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Biomedical subjects

J Lin

Publications and source records attributed to J Lin.

At least 721 records · Page 40Linked to original sources
PubMed1987

Vestibular ototoxicity of gentamicin assessed by the recording of a short-latency vestibular-evoked response in cats.

The short-latency vestibular-evoked response (VsER) and the auditory brain stem response (ABR) were recorded with scalp electrodes in four cats before, during, and after systemic administration of gentamicin. The VsER was altered and later disappeared in three cats, and in one cat it became asymmetric, typical of a unilateral vestibular lesion. In all cats the ABR was unaffected and remained normal through the end of the experiment 4 months later. Histopathological examination of the temporal bones of three cats showed severe damage to the vestibular end-organ, particularly in the summit of the cristae, but in lesser amounts in the hair cells on the slopes of the cristae and in the maculae. In one cat, the pathological condition was greater in one ear, corresponding to the asymmetry in the VsER records. This new method of inducing and recording the VsER has been demonstrated by the present study to be an effective tool for experimentally assessing vestibular end-organ and nerve function in animal models. Furthermore, these results indicate that the VsER is generated in the vestibular labyrinth, most probably by the cristae of the semicircular canals.

Animals↗
PubMed1987

Antagonism of acute physostigmine and neostigmine toxicity in mice by hemicholinium-3.

Hemicholinium-3 (HC-3) was administered intraperitoneally to mice concurrently with the intraperitoneal administration of physostigmine or neostigmine. HC-3 increased the LD50 values for both physostigmine and neostigmine but did not alter the effect on brain ACh levels produced by these agents. Since HC-3 does not cross the blood brain barrier after intraperitoneal administration, the antidoting action of HC-3 is peripherally mediated and does not solely involve an inhibition of ACh synthesis. The increase in brain acetylcholine caused by neostigmine was related to a reduction in acetylcholinesterase activity, providing evidence that intraperitoneally administered neostigmine crosses the blood-brain barrier.

Acetylcholine↗
PubMed1987

Volumetric asymmetry in the human amygdaloid complex.

The amygdaloid complex was parcellated into 15 nuclei based on cytoarchitecture in 19 human brains. The volumes of the nuclei were determined in the right and in the left hemisphere for each case. A multivariate analysis showed that the amygdaloid complex is asymmetrical between the hemispheres, with the lateral nucleus of the amygdala, which is larger in the right hemisphere, showing the strongest volumetric asymmetry. These findings are discussed in relation to the amygdala's role as a mediator between limbic and cortical processing, and in light of the right hemisphere's specialization for emotional behaviors.

Aging↗
PubMed1986

Energy storage during DNA girase activity.

In this work, we develop a minimal two-cycle model for the action of DNA girase. One of the cycles describes the ATP dependent chemicomechanical transduction performed by the enzyme. The other cycle describes the relaxing activity exhibited by girase on supercoiled DNA in the absence of substrates. Supercoiling of DNA is described as a random walk on a topological index. The mechanical energy storage in DNA is manifested in the fact that in general, the kinetic constants for the cycles do not satisfy Wegscheider relations. Finally, a connection is established between the degree of DNA supercoiling and the hydrolysis of ATP.

Adenosine Triphosphate↗
PubMed1986

The effect of loop diuretics on the vestibular system. Assessment by recording the vestibular evoked response.

Whether or to what extent loop diuretics, e.g., ethacrynic acid and furosemide, affect the vestibular system is controversial. We studied this problem by recording in cats the short-latency vestibular evoked response (VsER) to acceleration stimuli by skin electrodes before and after local or systemic administration of loop diuretics. The effect on the VsER was minimal in contrast to the major changes that appeared in the auditory evoked response, in which, among the waves known to originate from the brain stem, the most affected was N1. These findings suggest that the vestibular end-organ function is minimally affected by loop diuretics and that the changes in the vestibulo-ocular reflex reported by several authors might be due to the effect of the drugs on the central nervous system. Thus, recording of the VsER in experimental animal models might serve as a useful tool for direct evaluation of the effect of certain drugs and conditions on the vestibular system.

Animals↗
PubMed1986

Supraophthalmic intracarotid infusion of BCNU for malignant glioma.

We treated five patients with 11 supraophthalmic infusions of BCNU at 200 mg/m2 every 2 months. All three patients with residual tumors showed marked CT response after one infusion. Two patients with bilateral tumors had no response on the contralateral side. All four evaluable cases showed evidence of BCNU neurotoxicity. CT findings superficially resembled tumor recurrence, but white matter changes, nonspecific gyral enhancement, and delayed calcification were more indicative of neurotoxicity. There were no procedure-related complications. One autopsy suggested that direct parenchymal damage might be responsible for delayed neurotoxicity. Supraophthalmic BCNU infusion, at this dosage, is too toxic for cerebral tissue.

Adult↗
PubMed1985

An unusual corneal complication of soft contact lens.

An unusual complication caused by hydrophilic soft contact lenses developed in 13 patients (ten women and three men, 16 to 39 years old), most of whom had tight eyelids. The lesion consisted of an arc-like opacity in the superior cornea. The opacity lay in the superficial cornea about 1 to 3 mm from the corneoscleral limbus and had fine spokes extending away from the main trunk. In some cases the problem was unilateral and in others bilateral.

Adolescent↗
PubMed1985

Decays of 117Xe-->

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Journal Article↗
PubMed1985

Exogenous ATP enhances calcium influx in intact thymocytes.

Recent observations have indicated that exogenous adenosine triphosphate (ATP) may influence lymphocyte functions such as proliferation and cytoxicity. Here we report a novel activity of extracellular ATP--it specifically increases Ca2+ uptake in murine lymphocytes. ATP added to thymocytes increases the rate of [45Ca2+] uptake by up to 20-fold. The increased rate is seen with ATP concentrations as low as 500 microM and is half-maximal at approximately 2 mM ATP. The magnitude of stimulation by ATP is dependent on Mg2+ concentration, and ATP-Mg2+ complex is probably the true activator. Of the high-energy phosphate-containing compounds tested, including deoxy-ATP, only GTP showed a modest stimulation of calcium uptake. ADP, AMP, cyclic AMP, and adenosine did not significantly increase calcium uptake. Cellular integrity as indicated by trypan blue exclusion and ethidium bromide/acridine orange staining was unaffected by ATP. Ca2+ influx is the major mode of action of ATP in raising intrathymocyte Ca2+ levels, because neither the Ca2+ efflux nor the [45Ca2+]-Ca2+ exchange was significantly altered in the presence of ATP. Verapamil, a Ca2+ channel blocking agent, could not prevent the ATP effect, suggesting that ATP may be acting by a mechanism other than the voltage-dependent Ca2+ channel. An analysis of intracellular and extracellular ATP levels by chemiluminescence assay indicated no significant ATP entry into intact lymphocytes. Also, ATP added to the medium containing thymocytes was destroyed (approximately 50% by 20 min). The nonhydrolyzable ATP analogs, AMPPCP and AMPPNP, were unable to stimulate a significant amount of Ca2+ uptake, suggesting the involvement of a cell surface phosphotransferase activity. This was supported by the demonstration of a threefold to fivefold increase in the labeling of protein and phospholipid fractions obtained from intact thymocytes exposed to [gamma 32P]ATP for 30 min. Ca2+ is believed to play an important role in a variety of lymphocyte functions, including mitogenesis and natural killer cell activity. The data herein thus provide a potential mechanism for the action of exogenous ATP on these lymphocyte functions.

Adenosine Triphosphate↗