Second Growth Phase Research Articles

Investigation of growth phases for bottlenose dolphins using a Bayesian modeling approach

The Gompertz function is the most commonly used growth function for cetacean studies. However, this function cannot represent multiple phases of growth. In this study, we present a Bayesian framework fitting parameters of a triple-logistic growth function to describe multiple phases of growth for bottlenose dolphins (Tursiops truncatus), simultaneously fitting and comparing all growth parameters between South Carolina (SC), Mississippi Sound (MSS), and Indian River Lagoon (IRL) cohorts. The fitted functions indicated a preliminary early, rapid growth phase, followed by a second phase of slower growth, and then a moderate growth

Spatial localization of EGF family ligands and receptors in the zebrafish ovarian follicle and their expression profiles during folliculogenesis

The roles of epidermal growth factor (EGF) family in the ovary have received increasing attention recently. Despite this, the production sites of EGF family members in the ovarian follicle still remain controversial. Using zebrafish as the model, the present study investigated spatial distribution of several EGF family ligands and receptors in the follicle as well as their temporal expression profiles during folliculogenesis. RT-PCR analysis on the somatic follicle layer and oocyte revealed that all EGF family ligands examined ( egf, tgfa, btc and hbegf) were mostly or exclusively expressed in the oocyte. In contrast, their common receptor ( egfr) was expressed exclusively in the follicle layer. By comparison, members of activin family showed an opposite pattern of distribution. Activin subunits ( inhbaa and inhbb) were both expressed exclusively in the follicle layer whereas activin receptors and follistatin were abundantly present in the oocyte. During folliculogenesis, egf, tgfa and hbegf increased their expression together with egfr in the fast secondary growth phase. The developmental profiles of EGF family during embryogenesis appeared to argue for an important role for EGF family in folliculogenesis rather than embryogenesis as maternal molecules. The present study provided clear evidence for the existence of two paracrine pathways in the follicle, the oocyte-derived EGF family ligands and follicle cell-derived activins, which may mediate oocyte-to-follicle cell and follicle cell-to-oocyte communications, respectively. The functional relationship between these two signaling systems in the follicle is suggested by the observation that all four EGFR ligands examined significantly stimulated activin subunit expression in cultured follicle cells.

Looking Through the Glass Ceiling: Projecting Women’s Future Participation in the Solicitor’s Profession in England and Wales

It is 90 years since legislation introduced a right for women to practice as solicitors in England and Wales, yet women still comprise just 24 per cent of partners in private practice. In this paper we employ data derived from Law Society reports from the past 22 years to model past and future growth of women’s participation in the solicitors’ profession in England and Wales. Our findings indicate that a clear majority of assistant/associate solicitors will see women making up a majority of private practitioners in the future. However, our findings also suggest that that parity between women and men will never be reached at partnership level in private practice, unless there is a change in the current growth pattern of female representation. One possible change may stem from the lagged influence of a second phase of growth in female representation among assistant/associate solicitors that commenced in the 1990s and is peaking today.

Syndepositional fault control on lower Frasnian platform evolution, Lennard Shelf, Canning Basin, Australia

Syndepositional faulting was a major control on internal platform stratigraphy in a Frasnian reef complex on the southeastern Lennard Shelf, northern Canning Basin, Australia. By combining platform (mostly backreef) facies distributions with key stratal surfaces and biostratigraphic data, we have developed a temporal framework for the Hull Range area. Platform evolution was controlled by normal faults via an initial tilt block geometry and subsequent differential subsidence and accommodation across the platform. Three third-order, flooding surface–bounded platform phases are recorded. Basal shallow marine siliciclastic facies were deposited in topographic lows adjacent to the hanging wall and close to internal faults. Early carbonate deposition in dominantly deep subtidal environments suggests an overall ramp-style setting that deepened toward the southeast. This phase is capped by a sequence boundary represented by multiple paleokarst surfaces in the northwest that pass laterally into a major flooding surface to the southeast, above which the platform expanded toward the Mount Elma–Painted Rocks fault system. The overall stacking pattern above the sequence boundary–flooding surface is aggradational to progradational with higher-frequency shoaling trends, and locally developed exposure surfaces, related to higher-order relative sea-level changes. This second phase of platform growth ended with major flooding and a pronounced backstep of the leeward margin.

Berberis buxifolia fruiting: Kinetic growth behavior and evolution of chemical properties during the fruiting period and different growing seasons

This work studied the growth of Berberis buxifolia fruits and some of their chemical attributes during the fruiting period and different growing seasons (2004/2005, 2005/2006, 2006/2007) from November (14 days from full flower phase) till March (126 days from full flower phase) for plants growing in a natural environment near Ushuaia city (Tierra del Fuego, Argentina). B. buxifolia fruit growth and composition presented significant changes during the fruiting period and the studied growing seasons. Fresh and dry weight of B. buxifolia fruits exhibited a typical double sigmoid curve. The first period of rapid growth was from full flower phase till 42–56 days after, while the second phase of rapid growth began around the 56–70 days from full flower and ended approximately 4 months later. On a dry weight basis the maximum fruit biomass (119.5 mg) was reached 112 days after full flower while maximum fresh weight fruit biomass (424.3 mg) occurred by day 84. Evolution of fruit growth was related with the compositional changes evaluated. By day 126 from full flower, soluble solids (24.9°Brix) and anthocyanin concentration (761.3 mg/100 g fruit fresh weight) were at their maximum values, while at this time the total titratable acidity was at a minimum value (2.56%). The results obtained not only contributes to the knowledge of the quantitative content of anthocyanin, a metabolite with nutraceutical value but, gives some tools for the definition of the optimal harvest time of B. buxifolia fruits, what it is important for fruit destination.

Reproductive guilds (maturation, spawning frequency and fecundity) in the black pomfret,Parastromateus niger(Carangidae) in the Kuwaiti waters of the Arabian Gulf

Summary Oogenesis, oocyte maturation pattern, spawning rhythm, spawning frequency, batch fecundity and oocyte diameter–frequency distribution of the black pomfret, Parastromateus niger (Bloch, 1795) in Kuwaiti waters were investigated from October 2003 to September 2005, using histological and morphological methods. The process of development is divided into four major phases: (i) primary growth phase; (ii) secondary growth phase; (iii) maturation phase; and (iv) spawning phase, followed by the regressed phase. Development of the yolky oocyte is an asynchronous process resulting, by the time of oocyte maturation, in a clear differentiation between a ready batch of oocytes (ready for spawning) and a reserve pool. Consequently, P. niger is capable of spawning multiple times throughout the reproductive season. Spawning frequency estimates, based on final oocyte maturation (FOM) method indicated that the species spawns once every 2.8 days during an 8-month spawning season lasting from February to September, with a potential annual number of 22.4 spawns. Batch fecundity (BF) (2132–2001 648, mean 406 010 eggs), was significantly positively related to both standard length (SL) (P < 0.05) and ovary-free body weight (OFBW) (P < 0.05), both parameters being good predictors of BF (r2 = 30.8% for SL, from 22 cm onwards, and r2 = 29.6% for OFBW, from 129.5 g onwards). No significant differences in monthly BF were found throughout the spawning season. Relative batch fecundity was 336 eggs/g OFBW; thus, estimate for potential annual relative batch fecundity was 7526 eggs g−1 OFBW. The oocyte diameter–frequency distribution analysis revealed a multimodal distribution (at 100–200, 300–400 and 500–700 μm), confirming the evidence of multiple spawning.

Spawning pattern and type of fecundity in relation to ovarian allometry in the round herring Etrumeus teres

Spawning pattern (assessed by seasonal changes in ovarian developmental stages) and type of fecundity (assessed by analysis of oocyte-size frequency distributions) of the round herring Etrumeus teres were studied in relation to ovarian growth and seasonal changes in the gonadosomatic (GSI), hepatosomatic (HSI) and liposomatic (LSI) index as well as the somatic condition of spawners (CS) in a spawning ground of southern Japan. Except for summer, mature and recently spawned ovaries occurred all year round. Oogonia and primary oocytes were present in all ovaries, and cortical alveoli stage (CA) oocytes occurred in all mature, hydrated and partially spent (PS) females (PS: females containing post-ovulatory follicles). Before hydration, a clutch of larger yolked oocytes, undergoing synchronous growth (range 0.7–1.1 mm), was present in mature ovaries which was completely separated from a more heterogeneous clutch of oogonia, primary and secondary oocytes (<0.150 mm) and oocytes in the CA stage (range 0.15–0.60 mm). As vitellogenesis progressed, the yolked clutch increased in size but the CA oocytes remained arrested. The latter entered into the secondary growth phase when hydration started in the advanced batch. Ovarian growth was isometric in all developmental stages, validating the use of GSI, which showed a consistent monthly evolution among years. Spawning stopped in summer (July and August) and peaked in winter and spring. HSI correlated positively with GSI on both a monthly mean basis (r = 0.76) and individual fish basis (liver weight explained 67–83% of the variability in ovary weight when females were grouped into 1-unit GSI intervals) suggesting a significant role of liver in vitellogenesis. LSI and CS also showed marked seasonal changes peaking from summer to middle autumn. Overall results suggest that E. teres is a multiple spawner with a group-synchronous ovarian development and indeterminate annual fecundity, with the three processes linked to an isometric growth of the ovary. We propose that such a reproductive pattern is an adaptation to produce batches of large pelagic eggs through a protracted spawning season.

Pregnane X receptor is essential for normal progression of liver regeneration†

Pregnane X receptor (PXR) mediates xenobiotic and endobiotic metabolism as well as hepatocyte proliferation. To determine the role of PXR in liver regeneration, 2/3 partial hepatectomy (PH) was performed on wild-type and PXR-null mice. Our results showed that hepatic steatosis was markedly suppressed in mice lacking PXR 36 hours after PH, concomitant with reduction of hepatocyte proliferation at the same time point. Gene expression analysis revealed the role of PXR in regulating the transcription of genes involved in lipid uptake, transport, biosynthesis, oxidation, and storage during liver regeneration. When PXR was absent, the second wave of hepatocyte proliferation was severely suppressed, which was accompanied by the inactivation of STAT3. Lack of PXR inhibited the second phase of liver growth, leading to 17% less liver mass at the anticipated end point of liver regeneration (day 10). PXR is required for normal progression of liver regeneration by modulating lipid homeostasis and regulating hepatocyte proliferation.

Reproductive features of the non-native Siganus luridus (Teleostei, Siganidae) during early colonization at Linosa Island (Sicily Strait, Mediterranean Sea)

Summary In July 2003, the finding of a newly settled population of Siganus luridus at Linosa Island (Sicily Strait, Mediterranean Sea) gave us the unusual opportunity to examine the reproductive condition of a Lessepsian migrant during early phases of colonization. Aspects of gonad morphology, fecundity, atresia and oocyte dynamics were investigated by using 43 pioneer specimens collected in concomitance with their first record in the Pelagie Islands. Ovarian development was consistent with the group-synchronous type, and testicular organization was of the unrestricted spermatogonial testis type, with cystic spermatogenesis. Both males and females had reached final stages of gonad maturation. The rates of follicular atresia were moderate: out of 17 adult females, 10 individuals did not present atretic oocytes; six exhibited <15.1% of secondary growth phase (SGP) oocytes in α-atresia, while one female presented 45.7% of SGP in α-atresia. Fecundity estimates did not diverge from what was observed in a reference population along the Lebanese coast. Absolute fecundity ranged from 115 739 to 740 433 oocytes per female (16.5–24.5 cm LT). Relative fecundity ranged from 1239 to 3162 oocytes g−1, with a mean of 1885 ± 868 oocytes g−1. Our observations indicated that these early settled siganids are reproductively active at Linosa and suggested the forthcoming of self-maintaining populations across the central Mediterranean area.

Retinopathy of prematurity

Retinopathy of prematurity (ROP) is a common blinding disease in children in the developed world despite current treatment, and is becoming increasingly prevalent in the developing world. ROP progresses in two phases. The first phase begins with delayed retinal vascular growth after birth and partial regression of existing vessels, followed by a second phase of hypoxia-induced pathological vessel growth. Two major risk factors of ROP are the use of oxygen and a decreased gestation period. Excessive oxygen contributes to ROP through regulation of vascular endothelial growth factor (VEGF). Suppression of VEGF by oxygen in phase I of ROP inhibits normal vessel growth, whereas elevated levels of VEGF induced by hypoxia in phase II of ROP precipitate pathological vessel proliferation. Insulin-like growth factor 1 (IGF-1) is a critical non-oxygen-regulated factor in ROP. We have found that serum levels of IGF-1 in premature babies directly correlate with the severity of clinical ROP. IGF-1 acts indirectly as a permissive factor by allowing maximal VEGF stimulation of vessel growth. Lack of IGF-1 in preterm infants prevents normal retinal vascular growth in phase I of ROP, despite the presence of VEGF. As infants mature, rising levels of IGF-1 in phase II of ROP allows VEGF stimulated pathological neovascularization. These findings suggest that restoration of IGF-1 to normal levels might be useful in preventing ROP in preterm infants.

Metabolic changes during carcinogenesis: Potential impact on invasiveness

Successful adaptation to varying microenvironmental constraints plays a crucial role during carcinogenesis. We develop a hybrid cellular automation approach to investigate the cell–microenvironmental interactions that mediate somatic evolution of cancer cells. This allows investigation of the hypothesis that regions of premalignant lesions develop a substrate-limited environment as proliferation carries cells away from blood vessels which remain separated by the intact basement membrane. We find that selective forces in tumoural regions furthest from the blood supply act to favour cells whose metabolism is best suited to respond to local changes in oxygen, glucose and pH levels. The model predicts three phases of somatic evolution. Initially, cell survival and proliferation is limited due to diminished oxygen levels. This promotes adaptation to a second phase of growth dominated by cells with constitutively up-regulated glycolysis, less reliant on oxygen for ATP production. Increased glycolysis induces acidification of the local environment, limiting proliferation and inducing cell death through necrosis and apoptosis. This promotes a third phase of cellular evolution, with emergence of phenotypes resistant to acid-induced toxicity. This emergent cellular phenotype has a significant proliferative advantage because it will consistently acidify the local environment in a way that is toxic to its competitors but harmless to itself. The model's results suggest this sequence is essential in the transition from self-limited premalignant growth to invasive cancer, and, therefore, that this transition may be delayed or prevented through novel strategies directed towards interrupting the hypoxia–glycolysis–acidosis cycle.

Quantifying growth kinetics of Phanerochaete chrysosporium immobilised on a vertically orientated polysulphone capillary membrane: Biofilm development and substrate consumption

Growth kinetics is one of the most important and critical parameters for studying biofilms as they can be used to model mass transfer and biological reactions. Growth parameters of Phanerochaete chrysosporium were quantified based on the utilisation rate of glucose and biofilm generated in single fibre capillary membrane bioreactors (SFCMBR) operated vertically at 37 °C for 264 h. The growth rate constant value of 0.0348 h −1 was used to model the dry biofilm density profile, which was also classified as equivalent to the specific growth rate. The mass of glucose consumed, increased from 0.051 g/day during the lag phase, to 0.145 g/day in the secondary growth phase. An average glucose consumption rate of 94.0 g/m 3 h was determined over the period of 264 h. The average glucose-based growth yield coefficient of approximately 0.202 g biofilm/g glucose was determined. The primary growth phase reached a structural equilibrium (steady state) at an average density of 9.7E05 g/m 3 in the period 168–216 h, with the secondary growth phase occurring after 216 h. The glucose maintenance coefficient value of 0.028 h −1, was obtained during the biofilm structural equilibrium phase.

Forming supermassive black holes by accreting dark and baryon matter

Given a large-scale mixture of self-interacting dark matter (SIDM) particles and baryon matter distributed in the early Universe, we advance here a two-phase accretion scenario for forming supermassive black holes (SMBHs) with masses around ∼109 M⊙ at high redshifts z(⋆6). The first phase is conceived to involve a rapid quasi-spherical and quasi-steady Bondi accretion of mainly SIDM particles embedded with baryon matter on to seed black holes (BHs) created at redshifts z≲ 30 by the first generation of massive Population III stars; this earlier phase rapidly gives birth to significantly enlarged seed BH masses of during z∼ 20-15, where σ0 is the cross-section per unit mass of SIDM particles and Cs is the velocity dispersion in the SIDM halo referred to as an effective ‘sound speed'. The second phase of BH mass growth is envisaged to proceed primarily via baryon accretion, eventually leading to SMBH masses of MBH∼ 109 M⊙; such SMBHs may form either by z∼ 6 for a sustained accretion at the Eddington limit or later at lower z for sub-Eddington mean accretion rates. In between these two phases, there is a transitional yet sustained diffusively limited accretion of SIDM particles which in an eventual steady state would be much lower than the accretion rates of the two main phases. We intend to account for the reported detections of a few SMBHs at early epochs, e.g. Sloan Digital Sky Survey (SDSS) 1148+5251 and so forth, without necessarily resorting to either super-Eddington baryon accretion or very frequent BH merging processes. Only extremely massive dark SIDM haloes associated with rare peaks of density fluctuations in the early Universe may harbour such early SMBHs or quasars. Observational consequences are discussed. During the final stage of accumulating a SMBH mass, violent feedback in circumnuclear environs of a galactic nucleus leads to the central bulge formation and gives rise to the familiar empirical MBH−σb correlation inferred for nearby normal galaxies with σb being the stellar velocity dispersion in the galactic bulge; in our scenario, the central SMBH formation precedes that of the galactic bulge.

Short and long germ segmentation: unanswered questions in the evolution of a developmental mode

The insect body plan is very well conserved, yet the developmental mechanisms of segmentation are surprisingly varied. Less evolutionarily derived insects undergo short germ segmentation where only the anterior segments are specified before gastrulation whereas the remaining posterior segments are formed during a later secondary growth phase. In contrast, derived long germ insects such as Drosophila specify their entire bodies essentially simultaneously. These fundamental embryological differences imply potentially divergent molecular patterning events. Numerous studies have focused on comparing the expression and function of the homologs of Drosophila segmentation genes between Drosophila and different short and long germ insects. Here we review these comparative data with special emphasis on understanding how short germ insects generate segments and how this ancestral mechanism may have been modified in derived long germ insects such as Drosophila. We break down the larger issue of short versus long germ segmentation into its component developmental problems and structure our discussion in order to highlight the unanswered questions in the evolution of insect segmentation.

Microstructural investigations on CdTe thin films electrodeposited using high current pulses

CdTe thin films were electrochemically deposited over FTO-coated glass substrates by singular unipolar current pulses of high magnitude. A wide range of periodic current pulse parameters was investigated in CdTe thin film deposition and the growth properties of the deposited film were determined as a function of variables viz. applied current density, average current and ON/OFF pulse duration and the conditions were optimized for stoichiometric CdTe film growth. A detailed investigation has been carried out to understand the effect of pulse parameters on CdTe growth phases and film microstructure. As evidenced by the diffraction patterns of pulse electrodeposited CdTe films mean current density of 0.36 mA/cm 2 represents an upper limit to form crystalline—CdTe film without secondary phases. Increase in pulse current show inclusion of secondary growth phases. A highly oriented cubic phase was obtained at low current pulse, due to low nucleation rate and surface diffusion of adions on the substrate to growth sites. The crystalline structure and morphology of films were analyzed using powder X-ray diffraction and scanning electron microscopy suggest that OFF time contributes more on the grain size, whereas ON time affects the rate of deposition and grain morphology.

Macromolecular composition of unsaturated Pseudomonas aeruginosa biofilms with time and carbon source

Bacteria in nature grow mostly as biofilms, surface-associated cells enveloped by hydrated extracellular polymeric substances (EPS) of bacterial origin. The composite of EPS and biofilm cells is measured when quantifying bacterial biomass from natural samples. However, little is known regarding the relative magnitude of the EPS and cellular fractions of biofilm biomass, particularly in unsaturated systems such as soil and food surfaces. In this study, we examined the cellular and extracellular fractions of Pseudomonas aeruginosa biofilms for DNA, protein and carbohydrate content. Biofilms were cultured in a model laboratory system that simulates the nutrient gradients and poorly mixed nature of unsaturated systems. We found that unsaturated biofilms exhibited two growth phases – an initial rapid phase and a second phase of slower or negligible development. However, no lag phase was observed for either carbon source. Cellular DNA accumulated linearly with biomass whereas cellular protein and carbohydrates accumulated exponentially with biomass. High levels of carbohydrate, protein and DNA were observed in the EPS of all samples, representing as much as 50% of these macromolecules in the biofilm. Most EPS accumulated during the second phase of growth, when cellular DNA increased only slightly. However, for biofilms cultured on a poorly bioavailable carbon source, EPS DNA decreased during the second phase, suggesting that EPS may affect bacterial survival under nutrient-limited conditions. Whether a product of overflow metabolism or cell lysis, EPS is a significant component of unsaturated biofilm biomass that probably impacts on bacterial ecology.

Endocrine regulation of ovarian antral follicle development in cattle

Antral follicle growth in cattle occurs in two distinct phases; the first ‘slow’ growth phase spans the time from antrum acquisition to a size of approximately 3 mm detectable by transrectal ultrasound, and the second ‘fast’ phase is gondadotrophin-dependent and includes cohort growth, dominant follicle (DF) selection, and DF growth. This review summarises current concepts of the relative roles FSH and LH, ovarian and metabolic hormones play mainly in the second phase of antral follicle growth in animals of different reproductive and nutritional states. It is proposed that differential FSH response may enable one cohort follicle to become selected, and that follicular secretions, particularly inhibin, suppress FSH and thus are responsible for DF selection and dominance. Acute dependence of the DF on LH pulses will determine DF lifespan, and the LH pulse profile can be influenced by metabolic hormones such as leptin, providing one possible link for nutritional state and reproduction. Direct ovarian effects of acute and chronic changes in growth hormone, insulin and insulin-like growth factor (IGF)-I have been described on cohort follicles, DF oestrogen activity and on DF growth. Influences of metabolic hormones on early antral follicles undergoing their first ‘slow’ growth phase are less well described, yet metabolic hormones appear to enhance growth into the cohort available for FSH-induced emergence, and may influence subsequent developmental competence of oocytes.

SO 2 emissions from Soufrière Hills Volcano and their relationship to conduit permeability, hydrothermal interaction and degassing regime

The time series of sulphur dioxide (SO 2) emissions during the continuing eruption of Soufrière Hills Volcano, Montserrat, yields insights into conduit permeability and driving pressures, the role of the hydrothermal system and changes in magma flux both at depth and to the surface. On a time scale of years, an effectively constant supply of sulphur from a more mafic magma at depth permits evaluation of changes in the permeability of the plumbing system between 1995 and 2002 (due to magma rheology changes and hydrothermal sealing), most of which take place in the upper few hundreds of metres (dome and upper conduit). A broadly increasing SO 2 emission rate from 1995 to 1997 can be attributed to a constant or increasing supply of exsolving sulphur from depth, combined with a broadly increasing magma discharge rate at the surface. Decreases in SO 2 flux over three orders of magnitude, from July 1998 to November 1999, were due to a corresponding decrease in permeability of the upper conduit and dome due to cooling and ‘sealing’ by the precipitation of hydrothermal minerals and the closure of fracture and bubble networks. The second phase of dome growth, from November 1999 to the present, April 2002, has been associated with a similar range of SO 2 fluxes to the first phase. Large dome collapses in 1997 and during a period of zero magma flux in 1998 were associated with instantaneous SO 2 emissions of >10 kt, which indicate a capacity for significant SO 2 storage in the conduit and dome prior to the collapses. SO 2 data suggest that the second phase of dome building, despite a similar sulphur budget in terms of supply from depth and mean SO 2 emission rate at the surface (around 500 t/d), is characterised by a higher bulk permeability at shallow depths and is a more ‘open’ system with respect to fluid through-flow than the first phase of dome building from 1995 to 1998. The lack of large SO 2 emissions after large dome collapses, in 2000 and 2001, suggests limited storage of SO 2 in the conduit system. The data suggest that the likelihood of a switch to explosive activity after a large collapse is more unlikely now than during the first phase of dome building. Over shorter time scales, permeability changes may be recognised from the SO 2 flux data prior to the onset of dome growth and during cycles of small explosions in 1999. On time scales of minutes to hours, pulses of SO 2-rich gas emissions occur after rockfalls and pyroclastic flows, due to the release of a SO 2-rich fluid phase stored in closed fractures and pore spaces within the dome. Long period and hybrid seismic events may be associated with changes in SO 2 emission rate at the surface at various times of the eruption, although only when the temporal resolution of SO 2 monitoring is improved, will it be possible for these short-term changes to be correlated and evaluated effectively. Monitoring SO 2 emission rates from Soufrière Hills Volcano is, at this stage, of primary value in the long run, on the time scale of years, where the relationships between deep supply and surface emissions can be used to evaluate whether the eruption might be waning, or has merely paused, which is of considerable value for hazard assessment.

Follicular epithelium, theca and egg envelope formation in Serrasalmus spilopleura (Teleostei, Characiformes, Characidae)

AbstractThe follicular epithelium and theca of oocytes in Serrasalmus spilopleura differentiates during the initial primary growth phase. The follicular cells are squamous and the thecal cells are disposed in two layers. During the secondary growth phase, follicular cells become cuboidal, acquire characteristics typical of protein‐ or glycoprotein‐producing cells, and show dilated intercellular spaces. Formation of the egg envelope in S. spilopleura begins in the previtellogenic oocytes as a layer of amorphous electron‐dense material is laid down on the oolemma. During vitellogenesis, another layer of electron‐dense material appears beneath the first layer. Also during this phase, a layer of amorphous, less electron‐dense material is formed adjacent to the follicular epithelium. The secondary egg envelope appears at the postvitellogenic phase and is composed of a filamentous and undulant material. The morphology of the egg envelopes in S. spilopleura reflects not only its oviparous nature but also the fact that its eggs are adhesive.

Diacetyl production and growth of Lactobacillus rhamnosus on multiple substrates

Lactobacillus rhamnosus is a heterolactic acid bacterium, which can be used to produce flavour compounds like diacetyl and acetoin. Various startegies have been applied to improve the growth rate and diacetyl yield. The use of multiple substrates affected growth as well as the yield of diacetyl. Growth on a medium containing glucose demonstrated a diauxic growth profile, with the second phase of growth being on the product, lactic acid. L. rhamnosus also grew on a medium containing citrate. Growth on medium containing glucose+citrate demonstrated simultaneous utilization of carbon sources. L. rhamnosus did not grow in a medium containing acetate and also did not co-metabolize it with glucose. Maximum specific growth rate (μmax) was found to increase in the case of simultaneous utilization of glucose+citrate (0.38 h−1) as compared to glucose as the sole carbon source (0.28 h−1). The yields of diacetyl were also found to increase for glucose + pyruvate and glucose + citrate (0.10 and 0.05 g g−1 of glucose, respectively) as compared to glucose alone (0.01 g g−1 of glucose). The productivity of diacetyl on medium containing glucose and citrate was double that of a medium containing only citrate, although the yields were comparable.