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M Jacobson

Publications and source records attributed to M Jacobson.

At least 109 records · Page 6Linked to original sources
PubMed1986

Neurites show pathway specificity but lack directional specificity or predetermined lengths in Xenopus embryos.

The earliest outgrowth of nerve fibers from identified spinal neurons labeled with horseradish peroxidase (HRP) was traced along surgically rearranged pathways in the central nervous system (CNS) of Xenopus embryos. Parts of the CNS were misaligned or inverted rostrocaudally by grafting a segment of labeled spinal cord in place of the same or different spinal cord segment of an unlabeled embryo or by joining two rostral half embryos (head-to-head) or two caudal half embryos (tail-to-tail), one half of which was derived from a labeled embryo in each combination. Donor embryos were labeled by injection of HRP into a selected blastomere at the 16- or 32-cell stage. Host embryos were unlabeled. Grafts from labeled donors to unlabeled host embryos were made at early neural tube stages before outgrowth of any nerve fibers had started (Jacobson and Huang, 1985). Routes taken by labeled nerve fibers growing into unlabeled CNS were observed at later stages, and the rates of nerve fiber elongation were calculated. Labeled nerve fibers were normal in appearance, and elongated without branching, at normal rates (22-71 micron/h). In head-to-head and tail-to-tail embryos and in embryos with inverted spinal cord grafts, nerve fibers continued elongating without branching in the direction opposite to normal in the CNS. Many fibers reached lengths that were far greater than normal. No reorientation of such maldirected nerve fibers was seen. These results indicate that nerve fiber elongation is not guided by axially polarized pathway cues or markers and that nerve fibers do not grow to predetermined lengths. However, neurites preferred to grow along stereotyped nerve fiber pathways even when forced to grow in the wrong direction or when confronted with nonneural tissue.

Animals↗
PubMed1986

Induction of neural cell adhesion molecule (NCAM) in Xenopus embryos.

Using a classical neural induction protocol (H. Spemann and H. Mangold (1924). Roux' Arch. Entwicklungsmech. Org. 123, 389-517), it has been demonstrated that the sustained presence of NCAM in Xenopus embryos, as detected by immunohistochemistry, was confined to the experimentally induced nervous system and the primary host nervous system. Furthermore, in vitro NCAM expression by dorsal blastopore lip and animal pole tissue was detected only when the two tissues were cultured in contact. These and other results show that readily detected and sustained levels of NCAM expression in Xenopus can be used as a marker for neural tissue and an early positive indicator that neural induction has occurred. They suggest that the observed levels of NCAM are a consequence of and not a prerequisite for induction. Using NCAM expression in vitro to determine the minimum time necessary for this induction to occur in vivo, it was found that NCAM was first detected in cultured animal pole that had been removed at stage 10.75 or later. Thus, an inductive step necessary and sufficient for stimulation of NCAM expression in animal pole tissues had not occurred or was reversible prior to the first 2 to 2.5 hr of gastrulation.

Age Factors↗
PubMed1986

Ontogenesis of microtubule-associated protein 2 (MAP2) in embryonic mouse cortex.

The developing neocortex in mice from embryonic day 13 (E13) until birth (E19) was immunoreacted with a monoclonal antibody for microtubule-associated protein 2 (MAP2) that is highly specific for neuronal somata and dendrites. In E13 neocortex there was no detectable MAP2 immunoreactivity on tissue sections or on gel blots. From E14 to birth the MAP2 immunoreactivity was present in both tissue sections and immunoblots of homogenized cortex. In the neocortex the staining pattern was lamina-specific. The molecular layer and the cortical subplate contained the most dense staining of dendrites and cell somata. The cortical plate showed weak to moderate staining at these ages while the intermediate and ventricular zones were not stained above background control levels. Gel blots correspondingly did not show detectable levels of MAP2 until E14. Ultrastructural data suggest that MAP2 is present in dendrites in each of the laminae. The laminar pattern of MAP2 immunoreactivity may be due to either the higher density of differentiating dendrites in the molecular and subplate layers or to compartmentalization of MAP2 within individual cortical neurons.

Animals↗
PubMed1986

Architecture of apical dendrites in the murine neocortex: dual apical dendritic systems.

A monoclonal antibody (5F9) against microtubule-associated protein 2 is a selective and sensitive marker for neocortical dendrites in the mouse. The marker stains all dendrites. It affords a particularly comprehensive picture of the patterns of arrangements of apical dendrites which are most intensely stained with this antibody. Dual systems of apical dendrites arise from the polymorphic neurons of layer VI, on the one hand, and the pyramidal neurons of layers II-V, on the other. Terminal arborization of the former is concentrated principally at the interface of layers V and IV, while that of the latter is in the molecular layer. Apical dendrites of both systems are grouped into fascicles. In supragranular layers and in upper layer VI-lower layer V, where apical dendrites are most abundant, the fascicles coalesce into septa. These generate a honeycomb-like pattern, subdividing these cortical levels into columnar spaces of approximately 20-40 micron diameter. At the level of layer IV, where the number of apical dendrites is greatly reduced, the fascicles are isolated bundles. These bundles have the form of circular, elliptical or rectangular columns in the primary somatosensory, temporal and frontal regions, respectively. Those in the barrel field are preferentially concentrated in the sides of barrels and the interbarrel septa. The configurations of the dendritic fascicles, particularly the midcortical bundles, may conform to the spatial configuration of investing axons of interneurons.

Animals↗
PubMed1986

Zinc status and sexual development in adolescent girls.

Forty-eight black adolescent girls, aged 8 to 16, from the inner city of Baltimore were divided into five groups according to breast and pubic hair development. Blood and hair zinc concentrations as analyzed by atomic absorption spectrophotometry were within ranges reported by other investigators. Hair zinc levels significantly increased (p less than .05) from the second to the last stage of puberty and were significantly correlated (p less than .05) with erythrocyte zinc levels, height, and weight. Mean dietary intakes of calories and protein, as measured from a 24-hour recall, were adequate and increased with stage of breast and pubic hair development. Mean zinc intakes reported in the 24-hour recall averaged 66% of the RDA in the latter half of puberty. It appeared that zinc nutriture was generally adequate in this population, even though the dietary intake of zinc was below the recommended level.

Adolescent↗
PubMed1985

What do breast symptoms mean?

Breast symptoms of pain, tenderness, and engorgement correlate with objective findings of nodularity on physical examination. Like all other factors for breast disease, they are not a single determinant of diagnosis, as shown by the 3 X 3 contingency table, but they are a useful addition to our understanding. From the available data, symptoms seem as accurate as physical examination for evaluating changes in benign diseases. By extrapolation, we expect they will be useful for management of premalignant breast lesions. We conclude that a complete breast evaluation should include inquiry about breast symptoms and whether these symptoms have changed.

Adult↗
PubMed1985

Neurite outgrowth traced by means of horseradish peroxidase inherited from neuronal ancestral cells in frog embryos.

Outgrowing neurites in Xenopus embryos were labeled with horseradish peroxidase which had been injected into a single blastomere at the 32-cell stage and had been inherited by all the descendants, including neurons. Neurite outgrowth was traced from labeled trigeminal ganglion cells and most or all types of neurons present in the spinal cord at embryonic stages 20-30: primary motoneurons, commissural, dorsal longitudinal, ventral longitudinal, and Rohon-Beard neurons. All types of nerve fibers grew by the most direct pathway, apparently without errors of initial outgrowth, pathway selection, or target selection. An initial transient phase of outgrowth of filopodial processes from neuronal cell bodies and shafts of short neurites was observed which disappeared after further elongation of the neurites. The first pioneer fibers grew out from all types in a 2-hr period, from stage 20 to 22, and these fibers arrived at the targets within 3.5 hr after initial outgrowth. Additional fibers grew later in contact with the pioneers to form fascicles. Nerve fibers elongated without branching until they neared or contacted their targets. The rate of elongation at 20 degrees C was 30-75 micron/hr. The rapid, unbranched, error-free initial outgrowth and elongation of neurites to their targets is discussed in relation to theories of development of nerve pathways.

Animals↗
PubMed1984

Fatty acid metabolism in adipose tissue of aging mice after direct tracer injection into fat pads.

We have examined previously reported age-related defects in triglyceride synthesis from [1-14C]palmitate in adipose tissue of mice. Three techniques were used: in vitro, using adipocytes isolated from epididymal fat pads of young and old mice; and in vivo, using two new methods to measure free fatty acid (FFA) esterification by adipose tissue (direct injection of labeled palmitate-albumin complexes in large or small volumes into the extracellular spaces of the epididymal or inguinal fat pads of young and old mice). When the entire fat pad was filled with tracer we no longer observed heterogeneous labeling of adipocytes in epididymal fat pads that occurred in an earlier study in which an in vivo-in vitro method has been used. Free fatty acids were converted to triacyglycerol faster by adipocytes of large cells from older animal than by those of small cells from young mice; when the cell sizes of young and old mice were approximately equal, then the rates of FFA esterification were the same in young and old adipocytes. When FFA was injected as a small bolus the fractional rates of FFA disappearance and of FFA incorporation into triacylglycerol in the different fat pads, observed during a 60-min period, were the same (about 5 min or less) regardless of the region of the fat pad studied (distal or proximal epididymal fat pad), the type of fat pad (epididymal or inguinal), or the age of the mice (12-92 weeks). Other potential applications of the direct injection technique for studying FFA metabolism and structure-function in adipose tissue in vivo are discussed. Our findings, coupled with the earlier study in which labeled FFA was added to the outside of fat pads, indicate that, in adipose tissue of old mice, there exist barriers comprising mesothelial cells, collagenous structures, and/or the outer layer of adipocytes in fat pads, that interfere in the transport of FFA to the interior adipocytes when FFA is added outside the fat pad. This age-related defect may be circumvented by injecting tracer directly into the interstitial fluid compartment.

Adipose Tissue↗
PubMed1984

Effects of permeability of midtectal barriers in goldfish on compression of the visuotectal projection rostrally and regenerative escape caudally.

Physiological mapping and anatomical methods were used to evaluate changes in the retinotectal projection of goldfish 16-200 days after insertion of permeable or impermeable barriers that bisected the tectum into rostral and caudal halves. The projection to rostral tectum was left intact. Barriers composed of Gelfilm or impermeable Nucleopore material induced within 2-3 months an orderly compression of the visual field representation in rostral tectum only slightly less complete than that observed in animals with caudal half-tectal ablation. In contrast, Nucleopore filter barriers with 0.1-micron or 8-micron holes did not cause significant compression. According to both mapping and autoradiographic tracing, reinnervation of tectum behind the barriers occurred among all groups within 1-2 months. Physiologically, the projection caudal to permeable barriers was typically complete and appropriate, whereas the caudal projection in fish with impermeable barriers eventually consisted of a greatly expanded representation of the extreme temporal visual field. Autoradiography, normal fiber impregnations, and the orthograde horseradish peroxidase method revealed that regeneration past the barriers involved the formation of large bundles passing vertically along the cut tectal margin and through the underlying valvula cerebelli or lateral tegmentum. The simultaneous rostral compression and caudal expansion in the visual representation formed when more impermeable barriers were used provides evidence that, in addition to the influence of position-dependent properties, axonal competition for target territory contributes to the control of the distribution of optic arbors. Further research is required to determine why reinnervation of tectum caudal to the more permeable barriers was more complete with respect to visual representation.

Animals↗
PubMed1984

Cell lineage analysis of neural induction: origins of cells forming the induced nervous system.

Horseradish peroxidase (HRP) was used as an intracellular lineage tracer in two experiments designed to reveal the sites of origin of cells that formed the duplicate embryo which developed in relation to an organizer grafted in the ventral marginal zone (VMZ) of Xenopus laevis embryos. In the first experiment a dorsal blastoporal lip fully labeled with HRP was grafted in the VMZ of an unlabeled embryo at the beginning of gastrulation. This resulted in development of a second embryo in which labeled cells, of graft origin, formed the notochord, and parts of the somites, endoderm, and neural tube. The second experiment was designed to show the sites of origin of the host's cells that formed parts of the induced embryo. HRP was injected into individual blastomeres in a series of Xenopus embryos at the 32-cell stage and each embryo received an unlabeled organizer graft in the VMZ at the beginning of gastrulation. In these embryos the lineages that contributed to the host's primary neural tube did not contribute any cells to the induced neural tube. All the cells in the induced neural tube which originated from the host were descendants of ventral blastomeres that did not contribute to the neural tube normally. This shows that the second neural tube is formed as a result of the action of the organizer on cells in its immediate vicinity which would not normally have entered neural pathways of differentiation.

Animals↗
PubMed1984

Effect of the B-D Urine Culture Kit on an automated bacteriuria screen.

The effect of urine collected in the B-D Urine Culture Kit (BDT; Becton, Dickinson & Co., Rutherford, N.J.) on the Autobac urine screen (General Diagnostics, Warner-Lambert Co., Morris Plains, N.J.) was investigated. Upon collection, 1,000 clean-voided urine specimens were divided into sterile urine tubes and BDTs. Within 24 h of collection, urine from each tube was cultured by a semiquantitative plate method and screened by the Autobac system. Overall, when screened by the Autobac system, urine collected in the BDT gave fewer false-positive results: 14.4 compared with 22.7% from the sterile urine tubes. However, in comparison with the sterile urine tubes, the BDT false-negative rate was 10.5 versus 4.7%, the detection time was longer, and the cost was increased.

Bacteria↗
PubMed1984

Quantitative lineage analysis of the frog's nervous system. I. Lineages of Rohon-Beard neurons and primary motoneurons.

After injection of horseradish peroxidase into single blastomeres in Xenopus embryos at 2- to 512-cell stages, all of the descendants could be traced and counted at tailbud stages. Progenitors of Rohon-Beard neurons and of primary spinal motoneurons were identified, and all neurons of each type that originated from individual progenitors were counted. From these data were derived the geometric mean of the number (N) of Rohon-Beard neurons (or primary motoneurons) that descended from a single progenitor at each generation from the first to ninth, the mean number of progenitors of each generation, and the probability that, following mitosis, daughter cells continue in the Rohon-Beard (or primary motoneuron) lineages (the continuation probability). On a log-log plot a straight line fitted to the N values intercepts the abscissa at the 13th generation for Rohon-Beard progenitors and the 16th generation for primary motoneuron progenitors. This indicates the number of generations before the entire set of each type of neuron is finally produced. The Rohon-Beard neurons and primary motoneurons each originated from a separate group of progenitors at the 9th generation (512-cell stage), but those progenitors gave rise to mesodermal, endodermal, and ectodermal cells in addition to neurons. Nevertheless, the continuation probability significantly greater than 0.5 shows that there is a bias toward recruitment of progenitors into lineages leading to production of those two types of neurons.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗