The structure and evolution of the spider monkey delta-globin gene

We have isolated the delta-globin gene of the New-World spider monkey, Ateles geoffroyi, and compared its nucleotide sequence with those of other primate delta- and beta-globin genes. Among primate delta-globin genes, the rate of nonsynonymous substitutions is much less than the rate of synonymous substitutions. This suggests that primate delta- globin genes may remain under evolutionary conservation, perhaps because hemoglobin A2 has an as yet unknown physiological importance.      

A lipoprotein signal peptide encoded by the staphylococcal conjugative plasmid pSK41 exhibits an activity resembling that of Enterococcus faecalis pheromone cAD1.

The traH gene of the staphylococcal conjugative plasmid pSK41 has recently been shown to encode a lipoprotein (N. Firth, K. P. Ridgway, M. E. Byrne, P. D. Fink, L. Johnson, I. T. Paulsen, and R. A. Skurray, Gene 136:13-25, 1993). Here we report that traH encodes a product recognized as a pheromone by Enterococcus faecalis cells harboring the conjugative plasmid pAD1. The mature traH product is not essential for this phenomenon, as expression of pheromone-like activity was found to require sequences encoding only the pro-TraH signal peptide.     

Human cyclins B1 and B2 are localized to strikingly different structures: B1 to microtubules, B2 primarily to the Golgi apparatus.

We have raised and characterized antibodies specific for human cyclin B2 and have compared the properties of cyclins B1 and B2 in human tissue culture cells. Cyclin B1 and B2 levels are very low in G1 phase, increase in S and G2 phases and peak at mitosis. Both B-type cyclins associate with p34cdc2; their associated kinase activities appear when cells enter mitosis and disappear as the cyclins are destroyed in anaphase. However, human cyclins B1 and B2 differ dramatically in their subcellular localization. Cyclin B1 co-localizes with microtubules, whereas cyclin B2 is primarily associated with the Golgi region. In contrast to cyclin B1, cyclin B2 does not relocate to the nucleus at prophase, but becomes uniformly distributed throughout the cell. The different subcellular locations of human cyclins B1 and B2 implicate them in the reorganization of different aspects of the cellular architecture at mitosis and indicate that different mitotic cyclin-cyclin-dependent kinase complexes may have distinct roles in the cell cycle.     

A comparison of the effects of different perfusion regimes on the structure of the isolated human placental lobule

Summary Isolated lobules of normal term human placentas were perfused using two different procedures. In the first more conventional system, open-circuit perfusion of both the maternal and the fetal circulations with Earle's solution containing dextran was established and maintained for either 30 min or 1 h. In the second series of experiments both circulations were perfused in separate closed circuits with a mixture of fresh autologous fetal blood and Earle's solution for 0, 1, 2 or 3 h. In both series the lobule was then fixed by perfusion through the fetal circulation.Light and electron-microscopic examination of a set of tissue samples from each perfused lobule showed substantial differences between the effects of these two types of perfusion procedure. Tissue from lobules perfused by the open-circuit blood-free procedure showed patchy but severe cell swelling and vacuolation of the trophoblast after only one hour's perfusion. Particularly striking was swelling and disruption of a large proportion of the mitochondria in all placental cell types. By contrast, placental tissue from the closed-circuit perfusion with blood-containing medium showed little change over a period of two hours, while after three hours it showed oedema and microvillous damage, but no sign of cell swelling and little mitochondrial damage.It is concluded that the viability of the perfused human placental lobule depends on the type of perfusate used, and that the use of a fetal blood-enriched perfusate is of considerable value in maintenance of the preparation as assessed by structural criteria.     

Ultrastructural study of the permeability of the guinea-pig placenta to horseradish peroxidase

Summary Horseradish peroxidase (HRP) was used to study macromolecule permeation into the guinea-pig placenta perfused in situ. When tissue culture medium 199 (TC 199) was used as fetal-side perfusate, the tracer reaction product was found only lining the fetal endothelium. When a longer period of perfusion with HRP in TC 199 was used, a small amount of reaction product was found in the subendothelial space and syncytiotrophoblastic vesicles, but not in maternal lacunae. In similar experiments using a Krebs bicarbonate Ringer (KRBG) as perfusate the tracer was found (i) lining the fetal endothelium, (ii) in the lateral intercellular spaces of the endothelium, (iii) in the subendothelial space, and (iv) in the maternal lacunae.It is therefore evident that the vehicle influenced the permeability of the guinea-pig placenta to horseradish peroxidase. As other studies have shown that perfusion of the fetal side with salt solution increases pore size, the results with TC 199 are regarded as more representative of the situation in the intact animal. It is therefore suggested that the fetal endothelium of the guinea-pig placenta may be largely impermeable to molecules of the size of horseradish peroxidase (4 nm) or larger.     

Structural features and quantitative age-dependent changes in the intervascular barrier of the guinea-pig haemochorial placenta

Summary The haemomonochorial placenta of the guinea-pig undergoes several quantitative changes between the 49th and 64th days of gestation, all of which are in such a direction as to increase the efficiency of transplacental transport. The fetal vessels become larger, the maternal vessels increase in surface area by proliferation of microvilli, and the effective mean distance between the two vessel sets decreases. The magnitude of these changes suggests that the efficiency of transport of hydrophilic solutes across the maternal-fetal interface could double, although changes in the number of permeation sites per unit area may modify this relationship. The presence of open intercellular spaces and fenestrations in the fetal endothelium suggests that this layer may not be a major permeability barrier in the guinea-pig, but may create an unstirred layer of extracellular fluid between endothelium and syncytiotrophoblast.     

Home accidents in older people: role of primary health care team.

OBJECTIVES--To determine the incidence and nature of unreported and reported home accidents in older people and to investigate associated environmental factors. DESIGN--Postal questionnaire requesting information on home accidents in the preceding month. SETTING--Inner London general practice. SUBJECTS--All registered patients aged over 65 years (n = 1662), of whom 120 were inappropriately registered and 1293 responded. MAIN OUTCOME MEASURE--Circumstances and consequences of accidents in the home. RESULTS--108 accidents were recorded in 100 patients, giving a home accident rate of 84/1000 patients, equivalent to an annual rate of 1002/1000. 73 accidents were falls, and 83 were unreported. Of the 25 reported accidents, 19 were reported to general practice and six to accident and emergency departments (5.6% of all events). Rates of home accidents increased with age and were higher in women than men (79/819 upsilon 29/474; chi 2 = 4.5, df = 1, p less than 0.05). CONCLUSIONS--The incidence of home accidents in people aged over 65 years was high but few events were reported to medical services. General practice provided the main contact for patients who reported home accidents, and primary care workers have important opportunities for advising elderly patients on home accident prevention. Improved publicity on home safety targeted at older people and their carers would support the primary health care team in this role.