Tooth scaling and evolutionary dwarfism: an investigation of allometry in human pygmies

Gould has predicted that in rapidly dwarfed lineages the postcanine teeth exhibit a different scaling pattern than is the normal interspecific trend. His prediction of strong negative allometry has not been frequently tested in quantitative detail. Here we present results of scaling analyses of the molar teeth in African pygmies compared with other Africans of larger size and in Philippine pygmies compared with Filipinos of larger size. We find a pattern of strong negative allometry of tooth size to skull and body size in both these comparisons. This scaling pattern is explained by recourse to the developmental bases (known or inferred) of dwarfing in these populations. Body size decrease is related to low levels of the growth control substance insulin-like growth factor I (IGF-I), which does not appear to affect the size of the dentition. The implications of such developmental information for our understanding of allometric patterns in general, and dwarfing events in particular, are discussed.     

Molecular recognition between oligopeptides and nucleic acids. Specificity of binding of a monocationic bis-furan lexitropsin to DNA deduced from footprinting and 1H NMR studies

MPE-Fe(EDTA) footprinting of a novel monocationic bis-furan lexitropsin 6 on a HindIII/EcoRI restriction fragment of pBR322 DNA revealed a series of four-base binding sites (all 5'----3') of (primary) TGTA, TGAA, AAAT, ACAA, TTAT, and (secondary) CTAA, TCGT, TGTA, GTCA, and GGTT. Thus 6 can accept a GC pair at positions 1, 2 or 3 of the binding site with a strict 3' (4 position) AT requirement. Marked enhancement of cleavage, particularly at GC rich sequences, is observed at regions flanking or even up to 18 base pairs remote from a given binding site. The non-exchangeable and imino 1H NMR resonances of the 1:1 complex and d-[CATGGCCATG]2 were assigned using a combination of NOE differences, NOESY and COSY techniques. 1H NMR studies (ligand induced chemical shifts and NOE differences) of Lexitropsin 6 with d-[CATGGCCATG]2 show unambiguously the location and orientation of the N to C termini of 6 on the sequence 5'-G5C6C7A8-3', with the C terminus oriented to A8. This orientation of 6 in the minor groove of 5'-GCCA is confirmed by an NOE observed between H1 2a of 6 and AH8(8). This preference for binding of 6 to the sequence 5'-GCCA when challenged with d-[CATGGCCATG]2 is in accord with the conclusions of the footprinting experiments wherein GC base pairs can be accepted in the first three positions and with a strict 3' terminus AT reading requirement. Collectively the data support the inference of a GC recognizing capacity for a 2,5-substituted furan moiety within a lexitropsin. The 1H NMR data indicate that the decadeoxyribonucleotide duplex exists in the B conformation in both the 1:1 complex and the free form. The apparent binding constant of 6 to calf thymus DNA is 1.68 X 10(5) M-1 whereas netropsin under similar conditions gives a value of 1.85 X 10(7) M-1. This suggests that if advantage is to be taken of the GC recognizing property of a 2,5-substituted furan in longer lexitropsins it should be flanked by more strongly bound moieties.     

Interactions among phytophagous insect species colonizing cones of white fir (Abies concolor)

Summary The insect complex colonizing white fir (Abies concolor [Gord. and Glend.] Lindl.) cones is composed of eleven species that can be separated into three feeding guilds: the seed-mining guild, Megastigmus pinus Parfitt, M. rafni Hoffmeyer, Earomyia abietum McAlpine; the cone-and seed-mining guild, Dioryctria abietivorella Grote, Eucosma prob. siskiyouana (Kearfoot), Cydia prob. bracteatana (Fernald), Barbara sp.; the scale-and bract-feeding guild, Asynapta hokinsi (Felt), Dasineura prob. abiesemia Foote, Ressiliella conicola (Foote), Lasiomma abietis Huckett). In three of four study sites the cone crop decreased from one year to the next. As cone crop size decreased there was a concomitant increase in the percent of cones with more than one species. In addition, there was a shift toward an increased co-occurrence of members of different guilds within a single cone. Both positive and negative interactions were detected between selected species-pairs. Present-day competition was only inferred between species-pairs belonging to the cone and seed-mining guild. Decreasing resources over time, combined with increasing insect populations and the absence of acceptable alternate hosts appeared to be important factors for setting conditions conducive to interspecific competition. It is hypothesized, that the aperiodicity of white fir cone crops was important in keeping insect populations below levels which would result in interspecific competition. The possible elimination of aperiodicity in cone crops of white fir, such as might occur in managed seed orchards, may lead to decreased species diversity via competitive exclusion and thereby simplify development of IPM programs.     

Strategies to Improve Survival from Surgery for Heart Valve Implantation in Sheep

Sheep are a commonly used and validated model for cardiovascular research and, more specifically, for heart valve research. Implanting a heart valve on the arrested heart in sheep is complex and is often complicated by difficulties in restarting the heart, causing significant on-table mortality. Therefore, optimal cardioprotective management during heart valve implantation in sheep is essential. However, little is known about successful cardioprotective management techniques in sheep. This article reports our experience in the cardioprotective management of 20 female sheep that underwent surgical aortic valve replacement with a stented tissue-engineered heart valve prosthesis. During this series of experiments, we modified our cardioprotection protocol to improve survival. We emphasize the importance of total body hypothermia and external cooling of the heart. Furthermore, we recommend repeated cardioplegia administration at 20 min intervals during surgery, with the final dosage of cardioplegia given immediately before the de-clamping of the aorta. To reduce the number of defibrillator shocks during a state of ventricular fibrillation (VF), we have learned to restart the heart by reclamping the aorta, administering cardioplegia until cardiac arrest, and de-clamping the aorta thereafter. Despite these encouraging results, more research is needed to finalize a protocol for this procedure.

Sheep are a commonly used and well-validated model for cardiovascular research, particularly for heart valve research, as blood pressure, heart rate, cardiac output, and intracardiac pressures are similar between sheep and humans. Sheep are particularly useful for heart valve research because observable changes in implanted heart valve bioprostheses that would take several years to develop in humans are apparent after only a few months in sheep.^3,11 This feature allows the ovine model to provide relevant and important information about heart valve prostheses in a relatively short time span. The first preclinical step in developing novel heart valves is to test the valve in the pulmonary position in sheep. This surgical technique is relatively easy, as the procedure can be performed on a beating heart in a low-pressure circulation. However, aortic valve surgery is the most frequently performed valvular surgical intervention in human patients.¹² Thus, an important next step is to prove the clinical applicability of a new valve by testing the valve in-vivo in the aortic position in an animal model. In contrast to pulmonary valve replacement, aortic valve replacement must be performed on an arrested heart, which makes the surgical procedure significantly more complex. The sheep is a difficult model for aortic valve replacements due to its narrow annulus, short distance between the annulus and coronary ostia, a short ascending aorta, and difficulty in de-airing of the heart prior to suturing the aortotomy.¹⁹ Consequently, high on-table mortality rates, ranging from 9% to 33%, have been reported.^1,18,21,24 Furthermore, the incidence of mortality during the first 30 d after surgery, directly related to the surgical procedure, is often high, ranging from 17% to 50%.^1,2,16,18,21 Therefore, optimizing cardioprotective strategies during surgery would improve postoperative survival. However, little is known about protective strategies in sheep. In the current series of experiments, we implanted stented, tissue engineered, aortic heart valve prostheses in 20 adult domestic sheep and developed cardioprotective techniques to increase survival rates. In this observational study, we share our experience and insights regarding cardioprotective management to potentially improve the outcome of future surgeries that require an arrested heart in sheep.