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Biomedical subjects

S F Contractor

Publications and source records attributed to S F Contractor.

At least 37 records · Page 2Linked to original sources
PubMed1985

A monoclonal antibody based solid-phase enzyme-binding assay to measure levels of placental alkaline phosphatase in serum of women during pregnancy.

Monoclonal antibodies raised against highly purified placental alkaline phosphatase (PALP) reacted specifically with PALP and were found not to cross-react with the liver, kidney and intestinal enzymes. One of these antibodies (AP-3) was selected to develop an enzyme-binding assay to measure levels of PALP in the sera of 11 women throughout pregnancy. PALP activity rose sharply after 28 weeks of gestation reaching a peak at delivery followed by an immediate drop within 4 days to values approaching non-pregnant levels. The potential of using this assay as an index of placental function to monitor progress of a pregnancy is discussed.

Alkaline Phosphatase↗
PubMed1984

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

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.

Culture Media↗
PubMed1983

Uptake and fate of exogenous immunoglobulin G in the perfused human placenta.

The steady-state transfer of 125I-labelled human or bovine immunoglobulin G from the maternal circulation and its fate during transport to the fetal circulation were studied over a 2 h period in an intact perfused human placental lobule. The 125I activity in the closed-circuit fetal circulation rose linearly throughout this time. The transfer rate, expressed as a percentage of the total activity administered, was 0.11% per hour for human IgG and 0.04% per hour for bovine IgG. 97-99% of the 125I activity in the maternal circulation was associated with high molecular weight protein which was characterised as IgG. The corresponding figure for the fetal side was 10-30%. It is concluded that human IgG is taken up in preference to bovine IgG at the maternal surface of the syncytiotrophoblast but subsequently the majority of the internalised immunoglobulin is broken down intracellularly and the fragments released into the fetal circulation.

Biological Transport↗
PubMed1982

3H-thymidine incorporation into human placental cells in culture.

Cell cultures of early human placenta were incubated with tritiated thymidine and, with the exception of macrophage-like cells, all cell types were found to synthesize new DNA. The possibility that at least some of the multinucleated cells seen in these cultures have originated from the fusion of mononucleated cells in vitro is discussed.

Autoradiography↗
PubMed1981

Extracorporeal perfusion of the whole human placenta--a new model.

An extracorporeal dual perfusion system of the whole human placenta was developed using a technique of multiple blunt cannulations of the intervillous space. The system was evaluated according to various perfusion-dynamic, metabolic and morphological criteria. Angiographic and dye distribution studies showed 80 to 100 per cent perfusion of the placenta. The perfused organ consumed oxygen, utilized glucose and produced HCG. The flow rates and acid-base values were within acceptable limits. However, problems with high fetoplacental vascular resistance, tendency to metabolic acidosis and fetomaternal fluid transfer were encountered. Ultrastructural studies showed variations in the syncytiotrophoblast and the microvilli.

Acid-Base Equilibrium↗
PubMed1977

A possible role for placental lysosomes in the formation of villous syncytiotrophoblast.

An ultrastructural and ultrahistochemical study of first trimester human placentae confirms previous reports that the cytotrophoblastic cells show a spectrum of differentiation, that dissolution of the limiting membrane of the cytotrophoblastic cells occurs and that fragments of free membrane can be found in the syncytiotrophoblast. There is an aggregation of primary lysosomes in the region of approximation of the cytotrophoblast to the syncytiotrophoblast, free lysosomal enzymes are found in the space between the two trophoblastic components, secondary lysosomes have been noted in the vicinity of fragmenting cytotrophoblastic cell membrane and the incorporation of a segment of free membrane into a vesicular structure has been noted. It is suggested that placental lysosomes mediate the dissolution of the cytotrophoblastic cell membranes that is a necessary prerequisite for their full differentiation into syncytiotrophoblast and it is further suggested that one of the principal roles of placental lysosomes is in the structural refashioning of the organ that occurs during the first trimester.

Acid Phosphatase↗
PubMed1976

Immunofluorescent localisation of cathepsin D in trophoblastic cells in tissue culture.

Cathepsin D was localised by immunofluorescence within four different types of cells derived from human trophoblast in monolayer culture. Cells were stained with freshly reduced Fab' fragments of sheep anti-(human cathepsin D) antiserum followed by FITC conjugate of pig anti-(sheep Fab') Fab' fragments. The green fluorescence seen in cytoplasmic droplets were characteristic of the appearance of lysosomes in other cells.

Cathepsins↗
PubMed1976

Pinocytosis and intracellular digestion of 125I-labelled haemoglobin by trophoblastic cells in tissue culture in the presence and absence of serum.

One aspect of human placental function which has not hitherto been studied is the ability of the placenta to digest proteins intracellularly and use the products of hydrolysis to supply its own and foetall complement of hydrolytic enzymes, including the acid proteases cathepsin C and D. We have used trophoblast cells in monolayer tissue culture as a model for the study of endocytosis and intracellular digestion of 125I-haemoglobin. The normal use of serum in tissue culture medium has shown up differences from the pattern observed with other phagocytic cells such as macrophages, in that serum allows endocytosis but prevents intracellular digestion of 125I-haemoglobin. Replacement of serum by lactalbumin hydrolysate enables both endocytosis and intracellular digestion of 125I-haemoglobin to occur as in other phagocytic cells. Digestion is followed by release into the medium of acid-soluble, lower-molecular-weight compounds. The reasons for this major difference between trophoblast and other cells are discussed in the light of our results and their possible relevance to placental function.

Blood↗
PubMed1975

Assessment of vitamin B 6 status. Studies on pregnant women and oral contraceptive users.

The vitamin B6 status of 10 pregnant women (third trimester), 9 oral contraceptive agent users, and 12 notnpregnant women (controls) was investigated over a 10-week period by means of the erythrocyte glutamate-oxaloacetate transaminase (E-GOT) activation test and by measurements of whole blood pyridoxal phosphate levels. Blood pyridoxal phosphate levels in oral contraceptive agent users (7.6 plus or minus 1.1 ng/ml) were significantly lower than in the control group (9.6 plus or minus 1.7 mg/ml)indicating a relative vitamin B6 deficiency. Pyridoxal phosphate levels in pregnant women(5.1 plus or minus 1.3ng/ml) were even lower; in fact, no overlap was found in individual mean values between the pregnant and control groups. The E-GOT activation test did not indicate a vitamin deficiency in the pregnant women or in oral contraceptive agent users and the E-GOT activation factor did not correlate with blood pyridoxal phosphate levels unless results obtained after pyridoxine hydrochloride (20 mg/day) administration were included. The E-GOT activation test appears to be a poor indicator of vitamin B6 status, except in pronounced deficiency as it is less responsive to vitamin depletion than blood pyridoxal phosphate levels, and suffers from relatively large variations in individual control values. This may be a result of factors unrelated to vitamin B6 as blood pyridoxal phosphate levels remained fairly constant in the individuals investigated.

Adolescent↗
PubMed1972

Purification and characterization of lysosomal -glucuronidase from human placenta.

1. Subcellular fractions of human placenta were prepared by nitrogen-bomb homogenization and differential centrifugation. 2. beta-Glucuronidase from placental lysosomes was purified 2100-fold on a protein basis. 3. The lysosomal enzyme, at different stages of purification, was characterized by using 4-methylumbelliferyl beta-d-glucuronide and phenolphthalein beta-d-glucuronide as substrates. 4. Only one isoenzyme of beta-glucuronidase was found in placenta; the enzyme in the endoplasmic reticulum appeared to be the same as the lysosomal enzyme. 5. The isoenzyme contained in normal plasma was different from that of the placenta. 6. The elevated beta-glucuronidase activity found in plasma obtained during pregnancy was due to increased activity of the normal plasma isoenzyme; no contribution was made by placental isoenzyme. 7. Plasma contained a heat-stable, non-diffusible activator of placental beta-glucuronidase. 8. A heat-stable competitive inhibitor of placental and plasma beta-glucuronidase was also present in plasma.

Centrifugation↗