Biomedical subjects
Publications and source records attributed to A Shahar.
Dorsal root ganglia from newborn mice develop and myelinate following transplantation under the kidney capsule of adult syngeneic mice. The transplanted dorsal root ganglia in the subcapsular environment developed more rapidly and formed more abundant myelin than comparable ganglia in an in vitro culture.
Persons referred to the clinic for hearing evaluation, aged 17--35 yrs, who during the evaluation yielded inconsistent pure-tone and speech data and were suspected of malingering, were given a monosyllabic Hebraic PB test at 5, 10, 15, and 20 db re their admitted SRT. Group performances were compared at every presentation level to those of normal-hearing young adults. Both groups performed better as levels increased, but the suspected malingerers yielded SDSs at 5, 10, and 15 db significantly higher than controls by 20.8, 12.5, and 5.2 percentage points, respectively. The higher SDSs at low sensation levels (SLs) yielded by the suspected malingerers were assumed to be due to the exaggerated SRTs admitted by them. Furthermore, the performance - vs - level curve of the normals corresponded to that in the literature for English material, while the curve of the suspected malingerers was, in contrast, essentially different. It was concluded that with careful standardization and wide clinical and experimental use, collecting SDSs at low SLs re admitted SRT might produce a potentially valuable additional tool for uncovering malingering.
Microgranular DEAE-cellulose anion exchanger with exchange capacities ranging between 0-2.7 meq/gr dry materials were tested for their suitability to be used as microcarriers for culturing several anchorage-dependent-cells. It was found that cells from established cell lines (BHK, MDCK), grew as confluent monolayer on DEAE-cellulose microcarriers with exchange capacity ranging between 1.00-2.0 meq/gr dry materials. Primary cells (chick embryo fibroblast) grow as a cell-microcarriers aggregate on DEAE-cellulose microcarriers with an exchange capacity ranging between 1.59-2.0 meq/gr dry materials. Cells from human diploid cell strains grew poorly on these microcarriers. Cell yields obtained using the DEAE-cellulose microcarriers were similar to those obtained on commercially available DEAE-dextran microcarrier culturing systems. Several viruses were propagated on cells grown in DEAE-cellulose microcarrier culturing systems. Virus yields per cell were similar to those obtained in conventional monolayer cultures.
Immune electron microscopy (IEM) is one of the fastest and most sensitive methods for the detection and diagnosis of viruses. This technique is based on formation of immune complexes of the virus with its corresponding antibody. In IEM optimal precipitation depends on a correct ratio, and there is a prozone effect. These problems can be overcome by using the solid-phase immune electron microscopic (SPIEM) technique. In this technique the antibody is attached to a particle which is used for 'fishing' the virus to be examined out of the suspension. After low speed centrifugation the preparation is treated either for observation in the transmission electron microscope or in the scanning electron microscope. In 'positive' samples the virus is seen attached to the surface of the particle. We report here results with S. aureus as the solid phase for the detection of Sindbis virus. The anti-Sindbis gamma globulins are attached to the bacteria by means of protein A present on their surface.
Amorphous silicates having small particles with a large surface area were found to have high nonspecific adsorption capacity. Investigations with Escherichia coli T4 bacteriophage have shown adsorption capacity of up to 99.9% on different tested silicates. Optimal conditions for the adsorption of T4 bacteriophage on various commercially available silicates were determined. A continuous-flow adsorption of T4 bacteriophage on silicates appears to be a model system for the removal of viruses from potable water and sewage.
Aging of acetylcholinesterase (AChE) inhibited by certain organophosphates such as diisopropylfluorophosphate apparently involves dealkylation of the bound organophosphoryl moiety; this renders the inactive enzyme resistant to reactivation by quaternary oximes such as 2-pyridinealdoxime methiodide (2-PAM) which are used in therapy of organophosphate intoxication. The fluorescent pyrenyl organophosphates synthesized in this study were designed to detect putative conformational changes which might explain this resistance. The following inhibitors: 1-pyrenebutyl phosphorodichloride (PBPDC), 1-pyrenebutyl ethylphosphorochloridate (PBEPC), and 1-pyrenebutyl ethylphosphorofluoridate (PBEPF), react specifically with purified electric eel AChE (ki = 10(6)-10(7) M-1 min-1). AChE inhibited by PBEPC and PBEPF was readily reactivated by 2-PAM, while enzyme inhibited PBPDC could not be reactivated. Conjugates were prepared of both PBEPC and PBPDC with AChE, each containing one molecule of florophore per catalytic subunit. Thus two stoichiometric conjugates, PBEP-AChE (non-aged) and POBP-AChE (aged), were obtained. The two complexes exhibited identical absorption spectra, but differed in their steady-state fluorescence spectra. Although the wave-lenths of the excitation and emission spectra were similar, the pyrene fluorescence of the non-aged conjugate was ca. 50% quenched relative to the aged conjugate. Nanosecond fluorescence decay studies revealed two principal lifetime components of pyrene fluorescence. Both were longer for the aged (PBP-AChE) than for the non-aged (PBEP-AChE) conjugate and revealed a ca. 50% lower quantum yield for the non-aged as compared to the aged conjugate. A possible interpretation for these results is that in the aged conjugate the organophosphoryl moiety is less acessible to the external medium. Measurement of quenching of pyrene fluorescence in the aged and non-aged conjugates by the peripheral anionic site ligand propidium also indicated marked conformational differences between the two conjugates, and circular polarization of luminescence measurements revealed that propidium itself induced a substantial conformational change in both conjugates. Fluorescence lifetime measurements revealed that whereas propidium had little effect on the decay parameters for the non-aged conjugate it caused a decrease in lifetime and in relative quantum yield for the aged conjugate. PBEPF virtually eliminated cholinesterase activity in dissociated cord and brain cultures. Fluorescence microscopy reveals fine green fluorescent grains distinctly located throughout many neurons and glia. Labelling is much more pronounced in larger and older neurons. No specific fluorescence could be detected in cultures preincubated with nonfluorescent organophosphates.
Amorphous silicates having small particles with large surface area, were found to have high non-specific adsorption capacity. Escherichia coli T4 bacteriophage was used as a model in this research. Investigations have shown an adsorption capacity of up to 99% on different tested commercially available silicates. Optimal conditions for the adsorption of T4 bacteriophage on various silicates were determined. Amorphous silicates may be used in purification of water from viral contaminants. A silicate-containing model unit for filtration by adsorption of viruses is described.
Although some biochemical dose-dependent effects are revealed in erythrocytes exposed to delta 1-tetrahydrocannabinol (THC) already at concentrations well below 10 microM, marked morphological changes of the erythrocyte membrane become evident, by scanning electron microscopy, only at THC concentrations beyond 15 microM. These observations provide evidence additional to previous chemical and physical studies, in which 15 microM is found to be a critical concentration with respect to the effects of TCH on erythrocyte membrane.
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A study of acute gastroenteritis in children was carried out with the aim of establishing the prevalence of human reoviruslike agent (HRLA) and its relation to other enteric pathogens in Israel. The stools of 384 children with acute diarrhea referred to a pediatric emergency service were screened for HRLA by counterimmunoelectroosmorphoresis (CIEOP) and for pathogenic bacteria. Evidence of HRLA infection was found in 65 patients (17%). The highest infection rate prevailed during the cool season (25%), with a peak prevalence (41%) in November, when both the temperature and humidity were low. A very high proportion of HRLA was found in children younger than 36 months and no HRLA infection was observed in those older than nine years. The highest prevalence occurred in infants younger than six months, a situation rarely encountered in other countries. The main clinical features of HRLA infection were fever, vomiting, dehydration, signs of upper respiratory infection and carbohydrate intolerance. Bacterial pathogens accounted for 45% of enteric infections. Shigella species predominated (28%) during the summer season, especially in older children. In 38% of the study group, no etiologic agent could be detected. None of the 50 control subjects showed evidence of viral or bacterial pathogens in stools.
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Replication of encephalomyocarditis virus and its cytopathic effects were studied in myelinated cultures of dorsal root ganglia obtained from newborn mice. Six hours after infection virus progeny was detected in the culture. At 24 h the virus titer reached 2 times 10(6) PFU per culture and remained at this level until 48 h. The first cytopathic alterations began at 24 h and consisted of rounding of Schwann and satellites cells and their detachment from neurons. Later, bead-like swellings of the myelin appeared along the axons followed by splitting and degeneration of lamellae. The cytopathic effect in the neurons started 29 h after infection, reaching complete neuronolysis at 48 h. Virus particles, scattered or arranged in crystal-like aggregates, were first seen in the cytoplasm of glial cells and then in neurons and axons.
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