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Biomedical subjects

A M Khalil

Publications and source records attributed to A M Khalil.

At least 19 recordsLinked to original sources
PubMed2006

Microcystin-induced 8-hydroxydeoxyguanosine in DNA and its reduction by melatonin, vitamin C, and vitamin E in mice.

Microcystin LR (MC-LR), a liver-specific toxin synthesized by Microcystis aeruginosa, was investigated. MC-LR initiated reactive oxygen species formation followed by damaging DNA and some other cellular components. We investigated the ability of MC-LR to induce oxidative DNA damage by examining the formation of 8-hydroxydeoxyguanosine (8-OH-dG) using HPLC with electrochemical detection. Melatonin, vitamin C (ascorbate), and vitamin E (as Trolox), all of which are free radical scavengers, markedly inhibited the formation of 8-OH-dG in a concentration-dependent manner. The concentration that reduced DNA damage by 50% (IC(50)) was 0.55, 31.4, and 36.8 microM for melatonin, ascorbate, and Trolox, respectively. The results show that melatonin is 60- and 70-fold more effective than vitamin C or vitamin E, respectively, in reducing oxidative DNA damage. These findings are consistent with the conclusion that melatonin's highly protective effect against microcystin toxicity relates, at least in part, to its direct hydroxyl radical scavenging ability.

8-Hydroxy-2'-Deoxyguanosine↗
PubMed2006

Histone H3 lysine 4 dimethylation is enriched on the inactive sex chromosomes in male meiosis but absent on the inactive X in female somatic cells.

Inactivation of the X chromosome occurs in female somatic cells and in male meiosis. In both cases, the inactive X chromosome undergoes changes in histone modifications including deacetylation of core histone proteins and enrichment with histone H3 lysine 9 (H3-K9) dimethylation. In this study we show that while the inactive X in female somatic cells is largely devoid of H3-K4 dimethylation, the inactive X in male meiosis is enriched with this modification. However, the inactive X chromosome in female somatic cells and the inactive X and Y in male meiosis are devoid of H3-K4 trimethylation. Further, trimethylation of H3-K4 is present at discrete regions along most of the autosomes, while H3-K4 dimethylation shows a more homogenous staining. Also, the Y chromosome is largely devoid of H3-K4 di- and trimethylation in somatic cells of both humans and mice, however, the Y chromosome is enriched with H3-K4 di- but not trimethylation throughout spermatogenesis. Our results provide insights into the differences between female somatic cells and male germ cells in inactivating the X chromosome, and suggest that trimethylation, and not dimethylation, of H3-K4 is a more robust indicator of the active regions of the genome.

Animals↗
PubMed2005

Mode of delivery for vertex-nonvertex twin gestations.

OBJECTIVE: To compare the neonatal outcome of vaginally delivered (VD) to that of abdominally delivered (CS) vertex-nonvertex (Vx/NVx) twins. METHODS: Vx/NVx live nonanomalous twin gestations >or=25 weeks delivered from 1984 to 2000 were divided into two groups: VD (N=138), and CS (N=79). The outcome of the second twin was compared. RESULTS: The vaginal delivery rate for the Vx/NVx twins was 63.6%. The median Apgar scores at 1 and 5 min, respectively, were significantly lower in VD [7 (0-9) and 9 (1-10)] compared to CS [8 (2-10) and 9 (2-10)]. The neonatal mortality was also higher in VD (109/1000 vs. 38/1000, p=0.040). Differences in the 1-min Apgar scores persisted when infants <1500 g were excluded. All other neonatal outcome variables studied including respiratory distress syndrome, necrotizing enterocolitis, intraventricular hemorrhage, trauma, seizures, and length of nursery stay were similar. On logistic regression analysis, vaginal delivery of Vx/NVx twins marginally increased low 5-min Apgar scores and neonatal deaths. CONCLUSION: Vaginal delivery in vertex-nonvertex twins was achieved in 63.6% of cases at the expense of a higher incidence of low 1- and 5-min Apgar scores and neonatal death.

Adult↗
PubMed2002

Primary umbilical endometriosis.

A case of primary solitary umbilical endometriosis is presented. The presentation, differential diagnosis and work-up is discussed and the literature is reviewed.

Adult↗
PubMed2001

Humoral immunity to cholera toxin and ovalbumin in the brushtail possum (Trichosurus vulpecula).

AIM: To compare the humoral immune responses of female possums to ovalbumin (OVA) and cholera toxin (CT) administered using different routes and dosage regimes. METHODS: Three groups of mature female possums were immunised intragastrically (n=15) or surgically (intraileal, n=4; Peyer's patches, n=4). Levels of antibodies to OVA and CT in serum, ileal, vaginal, oviduct and uterine secretions were measured by indirect enzyme-linked immunosorbent assay (ELISA). All manipulations were conducted under general anaesthesia. RESULTS: Antibodies to CT increased significantly in serum (p<0.001) and in lateral vaginal secretions (p<0.05) after intragastric immunisation using 250-1000 microg CT. Simultaneous intragastric administration of CT with 3 mg OVA did not significantly increase antibody levels to OVA. When OVA (3 mg) and CT (250 microg) were injected into the ileum, followed by intragastric administration 4 weeks later, antibody levels to CT were significantly (p<0.05) increased in serum, uterine and medial vaginal secretions, and antibody levels to OVA were significantly (p<0.05) increased in serum and medial vaginal secretions. When OVA (3 mg) with Incomplete Freund's adjuvant was injected directly into Peyer's patches, followed by peritoneal administration 4 weeks later, antibody levels in serum, ileal and reproductive-tract secretions were generally higher than those that resulted from the other immunisation treatments. CONCLUSIONS: Administration of OVA induced an antibody response in serum and in reproductive and alimentary tract secretions when administered with CT directly into the ileum, or when injected into Peyer's patches and peritoneum. CT was a potent enteric immunogen.

Journal Article↗
PubMed1999

Factors affecting the harem formation process by young Misaki feral stallions.

For the past 12 years, a study was conducted in the Misaki area (southern Kyushu Island, Japan) to investigate young males form new harems, how they acquire the mares and the factors affecting the process of new harem formation. Young males formed new harems between the ages of 3.8 and 7.6 yr, and 93% of these new harem groups were formed at the beginning of the breeding season. The most common way (87%) for young males to form a new harem was by acquiring wandering mares which had separated from their groups, whereas 13% stole unstable mares from established bands. The fact that all young males obtained harems the new at an early age, with an average age of 5.2 yr (n = 15) could be explained high female biased sex ratio (3:1), and great number of wandering mares per stallion (2.5:1). At the time new harem groups were formed, aggression, fighting or such behavior as active herding or driving mares was not observed among stallions because the "unstable" mares were most likely to be abducted by stallions.

Age Factors↗
PubMed1998

Relationship between plasma testosterone concentrations and age, breeding season and harem size in Misaki feral horses.

Jugular vein blood samples were collected from 23 young and sexual mature feral stallions to examine the relationship between plasma testosterone concentration and age, breeding season or harem size. Testosterone concentration increased with the age of the stallions until they formed their own harems, at about 4 to 6 years old. Seasonal variations in testosterone concentrations were observed, and found to be significantly higher (P<0.001) throughout the breeding season than non-breeding season, from 3 years of age. Testosterone levels were correlated with harem size for individual stallions. It can be inferred from these results that there is a relationship between plasma testosterone concentration and age, breeding season and harem size.

Age Factors↗
PubMed1998

Case report: endometrial cancer implanting in the laparotomy scar.

A 58-year-old woman underwent abdominal hysterectomy and bilateral salpingo-oophorectomy for stage Ib, grade 2 endometrial adenocarcinoma followed by external pelvic irradiation. Five years later she presented with a 7 cm solitary infraumbilical incisional tumor recurrence that was resected. Histology of the tumor implant was similar to that of the primary cancer. The patient was then started on progestin therapy with no evidence of recurrence for four years. To our knowledge this is the fourth reported case of endometrial cancer implanting in an abdominal scar.

Adenocarcinoma↗
PubMed1997

Causes of natal dispersal and emigration and their effects on harem formation in Misaki feral horses.

Misaki feral horses were separated into 2 herds and the difference between dispersal from natal group (natal dispersal) and dispersal from natal area (natal emigration) was studied. The causes of dispersal and emigration and their effects on harem formation were studied 1979-1994. The number of horses ranged from 73 (mature males: 8, mature females: 26, young males: 8, young females: 3, colt foals: 6, filly foals: 10 and geldings: 12) in 1979 and 86 (mature males: 14, mature females: 37, young males: 12, young females: 7, colt foals: 5, filly foals: 7 and geldings: 4) in 1994 when the present study ended. All 29 males which survived to age 4 years and 58 females which survived to age 3 years left their natal or mother groups at age one to 3. Seventeen of 22 dispersing males and 29 of 39 dispersing females left their natal groups around the birth of their siblings and significant correlations were found between natal dispersal and birth of a sibling. The number of emigrating young males correlated negatively and significantly with the total number of young males in another herd and the number of emigrating young females correlated positively and significantly with the total number of young females in the natal herd. All 13 emigrating stallions which survived to age 5 years formed stable harem groups and a significant correlation was found between natal emigration and harem formation. Twenty-three of 35 resident mares formed stable consort relations with harem stallions and a significant correlation was found between residence and formation of stable consort relations.

Age Factors↗