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Biomedical subjects

A Friedman

Publications and source records attributed to A Friedman.

At least 19 recordsLinked to original sources
PubMed1992

Pore formation and mitogenicity in blood cells by the class 2 protein of Neisseria meningitidis.

The class 2 outer membrane protein (MIEP) of Neisseria meningitidis has recently been shown to be mitogenic for lymphocytes (Liu, M.A., Friedman, A., Tai, J., Martinez, D., Deck, R. R., Hawe, L. A., Shieh, J. T.-C., Jenkins, T. D., Donnelly, J. J., and Oliff, A. I. (1992) Proc. Natl. Acad. Sci. U.S.A. 89, 4633-4637. In this study, a possible connection between MIEP's mitogenicity and its possible action as a porin was investigated. MIEP, purified from the bacterial outer membrane protein complex under denaturing conditions, caused a modest but specific release of ions (86Rb) from both erythrocytes and lymphocytes, ultimately resulting in cell lysis. The dose-response of MIEP on erythrocyte lysis was qualitatively similar to a known porin (protein I from Neisseria gonorrhoeae) but was much less efficient. Induction or preservation of native structure in MIEP increased pore formation, resulting in levels comparable to that of the protein I porin. These observations suggest that native MIEP, free of the other outer membrane proteins of Neisseria meningitidis, can efficiently form pores in cells, but that denatured MIEP is variably and marginally effective. However, pore formation by MIEP was not related to its mitogenicity in lymphocytes, based on: (i) native MIEP was not mitogenic; (ii) denatured MIEP was highly mitogenic; and (iii) denatured MIEP was mitogenic at concentrations below the threshold level for pore formation. Therefore, mitogenicity is dependent upon MIEP being in a denatured, monomeric state and is masked by native conformation.

Bacterial Outer Membrane Proteins↗
PubMed1992

Induction of experimental autoimmune encephalomyelitis by native myelin basic protein-activated T lymphocyte lines.

Self antigens bind to MHC class II molecules in vivo. The capacity of class II molecules to bind native self antigen, namely antigen that has not been processed through an endososomal pathway, could increase susceptibility to autoimmune diseases if recognized by autoreactive T lymphocytes. To confirm this prediction we designed experiments to show that: (a) native myelin basic protein (BP) activates encephalitogenic T lymphocyte lines, and (b) these activated lines cause experimental autoimmune encephalomyelitis (EAE) in naive rats. We show that two encephalitogenic T lymphocytes lines, LEW and BN, are activated by native BP in the presence of paraformaldehyde pre-fixed antigen-presenting cells (APC). The degree of activation, as measured by T lymphocyte proliferation, was equal to that obtained in response to BP processed by APC prior to paraformaldehyde fixing. The response to native BP was confirmed by demonstrating insensitivity to the presence of the lysosomotropic agent chloroquine or protease inhibitors. Activation of T lymphocytes by BP required the presence of syngeneic APC. The activated T lymphocyte lines were injected into naive recipient rats that developed EAE within 5 days. Both disease incidence and severity were equal to that observed in rats that were treated with T lymphocytes activated by processed BP. Hence, at least in EAE, the risk of an autoimmune event could be precipitated by a complex of native antigen and class II molecules on cells that do not possess an endososomal pathway for antigen processing and presentation.

Animals↗
PubMed1979

Framing pictures: the role of knowledge in automatized encoding and memory for gist.

In general, frame theories are theories about the representation and use of knowledge for pattern recognition. In the present article, the general properties of frame theories are discussed with regard to their implications for psychological processes, and an experiment is presented which tests whether this approach yields viable predictions about the manner in which people comprehend and remember pictures of real-world scenes. Normative ratings were used to construct six target pictures, each of which contained both expected and unexpected objects. Eye movements were then recorded as subjects who anticipated a difficult recognition test viewed the targets for 30 sec each. Then, the subjects were asked to discriminate the target pictures from distractors in which either expected or unexpected objects had been changed. One consequence of the embeddedness of frame systems is that global frames may function as "semantic pattern detectors," so that the perceptual knowledge in them could be used for relatively automatic pattern recognition and comprehension. Thus, subjects might be able to identify expected objects by using automatized encoding procedures that operate on global physical features. In contrast, identification of unexpected objects (i.e., objects not represented in the currently active frame) should generally require more analysis of local visual details. These hypotheses were confirmed with the fixation duration data: First fixations to the unexpected objects were approximately twice as long as first fixations to the expected objects. On the recognition test, subjects generally noticed only the changes that had been made to the unexpected objects, despite the fact that the proportions of correct rejections were made conditional on whether the target objects had been fixated. These data are again consistent with the idea that local visual details of objects represented in the frame are not neccesary for identification and are thus not generally encoded. Further, since subjects usually did not notice when expected objects were deleted or replaced with different expected objects, it was concluded that if two events instantiate the same frame, they may often be indistinguishable, as long as any differences between them are represented as arguments in the frame. Thus, for the most part, the only information about an event that is episodically "tagged" is information which distinguishes that particular event from others of the same general class. The data reinforce the utility of a frame theory approach to perception and memory.

Discrimination Learning↗
PubMed1979

Hemiagenesis of the thyroid.

Congenital absence of a lobe of the thyroid gland is discussed and the literature is reviewed. Sixty-six cases have been gathered from the literature in approximately the past 100 years, and another six have been documented. Although no particular explanation has been forthcoming for the development of this anomaly, left lobe aplasia and predominance of occurrence in women have been noted. A variety of other thyroidal abnormalities have coexisted with hemiagenesis.

Adolescent↗
PubMed1979

Effects of thoracic epidural block and the beta-1-adrenoreceptor agonist prenalterol on the cardiovascular response to infrarenal aortic cross-clamping in man.

Sixteen patients scheduled for abdominal aortic resection and grafting were randomly assigned to two groups to study the cardiovascular effects of infrarenal aortic cross-clamping. The patients in the first group had received a thoracic epidural block followed by intravenous administration of the selective beta-1-adrenoreceptor agonist prenalterol prior to induction of general anaesthesia. The patients in the second group served as controls and received no specific treatment prior to general anaesthesia. In both groups, aortic cross-clamping was followed by an equal rise in pulmonary artery diastolic pressure and mean systemic arterial pressure. There was a significant difference in systemic vascular resistance, as the control group had a 46% increase 30 s after cross-clamping, while the pretreated patients had only a 7% increase at the same time. Moreover, the patients given the thoracic epidural block followed by prenalterol increased their stroke volume and cardiac indices, as compared to the patients in the control group who showed a significant decrease in these parameters. Possible mechanisms for the mode of action of the combined thoracic epidural block and beta-1-adrenoreceptor agonist pretreatment are discussed.

Adrenergic beta-Agonists↗
PubMed1979

Deletions, rearrangements and tandem duplications of recombinant plasmids containing yeast ribosomal DNA.

Recombinant DNA plasmids, formed by the insertion of yeast ribosomal DNA into Escherichia coli plasmids pSC101 or pMB9, underwent deletions, rearrangements and tandem duplications. Independently derived deletion products of plasmids, constructed using pMB9 as a vector, are indistinguishable from each other. These deletion products from multimers composed of tandem repeats. In at least one case a plasmid, constructed by inserting an SmaI fragment of yeast ribosomal DNA into pSC101, underwent deletion and rearrangement to form a product in which a segment, consisting of part of the pSC101 sequence and part of the yeast ribosomal DNA sequence, was duplicated to form a tandem repeat. Deletion and rearrangement take place in Rec+, recA- and recB- recC- cells. The rate of deletion in Rec+ cells is higher than in recA- cells. The rate of deletion in minicell-producing, X-ray resistant strains is much higher than in other Rec+ strains.

Chromosome Deletion↗
PubMed1979

Neurological sequelae of septic meningitis. A follow-up study of 65 children.

Seventy-two children who survived septic meningitis were reevaluated after 3 to 11 years. Thirty-four (52%) of 65 children were found to have neurological sequelae. Of the 34, 15 had major sequelae and 19 showed evidence of only minimal brain dysfunction--namely, hyperkinetic behavior, organic learning disturbances and minor motor disabilities. Acute-phase findings that were significantly associated with the rate of neurological sequelae were age, time between onset and admission, seizures, spinal fluid glucose level and the number of polymorphonuclear cells. In view of the high frequency of late neurological sequelae, it is advisable that children who survive septic meningitis have long-term follow-up in order to detect evidence of minimal brain dysfunction. An early diagnosis will help in proper management.

Adolescent↗
PubMed1978

A comparison between spironolactone and hydrochlorothiazide with and without alpha-methyldopa in the treatment of hypertension.

In a single blind crossover trial, spironolactone (50 mg twice a day), and hydrochlorothiazide (50 mg twice a day) were equally effective hypotensive agents in 16 patients with untreated essential hypertension. The addition of alpha-methyldopa (250 mg three times a day) to each agent produced a further significant and equal fall in blood pressure. Spironolactone therapy was assoicated with fewer clinical and biochemical side effects. The hypotensive effect of the diuretics was independent of the renin status of the patients.

Adult↗
PubMed1978

Supersaturation of urine with uric acid and urate: response to a uricosuric diuretic.

In order to assess the possibility that treatment with the uricosuric diuretic ticrynafen (tienilic acid) could lead to UA or MSU crystalluria, the degree of urinary supersaturation with respect to these crystalloids was assessed in persons receiving the diuretic for 1 week, and the results were compared with similar data generated from the use of probenecid. Initially, only probenecid significantly increased the degree of urinary suspersaturation with respect to MSU, and after adjustment of urine pH values to 5.5, probenecid also increased the degree of urinary supersaturation with respect to nonionized UA. At a pH of 5.5, the urine was significantly more supersaturated with nonionized UA after a single dose of probenecid than after ticrynafen (tienilic acid). Ticrynafen never significantly affected the degree of urinary supersaturation with respect to UA or MSU. Neither agent affected small amounts of "colloidal" or "bound" urinary urate. Insofar as the degree of urinary supersaturation with these crystalloids predisposes to crystalluria and calculus formation, ticrynafen (tienilic acid) appears to present no increased risk.

Crystallization↗
PubMed1978

Urinary tract infection presenting with jaundice.

Jaundice was the presenting feature in an 8-year-old girl suffering from urinary tract infection (UTI) due to Escherichia coli. The jaundice cleared with the cure of the infection. The mechanisms of jaundice complicating UTI are discussed, and the importance of urine culture in infants and children with jaundice is stressed.

Child↗