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Biomedical subjects

D Cohen

Publications and source records attributed to D Cohen.

At least 775 records · Page 43Linked to original sources
PubMed1972

Magnetoencephalography: detection of the brain's electrical activity with a superconducting magnetometer.

Measurements of the brain's magnetic field, called magnetoencephalograms (MEG's), have been taken with a superconducting magnetometer in a heavily shielded room. This magnetometer has been adjusted to a much higher sensitivity than was previously attainable, and as a result MEG's can, for the first time, be taken directly, without noise averaging. MEG's are shown, simultaneously with the electroencephalogram (EEG), of the alpha rhythm of a normal subject and of the slow waves from an abnormal subject. The normal MEG shows the alpha rhythm, as does the EEG, when the subject's eyes are closed; however, this MEG also shows that higher detector sensitivity, by a factor of 3, would be necessary in order to clearly show the smaller brain events when the eyes are open. The abnormal MEG, including a measurenment of the direct-current component, suggests that the MEG may yield some information which is new and different from that provided by the EEG.

Brain↗
PubMed1972

Thymidine labelling studies in a transmissible venereal tumour of the dog.

The cell population kinetics of the transmissible venereal tumour of the dog was studied at two different stages of tumour growth using the labelled mitoses technique. At the first stage the tumours were growing with a doubling time of about 4 days; at the second stage their growth rate was limited, probably by an immune reaction on the part of the host, to a doubling time greater than 20 days.Labelling of the tumour cells was found to be extremely heterogeneous throughout the tumour. Mitotic figures, however, were present in well labelled as well as in poorly labelled fields, suggesting that thymidine did not reach all regions of the tumour nodules. The data were therefore analysed assuming that the cells in well labelled areas were representative of the total cell population in the neoplasm. The timing of the cell cycle was found to be similar in the rapidly growing tumours and in those growing more slowly. It is concluded that the slowing of growth was due to a considerable increase in the rate of cell loss as a result of the immune reaction.

Animals↗
PubMed1972

Epidemiological studies of A-Hong Kong-68 virus infection in dogs.

Experimental inoculation of dogs with the A/Hong Kong/68 influenzavirus resulted in subclinical infection. The virus was readily passed to contacts in the same cage when the latter were exposed in the same inoculation room 24 hours after experimental infection. Removing the site of contact to a noncontaminated room or delaying contact until 48 hours after experimental inoculation greatly reduced the possibility of infection in contact animals. A survey of 271 canine serum samples obtained after a human epidemic from different geographical areas of the USA and the United Kingdom showed that 5.9% of the samples were positive; no positive reactions were found among 111 pre-epidemic samples. These studies demonstrated the laboratory and natural susceptibility of dogs to the Hong Kong variant and suggest the possible role of dogs in the epidemiology of human influenza.

Animals↗
PubMed1971

Magnetocardiography of direct currents: S-T segment and baseline shifts during experimental myocardial infarction.

Magnetocardiograms with a bandwidth of 0 to 40 hertz were recorded from intact dogs undergoing myocardial infarction. This was done with a superconducting magnetometer in a magnetically shielded room. The purpose was to look for the steady currents of injury from the heart which supposedly produce much of the S-T segment shifts during infarction. These heart currents cannot be measured with surface electrodes because of direct-current interference from other sources, such as from the contact potential between electrode and skin. The magnetocardiograms showed both S-T segment shifts and direct currents as a result of infarction. However, they also showed that the S-T segment shifts were not produced by the direct currents. It is unlikely that these direct currents originated from the infarcted area, and their exact origin is not yet known.

Animals↗
PubMed1971

Automation of a hemagglutination-inhibition test for parainfluenza 3 antibodies in bovine sera.

An automated hemagglutination-inhibition (HI) test for the "shipping fever" strain (SF-4) of parainfluenza 3 antibody in bovine sera was developed and compared to manual tube and microtiter test procedures. The automated system operating at 60 samples per hr provided the most test results per specified time period, and the manual tube test provided the least. The manual microtiter test and the automated system at 40 samples per hr, falling between the two above procedures, were comparable in the number of sera that could be titrated in 1 day by one technician. There was little difference between automated and manual test reproducibility when measured at the twofold titer one-dilution difference level. However, the automated system titrated a higher number of sera at the same titer on repeat runs than either of the manual test procedures. The automated one-quartile difference reproducibility (each twofold dilution subdivided into 4 units-"quartiles") was equal to the manual test one-dilution difference reproducibility. The standard deviation of the per cent variation from the mean of paired serum titers for 40-sample-per-hr runs ranged from +/-3.49 to +/-5.36%. The manual and automated systems were of comparable sensitivity in their detection of negative sera.

Animals↗