Lens intracellular hydrostatic pressure is generated by the circulation of sodium and modulated by gap junction coupling

We recently modeled fluid flow through gap junction channels coupling the pigmented and nonpigmented layers of the ciliary body. The model suggested the channels could transport the secretion of aqueous humor, but flow would be driven by hydrostatic pressure rather than osmosis. The pressure required to drive fluid through a single layer of gap junctions might be just a few mmHg and difficult to measure. In the lens, however, there is a circulation of Na+ that may be coupled to intracellular fluid flow. Based on this hypothesis, the fluid would cross hundreds of layers of gap junctions, and this might require a large hydrostatic gradient. Therefore, we measured hydrostatic pressure as a function of distance from the center of the lens using an intracellular microelectrode-based pressure-sensing system. In wild-type mouse lenses, intracellular pressure varied from ∼330 mmHg at the center to zero at the surface. We have several knockout/knock-in mouse models with differing levels of expression of gap junction channels coupling lens fiber cells. Intracellular hydrostatic pressure in lenses from these mouse models varied inversely with the number of channels. When the lens’ circulation of Na+ was either blocked or reduced, intracellular hydrostatic pressure in central fiber cells was either eliminated or reduced proportionally. These data are consistent with our hypotheses: fluid circulates through the lens; the intracellular leg of fluid circulation is through gap junction channels and is driven by hydrostatic pressure; and the fluid flow is generated by membrane transport of sodium

Barriers to integration of bioinformatics into undergraduate life sciences education: A national study of US life sciences faculty uncover significant barriers to integrating bioinformatics into undergraduate instruction

Bioinformatics, a discipline that combines aspects of biology, statistics, mathematics, and computer science, is becoming increasingly important for biological research. However, bioinformatics instruction is not yet generally integrated into undergraduate life sciences curricula. To understand why we studied how bioinformatics is being included in biology education in the US by conducting a nationwide survey of faculty at two- and four-year institutions. The survey asked several open-ended questions that probed barriers to integration, the answers to which were analyzed using a mixed-methods approach. The barrier most frequently reported by the 1,260 respondents was lack of faculty expertise/training, but other deterrents-lack of student interest, overly-full curricula, and lack of student preparation-were also common. Interestingly, the barriers faculty face depended strongly on whether they are members of an underrepresented group and on the Carnegie Classification of their home institution. We were surprised to discover that the cohort of faculty who were awarded their terminal degree most recently reported the most preparation in bioinformatics but teach it at the lowest rate

LETHAL PHOTOSENSITIZATION OF BACTERIA WITH 8-METHOXYPSORALEN TO LONG WAVE LENGTH ULTRAVIOLET RADIATION

Severe, or even lethal, cellular damage can follow the conjoint action of a chemical photo-sensitizer and effective frequencies of the elec-tromagnetic spectrum. The fact that bacteria, as well as other cellular systems, are subject to photosensitization by such compounds as methyl-ene blue was known fifty years ago (Reitz, 1908). The relatively limited number of studies of bacterial photosensitization over the years since then has been concerned primarily with the photodynamic action of methylene blue. Re-cently, Sistrom et al. (1956) demonstrated a lethal photosensitizing effect of bacteriochloro-phyll in the absence of carotenoids in Rhodo-pseudomonas spheroides. The photosensitizing ac-tion of both dyes and bacteriochlorophyll is dependent primarily on wave lengths in the red region of the visible spectrum. Another group of photosensitizing compounds was disclosed by the finding that certain furo-coumarins of plant origin, particularly 8-meth-oxypsoralen, are useful in the deliberate photo-sensitization of the skin of patients with vitiligo (Fahmy and Abu-Shady, 1947), and indeed, the compounds were present in certain folk remedies used for this skin disease in India for at least 3000 years and in Egypt almost as long (Pathak, 1958). While early studies with 8-methoxy-psoralen used sunlight as the radiation source, Musajo et al. (1954) demonstrated with an arti-ficial light source the effectiveness of frequencies in the long wave length ultraviolet region in pro-ducing typical skin responses of erythema and edema. Clinical studies on the use of 8-methoxy-psoralen to augment the normal tanning proces