Inverse Relationship of Polyoma Tumour Specific Cell Surface Antigen to H-2 Histocompatibility Antigens

NEOPLASTIC transformation is known to be associated with changes in the strength of normal cellular antigens, but the effect can be either an increase or a decrease. In the former category are Forssman antigens in guinea-pig hepatoma¹ and SV40 transformed cells²; HL-A antigens in leukaemic cells³; and “G” antigen in human tumour cells⁴. On the other hand, the intensity of the expression of mouse H-2 histocompatibility antigens is decreased in TL(+) leukaemia⁵ and methylcholanthrene (MCA)-induced tumours⁶. We set out to tell whether the expression of histocompatibility antigens was also affected by transformation with an oncogenic virus and have found that in tumours induced by polyoma virus, the quantity of H-2 antigens varied inversely with the amount of tumour-specific cell surface antigen.     

ON THE INDEPENDENCE OF SYSTEMATICS

Abstract— Before the publication of On the Origin of Species the standing patterns of natural history—common plan, homology, ontogenetic parallelism, and the hierarchy of groups — were taken as indications of a biological order that had not yet been understood. Darwin covered all of these in chapter 13 of the Origin , arguing that his theory was the first to provide a reasonable explanation for the existence of such patterns. Since Darwin took these relations to be established by previous biology, and used them as evidence for the explanatory power of his theory, he was clearly of the opinion that they were independent of that theory. Although several modern figures have argued to the contrary, it seems that Darwin was right. The patterns listed above are recoverable from observation without reference to evolutionary theory, which theory may then be applied to provide an account of the processes by which they may have come about. That aspect of systematics concerned with the identification of the empirical patterns evidently constitutes a study prior to and independent of theories of process.     

Importance of hydrogen ions and aluminium in regulating the structure and function of stream ecosystems: an experimental test

1. Experiments simulating spring acidic snowmelt episodes were conducted to determine the effects of short-term inputs of H⁺ and Al on the chemistry and biology of a poorly buffered mountain stream. HC1 and A1C1₃ were added in separate experiments to first- to third-order reaches of a New Hampshire stream. 2. Cation exchange and Alⁿ⁺ dissolution reactions neutralized experimentally added H ⁺, whereas groundwater dilution was insignificant. Mobilized Ca⁺⁺, Mg⁺⁺ and Alⁿ⁺ concentrations progressively increased from third- to first-order reaches during HC1 additions. Mobilization of Ca⁺⁺ and Mg⁺⁺ was greater during A1C1₃ than HC1 addition. 3. Total phosphorus was mobilized from stream sediments during both HCI and A1C1₃ addition. Dissolved organic carbon (DOC) decreased during A1C1₃ addition in the second-order but not in the third-order reach. DOC concentration decreased during HCI addition only when Al^{n +} mobilized from the stream bottom was >0.28 mg AI 1¹. 4. Production of foam at the water surface during AlCl₃ addition to a second-order and HCl addition to a first-order reach indicated a reduction in surface tension of the streamwater and may be related to complexation reactions between Al and DOC at low pH (4–5). 5. Mayfly nymphs and blackfly and chironomid larvae drifted at greater rates from HCl- and AlCl₃treated sections of first- and second-order streams than from corresponding reference areas. 6. When stream pH was lowered to 5.25–5.5 by HCI alone (15 μg monomeric inorganic Al l^?1), the behaviour of aquatic invertebrates did not change, but pH reduced to the same range during Al additions (280μg Al 1^?1) did affect it. Therefore, fluctuating aluminium concentrations in low-order streams at a pH range of 4.5–5.5 may alter the biology and geochemistry of poorly buffered waters.     

Phylogenetic relationships of flesh flies in the subfamily Sarcophaginae based on three mtDNA fragments (Diptera: Sarcophagidae)

In an effort to improve our knowledge of the phylogenetic relationships among species and genera of the subfamily Sarcophaginae, we analysed data from three mitochondrial gene fragments. Sequence data for portions of the genes cytochrome oxidase I (COI), cytochrome oxidase II (COII) and dehydrogenase subunit 4 (ND4) were obtained from 43 species of Sarcophagidae representing 15 genera. We used a Bayesian approach to simultaneously choose how best to partition the data and which substitution model to apply to each partition. Phylogenetic relationships were inferred using Bayesian Inference and Maximum Likelihood methods. Our results are consistent with monophyly of the subfamily Sarcophaginae (posterior probability 1; bootstrap support 93%), as well as with monophyly of several genera within the Sarcophaginae (including Sarcophaga s.l.; posterior probability 1; bootstrap support 97%). We found support for a sister‐group relationship between Ravinia Robineau‐Desvoidy and Oxysarcodexia Townsend, which has been hypothesised by past authors on the basis of morphological similarities, although this was supported only in the Bayesian analyses (posterior probability 0. 81–0. 98), and for some novel supra‐generic clades. Contrary to a recent morphological hypothesis, we do not find Helicobia Coquillett to be nested within Sarcophaga Meigen; our data suggest, but do not strongly support, a hypothesis that Peckia Robineau‐Desvoidy is the sister group to Sarcophaga.     

Effects of aggregative behaviour on the bioenergetics of the freshwater predatory leech Nephelopsis obscura (Erpobdellidae)

1. Supplied with ad libitum prey, the effects of different group sizes (one, five, ten, twenty-five, fifty or 100) on the acquisition and allocation of energy were examined over the entire life cycle of the freshwater predatory leech Nephelopsis obscura , to evaluate the bioenergetic costs and/or benefits of aggregation.
2. In terms of growth, asymptotic biomass and ingestion, group sizes larger than one and less than ten are optimal. As group size increases from ten to 100, N. obscura has slower growth and lower weekly food ingestion, suggesting interference competition. Single leeches had lower food consumption than group sizes of less than 100 animals. With a lower asymptotic biomass, single leeches have lower fecundity and presumed lower fitness. Lipid deposition was unaffected by group size.
3. Size- and time-specific respiration rates declined with increasing group size. For group sizes between five and fifty, the same relative proportion of ingested energy was allocated to respiration. Above this threshold group size, leeches allocated a higher proportion of ingested energy to growth, i.e. had higher growth efficiency, as did leeches cultured individually.
4. In the largest group size, total time spent in activity was highest (reflecting the high degree of interference between conspecifics), but as a result of the lower hourly costs of respiration they allocated a lower proportion of ingested energy to total respiration.
5. Optimum group size of N. obscura in the laboratory is within the typical range of group sizes found on stony shores in the field.     

Development of Hepatozoon griseisciuri in Cultured Squirrel Cells*

Sporocysts of Hepatozoon griseisciuri obtained from laboratory-reared spiny rat mites (Echinolaelaps echidninus) and laboratory-reared squirrel mites (Haemogamasus reidi) were made bacteria-free and incubated in trypsin-bile for 30 min at 37 C to release sporozoites. Hepatozoon griseisciuri sporozoites were inoculated into monolayer cultures of primary adult squirrel kidney (PSK) cells and cell line cultures of neonatal squirrel kidney (SK), heart (SH), and spleen (SS) cells. Extracellular sporozoites underwent flexing, gliding, and pivoting movements similar to other coccidian sporozoites. Sporozoites entered cells in all the cultures used and were found intracellularly as early as 1 hr and as late as 10 days after inoculation. In SK, SH, and SS cells, development proceeded only to the trophozoite stage. In PSK cells, immature schizonts and mature schizonts containing 12–40 merozoites were present from 5 through 10 days after inoculation. The finding of pairs of intracellular organisms within a single parasitophorous vacuole in PSK cells suggested that endodyogeny or limited schizogony had occurred.     

The Effects of Breeder Loss on Wolves

Abstract Managers of recovering wolf (Canis lupus) populations require knowledge regarding the potential impacts caused by the loss of territorial, breeding wolves when devising plans that aim to balance population goals with human concerns. Although ecologists have studied wolves extensively, we lack an understanding of this phenomenon as published records are sparse. Therefore, we pooled data (n = 134 cases) on 148 territorial breeding wolves (75 M and 73 F) from our research and published accounts to assess the impacts of breeder loss on wolf pup survival, reproduction, and territorial social groups. In 58 of 71 cases (84%), ≥1 pup survived, and the number or sex of remaining breeders (including multiple breeders) did not influence pup survival. Pups survived more frequently in groups of ≥6 wolves (90%) compared with smaller groups (68%). Auxiliary nonbreeders benefited pup survival, with pups surviving in 92% of cases where auxiliaries were present and 64% where they were absent. Logistic regression analysis indicated that the number of adult-sized wolves remaining after breeder loss, along with pup age, had the greatest influence on pup survival. Territorial wolves reproduced the following season in 47% of cases, and a greater proportion reproduced where one breeder had to be replaced (56%) versus cases where both breeders had to be replaced (9%). Group size was greater for wolves that reproduced the following season compared with those that did not reproduce. Large recolonizing (>75 wolves) and saturated wolf populations had similar times to breeder replacement and next reproduction, which was about half that for small recolonizing (≤75 wolves) populations. We found inverse relationships between recolonizing population size and time to breeder replacement (r= —0.37) and time to next reproduction (r= —0.36). Time to breeder replacement correlated strongly with time to next reproduction (r=0.97). Wolf social groups dissolved and abandoned their territories subsequent to breeder loss in 38% of cases. Where groups dissolved, wolves reestablished territories in 53% of cases, and neighboring wolves usurped territories in an additional 21% of cases. Fewer groups dissolved where breeders remained (26%) versus cases where breeders were absent (85%). Group size after breeder loss was smaller where groups dissolved versus cases where groups did not dissolve. To minimize negative impacts, we recommend that managers of recolonizing wolf populations limit lethal control to solitary individuals or territorial pairs where possible, because selective removal of pack members can be difficult. When reproductive packs are to be managed, we recommend that managers only remove wolves from reproductive packs when pups are ≥6 months old and packs contain ≥6 members (including ≥3 ad-sized wolves). Ideally, such packs should be close to neighboring packs and occur within larger (≥75 wolves) recolonizing populations.     

A partial systematic revision of the day geckos, Phelsuma Gray, of Madagascar (Reptilia: Squamata: Gekkonidae)

Recent survey work in Madagascar has led to significant changes in the systematics of Madagascan Phelsuma. A new species from the Masoala Peninsula in northeastern Madagascar is described, which has a nostril position typical of Phelsuma from Mauritius, Reunion and Rodriguez islands. Phelsuma breviceps was rediscovered in extreme southern Madagascar and is resurrected from the synonymy of P. mutabilis. Phelsuma breviceps has fragile skin, a probable predator escape mechanism, similar to the condition found in geckos of the genera Ailuronyx and Geckokpis. Three new synonyms are recognized. Phelsuma befotahensis and P. checki are junior synonyms of P. abbotti , and P. minuthi is a junior synonym of P. lineata. Twenty species of Phelsuma occur in Madagascar, of which 16 are endemic. A checklist and identification key are provided. Conservation problems of Phelsuma in the coastal regions of Madagascar are briefly discussed.     

Organotypic Culture of Human Skin to Study Melanocyte Migration

An ex vivo model system was developed to investigate melanocyte migration. Within this model system, melanocytes migrate among other epidermal cells in the epibolic outgrowth of skin explants. This process is initiated by loss of contact inhibition of epidermal cells at the rim of the explants and by locally produced chemotactic factors. Punch biopsies provided explants of reproducible diameter. Optimal culture conditions include medium consisting of Dulbecco's Minimal Essential Medium containing 10% inactivated normal human serum and placement of explants epidermal side up at the air-liquid interphase. Within 7 days, epidermal cells completely surround the explant. Approximately 3 days after the onset of keratinocyte migration, melanocytes distribute themselves within the newly formed epidermis. Throughout the 7-day culture period, melanocytes and keratinocytes show maintenance of subcellular morphology, and the dermo-epidermal junction remains intact. Melanocyte migration was quantified using immunoperoxidase staining in combination with light microscopy and computer-aided image analysis. Preliminary results using the model system to compare migration in control and nonlesional vitiligo skin indicate that no inherent migration defect is responsible for impaired repigmentation of vitiligo lesions. The organotypic culture model system allows for investigations on melanocytes within their environment of autologous epidermal and dermal components, closely resembling in vivo circumstances in human skin.