Rapid and extensive surface changes near Titan's equator: evidence of April showers.

Although there is evidence that liquids have flowed on the surface at Titan's equator in the past, to date, liquids have only been confirmed on the surface at polar latitudes, and the vast expanses of dunes that dominate Titan's equatorial regions require a predominantly arid climate. We report the detection by Cassini's Imaging Science Subsystem of a large low-latitude cloud system early in Titan's northern spring and extensive surface changes (spanning more than 500,000 square kilometers) in the wake of this storm. The changes are most consistent with widespread methane rainfall reaching the surface, which suggests that the dry channels observed at Titan's low latitudes are carved by seasonal precipitation.

Io volcanism seen by new horizons: a major eruption of the Tvashtar volcano.

Jupiter's moon Io is known to host active volcanoes. In February and March 2007, the New Horizons spacecraft obtained a global snapshot of Io's volcanism. A 350-kilometer-high volcanic plume was seen to emanate from the Tvashtar volcano (62 degrees N, 122 degrees W), and its motion was observed. The plume's morphology and dynamics support nonballistic models of large Io plumes and also suggest that most visible plume particles condensed within the plume rather than being ejected from the source. In images taken in Jupiter eclipse, nonthermal visible-wavelength emission was seen from individual volcanoes near Io's sub-Jupiter and anti-Jupiter points. Near-infrared emission from the brightest volcanoes indicates minimum magma temperatures in the 1150- to 1335-kelvin range, consistent with basaltic composition.

Early secondary succession in bottomland hardwood forests of southeastern Virginia.

Addressing the need for reference sites that permit wetland managers to evaluate the relative success of wetland restoration efforts, this project examines the early successional properties of a chronosequence of 17 forested wetlands that have been clear-cut and allowed to naturally revegetate. Ordinations performed on the data using CANOCO software indicated three general types of communities- one dominated by bald cypress (Taxodium distichum) and water tupelo (Nyssa aquatica), one dominated by black willow (Salix nigra), and one with a species composition similar to that of a mature stand of bottomland hardwoods. These divisions were correlated with the percentage of stems originating as coppice on stumps leftover from the clear-cut. In particular, the bottomland hardwood stands were regenerating predominantly as coppice, while the cypress/tupelo and black willow stands were regenerating primarily as seedlings. As indicated by the earlier development of overstory basal area, coppice sites were also regenerating much faster. The hydrology of a site also exhibited a strong impact on the rate of regeneration, with the semipermanently to permanently flooded portions of sites often exhibiting little or no regeneration. The results indicate that, because of the overwhelming reliance on coppice sprouts as the main source of stems and the concomitant enhanced rates of regeneration, certain vegetative parameters of clear-cut bottomiand hardwood stands would not be effective benchmarks by which to judge the relative success of creation and restoration efforts.

Quantifying muscle activity in non-ambulatory children with spastic cerebral palsy before and after selective dorsal rhizotomy.

Cerebral palsy is a condition that results in varying degrees of functional deficits. The goal of this study was to develop an objective measure of muscle activity during a prescribed voluntary motor task in non-ambulatory children with spastic cerebral palsy. While performing a simultaneous hip/knee flexion task from the supine position, followed by return to the starting position, electromyographic and kinematic data were obtained from the right leg of eight children before and after selective dorsal rhizotomy and compared with eight age-matched controls. The electromyographic and kinematic data were combined to determine for each muscle of interest (tibialis anterior, soleus, vastus lateralis, biceps femoris) the percentage of the movement cycle for which the muscle was acting concentrically, eccentrically, isometrically or was considered inactive. Averaged over the four muscles, isometric activity decreased by 38% post-op and the time the muscles were inactive increased by 37% following surgery. The percentages of concentric and eccentric activity did not differ significantly between pre- and post-op conditions. Post-operatively, the percentage muscle activity patterns of the children with cerebral palsy more closely resembled that of the control children: averaged across all muscles and contraction types, the difference between the control children and the children with cerebral palsy was reduced by 50% following surgery. This measurement technique indicates promise as a method for quantifying muscle activity during voluntary motor tasks in non-ambulatory children with cerebral palsy.

A biomechanical evaluation of one-stage vs two-stage bilateral knee arthroplasty patients.

In this study the functional abilities of eight one-stage bilateral total knee replacement (TKR) patients were compared to five two-stage bilateral TKR and nine control subjects. The TKR individuals were an average of 62 months post-operative. Based on gait analysis, ground reaction force profiles during walking and isometric knee strength assessment, the one-stage individuals did not differ significantly from the control subjects. The two-stage individuals had significantly less knee range of motion during gait and smaller vertical ground reaction forces during the braking phase than the control and one-stage individuals. To compare left and right sides, a symmetry index was computed and there were no significant differences among the three groups. Based on the variables tested in this biomechanical evaluation it can be concluded that for individuals facing bilateral knee replacement a one-stage procedure can result in functional capabilities at least comparable to a two-stage procedure.

Epidermal growth factor induces cyclin D1 in a human prostate cancer cell line.

BACKGROUND: The human prostate carcinoma cell line, LNCaP, proliferates under stimulation by a limited number of mitogenic signals, which include members of the growth factor and steroid hormone families. Androgens and epidermal growth factor (EGF) are among the LNCaP cell mitogens. We tested the hypothesis that these mitogens stimulate LNCaP cell proliferation at least in part through the induction of cyclin D1, a protein requisite for cell cycle progression, which is expressed in the G1 phase of the cell cycle. METHODS: LNCaP cells were grown in serum-free medium with 10 ng/ml or 100 ng/ml EGF, 0.1 nM or 1.0 nM mibolerone (a potent androgen agonist), or vehicle (distilled water or 0.01% ethanol). Expression of cyclin D, mRNA, and protein were assessed by Northern and Western blot analyses. Transcription regulation was assessed by nuclear runoff assay. RESULTS: Western analyses demonstrated that EGF stimulated cyclin D1 protein expression 4-fold over 12 hr. Northern analyses showed a 4-fold increase in mRNA expression, peaking within 4 hr of EGF stimulation. There were no effects on cyclin D1 protein or mRNA expression with mibolerone treatments. We further explored the mechanism of cyclin D1 induction. LNCaP cells stimulated for 1 hr with EGF demonstrated a 2-fold increase in cyclin D1 message, as assayed by nuclear runoff transcription assay. In addition, we demonstrated the involvement of the protein kinase C pathway in mediating the EGF induction of cyclin D1. CONCLUSIONS: We conclude that one of the mechanisms by which growth factors such as EGF may stimulate prostate cell proliferation is through the direct induction of cyclin proteins, which are necessary for entry of cells into mitosis.

Frequency content of normal and diabetic plantar pressure profiles: implications for the selection of transducer sizes.

How small do pressure transducers need to be in order to faithfully measure the plantar pressure profiles (PPPs) under normal and diabetic feet? In this study, pressures were collected from five diabetic and six non-diabetic subjects using a commercial measurement system with 25 mm2 transducers. Discrete Fourier Transform techniques were then used to determine (i) the spatial frequency content of diabetic and non-diabetic PPPs, and (ii) the effects of quadrupling the transducer area (from 5 mm x 5 mm to 10 mm x 10 mm). When the data were filtered to represent the effects of using 10 mm x 10 mm transducers, it was found that the ensuing reductions in peak pressure in the toe region (50 kPa) were significantly greater than in all other regions of the foot (p < 0.05). There was a significant correlation between pressure underestimations and measured peak pressures in the metatarsal regions. Based on data collected with 25 mm2 transducers it was concluded that transducer sizes greater than 6.36 mm x 6.18 mm (medio-lateral and antero-posterior directions) would result in sub-optimal sampling of PPPs.

Androgens regulate the expression of proliferating cell nuclear antigen posttranscriptionally in the human prostate cancer cell line, LNCaP.

Proliferating cell nuclear antigen (PCNA) expression is required for DNA replication. Because androgens are critical for prostate cell proliferation, we investigated the effects of androgen on PCNA expression in the prostatic cancer cell line LNCaP. Flow cytometric analysis was used to measure cellular DNA content with dual labeling of PCNA. Semiconfluent LNCaP cells were grown in serum-free medium containing varying concentrations of the synthetic androgen mibolerone and processed for either fluorescence-activated cell sorting or Western analysis. Supplementation of serum-free medium with androgens resulted in dose-dependent changes in PCNA immunoreactivity, with maximum stimulation (2-fold) being achieved at 48 h with 10(-9)M mibolerone. Non-androgenic steroids did not change PCNA immunoreactivity compared with untreated controls, and the antiandrogen, casodex, inhibited the mibolerone-stimulated increase in PCNA immunoreactivity, suggesting that the androgenic induction of PCNA is mediated through the androgen receptor. The presence of a non-consensus androgen response element in the promoter region of the PCNA gene led us to investigate wether androgen responsiveness of the PCNA gene in LNCaP cells might be mediated at the transcriptional level. No change in steady-state mRNA for PCNA with androgen administration was observed. However, an investigation of the androgenic regulation of PCNA protein stability indicated that androgen treatment increased the half-life of 35S-labeled PCNA protein. In addition, polysome run-off translation assays demonstrated an increase in PCNA protein after a 6-h stimulation of LNCaP cells with 10(-9)M mibolerone. These data suggest that androgen induction of prostate cell proliferation may be mediated, at least in part, through PCNA at the posttranscriptional level.

Androgen regulation of gene expression.

Androgen receptors are important transcription factors regulating the expression of a number of genes in androgen-responsive cells and may play a role in prostate cancer. This article describes transcriptional suppressors and other transcription factors which may play important roles in modulating the expression of androgen receptors.

The use of running shoes to reduce plantar pressures in patients who have diabetes.

We compared the plantar pressures generated by walking in leather-soled Oxford-style shoes and by walking in inexpensive running shoes with those generated by walking in thin socks on a hard surface for thirty-nine individuals (thirteen who had diabetes and neuropathy, and thirteen who had diabetes without neuropathy, and thirteen who had neither diabetes nor neuropathy [controls]). Except for two anatomical regions, the plantar pressure associated with the Oxford-style shoes were not different from those associated with walking without shoes. In comparison, the inexpensive running shoes relieved plantar pressure in the forefoot and heel by a mean (and standard deviation) of 31 +/- 9.1 per cent, with the most relief occurring in the feet that had the highest pressures when they were unshod. There were significant reductions in pressure in all regions of the foot except for the midfoot (p < 0.01), and there were no significant differences between the groups. Individuals who have insensate feet should be discouraged from wearing leather-soled Oxford-style shoes because of the risk of ulceration due to elevated plantar pressures. Inexpensive running shoes should be viewed as the very minimally acceptable choice for footwear for these individuals if the feet are free of deformity.

Characterization of an early growth response gene, which encodes a zinc finger transcription factor, potentially involved in cell cycle regulation.

Using differential display polymerase chain reaction, early growth response gene alpha (EGR alpha) was first isolated as a 291-base pair 3'-cDNA clone, which was highly expressed in the androgen-independent prostate carcinoma cell lines PC3 and DU145, as compared with the androgen-responsive prostate carcinoma cell line LNCaP. Full length cloning of the EGR alpha coding region revealed that EGR alpha was a new member of an important subfamily of nuclear zinc finger transcription factors (others members e.g. Sp1, EGR-2, and Wilms' tumor gene). Moreover, it was observed that EGR alpha, as with most Sp1 subfamily members, was conserved between mammalian species ranging from human to rabbit. Two hormones important for prostate development and differentiation were found to be potent regulators of EGR alpha mRNA expression. Androgens were observed to induce a down-regulation of EGR alpha mRNA expression (70% in 72 h), while epidermal growth factor induced a rapid transient up-regulation (6-fold in 100 min). The up-regulation was controlled at the transcriptional level and effectively blocked by staurosporine (which suggests the involvement of the protein kinase C pathway). Functional analysis demonstrated that EGR alpha could bind to, and stimulate transcription from, a basic transcription element (BTE) consensus sequence on DNA (BTE is a transcription-modulating sequence in the promoter region of some cytochrome P450 family members). Furthermore, in stage-synchronized prostate cells, EGR alpha mRNA was highly expressed in the early G1 phase of the cell cycle, similar to c-fos mRNA expression. These results indicated that the zinc finger transcription factor EGR alpha seems to play a role in cell cycle regulation.

Calcium regulation of androgen receptor expression in the human prostate cancer cell line LNCaP.

Elevation of intracellular calcium levels in the presence of normal androgen levels has been implicated in apoptotic prostate cell death. Since the androgen receptor (AR) plays a critical role in the regulation of growth and differentiation of the prostate, it was of interest to determine whether Ca2+ would affect the expression of androgen receptor messenger RNA (mRNA) and protein, thus affecting the ability of androgens to control prostate function. AR-positive human prostate cancer cells, LNCaP, were incubated with either the calcium ionophore A23187 or the intracellular endoplasmic reticulum Ca(2+)-ATPase inhibitor thapsigargin. Subsequently, AR mRNA and protein levels were assessed by Northern and Western blot analysis. Both A23187 and thapsigargin were found to down-regulate steady state AR mRNA levels in a time- and dose-dependent manner. AR mRNA began to decrease after 6-8 h of incubation with 10(-6) M A23187 or 10(-7) M thapsigargin, reaching a nadir at 16 and 10 h of incubation, respectively. In contrast, control mRNA (glyceraldehyde 3-phosphate dehydrogenase) did not change significantly during the treatments with either A23187 or thapsigargin. AR protein levels were found to be decreased after 12 h of incubation with either 10(-6) M A23187 or 10(-7) M thapsigargin. The decrease in AR mRNA and protein seemed to precede apoptosis, since neither A23187 (24 h) nor thapsigargin (30 h) was found to alter cell morphology within the treatment time. Cycloheximide and actinomycin D were unable to change the calcium-mediated decrease in AR mRNA, ruling out the necessity for de novo protein synthesis or a change in mRNA stability. Moreover, the decrease in AR mRNA induced by calcium does not seem to involve protein kinase C- or calmodulin-dependent pathways, since inhibitors of these cellular components had no effect. Nuclear run-on assays demonstrated little or no effects of either A23187 or thapsigargin treatment on AR gene transcription (8 h and 10 h). In conclusion, these studies show that intracellular calcium seems to be a potent regulator of AR gene expression in LNCaP cells.

Endogenous cathepsin D-mediated hydrolysis of insulin-like growth factor-binding proteins in cultured human prostatic carcinoma cells.

Insulin-like growth factor I (IGF-I) seems to play an important role in prostate cell growth and its actions may be modified by IGF-binding proteins (IGFBPs) secreted by prostate epithelial cells. The IGFBP system was studied in two human prostate carcinoma cell lines, PC3 and LNCaP. Androgen receptor-negative PC3 cells secrete IGFBP-3, IGFBP-4, and IGFBP-5, as determined by immunoprecipitation of the serum-free conditioned medium with specific IGFBP antibodies. Androgen receptor-positive LNCaP cells secrete IGFBP-2 and IGFBP-3. At neutral pH, there was little or no effect of a 24-h, 37 C cell-free incubation of PC3 and LNCaP conditioned media on IGFBP. On the other hand, when media was incubated at pH 3 for 24 h, [125I]IGFBP-3 hydrolysis and the virtual elimination of endogenous IGFBP detected by Western ligand blotting were observed. This loss was not due to the acid treatment, per se, since IGFBPs remained intact if the incubation at pH 3 was carried out at 4 C. The acid-activated IGFBP protease in LNCaP and PC3 cell-conditioned media was identified as cathepsin D based on acidic pH optimum and immunoblotting. Furthermore, immunoadsorption of cathepsin D from the media attenuated the acid-activated IGFBP hydrolysis [125I]IGF-I binding to prostate cancer cells was reduced in the presence of LNCaP conditioned media that had been incubated at neutral pH for 24 h (i.e. containing intact IGFBP) but not by acid-incubated conditioned media (i.e. cathepsin D-mediated hydrolyzed IGFBP). These data indicate that prostate carcinoma cells secrete specific IGFBPs, as well as a general IGFBP protease, cathepsin D. In the proper environment, cathepsin D is capable of hydrolyzing all endogenous IGFBP and, thus, modifying IGF-I action in prostatic cells.

HIV-1 recombinant gp160 vaccine induced antibodies in serum and saliva. The NIAID AIDS Vaccine Clinical Trials Network.

As part of a phase I safety and immunogenicity trial of a vaccinia-expressed HIV-1 recombinant gp160 (rgp160) candidate vaccine, we measured serum and saliva antibody responses in low risk, uninfected volunteers. Six healthy adult volunteers received 50 micrograms doses of rgp160 vaccine adjuvanted in alum and deoxycholate at months 0, 1, 6, and 12. A 200 micrograms rgp160 immunization was given to four volunteers at 18 months. The vaccine induced anti-envelope glycoprotein IgG and IgA serum antibodies in all six volunteers. Saliva antibodies to envelope glycoprotein appeared in some volunteers at certain timepoints. Three volunteers appeared to transiently develop vaccine-induced secretory IgA antibody to envelope glycoprotein in whole saliva.

The mouse androgen receptor gene contains a second functional promoter which is regulated by dihydrotestosterone.

The androgen receptor (AR) is a developmental and tissue-specific transcription factor which is activated by binding testosterone or dihydrotestosterone. Several different methods of transcriptional regulation of the AR have been shown, including regulation by androgens, follicle-stimulating hormone, epidermal growth factor, and the cAMP pathway. In order to further characterize the transcriptional regulation of the AR, portions of the mouse androgen receptor (mAR) promoter were cloned into the promoterless pBLCAT3 vector and assayed for chloramphenicol acetyltransferase activity. The results indicate that in addition to the previously characterized promoter (+1) there is a second distinct promoter located 3' to the first promoter. Amplification of the 5'-end of the AR gene indicates that RNA originating from the second promoter is initiated from 162 and 170 bases downstream from the 5'-most previously characterized site. Northern blot analysis indicated that RNA initiated from the two promoters is differentially expressed in several cell lines and multiple tissues. Androgen ablation by castration showed that both promoters are controlled by androgens in the kidney. Sequence analysis revealed that the second promoter does not contain a TATA or CAAT box. Further characterization of this promoter may provide important insights into the transcriptional regulation of the androgen receptor since previous studies have often included only the first promoter.

Locomotion in a rotating space station: a synthesis of new data with established concepts.

Despite technical problems associated with designing a rotating space station it is still thought that such a device may provide a more tolerable work environment and prevent some of the physiological changes that currently pose a threat to long-duration space missions. In the present analysis four case studies are presented and the results show that centrifugal and Coriolis effects could hinder one's ability to walk or run in a natural way in such an environment. In a rotating station that has a nominal 'G-level' equal to that on earth it can be shown that a person running at 3.8 m s -1 could experience foot 'heaviness' effects that range from 1 to 3 g and fore-aft foot 'forces' that range fom -0.5 to +0.5 g. In contrast the hip region could sense a relatively constant 'force' equal to 2 g. With regard to the body as a whole there would be 'weight changes' that depended on the direction of gait. While these conditions imply that locomotion in a rotating space station would be different from normal gait, it is likely that given sufficient training, astronauts could learn optimal strategies to account for centrifugal and Coriolis effects on individual body segments. The learning process would also entail developing strategies on which route to take when moving from one location to another, since in many cases the shortest route would not be the least energy consuming. Such training would be justified if it were shown that artificial gravity was an effective countermeasure to the problems of muscle atrophy and bone loss.

Gonadal steroids modulate adrenal fasciculata 3 beta-hydroxysteroid dehydrogenase-isomerase activity in mice.

The observation that adrenal 3 beta-hydroxysteroid dehydrogenase-delta 5----delta 4-isomerase (3 beta HSD) activity is greater in females than in males of both C57BL/6J and C3H/HeJ inbred strains of mice led us to test the hypothesis that this enzyme's activity within the adrenal gland may be modulated by gonadal steroids. Two weeks after sham-operation or castration, no castration effect was seen in adrenal 3 beta HSD activity, but the sex difference had been eliminated in C57BL/6J animals. Gonadal steroids were replaced in castrated animals of both sexes of C57BL/6J and C3H/HeJ mice. Daily injections of androgenic steroids (testosterone propionate or dihydrotestosterone) decreased adrenal 3 beta HSD activity in both sexes of both strains of mouse. Although estradiol benzoate did not alter adrenal 3 beta HSD activity in either sex or strain tested when the activity was expressed on a per adrenal gland basis, it did inhibit adrenal 3 beta HSD activity when expressed on a per milligram of adrenal tissue basis in C57BL/6J but not in C3H/HeJ animals. Histochemical staining for 3 beta HSD and the relationship between adrenal weight and the cross-sectional area of the zona fasciculata suggested that the adrenal zona fasciculata was the target of the inhibitory effects of androgens on adrenal 3 beta HSD activity.

Subcellular distribution of 3 beta-hydroxysteroid dehydrogenase-isomerase in bovine and murine adrenocortical tissue: species differences in the localization of activity and immunoreactivity.

Key to the production of biologically active steroids is the enzyme 3 beta-hydroxysteroid dehydrogenase-isomerase. Some controversy has arisen concerning the subcellular distribution of this enzyme within steroidogenic cells. The distribution of 3 beta-hydroxysteroid dehydrogenase-isomerase was assessed in subcellular fractions obtained from homogenates of rat, bovine, and mouse adrenal glands in two ways. The activity of 3 beta-hydroxysteroid dehydrogenase-isomerase was quantitated by measuring the conversion of radiolabeled pregnenolone to radiolabeled progesterone in an aliquot of each of the fractions obtained. The presence of the enzyme was assessed by performing Western analyses on aliquots of each of the fractions obtained with the use of a specific polyclonal antiserum against 3 beta-hydroxysteroid dehydrogenase-isomerase, the characterization of which is described. In control experiments, the degree of contamination of the fractions was determined by assessing the presence of known subcellular fraction markers with Western analysis. In the bovine and mouse adrenal glands, 3 beta-hydroxysteroid dehydrogenase-isomerase appears to be localized solely in the microsomal fraction, while in the rat, 3 beta-hydroxysteroid dehydrogenase-isomerase appears to have dual subcellular distribution: the microsomes and the inner mitochondrial membrane. We conclude that there is a species difference in the subcellular distribution of this important steroidogenic enzyme and that this species difference may be related to the steroidogenic pathway preferred in that species.