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Biomedical subjects

C Hayes

Publications and source records attributed to C Hayes.

At least 145 records · Page 8Linked to original sources
PubMed1985

Surface coil magnetic resonance imaging.

Detection of MR signals with surface coils provides increased signal-to-noise ratio for superficial structures relative to detection by circumferential coils, permitting improved spatial resolution. Different geometries of surface coils can be used for different regions. Coils that are flat or curved to fit body contours are good for general imaging, with a range of coil sizes useful for structures of different size or depth. Solenoidal coils are useful for imaging protruding structures such as breasts, while smaller versions of conventional circumferential coils that can be slipped over limbs are useful for imaging extremities.

Magnetic Resonance Spectroscopy↗
PubMed1984

RK bacterial test for independently measuring chemical toxicity and mutagenicity: short-term forward selection assay.

A short-term bacterial assay system for determining the mutagenic potential of environmental substances was developed and validated. Genotoxic activity was demonstrated for selected substances from 10 categories of chemical agents. The RK test results were obtained with one Escherichia coli assay strain that was transiently exposed to, and then removed from the test substance prior to the selection step for mutant cells. The RK test employs a hitherto unused short-term assay technique for selecting forward mutations in the wild-type selector strain cells. The cells of the selector strain are killed upon shifting to 42 degrees C as a consequence of thermal derepression and subsequent expression of the replication genes from an integrated 10-kilobase fragment of phage lambda. Cells that acquire mutations in the responsible killing genes are detected by their colony-forming ability at 42 degrees C. A substance is determined to be genotoxic if it is capable of increasing the forward mutation frequency for appearance of these mutant cells. Toxicity of the agent is independently evaluated by examining its effect on the viability of the selector strain at 30 degrees C, when the viral replication genes remain repressed. The flexible assay protocol enables determination of the effect of pH on mutagenic activity, the requirement for metabolic activation, and assays of nearly insoluble or highly toxic substances.

Biotransformation↗
PubMed1983

A hypo-osmotic medium to disaggregate tumor cell clumps into viable and clonogenic single cells for the human tumor stem cell clonogenic assay.

A hypo-osmolar medium and tissue processing technique is described which is useful for disaggregation of residual human tumor cell clumps persisting after mechanical or enzymatic treatment of solid tumors and malignant effusions. The addition of the hypo-osmolar procedure to the standard methods for disaggregation increased the viable single cell yield in solid tumors by 47% and in malignant effusions by 67%. In 5 of the 26 solid tumor specimens tested in the human tumor stem cell assay, clonogenic single cells were obtained with the hypo-osmolar procedure, whereas no growth was observed using standard methods. Overall, the success rate for clonogenicity increased from 46% to 65% for the 26 solid tumors, with the major improvement occurring in ovarian cancer. Clonogenicity was obtained in 80% of malignant effusions both by standard methods and the hypo-osmolar techniques. The increased total yield of clonogenic cells obtained with this procedure enhances the opportunity for experimental versatility and in vitro drug testing.

Cell Aggregation↗
PubMed1983

Usefulness of abrin as a positive control for the human tumor clonogenic assay.

A series of approaches were tested in order to develop a simple technique for introducing a routine positive control into the Human Tumor Clonogenic Assay. Of the various techniques tested, the best proved to be the addition of the toxic plant lectin abrin to the culture system. When added to the agar underlayer of the culture system so that the final abrin concentration in culture was 10 micrograms/ml, survival of human tumor colony-forming units (TCFU) was reduced to less than 1% of control in 16/34 (47%) of human tumors, to less than 10% in 33/34 (97%) and to less than 30% in all tumors tested (100%). A clear dose-response relationship to fractional survival was observed for individual tumors tested at multiple dose levels of abrin. When the dosage of abrin was reduced to 1 micrograms/ml, survival of TCFU was reduced to less than 30% in 25/28 (89.2%) of experiments. Inclusion of abrin controls in clonogenic assays thus provides an excellent and reproducible positive control to which cytotoxic effects of a variety of therapeutic agents can be compared.

Abrin↗
PubMed1981

Polycycloidal corrected tomography of the temporomandibular joint.

Historically, radiographic evaluation of the temporomandibular joint has been of limited value. A step-by-step technique which is more correct anatomically is suggested. This technique involves polycycloidal corrected tomography of the temporomandibular joint. Radiographic samples are presented, as well as the results of a random sampling of 300 cases. Fifty-seven percent of the cases showed radiographic changes, and the reasons and limitations of these results are interpreted.

Humans↗
PubMed1979

Control of bacteriophage lambda repressor establishment transcription: kinetics of l-strand transcription from the y-cII-oop-O-P region.

The kinetics of lambda l-strand repressor establishment RNA synthesis were measured from the y-cII region of induced tof- prophage. The activity of the repressor is epistatic to the expression of gene tof coding for the antirepressor (Tof). The activity of Tof, is epistatic to the expression of repressor gene cI transcription from Prm and the expression of repressor establishment transcription from a site 600 to 800 nucleotides upstream from Prm. Three modes of l-strand rex-cI-tof-y-cII-oop transcription occur: (a) Prm promoted cI-rex mRNA synthesis from noninduced prophage, (b) coordinate lit and oop synthesis from induced tof+ prophage and (c) establishment transcription from induced tof- prophage. The synthesis or stability of oop RNA is much reduced from induced tof-, compared with tof+ prophage. The oop transcription from tof- prophage is not coordinate with RNA synthesis from the y-cII interval. The y-cII-(oop) portion of the establishment transcript appears more unstable than the translated downstream copy of genes rex-cI. The initiation of any repressor establishment transcription requires the products of lambda genes cIII, cII, P and Escherichia coli genes dnaB, dnaG, but not actual lambda DNA synthesis. This result demonstrates that common factors, i.e. replication gene products, are required for the initiation of establishment transcription, lambda replication and lit, oop RNA synthesis; and explains why cIII+ cI+ cII+ replication defective phage lysogenize poorly at low multiplicities of infection. The cIII and cII products were shown to act after an earlier replication initiation or activation event. Repressor establishment transcription and repressor mRNA synthesis from Prm (from induced cI- tof-, cIII- cI- tof- or cI- tof- cii- prophage) are amplified by gene dosage. The extent of lysogenization of E. coli by lambda cIII-, cII- or replication minus mutants, defective for initiation of establishment synthesis, is attributed to gene dosage dependent transcription from Prm. The mechanism by which Tof inhibits the initiation of establishment transcription does not appear to require repression of RNA synthesis from PL and PR. RNA synthesis from these promoters is blocked by renaturation of the repressor 5 min after induction, before establishment transcription is detected; however, establishment RNA synthesis measured between 12-13 min after induction, i.e. 7 min after renaturation of the repressor, is only partially reduced.

Coliphages↗
PubMed1979

REM sleep deprivation increases preference for novelty in rats.

As a further test of the hypothesis that REM deprivation decreases fear, the behavior of 40 male rats was measured in a Y-maze adapted to test for preference for novelty. Prior to this test, the animals were exposed for 4 days to one of four treatments, i.e., either a dry environment control, a wet environment control, a 2-day REM deprivation period or a 4-day REM deprivation period. During the test both number of grid crossing in the novel and non-novel arms of the Y-maze and three indices of emotionality were recorded. The results were congruent with data we had reported earlier and offered convincing evidence in support of the hypothesis.

Animals↗
PubMed1979

Movement coding and memory in retarded children.

Three experiments on the coding and retention of movement-generated information were performed on two groups of mildly retarded children varying in MA. The cue to be reproduced in each case was the terminal position of the limb that studies with adults have shown to require central processing activity for maintained performance. In Experiment 1, although the older MA group was superior, both groups showed similar decrements in performance over a 15-second retention interval. In Experiment 2 the procedures were adopted in an attempt to overcome performance deficits. Subjects were allowed to choose (preselect) their own movements voluntarily in addition to performing constrained, experimenter-defined movements. Preselected reproduction was superior to constrained at all three retention intervals (0, 7, and 15 seconds) but was not statistically different among age groups. Also, performance was maintained for both groups over 7 seconds but deteriorated over 15 seconds. These results were replicated in Experiment 3, which also showed that an interpolated motor task designed to block rehearsal processes interfered with reproduction at the 7- and 15-second retention-interval conditions. The findings indicated that mildly retarded children could maintain motor information over brief time periods and also illustrated the important contribution of the planning component in facilitating the coding of motoric information.

Adolescent↗
PubMed1978

Control of lambda repressor prophage and establishment transcription by the product of gene tof.

Control of expression of the bacteriophage lambda (lambda) repressor was studied by measuring repressor transcription in noninduced and derepressed lambda lysogens. Three distinct modes of leftward transcription were observed from cI and the adjacent genes associated with the control of repressor synthesis: The prophage or maintenance mode Prm-cI-rex-ti repressor transcript occurs from repressed lysogens; the oop (Po-oop-to) transcript, and the lit (lit-ti) RNA, from the distal half of gene rex, both occur from induced tof+ prophage; the repressor establishment mode of transcription is observed throughout the rex-cI-tof-y-cII-oop interval between Po and ti from induced tof- prophage. The overall level of establishment mRNA synthesis is partially template dependent. However, the actual initiation step for repressor establishment transcription requires the participation of the lambda cIII, cII products, and also either requires the activity of Escherichia coli replication proteins, or is triggered by a replication initiation event. The cII cIII products do not positively stimulate de novo initiation of establishment transcription, but rather act after an initial replication-dependent step. Initiation of the establishment mode of repressor transcription is totally inhibited by more than 125-fold, in an all or none fashion, by the lambda antirepressor (Tof), the product of gene tof (cro). Since Tof only reduces the in vivo rightward transcription of cII from Pr by about 2-fold, we suggest that Tof inhibits repressor establishment transcription by either uncoupling the replication and cII-cIII dependent events, or by inhibiting the activity rather than the expression of the cIII, cII products. Our results do not fully support either of the present hypotheses that establishment transcription is initiated from the hypothetical Pre promoter in the y-interval, or arises through antitermination of the oop RNA. Since the initiation and control of the establishment mode of repressor transcription parallels the control of lit RNA synthesis, we propose a common mechanism underlies the initiation of these transcripts.

Coliphages↗
PubMed1978

Epidemic kepone poisoning in chemical workers.

From March 1974 through July 1975, 76 (56%) of 133 persons who had worked at a pesticide plant that produced Kepone, a chlorinated hydrocarbon insecticide, contracted a previously unrecognized clinical illness characterized by nervousness, tremor, weight loss, opsoclonus, pleuritic and joint pain, and oligospermia. Illness incidence rates for production workers (64%) were significantly higher than for nonproduction personnel (16%). The mean blood Kepone level for workers with illness was 2.53 ppm and for those without disease 0.60 ppm (p less than 0.001). Blood Kepone levels in current workers (mean, 3.12 ppm) were higher than those in former employees (1.22 ppm). Blood Kepone levels for workers in nearby businesses and for residents of a community within 1.6 km of the plant ranged from undetectable to 32.5 ppb. Illness attributable to Kepone was found in two wives of Kepone workers; there was no apparent association between frequency of symptoms and proximity to the plant in the survey of the community population.

Chemical Industry↗
PubMed1976

Comparison of bacteriological methods for the isolation of group of B Streptococcus from vaginal cultures.

Three bacteriological techniques for the isolation of group B streptococci in vaginal cultures were compared. A selective broth medium (SBM) containing gentamicin and nalidixic acid was more sensitive for the detection of vaginal isolates (28/76, 36.8%) from 76 women enrolled in a venereal disease clinic than was an identical selective plate medium (SPM) (17/76, 25%). Similarly, SBM allowed identification of positive cultures from college women (82/459, 17.9%) significantly more often than direct inoculation of swabs onto nonselective blood agar medium (43/460, 9.4%; chi2 = 42.2, P = less than 0.001). Failure to isolate group B streptococci detected in SBM occurred in 32.1% cultures by SPM and 49.4% of cultures by nonselective agar medium. Multiple serotypes were detected in a single vaginal culture from approximately 5% of the patients studied. These data support the routine use of SBM for the most accurate identification of women vaginally colonized with group B Streptococcus.

Bacteriological Techniques↗