A refined linkage map for DNA markers around the pericentromeric region of chromosome 10

A refined genetic linkage map for the pericentromeric region of human chromosome 10 has been constructed from data on 12 distinct polymorphic DNA loci as well as the locus for multiple endocrine neoplasia type 2A (MEN 2A), a dominantly inherited cancer syndrome. The map extends from D10S24 (at 10p13-p12.2) to D10S3 (at 10q21-q23) and is about 70 cM long. Overall, higher female than male recombination frequencies were observed for this region, with the most remarkable female excess in the immediate vicinity of the centromere, as previously reported. Most of the DNA markers in this map are highly informative for linkage and the majority of the interlocus intervals are no more than 6 cM apart. Thus this map should provide a fine framework for future efforts in more detailed mapping studies around the centromeric area. A set of ordered cross-overs identified in this work is a valuable resource for rapidly and accurately localizing new DNA clones isolated from the pericentromeric region.     

Development of left/right handedness in the chick heart.

The chick heart tube develops from the fusion of the right and left areas of precardiac mesoderm and in almost all cases loops to the embryo's right-hand side. We have investigated whether any intrinsic difference exists in the right and left areas of precardiac mesoderm, that influences the direction of looping of the heart tube. Chick embryos incubated to stages 4,5 and 6 were cultured by the New method. Areas of precardiac mesoderm were exchanged between donor and host embryos of the same stage and different stages to form control, double-right and double-left sided embryos. Overall, double-right sided embryos formed many more left-hand loops than double-left sided embryos. At stages 4 and 5 a small percentage of double-right embryos formed left-hand loops (13%) whereas at stage 6 almost 50% of hearts had left-hand loops. Control embryos formed right-hand loops in 97% of cases. The stability of right-hand heart looping by double-left sided embryos, may be related to the process of 'conversion', whereas the direction of looping by double-right sided embryos has become randomised. There is some indication that an intrinsic change occurred in the precardiac mesoderm between stages 5 and 6 that later influenced the direction of looping of the heart tube. The direction of body turning is suggested to be linked to the direction of heart looping.     

Histochemical characterization of myotomal muscle in the grass pickerel, Esox americanus vermiculatus (LeSeuer), and the muskellunge, E. masquinongy (Mitchell)

A histochemical study of the myotomal muscles in the grass pickerel, Esox americanus vermiculatus , and the muskellunge, E. masquinongy , was performed using actomyosin ATPase and NADH diaphorase activities. Three fibre types, i.e., red, white and pink were distinguished on the basis of their enzyme activities. White muscle fibres comprised the bulk of the myotomal musculature. The relative proportion of red muscle fibres was greater in the caudal region than in more anterior regions of the body. Pink fibres formed only a few layers between red and white. These findings are discussed in relation to the possible functional significance of the muscle fibre types in swimming and feeding behaviour in these species.     

Glutamatergic central nervous transmission in locusts

It is generally believed that neural transmission in the central nervous systems of insects is cholinergic, on the basis of secondary evidence: the presence of cholinesterase, and sensitivity of a nonsynaptic region of the neuron, its cell body, to iontophoresed acetylcholine. In the present work a preparation has been developed which takes advantage of the availability of identified motor neurons in the locust metathoracic ganglion with known 3-dimensional geometry of dendritic fields. These neurons transmit at their peripheral neuromuscular junctions with glutamate. The fast extensor tibiae motor neuron also makes excitatory central connections onto its functional antagonists the flexor tibiae motor neurons. Unless Dale's principle is contravened, transmission at these central synapses should also be glutamatergic. This transmission onto flexor motor neurons was found to be attenuated 70% by a glutamatergic blocker. Glutamate iontophoresed into selected areas of neuropil into which the motor neurons have dendritic branches caused the neurons to be depolarized, in a dose-dependent manner. Individual motor neurons were directly excited to spike with suprathreshold iontophoretic current. With long durations of release they were desensitized, but recovered quickly with rest. The data provide evidence that central transmission onto motor neurons in the locust metathoracic ganglion is glutamatergic.     

Backwrd population projection by a generalized inverse

The Leslie population projection matrix may be used to project forward in time the age distribution or age-sex distribution of a population. As it is a singular matrix, it does not have an inverse, and so it is not clear that there is a corresponding procedure for backward projection. In terms of the eigenvalues and eigenvectors of the Leslie matrix, certain generalized inverses are constructed that can sometimes be used advantageously for backward projection.     

Xylene Poisoning: A Report on One Fatal Case and Two Cases of Recovery after Prolonged Unconsciousness

Three cases of xylene poisoning occurred after prolonged inhalation of paint fumes. Analysis showed that xylene comprised more than 90% of the solvent in the paint, the total solvent comprising 34% of the paint by weight. One patient was dead on admission, while the other two recovered after at least 15 hours'' loss of consciousness. Both patients had transient liver cell damage, and one temporary impairment of renal function.