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Biomedical subjects

M D Stern

Publications and source records attributed to M D Stern.

122 records · Page 7Linked to original sources
PubMed1977

Continuous measurement of tissue blood flow by laser-Doppler spectroscopy.

Laser light scattered from tissue in vivo is broadened in line width as a result of the Doppler shift produced by moving red cells in the microcirculation. A feasibility study was carried out to demonstrate use of this effect to measure and monitor tissue blood flow. Light from a helium-neon laser illuminated a 1-mm area of tissue (human skin or rat renal cortex), and the backscattered light was detected with a photomultiplier. The spectrum of the Doppler beat notes was analyzed directly with a digital spectrum analyzer, or processed by analog circuitry to yield a flow parameter based on the root-mean-square Doppler line width. This parameter was compared with 133Xe washout in the skin of volunteers subjected to UV-induced erythema and the skin of volunteers subjected to UV-induced erythema and was found to vary in an approximately linear manner with skin blood flow. The laser instrument provided continuous monitoring of blood flow fluctuations, including the pulsatile component. The instrument was used to monitor flow in the outer cortex of the rat kidney during administration of norepinephrine, angiotensin, hydralazine, dextran, dopamine, nitroprusside, and angiotensin blocked by saralasin. Dynamic and steady-state responses were consistent with known pharmacology and renal physiology, and with the assumption that vasoconstrictor angiotensin II receptors in the kidney are accessible to blood-borne inhibitors. The laser-Doppler method is a promising tool for rapid monitoring of dynamic changes in tissue perfusion.

Adult↗
PubMed1977

Ultrastructure of rumen entodiniomorphs by electron microscopy.

Thin sections of rumen ciliated protozoa of the subclass Spirotrichia were studied by electron microscopy to elucidate their ultrastructure. To prevent retraction of their adoral cilia, menthol crystals were used to relax the retrociliary region. These protozoa had a distinct ectoplasm and endoplasm with the macro- and micronuclei located in the ectoplasm. At the surface of the entodiniomorph body was a highly differentiated cortical zone of four layers. Ribosomes were abundant throughout the cytoplasm, suggesting a substantial potential for protein synthesis. These protozoa appeared to engulf bacteria into large vacuoles, and subsequently the bacteria were taken into the endoplasm in vesicles containing only one bacterium each. The bacteria were digested partially, and only in isolated cases were the bacterial cell walls still intact.

Animals↗
PubMed1977

Ultrastructure of rumen holotrichs by electron microscopy.

Thin sections of rumen diliated protozoa of the subclass Holotrichia were observed with a transmission electron microscope. These protozoa had a double layered boundary separating the ectoplasm from the endoplasm. Starch granules were abundant throughout the endoplasm and are probably storage starch. Also in the endoplasm of the holotrichs were the macro- and micronuclei. They were adjacent to one another, apparantly surrounded by a continuous membrane. Many unidentified dense bodies appeared in the endoplasm adjacent to the inner layer of the ectoplasmic-endoplasmic boundary. These inclusions could be precursor material to the boundary. The cuticle contained granular inclusions which might be secreted to facilitate ciliary movement. The holotrichs ingested chloroplasts as these were in vacuoles throughout the cytoplasm. The anal pore appeared to be open to the exterior and lined by a unit membrane.

Animals↗
PubMed1975

Measurement of serum clogestone acetate (AY-11,440) by a radioreceptor assay: a practical approach to the quantitative determination of synthetic progestins.

A novel method is described for the measurement of nanogram quantities of clogestone acetate (3beta, 17alpha-dihydroxy-6-chloropregna-4,6-dien-20-one 3,17-diacetate) in serum:clogestone acetate (CgAc) is converted to chlormadinone acetate in the presence of wheat germ lipase and hydroxysteroid dehydrogenase. The ketonic steroid formed is then incubated with rat uterine cytosol and 3-H-progesterone. The concentration of 3CgAc is estimated from a standard curve derived by incubating cytosol with 3-H-progesterone and varying amounts of chlormadinone acetate. The statistically validated method has been used for the estimation of serum CgAc in humans and dogs given an oral dose of the steroid. The radioreceptor assay (RRA), has practical advantages over related techniques such as radioimmunoassay (RIA) especially with respect to the developmental work. This is the first time that a quantitative assay of a progestin by the tissue receptor approach has been described.

Animals↗
PubMed1975

Metabolism of testosterone in previable human fetuses.

Labeled testosterone was injected into the umbilical vein of each of 4 male and 3 female previable fetuses at the time of laparotomy. After leaving the circulation intact for 3 min, the fetal tissues of each fetus were removed and the labeled metabolites present in each tissue were extracted, separated and isolated. Aliquots of tissue extracts were used for the qualitative analysis of metabolites following which metabolites were reisolated quantitatively from other tissue aliquots with the aid of the corresponding 3-H-labeled recovery markers. Testosterone and 11beta-hydroxyandrostenedione-4 were isolated from the adrenals and 5beta-androstanedione, androstenedione, etiocholanolone, androsterone, 5alpha-androstanediol, 5beta-androstanediol and testosterone were isolated from the livers. In addition, etiocholanolone and 5beta-androstanediol were isolated from the sulfate and glucuronide fractions of the livers. A sex difference in fetal testosterone metabolism was observed in the liver where the amounts of unconjugated 5beta-androstanediol in the male livers with no overlap in values. This conclusion has to be viewed with caution as only 4 males and 3 female fetuses were examined in these studies.

Abortion, Therapeutic↗
PubMedDate not supplied

Optimum spectral windows to minimize quantum noise of ratiometric intracellular fluorescent probes.

When fluorescent indicators are used to measure intracellular ligands in single cells, the quality of the data is usually limited by quantum (shot) noise. For indicators which shift excitation or emission wavelengths upon ligand binding, a ratiometric method is usually employed. In choosing the spectral windows for excitation or collection of fluorescence, there is a trade-off between maximum sensitivity to ligand binding, and maximum collection of light. We show that there is a well-defined optimum choice of windows which minimizes the error caused by quantum noise in the estimated ligand concentration. An algorithm for determining these optimum windows is presented. As an example, we consider the measurement of intracellular calcium by indo-1 fluorescence emission ratio in cardiac myocytes. The optimum wavelength bands for collection of fluorescence are considerably wider than those commonly employed. The use of these windows in a pulsed-excitation time-resolved calcium measurement instrument resulted in improved signal to noise ratio of the calcium signal.

Calcium↗
PubMedDate not supplied

Protein synthetic rate in the sheep placenta in vivo: the influence of insulin.

The metabolic gradient between the placenta and maternal tissues is large when expressed as fractional protein synthesis rate; the half-life of the mixed placental proteins is one-fifth of these in the maternal liver, but a little longer than those of the fetal liver and heart. This high turnover rate provides the priority of the uptake of the feto-placental unit for nutrients, to satisfy the genetic growth potential, enabling equivalent weights of the conceptus to take up amino acids in greater quantities than the maternal liver, the adult organ with the highest protein synthetic rate. The results suggest that fractional synthesis rate of the placental proteins was increased when fetal plasma insulin concentrations were raised. Should this enhancement of protein synthetic rate occur in the human subject, it might be responsible for the heavy placentae found in diabetic subjects whose blood sugar is uncontrolled, and account for their apparently large functional capacity.

Animals↗