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PubMed1992

Hypertrophy of gonadotropin releasing hormone-containing neurons after castration in the teleost, Haplochromis burtoni.

In the African cichlid fish, Haplochromis burtoni, males are either territorial or nonterritorial. Territorial males suppress reproductive function in the nonterritorial males, and have larger gonads and larger gonadotropin-releasing hormone- (GnRH) containing neurons in the preoptic area (POA). We describe an experiment designed to establish the causal relationship between large GnRH neurons and large testes in these males by determining the feedback effects of gonadal sex steroids on the GnRH neurons. Territorial males were either castrated or sham-operated, 4 weeks after which they were sacrificed. Circulating steroid levels were measured, and the GnRH-containing neurons were visualized by staining sagittal sections of the brains with an antibody to salmon GnRH. The soma areas of antibody-stained neurons were measured with a computer-aided imaging system. Completely castrated males had markedly reduced levels of circulating sex steroids [11-ketotestosterone (11KT) and testosterone (T)], as well as 17 beta-estradiol (E2). POA GnRH neurons in castrates showed a significant increase in mean soma size relative to the intact territorial males. Hence, in mature animals, gonadal steroids act as a brake on the growth of GnRH-containing neurons, and gonadal products are not responsible for the large GnRH neurons characteristic of territorial males.

Animals↗

PubMed1992

Formation of reactive oxygen species in spermatozoa of infertile patients.

OBJECTIVE: To determine the incidence of reactive oxygen species formation in semen of a population of patients consulting for infertility. DESIGN: The incidence of reactive oxygen species formation in whole semen and in washed spermatozoa was studied. The values obtained were correlated with semen parameters. The effect of the type of sperm washing on reactive oxygen species formation was also investigated. SETTING: Semen samples from patients consulting for infertility and control subjects were obtained by masturbation after 3 days of sexual abstinence. Reactive oxygen species formation was measured in whole semen, sperm suspension washed by Percoll gradients, or repeated centrifugations. Sperm motility parameters were measured by computer-aided sperm analysis. PATIENTS, PARTICIPANTS: Fertile control men and an unselected population of patients consulting for infertility. INTERVENTIONS: None. MAIN OUTCOME MEASURE: Reactive oxygen species formation by fresh semen specimen or washed spermatozoa was measured in a computer-driven LKB 1251 Luminometer (LKB-Wallac, Turku, Finland). RESULTS: Reactive oxygen species formation was detected in 40% of the semen with spermatozoa from infertile patients, whereas none was found in 6 azoospermic men and 10 control men. The level of reactive oxygen species formation was inversely correlated to the semen volume, the percentage of motile spermatozoa, and sperm linearity both in semen and in Percoll-washed spermatozoa. Washing by repeated centrifugation-resuspension increased 20- to 50-fold sperm reactive oxygen species formation. This enhancement was caused by the centrifugation itself and by the removal of seminal plasma. Both morphologically normal and abnormal spermatozoa produced reactive oxygen species. CONCLUSION: The data suggest that reactive oxygen species formation by spermatozoa may be a significant cause for male infertility.

Centrifugation↗

PubMed1991

Interaction of the regulatory subunit (RII) of cAMP-dependent protein kinase with RII-anchoring proteins occurs through an amphipathic helix binding motif.

The type II cAMP-dependent protein kinase is localized to specific subcellular environments through the binding of the regulatory subunit (RII) dimer to RII-anchoring proteins. Computer-aided analysis of secondary structure, performed on four RII-anchoring protein sequences (the microtubule-associated protein 2, P150, and two thyroid proteins Ht 21 and Ht 31), has identified common regions of approximately 14 residues which display high probabilities of forming amphipathic helices. The potential amphipathic helix region of Ht 31 (Leu-Ile-Glu-Glu-Ala-Ala-Ser-Arg-Ile-Val-Asp-Ala-Val-Ile) lies between residues 494 and 507. A bacterially expressed 318-amino acid fragment, Ht 31 (418-736), containing the amphipathic helix region, was able to bind RII alpha. Site-directed mutagenesis designed to disrupt the secondary structure in the putative binding helix reduced binding dramatically. Specifically, substitution of proline for Ala-498 significantly diminished RII alpha binding, and similar mutation of Ile-502 or Ile-507 abolished interaction. Mutation of Ala-522 to proline, which is located outside the predicted amphipathic helix region, had no effect on RII alpha binding. These data suggest that anchoring proteins interact with RII alpha via an amphipathic helix binding motif.

A Kinase Anchor Proteins↗

PubMed1991

Protein antigenicity: a thermodynamic approach.

This article summarizes computer-aided analyses of X-ray crystallographic data aimed at understanding the immunologically important aspects of the structure of antibody combining sites and protein antigens. In these calculations we use an empirical free energy potential function to estimate the atomic origin of binding specificity. By evaluating contributions of individual amino acid residues towards the Gibbs free energy of antibody-antigen complex formation, we arrive at a better understanding of the essential antigenic features of protein surfaces, as well as the inherent "binding" properties of the antibody combining sites. Such an "energetic" understanding of antigenicity may well be of practical importance in vaccine design. This article both reviews published data and discusses new results, i.e. delta G calculations on the HyHEL-10 complex with lysozyme, and an alternative treatment of the McPC 603 complex with phosphoryl choline.

Antigen-Antibody Complex↗

PubMed1990

Microtubules and their protofilaments in the flagellum of an insect spermatozoon.

Spermatozoa of stick insects have nine accessory tubules, which surround the nine outer microtubular doublets and the two inner microtubular singlets. When fixed in a fixative that was designed to minimize protein denaturation (glutaraldehyde and tannic acid, no osmium post-fixation but block staining with uranyl acetate in water) the accessory tubules were seen to contain 17 protofilaments of the same type as those in the 9 + 2 microtubular doublets and singlets. The protofilaments in accessory tubules and other microtubules were roughly triangular. When studied by Markham's photographic method a somewhat different tilt of the two longer sides was seen; this makes it possible to distinguish a polarity in the microtubules, i.e. to differentiate between a microtubule that is viewed from its (-)end to its (+)end from one that is viewed in the opposite direction. The dynein arms of the doublets can be used as an independent type of marker for the polarity. In a computer-aided analysis of the fine structure of the tail axoneme, the A-subtubules of the outer doublets were seen to be not quite equidistant; rather, there were somewhat widened electron-dense interspaces in the ring of protofilaments in four places. The locations of these widened interspaces coincide with the attachment sites for the spoke, the inner dynein arm, the outer dynein arm, and the intertubular material. It is tentatively concluded that proteins of these structures, and perhaps also other microtubule-associated proteins, may be anchored deep within the wall of a microtubule rather than just superficially along it.

Animals↗

PubMed1991

Receptor-recycling model of clearance and distribution of insulin in the perfused mouse liver.

After perfusion of mouse livers with A14-125I-insulin for designated intervals, an acid-wash technique was employed to separately measure the surface-bound (Xs) and intracellular (Xi) A14-125I-insulin, as well as intracellular degradation products (Xdeg) of labelled insulin. From the perfusate concentrations (Cp) of A14-125I-insulin, the apparent intrinsic hepatic clearance of labelled insulin at a high dose (0.2 nmol/l) was shown to be 60% smaller than that at a low dose (0.018 nmol/l), indicating that the cellular uptake of insulin is remarkably nonlinear at the concentration range examined. From the time courses of Cp, Xs, Xi and Xdeg, the hepatic insulin disposition was shown to be largely accounted for by the receptor-mediated endocytosis. The observed data at the low dose were analysed to estimate biochemical parameters, (i.e., total receptor number, endocytotic rate constant and intracellular degradation rate constant) according to "receptor-recycling" and "non-receptor-recycling" models, using a computer-aided optimization procedure. The "receptor-recycling" model could not only adequately explain the Cp, Xs, Xi and Xdeg at the low dose, but also predict the Cp at the high dose. On the other hand, a "non-receptor-recycling" model, in which recycling of receptors was not assumed, could also explain the observed data at the low dose, but failed to predict the Cp at the high dose, indicating that the receptor recycling process is necessary to explain the hepatic insulin clearance at high insulin concentrations, at which hepatic insulin clearance should be limited by the rate of receptor recycling.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1992

Isoresponse time regions for the evaluation of visual search performance in ergonomic interface models.

Computer-aided ergonomic evaluation models often provide a limited function of visual performance, usually in the form of visibility tests at any given location. It is, however, of great importance to complete a visual task in a predetermined time successfully or to predict the time to complete the task, e.g., a task of high-level control such as aircraft flight operations. In this study, isoresponse time regions which have an effect on visual performance in real-life situations are presented as an effort to complement aforementioned shortcomings of ergonomic interface models. A multiple regression was used to provide equal response time regions, being asymmetrical in shape. In addition, the fuzzy linear regression (FLR) model was introduced to provide a fuzzy set from which a decision-maker might select appropriately. It provided similar fitted values with having the advantage of utilizing the interval of those fitted values over the conventional regression model. The results can be applied effectively to the design of an interface for diverse visual tasks in real situations.

Adult↗

PubMed1992

Computer-assisted three-dimensional volumetry of the human pulmonary acini.

Computer-aided three-dimensional (3-D) volumetry of human pulmonary acini was undertaken using the left upper lobe of a 51-year-old female operated for small lung cancer. A normal part of this lobe, fixed by intrabronchial infusion with a mixture of polyethylene glycol and formalin, was subjected to serial sectioning, using a special slicer, into 48 serial slices of 0.5 mm in thickness. A soft x-ray radiograph was prepared from each slice at x 12, and the contours of airways and acinar boundaries contained in it were input by digitization into a microcomputer for 3-D reconstruction and volumetry. The estimated volumes of 130 acini were unexpectedly uniform, showing a normal type distribution with a mean of 172.7 +/- 37.9 mm3. No significant correlation proved to exist between the volume of acini and the number of branching generation of the terminal bronchioles (TBs) they received. Furthermore, there was no significant difference in volume among the acini facing the costal surface, those facing the mediastinal surface and those not facing any pleural surface. However, the generation number of TBs was shown to differ significantly with the location of acini. These results suggest that the tree of conductive airways is designed so as to meet the requirement of constant acinar volume.

Adenocarcinoma↗

PubMed1991

Modeling and conformation analysis of beta-cyclodextrin complexes.

A series of beta-cyclodextrin complexes containing various guest molecules was studied using computer-aided molecular modeling and conformation analysis techniques. The geometry of each complex was studied using crystallographic data. The positions of the glycosidic O4 atoms indicate that the beta-cyclodextrin molecules are elliptically distorted. This distortion can be related to the van der Waals volume of the guest molecules. This correlation is different for aromatic and non-aromatic guest compounds. Rigid body docking experiments demonstrated that in crystal structures the guest molecule occupies a position in the cavity of nearly minimum interaction energy when there are no other molecules having interactions with the guest molecule. From the crystallographic data several rules could be deduced which seem to determine the conformation of beta-cyclodextrin molecules in complexes. A procedure was developed to construct beta-cyclodextrin molecules that are able to encompass guest molecules having a given van der Waals volume.

Carbohydrate Conformation↗

PubMed1975

Computer-aided diagnosis of "dyspepsia".

Experience with computer-aided diagnosis of "dyspepsia" in a consecutive prospective series of 212 patients coming to surgery is described. Analysis is concentrated upon 122 patients who presented to an outpatient clinic de novo for diagnosis. During their first (outpatient) hospital contact, a firm diagnosis was made in just over half of these patients (though where made, it was usually correct). After full investigation, the diagnostic accuracy (prior to operation) was 92.6%. Using data elicited solely from the house surgeon's interview at the time of admission, the computer's overall diagnostic accuracy was 87.7%. The cost of each new computer diagnosis was around 25 new pence ($0.60). and the time taken was about 5 minutes. In a further small series designed to discriminate between organic and functional dyspepsia, the computer correctly assigned all but 1 of 23 patients with organic disease to the correct disease category. However, almost half of 33 patients with x-ray negative dyspepsia were predicted by the computer to have organic lesions. Time alone will tell whether the computer is a better early predictor of eventual organic disease than currently available radiologic methods.

Bayes Theorem↗

PubMed1991

Construction of new ligand binding sites in proteins of known structure. I. Computer-aided modeling of sites with pre-defined geometry.

We have devised a molecular model building computer program (DEZYMER) which builds new ligand binding sites into a protein of known three-dimensional structure. It alters only the sequence and the side-chain structure of the protein, leaving the protein backbone fold intact by definition. The program searches for a constellation of backbone positions arranged such that if appropriate side-chains were placed there, they would bind the ligand according to a pre-defined geometry of interaction specified by the experimentalist. These binding sites are introduced by the program by taking into account simple rules such as steric hindrance, atomic close-packing and hydrogen bond patterns, which are known to maintain the integrity of a protein structure to a first approximation. A test case is presented in this paper where the copper binding site found in blue-copper proteins such as plastocyanin, azurin and cupredoxin is introduced into Escherichia coli thioredoxin. The model building of one of the solutions found by the program is presented in some detail. The experimental construction and properties of this new protein are described in an accompanying paper. It is hoped that this program provides a general method for the design of ligand binding sites and enzyme active sites, which can then be tested experimentally.

Algorithms↗

PubMed1991

Comparison of computer-aided and human review of general practitioners' management of hypertension.

Computer programs that automatically review decisions can help physicians provide better patient care. In the Netherlands, the ELIAS computer information system has replaced paper medical records in some general practices. We have written a computer program called 'HyperCritic' that audits general practitioners' management of patients with essential hypertension by taking patient-specific data from the ELIAS system. We investigated whether the computer-based medical records contain sufficient information to generate critiques, and compared the limitations of audit by hypercritic with those of review by a panel of eight physicians. Hypercritic and the physicians independently reviewed the medical records of 20 randomly selected patients with hypertension and commented on the decisions made at each of 243 patient visits. Of 468 comments on patient management, 260 were judged correct by six or more of the physicians; hypercritic also made 118 of these 260 comments. The main reasons why the program did not produce the other 142 comments were: insufficient data in the computer-based medical record; absence of sufficient medical consensus; and omissions in the database of hypercritic. Calculation of an "index of merit" ([sensitivity + specificity] - 1) for individual reviewers showed that hypercritic performed better (index of merit 0.62) in its limited domain than did physician reviewers (0.3-0.56). At least in hypertension management, automated review of computer-based medical records compares favourably with review by physicians. Further development of computer-aided clinical audit requires the introduction of computer-based medical records that capture the reasoning of physicians, and of widely accepted practice guidelines.

Adult↗

PubMed1992

Computer-aided optimization of choice and positioning of bone plates and screws used for internal fixation of mandibular fractures.

The present study describes a biomechanical integrated model of the mandibular system in which the maxilla and mandible, the masticatory muscles, and the temporomandibular joints are regarded as one system. In this model, strains in plate-osteosynthesis devices for internal fixation of mandibular fractures can be minimized by optimizing their positions. The model evaluates maximal bite force strategies on all possible dental elements; it uses a linear programming technique and a muscle architecture model, resulting in muscle recruitment patterns. The shape of a "standard" lower jaw is digitized by means of a three-dimensional (3-D) coordinate retrieval device and drawn on a computer screen after its dimensions have been changed according to the clinical case at hand. The 3-D location of the fracture as well as the anatomic restrictions for screw placement can be indicated on the screen. Osteosynthesis devices can be indicated in terms of dimensions, number, and material properties.

Biomechanical Phenomena↗

PubMed1991

The use of modified constellation graph method for computer-aided classification of congenital heart diseases.

This paper describes a new method of data reduction and classification in a multidimensional symptom space for diagnostic aid of congenital heart diseases. The algorithm developed here is to reduce interactively a multidimensional symptom space to sectorial regions representing each disease in a semicircle using the modified constellation graph method. This method enables us to classify patients using the angle in the semicircle as a single classifying parameter with an accuracy of about 90%, that is, with little overlapping between disease sectors. Comparing this method with conventional factor analysis, we have found the former far more effective than the latter for disease region separation.

Algorithms↗

PubMedDate not supplied

Bayesian statistics: a guided tour.

An overview of Bayesian statistical decision theory is presented in the tutorial spirit. A section on fundamental principles is followed by selected applications of the Bayesian approach to parameter estimation, pattern recognition, image processing, computer-aided medical diagnosis, optimal diagnostic test selection, and radiotherapy treatment planning.

Decision Making↗

PubMed1992

Patch test results of the Dermatology Clinic Zurich in 1989: personal computer-aided statistical evaluation.

The patch test results of 921 consecutively tested patients were registered on an IBM personal computer. A computer program based on the dBase III plus database software, especially designed for this purpose, was used. The statistical evaluation was performed with dBase III plus. 59% of the probands were females and 41% males. The average age was 42.8 years. 26% of the probands were inpatients and 74% outpatients. A majority of the patients presented with eczema of the hands, face or the lower legs. The largest occupational groups were houseworkers and cleaning personnel, office workers and pensioners. To 450 of the 921 patients, at least 4 test series were applied simultaneously. These included European standard, vehicles and emulgators, topical medications, and preservatives and biocides. The other 20 test series available were employed only by 2-81 patients each. The highest sensitization rates were found with: nickel, 18.7%; cobalt, 10.2%; balsam of Peru, 8.8%; framycetin, 8.0%; neomycin, 6.8%; potassium dichromate, 6.1%; p-phenylene diamine, 5.4%; paramix, 4.9%; formaldehyde, 4.8%, and (chlor)methylisothiazolinone, 4.7%. The critical evaluation of the data showed two kinds of problems: first, test-specific aspects led to optimization of the patch test procedures; second, the crucial importance of an adequate statistical analysis for epidemiological investigation was revealed.

Adolescent↗

PubMed1992

A comparison of conventional intra-oral radiography and computer imaging techniques for the detection of proximal surface dental caries.

The detection of proximal surface caries by the visual interpretation of bitewing radiographs is known to be relatively inaccurate. The present study was designed to examine whether computer image processing could improve the diagnostic accuracy. A computer-aided, software-driven, TV-based system was used to digitize conventional radiographs and digitally process the images using histogram equalization and grey-scale inversion to enhance the images. The computer-enhanced images were compared with conventional intra-oral radiographs for the detection of proximal surface caries using receiver operating characteristic analysis. The results indicate that the digital image processing techniques used did not improve the diagnostic accuracy of dental radiographs. No significant difference in diagnostic accuracy could be detected between the non-enhanced digital images and conventional film-based images for the detection of proximal surface caries.

Dental Caries↗

PubMed1992

[Computer-aided prediction of optimal composition of multicomponent mobile phase in high performance liquid chromatography].

This paper proposed a systematic optimizing method for the composition of multicomponent mobile phase in high performance liquid chromatography. A new chromatographic response function (CRF) has been constructed according to the fundamental retention equation and rule of peak width at half-height, and the optimal composition of multicomponent mobile phase can be automatically predicted by a computer with CRF. This paper improved the known complex method, therefore, the optimal mobile phase composition in the global area may be found by means of this modified complex method. The optimal separation conditions of four vitamins and three nitrophenols were determined by use of the optimizing method reported in this paper. The results predicted by the computer were verified by the experimental data obtained in HPLC using ternary mobile phase.

Chromatography, High Pressure Liquid↗