Trichinella spiralis: nonspecific resistance and immunity to newborn larvae in inbred mice

The implantation and development of intravenously injected Trichinella spiralis newborn larvae were examined in different strains of inbred mice by determining muscle larvae burden. This was compared to the numbers of muscle larvae that established after a natural infection during which a quantitative assessment of intestinal newborn larvae production was made. In most inbred strains of mice, newborn larvae do not all successfully implant in muscle. Mice of the DBA/1 strain are the most resistant to successful implantation, and C3H mice are the most permissive. This pattern is evident in the strains studied whether newborn larvae are injected intravenously or are produced by intestinal adults. Thus, after a natural infection, 100% of intestinally produced newborn larvae implanted in C3H mice, whereas in NFR 68% and DBA/1 mice 62% successfully matured in muscle. Immunity to newborn larvae could be demonstrated as early as 10 days after exposure to this stage of the life cycle. This immunity was protective against a complete challenge infection given 9 days after newborn larvae had been injected intravenously. Protection against newborn larvae was identical in male and female mice or in mice from 1 to 9 months of age. We conclude that there are two mechanisms by which mice impair newborn larvae establishment or development in muscle. The first appears to be nonimmunological (non-specific resistance), and the second is immunological. Genetically determined variation in strain-specific expression is apparent with both mechanisms. In strains displaying high intrinsic "resistance" (DBA/1), this process is likely to account for most of the 38% reduction in newborn larvae establishment in a primary infection. However, immunity against newborn larvae develops quickly enough to have a significant effect on migratory larvae in primary infections where adults persist in the intestine (e.g., the B10 congenic mice), or when high adult worm burdens delay adult worm rejection. Muscle larvae burden, therefore, reflects systemic nonspecific resistance to newborn larvae as well as immunological processes that occur in the intestine and systemically.

Genetic considerations in the effects of ethanol in mice. I. Genotype-dependent alterations in alcohol dehydrogenase activity

Most genetic studies on individual and racial differences in sensitivity to alcohol intoxication have concentrated on genetic variations associated with structural genes for the enzymes involved in alcohol metabolism, including alcohol dehydrogenase (ADH; E.C. 1.1.1.1). We studied the ethanol-induced regulation of ADH following chronic administration of ethanol in mice. Newly weaned males from six inbred strains (BALB/c, C3H/HeSnJ, C3H/S, C57BL/6J, S.W., and 129/ReJ) were subjected to ethanol administration. Alterations in the level of liver ADH activity, relative to matched littermate controls, were evaluated. The change in ADH activity was found to be strain (genotype) specific, which may explain the contradictory results in the literature. Strains which showed induction of ADH activity, in general, reflected a strain-specific time-dependent profile. Strains which showed repression, however, were independent in the degree of repression to the duration of ethanol exposure. Such variable, ethanol-induced regulatory responses (induction/repression) in ADH activity of different genotypes may account for individual and population variations in response to alcohol. Additional work, however, is needed to establish the molecular bases of ADH inducibility and its specific role in relative susceptibility to alcohols.

Changes in brain alpha-adrenergic receptors after alpha-methyldopa administration to spontaneously hypertensive rats

The hypotensive action of methyldopa has been linked to production of the metabolites methyldopamine and methylnorepinephrine in brain. We have studied the effect of long-term (72 hour) intravenous infusions of methyldopa to awake restrained spontaneously hypertensive rats and normotensive Wistar-Kyoto control animals to look for differences in hypotensive effect, differences in concentrations of natural and alpha-methylated catecholamines, and differences in alpha 1 and alpha 2-adrenergic receptor populations. Results described here indicate that hypertensive rats have a greater reduction in blood pressure and a larger increase in hypothalamic and brain stem methylnorepinephrine concentrations than do the normotensive animals. The methylnorepinephrine concentration reached a plateau value in hypothalamus in both strains while pons and medulla showed progressive, dose-related increases in concentration. These regional and strain differences in the metabolism of alpha-methyldopa suggest that the production of methylnorepinephrine in brain stem nuclei is most correlated with the hypotensive action of methyldopa. alpha 2 Agonist binding (p-amino-clonidine) declined in both hypothalamus and brain stem, and the fall was greater in hypertensive than in normotensive rats. alpha 1-Adrenergic receptor binding (prazosin) was increased, again more in hypertensive than in normotensive rats. The down regulation of alpha 2-adrenergic receptors and the up regulation of alpha 1-adrenergic receptors are compatible with increased alpha 2-adrenergic agonist presynaptic inhibition of catecholamine release with resultant postsynaptic alpha 1-adrenergic receptor supersensitivity. Spontaneously hypertensive rats showed greater methylnorepinephrine production, larger up regulation of alpha 1-adrenergic receptors, and greater down regulation of alpha 2-adrenergic receptors than did the normotensive animals; these changes may be physiological markers for the greater antisympathetic action of methyldopa in hypertensive animals.

Anti-HTLV antibodies in cancer patients, hemophiliacs and uremics: a preliminary report

A total of 132 sera were studied for anti-HTLV antibodies using the Biotech ELISA test. Among the HTL group, two were, one, and the other two (+/-). Among 23 hemophiliacs one was. None of the lympho- and myelo-proliferative disorders, chronic uremics and normal controls showed positive results. Our results show that the ELISA anti-HTLV test is quite specific for HTL and related disorders, but the antibody titers may be low in some cases in the late stage. The significance of frequent high ELISA readings in hepatomas and NPCs awaits for further studies. The occurrence of one hemophiliac with definite positive anti-HTLV calls for a routine screening of the blood preparations for HTLV.

Genetic considerations in the effects of ethanol in mice. II. A trans-acting inducibility regulator(s) affecting alcohol dehydrogenase (ADH) activity

The inducibility of alcohol dehydrogenase (ADH) has been recognized in different systems including maize, Drosophila, and mice. Our earlier results showed strain-specific ADH responses to chronic ethanol administration relative to matched littermate controls in mice. For this study we used two strains which showed "induction" (BALB/c and S.W.) and two strains which showed "repression" (C57BL/6J and 129/ReJ) to produce three sets of F1 hybrids and their reciprocals and one set (BALB/c X C57BL/6J) of recombinant inbred (RI) lines. The ADH properties of the resulting genotypes were again evaluated following 15% ethanol treatment in drinking water (2 weeks) in relation to their littermate matched controls in replicated trials. Our F1 results suggest complete dominance for induction over repression at the phenotypic level, and the two repressed strains showed complementation. No significant differences were observed in the reciprocal F1's and all pairs of a given genotype-treatment combination yielded consistent results. The 1:1 segregation of RI lines suggests a single gene difference for ADH inducibility between BALB/c and C57BL/6J. These findings suggest the presence of a trans-acting inducibility regulator(s) for ADH which may or may not represent a single locus. Variability for such regulatory elements may provide an explanation for the commonly observed individual differences in natural populations for response to alcohol including alcohol metabolism.

Proliferation of arterial smooth muscle cells incubated in serum from brain-stimulated rats

Platelet deficient serum prepared from rats subjected to acute electrical stimulation of the lateral hypothalamus demonstrated mitogenic activity when added to incubating media supporting growth of homologous arterial smooth muscle cells in vitro. This activity did not appear to be related to the presence of platelet-derived growth factor, hyperlipidemic lipoproteins or increased amounts of insulin. Plasma arginine vasopressin concentration was elevated in these animals, but further investigation is required to determine if this elevation is causally related. Since hypothalamic stimulation is also associated with severe endothelial injury in vivo, the mitogenic activity of the blood of such animals could induce proliferation of SMC which have migrated into the arterial intima. Such features have been observed in chronically stimulated animals and may be of relevance for the role of neural factors in atherogenesis.

Particle concentration fluorescence immunoassay (PCFIA): a new, rapid immunoassay technique with high sensitivity

A new solid-phase fluorescence immunoassay technique is described and is exemplified by the detection of murine monoclonal antibodies to human IgG in hybridoma culture supernatants and the detection of murine IgG. The assay is performed in a specially designed 96-well plate. For antibody detection, antigen bound to submicron polystyrene particles is bound to its specific antibody, which is in turn reacted with fluorescein-labeled affinity-purified goat anti-mouse IgG. The reaction is complete in 10 min at ambient temperature. The solid phase is separated from the reaction mixture by filtration, washed and the total particle-bound fluorescence is determined by front-surface fluorimetry. The sensitivity of the technique for antibody detection is equivalent to enzyme-linked immunoabsorbent assay and 2-4 ng/ml for murine IgG detection. It is readily amenable to automation.

Expression of GM1 and GD1a in liver of wild mice

Wild mice are divided into two groups with different ganglioside compositions in the liver. Most Japanese and a few Chinese wild mice have GM2(NeuGc) as a major ganglioside, whereas all wild mice caught at other places distributed all over the world other than Japan and China express GM1(NeuGc) and GD1a(NeuGc) in addition to GM2(NeuGC). We recently reported that inbred strains of laboratory mice were also grouped into the same two types based on the ganglioside composition in the liver, and that the expression of GM1(NeuGc) and GD1a(NeuGc) was regulated by a gene located at the left outside the H-2 complex on chromosome 17 (Hashimoto, Y., Suzuki, A., Yamakawa, T., Miyashita, N., & Moriwaki, K. (1983) J. Biochem. 94, 2049-2054). The present study suggests that oriental wild mice would be a donor of a defective gene for expression of GM1(NeuGc) and GD1a(NeuGc) in mice of laboratory stocks which are commonly used for biochemical and immunological studies, such as C57BL/6, C57BL/10, BALB/c, DBA/2, C3H/He, and CBA mice.

Induction of (2'-5')An-dependent endoribonuclease activity by interferon in cultured guinea pig macrophages

By a radiobinding assay, an affinity labeling technique, and a column procedure which quantitates mRNA intactness, evidence is presented on the induction of the (2'-5')An-dependent endoribonuclease by interferon in cultured guinea pig macrophages.

Automated fluorescence polarization immunoassay for monitoring vancomycin

We have extended fluorescence polarization immunoassay (FPIA) technology for the measurement of drugs to include the complex amphoteric glycopeptide antibiotic vancomycin (molecular weight, 1,449). Fluorescein-labeled vancomycin was employed as a tracer, and antisera specific for vancomycin were raised in rabbits by conventional procedures. Tracer, sample, and diluted antiserum were combined, and the polarization of tracer fluorescence is determined in a specially designed fluorometer (Abbott TDx). Because of instrument design, the possibility of fluorescent interferences is minimized. The assay can measure as little as 0.6 mg/L of vancomycin and is free of interferences from hemolysis, lipemia, bilirubin, and changes in protein concentration. The coefficient of variation within assay was 3% (n = 5) and between assays was 5% (n = 5). The FPIA assay (TDx Vancomycin) was compared to a liquid chromatographic (LC) assay for vancomycin and to a commercially available radioimmunoassay (RIA) for 98 clinical specimens. A linear least-squares regression analysis gave a correlation coefficient for LC of 0.980 from the equation FPIA = 1.09 LC + 3.04, and a correlation coefficient for RIA of 0.957 from the equation FPIA = 1.036 RIA + 1.66.

Hematobilia from ruptured hepatic artery aneurysm. Report of two cases

Hematobilia secondary to hepatic artery aneurysm must be considered in the differential diagnosis of unexplained gastrointestinal tract hemorrhage. We treated two patients with ruptured hepatic artery aneurysm. One had hepatic artery aneurysm proximal to the gastroduodenal artery; the other had an intrahepatic pseudoaneurysm in the right lobe of the liver. The first patient was treated with obliterative endoaneurysmorrhaphy. The second required ligation of feeding vessels, cholecystectomy, and reconstruction of cholecystoduodenal fistula.

Continuous infusion of cholecystokinin and meal pattern in the rat

Purified natural cholecystokinin (CCK-33) was infused continuously for two days at a rate of 5.9 micrograms/hr in two rats trained to bar-press for food (Noyes pellet 45 mg) on a fixed ratio of five bar presses to obtain one pellet. The animals also received control surgery and were tested in the operant chamber for two days, one prior to and the other following the CCK-33 treatment. CCK-33 suppressed the number of meals, the total amount of food eaten, and the total duration of time spent eating. However, the size of each meal and the rate of intake were not affected. The CCK effect did not interact with the light-dark phases of diurnal cycle. It appears that a major effect of continuous systemic elevation of CCK-33 is to reduce food intake by prolonging the satiety period rather than by decreasing the individual meal size.

Dystrophic mutation (dy2J) affecting regulation of lactate dehydrogenase (LDH) and pyruvate kinase (PK) in C57BL/6J mice

The genotype difference (dystrophic vs nondystrophic) in the LDH isozymes is observed in kidney. These differences are evident only at birth and at early developmental stages (before the expression of dystrophic symptoms). The tissue specific genotype differences for PK are limited to the thigh muscle (M form) and heart (L form), after the onset of the condition. These differences may reflect the pleiotropic effect of the dy2J locus during the temporal regulation of these and other enzymes implicated in muscular dystrophy (MD).

Fluorescence polarization immunoassay IV. Determination of phenytoin and phenobarbital in human serum and plasma

Fluorescence polarization immunoassays for phenytoin and phenobarbital in human serum or plasma are described and shown to be clinically useful. No sample pretreatment, extraction, or phase separation is required. A determination can be made with less than 20 microL of sample in 15 min, with incubation at ambient temperature. Abnormal concentrations of protein, lipid, hemoglobin, or bilirubin do not interfere. In addition, drug metabolites and commonly co-administered drugs do not affect the assay results at clinically significant concentrations. Analytical recoveries of each of the two anticonvulsant drugs from serum averaged 101%. Between-assay CVs were less than 6.5%, with sensitivities of 0.5 mg/L. Comparison of this method with "high-performance" liquid chromatography, homogeneous enzyme immunoassay, and radioimmunoassay for phenytoin determinations yielded correlations of 0.99, 0.98, and 0.99, respectively. Similar comparison studies for phenobarbital yielded correlation coefficients of 0.99, 0.98, and 0.99, respectively.

Fluorescence polarization immunoassay IV. Determination of phenytoin and phenobarbital in human serum and plasma

Fluorescence polarization immunoassays for phenytoin and phenobarbital in human serum or plasma are described and shown to be clinically useful. No sample pretreatment, extraction, or phase separation is required. A determination can be made with less than 20 microL of sample in 15 min, with incubation at ambient temperature. Abnormal concentrations of protein, lipid, hemoglobin, or bilirubin do not interfere. In addition, drug metabolites and commonly co-administered drugs do not affect the assay results at clinically significant concentrations. Analytical recoveries of each of the two anticonvulsant drugs from serum averaged 101%. Between-assay CVs were less than 6.5%, with sensitivities of 0.5 mg/L. Comparison of this method with "high-performance" liquid chromatography, homogeneous enzyme immunoassay, and radioimmunoassay for phenytoin determinations yielded correlations of 0.99, 0.98, and 0.99, respectively. Similar comparison studies for phenobarbital yielded correlation coefficients of 0.99, 0.98, and 0.99, respectively.

Urgent hemorrhoidectomy for hemorrhoidal crisis

Fifty-six patients who had hemorrhoidal crisis underwent urgent radical hemorrhoidectomy with anoderm-flap repair. There was no significant increase in complications as compared with elective hemorrhoidectomy. One patient (1.8 per cent) had one of his three flaps separate. Anal packing with a central-tubed cotton plaque is of benefit to ensure takes of anoderm flaps and in reducing postoperative hemorrhage.

How close to the theoretical diffusion limit do bacterial uptake systems function?

Using a 10 cm flow-through cuvette in a high precision spectrophotometer linked to a mini-computer, the growth rate dependence of Escherichia coli on glucose concentration has been studied. The specific growth rate vs bacterial mass of single cultures consuming small amounts of glucose was followed. The data were analyzed with the computer programs described previously. For neither batch nor chemostat-cultured organisms did growth follow the Monod growth law. Rather, the growth rate vs residual glucose concentration has an almost abrupt change in slope, indicative of a passive diffusion barrier prior to an uptake system possessing hyperbolic dependency. Calculations showed that the diffusion through the outer membrane via the porin channels could quantitatively account for the deviations from hyperbolic dependency. Long term chemostat culture alters the bacteria so that the maximum specific growth rate is reduced, but the initial dependence on glucose concentration is increased approaching more closely the theoretical limit. Therefore there was both a change inthe outer membrane channels and the uptake activity of the cytoplasmic membrane.

The structure of methylated xanthines in relation to their effects on DNA synthesis and cell lethality in nitrogen mustard-treated cells

The variation in cellular response to alkylated xanthines possessing different side chains has been used to evaluate more fully the effect of caffeine on both survival and DNA synthesis in cells with DNA damage. A correlation is observed between the ability of these xanthines to reverse the inhibitory effects of nitrogen mustard damage on DNA synthesis and their ability to enhance nitrogen mustard lethality in human HT-29 cells. These findings are consistent with our theory that regulation of damaged replicon initiation protects against potentially lethal damage in the form of unrepaired DNA alkylations. Enhancement of nitrogen mustard lethality is observed to have a maximum limit, which can be reduced by highly toxic xanthine concentrations. The lethal effects of xanthines alone at higher concentrations are unrelated to the effects of caffeine specific to nitrogen mustard treated cells, and appear to be related to an immediate reduction in thymidine incorporation most likely caused by inhibition of other enzyme systems influencing DNA synthesis such as de novo and salvage pathways for purine biosynthesis.

Fluorescence polarization immunoassay. I. Monitoring aminoglycoside antibiotics in serum and plasma

Fluorescence polarization immunoassays of the aminoglycoside antibiotics gentamicin, tobramycin, and amikacin in plasma and serum are described and shown to be clinically useful. The aminoglycoside tracers were prepared by reacting the parent compounds with 5-[(4,6-dichlorotriazin-2-yl)-amino] fluorescein. Antisera specific for the compounds were raised in rabbits by conventional procedures. Tracer, sample, and diluted antiserum are combined and, after a 15-min incubation at ambient temperature, the polarization of the fluorescence of the tracer is determined in a specially designed fluorometer. The assays are designed to give accurate trough (i.e., minimum during therapy) values and to be free of matrix effects. Severely icteric samples may interfere, but this can be overcome by blank subtraction. The performance of the assays with clinical specimens compared favorably with that of some commercially available assays.

Fluorescence polarization immunoassay. I. Monitoring aminoglycoside antibiotics in serum and plasma

Fluorescence polarization immunoassays of the aminoglycoside antibiotics gentamicin, tobramycin, and amikacin in plasma and serum are described and shown to be clinically useful. The aminoglycoside tracers were prepared by reacting the parent compounds with 5-[(4,6-dichlorotriazin-2-yl)-amino] fluorescein. Antisera specific for the compounds were raised in rabbits by conventional procedures. Tracer, sample, and diluted antiserum are combined and, after a 15-min incubation at ambient temperature, the polarization of the fluorescence of the tracer is determined in a specially designed fluorometer. The assays are designed to give accurate trough (i.e., minimum during therapy) values and to be free of matrix effects. Severely icteric samples may interfere, but this can be overcome by blank subtraction. The performance of the assays with clinical specimens compared favorably with that of some commercially available assays.

Improvements in optical methods for measuring rapid changes in membrane potential

In an effort to increase the utility of optical methods for measuring membrane potential in excitable cells, an additional 369 dyes were tested on giant axons from the squid. Several promising dyes with relatively large absorption and fluorescence signals are described. In addition, a simple modification of the apparatus led to a sixfold increase in the size of dye-related birefringence signals. In preparations with a suitable geometry, these signals are as large as absorption signals but photodynamic damage and bleaching are eliminated when wavelengths longer than the absorption band are used.

Determination of urinary amino acids by liquid chromatography with "dabsyl chloride"

We describe a "high-performance" liquid-chromatographic procedure for measuring amino acids in 0.5 mL of urine. The procedure includes direct derivatization of amino acids in urine samples with "dabsyl chloride" (4-dimethylaminoazobenzene-4'-sulfonyl chloride). An aliquot of this dabsylated amino acid solution is analyzed on a muBondapak C18 column with ethanol/sodium acetate (20 mmol/L, pH 4.0) 4/6 (by vol.), as mobile phase. Dabsylated amino acids are detected by their absorbance at 425 nm and quantitated by measuring peak heights. The procedure allows for the reliable analysis of amino acids in urine at concentrations near 16 mg/L. The sensitivity of this analysis on column approaches 5 ng/sample. Higher urinary tryptophan concentrations were found in the urines of some cancer patients, whereas we saw no significant difference in urinary glycine between cancer patients and control subjects. The present method was shown to be a straightforward procedure for detecting phenylalanine in phenylketonuric urine. Extension of this procedure to screening for other inborn errors of aminoaciduria is recommended.

Determination of urinary amino acids by liquid chromatography with “dabsyl chloride"

We describe a “high-performance” liquid-chromatographic procedure for measuring amino acids in 0.5 mL of urine. The procedure includes direct derivatization of amino acids in urine samples with “dabsyl chloride" (4-dimethylaminoazobenzene-4’-sulfonyl chloride). An aliquot of this dabsylated amino acid solution is analyzed on a muBondapak C18 column with ethanol/sodium acetate (20 mmol/L, pH 4.0) 4/6 (by vol.), as mobile phase. Dabsylated amino acids are detected by their absorbance at 425 nm and quantitated by measuring peak heights. The procedure allows for the reliable analysis of amino acids in urine at concentrations near 16 mg/L. The sensitivity of this analysis on column approaches 5 ng/sample. Higher urinary tryptophan concentrations were found in the urines of some cancer patients, whereas we saw no significant difference in urinary glycine between cancer patients and control subjects. The present method was shown to be a straightforward procedure for detecting phenylalanine in phenylketonuric urine. Extension of this procedure to screening for other inborn errors of aminoaciduria is recommended.

Determination of urinary amino acids by liquid chromatography with “dabsyl chloride"

We describe a “high-performance” liquid-chromatographic procedure for measuring amino acids in 0.5 mL of urine. The procedure includes direct derivatization of amino acids in urine samples with “dabsyl chloride" (4-dimethylaminoazobenzene-4’-sulfonyl chloride). An aliquot of this dabsylated amino acid solution is analyzed on a muBondapak C18 column with ethanol/sodium acetate (20 mmol/L, pH 4.0) 4/6 (by vol.), as mobile phase. Dabsylated amino acids are detected by their absorbance at 425 nm and quantitated by measuring peak heights. The procedure allows for the reliable analysis of amino acids in urine at concentrations near 16 mg/L. The sensitivity of this analysis on column approaches 5 ng/sample. Higher urinary tryptophan concentrations were found in the urines of some cancer patients, whereas we saw no significant difference in urinary glycine between cancer patients and control subjects. The present method was shown to be a straightforward procedure for detecting phenylalanine in phenylketonuric urine. Extension of this procedure to screening for other inborn errors of aminoaciduria is recommended.

Construction of a new unclipped digital correlator for quasielastic light scattering

An unclipped digital correlator that we have built has been described. Our digital correlator can be easily incorporated (with only a moderate cost) in an established light scattering laboratory equipped with a computer.

Constancy of growth on simple and complex media

An apparatus has been developed in which bacterial growth can be measured very precisely over short intervals of time. Its precision is presented and used to assess the constancy of growth in batch culture. Under certain conditions, i.e., Luria broth or 0.2% glucose-M9 medium at very low cell densities, the specific growth rate of Escherichia coli appeared to be constant within the measurement limits of the method. In succinate minimal medium, the growth rate increased gradually over several days and never became constant. With nutrient broth and with Luria broth, growth slowed progressively at moderate cell densities within the range considered to be in the logarithmic phase of growth. In addition, temporary slowdown in growth rate occurred in these two complex media at characteristic cell densities. These gradual increases in succinate minimal medium and temporary slowdowns in the complex media would be undetectable without precise measurements and may have been a source of variability in many bacteriological studies.

Suppression of 3-hydroxy-3-methylglutaryl coenzyme A reductase activity and of incorporation of acetate into cholesterol in homozygous hypercholesterolemic fibroblasts by ferritin-low density lipoprotein conjugates

Conjugates of ferritin with low density lipoproteins (LDL) were prepared and separated by sucrose gradient centrifugation. These conjugates, at cholesterol concentration of 100--132 microgram/ml, caused a greater than 90% suppression of hydroxymethylglutaryl coenzyme A reductase activity and of acetate incorporation into cholesterol in cultured skin fibroblasts from a normal subject as well as from a subject with homozygous familial hypercholesterolemia. The half maximal inhibition concentration was approx. 10 microgram/ml cholesterol for LDL and ferritin . (LDL)2 and 5 microgram/ml for (ferritin)2 . LDL in both cell lines. In contrast, native low density lipoproteins have only a minimal inhibitory effect in homozygous cells. The ability of the conjugates to stimulate the incorporation of oleate into cholesteryl esters was also equal in the two cell lines, although the conjugates were only 10% as active as low density lipoproteins in the normal cells. LDL reduced the ferritin . (LDL)2-mediated suppression of hydroxymethylglutaryl-CoA reductase activity in homozygous cells while ferritin . (LDL)2 reduced the LDL-mediated stimulation of cholesteryl ester formation in normal cells.

Changes in absorption, fluorescence, dichroism, and Birefringence in stained giant axons: : optical measurement of membrane potential

The absorption, fluorescence, dichroism, and birefringence of stained squid axons were measured during action potentials and voltage clamp steps in an effort to find large optical signals that could be used to monitor membrane potential. Changes in all four optical properties were found that were linearly related to membrane potential and, with several new dyes, the signal-to-noise ratios were larger than any obtained previously. The problem of photodynamic damage was greatly diminished; with a merocyaninerhodanine dye, the photodynamic damage associated with intense light and the presence of oxygen was negligible. The absorption change obtained with this dye was relatively large; it could be measured with a signal-to-noise ratio of 100:1 during a single action potential.