Phase response versus positive and negative division delay in animal cells

The time of median cell division in V79 Chinese hamster cells following high serum pulses was determined for two synchronous cell generations following mitotic selection. Differences in cell cycle time for each pair of pulse and control cultures were computed and plotted as a function of time of serum pulse. This phase response curve for hamster cells with an 8.5 h cell cycle shows a characteristic biphasic pattern. Beginning 0.5 h after mitotic selection, pulses with serum produce delays in the midpoint of the subsequent mitotic waves. Delay is maximum at 1.5 h. Delays give way abruptly to advances at 2.5 h and the amount of advance then decreases as pulses are given between 3 and 5 h into the cycle. At 5 h decreasing advances become delays, with increasing delays due to serum pulses occurring between 5 and 6 h. Delays again give way abruptly to advances at 6 h and again the amount of advance decreases through the late portion of the cycle. Pulses very late in the cycle appear to generate phase delays. This biphasic response to serum is interpreted as an expression of an underlying time-keeping oscillator whose period is nominally of 4 h duration.     

Fluorosis in black-tailed deer.

Marked dental disfigurement and abnormal tooth wear patterns were observed in black-tailed deer (Odocoileus hemionus columbianus) taken from an area near an industrial fluoride source in northwestern Washington. Fluoride levels in the bones of these deer were from 10 to 35 times higher than levels in the bones of normal animals. These levels are similar to those associated with fluorosis of cattle.     

Comparison of propranolol,metoprolol, and acebutolol on insulin-induced hypoglycaemia.

Metoprolol and acebutolol, two supposedly cardio-selective beta-adrenergic recptor blocking agents, were tested in healthy volunteers against propranolol, a non-selective drug, for their effect on blood glucose levels during insulin-induced hypoglycaemia. There was not significant difference between propranolol and metoprolol, which both potentiated the initial hypoglycaemic action of the insulin and delayed the return to normoglycaemia. Acebutolol, even though potentiating the initial hypoglycaemia, did not possess a significant delaying effect. A similar trial should be undertaken in diabetics to determine with certainty the safety of such drugs in diabetes mellitus.     

Etiology of two virus diseases of lilac (Syringa vulgaris L.) occurring in Czechoslovakia

Virus origin of lilac ringspot and chlorotic ringspot of lilac was identified serologically by means of double gel diffusion method. The former of these diseases is due to Arabis mosaic virus, the latter to a mixture of Arabis mosaic virus and cherry leaf roll virus. The occurrence of these viruses has been detected for the first time in Czechoslovakia.     

T cell stimulation remodels the latently HIV-1 infected cell population by differential activation of proviral chromatin

The reservoir of latently HIV-1 infected cells is heterogeneous. To achieve an HIV-1 cure, the reservoir of activatable proviruses must be eliminated while permanently silenced proviruses may be tolerated. We have developed a method to assess the proviral nuclear microenvironment in single cells. In latently HIV-1 infected cells, a zinc finger protein tethered to the HIV-1 promoter produced a fluorescent signal as a protein of interest came in its proximity, such as the viral transactivator Tat when recruited to the nascent RNA. Tat is essential for viral replication. In these cells we assessed the proviral activation and chromatin composition. By linking Tat recruitment to proviral activity, we dissected the mechanisms of HIV-1 latency reversal and the consequences of HIV-1 production. A pulse of promoter-associated Tat was identified that contrasted to the continuous production of viral proteins. As expected, promoter H3K4me3 led to substantial expression of the provirus following T cell stimulation. However, the activation-induced cell cycle arrest and death led to a surviving cell fraction with proviruses encapsulated in repressive chromatin. Further, this cellular model was used to reveal mechanisms of action of small molecules. In a proof-of-concept study we determined the effect of modifying enhancer chromatin on HIV-1 latency reversal. Only proviruses resembling active enhancers, associated with H3K4me1 and H3K27ac and subsequentially recognized by BRD4, efficiently recruited Tat upon cell stimulation. Tat-independent HIV-1 latency reversal of unknown significance still occurred. We present a method for single cell assessment of the microenvironment of the latent HIV-1 proviruses, used here to reveal how T cell stimulation modulates the proviral activity and how the subsequent fate of the infected cell depends on the chromatin context.     

Extensive gaps and biases in our knowledge of a well‐known fauna: implications for integrating biological traits into macroecology

Aim Ecologists seeking to describe patterns at ever larger scales require compilations of data on the global abundance and distribution of species. Comparable compilations of biological data are needed to elucidate the mechanisms behind these patterns, but have received far less attention. We assess the availability of biological data across an entire assemblage: the well‐documented demersal marine fauna of the United Kingdom. We also test whether data availability for a species depends on its taxonomic group, maximum body size, the number of times it has been recorded in a global biogeographic database, or its commercial and conservation importance. Location Seas of the United Kingdom. Methods We defined a demersal marine fauna of 973 species from 15 phyla and 40 classes using five extensive surveys around the British Isles. We then quantified the availability of data on eight key biological traits (termed biological knowledge) for each species from online databases. Relationships between biological knowledge and our predictors were tested with generalized linear models. Results Full data on eight fundamental biological traits exist for only 9% (n= 88) of the UK demersal marine fauna, and 20% of species completely lack data. Clear trends in our knowledge exist: fish (median biological knowledge score = six traits) are much better known than invertebrates (one trait). Biological knowledge increases with biogeographic knowledge and (to a lesser extent) with body size, and is greater in species that are commercially exploited or of conservation concern. Main conclusions Our analysis reveals deep ignorance of the basic biology of a well‐studied fauna, highlighting the need for far greater efforts to compile biological trait data. Clear biases in our knowledge, relating to how well sampled or ‘important’ species are suggests that caution is required in extrapolating small subsets of biologically well‐known species to ecosystem‐level studies.     

Carbohydrate residues downstream of the terminal Galalpha(1,3)Gal epitope modulate the specificity of xenoreactive antibodies

Carbohydrates are involved in many immunological responses including the rejection of incompatible blood, tissues and organs. Carbohydrate antigens with Galalpha(1,3)Gal epitopes are recognized by natural antibodies in humans and pose a major barrier for pig-to-human xenotransplantation. Genetically modified pigs have been established that have no functional alpha1,3-galactosyltransferase (alpha1,3GT), which transfers alphaGal to N-acetyllactosamine (LacNAc) type oligosaccharides. However, a low level of Galalpha(1,3)Gal is still expressed in alpha1,3GT knockout animals in the form of a lipid, isoglobotrihexosylceramide (iGb3), which is produced by iGb3 synthase on lactose (Lac) type core structures. Here, we define the reactivity of a series of monoclonal antibodies (mAb) generated in alpha1,3GT-/- mice immunized with rabbit red blood cells (RbRBC), as a rich source of lipid-linked antigens. Interestingly, one mAb (15.101) binds weakly to synthetic and cell surface-expressed Galalpha(1,3)Gal on LacNAc, but strongly to versions of the antigen on Lac cores, including iGb3. Three-dimensional models suggest that the terminal alpha-linked Gal binds tightly into the antibody-binding cavity. Furthermore, antibody interactions were predicted with the second and third monosaccharide units. Collectively, our findings suggest that although the terminal carbohydrate residues confer most of the binding affinity, the fine specificity is determined by subsequent residues in the oligosaccharide.