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Biomedical subjects

M Singer

Publications and source records attributed to M Singer.

At least 253 records · Page 14Linked to original sources
PubMed1981

An ultrastructural examination of early ventral root formation in amphibia.

The morphology of early interactions between neural tube and myotome in the amphibian embryo and tail regenerate was examined using the electron microscope. Two types of contacts were observed. At the most primitive level where the myotome was yet unsegmented, multiple adhesive-type contacts linked neural tube and myotome. In newly segmented areas early ventral roots were recognizable as small bundles of one to five axons extending the short distance to the myotome. There was only one bundle per segment and in addition to axons, each bundle always contained one or more primitive glial cell processes which accompanied axons as they left the cord. At points of root exit primitive glial processes appeared to funnel axons into the root. The cytoarchitecture of the cord and the new roots suggested that the primitive glia may play a role in pathfinding for motor axons as they leave the cord and extend toward their targets.

Animals↗
PubMed1981

Scanning electron microscopy of the normal and denervated limb regenerate in the newt, Notophthalmus, including observations on embryonic amphibia limb-bud mesenchyme and blastemas of fish-fin regenerates.

The present work deals with the morphology of normal and denervated early limb regenerates in the newt and compares them with early limb-bud mesenchyme and blastemas of fish-fin regenerates using the three-dimensional properties of the SEM. It shows that blastemal cells are polymorphic, in contrast to those of the stump-cell population, which are fairly homogeneous and from which blastema cells are said to arise by "dedifferentiation." The appearance of cells had not changed by two days following denervation even though previous biochemical studies have detected many changes in metabolism. Longterm denervation (7 days) did result in morphological changes. A comparison between well-known cell types-myoblasts, Schwann cells, osteoblasts observed in vitro, limb-bud mesenchyme and mesenchymatous fin blastema-was carried out in order to suggest explanations for the blastema-cell polymorphism.

Amphibians↗
PubMed1981

The effect of prolactin on the rate of forelimb regeneration in newts exposed to photoperiod extremes.

Four groups of bilaterally amputated newts were exposed to (1) continuous light, LL; (2) continuous light with daily prolactin injections, LL-PRL; (3) total darkness, DD; or (4) total darkness with daily prolactin injections, DD-PRL. The results confirmed that LL animals regenerate their limbs more rapidly than DD. The results also showed that LL-PRL animals do not respond to the exogenous prolactin but that DD-PRL animals do respond and in fact regenerate at a rate which exceeds not only DD but also LL and LL-PRL. The possible synergism between prolactin and photoperiod is discussed.

Animals↗
PubMed1981

Predicting offspring vulnerability to psychopathology from parents' test data.

Interpretation of parents' psychological test data was used to predict vulnerability to psychopathology of male offspring ages 4, 7, and 10. Families were chosen for the study according to the previous psychiatric diagnosis of at least one parent. The prediction of procedure was styled after methods used in previous studies with adolescent and young adult offspring. Vulnerability was measured by a global rating score obtained from the Rochester Adaptive Behavior Inventory, a scale based on behavioral observations of the offspring's behavior. Evaluation of 11 families at each age level resulted in significantly accurate predictions at the 10-year-old level, but less than significantly accurate predictions at the 7- and 4-year-old levels. These findings have important implications for the family development of schizophrenia and related disorders.

Adult↗
PubMed1981

[Epidural morphine for obstetrical pain relief (author's transl)].

Twenty five healthy pregnant women received an epidural injection (at levels varying from T11-T12 to L3-L4) of morphine (2 or 3 mg in 10 ml of saline solution 9 p. thousand) in order to achieve pain relief for delivery. The degree of dilation never exceeded 5 cm at time of injection. Pain level decreased in 22 cases (88 p. cent) but only 16 women (64 p. cent) were fully satisfied. Hypoalgesia begun after 25 minutes and disappeared after 19 hours. No respiratory or haemodynamic changes were noted. On the other hand, the duration of the first stage of labour decreased. The best results are seen when injection is achieved at highest levels, facing spinal cord segments supplying the cervix and the perineum. No newborn showed any sign of respiratory or neurologic depression.

Adult↗
PubMed1980

Structure of a newly isolated variant of Simian virus 40 DNA containing monkey DNA and its similarity to previously isolated variants.

The structure of a newly and independently isolated defective variant of simian virus 40 that contains covalently linked monkey and SV40 DNA sequences is described. This variant, termed 290, has a structure essentially identical with a previously isolated and characterized variant named CVP8/1/P2 (Eco RI res). The structural similarities include the monkey (host) DNA segment that is combined with viral DNA sequences, the particular viral DNA segment that is present, and the arrangement of these within the defective genome. The monkey DNA segment contains sequences derived from both low and high reiteration frequency monkey DNA. The viral sequences include the origin of replication. The separate isolation of essentially identical variants suggests a high level of specificity in the events leading to the formation and amplification of this type of defective genome.

Animals↗
PubMed1980

Effect of cetiedil on erythrocyte sickling: new type of antisickling agent that may affect erythrocyte membranes.

The antisickling effect of cetiedil, alpha-cyclohexyl-3-thiopheneacetic acid 2-(hexahydro-1H-azepin-1-yl)-ethyl ester, has been investigated. The concentration of cetiedil required for 50% inhibition of erythrocyte sickling was about 140 micro M. An antisickling effect was achieved regardless of whether cetiedil was added before or after deoxygenation. The minimal gelling concentration of deoxy Hb S was increased by less than 10% in the presence of 218 micro M cetiedil. The oxygen equilibrium curves of Hb S were not significantly affected by cetiedil. Erythrocytes treated with high concentrations of cetiedil were swollen and became spheroidal. The antisickling effects of cetiedil might be due to an effect on erythrocyte membranes.

Antisickling Agents↗
PubMed1979

Structure of simian virus 40 recombinants that contain both host and viral DNA sequences. I. The structure of variant CVPS/1/P2 (EcoRI res).

The entire nucleotide sequence (1210-base-pair repeating units) of a defective variant of simian virus 40 is presented. Within this variant there are deletions of large portions of the wild type genome and an inversion within the remaining wild type viral sequences. In addition, the defective variant contains DNA sequences derived from the permissive monkey cells in which the virus was propagated. The monkey sequences include a portion that is homologous to sequences within highly repeated monkey DNA (alpha component) as well as portions derived from sequences that are infrequently repeated in the monkey genome. One out of every three to four of the tandem 1210-base-pair repeat units contains in addition, a duplication of a part of the monkey sequences. The sequence information defines the structures of a number of recombinational joints which result from deletions, inversions, duplications, and insertions of host sequences into the viral genome. The data demonstrate that the various recombinational events that resulted in the formation of this defective variant did not depend on extensive homology between recombining segments.

Animals↗
PubMed1979

Structure of simian virus 40 recombinants that contain both host and viral DNA sequences. II. The structure of variant 1103 and its comparison to variant CVPS/1P2 (EcoRI res).

In an effort to characterize sites of recombination between SV40 and monkey DNA, we have determined the primary sequence of a large portion of the SV40 variant, designated 1103. This virus contains DNA sequences derived both from the wild type SV40 genome and from the permissive monkey cell in which the virus was propagated. Further, the monkey sequences included in the defective genome are homologous to both highly repeated monkey DNA (alpha component) and sequences that are infrequently repeated in the monkey genome. The regions of the 1103 genome where DNA sequences were determined include 1) the segments of the variant that surround joints connecting SV40 and monkey sequences, 2) the segment that contains the joint between monkey sequences of high and low reiteration frequency, and 3) the DNA segment of the variant that is homologous to monkey alpha component DNA. Comparison of the data obtained from the sequences analysis of the SV40 variants 1103 and CVP8/1/P2 (EcoRI res) (described in Wakamiya, T., McCutchan, T., Rosenberg, M., and Singer, M. (1979) J. Biol. Chem 254, 3584-3591) reveals certain similarities between the two that may be involved in eukaryotic recombination and defective variant formation.

Animals↗
PubMed1979

Axonal guidance during embryogenesis and regeneration in the spinal cord of the newt: the blueprint hypothesis of neuronal pathway patterning.

In our previous studies on studies on spinal cord regeneration in the adult lizard and the newt, we observed that the radial processes of the regenerating ependyma form between them channels which are subsequently invaded by growing neurites. In the present study we compare embryogenesis of the newt spinal cord with regeneration in the adult. Except for minor differences, we observed that the germinal neuroepithelium of the embryo and larva patterns the longitudinal neural tracts in a similar manner. With these facts in mind we propose the blueprint hypothesis which asserts that inherent in the primitive germinal neuroepithelium and its derivative primitive glia is the pattern of the primary neuronal pathways which is expressed in neurogenesis as formed channels or spaces between the processes of the epithelial cells, the surfaces of which contain trace pathways which the growing neurites follow toward their destination. The trace pathways are envisoned as mechanical-chemical itineraries which the neurities follow according to their individual affinities. The hypothesis is compared to extant theories and the limitations in central nervous regeneration of vertebrates is compared.

Animals↗