Segmental pulmonary vascular resistance in progressive hydrostatic and permeability edema

We used the in situ blood-perfused left lower lobe preparation of the dog to examine the effect of hydrostatic and permeability edema on the slope and intercept of the vascular pressure-flow (P/Q) relationship and on the longitudinal distribution of vascular resistance with the arterial and venous occlusion technique. Hydrostatic edema (HE) was induced by raising the venous pressure, and permeability edema (PE) was induced with alpha-naphthylthiourea. When the hematocrit (Hct) of the perfusate was kept normal (approximately 40%), HE had no significant effect on either the slope or the intercept of the P/Q relationship or on the distribution of vascular resistance. PE caused a small increase in the intercept of the P/Q relationship and a small rise in the resistance of the vessels in the middle segment. In another series of HE experiments in which Hct was allowed to increase during edema formation, there was a marked increase in vascular resistance. We conclude that edema per se does not increase vascular resistance significantly and that the increases in vascular resistance which were observed previously by other investigators in the isolated lungs may be due to increases in blood hematocrit.     

Microlocating lithium in the mouse embryo by use of a (n, α) nuclear reaction

Summary The quantitative imaging of lithium distribution, in histological sections of 15-days old mouse embryos (whose mother had been submitted to Li-treatment), was performed using⁶Li isotope as tracer,⁶Li(n,)³H nuclear reaction for detection, and dielectric track detectors. Despite the particular difficulties of cryosectioning the embryos without disturbing the lithium distribution, the Li regionalization appeared to be very clear-cut. The ectomesodermic tissues were significantly more loaded with lithium than the endodermic ones. This is probably related to the ectomesodermic tissues being also those most sensitive to the teratogenic effect of lithium. The Li-distribution in the embryo brain was almost homogeneous, instead of being heterogeneous as in adult brain. The mean Li-concentration in the embryo brain was not much below the Li concentration in the grey matter of the mother brain, but it was significantly larger than that in the white matter of the mother brain. Our results are discussed in the context of teratogenic effects observed in situ during mammalian development.     

Bufonid nucleocytoplasmic hybrids arrested at the early gastrula stage lack a fibronectin-containing fibrillar extracellular matrix

Summary Most hybrids betweenBufo bufo andB. calamita obtained by nuclear transplantation become arrested at the early gastrula stage. In both parental controls and the hybrid embryos, the presence and distribution of extracellular matrix was analysed with fluorescent wheat germ agglutinin and by immunolabelling with antibodies directed against fibronectin. InB. bufo andB. calamita gastrulae and in the few hybrids that complete gastrulation, the inner surface of the blastocoel roof is covered by a fibronectin-rich fibrillar matrix. In nucleocytoplasmic hybrids whose development was arrested at the gastrula stage, the fibronectin-containing extracellular matrix was either totally absent or poorly developed and disorganized.     

Inhibition of prostaglandin biosynthesis by SQ 28,852, a 7-oxabicyclo[2.2.1]heptane analog

7-Oxabicyclo[2.2.1]heptane analogs of prostaglandin (PG) H2 can act as thromboxane (Tx) A2 receptor antagonists or agonists, PGI2 and/or PGD2 receptor agonists, or exhibit a mixture of the above activities. SQ 28,852, a new analog with a hexyloxymethyl omega side chain, is a potent inhibitor of PG synthesis. SQ 28,852 inhibited collagen and arachidonic acid (AA)-induced platelet aggregation and TxB2 and PGE2 formation, but did not block platelet aggregation induced by ADP or the TxA2 mimics, 9,11-azo PGH2, SQ 26,655, and U-46,619. It also blocked conversion of AA to TxB2, PGE2, and 6-keto PGF1 alpha by microsomal preparations of human platelets, bovine seminal vesicles, and bovine aortas, respectively, but did not inhibit the conversion of PGH2 to TxA2 by the platelet microsomal preparation. SQ 28,852 (p.o.) protected mice against the lethal effects of AA (75 mg/kg, i.v.). The I50 values for SQ 28,852, indomethacin and aspirin were 0.025, 0.05 and 15 mg/kg, respectively. Neither SQ 28,852 nor indomethacin protected mice from death caused by 9,11-azo PGH2. SQ 28,852 (0.01 to 1 mg/kg, i.v.) inhibited AA-induced bronchoconstriction in anesthetized guinea pigs for at least 60 min. As an inhibitor of AA-induced bronchoconstriction, SQ 28,852 was 16- and 45-times more potent than indomethacin at 3 and 60 min after i.v. administration, respectively. SQ 28,852 did not inhibit bronchoconstriction induced by histamine or 9,11-azo PGH2, indicating its specificity of action in vivo. SQ 28,852 is the first example of a new class of cyclooxygenase inhibitors whose structure is similar to that of the naturally occurring endoperoxide, PGH2.     

The dopaminergic innervation of the goldfish pituitary

Summary The dopaminergic innervation of the goldfish pituitary gland was studied by immunocytochemistry at the electron-microscope level using highly specific antibodies against dopamine coupled to bovine serum albumin with glutaraldehyde. A satisfactory preservation of the tissue was achieved after immersion in 5% glutaraldehyde in phosphate buffer containing sodium metabisulfite to prevent oxidation of the endogenous dopamine. The immunocyto-chemical procedure was performed on Vibratome sections using the preembedding method. Immunoreactivity was restricted to part of the neurosecretory type-B fibers (diameter of the secretory vesicles lower than 100 nm) in which it was found to occupy the whole cytoplasm. Labeled fibers were observed within the neurohypophysis in the different parts of the gland and in the adenohypophyseal tissue where immunoreactive profiles were detected in close apposition to the different cell types. These data are in agreement with previous results obtained by means of radioautography and further support a role for dopamine in the neuroendocrine regulation of pituitary functions in teleosts.     

Experimentally induced true hermaphroditism in genetically female fowl

Summary Two types of hermaphroditism were experimentally induced in genetically female fowls by grafting of embryonic testes in embryos. Of the 27 hermaphrodites observed during the 8 months after hatching, 20 possessed a right testis and a left ovary and 7 a right testis and a left ovotestis. The testes and ovotestes contained seminiferous tubules with a more or less developed germ cell complement, attaining in many cases the early spermatid stage. The interstitial tissue was poorly functional, as shown by the absence of male secondary sex characters. The ovary or ovarian part of the ovotestes possessed numerous small ovarian follicles. The female arrangement of the plumage and the absence of spurs demonstrated the secretion of oestrogens. A mechanism is proposed for explaining this partial masculinization of genetically female gonads, a phenomenon which occurs during the period of embryonic sex differentiation, and is responsible for this experimental true hermaphroditism.