The anatomy of tissue cultured red raspberry prior to and after transfer to soil

The leaf, petiole, stem and root anatomy of an aseptically cultured red raspberry clone (Rubus idaeus L.) was studied before and 5 weeks after transfer to soil under controlled environmental conditions. Tissues persistent from culture showed little or no change with time in soil; they grew minimally and slight secondary wall deposition occurred. New organs formed in successive weeks after transplantation showed a graded increase in potential size and development. Some features, such as collenchyma formation, rapidly returned to control levels; this was seen in new leaves expanding in the first week after transplantation. Other features, such as sclerenchyma formation, did not occur in leaves expanding during the first 2 weeks after transplantation, even when these were a month or more in age. Some sclerenchyma was seen in leaves expanding in the third week after transplantation, increasing in later-formed leaves. Increasing the light intensity of transplant accelerated the return to control-type organ size and appearance. During acclimatization transitional forms of leaves, petioles, stems and roots develop that ranged anatomically from culture-to control-type. This trend is analagous to the normal developmental sequence of organ formation as it affects the potential for development of successily formed organs.     

The thiol groups of mouse immunoglobulin A. Incomplete formation of the C alpha 1-domain disulphide bridge.

The BALB/c IgA (immunoglobulin A) myeloma protein M167 contained on average 5.7 free SH groups per IgA dimer. These groups were preponderantly on the heavy chains and comprised two distinct populations: 3.3 exposed SH groups per dimer in the Fc region, and 2.4 buried SH groups per dimer in the Fd region, detectable o only after denaturation. To locate the cysteine residues involved, labelled peptides were purified from thermolysin digests of radioalkylated IgA by high-performance liquid chromatography. From the amino acid compositions of the peptides, the exposed thiol groups were assigned to Cys-307 in the C alpha 2 domain, which thus existed in the reduced form to an extent exceeding 80%. This residue may allow attachment of secretory component to dimer IgA in the mouse to proceed via thiol-disulphide exchange. The buried thiol groups were assigned to Cys-150 and Cys-208, in the C alpha 1 domain, each being in the reduced form to the extent of approx. 30%. This pair of residues would normally give rise to the characteristic intradomain disulphide bridge. It appears that disulphide formation is not a crucial event during folding of the C alpha 1 domain in IgA biosynthesis. The sequence in the region 140-151 was re-investigated, and residue 142 was shown to be serine, not cysteine, helping explain the lack of heavy-chain-light chain bonding in BALB/c mouse IgA. A disulphide-bond model for mouse IgA is proposed on the basis of these assignments and other features of the mouse alpha-chain sequence.     

Characterization of algae using regularities

The weight fraction carbon and reductance degree of algae are reviewed for literature data. Average values are compared with values for yeast and bacteria. The results show that the standard deviation and coefficient of variation are small as long as the algae are grown under adequate nutritional conditions. For nitrogen-deficient growth conditions, the storage of lipids has been observed; this results in values of weight fraction carbon and reductance degree which are larger than the average values.     

Gene amplification in Bacillus subtilis

A strain of Bacillus subtilis that carries in its genome a staphylococcal chloramphenicol acetyltransferase gene (from pC194) responds to growth at different concentrations of chloramphenicol by an alteration in the number of copies per genome of the sequences encoding the gene. Growth at 20 micrograms chloramphenicol ml-1 results in a 15-fold amplification of the sequences, whereas growth in the absence of chloramphenicol results in their loss. The mechanism of in situ amplification probably has much in common with that involved in 'R factor transitioning'. The hybridization procedures that have been used for accurately determining the number of copies of the amplified DNA sequences are potentially useful for plasmid copy number determination. The findings reported here also provide a potentially useful alternative to more conventional cloning strategies that are based on autonomous plasmids in B. subtilis. The particular advantages that can be envisaged include enhanced stability of the cloned sequences and control of the number of copies that are present.     

Interaction of fatty acids with lipid bilayers

We present a method by which it is possible to describe the binding of fatty acids to phospholipid bilayers. Binding constants for oleic acid and a number of fatty acids used as spectroscopic probes are deduced from electrophoresis measurements. There is a large shift in $\text{p}\text{K}$ value for the fatty acids on binding to the phospholipid bilayers, consistent with stronger binding of the uncharged form of the fatty acid. For dansylundecanoic acid, fluorescence titrations are consistent with the binding constants derived from the electrophoresis experiments. For 12-(9-anthroyloxy)stearic acid, fluorescence and electrophoresis data are inconsistent, and we attribute this to quenching of fluorescence at high molar ratios of 12-anthroylstearic acid to phospholipid in the bilayer.     

Effects of Age, Water Stress, and 1-Aminocyclopropane-1-carboxylic Acid on Leaflet Movement in Albizzia julibrissin

The movement patterns of Albizzia julibrissin leaflets transferred from light to darkness differ for leaflets of different age: the older the leaflet, the slower and less completely it closes. Water stress, which enhances ethylene synthesis in other plants, and 1-aminocyclopropane-1-carboxylic acid (ACC), precursor of ethylene, both mimic the effect of aging by reducing the rate and extent of dark-induced closure. Brief far-red compared to red irradiation before darkness does not appear to alter the closure of young leaflets, but far-red preirradiation retards the closure of middle-aged and old leaflets floating on water, and middle-aged leaflets treated with ACC. A change in some membrane property and/or cell wall lignification are suggested as possible explanations for the alteration of leaflet movement.     

Control of respiratory pattern in conscious dog: effects of heat and CO2

We measured tidal volume (VT) and inspiratory (TI) and expiratory (TE) durations in five conscious tracheostomized dogs breathing air or 5% CO2 in air either at normal (20 degrees C) or elevated (30 degrees C) ambient temperatures. Respiratory frequency ranged between 16 and 333/min due to changes in both TI and TE. During panting TI exceeded TE. During air inhalation instantaneous ventilation (V) spontaneously ranged from 100 to 1,600 ml . kg-1 . min-1. Hypercapnia, heat stress, or both, increased this range of V by increasing maximum V, primarily due to increases in mean inspiratory flow. Under these conditions, changes in TI accounted for more of the spontaneous changes in breath duration. During inhalation of air and 5% CO2, a positive correlation between VT and TI was obtained for TI between 0.13 and 1.05 s; above 1.05 s VT decreased. Heat stress increased VT at a given TI. We suggest that either the decay rate or position of the inspiratory off-switch threshold curve (Clark and von Euler, J. Physiol. London 222: 267, 1972) varies in conscious dogs. Shifts in either the reset (onset) value or decay rate of the curve yield a positive correlation between VT and TI. This modification to the Clark-von Euler model implies that the primary effect of anesthesia on respiratory control is fixation of the inspiratory off-switch threshold curve.     

Life-cycles of some invertebrate taxa in a small pond together with changes in their numbers over a period of three years

1. Monthly quantitative samples of the invertebrate fauna (except Protozoa) in a small pond were taken over a period of three years. During one year, insect emergence traps were in operation. Water temperatures were recorded during the investigation.
2. The most abundant organisms in the pond were Phaenocora typhlops, Limnodrilus hoffmeisteri and Chaoborus crystallinus. Certain species of Micro-Crustacea and Chironomidae were also abundant but these groups have been dealt with elsewhere (see p. 66). Dendrocoelum lacteum, Polycelis nigra, Helobdella stagnalis, Lumbriculus aariegatus, Tubifex tubifex, Planorbis complanatus, and Asellus meridianus also occurred in considerable though lower numbers; other species occurred in low numbers.
3. The life-cycles and changes in numbers of the more numerous species are considered. The life-histories of D. lacteum, P. nigra, H. stagnalis, P. complanatus, A. meridianus are in agreement with published information. P. typhlops is seasonal in occurrence, being active from May to Sept. inclusive. Times of emergence of adults of various insect species agree with information available in the literature.
4. The life-cycle of L. hoffmeisteri in the pond is as follows: young worms hatch in spring/summer and form the bulk of the population from April to July/Aug; they mature from Aug. onwards and breeding starts in earnest from Feb./March. The life-cycle of T. tubifex is as follows: breeding starts in Feb., recruitment of young takes place from April till June, and these start to mature in Nov./Dec. It is not certain if some animals which breed in the spring/early summer survive to breed the following year.
5. The life-cycle of C. crystallinus appears to be as follows: first instars present from May to Oct., second instars from May to Dec., third instars from June till following Jan., fourth instars all the year round, pupae from May till Aug., and eggs from May to Sept. Adult emergence takes place from late April till mid-Sept.
6. A six-week drought in Oct/beginning Nov. in the second year of the investigation caused considerable mortality in most species, but most survived with only a few exceptions.

     

Inhibition of Transformation of Bacillus subtilis by Heavy Metals

Mercuric ions, as well as organomercuric ions and cadmium ions, can inhibit deoxyribonucleic acid-mediated transformation in Bacillus subtilis 168 without decreasing the viability of the total population. Differences in the inhibition of transformation by mercuric ions are identifiable on a temporal and concentration dependence basis. Sensitivity to low concentrations (9.2 x 10(-8) M) appears early in the uptake of deoxyribonucleic acid before the transformed markers have become insensitive to deoxyribonuclease. Resistance to "low concentrations" of Hg(2+) is kinetically indistinguishable from the requirement for magnesium in the transformation process. This inactivation is not reversed by the mercury-binding compound glutathione. Sensitivity to mercuric ions at a higher concentration (5.52 x 10(-7) M) occurs after the donor deoxyribonucleic acid has become insensitive to deoxyribonuclease. These complex interactions between mercuric ions and the process of transformation are discussed.