The SATB1-MIR22-GBA axis mediates glucocerebroside accumulation inducing a cellular senescence-like phenotype in dopaminergic neurons

Idiopathic Parkinson's disease (PD) is characterized by the loss of dopaminergic neurons in the substantia nigra pars compacta, which is associated with neuroinflammation and reactive gliosis. The underlying cause of PD and the concurrent neuroinflammation are not well understood. In this study, we utilize human and murine neuronal lines, stem cell-derived dopaminergic neurons, and mice to demonstrate that three previously identified genetic risk factors for PD, namely SATB1, MIR22HG, and GBA, are components of a single gene regulatory pathway. Our findings indicate that dysregulation of this pathway leads to the upregulation of glucocerebrosides (GluCer), which triggers a cellular senescence-like phenotype in dopaminergic neurons. Specifically, we discovered that downregulation of the transcriptional repressor SATB1 results in the derepression of the microRNA miR-22-3p, leading to decreased GBA expression and subsequent accumulation of GluCer. Furthermore, our results demonstrate that an increase in GluCer alone is sufficient to impair lysosomal and mitochondrial function, thereby inducing cellular senescence. Dysregulation of the SATB1-MIR22-GBA pathway, observed in both PD patients and normal aging, leads to lysosomal and mitochondrial dysfunction due to the GluCer accumulation, ultimately resulting in a cellular senescence-like phenotype in dopaminergic neurons. Therefore, our study highlights a novel pathway involving three genetic risk factors for PD and provides a potential mechanism for the senescence-induced neuroinflammation and reactive gliosis observed in both PD and normal aging.

The SATB1-MIR22-GBA axis mediates glucocerebroside accumulation inducing a cellular senescence-like phenotype in dopaminergic neurons

Idiopathic Parkinson's Disease (PD) is characterized by the loss of dopaminergic neurons in the substantia nigra pars compacta, which is associated with neuroinflammation and reactive gliosis. The underlying cause of PD and the concurrent neuroinflammation are not well understood. In this study, we utilized human and murine neuronal lines, stem cell-derived dopaminergic neurons, and mice to demonstrate that three previously identified genetic risk factors for PD, namely SATB1, MIR22HG, and GBA, are components of a single gene regulatory pathway. Our findings indicate that dysregulation of this pathway leads to the upregulation of glucocerebrosides (GluCer), which triggers a cellular senescence-like phenotype in dopaminergic neurons. Specifically, we discovered that downregulation of the transcriptional repressor SATB1 results in the derepression of the microRNA miR-22-3p, leading to decreased GBA expression and subsequent accumulation of GluCer. Furthermore, our results demonstrate that an increase in GluCer alone is sufficient to impair lysosomal and mitochondrial function, thereby inducing cellular senescence dependent on S100A9 and stress factors. Dysregulation of the SATB1-MIR22-GBA pathway, observed in both PD patients and normal aging, leads to lysosomal and mitochondrial dysfunction due to the GluCer accumulation, ultimately resulting in a cellular senescence-like phenotype in dopaminergic neurons. Therefore, our study highlights a novel pathway involving three genetic risk factors for PD and provides a potential mechanism for the senescence-induced neuroinflammation and reactive gliosis observed in both PD and normal aging.

Loss of SATB1 Induces p21-Dependent Cellular Senescence in Post-mitotic Dopaminergic Neurons

Cellular senescence is a mechanism used by mitotic cells to prevent uncontrolled cell division. As senescent cells persist in tissues, they cause local inflammation and are harmful to surrounding cells, contributing to aging. Generally, neurodegenerative diseases, such as Parkinson's, are disorders of aging. The contribution of cellular senescence to neurodegeneration is still unclear. SATB1 is a DNA binding protein associated with Parkinson's disease. We report that SATB1 prevents cellular senescence in post-mitotic dopaminergic neurons. Loss of SATB1 causes activation of a cellular senescence transcriptional program in dopamine neurons both in human stem cell-derived dopaminergic neurons and in mice. We observed phenotypes that are central to cellular senescence in SATB1 knockout dopamine neurons in vitro and in vivo. Moreover, we found that SATB1 directly represses expression of the pro-senescence factor p21 in dopaminergic neurons. Our data implicate senescence of dopamine neurons as a contributing factor in the pathology of Parkinson's disease.

Does eating good-tasting food influence body weight?

Does eating good-tasting food influence body weight? To investigate, we first established some concentrations of sucralose and mineral oil in chow that mice strongly preferred. Then, in Experiment 1, we compared groups of 16 mice fed plain chow (i.e., chow with no additives) to groups fed chow with added (a) sucralose, (b) mineral oil, (c) sucralose and mineral oil, or (d) sucralose on odd days and mineral oil on even days. During a 6-week test, the body weights and body compositions of the five groups never differed. In Experiment 2, we compared groups of 18 mice fed plain chow or plain high-fat diet to groups fed these diets with added sucralose. During a 9-week test, the high-fat diet caused weight gain, but the body weights of mice fed the sucralose-sweetened diets did not differ from those fed the corresponding plain versions. Two-cup choice tests conducted at the end of each experiment showed persisting strong preferences for the diets with added sucralose and/or mineral oil. In concert with earlier work, our results challenge the hypothesis that the orosensory properties of a food influence body weight gain. A good taste can stimulate food intake acutely, and guide selection toward nutrient-dense foods that cause weight gain, but it does not determine how much is eaten chronically.

The reaction of methyl sterculate and malvalate with silver nitrate-silica gel and its use as a basis for the estimation of cyclopropene fatty acids

When in contact with silver nitratesilica gel, methyl esters of cyclopropene fatty acids undergo ring opening to yield pairs of isomers with methylene, hydroxymethyl, or nitratomethyl side-chains at the original ring positions. Thus the main products from methyl sterculate were the methyl 9 (or 10)-methylene octadec-10 (or 8)-enoates, and, in lesser quantities, the methyl 9 (or 10)-(nitratomethyl)-octadec-9-enoates and the methyl 9 (or 10)-(hydroxymethyl)-octadec-9-enoates. Hydrogenation quantitatively converted this mixture of isomeric pairs to a mixture of methyl 9- and methyl 10-methyloctadecanoates.Chromatography on silver nitrate-silica gel, followed by gas chromatography of the hydrogenated products, has been used as the basis of a new method for estimating individual cyclopropene and cyclopropane acids in lipids.

Inhibition by cyclopropene fatty acids of the desaturation of stearic acid in hen liver

The mechanism of the hardening of body fats of animals by dietary lipids which contain cyclopropene fatty acids has been studied. Dietary methyl sterculate increased the stearic acid content of egg yolk lipid and decreased the activity of the stearic acid desaturase system of hen liver. The cyclopropene fatty acids were specific inhibitors of the stearic acid desaturase system of hen livers since other fatty acids, including two possible metabolites of sterculic acid, failed to inhibit the system at equivalent concentrations. Sterculic acid was a more effective inhibitor of the system than malvalic acid. Kinetic studies have shown that the inhibition is irreversible. Apparent kinetic constants were determined for the system.The results support the hypotheses that cyclopropene fatty acids inactivate an essential component of the desaturase system, probably by combination with-SH groups, and that this inhibition causes many of the effects of dietary cyclopropene fatty acids, including permeability disorders of eggs.

Exploring the relationship between weaning and infant mortality: an isotope case study from Aşıklı Höyük and Çayönü Tepesi

We measured stable nitrogen isotope ratios in bone collagen of 60 individuals from the early Neolithic (9th-8th millennium Cal. BC) sites of Çayönü Tepesi and Aşıklı Höyük. Our aim was to identify the duration of exclusive breastfeeding (EBF), compare this with juvenile mortality at each site, and assess whether there was a relationship between them. The isotope analysis suggests that weaning commenced at about 1 year at Aşıklı Höyük and around 2 years at Çayönü Tepesi. The mortality data show equal numbers of infant deaths up to 24 months; however, after 24 months, the mortality rate increases at Çayönü Tepesi, and a Student's t-test confirms a significant difference in infant mortality between the sites. Weaning foods prepared in the early Neolithic from agricultural crops would have had low-iron content, poor nutritional value, and would have been prepared in nonsterilized containers. Therefore, later weaned infants in early Neolithic farming settlements, although capable of some immunological response, were probably undernourished putting them at a disadvantage when encountering bacteria in their weaning food. Our results suggest that infant feeding regimes that introduced infants to weaning foods in the first year of life may have had a positive effect on their survival.

The risk of seizures after receipt of whole-cell pertussis or measles, mumps, and rubella vaccine

BACKGROUND

The administration of the diphtheria and tetanus toxoids and whole-cell pertussis (DTP) vaccine and measles, mumps, and rubella (MMR) vaccine has been associated with adverse neurologic events, including seizures. We studied the relation between these vaccinations and the risk of a first seizure, subsequent seizures, and neurodevelopmental disability in children.

METHODS

This cohort study was conducted at four large health maintenance organizations and included reviews of the medical records of children with seizures. We calculated the relative risks of febrile and nonfebrile seizures among 679,942 children after 340,386 vaccinations with DTP vaccine, 137,457 vaccinations with MMR vaccine, or no recent vaccination. Children who had febrile seizures after vaccination were followed to identify the risk of subsequent seizures and other neurologic disabilities.

RESULTS

Receipt of DTP vaccine was associated with an increased risk of febrile seizures only on the day of vaccination (adjusted relative risk, 5.70; 95 percent confidence interval, 1.98 to 16.42). Receipt of MMR vaccine was associated with an increased risk of febrile seizures 8 to 14 days after vaccination (relative risk, 2.83; 95 percent confidence interval, 1.44 to 5.55). Neither vaccination was associated with an increased risk of nonfebrile seizures. Analyses of automated data alone gave results similar to the analyses of the data from medical-record reviews. The number of febrile seizures attributable to the administration of DTP and MMR vaccines was estimated to be 6 to 9 and 25 to 34 per 100,000 children, respectively. As compared with other children with febrile seizures that were not associated with vaccination, the children who had febrile seizures after vaccination were not found to be at higher risk for subsequent seizures or neurodevelopmental disabilities.

CONCLUSIONS

There are significantly elevated risks of febrile seizures on the day of receipt of DTP vaccine and 8 to 14 days after the receipt of MMR vaccine, but these risks do not appear to be associated with any long-term, adverse consequences.

Ultraviolet radiation triggers the ribotoxic stress response in mammalian cells

The ribotoxic stress response, which is conserved between prokaryotes and eukaryotes, is a cellular reaction to cytotoxic interference with the function of the 3'-end of the large (23 S/28 S) ribosomal RNA. The 3'-end of the large rRNA is directly involved in the three sequential steps of translational elongation: the aminoacyl-tRNA binding, the peptidyl transfer, and the ribosomal translocation. In mammalian cells, the ribotoxic stress response involves activation of the stress-activated protein kinase/c-Jun NH2-terminal kinase and the p38 mitogen-activated protein kinase and transcriptional induction of immediate early genes such as c-fos and c-jun. Active ribosomes are essential mediators of the ribotoxic stress response. We demonstrate here that the transcriptional response of mammalian cells to ultraviolet radiation (UV response) displays the characteristics of a ribotoxic stress response, inasmuch as (i) the activation of stress kinases and gene expression in response to UV requires the presence of active ribosomes at the moment of irradiation; (ii) UV irradiation inhibits protein synthesis; and (iii) irradiation of cells with UV causes specific damage to the 3'-end of the 28 S rRNA. In contrast, the activation of the stress kinases by hyperosmolarity, by the DNA-cross-linking agent diepoxybutane, or by growth factors and cytokines does not depend on the presence of active ribosomes. Our results identify UV as a potential ribotoxic stressor and support the notion that some of the cellular signaling cascades in response to UV might be generated in the ribosome, possibly triggered by damage to rRNA.

Ribotoxic stress response: activation of the stress-activated protein kinase JNK1 by inhibitors of the peptidyl transferase reaction and by sequence-specific RNA damage to the alpha-sarcin/ricin loop in the 28S rRNA

Inhibition of protein synthesis per se does not potentiate the stress-activated protein kinases (SAPKs; also known as cJun NH2-terminal kinases [JNKs]). The protein synthesis inhibitor anisomycin, however, is a potent activator of SAPKs/JNKs. The mechanism of this activation is unknown. We provide evidence that in order to activate SAPK/JNK1, anisomycin requires ribosomes that are translationally active at the time of contact with the drug, suggesting a ribosomal origin of the anisomycin-induced signaling to SAPK/JNK1. In support of this notion, we have found that aminohexose pyrimidine nucleoside antibiotics, which bind to the same region in the 28S rRNA that is the target site for anisomycin, are also potent activators of SAPK/JNK1. Binding of an antibiotic to the 28S rRNA interferes with the functioning of the molecule by altering the structural interactions of critical regions. We hypothesized, therefore, that such alterations in the 28S rRNA may act as recognition signals to activate SAPK/JNK1. To test this hypothesis, we made use of two ribotoxic enzymes, ricin A chain and alpha-sarcin, both of which catalyze sequence-specific RNA damage in the 28S rRNA. Consistent with our hypothesis, ricin A chain and alpha-sarcin were strong agonists of SAPK/JNK1 and of its activator SEK1/MKK4 and induced the expression of the immediate-early genes c-fos and c-jun. As in the case of anisomycin, ribosomes that were active at the time of exposure to ricin A chain or alpha-sarcin were able to initiate signal transduction from the damaged 28S rRNA to SAPK/JNK1 while inactive ribosomes were not.

An evaluation of measles revaccination among school-entry-aged children

BACKGROUND

A two dose measles vaccination schedule is recommended routinely for all school-entry-aged children. We evaluated this recommendation by determining both measles antibody seroprevalence and the response to revaccination in seronegative children in this age group.

METHODS

Children 4 to 6 years of age who had received a single dose of measles vaccine between the ages of 15 to 17 months were tested for measles antibody by using enzyme-linked immunosorbent assay (ELISA) microneutralization technique. Seronegative children were revaccinated and again tested for measles antibody (immunoglobulin M [IgM] and neutralizing).

RESULTS

Of 679 children tested, 37 (5.4%) were seronegative. Seronegativity was not significantly associated with age, sex, race, age at initial vaccination, time since vaccination, or maternal year of birth. However, children mothers with a college degree were 12 times more likely to be seronegative than children of mothers who never attended college (P < .01). Of the 37 seronegative children, 36 seroconverted after revaccination--33 producing IgM measles antibody, suggestive of a primary immune response. The cost per seroconversion would have been an estimated $415 if all 679 children had been revaccinated.

CONCLUSIONS

Revaccination reduces the pool of children who are susceptible to measles. Although the cost per seroconversion is high, a two-dose schedule should reduce the substantial costs of controlling measles out breaks by reducing the number of outbreaks.

Changes in "inflammatory" mediators and total body water during extra-corporeal membrane oxygenation (ECMO). A preliminary study

We studied six patients (5 paediatric, 1 neonate) treated with ECMO to quantify changes in inflammatory mediators (neutrophil elastase (NE), free radical activity (FR), interleukin 8 (IL8)) and total body water (TBW). Blood samples were taken before instigation of ECMO, 4, 12, 24 hours post-ECMO and daily for six days. FR activity was quantified using the oxidised IgG FI/UV ration. NE and IL8 levels were measured by ELISA. TBW was assessed by electrical bioimpedance. Statistical analysis was made using repeated measures analysis of variance and modified t-test where appropriate. Results are presented as mean +/- standard error of the mean. FR activity increased 4 hours after instigation of ECMO (IgG FI/UV 32.1 +/- 3.2 from 24.1 +/- 3.0 p = 0.005) and remained elevated. NE also increased by 4 hours (94.8 micrograms/L +/- 8.9 to 678 micrograms/L +/- 153.4, p = 0.005) but returned to pre-ECMO values by day 6. IL8 levels rose after ECMO (from 98 pg/ml +/- 39, to 24 pg/ml +/- 117.4) although no statistical difference was noted over time due to the large variation between subjects (p = 0.009). TBW (% pre-ECMO body weight) fell by 24 hours (from 118.6 +/- 12.6 to 96.5 +/- 8.2 p = 0.0004). This study demonstrated that ECMO stimulates an 'inflammatory' response to extracorporeal perfusion (increased FR, NE) but despite this, results in a reduction in total body water. The complex relationship between the inflammatory response to prolonged extracorporeal perfusion and its effect on tissue oedema merits further investigation.

Molecular aspects of the synthesis and deposition of hens' egg yolk with special reference to low density lipoprotein

Avian egg yolk contains three main macromolecular constituents: 1) the yolk granules; insoluble particles consisting largely of lipovitellin and phosvitin. They are synthesized in response to hormones in the liver as a precursor protein, vitellogenin, which is soluble in blood. It passes through the oolemma by receptor-mediated endocytosis and is split up enzymically to give fragments that precipitate as granules in the yolk. 2) The livetins; essentially blood serum proteins. The mechanism for their transfer to yolk is not clear. 3) The yolk low density lipoprotein; the major part of yolk (60% of the dry weight). It is synthesized and assembled in the liver as a modified blood very low density lipoprotein, whose main apoprotein is apo B. As with vitellogenin, it enters yolk by endocytosis. Furthermore it is split enzymically to give most of the yolk-lipoprotein apoproteins (apovitellenins III to VI). New evidence for the relationship between yolk apoproteins and apo B has been derived from a comparison of the N-terminal amino acid sequences of apovitellenin IV and apo B.

Studies on the subunit structure of textilotoxin, a potent presynaptic neurotoxin from the venom of the Australian common brown snake (Pseudonaja textilis). 3. The complete amino-acid sequences of all the subunits

The complete amino-acid sequences of subunits A, B, C and D of textilotoxin, the presynaptic neurotoxin from the venom of the Australian common brown snake, Pseudonaja textilis, were determined. These confirmed that it is structurally the most complex of any of the known snake venom neurotoxins. Textilotoxin consists of 623 amino-acid residues in five subunits (subunit A, 118 residues; subunit B, 121 residues; subunit C, 118 residues; subunit D, two chains of 133 residues each). All subunits A, B, C and D contain the putative phospholipase A2 active site. Only subunit A showed any lethality on its own (4 mg/kg i.v. in mice). Subunit D contained two identical covalently-linked subunits and was weakly glycosylated. All subunits were necessary for maximum lethality at 1 micrograms/kg mice intraperitoneally. Details of the sequences of the subunits A, B and C are reported and interesting homology with other snake venom phospholipase A2 neurotoxins indicated.

Long-term effects of flavone acetic acid on the growth of a rat tumour

A rat tumour (MC7 sarcoma), growing subcutaneously, has been shown to be sensitive to a single application of flavone acetic acid. Thirteen rats were still alive after 50 days and 8 of these were tumour free, as compared with control rats which survived for 15.7 +/- 2.53 days. The 8 tumour free animals were rechallenged with MC7 sarcoma 40 weeks later, without further FAA treatment. The tumour grew initially but in all cases the animals became tumour free within 24 days. After a further 30 days they were rechallenged with D23 hepatoma which grew as effectively as in the controls.

Studies on the subunit structure of textilotoxin, a potent presynaptic neurotoxin from the venom of the Australian common brown snake (Pseudonaja textilis). 2. The amino acid sequence and toxicity studies of subunit D

Textilotoxin is a presynaptic neurotoxin in the venom of the Australian common brown snake, Pseudonaja textilis. It has the highest lethality and is structurally the most complex of any known snake venom neurotoxin. Reverse-phase HPLC was used to resolve textilotoxin into subunits A, B, C and D. Subunit D consists of two identical covalently linked polypeptide chains. Its sequence is now reported. It is an acidic, slightly glycosylated polypeptide of 133 amino acid residues in each chain. Although it is not itself neurotoxic, it was found to be essential for the neurotoxicity of textilotoxin.

Immunological relationships between the subunits of textilotoxin and rabbit antisera raised against textilotoxin and some snake venoms

The binding of textilotoxin and its subunits A, B, C and D to polyclonal rabbit antisera directed against textilotoxin, Australian common brown snake (Pseudonaja textilis) and tiger snake (Notechis scutatus scutatus) venoms was studied by ELISA. Subunit D showed greatest reactivity with antisera to textilotoxin and brown snake venom. The phospholipase A2 active subunit A reacted more strongly with antisera to tiger snake venom in keeping with the high degree of homology between the amino acid sequences of subunit A and notexin from tiger snake venom. Subunit A was the only subunit lethal to mice, but at doses 1000-fold greater than for textilotoxin.

Inhibition of spinal interneuronal activity by repeated cutaneous stimulation: a possible substrate of flexor reflex habituation

The responses of interneurones, situated in the lumbar region of the rat spinal cord, to repeated cutaneous stimulation, were studied. The main purpose of this investigation was to attempt to determine the extent to which habituation of the flexor reflex might be explained on the basis of a progressive development of inhibition. Spontaneously active interneurones, which were inhibited by cutaneous stimuli, were investigated in detail. In rats whose spinal cords were intact, the period of inhibition was shown to increase with successive stimuli. This increase in inhibition was directly related to the intensity and frequency of stimulation, occurred more rapidly during a second series of stimuli and was antagonized by strychnine. In spinal animals, an increase in the duration of the period of inhibition to repeated stimulation could not be demonstrated. In this preparation, a gradual decrease in inhibition occurred. It is tentatively concluded that inhibition of spinal interneurones, the development of which depends upon descending influences from supraspinal centres, may be partially responsible for habituation.

Some observations on habituation of the flexor reflex in the rat: the influence of strychnine, bicuculline, spinal transection, and decerebration

The involvement of inhibition in habituation of the flexor reflex was investigated in intact, spinal, and decerebrate rats. Strychnine and bicuculline were administered in order to determine the contribution of certain forms of central inhibition to the development of habituation. Both strychnine and bicuculline reduced habituation in the intact rat but did not do so in the spinal preparation. Strychnine, in fact, caused a facilitation of habituation in the spinal rat. The impairment of habituation by strychnine was related to the intensity of stimulation used to elicit the reflex. Thus, the effect of strychnine was only demonstrable when relatively high intensities were used. Flexor reflex habituation was shown to be more pronounced in the decerebrate than in the spinal preparation. This difference could be demonstrated only when stimuli of high intensity were given. It is concluded that, in the absence of supraspinal influences, habituation of the flexor reflex does not require inhibitory mechanisms. However, inhibition may play a role in habituation of the component of the reflex that utilizes descending influences.

Organizational response to occupational injury and disease: the case of the uranium industry

This study explores the factors associated with organizational action and inaction in the solution of an industrial health hazard. Obstructive and remedial variables are identified, measured, and tested. The research setting is the uranium mining industry, whose working population is experiencing a lung cancer epidemic due to radiation in uranium mines. The delay in actions leading to the reduction of hazardous radiation in mines is tied to national demands for uranium ore, the visibility of the hazard, and the structure of the industry. The eventual solution of the problem is shown to be affected by government pressure on uranium mining companies to purchase ventilation equipment.

Evaluation of fenitrothion for the control of malaria

Fenitrothion was evaluated for residual spraying in antimalaria programmes in a large-scale field trial near Kisumu, Kenya from 1972 to 1976. The insecticide was applied in a hyper/holoendemic malarious area of 200 km(2) inhabited by about 50 000 people. All houses and animal shelters were sprayed at a target dosage rate of 2 g/m(2) at 3-month intervals for a total of 8 consecutive spray rounds in 2 years. The malaria vectors Anopheles gambiae species A and B and A. funestus were reduced to negligible densities indoors and outdoors immediately after initiation of spraying and for 10 months after the last spray round. However, A. gambiae reappeared during the main wet season at densities high enough to reestablish low-level transmission for short periods. Spraying produced a marked and rapid decrease in both the incidence and prevalence of malaria. The daily probability of acquiring malaria infection was reduced from 0.009 before spraying to 0.0003 under spray protection, a reduction of 96%. Data collected on a longitudinal basis indicated that sustained spray protection would reduce malaria prevalence to an asymptotic limit of 6.9% under the assumption that the inoculation and recovery rates remain stable. However, to attain malaria eradication in this type of epidemiological situation, complementary measures such as mass drug administration appear to be necessary.

Nucleic acids from leaves of a yellowing and a non-yellowing variety of Festuca pratensis Huds

High molecular weight ribosomal RNA components and their pattern of loss on ageing of excised leaf sections were the same in the non-yellowing mutant and the normal genotype of Festuca pratensis even though the mutant showed retarded chlorophyll loss. Thus it appears that the genetic lesion does not extend to changes in the ribosomal RNA components of chloroplasts or cytoplasm.

A progressive and cumulative suppression of the activity of spinal neurones in the nonspinal rat

Electrical stimulation of the skin of the hindpaw of the rat, at frequencies ranging from 2 to 0.2 s-1, halted the tonic or evoked activity of spinal neurones. The duration of this effect increased with each successive stimulus until it outlasted the interstimulus interval. Tonic activity did not return immediately following termination of the stimulation, and activity was often depressed for periods of up to 5 min. Neurones displaying this behaviour were found in laminae 1 and 4--7 of the cord. Some neurones failed to demonstrate this behaviour following the administration of strychnine. This phenomenon provides a possible substrate for habituation of the flexor reflex that occurs with repetitive and noxious stimulation of the skin.

Fatty liver and kidney syndrome in chicks. II. Biochemical role of biotin

The role of biotin-dependent enzymes in the fatty liver and kidney syndrome of young chicks was studied. Under conditions of a marginal deficiency of dietary biotin, the level of biotin in the liver has differing effects on the activities of two biotin-dependent enzymes, pyruvate carboxylase and acetyl-CoA carboxylase. The activity of acetyl-CoA carboxylase is increased, but when the dietary deficiency of biotin produces biotin levels which are below 0-8 mug/g of liver, the activity of pyruvate carboxylase may be insufficient to completely metabolize pyruvate via gluconeogenesis. There is an increase in liver size and in the activities of enzymes involved in alternate pathways for the removal of pyruvate. Blood lactate accumulates and there is increased synthesis of fatty acids, and an accumulation of palmitoleic acid; these steps are accomplished by increased activities of at least the following enzymes: acetyl-CoA carboxylase, malate dehydrogenase (decarboxylating) (NADP+) and the desaturase enzyme. When the biotin level is below 0-35 mug/g of liver and the chick is subjected to a stress, physiological defence mechanisms of the chick may be inadequate to maintain homeostasis and they finally collapse, resulting in accumulation of triacylglycerol in the liver and blood; the chick is unable to maintain blood glucose levels and death occurs, often only a few hours after the imposition of the stress.

Fatty liver and kidney syndrome in chicks. I. Effect of biotin in diet

Fatty liver and kidney syndrome, a disorder of young chicks, was studied under laboratory conditions. Affected chicks had enlarged livers (hepatomegaly), an increased content of lipid in the liver, and an increased level of palmitoleic acid in the liver lipids. The disorder was observed mainly in chicks from young parent flocks, and was associated either with commerical diets which were subsequently found to be low in biotin, or with specially formulated low-biotin diets. A third factor, imposition of stress, was required to initiate the disorder. There was evidence of increased lipogenesis causing an increase of triacylglycerols in the liver lipids and an increased production of saturated fatty acids, particularly palmitic acid. Increased levels of palmitoleic acid resulted from an increased desaturation of palmitic acid. Under stress, affected chicks had low blood glucose levels, suggesting that gluconeogenesis was impaired. Since biotin-dependent enzymes are involved in both gluconeogenesis and lipogenesis, it would appear that the relevant enzymes respond differently to a deficiency of biotin.

Ribosomal RNA synthesis in the mycelium of Phycomyces blakesleeanus. High molecular weight RNA

Total RNA was extracted from 24 h old mycelia of Phycomyces blakesleeanus which had been grown in liquid culture. Heavy molecular weight RNA was fractionated on 2.6% polyacrylamide gels. 1. The main cytoplasmic ribosomal RNA fractions had molecular weights of 1.34 and 0.72-16(6). 2. [3H]Uridine pulse labelling of cultures revealed an initial ribosomal RNA precursor of molecular weight 2.5-10(6). 3. An intermediate precursor for the 1.34 - 10(6) dalton peak was found, having a molecular weight of 1.6-10(6). 4. Pulse-chase experiments, using [3H]methionine, showed the flow of synthesis as being (see article). 5. Mature 0.72-10(6) dalton RNA appeared prior to the 1.34-10(6) dalton RNA but no immediate precursor for it was detected.

Collective coping with stress: group reactions to fear, anxiety, and ambiguity

A review of studies examining the fear-affiliation relationship revealed that none had ever observed groups in interaction while awaiting a fearful event. It was predicted that such groups would, consistent with individual member's previously studied affiliative preferences, spend more time interacting in the service of social comparison needs than would groups facing anxiety or ambiguity. This prediction was strongly supported, and in addition, it was found, as expected, that groups in the fear condition developed a relatively high degree of cohesiveness as measured by intragroup attraction ratings. The implication of these results for the interpretation of the functional relationship between stress and cohesiveness was discussed.

Collective coping with stress: Group reactions to fear, anxiety, and ambiguity

A review of studies examining the fear-affiliation relationship revealed that none had ever observed groups in interaction while awaiting a fearful event. It was predicted that such groups would, consistent with individual member's previously studied affiliative preferences, spend more time interacting in the service of social comparison needs than would groups facing anxiety or ambiguity. This prediction was strongly supported, and in addition, it was found, as expected, that groups in the fear condition developed a relatively high degree of cohesiveness as measured by intragroup attraction ratings. The implication of these results for the interpretation of the functional relationship between stress and cohesiveness was discussed.

The time-course of recovery of flexor reflex responses after habituation and sensitization

(1) Habituation of the flexor was studied in unanaesthetized rats.(2) After habituation had been established as a result of the application of 500 uniform stimuli, the time-course of recovery of response was assessed. (3) Recovery was shown to be complete 9 h after the last stimulus had been applied. A linear relationship was shown to exist between the magnitude of the response to the first stimulus applied after the recovery period, and the time allowed for recovery to take place. (4) After partial or complete recovery of response, a second series of 500 stimuli was applied. The rate of habituation to this second series of stimuli was not significantly different to the rate during the initial session, but in those experiments in which the recovery period was 320 min or less, the overall levels of response during the second series were lower than those to the first. (5) Sensitization of the flexor reflex, when tested in spinal rats, was shown to be a relatively transient phenomenon. Responses fell to pre-sensitization levels within 60 sec after stimuli were withheld.

A simple flowmeter for measuring variation in the discharge rates of sprayer nozzle tips

This communication describes a method for the rapid measurement of variations in the discharge rates of nozzle tips in the field and the percentage of increase in output. This method would facilitate the establishment of a replacement schedule for nozzle tips used in spraying programmes, and periodic adjustments when new formulations of insecticides or other types of nozzle tip are supplied.

Polysomal changes in developing wheat leaves

When leaf sections of 7-day old dark grown wheat leaves were incubated in white light, they unrolled and greened. Gibberellic acid was able to replace the light requirement and abscisic acid (ABA) inhibited the response to light. The percentage of ribosomes occurring as polysomes increased in response to light but not in response to GA3 treatment. Although ABA inhibited the unrolling and greening in light, it did not cause a preferential decrease or inhibition of polysome formation.

Phytochrome and hormonal control of expansion and greening of etiolated wheat leaves

Unrolling of etiolated wheat leaf segments is stimulated by short periods of exposure to red light. Both gibberellic acid and kinetin will stimulate unrolling in the dark, whereas abscisic acid (ABA) inhibits the unrolling response to these two hormones and to red light. Exposure to 5 minutes of red light leads to a rapid increase in endogenous gibberellin levels in etiolated wheat leaves, and this increase is followed by a rapid decline. Pre-treatment with ABA inhibits the increase in gibberellin levels in response to red light, but the ihibitory effect of ABA on unrolling cannot be ascribed only to its effect on gibberellin levels. Pre-treatment with red light reduces the lag-phase in chlorophyll development when wheat leaf segments are subsequently exposed to white light; the effect of red light may be replaced by pre-treatment with kinetin, but gibberellic acid is relatively ineffective in this respect.