Search PubMed⌕ Search

Biomedical subjects

A Nassar

Publications and source records attributed to A Nassar.

At least 37 records · Page 2Linked to original sources
PubMed1998

Comparison of various methods of processing human cryopreserved-thawed semen samples.

We compared the efficacy of various methods of processing cryopreserved-thawed samples for the recovery of functionally adequate spermatozoa as assessed by the response to the sperm stress test (SST), an index of temperature activated sperm membrane lipid peroxidation, and immediate and delayed changes in sperm viability and motion parameters. Donor semen samples (n = 28) were cryopreserved-thawed and divided into six equal parts, one part was used as control and the remaining parts were used to compare five methods of sperm processing as follows: direct Percoll gradient processing, washing by one-step or stepwise addition of the washing medium followed by Percoll processing, and washing by one-step or stepwise addition of the washing medium. Additional samples (n = 10) were evaluated for the immediate and delayed (6 h at 37 degrees C) impact of one-step and stepwise washing (without Percoll separation). Compared with wash-only methods, samples processed using Percoll had a significantly higher SST score (P = 0.001), motility, rapid spermatozoa (>50 microm/s), curvilinear velocity and motility index (P < 0.001). Comparing various Percoll methods, direct Percoll processing resulted in the highest number of motile spermatozoa recovered (P < 0.00001) and a higher SST score based on curvilinear velocity (P = 0.001). Stepwise washing gave a significantly higher number of motile spermatozoa (P < 0.001) but with a significantly lower SST score based on the concentration of motile spermatozoa (P = 0.001), motility (P = 0.001) and motility index (P = 0.01). Sperm viability and motion parameters after 6 h of incubation showed no difference between one-step and stepwise washing. In conclusion, compared with wash-only methods, Percoll processed samples resulted in the recovery of spermatozoa with superior quality as assessed by SST and motion analysis. One-step washing of the samples gave an overall comparable recovery compared to the samples prepared stepwise. Having significantly higher SST scores, similar viability and the maintenance of motility, one-step washing may be a better method of processing thawed samples than the stepwise washing.

Cell Survival↗
PubMed1998

Concomitant fibrous dysplasia and aneurysmal bone cyst of the skull base. Case report and review of the literature.

The combination of fibrous dysplasia and aneurysmal bone cyst of the skull base is extremely rare yet it should be recognized, lest the rapid growth of the lesion and the radiological picture lead to the wrong diagnosis of a malignant process. We report on a 6(1/2)-year-old patient who suffered from concomitant fibrous dysplasia and aneurysmal bone cyst of the skull base. He is still disease-free 4 years postoperatively. The treatment of choice remains early surgical removal of the maximal amount of involved bone that can safely be achieved. There is no role for radiotherapy in the treatment of these lesions. A review of the literature is included.

Bone Cysts, Aneurysmal↗
PubMed1996

Characterization of Erwinia chrysanthemi by pectinolytic isozyme polymorphism and restriction fragment length polymorphism analysis of PCR-amplified fragments of pel genes.

Conserved regions about 420 bp long of the pelADE cluster specific to Erwinia chrysanthemi were amplified by PCR and used to differentiate 78 strains of E. chrysanthemi that were obtained from different hosts and geographical areas. No PCR products were obtained from DNA samples extracted from other pectinolytic and nonpectinolytic species and genera. The pel fragments amplified from the E. chrysanthemi strains studied were compared by performing a restriction fragment length polymorphism (RFLP) analysis. On the basis of similarity coefficients derived from the RFLP analysis, the strains were separated into 16 PCR RFLP patterns grouped in six clusters, These clusters appeared to be correlated with other infraspecific levels of E. chrysanthemi classification, such as pathovar and biovar, and occasionally with geographical origin. Moreover, the clusters correlated well with the polymorphism of pectate lyase and pectin methylesterase isoenzymes. While the pectin methylesterase profiles correlated with host monocot-dicot classification, the pectate lyase polymorphism might reflect the cell wall microdomains of the plants belonging to these classes.

Base Sequence↗
PubMed1994

Ribotyping of Erwinia chrysanthemi Strains in Relation to Their Pathogenic and Geographic Distribution.

16S and 23S rRNAs from Escherichia coli were used to study the relationship among a representative collection of strains of Erwinia chrysanthemi differing in their original host and geographical origin. Phenetic analysis of restriction fragment length polymorphisms allowed the distribution of the studied strains into seven clusters. These clusters were similar to those obtained by cladistic methods and appeared to correlate well with the established pathovars and biovars but to a lesser extent with geographical distribution. Except for two groups of strains defined as tropical and temperate isolates (clusters 3 and 4, respectively), our clustering correlated well with botanical classifications of host plants. However, the rRNA groupings were shown to be more discriminative than biovar analysis. To assess the relationship between rRNA clusters and pathogenicity, 12 representative strains from different clusters were tested for pathogenicity on different plants. The two typical symptoms, maceration and wilting, were observed for these strains. The occurrence of the tobacco hypersensitivity reaction for a subset of these strains is discussed in light of recent results concerning the presence of an hrp gene. Considering symptom expression only, rather than the capacity for plant infection, strains from the same cluster were shown to induce similar symptoms in test plants. Thus, since host specificity is still quite controversial, rRNA patterns may constitute a useful tool in taxonomic and epidemiological studies of Erwinia chrysanthemi species.

Journal Article↗
PubMed1994

[The nutritive value of carp (Cyprinus carpio)].

From January 1991 to February 1992 the composition of filleted carps was investigated. Special attention was given to a possible correlation to origin and season. The gutted, fresh fish were weighted and only the fillets were used for the investigation. All samples were analysed in duplicate by official methods. The results showed that the protein concentration ranged between 13.0 and 21.9%, the lipids content ranged between 0.3 and 23.9%, moisture ranged between 59.8 and 84.2%, and ash content ranged between 0.0 and 1.6%.

Animals↗
PubMed1989

Vitrectomy in aphakia: a simplified technique for fundus visualisation.

By using a small air bubble that fills about two thirds of the anterior chamber the erect image of the fundus of the aphakic human eye can be visualised clearly during vitrectomy, enabling the surgeon to operate without the need for vitrectomy lenses. The refractive power of the human aphakic eye is calculated here and the image site and size are presented.

Air↗
PubMed1987

Light and electron microscopic studies of pityriasis rosea.

Light and electron microscopic studies of biopsy specimens taken from five patients with pityriasis rosea revealed the most conspicuous finding to be the presence of dyskeratotic cells within the epidermis. Ultrastructurally, these cells contained an aggregation of tonofilaments, intracytoplasmic desmosomes, many vacuoles, and viral-like particles. It is assumed that pityriasis rosea is caused by a virus to which these changes are related.

Adolescent↗
PubMed1987

Experimental study on developing rat kidney after Naja haje envenomation.

In the present experiment 164 pregnant white Wistar rats were used to study the effect of Naja haje (Egyptian cobra) venom on the developing kidney. The rats were divided into 3 groups; a control group, a group receiving one LD50 of N. haje venom and the third injected with 1/8 of LD50. The injection was performed at different stages of gestation. After birth, the neonates of group I and III and embryos of group II were examined histologically, histochemically and electron-microscopically. Both lethal and sublethal doses of N. haje venom produced haemorrhages and vascular congestion of the developing kidney. The lethal dose had degenerative effects on the podocytes and endothelium. Tubular damage appeared mainly as mitochondrial degeneration and bud-like extension, protrusions of cytoplasm and vacuolization. The succinic dehydrogenase enzyme showed decreased activity. The sublethal dose had an effect on the glomerular basement membrane in the form of splitting, increased mesangial cells and matrix, mitochondrial degeneration and fusion of podocyte processes. Tubulization of the parietal epithelium, vacuolization of the proximal tubules, mitochondrial degeneration and apical budding were evident.

Animals↗