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Biomedical subjects

J Alvarez

Publications and source records attributed to J Alvarez.

At least 307 records · Page 17Linked to original sources
PubMed1986

Candida glabrata meningitis.

We have reported an unusual case of Candida glabrata meningitis causing acute changes in mental status in a chronically ill, elderly patient with non-insulin-dependent diabetes mellitus. Candida glabrata was identified by Gram stain, culture, and fermentation pattern from the CSF. Although the patient died of foreign body aspiration, an excellent clinical response was initially obtained with amphotericin B and 5-flucytosine. This is the first report of a symptomatic Candida glabrata meningitis.

Aged↗
PubMed1985

Microtubules and caliber of central and peripheral processes of sensory axons.

The microtubular content and caliber of sensory axons were studied in the L7 dorsal root, at the distal pole of the L7 spinal ganglion, and in the sural nerve of cats. Calibers of myelinated axons were symmetrical about the ganglion. In contrast, nonmedullated axons were strikingly different; 80% of the population at the root were smaller than 0.4 micron2, whilst just across the ganglion the same group was less than 20%. The microtubule densities of myelinated axons of the root were 11.8 and 6.1 microtubules/micron2 for 3- and 10 microns diameter axons, respectively. Across the ganglion the densities of myelinated axons of equal sizes were 24.2 and 14.4 microtubules/micron2, respectively. These values represent an approximate ratio of 1:2 between central and peripheral microtubule densities. Microtubule densities for nonmedullated axons also decreased with the increase in the cross-sectional area. The densities of root nonmedullated axons ranged between 90 and 10 microtubules/micron2; these were smaller, usually by a factor of three, than the densities of peripheral axons of a similar size (range: 367-44). Contrasting with the differences observed across the ganglion, the microtubular content and caliber of sensory axons seems to be quite uniform along their peripheral course. This is supported by the similar values found in the juxtaganglionic and sural nerves. It is estimated that an axon that contains 90 microtubules/micron2 has 26.7 mg of tubulin per ml of axoplasm in its assembled form, and 3.0 mg/ml if it contains 10 microtubules/micron2; these values are the practical limits of assembled tubulin in axoplasms.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1985

[Transient neonatal hyperthyroidism in the child of a treated hyperthyroid mother. Subsequent appearance of sexual precocity].

We report a newborn female with neonatal hyperthyroidism, born to a mother with Graves disease treated with potassium iodide and carbimazole. At four months she had some breast development, a bone age advance of one year, and elevated levels of FSH and estradiol. Later on the prolactin level was also raised, while LH and TSH values continued low. Posteriorly, irregular cutaneous pigmentation, brown in colour, was evident on the neck and trunk, and a McCune-Albright syndrome was suspected. The relationship between these conditions and treatment of them is discussed.

Carbimazole↗
PubMed1985

Slow axoplasmic transport: a fiction?

Ribosomes have not been observed in axoplasm. This had led to the notions that the perikaryon is the only source of neuronal proteins and that the axoplasm is supplied by a (slow) transport mechanism. However, we question these two notions because they are unable to give an account of real neurones in accordance with the body of biological knowledge. We point out, for example, that the synthetic rate of perikarya or the life span of axoplasmic proteins should be beyond known ranges for animal cells and that a uniform axon is unlikely to result if it is fed from one end. We propose an alternative view for the maintenance of the axon which accepts the controversial idea of axoplasmic synthesis of proteins; as a result, the slow transport becomes unnecessary. Our view gives a qualitative account of the observations dealing with the maintenance of the axoplasm. To account for the phenomenology in a more quantitative fashion, a computer simulation was carried out where the equations of the program provided only for axoplasmic synthesis of proteins; the set of curves retrieved were in good agreement with experimental findings believed so far to support the notion of slow transport. In conclusion, we think that the notion of "slow axoplasmic transport" has been a misinterpretation of good observations because the frame of reference was incomplete in not providing for axoplasmic synthesis of proteins.

Animals↗
PubMed1984

Effects of electron donors on Ca2+-dependent K+ transport in one-step inside-out vesicles from the human erythrocyte membrane.

The interactions between reducing agents and Ca2+ in the activation of Ca2+-dependent K+ transport have been studied in one-step inside-out vesicles. The artificial electron donor system ascorbate + phenazine methosulphate increases the apparent sensitivity to Ca2+ by about 5-times over control values (half activation constant, about 5 X 10(-8) M) while oxidized cytochrome c decreases the sensitivity to about 1/3 of the controls. Using redox buffers at a fixed pCa it is shown that the shift from the low to the high-affinity state can be accounted by the reduction of a membrane component accepting two electrons and with an apparent standard redox potential (pH 7.5) of 47 mV. The electrons can be transferred directly from reduced PMS or to oxidized cytochrome c, but not from ascorbate, NADH or reduced glutathione.

Ascorbic Acid↗
PubMed1984

Effects of moderate hypoxia on premature action potentials of rabbit papillary muscle.

Experiments were performed to study the effects of hypoxia on the characteristics of premature action potentials of rabbit papillary muscles. At normal resting potential, the duration of the premature action potential at the shortest coupling intervals was always greater than that of the control response. As the coupling interval was increased beyond 150 ms, the duration of the premature action potential regained control values. In cells depolarized to -70 mV by KCl, early lengthening of the premature response was attenuated. After 60 min of hypoxia, recovery of action potential duration at normal and reduced resting potentials was accelerated. The maximum rate of depolarization and its reactivation time constant were not affected by 60 min of hypoxia. It is suggested that intracellular free Ca is important in the control of action potential duration via the outward background potassium current.

Action Potentials↗
PubMed1984

Role of the slow inward current during the repolarisation process in frog atrial trabeculae.

Voltage clamp experiments were performed to analyse the influence of the slow inward current (isi) on the repolarisation process in frog atrium. MnCl2 was used as isi blocker. The action potential was prolonged by depolarising pulses applied during the plateau. This was an expected result considering that, at positive potentials the time constant for isi inactivation increases. This effect was abolished by Mn ions which in turn block isi. The results suggest that inactivation of isi is of primary importance in determining the repolarisation rate. The action of Mn was not selective, since it reduced the background K current. This effect seems to be related to the decrease in Ca influx.

Action Potentials↗
PubMed1983

Axoplasmic incorporation of amino acids in myelinated fibers of the cat.

Incorporation of amino acids into the axoplasm of nerve fibers of the cat was studied with radioautography. The dorsal funiculus of the spinal cord, or the sciatic nerve, was exposed to tritiated leucine, lysine, and proline; the tissue was processed 1 h later or the following day. In all instances, a radioautographic response of widely varying intensity was observed over the axoplasm; this response could not be adscribed to emissions originating from axonal mitochondria or myelin. The axoplasmic response ranged to as much as 56% compared with that over nearby glial cytoplasm and was often conspicuously greater than that over the surrounding myelin. We interpret our findings as axoplasmic synthesis of proteins. This finding has implications in the maintenance of the neuron.

Amino Acids↗
PubMed1983

Axoplasmic incorporation of amino acids in a myelinated fiber exceeds that of its soma: a radioautographic study.

The axoplasmic incorporation of amino acids was studied in the giant Mauthner axon to determine its magnitude, to estimate the half-life of the resulting material, and to establish whether or not it undergoes transport. The incorporation of labeled leucine, lysine, and proline was followed by radioautography. The tracers were injected away from the cell body, either in the floor of the IV ventricle or into the spinal cord. Radioautographic reaction on the Mauthner somata was barely discernible. However, at the site of injection, for survivals to 5.6 days, a peak of reaction was observed on the Mauthner axoplasm, with a sharp and symmetric decrement in both central and distal directions; the intensity of the peak decreased with survival (14% at 5.6 days). In intact fibers, the intensity of the reaction was 1.4% compared with that over the Nissl substance of neighboring somata; by contrast, in severed fibers whose axoplasm had been directly exposed to the tracers the reaction rose to 4.1%. At early times, the intensity of the response of the axoplasm as a function of survival of the fish did not have a lag time. In high-resolution radioautograms, most of the grains overlay the ground axoplasm. Cycloheximide depressed the reaction over the fiber open to the extracellular space by 55% whereas only by 20% over the intact fiber. Adsorption of free amino acids or their binding to tRNA were ruled out as a cause of the radioautographic response. Our results indicated that incorporation of amino acids into macromolecules of the Mauthner fiber occurred locally, and its magnitude over the whole axoplasm was estimated to be one order of magnitude larger than that occurring in the soma. The bulk of the material resulting from this incorporation did not undergo transport and survived some days. We suggest that the amino acids were incorporated by a ribosomal mechanism.

Amino Acids↗
PubMed1983

Microtubules in short and in long axons of the same caliber: implications for the maintenance of the neuron.

Microtubules are the morphological manifestation of a defined protein, tubulin, and they sustain axonal transport. Phrenic fibers are seven times longer than abducent fibers; however, in 5-micrometers axons of either nerve the density of the microtubules is the same (approximately 21 microtubules/micrometers2). In addition, no difference was found in microtubule density between the cervical and juxtadiaphragmatic levels of the phrenic axons. These findings are contrasted with predictions based on the perikaryal theory of the origin of axoplasm.

Abducens Nerve↗
PubMed1983

Early apocrine change in hyperplastic cystic disease.

Biopsy material from 42 cases of florid hyperplastic cystic disease of the breast were reviewed and were found to have foci of apocrine metaplasia. This appearance was limited to the ductular epithelium of hyperplastic lobules. It is believed that this scattered change is an initial feature in relation to the genesis of apocrine-lined and fully developed cysts.

Breast↗