Is there evidence of shifting baseline syndrome in environmental managers? An assessment using perceptions of bird population targets in UK nature reserves

Shifting baseline syndrome (SBS) describes changing perceptions of biological conditions due to a loss of historical knowledge. Perceptions of 'normal' environmental conditions are continually updated, leading to underestimation of the true magnitude of long-term ecological change and potential setting of unambitious management targets. There has been speculation as to the presence and impacts of SBS within conservation management since Daniel Pauly's seminal paper in 1995, which outlined the potential effects of SBS on target-setting in fisheries management. Previous case studies have suggested that SBS may not occur in management, despite empirical evidence of SBS in other systems. In this study, 44 professionals and volunteers involved in bird species management, monitoring and target-setting across England were interviewed. Interviews asked for personal perceptions of current, maximum and target abundance, long-term trends, and perceived conservation priority for six bird species. Using paired tests, this study found no significant effect of experience on perceptions of current, maximum or target abundance of all species, despite differences in national abundance and trends, and differences in participant experience. Further power analysis indicated that even if SBS was statistically detectible with a larger sample, the practical implications of the syndrome would be minimal due to small effect sizes. Finally, the effect of experience on individual perceptions of species conservation priority varied between species, with generational amnesia in the form of 'lifting baselines' suggested for only one of the six species. This study suggests that shifting baseline syndrome may not be as significant a threat in conservation management as first thought.

Activation of estrogen signaling pathways collaborates with loss of Brca1 to promote development of ERalpha-negative and ERalpha-positive mammary preneoplasia and cancer

BRCA1 can regulate estrogen receptor-alpha (ERalpha) activity. This study tested the hypotheses that Brca1 loss in mammary epithelium alters the estrogenic growth response and that exposure to increased estrogen or ERalpha collaborates with Brca1 deficiency to accelerate preneoplasia and cancer development. Longer ductal extension was found in mammary glands of Brca1(f/f;MMTV-Cre) mice during puberty as compared to wild-type mice. Terminal end bud differentiation was impaired in Brca1 mutant mice with preservation of prolactin-induced alveolar differentiation. Exogenous estrogen stimulated an abnormal sustained increase in mammary epithelial cell proliferation and the appearance of ERalpha-negative preneoplasia in postpubertal Brca1 mutant mice. Carcinogenesis was investigated using Brca1(f/f;MMTV-Cre) mice hemizygous for p53. Exogenous estrogen increased the percentage of mice with multiple hyperplastic alveolar nodules. Targeted conditional ERalpha overexpression in mammary epithelial cells of mice that were Brca1 mutant and hemizygous for p53 increased the percentage of mice exhibiting multiple hyperplastic nodules, invasive mammary cancers and cancer multiplicity. Significantly more than half of the preneoplasia and cancers were ERalpha negative even as their initiation was promoted by ERalpha overexpression.

CX3C chemokine mimicry by respiratory syncytial virus G glycoprotein

Chemokines are chemoattractant proteins that are divided into subfamilies based upon cysteine signature motifs termed C, CC, CXC and CX3C. Chemokines have roles in immunity and inflammation that affect cell trafficking and activation of T cells as well as cells of the innate immune system. We report here CX3C chemokine mimicry for the G glycoprotein of respiratory syncytial virus (RSV) and show binding to CX3CR1--the specific receptor for the CX3C chemokine fractalkine--and induction of leukocyte chemotaxis. We also show that CX3CR1 facilitates RSV infection of cells. Thus, G glycoprotein interaction with CX3CR1 probably plays a key role in the biology of RSV infection.

Pattern recognition receptors TLR4 and CD14 mediate response to respiratory syncytial virus

The innate immune system contributes to the earliest phase of the host defense against foreign organisms and has both soluble and cellular pattern recognition receptors for microbial products. Two important members of this receptor group, CD14 and the Toll-like receptor (TLR) pattern recognition receptors, are essential for the innate immune response to components of Gram-negative and Gram-positive bacteria, mycobacteria, spirochetes and yeast. We now find that these receptors function in an antiviral response as well. The innate immune response to the fusion protein of an important respiratory pathogen of humans, respiratory syncytial virus (RSV), was mediated by TLR4 and CD14. RSV persisted longer in the lungs of infected TLR4-deficient mice compared to normal mice. Thus, a common receptor activation pathway can initiate innate immune responses to both bacterial and viral pathogens.

Prevalence of antibodies to human parvovirus B19 nonstructural protein in persons with various clinical outcomes following B19 infection

Persistent infections with human parvovirus B19 (B19) associated with debilitating chronic disease have been described, although evidence linking B19 to these more unusual clinical outcomes has been inconclusive. Recent reports have suggested that the development of antibodies to the B19 nonstructural protein (NS1) following B19 infection might be linked to development of severe arthropathy and chronic infection. To confirm these findings, the C-terminal region of the NS1 protein was expressed for use in Western blot assays for detection of anti-NS1 IgG antibodies in human serum. Among 91 persons tested, 0 of 20 not previously infected with B19, 9(36%) of 25 with past B19 infection, and 5 (12.5%) of 40 with recent B19 infection, had detectable anti-NS1 antibodies. Of 6 persons with chronic B19 infection, 2 had detectable antibodies to NS1. The presence of anti-NS1 antibodies did not appear to correlate with unusual clinical outcomes or chronic B19 infection.

N-type calcium channel inactivation probed by gating-current analysis

N-type calcium channels inactivate most rapidly in response to moderate, not extreme depolarization. This behavior reflects an inactivation rate that bears a U-shaped dependence on voltage. Despite this apparent similarity to calcium-dependent inactivation, N-type channel inactivation is insensitive to the identity of divalent charge carrier and, in some reports, to the level of internal buffering of divalent cations. Hence, the inactivation of N-type channels fits poorly with the "classic" profile for either voltage-dependent or calcium-dependent inactivation. To investigate this unusual inactivation behavior, we expressed recombinant N-type calcium channels in mammalian HEK 293 cells, permitting in-depth correlation of ionic current inactivation with potential alterations of gating current properties. Such correlative measurements have been particularly useful in distinguishing among various inactivation mechanisms in other voltage-gated channels. Our main results are the following: 1) The degree of gating charge immobilization was unchanged by the block of ionic current and precisely matched by the extent of ionic current inactivation. These results argue for a purely voltage-dependent mechanism of inactivation. 2) The inactivation rate was fastest at a voltage where only approximately (1)/(3) of the total gating charge had moved. This unusual experimental finding implies that inactivation occurs most rapidly from intermediate closed conformations along the activation pathway, as we demonstrate with novel analytic arguments applied to coupled-inactivation schemes. These results provide strong, complementary support for a "preferential closed-state" inactivation mechanism, recently proposed on the basis of ionic current measurements of recombinant N-type channels (Patil et al., . Neuron. 20:1027-1038).

Mechanism of auxiliary subunit modulation of neuronal alpha1E calcium channels

Voltage-gated calcium channels are composed of a main pore-forming alpha1 moiety, and one or more auxiliary subunits (beta, alpha2 delta) that modulate channel properties. Because modulatory properties may vary greatly with different channels, expression systems, and protocols, it is advantageous to study subunit regulation with a uniform experimental strategy. Here, in HEK 293 cells, we examine the expression and activation gating of alpha1E calcium channels in combination with a beta (beta1-beta4) and/or the alpha2 delta subunit, exploiting both ionic- and gating-current measurements. Furthermore, to explore whether more than one auxiliary subunit can concomitantly specify gating properties, we investigate the effects of cotransfecting alpha2delta with beta subunits, of transfecting two different beta subunits simultaneously, and of COOH-terminal truncation of alpha1E to remove a second beta binding site. The main results are as follows. (a) The alpha2delta and beta subunits modulate alpha1E in fundamentally different ways. The sole effect of alpha2 delta is to increase current density by elevating channel density. By contrast, though beta subunits also increase functional channel number, they also enhance maximum open probability (Gmax/Qmax) and hyperpolarize the voltage dependence of ionic-current activation and gating-charge movement, all without discernible effect on activation kinetics. Different beta isoforms produce nearly indistinguishable effects on activation. However, beta subunits produced clear, isoform-specific effects on inactivation properties. (b) All the beta subunit effects can be explained by a gating model in which subunits act only on weakly voltage-dependent steps near the open state. (c) We find no clear evidence for simultaneous modulation by two different beta subunits. (d) The modulatory features found here for alpha1E do not generalize uniformly to other alpha1 channel types, as alpha1C activation gating shows marked beta isoform dependence that is absent for alpha1E. Together, these results help to establish a more comprehensive picture of auxiliary-subunit regulation of alpha1E calcium channels.

Children's and parents' perceptions of children's exposure to violence in urban neighborhoods

This study examined child and parent perceptions of children's exposure to community violence in a sample of 9 to 12 year olds from high- and low-violence neighborhoods in Washington, DC. More than 75% of the African-American elementary school children sampled indicated that they had witnessed incidents of community violence ranging from homicides to nonfatal shootings, physical assaults, gang violence, robbery with assaults, and rape in their neighborhoods. Yet, almost half of the parents in the study denied that their children had been exposed to any community violence. When these discrepancies were examined, results revealed that children whose parents were in disagreement regarding their exposure to community violence were less likely to experience social support from their peers. Parents' possible lack of awareness as to the experience of their children may place them at further risk by eliminating the possibility for adult-child interaction and guidance regarding their experience with violence in their neighborhoods. Recommendations are provided to assist adults in addressing the needs of children exposed to community violence.

G-protein modulation of N-type calcium channel gating current in human embryonic kidney cells (HEK 293)

1. Voltage-dependent inhibition of N-type calcium currents by G-proteins contributes importantly to presynaptic inhibition. To examine the effect of G-proteins on key intermediary transitions leading to channel opening, we measured both gating and ionic currents arising from recombinant N-type channels (alpha 1B, beta 1b and alpha 2) expressed in transiently transfected human embryonic kidney cells (HEK 293). Recombinant expression of a homogeneous population of channels provided a favourable system for rigorous examination of the mechanisms underlying G-protein modulation. 2. During intracellular dialysis with GTP gamma S to activate G-proteins, ionic currents demonstrated classic features of voltage-dependent inhibition, i.e. strong depolarizing prepulses increased ionic currents and produced hyperpolarizing shifts in the voltage-dependent activation of ionic current. No such effects were observed with GDP beta S present to minimize G-protein activity. 3. Gating currents were clearly resolved after ionic current blockade with 0.1 mM free La3+, enabling this first report of gating charge translocation arising exclusively from N-type channels. G-proteins decreased the amplitude of gating currents and produced depolarizing shifts in the voltage-dependent activation of gating charge movement. However, the greatest effect was to induce a approximately 20 mV separation between the voltage-dependent activation of gating charge movement and ionic current. Strong depolarizing prepulses largely reversed these effects. These modulatory features provide telling clues about the kinetic steps affected by G-proteins because gating currents arise from the movement of voltage sensors that trigger channel activation. 4. The mechanistic implications of concomitant G-protein-mediated changes in gating and ionic currents are discussed. We argue that G-proteins act to inhibit both voltage-sensor movement and the transduction of voltage-sensor activation into channel opening.

The alpha 1E calcium channel exhibits permeation properties similar to low-voltage-activated calcium channels

The physiological and pharmacological properties of the alpha 1E calcium (Ca) channel subtype do not exactly match any of the established categories described for native neuronal Ca currents. Many of the key diagnostic features used to assign cloned Ca channels to their native counterparts, however, are dependent on a number of factors, including cellular environment, beta subunit coexpression, and modulation by second messengers and G-proteins. Here, by examining the intrinsic pore characteristics of a family of transiently expressed neuronal Ca channels, we demonstrate that the permeation properties of alpha 1E closely resemble those described for a subset of low-threshold Ca channels. The alpha 1A (P-/Q-type), alpha 1B (N-type), and alpha 1C (L-type) high-threshold Ca channels all exhibit larger whole-cell currents with barium (Ba) as the charge carrier as compared with Ca or strontium (Sr). In contrast, macroscopic alpha 1E currents are largest in Sr, followed by Ca and then Ba. The unique permeation properties of alpha 1E are maintained at the single-channel level, are independent of the nature of the expression system, and are not affected by coexpression of alpha 2 and beta subunits. Overall, the permeation characteristics of alpha 1E are distinct from those described for R-type currents and share some similarities with native low-threshold Ca channels.

Protozoal abortion in a herd of cattle concurrently infected with Hammondia pardalis

Protozoal infection was diagnosed as the cause of abortion in a large drylot dairy herd located in northeastern Mexico. Diagnosis was made on the basis of finding encephalitis, myocarditis, protozoal cysts, and protozoal tachyzoites in aborted fetuses. The blended ration fed to the cows had been contaminated by the feces of a large resident population of feral domestic cats that used components of the blended ration for den sites (stored hay) or as a latrine (grain). The cows that aborted contained tissue phases of a protozoan infective for domestic cats. The morphologic features of the oocyst and biologic features of the protozoan were identical to those of Hammondia pardalis.

Naturally occurring apicomplexan acute interstitial pneumonitis in thick-billed parrots (Rhynchopsitta pachyrhyncha)

This report describes acute interstitial pneumonitis due to an apicomplexan parasite with schizogony in endothelial cells of pulmonary vessels accompanied by early and metrocyte stages of sarcocysts in the heart of a thick-billed parrot (Rhynchopsitta pachyrhyncha). The pattern of this disease is similar to that of the acute phase (approximately 10-15 days postinoculation) of experimental infections of budgerigars, Melopsittacus undulatus, with high doses of sporocysts of Sarcocystis falcatula.

Bilateral kidney translocation in sheep

Bilateral kidney translocation was performed on 7 adult sheep. In each sheep, we took 9 renal biopsy specimens (40 mg each) percutaneously between 36 and 110 days after surgery. The serum urea nitrogen and creatinine concentrations remained normal, at least through postoperative day 66 (7 biopsy specimens). The 7 sheep were euthanatized and necropsied 113 days after surgery; 75 to 90% of each kidney was normal. The only abnormal areas of each kidney were attributable to resolving biopsy lesions. This surgical model may allow for fewer animals to be used for tissue residue or nephrotoxicity studies.

Hepatozoon sp. in wild carnivores in Texas

Twelve coyotes (Canis latrans), three bobcats (Lynx rufus) and six ocelots (Felis pardalis) from the Gulf Coast of Texas were infected with Hepatozoon sp. The geographic distribution of infected wild animals coincides with the highest prevalence of Hepatozoon canis infection in domestic dogs for which the wild species may act as a reservoir.

The effects of plaster of Paris and autogenous cancellous bone on the healing of cortical defects in the femurs of dogs

Four one quarter inch evenly spaced circular defects were created bilaterally in the lateral femoral diaphysis of 12 clinically normal adult dogs. The defects were left unfilled (control), or were filled with one of the following: (1) plaster of Paris, (2) an equal-volume mixture of plaster of Paris and autogenous cancellous bone, and (3) autogenous cancellous bone. The degree of bone healing was evaluated radiographically and histologically at 2, 4, 6, 8, 10, and 12 weeks. Radiographically, no objective conclusions could be drawn due to the small size of the defects and limited amount of plaster of Paris implanted. Histologically, there was no inflammatory reaction to the plaster of Paris. No differences were determined in the degree of bone healing between autogenous cancellous bone, plaster of Paris, and a mixture of plaster of Paris and autogenous cancellous bone. All implants were superior to the control defect in degree of bone healing.

Experimentally induced Cassia roemeriana poisoning in cattle and goats

The dried, ground aerial portions of the plant Cassia roemeriana were administered to each of seven calves at a dosage of 10 g/kg of body weight/day for 2 to 10.5 days and to each of six goats at a dosage of 10 g/kg/day for 5 days or 5 or 7 g/kg/day for 23 to 25 days. Experimentally induced C roemeriana poisoning in both species resulted in hepatopathic poisoning characterized by a brief survival period (3.9 to 7.9 days), moderate-to-severe hepatocellular damage, and little or no evidence of injury to skeletal muscle or resulted in myopathic poisoning characterized by a longer period of survival, mild-to-severe skeletal myopathy, and mild hepatocellular injury. The minimal dosage that induced hepatopathic poisoning (also the minimal lethal dosage) was 10 g/kg/day for 3 days in calves and for 5 days in goats. The minimal dosage that induced the myopathic syndrome (as determined by the earliest increase in serum creatine kinase activity) was 10 g/kg/day for 6 days for calves and 5 g/kg/day for 10 to 16 days for goats.

Dermal leishmaniasis in a Texas cat

Leishmaniasis was diagnosed by demonstrating amastigotes of Leishmania from dermal lesions on the ear of a male long-haired domestic cat from Uvalde, Texas. Leishmania from the cat were propagated in Syrian hamsters, bovine macrophages, and in NNN medium. The organism, in the L. mexicana complex, is apparently the same as that reported from recent human cases in the same area.

Mycetoma in a grand Eclectus (Eclectus roratus roratus) parrot

A Grand Eclectus parrot with central nervous system disturbances and wing paralysis was necropsied. There were two grayish-black nodules in the upper left thoracic cavity and one nodule in the lower left lung. In addition, several nodules were present in the cerebral hemispheres and optic lobes. The cerebellum had extensive areas of granulomatous lesions. Microscopically, brown-staining hyphae were observed in the nodules. Curvularia geniculata was isolated from the lesions. A diagnosis of mycetoma was based on histologic lesions and isolation of fungus from the lesions.

Anxiety, as experienced by chronic pain patients

This article developed out of the author's work with patients at the Pain Control Center at Emory University Hospital in Atlanta, Georgia. The purpose of the article is to show how anxiety, an experience common to all persons, is particularly experienced by chronic pain patients.

Sampling bias in estimating Design II variance components with S1 families

The use of several S1 individuals to represent an S0 individual permits the use of a Design II mating scheme for plants with only one pistillate flower per plant. Estimates of additive (V A ) and dominance (V D ) variance from this mating scheme will be biased upwards, when a small number (10) of individuals of each S1 line are used. This bias can be computed, and the additive and dominance estimates can be corrected. Of particular interest is the observation that the additive genetic variance contributes to bias in estimates of V D . When S0 plants are non inbred and their selfedprogeny (S1 lines) are used to represent them in developing families for use in the Design II, [Formula: see text] where m1 is the number of individuals used to represent an S1 line in developing half sib-families and m2 is the number of individuals used to represent the S1 line in making up full sib-families. For example, in a 3×3 Design II, with about 10 individuals used to represent each S1 line in each cross, m2 = 10 and m1 = 30. When m1 = m2 = 1, [Formula: see text] and [Formula: see text].

1,3 Butanediol treatment of ethylene glycol toxicosis in dogs

In order to assess the therapeutic value of 1,3 butanediol in ethylene glycol toxicosis, mixed-bred dogs were given an oral dose of commercial antifreeze at 6 ml/kg of body weight (0 hour) and treated (IV) 7 times at 6-hour intervals with 5.5 ml/kg of body weight 1,3 butanediol solution (20% in physiological saline solution) beginning at 8, 12, and 21 hours. Serum glycolic acid concentration was quantitated by high-pressure liquid chromatography. Three dogs that were given ethylene glycol, but no 1,3 butanediol treatment, died with elevated serum glycolic acid concentrations. Five dogs were given ethylene glycol and 1,3 butanediol treatment. Of 2 dogs treated at 8 hours, 1 survived and 1 died at 39 hours; 1 treated at 12 hours and 1 treated at 21 hours survived; 1 dog died soon (27 hours) after treatment was initiated at 21 hours. Four of the 5 dogs had dramatically decreased serum glycolic acid concentrations after 1,3 butanediol treatment, indicating its effectiveness in inhibiting alcohol dehydrogenase-dependent glycolic acid formation in vivo.

Primary hyperparathyroidism in German shepherd dogs: a disorder of probable genetic origin

Primary hyperparathyroidism was diagnosed in two German shepherd pups from a litter of four females. Clinical signs were apparent by two weeks of age and included stunted growth, muscular weakness, and polydipsia/polyuria. Radiography revealed diffuse reduction in bone density. Both pups had marked hypercalcemia, hypophosphatemia, increased plasma immunoreactive parathyroid hormone concentrations and increased fractional clearance of inorganic phosphate in the urine. Intravenous infusion of one affected pup with calcium gluconate failed to suppress the plasma concentration of immunoreactive parathyroid hormone, suggesting autonomous secretion of parathyroid hormone. Necropsy of the other pup at eight weeks of age revealed diffuse hyperplasia of parathyroid chief cells, nodular hyperplasia of thyroid C-cells, skeletal alterations consistent with fibrous osteodystrophy, hypercalcemic nephropathy, and extensive mineralization of the lungs and gastric mucosa. The dam and sire were half sibs. One male pup from a previous litter of six had developed similar clinical signs and radiographic lesions, suggesting autosomal recessive inheritance. This is the first report of hereditary primary hyperparathyroidism in domestic animals, a disease which may be analogous to hereditary neonatal primary hyperparathyroidism in children.

Space and time efficient virtual quadtress

The quadtree has recently become a major data structure in image processing. This correspondence investigates ways in which quadtrees may be efficiently stored as a forest of quadtrees and as a new structure we call a compact quadtree. These new structures are called virtual quadtrees because the basic operations we expect to perform in moving about within a quadtree can also be performed on the new representations. Space and time efficiency are investigated and it is shown these new structures often given an improvement in both.

Elimination of adverse effects of ethoxyquin (EQ) by methionine hydroxy analog (MHA). Protective effects of EQ and MHA for bitterweed poisoning in sheep

Dietary ethoxyquin (EQ) and methionine hydroxy analog (MHA) protected 6-8-month-old wethers from toxic doses of bitterweed (Hymenoxys odorata DC.). The EQ-MHA group received sweet feed (corn, oats, dehydrated alfalfa pellets, cane molasses and minerals), 500 g/day/sheep, supplemented with EQ and MHA (0.5% and 1.0% of feed, respectively) for 9 days prior to the poisoning with bitterweed while the MHA group received the same feed without EQ and controls received the same amount of feed with no additives. Two of 6 MHA-treated and 3 of 7 controls died whereas all 7 EQ-MHA-treated sheep survived after receiving 5 doses of bitterweed (5 X 5.5 g/kg) in 6 days. Coadministration of MHA and EQ eliminated the adverse effect of EQ; dietary EQ lowered the serum albumin, calcium, and alkaline phosphatase content while protecting the animals from bitterweed poisoning. EQ is the most promising protective agent tested for bitterweed poisoning in sheep.

Isolation of an anticomplement factor from the venom of the Mojave rattlesnake (Crotalus scutulatus scutulatus)

The venom of the Mojave rattlesnake was fractionated by DEAE-Sephadex column chromatography. A venom fraction, F5, inactivated both human and guinea pig complement. Both serum and purified C3 were partially converted to a protein of faster electrophoretic mobility, indicating that F5 had a direct proteolytic effect on C3. This product was capable of passively lysing guinea pig red blood cells. F5 very effectively inactivated the classical pathway, but only partially inactivated the alternative pathway. The venom fraction worked in a dose-dependent fashion, was heat labile but not lethal to mice at concentrations as high as 10 micrograms/g mouse weight. Antibodies were produced by immunizing rabbits with F5. The antibodies formed one precipitin line in gels against F5 and also neutralized the complement inactivating activity. The antibodies recognized the venom of the western diamondback rattlesnake, Crotalus atrox, but did not, however, recognize the crude venom of the Mojave rattlesnake.

Protective effects of antioxidants on bitterweed (Hymenoxys odorata DC) toxicity in sheep

Antidotal effects of the 2 antioxidants butylated hydroxyanisole (BHA) and ethoxyquin (EQ) were evaluated in bitterweed (Hymenoxys odorata DC) toxicosis in sheep. Bitteerweed contains a toxic sesquiterpene lactone, hymenoxon, the toxicity of which is reduced by cysteine. Both BHA and EQ are known to induce hepatic glutathione production in rodents. Treatment of sheep with EQ (2.5 g/sheep/day for 9 days before poisoning) gave significant protection from toxic doses of bitterweed, but the protective effect of BHA was insignificant. Of 6 sheep given EQ in the feed, 5 survived 7 doses of bitterweed (4 g/kg/day or higher for 7 days), whereas 5 of 7 controls and 4 of 7 sheep given feed with added BHA died. The added EQ in the feed decreased the serum alkaline phosphatase activity and total protein, albumin, and calcium concentrations. Seemingly, EQ is the first protective agent with field application potential for bitterweed toxicity.

Protective effects of butylated hydroxyanisole, ethoxyquin, and disulfiram on acute pyrrolizidine alkaloids poisoning in mice

Administration of butylated hydroxyanisole (BHA), ethoxyquin (EQ), and disulfiram (DSF) in the diet for 7 days reduced the acute toxicity of pyrrolizidine alkaloids isolated from Senecio longilobus. The LD50 values of the BHA- and EQ-fed mice were about twofold of the controls but the protective effect of DSF was inferior to that of either BHA or EQ.

Fructose-1,6-bisphosphate aldolase from Vibrio marinus, a psychrophilic marine bacterium

Fructose-1,6-bisphosphate aldolase (Fru-P2A) from a psychrophilic marine bacterium was found to be Class II aldolase based on activation by K+, activation by divalent cations, inactivation by EDTA, low molecular weight, and similar values for Km, Vmax, and Arrhenius activation energy. This enzyme was not markedly different in amino acid composition from the enzymes from mesophilic and thermophilic organisms, yet it has unusual thermal properties.

Chronic lead poisoning in horses

Lead acetate was fed to 4 groups of 2 horses each to study chronic lead intoxication. A 5th group of 3 horses was maintained as controls. The leas was fed in capsules, with the minimum dosage of 6.25 mg/kg/day of lead as lead acetate (group I). The dose was increased from group I through group IV in an approximate geometric series, with each group being given about 125% of the dose given the previous group. These doses were given for 105 days, a period designated as phase 1. Since clinical signs were not observed after 105 days, the doses were increased and fed for an additional 190 days (days 106 to 295). This period was designated phase 2. The smallest daily dose in phase 2 was set at about 125% of the largest daily dose in phase 1. The doses in each group was increased by about 125% of that of the previous group, as was done in phase 1. Seven horses died or were euthanatized after 18 to 190 days of phase 2 (123 to 295 days after the 1st dose). One horse in group I did not develop any clinical signs of intoxication. Dose-related responses were unnoticed with doses larger than 15.3 mg/kg/day. All horses given lead had increased blood lead and serum iron concentrations. During phase 2, the hematocrit (erythrocyte volume) and hemoglobin contents were depressed. The lead concentration in kidney, liver, spleen, pancreas, brain, bone, and heart was increased in the treated horses. The dose level required to produce lead intoxication was greater than that reported for cattle and that estimated in epizootiologic studies of horses.

Photosensitization in sheep fed Ammi majus (Bishop's weed) seed

Ammi majus (bishop's weed) grows on the coastal region of southern United States and in other parts of the world. This plant causes severe photosensitization in livestock and probably contributes to the severe photosensitization outbreaks seen in Texas. Sheep were fed finely ground seed of A majus via stomach tube at dose rates of 1, 2, 4, and 8 g/kg of body weight and exposed to sunlight. The single dose of 8 g/kg produced severe clinical signs (in 24 to 48 hours): cloudy cornea, conjunctivokeratitis, photophobia, and edema of the muzzle, ears, and vulva. Daily dosing at 2 and 4 g/kg produced (in 72 to 96 hours) similar signs, whereas the smallest dose (1 g/kg) produced mild irritation of the muzzle. Pathologic changes included (1) corneal edema and marked neutrophilic infiltration of the cornea and corneal/ciliary process, (2) subacute ulcerative and exudative dermatitis of the skin of ears, muzzle, and vulva, and (3) mild focal tubular degeneration (vacuolar type) of the kidney.

Pathology of subacute bitterweed (Hymenoxys odorata) poisoning in sheep

Subacute bitterweed (Hymenoxys odorata) poisoning was produced in sheep by force feeding them ground plant material (1 gm/kg/day) for 15 days. Five sheep died and two became moribund and were killed at the end of the experiment. The forestomach and abomasum were severely congested and occasionally eroded on the mucosal surface. There was an accumulation of edematous fluids along the rumino-reticular folds and ruminal sulci. Gaseous and fluid distension of the forestomachs, abomasum and cecum was a consistent finding. The gall bladder was greatly distended and occasionally the mucosa was sprinkled with petechiae. The most common finding was severe glomerulonephrosis characterized by proteinaceous casts, swollen and degenerated glomerular tufts and degeneration and necrosis in the inner renal cortex and outer medulla. Mild to moderate toxic hepatosis, characterized by vacuolar degeneration of hepatocytes primarily around the central vein, was consistent.

Comparison of full and half-sib reciprocal recurrent selection

Full and half-sib reciprocal recurrent selection (RRS) were compared algebraically and with computer simulation. The relative performance of the two schemes depended on the selection intensity and the environmental variance. Full-sib RRS was favoured at less intense selection and when the environmental variance was large relative to the total genetic variation. As selection intensity increased its advantage declined. Full-sib RRS enables a breeder to combine the efficient development of new hybrids with population improvement and should be a valuable technique in plant breeding.

Correlation Between Bristle Systems in Drosophila Melanogaster

The correlation between several bristle systems of Drosophila melanogaster was investigated. The changes in sternopleural, second coxal, third coxal, and scutellar bristle numbers were measured in 26 lines selected for increased abdominal bristle number for 46 or 50 generations. The changes in abdominal, second coxal, and scutellar bristle numbers were measured in 16 lines selected with independent culling levels for high or low sternopleural and high or low third coxal bristle numbers for 22 generations.

Effects of Artificial Selection on Rates of Inbreeding in Populations of Drosophila Melanogaster

Three lines from the Canberra base population were selected for increased abdominal bristle number for up to 28 generations with 10 pairs of parents and 20% selection intensity. The effective population size as measured by either variance of family contributions to the next generation or by the rate of inbreeding was gener-ally lowest when the lines were responding rapidly to selection. Consideration of the contributions of families in any generation to the lines five generations later showed that much of the genetic variation came from only few families in some generations.

Effects of Artificial Selection on Rates of Inbreeding in Populations of Drosophila Melanogaster

The rate of inbreeding was studied using the conventional F value, as well as the "percentage of genes" technique of James and McBride (1958), in lines of D. melanogaster selected for increased abdominal bristle number for seven generations at intensities of 10, 20, and 50% with 10 pairs of parents.

The effects of population size and selection intesnity in selection for a quantitative character in Drosophila. II. Long-term response to selection

1. An experimental evaluation of Robertson's (1960) theory of limits in artificial selection was attempted. A number of lines from the Canberra base population were selected for abdominal bristle number over 50 generations with population sizes of 10, 20, and 40 pairs of parents and selection intensities of 10, 20 and 40% as well as unselected controls.

2. In general, the total response obtained increased with an increase inNī(product of population size and standardized selection differential).

3. Thus, total response increased with increase in the number of individuals scored, or, for a fixed number of parents, increase in selection intensity increased both rates of response per generation and total response.

4. But for the same total number scored, the response increased as selection intensity decreased. However, the proportion selected had only a small effect as compared with that of the total number scored.

5. Sublines in which the population size was reduced after 16 generations of selection but with the selection intensity kept constant, immediately fell behind their parent lines and gave much less response.

6. Agreement between replicate lines was generally poor, particularly for the 10- and 20-pair lines.

7. Patterns of response in individual lines were frequently irregular and ‘waves of response’ were not uncommon.

8. The results are discussed in terms of several theoretical models of selection limits. In general, agreement with these models was poor, as much of the response appeared to be due to a few genes (or gene combinations) with large effects on bristle number.

The effects of population size and selection intensity in selection for a quantitative character in Drosophila. 3. Analyses of the lines

1. In order to determine the nature of the genetic variation causing the response to selection in our lines (Joneset al.1968), various analyses were performed.

2. There was no consistent change in heritability, estimated from half-sib correlation or from the phenotypic correlation between the bristle numbers of two abdominal segments, after 10 to 20 generations of selection.

3. Realized heritabilities over the 10 generations subsequent to the heritability estimations were less than in the early generations but bore little relationship to the estimated values.

4. Six lines contained recessive lethals with appreciable effects on bristle number as indicated by high variances, large regression on relaxation and large response to reverse selection.

5. Reverse selection lines taken from the main lines at generation 40 indicated that genetic variation was still present in almost all of the lines. Only one line failed to respond to further forward or to reverse selection.

6. The three highest lines were crossed in pairs and reselected. Two of the three possible crosses gave further response, exceeding the higher parent after one and three generations, but the other cross failed to pass the highest parent line.

7. A combination of large gene effects, linkage, and gene interaction effects have been suggested as the cause of irregularities in the response of the lines. It has not been possible to determine the relative importance of these effects.

The effects of population size and selection intensity in selection for a quantitative character in Drosophila. I. Short-term response to selection

1. The response to selection for increased number of bristles on one abdominal segment was studied over 12 generations using a factorial design of three population sizes (10, 20 and 40 pairs of parents) and five selection intensities (10, 20, 40, 80% and controls).

2. The responses on the average agreed well with those expected from the estimated base population heritability, but individual replicates diverged considerably.

3. Larger populations tended to give greater response to selection, due mainly to larger realized heritabilities.

4. There was no consistent effect of selection intensity on realized heritability.

5. For populations with the same number of individuals scored, less intense selection gave greater realized heritabilities.

Rhizopterin biosynthesis in Staphylococcus epidermidis

The biosynthetic pathway from 2-amino-4-hydroxy-6-hydroxymethyldihydropteridine (hydroxymethyldihydropteridine) to 10-formyldihydropteroic acid (dihydrorhizopterin), as found in cell-free extracts of Staphylococcus epidermidis grown in a glucose–casein hydrolysate medium, is described. In the first of at least three reactions, hydroxymethyldihydropteridine enzymatically reacts with adenosine triphosphate (ATP) in the presence of MgCl2 to form the pyrophosphate ester of this dihydropteridine and adenosine monophosphate. Cell-free enzyme preparations couple the dihydropteridine pyrophosphate with p-aminobenzoic acid (PABA) to form a phosphate containing dihydropteroic acid derivative. Enzymatic incubation of dihydropteroic acid phosphate with one-carbon donor compounds and adenosine diphosphate results in the formation of dihydrorhizopterin and ATP. Evidence is presented that the phosphorylated dihydropteroic acid compound can only be formed from the pyrophosphate ester of hydroxymethyldihydropteridine and not from dihydropteroic acid and ATP. Dihydrorhizopterin biosynthesis proceeds only from the dihydropteroic acid phosphate derivative and could not be shown to occur from 5-formyltetrahydrofolic acid. Cell-free extracts prepared from cells grown in brain heart infusion broth do not form any rhizopterin-like compounds, but form dihydropteroic acid from the phosphorylated dihydropteroic acid.