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Biomedical subjects

R Oren

Publications and source records attributed to R Oren.

At least 73 records · Page 4Linked to original sources
PubMed1994

New mollusc-specific alpha-conotoxins block Aplysia neuronal acetylcholine receptors.

Two mollusc-specific neurotoxic peptides from the venom of the molluscivorous snail Conus pennaceus are described. These new toxins block acetylcholine receptors (AChR) of cultured Aplysia neurons. Bath application of 0.5-1 microM toxin induces 5-10-mV membrane depolarization, which recovers to the control level within 1-3 min in the presence of the toxin. This response is blocked by 1 mM hexamethonium. Concomitantly with the transient depolarization, the toxins block approximately 90% of the depolarizing responses evoked by brief iontophoretic application of acetylcholine. The pharmacology and amino acid sequences of the toxins (alpha PnIA, GCCSLPPCAANNPDYC-NH2; alpha PnIB, GCCSLPPCALSNPDYC-NH2) enable their classification as novel alpha-conotoxins. The sequences differ from those of previously described alpha-conotoxins in a number of features, the most striking of which is the presence of a single negatively charged residue in the C-terminal loop. This loop contains a positively charged residue in piscivorous venom alpha-conotoxins. In contrast to other alpha-conotoxins, which are selective for vertebrate skeletal muscle nicotinic ACh receptors, these Conus pennaceus toxins block neuronal ACh receptors in molluscs. As such they are new probes which can be used to define subtypes of ACh receptors, and they should be useful tools in the study of structure-function relationships in ACh receptors.

Amino Acid Sequence↗
PubMed1994

Element concentrations in the xylem sap of Picea abies (L.) Karst. seedlings extracted by various methods under different environmental conditions.

We used a Scholander pressure chamber to assess the effects of various extraction methods under different environmental conditions on element concentrations in xylem sap of 3-year-old Picea abies (L.) Karst. seedlings. Sap from excised shoots contained higher element concentrations when extracted at low than at high over-pressures. When comparing plants differing in water status, we found that a high extraction over-pressure introduced a systematic error into the data. For example, in well-watered non-transpiring plants relative to unwatered transpiring plants, potassium concentrations were 70% higher in sap extracted at 0.1 MPa over-pressure, but only 10% higher in sap extracted at 1.0 MPa over-pressure. Moreover, treatment effects depended on the time of day when the sap was extracted. Increased water flux in transpiring plants relative to non-transpiring plants resulted in reduced xylem sap element concentrations when samples were collected after 9 h of transpiration, but not after 4 to 6 h of transpiration. Drought had little effect on xylem sap element concentrations, indicating that rates of element release into xylem conduits, element depletion by growing tissues, and water flow maintained a balance that may prevent nutrient stress during short-term drought.

Journal Article↗
PubMed1993

Colchicine induced remission in amyloid nephrotic syndrome.

An unusual case of reversible reactive amyloidosis (AA) is described. A patient in the course of lobar pneumonia developed acute transient nephrotic syndrome and renal failure. Renal and liver biopsy showed amyloidosis and positive immunohistochemistry stains for amyloid A protein. The nephrotic syndrome resolved completely following 6 months of colchicine treatment and the urine is protein free after 6 years of follow-up.

Aged↗
PubMed1993

Thrombocytopenic purpura as a manifestation of acute hepatitis A.

Extrahepatic autoimmune manifestations are rare in patients with acute hepatitis A infection. We describe a 34-year-old man in whom severe autoimmune thrombocytopenic purpura developed as the manifestation of acute hepatitis A infection. Thrombocytopenic purpura is rarely described in association with hepatitis A, but to our knowledge has never been reported as a manifestation of acute hepatitis A.

Acute Disease↗
PubMed1993

Gastro-duodenal injury associated with intake of 100-325 mg aspirin daily.

During the year 1991, 43 patients with upper gastrointestinal bleeding and one with severe epigastric pain associated with intake of non-steroidal anti-inflammatory drugs were admitted for emergency endoscopy to our unit. Fourteen patients (33%) had been treated with 100-325 mg aspirin daily, 11 of them for at least one year. The mean age of this group was 71. Only two patients had a previous history of peptic ulcer. Five patients used anticoagulants or antiplatelet drugs concomitantly with aspirin. The endoscopic diagnosis of the sources of bleeding was erosive gastritis in eight patients, gastric ulcer in four, duodenal ulcer in five and oesophageal ulcer in one. Our results support findings by other groups, showing that doses of aspirin as low as 75 mg daily should be used in the management of elderly patients with thrombo-embolic disease.

Acute Disease↗
PubMed1993

Recurrent infective endocarditis.

Infective endocarditis is a serious disease associated with high mortality. Patients surviving recurrent bouts of infective endocarditis are reported infrequently. We report on a non-drug abuser patient who experienced seven episodes of infective endocarditis--the largest number reported to our knowledge in a single non-drug abuser patient.

Aged↗
PubMed1992

Preoperative clues to Crohn's disease in suspected, acute appendicitis. Report of 12 cases and review of the literature.

Twelve patients who underwent laparotomy for suspected acute appendicitis were found to have Crohn's disease of the terminal ileum. Appendectomy was performed in all although in only four patients was the appendix grossly inflamed. Postoperative complications, either abscess or fistula, developed in four patients (33%). Careful investigation of the records revealed some preoperative diagnostic clues: a history of recurrent abdominal pain and/or diarrhea (83%), physical examination revealing normal temperature (50%), and laboratory results compatible with a chronic process such as microcytic anemia (33%) and hypoproteinemia/hypoalbuminemia/hypocholesterolemia (50%). As the differential diagnosis between Crohn's disease and appendicitis is difficult and the surgical approach to the appendix in the presence of Crohn's disease is controversial, we illuminate some practical points in the preoperative evaluation of these patients and deal with the question of whether appendectomy should be performed in these patients.

Acute Disease↗
PubMed1992

Relapsing hepatitis A. Review of 14 cases and literature survey.

We have reviewed our experience with 14 cases of relapsing hepatitis A (RH-A), as well as 68 cases reported in the literature. Relapse occurs in 3 to 20% of patients with acute hepatitis A, and rarely takes the form of a polyphasic disease (multiple relapses). After a stage of typical hepatitis A, remission phase ensues, with partial or complete resolution of clinical and biochemical manifestations. Relapse usually occurs after a short period (usually less than 3 weeks). Relapse is usually clinically milder than the first phase, with variable liver function abnormalities and a tendency toward more marked cholestatic features. Not uncommonly, immune manifestations occur during this phase, including purpura, nephritis, and arthralgia, with common laboratory findings of rheumatoid factor as well as false-positive reaction to HCV-EIA tests. The clinical course in relapsing hepatitis A is almost always benign, and uneventful recovery is the rule with few exceptions. Steroid treatment, first reported in the present series, resulted in marked clinical improvement. Preliminary results suggest that R-HA is associated with a continuing viremia as well as shedding of virus in stools during the relapse phase. The pathogenesis of R-HA probably involves an interaction between persistent viral infection and immune mechanisms responding to the continuing antigenic stimulation.

Adult↗
PubMed1992

[Kaposi's sarcoma following liver transplantation].

A 54-year-old man developed Kaposi's sarcoma 2 months following orthotopic liver transplantation for hepatitis B-associated liver cirrhosis. At that time he was on combined immunosuppressive therapy (azathioprine, prednisone and cyclosporine A). The disease is very prevalent among immunosuppressed patients following renal transplantation, but is considered to be relatively rare following liver transplantation. The patient ran a relatively benign course without organ involvement and with only the skin disease. This is the first case of Kaposi's sarcoma following liver transplantation reported in Israel.

Humans↗
PubMed1991

Genomic organization and chromosomal localization of the TAPA-1 gene.

TAPA-1 is a 26-kDa integral membrane protein expressed on many human cell types. Antibodies against TAPA-1 induce homotypic aggregation of cells and can inhibit their growth. The murine homologue of TAPA-1 was cloned from both cDNA and genomic DNA libraries. A very high level of homology was found between human and mouse TAPA-1. The 5' untranslated region of the TAPA-1 gene resembles housekeeping gene promoters with respect to G + C content and the presence of potential Sp1 binding sites. The chromosomal localization of human and murine TAPA-1 genes was determined by Southern blot experiments using DNA from somatic cell hybrids. The genes were found to be part of a conserved syntenic group in mouse chromosome 7 and the short arm of human chromosome 11. The organization of the TAPA-1 gene and the projection of the exon boundaries on the proposed protein structure are presented.

Amino Acid Sequence↗