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Biomedical subjects

D Hassin

Publications and source records attributed to D Hassin.

17 recordsLinked to original sources
PubMed1997

Identification of a new strain of fastidious enterovirus 70 as the causative agent of an outbreak of hemorrhagic conjunctivitis.

A 1994 outbreak of acute hemorrhagic conjunctivitis in Israel was caused by an enterovirus 70 strain that was distinct from previously reported strains. Characterization was by electron microscopy (eye washes), reverse transcription-PCR (RT-PCR; eyewash, specimens, eye swabs, and tears), and sequence analysis of RT-PCR-amplified fragments from the 5' noncoding region and VP1.

Amino Acid Sequence↗
PubMed1995

The effect of cytotoxic lymphocytes on contraction, action potential and calcium handling in cultured myocardial cells.

Cytotoxic T lymphocytes are important in the pathogenesis of several disease states, yet the pathophysiology of the lymphocyte-myocyte interaction is not well known. We have developed in vitro viral and autoimmune models to study the physiological phenomena associated with this interaction. To produce these models, lymphocytes were obtained from adult rats injected either with mengo virus or autologous cardiac myocytes. Cardiac myocytes from neonatal rats were then exposed to these lymphocytes. In both models, reversible physiologic changes in myocytes preceded irreversible cell damage. The physiologic changes included reduced amplitude of myocyte contraction, impairment of relaxation and prolongation of the duration of contraction and action potential. In addition, oscillations were noted in the plateau phase of the action potentials. These physiologic changes were accompanied by an early elevation in the cytosolic free calcium concentration, a late elevation in the total exchangeable calcium pool, and attenuation of the [Ca2+]i transient signals. Verapamil inhibited the late elevation in the total exchangeable calcium pool, but failed to inhibit the early elevation in the cytosolic free calcium concentration. These phenomena may explain transient cardiac functional abnormalities that may appear during myocarditis prior to cell destruction.

Action Potentials↗
PubMed1995

Double-blind randomized study of 1 g versus 2 g intravenous ceftriaxone daily in the therapy of community-acquired infections.

In a multicentre, double-blind, randomized study involving four general hospitals in Israel, the efficacy and safety of ceftriaxone 1 g/day i.v. was compared to that of 2 g/day i.v. in the treatment of moderate to severe community-acquired infections requiring hospitalization. Two hundred and twenty-two patients were enrolled; 112 received intravenous ceftriaxone 1 g/day, and 110 received 2 g/day. The two groups were matched demographically, and their mean APACHE II score (10 points) and mean duration of successful therapy (7 days) were identical. The sites of infection in the 1 g and 2 g groups respectively were lower respiratory tract in 57 versus 51 patients, urinary tract in 31 versus 40 patients, and soft tissue in 24 versus 19 patients. There were no significant differences in clinical outcome between the 1 g and 2 g groups, the outcome being cure in 91% versus 86% of patients, improvement in 3% versus 3% of patients, failure in 3% versus 8% of patients, and relapse in 3% versus 3% of patients. The findings of this study indicate that ceftriaxone 1 g/day is as effective as 2 g/day in the treatment of moderate to severe community-acquired infections. The low-dose form is a more economical means of treating these infections.

Adult↗
PubMed1994

Physiological changes induced in cardiac myocytes by cytotoxic lymphocytes: an autoimmune model.

BACKGROUND: cytotoxic lymphocytes are important in the pathogenesis of several disease states, yet, the pathophysiology of lymphocyte-myocyte interaction is not well known. METHODS AND RESULTS: We have developed a model for the in vitro evaluation of autoimmune cytotoxic myocardial damage. Cardiac myocytes were repeatedly injected to adult autologous rats. Following 3 months, histological evidence of myocarditis was seen in 20% of the hearts. Cultured myocytes obtained from newborn rats were exposed to lymphocytes isolated from the immunized animals. Cytotoxic activity was measured using crystal violet staining test. The percentage of killing was increased as the ratio of lymphocytes/myocytes was increased. Verapamil did not block this cytotoxic effect. No killing was seen when myocytes were exposed to non-sensitized lymphocytes. Physiological changes induced in myocytes by cytotoxic lymphocytes were studied. Cell wall motion was measured by an optical method and action potentials with intracellular microelectrodes. Physiological changes observed in myocytes following exposure to cytotoxic lymphocytes included: Impaired relaxation with prolonged contractions, oscillations and prolongation of the plateau of the action potential. Cellular contraction was prolonged up to 4 s before total arrest of spontaneous activity. Verapamil but not tetrodotoxin restored action potentials and contractions to normal. Supernatant collected from cultures of myocytes and lymphocytes had the same effect on myocytes contractility as observed following exposure of myocytes to cytotoxic lymphocytes. CONCLUSIONS: This supports our hypothesis that these physiological alterations observed in myocytes are mediated by a soluble factor secreted by cytotoxic lymphocytes.

Action Potentials↗
PubMed1994

Pacemaker endocarditis. Report of 44 cases and review of the literature.

We conducted a retrospective study to characterize the clinical course, microbiologic spectrum, and risk factors for endocarditis and for associated mortality in a large series of patients with documented pacemaker endocarditis. Using a computerized search through the medical records of 10 major hospitals in Israel from 1982 to 1992, and carefully reviewing the charts, we identified 44 patients with pacemaker endocarditis. The cases were categorized as definite (n = 25), probable (n = 12), or possible (n = 7) infective endocarditis based on strict case definition. Fever and chills were the most common symptoms. Increased ESR, leukocytosis, microscopic hematuria, and anemia were the most common laboratory findings. A relatively high proportion of the patients were diabetic. The most common source of endocarditis was infection acquired by the placement procedure or infection of the pacemaker pouch. Demographic, clinical, and laboratory features were similar to those of endocarditis patients of a similar age range without pacemakers, although the frequency of fever and chills was higher in our patients than in those patients and splenomegaly, vascular embolic phenomena, and new or changing murmurs were rare in our patients. The major pathogens were Staphylococcus aureus and Staphylococcus epidermidis, similar to other series of pacemaker-associated bacteremia and similar to the microbiologic findings of early prosthetic-valve endocarditis. However, this microbiologic profile is different from that of native-valve endocarditis. Although the present series did not show a statistically significant advantage to electrode removal over conservative treatment, when analyzed together with pooled data from other studies, it suggests that the surgical approach is preferable.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1994

Hairpin structures are the primary amplification products: a novel mechanism for generation of inverted repeats during gene amplification.

Early events of DNA amplification which occur during perturbed replication were studied by using simian virus 40 (SV40)-transformed Chinese hamster cells (CO60) as a model system. The amplification is observed shortly after carcinogen treatment, and the amplified sequences contain molecules organized as inverted repeats (IRs). SV40 amplification in vitro was studied by using extracts from carcinogen-treated CO60 cells. In the amplified DNA the SV40 origin region was rereplicated, while more distal sequences were not replicated even once. Using several experimental procedures such as sucrose gradients, "snap-back" assay, and two-dimensional gel electrophoresis, we show that the overreplicated DNA contains IRs which are synthesized de novo as hairpins or stem-loop structures which were detached from the template molecules. The fully replicated SV40 molecules synthesized by the HeLa extracts do not contain such IRs. We propose "U-turn replication" as a novel mechanism for gene amplification, accounting for the generation of extrachromosomal inverted duplications as a result of perturbed replication and template switching of the DNA polymerases.

Animals↗
PubMed1994

Cryptococcus neoformans vertebral osteomyelitis.

A 67-year-old previously healthy woman presented with low back pain of 2 months duration and daily fever of 39 degrees C for 3 weeks. CT scan showed a lytic lesion in the third lumbar vertebra and a small right lower lobe lung infiltrate with mediastinal lymphadenopathy. Culture of material obtained from open biopsy of the vertebra grew Cryptococcus neoformans var. neoformans, which was also demonstrated on histology. Cryptococcal antigen was detected in the patient's serum. Treatment with amphotericin B (1000 mg total dose) and oral 5-fluorocytosine, resulted in complete recovery and resolution of the chest X-ray findings with a follow-up of 2 years. Since this case, as well as most of the previously described cases of cryptococcal osteomyelitis, were in normal hosts, cryptococcal osteomyelitis should be considered in the differential diagnosis even in a normal host, and therefore, prior to possible invasive diagnostic procedures, cryptococcal antigen in the serum should be determined.

Aged↗
PubMed1994

Wernicke's encephalopathy in hyperemesis gravidarum: association with abnormal liver function.

A 27-year-old woman developed Wernicke's encephalopathy in the 18th week of her pregnancy after 11 weeks of vomiting accompanied by weight loss of 21 kg and moderately abnormal liver function tests. The patient recovered after thiamine therapy but the fetus was lost. Review of the literature published during the last 25 years revealed an additional 14 cases of Wernicke's encephalopathy complicating hyperemesis gravidarum. All patients vomited for at least 4 weeks. Six of the 15 patients (40%) had aspartate aminotransferase values > 100 U/l, much higher than the rate reported in previous series of patients with hyperemesis gravidarum (7%). This suggests the need for parenteral thiamine supplementation in patients with severe hyperemesis gravidarum lasting more than 3 weeks, especially those with abnormal liver function, and supports the hypothesis that the hepatic abnormality plays a pathogenetic role in the development of Wernicke's encephalopathy in hyperemesis gravidarum.

Adult↗
PubMed1990

Carcinogen-induced DNA amplification in vitro: overreplication of the simian virus 40 origin region in extracts from carcinogen-treated CO60 cells.

An in vitro system to study carcinogen-induced amplification in simian virus 40 (SV40)-transformed Chinese hamster (CO60) cells is described. SV40 amplification in this system resembled in many aspects the viral overreplication observed in drug-treated CO60 cells. Cytosolic extracts from N-methyl-N'-nitro-N-nitrosoguanidine-treated cells supported de novo DNA synthesis in the presence of excess exogenous T antigen and the SV40-containing plasmid pSVK1. The pattern of viral replication in these extracts was unique, since only the 2.4-kilobase-pair region spanning the origin was overreplicated, whereas distal sequences were not replicated significantly. Extracts from control cells supported only marginal levels of replication. In HeLa extracts, complete SV40 DNA molecules were replicated efficiently. The overreplication of the origin region in CO60 cell extracts was bidirectional and symmetrical. A fraction of the newly synthesized DNA molecules underwent a second round of replication, yielding MboI-sensitive fragments representing the 2.4-kilobase-pair region around the origin. The mechanisms controlling the amplification of the viral origin region, the nature of the cellular factors induced in the carcinogen-treated cells, and their putative association with general drug-induced SOS-like responses are discussed.

Animals↗
PubMed1987

Physiological changes induced in cardiac myocytes by cytotoxic T lymphocytes.

The "lethal hit" induced by viral specific, sensitized, cytotoxic T lymphocytes (CTL) attacking virus-infected heart cells is important in the pathogenesis of viral myocarditis and reflects the key role of CTL in this immune response. The mechanisms involved are incompletely understood. Studies of the physiological changes induced in mengovirus-infected, cultured, neonatal, rat heart cells by CTL that had been previously sensitized by the same virus are presented. The CTL were obtained from spleens of mengovirus-infected, major histocompatibility complex (MHC) matched adult rats. Cell wall motion was measured by an optical method, action potentials with intracellular microelectrodes, and total exchangeable calcium content by 45Ca tracer measurements after loading the myocytes with 45Ca and then exposing them to CTL. After 50 min (mean time) of exposing mengovirus-infected myocytes to the CTL, the mechanical relaxation of the myocyte was slowed, with a subsequent slowing of beating rate and a reduced amplitude of contraction. Impaired relaxation progressed, and prolonged oscillatory contractions lasting up to several seconds appeared, with accompanying oscillations in the prolonged plateau phase of the action potentials. Arrest of the myocyte contractions appeared 98 min (mean time) after exposure to CTL. These changes in action potentials and contractions were reversible either by washout with the normal medium or by the addition of verapamil. The amount of total exchangeable calcium in the cultured myocytes, 1 h after exposure to CTL, was significantly increased. This increase was prevented by pretreatment with verapamil. (ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1986

A major internal initiation site for the in vitro translation of the adenovirus DNA polymerase.

An open reading frame which encodes at least 90% of the adenovirus type 2 DNA polymerase gene was cloned behind the SP6 promoter and transcribed in vitro using the SP6 RNA polymerase. The resultant RNA was translated in a rabbit reticulocyte cell free system. In addition to the translation of a 120-kDa protein corresponding to the size of the complete open reading frame, the synthesis of a 62-kDa polypeptide was demonstrated. Data is presented to show that the synthesis of the 62-kDa polypeptide resulted from internal initiation of translation in frame in the middle of the message at the 11th or 12th AUG. Capping of the mRNA resulted in an increase in synthesis of the 120-kDa protein and a concordant decrease of the internally initiated polypeptide. We propose that there may be competition between the binding of the translational preinitiation complex at or near the 5' end of the mRNA and at the internal initiation site. Because of inhibition of synthesis of the 120-kDa but not the 62-kDa polypeptide by hybrid arrested translation using DNA complementary to approximately one third of the 5' Ad Pol mRNA sequences, scanning of the ribosome from the 5' end of the mRNA to the internal initiation site seemed unlikely. The sequence proximal to the 12th AUG is ACCCACCCCAUG which is similar to a noncontinuous sequence 5'AUCCACC(X)nAUG complementary to the 3' end of the 18 S rRNA. This sequence is a favored ribosome binding site based on the observation that it is the most commonly observed one at or near the 5' end of 162 mRNA's analyzed (D. R. Sargan, S. P. Gregory, and P. H. W. Butterworth, 1982, FEBS Lett. 147, 133-136).

Adenoviruses, Human↗
PubMed1985

Cytotoxic T lymphocytes and natural killer cell activity in the course of mengo virus infection of mice.

Inbred C57BL/6 mice were inoculated intraperitoneally (i.p.) with mengo virus. The activity of cytotoxic T lymphocytes (CTL) and natural killer (NK) cells were measured during the first 22 days following infection. The CTL response began 7 days after virus inoculation, persisted for at least 22 days and was related to the dose of the virus inoculated. NK cell activity was elevated within 24 hr, reached its peak level on the fourth day and declined to normal levels on the eleventh day after exposure to the virus. These results suggest that NK cells represent the first cellular immune response to restrict mengo virus spread while specific CTL appear later and are probably responsible for further restriction, elimination and prevention of the viral disease.

Animals↗
PubMed1980

Propylthiouracil-induced hepatic damage.

Two cases of propylthiouracil-induced liver damage have been observed. The first case is of an acute type of damage, proven by rechallenge; the second presents a clinical and histologic picture resembling chronic active hepatitis, with spontaneous remission.

Adult↗
PubMedDate not supplied

Spinal epidural abscess: an unusual complication of bacterial endocarditis.

We are reporting a case of epidural abscess complicating bacterial endocarditis. To the best of our knowledge, this association has not been reported before. Streptococcus sanguis was isolated from the blood. A full recovery followed surgery and antibiotic therapy. The relevant characteristics of both diseases are reviewed. No explanation for this rare association is available as yet.

Abscess↗