Mutations affecting cell division in Tetrahymena pyriformis, syngen 1. II. Phenotypes of single and double homozygotes.

The surface patterns associated with arrest of cell division by temperature-sensitive mutations at five different loci are described. Mutations at the mo1 locus prevent both the subdivision of ciliary meridians that mark the fission zone and the subsequent furrowing. Mutations at mo8 and mo12 cause abnormal configurations in the fission zone and aborted furrowing. Mutations in mo3 and mo6 bring about fission arrest with associated elongation (mo3) or twisting (mo6), even though complete fission zones do develop. The defects in mo1, mo3, and mo12 are expressed in the first division after shift to restrictive temperature, whereas expression of mo6 and of one allele of mo8 are delayed. Following preincubation in an amino acid-free medium at the restrictive temperature, mo8 causes arrest at the first division after readdition of nutrients, while mo6 blocks fission only after one or more divisions at the restrictive temperature. Double homozygotes were constructed containing the mo3^a mutation and mutations at each of the other loci. In addition, mo1^a was combined with mo8^a. In each of the double homozygotes, the characteristic phenotypes of both mutations were simultaneously expressed, and the penetrance of division blockage was very greatly enhanced. The results suggest that the functions of these five loci are not ordered in a single dependent sequence of steps, but rather that these loci probably mediate independent processes required for cytokinesis.     

Bioaccumulation of selected metals in the gill,liver and muscle tissue of rednose labeo Labeo rosae from two impoundments on the Olifants River,Limpopo river system,South Africa

Metal concentrations in the gill, muscle and liver tissues of Labeo rosae from two impoundments, Loskop and Flag Boshielo dams on the Olifants River, were evaluated in 2011 to detect patterns in metal associations between tissues and impoundments. Elevated concentrations of Ba, Zn, B, Al, Si and Fe, relative to a pristine site in the catchment, were found in the muscle, liver and gill tissues at both impoundments. Molybdenum concentrations were exceptionally high in all tissues at Loskop Dam and in liver at Flag Boshielo Dam. No definite pattern in the ratio metal concentrations within, or between, fish tissues was identified. The expected trend, liver > gills > muscle, was found at both impoundments, but was less prominent at Loskop Dam. Metal concentrations in muscle of Loskop Dam fish were significantly higher than in those at Flag Boshielo Dam. The inverse was true for liver. The long-term impact of elevated metal concentrations on fish health at both impoundments raises concern.     

Experimentally induced variations in vitelline artery development and circulatory pattern in the early chick embryo

White Leghorn eggs were incubated to desired prevasular stages. Each embryo, upon its intact yolk and surrounded by albumen, was rolled from the shell into a sterile 50 ml beaker. In an uppermost position, the blastoderm was lightly stained with neutral red. Three types of localized cuts were made as indicated below, and the beaker-embryo unit placed in a sterile humidified chamber for further incubation. Results: (1) Unilateral cuts adjacent to the body and parallel with its axis blocked or suppressed formation of the vitelline artery on the cut side, even though healing occurred; (2) A specific site was found in the area pellucida opposite the sinus rhomboidalis which, when lightly cut perpendicular to the body axis, resulted in blockage or shifting of the final junction between aorta and vitelline artery as far cephalad as the thirteenth somite level. Formation of a dual final junction with the aorta also occurred. (3)Transverse cuts through the body axis and into the area pellucida bilaterally, frequently resulted in bilateral blockage or bilateral shifting. In still other cases, growth of a functional loop around the cut to connect the aortae in anterior and posterior segments with the vitelline artery were observed. Other unique circulatory patterns are described. Apparently, slight interference with the capillary plexus which precedes the vitelline artery causes anomalous development. Circulation is considered a major factor in arterial differentiation. Cutting probably alters the plexus and relation of its components to the onset of blood flow.     

Identified taste bud cell proliferation in the perihatching chick [published erratum appears in Chem Senses 1998 Aug;23(4):459]

Developing taste buds in the anterior mandibular floor of perihatching chicks were studied by high voltage electron microscopic autoradiography in order to identify proliferating gemmal cell types. Montaged profiles of 29 taste buds in five cases euthanized between embryonic day 21 and posthatching day 2 were analyzed after a single [3H]thymidine injection administered on embryonic day 16, 17 or 18. Results showed that dark cells comprised 55% of identified (n = 900 cells) and 62% of labeled (n = 568 cells) gemmal cells as compared with light, intermediate, basal or perigemmal bud cells. Dark cells had both a greater (P < 0.05) number of labeled cells and a greater amount of label (grains/nucleus) than the other four bud cell types, irrespective of injection day. The nuclear area (micron 2) of dark cells was not significantly larger (P > 0.05) than that of the other gemmal cell types and therefore cannot account for the greater amount for label in the dark cells. Interestingly, only dark cells showed a positive correlation (P < 0.003) between amount of label and nuclear area. Results suggest that, during the perihatching period of robust cell proliferation, dividing dark cells may give rise primarily, but not exclusively, to dark cell progeny.      

The ecological integrity of the Lower Olifants River,Limpopo province,South Africa: 2009–2015 – Part A: Olifants River main stem

The major rivers of the South African ‘Lowveld’ (low-latitude savanna) suffer numerous impacts from upstream economic activities. Whereas monitoring these rivers is required to detect biodiversity losses, record pollution events and devise mitigation strategies, current monitoring programmes are inadequate. In 2009, the South African Earth Observation Network initiated an intensive long-term research programme on the Lowveld reaches of the Olifants River. Physico-chemical parameters, aquatic macroinvertebrates and fish abundances were recorded at four Lowveld sites in the Olifants River. We review six years of this programme. The results suggest deterioration in the ecological condition of the Olifants River with no discernible improvement through protected areas. Trends could not be detected. The parameters measured, sampling methods and/or sampling frequency might be responsible for the limited trends observed, or alternatively the results simply reflect stable conditions despite on-going pollution. Real time monitoring and an expansion in the parameters monitored would add value to the monitoring programme.     

A Medical Resident in Ponape

The University of Hawaii has an elective two-month primary care rotation in Ponape, in the Eastern Caroline Islands, for senior medical residents. Many diagnostic and therapeutic situations provide unusual challenges because of the tropical environment and the paucity of medical facilities. Parasitoses, tuberculosis and trauma are common, and certain diseases, such as cholelithiasis and coronary artery disease, have a low incidence, reflecting the socio-economic conditions. The local intoxicant, sakau, seems to be responsible for dermatologic, pulmonary, and possibly hepatic and neurologic disorders.The rotation has proved to be a worthwhile educational experience for residents and a benefit to the people of Ponape.     

Dusky Sap Beetle Mediated Dispersal of Bacillus subtilis to Inhibit Aspergillus flavus and Aflatoxin Production in Maize Zea mays L.

Laboratory assays were performed with detached milk stage maize ( Zea mays L.) ears and dusky sap beetles ( Carpophilus lugubris Murray) carrying the Kodiak Concentrate formulation of the bacterium, Bacillus subtilis (Ehrenberg) Cohn. After 1 day of exposure to the B. subtilis- contaminated C. lugubris , the colonization of mechanically damaged kernels by Aspergillus flavus Link ex. Fries was reduced from 82% (if the A. flavus was inoculated first) to 41% (if B. subtilis was added by C. lugubris before the A. flavus ). Field cage studies were performed with an autoinoculative device containing B. subtilis into which C. lugubris beetles were introduced. C. lugubris -dispersed B. subtilis reduced visible A. flavus colonization by 97% when the A. flavus was added to purposely damaged maize ears 4 days after C. lugubris were released from the autoinoculator. In 1993 field studies, none of the purposely damaged ears that allowed access to C. lugubris beetles emerging from autoinoculators containing B. subtilis had visible sporulating A. flavus compared with 92% of ears that did not allow access of C. lugubris but that subsequently had the A. flavus inoculum added. In 1994 field studies, 70% of the ears that excluded C. lugubris had aflatoxin levels greater than 200 ppb in purposely damaged kernels, as opposed to less than 10% of kernels that permitted access by natural populations of C. lugubris that probably acquired B. subtilis from a single autoinoculator. Aflatoxin levels in these ears were negatively correlated with the presence of both B. subtilis and C. lugubris . The B. subtilis was widely dispersed over a 16-ha area as indicated by maize ear and C. lugubris trap sampling. These studies indicate that autoinoculative dispersal of B. subtilis by natural populations of C. lugubris is a potentially useful means for reducing A. flavus and aflatoxin in maize.