Visual behavior of adult goldfish with regenerating retina

To determine whether regenerating neural pathways can support visual behavior, adult goldfish (Carassius auratus) were injected intraocularly with ouabain and tested for the presence of reflexive visual behaviors (dorsal light reflex and optokinetic nystagmus) and the ability to respond to visual stimuli in a classical conditioning paradigm. All visual behaviors were absent or greatly diminished until 8 to 10 weeks, when retinal layering had returned. At 10 weeks post-ouabain, reflexive behaviors to supra-threshold stimuli were near normal; however the ability to detect supra-threshold stimuli in the conditioning paradigm did not recover until 13 weeks. Absolute dark-adapted threshold and light-adapted spectral sensitivity measured at 13 to 17 weeks were abnormal: Dark-adapted threshold was elevated by 1.5 log units and light-adapted spectral sensitivity was markedly narrower than normal. No responses to 50% contrast sinusoidal gratings could be obtained through ouabain-treated eyes using the classical conditioning technique, even though responses through the untreated eye remained. Results demonstrate that: (a) visually mediated behaviors return in goldfish with ouabain-treated retinas; (b) the time course of recovery of reflexive responses in luminance and spatial domains parallels return of ERG function and of tectal activity; and (c) visual function that is mediated by regenerating retina appears not to be as sensitive as vision via normally developed retinal pathways.

[Membrane cholesterol and insulin receptor in erythrocytes]

The author studied influence of membrane cholesterol on insulin receptor behavior using human erythrocytes after modification of their membrane cholesterol contents. Insulin binding to the erythrocytes containing higher membrane cholesterol which were obtained from alcoholic liver cirrhosis (ALC) and familial lecithin: cholesterol acyl transferase (LCAT) deficiency patients was also examined. 1) Influence of modified membrane cholesterol contents on insulin binding to erythrocytes (in vitro experiments): The cholesterol content of human erythrocyte membranes was modified by incubating the cells with phosphatidylcholine/cholesterol and phosphatidylcholine vesicles. Then insulin binding to the erythrocytes was measured as a function of membrane cholesterol content. Low membrane cholesterol decreased insulin binding at 10 degrees C and 15 degrees C, but increased insulin binding at 25 degrees C and 37 degrees C. Scatchard plot analysis showed that low membrane cholesterol decreased a number of the receptor without alteration of affinity. Phosphatidylcholine spin probe showed a dual effect of cholesterol on membrane fluidity, fluidizing below but rigidifying membranes above 20 degrees C. It is suggested that membrane cholesterol affects insulin receptor behavior through alteration of membrane fluidity, depending on the phase state of the membranes. 2) Insulin binding and membrane lipid composition of erythrocytes from ALC and LCAT deficiency patients: The erythrocytes from both ALC and LCAT deficiency patients are known to have higher content of membrane cholesterol. Insulin binding and membrane lipid composition of erythrocytes in both diseases were measured to see the influence of cholesterol on insulin binding in sites. a) Erythrocytes from ALC patients: In the erythrocytes from ALC patients, cholesterol to phospholipid molar ratio was significantly increased as compared with normal subjects. In phospholipid acyl chains, contents of polyunsaturated fatty acid significantly decreased in ALC patients. Insulin binding to erythrocytes was significantly increased in the patients of ALC. Scatchard plot analysis (at 15 degrees C) showed significant increase of the receptor number in erythrocytes from the ALC patients as compared to the normal subjects, while the affinity did not differ between the groups. The increased cholesterol content in the erythrocyte membranes was suggested to be responsible for the increased receptor number and insulin binding to the erythrocytes from ALC patients. b) Erythrocytes from LCAT deficiency patients: Membrane cholesterol to phospholipid molar ratio was increased in two patients of LCAT deficiency studied. In phospholipid classes, increase of phosphatidylcholine and decreases of both phosphatidylethanolamine and sphingomyelin were observed in the erythrocytes from both patients.(ABSTRACT TRUNCATED AT 400 WORDS)

Thrombin binding and response in platelets from patients with dyslipoproteinemias: increased stimulus-response coupling in type II hyperlipoproteinemia

Platelets were obtained from patients with various hyperlipidemias [type II, type V, lecithin-cholesterol acyltransferase (LCAT) deficiency] and hypolipidemias (abetalipoproteinemia, Tangier disease) to ascertain relationships among plasma lipids, platelet lipids, thrombin binding and thrombin-induced platelet aggregation, and to compare these data with those previously obtained on stimulus-response coupling in platelets following in vitro modification of membrane microviscosity. Washed platelets were studied for their ability to bind 125I-thrombin in the range of 10(-10) to 10(-6) mol/L (10 mU/mL to 100 U/mL) and to aggregate with thrombin at concentrations less than 10(-9) mol/L (100 mU/mL). The values for binding and aggregation in eight patients from six kindred with familial hypercholesterolemia, taken as a group, fell in the low normal range. If divided into two groups, patients with overt cardiovascular disease bound normal amounts of thrombin but were more responsive to it, whereas patients without overt cardiovascular disease bound lower amounts of thrombin but gave an aggregation response in the normal range. These results suggest that platelet hyperresponsiveness in familial hypercholesterolemia arises from an alteration in the coupling mechanism between thrombin binding and response such that platelets from patients with familial hypercholesterolemia are able to respond with lower receptor occupancy than is the case with normal platelets. Thrombin binding and aggregation were within normal ranges for platelets from abetalipoproteinemia patients (N = 4) and type V hyperlipoproteinemia (N = 2), although in the latter case the response appeared to be less at very low thrombin concentrations (less than 30 mU/mL). Thrombin binding was elevated in Tangier disease (N = 3) but with lower responsiveness at lower thrombin concentrations. Thrombin binding was also elevated in LCAT deficiency (N = 2), and one patient showed increased and another showed decreased aggregation responses. In general, increased plasma cholesterol levels resulted in increased stimulus-response coupling (type II), whereas increased triglyceride levels resulted in decreased coupling (type V, Tangier), and there was no apparent alteration in the coupling mechanism with overall reduction in plasma lipid levels as in abetalipoproteinemia.

Corneal opacification and lecithin-cholesterol acyltransferase (LCAT) deficiency: a case report

Bilateral corneal opacities are the first clinical sign of a familial lecithin-cholesterol acyltransferase (LCAT) deficiency and can be found in early childhood. Familial LCAT deficiency includes the following typical clinical findings: corneal opacification, proteinuria, anemia, turbid or milky plasma, very low plasma HDL, very low plasma cholesterol esters and lysolecithin, hyperlipidemia, and very low or absent LCAT enzymatic activity. Several patients have had fundus findings including angioid streaks and papilledema. This disease is autosomal recessive and has been reported in a total of 19 patients previously. Progression of the disease has resulted in premature atherosclerosis, renal failure and transplantation, decreasing visual acuity and corneal transplantation.

Decreased sodium influx and abnormal red cell membrane lipids in a patient with familial plasma lecithin: cholesterol acyltransferase deficiency

Red cell membrane metabolism in familial lecithin:cholesterol acyltransferase (LCAT) deficiency was investigated. The family presented here is the third case discovered in Japan. An increase of free cholesterol was observed in the red cell membranes, concomitant with increased phosphatidyl choline. Osmotic fragility of the patient's red cells was diminished rather than increased. Red cell survival (51Cr T1/2) was shortened (15 days). Sodium influx was markedly decreased, although sodium efflux, both ouabain-sensitive and ouabain-insensitive, was normal. The activity of acetyl-cholinesterase as a marker of the outer leaflet of the red cell membranes was decreased, while the activity of glyceraldehyde-3-phosphate dehydrogenase as a marker of the inner leaflet was normal. No abnormalities of adenosine triphosphatases in red cell membranes were observed. These results suggest that the alteration of cholesterol metabolism in the plasma of LCAT deficiency increases the red cell membrane cholesterol and affects the functions of the red cell membranes, especially of the outer leaflet, which may result in decreased sodium influx.

Abnormalities in lipoproteins of d < 1.006 g/ml in familial lecithin:cholesterol acyltransferase deficiency

Studies of different sized lipoproteins of d < 1.006 g/ml from patients with familial lecithin:cholesterol acyltransferase deficiency have yielded new evidence of abnormalities in this lipoprotein class. Lipoproteins of all sizes contain high amounts of unesterified cholesterol, low amounts of total protein, and particularly low amounts of apolipoproteins C-II and C-III. Lipoproteins 60 nm in diameter or larger include particles that show a notched appearance upon electron microscopy, and contain a) a high combined volume of phospholipid, unesterified cholesterol, and protein; b) high amounts of cholesteryl ester and apolipoproteins C-I and E, and c) two major tetramethylurea-insoluble proteins that can be separated by electrophoresis in the presence of sodium dodecylsulfate. In contrast, lipoproteins that are 40 nm in diameter or less appear to contain low amounts of cholesteryl ester, normal amounts of apolipoproteins C-I and E, and a single tetramethylurea-insoluble protein the size of that in control lipoproteins. Since these abnormalities occur in the lipoproteins of four different patients from four different families, they are probably effects of the enzyme deficiency. Most, however, appear to arise indirectly because in vitro experiments published earlier indicate that few are reversed by incubation in the presence of the enzyme and patient high density lipoproteins.