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Biomedical subjects

M Shalit

Publications and source records attributed to M Shalit.

At least 55 records · Page 3Linked to original sources
PubMed1992

Restriction-stimulated homologous recombination of plasmids by the RecE pathway of Escherichia coli.

To test the double-strand break (DSB) repair model in recombination by the RecE pathway of Escherichia coli, we constructed chimeric phages that allow restriction-mediated release of linear plasmid substrates of the bioluminescence recombination assay in infected EcoRI+ cells. Kinetics of DSB repair and expression of recombination products were followed by Southern hybridization and by the bioluminescence recombination assay, respectively. Plasmid recombinants were analyzed with restriction endonucleases. Our results indicate that a DSB can induce more than one type of RecE-mediated recombination. A DSB within the homology induced intermolecular recombination that followed the rules of the DSB repair model: (1) Recombination was enhanced by in vivo restriction. (2) Repair of the break depended on homologous sequences on the resident plasmid. (3) Break-repair was frequently associated with conversion of alleles that were cis to the break. (4) Conversion frequency decreased as the distance from the break increased. (5) Some clones contained a mixture of plasmid recombinants as expected by replication of a heteroduplex in the primary recombinant. The rules of the DSB repair model were not followed when recombination was induced by a DSB outside the homology. Both the cut and the uncut substrates were recipients in conversion events. Recombination events were associated with deletions that spanned the break site, but these deletions did not reach the homology. We propose that a break outside the homology may stimulate a RecE-mediated recombination pathway that does not involve direct participation of DNA ends in the homologous pairing reaction.

Blotting, Southern↗
PubMed1992

Pyrexia of unknown origin as the only manifestation of colorectal carcinoma.

Patients with colon cancer rarely present with pyrexia of unknown origin (PUO) without other manifestations or symptoms. The present paper reports a patient who presented with a 6-month history of fever. The patient was found to suffer from well-differentiated adenocarcinoma of the sigmoid colon. A few days after sigmoidectomy the fever subsided and the patient recovered. Investigation of the large bowel should always form part of the evaluation in patients with pyrexia of unknown origin.

Adenocarcinoma↗
PubMed1991

Desferal (desferrioxamine)--a novel activator of connective tissue-type mast cells.

The effect of Desferal (desferrioxamine), an iron-chelating agent with allergic side effects, was examined on human basophils and rodent mast cells (MCs) in vitro and in the human skin. Even at a high concentration (100 mg/ml), the drug neither induced histamine release (HR) from human basophils nor primed these cells to release higher amounts of histamine when they were activated with f-met-peptide or anti-IgE antibodies. In contrast, in all seven subjects studied, intradermal injection of Desferal (0.1 mg/ml to 100 mg/ml) elicited classic wheal-and-flare responses. Ingestion of 10 mg of cetirizine, an H1 antagonist, 3 hours before the intracutaneous administration of Desferal, significantly reduced the diameters of both wheal-and-flare reactions, indicating that the drug caused local HR. Desferal also induced HR from rat peritoneal MCs in vitro but had no effect on mouse bone marrow-derived MCs. These results suggest that Desferal has a direct, IgE-independent, stimulatory effect on connective tissue-type MCs. Thus, it may be used as a positive control in skin testing.

Animals↗
PubMed1991

Wilderness emergency medical services: the experiences at Sequoia and Kings Canyon National Parks.

This article describes the National Park Service wilderness emergency medical services (EMS) system, as implemented at Sequoia-Kings Canyon National Park. EMS records on all 434 patients in the period from August 1, 1986, to July 31, 1987, were reviewed. Most patients had minor problems. Overall, 77% of patients contacting the EMS system were released at the scene, and base hospital contact was made in only 28% of cases. However, there were three deaths, 44 (10%) patients who received advanced life support, and 292 (67%) patients who received basic life support. Seven patients who received advanced life support were released without transport. Decisions regarding scope of practice in a low-volume, wilderness EMS system are complicated by long transport times and problems with skills maintenance. Differences between the times and problems with skills maintenance. Differences between the patients treated by a wilderness system and those seen in most urban systems may make it appropriate to release a greater portion of patients without ambulance transport. In a system with long response and transport times, use of personnel with different training than in the urban setting becomes necessary.

Adolescent↗
PubMed1991

Long-term cultures of mast cells: a new model for studying the allergic response.

Mast cells are the key cells of allergic reactions and probably play also a role in chronic inflammatory reactions resulting in fibrosis. Although their biochemical and functional properties have been extensively investigated, several studies have been hampered by the absence of a tissue culture system to keep these cells alive and functionally active for long periods of time. Recently we have developed an in vitro system in which rat peritoneal mast cells are cocultured with 3T3 mouse skin derived fibroblasts (MC/3T3). Under these tissue culture conditions, mast cells do not proliferate and maintain their viability and functional activity for more than a month. This system allowed us to carry out long-term studies on the functional properties of mast cells. We have found that mast cells activated both by IgE-dependent and IgE-independent stimuli survive, and slowly replenish their histamine content. After a non-immunological challenge mast cells retain their full potential to release histamine upon a repeated similar challenge. In contrast, immunologically challenged mast cells become partially unresponsive to a similar activation event for up to 3 weeks. By exploiting this long-term culture system we described a novel type of mast cell activation induced by cytokines. The onset of this activation is slow and its course appears to be chronic-continuous, very different from the classical anaphylactic type activation that is completed within few minutes. Since MC/3T3 release higher amounts of histamine, this system is a sensitive tool to investigate the antiallergic properties of various drugs. By employing MC/3T3 cultures we were able to show that the gold salt auranofin inhibits histamine release from mast cells stimulated by different secretagogues. In addition, salbutamol inhibited histamine release from repeatedly challenged mast cells; and nedocromil sodium was effective in preventing mast cell activation when incubated for a week with MC/3T3.

3T3 Cells↗
PubMed1991

Undetectable caeruloplasmin values in a patient with autoimmune chronic active hepatitis.

Caeruloplasmin is an alpha 2 protein produced in the liver that is responsible for transporting copper in the blood. Caeruloplasmin values are usually high in patients with chronic liver diseases, including chronic active hepatitis: low values, however, are characteristic of Wilson's disease. The case of a 17 year old woman with very low caeruloplasmin values and chronic active hepatitis of the lupoid type is described. Steroid treatment resulted in an increase in the caeruloplasmin concentration and clinical improvement.

Adolescent↗
PubMed1991

Acute nonrheumatic perimyocarditis complicating streptococcal tonsillitis.

Streptococcal infection is a rarely recognized cause of nonrheumatic perimyocarditis. We report a case of a young patient who developed acute perimyocarditis as manifested by diffuse electrocardiogram changes, and markedly elevated cardiac enzymes, concurrently with streptococcal tonsillitis. Despite the dramatic presentation, the patient recovered uneventfully. We conclude that streptococci can involve the heart also directly by a bacterial component or toxin, and not only through a delayed immunologic mechanism as in rheumatic fever. Further studies are necessary to accurately determine the incidence of myocardial involvement during early stages of streptococcal infection.

Adult↗
PubMed1991

Increased numbers of mast cells in pemphigus vulgaris skin lesions. A histochemical study.

We have used a histochemical technique to study mast cells (MC) in skin biopsies of 8 patients suffering from pemphigus vulgaris (PV) and from 4 control volunteers. The MC were stained for 30 min with 0.5% toluidine blue, pH 0.5, counted and then restained for 5 days under the same conditions. This staining method allows the identification of two groups of MC, one that stains promptly (30 min) and one that stains after longer incubation times (5 days). After 30 min of staining, a slight increase was found in the number of MC in PV sections, in comparison with normal controls. However, when the 30 min stained sections were reincubated under the same conditions for 5 days, a significant increase in the number of MC in PV was found in comparison with 5-day-stained normal skin sections (p less than 0.005) and in comparison with 30-min-stained PV sections (p less than 0.005). The MC were distributed throughout the dermis and were concentrated in the upper dermis near hair follicles and vessels. The possible importance of the increased numbers of MC in PV is discussed.

Adult↗
PubMed1991

Cyclic anaphylaxis associated with menstruation.

A middle-aged woman developed recurrent episodes of severe life-threatening anaphylaxis. All episodes were strikingly associated with the first day of menstrual bleeding. Temporary relief was achieved with indomethacin therapy. The patient fully recovered following abdominal hysterectomy and salpingoophorectomy. The possible role of sex hormones and prostaglandin F2 alpha in the pathogenesis of this problem is discussed.

Adult↗
PubMed1991

Effects of interleukins on connective tissue type mast cells co-cultured with fibroblasts.

We investigated the effects of interleukin-2 (IL-2), interleukin-3 (IL-3) and interleukin-4 (IL-4) on mouse and rat peritoneal mast cells (MC) co-cultured with 3T3 fibroblasts (MC/3T3). The continuous presence of these cytokines for 7-9 days in the culture media was neither toxic nor caused proliferation of MC, as determined by the stability of MC numbers in culture. Long-term incubation of mouse MC/3T3 with IL-2 (100 U/ml), IL-3 (50 U/ml), IL-4 (50 U/ml) or a mixture of IL-3 and IL-4 (25 U/ml) induced an increase in basal histamine release of 79.3 +/- 19.0%, 41.0 +/- 17.3%, 25.2 +/- 10.4% and 30.2 +/- 3.2%, respectively, over control cells incubated with medium alone. When rat MC/3T3 were incubated for 7 days with the various interleukins an enhancement in histamine release similar to that observed with mouse MC/3T3 was found. Preincubation (1 hr) of rat MC/3T3 with interleukins prior to immunological activation with anti-IgE antibodies enhanced histamine release. The highest effect was observed with IL-3 + IL-4 (60.4 +/- 10.8% increase) followed by IL-2 (51.5 +/- 4.5%), IL-4 (28.6 +/- 10.3%) and IL-3 (13.2 +/- 4.2%). This study demonstrates that when mouse and rat peritoneal MC are cultured with fibroblasts in the presence of interleukins they do not proliferate, suggesting that they preserve their connective tissue type MC phenotype. Moreover, interleukins display a pro-inflammatory effect on these cells by enhancing both basal and anti-IgE-mediated histamine release.

Animals↗
PubMed1990

[Surgery for craniopharyngioma].

We present a series of 20 patients (11 males) operated on for craniopharyngioma through a frontal craniotomy during an 11-year period. They ranged in age from 7 months to 58 years (mean 20 years). The most common symptoms were headaches, blurred vision and endocrine disorders. The perioperative mortality was 5% and morbidity 25%. 5 (25%) patients need reoperation; 13 (65%) received additional radiation therapy. In 94% visual function improved. 65% continued to have or developed endocrine problems, although all were well controlled with supplemental therapy. These results, similar to those reported from other centers, justify a combination of radical surgery and radiation therapy for this condition.

Adolescent↗
PubMed1990

Unresponsiveness of rat peritoneal mast cells to immunologic reactivation.

Rat peritoneal mast cells cocultured with 3T3 fibroblasts (MC/3T3) were activated with Ag or with anti-IgE antibodies in the presence of Ca2+, and their responsiveness to a second similar challenge was evaluated. MC/3T3 were presensitized with IgE anti-DNP antibodies and activated with DNP-human serum albumin. When these MC/3T3 were reactivated with the same Ag 2 and 6 h later, they released only a minimal percentage of histamine. A gradual recovery of responsiveness was detected during the first 7 days after activation, and a full recovery was attained by days 14 to 21. A similar pattern of unresponsiveness was observed when MC/3T3 were challenged and rechallenged with cercarial Ag after presensitization with anticercarial serum. Activation of MC/3T3 with one Ag (DNP-human serum albumin or cercarial) and rechallenge 3 days later with the other Ag did not overcome the state of partial unresponsiveness. Challenging MC/3T3 with anti-IgE led to a subsequent unresponsiveness to rechallenge with the same ligand, regardless of whether or not the cells were presensitized with IgE antibodies. Cross-linkage with anti-IgE resulted in a more intense and prolonged state of unresponsiveness in comparison with that observed with Ag. When MC/3T3 activated with anti-IgE were rechallenged with various IgE-independent agents they released a percentage of histamine comparable to that of control cultures challenged with these secretagogues for the first time. MC/3T3 partially resynthesized their histamine content during the two-week period after activation. Our results suggest that MC undergo a temporary state of "physiologic" unresponsiveness after immunologic activation in the presence of calcium ions.

Animals↗
PubMed1990

Release of lactoferrin and elastase in human allergic skin reactions.

Our previous skin chamber studies have shown prominent accumulation of viable neutrophils in human allergic skin reaction sites. To determine whether such neutrophils release components that may be pathogenic in allergic reactions, we have compared the patterns of release of five components: 1) lactoferrin, present in specific granules; 2) and 3) elastase and myeloperoxidase, present mainly in azurophilic granules; 4) lactic dehydrogenase, a cytosolic component generally released during cell damage; 5) histamine, present in mast cells and basophils but not in neutrophils. In 13 pollen-sensitive subjects we found that continuous antigen challenge for 5 h lead to a peak of histamine release into overlying skin chambers during the 1st h, followed by a plateau of low level histamine release over the succeeding 4 h. In contrast, there was no significantly increased released of lactoferrin or elastase during the first h, but significantly increased accumulation of these components at Ag challenge sites over the next 4 h. There was no significant difference at Ag vs buffer control sites in the levels of either myeloperoxidase or lactic dehydrogenase. The increased levels of lactoferrin and elastase at antigen challenge sites in the 2nd to 5th h were not simply a reflection of the greater numbers of neutrophils present in such sites because the levels of these components did not correlate significantly with the number of neutrophils in chamber fluids obtained from individual sites. However, such lactoferrin levels did correlate significantly with the amount of histamine released earlier during the 1st h of Ag challenge at individual sites. These findings suggest a selective in vivo release of neutrophil components in IgE-mediated human allergic skin reactions, possibly related in degree to earlier mast cell activation. Inasmuch as lactoferrin likely plays a role in reactive oxidants effects and elastase is a potent nonspecific protease, release of these agents could play a pathogenic role in late phase allergic reactions.

Adult↗
PubMed1990

"Rubral" tremor following radiation of a pineal region vascular hamartoma.

Tumours of the pineal region have historically been difficult to remove safely. Only recently have large series of successful pineal area operations been reported, and there are many advocates for surgical reticence with these tumours. We report a case of a 20-year-ol women whose pineal region tumour was irradiated, whereupon a unilateral low-frequency resting and intention tremor developed. Following resection of the lesion, a vascular hamartoma, the tremor virtually disappeared. We believe the tremor was secondary to radiation induced tumour shrinkage and distortion of the mesencephalon. This case is demonstration of the importance of exploration and histological verification of pineal region tumours.

Adult↗
PubMed1990

Auranofin inhibits histamine release from rat peritoneal mast cells.

The effect of auranofin on histamine release from immunologic and non-immunologic activated rat peritoneal mast cells cocultured with 3T3 fibroblasts (MC/3T3) was investigated. When MC/3T3 were preincubated with 2 x 10(-5) M auranofin and thereafter challenged with anti-IgE antibodies, a maximal inhibition of histamine release (86.2%) was obtained. Non-immunological histamine release induced by compound 48/80, substance P and bradykinin was inhibited to a lesser degree, i.e. 36.0%, 37.6% and 24.0% respectively. Simultaneous incubation of auranofin and the stimulating agents resulted in a higher inhibition of histamine release: anti-IgE antibodies--92.0%; compound 48/80--73.5%; substance P--46.1%. We conclude that auranofin effectively reduces histamine release from immunologic and non-immunologic activated mast cells. This may be relevant to the control of allergic reactions.

Animals↗