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Biomedical subjects

J Ochoa

Publications and source records attributed to J Ochoa.

At least 55 records · Page 3Linked to original sources
PubMed1987

The role of melatonin and serotonin in aging.

The hypothesis presented in this paper defines aging as a pathological process originating in the pineal gland. This results in a diminished output of melatonin, along with a diminished melatonin to serotonin ratio, leading to a decline in adaptive processes and a predictable syndrome manifested by the "diseases of the aged" (DOA) and subsequent death of the organism. That is, aging is a syndrome of relative melatonin deficiency resulting from the gradual failure of the pineal gland.

Aging↗
PubMed1984

Sensory correlates of somatic afferent fibre activation.

This paper reviews advances in our knowledge of mechanoreception and nociception. Conventional microneurography has been used in combination with a new method of intraneural microstimulation to classify and activate single myelinated or small groups of unmyelinated sensory units in intact peripheral nerves in alert subjects. The results indicate exquisite capacity of the human brain to detect, localise, delineate, classify and quantify specific sensations from the input of certain types of single sensory units, particularly in fingertips. Application of the powerful technique of microstimulation has improved our understanding of the mechanisms underlying clinical tests such as two-point discrimination and point localization, and has shed new light on peripheral and central modulation of pain.

Afferent Pathways↗
PubMed1983

Sensations evoked by intraneural microstimulation of single mechanoreceptor units innervating the human hand.

Intraneural microstimulation (i.n.m.s.) was performed in awake human volunteers, using tungsten micro-electrodes inserted into median and ulnar nerve fascicles supplying the skin of the hand. The same electrodes were used alternatively to record impulse activity from single nerve fibres at the i.n.m.s. sites. Monitoring occasionally, with a proximal electrode, the impulse traffic evoked by i.n.m.s. distally in the same fascicle, established that the stimulation procedure could be made selective enough to activate single myelinated fibres in isolation, while also permitting multifibre recruitment. Monitoring propagated impulses also established that i.n.m.s. of a single myelinated fibre supplying a low-threshold mechanoreceptor in the hand might evoke an elementary sensation. Such sensations were fully endowed with cognitive attributes amenable to psychophysical estimation: quality, magnitude and localized projection. Psychophysical tests were made during i.n.m.s. at intraneural sites where single-unit activity was recorded from classified RA, PC, SA I or SA II mechanoreceptors. Changes in excitability of the nerve fibre of an identified unit, induced by further i.n.m.s., certified that the recorded unit had been stimulated during psychophysical tests. Comparing physical location of the receptive field of a recorded unit and localization of the projected field of the corresponding elementary sensation, revealed that either predicted the other accurately. This further assisted identification of the unit activated by i.n.m.s. The type of a recorded unit and the quality of the elementary sensation evoked by its activation were also reciprocally predictive. RA units evoked intermittent tapping, PC units vibration or tickle and SA I units evoked pressure. SA II units evoked no sensation when activated in isolation. Afferent impulse frequency determined magnitude of pressure in the SA I system, and frequency of vibration in the PC system. In the RA system, stimulation frequency determined frequency of tapping-flutter-vibration sensation at relatively low rates and subjective intensity of sensation at high rates. These findings endorse the concept that quality of sensation is coded in specific sensory systems. Further, they provide novel evidence that sensory quality, magnitude and localization can be exquisitely resolved at cognitive levels on the basis of input initiated in a single mechanoreceptor unit.

Adult↗
PubMed1982

Abnormal spontaneous activity in single sensory nerve fibers in humans.

Spontaneous discharges generated in human motor nerve fibers have long been recognized, and their effects have been comfortably recorded from the muscle target with needle electrodes. Delay in documenting comparable phenomena from sensory fibers is explained by the need to record the abnormal activity directly from nerve fibers using intraneural microelectrodes. The hypothesis that a variety of positive sensory phenomena associated with nerve disease is the result of ectopic impulse generation from within the sensory unit can now be tested with microneurographic techniques. Research inaugurating microneurography in the study of positive sensory phenomena has yielded evidence of ectopic impulse generation from sensory units in subjects actually experiencing paresthesia or pain. The phenomenology of ectopic discharges in sensory fibers has been recorded with intraneural microelectrodes in: (1) transient postischemic paresthesia induced experimentally in otherwise normal nerves; (2) spontaneous paresthesia symptomatic to (probable) structural nerve pathology; and (3) in the sign of Tinel in traumatic neuromas.

Action Potentials↗
PubMed1980

Remission of the Lambert-Eaton syndrome and small cell anaplastic carcinoma of the lung induced by chemotherapy and radiotherapy.

A patient presented with the Lambert-Eaton syndrome and small cell anaplastic carcinoma of the lung was subsequently diagnosed. Treatment with cytotoxic chemotherapy and radiotherapy resulted in remission of both the cancer and the neuromuscular disorder. This case represents the first documented remission of the Lambert-Eaton syndrome following nonoperative treatment of the primary malignancy and emphasizes the therapeutic value of early diagnosis of this disorder.

Antineoplastic Agents↗
PubMed1980

Poliomyelitis-like syndrome associated with asthma. A case report and review of the literature.

A 5-year-old asthmatic boy had flaccid monoplegia six days after an asthma attack. A similar association has been reported in 13 previous cases. However, to our knowledge, this is the first report from the American continent. This syndrome has a poor prognosis and can be confused with poliomyelitis. The localizing effect of abnormal inspiratory-biceps synkinesis may be important.

Asthma↗
PubMed1976

Postradiation motor neuron syndrome.

We report an unusual case of selective lower motor neuron syndrome (MNS) complicating whole neuraxis radiation therapy. Only three well-documented similar cases have been found in a thorough review of the literature. The syndrome has a stereotyped time course and is self-limited. We discuss here possible pathogenetic mechanisms and their relationship to motor neuron disease.

Adolescent↗
PubMed1975

Sub-clinical entrapment neuropathy in man.

Twelve median and 12 ulnar nerves were obtained at routine autopsies from patients without known disease of the peripheral nervous system. Enlargement of cross-sectional area due to an increase in connective tissue elements was commonly present in the ulnar nerve at the elbow and in the median nerve under the flexor retinaculum. Renaut bodies were also prominent at these two sites. The connective tissue changes did not appear to be related to the presence or absence of nerve fibre damage. When nerve fibres were teased apart and examined individually, localised changes were found at the elbow in 5 ulnar nerves and under the flexor retinaculum in 5 median nerves. The changes were mild and transverse sections at the same levels showed few abnormalities. However, the changes were similar in character to those described previously in experimental animals with entrapment syndromes. They are therefore considered to be valid evidence of sub-clinical entrapment in apparently unaffected human subjects.

Acute Disease↗