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Biomedical subjects

F E Hytten

Publications and source records attributed to F E Hytten.

17 recordsLinked to original sources
PubMed1979

Is the fetus "scalped" in labour?

Capillary blood-flow and tissue oxygenation of the scalp and/or forearm skin were measured in the three adult volunteers. Skin pressure required to occlude circulation was much lower for the scalp than for the forearm skin, and tissue oxygenation fell rapidly when capillary blood-flow fell below about 3 ml/100 g tissue/min. Since scalp circulation is not representative of the general circulation when pressure is applied, the tissue oxygenation level of the fetal scalp in labour (obtained by direct sampling or by transcutaneous electrodes) is not a good indicator of the well-being of a fetus.

Adult↗
PubMed1979

Case note descriptions of the placenta: are they worthwhile?

In 429 placentae, measurements were made of weight, diameter, shape, eccentricity of the cord and weight and length of the cord, and the results were compared with Apgar score of the infant at birth and its standardized birth weight. There was no evidence that cord eccentricity, placental shape or "thickness", or the dimensions of the cord had any significant relation to the growth of the fetus or its condition at birth. The value of routine recording of crude measurements and qualitative assessments of the placenta in case notes is questioned.

Apgar Score↗
PubMed1979

Measurement of fetal transcutaneous oxygen tension--problems and potential.

In a series of 39 fetuses, continuous intrapartum transcutaneous PO2 recordings were made using a commercially available skin electrode, applied to the shaven fetal scalp. The weak correlation between transcutaneous measurements and umbilical blood PO2 at delivery is believed to be due to scalp ischaemia produced by 'head to cervix' pressure during labour. This 'tonsure' effect presents a major obstacle to the use of surface electrodes for intrapartum blood gas monitoring from the fetal scalp in clinical obstetrics. Modification of the current technique may allow it to be used reliably for research.

Female↗
PubMed1979

Restriction of weight gain in pregnancy: is it justified?

The management of pregnant women seems always to have contained a component of dietary constraint, but today two claims are made for restricting weight gain: that it reduces the risk of pre-eclampsia, and of middle-aged obesity. Neither claim can be sustained and there would appear to be no case for the technically difficult effort required to limit weight gain in pregnancy.

Body Weight↗
PubMed1976

Placental glycogen.

The quantity and distribution of glycogen has been studied in 86 placentae from the last trimester of pregnancy and 8 of 8 to 16 weeks gestational age. In the first trimester glycogen concentrations were high, between 4-5 to 6-5 mg/g of blood-free tissue, but from about 12 weeks to term the concentrations were within a narrow range around 1-5 mg/g. The level did not deviate appreciably from normal in a range of clinical conditions: diabetes, intrauterine growth retardation, pre-eclampsia or acute fetal distress, and was unaffected by the length of labour and whether or not the mother had been given an infusion of dextrose. Nor was it affected by a wide range of glucose concentrations in the maternal and fetal plasma and in the placental tissue itself or by insulin concentrations in either circulation. After the first few weeks of pregnancy glycogen in the placenta was shown to be restricted to the vicinity of major fetal blood vessels. Here it may be presumed to act as an energy reserve for vasomotor activity. All the evidence suggests that any importance placental glycogen may have is likely to be local, in relation to the placental vessels; a more general role, as an emergency energy source for the fetus, seems unlikely.

Birth Weight↗
PubMed1976

Is viviparity the best means of reproduction?

Successful reproduction in the context of evolution demands no more than perpetuation of the species, but an ideal system of reproduction should also aim for high efficiency. Two basic systems have predominated: egg laying and viviparity with placental attachment of the embryo to the mother. Egg-laying is inefficient in allowing huge losses and greatly limits the size of the newborn, although it has the advantage of causing little physiological upheaval to the mother. Viviparity, on the other hand, allows the growth of a much larger fetus, offers great protection and is highly efficient. Its major disadvantage is the enormous disturbance of the mother's physiology in the interests of ensuring that the fetus will not be rejected immunologically and that a continuous supply of nutrients can be provided and waste products removed. Only the marsupial seems to have achieved a sensible compromise by producing the young at a very early stage when it is living as an egg embryo without the need for placentation, and then giving it continuous nourishment and great protection by milk feeding in an external pouch.

Biological Evolution↗
PubMed1975

Transfer of folate to the fetus.

The accumulation of tritium-labelled folate in the product of conception was examined in eight women undergoing hysterotomy for termination of pregnancy. Folic acid containing a small quantity of tracer material (50n Ci/mug.) was injected intravenously 20 minutes before operation in 4 patients but 24 hours beforehand in the remainder. After operation, maternal blood, placenta, fetal blood, and fetal liver were examined for radioactivity as was the daily urine output during the patient's postoperative hospital stay. The results indicated that only 1/2 per cent of the injected material accumulated in the product of conception--uptake was primarily by fetal liver and no large placental pool of folate was involved. Approximately half of the injected load was excreted in the urine--the majority in the first 24 hours--and the remainder was presumed to have been retained by maternal tissues. Bioassay with L. casei and chromatography on TEAE cellulose suggested that extensive metabolism of the injected material had taken place and that fetal uptake might be more efficient than indicated by counting radioactivity alone.

Abortion, Induced↗
PubMed1975

The effect of pregnancy on the renal handling of glucose.

Tubular reabsorption of glucose has been measured during glucose infusion in 29 healthy women during and after pregnancy. All the women had normal glucose tolerance to an oral load, and normal glucose excretion when not pregnant, but exhibited a wide range of daily glucose excretion in pregnancy. Throughout pregnancy the renal reabsorption of glucose is less effective than in the non-pregnant state and, in general, the greater the amount fo glycosuria which develops in pregnancy, the less effective is the reabsorption during infusion. Post partum, women with minor degrees of glycosuria during the preceding pregnancy return to a normal highly efficient reabsorption performance during infusion, but women who exhibit greater degrees of glycosuria have a reduced capacity to reabsorb even though they are no longer glycosuric after the pregnancy. It is concluded that pregnancy imposes some specific change in the glucose reabsorptive capacity of the proximal tubule and that women with more than usual degrees of glycosuria in pregnancy may, in addition, have an element of tubular damage. This is discussed in relation to other renal function changes in pregnancy in an attempt to explain the characteristic intermittency of clinical glycosuria in pregnancy.

Absorption↗
PubMed1975

Changes in plasma non esterified fatty acids and serum glycerol in pregnancy.

Changes in plasma nonesterified fatty acids (NEFA) and serum glycerol in pregnancy were examined in a semi-serial study of 85 women. A preliminary study showed that it was almost impossible to achieve standardized conditions for sampling, and the compromise of taking a single venous sample without stasis, after 30 minutes rest and about 12 hours fasting, was adopted. Although there were large individual variations the patterns of change were, in general, the same for NEFA and glycereo although the two were not closely correlated. There was no +convincing change before 30 weeks of pregnancy but both increased in the last ten weeks, fell sharply in the first week post partum, and then rose again to late pregnancy levels by 6 weeks post partum before falling to non-pregnant levels by between 3 and 6 months post partum. Those patterns of change are in broad accordin with changes of fat storage and lipolysis associated with the reporoductive cycle. Changes in the patterms of NEFA were triviax the only significant alteration was a small rise in the proportion of C16:0 (palmitic) in late pregnancy.

Chromatography, Gas↗
PubMed1975

Lactation and reproduction.

The authors review the literature on the effect of lactation on fertility in the absence of contraception and on the effects of contraceptive measures on lactation. They examine data from several countries on the intervals between births and on the return of menstruation and ovulation after childbirth, comparing lactating with nonlactating women. They conclude that lactation is an inefficient contraceptive for the individual, but that in populations sustained lactation is associated with reduced fertility. Possible physiological mechanisms causing lactation amenorrhoea are discussed. Though much of the literature on the effect of contraceptives on lactation is inadequate, there is general agreement that the estrogen component of hormonal preparations has an adverse effect on lactation, but that progestins alone do not. Many questions remain. Is this effect seen in established lactation, or only in the puerperal period? Is it a direct pharmacological effect, or are pill-users the mothers least motivated to maintain breast-feeding? Does a close relationship exist between hormones given and lactation performance? The authors comment on some of the technical deficiencies of previous studies in this field and discuss practical possibilities of, and limitations to, obtaining adequate scientific information in the future.

Amenorrhea↗