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Biomedical subjects

J J Lucas

Publications and source records attributed to J J Lucas.

At least 109 records · Page 6Linked to original sources
PubMed1978

Recent developments with karyoplast regeneration and nuclear transplantation.

Karyoplasts and cytoplasts prepared by cytochalasin-induced enucleation techniques were used in the development of systems for large-scale nuclear transplantation and the regeneration of karyoplasts to reform whole viable cells. Ten to 20% of a preparation of mouse L929 karyoplasts remained viable. These bodies, purified from whole cells, cytoplasts, and nonviable karyoplats, contained less than 10% of the cytoplasm in whole cells. By the technique of mass nuclear transplantation, up to 40% of a culture of cytoplasts could be renucleated by fusion of karyoplasts to a monolayer of enucleated cells. More than 5 x 10(5) renucleated or true cytoplasmic-nuclear hybrid cells could be prepared from a single cytoplast monolayer culture.

Animals↗
PubMed1976

Polyisoprenoid glycolipids involved in glycoprotein biosynthesis.

Until five years ago, it was believed that the oligosaccharide chains of most, if not all, glycoproteins were assembled by the stepwise transfer of single sugar residues from their nucleotide derivatives to growing oligosaccharide chains attached to a polypeptide core. It is now becoming widely accepted that polyisoprenol-linked mono- and oligosaccharides function as activated glycosyl carriers in the biosynthesis of some glycoproteins in animal tissues. The lipophilic glycosyl carrier of monosaccharides is the phosphomonoester of dolichol, the C(80-100)-polyisoprenol, containing a saturated terminal isoprene unit. In this biosynthetic process, sugars are initially transferred to dolichol monophosphate from their nucleotide derivatives by membrane-associated glycosyltransferases. These dolichol-linked monosaccharides serve as glycosyl donors in the glycosylation of oligosaccharide phospholipids. It appears likely that dolichol is also the lipid moity of the oligosaccharide intermediates. Detailed enzymatic studies with oligosaccharide phospholipids formed by rat liver, a mouse myeloma tumor and hen oviduct have revealed that these intermediates function as oligosaccharide donors in the assembly of at least one class of glycoproteins. The exact nature of the glycoproteins glycosylated by lipid intermediates and the sub-cellular site(s) of this assembly process remain to be established. The possibility, that the mannose and GlcNAc-containing core found in many glycoproteins, is assembled at the lipid-level is now being investigated. At the current rate of progress in this area of research, the identity of the glycoproteins glycosylated via lipid intermediated and the subcellular site of this assmebly process will soon be known.

Acetylglucosamine↗
PubMed1976

The construction of viable nuclear-cytoplasmic hybrid cells by nuclear transplantation.

Using the mouse L-cell line as a model system, a generalized approach is presented for nuclear transplantation in cultured cells resulting in the construction of cytoplasmic-nuclear hybrid cells. Techniques were developed for the preparation of cytoplast and karyoplasts having minimum contamination by parent whole cells. Sendai virusmediated fusion was performed in a manner which maximized the formation of the desired fusion products-cells having one cell equivalent of cytoplasm from one parent and a nucleus from a second parent. The viability of the fusion products was established by examination of photographic records of the developing cultures. Using these techniques, we found that nuclei could be introduced routinely into 10-30% of a cytoplast culture. From determinations of the increase in cell number with time, it was estimated that at least 30% of the reconstructed cells were capable of division. The approach was next applied to the formation of hybrid cells from L-cell cytoplasts and A9 cell karyoplasts. The A9 cell line is an azaguanine-resistant derivative of L cells. Thus any whole cells remaining in the culture of fused cells were readily eliminated by treatment with the purine analogue. The culture of remaining cytoplasmic-nuclear hybrid cells grew to confluence in the presence of azaguanine. The applicability of the approach to the construction of hybrid cells using parent lines from different organisms is briefly discussed.

Azaguanine↗
PubMed1976

The regeneration and division of mouse L-cell karyoplasts.

A technique for efficient cytochalasin-induced enucleation was used to prepare "karyoplasts"--nuclei surrounded by a thin shell of cytoplasm and an outer cell membrane. Methods for estimating the quantity of cytoplasm remaining in karyoplasts indicated that they contained less than 10% of the amount found in whole cells. Procedures for separating karyoplasts from contaminating cytoplasmic fragments and whole cells are also described. Freshly prepared L-cell karyoplasts were unable to adhere to and spread upon a surface. However, after incubation for several days, about 30% of the karyoplasts regained these abilities to some degree. A portion of the regenerating karyoplasts were then observed to divide. These events were confirmed and recorded by time-lapse cinematography. In addition, by culturing karyoplasts under appropriate conditions, clones were isolated.

Cell Adhesion↗
PubMed1975

The participation of lipid-linked oligosaccharide in synthesis of membrane glycoproteins.

Membrane preparations from hen oviduct catalyze the transfer of mannose from GDP-mannose into three components: mannosyl phosphoryl polyisoprenol, oligosaccharide-lipid, and glycoprotein. Eivence that mannosyl phosphoryl polyisoprenol serves as a mannosyl donor for synthesis of both oligosaccharide-lipid and glycoproteins was previously reported (Waechter, C.J., Lucas, J.J., and Lennarz, W.J. (1973) J. Biol. Chem. 248, 7570-7579). In this study the oligosaccharide-lipid has been isolated, and the oligosaccharide has been partially characterized. Based on paper chromatography the oligosaccharide chain contains 7 to 9 glycose units. The glycose at the reducing terminus is N-acetylglucosamine, whereas mannose is found at the nonreducing end. When UDP-N-acetyl[14C]glucosamine is incubated with oviduct membranes in the absence of GDP-mannose, a 14C-labeled chitobiosyl lipid, but little oligosaccharide-lipid is synthesized. When GDP-mannose is also present in the incubation mixture an oligosaccharide-lipid is formed containing N-acetyl[14C]glucosaminyl residues. This oligosaccharide-lipid is chromatographically identical with the [14C]mannose-containing oligosaccharide-lipid isolated in the earlier study cited above. When the N-acetyl[14C]glucosamine-oligosaccharide released from the oligosaccharide-lipid by mild acid is treated with partially purified alpha-mannosidase the major radioactive product is [14C]chitobiose. Evidence that the [14C]mannose-containing oligosaccharide-lipid serves as an oligosaccharide donor for glycoprotein synthesis was obtained by incubation of partially purified oligosaccharide-lipid with the membranes. The products of this incubation were shown to be glycoproteins on the basis of their sensitivity to pronase, as determined by both gel filtration and paper electrophoresis. Similar experiments, using oligosaccharide-lipid doubly labeled with [14C]mannose and N-acetyl[3H]glucosamine, provided evidence that the oligosaccharide chain of the oligosaccharide-lipid is transferred en bloc to glycoprotein s.

Acetamides↗
PubMed1972

Transcription and transport of virus-specific ribonucleic acids in African green monkey kidney cells abortively infected with type 2 adenovirus.

The techniques of deoxyribonucleic acid-ribonucleic acid (DNA-RNA) hybridization and immunological precipitation were used to compare the synthesis of adenovirus-specific macromolecules in African green monkey kidney (AGMK) cells infected with adenovirus, an abortive infection, and coinfected with both adenovirus and simian virus 40 (SV40), which renders the cells permissive for adenovirus replication. When viral protein synthesis was proceeding at its maximum rate, the incorporation of (14)C-amino acids into adenovirus structural proteins was about 90 times greater in the doubly infected cells than in cells infected only with adenovirus. However, the rates of synthesis of virus-specific ribonucleic acid appeared to be comparable in the two infections at all times measured. A time-dependent increase in the rate of RNA synthesis observed late in the abortive infection was dependent upon the prior replication of viral DNA. Moreover, all virus-specific RNA species that are normally made late in a productive adenovirus infection (i.e., the true late and class II early RNA species) were also detected in the abortive infection. Adenovirus-specific RNA was detected by molecular hybridization in both the cytoplasm and nuclei of abortively infected cells. Comparable amounts of viral RNA were found in the cytoplasmic fractions of AGMK cells infected either with adenovirus or with both adenovirus and SV40. The results of hybridization-inhibition experiments clearly showed that there was a class of virus-specific RNA molecules, representing about 30% of the total, in the nucleus that was not transported to the cytoplasm. This class of RNA was also identified in similar amounts in productively infected human KB cells. The difference in the abilities of cytoplasmic and nuclear RNA to inhibit the hybridization of virus-specific RNA from whole cells was shown not to be due to a difference in the molecular size of the RNA species from the two cell fractions or to the specific loss of a cytoplasmic species during RNA extraction procedures.

Adenoviridae↗
PubMed1971

Synthesis of virus-specific ribonucleic acid in KB cells infected with type 2 adenovirus.

By using the technique of deoxyribonucleic acid (DNA)-ribonucleic acid (RNA) hybridization, virus-specific RNA (cRNA) was detected 6 hr after infection in preparations of total RNA from cells infected with type 2 adenovirus in the presence of 2 mum 5-fluorodeoxyuridine. In the absence of 5-fluorodeoxyuridine, there was a continuous increase in the incorporation of (3)H-uridine into viral cRNA until 20 hr after infection, at which time approximately 40% of the (3)H-uridine entering RNA was found in virus-specific RNA. When RNA was prepared from polyribosome fractions obtained from cytoplasmic extracts of infected cells, virus-directed transcription was detected at 3 hr after infection (i.e., 3 to 4 hr before the initiation of viral DNA synthesis). Viral cRNA species synthesized at different times after infection were compared by the technique of DNA-RNA hybridization-inhibition ("presaturation" hybridization-competition). Three hybridization-inhibition techniques were compared. The techniques differed in the manner in which the DNA-RNA complex was isolated after the first hybridization reaction. Depending on the procedure employed, various degrees of inhibition were measured. The variation could be essentially eliminated if prior to hybridization the inhibitory RNA species were alkali-degraded to a uniform size of about 4S. Undegraded RNA could be used if the DNA-RNA complex was isolated by using a procedure involving rigorous washing (preferably including ribonuclease treatment) before the second hybridization with labeled RNA. When a rigorous hybridization-inhibition procedure was used, three classes of virus-specific RNA species could be distinguished: (i) early RNA class I whose synthesis began prior to viral DNA replication and stopped at some time after the initiation of viral DNA replication-it comprised about 70% of the early RNA species and was apparently degraded by 18 hr after infection; (ii) early RNA class II whose synthesis began prior to viral DNA replication and apparently continued at an enhanced rate late in infection; and (iii) late RNA whose synthesis began after the initiation of viral DNA synthesis.

Adenoviridae↗