Similarity Hodgkin

The resulting similarity measures are overlap-like Sa b = J Pxi ) / B(r) Coulomblike, etc. The Carbo similarity coefficient is obtained after geometric-mean normalization Sa,b/ /Sa,a Sb,b (cosine), while the Hodgkin-Richards similarity coefficient uses arithmetic-mean normalization Sa,b/0-5 (Saa+ b b) (Dice). The Cioslowski [18] similarity measure NOEL - Number of Overlapping Electrons (Eq. (10)) - uses reduced first-order density matrices (one-matrices) rather than density functions to characterize A and B. No normalization is necessary, since NOEL has a direct interpretation, at the Hartree-Fodt level of theory. 

Dice similarity coefficient Also known as the Hodgkin index c. 2 El 1 ... 

C, E E Hodgkin and Richards W G 1993. The Utilisation of Gaussian Functions for the Rapid nation of Molecular Similarity. Journal of Chemical Information and Computer Science 32 188-192. C and I D Kuntz 1995, Investigating the Extension of Pairwise Distance Pharmacophore sures to Triplet-based Descriptors, Journal of Computer-Aided Molecular Design 9 373-379. 

Hodgkin E E and W G Richards 1987. Molecular Similarity Based on Electrostatic Potential and Electri Field. International Journal of Quantum Chemistry. Quantum Biology Symposia 14 105-110. 

Lomustine is an orally available nitrosurea alkylating agent. Lomustine is converted rapidly to the cis- and frans-4-hydroxy metabolites the range of half-lives of these two metabolites is 2 to 4 hours.25 Lomustine has shown clinical activity in the treatment of Hodgkin s lymphoma and melanoma. Side effects are similar to those of carmustine. Patients should receive only enough drug for one cycle at a time to prevent confusion and accidental overdose. 

Until the 1950s, the rare periodic phenomena known in chemistry, such as the reaction of Bray [1], represented laboratory curiosities. Some oscillatory reactions were also known in electrochemistry. The link was made between the cardiac rhythm and electrical oscillators [2]. New examples of oscillatory chemical reactions were later discovered [3, 4]. From a theoretical point of view, the first kinetic model for oscillatory reactions was analyzed by Lotka [5], while similar equations were proposed soon after by Volterra [6] to account for oscillations in predator-prey systems in ecology. The next important advance on biological oscillations came from the experimental and theoretical studies of Hodgkin and Huxley [7], which clarified the physicochemical bases of the action potential in electrically excitable cells. The theory that they developed was later applied [8] to account for sustained oscillations of the membrane potential in these cells. Remarkably, the classic study by Hodgkin and Huxley appeared in the same year as Turing s pioneering analysis of spatial patterns in chemical systems [9]. 

Fields can be utilized in virtual screening applications for assessing the similarity (alignment) or complementarity (docking) of molecules. Two similarity measures have achieved the most attention. These are the so-called Garbo- [195] and Hodgkin indexes [196] respectively. Others are Pearson s product moment correlation coefficient [169] and Spearman s rank correlation coefficient [169]. 

Hodgkin, E.E. and Richards, W.G. Molecular similarity based on electrostatic potential and electric field. Int.J. Quantum Chem. 1987, 34, 105-110. 

As has been pointed out numerous times, if vA = kvb => SCar(vA,vB) = 1, for all K. This prompted Hodgkin and Richards (49) to define a slightly modified form of the similarity, usually called the Hodgkin similarity index, that does not suffer from this problem, namely,... 

Petke (33) has developed two additional indices that bound both the Carbo and Hodgkin similarity indices, namely,... 

As discussed in the previous section for vectors, if F and Fg differ only by a constant, that is, if F = K Fg, then SCar(F ,Fg) = 1 regardless of the specific form of the functions. While this is not a likely occurrence in practical applications, Hodgkin and Richards (49) nonetheless defined a slightly altered similarity measure, usually referred to as the Hodgkin similarity index, which is not affected by this problem and is given by... 

In Subheading 2.3. the important class of vectors with continuous-valued components is described. A number of issues arise in this case. Importantly, since the objects of concern here are vectors, the mathematical operations employed are those applied to vectors such as addition, multiplication by a scalar, and formation of inner products. While distances between vectors are used in similarity studies, inner products are the most prevalent type of terms found in MSA. Such similarities, usually associated with the names Carbo and Hodgkin, are computed as ratios, where the inner product term in the numerator is normalized by a term in the denominator that is some form of mean (e.g., geometric or arithmetic) of the norms of the two vectors. 

Vincamine, vinblastine and vincristine are very important clinic alkaloids. They are produced naturally by plants vincamine by Vinca minor, and vinblascine and vincristine by Madagascar periwinkle Catharanthus roseus). The vindoline synthesis pathway starts with strictosidine and, via dehydrogeissoschizine, preakuammicine, stemmadenine and tabersonine, is converted to vindoline and vincristine (Figure 42). Conversion from vindoline to vinblastine is based on the NADH enzyme activity. Vinblastine and vincristine are very similar alkaloids. The difference is that vincristine has CHO connected to N, whereas vinblastine in the same situation has only CO3. This synthetic structural differences influence their activity. Vinblastine is used to treat Hodgkin s disease (a form of lymphoid cancer), while vincristine is used clinically in the treatment of children s leukaemia. Vincristine is more neurotoxic than vinblastine. 

Corticosteroids suppress proliferation of lymphocytic cells, thus they are useful at combating acute lymphoblastic or undifferentiated leukemia of childhood, chronic lymphocytic leukemia, Hodgkin s lymphoma, other lymphomas. Therapy is often initiated with a steroid in combination with other agents. There is no evidence of cross resistance to unrelated agents. Mostly prednison is used however at appropriate dosages similar effects can be obtained with other glucocorticosteroids. 

Hodgkin s disease accounts for 1% of all new cancers diagnosed in Western countries and for 15% of all malignant lymphomas. In patients with early stage lA-IIA disease without B-symptoms or bulky adenopathy, therapy consists of either extended field radiotherapy or limited duration chemotherapy, e.g. ABVD (anthracycline, bleomycin, vinblastine, dacarbazine) for 3-4 cycles followed by involved field radiotherapy. Radiation alone results in a 10-year relapse free survival of 70-75% and, because of the efficacy of salvage chemotherapy for those who relapse, an overall survival of 80-85%. The combined modality approach results in fewer relapses but overall survival is similar. In order to reduce the long term morbidity of radiation current trials are exploring combined modality treatment with lower radiation doses versus chemotherapy alone. 

Tositumomab is another anti-CD20 monoclonal antibody and is complexed with iodine 131 (131I). Tositumomab is used in two-step therapy in patients with CD20-positive, follicular non-Hodgkin s lymphoma whose disease is refractory to rituximab and standard chemotherapy. Toxicities are similar to those for ibritumomab and include severe cytopenias such as thrombocytopenia and neutropenia. Tositumomab should not be administered to patients with greater than 25% bone marrow involvement. 

The committee also decided that there was sufficient evidence for an association between herbicides and Hodgkin s disease. This addition was almost inevitable in light of IOM s evaluation of the evidence about soft-tissue sarcoma and non-Hodgkin s leukemia, for which the committee had depended on the epidemiological studies done by a group of Swedish researchers. The same researchers had published similar results from their studies of Hodgkin s disease ... 

Doxorubicin Adriamycin RDF, Rubex, others Acute leukemias carcinoma of bladder, breast, ovary, thyroid, and other tissues Hodgkin disease non-Hodgkin lymphomas several sarcomas Similar to daunorubicin... 

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