Exposure to a combination of heat and hyperoxia during cycling at submaximal intensity does not alter thermoregulatory responses

In this study, we tested the hypothesis that breathing hyperoxic air (F_inO₂ = 0.40) while exercising in a hot environment exerts negative effects on the total tissue level of haemoglobin concentration (tHb); core (T_core) and skin (T_skin) temperatures; muscle activity; heart rate; blood concentration of lactate; pH; partial pressure of oxygen (P_aO₂) and carbon dioxide; arterial oxygen saturation (S_aO₂); and perceptual responses. Ten well-trained male athletes cycled at submaximal intensity at 21°C or 33°C in randomized order: first for 20 min while breathing normal air (F_inO₂ = 0.21) and then 10 min with F_inO₂ = 0.40 (HOX). At both temperatures, S_aO₂ and P_aO₂, but not tHb, were increased by HOX. Tskin and perception of exertion and thermal discomfort were higher at 33°C than 21°C (p < 0.01), but independent of F_inO₂. T_core and muscle activity were the same under all conditions (p > 0.07). Blood lactate and heart rate were higher at 33°C than 21°C. In conclusion, during 30 min of submaximal cycling at 21°C or 33°C, T_core, T_skin and T_body, tHb, muscle activity and ratings of perceived exertion and thermal discomfort were the same under normoxic and hyperoxic conditions. Accordingly, breathing hyperoxic air (F_inO₂ = 0.40) did not affect thermoregulation under these conditions.     

Biochemical Approaches to Mating Type Expression in Tetrahymena thermophila1

Two-dimensional gel electrophoresis was used to identify the patterns of protein synthesis during initiation, and the patterns of membrane protein expression following initiation, in all of the mating types of the Tetrahymena thermophila B family. In addition, one-dimensional analysis was used to survey ¹²⁵I-Concanavalin A-binding proteins. Although a large number of proteins was identified by each technique, no variation among the mating types was observed.     

Ultrastructural localization of the high molecular weight proteins associated with in vitro-assembled brain microtubules

Microtubules isolated from brain extracts by in vitro assembly (1, 19, 23) are composed principally of two tubulins and two high molecular weight proteins (microtubule-associated proteins [MAPS] 1 and 2) (2,5,7,20). Recently, it was demonstrated that in vitro-assembled brain microtubules (neurotubules) are coated with filaments (5, 7) which are similar to the filaments attached to neurotubules in situ (4, 15, 21, 24, 25), and it was suggested that the filaments are composed of the higher molecular weight MAPs (5, 7, 12). In this study, microtubules were assembled in the presence and absence of the MAPs, and thin sections of the microtubules were examined by electron microscopy. The results show that the filaments only occur on microtubules assembled in the presence of the MAPs and it is therefore concluded that the filaments are composed of the high molecular weight MAP's.     

Initiation of Yolk Deposition by Juvenile Hormone

JUVENILE hormone is secreted by the corpus allatum gland, in insects. It was first implicated in the control of yolk deposition in 1936¹ and has recently been found to stimulate fat body synthesis of vitellogenic blood proteins (vitellogenins)^2,3 which are selectively incorporated into yolk by the oocytes^4–6.     

Interacting evolutionary constraints in pelvic reduction of threespine sticklebacks, Gasterosteus aculeatus (Pisces, Gasterosteidae)

The pelvic girdle of Gasterosteus aculeatus is normally a complex and robust structure that varies moderately among and within populations, but in several populations it occurs as a vestigial series. Based on 14 Recent and fossil populations from North America and Scotland, three general patterns of intrapopulation variation of vestigial pelvic structures can be recognized. In most cases of pelvic reduction, the size and complexity of the pelvic girdle are reduced mostly by progressive truncation of distal structures, but two patterns of distal truncation occur. Paedomorphosis appears to play a role in all cases of pelvic reduction, but in a fossil assemblage and one extant population it accounts for most of the structural simplification.
Pelvic reduction in populations of Gasterosteus depends on an interaction between natural selection, which appears to determine whether or not pelvic reduction occurs, and phylogenetic constraint (especially developmental constraint), which strongly influences the form of pelvic vestiges. The empirical difficulty of discriminating between phylogenetic constraint and effects of natural selection, and the potential for phylogenetic constraint to produce homoplasy are discussed. Pelvic reduction apparently has been a recurrent phenomenon in Gasterosteus since at least the early Pliocene, but it has not resulted in evolution of a separate lineage of 'pelvicless' sticklebacks because such populations are restricted to lakes, which are ephemeral over evolutionary time. Rapid phyletic pelvic reduction coupled with selective extinction of populations with vestigial pelvic structures has resulted in phylogenetic stasis.     

Nucleocytoplasmic Interaction During Maturation of the Egg of the Fern Histiopteris incisa (Thunb.) J. Smith

The maturing egg of Histiopteris incisa has many features incommon with that of Pteridium, with which the species may berelated. The nuclear evaginations are however conspicuous inrespect of the extensive development of internal membrane systems,involving dilatation of the perinuclear space. In some in stancesthe inner membrane of the nuclear envelope, the proliferationof which gives rise to the dilatations, was strikingly tenuous,possibly indicating an extensive interchange between the perinuclearspace and that part of the nucleoplasm sequestered in the evaginations.The evaginations frequently contain an aggregate of electron-opaquematerial resembling structurally and in staining propertiessimilar aggregates in Pteridium, but in contrast to Pteridiumthere was no evidence that these aggregates were organized inor near the nucleolus. Histiopteris inciso (Thunb.)J. Smith, Pteridophyta, egg maturation, nucleocytoplasmic interaction, ultrastructure     

THE ADVANTAGES OF A PLATINUM TUBE DROPPING PIPETTE FOR MAKING COLONY COUNTS

SUMMARY: For routine purposes where a large number of tests is involved the dropping pipette technique has many advantages over other methods of determining the colony count. However, glass pipettes are fragile and much time and labour have to be used in making and calibrating replacements. A robust platinum tube dropping pipette has been found very satisfactory. No difficulty was experienced in obtaining complete sterility of the pipettes in the technique described, and reproducibility of drop size was good.