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Biomedical subjects

J Bruner

Publications and source records attributed to J Bruner.

17 recordsLinked to original sources
PubMed1991

Long-lasting decrease in the crayfish giant motoneuron soma excitability induced by Ca2+ influx.

After a single Ca-dependent action-potential or a 300 ms clamp pulse to 0 mV in the motor giant somata of the crayfish abdominal nerve cord, a decrease in input resistance, an afterhyperpolarisation and a shortening of the test action potentials were observed during 10-15 min. These effects were due to a novel type of long-lasting outward current, triggered by a single influx of Ca2+, resistant to TEA+ and blocked by Ba2+.

Action Potentials↗
PubMed1991

Transthyretin immunoreactivity in choroid plexus neoplasms and brain metastases.

Although choroid plexus papillomas (CPP) and primary choroid plexus carcinomas (CPC) are rare neoplasms of the central nervous system, they have been the subject of a number of immunohistochemical studies. To date, no unique or specific marker for these neoplasms has been found, however. Normal choroid plexus is a major site of transthyretin (TTR) synthesis, and recently this protein has been proposed as a possible specific marker of choroid plexus differentiation in tumors. In this study, we performed immunohistochemistry for TTR on 13 choroid plexus tumors (six CPP and seven CPC) and on 23 carcinomas metastatic to the brain, four of which had a papillary architecture. We also included four ovarian teratomas that contained choroid plexus elements. Two of the CPP had diffuse staining for TTR, while the four others stained only focally. Five of the CPC stained only focally and less intensely than the control, while one case was negative. Only one CPC stained as strongly and diffusely as normal choroid plexus. Two of the papillary and six of the nonpapillary metastases had focal staining similar to that seen in the five focally positive CPC. The choroid plexus elements of the ovarian teratomas stained as strongly as the positive control. These findings indicate that TTR immunoreactivity is not restricted to primary choroid plexus tumors. Furthermore, most choroid plexus carcinomas stain only weakly or not at all. This limits the usefulness of TTR immunohistochemistry in the diagnosis of primary choroid plexus neoplasms and in the distinction of CPC from metastatic carcinoma.

Adenocarcinoma↗
PubMed1988

Sodium-dependent depolarizing potentials in veratrinized crayfish muscle fibres.

In the slow abdominal flexor muscle fibers of the crayfish Procambarus clarkii, veratrine or veratridine applied during several minutes produced the persistent transformation of the muscle fibre from a nonspiking into a Ca-dependent spiking one and spikes were followed by a long-duration depolarization. The long-duration potential depends on external Na+ but is not blocked by 30 microM tetrodotoxin (TTX). In solutions containing normal concentrations of Na+ (207 mM) the absence of Ca2+ or the presence of calcium channel blockers abolished both potentials. The results show that alkaloid toxins reveal a Ca2+-dependent, TTX-resistant Na+ conductance in crayfish tonic muscle fibres.

Action Potentials↗
PubMed1986

Arsenazo III transients and calcium current in a normally non-spiking neuronal soma of crayfish.

Arsenazo III was used to investigate Ca2+ transients in the normally non-excitable soma of the motor giant neurones of the crayfish Procambarus clarkii. Two kinds of regenerative potentials could be obtained depending on membrane potential conditioning: a fast spike after a pre-hyperpolarization to -90 mV and a slow action potential after a pre-depolarization to -50 mV. Only the second of these was accompanied by an Arsenazo III transient. In voltage-clamped, somata injected, with tetraethylammonium chloride, an absorbance change could be obtained by pulsing the membrane potential above -44 mV. The relationship between absorbance change and potential peaked between 0 and +10 mV then fell off to zero at ca. +150 mV. Changes in light absorbance studied using double-pulse protocols suggested that the inactivation of Ca2+ entry was predominantly mediated by the intracellular free Ca2+ concentration. External application of 1 mM-CdCl2 abolished both the absorbance changes and the (Ca2+) inward current. The voltage dependence of this current was similar to that of the absorbance change. For positive membrane potential the current-voltage relationship showed a voltage-dependent conductance property, the origin of which is discussed.

Action Potentials↗
PubMed1986

Treatment-related leukoencephalopathy. A study of three cases and literature review.

The etiology and pathogenesis of treatment-related leukoencephalopathy remain obscure. The evidence is substantial, however, that radiation therapy in combination with higher cerebral concentrations of certain chemotherapeutic agents such as MTX increases the likelihood of permanent damage. There is no therapy of apparent benefit for treatment-related leukoencephalopathy, but reasonable alternatives include 1) withholding chemotherapy and/or radiation, 2) administering calcium leucovorin in high doses intravenously in methotrexate-induced leukoencephalopathy (26), or 3) perfusing the subarachnoid space (2) from above through an Ommaya reservoir and out from below through a lumbar puncture needle or lumbar subarachnoid catheter. Because CT scan abnormalities and subtle mental or intellectual changes are often noted before the full-blown clinical presentation, a prospective study involving periodic CT scanning as well as formal neuropsychologic testing appears worthwhile in all patients who are to receive cranial irradiation and/or chemotherapy in the prophylaxis or active treatment of CNS disease in order to detect and perhaps even to prevent this adverse side effect of cancer therapy.

Adolescent↗
PubMed1985

Guillain-Barré syndrome with cytomegalovirus infection of peripheral nerves.

Cytomegalovirus (CMV) infection involving multiple organ systems is a common finding in the acquired immunodeficiency syndrome. Acute CMV neuritis was a complication in two patients with acquired immunodeficiency syndrome. The diagnosis was made in both patients at autopsy, where typical CMV inclusions in the lumbar dorsal roots were noted in one patient and the same inclusions were found in the retroperitoneal peripheral nerves in a second patient. Electron microscopy confirmed the presence of viral particles in affected nerve segments. Patient 1 was hospitalized for ascending motor paralysis that remained unexplained at the time of death. In patient 2 the finding of CMV neuritis was incidental. Although CMV infection has been cited as an event antecedent to acute inflammatory polyradiculopathy (Guillain-Barré syndrome), to our knowledge morphologic evidence of the presence of virus has not been documented in this disease previously.

Acquired Immunodeficiency Syndrome↗
PubMed1979

Maintained contraction of the crayfish claw opener muscle in the absence of motor neuron activity.

In the whole crayfish (Astacus sp.), contraction of the dactyl opener muscle may persist for many minutes in the complete absence of action potentials in the excitor nerve or muscle. Such maintained contraction has not been observed in isolated claw preparations. Generally, maintained contraction resembles catch in that the muscle holds its previous position and does not recontract if stretched. In one animal, however, the muscle continued to slowly open in the absence of nerve activity. Maintained contraction occurred in 5 of 6 whole animal preparations; in those 5 animals it occurred on 49% of trials. We could find no difference in nerve activity or muscle potentials on trials when such contraction occurred and on those when it did not. It is proposed that in the whole animal maintained contraction may be controlled by a factor which is released into the blood supply when the animal is aroused.

Animals↗
PubMed1979

The presynaptic action of L-glutamate at the crayfish neuromuscular junction. Results obtained by intra-axonal recordings and nerve terminal damage.

The presynaptic action of glutamate was investigated in crayfish neuromuscular preparations. The excitability of locally stimulated nerve terminals increased during the perfusion of glutamate. Electrotonically propagated depolarizations were recorded in the excitatory axons when glutamate was ionophoretically applied to sensitive spots on the muscle membrane. Depolarizations of the axon were also obtained when glutamate, GABA and aspartate were added to the bath. In order to evaluate the part of the presynaptic effect in the depolarization induced in muscle fibres, nerve terminals were damaged either by treatment with high-Ca solutions or by denervation. In both cases, a decreased sensitivity to glutamate was found. Possible relationships between the nerve terminal damage and the change in the response to glutamate are proposed.

Animals↗
PubMed1977

Tuberculin-specific transfer factor in dogs.

Five mongrel dogs were sensitized to tuberculoprotein with Freund adjuvant, as determined by responses to tuberculin skin tests and by in vitro lymphocyte cultures. These animals served as blood donors for production of transfer factor. Nine mongrel dogs received single doses of transfer factor that was tuberculin specific. Successful transfer of tuberculin sensitivity as measured by lymphocyte transformations was achieved in five of nine animals. Canine lymphocyte cultures frequently showed relatively low transformations to mitogens as compared with responses noted in other animals. Dissociation between skin test reactivity and in vitro lymphocyte transformation to tuberculoprotein was noted in two of nine animals. Increases in lymphocyte transformations to phytochemagglutinin were seen in three of nine recipient animals after transfer factor administration. Successful transfer from an animal sensitized by prior transfer factor administration was achieved in one instance. These data indicate that transfer factor-like substances are present in dogs. The reasons why successful transfer was achieved in only half of the recipient animals needs further explanation.

Animals↗
PubMed1975

[Short and long term depression of neuromuscular transmission in crayfish].

Following single excitation of the abdominal giant motoneuron of crayfish, an important depression of neuro-muscular transmission is observed for about 15 mn. The time course of recovery is not modified even after low frequency (1/30 Hz) repetitive stimulation. Recovery curves obtained for different Mg++ concentration in physiological solutions show two phases of depression: short-term depression which is largely reduced in high Mg++ concentrations - thus probably depending on transmitter depletion in motoneuron terminals - long-term depression which is not modified by changing Mg++ concentration and seems to be independent of depletion.

Abdomen↗