nor cetirizine, 20 mg, produced any significant change in CNS parameters. Both the intensity and time course of CNS effects were related significantly (P less than 0.05) to hydroxyzine concentrations. The CNS changes measured after oral hydroxyzine are the result of the parent drug, whereas its metabolite cetirizine when administered alone produced significant antihistaminic effects without CNS changes.

A controlled study of survival with dementia.

Widely conflicting data exist regarding the relationship of dementia to mortality and the relative risk of senile dementia of the Alzheimer type vs multi-infarct dementia with respect to mortality. In a historic prospective study, 202 patients with dementia were matched by age and sex with 202 nondemented controls attending the same geriatric assessment clinic and receiving comparable medical and psychiatric care. The three-year survival rate was 70% for patients with dementia and 84% for controls. Patients with multi-infarct dementia survived more poorly than patients with senile dementia of the Alzheimer type, but the difference did not reach statistical significance. The relative risk associated with dementia in the context of a multivariate analysis was 1.92 (95% confidence [1.25, 2.97]). We conclude that dementia carries a significantly increased risk of mortality but that the survival of patients with dementia may be better than previous reports would suggest.

Endogenous nucleotide pools and protein incorporation into liver nuclei from young and old rats.

To test the validity of estimating age-related changes in rat liver nuclear RNA synthesis by following the incorporation of radioactive nucleotides into an acid-insoluble product, age-related changes in endogenous nucleotide concentration were investigated. Both the total nucleotide and the nucleoside monophosphate (NMP) concentration decreased as a function of age. Although NMP concentration decreased linearly from 6 months of age, total nucleotide concentration decreased in an exponential manner beginning at 2 months of age. These age-related changes in endogenous nucleotide pool concentration cannot, therefore, be due to changes in nuclear permeability alone but may also involve age-related changes in nuclear metabolism of endogenous nucleotides. Since nuclear functioning proteins must be synthesized in the cytoplasm and subsequently incorporated into the nucleus, the effect of age on the uptake and specific incorporation of several of these proteins involved in transcription was investigated. There was no age-related difference in either the rate of uptake or in the total amount of general cytosol proteins, histones, ribosomal proteins or RNA polymerase incorporated by rat liver nuclei in vitro.

Developmental regulation of metabotropic glutamate receptor 5b protein in rodent brain.

The metabotropic glutamate receptor type 5 (mGlu5) is expressed in two splice variants, mGlu5a and mGlu5b, which differ in that mGlu5b has a 33-amino acid insert in the intracellular C-terminal domain. This receptor subtype is highly regulated, with higher levels found in developing animals, but the contributions of the individual splice variants to the receptor population at any time are unknown. An antibody that specifically reacts with the insert was developed and used to measure the regional and developmental distribution of mGlu5b in the mouse and rat brain. In contrast to total mGlu5 receptor protein, most brain regions exhibit a less than two-fold alteration between post-natal day 7 and adult levels of mGlu5b. In the adult cortex, there is a three-fold increase of mGlu5b protein relative to at post-natal day 7. Estimates of mGlu5a protein indicate that most of the developmental alteration in total mGlu5 is due to changes in expression of this variant. Comparison of mGlu5b protein and mRNA levels indicates that greatly different post-transcriptional regulation occurs across brain regions. These results indicate that mGlu5 expression is precisely and complexly controlled at the level of transcription and that different functions of mGlu5 during different developmental periods and in distinct regions are likely mediated by different splice variants.

Corneal Langerhans cell dynamics after herpes simplex virus reactivation.

PURPOSE: The authors investigated the progressive changes in the distribution of corneal Langerhans cells (LC) after reactivation of latent herpes simplex virus type 1 (HSV-1) in mice. METHODS: After corneal inoculation of National Institutes of Health inbred mice with HSV-1 and the establishment of latency, viral reactivation was induced by irradiating the ocular surface with 250 mJ/cm2 of ultraviolet B (UV-B) light. RESULTS: Subsequent viral replication in the cornea was followed by the migration of the LC toward the paracentral and central corneal epithelium. These areas are normally devoid of LC. The number of LC in the paracentral and central regions of the eye reached a peak at day 14 post-UV-B irradiation. After UV-B irradiation of mice latently infected with HSV-1, the development of corneal stromal opacification and neovascularization closely followed the migration of LC toward the central cornea and paralleled the influx of T-cells into the corneal stroma. This pattern was not observed in irradiated uninfected mice. CONCLUSIONS: LC migrate centrally in the corneal epithelium after viral reactivation. There is a direct correlation between the number of LC in the cornea and the degree of persistent stromal opacification.

IL-1 and TNF-alpha are important factors in the pathogenesis of murine recurrent herpetic stromal keratitis.

PURPOSE: To better understand the role of interleukin (IL)-1 and tumor necrosis factor (NF)alpha in recurrent herpetic stromal keratitis (HSK), the cytokine content and the effects of anti-cytokine antibodies on mouse corneas with the disease were examined. METHODS: Competitive reverse transcription-polymerase chain reaction and enzyme-linked immunosorbent analyses of IL-1alpha and TNF-alpha content were performed on corneas removed 3, 5, 7, 10, 14, and 21 days after latently infected NIH mice were irradiated with UV-B light to reactivate herpes simplex virus (HSV). In separate experiments, mice were injected with anti-IL-1 or anti-TNF-a antibodies 1 day before and 7 days after reactivation. RESULTS: UV-B irradiation stimulated an increase in corneal IL-la mRNA in reactivated (virus shedding) mice. This increase persisted longer and was higher than in UV-B irradiated uninfected control animals. IL-1alpha and TNF-alpha protein in corneas of reactivated mice was significantly elevated on days 3 to 10 compared with day 0 levels, and exceeded levels in control corneas on the same days. Anti-IL-1 and anti-TNF-alpha antibody administration both resulted in significantly decreased virus-induced corneal opacity between 7 and 21 days after UV-B exposure. CONCLUSIONS: IL-1alpha and TNF-alpha are upregulated in corneas in mice experiencing recurrent HSK. Abrogation of virus-induced corneal disease by anti-cytokine antibodies suggests that these cytokines play important roles in the pathogenesis of recurrent disease. Therefore, neutralization of specific proinflammatory cytokines may have potential therapeutic value.

Escaping senescence: demographic data from the three-toed box turtle (Terrapene carolina triunguis).

Two criteria have been proposed for the demonstration of negligible senescence. These include (1) no increase in age-related mortality and (2) negligible functional impairments with age. Although researchers have suspected turtles to exhibit negligible senescence, this has been largely based on the former rather than the latter criteria for which scant evidence is available. Using a long-term study on a population of three-toed box turtles (Terrapene carolina triunguis) in Cole County, Missouri, I combine known minimum age ranges and reproductive evidence to demonstrate their apparent escape from senescence. During 1998 and 1999, eight females >60 years of age were found gravid. The oldest of these is estimated to be at least 65-74 years of age. Of females >60 years, the mean clutch size and the proportion gravid were greater, although not significantly different, when compared to females <60 years. These findings indicate that the reproductive function in these turtles does not become impaired with age, thus supporting the second criteria for demonstrating negligible senescence.

A new method of preparing human whole brain sections for in vitro receptor autoradiography.

In vitro receptor autoradiography is a widely used technique for determining the distribution of radioligand binding sites. By using this technique it is possible to investigate alterations in receptor number and affinity caused by trauma or a disease state. To date, however, the largest sections prepared for in vitro autoradiography have been from single human hemispheres, with the adjacent hemisphere being used for neuropathological investigations. Therefore, a method for cutting large cryosections of human whole brain tissue is described. Whole brains obtained less than 2 days postmortem were frozen at -80 degrees C. 1.5-2 cm coronal slices were cut from the brain and embedded and frozen in a carboxymethylcellulose solution. Sections 40 microm in size were sliced from the frozen block at -16 degrees C in a whole body cryostat. The sections were lifted by means of a nylon membrane backing material and subsequently incubated with tritiated ligand to produce autoradiograms of each whole brain coronal section. [(3)H]paroxetine was used in the present study as an example.

Reactivation of latent herpes simplex virus by excimer laser photokeratectomy.

We tested whether excimer laser photorefractive and phototherapeutic keratectomy may reactivate latent herpes simplex and cause recurrent keratitis in mice. Two of ten latently infected mice that were treated with ten excimer laser pulses to the corneal epithelium shed herpes simplex virus type 1, as did four of ten mice that were treated with 50 excimer laser pulses. Ocular shedding of herpes simplex virus was detected in four of ten mice that were treated with ethylenediamine-tetraacetic acid (EDTA) scraping of the corneal epithelium without laser keratectomy, and in six of ten mice on which combined EDTA-facilitated epithelial removal was performed followed by the application of ten excimer laser pulses. In both EDTA-treated groups, viral shedding was prolonged and 18 of 20 mice developed marked corneal opacification or neovascularization, or both. Corneal photoablation with the excimer laser may induce reactivation of latent herpes simplex virus, even in mice with clear and smooth-appearing corneas, and should be considered in the differential diagnosis of humans with persistent corneal epithelial defects after refractive or therapeutic excimer procedures.

A comparison of recurrent and primary herpes simplex keratitis in NIH inbred mice.

Herpes simplex virus (HSV) infection is one of the leading causes of corneal blindness. This study compared the clinical, virologic, and immunopathologic features of primary and recurrent murine models of herpes simplex keratitis (HSK) in the National Institutes of Health (NIH) inbred mouse strain. Primary infection resulted in multiple epithelial dendrites, followed by diffuse stromal opacification, symptoms that do not mimic what is seen in human HSK. In contrast, recurrent infection presented clinical features that included microdendrites, focal stromal opacities, disciform endotheliitis, and corneal neovascularization, which were similar to those observed in human disease. Immunohistochemical characterizations indicated that the number and duration of T cells and macrophages in recurrent HSK resemble those observed in primary disease. Results also indicated that the amount of infectious virus detected in the cornea during primary and recurrent disease was similar. However, when corneas were stained for HSV-1 antigens, mice with primary HSK displayed diffuse HSV antigen expression throughout the cornea, whereas HSV antigens were more focally distributed in recurrent disease. These data suggest that the clinical differences between the recurrent and primary herpetic keratitis may, in part, reflect the different distribution of HSV-1 antigens within the cornea.

Phenotypic and reversion analysis of a Salmonella typhimurium constructed to have an arginine codon at the hisG46 missense codon.

Of the 6 single-base mutations that would be predicted to change the missense mutation hisG46 away from a proline codon in the Salmonella/microsome mutagen selection assay for histidine-independent revertants, only 5 have been observed. We have used site-specific mutagenesis to make the unobserved mutant [CCC (proline)----CGC (arginine)] codon in the Salmonella genome. Experiments with this arginine mutant demonstrate that, like bacteria containing the hisG46 mutation, bacteria with the arginine missense mutation are histidine auxotrophs which are capable of reversion to histidine independence. However, unlike the ATP phosphoribosyltransferase coded by the hisG46 his G gene (with a proline), the arginine mutant enzyme is partially active. This is indicated by a histidine-independent phenotype when the arginine hisG gene is present in multiple copies.

Influence of uvrB and pKM101 on the spectrum of spontaneous, UV- and gamma-ray-induced base substitutions that revert hisG46 in Salmonella typhimurium.

Oligonucleotide probes were used to identify base substitutions in 1089 revertants of hisG46 in Salmonella typhimurium that arose spontaneously or following irradiation with UV- or gamma-rays. The hisG46 allele, carrying a mutant CCC codon (Pro) in place of the wild-type codon CTC (Leu69) reverted via 6 distinguishable mutational events--C to T transitions at codon sites 1 or 2, C to A or C to G transversions at codon site 1, C to A at codon site 2, and an extragenic suppressor mutation. The distribution of hisG46 revertants differed among treatments and was influenced by the DNA-repair capacity of the bacteria. Plasmid pKM101 enhanced the frequencies of both spontaneous and induced mutations; transversion events were enhanced more efficiently by pKM101 than were transition events. Compared to Uvr+ bacteria, Uvr- bacteria had higher frequencies of spontaneous and induced mutations; transition mutations were enhanced more efficiently than were transversion mutations. The influence of DNA-repair activities on the mutational spectra provides some insights on the origins of spontaneous and UV-induced mutations.

An analysis of the mutagenicity of 1,2-dibromoethane to Escherichia coli: influence of DNA repair activities and metabolic pathways.

The mutagenicity of 1,2-dibromoethane (EDB) to Escherichia coli was reduced by the UV light-induced excision repair system but unaffected by the loss of a major apurinic/apyrimidinic site repair function. At high doses, 70-90% of the EDB-induced mutations were independent of SOS-mutagenic processing and approximately 50% were independent of glutathione conjugation. The SOS-independent mutations induced by EDB were unaffected by the enzymes that repair alkylation-induced DNA lesions. EDB-induced base substitutions were dominated by GC to AT and AT to GC transitions. These results suggest that EDB-induced premutagenic lesions have some, but not all, of the characteristics of simple alkyl lesions.

Development of a screen for predicting clinical outcomes in patients with work-related upper extremity disorders.

This study prospectively examined the extent to which a set of medical, physical, ergonomic, occupational psychosocial, and individual psychosocial variables would predict clinical outcome associated with a diverse set of work-related upper extremity disorders in recently diagnosed individuals. This investigation was designed to develop a tool for use in a clinical setting to assist in identifying patients at risk for poorer outcome. Outcome was measured at 1, 3, and 12 months after completing a baseline questionnaire. Outcome status was based on a median split of a standardized composite index (symptoms, function, workdays lost, and mental health). Logistic regression indicated that predictors of poorer outcome at 1 month were: upper extremity comorbidity (risk ratio [RR], 1.58), pain severity (RR, 1.45), ergonomic risk exposure (RR, 1.07), low job support (RR, 1.03), and pain coping style (RR, 1.54). At 3 months, poorer outcome was predicted by: symptom severity (RR, 10.46), job stress (RR, 1.20), and pain coping style (RR, 1.98). The number of prior treatments/providers (RR, 1.77), past recommendation for surgery (RR, 6.43), and pain coping style were found to predict poorer outcome at 12 months. Sensitivity and specificity, respectively, for the models were 77.4% and 71.8% at 1 month, 80.6% and 82.4% at 3 months, and 80.6% and 83.3% at 12 months. The results indicate that baseline measures of ergonomic and psychosocial stress, pain severity, and pain coping style predict clinical outcome at shorter intervals, whereas number of past treatments/providers, recommendation for surgery and pain coping style predict longer-term outcome. The resulting prognostic screen provides a simple tool that assesses the multidimensional nature of work-related upper extremity disorders and predicts clinical outcome. Furthermore, the findings suggest the importance of early intervention that addresses both physical and psychosocial stressors at work. Specific recommendations to reduce the impact of observed risk factors are discussed.

The effects of chronic administration of chlorine dioxide, chlorite and chlorate to normal healthy adult male volunteers.

The physiological impact of chronic 12 week ingestion of chlorine dioxide and its byproducts, chlorite and chlorate, was compared to the effects of chlorine, chloramine and untreated water. The water disinfectant solutions were administered daily (500 ml, 5 ppm) to normal healthy adult male volunteers. An extensive battery of tests was used to evaluate the physiological impact of the ingested water disinfectants. Upon analysis of both quantitative and qualitative parameters it was concluded that the 12 week chronic administration of chlorine dioxide and its byproducts was accompanied by no clinically important physiological effects.

The effects of chronic administration of chlorite to glucose-6-phosphate dehydrogenase deficient healthy adult male volunteers.

Under controlled laboratory conditions, the safety of daily ingestion of 5 ppm chlorine dioxide, chlorite and chlorate by normal healthy adult males has been established. To determine the effect upon potentially susceptible individuals, a parallel chronic human investigation was undertaken. Study subjects were three healthy adult males deficient in glucose-6-phosphate dehydrogenase. These volunteers received 500 ml of sodium chlorite at a concentration of 5 ppm daily for twelve consecutive weeks; the subsequent observation period extended an additional eight weeks. Upon evaluation of an extensive battery of tests designed to measure the biochemical and physiological response to chlorite ingestion, no clinically significant changes were detected.