Localization and functions of protein kinase A during Drosophila oogenesis

We have characterized the requirements for the Protein Kinase A (PKA) catalytic subunit, DC0, in Drosophila oogenesis. Intercellular bridges in egg chambers from PKA deficient females are unstable, leading to the formation of multinucleate nurse cells by fusions of adjacent cells. Germline clones of cells homozygous for null mutations of DC0 indicate that PKA acts autonomously in the germline. Highest levels of PKA catalytic subunit protein are associated with germ cell membranes, suggesting that targets of PKA are associated with the membrane or membrane skeleton and contribute to the stabilization of intercellular bridges. The migration of a subset of follicle cells, the border cells, is also disrupted by germline PKA mutations, implying that nurse cell junctions provide an essential path for border cell migrations.

RNA localization along the anteroposterior axis of the Drosophila oocyte requires PKA-mediated signal transduction to direct normal microtubule organization

Microtubule polarity has been implicated as the basis for polarized localization of morphogenetic determinants that specify the anteroposterior axis in Drosophila oocytes. We describe mutation affecting Protein Kinase A (PKA) that act in the germ line to disrupt both microtubule distribution and RNA localization along this axis. In normal oocytes, the site of microtubule nucleation shifts from posterior to anterior immediately prior to polarized localization of bicoid and oskar RNAs. In PKA-deficient oocytes, posterior microtubules are present during this transition, oskar RNA fails to accumulate at the posterior, and bicoid RNA accumulates at both ends of the oocyte. Similar RNA mislocalization patterns previously reported for Notch and Delta mutants suggest that PKA transduces a signal for microtubule reorganization that is sent by posteriorly located follicle cells.

Genetic investigation of cAMP-dependent protein kinase function in Drosophila development

The cAMP-dependent protein kinase (PKA) has been shown to mediate the vast majority of cellular responses to the intracellular second messenger, cAMP, in eukaryotes. To study the role of cAMP signal transduction in Drosophila development, we have isolated and molecularly characterized mutations of varying severity in the Drosophila PKA gene, DC0. Biochemical measurements indicate that DC0 is either the sole or the major PKA catalytic subunit gene in Drosophila. Adult females heterozygous for a strong and a weak DC0 allele fail to lay eggs and show a striking and novel defect in oogenesis that includes the formation of egg chambers containing multinucleate nurse cells. Females heterozygous for two weak DC0 alleles are fertile but produce offspring showing a variety of defects in embryogenesis, including preblastoderm arrest and alterations in cuticular patterning. Animals zygotically null for DC0 die as morphologically normal first-instar larvae, implying that maternally encoded protein, which perdures for at least 12 hr, suffices for embryogenesis. Animals hemizygous for weak DC0 alleles survive for several days as larvae but grow slowly. Mitotic recombination experiments in the adult eye indicate that the DC0 gene is not required autonomously either for cell viability or normal growth rates. These results argue that cAMP-mediated signal transduction is essential at a variety of stages during the development of a metazoan.

Microporosity of the substratum regulates differentiation of MDCK cells in vitro

We have analyzed the ability of the physical substratum to modulate both the ultrastructural and protein synthetic characteristics of the Madin-Darby canine kidney (MDCK) renal cell line. When MDCK cells were seeded on Millipore Millicell CM microporous membrane cell culture inserts they demonstrated a more columnar organization with an increase in cell density sixfold greater than the same cells seeded on conventional plastic substrata. After 1 wk postseeding on the microporous membrane a partial basal lamina was noted, with a contiguous basement membrane being apparent after 2 wk. One-dimensional sodium dodecyl sulfate gel electrophoresis was used to analyze detergent-solubilized proteins from MDCK cells maintained on plastic substrata vs. microporous membranes. When proteins were pulse-labeled with [35S]methionine, a 55 kDa protein was evident in the cytosolic extract of cells grown on collagen, laminin, and nontreated plastic substrata; but this labeled protein was not evident in similar extracts from cells grown on collagen and laminin-coated microporous membranes. To test if the polarized, basement-membrane secreting phenotype of the MDCK cells could be generated on a microporous membrane without pretreatment with any extracellular matrix (ECM) components, cells were seeded on the Millipore Millicell HA (cellulosic) microporous membrane. This type of substrata does not need a coating of ECM components for cell attachment. A partial basement membrane was formed below cells where the basal surface of the cell was planar, but not in areas where the cell formed large cytoplasmic extensions into the filter. This led us to the conclusion that the microporous nature of the substrata can dictate both ultrastructural and protein synthetic activities of MDCK cells. Furthermore, we suggest that both the planar nature of the basal surface and the microporosity of the substrate are corequisites for the deposition of the basement membrane.

Somatosensory evoked potentials following pudendal nerve stimulation as indicators of low sacral root involvement in a postlaminectomy patient

Somatosensory cortical evoked potential studies (SEPs) following stimulation of the pudendal nerves proved useful in objectively documenting preoperative low sacral root involvement in a 33-year-old postlaminectomy patient, presenting with impending cauda equina syndrome and treated by piriformis muscle release with good clinical results. Preoperative P40(P1) latencies of SEPs were abnormally prolonged (47 msec) and returned to normal values (38 msec) postoperatively. This new noninvasive electrodiagnostic method has been described previously for normal subjects only. Further experience with this method is still needed, especially to elucidate the diagnostic reliability of various SEP parameters.

Undergraduate curricula in PM&R: implications for resident recruitment and general image of the specialty

Comprehensive data on undergraduate curricula in Physical Medicine and Rehabilitation were obtained in a 1980 questionnaire survey of approved residency programs. Survey parameters included curriculum content (type and duration per academic year), teaching format and educational methodologies, academic exposure and student enrollment, faculty characteristics, and curriculum impact on resident recruitment. Of 53 responding programs 44 reported undergraduate education activities in PM&R. Curriculum content was predominantly clinical in all programs. The teaching format used by 70% of respondents consisted of a combination of lectures, clinical case presentations, conferences, demonstrations and clinical clerkships. Seventy-two percent of this sample were either compulsory or contained a compulsory component. An academic exposure to PM&R of two or more years and a curriculum duration of more than four weeks per academic year was reported by 81% and 75% of respondents respectively. Compulsory programs were offered most frequently in the first two years, while electives were offered mostly in the last two years of study. A low enrollment in electives (less than 50% of class) is reported, regardless of year of study. A teaching faculty of more than five was reported by 63% of programs. A positive curriculum impact on resident recruitment was reported by 72% of the respondents. Positive and negative implications of these findings for the PM&R specialty image and for a career choice in PM&R are discussed.

Successful use of the diaphragm and jelly by a young population: report of a clinical study

In the largest contemporary study of diaphragm use in the United States, the authors examine the experience of 2,168 women who selected this method of contraception at the Margaret Sanger Research Bureau over a recent two-year period. Eight in 10 of the study group were younger than 30 years and three in 10 were aged 21-24. Seven in 10 had never been married and the same proportion had never been pregnant. Accidental pregnancies in the first 12 months of use ranged from a low of 1.9 per 100 users younger than 18 years old to a high of 3.0 among 30-34-year-olds; and more than eight in 10 were still using the diaphragm at the year's end. These rates compare favorably with those reported for the pill and IUD in other clinical studies.