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We have determined the permeability properties of freshly isolated frog rod outer segments by observing their osmotic behavior in a simple continuous flow apparatus. Outer segments obtained by gently shaking a retina are sensitive but nonideal osmometers; a small restoring force prevents them from shrinking or swelling quite as much as expected for ideal behavior. We find that Na(+), Cl(-), No(3) (-), glycerol, acetate, and ammonium rapidly enter the outer segment, but K(+), SO(4) (=), and melezitose appear impermeable. The Na flux is rectified; for concentration gradients in the physiological range, 2 x 10(9) Na(+) ions/sec enter the outer segment, but we detect no efflux of Na(+), under our conditions, when the gradient is reversed. Illumination of the outer segment produces a specific increase in the resistance to Na(+) influx, but has no effect on the flux of other solutes. This light-dependent Na(+) resistance increases linearly with the number of rhodopsin molecules bleached. We find that excitation of a single rhodopsin molecule produces a transient ( approximately 1 sec) "photoresistance" which reduces the Na(+) influx by about 1%, thus preventing the entry of about 10(7) Na(+) ions. At considerably higher light levels, a stable afterimage resistance appears which reduces the Na influx by one-half when 10(6) rhodopsin molecules are bleached per rod. We have incorporated these findings into a model for the electrophysiological characteristics of the receptor.
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PMID:Dark ionic flux and the effects of light in isolated rod outer segments. 453 79

The growth of three pathogenic goat mycoplasmas, strains Y, KH1 and Mycoplasma mycoides var. capri (PG3), was studied. They formed classical colonies on agar containing 1/500 thallium acetate. They were inactivated during storage at 2 to 4 C and by freezing and thawing but not by shaking. Only KH1 was killed by sonic treatment. Ultraviolet inactivation curves showed that their colony-forming units were single binucleate cells. Details of their growth curves are given. Filtration through 0.45- or 0.3-mum membrane filters removed up to 97% of the cells. Less than 0.003% passed 0.22-mum membranes. In electron micrographs, the cells were seen replicating by budding and most were 0.6 to 0.9 mum in diameter; but cells between 0.1 and 0.2 mum reproduced. They usually multiplied by producing one bud, a form of binary fission. However, two buds were produced by some synchronized cells, indicating that both nuclei had divided simultaneously to form progeny, an alternate method of multiplication.
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PMID:Binucleate classical mycoplasmas pathogenic for goats. 456 75

Extracts containing penicillin acylase were obtained by shaking the mycelium of Fusarium avenaceum and of Penicillium chrysogenum in 0.2 M sodium acetate or sodium chloride solution. The optimum pH for conversion of penicillin V into 6-aminopenicillanic acid (6-APA) by the enzyme of Fusarium was about 7.5, and the reaction velocity was increased by a rise in temperature from 27 to 37 C. Penicillin G and penicillins with an aliphatic side chain were cleaved much less readily than was penicillin V. With the enzyme preparation obtained from a nonpenicillin-producing strain of P. chrysogenum, the reaction rate was higher at pH 8.5 than at pH 7.5 and pH 6.5. The acylase of P. chrysogenum hydrolyzes penicillin V more readily than penicillin G. In a series of aliphatic penicillins, the amount of 6-APA formed through the action of this enzyme increased with the number of carbon atoms of the side chain. Penicillins with a glutaryl or an adipyl group as side chain were unaffected by the enzyme of Fusarium and of Penicillium. No reaction was observed upon incubation of penicillin N (with a D-aminoadipyl side chain) or isopenicillin N (with an L-aminoadipyl side chain) with Fusarium and Penicillium extract. When the carboxy group of the side chain of these penicillins was esterified, formation of 6-APA was observed upon incubation with Penicillium extract, whereas no 6-APA or only very small amounts were obtained by acylase of Fusarium.
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PMID:Specificity of penicillin acylase of Fusarium and of Penicillium chrysogenum. 497 22

When Neurospora mycelium is transferred from a medium containing sucrose to one containing acetate as sole source of carbon, a preferential synthesis of many Krebs cycle, glyoxylate cycle, and associated enzymes occurs. Respiration was inhibited during preferential enzyme synthesis in the following ways. (i) The amount of aeration (shaking) was reduced, (ii) cyanide was added to the culture, (iii) the carbon source, acetate, was removed, (iv) a mutant strain was starved of its Krebs cycle intermediates, and (v) respiration was inhibited by mutation. The effect of this respiratory inhibition on the synthesis of a number of enzymes was measured. It was found that the synthesis of nicotinamide adenine dinucleotide (NAD)-linked glutamate dehydrogenase and phosphoenolpyruvate carboxykinase was significantly less inhibited under conditions of respiratory inhibition than was the synthesis of Krebs cycle, glyoxylate cycle, and most other cell proteins synthesized during the adaptation period. This differential inhibition of enzyme synthesis was almost certainly not due to differential repression by regulatory metabolic end product effectors. Inhibition of mitochondrial respiration under these conditions most likely results in a limitation of the energy supply of the cell. Thus, it is suggested that the inhibition of synthesis of most proteins after inhibition of mitochondrial respiration results from a lack of energy in a utilizable form. Possible reasons to account for the relative insensitivity of NAD-linked glutamate dehydrogenase and phosphoenolpyruvate carboxykinase to inhibition under these conditions are discussed.
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PMID:Selective inhibition of enzyme synthesis under conditions of respiratory inhibition. 509 92

The most recently published method for the assay of testicular hyaluronidase preparations was based on the premise that the enzyme also exhibited carboxylesterase activity towards indoxyl acetate. Studies on the relative enzyme activities of various hyaluronidase preparations towards hyaluronate and indoxyl acetate, the relative stabilities towards pH, temperature and mechanical shaking and the behaviour towards a variety of inhibitors, showed that the activities towards the two substrates reflected the presence of at least two different enzyme systems in the preparations. Gel chromatography and polyacrylamide-gel-electrophoresis experiments confirmed these conclusions and the collective findings clearly establish that methods based on the use of indoxyl acetate cannot be employed to measure testicular hyaluronidase activity.
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PMID:Unsuitability of indoxyl acetate as a substrate for the assay of testicular hyaluronidase. 516 30

In man the clinical patterns of inorganic and organic mercury toxicity are different. Inorganic mercuric chloride mainly affects the renal and gastrointestinal systems. The characteristic neurological feature is a fine tremor, particularly of the hands and fingers. In contrast organic methyl mercury toxicity results in an exclusively neurological disorder, the characteristic features being ataxia, dysarthria, paresthesia and tunnel vision. To study the action of these classes of mercury compounds on neurones small amounts of mercuric chloride or methyl mercuric acetate were injected or iontophoresed into the rat cerebrum. The ultrastructural changes which followed were identical. Progressive and often pronounced cytoplasmic swelling of neurones suggested a defect at the cell membrane level. Thus is spite of their distinctive clinical syndromes these 2 classes of mercury compounds are capable of inducing neuronal necrosis.
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PMID:Identity of ultrastructural effects of mercuric chloride and methyl mercury after intracerebral injection. 621 46

We treated 105 patients with advanced breast cancer, using the progestational agent medroxyprogesterone acetate (MPA), 200 mg orally tds in a non-randomised trial. In general they were a poor risk population, since 78 had received prior endocrine therapy (21 more than one type) and 58 prior chemotherapy. Treatment was well tolerated. Side effects included weight gain, muscle cramps, fine tremor and fluid retention, but these were usually mild, resolved if the dose of drug was reduced, and only one patient stopped treatment because of toxicity. Seventeen patients died within six weeks of starting MPA, and disease progression occurred in a further 58. Nine have had stable disease for periods ranging from two to 11 months, and there were 21 who showed disease regression. Response to treatment continues in 13 of these patients, and at the time of writing the median duration of response is 10 months. Response rates were similar in pre- and post-menopausal patients. The dose of MPA was double to 400 mg tds in 16 patients whose disease had progressed on 200 mg tds, but no additional responses were seen in this group. Seven out of 24 (29%) patients who had not received prior endocrine therapy responded to high dose oral MPA, a response rate similar to that seen following other hormonal manipulations, but because the drug also has activity against hormone-resistant tumours and is well tolerated, it should have role in the treatment of advanced breast cancer.
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PMID:Advanced breast cancer: response to high dose oral medroxyprogesterone acetate. 623 89

Responses of rumen microbes to fatty acids were evaluated by production of total volatile fatty acid and ratio of acetate to propionate. Fermentations were under carbon dioxide for 20 h in 50-ml Erlenmeyer flasks in a Dubnoff metabolic shaking incubator. Flasks contained 20 ml medium, 1 ml reducing solution, 750 mg substrate (450 mg hay plus 300 mg grain), and varying amounts of long-chain fatty acids supplied as free acids, as calcium salts, or as triglycerides. They were inoculated with 5 ml rumen fluid obtained from a cow fed 3.6 kg grass hay, 2.3 kg grain, and .2 kg tallow daily. Volatile fatty acid production was decreased by long-chain fatty acids that contained less than 18 carbon atoms and by unsaturated long-chain fatty acids with 18 carbon atoms. Lauric acid decreased volatile fatty acid production by 69% and induced unusual acetate/propionate ratio (40:1). Stearic acid, however, did not affect volatile fatty acid production or acetate/propionate ratio. Within two series of long chain fatty acids (myristic, palmitic, stearic, arachidic; stearic, oleic, linolenic), melting point accounted for 93 to 95% of the variation of volatile fatty acid production and acetate/propionate. As calcium salts, long chain fatty acids caused small changes of fermentation. Our data support the proposition that hard fats and calcium salts of long-chain fatty acids do not interfere with ruminal fermentation.
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PMID:Rumen fermentation in vitro as influenced by long chain fatty acids. 674 49

Large intramuscular doses of a water-miscible preparation of vitamin A (500,000 I.U. retinyl acetate/ml), vitamin E (50 I.U./ml) and vitamin D2 (50,000 I.U./ml) were administered to young monkeys (Macacus fascicularis) weighing 1-1.8 kg. At vitamin A doses equivalent to 200 mg retinol/kg or higher, early signs of acute toxicity included yawning, apparent drowsiness, nausea and vomiting, head shaking, neck hyperextension, motor hyperactivity and coordination. These immediate signs were first noted 3-35 minutes after injection. Following apparent recovery at 1-2 hrs, longer term signs of toxicity, such as decreased activity, malaise, drowsiness, loss of appetite, loss of weight, and itchiness of the skin, appeared within 1-6 days, depending on the dose. Monkeys receiving the highest lethal doses became progressively weaker, showed labored breathing, lapsed into a coma, lost simple reflexes and then died. Respiratory failure usually preceded the cessation of heart beat. In some monkeys on a lower but lethal dose, death was preceded by generalized convulsive seizures. The time of onset of the first sign and survival time were inversely proportional to the dosage, but in individual monkeys no correlation existed between onset time and survival time. Female monkeys seemed to succumb faster to a lethal dose than male monkeys. All animals receiving the equivalent of 300 mg retinol/kg died. Under the conditions used, the LD50 was estimated to be 168 mg retinol (560 000 I>U.) per body weight.
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PMID:A lethal hypervitaminosis A syndrome in young monkeys (Macacus fascicularis) following a single intramuscular dose of a water-miscible preparation containing vitamins A, D2 and E. 697 50

Vitreoscilla, a gliding bacterium in the Beggiatoaceae, is an obligate aerobe in which cytochrome o functions as the terminal oxidase. Protoheme IX is the only heme type present in this organism. The yield and heme content of Vitreoscilla cells grown in yeast extract, peptone, and acetate were dependent on growth conditions. Cells harvested in early stationary phase contained roughly three times as much heme as cells in early log phase. There was an optimal shaking rate for maximum heme content of cells harvested in stationary phase at fixed initial nutrient concentration. The heme content of cells grown at a fixed shaking rate increased from 5 nmol/g (wet weight) in media which had low nutrient concentration to a maximum of 45 nmol/g (wet weight) in media which had high nutrient concentration, and there was a corresponding sixfold increase in cytochrome o content and an eightfold increase in respiratory rate, evidence that some of the additional heme was incorporated into respiratory pigments. Heme content may be controlled jointly by competition for oxygen and availability of nutrients. Temperature and initial pH affected the growth rate but not the final yield or heme content. Growth rate was optimal at pH 8.0 to 8.5. A defined medium for Vitreoscilla, which is based on glutamate as the carbon source, is described; the other organic components of this medium are acetate, tryptophan, thiamine, biotin, and riboflavin.
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PMID:Effect of growth conditions on yield and heme content of Vitreoscilla. 737 68


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