Melanosis of the urinary bladder

Melanosis bladder refers to the urothelium of the bladder appearing black and velvety, with microscopic evaluation describing melanin deposition. Risk factors, pathogenesis and clinical implications are unknown because only sporadic cases are reported in the literature, both with and without the presence of urinary tract symptoms or malignancy. We report a case of melanosis bladder in a male patient with voiding urinary symptoms and an untreated hypospadias.

Hydrous mantle transition zone indicated by ringwoodite included within diamond

The ultimate origin of water in the Earth's hydrosphere is in the deep Earth--the mantle. Theory and experiments have shown that although the water storage capacity of olivine-dominated shallow mantle is limited, the Earth's transition zone, at depths between 410 and 660 kilometres, could be a major repository for water, owing to the ability of the higher-pressure polymorphs of olivine--wadsleyite and ringwoodite--to host enough water to comprise up to around 2.5 per cent of their weight. A hydrous transition zone may have a key role in terrestrial magmatism and plate tectonics, yet despite experimental demonstration of the water-bearing capacity of these phases, geophysical probes such as electrical conductivity have provided conflicting results, and the issue of whether the transition zone contains abundant water remains highly controversial. Here we report X-ray diffraction, Raman and infrared spectroscopic data that provide, to our knowledge, the first evidence for the terrestrial occurrence of any higher-pressure polymorph of olivine: we find ringwoodite included in a diamond from Juína, Brazil. The water-rich nature of this inclusion, indicated by infrared absorption, along with the preservation of the ringwoodite, is direct evidence that, at least locally, the transition zone is hydrous, to about 1 weight per cent. The finding also indicates that some kimberlites must have their primary sources in this deep mantle region.

Lifestyle and metformin treatment favorably influence lipoprotein subfraction distribution in the Diabetes Prevention Program

CONTEXT

Although intensive lifestyle change (ILS) and metformin reduce diabetes incidence in subjects with impaired glucose tolerance (IGT), their effects on lipoprotein subfractions have not been studied.

OBJECTIVE

The objective of the study was to characterize the effects of ILS and metformin vs placebo interventions on lipoprotein subfractions in the Diabetes Prevention Program.

DESIGN

This was a randomized clinical trial, testing the effects of ILS, metformin, and placebo on diabetes development in subjects with IGT.

PARTICIPANTS

Selected individuals with IGT randomized in the Diabetes Prevention Program participated in the study.

INTERVENTIONS

Interventions included randomization to metformin 850 mg or placebo twice daily or ILS aimed at a 7% weight loss using a low-fat diet with increased physical activity.

MAIN OUTCOME MEASURES

Lipoprotein subfraction size, density, and concentration measured by magnetic resonance and density gradient ultracentrifugation at baseline and 1 year were measured.

RESULTS

ILS decreased large and buoyant very low-density lipoprotein, small and dense low-density lipoprotein (LDL), and small high-density lipoprotein (HDL) and raised large HDL. Metformin modestly reduced small and dense LDL and raised small and large HDL. Change in insulin resistance largely accounted for the intervention-associated decreases in large very low-density lipoprotein, whereas changes in body mass index (BMI) and adiponectin were strongly associated with changes in LDL. Baseline and a change in adiponectin were related to change in large HDL, and BMI change associated with small HDL change. The effect of metformin to increase small HDL was independent of adiponectin, BMI, and insulin resistance.

CONCLUSION

ILS and metformin treatment have favorable effects on lipoprotein subfractions that are primarily mediated by intervention-related changes in insulin resistance, BMI, and adiponectin. Interventions that slow the development of diabetes may also retard the progression of atherosclerosis.

Adaptation of a genotype 3 hepatitis E virus to efficient growth in cell culture depends on an inserted human gene segment acquired by recombination

An infectious cDNA clone of a genotype 3 strain of hepatitis E virus adapted to growth in HepG2/C3A human hepatoma cells was constructed. This virus was unusual in that the hypervariable region of the adapted virus contained a 171-nucleotide insertion that encoded 58 amino acids of human S17 ribosomal protein. Analyses of virus from six serial passages indicated that genomes with this insert, although initially rare, were selected during the first passage, suggesting it conferred a significant growth advantage. RNA transcripts from this cDNA and the viruses encoded by them were infectious for cells of both human and swine origin, the major host species for this zoonotic virus. Mutagenesis studies demonstrated that the S17 insert was a major factor in cell culture adaptation. Introduction of 54 synonymous mutations into the insert had no detectable effect, thus implicating protein, rather than RNA, as the important component. Truncation of the insert by 50% decreased the levels of successful transfection by ~3-fold. Substitution of the S17 sequence by a different ribosomal protein sequence or by GTPase-activating protein sequence resulted in a partial enhancement of transfection levels, whereas substitution with 58 amino acids of green fluorescent protein had no effect. Therefore, both the sequence length and the amino acid composition of the insert were important. The S17 sequence did not affect transfection of human hepatoma cells when inserted into the hypervariable region of a genotype 1 strain, but this chimeric genome acquired a dramatic ability to replicate in hamster cells.

A naturally occurring human/hepatitis E recombinant virus predominates in serum but not in faeces of a chronic hepatitis E patient and has a growth advantage in cell culture

Hepatitis E virus is the aetiological agent of acute hepatitis E, a self-limiting disease prevalent in developing countries. Molecular analysis of viral genomic RNA from a chronically infected patient confirmed the recent discovery that chronic infection correlated with extensive diversification of the virus quasispecies: the hypervariable region of some virus genomes in this USA patient contained large continuous deletions and a minor proportion of genomes in faeces and serum had acquired a mammalian sequence that encoded 39 aa of S19 ribosomal protein fused to the virus non-structural protein. Genomes with this insert were selected during virus passage in cultured cells to become the predominant species, suggesting that the inserted sequence promoted virus growth. The results demonstrated that hepatitis E virus can mutate dramatically during a prolonged infection and suggests it may be important to prevent or cure chronic infections before new variants with unpredictable properties arise.

Postprandial lipaemia, oxidative stress and endothelial function: a review

AIMS

Postprandial lipaemia-induced endothelial dysfunction is felt to be mediated by increases in oxidative stress. In this review, we have examined the cross-sectional relationships found among these three variables.

METHODS

We found 20 studies conducted by 16 independent investigative teams through a Medline search from 1980 to 2008; studies were required to report correlations between at least two of the three variables of interest in studies of humans. This review is divided into (i) discussions on the biomarkers and other measures of postprandial lipaemia, oxidative stress and endothelial function; (ii) associations reported among the three variables; and (iii) other considerations including alternative intervention studies.

RESULTS

Triglycerides and free fatty acids are robust and well-standardised biomarkers of lipaemia. Measures of oxidative stress ranged from electron spin techniques to measures of lipid peroxidation and are limited by lack of standardisation. Brachial artery flow-mediated dilatation is the most commonly used measure of endothelial function. The associations between postprandial lipaemia and oxidative stress and between postprandial lipaemia and endothelial function are strong and consistent. However, the association between postprandial oxidative stress and endothelial function appears weak, at least using current approaches to measurement of oxidative stress.

DISCUSSION AND CONCLUSIONS

These observations are consistent with the proposed concept that oxidative stress mediates the adverse effects of postprandial lipaemia on endothelial function; they are limited by the difficulties in measuring oxidative stress. Efforts directed at optimising and standardising the measurement of oxidative stress will be of value in future works in this area.

Insulin action in the vasculature: physiology and pathophysiology

Studies to date have provided convincing evidence that insulin has an important role in the normal functioning of the vasculature from the perspective of the regulated delivery of nutrients to a tissue bed. This is mediated by an effect on the endothelium analogous to other endothelial responses, and insulin resistance is reflected in, and in part due to, impaired vasodilatory actions of insulin. Because insulin normally stimulates the net production of nitric oxide, which is beneficial in both the short term for vasomotion and antithrombosis, and the long term for inhibition of smooth muscle cell growth and migration, vascular insulin resistance also has important implications for vascular pathophysiology. Further, recent evidence suggests that the hyperinsulinemia accompanying insulin resistance may aggravate this situation by augmenting the endothelial production and release of endothelin-1. The investigation of insulin resistance in the vasculature provides not only a unique and physiologically relevant window onto vascular pathology, but also an opportunity for therapeutic targeting in individuals affected by the clinical states of insulin resistance. The present review highlights the importance of insulin sensitivity in the maintenance of endothelial function and explores the relationships between vascular insulin resistance and whole body glucose disposal. In addition, the recent evidence linking insulin to endothelin-1 production is discussed. Improving insulin sensitivity with insulin sensitizers such as rosiglitazone may represent an important advance in our ability to improve vascular dysfunction in diabetes.

Evidence for physiological coupling of insulin-mediated glucose metabolism and limb blood flow

We hypothesized that the vasodilation observed during insulin stimulation is closely coupled to the rate of glucose metabolism. Lean (L, n = 13), obese nondiabetic (OB, n = 13), and obese type 2 diabetic subjects (Type 2 DM, n = 16) were studied. Leg blood flow (LBF) was examined under conditions of euglycemic hyperinsulinemia (EH) and hyperglycemic hyperinsulinemia (HH), which produced a steady-state whole body glucose disposal rate (GDR) of approximately 2,000 micromol. m(-2). min(-1). At this GDR, under both conditions, subjects across the range of insulin sensitivity exhibited equivalent LBF (l/min EH: L, 0.42 +/- 0.03; OB, 0.43 +/- 0. 03; Type 2 DM, 0.38 +/- 0.07; P = 0.72 by ANOVA. HH: L, 0.44 +/- 0. 04; OB, 0.39 +/- 0.05; Type 2 DM, 0.41 +/- 0.04; P = 0.71). The continuous relationship between LBF and GDR did not differ across subject groups [slope x 10(-5) l/(micromol. m(-2). min(-1)) by ANOVA. EH: L, 8.6; OB, 9.2; Type 2 DM, 7.9; P = 0.91. HH: L, 4.2; OB, 2.5; Type 2 DM, 4.1; P = 0.77], although this relationship did differ between the EH and HH conditions (P = 0.001). These findings support a physiological coupling of LBF and insulin-mediated glucose metabolism. The mechanism(s) linking substrate delivery and metabolism appears to be intact in insulin-resistant states.

Quantitative insulin sensitivity check index: a simple, accurate method for assessing insulin sensitivity in humans

Insulin resistance plays an important role in the pathophysiology of diabetes and is associated with obesity and other cardiovascular risk factors. The "gold standard" glucose clamp and minimal model analysis are two established methods for determining insulin sensitivity in vivo, but neither is easily implemented in large studies. Thus, it is of interest to develop a simple, accurate method for assessing insulin sensitivity that is useful for clinical investigations. We performed both hyperinsulinemic isoglycemic glucose clamp and insulin-modified frequently sampled iv glucose tolerance tests on 28 nonobese, 13 obese, and 15 type 2 diabetic subjects. We obtained correlations between indexes of insulin sensitivity from glucose clamp studies (SI(Clamp)) and minimal model analysis (SI(MM)) that were comparable to previous reports (r = 0.57). We performed a sensitivity analysis on our data and discovered that physiological steady state values [i.e. fasting insulin (I(0)) and glucose (G(0))] contain critical information about insulin sensitivity. We defined a quantitative insulin sensitivity check index (QUICKI = 1/[log(I(0)) + log(G(0))]) that has substantially better correlation with SI(Clamp) (r = 0.78) than the correlation we observed between SI(MM) and SI(Clamp). Moreover, we observed a comparable overall correlation between QUICKI and SI(Clamp) in a totally independent group of 21 obese and 14 nonobese subjects from another institution. We conclude that QUICKI is an index of insulin sensitivity obtained from a fasting blood sample that may be useful for clinical research.

Quantitative insulin sensitivity check index: a simple, accurate method for assessing insulin sensitivity in humans

Insulin resistance plays an important role in the pathophysiology of diabetes and is associated with obesity and other cardiovascular risk factors. The "gold standard" glucose clamp and minimal model analysis are two established methods for determining insulin sensitivity in vivo, but neither is easily implemented in large studies. Thus, it is of interest to develop a simple, accurate method for assessing insulin sensitivity that is useful for clinical investigations. We performed both hyperinsulinemic isoglycemic glucose clamp and insulin-modified frequently sampled iv glucose tolerance tests on 28 nonobese, 13 obese, and 15 type 2 diabetic subjects. We obtained correlations between indexes of insulin sensitivity from glucose clamp studies (SI(Clamp)) and minimal model analysis (SI(MM)) that were comparable to previous reports (r = 0.57). We performed a sensitivity analysis on our data and discovered that physiological steady state values [i.e. fasting insulin (I(0)) and glucose (G(0))] contain critical information about insulin sensitivity. We defined a quantitative insulin sensitivity check index (QUICKI = 1/[log(I(0)) + log(G(0))]) that has substantially better correlation with SI(Clamp) (r = 0.78) than the correlation we observed between SI(MM) and SI(Clamp). Moreover, we observed a comparable overall correlation between QUICKI and SI(Clamp) in a totally independent group of 21 obese and 14 nonobese subjects from another institution. We conclude that QUICKI is an index of insulin sensitivity obtained from a fasting blood sample that may be useful for clinical research.

Feasibility of external beam radiation for prevention of restenosis following balloon angioplasty

PURPOSE

Brachytherapy has been shown to inhibit neointima formation after vascular balloon injury. This study was done to test the feasibility of low dose external radiation for prevention of restenosis in a non-stented balloon injury model.

MATERIALS AND METHODS

Twelve red Duroc swine underwent balloon overdilation injury of both iliac arteries. Twelve Gy was delivered to one side using a Theratron T-1000 Cobalt unit with the other side used as the control. Twelve weeks post injury arteriograms were performed. The animals were then sacrificed and iliac arteries explanted. Histomorphometric analysis of arterial cross sections was performed.

RESULTS

Neointima formation was observed in all arteries. Unilateral thrombosis was noted in two animals. The mean neointimal thickness in the radiated and control arteries was 0.63 +/- 0.17 mm and 0.72 +/- 0.31 mm, respectively. The differences in minimal luminal diameter and the neointimal thickness between the two groups were not statistically significant. Complications included superficial hair loss in the radiation port in 4 animals, and 2 deaths prior to the completion date (1 of hemorrhagic enteritis possibly related to the radiation, and 1 of iliac rupture).

CONCLUSION

External radiation at this low dose is not effective in preventing vascular restenosis following balloon injury in this animal model.

Antibody to an abnormal protein in amyotrophic lateral sclerosis identifies Lewy body-like inclusions in ALS and Lewy bodies in Parkinson's disease

Ubiquitinated cytoplasmic inclusions are a characteristic feature of the neuronal pathology of neurodegenerative diseases. Immunocytochemical techniques have identified intermediate filaments associated with ubiquitin-immunoreactive inclusions in Alzheimer's disease (AD), Parkinson's disease (PD), and Pick's disease; however, no core protein has been detected in the ubiquitinated inclusions in amyotrophic lateral sclerosis (ALS). The pathogenesis of these inclusions is not known, but the inclusion may result from an accumulation of an abnormal proteins. Here we report a novel protein of 32.5 kDa detected by polyacrylamide gel electrophoresis, in the spinal cord in ALS patients. A polyclonal antibody raised against this protein and used for Western blotting, suggests that the novel protein is related to actin. Immunocytochemical studies using this antibody indicate that the protein is found in Lewy body-like inclusions in anterior horn cells of ALS, and in Lewy bodies in the substantia nigra in PD.

Expression of the human groEL stress-protein homologue in the brain and spinal cord

A monoclonal antibody (ML30), previously shown to identify a human mitochondrial protein epitope homologous with the groEL heat-shock protein of bacteria (hsp60), was used in an immunohistochemical survey of the central nervous system in patients dying with no evidence of neurological disease and in tissue from patients dying with various neurological disorders. Staining was performed on frozen tissue sections and on formalin fixed, paraffin embedded tissue. Astrocytes in all areas showed a strong pattern of punctate granular staining, which was increased in astrocytes showing reactive changes. Oligodendrocytes stained lightly in a diffuse granular pattern as did most neurons. Ependymal cells showed apical granular positivity. Expression of the hsp60 epitope recognised by ML30 was not seen in ubiquitinated inclusion bodies in motor neuron disease, neurofibrillary tangles in Alzheimer's disease or Lewy bodies in Parkinson's disease. The epitope recognised by ML30 was stable after formalin fixation and in post mortem tissue up to 96 h after death. Expression of the human groEL stress-protein homologue in brain and spinal cord is consistent with a mitochondrial location and may provide a morphological indicator of the functional or metabolic state of cells, especially glial cells.

Heterotopic neurons in amyotrophic lateral sclerosis

Heterotopic neurons in ALS have suggested aberrant neuronal migration during development. We studied 10 cases with ALS, 10 normal controls, and 10 cases with anterior horn cell disease, including spinal muscular atrophy and acute and remote poliomyelitis. There was no excess of heterotopic neurons in ALS compared with either control group and therefore no failure of neuronal migration in ALS.

Expression of heat shock protein epitopes in renal disease

We have examined the immunohistochemical pattern of staining with antibodies to the 72 kD heat shock protein (HSP72) and ubiquitin in 28 cases of human renal disease. Three distinct patterns of staining were seen with the use of an antibody to HSP72: tubular, intraluminal and interstitial. No glomerular staining was detected. In no cases were ubiquitin epitopes detected. The pattern of staining was most strongly related to the activity of the disease process, positive staining often being present in relation to agents or processes known to upregulate stress protein expression in experimental isolated cellular systems. Stress protein upregulation in human renal disease may represent cellular attempts at cytoprotection in conditions of active sublethal cell toxicity.

Histochemical and immunocytochemical study of ubiquitinated neuronal inclusions in amyotrophic lateral sclerosis

Ubiquinated cytoplasmic inclusions are a characteristic feature of the anterior horn cell pathology of amyotrophic lateral sclerosis. The underlying abnormality leading to the production of these inclusions in this neurodegenerative motor system disease is unknown. Despite the application of a wide range of histochemical and immunocytochemical techniques we have been unable to identify a core constituent protein in these intraneuronal inclusions. A novel approach to this problem is required.

Purkinje cell toxicity of beta-aminopropionitrile in the rat

Compounds causing neurolathyrism are putative aetiological agents in neurodegenerative disorders including amyotrophic lateral sclerosis. beta-Aminopropionitrile (BAPN) is one such compound. We have administered this lathyrogenic agent at a dose of 1 g/kg by the intraperitoneal route in experiments in adult Sprague-Dawley rats during a period of 10 weeks. The rats developed marked kyphoscoliosis, ataxia with paralysis and muscle wasting of the hind limbs. Vacuolation and loss of Purkinje cells developed, but no anterior horn cell degeneration was noted. Immunohistochemical studies of phosphorylated neurofilaments and the 72 kDa heat shock protein were normal and no intraneuronal ubiquitinated inclusions were seen. High-dose intraperitoneal BAPN in the rat causes Purkinje cell changes, but no other central nervous system abnormalities.

Heat shock protein expression in corpora amylacea in the central nervous system: clues to their origin

Small bodies expressing epitopes of the 72 kD heat shock protein (HSP) have been identified in the brain and spinal cord in normal and neurologically abnormal individuals. These bodies resemble the 'pre-corpora amylacea' (pre-CA), thought to be the primary structure in the development of the mature body. Corpora amylacea are laminated hyaline bodies composed of polyglucosans. They are found in larger numbers with increasing age in the brain and spinal cord. Mature, histologically 'classical', corpora amylacea express epitopes of HSP chiefly at the periphery of the corpus, whilst smaller immature 'pre-corpora' stain intensely throughout the entire structure. A heat shock or stress response in neurons and glial cells may be part of the cellular reaction to accumulation of abnormal products.

Stress protein inclusions in cerebral vessels in dialysis encephalopathy

Dialysis encephalopathy, a complication of long-term haemodialysis, is a syndrome characterized by progressive dementia, myoclonus, dysarthria and ataxia associated with high serum and brain levels of aluminium. Expression of heat-shock or stress proteins, including ubiquitin can be induced in cell culture experiments by aluminium. We report immunohistochemical studies of heat shock protein (HSP) expression in the frontal cortex of three patients with dialysis dementia. Immunolabelling with antibody to the 72 kD heat shock protein revealed punctate granules in most endothelial cells of cortical vessels in patients with dialysis encephalopathy. These granules, 1-5 microns in diameter, aggregated to form inclusions that resembled stress-granules, typically induced in plant or animal cell culture by repeated insult. These granules did not express epitopes of ubiquitin. They were rare in endothelial cells in the brains of subjects dying with other neurological disorders or of non-neurological causes. We suggest that these stress granules represent a toxic response of endothelial cells in the brain to aluminium.

Expression of heat shock protein epitopes in tubular aggregates

Tubular aggregates may be found in a variety of conditions and have been associated with a wide range of chemical and ischemic insults. We report clinical and histological features in a case of myopathy with tubular aggregates. The structure of these tubular aggregates was examined using antibodies to cytoskeletal proteins and heat shock proteins. Epitopes of the 72 kD heat shock protein were expressed in the areas of abnormality in this case and in a case of hypokalemic periodic paralysis with tubular aggregates. Heat shock proteins have a role in the modulation of the tertiary structure of proteins and may be involved in the pathogenesis of tubular aggregates and other microtubular abnormalities in muscle.

Myopathy of internal anal sphincter with polyglucosan inclusions

In two members of an affected family with a hereditary syndrome of proctalgia fugax and constipation, a hypertrophied internal anal sphincter was found with histological features suggesting a myopathy of this muscle. In these two patients, and in an unrelated patient with a similar clinical syndrome, smooth muscle fibres of the internal anal sphincter showed numerous vacuoles, many of which contained ovoid inclusion bodies. The structural features and histochemical reactions of the inclusion bodies were consistent with a polyglucosan composition. Histological examination of the internal anal sphincter may reveal smooth muscle abnormalities in functional bowel disorders.

Microdissection: a novel method for the study of intracellular inclusion bodies

The purification of many intracellular and extracellular inclusions is often difficult to achieve due to the low concentration of the abnormalities in the tissue under study, or due to the degradation of components during extraction. We describe the use of microdissection for the isolation of neurons and intraneuronal inclusion bodies. The resulting suspension may be used for biochemical, immunological or ultrastructural studies. The technique is applicable to the study of a wide range of cellular abnormalities.

Consequences of stabilising selection for polygenic variation

A number of earlier authors have investigated the consequences for fitness of gene differences affecting the expression of a primary character where stabilising selection is acting in favour of an optimal expression. Assuming that the mean expression must be at or close to the optimum, deviations from the mean have been taken as measures of the deviation from the optimum, and the conclusion reached that, random drift apart, stabilising selection must ultimately lead to fixation of the commoner allele. It is now shown that this approach is incorrect: in an illustrative example the mean cannot be taken as synonymous with the optimum except in the trivial case where they have precisely the same value. Where the mean departs from the optimum, even by sampling variation only, continuing selection for it is effectively self-propagating and directional away from the optimum. Deviation from the optimum itself must be used in investigating the consequences of stabilising selection. The model used here is based on the biometrical description of the effects of a gene difference on a quantitative character as used by Mather and Jinks (1982). This includes a parameter, h, which allows dominance of any magnitude in either direction to be taken into account, and is adapted for the present purpose by introducing an additional parameter, m, measuring the departure from the optimum of the mid-point, or mid-parent, which is used biometrically as the origin for measurement of the gene effects. Assuming random mating and the absence of epistasis in the effects on the primary character, it is shown that stabilising selection acting on a pair of alleles (A and a) can have any one of three possible outcomes depending on the relative values of the m and h which characterise the effects of the gene difference on the primary character, viz: (i) a stable equilibrium in the population where in respect of the primary character Aa is nearer to the optimum than both homozygotes; (ii) fixation of the fitter allele where Aa is intermediate between the homozygotes in its departure from the optimum; (iii) a theoretical unstable equilibrium leading to fixation of the commoner allele, where Aa departs further from the optimum than both homozygotes. Only outcome (i) can lead to the conservation of variation in the population. Preliminary consideration is also given to the interaction in effect on fitness of two gene pairs affecting the same character and segregating simultaneously in the population.(ABSTRACT TRUNCATED AT 400 WORDS)

Joint scaling tests

It is shown that a joint scaling test developed by Tan (1974) is closely related to the widely used standard Cavalli joint scaling test (described by Mather and Jinks, 1971) which was not referred to in Tan's paper. With the numbers of individuals per generation observed in practice, the two tests give essentially similar results. The Cavalli procedure also provides estimates of genetical parameters and is more readily extended to a wider range of situations.

Genotype x environment interactions. IV. The effect of the background genotype

Experimental evidence from sternopleural chaeta number and yield of offspring in Drosophila melanogaster bears out the expectation (Mather, 1975) that the value of the regression of g, measuring genotype X environment interaction, on e, measuring the overall effect of environmental change , depends on genes in which the contrasting genotypes are alike as well as on the genes in which they differ. With yield of offspring there is evidence of some genotypes reacting to the environmental changes in the opposite direction to others.

Genotype--environment interaction. III. Interactions in Drosophila melanogaster

The responses of two characters, number of sternopleural chaetae and total yield of offspring (which depends on the mother’s genotype), to change in the temperature at which the flies were raised and type of culture container in which they bred were followed in the two inbred lines, Wellington (Well) and Samarkand (Sam). In respect of chaeta number Well was more sensitive to change of the environment than Sam, which furthermore responded in the opposite direction to Well. In respect of yield of offspring the two lines responded similarly. The genetic control of these responses to environmental change was investigated by using the eight substitution lines which comprise all the possible true breeding combinations of the three major chromosomes (X, II and III) from Well and Sam. Two experiments were carried out, the first a diallel experiment at three temperatures (18, 21.5 and 25 °C), and the second an experiment in which the eight lines were raised in nine environments comprising all combinations of the three temperatures and three types of culture. Chaeta number changes more with temperature than with type of culture, whereas the reverse is true of yield of offspring. In respect of chaeta number the genes chiefly responsible for response to environmental change are borne on a different chromosome (II) than those chiefly responsible for variation in mean chaeta number (III), and there are indications of a similar situation in respect of yield of offspring. It is concluded that different characters are separately adjustable by selection in their responses to enviromental change, that sensitivity of a character to environmental change is adjustable separately from mean expression of the character, and that the detailed patterns of response to a range of environments (e. g. temperatures) are separable from the magnitude of the overall change induced by these environments.

Genotype X environment interactions. II. Some genetical considerations

An algebraic formulation, alternative to that of Mather and Jones (1958) and hierarchial rather than factorial in nauture, is presented for describing the differences among the phenotypes produced by a number of genotypes each grown in each of a number of environments. This formuationdoes not include terms representing statistical interactions between genotypes and environments: it depends instead on comparisons between the different genotypes in their variation over the relevant ranges of environemnts. The two-line case is considered ant eht condition established for linearity of the regress ion of genotype X enviroment interaction (g in Mather and Jones' formulation) on overall effect of the envirronment (e in Mather and Jones' formulation)...

Variability and selection

Genetics has had a chequered career in the hundred years that have elapsed since Mendel published the paper in which he laid the methodological as well as the conceptual foundation for the science as we have come to know it. For the first thirty years or so the paper was ignored. It was ignored because it was out of keeping with the times, not perhaps so much in its concept of particulate inheritance (with which Galton at any rate was toying at one stage), but in the nature of its experimental approach. With the twentieth century both concepts and methods were accepted and developed: the new science, conceived in Mendel’s frustration and born into Bateson’s and Pearson’s strife, grew lustily. Yet for several further decades genetics was still not accepted into the main stream of biology. True, it attested the power of its techniques by the speed of its growth and it developed a theoretical structure more reminiscent of the physical sciences than of its contemporary biology. It opened up new vistas and in principle it promised to shed new light on the central problems of biology—evolution and development. But in practice it seemed to remain remote, dealing in its own currency of patho­logical effects instead of constructive adaptations, and abstract entities instead of analysable processes. Happily this has changed, as our Symposium bears witness. Genetics is no longer isolated, but at the core of biology. It is becoming recognized—albeit at times a little reluctantly—as having a necessary, if not of itself sufficient, part to play in our approach to all the great problems of biology. This change has come about primarily because genetics itself has grown, and grown in two directions. One of these has been in the analysis of mechanisms and materials of heredity. The abstract factor which Mendel postulated to explain the relation he found between parent and offspring has become a message coded into the macromolecule of DNA by the arrangement of its bases, and the hypothetical connexion between genotype and phenotype is materializing in RNA , cytoplasmic elements and protein synthesis. We are moving into the position where we can begin to give an account of development and its associated differentiation.