Stream flow and predation effects on the spatial dynamics of benthic invertebrates

Field experiments were carried out to determine the influence of predation and prey movements on the accumulation of prey in enclosures. Experimental enclosures permitted exchange of prey with the benthos, but not of the large, predatory larvae of the caddisfly, Plectrocnemia conspersa (Curtis). Unseasonally heavy rainfalls during the experiment resulted in high flows and enabled us to examine the effects of a major, abiotic disturbance on invertebrate spatial dynamics. Prey colonization rates of cages without predators were determined in nine 24 h periods. Colonization rates increased exponentially with flow and were species-specific, depending on dispersal behaviour. Prey accumulation and predator impacts were measured in cages, with and without P. conspersa larvae, placed in the stream for 1, 2 or 3 weeks. Prey densities in cages increased with exposure time, but increases were not gradual and depended on flow regime. Flow was reduced within cages and they accumulated large numbers of invertebrates during high discharge. Analogous, naturally occurring refugia in the stream channel could be important for the recovery of lotic communities after major disturbances. Overall, prey densities were lowest in cages with predators. For fast colonizers, predation effects were detectable early in the experiment, but quickly obscured thereafter by continuous exchange of prey. For slow colonists, predation effects were detectable later, but persisted longer. Consumption rates for P. conspersa varied with prey density and flow regime. We suggest that the spatial dynamics of benthic invertebrates, especially as they are influenced by stochastic events, are important in understanding and detecting predation effects in stream communities.     

Detection of Autographa californica and Heliothis zea baculovirus proteins by enzyme-linked immunosorbent assay (ELISA)

The structural proteins of Autographa californica (AcMNPV) and Heliothis zea (HzSNPV) nuclear polyhedrosis viruses were detected by indirect enzyme-linked immunosorbent assay (ELISA). The immunoassay detected less than 1 ng of AcMNPV protein. The extent of immunological relatedness between AcMNPV-occluded virus and AcMNPV polyhedral protein, AcMNPV-nonoccluded virus, Estigmene acrea granulosis virus, Amsacta moorei entomopoxvirus Heliothis zea NPV, and Lymantria dispar NPV was determined. No immunological relatedless was detected between HzSNPV, AcMNPV, and a persistent rod-shaped virus isolated from the Heliothis zea cell line (IMC-Hz-1). The polyhedral proteins of HzSNPV and AcMNPV were found to be immunologically identical.     

Effectors of lipoprotein lipase secretion from isolated cardiac muscle cells incubated in vitro

Cycloheximide, colchicine, tunicamycin, glucagon, dibutyryl-3′–5′-cyclic AMP, dexamethasone and hydrocortisone had no effect on the lipoprotein lipase activity associated with rat cardiac muscle cells incubated $\text{in vitro}$. However, the steroid hormones and inhibitors affected profoundly the appearance of extracellular enzyme during the incubations. The pattern of effects, was consistent with lipoprotein lipase being a normal secretory product of heart muscle cells.     

“Cytogenetic” studies of spermatids of mice carrying Cattanach's translocation by flow cytometry

The DNA content of spermatids of mice carrying Cattanach's translocation has been measured with high precision by flow cytometry. The observation that the two peaks of DNA content in the haploid region of the DNA histograms represent X-and Y-bearing spermatids was tested and confirmed. Using flow cytometry, the difference in DNA content between the X and Y chromosomes in these mice was measured to be 5.2±0.1% of the total haploid genome as compared to 3.4±0.1% in normal mice. These results demonstrated the precision of flow cytometry for cytogenetic studies. Additional information on spermatogenesis in mice bearing Cattanach's translocation was obtained and showed a gradual loss of cells during spermatogenesis in those bearing the balanced form of the translocation.     

Changes during development in transport processes of the blood-brain barrier

The permeability of the blood-brain barrier to several classes of compounds was studied in rats between the ages of 15 days and 9 weeks. ¹⁴C-labelled test substances were injected simultaneously with two reference isotopes, ³H₂O and ^113mIn-labelled EDTA, into the common carotid artery followed by decapitation 10 s later.There was evidence that a monocarboxylic acid transport system in 15 to 23 day-old rats had a capacity at least six times greater than that present in adult animals. l-Lactate and acetate showed the highest permeability. At all ages there was a constant ratio between l-lactate and (−)d-3-hydroxybutyrate values. d-Glucose permeability increased with age, while that of several amino acids tested was the same in young and adults rats.     

Amino acid sequence at the phosphorylated site of rat liver pyruvate kinase

One dominating peptic phosphopeptide, Asx-Thr-Lys-Gly-Pro-Glx-Ile-Glx-Thr-Gly-Val-Leu-Arg-Arg-Ala-(³²P)SerP-Val-Ala-Glx-Leu, was obtained from rat liver pyruvate kinase (type L) phosphorylated by cyclic 3′,5′-AMP-stimulated protein kinase from the same tissue. The sequence around the phosphorylated serine residue is similar to that of a corresponding but smaller peptic phosphopeptide previously isolated from pig liver (type L) pyruvate kinase, Leu-Arg-Arg-Ala-(³²P)SerP-Leu.     

The Influence of Anatomical Boundaries,Age, and Sex on the Assessment of Abdominal Visceral Fat

CLASEY, JODY L, CLAUDE BOUCHARD, LAURIE WIDEMAN, JILL KANALEY, C DAVID TEATES, MICHAEL O THORNER, MARK L HARTMAN, ARTHUR WELTMAN. The influence of anatomical boundaries, age, and sex on the assessment of abdominal visceral fat. Single-slice abdominal computed tomography (CT) scanning has been used extensively for the measurement of abdominal visceral fat (AYF). Optimal anatomical scan location and pixel density ranges have been proposed and are specifically reported to allow for the replication and standardization of AVF measurements. Standardization of the anatomical boundaries for CT measurement of AVF and the influence of age and gender on results obtained with different boundary locations have received much less attention. To determine the influence of three boundary analysis methods (AVF-1, AVF-2, and AVF-3) on the measurement of AVF by CT, 54 older (60 years to 79 years) and 37 younger (20 years to 29 years) healthy men and women were examined. The measurement boundary for AVF-1 was the internal most aspect of the abdominal and oblique muscle walls, and the posterior aspect of the vertebral body. AVF-2 used fat measurements enclosed in a boundary formed by the midpoint of the abdominal and oblique muscle walls, and the most posterior aspect of the spinous process. AVF-3 used fat measurements enclosed in a boundary formed by the external border of the abdominal and oblique muscle walls, and the external border of the erector spinae. Greater AVF measures were obtained with AVF-2 and AVF-3 compared with AVF-1 (p<0.0001). These differences were greater in older compared with younger subjects (p<0.0001) and greater in women compared with men (p<0.02). The significantly greater AVF measurements obtained with AVF-2 and AVF-3 resulted from the inclusion of larger amounts of fat that are not drained by the portal circulation. This included retroperitoneal, intermuscular, and intramuscular lipid droplets, which increase with aging. On the basis of these results, we recommend the AVF-1 anatomical boundaries for the measurement of AVF in clinical investigations, particularly with older subjects. These data demonstrate the importance of precise and reproducible anatomical boundaries for the measurement of AVF, particularly in longitudinal studies.