Segregation distortion for seed testa color in Mungbean (Vigna radiata L. Wilcek)

Genetic segregation experiments with plant species are commonly used for understanding the inheritance of traits. A basic assumption in these experiments is that each gamete developed from megasporogenesis has an equal chance of fusing with a gamete developed from microsporogenesis, and every zygote formed has an equal chance of survival. If gametic and/or zygotic selection occurs whereby certain gametes or zygotic combinations have a reduced chance of survival, progeny distributions are skewed and are said to exhibit segregation distortion. In this study, inheritance data are presented for the trait seed testa color segregating in large populations (more than 200 individuals) derived from closely related mungbean (Vigna radiata L. Wilcek) taxa. Segregation ratios suggested complex inheritance, including dominant and recessive epistasis. However, this genetic model was rejected in favor of a single-gene model based on evidence of segregation distortion provided by molecular marker data. The segregation distortion occurred after each generation of self-pollination from F1 thru F7 resulting in F7 phenotypic frequencies of 151:56 instead of the expected 103.5:103.5. This study highlights the value of molecular markers for understanding the inheritance of a simply inherited trait influenced by segregation distortion.     

Investigation into the possible cause of subjective decreased sensory perception in the nipple-areola complex of women with macromastia

Patients with macromastia often comment on a lack of sensation in their nipple-areola complex. A study was designed to investigate the cause of this decreased sensation. Two hypotheses were proposed. First, the decreased sensation could result from neuropraxia of the sensory nerve fibers secondary to traction caused by the heavy breast parenchyma. The second hypothesis proposed that tissue expansion of the nipple and areola by the voluminous breast parenchyma caused a decrease in nerve fibers per surface area and hence decreased sensory perception. Sixty-one patients were assessed in the study. All patients underwent surgery in which histological biopsy of either the areola alone (31 reduction mammaplasty patients) or the nipple and areola (30 mastectomy patients) was possible. Before surgery, each nipple-areola complex was tested with Weinstein Enhanced Sensory Test monofilaments as a quantitative test of tactile sensation. Breast cup size, ptosis, and weight of tissue excised were recorded to allow general assessment of the breast size. The nipple and areola biopsy specimens were assessed using immunohistochemistry (S-100 polyclonal antibody, Dako Z311) to measure nerve fiber count per unit area. Statistical analysis was undertaken to find any association among sensitivity, breast cup size, ptosis, weight of tissue resected, and nerve fiber density in the nipple and areola biopsy specimens. Sensitivity at the areola decreased with increasing breast cup size (r = 0.47, p < 0.001) and ptosis (r = 0.42, p = 0.002 for increasing distance between inframammary crease and nipple; r = 0.49, p < 0.001 for increasing manubrium to nipple distance). There was a weak correlation between nerve fiber density at the areola and breast cup size (r = -0.22, p = 0.1). Sensitivity at the nipple was higher than at the areola. Nerve fiber density count at the nipple was higher than at the areola, but there was no statistically significant correlation between nipple sensitivity and breast cup size, ptosis, or weight of tissue resected. The results suggest that the areola and nipple are different in their neuroanatomy. The areola is a thin, pliable structure that is predisposed to stretch as the breast enlarges and therefore experience a decrease in nerve fiber density. The nipple is a compact structure that is less likely to stretch with breast enlargement. In the nipple, neither sensory perception nor nerve fiber density varied with size or breast ptosis. The perceived lack of sensation in the nipple-areola complex is multifactorial. This study shows that neither traction injury to the sensory nerves nor decreased nerve density alone can explain the subjective numbness reported by patients with macromastia. Psychological factors, such as dissatisfaction with body form or interpretation of lack of sensation in the areola as also affecting the nipple, may influence the patient's assessment of the nipple-areola sensitivity.     

Effect of ethylene and culture environment on development of papaya nodal cultures

Papaya (Carica papaya L.) nodal cultures modified the atmosphere of the headspace of the vessel used for culture maintenance by producing ethylene. Under culture maintenance nodal cultures grew poorly and leaves senesced. Incubating nodal cultures under a range of ethylene concentrations suggested that this poor performance was caused in part, by the production of ethylene and its accumulation in the headspace of the vessel. To further evaluate the role of ethylene accumulation in growth suppression, aminoethoxyvinylglycine (AVG), 1-aminocyclopropane-1-carboxylic acid (ACC) and silver thiosulphate (STS), were added to the nutrient medium and ethylene measurements performed during culture growth. The ethylene-suppressant, AVG, (1.2 μM) and the ethylene-antagonist, STS, (0.3 mM) significantly improved nodal culture growth (283 and 289% respectively), leaf area production (350 and 211% respectively) and reduced leaf senescence, while the ethylene-precursor, ACC, (1.5 mM) significantly decreased culture growth (71%), leaf area production (88%) and promoted leaf senescence. Furthermore, nodal culture growth was significantly better at 20 °C than 30 °C since ethylene production and accumulation were less in these conditions. Better control or management of ethylene accumulation produces healthier nodal cultures for micro-propagation and may be a way of improving productivity of other papaya shoot culture systems. This revised version was published online in June 2006 with corrections to the Cover Date.     

The impact of Ixodiphagus hookeri, a tick parasitoid, on Ambl yomma variegatum (Acari: Ixodidae) in a field trial in Kenya

In an experiment to investigate the effect of the tick parasitoid, Ixodiphagus hookeri, on tick numbers on cattle, 150 000 parasitoids were released over a period of 1 year in a field where ten cattle infested with multiple tick species were kept. Amblyomma variegatum was reduced from 44 to two ticks per animal while Rhipicephalus appendiculatus increased over the time of parasitoid release. During the time of release 51% of the nymphs of A. variegatum collected from the animals were parasitized. The recovery of the parasitoids after the releases were stopped was only 9%. The total numbers of A. variegatum remained low up to 1 year after the parasitoid release was stopped. This study gives an insight into how I. hookeri could be used strategically for the management of A. variegatum on small-scale farms.     

Courtship behavior of male white perch, Morone americana: evidence for control by androgens.

Courtship behaviors are androgen-dependent in many vertebrates and castration often decreases courtship. We examined the effectiveness of castration in reducing courtship behaviors and 11-ketotestosterone (KT) and testosterone (T) in restoring them in male white perch. Castrates were given implants containing KT, T or no hormone. Sham-operated males received implants without hormone. Three weeks later, males were exposed to an ovulated female for 1 h and two courtship behaviors were quantified. Attending behavior involves close and continuous following of a female with occasional contact. Circling involves rapid transits around the female in a circular pattern or back and forth in front of her. In plasma samples taken immediately after observations, KT and T were below detectable levels in castrated males but at high physiological levels in males implanted with KT or T. Castrated males given KT attended females more than castrated males given T implants or implants containing no hormone, but not more than sham-operated males. Circling was eliminated by castration but restored by implantation with T or 11-KT to values exhibited by sham-operated males. This is one of the few demonstrations that KT can regulate courtship behavior in a non-territorial and economically important fish species.     

Mutation detection using a novel plant endonuclease.

We have discovered a useful new reagent for mutation detection, a novel nuclease CEL I from celery. It is specific for DNA distortions and mismatches from pH 6 to 9. Incision is on the 3'-side of the mismatch site in one of the two DNA strands in a heteroduplex. CEL I-like nucleases are found in many plants. We report here that a simple method of enzyme mutation detection using CEL I can efficiently identify mutations and polymorphisms. To illustrate the efficacy of this approach, the exons of the BRCA1 gene were amplified by PCR using primers 5'-labeled with fluorescent dyes of two colors. The PCR products were annealed to form heteroduplexes and subjected to CEL I incision. In GeneScan analyses with a PE Applied Biosystems automated DNA sequencer, two independent incision events, one in each strand, produce truncated fragments of two colors that complement each other to confirm the position of the mismatch. CEL I can detect 100% of the sequence variants present, including deletions, insertions and missense alterations. Our results indicate that CEL I mutation detection is a highly sensitive method for detecting both polymorphisms and disease-causing mutations in DNA fragments as long as 1120 bp in length.     

Historical aspects of protandrous sex change in the anemonefish Amphiprion melanopus (Pomacentridae, Teleostei)

Gonadal structure and cellular composition were examined in juveniles, males and females of the protandric hermaphrodite, Amphiprion melanopus. Functional sex change was experimentally induced in the field and gonad structure was histologically examined both qualitatively and quantitatively at 10, 20, 30 and 45 days after its initiation. Juvenile gonads consist primarily of immature ovarian tissue. Functional male gonads are ovotestes with co-existing mature spermatogenic tissue and immature ovarian tissue, while females possess only ovarian tissue. The initiation of sex change is marked by a rapid maturation of spermatogenic tissue and proliferation of putative oogonia. Gonads were essentially female by 20 days into sex change, but evidence of mature female function (marked by the initiation of vitellogenesis) was not observed until 45 days. Considerable variation between individuals was seen in quantitative measures of gonadal change in the early stages of sex change, but not in later stages. Progress in sex change as indicated by histological indicators was, however, consistent within stages. Duet systems for gamete transport changed from the male to the female form after all male tissue had been replaced.     

Comparing multiple sampling platforms for measuring the behavior of humpback whales (Megaptera novaeangliae)

Multiple platform approaches for measuring the behavior of marine mammals may strengthen data quality and quantity. However, if this approach is chosen, reconciliation of behavioral measures between each platform is required. This study compared typical measures of humpback whale (Megaptera novaeangliae) behavior collected from three different sampling platforms; land‐based, boat‐based, and digital tags (Dtags), to explore similarities and/or discrepancies in data. Visual observations from land‐based platforms significantly underestimated group blow rate when compared to boat‐based platforms, whereas broad‐scale spatial movements (speed and course traveled) were measured similarly by these two platforms. Dtags were used to define dive behavior based on a time and depth criteria, where bouts of short shallow respiration dives (≤80 s and ≤10 m) were separated from longer, deeper dives (>80 s and >10 m). At a group level, land and boat platforms agreed on the number of long dives but land platforms missed bouts of short dives. At an individual level, the number of short and long dives observed by boat‐based platforms agreed with Dtag recordings. This study highlights the importance of data exploration prior to analyses in multiple platform studies to identify potential discrepancies and appropriately account for any biases.