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Biomedical subjects

L Fedina

Publications and source records attributed to L Fedina.

31 records · Page 2Linked to original sources
PubMed1971

Spatial synaptic distribution of recurrent and group Ia inhibitory systems in cat spinal motoneurones.

1. The reversal potentials of several types of inhibitory post-synaptic potentials (IPSPs) have been studied in cat spinal motoneurones with and without modification of intracellular chloride ion (Cl(-)) concentration. Single barrel intracellular micropipette electrodes have been used.2. When studied with potassium citrate filled micropipettes, the reversal potential for IPSPs evoked by stimulation of antagonist group Ia afferents is the same as that for recurrent IPSPs evoked by antidromic stimulation of motoneurone axon collaterals, confirming earlier observations (Araki, Ito & Oscarsson, 1961; Coombs, Eccles & Fatt, 1955).3. Studied with potassium chloride filled micropipettes. the reversal potential for the group Ia IPSP was found to be different from that for the recurrent IPSP when the amount of Cl(-) diffusing or iontophoretically injected into the motoneurone was small. The amount of difference in reversal potential varied from cell to cell but when present the group Ia IPSP reversed to a depolarizing potential more readily than the recurrent IPSP in all cases.4. Interaction between recurrent IPSPs and monosynaptic excitatory post-synaptic potentials (EPSPs) was also studied and the amount of non-linearity of potential summation was measured.5. The results are consistent with the hypothesis that the terminations of Renshaw cells responsible for the recurrent IPSP are located largely on the proximal dendrites of motoneurones, while the terminations of the interneurones generating the group Ia IPSP appear to be closer to or on the cell somata.

Animals↗
PubMedDate not supplied

In vitro assessment of MR relaxation properties of pituitary adenomas.

Proton magnetic relaxation times (T1 and T2) and bound water content were measured in vitro in pituitary adenomas from 15 patients using 90 MHz radiofrequency excitation. These data were compared with those measured in normal pituitary glands obtained from four cats and seven fresh human cadavers. The T1 and T2 measured at 24 degrees C in the tumors (mean +/- SD: 1,170 +/- 80 and 123 +/- 35 ms, respectively) were significantly higher than those of cadaver pituitary (830 +/- 200 and 76 +/- 12 ms) and cat pituitary gland (790 +/- 120 and 69 +/- 10 ms). Although the absolute values were lower, similar differences were present in T1 measured at 4 degrees C. Two-dimensional T2 versus T1 plot was particularly helpful in distinguishing tumor from the normal gland. When tumors were grouped according to density on CT, histology or previous treatment (e.g., irradiation or bromocriptine), there were no significant differences in T1 values between the groups. Bound water content was not found to correlate with T1 or T2 values. We concluded that pituitary adenomas can be distinguished from normal pituitary glands by their different relaxation properties when measured at high frequency in vitro MR.

Adenoma↗