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Biomedical subjects

M Jacobson

Publications and source records attributed to M Jacobson.

At least 127 records · Page 7Linked to original sources
PubMed1983

Diabetic complications in lens and nerve and their prevention by sulindac or sorbinil: two novel aldose reductase inhibitors.

Sorbitol, resulting from glucose metabolism through aldose reductase, may play a role in diabetic complications such as cataracts, neuropathy, and vasculopathy. Sulindac (Clinoril) and sorbinil, two inhibitors of aldose reductase, decreased sorbitol formation in cataract or nerve tissue incubated in high glucose TC-199 media. Sulindac, a widely used anti-rheumatic drug, may have clinical applications in preventing diabetic complications.

Aldehyde Reductase↗
PubMed1983

Clonal organization of the central nervous system of the frog. III. Clones stemming from individual blastomeres of the 128-, 256-, and 512-cell stages.

Horseradish peroxidase injected into individual blastomeres of 128-, 256-, and 512-cell embyros of Xenopus laevis was identified in cells of the central nervous system (CNS) at early to middle larval stages. Labeled cells were dispersed, mingled with unlabeled cells. Four boundaries in the CNS could be defined by the behavior of clones of labeled cells: in the transverse plane at the level of the isthmus; in the horizontal plane between dorsal and ventral regions extending the entire length of the CNS; in the dorsal midline extending the entire length; and in the ventral midline of rhombencephalon and spinal cord but absent more rostrally. Cells injected with HRP at the 512-cell stage produced clones that, with rare exceptions, did not cross any boundary, whereas labeled clones initiated at earlier stages frequently crossed boundaries. Axons and dendrites were not restricted by these boundaries. These boundaries subdivided the CNS into seven compartments, each of which was occupied exclusively by the descendants of a group of 14 to 26 blastomeres in the 512-cell embryo. These groups of blastomeres formed a bilaterally symmetrical pattern composed of a single anterior median group straddling the dorsal midline near the animal pole and three groups on each side. Because cells mingled in each compartment but not across compartmental boundaries, there was a one-to-one relationship between individual blastomeres and CNS compartments but one-many and many-one relationships between individual blastomeres and neuroanatomical subdivisions smaller than a compartment. There was no constant relationship between phenotypes of nerve cells and their ancestry from individual blastomeres of the 512-cell or earlier stages.

Animals↗
PubMed1983

Compartmental relationships between anuran primary spinal motoneurons and somitic muscle fibers that they first innervate.

The compartmental and clonal relationships between primary motoneurons and the myotubes they innervate have been studied in Xenopus laevis embryos by initiating clones at blastula stages (32 to 512 cells) with intracellular injections of horseradish peroxidase (HRP). Primary motoneurons and ventral myotome belong to the posterior-ventral compartment, whereas sensory neurons and dorsal myotome belong to the posterior-dorsal compartment (Jacobson, M. (1983) J. Neurosci. 3: 1019-1038). The pathways of HRP-labeled primary motor axons, which pioneer the peripheral pathway to the adjacent myotome beginning at stage 21/22, were traced. Within the spinal cord, the axons remained in the posterior-ventral compartment. Upon leaving the cord they were confronted with both dorsal and ventral myotome; they remained almost exclusively in the ventral myotome. At late embryonic stages (40/42) primary motoneurons could be retrogradely labeled by applying HRP to the dorsal myotome, indicating that their axons or a branch had crossed the compartmental boundary. The primary motor axon also displayed a highly significant preferred association with clonally related myotubes within the ventral myotome. Axon growth only in the compartmentally related myotome and preferred association with clonally related myotubes suggest that the guidance of pioneer axons in the periphery may be based upon factors derived from common ancestry and lineage.

Animals↗
PubMed1981

Clonal organization of the central nervous system of the frog. II. Clones stemming from individual blastomeres of the 32- and 64-cell stages.

Horseradish peroxidase injected into individual blastomeres of 32- and 64-cell embryos of Xenopus laevis was identified in cells of the central nervous system (CNS) at larval stages 31 to 39. The CNS received contributions from 24 blastomeres of the 32-cell stage and 38 blastomeres of the 64-cell stage. The region of CNS in which all of the labeled descendants of a single blastomere were dispersed is called a clonal domain. Mingling of labeled and unlabeled cells always occurred in a clonal domain, but boundaries were seen between such a labeled region and completely unlabeled regions. These boundaries occurred at various places in the CNS but were most frequently seen in the transverse plane at the level of the isthmus between mesencephalon and rhombencephalon and in the horizontal plane between dorsal and ventral regions of the CNS. When the maternal clonal domain was partitioned between the descendants of the daughter cells, the partitioning occurred only at one or both of those boundaries. The constant relationship between the position of each of the initially labeled blastomeres and the final spatial distribution of the labeled descendants in the CNS provided a detailed fate map of the main regions of the CNS in the 32- and 64-cell embryo.

Animals↗
PubMed1981

Rohon-Beard neuron origin from blastomeres of the 16-cell frog embryo.

Clonal origins of Rohon-Beard neurons in Xenopus were determined quantitatively by injecting horseradish peroxidase into individual blastomeres at the 16-cell stage and later counting labeled and unlabeled Rohon-Beard neurons. Two different patterns of cleavage were selected. In pattern X, all Rohon-Beard neurons originated from three blastomeres (V1.1, V1.2, and V2.2) on each side; in pattern Y, all Rohon Beard neurons originated from two blastomeres (V1.2 and V2.2) on each side. Counts of Rohon-Beard neurons at larval stages 32 to 34 showed that 96 to 100% (mean 99%) originated from blastomeres on the same side; of these, 68 to 90% (mean 75%) descended from V1.2, 20 to 31% (mean 24%) descended from V2.2, 0 to 7% descended from V1.1. The significance of the regionally restricted origin of Rohon-Beard neurons is discussed.

Animals↗
PubMed1981

Rohon-Beard neurons arise from a substitute ancestral cell after removal of the cell from which they normally arise in the 16-cell frog embryo.

In 16-cell Xenopus embryos, horseradish peroxidase (HRP) was injected into blastomere D1.2 on one side. No Rohon-Beard neurons originated from D1.2 in either of the two patterns of cleavage that were studied (Jacobson, M. (1981) J. Neurosci. 1: 918-922). In other embryos, after injection of HRP into D1.2, the neighboring ventral blastomere V1.2, from which 68 to 90% of Rohon-Beard neurons normally originate, was removed. In the cases that developed normally to larval stages 32 to 34, the number and sizes of Rohon-Beard neurons were normal, but 14.9 to 73.9% of Rohon-Beard neurons were labeled, showing that they originated from the injected blastomere D1.2. Labeling also occurred in cells of the spinal dorsal root ganglia that normally descend from V1.2 but not from D1.2. This proves that individual blastomeres at the 16-cell stage are not committed to form specific types of neurons or restricted parts of the central nervous system.

Animals↗
PubMed1980

Transsynaptic labeling of neurons in the optic tectum of xenopus after intraocular [3H]proline injection.

Quantitative assays of labeling patterns in the optic tectum of the frog Xenopus after intraocular [3H]proline injection have been made by light and electron microscopy. Peaks in grain density were seen in layers 9, 8 and 6 of the optic tectum contralateral to the injected eye. This label persisted with little diminution for up to 50 days after eye injection. Electron microscopic autoradiography showed that silver grains in layers 9 and 8 were mainly located on optic nerve terminals and their postsynaptic structures. A considerable number of neuron somata in layer 6 were labelled. Label in layer 7 was concentrated over vertically oriented dendrites of neurons in layer 6 and deeper layers. It is concluded that radioactive labeled material was transported transsynaptically from optic nerve terminals synapsing on dendrites in layers 8 and 9 and that labeled material was transported in those dendrites to their cell bodies mainly located in layer 6.

Animals↗
PubMed1979

Patterns of cell proliferation in the retina of the clawed frog during development.

Quantitative assays of the spatial pattern of cell production in the developing retina of Xenopus have been made using 3H-thymidine labelling and colcemid blockade of mitosis. Reconstructions were made from serial sections showing the position of every mitotic figure in the retina. After stage 54 the number of mitotic figures decreases at the dorsal margin of the retina and increases at the ventral margin. The ventral:dorsal ratio of mitoses reaches 10:1 by metamorphosis. Density of mitotic figures is maximum at the point of entry of the ophthalmic vessels at the ventral margin. In spite of asymmetrical production of retinal cells the cell density remains constant throughout the retina, probably as a result of displacement of retinal cells dorsally to compensate for the relatively greater proliferation ventrally. It is also proposed that the asymmetrical retinal growth serves to maintain the relationship between each point in visual space and corresponding points in the two retinae as the eyes are displaced dorsally on the head during metamorphosis.

Animals↗
PubMed1979

Influences of thyroxine on cell proliferation in the retina of the clawed frog at different ages.

The change in spatial pattern of retinal cell production that occurs after midlarvae stages in Xenopus is shown to occur because of a greater proliferative response to thyroxine in the ventral than in the dorsal margin of the retina. The asymmetry of retinal cell production is not caused by a dorsoventral difference in the duration of the mitotic cycle. It is concluded that the asymmetry is due to differences in the number of proliferative cells in different parts of the retinal margin.

Age Factors↗
PubMed1979

Patterns of cell proliferation in the developing retina of the clawed frog in relation to blood supply and position of the choroidal fissure.

The pattern of retinal vasculative is described and the position at which cell proliferation at the ventral retinal margin is maximal was shown to be at the point of entry of the ventral blood vessels. To test whether there is a causal relation between retinal blood supply and retinal cell production, surgical inversion of the eye, transplantations and excisions of retina were done to change the pattern of retinal vasculature. The growth pattern of inverted eyes was normal with respect to the internal axes of the eyes. After excision of part of the retina or after fusion of retinal fragments to form compound eyes, the pattern of retinal cell proliferation was not correlated with the distribution of retinal blood vessels, but was correlated with the position(s) of the choroidal fissure(s).

Animals↗