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Biomedical subjects

J Adler

Publications and source records attributed to J Adler.

At least 235 records · Page 13Linked to original sources
PubMed1979

Venous calcifications associated with cavernous transformation of the portal vein: computed tomographic and angiographic correlations.

A case of rare venous calcifications involving cavernous transformation of the portal vein and spontaneous splenocaval shunt is presented. Findings were obtained with plain abdominal radiography, computed tomography, and angiography. Inflammation of the portal vein with subsequent occlusion could account for splenomegaly and hypertrophy of the splenic artery and vein with atheromatous calcifications due to turbulence and sclerosis. Angiography is essential prior to surgical intervention in order to select the appropriate shunt.

Aged↗
PubMed1979

On the mechanism of sensory transduction in bacterial chemotaxis.

Sensory transduction in bacterial chemotaxis is beginning to be understood at the molecular level. At the receptor end, we have some considerable knowledge about the molecular properties of chemoreceptors. At the effector end, we know that flagella rotate and that the direction of rotation is determined by attractants and repellents, although we do not yet know the molecular features of the motor and the gear shift. Between the receptors and the effectors is a system for integrating the sensory transduction, which somewhow involves methylation of membrane proteins and possibly a change in membrane potential, but further details of how the mechanism works remain to be elucidated. It seems to us likely that the facts and concepts learned from a study of sensory transduction in bacteria can be applied to answering questions about transduction mechanisms in eukaryotic cells. Examples include the following: How do sensory stimuli produce their effects in sensory receptor cells? How do neurotransmitters act at receptors of postsynaptic cells to produce the variety of effects possible (changes in membrane potential, in secretion, in contraction, etc.)? How do hormones interact with their receptors to bring about various responses?

Carrier Proteins↗
PubMed1979

The behavior of bacteria: on the mechanism of sensory transduction in bacterial chemotaxis.

The mechanism of bacterial chemotaxis is beginning to be understood. At the receptor end, we have considerable knowledge about the molecular properies of chemoreceptors. At the effector end, we know that flagella rotate and that the direction of rotation is determined by attractants and repellents, although we do not yet know the molecular features of the motor and the gear shift. Between the receptors and the effectors is a system for integrating the sensory information and transmitting a message to the flagella. This system, sensory transduction, somehow involves methylation of membrane proteins and probably a change in membrane potential, but further details of how the mechanism works remain to be elucidated.

Bacterial Physiological Phenomena↗
PubMed1978

Attraction by repellents: an error in sensory information processing by bacterial mutants.

Normal Escherichia coli bacteria are repelled by acetate, benzoate, and indole and attracted by alpha-aminoisobutyrate. We have isolated mutants that are attracted to acetate, benzoate, and indole and may be repelled by alpha-aminoisobutyrate. These reversed-taxis mutants are defective in a central processing component: a set of methylated proteins known as MCP 1. The mechanism of reversal of taxis is discussed.

Acetates↗
PubMed1978

Failure of sensory adaptation in bacterial mutants that are defective in a protein methylation reaction.

Chemotactic bacteria, such as E. coli, detect changes in the chemical composition of the environment. Addition of an attractant or repellent leads to an immediate response, characterized by a change in the swimming behavior of the cells--a process known as sensory excitation. However, the response gradually disappears with time, despite the continued presence of the chemical--a process known as sensory adaptation. We report here the behavior of a class of nonchemotactic mutants (cheX) that can carry out sensory excitation but are defective in the process of sensory adaptation. These mutants are also defective in the ability to carry out a protein methylation reaction which has previously been implicated in the adaptation process (Goy, Springer and Adler, 1977). The results presented here establish a firm relationship between the methylation reaction and sensory adaptation.

Adaptation, Physiological↗
PubMed1978

Gelfoam embolization of the kidneys for treatment of malignant hypertension.

Some chronic renal failure patients maintained on dialysis have uncontrollable hypertension. Those with elevated renin levels require bilateral nephrectomies prior to kidney transplant to avoid nephrosclerosis. The morbidity and mortality from surgical nephrectomies are high. In 2 such patients we embolized the renal arteries with gelfoam and successfully occluded all the major vessels. One patient became normotensive. The second remained hypertensive and had increased renin levels, probably on the basis of ischemia. Subsequent surgical nephrectomies demonstrated completely occluded segmental branches but only focal areas of infarction. Collateral blood supply determines the success of the procedure.

Adult↗
PubMed1978

Arteriovenous shunts involving the liver.

Arteriovenous shunting in the liver is a rare angiographic finding. Review of the literature shows that most cases are related to trauma or neoplasm. The authors discuss several entities which should also be included in the differential diagnosis, among them congenital arteriovenous malformations or hemangiomas of the liver and pancreas, cirrhosis with rearterialization of the liver, hepatic abscess, hypervascular liver metastases, and primary tumors with invasion of the portal and hepatic veins by arterial neovasculature.

Abdominal Injuries↗
PubMed1978

Chemotaxis in bacteria.

Explore the source record for details and available documents.

Bacterial Physiological Phenomena↗
PubMed1977

Isolation of glutamic acid methyl ester from an Escherichia coli membrane protein involved in chemotaxis.

We have isolated glutamic acid 5-methyl ester from an Escherichia coli protein that is involved in chemotaxis. The bacteria were first incubated with [methyl-3H]methionine under conditions which are known to result in methylation of the protein. The protein, isolated by gel electrophoresis, was then digested by successive treatment with three proteolytic enzymes. One of the products was [methyl-3H]glutamic acid 5-methyl ester, identified by comparison with an authentic sample in the following studies: (a) chromatography on an automatic amino acid analyzer, (b) chromatography on paper in two solvent systems, (c) chromatography on paper of the N-acetyl derivatives, and (d) stability of the ester bond to various pH conditions. No aspartic acid 4-methyl ester was found in the enzymatic digest. Treatment of the methylated protein with alkali released the radioactivity as [3H]methanol, which was identified by gas chromatography and by preparation of the 3,5-dinitrobenzoate.

Amino Acids↗
PubMed1977

Sensory transduction in Escherichia coli: a requirement for methionine in sensory adaptation.

Chemotaxis of E. coli is a behavioral response to a change in the concentration of a stimulatory compound. The response is transient; thus, E. coli undergoes sensory adaptation. In this communication, we show that L-methionine is required by E. coli for adaptation to increases in the concentration of chemical attractants, but is not required for the maintenance of the adapted state. When the concentration of the attractant is lowered to its initial level, cells regain their sensitivity to the attractant. This process of deadaptation does not require methionine. We suggest that the methylation of a membrane protein, a reaction previously shown to be involved in chemotaxis [Kort, E.N., Goy, M.F., Larsen, S.H. & Adler J. (1975) Proc. Natl. Acad. Sci. USA 72, 3939-3943] underlies these phenomena.

Chemotaxis↗
PubMed1977

Sensory transduction in Escherichia coli: role of a protein methylation reaction in sensory adaptation.

The behavioral response of Escherichia coli to the addition of a stimulatory compound is transient; thus the organism undergoes sensory adaptation. When the compound is removed, E. coli undergoes the inverse process, called deadaptation, and very rapidly regains its sensitivity to the stimulus. In this communication we demonstrate that the previously reported methylation of several cytoplasmic membrane proteins is correlated with, and very likely controls, the state of adaptation of the cell. In the absence of an added stimulus these proteins are methylated to a basal level. When the bacteria are stimulated by the addition of an attractant, the extent of methylation increases over a period of several minutes to a new level, which is maintained as long as the attractant is present. The magnitude of the increase in methylation is a function of the size of the stimulus and is directly proportional to the duration of the behavioral response. Upon removal of the attractant the level of methylation very rapidly falls to the basal value. Previously we have shown that adaptation requires methionine, but maintenance of the adapted state and de-adaptation do not [Springer, M. S., Goy, M. F. & Adler, J. (1975) Proc. Natl. Acad. Sci. USA 74, 183-187]; here we demonstrate that methylation requires methionine but maintenance of an attractant-induced level of methylation and the demethylation that occurs following removal of the attractant do not. These results strongly indicate a role for protein methylation in sensory adaptation.

Adaptation, Physiological↗