New roles for DIF? Effects on early development in Dictyostelium

The DIFs are unusual, chlorinated molecules which induce stalk cell differentiation during the later, multicellular phase of Dictyostelium development. Here we provide evidence that one or more DIFs have a role during early development, when small amounts are known to be made. Initial indications came from an optical technique which detects changes in shape or cohesion of cells in suspension (Gerisch and Hess, PNAS 71, 2118, 1974). After a period of optical inactivity at the start of development, cell suspensions normally produce spontaneous spike-shaped light-scattering oscillations synchronised by oscillations in extracellular cAMP levels, followed by sinusoidal oscillations where the synchroniser is not known. DIFs 1 and 2 produce optical responses from cells at all these early stages of development. The phase of both spiked and sinusoidal oscillations can be shifted, indicating an effect on the oscillator in each case. We find further: (1) cAMP oscillations and cAMP relay during spiked oscillations are transiently inhibited by DIF-1. (2) DIF-1 causes a transient decrease in cellular cGMP levels in cells taken before oscillations commence and likewise inhibits the cGMP response to a cAMP stimulus in cells taken later in development. Cytoskeletal organization and hence cell shape might be affected by DIF-1 by this indirect route. (3) The effects of DIF-1 are transient, even though it is essentially stable in the cell suspension. Cells somehow adapt to DIF-1. (4) The effects are chemically specific: DIF-1 and DIF-2 are active at 10(-7) to 10(-8) M, with DIF-2 being the more active, whereas related compounds have little or no activity at 10(-6) M. These results indicate that cells are responsive to DIFs 1 and 2 from the start of development and suggest a wider role for the DIFs. This role might involve effects on cAMP signalling and on intracellular second messengers.     

Degradation of myofibrillar proteins by trypsin-like serine proteinases.

The effects of the Ca2+-activated cysteine proteinase, the rat trypsin-like serine proteinase and bovine trypsin on myofibrillar proteins from rabbit skeletal muscle are compared. 2. Myofibrils that had been treated at neutral pH with the Ca2+-dependent proteinase and with the rat enzyme were (a) analyzed by sodium dodecyl sulphate/polyacrylamide-gel electrophoresis and (b) examined in the electron microscope. Treatment with each proteinase resulted in the loss of the Z-discs, but the rat enzyme caused much more extensive disruption of the ultrastructure and degraded more of the myofibrillar proteins. 3. Purified F-actin was almost totally resistant to the proteinases, whereas G-actin was degraded by the rat trypsin-like proteinase at a rate approx. 15 times faster than was obtained with bovine trypsin. 4. Similar results were obtained with alpha-actinin, whereas tropomyosin was degraded more readily by bovine trypsin than by the rat trypsin-like proteinase. 5. The implications of these findings for the non-lysosomal breakdown of myofibrillar proteins in vivo are considered.     

The mendelian inheritance of a human X chromosome-specific DNA sequence polymorphism and its use in linkage studies of genetic disease

Summary A recombinant DNA sequence, RB6, was isolated from a human X chromosome library and shown to be X-specific by hybridisation to DNA from a human-mouse somatic cell hybrid containing X as the only human chromosome. The cloned sequence was located on the long arm distal to Xq13 using a human-mouse somatic cell hybrid containing a partial human X chromosome. DNA samples isolated from control human females were digested with the restriction enzyme MspI, and analysed by blotting and hybridisation to the radioactive cloned DNA. Eight of 14 individuals from a random population showed a single hybridising band 7.5 kilobase pairs (kb) in length, but six showed an additional band 10.1 kb in length. DNA from 12 members of a family with X-linked thyroxine-binding globulin deficiency was analysed for the segregation of this polymorphism. The results show that the polymorphism is inherited in a Mendelian fashion, and that the disease locus is not closely linked to the polymorphic site. Such polymorphisms will be useful as markers for chromosome mapping and for the antenatal diagnosis of genetic diseases.     

The ontogeny of premolar dental wear in Cercocebus albigena (cercopithecidae)

The orientation of striated wear facets on primate teeth serves as a useful guide for reconstructing jaw movements during mastication. Most wear facets on the molars are formed during one of the two well-documented movements, Phase I or Phase II, of the power stroke. Another jaw movement direction, “orthal retraction” (OR) has been proposed to account for a third set of facets occasionally present on the pointed tips of premolars and molars. Evidence advanced here indicates that OR facets on pointed anterior premolars (P₃) of cercopithecoids are actually Phase I facets that have become reoriented as a result of a rotation of this tooth during its eruption. “Orthal retraction” probably does not exist as a discrete masticatory phase.     

Increased Noradrenergic Metabolism in the Cerebellum of the Mouse Mutant Dystonia Musculorum

Abstract: The neurological mouse mutant dystonia musculorum exhibits bizarre appendicular and truncal dystonia without known cerebellar histopathology. We evaluated striatal dopamine and cerebellar norepinephrine metabolism in this mutant and compared the results with those obtained in wild-type BALB/c and B6C3 controls. Tyrosine hydroxylase activity and dopamine metabolite levels (homovanillic acid and 3,4-dihydroxyphenylacetic acid) in the striatum of the mutant were similar to controls. Tyrosine hydroxylase activity and the steady-state level of 3-methoxy-4-hydroxyphenethyleneglycol, a metabolite of norepinephrine, in the cerebellum were 38% and 42-66%, respectively, greater in the mutant. However, the level of norepinephrine was similar (∼350 ng/g). Further, a Purkinje cell-specific marker, cGMP-dependent protein kinase, was unchanged in the mutant and no Purkinje cell pathology was observed with light microscopy. The lack of Purkinje cell derangement and similar levels of cerebellar norepinephrine and cGMP-dependent protein kinase activity suggest that increased norepinephrine metabolism in the cerebellum of this mutant is not a morphological response to gross target cell loss during morphogenesis. The observed changes may be a reaction to abnormal impulse traffic or altered input/output pathways to the mutant cerebellum during its development.     

The in vitro loss of penicillamine in plasma,albumin solutions,and whole blood: Implications for pharmacokinetic studies of penicillamine

The recent development of a high performance liquid chromatography assay method for the analysis of penicillamine in biological samples such as plasma, whole blood, and urine has provided a specific and sensitive assay method to aid in the study of penicillamine pharmacokinetics. Several investigators have reported measuring the plasma concentration of penicillamine. Some of these investigators have indicated that the plasma must be assayed immediately. However, such restrictions can limit the feasibility of a pharmacokinetic study. The results of this paper demonstrate the instability of penicillamine in plasma, albumin solutions, and whole blood. The rate of loss of penicillamine was shown to be influenced by the concentration of albumin. As a result of the significant loss of penicillamine over a short period of time, plasma or whole blood samples must be deproteinated immediately upon collection to avoid the loss of reduced penicillamine. Methods are presented for the preparation of biological samples so that the oxidation of penicillamine is prevented and the samples can be held for several days prior to analysis.     

Sivapithecus simonsi,a new species of miocene hominoid,with comments on the phylogenetic status of the ramapithecinae

The Ramapithecinae are an extinct, mainly Miocene group of hominoids, whose relationship to modern taxa is disputed. Some regard them as hominids, while others view them as ancestral toPongo,or even as the group ancestral to both hominids and extant apes. In this paper a systematic revision of Ramapithecinae is undertaken. Sivapithecus sivalensis andRamapithecus punjabicus are considered the same species, with the former name having priority. A new Indian species,Sivapithecus simonsi,is recognized. Ramapithecine anatomy is reviewed and compared with that of gracileAustralopithecus, early and middle MioceneProconsul andDryopithecus, and living pongidsPan, Gorilla, andPongo.Ramapithecines are shown to be much more primitive or “ape-like” than some have argued. Anatomical data are evaluated cladistically with several results. Parallel evolution in the jaws, teeth, and facial structure of hominoids appears to be the rule rather than the exception. Bearing this in mind, nevertheless, from the available evidence of anatomy, ramapithecines are cladistically hominids.     

Amino acid transport in pig lymphocytes Enhanced activity of transport system asc following mitogenic stimulation

Changes in neutral amino acid transport activity caused by addition of phytohaemagglutinin-P to quiescent peripheral pig lymphocytes have been evaluated by measurements of ¹⁴C-labelled neutral and analogue amino acids under conditions approaching initial entry rates. Utilizing methylaminoisobutyric acid, the best model substrate of System A, we confirmed our previous report (Borghetti, A.F., Kay, J.E. and Wheeler, K.P. (1979) Biochem. J. 182, 27–32) on the absence of this transport system in quiescent cells and its emergence following stimulation. Furthermore, we demonstrated the presence in quiescent cells of an Na⁺-dependent transport system for neutral amino acids that has been characterized as System ASC by several criteria including intolerance to methylaminoisobutyric acid, strict Na⁺-dependence, the property of transtimulation and specificity for pertinent substrates such as alanine, serine, cysteine and threonine. Analysis of the relationship between influx and substrate concentration revealed that two independent saturable components contribute to entry of alanine in quiescent cells: a low affinity ($\text{K}{}_{\mathrm{<mtext>m</mtext>}}\text{= ≈4}\text{mM}$) and a high affinity ($\text{K}{}_{\mathrm{<mtext>m</mtext>}}\text{= ≈0.2}\text{mM}$) component. The high affinity component could be inhibited in a competitive way by serine, cysteine and threonine, but methylaminoisobutyric acid did not change appreciably its constants. The enhanced activity of alanine transport through the ASC system observed in activated cells resulted from a large increase in the capacity ($\text{V}$) of the high affinity component without any substantial change in the apparent affinity constant ($\text{K}{}_{\mathrm{<mtext>m</mtext>}}$).