Genetic associations with longevity are on average stronger in females than in males

It is long observed that females tend to live longer than males in nearly every country. However, the underlying mechanism remains elusive. In this study, we discovered that genetic associations with longevity are on average stronger in females than in males through bio-demographic analyses of genome-wide association studies (GWAS) dataset of 2178 centenarians and 2299 middle-age controls of Chinese Longitudinal Healthy Longevity Study (CLHLS). This discovery is replicated across North and South regions of China, and is further confirmed by North-South discovery/replication analyses of different and independent datasets of Chinese healthy aging candidate genes with CLHLS participants who are not in CLHLS GWAS, including 2972 centenarians and 1992 middle-age controls. Our polygenic risk score analyses of eight exclusive groups of sex-specific genes, analyses of sex-specific and not-sex-specific individual genes, and Genome-wide Complex Trait Analysis using all SNPs all reconfirm that genetic associations with longevity are on average stronger in females than in males. Our discovery/replication analyses are based on genetic datasets of in total 5150 centenarians and compatible middle-age controls, which comprises the worldwide largest sample of centenarians. The present study's findings may partially explain the well-known male-female health-survival paradox and suggest that genetic variants may be associated with different reactions between males and females to the same vaccine, drug treatment and/or nutritional intervention. Thus, our findings provide evidence to steer away from traditional view that "one-size-fits-all" for clinical interventions, and to consider sex differences for improving healthcare efficiency. We suggest future investigations focusing on effects of interactions between sex-specific genetic variants and environment on longevity as well as biological function.

The correlation of copy number variations with longevity in a genome-wide association study of Han Chinese

Copy number variations (CNVs) have been shown to cause numerous diseases, however, their roles in human lifespan remain elusive. In this study, we investigate the association of CNVs with longevity by comparing the Han Chinese genomes of long-lived individuals from 90 to 117 years of age and the middle-aged from 30 to 65. Our data demonstrate that the numbers of CNVs, especially deletions, increase significantly in a direct correlation with longevity. We identify eleven CNVs that strongly associate with longevity; four of them locate in the chromosome bands, 7p11.2, 20q13.33, 19p12 and 8p23.3 and overlap partially with the CNVs identified in long-lived Danish or U.S. populations, while the other seven have not been reported previously. These CNV regions encode nineteen known genes, and some of which have been shown to affect aging-related phenotypes such as the shortening of telomere length (ZNF208), the risk of cancer (FOXA1, LAMA5, ZNF716), and vascular and immune-related diseases (ARHGEF10, TOR2A, SH2D3C). In addition, we found several pathways enriched in long-lived genomes, including FOXA1 and FOXA transcription factor networks involved in regulating aging or age-dependent diseases such as cancer. Thus, our study has identified longevity-associated CNV regions and their affected genes and pathways. Our results suggest that the human genome structures such as CNVs might play an important role in determining a long life in human.

Sex Differences in Genetic Associations With Longevity

IMPORTANCE

Sex differences in genetic associations with human longevity remain largely unknown; investigations on this topic are important for individualized health care.

OBJECTIVE

To explore sex differences in genetic associations with longevity.

DESIGN SETTING AND PARTICIPANTS

This population-based case-control study used sex-specific genome-wide association study and polygenic risk score (PRS) analyses to examine sex differences in genetic associations with longevity. Five hundred sixty-four male and 1614 female participants older than 100 years were compared with a control group of 773 male and 1526 female individuals aged 40 to 64 years. All were Chinese Longitudinal Healthy Longevity Study participants with Han ethnicity who were recruited in 1998 and 2008 to 2014.

MAIN OUTCOMES AND MEASURES

Sex-specific loci and pathways associated with longevity and PRS measures of joint effects of sex-specific loci.

RESULTS

Eleven male-specific and 11 female-specific longevity loci (P < 10-5) and 35 male-specific and 25 female-specific longevity loci (10-5 ≤ P < 10-4) were identified. Each of these loci's associations with longevity were replicated in north and south regions of China in one sex but were not significant in the other sex (P = .13-.97), and loci-sex interaction effects were significant (P < .05). The associations of loci rs60210535 of the LINC00871 gene with longevity were replicated in Chinese women (P = 9.0 × 10-5) and US women (P = 4.6 × 10-5) but not significant in Chinese and US men. The associations of the loci rs2622624 of the ABCG2 gene were replicated in Chinese women (P = 6.8 × 10-5) and European women (P = .003) but not significant in both Chinese and European men. Eleven male-specific pathways (inflammation and immunity genes) and 34 female-specific pathways (tryptophan metabolism and PGC-1α induced) were significantly associated with longevity (P < .005; false discovery rate < 0.05). The PRS analyses demonstrated that sex-specific associations with longevity of the 4 exclusive groups of 11 male-specific and 11 female-specific loci (P < 10-5) and 35 male-specific and 25 female-specific loci (10-5 ≤P < 10-4) were jointly replicated across north and south discovery and target samples. Analyses using the combined data set of north and south showed that these 4 groups of sex-specific loci were jointly and significantly associated with longevity in one sex (P = 2.9 × 10-70 to 1.3 × 10-39) but not jointly significant in the other sex (P = .11 to .70), while interaction effects between PRS and sex were significant (P = 4.8 × 10-50 to 1.2 × 10-16).

CONCLUSION AND RELEVANCE

The sex differences in genetic associations with longevity are remarkable, but have been overlooked by previously published genome-wide association studies on longevity. This study contributes to filling this research gap and provides a scientific basis for further investigating effects of sex-specific genetic variants and their interactions with environment on healthy aging, which may substantially contribute to more effective and targeted individualized health care for male and female elderly individuals.

Understanding the genetics of APOE and TOMM40 and role of mitochondrial structure and function in clinical pharmacology of Alzheimer's disease

The methodology of Genome-Wide Association Screening (GWAS) has been applied for more than a decade. Translation to clinical utility has been limited, especially in Alzheimer's Disease (AD). It has become standard practice in the analyses of more than two dozen AD GWAS studies to exclude the apolipoprotein E (APOE) region because of its extraordinary statistical support, unique thus far in complex human diseases. New genes associated with AD are proposed frequently based on SNPs associated with odds ratio (OR) < 1.2. Most of these SNPs are not located within the associated gene exons or introns but are located variable distances away. Often pathologic hypotheses for these genes are presented, with little or no experimental support. By eliminating the analyses of the APOE-TOMM40 linkage disequilibrium region, the relationship and data of several genes that are co-located in that LD region have been largely ignored. Early negative interpretations limited the interest of understanding the genetic data derived from GWAS, particularly regarding the TOMM40 gene. This commentary describes the history and problem(s) in interpretation of the genetic interrogation of the "APOE" region and provides insight into a metabolic mitochondrial basis for the etiology of AD using both APOE and TOMM40 genetics.

Interaction Between the FOXO1A-209 Genotype and Tea Drinking Is Significantly Associated with Reduced Mortality at Advanced Ages

On the basis of the genotypic/phenotypic data from Chinese Longitudinal Healthy Longevity Survey (CLHLS) and Cox proportional hazard model, the present study demonstrates that interactions between carrying FOXO1A-209 genotypes and tea drinking are significantly associated with lower risk of mortality at advanced ages. Such a significant association is replicated in two independent Han Chinese CLHLS cohorts (p = 0.028-0.048 in the discovery and replication cohorts, and p = 0.003-0.016 in the combined dataset). We found the associations between tea drinking and reduced mortality are much stronger among carriers of the FOXO1A-209 genotype compared to non-carriers, and drinking tea is associated with a reversal of the negative effects of carrying FOXO1A-209 minor alleles, that is, from a substantially increased mortality risk to substantially reduced mortality risk at advanced ages. The impacts are considerably stronger among those who carry two copies of the FOXO1A minor allele than those who carry one copy. On the basis of previously reported experiments on human cell models concerning FOXO1A-by-tea-compounds interactions, we speculate that results in the present study indicate that tea drinking may inhibit FOXO1A-209 gene expression and its biological functions, which reduces the negative impacts of FOXO1A-209 gene on longevity (as reported in the literature) and offers protection against mortality risk at oldest-old ages. Our empirical findings imply that the health outcomes of particular nutritional interventions, including tea drinking, may, in part, depend upon individual genetic profiles, and the research on the effects of nutrigenomics interactions could potentially be useful for rejuvenation therapies in the clinic or associated healthy aging intervention programs.

The role of brain-derived neurotrophic factor receptors in the mature hippocampus: modulation of long-term potentiation through a presynaptic mechanism involving TrkB

The neurotrophin BDNF has been shown to modulate long-term potentiation (LTP) at Schaffer collateral-CA1 hippocampal synapses. Mutants in the BDNF receptor gene trkB and antibodies to its second receptor p75NTR have been used to determine the receptors and cells involved in this response. Inhibition of p75NTR does not detectably reduce LTP or affect presynaptic function, but analyses of newly generated trkB mutants implicate TrkB. One mutant has reduced expression in a normal pattern of TrkB throughout the brain. The second mutant was created by cre-loxP-mediated removal of TrkB in CA1 pyramidal neurons of this mouse. Neither mutant detectably impacts survival or morphology of hippocampal neurons. TrkB reduction, however, affects presynaptic function and reduces the ability of tetanic stimulation to induce LTP. Postsynaptic glutamate receptors are not affected by TrkB reduction, indicating that BDNF does not modulate plasticity through postsynaptic TrkB. Consistent with this, elimination of TrkB in postsynaptic neurons does not affect LTP. Moreover, normal LTP is generated in the mutant with reduced TrkB by a depolarization-low-frequency stimulation pairing protocol that puts minimal demands on presynaptic terminal function. Thus, BDNF appears to act through TrkB presynaptically, but not postsynaptically, to modulate LTP.

High-voltage-activated calcium channel messenger RNA expression in the 140-3 neuroblastoma-glioma cell line

Expression of calcium channel alpha1 subunits in oocytes or cell lines has proven to be a powerful method in the analysis of structure-function relations, but these experimental systems are of limited value in the examination of neuron-specific functions such as transmitter release. Cell lines derived from neurons are often capable of these functions, but their intrinsic calcium channel alpha1 subunits are complicating factors in experimental design. We have examined the biophysical and molecular properties of calcium channels in a little studied neuroblastoma-glioma hybrid cell line, 140-3, a close relative of the NG108-15 cell line, to test whether this cell line might serve a role as an expression system for neural mechanisms. This cell was selected as it contains an intact transmitter release mechanism yet secretes little in response to depolarization. Patch-clamp recording revealed only a prominent low-threshold, rapidly inactivating calcium current with a single-channel conductance of approximately 7 pS that was identified as T type. A search for calcium channel alpha1 subunit messenger RNA in the 140-3 cells with three different tests only revealed alpha1C, whereas alpha1A-alpha1C were present in the parent NG108-15 line. We made a particular effort to search for alpha1E, since this subunit has been associated with a low-voltage-activated current. Our findings suggest that, since the principal nerve terminal-associated calcium channels (alpha1A, alpha1B, alpha1E) are absent in the 140-3 cell, this cell line may prove a particularly useful model for the analysis of the role of high-voltage-activated calcium channels in complex functions of neuronal cells.

Impairments in high-frequency transmission, synaptic vesicle docking, and synaptic protein distribution in the hippocampus of BDNF knockout mice

Brain-derived neurotrophic factor (BDNF) promotes long-term potentiation (LTP) at hippocampal CA1 synapses by a presynaptic enhancement of synaptic transmission during high-frequency stimulation (HFS). Here we have investigated the mechanisms of BDNF action using two lines of BDNF knockout mice. Among other presynaptic impairments, the mutant mice exhibited more pronounced synaptic fatigue at CA1 synapses during high-frequency stimulation, compared with wild-type animals. Quantitative analysis of CA1 synapses revealed a significant reduction in the number of vesicles docked at presynaptic active zones in the mutant mice. Synaptosomes prepared from the mutant hippocampus exhibited a marked decrease in the levels of synaptophysin as well as synaptobrevin [vesicle-associated membrane protein (VAMP-2)], a protein known to be involved in vesicle docking and fusion. Treatment of the mutant slices with BDNF reversed the electrophysiological and biochemical deficits in the hippocampal synapses. Taken together, these results suggest a novel role for BDNF in the mobilization and/or docking of synaptic vesicles to presynaptic active zones.

Presynaptic modulation of synaptic transmission and plasticity by brain-derived neurotrophic factor in the developing hippocampus

In addition to the regulation of neuronal survival and differentiation, neurotrophins may play a role in synapse development and plasticity. Application of brain-derived neurotrophic factor (BDNF) promotes long-term potentiation (LTP) in CA1 synapses of neonatal hippocampus, which otherwise exhibit only short-term potentiation. This is attributable, at least in part, to an attenuation of the synaptic fatigue induced by high-frequency stimulation (HFS). However, the prevention of synaptic fatigue by BDNF could be mediated by an attenuation of synaptic vesicle depletion from presynaptic terminals and/or a reduction of the desensitization of postsynaptic receptors. Here we provide evidence supporting a presynaptic effect of BDNF. The effect of BDNF on synaptic fatigue depended on the stimulation frequency, not on the stimulus duration nor on the number of stimulation pulses. BDNF was only effective when the synapses were stimulated at frequencies >50 Hz. Treatment with BDNF also potentiated paired-pulse facilitation (PPF), a parameter reflecting changes in the properties of presynaptic terminals. This effect of BDNF was restricted only to PPF elicited with interpulse intervals </=20 msec. Changes in the extracellular calcium concentration altered the magnitude of the BDNF effect on PPF and synaptic responses to HFS, suggesting that BDNF regulates neurotransmitter release. When the desensitization of glutamate receptors was blocked by cyclothiazide or aniracetam, the BDNF potentiation of the synaptic responses to HFS was unaltered. Taken together, these results suggest that BDNF acts presynaptically. When two pathways in the same slice were monitored simultaneously, BDNF treatment potentiated the tetanized pathway without affecting the synaptic efficacy of the untetanized pathway. The selective potentiation of high-frequency transmission by BDNF appears to contribute directly to the effect of BDNF on LTP rather than indirectly by inducing the release of additional diffusible factors. The preferential potentiation of highly active synapses by BDNF may have implications in the Hebbian mechanism of synaptic plasticity.

[Atypical symptoms in patients with germinal testicular tumors]

The cardinal syndrome of a testicular germ cell tumour is typically scrotal enlargement. The present paper compares the group of patients with typical scrotal presentation and those who present with atypical symptoms caused by metastases. Among 284 retrospectively studied patients, 34 (12%) presented with extrascrotal symptoms. The most important were abdominal pain (n = 16) and pulmonary symptoms (n = 10). The group of patients with extrascrotal symptoms was characterized by the following parameters: percentage of pure seminoma in 35% (versus 56% in the patients with typical presentation), elevation of alpha-feto-protein in 47% (versus 27%), and elevation of beta-HCG in 61% (versus 29%). The outcome was lethal in 35% of the patients with atypical presentation, as opposed to 6% of those with typical presentation. In 22 patients with extrascrotal presenting signs a palpable testicular mass was found on clinical examination. Occult testicular tumour proved to be present in 9 patients, and burned-out tumours in 3. Unawareness of testicular cancer is a significant factor in diagnostic delay. Scrotal palpation should be part of every clinical examination in younger male patients with cancer from an unknown primary.

Phytotron experiments in Pisum : 1. Influence of temperature on the flowering behaviour of different genotypes

The flowering behaviour of 17 Pisum mutants and 20 recombinants was studied under three different temperatures using long-day phytotron conditions. A constant low temperature of 12.5 ° C led to a strong delay in flowering in all the genotypes tested but distinct relative differences could be found between them. Relative differences were also present with regard to speed of ontogenetic development under a permanent high temperature of 25.5 °C or under an alternating change between low and high temperature. Under the low temperature, recombinants R 20D and R 20E, carrying gene efr for earliness, entered the flowering period more than 4 weeks later than the donor of efr, demonstrating thereby a negative influence of one of the other mutant genes on efr. The high temperature of 25 °C influenced the flowering behaviour of 4 fasciated genotypes negatively - in contrast to the other strains studied. The plants of recombinant R 405 produced only tiny flower buds under these conditions. None of the plants of recombinant R 142F flowered under either the constant low or high temperature - they need the change of low and higher temperature for normal flower formation. The experiments show that most of the genotypes tested react specifically to the three temperature conditions offered to them.

Cancer pain relief using chronic morphine infusion. Early experience with a programmable implanted drug pump

Fourteen patients were implanted with drug pumps to provide chronic epidural or intrathecal morphine to relieve pain due to cancer. A new programmable pump was used in seven of the patients and a constant infusion device was used in the other seven patients. Results, judged by subjective pain reports (on a 0 to 10 scale), decrease in oral narcotics, and change in activity level, were excellent in eight patients, good in five patients, and poor in one patient. The programmable device has the obvious advantage of being able to vary dose according to patient need and requires less frequent refilling. Four programmable pump failures occurred, two requiring replacement.

Gene-ecological investigations in Pisum mutants : Part 2: comparative performance in Germany and North India

Six mutants and nine recombinants of Pisum sativum were grown along with the mother variety at Kurukshetra, North India. The findings obtained were compared with those obtained for the same material grown at Bonn, Germany. The following observations were made.Stem length and degree of branching are influenced differentially in the various genotypes tested in India as a consequence of a specific reaction of the genes to the climatic conditions. A gene for weak stem fasciation and gene efr for earliness in a specific gene combination are unable to express their action in North India whereas they are fully active in Germany. Furthermore, in Kurukshetra early flowering of some recombinants does not result in early ripening because their seeds require about double the time for full ripening than those of the mother variety.At Kurukshetra, recombinant R 674A proved to be highly heat susceptible. All the plants died in early stages of ontogenetic development. Four other genotypes died due to heat before completing seed ripening. One mutant and three recombinants were found to be more tolerant to powdery mildew attack than the mother variety and Indian local lines. The seed production of eight genotypes in relation to that of the initial line was essentially better in North India than in Germany. They are obviously better adapted to the semi-arid conditions. Some of them appear to be useful for pea breeding in India. In contrast, a fasciated mutant, high yielding in Germany, is not able to express this potentiality at Kurukshetra. At Udaipur (Rajasthan, Western India), this mutant is unable to flower. Another four genotypes, tested at both Indian locations, exhibited an essentially poorer seed production at Udaipur than at Kurukshetra due to some ecological factors.The findings indicate a specific response of some of the genotypes tested to the specific ecological conditions of the three locations, their response differing from that of the mother variety demonstrating thereby a different adaptational optimum.

Effects of monitoring high-risk pregnancies and intrapartum FHR monitoring on perinates

A protocol of chronic antepartum surveillance was initiated at the University of Illinois hospitals in 1973 to assess the impact on perinatal mortality. At the same time, a policy of unselected fetal heart rate (FHR) monitoring was initiated to judge the effect on the intrapartum stillbirth rate. The impact of both programs played a significant role in the decline of perinatal mortality rates for infants weighing more than 1 500 g, from 21.1/1 000 births in 1970--1971 to 14.4/1 000 births in the monitored years 1973 and 1974 (p less than 0.02).

Interactions between carotid sinus mechanoreceptor and chemoreceptor reflex loops

Our experiments were designed to evaluate the combined influence of the mechanoreceptor and chemoreceptor control loops on the cardiovascular and respiratory systems. Both carotid sinus areas were isolated by a complete blind sac preparation in chloralose anesthetized dogs in which a flow probe had been implanted previously on the ascending aorta. The following variables were continuously monitored: central aortic pressure, heart rate, cardiac output, vascular resistance of a hind limb, tidal volume, respiratory rate, and oxygen consumption. While one sinus was submitted to step changes of pressure, the opposite sinus was kept at constant mean pressure. In addition, one sinus was perfused with either oxygenated of deoxygenated blood at constant flow rate. These studies show a definite interaction between the control loops initiated by the carotid sinus mechanoreceptors and those initiated by the chemoreceptors. The influence of the chemoreceptors is most marked in the peripheral beds, where it shifts the whole response curve of the mechanoreceptor control loop upward. This response accounts for most of the upward shift of the pressure response curve. On the other hand, the mechanoreceptor loop affects the ventilation, but this effect is range dependent, being most marked for the low pressure perfusion of the carotid sinus.

The influence of mutated genes on sporogenesis : A survey on the genetic control of meiosis in Pisum sativum

The course of meiosis in higher plants is controlled by a large number of genes, the function of which can be discerned by means of mutants showing any kind of meiotic anomaly. In general, there are three main groups of genes belonging to this system. The as-genes control the pairing behaviour of the homologous chromosomes, causing asynapsis in the mutated condition. The ds-genes are responsible for chiasma formation and chiasma frequency, causing desynapsis in the mutated condition. As- and ds-genes influence micro- and macrosporogenesis in a similar way but the ms-genes become effective only in microsporogenesis, resulting in a complete breakdown of meiosis at a stage specific for each gene of the group.In Pisum sativum, 58 mutants showing genetically conditioned meiotic anomalies have been cytogenetically analysed: 34 of them belong to the ds- and 7 to the as-group; one gene causes asynaptic as well as desynaptic effects; 13 genotypes are male sterile due to degeneration of the chromosomes; the remaining 3 genes cause less specific meiotic disturbances. The lethality of a mutant can be overcome by distinct environmental conditions but the mutant is sterile because of manifold meiotic anomalies.One gene in the Pisum genome controls the transition from the vegetative to the reproductive stage of the plants. Other genes influence the differentiation of the growing points in such a way that the sporogenic tissues are not formed. In these mutants, no sporocytes are present which can undergo meiosis.From the findings available for many species of the plant kingdom, it can be assumed that hundreds of genes controlling meiosis are present in the genome of each higher plant.

Quantitative and qualitative investigations on the seed proteins of mutants and recombinants of Pisum sativum

The proteins of the seed flour of 26 X-ray induced mutants and 5 recombinants of the species Pisum sativum were analysed quantitatively and qualitatively. The values obtained were related to the seed yield of the genotypes In this way, the protein yield as well as the production of specific amino acids per genotype were determined. The following results were obtained. 1. The mean values for the character "total protein content of the seed flour" of the genotypes studied varied between 14 and 23%. The fasciated mutant 489C produced 18-23% more seed proteins than the initial line in three subsequent generations. The mean values of some other mutants and recombinants were 10-17% higher, the lowest value being 27% lower than that of the control values. In the material investigated there is no correlation between seed size and seed protein content. 2. The buffer-soluble seed proteins of 55 mutants were electrophoretically subdivided in different subfractions and the protein patterns were determined. They are extraordinarily variable. Distinct groups of mutants do not only differ from the initial line but also from one another with regard to the number, position and breadth of their bands. A correlation between the degree of morphological deviations of specific genotypes and the composition of their seed proteins was not observed. Moreover, differences in the concentration of specific protein fractions between the genotypes were densitometrically ascertained. 3. The globulins and albumins of some genotypes were quantitatively determined and electrophoretically subdivided into subfractions which differ between different mutants with regard to their number as well as their concentration. This is especially valid for the albumins which could be essentially stronger subdivided than the globulins. 4. The amino acid spectra of all the mutants investigated agree qualitatively with the spectrum of the initial line, however, clear quantitative differences in distinct amino acids were observed. The proportion of the essential amino acids is increased in two mutants by 5 and 20% in relation to the control line. 5. The protein production of the fasciated mutant 489C was 20-70% higher than the corresponding values of the initial line in three subsequent generations regarding its high seed production. The protein yield of the early flowering mutant 46C was about 20% lower and that of the bifurcated mutant 1201A 12-31% higher as related to the initial line. Mutant 1201A shows an equally favourable situation with regard to the total content of the essential amino acids. Its lysine production exceeded the control values by 20-40%. 6. The different components of the protein synthesis can negatively be influenced by the co-operation of the mutant genes. The protein production per plant, the total production of essential amino acids as well as the lysine production are lower in the recombinants 68C/176A and 68C/1201A as compared to the parental mutants. The combination of genes 68C and 46C does not show any negative interactions.

[The pollen tube growth of Pisum mutants under consideration of the free amino acids]

The germination of the pollen grains and the growth rate of the pollen tubes of eight mutants of Pisum sativum were compared with the parent line by in vitro investigations. All of the mutants studied showed a retardation of pollen tube growth as compared to the parent line, resulting in competitive elimination of some of the gametes in plants heterozygous for the respective mutant genes. The deficit of recessive plants in the progenies of heterozygous mutant strains of peas can be attributed to this retardation. Marked differences between the various mutants with regard to the levels of various free amino acids in their pollen grains were found. Certain amino acids may be present in greatly reduced concentration or may be present in excess. In some genotypes pollen tube growth can be stimulated by adding the deficient amino acid. This is especially true for proline, valine and threonine. As far as the other amino acids are concerned, the mutants studied showed varying reactions. The germination rate of the pollen grains is reduced by proline and threonine; germination is completely inhibited by glutamine. The amino acids isoleucine, histidine and cysteine retard pollen tube growth in all the mutants investigated. This is also true for leucine which, however, has a stimulating effect in one of the chlorophyll mutants.

DESYNAPSIS IN PISUM SATIVUM INDUCED THROUGH GENE MUTATION

A mutant of Pisum sativum showing various meiotic anomalies was isolated from X-irradiated material. These irregularities are due to a severe reduction of chiasmata frequency in pachytene resulting in univalent formation in the following meiotic stages. The action of this recessive gene shows considerable variations from PMC to PMC. As a consequence of this behaviour a large number of microspores is produced in each PMC having different chromosome numbers. The mutant is completely sterile in both sexes. Only very negligible differences were noted in the meiotic behaviour of this mutant in subsequent generations demonstrating that the action of gene ds82A is not influenced by extrinsic factors. It has been demonstrated that mutant 82A attains an extreme position in the scheme as compared with other desynaptic genotypes.