Adaptive information processing in microtubule networks

Microtubule networks provide a wide range of microskeletal and micromuscular functionalities. Evidence from a number of directions suggests that they can also serve as a medium for intracellular signaling processing. The model presented here comprises an empirically motivated representation of microtubule growth dynamics, an abstract representation of signal processing, and a feedback learning mechanism that we refer to as adaptive self-stabilization. The growth model mimics the dynamic instability picture of microtubule formation and decomposition, but as modulated by the binding activity of microtubule associated proteins (or MAPs). The signal processing submodel treats each microtubule as a string of linked discrete oscillators capable of propagating signals that are introduced, manipulated, and extracted by bound MAP activity. Adaptive self-stabilization is essentially feedback acting on signal processing capabilities via the growth dynamics. The network is presented with a training set of patterns. If the input-output behavior is satisfactory MAP binding affinity increases, thereby stabilizing the network structure; otherwise the binding affinity decreases, allowing for more structural variation. The results obtained suggest that adaptive capabilities are practically inevitable in microtubule networks, a conclusion strengthened by the fact that the signal processing and growth dynamics mechanisms available in nature are undoubtedly much richer than those represented in the model.

Molecular and evolutionary computation: the tug of war between context freedom and context sensitivity

Proteins and nucleic acids constitute a vast potential reservoir of pattern recognizers that operate on the basis of shape complementarity. It is possible to construct models of computing in which these shape-based interactions contribute directly to recognition of signal patterns at the device (or cell) level. The input-output transform is molded by variation-selection evolution. Such models provide clues as to the organizational features that enable biomolecular matter to acquire nonevolutionary modes of problem solving through the evolutionary process. The requisite organizations are characterized by a high dimensionality that allows them to simultaneously exhibit aspects of context-sensitivity and context-independence.

Antiviral effects of synthetic membrane-active peptides on herpes simplex virus, type 1

Magainins are cationic peptides with antimicrobial activity which were originally isolated from the skin of the African clawed frog (Xenopus laevis). Several synthetic derivatives of this class of peptides were evaluated for antiviral activity against herpes simplex virus, type 1 (HSV). Some of the peptides (MSI-102, -248, -420, -499/500 combination, -591, -594, and -1251) showed significant reduction of HSV plaque-forming units. The antiviral effect was enhanced when HSV was pretreated with the peptides prior to inoculation onto Vero monolayers, suggesting a direct effect on the virion. Most of the peptides with anti-HSV activity were lysine-rich, and the addition of octanoyl groups to the peptides appeared to enhance the antiviral effect.

Immunoscintigraphy (BW 250/183) in neonates and infants with fever of unknown origin

Fever of unknown origin is defined as a temperature above 39.0 degrees C together with a white blood cell count > or = 15,000 mm-3, the duration of fever exceeding 2 weeks and a correct diagnosis not being obtained in the first week of hospitalization. In neonates and infants with fever of unknown origin, the localization of the infectious focus is often difficult and unsatisfactory. In this retrospective study, the clinical value of 99Tcm-labelled antigranulocyte antibodies for this group of patients was investigated. Thirty-two immunoscintigrams were performed using 185-259 MBq 99Tcm-labelled antigranulocyte antibodies (BW 250/183) in 30 neonates and infants (21 boys, 9 girls, mean age 29.4 +/- 2 months), who had fever of unknown origin. Immunoscintigraphy was carried out as whole-body images (n = 7) or single planar images (n = 25) 4 h and 24 h post-injection. In children with known cardiac failure, single photon emission tomography of the thorax was performed to diagnose endocarditis (n = 2). For verification, the results of the immunoscintigrams were compared with radiology (conventional radiography = 14, MRI = 5, CT = 3), biopsy (n = 2), blood culture (n = 10) and clinical follow-up after specific therapy. In 11 of 30 children (36%), the diagnosis of an infective focus was possible with immunoscintigraphy. The sensitivity and specificity of diagnosing infective foci was 72% and 95% respectively (n = 11; colitis = 2, infection of the central permanent catheter tip = 2, middle ear infection = 1, spondylitis/discitis = 3, osteomyelitis = 2, umbilical infection = 1). In vertebral body infections, all lesions were photopenic. In 18 children (60%), no infective focus was found on immunoscintigraphy. In this group of children, the main reason (n = 5) for fever of unknown origin was chronic juvenile rheumatoid arthritis. No uptake was seen in two infants with cardiac failure and suspected endocarditis on SPET. In 3 of the 18 patients (17%), localization of an infective focus was not possible with immunoscintigraphy or on other examinations. In these patients, the fever disappeared spontaneously after a few days of antibiotic therapy. In conclusion, we have shown that 99Tcm-anti-NCA-95 scanning is a safe method with a high sensitivity and specificity for detecting infectious foci in neonates and infants with fever of unknown origin. Furthermore, this method is easy to perform, since no withdrawal of blood is necessary.

Zebrafish vimentin: molecular characterization, assembly properties and developmental expression

To provide a basis for the investigation of the intermediate filament (IF) protein vimentin in one of the most promising experimental vertebrate systems, the zebrafish (Danio rerio), we have isolated a cDNA clone of high sequence identity to and with the characteristic features of human vimentin. Using this clone we produced recombinant zebrafish vimentin and studied its assembly behaviour. Unlike other vimentins, zebrafish vimentin formed unusually thick filaments when assembled at temperatures below 21 degrees C. At 37 degrees C few filaments were observed, which often also terminated in aggregated masses, indicating that its assembly was severely disturbed at this temperature. Between 21 and 34 degrees C apparently normal IFs were generated. By viscometry, the temperature optimum of assembly was determined to be around 28 degrees C. At this temperature, zebrafish vimentin partially rescued, in mixing experiments, the temperature-dependent assembly defect of trout vimentin. Therefore it is apparently able to "instruct" the misorganized trout vimentin such that it can enter normal IFs. This feature, that assembly is best at the normal body temperature of various species, puts more weight on the assumption that vimentin is vital for some aspects of generating functional adult tissues. Remarkably, like in most other vertebrates, zebrafish vimentin appears to be an abundant factor in the lens and the retina as well as transiently, during development, in various parts of the central and peripheral nervous system. Therefore, promising cell biological investigations may now be performed with cells involved in the generation of the vertebrate eye and brain, and, in particular, the retina. Moreover, the power of genetics of the zebrafish system may be employed to investigate functional properties of vimentin in vivo.

[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.

Biochemical identification and tissue-specific expression patterns of keratins in the zebrafish Danio rerio

We have identified a number of type I and type II keratins in the zebrafish Danio rerio by two-dimensional polyacrylamide gel electrophoresis, complementary keratin blot-binding assay and immunoblotting. These keratins range from 56 kDa to 46 kDa in molecular mass and from pH 6.6 to pH 5.2 in isoelectric point. Type II zebrafish keratins exhibit significantly higher molecular masses (56-52 kDa) compared with the type I keratins (50-48 kDa), but the isoelectric points show no significant difference between the two keratin subclasses (type II: pH 6.0-5.5; type I: pH 6.1-5.2). According to their occurrence in various zebrafish tissues, the identified keratins can be classified into "E" (epidermal) and "S" (simple epithelial) proteins. A panel of monoclonal anti-keratin antibodies has been used for immunoblotting of zebrafish cytoskeletal preparations and immunofluorescence microscopy of frozen tissue sections. These antibodies have revealed differential cytoplasmic expression of keratins; this not only includes epithelia, but also a variety of mesenchymally derived cells and tissues. Thus, previously detected fundamental differences in keratin expression patterns between higher vertebrates and a salmonid, the rainbow trout Oncorhynchus mykiss, also apply between vertebrates and the zebrafish, a cyprinid. However, in spite of notable similarities, trout and zebrafish keratins differ from each other in many details. The present data provide a firm basis from which the application of keratins as cell differentiation markers in the well-established genetic model organism, the zebrafish, can be developed.

Safety and long-term durability of completion gastrectomy in 81 patients with postsurgical gastroparesis syndrome

Postsurgical gastroparesis syndrome (PGS) is characterized by postcibal nausea and vomiting and is associated with functional gastric dysmotility. Patients frequently present with marked weight loss and malnutrition requiring hospitalization and prolonged parenteral nutrition. Typically, these patients fail to respond to prokinetic agents. Gastric reoperations are frequent and usually unsuccessful. Near-completion gastrectomy (NCG) has proved useful in small series of patients, but long-term follow-up has been lacking. The purpose of this study is to assess the safety and durability of NCG in a large group of patients with PGS. Eighty-one patients with documented PGS who failed to respond to prokinetic drug therapy were treated with NCG over an 11-year period. NCG was standardized with a 55-cm Roux-en-Y reconstruction. Patients were evaluated by a retrospective chart review and a prospective phone interview that compared pre- and postoperative health status based on a standardized severity of symptoms score. There were no operative deaths or complications related to the anastomosis. Average patient follow-up was 56.1 months (range, 2-142 months). Fifteen patients died of unrelated causes, and 14 patients were lost to follow-up. The remaining 52 patients showed a significant overall decrease in severity of symptoms score largely due to reduction in gastrointestinal symptoms and to a smaller but significant reduction in systemic symptoms. Nearly 80 per cent of patients reported long-term relief of symptoms. NCG is the procedure of choice for carefully selected patients with documented. Low morbidity and durable results can be anticipated in the majority of patients.

The Role of Weak Interactions in Biological Systems: the Dual Dynamics Model

The dual dynamics model is a random autonomous network of nodes whose dynamical behavior is determined by both strong and weak interactions. The model combines discrete decision-making features reflective of logical operations with arithmetic features that represent graded influences. Dual dynamics abstracts the ubiquitous fact that biological systems at all levels of organization consist of components that respond both to specific (strong) signals and to the cumulative effect of numerous weak interactions. We have thoroughly studied the dynamical characteristics of three-valued dual dynamics networks in the range from four to 14 nodes and have compared these characteristics to those of non-boolean three-valued networks (without weak interaction) and to Kauffman boolean networks. Properties studied include: attractor length, number of attractors, basin sizes, orbital stability, and evolutionary transformability in response both to individual and cumulative mutations (where mutations are implemented as random changes in the response of a node to the pattern of strong influences impinging on it). The introduction of weak interactions and their manner of coupling to strong interactions has major altering effects on these properties. With suitable coupling it is possible to significantly enhance equifinality and evolutionary transformability. The model demonstrates that self-organizing dynamics are compatible with evolutionary plasticity when weak interactions are taken into account.Copyright 1998 Academic Press

Clinical value of immunoscintigraphy in patients with fever of unknown origin

The aim of our study was to evaluate the clinical value of immunoscintigraphy with the monoclonal antibody 99mTc-BW 250/183 in patients with fever of unknown origin (FUO). The antibody BW 250/183 is an immunoglobulin G1 subtype that binds to the antigen NCA-95, which is expressed on the cell membrane surface of granulocytes.

METHODS

We studied 51 patients who were referred with the diagnosis of FUO. Thirty-five percent of the patients suffered from infection, 17% had autoimmune diseases, 14% had neoplasms and 8% had other diseases. The remaining 28% of the patients did not have a diagnosis. Planar imaging was performed in all patients, and 19 patients underwent SPECT. In our analysis, both cold and hot spots were considered diagnostic.

RESULTS

Pyogenic infections were visualized correctly in 13 foci. The diagnosis of endocarditis (n = 4) could be determined only by SPECT. False-negative results were found in 4 patients and false-positive uptake was seen in 2 patients. No false-positive uptake or cold spots in the central bone marrow were found in patients with viral, granulomatous and autoimmune diseases or in those patients in whom no FUO cause was found in a 6-mo follow-up. In these patients, a negative scan did not change their diagnostic work-up. Cold spots in the central bone marrow were correctly interpreted in 5 of 6 patients. Sensitivity in detecting pyogenic foci was 73% and specificity was 97%. Positive and negative predictive values were 93% and 87%, respectively. Including areas of decreased uptake in the analysis, sensitivity for detecting an underlying inflammatory or malignant process for FUO was 81 % and specificity was 87%. Positive and negative predictive values were 81% and 87%, respectively.

CONCLUSION

Immunoscintigraphy with 99mTc-BW 250/183 in patients with FUO has clinical potential for the diagnosis and exclusion of pyogenic causes of FUO. Metastatic malignant disease and high-grade spondylodiskitis could be diagnosed early in a diagnostic work-up by a characteristic cold spot pattern in the bone marrow. SPECT is indispensible for scintigraphic imaging of endocarditis.

Diagnostic value of 123iodine scintigraphy and perchlorate discharge test in the diagnosis of congenital hypothyroidism

AIM

Forty children suffering from congenital primary permanent hypothyroidism were studied to determine the diagnostic impact of 123I scintigraphy in comparison to laboratory findings and ultrasonography.

METHODS

In all patients 123I scintigraphy was performed after intravenous administration of 3.7 MBq 123I. If accumulation of the radiotracer in thyroid tissue occurred a perchlorate discharge test was performed subsequently.

RESULTS

Scintigraphy revealed athyrosis in 7 children. In 11 children a lingual thyroid was observed. Deficiency in iodine organification was diagnosed by a significant discharge of 123I in 15 patients. In four of these children the diagnosis of Pendred's syndrome could be established. Ectopic thyroid tissue could be demonstrated only by scintigraphy where clinical examination and sonography failed in the diagnosis in all cases. Hypoplasia of the thyroid gland as it was diagnosed in 2 cases by ultrasonography appeared to be unlikely because a normal 123I uptake was seen in these patients. In 2 patients with scintigraphic proven athyrosis an orthotopic gland had been considered by ultrasound. In 50% of our patients the final diagnosis could only be established if 123I scintigraphy and perchlorate discharge test were performed.

CONCLUSION

This findings suggest that scintigraphy is indispensible in the correct diagnostic work up of congenital hypothyroidism.

DNA as a vehicle for the self-assembly model of computing

A DNA version of the self-assembly model of computing, feasible using currently available laboratory techniques, is proposed. Input signals are coded into unmethylated and methylated oligonucleotides which then hybridize with a backbone that contains complementary sequences. Different input signal patterns are thus represented as DNA duplexes with distinctly different conformational dynamics, in particular different equilibria of B and Z DNA. The pattern classification activity of the system is mediated by the interactions that lead to the secondary structural organization. Circular dichroism may be used for readout.

123I-Szintigraphie und Perchlorat-Depletionstest bei der Diagnostik der kongenitalen Hypothyreose

Ziel: Die vorliegende retrospektive Studie an 38 Kindern soll Aufschluß über den aktuellen Stellenwert der 123I-Szintigraphie im Vergleich mit der Sonographie und laborchemischen Methoden bei der Diagnostik der kongenitalen primären Hypothyreose geben.

Methoden: Alle Patienten erhielten 3,7 MBq 123I intravenös zur Lokali-sationsdiagnostik der Schilddrüse. Ließ sich 123I speicherndes Schilddrüsengewebe nachweisen, wurde ein Depletionstest nach oraler Gabe von 300 mg Perchlorat (Irenat®) durchgeführt.

Ergebnisse: Bei 7 Kindern lag szintigraphisch eine Athyreose und bei 9 Kindern eine Zungengrundschilddrüse vor. Bei 15 Patienten mit ortho-top gelegener Schilddrüse wurde aufgrund einer signifikanten Depletion nach Perchlorat eine lodinationsstörung diagnostiziert. Vier von diesen Kindern hatten ein Pendred-Syndrom. Der Nachweis einer Zungengrundschilddrüse gelang klinisch oder sonographisch in keinem einzigen Fall. Bei zwei Patienten mit einem Enzymdefekt wurde sonographisch fälschlicherweise von einer Hypoplasie ausgegangen. Bei zwei athyreo-ten Kindern war aufgrund der Sonographie orthotop gelegenes funktionsfähiges Schilddrüsengewebe vermutet worden. Insgesamt konnte bei 44% der Kinder die endgültige Diagnose erst durch die 123I-Szintigraphie und den Perchlorat-Depletionstest gestellt werden.

Schlußfolgerung: Die Ergebnisse belegen, daß szintigraphische Methoden bei der Diagnostik kongenitaler Hypothyreosen unverändert ihren Stellenwert besitzen und durch die Sonographie oder laborchemische Verfahren z. Z. nicht ersetzbar sind.

[123I-scintigraphy and perchlorate depletion test in the diagnosis of congenital hypothyroidism]

AIM

Thirty eight children suffering from congenital primary permanent hypothyroidism were studied to determine the diagnostic impact of 123I scintigraphy in comparison to laboratory findings and ultrasonography.

METHODS

In all patients 123I scintigraphy was performed after intravenous administration of 3.7 MBq 123I. If accumulation of the radiotracer in thyroid tissue occurred a perchlorate discharge test was performed subsequently.

RESULTS

Scintigraphy revealed athyrosis in 7 children. In 9 children a lingual thyroid was observed. Deficiency in iodine organification was diagnosed by a significant discharge of 123I in 15 patients. In four of these children the diagnosis of Pendred's syndrome could be established. Ectopic thyroid tissue could be demonstrated only by scintigraphy where clinical examination and sonography failed in the diagnosis in all cases. Hypoplasia of the thyroid gland as it was diagnosed in 2 cases by ultrasonography appeared to be unlikely because a normal 123I uptake was seen in these patients. In 2 patients with scintigraphic proven athyrosis an orthotopic gland had been falsely considered by ultrasound. In 44% of our patients the final diagnosis could only be established if 123I scintigraphy and perchlorate discharge test were performed.

CONCLUSION

This findings suggest that scintigraphy is indispensible in the correct diagnostic work up of congenital hypothyroidism.

[Importance of iterative reconstruction ISA in the diagnosis of liver hemangioma]

AIM

To evaluate whether the iterative reconstruction methodology ISA is superior to the standard technique of filtered back-projection.

METHODS

In a retrospective study, we evaluated images of 39 patients with solitary or multiple liver tumors who underwent blood pool imaging in SPECT technique in order to prove or exclude the presence of hemangioma.

RESULTS

Activity accumulations in accordance with the diagnosis of liver hemangioma could be visualized in 34 cases by the iterative, in 31 cases by the filtered back-projection methodology. As compared to filtered back-projection, the iteratively reconstructed lesions showed higher tumor-to-background ratios and were more easily distinguished from structures in their neighborhood. Furthermore, the iterative methodology resulted in a more homogeneous activity distribution in the liver, whereas the inhomogeneous "patchy" structure of the liver parenchyma in filtered back-projection provokes difficulties in the distinction from reconstruction artifacts. A clearer visualization of vessels and a better distinction between the right kidney and the liver was possible by the iterative algorithm, leading to advantages in the recognition of centrally or dorsally located lesions in the right hepatic lobe.

CONCLUSION

These data indicate that the use of our iterative algorithm in performing liver blood pool imaging yields a higher sensitivity and a better diagnostic accuracy in diagnosing liver hemangioma.

Photopenia in chronic vertebral osteomyelitis with technetium-99m-antigranulocyte antibody (BW 250/183)

Photon-deficient areas in 99mTc/111 in white blood cell (WBC) images for diagnosing vertebral osteomyelitis have been published often. This study retrospectively evaluated whether the use of 99mTc-labeled monoclonal antigranulocyte antibodies (BW 250/183) is superior to WBC and whether it offers higher specificity.

METHODS

The study included 81 patients (46 men, 35 women; mean age 55 +/- 2 yr; from 1989 to 1995) with clinically suspected vertebral osteomyelitis who underwent scintigraphic imaging after intravenous injection of 555 MBq 99mTc-labeled monoclonal antigranulocyte antibodies. Forty patients suffered from osteomyelitis (20 men, 20 women; mean age 56 +/- 6 yr), 6 patients had metastases, 28 patients had spondylosis and disk herniation and 5 patients vertebral compression fractures. Diagnosis was not histologically verified in 2 patients. Planar imaging was performed at 4 and 24 hr postinjection. Histology of osteomyelitis was available in 30 patients, clinical follow-up in 10 patients. Visual uptake scores and quantitative uptake scores of the suspected areas were calculated. The results were compared to a semiquantitative histological score (high, medium, low grade) as well as to the scintigraphic scores.

RESULTS

Scintigraphy showed photopenia in all patients with histologically proven vertebral osteomyelitis, independent of the grade of infection. A quantitative evaluation of 4 and 24 hr postinjection demonstrated a 58% increase of the uptake score in cases of histologically proven high-grade infections. This increase was seen predominantly in the thoracic spine but not in lumbar spine. All nonosseous paravertebral abscesses (n = 2) showed positive images and an increasing uptake over 24 hr.

CONCLUSION

Paravertebral soft tissue infections can be differentiated excellently, whereas vertebral osteomyelitis, vertebral tumors or fractures can be localized, but no differentiation is possible.

Bedeutung der iterativen Rekonstruktion ISA bei der Diagnostik von Leberhämangiomen

Ziel: In dieser Studie sollte überprüft werden, ob das iterative Rekonstruktionsverfahren ISA Vorteile gegenüber der Standardmethode der gefilterten Rückprojektion besitzt. Methoden: Die Aufnahmen von 39 Patienten mit solitären oder multiplen Raumforderungen der Leber, bei denen eine Leberblutpoolszintigraphie in SPECT-Technik zum Nachweis oder Ausschluß von Leberhämangiomen durchgeführt worden war, wurden retrospektiv ausgewertet. Ergebnisse: Aktivitätsmehranreicherungen, die mit einem Leberhämangiom vereinbar waren, konnten durch die iterative Rekonstruktion bei 34 Herden und mittels gefilterter Rückprojektion bei 31 Herden in allen drei Schnittebenen dargestellt werden. Im Vergleich zur gefilterten Rückprojektion stellten sich die Läsionen nach iterativer Rekonstruktion meist kontrastreicher dar und waren von benachbarten Strukturen besser abzugrenzen. Darüber hinaus zeichnete sich das iterative Verfahren durch eine homogenere Aktivitätsbelegung der Leber aus. Die unregelmäßige Strukturierung des Leberparenchyms, wie sie sich nach gefilterter Rückprojektion fast regelhaft ergab, erschwerte hingegen häufig die sichere Trennung von Rekonstruktionsartefakten und Herdbefunden. Durch unseren iterativen Algorithmus konnte eine klarere Abbildung der Gefäße und eine verbesserte Abgrenzbarkeit der rechten Niere vom Leberparenchym erreicht werden, woraus sich Vorteile bei der Erkennung von zentral oder dorsal im rechten Leberlappen gelegenen Aktivitätsanreicherungen ergeben. Schlußfolgerung: Die vorgelegten Ergebnisse belegen, daß durch den Einsatz des iterativen Algorithmus bei der Leberblutpool-SPECT eine verbesserte Sensitivität und höhere diagnostische Sicherheit bei der Diagnostik von Leberhämangiomen erreicht werden kann.

Origin of life and the underlying physics of the universe

The thesis is put forward that the non-linear self-organizing dynamics of biological systems are inherent in any physical theory that satisfies the requirements of both quantum mechanics and general relativity. Biological life is viewed as an extension of these underlying dynamics rather than as an emergent property of systems that reached a requisite threshold of complexity at a definite point in time. The underlying dynamics are based on interactions between manifest material organizations and an unmanifest vacuum sea whose density structure is isomorphic to the metric structure of space-time. These interactions possess an intrinsic self-corrective character, due to the fact that quantum processes lead to changes in particle states that have a random aspect, while general relativity requires that the distribution of manifest and unmanifest particles be self-consistent. The model implies vacuum hysteretic effects that would bear on nanobiological phenomena and that might be detected through nanobiological techniques.

Antibody-antigen recognition: a canonical structure paradigm

The antibodies of known three-dimensional structure exhibit a definite number of conformations (canonical structures) for five of six hypervariable loops. In the present study it was found that approximately 85% of the immunoglobulin sequences analyzed fall into a small number of canonical structure combinations, representing only 3% of the total possible. These structures were classified into six distinct groups, depending on the type of antigen with which they interact. Within each loop, the positions responsible for maintaining these canonical structures show a use frequency of amino acids that fits an inverse power law, whereas the use frequency of the amino acids responsible for the detailed antigenic specificity follows an exponential distribution. We propose an evolutionary interpretation that connects these data, using the fact that the inverse power law is generated by statistical processes of the type that yield a wealth curve and the fact that exponential distribution is generated by processes that are not biased by past history.

Biosynthesis of the endogenous cyclic adenosine monophosphate (AMP) antagonist, prostaglandylinositol cyclic phosphate (cyclic PIP), from prostaglandin E and activated inositol polyphosphate in rat liver plasma membranes

The endogenous cyclic adenosine monophosphate (AMP) antagonist, cyclic PIP, has been identified as a prostaglandylinositol cyclic phosphate. It inhibits protein kinase A 100% and activates protein serine phosphatase about sevenfold. It is biosynthesized by an enzyme of the plasma membrane when the assay mixture contains adenosine triphosphate (ATP), Mg2+, prostaglandin E and a novel inositol polyphosphate, which cannot be substituted by commercially available inositol phosphates. This novel inositol polyphosphate is a very labile compound. On anion exchange chromatography it elutes in the range of ATP, which may indicate the presence of three phosphate groups. It adsorbs on charcoal, which suggests the presence of a hydrophobic component, possibly a guanosine. Pyrophosphates obtained from inositol 1,4- and inositol 2,4-bisphosphate are accepted by cyclic PIP synthetase for the synthesis of cyclic PIP. The biosynthesis is characterized by enzyme kinetic parameters like dependence on time, enzyme and substrate concentration. The pH optimum of the enzyme is in the range 7.5-8. The enzyme functions optimally with prostaglandin E and poorly with prostaglandin A as the substrate. The presence of fluoride in the assay causes a three- to fourfold increase in cyclic PIP synthesis, which may be correlated with activation via G proteins. These data support previous reports on the chemical structure and action of cyclic PIP. With respect to the possible isomers of cyclic PIP, these indicate that it is most likely the C4-hydroxyl group of the inositol which binds the C15-hydroxyl group of prostaglandin E. A model of hormone-stimulated synthesis of cyclic PIP is proposed: phospholipase A2 and phospholipase C, activated by G proteins upon alpha-adrenergic stimulation, liberate either unsaturated fatty acids or inositol phosphates, which are transformed to prostaglandins and to novel inositol polyphosphate with an energy-rich bond. The cyclic PIP synthetase combines these two substrates to cyclic PIP.