Field sensitivity action spectra of cone photoreceptors in the turtle retina.

1. The Stiles two-colour increment threshold technique was applied to turtle cone photoreceptors in order to derive their field sensitivity action spectra. 2. Photoresponses of cone photoreceptors were recorded intracellularly. Flash sensitivities were calculated from small amplitude (< 1 mV) responses. The desensitizing effects of backgrounds of different wavelengths were measured and the background irradiance needed to desensitize the cone by a factor of 10 (1 log unit) was defined as threshold. The reciprocals of these thresholds were used to construct the field sensitivity action spectrum. 3. The field sensitivity action spectra of long-wavelength-sensitive (L) and medium-wavelength-sensitive (M) cones depended upon the wavelength of the test flash used to measure them. This excludes the possibility that turtle cones can function as single-colour mechanisms in the Stiles sense. 4. In fourteen L-cones, the average wavelength of peak sensitivity of the field sensitivity action spectrum was 613.7 +/- 7.7 nm for the 500 nm test and 635.6 +/- 9.6 nm for the 700 nm test. For six M-cones, these values were 558.5 +/- 6.8 and 628.8 +/- 10.6 nm for the 500 and 700 nm tests, respectively. 5. Two physiological mechanisms are suggested as contributing to the dependency of the field sensitivity action spectrum upon test wavelength. One is based upon the transmissivity properties of the coloured oil droplets, while the other hypothesizes excitatory interactions between cones of different spectral type. 6. Computer simulations of the field sensitivity action spectra indicate that both mechanisms are needed in order to account for the dependency of the field sensitivity action spectrum upon the wavelength of the test flash.

Gender risk for anaphylactoid reaction to radiographic contrast media.

BACKGROUND: Female predominance has been reported previously in series of anaphylaxis cases; however, no definite precedent has been established for greater risk of anaphylactoid reaction caused by contrast media infusion on the basis of gender. OBJECTIVE: This study was designed to determine whether greater risk for anaphylactoid reaction caused by intravenous contrast media infusion exists in association with female gender. METHODS: Rates of anaphylactoid and severe anaphylactoid reaction, according to gender, were determined in a sample of 5264 consecutive patients receiving conventional radiocontrast media during performance of computed tomography. RESULTS: Of 80 adverse reactions caused by contrast media infusion, 73 (1.39%) were classified as anaphylactoid in nature. Among 5191 patients who received intravenous contrast media without experiencing an anaphylactoid reaction, there were 2642 male patients (51%) and 2549 female patients (49%); reactors included 22 male patients and 51 female patients (odds ratio = 2.40, 95% confidence interval = 1.42-4.10, p < 0.0005). Female patients also comprised 21 of 22 cases of severe anaphylactoid reaction (odds ratio = 21.77, 95% confidence interval = 3.13-435.12, p < 0.0005). CONCLUSION: Greater risk for anaphylactoid and severe anaphylactoid reaction exists in association with female gender. Further studies are needed to identify mechanisms that can explain this risk. The importance of these findings for cost-effective use of lower osmolality contrast media need to be determined.

Abdominal aortic aneurysms: CT evaluation of renal artery involvement.

PURPOSE: To determine whether computed tomography (CT) assessment of the proximal extent of ruptured aneurysms can help the surgeon determine whether to initially clamp the pararenal aneurysm neck or the supraceliac aorta. MATERIALS AND METHODS: CT scans and medical records were reviewed and compared for 30 patients with ruptured abdominal aortic aneurysms (AAAs) who underwent immediate surgical repair. RESULTS: For 49 of 50 vessels in 25 patients, the authors correctly predicted at CT that AAAs originated caudal to the main renal artery origins. They also predicted that nine main renal arteries in five patients originated directly from the AAAs, but this was correct in only five arteries. Suprarenal clamping was required in all five patients. Infrarenal clamps were used before reconstruction in all 12 of the patients whose AAAs appeared to originate at least 30 mm below the main renal arteries. CONCLUSION: CT can help predict whether an initial aortic clamp can be placed caudal to the main renal artery orifices. Its use can be predicted with 100% certainty only when an aneurysm appears to originate at least 3 cm caudal to the origin of the main renal artery.

Dark-light: model for nightblindness from the human rhodopsin Gly-90-->Asp mutation.

A human rhodopsin mutation, Gly-90-->Asp (Gly90Asp), cosegregated with an unusual trait of congenital nightblindness in 22 at-risk members of a large autosomal dominant kindred. Although rhodopsin mutations typically are associated with retinal degeneration, Gly90Asp-affected subjects up to age 33 did not show clinical retinal changes. Absolute threshold for visual perception was elevated nearly 3 logarithmic units in 7 individuals tested (ages 11-64), indicating greatly compromised rod threshold signaling. However, in vivo rhodopsin density was normal. Although the 38-year-old proband could not perceive dim lights, his rod increment threshold function was normal on brighter backgrounds. The impaired rod vision for dim but not bright backgrounds is consistent with a mechanism of increased basal "dark-light" from thermal isomerization equivalent to an increase of > 10(4) over that of wild-type rhodopsin. The Gly90Asp mutation on the second transmembrane helix places an extra negative charge in the opsin pocket; this could contribute to partial deprotonation of the retinal Schiff base and thereby increase photoreceptor noise. In vitro evidence had suggested that transducin is activated by the Gly90Asp mutation in the absence of both the retinal chromophore and light, termed "constitutive activity." The apparent preservation of functioning rods despite extensive and lifelong night-blindness in this kindred is inconsistent with one current hypothesis that chronic rod activation from constitutively active mutant rhodopsin necessarily contributes significantly to photoreceptor demise in human retinal dystrophies.

Abdominal aortic aneurysm morphology: CT features in patients with ruptured and nonruptured aneurysms.

OBJECTIVE: We evaluated a variety of internal architectural features in ruptured and nonruptured abdominal aortic aneurysms to determine whether any features are associated more frequently with ruptured abdominal aortic aneurysms. These features may be useful in identifying subtle ruptures when no obvious retroperitoneal hematoma is present and may be helpful in predicting unstable aneurysms at risk for rupture. MATERIALS AND METHODS: The CT scans of 52 patients with ruptured abdominal aortic aneurysms were reviewed and compared with those of 56 patients with asymptomatic nonruptured aneurysms exceeding 4.5 cm in diameter. All aneurysms were evaluated for size, rim calcification, thrombus amount, thrombus calcification, and lumen irregularity. In addition, four different thrombus patterns were identified and evaluated, including homogeneous, diffusely heterogeneous, periluminal halo, and crescent patterns. Statistical comparisons were adjusted for differences in size between the two groups. RESULTS: Age, gender, and aneurysm length were not statistically different between the two groups. A larger diameter was found in the ruptured aneurysm group: 7.4 (anteroposterior) x 7.9 (transverse) cm versus 5.9 x 6.1 cm (p = .00001). More thrombus surrounded the nonruptured aneurysms (p = .014). Thrombus calcification was seen in 25% (14/56) of the control group and in 13% (7/52) of the rupture group (p = .01). Two thrombus patterns, homogeneous and periluminal halo, were encountered with similar frequencies in both groups. The diffusely heterogeneous pattern was seen more in the control group. A crescent of increased attenuation was encountered only in patients with ruptured aneurysms, at an incidence of 21% (11/52) (p = .0005). Thick and thin wall calcifications were seen in both groups, but a focal discontinuity in circumferential calcification was seen only in association with ruptured aneurysms, at an incidence of 8% (4/52) (p = .008). There was no significant difference in the number of patients whose patent lumen was irregular. CONCLUSION: In our series, detection of a high-attenuation crescent or focal gap of otherwise circumferential wall calcification is associated with aneurysm rupture. The homogeneous, diffusely heterogeneous, and periluminal halo patterns are not specifically associated with aortic rupture. There were no significant differences in the amount of wall calcification or frequency of lumenal irregularity between patients with ruptured and those with nonruptured aneurysms.

The action spectra of cone photoreceptors in the turtle (Mauremys caspica) retina.

Cone photoreceptors in the turtle retina are involved in intricate neuronal interactions with other retinal neurons that modify the responses of the cones to photons absorbed in their outer segments. Therefore, the action spectra of cones strongly depend upon the conditions of measurements. This study describes an attempt to derive the action spectra of turtle cones which are the least distorted by neuronal interactions. To achieve this goal, the photoresponses of cones and horizontal cells were recorded from the turtle retina under different conditions of adaptation using different patterns of the stimulating test flashes. The sensitivity action spectra, derived from small-amplitude (<1 mV) photoresponses, were strongly affected by the recording conditions indicating the contributions of multiple neuronal inputs. Action spectra, constructed from large criterion photoresponses, were less distorted by neuronal interactions and better described the spectral properties of the "isolated" cones. The action spectra of the hyperpolarizing inputs to chromaticity-type horizontal cells were derived by stimulating these cells with mixtures of a saturating red light and a monochromatic light of different wavelength and intensity. The action spectra were constructed from the intensity of the addend component needed to "pull down" the depolarizing response to the red component by a fixed criterion. These spectra, measured in red/green and yellow/blue C-type horizontal cells, are suggested to best represent the "isolated" M-cones and S-cones, respectively.

Chromosomal rearrangement segregating with adrenoleukodystrophy: a molecular analysis.

The relationship between X chromosome-linked adrenoleukodystrophy and the red/green color pigment gene cluster on Xq28 was investigated in a large kindred. The DNA in a hemizygous male showed altered restriction fragment sizes compatible with at least a deletion extending from the 5' end of the color pigment genes. Segregation analysis using a DNA probe within the color pigment gene cluster showed significant linkage with adrenoleukodystrophy (logarithm of odds score of 3.19 at theta = 0.0). These data demonstrate linkage, rather than association, between a unique molecular rearrangement in the color pigment gene cluster and adrenoleukodystrophy. The DNA changes in this region are thus likely to be helpful for determining the location and identity of the responsible gene.

Chromosomal rearrangement segregating with adrenoleukodystrophy: associated changes in color vision.

A patient from a large kindred with adrenoleukodystrophy showed profound disturbance of color ordering, color matching, increment thresholds, and luminosity. Except for color matching, his performance was similar to blue-cone "monochromacy," an X chromosome-linked recessive retinal dystrophy in which color vision is dichromatic, mediated by the visual pigments of rods and short-wave-sensitive cones. Color matching, however, indicated that an abnormal rudimentary visual pigment was also present. This may reflect the presence of a recombinant visual pigment protein or altered regulation of residual pigment genes, due to DNA changes--deletion of the long-wave pigment gene and reorganized sequences 5' to the pigment gene cluster--that segregate with the metabolic defect in this kindred.

Elevated risk of anaphylactoid reaction from radiographic contrast media is associated with both beta-blocker exposure and cardiovascular disorders.

BACKGROUND: A case-control study, with both retrospective and concurrent subject selection, was performed (1) to determine whether greater risk for anaphylactoid reaction from contrast media associated with beta-blocker exposure reflects presence, or is independent of underlying cardiovascular disorder; and (2) to characterize further the risk of anaphylactoid reaction from contrast media in patients with cardiovascular disorders and patients with asthma. METHODS: Adverse reactions from intravenous contrast media were recorded in accordance with quality assurance guidelines. Anaphylactoid reactions were classified as mild to moderate (urticaria/angioedema), severe (stridor, bronchospasm, or hypotension), or major and life-threatening (hypotension with or without the need for subsequent hospitalization). Medical records from reactors were compared with those from matched (gender, age, date, and type of contrast study) controls who received conventional contrast media without adverse reaction. RESULTS: Of 34,371 intravenous contrast media procedures performed, 122 anaphylactoid reactions were recorded. The risk of anaphylactoid reaction was significantly associated with asthma (odds ratio [OR], 8.74; 95% confidence interval [CI], 2.36 to 32.35; P = .0012). The risk of bronchospasm was associated with beta-blocker exposure (OR, 3.73; 95% CI, 1.18 to 11.75; P = .025) and with asthma (OR, 16.39; 95% CI, 4.30 to 62.46; P = .0001). The risk of major and life-threatening reaction was associated with the presence of cardiovascular disorder (OR, 7.71; 95% CI, 1.04 to 57.23; P = .046). Among patients with severe reactions, the risk of hospitalization was elevated by the presence of cardiovascular disorder (P = .001), exposure to beta-blockers (OR, 7.67; 95% CI, 1.79 to 32.85; P = .029), or asthma (OR, 20.7; 95% CI, 1.21 to 355.55; P = .065). Although beta-blocker exposure and the presence of cardiovascular disorder were highly associated (chi 2 = 49, P < .001), a greater risk of bronchospasm with severe reaction was observed in nonasthmatic patients with cardiovascular disorders receiving beta-blockers (OR, 15.75; P = .023). Among reactors with asthma, receiving beta-blockers, or with a cardiovascular disorder, 60.8% (31/51) experienced severe anaphylactoid reactions, compared with 35.2% (25/71) of patients without these risk factors (OR, 3.62; P = .005). CONCLUSIONS: beta-Blocker exposure and cardiovascular disorder are both statistically significant risk factors for severe anaphylactoid reaction from contrast media. Thus, patients receiving beta-adrenergic blockers and patients with asthma, on the basis of greater risk for bronchospasm, and patients with cardiovascular disorders, on the basis of elevated risk of major and life-threatening reaction, are appropriate target populations for risk reduction measures before receiving intravenous infusion of contrast media.

TMJ biocompatible orthodontic treatment.

The papers summarized here indicate that TMJ dysfunction remains a complicated problem, requiring a multidisciplinary team approach. Psychological stress is an important factor in diagnosis. New concepts of joint function must be considered. The functional anatomy of the TMJ from an arthroscopic perspective should be studied. New treatment methods, such as the polycentric hinge joint articulator, should be considered. And finally, orthodontic diagnosis and treatment conventions need to be modified, from obtaining a complete history, clinical examination, arriving at a diagnosis and obtaining informed consent for treatment that may include psychological counseling, splint therapy, simultaneous fixed orthodontics and splint therapy and possible TMJ arthroscopic surgery for nearly all orthodontic patients.

Increased risk for anaphylactoid reaction from contrast media in patients on beta-adrenergic blockers or with asthma.

OBJECTIVE: To determine whether greater risk for anaphylactoid reaction from intravenous urographic contrast media exists in patients receiving beta-adrenergic blockers or in asthmatic patients. DESIGN: Case-control study. SETTING: Tertiary care, referral-based medical center. PATIENTS: Of 28,978 intravenous urographic contrast media procedures done from July 1987 to June 1988, 49 patients experienced moderate to severe anaphylactoid reaction. Medical records from these 49 reactors were compared with those from a control group matched for gender, age, and date and type of contrast study who received intravenous urographic contrast media without adverse reaction. MAIN RESULTS: Patients exposed to beta-adrenergic blockers or with asthma comprised 39% (19 of 49) of reactors, compared to 16% (13 of 83) of matched controls (odds ratio, 3.43; 95% CI, 1.45 to 8.15; P = 0.005). Exposure to beta-blockers was 27% among reactors and 12% in matched controls (odds ratio, 2.67; CI, 1.01 to 7.05; P = 0.036). Asthma was found in 12% of reactors and 4% of controls; after correction for beta-blocker use, asthma was also associated with increased risk for anaphylactoid reaction (odds ratio, 4.54; CI, 1.03 to 20.05; P = 0.046). Compared with nonasthmatic patients not taking beta-blockers, asthmatic patients were at greater risk for anaphylactoid reaction with bronchospasm (P = 0.02). Five of 13 reactors receiving beta-blockers became hypotensive, and three needed hospitalization. Compared with nonasthmatic patients not taking beta-blockers, patients exposed to beta-blocking drugs were almost nine times (odds ratio, 8.7; CI, 0.81 to 93.5; P = 0.075) more likely to be hospitalized after an anaphylactoid reaction. CONCLUSION: Increased risk for moderate to severe anaphylactoid reaction from intravenous urographic contrast media exists in patients receiving beta-adrenergic blockers or with asthma. These patients are appropriate target populations for efforts to reduce risk before intravenous urographic contrast media are administered.

Upper abdominal lymph nodes: criteria for normal size determined with CT.

Reports of the upper limits of normal for lymph node size at abdominal computed tomography have varied from 6 to 20 mm. Establishment of an upper limit for node size by specific location, analogous to that which has been reported for mediastinal lymph nodes, was sought. Short-axis diameters of the lymph nodes were measured in 130 patients who were not likely to have enlarged abdominal lymph nodes. Seven locations were defined, and the largest nodal measurement for each was recorded. Histographic analysis and nonparametric statistical methods were used to determine threshold values for the maximum node size in each region. The upper limits of normal by location were as follows: retrocrural space, 6 mm; paracardiac, 8 mm; gastrohepatic ligament, 8 mm; upper paraaortic region, 9 mm; portacaval space, 10 mm; porta hepatis, 7 mm; and lower paraaortic region, 11 mm. Lower paraaortic lymph nodes larger than 11 mm by short-axis measurement are abnormal. In other locations, nodes smaller than 1 cm may be abnormal if the determined thresholds are exceeded.

Seminal vesicle cysts: association with adult polycystic kidney disease.

Adult polycystic kidney disease (APKD) is associated with cyst formation in the kidney, liver, pancreas, esophagus, ovary, uterus, and brain. Four patients with APKD (aged 45-65 years) with computed tomographic evidence of seminal vesicle cysts are described. All seminal vesicles contained cystic masses with attenuation values of 0-30 HU. Seminal vesicle thickness was 3-4 cm (normal, 1.5 cm). High-attenuation walls separated the cysts, which were 3-35 mm in diameter. All patients had typical renal stigmata of APKD. None had cysts elsewhere, except one patient with hepatic cysts. Postmortem examination in one patient confirmed the seminal vesicle cysts as well as APKD. It is likely that a basement membrane defect allows cyst formation in multiple organs, presumably including the seminal vesicles. Because of the association of seminal vesicle cysts with ipsilateral urogenital anomalies, and because only 60% of patients with APKD have a relevant familial history, the kidneys of patients with cross-sectional imaging evidence of seminal vesicle cysts should also be studied.

The change in the neutral point of dichromats with change in the angle of incidence of monochromatic light on the retina.

The hypothesis was tested that the change in the perceived color of monochromatic light with change in its angle of incidence on the retina can be accounted for completely by prereceptor factors alone. This was evaluated by measuring the change in the match of a monochromatic light to a fixed (and normally incident) white light as the monochromatic beam changed its traverse through the eye from chief ray to "off-axis" retina incidence at the margin of the exit pupil. Two protanopes and four deuteranopes were tested. In each case, the wavelength of the chief ray at the match was consistently, reliably, and (statistically) significantly larger than that of the match with the "off-axis" beam. The result cannot be accounted for by prereceptor factors alone.