Influence of auxin type and concentration on peanut somatic embryogenesis

Somatic embryogenesis in peanut (Arachis hypogaea L.) using immature cotyledonary explants was induced on a wide range of 2,4-dichlorophenoxyacetic acid (2,4-D) (5 to 60mg l^–1) and naphthaleneacetic acid (NAA) (20 to 50 mg l^–1) levels. Percent embryogenesis ranged from 31 to 94%. As auxin level increased in induction medium, percent embryogenesis decreased and was associated with browning of explants. However, with higher 2,4-D induction levels (40 mg l^–1 and over), embryogenic explants had dense masses of embryogenic areas and repetitive embryogenesis was enhanced. Higher auxin concentrations during induction decreased precocious germination of embryos, but had no marked effect on somatic embryo morphology. The use of 2,4-D compared to NAA in the induction medium resulted in greater per cent embryogenesis and mean number of embryos. Embryos induced on NAA were harder, less pliant, and less succulent; cultures exhibited more extensive root development and nonembryogenic callus proliferation.Abbreviations B5 Gamborg et al. (1968) - BA benzyladenine - 2,4-D dichlorophenoxyacetic acid - IAA indole-3-acetic acid - MS Murashige & Skoog (1962) - NAA naphthaleneacetic acid - picloram 4-amino-3,5,6-trichloropicolinic acid     

pH modification of the effects of detergents on the stability of enteric viruses.

The effect of detergents on the stability of enteric viruses was found to be highly dependent on pH. This was demonstrated primarily with two ionic detergents, sodium dodecyl sulfate (an anionic detergent) and dodecyltrimethylammonium chloride (a cationic detergent). Both detergents were shown to be potent virucidal agents for reovirus, but the effects of sodium dodecyl sulfate were minimal near neutrality and much more pronounced at low than at high pH values. Dodecyltrimethylammonium chloride was extremely virucidal at high pH's but had little observable effect on reovirus stability at low pH values. In contrast, both detergents protected enteroviruses against heat at neutral and alkaline pH's. However, as was found with reovirus, sodium dodecyl sulfate was extremely virucidal at pH values below 5, even when the virus samples were incubated in ice. At different pH's the effects of detergents on the stabilities of coliphages T4, f1, and Q beta were qualitatively similar to those found with reovirus. Differences in viral stability in these experiments appeared to be due to the effects of pH on the ionic states of the viral capsid proteins.     

Discovery of an agent in wastewater sludge that reduces the heat required to inactivate reovirus.

An agent that causes heat inactivation of reovirus to occur at reduced temperatures has been found in both raw and anaerobically digested sludge. This agent is originally associated with sludge solids but can be washed from these solids by blending with water. The activity of the agent was considerably greater in alkaline than in acid solutions, probably because it is insoluble at low pH. The agent was shown to be nonvolatile and heat stable up to 300 degrees C but was inactivated within 30 min at 400 degrees C. The rate of heat inactivation of reovirus by the agent was found to occur in a bimodal fashion and to be relatively rapid, even at 35 degrees C. Finally, it was found that this agent did not accelerate heat inactivation of poliovirus, but instead may be the component of sludge previously found to protect poliovirus against inactivation by heat.     

Comparative effects of ammonia and related compounds on poliovirus.

The abilities of ammonia and related compounds to inactivate poliovirus were compared. Compounds virucidal at pH 9.5 had the following order of activities: ethylamine greater than propylamine, dimethylamine, methylamine greater than ammonia greater than 2-methoxyethylamine.     

Effects of parasite density and host availability on progeny production byBiosteres (Opius) longicaudatus, [Hym.: Braconidae], a parasite ofAnastrepha suspensa [Dip.: Tephritidae]

Progeny production ofBiosteres (Opius) longicaudatus Ashmead, a larvalpupal parasite of the Caribbean fruit fly,Anastrepha suspensa (Loew) was affected by host availability, previous ovipositional experience, and parasite density and age. Parasitization rates were evaluated in 24.5 cm³ ovipositional cages at parasite densities of 25, 125, and 250 male-female pairs by exposingB. longicaudatus adults to (a) 500A. suspensa larvae for a 24 h period or (b)ad libitum host larvae for each of the 14 days following eclosion. The mean numbers of parasite progeny produced at the 25, 125, and 250 densities were 1076, 1896, and 2038, respectively. The number of progeny produced per surviving female parasite was inversely proportional to the adult parasite density and relatively more female progeny were produced as the adult parasites aged. Host mortality was significantly higher among parasitized larvae. Maximum rearing efficiency was achieved at the 125 density.     

A proposed model of chromosomal organization in nuclei at fertilization

Evidence is presented to support the proposition that the position of chromosomes within nuclei is determined by the following factors: (1) the location of centromeres on one side of the nucleus and telomeres(ends) on the other (reflecting the telophase orientation brought about by their poleward anaphase migration); (2) attachment of telomeres to the nuclear membrane (site of attachment in relation to the poles and equator being dependent on the length of the individual arms and point 1 above); (3) telomere-to-telomere attachment of nonhomologues in a specific sequence; (4) telomere-to-telomere attachment of certain homologous chromosomes.It is proposed that a specific arrangement of nonhomologues occurs within gametic nuclei following meiosis, while initial homologous alignment takes place during karyogamy (fusion of gametic nuclei). The method of homologous association of telomeres is dependent on whether or not karyogamy within the species is between interphase pronuclei or occurs during the first cleavage division. A model of chromosome behavior for both these type of karyogamy is presented.     

Human Brain βA4 Amyloid Protein Precursor of Alzheimer''s Disease: Purification and Partial Characterization

The major component of the amyloid deposition that characterizes Alzheimer's disease is the 4-kDa beta A4 protein, which is derived from a much larger amyloid protein precursor (APP). A procedure for the complete purification of APP from human brain is described. The same amino terminal sequence of APP was found in two patients with Alzheimer's disease and one control subject. Two major forms of APP were identified in human brain with apparent molecular masses of 100-110 kDa and 120-130 kDa. Soluble and membrane fractions of brain contained nearly equal amounts of APP in both humans and rats. Immunoprecipitation with carboxyl terminus-directed antibodies indicates that the soluble forms of APP are truncated. Carboxyl terminus truncation of membrane-associated forms of human brain APP was also found to occur during postmortem autolysis. The availability of purified human brain APP will facilitate the investigation of its normal function and the events that lead to its abnormal cleavage in patients with Alzheimer's disease.     

Striated scallop muscle relaxation: fast force transients produced by photolysis of Diazo-2

Relaxation of the myosin regulated striated adductor muscles of Pecten maximus was initiated by the photolysis of the caged Ca2+ chelator, Diazo-2. The fibres relaxed to approximately 30% of the maximum tension with a mean half-time of 17.9 +/- 1.6 ms (n = 7, temp 12 degrees C), much faster than the rates observed in intact muscle at the same temperature. This indicates that in the intact adductor muscle the slower relaxation rate is determined by the speed of Ca2+ removal from the sarcoplasm. The faster rate of relaxation of scallop muscle in vitro, compared with frog skeletal muscle may reflect different mechanisms of regulation of the crossbridge cycle.     

Turnover of the fatty acyl and glycerol moieties of microsomal membrane lipids from liver, gill and muscle tissue of thermally acclimated rainbow trout,Salmo gairdneri

Summary Rainbow trout (Salmo gairdneri) acclimated to 5°C or 20°C were administered 2-³H-glycerol and 1-¹⁴C-acetate (63 Ci of each isotope/100 g body weight) via intraperitoneal injection, and subsequently maintained at their respective acclimation temperatures. Total lipid extracts (>80% phospholipid) were prepared from isolated microsomes of liver, gill and muscle tissue at various times over a three week period. Half-lives were determined independently for the fatty acyl and glycerol moieties from slopes of regression lines relating dpm/nmole phospholipidP _i vs time. In liver tissue, rates of phosphatidylcholine (PC) and phosphatidylethanolamine (PE) turnover were also determined. Membrane turnover was most rapid in liver followed by gill and muscle. In liver, membrane fatty acids turned over more rapidly in warm-(t _1/2=3.4 days) than in cold-(t _1/2=6.8 days) acclimated fish, whereas in gill, rates of fatty acid turnover, did not differ significantly between acclimation groups. In contrast, rates of glycerol turnover were independent of acclimation temperature in liver, but faster (t _1/2=6.7 days) in warm- than cold- (t _1/2=15.1 days) acclimated fish in gill. In total lipid extracts, rates of fatty acid and glycerol turnover were equivalent in warm-acclimated fish, however, in cold-acclimated trout, there was a tendency for fatty acids (t _1/2=9.1 days) to turnover more rapidly than glycerol (t _1/2=15.1 days) in gill tissue, but more slowly (t _1/2=6.82 days) than glycerol (t _1/2=4.1 days) in liver. Although rates of glycerol turnover were equivalent in PC and PE of liver microsomes, the fatty acyl component turned over significantly more rapidly in PC at both acclimation temperatures. In cold-acclimated trout, rates of fatty acid and glycerol turnover were equivalent in PE, but the fatty acyl moiety of PC (t _1/2=4.7 days) turned over significantly more rapidly than glycerol (t _1/2=7.5 days). These results were interpreted as indicating that: (1) acclimation temperature independently influenced rates of fatty acid and glycerol turnover in a tissue specific manner, (2) a deacylation-reacylation pathway was activated in both liver and gill as a consequence of cold acclimation, but that liver tissue was more effective than gill in reutilizing the fatty acids released by phospholipase activity, and (3), in liver microsomes, patterns of turnover were phospholipid specific, with PC and PE differing either in the susceptibility of their acyl groups to degradation, or in their ability to reutilize fatty acids cleaved during membrane turnover at cold temperatures.     

Inhibition, by 2-Oxo Acids That Accumulate in Maple-Syrup-Urine Disease, of Lactate, Pyruvate, and 3-Hydroxybutyrate Transport Across the Blood-Brain Barrier

Abstract: Data are presented in support of the transport of (-)- d -3-hydroxybutyrate across the blood-brain barrier (BBB) being a carrier-mediated process. The kinetic parameters in 21-day-old pentobarbital-anaesthetized rats were V_max 2.0 μmol.g⁻¹.min⁻¹, K _m 29 m M , and K _D 0.024 ml.g⁻¹.min⁻¹. The value for V_max was the same as that for l -lactate and pyruvate transport in animals of the same age. The transport of all three substrates was sensitive to inhibition by low concentrations of either 2-oxo-3-methylbutanoate or 2-0x0-4-methylpentanoate, the 2-oxo acids that can accumulate in patients with maple-syrup-urine disease. The K _m values for the 2-oxo acids were severalfold lower than the respective K _m values. 2-oxo-3-phenylpropionate was a poor inhibitor. The relative affinities of the various monocarboxylic acids for the transport system of the BBB distinguished it from similar systems described in brain, heart, and liver mitochondria; human erythrocytes; and Ehrlich ascites-tumour cells.