Medicine and the Internet. What can I learn from the Internet?

What is the Internet? The Internet is the biggest network of information resources the world has ever seen and is growing rapidly each day. The Internet and the World Wide Web (The Web) represent the first technology to fully integrate the communications found on bookshelves, magazine racks, catalog files, fax machines, symposiums, in television/radio studios and the common mail system into a global infrastructure with extraordinary capabilities to deliver timely health care information. Unlike conventional media like newspapers or television, the Internet provides rapid one-to-one communication between millions of individuals. Television and newspapers communicate from "a few" (the writers and advertisers) to "many" (the readership). On the Internet, everyone is a "peer," being both an information provider and consumer on a 24-hour, 7-day a week basis. This article will discuss ways you can use the Internet's information resources in your own personal and professional life.

Using the Internet for data collection. An innovative electronic strategy.

Computer hardware and software have revolutionized research data management. Data collection has, however, remained a time-consuming and expensive component of most research projects. This article presents a description of an innovative strategy for data collection using computer network forums on the Internet (the "information superhighway"). The success of the electronic data collection strategy is illustrated by a report of the results of a survey of the needs and coping mechanisms of cancer survivors.

OncoLink: a multimedia oncology information resource on the Internet.

This paper describes OncoLink, the first multimedia World-Wide-Web (WWW) and gopher server focusing on cancer information for both the health care professional and the patient. OncoLink provides an internetworked hypertext and multimedia resource linking people, computers and information together in an easy to use fashion. Our objective in developing OncoLink is to provide comprehensive and timely information about many aspects of oncology for both patients and healthcare providers. Specifically, OncoLink's purposes are: (1) the rapid dissemination of information relevant to treatment of cancer and concomitant problems; (2) education of health care personnel (at all levels) in the field; (3) education of patients and families of patients who have cancer; (4) posting of clinical trials and eligibility criteria; (5) the rapid collection and dissemination of quality, peer-reviewed information pertinent to oncology in general and specific subspecialties; (6) provide a well-organized, frequently updated hypertext system to access other quality cancer information resources on the Internet. OncoLink attempts to provide one-stop shopping for the patient, healthcare provider, researcher or Internet browser searching for cancer-related information. Since its inception on March 7, 1994, OncoLink has averaged more than 36,000 accesses per month from around the world. While also accessible by text-based gopher servers, preliminary observations infer increased use of multimedia and hypertext documents over traditional text-only resources. From the large following of users, it is clear that electronic dissemination of high quality, peer-reviewed cancer information is very popular. We conclude OncoLink is both useful and has wide interest in the international community.(ABSTRACT TRUNCATED AT 250 WORDS)

The use of T2 distribution to study tumor extent and heterogeneity in head and neck cancer.

Demarcation of the extent of malignant tissue is essential for planning a course of radiotherapy. MR images may provide additional information for delineating the target volume because of the large difference in the proton magnetic resonance relaxation times between normal and malignant tissues. In 13 patients with head and neck tumors the distribution of the proton spin-spin relaxation times, T2, at 1.5 Tesla were evaluated throughout the physician designated target volume and normal surrounding tissue. The T2 values within the tumor were always elevated compared with normal tissue, the highest values being in the nominal center of the tumor and decreasing toward the periphery. The regional distribution of T2 values within the tumor is a measure of the tissue heterogeneity within the tumor volume. In addition, the large differences in T2 relaxation times between normal and disease tissues were used in a computer algorithm to automatically demarcate the boundary of abnormal tissue in each axial MRI section. This potentially could significantly expedite the time required to identify the target volume on multiple sections and thus remove one of the major time constraints for 3D treatment planning.

Noise reduction for T2 derived magnetic resonance images.

Calculation of magnetic resonance images composed of signals arising from T2 and proton densities can be performed using a least squares fitting procedure from three or four multiple spin-echo images. This procedure works well in regions of high signal-to-noise (S/N) in the multiple spin-echoes. Erroneous T2 values predominate in regions of low S/N, precluding the routine use of T2 images in diagnostic and quantitative analysis. This study demonstrates that only three spin-echoes signals (TE = 20, 40, and 60 msec) and a simple preprocessing selection criteria are necessary to significantly reduce erroneous T2 values. This simple selection criteria obviates the need to apply a median filter to the T2 image and thus preserve both the high inherent contrast and spatial resolution of the T2 derived image.

Correlation between structure and mass distribution of the nuclear pore complex and of distinct pore complex components.

Nuclear pore complexes (NPCs) prepared from Xenopus laevis oocyte nuclear envelopes were studied in "intact" form (i.e., unexposed to detergent) and after detergent treatment by a combination of conventional transmission electron microscopy (CTEM) and quantitative scanning transmission electron microscopy (STEM). In correlation-averaged CTEM pictures of negatively stained intact NPCs and of distinct NPC components (i.e., "rings," "spoke" complexes, and "plug-spoke" complexes), several fine structural features arranged with octagonal symmetry about a central axis could reproducibly be identified. STEM micrographs of unstained/freeze-dried intact NPCs as well as of their components yielded comparable but less distinct features. Mass determination by STEM revealed the following molecular masses: intact NPC with plug, 124 +/- 11 MD; intact NPC without plug, 112 +/- 11 MD; heavy ring, 32 +/- 5 MD; light ring, 21 +/- 4 MD; plug-spoke complex, 66 +/- 8 MD; and spoke complex, 52 +/- 3 MD. Based on these combined CTEM and STEM data, a three-dimensional model of the NPC exhibiting eightfold centrosymmetry about an axis perpendicular to the plane of the nuclear envelope but asymmetric along this axis is proposed. This structural polarity of the NPC across the nuclear envelope is in accord with its well-documented functional polarity facilitating mediated nucleocytoplasmic exchange of molecules and particles.

Semi-automated radiotherapy treatment planning with a mathematical model to satisfy treatment goals.

Iterative algorithms can provide a feasible solution, if any exists, to specified treatment goals. Our model subdivides both the patient's cross section into a fine grid of points and the radiation beam into a set of "pencil" rays. The anatomy, treatment machine parameters, dose limits and homogeneity, are all defined. This process of subdivision leads to a large system of linear inequalities with a solution that provides a radiation intensity distribution that will deliver a prescribed dose distribution. The clinical results from two different algorithms will be presented and contrasted. Once the anatomy, treatment, and machine parameters have been entered, the computerized algorithms yield an answer in several minutes. The Cimmino algorithm also allows "weights" or priority assignments of the treatment goals. The resulting solution is biased towards fulfilling the specified doses for the anatomic regions which were given greater weight. It is desirable to have a systematic search of possible treatment alternatives in complex clinical situations, including 3-dimensional radiation therapy treatment planning (RTTP). Our method has been applied to 2-D RTTP, but is equally applicable to 3-D RTTP with minor modifications.

Atrial-specific granules in situ have high calcium content, are acidic, and maintain anion gradients.

The composition and pH of atrial-specific granules of rat heart were determined by electron probe x-ray microanalysis and fluorescence microscopy, respectively. The high (75 mmol/kg of dry weight) calcium content and higher than cytoplasmic concentration of chloride in atrial-specific granules were visualized in high-resolution x-ray maps. The Cl- content of granules and cytoplasm decreased and a bromide gradient (granule greater than cytoplasm) was established during incubation in low-chloride, NaBr-containing solutions. Scanning confocal fluorescence light microscopy of live atria incubated with acridine orange demonstrated dye accumulation, indicative of low intragranular pH. We conclude that the granules represent a hitherto unrecognized intracellular store of cardiac calcium and can develop and maintain an anion gradient, presumably through cotransport by means of a proton-pumping ATPase.

The cell wall structure of a magnesium-dependent halobacterium, Halobacterium volcanii CD-2, from the Dead Sea.

Cell wall preparations from the magnesium-dependent halophilic bacterium, Halobacterium volcanii, were studied by high-resolution electron microscopy complemented with image analysis and processing. For ultrastructural studies, specimens were prepared by a variety of methods, including negative staining, and metal shadowing after air-drying, freeze-drying, or freeze-fracturing and etching. All methods revealed the cell wall to be composed of a near-hexagonal lattice of unit cells having a center-to-center spacing of 15.5 nm. While negatively stained samples yielded two types variably revealed the unit cell to be composed of six protomers surrounding a central mass depression. This low-resolution unit cell morphology appears very similar to that of other bacterial cell wall S-layers studied to date.

Correlation of surface topography of metal-shadowed specimens with their negatively stained reconstructions.

We present a comparison of surface reconstructions from three different freeze-dried and unidirectionally metal-shadowed specimens (i.e. bacteriophage T4 polyheads, crystalline actin sheets and nuclear pore complexes) with two- or three-dimensional reconstructions of the same specimens when prepared by negative staining. Based on these and many published results, the following conclusions have been reached: With a "cooperative" specimen (e.g. the polyheads), the surface reconstruction computed from a metal-shadowed replica compares favorably with two- or three-dimensional reconstructions obtained from the same specimen after negative staining at the 3-4 nm resolution level. This relatively "poor" level at which the surface topographies of the two preparations can be compared appears to be set by a "practical" resolution limit (i.e. of distinct and reproducible structural detail) of metal replicas of biological specimens, despite the appearance of weak higher-order diffraction spots (i.e. corresponding to 2-3 nm). While in some cases (e.g. the crystalline actin sheets) the surface reliefs of metal replicas may bear little resemblance to the actual structure under investigation, the replicas may still contain sufficient features to establish the polarity or handedness of the structure (i.e., the "top" and "bottom" surfaces of a crystalline sheet). Information from negatively stained specimens is usually complementary with information from freeze-dried and metal-shadowed specimens. However, there are artifacts in both techniques, and we present an example with the nuclear pore complex, where these techniques yield confusing results.

Specific labeling of protein domains with antibody fragments.

Monovalent antibody Fab fragments, prepared from antisera raised against two different types of crystalline arrays made of either intact, or a proteolytic fragment of bacteriophage T4 major capsid protein, gp23*, were employed to stoichiometrically label different gp23* protein domains on the outer surface of a tubular variant (i.e., "polyheads") of bacteriophage T4 capsids. Computer filtrations of both negatively stained and freeze-dried/metal-shadowed specimens permitted approximate mapping of the Fab binding sites within the capsomere of the polyheads.

Electron microscopy and image processing applied to the study of protein structure and protein-protein interactions.

We review the application of electron microscopy and image processing at the molecular level to an ever increasing range of biological specimens. Although recent advances have been due in part to development of more sophisticated instrumentation and/or processing algorithms, widespread application of the well-known techniques of image enhancement and structure reconstruction has depended on new strategies of in vitro crystallization and polymerization, some of which are outlined here. We also discuss the use of stoichiometric labeling and/or "cocrystallization" in identifying the different subunits in multisubunit complexes and in studying protein-protein interactions.

Proton ATPase of rat liver mitochondria. Preparation and visualization of a functional complex using the novel zwitterionic detergent 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate.

The proton ATPase of rat liver mitochondria has been purified by a simple procedure which involves the use of the novel, zwitterionic detergent 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate to solubilize the membrane-bound complex. The purified enzyme has a high, oligomycin-sensitive ATPase activity (11.3 +/- 2.9 mumol/min/mg) in the absence of added phospholipids. It shows, in four different gel electrophoretic systems, the five bands characteristic of the F1 portion of the complex and three additional Coomassie blue-stainable bands which have apparent molecular weights of 28,000, 19,000, and 13,600. A fourth Coomassie blue-stainable component of about 10,000-12,500 daltons comigrates with the delta subunit, whereas a fifth component, detectable only by absorption at 280 nm, is observed between the dye front and the 10,000-dalton species. The enzyme complex has been reconstituted into liposomal vesicles of asolectin. Under these conditions the enzyme catalyzes an ATP-Pi exchange reaction and is capable of translocating protons in an ATP-dependent manner as assayed by quenching of 9-amino-6-chloro-2-methoxyacridine. Both activities are inhibited by the addition of oligomycin, uncoupler, dicyclohexylcarbodiimide, and cadmium. At high detergent concentration, the complex appears in negative stain electron microscopy in a dispersed state. The tripartite structure is clearly visible in monomeric, dimeric, or trimeric forms of the molecule. At the low detergent concentration, the proton ATPase tends to cluster into densely packed arrays. This represents the first report of the properties of a functionally active proton ATPase solubilized and purified in the presence of a zwitterionic detergent.

Tubular arrays of the actin-DNase I complex induced by gadolinium.

We describe the preparation and structural analysis of ordered tubular arrays of the actin-DNase I complex. These structures consist of helically stacked rings; each ring is 73 A thick, has a 240 A outer and a 120 A inner diameter, and has 7-fold rotational symmetry. The actin-DNase I complex forms tubes under conditions in which actin alone aggregates into crystalline sheets-i.e., in the presence of the trivalent cation gadolinium. Moreover, upon addition of an equimolar amount of DNase I, crystalline actin sheets are slowly converted to tubes. The rings making the tubes contain a radial dyad axis that may be identical to the dyad axis of the unit cell of the crystalline actin sheet. Evidence is presented for this identification, which in turn allows tentative assignment of actin- and DNase I-containing regions in three-dimensional reconstructions of the rings. The structural analysis presented here may be useful in aligning available three-dimensional molecular models of actin determined from crystals of the actin-DNase I complex and from crystalline actin sheets with each other and ultimately within the biologically important actin filament.

The structure of the Ca2+ ATPase as revealed by electron microscopy and image processing of ordered arrays.

Two-dimensional ordered arrays of the membrane-bound Ca2+ ATPase, were formed over a wide range of conditions (i.e., pH, ionic strength, temperature) in the presence of vanadate, and studied by electron microscopy and image processing. These ordered tubular and spherical membrane vesicles of Ca2+ ATPase could also be formed with approximately one bound ATP and between one and two nonchelatable Ca2+ bound. The tubular arrays ranged between 1 and 10 microns in length and had an average flattened diameter of 90 nm, as observed in negatively stained preparations. The basic building blocks of these ordered arrays appear to be linear ribbons of Ca2+ ATPase dimers. Fourier analysis of electron micrographs of these flattened tubes revealed a near-rectangular lattice (lattice angle 73.3 +/- 4.6 degrees with average lattice constants of a = 6.2 +/- 0.25 nm, and b = 11.5 +/- 0.30 nm). The double-stranded ribbons (i.e., parallel to a) are inclined by 56 +/- 3.7 degrees relative to the tube axis in a right-handed sense, as determined from freeze-dried metal-shadowed specimens. Computer averaging of negatively stained arrays reveals a crystallographic dimer of stain-excluding matter. The dimensions of each monomer within this dimer are consistent with established structural parameters, leading us to believe a form of the Ca2+ ATPase, capable of binding at least one ATP and of binding Ca2+ ions, may exist as a dimer in the sarcoplasmic reticulum.

Kinetic evidence for a monomer activation step in actin polymerization.

We measured the time course of skeletal muscle actin polymerization at different actin concentrations. In 0.1 M KCl with 1 mM Mg2+, log/log plots of the rate of the early, slow phase of polymerization vs. actin concentration were linear with slopes from 1.0 to 1.3. Computer-assisted calculations of similar curves from theoretical models with different sizes for the nucleus showed that no simple model gave a log/log plot with a slope less than 1.5. Addition of a first-order, monomer activation step before nucleation allowed models of any reasonable nucleus size to have a slope of 1. This is the first evidence that such a step is part of the kinetic pathway for actin polymerization. In 0.1 M KCl with 0.2 mM Ca2+, log/log plots of the rate of the slow phase vs. actin concentration were linear with slopes from 2.0 to 2.5. Monomer activation was not necessary to account for this slope. However, fits of kinetic curves calculated from theoretical models to experimental kinetic curves showed that filament fragmentation was important to achieve a good fit, confirming the finding of Wegner and Savko [Wegner, A., & Savko, P. (1982) Biochemistry 21, 1909-1913]. Our fit procedure also allowed us to estimate the size of the nucleus and the rate constants for activation, nucleation, and fragmentation. In 0.1 M KCl with 1 mM Mg2+, the nucleus was a dimer or trimer, and nucleation was fast. In 0.1 M KCl with 2.0 mM Ca2+, the nucleus was a trimer, and nucleation was slow.