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Biomedical subjects

T F Roth

Publications and source records attributed to T F Roth.

34 records · Page 2Linked to original sources
PubMed1978

Common features of coated vesicles from dissimilar tissues: composition and structure.

Coated vesicles were purified and characterized from porcine brain and chicken oocyte. Electrophoresis on sodium dodecylsulphate (SDS) gels showed that coated vesicles from either source have three major proteins in common with apparent molecular weights of 180000, 120000, and 55000 Daltons. Negatively stained specimens from both sources appear to consist of a highly ordered array of short interconnected rods or ridges of material on the exterior surface of a membrane vesicle. Coated vesicles purified from porcine brain and chicken oocyte have mean external diameters of 75.0 and 85.0 nm, respectively. In coated vesicles of the appropriate orientation, portions of the coat material appear to be organized into hexagons and pentagons. Based on the observed variability of size and apparent structure, it is postulated that the basic structural subunits of coated vesicles are the short rods or ridges of material observed on the exterior membrane vesicle surface. It is suggested that multiples of the subunits can be assembled into many arrangements to yield coated vesicles of different sizes and coat structure. It is also proposed that the structural subunit is a complex of 3 proteins of molecular weight of 180000, 120000 and 55000 Daltons.

Animals↗
PubMed1978

IgG receptors on foetal chick yolk sac.

In the chicken, maternal IgG is deposited in the oocyte yolk and subsequently transported intact by the foetal chick yolk sac into the chick circulation. Such transport appears to require a specific membrane-localized IgG receptor. Using the assay of 125I-yolk IgG binding, we have investigated the existence and properties of such receptors in yolk sac tissue disks. We find that: (1) There are specific, 125I-IgG binding sites on yolk sac tissue; (2) specific yolk 125I-IgG binding has a distinct pH optimum at pH 6.0--6.3; (3) the apparent equilibrium dissociation constant of specific 125I-IgG binding is 2--3 X 10(-6) M; and (4) heterologous proteins compete less efficently than yolk IgG for 125I-IgG binding.

Animals↗
PubMed1976

Binding to specific receptors on oocyte plasma membranes by serum phosvitin-lipovitellin.

Specific binding sites for the serum complex of phosvitin and lipovitellin have been shown to exist on the outer surface of rapidly growing chicken oocytes. The existence and specificity of these sites were demonstrated by competition for binding to unfixed oocyte membrane fragments and by displacement of already bound and labeled phosvitin-lipovitellin from formaldehyde-fixed membranes. Only unlabeled phosvitin-lipovitellin competed with the 125I-labeled complex for binding to the fragments of displacement of bound label; IgG isolated from egg yolks and bovine serum albumin were ineffective.

Animals↗
PubMed1976

Protein transport: a selective membrane mechanism.

Proteins are selectively sequestered by a number of cell types. However, only in oocytes is the process sufficiently aggravated and specific to be readily studied. In these cells certain serum proteins are taken up in proportions different from those found in the serum. In vitro incubations of hormonally stimulated and synchronous mosquito oocytes show that the only protein capable of initiating the transport process is the female specific yolk protein. Heterologous proteins such as IgG, bovine serum albumin, cytochrome C, and ferritin are inactive. The female specific protein is a phosphoglycolipoprotein. It is synthesized in the fat body, a liver analog in the insect, and passed into the serum before being transported into the oocytes. Preliminary kinetic analysis shows the uptake process to be specific with an apparent Km of about 10(-7) M. Glycolytic inhibitors stop protein uptake. The receptor-mediated binding steps in the transport process are most easily studied in the chicken because of the enormous amount of oocyte membrane available from a given oocyte and because up to 1 gm of protein is normally transported per day per oocyte. IgG and the hen specific phosvitin lipovitellin are two of the physiologically important proteins that are transported intact into the chicken oocytes. The uptake appears selective as shown by studies with iodinated proteins. Ferritin conjugated to IgG is shown by electron microscopy to bind to isolated plasma membranes only where coated pits have formed, whereas ferritin alone is not seen localized on any membrane surface. These very specialized regions of the membrane are similar to micropinocytotic pits but, in addition, possess on their cytoplasmic side dense ridges that form the coat. Transport involves binding to the coated pits, the pinching off of the pits, and the subsequent movement of the coated vesicles in the cytoplasm.

Animals↗
PubMed1971

Greening of etiolated bean leaves in far red light.

Eight-day-old dark-grown bean leaves were greened by prolonged irradiation with far red light. Growth, chlorophyll content, oxygen-evolving capacity, photophosphorylation capacity, chloroplast structure (by electron microscopy), and in vivo forms of chlorophyll (by low temperature absorption and derivative spectroscopy on intact leaves) were followed during the greening process. Chlorophyll a accumulated slowly but continuously during the 7 days of the experiment (each day consisted of 12 hours of far red light and 12 hours of darkness). Chlorophyll b was not detected until the 5th day. The capacity for oxygen evolution and photophosphorylation began at about the 2nd day. Electron microscopy showed little formation of grana during the 7 days but rather unfused stacks of primary thylakoids. The thylakoids would fuse to give grana if the leaves were placed subsequently in white light. The low temperature spectroscopy of intact leaves showed that the chlorophyll a was differentiated into three forms with absorption maxima near 670, 677, and 683 nanometers at -196 C during the first few hours and that these forms accumulated throughout the greening process. Small amounts of two longer wavelength forms with maxima near 690 and 698 nanometers appeared at about the same time as photosynthetic activity.

Journal Article↗
PubMed1971

Control of senescence in marchantia by phytochrome.

Mature green tissue of Marchantia polymorpha L. bleaches markedly when placed in continuous darkness for 4 days but remains green when given daily 1-hour photoperiods of white light. The tissue, however, is induced to bleach when each daily 1-hour photoperiod is terminated with a brief irradiation with far red light. The bleaching does not occur when each irradiation with far red light is followed by a brief irradiation with red light. The bleaching is taken as an index of senescence since the loss of chlorophyll in the bleached tissue is accompanied by a breakdown of cell organelles and cytoplasm. Phytochrome is clearly implicated in the control of senescence by light. It was also found that 5 minutes of red light given once a day was as effective as the 1-hour photoperiods with white light in preventing the bleaching and that bleaching was induced when each daily 5-minute irradiation with red light was followed by a 10-minute irradiation with far red light.

Journal Article↗
PubMed1967

DNA-dependent formation of the synaptinemal complex at meiotic prophase.

EVALAUTION OF MICROSPOROCYTES CULTURED DURING DISCRETE PERIODS OF MEIOTIC PROPHASE IN THE PRESENCE OF DEOXYADENOSINE, AN INHIBITOR OF DNA SYNTHESIS, INDICATE THAT: (1) late leptonema or early zygonema DNA synthesis is required to initiate the formation of the synaptinemal complex; (2) DNA synthesized during late zygonema is necessary for the disjunction of the paired homologs at diplonema; and (3) DNA synthesis in pachynema is a requisite for normal anaphase II separation of sister chromatids.

Chromosomes↗
PubMed1966

Allomorphic forms of bacteriophage phiX-174 replicative DNA.

The bacteriophage øX-174 replicative form of DNA exists in two configurations, as judged by electron microscopy and sucrose density gradient sedimentation, and on methylated albumin-coated kieselguhr column chromatography. The predominant 21S form of the DNA is a tightly twisted circle. Treatment with deoxyribonuclease causes a single scission in one of the two strands, resulting in an open circle which sediments at 16S.

Chemical Phenomena↗
PubMed1966

An electron microscope study of yolk formation during oogenesis in Lebistes reticulatus guppyi.

The present investigation describes the fine structural changes that occur during proteid yolk formation in the developing oocytes of the guppy (Lebistes reticulatus), an ovoviviparous teleost. These changes suggest the operation of a number of different intra- and extraoocyte processes that may account for the synthesis and deposition of the proteid yolk. Early in oogenesis, the egg's Golgi systems proliferate and begin to disclose an electron-opaque content. Numerous 70-mmicro diameter vesicles apparently pinch off from the Golgi systems, transport this material through the egg, and probably then fuse to form a crenate, membrane-limited yolk droplet. At the same time, the rough-surfaced endoplasmic reticulum accumulates a flocculent substance that differs in appearance from the Golgi content. Smooth vesicles, presumably derived from the ER, then coalesce to form a second type of intraoocyte yolk droplet. These dissimilar, separately derived droplets subsequently fuse, thus combining the materials that constitute the intraoocyte contribution to the proteid yolk. Somewhat later in development, the egg appears to ingest extracellular material via 75-mmicro diameter bristle-coated micropinocytotic pits and vesicles. These structures apparently fuse to form tubules which then coalesce into large yolk droplets. At a later stage, bristle-coated micropinocytotic vesicles of 100 mmicro diameter presumably take up a material that is then probably immediately deposited into a second type of proteid yolk droplet. It is postulated that these two different micropinocytotic structures are specifically involved with the selective uptake of dissimilar extracellular proteid materials.

Animals↗