Role of microtubules in the intracellular transport of growth hormone

Summary Pulse-chase experiments utilising(³H)leucine have been used to study the effects of colchicine and vinblastine on intracellular transport and secretion of newly synthesised growth hormone from rat anterior pituitary fragments. Growth hormone was isolated from medium and fragments by polyacrylamide gel electrophoresis. When colchicine or vinblastine, which disrupt microtubules, were added immediately after pulse labelling, inhibition of the subsequent secretion of newly synthesised growth hormone was detected throughout the succeeding 5 h. Similar inhibition was seen if the drugs were added after a 1 h delay. However, if colchicine or vinblastine were added only after a 2 h chase incubation, then no significant effect on subsequent release of labelled growth hormone was seen. The results suggest that these agents may inhibit the transport of newly formed growth hormone storage granules from the Golgi complex to the cytoplasmic pool. Microtubules do not appear to be involved in the mechanism of the final secretion of newly synthesised hormone by exocytosis.These studies were supported by grants from the Medical Research Council and British Diabetic Association     

Stimulation of growth and glucose catabolite enzymes by succinate in some thermophilic fungi

Thermophilic Humicola lanuginosa, Penicillium duponti, Sporotrichum thermophile and Mucor pusillus required succinate in addition to glucose for optimal growth. The requirement for succinate was concentration-dependent and the concentration needed for one half of the maximal growth was 6.14 mM. In the presence of succinate, glucose utilization from the medium was markedly increased and this was associated with increased levels of the enzymes of the glycolytic and Krebs cycle pathways. Addition of succinate to cultures growing in glucose at any stage of growth stimulated the growth with the resulting rate of growth remaining high if the addition was made within 3 days of inoculation. Cycloheximide (71.4 M) prevented the succinate-mediated derepression of the enzymes suggesting that succinate may remove the catabolite repression in the presence of glucose.A preliminary part of this work was presented at the 17th annual meeting of the Association of Microbiologists of India at Manipal (India) held from Dec. 13 to 15, 1976     

Growth of host dependent Bdellovibrio in host cell free system

A particulate, subcellular fraction of Escherichia coli was shown to promote the growth of host dependent (H-D) Bdellovibrio in the absence of host cells. The growth promoting activity was enhanced by both cations and trypsin, and destroyed by pronase. During the axenic growth unipolar spheres appear in the elongating Bdellovibrio forms. Thymidine monophosphate was more readily incorporated than thymidine into the Bdellovibrio DNA during growth in the host free system.     

An Automated Technique for the Radiographic Determination of Bone Age

We have developed an automated procedure for determining bone-age in the monkey, Macaca fascicularis. The status of epiphysial junctions and sesamoids were determined from radiographs. Epiphyses were scored as either open or closed, and sesamoids were scored as either present or absent. Bone-age was calculated by a computer program that stored and used a data base of probabilities for epiphysial closure and sesamoid appearance. The simplicity of scoring, combined with the speed and accuracy of the calculations, make this technique potentially adaptable for use in a variety of primate species.     

Spiral growth in the radially-expanding piloboloid mutants ofPhycomyces blakesleeanus

The growth zone of the sporangiophore of a piloboloid mutant,pil, ofPhycomyces expands radially at an increased rate until the growth zone becomes nearly spherical, in sharp contrast to that of the wild-type sporangiophore which exhibits longitudinal elongation only and is conical. The rotation of thepil sporangiophore reverses its direction from clockwise (CW) to counterclockwise (CCW) during the period of increased radial expansion, and the CCW rotation continues as long as does the radial expansion. The direction of rotation and the time of reversal are correlated with the relative rates of cell-wall expansion in the longitudinal and transverse directions. The CCW rotation of the sporangiophore of this mutant can be explained by the behavior of the microfibrils, as previously proposed to explain the rotation of the wild-type sporangiophore.Abbreviations CW clockwise - CCW counterclockwise — both as viewed from above     

Effect of Oryzalin and 1,1-Dimethylpiperidinium Chloride on Cotton and Tomato Roots Infected with the Root-knot Nematode,Meloidogyne incognita

Oryzalin (3,5-dinitro-N4,N4-dipropyl-sulfanilamide) and BAS 083 (l,l-dimethylpiperdinium chloride) reduced root-knot infection in tomato roots when respectively applied as a soil drench at 20 ppm and 10,000 ppm. Oryzalin reduced knot counts with various intervals between treatment and inoculation. BAS 083 reduced knot counts only when applied before inoculation. Oryzalin was shown not to be a contact nematicide, and BAS 083 was only a weak one. Neither compound reduced penetration by infective larvae. Postinfection reduction in knot counts by Oryzalin and BAS 083 resulted, in part, from activation of natural defense mechanisms of the host. Giant-cell development in cotton roots inoculated with nematodes was inhibited by Oryzalin. Lateral root development was inhibited by BAS 083.     

Nodulation,nitrogen fixation,leaf area,and sugars content inLablab purpureus as affected by sulfur nutrition

Summary In order to explore interrelations between S nutrition, soluble sugars, leaf area, nodulation and N₂ fixation, greenhouse experiments were done with several levels of S added to perlite-sand cultures or to a moderately S-deficient soil. Sulfur had indirect effects on nodulation and N₂ fixation, possibly by improving sugars supply and N metabolism.In perlite-sand culture, leaf area increased with concentrations of supplied S up to 50 and 200 M for symbiotic and N-treated plants respectively, then decreased at higher concentrations. Plant yield and total sugars content (mg per plant) for the N-treated plants behaved similar to leaf area in response to added S but in the symbiotic plants maximum values were obtained at 100 M S. In soil, Mo had no effect on growth but interacted significantly with S in affecting total sugars content. High levels of S depressed sugars content at low Mo but raised it at high Mo.Sulfur increased the N content of soil-grown plants. It increased the N content of plants grown in perlite-sand culture except at very high levels of S. There was little effect on concentration of N in the shoots. Nitrogen content correlated significantly with leaf area and sugar content, and highly significantly with S concentration in the shoots.     

Influence of a carbamate pesticide on growth,respiration (14C)-carbon metabolism and symbiosis of aRhizobium sp.

Summary Addition of aldicarb (2 methyl-2(methyl thio) propionaldehyde-0-methyl carbamoyl oxime) in the growth medium enhanced the growth ofRhizobium sp. (cowpea group) at 2 ppm level while an inhibition was observed at the normal (5 ppm) and higher (10 ppm) concentrations. Respiration of the cells was also inhibited by 5 and 10 ppm levels of the chemical eventhough a stimulation was observed at 2 ppm (lower) concentration. The insecticide, when incorporated at 5 and 10 ppm levels in the medium increased the¹⁴C-glucose incorporation and considerably altered the assimilation of the radioactive carbon in different fractions of rhizobium cells. Soil application of this insecticide (Temik 10 G) reduced the number of nodules formed and the total nitrogen content in cowpea plants inoculated with theRhizobium sp. but enhanced the dry matter production of cowpea plants.Based on the M. Sc. thesis submitted by the first author to the Tamil Nadu Agricultural University, Coimbatore-3.     

Interaction of [3H]gibberellin A1 with a sub-cellular fraction from lettuce (Lactuca sativa L.) hypocotyls

The relationship between protein synthesis and the incorporation of [³H]gibberellin A₁ ([³H]GA₁) into a 2,000xg pelletable (2KP) fraction from lettuce (Lactuca sativa L.) hypocotyl sections has been investigated. Concentrations of D-2-(4-methyl-2,6-dinitroanilino)-N-methylpropionamide (MDMP) between 10^-7 M and 10^-4 M caused increasing inhibition of growth, 2KP labelling and incorporation of [¹⁴C]leucine into soluble protein. Growth and 2KP radioactivity were highly correlated (r=0.996). Transfer to MDMP early or late in the course of GA response caused reductions in both growth and incorporation into the 2KP fraction. Exposure to the inhibitor had more effect at 4 h than at 20 h. The proportions of alkali-soluble and insoluble radioactivity in the 2KP fraction were also altered by this treatment. The implications of these findings are discussed.Abbreviations GA₁ gibberellin A₁ - MDMP D-2-(4-methyl-2,6-dinitroanilino)-N-methylpropionamide - 2KP a2,000xg pelletable fraction     

The influence of plant growth regulators on the growth of the embryonic axes of red- and far-red-treated lettuce seeds

The influence of several plant growth regulators on the growth of the embryonic axes from red- and far-red-(R- and FR-)treated lettuce (Lactuca sativa L., cv. Grand Rapids) seeds was examined; as shown previously, the water potential of the axes from R-treated seeds has been lowered by 3.5–5.6 bars compared to that in axes from FR-treated ones. Kinetin and abscisic acid (ABA), when included in the incubation medium, reduced the elongation of the axes whereas fusicoccin stimulated it; however, these effects were the same in axes of both R- and FR-treated seeds. In contrast, elongation of axes from FR-treated seeds was stimulated by gibberellic acid (GA₃, but elongation of axes from R-treated ones was not affected by this hormone. This latter result indicates that gibberellins may be involved in the phytochrome-mediated growth responses in lettuce axes.When the root caps of the embryos were removed prior to light treatment, R was still able to induce a water-potential decrease in the embryonic axes, indicating that at least a portion of the active Pfr resides in the axis and not the root cap.Abbreviations ABA abscisic acid - FR far red light - GA₃ gibberellic acid - PEG polyethylene glycol - Pfr far-red-absorbing form of phytochrome - R red light