PubMed Health⌕ Search

Biomedical subjects

B Zipser

Publications and source records attributed to B Zipser.

54 records · Page 3Linked to original sources
PubMed1985

The embryonic development of peripheral neurons in the body wall of the leech Haemopis marmorata.

The appearance of peripheral neurons within the skin during embryonic development of the leech is described. These neurons were labeled using a monoclonal antibody, Lan3-6, which recognizes antigens in both the cell body and the axons of these cells. Within the 5 annuli that are found in each midbody segment, peripheral neurons first label in the middle and last in the most anterior and posterior ones. In each annulus, the number of cells labeled is initially 4 and increases as development proceeds. By the end of embryogenesis, all annuli show approximately equal numbers of Lan3-6 labeled neurons. The development of peripheral neurons in the skin of the rear sucker is also described.

Animals↗
PubMed1985

Varicosity-associated antigens define neuropile subfields in the leech central nervous system.

A panel of twelve monoclonal antibodies raised against homogenates of leech nerve cords and four polyclonal antisera raised against purified neurotransmitters were used to label varicosities immunocytologically in the central neuropile of leech segmental ganglia. These immunoreactive varicosities occur in distinct patterns, some of which have a simple geometry. Three antibodies label immunoreactive varicosities distributed in a single dorsoventrally-oriented plane, two label varicosities distributed in lateral hemi-neuropiles (leaving void a central cephalocaudal passageway), and five label varicosities distributed throughout the neuropile. Six antibodies tested label varicosities across leech species, and five of these varicosity populations are distributed in patterns conserved across leech species. Immunocytologically-defined neuropile subfields do not correspond with previously identified histological and ultrastructural features of leech segmental ganglia. Analysis of immunocytologically-defined subfields is extended to include identification of sets of neurons which appear to project into these subfields, and to include an intracellular characterization of one of these neuron sets.

Animals↗
PubMed1983

Cross-reactivities of monoclonal antibodies between select leech neuronal and epithelial tissues.

Three monoclonal antibodies, originally studied because of their neuron-specific staining in the leech central nervous system, are characterized further here, both immunocytochemically and biochemically, with Western blot staining using the central nervous system and peripheral tissues. The three antibodies react both with neurons and select epithelial tissue in the central nervous system, gut, and penis. Antibody Lan3-8 reacts with neurons in the nerve cord and gut but with epithelial cells in the penis; it binds to a 65K molecule in all three tissues. Lan3-2 and Laz2-369 are considered as a related pair because in the central nervous system the former stains all (four) and the latter generally only half (two) of the neurons in a standard midbody ganglion responding to nociceptive stimulation. In the gut, both antibodies label patches of epithelial cells and Laz2-369 stains a previously unknown type of gut neuron. While a given antibody stains different bands in gut and central nervous system immunoblots, comparing the bands of both antibodies for the same tissue extract makes it apparent that there are similarities in the molecular species that both antibodies recognize. For each monoclonal antibody, the histologically identified tissue antigens need to be correlated with proteins identified on Western blots. Of particular interest are the broad 130K bands to which Lan3-2 and Laz2-369 bind. The question is raised whether the molecular species in these bands represent a family of proteins that serve a specific nociceptive cell function.

Animals↗
PubMed1983

The expression of antigens by embryonic neurons and glia in segmental ganglia of the leech Haemopis marmorata.

Monoclonal antibodies (mAbs) raised against adult leech nervous systems were screened on embryos of the leech Haemopis marmorata in order to determine when in development specific antigens are first expressed and the order in which they are expressed by different cells or tissues. Three of the mAbs produced by Zipser and McKay (Zipser, B., and R. McKay (1981) Nature 289: 549-554) were screened: Lan3-1, Lan3-5, and Lan3-6. Each mAb shows a different pattern of labeling in the adult leech nerve cord (Zipser, B. (1982) J. Neurosci. 2: 1453-1464). The embryonic stages studied were from 5 days after egg deposition to 30 days (emergence from the cocoon). The pattern of labeling was assayed in whole mounts using horseradish peroxidase-conjugated second antibodies. The principal results are as follows. (1) Antigens recognized by Lan3-5 are first expressed by the glia of the roots of the anterior segmental ganglia at 6 to 7 days, several days later by the interganglionic connective glia, and near the end of embryonic development by ganglionic neurons. An anterior to posterior temporal gradient is observed in the expression of these antigens. In addition, Lan3-5 also labels the protonephridia and nephridia from early development onward. (2) Antigens recognized by Lan3-6 are first expressed by a pair of neurons in each segmental ganglion and later in development by additional neurons. By the time of emergence, however, only about half of the neurons that label in the adult have done so, implying that some neurons express these antigens postembryonically. Labeling with Lan3-6 is first seen in neuronal somata and only later in neuronal processes. (3) Antigens recognized by Lan3-1 and expressed by segmentally specific neurons in ganglia 5 and 6 are not detectable during embryonic development, but are so at early postembryonic stages. Thus, these three mAbs provide an approach to study different aspects of the development of the leech nervous system, specifically the relation between glial and neuronal differentiation and the genesis of segmentally specific phenotypes.

Animals↗
PubMed1982

Complete distribution patterns of neurons with characteristic antigens in the leech central nervous system.

Monoclonal antibodies were used to map the distribution of neurons in the leech which contain a particular antigen. This technique reveals the genetically determined variation in cell body distribution along the nerve cord. In addition, antibodies also reveal developmental deviations, such as the occurrence of supernumerary cell bodies. Three antibodies that bind either to single types or small sets of different neurons are used to construct complete distribution patterns of antigenically related cells. Three other antibodies are used to create cell body distribution maps of antigenically homologous primary mechanosensory cells responding to noxious or pressure stimulation which form a subset of the cells stained by the antibody. Furthermore, antibodies against the pressure cells helped in the location of two different specific antigens for the same identified nerve cell.

Animals↗
PubMed1981

Monoclonal antibodies distinguish identifiable neurones in the leech.

Monoclonal antibodies were isolated by screening 475 hybridomas obtained from mice immunized with whole leech nerve cords. The majority (about 300) reacted with leech nervous tissue, but only about 40 made antibodies that identified single kinds or small sets of cells. Twenty of the antibodies which react with specific neurones were studied in greater detail and are described here. They include antibodies against identified sensory neurones and motor neurones as well as against numerous unidentified cells.

Animals↗
PubMed1980

Identification of specific leech neurones immunoreactive to enkephalin.

The small endogenous peptides, Met- and Leu-enkephalin, bind to the same specific receptors as opiate analgesics. They, and the larger endorphin peptides, have been widely found in mammals, where they seem to have a significant role in neuronal pathways mediating pain and emotional behaviour. Only recently has enkephalin-like activity been identified in an invertebrate, the earthworm, although there is some preliminary evidence for opiate receptors in a marine mollusc. Here I report the detection, by an immunocytochemical technique, of an enkephalin-like moiety which is localised in one of the 400 cells of each posterior midbody ganglion of the leech. The presence of enkephalin-like activity in an identifiable easily accessible neurone of a well characterised nervous system such as that of the leech could greatly facilitate elucidation of its mechanism of action.

Animals↗
PubMed1979

Identifiable neurons controlling penile eversion in the leech.

1. This paper describes the neuroanatomy and electrophysiology of motor neurons causing penile eversion in the leech. 2. The male organ is innervated by ganglia 5 and 6 of the 34 ganglia in the leech brain through special sex nerves deriving from anterior roots. These sex ganglia have at least 200 more neurons than the other midbody ganglia. Many of the extra neurons are involved in reproductive behavior. 3. Two pairs of motor neurons on the ventral side of ganglion 6, named rostral and lateral neurons, are the only ones that elicit full penile eversion. Evidence that the lateral and rostral neurons are, in fact, motor neurons comes from HRP and electrophysiological studies. HRP injections reveal that each neuron's single primary axon grows into the sex nerve. Electrophysiological evidence is twofold: a) action potentials of lateral and rostral cells can still contract the genitalia after the neurons are deafferented from chemical synaptic input in the ganglion by high Mg2+, b) their action potentials are followed by junction potentials in male organ muscle fibers.

Animals↗
PubMed1979

Voltage-modulated membrane resistance in coupled leech neurons.

1. Resistive interactions have been studied between two pairs of large identifiable neurons in ganglion 6 of the leech CNS, called the lateral and rostral cells. Both are motor neurons causing penile eversion. 2. Lateral and rostral neurons have different membrane resistance properties. Input resistances of lateral neurons are virtually constant. By contrast, membrane resistances of rostral neurons are highly voltage dependent. When depolarized from resting potential to firing level, a rostral neuron's input resistance can increase 10-fold, from 30 to 300 Momega. 3. Voltage-dependent membrane characteristics of rostral neurons cause resistive interactions with lateral neurons to be nonlinear. DC potentials evoked in lateral cells are transmitted to rostral cells with an efficiency varying over a 10-fold range. Hyperpolarizing coupling is weak, with coupling factors of about 0.03. Depolarizing coupling factors increase progressively with increasing lateral neuron depolarization, reaching values of up to 0.3. 4. Membrane resistance changes in rostral neurons accompany lateral to rostral cell interactions. Input resistances increase during depolarizing and decrease during hyperpolarizing coupling potentials. The lateral to rostral cell junctional resistance is high and invariant, as evidenced by uniformly weak coupling in the reverse direction, from rostral to lateral neurons. 5. In conclusion, asymmetries in lateral to rostral cell interaction are based on postsynaptic rather than junctional resistance changes. The impact of the lateral onto the rostral cell's excitability contains a nonlinear component besides the usual linear additive one. As in conventional resistive coupling, depolarizing coupling potentials raise the rostral neuron closer to its voltage threshold. But more significantly, depolarizing coupling potentials lower the rostral neuron's current threshold because increases in resistance proportionately reduce the amount of excitatory current needed to reach firing level. Thus, the resistance change acts to amplify the input signal efficiency. In addition to the static changes in current threshold, the reostral neuron also changes dynamically. Membrane resistance increases lead to increases in space constant shrinking the neuron's electrical lenght. 6. Other properties of the network have been analyzed. The pair of lateral neurons is strongly coupled, whereas the pair of rostral neurons is weakly coupled, the coupling factors are 0.3 and 0.05, respectively. Hyperpolarizing membrane time constants for the lateral and rostral neurons are estimated to be between 100 and 200 ms. Time constants of depolarized rostral neurons are significantly larger.

Animals↗
PubMed1976

Responses of cells of posterior lateral line lobe to activation of electroreceptors in a mormyrid fish.

Activity of neurons in the lateral line lobe was studied by intracellular recording of responses to stimulation of the lateral line nerves and of electroreceptors on the skin surface. Two modes of activation occur for cells responding to inputs from medium receptors. There is a direct monosynaptic input mediated by a single fiber. Short latency of response and antidromic spread from cell to afferent fiber indicate that the mediating synapse is electrotonic. The second input is from a number of additional fibers and is relayed, presumably by the granule cells. At shortest latency this input is disynaptic, probably involving at least one electrotonic synapse. A relay is indicated by heterosynaptic facilitation of the PSP and by pronounced depression with repetitive stimulation. The monosynaptic input may be on the axon. Disynaptic inputs are distributed over the dendrites, and impulses can arise in the dendrites. What appear to be spikes restricted to dendritic regions are often recorded as small brief potentials in the cell body. There is a somatotopic projection of the electroreceptors to the lateral line lobe. The monosynaptic input comes from a specific receptor in the periphery. Strong disynaptic inputs come from a group of receptors generally found anterior, but less commonly posterior or lateral, to the receptor giving rise to the monosynaptic input. Additional inputs that are inhibitory come from surrounding receptors. The inhibition only affects responses to the disynaptic input. The different inputs and multiple sites of impulse initiation must modify the cell's response as compared with the input-output relations that would be obtained with inputs acting on a single summation point. Cells responding to activation of large receptors are infrequent. They are characterized by low threshold, little latency change near threshold, and ability to follow high frequencies of stimulation.

Animals↗
PubMed1976

Interaction of electrosensory and electromotor signals in lateral line lobe of a mormyrid fish.

A signal associated with the neural command to discharge the electric organ is recorded in cells of the lateral line lobe. Responses of cells activated by medium receptor inputs are facilitated or less frequently inhibited during this command-associated signal. Only responses to disynaptic inputs are affected, the monosynaptic response is not altered. The periods of facilitation and inhibition occur at times at which electroreceptor activity evoked by organ discharge reaches the lateral line lobe. Presumably the command-associated signal is important in electrolocation. Cells responding to large receptor inputs are inhibited by the command-associated signal. Activity evoked by large receptors is transmitted in a mesencephalic fiber tract. The tract response is also inhibited by the command-associated signal. Since each organ discharge would excite all the large receptors at short latency, there would be little information contained in their responses. Inhibiting discharge-evoked activity may allow the system to return to maximum sensitivity most rapidly.

Animals↗