Response Characteristics Study of Ethylene Sensor for Fruit Ripening under Temperature Control

Post-ripening fruits need to be ripened to reach edible conditions, as they are not yet mature enough when picked. Ripening technology is based mainly on temperature control and gas regulation, with the proportion of ethylene being one of the key gas regulation parameters. A sensor's time domain response characteristic curve was obtained through the ethylene monitoring system. The first experiment showed that the sensor has good response speed (maximum of first derivative: 2.01714; minimum of first derivative: -2.01714), stability (xg: 2.42%; trec: 2.05%; Dres: 3.28%), and repeatability (xg: 20.6; trec: 52.4; Dres: 2.31). The second experiment showed that optimal ripening parameters include color, hardness (Change Ⅰ: 88.53%, Change Ⅱ: 75.28%), adhesiveness (Change Ⅰ: 95.29%, Change Ⅱ: 74.72%), and chewiness (Change Ⅰ: 95.18%, Change Ⅱ: 74.25%), verifying the response characteristics of the sensor. This paper proves that the sensor was able to accurately monitor changes in concentration which reflect changes in fruit ripeness, and that the optimal parameters were the ethylene response parameter (Change Ⅰ: 27.78%, Change Ⅱ: 32.53%) and the first derivative parameter (Change Ⅰ: 202.38%, Change Ⅱ: -293.28%). Developing a gas-sensing technology suitable for fruit ripening is of great significance.

GLUCOSAMINE SULFATE EFFICACY IN TREATING KNEE OSTEOARTHRITIS: A FOLLOW-UP STUDY

Osteoarthritis (OA) can be treated using either a pharmacological or non-pharmacological approach, or a combination of both. The purpose of the present study was to investigate the efficacy of crystalline glucosamine sulfate (CGS) in patients with knee OA. This open-label prospective study (with a 12-month follow-up) included 111 patients of both genders suffering from knee OA, who attended the Special Hospital for Rheumatic Diseases in Novi Sad, Serbia during the 2011-2013 period. Patients were divided into the experimental (n=52) and the control (n=59) group. While the former was prescribed CGS 1500 mg/day, the latter was treated with nonsteroidal anti-inflammatory drugs (NSAIDs) according to the standard protocol. The efficacy of both treatment modes was assessed using the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) and Lequesne index, along with the radiological findings which involved knee joint space width (JSW) measurements. One year following the initial assessment, all patients reported pain intensity reduction; however, those in the CGS group experienced significantly lower pain intensity when compared with controls. At the end of the study, no reduction in the progression of joint structure damage (p>0.5) was noted in either group. Thus, while CGS demonstrated symptomatic efficacy, it failed to delay the progression of knee OA.

The isokinetic strength profile of semi-professional soccer players according to low back pain

BACKGROUND

Soccer as a sport has a very high injury rate and low back pain (LBP) is considered to be the most common overuse injury typically occurring in the back and spine in elite soccer players.

OBJECTIVE

This study aimed to investigate differences in knee muscle strength and muscle imbalances in soccer players according to lower back pain.

METHODS

One hundred and thirty-six male professional soccer players (20.49 ± 3.73 years, 76.57 ± 8.24 kg, 182.63 ± 6.73 cm) volunteered for the study. The isokinetic dynamometer PrimaDOC (EASYTECH, Italy) was used to assess the hamstring and quadriceps strength at the selected speeds of 60∘/s, whereas the Roland-Morris Disability Questionnaire (RDQ) was used as a health status measure to assess physical disability caused by low back pain.

RESULTS

A univariate analysis of variance has shown that there is a statistically significant difference among the groups divided into Absolute peak torque right knee flexors, Absolute peak torque left knee flexors, Ratio between hamstrings and quadriceps strength right leg, and Ratio between hamstrings and quadriceps strength left leg based on the RDQ scores. On the other hand, no other significant differences among the groups were found in other parametersCONCLUSION: The current study indicates that knee muscle strength variables, resulting from an isokinetic testing, have the potential to discriminate between soccer players with and without a history of low back pain. However, low back pain is a multidimensional phenomenon and knee muscle strength or imbalance alone cannot be expected to explain low back pain.

COMPARISON OF THREE FUZZY MCDM METHODS FOR SOLVING THE SUPPLIER SELECTION PROBLEM

The evaluation and selection of an optimal, efficient and reliable supplier is becoming more and more important for companies in today’s logistics and supply chain management. Decision-making in the supplier selection domain, as an essential component of the supply chain management, is a complex process since a wide range of diverse criteria, stakeholders and possible solutions are embedded into this process. This paper shows a fuzzy approach in multi – criteria decision-making (MCDM) process. Criteria weights have been determined by fuzzy SWARA (Step-wise Weight Assessment Ratio Analysis) method. Chosen methods, fuzzy TOPSIS (Technique for the Order Preference by Similarity to Ideal Solution), fuzzy WASPAS (Weighted Aggregated Sum Product Assessment) and fuzzy ARAS (Additive Ratio Assessment) have been used for evaluation and selection of suppliers in the case of procurement of THK Linear motion guide components by the group of specialists in the “Lagerton” company in Serbia. Finally, results obtained using different MCDM approaches were compared in order to help managers to identify appropriate method for supplier selection problem solving.

Relationship between obesity and health-related quality of life in children aged 7-8 years

BACKGROUND

The dramatic increase in the prevalence of obesity in developed and developing countries has become a major health care concern. Accordingly, there is growing recognition of the relationship between health-related quality of life (HRQOL) and obesity in the pediatric population. This study aimed to explore the relationship between HRQOL and different indicators of obesity in children aged 7-8 years.

METHOD

In total, 182 children participated in this study (mean age 7.71 (0.29) years, 48.91% girls). To assess obesity, an InBody 230 analyzer was used to calculate body mass index (BMI) and body fat percentage (BFP). The proxy version of the KIDSCREEN-27 questionnaire was used to assess HRQOL.

RESULTS

Among boys, 17.2% were overweight and 4.3% were obese according to BMI, while in terms of body fat percentage (BFP), the corresponding percentages were 12.9 and 9.7%, respectively. Among girls, the prevalence of overweight and obesity was 11.2 and 9.0% by BMI and 10.1 and 7.9% in terms of BFP, respectively. The analysis of BFP showed a significantly higher score in normal weight boys than in obese boys in the Social Support & Peers domains (KW H-test = 10.472, p = 0.03), while in girls, there were no significant differences between weight categories and any HRQOL dimensions.

CONCLUSION

Obesity at 7-8 years of age could negatively affect some HRQOL domains; in particular, obese boys may have low social support and peer functioning.

Redox imbalance in peripheral blood of type 1 myotonic dystrophy patients

OBJECTIVES

The aim of our study was to determine if redox imbalance caused by the activities of antioxidant enzymes existed in erythrocytes of type 1 myotonic dystrophy (DM1) patients.

METHODS

The activities of erythrocyte superoxide dismutase, catalase, glutathione peroxidase, and glutathione reductase were measured in 30 DM1 patients and 15 healthy controls (HCs). The obtained values were correlated with the Muscular Impairment Rating Scale (MIRS) score and creatine kinase (CK).

RESULTS

Superoxide dismutase and catalase activities were lower in DM1 patients compared to HCs. A positive correlation was found between disease duration and MIRS score as well as with glutathione reductase activity. In DM1 patients, there were positive correlations between catalase, glutathione peroxidase, and glutathione reductase activities. After sub-dividing DM1 patients according to CK levels, superoxide dismutase activity was still statistically different from HCs. However, catalase activity was significantly lower only in DM1 patients with increased CK.

DISCUSSION

Undesirable alterations in antioxidant enzyme activities during DM1 disease progression may result in conditions favoring oxidative stress and changes in metabolism which together could contribute to muscle wasting.

An outbreak of fumonisin toxicosis in horses in Serbia

This paper reports on an outbreak of fumonisin toxicosis in a stable with 100 horses. Twenty-one horses were affected and fifteen died within a month. The animals were not febrile and exhibited poor appetite, somnolence, head pressing, blindness, ataxia, lethargy, and seizures, ending with death. The post mortem examination of the head of one 18-month-old colt revealed large, bilateral, slightly asymmetrical large areas of necrosis of the cerebral white matter. The lesions involved the frontal, parietal and occipital lobes only. Histological findings revealed leukomalacia with necrosis, infiltration of macrophages, neutrophils and eosinophils, haemorrhage and oedema of the surrounding grey matter. In response to the pathological findings, which indicated equine leukoencephalomalacia (ELEM), feed samples from the premises were tested for fumonisin B1 and B2 (FB1 and FB2). The milled maize samples contained 6.0 mg/kg FB1 and 2.4 mg/kg FB2, while the maize bran contained 6.05 mg/kg FB1 and 1.68 mg/kg FB2. These findings confirmed the diagnosis of fumonisin toxicosis. Hence, this report indicates that Serbia is one of the few regions in Europe with proven cases of ELEM.

Differences in motor and cognitive abilities of children depending on their body mass index and subcutaneous adipose tissue

The aim of the present study was to analyze differences in motor and cognitive abilities of children depending on their value in quantitative indicators of Body Mass Index (BMI) and subcutaneous fatty tissue. The study sample consisted of overall 910 boys and girls, aged 11 to 14, all from elementary schools in Vojvodina (Serbia). Six anthropometric, eight motor and one cognitive variable were analyzed to identify quantitative and qualitative differences in motor and cognitive functioning of children. Children were divided into three groups within gender based on their body mass index calculated and subcutaneous fatty tissue measured. The results obtained from the study indicate the existence of differences in motor and only partly in intellectual abilities between groups of subjects. The greatest differences between the clusters were found in the level of coordination of the entire body, and the static strength of arms and shoulders.

In vitro evaluation of the genotoxicity of ritodrine and verapamil in human lymphocytes

The aim of this study was to investigate the genotoxic effects of ritodrine and verapamil on human peripheral lymphocytes in vitro using micronucleus (MN) test. Also, fluorescence in situ hybridization (FISH) with a centromeric probe was performed to determine the origin of the induced MN. Cells were treated with 8.4 × 10(-6) M - 25.2 × 10(-4) M concentrations for ritodrine and 0.56 - 11 × 10(-5) M concentrations for verapamil, separately and combined. The MN frequencies showed increase after all treatments, but the difference between treated cells and untreated controls were found to be statistically significant only in the concentration range from 8.4 × 10(-5) M - 4.5 × 10(-4) M for ritodrine, 1.1 - 3.3 × 10(-5) M for verapamil, and in combined treatment with concentrations 8.4 × 10(-5) M + 1.1 × 10(-5) M for ritodrine and verapamil. The highest tested concentrations of both medicaments showed cytotoxic effect. Both medicaments decreased the nuclear division index (NDI) in tested concentrations. The results of FISH analysis suggest that verapamil, separately or combined with ritodrine, shows to a larger extent aneugenic than clastogenic effect.

The effect of combined therapy with ritodrine, erythromycin and verapamil on the frequency of micronuclei in peripheral blood lymphocytes of pregnant women

The main aim of this study was to investigate the genotoxic effect of combined pharmacotherapy applied in post-operative treatment of cervical cerclage in pregnant women over six days. This study included 19 phenotypically healthy pregnant women in mid-trimester with a diagnosis of cervical insufficiency, mean age 28+/-5.33. The frequency of micronuclei (MN) was estimated in peripheral blood lymphocytes of patients before surgical intervention and after the end of applied pharmacotherapy by application of cytokinesis block micronucleus (CBMN) test. Mean value of baseline MN frequency was 6.84+/-2.91 MN/1000 binucleated cells, and after the end of the applied therapy, 10.32+/-4.27 MN/1000 binucleated cells (P<0.001) were found. The data of cell proliferation index showed that the combined therapy did not induce significant difference in cell kinetics (P>0.05). Our results showed that combined pharmacotherapy treatment over six days significantly increased the frequency of MN in peripheral blood lymphocytes of pregnant women.

[Executive functions in young patients with unipolar depression]

Neuropsychological deficits associated with unipolar depression are seen in a broad range of cognitive domains. Executive deficits may be prominent in depression. Investigation of executive functions in younger adult patients with unipolar depression has been the focus of our study. Twenty-two consecutively depressive inpatients (24-36 years) and 21 healthy control subjects, matched on age, gender, education and verbal IQ were included in the study. Neuropsychological tests for executive functions were applied to all subjects. Unipolar young depressives showed significantly reduced number of completed categories and more trials for completion of the first category on Wisconsin Card Sorting Test (WCST). No difference of tasks assessing the short-term memory, total errors on WCST, perseverative and non-perseverative errors, and of both phonemic and semantic conditions of verbal fluency was found between groups. The results suggested that unipolar depressives had specific cognitive style characterized by "negative cognitive set" (stronger negative reaction to negative feedback) and by failure to use negative feedback to improve their performance.

Neuropsychological profile of patients with bipolar depression in remission

Aim. To determine if the patients with bipolar affective disorder, after the depressive phase, would exhibit cognitive impairment in remission. Methods. Twenty three euthymic patients with bipolar disorder were matched, on a case-by-case basis, to twenty-one healthy subjects in the control group, for the presence of the symptoms of depression. The patients and the control group were tested with a battery of neuropsychological tests. Results. Impairments were found in the patients compared with the control group in tests of verbal learning and memory and in tests of executive function. Verbal learning and memory, as well as executive functions, did not correlate either with the clinical indices of patients, or with the demographic and baseline clinical measures of depression. Conclusion. Impaired verbal learning and memory and executive functions may represent a trait rather than the state variables in bipolar disorder.

Carbamazepine for acute psychosis with EEG abnormalities

AIM

To investigate the efficacy of carbamazepine as adjuvant drug therapy in acute paranoid psychosis with associated EEG abnormalities, compared to sole antipsychotic treatment.

METHODS

Eleven medication-naive patients, diagnosed with acute paranoid psychosis with associated EEG abnormalities, were divided into two treatment groups: sole fluphenazine group, with flexible dosing of 5-10 mg/day (n=6), and carbamazepine group (n=5) with the addition of carbamazepine (600 mg/day) to fluphenazine treatment. Clinical Global Impression (CGI), Brief Psychiatric Rating Scale (BPRS), Scale for the Assessment of Negative Symptoms (SANS), and EEG were assessed on the baseline and after 6 weeks of treatment. Paired and two-tailed t-tests were used for statistical significance.

RESULTS

All the patients showed significant improvement of mental state after 6 weeks of treatment with no significant differences in CGI, BPRS, and total SANS scores in relation to the therapy with carbamazepine. Nevertheless, after 6 weeks of the treatment, EEG findings were significantly better in carbamazepine group, in relation to the findings from the onset of the treatment, as well as in comparison to sole fluphenazine group.

CONCLUSION

Although carbamazepine stabilized abnormal brain electrical activities it seemed that the associated EEG abnormalities were not significant for acute psychosis observed. These preliminary results suggested that there was no convincing evidence that carbamazepine was efficient as the augmentation of antipsychotic treatment for patients with both acute paranoid psychosis and EEG abnormalities.

Substrate kinetics of erythrocyte membrane Na,K-ATPase and lipid peroxides in schizophrenia

Previous studies have shown decreased erythrocyte membrane (EM) Na,K-ATPase activity in chronic patients suffering from schizophrenia (SCH). There are no data about changes at the onset of psychosis and enzyme kinetics. Increased lipid peroxidation could be responsible for alterations in Na,K-ATPase activity. Substrate kinetics pattern of EM Na,K-ATPase and levels of lipid peroxides in plasma and erythrocytes were measured in (1) patients with first episode of psychosis (n=20) before medication and after the first 3 weeks of treatment, (2) chronic medicated schizophrenic patients (n=52) in the exacerbation phase, and (3) age- and sex-matched control subjects (n=30). All patients were assigned to groups with predominantly positive or predominantly negative symptoms on the basis of their scores on Positive and Negative Syndrome Scale (PANSS). In first-episode patients with predominantly negative symptoms before treatment, uncompetitive inhibition of Na,K-ATPase was noticed. The first-episode patients with predominantly positive symptoms had increased enzyme catalytic activity. After 3 weeks of treatment, activities were normalized in both groups. Among chronic patients, uncompetitive inhibition was found only in patients with predominantly negative symptoms. Plasma lipid peroxides (thiobarbituric acid-reactive substances [TBARS]) were elevated in both groups of patients with first episode of psychosis. Despite the presence of peroxidative injury indicative for the loss of membrane phospholipid essential fatty acids, the activities of Na,K-ATPase differ between SCH (+) and SCH (-) patients.

Variability of haptoglobin and alpha 2-macroglobulin in Albino Oxford and Dark Augustin inbred strains of rats before and after trauma

Increased synthesis of acute-phase proteins (APP) in the liver represents the most prominent aspect of acute phase reaction (APR). Haptoglobin (Hp) and alpha 2-macroglobulin (alpha 2-M) are among the most important APP in rats. In this study AO (Albino Oxford) and DA (Dark Augustin) inbred strains of rats, with different resistance to trauma, were used to compare concentrations of Hp, alpha 2-M, IL-1, IL-6 and TNF, before and after tourniquet trauma. Cytokines IL-1, IL-6 and TNF have an important role in APP gene expression. Our results showed that before trauma, more resistant AO rats had higher concentrations of Hp and alpha 2-M compared to DA rats. The influence of genetic elements of these differences is significant. Tourniquet trauma caused an early increase of IL-1, IL-6 and TNF activities in the serum which preceded the increase in the Hp and alpha 2-M concentrations but differences between strains were not found.

Adaptive significance of amylase polymorphism in Drosophila. X. Analysis of alpha-amylase activity of two amylase variants in individual Drosophila subobscura flies

Experiments were designed to estimate the variation of alpha-amylase activity in Drosophila subobscura individuals homozygous for AmyS and AmyF alleles at the Amy locus. The measurements of enzyme activities in six groups of male progenies determined in each individual have shown that degree of variation differs between S and F strains. Variability of amylase activity among male progenies of S strain was substantially greater, which also had significantly higher specific amylase activity than in F strain. The analysis of amylase activity variance showed that this variance among the males is 40 times, and among the females 2.7 times smaller in F than in S strain.

Neuroleptic actions on the thyroid axis: different effects of clozapine and haloperidol

Twenty-six in-patients treated for schizophrenia, were divided in two groups. The first group received haloperidol, 20-40 mg p.d., and the second, clozapine, 150-250 mg p.d. TRH-TSH test was performed by injecting 0.2 mg TRH. Four drug-free schizophrenic patients gave normal TSH response to TRH, as well as the group of patients treated with haloperidol. Contrary to that, the clozapine-treated group showed a blunted TSH response. The results obtained are discussed in terms of the different pharmacological profiles of haloperidol and clozapine, especially regarding their dopaminergic actions, alpha-adrenergic and serotonergic control upon thyroid axis.

Inheritance of acute appendicitis: familial aggregation and evidence of polygenic transmission

We explored familiality as well as the heritability and possible mode(s) of inheritance of acute appendicitis in childhood and early adolescence. Our case-control study showed that a positive family history for reported appendectomy was significantly more frequent in families of 80 consecutive patients eventually proved to have histopathologic acute appendicitis than in families of surgical controls matched for sex, age, and number of siblings. The relative risk was 10.0 (95% confidence limits 4.7-21.4). The pattern of familial aggregation was further supported by the fact that the age-standardized morbidity ratio was four times greater among family members of cases than among controls. We then applied the unified mixed model of segregation analysis, as implemented in the computer program POINTER, to a new set of 100 multigenerational pedigrees of children with histopathologically confirmed acute appendicitis that were broken down into 674 nuclear families. Age-specific morbidity risk and lifetime incidence of acute appendicitis were estimated from relatives of controls matched for age and sex to probands. Complex segregation analysis supported a polygenic or multifactorial model with a total heritability of 56%. There was no evidence to support a major gene, although a rare gene could not be ruled out as the cause of a small proportion of cases. Specific studies to address genetic and environmental factors in this serious disease seem worthwhile; but, for now, a positive family history of appendicitis might join other evidence leading to improved clinical recognition of acute appendicitis.

Genetic basis of resistance to trauma in inbred strains of mice

In this study the resistance to mechanical, thermal, and radiation trauma in four inbred strains of mice (AKR, BALB/c, CBA, and C57Bl/6) was compared with the degree of genetic resemblance, by analyzing the allozyme variabilities of these strains. It was shown that the highest degree of genetic resemblance was among CBA and AKR strains, which correlated with a similar degree of resistance to trauma. On the other hand, BALB/c and C57Bl/6 strains expressed significant differences, both genetically and with respect to the responses to trauma. The hypothesis is introduced that the genetic determination of the resistance to trauma is based on: a) a polygenic control of general physiological homeostasis, with the possibility that b) some specific genes or single loci may contribute more than others to such adaptations of the strains tested.

Parental age dependent changes as a source of genetic variation in Drosophila melanogaster

It has been shown repeatedly that numerous cumulative changes occur in chromosomes of D. melanogaster, as an effect of ageing which, especially in the homozygous state, significantly affect different fitness components of their carriers. It appears that the observed age-affected events are produced by systematic and ontogenetically programmed changes in genetic loads at specific chromosomes, which are transferable to following generations. It has been suggested that such changes could be of mutational origin, and that they could be more frequent at gene loci which are epigenetically active during ontogenesis. It was demonstrated that a large sample of identical chromosomes behave quite differently in the homozygous state when obtained from aged compared to non-aged parents, producing a significant decrease in relative viability, length of preadult development, and longevity of their carriers, as well as in the frequency of recombinations of corresponding chromosomes. A specific treatment by streptomycin resulted in remarkably milder effects of ageing, which is in accordance with the statement of some authors that such a treatment may diminish the frequency of spontaneous recessive mutations in their carriers. Thus the observed age-affected changes could be an important source of developmental and evolutionary variation of living organisms.

Genetic Diversity and Linkage Disequilibrium in Drosophila melanogaster With Different Rates of Development

We have examined eight enzyme polymorphisms in groups of Drosophila melanogaster flies with fast, intermediate and slow development. The allelic frequencies are similar in all three developmental classes, but the distribution of the genotypes among the classes is significantly heterogenous for the three loci on the second chromosome. When the total sample of 300 individuals is examined, significant gametic disequilibrium appears in 3 out of 13 pairs of genes located on the same chromosome and in 4 out of 15 pairs of genes located on different chromosomes. This 25% incidence of disequilibrium between pairs of genes is larger than previously observed in other natural populations (but similar to the incidence observed in laboratory populations). The greater frequency of significant gametic disequilibrium in our study is probably due to the larger number of genomes sampled.—Some models specifically predict that individuals with faster rates of development (i.e., greater fitness) should be more heterozygous (and exhibit more linkage disequilibrium) than individuals with slower development. This hypothesis is not supported by our results.

Correlations between development rates, enzyme activities, ribosomal DNA spacer-length phenotypes, and adaptation in Drosophila melanogaster

Selection for "fast" preadult development rate among the progeny of flies collected in a natural population of Drosophila melanogaster produced a line that developed more rapidly than a line selected for "slow" preadult development rate. Assays for enzyme activity levels showed that the activities of alpha-glycerophosphate dehydrogenase, alcohol dehydrogenase, and malic enzyme were higher in the fast than in the slow line, but that the activity of superoxide dismutase was lower in the fast line. Differences in the frequencies of spacer-length phenotypes of X chromosome-linked rRNA genes (rDNA), which developed between the lines during the selection process, are larger than can be explained on the basis of genetic drift alone. Long rDNA spacers had high frequency in the fast line; short spacers, in the slow line. We conclude that enzyme levels affected adaptation under the selective regimes imposed and that the different X-linked rDNA spacer-length phenotypes are either adaptive in themselves or that they mark chromosomal segments carrying genes relevant to adaptation.

Erythropoietin in patients with anaemia in rheumatoid arthritis

Iron status and erythropoietin (Ep) level in serum and urine were determined in 30 patients with anaemia in rheumatoid arthritis. The anaemia in these patients was mild and fulfilled the criteria for anaemia of chronic disorders. The iron status of these patients differed from the iron status in patients with sideropenic anaemia. Serum Ep, level, measured indirectly by the polycythaemic mouse bioassay, was either not detected or when detected it did not correspond to the degree of anaemia. The data suggest that the failure to produce sufficient amount of Ep, among other causes, could be important in the pathogenesis of anaemia in rheumatoid arthritis.

Fitness of allozyme variants in Drosophila pseudoobscura. I. Selection at the PGM-1 and Me-2 loci

We have studied in Drosophila pseudoobscura the effect of allozyme variation on seven fitness components: female fecundity, egg hatchability, egg-to-adult survival under near-optimal and under competitive conditions, rate of development under near-optimal and under competitive conditions, and mating capacity of males. Three genotypes at each of two loci, Pgm-1 and Me-2, have been studied in various combinations. These two loci are highly polymorphic in natural populations of D. pseudoobscura. Statistically significant differences involving one or more genotypes exist for all components of fitness. No single genotype is best for all fitness components; rather the relative fitnesses of genotypes are reversed when different parameters are considered, or when they are studied in different environmental conditions. Also, the average egg-to-adult survival and rate of development are better when different genotypes are reared together than when they occur in pure culture. Four different modes of selection have been uncovered by our experiments. These forms of selection may account for the persistence of the two allozyme polymorphisms in nature, and for previously observed seasonal fluctuations of the allelic frequencies in natural populations.

Fitness of allozyme variants in Drosophila pseudoobscura. II. Selection at the Est-5, Odh and Mdh-2 loci

We have studied the effects on fitness of allelic variation at three gene loci (Est-5, Odh, andMdh-2)coding for enzymes inDrosophila pseudoobscura. Genotype has a significant effect on fitness for all six parameters measured (female fecundity, male mating capacity, egg-to-adult survival under near-optimal and under competitive conditions, and rate of development under near-optimal and under competitive conditions). No single genotype is best for all six fitness parameters; rather, genotypes with superior performance during a certain stage of the life-cycle may have low fitness at some other stage, or in different environmental conditions. Heterozygotes are sometimes best when all fitness parameters are considered. There are significant interactions between loci. The various forms of balancing selection uncovered in our experiments may account for the polymorphisms occurring in natural populations ofD. pseudoobscuraat the three loci studied.