PubMed Health⌕ Search

Biomedical subjects

M E Bernstein

Publications and source records attributed to M E Bernstein.

36 records · Page 2Linked to original sources
PubMed1977

Synaptic frequency alteration on rat ventral horn neurons in the first segment proximal to spinal cord hemisection: an ultrastructural statistical study of regenerative capacity.

To study the regenerative capacity of the spinal cord in adult rat, presynaptic boutons were classified as S (spherical vesicles), F (flattened vesicles) and C complexes, and analysed statistically on alpha-motoneuron somata and lamina VII interneurons on the operated side in the first segment rostral to a spinal cord hemisection. Following chloral hydrate anesthesia left spinal cord hemisections were made on twenty adult rats (225 gms) at vertebral level T-2. Animals were prepared for electron microscopy at 7, 14, 30, 45, 60 and 90 DPO and compared with normals. All counts were made on coded material and subjected to statistical analysis. The normal frequency of presynaptic bouton types on alpha-motoneuron somata at 30 DPO. At 45 DPO, massive degeneration with concomitant synaptic remodeling resulted in a return to near normal frequencies of S and F presynaptic boutons. At 60 and 90 DPO a gain in S presynaptic boutons and a concomitant loss in F presynaptic boutons resulted in frequencies different from normal and decreased absolute numbers of presynaptic boutons. The interneuron somata also exhibited alterations over the postoperative period. There was a reversal of frequency of presynaptic boutons at 45 DPO. However unlike on alpha-motoneuron somata the frequency of S and F presynaptic boutons returned to normal at 60 and 90 DPO. The alpha-motoneuron somata appeared to be cyclically and nonselectively reinnervated by ventral horn interneurons over 90 DPO.

Animals↗
PubMed1976

Ventral horn synaptology in the rat.

The synaptology of the normal ventral horn of the rat was studied. Presynaptic boutons were classified as S (Spherical vesicles), F (flattened vesicles), and G (predominance of 700-1200 A granular vesicles). In addition, Cf, Cs, M, and T synaptic complexes were defined and quantitated. Synaptology was studied on alpha-motoneuron somata, alpha-motoneuron primary dendrites, peripheral dendrites and interneuron somata. In addition, organelles were quantified for the pre- and postsynaptic members of the synaptic complex. All counts were made on coded material and these data were analyzed statistically. Motoneuron somata had significantly more (P less than 0.01) F (58%) than S (33%) boutons. This was also the case for the motoneuron primary dendrite (P less than 0.01; F, 61%; S, 37%). The small dendrites had more (P less than 0.05) S (56%) than F (44%) boutons. More Cf bulbs (P less than 0.01) were found on motoneuron somata (9%) than on motoneuron primary dendrites (2%) or interneruon somata (3%). The C complex presynaptic bouton contained spherical (Cs) or flattened (Cf) synaptic vesicles which were attributed to the fixation employed. Cf bulbs were not observed on small dendrites. G bulbs were observed (less than 1%) only on small dendrites M bulbs were not observed on any postsynaptic structure. The boutons of the motoneuron primary dendrites (15% of total afferents) and peripheral dendrites (14% of total afferents) were frequently branched whereas there was significantly (P less than 0.01) less branching of boutons on motoneuron and interneuron somata. Small postsynaptic subsurface cisterns were associated with boutons of both the S and F type on all structures. In addition, these cisterns were observed in motoneuron somata (4%) and interneuron somata (2%) without an accompanying bouton. C postsynaptic organelles were observed in motoneuron somata (3%) and primary dendrites (1%) with an overlying neuroglial cell process and no presynaptic bouton. The synaptology of the rat ventral horn is comparable to that in the cat and monkey. However, M (R) and P bulbs were not observed in the rat. This could be due to the sampling method which indicated that synapses with less than 1% occurrence fall at the level of statistical resolution in quantitative electron microscopy. The presence of postsynaptic specialization usually associated with presynaptic boutons with no presynaptic component may be a reflection of the dynamics of normal bouton renewal in the rat ventral horn.

Animals↗
PubMed1975

Dendrites and neuroglia following hemisection of rat spinal cord: effects of puromycin.

Within 60 to 90 days of spinal cord hemisection or hemisection, Gelfoam, water implantation in the lesion site, ventral horn neurons 0 to 5 mm proximal to the site of lesion form varicosities along the dendrite. The varicosities form on peripheral dendrites at 10 days and progressively involve the entire dendritic shaft by 60 to 90 days. Following spinal cord hemisection and Gelfoam puromycin implantation the neurons in the ventral horn are resistant to varicosity formation. Sixty days after hemisection puromycin-treated neurons form a few varicosities on occasional peripheral dendrites with no further involvement of the dendrite by 90 days postlesion. The neuroglial reaction to hemisection is not altered by puromycin treatment. The correlation of inhibition of protein synthesis and resistance to dendritic varicosity formation is discussed.

Animals↗
PubMedDate not supplied

Sex distribution in sibships according to occupation of parents.

The relationship between sex distribution in sibships and the occupation of parents is examined to determine if nongenetic factors influence sex ratios in families of three or more children. The study is based on data for 2,759 families listed in the U.S. reference book "Who Is Who in the East", as well as additional data from "Who Is Who in American Women". It is found that "parents in aggressive, extrovert occupations are more likely to continue procreation if the first two children are both female rather than male, whereas parents in humanistic or artistic occupations are more likely to continue procreation if the first two children are male rather than female. This relationship between occupation and reproduction decreases the percentage of unisexual sibships." (summary in FRE, ITA)

Americas↗