The influence of feeding on the evolution of sensory signals: a comparative test of an evolutionary trade-off between masticatory and sensory functions of skulls in southern African horseshoe bats (Rhinolophidae).

The skulls of animals have to perform many functions. Optimization for one function may mean another function is less optimized, resulting in evolutionary trade-offs. Here, we investigate whether a trade-off exists between the masticatory and sensory functions of animal skulls using echolocating bats as model species. Several species of rhinolophid bats deviate from the allometric relationship between body size and echolocation frequency. Such deviation may be the result of selection for increased bite force, resulting in a decrease in snout length which could in turn lead to higher echolocation frequencies. If so, there should be a positive relationship between bite force and echolocation frequency. We investigated this relationship in several species of southern African rhinolophids using phylogenetically informed analyses of the allometry of their bite force and echolocation frequency and of the three-dimensional shape of their skulls. As predicted, echolocation frequency was positively correlated with bite force, suggesting that its evolution is influenced by a trade-off between the masticatory and sensory functions of the skull. In support of this, variation in skull shape was explained by both echolocation frequency (80%) and bite force (20%). Furthermore, it appears that selection has acted on the nasal capsules, which have a frequency-specific impedance matching function during vocalization. There was a negative correlation between echolocation frequency and capsule volume across species. Optimization of the masticatory function of the skull may have been achieved through changes in the shape of the mandible and associated musculature, elements not considered in this study.

Karyotypic differences in two sibling species of Scotophilus from South Africa (Vespertilionidae, Chiroptera, Mammalia).

Karyotype descriptions are given for Scotophilus dinganii (2n = 36, FNa = 50) and a recently discovered sister-species, Scotophilus sp. nov. (2n = 36, FNa = 52). These two sibling species occur sympatrically and are distinguished by body size, echolocation frequency and cytochrome b sequence. Cytogenetically, both species differ from other Scotophilus species in the subtelocentric morphology of chromosome 2 and a terminal heterochromatic segment on the X chromosome. Further, Scotophilus sp. nov. is characterized by a subtelocentric chromosome 4 not found in any other Scotophilus species. Comparing the Scotophilus karyotype with that of the vespertilionid genus Myotis, extensive conservation of whole chromosome arms has been found recently. However, out of 25 chromosomal arms six could not be identified in Scotophilus. Therefore, in the present study fluorescence in situ hybridization with whole chromosome painting probes from Myotis myotis was carried out on metaphase preparations from Scotophilus dinganii and Scotophilus sp. nov. These experiments revealed that three previously unidentified Scotophilus chromosomes (A, B, C) contain homologous sequences to Myotis chromosomes 18 plus 22, 19 plus 25, and 16/17, respectively.

Human immunodeficiency virus-positive patients with posterior intracorneal precipitates.

PURPOSE: To describe an unusual and possibly new keratopathy in human immunodeficiency virus (HIV)-positive patients. DESIGN: Retrospective observational case series. PARTICIPANTS: : Six HIV-positive patients at four centers. METHODS: A complete medical history was obtained and a thorough ophthalmic examination was performed on each of the patients. RESULTS: Each patient had bilaterally symmetrical keratopathy consisting of variably pigmented round and reticular posterior intracorneal precipitates at the level of Descemet's membrane. The precipitates were diffuse, but larger and more prominent near the limbus and finer toward the central cornea. None of the eyes were inflamed, and all had normal vision. No patient had uveitis on presentation or any history of cytomegalovirus retinitis. CONCLUSION: These patients have a unique posterior keratopathy, which requires further investigation.

Intracameral anesthesia: a report by the American Academy of Ophthalmology.

OBJECTIVE: This document describes the technique of intracameral anesthesia and examines the available evidence to address questions about its effectiveness, possible corneal endothelial and retinal toxicity, and the optimal and maximal dose. METHODS: A literature search conducted for the years 1968 to 2000 retrieved over 180 citations that matched the search criteria. Panel members and a methodologist reviewed this information, and it was evaluated for the quality of the evidence presented. RESULTS: Some studies report effectiveness of intracameral anesthesia while others report no effect. In those studies showing an effect, levels of pain in the groups that were compared were low. Short-term studies seem to indicate that preservative (methylparaben)-free lidocaine 1% is well tolerated by the corneal endothelium but that higher concentrations of lidocaine are toxic. There is some evidence of electroretinogram changes after exposure to lidocaine or bupivacaine. CONCLUSIONS: The ideal timing and placement of intracameral anesthesia has not been determined. Because topical anesthesia alone is effective, surgeons may elect to use intracameral anesthesia for incremental pain control in patients who cannot be adequately managed with topical alone. Appropriate patient selection is important when using this method of anesthesia. While short-term studies seem to indicate safety, long-term effects are unknown. Patient preferences for anesthesia are not well studied.

Five-year results of a randomized, prospective, clinical trial of diode vs argon laser trabeculoplasty for open-angle glaucoma.

PURPOSE: To evaluate the safety and efficacy of laser trabeculoplasty (LTP) with a semiconductor diode laser (810 nm, [DLT]) vs an argon blue-green laser (488 to 514 nm, [ALT]). METHODS: In a prospective, randomized clinical trial, 50 eyes of 46 patients with uncontrolled open-angle glaucoma on maximally tolerated medical therapy were treated and followed at regular intervals for 5 years. Fifty laser spots were applied over 180 degrees using either maximal laser power or sufficient power to produce blanching or a small bubble (570 to 850 mW, DLT; 400 to 1,100 mW, ALT). We performed DLT using a 100-microm spot size, a 0.5-second exposure, and a Ritch lens; we conducted ALT with a 50-microm spot, a 0.1-second exposure, and a Goldmann lens. Patients in the study were followed until trabeculectomy was required. RESULTS: The mean follow-up times +/- SD for all eyes were 38.6 +/- 5.4 months, DLT (n = 22; range, 1 to 68 months) and 35.5 +/- 4.8 months, ALT (n = 28; range, 1 to 66 months). Those in the diode laser group (n = 16) who had more than 1 year of follow-up were tracked for 49.4 months, and those in the argon laser group (n = 21) were tracked for 45.8 months. There were no significant differences in the mean pretreatment intraocular pressures (IOPs): 21.2 mm Hg, DLT (n = 22) and 21.5, ALT 21.5 mm Hg (n = 28); P = .81] or in mean final IOPs (15.7 mm Hg, DLT and 17.1 mm Hg, ALT; P = .19). Time to surgical failure showed no significant differences, with 50% of the DLT eyes and 58% of the ALT eyes surviving at 5 years (P = .59). CONCLUSION: In eyes with open-angle glaucoma and unsatisfactory IOP control on maximally tolerated medical therapy, DLT and ALT are equally effective in lowering IOP over a 5-year period.

Teaching doctors about the eye: trends in the education of medical students and primary care residents.

Ophthalmologists play a relatively peripheral role in medical student and resident education. A review of the evolution, funding, and administration of medical education in the United States lends insight into why this is so. The author reviews the current status of education in ophthalmology for medical students and residents; the development of an ophthalmology curriculum; alternatives to the traditional medical school curriculum and how these have been incorporated into ophthalmic education; and the effect of new trends in medical education and pressures created by health care reform on the education of medical students and residents. The role of ophthalmologists in the general practice of medicine and in teaching doctors about the eye is discussed. Finally, the opportunity that the current climate presents for ophthalmologists to define their role in health care through education is considered.

Acute uveitis associated with rifabutin use in patients with human immunodeficiency virus infection.

PURPOSE: We studied patients with a new anterior uveitis syndrome associated with rifabutin use. METHODS: Nine patients with the acquired immunodeficiency syndrome (AIDS) who developed acute anterior uveitis were identified retrospectively from institutional ophthalmology, infectious disease, and AIDS primary care practices. Five patients initially had hypopyon; in three patients hypopyon was bilateral and recurrent. The medical history, initial signs and symptoms, diagnostic examination, clinical course, and response to therapy were ascertained by a review of the medical records. RESULTS: All nine patients were being treated with rifabutin for treatment of, or prophylaxis against, Mycobacterium avium complex. In no patient was another untreated cause of uveitis found. In each patient the uveitis resolved rapidly without sequelae with treatment with topical corticosteroids alone. In eight patients uveitis resolved completely while treatment or prophylaxis for M. avium complex was maintained. CONCLUSIONS: We studied a new hypopyon uveitis syndrome in patients with AIDS who are being treated with rifabutin. The interaction of multiple drugs may contribute to this uveitis syndrome. This uveitis is remarkable because it is fulminant yet responds rapidly to topical corticosteroids. Characterization of this syndrome is important because hypopyon in the immunocompromised patient generally mandates intensive, and sometimes invasive, ophthalmic and systemic examination and therapy. Additional study is required to determine whether immune status, underlying infection, or drug-related factors contribute to the development of this uveitis syndrome. Although this syndrome remains a diagnosis of exclusion, ophthalmologists must be aware of it, so that intervention is guided appropriately.

Menkes kinky hair disease: characteristic MR angiographic findings.

We report two cases of Menkes kinky hair disease in which MR and MR angiography were performed. The clinical and imaging features are reviewed. MR demonstrated characteristic cerebrovascular tortuousity and thus may be a valuable aid in diagnosis and follow-up.

Factors limiting the postnatal development of visual acuity in the monkey.

A major factor underlying the prolonged postnatal improvement of visual acuity in primates is an increase in the sampling limit imposed by the photoreceptor mosaic, which may be as much as 5-fold. Further factors operating peripheral to neurons of the lateral geniculate nucleus, which might include changes in neural connectivity, appear to contribute at most 1.5 octaves, between 3 weeks and 6 months of age. Neural factors at the geniculo-cortical synapse may add another half-octave between 10 weeks and 1 yr. Factors operating after the level of the striate cortex (changes in spatial degradation, attention, motivation, etc.) contribute up to another octave or more to the increase in behavioural acuity between birth and about 11 weeks of age. The foveal image is substantially undersampled in young animals and therefore aliasing could occur over a wide range of spatial frequencies.

The postnatal reduction of the uncrossed projection from the nasal retina in the cat.

We have investigated the postnatal reduction of the uncrossed projection from the nasal retina in the cat by injecting horseradish peroxidase into one optic tract of kittens and cats and retrogradely labeling the cells in the ipsilateral retina that have an uncrossed projection to the brain. The newborn kitten has over 600 uncrossed cells in the nasal retina. The number is reduced to about one-quarter of that value by postnatal day 10. The two adult cats examined had 75 and 100 of these ipsilaterally projecting nasal cells. They are distributed all across the nasal retina, and most have the morphology characteristic of gamma cells. A lesion in one optic tract in the newborn kitten results in an increase in the number of cells from the nasal retina with an ipsilateral projection at maturity. There are more of these cells in the region that has been depleted of ganglion cells by the lesion. This excess consists mostly of gamma and epsilon cells. These findings indicate that competitive factors play a role in the elimination of inappropriate ganglion cell projections in the cat, and that this process contributes to the precision of the nasotemporal division of the retina.

A syphilis epidemic in a northern territory Aboriginal community.

An epidemic of syphilis in an Australian Aboriginal community with no previous experience of the disease is described. Syphilis was diagnosed in 214 cases during the five-year period 1975 to 1979 inclusive. The epidemic was controlled by an intensive programme based on active case detection by serological screening and community education, implemented through the local community health centre.

Listeria monocytogenes. Macroabscesses of placenta.

Macroabscesses of placenta caused by Listeria monocytogenes were observed in a 37-year-old febrile primigravida. She was prematurely delivered of a depressed 2310-g infant, who was resuscitated and promptly treated with antibiotics. Mother and child are well at 10-year followup. Although perinatal listeriosis with placentitis is not rare, its presentation as macroabscesses of the placenta has until now gone unreported in the English language literature.

Syphilis in Australian aborigines in the northern territory.

A marked increase in the incidence of syphilis in Australian Aborigines in the Northern Territory has occurred in recent years. A total of 287 syphilis notifications relating to Aborigines in the north west of the Northern Territory during the 12-month period from June, 1976, to May, 1977, are analysed. An outline of how the Northern Territory Medical Service plans to deal with the situation is described.

Clinical significance of the isomorphic pattern of the isoenzymes of serum lactate dehydrogenase.

Five hundred patients with the isomorphic pattern of the isoenzymes of serum lactate dehydrogenase (LDH) were surveyed. The isomorphic pattern of LDH isoenzymes is defined as a significant increase of total LDH with normal or low percentage of individual fractions, but with the LDH1:2 ratio less than unity. Diagnoses were, in descending order of frequency, cardiorespiratory diseases, malignancy, fracture, diseases of the central nervous system, infection/inflammation, hepatic cirrhosis and/or alcoholism, trauma without fracture, infectious mononucleosis, hypothyroidism, uremia, necrosis, pseudomononucleosis, viremia and intestinal obstruction. Incidence of increased serum activity in individuals without evidence of disease or drug explanation was 3 percent. Low PaO2 was observed in 88 percent of the 67 patients in whom it was measured.