Quantitative histology of changes with age in rat bone cortex

Changes with age in bone cortex of the rat were investigated by establishing histological parameters which could be quantitated to estimate age at death. Decalcified cross sections of mandible, femur and tibia were prepared from rats two to 120 days old, and measurements were made of: (1) number of osteons, (2) average number of lamellae per osteon, (3) average Haversian canal diameter, and (4) number of non-Haversian (primary) canals. Multiple regression techniques were used to estimate age at death from several combinations of these variables. With age, the number of osteons per unit area of bone and the number of lamellae per osteon increased, but Haversian canal diameter and the number of primary canals decreased. Multiple regression analyses indicated that age at death could be estimated to ± 3 days of the true value in 95% of the cases. Nomographs based on histological measurements of each bone were prepared which can provide accurate estimates of age between two and 120 days in the Sprague-Dawley female rat. It was concluded that microstructure of bone cortex can not only be quantitated to provide accurate estimates of age but it may also constitute a sensitive measure of the metabolic state of the organism. The techniques utilized should prove useful in anthropology as well in studies of bone aging.     

Birth Weight and Its Relationship to Size Attained and Relative Fat Distribution at 7 to 12 Years of Age

The relationship between birth weight and relative subcutaneous fat distribution at school age was considered in 131 boys and 106 girls 7 to 12 years of age. Relative fat distribution at school age was estimated with the ratio of the subscapular to triceps skinfolds (S/T) for the total sample, and with the ratio of the sum of two trunk (subscapular, midaxillary) to the sum of two extremity (triceps, medial calf) skinfolds (T/E) for subsamples of 102 boys and 63 girls. There were no sex differences in the S/T ratio (mm/mm), boys 0.62 ± 0.15, girls 0.63 ± 0.18; T/E ratio (mm/mm), boys 0.58 ± 0.13, girls 0.59 ± 0.16; and BMI (kg/m²), boys 17.1 ± 2.4, girls 16.9 ± 2.2. Second order partial correlations, controlling for age and the BMI or age and sum of skinfolds, between birth weight and the skinfold ratios are, respectively, ?0.22 and ?0.20 (p<0.01) for S/T and ?0.29 and ?032 (p<0.01) for T/E in girls, and ?0.18 and ?0.17 (p<0.05) for S/T and ?0.06 and ?0.6 for T/E in boys. Though low, the correlations suggest that as birth weight decreases proportionally more subcutaneous fat is accumulated on the trunk than on the extremities, more so in females than in males. Results of stepwise multiple regression analyses indicate that birth weight accounts for from 2% to 8% of the variance in relative subcutaneous fat distribution at school age.     

Brain-stem auditory evoked potential monitoring. Variations of stimulus artifact in brain death

Brain-stem auditory evoked potentials (BAEPs) were recorded in 20 subjects with brain death (mean age, 33.2 ± 15.1 years) and 20 healthy volunteers (mean age, 29.8 ± 6.8 years). Brain death was due to head injury (n = 14), encephalitis (n = 3), brain-stem hemorrhage (n = 1), cerebellar hemorrhage (n = 1) or cerebral infarction (n = 1). The presence, latency and amplitude of the individual BAEP components and variations of the stimulus artifact were evaluated. The mean ( ± S.D.) amplitude of the stimulus artifact was 0.26 ± 0.12 μV in the brain-dead subjects and 0.09 ± 0.05 μv in the control group (P < 0.001, t test). The causes of the phenomenon of increasing stimulus artifacts in the evolution of brain death remain unclear.     

Double trisomy in spontaneous abortions

Cytogenetic data on products of conception from spontaneous abortions studied over a 10-year period have been reviewed for double trisomies. A total of 3034 spontaneous abortions were karyotyped between 1986 and 1997. Twenty-two cases with double trisomy, one case with triple trisomy, and a case with a trisomy and monosomy were found. The tissues studied were mostly sac, villi, or placenta. The gestational age ranged from 6 to 11 weeks and the mean age was 8.2 ± 1.7 (SD) weeks. The mean maternal age in years was 35.9 ± 5.3. Of the twenty-two cases, four were mosaics. All but two of the cases involved autosomal aneuploidies. The double trisomies included chromosomes 2, 4, 5, 7, 8, 12, 13, 14, 15, 16, 17, 18, 20, 21, and 22. The chromosomes that were trisomic in more than one double trisomy case were numbers 16 (8 cases), 8 (5 cases), 15 (4 cases), 2, 13, and 21 (3 cases each), and 5, 7, 14, 18, 20, 22, and X (2 cases). The triple trisomy involved chromosomes 18, 21, and X. The monosomy and trisomy case was a mosaic, with a monosomy 21 in all cells and some cells also with a trisomy 5. The double trisomies cited for the first time in this study were 4/13, 5/16, 8/14, 8/15, 14/21, 15/20, and 7/12. The pooled mean maternal age for double trisomy cases (34.1 ± 5.7 years) was higher than that for single trisomy cases (31 ± 6.1 years). The difference was statistically significant at P = < 0.001. The pooled mean gestational age of spontaneous abortions was lower for double trisomy (8.7 ± 2.2 weeks) than for reported single trisomy cases (10.1 ± 2.9 weeks). This difference is also statistically significant at P = < 0.001. The sex ratio among double trisomies was 15 females to 13 males. This difference was not statistically significant from the expected 1 : 1. Received: 27 June 1997 / Accepted: 4 September 1997     

Geographic latitude and sleep duration: A population-based survey from the Tropic of Capricorn to the Antarctic Circle

The impact of latitude on sleep duration remains virtually unexplored, even though latitude exerts profound influences on daylight duration. Using Chile as a one-country model, we explored on the potential associations between sleep duration and latitude. Based on the 2nd Chilean Health Survey, we identified reported sleep data during spring of people living from north to south in Chilean cities, located between 18°29?S to 53°18?S (4329 km distance at same longitude). A total of n = 2493 participants were included (mean age 45.3 ± 18.4 years, 41.8% males). Mean sleep duration on workdays and weekends was 7.42 ± 1.71 h, and 7.91 ± 2.13 h, respectively, ranging from 7.91 ± 1.92 h in the north to 8.33 ± 1.89 h in the south, such that more northern latitudes (i.e., 18°29?S to 39°50?S) slept less compared to more southern latitudes (i.e., 51°43?S–53°18?), even after controlling for age, gender, and socioeconomic status. In the logistic regression models, men residing at northern latitudes exhibited an odds ratio of 3.348 [95% CI: 1.905–5.882; p < 0.0001] for having shorter sleep on weekends than their southern counterparts. Latitude appears to strongly affect reported sleep patterns, leading to longer sleep duration with increasing latitude, particularly in men during weekends. Whether environmental factors such as photoperiod are causally involved in theses associations needs to be elucidated in future studies.     

Clinical course of homozygous familial hypercholesterolemia during childhood: report on 4 unrelated patients with homozygous or compound heterozygous mutations in theLDLR gene

Natural history of the disease in 4 unrelated Polish children with homozygous familial hypercholesterolemia (FH) is described. Their phenotypic homozygosity was established by identification of known LDLR gene mutations on both alleles, respectively: p.G592E & p.G592E in Patient 1; p.G592E & p.C667Y in Patient 2; p.S177L & p.R350X in Patient 3; and p.G592E & deletion in the promoter region, exons 1 and 2 in Patient 4. Heterozygosity of the mutations was revealed in all patients' mothers and fathers (obligatory heterozygotes) and in 1 out of 4 siblings studied. FH was diagnosed at the age of 4 months to 9 years by cholesterol screening among family members of patients with early cardiovascular disease episodes. At the time of FH detection, the children were asymptomatic. Only in 2, some skin eruptions were found. Antihyperlipidemic therapy was started, including a lipid-lowering diet, cholestyramine, and HMG-CoA inhibitors if necessary. No cardiovascular symptoms appeared during the observation up to the age of 18, 20, 19, and 17 years, respectively. An increase in external carotid artery diameter was found in a patient at the age of 9 years, and LDL-apheresis was introduced in his therapy. We conclude that the analysis of LDLR gene mutations in the studied FH children made it possible to identify 4 presymptomatic FH homozygotes and to introduce early appropriate treatment. Multicenter analysis of such persons would finally determine if the early lipid-lowering procedures can significantly reduce the risk of premature cardiovascular disease in homozygous FH.     

Immunocontraception and increased longevity in equids

Intensive population management by means of fertility control has been shown to change the age profile of a wild horse herd. The primary change has been an increase in the number and percent of older animals, as expected, but also the appearance of new and older age classes. An examination of direct effects of fertility control on two groups of treated animals shows a significant increase in longevity over non‐treated animals that is associated with contraceptive treatment. The mean age at death (MAD) was calculated for 128 wild horses for which precise birth and death dates were known, including 56 stallions, 42 untreated mares, 11 mares treated with a porcine zona pellucida contraceptive vaccine for 1–2 years, and 19 mares treated with the same vaccine for ≥3 years. The MAD for stallions (10.3±0.84 [SEM] years), and mares treated for 1–2 years (10.2±0.56), was significantly greater (P<0.05) than for untreated mares (6.4±0.85), and significantly <19.9±1.66 for mares treated ≥3 years (19.9±1.66). Zoo Biol 26:237–244, 2007. © 2006 Wiley‐Liss, Inc.     

Effects of supplementation of tris-egg yolk extender with different sugars and antioxidants on freezability of ram semen

This study was designed to determine the effects of the combined addition of different levels of certain sugars (trehalose, sucrose and raffinose) and antioxidants (vitamin E, C and taurine), in Tris-egg yolk extender on frozen-thawed ram semen parameters. Semen samples were collected from five healthy, mature and fertile Iranian Afshari rams, twice a week for 8 weeks. Selected samples were pooled and diluted with a Tris-egg yolk extender containing different levels of sugars and antioxidants. In Experiment 1, different levels of trehalose (0, 50 and 100 mM) were tested with different levels of taurine (0, 25 and 50 mM), vitamin E and C (0, 1 and 2 mM). In Experiment 2, different levels of sucrose (0, 60 and 80 mM) were tested with different levels of taurine (0, 25 and 50 mM), vitamin E and C (0, 1 and 2 mM). In Experiment 3, different levels of raffinose (0, 5, 10 mM) were tested with different levels of taurine (0, 25 and 50 mM), and vitamin E and C (0, 1 and 2 mM). In Experiment 4, the selected extenders of experiments 1, 2 and 3 were compared statistically with control (no selected sugar and antioxidant) extender. The results of experiments 1, 2 and 3 revealed that the highest frozen–thawed sperm parameters were recorded for the selected extenders containing 100 mM trehalose +2 mM vitamin E (T100E2), 60 mM sucrose + 2 mM vitamin E (S60E2) and 10 mM raffinose + 2 mM vitamin E (R10E2), respectively. The results of experiment 4 revealed that the post-thaw sperm total motility in T100E2 (62.41 ± 2.41%), S60E2 (59.52 ± 1.91%) and R10E2 (58.33 ± 2.00%) was higher than that of the control extender (46.00 ± 1.79%; P ≤ 0.05). Similarly, the progressive sperm motility in T100E2 (57.18 ± 1.96%), S60E2 (57.49 ± 1.94%) and R10E2 (55.03 ± 2.99%) was also higher than that of the control extender (41.20 ± 1.70%; P ≤ 0.05). Post-thaw sperm viability in selected extenders of T100E2 (65.20 ± 2.67%), S60E2 (62.00 ± 2.07%) and R10E2 (61.80 ± 2.46%) was higher than that of control extender (51.00 ± 1.88%; P ≤ 0.05). In conclusion, the addition of 100 mM trehalose, 60 mM sucrose and 10 mM raffinose combined with 2 mM vitamin E in Tris-egg yolk extender significantly improved frozen-thawed ram semen parameters.     

Production,clearance rates and metabolic fate of estradiol-17β in the plasma of the laying hen

A single dose of tritiated estradiol-17β (³H-E₂β) was injected i.v. into 5 high egg producing White Leghorn hens, 31 weeks of age, at 19.2 ± 2.1 (mean ± S.D.) hr before oviposition. Blood (2 ml) was sampled at approximately 5 min intervals over 40 min. Whenever possible, metabolites were monitored and identified by the double isotope technique with the addition of the corresponding ¹⁴C-labelled standards to plasma prior to analysis. The metabolic half-life and clearance rate of ³H-E₂β in plasma were 10.9 ± 1.9 min and 118 ± 18 ml/min/kg body weight, respectively. The calculated production rate of E₂β at 19.2 hr before oviposition was 19.5 ± 5.7 ng/min based on the plasma level (93±22 pg/ml) measured at that time. The relative concentrations (% of plasma radioactivity) of the major metabolites isolated at 5.7 ± 0.6 min post injection were, in descending order: estradiol-17β-3-sulfate (E₂β-3S : 14.9 ± 2.7), estradiol-17α-3-sulfate (E₂α-3S; 5.7 ± 0.3), estrone (E₁; 4.6 ± 0.5), estrone sulfate (E₁S; 2.2 ± 0.5), and estradiol-17 α (E₂α; 1.2 ± 0.4). As time proceeded, the relative concentration of E₂α-3S gradually increased so that by 43.2 ± 1.0 min it became the most abundant identifiable metabolite (12.3 ± 1.1) followed by E₂β-3S (9.1 ± 1.7), E₂S (1.2 ± 0.6), E₁ (0.7 ± 0.4) and E₂α (0.3 ± 0.2). These findings are consistent with the view that one of the major pathways of E₂β metabolism in the circulation of the hen is via E₂β

E₂β?3S ?E₁S

E₂α-3S.     

Bimodal oxygen uptake in a freshwater air-breathing fish,Notopterus chitala

Measurements of bimodal oxygen uptake have been made in a freshwater air-breathing fish,Notopterus chitala at 29.0±1(S.D.)°C. xhe mean oxygen uptake from continuously flowing water without any access to air, was found to be 3.58±0.37 (S.E.) ml O₂ · h^?1 and 56.84+4.29 (S.E.) ml O₂ · kg^?1 · h^?1 for a fish weighing 66.92 + 11.27 (S.E.) g body weight. In still water with access to air, the mean oxygen uptake through the gills were recorded to be 2.49 ± 0.31 (S.E.) ml O₂ · h^?1 and 38.78 ± 1.92 (S.E.) ml O₂ · kg^?1 · h^?1 and through the accessory respiratory organs (swim-bladder) 6.04±0.87 (S.E.) ml O₂ · h^?1 and 92.32±2.91 (S.E.) ml O₂ · kg^?1 · h^?1 for a fish averaging 66.92±11.27 (S.E.) g. Out of the total oxygen uptake (131.10 ml O₂ · kg^?1 · h^?1), about 70% was obtained through the aerial route and the remainder 30% through the gills.     

Effect of forage particle length on rumen fermentation,sorting and chewing activity of late-lactation and non-lactating dairy cows

The objective of this study was to determine the effects of varying forage particle length on chewing activity, sorting behavior, rumen pH and rumen fill in late lactation and dry dairy cattle, fed rations with similar physically effective NDF but different mean particle length. Treatments consisted of three diets differing only in geometric mean length of forage: hay (5.40, 8.96 and 77.90 mm, for short (S), medium (M) and long (L) diets, respectively) for Experiment 1 (E1), and straw (10.16, 24.68 and 80.37 mm) for S, M and L diets, respectively, for Experiment 2 (E2). Hay or straw comprised the sole source of forage (50% and 75% of ration dry matter (DM) for E1 and E2, respectively). Both experiments used three rumen cannulated Holstein dairy cows, in late lactation for E1 and dry in E2, with 3 × 3 Latin square designs with 14 day periods. In E1, DM intake (DMI; 18.3 ± 2.1 kg/day; mean ± s.e.), pH (6.4 ± 0.1), time spent eating (280 ± 22.5 min/day), time spent ruminating (487 ± 17 min/day), and total time spent chewing (767 ± 34 min/day) were not different, whereas eating minutes per kilogram of DMI and NDF intake (NDFI) tended to increase linearly as forage length increased. Rumen digesta volume (l; 113.3 S, 117.8 M and 114.4 L ± 17.1) had a quadratic response, and rumen digesta weight tended to respond quadratically; however, differences were numerically small. In E2, DMI (8.3 ± 1.3 kg/day), pH (6.7 ± 0.1), time spent eating (236 ± 23.5 min/day), time spent ruminating (468 ± 45.2 min/day), total time spent chewing (704 ± 67.7 min/day) and minutes per kilogram NDFI were not different, whereas minutes per kilogram of DMI had a trend for a quadratic effect. Rumen digesta volume (111 ± 18.8 l) and weight (103 ± 17.4 kg) were not different. In both experiments, cows sorted against longer particles as determined by a particle length selection index; this behavior increased linearly as particle length increased. Greater forage particle length increased sorting behavior, but had no effect on rumen fermentation or chewing behavior.     

Killer whale (Orcinus orca) reproduction at Sea World

Sea World has maintained killer whales (Orcinus orca) since 1965. The total killer whale inventory (1965–1993) has included 39 whales (25 females, 14 males); 28 were wild-caught and 11 captive-born, including one second-generation calf. As of September, 1993, there were 19 whales in the breeding program. Ten of these whales (53%) were captive-born, either at Sea World or other facilities in North America. The live wild-caught whales ranged in estimated age from 12–27 years (x? ± sd = 17.6 ± 4.2 years). The captive-born whales ranged in age from <1 to 8 years. In the Sea World breeding program (through September, 1993), there have been nine live births and one stillbirth, with eight calves part of the current inventory. Births occurred from July to February. Calving intervals ranged from 32–58 months. Female age at birth of first calves ranged from 8 years to an estimated 17 years (x? ± sd = 12.7 ± 3.0 years). Gestation, based on conception estimates from serum progesterone analysis, averaged 17 months (x? ± sd = 517 ± 20 days), but successful pregnancies with viable calves occurred from 15–18 months (468–539 days). Females, in the presence and absence of males, were polyestrus with periods of cycling interspersed with individually variable noncycling (presumed anestrous) periods ranging from 3–16 months. Mean serum progesterone levels (±se) were as follows: noncycling periods = 121 ± 20 pg/ml; peak elevations during nonconceptive ovulatory (estrous) cycles = 3,962 ± 2,280 pg/ml; first pregnancies = 14,592 ± 3,854 pg/ml; second pregnancies = 8,389 ± 395 pg/ml; and third pregnancy = 8,180 ± 4,556. © 1995 Wiley-Liss, Inc.     

A non-chromatographic radioimmunoassay of estrone and estradiol-17beta serum

A sensitive and efficient non-chromatographic procedure employing the Girard reagent and solvent-partitioning has been developed for the accurate radioimmunoassay (RIA) of estrone (E1) and estradiol-17β(E2) in a single 1.0 ml specimen of male or female serum. Using standard curves which permitted the discrimination of zero from 0.75–1.5 pg (p=0.05), the following mean procedural blanks (pg ± S.D.) were determined (1.0 ml water, n= 24): estrone, 2. 1 ± 1.1 (range 0–4.1); estradiol 1.0± 1.1 (range 0–3.6).A comparison of RIA of estrogens (1) in serum after separation by the Girard procedure and by TLC yielded correlation coefficients of 0.99 and 0.98 for E1 and E2 respectively. The following results (pg/ml ± S.D.) were obtained on RIA of E1 and E2 in 12 different 1.0 ml specimens of male and female serum using the Girard procedure: male. E1 (32.0 ± 9.2), E2 (24.1 ± 10.9); female, E1 (108.5 ± 60.8), E2 (126.4 ± 63.2).The intra-assay variability (c.v.) was found to be 12.6% for E1 and 9.4% for E2. The interassay variability was 14.2% for both estrogens.Twenty-four assays of E1 and E2 can be completed by one person in 2 working days.     

Actigraphic motor activity during sleep from infancy to adulthood

A secondary analysis of longitudinal and cohort studies was carried out to quantitatively investigate the motor activity pattern, recorded through actigraphy, during the first six hours of nocturnal sleep. The first study was of longitudinal nature. Ten healthy participants (four females) were monitored three times, at baseline (T1) when they were infants (mean age 7.10 ± 0.32 months), at the first follow-up examination (T2) around 4 months later (mean age 11.20 ± 0.63 months) and at the second follow-up (T3) around three years later, when they were preschoolers (mean age 4.68 ± 0.14 years). At T1, T2 and T3 each participant wore the actigraph Basic Mini-Motionlogger (Ambulatory Monitoring, Inc., Ardsley, NY, USA) over at least two consecutive nycthemeral cycles, with the aim to measure the mean hourly motor activity count. Seven- and 11-month-old infants had a higher level of motor activity over the night compared to preschoolers. Furthermore, motor activity increased as the night progressed, with a pronounced increment at both T1 and T2, while at T3 such an increase was less marked. The second study was cross-sectional and aimed to explore the motor activity pattern, using actigraphy, during the first six hours of nocturnal sleep in multiple-age healthy groups, from infancy to adulthood. We assigned participants to eight groups according to age: 20 (five females) aged around 10 months old (mean age 10.65 ± 0.67 months); 13 (nine females) aged around 4 years (mean age 4.38 ± 0.51 years); 21 (10 females) aged around 10 years (mean age 9.67 ± 0.91 years); 21 (nine females) aged around 20 years (mean age 19.33 ± 2.44 years); 20 (10 females) aged around 30 years (mean age 29.80 ± 1.99 years); 20 (15 females) aged around 40 years (mean age 40.70 ± 1.26 years); 20 (11 females) aged around 50 years (mean age 50.15 ± 2.80 years) and 20 (nine females) aged around 60 years (mean age 59.25 ± 3.23 years). The participants aged between 10 and 60 years wore the actigraph Basic Mini-Motionlogger over seven consecutive nycthemeral cycles (infants and preschoolers wore the actigraph over at least two consecutive nycthemeral cycles), with the aim to measure the mean hourly motor activity count. The results indicated a significantly higher motor activity count in 10-month-old infants compared to all the remaining age groups. Moreover, the pattern of motor activity of 10-month-old infants was different from that of all other groups, with the highest motor activity counts from the second to the sixth hour of sleep. Considered as a whole, the results of both studies converge regarding the high motor activity detected among infants, which could be explained by the presence of a maturational process that has not yet been fully completed at this stage of life. In both studies, only the motor activity of infants was above the cutoff level established for normal adults, highlighting the need to establish a specific cutoff value for infants.     

Time-Dependent Variations in the Coagulation Factors II,VII, IX,and X in Young and Elderly Volunteers

The existence of circadian (24-h) rhythms in the coagulation activity of vitamin K-dependent coagulation factors (Factors II, VII, IX, and X) were studied in six healthy young (18–30 years old) and six healthy elderly (69–75 years old) men. Aliquots of 5 ml of blood were obtained from each of the 12 subjects at six different time points over a 24-h period. Factors II, VII, and X were quantified by the prothrombin time test, whereas Factor IX was analyzed by the activated partial thromboplastin time test. Significant circadian variations were found for Factors II and VII in both age groups. The peak and trough values for Factor II were observed at 16: 00 and 00: 00 in young men and at 12: 00 and 16: 00 in elderly men. The amplitude of the rhythmic variation of Factor II was 3.3 ± 1.0 and 4.2 ± 0.9% in young and elderly volunteers, respectively. For Factor VII, the highest values were found during the activity period (08: 00–16: 00), while the lowest values occurred at night (00: 00) for both groups of subjects. The amplitude of the rhythms was twice as large in the young (6.2 ± 2.3%) as in the elderly (3.7 ± 0.8%). The data suggest that age does not alter significantly the chronobiology of Factors II and VII.     

Effect of ageing on human plasma glutathione concentrations as determined by high-performance liquid chromatography with fluorimetric detection

A convenient method for the determination of reduced glutathione (GSH) and oxidized glutathione (GSSG) in human plasma by high-performance liquid chromatography with fluorescence detection is reported. This assay involves direct addition of human plasma to methanolic monobrombimane. for simultaneous protein precipitation and thiol derivatization. The assay was validated by addition of authentic GSH and GSSG to plasma samples. Plasma glutathione levels in Chinese male and female volunteers were found to decrease with increasing age (age groups, 20–30, 30–40, 40–50, 50–60, and >60; mean ± S.E.M. 0.97 ± 0.03, 0.77 ± 0.02, 0.67 ± 0.03, 0.51 ± 0.02, 0.48 ± 0.02 μM for male volunteers and 1.11 ± 0.06, 0.76 ± 0.03, 0.61 ± 0.03, 0.53 ± 0.04 and 0.43 ± 0.04 μM for female volunteers). GSSG levels, in both males and females, did not show a correlation with age. There were no significant differences in GSH or GSSG levels among male and female volunteers of the same age group. These results suggest that elderly persons might be more susceptible to oxidative injury due to decreased plasma glutathione levels.     

Effects of age on segregation of the X and Y chromosomes in cultured lymphocytes from Chinese men

Chromosome malsegregation in binucleated lymphocytes is a useful endpoint to evaluate age effect on genetic stability. However, the investigations on chromosome malsegregation in binucleated lymphocytes from Chinese are scarce. In this study, peripheral blood lym- phocytes were collected from 14 old （60-70 years） and 10 young （22-26 years） healthy Chinese men. To detect malsegregation of the sex chromosomes, multi-color fluorescence in situ hybridization （FISH） was performed on binucleated lymphocytes, cytokinesis-blocked by cytochalasin B at the first mitosis after phytohaemagglutinin stimulation. Compared with that in young men, a significant increase in frequencies of loss of chromosome X （9.2± 3.2‰ vs. 1.1 ± 0.9‰, P 〈 0.001） and Y （2.5 ± 1.9‰ vs. 0.2± 0.3‰, P 〈 0.001） was found in old men. Similarly, nondisjunction of chromosome X （16.5± 3.4‰ vs. 3.5 ± 1.1‰, P 〈 0.001） and Y （7.2 ± 2.6‰ vs. 2.4 ± 1.3‰, P 〈 0.001） occurred more frequently in old men than in young men. Regardless of donor＇s age, nondisjunction is more prevalent than loss for both chromosome X and Y. The frequencies of observed simultaneous malsegregation were relatively higher than the expected, suggest- ing an association between malsegregation. These results indicated that in Chinese men, malsegregation of the sex chromosomes increases with age in an associated fashion, and nondisjunction accounts for the majority of spontaneous chromosome malsegregation.