The lived experience of college student lesbians' encounters with health care providers. A preliminary investigation.

The purpose of this preliminary study was to explore the lived experience of four self-identified college student lesbians coming out and their encounters with health care providers. This study used a qualitative method of phenomenology for data collection and analysis. Results of the study revealed a phenomenological model that embodied the core theme of navigating self-disclosure. Two major themes stemming from the core theme were also uncovered. Navigating self-disclosure in homophobic waters and navigating self-disclosure encounters with health care providers unveiled a continuum of self-disclosure to nondisclosure experiences encountered by lesbians. Strategies are offered to enhance interactions between lesbians and health care providers in primary and acute care settings.

Polypeptide composition of squid neurofilaments.

Neurofilaments, 10 nm in diameter, from the axoplasm of the squid Loligo pealei have been isolated by a combination of sonication and Millipore filtration. The presence of neurofilaments during the isolation procedure was confirmed by negative staining and transmission electron microscopy. By use of this technique, which results in minimal or no chemical alteration of the native neurofilament proteins, it was shown that actin (43,000 daltons) and tubulin (56,000 daltons) are physically separable from intact neurofilaments. The neurofilament-rich retentate contained two major proteins of 200,000 and 63,000 daltons and larger polypeptides.

The organization of contractile filaments in a mammalian smooth muscle.

Ordered arrays of thin filaments (65 A diameter) along with other apparently random arrangements of thin and thick filaments (100-200 A diameter) are observed in contracted guinea pig taenia coli rapidly fixed in glutaraldehyde. The thin-filament arrays vary from a few to more than 100 filaments in each array. The arrays are scattered among isolated thin and thick filaments. Some arrays are regular such as hexagonal; other arrays tend to be circular. However, few examples of rosettes with regular arrangements of thin filaments surrounding thick filaments are seen. Optical transforms of electron micrographs of thin-filament arrays give a nearest-neighbor spacing of the thin filaments in agreement with the "actin" filament spacing from x-ray diffraction experiments. Many thick filaments are closely associated with thin-filament arrays. Some thick filaments are hollow circles, although triangular shapes are also found. Thin-filament arrays and thick filaments extend into the cell for distances of at least a micron. Partially relaxed taenia coli shows thin-filament arrays but few thick filaments. The suggestion that thick filaments aggregate prior to contraction and disaggregate during relaxation is promoted by these observations. The results suggest that a sliding filament mechanism operates in smooth muscle as well as in striated muscle.

Ultrastructural studies on the contractile mechanism of smooth muscle.

Fresh taenia coli and chicken gizzard smooth muscle were studied in the contracted and relaxed states. Thick and thin filaments were observed in certain (but not all) cells fixed in contraction. Relaxed smooth muscle contained only thin filaments. Several other morphological differences were observed between contracted and relaxed smooth muscle. The nuclear chromatin is clumped in contraction and evenly dispersed in the relaxed state. The sarcolemma is more highly vesiculated in contraction than in relaxation. In contraction, the sarcoplasm also appears more electron opaque. Over-all morphological differences between cells fixed in isometric and in unloaded contraction were also noticeable. The results suggest a sliding filament mechanism of smooth muscle contraction; however, in smooth muscle, unlike striated muscle, the thick filaments appear to be in a highly labile condition in the contractile process. The relation between contraction and a possible change in pH is also discussed.

The effect of various protein fractions on Z- and M-line reconstitution.

Extraction of thin, glycerinated bundles of rabbit psoas muscle with a low ionic strength solvent results in removal first of M lines and then of Z lines. When these extracted myofibrillar bundles are allowed to interact, at adjusted ionic conditions, with the dilute myofibrillar extract or with the fractions obtained at 40% ammonium sulfate saturation from either the myofibrillar extract or from the Bailey extract of natural actomyosin, reconstitution of Z lines occurs. The ammonium sulfate fraction from the Bailey extract of natural actomyosin restores the tetragonal lattice structure of the Z line. Other structural features such as I-band tufts or cross-bridges, M lines and H-zone binding also occur with some of the proteins used for recombination. Although it has not yet been possible to identify exactly the protein(s) constituting the Z line, it appears unlikely that tropomyosin or troponin alone is the major protein of the Z line. A more likely candidate is alpha-actinin or a combination of alpha-actinin with another protein(s). In addition, this study demonstrates that basic morphological differences exist between cross-sections through the Z-line lattice and cross-sections through tropomyosin crystals.

Localization of myosin filaments in smooth muscle.

Thick myosin filaments, in addition to actin filaments, were found in sections of glycerinated chicken gizzard smooth muscle when fixed at a pH below 6.6. The thick filaments were often grouped into bundles and run in the longitudinal axis of the smooth muscle cell. Each thick filament was surrounded by a number of thin filaments, giving the filament arrangement a rosette appearance in cross-section. The exact ratio of thick filaments to thin filaments could not be determined since most arrays were not so regular as those commonly found in striated muscle. Some rosettes had seven or eight thin filaments surrounding a single thick filament. Homogenates of smooth muscle of chicken gizzard also showed both thick and thin filaments when the isolation was carried out at a pH below 6.6, but only thin filaments were found at pH 7.4. No Z or M lines were observed in chicken gizzard muscle containing both thick and thin filaments. The lack of these organizing structures may allow smooth muscle myosin to disaggregate readily at pH 7.4.

Abductin: a rubber-like protein from the internal triangular hinge ligament of pecten.

The rubber-like internal triangular hinge ligament from Pecten was studied by light and electron microscopy, x-ray diffraction, and chemical analysis. The ligament is composed of an amorphous protein, abductin. In physical properties abductin is similar to elastin and resilin but distinct by amino acid analysis. It is characterized by high concentrations of glycine and methionine.