Diterpenes from Baccharis species

The aerial parts of Baccharis minutiflora afforded in addition to known compounds eight new ent-kaurane derivatives, one being a homo kaurane, while the aerial parts of B. alatemoides gave two pairs of epimeric clerodane derivatives, which, however, had to be modified chemically before they could be separated. The stereochemistry of these diterpenes could not be elucidated with certainty.     

Labdane and dehydronerolidol derivatives from Brickellia diffusa

An investigation of Brickellia diffusa afforded three new dehydronerolidol derivatives and five new labdane derivatives, all highly oxygenated. The structures were elucidated by spectroscopic methods and a few chemical transformations. The compounds isolated showed close relationships to those isolated from Brickellia sp.     

A dimeric germacranolide and other sesquiterpene lactones from Mikania species

The investigation of two Mikania species, both previously placed in the genus Kanimia, afforded in addition to known compounds several new germ     

Four guaianolides,a eudesmanolide and a germacranolide from Ursinia saxatilis

An investigation of Ursinia saxatilis afforded in addition to known compounds a new eudesmanolide derived from ursialpinolide, a germacranolide rel     

Types of sesquiterpenes from Artemisia douglasiana

Artemisia douglasiana afforded, in addition to known compounds, two new C₁₄-acetylenes, five longipinene derivatives, three nerolidol derivatives, a lactone and a ketone with a new carbon skeleton and lavendulol-2-methylbutyrate. The structures were elucidated by spectroscopic methods and some chemical transformations. The configurations of several oxo longipinene-7, 9-di- and 7, 8, 9-triesters isolated previously were corrected. The biogenesis of the new lactones is discussed briefly.     

Computer modeling of fibrin polymerization kinetics correlated with electron microscope and turbidity observations: clot structure and assembly are kinetically controlled.

Although much is known about fibrin polymerization, because it is complex, the effects of various modifications are not intuitively obvious and many experimental observations remain unexplained. A kinetic model presented here that is based on information about mechanisms of assembly accounts for most experimental observations and allows hypotheses about the effects of various factors to be tested. Differential equations describing the kinetics of polymerization were written and then solved numerically. The results have been related to turbidity profiles and electron microscope observations. The concentrations of intermediates in fibrin polymerization, and fiber diameters, fiber and protofibril lengths have been calculated from these models. The simplest model considered has three steps; fibrinopeptide A cleavage, protofibril formation, and lateral aggregation of protofibrils to form fibers. The average number of protofibrils per fiber, which is directly related to turbidity, can be calculated and plotted as a function of time. The lag period observed in turbidity profiles cannot be accurately simulated by such a model, but can be simulated by modifying the model such that oligomers must reach a minimum length before they aggregate. Many observations, reported here and elsewhere, can be accounted for by this model; the basic model may be modified to account for other experimental observations. Modeling predicts effects of changes in the rate of fibrinopeptide cleavage consistent with electron microscope and turbidity observations. Changes only in the rate constants for initiation of fiber growth or for addition of protofibrils to fibers are sufficient to account for a wide variety of other observations, e.g., the effects of ionic strength or fibrinopeptide B removal or thrombospondin. The effects of lateral aggregation of fibers has also been modeled: such behavior has been observed in turbidity curves and electron micrographs of clots formed in the presence of platelet factor 4. Thus, many aspects of clot structure and factors that influence structure are directly related to the rates of these steps of polymerization, even though these effects are often not obvious. Thus, to a large extent, clot structure is kinetically determined.     

Cellular proliferation kinetics of the murine sarcoma induced by the Moloney sarcoma virus

Abstract. Cell proliferation kinetics of the sarcoma induced by Moloney virus was studied in newborn Swiss OFl mice.
After in vivo injection of tritiated thymidine, followed by autoradiography, it was shown that the majority of cells were actively proliferating (labelling index; 31%, growth fraction 78%). The mean cell cycle was 16 hr and cell loss was relatively low (cell loss factor 48%). The study of tumour specific activity with time after a single [ in vivo ] injection of [³H]dR or [¹²⁵I]UdR did not demonstrate the same degree of cell loss as that calculated by autoradiography. This result is consistent with a massive reutilization of radioactivity released by normal tissues.     

Inheritance of susceptibility to the myeloproliferative sarcoma virus: effect of the Fv-2 locus and evidence for a myeloproliferative sarcoma virus resistance locus.

Myeloproliferative sarcoma virus (MPSV) causes a generalized stem cell leukemia with erythroid and myeloid hyperplasia in adult mice. MPSV also transforms fibroblasts. Mice congenic for the Fv-2 locus showed marked differences in susceptibility to MPSV according to the Fv-2 genotype. MPSV was injected into C57BL/6 Fvs and C57BL/6 Fv-2r mice congenic except for the Fv-2 locus. C57BL/6 mice with the Fvs genotype were much more susceptible to MPSV than were those with the Fvr genotype. Both DDD Fv-2r mice congenic with DDD Fv-2s mice except for the Fv-2 locus and DDD Fv-2s mice, however, were sensitive to spleen focus formation by MPSV. These data indicate that at least one additional resistance locus to MPSV is present in C57BL/6 mice but not in DDD mice. Both the Fv-2 locus and the putative MSPV resistance locus (loci) Mpsvr appear to be epistatic to either of the sensitivity loci. Fibroblast focus formation by MPSV was obtained well in C57BL/6 Fv-2r and C57BL/6 Fvs fibroblasts, indicating that the genes for MPSV resistance (Fv-2r and Mpsvr) were not operating in fibroblast cells. A model is proposed which may account for the differences in response of genetically different mice to MPSV and Friend spleen focus-forming virus.     

Two sesquiterpene lactones with an additional propiolactone ring from Disynaphia halimifolia

The investigation of D. halimifolia afrorded a new glaucolide and two sesquiterpene lactones with an additional propiolactone ring, one elemanolide and one modified germacranolide with an additional ring. Furthermore, two tremetone derivatives were present, a hydroxy-geranylgeraniol, also present in a Kingianthus species, and several known compounds.     

Trixikingolides and germacrene derivatives from Trixis species

The investigation of two further Trixis species afforded five new sesquiterpenes related to trixikingolide, six new germacrene derivatives and a sesquiterpene derived from rotundene. Some further known compounds were isolated too, which in part may be of chemotaxonomic significance. The structures were elucidated by spectroscopic methods and a few chemical transformations. The relative position of the ester groups in eight of the new sesquiterpenoids however, could not be established with certainty as partial saponifications were not successful.