An immunocompromised host with bilateral pulmonary infiltrates.
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Adult↗
Biomedical subjects
M D Levin
Publications and source records attributed to M D Levin.
Noise in gene expression as the source of non-genetic individuality in the chemotactic response of Escherichia coli.
A deterministic computer model of the signal transduction pathway mediating bacterial chemotaxis was used to examine the variation in both unstimulated swimming behaviour and adaptation time to stimuli in clonal populations of cells. Copy numbers of proteins in the pathway were computed from a simplified model of transcription and translation that predicts greater-than-Poissonian statistics. Simulated and experimental individuality data could be brought into good agreement on varying the noise strength of the protein copy number distributions. In the simulations, all the proteins in the pathway are involved to a significant degree in the appearance of phenotypic diversity, although there is a modest decrease in influence with increasing copy number.
Adaptation, Biological↗
Two patients with acute thrombocytopenia following gold administration and five-year follow-up.
Thrombocytopenia is a well-known side effect following intramuscular gold therapy in patients with rheumatoid arthritis. Thrombocytopenia may occur at any time and it can be irreversible and sometimes fatal despite cytotoxic or immunosuppressive therapy. We describe two patients who presented with haemorrhagic diathesis on the day after the administration of aurothioglucose. The thrombocytopenia in these patients was caused by aurothioglucose-induced antibody-mediated platelet destruction. Both patients made an uneventful recovery and the platelet count returned to normal within several weeks without further treatment. Antibody-detecting tests were repeated five years later and could not demonstrate the presence of antibodies. Also after incubation with aurothioglucose no antibodies could be demonstrated.
Acute Disease↗
Partially bridge-fluorinated dimethyl bicyclo[1.1.1]pentane-1,3-dicarboxylates: preparation and NMR spectra.
Direct fluorination of dimethyl bicyclo[1.1.1]pentane-1,3-dicarboxylate, obtained from [1.1.1]propellane prepared by an improved synthetic procedure, furnished esters of 14 of the 15 possible bridge-fluorinated bicyclo[1.1.1]pentane-1,3-dicarboxylic acids, isolated by preparative GC. Calculated geometries reflect the substitution pattern in a regular fashion compatible with Bent's rules. Considerable additional strain is introduced into the bicyclo[1.1.1]pentane cage by polyfluorination; it is calculated to be as high as 33-35 kcal/mol for hexasubstitution. Three arrangements of the fluorine substituents are especially strain-rich: geminal, proximate, and W-related. The (1)H, (13)C, and (19)F NMR spectra exhibit a striking variety of chemical shifts and long-range coupling constants. These are in good agreement with results calculated with neglect of the bridgehead substituents for all of the chemical shifts by the GIAO-RHF/6-31G//RHF/6-31G and GIAO-RHF/6-31G//MP2/6-31G methods and for many of the coupling constants by the EOM-CCSD/6-311G//MP2/6-311G method. The proximate (4)J(FF) constants are particularly large (50-100 Hz) and show an inverse linear dependence on the calculated F-F distance in the range 2.43-2.58 A.
Journal Article↗
Bicyclo[1.1.1]pentanes, [n]Staffanes, [1.1.1]Propellanes, and Tricyclo[2.1.0.0(2,5)]pentanes.
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Journal Article↗
Molecular model of a lattice of signalling proteins involved in bacterial chemotaxis.
Coliform bacteria detect chemical attractants by means of a membrane-associated cluster of receptors and signalling molecules. We have used recently determined molecular structures, in conjunction with plastic models generated by three-dimensional printer technology, to predict how the proteins of the complex are arranged in relation to the plasma membrane. The proposed structure is a regular two-dimensional lattice in which the cytoplasmic ends of chemotactic-receptor dimers are inserted into a hexagonal array of CheA and CheW molecules. This structure creates separate compartments for adaptation and downstream signalling, and indicates a possible basis for the spread of activity within the cluster.
Bacterial Proteins↗
Myocarditis and primary Sjögren's syndrome.
We describe congestive heart failure caused by autoimmune myocarditis in a patient with primary Sjögren's syndrome. Only after corticosteroids were given did the symptoms and laboratory abnormalities disappear.
Autoimmune Diseases↗
Platelet-bound immunogloblins before and after platelet transfusion: measurement of in vivo binding.
In routine tests to investigate immunological mechanisms as a cause for enhanced destruction of transfused platelets; serum from the patient is tested against a panel of donor lymphocytes and platelets to demonstrate the presence of antibodies against HLA or platelet specific antibodies. Here we describe a flow cytometric technique in which in vivo binding of immunoglobulins (Ig) is measured. By comparing the histograms of the platelet suspensions before and after transfusion, four different patterns were obtained: no Ig binding before and after transfusion (pattern 1), pre-existent Ig binding (patterns 2 and 3) or preferential Ig binding to the transfused platelets (pattern 4). This technique was tested in 164 random platelet transfusions and 34 HLA-matched platelet transfusions. A statistically significant association was found between pattern 1 and a negative result of the indirect platelet immunofluorescence test for the detection of antibodies in the serum taken before the transfusion studied or a good platelet recovery and between pattern 4 and a positive indirect platelet immunofluorescence test or a low platelet recovery.
Autoimmunity↗
Design of organic molecules with large two-photon absorption cross sections.
A strategy for the design of molecules with large two-photon absorption cross sections, delta, was developed, on the basis of the concept that symmetric charge transfer, from the ends of a conjugated system to the middle, or vice versa, upon excitation is correlated to enhanced values of delta. Synthesized bis(styryl)benzene derivatives with donor-pi-donor, donor-acceptor-donor, and acceptor-donor-acceptor structural motifs exhibit exceptionally large values of delta, up to about 400 times that of trans-stilbene. Quantum chemical calculations performed on these molecules indicate that substantial symmetric charge redistribution occurs upon excitation and provide delta values in good agreement with experimental values. The combination of large delta and high fluorescence quantum yield or triplet yield exhibited by molecules developed here offers potential for unprecedented brightness in two-photon fluorescent imaging or enhanced photosensitivity in two-photon sensitization, respectively.
Aniline Compounds↗
Receptor clustering as a cellular mechanism to control sensitivity.
Chemotactic bacteria such as Escherichia coli can detect and respond to extremely low concentrations of attractants, concentrations of less than 5 nM in the case of aspartate. They also sense gradients of attractants extending over five orders of magnitude in concentration (up to 1 mM aspartate). Here we consider the possibility that this combination of sensitivity and range of response depends on the clustering of chemotactic receptors on the surface of the bacterium. We examine what will happen if ligand binding changes the activity of a receptor, propagating this change in activity to neighbouring receptors in a cluster. Calculations based on these assumptions show that sensitivity to extracellular ligands increases with the extent of spread of activity through an array of receptors, but that the range of concentrations over which the array works is severely diminished. However, a combination of low threshold of response and wide dynamic range can be attained if the cell has both clusters and single receptors on its surface, particularly if the extent of activity spread can adapt to external conditions. A mechanism of this kind can account quantitatively for the sensitivity and response range of E. coli to aspartate.
Aspartic Acid↗
Origins of individual swimming behavior in bacteria.
Cells in a cloned population of coliform bacteria exhibit a wide range of swimming behaviors--a form of non-genetic individuality. We used computer models to examine the proposition that these variations are due to differences in the number of chemotaxis signaling molecules from one cell to the next. Simulations were run in which the concentrations of seven gene products in the chemotaxis pathway were changed either deterministically or stochastically, with the changes derived from independent normal distributions. Computer models with two adaptation mechanisms were compared with experimental results from observations on individuals drawn from genetically identical populations. The range of swimming behavior predicted for cells with a standard deviation of protein copy number per cell of 10% of the mean was found to match closely the experimental range of the wild-type population. We also make predictions for the swimming behaviors of mutant strains lacking the adaptational mechanism that can be tested experimentally.
Bacteria↗
Localization of AMPA-selective glutamate receptors in the auditory brainstem of the barn owl.
AMPA receptor subunit-specific antibodies were used to determine if the distribution of excitatory amino acid receptors in the owl's auditory brainstem and midbrain nuclei reflected specializations for temporal processing. Each auditory nucleus displays characteristic levels of immunostaining for the AMPA receptor subunits GluR1-4, with high levels of the subtypes which exhibit rapid desensitization (GluR4 and 2/3). In the auditory brainstem, levels of GluR2/3 and GluR4 were very high in the cochlear nucleus magnocellularis and the nucleus laminaris. The different cell types of the cochlear nucleus angularis and the superior olive were characterized by heterogeneous GluR2/3 and 4 immunostaining. GluR1 levels were very low or undetectable. In the lemniscal nuclei, most neurons contained low levels of GluR1, and dense GluR2/3 and GluR4 immunoreactivity, with high levels of GluR4 in the dendrites. Levels of GluR4 were higher in the anterior portion of the ventral nucleus of the lateral lemniscus. The divisions of the inferior colliculus could be distinguished on the basis of GluR1-4 immunoreactivity, with high levels of GluR4 and moderate levels of GluR1 in the external nucleus. No major differences were observed between the pathways for encoding time and sound level cues.
Animals↗
[Diagnosis and treatment of ectopy of the anal canal].
An analysis of findings of clinical and ++roentgenological examinations of 55 patients with ectopy of the anal canal prior to operation and 68 patients after correction of the defect has shown that secondary megacolon developed in proportion with the age and degree of the outlet opening stenosis and there appeared injuries of elements of the normally formed anal canal. The authors described their original many-steps operation of the formation of the anus which allows all elements of retaining feces to be preserved. The amount of good long-term results increased from 22-26% up to 75% as compared with those of operations after Stone.
Adolescent↗
[Roentgenologic diagnosis of congenital hypertrophic pyloric stenosis].
In 1983-1988, in the city of Minsk 196 patients with congenital hypertrophic pylorostenosis (CHRS) were under treatment. The mean CHPS incidence is 1.06 per 1,000 neonates. X-ray examination was performed in 170 cases. CHPS was excluded by error only in one case (0.5%) on day 3 of the disease. In 8 cases, compensated pylorostenosis was diagnosed. It was characterized by proper evacuation from the stomach and positive dynamics of the body weight at the moment of examination. It is suggested that CHPS develops in response to the enhancement of hydrochloric acid secretion. The study points to the high efficacy, simplicity and safety of the method proposed.
Female↗
[Chronic colitis in children].
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Abdominal Pain↗
[Gastroesophageal reflux in children].
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Adolescent↗
[The possibility of x-ray diagnosis of acute appendicitis in children].
The plain roentgenograms of the abdominal cavity, performed in 87 children at the age of from 7 to 14 years, who were hospitalized for suspected, acute appendicitis, are analysed. The findings of roentgenometry of the stomach were processed statistically. The conclusion of a low diagnostic accuracy of the plain roentgenography was made. It is shown, that in acute appendicitis, the tonicity of the walls of a stomach increases, manifesting by the reduction in its size.
Acute Disease↗
[Functional megacolon in children].
During 1980-1985, 304 children with functional megacolon were examined. Group I was made up of 95 patients with chronic constipation; group II of 130 patients with associated megacolon and encopresis; group III of 54 patients who mainly complained of abdominal pain (the mean age was 5.2, 7.5 and 8.8 years, respectively); group IV included 25 children (19.6%) with megacolon recognized from the group of 127 patients in whom acute appendicitis was excluded according to irrigoscopy. In the children of the first 3 groups, the x-ray signs of colitis or irritated colon were identified in 54, 72 and 87%, respectively. These groups may in fact illustrate the natural time-course of changes in the disease development. It has been demonstrated that with age functional megacolon may be aggravated by colitis. A pathogenetic diagram of the development of functional megacolon is provided.
Abdominal Pain↗