Search PubMed⌕ Search

Biomedical subjects

R L Schultz

Publications and source records attributed to R L Schultz.

At least 37 records · Page 2Linked to original sources
PubMed1986

Membrane alterations in cerebral cortex when using PIPES buffer.

When used for vascular perfusion of brain, 0.1 M PIPES-buffered 3% glutaraldehyde resulted in the formation of expanded, vesicle-filled cell processes limited by multiple membrane layers. These structures, termed multivesicular myelin figures and interpreted as artefacts, were most common in layer 2 of the cerebral cortex. When cacodylate or phosphate buffer was used instead of PIPES buffer in the primary fixative, such structures were not seen. The use of a more concentrated initial aldehyde fixative, PIPES-buffered, markedly reduced the size and numbers of these artefacts when compared to PIPES-buffered 3% glutaraldehyde only. Slowing the initial perfusion rate increased the size and frequency of occurrence of multivesicular myelin figures with PIPES buffer when compared to optimum perfusions. Prolonged initial exposure to PIPES buffer by using it to wash out the blood and then perfusing with fixative 5 min later did not increase the number or size of multivesicular myelin figures but did reduce the multivesicular nature of the artefacts. We suggest that the non-toxic nature of PIPES buffer allowed the formation of these membranous artefacts, while phosphate and cacodylate interfered with the cellular activity during the process of fixation.

Alkanesulfonates↗
PubMed1984

Ultrastructural characterization of glial cells in the rat pineal gland with special reference to the pineal stalk.

In the present study the "interstitial" cells of the superficial pineal gland and the nonparenchymal cells of the pineal stalk in Sprague-Dawley rats were examined ultrastructurally with the aim of defining the cells more closely. The "interstitial" cells of the superficial pineal gland do not represent a homogeneous cell population. The most abundant cell type is the mononuclear phagocyte, most easily recognized by its dark appearance and its content of primary and conspicuous secondary lysosomes. Astrocytes can be distinguished by the typical appearance of their nuclei (i.e., a thin continuous rim of heterochromatin adjacent to the nuclear membrane), identical to that of astrocytes in the CNS. Depending on the absence or presence of glial filaments and their amount, a spectrum of astrocytic cells is present. Mature astrocytes with filaments throughout their cytoplasm are rare. Immature glial cells with few or no filaments predominate. In the vicinity of blood vessels pericytes are present. In view of the fact that the "interstitial" cells could generally be identified it is suggested to abandon the term interstitial for the cells in question. In the pineal stalk mature astrocytes predominate; they have some features in common with pinealocytes, i.e., the presence of intergrade endoplasmic reticulum and grumose bodies (lysosomes). Other unusual features are a relative abundance of coated pits and vesicles. Oligodendrocytes are restricted to the proximal part of the stalk, near the deep pineal, where myelinated axons are abundant. More distally a few Schwann cells were seen.

Animals↗
PubMed1984

The ultrastructure of the nerve fibers and pinealocytes in the rat pineal stalk.

In view of the increasing interest in the central innervation of the mammalian pineal gland, this aspect was studied in depth in the rat. This species is especially suited since the nerve fibers in question form a distinct bundle running from the deep to the superficial pineal gland through the pineal stalk. The axons were counted and analysed ultrastructurally in the pineal stalks cut transversely at three levels (proximal, intermediate, and distal) relative to the neural axis and in longitudinal sections. The number of nerve fibers was highly variable, ranging from 551 to 1,132 proximally and from 110 to 448 distally, indicating that many fibers terminate in the stalk or leave the stalk after forming a loop. Large myelinated axons, which are abundant proximally, appear to lose their sheaths along their course through the stalk. Most of the axons were small and unmyelinated. A few of these had the appearance of sympathetic fibers and disappeared after sympathectomy. Others contained abundant neurosecretory granules, and, according to the literature, may originate in the hypothalamic paraventricular nuclei. The majority of the small axons which are apparently devoid of granules and dense-cored vesicles may come from the habenular nuclei and the stria medullaris. In addition to axons, the stalk contains astrocytes, a few oligodendrocytes and Schwann cells, as well as pinealocytes identical to those of the superficial pineal gland.

Acid Phosphatase↗
PubMed1983

"Synaptic" ribbons and spherules of the guinea pig pineal gland: inverse day/night differences in number.

The present study deals with the functionally enigmatic "synaptic" ribbons and spherules of guinea pig pinealocytes. Whereas the ribbons have been shown to exhibit a 24-hr rhythmicity with low numbers during the day and high numbers at night, very little of a definitive nature is known about the spherules. Sixteen male guinea pigs of the Hartley strain were perfusion fixed, 8 between 0900-1100 hr, and 8 between 2100-2300 hr. The ribbons and spherules were counted in the pineal parenchyma of the proximal, intermediate, and distal regions. In confirmation of earlier studies, it was found that "synaptic" ribbons are equally abundant in the proximal, intermediate, and distal regions of the gland, during both the day and the night, and that they increase significantly in number at night when compared with daytime values. The spherules, by contrast, are more abundant proximally and are present in greater numbers during the day than at night. As ribbons and spherules are usually not found in one and the same pinealocytic profile, and based on previous electrophysiological studies, it is proposed that the ribbons are morphological markers of nocturnally active pinealocytes, whereas spherules characterize diurnally active pinealocytes.

Animals↗
PubMed1983

The principal projection pathway between the olfactory bulb and the prepyriform cortex in the cat.

The anatomy and neuroelectric properties of the lateral olfactory tract (LOT) were investigated in the cat. Electron micrographs were obtained from sampled areas across the rostro-caudal projection of the pathway. Fiber diameters were estimated and axon spectra were obtained from three regions corresponding to peduncle, mid-LOT, and caudal-LOT. The mean inside diameter for all measured axons was 1.13 +/- 0.53 microns. The greatest number was found in the peduncle (approximately 600,000 axons). Mid-LOT and caudal-LOT each contained approximately 250,000 axons. Unmyelinated processes were estimated to be more numerous than the myelinated axons. Synaptic structures were also observed in the LOT. Cross-sectional area measurements of the LOT were obtained from tissue prepared for light microscopy. The area decreased from about 0.3 to 0.2 mm2 across the projection from olfactory bulb to cortex. The anatomical data were used to predict the conduction properties of transmission over the LOT. The olfactory bulb mitral cells were stimulated electrically and conduction velocity and temporal dispersion were evaluated in the tract. The strength-duration and stimulus-response curves and the potential profile during stimulation were also obtained. The time constant for LOT axons was 0.3 msec. The stimulus-response curve was sigmoidal in shape for both presynaptic and postsynaptic responses. The relationship between input (the action potentials) and output (cortical postsynaptic potentials) was linear up to 90 times threshold. Action potentials were conducted at 20 m/sec across the pathway over the peduncle and decreased to about 10 m/sec in caudal aspects. The potential profile for action potentials decayed exponentially into the depths of the cortex whereas the synaptic potential was a surface negative dipole field. The axon spectra were convolved with the electrophysiological properties of the LOT to mathematically reconstruct action potentials. The empirically derived mono- and biphasic curves fitted reasonably well with experimentally derived data under various stimulus conditions.

Action Potentials↗
PubMed1982

Short-term intubation in children with acute epiglottitis.

Management of the airway in acute epiglottitis is still controversial. One argument against intubation as opposed to tracheostomy is the increased complications from prolonged intubation. We describe a study of 26 children treated for acute epiglottitis from 1971 to 1979. Included in this series are 16 consecutive patients who were treated by nasotracheal intubation and simultaneous medical therapy. Fifteen of the 16 patients extubated safely in less than 48 hours, significantly decreasing the possibility for complications.

Acute Disease↗
PubMed1978

The origin of lipofuscin and possible consequences to the myocardium.

Examination by light and electron microscopy of human myocardium from necropsies and biopsy specimens has revealed evidence that mitochondria can be transformed into granules of lipofuscin. This pigment has been shown to arise from peroxidative destruction of polyunsaturated lipid membranes. A high rate of lipofuscin formation is indicated by the occurrence of brown atrophy of the heart in relatively young persons who died of conditions that were associated with inanition. Such lipofuscin formation suggests the importance of dietary antioxidants in preventing peroxidative damage to mitochondria. A by-product of lipid peroxidation, malonaldehyde, can react with nuclear DNA, blocking template activity. Nuclear damage of this kind could reduce the capacity for protein synthesis and limit mitochondrial and contractile protein replacement. Such a limitation would contribute to heart failure during stress. Peroxidative damage to the myocardium is cumulative and irreversible.

Adult↗
PubMed1976

The ultrastructure of the sheath around chronically implanted electrodes in brain.

Insulated, bipolar stainless steel electrodes were chronically implanted in various regions of the cat brain and the long-term structural changes in the tissue surrounding the electrodes were studied by light and electron microscopy. A sheath surrounded and separated the electrode from normal grey or white matter. A layer of foreign body giant cells of variable thickness was formed adjacent to the electrode. This layer was attenuated in some places so that it was unrecognizable by light microscopy. The bulk of the sheath structure consisted of collagen fibrils, leptomeningeal cells and hypertrophied astrocytes. Areas consisting of modified leptomeningeal cells with long thin processes we designated as spongy areas. These have not been previously reported using the electron microscope. Glycogen bodies were seen in leptomeningeal cells. Astrocytes became greatly enlarged and were more numerous in and around the sheath. Oligodendrocytes contained lamellar bodies, and direct continuity was shown between a lamellar body and an adjacent myelin sheath. Myelin was seen in abnormal sites (around oligodendrocytes and neurons) and in unusual configurations. Neuronal changes near the sheath included whorls and stacks of modified endoplasmic reticulum and the presence of cytoplasmic nucleolus-like bodies. Reactive, regenerative and degenerative axons were observed. Blood vessels were more numerous in the sheath and surrounding tissue than normal. Perivascular spaces were prominent even around capillaries and often plasma cells and monocytes were in these spaces. As compared to normal tissue the extracellular space is noticeably increased. Electrodes passing through ventricles were surrounded with a sheath covered with ependymal cells. This sheath was comparable in structure to the sheath present around the electrode in other locations.

Animals↗
PubMed1975

Cation-dependent structures associated with membranes in the rat central nervous system.

As observed by high magnification electron microscopy, potassium ions induce osmiophilia at the extracellular side of triple layered plasma membranes in the central nervous system of the rat. In contrast, sodium ions induce a widening of the intracellular lamina of these membranes, and do not result in observable extracellular deposits. The observations suggest the existence of potassium and sodium ion-selective structures associated with opposite surfaces of the neuron membrane. Use of the fixative vehicle as a cytochemical reagent is proposed.

Animals↗