Effect of lactation stage and concurrent pregnancy on milk composition in the bottlenose dolphin

Although many toothed whales (Cetacea: Odontoceti) lactate for 2–3 years or more, it is not known whether milk composition is affected by lactation stage in any odontocete species. We collected 64 pooled milk samples spanning 1–30 months postpartum from three captive bottlenose dolphins Tursiops truncatus . Milks were assayed for water, fat, crude protein (TN × 6.38) and sugar; gross energy was calculated. Ovulation and pregnancy were determined via monitoring of milk progesterone. Based on analysis of changes in milk composition for each individual dolphin, there were significant increases ( P <0.05) in fat (in all three dolphins) and crude protein (in two of three), and a decrease ( P <0.05) in water (in two of three) over the course of lactation, but the sugar content did not change. In all three animals, the energy content was positively correlated with month of lactation, but the percentage of energy provided by crude protein declined slightly but significantly ( P <0.05). At mid-lactation (7–12 months postpartum, n =17), milk averaged 73.0±1.0% water, 12.8±1.0% fat, 8.9±0.5% crude protein, 1.0±0.1% sugar, 1.76±0.09 kcal g⁻¹ (=7.25 kJ g⁻¹) and 30.3±1.3% protein:energy per cent. This protein:energy per cent was surprisingly high compared with other cetaceans and in relation to the growth rates of calves. Milk progesterone indicated that dolphins ovulated and conceived between 413 and 673 days postpartum, following an increase in milk energy density. The significance of these observed compositional changes to calf nutrition will depend on the amounts of milk produced at different stages of lactation, and how milk composition and yield are influenced by sampling procedure, maternal diet and maternal condition, none of which are known.     

Pressure wave propagation in fluid-filled co-axial elastic tubes. Part 2: Mechanisms for the pathogenesis of syringomyelia

Our aim in this paper is to use a simple theoretical model of the intraspinal cerebrospinal-fluid system to investigate mechanisms proposed for the pathogenesis of syringomyelia. The model is based on an inviscid theory for the propagation of pressure waves in co-axial, fluid-filled, elastic tubes. According to this model, the leading edge of a pressure pulse tends to steepen and form an elastic jump, as it propagates up the intraspinal cerebrospinal-fluid system. We show that when an elastic jump is incident on a stenosis of the spinal subarachnoid space, it reflects to form a transient, localized region of high pressure within the spinal cord that for a cough-induced pulse is estimated to be 50 to 70 mm Hg or more above the normal level in the spinal subarachnoid space. We propose this as a new mechanism whereby pressure pulses created by coughing or sneezing can generate syrinxes. We also use the same analysis to investigate Williams' suck mechanism. Our results do not support his concept, nor, in cases where the stenosis is severe, the differential-pressure-propagation mechanism recently proposed by Greitz et al. Our analysis does provide some support for the piston mechanism recently proposed by Oldfield et al. and Heiss et al. For instance, it shows clearly how the spinal cord is compressed by the formation of elastic jumps over part of the cardiac cycle. What appears to be absent for this piston mechanism is any means whereby the elastic jumps can be focused (e.g., by reflecting from a stenosis) to form a transient, localized region of high pressure within the spinal cord. Thus it would seem to offer a mechanism for syrinx progression, but not for its formation.     

The EGF receptor: a nexus for trafficking and signaling

Ligand binding to the EGF receptor initiates both the activation of mitogenic signal transduction pathways plus trafficking events that relocalize the receptor on the cell surface and within intracellular compartments. The trafficking compartments include caveolae, clathrin-coated pits, and various endosome populations prior to receptor degradation in lysosomes. Evidence is presented that distinct signaling pathways are initiated from these different compartments. These include the Ras/MAP kinase cascade and the PLC-dependent hydrolysis of PI-4,5 P(2). Multiple tyrosine kinase substrates that facilitate EGF receptor trafficking between these various compartments, as well as the participation of phosphoinositides and Ras-like G proteins in the trafficking pathway are also described.     

Mobility of mass-reared diapaused and nondiapaused Cydia pomonella (Lepidoptera: Tortricidae): effect of different constant temperatures and lengths of cold storage

Desirable behavioral attributes in mass-reared insects should include the ability to perform favorably under the various environmental conditions they encounter upon release in the field. Insect quality also may be influenced by storage conditions and storage duration before field release. We studied the effects of three different constant ambient temperatures (15, 20, and 25 degrees C) and different lengths of adult cold storage (0, 24, 48, and 72 h at 2 degrees C) on the locomotor activity of adult Cydia pomonella (L.) mass reared through diapause or standard production protocols. Mobility was assessed in actographs housed in a climate controlled chamber; tests lasted 24 h. We found that adult mobility was significantly higher for both males and females at 25 and 20 degrees C than at 15 degrees C. There were no significant differences in mobility in moths reared through diapause or nondiapaused production protocols. In addition, temporal analysis of the data revealed a significant shift in the diel patterns of activity for both genders when adults were tested at the three different temperatures. Moths exposed to the lower temperature shifted their activity pattern from evening to mid-afternoon, which may be an adaptive behavior to take advantage of the expected warmest period of the day. Diapaused adults were significantly less mobile when stored in the cold (24, 48, or 72 h of storage at 2 degrees C) than were diapaused adults that did not experience cold storage (0 h). However, length of time in cold storage did not significantly influence the mobility of adult codling moths reared through standard production protocols.     

Reaching out: Cortical Mechanisms of Directed Action

Recordings from monkey cortex have demonstrated a sophisticated neural mechanism for the complex transformational mapping demanded by visually guided reaching.     

Technical pitfalls encountered in PCR quantification using microsatellites

Quantitative PCR has proved useful for different purposes, including the detection of particular genetic changes, such as deletions and duplications in several inherited disorders. Using patients with the known duplication mutation for Charcot-Marie-Tooth disease Type 1A as examples, the importance of selecting informative microsatellite loci and proper electrophoretic conditions so as to eliminate potential sources of error in quantitative PCR studies is discussed.     

Stable antisense RNA expression neutralizes the activity of low-density lipoprotein receptor-related protein and promotes urokinase accumulation in the medium of an astrocytic tumor cell line.

Low-density lipoprotein receptor-related protein (LRP) binds and internalizes multiple ligands that are structurally and functionally diverse. However, the effects of LRP on cellular phenotype remain unclear. To study LRP in human astrocytic tumor cells, we designed LRP antisense RNA expression constructs in which the antisense cDNA fragment was expressed under the control of the cytomegalovirus (CMV) promoter. U-1242 MG astrocytic tumor cells were transfected with the antisense constructs and cloned from single cells to yield multiple cell lines with decreased LRP expression. Further studies were performed with two cell lines in which LRP antigen was completely eliminated (L(alpha)42) or substantially decreased (Lalpha47), as determined by Western blot analysis. Untransfected U-1242 MG cells and cells that were stably transfected with empty vector (pBK-CMV) bound activated alpha2-macroglobulin (alpha2M) in a specific and saturable manner. The Bmax was about 5000 receptors/cell. Lalpha42 cells did not bind alpha2M, and binding was decreased by >60% in Lalpha47 cells. Lalpha42 and Lalpha47 cells also demonstrated reduced susceptibility to the cytotoxin, Pseudomonas exotoxin A, and accumulated greatly increased levels of urokinase-type plasminogen activator (uPA) in conditioned medium. The accumulation of uPA demonstrates a major role for LRP in the catabolism of this protein in astrocytic tumor cells. The LRP-deficient cell lines, developed using antisense technology, represent a new model system for studying LRP function in astrocytes.     

Enumeration of an Extremely High Particle-to-PFU Ratio for Varicella-Zoster Virus

Varicella-zoster virus (VZV) is renowned for its low titers. Yet investigations to explore the low infectivity are hampered by the fact that the VZV particle-to-PFU ratio has never been determined with precision. Herein, we accomplish that task by applying newer imaging technology. More than 300 images were taken of VZV-infected cells on 4 different samples at high magnification. We enumerated the total number of viral particles within 25 cm² of the infected monolayer at 415 million. Based on these numbers, the VZV particle:PFU ratio was approximately 40,000:1 for a cell-free inoculum.A precise ratio of particles to PFU of varicella-zoster virus (VZV) has never been determined, even though VZV was first isolated in cell culture by the Nobel laureate T. H. Weller in 1952 (21). His group determined that VZV replicated in a few embryonic tissues and in amnion cells. Subsequently, Taylor-Robinson and Caunt found that VZV replication was restricted to a small number of mainly embryonic cells by testing more than 20 primary and continuous cell lines (19). A decade later, VZV was propagated in melanoma cell lines, which are derived from the neural crest (8). In all of these cultured cells, the titer was found to be low, particularly when compared with that of the closely related herpes simplex type 1 virus (HSV-1). Again, in sharp contrast with HSV-1, the virus remained strongly cell associated.The term particle/PFU ratio refers to the number of viral particles required to form one plaque in a plaque assay. It is a measure of the efficiency by which a virus infects cultured cells. Early in the 1960s, investigators began using negative staining electron microscopy to count viral particles in inoculum material and compare those counts to the measured titer, thereby measuring ratios for a few animal viruses (6). For example, the ratio for HSV-1 is around 10:1 (10, 20). Due to the strong cell association of VZV infection of cultured cells, no precise VZV particle/PFU ratio has ever been determined. The lack of any widely accepted VZV ratio severely limits our ability to assess whether mutated or recombinant viruses produce more or fewer complete infectious particles in cultured cells (4, 5, 15, 17). In other words, if an attenuated virus has a lower titer, we do not know whether fewer viral particles are produced per square centimeter of cellular monolayer (without a change in the particle/PFU ratio) or alternatively fewer infectious viral particles are produced overall (with a higher particle/PFU ratio).In this report, we successfully define a VZV particle/PFU ratio by imaging viral particles with advanced scanning electron microscopic (SEM) technology not available during our earlier investigations of viral structure (12). We demonstrate that the VZV ratio is much higher than that for other common human viruses grown in cultured cells and remarkably higher than that for HSV. Finally, this report documents evidence of an ever-widening difference between HSV and VZV replication and assembly in cultured cells (7, 13, 18).