Human and rat chromosomal localization of two genes for 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase by analysis of somatic cell hybrids and in situ hybridization

Two genes encoding 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase were localized in human and rat chromosomes. PFKFB1 (previously PFRX), which encodes the liver and muscle isozymes, was assigned to Xq22-q31 in the rat and to Xq27–q28 in the human by in situ hybridization using probes generated by the polymerase chain reaction. PFKFB2, which encodes the heart isozyme of 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase, was assigned to chromosome 13 in the rat and to chromosome 1 in the human by hybridization of DNA from somatic cell hybrids. By in situ hybridization, this gene was localized to the regions 13q24–25 in the rat and 1q31 in the human.     

Muscle and nerve in muscular dysgenesis in the mouse at birth: Sprouting and multiple innervation

Muscular dysgenesis (mdg) in the mouse is a recessive autosomal mutation affecting the striated musculature: during the whole gestation period, the muscles never show any sign of contractile activity. They are cytologically immature at birth, although the diaphragm is more mature than limb muscles, as confirmed by the levels of creatine phosphokinase. In both limb muscles and diaphragm the cytochemical localization of acetylcholinesterase demonstrates focal accumulations on the entire surface of $\text{mdg}\text{mdg}$ muscles, whereas such foci of acetylcholinesterase activity are restricted to a narrow end plate-rich region in $\text{+}\text{mdg}$? diaphragms. Teased single $\text{mdg}\text{mdg}$ myofiber preparations show that one myofiber can possess several foci of acetylcholinesterase, generally presenting aspects of very immature motor end plates. A study of the motor innervation, after silver nitrate impregnation, provides evidence for a spectacular overgrowth and a generalized sprouting of $\text{mdg}\text{mdg}$ nerves and axons. The $\text{mdg}\text{mdg}$ nerve terminals are generally very immature-looking, with an intense ultraterminal sprouting. Aspects suggesting a denser multiple innervation of $\text{mdg}\text{mdg}$ than $\text{+}\text{mdg}$? myofibers have been observed and choline acetyltransferase activity is increased in $\text{mdg}\text{mdg}$ tissues. Acetylcholinesterase specific activity and the number of α-bungarotoxin binding sites per milligram protein increased in $\text{mdg}\text{mdg}$ compared to $\text{+}\text{mdg}$? diaphragms. The very low amount of 16 S (and 12 S) acetylcholinesterase is probably related to $\text{mdg}\text{mdg}$ muscle inactivity. If the cytological and biochemical data are compared, it seems possible to propose that $\text{mdg}\text{mdg}$ myofibers and axons are in contact in several regions of the same myofiber, in variably mature appositions, and with a very dense multi-innervation.     

Le prétendu rhinocéros de Nouvelle Calédonie est un marsupial (Zygomaturus diahotensis nov. sp.): Solution d'une énigmeet conséquences paléogéographiques

The first mammalian remain ever found in NewCaledonia is an upper tooth found by golddiggers in the Plio-Pleistocene terrace from the Diahot river. This tooth, given to the Muséum national d'Histoire naturelle (Paris) in 1876, was determined as a rhinoceros tooth and then completely forgotten. Its detailed study shows that it belongs to Zygomaturus, a large marsupial diprotodontid genus whose story is rather complicated. The Diahot tooth represents a new species of Zygomaturus, Z. diahotensis nov. sp., close to Z. trilobus from the Australian Pleistocene. That kinship suggests a Plio-Pleistocene land connection between Australia and New Caledonia, whereas till now New Caledonia was supposed to be separated from Australia since the end of the Cretaceous, because of the total absence of indigenous mammals, fossil or recent, in New Caledonia. The latest geological studies in the East Pacific do not contradict our hypothesis.     

The palisade endings of cat extraocular muscles: a light and electron microscope study.

The palisade endings (PEs), a particular type of nerve ending found only in extraocular muscles of mammals, have been studied using both silver-stained teased preparations and electron microscope techniques. They have been found, in act, in both the proximal and distal muscle insertions of the four recti and the two oblique mucles. PEs are exclusively associated with some of the mitochondria-poor, multiply-innervated muscle fibres present in the globar layer os these muscles, and consist of a multitude of terminal branches embracing the extremity of the muscle fibre and penetrating the infoldings formed by the muscle fibre at its tendinous attachment. The whole formation is surrounded by a thin capsule. These nerve endings present striking similarities to the developing Golgi tendon organ; the terminal branches lying among the collagen fibrils and occasionally making 'sensory-like' close contacts with the muscle fibre are disposed in such a way that they could easily have a sensory role. It was concluded that PEs present sufficient morphological evidence to be considered as sensory, encapsulated, myotendinous receptors, each related to a single multiply-innervated muscle fibre.     

Involvement of glycoconjugates in insulin-receptor interactions Studies in liver plasma membranes of control and diabetic mice

The involvement of glycoconjugates in the insulin-receptor interactions in mouse liver is tested by digestions of membranes with various enzymes. Trypsin decreased the binding of [¹²⁵I]insulin to liver membranes. After digestion with β-galactosidase no “high affinity” receptor sites could be detected. The effects observed with plant lectins confirm the involvement of galactoconjugates in the insulin binding process. Sophora japonica and Ricinus communis lectins (with galactose specificity) and concanavalin A largely inhibit the binding process of insulin and those effects concern the “high affinity” receptor sites. Other lectins (wheat germ agglutinin, Dolichos) and enzymes (α-l-fucosidase, $\text{β-N-}\text{acetyl-hexosaminidase and neuraminidase}$) are without effect on insulin binding.Comparative studies performed on diabetic mouse liver membrane (KK mice), previously characterized by decreased number of insulin receptors, are in good agreement with qualitatively similar receptor sites in both non-diabetic (control) and diabetic mice. Effects of enzymes and lectins yielded same results as compared to control membranes. Plasma membrane proteins and glycoproteins in both types of mouse are indistinguishable with respect to enzymic and chemical analysis. Sodium dodecyl sulphate acrylamide gel electrophoresis shows identical patterns. Moreover, the decrease in the number of insulin receptors is easily reversed with diet restriction. These data are consistent with the similarity of receptor sites in control and diabetic liver membrane.     

Biosynthesis and metabolism of testosterone by sertoli cell-enriched seminiferous tubules

Sertoli cell-enriched tubules isolated from rats which had been treated with 1,4-dimethyl sulfonyloxybutane were incubated with either [¹⁴C] progesterone or [¹⁴C] testosterone for 2 hours. Tubules of normal rats and fragments of Sertoli cell-enriched testes were incubated under the same conditions. Sertoli cell-enriched tubules converted progesterone to 20α-dihydroprogesterone, 17α-hydroxyprogesterone, androstenedione and testosterone. The major metabolite was 20α-dihydroprogesterone. The percentage conversion of progesterone into testosterone corresponded to a production of 10–20 ng testosterone. Sertoli cell-enriched tubules converted testosterone to dihydrotestosterone, androstenedione, 3α-androstanediol and 3β-androstanediol. Under our experimental conditions, dihydrotestosterone was the major 5α-reduced metabolite. Normal tubules converted progesterone and testosterone to the same metabolites as Sertoli cell-enriched tubules. Fragments of Sertoli cell-enriched testes were much more active than isolated tubules in metabolizing progesterone. They produced the same amounts of 5α-reduced metabolites of testosterone.     

Plant community composition steers grassland vegetation via soil legacy effects

Soil legacy effects are commonly highlighted as drivers of plant community dynamics and species co‐existence. However, experimental evidence for soil legacy effects of conditioning plant communities on responding plant communities under natural conditions is lacking. We conditioned 192 grassland plots using six different plant communities with different ratios of grasses and forbs and for different durations. Soil microbial legacies were evident for soil fungi, but not for soil bacteria, while soil abiotic parameters did not significantly change in response to conditioning. The soil legacies affected the composition of the succeeding vegetation. Plant communities with different ratios of grasses and forbs left soil legacies that negatively affected succeeding plants of the same functional type. We conclude that fungal‐mediated soil legacy effects play a significant role in vegetation assembly of natural plant communities.