A proteomics approach to cloning fenestrin from the nuclear exchange junction of tetrahymena

We set out to find the "fenestrin" gene, a gene whose protein is associated with numerous cellular apertures, including the nuclear exchange junction in mating Tetrahymena thermophila. First we developed protocols for imaging and isolating intact nuclear exchange junctions from conjugating cells. Proteins from these junctions were purified using SDS-PAGE, subjected to limited proteolysis, and precise molecular weights were determined by mass spectrometry. Using Protein Prospector software and the published Tetrahymena Genome Database, genes for 15 of the most abundant proteins found in our extracts were identified. The most promising candidate was cloned by PCR, fused to yellow fluorescent protein (YFP), and placed under the control of an inducible metallothionein promoter. YFP-localization within live Tetrahymena transformants strongly suggested that one of these genes encoded the fenestrin protein, a result that was subsequently confirmed by Western blotting.

Rat hepatic xanthine oxidase activity: age and sex specific differences

The effect of maturation, castration, and sex hormonal treatment on hepatic xanthine oxidase activity (XOA) was evaluated in Sprague-Dawley rats. In mature rats XOA was 59% greater in males than in females, whereas in the immature animal the differences between sexes were insignificant. Pubescence resulted in a twofold increase in activity in the male which was prevented by prepubertal orchiectomy. Conversely, prepubertal oophorectomy caused a twofold increase in XOA in females. Urinary uric acid excretion paralleled XOA in rats fed 1% oxonic acid. XOA was significantly elevated in females after postpubertal castration or testosterone treatment while orchiectomy or estradiol-17 beta treatment in the mature male showed no effect. In summary, these data suggest that androgens are required during puberty for full expression of hepatic XOA, and furthermore, an ovarian suppressive effect is evident. In the adult rat only the female responds appreciably to hormonal manipulation.

An attempt to use vincristine and colcemid to measure proliferative rates in normal human epidermis in vivo

A range of doses of vincristine (0.5-10 micrograms) or colcemid (5-100 micrograms) injected intradermally into normal volunteers failed to yield any significant accumulation of arrested mitoses. This was despite an apparently successful block of cells in metaphase by the highest three doses of each drug. Possible reasons for the failure to see accumulation are discussed. The results suggest that normal human epidermis is not a suitable system for application of the metaphase-arrest technique using intradermal injection.

Setting boundaries for genome-wide heterochromatic DNA deletions through flanking inverted repeats in Tetrahymena thermophila

Eukaryotic cells pack their genomic DNA into euchromatin and heterochromatin. Boundaries between these domains have been shown to be set by boundary elements. In Tetrahymena, heterochromatin domains are targeted for deletion from the somatic nuclei through a sophisticated programmed DNA rearrangement mechanism, resulting in the elimination of 34% of the germline genome in ∼10,000 dispersed segments. Here we showed that most of these deletions occur consistently with very limited variations in their boundaries among inbred lines. We identified several potential flanking regulatory sequences, each associated with a subset of deletions, using a genome-wide motif finding approach. These flanking sequences are inverted repeats with the copies located at nearly identical distances from the opposite ends of the deleted regions, suggesting potential roles in boundary determination. By removing and testing two such inverted repeats in vivo, we found that the ability for boundary maintenance of the associated deletion were lost. Furthermore, we analyzed the deletion boundaries in mutants of a known boundary-determining protein, Lia3p and found that the subset of deletions that are affected by LIA3 knockout contained common features of flanking regulatory sequences. This study suggests a common mechanism for setting deletion boundaries by flanking inverted repeats in Tetrahymena thermophila.

Shigellosis outbreaks at summer camps for the mentally retarded in New York State

During 1987, four New York State summer camps for the mentally retarded and developmentally disabled experienced outbreaks of Shigella sonnei gastroenteritis. Cases occurred in 150 of 286 (attack rate (AR) = 52%), 167 of 295 (AR = 57%), and 25 of 114 (AR = 22%) persons in three camps, respectively; a fourth camp reported eight cases. Epidemiologic investigation suggested point-source foodborne outbreaks in two camps, while person-to-person spread appeared to predominate in the other two. Numerous secondary cases were identified among contacts outside the facilities in the second and third camps. To quantify the extent of the problem, the authors reviewed data on 77 infectious disease outbreaks (12 in camps for the handicapped and 65 in camps for the nonhandicapped) that occurred in the 12,484 registered camp sessions (316 for the handicapped and 12,168 for the nonhandicapped) held during the six-year period 1982-1987. Camps for the handicapped demonstrated approximately a seven times greater risk for all types of infectious disease outbreaks (AR = 38 outbreaks/1,000 camp sessions vs. five outbreaks/1,000 camp sessions; relative risk (RR) = 7.1, 95% confidence interval (CI) 3.9-13.0), including those of gastrointestinal etiology (RR = 8.6, 95% CI 4.4-16.8) and those due to Shigella (RR = infinity). Large camp size (RR = 2.3, 95% CI 1.3-4.1) and long duration of camp sessions (RR = 3.9, 95% CI 1.3-11.6) also increased the risk for outbreaks; however, this risk was predominantly in the camps for the nonhandicapped--other factors relating to personal hygiene and close camper-staff contact were probably more important in the camps for the handicapped. These outbreaks demonstrate the impact of shigellosis at summer camps for the mentally retarded and the need for early preventive action.

Mitotic and labelling activity in normal human epidermis in vivo

Labelling and mitotic indices were studied in the epidermis of twenty-eight young men. A mean labelling index of 5.5% was found from the whole study and a mean mitotic index of 0.06%. Mitotic index particularly was extremely variable; indices between 0.002 and 0.438% were found in individual biopsies. In the first two of three experiments in which mitotic index at 09.00 hours was compared with that at 15.00 hours, significant differences were found (15.00 hours greater than 09.00 hours by a factor of 2.6, P less than 0.001). However, in the third such experiment no such difference was found, suggesting that the timing and occurrence of diurnal rhythms of mitotic activity may not be consistent in normal human epidermis. In the one experiment in which it was investigated, a significantly higher mitotic index was found at 21.00 hours compared to 09.00 and 15.00 hours. Labelling index did not vary significantly at 09.00, 15.00 or 21.00 hours. However, labelling index did show a significant pattern of change over a 12-month period in two groups of subjects; peaks of labelling were seen in July and troughs in January. Very high ratios of labelled: mitotic cells were found, the median ratio for the whole study being ninety-eight labelled: one mitotic cell. This finding supports the possibility that not all labelled cells subsequently go on to divide in normal human epidermis.

The Tetrahymena bcd1 mutant implicates endosome trafficking in ciliate, cortical pattern formation

Ciliates, such as Tetrahymena thermophila, evolved complex mechanisms to determine both the location and dimensions of cortical organelles such as the oral apparatus (OA: involved in phagocytosis), cytoproct (Cyp: for eliminating wastes), and contractile vacuole pores (CVPs: involved in water expulsion). Mutations have been recovered in Tetrahymena that affect both the localization of such organelles along anterior-posterior and circumferential body axes and their dimensions. Here we describe BCD1, a ciliate pattern gene that encodes a conserved Beige-BEACH domain-containing protein a with possible protein kinase A (PKA)-anchoring activity. Similar proteins have been implicated in endosome trafficking and are linked to human Chediak-Higashi syndrome and autism. Mutations in the BCD1 gene broaden cortical organelle domains as they assemble during predivision development. The Bcd1 protein localizes to membrane pockets at the base of every cilium that are active in endocytosis. PKA activity has been shown to promote endocytosis in other organisms, so we blocked clathrin-mediated endocytosis (using "dynasore") and inhibited PKA (using H89). In both cases, treatment produced partial phenocopies of the bcd1 pattern mutant. This study supports a model in which the dimensions of diverse cortical organelle assembly-platforms may be determined by regulated balance between constitutive exocytic delivery and PKA-regulated endocytic retrieval of organelle materials and determinants.

A genomics learning framework for undergraduates

Genomics is an increasingly important part of biology research. However, educating undergraduates in genomics is not yet a standard part of life sciences curricula. We believe this is, in part, due to a lack of standard concepts for the teaching of genomics. To address this deficit, the members of the Genomics Education Alliance created a set of genomics concepts that was then further refined by input from a community of undergraduate educators who engage in genomics instruction. The final genomics concepts list was compared to existing learning frameworks, including the Vision and Change initiative (V&C), as well as ones for genetics, biochemistry and molecular biology, and bioinformatics. Our results demonstrate that the new genomics framework fills a niche not addressed by previous inventories. This new framework should be useful to educators seeking to design stand-alone courses in genomics as well as those seeking to incorporate genomics into existing coursework. Future work will involve designing curriculum and assessments to go along with this genomics learning framework.