Analysis of lens cell fate and eye morphogenesis in transgenic mice ablated for cells of the lens lineage

Transgenic mice carrying the diphtheria toxin A gene driven by mouse gamma 2-crystallin promoter sequences manifest microphthalmia due to ablation of fiber cells in the ocular lens. Here we map ablation events in the lens by crossing animals hemizygous for the ablation construct with transgenic mice homozygous for the in situ lacZ reporter gene driven by identical gamma 2-crystallin promoter sequences. By comparing the spatial distribution of lacZ-expressing cells and the profile of gamma-crystallin gene expression in the lenses of normal and microphthalmic offspring, the contributions of specific cell types to lens development were examined. The results suggest that phenotypically and developmentally distinct populations of lens fiber cells are able to contribute to the lens nucleus during organogenesis. We also show that dosage of the transgene and its site of integration influence the extent of ablation. In those mice homozygous for the transgene and completely lacking cells of the lens lineage, we show that the sclera, cornea, and ciliary epithelium are reduced in size but, otherwise, reasonably well formed. In contrast, the anterior chamber, iris, and vitreous body are not discernible while the sensory retina is highly convoluted and extensively fills the vitreous chamber.     

The binding of divalent cations to myosin.

Centrifuge transport, equilibrium dialysis, and electron paramagnetic resonance studies on the binding of Mn2+ to myosin revealed two sets of noninteracting binding sites which are characterized at low ionic strength (0.016 M KCl) by affinity constants of 10(6) M-1 (Class I) and 10(3) M-1 (Class II), respectively. At 0.6 M KCl concentration, the affinity of Mn2+ for both sets of sites is reduced. The maximum number of binding sites is 2 for the high affinity and 20 to 25 for the low affinity set. Other divalent metal ions displace Mn2+ from the high affinity sites in the following order of effectiveness: Ca greater than Mg = Zn = Co greater than Sr greater than Ni. The inhibitory effects of Mg2+ and Ca2+ upon the Mn2+ binding are competitive with inhibitor constants of 0.75 to 1 mM which is similar to that of the low affinity divalent metal ion binding sites. Exposure of myosin to 37 degrees partially inhibits Mn2+ binding to Class I parallel with inhibition of ATPase activity. The binding of Mn2+ to the high affinity binding sites is not significantly influenced by ADP or PPi, although Mn2+ increases the affinity of ADP binding to myosin at high ionic strength.     

Suppression of nitrate formation within an exotic conifer plantation

Summary Nitrate-N losses to stream waters and soil inorganic N pools, nitrifying potentials and NO₃-N production rates were measured in 2 adjacent watersheds, one used as pasture and the other planted in exotic conifer forest (Pinus radiata D. Don). Estimated NO₃-N loss to stream waters draining the pine and pasture watersheds were 0.6kg ha⁻¹ y⁻¹ and 7.6 kg ha⁻¹ y⁻¹ respectively. Ammonium-N pool sizes were not significantly different between soils in the two watersheds but NO₃−N pools and nitrifying potentials were always lower in the pine watershed soil samples. Laboratory incubation experiments indicated that suppression of NO₃−N formation in pine watershed soils required the presence of live tree roots and was not due to the direct action of allelopathic chemicals on nitrifiers.     

The ultrastructural basis for the identification of cell types in the pancreatic islets I. Guinea pig

Summary The pancreatic islets of the guinea pig have been studied by light and electron microscopy. The B granules in glutaraldehyde-fixed tissue often are cup-shaped with an indentation visible on one side of the granule. Phosphotungstic acid hematoxylin (PTAH) positive cells have been characterized by electron microscopy as three subtypes based on the size of the secretory granules. A_a cells are the most common and have secretory granules around 200 m in diameter. A_b cells have large secretory granules around 300 m in diameter and are relatively infrequent. A_c cells are the least common and have small (160 m) granules. Characteristic D cells are identifiable by electron microscopy and, on the basis of the subsequent study (Munger, Caramia, and Lacy, 1965), are identified as the silver positive cells observed by light microscopy.This investigation was supported in part by United States Public Health Service research grants GM-10102 and GM-03784 from the Institute of General Medical Sciences, and AM-01226 from the Institute of Arthritis and Metabolic Diseases.-The authors wish to acknowledge the valuable technical assistance of Mrs. Aileen Sevier and Mrs. Lidia Donohue.     

Biological characterization of two biotypes of pea aphid, one susceptible and the other resistant to fungal pathogens, coexisting on lucerne in Australia

In Australia, field infestations of lucerne, Medicago sativa L., by the pea aphid, Acyrthosiphon pisum (Harris), have been found to contain a sub-dominant biotype resistant to some fungal pathogens of the genus, Erynia. Population parameters have been studied in laboratory cultures of the susceptible and resistant biotypes from two localities. Compared with the susceptible one the resistant biotype had a greater intrinsic rate of increase at high temperature and a reduced propensity to form wings in response to a crowding stimulus. As both these characteristics would help to increase the proportion of the resistant biotype in infestations, the continued co-existence of the two biotypes poses an interesting ecological problem.

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Résumé En Australie, quand il y a contamination de la luzerne par Acrythosiphon pisum Harris, on observe un biotype sub-dominant résistant au champignon pathogène Erynia ssp. L'élevage au laboratoire a permis l'étude des paramètres démographiques comprenant le taux de développement, la survie et la fécondité sur les deux types (sensible et résistant) de deux origines géographiques. Le biotype résistant a présenté un taux intrinsèque d'accroissement plus élevé à 24°C; assez pour doubler le nombre de pucerons résistants par rapport aux sensibles en une génération. Le biotype résistant a montré aussi une tendance plus faible à produire des ailés en réponse à des stimulus de surpeuplement. Comme ces deux caractères devraient provoquer l'accroissement du biotype résistant pendant les pullulations, la coexistence continue des deux biotypes pose un problème écologique intéressant.

     

General practitioner obstetrics in Bradford.

The standard of obstetrics care by general practitioners in Bradford was assessed by reviewing the case records of all women who in 1988 were booked for delivery under their general practitioner but subsequently required transfer to consultant care. A total of 5885 women were delivered in Bradford during 1988. Of 1289 booked under their general practitioner, 637 required transfer to consultant care. In 259 cases transfer occurred during labour; only 37 of these women were visited by their general practitioner. Many of the problems that precipitated transfer were predictable and some were considered preventable: 263 of the women transferred were considered unsuitable for booking by general practitioners. The perinatal mortality among women booked under their general practitioner was 10.1/1000 and the stillbirth rate 7.8/1000. These figures are high and suggest a need for tighter controls over the qualifications and experience of doctors participating in a fully integrated system of obstetric care.     

Biaryl piperidines as potent and selective delta opioid receptor ligands

The design and synthesis of novel opiates are reported. Based on the message-address principle a novel class of 4,4- and 3,3-biaryl piperidines was designed and synthesized. Biological evaluation confirmed that these compounds exhibit high affinity and selectivity for the delta opioid receptor. Key structure–activity relationships that influence affinity, selectivity, functional activity and clearance are reported.