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R Thomas

Publications and source records attributed to R Thomas.

At least 685 records · Page 38Linked to original sources
PubMed1976

Familial Hodgkin's disease and associated cancer. A clinical-pathologic study.

The etiology of Hodgkin's disease is complex, as is evident in studies suggesting the importance of horizontal transmission, occupational factors, racial and ethnic background, and familial, genetic factors, or both, including HL-A associations. The present study is of a remarkable kindred in which Hodgkin's disease was histologically verified in two sibships involving second-cousins related through maternal great-grandparents. Cancer of the lung, breast, endometrium, ovary, pancreas, and brain, as well as leukemia and Wilms' tumor, occurred in first and second-degree relatives of the Hodgkin's patients. HL-A haplotypes in patients with Hodgkin's disease in this family showed HL-AB5 or HL-ABW35, an association confirmed in other reports. The findings of associated malignant neoplasms in familial Hodgkin's disease, here and elsewhere in the literature, suggest that in the quest for etiology of Hodgkin's disease one must view the disorder eclectically, with a painstaking search for multiple etiologies, genetic and environmental.

Adult↗
PubMed1976

A complex control circuit. Regulation of immunity in temperate bacteriophages.

Temperate bacteriophages can display in a stable way two essentially different behaviours. In the immune state, a gene (cI) produces a repressor which prevents expression of all the other viral genes; in the non-immune state the typically viral functions are expressed. The choice between the two pathways and the establishment of one of them have much in common with cell determination and differentiation. This choice depends on a complex control system, in fact one of the most intricate nets of regulation known in some detail. Our paper provides a formal description and partial analysis of this regulatory net. It is shown that even for relatively simple known models, this kind of analysis uncovers predictions which had previously remained hidden. Some of these predictions were checked experimentally. The experimental part chiefly deals with the efficiency of lysogenization by thermoinducible lambda phage carrying mutations in one or more of the regulatory genes, N, cro and cII. Although N- mutations are widely known for preventing efficient integration, and both N- and cII mutations for preventing efficient establishment of immunity, it is shown that, as predicted by a simple model, both N- and cII- phage efficiently lysogenize at low temperature if they are in addition cro-. In contrast with lambda N- cro+, lambda N- cro- is not propagated as a plasmid at low temperature, precisely because it establishes immunity too efficiently. Genetic control circuits are described in terms of sets of logic equations, which relate the state of expression of genes or of chemical reactions (functions) to input (genetic and environmental) variables and to the presence of gene and reaction products (internal, or memorization varibles). From the set of equations, one derives a matrix which shows the stable stationary states (if any) of the system, and from which one can derive the pathways (temporal sequences of states) consistent with the model. This kind of analysis is complementary to the more widely used analysis based on differential equations; it allows one to analyze in less detail more complex systems. The language might be used as well, mutatis mutandis, in fields very different from genetics. The last part of the discussion deals with the role of positive feedback loops in our specific problem (establishment and maintenance of immunity in temperate bacteriophages) and in developmental genetics in general. As a generalization of an old idea, it is suggested that cell determination (for a given character) depends on a set of genes whose interaction constitutes a positive feedback loop. Such a system has two stable stationary states: which one is chosen will usually depend on additional controls grafted on the loop.

Bacteriophages↗
PubMed1976

[Aseptic meningitis after isotope cisternography. 2 Cases].

In these two patients, as in 13 others described in the literature, a typical meningitic syndrome with excitement, confusion and a fever of 104degrees F (40degrees C) appeared 4-6 hours following the intra-thecal injection. Subsequent lumbar puncture usually reveals a cloudy C.S.F. under increased pressure. The polymorphs and proteins are increased but the glucose remains normal. There are no bacteria either on direct examination or after culture. All the patients receive antibiotics. After a course of three days, the symptoms and the fever have disappeared and the C.S.F. became normal. Bacterial contamination can be ruled out. The relative roles of iodine, radio-acitivity itself, albumine and of the radio-active element which are only used for this radiotracer are discussed. The tracer contains neither stabilizer nor pH buffer. One must presume that the syndrome is due to a direct toxic action rather than to an immunological or allergic reaction. Furthermore, it is of interest that similar reactions, without infection, are seen after spinal anaesthesia and intra-thecal injection of such differing substances such as iodine contrast media, gamma globulins, other isotopes or toxic substances (Lysol) (111In-DTPA).

Adult↗
PubMed1975

[Pneumocystis carinii pneumonia after kidney transplantation. Early diagnosis by distal bronchial brushing].

Distal bronchial brushing is one of the methods used in the in vivo indentification of Pneumocystis carinii, a parasite associated with severe pneumonia, the development of which is induced by immuno-depression, particularly after renal transplantation. In three patients the pathogenic agent was demonstrated in alveolar material obtained in this way. The technique is simple and risk-free. It may be used early and repeatedly.

Adult↗
PubMed1975

[Circulatory survival of irreversible comas].

On the basis of a series of 53 cases of irreversible coma maintained in circulatory survival with the aim of removing the kidneys, the authors discuss the mode of treatment, with particular reference to the intravenous fluids used and the use of medications influencing the circulation. Fluid and electrolytes given must be adjusted hourly to ensure the exact replacement of urinary losses. Isoprotenerol is the only medication usually necessary. In the event of circulatory insufficiency, which is difficult to foresee and hence prevent, immediate volume expansion in a short a time as possible and isoprotenerol most frequently correct the situation (14 out of 17 cases). Thus effective circulation may be maintained until the kidneys are removed (48 out of 53 cases). 92 p.cent of the grafted kidneys functioned from the first day onwards.

Adolescent↗
PubMed1975

Expression of ribosomal protein genes in Escherichia coli.

Streptomycin or spectinomycin treatment of an E. coli strain, carrying the strR and spcR alleles on the chromosome and the wild-type (sensitive) alleles on the episome, selects for inactivation of the relevant sensitive allele. After Mu induced mutagenesis, in the absence of selection against extended deletions upon the episome, a large proportion of stro mutants are also spco, and vice versa. However, when markers flanking the strA and spcA gene cluster are simultaneously selected, effectively eliminating long deletions, the majority of stro mutants continue to express the spcs allele, and vice versa. Insofar as inactivation after Mu treatment is due to prophage insertion within or proximal to the genes in question, this result indicates that the genes strA and spcA are not parts of a single operon. In virtue of the high frequency of extended deletions observed in the absence of suitable counter-selection, we must place a word of caution upon the use of phage Mu-1 as a means of isolating polar mutations and defining transcriptional units.

Bacterial Proteins↗