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Biomedical subjects

R Freeman

Publications and source records attributed to R Freeman.

At least 109 records · Page 6Linked to original sources
PubMed1985

Rises in antibody to enteric gram negative bacilli after open heart surgery: a possible mechanism for postoperative pyrexia.

Paired sera, taken before operation and 10-14 days after operation from 64 patients having open heart surgery and 10 having closed heart surgery, were examined for agglutinins to seven common serotypes of Escherichia coli. The results showed that, while 20% of both groups of patients had detectable agglutinins before operation, new antibodies appeared after operation in 69% of patients having open heart surgery compared with only 10% of those having closed heart surgery, a significant difference. Thirty six pairs of sera were also examined for the preoperative presence and postoperative development of antiendotoxin. Of 22 open heart patients shown not to possess antiendotoxin before operation, 18 showed the antibody after operation, whereas none of the eight seronegative patients acquired the antibody after closed heart surgery-again a highly significant difference. These results are consistent with the hypothesis that endotoxin and other products of enteric Gram negative bacilli circulate shortly after cardiopulmonary bypass, possibly arising directly from the gut and perhaps explaining the pyrexia seen commonly at this time.

Agglutination Tests↗
PubMed1984

Methods for specimen thickness determination in electron microscopy.

A new method is described for specimen thickness determination in transmission electron microscopy. This is carried out by marking specimens with gold particles and analysing the images of a tilt series by computer. The method makes it possible to distinguish populations of particles on different planes and calculate the distance between the planes with statistical variation. We have applied it to carbon films as test objects and compared the results with those obtained by transverse sectioning, STEM mass measurement, optical density and frequency change of a quartz crystal oscillator. We have then used the method for thickness measurement of multilayered protein crystals and thin sectioned cells.

Animals↗
PubMed1984

Maternal plasma and amniotic fluid levels of estradiol, estrone, progesterone, and prolactin in early pregnancy.

During the 16th to 20th weeks of gestation, maternal plasma (mean) level of estradiol is 5.2 ng/mL; estrone, 3.0 ng/mL; estriol, 2.1 ng/mL; progesterone, 4235 ng/dL; and prolactin, 74 ng/mL. Amniotic fluid levels are: estradiol, 446.8 pg/mL; estrone, 234.1 pg/mL; progesterone, 5200 ng/dL; and prolactin, 2633.5 ng/mL. Maternal prolactin concentrations correlate with plasma estradiol. Amniotic fluid prolactin levels correlate significantly with maternal plasma concentrations of estradiol and estrone. The mechanisms for the possible relationship between maternal estradiol and pituitary and decidual tissue production of prolactin are discussed.

Amniotic Fluid↗
PubMed1983

A chronobiologic abnormality in luteinizing hormone secretion in teenage girls with the polycystic-ovary syndrome.

We investigated possible abnormalities of central-nervous-system regulation of luteinizing hormone secretion in the polycystic-ovary syndrome by determining the plasma concentrations of luteinizing hormone over a 24-hour period in five teenage girls with the syndrome; profiles of prolactin and cortisol were also obtained. Four of the five patients had strikingly abnormal plasma luteinizing hormone profiles: whereas normal pubertal girls have a daily surge in secretion of luteinizing hormone that is coterminous with their nocturnal sleep period, our patients had surges that were grossly desynchronized from their sleep period, occurring seven to eight hours later in the daytime than normal. The chronobiologic disturbance involved only luteinizing hormone; the profiles of cortisol and prolactin were normal. This finding points to the central nervous system as the probable locus of the initiating pathophysiology of polycystic-ovary syndrome.

Adolescent↗
PubMed1983

Norepinephrine level in the hypothalamus of the genetically hypertensive mouse.

The norepinephrine content of the hypothalamus of young mice with high blood pressure was statistically lower than that of mice with low blood pressure. The difference was not evident in older mice from these same strains. No differences in dopamine content were found suggesting a genetic difference in the activity of the converting enzyme.

Aging↗
PubMed1983

Electron microscopy of frozen hydrated sections of vitreous ice and vitrified biological samples.

The preparation and high resolution observation of frozen hydrated thin sections has been studied by transmission electron microscopy (TEM and STEM) on model systems, including pure water, protein solutions, catalase crystals, myelin sheath and various tissues. The state of the ice is determined by electron diffraction. Mass measurement in the electron microscope is used to determine section thickness and control hydration. An adequate depth of vitrified material for sectioning can be obtained from many biological suspensions or untreated tissues. Frozen hydrated sections around 100 nm thick can be produced under optimal conditions from vitreous ice or from vitrified biological samples. Sectioning, transfer and observation in the electron microscope is feasible without alteration of the sample hydration or its initial vitrification. Biological structures can be preserved and observed down to 10 nm. Under favourable working conditions, specimen compression during sectioning and electron beam damage are the factors limiting high resolution observations.

Animals↗
PubMed1983

Serum thyroid hormone levels in patients on continuous ambulatory peritoneal dialysis and regular hemodialysis.

In vitro thyroid function tests were performed on clinically euthyroid patients undergoing regular hemodialysis (HD) or continuous ambulatory peritoneal dialysis (CAPD). The mean serum total thyroxine (TT4) and total triiodothyronine (TT3) values measured before HD were significantly subnormal. Similarly, CAPD subjects had reduced TT3 concentrations with low normal TT4 levels. Free thyroxine measurements, estimated by two different methods were aberrant in CAPD patients. Low normal reverse triiodothyronine (rT3) values were found in HD, in contrast to high normal rT3 levels in CAPD. Thyroid stimulating hormone determinations were normal, corresponding with the euthyroid status in both patient groups.

Adult↗
PubMed1983

Plasma oxytocin concentrations in a pregnant woman with total vasopressin deficiency.

Plasma concentrations of oxytocin and vasopressin were determined by radioimmunoassay in a woman with clinical diabetes insipidus. Plasma oxytocin levels were normal and ranged from less than 0.25 microU/ml to 76 microU/ml during the last month of pregnancy and during spontaneous labor. Vasopressin requirements did not change during pregnancy. Unexplained vasopressin resistance and massive diuresis occurred early in the postpartum period. Plasma vasopressin concentrations were undetectable in the nonpregnant state. The documentation of normal oxytocin production and total vasopressin deficiency suggests that an anatomic defect is unlikely to cause this disorder unless it is limited to axons and cell bodies containing vasopressin and not oxytocin.

Adult↗
PubMed1982

Replanning of an intensive therapy unit.

Considerable effort is needed when replanning an intensive therapy unit to avoid repeating mistakes in design, such as lack of windows and an impractical working area. Early consultation with the nursing and medical staff primarily responsible for such a unit is essential. The considerable technological innovations in intensive care will require flexibility in the future if they are to be incorporated into existing facilities.

England↗