The intravascular volume of isolated perfused human placental cotyledons was measured by the mean transit time of injected radio-iodine labelled human serum albumin. The technique gives highly reproducible results with no evidence of change with time. The mean intravascular volume was about 6 ml per 100 g of tissue, some 20 ml for an average placenta at term.

Blood Vessels↗

PubMedDate not supplied

Studies of a single placental cotyledon in vitro: III. The dimensions of the villous capillaries.

The capillary beds of ten isolated perfused placental cotyledons were examined by injecting microspheres ranging from 2 microgram to more than 20 microgram diameter into the villous circulation. As many as 25 per cent of capillaries may be less than 4 microgram in diameter; there are virtually none whose diameter exceeds 11 microgram and there is no evidence of large diameter vascular shunts.

Capillaries↗

PubMedDate not supplied

Nucleotide, nucleoside and purine base concentrations in human placentae.

Nucleotides, nucleosides and purine bases in trichloroacetic acid extracts of freeze clamped samples of human placenta have been measured by high-pressure liquid chromatography. The concentrations of the nucleotides concerned with energy transduction, ATP, ADP and AMP, and especially the energy charge, are stable over periods of ischaemia of 30 min. Concentrations of 14 nucleotides, including UDPAG, GDP Man, UDP and CTP, have now been defined. In addition, the concentrations of hypoxanthine, xanthine, uridine, adenine and inosine are indicated. Concentrations of the vasodilator adenosine are similar to the apparent Michaelis constants of its main metabolizing enzymes adenosine kinase and adenosine deaminase. The availability of 'normal' values of adenine nucleotide concentrations in human placenta should permit the detection of 'placental insufficiency' of energy supply, if this condition exists.

Cesarean Section↗