Cytochemical and biochemical observations on the alveolar guanylate cyclase of golden hamster lung.

Particulate guanylate cyclase (GTP pyrophosphate-lyase (cyclizing] has been cytochemically evidentiated in the cells which make-up the lung air-blood barrier. The cytochemical procedure utilized demonstrates the presence of membrane-bound guanylate cyclase activity through precipitation of lead pyrophosphate in tissues incubated with GTP or with guanylyl imidodiphosphate. Electron microscopic examination reveals that guanylate cyclase (GC) is localized, as micropinocytic vesicles, within endothelial components of small blood vessels, in basal lamina and in the flat alveolar cells. The secretory alveolar cells also exhibit the positive GC reactivity in their peripheric cytoplasm and in their microvilli. The observations support that GC and cGMP are involved in cellular transport phenomena. The enzyme might play a role in the secretion process of surface active material. Positive staining has been found also in other types of cells, namely alveolar macrophages and fibroblasts. A biochemical evaluation of GC activity shows that about 30-40% of this activity is associated with the particulate fraction, which justifies its abundance in the cytochemical reports shown in the paper.

A new funipuncture technique: two-needle ultrasound- and needle biopsy-guided procedure.

A new technique is presented for funipuncture under ultrasound guidance using a biopsy guide and a 20/25-gauge needle combination. The 20-gauge needle was used for uterine entry and the 25-gauge needle for the actual cord puncture. The method was used for sampling fetal blood in 262 pregnancies with 264 fetuses (two sets of twins) between 17-39 weeks, at risk for beta-thalassemia, chromosomal disorders, TORCH infection, fetal hypoxia, and Rh-isoimmunization. Pure fetal blood was aspirated from 241 fetuses (91.3%), including the twins. The procedure lasted less than 5 minutes in 76.5% of the cases and less than 10 minutes in 90.1% of the cases. Intra-amniotic bleeding was seen in only 23.1% of the cases, and fetal bradycardia was not noted. Forty-four pregnancies were terminated after the diagnosis of genetic or infectious disease. Seven fetuses at risk for Rh-isoimmunization, found to be Rh-positive and anemic, were transfused immediately after blood sampling using the same needle. Of the 220 continuing pregnancies, there were 14 fetal losses (three before 28 weeks and 11 after 28 weeks or during the perinatal period). A probable etiology for the loss was found in 11 cases. These included one severely Rh-isoimmunized hydropic fetus who died in utero after transfusion at 26 weeks, one fetus who died in utero at 31 weeks following a car accident, and nine malformed newborns. The corrected rate for fetal losses probably related to the procedure was thus 0.9% before 28 weeks and 0.8% after 28 weeks. This new funipuncture technique seems to have several advantages over the freehand and/or biopsy-guided single-needle techniques.

Erythropoietin levels in heterozygous alpha-thalassemia.

In guinea pig bone marrow cultures with heterozygous alpha-thalassemic serum, 59Fe uptake values are elevated above iron values of cultures with serum of normal subjects. These results show that erythropoietin (EP) activity values in heterozygous alpha-thalassemia are comparable to those previously observed by ourselves in heterozygous beta-thalassemia despite of the different Hb concentration in these thalassemic syndromes. This points to the existence of signals which regulate Ep synthesis independently of Hb levels.

Evidence for an inotropic positive action of cGMP during excitation-contraction coupling in frog sartorius muscle.

Within the realm of the general hypothesis concerning the role of cGMP on intracellular calcium regulation in biological systems, we have investigated the action of cyclic nucleotides during excitation-contraction coupling in frog sartorius muscle. Our data show that several guanosine nucleotides (GTP, GDP, dibutyryl-cGMP) can increase the isometric twitch tension with a maximum increase of 40% in the muscles treated with cGMP. This increase is completely independent of external Ca2+ concentration. The use of dantrolene sodium (known to inhibit calcium release from sarcoplasmic reticulum) results in a decrease in the twitch tension with a contemporary decrease in the intracellular levels of cGMP; whereas, the addition of cGMP to the muscles treated with dantrolene antagonizes, at least partially, the effect of the drug on tension development. Finally, in chemically skinned muscles, cGMP induces a reversible contracture equal to approximately one-half of that evoked by 10(-4) M Ca2+.