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Biomedical subjects

M Tal

Publications and source records attributed to M Tal.

At least 55 records · Page 3Linked to original sources
PubMed1988

Sporadic amplification of the HER2/neu protooncogene in adenocarcinomas of various tissues.

The HER2/neu protooncogene was found to be amplified in 6 of 109 primary adenocarcinoma tumors. No HER2/neu amplification was found in 29 other primary nonadenocarcinomatous tumors. In two colon tumors, in addition to the amplification, DNA rearrangement of HER2/neu gene was also observed. The rearrangement was explored in detail in one tumor and it was shown to be confined to the 3' region of the gene. Moreover, this tumor expressed an aberrant HER2/neu polypeptide with a molecular weight of 190,000, which is larger by approximately 5,000 than the molecular weight of the normal HER2/neu protein. The aberrant HER2/neu protein was immunoprecipitated with site-specific antibodies against a synthetic peptide from the COOH-terminal end of the normal HER2/neu protein; it also displayed intrinsic protein tyrosine kinase activity leading to self-phosphorylation.

Adenocarcinoma↗
PubMed1987

Neural basis for initiation of rhythmic digastric activity upon midbrain stimulation in the guinea pig.

The central pattern generator for rhythmic jaw movements is readily activated by repetitive stimulation (40 Hz) of the midbrain in the region of the cerebral peduncle in anaesthetized guinea pigs. The pattern of rhythmic digastric EMG evoked by midbrain stimulation after acute decerebration closely resembled that evoked by electrical stimulation of the masticatory cortex. Since the decerebration boundary was caudal to the substantia nigra and the thalamus, impulses ascending to these centers and others further rostral are not necessary for the generation of rhythmic jaw movements. This leaves local midbrain nuclei, and pathways descending from the forebrain (fibers-of-passage) as possible substrates for activating the rhythmic jaw movements. To distinguish between these two possibilities, midbrain stimulation was delivered in guinea pigs that underwent unilateral ablation of the masticatory cortex, and survived long enough to permit degeneration of all corticobulbar fibers that pass through the midbrain. In these animals no response was detected from stimulation of the ipsilateral midbrain. However, stimulation of the contralateral midbrain did evoke bilateral rhythmic digastric activity. These results suggest that rhythmic digastric activity and jaw movements evoked by midbrain stimulation are caused by activation of fibers that descend from the masticatory cortex, travel down through the midbrain, probably in the cerebral peduncle, and decussate only just rostral to the motor nucleus of the Vth cranial nerve.

Animals↗
PubMed1987

Human HER2 (neu) promoter: evidence for multiple mechanisms for transcriptional initiation.

We localized the 5' region of the human gene HER2 in a cloned fragment of genomic DNA. This clone contained exons 1 to 4 of HER2, spanning the coding sequence for the first 191 amino acids. The promoter region of HER2 was identified upstream to exon 1 by nuclease S1 mapping and by a functional assay in which the promoter region drives the expression of a chloramphenicol acetyltransferase gene. The HER2 promoter is different from the promoter of the epidermal growth factor receptor gene (HER1), and the GC boxes which are typical of the promoter of the epidermal growth factor receptor gene are absent from the HER2 promoter. One major and two minor RNA start sites located at nucleotides 178, 244, and 257 upstream to the initiator ATG were identified. The first one is 21 and 70 base pairs downstream from typical TATAA and CAAT boxes, respectively. This indicates that transcription of HER2/neu can be regulated by a mechanism involving a TATA box, as well as by other unidentified regulatory elements.

Base Sequence↗
PubMed1987

The organization and activity patterns of the anterior and posterior heads of the guinea pig digastric muscle.

The structure and activity patterns of the anterior and posterior heads of the guinea pig digastric muscle (DG) were studied in ketamine-anesthetized guinea pigs. Collagen staining of longitudinal and transverse sections of the muscle revealed that the guinea pig DG is comprised of a unicompartmental anterior head (ADG) and a multicompartmental posterior head (PDG). The two heads are separated by a thin tendinous inscription that, unlike the intermediate tendon of the DG in humans, is not attached to the hyoid bone. The motor nuclei of the guinea pig DG were reconstructed using retrograde labeling with horseradish peroxidase. The motoneurons of the ADG were clustered in a longitudinal column within the trigeminal motor nucleus. The motoneurons of the PDG were segregated into two clusters within the facial motor nucleus. The cross-sectional areas of the ADG and PDG motoneuron somata exhibited unimodal frequency distributions and the average soma area was larger for ADG than PDG motoneurons. Histochemical characterization of ADG and PDG revealed that the two muscle heads contained the three main histochemical types of muscle fibers identified in limb muscles. The frequency distribution of fiber types in ADG and PDG were not significantly different. Both muscle heads were predominantly fast with slow oxidative fibers accounting for only 1.1 and 0.3% of the fibers in narrow dorsal regions of ADG and PDG, respectively, and 13.6 and 12.9% in the more ventral regions of ADG and PDG, respectively. Simultaneous recordings of EMGs from the ADG and PDG were carried out during spontaneously occurring rhythmical jaw movements. These recordings revealed a high degree of synchrony between the activities of the two heads, although differences were observed in the onset and duration of the EMG bursts. Activity in the PDG preceded activity in the ADG in most of the rhythmical cycles and persisted longer. The differences in latencies of time-locked EMGs evoked in the ADG and PDG by four-pulse cortical stimulation were much smaller than those observed between the activity bursts of the two heads during rhythmical jaw movements. It is suggested that the early activity in the PDG is accounted for by shorter central conduction times in the pathways onto it and/or by higher recruitability of its motor units. The early activity in PDG may serve to optimize the location of ADG on its length-tension curve prior to and during the active state.

Animals↗
PubMed1987

Brain-stem perturbations during cortically evoked rhythmical jaw movements: effects of activation of brain-stem loci on jaw muscle cycle characteristics.

The purpose of the present study was to further elucidate with the use of microstimulation techniques the influences of rostral pons and midbrain loci on the neuronal networks responsible for cortically induced rhythmical jaw movement (RJM) activity in the anesthetized guinea pig and to establish if these rostral brain-stem loci are capable of modulating the timing as well as the amplitude of rhythmical digastric (DIG) EMG activity. It was found that repetitive electrical stimulation of widespread areas of the rostral pons and mid-brain produced suppression of ongoing cortically induced rhythmical EMG activity. Prior to complete EMG suppression there was a reduction in amplitude of the DIG EMG and an increase in cycle duration. Repetitive stimulation of these suppressive loci also produced a reduction in the amplitude of the short-latency DIG EMG response produced by short pulse train stimulation of the masticatory cortex. This indicates that part of the suppression of cortically induced rhythmical EMG activity was due to a reduction in excitability of the polysynaptic short-latency pathway from cortex to DIG motoneurons. Short pulse train stimulation of these brain-stem suppressive loci during various phases of the rhythmical DIG cycle produced a phase-dependent increase in duration of the ongoing perturbed cycle. The cycles following the stimulus perturbation did not show any compensatory shortening in their durations suggesting that the stimulus produced a true resetting of the cycle. These data suggest that the brain-stem loci that produce suppression of RJMs evoked by repetitive cortical stimulation can affect the excitability of the central circuits responsible for cycle oscillation and timing as well as the excitability of the polysynaptic short-latency corticotrigeminal pathway to DIG motoneurons.

Action Potentials↗
PubMed1986

The effects of brain stem transections on the neuronal networks responsible for rhythmical jaw muscle activity in the guinea pig.

The purpose of this study was to determine the critical areas of brain stem necessary for the production of cortically induced rhythmical jaw muscle activity (RJMs) in the anesthetized guinea pig. It was found that longitudinal midline transections of the lower brain stem starting at the obex and extending to the rostral third of the inferior olivary nucleus (IO) were able to abolish rhythmical EMG activity in the jaw-opener muscle (digastric) on the same side (ipsilateral) as the cortical stimulus. Under these conditions, rhythmical activity in the contralateral digastric (DIG) EMG was not affected. Midline transections extending from the rostral superior colliculus to 500 microns rostral to the trigeminal motor nucleus had no effect on cortically evoked bilateral DIG rhythmical EMG activity. Serial transverse hemisections of the left side of the medulla, starting at the obex and extending to the rostral third of the IO, reduced the amplitude of the left DIG EMG without producing significant effects in the cycle characteristics [cycle duration (CD) or burst duration (BD)] of that muscle during stimulation of the contralateral (right) cortex. Hemisections more rostral to the IO completely abolished bilateral rhythmical DIG activity induced by stimulation of the cortex on the side opposite to the transection (right cortex). Under these conditions, stimulation of the cortex on the side ipsilateral to the left hemisection (left cortex) initiated rhythmical EMG activity with normal cycle characteristics in only the contralateral (right) DIG muscle. Transverse hemisections as little as 500 microns rostral to the trigeminal motor nucleus (Mot V), which spared the pyramidal tract, had no effect on RJMs induced by stimulation of either cortex. These data suggest that each ipsilateral cortex initiates activity in neuronal oscillatory networks located exclusively in the contralateral brain stem; bilateral rhythmical DIG activity is produced by neurons in the contralateral brain stem; each side of the lower brain stem is capable of producing rhythmical DIG activity independent of the integrity of the other side; and the location of the neuronal oscillators responsible for RJMs is between the rostral IO and the trigeminal motor nucleus.

Animals↗
PubMed1985

Why does Coomassie Brilliant Blue R interact differently with different proteins? A partial answer.

Dimethyl sulfoxide was found to be effective for extraction of Coomassie Brilliant Blue R-250 (Coomassie R) from stained proteins on polyacrylamide gel slices. A good correlation was found between the ability of different proteins to bind Coomassie R and their capacity for interaction with Coomassie Brilliant Blue G-250 (Coomassie G) in solution. Scatchard analysis showed that the number of Coomassie R ligands bound to each protein molecule is approximately proportional to the number of positive charges on the protein, about 1.5-3 dye molecules/charge.

Electrophoresis, Polyacrylamide Gel↗
PubMed1985

Development of sensory and reflex responses to tooth-pulp stimulation in children.

Electric stimulation was applied to the tooth-pulp and tongue in 12 children divided into 3 groups according to the development of the roots of the upper first incisors, i.e. 1/2, 3/4 and fully formed. The masseter inhibitory periods (MIP) could be evoked by electric stimulation of the tongue at sensory threshold current levels in all children, but only for incisors with fully-formed roots. Stimulation of incisors with 3/4 formed roots at detection-threshold currents produced sensation 56 per cent of the time and detectable MIP on 65 per cent of stimuli. No sensation was obtained with stimuli up to 100 microA in incisors with 1/2-formed roots, but MIP was recorded with 31 per cent of stimuli. The findings indicate that reflex activity precedes sensation in the normal development of teeth, and that segmental, reflex, connections appear to be established before the cortical, sensory, projections are fully functional.

Child↗
PubMed1985

Quantitative determination of Coomassie R bound to proteins in polyacrylamide gel. A facilitated method for multi-spot analysis of electrograms.

Dimethylsulfoxide (DMSO) was found to be an efficient solvent for extraction of Coomassie Blue R 250 (Coomassie R) from stained proteins on polyacrylamide gels. Kinetic measurements show that the extraction of the dye from a 2-D gel reached equilibrium in 48 h. Staining of E. coli ribosomal proteins by Coomassie R dissolved in trichloroacetic acid exhibited two types of dye-protein complexes, the majority of them yield a blue-purple colour, while the rest are stained with a light-blue tone and fluorescent appearance as well. The absorbance spectra of the complexes in the gel matrix differ significantly from each other. However, the DMSO-extracted Coomassie show identical absorbance profiles with lambda max at 602 nm, thus the amount of the bound dye can easily be measured spectrophotometrically.

Electrophoresis, Polyacrylamide Gel↗
PubMed1985

The transneuronal induction of sprouting and synapse formation in intact mouse muscles.

The pattern of innervation to intact peroneal and extensor digitorum longus muscles of normal and experimental young adult mice was studied by light microscopy after staining neuromuscular junctions by a combined silver-cholinesterase stain. Spontaneous sprouting and synapse formation occur in intact muscles of normal mice. In about 7% of the junctions, sprouts contribute to the innervation of muscle fibres already innervated by their parent axons. Axotomy of the sciatic nerve in one hind limb is followed by an average 3-fold increase over normal in the incidence of sprouting and synapse formation in the intact muscles of the opposite hind limb. The time to onset of sprouting and synapse formation becomes shorter as the site of the contralateral axotomy is placed closer to the spinal cord. A significant increase over normal in the incidence of sprouting is first observed 5 days after a proximal sciatic nerve cut and only 12 days after a distal sciatic nerve cut. The timing of sprouting is independent of the difference in the number of axons that are involved in the contralateral axotomies at different sites. These findings suggest that, in the intact muscles of normal mice, sprouting and synapse formation is an ongoing process which can be enhanced by contralateral axotomy. As in frogs (Rotshenker, 1979, 1982) the underlying mechanism may be the transneuronal induction of sprouting and synapse formation.

Animals↗
PubMed1984

Isolation and characterization of a novel retrovirus from sheep affected by pulmonary carcinoma.

Sheep pulmonary carcinoma (SPC) has been shown to be associated in nature with a retrovirus, by electron microscopic, biochemical, and epidemiological criteria and by experimental transmission. In this study, a retrovirus has been isolated from SPC tumors which were experimentally induced by inoculation with a cell-free, reverse transcriptase containing fraction from a spontaneous field case of SPC, and propagated in culture. This novel virus was shown to be unrelated to murine, avian, and bovine leukemia viruses, to be exogenous to the ovine species, and to have only limited genetic relatedness to the lentiviridae (maedi-visna and caprine arthritis encephalitis virus).

Animals↗
PubMed1984

The threshold for eliciting the jaw opening reflex in rats is not increased by neonatal capsaicin.

Neonatal capsaicin administration has previously been shown to increase the threshold for withdrawal and escape response to noxious thermal, chemical and mechanical stimuli. The reason for these effects is destruction of afferent C-fibers and associated reduction in central substance P levels. In contrast, neonatal capsaicin treatment did not eliminate the "jaw opening reflex" (JOR) or even significantly increases its threshold when tested in rats 2-8 months of age. There was no significant difference in the voltage required to elicit the JOR nor was there any difference in its latency, in the animal that had received an intraperitoneal injection of 50 mg/kg capsaicin on the second day of life. A reduction of 85% unmyelinated fibers was found as compared with untreated animals. This data support earlier indications that upon incisor tooth pulp chamber stimulation in rats, the JOR is affectively activated by low-threshold myelinated fibers in the tooth pulp and surrounding periodontal ligament. Destruction of tooth pulp C-afferents, therefore, does not affect jaw opening reflex threshold.

Animals↗
PubMed1984

The effect of ultrasonic scaling on the surface of Class V amalgam restorations--a scanning electron microscopy study.

Class V cavities were prepared on twelve extracted teeth and then filled with amalgam which was condensed in six cases by hand and six by mechanical means. SEM records were obtained before and after ultrasonic scaling of the restored area. They showed that such scaling had a deleterious effect on the surface of the amalgam and its marginal integrity. However the mechanically condensed specimens were less affected.

Dental Amalgam↗
PubMed1984

Sprouting and synapse formation produced by Carbocaine.

Injury to one cutaneous pectoris nerve of the frog induces sprouting of and synapse formation by the contralateral homologous intact nerve. It was previously suggested that axotomy initiates a signal for growth in the cell bodies of the injured motor neurons and that this signal is transferred transneuronally across the spinal cord to intact motor neurons (e.g., Rotshenker, S. (1982) J. Neurosci. 2: 1359-1368). The present study was designed to test the hypothesis that axotomy initiated the signal for growth by depriving neuronal somata of a trophic substance derived from the target muscle. The superficial layer of muscle fibers comprising one cutaneous pectoris muscle, the source of the hypothetical trophic substance, was removed by means of local application of the myotoxic local anesthetic Carbocaine. An increased supernumerary pattern of innervation developed in drug-treated muscles first and in contralateral intact muscles thereafter. These results raise the possibility that target muscle fibers play a role as regulators of a signal for growth in the cell bodies of their innervating motor neurons.

Animals↗
PubMed1983

Recycling of synaptic vesicles in motor nerve endings separated from their target muscle fibers.

The application of the myotoxic local anesthetic Carbocaine to the cutaneous-pectoris muscle of the frog produced muscle fiber degeneration. The degenerating muscle fibers were phagocytozed by macrophages leaving behind structurally intact motor nerve endings in close apposition to the sheath of basal lamina that normally surrounds muscle fibers. These target deprived nerve terminals retained their ability to recycle synaptic vesicles in that they showed a low basal rate of spontaneous uptake of HRP that increased several fold upon nerve stimulation.

Animals↗
PubMed1982

The effect of a long-acting local anaesthetic agent (Marcaine) on the masticatory muscle in rats.

Marcaine, a long-acting local anaesthetic was administered subcutaneously over the rat's superficial masseter muscle. Rapid muscle fibre destruction with infiltration of mononuclear and polymorphonuclear leukocytes and degeneration of muscle fibers are the notable morphological changes following treatment with Marcaine. However, this degeneration was rapidly replaced by a regeneration process. Sequential injections of Marcaine produced even more serious muscle damage. However, successive injections of the drug did not prevent the regeneration process.

Anesthesia, Dental↗