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E Holtzman

Publications and source records attributed to E Holtzman.

At least 19 recordsLinked to original sources
PubMed2001

Dietary electrolytes and hypertension in the elderly.

The effect of age on older hypertensive patient's blood pressure response to increased sodium intake is well known. Salt sensitivity which does increase with age and the decrease in renal function limiting the ability of aged kidney to excrete sodium load are major factors, responsible for rise in blood pressure during Na consumption in the elderly. Clinical studies encourage salt reduction with and without weight loss. Although potassium consumption is highly recommended, one should be aware of potassium overload in the elderly.

Aged↗
PubMed1993

Features of the polarity of the Golgi apparatus of frog photoreceptors: studies with lectins and with Brefeldin A.

The cis-trans polarity of the Golgi apparatus is important in Golgi functioning in glycosylation, sorting and other processes. The present work extends our prior studies on the polarity of the Golgi apparatus of frog (Rana) rod photoreceptors. We demonstrate that Golgi structures with the morphology and distribution of cis elements show the heaviest deposition of osmium. Elements with morphology and cytochemical reactivities resembling trans Golgi structures remain discernible as discrete arrays after exposure of the cells to Brefeldin A. These properties strengthen our identification of cis and trans elements since they are shared with corresponding Golgi structures in other cell types. We have also investigated the binding of lectins to sections prepared by cryoultramicrotomy. We find that Concanavalin A, with probable chief affinity for core mannoses in oligosaccharides, localizes to cis, medial and trans elements of the photoreceptor's Golgi apparatus. Wheat germ agglutinin, with likely affinity at least partly for terminal N-acetylglucosamines, localizes to trans and medial elements. A trans localization is seen with Ricinus communis agglutinin (RCA 120), but this lectin binds extensively only after neuraminidase treatments suggesting that its chief affinity is for galactose residues that are penultimate to sialic acids (neuraminic acids) in the native oligosaccharides. Overall, the pattern of lectin binding to Golgi structures that we observe resembles that seen in a variety of other cell types. The distribution of glycosylated molecules we detect in the photoreceptor's Golgi apparatus may bear upon such matters as the unusual features of the glycosylation of mature opsin.

Animals↗
PubMed1993

Properties of acidified compartments in hippocampal neurons.

We have studied cultured rat hippocampal neurons using electron microscopic procedures based on the accumulation of DAMP (dinitroanilino-aminomethyl-dipropylamine) to identify acidified locales, fluorescence procedures to provide information about the pHs within certain endocytic compartments, and the uptake of horseradish peroxidase to evaluate effects of altering pH on membrane cycling in the axonal varicosities. We find that the endocytic compartments related to the lysosome-endosome system in the cell bodies and dendrites of these neurons maintain pHs in the range of about 5 to 6.5. This is the range that would be expected for structures participating in lysosomal digestion and for such functions as the endosomal dissociation of ligands from receptors. We also find that, as judged by uptake of horseradish peroxidase, exposure of the preparations to weak bases that neutralize intracellular compartments does not abolish the endocytic labeling of synaptic vesicles in the axonal varicosities. This suggests that passage through a markedly acidified compartment or stage is not obligatory for the endocytic phase of the cycling of synaptic vesicles.

Acids↗
PubMed1992

Frog cones as well as Müller cells have peroxisomes.

We have localized D-amino acid oxidase in peroxisomes of frog retina using cerium procedures on tissue fixed in mixtures containing lower concentrations of glutaraldehyde than we had previously used in our cytochemical studies of this enzyme. We find the Müller cells of these preparations contain a more striking population of peroxisomes than had previously been thought: the D-amino acid oxidase-containing bodies are especially concentrated near the outer limiting membrane, but appreciable numbers are also found in the outer plexiform layer and near the inner limiting membrane. In addition, we find peroxisomes to be present in frog cone photoreceptors, particularly in zones near the ellipsoid. To our knowledge peroxisomes have not been described hitherto in vertebrate photoreceptors. Possible roles for the peroxisomes of the neural retina include participation in the metabolism of lipids (e.g. those of the cones' oil droplets, or of the outer segment) and involvement in oxidation of transmitter-related amino acids and of other small molecules.

Animals↗
PubMed1992

Membrane trafficking in neurons.

Neurons possess an unusually extensive Golgi apparatus and exhibit a variety of active endocytic-like processes. The Golgi apparatus and the endocytic phenomena both contribute, probably in multiple overlapping ways, to the genesis and fate of the membrane systems in axons and terminals.

Animals↗
PubMed1991

Peroxisomal oxidation of thiazolidine carboxylates in firefly fat body, frog retina, and rat liver and kidney.

D-amino acid oxidase is a widely distributed peroxisomal enzyme whose principal natural substrates are still unknown. Thiazolidine carboxylates, their derivatives and relatives, and the intermediates in their metabolism are among the more plausible substrate candidates. Using a cytochemical procedure, we have explored the distribution of peroxide-generating enzymatic activity against two thiazolidine carboxylates. We find that these compounds are effective substrates for peroxisomal oxidation in a variety of tissues that contain peroxisomal D-amino acid oxidase. Reaction was seen in the "classical" peroxisomes of rat liver and kidney, the peroxisomes of the fat body of firefly and of Drosophila and the peroxisomes of frog retina. Interestingly, both with the thiazolidine compounds and with more traditional D-amino acid oxidase substrates, the fireflies' photocyte granules, which are peroxisomes, lack activity.

Animals↗
PubMed1990

Peroxisomes in the head of Drosophila melanogaster.

Peroxisomes were localized in the head of wild-type and mutant strains of Drosophila melanogaster by use of a cytochemical method for the demonstration of D-amino acid oxidase activity. With similar techniques we had found previously that vertebrate photoreceptors have few, if any, bodies with cytochemically demonstrable oxidase activity, but that the pigment epithelial cells adjacent to the photoreceptors have a substantial population of such bodies. Peroxisomes in Drosophila were very abundant in the fat body. Probable peroxisomes were also present in the peripheral retina of the eye, including in retinular (retinula) and pigment cells, but there were very few of them. Thus, our results suggest that the fat body, which lies adjacent to the eye, is the principal site of peroxisomal function in the head. Peroxisome functions in the Drosophila head may include participation in the genesis of eye pigments.

Allopurinol↗
PubMed1990

Experiments on the use of DAMP to study retina and cultured neurons.

Immunocytochemical localization of DAMP, a reagent used to detect low pH intracellular compartments, was studied in cultured neurons from rat hippocampus and in frog retinas. We find that DAMP is more sharply localized and that the immunocytochemical reaction is stronger when horseradish peroxidase or other proteins are included in the medium used to administer DAMP to the cells. A likely explanation is that the proteins enter acidified endocytic compartments and there provide sites to which DAMP molecules can be attached during fixation.

Animals↗
PubMed1989

The intactness and orientation of acetylcholine receptor-rich membrane from Torpedo californica electric tissue.

By a mild and highly reproducible fractionation of Torpedo californica electric tissue, we prepared membrane which was 30 times enriched in nicotinic acetylcholine receptor (AChR). This preparation was neither alkali-stripped nor reconstituted and consequently contained nu (43-kDa protein), which is associated with the cytoplasmic aspect of the receptor. We tested this membrane for the presence of sealed vesicles and determined the orientation of these vesicles by combining three methods. Two of these methods were based on the accessibilities, in the presence and absence of detergent, of the extracellular acetylcholine binding site to alpha-bungarotoxin and of the intracellular nu to trypsin. These two methods are specific for AChR-containing membrane. The third method was morphometry of electron micrographs, by which we estimated the proportion of sequestered membrane. These methods taken together indicated that approximately 45% of the AChR-containing membrane was in the form of leaky vesicles or sheets, 33% was sealed right-side-out vesicles, 11% was sealed inside-out vesicles, and 11% was sequestered within multilamellar or multivesicular vesicles. The complexity of this membrane needs to be taken into account in sidedness studies of the AChR.

Animals↗
PubMed1989

Involvement of the Golgi apparatus in sorting of materials to opposite ends of frog rod retinal photoreceptors.

We have studied the rod cells of retinas of Rana pipiens by phosphatase cytochemistry and immunocytochemistry. We find that the Golgi apparatus of these cells, although different in its intracellular distribution from that of other neurons, has a cis-trans organization like that of other neurons as regards morphological features and the distribution of phosphatase activities. Antibodies against opsin bind to several sacs of the rod Golgi apparatus, especially those at the trans side of the Golgi stack. This suggests that Golgi involvement in the packaging of opsin for eventual delivery to the photoreceptive outer segments of the cell involves passage through trans Golgi systems. Proteins destined for the opposite end of the cell--the presynaptic terminal--also seem to pass through trans Golgi systems, as is indicated both by immunocytochemical localization of the synaptic vesicle protein p38 (synaptophysin) and by the presence of thiamine pyrophosphatase activity in some of the synaptic vesicles. Our findings suggest that sorting of membrane proteins destined for opposite ends of the photoreceptor takes place in systems at or near the trans Golgi face.

Animals↗
PubMed1989

Acidification and endosome-like compartments in the presynaptic terminals of frog retinal photoreceptors.

By using the 'acidotropic' vital dye, Acridine Orange, we have found that the presynaptic terminals of rod and cone photoreceptors in retinas of Rana pipiens maintain a low pH relative to the surrounding medium through an energy dependent mechanism. When this pH is raised, by exposing the retinas to weak bases like ammonium chloride, the terminals exhibit large, membrane-delimited compartments, many of which accumulate endocytic tracers. This effect is partly reversed when the weak bases are removed. We infer that among the acidified structures within the terminals are endocytic compartments with at least some of the characteristics of the endosomes that participate in receptor-mediated endocytosis in other cell types. One role of these structures in the terminals may be in the recycling of synaptic vesicles.

Acridine Orange↗
PubMed1989

Cytochemical localization of a D-amino acid oxidizing enzyme in peroxisomes of Drosophila melanogaster.

A peroxide generating oxidase is demonstrated cytochemically in the peroxisomes of adult and larval Drosophila melanogaster, Oregon R and Rosy-506 strains. This enzyme activity is demonstrable using D-pipecolate or D-proline, but not L-proline, as substrate and is inhibited by kojic acid. Thus this enzyme shares cytochemical characteristics with vertebrate D-amino acid oxidase.

Aging↗
PubMed1989

Rate of activation of renin-angiotensin-aldosterone axis and sodium intake in rats.

When sodium intake in the rat is reduced abruptly from the typical high level to a very low level (0.02%), sodium excretion falls exponentially, with a half time of 2-3 h. The result is that the rat achieves external sodium balance, in which intake equals excretion, on the new low intake within a few hours. In this study, we assessed the rate of activation of the renin-angiotensin-aldosterone axis and its contribution to blood pressure during that interval. Plasma renin activity and angiotensin II concentration had risen sharply within 8 h and did not change over the next 40 h. Plasma aldosterone concentration, on the other hand, continued to rise over 48 h. Within 8 h, blood pressure dependency on angiotensin II had increased sharply, as assessed by depressor responses to an angiotensin antagonist (Sar1-Ala8-angiotensin II) and to converting-enzyme inhibition (captopril). The depressor response to neither agent changed over the next 40 h. The pressor response to angiotensin II was blunted significantly by 8 h and also did not change over the next 40 h. The findings indicate that the rapid tempo of sodium homeostasis in the rat is matched by an equally rapid tempo of activation of the renin-angiotensin system, although the factors responsible for aldosterone release are probably more complex. Experiments to assess the renin-angiotensin system in the rat must be designed with this rapid tempo in mind.

Aldosterone↗
PubMed1989

Renal vasomotion in essential hypertension: influence of vasodilators.

To assess factors responsible for phasic behavior of renal blood flow in essential hypertension, we applied an analytic method based on the estimation of power spectral density to xenon transit through the kidney and examined the renal vasodilator response to a range of agents in 53 normal subjects and 53 patients with essential hypertension. The renal vasodilator response to the calcium channel blocking agent diltiazem, but not the response to alpha-adrenergic blockade (phentolamine) or angiotensin converting enzyme inhibition (teprotide or captopril), was associated with a significant reduction in the amplitude of renal vasomotion. Acetylcholine, a vasodilator that acts through the release of a vasorelaxant factor or factors from endothelium, induced an unanticipated increase in renal vasomotion. These observations further dissociate factors responsible for basal renal vascular tone and periodic changes in renal vascular tone and raise the possibility that abnormalities in the flux of calcium into renal arterioles contribute to increased renal vasomotion in essential hypertension.

Angiotensin II↗
PubMed1988

Peroxisomes in pigment epithelium and Müller cells of amphibian retina possess D-amino acid oxidase as well as catalase.

In this paper we identify peroxisomes in Müller cells and retinal pigment epithelial cells of Rana pipiens and Xenopus laevis by virtue of their content of cytochemically stainable catalase. These organelles have the form of an extensive, branched system of tubules in the retinal pigment epithelium and appear as discrete ovoid structures in the Müller cells. In both the pigment epithelium and the Müller cells a second peroxisomal enzyme, D-amino acid oxidase, can be detected in the same structures as catalase by means of a cerium-based cytochemical staining procedure. This oxidase is active only against nonpolar and polar, uncharged D-amino acids.

Animals↗
PubMed1987

Lead-dependent deposits in diverse synaptic vesicles: suggestive evidence for the presence of anionic binding sites.

We have observed electron dense deposits dependent on incubation of aldehyde-fixed tissues with lead ions within synaptic vesicles of several types of neurons that differ in the neurotransmitters utilized and in the secretory granules of the adrenal medulla. Evidently, vesicle components that can interact with lead ions are widespread. A plausible explanation for the occurrence of the deposits is the presence of anionic binding sites within the vesicles. This would agree well with other biochemical, cytochemical, and immunocytochemical evidence, such as that indicating the presence of sulfated macromolecules in certain synaptic vesicles. Anionic binding sites could play significant roles by participating in processes such as Ca2+ storage, stabilization of pH gradients, or the control of osmotic phenomena.

Adrenal Medulla↗
PubMed1987

A phosphatase activity and a synaptic vesicle antigen in multivesicular bodies of frog retinal photoreceptor terminals.

Previous work has suggested that multivesicular bodies participate in endocytosis and membrane cycling at nerve terminals, including the presynaptic terminals of retinal photoreceptors. We now have found that multivesicular bodies located in the presynaptic terminals of photoreceptors in retinae of Rana pipiens show reaction product in preparations incubated to demonstrate phosphatase activity at pH 5, using cytidine monophosphate as the substrate. Evidently, multivesicular bodies in photoreceptors can possess at least some hydrolytic enzymes during their sojourn in the terminals. We have also found that the multivesicular bodies in frog retinal photoreceptor terminal stain, immunocytochemically, for the presence of SV2, an antigen of synaptic vesicles. This observation supports the suggestion that, along with the extensive, repeated reuse of membrane components for synaptic vesicle recycling, there is some incorporation of the components into structures that are potentially degradative.

Animals↗