Cytogenetic and blood group studies of sheep/goat chimaeras

Aggregation chimaeras were composed of quarter (or 1 cell) contributions from 4-cell blastocysts of sheep or goats, or of an 8-cell blastocyst of one species enveloped in three 8-cell blastocysts of the other. Gestation was in sheep or goat recipient females. Of the 10 living animals born, 3 were identified as interspecific chimaeras by body conformation and coat type among the 7 quarter/quarter aggregations and 1 among the 3 giant aggregates. Interspecific chimaerism was identified by cytogenetic study of umbilicus and blood lymphocytes respectively of 2 of these, one from each type of aggregate. Intraspecific sex chimaerism was found in 3 other animals; 2 were of giant aggregate origin, but the 1 of quarter/quarter origin must have acquired it by placental anastomosis with a twin conceptus. Tests using species-specific monoclonal antibodies and electrophoretic separation of haemoglobins and isoenzymes demonstrated sheep and goat erythrocytes in one giant aggregate chimaera; their relative proportions and those of the blood lymphocytes changed over a period of 31 months from approximately 60% goat and 40% sheep to more than 90% sheep. The plasma transferrins and amylases did not show similar relative changes from their predominantly goat-like character and, by implication, neither did their tissues of origin.     

Responsiveness of the olfactory receptor cells in dog to some odors

A preparation has been developed in the dog which allows recording the electrical activity from an olfactory nerve twig containing the axons of a small group of olfactory receptor cells. The dog's response to n-pentyl acetate is vigorous and stable, like that of other air-breathing animals. The dog's response magnitude dependence on the nasal flow rate was noticeable for n-pentyl acetates, but not so great as for n-butyric acid. The response to n-butyric acid strongly depends on the nasal flow. The start of the nasal air flow caused an increase of neural activity, which is called flow response. The results show that the nasal flow rate is a very important factor which determines the response to odors. Methyl p-hydroxybenzoate is known as a dog's pheromone, however, this odor caused the feeble response in the electrical activity of the dog's olfactory receptor cells. The differences may be dependent on several factors.     

Differentiation of the mechanisms by which leukotrienes C4 and D4 elicit contraction of the guinea pig trachea

The contractions elicited by leukotriene (LT) C4 and D4 in isolated guinea pig trachea were characterized under conditions in which LTC4 to LTD4 metabolism was blocked by the presence of 45 mM l-serine-borate complex (SB). The presence of SB caused a shift of the LTC4-concentration-response curve to the left by 7.5-fold, and blocked the bioconversion of LTC4 to LTD4 by the trachea as estimated by HPLC analysis of the LTs present in the tissue bath fluid. The potency of FPL 55712 as an antagonist of the LTC4-induced contractions in the presence of SB was 15-30-fold less than its potency as an antagonist of the LTD4-induced contractions. In contrast, another LT antagonist, SK&F 101132, equally antagonized the contractions elicited by LTC4 and LTD4 in either the presence or absence of SB. The differential antagonism of LTC4 and LTD4 implies the existence of multiple pharmacologic receptors for the LTs. The calcium channel entry blockers, nifedipine and verapamil, at concentrations as high as 10 microM, suppressed the maximal LTC4-induced contraction by no more than 20%, whereas the purported intracellular calcium antagonist, TMB-8, completely suppressed the LTC4 concentration-response curve in the presence of SB, a profile identical to that previously reported for LTD4. Thus, if multiple LT receptors exist, they appear to mobilize calcium in a qualitatively similar fashion following LT stimulation.     

Headache at high altitude is not related to internal carotid arterial blood velocity

The cause of headache in persons going to high altitude is unknown. Relatively severe hypoxemia in susceptible subjects could induce large increases in cerebral blood flow that then could initiate the headache. Thus we measured noninvasively, by Doppler ultrasound, changes in internal carotid arterial blood velocity (velocity) in 12 subjects in Denver (1,600 m) and repeatedly up to 7 h at a simulated altitude of 4,800 m (barometric pressure = 430 Torr). Six subjects, selected because of prior history of high-altitude headache, developed comparatively severe headache at 4,800 m, and four subjects, without such history, remained well. Two subjects developed moderate headache. Velocity at 4,800 m did not correlate with symptom development, arterial O2 saturation, or end-tidal PCO2. Also, neither velocity nor blood pressure was consistently elevated above the Denver base-line values. During measurements of hypercapnic ventilatory response in Denver, velocity increased linearly with end-tidal PCO2, confirming that our Doppler method could demonstrate an increase. Also, 30 min of isocapnic or poikilocapnic hypoxia caused small increases in velocity (+8 and +6%) during the base-line measurement at low altitude. Although even a small increase in cerebral perfusion could contribute to headache symptoms at high altitude, cerebral blood flow does not appear to play a primary role.     

Plasma volume changes in middle-aged male and female subjects during marathon running

Circulatory fluid shifts were studied in middle-aged runners (6 males and 5 females, ages 32-58 yr) during a 42.2-km marathon race run in mild weather (dry-bulb temperature = 17.5-20.4 degrees C). Running times for the subjects were 3:12-4:40 (mean values were 3:34 for males and 4:10 for females). Venous blood samples were taken without stasis in all subjects seated at rest before the start of the race and within 3 min of finishing; eight of the subjects also paused for samples at 6 and 27 km during the race. At 6 km, body weight loss averaged less than 1%, whereas plasma volume (PV) had decreased by 6.5% in male subjects and 8.6% in female subjects. By the end of the race, hypohydration had reached 3.2% in male subjects and 2.9% in female subjects, but PV in both groups remained stable. Sweat rates during the race averaged 545 and 429 g X m-2 X h-1 for male and female subjects, respectively, with ad lib. water intake replacing 21-72% of fluid loss. Increases in plasma protein concentration throughout the race reflected the observed initial decrease in PV. The interpretation of PV responses to exercise and/or hypohydration is critically dependent on selection of base-line conditions; we were able to control for posture-exercise effects by treating the early exercise (6 km) sample as the base line for examining the effects of later fluid loss. Under these conditions, the vascular compartment resisted volume depletion. The ability to maintain stable PV can be explained in part by relationships among oncotic and hydrostatic pressures in the intra- and extravascular fluid compartments.     

The response of stream macroinvertebrates to substrate size and heterogeneity

Manipulations of substrate size and components of heterogeneity were designed to test their independent effects and interactions on the abundance and species richness of stream macroinvertebrates. Two components of substrate heterogeneity, variation in size class proportions and number of size classes, had no independent effect on abundance or richness; and in general did not interact with median particle size. Median particle size, stream current, and detritus accounted for most of the significant variation in macroinvertebrates colonizing the experimental substrates. Rocks with high surface heterogeneity (roughness) were colonized by more individuals (but not taxa) than rocks with low surface heterogeneity.     

A survey of the pathology of marmosets (Callithrix jacchus) under experiment

A survey of the pathology of 567 laboratory-bred cotton-eared marmosets (Callithrix jacchus) is presented. There were few significant pathological changes in animals used in studies up to 6 months in duration, suggesting that the marmoset can be a useful non-human primate species for routine toxicology. The most common pathological changes encountered were chronic colitis, chronic thyroiditis and interstitial mononuclear infiltration in the kidney. No internal parasites were encountered, nor were any viral or bacterial diseases identified. Fungal disease was confined to a few cases of oesophageal mycoses. In a long term study a variety of pathological changes have been observed, including a 'wasting' syndrome, not related to skeletal muscle myopathy, with atrophy of the gastrointestinal tract, salivary glands and gonads, haemosiderosis and fatty change in the liver and osteoporosis. It is suggested that these changes may be related to protein deficiency and that the nutritional requirements of the marmoset require further investigation.     

Experimental chimaerism in sheep

Composite sheep embryos (N = 110) were produced by aggregation of blastomeres from 2-, 4- or 8-cell embryos. Each composite embryo consisted of equal numbers of blastomeres from 2-8 parent embryos, the total cell number ranging from one quarter of the normal cell number to 8 times the normal cell number. The embryos were embedded in agar and transferred to ligated sheep oviducts to allow development up to the early blastocyst stage. Of the 101 embryos subsequently recovered, 77 had formed normally organized blastocysts and 74 of these were transferred to 51 recipients. Thirty-eight recipients went to full term, producing a total of 53 lambs. Of the 48 lambs which survived to be blood typed at 60 days of age, 36 were judged to be chimaeric on the basis of their blood type and/or on the basis of external features. The proportion of chimaeras was larger amongst the lambs produced from composite embryos of the normal number of cells or more (25/26) than amongst lambs produced from composite embryos of less than the normal cell number (11/22).     

The effect of seed drying and gibberellin treatment on the germination performance of developing carrot seed

In a succession of seed harvests of carrot, the highest percentage and most rapid germination was obtained from seed harvested 51 days after anthesis (DAA) when dried by conditioning at 25°C and 60% RH for one week and from seeeds harvested 65 or 79 DAA with or without conditioning treatment. Seed from these harvests had reached maximum weight when dried, had embryos of maximum length and were considered mature. The germinaton of seed from these treatments was unaffected by a mixture of the gibberellins A₄ and A₇ (GA_4/7) applied in the incubation medium. Seed harvested 37 DAA also gave maximum percentage germination when it was both conditioned and incubated in GA_4/7 solution. Seed harvested earlier than this germinated poorly. Germination times of both mature and immature seed were reduced after storage for 18 months but there was no response to GA_4/7.Abbreviations ABA abscisic acid - DAA days after anthesis - GA gibberellin     

Chemolithotrophic metabolism of the newly-isolated moderately thermophilic,obligately autotrophic Thiobacillus tepidarius

Thiobacillus tepidarius, isolated from the hot springs at Bath, Avon, UK, grew optimally at 43–45°C and pH 6.0–7.5 on thiosulphate or tetrathionate. In batch culture, thiosulphate was oxidized stoichiometrically to tetrathionate, with a rise in pH. The tetrathionate was then oxidized to sulphate, supporting growth and producing a fall in pH to a minimum of ph 4.8. The organism contained high levels of thiosulphate-oxidizing enzyme, rhodanese and ribulose bisphosphate carboxylase. It was obligately chemolithotrophic and autotrophic. In chemostat culture, T. tepidarius grew autotrophically with the following sole energy-substrates: sulphide, thiosulphate, trithionate, tetrathionate, hexathionate or heptathionate. Thiocyanate, dithionate and sulphite were not used as sole substrates, although sulphite enhanced growth yields in the presence of thiosulphate. Maximum specific growth rate on tetrathionate was 0.44 h^-1. True growth yields (Y _max) and maintenance coefficients (m) were calculated for sulphide, thiosulphate, trithionate and tetrathionate and observed yields at a single fixed dilution rate compared with those on hexathionate and heptathionate. Mean values for Y _max, determined from measurements of absorbance, dry wt, total organic carbon and cell protein, were similar for sulphide, thiosulphate and trithionate (10.9 g dry wt/mol substrate) as expected from their equivalent oxygen consumption for oxidation. Y _max for tetrathionate (20.5) and the relative Y _o values (as g dry wt/g atom oxygen consumed) for thiosulphate and all four polythionates indicated that substrate level phosphorylation did not contribute significantly to energy conservation. These Y _max values were 40–70% higher than any of those previously reported for obligately aerobic thiobacilli. Mean values for m were 6.7 mmol substrate oxidized/g dry wt·h for sulphide, thiosulphate and trithionate, and 2.6 for tetrathionate.Abbreviation PIPES Piperazine-N,N-bis(ethane sulphonic acid)