Biomedical subjects

M Conrad

Publications and source records attributed to M Conrad.

131 records · Page 8Linked to original sources

PubMedDate not supplied

Unity of measurement and motion.

Issues addressed in H.H. Pattee's origin of life laboratory in the 1960s and their connection to the physics-evolution-language problematic are indicated. The problem of quantum measurement played a central role. The problem is herein examined in the light of the fluctuon model; in particular, as the model applies to gravity. The main conclusion is that measurement and motion are a unitary process. All accelerations are accompanied by a cycle involving the annihilation and creation of superpositions. Gravitational collapse is also a cyclic process in the fluctuon model. By a suitable transformation, it can be seen that interactions underlying superpositional collapse are the same as those operative in gravitational collapse. Implications for the origin of cellular life and the development of symbolic systems are considered.

Biological Evolution↗

PubMedDate not supplied

Enzymatic computing.

The conformational dynamics of enzymes is a computational resource that fuses milieu signals in a nonlinear fashion. Response surface methodology can be used to elicit computational functionality from enzyme dynamics. We constructed a tabletop prototype to implement enzymatic signal processing in a device context and employed it in conjunction with malate dehydrogenase to perform the linearly inseparable exclusive-or operation. This shows that proteins can execute signal processing operations that are more complex than those performed by individual threshold elements. We view the experiments reported, though restricted to the two-variable case, as a stepping stone to computational networks that utilize the precise reproducibility of proteins, and the concomitant reproducibility of their nonlinear dynamics, to implement complex pattern transformations.

Calcium↗

PubMedDate not supplied

Mechanism of mutagenesis by O6-methylguanine.

O6-methylguanine (O6meG) lesions of double-stranded DNA have been associated with mutation and neoplastic transformation. These lesions can, in principle, be produced by at least three different mechanisms: direct alkylation of G X C base pairs in double-stranded DNA; alkylation of guanine residues in single-stranded regions of DNA associated with replication forks; and alkylation of the DNA precursor pool followed by incorporation of O6-methyl deoxyguanosine triphosphate (O6-medGTP) during DNA replication. DNA biosynthesis subsequent to all three events will generate predominantly O6-meG X T base pairs as O6meG preferentially pairs with T. We show here that O6meG X T base pairs are mutagenic; that transalkylase repair has a direct role in the generation of mutations induced by alkylated pool nucleotides; and that the Escherichia coli mismatch repair system is capable of repairing mutagenic G X T intermediates.

Base Sequence↗

PubMedDate not supplied

[Differentiated thyroid gland carcinoma in children and adolescents].

Differentiated thyroid cancer is a rare disease in childhood and adolescence. Most frequently, thyroid cancer in children belongs to the papillary variant, whereas a follicular histological pattern is much less frequently encountered. Dedifferentiated (anaplastic) cancers are very rare at this age. Especially indolent cervical lymph node enlargement is suspicious for a thyroid cancer, even more when occurring together with a solitary, rapidly growing, and indurated thyroid nodule. Every nodule in the thyroid of children and adolescents, if not unequivocally cystic, is suspicious of a malignancy. In contrast to adults, multifocal tumor manifestations are frequently found in children and adolescents which often have spread beyond the capsule of the thyroid at the time of diagnosis. Regional lymph nodes are involved in up to 90%, and distant metastases are present in up to 20% of the cases. Despite these much more advanced stages as usually found in adults, the prognosis of children is better than at advanced age, since these tumors are highly differentiated, and, even in the case of distant metastases, a curative approach is still possible. The therapy (surgery/radioiodine) and the follow-up follows the same principles as those which have been established for older patients.

Adenocarcinoma, Follicular↗

PubMedDate not supplied

[Change of mechanical parameters as a possible means for information processing by the neuron].

The depolarization of neuronal membrane during cAMP injection by means of both iontophoresis and pressure was shown. Neuron blowing by solutions without cAMP gave the similar effect. The effect of cAMP can be differentiated in the presence of phosphodiesterase inhibitors. The experiments support the hypothesis that cyclic nucleotides and mechanical excitation interact with intraneuronal mechanical analog device (MAD) which consists of microtubules and microfilaments. It is supposed that MAD controlled by cyclic nucleotides and Ca2+ is the intraneuronal information processing system.

Animals↗