SEASONAL TRENDS IN RATES OF PHOTOSYNTHESIS AND RESPIRATION OF LOBLOLLY PINE AND WHITE PINE SEEDLINGS

Mc Gregor , William H. Davis (Clemson Coll., Clemson, S.C.), and Paul J. Kramer . Seasonal trends in rates of photosynthesis and respiration of loblolly pine and white pine seedlings. Amer. Jour. Bot. 50(8): 760–765. Illus. 1963.—Seasonal trends in the rates of photosynthesis and respiration of potted loblolly and white pine seedlings were studied by measuring CO₂ exchange with an infra-red gas analyzer at intervals during a year. The seedlings were kept out-of-doors, but measurements were made indoors at 25 C and 4000 ft-c of light. Beginning in February, the rate of photosynthesis per plant of both species increased, reaching a peak in mid-September for loblolly pine and in mid-July for white pine and then declining rapidly after mid-September for both species. The spring increase began before new needles emerged and the autumn decline was not accompanied by appreciable loss of foliage. The respiration rate of loblolly pine increased steadily throughout the year. Respiration of white pine increased until mid-May and then remained fairly constant through the remainder of the year. Maximum rate of photosynthesis per unit of fascicle length occurred in July for the white pine and in May for the loblolly pine, and rates declined after September in both species. Respiration rate per unit of fascicle length showed a marked increase as spring growth began in April, then decreased to a minimum in September and increased during the winter in both species. Total chlorophyll per seedling reached a maximum in September for both species and declined slightly during winter. Total chlorophyll per unit of fascicle length increased in the spring, declined slightly in midseason, and increased again in September. Photosynthesis per unit of chlorophyll reached a maximum in May for loblolly pine and in July for white pine. Stem elongation of white pine was 88% completed by May 15. On the same date, stem elongation of loblolly pine was only 42% completed.     

Effects of bromocriptine on pituitary tumour size.

In a prospective study designed to assess the influence of bromocriptine on pituitary tumour size 12 patients with pituitary tumours, eight of whom had suprasellar extensions, were treated for three months with 20 mg of bromocriptine daily after a gradual increase to this dose. The group comprised eight women and four men, five with prolactin-secreting adenomas, four with acromegaly, two with functionless adenomas, and one with Nelson''s syndrome. All five patients with prolactin-secreting adenomas showed a reduction in pituitary tumour size as assessed by computerised tomography and metrizamide cisternography accompanied by a fall in prolactin concentrations and clinical and biochemical improvement in their hypopituitarism. One patient in this group had a visual-field defect before treatment, and this resolved. There was no radiological evidence of reduction in tumour size in the remaining seven patients, though this might refect the fairly short duration of treatment, particularly in view of the ancillary evidence of clinical, biochemical, and visual-field improvement in some of the patients. These results emphasise the potential value of bromocriptine in treating patients with large prolactinomas or recurrences of such tumours after previous chiasmal decompression and conventional external megavoltage irradiation on the pituitary.     

The influence of manganese on the development of potato scab

Summary The development of common scab on potato crops growing in slightly acid to neutral soils has been shown to be greatly reduced by application of manganese sulphate to the soil at planting time. A general improvement in health and appearance of tubers was noted and increased yields of marketable tubers were obtained. The possibility that environmental factors known to influence the development of scab are only important in so far as they affect the solubility of soil manganese is discussed.     

T cell-mediated cytotoxicity induced by Listeria monocytogenes. III. Phenotypic characteristics of mediator T cells

Cytotoxic thymus-derived lymphocytes (CTL) generated in vitro by restimulating rat cells with Listeria antigen- (LMA) pulsed syngeneic accessory cells were characterized in respect to their surface membrane markers. LM-dependent CTL were devoid of detectable surface immunoglobulin (Ig) and receptors for the Fc region of rabbit IgG. Experiments with monoclonal antibodies to rat T cell markers revealed that these cytotoxic cells have the phenotypic profile W3/13+, W3/25-, MRC OX 8+. LM-dependent CTL also bind the monoclonal antibody, MRC OX 3, which recognizes an Ia-antigen-like determinant on rat cells. Although LM-dependent CTL lack the W3/25 marker, their generation depends on the cooperative interplay of W3/25+ and W3/25- T cells.     

Manganese neurotoxicity: a model for free radical mediated neurodegeneration?

In man, manganese neurointoxication is characterised in the early phase by behavior reminiscent of that observed in schizophrenia. During chronic manganese intoxication the neuropsychiatric symptoms manifested earlier disappear and are followed by a permanent neurological phase typified by extrapyramidal symptoms similar to those of Parkinson's disease. Study of manganese intoxication in animals may provide important clues towards elucidation of the biochemical defect underlying neuropsychiatric as well as extrapyramidal disease. Investigations in our laboratory suggest that neurotoxicity of manganese is an exaggeration of function in normal neuronal homeostasis. Manganese neurointoxication in neonatal rats resulted in significant depression of lipid peroxidation in several rat brain regions examined. In the striatum, lipid peroxidative activity was abolished, an effect which may be related to alteration in neurotransmitters often observed in the striatum of manganese treated rats. The chronic, extrapyramidal stage of manganism, may ensue when excess Mn2+ is oxidised to higher valency forms where it can potentiate the autoxidation of catecholamines, like dopamine, resulting in concomitant formation of free radicals and cytotoxic quinones. This latter effect may arise preferentially in the substantia nigra, where neuromelanin is formed nonenzymatically by autoxidation of dopamine.     

The application of the minimal energy hypothesis to a casson fluid

Deakin (1967b) suggested that flow of blood might obey a law of minimal energy dissipation. The present paper presents a simpler derivation of Deakin’s equations pointing out several previously unrecognized features. It is shown that these equations are unlikely to be applicable. In particular, the solution obtained by Deakin and Jones (1968) does not yield a true minimum for energy dissipation. The solution for which energy dissipation is actually minimized is shown to possess features which render it unlikely to apply to a real flow.     

The relationship between permanent incisor wear and mohair production and attributes in grazing adult Angora goats

We aimed to quantify if and to what extent permanent incisor wear affected mohair production in adult Angora castrate goats. The goats were grazed on annual temperate pastures for 6 years. During their sixth year mohair was harvested every 6 months and liveweight measured. Incisors were inspected at age 6 years and the amount and pattern of wear quantified. Restricted maximum likelihood (REML) base models were developed to account for background sources of variation. Once a base model had been selected for each fleece attribute, an extra term for the linear effect of the first and other permanent incisor wear were added to the model. During the year mean liveweight, greasy mohair production, clean mohair production and mean fibre diameter were (S.D.): 55.6 (5.85) kg, 4.97 (1.00) kg, 4.16 (0.87) kg, 34.8 (4.02) μm. Mean wear on permanent first incisors was 9% (range 0–30%). There was little wear on other permanent incisors. Greasy fleece weight, clean fleece weight, staple length and fleece entanglement were reduced significantly with increased wear of first permanent incisors. There were no significant effects of incisor wear detected for nine other fleece attributes or liveweight. The results indicate that 30% wear of the permanent first incisors reduced greasy fleece production by 20% and reduced clean fleece production by 30%. Given the magnitude of the effects detected it is clear that relatively small amounts of wear of permanent incisors in adult Angora goats reduce production of mohair and consequently will reduce financial returns from mohair sales. The clear implication is that managers of mohair producing enterprises should assess the incisors of adult Angora goats and use this information in determining which animals to cull from their flocks.