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Biomedical subjects

J V Trontelj

Publications and source records attributed to J V Trontelj.

At least 19 recordsLinked to original sources
PubMed1998

Acetylcholinesterase mRNA level and synaptic activity in rat muscles depend on nerve-induced pattern of muscle activation.

Acetylcholinesterase (AChE) mRNA levels are severalfold higher in fast rat muscles compared with slow. We hypothesized that AChE mRNA levels and AChE activity in the neuromuscular junction depend on a specific nerve-induced pattern of motor unit activation. Chronic low-frequency stimulation, mimicking the activation pattern in slow muscles, was applied to fast muscles in rats. Molecular forms of AChE were analyzed by velocity sedimentation, and AChE mRNA levels were analyzed by Northern blots. AChE mRNA levels in stimulated fast muscles dropped to 10-20% of control after 1 week and became comparable to those in slow soleus muscles. The activity of the junctional A12 AChE form in 35 d stimulated fast muscles decreased to 56% of control value, reaching that in the soleus muscle. Therefore, synaptic AChE itself depends on the muscle activation pattern. Complete inactivity after denervation also decreased the AChE mRNA level in fast muscles to <10% in 48 hr. In contrast, profuse fibrillations observed in noninnervated immature regenerating muscles maintain AChE mRNA levels at 80% of that in the innervated fast muscles. If protein synthesis was inhibited by cycloheximide, AChE mRNA levels in 3-d-old regenerating muscle, still containing myoblasts, increased approximately twofold. No significant increase after cycloheximide application was observed either in denervated mature fast muscles or in normal slow muscles. Low AChE mRNA levels observed in those muscles are probably not caused by decreased stability of AChE mRNA as demonstrated in myoblasts.

Acetylcholinesterase↗
PubMed1998

Axonal and demyelinating neuropathy with reversible proximal conduction block, an unusual feature of vitamin B12 deficiency.

We report a 35-year-old patient with megaloblastic anemia who presented with features of subacute combined degeneration of the cord. Electrophysiological studies showed features of axonal neuropathy. In addition, there was evidence of prominent focal proximal conduction block in several nerves. After treatment with cyanocobalamin the neuropathy improved, and the peripheral nerve conduction block detected earlier disappeared. Reversible nerve conduction block as a feature of vitamin B12 deficiency in man, to our knowledge, has not been reported in literature, so far.

Adult↗
PubMed1998

Behçet's syndrome: a report of 41 patients with emphasis on neurological manifestations.

Forty one patients with the clinical diagnosis of Behçet's syndrome from two teaching hospitals in Kuwait were studied. There were 34 male and seven female patients. Age at presentation ranged from 14 to 48 years. Neurological manifestations were present in 24 patients. Eleven patients showed evidence of increased intracranial pressure, and 10 of these had radiologically confirmed dural sinus thrombosis. Five patients presented with a meningoencephalitic or meningomyelitic picture, three with a stroke-like picture, and three with primarily brain stem signs. One patient developed trigeminal neuritis, and five patients exhibited (along with other features) variable degrees of psychological manifestations. All patients with neurological involvement were treated with steroids, and some also had courses of other immunosuppressant drugs and colchicine. The disease took a relatively benign course, except those patients with meningoencephalitic and meningomyelitic presentation, one of whom died from the disease. Those treated early had a better prognosis. The incidence of dural sinus thrombosis in this series of patients is unusually high. In most patients, the course of the disease was more favourable than reported in the literature. This may be attributed to early and aggressive treatment.

Adolescent↗
PubMed1997

The study of normal and abnormal neuromuscular transmission with single fibre electromyography.

The use of single fibre electromyography (SFEMG) in the study of neuromuscular transmission across individual motor endplates in situ is reviewed. The neuromuscular jitter can be studied both during voluntary contraction and electrical activation of the muscle fibre. The differences, pitfalls and advantages of these methods are discussed. Findings in myasthenia gravis and other disorders of the neuromuscular transmission are examined.

Electric Stimulation↗
PubMed1995

Multiple innervation of muscle fibers in myasthenia gravis.

Single fiber EMG recordings from patients with myasthenia gravis obtained during axonal microstimulation revealed an occasional bimodal distribution of response latencies. This phenomenon could be dependent on stimulus strength, however, in a way different from that in the axon reflex. It is suggested to be due to dual neuromuscular junctions (NMJs) supplied by two different motor neurons. Some cases of bimodal jitter were not dependent on stimulus strength and are assumed to be due to dual innervation by the same neuron. The phenomenon could only be demonstrated at abnormal NMJs with partial impulse blocking. It is suggested to reflect multiple reinnervation of muscle fibers that had undergone functional or structural denervation in the course of the immune attack against the original NMJ. This study suggests that the coexisting NMJs from the same or different motor neurons may be functional at the same time.

Adult↗
PubMed1995

Single fiber electromyography in studies of neuromuscular function.

Single-fiber electromyography (SFEMG) allows precise study of the microphysiology of the human motor unit under normal conditions. The physiological parameters that can be quantified include impulse transmission along the intramuscular axon collaterals, pre- and post synaptic events at the neuromuscular junction, and muscle fiber membrane properties. This chapter illustrates some of the advantages of SFEMG in studies of neuromuscular fatigue in normal muscle, as well as in disorders of neuromuscular transmission, and conditions associated with disturbed muscle fiber depolarization-repolarization.

Animals↗
PubMed1994

Neuro-ophthalmic manifestations of the syndrome of ophthalmoplegia, ataxia and areflexia. Observations on 20 patients.

The neuro-ophthalmological manifestations of 20 patients with the syndrome of ophthalmoplegia, ataxia and areflexia are described. The symmetrical nature of the ophthalmoplegia and the associated cerebellar ataxia point to centrally placed lesions. Several supranuclear, nuclear and internuclear ophthalmological signs are identified. Some of these, like partial sparing of the levator palpebrae and normal downgaze in the presence of severe ophthalmoplegia are noted too frequently to be just unusual signs of peripheral oculomotor dysfunction. Other identified features included upper lid retraction on attempted upgaze and preserved Bell's phenomenon in the presence of paralysis of the latter, as well as several other central ophthalmological signs. These findings contrast with those seen in the Guillain-Barré syndrome and, thus, the syndrome of ophthalmoplegia, ataxia and areflexia is not a mere variant of it.

Adolescent↗
PubMed1994

Neuro-ophthalmic manifestations of the syndrome of ophthalmoplegia, ataxia and areflexia: a review.

Controversy regarding the nosological position of the syndrome of ophthalmoplegia, ataxia and areflexia (Miller Fisher syndrome) exists. The oculomotor dysfunction was presumed to represent an unusually symmetrical peripheral cranial nerve dysfunction. To investigate the neuro-ophthalmic manifestations in this rare syndrome we reviewed 109 reports describing 243 cases. The ophthalmoplegia was remarkable in its constant association with a cerebellar type ataxia. It was described to be remarkably symmetrical at all stages of development and recovery. From the early description of the syndrome by Fisher the ophthalmoplegia was observed to evolve as a symmetrical failure of upgaze followed by loss of lateral gaze and last by downgaze, recovery develops in the opposite pattern. Despite the severe nature of the ophthalmoplegia, 58 patients were reported to have sparing of downgaze and 192 (79%) had relative sparing of the eye lids. Active lid retraction and preserved Bell's phenomenon, despite upgaze paralysis, were described in 22 and 15 patients respectively. Upper lid jerks were described in 2, Parinaud's syndrome in 2, convergence spasm in 6, internuclear ophthalmoplegia in 15 and horizontal dissociated nystagmus in 11. Interestingly 23 were reported to present with paralysis of abduction progressing to lateral gaze paralysis and 5 had paralysis of abduction and contralateral gaze paralysis. Four had defective vestibulo-ocular reflex despite recovery of upgaze, 10 had central type nystagmus including rotatory, retractory and rebound nystagmus. Relative preservation of optokinetic nystagmus and preservation of vestibulo-ocular reflex despite an otherwise complete ophthalmoplegia were reported in 6 and 2 patients respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Blepharoptosis↗
PubMed1993

Muscle fiber conduction velocity changes with length.

While recording activity from individual muscle fibers by single fiber EMG (SFEMG), stimulated either through their axons or directly, the length of the recorded muscle fiber was changed--stretched or made shorter--by manipulating the recording needle or by passive joint movements. This resulted in significant changes of latency corresponding to an increase in propagation velocity on shortening of the muscle fiber and to a slowing of its lengthening. The maximum increase in velocity was estimated to 33% and slowing to about 22%. These length-dependent changes of muscle fiber propagation velocity are suggested to contribute to the supernormal phase of propagation velocity recovery function and to be responsible for an important part of the myogenic, interdischarge interval-dependent, jitter.

Electric Stimulation↗
PubMed1993

Ataxia and areflexia in SOAA.

Fifteen patients with the classical syndrome of ophthalmoplegia, ataxia, and tendon areflexia (SOAA) were studied in an attempt to clarify the mechanisms of ataxia and myotatic hyporeflexia. All showed features of cerebellar rather than sensory ataxia. Peripheral nerve conduction studies, including F-waves, were normal in a majority of the patients, as was needle EMG. Low-amplitude compound sensory nerve potentials were seen in four patients only, and mild slowing of sensory conduction velocity in two. Three had abnormal blink reflex studies, suggestive of a central lesion in two, and another two showed a transient delay of N5 peak of brainstem auditory evoked potentials. Somatosensory evoked potentials were normal. Despite clinically depressed or absent tendon jerks, T-waves were elicited at normal latencies. These findings do not support the prevailing view that the neurological abnormalities in SOAA are due to involvement of sensory fibres in the peripheral nerves and dorsal roots. We suggest that lesions scattered in the brainstem tegmentum and in the cerebellar peduncles are responsible for the ataxia and the depressed tendon jerks.

Adolescent↗
PubMed1992

Jitter of the stimulated motor axon.

Electrical microstimulation of motor axons in conjunction with single fiber EMG (SFEMG) is increasingly used to measure the jitter of the motor endplates. This study examines the jitter of the stimulation site on the axon when stimulus strength is at threshold. In the absence of spurious blocking, this was found to be 5 microseconds on the average. With intermittent blocking, however, a mean additional jitter of 40 microseconds was obtained. The latter is considered to result from changing propagation velocity in the muscle fiber due to irregularity of activation rate. In clinical jitter studies, inadvertent threshold stimulation can result in significant error when associated with intermittent blocking.

Adult↗
PubMed1992

Jitter measurement by axonal micro-stimulation. Guidelines and technical notes.

Single fiber EMG (SFEMG) with axonal micro-stimulation is a convenient method to study the neuromuscular jitter at the individual motor end-plates. Compared to the original method of jitter measurement in voluntarily activated muscle, it has the advantage of perfect control of the discharge rate, including pauses in activity, useful in quantitative estimation of the neuromuscular transmission defect. It obviates the need to search for muscle fiber pairs. It can be used in young children and in uncooperative patients, as well as those with impaired voluntary motor control. It is useful in animal experiments as well as veterinary medicine. The technique eliminates the possibility of overestimating the jitter due to unrecognized interdischarge interval dependent jitter, as well as that of underestimating it due to unrecognized low jitter in split muscle fibers. The technique has certain pitfalls causing under- or overestimation. The paper gives practical guidelines and hints as to how to avoid some of these, particularly errors due to overlooked threshold stimulation and to unrecognized direct muscle fiber stimulation.

Action Potentials↗
PubMed1992

Calf-tendon jerks are altered in congenital equinovarus deformity.

Stretch reflexes of posterior tibial (PT) and triceps surae (TS) muscles were studied electrophysiologically in 27 children with unoperated unilateral congenital equinovarus deformity, in an attempt to evaluate changes in tone of the leg muscles as a possible pathogenetic factor. Significantly reduced latency of the PT responses on the affected side was recorded in a majority of patients. In most patients the amplitudes of the PT responses were asymmetrical; however, lateralization was inconsistent. The TS responses were asymmetrical in a smaller proportion of the patients, though still significantly different from the controls. The findings suggest an asymmetrical increase in excitability level of the PT motoneuron pool on the affected side.

Child, Preschool↗