Bioenergetics, Trophic Ecology, and Niche Separation of Tunas.

Tunas are highly specialized predators that have evolved numerous adaptations for a lifestyle that requires large amounts of energy consumption. Here we review our understanding of the bioenergetics and feeding dynamics of tunas on a global scale, with an emphasis on yellowfin, bigeye, skipjack, albacore, and Atlantic bluefin tunas. Food consumption balances bioenergetics expenditures for respiration, growth (including gonad production), specific dynamic action, egestion, and excretion. Tunas feed across the micronekton and some large zooplankton. Some tunas appear to time their life history to take advantage of ephemeral aggregations of crustacean, fish, and molluscan prey. Ontogenetic and spatial diet differences are substantial, and significant interdecadal changes in prey composition have been observed. Diet shifts from larger to smaller prey taxa highlight ecosystem-wide changes in prey availability and diversity and provide implications for changing bioenergetics requirements into the future. Where tunas overlap, we show evidence of niche separation between them; resources are divided largely by differences in diet percentages and size ranges of prey taxa. The lack of long-term data limits the ability to predict impacts of climate change on tuna feeding behaviour. We note the need for systematic collection of feeding data as part of routine monitoring of these species, and we highlight the advantages of using biochemical techniques for broad-scale analyses of trophic relations. We support the continued development of ecosystem models, which all too often lack the regional-specific trophic data needed to adequately investigate climate and fishing impacts.

Growth of prochlorococcus, a photosynthetic prokaryote, in the equatorial pacific ocean.

The cell cycle of Prochlorococcus, a prokaryote that accounts for a sizable fraction of the photosynthetic biomass in the eastern equatorial Pacific, progressed in phase with the daily light cycle. DNA replication occurred in the afternoon and cell division occurred at night. Growth rates were maximal (about one doubling per day) at 30 meters and decreased toward the surface and the bottom of the ocean. Estimated Prochlorococcus production varied between 174 and 498 milligrams of carbon per square meter per day and accounted for 5 to 19 percent of total gross primary production at the equator. Because Prochlorococcus multiplies close to its maximum possible rate, it is probably not severely nutrient-limited in this region of the oceans.

Radiation effects in free-ranging pocket mice, Perognathus parvus, during the breeding season.

Captive and free-ranging Great Basin pocket mice, Perognathus parvus, were exposed to ionizing radiation during the breeding season, April-June, in 1971. The values for the median lethal dose (LD(50)) at 30 days plus or minus the standard deviation were 880 +/- 14 rads and 780 +/- 27 rads, respectively, and the slopes of the survivorship curves were significantly different. These differences suggested that there was a synergism between radiation-induced and environmental sources of mortality, since the field data were corrected for natural mortality (5 percent) in the controls.

Effects of diethylnitrosamine and cigarette smoke on hamsters.

One hundred two 2-month-old male Syrian hamsters received 12 weekly sc injections of 0.25 mg diethylnitrosamine (DEN). Half the animals were also exposed for 10 minutes to cigarette smoke in Hamburg II-type smoking machines, three times per day, 5 days per week, for their life-span. The other half received sham exposure. Two additional groups of 51 hamsters each, serving as controls, received either only smoke or sham smoke exposures. The DEN treatment resulted in a significant increase (P less than 0.01) in epithelial lesions of the larynx, including laryngeal papillomas. Cigarette smoke inhalation had a significant (P less than 0.01) potentiating effect on the incidence of these lesions. We did not observe the high incidence of tumors of the nasal cavity, trachea, and the lower respiratory tract, or a significant development of malignant tumors, reported by several other investigators. The life-spans of the animals were unaffected by DEN and significantly increased (P less than 0.01) by exposure to smoke. The smoke-exposed groups had significantly lower mean body weights than their sham smoke-exposed cohorts.

A mathematical description of causative factors and prevention of elevated intraocular pressure after keratoplasty.

In keratoplasty with grafts the same size as the recipient bed, tight sutures and thick recipient corneal periphery distort the angle and may collapse the filtering meshwork. This can cause very high postoperative pressures, which can be avoided by the use of donor grafts larger than the recipient bed. These relationships can be mathematically predicted.

Sedimentation field-flow fractionation: a method for studying particulates in cataractous lens.

It is shown that the technique of sedimentation field-flow fractionation (sedimentation [sed] FFF) can be used to determine the particle content and particle size distribution of normal and cataractous lenses. A 31-year-old normal human lens, for example, showed a particle content of 1.5% by weight with diameters ranging from 0.12 micron to 0.9 micron. The urea insoluble material present in the nuclear and cortical fractions from a densely cataractous lens contained particles ranging from 0.12 micron to 1.7 micron, with average sizes of 0.83 micron and 0.82 micron respectively, for the two fractions. These numbers offer a basis for comparison; their actual values may be shifted slightly either up or down depending on the assessment of particle density. These sizes, which correspond to molecular weights of around 2 X 10(9) dalton, are larger than previously reported for lens particulates. The sed FFF method is thus seen to permit fractionation and size analysis of small amounts of lens material in times less than one hour.

Variation in corneal graft size related to trephine technique.

To determine the range of variation in corneal transplant tissue size induced by slight changes in trephination technique, four human corneas that had been stored in McCarey-Kaufman medium and 11 intact human globes were used. Endothelial surface trephination yielded a smaller corneal button than epithelial trephination. In the intact eye, the higher the intraocular pressure was, the larger the resulting corneal diameter. With use of a trephine with a central plunger, the higher the obturator was, the larger the diameter of the resulting tissue. Also, the duller the trephine was, the larger the diameter of the cut, due to difficulty in tissue penetration. Thus, slight variations can markedly affect the match in size between donor and recipient.

Air and the corneal endothelium: an in vivo specular microscopy study in cats.

In 25 cat eyes 0.7 mL of air and in 11 cat eyes 0.7 mL of balanced salt solution were injected into the anterior chamber after paracentesis. This air persisted for three to four days, and specular microscopy was performed before and two months after air injection. There was an overall significant decrease in the endothelial cell density as a percentage of the preinjection density for the eyes with air when compared with those with balanced salt solution (102% +/- 7% for balanced salt solution and 93% +/- 11% for air). Thus, while air is generally well tolerated by the corneal endothelium, it is a toxic material in the anterior chamber and probably can cause endothelial damage. If not otherwise indicated and if safe to do so, it seems best to avoid its use or to replace it with physiologic solutions after its use.

The position of the posterior chamber intraocular lens.

Six human cadaver eyes were used for intraocular lens (Shearing) insertion, and the results were photographed. It was found that with the posterior capsule intact, insertion was relatively simple and the feet were found to lie in the ciliary body sulcus with good fixation. Some decentering was common and difficult to correct, but not optically important. With the posterior capsule torn or missing, misplacement was common. After correct insertion, the lens was well fixated without pseudophakodonesis, and there was still found to be room for an additional 1.5 to 2.0 mm of movement.

The clinical use, accuracy, and reliability of the Veri-Vu lensometer.

One hundred forty-six lenses from 11 manufactures were tested with the Veri-Vu lensometer and optical power plus resolution compared with results from an optical bench. Accuracy was found to be +/- 0.2 diopter in 95% of the lenses tested. The greatest error was 0.37 D. The lensometer correctly identified 125 of 128 lenses that were greater than 160 line pairs per millimeter (LP/mm) resolution and correctly identified nine lenses that had less than 100-LP/mm resolution. All other important optical aberrations were identified with the lensometer. The greatest problem was the variation from company to company in terms of the calculated power in aqueous as determined from the back focal length in air. This, however, was felt to be an asset for those doing A-scan intraocular lens power determination in giving one simple reliable power for all lens companies.

Vaulting characteristics of flexible loop anterior chamber intraocular lenses.

Fourteen flexible loop anterior chamber intraocular lenses were tested under controlled laboratory conditions. Lens vault was precisely measured as a function of loop compression and of force applied to the loops. A wide range of vaulting characteristics were observed. Some lenses did not vault at all while others vaulted more than the amount of compression. Advantages, disadvantages, and possible clinical implications of lens vault are discussed.

Factors associated with poor predictability by intraocular lens calculation formulas.

In this study, we evaluated and compared two groups of posterior chamber intraocular lens (IOL) implantation cases. One group consisted of patients whose postoperative refraction was accurately predicted by IOL calculation formulas, while the other group included patients whose postoperative refraction was poorly predicted by the same formulas. We found that although postoperative astigmatism was greater in the poorly predicted group, preoperative to postoperative changes in astigmatism did not differ between the two groups. The poorly predicted group also had a shorter average axial length, a greater proportion of females, and an increased variability in most of the measurements we performed. The two groups did not differ significantly in terms of measured postoperative anterior chamber depth, age at the time of the surgery, IOL power and style implanted, complication rate, or preoperative corneal integrity.

Dominantly inherited keratitis.

A new, autosomal dominant keratitis is presented. The onset occurs in early childhood with episodes of red, irritated eyes but not recurrent erosions. There are no associated systemic abnormalities. The primary histopathologic features are vascularization and inflammation of the anterior corneal stroma, and replacement of Bowman's layer by fibrovascular tissue. Thus, this disease demonstrates characteristics of both a dystrophy with familial occurrence and early onset, and a degeneration with primary inflammation and vascularization.

Crystallization on intraocular lens surfaces associated with the use of Healon GV.

OBJECTIVE: To describe a series of patients who had visually significant crystalline deposits on their intraocular lenses during cataract surgery with the use of Healon GV (a high concentration and high molecular-weight hyaluronate sodium). METHODS: Patients were examined for crystalline deposits on their intraocular lenses. These deposits were compared with intraocular lens type, viscoelastic solutions, any other intraocular substance used, type of surgery, and perioperative medications. RESULTS: In the 11 patients with documented changes (six photographically), the only consistent finding was the use of Healon GV. Furthermore, since we discontinued the use of Healon GV, we have not seen a recurrence of these deposits in more than 500 consecutive patients. The deposits could last a long time (at least 6 months) if sequestered by the posterior capsule, and they are believed to be visually significant at times (Snellen visual acuity of 20/40 or worse). CONCLUSION: Healon GV use is associated with a new clinical finding of crystalline deposits on intraocular lenses. These deposits can be clinically significant.

Commonly used intraocular medications and the corneal endothelium.

Forty-one cats had balanced salt solution, chymotrypsin, epinephrine hydrochloride with preservatives in varying concentrations, acetylcholine chloride, and carbachol injected intracamerally to determine the toxic effects on the endothelium. Specular microscopy was performed both before and after injection, and for each of the medications, the cell densities were compared with the results obtained with the balanced salt solution. The mean postinjection density as compared with the preinjection density for the medications varied between 98% and 108%, and there were no statistically significant differences between each medication group and the balanced salt solution results. From the results of this study, it is believed that when indicated, these medications probably do not produce substantial toxic effects on the corneal endothelium.

Refractive variation and donor tissue size in aphakic keratoplasty. A prospective randomized study.

Forty-six patients were examined in a prospective, randomized clinical study to compare the use of the same size trephine on both donor and recipient with the use of a 0.5-mm larger trephine on the donor in aphakic keratoplasty and in keratoplasty combined with lens extraction. The results showed no statistically significant difference in refractive error, either in spherical equivalents or in astigmatism. The larger donor tissue may have some value in reducing high plus-refractive error and in reducing intraocular pressure after surgery.

Polyvinyl alcohol as a protective coating on intraocular lenses.

Sixty-eight intraocular lenses were implanted in cats to compare the efficacy of a new polyvinyl alcohol coating in protecting the corneal endothelium from lens-cell contact damage. The mean endothelial density after implantation of the coated lens was significantly higher than the cell density in those eyes receiving the uncoated lens. We saw no clinical signs of unusual inflammation; whole-eye histopathologic study disclosed no signs of inflammation or toxicity related to the coating. Ten coated lenses were placed in balanced salt solution or perfused with balanced salt solution at 0.5 mL/min. The coating remained intact for 60 minutes, affording corneal endothelial protection for this period. In a rabbit anterior chamber toxicity study, using balanced salt solution as a control, no differencs in reaction in the anterior chamber or intraocular pressure were noted.

Fungal endophthalmitis following intraocular lens implantation. A surgical epidemic.

Thirteen cases of fungal endophthalmitis were caused by Paecilomyces lilacinus. In all cases an intraocular lens was inserted that had been sterilized in sodium hydroxide and neutralized in sodium bicarbonate. In 12 of the 13 cases, it was absolutely determined that a manufacturer's lot 128 was the neutralizing solution used. The same fungus that caused the endophthalmitis was cultured from several of the neutralizing solutions from lot 128. Eight of the 13 eyes eventually required enucleation. Of the remaining five eyes, one eventually recovered 20/25 vision, one recovered 20/80 vision, one had light perception, and two lost light perception (one of these became phthisical). This surgically induced epidemic of fungal endophthalmitis clearly shows the major consequences of a breakdown in quality control for any substance or material used intraocularly.

Peters' anomaly as a consequence of genetic and nongenetic syndromes.

A new syndrome includes Peters' anomaly and short-limbed dwarfism. A balanced chromosomal translocation in the brother (patient 1) appears to be coincidental to the physical abnormalities, because his sister (patient 2) has identical findings but normal fibroblast and lymphocyte karyotypes. Peters' anomaly, which includes corneal clouding, iris and/or lens adhesions to the cornea, and the absence of endothelium and Descemet's membrane, is often associated with systemic abnormalities. Since there are different genetic and nongenetic systemic conditions that include Peters' anomaly, and there are several ocular syndromes with features overlapping this disorder, we believe that Peters' anomaly is a morphologic finding rather than a distinct entity.

Changing trends in the indications for penetrating keratoplasty.

The indications for penetrating keratoplasty have changed over the past several years. Nine hundred ninety-nine penetrating keratoplasty specimens from 1981 through 1990 were analyzed. Overall, keratoconus was the most common indication for penetrating keratoplasty (24.2%). This was followed by pseudophakic bullous keratopathy (23.0%), regraft (13.1%), scarring (8.2%), and Fuchs' endothelial dystrophy (5.8%). Pseudophakic bullous keratopathy was the most common indication for penetrating keratoplasty in each year from 1984 through 1989 with a peak in 1987 (33%). Since 1987, the number of pseudophakic bullous keratopathy cases has decreased; and in 1990, keratoconus (33.1%) surpassed pseudophakic bullous keratopathy (24.1%) as the most common indication for penetrating keratoplasty. This decreasing incidence of pseudophakic bullous keratopathy may reflect the discontinued use of closed-looped anterior chamber and iris-plane intraocular lenses most commonly associated with this complication.