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Biomedical subjects

J Jacoby

Publications and source records attributed to J Jacoby.

At least 19 recordsLinked to original sources
PubMed1991

Uptake and reutilization of surfactant phospholipids by type II cells of isolated perfused lung.

To investigate the role of type II alveolar cells in surfactant uptake and reutilization while cells are in situ, the combination of isolated perfused rat lung and type II cell isolation has been used. After an equilibration period, isolated perfused rat lungs received an intratracheal injection of labeled rat surfactant or a labeled bovine-derived preparation, and the perfusion continued. At time intervals less than or equal to 3 h, lungs were lavaged and type II cells isolated. Freshly isolated cells from perfused lungs were highly viable as judged by trypan blue exclusion and by linear incorporation of labeled leucine into trichloroacetic acid precipitable protein during perfusion. After cell isolation, total phospholipid or phosphatidylcholine was extracted from cells. Incorporation of surfactant phosphatidylcholine label into cellular phosphatidylcholine was shown to be linear with time whether lungs received natural rat surfactant or bovine-derived surfactant preparation. Uptake of natural surfactant from alveoli into type II cells was approximately three times greater than uptake of bovine-derived material. Results of administration of 0.5 mumol surfactant phospholipid or 2.0 mumol were similar except that administration of 2.0 mumol of natural rat surfactant caused uptake to become saturated at 1 h of perfusion. An increase in cell-associated phosphatidylcholine occurred whether results were expressed on basis of cellular DNA or specific activity of cellular phosphatidylcholine. Majority of administered surfactant label remained lavage fluid associated at 3 h, whereas remainder was associated with isolated cells or debris from cell preparation. Little label was detected in perfusion medium.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Sex differences in personality traits and coping styles of hospitalized alcoholics.

Forty inpatients on an alcohol detoxication unit of a large municipal hospital were administered a battery of tests consisting of a Coping Styles scale, a Personality Profile scale, a Depression scale and the Brief MAST. A demographically comparable comparison group of 40 outpatients attending the medical screening clinic at the same hospital also completed the battery. The two groups did not differ in terms of age, education or the ratio of men to women. There were significant differences in coping styles and personality characteristics between alcoholics and nonalcoholics and, to a large extent, between men and women within the alcoholic group. Practically no significant differences were found between the men in the two groups, but female alcoholics differed greatly from nonalcoholic women in terms of coping styles, personality variables and also in terms of conflict. These findings indicate that the differences between alcoholic and nonalcoholics in the sample were due largely to patterns uniquely characterizing the female alcoholic group. Results are discussed in terms of cultural expectations.

Adaptation, Psychological↗
PubMed1990

Diltiazem reduces the contractility of extraocular muscles in vitro and in vivo.

Diltiazem, a Ca-channel blocker that is used clinically for the treatment of hypertension and cardiac arrhythmias, reduces the contractility of extraocular muscles. Exposure of rabbit extraocular muscle to diltiazem in vitro reduces the sustained tension that is generated by the tonic, multiply innervated fibers, and decreases the baseline, or resting, tension of the muscle. When diltiazem is injected into a selected extraocular muscle in the rabbit in vivo, it causes a temporary weakening of the muscle, which is indicated by a deviation of eye position. These in vivo effects are of short duration, are easily reproducible, and vary with dosage. The results of this study raise the possibility that diltiazem may be used as an alternative to the surgical treatment of strabismus and other oculomotor dysfunctions including blepharospasm.

Adenosine Triphosphatases↗
PubMed1990

Systematic variation in myosin expression along extraocular muscle fibres of the adult rat.

Monoclonal antibodies (McAB) specific for fast (C14) and slow (S58) myosin, and a myosin antigenically similar to neonatal/embryonic myosin in mammals (ALD180), were used to characterize the myosin distribution in orbital layer fibres of rat extraocular muscles (EOM) in relation to innervation patterns. The orbital layer is composed of both singly-innervated (SIF) and multiply-innervated (MIF) fibres. The SIFs have the characteristics of twitch fibres, while the MIFs, in addition to possessing many small endings characteristic of tonic fibres, also have an en-plaque-like innervation in the endplate band resembling that of the adjacent SIFs. Myosin expression in MIFs and SIFs is unusual and varies systematically along the length of the fibres. Both SIFs and MIFs label with ALD180, but this labelling is absent in both fibre types in the endplate band region, where all fibres label with C14. Distally and also proximally to the endplate band, SIFs label with both ALD180 and C14, while the MIFs, innervated by many small, superficial endings in these regions, label with ALD180 only. This pattern of myosin expression could also be demonstrated in isolated fibres. The results are discussed in relation to the hypothesis that both populations of orbital layer fibres express constitutively both fast and the neonatal-like myosin, and that superimposed on this constitutive expression twitch or tonic innervation acts locally to selectively suppress either neonatal-like or fast myosin, respectively.

Adenosine Triphosphatases↗
PubMed1989

Electrical properties and innervation of fibers in the orbital layer of rat extraocular muscles.

1. The inferior rectus muscle of rat, one of the extraocular muscles, contains two populations of multiply innervated fibers (MIFs): orbital MIFs, located in the orbital layer of the muscle and global MIFs, found in the global layer. The electrical properties and the responses to nerve stimulation of orbital MIFs were studied with single intracellular electrodes and compared with those of twitch fibers of the orbital layer, MIFs of the global layer, and tonic fibers of the frog. 2. About 90% of the orbital MIFs did not produce overshooting action potentials. In these fibers the characteristics and time course of the responses to nerve stimulation varied along the length of the fibers. Within 2 mm of the end-plate band of the muscle, the responses consisted of several small end-plate potentials (EPPs) and a nonovershooting spike. Distal to 2 mm, the responses in most fibers consisted of large and small EPPs with no spiking response. Some fibers produced very small spikes surmounted on large EPPs. 3. Overshooting action potentials were observed in approximately 10% of the orbital MIFs recorded between the end-plate band and 2 mm distal. The presence or absence of action potentials was not related to the magnitude of the resting potential of the fibers. 4. The threshold of nerve stimulated responses in orbital MIFs was the same as that in orbital twitch fibers. A large number of orbital MIFs had latencies equal to those for the orbital twitch fibers recorded at the same distance from the end-plate band, but the average latency was greater in the MIFs. The latency of orbital MIFs was about one-half of that for the MIFs of the global layer. The values for the effective resistance and membrane time constant of orbital MIFs fell between those for orbital twitch fibers on the one hand, and global MIFs and frog tonic fibers on the other. 5. In order to compare electrical properties with innervation patterns, fibers identified electrophysiologically as orbital MIFs were injected with the fluorescent dye Lucifer yellow and then traced in Epon-embedded, serial transverse sections. In addition to numerous superficial endings distributed along the fibers, a single "en plaque" ending was also found in the end-plate band that resembled the end plates of the adjacent orbital twitch fibers. 6. From these results we conclude that the electrical activity of orbital MIFs varies along the length of the fibers.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1988

Expression of a novel combination of fast and slow troponin T isoforms in rabbit extraocular muscles.

The properties of extraocular muscles (EOMs) are quite different from those of the trunk and limb. Here we show that there is a novel pattern of troponin T (TnT) expression in EOMs which most likely contributes to the fine control of ocular movement and may reflect their innervation by cranial motoneurons. Three regions of the muscle were analysed to distinguish the TnT isoforms present in the fast singly-innervated fibres from those in the multiply-innervated fibres. More than 95% of the TnT in the singly-innervated fibres is TnT3f, which exhibits the most graded response to changes in calcium concentration during activation (Schachat et al., J. molec. Biol. 198, 551-4). In multiply-innervated fibres, which exhibit tonic contractures, the slow troponin T TnT2s is expressed. While neither TnT3f nor TnT2s is unique to EOM, this pattern is unusual in two respects: first, both TnT3f and TnT2s are minor components of the trunk and limb musculature, and second, most muscles express several fast and both slow TnT species. Although EOM occupies a highly specialized physiological niche, its unusual physiology is not reflected in the presence of new TnT isoforms but in the expression of a different ratio of the known species of TnT.

Animals↗
PubMed1987

Dependence of tonic tension on extracellular calcium in rat extraocular muscle.

Ca2+-free saline containing 3.0 mM Mg2+ virtually abolishes the tonic tension evoked by depolarization with a high K+ concentration of the tonic multiply innervated fibers of rat extraocular muscles. The tonic tension abolished by Ca2+ withdrawal is restored when Ca2+ is substituted by Sr2+ but not by Ni2+. The increase of Mg2+ reduces the tonic tension and displaces the tension-log K+ relationship to the right. Cd2+ significantly reduces the tension amplitude but does not shift the tension-log K+ relationship. The organic blocker of Ca2+ channels, nifedipine (1-10 microM), has no effect on the tonic tension. In contrast, diltiazem (20 microM) reduces the amplitude of the responses without changing the tension-log K+ relationship. Both foreign anions NO3- and SCN- potentiate tonic tension without changing the tension-log K+ relationship. SCN- increases the resting tension of the muscle; this effect depends on Ca2+. In conclusion, the disappearance of tonic tension after Ca2+ withdrawal is not due to depolarization of the fibers or inactivation of the contractile responses. It is suggested that entry of extracellular Ca2+, via a voltage-dependent Ca2+ conductance, or specific interactions of Ca2+ with membrane sites involved in the regulation of excitation-contraction coupling play a role in evoking tension in tonic fibers.

Animals↗
PubMed1986

Induction of action potentials by denervation of tonic fibres in rat extraocular muscles.

The effects of denervation by nerve section on the electrical properties of tonic and twitch fibres of rat extraocular muscles were examined. Normally innervated tonic fibres lack action potentials. Upon direct stimulation they generate graded, voltage-dependent responses or slow peak potentials (s.p.p.s). However, one week after denervation the s.p.p.s are transformed into action potentials which are slower and broader than those of twitch fibres. The action potentials are Na dependent and partially resistant to blockade with 10(-5) M-tetrodotoxin and 10(-6) M-saxitoxin. Changing the holding potential of the fibres from -80 mV to more negative levels increases the maximal rate of rise of the action potential. This effect is not observed on the s.p.p.s of normally innervated fibres. Following denervation the resting potential of tonic and twitch fibres becomes about 10-15 mV less negative. In denervated muscles stimulation with pulses of hyperpolarizing current evokes graded responses in tonic fibres and action potentials in twitch fibres. In normally innervated muscles, these anodal break responses are never observed in tonic fibres and are very rare in twitch fibres. By two weeks after nerve section, reinnervation is present. The action potentials of tonic fibres are still present but stronger stimulation is needed to evoke anodal break responses. By three weeks, direct stimulation of tonic fibres evokes normal s.p.p.s in about 25% of the studied fibres and action potentials in the rest. By four weeks, most tonic fibres have lost the action potential but small anodal break responses can be evoked in most. It is suggested that following denervation a new population of Na channels appears in tonic fibres. The properties of these channels are different from those of the channels normally present in innervated tonic fibres but they are in some ways similar to those of the channels which appear in twitch fibres following denervation.

Action Potentials↗
PubMed1984

Efferent projections of the torus semicircularis to the medulla of the tadpole, Rana catesbeiana.

Horseradish peroxidase injections into the medulla of tadpoles demonstrate, by back-filling, efferent neurons in the torus semicircularis which project to the ipsilateral superior olive. This projection, as well as one to the vicinity of the efferent neurons of the contralateral VIII and lateral line nerves, is confirmed by tracing anterograde transport following HRP injections into the torus semicircularis. These efferent neurons, located primarily in the principal nucleus of the torus within the terminal field of the projection from the superior olive, represent the only reported descending path to the superior olive and efferent nuclei in a non-mammalian vertebrate.

Animals↗
PubMed1983

The acoustic and lateral line nuclei are distinct in the premetamorphic frog, Rana catesbeiana.

The transition from aquatic to terrestrial hearing in the frog occurs during metamorphosis and during the disappearance of the lateral line system. The coincidence in time of these two processes and morphological similarities between the acoustic and lateral line systems has led to the suggestion (Larsell, '34) that the lateral line nuclei are transformed into the acoustic nuclei. The relation between the acoustic and lateral line systems was investigated by studying the distribution of primary afferents, the dendritic patterns of the cells in the primary nuclei, and the development of the nuclei in the premetamorphic bullfrog, Rana catesbeiana. The posterior and anterior lateral line roots distribute to a neuropil located medial to the dorsal medullary nucleus. Horseradish peroxidase (HRP) injections into the contralateral tegmentum fill cells in the periventricular region whose dendrites ramify within the neuropil. These cells constitute the lateral line nuclei. The amphibian and basilar papillary roots of the acoustic system distribute to the more lateral nuclear region. The dendrites of these cells arborize within the nucleus and not in the lateral line neuropil. The dorsal medullary nucleus is, therefore, the acoustic nucleus (AcN). [3H]-thymidine labeling reveals that newly generated cells occupy the AcN within a few hours of their formation throughout the period when anatomical analysis shows the parallel growth and diminution of the lateral line neuropil and nuclei. This study indicates that the lateral line and acoustic systems are morphologically independent at the level of the primary afferents and primary nuclei throughout early development.

Animals↗
PubMed1978

Nutrition and fertility: some iconoclastic results.

In this paper, the evidence available is used to conclude that, as levels of nutrition increase from insufficient to excessive, fertility first increases and then decreases. This suggests that the relationship between fertility and nutrition has the shape of an inverted U. Next, the hypothesis is explicitly tested using countries as units of observation. In the statistical analysis, the possibility of spurious relationships is carefully controlled. The results strongly support the hypothesis that, for existing levels, additional intake of nutrients decreases the levels of fertility.

Animals↗