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Results for “multiple exposures”

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PubMed2006

Laser autofocusing system for high-resolution cell biological imaging.

Automated acquisition of high resolution, light microscope images of cells is becoming a common requirement in modern proteomic and cellomic research. A prerequisite for such microscopy is fine focus tuning, commonly optimized by multiple exposures, followed by image sharpness analysis. We describe here an extremely fast and accurate laser autofocusing system with distinct advantages for large-scale cell-based screening.

Automation↗
PubMed1995

Teaching microbiology with hypertext: first steps towards a virtual textbook.

Computer-assisted learning materials for medical microbiology were developed using hypertext-authoring software (Folio 3.1). Two versions of a text-only introductory tutorial (detailed, read only, and read-write noteform) were then evaluated in a prospective, randomized trial. Evaluation was by pre- and post-exposure multiple choice questions, and by self-administered questionnaire. There was a small difference in outcome between the two groups; the read-write group scoring higher, and students who used either software performed better than those who did not (P = 0.014). Responses to the post-test questionnaires showed that many students regarded the read-only software as an electronic handout, more frequent users requesting the addition of illustrations, self-assessment questions, and greater interactivity. A small group of students made use of the read-write version of the tutorial as a 'virtual textbook' by adding extra material to the starter file. Our experience suggests that the low-cost option of text-only hypermedia produces only modest learning gains for medical undergraduates.

Computer-Assisted Instruction↗
PubMed1976

Halothane-induced liver damage: an analysis of the material reported to the Swedish Adverse Drug Reaction Committee, 1966-1973.

An analysis of 94 reports to the Swedish Adverse Drug Reaction Committee of patients with liver injury after surgery and halothane anaesthesia (including 13 fatal cases) has not been able to reveal any other factors responsible for the liver injury than the halothane administration. Eighty-two per cent of the total material and 12 out of 13 fatal cases had had multiple exposures. Our results suggest that the liver injury becomes more severe after repeated exposures; maximum serum bilirubin and SGOT values are higher after an increasing number of halothane exposures.

Adolescent↗
PubMedDate not supplied

Motility and morphology of human spermatozoa in split ejaculates.

Sperm concentration and four motility characteristics (per cent motile spermatozoa, average velocity, average straight line approach and average speed constancy) were determined in three fractions of human split ejaculated from healthy volunteers. A semi-automatic analysis technique was used to determine sperm parameters from multiple exposure photographs (MEP). Sperm concentration and percentage motility were significantly higher in the first fraction as compared to the third fraction of split ejaculates. The average spermatozoal velocity, average speed constancy and average straight line approach were the same in all fractions. Differences in the percentage of motile spermatozoa were also found after collection of split ejaculates in culture medium. This phenomenon may have been caused by differences in sperm morphology. Significantly more normal spermatozoa were present in the first fractions of 19 split ejaculates as compared to the last fractions.

Ejaculation↗
PubMedDate not supplied

The effects of laser light on sperm motility and velocity in vitro.

The effect of Laser light on the motility and the velocity of human spermatozoa were measured by means of multiple exposure photography. Total sperm motility increased after Laser irradiation at 4 J/cm2, 8 J/cm2 and 32 J/cm2 respectively with respect to control. However, no influence on sperm velocity was demonstrated after Laser irradiation. This observation suggests that Laser light stimulates non-motile live spermatozoa.

Dose-Response Relationship, Radiation↗
PubMedDate not supplied

Motility of seminal plasma-free spermatozoa in the presence of several physiological compounds.

The purpose of this pilot study was to get information whether the motility and velocity of washed human spermatozoa can be affected by different compounds usually found in seminal plasma. The following purified substances wee added to washed spermatozoa in physiological concentrations: bradykinin, angiotensin I, II, III, spermine, spermidine, acetylcarnitine, LH and FSH. Sperm motility and velocity were measured by the method of multiple exposure photography after 30 minutes of incubation at 22 degrees C and 37 degrees C including appropriate controls. Bradykinin improved sperm velocity at 22 degrees C. Angiotensin I and II, acetylcarnitine and LH stimulated sperm velocity at 37 degrees C. The latter two substances increased also sperm motility at 37 degrees C. Angiotensin III, spermine, spermidine and FSH showed no effect on sperm motility neither at 22 degrees C nor at 37 degrees C. These observations indicate that distinct physiological compounds found in seminal plasma stimulate directly sperm motility and/or velocity in vitro and support the assumption that the sperm motility stimulating principle of human semen is complex and of multifactorial origin.

Acetylcarnitine↗
PubMedDate not supplied

The effects of consecutive day propofol anesthesia on feline red blood cells.

This study investigated the potential for multiple exposures of propofol to induce oxidative injury, in the form of Heinz body production, to feline red blood cells. Anesthesia was induced in six healthy cats with propofol (6 mg/kg, intravenous [IV]) and maintained for 30 minutes with a propofol infusion (0.20 to 0.30 mg/kg/min, IV). The initial protocol was designed for each cat to receive 10 consecutive days of propofol anesthesia. All cats spontaneously breathed room air. Heart rate, respiratory rate, and indirect blood pressure were measured and recorded before and during anesthesia. Time to complete recovery after each infusion was measured and recorded. Heinz body analysis was performed before and after each day of propofol anesthesia. Based on predetermined criteria for discontinuing daily infusions, the mean number of consecutive days of propofol anesthesia was six and propofol administration did not continue beyond 7 days in any cat. Heart rate, respiratory rate, and indirect blood pressure did not change significantly during propofol anesthesia compared with awake values. Following the third consecutive day of propofol anesthesia, there was a significant increase from baseline in the mean percentage of Heinz bodies. Hemolysis was not detected in any cat. Recovery time significantly increased after the second consecutive day of propofol anesthesia compared with the first day. Five of six cats developed generalized malaise, anorexia, and diarrhea on day 5, 6, or 7, and two cats developed facial edema.(ABSTRACT TRUNCATED AT 250 WORDS)

Anesthesia, Intravenous↗
PubMed2006

Visualization of gunshot residue patterns on dark clothing.

Determination of the muzzle-to-target distance is often a critical factor in criminal and civil investigations involving firearms. However, seeing and recording gunshot residue patterns can be difficult if the victim's clothing is dark and/or bloodstained. Trostle reported the use of infrared film for the detection of burn patterns. However, only after the film is developed are the results visible and multiple exposures at different settings may be needed. The Video Spectral Comparator 2000 (Foster & Freeman Ltd., Evesham, Worcestershire, U.K.) is an imaging instrument routinely used by forensic document examiners. Without use of specialized film could the VSC 2000 (at appropriate instrument settings) quickly, easily, and reliably provide instantaneous viewing, saving, and printing of gunshot residue patterns on dark and/or blood soaked clothing? At muzzle-to-target distances of 6, 12, and 18 in., test fires were made into five different types of dark clothing using eight different handguns of different calibers. Gunshot residues were detected for all eight calibers, and powder burn patterns were seen on dark clothing for all three target distances and calibers except 0.22 long rifle and 0.25 ACP. Bloodstains did not preclude the viewing of these patterns.

Journal Article↗
PubMed1991

Hepatotoxicity induced by the Oriental hornet (Vespa orientalis) venom sac extract.

Experiments were performed to investigate the nature of the in vitro and human liver damage exposed to hornets' acute or repeated stings. The hornet investigated is the one ubiquitous in Israel - Vespa orientalis. Experiments were performed in living cats and rats, after single or multiple exposures to venom-sac extracts (VSE) and in various doses. The injury was demonstrated by the increased levels of enzymes, bile acids and cholesterol in serum. Also measured was Beta-N-acetyl hexosaminidase (BNAH) which probably is the only biochemical indicator available of Kupffer-cell function. This, too, was found increased. Other experiments consisted of perfusion of the isolated, intact, rat liver in situ with measurements of enzyme leakage into perfusate and of bile flow. Another set of experiments involved the effects of VSE on in vitro monolayer tissue culture of rat embryos' livers. We examined damage to organelles and compared the damage produced by intact VSE with that produced by the venom sac extract after treatment by heat or dialysis. Light morphology, special stains, electron microscopy and morphometry were all performed. In the first set of experiments no shock was observed in cats and rats exposed to VSE. The increases in enzymes' activity in serum and liver perfusion fluid were significant. Histochemistry indicated decrease of hepatic glycogen and of cellular succinic dehydrogenase as well as hepatic fat infiltration and an increase of alkaline phosphatase activity in liver cells close to the bile capillaries.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1996

Development of cutaneous tolerance to ultraviolet B during ultraviolet B phototherapy for psoriasis.

During a schedule of multiple exposures to ultraviolet B radiation (UVB, 280-320 nm), skin develops a reduced sensitivity, variously called tolerance, photoadaptation, accommodation or acclimatization. In this study we have investigated the development of tolerance in the normal skin of a group of psoriatic patients during the course of UVB therapy. Tolerance was assessed by phototests carried out on non-lesional skin as frequently as possible throughout the treatment. Maximum tolerance was developed by the group of individuals most sensitive to UVB, which was twice that of the least sensitive group. The minimal perceptible erythema dose (MPE) increased rapidly in the first 2 weeks (220% per week) and reached a plateau by the eighth week of 800% above the baseline MPE dose. For the more sensitive patients there was a further increase in sensitivity (decrease in MPE dose) after the ninth week of continuous treatment. Tolerance to UVB also involves pigmentation in the first few weeks, but in these patients there was no evidence of hyperpigmentation by the end of treatment. While epidermal hyperplasia is most likely to play a leading role in the development of tolerance to UV, there is no reason to expect this protection to decrease under conditions of continuous exposure. Thus, accommodation to ultraviolet radiation (UVR) is not a monotonically increasing process but appears to alter the accepted reactions of human skin to UVR.

Humans↗
PubMed1989

Ultraviolet radiation--induced malignant melanoma in Monodelphis domestica.

Several lines of evidence support the hypothesis that ultraviolet radiation (UVR) is involved in the etiology of cutaneous melanoma in humans. However, progress in understanding the mechanisms involved in induction of melanotic tumors by UVR has been hindered by lack of a suitable animal model. During the course of multiple exposures (3 times/wk for 70 wk) of the South American opossum, Monodelphis domestica, to UVR, we first observed the appearance of areas of dermal melanocytic hyperplasia (MH) on the exposed skin. Post-UVR exposure to photoreactivating light (320-500 nm) suppressed the occurrence of MH. We also observed at 100 weeks from first exposure that 10 of 46 surviving animals had developed melanotic tumors which arose, presumably, from areas of MH. Tumors on three of the 10 animals have been classified as malignant melanomas based on metastasis to lymph nodes. We conclude from these results that UVR can act as a complete carcinogen for melanoma induction and, based on the photoreactivation of MH induction, that DNA damage is involved in melanoma formation.

Animals↗
PubMed2002

A personal-computer-based method to obtain "star-shots" of mechanical and optical isocenters for gantry rotation of linear accelerators.

This work describes a method to obtain "star-shots" of the mechanical and optical isocenters of linear accelerators, similar to the star-shots of radiation isocenters normally obtained using films. In this method a digital camera is connected to a personal computer so that multiply exposed images can be taken at a fixed camera position. A mechanical pointer or a wire aligned along the optical axis can then be imaged by the camera. Multiple exposures at varying gantry angles are then superimposed on a digital image which can be analyzed by the computer to give a high-resolution star-shot. The method provides a convenient way for a linear accelerator quality assurance procedure.

Computer Simulation↗
PubMed2003

Balancing selection at the prion protein gene consistent with prehistoric kurulike epidemics.

Kuru is an acquired prion disease largely restricted to the Fore linguistic group of the Papua New Guinea Highlands, which was transmitted during endocannibalistic feasts. Heterozygosity for a common polymorphism in the human prion protein gene (PRNP) confers relative resistance to prion diseases. Elderly survivors of the kuru epidemic, who had multiple exposures at mortuary feasts, are, in marked contrast to younger unexposed Fore, predominantly PRNP 129 heterozygotes. Kuru imposed strong balancing selection on the Fore, essentially eliminating PRNP 129 homozygotes. Worldwide PRNP haplotype diversity and coding allele frequencies suggest that strong balancing selection at this locus occurred during the evolution of modern humans.

Adult↗
PubMed1983

Colonization of the rabbit small intestine by clinical and environmental isolates of non-O1 Vibrio cholerae and Vibrio mimicus.

We examined the capability of 12 isolates of non-cholera toxin-producing O1 and non-O1 Vibrio cholerae to colonize the small intestine of adult rabbits and cause diarrhea. Using the removable intestinal tie-adult rabbit diarrhea model, we found that eight environmental isolates that showed no or marginal biological activity in other diarrhea models (rabbit ileal loop, infant rabbit, and suckling mouse) appeared to be incapable of attaching to and colonizing, even transiently, the small intestinal mucosa of animals with normal clearance mechanisms. In contrast, three clinical isolates attached, proliferated rapidly, and colonized mucosal surfaces of the entire small intestine within 8 h of challenge. This led to diarrhea with strikingly high rates of mortality compared with that of rabbits given similar challenges doses with strains of O1 V. cholerae that produce cholera toxin and Vibrio mimicus, which produces a toxin similar to cholera toxin. We have further demonstrated that multiple exposures to enteric infection by these strains elicited local and serum antibodies that reacted strongly with cell surface antigens of the homologous strain and showed a high degree of cross-reactivity against the cell surface antigens of the two heterologous strains. The enteric infections appeared to engender protection against subsequent infection as well, as evidenced by reduced incidence of diarrhea and duration of fecal shedding of the challenge organism upon subsequent challenges.

Animals↗
PubMed1999

Targeted disruption of fibronectin-integrin interactions in human gingival fibroblasts by the RI protease of Porphyromonas gingivalis W50.

Cell surface integrins mediate interactions between cells and their extracellular matrix and are frequently exploited by a range of bacterial pathogens to facilitate adherence and/or invasion. In this study we examined the effects of Porphyromonas gingivalis proteases on human gingival fibroblast (HGF) integrins and their fibronectin matrix. Culture supernatant from the virulent strain W50 caused considerably greater loss of the beta1 integrin subunit from HGF in vitro than did that of the beige-pigmented strain W50/BE1. Prior treatment of the W50 culture supernatant with the protease inhibitor Nalpha-p-tosyl-L-lysine chloromethyl ketone (TLCK) blocked its effects on cultured cells, indicating that this process is proteolytically mediated. Purified arginine-specific proteases from P. gingivalis W50 were able to mimic the effects of the whole-culture supernatant on loss of beta1 integrin expression. However purified RI, an alpha/beta heterodimer in which the catalytic chain is associated with an adhesin chain, was 12 times more active than RIA, the catalytic monomer, in causing loss of the alpha5beta1 integrin (fibronectin receptor) from HGF. No effect was observed on the alphaVbeta3 integrin (vitronectin receptor). The sites of action of RI and RIA were investigated in cells exposed to proteases pretreated with TLCK to inactivate the catalytic component. Use of both monoclonal antibody 1A1, which recognizes only the adhesin chain of RI, and a rabbit antibody against P. gingivalis whole cells indicated localization of RI on the fibroblasts in a clear, linear pattern typical of that seen with fibronectin and alpha5beta1 integrin. Exact colocalization of RI with fibronectin and its alpha5beta1 receptor was confirmed by double labeling and multiple-exposure photomicroscopy. In contrast, RIA bound to fibroblasts in a weak, patchy manner, showing only fine linear or granular staining. It is concluded that the adhesin component of RI targets the P. gingivalis arginine-protease to sites of fibronectin deposition on HGF, contributing to the rapid loss of both fibronectin and its main alpha5beta1 integrin receptor. Given the importance of integrin-ligand interactions in fibroblast function, their targeted disruption by RI may represent a novel mechanism of damage in periodontal disease.

Animals↗
PubMed2003

A humoral immune response confers protection against Haemophilus ducreyi infection.

Haemophilus ducreyi is the etiologic agent of the sexually transmitted genital ulcer disease chancroid. Neither naturally occurring chancroid nor experimental infection with H. ducreyi results in protective immunity. Likewise, a single inoculation of H. ducreyi does not protect pigs against subsequent infection. Accordingly, we used the swine model of chancroid infection to examine the impact of multiple inoculations on a host's immune response. After three successive inoculations with H. ducreyi, pigs developed a modestly protective immune response evidenced by the decreased recovery of viable bacteria from lesions. All lesions biopsied 2 days after the first and second inoculations contained viable H. ducreyi cells, yet only 55% of the lesions biopsied 2 days after the third inoculation did. Nearly 90% of the lesions biopsied 7 days after the first inoculation contained viable H. ducreyi cells, but this percentage dropped to only 16% after the third inoculation. Between the first and third inoculations, the average recovery of CFU from lesions decreased approximately 100-fold. The reduced recovery of bacteria corresponded directly with a fivefold increase in H. ducreyi-specific antibody titers and the emergence of bactericidal activity. These immune sera were protective when administered to naïve pigs prior to challenge with H. ducreyi. These data suggest that pigs mount an effective humoral immune response to H. ducreyi after multiple exposures to the organism.

Animals↗
PubMed2001

Exposure of hepatitis C virus (HCV) RNA-positive recipients to HCV RNA-positive blood donors results in rapid predominance of a single donor strain and exclusion and/or suppression of the recipient strain.

We have analyzed three cases of hepatitis C virus (HCV)-infected recipients who received blood from HCV-infected donors. Two recipients were exposed to two different HCV RNA-positive donors, and one was exposed to a single donor. All parental genomes from the actual infecting units of blood and the recipients were defined, and their presence in the follow-up serum samples was determined using sensitive strain-specific assays. The strain from one of the donors was found to predominate in all recipients' serum samples collected throughout the follow-up period of 10 to 30 months. In two recipients exposed to two infected donors, the strain from the second donor was occasionally found at very low level. However, the original recipients' strains were not detected. Our observations show that HCV-infected individuals can be superinfected with different strains, and this event may lead to eradication or suppression of the original infecting strain. Furthermore, our findings demonstrate that simultaneous exposure to multiple HCV strains may result in concomitant infection by more than one strain, although a single strain could rapidly establish its dominance. The results of the present study suggest the existence of competition among infecting HCV strains which determines the ultimate outcome of multiple HCV exposure.

Adult↗
PubMed2003

A live attenuated equine infectious anemia virus proviral vaccine with a modified S2 gene provides protection from detectable infection by intravenous virulent virus challenge of experimentally inoculated horses.

Previous evaluations of inactivated whole-virus and envelope subunit vaccines to equine infectious anemia virus (EIAV) have revealed a broad spectrum of efficacy ranging from highly type-specific protection to severe enhancement of viral replication and disease in experimentally immunized equids. Among experimental animal lentivirus vaccines, immunizations with live attenuated viral strains have proven most effective, but the vaccine efficacy has been shown to be highly dependent on the nature and severity of the vaccine virus attenuation. We describe here for the first time the characterization of an experimental attenuated proviral vaccine, EIAV(UK)deltaS2, based on inactivation of the S2 accessory gene to down regulate in vivo replication without affecting in vitro growth properties. The results of these studies demonstrated that immunization with EIAV(UK)deltaS2 elicited mature virus-specific immune responses by 6 months and that this vaccine immunity provided protection from disease and detectable infection by intravenous challenge with a reference virulent biological clone, EIAV(PV). This level of protection was observed in each of the six experimental horses challenged with the reference virulent EIAV(PV) by using a low-dose multiple-exposure protocol (three administrations of 10 median horse infectious doses [HID(50)], intravenous) designed to mimic field exposures and in all three experimentally immunized ponies challenged intravenously with a single inoculation of 3,000 HID(50). In contrast, naïve equids subjected to the low- or high-dose challenge develop a detectable infection of challenge virus and acute disease within several weeks. Thus, these data demonstrate that the EIAV S2 gene provides an optimal site for modification to achieve the necessary balance between attenuation to suppress virulence and replication potential to sufficiently drive host immune responses to produce vaccine immunity to viral exposure.

Animals↗