Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “multiple exposures”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 55 records · Page 3Linked to original sources
PubMed1977

Frequency and pattern of radionuclide administration to medical patients in a general hospital.

As part of a drug surveillance programme details of nuclide administration were recorded for 5288 consecutive patients admitted to the medical wards of a large general hospital. Overall use of nuclides amongst this group was found to be low, and multiple exposure to radiation as a result of nuclide administration is not a major hazard when compared to the diagnostic information provided.

Hospitals, General↗
PubMed1979

Factors affecting sperm motility. I. In vitro change in motility with time after ejaculation.

Semen specimens from 33 donors were analyzed intermittently between 1 and 24 hours after ejaculation. Motility was determined objectively by analyzing still-camera photomicrographs taken with the aid of the new multiple exposure photography (MEP) technique, from which the following information was obtained: the percentage of motile spermatozoa, the average velocity and frequency distribution of spermatozoal velocities, and index of motility as well as sperm concentration. From curves drawn for each of the 33 analyzed specimens, these conclusions were drawn: 1. The percentage of motile spermatozoa decreases progressively, beginning 1 hour after ejaculation, at a rate of about 5% to 10%/hour. 2. In the majority of cases, sperm velocity increases for the first 4 hours and then decreases gradually. 3. There is no unique pattern of sperm motility and velocity with time for all specimens, especially during the first 4 hours. However, three typical curves of motility change were found during the first 4 hours: increase in motility, moderate decline in motility, and rapid loss of motility. 4. The frequency distribution of velocities of motile spermatozoa revealed typical normal curves at all times, but these curves became flatter as time elapsed. An explanation for these divergent patterns and the possible role of these findings in some physiologic and clinical problems are discussed.

Ejaculation↗
PubMed1979

Factors affecting sperm motility. II. Human sperm velocity and percentage of motility as influenced by semen dilution.

Spermatozoal velocity and percentage of motility were analyzed objectively with the multiple exposure photography method before and after specimens from fertile and infertile men were diluted in their own seminal plasma or normal saline. No significant change in percentage of motility was found in samples diluted up to 1:6 in both kinds of diluents. However, a significant relative increase (up to 25% of the original velocity) was found when a specimen was diluted with its own seminal plasma, and an even greater increase (up to 37% of the original velocity) was found when it was diluted with saline. Compared with undiluted specimens, there was no delayed effect on spermatozoal motility when semen was diluted with saline after up to 4 hours' incubation time. Contrary to the findings in animal and human semen described by others, there was no deleterious effect on sperm motility with this kind and rate of dilution and duration of time. The assumption that the increase in sperm velocity caused by dilution is not excitatory but is due only to a decrease of seminal fluid viscosity and a reduced number of spermatozoa which interfere with sperm free movement is discussed. We recommend evaluation of spermatozoal motility in diluted specimens in addition to evaluation of the original specimen in any routine semen analysis in order to determine true spermatozoal motility potential under optimal conditions.

Culture Media↗
PubMed1976

Habituation and tonic immobility in domestic chickens.

The habituation of tonic immobility in chickens was examined in six studies. It was shown that repeated elicitation of immobility, and not just handling, was responsible for reduced response durations after multiple exposures to manual restraint. Habituation was a function of the number of stimulus presentations and, in addition, proved surprisingly durable, with diminished reactions using lasting at least 2.5 mo. Strain differences were found in the number of trials required to reach a criteria of habituation, and habituation proceeded faster when immobility termination was self-paced as opposed to experimenter induced. Also, massed trials produced robust sensitization effects rather than diminished responsiveness.

Animals↗
PubMed1977

Heart rate and cardiac phase influences on visual perception.

Twenty-six subjects were tested with a tachistoscopic recognition task while heart rate and several other autonomic indexes were monitored. In Experiment 1, heart rate was employed as an independent variable, and stimulus presentation was contingent upon the presence of individually determined low, middle, and high heart rates. The results indicated that low heart rate facilitated performance especially for stimuli presented at the fastest exposure. In Experiment 2, stimulus presentation was dependent upon cardiac phase. The findings indicated that stimulus recognition was enhanced during the cardiac P wave, but the effect was apparent only during the fastest exposure. Multiple regression analyses of the individual subject's data during both experiments indicated that highly idiosyncratic patterns of physiological responses predicted perceptual performance. The results were interpreted as being consistent with the formulations of the Laceys and also suggested that cerebral perfusion be considered as a relevant determinant of behavior.

Adult↗
PubMed1975

Tumor induction by carcinogenic agents in aquarium fish.

The effects of nine carcinogens on 1,220 guppies [Poecilea reticulata (Lebistes reticulatus)] and 40 zebra fish (Danio rerio) were studied. Multiple exposure techniques included skin application, im and ip injections, feeding, implantation in pellets, and dissolving of the compound in the aquarium water. 7-12-Dimethylbenz[a]anthracene, 3-methylcholanthrene, and benzidine produced no tumors in the fish. N-2-Fluorenylacetamide, omicron-aminoazotoluene, 4-dimethylaminoazobenzene, diethylnitrosamine, and dimethylnitrosamine induced tumors in the livers of some of the fish. These neoplasms included cholangiomas, hepatoadenomas, cholangiocarcinomas, and hepatocellular cancers. Nitrosomorpholine caused not only hepatic tumors in guppies and zebra fish but also intestinal adenocarcinomas and poorly differentiated connective-tissue lesions in the abdominal cavities of zebra fish. Experimental induction of tumors in aquarium fish offers wide possibilities for comparative cancer research. Fish are a suitable model for the testing of compounds for carcinogenic activity and for the screening of environmental carcinogens.

2-Acetylaminofluorene↗
PubMed1978

Effect of reovirus infection on pulmonary tumor response to urethan in strain A mice.

The effect of reovirus type 3 infection on the pulmonary adenoma response to urethan in strain A mice was examined. Urethan carcinogenesis in this system was suppressed from 30 to 60% when mice were exposed to reovirus either 6 days before, on the same day as, or 14 days after urethan administration. These findings suggested that reovirus infection interfered with the progression of urethan-induced pulmonary adenoma rather than the induction of lung tumors by urethan. When mice received multiple exposures to reovirus, the lung tumor response was enhanced. These findings indicated that reovirus infection in particular and virus infection in general may play an important role in the carcinogenic response to environmental chemicals.

Adenoma↗
PubMed1975

Effect of training on the use of weight-bearing orthoses.

Weight-bearing orthoses have been disigned with the primary goal of reducing or eliminating weight bearing in skeletal structures. In evaluating various designs and adjustments of these orthoses, we found that the training of the subject in the use of his orthosis was one of the most significant factors in controlling weight bearing. Subjects fitted with instrumented ischial weight-bearing and patellar-tendon-bearing orthoses walked over a force plate which measured forces imparted to the floor. The force data from the orthoses and force plate were computer-processed with single frame, multiple exposure photographic data to provide plots of axial loading in the orthosis and total axial loading imparted to the floor during the duration of the stance phase. The difference between these two forces represents the load carried by the skeletal system. Measurements were made first with subjects who had no specific instructions about the use of their orthoses. The subjects were then instructed how to use their orthoses more efficiently. In all cases, the effect of training produced a 30 to 50 percent increase in loading borne through the orthosis.

Biomechanical Phenomena↗
PubMed1975

Elbow Arthrography with the Application of Tomography.

The intra-articular structure of the elbow joint was studied in 18 patients with double contrast arthrography and tomography. All tomographic examinations were made with the hypocycloid motion. The authors feel that the disadvantages of the method, i.e., getting access to tomographic equipment, the 30 to 45 minutes required to complete the examination, and the radiation from multiple exposures needed for tomographic sections are obviated by the results: the arthrographic findings were confirmed in all 7 patients who later underwent surgery.

Adolescent↗
PubMed1977

Asymmetric waveforms in echinoderm sperm flagella.

1.Dark-field, multiple-exposure photographs of live spermatozoa of a number of echinoderms were analysed. 2. Bends develop at the base in pairs, as they do in flagella with symmetrical waveforms. However, the angles of these bends do not cancel, so that microtubular sliding-of up to over 50% of that associated with bend propagation-is transferred distally. This sliding implies that (a) microtubules are not rigidly cross-linked within straight regions, and (b) bends can propagate normally in spite of appreciable extrinsic microtubular sliding. 3. Both the sperm head and the asymmetry of the waveform appear to affect the swim path of a spermatozoon.

Animals↗
PubMed1975

Halothane-related hepatitis. A clinical study of twenty-six cases.

Twenty-six patients are described who had otherwise unexplained hepatitis after halothane anaesthesia. Twenty-four (92 per cent) had multiple exposures, and 11 (42 per cent) died. In eight patients a characteristic pattern of delayed postoperative pyrexia has been found. Obesity was common, but the clinical features and complications were those of any severe hepatitis. Obesity, early onset of jaundice after anaesthesia, and low thrombotest, were associated with a fatal outcome. None of those who were followed up after recovery developed clinical or biochemical evidence of chronic liver disease. The differential diagnosis of postoperative jaundice is discussed, and it is shown that halothane patients with hepatic encephalopathy are significantly older (25.4 plus or minus 11.6 years) than those referred to this unit with viral hepatitis of equal severity (34.1 plus or minus 16.4 years). Unexplained jaundice or delayed pyrexia after a previous administration of halothane should be a contraindication to its further use.

Adult↗
PubMed1976

Myiasis due to Cordylobia anthropophaga in Zambia.

Dermal or subdermal myiasis due to larvae of the African tumbu fly Cordylobia anthropophaga is described from Zambia for the first time. Differential diagnosis from the closely allied C. rodhaini is considered. A patient presenting with the lesion on the penis is described. Multiple infection with different developmental stages is discussed in relation to multiple exposure or immunity. Many cases of myiasis may not reach the attention of medical personnel because of the tendency of the mature larvae to migrate out of the lesion which subsequently heals; traditional healers, to whom the condition has been known for long, also successfully extract the larvae.

Adolescent↗
PubMed1978

Distribution of alpha-fetoprotein- and albumin-containing cells in the livers of Fischer rats fed four cycles of N-2-fluorenylacetamide.

Immunofluorescent localization of alpha-fetoprotein (AFP)- and albumin-containing cells was determined in the livers of Fischer rats fed 0.05% N-2-acetylfluorenamide for four 2-weeks-on, 1-week-off cycles. After this exposure multiple changes in the liver include over 1000 neoplastic nodules/liver, as well as extensive production of so-called oval cells and focal zones of atypical hepatocellular hyperplasia. Approximately 1% of the oval cells contain AFP, and about half of the zones of atypical hyperplasia include cells that contain AFP, but none of the neoplastic nodules or normal hepatocytes have any AFP-containing cells. Since up to 60% of the hepatocellular carcinomas developing from this regimen will predictably produce AFP, it is tentatively concluded that hepatocellular carcinoma may arise not only from "premalignant" neoplastic nodules but also from oval cells or the atpyical differentiation of hepatocytes.

2-Acetylaminofluorene↗
PubMed1977

Surgical repositioning of the medial collateral ligament. An anatomical and mechanical analysis.

Analytical techniques using multiple-exposure roentgenograms were employed to investigate surgical repositioning of either the femoral or the tibial attachment of the medial collateral ligament. The motion of the femoral attachment of the ligament with respect to the tibial attachment was used to compute the changes in length of the borders of the ligament for normal knees and for knees with repositioned attachments. The results support the conclusion that when advancement of the medial collateral ligament is utilized in the treatment of medial instability, optimization is accomplished by distal and anterior advancement with the knee in 30 degrees of flexion. Femoral displacement (proximal realignment) or tibial displacement at knee-flexion angles greater than 45 degrees is not recommended.

Biomechanical Phenomena↗
PubMed1978

Another possible precipitating factor in multiple sclerosis: the exposure to organic solvents.

Recent clinical observations seem to indicate that a possible correlation may exist between the appearance of inflammatory diseases of the nervous system and exposure to organic solvents. In certain cases the patients could not be distinguished, either from the clinical or laboratory point of view, from typical cases of multiple sclerosis. These observations raise the problem of a possible action of organic solvents on the immunological responses, already described in different pathological conditions as a further possible precipitating factor in MS.

Adult↗
PubMed1978

The urinary melanogen cysteinyldopa in melanoma and in suntanning: Australian experience.

Determination of urine cysteinyldopa excretion is the most sensitive chemical test for the detection of melanoma metastases and has been successfully applied during the Scandinavian winter, when sun irradiation is low. The value of this determination, under Australian conditions of greater sun irradiation, has been assessed by comparing the cysteinyldopa excretion of patients with that of normal subjects exposed to sunlight. Cysteinyldopa is an intermediate in the biosynthesis of the red-brown phaeomelanin. Of 20 patients without known secondary melanoma, the cysteinyldopa concentration of "spot" urines ranged from 0 to 190 (mean 48) microgram/ml; of six known to have local metastases, 0 to 80 (mean 19) microgram/ml; and of four known to have extensive metastases 80 to 1350 (mean 330) microgram/ml. The effect of sun irradiation alone was assessed in nine healthy subjects followed one to 11 weeks before and after recorded periods of sun exposure. The cysteinyldopa concentrations of 24-hour urines ranged from 40 to 3100 microgram/ml. Increases occurred three to 10 days following sun exposure and were greatest following multiple small exposures in an individual with "Celtic" complexion. It is concluded that measurement of cysteinyldopa concentration would be of value in the follow-up of melanoma patients in Australia only if patients could be persuaded to live under conditions free of all direct sun-irradiation.

Adolescent↗
PubMed1975

A syndrome of multiple congenital anomalies associated with teratogenic exposure.

A study of 19 patients with multiple congenital anomalies described by the acronym VACTERL (Vertebral, Anal, Cardiac, Tracheoesophageal, Renal, and Limb) revealed exposure at the vulnerable period of embryogenesis to a progestogen/estrogen compound or a progestogen alone in 13 patients. These hormones were taken as a "pregnancy test," and for a variety of other reasons. Comparison of VACTERL patients with paired and matched controls, one group with chromosomal anomalies (other than Down syndrome) and another group with functional murmurs, revealed a significant difference with respect to exposure to hormonal contraceptives. The multiple anomalies of skeletal, cardiovascular, and gastrointestinal structures recapitulate the systems involved in the thalidomide syndrome, but present a variation of the pattern. Until more definitive data are available it would be prudent to emphasize the need to verify the absence of pregnancy before initiation of oral contraception and to discontinue hormonal agents as tests for pregnancy.

Abnormalities, Drug-Induced↗