Effective and ineffective behavior of teachers of nursing as determined by their students.
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Attitude↗
Biomedical subjects
M D Jacobson
Publications and source records attributed to M D Jacobson.
Synthesis and conformation of a dinucleoside monophosphate modified by aniline.
The modified dinucleoside monophosphate, N-[deoxycytidylyl-(3'-5')-guanosin-8-yl]aniline (dCprG-An) has been prepared by the phosphotriester synthesis approach, using suitably blocked derivatives of dCp and N-guanosin-8-ylaniline (rG-An). The latter compound was synthesized by a route that featured nucleophilic displacement by antiline upon an 8-bromoguanosine derivative. A number of attempts to prepare N-(deoxyguanosin-8-yl)aniline (dG-An) by electrophilic substitution, using activated aniline derivatives, failed. Nucleophilic substitution reactions of aniline with 8-bromodeoxyguanosine derivatives afforded only the base, N-guanin-8-ylaniline. The conformation of dCprG-An has been studied by CD, proton magnetic resonance, and minimized potential energy calculations. A flexible molecule with a mixture of conformers is indicated. Base-base stacked states predominate, in contrast to the case of a dimer containing 4-aminobiphenyl bound to the 8-position of guanine, where carcinogen-base stacked states are dominant. The mutagenic and carcinogenic activities of aniline are much less than those of many polycyclic aromatic amines. The diminished stacking ability of the aniline ring, as well as the weak electrophilic reactivity of activated aniline derivatives, may be a cause of this weak biological activity.
Dinucleoside Phosphates↗
Ocular dominance shift in kitten visual cortex caused by imbalance in retinal electrical activity.
Monocular lid suture during the sensitive period early in the life of a kitten disrupts normal development of inputs from the two eyes to the visual cortex, causing a decrease in the fraction of cortical cells responding to the deprived eye. Such an ocular dominance shift has been assumed to depend on patterned visual experience, because no change in cortical physiology is produced by inequalities between the two eyes in retinal illumination or temporally modulated diffuse light stimulation. A higher-level process, involving gating signals from areas outside striate cortex, has been proposed to ensure that sustained changes in synaptic efficacy occur only in response to behaviourally significant visual inputs. To test whether such a process is necessary for ocular dominance plasticity, we treated 4-week-old kittens with visual deprivation and monocular tetrodotoxin (TTX) injections to create an imbalance in the electrical activities of the two retinas in the absence of patterned vision. After 1 week of treatment we determined the ocular dominance distribution of single units in primary visual cortex. In all kittens studied, a significant ocular dominance shift was found. In addition to this physiological change, there was an anatomical change in the lateral geniculate nucleus, where cells were larger in laminae receiving input from the more active eye. Our results indicate that patterned vision is not necessary for visual cortical plasticity, and that an imbalance in spontaneous retinal activity alone can produce a significant ocular dominance shift.
Animals↗
Muscle functional deficits after tourniquet ischemia.
The contractile properties of the rabbit tibialis anterior muscle were studied 48 hours after an ischemic episode induced by pneumatic tourniquet compression of the thigh. Forty animals were divided into five groups, each of which had continuous ischemia of either 1, 2, or 4 hours, or a total of 2 or 4 hours of ischemia interrupted by 10 minutes of reperfusion at 1-hour intervals. Contralateral limbs served as controls. Muscle contractile properties were tested by stimulation of the peroneal nerve distal to the site of tourniquet compression. Peak tetanic tension in the 1-hour group did not differ significantly from controls. In the 2- and 4-hour groups, peak tetanic tensions were 31% and 2% of controls, respectively, and twitch tensions were 25% and 1% of controls, respectively. Hourly reperfusion intervals had no significant effect on maximum tetanic or twitch tension compared with continuous ischemia for either 2 or 4 hours. Clinically significant muscle dysfunction may be induced by 2 or more hours of pneumatic tourniquet application. Hourly reperfusion intervals may not improve skeletal muscle function distal to the tourniquet. However, reperfusion intervals could still affect muscle that is compressed beneath the cuff. Tourniquet-induced contractile deficits may interfere with postoperative functional recovery.
Animals↗